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422445a2-f408-40a5-956e-3b5188039b01 | 422445a2-f408-40a5-956e-3b5188039b01 | 422445a2-f408-40a5-956e-3b5188039b01 | human | null | null | none | abstracts | Calculation of prompt diphoton production cross sections at Tevatron and
LHC energies | null | A fully differential calculation in perturbative quantum chromodynamics is
presented for the production of massive photon pairs at hadron colliders. All
next-to-leading order perturbative contributions from quark-antiquark,
gluon-(anti)quark, and gluon-gluon subprocesses are included, as well as
all-orders resummation of initial-state gluon radiation valid at
next-to-next-to-leading logarithmic accuracy. The region of phase space is
specified in which the calculation is most reliable. Good agreement is
demonstrated with data from the Fermilab Tevatron, and predictions are made for
more detailed tests with CDF and DO data. Predictions are shown for
distributions of diphoton pairs produced at the energy of the Large Hadron
Collider (LHC). Distributions of the diphoton pairs from the decay of a Higgs
boson are contrasted with those produced from QCD processes at the LHC, showing
that enhanced sensitivity to the signal can be obtained with judicious
selection of events.
|
b06a8304-c36e-427c-8ace-0addb2a85b55 | b06a8304-c36e-427c-8ace-0addb2a85b55 | b06a8304-c36e-427c-8ace-0addb2a85b55 | human | null | null | none | abstracts | Sparsity-certifying Graph Decompositions | null | We describe a new algorithm, the $(k,\ell)$-pebble game with colors, and use
it obtain a characterization of the family of $(k,\ell)$-sparse graphs and
algorithmic solutions to a family of problems concerning tree decompositions of
graphs. Special instances of sparse graphs appear in rigidity theory and have
received increased attention in recent years. In particular, our colored
pebbles generalize and strengthen the previous results of Lee and Streinu and
give a new proof of the Tutte-Nash-Williams characterization of arboricity. We
also present a new decomposition that certifies sparsity based on the
$(k,\ell)$-pebble game with colors. Our work also exposes connections between
pebble game algorithms and previous sparse graph algorithms by Gabow, Gabow and
Westermann and Hendrickson.
|
e5b5a05e-4410-4e54-9745-58f14edfa030 | e5b5a05e-4410-4e54-9745-58f14edfa030 | e5b5a05e-4410-4e54-9745-58f14edfa030 | human | null | null | none | abstracts | The evolution of the Earth-Moon system based on the dark matter field
fluid model | null | The evolution of Earth-Moon system is described by the dark matter field
fluid model proposed in the Meeting of Division of Particle and Field 2004,
American Physical Society. The current behavior of the Earth-Moon system agrees
with this model very well and the general pattern of the evolution of the
Moon-Earth system described by this model agrees with geological and fossil
evidence. The closest distance of the Moon to Earth was about 259000 km at 4.5
billion years ago, which is far beyond the Roche's limit. The result suggests
that the tidal friction may not be the primary cause for the evolution of the
Earth-Moon system. The average dark matter field fluid constant derived from
Earth-Moon system data is 4.39 x 10^(-22) s^(-1)m^(-1). This model predicts
that the Mars's rotation is also slowing with the angular acceleration rate
about -4.38 x 10^(-22) rad s^(-2).
|
0ed2a1cb-2035-4fc7-8ca6-0d95880e4b54 | 0ed2a1cb-2035-4fc7-8ca6-0d95880e4b54 | 0ed2a1cb-2035-4fc7-8ca6-0d95880e4b54 | human | null | null | none | abstracts | Bosonic characters of atomic Cooper pairs across resonance | null | We study the two-particle wave function of paired atoms in a Fermi gas with
tunable interaction strengths controlled by Feshbach resonance. The Cooper pair
wave function is examined for its bosonic characters, which is quantified by
the correction of Bose enhancement factor associated with the creation and
annihilation composite particle operators. An example is given for a
three-dimensional uniform gas. Two definitions of Cooper pair wave function are
examined. One of which is chosen to reflect the off-diagonal long range order
(ODLRO). Another one corresponds to a pair projection of a BCS state. On the
side with negative scattering length, we found that paired atoms described by
ODLRO are more bosonic than the pair projected definition. It is also found
that at $(k_F a)^{-1} \ge 1$, both definitions give similar results, where more
than 90% of the atoms occupy the corresponding molecular condensates.
|
900b4d48-57d7-4d1e-b9c8-3408f6862441 | 900b4d48-57d7-4d1e-b9c8-3408f6862441 | 900b4d48-57d7-4d1e-b9c8-3408f6862441 | human | null | null | none | abstracts | Polymer Quantum Mechanics and its Continuum Limit | null | A rather non-standard quantum representation of the canonical commutation
relations of quantum mechanics systems, known as the polymer representation has
gained some attention in recent years, due to its possible relation with Planck
scale physics. In particular, this approach has been followed in a symmetric
sector of loop quantum gravity known as loop quantum cosmology. Here we explore
different aspects of the relation between the ordinary Schroedinger theory and
the polymer description. The paper has two parts. In the first one, we derive
the polymer quantum mechanics starting from the ordinary Schroedinger theory
and show that the polymer description arises as an appropriate limit. In the
second part we consider the continuum limit of this theory, namely, the reverse
process in which one starts from the discrete theory and tries to recover back
the ordinary Schroedinger quantum mechanics. We consider several examples of
interest, including the harmonic oscillator, the free particle and a simple
cosmological model.
|
4ef380ba-c317-41ac-a73a-4ff2c4a4b3c9 | 4ef380ba-c317-41ac-a73a-4ff2c4a4b3c9 | 4ef380ba-c317-41ac-a73a-4ff2c4a4b3c9 | human | null | null | none | abstracts | Numerical solution of shock and ramp compression for general material
properties | null | A general formulation was developed to represent material models for
applications in dynamic loading. Numerical methods were devised to calculate
response to shock and ramp compression, and ramp decompression, generalizing
previous solutions for scalar equations of state. The numerical methods were
found to be flexible and robust, and matched analytic results to a high
accuracy. The basic ramp and shock solution methods were coupled to solve for
composite deformation paths, such as shock-induced impacts, and shock
interactions with a planar interface between different materials. These
calculations capture much of the physics of typical material dynamics
experiments, without requiring spatially-resolving simulations. Example
calculations were made of loading histories in metals, illustrating the effects
of plastic work on the temperatures induced in quasi-isentropic and
shock-release experiments, and the effect of a phase transition.
|
a67c9ee2-8887-47b3-999d-9015c577cc11 | a67c9ee2-8887-47b3-999d-9015c577cc11 | a67c9ee2-8887-47b3-999d-9015c577cc11 | human | null | null | none | abstracts | Partial cubes: structures, characterizations, and constructions | null | Partial cubes are isometric subgraphs of hypercubes. Structures on a graph
defined by means of semicubes, and Djokovi\'{c}'s and Winkler's relations play
an important role in the theory of partial cubes. These structures are employed
in the paper to characterize bipartite graphs and partial cubes of arbitrary
dimension. New characterizations are established and new proofs of some known
results are given.
The operations of Cartesian product and pasting, and expansion and
contraction processes are utilized in the paper to construct new partial cubes
from old ones. In particular, the isometric and lattice dimensions of finite
partial cubes obtained by means of these operations are calculated.
|
b61d4f55-4737-4ffc-90c8-abeed6d5323e | b61d4f55-4737-4ffc-90c8-abeed6d5323e | b61d4f55-4737-4ffc-90c8-abeed6d5323e | human | null | null | none | abstracts | Lifetime of doubly charmed baryons | null | In this work, we evaluate the lifetimes of the doubly charmed baryons
$\Xi_{cc}^{+}$, $\Xi_{cc}^{++}$ and $\Omega_{cc}^{+}$. We carefully calculate
the non-spectator contributions at the quark level where the Cabibbo-suppressed
diagrams are also included. The hadronic matrix elements are evaluated in the
simple non-relativistic harmonic oscillator model. Our numerical results are
generally consistent with that obtained by other authors who used the diquark
model. However, all the theoretical predictions on the lifetimes are one order
larger than the upper limit set by the recent SELEX measurement. This
discrepancy would be clarified by the future experiment, if more accurate
experiment still confirms the value of the SELEX collaboration, there must be
some unknown mechanism to be explored.
|
155af688-1516-45dc-acf1-0c2da584f37c | 155af688-1516-45dc-acf1-0c2da584f37c | 155af688-1516-45dc-acf1-0c2da584f37c | human | null | null | none | abstracts | Spectroscopic Observations of the Intermediate Polar EX Hydrae in
Quiescence | null | Results from spectroscopic observations of the Intermediate Polar (IP) EX Hya
in quiescence during 1991 and 2001 are presented. Spin-modulated radial
velocities consistent with an outer disc origin were detected for the first
time in an IP. The spin pulsation was modulated with velocities near ~500-600
km/s. These velocities are consistent with those of material circulating at the
outer edge of the accretion disc, suggesting corotation of the accretion
curtain with material near the Roche lobe radius. Furthermore, spin Doppler
tomograms have revealed evidence of the accretion curtain emission extending
from velocities of ~500 km/s to ~1000 km/s. These findings have confirmed the
theoretical model predictions of King & Wynn (1999), Belle et al. (2002) and
Norton et al. (2004) for EX Hya, which predict large accretion curtains that
extend to a distance close to the Roche lobe radius in this system. Evidence
for overflow stream of material falling onto the magnetosphere was observed,
confirming the result of Belle et al. (2005) that disc overflow in EX Hya is
present during quiescence as well as outburst. It appears that the hbeta and
hgamma spin radial velocities originated from the rotation of the funnel at the
outer disc edge, while those of halpha were produced due to the flow of
material along the field lines far from the white dwarf (narrow component) and
close to the white dwarf (broad-base component), in agreement with the
accretion curtain model.
|
a68d4050-892a-473e-8332-efe277a36b29 | a68d4050-892a-473e-8332-efe277a36b29 | a68d4050-892a-473e-8332-efe277a36b29 | human | null | null | none | abstracts | Measurement of the Hadronic Form Factor in D0 --> K- e+ nue Decays | null | The shape of the hadronic form factor f+(q2) in the decay D0 --> K- e+ nue
has been measured in a model independent analysis and compared with theoretical
calculations. We use 75 fb(-1) of data recorded by the BABAR detector at the
PEPII electron-positron collider. The corresponding decay branching fraction,
relative to the decay D0 --> K- pi+, has also been measured to be RD = BR(D0
--> K- e+ nue)/BR(D0 --> K- pi+) = 0.927 +/- 0.007 +/- 0.012. From these
results, and using the present world average value for BR(D0 --> K- pi+), the
normalization of the form factor at q2=0 is determined to be f+(0)=0.727 +/-
0.007 +/- 0.005 +/- 0.007 where the uncertainties are statistical, systematic,
and from external inputs, respectively.
|
5a2e5e1f-a4b5-418d-8ece-5671b48563e4 | 5a2e5e1f-a4b5-418d-8ece-5671b48563e4 | 5a2e5e1f-a4b5-418d-8ece-5671b48563e4 | human | null | null | none | abstracts | Stochastic Lie group integrators | null | We present Lie group integrators for nonlinear stochastic differential
equations with non-commutative vector fields whose solution evolves on a smooth
finite dimensional manifold. Given a Lie group action that generates transport
along the manifold, we pull back the stochastic flow on the manifold to the Lie
group via the action, and subsequently pull back the flow to the corresponding
Lie algebra via the exponential map. We construct an approximation to the
stochastic flow in the Lie algebra via closed operations and then push back to
the Lie group and then to the manifold, thus ensuring our approximation lies in
the manifold. We call such schemes stochastic Munthe-Kaas methods after their
deterministic counterparts. We also present stochastic Lie group integration
schemes based on Castell--Gaines methods. These involve using an underlying
ordinary differential integrator to approximate the flow generated by a
truncated stochastic exponential Lie series. They become stochastic Lie group
integrator schemes if we use Munthe-Kaas methods as the underlying ordinary
differential integrator. Further, we show that some Castell--Gaines methods are
uniformly more accurate than the corresponding stochastic Taylor schemes.
Lastly we demonstrate our methods by simulating the dynamics of a free rigid
body such as a satellite and an autonomous underwater vehicle both perturbed by
two independent multiplicative stochastic noise processes.
|
a383f716-79f7-4c56-89c4-6faf0fa5214b | a383f716-79f7-4c56-89c4-6faf0fa5214b | a383f716-79f7-4c56-89c4-6faf0fa5214b | human | null | null | none | abstracts | ALMA as the ideal probe of the solar chromosphere | null | The very nature of the solar chromosphere, its structuring and dynamics,
remains far from being properly understood, in spite of intensive research.
Here we point out the potential of chromospheric observations at millimeter
wavelengths to resolve this long-standing problem. Computations carried out
with a sophisticated dynamic model of the solar chromosphere due to Carlsson
and Stein demonstrate that millimeter emission is extremely sensitive to
dynamic processes in the chromosphere and the appropriate wavelengths to look
for dynamic signatures are in the range 0.8-5.0 mm. The model also suggests
that high resolution observations at mm wavelengths, as will be provided by
ALMA, will have the unique property of reacting to both the hot and the cool
gas, and thus will have the potential of distinguishing between rival models of
the solar atmosphere. Thus, initial results obtained from the observations of
the quiet Sun at 3.5 mm with the BIMA array (resolution of 12 arcsec) reveal
significant oscillations with amplitudes of 50-150 K and frequencies of 1.5-8
mHz with a tendency toward short-period oscillations in internetwork and longer
periods in network regions. However higher spatial resolution, such as that
provided by ALMA, is required for a clean separation between the features
within the solar atmosphere and for an adequate comparison with the output of
the comprehensive dynamic simulations.
|
c531ca3e-a38f-4ca3-9420-59243afeff02 | c531ca3e-a38f-4ca3-9420-59243afeff02 | c531ca3e-a38f-4ca3-9420-59243afeff02 | human | null | null | none | abstracts | Formation of quasi-solitons in transverse confined ferromagnetic film
media | null | The formation of quasi-2D spin-wave waveforms in longitudinally magnetized
stripes of ferrimagnetic film was observed by using time- and space-resolved
Brillouin light scattering technique. In the linear regime it was found that
the confinement decreases the amplitude of dynamic magnetization near the
lateral stripe edges. Thus, the so-called effective dipolar pinning of dynamic
magnetization takes place at the edges.
