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0aaf6ac5-3cb1-440c-8d3c-fd8640487c70 | 0aaf6ac5-3cb1-440c-8d3c-fd8640487c70 | 0aaf6ac5-3cb1-440c-8d3c-fd8640487c70 | human | null | null | none | abstracts | The redshift and geometrical aspect of photons | null | The cosmological redshift phenomenon can be described by the dark matter
field fluid model, the results deduced from this model agree very well with the
observations. The observed cosmological redshift of light depends on both the
speed of the emitter and the distance between the emitter and the observer. If
the emitter moves away from us, a redshift is observed. If the emitter moves
towards us, whether a redshift, a blueshift or no shift is observed will depend
on the speed vs. the distance. If the speed is in the range of
c(exp[-beta*D]-1) < v < 0, a redshift is observed; if the speed equals
c(exp[-beta*D]-1), no shift is observed; if the speed v less than
c(exp[-beta*D]-1), a blueshift is observed. A redshift will be always observed
in all directions for any celestial objects as long as their distance from us
is large enough. Therefore, many more redshifts than blueshifts should be
observed for galaxies and supernovae, etc in the sky. This conclusion agrees
with current observations. The estimated value of the redshift constant beta of
the dark matter field fluid is in the range of 10^(-3) ~ 10^(-5)/Mpc. A large
redshift value from a distant celestial object may not necessarily indicate
that it has a large receding speed. Based on the redshift effect of dark matter
field fluid, it is concluded that at least in time average all photons have the
same geometry (size and shape) in all inertial reference frames and do not have
length contraction effect.
|
9d8253d5-dffc-4ec0-9d4c-3ad792dd1180 | 9d8253d5-dffc-4ec0-9d4c-3ad792dd1180 | 9d8253d5-dffc-4ec0-9d4c-3ad792dd1180 | human | null | null | none | abstracts | Cool Stars in Hot Places | null | During the last three decades, evidence has mounted that star and planet
formation is not an isolated process, but is influenced by current and previous
generations of stars. Although cool stars form in a range of environments, from
isolated globules to rich embedded clusters, the influences of other stars on
cool star and planet formation may be most significant in embedded clusters,
where hundreds to thousands of cool stars form in close proximity to OB stars.
At the cool stars 14 meeting, a splinter session was convened to discuss the
role of environment in the formation of cool stars and planetary systems; with
an emphasis on the ``hot'' environment found in rich clusters. We review here
the basic results, ideas and questions presented at the session. We have
organized this contribution into five basic questions: what is the typical
environment of cool star formation, what role do hot star play in cool star
formation, what role does environment play in planet formation, what is the
role of hot star winds and supernovae, and what was the formation environment
of the Sun? The intention is to review progress made in addressing each
question, and to underscore areas of agreement and contention.
|
34b072f3-92b3-4eab-928b-67d73c99c2f0 | 34b072f3-92b3-4eab-928b-67d73c99c2f0 | 34b072f3-92b3-4eab-928b-67d73c99c2f0 | human | null | null | none | abstracts | Heights and metrics with logarithmic singularities | null | We prove lower bound and finiteness properties for arakelovian heights with
respect to pre-log-log hermitian ample line bundles. These heights were
introduced by Burgos, Kramer and K\"uhn, in their extension of the arithmetic
intersection theory of Gillet and Soul\'e, aimed to deal with hermitian vector
bundles equipped with metrics admitting suitable logarithmic singularities. Our
results generalize the corresponding properties for the heights of
Bost-Gillet-Soul\'e, as well as the properties established by Faltings for
heights of points attached to hermitian line bundles whose metrics have
logarithmic singularities. We also discuss various geometric constructions
where such pre-log-log hermitian ample line bundles naturally arise.
|
f81c8a46-f32b-4c43-bf3a-8ab6eb8ee507 | f81c8a46-f32b-4c43-bf3a-8ab6eb8ee507 | f81c8a46-f32b-4c43-bf3a-8ab6eb8ee507 | human | null | null | none | abstracts | Bar-Halo Friction in Galaxies III: Particle Number Requirements for
Simulations | null | The question whether the dark matter halo density in the centers of galaxies
could be changed through interactions with a rotating bar in the baryonic disk
is of considerable current interest. While N-body simulations have been used to
address this question, it has also been claimed that results from such
simulations cannot be trusted. Based on a perturbative treatment of resonant
exchanges between orbits and a rotating perturbation, Weinberg & Katz contend
that N-body simulations of this process will not reveal the continuum result
unless many more than the usual numbers of particles are employed. Here I
report a study designed to examine their contention, finding results that show
no dependence on the number of particles over the range usually employed up to
that advocated by these authors. I show that my results are independent of all
numerical parameters, and that field methods perform equally with grid methods
in this respect. I also identify the reasons that the required particle number
suggested by Weinberg & Katz is excessive.
|
a2442b76-d4ab-4a6e-8caf-8f3cd9e4f15c | a2442b76-d4ab-4a6e-8caf-8f3cd9e4f15c | a2442b76-d4ab-4a6e-8caf-8f3cd9e4f15c | human | null | null | none | abstracts | Electrical transport properties of polar heterointerface between KTaO3
and SrTiO3 | null | Electrical transport of a polar heterointerface between two insulating
perovskites, KTaO3 and SrTiO3, is studied. It is formed between a thin KTaO3
film deposited on a top of TiO2- terminated (100) SrTiO3 substrate. The
resulting (KO)1-(TiO2)0 heterointerface is expected to be hole-doped according
to formal valences of K (1+) and Ti (4+). We observed electrical conductivity
and mobility in the KTaO3/SrTiO3 similar to values measured earlier in
electron-doped LaAlO3/SrTiO3 heterointerfaces. However, the sign of the charge
carriers in KTaO3/SrTiO3 obtained from the Hall measurements is negative. The
result is an important clue to the true origin of the doping at perovskite
oxide hetero-interfaces.
|
0e364237-eded-483a-a0fe-dc74ca4a5d58 | 0e364237-eded-483a-a0fe-dc74ca4a5d58 | 0e364237-eded-483a-a0fe-dc74ca4a5d58 | human | null | null | none | abstracts | The Angular Separation of the Components of the Cepheid AW Per | null | The 6.4 day classical Cepheid AW Per is a spectroscopic binary with a period
of 40 years. Analyzing the centroids of HST/STIS spectra obtained in November
2001, we have determined the angular separation of the binary system. Although
we currently have spatially resolved data for a single epoch in the orbit, the
success of our approach opens the possibility of determining the inclination,
sini, for the system if the measurements are repeated at additional epochs.
Since the system is potentially a double lined spectroscopic binary, the
combination of spectroscopic orbits for both components and the visual orbit
would give the distance to the system and the masses of its components, thereby
providing a direct measurement of a Cepheid mass.
|
2606b910-fe8d-4a6d-992e-3bc896f12bc7 | 2606b910-fe8d-4a6d-992e-3bc896f12bc7 | 2606b910-fe8d-4a6d-992e-3bc896f12bc7 | human | null | null | none | abstracts | Geometry of Time, Axiom of Choice and Neuro-Biological Quantum Zeno
Effect | null | Role of axiom of choice in quantum measurement is highlighted by suggesting
that the conscious observer chooses the outcome from a mixed state. Further, in
a periodically repeating universe, these outcomes must be pre-recorded within
the non-physical conscious observers, which precludes free will. Free will
however exists in a universe with open time, It is suggested that psychology's
binding problem is connected with Cantor's original definition of set.
Influence of consciousness on material outcome through quantum processes is
discussed and interesting constraints derived. For example, it is predicted
that quantum mechanical brain states should get frozen if monitored at
sufficiently small space-time intervals - a neuro-biological version of the so
called quantum zeno effect, which has been verified in domain of micro-physics.
Existence of a very small micro-mini-black-hole in brain is predicted as a
space-time structural interface between consciousness and brain, whose
vaporization explains mass-loss reported in weighing experiments, conducting
during the moments of death.
|
14e44409-7271-45a4-be40-35a2f0e2203f | 14e44409-7271-45a4-be40-35a2f0e2203f | 14e44409-7271-45a4-be40-35a2f0e2203f | human | null | null | none | abstracts | Probing the Structure of Gamma-Ray Burst Jets with Steep Decay Phase of
their Early X-ray Afterglows | null | We show that the jet structure of gamma-ray bursts (GRBs) can be investigated
with the tail emission of the prompt GRB. The tail emission which we consider
is identified as a steep-decay component of the early X-ray afterglow observed
by the X-ray Telescope onboard Swift. Using a Monte Carlo method, we derive,
for the first time, the distribution of the decay index of the GRB tail
emission for various jet models. The new definitions of the zero of time and
the time interval of a fitting region are proposed. These definitions for
fitting the light curve lead us an unique definition of the decay index, which
is useful to investigate the structure of the GRB jet. We find that if the GRB
jet has a core-envelope structure, the predicted distribution of the decay
index of the tail has a wide scatter and has multiple peaks, which cannot be
seen for the case of the uniform and the Gaussian jet. Therefore, the decay
index distribution tells us the information on the jet structure. Especially,
if we observe events whose decay index is less than about 2, both the uniform
and the Gaussian jet models will be disfavored according to our simulation
study.
|
80320a0d-150f-4752-9deb-a3313e173f98 | 80320a0d-150f-4752-9deb-a3313e173f98 | 80320a0d-150f-4752-9deb-a3313e173f98 | human | null | null | none | abstracts | SiO maser observations of a wide dust-temperature range sample | null | We present the results of SiO line observations of a sample of known SiO
maser sources covering a wide dust-temperature range. The aim of the present
research is to investigate the causes of the correlation between infrared
colors and SiO maser intensity ratios among different transition lines. We
observed in total 75 SiO maser sources with the Nobeyama 45m telescope
quasi-simultaneously in the SiO J=1-0 v=0, 1, 2, 3, 4 and J=2-1 v=1, 2 lines.
We also observed the sample in the 29SiO J=1-0 v=0 and J=2-1 v=0, and 30SiO
J=1-0 v=0 lines, and the H2O 6(1,6)-5(2,3) line. As reported in previous
papers, we confirmed that the intensity ratios of the SiO J=1-0 v=2 to v=1
lines clearly correlate with infrared colors. In addition, we found possible
correlation between infrared colors and the intensity ratios of the SiO J=1-0
v=3 to v=1&2 lines.
|
dd1e2faf-cded-456c-a21a-0e81db7d2e3d | dd1e2faf-cded-456c-a21a-0e81db7d2e3d | dd1e2faf-cded-456c-a21a-0e81db7d2e3d | human | null | null | none | abstracts | Excitation Spectrum Gap and Spin-Wave Stiffness of XXZ Heisenberg
Chains: Global Renormalization-Group Calculation | null | The anisotropic XXZ spin-1/2 Heisenberg chain is studied using
renormalization-group theory. The specific heats and nearest-neighbor spin-spin
correlations are calculated thoughout the entire temperature and anisotropy
ranges in both ferromagnetic and antiferromagnetic regions, obtaining a global
description and quantitative results. We obtain, for all anisotropies, the
antiferromagnetic spin-liquid spin-wave velocity and the Isinglike
ferromagnetic excitation spectrum gap, exhibiting the spin-wave to spinon
crossover. A number of characteristics of purely quantum nature are found: The
in-plane interaction s_i^x s_j^x + s_i^y s_j^y induces an antiferromagnetic
correlation in the out-of-plane s_i^z component, at higher temperatures in the
antiferromagnetic XXZ chain, dominantly at low temperatures in the
ferromagnetic XXZ chain, and, in-between, at all temperatures in the XY chain.
We find that the converse effect also occurs in the antiferromagnetic XXZ
chain: an antiferromagnetic s_i^z s_j^z interaction induces a correlation in
the s_i^xy component. As another purely quantum effect, (i) in the
antiferromagnet, the value of the specific heat peak is insensitive to
anisotropy and the temperature of the specific heat peak decreases from the
isotropic (Heisenberg) with introduction of either type (Ising or XY)
anisotropy; (ii) in complete contrast, in the ferromagnet, the value and
temperature of the specific heat peak increase with either type of anisotropy.
|
5e0bf6dd-2a4a-4b9d-bf77-7f6e12b881e8 | 5e0bf6dd-2a4a-4b9d-bf77-7f6e12b881e8 | 5e0bf6dd-2a4a-4b9d-bf77-7f6e12b881e8 | human | null | null | none | abstracts | Precise Control of Band Filling in NaxCoO2 | null | Electronic properties of the sodium cobaltate NaxCoO2 are systematically
studied through a precise control of band filling. Resistivity, magnetic
susceptibility and specific heat measurements are carried out on a series of
high-quality polycrystalline samples prepared at 200 C with Na content in a
wide range of 0.35 =< x =< 0.70. It is found that dramatic changes in
electronic properties take place at a critical Na concentration x* that lies
between 0.58 and 0.59, which separates a Pauli paramagnetic and a Curie-Weiss
metals. It is suggested that at x* the Fermi level touches the bottom of the
a1g band at the gamma point, leading to a crucial change in the density of
states across x* and the emergence of a small electron pocket around the gamma
point for x > x*.
|
cdb10ff6-8e93-43ba-84a6-5090c0b82f58 | cdb10ff6-8e93-43ba-84a6-5090c0b82f58 | cdb10ff6-8e93-43ba-84a6-5090c0b82f58 | human | null | null | none | abstracts | Observations on degenerate saddle point problems | null | We investigate degenerate saddle point problems, which can be viewed as limit
cases of standard mixed formulations of symmetric problems with large jumps in
coefficients. We prove that they are well-posed in a standard norm despite the
degeneracy. By wellposedness we mean a stable dependence of the solution on the
right-hand side. A known approach of splitting the saddle point problem into
separate equations for the primary unknown and for the Lagrange multiplier is
used. We revisit the traditional Ladygenskaya--Babu\v{s}ka--Brezzi (LBB) or
inf--sup condition as well as the standard coercivity condition, and analyze
how they are affected by the degeneracy of the corresponding bilinear forms. We
suggest and discuss generalized conditions that cover the degenerate case. The
LBB or inf--sup condition is necessary and sufficient for wellposedness of the
problem with respect to the Lagrange multiplier under some assumptions. The
generalized coercivity condition is necessary and sufficient for wellposedness
of the problem with respect to the primary unknown under some other
assumptions. We connect the generalized coercivity condition to the
positiveness of the minimum gap of relevant subspaces, and propose several
equivalent expressions for the minimum gap. Our results provide a foundation
for research on uniform wellposedness of mixed formulations of symmetric
problems with large jumps in coefficients in a standard norm, independent of
the jumps. Such problems appear, e.g., in numerical simulations of composite
materials made of components with contrasting properties.
