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arxiv_dataset-62001504.08095 | Inverse coherence effects in nuclear magnetic relaxation rates as a sign
of topological superconductivity
cond-mat.supr-con
We reveal that three-dimensional multi-orbital topological superconductivity
can be identified by a bulk measurement, i.e., the temperature dependence of
nuclear magnetic relaxation (NMR) rates. Below a critical temperature $T_{\rm
c}$, the NMR rate in the topological state exhibits an anti-peak profile, which
is opposite to the conventional $s$-wave state. This inversion coherence effect
comes from a twist of order parameters with respect to orbital and spin degrees
of freedom. Our self-consistent calculations in the model for
Cu$_{x}$Bi$_{2}$Se$_{3}$ prove that the inverse coherence effect appears as a
concave temperature dependence of the NMR rates. We propose that a
time-reversal-invariant orbital-singlet spin-triplet topological
superconductivity is characterized by the temperature dependence of the NMR
rate.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-62011504.08195 | The Intermediate Set and Limiting Superdifferential for Coalition Games:
Between the Core and the Weber Set
math.OC
We introduce the intermediate set as an interpolating solution concept
between the core and the Weber set of a coalitional game. The new solution is
defined as the limiting superdifferential of the Lovasz extension and thus it
completes the hierarchy of variational objects used to represent the core
(Frechet superdifferential) and the Weber set (Clarke superdifferential). It is
shown that the intermediate set is a non-convex solution containing the Pareto
optimal payoff vectors that depend on some chain of coalitions and marginal
coalitional contributions with respect to the chain. A detailed comparison
between the intermediate set and other set-valued solutions is provided. We
compute the exact form of intermediate set for all games and provide its
simplified characterization for the simple games and the glove game.
| arxiv topic:math.OC |
arxiv_dataset-62021504.08295 | Spectral thresholding quantum tomography for low rank states
quant-ph math-ph math.MP math.ST stat.TH
The estimation of high dimensional quantum states is an important statistical
problem arising in current quantum technology applications. A key example is
the tomography of multiple ions states, employed in the validation of state
preparation in ion trap experiments \cite{Haffner2005}. Since full tomography
becomes unfeasible even for a small number of ions, there is a need to
investigate lower dimensional statistical models which capture prior
information about the state, and to devise estimation methods tailored to such
models. In this paper we propose several new methods aimed at the efficient
estimation of low rank states in multiple ions tomography. All methods consist
in first computing the least squares estimator, followed by its truncation to
an appropriately chosen smaller rank. The latter is done by setting eigenvalues
below a certain "noise level" to zero, while keeping the rest unchanged, or
normalising them appropriately. We show that (up to logarithmic factors in the
space dimension) the mean square error of the resulting estimators scales as
$r\cdot d/N$ where $r$ is the rank, $d=2^k$ is the dimension of the Hilbert
space, and $N$ is the number of quantum samples. Furthermore we establish a
lower bound for the asymptotic minimax risk which shows that the above scaling
is optimal. The performance of the estimators is analysed in an extensive
simulations study, with emphasis on the dependence on the state rank, and the
number of measurement repetitions. We find that all estimators perform
significantly better that the least squares, with the "physical estimator"
(which is a bona fide density matrix) slightly outperforming the other
estimators.
| arxiv topic:quant-ph math-ph math.MP math.ST stat.TH |
arxiv_dataset-62031505.00028 | The Leptoquark Implication from the CMS and IceCube Experiments
hep-ph astro-ph.HE
The recent excess in the CMS measurements of $eejj$ and $e\nu jj$ channels
and the emergence of PeV comsic neutrino events at the IceCube experiment share
an intriguing implication for a leptoquark with a 600-650 GeV mass. We
investigate the CMS constraints on the flavor structure of a scenario with the
minimal leptoquark Yukawa couplings and correlate such a scenario to the
resonant enhancement in the very high energy shower event rates at the IceCube.
We find for a single leptoquark, the CMS signals require large couplings to the
third generation leptons. This leads to an enhancement in the
$\nu_\tau$-nucleon scattering cross-section and subsequently more $\nu_\tau$
events at PeV energies. However, a visible enhancement above the Standard Model
scattering would require a leptoquark Yukawa coupling larger than one that can
be easily tested at the upcoming LHC runs.
| arxiv topic:hep-ph astro-ph.HE |
arxiv_dataset-62041505.00128 | Nambu-Goldstone Dark Matter in a Scale Invariant Bright Hidden Sector
hep-ph
We consider a scale invariant extension of the standard model (SM) with a
combined breaking of conformal and electroweak symmetry in a strongly
interacting hidden $SU(n_c)$ gauge sector with $n_f$ vector-like hidden
fermions. The (pseudo) Nambu-Goldstone bosons that arise due to dynamical
chiral symmetry breaking are dark matter (DM) candidates. We focus on
$n_f=n_c=3$, where $SU(3)$ is the largest symmetry group of hidden flavor which
can be explicitly broken into either $U(1) \times U(1)$ or $SU(2)\times U(1)$.
We study DM properties and discuss consistent parameter space for each case.
Because of different mechanisms of DM annihilation the consistent parameter
space in the case of $SU(2)\times U(1)$ is significantly different from that of
$SU(3)$ if the hidden fermions have a SM $U(1)_Y$ charge of $O(1)$.
| arxiv topic:hep-ph |
arxiv_dataset-62051505.00228 | Criticality and Big Brake singularities in the tachyonic evolutions of
closed Friedmann universes with cold dark matter
gr-qc
The evolution of a closed Friedmann universe filled by a tachyon scalar field
with a trigonometric potential and cold dark matter (CDM) is investigated. A
subset of the evolutions consistent to 1$\sigma $ confidence level with the
Union 2.1 supernova data set is identified. The evolutions of the tachyon field
are classified. Some of them evolve into a de Sitter attractor, while others
proceed through a pseudo-tachyonic regime into a sudden future singularity.
Critical evolutions leading to Big Brake singularities in the presence of CDM
are found and a new type of cosmological evolution characterized by singularity
avoidance in the pseudo-tachyon regime is presented.
| arxiv topic:gr-qc |
arxiv_dataset-62061505.00328 | Profitability of contrarian strategies in the Chinese stock market
q-fin.TR q-fin.ST
This paper reexamines the profitability of loser, winner and contrarian
portfolios in the Chinese stock market using monthly data of all stocks traded
on the Shanghai Stock Exchange and Shenzhen Stock Exchange covering the period
from January 1997 to December 2012. We find evidence of short-term and
long-term contrarian profitability in the whole sample period when the
estimation and holding horizons are 1 month or longer than 12 months and the
annualized returns of contrarian portfolios increases with the estimation and
holding horizons. We perform subperiod analysis and find that the long-term
contrarian effect is significant in both bullish and bearish states while the
short-term contrarian effect disappears in bullish states. We compare the
performance of contrarian portfolios based on different grouping manners in the
estimation period and unveil that decile grouping outperforms quintile grouping
and tertile grouping, which is more evident and robust in the long run.
Generally, loser portfolios and winner portfolios have positive returns and
loser portfolios perform much better than winner portfolios. Both loser and
winner portfolios in bullish states perform better than those in the whole
sample period. In contrast, loser and winner portfolios have smaller returns in
bearish states in which loser portfolio returns are significant only in the
long term and winner portfolio returns become insignificant. These results are
robust to the one-month skipping between the estimation and holding periods and
for the two stock exchanges. Our findings show that the Chinese stock market is
not efficient in the weak form. These findings also have obvious practical
implications for financial practitioners.
| arxiv topic:q-fin.TR q-fin.ST |
arxiv_dataset-62071505.00428 | A Linear-Time Particle Gibbs Sampler for Infinite Hidden Markov Models
stat.ML
Infinite Hidden Markov Models (iHMM's) are an attractive, nonparametric
generalization of the classical Hidden Markov Model which can automatically
infer the number of hidden states in the system. However, due to the
infinite-dimensional nature of transition dynamics performing inference in the
iHMM is difficult. In this paper, we present an infinite-state Particle Gibbs
(PG) algorithm to resample state trajectories for the iHMM. The proposed
algorithm uses an efficient proposal optimized for iHMMs and leverages ancestor
sampling to suppress degeneracy of the standard PG algorithm. Our algorithm
demonstrates significant convergence improvements on synthetic and real world
data sets. Additionally, the infinite-state PG algorithm has linear-time
complexity in the number of states in the sampler, while competing methods
scale quadratically.
| arxiv topic:stat.ML |
arxiv_dataset-62081505.00528 | A critical regularity condition on the angular velocity of axially
symmetric Navier-Stokes equations
math.AP
Let $v$ be the velocity of Leray-Hopf solutions to the axially symmetric
three-dimensional Navier-Stokes equations. It is shown that $v$ is regular if
the angular velocity $v_\theta$ satisfies an integral condition which is
critical under the standard scaling. This condition allows functions satisfying
\[ |v_\theta(x, t)| \le \frac{C}{r |\ln r|^{2+\epsilon}}, \quad r<1/2, \] where
$r$ is the distance from $x$ to the axis, $C$ and $\epsilon$ are any positive
constants.
Comparing with the critical a priori bound \[ |v_\theta(x, t)| \le
\frac{C}{r}, \qquad 0< r \le 1/2, \]our condition is off by the log factor
$|\ln r|^{2+\epsilon}$ at worst. This is inspired by the recent interesting
paper \cite{CFZ:1} where H. Chen, D. Y. Fang and T. Zhang establish, among
other things, an almost critical regularity condition on the angular velocity.
Previous regularity conditions are off by a factor $r^{-1}$.
The proof is based on the new observation that, when viewed differently, all
the vortex stretching terms in the 3 dimensional axially symmetric
Navier-Stokes equations are critical instead of supercritical as commonly
believed.
| arxiv topic:math.AP |
arxiv_dataset-62091505.00628 | Matrices de rotaciones, simetr\'{\i}as y roto-simetr\'{\i}as
math.HO
In this note we find the orthogonal matrices $R,S\in M_3(\mathbb{R})$
corresponding to the clockwise rotation $r$ in $\mathbb{R}^3$ around the axis
generated by a unit vector $u=(a,b,c)^t$ through an angle $\alpha\in [0,2\pi)$,
and to the symmetry $s$ in $\mathbb{R}^3$ on the plane perpendicular to $u$.
Matrix $S$ depends on $a,b,c$ and matrix $R$ depends on $a,b,c, \cos \alpha$
and $\sin \alpha$. We show $SR=RS$. The matrix $R$ is due to Alperin.
| arxiv topic:math.HO |
arxiv_dataset-62101505.00728 | Resonant magneto-optic Kerr effect in the magnetic topological insulator
Cr:(Sb$_x$,Bi$_{1-x}$)$_2$Te$_3$
cond-mat.mes-hall cond-mat.mtrl-sci
We report measurements of the polar Kerr effect, proportional to the
out-of-plane component of the magnetization, in thin films of the magnetically
doped topological insulator
$(\text{Cr}_{0.12}\text{Bi}_{0.26}\text{Sb}_{0.62})_2\text{Te}_3$. Measurements
of the complex Kerr angle, $\Theta_K$, were performed as a function of photon
energy in the range $0.8\text{ eV}<\hbar\omega<3.0\text{ eV}$. We observed a
peak in the real part of $\Theta_K(\omega)$ and zero crossing in the imaginary
part that we attribute to resonant interaction with a spin-orbit avoided
crossing located $\approx$ 1.6 eV above the Fermi energy. The resonant
enhancement allows measurement of the temperature and magnetic field dependence
of $\Theta_K$ in the ultrathin film limit, $d\geq2$ quintuple layers. We find a
sharp transition to zero remanent magnetization at 6 K for $d<8$~QL, consistent
with theories of the dependence of impurity spin interactions on film thickness
and their location relative to topological insulator surfaces.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-62111505.00828 | Dynamic Consistency of Conditional Simple Temporal Networks via Mean
Payoff Games: a Singly-Exponential Time DC-Checking
cs.DS cs.AI cs.GT
Conditional Simple Temporal Network (CSTN) is a constraint-based
graph-formalism for conditional temporal planning. It offers a more flexible
formalism than the equivalent CSTP model of Tsamardinos, Vidal and Pollack,
from which it was derived mainly as a sound formalization. Three notions of
consistency arise for CSTNs and CSTPs: weak, strong, and dynamic. Dynamic
consistency is the most interesting notion, but it is also the most challenging
and it was conjectured to be hard to assess. Tsamardinos, Vidal and Pollack
gave a doubly-exponential time algorithm for deciding whether a CSTN is
dynamically-consistent and to produce, in the positive case, a dynamic
execution strategy of exponential size. In the present work we offer a proof
that deciding whether a CSTN is dynamically-consistent is coNP-hard and provide
the first singly-exponential time algorithm for this problem, also producing a
dynamic execution strategy whenever the input CSTN is dynamically-consistent.