In the nonlinear regime a new stable spin wave packet propagating along a
waveguide structure, for which both transversal instability and interaction
with the side walls of the waveguide are important was observed. The
experiments and a numerical simulation of the pulse evolution show that the
shape of the formed waveforms and their behavior are strongly influenced by the
confinement.
|
1363888e-dac0-4851-98e7-c84b72b18f26 | 1363888e-dac0-4851-98e7-c84b72b18f26 | 1363888e-dac0-4851-98e7-c84b72b18f26 | human | null | null | none | abstracts | Tuning correlation effects with electron-phonon interactions | null | We investigate the effect of tuning the phonon energy on the correlation
effects in models of electron-phonon interactions using DMFT. In the regime
where itinerant electrons, instantaneous electron-phonon driven correlations
and static distortions compete on similar energy scales, we find several
interesting results including (1) A crossover from band to Mott behavior in the
spectral function, leading to hybrid band/Mott features in the spectral
function for phonon frequencies slightly larger than the band width. (2) Since
the optical conductivity depends sensitively on the form of the spectral
function, we show that such a regime should be observable through the low
frequency form of the optical conductivity. (3) The resistivity has a double
kondo peak arrangement
|
238265c8-6594-4f87-a769-10c8d20abb7d | 238265c8-6594-4f87-a769-10c8d20abb7d | 238265c8-6594-4f87-a769-10c8d20abb7d | human | null | null | none | abstracts | Crystal channeling of LHC forward protons with preserved distribution in
phase space | null | We show that crystal can trap a broad (x, x', y, y', E) distribution of
particles and channel it preserved with a high precision. This sampled-and-hold
distribution can be steered by a bent crystal for analysis downstream. In
simulations for the 7 TeV Large Hadron Collider, a crystal adapted to the
accelerator lattice traps 90% of diffractively scattered protons emerging from
the interaction point with a divergence 100 times the critical angle. We set
the criterion for crystal adaptation improving efficiency ~100-fold. Proton
angles are preserved in crystal transmission with accuracy down to 0.1
microrad. This makes feasible a crystal application for measuring very forward
protons at the LHC.
|
fb6613ca-b272-4f6a-9675-12438ac3cfae | fb6613ca-b272-4f6a-9675-12438ac3cfae | fb6613ca-b272-4f6a-9675-12438ac3cfae | human | null | null | none | abstracts | Probing non-standard neutrino interactions with supernova neutrinos | null | We analyze the possibility of probing non-standard neutrino interactions
(NSI, for short) through the detection of neutrinos produced in a future
galactic supernova (SN).We consider the effect of NSI on the neutrino
propagation through the SN envelope within a three-neutrino framework, paying
special attention to the inclusion of NSI-induced resonant conversions, which
may take place in the most deleptonised inner layers. We study the possibility
of detecting NSI effects in a Megaton water Cherenkov detector, either through
modulation effects in the $\bar\nu_e$ spectrum due to (i) the passage of shock
waves through the SN envelope, (ii) the time dependence of the electron
fraction and (iii) the Earth matter effects; or, finally, through the possible
detectability of the neutronization $\nu_e$ burst. We find that the $\bar\nu_e$
spectrum can exhibit dramatic features due to the internal NSI-induced resonant
conversion. This occurs for non-universal NSI strengths of a few %, and for
very small flavor-changing NSI above a few$\times 10^{-5}$.
|
2642b285-1879-4706-853d-956dc2730cfc | 2642b285-1879-4706-853d-956dc2730cfc | 2642b285-1879-4706-853d-956dc2730cfc | human | null | null | none | abstracts | Convergence of the discrete dipole approximation. I. Theoretical
analysis | null | We performed a rigorous theoretical convergence analysis of the discrete
dipole approximation (DDA). We prove that errors in any measured quantity are
bounded by a sum of a linear and quadratic term in the size of a dipole d, when
the latter is in the range of DDA applicability. Moreover, the linear term is
significantly smaller for cubically than for non-cubically shaped scatterers.
Therefore, for small d errors for cubically shaped particles are much smaller
than for non-cubically shaped. The relative importance of the linear term
decreases with increasing size, hence convergence of DDA for large enough
scatterers is quadratic in the common range of d. Extensive numerical
simulations were carried out for a wide range of d. Finally we discuss a number
of new developments in DDA and their consequences for convergence.
|
d1918e2e-5034-419e-8fd4-9d51887abb1d | d1918e2e-5034-419e-8fd4-9d51887abb1d | d1918e2e-5034-419e-8fd4-9d51887abb1d | human | null | null | none | abstracts | A remark on the number of steady states in a multiple futile cycle | null | The multisite phosphorylation-dephosphorylation cycle is a motif repeatedly
used in cell signaling. This motif itself can generate a variety of dynamic
behaviors like bistability and ultrasensitivity without direct positive
feedbacks. In this paper, we study the number of positive steady states of a
general multisite phosphorylation-dephosphorylation cycle, and how the number
of positive steady states varies by changing the biological parameters. We show
analytically that (1) for some parameter ranges, there are at least n+1 (if n
is even) or n (if n is odd) steady states; (2) there never are more than 2n-1
steady states (in particular, this implies that for n=2, including single
levels of MAPK cascades, there are at most three steady states); (3) for
parameters near the standard Michaelis-Menten quasi-steady state conditions,
there are at most n+1 steady states; and (4) for parameters far from the
standard Michaelis-Menten quasi-steady state conditions, there is at most one
steady state.
|
eae08989-2da4-4116-b438-8570c70ede0f | eae08989-2da4-4116-b438-8570c70ede0f | eae08989-2da4-4116-b438-8570c70ede0f | human | null | null | none | abstracts | The discrete dipole approximation for simulation of light scattering by
particles much larger than the wavelength | null | In this manuscript we investigate the capabilities of the Discrete Dipole
Approximation (DDA) to simulate scattering from particles that are much larger
than the wavelength of the incident light, and describe an optimized publicly
available DDA computer program that processes the large number of dipoles
required for such simulations. Numerical simulations of light scattering by
spheres with size parameters x up to 160 and 40 for refractive index m=1.05 and
2 respectively are presented and compared with exact results of the Mie theory.
Errors of both integral and angle-resolved scattering quantities generally
increase with m and show no systematic dependence on x. Computational times
increase steeply with both x and m, reaching values of more than 2 weeks on a
cluster of 64 processors. The main distinctive feature of the computer program
is the ability to parallelize a single DDA simulation over a cluster of
computers, which allows it to simulate light scattering by very large
particles, like the ones that are considered in this manuscript. Current
limitations and possible ways for improvement are discussed.
|
f6ac770a-910d-4384-ac2a-fd1c45fa6e87 | f6ac770a-910d-4384-ac2a-fd1c45fa6e87 | f6ac770a-910d-4384-ac2a-fd1c45fa6e87 | human | null | null | none | abstracts | Scalar radius of the pion and zeros in the form factor | null | The quadratic pion scalar radius, \la r^2\ra^\pi_s, plays an important role
for present precise determinations of \pi\pi scattering. Recently, Yndur\'ain,
using an Omn\`es representation of the null isospin(I) non-strange pion scalar
form factor, obtains \la r^2\ra^\pi_s=0.75\pm 0.07 fm^2. This value is larger
than the one calculated by solving the corresponding Muskhelishvili-Omn\`es
equations, \la r^2\ra^\pi_s=0.61\pm 0.04 fm^2. A large discrepancy between both
values, given the precision, then results. We reanalyze Yndur\'ain's method and
show that by imposing continuity of the resulting pion scalar form factor under
tiny changes in the input \pi\pi phase shifts, a zero in the form factor for
some S-wave I=0 T-matrices is then required. Once this is accounted for, the
resulting value is \la r^2\ra_s^\pi=0.65\pm 0.05 fm^2. The main source of error
in our determination is present experimental uncertainties in low energy S-wave
I=0 \pi\pi phase shifts. Another important contribution to our error is the not
yet settled asymptotic behaviour of the phase of the scalar form factor from
QCD.
|
f1547b8e-916b-49f0-a882-8c9c1246399c | f1547b8e-916b-49f0-a882-8c9c1246399c | f1547b8e-916b-49f0-a882-8c9c1246399c | human | null | null | none | abstracts | Quantum Group of Isometries in Classical and Noncommutative Geometry | null | We formulate a quantum generalization of the notion of the group of
Riemannian isometries for a compact Riemannian manifold, by introducing a
natural notion of smooth and isometric action by a compact quantum group on a
classical or noncommutative manifold described by spectral triples, and then
proving the existence of a universal object (called the quantum isometry group)
in the category of compact quantum groups acting smoothly and isometrically on
a given (possibly noncommutative) manifold satisfying certain regularity
assumptions. In fact, we identify the quantum isometry group with the universal
object in a bigger category, namely the category of `quantum families of smooth
isometries', defined along the line of Woronowicz and Soltan. We also construct
a spectral triple on the Hilbert space of forms on a noncommutative manifold
which is equivariant with respect to a natural unitary representation of the
quantum isometry group. We give explicit description of quantum isometry groups
of commutative and noncommutative tori, and in this context, obtain the quantum
double torus defined in \cite{hajac} as the universal quantum group of
holomorphic isometries of the noncommutative torus.
|
3a681765-f380-4ba1-8a3a-8f6115e26f7c | 3a681765-f380-4ba1-8a3a-8f6115e26f7c | 3a681765-f380-4ba1-8a3a-8f6115e26f7c | human | null | null | none | abstracts | Nonequilibrium entropy limiters in lattice Boltzmann methods | null | We construct a system of nonequilibrium entropy limiters for the lattice
Boltzmann methods (LBM). These limiters erase spurious oscillations without
blurring of shocks, and do not affect smooth solutions. In general, they do the
same work for LBM as flux limiters do for finite differences, finite volumes
and finite elements methods, but for LBM the main idea behind the construction
of nonequilibrium entropy limiter schemes is to transform a field of a scalar
quantity - nonequilibrium entropy. There are two families of limiters: (i)
based on restriction of nonequilibrium entropy (entropy "trimming") and (ii)
based on filtering of nonequilibrium entropy (entropy filtering). The physical
properties of LBM provide some additional benefits: the control of entropy
production and accurate estimate of introduced artificial dissipation are
possible. The constructed limiters are tested on classical numerical examples:
1D athermal shock tubes with an initial density ratio 1:2 and the 2D lid-driven
cavity for Reynolds numbers Re between 2000 and 7500 on a coarse 100*100 grid.
All limiter constructions are applicable for both entropic and non-entropic
quasiequilibria.
|
5a6a5750-9f67-4d02-947b-867ae538899b | 5a6a5750-9f67-4d02-947b-867ae538899b | 5a6a5750-9f67-4d02-947b-867ae538899b | human | null | null | none | abstracts | Evolution of solitary waves and undular bores in shallow-water flows
over a gradual slope with bottom friction | null | This paper considers the propagation of shallow-water solitary and nonlinear
periodic waves over a gradual slope with bottom friction in the framework of a
variable-coefficient Korteweg-de Vries equation. We use the Whitham averaging
method, using a recent development of this theory for perturbed integrable
equations. This general approach enables us not only to improve known results
on the adiabatic evolution of isolated solitary waves and periodic wave trains
in the presence of variable topography and bottom friction, modeled by the
Chezy law, but also importantly, to study the effects of these factors on the
propagation of undular bores, which are essentially unsteady in the system
under consideration. In particular, it is shown that the combined action of
variable topography and bottom friction generally imposes certain global
restrictions on the undular bore propagation so that the evolution of the
leading solitary wave can be substantially different from that of an isolated
solitary wave with the same initial amplitude. This non-local effect is due to
nonlinear wave interactions within the undular bore and can lead to an
additional solitary wave amplitude growth, which cannot be predicted in the
framework of the traditional adiabatic approach to the propagation of solitary
waves in slowly varying media.
|
233c25a7-5423-42cb-a2ab-08f98ae4661d | 233c25a7-5423-42cb-a2ab-08f98ae4661d | 233c25a7-5423-42cb-a2ab-08f98ae4661d | human | null | null | none | abstracts | Intelligent location of simultaneously active acoustic emission sources:
Part I | null | The intelligent acoustic emission locator is described in Part I, while Part
II discusses blind source separation, time delay estimation and location of two
simultaneously active continuous acoustic emission sources.
The location of acoustic emission on complicated aircraft frame structures is
a difficult problem of non-destructive testing. This article describes an
intelligent acoustic emission source locator. The intelligent locator comprises
a sensor antenna and a general regression neural network, which solves the
location problem based on learning from examples. Locator performance was
tested on different test specimens. Tests have shown that the accuracy of
location depends on sound velocity and attenuation in the specimen, the
dimensions of the tested area, and the properties of stored data. The location
accuracy achieved by the intelligent locator is comparable to that obtained by
the conventional triangulation method, while the applicability of the
intelligent locator is more general since analysis of sonic ray paths is
avoided. This is a promising method for non-destructive testing of aircraft
frame structures by the acoustic emission method.
|
6e5cbbea-b813-4fff-85b5-4e313dd9f598 | 6e5cbbea-b813-4fff-85b5-4e313dd9f598 | 6e5cbbea-b813-4fff-85b5-4e313dd9f598 | human | null | null | none | abstracts | Inference on white dwarf binary systems using the first round Mock LISA
Data Challenges data sets | null | We report on the analysis of selected single source data sets from the first
round of the Mock LISA Data Challenges (MLDC) for white dwarf binaries. We
implemented an end-to-end pipeline consisting of a grid-based coherent
pre-processing unit for signal detection, and an automatic Markov Chain Monte
Carlo post-processing unit for signal evaluation. We demonstrate that signal
detection with our coherent approach is secure and accurate, and is increased
in accuracy and supplemented with additional information on the signal
parameters by our Markov Chain Monte Carlo approach. We also demonstrate that
the Markov Chain Monte Carlo routine is additionally able to determine
accurately the noise level in the frequency window of interest.
|
0ca28ddc-d048-4208-a6cb-63d05699abc9 | 0ca28ddc-d048-4208-a6cb-63d05699abc9 | 0ca28ddc-d048-4208-a6cb-63d05699abc9 | human | null | null | none | abstracts | Intelligent location of simultaneously active acoustic emission sources:
Part II | null | Part I describes an intelligent acoustic emission locator, while Part II
discusses blind source separation, time delay estimation and location of two
continuous acoustic emission sources.
