title:
A Bayesian changepoint methodology for high dimensional multivariate
  time series and space-time data: A study of structural change using remotely
  sensed data

abstract:
  A Bayesian approach is developed to analyze change points in multivariate
time series and space-time data. The methodology is used to assess the impact
of extended inundation on the ecosystem of the Gulf Plains bioregion in
northern Australia. The proposed approach can be implemented for dynamic
mixture models that have a conditionally Gaussian state space representation.
Details are given on how to efficiently implement the algorithm for a general
class of multivariate time series and space-time models. This efficient
implementation makes it feasible to analyze high dimensional, but of realistic
size, space-time data sets because our approach can be appreciably faster,
possibly millions of times, than a standard implementation in such cases.


title: Computer simulation based parameter selection for resistance exercise

abstract:
  In contrast to most scientific disciplines, sports science research has been
characterized by comparatively little effort investment in the development of
relevant phenomenological models. Scarcer yet is the application of said models
in practice. We present a framework which allows resistance training
practitioners to employ a recently proposed neuromuscular model in actual
training program design. The first novelty concerns the monitoring aspect of
coaching. A method for extracting training performance characteristics from
loosely constrained video sequences, effortlessly and with minimal human input,
using computer vision is described. The extracted data is subsequently used to
fit the underlying neuromuscular model. This is achieved by solving an inverse
dynamics problem corresponding to a particular exercise. Lastly, a computer
simulation of hypothetical training bouts, using athlete-specific capability
parameters, is used to predict the effected adaptation and changes in
performance. The software described here allows the practitioner to manipulate
hypothetical training parameters and immediately see their effect on predicted
adaptation for a specific athlete. Thus, this work presents a holistic view of
the monitoring-assessment-adjustment loop.


title: Naive motivic Donaldson-Thomas type Hirzebruch classes and some problems

abstract:
  Donaldson-Thomas invariant is expressed as the weighted Euler characteristic
of the so-called Behrend (constructible) function. In \cite{Behrend} Behrend
introduced a DT-type invariant for a morphism. Motivated by this invariant, we
extend the motivic Hirzebruch class to naive Donaldson-Thomas type analogues.
We also discuss a categorification of the DT-type invariant for a morphism from
a bivariant-theoretic viewpoint, and we finally pose some related questions for
further investigations.


title:
A secure and effective anonymous authentication scheme for roaming
  service in global mobility networks

abstract:
  Recently, Mun et al. analyzed Wu et al.'s authentication scheme and proposed
a enhanced anonymous authentication scheme for roaming service in global
mobility networks. However, through careful analysis, we find that Mun et al.'s
scheme is vulnerable to impersonation attacks, off-line password guessing
attacks and insider attacks, and cannot provide user friendliness, user's
anonymity, proper mutual authentication and local verification. To remedy these
weaknesses, in this paper we propose a novel anonymous authentication scheme
for roaming service in global mobility networks. Security and performance
analyses show the proposed scheme is more suitable for the low-power and
resource-limited mobile devices, and is secure against various attacks and has
many excellent features.


title: On the second Hamming weight of some Reed-Muller type codes

abstract:
  We study affine cartesian codes, which are a Reed-Muller type of evaluation
codes, where polynomials are evaluated at the cartesian product of n subsets of
a finite field F_q. These codes appeared recently in a work by H. Lopez, C.
Renteria-Marquez and R. Villareal and, in a generalized form, in a work by O.
Geil and C. Thomsen. Using methods from Gr\"obner basis theory we determine the
second Hamming weight (also called next-to-minimal weight) for particular cases
of affine cartesian codes and also some higher Hamming weights of this type of
code.