The algorithm is based on a novel connection with Mean Payoff Games, a family
of two-player combinatorial games on graphs well known for having applications
in model-checking and formal verification. The presentation of such connection
is mediated by the Hyper Temporal Network model, a tractable generalization of
Simple Temporal Networks whose consistency checking is equivalent to
determining Mean Payoff Games. In order to analyze the algorithm we introduce a
refined notion of dynamic-consistency, named \epsilon-dynamic-consistency, and
present a sharp lower bounding analysis on the critical value of the reaction
time \hat{\varepsilon} where the CSTN transits from being, to not being,
dynamically-consistent. The proof technique introduced in this analysis of
\hat{\varepsilon} is applicable more in general when dealing with linear
difference constraints which include strict inequalities.
| arxiv topic:cs.DS cs.AI cs.GT |
arxiv_dataset-62121505.00928 | Convergence of fully discrete schemes for diffusive dispersive
conservation laws with discontinuous coefficient
math.NA math.AP
We are concerned with fully-discrete schemes for the numerical approximation
of diffusive-dispersive hyperbolic conservation laws with a discontinuous flux
function in one-space dimension. More precisely, we show the convergence of
approximate solutions, generated by the scheme corresponding to vanishing
diffusive-dispersive scalar conservation laws with a discontinuous coefficient,
to the corresponding scalar conservation law with discontinuous coefficient.
Finally, the convergence is illustrated by several examples. In particular, it
is delineated that the limiting solutions generated by the scheme need not
coincide, depending on the relation between diffusion and the dispersion
coefficients, with the classical Kruzkov-Oleinik entropy solutions, but contain
nonclassical undercompressive shock waves.
| arxiv topic:math.NA math.AP |
arxiv_dataset-62131505.01028 | Double Higgs Production with a Jet Substructure Analysis to Probe Extra
Dimensions
hep-ph
In this paper, we perform a comprehensive study to probe the effects of large
extra dimensions through double Higgs production in proton-proton collisions at
the center-of-mass energies of 14, 33, 100 TeV. We concentrate on the channel
in which both Higgs bosons decay into $b\bar{b}$ pair and take into account the
main background contributions through realistic Monte-Carlo simulations. In
order to achieve an efficient event reconstruction and a good background
rejection, jet substructure techniques are used to efficiently capture the
boosted Higgs bosons in the final state. The expected limits on the model
parameters are obtained based on the invariant mass and the angular properties
of the final state objects. Depending on the number of extra dimensions, bounds
up to 6.1, 12.5, 28.1 TeV are set on the model parameter at proton-proton
collisions with the center-of-mass energies of 14, 33, and 100 TeV,
respectively.
| arxiv topic:hep-ph |
arxiv_dataset-62141505.01128 | A Coinductive Framework for Infinitary Rewriting and Equational
Reasoning (Extended Version)
cs.LO
We present a coinductive framework for defining infinitary analogues of
equational reasoning and rewriting in a uniform way. We define the relation
=^infty, notion of infinitary equational reasoning, and ->^infty, the standard
notion of infinitary rewriting as follows:
=^infty := nu R. ( <-_root + ->_root + lift(R) )^*
->^infty := mu R. nu S. ( ->_root + lift(R) )^* ; lift(S)
where
lift(R) := { (f(s_1,...,s_n), f(t_1,...,t_n)) | s_1 R t_1,...,s_n R t_n } +
id ,
and where mu is the least fixed point operator and nu is the greatest fixed
point operator.
The setup captures rewrite sequences of arbitrary ordinal length, but it has
neither the need for ordinals nor for metric convergence. This makes the
framework especially suitable for formalizations in theorem provers.
| arxiv topic:cs.LO |
arxiv_dataset-62151505.01228 | Superchords: the atoms of thought
q-bio.NC q-bio.QM
Electroencephalography (EEG) signals' interpretation is based on waveform
analysis, where meaningful information should emerge from a plethora of data.
Nonetheless, the continuous increase in computational power and the development
of new data processing algorithms in the recent years have put into reach the
possibility of analysing raw EEG signals. Bearing that motivation, the authors
propose a new approach using raw data EEG signals and deep learning neural
networks, for the classification of motor activities (executed and imagery).
The hypothesis to be presented here is: each instantaneous measurement of the
raw signal of all EEG channels (superchord) is unique per motor activity
regardless the moment of measurement. This study has confirmed the hypothesis
(results with accuracy over 80%, mean for 109 subjects), reinforcing the need
of further research for the understanding of mental processes.
| arxiv topic:q-bio.NC q-bio.QM |
arxiv_dataset-62161505.01328 | An $\epsilon$-Nash equilibrium with high probability for strategic
customers in heavy traffic
math.OC
A multiclass queue with many servers is considered, where customers make a
join-or-leave decision upon arrival based on queue length information, without
knowing the scheduling policy or the state of other queues. A game theoretic
formulation is proposed and analyzed, that takes advantage of a phenomenon
unique to heavy traffic regimes, namely Reiman's snaphshot principle, by which
waiting times are predicted with high precision by the information available
upon arrival. The payoff considered is given as a random variable, which
depends on the customer's decision, accounting for waiting time in the queue
and penalty for leaving. The notion of an equilibrium is only meaningful in an
asymptotic framework, which is taken here to be the Halfin-Whitt heavy traffic
regime. The main result is the identification of an $\epsilon$-Nash equilibrium
with probability approaching 1. On way to proving this result, new diffusion
limit results for systems with finite buffers are obtained.
| arxiv topic:math.OC |
arxiv_dataset-62171505.01428 | Birkhoff sum fluctuations in substitution dynamical systems
math.DS math.CO math.PR
We consider the deviation of Birkhoff sums along fixed orbits of substitution
dynamical systems. We show distributional convergence for the Birkhoff sums of
eigenfunctions of the substitution matrix. For noncoboundary eigenfunctions
with eigenvalue of modulus 1, we obtain a central limit theorem. For other
eigenfunctions, we show convergence to distributions supported on Cantor sets.
We also give a new criterion for such an eigenfunction to be a coboundary, as
well as a new characterization of substitution dynamical systems with bounded
discrepancy
| arxiv topic:math.DS math.CO math.PR |
arxiv_dataset-62181505.01528 | On polynomials associated with an Uvarov modification of a quartic
potential Freud-like weight
math.CA
In this contribution we consider sequences of monic polynomials orthogonal
with respect to the standard Freud-like inner product involving a quartic
potential
$\left\langle
p,q\right\rangle_{M}=\int_{\mathbb{R}}p(x)q(x)e^{-x^{4}+2tx^{2}}dx+Mp(0)q(0).$
We analyze some properties of these polynomials, such as the ladder operators
and the holonomic equation that they satisfy and, as an application, we give an
electrostatic interpretation of their zero distribution in terms of a
logarithmic potential interaction under the action of an external field. It is
also shown that the coefficients of their three term recurrence relation
satisfy a nonlinear difference string equation. Finally, an equation of motion
for their zeros in terms of their dependence on $t$ is given.
| arxiv topic:math.CA |
arxiv_dataset-62191505.01628 | Suppression of excess oxygen for environmentally stable amorphous
In-Si-O thin-film transistors
cond-mat.mtrl-sci
We discuss the environmental instability of amorphous indium oxide
(InOx)-based thin-film transistors (TFTs) in terms of the excess oxygen in the
semiconductor films. A comparison between amorphous InOx doped with low and
high concentrations of oxygen binder (SiO2) showed that out-diffusion of oxygen
molecules causes drastic changes in the film conductivity and TFT turn-on
voltages. Incorporation of sufficient SiO2 could suppress fluctuations in
excess oxygen because of the high oxygen bond-dissociation energy and low Gibbs
free energy. Consequently, the TFT operation became rather stable. The results
would be useful for the design of reliable oxide TFTs with stable electrical
properties.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-62201505.01728 | Integrating K-means with Quadratic Programming Feature Selection
cs.CV cs.LG
Several data mining problems are characterized by data in high dimensions.
One of the popular ways to reduce the dimensionality of the data is to perform
feature selection, i.e, select a subset of relevant and non-redundant features.
Recently, Quadratic Programming Feature Selection (QPFS) has been proposed
which formulates the feature selection problem as a quadratic program. It has
been shown to outperform many of the existing feature selection methods for a
variety of applications. Though, better than many existing approaches, the
running time complexity of QPFS is cubic in the number of features, which can
be quite computationally expensive even for moderately sized datasets. In this
paper we propose a novel method for feature selection by integrating k-means
clustering with QPFS. The basic variant of our approach runs k-means to bring
down the number of features which need to be passed on to QPFS. We then enhance
this idea, wherein we gradually refine the feature space from a very coarse
clustering to a fine-grained one, by interleaving steps of QPFS with k-means
clustering. Every step of QPFS helps in identifying the clusters of irrelevant
features (which can then be thrown away), whereas every step of k-means further
refines the clusters which are potentially relevant. We show that our iterative
refinement of clusters is guaranteed to converge. We provide bounds on the
number of distance computations involved in the k-means algorithm. Further,
each QPFS run is now cubic in number of clusters, which can be much smaller
than actual number of features. Experiments on eight publicly available
datasets show that our approach gives significant computational gains (both in
time and memory), over standard QPFS as well as other state of the art feature
selection methods, even while improving the overall accuracy.
| arxiv topic:cs.CV cs.LG |
arxiv_dataset-62211505.01828 | Velocity tuning of friction with two trapped atoms
physics.atom-ph cond-mat.mtrl-sci
Friction is the basic, ubiquitous mechanical interaction between two surfaces
that results in resistance to motion and energy dissipation. In spite of its
technological and economic significance, our ability to control friction
remains modest, and our understanding of the microscopic processes incomplete.
At the atomic scale, mismatch between the two contacting crystal lattices can
lead to a reduction of stick-slip friction (structural lubricity), while
thermally activated atomic motion can give rise to a complex velocity
dependence, and nearly vanishing friction at sufficiently low velocities
(thermal lubricity). Atomic force microscopy has provided a wealth of
experimental results, but limitations in the dynamic range, time resolution,
and control at the single-atom level have hampered a full quantitative
description from first principles. Here, using an ion-crystal friction emulator
with single-atom, single substrate-site spatial resolution and single-slip
temporal resolution, we measure the friction force over nearly five orders of
magnitude in velocity, and contiguously observe four distinct regimes, while
controlling temperature and dissipation. We elucidate the interplay between
thermal and structural lubricity in a system of two coupled atoms, and provide
a simple explanation in terms of the Peierls-Nabarro potential. This extensive
control at the atomic scale paves the way for fundamental studies of the
interaction of many-atom surfaces, as for example in the Frenkel-Kontorova
model, and possibly into the quantum regime.
| arxiv topic:physics.atom-ph cond-mat.mtrl-sci |
arxiv_dataset-62221505.01928 | Hybrid chiral condensate in the external magnetic field
nucl-th hep-ph
We study the phase diagram of the Nambu-Jona-Lasinio model in the external
magnetic field within the mean-field approximation, taking into account the
inhomogeneous chiral condensate. It is shown that there appears a new type of
the chiral condensate, endowed with two features of real kink crystal and dual
chiral density wave, in the magnetic field. We also show that there are first
order phase transitions between different inhomogeneous phases in the presence
of magnetic field.
| arxiv topic:nucl-th hep-ph |
arxiv_dataset-62231505.02028 | Out-of-equilibrium states and quasi-many-body localization in polar
lattice gases
cond-mat.quant-gas
The absence of energy dissipation leads to an intriguing out-of-equilibrium
dynamics for ultracold polar gases in optical lattices, characterized by the
formation of dynamically-bound on-site and inter-site clusters of two or more
particles, and by an effective blockade repulsion. These effects combined with
the controlled preparation of initial states available in cold gases
experiments can be employed to create interesting out-of-equilibrium states.
