id stringlengths 16 29 | text stringlengths 86 3.49k | source stringlengths 14 112 |
|---|---|---|
arxiv_dataset-1200904.3334 | The Influence of Galaxy Formation Physics on Weak Lensing Tests of
General Relativity
astro-ph.CO astro-ph.GA
Forthcoming projects such as the DES, a JDEM, and LSST, aim to measure weak
lensing shear correlations with unprecedented accuracy. Weak lensing
observables are sensitive to both the distance-redshift relation and the growth
of structure in the Universe. If the cause of accelerated cosmic expansion is
dark energy within general relativity (GR), both cosmic distances and structure
growth are governed by the properties of dark energy. Consequently, one may use
lensing to check for this consistency and test GR. After reviewing the
phenomenology of such tests, we address one major challenge to such a program.
The evolution of the baryonic component of the Universe is highly uncertain and
can influence lensing observables, manifesting as modified structure growth for
a fixed cosmic distance scale. Using two proposed methods, we show that one
could be led to reject the null hypothesis of GR when it is the true theory if
this uncertainty in baryonic processes is neglected. Recent simulations suggest
that we can correct for baryonic effects using a parametrized model in which
the halo mass-concentration relation is modified. The correction renders biases
small compared to statistical uncertainties. We study the ability of future
weak lensing surveys to constrain the internal structures of halos and test the
null hypothesis of GR simultaneously. Compared to nulling information from
small-scales to mitigate sensitivity to baryonic physics, this internal
calibration program should provide limits on deviations from GR that are
several times more constraining. Specifically, we find that limits on general
relativity in the case of internal calibration are degraded by only ~30% or
less compared to the case of perfect knowledge of nonlinear structure.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-1201904.3434 | Drinfeld-Sokolov hierarchies of type A and fourth order Painleve systems
math-ph math.MP math.RT
We study the Drinfeld-Sokolov hierarchies of type A_n^{(1)} associated with
the regular conjugacy classes of W(A_n). A class of fourth order Painleve
systems is derived from them by similarity reductions.
| arxiv topic:math-ph math.MP math.RT |
arxiv_dataset-1202904.3534 | Solubilization of Proteins in 2DE: An Outline
q-bio.GN
Protein solubilization for two-dimensional electrophoresis (2DE) has to break
molecular interactions to separate the biological contents of the material of
interest into isolated and intact polypeptides. This must be carried out in
conditions compatible with the first dimension of 2DE, namely isoelectric
focusing. In addition, the extraction process must enable easy removal of any
nonprotein component interfering with the isoelectric focusing. The constraints
brought in this process by the peculiar features of isoelectric focusing are
discussed, as well as their consequences in terms of possible solutions and
limits for the solubilization process.
| arxiv topic:q-bio.GN |
arxiv_dataset-1203904.3634 | Tailored business solutions by workflow technologies
cs.SE
VISP (Virtual Internet Service Provider) is an IST-STREP project, which is
conducting research in the field of these new technologies, targeted to
telecom/ISP companies. One of the first tasks of the VISP project is to
identify the most appropriate technologies in order to construct the VISP
platform. This paper presents the most significant results in the field of
choreography and orchestration, two key domains that must accompany process
modeling in the construction of a workflow environment.
| arxiv topic:cs.SE |
arxiv_dataset-1204904.3734 | Experimental and theoretical study of oxygen adsorption structures on
Ag(111)
cond-mat.mtrl-sci
The oxidized Ag(111) surface has been studied by a combination of
experimental and theoretical methods, scanning tunneling microscopy (STM),
x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). A
large variety of different surface structures is found, depending on the
detailed preparation conditions. The observed structures fall into four
classes: (a) individually chemisorbed atomic oxygen atoms, (b) three different
oxygen overlayer structures, including the well-known p(4 x 4) phase, formed
from the same Ag$_6$ and Ag$_{10}$ building blocks, (c) a c(4 x 8) structure
not previously observed, and (d) at higher oxygen coverages structures
characterized by stripes along the high-symmetry directions of the Ag(111)
substrate. Our analysis provides a detailed explanation of the atomic-scale
geometry of the Ag$_6$/Ag$_{10}$ building block structures, and the c(4 x 8)
and stripe structures are discussed in detail. The observation of many
different and co-existing structures implies that the O/Ag(111) system is
characterized by a significantly larger degree of complexity than previously
anticipated, and this will impact our understanding of oxidation catalysis
processes on Ag catalysts.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-1205904.3834 | On the Kohn--Sham density response in a localized basis set
cond-mat.other physics.chem-ph physics.comp-ph
We construct the Kohn--Sham density response function $\chi_{0}$ in a
previously described basis of the space of orbital products. The calculational
complexity of our construction is $O(N^{2}N_{\omega})$ for a molecule of $N$
atoms and in a spectroscopic window of $N_{\omega}$ frequency points. As a
first application, we use $\chi_{0}$ to calculate molecular spectra from the
Petersilka--Gossmann--Gross equation. With $\chi_{0}$ as input, we obtain
correct spectra with an extra computational effort that grows also as $O(N^2
N_{\omega})$ and, therefore, less steeply in $N$ than the $O(N^{3})$ complexity
of solving Casida's equations. Our construction should be useful for the study
of excitons in molecular physics and in related areas where $\chi_{0}$ is a
crucial ingredient.
| arxiv topic:cond-mat.other physics.chem-ph physics.comp-ph |
arxiv_dataset-1206904.3934 | Effects of Primordial Mass Segregation on the Dynamical Evolution of
Star Clusters
astro-ph.GA
In this paper we use N-body simulations to study the effects of primordial
mass segregation on the early and long-term evolution of star clusters. Our
simulations show that in segregated clusters early mass loss due to stellar
evolution triggers a stronger expansion than for unsegregated clusters. Tidally
limited, strongly segregated clusters may dissolve rapidly as a consequence of
this early expansion, while segregated clusters initially underfilling their
Roche lobe can survive the early expansion and have a lifetime similar to that
of unsegregated clusters. Long-lived initially segregated clusters tend to have
looser structure and reach core collapse later in their evolution than
initially unsegregated clusters. We have also compared the effects of dynamical
evolution on the global stellar mass function (MF) of low-mass main sequence
stars. In all cases the MF flattens as the cluster loses stars. The amount of
MF flattening induced by a given amount of mass loss in a rapidly dissolving
initially segregated cluster is less than for an unsegregated cluster. The
evolution of the MF of a long-lived segregated cluster, on the other hand, is
very similar to that of an initially unsegregated cluster.
| arxiv topic:astro-ph.GA |
arxiv_dataset-1207904.4034 | Multiple-quantized vortices in rotating LOFF state of ultracold Fermi
superfluid gas
cond-mat.quant-gas cond-mat.supr-con hep-ph nucl-th
A rotating ultracold S-wave superfluid Fermi gas is considered, when the
population imbalance (or equivalently the mismatch in chemical potentials)
corresponds to the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state in the
vicinity of the Lifshitz critical point. It is shown that under these
conditions the critical angular velocity in two-dimensional systems is an
oscillating function of temperature and population imbalance giving rise to
reentrant superfluid phases. This leads to vortex lattices with
multiple-quantized circulation quanta. The reason for this behavior is the
population by Cooper pairs of the Landau levels above the lowest one.
| arxiv topic:cond-mat.quant-gas cond-mat.supr-con hep-ph nucl-th |
arxiv_dataset-1208904.4134 | AKARI/IRC observations of heavily obscured oxygen-rich AGB and post-AGB
stars
astro-ph.SR
We present AKARI/IRC observations of a sample of six extremely red IRAS
sources, of which three are variable OH/IR stars and the rest are early
post-AGB stars. The OH/IR stars show a red continuum with the expected strong
10 micron silicate absorption feature, while the post-AGB stars show an even
redder continuum accompanied with a comparably weak silicate absorption. We
modelled the spectral energy distributions with DUSTY. While for the OH/IR
stars a reasonable fit can be obtained with almost pure silicate dust, the
post-AGB stars require a mixture of silicate and carbon-rich dust. We assume
that in the latter objects the inner dust shell is carbon-rich, while the outer
shells are still oxygen-rich.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1209904.4234 | A reassessment of the Burns temperature and its relationship to the
diffuse scattering, lattice dynamics, and thermal expansion in the relaxor
PMN
cond-mat.mtrl-sci
We have used neutron scattering techniques to characterize the diffuse
scattering and lattice dynamics in single crystals of the relaxor PMN from 10K
to 900K. We observed two distinct types of diffuse scattering. The first is
weak, relatively temperature independent, persists to at least 900 K, and forms
bow-tie-shaped patterns in reciprocal space centered on (h00) Bragg peaks. We
associate this primarily with chemical short-range order. The second is strong,
temperature dependent, and forms butterfly-shaped patterns centered on (h00)
Bragg peaks. This diffuse scattering has been attributed to the PNR because it
responds to an electric field and vanishes near Td ~ 620K when measured with
thermal neutrons. Surprisingly, it vanishes at 420K when measured with cold
neutrons, which provide ~4 times superior energy resolution. That this onset
temperature depends on the instrumental energy resolution demands a
reassessment of the Burns temperature Td. Neutron backscattering measurements
made with 300 times better energy resolution confirm the onset temperature of
420+/-20K. The energy width of the diffuse scattering is resolution limited,
indicating that the PNR are static on timescales of at least 2 nsec. Transverse
acoustic (TA) phonon lifetimes are temperature independent up to 900K for q <
0.2 1/A. This motivates a physical picture in which sufficiently
long-wavelength TA phonons average over the PNR; only those TA phonons having
wavelengths comparable to the size of the PNR are affected. The PMN lattice
constant changes by less than 0.001 Angstroms below 300K, but expands rapidly
at a rate of 2.5x10^-5 1/K at high temperature. The regimes of low and high
thermal expansion bracket the revised value of Td, which suggests the anomalous
thermal expansion results from the condensation of static PNR.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-1210904.4334 | Spin-1/2 fermions with attractive interaction in an optical lattice
cond-mat.quant-gas
We study attractive fermions in an optical lattice superimposed by a trapping
potential, such that fermions may form bosonic molecules. We map the model onto
nonlinear field equations depending on the Nambu-Gor'kov propagator. The
resulting field equations where solved numerically by a relaxation technique
that allowed us to calculate the inhomogeneous densities of fermions and
condensed molecules at zero temperature. When the interactions between fermions
are strong there is a competition between unbound fermions and bound molecules
leading to an unexpected reduction of the non-homogeneous density of fermions
at the center of the trap.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-1211904.4434 | Uneven horizon or several words about the superfluid He-4 theory
cond-mat.other
The state of the superfluid He-II theory is briefly surveyed - some aspects
of its history, achievements, and unsolved problems.
| arxiv topic:cond-mat.other |
arxiv_dataset-1212904.4534 | Texture specific mass matrices with Dirac neutrinos and their
implications
hep-ph
Considering Dirac neutrinos and Fritzsch-like texture 6 zero and 5 zero mass
matrices, detailed predictions for cases pertaining to normal/inverted
hierarchy as well as degenerate scenario of neutrino masses have been carried
out. All the cases considered here pertaining to inverted hierarchy and
degenerate scenario of neutrino masses are ruled out by the existing data. For
the normal hierarchy cases, the lower limit of m_nu_1 and of s_13 as well as
the range of Dirac-like CP violating phase delta_l would have implications for
the texture specific cases considered here.
| arxiv topic:hep-ph |
arxiv_dataset-1213904.4634 | High-resolution Resonance Bragg-scattering spectroscopy of an atomic
transition from a population difference grating in a vapor cell
physics.atom-ph physics.optics
The laser spectroscopy with a narrow linewidth and high signal to noise ratio
(S/N) is very important in the precise measurement of optical frequencies.