|
3128efea-83a6-4369-bcb3-11cf3dae45c8 | 3128efea-83a6-4369-bcb3-11cf3dae45c8 | 3128efea-83a6-4369-bcb3-11cf3dae45c8 | human | null | null | none | abstracts | Expected Planets in Globular Clusters | null | We argue that all transient searches for planets in globular clusters have a
very low detection probability. Planets of low metallicity stars typically do
not reside at small orbital separations. The dependance of planetary system
properties on metallicity is clearly seen when the quantity Ie=Mp[a(1-e)]^2 is
considered; Mp, a, e, are the planet mass, semi-major axis, and eccentricity,
respectively. In high metallicity systems there is a concentration of systems
at high and low values of Ie, with a low-populated gap near Ie~0.3 M_J AU^2,
where M_J is Jupiter's mass. In low metallicity systems the concentration is
only at the higher range of I_e, with a tail to low values of Ie. Therefore, it
is still possible that planets exist around main sequence stars in globular
clusters, although at small numbers because of the low metallicity, and at
orbital periods of >~10 days. We discuss the implications of our conclusions on
the role that companions can play in the evolution of their parent stars in
globular clusters, e.g., influencing the distribution of horizontal branch
stars on the Hertzsprung-Russell diagram of some globular clusters, and in
forming low mass white dwarfs.
|
19d4fcc9-4613-4189-b870-46a906205b8d | 19d4fcc9-4613-4189-b870-46a906205b8d | 19d4fcc9-4613-4189-b870-46a906205b8d | human | null | null | none | abstracts | Optical Zeno Gate: Bounds for Fault Tolerant Operation | null | In principle the Zeno effect controlled-sign gate of Franson et al's (PRA 70,
062302, 2004) is a deterministic two-qubit optical gate. However, when
realistic values of photon loss are considered its fidelity is significantly
reduced. Here we consider the use of measurement based quantum processing
techniques to enhance the operation of the Zeno gate. With the help of quantum
teleportation, we show that it is possible to achieve a Zeno CNOT gate (GC-Zeno
gate) that gives (near) unit fidelity and moderate probability of success of
0.76 with a one-photon to two-photon transmission ratio $\kappa=10^4$. We
include some mode-mismatch effects and estimate the bounds on the mode overlap
and $\kappa$ for which fault tolerant operation would be possible.
|
bf600943-e5e0-4179-a417-c5ddf88afa0e | bf600943-e5e0-4179-a417-c5ddf88afa0e | bf600943-e5e0-4179-a417-c5ddf88afa0e | human | null | null | none | abstracts | Differential Diversity Reception of MDPSK over Independent Rayleigh
Channels with Nonidentical Branch Statistics and Asymmetric Fading Spectrum | null | This paper is concerned with optimum diversity receiver structure and its
performance analysis of differential phase shift keying (DPSK) with
differential detection over nonselective, independent, nonidentically
distributed, Rayleigh fading channels. The fading process in each branch is
assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth,
but to have distinct, asymmetric fading power spectral density characteristic.
Using 8-DPSK as an example, the average bit error probability (BEP) of the
optimum diversity receiver is obtained by calculating the BEP for each of the
three individual bits. The BEP results derived are given in exact, explicit,
closed-form expressions which show clearly the behavior of the performance as a
function of various system parameters.
|
a07f92e6-61a1-46ba-a10a-fc9659887d58 | a07f92e6-61a1-46ba-a10a-fc9659887d58 | a07f92e6-61a1-46ba-a10a-fc9659887d58 | human | null | null | none | abstracts | Markov basis and Groebner basis of Segre-Veronese configuration for
testing independence in group-wise selections | null | We consider testing independence in group-wise selections with some
restrictions on combinations of choices. We present models for frequency data
of selections for which it is easy to perform conditional tests by Markov chain
Monte Carlo (MCMC) methods. When the restrictions on the combinations can be
described in terms of a Segre-Veronese configuration, an explicit form of a
Gr\"obner basis consisting of moves of degree two is readily available for
performing a Markov chain. We illustrate our setting with the National Center
Test for university entrance examinations in Japan. We also apply our method to
testing independence hypotheses involving genotypes at more than one locus or
haplotypes of alleles on the same chromosome.
|
ef38c7f9-92f1-488c-85a9-c3cd18099cab | ef38c7f9-92f1-488c-85a9-c3cd18099cab | ef38c7f9-92f1-488c-85a9-c3cd18099cab | human | null | null | none | abstracts | Seeing maximum entropy from the principle of virtual work | null | We propose an extension of the principle of virtual work of mechanics to
random dynamics of mechanical systems. The total virtual work of the
interacting forces and inertial forces on every particle of the system is
calculated by considering the motion of each particle. Then according to the
principle of Lagrange-d'Alembert for dynamical equilibrium, the vanishing
ensemble average of the virtual work gives rise to the thermodynamic
equilibrium state with maximization of thermodynamic entropy. This approach
establishes a close relationship between the maximum entropy approach for
statistical mechanics and a fundamental principle of mechanics, and constitutes
an attempt to give the maximum entropy approach, considered by many as only an
inference principle based on the subjectivity of probability and entropy, the
status of fundamental physics law.
|
b01f521f-681c-470d-996a-1dce6f466de3 | b01f521f-681c-470d-996a-1dce6f466de3 | b01f521f-681c-470d-996a-1dce6f466de3 | human | null | null | none | abstracts | Instanton Induced Neutrino Majorana Masses in CFT Orientifolds with
MSSM-like spectra | null | Recently it has been shown that string instanton effects may give rise to
neutrino Majorana masses in certain classes of semi-realistic string
compactifications. In this paper we make a systematic search for supersymmetric
MSSM-like Type II Gepner orientifold constructions admitting boundary states
associated with instantons giving rise to neutrino Majorana masses and other L-
and/or B-violating operators. We analyze the zero mode structure of D-brane
instantons on general type II orientifold compactifications, and show that only
instantons with O(1) symmetry can have just the two zero modes required to
contribute to the 4d superpotential. We however discuss how the addition of
fluxes and/or possible non-perturbative extensions of the orientifold
compactifications would allow also instantons with $Sp(2)$ and U(1) symmetries
to generate such superpotentials. In the context of Gepner orientifolds with
MSSM-like spectra, we find no models with O(1) instantons with just the
required zero modes to generate a neutrino mass superpotential. On the other
hand we find a number of models in one particular orientifold of the Gepner
model $(2,4,22,22)$ with $Sp(2)$ instantons with a few extra uncharged
non-chiral zero modes which could be easily lifted by the mentioned effects. A
few more orientifold examples are also found under less stringent constraints
on the zero modes. This class of $Sp(2)$ instantons have the interesting
property that R-parity conservation is automatic and the flavour structure of
the neutrino Majorana mass matrices has a simple factorized form.
|
fc7dc7f3-8e1e-4f70-829c-5e942e9be3a2 | fc7dc7f3-8e1e-4f70-829c-5e942e9be3a2 | fc7dc7f3-8e1e-4f70-829c-5e942e9be3a2 | human | null | null | none | abstracts | Superconductivity and magnetic order in CeRhIn$_{5}$; spectra of
coexistence | null | We discuss the fixed-point Hamiltonian and the spectrum of excitations of a
quasi-bidimensional electronic system supporting simultaneously
antiferromamagnetic ordering and superconductivity. The coexistence of these
two order parameters in a single phase is possible because the magnetic order
is linked to the formation of a spin density wave, and its order parameter is
not associated to a spectral gap but to an energy shift of the paramagnetic
bands. This peculiarity entails several distinct features in the phase diagram
and the spectral properties of the model, which may have been observed in
CeRhIn$_5$. Apart from the coexistence, we find an abrupt suppression of the
spin density wave when the superconducting and magnetic ordering temperatures
are equal. The divergence of the cyclotron mass extracted from de Haas-van
Alphen experiments is also analyzed in the same framework.
|
483ba0a1-c8e7-484c-9a38-e834fe50cc8b | 483ba0a1-c8e7-484c-9a38-e834fe50cc8b | 483ba0a1-c8e7-484c-9a38-e834fe50cc8b | human | null | null | none | abstracts | Vacuum Energy and Renormalization on the Edge | null | The vacuum dependence on boundary conditions in quantum field theories is
analysed from a very general viewpoint. From this perspective the
renormalization prescriptions not only imply the renormalization of the
couplings of the theory in the bulk but also the appearance of a flow in the
space of boundary conditions. For regular boundaries this flow has a large
variety of fixed points and no cyclic orbit. The family of fixed points
includes Neumann and Dirichlet boundary conditions. In one-dimensional field
theories pseudoperiodic and quasiperiodic boundary conditions are also RG fixed
points. Under these conditions massless bosonic free field theories are
conformally invariant. Among all fixed points only Neumann boundary conditions
are infrared stable fixed points. All other conformal invariant boundary
conditions become unstable under some relevant perturbations. In finite volumes
we analyse the dependence of the vacuum energy along the trajectories of the
renormalization group flow providing an interesting framework for dark energy
evolution. On the contrary, the renormalization group flow on the boundary does
not affect the leading behaviour of the entanglement entropy of the vacuum in
one-dimensional conformally invariant bosonic theories.
|
00282bc5-15ba-4988-8b56-01ffb8a80186 | 00282bc5-15ba-4988-8b56-01ffb8a80186 | 00282bc5-15ba-4988-8b56-01ffb8a80186 | human | null | null | none | abstracts | Higher harmonics increase LISA's mass reach for supermassive black holes | null | Current expectations on the signal to noise ratios and masses of supermassive
black holes which the Laser Interferometer Space Antenna (LISA) can observe are
based on using in matched filtering only the dominant harmonic of the inspiral
waveform at twice the orbital frequency. Other harmonics will affect the
signal-to-noise ratio of systems currently believed to be observable by LISA.
More significantly, inclusion of other harmonics in our matched filters would
mean that more massive systems that were previously thought to be {\it not}
visible in LISA should be detectable with reasonable SNRs. Our estimates show
that we should be able to significantly increase the mass reach of LISA and
observe the more commonly occurring supermassive black holes of masses $\sim
10^8M_\odot.$ More specifically, with the inclusion of all known harmonics LISA
will be able to observe even supermassive black hole coalescences with total
mass $\sim 10^8 M_\odot (10^9M_\odot)$ (and mass-ratio 0.1) for a low frequency
cut-off of $10^{-4}{\rm Hz}$ $(10^{-5}{\rm Hz})$ with an SNR up to $\sim 60$
$(\sim 30)$ at a distance of 3 Gpc. This is important from the astrophysical
viewpoint since observational evidence for the existence of black holes in this
mass range is quite strong and binaries containing such supermassive black
holes will be inaccessible to LISA if one uses as detection templates only the
dominant harmonic.
|
616e071c-207c-4047-9b16-fc5dcd2401cf | 616e071c-207c-4047-9b16-fc5dcd2401cf | 616e071c-207c-4047-9b16-fc5dcd2401cf | human | null | null | none | abstracts | SUBARU HDS Observations of a Balmer-Dominated Shock in Tycho's Supernova
Remnant | null | We present an Ha spectral observation of a Balmer-dominated shock on the
eastern side of Tycho's supernova remnant using the Subaru Telescope. Utilizing
the High Dispersion Spectrograph (HDS), we measure the spatial variation of the
line profile between preshock and postshock gas. Our observation clearly shows
a broadening and centroid shift of the narrow-component postshock Ha line
relative to the Ha emission from the preshock gas. The observation supports the
existence of a thin precursor where gas is heated and accelerated ahead of the
shock. Furthermore, the spatial profile of the emission ahead of the Balmer
filament shows a gradual gradient in the Ha intensity and line width ahead of
the shock. We propose that this region (~10^16 cm) is likely to be the
spatially resolved precursor. The line width increases from ~30 up to ~45 km/s,
and its central velocity shows a redshift of ~5 km/s across the shock front.
The characteristics of the precursor are consistent with a cosmic-ray
precursor, although the possibility of a fast neutral precursor is not ruled
out.
|
20b5f6bc-2dad-4e80-932f-fce3e4d82cbb | 20b5f6bc-2dad-4e80-932f-fce3e4d82cbb | 20b5f6bc-2dad-4e80-932f-fce3e4d82cbb | human | null | null | none | abstracts | Orbits of tori extended by finite groups and their polynomial hulls: the
case of connected complex orbits | null | Let $V$ be a complex linear space, $G\subset\GL(V)$ be a compact group. We
consider the problem of description of polynomial hulls $\wh{Gv}$ for orbits
$Gv$, $v\in V$, assuming that the identity component of $G$ is a torus $T$. The
paper contains a universal construction for orbits which satisfy the inclusion
$Gv\subset T^\bbC v$ and a characterization of pairs $(G,V)$ such that it is
true for a generic $v\in V$. The hull of a finite union of $T$-orbits in
$T^\bbC v$ can be distinguished in $\clos T^\bbC v$ by a finite collection of
inequalities of the type $\abs{z_1}^{s_1}...\abs{z_n}^{s_n}\leq c$. In
particular, this is true for $Gv$. If powers in the monomials are independent
of $v$, $Gv\subset T^\bbC v$ for a generic $v$, and either the center of $G$ is
finite or $T^\bbC$ has an open orbit, then the space $V$ and the group $G$ are
products of standard ones; the latter means that $G=S_nT$, where $S_n$ is the
group of all permutations of coordinates and $T$ is either $\bbT^n$ or
$\SU(n)\cap\bbT^n$, where $\bbT^n$ is the torus of all diagonal matrices in
$\rU(n)$. The paper also contains a description of polynomial hulls for orbits
of isotropy groups of bounded symmetric domains. This result is already known,
but we formulate it in a different form and supply with a shorter proof.
|
afa87975-d667-4919-9360-1f98b01f0ab4 | afa87975-d667-4919-9360-1f98b01f0ab4 | afa87975-d667-4919-9360-1f98b01f0ab4 | human | null | null | none | abstracts | Zero-temperature resistive transition in Josephson-junction arrays at
irrational frustration | null | We use a driven Monte Carlo dynamics in the phase representation to determine
the linear resistivity and current-voltage scaling of a two-dimensional
Josephson-junction array at an irrational flux quantum per plaquette. The
results are consistent with a phase-coherence transition scenario where the
critical temperature vanishes. The linear resistivity is nonzero at any finite
temperatures but nonlinear behavior sets in at a temperature-dependent
crossover current determined by the thermal critical exponent. From a dynamic
scaling analysis we determine this critical exponent and the thermally
activated behavior of the linear resistivity. The results are in agreement with
earlier calculations using the resistively shunted-junction model for the
dynamics of the array. The linear resistivity behavior is consistent with some
experimental results on arrays of superconducting grains but not on wire
networks, which we argue have been obtained in a current regime above the
crossover current.
|
91bbb76e-8e4c-451a-a84f-0e29cd34f3bb | 91bbb76e-8e4c-451a-a84f-0e29cd34f3bb | 91bbb76e-8e4c-451a-a84f-0e29cd34f3bb | human | null | null | none | abstracts | Protostellar clusters in intermediate-mass (IM) star forming regions | null | The transition between the low density groups of T Tauri stars and the high
density clusters around massive stars occurs in the intermediate-mass (IM)
range (M$_*$$\sim$2--8 M$_\odot$). High spatial resolution studies of IM young
stellar objects (YSO) can provide important clues to understand the clustering
in massive star forming regions.
Aims: Our aim is to search for clustering in IM Class 0 protostars. The high
spatial resolution and sensitivity provided by the new A configuration of the
Plateau de Bure Interferometer (PdBI) allow us to study the clustering in these
nearby objects.