These include quasi-equilibrated effectively repulsive 1D gases for attractive
dipolar interactions and dynamically-bound crystals. Furthermore,
non-equilibrium polar lattice gases can offer a promising scenario for the
study of many-body localization in the absence of quenched disorder. This
fascinating out-of-equilibrium dynamics for ultra-cold polar gases in optical
lattices may be accessible in on-going experiments.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-62241505.02128 | Onset of fingering instability in a finite slice of adsorbed solute
physics.flu-dyn
The effect of a linear adsorption isotherm on the onset of fingering
instability in a miscible displacement in the application of liquid
chromatography, pollutant contamination in aquifers etc. is investigated. Such
fingering instability on the solute dynamics arise due to the miscible viscus
fingering (VF) between the displacing fluid and sample solvent. We use a
Fourier pseudo-spectral method to solve the initial value problem appeared in
the linear stability analysis. The present linear stability analysis is of
generic type and it captures the early time diffusion dominated region which
was never expressible through the quasi-steady state analysis (QSSA). In
addition, it measures the onset of instability more accurately than the QSSA
methods. It is shown that the onset time depends non-monotonically on the
retention parameter of the solute adsorption. This qualitative influence of the
retention parameter on the onset of instability resemblances with the results
obtained from direct numerical simulations of the nonlinear equations.
Moreover, the present linear stability method helps for an appropriate
characterisation of the linear and the nonlinear regimes of miscible VF
instability and also can be useful for the fluid flow problems with the
unsteady base-state.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-62251505.02228 | The point-charge self-energy in Lee-Wick Theories
hep-th math-ph math.MP
In this paper we study the ultraviolet and infrared behaviour of the self
energy of a point-like charge in the vector and scalar Lee-Wick electrodynamics
in a $d+1$ dimensional space time. It is shown that in the vector case, the
self energy is strictly ultraviolet finite up to $d=3$ spatial dimensions,
finite in the renormalized sense for any $d$ odd, infrared divergent for $d=2$
and ultraviolet divergent for $d>2$ even. On the other hand, in the scalar
case, the self energy is striclty finite for $d\leq 3$, and finite, in the
renormalized sense, for any $d$ odd.
| arxiv topic:hep-th math-ph math.MP |
arxiv_dataset-62261505.02328 | Effects of electron drift on the collisionless damping of kinetic
Alfv\'en waves in the solar wind
astro-ph.SR physics.space-ph
The collisionless dissipation of anisotropic Alfv\'enic turbulence is a
promising candidate to solve the solar wind heating problem. Extensive studies
examined the kinetic properties of Alfv\'en waves in simple Maxwellian or
bi-Maxwellian plasmas. However, the observed electron velocity distribution
functions in the solar wind are more complex. In this study, we analyze the
properties of kinetic Alfv\'en waves in a plasma with two drifting electron
populations. We numerically solve the linearized Maxwell-Vlasov equations and
find that the damping rate and the proton-electron energy partition for kinetic
Alfv\'en waves are significantly modified in such plasmas, compared to plasmas
without electron drifts. We suggest that electron drift is an important factor
to take into account when considering the dissipation of Alfv\'enic turbulence
in the solar wind or other $\beta \sim 1$ astrophysical plasmas.
| arxiv topic:astro-ph.SR physics.space-ph |
arxiv_dataset-62271505.02428 | Live Inspection of Spreadsheets
cs.SE
Existing approaches for detecting anomalies in spreadsheets can help to
discover faults, but they are often applied too late in the spreadsheet
lifecycle. By contrast, our approach detects anomalies immediately whenever
users change their spreadsheets. This live inspection approach has been
implemented as part of the Spreadsheet Inspection Framework, enabling the tool
to visually report findings without disturbing the users' workflow. An advanced
list representation allows users to keep track of the latest findings,
prioritize open problems, and check progress on solving the issues. Results
from a first user study indicate that users find the approach useful.
| arxiv topic:cs.SE |
arxiv_dataset-62281505.02528 | Inheritance Properties and Sum-of-Squares Decomposition of Hankel
Tensors: Theory and Algorithms
math.SP
In this paper, we show that if a lower-order Hankel tensor is positive
semi-definite (or positive definite, or negative semi-definite, or negative
definite, or SOS), then its associated higher-order Hankel tensor with the same
generating vector, where the higher order is a multiple of the lower order, is
also positive semi-definite (or positive definite, or negative semi-definite,
or negative definite, or SOS, respectively). Furthermore, in this case, the
extremal H-eigenvalues of the higher order tensor are bounded by the extremal
H-eigenvalues of the lower order tensor, multiplied with some constants. Based
on this inheritance property, we give a concrete sum-of-squares decomposition
for each strong Hankel tensor. Then we prove the second inheritance property of
Hankel tensors, i.e., a Hankel tensor has no negative (or non-positive, or
positive, or nonnegative) H-eigenvalues if the associated Hankel matrix of that
Hankel tensor has no negative (or non-positive, or positive, or nonnegative,
respectively) eigenvalues. In this case, the extremal H-eigenvalues of the
Hankel tensor are also bounded by the extremal eigenvalues of the associated
Hankel matrix, multiplied with some constants. The third inheritance property
of Hankel tensors is raised as a conjecture.
| arxiv topic:math.SP |
arxiv_dataset-62291505.02628 | Criticality of the Axially Symmetric Navier-Stokes Equations
math.AP
Smooth solutions to the axi-symmetric Navier-Stokes equations obey the
following maximum principle: $$\sup_{t\geq 0}\|rv^\theta(t, \cdot)\|_{L^\infty}
\leq \|rv^\theta(0, \cdot)\|_{L^\infty}.$$ We prove that all solutions with
initial data in $H^{\frac{1}{2}}$ is smooth globally in time if $rv^\theta$
satisfies a kind of Form Boundedness Condition (FBC) which is invariant under
the natural scaling of the Navier-Stokes equations. In particular, if
$rv^\theta$ satisfies \begin{equation}\nonumber \sup_{t \geq 0}|rv^\theta(t, r,
z)| \leq C_\ast|\ln r|^{- 2},\ \ r \leq \delta_0 \in (0, \frac{1}{2}),\ C_\ast
< \infty, \end{equation} then our FBC is satisfied. Here $\delta_0$ and
$C_\ast$ are independent of neither the profile nor the norm of the initial
data. So the gap from regularity is logarithmic in nature. We also prove the
global regularity of solutions if $\|rv^\theta(0, \cdot)\|_{L^\infty}$ or
$\sup_{t \geq 0}\|rv^\theta(t, \cdot)\|_{L^\infty(r \leq r_0)}$ is small but
the smallness depends on certain dimensionless quantity of the initial data.
| arxiv topic:math.AP |
arxiv_dataset-62301505.02728 | Adaptive Partitioning for Very Large RDF Data
cs.DB
Distributed RDF systems partition data across multiple computer nodes
(workers). Some systems perform cheap hash partitioning, which may result in
expensive query evaluation, while others apply heuristics aiming at minimizing
inter-node communication during query evaluation. This requires an expensive
data preprocessing phase, leading to high startup costs for very large RDF
knowledge bases. Apriori knowledge of the query workload has also been used to
create partitions, which however are static and do not adapt to workload
changes; hence, inter-node communication cannot be consistently avoided for
queries that are not favored by the initial data partitioning.
In this paper, we propose AdHash, a distributed RDF system, which addresses
the shortcomings of previous work. First, AdHash applies lightweight
partitioning on the initial data, that distributes triples by hashing on their
subjects; this renders its startup overhead low. At the same time, the
locality-aware query optimizer of AdHash takes full advantage of the
partitioning to (i)support the fully parallel processing of join patterns on
subjects and (ii) minimize data communication for general queries by applying
hash distribution of intermediate results instead of broadcasting, wherever
possible. Second, AdHash monitors the data access patterns and dynamically
redistributes and replicates the instances of the most frequent ones among
workers. As a result, the communication cost for future queries is drastically
reduced or even eliminated. To control replication, AdHash implements an
eviction policy for the redistributed patterns. Our experiments with synthetic
and real data verify that AdHash (i) starts faster than all existing systems,
(ii) processes thousands of queries before other systems become online, and
(iii) gracefully adapts to the query load, being able to evaluate queries on
billion-scale RDF data in sub-seconds.
| arxiv topic:cs.DB |
arxiv_dataset-62311505.02828 | A New Dust Budget In The Large Magellanic Cloud
astro-ph.SR
The origin of dust in a galaxy is poorly understood. Recently, the surveys of
the Large Magellanic Cloud (LMC) provide astrophysical laboratories for the
dust studies. By a method of population synthesis, we investigate the
contributions of dust produced by asymptotic giant branch (AGB) stars, common
envelope (CE) ejecta and type II supernovae (SNe II) to the total dust budget
in the LMC. Based on our models, the dust production rates (DPRs) of AGB stars
in the LMC are between about $2.5\times10^{-5}$ and
$4.0\times10^{-6}M_\odot{\rm yr^{-1}}$. The uncertainty mainly results from
different models for the dust yields of AGB stars. The DPRs of CE ejecta are
about $6.3\times10^{-6}$(The initial binary fraction is 50\%). These results
are within the large scatter of several observational estimates. AGB stars
mainly produce carbon grains, which is consistent with the observations. Most
of dust grains manufactured by CE ejecta are silicate and iron grains. The
contributions of SNe II are very uncertain. Compared with SNe II without
reverse shock, the DPRs of AGB stars and CE ejecta are negligible. However, if
only 2 \% of dust grains produced by SNe II can survive after reverse shock,
the contributions of SNe II are very small. The total dust masses produced by
AGB stars in the LMC are between $2.8\times10^4$ and $3.2\times10^5M_\odot$,
and those produced by CE ejecta are about $6.3\times10^4$. They are much lower
than the values estimated by observations. Therefore, there should be other
dust sources in the LMC.
| arxiv topic:astro-ph.SR |
arxiv_dataset-62321505.02928 | A Low Dimensional Approximation For Competence In Bacillus Subtilis
q-bio.QM physics.bio-ph q-bio.MN
The behaviour of a high dimensional stochastic system described by a Chemical
Master Equation (CME) depends on many parameters, rendering explicit simulation
an inefficient method for exploring the properties of such models. Capturing
their behaviour by low-dimensional models makes analysis of system behaviour
tractable. In this paper, we present low dimensional models for the
noise-induced excitable dynamics in Bacillus subtilis, whereby a key protein
ComK, which drives a complex chain of reactions leading to bacterial
competence, gets expressed rapidly in large quantities (competent state) before
subsiding to low levels of expression (vegetative state). These rapid reactions
suggest the application of an adiabatic approximation of the dynamics of the
regulatory model that, however, lead to competence durations that are incorrect
by a factor of 2. We apply a modified version of an iterative functional
procedure that faithfully approximates the time-course of the trajectories in
terms of a 2-dimensional model involving proteins ComK and ComS. Furthermore,
in order to describe the bimodal bivariate marginal probability distribution
obtained from the Gillespie simulations of the CME, we introduce a tunable
multiplicative noise term in a 2-dimensional Langevin model whose stationary
state is described by the time-independent solution of the corresponding
Fokker-Planck equation.
| arxiv topic:q-bio.QM physics.bio-ph q-bio.MN |
arxiv_dataset-62331505.03028 | Loss-induced lasing: new findings in laser theory?
physics.optics quant-ph
In a recent work, using a coupled microresonator system with tailored gain
and loss parameters B. Peng et al. [Science 346, 328 (2014)] have
experimentally reported on an apparently counterintuitive effect in laser
theory, namely the possibility to enhance lasing by increasing loss in the
system. The observed phenomenon was related to the existence of an exceptional
point in the system and was presented somehow as an unexpected and novel
effect, especially by some reporters and scientific blogs. In this
communication it is pointed out that the phenomenon of loss-induced lasing does
not come as a surprise in known laser theory and that it is not necessarily
related to the physics of exceptional points. Loss-induced lasing is basically
the lasing mechanism that occurs in loss-coupled distributed feedback lasers.
This mechanism dates back to the 1970's, has a simple physical explanation and
does not rely on the physics of exceptional points.
| arxiv topic:physics.optics quant-ph |
arxiv_dataset-62341505.03128 | A Parallel Distributed Strategy for Arraying a Scattered Robot Swarm
cs.RO
We consider the problem of organizing a scattered group of $n$ robots in
two-dimensional space, with geometric maximum distance $D$ between robots. The
communication graph of the swarm is connected, but there is no central
authority for organizing it. We want to arrange them into a sorted and
equally-spaced array between the robots with lowest and highest label, while
maintaining a connected communication network.