Here, we present a novel high-resolution backward resonance Bragg-scattering
(RBS) spectroscopy from a population difference grating (PDG). The PDG is
formed by a standing-wave (SW) pump field in thermal 87Rb vapor, which
periodically modulates the space population distribution of two levels in the
87Rb D1 line. A probe beam, having the identical frequency and the orthogonal
polarization with the SW pump field, is Bragg-scattered by the PDG. Such
Bragg-scattered light becomes stronger at an atomic resonance transition, which
forms the RBS spectrum with a high S/N and sub-natural linewidth. Using the
scheme of the coherent superposition of the individual Rayleigh-scattered light
emitted from the atomic dipole oscillators on the PDG, the experimentally
observed RBS spectroscopy is theoretically explained.
| arxiv topic:physics.atom-ph physics.optics |
arxiv_dataset-1214904.4734 | Fundamental asymmetry in interfacial electronic reconstruction between
insulating oxides
cond-mat.mtrl-sci cond-mat.str-el
We present an ab initio study of the (001) interfaces between two insulating
perovskites, the polar LaAlO3 and the nonpolar SrTiO3. We observe an
insulating-to-metallic transition above a critical LaAlO3 thickness. We explain
that the high conductivity observed at the TiO2 /LaO interface and the lack of
similar conductivity at the SrO/AlO2 interface are inherent in the atomic
geometry of the system. A large interfacial hopping matrix element between
cations causes the formation of a bound electron state at the TiO2 /LaO
interface. This mechanism for the formation of interfacial bound states
suggests a robust means for tuning conductivities at various oxide
heterointerfaces.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-1215904.4834 | Gromov-Witten Gauge Theory I
math.AG hep-th math-ph math.MP math.QA
We introduce a geometric completion of the stack of maps from stable marked
curves to the quotient stack [point/GL(1)], and use it to construct some
gauge-theoretic analogues of the Gromov-Witten invariants. We also indicate the
generalization of these invariants to the quotient stacks [X/GL(1)], where X is
a smooth proper complex algebraic variety.
| arxiv topic:math.AG hep-th math-ph math.MP math.QA |
arxiv_dataset-1216905.0004 | Lattice defects and boundaries in conducting carbon nanotubes
cond-mat.mes-hall cond-mat.str-el
We consider the effect of various defects and boundary structures on the low
energy electronic properties in conducting zigzag and armchair carbon
nanotubes. The tight binding model of the conduction bands is mapped exactly
onto simple lattice models consisting of two uncoupled parallel chains.
Imperfections such as impurities, structural defects or caps can be easily
included into the effective lattice models, allowing a detailed physical
interpretation of their consequences. The method is quite general and can be
used to study a wide range of possible imperfections in carbon nanotubes. We
obtain the electron density patterns expected from a scanning tunneling
microscopy experiment for half fullerene caps and two typical impurities in the
bulk of a tube, namely the Stone-Wales defect and a single vacancy.
| arxiv topic:cond-mat.mes-hall cond-mat.str-el |
arxiv_dataset-1217905.0104 | Surgery obstructions on closed manifolds and the Inertia subgroup
math.GT math.AT
The Wall surgery obstruction groups have two interesting geometrically
defined subgroups, consisting of the surgery obstructions between closed
manifolds, and the inertial elements. We show that the inertia group
$I_{n+1}(\pi,w)$ and the closed manifold subgroup $C_{n+1}(\pi,w)$ are equal in
dimensions $n+1\geq 6$, for any finitely-presented group $\pi$ and any
orientation character $w\colon \pi \to \cy 2$.
| arxiv topic:math.GT math.AT |
arxiv_dataset-1218905.0204 | Interaction mediated asymmetries of the quantized Hall effect
cond-mat.mes-hall
Experimental and theoretical investigations on the integer quantized Hall
effect in gate defined narrow Hall bars are presented. At low electron mobility
the classical (high temperature) Hall resistance line RH(B) cuts through the
center of all Hall plateaus. In contrast, for our high mobility samples the
intersection point, at even filling factors \nu = 2; 4 ..., is clearly shifted
towards larger magnetic fields B. This asymmetry is in good agreement with
predictions of the screening theory, i. e. taking Coulomb interaction into
account. The observed effect is directly related to the formation of
incompressible strips in the Hall bar. The spin-split plateau at \nu= 1 is
found to be almost symmetric regardless of the mobility. We explain this within
the so-called effective g-model.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-1219905.0304 | A simplified Binet formula for k-generalized Fibonacci numbers
math.NT
We present a particularly nice Binet-style formula that can be used to
produce the k-generalized Fibonacci numbers (that is, the Tribonaccis,
Tetranaccis, etc). Furthermore, we show that in fact one needs only take the
integer closest to the first term of this Binet-style formula to generate the
desired sequence. These results were also found (independently) at about the
same time by Zhaohui Du of Singapore, China. We are working on a joint paper.
| arxiv topic:math.NT |
arxiv_dataset-1220905.0404 | Globally $F$-regular and log Fano varieties
math.AG math.AC
We prove that every globally $F$-regular variety is log Fano. In other words,
if a prime characteristic variety $X$ is globally $F$-regular, then it admits
an effective $\bQ$-divisor $\Delta$ such that $-K_X - \Delta$ is ample and $(X,
\Delta)$ has controlled (Kawamata log terminal, in fact globally $F$-regular)
singularities. A weak form of this result can be viewed as a prime
characteristic analog of de Fernex and Hacon's new point of view on Kawamata
log terminal singularities in the non-$\bQ$-Gorenstein case. We also prove a
converse statement in characteristic zero: every log Fano variety has globally
$F$-regular type. Our techniques apply also to $F$-split varieties, which we
show to satisfy a "log Calabi-Yau" condition. We also prove a Kawamata-Viehweg
vanishing theorem for globally $F$-regular pairs.
| arxiv topic:math.AG math.AC |
arxiv_dataset-1221905.0504 | Testing AdS/CFT at LHC
hep-ph nucl-th
After an introduction to jet phenomenology and tests of AdS/CFT at LHC we
derive the heavy quark drag of a string dangling in a shock metric of AdS
space, thus generalizing the AdS/CFT drag calculations in strongly coupled
thermal media to momentum loss in both hot and cold nuclear matter.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-1222905.0604 | Mahler measures and Fuglede--Kadison determinants
math.FA math.GR
The Mahler measure of a function on the real d-torus is its geometric mean
over the torus. It appears in number theory, ergodic theory and other fields.
The Fuglede-Kadison determinant is defined in the context of von Neumann
algebra theory and can be seen as a noncommutative generalization of the Mahler
measure. In the paper we discuss and compare theorems in both fields,
especially approximation theorems by finite dimensional determinants. We also
explain how to view Fuglede-Kadison determinants as continuous functions on the
space of marked groups.
| arxiv topic:math.FA math.GR |
arxiv_dataset-1223905.0704 | Earth's Heat Source - The Sun
physics.gen-ph
The Sun encompasses planet Earth, supplies the heat that warms it, and even
shakes it. The United Nation Intergovernmental Panel on Climate Change (IPCC)
assumed that solar influence on our climate is limited to changes in solar
irradiance and adopted the consensus opinion of a Hydrogen-filled Sun, the
Standard Solar Model (SSM). They did not consider the alternative solar model
and instead adopted another consensus opinion: Anthropogenic greenhouse gases
play a dominant role in climate change. The SSM fails to explain the solar
wind, solar cycles, and the empirical link of solar surface activity with Earth
changing climate. The alternative solar model, that was molded from an
embarrassingly large number of unexpected observations revealed by space-age
measurements since 1959, explains not only these puzzles but also how closely
linked interactions between the Sun and its planets and other celestial bodies
induce turbulent cycles of secondary solar characteristics that significantly
affect Earth climate.
| arxiv topic:physics.gen-ph |
arxiv_dataset-1224905.0804 | Vector and Axial Currents in Wilson Chiral Perturbation Theory
hep-lat
We reconsider the construction of the vector and axial-vector currents in
Wilson Chiral Perturbation Theory (WChPT), the low-energy effective theory for
lattice QCD with Wilson fermions. We discuss in detail the finite
renormalization of the currents that has to be taken into account in order to
properly match the currents. We explicitly show that imposing the chiral Ward
identities on the currents does, in general, affect the axial-vector current at
O(a). As an application of our results we compute the pion decay constant to
one loop in the two flavor theory. Our result differs from previously published
ones.
| arxiv topic:hep-lat |
arxiv_dataset-1225905.0904 | Inhomogeneity in the Supernova Remnants as a Natural Explanation of the
PAMELA/ATIC Observations
astro-ph.HE
Recent measurements of the positron/electron ratio in the cosmic ray (CR)
flux exhibits an apparent anomaly, whereby this ratio increases between 10 and
100 GeV. In contrast, this ratio should decrease according to the standard
scenario, in which CR positrons are secondaries formed by hadronic interactions
between the primary CR protons and the interstellar medium (ISM). The positron
excess is therefore interpreted as evidence for either an annihilation/decay of
weakly interacting massive particles, or for a direct astrophysical source of
pairs. The common feature of all proposed models is that they invoke new
physics or new astrophysical sources. However, this line of argumentation
relies implicitly on the assumption of a relatively homogeneous CR source
distribution. Inhomogeneity of CR sources on a scale of order a kpc, can
naturally explain this anomaly. If the nearest major CR source is about a kpc
away, then low energy electrons (~GeV) can easily reach us. At higher energies
(> 10 GeV), the source electrons cool via synchrotron and inverse-Compton
before reaching the solar vicinity. Pairs formed in the local vicinity through
the proton/ISM interactions can reach the solar system also at high energies,
thus increasing the positron/electron ratio. A natural origin of source
inhomogeneity is the strong concentration of supernovae to the galactic spiral
arms. Assuming supernova remnants (SNRs) as the sole primary source of CRs, and
taking into account their concentration near the galactic spiral arms, we
consistently predict the observed positron fraction between 1 and 100 GeV,
while abiding to different constraints such as the observed electron spectrum
and the CRs cosmogenic age. An ATIC like spectral excess at ~600 GeV can be
explained, in this picture, as the contribution of a few known nearby SNRs.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1226905.1004 | Decoherence and entanglement in a bosonic Josephson junction:
Bose-enhanced quantum-Zeno control of phase-diffusion
cond-mat.quant-gas
We study the effect of decoherence on dynamical phase diffusion in the
two-site Bose-Hubbard model. Starting with an odd parity excited coherent
state, the initial loss of single particle coherence varies from small bound
oscillations in the Rabi regime, through hyperbolic depletion in the Josephson
regime, to a Gaussian decay in the Fock regime. The inclusion of local-site
noise, measuring the relative number difference between the modes, is shown to
enhance phase-diffusion. In comparison, site-indiscriminate noise measuring the
population imbalance between the two quasi-momentum modes, slows down the loss
of single-particle coherence. Decoherence thus either enhances or suppresses
phase-diffusion, depending on the details of system-bath coupling and the
overlap of decoherence pointer states with collisional-entanglement pointer
states. The deceleration of phase-diffusion due to the coupling with the
environment may be viewed as a many-body quantum-Zeno effect. The extended
effective decay times in the presence of projective measurement, are further
enhanced with increasing number of particles $N$, by a bosonic factor of
$\sqrt{N}$ in the Fock regime and $N/\log{N}$ in the Josephson regime.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-1227905.1104 | Grassmann techniques applied to classical spin systems
cond-mat.stat-mech
We review problems involving the use of Grassmann techniques in the field of
classical spin systems in two dimensions. These techniques are useful to
perform exact correspondences between classical spin Hamiltonians and
field-theory fermionic actions. This contributes to a better understanding of
critical behavior of these models in term of non-quadratic effective actions
which can been seen as an extension of the free fermion Ising model. Within
this method, identification of bare masses allows for an accurate estimation of
critical points or lines and which is supported by Monte-Carlo results and
diagrammatic techniques.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-1228905.1204 | Off-resonance absorption and dispersion in a Doppler-broadened medium
physics.atom-ph
We study the absorptive and dispersive properties of Doppler-broadened atomic
media as a function of detuning. Beginning from the exact lineshape calculated
for a two-level atom, a series of approximations to the electric susceptibility
are made. These simplified functions facilitate direct comparison between
absorption and dispersion, and show that dispersion dominates the atom-light
interaction far from resonance. The calculated absorption and dispersion are
compared to experimental data, showing the validity of the approximations.