Methods: We have imaged three IM Class 0 protostars (Serpens-FIRS 1, IC 1396
N, CB 3) in the continuum at 3.3 and 1.3mm using the PdBI. The sources have
been selected with different luminosity to investigate the dependence of the
clustering process on the luminosity of the source.
Results: Only one millimeter (mm) source is detected towards the low
luminosity source Serpens--FIRS 1. Towards CB 3 and IC1396 N, we detect two
compact sources separated by $\sim$0.05 pc. The 1.3mm image of IC 1396 N, which
provides the highest spatial resolution, reveal that one of these cores is
splitted in, at least, three individual sources.
|
3823c80a-a53f-491e-a3e6-07490089b38a | 3823c80a-a53f-491e-a3e6-07490089b38a | 3823c80a-a53f-491e-a3e6-07490089b38a | human | null | null | none | abstracts | The Epps effect revisited | null | We analyse the dependence of stock return cross-correlations on the sampling
frequency of the data known as the Epps effect: For high resolution data the
cross-correlations are significantly smaller than their asymptotic value as
observed on daily data. The former description implies that changing trading
frequency should alter the characteristic time of the phenomenon. This is not
true for the empirical data: The Epps curves do not scale with market activity.
The latter result indicates that the time scale of the phenomenon is connected
to the reaction time of market participants (this we denote as human time
scale), independent of market activity. In this paper we give a new description
of the Epps effect through the decomposition of cross-correlations. After
testing our method on a model of generated random walk price changes we justify
our analytical results by fitting the Epps curves of real world data.
|
2565412d-e295-4e87-a876-09f367615aa8 | 2565412d-e295-4e87-a876-09f367615aa8 | 2565412d-e295-4e87-a876-09f367615aa8 | human | null | null | none | abstracts | Transitive powers of Young-Jucys-Murphy elements are central | null | Although powers of the Young-Jucys-Murphya elements X_i = (1 i) + ... +(i-1
i), i = 1, ..., n, in the symmetric group S_n acting on {1, ...,n} do not lie
in the centre of the group algebra of S_n, we show that transitive powers,
namely the sum of the contributions from elements that act transitively on {1,
>...,n}, are central. We determine the coefficients, which we call star
factorization numbers, that occur in the resolution of transitive powers with
respect to the class basis of the centre of S_n, and show that they have a
polynomiality property. These centrality and polynomiality properties have
seemingly unrelated consequences. First, they answer a question raised by Pak
about reduced decompositions; second, they explain and extend the beautiful
symmetry result discovered by Irving and Rattan; and thirdly, we relate the
polynomiality to an existing polynomiality result for a class of double Hurwitz
numbers associated with branched covers of the sphere, which therefore suggests
that there may be an ELSV-type formula associated with the star factorization
numbers.
|
99db9a57-51de-43ca-aa5b-72b000c933df | 99db9a57-51de-43ca-aa5b-72b000c933df | 99db9a57-51de-43ca-aa5b-72b000c933df | human | null | null | none | abstracts | Spin Dynamics Of $qqq$ Wave Function On Light Front In High Momentum
Limit Of QCD : Role Of $qqq$ Force | null | The contribution of a spin-rich $qqq$ force (in conjunction with pairwise
$qq$ forces) to the analytical structure of the $qqq$ wave function is worked
out in the high momentum regime of QCD where the confining interaction may be
ignored, so that the dominant effect is $Coulombic$. A distinctive feature of
this study is that the spin-rich $qqq$ force is generated by a $ggg$ vertex (a
genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on
as many quark lines, giving rise to a (Mercedes-Benz type) $Y$-shaped diagram.
The dynamics is that of a Salpeter-like equation (3D support for the kernel)
formulated covariantly on the light front, a la Markov-Yukawa Transversality
Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D
Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these
ingredients, the differential equation for the 3D wave function $\phi$ receives
well-defined contributions from the $qq$ and $qqq$ forces. In particular a
$negative$ eigenvalue of the spin operator $i \sigma_1.\sigma_2\times \sigma_3$
which is an integral part of the $qqq$ force, causes a characteristic
singularity in the differential equation, signalling the dynamical effect of a
spin-rich $qqq$ force not yet considered in the literature. The potentially
crucial role of this interesting effect vis-a-vis the so-called `spin anomaly'
of the proton, is a subject of considerable physical interest.
|
38d73854-540e-4107-80e4-8120b0996a21 | 38d73854-540e-4107-80e4-8120b0996a21 | 38d73854-540e-4107-80e4-8120b0996a21 | human | null | null | none | abstracts | Neutrino Astronomy with High Spatial Resolution is Already Existing | null | By basing on observations of skeletal structures of the Sun and assuming that
some of them are located inside of star, and also that a filamentary (linear)
matter (whose a model earlier was put forward by B.U. Rodionov) is in basis of
these internal structures the author consider possible processes of images
formation of these structures inside the Sun and theirs coming out into space
and also gives an elementary estimations of its parameters, which allow: i) to
form their images in a flux of electronic neutrinos; ii) to carry out these
images from within of the Sun into space; iii) to develop these images in form
of a concomitant flux of soft x-ray, which next is recorded by telescope of
soft x-ray. It is supposed the processes considered here, actually, can be
accepted as future base of neutrino astronomy with high spatial resolution.
|
42c3ae42-51be-48ae-8bd4-bc3874110f26 | 42c3ae42-51be-48ae-8bd4-bc3874110f26 | 42c3ae42-51be-48ae-8bd4-bc3874110f26 | human | null | null | none | abstracts | Evidence for Symplectic Symmetry in Ab Initio No-Core Shell Model
Results for Light Nuclei | null | Clear evidence for symplectic symmetry in low-lying states of $^{12}$C and
$^{16}$O is reported. Eigenstates of $^{12}$C and $^{16}$O, determined within
the framework of the no-core shell model using the JISP16 $NN$ realistic
interaction, typically project at the 85-90% level onto a few of the most
deformed symplectic basis states that span only a small fraction of the full
model space. The results are nearly independent of whether the bare or
renormalized effective interactions are used in the analysis. The outcome
confirms Elliott's \SU{3} model which underpins the symplectic scheme, and
above all, points to the relevance of a symplectic no-core shell model that can
reproduce experimental B(E2) values without effective charges as well as
deformed spatial modes associated with clustering phenomena in nuclei.
|
7d2bb5dc-7167-4d65-8072-640312603af3 | 7d2bb5dc-7167-4d65-8072-640312603af3 | 7d2bb5dc-7167-4d65-8072-640312603af3 | human | null | null | none | abstracts | On spherically symmetrical accretion in fractal media | null | We use fractional integrals to generalize the description of hydrodynamic
accretion in fractal media. The fractional continuous medium model allows the
generalization of the equations of balance of mass density and momentum
density. These make it possible to consider the general case of spherical
hydrodynamic accretion onto a gravitating mass embedded in a fractal medium.
The general nature of the solution is similar to the "Bondi solution", but the
accretion rate may vary substantially and the dependence on central mass may
change significantly depending on dimensionality of the fractal medium. The
theory shows consistency with the observational data and numerical simulation
results for the particular case of accretion onto pre-main-sequence stars.
|
c5ab6ac9-4255-4991-a183-795a846596b1 | c5ab6ac9-4255-4991-a183-795a846596b1 | c5ab6ac9-4255-4991-a183-795a846596b1 | human | null | null | none | abstracts | QCD in One Dimension at Nonzero Chemical Potential | null | Using an integration formula recently derived by Conrey, Farmer and
Zirnbauer, we calculate the expectation value of the phase factor of the
fermion determinant for the staggered lattice QCD action in one dimension. We
show that the chemical potential can be absorbed into the quark masses; the
theory is in the same chiral symmetry class as QCD in three dimensions at zero
chemical potential. In the limit of a large number of colors and fixed number
of lattice points, chiral symmetry is broken spontaneously, and our results are
in agreement with expressions based on a chiral Lagrangian. In this limit, the
eigenvalues of the Dirac operator are correlated according to random matrix
theory for QCD in three dimensions. The discontinuity of the chiral condensate
is due to an alternative to the Banks-Casher formula recently discovered for
QCD in four dimensions at nonzero chemical potential. The effect of temperature
on the average phase factor is discussed in a schematic random matrix model.
|
f12226e0-3a35-4092-ba5c-a5078804f2cb | f12226e0-3a35-4092-ba5c-a5078804f2cb | f12226e0-3a35-4092-ba5c-a5078804f2cb | human | null | null | none | abstracts | The VLT-FLAMES survey of massive stars: Wind properties and evolution of
hot massive stars in the LMC | null | [Abridged] We have studied the optical spectra of 28 O- and early B-type
stars in the Large Magellanic Cloud, 22 of which are associated with the young
star-forming region N11. Stellar parameters are determined using an automated
fitting method, combining the stellar atmosphere code FASTWIND with the
genetic-algorithm optimisation routine PIKAIA. Results for stars in the LH9 and
LH10 associations of N11 are consistent with a sequential star formation
scenario, in which activity in LH9 triggered the formation of LH10. Our sample
contains four stars of spectral type O2, of which the hottest is found to be
~49-54 kK (cf. ~45-46 kK for O3 stars). The masses of helium-enriched dwarfs
and giants are systematically lower than those implied by non-rotating
evolutionary tracks. We interpret this as evidence for efficient
rotationally-enhanced mixing, leading to the surfacing of primary helium and to
an increase of the stellar luminosity. This result is consistent with findings
for SMC stars by Mokiem et al. For bright giants and supergiants no such
mass-discrepancy is found, implying that these stars follow tracks of modestly
(or non-)rotating objects. Stellar mass-loss properties were found to be
intermediate to those found in massive stars in the Galaxy and the SMC, and
comparisons with theoretical predictions at LMC metallicity yielded good
agreement over the luminosity range of our targets, i.e. 5.0 < log L/L(sun) <
6.1.
|
f97779e6-0928-4999-a406-a41fe882ec36 | f97779e6-0928-4999-a406-a41fe882ec36 | f97779e6-0928-4999-a406-a41fe882ec36 | human | null | null | none | abstracts | Strange Nucleon Form Factors from $ep$ and $\nu p$ Elastic Scattering | null | The recent parity-violating $ep$ forward-scattering elastic asymmetry data
from Jefferson Lab (HAPPEx and G0), when combined with the $\nu p$ elastic
cross section data from Brookhaven (E734), permit an extraction of the
strangeness contribution to the vector and axial nucleon form factors for
momentum transfers in the range $0.45 < Q^2 < 1.0$ GeV$^2$. These results,
combined with the recent determination of the strange vector form factors at
$Q^2 = 0.1$ GeV$^2$ (SAMPLE, HAPPEx, PVA4, G0) have been interpreted in terms
of $uuds\bar{s}$ configurations very different from the kaon-loop
configurations usually associated with strangeness in the nucleon. New
experiments are being proposed to improve the state of our knowledge of the
$\nu p$ elastic cross section -- these new experiments will push the range of
$Q^2$ to much lower values, and greatly increase the precision of the $\nu p$
elastic data. One outcome of this can be a measurement of the strangeness
contribution to the nucleon spin, $\Delta s$. Nuclear targets (e.g. C or Ar)
are to be used in these neutrino experiments, and so a deep understanding of
the nuclear physics, particularly in regard to final state effects, is needed
before the potential of these precision experiments can be fully realized.
|
bfb49b19-2598-42d6-9413-900366861144 | bfb49b19-2598-42d6-9413-900366861144 | bfb49b19-2598-42d6-9413-900366861144 | human | null | null | none | abstracts | VIMOS-VLT spectroscopy of the giant Ly-alpha nebulae associated with
three z~2.5 radio galaxies | null | The morphological and spectroscopic properties of the giant (>60 kpc)
Ly-alpha nebulae associated with three radio galaxies at z~2.5 (MRC 1558-003,
MRC 2025-218 and MRC 0140-257) have been investigated using integral field
spectroscopic data obtained with VIMOS on VLT.
The morphologies are varied. The nebula of one source has a centrally peaked,
rounded appearance. In the other two objects, it consists of two spatial
components. The three nebulae are aligned with the radio axis within <30 deg.
The total Ly-alpha luminosities are in the range (0.3-3.4) x 1e44 erg s-1. The
Ly-alpha spectral profile shows strong variation through the nebulae, with FWHM
values in the range ~400-1500 km s-1 and velocity shifts V~120-600 km s-1.
We present an infall model which can explain successfully most Ly-alpha
morphological and spectroscopic properties of the nebula associated with MRC
1558-003. This adds further support to our previous conclusion that the
_quiescent_ giant nebulae associated with this and other high redshift powerful
radio galaxies are in infall. A problem for this model is the difficulty to
reproduce the large Ly-alpha FWHM values.
We have discovered a giant (~85 kpc) Ly-alpha nebula associated with the
radio galaxy MRC 0140-257 at z=2.64. It shows strikingly relaxed kinematics
(FWHM< 300 km s-1 and V<120 km s-1), unique among high z (>2) radio galaxies.
|
4fbfe04d-51ba-4c86-bc70-5de8faecb4b7 | 4fbfe04d-51ba-4c86-bc70-5de8faecb4b7 | 4fbfe04d-51ba-4c86-bc70-5de8faecb4b7 | human | null | null | none | abstracts | Condensation of Vortex-Strings: Effective Potential Contribution Through
Dual Actions | null | Topological excitations are believed to play an important role in different
areas of physics. For example, one case of topical interest is the use of dual
models of quantum cromodynamics to understand properties of its vacuum and
confinement through the condensation of magnetic monopoles and vortices. Other
applications are related to the role of these topological excitations,
nonhomogeneous solutions of the field equations, in phase transitions
associated to spontaneous symmetry breaking in gauge theories, whose study is
of importance in phase transitions in the early universe, for instance. Here we
show a derivation of a model dual to the scalar Abelian Higgs model where its
topological excitations, namely vortex-strings, become manifest and can be
treated in a quantum field theory way. The derivation of the nontrivial
contribution of these vacuum excitations to phase transitions and its analogy
with superconductivity is then made possible and they are studied here.
|
41eadb02-6212-4cba-8c33-f86525e8fb5f | 41eadb02-6212-4cba-8c33-f86525e8fb5f | 41eadb02-6212-4cba-8c33-f86525e8fb5f | human | null | null | none | abstracts | Observation of Anti-correlation between Scintillation and Ionization for
MeV Gamma-Rays in Liquid Xenon | null | A strong anti-correlation between ionization and scintillation signals
produced by MeV gamma-rays in liquid xenon has been measured and used to
improve the energy resolution by combining the two signals. The improvement is
explained by reduced electron-ion recombination fluctuations of the combined
signal compared to fluctuations of the individual signals. Simultaneous
measurements of ionization and scintillation signals were carried out with
Cs-137, Na-22 and Co-60 gamma rays, as a function of electric field in the
liquid. A resolution of 1.7%(sigma) at 662 keV was measured at 1 kV/cm,
significantly better than the resolution from either scintillation or
ionization alone. A detailed analysis indicates that further improvement to
less than 1%(sigma) is possible with higher light collection efficiency and
lower electronic noise.
|
df8c2c91-0033-49b6-abba-dbacac497eb2 | df8c2c91-0033-49b6-abba-dbacac497eb2 | df8c2c91-0033-49b6-abba-dbacac497eb2 | human | null | null | none | abstracts | Massive Stars: From the VLT to the ELT | null | New facilities and technologies have advanced our understanding of massive
stars significantly over the past 30 years. Here I introduce a new large survey
of massive stars using VLT-FLAMES, noting the target fields and observed binary
fractions. These data have been used for the first empirical test of the
metallicity dependence of the intensity of stellar winds, finding good
agreement with theory -- an important result for the evolutionary models that
are used to interpret distant clusters, starbursts, and star-forming galaxies.
