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arxiv_dataset-26001105.0735 | \eta(1475) and f_1(1420) resonances in \gamma\gamma* collisions and
J/\psi\to\gamma(\rho\rho, \gamma\rho^0, \gamma\phi) decays
hep-ph hep-ex nucl-th
The available data on the $Q^2$ dependence of the $\gamma\gamma*(Q^2)\to
K\bar K\pi$ reaction cross section in the energy region 1.35-1.55 GeV is
explained by the $\eta(1475)$ resonance production in contrast to their
conventional interpretation with the use of the $f_1(1420)$ resonance. It
resolves theoretically the contradiction between the suppression of the
$\eta(1475)\to\gamma\gamma$ decay width and the strong couplings of the
$\eta(1475)$ to the $\rho\rho$, $\omega\omega$, and $\gamma\rho^0$ channels.
The experimental check of our explanation requires definition of the
spin-parity of the resonance contributions, $R$, in $\gamma\gamma*(Q^2)\to R\to
K\bar K\pi$ and in $J/\psi\to\gammaR\to\gamma\gamma(\rho^0, \phi)$. This will
help to solve difficulties accumulated in understanding properties of the
$\eta(1475)$ state and its nearest partners.
| arxiv topic:hep-ph hep-ex nucl-th |
arxiv_dataset-26011105.0835 | Tiling Spaces, Codimension One Attractors and Shape
math.DS
We show that any codimension one hyperbolic attractor of a diffeomorphism of
a (d+1)-dimensional closed manifold is shape equivalent to a (d+1)-dimensional
torus with a finite number of points removed, or, in the non-orientable case,
to a space with a 2 to 1 covering by such a torus-less-points. Furthermore, we
show that each orientable attractor is homeomorphic to a tiling space
associated to an aperiodic tiling of Rd, but that the converse is generally not
true. This work allows the definition of a new invariant for aperiodic tilings,
in many cases finer than the cohomological or K-theoretic invariants studied to
date.
| arxiv topic:math.DS |
arxiv_dataset-26021105.0935 | Criticality of compact and noncompact quantum dissipative $Z_4$ models
in $(1+1)$ dimensions
cond-mat.stat-mech cond-mat.str-el
Using large-scale Monte Carlo computations, we study two versions of a
$(1+1)D$ $Z_4$-symmetric model with Ohmic bond dissipation. In one of these
versions, the variables are restricted to the interval $[0,2\pi>$, while the
domain is unrestricted in the other version. The compact model features a
completely ordered phase with a broken $Z_4$ symmetry and a disordered phase,
separated by a critical line. The noncompact model features three phases. In
addition to the two phases exhibited by the compact model, there is also an
intermediate phase with isotropic quasi-long-range order. We calculate the
dynamical critical exponent $z$ along the critical lines of both models to see
if the compactness of the variable is relevant to the critical scaling between
space and imaginary time. There appears to be no difference between the two
models in that respect, and we find $z\approx1$ for the single phase transition
in the compact model as well as for both transitions in the noncompact model.
| arxiv topic:cond-mat.stat-mech cond-mat.str-el |
arxiv_dataset-26031105.1035 | Chromomagnetism in nuclear matter
nucl-th
Quarks are color charged particles. Due to their motion there is a strong
possibility of generation of color magnetic field. It is shown that however
hadrons are color singlet particles they may have non-zero color magnetic
moment. Due to this color magnetic moment hadrons can show color interaction.
In this paper we have studied the chromomagnetic properties of nuclear matter.
| arxiv topic:nucl-th |
arxiv_dataset-26041105.1135 | Robustness of s-wave Pairing in Electron-Overdoped
$\text{A}_{1-y}\text{Fe}_{2-x}\text{Se}_2$
cond-mat.supr-con
Using self consistent mean field and functional renormalization group
approaches we show that s-wave pairing symmetry is robust in the heavily
electron-doped iron chalcogenides $(\text{K, Cs}) \text{Fe}_{2-x}\text{Se}_2 $.
This is because in these materials the leading antiferromagnetic (AFM) exchange
coupling is between next-nearest-neighbor (NNN) sites while the nearest
neighbor (NN) magnetic exchange coupling is ferromagnetic (FM). This is
different from the iron pnictides, where the NN magnetic exchange coupling is
AFM and leads to strong competition between s-wave and d-wave pairing in the
electron overdoped region. Our finding of a robust s-wave pairing in $(\text{K,
Cs}) \text{Fe}_{2-x}\text{Se}_2$ differs from the d-wave pairing result
obtained by other theories where non-local bare interaction terms and the NNN
$J_2$ term are underestimated. Detecting the pairing symmetry in $(\text{K,
Cs}) \text{Fe}_{2-x}\text{Se}_2 $ may hence provide important insights
regarding the mechanism of superconducting pairing in iron based
superconductors.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-26051105.1235 | Radio frequency readout of electrically detected magnetic resonance in
phosphorus-doped silicon MOSFETs
cond-mat.mes-hall cond-mat.mtrl-sci
We demonstrate radio frequency (RF) readout of electrically detected magnetic
resonance in phosphorus-doped silicon metal-oxide field-effecttransistors
(MOSFETs), operated at liquid helium temperatures. For the first time, the Si:P
hyperfine lines have been observed using radio frequency reflectometry, which
is promising for high-bandwidth operation and possibly time-resolved detection
of spin resonance in donor-based semiconductor devices. Here we present the
effect of microwave (MW) power and MOSFET biasing conditions on the EDMR
signals.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-26061105.1335 | Further Evidence Suggestive of a Solar Influence on Nuclear Decay Rates
astro-ph.SR nucl-ex
Recent analyses of nuclear decay data show evidence of variations suggestive
of a solar influence. Analyses of datasets acquired at the Brookhaven National
Laboratory (BNL) and at the Physikalisch-Technische Bundesanstalt (PTB) both
show evidence of an annual periodicity and of periodicities with sidereal
frequencies in the neighborhood of 12.25 year^{-1} (at a significance level
that we have estimated to be 10^{-17}). It is notable that this implied
rotation rate is lower than that attributed to the solar radiative zone,
suggestive of a slowly rotating solar core. This leads us to hypothesize that
there may be an "inner tachocline" separating the core from the radiative zone,
analogous to the "outer tachocline" that separates the radiative zone from the
convection zone. The Rieger periodicity (which has a period of about 154 days,
corresponding to a frequency of 2.37 year^{-1}) may be attributed to an r-mode
oscillation with spherical-harmonic indices l=3, m=1, located in the outer
tachocline. This suggests that we may test the hypothesis of a solar influence
on nuclear decay rates by searching BNL and PTB data for evidence of a
"Rieger-like" r-mode oscillation, with l=3, m=1, in the inner tachocline. The
appropriate search band for such an oscillation is estimated to be 2.00-2.28
year^{-1}. We find, in both datasets, strong evidence of a periodicity at 2.11
year^{-1}. We estimate that the probability of obtaining these results by
chance is 10^{-12}.
| arxiv topic:astro-ph.SR nucl-ex |
arxiv_dataset-26071105.1435 | Levy targeting and the principle of detailed balance
cond-mat.stat-mech math-ph math.MP math.PR
We investigate confined L\'{e}vy flights under premises of the principle of
detailed balance. The master equation admits a transformation to L\'{e}vy -
Schr\"{o}dinger semigroup dynamics (akin to a mapping of the Fokker-Planck
equation into the generalized diffusion equation). We solve a stochastic
targeting problem for arbitrary stability index $0<\mu <2$ of L\'{e}vy drivers:
given an invariant probability density function (pdf), specify the jump - type
dynamics for which this pdf is a long-time asymptotic target. Our
("$\mu$-targeting") method is exemplified by Cauchy family and Gaussian target
pdfs. We solve the reverse engineering problem for so-called L\'{e}vy
oscillators: given a quadratic semigroup potential, find an asymptotic pdf for
the associated master equation for arbitrary $\mu$.
| arxiv topic:cond-mat.stat-mech math-ph math.MP math.PR |
arxiv_dataset-26081105.1535 | Hyperbolic hydra
math.GR
We give examples of hyperbolic groups with finite-rank free subgroups of huge
(Ackermannian) distortion.
| arxiv topic:math.GR |
arxiv_dataset-26091105.1635 | Molecular Orientation by Intense Single Cycle THz Pulses
physics.chem-ph physics.optics
Intense single-cycle THz pulses resonantly interacting with molecular
rotations are shown to induce significant field-free orientation under ambient
conditions. We calculate and measure the angular distribution associated with
THz-driven rotational motion and correlate the THz-induced orientation and
alignment in an OCS gas sample.
| arxiv topic:physics.chem-ph physics.optics |
arxiv_dataset-26101105.1735 | The energy source of the filaments around the giant galaxy NGC1275
astro-ph.GA astro-ph.CO
The brightest galaxy in the nearby Perseus cluster, NGC1275, is surrounded by
a network of filaments. These were first observed through their Halpha emission
but are now known to have a large molecular component with a total mass
approaching 10^11Msun of gas. The filaments are embedded in hot intracluster
gas and stretch over 80 kpc. They have an unusual low excitation spectrum which
is well modelled by collisional heating and ionization by secondary electrons.
Here we note that the surface radiative flux from the outer filaments is close
to the energy flux impacting on them from particles in the hot gas. We propose
that the secondary electrons within the cold filaments, which excite the
observed submillimetre through UV emission, are due to the hot surrounding gas
efficiently penetrating the cold gas through reconnection diffusion. Some of
the soft X-ray emission seen from the filaments is then due to charge exchange,
although this is insufficient to account for all the observed X-ray flux. The
filaments are complex with multiphase gas. Interpenetration of hot and cold gas
leads to the filaments growing in mass, at a rate of up to 100Msunpyr. The lack
of soft X-ray cooling emission in cool core clusters is then due to the
non-radiative cooling of hot gas on mixing with cold gas around and within the
central galaxy.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-26111105.1835 | Gluon saturation and baryon stopping in the SPS, RHIC and LHC energy
regions
hep-ph
A new geometrical scaling method with gluon saturation rapidity limit is
proposed to study the gluon saturation feature of the central rapidity region
of relativistic nuclear collisions. The net-baryon number is essentially
transported by valence quarks that probe the saturation regime in the target by
multiple scattering. We take advantage of the gluon saturation model with
geometric scaling of the rapidity limit to investigate the net baryon
distributions, nuclear stopping power and gluon saturation features in the SPS
and RHIC energy regions. Predictions for net-baryon rapidity distributions, the
mean rapidity loss and gluon saturation feature in central Pb + Pb collisions
at LHC are made in this paper.
| arxiv topic:hep-ph |
arxiv_dataset-26121105.1935 | Group entropies, correlation laws and zeta functions
cond-mat.stat-mech hep-th math-ph math.MP
The notion of group entropy is proposed. It enables to unify and generalize
many different definitions of entropy known in the literature, as those of
Boltzmann-Gibbs, Tsallis, Abe and Kaniadakis. Other new entropic functionals
are presented, related to nontrivial correlation laws characterizing
universality classes of systems out of equilibrium, when the dynamics is weakly
chaotic. The associated thermostatistics are discussed. The mathematical
structure underlying our construction is that of formal group theory, which
provides the general structure of the correlations among particles and dictates
the associated entropic functionals. As an example of application, the role of
group entropies in information theory is illustrated and generalizations of the
Kullback-Leibler divergence are proposed. A new connection between statistical
mechanics and zeta functions is established. In particular, Tsallis entropy is
related to the classical Riemann zeta function.
| arxiv topic:cond-mat.stat-mech hep-th math-ph math.MP |
arxiv_dataset-26131105.2035 | Scaling dimensions in hidden Kerr/CFT
hep-th gr-qc
It has been proposed that a hidden conformal field theory (CFT) governs the
dynamics of low frequency scattering in a general Kerr black hole background.