| arxiv topic:physics.atom-ph |
arxiv_dataset-1229905.1304 | Plancherel averages: Remarks on a paper by Stanley
math.CO
Let M_n stand for the Plancherel measure on Y_n, the set of Young diagrams
with n boxes. A recent result of Stanley (arXiv:0807.0383) says that for
certain functions G defined on the set Y of all Young diagrams, the average of
G with respect to M_n depends on n polynomially. We propose two other proofs of
this result together with a generalization to the Jack deformation of the
Plancherel measure.
| arxiv topic:math.CO |
arxiv_dataset-1230905.1404 | Time-like Salkowski and anti-Salkowski curves in Minkowski space
$\e_1^3$
math.DG
Salkowski \cite{salkow}, one century ago, introduced a family of curves with
constant curvature but non-constant torsion (Salkowski curves) and a family of
curves with constant torsion but non-constant curvature (anti-Salkowski curves)
in Euclidean 3-space $\e^3$. In this paper, we adapt definition of such curves
to time-like curves in Minkowski 3-space $\e_1^3$. Thereafter, we introduce an
explicit parametrization of a time-like Salkowski curves and a time-like
Anti-Salkowski curves in Minkowski space $\e_1^3$. Also, we characterize them
as space curve with constant curvature or constant torsion and whose normal
vector makes a constant angle with a fixed line.
| arxiv topic:math.DG |
arxiv_dataset-1231905.1504 | Signal Recovery in Pulsed Terahertz Integrated Circuits
physics.optics physics.data-an
In this article, a time-domain calibration procedure is proposed for pulsed
Terahertz Integrated Circuits (TIC) used in on-chip applications, where the
conventional calibration methods are not applicable. The proposed
post-detection method removes the unwanted linear distortions, such as
interfering echoes and frequency dispersion, by using only one single-port
measurement. The method employs a wave-transfer model for analysis of the TIC,
and the model parameters are obtained by a proposed blind estimation algorithm.
A complete implementation of the method is demonstrated for a fabricated TIC,
when used in an on-chip sensing application. The features of interest in the
measured signal, such as absorption lines, can be masked or weakened by the
distortion of the THz signal happening in a TIC. The proposed signal recovery
approach improves the detection of those otherwise hidden features, and can
significantly enhance the performance of existing TICs. To show the
effectiveness of the proposed de-embedding method, numerical results are
presented for simulated and measured signals. The method presented in this
article is enabling for accurate TIC applications, and can be utilized to
optimally design novel TIC structures for specific purposes.
| arxiv topic:physics.optics physics.data-an |
arxiv_dataset-1232905.1604 | Heterogeneity and anomalous critical indices in the aftershocks
distribution of L Aquila earthquake
physics.geo-ph
The data analysis of aftershock events of L Aquila earthquake in Apennines
following the main 6.3 Mw event of April 6, 2009 has been carried out by
standard statistical geophysical tools. The results show the heterogeneity of
seismic activity in five different geographical sub-regions indicated by
anomalous critical indices of power law distributions: the exponents of the
Omori law, the b values of Gutenberg-Richter magnitude-frequency distribution,
and the distribution of waiting times. The heterogeneous distribution of
dynamic stress and a different morphology in the five sub-regions has been
found and two anomalous sub-regions have been identified.
| arxiv topic:physics.geo-ph |
arxiv_dataset-1233905.1704 | Orbital-Ordering Induces Structural Phase Transition and the Resistivity
Anomaly in Iron Pnictides
cond-mat.str-el
We attribute the structural phase transition (SPT) in the parent compounds of
the iron pnictides to orbital ordering. Due to the anisotropy of the $d_{xz}$
and $d_{yz}$ orbitals in the $xy$ plane, a ferro-orbital ordering makes the
orthorhombic structure more energetically favorable, thus inducing the SPT. In
this orbital-ordered system, the sites with orbitals that do not order have
higher energies. Scattering of the itinerant electrons by these localized
two-level systems causes a resistivity anomaly upon the onset of the SPT. The
proposed orbital ordering also leads to the stripe-like anti-ferromagnetism and
anisotropy of the magnetic exchanges. This model is quantitatively consistent
with available experimental observations.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-1234905.1804 | S-wave DK interactions in the chiral SU(3) quark model
nucl-th
The $DK$ interaction is relevant to the interpretation of the $D_{sJ}(2317)$.
We dynamically investigate $S$-wave $DK$ interactions in the chiral SU(3) quark
model by solving the resonating group method equation. The numerical results
show an attraction between $D$ and $K$, which is from boson exchanges between
light quarks. However, such an attraction is not strong enough to form a $DK$
molecule. Meanwhile, $S$ partial wave phase shifts of $DK$ elastic scattering
are obtained. The case of $S$-wave $D^*K$ is rather similar to that of $DK$. To
draw a definite conclusion whether a molecular state exists in $DK$ or $D^*K$
system, more details of dynamics should be considered in further study.
| arxiv topic:nucl-th |
arxiv_dataset-1235905.1904 | Rates of K-shell Electron Capture Decays of 180Re and 142Pm Atoms
nucl-th astro-ph.SR hep-ph nucl-ex
We propose a theoretical analysis of the experimental data on the time
behaviour K-shell electron capture (EC) decays of atoms 180Re and 142Pm in
solid targets, obtained recently by Faestermann et al. Phys. Lett. B 672, 227
(2009) and Vetter et al., Phys. Lett. B 670, 149 (2008). We show that the
absence of the time modulation in these data rules out the explanation of the
"GSI Oscillations" (Yu. A. Litvinov et al., Phys. Lett. B 664, 162 (2008)) by
means of two closely spaced ground mass-eigenstates of mother nuclei.
| arxiv topic:nucl-th astro-ph.SR hep-ph nucl-ex |
arxiv_dataset-1236905.2004 | Termination Prediction for General Logic Programs
cs.PL cs.AI cs.LO
We present a heuristic framework for attacking the undecidable termination
problem of logic programs, as an alternative to current
termination/non-termination proof approaches. We introduce an idea of
termination prediction, which predicts termination of a logic program in case
that neither a termination nor a non-termination proof is applicable. We
establish a necessary and sufficient characterization of infinite (generalized)
SLDNF-derivations with arbitrary (concrete or moded) queries, and develop an
algorithm that predicts termination of general logic programs with arbitrary
non-floundering queries. We have implemented a termination prediction tool and
obtained quite satisfactory experimental results. Except for five programs
which break the experiment time limit, our prediction is 100% correct for all
296 benchmark programs of the Termination Competition 2007, of which eighteen
programs cannot be proved by any of the existing state-of-the-art analyzers
like AProVE07, NTI, Polytool and TALP.
| arxiv topic:cs.PL cs.AI cs.LO |
arxiv_dataset-1237905.2104 | Growth rate and the cutoff wavelength of the Darrieus-Landau instability
in laser ablation
physics.plasm-ph
The main characteristics of the linear Darrieus-Landau instability in the
laser ablation flow are investigated. The dispersion relation of the
instability is found numerically as a solution to an eigenvalue stability
problem, taking into account the continuous structure of the flow. The results
are compared to the classical Darrieus-Landau instability of a usual slow
flame. The difference between the two cases is due to the specific features of
laser ablation: high plasma compression and strong temperature dependence of
electron thermal conduction. It is demonstrated that the Darrieus-Landau
instability in laser ablation is much stronger than in the classical case. In
particular, the maximum growth rate in the case of laser ablation is about
three times larger than that for slow flames. The characteristic length scale
of the Darrieus-Landau instability in the ablation flow is comparable to the
total distance from the ablation zone to the critical zone of laser light
absorption. The possibility of experimental observations of the Darrieus-Landau
instability in laser ablation is discussed.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-1238905.2204 | Absorption enhancement in amorphous silicon photonic crystals for thin
film photovoltaic solar cells
cond-mat.mtrl-sci cond-mat.mes-hall
We report on very high enhancement of thin layer's absorption through
band-engineering of a photonic crystal structure. We realized amorphous silicon
(aSi) photonic crystals, where slow light modes improve absorption efficiency.
We show through simulation that an increase of the absorption by a factor of
1.5 is expected for a film of aSi. The proposal is then validated by an
experimental demonstration, showing an important increase of the absorption of
a layer of aSi over a spectral range of 0.32-0.76 microns.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-1239905.2304 | Evolution of light trapped by a soliton in a microstructured fiber
physics.optics
We observe the dynamics of pulse trapping in a microstructured fiber.
