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arxiv_dataset-48001311.6339 | Series expansions for $1/\pi^m$ and $\pi^m$
math.CO math.CA
By means of the telescoping method, we establish two sum- mation formulas on
sine function. As the special cases of them, several interesting series
expansions for $1/\pi^m$ and $\pi^m$.
| arxiv topic:math.CO math.CA |
arxiv_dataset-48011311.6439 | Robust Transceiver Optimization for Downlink Multiuser MIMO Systems
math.OC
This paper addresses the joint transceiver design for downlink multiuser
multiple-input multiple-output (MIMO) systems, with imperfect channel state
information (CSI) at the base station (BS) and mobile stations (MSs). By
incorporating antenna correlation at both ends of the channel and taking
channel estimation errors into account, we solve two robust design problems:
minimization of the weighted sum mean-square-error (MSE) and minimization of
the maximum weighted MSE. These problems are solved as follows: first, we
establish three kinds of MSE uplink-downlink duality by transforming only the
power allocation matrices from uplink channel to downlink channel and vice
versa. Second, in the uplink channel, we formulate the power allocation part of
each problem ensuring global optimality. Finally, based on the solution of the
uplink power allocation and the MSE duality results, for each problem, we
propose an iterative algorithm that performs optimization alternatively between
the uplink and downlink channels. Computer simulations verify the robustness of
the proposed design compared to the non-robust/naive design.
| arxiv topic:math.OC |
arxiv_dataset-48021311.6539 | Quantum Raychaudhuri equation
gr-qc hep-th quant-ph
We compute quantum corrections to the Raychaudhuri equation, by replacing
classical geodesics with quantal (Bohmian) trajectories, and show that they
prevent focusing of geodesics, and the formation of conjugate points. We
discuss implications for the Hawking-Penrose singularity theorems, and for
curvature singularities.
| arxiv topic:gr-qc hep-th quant-ph |
arxiv_dataset-48031311.6639 | Computational screening study towards redox-active metal-organic
frameworks
cond-mat.mtrl-sci
The metal-organic framework (MOF) MFU-4l containing Co(II) centers and Cl-
ligands has recently shown promising redox activity. Aiming for further
improved MOF catalysts for oxidation processes employing molecular oxygen we
present a density-functional theory (DFT) based computational screening
approach to identify promising metal center and ligand combinations within the
MFU-4l structural family. Using the O2 binding energy as a descriptor for the
redox property, we show that relative energetic trends in this descriptor can
reliably be obtained at the hybrid functional DFT level and using small cluster
(scorpionate-type complex) models. Within this efficient computational protocol
we screen a range of metal center / ligand combinations and identify several
candidate systems that offer more exothermic O2 binding than the original
Co/Cl-based MFU-4l framework.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-48041311.6739 | On optimal control problems with impulsive commutative dynamics
math.OC
We consider control systems governed by nonlinear O.D.E.'s that are affine in
the time-derivative du/dt of the control u. The latter is allowed to be an
integrable, possibly of unbounded variation function, which gives the system an
impulsive character. As is well-known, the corresponding Cauchy problem cannot
be interpreted in terms of Schwartz distributions, even in the commutative
case. A robust notion of solution already proposed in the literature is here
adopted and slightly generalized to the case where an ordinary, bounded,
control is present in the dynamics as well. For a problem in the Mayer form we
then investigate the question whether this notion of solution provides a
"proper extension" of the standard problem with absolutely continuous controls
u. Furthermore, we show that this impulsive problem is a variational limit of
problems corresponding to controls u with bounded variation.
| arxiv topic:math.OC |
arxiv_dataset-48051311.6839 | Picking Planar Edges; or, Drawing a Graph with a Planar Subgraph
cs.CG cs.DM math.CO
Given a graph $G$ and a subset $F \subseteq E(G)$ of its edges, is there a
drawing of $G$ in which all edges of $F$ are free of crossings? We show that
this question can be solved in polynomial time using a Hanani-Tutte style
approach. If we require the drawing of $G$ to be straight-line, and allow at
most one crossing along each edge in $F$, the problem turns out to be as hard
as the existential theory of the real numbers.
| arxiv topic:cs.CG cs.DM math.CO |
arxiv_dataset-48061311.6939 | Inhomogeneous viscous fluids in FRW universe and finite-future time
singularities
gr-qc
We consider inhomogeneous viscous fluids in flat Friedmann-Robertson-Walker
universe. We analyze different kinds of such fluids and investigate the
possibility to reproduce the current cosmic acceleration providing a different
future evolution with respect to the Cosmological Constant case. In particular,
we study the presence of finite-future time singularities. We also discuss a
general class of "integrable" viscous fluid models whose bulk viscosities obey
to a common differential equation.
| arxiv topic:gr-qc |
arxiv_dataset-48071311.7039 | Large deviations for the Ornstein-Uhlenbeck process with shift
math.PR math.ST stat.TH
We investigate the large deviation properties of the maximum likelihood
estimators for the Ornstein-Uhlenbeck process with shift. We estimate
simultaneously the drift and shift parameters. On the one hand, we establish a
large deviation principle for the maximum likelihood estimates of the drift and
shift parameters. Surprisingly, we find that the drift estimator shares the
same large deviation principle as the one previously established for the
Ornstein-Uhlenbeck process without shift. Sharp large deviation principles are
also provided. On the other hand, we show that the maximum likelihood estimator
of the shift parameter satisfies a large deviation principle with a very
unusual implicit rate function.
| arxiv topic:math.PR math.ST stat.TH |
arxiv_dataset-48081311.7139 | Introduction to Neutrosophic Measure, Neutrosophic Integral, and
Neutrosophic Probability
cs.AI
In this paper, we introduce for the first time the notions of neutrosophic
measure and neutrosophic integral, and we develop the 1995 notion of
neutrosophic probability. We present many practical examples. It is possible to
define the neutrosophic measure and consequently the neutrosophic integral and
neutrosophic probability in many ways, because there are various types of
indeterminacies, depending on the problem we need to solve. Neutrosophics study
the indeterminacy. Indeterminacy is different from randomness. It can be caused
by physical space materials and type of construction, by items involved in the
space, etc.
| arxiv topic:cs.AI |
arxiv_dataset-48091311.7239 | Multiple-relaxation-time lattice Boltzmann modeling of incompressible
flows in porous media
physics.comp-ph cond-mat.soft physics.flu-dyn
In this paper, a two-dimensional eight-velocity (D2Q8)
multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is proposed for
incompressible porous flows at the representative elementary volume scale based
on the Brinkman-Forchheimer-extended Darcy formulation. In the model, the
porosity is included into the pressure-based equilibrium moments, and the
linear and nonlinear drag forces of the porous media are incorporated into the
model by adding a forcing term to the MRT-LB equation in the moment space.
Through the Chapman-Enskog analysis, the generalized Navier-Stokes equations
can be recovered exactly without artificial compressible errors. Numerical
simulations of several typical two-dimensional porous flows are carried out to
validate the present MRT-LB model. The numerical results of the present MRT-LB
model are in good agreement with the analytical solutions and/or other
numerical solutions reported in the literature.
| arxiv topic:physics.comp-ph cond-mat.soft physics.flu-dyn |
arxiv_dataset-48101311.7339 | Aspects of the zero $\Lambda$ limit in the AdS/CFT correspondence
hep-th
We examine the correspondence between QFT observables and bulk solutions in
the context of AdS/CFT in the limit as the cosmological constant $\Lambda \to
0$. We focus specifically on the spacetime metric and a non-backreacting scalar
in the bulk, compute the one-point functions of the dual operators and
determine the necessary conditions for the correspondence to admit a
well-behaved zero $\Lambda$ limit. We discuss holographic renormalization in
this limit and find that it requires schemes that partially break
diffeomorphism invariance of the bulk theory. In the specific case of three
bulk dimensions, we compute the zero $\Lambda$ limit of the holographic Weyl
anomaly and reproduce the central charge that arises in the central extension
of $\mathfrak{bms}_{3}$. We compute holographically the energy and momentum of
those QFT states dual to flat cosmological solutions and to the Kerr solution
and find an agreement with the bulk theory. We also compute holographically the
renormalized 2-point function of a scalar operator in the zero $\Lambda$ limit
and find it to be consistent with that of a conformal operator in two
dimensions less. Finally, our results can be used in a new definition of
asymptotic Ricci-flatness at null infinity based on the zero $\Lambda$ limit of
asymptotically Einstein manifolds.
| arxiv topic:hep-th |
arxiv_dataset-48111311.7439 | Excited random walk with periodic cookies
math.PR
In this paper we consider an excited random walk on $\mathbb{Z}$ in
identically piled periodic environment. This is a discrete time process on
$\mathbb{Z}$ defined by parameters $(p_1,\dots p_M) \in [0,1]^M$ for some
positive integer $M$, where the walker upon the $i$-th visit to $z \in
\mathbb{Z}$ moves to $z+1$ with probability $p_{i\pmod M}$, and moves to $z-1$
with probability $1-p_{i \pmod M}$. We give an explicit formula in terms of the
parameters $(p_1,\dots,p_M)$ which determines whether the walk is recurrent,
transient to the left, or transient to the right. In particular, in the case
that $\frac{1}{M}\sum_{i=1}^{M}p_{i}=\frac {1}{2}$ all behaviors are possible,
and may depend on the order of the $p_i$. Our framework allows us to reprove
some known results on ERW with no additional effort.
| arxiv topic:math.PR |
arxiv_dataset-48121311.7539 | A Hamiltonian Monte Carlo method for Bayesian Inference of Supermassive
Black Hole Binaries
gr-qc
We investigate the use of a Hamiltonian Monte Carlo to map out the posterior
density function for supermassive black hole binaries. While previous Markov
Chain Monte Carlo (MCMC) methods, such as Metropolis-Hastings MCMC, have been
successfully employed for a number of different gravitational wave sources,
these methods are essentially random walk algorithms. The Hamiltonian Monte
Carlo treats the inverse likelihood surface as a "gravitational potential" and
by introducing canonical positions and momenta, dynamically evolves the Markov
chain by solving Hamilton's equations of motion. We present an implementation
of the Hamiltonian Markov Chain that is faster, and more efficient by a factor
of approximately the dimension of the parameter space, than the standard MCMC.
| arxiv topic:gr-qc |
arxiv_dataset-48131311.7639 | Pion structure from lattice QCD
hep-lat
We report on the lowest moment of parton distribution functions and
generalized form factors for the pion at several values of the momentum
transfer. Calculations are performed for N_f=2 flavors of O(a) improved Wilson
fermions with pion masses down to 150 MeV.
| arxiv topic:hep-lat |
arxiv_dataset-48141312.0047 | Updating constraint preconditioners for KKT systems in quadratic
programming via low-rank corrections
math.NA math.OC
This work focuses on the iterative solution of sequences of KKT linear
systems arising in interior point methods applied to large convex quadratic
programming problems. This task is the computational core of the interior point
procedure and an efficient preconditioning strategy is crucial for the
efficiency of the overall method. Constraint preconditioners are very effective
in this context; nevertheless, their computation may be very expensive for
large-scale problems, and resorting to approximations of them may be
convenient. Here we propose a procedure for building inexact constraint
preconditioners by updating a "seed" constraint preconditioner computed for a
KKT matrix at a previous interior point iteration. These updates are obtained
through low-rank corrections of the Schur complement of the (1,1) block of the
seed preconditioner. The updated preconditioners are analyzed both
theoretically and computationally. The results obtained show that our updating
procedure, coupled with an adaptive strategy for determining whether to
reinitialize or update the preconditioner, can enhance the performance of
interior point methods on large problems.
| arxiv topic:math.NA math.OC |
arxiv_dataset-48151312.0147 | Quantum probes of timelike naked singularities in $2+1-$ dimensional
power - law spacetimes
physics.gen-ph
The formation of naked singularities in $2+1-$ dimensional power - law
spacetimes in linear Einstein-Maxwell and Einstein-scalar theories sourced by
azimuthally symmetric electric field and a self-interacting real scalar field
respectively, are considered in view of quantum mechanics. Quantum test fields
obeying the Klein-Gordon and Dirac equations are used to probe the classical
timelike naked singularities developed at $r=0$. We show that when the
classically singular spacetimes probed with scalar waves, the considered
spacetimes remains singular. However, the spinorial wave probe of the
singularity in the metric of a self-interacting real scalar field remains
quantum regular. The notable outcome in this study is that the quantum
regularity/singularity can not be associated with the energy conditions.
| arxiv topic:physics.gen-ph |
arxiv_dataset-48161312.0247 | Vector bundles from generalized pairs of cocycles
math.KT
It is interesting to know, how far we can generalize the notion of a
group-valued cocycle keeping the property to determine a bundle. We find a
generalization for pairs of cocycles and show how these generalized pairs of
cocycles can still determine vector bundles.
| arxiv topic:math.KT |
arxiv_dataset-48171312.0347 | Solving the TTC 2013 Flowgraphs Case with FunnyQT
cs.SE
FunnyQT is a model querying and model transformation library for the
functional Lisp-dialect Clojure providing a rich and efficient querying and
transformation API.