In this paper, we describe a distributed method to accomplish these goals,
without using central control, while also keeping time, travel distance and
communication cost at a minimum. We proceed in a number of stages (leader
election, initial path construction, subtree contraction, geometric
straightening, and distributed sorting), none of which requires a central
authority, but still accomplishes best possible parallelization. The overall
arraying is performed in $O(n)$ time, $O(n^2)$ individual messages, and $O(nD)$
travel distance. Implementation of the sorting and navigation use communication
messages of fixed size, and are a practical solution for large populations of
low-cost robots.
| arxiv topic:cs.RO |
arxiv_dataset-62351505.03228 | Some Properties of Reflected Backward Stochastic Differential Equations
for a Finite State Markov Chain Model
math.PR
In this paper, we provide an estimate for the solutions of reflected backward
stochastic differential equations (RBSDEs) driven by a Markov chain, derive a
continuous dependence property for their solutions with respect to the
parameters of the equations, and show similar properties for solutions of
backward stochastic differential equations (BSDEs). We finally establish a
comparison result for the solutions of RBSDEs driven by a Markov chain.
| arxiv topic:math.PR |
arxiv_dataset-62361505.03328 | A multiplicative analogue of Schnirelmann's theorem
math.NT math.CO
The classical theorem of Schnirelmann states that the primes are an additive
basis for the integers. In this paper we consider the analogous multiplicative
setting of the cyclic group $\left(\mathbb{Z}/ q\mathbb{Z}\right)^{\times}$,
and prove a similar result. For all suitably large primes $q$ we define
$P_\eta$ to be the set of primes less than $\eta q$, viewed naturally as a
subset of $\left(\mathbb{Z}/ q\mathbb{Z}\right)^{\times}$. Considering the
$k$-fold product set $P_\eta^{(k)}=\{p_1p_2\cdots p_k:p_i\in P_\eta \}$, we
show that for $\eta \gg q^{-\frac{1}{4}+\epsilon}$ there exists a constant $k$
depending only on $\epsilon$ such that $P_\eta^{(k)}=\left(\mathbb{Z}/
q\mathbb{Z}\right)^{\times}$. Erd\H{o}s conjectured that for $\eta = 1$ the
value $k=2$ should suffice: although we have not been able to prove this
conjecture, we do establish that $P_1 ^{(2)}$ has density at least
$\frac{1}{64}(1+o(1))$. We also formulate a similar theorem in almost-primes,
improving on existing results.
| arxiv topic:math.NT math.CO |
arxiv_dataset-62371505.03428 | The Singular Structure and Regularity of Stationary and Minimizing
Varifolds
math.DG math.AP
If one considers an integral varifold $I^m\subseteq M$ with bounded mean
curvature, and if $S^k(I)\equiv\{x\in M: \text{ no tangent cone at $x$ is
}k+1\text{-symmetric}\}$ is the standard stratification of the singular set,
then it is well known that $\dim S^k\leq k$. In complete generality nothing
else is known about the singular sets $S^k(I)$. In this paper we prove for a
general integral varifold with bounded mean curvature, in particular a
stationary varifold, that every stratum $S^k(I)$ is $k$-rectifiable. In fact,
we prove for $k$-a.e. point $x\in S^k$ that there exists a unique $k$-plane
$V^k$ such that every tangent cone at $x$ is of the form $V\times C$ for some
cone $C$.
In the case of minimizing hypersurfaces $I^{n-1}\subseteq M^n$ we can go
further. Indeed, we can show that the singular set $S(I)$, which is known to
satisfy $\dim S(I)\leq n-8$, is in fact $n-8$ rectifiable with uniformly finite
$n-8$ measure. An effective version of this allows us to prove that the second
fundamental form $A$ has apriori estimates in $L^7_{weak}$ on $I$, an estimate
which is sharp as $|A|$ is not in $L^7$ for the Simons cone. In fact, we prove
the much stronger estimate that the regularity scale $r_I$ has
$L^7_{weak}$-estimates.
The above results are in fact just applications of a new class of estimates
we prove on the quantitative stratifications $S^k_{\epsilon,r}$ and
$S^k_{\epsilon}\equiv S^k_{\epsilon,0}$. Roughly, $x\in S^k_{\epsilon}\subseteq
I$ if no ball $B_r(x)$ is $\epsilon$-close to being $k+1$-symmetric. We show
that $S^k_\epsilon$ is $k$-rectifiable and satisfies the Minkowski estimate
$Vol(B_r\,S_\epsilon^k)\leq C_\epsilon r^{n-k}$. The proof requires a new
$L^2$-subspace approximation theorem for integral varifolds with bounded mean
curvature, and a $W^{1,p}$-Reifenberg type theorem proved by the authors in
\cite{NaVa+}.
| arxiv topic:math.DG math.AP |
arxiv_dataset-62381505.03528 | Halo detection via large-scale Bayesian inference
astro-ph.CO astro-ph.IM
We present a proof-of-concept of a novel and fully Bayesian methodology
designed to detect halos of different masses in cosmological observations
subject to noise and systematic uncertainties. Our methodology combines the
previously published Bayesian large-scale structure inference algorithm, HADES,
and a Bayesian chain rule (the Blackwell-Rao Estimator), which we use to
connect the inferred density field to the properties of dark matter halos. To
demonstrate the capability of our approach we construct a realistic galaxy mock
catalogue emulating the wide-area 6-degree Field Galaxy Survey, which has a
median redshift of approximately 0.05. Application of HADES to the catalogue
provides us with accurately inferred three-dimensional density fields and
corresponding quantification of uncertainties inherent to any cosmological
observation. We then use a cosmological simulation to relate the amplitude of
the density field to the probability of detecting a halo with mass above a
specified threshold. With this information we can sum over the HADES density
field realisations to construct maps of detection probabilities and demonstrate
the validity of this approach within our mock scenario. We find that the
probability of successful of detection of halos in the mock catalogue increases
as a function of the signal-to-noise of the local galaxy observations. Our
proposed methodology can easily be extended to account for more complex
scientific questions and is a promising novel tool to analyse the cosmic
large-scale structure in observations.
| arxiv topic:astro-ph.CO astro-ph.IM |
arxiv_dataset-62391505.03628 | High-Q coupled resonances on a PhC waveguide using a tapered nanofiber
with high coupling efficiency
physics.optics
We experimentally demonstrate high-Q cavity formation at an arbitrary
position on a silicon photonic crystal waveguide by bringing a tapered
nanofiber into contact with the surface of the slab. An ultrahigh Q of 5.1 x
10^5 is obtained with a coupling efficiency of 39%, whose resonant wavelength
can be finely tuned by 27 pm by adjusting the contact length of the nanofiber.
We also demonstrate an extremely high coupling efficiency of 99.6% with a
loaded Q of 6.1 x 10^3. In addition, we show that we can obtain an all-pass
filter type coupled resonator system, which has the potential to be used for
slow light generation.
| arxiv topic:physics.optics |
arxiv_dataset-62401505.03728 | Equivariant Wave Maps on the Hyperbolic Plane with Large Energy
math.AP
In this paper we continue the analysis of equivariant wave maps from
2-dimensional hyperbolic space into surfaces of revolution that was initiated
in [13, 14]. When the target is the hyperbolic plane we proved in [13] the
existence and asymptotic stability of a 1-parameter family of finite energy
harmonic maps indexed by how far each map wraps around the target. Here we
conjecture that each of these harmonic maps is globally asymptotically stable,
meaning that the evolution of any arbitrarily large finite energy perturbation
of a harmonic map asymptotically resolves into the harmonic map itself plus
free radiation. Since such initial data exhaust the energy space, this is the
soliton resolution conjecture for this equation. The main result is a
verification of this conjecture for a nonperturbative subset of the harmonic
maps
| arxiv topic:math.AP |
arxiv_dataset-62411505.03828 | Heavy-flavor production in heavy-ion collisions and implications for the
properties of hot QCD matter
nucl-ex hep-ex
Hadrons carrying open heavy flavor, i.e. single charm or bottom quarks, are
among the key diagnostic tools available today for the hot and dense state of
strongly interacting matter which is produced in collisions of heavy atomic
nuclei at ultra-relativistic energies. First systematic heavy-flavor
measurements in nucleus-nucleus collisions and the reference proton-proton
system at Brookhaven National Laboratory's (BNL) Relativistic Heavy Ion
Collider (RHIC) have led to tantalizing results. These studies are now
continued and extended at RHIC and at CERN's Large Hadron Collider (LHC), where
considerably higher collision energies are available. This review focuses on
experimental results on open heavy-flavor observables at RHIC and the LHC
published until July 2012. Yields of heavy-flavor hadrons and their decay
products, their transverse momentum and rapidity distributions, as well as
their azimuthal distributions with respect to the reaction plane in heavy-ion
collisions are investigated. Various theoretical approaches are confronted with
the data and implications for the properties of the hot and dense medium
produced in ultra-relativistic heavy-ion collisions are discussed.
| arxiv topic:nucl-ex hep-ex |
arxiv_dataset-62421505.03928 | Hypoelliptic heat kernel on nilpotent Lie groups
math.DG math.AP math.PR math.RT
The starting point of our analysis is an old idea of writing an eigenfunction
expansion for a heat kernel considered in the case of a hypoelliptic heat
kernel on a nilpotent Lie group $G$. One of the ingredients of this approach is
the generalized Fourier transform. The formula one gets using this approach is
explicit as long as we can find all unitary irreducible representations of $G$.
In the current paper we consider an $n$-step nilpotent Lie group $G_{n}$ as an
illustration of this technique. First we apply Kirillov's orbit method to
describe these representations for $G_{n}$. This allows us to write the
corresponding hypoelliptic heat kernel using an integral formula over a
Euclidean space. As an application, we describe a short-time behavior of the
hypoelliptic heat kernel in our case.
| arxiv topic:math.DG math.AP math.PR math.RT |
arxiv_dataset-62431505.04028 | Biometric Matching and Fusion System for Fingerprints from Non-Distal
Phalanges
cs.CV
Market research indicates that fingerprints are still the most popular
biometric modality for personal authentication. Even with the onset of new
modalities (e.g. vein matching), many applications within different domains
(e-ID, banking, border control...) and geographies rely on fingerprints
obtained from the distal phalanges (a.k.a. sections, digits) of the human hand
structure. Motivated by the problem of poor quality distal fingerprint images
affecting a non-trivial portion of the population (which decreases associated
authentication accuracy), we designed and tested a multifinger, multiphalanx
fusion scheme, that combines minutiae matching scores originating from
non-distal (ie. middle and proximal) phalanges based on (i) simple sum fusion,
(ii) NFIQ image-quality-based fusion, and (iii) phalanx-type-based fusion.