We further investigate this correspondence by mapping higher order corrections
to the massless wave equations in a Kerr background to an expansion within the
CFT in terms of higher dimension operators. This implies the presence of
infinite towers of CFT primary operators with positive conformal dimensions
compatible with unitarity. The exact Kerr background softly breaks the
conformal symmetry and the scaling dimensions of these operators run with
frequency. The scale-invariant fixed point is dual to a degenerate case of flat
spacetime.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-26141105.2135 | Confidence bands for Horvitz-Thompson estimators using sampled noisy
functional data
math.ST stat.ME stat.TH
When collections of functional data are too large to be exhaustively
observed, survey sampling techniques provide an effective way to estimate
global quantities such as the population mean function. Assuming functional
data are collected from a finite population according to a probabilistic
sampling scheme, with the measurements being discrete in time and noisy, we
propose to first smooth the sampled trajectories with local polynomials and
then estimate the mean function with a Horvitz-Thompson estimator. Under mild
conditions on the population size, observation times, regularity of the
trajectories, sampling scheme, and smoothing bandwidth, we prove a Central
Limit theorem in the space of continuous functions. We also establish the
uniform consistency of a covariance function estimator and apply the former
results to build confidence bands for the mean function. The bands attain
nominal coverage and are obtained through Gaussian process simulations
conditional on the estimated covariance function. To select the bandwidth, we
propose a cross-validation method that accounts for the sampling weights. A
simulation study assesses the performance of our approach and highlights the
influence of the sampling scheme and bandwidth choice.
| arxiv topic:math.ST stat.ME stat.TH |
arxiv_dataset-26151105.2235 | 3D MHD Simulations of Planet Migration in Turbulent Stratified Disks
astro-ph.EP
We performed 3D MHD simulations of planet migration in stratified disks using
the Godunov code PLUTO, where the disk is turbulent due to the
magnetorotational instability. We study the migration for planets with
different planet-star mass ratios $q=M_{p}/M_{s}$. In agreement with previous
studies, for the low-mass planet cases ($q=5\times10^{-6}$ and $10^{-5}$),
migration is dominated by random fluctuations in the torque. For a Jupiter-mass
planet $(q=M_{p}/M_{s}=10^{-3}$ for $M_{s}=1M_{\odot})$, we find a reduction of
the magnetic stress inside the orbit of the planet and around the gap region.
After an initial stage where the torque on the planet is positive, it reverses
and we recover migration rates similar to those found in disks where the
turbulent viscosity is modelled by an $\alpha$ viscosity. For the
intermediate-mass planets ($q=5\times10^{-5}, 10^{-4}$ and $2\times10^{-4}$) we
find a new and so far unexpected behavior. In some cases they experience
sustained and systematic outwards migration for the entire duration of the
simulation. For this case, the horseshoe region is resolved and torques coming
from the corotation region can remain unsaturated due to the stresses in the
disk. These stresses are generated directly by the magnetic field. The
magnitude of the horseshoe drag can overcome the negative Lindblad contribution
when the local surface density profile is flat or increasing outwards, which we
see in certain locations in our simulations due to the presence of a zonal
flow. The intermediate-mass planet is migrating radially outwards in locations
where there is a positive gradient of a pressure bump (zonal flow).
| arxiv topic:astro-ph.EP |
arxiv_dataset-26161105.2335 | Hierarchical Complexity: Measures of High Level Modularity
cs.SE
Software is among the most complex endeavors of the human mind; large scale
systems can have tens of millions of lines of source code. However, seldom is
complexity measured above the lowest level of code, and sometimes source code
files or low level modules. In this paper a hierarchical approach is explored
in order to find a set of metrics that can measure higher levels of
organization. These metrics are then used on a few popular free software
packages (totaling more than 25 million lines of code) to check their
efficiency and coherency.
| arxiv topic:cs.SE |
arxiv_dataset-26171105.2437 | Continuous-time model for multi-product scheduling in production
math.OC
We consider a problem of multi-product scheduling in production. Each product
can be produced by a family of alternative multi-machine technologies.
Multi-machine technologies require more than one machine at the same time. A
sequence dependent setup time is needed between different technologies. We
formulate a mixed integer linear programming model for the general case of the
problem and for the case, when the setup times satisfy the triangle inequality.
The proposed models are experimentally tested on randomly generated instances.
| arxiv topic:math.OC |
arxiv_dataset-26181105.2539 | Nuclear Spin 3=2 Electric Quadrupole Relaxation as a Quantum Computation
quant-ph
In this work we applied a quantum circuit treatment to describe the nuclear
spin relax- ation. From the Redfield theory, we were able to describe the
quadrupolar relaxation as a computational process in the case of spin 3/2
systems, through a model in which the environment is comprised by seven qubits
and three different quantum noise channels. The interaction between the
environment and the spin 3/2 nuclei is then described by a quantum circuit
fully compatible with the Redfield theory of relaxation. Theoretical
predictions are compared to experimental data, a short review of quantum
channels and relaxation in NMR qubits is also present.
| arxiv topic:quant-ph |
arxiv_dataset-26191105.2639 | Fonctions L de paires pour les groupes classiques
math.RT math.NT
Let $\pi$ be a square integrable representation of a classical group and let
$\rho$ be a cuspidal representation of a general linear group. We can define in
two different ways an L-function $L(\rho \times \pi,s)$: first we can use the
Langlands parametrization at each places which is now available, thanks to
Arthur's work, and secondly we can transfer $\pi$ to a general linear group,
using the twisted endoscopy as established by Arthur. In this paper, we compare
the two definitions and we prove, as expected, that the first one has less
poles that the second one. Assuming that $\pi$ is cuspidal, we link the poles
of the first L-function to the poles of the Eisensteins series and when $\rho$
is a quadratic character and when the groupe is a special orthogonal group, we
also link theses poles with the theta lifts. We have some hypothesis at the
archimedean places.
| arxiv topic:math.RT math.NT |
arxiv_dataset-26201105.2739 | Spin dephasing and photoinduced spin diffusion in high-mobility
110-grown GaAs-AlGaAs two-dimensional electron systems
cond-mat.mes-hall
We have studied spin dephasing and spin diffusion in a high-mobility
two-dimensional electron system, embedded in a GaAs/AlGaAs quantum well grown
in the [110] direction, by a two-beam Hanle experiment. For very low excitation
density, we observe spin lifetimes of more than 16 ns, which rapidly decrease
as the pump intensity is increased. Two mechanisms contribute to this decrease:
the optical excitation produces holes, which lead to a decay of electron spin
via the Bir-Aranov-Pikus mechanism and recombination with spin-polarized
electrons. By scanning the distance between the pump and probe beams, we
observe the diffusion of spin-polarized electrons over more than 20 microns.
For high pump intensity, the spin polarization in a distance of several microns
from the pump beam is larger than at the pump spot, due to the reduced
influence of photogenerated holes.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-26211105.2839 | RHESSI Line and Continuum Observations of Super-hot Flare Plasma
astro-ph.SR astro-ph.HE physics.plasm-ph physics.space-ph
We use RHESSI high-resolution imaging and spectroscopy observations from ~5
to 100 keV to characterize the hot thermal plasma during the 2002 July 23 X4.8
flare. These measurements of the steeply falling thermal X-ray continuum are
well fit throughout the flare by two distinct isothermal components: a
super-hot (T > 30 MK) component that peaks at ~44 MK and a lower-altitude hot
(T < 25 MK) component whose temperature and emission measure closely track
those derived from GOES measurements. The two components appear to be spatially
distinct, and their evolution suggests that the super-hot plasma originates in
the corona, while the GOES plasma results from chromospheric evaporation.
Throughout the flare, the measured fluxes and ratio of the Fe and Fe-Ni
excitation line complexes at ~6.7 and ~8 keV show a close dependence on the
super-hot continuum temperature. During the pre-impulsive phase, when the
coronal thermal and non-thermal continua overlap both spectrally and spatially,
we use this relationship to obtain limits on the thermal and non-thermal
emission.
| arxiv topic:astro-ph.SR astro-ph.HE physics.plasm-ph physics.space-ph |
arxiv_dataset-26221105.2939 | Compound Hertzian Chain Model for Copper-Carbon Nanocomposites'
Absorption Spectrum
physics.optics
The infrared range optical absorption mechanism of Carbon-Copper composite
thin layer coated on the Diamond-Like Carbon (DLC) buffer layer has been
investigated. By consideration of weak interactions between copper
nanoparticles in their network, optical absorption is modeled using their
coherent dipole behavior induced by the electromagnetic radiation. The copper
nanoparticles in the bulk of carbon are assumed as a chain of plasmonic
dipoles, which have coupling resonance. Considering nearest neighbor
interactions for this metallic nanoparticles, surface plasmon resonance
frequency ({\omega}\neg0) and coupled plasmon resonance frequency
({\omega}\neg1) have been computed. The damping rate versus wavelength is
derived which leads to the derivation of the optical absorption spectrum in the
term of {\omega}\neg0 and {\omega}\neg1. The dependency of the absorption peaks
to the particle-size and the particle mean spacing is also investigated. The
absorption spectrum is measured for different Cu-C thin films with various Cu
particle size and spacing. The experimental results of absorption are compared
with the obtained analytical ones.
| arxiv topic:physics.optics |
arxiv_dataset-26231105.3039 | Testing composite hypotheses, Hermite polynomials and optimal estimation
of a nonsmooth functional
math.ST stat.TH
A general lower bound is developed for the minimax risk when estimating an
arbitrary functional. The bound is based on testing two composite hypotheses
and is shown to be effective in estimating the nonsmooth functional
${\frac{1}{n}}\sum|\theta_i|$ from an observation $Y\sim N(\theta,I_n)$. This
problem exhibits some features that are significantly different from those that
occur in estimating conventional smooth functionals. This is a setting where
standard techniques fail to yield sharp results. A sharp minimax lower bound is
established by applying the general lower bound technique based on testing two
composite hypotheses. A key step is the construction of two special priors and
bounding the chi-square distance between two normal mixtures. An estimator is
constructed using approximation theory and Hermite polynomials and is shown to
be asymptotically sharp minimax when the means are bounded by a given value
$M$. It is shown that the minimax risk equals $\beta_*^2M^2({\frac{\log\log
n}{\log n}})^2$ asymptotically, where $\beta_*$ is the Bernstein constant. The
general techniques and results developed in the present paper can also be used
to solve other related problems.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-26241105.3139 | The cone of type A, level one conformal blocks divisors
math.AG
We prove that the type A, level one, conformal blocks divisors on
$\bar{M}_{0,n}$ span a finitely generated, full-dimensional subcone of the nef
cone. Each such divisor induces a morphism from $\bar{M}_{0,n}$, and we
identify its image as a GIT quotient parameterizing configurations of points
supported on a flat limit of Veronese curves. We show how scaling GIT
linearizations gives geometric meaning to certain identities among conformal
blocks divisor classes. This also gives modular interpretations, in the form of
GIT constructions, to the images of the hyperelliptic and cyclic trigonal loci
in $\bar{M}_{g}$ under an extended Torelli map.
| arxiv topic:math.AG |
arxiv_dataset-26251105.3239 | Double Blind Comparisons: A New Approach to the Database Aggregation
Problem
cs.CR
The Data Aggregation Problem occurs when a large collection of data takes on
a higher security level than any of its individual component records.
Traditional approaches of breaking up the data and restricting access on a
"need to know" basis take away one of the great advantages of collecting the
data in the first place. This paper introduces a new cryptographic primitive,
Double Blind Comparisons, which allows two co-operating users, who each have an
encrypted secret, to determine the equality or inequality of those two secrets,
even though neither user can discover any information about what the secret is.