Acoustic emission (AE) analysis is used for characterization and location of
developing defects in materials. AE sources often generate a mixture of various
statistically independent signals. A difficult problem of AE analysis is
separation and characterization of signal components when the signals from
various sources and the mode of mixing are unknown. Recently, blind source
separation (BSS) by independent component analysis (ICA) has been used to solve
these problems. The purpose of this paper is to demonstrate the applicability
of ICA to locate two independent simultaneously active acoustic emission
sources on an aluminum band specimen. The method is promising for
non-destructive testing of aircraft frame structures by acoustic emission
analysis.
|
355df5df-b616-43d9-a708-570f4d6305e9 | 355df5df-b616-43d9-a708-570f4d6305e9 | 355df5df-b616-43d9-a708-570f4d6305e9 | human | null | null | none | abstracts | A Global Approach to the Theory of Special Finsler Manifolds | null | The aim of the present paper is to provide a global presentation of the
theory of special Finsler manifolds. We introduce and investigate globally (or
intrinsically, free from local coordinates) many of the most important and most
commonly used special Finsler manifolds: locally Minkowskian, Berwald,
Landesberg, general Landesberg, $P$-reducible, $C$-reducible,
semi-$C$-reducible, quasi-$C$-reducible, $P^{*}$-Finsler, $C^{h}$-recurrent,
$C^{v}$-recurrent, $C^{0}$-recurrent, $S^{v}$-recurrent, $S^{v}$-recurrent of
the second order, $C_{2}$-like, $S_{3}$-like, $S_{4}$-like, $P_{2}$-like,
$R_{3}$-like, $P$-symmetric, $h$-isotropic, of scalar curvature, of constant
curvature, of $p$-scalar curvature, of $s$-$ps$-curvature. The global
definitions of these special Finsler manifolds are introduced. Various
relationships between the different types of the considered special Finsler
manifolds are found. Many local results, known in the literature, are proved
globally and several new results are obtained. As a by-product, interesting
identities and properties concerning the torsion tensor fields and the
curvature tensor fields are deduced. Although our investigation is entirely
global, we provide; for comparison reasons, an appendix presenting a local
counterpart of our global approach and the local definitions of the special
Finsler spaces considered.
|
0d03f97e-6045-47fc-aeab-1f39c2fa8b43 | 0d03f97e-6045-47fc-aeab-1f39c2fa8b43 | 0d03f97e-6045-47fc-aeab-1f39c2fa8b43 | human | null | null | none | abstracts | Potassium intercalation in graphite: A van der Waals density-functional
study | null | Potassium intercalation in graphite is investigated by first-principles
theory. The bonding in the potassium-graphite compound is reasonably well
accounted for by traditional semilocal density functional theory (DFT)
calculations. However, to investigate the intercalate formation energy from
pure potassium atoms and graphite requires use of a description of the graphite
interlayer binding and thus a consistent account of the nonlocal dispersive
interactions. This is included seamlessly with ordinary DFT by a van der Waals
density functional (vdW-DF) approach [Phys. Rev. Lett. 92, 246401 (2004)]. The
use of the vdW-DF is found to stabilize the graphite crystal, with crystal
parameters in fair agreement with experiments. For graphite and
potassium-intercalated graphite structural parameters such as binding
separation, layer binding energy, formation energy, and bulk modulus are
reported. Also the adsorption and sub-surface potassium absorption energies are
reported. The vdW-DF description, compared with the traditional semilocal
approach, is found to weakly soften the elastic response.
|
9224491a-a812-4d1a-b069-a19e573a2aa6 | 9224491a-a812-4d1a-b069-a19e573a2aa6 | 9224491a-a812-4d1a-b069-a19e573a2aa6 | human | null | null | none | abstracts | High-spin to low-spin and orbital polarization transitions in
multiorbital Mott systems | null | We study the interplay of crystal field splitting and Hund coupling in a
two-orbital model which captures the essential physics of systems with two
electrons or holes in the e_g shell. We use single site dynamical mean field
theory with a recently developed impurity solver which is able to access strong
couplings and low temperatures. The fillings of the orbitals and the location
of phase boundaries are computed as a function of Coulomb repulsion, exchange
coupling and crystal field splitting. We find that the Hund coupling can drive
the system into a novel Mott insulating phase with vanishing orbital
susceptibility. Away from half-filling, the crystal field splitting can induce
an orbital selective Mott state.
|
e4f50801-7727-4a65-a35f-fd4aa7f0e69b | e4f50801-7727-4a65-a35f-fd4aa7f0e69b | e4f50801-7727-4a65-a35f-fd4aa7f0e69b | human | null | null | none | abstracts | Intelligent Life in Cosmology | null | I shall present three arguments for the proposition that intelligent life is
very rare in the universe. First, I shall summarize the consensus opinion of
the founders of the Modern Synthesis (Simpson, Dobzhanski, and Mayr) that the
evolution of intelligent life is exceedingly improbable. Second, I shall
develop the Fermi Paradox: if they existed they'd be here. Third, I shall show
that if intelligent life were too common, it would use up all available
resources and die out. But I shall show that the quantum mechanical principle
of unitarity (actually a form of teleology!) requires intelligent life to
survive to the end of time. Finally, I shall argue that, if the universe is
indeed accelerating, then survival to the end of time requires that intelligent
life, though rare, to have evolved several times in the visible universe. I
shall argue that the acceleration is a consequence of the excess of matter over
antimatter in the universe. I shall suggest experiments to test these claims.
|
f46ab681-2468-4c51-aad1-2fff117fff11 | f46ab681-2468-4c51-aad1-2fff117fff11 | f46ab681-2468-4c51-aad1-2fff117fff11 | human | null | null | none | abstracts | The Mass and Radius of the Unseen M-Dwarf Companion in the Single-Lined
Eclipsing Binary HAT-TR-205-013 | null | We derive masses and radii for both components in the single-lined eclipsing
binary HAT-TR-205-013, which consists of a F7V primary and a late M-dwarf
secondary. The system's period is short, $P=2.230736 \pm 0.000010$ days, with
an orbit indistinguishable from circular, $e=0.012 \pm 0.021$. We demonstrate
generally that the surface gravity of the secondary star in a single-lined
binary undergoing total eclipses can be derived from characteristics of the
light curve and spectroscopic orbit. This constrains the secondary to a unique
line in the mass-radius diagram with $M/R^2$ = constant. For HAT-TR-205-013, we
assume the orbit has been tidally circularized, and that the primary's rotation
has been synchronized and aligned with the orbital axis. Our observed line
broadening, $V_{\rm rot} \sin i_{\rm rot} = 28.9 \pm 1.0$ \kms, gives a primary
radius of $R_{\rm A} = 1.28 \pm 0.04$ \rsun. Our light curve analysis leads to
the radius of the secondary, $R_{\rm B} = 0.167 \pm 0.006$ \rsun, and the
semimajor axis of the orbit, $a = 7.54 \pm 0.30 \rsun = 0.0351 \pm 0.0014$ AU.
Our single-lined spectroscopic orbit and the semimajor axis then yield the
individual masses, $M_{\rm B} = 0.124 \pm 0.010$ \msun and $M_{\rm A} = 1.04
\pm 0.13$ \msun. Our result for HAT-TR-205-013 B lies above the theoretical
mass-radius models from the Lyon group, consistent with results from
double-lined eclipsing binaries. The method we describe offers the opportunity
to study the very low end of the stellar mass-radius relation.
|
8d3c8295-a47f-485b-9c6f-5553a4a47b3b | 8d3c8295-a47f-485b-9c6f-5553a4a47b3b | 8d3c8295-a47f-485b-9c6f-5553a4a47b3b | human | null | null | none | abstracts | Intersection Bodies and Generalized Cosine Transforms | null | Intersection bodies represent a remarkable class of geometric objects
associated with sections of star bodies and invoking
Radon transforms, generalized cosine transforms, and the relevant Fourier
analysis. The main focus of this article is interrelation between generalized
cosine transforms of different kinds in the context of their application to
investigation of a certain family of intersection bodies, which we call
$\lam$-intersection bodies. The latter include $k$-intersection bodies (in the
sense of A. Koldobsky) and unit balls of finite-dimensional subspaces of
$L_p$-spaces. In particular, we show that restrictions onto lower dimensional
subspaces of the spherical Radon transforms and the generalized cosine
transforms preserve their integral-geometric structure. We apply this result to
the study of sections of $\lam$-intersection bodies. New characterizations of
this class of bodies are obtained and examples are given. We also review some
known facts and give them new proofs.
|
535d8fdc-bf55-4aeb-b2c9-caa84418083f | 535d8fdc-bf55-4aeb-b2c9-caa84418083f | 535d8fdc-bf55-4aeb-b2c9-caa84418083f | human | null | null | none | abstracts | On-line Viterbi Algorithm and Its Relationship to Random Walks | null | In this paper, we introduce the on-line Viterbi algorithm for decoding hidden
Markov models (HMMs) in much smaller than linear space. Our analysis on
two-state HMMs suggests that the expected maximum memory used to decode
sequence of length $n$ with $m$-state HMM can be as low as $\Theta(m\log n)$,
without a significant slow-down compared to the classical Viterbi algorithm.
Classical Viterbi algorithm requires $O(mn)$ space, which is impractical for
analysis of long DNA sequences (such as complete human genome chromosomes) and
for continuous data streams. We also experimentally demonstrate the performance
of the on-line Viterbi algorithm on a simple HMM for gene finding on both
simulated and real DNA sequences.
|
46e728bb-a402-4a13-9c4b-55a443e69794 | 46e728bb-a402-4a13-9c4b-55a443e69794 | 46e728bb-a402-4a13-9c4b-55a443e69794 | human | null | null | none | abstracts | Experimental efforts in search of 76Ge Neutrinoless Double Beta Decay | null | Neutrinoless double beta decay is one of the most sensitive approaches in
non-accelerator particle physics to take us into a regime of physics beyond the
standard model. This article is a brief review of the experiments in search of
neutrinoless double beta decay from 76Ge. Following a brief introduction of the
process of double beta decay from 76Ge, the results of the very first
experiments IGEX and Heidelberg-Moscow which give indications of the existence
of possible neutrinoless double beta decay mode has been reviewed. Then ongoing
efforts to substantiate the early findings are presented and the Majorana
experiment as a future experimental approach which will allow a very detailed
study of the neutrinoless decay mode is discussed.
|
109883f5-9344-4a74-9405-47a05ac21e1f | 109883f5-9344-4a74-9405-47a05ac21e1f | 109883f5-9344-4a74-9405-47a05ac21e1f | human | null | null | none | abstracts | Nilpotent symmetry invariance in the superfield formulation: the
(non-)Abelian 1-form gauge theories | null | We capture the off-shell as well as the on-shell nilpotent
Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST symmetry invariance of the
Lagrangian densities of the four (3 + 1)-dimensional (4D) (non-)Abelian 1-form
gauge theories within the framework of the superfield formalism. In particular,
we provide the geometrical interpretations for (i) the above nilpotent symmetry
invariance, and (ii) the above Lagrangian densities, in the language of the
specific quantities defined in the domain of the above superfield formalism.
Some of the subtle points, connected with the 4D (non-)Abelian 1-form gauge
theories, are clarified within the framework of the above superfield formalism
where the 4D ordinary gauge theories are considered on the (4, 2)-dimensional
supermanifold parametrized by the four spacetime coordinates x^\mu (with \mu =
0, 1, 2, 3) and a pair of Grassmannian variables \theta and \bar\theta. One of
the key results of our present investigation is a great deal of simplification
in the geometrical understanding of the nilpotent (anti-)BRST symmetry
invariance.
|
120ac19a-80fe-4e24-9a04-57a93feaed67 | 120ac19a-80fe-4e24-9a04-57a93feaed67 | 120ac19a-80fe-4e24-9a04-57a93feaed67 | human | null | null | none | abstracts | Littlewood-Richardson polynomials | null | We introduce a family of rings of symmetric functions depending on an
infinite sequence of parameters. A distinguished basis of such a ring is
comprised by analogues of the Schur functions. The corresponding structure
coefficients are polynomials in the parameters which we call the
Littlewood-Richardson polynomials. We give a combinatorial rule for their
calculation by modifying an earlier result of B. Sagan and the author. The new
rule provides a formula for these polynomials which is manifestly positive in
the sense of W. Graham. We apply this formula for the calculation of the
product of equivariant Schubert classes on Grassmannians which implies a
stability property of the structure coefficients. The first manifestly positive
formula for such an expansion was given by A. Knutson and T. Tao by using
combinatorics of puzzles while the stability property was not apparent from
that formula. We also use the Littlewood-Richardson polynomials to describe the
multiplication rule in the algebra of the Casimir elements for the general
linear Lie algebra in the basis of the quantum immanants constructed by A.