title: Theory of amorphous ices

abstract:
  We derive a phase diagram for amorphous solids and liquid supercooled water
and explain why the amorphous solids of water exist in several different forms.
Application of large-deviation theory allows us to prepare such phases in
computer simulations. Along with nonequilibrium transitions between the ergodic
liquid and two distinct amorphous solids, we establish coexistence between
these two amorphous solids. The phase diagram we predict includes a
nonequilibrium triple point where two amorphous phases and the liquid coexist.
While the amorphous solids are long-lived and slowly-aging glasses, their
melting can lead quickly to the formation of crystalline ice. Further, melting
of the higher density amorphous solid at low pressures takes place in steps,
transitioning to the lower density glass before accessing a nonequilibrium
liquid from which ice coarsens.

categories: cond-mat.stat-mech cond-mat.dis-nn cond-mat.mtrl-sci cond-mat.soft


title:
Beam dynamics design of the main accelerating section with KONUS in the
  CSR-LINAC

abstract:
  The CSR-LINAC injector has been proposed in Heavy Ion Research Facility in
Lanzhou (HIRFL). The linac mainly consists of two parts, the RFQ and the
IH-DTL. The KONUS (Kombinierte Null Grad Struktur) concept has been introduced
into the DTL section. In this paper, the re-matching of the main accelerating
section will be finished in the 3.7 MeV/u scheme and the new beam dynamics
design up to 7 MeV/u will be also shown. Through the beam re-matching, the
relative emittance growth has been suppressed greatly along the linac.


title: Magnetic orders, excitations, and phase transitions in Fe_1+yTe

abstract:
  We study the magnetic properties of Fe_1+y Te, a parent compound of the
iron-based high-temperature superconductors. Motivated by recent neutron
scattering experiments, we show that a spin-1 exchange model, supplemented by a
single-ion spin anisotropy, accounts well for the experimentally observed low
temperature magnetic phase diagram, that exhibits a commensurate bicollinear
order at low Fe dopings (y < 0.12) and an incommensurate spin-spiral order at
high Fe dopings (y > 0.12). We suggest that the commensurate-incommensurate
transition at y = 0.12 is due to the competition between the exchange
interaction and the local spin anisotropy. At low Fe dopings, the single-ion
spin anisotropy is strong and pins the spins along the easy axis, which,
together with the spatially anisotropic exchanges, induces a unusual
bicollinear commensurate magnetic order. The low-energy spin-wave excitation is
gapped due to the explict breaking of spin-rotational symmetry by the local
spin anisotropy. At high Fe dopings, the single-ion anisotropy is weak, and the
exchange favors an incommensurate coplanar state. The incommensurate magnetic
wavevector averages out the spin anisotropy so that a gapless low-energy
spin-wave excitation is obtained. We also analyze the low-energy hydrodynamic
model and use it to describe the magneto-structural transition and the static
and dynamical spin structure factors across the magnetic ordering transitions.


title: Straight segments in the galactic discs

abstract:
  We study the properties of the straight segments forming in N-body
simulations of the galactic discs. The properties of these features are
consistent with the observational ones summarized by Chernin at al. (2001).
Unlike some previous suggestions to explain the straight segments as gas
dynamical instabilities, they form in our models in the stellar system. We
suggest that the straight segments are forming as a response of the rotating
disc to a gravity of the regions of enhanced density (overdensities) corotating
with the disc. The kinematics of stars near the prominent overdensities is
consistent with this hypothesis.