This paper also introduces a new problem in bilinear groups, conjectured to be
a hard problem. Assuming this conjecture, it is shown that neither user can
discover any information about whether the secrets are equal, without the other
user's co-operation. We then look at how Double Blind Comparisons can be used
to mitigate the Data Aggregation Problem. Finally, the paper concludes with
some suggested possibilities for future research and some other potential uses
for Double Blind Comparisons.
| arxiv topic:cs.CR |
arxiv_dataset-26261105.3339 | Experimental Optimum Maximum-Confidence Discrimination and Optimum
Unambiguous Discrimination of Two Mixed Single-Photon States
quant-ph
We present an experimental implementation of optimum measurements for quantum
state discrimination. Optimum maximum-confidence discrimination and optimum
unambiguous discrimination of two mixed single-photon polarization states were
performed. For the latter the states of rank two in a four-dimensional Hilbert
space are prepared using both path and polarization encoding. Linear optics and
single photons from a true single-photon source based on a semiconductor
quantum dot are utilized.
| arxiv topic:quant-ph |
arxiv_dataset-26271105.3439 | On uniformly effective birationality and the Shafarevich Conjecture over
curves
math.AG math.CV math.NT
Let $B$ be a smooth projective curve of genus $g$, and $S \subset B$ be a
finite subset of cardinality $s$. We give an effective upper bound on the
number of deformation types of admissible families of canonically polarized
manifolds of dimension $n$ with canonical volume $v$ over $B$ with prescribed
degeneracy locus $S$. The effective bound only depends on the invariants $g, s,
n$ and $v$. The key new ingredient which allows for this kind of result is a
careful study of effective birationality for families of canonically polarized
manifolds.
| arxiv topic:math.AG math.CV math.NT |
arxiv_dataset-26281105.3539 | Charge Exchange X-ray Emission of M82: K{\alpha} triplets of O VII, Ne
IX, and Mg XI
astro-ph.GA astro-ph.HE
Starburst galaxies are primary feedback sources of mechanical energy and
metals, which are generally measured from associated X-ray emission lines
assuming that they are from the thermal emission of the outflowing hot gas.
Such line emission, however, can also arise from the charge exchange X-ray
emission (CXE) between highly ionized ions and neutral species. To understand
the feedback of energy and metals, it is crucial to determine the origin of the
X-ray emission lines and to distinguish the contributions from the CXE and the
thermal emission. The origin of the lines can be diagnosed by the K{\alpha}
triplets of He-like ions, because the CXE favors the inter-combination and
forbidden lines, while the thermal emission favors the resonance line. We
analyze the triplets of O VII, Ne IX, and Mg XI observed in the XMM- Newton
reflection grating spectra of the starburst galaxy M82. The flux contribution
of the CXE is 90%, 50%, and 30% to the O VII, Ne IX, and Mg XI triplet,
respectively. Averaged over all the three triplets, the contribution of the CXE
is \sim 50% of the total observed triplet flux. To correctly understand the hot
outflow of starburst galaxies, it is necessary to include the CXE. Based on the
measured CXE contributions to the O VII, Ne IX, and Mg XI triplets, we estimate
the relative abundances of O, Ne, and Mg of the outflow and find they are
similar to the solar ratios.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-26291105.3639 | On the uniqueness of solution to the steady Euler equations with
perturbations
math.AP
In this paper we study the uniqueness property of solutions to the steady
incompressible Euler equations with perturbations in $\Bbb R^N$. Our
perturbations include as special cases the Euler equations with a `single
signed' nonlinear term, the self-similar Euler equations, and the steady
Navier-Stokes equations. For these equations show that suitable decay
assumptions at infinity on the solution or its derivatives, imposed by the
$L^q$ conditions imply that the only possible solution is zero.
| arxiv topic:math.AP |
arxiv_dataset-26301105.3739 | On Automorphisms of the Affine Cremona Group
math.AG
We show that every automorphism of the group $\mathcal{G}_n:=
\textrm{Aut}(\mathbb{A}^n)$ of polynomial automorphisms of complex affine
$n$-space $\mathbb{A}^n=\mathbb{C}^n$ is inner up to field automorphisms when
restricted to the subgroup $T \mathcal{G}_n$ of tame automorphisms. This
generalizes a result of \textsc{Julie Deserti} who proved this in dimension
$n=2$ where all automorphisms are tame: $T \mathcal{G}_2 = \mathcal{G}_2$.
| arxiv topic:math.AG |
arxiv_dataset-26311105.3839 | Random fields and the geometry of Wiener space
math.PR
In this work we consider infinite dimensional extensions of some finite
dimensional Gaussian geometric functionals called the Gaussian Minkowski
functionals. These functionals appear as coefficients in the probability
content of a tube around a convex set $D\subset\mathbb{R}^k$ under the standard
Gaussian law $N(0,I_{k\times k})$. Using these infinite dimensional extensions,
we consider geometric properties of some smooth random fields in the spirit of
[Random Fields and Geometry (2007) Springer] that can be expressed in terms of
reasonably smooth Wiener functionals.
| arxiv topic:math.PR |
arxiv_dataset-26321105.3939 | High energy pseudogap and its evolution with doping in Fe-based
superconductors as revealed by optical spectroscopy
cond-mat.supr-con cond-mat.str-el
We report optical spectroscopic measurements on electron- and hole-doped
BaFe2As2. We show that the compounds in the normal state are not simple metals.
The optical conductivity spectra contain, in addition to the free carrier
response at low frequency, a temperature-dependent gap-like suppression at
rather high energy scale near 0.6 eV. This suppression evolves with the
As-Fe-As bond angle induced by electron- or hole-doping. Furthermore, the
feature becomes much weaker in the Fe-chalcogenide compounds. We elaborate that
the feature is caused by the strong Hund's rule coupling effect between the
itinerant electrons and localized electron moment arising from the multiple Fe
3d orbitals. Our experiments demonstrate the coexistence of itinerant and
localized electrons in iron-based compounds, which would then lead to a more
comprehensive picture about the metallic magnetism in the materials.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-26331105.4039 | An Elementary Extension of Korn's First Inequality to H(Curl) motivated
by Gradient Plasticity with Plastic Spin
math.AP math-ph math.FA math.MP
We prove a Korn-type inequality for tensor fields without gradient structure,
which generalizes Korn's first inequality.
| arxiv topic:math.AP math-ph math.FA math.MP |
arxiv_dataset-26341105.4139 | Jet Formation in the magnetospheres of supermassive black holes:
analytic solutions describing energy loss through Blandford-Znajek processes
astro-ph.HE
In this paper, we provide exact solutions for the extraction of energy from a
rotating black hole via both the electromagnetic Poynting flux and matter
currents. By appropriate choice of a radially independent poloidal function
$\Lambda(\theta)$, we find solutions where the dominant outward energy flux is
along the polar axis, consistent with a jet-like collimated outflow, but also
with a weaker flux of energy along the equatorial plane. Unlike all the
previously obtained solutions (Blandford & Znajek (1977), Menon & Dermer
(2005)), the magnetosphere is free of magnetic monopoles everywhere.
| arxiv topic:astro-ph.HE |
arxiv_dataset-26351105.4239 | Retrieval of phase memory in two independent atomic ensembles by Raman
process
quant-ph
In spontaneous Raman process in atomic cell at high gain, both the Stokes
field and the accompanying collective atomic excitation (atomic spin wave) are
coherent. We find that, due to the spontaneous nature of the process, the
phases of the Stokes field and the atomic spin wave change randomly from one
realization to another but are anti-correlated. The phases of the atomic
ensembles are read out via another Raman process at a later time, thus
realizing phase memory in atoms. The observation of phase correlation between
the Stokes field and the collective atomic excitations is an important step
towards macroscopic EPR-type entanglement of continuous variables between light
and atoms.
| arxiv topic:quant-ph |
arxiv_dataset-26361105.4339 | Design and performance of the South Pole Acoustic Test Setup
astro-ph.IM
The South Pole Acoustic Test Setup (SPATS) was built to evaluate the acoustic
characteristics of the South Pole ice in the 10 kHz to 100 kHz frequency range,
for the purpose of assessing the feasibility of an acoustic neutrino detection
array at the South Pole. The SPATS hardware consists of four vertical strings
deployed in the upper 500 m of the South Pole ice cap. The strings form a
trapezoidal array with a maximum baseline of 543 m. Each string has 7 stages
equipped with one transmitter and one sensor module. Sound is detected or
generated by piezoelectric ceramic elements inside the modules. Analogue
signals are sent to the surface on electric cables where they are digitized by
a PC-based data acquisition system. The data from all strings are collected on
a central computer in the IceCube Laboratory from where they are send to a
central data storage facility via a satellite link or stored locally on tape. A
technical overview of SPATS and its performance is presented.
| arxiv topic:astro-ph.IM |
arxiv_dataset-26371105.4439 | Fermionic screenings and chiral de Rham complex on CY manifolds with
line bundles
hep-th
We represent a generalization of Borisov's construction of chiral de Rham
complex for the case of line bundle twisted chiral de Rham complex on
Calabi-Yau hypersurface in projective space. We generalize the differential
associated to the polytope $\Delta$ of the projective space $\mathbb{P}^{d-1}$
by allowing nonzero modes for the screening currents forming this differential.
It is shown that the numbers of screening current modes define the support
function of toric divisor of a line bundle on $\mathbb{P}^{d-1}$ that twists
the chiral de Rham complex on Calabi-Yau hypersurface.
| arxiv topic:hep-th |
arxiv_dataset-26381105.4539 | Effective potential for quantum scalar fields on a de Sitter geometry
hep-th astro-ph.CO gr-qc hep-ph nucl-th
We study the quantum theory of an O(N) scalar field on de Sitter geometry at
leading order in a nonperturbative 1/N-expansion. This resums the infinite
series of so-called superdaisy loop diagrams. We obtain the de Sitter symmetric
solutions of the corresponding, properly renormalized, dynamical field
equations and compute the complete effective potential. Because of its
self-interactions, the field acquires a strictly positive square mass which
screens potential infrared divergences. Moreover, strongly enhanced
ultralong-wavelength fluctuations prevent the existence of a spontaneously
broken symmetry state in any dimension.
| arxiv topic:hep-th astro-ph.CO gr-qc hep-ph nucl-th |
arxiv_dataset-26391105.4639 | Gas Condensation in the Galactic Halo
astro-ph.CO
Using adaptive mesh refinement (AMR) hydrodynamic simulations of vertically
stratified hot halo gas, we examine the conditions under which clouds can form
and condense out of the hot halo medium to potentially fuel star formation in
the gaseous disk. We find that halo clouds do not develop from linear isobaric
perturbations. This is a regime where the cooling time is longer than the
Brunt-Vaisala time, confirming previous linear analysis. We extend the analysis
into the nonlinear regime by considering mildly or strongly nonlinear
perturbations with overdensities up to 100, also varying the initial height,
the cloud size, and the metallicity of the gas. Here, the result depends on the
ratio of cooling time to the time required to accelerate the cloud to the sound
speed (similar to the dynamical time). If the ratio exceeds a critical value
near unity, the cloud is accelerated without further cooling and gets disrupted
by Kelvin-Helmholtz and/or Rayleigh-Taylor instabilities. If it is less than
the critical value, the cloud cools and condenses before disruption. Accreting
gas with overdensities of 10-20 is expected to be marginally unstable; the
cooling fraction will depend on the metallicity, the size of the incoming
cloud, and the distance to the galaxy. Locally enhanced overdensities within
cold streams have a higher likelihood of cooling out. Our results have
implications on the evolution of clouds seeded by cold accretion that are
barely resolved in current cosmological hydrodynamic simulations and absorption
line systems detected in galaxy halos.