Few-cycle pulses create a system of two pulses: a Raman shifting soliton traps
a pulse in the normal dispersion regime. When the soliton approaches a
wavelength of zero group velocity dispersion the Raman shifting abruptly
terminates and the trapped pulse is released. In particular, the trap is less
than 4ps long and contains a 1ps pulse. After being released, this pulse
asymmetrically expands to more than 10ps. Additionally, there is no disturbance
of the trapping dynamics at high input pulse energies as the supercontinuum
develops further.
| arxiv topic:physics.optics |
arxiv_dataset-1240905.2404 | A Convergent Overlapping Domain Decomposition Method for Total Variation
Minimization
math.NA
This paper is concerned with the analysis of convergent sequential and
parallel overlapping domain decomposition methods for the minimization of
functionals formed by a discrepancy term with respect to data and a total
variation constraint. To our knowledge, this is the first successful attempt of
addressing such strategy for the nonlinear, nonadditive, and nonsmooth problem
of total variation minimization. We provide several numerical experiments,
showing the successful application of the algorithm for the restoration of 1D
signals and 2D images in interpolation/inpainting problems respectively, and in
a compressed sensing problem, for recovering piecewise constant medical-type
images from partial Fourier ensembles.
| arxiv topic:math.NA |
arxiv_dataset-1241905.2504 | Tracking anisotropic scattering in overdoped
Tl$_2$Ba$_2$CuO$_{6+\delta}$ above 100 K
cond-mat.supr-con cond-mat.str-el
This article describes new polar angle-dependent magnetoresistance (ADMR)
measurements in the overdoped cuprate Tl$_2$Ba$_2$CuO$_{6+\delta}$ over an
expanded range of temperatures and azimuthal angles. These detailed
measurements re-affirm the analysis of earlier data taken over a more
restricted temperature range and at a single azimuthal orientation, in
particular the delineation of the intraplane scattering rate into isotropic and
anisotropic components. These new measurements also reveal additional features
in the temperature and momentum dependence of the scattering rate, including
anisotropy in the $T^2$ component and the preservation of both the $T$-linear
and $T^2$ components up to 100 K. The resultant form of the scattering rate
places firm constraints on the development of any forthcoming theoretical
framework for the normal state charge response of high temperature
superconducting cuprates.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-1242905.2604 | A Riemannian Bieberbach estimate
math.DG math.CV
The Bieberbach estimate, a pivotal result in the classical theory of
univalent functions, states that any injective holomorphic function $f$ on the
open unit disc $D$ satisfies $|f"(0)|\leq 4 |f'(0)|$. We generalize the
Bieberbach estimate by proving a version of the inequality that applies to all
injective smooth conformal immersions $f : D\to \Bbb R^n, n\geq 2$. The new
estimate involves two correction terms. The first one is geometric, coming from
the second fundamental form of the image surface $f(D)$. The second term is of
a dynamical nature, and involves certain Riemannian quantities associated to
conformal attractors. Our results are partly motivated by a conjecture in the
theory of embedded minimal surfaces.
| arxiv topic:math.DG math.CV |
arxiv_dataset-1243905.2704 | Energy conservation and blowup of solutions for focusing
Gross-Pitaevskii hierarchies
math-ph math.AP math.MP
We consider solutions of the focusing cubic and quintic Gross-Pitaevskii (GP)
hierarchies. We identify an observable corresponding to the average energy per
particle, and we prove that it is a conserved quantity. We prove that all
solutions to the focusing GP hierarchy at the $L^2$-critical or
$L^2$-supercritical level blow up in finite time if the energy per particle in
the initial condition is negative. Our results do not assume any factorization
of the initial data.
| arxiv topic:math-ph math.AP math.MP |
arxiv_dataset-1244905.2804 | Long-term evolution and gravitational wave radiation of neutron stars
with differential rotation induced by r-modes
astro-ph.SR astro-ph.HE
In a second-order r-mode theory, S'a & Tom'e found that the r-mode
oscillation in neutron stars (NSs) could induce stellar differential rotation,
which leads to a saturation state of the oscillation spontaneously. Based on a
consideration of the coupling of the r-modes and the stellar spin and thermal
evolutions, we carefully investigate the influences of the r-mode-induced
differential rotation on the long-term evolutions of isolated NSs and NSs in
low-mass X-ray binaries, where the viscous damping of the r-modes and its
resultant effects are taken into account. The numerical results show that, for
both kinds of NSs, the differential rotation can prolong the duration of the
r-mode saturation state significantly. As a result, the stars can keep nearly
constant temperature and angular velocity over a thousand years. Moreover, due
to the long-term steady rotation of the stars, persistent quasi-monochromatic
gravitational wave radiation could be expected, which increases the
detectibility of gravitational waves from both nascent and accreting old NSs.
| arxiv topic:astro-ph.SR astro-ph.HE |
arxiv_dataset-1245905.2904 | Origin of power-law X-ray emission in the Steep power-law state of X-ray
Binaries
astro-ph.HE
We present a new scenario of the emissive origin in the Steep Power Law (SPL)
state of X-ray Binaries. The power-law component of X-ray emission is the
synchrotron radiation of relativistic electrons in highly magnetized compact
spots orbiting near the inner stable circular orbit (ISCO) of black hole and
has a hard spectrum that extends to above MeV bands determined by electron
acceleration rate. These photons are then down-scattered by the surrounding
plasma and form an observed steep spectrum. The relevance of this model with
high-frequency quasi-periodic oscillations (HFQPOs) and extremely high
luminosity of the SPL state is discussed.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1246905.3004 | Renaissance of the ~1 TeV Fixed-Target Program
hep-ex
This document describes the physics potential of a new fixed-target program
based on a ~1 TeV proton source. Two proton sources are potentially available
in the future: the existing Tevatron at Fermilab, which can provide 800 GeV
protons for fixed-target physics, and a possible upgrade to the SPS at CERN,
called SPS+, which would produce 1 TeV protons on target. In this paper we use
an example Tevatron fixed-target program to illustrate the high discovery
potential possible in the charm and neutrino sectors. We highlight examples
which are either unique to the program or difficult to accomplish at other
venues.
| arxiv topic:hep-ex |
arxiv_dataset-1247905.3104 | Initiation of the detonation in the gravitationally confined detonation
model of Type Ia supernovae
astro-ph.SR astro-ph.CO
We study the initiation of the detonation in the gravitationally confined
detonation (GCD) model of Type Ia supernovae (SNe Ia). Initiation of the
detonation occurs spontaneously in a region where the length scale of the
temperature gradient extending from a flow (in which carbon burning is already
occurring) into unburned fuel is commensurate to the range of critical length
scales which have been derived from 1D simulations that resolve the initiation
of a detonation. By increasing the maximum resolution in a truncated cone that
encompasses this region, beginning somewhat before initiation of the detonation
occurs, we successfully simulate in situ the first gradient-initiated
detonation in a whole-star simulation. The detonation emerges when a
compression wave overruns a pocket of fuel situated in a Kelvin-Helmholtz cusp
at the leading edge of the inwardly directed jet of burning carbon. The
compression wave pre-conditions the temperature in the fuel in such a way that
the Zel'dovich gradient mechanism can operate and a detonation ensues. We
explore the dependence of the length scale of the temperature gradient on
spatial resolution and discuss the implications for the robustness of this
detonation mechanism. We find that the time and the location at which
initiation of the detonation occurs varies with resolution. In particular,
initiation of a detonation had not yet occurred in our highest resolution
simulation by the time we ended the simulation because of the computational
demand it required. We suggest that the turbulent shear layer surrounding the
inwardly directed jet provides the most favorable physical conditions, and
therefore the most likely location, for initiation of a detonation in the GCD
model.
| arxiv topic:astro-ph.SR astro-ph.CO |
arxiv_dataset-1248905.3204 | Measuring magnetic profiles at manganite surfaces with monolayer
resolution
cond-mat.str-el cond-mat.mtrl-sci
The performance of manganite-based magnetic tunnel junctions (MTJs) has
suffered from reduced magnetization present at the junction interfaces that is
ultimately responsible for the spin polarization of injected currents; this
behavior has been attributed to a magnetic "dead layer" that typically extends
a few unit cells into the manganite. X-ray magnetic scattering in resonant
conditions (XRMS) is one of the most innovative and effective techniques to
extract surface or interfacial magnetization profiles with subnanometer
resolution, and has only recently been applied to oxide heterostructures. Here
we present our approach to characterizing the surface and interfacial
magnetization of such heterostructures using the XRMS technique, conducted at
the BEAR beamline (Elettra synchrotron, Trieste). Measurements were carried out
in specular reflectivity geometry, switching the left/right elliptical
polarization of light as well the magnetization direction in the scattering
plane. Spectra were collected across the Mn L2,3 edge for at least four
different grazing angles in order to better analyse the interference phenomena.
The resulting reflectivity spectra have been carefully fit to obtain the
magnetization profiles, minimizing the number of free parameters as much as
possible. Optical constants of the samples (real and imaginary part of the
refractive index) in the interested frequency range are obtained through
absorption measurements in two magnetization states and subsequent
Kramers-Kronig transformation, allowing quantitative fits of the magnetization
profile at different temperatures. We apply this method to the study of
air-exposed surfaces of epitaxial La2/3Sr1/3MnO3 (001) films grown on SrTiO3
(001) substrates.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-1249905.3304 | Frobenius manifolds, projective special geometry and Hitchin systems
math.AG
We consider the construction of Frobenius manifolds associated to projective
special geometry and analyse the dependence on choices involved. In particular,
we prove that the underlying F-manifold is canonical. We then apply this
construction to integrable systems of Hitchin type.
| arxiv topic:math.AG |
arxiv_dataset-1250905.3404 | Sky Surface Brightness at Mount Graham: UBVRI Science Observations with
the Large Binocular Telescope
astro-ph.EP
We present the measurements of sky surface brightness on Mount Graham
International Observatory obtained during the first binocular-mode science runs
at the Large Binocular Telescope (LBT). A total of 860 images obtained on 23
moonless nights in the period Feb 2008-Jun 2008 were analyzed with our data
quality assessment procedure. These data, taken at the solar minimum, show that
Mt.Graham, in photometric conditions, still has one of the darkest skies,
competing with the other first-class observatories. The zenith-corrected values
are 21.98, 22.81, 21.81, 20.82 and 19.78 mag/arcsec^2 in U, B, V R and I,
respectively. In photometric conditions, the sky background is ~0.1
mag/arcsec^2 higher than the median when observing toward Tucson and Phoenix
but it may be up to ~0.5 mag/arcsec^2 higher in non-photometric conditions. The
sky at Mt.Graham is ~0.32 mag/arcsec^2 brighter at airmass ~1.4 than at zenith
but no significant trend was found with the time of the night. We demonstrated
the dependence of the sky background at Mt.Graham on the solar activity for the
first time. In fact in 2008, at B and V bands, the sky was ~0.3 mag /arcsec^2
darker than in 1999-2002. With these results we conclude that Mt.Graham is
still a first-class observing site, comparable to the darkest sites in Hawaii,
Chile and Canary Islands.
| arxiv topic:astro-ph.EP |
arxiv_dataset-1251905.3504 | An Eberhard-like theorem for pentagons and heptagons
math.CO
Eberhard proved that for every sequence $(p_k), 3\le k\le r, k\ne 5,7$ of
non-negative integers satisfying Euler's formula $\sum_{k\ge3} (6-k) p_k = 12$,
there are infinitely many values $p_6$ such that there exists a simple convex
polyhedron having precisely $p_k$ faces of length $k$ for every $k\ge3$, where
$p_k=0$ if $k>r$. In this paper we prove a similar statement when non-negative
integers $p_k$ are given for $3\le k\le r$, except for $k=5$ and $k=7$. We
prove that there are infinitely many values $p_5,p_7$ such that there exists a
simple convex polyhedron having precisely $p_k$ faces of length $k$ for every
$k\ge3$. %, where $p_k=0$ if $k>r$. We derive an extension to arbitrary closed
surfaces, yielding maps of arbitrarily high face-width. Our proof suggests a
general method for obtaining results of this kind.
| arxiv topic:math.CO |
arxiv_dataset-1252905.3604 | Formal multiplications, bialgebras of distributions and non-associative
Lie theory
math.RA math.RT
We describe the general non-associative version of Lie theory that relates
unital formal multiplications (formal loops), Sabinin algebras and
non-associative bialgebras. Starting with a formal multiplication we construct
a non-associative bialgebra, namely, the bialgebra of distributions with the
convolution product. Considering the primitive elements in this bialgebra gives
a functor from formal loops to Sabinin algebras. We compare this functor to
that of Mikheev and Sabinin and show that although the brackets given by both
constructions coincide, the multioperator does not. We also show how identities
in loops produce identities in bialgebras. While associativity in loops
translates into associativity in algebras, other loop identities (such as the
Moufang identity) produce new algebra identities. Finally, we define a class of
unital formal multiplications for which Ado's theorem holds and give examples
of formal loops outside this class. A by-product of the constructions of this
paper is a new identity on Bernoulli numbers. We give two proofs: one coming
from the formula for the non-associative logarithm, and the other (due to D.