title: Cosmology from gravitational lens time delays and Planck data

abstract:
  Under the assumption of a flat Lambda-CDM cosmology, recent data from the
Planck satellite point toward a Hubble constant that is in tension with that
measured by gravitational lens time delays and by the local distance ladder.
Prosaically, this difference could arise from unknown systematic uncertainties
in some of the measurements. More interestingly -- if systematics were ruled
out -- resolving the tension would require a departure from the flat Lambda-CDM
cosmology, introducing for example a modest amount of spatial curvature, or a
non-trivial dark energy equation of state. To begin to address these issues, we
present here an analysis of the gravitational lens RXJ1131-1231 that is
improved in one particular regard: we examine the issue of systematic error
introduced by an assumed lens model density profile. We use more flexible
gravitational lens models with baryonic and dark matter components, and find
that the exquisite Hubble Space Telescope image with thousands of intensity
pixels in the Einstein ring and the stellar velocity dispersion of the lens
contain sufficient information to constrain these more flexible models. The
total uncertainty on the time-delay distance is 6.6% for a single system. We
proceed to combine our improved time-delay distance measurements with the WMAP9
and Planck posteriors. In an open Lambda-CDM model, the data for RXJ1131-1231
in combination with Planck favor a flat universe with Omega_k = 0.00+0.01/-0.02
(68% CI). In a flat wCDM model, the combination of RXJ1131-1231 and Planck
yields w = -1.52+0.19/-0.20 (68% CI).


title:
Valuation and hedging of OTC contracts with funding costs,
  collateralization and counterparty credit risk: Part 1

abstract:
  The research presented in this work is motivated by some recent papers
regarding hedging and valuation of financial securities subject to funding
costs, collateralization and counterparty credit risk. Our goal is to provide a
sound theoretical underpinning for some results presented in these papers by
developing a unified martingale framework for the non-linear approach to
hedging and pricing of OTC financial contracts. The impact that various funding
bases and margin covenants exert on the values and hedging strategies for OTC
contracts is examined.


title: Real-time semiparametric regression for distributed data sets

abstract:
  This paper proposes a method for semiparametric regression analysis of
large-scale data which are distributed over multiple hosts. This enables
modeling of nonlinear relationships and both the batch approach, where analysis
starts after all data have been collected, and the real-time setting are
addressed. The methodology is extended to operate in evolving environments,
where it can no longer be assumed that model parameters remain constant over
time. Two areas of application for the methodology are presented: regression
modeling when there are multiple data owners and regression modeling within the
MapReduce framework. A website, realtime-semiparametric-regression.net,
illustrates the use of the proposed method on United States domestic airline
data in real-time.


title: Timing interactions in social simulations: The voter model

abstract:
  The recent availability of huge high resolution datasets on human activities
has revealed the heavy-tailed nature of the interevent time distributions. In
social simulations of interacting agents the standard approach has been to use
Poisson processes to update the state of the agents, which gives rise to very
homogeneous activity patterns with a well defined characteristic interevent
time. As a paradigmatic opinion model we investigate the voter model and review
the standard update rules and propose two new update rules which are able to
account for heterogeneous activity patterns. For the new update rules each node
gets updated with a probability that depends on the time since the last event
of the node, where an event can be an update attempt (exogenous update) or a
change of state (endogenous update). We find that both update rules can give
rise to power law interevent time distributions, although the endogenous one
more robustly. Apart from that for the exogenous update rule and the standard
update rules the voter model does not reach consensus in the infinite size
limit, while for the endogenous update there exist a coarsening process that
drives the system toward consensus configurations.


title:
A curious relation between the flat cosmological model and the elliptic
  integral of the first kind

abstract:
  The dependence of the luminosity distance on the redshift has a key
importance in the cosmology. This dependence can well be given by standard
functions for the zero cosmological constant. The purpose of this article is to
present such a relation also for the non-zero cosmological constant, if the
universe is spatially flat. A definite integral is used. The integration ends
in the elliptic integral of the first kind. The result shows that no numerical
integration is needed for the non-zero cosmological constant, if the universe
is spatially flat.


title:
Optically controlled phase gate and teleportation of a controlled-NOT
  gate for spin qubits in quantum dot-microcavity coupled system

abstract:
  Assisted with linear optical manipulation, single photon, entangled photon
pairs, photon measurement, and classical communication, a scheme for two-spin
qubits phase gate and teleportation of a CNOT gate between two electron spins
from acting on local qubits to acting on remote qubits using quantum dots in
optical microcavities is proposed. The scheme is based on spin selective photon
reflection from the cavity and is achieved in a deterministic way by the
sequential detection of photons and the single-qubit rotations of a single
electron spin in a self-assembled GaAs/InAs quantum dot. The feasibility of the
scheme is assessed showing that high average fidelities of the gates are
achievable in the weak-coupling regime when the side leakage and cavity loss
are low. The scheme opens promising perspectives for long-distance quantum
communication, distributed quantum computation, and constructing remote quantum
information processing networks.