| arxiv topic:astro-ph.CO |
arxiv_dataset-26401105.4739 | Perturbations around the near horizon limit of charged Randall Sundrum
black holes
hep-th
In a previous paper we determined the near horizon limit of an extremal brane
world black hole, charged with respect to a Maxwell field on the brane, in the
single brane Randall-Sundrum model. This paper is largely an extension of that
work. The same black hole is considered. A metric expansion around the near
horizon limit is set up and the correction terms of the first two subleading
orders are determined. It is found that the corrected bulk metric can still be
sliced by a brane even though the $Ads_{2}$ symmetry of the near horizon metric
is broken by correction terms. The induced metric on the brane is determined to
second correction order and compared with the predictions of 4d General
Relativity. It is found that large black holes asymptote the extremal Reissner
Nordstr\"om solution and thus agreement with 4d General Realtivity is obtained
in this limit.
| arxiv topic:hep-th |
arxiv_dataset-26411105.4839 | On the fine spectrum of the second order difference operator over the
sequence spaces \ell_p and bv_p, (1 < p < \infty)
math.FA
In general, it is well known the behaviors of the symmetric tri-band matrices
on the Hilbert spaces. But the symmetric tri-band matrices have different the
behavior on the Banach spaces. The main purpose of this work is to determine
the fine spectra of the operator U(s, r, s) defined by symmetric tri-band
matrix over the sequence spaces {\ell}_p and bvp.
| arxiv topic:math.FA |
arxiv_dataset-26421105.4939 | Efficient Numerical Self-consistent Mean-field Approach for Fermionic
Many-body Systems by Polynomial Expansion on Spectral Density
cond-mat.supr-con cond-mat.mes-hall
We propose an efficient numerical algorithm to solve Bogoliubov de Gennes
equations self-consistently for inhomogeneous superconducting systems with a
reformulated polynomial expansion scheme. This proposed method is applied to
typical issues such as a vortex under randomly distributed impurities and a
normal conducting junction sandwiched between superconductors. With various
technical remarks, we show that its efficiency becomes remarkable in
large-scale parallel performance.
| arxiv topic:cond-mat.supr-con cond-mat.mes-hall |
arxiv_dataset-26431105.5039 | Evidence for long-lived quasiparticles trapped in superconducting point
contacts
cond-mat.mes-hall cond-mat.supr-con
We have observed that the supercurrent across phase-biased, highly
transmitting atomic size contacts is strongly reduced within a broad phase
interval around {\pi}. We attribute this effect to quasiparticle trapping in
one of the discrete sub-gap Andreev bound states formed at the contact.
Trapping occurs essentially when the Andreev energy is smaller than half the
superconducting gap {\Delta}, a situation in which the lifetime of trapped
quasiparticles is found to exceed 100 \mus. The origin of this sharp energy
threshold is presently not understood.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-26441105.5139 | The Morphology of the Thermal Sunyaev-Zel'dovich Sky
astro-ph.CO
At high angular frequencies the thermal Sunyaev-Zel'dovich (tSZ) effect
constitutes the dominant signal in the CMB sky. The tSZ effect is caused by
large scale pressure fluctuations in the baryonic distribution in the Universe
so its statistical properties provide estimates of corresponding properties of
the projected 3D pressure fluctuations. It's power spectrum is a sensitive
probe of the density fluctuations, and the bispectrum can be used to separate
the bias associated with pressure. The bispectrum is often probed with a
one-point real-space analogue, the skewness. In addition to the skewness the
morphological properties, as probed by the well known Minkowski Functionals
(MFs), also require the generalized one-point statistics, which at the lowest
order are identical to the skewness parameters. The concept of generalized
skewness parameters can be extended to define a set of three associated
generalized skew-spectra. We use these skew-spectra to probe the morphology of
the tSZ sky or the y-sky. We show how these power spectra can be recovered from
the data in the presence of arbitrary mask and noise templates using the well
known Pseudo-Cl (PCL) approach for arbitrary beam shape. We also employ an
approach based on the halo model to compute the tSZ bispectrum. The bispectrum
from each of these models is then used to construct the generalized
skew-spectra. We consider the performance of an all-sky survey with Planck-type
noise and compare the results against a noise-free ideal experiment using a
range of smoothing angles. We find that the skew-spectra can be estimated with
very high signal-to-noise ratio from future frequency cleaned tSZ maps that
will be available from experiments such as Planck. This will allow their mode
by mode estimation for a wide range of angular frequencies and will help us to
differentiate them from various other sources of non-Gaussianity.
| arxiv topic:astro-ph.CO |
arxiv_dataset-26451105.5239 | Search for {\nu}{\mu} {\to} {\nu}{\tau} oscillations in appearance mode
in the OPERA experiment
hep-ex
The OPERA experiment is aiming at the first direct detection of neutrino
oscillations in appearance mode through the study of the {\nu}{\mu} {\tp}
{\nu}{\tau} channel. The OPERA detector is placed in the CNGS long baseline
{\nu}{\mu} beam 730 km away from the neutrino source. The analysis of a
sub-sample of the data taken in the 2008-2009 runs was completed. After a brief
description of the beam and the experimental setup, we report on event analysis
and on a first candidate event, its background estimation and statistical
significance.
| arxiv topic:hep-ex |
arxiv_dataset-26461105.5339 | Classical harmonic oscillator with quantum energy spectrum
quant-ph
The classical dynamical system possessing a quantum spectrum of energy and
"quantum" behavior is suggested and investigated. The proposed model can be
considered as a dynamical variant of the old quantum theory for harmonic
oscillator in which the Bohr-Sommerfeld quantization rule is absent and
"quantum-mechanical" properties are the result of system behavior itself. For
this dynamical system the classical model of Franck-Hertz experiment which
allows explaining the experimentally observed regularities is suggested and
investigated. The examples of calculations of Franck-Hertz experiment of within
the limits of the suggested model of classical dynamical system are presented.
| arxiv topic:quant-ph |
arxiv_dataset-26471105.5439 | Adding to the Regulator's Toolbox: Integration and Extension of Two
Leading Market Models
q-fin.TR
As demonstrated during the recent financial crisis, regulators require
additional analytical tools to assess systemic risk in the financial sector.
This paper describes one such tool; namely a novel market modeling and analysis
capability. Our model builds upon two leading market models: one which
emphasizes market micro-structure and another which emphasizes an ecology of
trading strategies. We address a limitation of market modeling, namely the
consideration of only one dominant trading strategy (i.e., long positions). Our
model aligns closely with several widely held stylized facts of financial
markets. And a final contribution of this work stems from our empirical
analysis of the fractal nature of both empirical markets and our market model.
| arxiv topic:q-fin.TR |
arxiv_dataset-26481105.5539 | Semigroup C*-algebras and amenability of semigroups
math.OA
We construct reduced and full semigroup C*-algebras for left cancellative
semigroups. Our new construction covers particular cases already considered by
A. Nica and also Toeplitz algebras attached to rings of integers in number
fields due to J. Cuntz.
Moreover, we show how (left) amenability of semigroups can be expressed in
terms of these semigroup C*-algebras in analogy to the group case.
| arxiv topic:math.OA |
arxiv_dataset-26491105.5639 | Asynchronous Communication: Capacity Bounds and Suboptimality of
Training
cs.IT math.IT
Several aspects of the problem of asynchronous point-to-point communication
without feedback are developed when the source is highly intermittent. In the
system model of interest, the codeword is transmitted at a random time within a
prescribed window whose length corresponds to the level of asynchronism between
the transmitter and the receiver. The decoder operates sequentially and
communication rate is defined as the ratio between the message size and the
elapsed time between when transmission commences and when the decoder makes a
decision.
For such systems, general upper and lower bounds on capacity as a function of
the level of asynchronism are established, and are shown to coincide in some
nontrivial cases. From these bounds, several properties of this asynchronous
capacity are derived. In addition, the performance of training-based schemes is
investigated. It is shown that such schemes, which implement synchronization
and information transmission on separate degrees of freedom in the encoding,
cannot achieve the asynchronous capacity in general, and that the penalty is
particularly significant in the high-rate regime.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-26501105.5739 | Magnetic Flux Expulsion in Star Formation
astro-ph.SR
Stars form in dense cores of magnetized molecular clouds. If the magnetic
flux threading the cores is dragged into the stars, the stellar field would be
orders of magnitude stronger than observed. This well-known "magnetic flux
problem" demands that most of the core magnetic flux be decoupled from the
matter that enters the star. We carry out the first exploration of what happens
to the decoupled magnetic flux in 3D, using an MHD version of the ENZO adaptive
mesh refinement code. The field-matter decoupling is achieved through a sink
particle treatment, which is needed to follow the protostellar accretion phase
of star formation. We find that the accumulation of the decoupled flux near the
accreting protostar leads to a magnetic pressure buildup. The high pressure is
released anisotropically, along the path of least resistance. It drives a
low-density expanding region in which the decoupled magnetic flux is expelled.
This decoupling-enabled magnetic structure has never been seen before in 3D MHD
simulations of star formation. It generates a strong asymmetry in the
protostellar accretion flow, potentially giving a kick to the star. In the
presence of an initial core rotation, the structure presents an obstacle to the
formation of a rotationally supported disk, in addition to magnetic braking, by
acting as a rigid magnetic wall that prevents the rotating gas from completing
a full orbit around the central object. We conclude that the decoupled magnetic
flux from the stellar matter can strongly affect the protostellar collapse
dynamics.
| arxiv topic:astro-ph.SR |
arxiv_dataset-26511105.5839 | Intra-City Urban Network and Traffic Flow Analysis from GPS Mobility
Trace
physics.soc-ph cs.SI
We analyse two large-scale intra-city urban networks and traffic flows
therein measured by GPS traces of taxis in San Francisco and Shanghai. Our
results coincide with previous findings that, based purely on topological
means, it is often insufficient to characterise traffic flow. Traditional
shortest-path betweenness analysis, where shortest paths are calculated from
each pairs of nodes, carries an unrealistic implicit assumption that each node
or junction in the urban network generates and attracts an equal amount of
traffic. We also argue that weighting edges based only on euclidean distance is
inadequate, as primary roads are commonly favoured over secondary roads due to
the perceived and actual travel time required. We show that betweenness traffic
analysis can be improved by a simple extended framework which incorporates both
the notions of node weights and fastest-path betweenness. We demonstrate that
the framework is superior to traditional methods based solely on simple
topological perspectives.
| arxiv topic:physics.soc-ph cs.SI |
arxiv_dataset-26521105.5939 | Airborne TDMA for High Throughput and Fast Weather Conditions
Notification
cs.CE
As air traffic grows significantly, aircraft accidents increase. Many
aviation accidents could be prevented if the precise aircraft positions and
weather conditions on the aircraft's route were known. Existing studies propose
determining the precise aircraft positions via a VHF channel with an air-to-air
radio relay system that is based on mobile ad-hoc networks. However, due to the
long propagation delay, the existing TDMA MAC schemes underutilize the
networks. The existing TDMA MAC sends data and receives ACK in one time slot,
which requires two guard times in one time slot. Since aeronautical
communications spans a significant distance, the guard time occupies a
significantly large portion of the slot. To solve this problem, we propose a
piggybacking mechanism ACK. Our proposed MAC has one guard time in one time
slot, which enables the transmission of more data. Using this additional data,
we can send weather conditions that pertain to the aircraft's current position.