Looking ahead, plans for future Extremely Large Telescopes (ELTs) are now
undergoing significant development, and offer the exciting prospect of
observing spatially-resolved massive stars well beyond the Local Group.
|
5f72a075-06a0-4314-b3f1-c378e5034a9a | 5f72a075-06a0-4314-b3f1-c378e5034a9a | 5f72a075-06a0-4314-b3f1-c378e5034a9a | human | null | null | none | abstracts | "Illusion of control" in Minority and Parrondo Games | null | Human beings like to believe they are in control of their destiny. This
ubiquitous trait seems to increase motivation and persistence, and is probably
evolutionarily adaptive. But how good really is our ability to control? How
successful is our track record in these areas? There is little understanding of
when and under what circumstances we may over-estimate or even lose our ability
to control and optimize outcomes, especially when they are the result of
aggregations of individual optimization processes. Here, we demonstrate
analytically using the theory of Markov Chains and by numerical simulations in
two classes of games, the Minority game and the Parrondo Games, that agents who
optimize their strategy based on past information actually perform worse than
non-optimizing agents. In other words, low-entropy (more informative)
strategies under-perform high-entropy (or random) strategies. This provides a
precise definition of the "illusion of control" in set-ups a priori defined to
emphasize the importance of optimization.
|
83186c52-bc1c-4bed-89dd-e90f81770cfa | 83186c52-bc1c-4bed-89dd-e90f81770cfa | 83186c52-bc1c-4bed-89dd-e90f81770cfa | human | null | null | none | abstracts | Investigation of Energy Spectrum of EGRET Gamma-ray Sources by an
Extensive Air Shower Experiment | null | Ultra-High-Energy (UHE) ($E>100 $TeV) Extensive Air Showers (EASs) have been
monitored for a period of five years (1997-2003), using a small array of
scintillation detectors in Tehran, Iran. The data have been analyzed to take in
to account of the dependence of source counts on zenith angle. Because of
varying thickness of the overlaying atmosphere, the shower count rate is
extremely dependent on zenith angle. During a calendar year different sources
come in the field of view of the array at varying zenith angles and have
different effective observation time equivalent to zenith in a day. High energy
gamma-ray sources from the EGRET third catalogue where observed and the data
were analyzed using an excess method. Upper limits were obtained for 10 EGRET
sources. Then we investigated the EAS event rates for these 10 sources and
obtained a flux for each of them using parameters of our experiment results and
simulations. Finally we investigated the gamma-ray spectrum in the UHE range
using these fluxes with reported fluxes of the EGRET sources.
|
7c52b72f-42a0-4de6-8d72-d7c08c9fb1ac | 7c52b72f-42a0-4de6-8d72-d7c08c9fb1ac | 7c52b72f-42a0-4de6-8d72-d7c08c9fb1ac | human | null | null | none | abstracts | Conjugate field and fluctuation-dissipation relation for the dynamic
phase transition in the two-dimensional kinetic Ising model | null | The two-dimensional kinetic Ising model, when exposed to an oscillating
applied magnetic field, has been shown to exhibit a nonequilibrium,
second-order dynamic phase transition (DPT), whose order parameter Q is the
period-averaged magnetization. It has been established that this DPT falls in
the same universality class as the equilibrium phase transition in the
two-dimensional Ising model in zero applied field. Here we study for the first
time the scaling of the dynamic order parameter with respect to a nonzero,
period-averaged, magnetic `bias' field, H_b, for a DPT produced by a
square-wave applied field. We find evidence that the scaling exponent,
\delta_d, of H_b at the critical period of the DPT is equal to the exponent for
the critical isotherm, \delta_e, in the equilibrium Ising model. This implies
that H_b is a significant component of the field conjugate to Q. A finite-size
scaling analysis of the dynamic order parameter above the critical period
provides further support for this result. We also demonstrate numerically that,
for a range of periods and values of H_b in the critical region, a
fluctuation-dissipation relation (FDR), with an effective temperature
T_{eff}(T, P, H_0) depending on the period, and possibly the temperature and
field amplitude, holds for the variables Q and H_b. This FDR justifies the use
of the scaled variance of Q as a proxy for the nonequilibrium susceptibility,
\partial<Q> / \partial H_b, in the critical region.
|
0fd11579-566b-40e7-adeb-13f8a3df5891 | 0fd11579-566b-40e7-adeb-13f8a3df5891 | 0fd11579-566b-40e7-adeb-13f8a3df5891 | human | null | null | none | abstracts | High Galactic Latitude Interstellar Neutral Hydrogen Structure and
Associated (WMAP) High Frequency Continuum Emission | null | Spatial associations have been found between interstellar neutral hydrogen
(HI) emission morphology and small-scale structure observed by the Wilkinson
Microwave Anisotropy Probe (WMAP) in an area bounded by l = 60 & 180 deg, b =
30 & 70 deg, which was the primary target for this study. This area is marked
by the presence of highly disturbed local HI and a preponderance of
intermediate- and high-velocity gas. The HI distribution toward the brightest
peaks in the WMAP Internal Linear Combination (ILC) map for this area is
examined and by comparing with a second area on the sky it is demonstrated that
the associations do not appear to be the result of chance coincidence. Close
examination of several of the associations reveals important new properties of
diffuse interstellar neutral hydrogen structure. In the case of high-velocity
cloud MI, the HI and WMAP ILC morphologies are similar and an excess of soft
X-ray emission and H-alpha emission have been reported for this feature. It is
suggested that the small angular-scale, high frequency continuum emission
observed by WMAP may be produced at the surfaces of HI features interacting one
another, or at the interface between moving HI structures and regions of
enhanced plasma density in the surrounding interstellar medium. It is possible
that dust grains play a role in producing the emission. However, the primary
purpose of this report is to draw attention to these apparent associations
without offering an unambiguous explanation as to the relevant emission
mechanism(s).
|
184fc57d-5bc3-40a3-b262-ecf9b44436cb | 184fc57d-5bc3-40a3-b262-ecf9b44436cb | 184fc57d-5bc3-40a3-b262-ecf9b44436cb | human | null | null | none | abstracts | Negative- and positive-phase-velocity propagation in an isotropic chiral
medium moving at constant velocity | null | Analysis of electromagnetic planewave propagation in a medium which is a
spatiotemporally homogeneous, temporally nonlocal, isotropic, chiral medium in
a co-moving frame of reference shows that the medium is both spatially and
temporally nonlocal with respect to all non-co-moving inertial frames of
reference. Using the Lorentz transformations of electric and magnetic fields,
we show that plane waves which have positive phase velocity in the co-moving
frame of reference can have negative phase velocity in certain non-co-moving
frames of reference. Similarly, plane waves which have negative phase velocity
in the co-moving frame can have positive phase velocity in certain
non-co-moving frames.
|
853613c7-ec54-43d5-991a-7cd8cddd1b66 | 853613c7-ec54-43d5-991a-7cd8cddd1b66 | 853613c7-ec54-43d5-991a-7cd8cddd1b66 | human | null | null | none | abstracts | Finding (or not) New Gamma-ray Pulsars with GLAST | null | Young energetic pulsars will likely be the largest class of Galactic sources
observed by GLAST, with many hundreds detected. Many will be unknown as radio
pulsars, making pulsation detection dependent on radio and/or x-ray
observations or on blind periodicity searches of the gamma-rays. Estimates for
the number of pulsars GLAST will detect in blind searches have ranged from tens
to many hundreds. I argue that the number will be near the low end of this
range, partly due to observations being made in a scanning as opposed to a
pointing mode. This paper briefly reviews how blind pulsar searches will be
conducted using GLAST, what limits these searches, and how the computations and
statistics scale with various parameters.
|
05eec130-a2ef-4f27-b9e0-d8e146db263c | 05eec130-a2ef-4f27-b9e0-d8e146db263c | 05eec130-a2ef-4f27-b9e0-d8e146db263c | human | null | null | none | abstracts | Did time begin? Will time end? | null | Did time begin at a Big Bang? Will the present expansion of the universe last
for a finite or infinite time? These questions sound philosophical but are
becoming, now in the twenty-first century, central to the scientific study of
cosmology. The answers, which should become clarified in the next decade or
two, could have profound implications for how we see our own role in the
universe. Since the original publication of Stephen Hawking's {\it A Brief
History of Time} in 1988, the answers to these questions have progressed as a
result of research by the community of active theoretical physicists including
myself. To present the underlying ideas requires discussion of a wide range of
topics in cosmology, especially the make up of the energy content of the
universe. A brief summary of my conclusions, that of three different
possibilities concerning the history and future of time, the least likely is
the conventional wisdom (time began and will never end) and most likely is a
cyclic model (time never begins or ends), is in the short final Chapter which
could be read first. To understand the reasoning leading to my conclusions
could encourage reading of my entire book. My hope in writing this, my first
popular book, is that it will engender reflection about time. Many a
non-scientist may already hold a philosophical opinion about whether time
begins and ends. This book's aim is to present some recently discovered
scientific facts which can focus the reader's consideration of the two short
questions in my title.
|
0e7338ed-d0d1-4b8c-925e-e8b4e9f5b3d1 | 0e7338ed-d0d1-4b8c-925e-e8b4e9f5b3d1 | 0e7338ed-d0d1-4b8c-925e-e8b4e9f5b3d1 | human | null | null | none | abstracts | FUSE Observations of the Dwarf Novae UU Aql, BV Cen, and CH UMa in
Quiescence | null | We report on FUSE spectra of three U Gem-type, long period, dwarf novae, UU
Aql, BV Cen and CH UMa taken during their quiescence intervals. We discuss the
line identifications in their spectra and attempt to characterize the source(s)
of their FUV flux distribution. Archival IUE spectrum of CH UMa and BV Cen in
quiescence were identified as having a matching flux level with the FUSE
spectra and these were combined with each FUSE spectrum to broaden the
wavelength coverage and further constrain model fits. Multi-component synthetic
spectral fits from our model grids, consisting of single temperature white
dwarfs, two-temperature white dwarfs, accretion disks and white dwarfs plus
accretion disks, were applied to the FUSE spectra alone and to the combined
FUSE + IUE spectra. We present the results of our model analyses and their
implications.
|
9b85ffff-712d-46f7-b5ab-ca48e28e2155 | 9b85ffff-712d-46f7-b5ab-ca48e28e2155 | 9b85ffff-712d-46f7-b5ab-ca48e28e2155 | human | null | null | none | abstracts | Experimental and theoretical study of light scattering by individual
mature red blood cells by use of scanning flow cytometry and discrete dipole
approximation | null | Elastic light scattering by mature red blood cells (RBCs) was theoretically
and experimentally analyzed with the discrete dipole approximation (DDA) and
the scanning flow cytometry (SFC), respectively. SFC permits measurement of
angular dependence of light-scattering intensity (indicatrix) of single
particles. A mature RBC is modeled as a biconcave disk in DDA simulations of
light scattering. We have studied the effect of RBC orientation related to the
direction of the incident light upon the indicatrix. Numerical calculations of
indicatrices for several aspect ratios and volumes of RBC have been carried
out. Comparison of the simulated indicatrices and indicatrices measured by SFC
showed good agreement, validating the biconcave disk model for a mature RBC. We
simulated the light-scattering output signals from the SFC with the DDA for
RBCs modeled as a disk-sphere and as an oblate spheroid. The biconcave disk,
the disk-sphere, and the oblate spheroid models have been compared for two
orientations, i.e. face-on and rim-on incidence. Only the oblate spheroid model
for rim-on incidence gives results similar to the rigorous biconcave disk
model.
|
c57df4a8-4656-4265-b007-a2f51f57c338 | c57df4a8-4656-4265-b007-a2f51f57c338 | c57df4a8-4656-4265-b007-a2f51f57c338 | human | null | null | none | abstracts | Inflation, bifurcations of nonlinear curvature Lagrangians and dark
energy | null | A possible equivalence of scalar dark matter, the inflaton, and modified
gravity is analyzed. After a conformal mapping, the dependence of the effective
Lagrangian on the curvature is not only singular but also bifurcates into
several almost Einsteinian spaces, distinguished only by a different effective
gravitational strength and cosmological constant. A swallow tail catastrophe in
the bifurcation set indicates the possibility for the coexistence of different
Einsteinian domains in our Universe. This `triple unification' may shed new
light on the nature and large scale distribution not only of dark matter but
also on `dark energy', regarded as an effective cosmological constant, and
inflation.
|
d343c0ad-bce5-4ef7-85b0-f1ba449a666b | d343c0ad-bce5-4ef7-85b0-f1ba449a666b | d343c0ad-bce5-4ef7-85b0-f1ba449a666b | human | null | null | none | abstracts | Lattice refining loop quantum cosmology, anisotropic models and
stability | null | A general class of loop quantizations for anisotropic models is introduced
and discussed, which enhances loop quantum cosmology by relevant features seen
in inhomogeneous situations. The main new effect is an underlying lattice which
is being refined during dynamical changes of the volume. In general, this leads
to a new feature of dynamical difference equations which may not have constant
step-size, posing new mathematical problems. It is discussed how such models
can be evaluated and what lattice refinements imply for semiclassical behavior.