title: A modified W-W interatomic potential based on ab initio calculations

abstract:
  Based on ab initio calculations, a Finnis-Sinclair-type interatomic potential
for W-W interactions has been developed. The modified potential is able to
reproduce the correct formation energies of self-interstitial atom defects in
tungsten, offering a significant improvement over the Ackland-Thetford tungsten
potential. Using the modified potential, the thermal expansion is calculated in
a temperature range from 0 K to 3500 K, and the results are in reasonable
agreement with the experimental data, thus overcoming the shortcoming of the
negative thermal expansion using the Derlet-Nguyen-Manh-Dudarev tungsten
potential. The present W-W potential is also applied to study in detail the
diffusion of self-interstitial atoms in tungsten. It is revealed that the
initial self-interstitial atom initiates a sequence of W atom displacements and
replacements in the <111> direction. An Arrhenius fit to the diffusion data at
temperatures below 550 K indicates a migration energy of 0.022 eV, in
reasonable agreement with the experimental data.


title:
Lower Bounds for the Area of Black Holes in Terms of Mass, Charge, and
  Angular Momentum

abstract:
  The most general formulation of Penrose's inequality yields a lower bound for
ADM mass in terms of the area, charge, and angular momentum of black holes.
This inequality is in turn equivalent to an upper and lower bound for the area
in terms of the remaining quantities. In this note, we establish the lower
bound for a single black hole in the setting of axisymmetric maximal initial
data sets for the Einstein-Maxwell equations, when the non-electromagnetic
matter fields are not charged and satisfy the dominant energy condition. It is
shown that the inequality is saturated if and only if the initial data arise
from the extreme Kerr-Newman spacetime. Further refinements are given when
either charge or angular momentum vanish. Lastly, we discuss the validity of
the lower bound in the presence of multiple black holes.


title:
Generalized massive gravity in arbitrary dimensions and its Hamiltonian
  formulation

abstract:
  We extend the four-dimensional de Rham-Gabadadze-Tolley (dRGT) massive
gravity model to a general scalar massive-tensor theory in arbitrary
dimensions, coupling a dRGT massive graviton to multiple scalars and allowing
for generic kinetic and mass matrix mixing between the massive graviton and the
scalars, and derive its Hamiltonian formulation and associated constraint
system. When passing to the Hamiltonian formulation, two different sectors
arise: a general sector and a special sector. Although obtained via different
ways, there are two second class constraints in either of the two sectors,
eliminating the BD ghost. However, for the special sector, there are still
ghost instabilities except for the case of two dimensions. In particular, for
the special sector with one scalar, there is a "second BD ghost".


title:
Pinning consensus in networks of multiagents via a single impulsive
  controller

abstract:
  In this paper, we discuss pinning consensus in networks of multiagents via
impulsive controllers. In particular, we consider the case of using only one
impulsive controller. We provide a sufficient condition to pin the network to a
prescribed value. It is rigorously proven that in case the underlying graph of
the network has spanning trees, the network can reach consensus on the
prescribed value when the impulsive controller is imposed on the root with
appropriate impulsive strength and impulse intervals. Interestingly, we find
that the permissible range of the impulsive strength completely depends on the
left eigenvector of the graph Laplacian corresponding to the zero eigenvalue
and the pinning node we choose. The impulses can be very sparse, with the
impulsive intervals being lower bounded. Examples with numerical simulations
are also provided to illustrate the theoretical results.