This paper describes the FunnyQT solution to the TTC 2013 Flowgraphs
Transformation Case. It solves all four tasks, and it has won the best
efficiency award for this case.
| arxiv topic:cs.SE |
arxiv_dataset-48181312.0447 | Finite field-energy of a point charge in QED
hep-th
We consider a simple nonlinear (quartic in the fields) gauge-invariant
modification of classical electrodynamics, which possesses a regularizing
ability sufficient to make the field energy of a point charge finite. The model
is exactly solved in the class of static central-symmetric electric fields.
Collation with quantum electrodynamics (QED) results in the total field energy
about twice the electron mass. The proof of the finiteness of the field energy
is extended to include any polynomial selfinteraction, thereby the one that
stems from the truncated expansion of the Euler-Heisenberg local Lagrangian in
QED in powers of the field strenth.
| arxiv topic:hep-th |
arxiv_dataset-48191312.0547 | Capture and isolation of highly-charged ions in a unitary Penning trap
physics.atom-ph
We recently used a compact Penning trap to capture and isolate highly-charged
ions extracted from an electron beam ion trap (EBIT) at the National Institute
of Standards and Technology (NIST). Isolated charge states of highly-stripped
argon and neon ions with total charge $Q \geq 10$, extracted at energies of up
to $4\times 10^3\,Q$ eV, are captured in a trap with well depths of $\,\approx
(4\, {\rm to}\, 12)\,Q$ eV. Here we discuss in detail the process to optimize
velocity-tuning, capture, and storage of highly-charged ions in a unitary
Penning trap designed to provide easy radial access for atomic or laser beams
in charge exchange or spectroscopic experiments, such as those of interest for
proposed studies of one-electron ions in Rydberg states or optical transitions
of metastable states in multiply-charged ions. Under near-optimal conditions,
ions captured and isolated in such rare-earth Penning traps can be
characterized by an initial energy distribution that is $\approx$ 60 times
narrower than typically found in an EBIT. This reduction in thermal energy is
obtained passively, without the application of any active cooling scheme in the
ion-capture trap.
| arxiv topic:physics.atom-ph |
arxiv_dataset-48201312.0647 | Interactions of large amplitude solitary waves in viscous fluid conduits
nlin.PS physics.flu-dyn
The free interface separating an exterior, viscous fluid from an intrusive
conduit of buoyant, less viscous fluid is known to support strongly nonlinear
solitary waves due to a balance between viscosity-induced dispersion and
buoyancy-induced nonlinearity. The overtaking, pairwise interaction of weakly
nonlinear solitary waves has been classified theoretically for the Korteweg-de
Vries equation and experimentally in the context of shallow water waves, but a
theoretical and experimental classification of strongly nonlinear solitary wave
interactions is lacking. The interactions of large amplitude solitary waves in
viscous fluid conduits, a model physical system for the study of
one-dimensional, truly dissipationless, dispersive nonlinear waves, are
classified. Using a combined numerical and experimental approach, three classes
of nonlinear interaction behavior are identified: purely bimodal, purely
unimodal, and a mixed type. The magnitude of the dispersive radiation due to
solitary wave interactions is quantified numerically and observed to be beyond
the sensitivity of our experiments, suggesting that conduit solitary waves
behave as "physical solitons." Experimental data are shown to be in excellent
agreement with numerical simulations of the reduced model. Experimental movies
are available with the online version of the paper.
| arxiv topic:nlin.PS physics.flu-dyn |
arxiv_dataset-48211312.0747 | Clifford-Wolf homogeneous Finsler metrics on spheres
math.DG
An isometry of a Finsler space is called Clifford-Wolf translation
(CW-translation) if it moves all points the same distance. A Finsler space $(M,
F)$ is called Clifford-Wolf homogeneous (CW-homogeneous) if for any $x, y\in M$
there is a CW-translation $\sigma$ such that $\sigma (x)=y$. We prove that if
$F$ is a homogeneous Finsler metric on the sphere $S^n$ such that $(S^n, F)$ is
CW-homogeneous, then $F$ must be a Randers metric. This gives a complete
classification of CW-homogeneous Finsler metrics on spheres.
| arxiv topic:math.DG |
arxiv_dataset-48221312.0847 | Temperature and Magnetic Field Dependence of Spin Ice Correlations in
the Pyrochlore Magnet Tb2Ti2O7
cond-mat.str-el
We present a parametric study of the diffuse magnetic scattering at
(1/2,1/2,1/2) positions in reciprocal space, ascribed to a frozen
antiferromagnetic spin ice state in single crystalline Tb2Ti2O7. Our
high-resolution neutron scattering measurements show that the elastic (-0.02
meV < E < 0.02 meV) (1/2,1/2,1/2) scattering develops strongly below ~275 mK,
and correlates with the opening of a spin gap of ~0.06-0.08 meV over most of
the Brillouin zone. The concomitant low-lying magnetic spin excitations are
weakly dispersive and appear to soften near the (1/2,1/2,1/2) wave vector at 80
mK. The nature of the transition at 275 mK has many characteristics of spin
glass behavior, consistent with ac-susceptibility measurements. The application
of a magnetic field of 0.075 T applied along the [1-10] direction destroys the
(1/2,1/2,1/2) elastic scattering, revealing the fragility of this short-range
ordered ground state. We construct a refined H-T phase diagram for Tb2Ti2O7 and
[1-10] fields which incorporates this frozen spin ice regime and the
antiferromagnetic long-range order previously known to be induced in relatively
large fields. Specific heat measurements on the same crystal reveal a sharp
anomaly at Tc~450 mK and no indication of a transition near ~275 mK. We
conclude that the higher temperature specific heat peak is not related to the
magnetic ordering but is likely a signal of other, nonmagnetic, correlations.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-48231312.0947 | A Full-sky, High-resolution Atlas of Galactic 12 micron Dust Emission
with WISE
astro-ph.IM astro-ph.GA
We describe our custom processing of the entire Wide-field Infrared Survey
Explorer (WISE) 12 micron imaging data set, and present a high-resolution,
full-sky map of diffuse Galactic dust emission that is free of compact sources
and other contaminating artifacts. The principal distinctions between our
resulting co-added images and the WISE Atlas stacks are our removal of compact
sources, including their associated electronic and optical artifacts, and our
preservation of spatial modes larger than 1.5 degrees. We provide access to the
resulting full-sky map via a set of 430 12.5 degree by 12.5 degree mosaics.
These stacks have been smoothed to 15" resolution and are accompanied by
corresponding coverage maps, artifact images, and bit-masks for point sources,
resolved compact sources, and other defects. When combined appropriately with
other mid-infrared and far-infrared data sets, we expect our WISE 12 micron
co-adds to form the basis for a full-sky dust extinction map with angular
resolution several times better than Schlegel et al. (1998).
| arxiv topic:astro-ph.IM astro-ph.GA |
arxiv_dataset-48241312.1047 | Nonlocalized cluster dynamics and nuclear molecular structure
nucl-th
A container picture is proposed for understanding cluster dynamics where the
clusters make nonlocalized motion occupying the lowest orbit of the cluster
mean-field potential characterized by the size parameter $``B"$ in the THSR
(Tohsaki-Horiuchi-Schuck-R\"{o}pke) wave function. The nonlocalized cluster
aspects of the inversion-doublet bands in $^{20}$Ne which have been considered
as a typical manifestation of localized clustering are discussed. So far
unexplained puzzling features of the THSR wave function, namely that after
angular-momentum projection for two cluster systems the prolate THSR wave
function is almost 100$\%$ equivalent to an oblate THSR wave function is
clarified. It is shown that the true intrinsic two-cluster THSR configuration
is nonetheless prolate. The proposal of the container picture is based on the
fact that typical cluster systems, 2$\alpha$, 3$\alpha$, and $\alpha$+$^{16}$O,
are all well described by a single THSR wave function. It will be shown for the
case of linear-chain states with two and three $\alpha$-clusters as well as for
the $\alpha$+$^{16}$O system that localization is entirely of kinematical
origin, that is, due to the inter-cluster Pauli repulsion. It is concluded that
this feature is general for nuclear cluster states.
| arxiv topic:nucl-th |
arxiv_dataset-48251312.1147 | Optimality of Operator-Like Wavelets for Representing Sparse AR(1)
Processes
cs.IT math.IT
It is known that the Karhunen-Lo\`{e}ve transform (KLT) of Gaussian
first-order auto-regressive (AR(1)) processes results in sinusoidal basis
functions. The same sinusoidal bases come out of the independent-component
analysis (ICA) and actually correspond to processes with completely independent
samples. In this paper, we relax the Gaussian hypothesis and study how
orthogonal transforms decouple symmetric-alpha-stable (S$\alpha$S) AR(1)
processes. The Gaussian case is not sparse and corresponds to $\alpha=2$, while
$0<\alpha<2$ yields processes with sparse linear-prediction error. In the
presence of sparsity, we show that operator-like wavelet bases do outperform
the sinusoidal ones. Also, we observe that, for processes with very sparse
increments ($0<\alpha\leq 1$), the operator-like wavelet basis is
indistinguishable from the ICA solution obtained through numerical
optimization. We consider two criteria for independence. The first is the
Kullback-Leibler divergence between the joint probability density function
(pdf) of the original signal and the product of the marginals in the
transformed domain. The second is a divergence between the joint pdf of the
original signal and the product of the marginals in the transformed domain,
which is based on Stein's formula for the mean-square estimation error in
additive Gaussian noise. Our framework then offers a unified view that
encompasses the discrete cosine transform (known to be asymptotically optimal
for $\alpha=2$) and Haar-like wavelets (for which we achieve optimality for
$0<\alpha\leq1$).
| arxiv topic:cs.IT math.IT |
arxiv_dataset-48261312.1247 | Tunable strong nonlinearity of a micromechanical beam embedded in a
dc-SQUID
cond-mat.mes-hall
We present a study of the controllable nonlinear dynamics of a
micromechanical beam coupled to a dc-SQUID (superconducting quantum
interference device). The coupling between these systems places the modes of
the beam in a highly nonlinear potential, whose shape can be altered by varying
the control parameters of the SQUID. We detect the position of the beam by
placing it in an optical cavity, which frees the SQUID to be used solely for
actuation. This enables us to probe the previously unexplored full parameter
space of this device. We measure the frequency response of the beam and find
that it displays a periodic dependence on applied magnetic flux. To account for
this, we develop a model based on the standard theory for SQUID dynamics. In
addition, with the aim of understanding if the device can reach nonlinearity at
the single phonon level, we use this model to show that the responsivity of the
current circulating in the SQUID to the position of the beam can become
divergent, with its magnitude limited only by noise. This suggests a direction
for the generation of macroscopically distinguishable superposition states of
the beam.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-48271312.1347 | Ubiquitous Interplay between Charge Ordering and High-Temperature
Superconductivity in Cuprates
cond-mat.supr-con cond-mat.str-el
Besides superconductivity, copper-oxide high temperature superconductors are
susceptible to other types of ordering. We use scanning tunneling microscopy
and resonant elastic x-ray scattering measurements to establish the formation
of charge ordering in the high-temperature superconductor Bi2Sr2CaCu2O8+x.