Utilizing a medium-size (50 individuals, 400 unique fingers, 1600 distinct
images) database collected in our laboratory with a commercial optical
fingerprint sensor, and a commercial minutiae extractor & matcher (without any
modification), allowed us to simulate a real-world fingerprint authentication
setting. Detailed analyses including ROC curves with statistical confidence
intervals show that the proposed system can be a viable alternative for cases
where (i) distal phalanx images are not usable (e.g. due to missing digits, or
low quality finger surface due to manual labor), and (ii) switching to a new
biometric modality (e.g. iris) is not possible due to economical or
infrastructure limits. Further, we show that when distal phalanx images are in
fact usable, combining them with images from other phalanges increases accuracy
as well.
| arxiv topic:cs.CV |
arxiv_dataset-62441505.04128 | On the Classification of G-Graded Twisted Algebras over Finite Abelian
Groups
math.RA
Let G be a group and let W be an algebra over a field K. We will say that W
is a G-graded twisted algebra if W can be written as a direct sum over the
elements of G of one dimensional K-vector spaces. It is also assumed that W has
no monomial which is a zero divisor. We also demand that W has a multiplicative
identity element. We focus in the case where G is a finite abelian group and
the field K is either the real numbers or the complex numbers. In this article,
using methods of group cohomology, we classify all associative G-graded twisted
algebras in the case G is a finite abelian group. On the other hand, by
generalizing some of the arguments developed in (Velez et. al., 2014) we
present a classification of all G-graded twisted algebras that satisfy certain
symmetry condition.
| arxiv topic:math.RA |
arxiv_dataset-62451505.04228 | Fundamental limits on the accuracy of demographic inference based on the
sample frequency spectrum
q-bio.PE math.ST stat.TH
The sample frequency spectrum (SFS) of DNA sequences from a collection of
individuals is a summary statistic which is commonly used for parametric
inference in population genetics. Despite the popularity of SFS-based inference
methods, currently little is known about the information-theoretic limit on the
estimation accuracy as a function of sample size. Here, we show that using the
SFS to estimate the size history of a population has a minimax error of at
least $O(1/\log s)$, where $s$ is the number of independent segregating sites
used in the analysis. This rate is exponentially worse than known convergence
rates for many classical estimation problems in statistics. Another surprising
aspect of our theoretical bound is that it does not depend on the dimension of
the SFS, which is related to the number of sampled individuals. This means
that, for a fixed number $s$ of segregating sites considered, using more
individuals does not help to reduce the minimax error bound. Our result
pertains to populations that have experienced a bottleneck, and we argue that
it can be expected to apply to many populations in nature.
| arxiv topic:q-bio.PE math.ST stat.TH |
arxiv_dataset-62461505.04328 | Probing Hypergiant Mass Loss with Adaptive Optics Imaging & Polarimetry
in the Infrared: MMT-Pol and LMIRCam observations of IRC +10420 & VY Canis
Majoris
astro-ph.SR
We present 2 - 5 micron adaptive optics (AO) imaging and polarimetry of the
famous hypergiant stars IRC +10420 and VY Canis Majoris. The imaging
polarimetry of IRC +10420 with MMT-Pol at 2.2 micron resolves nebular emission
with intrinsic polarization of 30%, with a high surface brightness indicating
optically thick scattering. The relatively uniform distribution of this
polarized emission both radially and azimuthally around the star confirms
previous studies that place the scattering dust largely in the plane of the
sky. Using constraints on scattered light consistent with the polarimetry at
2.2 micron, extrapolation to wavelengths in the 3 - 5 micron band predicts a
scattered light component significantly below the nebular flux that is observed
in our LBT/LMIRCam 3 - 5 micron AO imaging. Under the assumption this excess
emission is thermal, we find a color temperature of ~ 500 K is required, well
in excess of the emissivity-modified equilibrium temperature for typical
astrophysical dust. The nebular features of VY CMa are found to be highly
polarized (up to 60%) at 1.3 micron, again with optically thick scattering
required to reproduce the observed surface brightness. This star's peculiar
nebular feature dubbed the "Southwest Clump" is clearly detected in the 3.1
micron polarimetry as well, which, unlike IRC+10420, is consistent with
scattered light alone. The high intrinsic polarizations of both hypergiants'
nebulae are compatible with optically thick scattering for typical dust around
evolved dusty stars, where the depolarizing effect of multiple scatters is
mitigated by the grains' low albedos.
| arxiv topic:astro-ph.SR |
arxiv_dataset-62471505.04428 | Reducible surgery in lens spaces and seiferters
math.GT
The Cabling Conjecture states that surgery on hyperbolic knots in $S^3$ never
produces reducible manifolds. In contrast, there do exist hyperbolic knots in
some lens spaces with non-prime surgeries. Baker constructed a family of such
hyperbolic knots and posed a conjecture that his examples encompass all
hyperbolic knots in lens spaces with non-prime surgeries. Using the idea of
seiferters we construct a counterexample to this conjecture. In the process of
construction, we also derive an obstruction for a small Seifert fibred space to
be obtainable by a surgery with a seiferter.
| arxiv topic:math.GT |
arxiv_dataset-62481505.04528 | Digital calculus and finite groups in quantum mechanics
math-ph hep-th math.GR math.MP
By means of a digit function that has been introduced in a recent formulation
of classical and quantum mechanics, we provide a new construction of some
infinite families of finite groups, both abelian and nonabelian, of importance
for theoretical, atomic and molecular physics. Our construction is not based on
algebraic relationships satisfied by generators, but in establishing the
appropriate law of composition that induces the group structure on a finite set
of nonnegative integers (the cardinal of the set being equal to the order of
the group) thus making computations with finite groups quite straightforward.
We establish the abstract laws of composition for infinite families of finite
groups including all cyclic groups (and any direct sums of them), dihedral,
dicyclic and other metacyclic groups, the symmetric groups of permutations of
$p$ symbols and the alternating groups of even permutations. Specific examples
are given to illustrate the expressions for the law of composition obtained in
each case.
| arxiv topic:math-ph hep-th math.GR math.MP |
arxiv_dataset-62491505.04628 | Building a fault tolerant application using the GASPI communication
layer
cs.DC
It is commonly agreed that highly parallel software on Exascale computers
will suffer from many more runtime failures due to the decreasing trend in the
mean time to failures (MTTF). Therefore, it is not surprising that a lot of
research is going on in the area of fault tolerance and fault mitigation.
Applications should survive a failure and/or be able to recover with minimal
cost. MPI is not yet very mature in handling failures, the User-Level Failure
Mitigation (ULFM) proposal being currently the most promising approach is still
in its prototype phase. In our work we use GASPI, which is a relatively new
communication library based on the PGAS model. It provides the missing features
to allow the design of fault-tolerant applications. Instead of introducing
algorithm-based fault tolerance in its true sense, we demonstrate how we can
build on (existing) clever checkpointing and extend applications to allow
integrate a low cost fault detection mechanism and, if necessary, recover the
application on the fly. The aspects of process management, the restoration of
groups and the recovery mechanism is presented in detail. We use a sparse
matrix vector multiplication based application to perform the analysis of the
overhead introduced by such modifications. Our fault detection mechanism causes
no overhead in failure-free cases, whereas in case of failure(s), the failure
detection and recovery cost is of reasonably acceptable order and shows good
scalability.
| arxiv topic:cs.DC |
arxiv_dataset-62501505.04728 | Collapsing of negative K\"ahler-Einstein metrics
math.DG math.AG math.MG
In this paper, we study the collapsing behaviour of negative
K\"{a}hler-Einstein metrics along degenerations of canonical polarized
manifolds. We prove that for a toroidal degeneration of canonical polarized
manifolds with the total space $\mathbb{Q}$-factorial, the K\"{a}hler-Einstein
metrics on fibers collapse to a lower dimensional complete Riemannian manifold
in the pointed Gromov-Hausdorff sense by suitably choosing the base points.
Furthermore, the most collapsed limit is a real affine K\"{a}hler manifold.
| arxiv topic:math.DG math.AG math.MG |
arxiv_dataset-62511505.04828 | An exact method to compute a $p$-value for the beyond-pairwise
correlations among cancer gene mutations
q-bio.QM q-bio.GN
The increasing observation of mutual exclusivity correlations among cancer
gene mutations is a key component for identifying driver events or pathways in
cancer genome analysis. Here we report a rigorous statistical method to compute
an exact $p$-value for the beyond-pairwise mutual exclusivity or co-occurrence
relationships among cancer gene mutations by enumerating a null distribution of
overlapping mutations across more than two genes. The validity and the
advantage of our method is explicitly demonstrated in both cancer gene
mutations and simulation data through the comparison to the permutation test.
| arxiv topic:q-bio.QM q-bio.GN |
arxiv_dataset-62521505.04928 | $K\to \pi \nu\bar\nu$ in the Standard Model and Beyond
hep-ph hep-ex
The precision expected for the rare $K\to \pi \nu\bar\nu$ decays by the NA62
and KOTO experiments in the coming decade will rival their current SM
predictions. In preparation for this upcoming opportunity, we review the SM
predictions and discuss the sensitivity of these decays to models beyond the
Standard Model, considering in particular simplified Z and Z' models as
benchmarks. In the latter case we also discuss how these decays could
ultimately probe distance scales as small as zeptometers i.e. peek into the
Zeptouniverse.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-62531505.05028 | Automatic and Transparent Transfer of Theorems along Isomorphisms in the
Coq Proof Assistant
cs.LO cs.MS
In mathematics, it is common practice to have several constructions for the
same objects. Mathematicians will identify them modulo isomorphism and will not
worry later on which construction they use, as theorems proved for one
construction will be valid for all.
When working with proof assistants, it is also common to see several
data-types representing the same objects. This work aims at making the use of
several isomorphic constructions as simple and as transparent as it can be done
informally in mathematics. This requires inferring automatically the missing
proof-steps.
We are designing an algorithm which finds and fills these missing proof-steps
and we are implementing it as a plugin for Coq.
| arxiv topic:cs.LO cs.MS |
arxiv_dataset-62541505.05128 | Pseudo-modularity and Iwasawa theory
math.NT
We prove, assuming Greenberg's conjecture, that the ordinary eigencurve is
Gorenstein at an intersection point between the Eisenstein family and the
cuspidal locus. As a corollary, we obtain new results on Sharifi's conjecture.
This result is achieved by constructing a universal ordinary pseudodeformation
ring and proving an $R = \mathbb T$ result.
| arxiv topic:math.NT |
arxiv_dataset-62551505.05228 | Quantitative uniqueness of some higher order elliptic equations
math.AP
We study the quantitative unique continuation property of some higher order
elliptic operators. In the case of $P=(-\Delta)^m$, where $m$ is a positive
integer, we derive lower bounds of decay at infinity for any nontrivial
solutions under some general assumptions. Furthermore, in dimension 2, we can
obtain essentially sharp lower bounds for some forth order elliptic operators,
the sharpness is shown by constructing a Meshkov type example.
| arxiv topic:math.AP |
arxiv_dataset-62561505.05328 | Methods for protein complex prediction and their contributions towards
understanding the organization, function and dynamics of complexes
q-bio.MN
Complexes of physically interacting proteins constitute fundamental
functional units responsible for driving biological processes within cells. A
faithful reconstruction of the entire set of complexes is therefore essential
to understand the functional organization of cells. In this review, we discuss
the key contributions of computational methods developed till date
(approximately between 2003 and 2015) for identifying complexes from the
network of interacting proteins (PPI network). We evaluate in depth the
performance of these methods on PPI datasets from yeast, and highlight
challenges faced by these methods, in particular detection of sparse and small
or sub- complexes and discerning of overlapping complexes. We describe methods
for integrating diverse information including expression profiles and 3D
structures of proteins with PPI networks to understand the dynamics of complex
formation, for instance, of time-based assembly of complex subunits and
formation of fuzzy complexes from intrinsically disordered proteins. Finally,
we discuss methods for identifying dysfunctional complexes in human diseases,
an application that is proving invaluable to understand disease mechanisms and
to discover novel therapeutic targets. We hope this review aptly commemorates a
decade of research on computational prediction of complexes and constitutes a
valuable reference for further advancements in this exciting area.
| arxiv topic:q-bio.MN |
arxiv_dataset-62571505.05428 | Simplex and MacDonald Codes over $R_{q}$
cs.IT math.IT
In this paper, we introduce the homogeneous weight and homogeneous Gray map
over the ring $R_{q}=\mathbb{F}_{2}[u_{1},u_{2},\ldots,u_{q}]/\left\langle
u_{i}^{2}=0,u_{i}u_{j}=u_{j}u_{i}\right\rangle$ for $q \geq 2$. We also
consider the construction of simplex and MacDonald codes of types $\alpha$ and
$\beta$ over this ring.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-62581505.05528 | Structural and magnetic phase transitions in EuTi1-xNbxO3
cond-mat.mtrl-sci
We investigate the structural and magnetic phase transitions in EuTi1-xNbxO3
with synchrotron powder X-ray diffraction (XRD), resonant ultrasound
spectroscopy (RUS), and magnetization measurements. Upon Nb-doping, the Pm-3m
to I4/mcm structural transition shifts to higher temperatures and the room
temperature lattice parameter increases while the magnitude of the octahedral
tilting decreases. In addition, Nb substitution for Ti destabilizes the
antiferromagnetic ground state of the parent compound and long range
ferromagnetic order is observed in the samples containing more than 10% Nb. The
structural transition in pure and doped compounds is marked by a step-like
softening of the elastic moduli in a narrow temperature interval near TS, which
resembles that of SrTiO3 and can be adequately modeled using the Landau free
energy model employing the same coupling between strain and octahedral tilting
order parameter as previously used to model SrTiO3.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-62591505.05628 | A generalization of Kung's theorem
cs.IT cs.DM math.IT
We give a generalization of Kung's theorem on critical exponents of linear
codes over a finite field, in terms of sums of extended weight polynomials of
linear codes. For all i=k+1,...,n, we give an upper bound on the smallest
integer m such that there exist m codewords whose union of supports has
cardinality at least i.