title:
On Synchronization: Comments on the paper "Synchronization in scale-free
  dynamical networks: robustness and fragility", IEEE Trans. Circuits Syst. I
  49 (1) (2002) 54-62

abstract:
  Synchronization problem for linear coupled networks is a hot topic in recent
decade. However, until now, some confused concepts and results still puzzle
people. To avoid further misleading researchers, it is necessary to point out
these misunderstandings, correct these mistakes and give precise results.


title: A parallel Heap-Cell Method for Eikonal equations

abstract:
  Numerous applications of Eikonal equations prompted the development of many
efficient numerical algorithms. The Heap-Cell Method (HCM) is a recent serial
two-scale technique that has been shown to have advantages over other serial
state-of-the-art solvers for a wide range of problems. This paper presents a
parallelization of HCM for a shared memory architecture. The numerical
experiments in $R^3$ show that the parallel HCM exhibits good algorithmic
behavior and scales well, resulting in a very fast and practical solver.
  We further explore the influence on performance and scaling of data
precision, early termination criteria, and the hardware architecture. A shorter
version of this manuscript (omitting these more detailed tests) has been
submitted to SIAM Journal on Scientific Computing in 2012.


title:
Signatures of the Berry curvature in the frequency dependent interlayer
  magnetoresistance in tilted magnetic fields

abstract:
  We show that in a layered metal, the angle dependent, finite frequency,
interlayer magnetoresistance is altered due to the presence of a non-zero Berry
curvature at the Fermi surface. At zero frequency, we find a conservation law
which demands that the `magic angle' condition for interlayer magnetoresistance
extrema as a function of magnetic field tilt angle is essentially both field
and Berry curvature independent. In the finite frequency case, however, we find
that surprisingly large signatures of a finite Berry curvature occur in the
periodic orbit resonances. We outline a method whereby the presence and
magnitude of the Berry curvature at the Fermi surface can be extracted.


title:
Origins of large enhancement in electromechanical coupling for nonpolar
  directions in ferroelectric BaTiO3

abstract:
  The origins of enhanced piezoelectric coupling along nonpolar
crystallographic directions in ferroelectric BaTiO3 are investigated using in
situ neutron spectroscopy. It is observed that an electric field applied away
from the equilibrium polarization direction causes changes in the phonon
spectra that lead to an increase in the interaction between the transverse
acoustic and transverse optic branches (TA-TO) near the Brillouin zone center.
This provides a direct lattice dynamics mechanism for enhanced
electromechanical coupling, and could act as a guide for designing improved
piezoelectric materials.


title: Felzenszwalb-Baum-Welch: Event Detection by Changing Appearance

abstract:
  We propose a method which can detect events in videos by modeling the change
in appearance of the event participants over time. This method makes it
possible to detect events which are characterized not by motion, but by the
changing state of the people or objects involved. This is accomplished by using
object detectors as output models for the states of a hidden Markov model
(HMM). The method allows an HMM to model the sequence of poses of the event
participants over time, and is effective for poses of humans and inanimate
objects. The ability to use existing object-detection methods as part of an
event model makes it possible to leverage ongoing work in the object-detection
community. A novel training method uses an EM loop to simultaneously learn the
temporal structure and object models automatically, without the need to specify
either the individual poses to be modeled or the frames in which they occur.
The E-step estimates the latent assignment of video frames to HMM states, while
the M-step estimates both the HMM transition probabilities and state output
models, including the object detectors, which are trained on the weighted
subset of frames assigned to their state. A new dataset was gathered because
little work has been done on events characterized by changing object pose, and
suitable datasets are not available. Our method produced results superior to
that of comparison systems on this dataset.