Depending on the hole concentration, the charge ordering in this system occurs
with the same period as those found in Y-based or La-based cuprates, and
displays the analogous competition with superconductivity. These results
indicate the similarity of charge organization competing with superconductivity
across different families of cuprates. We observe this charge ordering to leave
a distinct electron-hole asymmetric signature (and a broad resonance centered
at +20 meV) in spectroscopic measurements, thereby indicating that it is likely
related to the organization of holes in a doped Mott insulator.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-48281312.1447 | Asynchronous Convolutional-Coded Physical-Layer Network Coding
cs.IT math.IT
This paper investigates the decoding process of asynchronous
convolutional-coded physical-layer network coding (PNC) systems. Specifically,
we put forth a layered decoding framework for convolutional-coded PNC
consisting of three layers: symbol realignment layer, codeword realignment
layer, and joint channel-decoding network coding (Jt-CNC) decoding layer. Our
framework can deal with phase asynchrony and symbol arrival-time asynchrony
between the signals simultaneously transmitted by multiple sources. A salient
feature of this framework is that it can handle both fractional and integral
symbol offsets; previously proposed PNC decoding algorithms (e.g., XOR-CD and
reduced-state Viterbi algorithms) can only deal with fractional symbol offset.
Moreover, the Jt-CNC algorithm, based on belief propagation (BP), is
BER-optimal for synchronous PNC and near optimal for asynchronous PNC.
Extending beyond convolutional codes, we further generalize the Jt-CNC decoding
algorithm for all cyclic codes. Our simulation shows that Jt-CNC outperforms
the previously proposed XOR-CD algorithm and reduced-state Viterbi algorithm by
2dB for synchronous PNC. For phase-asynchronous PNC, Jt-CNC is 4dB better than
the other two algorithms. Importantly, for real wireless environment testing,
we have also implemented our decoding algorithm in a PNC system built on the
USRP software radio platform. Our experiment shows that the proposed Jt-CNC
decoder works well in practice.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-48291312.1547 | In-medium Eta-Nucleon interactions and Eta nuclear bound states
nucl-th hep-ph nucl-ex
The in-medium Eta-N interaction near and below threshold is constructed from
a free-space chirally-inspired meson-baryon coupled-channel model that captures
the physics of the N(1535) baryon resonance. Nucleon Pauli blocking and hadron
self-energies are accounted for. The resulting energy dependent in-medium
interaction is used in self-consistent dynamical calculations of Eta nuclear
bound states. Narrow states of width about or less than 2 MeV are found across
the periodic table, beginning with A=10, for this in-medium coupled-channel
interaction model. The binding energy of the 1s-Eta state increases with A,
reaching a value of B(1s-Eta) about 15 MeV. The implications of our
self-consistency procedure are discussed with respect to procedures used in
other works.
| arxiv topic:nucl-th hep-ph nucl-ex |
arxiv_dataset-48301312.1647 | Hysteresis behavior of the anisotropic quantum Heisenberg model driven
by periodic magnetic field
cond-mat.stat-mech
Dynamic behavior of a quantum Heisenberg ferromagnet in the presence of a
periodically oscillating magnetic field has been analyzed by means of the
effective field theory with two spin cluster. The dynamic equation of motion
has been constructed with the help of a Glauber type stochastic process and
solved for a simple cubic lattice. After the phase diagrams given, the behavior
of the hysteresis loop area, coercive field and remanent magnetization with the
anisotropy in the exchange interaction has been investigated in detail.
Especially, by comparing of the magnitudes of the hysteresis loop area in the
high anisotropy limit (i.e. Ising model) and low anisotropy limit (i.e.
isotropic Heisenberg model), detailed description of the hysteresis loop area
with the anisotropy in the exchange interaction given. Some interesting
features have been obtained about this behavior as well as in phase diagrams
such as tricritical points.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-48311312.1747 | Image cloning beyond diffraction based on coherent population trapping
in a hot Rubidium vapor
quant-ph physics.optics
Following the recent theoretical predictions given in a paper [PRA 88, 013810
(2013)], we reported on an experimental realization of an image cloning beyond
usual diffraction through coherent population trapping (CPT) effect in a hot
rubidium vapor. In our experiment, an alphabet image was transferred from a
coupling field to a probe field based on the CPT effect. Furthermore, we
demonstrated that the cloned probe field carrying the image transmitted without
usual diffraction. To our best knowledge, there is no any such an experimental
report about images cloning beyond diffraction. We believe this mechanism based
on CPT definitely has important applications in image metrology, image
processing and biological imaging.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-48321312.1847 | Understanding Deep Architectures using a Recursive Convolutional Network
cs.LG
A key challenge in designing convolutional network models is sizing them
appropriately. Many factors are involved in these decisions, including number
of layers, feature maps, kernel sizes, etc. Complicating this further is the
fact that each of these influence not only the numbers and dimensions of the
activation units, but also the total number of parameters. In this paper we
focus on assessing the independent contributions of three of these linked
variables: The numbers of layers, feature maps, and parameters. To accomplish
this, we employ a recursive convolutional network whose weights are tied
between layers; this allows us to vary each of the three factors in a
controlled setting. We find that while increasing the numbers of layers and
parameters each have clear benefit, the number of feature maps (and hence
dimensionality of the representation) appears ancillary, and finds most of its
benefit through the introduction of more weights. Our results (i) empirically
confirm the notion that adding layers alone increases computational power,
within the context of convolutional layers, and (ii) suggest that precise
sizing of convolutional feature map dimensions is itself of little concern;
more attention should be paid to the number of parameters in these layers
instead.
| arxiv topic:cs.LG |
arxiv_dataset-48331312.1947 | Thermal escape from extrasolar giant planets
astro-ph.EP
The detection of hot atomic hydrogen and heavy atoms and ions at high
altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b
imply that these planets have hot and rapidly escaping atmospheres that extend
to several planetary radii. These characteristics, however, cannot be
generalized to all close-in EGPs. The thermal escape mechanism and mass loss
rate from EGPs depend on a complex interplay between photochemistry and
radiative transfer driven by the stellar UV radiation. In this work we explore
how these processes change under different levels of irradiation on giant
planets with different characteristics. We confirm that there are two distinct
regimes of thermal escape from EGPs, and that the transition between these
regimes is relatively sharp. Our results have implications on thermal mass loss
rates from different EGPs that we discuss in the context of currently known
planets and the detectability of their upper atmospheres.
| arxiv topic:astro-ph.EP |
arxiv_dataset-48341312.2047 | Diagnosis of Switching Systems using Hybrid Bond Graph
cs.SY
Hybrid Bond Graph (HBG) is a Bond Graph-based modelling approach which
provides an effective tool not only for dynamic modeling but also for fault
detection and isolation (FDI) of switching systems. Bond graph (BG) has been
proven useful for FDI for continuous systems. In addition, BG provides the
causal relations between systems variables which allow FDI algorithms to be
developed systematically from the graph. There are many methods that exploit
structural relations and functional redundancy in the system model to find
efficient solutions for the residual generation and residual evaluation steps
in FDI of switching systems. This paper describes two different techniques,
quantitative and qualitative, based on common modelling approach that employs
HBG. In quantitative approach, global analytical redundancy relationships
(GARRs) are derived from the HBG model with a specified causality assignment
procedure. GARRs describe the system behaviour at all of its operating modes.
In qualitative approach, functional redundancy can be captured by a Temporal
Causal Graph (TCG), a directed graph that may include temporal information
| arxiv topic:cs.SY |
arxiv_dataset-48351312.2147 | How the presence of a gas giant affects the formation of mean-motion
resonances between two low-mass planets in a locally isothermal gaseous disc
astro-ph.EP
In this paper we investigate the possibility of a migration-induced resonance
locking in systems containing three planets, namely an Earth analog, a
super-Earth and a gas giant. The planets have been listed in order of
increasing orbital periods. All three bodies are embedded in a locally
isothermal gaseous disc and orbit around a solar mass star. We are interested
in answering the following question: Will the low-mass planets form the same
resonant structures with each other in the vicinity of the gas giant as in the
case when the gas giant is absent? When there is no gas giant in the system, it
has been already shown that if the two low-mass planets undergo a convergent
differential migration, they will capture each other in a mean-motion
resonance. For the choices of disc parameters and planet masses made in this
paper, the formation of the 5:4 resonance in the absence of the Jupiter has
been observed. In this work we add a gas giant on the most external orbit of
the system in such a way that its differential migration is convergent with the
low-mass planets. We show that the result of this set-up is the speeding up of
the migration of the super-Earth and, after that, all three planets become
locked in a triple mean-motion resonance. However, this resonance is not
maintained due to the low-mass planet eccentricity excitation, a fact that
leads to close encounters between planets and eventually to the ejection from
the internal orbits of one or both low-mass planets.
| arxiv topic:astro-ph.EP |
arxiv_dataset-48361312.2247 | The spectrum and toughness of regular graphs
math.CO cs.DM
In 1995, Brouwer proved that the toughness of a connected $k$-regular graph
$G$ is at least $k/\lambda-2$, where $\lambda$ is the maximum absolute value of
the non-trivial eigenvalues of $G$. Brouwer conjectured that one can improve
this lower bound to $k/\lambda-1$ and that many graphs (especially graphs
attaining equality in the Hoffman ratio bound for the independence number) have
toughness equal to $k/\lambda$. In this paper, we improve Brouwer's spectral
bound when the toughness is small and we determine the exact value of the
toughness for many strongly regular graphs attaining equality in the Hoffman
ratio bound such as Lattice graphs, Triangular graphs, complements of
Triangular graphs and complements of point-graphs of generalized quadrangles.
For all these graphs with the exception of the Petersen graph, we confirm
Brouwer's intuition by showing that the toughness equals $k/(-\lambda_{min})$,
where $\lambda_{min}$ is the smallest eigenvalue of the adjacency matrix of the
graph.
| arxiv topic:math.CO cs.DM |
arxiv_dataset-48371312.2347 | Fast Bayesian inference for slow-roll inflation
astro-ph.CO gr-qc hep-ph hep-th
We present and discuss a new approach increasing by orders of magnitude the
speed of performing Bayesian inference and parameter estimation within the
framework of slow-roll inflation. The method relies on the determination of an
effective likelihood for inflation which is a function of the primordial
amplitude of the scalar perturbations complemented with the necessary number of
the so-called Hubble flow functions to reach the desired accuracy. Starting
from any cosmological data set, the effective likelihood is obtained by
marginalisation over the standard cosmological parameters, here viewed as
"nuisance" from the early Universe point of view. As being low-dimensional,
basic machine-learning algorithms can be trained to accurately reproduce its
multidimensional shape and then be used as a proxy to perform fast Bayesian
inference on the inflationary models. The robustness and accuracy of the method
are illustrated using the Planck Cosmic Microwave Background (CMB) data to
perform primordial parameter estimation for the large field models of
inflation. In particular, marginalised over all possible reheating history, we
find the power index of the potential to verify p < 2.3 at 95% of confidence.
| arxiv topic:astro-ph.CO gr-qc hep-ph hep-th |
arxiv_dataset-48381312.2447 | Typologies of Computation and Computational Models
cs.GL
We need much better understanding of information processing and computation
as its primary form. Future progress of new computational devices capable of
dealing with problems of big data, internet of things, semantic web, cognitive
robotics and neuroinformatics depends on the adequate models of computation. In
this article we first present the current state of the art through
systematization of existing models and mechanisms, and outline basic structural
framework of computation. We argue that defining computation as information
processing, and given that there is no information without (physical)
representation, the dynamics of information on the fundamental level is
physical/ intrinsic/ natural computation. As a special case, intrinsic
computation is used for designed computation in computing machinery. Intrinsic
natural computation occurs on variety of levels of physical processes,
containing the levels of computation of living organisms (including highly
intelligent animals) as well as designed computational devices. The present
article offers a typology of current models of computation and indicates future
paths for the advancement of the field; both by the development of new
computational models and by learning from nature how to better compute using
different mechanisms of intrinsic computation.