Our analysis shows that this proposed MAC performs better than the existing
MAC, since it offers better throughput and network utilization. In addition,
our weather condition notification model achieves a much lower transmission
delay than a HF (high frequency) voice communication.
| arxiv topic:cs.CE |
arxiv_dataset-26531105.6039 | A random phase approximation study of one-dimensional fermions after a
quantum quench
cond-mat.str-el
The effect of interactions on a system of fermions that are in a
non-equilibrium steady state due to a quantum quench is studied employing the
random-phase-approximation (RPA). As a result of the quench, the distribution
function of the fermions is highly broadened. This gives rise to an enhanced
particle-hole spectrum and over-damped collective modes for attractive
interactions between fermions. On the other hand, for repulsive interactions,
an undamped mode above the particle-hole continuum survives. The sensitivity of
the result on the nature of the non-equilibrium steady state is explored by
also considering a quench that produces a current carrying steady-state.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-26541105.6139 | The interplay between real and pseudo magnetic field in graphene with
strain
cond-mat.mes-hall
We investigate electric and magnetic properties of graphene with rotationally
symmetric strain. The strain generates large pseudo magnetic field with
alternating sign in space, which forms a strongly confined quantum dot
connected to six chiral channels. The orbital magnetism, degeneracy, and
channel opening can be understood from the interplay between real and pseudo
magnetic field which have different parities under time reversal and mirror
reflection.
While the orbital magnetic response of the confined state is diamagnetic, it
can be paramagnetic if there is an accidental degeneracy with opposite mirror
reflection parity.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-26551105.6239 | On statistical properties of sets fulfilling rolling-type conditions
math.ST stat.TH
Motivated by set estimation problems, we consider three closely related shape
conditions for compact sets: positive reach, r-convexity and rolling condition.
First, the relations between these shape conditions are analyzed. Second, we
obtain for the estimation of sets fulfilling a rolling condition a result of
"full consistency" (i.e., consistency with respect to the Hausdorff metric for
the target set and for its boundary). Third, the class of uniformly bounded
compact sets whose reach is not smaller than a given constant r is shown to be
a P-uniformity class (in Billingsley and Topsoe's (1967) sense) and, in
particular, a Glivenko-Cantelli class. Fourth, under broad conditions, the
r-convex hull of the sample is proved to be a fully consistent estimator of an
r-convex support in the two-dimensional case. Moreover, its boundary length is
shown to converge (a.s.) to that of the underlying support. Fifth, the above
results are applied to get new consistency statements for level set estimators
based on the excess mass methodology (Polonik, 1995).
| arxiv topic:math.ST stat.TH |
arxiv_dataset-26561105.6339 | Limits on the local dark matter density
astro-ph.GA
We revisit systematics in determining the local dark matter density (rho_dm)
from the vertical motion of stars in the Solar Neighbourhood. Using a
simulation of a Milky Way-like galaxy, we determine the data-quality required
to detect the dark matter density at its expected local value. We introduce a
new method for recovering rho_dm that uses moments of the Jeans equations,
combined with a Monte Carlo Markov Chain technique to marginalise over the
unknown parameters. Given sufficiently good data, we show that our method can
recover the correct local dark matter density even in the face of disc
inhomogeneities, non-isothermal tracers and a non-separable distribution
function. We illustrate the power of our technique by applying it to Hipparcos
data [Holmberg & Flynn 2000,2004]. We first make the assumption that the A and
F star tracer populations are isothermal. This recovers
rho_dm=0.003^{+0.009}_{-0.007}Msun/pc^3 (with 90 per cent confidence),
consistent with previous determinations. However, the vertical dispersion
profile of these tracers is poorly known. If we assume instead a non-isothermal
profile similar to the blue disc stars from SDSS DR-7 [Abazajian et al. 2009]
measured by Bond et al. (2009), we obtain a fit with a very similar chi^2
value, but with rho_dm=0.033^{+0.008}_{-0.009}Msun/pc^3 (with 90 per cent
confidence). This highlights that it is vital to measure the vertical
dispersion profile of the tracers to recover an unbiased estimate of the local
dark matter density.
| arxiv topic:astro-ph.GA |
arxiv_dataset-26571106.0065 | Tests of Modified Gravity with Dwarf Galaxies
astro-ph.CO
In modified gravity theories that seek to explain cosmic acceleration, dwarf
galaxies in low density environments can be subject to enhanced forces. The
class of scalar-tensor theories, which includes f(R) gravity, predict such a
force enhancement (massive galaxies like the Milky Way can evade it through a
screening mechanism that protects the interior of the galaxy from this "fifth"
force). We study observable deviations from GR in the disks of late-type dwarf
galaxies moving under gravity. The fifth-force acts on the dark matter and HI
gas disk, but not on the stellar disk owing to the self-screening of main
sequence stars. We find four distinct observable effects in such disk galaxies:
1. A displacement of the stellar disk from the HI disk. 2. Warping of the
stellar disk along the direction of the external force. 3. Enhancement of the
rotation curve measured from the HI gas compared to that of the stellar disk.
4. Asymmetry in the rotation curve of the stellar disk. We estimate that the
spatial effects can be up to 1 kpc and the rotation velocity effects about 10
km/s in infalling dwarf galaxies. Such deviations are measurable: we expect
that with a careful analysis of a sample of nearby dwarf galaxies one can
improve astrophysical constraints on gravity theories by over three orders of
magnitude, and even solar system constraints by one order of magnitude. Thus
effective tests of gravity along the lines suggested by Hui et al (2009) and
Jain (2011) can be carried out with low-redshift galaxies, though care must be
exercised in understanding possible complications from astrophysical effects.
| arxiv topic:astro-ph.CO |
arxiv_dataset-26581106.0165 | Stationarity and Geometric Ergodicity of BEKK Multivariate GARCH Models
math.PR
Conditions for the existence of strictly stationary multivariate GARCH
processes in the so-called BEKK parametrisation, which is the most general form
of multivariate GARCH processes typically used in applications, and for their
geometric ergodicity are obtained. The conditions are that the driving noise is
absolutely continuous with respect to the Lebesgue measure and zero is in the
interior of its support and that a certain matrix built from the GARCH
coefficients has spectral radius smaller than one.
To establish the results semi-polynomial Markov chains are defined and
analysed using algebraic geometry.
| arxiv topic:math.PR |
arxiv_dataset-26591106.0265 | Coherent strong-field control of multiple states by a single chirped
femtosecond laser pulse
physics.atom-ph quant-ph
We present a joint experimental and theoretical study on strong-field
photo-ionization of sodium atoms using chirped femtosecond laser pulses. By
tuning the chirp parameter, selectivity among the population in the highly
excited states 5p, 6p, 7p and 5f, 6f is achieved. Different excitation pathways
enabling control are identified by simultaneous ionization and measurement of
photoelectron angular distributions employing the velocity map imaging
technique. Free electron wave packets at an energy of around 1 eV are observed.
These photoelectrons originate from two channels. The predominant 2+1+1
Resonance Enhanced Multi-Photon Ionization (REMPI) proceeds via the strongly
driven two-photon transition $4s\leftarrow\leftarrow3s$, and subsequent
ionization from the states 5p, 6p and 7p whereas the second pathway involves
3+1 REMPI via the states 5f and 6f. In addition, electron wave packets from
two-photon ionization of the non-resonant transiently populated state 3p are
observed close to the ionization threshold. A mainly qualitative five-state
model for the predominant excitation channel is studied theoretically to
provide insights into the physical mechanisms at play. Our analysis shows that
by tuning the chirp parameter the dynamics is effectively controlled by dynamic
Stark-shifts and level crossings. In particular, we show that under the
experimental conditions the passage through an uncommon three-state "bow-tie"
level crossing allows the preparation of coherent superposition states.
| arxiv topic:physics.atom-ph quant-ph |
arxiv_dataset-26601106.0365 | Lower Bounds for Sparse Recovery
cs.DS cs.IT math.IT
We consider the following k-sparse recovery problem: design an m x n matrix
A, such that for any signal x, given Ax we can efficiently recover x'
satisfying
||x-x'||_1 <= C min_{k-sparse} x"} ||x-x"||_1.
It is known that there exist matrices A with this property that have only O(k
log (n/k)) rows.
In this paper we show that this bound is tight. Our bound holds even for the
more general /randomized/ version of the problem, where A is a random variable
and the recovery algorithm is required to work for any fixed x with constant
probability (over A).
| arxiv topic:cs.DS cs.IT math.IT |
arxiv_dataset-26611106.0465 | A Proposal to Measure Photon-Photon Scattering
hep-ph
We discuss a possibility to measure the photon-photon scattering cross
section at low energy in a theoretical standpoint. The cross section of
photon-photon scattering at low energy can be written as
$\displaystyle{{d\sigma\over d\Omega} \simeq {\alpha^4\over (12\pi)^2 \omega^2}
(3+2\cos^2\theta +\cos^4\theta)}$ with $\omega$ the energy of photon. The
magnitude of the cross section at $\omega \simeq 1$ eV should be $10^{37}$
times larger than the prediction of Heisenberg and Euler who calculated the
photon scattering by the classical picture of field theory. Due to a difficulty
of the initial condition of photon-photon reaction process, we propose to first
measure $\gamma +\gamma \rightarrow e^++e^- $ reaction at a few MeV before
measuring $\gamma +\gamma \rightarrow \gamma +\gamma $ elastic scattering.
| arxiv topic:hep-ph |
arxiv_dataset-26621106.0565 | Multi-stage Convex Relaxation for Feature Selection
stat.ML
A number of recent work studied the effectiveness of feature selection using
Lasso. It is known that under the restricted isometry properties (RIP), Lasso
does not generally lead to the exact recovery of the set of nonzero
coefficients, due to the looseness of convex relaxation. This paper considers
the feature selection property of nonconvex regularization, where the solution
is given by a multi-stage convex relaxation scheme. Under appropriate
conditions, we show that the local solution obtained by this procedure recovers
the set of nonzero coefficients without suffering from the bias of Lasso
relaxation, which complements parameter estimation results of this procedure.
| arxiv topic:stat.ML |
arxiv_dataset-26631106.0665 | Infinite-Horizon Policy-Gradient Estimation
cs.AI
Gradient-based approaches to direct policy search in reinforcement learning
have received much recent attention as a means to solve problems of partial
observability and to avoid some of the problems associated with policy
degradation in value-function methods. In this paper we introduce GPOMDP, a
simulation-based algorithm for generating a {\em biased} estimate of the
gradient of the {\em average reward} in Partially Observable Markov Decision
Processes (POMDPs) controlled by parameterized stochastic policies. A similar
algorithm was proposed by Kimura, Yamamura, and Kobayashi (1995). The
algorithm's chief advantages are that it requires storage of only twice the
number of policy parameters, uses one free parameter $\beta\in [0,1)$ (which
has a natural interpretation in terms of bias-variance trade-off), and requires
no knowledge of the underlying state. We prove convergence of GPOMDP, and show
how the correct choice of the parameter $\beta$ is related to the {\em mixing
time} of the controlled POMDP. We briefly describe extensions of GPOMDP to
controlled Markov chains, continuous state, observation and control spaces,
multiple-agents, higher-order derivatives, and a version for training
stochastic policies with internal states. In a companion paper (Baxter,
Bartlett, & Weaver, 2001) we show how the gradient estimates generated by
GPOMDP can be used in both a traditional stochastic gradient algorithm and a
conjugate-gradient procedure to find local optima of the average reward
| arxiv topic:cs.AI |
arxiv_dataset-26641106.0765 | On rings of commuting partial differential operators
math.AG math-ph math.MP
We give a natural generalization of the classification of commutative rings
of ordinary differential operators, given in works of Krichever, Mumford,
Mulase, and determine commutative rings of operators in a completed ring of
partial differential operators in two variables (satisfying certain mild
conditions) in terms of Parshin's generalized geometric data. It uses a
generalization of M.Sato's theory and is constructible in both ways.