Zagier) using generating functions.
| arxiv topic:math.RA math.RT |
arxiv_dataset-1253905.3704 | Unravelling the size distribution of social groups with information
theory on complex networks
physics.soc-ph
The minimization of Fisher's information (MFI) approach of Frieden et al.
[Phys. Rev. E {\bf 60} 48 (1999)] is applied to the study of size distributions
in social groups on the basis of a recently established analogy between scale
invariant systems and classical gases [arXiv:0908.0504]. Going beyond the ideal
gas scenario is seen to be tantamount to simulating the interactions taking
place in a network's competitive cluster growth process. We find a scaling rule
that allows to classify the final cluster-size distributions using only one
parameter that we call the competitiveness. Empirical city-size distributions
and electoral results can be thus reproduced and classified according to this
competitiveness, which also allows to correctly predict well-established
assessments such as the "six-degrees of separation", which is shown here to be
a direct consequence of the maximum number of stable social relationships that
one person can maintain, known as Dunbar's number. Finally, we show that scaled
city-size distributions of large countries follow the same universal
distribution.
| arxiv topic:physics.soc-ph |
arxiv_dataset-1254905.3804 | Wormholes supported by chiral fields
gr-qc
We consider static, spherically symmetric solutions of general relativity
with a nonlinear sigma model (NSM) as a source, i.e., a set of scalar fields
$\Phi = (\Phi^1,...,\Phi^n)$ (so-called chiral fields) parametrizing a target
space with a metric $h_{ab}(\Phi)$. For NSM with zero potential $V(\Phi)$, it
is shown that the space-time geometry is the same as with a single scalar field
but depends on $h_{ab}$. If the matrix $h_{ab}$ is positive-definite, we obtain
the Fisher metric, originally found for a canonical scalar field with positive
kinetic energy; otherwise we obtain metrics corresponding to a phantom scalar
field, including singular and nonsingular horizons (of infinite area) and
wormholes. In particular, the Schwarzschild metric can correspond to a
nontrivial chiral field configuration, which in this case has zero
stress-energy. Some explicit examples of chiral field configurations are
considered. Some qualitative properties of NSM configurations with nonzero
potentials are pointed out.
| arxiv topic:gr-qc |
arxiv_dataset-1255905.3904 | Comment on ``Muon-spin rotation studies of the superconducting
properties of Mo_3Sb_7'', Phys.Rev.B 78, 172505 (2008)
cond-mat.supr-con
In a recent article Tran et al. [Phys. Rev.B 78, 172505 (2008)] report on the
result of the muon-spin rotation (\muSR) measurements of Mo_3Sb_7
superconductor. Based on the analysis of the temperature and the magnetic field
dependence of the Gaussian relaxation rate \sigma_{sc} they suggest that
Mo_3Sb_7 is the superconductor with two isotropic s-wave like gaps. An
additional confirmation was obtained from the specific heat data published
earlier by partly the same group of authors in [Acta Mater. 56, 5694 (2008)].
The purpose of this Comment is to point out that from the analysis made by Tran
et al. the presence of two superconducting energy gaps in Mo_3Sb_7 can not be
justified. The analysis of \muSR data does not account for the reduction of
\sigma_{sc} with increasing temperature, and, hence, yields inaccurate
information on the magnetic penetration depth. The specific heat data can be
satisfactory described within the framework of the one-gap model with the small
residual specific heat component. The experimental data of Tran et al., as well
as our earlier published \muSR data [Phys. Rev. B 78, 014502 (2008)] all seem
to be consistent with is the presence of single isotropic superconducting
energy gap in Mo_3Sb_7.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-1256905.4004 | Transition form factors of the pion in light-cone QCD sum rules with
next-to-next-to-leading order contributions
hep-ph hep-ex
The transition pion-photon form factor is studied within the framework of
Light-Cone QCD Sum Rules. The spectral density for the next-to-leading order
corrections is calculated for any Gegenbauer harmonic. At the level of the
next-to-next-to-leading (NNLO) radiative corrections, only that part of the
hard-scattering amplitude is included that is proportional to the
$\beta$-function, taking into account the leading zeroth-order harmonic. The
relative size of the NNLO contribution in the prediction for the form factor
$F^{\gamma^{*}\gamma\pi}(Q^2)$ has been analyzed, making use of the BLM
scale-setting procedure. In addition, predictions for the form factor
$F^{\gamma^{*}\rho\pi}$ are obtained that turn out to be sensitive to the
endpoint behavior of the pion distribution amplitude, thus providing in
connection with experimental data an additional adjudicator for the pion
distribution amplitude. In a note added, we comment on the preliminary
high-$Q^2$ BaBar data on $F^{\gamma^{*}\gamma\pi}$ arguing that the significant
growth of the form factor between 10 and 40 GeV$^2$ cannot be explained in
terms of higher-order perturbative corrections at the NNLO.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-1257905.4104 | An Equation of Motion with Quantum Effect in Spacetime
gr-qc
In this paper, we shall present a new equation of motion with Quantum effect
in spacetime. To do so, we propose a classical-quantum duality. We also
generalize the Schordinger equation to the spacetime and obtain a relativistic
wave equation. This will lead a generalization of Einstein's formula $E=m_0c^2$
in the spacetime. In general, we have $E=m_0c^2 + \frac{\hbar^2}{12m_0}R$ in a
spacetime.
| arxiv topic:gr-qc |
arxiv_dataset-1258905.4204 | Is nonrelativistic gravity possible?
hep-th astro-ph.CO gr-qc math.DS
We study nonrelativistic gravity using the Hamiltonian formalism. For the
dynamics of general relativity (relativistic gravity) the formalism is well
known and called the Arnowitt-Deser-Misner (ADM) formalism. We show that if the
lapse function is constrained correctly, then nonrelativistic gravity is
described by a consistent Hamiltonian system. Surprisingly, nonrelativistic
gravity can have solutions identical to relativistic gravity ones. In
particular, (anti-)de Sitter black holes of Einstein gravity and IR limit of
Horava gravity are locally identical.
| arxiv topic:hep-th astro-ph.CO gr-qc math.DS |
arxiv_dataset-1259905.4304 | Strong terahertz response in bilayer graphene nanoribbons
cond-mat.mes-hall
We reveal that there exists a class of graphene structures (a sub-class of
bilayer graphene nanoribbons) which has unusually strong optical response in
the terahertz (THz) and far infrared (FIR) regime. The peak conductance of
terahertz/FIR active bilayer ribbons is around two orders of magnitude higher
than the universal conductance of $e^2/4\hbar$ observed in graphene sheets. The
criterion for the terahertz/FIR active sub-class is a bilayer graphene
nanoribbon with one-dimensional massless Dirac Fermion energy dispersion near
the $\Gamma$ point. Our results overcome a significant obstacle that hinders
potential application of graphene in electronics and photonics.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-1260905.4404 | Two-fluid Instability of Dust and Gas in the Dust Layer of a
Protoplanetary Disk
astro-ph.EP
Instabilities of the dust layer in a protoplanetary disk are investigated. It
is known that the streaming instability develops and dust density concentration
occurs in a situation where the initial dust density is uniform. This work
considers the effect of initial dust density gradient vertical to the midplane.
Dust and gas are treated as different fluids. Pressure of dust fluid is assumed
to be zero. The gas friction time is assumed to be constant. Axisymmetric
two-dimensional numerical simulation was performed using the spectral method.
We found that an instability develops with a growth rate on the order of the
Keplerian angular velocity even if the gas friction time multiplied by the
Keplerian angular velocity is as small as 0.001.
This instability is powered by two sources: (1) the vertical shear of the
azimuthal velocity, and (2) the relative motion of dust and gas coupled with
the dust density fluctuation due to advection. This instability diffuses dust
by turbulent advection and the maximum dust density decreases. This means that
the dust concentration by the streaming instability which is seen in the case
of a uniform initial dust density becomes ineffective as dust density gradient
increases by the dust settling toward the midplane.
| arxiv topic:astro-ph.EP |
arxiv_dataset-1261905.4504 | Metal-Free Gas Supply at the Edge of Reionization: Late-Epoch Population
III Star Formation
astro-ph.CO astro-ph.SR
While the average metallicity of the intergalactic medium rises above
Z~10^{-3} Zsun by the end of the reionization, pockets of metal-free gas can
still exist at later times. We quantify the presence of a long tail in the
formation rate of metal-free halos during late stages of reionization (redshift
z~6), which might offer the best window to detect Population III stars. Using
cosmological simulations for the growth of dark matter halos, coupled with
analytical recipes for the metal enrichment of their interstellar medium, we
show that pockets of metal-free gas exist at z~6 even under the assumption of
high efficiency in metal pollution via winds. A comoving metal-free halo
formation rate d^2n/dtdV > 10^{-9} Mpc^{-3}yr^{-1} is expected at z=6 for halos
with virial temperature T_{vir}~10^4 K (mass ~10^8 Msun), sufficient to
initiate cooling even with strong negative radiative feedback. Under the
assumption of a single Population III supernova formed per metal-free halo, we
expect an observed supernova rate of 2.6x10^{-3} deg^{-2}yr^{-1} in the same
redshift range. These metal-free stars and their supernovae will be isolated
and outside galaxies (at distances >150 h^{-1} kpc) and thus significantly less
biased than the general population of ~10^8 Msun halos at z~6. Supernova
searches for metal-free explosions must thus rely on large area surveys. If
metal-free stars produce very luminous supernovae, like SN2006gy, then a
multi-epoch survey reaching m_AB =27 at 1 micron is sufficient for detecting
them at z=6. While the Large Synoptic Survey Telescope will not reach this
depth in the z band, it will be able to detect several tens of Population III
supernovae in the i and r bands at z <5.5, when their observed rate is down to
3-8x10^{-4} deg^{-2} yr^{-1}.