| arxiv topic:cs.GL |
arxiv_dataset-48391312.2547 | Weinberg's Higgs portal confronting recent LUX and LHC results together
with upper limits on B^+ and K^+ decay into invisibles
hep-ph astro-ph.HE
We discuss a number of experimental constraints on Weinberg's Higgs portal
model. In this framework, the standard model (SM) particle spectrum is extended
to include one complex scalar field S and one Dirac fermion \psi. These new
fields are singlets under the SM gauge group and are charged under a global
U(1) symmetry. Breaking of this U(1) symmetry results in a massless Goldstone
boson \alpha and a massive CP-even scalar r, and splits the Dirac fermion into
two new mass-eigenstates \psi_\pm, corresponding to Majorana fermions. The
interest on such a minimal SM extension is twofold. On the one hand, if the
Goldstone bosons are in thermal equilibrium with SM particles until the era of
muon annihilation their contribution to the effective number of neutrino
species can explain the hints from cosmological observations of extra
relativistic degrees of freedom at the epoch of last scattering. On the other
hand, the lightest Majorana fermion \psi_- provides a plausible dark matter
candidate. Mixing of r with the Higgs doublet \phi is characterized by the mass
of hidden scalar m_h and the mixing angle \theta. We constrain this parameter
space using a variety of experimental data, including heavy meson decays with
missing energy, the invisible Higgs width, and direct dark matter searches. We
show that different experimental results compress the allowed parameter space
in complementary ways, covering a large range of \psi_- masses (5 GeV \alt m_-
\alt 100 GeV). Though current results narrow the parameter space significantly
(for the mass range of interest, \theta \alt 10^{-3} to 10^{-4}), there is
still room for discovery (\alpha decoupling at the muon annihilation era
requires \theta \agt 10^{-5} to 10^{-4}). In the near future, measurements from
ATLAS, CMS, LHCb, NA62, XENON1T, LUX, and CDMSlite will probe nearly the full
parameter space.
| arxiv topic:hep-ph astro-ph.HE |
arxiv_dataset-48401312.2647 | Localization of $q-$form fields on $AdS_{p+1}$ branes
hep-th
In this paper, we investigate localization of a free massless $q-$form bulk
field on thin and thick $AdS_{p+1}$ branes with codimension one. It is found
that the zero mode of the $q-$form field with $q>(p+2)/2$ can be localized on
the thin negative tension brane, which is different from the flat brane case
given in [JHEP 10 (2012) 060]. For the thick $AdS_{p+1}$ branes, the $q-$form
field with $q>(p+2)/2$ also has a localized zero mode under some conditions.
Furthermore, we find that there are massive bound KK modes of the $q-$form
field, which are localized on this type $p-$branes.
| arxiv topic:hep-th |
arxiv_dataset-48411312.2747 | Chameleon Fragmentation
hep-ph
A scalar field dark energy candidate could couple to ordinary matter and
photons, enabling its detection in laboratory experiments. Here we study the
quantum properties of the chameleon field, one such dark energy candidate, in
an "afterglow" experiment designed to produce, trap, and detect chameleon
particles. In particular, we investigate the possible fragmentation of a beam
of chameleon particles into multiple particle states due to the highly
non-linear interaction terms in the chameleon Lagrangian. Fragmentation could
weaken the constraints of an afterglow experiment by reducing the energy of the
regenerated photons, but this energy reduction also provides a unique signature
which could be detected by a properly-designed experiment. We show that
constraints from the CHASE experiment are essentially unaffected by
fragmentation for $\phi^4$ and $1/\phi$ potentials, but are weakened for
steeper potentials, and we discuss possible future afterglow experiments.
| arxiv topic:hep-ph |
arxiv_dataset-48421312.2847 | Balanced double-loop mesoscopic interferometer based on Josephson
proximity nanojunctions
cond-mat.mes-hall cond-mat.supr-con
We report on the fabrication and characterization of a two-terminal
mesoscopic interferometer based on three V/Cu/V Josephson junctions having
nanoscale cross-section. The junctions have been arranged in a double-ring
geometry realized by metallic thin film deposition through a suspended mask
defined by electron beam lithography. Although a significant amount of
asymmetry between the critical current of each junction is observed we show
that the interferometer is able to suppress the supercurrent to a level lower
than 6 parts per thousand, being here limited by measurement resolution. The
present nano-device is suitable for low-temperature magnetometric and
gradiometric measurements over the micrometric scale.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-48431312.2947 | The MICE Grand Challenge Lightcone Simulation III: Galaxy lensing mocks
from all-sky lensing maps
astro-ph.CO
In paper I of this series (Fosalba et al. 2013), we presented a new N-body
lightcone simulation from the MICE collaboration, the MICE Grand Challenge
(MICE-GC), containing about 70 billion dark-matter particles in a (3 Gpc)^3
comoving volume, from which we built halo and galaxy catalogues using a Halo
Occupation Distribution and Halo Abundance Matching technique, as presented in
the companion Paper II (Crocce et al. 2013). Given its large volume and fine
mass resolution, the MICE-GC simulation also allows an accurate modeling of the
lensing observables from upcoming wide and deep galaxy surveys. In the last
paper of this series (Paper III), we describe the construction of all-sky
lensing maps, following the "Onion Universe" approach (Fosalba et al. 2008),
and discuss their properties in the lightcone up to z=1.4 with sub-arcmin
spatial resolution. By comparing the convergence power spectrum in the MICE-GC
to lower mass-resolution (i.e., particle mass ~ 10^11 Msun) simulations, we
find that resolution effects are at the 5 % level for multipoles l ~ 10^3 and
20 % for l ~ 10^4. Resolution effects have a much lower impact on our
simulation, as shown by comparing the MICE-GC to recent numerical fits by
Takahashi et al 2012. We use the all-sky lensing maps to model galaxy lensing
properties, such as the convergence, shear, and lensed magnitudes and
positions, and validate them thoroughly using galaxy shear auto and
cross-correlations in harmonic and configuration space. Our results show that
the galaxy lensing mocks here presented can be used to accurately model lensing
observables down to arcminute scales.
| arxiv topic:astro-ph.CO |
arxiv_dataset-48441312.3047 | Measurement of pretzelosity asymmetry of charged pion production in
Semi-Inclusive Deep Inelastic Scattering on a polarized $^3$He target
nucl-ex
An experiment to measure single-spin asymmetries in semi-inclusive production
of charged pions in deep-inelastic scattering on a transversely polarized
$^3$He target was performed at Jefferson Lab in the kinematic region of
$0.16<x<0.35$ and $1.4<Q^2<2.7$ ${\rm GeV^2}$. The pretzelosity asymmetries on
$^3$He, which can be expressed as the convolution of the $h^\perp_{1T}$
transverse momentum dependent distribution functions and the Collins
fragmentation functions in the leading order, were measured for the first time.
Using the effective polarization approximation, we extracted the corresponding
neutron asymmetries from the measured $^3$He asymmetries and cross-section
ratios between the proton and $^3$He. Our results show that for both
$\pi^{\pm}$ on $^3$He and on the neutron the pretzelosity asymmetries are
consistent with zero within experimental uncertainties.
| arxiv topic:nucl-ex |
arxiv_dataset-48451312.3147 | Selection rules for the Wheeler-DeWitt equation in quantum cosmology
gr-qc hep-th
Selection of physically meaningful solutions of the Wheeler-DeWitt equation
for the wavefunction in quantum cosmology, can be attained by a reduction of
the theory to the sector of true physical degrees of freedom and their
canonical quantization. The resulting physical wavefunction unitarily evolving
in the time variable introduced within this reduction can then be raised to the
level of the cosmological wavefunction in superspace of 3-metrics. We apply
this technique in several simple minisuperspace models and discuss both at
classical and quantum level physical reduction in {\em extrinsic} time -- the
time variable determined in terms of extrinsic curvature. Only this extrinsic
time gauge can be consistently used in vicinity of turning points and bounces
where the scale factor reaches extremum. Since the 3-metric scale factor is
canonically dual to extrinsic time variable, the transition from the physical
wavefunction to the wavefunction in superspace represents a kind of the
generalized Fourier transform. This transformation selects square integrable
solutions of the Wheeler-DeWitt equation, which guarantee Hermiticity of
canonical operators of the Dirac quantization scheme. Semiclassically this
means that wavefunctions are represented by oscillating waves in classically
allowed domains of superspace and exponentially fall off in classically
forbidden (underbarrier) regions. This is explicitly demonstrated in flat FRW
model with a scalar field having a constant negative potential and for the case
of phantom scalar field with a positive potential. The FRW model of a scalar
field with a vanishing potential does not lead to selection rules for solutions
of the Wheeler-DeWitt equation, but this does not violate Hermiticity
properties, because all these solutions are anyway of plane wave type and
describe cosmological dynamics without turning points and bounces.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-48461312.3247 | Emergent quantum mechanics of finances
q-fin.ST
This paper is an attempt at understanding the quantum-like dynamics of
financial markets in terms of non-differentiable price-time continuum having
fractal properties. The main steps of this development are the statistical
scaling, the non-differentiability hypothesis, and the equations of motion
entailed by this hypothesis. From perspective of the proposed theory the
dynamics of S&P500 index are analyzed.
| arxiv topic:q-fin.ST |
arxiv_dataset-48471312.3347 | A Distributed Deadlock Free Quorum Based Algorithm for Mutual Exclusion
cs.DC
Quorum based mutual exclusion algorithms enjoy many advantages such as low
message complexity and high failure resiliency. The use of quorums is a well
known approach to achieving mutual exclusion in distributed environments.
Several distributed based quorum mutual exclusion was presented.
| arxiv topic:cs.DC |
arxiv_dataset-48481312.3447 | Evolutionary game theory and the tower of Babel of cooperation:
Altruism, free-riding, parasitism and the structure of the interactions in a
world with finite resources
q-bio.PE physics.bio-ph physics.soc-ph
The study of the evolution of cooperative behaviours --which provide benefits
to others-- and altruism --which provides benefits to others at a cost to
oneself-- has been on the core of the evolutionary game theoretical framework
since its foundation. The fast development of the theory during the last years
has improved our knowledge of the issue, but carried attached a diversification
of concepts which affected communication between scientists. Furthermore, the
main root of conflict in the struggle for life identified by Darwin, the
limited amount of resources present in any ecosystem, which is assumed to keep
a constant population size in most game theoretical studies, has only recently
been taken into account as explicitly influencing the evolutionary process.
This review concerns about both issues, the conceptual diversification during
the last years and the new results of the resource dependent models. In
extenso: After a historical introduction, a review of the most important
concepts is carried out. Then it is shown that pairwise interactions and
additive fitness determine prisoner's dilemmas (PDs) or harmony games, that two
altruists interacting together may determine a PD, and that the interaction
environment of the most cooperative and less selfish individual in any
population is always a PD. After that, it is shown that in addition to
altruists versus free-riders, the combination of free-riders and parasites
determines a fundamentally different PD. Computer simulations are then carried
out to show that random exploration of parasitism, free-riding and altruism
enables coexistence of the three strategies without the need of reciprocating,
punishing or rewarding strategies. To finish, the problem of the limitation of
resources is reviewed, showing that...
| arxiv topic:q-bio.PE physics.bio-ph physics.soc-ph |
arxiv_dataset-48491312.3547 | Nonmonotonous pressure as a function of the density in a fluid without
attractive forces
cond-mat.soft
A simple result for the pressure of a hard sphere fluid that was developed
many years ago by Rennert is extended in a straightforward manner by adding the
terms that are of the same form as the Rennert's formula. The resulting
expression is moderately accurate but its accuracy does not necessarily improve
as additional terms are included. This expression has the interesting
consequence that the pressure can have a maximum, as the density increases,
which is consistent with the freezing of hard spheres. This occurs solely as a
consequence of repulsive interactions. Only the Born-Green-Yvon and Kirkwood
theories show such a behavior for hard spheres and they require a numerical
solution of an integral equation. The procedure outlined here is ad hoc but is,
perhaps, useful just as the popular Carnahan-Starling equation for the hard
sphere pressure is also ad hoc but useful.
| arxiv topic:cond-mat.soft |
arxiv_dataset-48501312.3647 | Coarse-grained analysis of stochastically simulated cell populations
with a positive feedback genetic network architecture
q-bio.MN q-bio.PE
Among the different computational approaches modelling the dynamics of
isogenic cell populations, discrete stochastic models can describe with
sufficient accuracy the evolution of small size populations. However, for a
systematic and efficient study of their long-time behaviour over a wide range
of parameter values, the performance of solely direct temporal simulations
requires significantly high computational time. In addition, when the dynamics
of the cell populations exhibit non-trivial bistable behaviour, such an
analysis becomes a prohibitive task, since a large ensemble of initial states
need to be tested for the quest of possibly co-existing steady state solutions.