Okounkov and G. Olshanski.
|
e1f42987-5127-477f-8a21-e1e272a2cf99 | e1f42987-5127-477f-8a21-e1e272a2cf99 | e1f42987-5127-477f-8a21-e1e272a2cf99 | human | null | null | none | abstracts | Lagrangian quantum field theory in momentum picture. IV. Commutation
relations for free fields | null | Possible (algebraic) commutation relations in the Lagrangian quantum theory
of free (scalar, spinor and vector) fields are considered from mathematical
view-point. As sources of these relations are employed the Heisenberg
equations/relations for the dynamical variables and a specific condition for
uniqueness of the operators of the dynamical variables (with respect to some
class of Lagrangians). The paracommutation relations or some their
generalizations are pointed as the most general ones that entail the validity
of all Heisenberg equations. The simultaneous fulfillment of the Heisenberg
equations and the uniqueness requirement turn to be impossible. This problem is
solved via a redefinition of the dynamical variables, similar to the normal
ordering procedure and containing it as a special case. That implies
corresponding changes in the admissible commutation relations. The introduction
of the concept of the vacuum makes narrow the class of the possible commutation
relations; in particular, the mentioned redefinition of the dynamical variables
is reduced to normal ordering. As a last restriction on that class is imposed
the requirement for existing of an effective procedure for calculating vacuum
mean values. The standard bilinear commutation relations are pointed as the
only known ones that satisfy all of the mentioned conditions and do not
contradict to the existing data.
|
4ad1cd03-f601-44d9-8f2d-7528c882ccba | 4ad1cd03-f601-44d9-8f2d-7528c882ccba | 4ad1cd03-f601-44d9-8f2d-7528c882ccba | human | null | null | none | abstracts | Order of Epitaxial Self-Assembled Quantum Dots: Linear Analysis | null | Epitaxial self-assembled quantum dots (SAQDs) are of interest for
nanostructured optoelectronic and electronic devices such as lasers,
photodetectors and nanoscale logic. Spatial order and size order of SAQDs are
important to the development of usable devices. It is likely that these two
types of order are strongly linked; thus, a study of spatial order will also
have strong implications for size order. Here a study of spatial order is
undertaken using a linear analysis of a commonly used model of SAQD formation
based on surface diffusion. Analytic formulas for film-height correlation
functions are found that characterize quantum dot spatial order and
corresponding correlation lengths that quantify order. Initial atomic-scale
random fluctuations result in relatively small correlation lengths (about two
dots) when the effect of a wetting potential is negligible; however, the
correlation lengths diverge when SAQDs are allowed to form at a near-critical
film height. The present work reinforces previous findings about anisotropy and
SAQD order and presents as explicit and transparent mechanism for ordering with
corresponding analytic equations. In addition, SAQD formation is by its nature
a stochastic process, and various mathematical aspects regarding statistical
analysis of SAQD formation and order are presented.
|
bd4b45ff-98ad-4361-9708-a156890bab63 | bd4b45ff-98ad-4361-9708-a156890bab63 | bd4b45ff-98ad-4361-9708-a156890bab63 | human | null | null | none | abstracts | Dynamical Objects for Cohomologically Expanding Maps | null | The goal of this paper is to construct invariant dynamical objects for a (not
necessarily invertible) smooth self map of a compact manifold. We prove a
result that takes advantage of differences in rates of expansion in the terms
of a sheaf cohomological long exact sequence to create unique lifts of finite
dimensional invariant subspaces of one term of the sequence to invariant
subspaces of the preceding term. This allows us to take invariant cohomological
classes and under the right circumstances construct unique currents of a given
type, including unique measures of a given type, that represent those classes
and are invariant under pullback. A dynamically interesting self map may have a
plethora of invariant measures, so the uniquess of the constructed currents is
important. It means that if local growth is not too big compared to the growth
rate of the cohomological class then the expanding cohomological class gives
sufficient "marching orders" to the system to prohibit the formation of any
other such invariant current of the same type (say from some local dynamical
subsystem). Because we use subsheaves of the sheaf of currents we give
conditions under which a subsheaf will have the same cohomology as the sheaf
containing it. Using a smoothing argument this allows us to show that the sheaf
cohomology of the currents under consideration can be canonically identified
with the deRham cohomology groups. Our main theorem can be applied in both the
smooth and holomorphic setting.
|
9d5d7b9e-4035-4db0-b259-8020ec301ffe | 9d5d7b9e-4035-4db0-b259-8020ec301ffe | 9d5d7b9e-4035-4db0-b259-8020ec301ffe | human | null | null | none | abstracts | The decomposition method and Maple procedure for finding first integrals
of nonlinear PDEs of any order with any number of independent variables | null | In present paper we propose seemingly new method for finding solutions of
some types of nonlinear PDEs in closed form. The method is based on
decomposition of nonlinear operators on sequence of operators of lower orders.
It is shown that decomposition process can be done by iterative procedure(s),
each step of which is reduced to solution of some auxiliary PDEs system(s) for
one dependent variable. Moreover, we find on this way the explicit expression
of the first-order PDE(s) for first integral of decomposable initial PDE.
Remarkably that this first-order PDE is linear if initial PDE is linear in its
highest derivatives.
The developed method is implemented in Maple procedure, which can really
solve many of different order PDEs with different number of independent
variables. Examples of PDEs with calculated their general solutions demonstrate
a potential of the method for automatic solving of nonlinear PDEs.
|
29b83835-3655-414d-bfc8-0b09c5f883b7 | 29b83835-3655-414d-bfc8-0b09c5f883b7 | 29b83835-3655-414d-bfc8-0b09c5f883b7 | human | null | null | none | abstracts | Injective Morita contexts (revisited) | null | This paper is an exposition of the so-called injective Morita contexts (in
which the connecting bimodule morphisms are injective) and Morita
$\alpha$contexts (in which the connecting bimodules enjoy some local
projectivity in the sense of Zimmermann-Huisgen). Motivated by situations in
which only one trace ideal is in action, or the compatibility between the
bimodule morphisms is not needed, we introduce the notions of Morita
semi-contexts and Morita data, and investigate them. Injective Morita data will
be used (with the help of static and adstatic modules) to establish
equivalences between some intersecting subcategories related to subcategories
of modules that are localized or colocalized by trace ideals of a Morita datum.
We end up with applications of Morita $\alpha$-contexts to $\ast$-modules and
injective right wide Morita contexts.
|
bf68e931-83a2-400d-a069-8f7f2dd575b0 | bf68e931-83a2-400d-a069-8f7f2dd575b0 | bf68e931-83a2-400d-a069-8f7f2dd575b0 | human | null | null | none | abstracts | Matter-Wave Bright Solitons with a Finite Background in Spinor
Bose-Einstein Condensates | null | We investigate dynamical properties of bright solitons with a finite
background in the F=1 spinor Bose-Einstein condensate (BEC), based on an
integrable spinor model which is equivalent to the matrix nonlinear
Schr\"{o}dinger equation with a self-focusing nonlineality. We apply the
inverse scattering method formulated for nonvanishing boundary conditions. The
resulting soliton solutions can be regarded as a generalization of those under
vanishing boundary conditions. One-soliton solutions are derived in an explicit
manner. According to the behaviors at the infinity, they are classified into
two kinds, domain-wall (DW) type and phase-shift (PS) type. The DW-type implies
the ferromagnetic state with nonzero total spin and the PS-type implies the
polar state, where the total spin amounts to zero. We also discuss two-soliton
collisions. In particular, the spin-mixing phenomenon is confirmed in a
collision involving the DW-type. The results are consistent with those of the
previous studies for bright solitons under vanishing boundary conditions and
dark solitons. As a result, we establish the robustness and the usefulness of
the multiple matter-wave solitons in the spinor BECs.
|
19daa111-c3a4-41ff-b96b-f822ed034f15 | 19daa111-c3a4-41ff-b96b-f822ed034f15 | 19daa111-c3a4-41ff-b96b-f822ed034f15 | human | null | null | none | abstracts | Why there is something rather than nothing (out of everything)? | null | The path integral over Euclidean geometries for the recently suggested
density matrix of the Universe is shown to describe a microcanonical ensemble
in quantum cosmology. This ensemble corresponds to a uniform (weight one)
distribution in phase space of true physical variables, but in terms of the
observable spacetime geometry it is peaked about complex saddle-points of the
{\em Lorentzian} path integral. They are represented by the recently obtained
cosmological instantons limited to a bounded range of the cosmological
constant. Inflationary cosmologies generated by these instantons at late stages
of expansion undergo acceleration whose low-energy scale can be attained within
the concept of dynamically evolving extra dimensions. Thus, together with the
bounded range of the early cosmological constant, this cosmological ensemble
suggests the mechanism of constraining the landscape of string vacua and,
simultaneously, a possible solution to the dark energy problem in the form of
the quasi-equilibrium decay of the microcanonical state of the Universe.
|
27fcc305-b6db-40e0-b39c-693cef987709 | 27fcc305-b6db-40e0-b39c-693cef987709 | 27fcc305-b6db-40e0-b39c-693cef987709 | human | null | null | none | abstracts | A Universality in PP-Waves | null | We discuss a universality property of any covariant field theory in
space-time expanded around pp-wave backgrounds. According to this property the
space-time lagrangian density evaluated on a restricted set of field
configurations, called universal sector, turns out to be same around all the
pp-waves, even off-shell, with same transverse space and same profiles for the
background scalars. In this paper we restrict our discussion to tensorial
fields only. In the context of bosonic string theory we consider on-shell
pp-waves and argue that universality requires the existence of a universal
sector of world-sheet operators whose correlation functions are insensitive to
the pp-wave nature of the metric and the background gauge flux. Such results
can also be reproduced using the world-sheet conformal field theory. We also
study such pp-waves in non-polynomial closed string field theory (CSFT). In
particular, we argue that for an off-shell pp-wave ansatz with flat transverse
space and dilaton independent of transverse coordinates the field redefinition
relating the low energy effective field theory and CSFT with all the massive
modes integrated out is at most quadratic in fields. Because of this
simplification it is expected that the off-shell pp-waves can be identified on
the two sides. Furthermore, given the massless pp-wave field configurations, an
iterative method for computing the higher massive modes using the CSFT
equations of motion has been discussed. All our bosonic string theory analyses
can be generalised to the common Neveu-Schwarz sector of superstrings.
|
ffc50c50-b054-4ab9-ac02-3e281b03bad8 | ffc50c50-b054-4ab9-ac02-3e281b03bad8 | ffc50c50-b054-4ab9-ac02-3e281b03bad8 | human | null | null | none | abstracts | Clustering in a stochastic model of one-dimensional gas | null | We give a quantitative analysis of clustering in a stochastic model of
one-dimensional gas. At time zero, the gas consists of $n$ identical particles
that are randomly distributed on the real line and have zero initial speeds.
Particles begin to move under the forces of mutual attraction. When particles
collide, they stick together forming a new particle, called cluster, whose mass
and speed are defined by the laws of conservation. We are interested in the
asymptotic behavior of $K_n(t)$ as $n\to \infty$, where $K_n(t)$ denotes the
number of clusters at time $t$ in the system with $n$ initial particles. Our
main result is a functional limit theorem for $K_n(t)$. Its proof is based on
the discovered localization property of the aggregation process, which states
that the behavior of each particle is essentially defined by the motion of
neighbor particles.
|
85eb0061-205f-47a8-b63f-08391f3587b7 | 85eb0061-205f-47a8-b63f-08391f3587b7 | 85eb0061-205f-47a8-b63f-08391f3587b7 | human | null | null | none | abstracts | Some new experimental photonic flame effect features | null | The results of the spectral, energetical and temporal characteristics of
radiation in the presence of the photonic flame effect are presented.
Artificial opal posed on Cu plate at the temperature of liquid nitrogen boiling
point (77 K) being irradiated by nanosecond ruby laser pulse produces long-
term luminiscence with a duration till ten seconds with a finely structured
spectrum in the the antistocks part of the spectrum. Analogous visible
luminescence manifesting time delay appeared in other samples of the artificial
opals posed on the same plate. In the case of the opal infiltrated with
different nonlinear liquids the threshold of the luminiscence is reduced and
the spatial disribution of the bright emmiting area on the opal surface is
being changed. In the case of the putting the frozen nonlinear liquids on the
Cu plate long-term blue bright luminiscence took place in the frozen species of
the liquids. Temporal characteristics of this luminiscence are nearly the same
as in opal matrixes.
|
4ff03e33-4563-409a-9eac-0ca5e656d556 | 4ff03e33-4563-409a-9eac-0ca5e656d556 | 4ff03e33-4563-409a-9eac-0ca5e656d556 | human | null | null | none | abstracts | A general approach to statistical modeling of physical laws:
nonparametric regression | null | Statistical modeling of experimental physical laws is based on the
probability density function of measured variables. It is expressed by
experimental data via a kernel estimator. The kernel is determined objectively
by the scattering of data during calibration of experimental setup. A physical
law, which relates measured variables, is optimally extracted from experimental
data by the conditional average estimator. It is derived directly from the
kernel estimator and corresponds to a general nonparametric regression. The
proposed method is demonstrated by the modeling of a return map of noisy
chaotic data. In this example, the nonparametric regression is used to predict
a future value of chaotic time series from the present one. The mean predictor
error is used in the definition of predictor quality, while the redundancy is
expressed by the mean square distance between data points. Both statistics are
used in a new definition of predictor cost function. From the minimum of the
predictor cost function, a proper number of data in the model is estimated.
|
fe51d184-a99f-4337-bbbf-600fb9f8c458 | fe51d184-a99f-4337-bbbf-600fb9f8c458 | fe51d184-a99f-4337-bbbf-600fb9f8c458 | human | null | null | none | abstracts | Aspects of Electron-Phonon Self-Energy Revealed from Angle-Resolved
Photoemission Spectroscopy | null | Lattice contribution to the electronic self-energy in complex correlated
oxides is a fascinating subject that has lately stimulated lively discussions.
Expectations of electron-phonon self-energy effects for simpler materials, such
as Pd and Al, have resulted in several misconceptions in strongly correlated
oxides. Here we analyze a number of arguments claiming that phonons cannot be
the origin of certain self-energy effects seen in high-$T_c$ cuprate
superconductors via angle resolved photoemission experiments (ARPES), including
the temperature dependence, doping dependence of the renormalization effects,
the inter-band scattering in the bilayer systems, and impurity substitution. We
show that in light of experimental evidences and detailed simulations, these
arguments are not well founded.
|
8a782ba1-ae93-48dc-bc39-3c245b34c9e5 | 8a782ba1-ae93-48dc-bc39-3c245b34c9e5 | 8a782ba1-ae93-48dc-bc39-3c245b34c9e5 | human | null | null | none | abstracts | Timing and Lensing of the Colliding Bullet Clusters: barely enough time
and gravity to accelerate the bullet | null | We present semi-analytical constraint on the amount of dark matter in the
merging bullet galaxy cluster using the classical Local Group timing arguments.
We consider particle orbits in potential models which fit the lensing data.