Two detailed examples illustrate that stability conditions can put strong
constraints on suitable refinement models, even in the absence of a fundamental
Hamiltonian which defines changes of the underlying lattice. Thus, a large
class of consistency tests of loop quantum gravity becomes available. In this
context, it will also be seen that quantum corrections due to inverse powers of
metric components in a constraint are much larger than they appeared recently
in more special treatments of isotropic, free scalar models where they were
artificially suppressed.
|
10c97e50-0065-48e5-a89f-f4f4f6a965fe | 10c97e50-0065-48e5-a89f-f4f4f6a965fe | 10c97e50-0065-48e5-a89f-f4f4f6a965fe | human | null | null | none | abstracts | Testing Disk Instability Models for Giant Planet Formation | null | Disk instability is an attractive yet controversial means for the rapid
formation of giant planets in our solar system and elsewhere. Recent concerns
regarding the first adiabatic exponent of molecular hydrogen gas are addressed
and shown not to lead to spurious clump formation in the author's disk
instability models. A number of disk instability models have been calculated in
order to further test the robustness of the mechanism, exploring the effects of
changing the pressure equation of state, the vertical temperature profile, and
other parameters affecting the temperature distribution. Possible reasons for
differences in results obtained by other workers are discussed. Disk
instability remains as a plausible formation mechanism for giant planets.
|
4e2a6db0-6dcf-4527-89c4-c0bbc9d66546 | 4e2a6db0-6dcf-4527-89c4-c0bbc9d66546 | 4e2a6db0-6dcf-4527-89c4-c0bbc9d66546 | human | null | null | none | abstracts | Observations of chemical differentiation in clumpy molecular clouds | null | We have extensively mapped a sample of dense molecular clouds (L1512, TMC-1C,
L1262, Per 7, L1389, L1251E) in lines of HC3N, CH3OH, SO and C^{18}O. We
demonstrate that a high degree of chemical differentiation is present in all of
the observed clouds. We analyse the molecular maps for each cloud,
demonstrating a systematic chemical differentiation across the sample, which we
relate to the evolutionary state of the cloud. We relate our observations to
the cloud physical, kinematical and evolutionary properties, and also compare
them to the predictions of simple chemical models. The implications of this
work for understanding the origin of the clumpy structures and chemical
differentiation observed in dense clouds are discussed.
|
5ab941e3-7c77-463f-9387-8e73887f3b4c | 5ab941e3-7c77-463f-9387-8e73887f3b4c | 5ab941e3-7c77-463f-9387-8e73887f3b4c | human | null | null | none | abstracts | Challenges for MSSM Higgs searches at Hadron Colliders | null | In this article we analyze the impact of B-physics and Higgs physics at LEP
on standard and non-standard Higgs bosons searches at the Tevatron and the LHC,
within the framework of minimal flavor violating supersymmetric models. The
B-physics constraints we consider come from the experimental measurements of
the rare B-decays b -> s gamma and B_u -> tau nu and the experimental limit on
the B_s -> mu+ mu- branching ratio. We show that these constraints are severe
for large values of the trilinear soft breaking parameter A_t, rendering the
non-standard Higgs searches at hadron colliders less promising. On the contrary
these bounds are relaxed for small values of A_t and large values of the
Higgsino mass parameter mu, enhancing the prospects for the direct detection of
non-standard Higgs bosons at both colliders. We also consider the available
ATLAS and CMS projected sensitivities in the standard model Higgs search
channels, and we discuss the LHC's ability in probing the whole MSSM parameter
space. In addition we also consider the expected Tevatron collider
sensitivities in the standard model Higgs h -> b bbar channel to show that it
may be able to find 3 sigma evidence in the B-physics allowed regions for small
or moderate values of the stop mixing parameter.
|
ca00443b-e716-46f2-af69-47b02d7cbeae | ca00443b-e716-46f2-af69-47b02d7cbeae | ca00443b-e716-46f2-af69-47b02d7cbeae | human | null | null | none | abstracts | The Plasma Puddle as a Perturbative Black Hole | null | We argue that the weak coupling regime of a large N gauge theory in the Higgs
phase contains black hole-like objects. These so-called ``plasma puddles'' are
meta-stable lumps of hot plasma lying in locally un-Higgsed regions of space.
They decay via O(1/N) thermal radiation and, perhaps surprisingly, absorb all
incident matter. We show that an incident particle of energy E striking the
plasma puddle will shower into an enormous number of decay products whose
multiplicity grows linearly with E, and whose average energy is independent of
E. Once these ultra-soft particles reach the interior they are thermalized by
the plasma within, and so the object appears ``black.'' We determine some gross
properties like the size and temperature of the the plasma puddle in terms of
fundamental parameters in the gauge theory. Interestingly, demanding that the
plasma puddle emit thermal Hawking radiation implies that the object is black
(i.e. absorbs all incident particles), which implies classical stability, which
implies satisfaction of the Bekenstein entropy bound. Because of the AdS/CFT
duality and the many similarities between plasma puddles and black holes, we
conjecture that black objects are a robust feature of quantum gravity.
|
6819ab6c-dcf5-4ddf-9910-2f54b1427b25 | 6819ab6c-dcf5-4ddf-9910-2f54b1427b25 | 6819ab6c-dcf5-4ddf-9910-2f54b1427b25 | human | null | null | none | abstracts | Aspects of stochastic resonance in reaction-diffusion systems: The
nonequilibrium-potential approach | null | We analyze several aspects of the phenomenon of stochastic resonance in
reaction-diffusion systems, exploiting the nonequilibrium potential's
framework. The generalization of this formalism (sketched in the appendix) to
extended systems is first carried out in the context of a simplified scalar
model, for which stationary patterns can be found analytically. We first show
how system-size stochastic resonance arises naturally in this framework, and
then how the phenomenon of array-enhanced stochastic resonance can be further
enhanced by letting the diffusion coefficient depend on the field. A yet less
trivial generalization is exemplified by a stylized version of the
FitzHugh-Nagumo system, a paradigm of the activator-inhibitor class. After
discussing for this system the second aspect enumerated above, we derive from
it -through an adiabatic-like elimination of the inhibitor field- an effective
scalar model that includes a nonlocal contribution. Studying the role played by
the range of the nonlocal kernel and its effect on stochastic resonance, we
find an optimal range that maximizes the system's response.
|
9da8d715-cb2e-49ae-8e74-521a3bdeed23 | 9da8d715-cb2e-49ae-8e74-521a3bdeed23 | 9da8d715-cb2e-49ae-8e74-521a3bdeed23 | human | null | null | none | abstracts | Distortion of Gravitational-Wave Packets Due to their Self-Gravity | null | When a source emits a gravity-wave (GW) pulse over a short period of time,
the leading edge of the GW signal is redshifted more than the inner boundary of
the pulse. The GW pulse is distorted by the gravitational effect of the
self-energy residing in between these shells. We illustrate this distortion for
GW pulses from the final plunge of black hole (BH) binaries, leading to the
evolution of the GW profile as a function of the radial distance from the
source. The distortion depends on the total GW energy released and the duration
of the emission, scaled by the total binary mass, M. The effect should be
relevant in finite box simulations where the waveforms are extracted within a
radius of <~ 100M. For characteristic emission parameters at the final plunge
between binary BHs of arbitrary spins, this effect could distort the simulated
GW templates for LIGO and LISA by a fraction of 0.001. Accounting for the wave
distortion would significantly decrease the waveform extraction errors in
numerical simulations.
|
656dd29a-8f5a-4d8f-9a75-ef96046bfcbb | 656dd29a-8f5a-4d8f-9a75-ef96046bfcbb | 656dd29a-8f5a-4d8f-9a75-ef96046bfcbb | human | null | null | none | abstracts | Curvature perturbations from ekpyrotic collapse with multiple fields | null | A scale-invariant spectrum of isocurvature perturbations is generated during
collapse in the ekpyrotic scaling solution in models where multiple fields have
steep negative exponential potentials. The scale invariance of the spectrum is
realized by a tachyonic instability in the isocurvature field. This instability
drives the scaling solution to the late time attractor that is the old
ekpyrotic collapse dominated by a single field. We show that the transition
from the scaling solution to the single field dominated ekpyrotic collapse
automatically converts the initial isocurvature perturbations about the scaling
solution to comoving curvature perturbations about the late-time attractor. The
final amplitude of the comoving curvature perturbation is determined by the
Hubble scale at the transition.
|
55e75823-10be-4864-a755-bafecc920360 | 55e75823-10be-4864-a755-bafecc920360 | 55e75823-10be-4864-a755-bafecc920360 | human | null | null | none | abstracts | Asymmetric Di-jet Production in Polarized Hadronic Collisions | null | Using the collinear QCD factorization approach, we study the
single-transverse-spin dependent cross section Delta sigma(S_perp) for the
hadronic production of two jets of momenta P_1=P+q/2 and P_2=-P+q/2. We
consider the kinematic region where the transverse components of the momentum
vectors satisfy P_perp >> q_perp >> Lambda_QCD. For the case of initial-state
gluon radiation, we show that at the leading power in q_perp/P_perp and at the
lowest non-trivial perturbative order, the dependence of Delta sigma(S_perp) on
q_perp decouples from that on P_perp, so that the cross section can be
factorized into a hard part that is a function only of the single scale P_perp,
and into perturbatively generated transverse-momentum dependent (TMD) parton
distributions with transverse momenta k_perp = O(q_perp).
|
a97cda63-75c6-4b3c-8470-6e46407f0605 | a97cda63-75c6-4b3c-8470-6e46407f0605 | a97cda63-75c6-4b3c-8470-6e46407f0605 | human | null | null | none | abstracts | Information, information processing and gravity | null | I discuss fundamental limits placed on information and information processing
by gravity. Such limits arise because both information and its processing
require energy, while gravitational collapse (formation of a horizon or black
hole) restricts the amount of energy allowed in a finite region. Specifically,
I use a criterion for gravitational collapse called the hoop conjecture. Once
the hoop conjecture is assumed a number of results can be obtained directly:
the existence of a fundamental uncertainty in spatial distance of order the
Planck length, bounds on information (entropy) in a finite region, and a bound
on the rate of information processing in a finite region. In the final section
I discuss some cosmological issues related to the total amount of information
in the universe, and note that almost all detailed aspects of the late universe
are determined by the randomness of quantum outcomes. This paper is based on a
talk presented at a 2007 Bellairs Research Institute (McGill University)
workshop on black holes and quantum information.
|
4b36762b-96bb-40d0-ab76-47db42cb6e85 | 4b36762b-96bb-40d0-ab76-47db42cb6e85 | 4b36762b-96bb-40d0-ab76-47db42cb6e85 | human | null | null | none | abstracts | Noise-induced phase transitions: Effects of the noises' statistics and
spectrum | null | The local, uncorrelated multiplicative noises driving a second-order, purely
noise-induced, ordering phase transition (NIPT) were assumed to be Gaussian and
white in the model of [Phys. Rev. Lett. \textbf{73}, 3395 (1994)]. The
potential scientific and technological interest of this phenomenon calls for a
study of the effects of the noises' statistics and spectrum. This task is
facilitated if these noises are dynamically generated by means of stochastic
differential equations (SDE) driven by white noises. One such case is that of
Ornstein--Uhlenbeck noises which are stationary, with Gaussian pdf and a
variance reduced by the self-correlation time (\tau), and whose effect on the
NIPT phase diagram has been studied some time ago. Another such case is when
the stationary pdf is a (colored) Tsallis' (q)--\emph{Gaussian} which, being a
\emph{fat-tail} distribution for (q>1) and a \emph{compact-support} one for
(q<1), allows for a controlled exploration of the effects of the departure from
Gaussian statistics. As done before with stochastic resonance and other
phenomena, we now exploit this tool to study--within a simple mean-field
approximation and with an emphasis on the \emph{order parameter} and the
``\emph{susceptibility}''--the combined effect on NIPT of the noises'
statistics and spectrum. Even for relatively small (\tau), it is shown that
whereas fat-tail noise distributions ((q>1)) counteract the effect of
self-correlation, compact-support ones ((q<1)) enhance it. Also, an interesting
effect on the susceptibility is seen in the last case.
|
3f314eb2-5238-40fd-a0db-2637d0a20b6d | 3f314eb2-5238-40fd-a0db-2637d0a20b6d | 3f314eb2-5238-40fd-a0db-2637d0a20b6d | human | null | null | none | abstracts | The Mid-Infrared Emission of M87 | null | We discuss Subaru and Spitzer Space Telescope imaging and spectroscopy of M87
in the mid-infrared from 5-35 um. These observations allow us to investigate
mid-IR emission mechanisms in the core of M87 and to establish that the
flaring, variable jet component HST-1 is not a major contributor to the mid-IR
flux. The Spitzer data include a high signal-to-noise 15-35 $\mu$m spectrum of
the knot A/B complex in the jet, which is consistent with synchrotron emission.
However, a synchrotron model cannot account for the observed {\it nuclear}
spectrum, even when contributions from the jet, necessary due to the degrading
of resolution with wavelength, are included. The Spitzer data show a clear
excess in the spectrum of the nucleus at wavelengths longer than 25 um, which
we model as thermal emission from cool dust at a characteristic temperature of
55 \pm 10 K, with an IR luminosity \sim 10^{39} {\rm ~erg ~s^{-1}}. Given
Spitzer's few-arcsecond angular resolution, the dust seen in the nuclear
spectrum could be located anywhere within ~5'' (390 pc) of the nucleus. In any
case, the ratio of AGN thermal to bolometric luminosity indicates that M87 does
not contain the IR-bright torus that classical unified AGN schemes invoke.
However, this result is consistent with theoretical predictions for
low-luminosity AGNs
|
804a971e-a34f-44b3-9a42-54303f449c7b | 804a971e-a34f-44b3-9a42-54303f449c7b | 804a971e-a34f-44b3-9a42-54303f449c7b | human | null | null | none | abstracts | The Fincher-Burke spin excitations and omega/T scaling in the insulating
5% Sr-doped La2CuO4 | null | Insulating La1.95Sr0.05CuO4 shares with superconducting cuprates the same
Fincher-Burke-like spin excitations, which usually are observed in itinerant
antiferromagnets. The local spectral function satisfies omega/T scaling above
~16 K for this incommensurate insulating cuprate. Together with previous
results in commensurate insulating and incommensurate superconducting cuprates,
these results further support the general scaling prediction for square-lattice
quantum spin S=1/2 systems. The width of incommensurate peaks in
La1.95Sr0.05CuO4 scales to a similar finite value as at optimal doping,
strongly suggesting that they are similarly distant from a quantum critical
point. They might both be limited to a finite correlation length by the partial
spin-glass freezing.
|
06e2ac3f-6c0d-47e1-8951-d1f5153866d8 | 06e2ac3f-6c0d-47e1-8951-d1f5153866d8 | 06e2ac3f-6c0d-47e1-8951-d1f5153866d8 | human | null | null | none | abstracts | Pulsating Front Speed-up and Quenching of Reaction by Fast Advection | null | We consider reaction-diffusion equations with combustion-type non-linearities
in two dimensions and study speed-up of their pulsating fronts by general
periodic incompressible flows with a cellular structure. We show that the
occurence of front speed-up in the sense $\lim_{A\to\infty} c_*(A)=\infty$,
with $A$ the amplitude of the flow and $c_*(A)$ the (minimal) front speed, only
depends on the geometry of the flow and not on the reaction function. In
particular, front speed-up happens for KPP reactions if and only if it does for
ignition reactions. We also show that the flows which achieve this speed-up are
precisely those which, when scaled properly, are able to quench any ignition
reaction.
|
34e818e0-2103-4a94-a654-e922d3e54a9b | 34e818e0-2103-4a94-a654-e922d3e54a9b | 34e818e0-2103-4a94-a654-e922d3e54a9b | human | null | null | none | abstracts | A linear reformulation of the Kuramoto model of self-synchronizing
oscillators | null | The present paper introduces a linear reformulation of the Kuramoto model
describing a self-synchronizing phase transition in a system of globally
coupled oscillators that in general have different characteristic frequencies.
The reformulated model provides an alternative coherent framework through which
one can analytically tackle synchronization problems that are not amenable to
the original Kuramoto analysis. It allows one to solve explicitly for the
synchronization order parameter and the critical point of 1) the full
phase-locking transition for a system with a finite number of oscillators
(unlike the original Kuramoto model, which is solvable implicitly only in the
mean-field limit) and 2) a new class of continuum systems. It also makes it
possible to probe the system's dynamics as it moves towards a steady state.