In this work, we study cell populations which carry the {\it lac} operon
network exhibiting solution multiplicity over a wide range of extracellular
conditions (inducer concentration). By adopting ideas from the so-called
``equation-free'' methodology, we perform systems-level analysis, which
includes numerical tasks such as the computation of {\it coarse} steady state
solutions, {\it coarse} bifurcation analysis, as well as {\it coarse} stability
analysis. Dynamically stable and unstable macroscopic (population level) steady
state solutions are computed by means of bifurcation analysis utilising short
bursts of fine-scale simulations, and the range of bistability is determined
for different sizes of cell populations. The results are compared with the
deterministic cell population balance (CPB) model, which is valid for large
populations, and we demonstrate the increased effect of stochasticity in small
size populations with asymmetric partitioning mechanisms.
| arxiv topic:q-bio.MN q-bio.PE |
arxiv_dataset-48511312.3747 | Convergence rates of the spectral distributions of large random
quaternion self-dual Hermitian matrices
math.PR
In this paper, convergence rates of the spectral distributions of quaternion
self-dual Hermitian matrices are investigated. We show that under conditions of
finite 6th moments, the expected spectral distribution of a large quaternion
self-dual Hermitian matrix converges to the semicircular law in a rate of
$O(n^{-1/2})$ and the spectral distribution itself converges to the
semicircular law in rates $O_p(n^{-2/5})$ and $O_{a.s.}(n^{-2/5+\eta})$. Those
results include GSE as a special case.
| arxiv topic:math.PR |
arxiv_dataset-48521312.3847 | Cloud Service-Aware Location Update in Mobile Cloud Computing
cs.NI
Mobile devices are becoming the primary platforms for many users who always
roam around when accessing the cloud computing services. From this, the cloud
computing is integrated into the mobile environment by introducing a new
paradigm, mobile cloud computing. In the context of mobile computing, the
battery life of mobile device is limited, and it is important to balance the
mobility performance and energy consumption. Fortunately, cloud services
provide both opportunities and challenges for mobility management. Taking the
activities of cloud services accessing into consideration, we propose a
service-aware location update mechanism, which can detect the presence and
location of the mobile device without traditional periodic registration update.
Analytic model and simulation are developed to investigate the new mechanism.
The results demonstrate that the service-aware location update management can
reduce the location update times and handoff signaling, which can efficiently
save power consumption for mobile devices.
| arxiv topic:cs.NI |
arxiv_dataset-48531312.3947 | Soft X-ray Excess in the Coma Cluster from a Cosmic Axion Background
astro-ph.HE hep-ph
We show that the soft X-ray excess in the Coma cluster can be explained by a
cosmic background of relativistic axions converting into photons in the cluster
magnetic field. We provide a detailed self-contained review of the cluster soft
X-ray excess, the proposed astrophysical explanations and the problems they
face, and explain how a 0.1-1 keV axion background naturally arises at
reheating in many string theory models of the early universe. We study the
morphology of the soft excess by numerically propagating axions through
stochastic, multi-scale magnetic field models that are consistent with
observations of Faraday rotation measures from Coma. By comparing to ROSAT
observations of the 0.2-0.4 keV soft excess, we find that the overall excess
luminosity is easily reproduced for $g_{a\gamma\gamma} \sim 2 \times 10^{-13}$
GeV$^{-1}$. The resulting morphology is highly sensitive to the magnetic field
power spectrum. For Gaussian magnetic field models, the observed soft excess
morphology prefers magnetic field spectra with most power in coherence lengths
on ${\cal O}(3 {\rm ~kpc})$ scales over those with most power on ${\cal O}(12
{\rm ~kpc})$ scales. Within this scenario, we bound the mean energy of the
axion background to $50\, {\rm eV}\lesssim \langle E_a \rangle \lesssim 250\,
{\rm eV}$, the axion mass to $m_a \lesssim 10^{-12}\,\hbox{eV}$, and derive a
lower bound on the axion-photon coupling $g_{a\gamma\gamma} \gtrsim
\sqrt{0.5/\Delta N_{\rm eff}}\, 1.4 \times 10^{-13}$ GeV$^{-1}$.
| arxiv topic:astro-ph.HE hep-ph |
arxiv_dataset-48541312.4047 | Tight-Binding Study of Boron Structures
cond-mat.mtrl-sci
We have performed Linearized Augmented Plane Wave (LAPW) calculations for
five crystal structures (alpha, dhcp, sc, fcc, bcc) of Boron which we then
fitted to a non-orthogonal tight-binding model following the Naval Research
Laboratory Tight-Binding (NRL-TB) method. The predictions of the NRL-TB
approach for complicated Boron structures such as R105 (or
\b{eta}-rhombohedral) and T190 are in agreement with recent first-principles
calculations. Fully utilizing the computational speed of the NRL-TB method we
calculated the energetic differences of various structures including those
containing vacancies using supercells with up to 5000 atoms.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-48551312.4147 | The Alpha Problem & Line Count Configurations
math.AC
Motivated by the work of Chudnovsky and the Eisenbud-Mazur Conjecture on
evolutions, Harbourne and Huneke give a series of conjectures that relate
symbolic and regular powers of ideals of fat points in $\mathbb P^n$. The
conjectures involve both containment statements and bounds for the initial
degree in which there is a non-zero form in an ideal. Working with initial
degrees, we verify two of these conjectures for special line count
configurations in projective 2-space over an algebraically closed field of
characteristic 0.
| arxiv topic:math.AC |
arxiv_dataset-48561312.4247 | Operator analogues of Mahler's measure
math.FA math.NT
Motivated by a geometric meaning of Mahler's measure, we introduce two
operator analogues of Mahler's measure. This leads to some interesting
equalities and inequalities between the two operator-theoretic Mahler measures
and the classical Mahler measure. In order to apply these results to the
operator version of Lehmer's problem, we introduce and study an important class
of operators, the so-called subharmonic operators. It is shown that the
operator version of Lehmer's problem fails under some mild condition.
| arxiv topic:math.FA math.NT |
arxiv_dataset-48571312.4347 | Black hole hair in Lovelock gravity
gr-qc hep-th
We present a method to analyse black hole hair in the spherical symmetric
sector of the Lovelock theory in arbitrary dimensions that is an alternative to
solving the equations of motion in their complete form. We explicitly show that
the method matches with the known black hole solutions for the vacuum and
electro-vacuum spacetimes in Lovelock gravity theories. We further apply the
method to the case of minimally coupled non-self-interacting massless scalar
field and prove that there is no (non-self-interacting) massless scalar hair
for the spherically symmetric Lovelock black holes.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-48581312.4447 | Falsifying High-Scale Leptogenesis at the LHC
hep-ph hep-ex
Measuring a non-zero value for the cross section of any lepton number
violating (LNV) process would put a strong lower limit on the washout factor
for the effective lepton number density in the early universe at times close to
the electroweak phase transition and thus would lead to important constraints
on any high-scale model for the generation of the observed baryon asymmetry
based on LNV. In particular, for leptogenesis models with masses of the
right-handed neutrinos heavier than the mass scale observed at the LHC, the
implied large washout factors would lead to a violation of the
out-of-equilibrium condition and exponentially suppress the net lepton number
produced in such leptogenesis models. We thus demonstrate that the observation
of LNV processes at the LHC results in the falsification of high-scale
leptogenesis models. However, no conclusions about the viability of
leptogenesis models can be drawn from the non-observation of LNV processes.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-48591312.4547 | Prompt emission of GRB 121217A from gamma-rays to the NIR
astro-ph.HE
The mechanism that causes the prompt-emission episode of gamma-ray bursts
(GRBs) is still widely debated despite there being thousands of prompt
detections. The favoured internal shock model relates this emission to
synchrotron radiation. However, it does not always explain the spectral indices
of the shape of the spectrum, often fit with empirical functions.
Multi-wavelength observations are therefore required to help investigate the
possible underlying mechanisms that causes the prompt emission. We present GRB
121217A, for which we were able to observe its near-infrared (NIR) emission
during a secondary prompt-emission episode with the Gamma-Ray Burst Optical
Near-infrared Detector (GROND) in combination with the Swift and Fermi
satellites, covering an energy range of 0.001 keV to 100 keV. We determine a
photometric redshift of z=3.1+/-0.1 with a line-of-sight extinction of A_V~0
mag, utilising the optical/NIR SED. From the afterglow, we determine a bulk
Lorentz factor of Gamma~250 and an emission radius of R<10^18 cm. The
prompt-emission broadband spectral energy distribution is well fit with a
broken power law with b1=-0.3+/-0.1, b2=0.6+/-0.1 that has a break at
E=6.6+/-0.9 keV, which can be interpreted as the maximum injection frequency.
Self-absorption by the electron population below energies of E_a<6 keV suggest
a magnetic field strength of B~10^5 G. However, all the best fit models
underpredict the flux observed in the NIR wavelengths, which also only
rebrightens by a factor of ~2 during the second prompt emission episode, in
stark contrast to the X-ray emission, which rebrightens by a factor of ~100,
suggesting an afterglow component is dominating the emission. We present GRB
121217A one of the few GRBs for which there are multi-wavelength observations
of the prompt-emission period and show that it can be understood with a
synchrotron radiation model.
| arxiv topic:astro-ph.HE |
arxiv_dataset-48601312.4647 | High-fidelity adiabatic inversion of a $^{31}\mathrm{P}$ electron spin
qubit in natural silicon
quant-ph cond-mat.mes-hall
The main limitation to the high-fidelity quantum control of spins in
semiconductors is the presence of strongly fluctuating fields arising from the
nuclear spin bath of the host material. We demonstrate here a substantial
improvement in single-qubit gate fidelities for an electron spin qubit bound to
a $^{31}$P atom in natural silicon, by applying adiabatic inversion instead of
narrow-band pulses. We achieve an inversion fidelity of 97%, and we observe
signatures in the spin resonance spectra and the spin coherence time that are
consistent with the presence of an additional exchange-coupled donor. This work
highlights the effectiveness of adiabatic inversion techniques for spin control
in fluctuating environments.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-48611312.4747 | Discovery of a large number of candidate proto-clusters traced by ~15
Mpc-scale galaxy overdensities in COSMOS
astro-ph.CO
To demonstrate the feasibility of studying the epoch of massive galaxy
cluster formation in a more systematic manner using current and future galaxy
surveys, we report the discovery of a large sample of proto-cluster candidates
in the 1.62 deg^2 COSMOS/UltraVISTA field traced by optical/IR selected
galaxies using photometric redshifts. By comparing properly smoothed 3D galaxy
density maps of the observations and a set of matched simulations incorporating
the dominant observational effects (galaxy selection and photometric redshift
uncertainties), we first confirm that the observed ~15 comoving Mpc scale
galaxy clustering is consistent with LCDM models. Using further the relation
between high-z overdensity and the present day cluster mass calibrated in these
matched simulations, we found 36 candidate structures at 1.6<z<3.1, showing
overdensities consistent with the progenitors of M_z=0 ~10^15 M_sun clusters.