{\it Marginally consistent} CDM models in Newtonian gravity are found with a
total mass M_{CDM} = 1 x 10^{15}Msun of Cold DM: the bullet subhalo can move
with V_{DM}=3000km/s, and the "bullet" X-ray gas can move with
V_{gas}=4200km/s. These are nearly the {\it maximum speeds} that are
accelerable by the gravity of two truncated CDM halos in a Hubble time even
without the ram pressure. Consistency breaks down if one adopts higher end of
the error bars for the bullet gas speed (5000-5400km/s), and the bullet gas
would not be bound by the sub-cluster halo for the Hubble time. Models with
V_{DM}~ 4500km/s ~ V_{gas} would invoke unrealistic large amount M_{CDM}=7x
10^{15}Msun of CDM for a cluster containing only ~ 10^{14}Msun of gas. Our
results are generalisable beyond General Relativity, e.g., a speed of
$4500\kms$ is easily obtained in the relativistic MONDian lensing model of
Angus et al. (2007). However, MONDian model with little hot dark matter
$M_{HDM} \le 0.6\times 10^{15}\msun$ and CDM model with a small halo mass $\le
1\times 10^{15}\msun$ are barely consistent with lensing and velocity data.
|
3e1b1a7d-42e6-4d6c-b86d-226a737f5751 | 3e1b1a7d-42e6-4d6c-b86d-226a737f5751 | 3e1b1a7d-42e6-4d6c-b86d-226a737f5751 | human | null | null | none | abstracts | Geometry of Locally Compact Groups of Polynomial Growth and Shape of
Large Balls | null | We get asymptotics for the volume of large balls in an arbitrary locally
compact group G with polynomial growth. This is done via a study of the
geometry of G and a generalization of P. Pansu's thesis. In particular, we show
that any such G is weakly commensurable to some simply connected solvable Lie
group S, the Lie shadow of G. We also show that large balls in G have an
asymptotic shape, i.e. after a suitable renormalization, they converge to a
limiting compact set which can be interpreted geometrically. We then discuss
the speed of convergence, treat some examples and give an application to
ergodic theory. We also answer a question of Burago about left invariant
metrics and recover some results of Stoll on the irrationality of growth series
of nilpotent groups.
|
d2d2b5e3-af80-40e7-b083-ecad1d00d40c | d2d2b5e3-af80-40e7-b083-ecad1d00d40c | d2d2b5e3-af80-40e7-b083-ecad1d00d40c | human | null | null | none | abstracts | On Ando's inequalities for convex and concave functions | null | For positive semidefinite matrices $A$ and $B$, Ando and Zhan proved the
inequalities $||| f(A)+f(B) ||| \ge ||| f(A+B) |||$ and $||| g(A)+g(B) ||| \le
||| g(A+B) |||$, for any unitarily invariant norm, and for any non-negative
operator monotone $f$ on $[0,\infty)$ with inverse function $g$. These
inequalities have very recently been generalised to non-negative concave
functions $f$ and non-negative convex functions $g$, by Bourin and Uchiyama,
and Kosem, respectively.
In this paper we consider the related question whether the inequalities $|||
f(A)-f(B) ||| \le ||| f(|A-B|) |||$, and $||| g(A)-g(B) ||| \ge ||| g(|A-B|)
|||$, obtained by Ando, for operator monotone $f$ with inverse $g$, also have a
similar generalisation to non-negative concave $f$ and convex $g$. We answer
exactly this question, in the negative for general matrices, and affirmatively
in the special case when $A\ge ||B||$.
In the course of this work, we introduce the novel notion of $Y$-dominated
majorisation between the spectra of two Hermitian matrices, where $Y$ is itself
a Hermitian matrix, and prove a certain property of this relation that allows
to strengthen the results of Bourin-Uchiyama and Kosem, mentioned above.
|
e566724d-ae81-4542-ac13-ce516f81ea97 | e566724d-ae81-4542-ac13-ce516f81ea97 | e566724d-ae81-4542-ac13-ce516f81ea97 | human | null | null | none | abstracts | Topology Change of Black Holes | null | The topological structure of the event horizon has been investigated in terms
of the Morse theory. The elementary process of topological evolution can be
understood as a handle attachment. It has been found that there are certain
constraints on the nature of black hole topological evolution: (i) There are n
kinds of handle attachments in (n+1)-dimensional black hole space-times. (ii)
Handles are further classified as either of black or white type, and only black
handles appear in real black hole space-times. (iii) The spatial section of an
exterior of the black hole region is always connected. As a corollary, it is
shown that the formation of a black hole with an S**(n-2) x S**1 horizon from
that with an S**(n-1) horizon must be non-axisymmetric in asymptotically flat
space-times.
|
8bcc675b-4e96-46ca-9e43-10fe1e4e4907 | 8bcc675b-4e96-46ca-9e43-10fe1e4e4907 | 8bcc675b-4e96-46ca-9e43-10fe1e4e4907 | human | null | null | none | abstracts | Rigid subsets of symplectic manifolds | null | We show that there is an hierarchy of intersection rigidity properties of
sets in a closed symplectic manifold: some sets cannot be displaced by
symplectomorphisms from more sets than the others. We also find new examples of
rigidity of intersections involving, in particular, specific fibers of moment
maps of Hamiltonian torus actions, monotone Lagrangian submanifolds (following
the works of P.Albers and P.Biran-O.Cornea), as well as certain, possibly
singular, sets defined in terms of Poisson-commutative subalgebras of smooth
functions. In addition, we get some geometric obstructions to semi-simplicity
of the quantum homology of symplectic manifolds. The proofs are based on the
Floer-theoretical machinery of partial symplectic quasi-states.
|
ebacde3d-cc94-4b89-9279-10b7ed14287a | ebacde3d-cc94-4b89-9279-10b7ed14287a | ebacde3d-cc94-4b89-9279-10b7ed14287a | human | null | null | none | abstracts | Multiple Parton Scattering in Nuclei: Quark-quark Scattering | null | Modifications to quark and antiquark fragmentation functions due to
quark-quark (antiquark) double scattering in nuclear medium are studied
systematically up to order \cal{O}(\alpha_{s}^2)$ in deeply inelastic
scattering (DIS) off nuclear targets. At the order $\cal{O}(\alpha_s^2)$,
twist-four contributions from quark-quark (antiquark) rescattering also exhibit
the Landau-Pomeranchuck-Midgal (LPM) interference feature similar to gluon
bremsstrahlung induced by multiple parton scattering. Compared to quark-gluon
scattering, the modification, which is dominated by $t$-channel quark-quark
(antiquark) scattering, is only smaller by a factor of $C_F/C_A=4/9$ times the
ratio of quark and gluon distributions in the medium. Such a modification is
not negligible for realistic kinematics and finite medium size. The
modifications to quark (antiquark) fragmentation functions from quark-antiquark
annihilation processes are shown to be determined by the antiquark (quark)
distribution density in the medium. The asymmetry in quark and antiquark
distributions in nuclei will lead to different modifications of quark and
antiquark fragmentation functions inside a nucleus, which qualitatively
explains the experimentally observed flavor dependence of the leading hadron
suppression in semi-inclusive DIS off nuclear targets. The quark-antiquark
annihilation processes also mix quark and gluon fragmentation functions in the
large fractional momentum region, leading to a flavor dependence of jet
quenching in heavy-ion collisions.
|
d52412c9-08cf-43b8-b4b0-5320dc617f1b | d52412c9-08cf-43b8-b4b0-5320dc617f1b | d52412c9-08cf-43b8-b4b0-5320dc617f1b | human | null | null | none | abstracts | Half-metallic silicon nanowires | null | From first-principles calculations, we predict that transition metal (TM)
atom doped silicon nanowires have a half-metallic ground state. They are
insulators for one spin-direction, but show metallic properties for the
opposite spin direction. At high coverage of TM atoms, ferromagnetic silicon
nanowires become metallic for both spin-directions with high magnetic moment
and may have also significant spin-polarization at the Fermi level. The
spin-dependent electronic properties can be engineered by changing the type of
dopant TM atoms, as well as the diameter of the nanowire. Present results are
not only of scientific interest, but can also initiate new research on
spintronic applications of silicon nanowires.
|
de3c568d-b7fe-450c-888c-504d1fe35308 | de3c568d-b7fe-450c-888c-504d1fe35308 | de3c568d-b7fe-450c-888c-504d1fe35308 | human | null | null | none | abstracts | Langmuir blodgett assembly of densely aligned single walled carbon
nanotubes from bulk materials | null | Single walled carbon nanotubes exhibit advanced electrical and surface
properties useful for high performance nanoelectronics. Important to future
manufacturing of nanotube circuits is large scale assembly of SWNTs into
aligned forms. Despite progress in assembly and oriented synthesis, pristine
SWNTs in aligned and close-packed form remain elusive and needed for high
current, speed and density devices through collective operations of parallel
SWNTs. Here, we develop a Langmuir Blodgett method achieving monolayers of
aligned SWNTs with dense packing, central to which is a non covalent polymer
functionalization by PmPV imparting high solubility and stability of SWNTs in
an organic solvent DCE. Pressure cycling or annealing during LB film
compression reduces hysteresis and facilitates high degree alignment and
packing of SWNTs characterized by microscopy and polarized Raman spectroscopy.
The monolayer SWNTs are readily patterned for device integration by
microfabrication, enabling the highest currents 3mA through the narrowest
regions packed with aligned SWNTs thus far.
|
c8484e35-cf19-4baf-bb54-2ad9b20009a7 | c8484e35-cf19-4baf-bb54-2ad9b20009a7 | c8484e35-cf19-4baf-bb54-2ad9b20009a7 | human | null | null | none | abstracts | Quantum Phase Transition in the Four-Spin Exchange Antiferromagnet | null | We study the S=1/2 Heisenberg antiferromagnet on a square lattice with
nearest-neighbor and plaquette four-spin exchanges (introduced by A.W. Sandvik,
Phys. Rev. Lett. {\bf 98}, 227202 (2007).)
This model undergoes a quantum phase transition from a spontaneously
dimerized phase to N\'eel order at a critical coupling. We show that as the
critical point is approached from the dimerized side, the system exhibits
strong fluctuations in the dimer background, reflected in the presence of a
low-energy singlet mode, with a simultaneous rise in the triplet quasiparticle
density. We find that both singlet and triplet modes of high density condense
at the transition, signaling restoration of lattice symmetry. In our approach,
which goes beyond mean-field theory in terms of the triplet excitations, the
transition appears sharp; however since our method breaks down near the
critical point, we argue that we cannot make a definite conclusion regarding
the order of the transition.
|
7a169428-2b18-492c-9822-567c03aaf2fc | 7a169428-2b18-492c-9822-567c03aaf2fc | 7a169428-2b18-492c-9822-567c03aaf2fc | human | null | null | none | abstracts | Lower ground state due to counter-rotating wave interaction in trapped
ion system | null | We consider a single ion confined in a trap under radiation of two traveling
waves of lasers. In the strong-excitation regime and without the restriction of
Lamb-Dicke limit, the Hamiltonian of the system is similar to a driving
Jaynes-Cummings model without rotating wave approximation (RWA). The approach
we developed enables us to present a complete eigensolutions, which makes it
available to compare with the solutions under the RWA. We find that, the ground
state in our non-RWA solution is energically lower than the counterpart under
the RWA. If we have the ion in the ground state, it is equivalent to a spin
dependent force on the trapped ion. Discussion is made for the difference
between the solutions with and without the RWA, and for the relevant
experimental test, as well as for the possible application in quantum
information processing.
|
e8998b11-fdba-4f01-9b17-c3169cfacbd1 | e8998b11-fdba-4f01-9b17-c3169cfacbd1 | e8998b11-fdba-4f01-9b17-c3169cfacbd1 | human | null | null | none | abstracts | Quasi-quartet crystal electric field ground state in a tetragonal
CeAg$_2$Ge$_2$ single crystal | null | We have successfully grown the single crystals of CeAg$_2$Ge$_2$, for the
first time, by flux method and studied the anisotropic physical properties by
measuring the electrical resistivity, magnetic susceptibility and specific
heat. We found that CeAg$_2$Ge$_2$ undergoes an antiferromagnetic transition at
$T_{\rm N}$ = 4.6 K. The electrical resistivity and susceptibility data reveal
strong anisotropic magnetic properties. The magnetization measured at $T$ = 2 K
exhibited two metamagnetic transitions at $H_{\rm m1}$ = 31 kOe and $H_{\rm
m2}$ = 44.7 kOe, for $H \parallel$ [100] with a saturation magnetization of 1.6
$\mu_{\rm B}$/Ce. The crystalline electric field (CEF) analysis of the inverse
susceptibility data reveals that the ground state and the first excited states
of CeAg$_2$Ge$_2$ are closely spaced indicating a quasi-quartet ground state.
The specific heat data lend further support to the presence of closely spaced
energy levels.
|
299488be-8583-496c-b5f8-41089fd0cb1a | 299488be-8583-496c-b5f8-41089fd0cb1a | 299488be-8583-496c-b5f8-41089fd0cb1a | human | null | null | none | abstracts | Nonlinear Dynamics of the Phonon Stimulated Emission in Microwave
Solid-State Resonator of the Nonautonomous Phaser Generator | null | The microwave phonon stimulated emission (SE) has been experimentally and
numerically investigated in a nonautonomous microwave acoustic quantum
generator, called also microwave phonon laser or phaser (see previous works
arXiv:cond-mat/0303188 ; arXiv:cond-mat/0402640 ; arXiv:nlin.CG/0703050)
Phenomena of branching and long-time refractority (absence of the reaction on
the external pulses) for deterministic chaotic and regular processes of SE were
observed in experiments with various levels of electromagnetic pumping. At the
pumping level growth, the clearly depined increasing of the number of
coexisting SE states has been observed both in real physical experiments and in
computer simulations. This confirms the analytical estimations of the branching
density in the phase space. The nature of the refractority of SE pulses is
closely connected with the pointed branching and reflects the crises of strange
attractors, i.e. their collisions with unstable periodic components of the
higher branches of SE states in the nonautonomous microwave phonon laser.
|
f64ee4f1-8c4a-4faa-9ae4-6690e2a83002 | f64ee4f1-8c4a-4faa-9ae4-6690e2a83002 | f64ee4f1-8c4a-4faa-9ae4-6690e2a83002 | human | null | null | none | abstracts | I-V characteristics of the vortex state in MgB2 thin films | null | The current-voltage (I-V) characteristics of various MgB2 films have been
studied at different magnetic fields parallel to c-axis. At fields \mu0H
between 0 and 5T, vortex liquid-glass transitions were found in the I-V
isotherms. Consistently, the I-V curves measured at different temperatures show
a scaling behavior in the framework of quasi-two-dimension (quasi-2D) vortex
glass theory. However, at \mu0 H >= 5T, a finite dissipation was observed down
to the lowest temperature here, T=1.7K, and the I-V isotherms did not scale in
terms of any known scaling law, of any dimensionality. We suggest that this may
be caused by a mixture of \sigma band vortices and \pi band quasiparticles.