title:
The equilibrium allele frequency distribution for a population with
  reproductive skew

abstract:
  We study the population genetics of two neutral alleles under reversible
mutation in the \Lambda-processes, a population model that features a skewed
offspring distribution. We describe the shape of the equilibrium allele
frequency distribution as a function of the model parameters. We show that the
mutation rates can be uniquely identified from the equilibrium distribution,
but that the form of the offspring distribution itself cannot be uniquely
identified. We also introduce an infinite-sites version of the \Lambda-process,
and we use it to study how reproductive skew influences standing genetic
diversity in a population. We derive asymptotic formulae for the expected
number of segregating sizes as a function of sample size. We find that the
Wright-Fisher model minimizes the equilibrium genetic diversity, for a given
mutation rate and variance effective population size, compared to all other
\Lambda-processes.


title:
New Analysis of Manifold Embeddings and Signal Recovery from Compressive
  Measurements

abstract:
  Compressive Sensing (CS) exploits the surprising fact that the information
contained in a sparse signal can be preserved in a small number of compressive,
often random linear measurements of that signal. Strong theoretical guarantees
have been established concerning the embedding of a sparse signal family under
a random measurement operator and on the accuracy to which sparse signals can
be recovered from noisy compressive measurements. In this paper, we address
similar questions in the context of a different modeling framework. Instead of
sparse models, we focus on the broad class of manifold models, which can arise
in both parametric and non-parametric signal families. Using tools from the
theory of empirical processes, we improve upon previous results concerning the
embedding of low-dimensional manifolds under random measurement operators. We
also establish both deterministic and probabilistic instance-optimal bounds in
$\ell_2$ for manifold-based signal recovery and parameter estimation from noisy
compressive measurements. In line with analogous results for sparsity-based CS,
we conclude that much stronger bounds are possible in the probabilistic
setting. Our work supports the growing evidence that manifold-based models can
be used with high accuracy in compressive signal processing.


title:
Pairing transitions in the finite-temperature relativistic
  Hartree-Bogoliubov theory

abstract:
  We formulate the finite-temperature relativistic Hartree-Bogoliubov theory
for spherical nuclei based on a point-coupling functional, with the Gogny or
separable pairing force. Using the functional PC-PK1, the framework is applied
to the study of pairing transitions in Ca, Ni, Sn, and Pb isotopic chains. The
separable pairing force reproduces the gaps calculated with the Gogny force not
only at zero temperature, but also at finite temperatures. By performing a
systematic calculation of the even-even Ca, Ni, Sn, and Pb isotopes, it is
found that the critical temperature for a pairing transition generally follows
the rule $T_c =0.6 \Delta_n(0)$, where $\Delta_n(0)$ is the neutron pairing gap
at zero temperature. This rule is further verified by adjusting the pairing gap
at zero temperature with a strength parameter.


title:
Looking for empty topological wormhole spacetimes in $F(R)$-modified
  gravity

abstract:
  Much attention has been recently devoted to modified theories of gravity in
the attempt to efficiently describe both early inflation and late-time
acceleration of our universe without referring to the cosmological constant or
other ad hoc kinds of fluids. The simplest models overcome General Relativity
simply by replacing $R$ with $F(R)$ in the Einstein--Hilbert action.
Unfortunately, such models typically lack most of the beautiful solutions
discovered in Einstein's gravity. Nonetheless, in $F(R)$ gravity, it has been
possible to get at least few black holes, but still we do not know any empty
wormhole-like spacetime solution. The present paper aims to explain why it is
so hard to get such solutions (given that they exist). Few solutions are
derived in the simplest cases while only an implicit form has been obtained in
the non-trivial case.


title: Interacting Holstein and extended-Holstein bipolarons

abstract:
  Employing the recently developed self-consistent variational basis generation
scheme, we have investigated the bipolaron-bipolaron interaction within the
purview of Holstein-Hubbard and the extended-Holstein-Hubbard (F2H) model on a
discrete one-dimensional lattice. The density-matrix renormalization group
(DMRG) method has also been used for the Holstein-Hubbard model. We have shown
that there exists no bipolaron-bipolaron attraction in the Holstein-Hubbard
model. In contrast, we have obtained clear-cut bipolaron-bipolaron attraction
in the F2H model. Composite bipolarons are formed above a critical
electron-phonon coupling strength, which can survive the finite Hubbard $U$
effect. We have constructed the phase diagram of F2H polarons and bipolarons,
and discussed the phase separation in terms of the formation of composite
bipolarons.