Taking into account the significant upward scattering of lower mass structures,
the probabilities for the candidates to have at least M_z=0 ~10^14 M_sun are
~70%. For each structure, about 15%-40% of photometric galaxy candidates are
expected to be true proto-cluster members that will merge into a cluster-scale
halo by z=0. With solely photometric redshifts, we successfully rediscover two
spectroscopically confirmed structures in this field, suggesting that our
algorithm is robust. This work generates a large sample of uniformly-selected
proto-cluster candidates, providing rich targets for spectroscopic follow-up
and subsequent studies of cluster formation. Meanwhile, it demonstrates the
potential for probing early cluster formation with upcoming redshift surveys
such as the Hobby-Eberly Telescope Dark Energy Experiment and the Subaru Prime
Focus Spectrograph survey.
| arxiv topic:astro-ph.CO |
arxiv_dataset-48621312.4847 | Low energy magnetic excitations in the spin-orbital Mott insulator
Sr$_2$IrO$_4$
cond-mat.str-el
We report a high-field electron spin resonance study in the sub-THz frequency
domain of a single crystal of Sr$_2$IrO$_4$ that has been recently proposed as
a prototypical spin-orbital Mott insulator. In the antiferromagnetically (AFM)
ordered state with noncollinear spin structure that occurs in this material at
$T_{\rm N} \approx 240$ K we observe both the "low" frequency mode due to the
precession of weak ferromagnetic moments arising from a spin canting, and the
"high" frequency modes due to the precession of the AFM sublattices.
Surprisingly, the energy gap for the AFM excitations appears to be very small,
amounting to 0.83 meV only. This suggests a rather isotropic Heisenberg
dynamics of interacting Ir$^{4+}$ effective spins despite the spin-orbital
entanglement in the ground state.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-48631312.4947 | Tight bonds between sterile neutrinos and dark matter
hep-ph astro-ph.CO
Despite the astonishing success of standard $\Lambda$CDM cosmology, there is
mounting evidence for a tension with observations at small and intermediate
scales. We introduce a simple model where both cold dark matter (DM) and
sterile neutrinos are charged under a new $U(1)_X$ gauge interaction. The
resulting DM self-interactions resolve the tension with the observed abundances
and internal density structures of dwarf galaxies. At the ame time, the sterile
neutrinos can account for both the small hot DM component favored by
cosmological observations and the neutrino anomalies found in short-baseline
experiments.
| arxiv topic:hep-ph astro-ph.CO |
arxiv_dataset-48641312.5047 | Stable Camera Motion Estimation Using Convex Programming
cs.CV
We study the inverse problem of estimating n locations $t_1, ..., t_n$ (up to
global scale, translation and negation) in $R^d$ from noisy measurements of a
subset of the (unsigned) pairwise lines that connect them, that is, from noisy
measurements of $\pm (t_i - t_j)/\|t_i - t_j\|$ for some pairs (i,j) (where the
signs are unknown). This problem is at the core of the structure from motion
(SfM) problem in computer vision, where the $t_i$'s represent camera locations
in $R^3$. The noiseless version of the problem, with exact line measurements,
has been considered previously under the general title of parallel rigidity
theory, mainly in order to characterize the conditions for unique realization
of locations. For noisy pairwise line measurements, current methods tend to
produce spurious solutions that are clustered around a few locations. This
sensitivity of the location estimates is a well-known problem in SfM,
especially for large, irregular collections of images.
In this paper we introduce a semidefinite programming (SDP) formulation,
specially tailored to overcome the clustering phenomenon. We further identify
the implications of parallel rigidity theory for the location estimation
problem to be well-posed, and prove exact (in the noiseless case) and stable
location recovery results. We also formulate an alternating direction method to
solve the resulting semidefinite program, and provide a distributed version of
our formulation for large numbers of locations. Specifically for the camera
location estimation problem, we formulate a pairwise line estimation method
based on robust camera orientation and subspace estimation. Lastly, we
demonstrate the utility of our algorithm through experiments on real images.
| arxiv topic:cs.CV |
arxiv_dataset-48651312.5147 | Collective-field-corrected strong field approximation for
laser-irradiated metal clusters
physics.atom-ph physics.atm-clus quant-ph
The strong field approximation (SFA) formulated in terms of so-called
"quantum orbits" led to much insight into intense-laser driven ionization
dynamics. In plain SFA, the emitted electron is treated as a free electron in
the laser field alone. However, with improving experimental techniques and more
advanced numerical simulations it becomes more and more obvious that the plain
SFA misses interesting effects even on a qualitative level. Examples are
holographic side lobes, the low-energy structure, radial patterns in
photoelectron spectra at low kinetic energies, and strongly rotated angular
distributions. For this reason increasing effort has been recently devoted to
Coulomb corrections of the SFA. In the current paper, we follow a similar line
but consider ionization of metal clusters. It is known that photoelectrons from
clusters can be much more energetic than those emitted from atoms or small
molecules, especially if the Mie resonance of the expanding cluster is evoked.
We develop a SFA that takes the collective field inside the cluster via the
simple rigid-sphere model into account. Our approach is based on
field-corrected quantum orbits so that the acceleration process (or any other
spectral feature of interest) can be investigated in detail.
| arxiv topic:physics.atom-ph physics.atm-clus quant-ph |
arxiv_dataset-48661312.5247 | Mode coupling mechanism for late-time Kerr tails
gr-qc
We consider the decay rate for scalar fields in Kerr spacetime. We consider
pure initial (azimuthal) multipoles $\ell'$ with respect to the class which
includes Boyer-Lindquist coordinates, and focus attention on the decay rate of
the multipole $\ell$. We use an iterative method proposed by Gleiser, Price,
and Pullin, and identify the mode coupling mechanism through the iterations in
powers of the square of the Kerr black hole's specific angular momentum that
gives rise to a decay rate formula recently proposed by Zengino\u{g}lu, Khanna,
and Burko. Modes $\ell$ may be excited through different channels, each leading
to its own decay rate. The asymptotic decay rate of the mode $\ell$ is the
slowest of the decay rate of the various channels. In some cases, more than one
channel leads to the same decay rate, and then the amplitude of the mode is the
sum of the amplitudes of the partial fields generated by the individual
channels. We also show that one may identify the asymptotically-dominant
channel of mode excitations, and obtain approximate results for the mode of
interest by studying the dominant channel. The results of the dominant channel
approximation approach the full-mode results at late times, and their
difference approaches zero quadratically in inverse time.
| arxiv topic:gr-qc |
arxiv_dataset-48671312.5347 | Cosmic star formation probed via parametric stack-fitting of known
sources to radio imaging
astro-ph.CO
The promise of multi-wavelength astronomy has been tempered by the large
disparity in sensitivity and resolution between different wavelength regimes.
Here we present a statistical approach which attempts to overcome this by
fitting parametric models directly to image data. Specifically, we fit a model
for the radio luminosity function (LF) of star-forming galaxies to pixel
intensity distributions at 1.4 GHz coincident with near-IR selected sources in
COSMOS. Taking a mass-limited sample in redshift bins across the range $0<z<4$
we are able to fit the radio LF with ~0.2 dex precision in the key parameters
(e.g. Phi*,L*). Good agreement is seen between our results and those using
standard methods at radio and other wavelengths. Integrating our luminosity
functions to get the star formation rate density we find that galaxies with a
stellar mass greater than $10^{9.5}\,$M$_{\odot}$ contribute at least 50 per
cent of cosmic star formation at since $z=4$. The scalability of our approach
is empirically estimated, with the precision in LF parameter estimates found to
scale with the number of sources in the stack as $\sqrt{N}$. This type of
approach will be invaluable in the multi-wavelength analysis of upcoming
surveys with the SKA pathfinder facilities; LOFAR, ASKAP and MeerKAT.
| arxiv topic:astro-ph.CO |
arxiv_dataset-48681312.5447 | Estimations of local thermal impact on living organisms irradiated by
non-thermal microwaves
physics.bio-ph cond-mat.mes-hall
Pennes' differential equation for bioheat transfer and the heat transfer
equation are solved for the temperature distribution in a living tissue with
spherical inclusions, irradiated by microwave power. It is shown that relative
temperature excess in a small inclusion in the tissue in some cases is
inversely proportional to its radius and does not depend on the applied power.
In pulsing RF fields the effect is amplified proportionally to the ratio of the
pulse period to the pulse duration. The local temperature rise significantly
outpaces the averaged one and therefore the Watt to Weight SAR limits may be
insufficient to estimate the safety of RF radiation and the conventional
division of the biological effects of electromagnetic fields on the thermal and
non-thermal needs to be revised.
| arxiv topic:physics.bio-ph cond-mat.mes-hall |
arxiv_dataset-48691312.5547 | Three Metrics for Measuring User Engagement with Online Media and a
YouTube Case Study
cs.HC cs.MM
This technical report discusses three metrics of user engagement with online
media. They are Commenting frequency, Voting frequency, and Voting balance.
These relative figures can be derived from established, basic statistics
available for many services, prominently YouTube. The paper includes case a
study of popular YouTube videos to illustrate the characteristics and
usefulness of the measures. The study documents the range of observed values
and their relationships. The empirical sample shows the three measures to be
only moderately correlated with the original statistics despite the common
numerators and denominators. The paper concludes by discussing future
applications and the needs of the quantification of user interaction with new
media services.
| arxiv topic:cs.HC cs.MM |
arxiv_dataset-48701312.5647 | On the first continuous $L^2$-cohomology of free group factors
math.OA
We prove that the first continuous $L^2$-cohomology of free group factors
vanishes. This answers a question by Andreas Thom regarding continuity
properties of free difference quotients and shows that one can not distinguish
free group factors by means of first continuous $L^2$-Betti number.
| arxiv topic:math.OA |
arxiv_dataset-48711312.5747 | Cyclotron dynamics of interacting bosons in artificial magnetic fields
cond-mat.quant-gas quant-ph
We study theoretically quantum dynamics of interacting bosons in artificial
magnetic fields as engineered in recent ultracold atomic experiments, where
quantum cyclotron orbital motion has been observed. With exact numerical
simulations and perturbative analyses, we find that interactions induce damping
in the cyclotron motion. The damping time is found to be dependent on
interaction and tunneling strengths monotonically, while its dependence on
magnetic flux is non-monotonic. Sufficiently strong interactions would render
bosons dynamically localized inhibiting the cyclotron motion. The damping
predicted by us can be construed as an interaction-induced quantum decoherence
of the cyclotron motion.
| arxiv topic:cond-mat.quant-gas quant-ph |
arxiv_dataset-48721312.5847 | Deep learning for neuroimaging: a validation study
cs.NE cs.LG stat.ML
Deep learning methods have recently made notable advances in the tasks of
classification and representation learning. These tasks are important for brain
imaging and neuroscience discovery, making the methods attractive for porting
to a neuroimager's toolbox. Success of these methods is, in part, explained by
the flexibility of deep learning models. However, this flexibility makes the
process of porting to new areas a difficult parameter optimization problem. In
this work we demonstrate our results (and feasible parameter ranges) in
application of deep learning methods to structural and functional brain imaging
data. We also describe a novel constraint-based approach to visualizing high
dimensional data. We use it to analyze the effect of parameter choices on data
transformations. Our results show that deep learning methods are able to learn
physiologically important representations and detect latent relations in
neuroimaging data.
| arxiv topic:cs.NE cs.LG stat.ML |
arxiv_dataset-48731312.5947 | Spectral asymptotics of a broken delta interaction
math.AP math-ph math.MP math.SP
This paper is concerned with the spectral analysis of a Hamiltonian with a
$\delta$-interaction supported along a broken line with angle $\theta$. The
bound states with energy slightly below the threshold of the essential spectrum
are estimated in the semiclassical regime $\theta\to 0$.
| arxiv topic:math.AP math-ph math.MP math.SP |
arxiv_dataset-48741312.6047 | Mixed Finite Element Analysis of Lognormal Diffusion and Multilevel
Monte Carlo Methods
math.NA
This work is motivated by the need to develop efficient tools for uncertainty
quantification in subsurface flows associated with radioactive waste disposal
studies. We consider single phase flow problems in random porous media
described by correlated lognormal distributions. We are interested in the error
introduced by a finite element discretisation of these problems. In contrast to
several recent works on the analysis of standard nodal finite element
discretisations, we consider here mass-conservative lowest order Raviart-Thomas
mixed finite elements. This is very important since local mass conservation is
highly desirable in realistic groundwater flow problems. Due to the limited
spatial regularity and the lack of uniform ellipticity and boundedness of the
operator the analysis is non-trivial in the presence of lognormal random
fields. We establish finite element error bounds for Darcy velocity and
pressure, as well as for a more accurate recovered pressure approximation. We
then apply the error bounds to prove convergence of the multilevel Monte Carlo
algorithm for estimating statistics of these quantities. Moreover, we prove
convergence for a class of bounded, linear functionals of the Darcy velocity.