| arxiv topic:astro-ph.CO astro-ph.SR |
arxiv_dataset-1262905.4604 | XML Technologies in Computer Assisted Learning and Testing Systems
cs.OH
The learning and assessment activities have undergone major changes due to
the development of modern technologies. The computer-assisted learning and
testing has proven a number of advantages in the development of modern
educational system. The paper suggests a solution for the computer-assisted
testing, which uses XML technologies, a solution that could make the basis for
developing a learning computer-assisted system.
| arxiv topic:cs.OH |
arxiv_dataset-1263905.4704 | Long-Range Models of Modified Gravity and Their Agreement with Solar
System and Double Pulsar Data
gr-qc astro-ph.CO astro-ph.EP astro-ph.GA hep-ph physics.space-ph
Many long-range modifications of the Newtonian/Einsteinian standard laws of
gravity have been proposed in the recent past to explain various celestial
phenomena occurring at different scales ranging from solar system to the entire
universe. The most famous ones are the so-called Pioneer anomaly, {i.e.} a
still unexplained acceleration detected in the telemetry of the Pioneer 10/11
spacecraft after they passed the 20 AU threshold in the solar system, the
non-Keplerian profiles of the velocity rotation curves of several galaxies and
the cosmic acceleration. We use the latest observational determinations of the
planetary motions in the solar system and in the double pulsar system to put
constraints on such models independently of the phenomena for which they were
originally proposed. We also deal with the recently detected anomalous
perihelion precession of Saturn and discuss the possibility that it can be
explained by some of the aforementioned models of modified gravity.
| arxiv topic:gr-qc astro-ph.CO astro-ph.EP astro-ph.GA hep-ph physics.space-ph |
arxiv_dataset-1264905.4804 | Comments on Six Degrees of Separation based on the le Pool and Kochen
Models
physics.soc-ph
In this article we discuss six degrees of separation, which has been
suggested by Milgram's famous experiment\cite{Milg},\cite{Milg2}, from a
theoretical point of view again. Though Milgram's experiment was partly
inspired to Pool and Kochen's study \cite{Pool} that was made from a
theoretical point of view. At the time numerically detailed study could not be
made because computers and important concepts, such as the clustering
coefficient, needed for a network analysis nowadays, have not yet developed. In
this article we devote deep study to the six degrees of separation based on
some models proposed by Pool and Kochen by using a computer, numerically.
Moreover we estimate the clustering coefficient along the method developed by
us \cite{Toyota1} and extend our analysis of the subject through marrying Pool
and Kochen's models to our method.
| arxiv topic:physics.soc-ph |
arxiv_dataset-1265905.4904 | Fundamental Theory of Statistical Particle Dynamics
cond-mat.stat-mech
We introduce a fundamental theory for the kinetics of systems of classical
particles. The theory represents a unification of kinetic theory, Brownian
motion and field theory. It is self-consistent and is the dynamic
generalization of the functional theory of static equilibrium fluids. This
gives one a powerful tool for investigating the existence of ergodic-nonergodic
transitions near the liquid-glass transition.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-1266906.0049 | Towards Automated Deduction in Blackmail Case Analysis with Forensic
Lucid
cs.LO cs.CR cs.PL
This work-in-progress focuses on the refinement of application of the
intensional logic to cyberforensic analysis and its benefits are compared with
the finite-state automata approach. This work extends the use of the scientific
intensional programming paradigm onto modeling and implementation of a
cyberforensics investigation process with the backtrace of event
reconstruction, modeling the evidence as multidimensional hierarchical
contexts, and proving or disproving the claims with it in the intensional
manner of evaluation. This is a practical, context-aware improvement over the
finite state automata (FSA) approach we have seen in the related works. As a
base implementation language model we use in this approach is a new dialect of
the Lucid programming language, that we call Forensic Lucid and in this paper
we focus on defining hierarchical contexts based on the intensional logic for
the evaluation of cyberforensic expressions.
| arxiv topic:cs.LO cs.CR cs.PL |
arxiv_dataset-1267906.0149 | Description of accretion induced outflows from ultra-luminous sources to
under-luminous AGNs
astro-ph.HE
We study the energetics of the accretion-induced outflow and then plausible
jet around black holes/compact objects using a newly developed disc-outflow
coupled model. Inter-connecting dynamics of outflow and accretion essentially
upholds the conservation laws. The energetics depend strongly on the viscosity
parameter \alpha and the cooling factor f which exhibit several interesting
features. The bolometric luminosities of ultra-luminous X-ray binaries (e.g.
SS433) and family of highly luminous AGNs and quasars can be reproduced by the
model under the super-Eddington accretion flows. Under appropriate conditions,
low-luminous AGNs (e.g. Sagittarius A^*) also fit reasonably well with the
luminosity corresponding to a sub-Eddington accretion flow with f\to 1.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1268906.0249 | Faster Projection in Sphere Decoding
cs.IT math.IT
Most of the calculations in standard sphere decoders are redundant, in the
sense that they either calculate quantities that are never used or calculate
some quantities more than once. A new method, which is applicable to lattices
as well as finite constellations, is proposed to avoid these redundant
calculations while still returning the same result. Pseudocode is given to
facilitate immediate implementation. Simulations show that the speed gain with
the proposed method increases linearly with the lattice dimension. At dimension
60, the new algorithms avoid about 75% of all floating-point operations.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-1269906.0349 | Gas in Simulations of High Redshift Galaxies and Minihalos
astro-ph.CO astro-ph.GA
We study the gas content of halos in the early universe using high resolution
hydrodynamical simulations. We extract from the simulations and also predict
based on linear theory the halo mass for which the enclosed baryon fraction
equals half of the mean cosmic fraction. We find a rough agreement between the
simulations and the predictions, which suggests that during the high-redshift
era before stellar heating, the minimum mass needed for a minihalo to keep most
of its baryons throughout its formation was $\sim 3 \times 10^4$ M$_\odot$. We
also carry out a detailed resolution analysis and show that in order to
determine a halo's gas fraction even to 20% accuracy the halo must be resolved
into at least 500 dark matter particles.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-1270906.0449 | Invariants of isospectral deformations and spectral rigidity
math.SP
We introduce a notion of weak isospectrality for continuous deformations.
Consider the Laplace-Beltrami operator on a compact Riemannian manifold with
boundary with Robin boundary conditions. Given a Kronecker invariant torus
$\Lambda$ of the billiard ball map with a vector of rotation satisfying a
Diophantine condition we prove that certain integrals on $\Lambda$ involving
the function in the Robin boundary conditions remain constant under weak
isospectral deformations. To this end we construct continuous families of
quasimodes associated with $\Lambda$. We obtain also isospectral invariants of
the Laplacian with a real-valued potential on a compact manifold for continuous
deformations of the potential. As an application we prove spectral rigidity in
the case of Liouville billiard tables of dimension two.
| arxiv topic:math.SP |
arxiv_dataset-1271906.0549 | Hidden Symmetry from Supersymmetry in One-Dimensional Quantum Mechanics
hep-th gr-qc math-ph math.MP nucl-th quant-ph
When several inequivalent supercharges form a closed superalgebra in Quantum
Mechanics it entails the appearance of hidden symmetries of a
Super-Hamiltonian. We examine this problem in one-dimensional QM for the case
of periodic potentials and potentials with finite number of bound states. After
the survey of the results existing in the subject the algebraic and analytic
properties of hidden-symmetry differential operators are rigorously elaborated
in the Theorems and illuminated by several examples.
| arxiv topic:hep-th gr-qc math-ph math.MP nucl-th quant-ph |
arxiv_dataset-1272906.0649 | Rate of convergence of stochastic processes with values in
$\mathbb{R}$-trees and Hadamard manifolds
math.PR math.MG
Under K.-T. Sturm's formulation, we obtain a Gaussian upper bound for tail
probability of mean value of independent, identically distributed random
variables with values in $\mathbb{R}$-trees and Hadamard manifolds.
| arxiv topic:math.PR math.MG |
arxiv_dataset-1273906.0749 | Proposal for a Raman X-ray Free Electron Laser
physics.optics
A scheme for an X-ray free electron laser is proposed, based on a Raman
process occurring during the interaction between a moderately relativistic
bunch of free electrons, and twin intense short pulse lasers interfering to
form a transverse standing wave along the electron trajectories. In the high
intensity regime of the Kapitza-Dirac effect, the laser ponderomotive potential
forces the electrons into a lateral oscillatory motion, resulting in a Raman
scattering process. I show how a parametric process is triggered, resulting in
the amplification of the Stokes component of the Raman-scattered photons.
Experimental operating parameters and implementations, based both on LINAC and
Laser Wakefield Acceleration techniques, are discussed.
| arxiv topic:physics.optics |
arxiv_dataset-1274906.0849 | The Quasar SDSS J1536+0441: An Unusual Double-Peaked Emitter
astro-ph.CO astro-ph.HE
The quasar SDSS J153636.22+044127.0, exhibiting peculiar broad emission-line
profiles with multiple components, was proposed as a candidate sub-parsec
binary supermassive black hole system. More recently, imaging revealed two
spatially distinct sources, leading some to suggest the system to be a quasar
pair separated by ~5 kpc. We present Palomar and Keck optical spectra of this
system from which we identify a third velocity component to the emission lines.
We argue that the system is more likely an unusual member of the class of
active galactic nuclei (AGNs) known as "double-peaked emitters" than a
sub-parsec black hole binary or quasar pair. We find no significant velocity
evolution of the two main peaks over the course of 0.95 yr, with a 3-sigma
upper limit on any secular change of 70 km/s/yr. We also find that the three
velocity components of the emission lines are spatially coincident to within
0.015" along the slit, apparently ruling out the double-quasar hypothesis.
| arxiv topic:astro-ph.CO astro-ph.HE |
arxiv_dataset-1275906.0949 | The W_k structure of the Z_k^(3/2) models
hep-th cond-mat.mes-hall
Generalized Z_k^(r/2) parafermionic theories - characterized by the dimension
(r/2)(1-1/k) of the basic parafermionic field - provide potentially interesting
quantum-Hall trial wavefunctions. Such wavefunctions reveal a W_k structure.