While discussion in this paper is restricted to systems with global coupling,
the new formalism introduced by the linear reformulation also lends itself to
solving systems that exhibit local or asymmetric coupling.
|
9eac3f57-b52e-4a54-859d-190448bed60b | 9eac3f57-b52e-4a54-859d-190448bed60b | 9eac3f57-b52e-4a54-859d-190448bed60b | human | null | null | none | abstracts | Electronic Properties of Carbon Nanotubes Calculated from Density
Functional Theory and the Empirical pi-Bond Model | null | The validity of the DFT models implemented by FIREBALL for CNT electronic
device modeling is assessed. The effective masses, band gaps, and transmission
coefficients of semi-conducting, zigzag, (n,0) carbon nanotubes (CNTs)
resulting from the ab initio tight-binding density functional theory (DFT) code
FIREBALL and the empirical, nearest-neighbor pi-bond model are compared for all
semiconducting n values 5 <(=) n <(=) 35. The DFT values for the effective
masses differ from the pi-bond values by +(-) 9% over the range of n values, 17
<(=) n <(=) 29, most important for electronic device applications. Over the
range 13 <(=) n <(=) 35, the DFT bandgaps are less than the empirical bandgaps
by 20-180 meV depending on the functional and the n value. The pi-bond model
gives results that differ signifcantly from the DFT results when the CNT
diameter goes below 1 nm due to the large curvature of the CNT. The pi-bond
model quickly becomes inaccurate away from the bandedges for a (10, 0) CNT, and
it is completely inaccurate for n <(=) 8.
|
4af844b4-d850-4ef1-9144-94d28a6501d4 | 4af844b4-d850-4ef1-9144-94d28a6501d4 | 4af844b4-d850-4ef1-9144-94d28a6501d4 | human | null | null | none | abstracts | The Deviation of the Vacuum Refractive Index Induced by a Static
Gravitational Field | null | We analyzed the influence of static gravitational field on the vacuum and
proposed the concept of inhomogeneous vacuum. According to the observational
result of the light deflection in solar gravitational field as well as the
corresponding Fermat's principle in the general relativity, we derived an
analytical expression of the refractive index of vacuum in a static
gravitational field. We found that the deviation of the vacuum refractive index
is composed of two parts: one is caused by the time dilation effect, the other
is caused by the length contraction effect. As an application, we simulated the
effect of the gravitational lensing through computer programming and found that
the missing central imaging could be interpreted in a reasonable way.
|
f8394fc3-8915-4ab6-9906-111019d66fa1 | f8394fc3-8915-4ab6-9906-111019d66fa1 | f8394fc3-8915-4ab6-9906-111019d66fa1 | human | null | null | none | abstracts | Deaconstructing Functions on Quadratic Surfaces into Multipoles | null | Any homogeneous polynomial $P(x, y, z)$ of degree $d$, being restricted to a
unit sphere $S^2$, admits essentially a unique representation of the form
$\lambda + \sum_{k = 1}^d [\prod_{j = 1}^k L_{kj}]$, where $L_{kj}$'s are
linear forms in $x, y$ and $z$ and $\lambda$ is a real number. The coefficients
of these linear forms, viewed as 3D vectors, are called \emph{multipole}
vectors of $P$. In this paper we consider similar multipole representations of
polynomial and analytic functions on other quadratic surfaces $Q(x, y, z) = c$,
real and complex. Over the complex numbers, the above representation is not
unique, although the ambiguity is essentially finite. We investigate the
combinatorics that depicts this ambiguity. We link these results with some
classical theorems of harmonic analysis, theorems that describe decompositions
of functions into sums of spherical harmonics. We extend these classical
theorems (which rely on our understanding of the Laplace operator
$\Delta_{S^2}$) to more general differential operators $\Delta_Q$ that are
constructed with the help of the quadratic form $Q(x, y, z)$. Then we introduce
modular spaces of multipoles. We study their intricate geometry and topology
using methods of algebraic geometry and singularity theory. The multipole
spaces are ramified over vector or projective spaces, and the compliments to
the ramification sets give rise to a rich family of $K(\pi, 1)$-spaces, where
$\pi$ runs over a variety of modified braid groups.
|
1779b839-b7bd-420b-aed5-0a9ccc3d3e5d | 1779b839-b7bd-420b-aed5-0a9ccc3d3e5d | 1779b839-b7bd-420b-aed5-0a9ccc3d3e5d | human | null | null | none | abstracts | Self-organized metal nanostructures through laser driven thermocapillary
convection | null | When ultrathin metal films are subjected to multiple cycles of rapid melting
and resolidification by a ns pulsed laser, spatially correlated interfacial
nanostructures can result from a competition among several possible thin film
self-organizing processes. Here we investigate self-organization and the
ensuing length scales when Co films (1-8 nm thick) on SiO_{\text{2}} surfaces
are repeatedly and rapidly melted by non-uniform (interference) laser
irradiation. Pattern evolution produces nanowires, which eventually break-up
into nanoparticles exhibiting spatial order in the nearest neighbor spacing,
\lambda_{NN2}.The scaling behavior is consistent with pattern formation by
thermocapillary flow and a Rayleigh-like instability. For h_{0}\leq2 nm, a
hydrodynamic instability of a spinodally unstable film leads to the formation
of nanoparticles.
|
3bea52f9-dadc-4603-b1c9-418af4a7ae44 | 3bea52f9-dadc-4603-b1c9-418af4a7ae44 | 3bea52f9-dadc-4603-b1c9-418af4a7ae44 | human | null | null | none | abstracts | An Optical Source Catalog of the North Ecliptic Pole Region | null | We present a five (u*,g',r',i',z') band optical photometry catalog of the
sources in the North Ecliptic Pole (NEP) region based on deep observations made
with MegaCam at CFHT. The source catalog covers about 2 square degree area
centered at the NEP and reaches depths of about 26 mag for u*, g', r' bands,
about 25 mag for i' band, and about 24 mag for z' band (4 sigma detection over
an 1 arcsec aperture). The total number of cataloged sources brighter than r'=
23 mag is about 56,000 including both point sources and extended sources. From
the investigation of photometric properties using the color-magnitude diagrams
and color-color diagrams, we have found that the colors of extended sources are
mostly (u*-r') < 3.0 and (g'-z') > 0.5. This can be used to separate the
extended sources from the point sources reliably, even for the faint source
domain where typical morphological classification schemes hardly work
efficiently. We have derived an empirical color-redshift relation of the red
sequence galaxies using the Sloan Digital Sky Survey data. By applying this
relation to our photometry catalog and searching for any spatial overdensities,
we have found two galaxy clusters and one nearby galaxy group.
|
58f15b32-31b9-458c-9efd-ece42f1ab373 | 58f15b32-31b9-458c-9efd-ece42f1ab373 | 58f15b32-31b9-458c-9efd-ece42f1ab373 | human | null | null | none | abstracts | Five-dimensional N = 1 AdS superspace: Geometry, off-shell multiplets
and dynamics | null | As a step towards formulating projective superspace techniques for
supergravity theories with eight supercharges, this work is devoted to field
theory in five-dimensional N = 1 anti-de Sitter superspace AdS^{5|8} =
SU(2,2|1)/SO(4,1) x U(1) which is a maximally symmetric curved background. We
develop the differential geometry of AdS^{5|8} and describe its isometries in
terms of Killing supervectors. Various off-shell supermultiplets in AdS^{5|8} x
S^2 are defined, and supersymmetric actions are constructed both in harmonic
and projective superspace approaches. Several families of supersymmetric
theories are presented including nonlinear sigma-models, Chern-Simons theories
and vector-tensor dynamical systems. Using a suitable coset representative, we
make use of the coset construction to develop an explicit realization for one
half of the superspace AdS^{5|8} as a trivial fiber bundle with fibers
isomorophic to four-dimensional Minkowski superspace.
|
8d367fd6-52c8-4ea4-9ecc-8e9d9bcdd1ff | 8d367fd6-52c8-4ea4-9ecc-8e9d9bcdd1ff | 8d367fd6-52c8-4ea4-9ecc-8e9d9bcdd1ff | human | null | null | none | abstracts | Magnetic structure of CeRhIn$_{5}$ under magnetic field | null | The magnetically ordered ground state of CeRhIn$_{5}$ at ambient pressure and
zero magnetic field is an incomensurate helicoidal phase with the propagation
vector $\bf{k}$=(1/2, 1/2, 0.298) and the magnetic moment in the basal plane of
the tetragonal structure. We determined by neutron diffraction the two
different magnetically ordered phases of CeRhIn$_{5}$ evidenced by bulk
measurements under applied magnetic field in its basal plane. The low
temperature high magnetic phase corresponds to a sine-wave structure of the
magnetization being commensurate with $\bf{k}$=(1/2, 1/2, 1/4). At high
temperature, the phase is incommensurate with $\bf{k}$=(1/2, 1/2, 0.298) and a
possible small ellipticity. The propagation vector of this phase is the same as
the one of the zero-field structure.
|
b94adfd7-1c4c-48cb-b387-dfb3cacf55de | b94adfd7-1c4c-48cb-b387-dfb3cacf55de | b94adfd7-1c4c-48cb-b387-dfb3cacf55de | human | null | null | none | abstracts | The Kinematics and Dynamics of the Globular Clusters and the Planetary
Nebulae of NGC 5128 | null | A new kinematic and dynamic study of the halo of the giant elliptical galaxy,
NGC 5128, is presented. From a spectroscopically confirmed sample of 340
globular clusters and 780 planetary nebulae, the rotation amplitude, rotation
axis, velocity dispersion, and the total dynamical mass are determined for the
halo of NGC 5128. The globular cluster kinematics were searched for both radial
dependence and metallicity dependence by subdividing the globular cluster
sample into 158 metal-rich ([Fe/H] > -1.0) and 178 metal-poor ([Fe/H] < -1.0)
globular clusters. Our results show the kinematics of the metal-rich and
metal-poor subpopulations are quite similar. The kinematics are compared to the
planetary nebula population where differences are apparent in the outer regions
of the halo. The total mass of NGC 5128 is found using the Tracer Mass
estimator (Evans et al. 2003), to determine the mass supported by internal
random motions, and the spherical component of the Jeans equation to determine
the mass supported by rotation. We find a total mass of (1.0+/-0.2) x 10^(12)
Msun from the planetary nebulae data out to a projected radius of 90 kpc and
(1.3+/-0.5) x 10^(12) Msun from the globular clusters out to a projected radius
of 50 kpc. Lastly, we present a new and homogeneous catalog of known globular
clusters in NGC 5128. This catalog combines all previous definitive cluster
identifications from radial velocity studies and HST imaging studies, as well
as 80 new globular clusters from a study of M.A. Beasley et al. (2007, in
preparation).
|
1330efec-3f17-401f-9898-7019148d305f | 1330efec-3f17-401f-9898-7019148d305f | 1330efec-3f17-401f-9898-7019148d305f | human | null | null | none | abstracts | Five Intermediate-Period Planets from the N2K Sample | null | We report the detection of five Jovian mass planets orbiting high metallicity
stars. Four of these stars were first observed as part of the N2K program and
exhibited low RMS velocity scatter after three consecutive observations.
However, follow-up observations over the last three years now reveal the
presence of longer period planets with orbital periods ranging from 21 days to
a few years. HD 11506 is a G0V star with a planet of \msini = 4.74 \mjup in a
3.85 year orbit. HD 17156 is a G0V star with a 3.12 \mjup planet in a 21.2 day
orbit. The eccentricity of this orbit is 0.67, one of the highest known for a
planet with a relatively short period. The orbital period for this planet
places it in a region of parameter space where relatively few planets have been
detected. HD 125612 is a G3V star with a planet of \msini = 3.5 \mjup in a 1.4
year orbit. HD 170469 is a G5IV star with a planet of \msini = 0.67 \mjup in a
3.13 year orbit. HD 231701 is an F8V star with planet of 1.08 \mjup in a 142
day orbit. All of these stars have supersolar metallicity. Three of the five
stars were observed photometrically but showed no evidence of brightness
variability. A transit search conducted for HD 17156 was negative but covered
only 25% of the search space and so is not conclusive.
|
e4cd1db4-327a-4622-8605-1767c19dfee2 | e4cd1db4-327a-4622-8605-1767c19dfee2 | e4cd1db4-327a-4622-8605-1767c19dfee2 | human | null | null | none | abstracts | Finite-size scaling of pseudo-critical point distributions in the random
transverse-field Ising chain | null | We study the distribution of finite size pseudo-critical points in a
one-dimensional random quantum magnet with a quantum phase transition described
by an infinite randomness fixed point. Pseudo-critical points are defined in
three different ways: the position of the maximum of the average entanglement
entropy, the scaling behavior of the surface magnetization, and the energy of a
soft mode. All three lead to a log-normal distribution of the pseudo-critical
transverse fields, where the width scales as $L^{-1/\nu}$ with $\nu=2$ and the
shift of the average value scales as $L^{-1/\nu_{typ}}$ with $\nu_{typ}=1$,
which we related to the scaling of average and typical quantities in the
critical region.
|
8cc4fd4f-c157-417d-a11a-09b39c1ac097 | 8cc4fd4f-c157-417d-a11a-09b39c1ac097 | 8cc4fd4f-c157-417d-a11a-09b39c1ac097 | human | null | null | none | abstracts | Novel algorithm to calculate hypervolume indicator of Pareto
approximation set | null | Hypervolume indicator is a commonly accepted quality measure for comparing
Pareto approximation set generated by multi-objective optimizers. The best
known algorithm to calculate it for $n$ points in $d$-dimensional space has a
run time of $O(n^{d/2})$ with special data structures. This paper presents a
recursive, vertex-splitting algorithm for calculating the hypervolume indicator
of a set of $n$ non-comparable points in $d>2$ dimensions. It splits out
multiple child hyper-cuboids which can not be dominated by a splitting
reference point. In special, the splitting reference point is carefully chosen
to minimize the number of points in the child hyper-cuboids. The complexity
analysis shows that the proposed algorithm achieves $O((\frac{d}{2})^n)$ time
and $O(dn^2)$ space complexity in the worst case.
|
d5bc3512-c016-416e-8075-a32074504368 | d5bc3512-c016-416e-8075-a32074504368 | d5bc3512-c016-416e-8075-a32074504368 | human | null | null | none | abstracts | Statistical properties of giant pulses from the Crab pulsar | null | We have studied the statistics of giant pulses from the Crab pulsar for the
first time with particular reference to their widths. We have analyzed data
collected during 3.5 hours of observations conducted with the Westerbork
Synthesis Radio Telescope operated in a tied-array mode at a frequency of 1200
MHz. The PuMa pulsar backend provided voltage recording of X and Y linear
polarization states in two conjugate 10 MHz bands. We restricted the time
resolution to 4 microseconds to match the scattering on the interstellar
inhomogeneities. In total about 18000 giant pulses (GP) were detected in full
intensity with a threshold level of 6 sigma. Cumulative probability
distributions (CPD) of giant pulse energies were analyzed for groups of GPs
with different effective widths in the range 4 to 65 microseconds. The CPDs
were found to manifest notable differences for the different GP width groups.