An important special case is the approximation of the effective permeability in
a 2D flow cell. We perform numerical experiments to confirm the convergence
results.
| arxiv topic:math.NA |
arxiv_dataset-48751312.6147 | Existence and Uniqueness of Mild Solutions to Neutral SFDE driven by a
Fractional Brownian Motion with non-Lipschitz Coefficients
math.DS
The article presents results on existence and uniqueness of mild solutions to
a class of non linear neutral stochastic functional differential equations
(NSFDEs) driven by Fractional Brownian motion in a Hilbert space with
non-Lipschitzian coefficients. The results are obtained by using the method of
Picard approximation.
| arxiv topic:math.DS |
arxiv_dataset-48761312.6247 | Lagrangian for Frenkel electron and position's non-commutativity due to
spin
hep-th math-ph math.MP quant-ph
We construct relativistic-invariant spinning-particle Lagrangian without
auxiliary variables. Spin is considered as a composed quantity constructed on
the base of non-Grassmann vector-like variable. The variational problem
guarantees both fixed value of spin and Frenkel condition on spin-tensor.
Taking into account the Frenkel condition, we obtain, inevitably, relativistic
corrections to the algebra of position variables: their classical brackets
became noncommutative, with the "parameter of non-commutativity" proportional
to the spin-tensor. This leads to a number of interesting consequences in
quantum theory. We construct the relativistic quantum mechanics in canonical
formalism (in physical-time parametrization) and in covariant formalism (in
arbitrary parametrization). We show how state-vectors and operators of
covariant formulation can be used to compute mean values of physical operators
of position and spin. This proves relativistic covariance of canonical
formalism. Various candidates for position and spin operators of an electron
acquire clear meaning and interpretation in the Lagrangian model of Frenkel
electron. We also establish the relation between Frenkel electron and
positive-energy sector of Dirac equation, this allowed us to turn to the
long-standing problem on spin and position operators of Dirac theory. Contrary
to widely assumed opinion, our results argue in favor of Pryce's (d)-type
operators. This implies that effects of non-commutativity could be presented at
the Compton wave length, in contrast to conventional expectations at the Planck
length. At last, we present the manifestly covariant form of spin and position
operators of Dirac equation.
| arxiv topic:hep-th math-ph math.MP quant-ph |
arxiv_dataset-48771312.6347 | 13C(alpha,n)16O background in a liquid scintillator based neutrino
experiment
physics.ins-det nucl-ex
Alpha from natural radioactivity may interact with a nucleus and emit a
neutron. The reaction introduces background to the liquid scintillator (LS)
based neutrino experiments. In the LS detector, alpha comes from 238U, 232Th
and 210Po decay chains. For Gadolinium-doped LS (Gd-LS) detector, alpha also
comes from 227Ac. The nucleus 13C is a natural component of Carbon which is
rich in the LS. The background rate and spectrum should be subtracted carefully
from the neutrino candidates. This paper describes the calculation of neutron
yield and spectrum with uncertainty estimated. The results are relevant for
many existing neutrino experiments and future LS or Gd-LS based experiments.
| arxiv topic:physics.ins-det nucl-ex |
arxiv_dataset-48781312.6447 | Incremental Network Design with Maximum Flows
cs.DM cs.DS
We study an incremental network design problem, where in each time period of
the planning horizon an arc can be added to the network and a maximum flow
problem is solved, and where the objective is to maximize the cumulative flow
over the entire planning horizon. After presenting two mixed integer
programming (MIP) formulations for this NP-complete problem, we describe
several heuristics and prove performance bounds for some special cases. In a
series of computational experiments, we compare the performance of the MIP
formulations as well as the heuristics.
| arxiv topic:cs.DM cs.DS |
arxiv_dataset-48791312.6547 | Polynomial-Time Amoeba Neighborhood Membership and Faster Localized
Solving
math.AG cs.CC math.OC
We derive efficient algorithms for coarse approximation of algebraic
hypersurfaces, useful for estimating the distance between an input polynomial
zero set and a given query point. Our methods work best on sparse polynomials
of high degree (in any number of variables) but are nevertheless completely
general. The underlying ideas, which we take the time to describe in an
elementary way, come from tropical geometry. We thus reduce a hard algebraic
problem to high-precision linear optimization, proving new upper and lower
complexity estimates along the way.
| arxiv topic:math.AG cs.CC math.OC |
arxiv_dataset-48801312.6647 | Misiurewicz parameters for Weierstrass elliptic functions based on
triangle and square lattices
math.DS
For two families of Weierstrass elliptic functions - based on triangular or
square lattices - we prove that the set of Misiurewicz parameters has the
Lebesgue measure zero in C.
| arxiv topic:math.DS |
arxiv_dataset-48811312.6747 | Controlling Factors of Tc-Dome Structure in 1111-Type Iron Arsenide
Superconductors
cond-mat.supr-con
We investigated the effects of phosphorus substitution on the shape of the
Tc(x) dome in 1111-type SmFeAs1-yPyO1-xHx (0 < x < 0.5). Hydride ion
substitution of oxide sites (O2- -> H-) exerts a chemical pressure effect,
i.e., a structural reduction of the Pn-Fe-Pn angle {\alpha} (Pn = P, As) and
also dopes electrons into the FePn layer to induce superconductivity. Isovalent
phosphorus substitution (P3- -> As3-) can induce only a chemical pressure
effect, i.e., an increase of {\alpha} for La-substitution of Sm-sites. As y
increases from 0.0 to 0.5, the single Tc dome gradually splits into two domes,
similar to those of LaFeAsO1-xHx with a Tc valley at x ~ 0.16. We found that
the Tc valley is located around (x, {\alpha}) ~ (0.16, 113{\deg}) for both
SmFeAs1-yPyO1-xHx and LaFeAsO1-xHx series, irrespective of changes in the Pn
anion and Ln cation species. This result suggests that suppression of Tc leads
to the emergence of a Tc valley when both the shape of FePn4 tetrahedra
represented by {\alpha} and electron doping level of x meet the above criterion
in 1111 type iron oxypnictide superconductors.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-48821312.6847 | $2D$ and $3D$ Antiferromagnetic Ising Model with topological term at
$\theta=\pi$
hep-lat
We study the two and three-dimensional Antiferromagnetic Ising Model with an
imaginary magnetic field $i\theta$ at $\theta = \pi$. We use a new geometric
algorithm which does not present a sign problem. This allows us to perform
efficient numerical simulations of this system.
| arxiv topic:hep-lat |
arxiv_dataset-48831312.6947 | Formal Ontology Learning on Factual IS-A Corpus in English using
Description Logics
cs.CL cs.AI
Ontology Learning (OL) is the computational task of generating a knowledge
base in the form of an ontology given an unstructured corpus whose content is
in natural language (NL). Several works can be found in this area most of which
are limited to statistical and lexico-syntactic pattern matching based
techniques Light-Weight OL. These techniques do not lead to very accurate
learning mostly because of several linguistic nuances in NL. Formal OL is an
alternative (less explored) methodology were deep linguistics analysis is made
using theory and tools found in computational linguistics to generate formal
axioms and definitions instead simply inducing a taxonomy. In this paper we
propose "Description Logic (DL)" based formal OL framework for learning factual
IS-A type sentences in English. We claim that semantic construction of IS-A
sentences is non trivial. Hence, we also claim that such sentences requires
special studies in the context of OL before any truly formal OL can be
proposed. We introduce a learner tool, called DLOL_IS-A, that generated such
ontologies in the owl format. We have adopted "Gold Standard" based OL
evaluation on IS-A rich WCL v.1.1 dataset and our own Community representative
IS-A dataset. We observed significant improvement of DLOL_IS-A when compared to
the light-weight OL tool Text2Onto and formal OL tool FRED.
| arxiv topic:cs.CL cs.AI |
arxiv_dataset-48841312.7047 | Poisson Reduction of Controlled Hamiltonian System by Controllability
Distribution
math.SG math.DG
In this paper, we first study the Poisson reductions of controlled
Hamiltonian (CH) system and symmetric CH system by controllability
distributions. These reductions are the extension of Poisson reductions by
distribution for Poisson manifolds to that for phase spaces of CH systems with
external force and control. We give Poisson reducible conditions of CH system
by controllability distribution, and prove that the Poisson reducible property
for CH systems leaves invariant under the CH-equivalence. Moreover, we study
the Poisson reduction of symmetric CH system by G-invariant controllability
distribution. Next, we consider the singular Poisson reduction and
SPR-CH-equivalence for CH system with symmetry, and prove the singular Poisson
reduction theorem of CH system. We also study the relationship between Poisson
reduction for singular Poisson reducible CH systems by G-invariant
controllability distribution and that for associated reduced CH system by
reduced controllability distribution. At last, some examples are given to state
the theoretical results.
| arxiv topic:math.SG math.DG |
arxiv_dataset-48851312.7147 | Coefficients of Sylvester's Denumerant
math.NT math.CO
For a given sequence $\mathbf{\alpha} =
[\alpha_1,\alpha_2,\dots,\alpha_{N+1}]$ of $N+1$ positive integers, we consider
the combinatorial function $E(\mathbf{\alpha})(t)$ that counts the nonnegative
integer solutions of the equation $\alpha_1x_1+\alpha_2 x_2+\cdots+\alpha_{N}
x_{N}+\alpha_{N+1}x_{N+1}=t$, where the right-hand side $t$ is a varying
nonnegative integer. It is well-known that $E(\mathbf{\alpha})(t)$ is a
quasi-polynomial function in the variable $t$ of degree $N$. In combinatorial
number theory this function is known as Sylvester's denumerant.
Our main result is a new algorithm that, for every fixed number $k$, computes
in polynomial time the highest $k+1$ coefficients of the quasi-polynomial
$E(\mathbf{\alpha})(t)$ as step polynomials of $t$ (a simpler and more explicit
representation). Our algorithm is a consequence of a nice poset structure on
the poles of the associated rational generating function for
$E(\mathbf{\alpha})(t)$ and the geometric reinterpretation of some rational
generating functions in terms of lattice points in polyhedral cones. Our
algorithm also uses Barvinok's fundamental fast decomposition of a polyhedral
cone into unimodular cones. This paper also presents a simple algorithm to
predict the first non-constant coefficient and concludes with a report of
several computational experiments using an implementation of our algorithm in
LattE integrale. We compare it with various Maple programs for partial or full
computation of the denumerant.
| arxiv topic:math.NT math.CO |
arxiv_dataset-48861312.7247 | Non-magnetic ground state of PuO$_2$
cond-mat.mtrl-sci cond-mat.str-el
The correlated band theory implemented as a combination of the local density
approximation with the exact diagonalization of the Anderson impurity model is
applied to PuO$_2$. We obtain an insulating electronic structure consistent
with the experimental photoemission spectra. The calculations yield the band
gap of 1.8 eV and a non-magnetic singlet ground state that is characterized by
a non-integer filling of the plutonium $f$ shell ($n_f\approx 4.5$). Due to
sizeable hybridization of the $f$ shell with the $p$ states of oxygen, the
ground state is more complex than the four-electron Russell--Saunders ${}^5{\rm
I}_4$ manifold split by the crystal field. The inclusion of hybridization
improves the agreement between the theory and experiment for the magnetic
susceptibility.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-48871312.7347 | Minding the Gap in N=4 Super-Yang-Mills
hep-th
We analyze fermionic response in the geometry holographically dual to
zero-temperature N=4 Super-Yang-Mills theory with two equal nonvanishing
chemical potentials, which is characterized by a singular horizon and zero
ground state entropy. We show that fermionic fluctuations are completely stable
within a gap in energy around a Fermi surface singularity, beyond which
non-Fermi liquid behavior returns. This gap disappears abruptly once the final
charge is turned on, and is associated to a discontinuity in the corresponding
chemical potential. We also show that the singular near-horizon geometry lifts
to a smooth AdS_3 x R^3, and interpret the gap as a region where the
quasiparticle momentum is spacelike in six dimensions due to the momentum
component in the Kaluza-Klein direction, corresponding to the final charge.