| arxiv topic:cs.IT cs.DM math.IT |
arxiv_dataset-62601505.05728 | Isofrequency pairing of spinning particles in Schwarzschild-de Sitter
spacetime
gr-qc
It has been established in Schwarzschild spacetime (and more generally in
Kerr spacetime) that pairs of geometrically different timelike geodesics with
the same radial and azimuthal frequencies exist in the strong field regime. The
occurrence of this socalled isofrequency pairing is of relevance in view of
gravitational-wave observations. In this paper we generalize the results on
isofrequency pairing in two directions. Firstly, we allow for a (positive)
cosmological constant, i.e., we replace the Schwarzschild spacetime with the
Schwarzschild-de Sitter spacetime. Secondly, we consider not only spinless
test-particles (i.e., timelike geodesics) but also test-particles with spin. In
the latter case we restrict to the case that the motion is in the equatorial
plane with the spin perpendicular to this plane. We find that the cosmological
constant as well as the spin have distinct impacts on the description of bound
motion in the frequency domain.
| arxiv topic:gr-qc |
arxiv_dataset-62611505.05828 | A conserved quantity in thin body dynamics
physics.class-ph cond-mat.soft math-ph math.MP
Thin, solid bodies with metric symmetries admit a restricted form of
reparameterization invariance. Their dynamical equilibria include motions with
both rigid and flowing aspects. On such configurations, a quantity is conserved
along the intrinsic coordinate corresponding to the symmetry. As an example of
its utility, this conserved quantity is combined with linear and angular
momentum currents to construct solutions for the equilibria of a rotating,
flowing string, for which it is akin to Bernoulli's constant.
| arxiv topic:physics.class-ph cond-mat.soft math-ph math.MP |
arxiv_dataset-62621505.05928 | On the minimal affinizations over the quantum affine algebras of type
$C_n$
math.QA
In this paper, we study the minimal affinizations over the quantum affine
algebras of type $C_n$ by using the theory of cluster algebras. We show that
the $q$-characters of a large family of minimal affinizations of type $C_n$
satisfy some systems of equations. These equations correspond to mutation
equations of some cluster algebras. Furthermore, we show that the minimal
affinizations in these equations correspond to cluster variables in these
cluster algebras.
| arxiv topic:math.QA |
arxiv_dataset-62631505.06028 | Spectral distortions of the CMB dipole
astro-ph.CO
We consider the distortions of the cosmic microwave background (CMB) dipole
anisotropy related to the primordial recombination radiation (PRR) and
primordial $y$- and $\mu$-distortions. The signals arise due to our motion
relative to the CMB restframe and appear as a frequency-dependent distortion of
the CMB temperature dipole. To leading order, the expected relative distortion
of the CMB dipole does not depend on the particular observation directions and
reaches the level of $10^{-6}$ for the PRR- and $\mu$-distortions and $10^{-5}$
for the $y$-distortion in the frequency range 1 -- 700 GHz. The temperature
differences arising from the dipole anisotropy of the relic CMB distortions
depend on the observation directions. For mutually opposite directions,
collinear to the CMB dipole axis, the temperature differences because of the
PRR- and $\mu$-dipole anisotropy attain values $\Delta T\simeq 10\,$nK in the
considered range. The temperature difference arising from the $y$-dipole
anisotropy may reach values of up to $1\,\mu$K. The key features of the
considered effect are as follow: (i) an observation of the effect does not
require absolute calibration; (ii) patches of sky with minimal foreground
contamination can be chosen. Future measurements of the CMB dipole distortion
thus will provide an alternative method for direct detection of the PRR-, $y$-,
and $\mu$-distortions. The $y$-distortion dipole may be detectable with PIXIE
at a few standard deviations.
| arxiv topic:astro-ph.CO |
arxiv_dataset-62641505.06128 | Double resonant Raman scattering and valley coherence generation in
monolayer WSe2
cond-mat.mtrl-sci cond-mat.mes-hall
The electronic states at the direct band gap of monolayer WSe2 at the $K^+$
and $K^-$ valleys are related by time reversal and may be viewed as
pseudo-spins. The corresponding optical interband transitions are governed by
robust excitons. In double resonant Raman spectroscopy, we uncover that the 2s
exciton state energy differs from the 1s state energy by exactly the energy of
the combination of several prominent phonons. Superimposed on the exciton
photoluminescence (PL) we observe the double resonant Raman signal. This
spectrally narrow peak shifts with the excitation laser energy as incoming
photons match the 2s and outgoing photons the 1s exciton transition. The
multi-phonon resonance has important consequences: Following linearly polarized
excitation of the 2s exciton a superposition of valley states is generated
which can relax fast via phonon emission and with minimal loss of coherence
from the 2s to 1s state. This explains the high degree of valley coherence
measured for the 1s exciton PL.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-62651505.06228 | Keyphrase Based Evaluation of Automatic Text Summarization
cs.CL
The development of methods to deal with the informative contents of the text
units in the matching process is a major challenge in automatic summary
evaluation systems that use fixed n-gram matching. The limitation causes
inaccurate matching between units in a peer and reference summaries. The
present study introduces a new Keyphrase based Summary Evaluator KpEval for
evaluating automatic summaries. The KpEval relies on the keyphrases since they
convey the most important concepts of a text. In the evaluation process, the
keyphrases are used in their lemma form as the matching text unit. The system
was applied to evaluate different summaries of Arabic multi-document data set
presented at TAC2011. The results showed that the new evaluation technique
correlates well with the known evaluation systems: Rouge1, Rouge2, RougeSU4,
and AutoSummENG MeMoG. KpEval has the strongest correlation with AutoSummENG
MeMoG, Pearson and spearman correlation coefficient measures are 0.8840, 0.9667
respectively.
| arxiv topic:cs.CL |
arxiv_dataset-62661505.06328 | Propositional Quantum Mechanics
quant-ph
Quantum mechanics is reformulated using Hartle's definition of the state of
an individual physical system and a variant of von Neumann's propositional
calculus. An elementary set of quantum postulates lead inductively to the
familiar formulas of quantum theory, including the canonical commutation
relation and Schr\"odinger's equation. The expected value of the frequency of
events for an ideal ensemble is equal to the expected value of a state operator
for an individual system, producing a binomial probability distribution for the
determination of indefinite experimental propositions.
| arxiv topic:quant-ph |
arxiv_dataset-62671505.06428 | Random Dirichlet series arising from records
math.PR math.CA math.DS
We study the distributions of the random Dirichlet series with parameters
$(s, \beta)$ defined by $$ S=\sum_{n=1}^{\infty}\frac{I_n}{n^s}, $$ where
$(I_n)$ is a sequence of independent Bernoulli random variables, $I_n$ taking
value $1$ with probability $1/n^\beta$ and value $0$ otherwise. Random series
of this type are motivated by the record indicator sequences which have been
studied in extreme value theory in statistics. We show that when $s>0$ and $0<
\beta \le 1$ with $s+\beta>1$ the distribution of $S$ has a density; otherwise
it is purely atomic or not defined because of divergence. In particular, in the
case when $s>0$ and $\beta=1$, we prove that for every $0<s<1$ the density is
bounded and continuous, whereas for every $s>1$ it is unbounded. In the case
when $s>0$ and $0<\beta<1$ with $s+\beta>1$, the density is smooth. To show the
absolute continuity, we obtain estimates of the Fourier transforms, employing
van der Corput's method to deal with number-theoretic problems. We also give
further regularity results of the densities, and present an example of non
atomic singular distribution which is induced by the series restricted to the
primes.
| arxiv topic:math.PR math.CA math.DS |
arxiv_dataset-62681505.06528 | Temperature and number evolution of cold cesium atoms inside a
wall-coated glass cell
physics.atom-ph physics.optics
We report an experimental study on the temperature and number evolution of
cold cesium atoms diffusively cooled inside a wall-coated glass cell by
measuring the absorption profile of the 62S1/2 (F=4)-62P3/2 (F'=5) transition
line with a weak probe laser in the evolution process. We found that the
temperature of the cold atoms first gradually decreases from 16 mK to 9 mK, and
then rapidly increases. The number of cold atoms first declines slowly from
2.1*10^9 to 3.7*10^8 and then falls drastically. A theoretical model for the
number evolution is built and includes the instantaneous temperature of the
cold atoms and a fraction p, which represents the part of cold cesium atoms
elastically reflected by the coated cell wall. The theory is overall in good
agreement with the experimental result and a nonzero value is obtained for the
fraction p, which indicates that the cold cesium atoms are not all heated to
the ambient temperature by a single collision with the coated cell wall. These
results can provide helpful insight for precision measurements based on diffuse
laser cooling.
| arxiv topic:physics.atom-ph physics.optics |
arxiv_dataset-62691505.06628 | Stratification and $\pi$-cosupport: Finite groups
math.RT math.GR
We introduce the notion of $\pi$-cosupport as a new tool for the stable
module category of a finite group scheme. In the case of a finite group, we use
this to give a new proof of the classification of tensor ideal localising
subcategories. In a sequel to this paper, we carry out the corresponding
classification for finite group schemes.
| arxiv topic:math.RT math.GR |
arxiv_dataset-62701505.06728 | Strong algebraization of fixed point properties
math.GR math.KT math.MG math.OA math.RA
The following natural question arises from Shalom's innovational work (1999,
Publ. IHES): "Can we establish an intrinsic criterion to synthesize relative
fixed point properties into the whole fixed point property without assuming
Bounded Generation?" This paper resolves this question in the affirmative. Our
criterion works for ones with respect to certain classes of Busemann NPC
spaces. It, moreover, suggests a further step toward constructing
super-expanders from finite simple groups of Lie type.
| arxiv topic:math.GR math.KT math.MG math.OA math.RA |
arxiv_dataset-62711505.06828 | Power Flow Modelling of Dynamic Systems - Introduction to Modern
Teaching Tools
cs.SY math.DS physics.ed-ph
As tools for dynamic system modelling both conventional methods such as
transfer function or state space representation and modern power flow based
methods are available. The latter methods do not depend on energy domain, are
able to preserve physical system structures, visualize power conversion or
coupling or split, identify power losses or storage, run on conventional
software and emphasize the relevance of energy as basic principle of known
physical domains. Nevertheless common control structures as well as analysis
and design tools may still be applied. Furthermore the generalization of power
flow methods as pseudo-power flow provides with a universal tool for any
dynamic modelling. The phenomenon of power flow constitutes an up to date
education methodology. Thus the paper summarizes fundamentals of selected power
flow oriented modelling methods, presents a Bond Graph block library for
teaching power oriented modelling as compact menu-driven freeware, introduces
selected examples and discusses special features.
| arxiv topic:cs.SY math.DS physics.ed-ph |
arxiv_dataset-62721505.06928 | Phase diagram for hard-core $\mathbb{Z}_3$ anyons on the ladder
cond-mat.str-el cond-mat.mes-hall quant-ph
Studies of free particles in low-dimensional quantum systems such as two-leg
ladders provide insight into the influence of statistics on collective
behaviour. The behaviours of bosons and fermions are well understood, but
two-dimensional systems also admit excitations with alternative statistics
known as anyons. Numerical analysis of hard-core $\mathbb{Z}_3$ anyons on the
ladder reveals qualitatively distinct behaviour, including a novel phase
transition associated with crystallisation of hole degrees of freedom into a
periodic foam. Qualitative predictions are extrapolated for all Abelian
$\mathbb{Z}_q$ anyon models.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall quant-ph |
arxiv_dataset-62731505.07028 | A Carrington-like geomagnetic storm observed in the 21st century
physics.geo-ph physics.space-ph
In September 1859 the Colaba observatory measured the most extreme
geomagnetic disturbance ever recorded at low latitudes related to solar
activity: the Carrington storm. This paper describes a geomagnetic disturbance
case with a profile extraordinarily similar to the disturbance of the
Carrington event at Colaba: the event on 29 October 2003 at Tihany magnetic
observatory in Hungary. The analysis of the H-field at different locations
during the "Carrington-like" event leads to a re-interpretation of the 1859
event. The major conclusions of the paper are the following: (a) the global Dst
or SYM-H, as indices based on averaging, missed the largest geomagnetic
disturbance in the 29 October 2003 event and might have missed the 1859
disturbance, since the large spike in the horizontal component (H) of
terrestrial magnetic field depends strongly on magnetic local time (MLT); (b)
the main cause of the large drop in H recorded at Colaba during the Carrington
storm was not the ring current but field-aligned currents (FACs), and (c) the
very local signatures of the H-spike imply that a Carrington-like event can
occur more often than expected.
| arxiv topic:physics.geo-ph physics.space-ph |
arxiv_dataset-62741505.07128 | New insights on the Galactic Bulge Initial Mass Function
astro-ph.SR astro-ph.GA
We have derived the Galactic bulge initial mass function of the SWEEPS field
in the mass range 0.15 $< M/M_{\odot}<$ 1.0, using deep photometry collected
with the Advanced Camera for Surveys on the Hubble Space Telescope.