This suggests the equivalence of (a subclass of) the Z_k^(r/2) models and the
W_k(k+1,k+r) ones. This is demonstrated here for r=3 (the gaffnian series). The
agreement of the parafermionic and the W spectra relies on the prior
determination of the field identifications in the parafermionic case.
| arxiv topic:hep-th cond-mat.mes-hall |
arxiv_dataset-1276906.1049 | Carbon Nanocone: A Promising Thermal Rectifier
cond-mat.mes-hall cond-mat.mtrl-sci
With molecular dynamics simulations, we demonstrate very obvious thermal
rectification in large temperature range from 200 to 400 K in nanocone. We also
observe that the rectification of nanocone does not depend on the length very
sensitively, which is in stark contrast with the nanotube thermal rectifier in
which the rectification decreases dramatically as the length increases. Our
work demonstrates that carbon nanocone is a promising practical phononic
device.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-1277906.1149 | Splittings and C-complexes
math.GR math.GT
The intersection pattern of the translates of the limit set of a quasi-convex
subgroup of a hyperbolic group can be coded in a natural incidence graph, which
suggests connections with the splittings of the ambient group. A similar
incidence graph exists for any subgroup of a group. We show that the
disconnectedness of this graph for codimension one subgroups leads to
splittings. We also reprove some results of Peter Kropholler on splittings of
groups over malnormal subgroups and variants of them.
| arxiv topic:math.GR math.GT |
arxiv_dataset-1278906.1249 | On the honeycomb conjecture and the Kepler problem
math.GM
This paper views the honeycomb conjecture and the Kepler problem essentially
as extreme value problems and solves them by partitioning 2-space and 3-space
into building blocks and determining those blocks that have the universal
extreme values that one needs. More precisely, we proved two results. First, we
proved that the regular hexagons are the only 2-dim blocks that have unit area
and the least perimeter (or contain a unit circle and have the least area) that
tile the plane. Secondly, we proved that the rhombic dodecahedron and the
rhombus-isosceles trapezoidal dodecahedron are the only two 3-dim blocks that
contain a unit sphere and have the least volume that can fill 3-space without
either overlapping or leaving gaps. Finally, the Kepler conjecture can also be
proved to be true by introducing the concept of the minimum 2-dim and 3-dim
Kepler building blocks.
| arxiv topic:math.GM |
arxiv_dataset-1279906.1349 | The Structure & Dynamics of Massive Early-type Galaxies: On Homology,
Isothermality and Isotropy inside one Effective Radius
astro-ph.CO astro-ph.GA
Based on 58 SLACS strong-lens early-type galaxies with direct total-mass and
stellar-velocity dispersion measurements, we find that inside one effective
radius massive elliptical galaxies with M_eff >= 3x10^10 M_sun are
well-approximated by a power-law ellipsoid with an average logaritmic density
slope of <gamma'_LD> = -dlog(rho_tot)/dlog(r)=2.085^{+0.025}_{-0.018} (random
error on mean) for isotropic orbits with beta_r=0, +-0.1 (syst.) and
sigma_gamma' <= 0.20^{+0.04}_{-0.02} intrinsic scatter (all errors indicate the
68 percent CL). We find no correlation of gamma'_LD with galaxy mass (M_eff),
rescaled radius (i.e. R_einst/R_eff) or redshift, despite intrinsic differences
in density-slope between galaxies. Based on scaling relations, the average
logarithmic density slope can be derived in an alternative manner, fully
independent from dynamics, yielding <gamma'_SR>=1.959 +- 0.077. Agreement
between the two values is reached for <beta_r> =0.45 +- 0.25, consistent with
mild radial anisotropy. This agreement supports the robustness of our results,
despite the increase in mass-to-light ratio with total galaxy mass: M_eff ~
L_{V,eff}^(1.363+-0.056). We conclude that massive early-type galaxies are
structurally close-to homologous with close-to isothermal total density
profiles (<=10 percent intrinsic scatter) and have at most some mild radial
anisotropy. Our results provide new observational limits on galaxy formation
and evolution scenarios, covering four Gyr look-back time.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-1280906.1449 | Dynamics of a quantum oscillator strongly and off-resonantly coupled
with a two-level system
cond-mat.mes-hall cond-mat.supr-con
Beyond the rotating-wave approximation, the dynamics of a quantum oscillator
interacting strongly and off-resonantly with a two-level system exhibit
beatings, whose period equals the revival time of the two-level system. On a
longer time scale, the quantum oscillator shows collapses, revivals and
fractional revivals, which are encountered in oscillator observables like the
mean number of oscillator quanta and in the two-level inversion population.
Also the scattered oscillator field shows doublets with symmetrically displaced
peaks.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-1281906.1549 | Timelike formfactors of pion, kaon, and proton at large momentum
transfers
hep-ex
Form factors of the proton, pion, and kaon for large timelike momentum
transfers have recently been measured with precision. The results and future
prospects are discussed.
| arxiv topic:hep-ex |
arxiv_dataset-1282906.1649 | Search for Life on Exoplanets: Toward an International Institutional
Coordination
astro-ph.EP astro-ph.IM
Searching for life in the universe will make use of several large space
missions in the visible and thermal infrared, each with increasing spectral and
angular resolution. They will require long-term planning over the coming
decades. We present the necessity for building an international structure to
coordinate activities for the next several decades and sketch the possible
structure and role of a dedicated international institution.
| arxiv topic:astro-ph.EP astro-ph.IM |
arxiv_dataset-1283906.1749 | Effective Sine(h)-Gordon-like equations for pair-condensates composed of
bosonic or fermionic constituents
cond-mat.stat-mech
An effective coherent state path integral for super-symmetric pair
condensates is investigated with specification on the nontrivial coset
integration measure. The nontrivial coset integration measure, determined by
the square root of the super-determinant of the coset metric tensor, is
eliminated by the inverse square root of this coset metric tensor; this results
into Euclidean path integration variables for the pair condensate fields.
According to the transformation to 'flat' anomalous path integration variables,
first order variations of fields can be performed for classical equations with
inclusion of second and higher even order variations for universal fluctuations
determined by the coset metric tensor of the ortho-symplectic super-manifold.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-1284906.1849 | A Randomized Algorithm for 3-SAT
cs.DS math.CO
In this work we propose and analyze a simple randomized algorithm to find a
satisfiable assignment for a Boolean formula in conjunctive normal form (CNF)
having at most 3 literals in every clause. Given a k-CNF formula phi on n
variables, and alpha in{0,1}^n that satisfies phi, a clause of phi is critical
if exactly one literal of that clause is satisfied under assignment alpha.
Paturi et. al. (Chicago Journal of Theoretical Computer Science 1999) proposed
a simple randomized algorithm (PPZ) for k-SAT for which success probability
increases with the number of critical clauses (with respect to a fixed
satisfiable solution of the input formula). Here, we first describe another
simple randomized algorithm DEL which performs better if the number of critical
clauses are less (with respect to a fixed satisfiable solution of the input
formula). Subsequently, we combine these two simple algorithms such that the
success probability of the combined algorithm is maximum of the success
probabilities of PPZ and DEL on every input instance. We show that when the
average number of clauses per variable that appear as unique true literal in
one or more critical clauses in phi is between 1 and 1.9317, combined algorithm
performs better than the PPZ algorithm.
| arxiv topic:cs.DS math.CO |
arxiv_dataset-1285906.1949 | Quantization of the black hole area as quantization of the angular
momentum component
gr-qc
In transforming from Schwarzschild to Euclidean Rindler coordinates the
Schwarzschild time transforms to a periodic angle. As is well-known, this
allows one to introduce the Hawking temperature and is an origin of black hole
thermodynamics. On the other hand, according to quantum mechanics this angle is
conjugate to the $z$ component of the angular momentum. From the commutation
relation and quantization condition for the angular momentum component it is
found that the area of the horizon of a Schwarzschild black hole is quantized
with the quantum $\Delta A = 8\pi l_P^{2}$. It is shown that this conclusion is
also valid for a generic Kerr-Newman black hole.
| arxiv topic:gr-qc |
arxiv_dataset-1286906.2049 | Separability of massive field equations for spin-0 and spin-1/2 charged
particles in the general non-extremal rotating charged black holes in minimal
five-dimensional gauged supergravity
hep-th gr-qc
We continue to investigate the separability of massive field equations for
spin-0 and spin-1/2 charged particles in the general, non-extremal, rotating,
charged, Chong-Cvetic-Lu-Pope black holes with two independent angular momenta
and a non-zero cosmological constant in minimal D = 5 gauged supergravity
theory. We show that the complex Klein-Gordon equation and the modified Dirac
equation with the inclusion of an extra counter-term can be separated by
variables into purely radial and purely angular parts in this general
Einstein-Maxwell-Chern-Simons background spacetime. A second order symmetry
operator that commutes with the complex Laplacian operator is constructed from
the separated solutions and expressed compactly in terms of a rank-2
Stackel-Killing tensor which admits a simple diagonal form in the chosen pentad
one-forms so that it can be understood as the square of a rank-3 totally
anti-symmetric tensor. A first order symmetry operator that commutes with the
modified Dirac operator is expressed in terms of a rank-3 generalized
Killing-Yano tensor and its covariant derivative. The Hodge dual of this
generalized Killing-Yano tensor is a generalized principal conformal
Killing-Yano tensor of rank-2, which can generate a `tower' of generalized
(conformal) Killing-Yano and Stackel-Killing tensors that are responsible for
the whole hidden symmetries of this general, rotating, charged, Kerr-AdS black
hole geometry. In addition, the first laws of black hole thermodynamics have
been generalized to the case that the cosmological constant can be viewed as a
thermodynamical variable.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-1287906.2149 | Emergence of a Broad-Absorption-Line Outflow in the Narrow-line Seyfert
1 Galaxy WPVS 007
astro-ph.CO
We report results from a 2003 FUSE observation, and reanalysis of a 1996 HST
observation of the unusual X-ray transient Narrow-line Seyfert 1 galaxy WPVS
007. The HST FOS spectrum revealed mini-BALs with V_max ~ 900 km s^-1 and FWHM
~ 550 km s^-1. The FUSE spectrum showed that an additional BAL outflow with
V_max ~ 6000 km s^-1 and FWHM ~ 3400 km s^-1 had appeared. WPVS 007 is a
low-luminosity object in which such a high velocity outflow is not expected;
therefore, it is an outlier on the M_V/V_max relationship. Template spectral
fitting yielded apparent ionic columns, and a Cloudy analysis showed that the
presence of PV requires a high ionization parameter log(U) >= 0 and high column
density log(N_H) >= 23 assuming solar abundances and a nominal SED for
low-luminosity NLS1s with alpha_ox=-1.28. A recent long Swift observation
revealed the first hard X-ray detection and an intrinsic (unabsorbed) alpha_ox
~ -1.9$. Using this SED in our analysis yielded lower column density
constraints (log(N_H) >= 22.2 for Z=1, or log(N_H) >= 21.6 if Z=5). The X-ray
weak continuum, combined with X-ray absorption consistent with the UV lines,
provides the best explanation for the observed Swift X-ray spectrum. The large
column densities and velocities implied by the UV data in any of these
scenarios could be problematic for radiative acceleration. We also point out
that since the observed PV absorption can be explained by lower total column
densities using an intrinsically X-ray weak spectrum, we might expect to find
PV absorption preferentially more often (or stronger) in quasars that are
intrinsically X-ray weak.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1288906.2249 | Three-Body Choreographies in Given Curves
math-ph math.MP
As shown by Johannes Kepler in 1609, in the two-body problem, the shape of
the orbit, a given ellipse, and a given non-vanishing constant angular momentum
determines the motion of the planet completely.