| arxiv topic:math.AG math-ph math.MP |
arxiv_dataset-26651106.0865 | Unpaired composite fermion, topological exciton, and zero mode
cond-mat.str-el
The paired state of composite fermions is expected to support two kinds of
excitations: vortices and unpaired composite fermions. We construct an explicit
microscopic description of the unpaired composite fermions, which we
demonstrate to be accurate for a 3-body model interaction, and, possibly,
adiabatically connected to the Coulomb solution. This understanding reveals
that an unpaired composite fermion carries with it a charge-neutral
"topological" exciton, which, in turn, helps provide microscopic insight into
the origin of zero modes, fusion rules, and energetics.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-26661106.0965 | A New Approach to Generalized Fractional Derivatives
math.CA math.CO
The author \mbox{(Appl. Math. Comput. 218(3):860-865, 2011)} introduced a new
fractional integral operator given by, \[ \big({}^\rho
\mathcal{I}^\alpha_{a+}f\big)(x) = \frac{\rho^{1- \alpha }}{\Gamma({\alpha})}
\int^x_a \frac{\tau^{\rho-1} f(\tau) }{(x^\rho - \tau^\rho)^{1-\alpha}}\,
d\tau, \] which generalizes the well-known Riemann-Liouville and the Hadamard
fractional integrals. In this paper we present a new fractional derivative
which generalizes the familiar Riemann-Liouville and the Hadamard fractional
derivatives to a single form. We also obtain two representations of the
generalized derivative in question. An example is given to illustrate the
results.
| arxiv topic:math.CA math.CO |
arxiv_dataset-26671106.1065 | WKB - Not So Bad After All
physics.plasm-ph
It was found recently that tunneling probabilities over a barrier is roughly
twice as large as that given by standard WKB formula. Here we explained how
this come from and showed that WKB method does give a good approximation over
almost entire energy range provided that we use appropriate connection
relations.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-26681106.1165 | The Race for Supersymmetric Dark Matter at XENON100 and the LHC: Stringy
Correlations from No-Scale F-SU(5)
hep-ph astro-ph.CO hep-ex
The discovery of supersymmetry (SUSY) via action of the cold dark matter
candidate is being led on the indirect collider production front by the LHC,
and correspondingly by the XENON100 collaboration on the direct detection
front. We undertake a dual case study of the specific SUSY signatures which the
No-Scale flipped SU(5) x U(1)_X grand unified theory with TeV-scale vector-like
particles (No-Scale F-SU(5)) would exhibit at each of these experiments. We
demonstrate a correlation between the near-term prospects of these two distinct
approaches. We feature a dark matter candidate which is over 99% bino due to a
comparatively large Higgs bilinear mass \mu-term around the electroweak scale,
and thus automatically satisfy the current constraints from the XENON100 and
CDMS/EDELWEISS experiments. We do however expect that the ongoing extension of
the XENON100 run may effectively probe our model. Likewise, our model is also
currently being probed by the LHC via a search for events with ultra-high
multiplicity hadronic jets, which are a characteristic feature of the
distinctive No-Scale F-SU(5) mass hierarchy.
| arxiv topic:hep-ph astro-ph.CO hep-ex |
arxiv_dataset-26691106.1265 | Modelling Complexity: the case of Climate Science
physics.hist-ph physics.ao-ph physics.class-ph physics.soc-ph
We briefly review some of the scientific challenges and epistemological
issues related to climate science. We discuss the formulation and testing of
theories and numerical models, which, given the presence of unavoidable
uncertainties in observational data, the non-repeatability of
world-experiments, and the fact that relevant processes occur in a large
variety of spatial and temporal scales, require a rather different approach
than in other scientific contexts. A brief discussion of the intrinsic
limitations of geo-engineering solutions to global warming is presented, and a
framework of investigation based upon non-equilibrium thermodynamics is
proposed. We also critically discuss recently proposed perspectives of
development of climate science based purely upon massive use of supercomputer
and centralized planning of scientific priorities.
| arxiv topic:physics.hist-ph physics.ao-ph physics.class-ph physics.soc-ph |
arxiv_dataset-26701106.1365 | Walther Bothe and Bruno Rossi: the birth and development of coincidence
methods in cosmic-ray physics
physics.hist-ph quant-ph
Theoretical and experimental developments in the 1920s that accompanied the
birth of coincidence methods, as well as later crucial applications during the
1930s and 1940s are presented. In 1924 Walther Bothe and Hans Geiger applied a
coincidence method to the study of Compton scattering with Geiger needle
counters. Their experiment confirmed the existence of radiation quanta and
established the validity of conservation principles in elementary processes. At
the end of the 1920s, Bothe and Werner Kolh\"orster coupled the coincidence
technique with the new Geiger-M\"uller counter to study cosmic rays, marking
the start of cosmic-ray research as a branch of physics. The coincidence method
was further refined by Bruno Rossi, who developed a vacuum-tube device capable
of registering the simultaneous occurrence of electrical pulses from any number
of counters with a tenfold improvement in time resolution. The electronic
coincidence circuit bearing Rossi's name was instrumental in his research on
the corpuscular nature and the properties of cosmic radiation during the early
1930s, a period characterized by a lively debate between Millikan and followers
of the corpuscular interpretation. The Rossi coincidence circuit was also at
the core of the counter-controlled cloud chamber developed by Patrick Blackett
and Giuseppe Occhialini, and became one of the important ingredients of
particle and nuclear physics. During the late 1930s and 1940s, coincidences,
anti-coincidences and delayed coincidences played a crucial role in a series of
experiments on the decay of the muon, which inaugurated the current era of
particle physics.
PACS numbers: 96.50.S-, 84.30.-r, 96.50.S-, 95.85.Ry, 29.40.-n, 13.35.Bv,
45.20.dh, 12.20.-m, 91.25.-r, 29.40.Cs, 13.20.-v, 14.60.Ef, 14.60.Cd, 78.70.Bj,
20.00.00, 95.00.00, 01.60.+q, 01.85.+f, 01.65.+g
| arxiv topic:physics.hist-ph quant-ph |
arxiv_dataset-26711106.1465 | Determinants and Perfect Matchings
math.CO cs.DM math.RA math.RT
We give a combinatorial interpretation of the determinant of a matrix as a
generating function over Brauer diagrams in two different but related ways. The
sign of a permutation associated to its number of inversions in the Leibniz
formula for the determinant is replaced by the number of crossings in the
Brauer diagram. This interpretation naturally explains why the determinant of
an even antisymmetric matrix is the square of a Pfaffian.
| arxiv topic:math.CO cs.DM math.RA math.RT |
arxiv_dataset-26721106.1565 | Tricritical point in heterogeneous k-core percolation
cond-mat.dis-nn cond-mat.stat-mech
k-core percolation is an extension of the concept of classical percolation
and is particularly relevant to understand the resilience of complex networks
under random damage. A new analytical formalism has been recently proposed to
deal with heterogeneous k-cores, where each vertex is assigned a local
threshold k_i. In this paper we identify a binary mixture of heterogeneous
k-core which exhibits a tricritical point. We investigate the new scaling
scenario and calculate the relevant critical exponents, by analytical and
computational methods, for Erdos-Renyi networks and 2d square lattices.
| arxiv topic:cond-mat.dis-nn cond-mat.stat-mech |
arxiv_dataset-26731106.1665 | What do cluster counts really tell us about the Universe?
astro-ph.CO astro-ph.GA
We study the covariance matrix of the cluster mass function in cosmology. We
adopt a two-line attack: firstly, we employ the counts-in-cells framework to
derive an analytic expression for the covariance of the mass function.
Secondly, we use a large ensemble of N-body simulations in the LCDM framework
to test this. Our theoretical results show that the covariance can be written
as the sum of two terms: a Poisson term, which dominates in the limit of rare
clusters; and a sample variance term, which dominates for more abundant
clusters. Our expressions are analogous to those of Hu & Kravtsov (2003) for
multiple cells and a single mass tracer. Calculating the covariance depends on:
the mass function and bias of clusters, and the variance of mass fluctuations
within the survey volume. The predictions show that there is a strong
bin-to-bin covariance between measurements. In terms of the cross-correlation
coefficient, we find r~0.5 for haloes with M<3e14 Msol at z=0. Comparison of
these predictions with estimates from simulations shows excellent agreement. We
use the Fisher matrix formalism to explore the cosmological information content
of the counts. We compare the Poisson likelihood model, with the more realistic
likelihood model of Lima & Hu (2004), and all terms entering the Fisher
matrices are evaluated using the simulations. We find that the Poisson
approximation should only be used for the rarest objects, M>3e14 Msol,
otherwise the information content of a survey of size V~13.5 [Gpc/h]^3 would be
overestimated, resulting in errors that are ~2 times smaller. As an auxiliary
result, we show that the bias of clusters, obtained from the cluster-mass
cross-variance, is linear on scales >50 Mpc/h, whereas that obtained from the
auto-variance is nonlinear.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-26741106.1765 | Stellar Streams as Probes of Dark Halo Mass and Morphology: A Bayesian
Reconstruction
astro-ph.GA astro-ph.CO
Tidal streams provide a powerful tool by means of which the matter
distribution of the dark matter halos of their host galaxies can be studied.
However, the analysis is not straightforward because streams do not delineate
orbits, and for most streams, especially those in external galaxies, kinematic
information is absent. We present a method wherein streams are fit with simple
corrections made to possible orbits of the progenitor, using a Bayesian
technique known as Parallel Tempering to efficiently explore the parameter
space. We show that it is possible to constrain the shape of the host halo
potential or its density distribution using only the projection of tidal
streams on the sky, if the host halo is considered to be axisymmetric. By
adding kinematic data or the circular velocity curve of the host to the fitting
data, we are able to recover other parameters of the matter distribution such
as its mass and profile. We test our method on several simulated low mass
stellar streams and also explore the cases for which additional data are
required.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-26751106.1865 | Time dependent simulations of multiwavelength variability of the blazar
Mrk 421 with a Monte Carlo multi-zone code
astro-ph.HE astro-ph.CO
(abridged) We present a new time-dependent multi-zone radiative transfer code
and its application to study the SSC emission of Mrk 421. The code couples
Fokker-Planck and Monte Carlo methods, in a 2D geometry. For the first time all
the light travel time effects (LCTE) are fully considered, along with a proper
treatment of Compton cooling, which depends on them. We study a set of simple
scenarios where the variability is produced by injection of relativistic
electrons as a `shock front' crosses the emission region. We consider emission
from two components, with the second one either being pre-existing and
co-spatial and participating in the evolution of the active region, or
spatially separated and independent, only diluting the observed variability.
Temporal and spectral results of the simulation are compared to the
multiwavelength observations of Mrk 421 in March 2001. We find parameters that
can adequately fit the observed SEDs and multiwavelength light curves and
correlations. There remain however a few open issues, most notably: i)
systematic soft intra-band X-ray lags. ii) The quadratic correlation between
the TeV and X-ray flux during the flare decay has not been reproduced. These
features are among those affected by the spatial extent and geometry of the
source. The difficulty of producing hard X-ray lags is exacerbated by a bias
towards soft lags caused by the combination of energy dependent radiative
cooling time-scales and LCTE. About the second emission component, our results
strongly favor the scenario where it is co-spatial and it participates in the
flare evolution, suggesting that different phases of activity may occur in the
same region. The cases presented in this paper represent only an initial study,
and despite their limited scope they make a strong case for the need of true
time-dependent and multi-zone modeling.
| arxiv topic:astro-ph.HE astro-ph.CO |
arxiv_dataset-26761106.1965 | Stress controlled magnetic properties of Cobalt nanowires
cond-mat.mes-hall cond-mat.mtrl-sci
We investigate the magnetic properties of a composite comprising of
ferromagnetic Cobalt nanowires embedded in nanoporous anodized alumina
template. We observe unusual increase in, the saturation magnetization and the
coercive field, of the nanowires below 100 K. We also report the appearance of
an unusual exchange bias effect in nanowires below 100 K. We argue our results
can be understood on the basis of a competition between different magnetic
energy scales induced by significant stresses acting on the nanowires at low
temperatures. The composite behaves as an effective medium in which the
magnetic anisotropy of nanowires can be conveniently controlled via stress on
the nanowires.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-26771106.2065 | Oblivious Collaboration
cs.DC
Communication is a crucial ingredient in every kind of collaborative work.