Interestingly, the I-V curves at zero magnetic field can still be scaled
according to the quasi-2D vortex glass formalism, indicating an equivalent
effect of self-field due to persistent current and applied magnetic field.
|
0c6e03f6-7e9a-4d71-bac4-637cd1e75205 | 0c6e03f6-7e9a-4d71-bac4-637cd1e75205 | 0c6e03f6-7e9a-4d71-bac4-637cd1e75205 | human | null | null | none | abstracts | Magnetic Fingerprints of sub-100 nm Fe Nanodots | null | Sub-100 nm nanomagnets not only are technologically important, but also
exhibit complex magnetization reversal behaviors as their dimensions are
comparable to typical magnetic domain wall widths. Here we capture magnetic
"fingerprints" of 1 billion Fe nanodots as they undergo a single domain to
vortex state transition, using a first-order reversal curve (FORC) method. As
the nanodot size increases from 52 nm to 67 nm, the FORC diagrams reveal
striking differences, despite only subtle changes in their major hysteresis
loops. The 52 nm nanodots exhibit single domain behavior and the coercivity
distribution extracted from the FORC distribution agrees well with a
calculation based on the measured nanodot size distribution. The 58 and 67 nm
nanodots exhibit vortex states, where the nucleation and annihilation of the
vortices are manifested as butterfly-like features in the FORC distribution and
confirmed by micromagnetic simulations. Furthermore, the FORC method gives
quantitative measures of the magnetic phase fractions, and vortex nucleation
and annihilation fields.
|
4a2ebec8-d6bf-4753-96fa-fdd9486acf44 | 4a2ebec8-d6bf-4753-96fa-fdd9486acf44 | 4a2ebec8-d6bf-4753-96fa-fdd9486acf44 | human | null | null | none | abstracts | An online repository of Swift/XRT light curves of GRBs | null | Context. Swift data are revolutionising our understanding of Gamma Ray
Bursts. Since bursts fade rapidly, it is desirable to create and disseminate
accurate light curves rapidly.
Aims. To provide the community with an online repository of X-ray light
curves obtained with Swift. The light curves should be of the quality expected
of published data, but automatically created and updated so as to be
self-consistent and rapidly available. Methods. We have produced a suite of
programs which automatically generates Swift/XRT light curves of GRBs. Effects
of the damage to the CCD, automatic readout-mode switching and pile-up are
appropriately handled, and the data are binned with variable bin durations, as
necessary for a fading source.
Results. The light curve repository website
(http://www.swift.ac.uk/xrt_curves) contains light curves, hardness ratios and
deep images for every GRB which Swift's XRT has observed. When new GRBs are
detected, light curves are created and updated within minutes of the data
arriving at the UK Swift Science Data Centre.
|
5d8d71f7-e1da-4371-be58-7691b988ddf5 | 5d8d71f7-e1da-4371-be58-7691b988ddf5 | 5d8d71f7-e1da-4371-be58-7691b988ddf5 | human | null | null | none | abstracts | Vacuum Structure and Potential | null | Based on overall experimental observations, especially the pair processes, I
developed a model structure of the vacuum along with a basic-particle formation
scheme begun in 2000 (with collaborator P-I Johansson). The model consists in
that the vacuum is, briefly, filled of neutral but polarizable vacuuons,
consisting each of a p-vaculeon and n- vaculeon of charges $+e$ and $-e$ of
zero rest masses but with spin motions, assumed interacting each other with a
Coulomb force. The model has been introduced in full in a book (Nova Sci, 2005)
and referred to in a number of journal/E-print papers. I outline in this easier
accessible paper the detailed derivation of the model and a corresponding
quantitative determination of the vacuuon size.
|
de32fdfb-265b-4e9f-8bb8-bab460a41e41 | de32fdfb-265b-4e9f-8bb8-bab460a41e41 | de32fdfb-265b-4e9f-8bb8-bab460a41e41 | human | null | null | none | abstracts | PAH emission and star formation in the host of the z~2.56 Cloverleaf QSO | null | We report the first detection of the 6.2micron and 7.7micron infrared `PAH'
emission features in the spectrum of a high redshift QSO, from the Spitzer-IRS
spectrum of the Cloverleaf lensed QSO (H1413+117, z~2.56). The ratio of PAH
features and rest frame far-infrared emission is the same as in lower
luminosity star forming ultraluminous infrared galaxies and in local PG QSOs,
supporting a predominantly starburst nature of the Cloverleaf's huge
far-infrared luminosity (5.4E12 Lsun, corrected for lensing). The Cloverleaf's
period of dominant QSO activity (Lbol ~ 7E13 Lsun) is coincident with an
intense (star formation rate ~1000 Msun/yr) and short (gas exhaustion time
~3E7yr) star forming event.
|
18530c33-7bf6-4d09-945e-43a8a39d2eb1 | 18530c33-7bf6-4d09-945e-43a8a39d2eb1 | 18530c33-7bf6-4d09-945e-43a8a39d2eb1 | human | null | null | none | abstracts | Causal dissipative hydrodynamics for QGP fluid in 2+1 dimensions | null | In 2nd order causal dissipative theory, space-time evolution of QGP fluid is
studied in 2+1 dimensions. Relaxation equations for shear stress tensors are
solved simultaneously with the energy-momentum conservation equations.
Comparison of evolution of ideal and viscous QGP fluid, initialized under the
same conditions, e.g. same equilibration time, energy density and velocity
profile, indicate that in a viscous dynamics, energy density or temperature of
the fluid evolve slowly, than in an ideal fluid. Cooling gets slower as
viscosity increases. Transverse expansion also increases in a viscous dynamics.
For the first time we have also studied elliptic flow of 'quarks' in causal
viscous dynamics. It is shown that elliptic flow of quarks saturates due to
non-equilibrium correction to equilibrium distribution function, and can not be
mimicked by an ideal hydrodynamics.
|
6fd2ef8d-b11a-4981-860c-f3593795bc54 | 6fd2ef8d-b11a-4981-860c-f3593795bc54 | 6fd2ef8d-b11a-4981-860c-f3593795bc54 | human | null | null | none | abstracts | A Single Trapped Ion as a Time-Dependent Harmonic Oscillator | null | We show how a single trapped ion may be used to test a variety of important
physical models realized as time-dependent harmonic oscillators. The ion itself
functions as its own motional detector through laser-induced electronic
transitions. Alsing et al. [Phys. Rev. Lett. 94, 220401 (2005)] proposed that
an exponentially decaying trap frequency could be used to simulate (thermal)
Gibbons-Hawking radiation in an expanding universe, but the Hamiltonian used
was incorrect. We apply our general solution to this experimental proposal,
correcting the result for a single ion and showing that while the actual
spectrum is different from the Gibbons-Hawking case, it nevertheless shares an
important experimental signature with this result.
|
8d82ca5e-b4e9-4075-a1fc-35229108b786 | 8d82ca5e-b4e9-4075-a1fc-35229108b786 | 8d82ca5e-b4e9-4075-a1fc-35229108b786 | human | null | null | none | abstracts | Compounding Fields and Their Quantum Equations in the Trigintaduonion
Space | null | The 32-dimensional compounding fields and their quantum interplays in the
trigintaduonion space can be presented by analogy with octonion and sedenion
electromagnetic, gravitational, strong and weak interactions. In the
trigintaduonion fields which are associated with the electromagnetic,
gravitational, strong and weak interactions, the study deduces some conclusions
of field source particles (quarks and leptons) and intermediate particles which
are consistent with current some sorts of interaction theories. In the
trigintaduonion fields which are associated with the hyper-strong and
strong-weak fields, the paper draws some predicts and conclusions of the field
source particles (sub-quarks) and intermediate particles. The research results
show that there may exist some new particles in the nature.
|
61bf6067-8774-4ea3-984b-0c40dd415822 | 61bf6067-8774-4ea3-984b-0c40dd415822 | 61bf6067-8774-4ea3-984b-0c40dd415822 | human | null | null | none | abstracts | The Blue Straggler Population of the Globular Cluster M5 | null | By combining high-resolution HST and wide-field ground based observations, in
ultraviolet and optical bands, we study the Blue Stragglers Star (BSS)
population of the galactic globular cluster M5 (NGC 5904) from its very central
regions up to its periphery. The BSS distribution is highly peaked in the
cluster center, decreases at intermediate radii and rises again outward. Such a
bimodal distribution is similar to those previously observed in other globular
clusters (M3, 47Tucanae, NGC6752). As for these clusters, dynamical simulations
suggest that, while the majority of BSS in M5 could be originated by stellar
collisions, a significant fraction (20-40%) of BSS generated by mass transfer
processes in primordial binaries is required to reproduce the observed radial
distribution. A candidate BSS has been detected beyond the cluster tidal
radius. If confirmed, this could represent an interesting case of an
"evaporating" BSS.
|
e90c11d3-b2a0-48a2-8224-9bf000036ced | e90c11d3-b2a0-48a2-8224-9bf000036ced | e90c11d3-b2a0-48a2-8224-9bf000036ced | human | null | null | none | abstracts | Entanglement entropy of two-dimensional Anti-de Sitter black holes | null | Using the AdS/CFT correspondence we derive a formula for the entanglement
entropy of the anti-de Sitter black hole in two spacetime dimensions. The
leading term in the large black hole mass expansion of our formula reproduces
exactly the Bekenstein-Hawking entropy S_{BH}, whereas the subleading term
behaves as ln S_{BH}. This subleading term has the universal form typical for
the entanglement entropy of physical systems described by effective conformal
fields theories (e.g. one-dimensional statistical models at the critical
point). The well-known form of the entanglement entropy for a two-dimensional
conformal field theory is obtained as analytic continuation of our result and
is related with the entanglement entropy of a black hole with negative mass.
|
9ebcac56-ced1-4053-a59e-cc590fb993b2 | 9ebcac56-ced1-4053-a59e-cc590fb993b2 | 9ebcac56-ced1-4053-a59e-cc590fb993b2 | human | null | null | none | abstracts | Some aspects of the nonperturbative renormalization of the phi^4 model | null | A nonperturbative renormalization of the phi^4 model is considered. First we
integrate out only a single pair of conjugated modes with wave vectors +/- q.
Then we are looking for the RG equation which would describe the transformation
of the Hamiltonian under the integration over a shell Lambda - d Lambda < k <
Lambda, where d Lambda -> 0. We show that the known Wegner--Houghton equation
is consistent with the assumption of a simple superposition of the integration
results for +/- q. The renormalized action can be expanded in powers of the
phi^4 coupling constant u in the high temperature phase at u -> 0. We compare
the expansion coefficients with those exactly calculated by the diagrammatic
perturbative method, and find some inconsistency. It causes a question in which
sense the Wegner-Houghton equation is really exact.
|
65dac653-b119-461a-be5c-3617cdc12148 | 65dac653-b119-461a-be5c-3617cdc12148 | 65dac653-b119-461a-be5c-3617cdc12148 | human | null | null | none | abstracts | Eternal inflation and localization on the landscape | null | We model the essential features of eternal inflation on the landscape of a
dense discretuum of vacua by the potential $V(\phi)=V_{0}+\delta V(\phi)$,
where $|\delta V(\phi)|\ll V_{0}$ is random. We find that the diffusion of the
distribution function $\rho(\phi,t)$ of the inflaton expectation value in
different Hubble patches may be suppressed due to the effect analogous to the
Anderson localization in disordered quantum systems. At $t \to \infty$ only the
localized part of the distribution function $\rho (\phi, t)$ survives which
leads to dynamical selection principle on the landscape. The probability to
measure any but a small value of the cosmological constant in a given Hubble
patch on the landscape is exponentially suppressed at $t\to \infty$.
|
fdf546e1-e622-4fb7-bc26-12796f93191b | fdf546e1-e622-4fb7-bc26-12796f93191b | fdf546e1-e622-4fb7-bc26-12796f93191b | human | null | null | none | abstracts | Vortices in Bose-Einstein Condensates: Theory | null | Vortices are pervasive in nature, representing the breakdown of laminar fluid
flow and hence playing a key role in turbulence. The fluid rotation associated
with a vortex can be parameterized by the circulation $\Gamma=\oint {\rm d}{\bf
r}\cdot{\bf v}({\bf r})$ about the vortex, where ${\bf v}({\bf r})$ is the
fluid velocity field. While classical vortices can take any value of
circulation, superfluids are irrotational, and any rotation or angular momentum
is constrained to occur through vortices with quantized circulation. Quantized
vortices also play a key role in the dissipation of transport in superfluids.
In BECs quantized vortices have been observed in several forms, including
single vortices, vortex lattices, and vortex pairs and rings. The recent
observation of quantized vortices in a fermionic gas was taken as a clear
signature of the underlying condensation and superfluidity of fermion pairs. In
addition to BECs, quantized vortices also occur in superfluid Helium, nonlinear
optics, and type-II superconductors.
|
7add211d-3532-43f1-a326-c8ef08012d9a | 7add211d-3532-43f1-a326-c8ef08012d9a | 7add211d-3532-43f1-a326-c8ef08012d9a | human | null | null | none | abstracts | A POVM view of the ensemble approach to polarization optics | null | Statistical ensemble formalism of Kim, Mandel and Wolf (J. Opt. Soc. Am. A 4,
433 (1987)) offers a realistic model for characterizing the effect of
stochastic non-image forming optical media on the state of polarization of
transmittedlight. With suitable choice of the Jones ensemble, various Mueller
transformations - some of which have been unknown so far - are deduced. It is
observed that the ensemble approach is formally identical to the positive
operator valued measures (POVM) on the quantum density matrix. This
observation, in combination with the recent suggestion by Ahnert and Payne
(Phys. Rev. A 71, 012330, (2005)) - in the context of generalized quantum
measurement on single photon polarization states - that linear optics elements
can be employed in setting up all possible POVMs, enables us to propose a way
of realizing different types of Mueller devices.
|
053ac8e0-ccd7-4f6e-b3f8-efebe310b3f8 | 053ac8e0-ccd7-4f6e-b3f8-efebe310b3f8 | 053ac8e0-ccd7-4f6e-b3f8-efebe310b3f8 | human | null | null | none | abstracts | Reexamination of spin decoherence in semiconductor quantum dots from
equation-of-motion approach | null | The longitudinal and transversal spin decoherence times, $T_1$ and $T_2$, in
semiconductor quantum dots are investigated from equation-of-motion approach
for different magnetic fields, quantum dot sizes, and temperatures. Various
mechanisms, such as the hyperfine interaction with the surrounding nuclei, the
Dresselhaus spin-orbit coupling together with the electron--bulk-phonon
interaction, the $g$-factor fluctuations, the direct spin-phonon coupling due
to the phonon-induced strain, and the coaction of the
electron--bulk/surface-phonon interaction together with the hyperfine
interaction are included. The relative contributions from these spin
decoherence mechanisms are compared in detail. In our calculation, the
spin-orbit coupling is included in each mechanism and is shown to have marked
effect in most cases. The equation-of-motion approach is applied in studying
both the spin relaxation time $T_1$ and the spin dephasing time $T_2$, either
in Markovian or in non-Markovian limit. When many levels are involved at finite
temperature, we demonstrate how to obtain the spin relaxation time from the
Fermi Golden rule in the limit of weak spin-orbit coupling. However, at high
temperature and/or for large spin-orbit coupling, one has to use the
equation-of-motion approach when many levels are involved. Moreover, spin
dephasing can be much more efficient than spin relaxation at high temperature,
though the two only differs by a factor of two at low temperature.
|
b7e46c1a-954c-45f3-b799-6047d881b031 | b7e46c1a-954c-45f3-b799-6047d881b031 | b7e46c1a-954c-45f3-b799-6047d881b031 | human | null | null | none | abstracts | Extraction of physical laws from joint experimental data | null | The extraction of a physical law y=yo(x) from joint experimental data about x
and y is treated. The joint, the marginal and the conditional probability
density functions (PDF) are expressed by given data over an estimator whose
kernel is the instrument scattering function. As an optimal estimator of yo(x)
the conditional average is proposed. The analysis of its properties is based
upon a new definition of prediction quality. The joint experimental information
and the redundancy of joint measurements are expressed by the relative entropy.