| arxiv topic:hep-th |
arxiv_dataset-48881312.7447 | Containment Control of Linear Multi-Agent Systems with Multiple Leaders
of Bounded Inputs Using Distributed Continuous Controllers
cs.SY math.OC
This paper considers the containment control problem for multi-agent systems
with general linear dynamics and multiple leaders whose control inputs are
possibly nonzero and time varying. Based on the relative states of neighboring
agents, a distributed static continuous controller is designed, under which the
containment error is uniformly ultimately bounded and the upper bound of the
containment error can be made arbitrarily small, if the subgraph associated
with the followers is undirected and for each follower there exists at least
one leader that has a directed path to that follower. It is noted that the
design of the static controller requires the knowledge of the eigenvalues of
the Laplacian matrix and the upper bounds of the leaders' control inputs. In
order to remove these requirements, a distributed adaptive continuous
controller is further proposed, which can be designed and implemented by each
follower in a fully distributed fashion. Extensions to the case where only
local output information is available are discussed.
| arxiv topic:cs.SY math.OC |
arxiv_dataset-48891312.7547 | Solutions of differential-algebraic equations as outputs of LTI systems:
application to LQ control problem
math.OC
In this paper we synthesize behavioral ideas with geometric control theory
and propose a unified geometric framework for representing all solutions of a
Linear Time Invariant Differential-Algebraic Equation (DAE-LTI) as outputs of
classical Linear Time Invariant systems (ODE-LTI). An algorithm for computing
an ODE-LTI that generates solutions of a given DAE-LTI is described. It is
shown that two different ODE-LTIs which represent the same DAE-LTI are feedback
equivalent. The proposed framework is then used to solve an LQ optimal control
problem for DAE-LTIs with rectangular matrices.
| arxiv topic:math.OC |
arxiv_dataset-48901312.7647 | Operator decomposable measures and stochastic difference equation
math.PR
We consider the following convolution equation or equivalently stochastic
difference equation $$\lam _k = \mu _k*\phi (\lam _{k-1}), k \in \Z \eqno (1)
$$ for a given bi-sequence $(\mu _k)$ of probability measures on $\R ^d$ and a
linear map $\phi $ on $\R ^d$. We study the solutions of equation (1) by
realizing the process $(\mu _k)$ as a measure on $(\R ^d)^\Z$ and rewriting the
stochastic difference equation as $\lam = \mu *\tau (\lam )$-any such measure
$\lam$ on $(\R ^d)^\Z$ is known as $\tau$-decomposable measure with co-factor
$\mu$-where $\tau$ is a suitable weighted shift operator on $(\R ^d)^\Z$. This
enables one to study the solutions of (1) in the settings of
$\tau$-decomposable measures. A solution $(\lam _k)$ of (1) will be called a
fundamental solution if any solution of (1) can be written as $\lam _k*\phi
^k(\rho )$ for some probability measure $\rho $ on $\R ^d$. Motivated by the
splitting/factorization theorems for operator decomposable measures, we address
the question of existence of fundamental solutions when a solution exists and
answer affirmatively via a one-one correspondence between fundamental solutions
of (1) and strongly $\tau$-decomposable measures on $(\R ^d)^\Z$ with co-factor
$\mu$. We also prove that fundamental solutions are extremal solutions and vice
versa. We provide a necessary and sufficient condition in terms of a
logarithmic moment condition for the existence of a (fundamental) solution when
the noise process is stationary and when the noise process has independent
$\ell _p$-paths.
| arxiv topic:math.PR |
arxiv_dataset-48911312.7747 | Lorentz Spin-Foam with Non Unitary Representations by use of Holomorphic
Peter-Weyl Theorem
gr-qc quant-ph
In quantum gravity the unitary evolution does not follow from the
Wheeler-DeWitt dynamics equation as it follows from the Schr\"odinger equation
in non-relativistic quantum mechanics. Therefore we can define a spin-foam
model based on SL(2,C) spinor finite non-unitary representations. The recently
discovered holomorphic Peter-Weyl theorem \cite{Huebschmann} made it possible
to decompose the delta function of a non-compact Lorentz group into the
convergent sum of the matrix coefficients. We calculate the vertex amplitude
with the help of that theorem and obtain a simple expression for our model. The
$SL(2,C)$ Hilbert space is defined from $SU(2)$ Hilbert space by
Huebschmann-Kirillov transform \cite{Huebschmann}. A new transform is simpler
than the well known Hall transform as it does not contain a heat kernel
convolution. We do not set Barbero-Immirzi constant $\gamma$ a priori, instead
we obtain it as a solution of the diagonal and off-diagonal simplicity
constraints being $\gamma = \frac{-in}{(|n| + 2p)}$ where $p$ is a non-negative
half-integer. When $p=0$ the solution corresponds to the Ashtekar's self-dual
connections. We point out that the Barbero-Immirzi becomes real when one
chooses a unitary representation. It is complex when the representation is
non-unitary principal series or non-unitary spinor representation.
| arxiv topic:gr-qc quant-ph |
arxiv_dataset-48921312.7847 | On Decentralized Estimation with Active Queries
cs.MA cs.IT cs.SY math.IT
We consider the problem of decentralized 20 questions with noise for multiple
players/agents under the minimum entropy criterion in the setting of stochastic
search over a parameter space, with application to target localization. We
propose decentralized extensions of the active query-based stochastic search
strategy that combines elements from the 20 questions approach and social
learning. We prove convergence to correct consensus on the value of the
parameter. This framework provides a flexible and tractable mathematical model
for decentralized parameter estimation systems based on active querying. We
illustrate the effectiveness and robustness of the proposed decentralized
collaborative 20 questions algorithm for random network topologies with
information sharing.
| arxiv topic:cs.MA cs.IT cs.SY math.IT |
arxiv_dataset-48931401.0069 | Determining Relevant Relations for Datalog Queries under Access
Limitations is Undecidable
cs.DB
Access limitations are restrictions in the way in which the tuples of a
relation can be accessed. Under access limitations, query answering becomes
more complex than in the traditional case, with no guarantee that the answer
tuples that can be extracted (aka maximal answer) are all those that would be
found without access limitations (aka complete answer). The field of query
answering under access limitations has been broadly investigated in the past.
Attention has been devoted to the problem of determining relations that are
relevant for a query, i.e., those (possibly off-query) relations that might
need to be accessed in order to find all tuples in the maximal answer. In this
short paper, we show that relevance is undecidable for Datalog queries.
| arxiv topic:cs.DB |
arxiv_dataset-48941401.0169 | Extremal Hypergraphs for Ryser's Conjecture: Connectedness of Line
Graphs of Bipartite Graphs
math.CO
In this paper we consider a natural extremal graph theoretic problem of
topological sort, concerning the minimization of the (topological)
connectedness of the independence complex of graphs in terms of its dimension.
We observe that the lower bound $\frac{\dim(\mathcal{I}(G))}{2} - 2$ on the
connectedness of the independence complex $\mathcal{I}(G)$ of line graphs of
bipartite graphs $G$ is tight. In our main theorem we characterize the extremal
examples. Our proof of this characterization is based on topological machinery.
Our motivation for studying this problem comes from a classical conjecture of
Ryser. Ryser's Conjecture states that any $r$-partite $r$-uniform hypergraph
has a vertex cover of size at most $(r - 1)$-times the size of the largest
matching. For $r = 2$, the conjecture is simply K\"onig's Theorem. It has also
been proven for $r = 3$ by Aharoni using a beautiful topological argument. In a
separate paper we characterize the extremal examples for the $3$-uniform case
of Ryser's Conjecture (i.e., Aharoni's Theorem), and in particular resolve an
old conjecture of Lov\'asz for the case of Ryser-extremal $3$-graphs.
Our main result in this paper will provide us with valuable structural
information for that characterization. Its proof is based on the observation
that link graphs of Ryser-extremal $3$-uniform hypergraphs are exactly the
bipartite graphs we study here.
| arxiv topic:math.CO |
arxiv_dataset-48951401.0269 | A symplectic prolegomenon
math.SG
A symplectic manifold gives rise to a triangulated A-infinity category, the
derived Fukaya category, which encodes information on Lagrangian submanifolds
and dynamics as probed by Floer cohomology. This survey aims to give some
insight into what the Fukaya category is, where it comes from and what
symplectic topologists want to do with it.
| arxiv topic:math.SG |
arxiv_dataset-48961401.0369 | Probing the metastability of protoneutron star with hyperon in
core-collapse supernova
astro-ph.HE
We investigate the role of hyperons in the dynamical collapse of a
non-rotating massive star to a black hole(BH) using one dimensional general
relativistic $GR1D$ code. We follow the dynamical formation and evolution of a
protoneutron star (PNS) to a black hole using various progenitor models,
adopting a hyperonic equation of state (EoS) generated by Shen et. al. We
compare the results with those of nuclear EoS by Shen et. al. and understand
the role of strange hyperons in the core collapse supernova. We discuss the
neutrino signals that may be used as a probe to core collapse. Further, an
exotic EoS can support a much lower maximum mass cold neutron star compared to
PNS. In this regard, we also study the metastability of PNS in the presence of
hyperon in the long-time evolution of the progenitors, relevant to supernova
SN1987A.
| arxiv topic:astro-ph.HE |
arxiv_dataset-48971401.0469 | Weighted Moore-Penrose invertible and weighted EP Banach algebra
elements
math.FA
The weighted Moore-Penrose inverse will be introduced and studied in the
context of Banach algebras. In addition, weighted EP Banach algebra elements
will be characterized. The Banach space operator case will be also considered.
| arxiv topic:math.FA |
arxiv_dataset-48981401.0569 | Natural Language Processing in Biomedicine: A Unified System
Architecture Overview
cs.CL
In modern electronic medical records (EMR) much of the clinically important
data - signs and symptoms, symptom severity, disease status, etc. - are not
provided in structured data fields, but rather are encoded in clinician
generated narrative text. Natural language processing (NLP) provides a means of
"unlocking" this important data source for applications in clinical decision
support, quality assurance, and public health. This chapter provides an
overview of representative NLP systems in biomedicine based on a unified
architectural view. A general architecture in an NLP system consists of two
main components: background knowledge that includes biomedical knowledge
resources and a framework that integrates NLP tools to process text. Systems
differ in both components, which we will review briefly. Additionally,
challenges facing current research efforts in biomedical NLP include the
paucity of large, publicly available annotated corpora, although initiatives
that facilitate data sharing, system evaluation, and collaborative work between
researchers in clinical NLP are starting to emerge.
| arxiv topic:cs.CL |
arxiv_dataset-48991401.0669 | Nonperturbative tests of the renormalization of mixed clover-staggered
currents in lattice QCD
hep-lat hep-ex hep-ph
The Fermilab Lattice and MILC collaborations have shown in one-loop lattice
QCD perturbation theory that the renormalization constants of vector and
axial-vector mixed clover-asqtad currents are closely related to the product of
those for clover-clover and asqtad-asqtad (local) vector currents. To be useful
for future higher precision calculations this relationship must be valid beyond
one-loop and very general. We test its validity nonperturbatively using clover
and Highly Improved Staggered (HISQ) strange quarks, utilising the absolute
normalization of the HISQ temporal axial current. We find that the
renormalization of the mixed current differs from the square root of the
product of the pure HISQ and pure clover currents by $2-3\%$. We also compare
discretization errors between the clover and HISQ formalisms.
| arxiv topic:hep-lat hep-ex hep-ph |
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