But what is the least possible amount of communication required for a given
task? We formalize this question by introducing a new framework for distributed
computation, called {\em oblivious protocols}.
We investigate the power of this model by considering two concrete examples,
the {\em musical chairs} task $MC(n,m)$ and the well-known {\em Renaming}
problem. The $MC(n,m)$ game is played by $n$ players (processors) with $m$
chairs. Players can {\em occupy} chairs, and the game terminates as soon as
each player occupies a unique chair. Thus we say that player $P$ is {\em in
conflict} if some other player $Q$ is occupying the same chair, i.e.,
termination means there are no conflicts. By known results from distributed
computing, if $m \le 2n-2$, no strategy of the players can guarantee
termination. However, there is a protocol with $m = 2n-1$ chairs that always
terminates. Here we consider an oblivious protocol where in every time step the
only communication is this: an adversarial {\em scheduler} chooses an arbitrary
nonempty set of players, and for each of them provides only one bit of
information, specifying whether the player is currently in conflict or not. A
player notified not to be in conflict halts and never changes its chair,
whereas a player notified to be in conflict changes its chair according to its
deterministic program. Remarkably, even with this minimal communication
termination can be guaranteed with only $m=2n-1$ chairs. Likewise, we obtain an
oblivious protocol for the Renaming problem whose name-space is small as that
of the optimal nonoblivious distributed protocol.
Other aspects suggest themselves, such as the efficiency (program length) of
our protocols. We make substantial progress here as well, though many
interesting questions remain open.
| arxiv topic:cs.DC |
arxiv_dataset-26781106.2165 | Resolved optical-infrared SEDs of galaxies: universal relations and
their break-down on local scales
astro-ph.CO
A large body of evidence has demonstrated that the global rest-frame optical
and IR colours of galaxies correlate well with each other, as well as with
other galactic properties such as surface brightness and morphology. However
the processes that lead to the observed correlations are contrary; the stellar
light that contributes to the optical is readily absorbed by dust which emits
in the IR. Thus on small scales we expect these correlations to break down. We
examine seven nearby galaxies ranging from early- to late-types, on a
pixel-by-pixel basis and we demonstrate that there is disconnect between the
optical and IR when normalized to the near-IR (H-band). We can decompose this
disconnect into two distinct components through a Principal Component Analysis
of the H-band normalized SED of the pixels: one mainly correlated with
variations in the IR, the other correlated with variations in the optical. By
mapping these two components it is clear they arise from distinct spatial
regions. The IR dominated component is strongly associated with the specific
star-formation rate, while the optical-dominated component is broadly
associated with the stellar mass density. However, when the pixels of all
galaxies are compared, the well known optical-IR colour correlations return,
demonstrating that the variance observed within galaxies is around a mean which
follows the well-known trend. We also examine the extremely strong correlations
between the IRAC-NIR colours and demonstrate that they are tight enough to use
a single IRAC-NIR colour (i.e. 8mum-H) to determine the fluxes in the other
IRAC bands. These correlations arise from the differing contribution of stellar
light and dust to the IRAC bands, enabling us to determine pure stellar colours
for these bands, but still demonstrating the need for dust (or stellar)
corrections in these bands when being used as stellar (dust) tracers.
| arxiv topic:astro-ph.CO |
arxiv_dataset-26791106.2265 | If Experts Converge on the Same Answer are they Less Creative than
Beginners? Redefining Creativity in Terms of Adaptive Landscapes
nlin.AO q-bio.NC
The standard view that creativity entails both originality and
appropriateness leads to the paradox that experts who converge on one optimal
solution are rated as no more creative than beginners who give many original
solutions. This paper asserts that there is no one-size-fits-all definition of
creativity; creativity must be assessed relative to the constraints and
affordances of the task. The flatter the adaptive landscape associated with the
task, the greater the extent to which creativity is a function of originality
only. For tasks with a single-peaked adaptive landscape, there is a tradeoff
between originality and appropriateness. Only for tasks with rugged adaptive
landscapes is creativity positively correlated with both originality and
appropriateness. It is suggested that the adaptive landscapes associated with
artistic and scientific pursuits are equally rugged, but for artistic pursuits
their topologies reflect idiosyncratic experiences and emotions (the peaks and
valleys are not aligned).
| arxiv topic:nlin.AO q-bio.NC |
arxiv_dataset-26801106.2365 | Subdirect products of finitely presented metabelian groups
math.GR
There has been substantial investigation in recent years of subdirect
products of limit groups and their finite presentability and homological
finiteness properties. To contrast the results obtained for limit groups,
Baumslag, Bridson, Holt and Miller investigated subdirect products (fibre
products) of finitely presented metabelian groups. They showed that, in
contrast to the case for limit groups, such subdirect products could have
diverse behaviour with respect to finite presentability.
We show that, in a sense that can be made precise, `most' subdirect products
of a finite set of finitely presented metabelian groups are again finitely
presented. To be a little more precise, we assign to each subdirect product a
point of an algebraic variety and show that, in most cases, those points which
correspond to non-finitely presented subdirect products form a subvariety of
smaller dimension.
| arxiv topic:math.GR |
arxiv_dataset-26811106.2465 | On the theory of indirect exchange in EuO
cond-mat.mtrl-sci
We present the calculations of the Curie temperature and magnetization of
doped EuO both in the absence and in the presence of external magnetic field.
The calculations were performed both for the free electrons model and for the
model with finite electron band width. Both models give similar results for the
magnetization, close to Brillouin function.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-26821106.2565 | The Yellow Supergiant Progenitor of the Type II Supernova 2011dh in M51
astro-ph.SR
We present the detection of the progenitor of the Type II SN 2011dh in
archival pre-explosion Hubble Space Telescope images. Using post-explosion
Adaptive Optics imaging with Gemini NIRI+ALTAIR, the position of the SN in the
pre-explosion images was determined to within 23mas. The progenitor object was
found to be consistent with a F8 supergiant star (log L/L_{\odot}=4.92+/-0.20
and T_{eff}=6000+/-280K). Through comparison with stellar evolution tracks,
this corresponds to a single star at the end of core C-burning with an initial
mass of M_{ZAMS}=13+/-3M_{\odot}. The possibility of the progenitor source
being a cluster is rejected, on the basis of: 1) the source is not spatially
extended; 2) the absence of excess H\alpha\, emission; and 3) the poor fit to
synthetic cluster SEDs. It is unclear if a binary companion is contributing to
the observed SED, although given the excellent correspondence of the observed
photometry to a single star SED we suggest the companion does not contribute
significantly. Early photometric and spectroscopic observations show fast
evolution similar to the transitional Type IIb SN 2008ax, and suggest that a
large amount of the progenitor's hydrogen envelope was removed before
explosion.
| arxiv topic:astro-ph.SR |
arxiv_dataset-26831106.2665 | Diffuse Thermal X-Ray Emission in the Core of the Young Massive Cluster
Westerlund 1
astro-ph.HE
We present an analysis of the diffuse hard X-ray emission in the core of the
young massive Galactic cluster Westerlund 1 based on a 48 ks XMM-Newton
observation. Chandra results for the diffuse X-ray emission have indicated a
soft thermal component together with a hard component that could be either
thermal or non-thermal. We seek to resolve this ambiguity regarding the hard
component exploiting the higher sensitivity of XMM-Newton to diffuse emission.
Our new X-ray spectra from the central (2' radius) diffuse emission are found
to exhibit He-like Fe 6.7 keV line emission, demonstrating that the hard
emission in the cluster core is predominantly thermal in origin. Potential
sources of this hard component are reviewed, namely an unresolved Pre-Main
Sequence population, a thermalized cluster wind and Supernova Remnants
interacting with stellar winds. We find that the thermalized cluster wind
likely contributes the majority of the hard emission with some contribution
from the Pre-Main Sequence population. It is unlikely that Supernova Remnants
are contributing significantly to the Wd1 diffuse emission at the current
epoch.
| arxiv topic:astro-ph.HE |
arxiv_dataset-26841106.2765 | Theta lifting and cohomology growth in p-adic towers
math.NT
We use the theta lift to study the multiplicity with which certain
automorphic representations of cohomological type occur in a family of
congruence covers of an arithmetic manifold. When the family of covers is a
so-called `p-adic congruence tower' we obtain sharp asymptotics for the number
of representations which occur as lifts. When combined with theorems on the
surjectivity of the theta lift due to Howe and Li, and Bergeron, Millson and
Moeglin, this allows us to verify certain cases of a conjecture of Sarnak and
Xue.
| arxiv topic:math.NT |
arxiv_dataset-26851106.2865 | Future cosmological evolution in $f(R)$ gravity using two equations of
state parameters
hep-th astro-ph.CO gr-qc
We investigate the issues of future oscillations around the phantom divide
for $f(R)$ gravity. For this purpose, we introduce two types of energy density
and pressure arisen from the $f(R)$-higher order curvature terms. One has the
conventional energy density and pressure even in the beginning of the Jordan
frame, whose continuity equation provides the native equation of state $w_{\rm
DE}$. On the other hand, the other has the different forms of energy density
and pressure which do not obviously satisfy the continuity equation. This needs
to introduce the effective equation of state $w_{\rm eff}$ to describe the
$f(R)$-fluid, in addition to the native equation of state $\tilde{w}_{\rm DE}$.
We confirm that future oscillations around the phantom divide occur in $f(R)$
gravities by introducing two types of equations of state. Finally, we point out
that the singularity appears ar $x=x_c$ because the stability condition of
$f(R)$ gravity violates.
| arxiv topic:hep-th astro-ph.CO gr-qc |
arxiv_dataset-26861106.2965 | The Quillen metric, analytic torsion and tunneling for high powers of a
holomorphic line bundle
math.DG math-ph math.AG math.MP
Let L be a line bundle over a compact complex manifold X (possibly
non-Kahler) and denote by h_{L} and h_{X} fixed Hermitian metrics on L and TX,
respectively. We generalize the asymptotics for the induced Quillen metric on
the determinant line associated to a higher tensor power of L to the non-Kahler
setting. In the case when L is ample we also obtain the leading asymptotics for
the Ray-Singer analytic torsion of a (possbly non-positively curved) metric on
L, without assuming h_{X} is K\"ahler. The key point of the proofs is to relate
the asymptotics of the torsions above to "tunneling", i.e. to the distribution
of the exponentially small eigenvalues of the corresponding Dolbeault-Kodaira
Laplacians. The proof thus avoids the use of the exact (i.e. non-asymptotic)
deep results of Bismut-Gillet-Soul\'e for the Quillen metric, which are only
known to hold under the assumption that h_{X} be Kahler. Accordingly the proofs
are comparatively simple also in the Kahler case. A brief comparison with the
tunneling effect for Witten Laplacians and large deviation principles for
fermions is also made.
| arxiv topic:math.DG math-ph math.AG math.MP |
arxiv_dataset-26871106.3065 | Comment on: I-Shih Liu: Constitutive theory of anisotropic rigid heat
conductors
math-ph math.MP
In I-Shih Liu's paper \C{1}, the compatibility of anisotropy and material
frame indifference of a rigid heat conductor is investigated. For this purpose,
the deformation gradient is introduced into the domain of the constitutive
mapping. Because of the presupposed rigidity, the deformation gradient is here
represented by an orthogonal tensor. The statement, that the usual procedure --
not to introduce the deformation gradient into the state space of rigid heat
conductors -- causes isotropy because of the material frame indifference, is
misleading.
| arxiv topic:math-ph math.MP |
arxiv_dataset-26881106.3165 | New approach to solution generation using SL(2,R)-duality of a
dimensionally reduced space in five-dimensional minimal supergravity and new
black holes
hep-th
The dimensional reduction of (the bosonic sector of) five-dimensional minimal
supergravity to four dimensions leads to a theory with a massless axion and a
dilaton coupled to gravity and two U(1) gauge fields (one of which has
Chern-Simons coupling), whose field equations have SL(2,R)-invariance.