With the number of experiments the redundancy on average increases, while the
experimental information converges to a certain limit value. The difference
between this limit value and the experimental information at a finite number of
data represents the discrepancy between the experimentally determined and the
true properties of the phenomenon. The sum of the discrepancy measure and the
redundancy is utilized as a cost function. By its minimum a reasonable number
of data for the extraction of the law yo(x) is specified. The mutual
information is defined by the marginal and the conditional PDFs of the
variables. The ratio between mutual information and marginal information is
used to indicate which variable is the independent one. The properties of the
introduced statistics are demonstrated on deterministically and randomly
related variables.
|
d693a8c5-1b93-43af-956b-c6ecc54929ed | d693a8c5-1b93-43af-956b-c6ecc54929ed | d693a8c5-1b93-43af-956b-c6ecc54929ed | human | null | null | none | abstracts | Kinetic equation for finite systems of fermions with pairing | null | The solutions of the Wigner-transformed time-dependent
Hartree--Fock--Bogoliubov equations are studied in the constant-$\Delta$
approximation. This approximation is known to violate particle-number
conservation. As a consequence, the density fluctuation and the longitudinal
response function given by this approximation contain spurious contributions. A
simple prescription for restoring both local and global particle-number
conservation is proposed. Explicit expressions for the eigenfrequencies of the
correlated systems and for the density response function are derived and it is
shown that the semiclassical analogous of the quantum single--particle spectrum
has an excitation gap of $2\Delta$, in agreement with the quantum result. The
collective response is studied for a simplified form of the residual
interaction.
|
c9f0f74d-08a2-4511-b47b-728c22d82242 | c9f0f74d-08a2-4511-b47b-728c22d82242 | c9f0f74d-08a2-4511-b47b-728c22d82242 | human | null | null | none | abstracts | Hadrons in Medium -- Theory confronts experiment | null | In this talk we briefly summarize our theoretical understanding of in-medium
selfenergies of hadrons. With the special case of the $\omega$ meson we
demonstrate that earlier calculations that predicted a significant lowering of
the mass in medium are based on an incorrect treatment of the model Lagrangian;
more consistent calculations lead to a significant broadening, but hardly any
mass shift. We stress that the experimental reconstruction of hadron spectral
functions from measured decay products always requires knowledge of the decay
branching ratios which may also be strongly mass-dependent. It also requires a
quantitatively reliable treatment of final state interactions which has to be
part of any reliable theory.
|
c7cced45-d2ce-4a8d-b728-edc7c9ed9d39 | c7cced45-d2ce-4a8d-b728-edc7c9ed9d39 | c7cced45-d2ce-4a8d-b728-edc7c9ed9d39 | human | null | null | none | abstracts | A computer program for fast non-LTE analysis of interstellar line
spectra | null | The large quantity and high quality of modern radio and infrared line
observations require efficient modeling techniques to infer physical and
chemical parameters such as temperature, density, and molecular abundances. We
present a computer program to calculate the intensities of atomic and molecular
lines produced in a uniform medium, based on statistical equilibrium
calculations involving collisional and radiative processes and including
radiation from background sources. Optical depth effects are treated with an
escape probability method. The program is available on the World Wide Web at
http://www.sron.rug.nl/~vdtak/radex/index.shtml . The program makes use of
molecular data files maintained in the Leiden Atomic and Molecular Database
(LAMDA), which will continue to be improved and expanded. The performance of
the program is compared with more approximate and with more sophisticated
methods. An Appendix provides diagnostic plots to estimate physical parameters
from line intensity ratios of commonly observed molecules. This program should
form an important tool in analyzing observations from current and future radio
and infrared telescopes.
|
07a94f40-7702-426c-8651-c5f4cf6cb24c | 07a94f40-7702-426c-8651-c5f4cf6cb24c | 07a94f40-7702-426c-8651-c5f4cf6cb24c | human | null | null | none | abstracts | Alternative Approaches to the Equilibrium Properties of Hard-Sphere
Liquids | null | An overview of some analytical approaches to the computation of the
structural and thermodynamic properties of single component and multicomponent
hard-sphere fluids is provided. For the structural properties, they yield a
thermodynamically consistent formulation, thus improving and extending the
known analytical results of the Percus-Yevick theory. Approximate expressions
for the contact values of the radial distribution functions and the
corresponding analytical equations of state are also discussed. Extensions of
this methodology to related systems, such as sticky hard spheres and
square-well fluids, as well as its use in connection with the perturbation
theory of fluids are briefly addressed.
|
650e2823-968a-490c-8956-a0eb560acc80 | 650e2823-968a-490c-8956-a0eb560acc80 | 650e2823-968a-490c-8956-a0eb560acc80 | human | null | null | none | abstracts | Evidence for an excitonic insulator phase in 1T-TiSe$_{2}$ | null | We present a new high-resolution angle-resolved photoemission study of
1\textit{T}-TiSe$_{2}$ in both, its room-temperature, normal phase and its
low-temperature, charge-density wave phase. At low temperature the
photoemission spectra are strongly modified, with large band renormalisations
at high-symmetry points of the Brillouin zone and a very large transfer of
spectral weight to backfolded bands. A theoretical calculation of the spectral
function for an excitonic insulator phase reproduces the experimental features
with very good agreement. This gives strong evidence in favour of the excitonic
insulator scenario as a driving force for the charge-density wave transition in
1\textit{T}-TiSe$_{2}$.
|
81b6d6b3-a8af-491a-8ef8-8b0e46157d28 | 81b6d6b3-a8af-491a-8ef8-8b0e46157d28 | 81b6d6b3-a8af-491a-8ef8-8b0e46157d28 | human | null | null | none | abstracts | Oxygen-rich droplets and the enrichment of the ISM | null | We argue that the discrepancies observed in HII regions between abundances
derived from optical recombination lines (ORLs) and collisionally excited lines
(CELs) might well be the signature of a scenario of the enrichment of the
interstellar medium (ISM) proposed by Tenorio-Tagle (1996). In this scenario,
the fresh oxygen released during massive supernova explosions is confined
within the hot superbubbles as long as supernovae continue to explode. Only
after the last massive supernova explosion, the metal-rich gas starts cooling
down and falls on the galaxy within metal-rich droplets. Full mixing of these
metal-rich droplets and the ISM occurs during photoionization by the next
generations of massive stars. During this process, the metal-rich droplets give
rise to strong recombination lines of the metals, leading to the observed
ORL-CEL discrepancy. (The full version of this work is submitted to Astronomy
and Astrophysics.)
|
42c464f3-e0f7-42ff-ae10-8b828f1f0bf3 | 42c464f3-e0f7-42ff-ae10-8b828f1f0bf3 | 42c464f3-e0f7-42ff-ae10-8b828f1f0bf3 | human | null | null | none | abstracts | Estimation of experimental data redundancy and related statistics | null | Redundancy of experimental data is the basic statistic from which the
complexity of a natural phenomenon and the proper number of experiments needed
for its exploration can be estimated. The redundancy is expressed by the
entropy of information pertaining to the probability density function of
experimental variables. Since the calculation of entropy is inconvenient due to
integration over a range of variables, an approximate expression for redundancy
is derived that includes only a sum over the set of experimental data about
these variables. The approximation makes feasible an efficient estimation of
the redundancy of data along with the related experimental information and
information cost function. From the experimental information the complexity of
the phenomenon can be simply estimated, while the proper number of experiments
needed for its exploration can be determined from the minimum of the cost
function. The performance of the approximate estimation of these statistics is
demonstrated on two-dimensional normally distributed random data.
|
7edc9fae-3fa6-420e-b412-bb721879cda4 | 7edc9fae-3fa6-420e-b412-bb721879cda4 | 7edc9fae-3fa6-420e-b412-bb721879cda4 | human | null | null | none | abstracts | Effective potentials for quasicrystals from ab-initio data | null | Classical effective potentials are indispensable for any large-scale
atomistic simulations, and the relevance of simulation results crucially
depends on the quality of the potentials used. For complex alloys like
quasicrystals, however, realistic effective potentials are practically
inexistent. We report here on our efforts to develop effective potentials
especially for quasicrystalline alloy systems. We use the so-called force
matching method, in which the potential parameters are adapted so as to
optimally reproduce the forces and energies in a set of suitably chosen
reference configurations. These reference data are calculated with ab-initio
methods. As a first application, EAM potentials for decagonal Al-Ni-Co,
icosahedral Ca-Cd, and both icosahedral and decagonal Mg-Zn quasicrystals have
been constructed. The influence of the potential range and degree of
specialisation on the accuracy and other properties is discussed and compared.
|
8ff00a19-3b77-436c-b435-33e23fa3dbfe | 8ff00a19-3b77-436c-b435-33e23fa3dbfe | 8ff00a19-3b77-436c-b435-33e23fa3dbfe | human | null | null | none | abstracts | Supersymmetry breaking metastable vacua in runaway quiver gauge theories | null | In this paper we consider quiver gauge theories with fractional branes whose
infrared dynamics removes the classical supersymmetric vacua (DSB branes). We
show that addition of flavors to these theories (via additional non-compact
branes) leads to local meta-stable supersymmetry breaking minima, closely
related to those of SQCD with massive flavors. We simplify the study of the
one-loop lifting of the accidental classical flat directions by direct
computation of the pseudomoduli masses via Feynman diagrams. This new approach
allows to obtain analytic results for all these theories. This work extends the
results for the $dP_1$ theory in hep-th/0607218. The new approach allows to
generalize the computation to general examples of DSB branes, and for arbitrary
values of the superpotential couplings.
|
b9dcf79d-3b4a-4760-9423-2cab26bb23fe | b9dcf79d-3b4a-4760-9423-2cab26bb23fe | b9dcf79d-3b4a-4760-9423-2cab26bb23fe | human | null | null | none | abstracts | Symmetry disquisition on the TiOX phase diagram | null | The sequence of phase transitions and the symmetry of in particular the low
temperature incommensurate and spin-Peierls phases of the quasi one-dimensional
inorganic spin-Peierls system TiOX (TiOBr and TiOCl) have been studied using
inelastic light scattering experiments. The anomalous first-order character of
the transition to the spin-Peierls phase is found to be a consequence of the
different symmetries of the incommensurate and spin-Peierls (P$2_{1}/m$)
phases.
The pressure dependence of the lowest transition temperature strongly
suggests that magnetic interchain interactions play an important role in the
formation of the spin-Peierls and the incommensurate phases. Finally, a
comparison of Raman data on VOCl to the TiOX spectra shows that the high energy
scattering observed previously has a phononic origin.
|
d0dd3bc7-355c-4ca6-bde9-51f26391ee1e | d0dd3bc7-355c-4ca6-bde9-51f26391ee1e | d0dd3bc7-355c-4ca6-bde9-51f26391ee1e | human | null | null | none | abstracts | Discovery of a point-like very-high-energy gamma-ray source in Monoceros | null | The complex Monoceros Loop SNR/Rosette Nebula region contains several
potential sources of very-high-energy (VHE) gamma-ray emission and two as yet
unidentified high-energy EGRET sources. Sensitive VHE observations are required
to probe acceleration processes in this region. The H.E.S.S. telescope array
has been used to search for very high-energy gamma-ray sources in this region.
CO data from the NANTEN telescope were used to map the molecular clouds in the
region, which could act as target material for gamma-ray production via
hadronic interactions. We announce the discovery of a new gamma-ray source,
HESS J0632+058, located close to the rim of the Monoceros SNR. This source is
unresolved by H.E.S.S. and has no clear counterpart at other wavelengths but is
possibly associated with the weak X-ray source 1RXS J063258.3+054857, the
Be-star MWC 148 and/or the lower energy gamma-ray source 3EG J0634+0521. No
evidence for an associated molecular cloud was found in the CO data.
|
915e6628-caff-4c99-8044-baecfbc68e54 | 915e6628-caff-4c99-8044-baecfbc68e54 | 915e6628-caff-4c99-8044-baecfbc68e54 | human | null | null | none | abstracts | Reparametrization Invariance, the controversial extraction of $\alpha$
from $B\to\pi\pi$ and New Physics | null | The extraction of the weak phase $\alpha$ from $B\to\pi\pi$ decays has been
controversial from a statistical point of view, as the frequentist vs. bayesian
confrontation shows. We analyse several relevant questions which have not
deserved full attention and pervade the extraction of $\alpha$.