The slope of a power-law fit to the high-energy portion of the CPDs evolves
from -1.7 to -3.2 when going from the shortest to the longest GPs. There are
breaks in the CPD power-law fits indicating flattening at low energies with
indices varying from -1.0 to -1.9 for the short and long GPs respectively. The
GPs with a stronger peak flux density were found to be of shorter duration. We
compare our results with previously published data and discuss the importance
of these peculiarities in the statistical properties of GPs for the heoretical
understanding of the emission mechanism responsible for GP generation.
|
42b52503-9784-471e-8a5a-3550e921a08f | 42b52503-9784-471e-8a5a-3550e921a08f | 42b52503-9784-471e-8a5a-3550e921a08f | human | null | null | none | abstracts | A Doubly Distributed Genetic Algorithm for Network Coding | null | We present a genetic algorithm which is distributed in two novel ways: along
genotype and temporal axes. Our algorithm first distributes, for every member
of the population, a subset of the genotype to each network node, rather than a
subset of the population to each. This genotype distribution is shown to offer
a significant gain in running time. Then, for efficient use of the
computational resources in the network, our algorithm divides the candidate
solutions into pipelined sets and thus the distribution is in the temporal
domain, rather that in the spatial domain. This temporal distribution may lead
to temporal inconsistency in selection and replacement, however our experiments
yield better efficiency in terms of the time to convergence without incurring
significant penalties.
|
4b1695d2-f870-4c40-909a-78f26a5f08db | 4b1695d2-f870-4c40-909a-78f26a5f08db | 4b1695d2-f870-4c40-909a-78f26a5f08db | human | null | null | none | abstracts | Evaluation of the Axial Vector Commutator Sum Rule for Pion-Pion
Scattering | null | We consider the sum rule proposed by one of us (SLA), obtained by taking the
expectation value of an axial vector commutator in a state with one pion. The
sum rule relates the pion decay constant to integrals of pion-pion cross
sections, with one pion off the mass shell. We remark that recent data on
pion-pion scattering allow a precise evaluation of the sum rule. We also
discuss the related Adler--Weisberger sum rule (obtained by taking the
expectation value of the same commutator in a state with one nucleon),
especially in connection with the problem of extrapolation of the pion momentum
off its mass shell. We find, with current data, that both the pion-pion and
pion-nucleon sum rules are satisfied to better than six percent, and we give
detailed estimates of the experimental and extrapolation errors in the closure
discrepancies.
|
c79646d3-70e9-439c-83cd-6affc94e04ae | c79646d3-70e9-439c-83cd-6affc94e04ae | c79646d3-70e9-439c-83cd-6affc94e04ae | human | null | null | none | abstracts | Elasticity with Arbitrarily Shaped Inhomogeneity | null | A classical problem in elasticity theory involves an inhomogeneity embedded
in a material of given stress and shear moduli. The inhomogeneity is a region
of arbitrary shape whose stress and shear moduli differ from those of the
surrounding medium. In this paper we present a new, semi-analytic method for
finding the stress tensor for an infinite plate with such an inhomogeneity. The
solution involves two conformal maps, one from the inside and the second from
the outside of the unit circle to the inside, and respectively outside, of the
inhomogeneity. The method provides a solution by matching the conformal maps on
the boundary between the inhomogeneity and the surrounding material. This
matching converges well only for relatively mild distortions of the unit circle
due to reasons which will be discussed in the article. We provide a comparison
of the present result to known previous results.
|
68ce64c8-d0ed-461a-bef1-23bfbccdc481 | 68ce64c8-d0ed-461a-bef1-23bfbccdc481 | 68ce64c8-d0ed-461a-bef1-23bfbccdc481 | human | null | null | none | abstracts | The dynamics of Jupiter and Saturn in the gaseous proto-planetary disk | null | We study the possibility that the mutual interactions between Jupiter and
Saturn prevented Type II migration from driving these planets much closer to
the Sun. Our work extends previous results by Masset and Snellgrove (2001), by
exploring a wider set of initial conditions and disk parameters, and by using a
new hydrodynamical code that properly describes for the global viscous
evolution of the disk. Initially both planets migrate towards the Sun, and
Saturn's migration tends to be faster. As a consequence, they eventually end up
locked in a mean motion resonance. If this happens in the 2:3 resonance, the
resonant motion is particularly stable, and the gaps opened by the planets in
the disk may overlap. This causes a drastic change in the torque balance for
the two planets, which substantially slows down the planets' inward migration.
If the gap overlap is substantial, planet migration may even be stopped or
reversed. As the widths of the gaps depend on disk viscosity and scale height,
this mechanism is particularly efficient in low viscosity, cool disks. We
discuss the compatibility of our results with the initial conditions adopted in
Tsiganis et al. (2005) and Gomes et al. (2005) to explain the current orbital
architecture of the giant planets and the origin of the Late Heavy Bombardment
of the Moon.
|
8849966b-eda6-476d-a233-170fdc6800ad | 8849966b-eda6-476d-a233-170fdc6800ad | 8849966b-eda6-476d-a233-170fdc6800ad | human | null | null | none | abstracts | Kinetic Theory for Binary Granular Mixtures at Low-Density | null | Many features of granular media can be modelled as a fluid of hard spheres
with {\em inelastic} collisions. Under rapid flow conditions, the macroscopic
behavior of grains can be described through hydrodynamic equations. At
low-density, a fundamental basis for the derivation of the hydrodynamic
equations and explicit expressions for the transport coefficients appearing in
them is provided by the Boltzmann kinetic theory conveniently modified to
account for inelastic binary collisions. The goal of this chapter is to give an
overview of the recent advances made for binary granular gases by using kinetic
theory tools. Some of the results presented here cover aspects such as
transport properties, energy nonequipartition, instabilities, segregation or
mixing, non-Newtonian behavior, .... In addition, comparison of the analytical
results with those obtained from Monte Carlo and molecular dynamics simulations
is also carried out, showing the reliability of kinetic theory to describe
granular flows even for strong dissipation.
|
1d144d1d-bb40-40f1-a4ee-e4a63b612fa4 | 1d144d1d-bb40-40f1-a4ee-e4a63b612fa4 | 1d144d1d-bb40-40f1-a4ee-e4a63b612fa4 | human | null | null | none | abstracts | Optical carrier wave shocking: detection and dispersion | null | Carrier wave shocking is studied using the Pseudo-Spectral Spatial Domain
(PSSD) technique. We describe the shock detection diagnostics necessary for
this numerical study, and verify them against theoretical shocking predictions
for the dispersionless case. These predictions show Carrier Envelope Phase
(CEP) and pulse bandwidth sensitivity in the single-cycle regime. The flexible
dispersion management offered by PSSD enables us to independently control the
linear and nonlinear dispersion. Customized dispersion profiles allow us to
analyze the development of both carrier self-steepening and shocks. The results
exhibit a marked asymmetry between normal and anomalous dispersion, both in the
limits of the shocking regime and in the (near) shocked pulse waveforms.
Combining these insights, we offer some suggestions on how carrier shocking (or
at least extreme self-steepening) might be realised experimentally.
|
f441b339-89ac-4720-ab8c-7b509e477785 | f441b339-89ac-4720-ab8c-7b509e477785 | f441b339-89ac-4720-ab8c-7b509e477785 | human | null | null | none | abstracts | Spin-polarized transport through weakly coupled double quantum dots in
the Coulomb-blockade regime | null | We analyze cotunneling transport through two quantum dots in series weakly
coupled to external ferromagnetic leads. In the Coulomb blockade regime the
electric current flows due to third-order tunneling, while the second-order
single-barrier processes have indirect impact on the current by changing the
occupation probabilities of the double dot system. We predict a zero-bias
maximum in the differential conductance, whose magnitude is conditioned by the
value of the inter-dot Coulomb interaction. This maximum is present in both
magnetic configurations of the system and results from asymmetry in cotunneling
through different virtual states. Furthermore, we show that tunnel
magnetoresistance exhibits a distinctively different behavior depending on
temperature, being rather independent of the value of inter-dot correlation.
Moreover, we find negative TMR in some range of the bias voltage.
|
82a91266-71a9-4bb8-bea7-7e8118216554 | 82a91266-71a9-4bb8-bea7-7e8118216554 | 82a91266-71a9-4bb8-bea7-7e8118216554 | human | null | null | none | abstracts | Double Neutron Stars: Evidence For Two Different Neutron-Star Formation
Mechanisms | null | Six of the eight double neutron stars known in the Galactic disk have low
orbital eccentricities (< 0.27) indicating that their second-born neutron stars
received only very small velocity kicks at birth. This is similar to the case
of the B-emission X-ray binaries, where a sizable fraction of the neutron stars
received hardly any velocity kick at birth (Pfahl et al. 2002). The masses of
the second-born neutron stars in five of the six low-eccentricity double
neutron stars are remarkably low (between 1.18 and 1.30 Msun). It is argued
that these low-mass, low-kick neutron stars were formed by the electron-capture
collapse of the degenerate O-Ne-Mg cores of helium stars less massive than
about 3.5 Msun, whereas the higher-mass, higher kick-velocity neutron stars
were formed by the collapses of the iron cores of higher initial mass. The
absence of low-velocity single young radio pulsars (Hobbs et al. 2005) is
consistent with the model proposed by Podsiadlowski et al. (2004), in which the
electron-capture collapse of degenerate O-Ne-Mg cores can only occur in binary
systems, and not in single stars.
|
e942129b-4424-4a4d-a24e-11292b872e89 | e942129b-4424-4a4d-a24e-11292b872e89 | e942129b-4424-4a4d-a24e-11292b872e89 | human | null | null | none | abstracts | A multi-transition molecular line study of candidate massive young
stellar objects associated with methanol masers | null | We characterize the molecular environment of candidate massive young stellar
objects (MYSOs) signposted by methanol masers. Single pixel observations of 10
transitions of HCO^+, CO and CS isotopomers were carried out, using the IRAM
30m telescope. We studied a sample of 28 targets for which the 6.7GHz maser
emission positions are known with a sub-arcsecond accuracy. The systemic
velocity inferred from the optically thin lines agrees within 3km/s with the
central velocity of the maser emission for most of the sources. About 64% of
the sources show line wings in one or more transitions of CO, HCO^+ and CS
species, indicating the presence of molecular outflows. Comparison of the
widths of line wings and methanol maser emission suggests that the 6.7GHz maser
line traces the environment of MYSO of various kinematic regimes. Therefore
conditions conducive for the methanol maser can exist in the inner parts of
molecular clouds or circumstellar discs as well as in the outer parts
associated with molecular outflows. Calculations of the physical conditions
based on the CO and HCO^+ lines and the CS line intensity ratios refine the
input parameters for maser models.
|
ea268c02-1cc4-4082-a501-12a8053263ea | ea268c02-1cc4-4082-a501-12a8053263ea | ea268c02-1cc4-4082-a501-12a8053263ea | human | null | null | none | abstracts | Patterns of dominant flows in the world trade web | null | The large-scale organization of the world economies is exhibiting
increasingly levels of local heterogeneity and global interdependency.
Understanding the relation between local and global features calls for
analytical tools able to uncover the global emerging organization of the
international trade network. Here we analyze the world network of bilateral
trade imbalances and characterize its overall flux organization, unraveling
local and global high-flux pathways that define the backbone of the trade
system. We develop a general procedure capable to progressively filter out in a
consistent and quantitative way the dominant trade channels. This procedure is
completely general and can be applied to any weighted network to detect the
underlying structure of transport flows. The trade fluxes properties of the
world trade web determines a ranking of trade partnerships that highlights
global interdependencies, providing information not accessible by simple local
analysis. The present work provides new quantitative tools for a dynamical
approach to the propagation of economic crises.
|
424f2586-7144-4e15-903f-b7008083a687 | 424f2586-7144-4e15-903f-b7008083a687 | 424f2586-7144-4e15-903f-b7008083a687 | human | null | null | none | abstracts | Hydrogen 2p--2s transition: signals from the epochs of recombination and
reionization | null | We propose a method to study the epoch of reionization based on the possible
observation of 2p--2s fine structure lines from the neutral hydrogen outside
the cosmological H {\sc ii} regions enveloping QSOs and other ionizing sources
in the reionization era. We show that for parameters typical of luminous
sources observed at $z \simeq 6.3$ the strength of this signal, which is
proportional to the H {\sc i} fraction, has a brightness temperature $\simeq 20
\mu K$ for a fully neutral medium. The fine structure line from this redshift
is observable at $\nu \simeq 1 \rm GHz$ and we discuss prospects for the
detection with several operational and future radio telescopes. We also compute
the characteristics of this signal from the epoch of recombination: the peak
brightness is expected to be $\simeq 100 \mu K$; this signal appears in the
frequency range 5-10 MHz. The signal from the recombination era is nearly
impossible to detect owing to the extreme brightness of the Galactic emission
at these frequencies.
|
629f021e-f787-439b-8ad3-a2b694175e90 | 629f021e-f787-439b-8ad3-a2b694175e90 | 629f021e-f787-439b-8ad3-a2b694175e90 | human | null | null | none | abstracts | CP Violation and Arrows of Time Evolution of a Neutral $K$ or $B$ Meson
from an Incoherent to a Coherent State | null | We study the evolution of a neutral $K$ meson prepared as an incoherent equal
mixture of $K^0$ and $\bar{K^0}$. Denoting the density matrix by $\rho(t) =
{1/2} N(t) [\1 + \vec{\zeta}(t) \cdot \vec{\sigma} ] $, the norm of the state
$N(t)$ is found to decrease monotonically from one to zero, while the magnitude
of the Stokes vector $|\vec{\zeta}(t)|$ increases monotonically from zero to
one. This property qualifies these observables as arrows of time. Requiring
monotonic behaviour of $N(t)$ for arbitrary values of $\gamma_L, \gamma_S$ and
$\Delta m$ yields a bound on the CP-violating overlap $\delta =
\braket{K_L}{K_S}$, which is similar to, but weaker than, the known unitarity
bound. A similar requirement on $|\vec{\zeta}(t)|$ yields a new bound,
$\delta^2 < {1/2} (\frac{\Delta \gamma}{\Delta m}) \sinh (\frac{3\pi}{4}
\frac{\Delta \gamma}{\Delta m})$ which is particularly effective in limiting
the CP-violating overlap in the $B^0$-$\bar{B^0}$ system. We obtain the Stokes
parameter $\zeta_3(t)$ which shows how the average strangeness of the beam
evolves from zero to $\delta$. The evolution of the Stokes vector from
$|\vec{\zeta}| = 0$ to $|\vec{\zeta}| = 1$ has a resemblance to an order
parameter of a system undergoing spontaneous symmetry breaking.
|
6409692c-0f52-46cd-82e7-7655884b09fe | 6409692c-0f52-46cd-82e7-7655884b09fe | 6409692c-0f52-46cd-82e7-7655884b09fe | human | null | null | none | abstracts | Fluctuations of the partial filling factors in competitive RSA from
binary mixtures | null | Competitive random sequential adsorption on a line from a binary mix of
incident particles is studied using both an analytic recursive approach and
Monte Carlo simulations. We find a strong correlation between the small and the
large particle distributions so that while both partial contributions to the
fill factor fluctuate widely, the variance of the total fill factor remains
relatively small. The variances of partial contributions themselves are quite
different between the smaller and the larger particles, with the larger
particle distribution being more correlated. The disparity in fluctuations of
partial fill factors increases with the particle size ratio. The additional
variance in the partial contribution of smaller particle originates from the
fluctuations in the size of gaps between larger particles. We discuss the
implications of our results to semiconductor high-energy gamma detectors where
the detector energy resolution is controlled by correlations in the cascade
energy branching process.
|
71c0577f-e66a-421d-9b11-5be236d6fd48 | 71c0577f-e66a-421d-9b11-5be236d6fd48 | 71c0577f-e66a-421d-9b11-5be236d6fd48 | human | null | null | none | abstracts | Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks.