Observations at several epochs, spread over 9 years, allowed us to separate the
disk and bulge stars down to very faint magnitudes, F814W $\sim$ 26 mag, with a
proper-motion accuracy better than 0.5 mas/yr. This allowed us to determine the
initial mass function of the pure bulge component uncontaminated by disk stars
for this low-reddening field in the Sagittarius window. In deriving the mass
function, we took into account the presence of unresolved binaries, errors in
photometry, distance modulus and reddening, as well as the metallicity
dispersion and the uncertainties caused by adopting different theoretical
color-temperature relations. We found that the Galactic bulge initial mass
function can be fitted with two power laws with a break at M $\sim$ 0.56
$M_{\odot}$, the slope being steeper ($\alpha$ = -2.41$\pm$0.50) for the higher
masses, and shallower ($\alpha$ = -1.25$\pm$0.20) for the lower masses. In the
high-mass range, our derived mass function agrees well with the mass function
derived for other regions of the bulge. In the low-mass range however, our mass
function is slightly shallower, which suggests that separating the disk and
bulge components is particularly important in the low-mass range. The slope of
the bulge mass function is also similar to the slope of the mass function
derived for the disk in the high-mass regime, but the bulge mass function is
slightly steeper in the low-mass regime. We used our new mass function to
derive stellar M/L values for the Galactic bulge and we obtained 2.1
$<M/L_{F814W}<$ 2.4 and 3.1 $< M/L_{F606W}<$ 3.6 according to different
assumptions on the slope of the IMF for masses larger than 1 $M_{\odot}$.
| arxiv topic:astro-ph.SR astro-ph.GA |
arxiv_dataset-62751505.07228 | Graph_sampler: a simple tool for fully Bayesian analyses of DAG-models
stat.CO
Bayesian networks (BNs) are widely used graphical models usable to draw
statistical inference about Directed acyclic graphs (DAGs). We presented here
Graph_sampler a fast free C language software for structural inference on BNs.
Graph_sampler uses a fully Bayesian approach in which the marginal likelihood
of the data and prior information about the network structure are considered.
This new software can handle both the continuous as well discrete data and
based on the data type two different models are formulated. The software also
provides a wide variety of structure priors which can be informative or
uninformative. We proposed a new and much faster jumping kernel strategy in the
Metropolis-Hastings algorithm. The source C code distributed is very compact,
fast, uses low memory and disk storage. We performed out several analyses based
on different simulated data sets and synthetic as well as real networks to
discuss the performance of Graph_sampler.
| arxiv topic:stat.CO |
arxiv_dataset-62761505.07328 | Dynamics of a bond-disordered $S=1$ quantum magnet near $z=1$
criticality
cond-mat.str-el
Neutron scattering is used to study
NiCl$_{2-2x}$Br$_{2x}\cdot$4SC(NH$_2$)$_2$, $x=0.06$, a bond-disordered
modification of the well-known gapped $S=1$ antiferromagnetic quantum spin
system NiCl$_{2}\cdot$4SC(NH$_2$)$_2$. The magnetic excitation spectrum
throughout Brillouin zone is mapped out at $T=60$ mK using high-resolution
time-of-flight spectroscopy. It is found that the dispersion of spin excitation
is renormalized, as compared to that in the parent compound. The lifetime of
excitations near the bottom of the band is substantially decreased. No
localized states are found below the gap energy $\Delta\simeq0.2$ meV. At the
same time, localized zero wave vector states are detected above the top of the
band. The results are consistent with a more or less continuous random
distribution of bond strengths, and a discrete, possibly bimodal, distribution
of single-ion anisotropies in the disordered material.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-62771505.07428 | Training a Convolutional Neural Network for Appearance-Invariant Place
Recognition
cs.CV cs.LG cs.RO
Place recognition is one of the most challenging problems in computer vision,
and has become a key part in mobile robotics and autonomous driving
applications for performing loop closure in visual SLAM systems. Moreover, the
difficulty of recognizing a revisited location increases with appearance
changes caused, for instance, by weather or illumination variations, which
hinders the long-term application of such algorithms in real environments. In
this paper we present a convolutional neural network (CNN), trained for the
first time with the purpose of recognizing revisited locations under severe
appearance changes, which maps images to a low dimensional space where
Euclidean distances represent place dissimilarity. In order for the network to
learn the desired invariances, we train it with triplets of images selected
from datasets which present a challenging variability in visual appearance. The
triplets are selected in such way that two samples are from the same location
and the third one is taken from a different place. We validate our system
through extensive experimentation, where we demonstrate better performance than
state-of-art algorithms in a number of popular datasets.
| arxiv topic:cs.CV cs.LG cs.RO |
arxiv_dataset-62781505.07528 | RF modulation studies on the S band pulse compressor
physics.acc-ph hep-ex
An S band SLED-type pulse compressor has been manufactured by IHEP to
challenge the 100 MW maximum input power, which means the output peak power is
about 500 MW at the phase reversal time. In order to deal with the RF breakdown
problem, the dual side-wall coupling irises model was used. To further improve
the reliability at very high power, amplitude modulation and phase modulation
with flat-top output were taken into account. The RF modulation studies on an
S-band SLED are presented in this paper. Furthermore, a method is developed by
using the CST Microwave Studio transient solver to simulate the time response
of the pulse compressor, which can be a verification of the modulate theory. In
addition, the experimental setup was constructed and the flat-top output is
obtained in the low power tests.
| arxiv topic:physics.acc-ph hep-ex |
arxiv_dataset-62791505.07628 | Extremal rotating black holes in Einstein-Maxwell-Chern-Simons theory:
radially excited solutions and non-uniqueness
gr-qc
We study 5-dimensional black holes in Einstein-Maxwell-Chern-Simons theory
with free Chern-Simons coupling parameter. We consider an event horizon with
spherical topology, and both angular momenta of equal magnitude. In particular,
we study extremal black holes, which can be used to obtain the boundary of the
domain of existence. Above a critical value of the Chern-Simons coupling
constant we find non-static extremal solutions with vanishing angular momentum.
These solutions form a sequence which can be labeled by the node number of the
magnetic $U(1)$ potential or the inertial dragging. As the node number
increases, their mass converges to the mass of the extremal
Reissner-Nordstr\"om solution. The near-horizon geometry of the solutions of
this sequence is the same. In general not all near-horizon solutions are found
as global solutions, and we show non-uniqueness between extremal solutions and
non-extremal ones.
| arxiv topic:gr-qc |
arxiv_dataset-62801505.07728 | Genesis of charge orders in high temperature superconductors
cond-mat.str-el
One of the most puzzling facts about cuprate high-temperature superconductors
in the lightly doped regime is the coexistence of uniform superconductivity
and/or antiferromagnetism with many low-energy charge-ordered states in a
unidirectional charge density wave or a bidirectional checkerboard structure.
Recent experiments have discovered that these charge density waves exhibit
different symmetries in their intra-unit-cell form factors for different
cuprate families. Using a renormalized mean-field theory for a well-known,
strongly correlated model of cuprates, we obtain a number of charge-ordered
states with nearly degenerate energies without invoking special features of the
Fermi surface. All of these self-consistent solutions have a pair density wave
intertwined with a charge density wave and sometimes a spin density wave. Most
of these states vanish in the underdoped regime, except for one with a large
d-form factor that vanishes at approximately 19% doping of the holes, as
reported by experiments. Furthermore, these states could be modified to have a
global superconducting order, with a nodal-like density of states at low
energy.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-62811505.07828 | Thermodynamics of asymptotically safe theories
hep-th hep-lat hep-ph
We investigate the thermodynamic properties of a novel class of gauge-Yukawa
theories that have recently been shown to be completely asymptotically safe,
because their short-distance behaviour is determined by the presence of an
interacting fixed point. Not only do all the coupling constants freeze at a
constant and calculable value in the ultraviolet, their values can even be made
arbitrarily small for an appropriate choice of the ratio $N_c/N_f$ of fermion
colours and flavours in the Veneziano limit. Thus, a perturbative treatment can
be justified. We compute the pressure, entropy density, and thermal degrees of
freedom of these theories to next-to-next-to-leading order in the coupling
constants.
| arxiv topic:hep-th hep-lat hep-ph |
arxiv_dataset-62821505.07928 | Security-Reliability Trade-off Analysis of Multi-Relay Aided
Decode-and-Forward Cooperation Systems
cs.IT math.IT
We consider a cooperative wireless network comprised of a source, a
destination and multiple relays operating in the presence of an eavesdropper,
which attempts to tap the source-destination transmission. We propose
multi-relay selection scheme for protecting the source against eavesdropping.
More specifically, multi-relay selection allows multiple relays to
simultaneously forward the source's transmission to the destination, differing
from the conventional single-relay selection where only the best relay is
chosen to assist the transmission from the source to destination. For the
purpose of comparison, we consider the classic direct transmission and
single-relay selection as benchmark schemes. We derive closed-form expressions
of the intercept probability and outage probability for the direct transmission
as well as for the single-relay and multi-relay selection schemes over Rayleigh
fading channels. It is demonstrated that as the outage requirement is relaxed,
the intercept performance of the three schemes improves and vice versa,
implying that there is a \emph{security versus reliability trade-off} (SRT). We
also show that both the single-relay and multi-relay selection schemes
outperform the direct transmission in terms of SRT, demonstrating the advantage
of the relay selection schemes for protecting the source's transmission against
the eavesdropping attacks. Finally, upon increasing the number of relays, the
SRTs of both the single-relay and multi-relay selection schemes improve
significantly and as expected, multi-relay selection outperforms single-relay
selection.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-62831505.08028 | RF front-end design and simulation for Sub-picosecond bunch length
measurement
physics.acc-ph
Cavity Beam Length Monitor is beam length measurement detector metering ultra
short bunch. We designed a RF front-end and make simulations to testify this
has high signal-to-noise ratio ensuring beam length measurement precision.
| arxiv topic:physics.acc-ph |
arxiv_dataset-62841505.08128 | Formation Stabilization with Collision Avoidance of Complex Systems
cs.SY
Two different aspects of formation control of multiple agents subjected to
linear transformation have been addressed in this paper. We consider a set of
complex single integrator systems so that the dimension of the system reduces
to half as opposed to the vector representation in Cartesian coordinate system.
We first design a stable formation controller in an attempt to solve the
formation control turned to stabilization problem and then find a collision
avoidance controller in the transformed domain, respectively. Different linear
transformations are used to facilitate the formation control task in a
different way. For example Jacobi transformation is used to separate the shape
control and trajectory control. The inverse of the transformation must have
nonzero eigenvalues with both positive and negative real parts which may lead
the system to instability. If the inverse of the transformation appears in
closed loop then a diagonal stabilizing matrix is required to reassign the
eigenvalues of the inverse of transformation in the right half of complex
plane. The algorithm to find such stabilizing matrix is provided. We then
define a matrix of potential in the actual domain which is the stepping stone
to find a matrix of potential in the transformed domain. Thus collision
avoidance controller can be designed directly in the transformed domain. The
mathematical proof is given that both the actual and transformed system behaves
identically. Simulation results are provided to support our claim.
| arxiv topic:cs.SY |
arxiv_dataset-62851506.00056 | Compactness and existence results in weighted Sobolev spaces of radial
functions. Part II: Existence
math.AP
We prove existence and multiplicity results for finite energy solutions to
the nonlinear elliptic equation \[ -\triangle u+V\left( \left| x\right| \right)
u=g\left( \left| x\right| ,u\right) \quad \textrm{in }\Omega \subseteq
\mathbb{R}^{N},\ N\geq 3, \] where $\Omega $ is a radial domain (bounded or
unbounded) and $u$ satisfies $u=0$ on $\partial \Omega $ if $\Omega \neq
\mathbb{R}^{N}$ and $u\rightarrow 0$ as $\left| x\right| \rightarrow \infty $
if $\Omega $ is unbounded. The potential $V$ may be vanishing or unbounded at
zero or at infinity and the nonlinearity $g$ may be superlinear or sublinear.