Even in the three-body problem, in some cases, the shape of the orbit,
conservation of the centre of mass and a constant of motion (the angular
momentum or the total energy) determines the motion of the three bodies. We
show, by a geometrical method, that choreographic motions, in which equal mass
three bodies chase each other around a same curve, will be uniquely determined
for the following two cases. (i) Convex curves that have point symmetry and
non-vanishing angular momentum are given. (ii) Eight-shaped curves which are
similar to the curve for the figure-eight solution and the energy constant are
given.
The reality of the motion should be tested whether the motion satisfies an
equation of motion or not.
Extensions of the method for generic curves are shown. The extended methods
are applicable to generic curves which does not have point symmetry. Each body
may have its own curve and its own non-vanishing masses.
| arxiv topic:math-ph math.MP |
arxiv_dataset-1289906.2349 | Non-perturbative methods for a chiral effective field theory of finite
density nuclear systems
nucl-th
Recently we have developed a novel chiral power counting scheme for an
effective field theory of nuclear matter with nucleons and pions as degrees of
freedom [1]. It allows for a systematic expansion taking into account both
local as well as pion-mediated multi-nucleon interactions. We apply this power
counting in the present study to the evaluation of the pion self-energy and the
energy density in nuclear and neutron matter at next-to-leading order. To
implement this power counting in actual calculations we develop here a
non-perturbative method based on Unitary Chiral Perturbation Theory for
performing the required resummations. We show explicitly that the contributions
to the pion self-energy with in-medium nucleon-nucleon interactions to this
order cancel. The main trends for the energy density of symmetric nuclear and
neutron matter are already reproduced at next-to-leading order. In addition, an
accurate description of the neutron matter equation of state, as compared with
sophisticated many-body calculations, is obtained by varying only slightly a
subtraction constant around its expected value. The case of symmetric nuclear
matter requires the introduction of an additional fine-tuned subtraction
constant, parameterizing the effects from higher order contributions. With
that, the empirical saturation point and the nuclear matter incompressiblity
are well reproduced while the energy per nucleon as a function of density
closely agrees with sophisticated calculations in the literature.
| arxiv topic:nucl-th |
arxiv_dataset-1290906.2449 | Combined Modeling of Acceleration, Transport, and Hydrodynamic Response
in Solar Flares: I. The Numerical Model
astro-ph.SR
Acceleration and transport of high-energy particles and fluid dynamics of
atmospheric plasma are interrelated aspects of solar flares. We present here
self-consistently combined Fokker-Planck modeling of particles and hydrodynamic
simulation of flare plasma. Energetic electrons are modeled with the Stanford
unified code of acceleration, transport, and radiation, while plasma is modeled
with the NRL flux tube code. We calculated the collisional heating rate from
the particle transport code, which is more accurate than those based on
approximate analytical solutions. We used a realistic spectrum of injected
electrons provided by the stochastic acceleration model, which has a smooth
transition from a quasi-thermal background at low energies to a nonthermal tail
at high energies. The inclusion of low-energy electrons results in relatively
more heating in the corona (vs. chromosphere), a larger downward conductive
flux, and thus a stronger chromospheric evaporation than obtained in previous
studies, which had a deficit in low-energy electrons due to an arbitrarily
assumed low-energy cutoff. The energy and spatial distributions of energetic
electrons and bremsstrahlung photons bear signatures of the changing density
distribution caused by chromospheric evaporation. In particular, the density
jump at the evaporation front gives rise to enhanced X-ray emission.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1291906.2549 | From Artifacts to Aggregations: Modeling Scientific Life Cycles on the
Semantic Web
cs.DL cs.CY
In the process of scientific research, many information objects are
generated, all of which may remain valuable indefinitely. However, artifacts
such as instrument data and associated calibration information may have little
value in isolation; their meaning is derived from their relationships to each
other. Individual artifacts are best represented as components of a life cycle
that is specific to a scientific research domain or project. Current cataloging
practices do not describe objects at a sufficient level of granularity nor do
they offer the globally persistent identifiers necessary to discover and manage
scholarly products with World Wide Web standards. The Open Archives
Initiative's Object Reuse and Exchange data model (OAI-ORE) meets these
requirements. We demonstrate a conceptual implementation of OAI-ORE to
represent the scientific life cycles of embedded networked sensor applications
in seismology and environmental sciences. By establishing relationships between
publications, data, and contextual research information, we illustrate how to
obtain a richer and more realistic view of scientific practices. That view can
facilitate new forms of scientific research and learning. Our analysis is
framed by studies of scientific practices in a large, multi-disciplinary,
multi-university science and engineering research center, the Center for
Embedded Networked Sensing (CENS).
| arxiv topic:cs.DL cs.CY |
arxiv_dataset-1292906.2649 | The crossed-field and single-field Hall effect in LuRh2Si2
cond-mat.str-el
The Hall effect of LuRh2Si2--the non-magnetic homologue of the heavy-fermion
material YbRh2Si2--is studied with two different setups: In the conventional
single-field geometry, the field dependence is analyzed in terms of the
differential Hall coefficient. Beyond that, the recently developed
crossed-field experiment allows to examine the linear-response Hall coefficient
as a function of magnetic field. The results reveal the expected analogy
between both experiments which corroborates the equivalent findings in
YbRh2Si2. This emphasizes the applicability to investigate field-induced
quantum critical points with both methods.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-1293906.2749 | On Linnik's constant
math.NT
Let a and q be coprime natural numbers. In 1944 Linnik proved that the least
prime in an arithmetic progression a mod q is less then C times q to the L.
Since then the admissible value for the constant L has been improved several
times, lastly by Heath-Brown in 1992 to L=5.5. In his article Heath-Brown
describes several improvement potentials for his paper. Using these potentials
we improve the intermediate results concerning zeros of Dirichlet L-Functions
and finally the admissible constant to L=5.2.
-----
Seien a und q teilerfremde natuerliche Zahlen. 1944 bewies Linnik, dass die
kleinste Primzahl in einer arithmetischen Progression a mod q kleiner als C mal
q hoch L ist. Seitdem wurde der zulaessige Wert fuer die Konstante L oft
verbessert, zuletzt 1992 durch Heath-Brown auf L=5.5. In letzterem Artikel gibt
Heath-Brown verschiedene Potentiale zur Verbesserung seiner Arbeit an. Mit
diesen Potentialen verbessern wir die Zwischenresultate betreffend den
Nullstellen von Dirichletschen L-Funktionen und schliesslich die zulaessige
Konstante auf L=5.2.
| arxiv topic:math.NT |
arxiv_dataset-1294906.2849 | New family of sine-Gordon models
hep-th
This work deals with a new family of models, which includes the sine-Gordon
model and the double-sine-Gordon, triple-sine-Gordon and so on. The
investigation is based on a deformation procedure, which is used to deform a
well-known model, to get to the family of sine-Gordon models. Due to properties
of the procedure, we get to the models and find the corresponding solutions
explicitly, together with all the important features they engender.
| arxiv topic:hep-th |
arxiv_dataset-1295906.2949 | The phase and pole structure of the N*(1535) in piN-->piN and
gammaN-->piN
nucl-th
The nature of some baryonic resonances is still an unresolved issue. The case
of the N*(1535) is particularly interesting in this respect due to the nearby
etaN threshold and interference with the N*(1650). The N*(1535) has been
described as a threshold effect, as a genuine 3-quark resonance, or as
dynamically generated from the interaction of the octet of baryons with the
octet of mesons. In the scheme of dynamical generation, predictions for the
interaction of the N*(1535) with the photon can be made. In this study, we
simultaneously analyze the role of the N*(1535) in the piN-->piN and
gammaN-->piN reactions and compare to the respective amplitudes from partial
wave analyses. This test is very sensitive to the meson-baryon components of
the N*(1535).
| arxiv topic:nucl-th |
arxiv_dataset-1296906.3049 | String Entanglement and D-branes as Pure States
hep-th
We study the entanglement of closed strings degrees of freedom in order to
investigate the microscopic structure and statistics of objects as D-branes. By
considering the macroscopic pure state (MPS) limit, whenever the entanglement
entropy goes to zero (in such a way that the macroscopic properties of the
state are preserved), we show that boundary states may be recovered in this
limit and, furthermore, the description through closed string (perturbative)
degrees of freedom collapses. We also show how the thermal properties of branes
and closed strings could be described by this model, and it requires that
dissipative effects be taken into account. Extensions of the MPS analysis to
more general systems at finite temperature are finally emphasized.
| arxiv topic:hep-th |
arxiv_dataset-1297906.3149 | Semi-Myopic Sensing Plans for Value Optimization
cs.AI
We consider the following sequential decision problem. Given a set of items
of unknown utility, we need to select one of as high a utility as possible
(``the selection problem''). Measurements (possibly noisy) of item values prior
to selection are allowed, at a known cost. The goal is to optimize the overall
sequential decision process of measurements and selection.
Value of information (VOI) is a well-known scheme for selecting measurements,
but the intractability of the problem typically leads to using myopic VOI
estimates. In the selection problem, myopic VOI frequently badly underestimates
the value of information, leading to inferior sensing plans. We relax the
strict myopic assumption into a scheme we term semi-myopic, providing a
spectrum of methods that can improve the performance of sensing plans. In
particular, we propose the efficiently computable method of ``blinkered'' VOI,
and examine theoretical bounds for special cases. Empirical evaluation of
``blinkered'' VOI in the selection problem with normally distributed item
values shows that is performs much better than pure myopic VOI.
| arxiv topic:cs.AI |
arxiv_dataset-1298906.3249 | The half-integral weight eigencurve
math.NT
In this paper we define Banach spaces of overconvergent half-integral weight
$p$-adic modular forms and Banach modules of families of overconvergent
half-integral weight $p$-adic modular forms over admissible open subsets of
weight space. Both spaces are equipped with a continuous Hecke action for which
$U_{p^2}$ is moreover compact. The modules of families of forms are used to
construct an eigencurve parameterizing all finite-slope systems of eigenvalues
of Hecke operators acting on these spaces. We also prove an analog of Coleman's
theorem stating that overconvergent eigenforms of suitably low slope are
classical.
| arxiv topic:math.NT |
arxiv_dataset-1299906.3349 | Dynamical evolutin of quintessence dark energy in collapsing dark matter
halos
astro-ph.CO
In this paper, we analyze the dynamical evolution of quintessence dark energy
induced by the collapse of dark matter halos. Different from other previous
studies, we develop a numerical strategy which allows us to calculate the dark
energy evolution for the entire history of the spherical collapse of dark
matter halos, without the need of separate treatments for linear, quasi-linear
and nonlinear stages of the halo formation. It is found that the dark energy
perturbations evolve with redshifts, and their specific behaviors depend on the
quintessence potential as well as the collapsing process. The overall energy
density perturbation is at the level of $10^{-6}$ for cluster-sized halos. The
perturbation amplitude decreases with the decrease of the halo mass. At a given
redshift, the dark energy perturbation changes with the radius to the halo
center, and can be either positive or negative depending on the contrast of
$\partial_t \phi$, $\partial_r \phi$ and $\phi$ with respect to the background,
where $\phi$ is the quintessence field. For shells where the contrast of
$\partial_r \phi$ is dominant, the dark energy perturbation is positive and can
be as high as about $10^{-5}$.
| arxiv topic:astro-ph.CO |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.