I. HR 4049 - The Winnowing Flow Observed? | null | High-resolution infrared spectroscopy in the 2.3-4.6 micron region is
reported for the peculiar A supergiant, single-lined spectroscopic binary HR
4049. Lines from the CO fundamental and first overtone, OH fundamental, and
several H2O vibration-rotation transitions have been observed in the
near-infrared spectrum. The spectrum of HR 4049 appears principally in emission
through the 3 and 4.6 micron region and in absorption in the 2 micron region.
The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the
spectral lines observed in the 2.3-4.6 micron spectrum are shown to be
circumbinary in origin. The presence of OH and H2O lines confirm the
oxygen-rich nature of the circumbinary gas which is in contrast to the
previously detected carbon-rich material. The emission and absorption line
profiles show that the circumbinary gas is located in a thin, rotating layer
near the dust disk. The properties of the dust and gas circumbinary disk and
the spectroscopic orbit yield masses for the individual stars, M_AI~0.58 Msolar
and M_MV~0.34 Msolar. Gas in the disk also has an outward flow with a velocity
of $\gtrsim$ 1 km/s. The severe depletion of refractory elements but near-solar
abundances of volatile elements observed in HR 4049 results from abundance
winnowing. The separation of the volatiles from the grains in the disk and the
subsequent accretion by the star are discussed. Contrary to prior reports, the
HR 4049 carbon and oxygen isotopic abundances are typical AGB values:
12C/13C=6^{+9}_{-4} and 16O/17O>200.
|
d6675882-5d84-4bf4-94e6-29c678554055 | d6675882-5d84-4bf4-94e6-29c678554055 | d6675882-5d84-4bf4-94e6-29c678554055 | human | null | null | none | abstracts | On the Entropy Function and the Attractor Mechanism for Spherically
Symmetric Extremal Black Holes | null | In this paper we elaborate on the relation between the entropy formula of
Wald and the "entropy function" method proposed by A. Sen. For spherically
symmetric extremal black holes, it is shown that the expression of extremal
black hole entropy given by A. Sen can be derived from the general entropy
definition of Wald, without help of the treatment of rescaling the AdS_2 part
of near horizon geometry of extremal black holes. In our procedure, we only
require that the surface gravity approaches to zero, and it is easy to
understand the Legendre transformation of f, the integration of Lagrangian
density on the horizon, with respect to the electric charges. Since the Noether
charge form can be defined in an "off-shell" form, we define a corresponding
entropy function, with which one can discuss the attractor mechanism for
extremal black holes with scalar fields.
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9cab79c5-8cee-4e16-802a-1e3476d2c799 | 9cab79c5-8cee-4e16-802a-1e3476d2c799 | 9cab79c5-8cee-4e16-802a-1e3476d2c799 | human | null | null | none | abstracts | Cooling and heating by adiabatic magnetization in the
Ni$_{50}$Mn$_{34}$In$_{16}$ magnetic shape memory alloy | null | We report on measurements of the adiabatic temperature change in the inverse
magnetocaloric Ni$_{50}$Mn$_{34}$In$_{16}$ alloy. It is shown that this alloy
heats up with the application of a magnetic field around the Curie point due to
the conventional magnetocaloric effect. In contrast, the inverse magnetocaloric
effect associated with the martensitic transition results in the unusual
decrease of temperature by adiabatic magnetization. We also provide
magnetization and specific heat data which enable to compare the measured
temperature changes to the values indirectly computed from thermodynamic
relationships. Good agreement is obtained for the conventional effect at the
second-order paramagnetic-ferromagnetic phase transition. However, at the first
order structural transition the measured values at high fields are lower than
the computed ones. Irreversible thermodynamics arguments are given to show that
such a discrepancy is due to the irreversibility of the first-order martensitic
transition.
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e3836b1c-058f-4fff-9a1d-8fafdcb42eab | e3836b1c-058f-4fff-9a1d-8fafdcb42eab | e3836b1c-058f-4fff-9a1d-8fafdcb42eab | human | null | null | none | abstracts | Outflow and Infall in a Sample of Massive Star Forming Regions | null | We present single pointing observations of SiO, HCO$^+$ and H$^{13}$CO$^+$
from the James Clerk Maxwell Telescope towards 23 massive star forming regions
previously known to contain molecular outflows and ultracompact HII regions. We
detected SiO towards 14 sources and suggest that the non-detections in the
other nine sources could be due to those outflows being older and without
ongoing shocks to replenish the SiO. We serendipitously detected SO$_2$ towards
17 sources in the same tuning as HCO$^+$. We detected HCO$^+$ towards all
sources, and suggest that it is tracing infall in nine cases. For seven infall
candidates, we estimate mass infall rates between 1$\times10^{-2}$ and
2$\times10^{-5}$ M$_{\odot}$ yr$^{-1}$. Seven sources show both SiO detections
(young outflows) and HCO$^+$ infall signatures. We also find that the abundance
of H$^{13}$CO$^+$ tends to increase along with the abundance of SiO in sources
for which we could determine abundances. We discuss these results with respect
to current theories of massive star formation via accretion. From this survey,
we suggest that perhaps both models of ionized accretion and halted accretion
may be important in describing the evolution of a massive protostar (or
protostars) beyond the formation of an HII region.
|
1c8b00af-a5b7-45d5-b41d-4fb541bb6ad9 | 1c8b00af-a5b7-45d5-b41d-4fb541bb6ad9 | 1c8b00af-a5b7-45d5-b41d-4fb541bb6ad9 | human | null | null | none | abstracts | A Rational Approach to Resonance Saturation in large-Nc QCD | null | We point out that resonance saturation in QCD can be understood in the
large-Nc limit from the mathematical theory of Pade Approximants to meromorphic
functions. These approximants are rational functions which encompass any
saturation with a finite number of resonances as a particular example,
explaining several results which have appeared in the literature. We review the
main properties of Pade Approximants with the help of a toy model for the
<VV-AA> two-point correlator, paying particular attention to the relationship
among the Chiral Expansion, the Operator Product Expansion and the resonance
spectrum. In passing, we also comment on an old proposal made by Migdal in 1977
which has recently attracted much attention in the context of AdS/QCD models.
Finally, we apply the simplest Pade Approximant to the <VV-AA> correlator in
the real case of QCD. The general conclusion is that a rational approximant may
reliably describe a Green's function in the Euclidean, but the same is not true
in the Minkowski regime due to the appearance of unphysical poles and/or
residues.
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e0732827-b2b6-428b-b8a9-512109d424ac | e0732827-b2b6-428b-b8a9-512109d424ac | e0732827-b2b6-428b-b8a9-512109d424ac | human | null | null | none | abstracts | Gemini Mid-IR Polarimetry of NGC1068: Polarized Structures Around the
Nucleus | null | We present diffraction limited, 10um imaging polarimetry data for the central
regions of the archetypal Seyfert AGN, NGC1068. The position angle of
polarization is consistent with three dominant polarizing mechanisms. We
identify three distinct regions of polarization: (a) north of the nucleus,
arising from aligned dust in the NLR, (b) south, east and west of the nucleus,
consistent with dust being channeled toward the central engine and (c) a
central minimum of polarization consistent with a compact (<22pc) torus. These
observations provide continuity between the geometrically and optically thick
torus and the host galaxy's nuclear environments. These images represent the
first published mid-IR polarimetry from an 8-m class telescope and illustrate
the potential of such observations.
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e530abe2-5e1c-433f-9fa7-798cd2dd81d4 | e530abe2-5e1c-433f-9fa7-798cd2dd81d4 | e530abe2-5e1c-433f-9fa7-798cd2dd81d4 | human | null | null | none | abstracts | Coupling between magnetic ordering and structural instabilities in
perovskite biferroics: A first-principles study | null | We use first-principles density functional theory-based calculations to
investigate structural instabilities in the high symmetry cubic perovskite
structure of rare-earth (R $=$ La, Y, Lu) and Bi-based biferroic chromites,
focusing on $\Gamma$ and $R$ point phonons of states with para-, ferro-, and
antiferromagnetic ordering. We find that (a) the structure with G-type
antiferromagnetic ordering is most stable, (b) the most dominant structural
instabilities in these oxides are the ones associated with rotations of oxygen
octahedra, and (c) structural instabilities involving changes in Cr-O-Cr bond
angle depend sensitively on the changes in magnetic ordering. The dependence of
structural instabilities on magnetic ordering can be understood in terms of how
super-exchange interactions depend on the Cr-O-Cr bond angles and Cr-O bond
lengths. We demonstrate how adequate buckling of Cr-O-Cr chains can favour
ferromagnetism. Born effective charges (BEC) calculated using the Berry phase
expression are found to be anomalously large for the A-cations, indicating
their chemical relevance to ferroelectric distortions.
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684e919e-e822-4fb0-9812-6da0f07fe9dc | 684e919e-e822-4fb0-9812-6da0f07fe9dc | 684e919e-e822-4fb0-9812-6da0f07fe9dc | human | null | null | none | abstracts | LNRF-velocity hump-induced oscillations of a Keplerian disc orbiting
near-extreme Kerr black hole: A possible explanation of high-frequency QPOs
in GRS 1915+105 | null | At least four high-frequency quasiperiodic oscillations (QPOs) at frequencies
41Hz, 67Hz, 113Hz, and 167Hz were reported in a binary system GRS 1915+105
hosting near-extreme Kerr black hole with a dimensionless spin a>0.98. We use
the idea of oscillations induced by the hump of the orbital velocity profile
(related to locally non-rotating frames - LNRF) in discs orbiting near-extreme
Kerr black holes, which are characterized by a "humpy frequency" f_h, that
could excite the radial and vertical epicyclic oscillations with frequencies
f_r, f_v. Due to non-linear resonant phenomena the combinational frequencies
are allowed as well. Assuming mass M=14.8M_sun and spin a=0.9998 for the GRS
1915+105 Kerr black hole, the model predicts frequencies f_h=41Hz, f_r=67Hz,
(f_h+f_r)=108Hz, (f_v-f_r)=170Hz corresponding quite well to the observed ones.
For black-hole parameters being in good agreement with those given
observationally, the forced resonant phenomena in non-linear oscillations,
excited by the "hump-induced" oscillations in a Keplerian disc, can explain
high-frequency QPOs in GRS 1915+105 within the range of observational errors.
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c74ad832-b821-436b-88fc-37aae7cebd32 | c74ad832-b821-436b-88fc-37aae7cebd32 | c74ad832-b821-436b-88fc-37aae7cebd32 | human | null | null | none | abstracts | Evidence for a merger of binary white dwarfs: the case of GD 362 | null | GD 362 is a massive white dwarf with a spectrum suggesting a H-rich
atmosphere which also shows very high abundances of Ca, Mg, Fe and other
metals. However, for pure H-atmospheres the diffusion timescales are so short
that very extreme assumptions have to be made to account for the observed
abundances of metals. The most favored hypothesis is that the metals are
accreted from either a dusty disk or from an asteroid belt. Here we propose
that the envelope of GD 362 is dominated by He, which at these effective
temperatures is almost completely invisible in the spectrum. This assumption
strongly alleviates the problem, since the diffusion timescales are much larger
for He-dominated atmospheres. We also propose that the He-dominated atmosphere
of GD 362 is likely to be the result of the merger of a binary white dwarf.
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c82c9488-c871-4240-a379-0d4ce546dbbb | c82c9488-c871-4240-a379-0d4ce546dbbb | c82c9488-c871-4240-a379-0d4ce546dbbb | human | null | null | none | abstracts | The Measurement Calculus | null | Measurement-based quantum computation has emerged from the physics community
as a new approach to quantum computation where the notion of measurement is the
main driving force of computation. This is in contrast with the more
traditional circuit model which is based on unitary operations. Among
measurement-based quantum computation methods, the recently introduced one-way
quantum computer stands out as fundamental.
We develop a rigorous mathematical model underlying the one-way quantum
computer and present a concrete syntax and operational semantics for programs,
which we call patterns, and an algebra of these patterns derived from a
denotational semantics. More importantly, we present a calculus for reasoning
locally and compositionally about these patterns.
We present a rewrite theory and prove a general standardization theorem which
allows all patterns to be put in a semantically equivalent standard form.
Standardization has far-reaching consequences: a new physical architecture
based on performing all the entanglement in the beginning, parallelization by
exposing the dependency structure of measurements and expressiveness theorems.
Furthermore we formalize several other measurement-based models:
Teleportation, Phase and Pauli models and present compositional embeddings of
them into and from the one-way model. This allows us to transfer all the theory
we develop for the one-way model to these models. This shows that the framework
we have developed has a general impact on measurement-based computation and is
not just particular to the one-way quantum computer.
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f4c39911-2abe-4650-9cf7-ff79e31caca6 | f4c39911-2abe-4650-9cf7-ff79e31caca6 | f4c39911-2abe-4650-9cf7-ff79e31caca6 | human | null | null | none | abstracts | Text Line Segmentation of Historical Documents: a Survey | null | There is a huge amount of historical documents in libraries and in various
National Archives that have not been exploited electronically. Although
automatic reading of complete pages remains, in most cases, a long-term
objective, tasks such as word spotting, text/image alignment, authentication
and extraction of specific fields are in use today. For all these tasks, a
major step is document segmentation into text lines. Because of the low quality
and the complexity of these documents (background noise, artifacts due to
aging, interfering lines),automatic text line segmentation remains an open
research field. The objective of this paper is to present a survey of existing
methods, developed during the last decade, and dedicated to documents of
historical interest.
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d8f73788-53c1-4046-8ae1-e2c34f07d9e3 | d8f73788-53c1-4046-8ae1-e2c34f07d9e3 | d8f73788-53c1-4046-8ae1-e2c34f07d9e3 | human | null | null | none | abstracts | On the interpretation of muon-spin-rotation experiments in the mixed
state of type-II superconductors | null | We argue that claims about magnetic field dependence of the magnetic field
penetration depth lambda, which were made on the basis of moun-spin-rotation
studies of some superconductors, originate from insufficient accuracy of
theoretical models employed for the data analysis. We also reanalyze some of
already published experimental data and demonstrate that numerical calculations
of Brandt [E.H. Brandt, Phys. Rev. B 68, 54506 (2003)] may serve as a reliable
and powerful tool for the analysis of the data collected in experiments with
conventional superconductors. Furthermore, one can use this approach in order
to distinguish between conventional and unconventional superconductors. It is
unfortunate that these calculations have practically never been employed for
such analyses.
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