Reparametrization Invariance proves appropriate to understand those issues. We
show that some Standard Model inspired parametrizations can be senseless or
inadequate if they go beyond the minimal Gronau and London assumptions: the
single weak phase $\alpha$ just in the $\Delta I=3/2$ amplitudes, the isospin
relations and experimental data. Beside those analyses, we extract $\alpha$
through the use of several adequate parametrizations, showing that there is no
relevant discrepancy between frequentist and bayesian results. The most
relevant information, in terms of $\alpha$, is the exclusion of values around
$\alpha\sim \pi/4$; this result is valid in the presence of arbitrary New
Physics contributions to the $\Delta I=1/2$ piece.
|
3745bd2d-efa9-44f9-93a9-84daff7eeb9e | 3745bd2d-efa9-44f9-93a9-84daff7eeb9e | 3745bd2d-efa9-44f9-93a9-84daff7eeb9e | human | null | null | none | abstracts | Solar System Constraints on Gauss-Bonnet Mediated Dark Energy | null | Although the Gauss-Bonnet term is a topological invariant for general
relativity, it couples naturally to a quintessence scalar field, modifying
gravity at solar system scales. We determine the solar system constraints due
to this term by evaluating the post-Newtonian metric for a distributional
source. We find a mass dependent, 1/r^7 correction to the Newtonian potential,
and also deviations from the Einstein gravity prediction for light-bending. We
constrain the parameters of the theory using planetary orbits, the Cassini
spacecraft data, and a laboratory test of Newton's law, always finding
extremely tight bounds on the energy associated to the Gauss-Bonnet term. We
discuss the relevance of these constraints to late-time cosmological
acceleration.
|
a64356af-9ee7-4b9c-9e18-3a9b4896f3df | a64356af-9ee7-4b9c-9e18-3a9b4896f3df | a64356af-9ee7-4b9c-9e18-3a9b4896f3df | human | null | null | none | abstracts | Switching mechanism of photochromic diarylethene derivatives molecular
junctions | null | The electronic transport properties and switching mechanism of single
photochromic diarylethene derivatives sandwiched between two gold surfaces with
closed and open configurations are investigated by a fully self-consistent
nonequilibrium Green's function method combined with density functional theory.
The calculated transmission spectra of two configurations are strikingly
distinctive. The open form lacks any significant transmission peak within a
wide energy window, while the closed structure has two significant transmission
peaks on the both sides of the Fermi level. The electronic transport properties
of the molecular junction with closed structure under a small bias voltage are
mainly determined by the tail of the transmission peak contributed unusually by
the perturbed lowest perturbed unoccupied molecular orbital. The calculated
on-off ratio of currents between the closed and open configurations is about
two orders of magnitude, which reproduces the essential features of the
experimental measured results. Moreover, we find that the switching behavior
within a wide bias voltage window is extremely robust to both substituting F or
S for H or O and varying end anchoring atoms from S to Se and Te.
|
9ec625e9-0d4a-4a6f-b845-c482fc50f61c | 9ec625e9-0d4a-4a6f-b845-c482fc50f61c | 9ec625e9-0d4a-4a6f-b845-c482fc50f61c | human | null | null | none | abstracts | Huge magneto-crystalline anisotropy of x-ray linear dichroism observed
on Co/FeMn bilayers | null | We present an x-ray spectromicroscopic investigation of single-crystalline
magnetic FeMn/Co bilayers on Cu(001), using X-ray magnetic circular (XMCD) and
linear (XMLD) dichroism at the Co and Fe L3 absorption edges in combination
with photoelectron emission microscopy (PEEM). Using the magnetic coupling
between the ferromagnetic Co layer and the antiferromagnetic FeMn layer we are
able to produce magnetic domains with two different crystallographic
orientations of the magnetic easy axis within the same sample at the same time.
We find a huge difference in the XMLD contrast between the two types of
magnetic domains, which we discuss in terms of intrinsic magneto-crystalline
anisotropy of XMLD of the Co layer. We also demonstrate that due to the high
sensitivity of the method, the small number of induced ferromagnetic Fe moments
at the FeMn-Co interface is sufficient to obtain magnetic contrast from XMLD in
a metallic system.
|
fdb29030-ce84-48a8-bd64-c404e6b358ea | fdb29030-ce84-48a8-bd64-c404e6b358ea | fdb29030-ce84-48a8-bd64-c404e6b358ea | human | null | null | none | abstracts | Temperature Dependence of the Tensile Properties of Single Walled Carbon
Nanotubes: O(N) Tight Binding MD Simulation | null | This paper examines the effect of temperature on the structural stability and
mechanical properties of 20 layered (10,10) single walled carbon nanotubes
(SWCNTs) under tensile loading using an O(N) tight binding molecular dynamics
(TBMD) simulation method. We observed that (10,10) tube can sustain its
structural stability for the strain values of 0.23 in elongation and 0.06 in
compression at 300K. Bond breaking strain value decreases with increasing
temperature under streching but not under compression. The elastic limit,
Young's modulus, tensile strength and Poisson ratio are calculated as 0.10,
0.395 TPa, 83.23 GPa, 0.285, respectively, at 300K. In the temperature range
from 300K to 900K; Young's modulus and the tensile strengths are decreasing
with increasing temperature while the Poisson ratio is increasing. At higher
temperatures, Young's modulus starts to increase while the Poisson ratio and
tensile strength decrease. In the temperature range from 1200K to 1800K, the
SWCNT is already deformed and softened. Applying strain on these deformed and
softened SWCNTs do not follow the same pattern as in the temperature range of
300K to 900K.
|
6f1a2ee2-1b96-409f-8ae3-3122e6c00ee2 | 6f1a2ee2-1b96-409f-8ae3-3122e6c00ee2 | 6f1a2ee2-1b96-409f-8ae3-3122e6c00ee2 | human | null | null | none | abstracts | Monoid generalizations of the Richard Thompson groups | null | The groups G_{k,1} of Richard Thompson and Graham Higman can be generalized
in a natural way to monoids, that we call M_{k,1}, and to inverse monoids,
called Inv_{k,1}; this is done by simply generalizing bijections to partial
functions or partial injective functions. The monoids M_{k,1} have connections
with circuit complexity (studied in another paper). Here we prove that M_{k,1}
and Inv_{k,1} are congruence-simple for all k. Their Green relations J and D
are characterized: M_{k,1} and Inv_{k,1} are J-0-simple, and they have k-1
non-zero D-classes. They are submonoids of the multiplicative part of the Cuntz
algebra O_k. They are finitely generated, and their word problem over any
finite generating set is in P. Their word problem is coNP-complete over certain
infinite generating sets.
Changes in this version: Section 4 has been thoroughly revised, and errors
have been corrected; however, the main results of Section 4 do not change.
Sections 1, 2, and 3 are unchanged, except for the proof of Theorem 2.3, which
was incomplete; a complete proof was published in the Appendix of reference
[6], and is also given here.
|
ce01e69e-93f1-4edb-9805-be4719456262 | ce01e69e-93f1-4edb-9805-be4719456262 | ce01e69e-93f1-4edb-9805-be4719456262 | human | null | null | none | abstracts | The Reliability on the Direction of the Incident Neutrino for the Fully
Contained Events and Partially Contained Events due to QEL in the
Super-Kamiokande | null | In the SK analysis of the neutrino events for [Fully Contained Events] and
[Partially Contained Events] on their zenith angle distribution, it is assumed
that the zenith angle of the incident neutrino is the same as that of the
detected charged lepton. In the present paper, we examine the validity of [the
SK assumption on the direction] of the incident neutrinos. Concretely speaking,
we analyze muon-like events due to QEL. For the purpose, we develop [Time
Sequential Monte Carlo Simulation] to extract the conclusion on the validity of
the SK assumption. In our [Time Sequential Simulation], we simulate every
physical process concerned as exactly as possible without any approximation.
From the comparison between the zenith angle distributon of the emitted muons
under [the SK assumption on the direction] and the corresponding one obtained
under our [Time Sequential Simulation], it is concluded that the measurement of
the direction of the incident neutrino for the neutrino events occurring inside
the detector in the SK analysis turns out to be unreliable, which holds
irrespective of the existence and/or non-existence of the neutrino oscillation.
|
00afe8c2-3519-4d8e-b343-e377a8767e81 | 00afe8c2-3519-4d8e-b343-e377a8767e81 | 00afe8c2-3519-4d8e-b343-e377a8767e81 | human | null | null | none | abstracts | Intricate Knots in Proteins: Function and Evolution | null | A number of recently discovered protein structures incorporate a rather
unexpected structural feature: a knot in the polypeptide backbone. These knots
are extremely rare, but their occurrence is likely connected to protein
function in as yet unexplored fashion. Our analysis of the complete Protein
Data Bank reveals several new knots which, along with previously discovered
ones, can shed light on such connections. In particular, we identify the most
complex knot discovered to date in human ubiquitin hydrolase, and suggest that
its entangled topology protects it against unfolding and degradation by the
proteasome. Knots in proteins are typically preserved across species and
sometimes even across kingdoms. However, we also identify a knot which only
appears in some transcarbamylases while being absent in homologous proteins of
similar structure. The emergence of the knot is accompanied by a shift in the
enzymatic function of the protein. We suggest that the simple insertion of a
short DNA fragment into the gene may suffice to turn an unknotted into a
knotted structure in this protein.
|
75e65872-3481-450a-a8c9-a8e2bbbcacf9 | 75e65872-3481-450a-a8c9-a8e2bbbcacf9 | 75e65872-3481-450a-a8c9-a8e2bbbcacf9 | human | null | null | none | abstracts | Star Formation in Galaxies with Large Lower Surface Brightness Disks | null | We present B, R, and Halpha imaging data of 19 large disk galaxies whose
properties are intermediate between classical low surface brightness galaxies
and ordinary high surface brightness galaxies. We use data taken from the
Lowell 1.8m Perkins telescope to determine the galaxies' overall morphology,
color, and star formation properties. Morphologically, the galaxies range from
Sb through Irr and include galaxies with and without nuclear bars. The colors
of the galaxies vary from B-R = 0.3 - 1.9, and most show at least a slight
bluing of the colors with increasing radius. The Halpha images of these
galaxies show an average star formation rate lower than is found for similar
samples with higher surface brightness disks. Additionally, the galaxies
studied have both higher gas mass-to-luminosity and diffuse Halpha emission
than is found in higher surface brightness samples.
|
ccecf094-ff51-4c78-81c3-46578263c8f7 | ccecf094-ff51-4c78-81c3-46578263c8f7 | ccecf094-ff51-4c78-81c3-46578263c8f7 | human | null | null | none | abstracts | Quantum mechanical approach to decoherence and relaxation generated by
fluctuating environment | null | We consider an electrostatic qubit, interacting with a fluctuating charge of
single electron transistor (SET) in the framework of exactly solvable model.
The SET plays a role of the fluctuating environment affecting the qubit's
parameters in a controllable way. We derive the rate equations describing
dynamics of the entire system for both weak and strong qubit-SET coupling.
Solving these equation we obtain decoherence and relaxation rates of the qubit,
as well as the spectral density of the fluctuating qubit's parameters. We found
that in the weak coupling regime the decoherence and relaxation rates are
directly related to the spectral density taken at Rabi or at zero frequency,
depending on what a particular qubit's parameters is fluctuating. This relation
holds also in the presence of weak back-action of the qubit on the fluctuating
environment. In the case of strong back-action, such simple relationship no
longer holds, even if the qubit-SET coupling is small. It does not hold either
in the strong-coupling regime, even in the absence of the back-action. In
addition, we found that our model predicts localization of the qubit in the
strong-coupling regime, resembling that of the spin-boson model.
|
4e0aa949-cb44-4bf1-9952-58356b417687 | 4e0aa949-cb44-4bf1-9952-58356b417687 | 4e0aa949-cb44-4bf1-9952-58356b417687 | human | null | null | none | abstracts | Group-theoretical properties of nilpotent modular categories | null | We characterize a natural class of modular categories of prime power
Frobenius-Perron dimension as representation categories of twisted doubles of
finite p-groups. We also show that a nilpotent braided fusion category C admits
an analogue of the Sylow decomposition. If the simple objects of C have
integral Frobenius-Perron dimensions then C is group-theoretical. As a
consequence, we obtain that semisimple quasi-Hopf algebras of prime power
dimension are group-theoretical. Our arguments are based on a reconstruction of
twisted group doubles from Lagrangian subcategories of modular categories (this
is reminiscent to the characterization of doubles of quasi-Lie bialgebras in
terms of Manin pairs).
|
0bd532ca-dd6e-43a8-9db4-f1a15924b3be | 0bd532ca-dd6e-43a8-9db4-f1a15924b3be | 0bd532ca-dd6e-43a8-9db4-f1a15924b3be | human | null | null | none | abstracts | Analysis of random Boolean networks using the average sensitivity | null | In this work we consider random Boolean networks that provide a general model
for genetic regulatory networks. We extend the analysis of James Lynch who was
able to proof Kauffman's conjecture that in the ordered phase of random
networks, the number of ineffective and freezing gates is large, where as in
the disordered phase their number is small. Lynch proved the conjecture only
for networks with connectivity two and non-uniform probabilities for the
Boolean functions. We show how to apply the proof to networks with arbitrary
connectivity $K$ and to random networks with biased Boolean functions. It turns
out that in these cases Lynch's parameter $\lambda$ is equivalent to the
expectation of average sensitivity of the Boolean functions used to construct
the network. Hence we can apply a known theorem for the expectation of the
average sensitivity. In order to prove the results for networks with biased
functions, we deduct the expectation of the average sensitivity when only
functions with specific connectivity and specific bias are chosen at random.
|
f73fa207-367f-4d58-a498-2286261970bc | f73fa207-367f-4d58-a498-2286261970bc | f73fa207-367f-4d58-a498-2286261970bc | human | null | null | none | abstracts | Electromagnetic polarizabilities and the excited states of the nucleon | null | The electromagnetic polarizabilities of the nucleon are shown to be
essentially composed of the nonresonant $\alpha_p(E_{0+})=+3.2$,
$\alpha_n(E_{0+})=+4.1$,the $t$-channel $\alpha^t_{p,n}=-\beta^t_{p,n}=+7.6$
and the resonant $\beta_{p,n}(P_{33}(1232))=+8.3$ contributions (in units of
$10^{-4}$fm$^3$. The remaining deviations from the experimental data
$\Delta\alpha_p=1.2\pm 0.6$, $\Delta\beta_p=1.2\mp 0.6$, \Delta\alpha_n=0.8\pm
1.7$ and $\Delta\beta_n=2.0\mp 1.8$ are contributed by a larger number of
resonant and nonresonant processes with cancellations between the
contributions. This result confirms that dominant contributions to the electric
and magnetic polarizabilities may be represented in terms of two-photon
couplings to the $\sigma$-meson having the predicted mass $m_\sigma=666$ MeV
and two-photon width $\Gamma_{\gamma\gamma}=2.6$ keV.
|
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