If $g$ is sublinear, the case with $g\left( \left| \cdot \right| ,0\right) \neq
0$ is also considered.
| arxiv topic:math.AP |
arxiv_dataset-62861506.00156 | Free vs. Locally Free Kleinian Groups
math.GT math.GR
We prove that Kleinian groups whose limit sets are Cantor sets of Hausdorff
dimension $<1$ are free. On the other hand we construct for any $\epsilon>0$
examples of non-free purely hyperbolic Kleinian groups whose limit set is a
Cantor set of Hausdorff dimension $<1+\epsilon$.
| arxiv topic:math.GT math.GR |
arxiv_dataset-62871506.00256 | The Fokker-Planck equation for bosons in 2D: well-possedness and
asymptotic analysis
math.AP
We show that solutions of the 2D Fokker-Planck equation for bosons are
defined globally in time and converge to equilibrium, and this convergence is
shown to be exponential for radially symmetric solutions. The main observation
is that a variant of the Hopf-Cole transformation relates the 2D equation in
radial coordinates to the usual linear Fokker-Planck equation. Hence, radially
symmetric solutions can be computed analytically, and our results for general
(non radially symmetric) solutions follow from comparison and entropy
arguments. In order to show convergence to equilibrium we also prove a version
of the Csisz\'ar-Kullback inequality for the Bose-Einstein-Fokker-Planck
entropy functional.
| arxiv topic:math.AP |
arxiv_dataset-62881506.00356 | Inferring causal impact using Bayesian structural time-series models
stat.AP
An important problem in econometrics and marketing is to infer the causal
impact that a designed market intervention has exerted on an outcome metric
over time. This paper proposes to infer causal impact on the basis of a
diffusion-regression state-space model that predicts the counterfactual market
response in a synthetic control that would have occurred had no intervention
taken place. In contrast to classical difference-in-differences schemes,
state-space models make it possible to (i) infer the temporal evolution of
attributable impact, (ii) incorporate empirical priors on the parameters in a
fully Bayesian treatment, and (iii) flexibly accommodate multiple sources of
variation, including local trends, seasonality and the time-varying influence
of contemporaneous covariates. Using a Markov chain Monte Carlo algorithm for
posterior inference, we illustrate the statistical properties of our approach
on simulated data. We then demonstrate its practical utility by estimating the
causal effect of an online advertising campaign on search-related site visits.
We discuss the strengths and limitations of state-space models in enabling
causal attribution in those settings where a randomised experiment is
unavailable. The CausalImpact R package provides an implementation of our
approach.
| arxiv topic:stat.AP |
arxiv_dataset-62891506.00456 | Derivation of a viscous KP equation including surface tension, and
related equations
physics.flu-dyn math.AP
The aim of this article is to derive surface wave models in the presence of
surface tension and viscosity. Using the Navier-Stokes equations with a free
surface, flat bottom and surface tension, we derive the viscous 2D Boussinesq
system with a weak transverse variation. The assumed transverse variation is on
a larger scale than along the main propagation direction. This Boussinesq
system is proved to be consistent with the Navier-Stokes equations. This system
is only an intermediate result that enables us to derive the
Kadomtsev-Petviashvili (KP) equation which is a 2D generalization of the KdV
equation. In addition, we get the 1D KdV equation, and lastly the Boussinesq
equation. All these equations are derived for non-vanishing initial conditions.
| arxiv topic:physics.flu-dyn math.AP |
arxiv_dataset-62901506.00556 | Indistinguishability of Trees in Uniform Spanning Forests
math.PR math-ph math.MP
We prove that in both the free and the wired uniform spanning forest (FUSF
and WUSF) of any unimodular random rooted network (in particular, of any Cayley
graph), it is impossible to distinguish the connected components of the forest
from each other by invariantly defined graph properties almost surely. This
confirms a conjecture of Benjamini, Lyons, Peres and Schramm.
We use this to answer positively two additional questions of Benjamini,
Lyons, Peres and Schramm under the assumption of unimodularity. We prove that
on any unimodular random rooted network, the FUSF is either connected or has
infinitely many connected components almost surely, and, if the FUSF and WUSF
are distinct, then every component of the FUSF is transient and
infinitely-ended almost surely. All of these results are new even for Cayley
graphs.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-62911506.00656 | Starbursts are preferentially interacting: confirmation from the nearest
galaxies
astro-ph.GA astro-ph.CO
We complement a recent ApJ Letter by Luo et al. by comparing the fraction of
starburst galaxies which are interacting with the overall fraction of
interacting galaxies in the nearby galaxy population (within 40 Mpc). We
confirm that in starburst galaxies the fraction of interacting galaxies is
enhanced, by a factor of around 2, but crucially we do so by studying a sample
of almost 1500 of the nearest galaxies, including many dwarfs and irregulars.
We discuss how adjusting the starburst definition influences the final result
and conclude that our result is stable. We find significantly lower fractions
of interacting galaxies than Luo et al. did from their larger but more distant
sample of galaxies, and argue that the difference is most likely due to various
biases in the sample selection, with a representative sample of the nearest
galaxies, such as the one used here, being the best possible representation of
a general picture. Our overall conclusion is that interactions can and do
increase the number of starburst galaxies, and that this result is extremely
robust. By far most starburst galaxies, however, show no evidence of a present
interaction.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-62921506.00756 | Stable limit cycles perturbed by noise
math.DS
Many physical and biological systems exhibit intrinsic cyclic dynamics that
are altered by random external perturbations. We examine continuous-time
autonomous dynamical systems exhibiting a stable limit cycle, perturbed by
additive Gaussian white noise. We derive a formal approximation for the
dynamics of sample paths that stay close to the limit cycle, in terms of a
phase coordinate and a deviation perpendicular to the limit cycle. To leading
order in the deviation, the phase advances at the deterministic speed
superimposed by a Brownian-motion-like drift. The deviation itself takes the
form of an (n-1)-dimensional Ornstein-Uhlenbeck process. We apply these results
to the case of limit cycles emerging through a supercritical Hopf bifurcation,
which is widespread in ecological and epidemiological models. We derive
approximation formulas for the system's stationary autocovariance and power
spectral density. The latter two reflect the effects of perturbations on the
temporal coherence and spectral bandwidth of perturbed limit cycles. We verify
our results using numerical simulations and exemplify their application to the
El Ni\~no Southern Oscillation.
| arxiv topic:math.DS |
arxiv_dataset-62931506.00856 | Aspects of Zeta-Function Theory in the Mathematical Works of Adolf
Hurwitz
math.HO math.NT
Adolf Hurwitz is rather famous for his celebrated contributions to Riemann
surfaces, modular forms, diophantine equations and approximation as well as to
certain aspects of algebra. His early work on an important generalization of
Dirichlet's $L$-series, nowadays called Hurwitz zeta-function, is the only
published work settled in the very active field of research around the Riemann
zeta-function and its relatives. His mathematical diaries, however, provide
another picture, namely a lifelong interest in the development of zeta-function
theory. In this note we shall investigate his early work, its origin and its
reception, as well as Hurwitz's further studies of the Riemann zeta-function
and allied Dirichlet series from his diaries. It turns out that Hurwitz already
in 1889 knew about the essential analytic properties of the Epstein
zeta-function (including its functional equation) 13 years before Paul Epstein.
| arxiv topic:math.HO math.NT |
arxiv_dataset-62941506.00956 | Nuclear excitation functions from 40-200 MeV proton irradiation of
terbium
nucl-ex
Nuclear formation cross sections are reported for 26 radionuclides, measured
with 40 to 200 MeV proton irradiations of terbium foils. These data are
relevant to the production of medically relevant radionuclides (e.g., 152Tb,
155Tb, 155Eu, and 156Eu) and to ongoing efforts to characterize stellar
nucleosynthesis routes passing through long-lived intermediaries (e.g., 153Gd).
Computational predictions from the ALICE2011, CEM03.03, Bertini, and INCL+ABLA
codes are compared with newly measured data to contribute to the ongoing
process of code development, and yields are calculated for selected
radionuclides using measured data.
| arxiv topic:nucl-ex |
arxiv_dataset-62951506.01056 | Performing Bayesian Risk Aggregation using Discrete Approximation
Algorithms with Graph Factorization
cs.AI
Risk aggregation is a popular method used to estimate the sum of a collection
of financial assets or events, where each asset or event is modelled as a
random variable. Applications, in the financial services industry, include
insurance, operational risk, stress testing, and sensitivity analysis, but the
problem is widely encountered in many other application domains. This thesis
has contributed two algorithms to perform Bayesian risk aggregation when model
exhibit hybrid dependency and high dimensional inter-dependency. The first
algorithm operates on a subset of the general problem, with an emphasis on
convolution problems, in the presence of continuous and discrete variables (so
called hybrid models) and the second algorithm offer a universal method for
general purpose inference over much wider classes of Bayesian Network models.
| arxiv topic:cs.AI |
arxiv_dataset-62961506.01156 | Quantization of charged fields in the presence of critical potential
steps
hep-th
QFT approaches elaborated for treating quantum effects in time-dependent
external electric fields are not directly applicable to time-independent
nonuniform electric fields that are given by a step potential and their
generalization for the such potentials was not sufficiently developed. Such
fields can also create particles from the vacuum, the Klein paradox being
closely related to this process. We believe that the present work presents a
consistent solution of the latter problem. Quantizing the Dirac and scalar
fields with time independent backgrounds, we have found in- and out-creation
and annihilation operators that allow one to have particle interpretation of
the physical system under consideration. To justify the proposed
identification, we have performed a detailed mathematical and physical analysis
of solutions of the corresponding relativistic wave equations with a subsequent
QFT analysis. We elaborated a nonperturbative technique that allows one to
calculate all characteristics of zero-order processes such scattering,
reflection, and electron-positron pair creation, and to calculate Feynman
diagrams that describe all characteristics of processes with interaction
between the in-, out-particles and photons. These diagrams have formally the
usual form, but contain special propagators. Expressions for these propagators
in terms of in- and out-solutions are presented. We apply the elaborated
approach to two popular exactly solvable cases: to the Sauter potential and to
the Klein step.
| arxiv topic:hep-th |
arxiv_dataset-62971506.01256 | PDF Steganography based on Chinese Remainder Theorem
cs.CR
We propose different approaches of PDF files based steganography, essentially
based on the Chinese Remainder Theorem. Here, after a cover PDF document has
been released from unnecessary A0, a secret message is hidden in it using one
of the proposed approaches, making it invisible to common PDF readers, and the
file is then transmitted through a non-secure communication channel. Where each
of our methods, ensure the condition that the number of inserted A0 is less
than the number of characters of the secret message s.
| arxiv topic:cs.CR |
arxiv_dataset-62981506.01356 | Development of hard x-ray photoelectron SPLEED-based spectrometer
applicable for probing of buried magnetic layer valence states
physics.ins-det
A novel design of high-voltage compatible polarimeter for spin-resolved hard
x-ray photoelectron spectroscopy (Spin-HAXPES) went into operation at beamline
BL09XU of SPring-8 in Hyogo, Japan. The detector is based on the
well-established principle of electron diffraction from a W(001) single-crystal
at a scattering energy of 103.5 eV. Its special feature is that it can be
operated at a high negative bias potential up to 10 kV, necessary to access the
HAXPES range. The polarimeter is operated behind a large hemispherical analyzer
(Scienta R-4000). It was optimized for high transmission of the transfer
optics. The exit plane of the analyzer contains a delay-line detector (20 mm
dia.) for conventional multichannel intensity spectroscopy simultaneously with
single-channel spin analysis. The performance of the combined setup is
demonstrated by the first spin-resolved data for the valence-region of a FeCo
functional layer of a tunneling device, buried beneath 3 nm of oxidic material.
The well-structured spin polarization spectrum validates Spin-HAXPES in the
valence energy range as powerful method for bulk electronic structure analysis.
The spin polarization spectrum exhibits a rich structure, originating from
clearly discernible transitions in the majority and minority partial spin
spectra.
| arxiv topic:physics.ins-det |
arxiv_dataset-62991506.01456 | No smooth Julia sets for polynomial diffeomorphisms of $\mathbb{C}^2$
with positive entropy
math.DS
For any polynomial diffeomorphism $f$ of $\mathbb{C}^2$ with positive
entropy, neither the Julia set of $f$ nor of its inverse $f^{-1}$ is $C^1$
smooth as a manifold-with-boundary.
| arxiv topic:math.DS |
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