Utilizing this SL(2,R)-duality, we provide a new formalism for solution
generation. As an example, applying it to the Rasheed solution, which are known
to describe dyonic rotating black holes (from the four-dimensional point of
view) of five-dimensional pure gravity, we obtain rotating Kaluza-Klein black
hole solutions in five-dimensional minimal supergravity. We also show that the
solutions have six charges: mass, angular momentum, Kaluza-Klein
electric/magnetic charges and electric/magnetic charges of the Maxwell field,
four of which are related by a constraint.
| arxiv topic:hep-th |
arxiv_dataset-26891106.3265 | Coagulation and Fragmentation in molecular clouds. II. The opacity of
the dust aggregate size distribution
astro-ph.SR astro-ph.EP
The dust size distribution in molecular clouds can be strongly affected by
ice-mantle formation and (subsequent) grain coagulation. Following previous
work where the dust size distribution has been calculated from a state-of-the
art collision model for dust aggregates that involves both coagulation and
fragmentation (Paper I), the corresponding opacities are presented in this
study. The opacities are calculated by applying the effective medium theory
assuming that the dust aggregates are a mix of 0.1{\mu}m silicate and graphite
grains and vacuum. In particular, we explore how the coagulation affects the
near-IR opacities and the opacity in the 9.7{\mu}m silicate feature. We find
that as dust aggregates grow to {\mu}m-sizes both the near-IR color excess and
the opacity in the 9.7 {\mu}m feature increases. Despite their coagulation,
porous aggregates help to prolong the presence of the 9.7{\mu}m feature. We
find that the ratio between the opacity in the silicate feature and the near-IR
color excess becomes lower with respect to the ISM, in accordance with many
observations of dark clouds. However, this trend is primarily a result of ice
mantle formation and the mixed material composition of the aggregates, rather
than being driven by coagulation. With stronger growth, when most of the dust
mass resides in particles of size 10{\mu}m or larger, both the near-IR color
excess and the 9.7{\mu}m silicate feature significantly diminish. Observations
at additional wavelengths, in particular in the sub-mm range, are essential to
provide quantitative constraints on the dust size distribution within dense
cores. Our results indicate that the sub-mm index {\beta} will increase
appreciably, if aggregates grow to ~100{\mu}m in size.
| arxiv topic:astro-ph.SR astro-ph.EP |
arxiv_dataset-26901106.3365 | Tunable multi-photon Rabi oscillations in an electronic spin system
cond-mat.mes-hall quant-ph
We report on multi-photon Rabi oscillations and controlled tuning of a
multi-level system at room temperature (S=5/2 for Mn2+:MgO) in and out of a
quasi-harmonic level configuration. The anisotropy is much smaller than the
Zeeman splittings, such as the six level scheme shows only a small deviation
from an equidistant diagram. This allows us to tune the spin dynamics by either
compensating the cubic anisotropy with a precise static field orientation, or
by microwave field intensity. Using the rotating frame approximation, the
experiments are very well explained by both an analytical model and a
generalized numerical model. The calculated multi-photon Rabi frequencies are
in excellent agreement with the experimental data.
| arxiv topic:cond-mat.mes-hall quant-ph |
arxiv_dataset-26911106.3465 | Wave Function Based Characteristics of Hybrid Mesons
hep-ph
We propose some extensions of the quark potential model to hybrids, fit them
to the lattice data and use them for the purpose of calculating the masses,
root mean square radii and wave functions at the origin of the conventional and
hybrid charmonium mesons. We treat the ground and excited gluonic field between
a quark and an antiquark as in the Born-Oppenheimer expansion, and use the
shooting method to numerically solve the required Schr$\ddot{\textrm{o}}$dinger
equation for the radial wave functions; from these wave functions we calculate
the mesonic properties. For masses we also check through a Crank Nichelson
discretization. For hybrid charmonium mesons, we consider the exotic quantum
number states with $ J^{PC} = 0^{+ -}, 1^{- +}$ and $2^{+ -}$. We also compare
our results with the experimentally observed masses and theoretically predicted
results of the other models. Our results have implications for scalar form
factors, energy shifts, magnetic polarizabilities, decay constants, decay
widths and differential cross sections of conventional and hybrid mesons.
| arxiv topic:hep-ph |
arxiv_dataset-26921106.3565 | The Relationship Between Black Hole Growth and Star Formation in Seyfert
Galaxies
astro-ph.CO astro-ph.GA
We present estimates of black hole accretion rates and nuclear, extended, and
total star-formation rates for a complete sample of Seyfert galaxies. Using
data from the Spitzer Space Telescope, we measure the active galactic nucleus
(AGN) luminosity using the [O IV] 25.89 micron emission line and the
star-forming luminosity using the 11.3 micron aromatic feature and extended 24
micron continuum emission. We find that black hole growth is strongly
correlated with nuclear (r<1 kpc) star formation, but only weakly correlated
with extended (r>1 kpc) star formation in the host galaxy. In particular, the
nuclear star-formation rate (SFR) traced by the 11.3 micron aromatic feature
follows a relationship with the black hole accretion rate (BHAR) of the form
SFR\proptoBHAR^0.8, with an observed scatter of 0.5 dex. This SFR-BHAR
relationship persists when additional star formation in physically matched r=1
kpc apertures is included, taking the form SFR\proptoBHAR^0.6. However, the
relationship becomes almost indiscernible when total SFRs are considered. This
suggests a physical connection between the gas on sub-kpc and sub-pc scales in
local Seyfert galaxies that is not related to external processes in the host
galaxy. It also suggests that the observed scaling between star formation and
black hole growth for samples of AGNs will depend on whether the star formation
is dominated by a nuclear or extended component. We estimate the integrated
black hole and bulge growth that occurs in these galaxies and find that an AGN
duty cycle of 5-10% would maintain the ratio between black hole and bulge
masses seen in the local universe.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-26931106.3665 | Orbital order and magnetism of FeNCN
cond-mat.str-el cond-mat.mtrl-sci
Based on density functional calculations, we report on the orbital order and
microscopic magnetic model of FeNCN, a prototype compound for orbital-only
models. Despite having a similar energy scale, the spin and orbital degrees of
freedom in FeNCN are only weakly coupled. The ground-state configuration
features the doubly occupied d_{3z^2-r^2} (a1g) orbital and four
singly-occupied d orbitals resulting in the spin S=2 on the Fe+2 atoms, whereas
alternative (Eg') configurations are about 75 meV/f.u. higher in energy.
Calculated exchange couplings and band gap are in good agreement with the
available experimental data. Experimental effects arising from possible orbital
excitations are discussed.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-26941106.3765 | The Real-Rootedness and Log-concavities of Coordinator Polynomials of
Weyl Group Lattices
math.CO
It is well-known that the coordinator polynomials of the classical root
lattice of type $A_n$ and those of type $C_n$ are real-rooted. They can be
obtained, either by the Aissen-Schoenberg-Whitney theorem, or from their
recurrence relations. In this paper, we develop a trigonometric substitution
approach which can be used to establish the real-rootedness of coordinator
polynomials of type $D_n$. We also find the coordinator polynomials of type
$B_n$ are not real-rooted in general. As a conclusion, we obtain that all
coordinator polynomials of Weyl group lattices are log-concave.
| arxiv topic:math.CO |
arxiv_dataset-26951106.3865 | On tail bounds for random recursive trees
math.PR
We consider a multivariate distributional recursion of sum-type as arising in
the probabilistic analysis of algorithms and random trees. We prove an upper
tail bound for the solution using Chernoff's bounding technique by estimating
the Laplace transform. The problem is traced back to the corresponding problem
for binary search trees by stochastic domination. The result obtained is
applied to the internal path length and Wiener index of random b-ary recursive
trees with weighted edges and random linear recursive trees. Finally, lower
tail bounds for the Wiener index of these trees are given.
| arxiv topic:math.PR |
arxiv_dataset-26961106.3965 | Controlled coupling of spin-resolved quantum Hall edge states
cond-mat.mes-hall quant-ph
Topologically-protected edge states are dissipationless conducting surface
states immune to impurity scattering and geometrical defects that occur in
electronic systems characterized by a bulk insulating gap. One example can be
found in a two-dimensional electron gas (2DEG) under high magnetic field in the
quantum Hall regime. Based on the coherent control of the coupling between
these protected states, several theoretical proposals for the implementation of
information processing architectures were proposed. Here we introduce and
experimentally demonstrate a new method that allows us to controllably couple
co-propagating spin-resolved edge states of a QH insulator. The scheme exploits
a spatially-periodic in-plane magnetic field that is created by an array of
Cobalt nano-magnets placed at the boundary of the 2DEG. A maximum charge/spin
transfer of about 28% is achieved at 250 mK. This result may open the way to
the realization of scalable quantum-information architectures exploiting the
spin degree of freedom of topologically-protected states.
| arxiv topic:cond-mat.mes-hall quant-ph |
arxiv_dataset-26971106.4065 | Knots in the canonical book representation of complete graphs
math.GT
We describe which knots can be obtained as cycles in the canonical book
representation of K_n, the complete graph on n vertices. We show that the
canonical book representation of K_n contains a Hamiltonian cycle that is a
composite knot if and only if n>11 and we show that when p and q are relatively
prime, the (p,q) torus knot is a Hamiltonian cycle in the canonical book
representation of K_{2p+q}. Finally, we list the number and type of all
non-trivial knots that occur as cycles in the canonical book representation of
K_n for n<12. We conjecture that the canonical book representation of K_n
attains the least possible number of knotted cycles for any embedding of K_n.
| arxiv topic:math.GT |
arxiv_dataset-26981106.4165 | Zariski density and finite quotients of mapping class groups
math.GR math.GT
Our main result is that the image of the quantum representation of a central
extension of the mapping class group of the genus $g\geq 3$ closed orientable
surface at a prime $p\geq 5$ is a Zariski dense discrete subgroup of some
higher rank algebraic semi-simple Lie group $\mathbb G_p$ defined over $\Q$. As
an application we find that, for any prime $p\geq 5$ a central extension of the
genus $g$ mapping class group surjects onto the finite groups $\mathbb
G_p(\Z/q\Z)$, for all but finitely many primes $q$. This method provides
infinitely many finite quotients of a given mapping class group outside the
realm of symplectic groups.
| arxiv topic:math.GR math.GT |
arxiv_dataset-26991106.4265 | Improvements in the determination of ISS Ca II K parameters
astro-ph.SR
Measurements of the ionized Ca II K line are one of the major resources for
long-term studies of solar and stellar activity. They also play a critical role
in many studies related to solar irradiance variability, particularly as a
ground-based proxy to model the solar ultraviolet flux variation that may
influence the Earth's climate. Full disk images of the Sun in Ca II K have been
available from various observatories for more than 100 years and latter
synoptic Sun-as-a-star observations in Ca II K began in the early 1970s. One of
these instruments, the Integrated Sunlight Spectrometer (ISS) has been in
operation at Kitt Peak (Arizona) since late 2006. The ISS takes daily
observations of solar spectra in nine spectra bands, including the Ca II K and
H line s. We describe recent improvements in data reduction of Ca II K
observations, and present time variations of nine parameters derived from the
profile of this spectral line.
| arxiv topic:astro-ph.SR |
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