title:
On Classical Solutions to the Cauchy Problem of the Two-Dimensional
  Barotropic Compressible Navier-Stokes Equations with Vacuum

abstract:
  This paper concerns the Cauchy problem of the barotropic compressible
Navier-Stokes equations on the whole two-dimensional space with vacuum as far
field density. In particular, the initial density can have compact support.
When the shear and the bulk viscosities are a positive constant and a power
function of the density respectively, it is proved that the two-dimensional
Cauchy problem of the compressible Navier-Stokes equations admits a unique
local strong solution provided the initial density decays not too slow at
infinity. Moreover, if the initial data satisfy some additional regularity and
compatibility conditions, the strong solution becomes a classical one.


title:
Galerkin Methods for Complementarity Problems and Variational
  Inequalities

abstract:
  Complementarity problems and variational inequalities arise in a wide variety
of areas, including machine learning, planning, game theory, and physical
simulation. In all of these areas, to handle large-scale problem instances, we
need fast approximate solution methods. One promising idea is Galerkin
approximation, in which we search for the best answer within the span of a
given set of basis functions. Bertsekas proposed one possible Galerkin method
for variational inequalities. However, this method can exhibit two problems in
practice: its approximation error is worse than might be expected based on the
ability of the basis to represent the desired solution, and each iteration
requires a projection step that is not always easy to implement efficiently.
So, in this paper, we present a new Galerkin method with improved behavior: our
new error bounds depend directly on the distance from the true solution to the
subspace spanned by our basis, and the only projections we require are onto the
feasible region or onto the span of our basis.


title: On Finite Block-Length Quantization Distortion

abstract:
  We investigate the upper and lower bounds on the quantization distortions for
independent and identically distributed sources in the finite block-length
regime. Based on the convex optimization framework of the rate-distortion
theory, we derive a lower bound on the quantization distortion under finite
block-length, which is shown to be greater than the asymptotic distortion given
by the rate-distortion theory. We also derive two upper bounds on the
quantization distortion based on random quantization codebooks, which can
achieve any distortion above the asymptotic one. Moreover, we apply the new
upper and lower bounds to two types of sources, the discrete binary symmetric
source and the continuous Gaussian source. For the binary symmetric source, we
obtain the closed-form expressions of the upper and lower bounds. For the
Gaussian source, we propose a computational tractable method to numerically
compute the upper and lower bounds, for both bounded and unbounded quantization
codebooks.Numerical results show that the gap between the upper and lower
bounds is small for reasonable block length and hence the bounds are tight.


title: Hybrid Group Decoding for Scalable Video over MIMO-OFDM Downlink Systems

abstract:
  We propose a scalable video broadcasting scheme over MIMO-OFDM systems. The
scalable video source layers are channel encoded and modulated into independent
signal streams, which are then transmitted from the allocated antennas in
certain time-frequency blocks. Each receiver employs the successive group
decoder to decode the signal streams of interest by treating other signal
streams as interference. The transmitter performs adaptive coding and
modulation, and transmission antenna and subcarrier allocation, based on the
rate feedback from the receivers. We also propose a hybrid receiver that
switches between the successive group decoder and the MMSE decoder depending on
the rate. Extensive simulations are provided to demonstrate the performance
gain of the proposed group-decoding-based scalable video broadcasting scheme
over the one based on the conventional MMSE decoding.


title:
Regularity of Stagnation Point-form Solutions of the Two-dimensional
  Euler Equations

abstract:
  A class of semi-bounded solutions of the two-dimensional incompressible Euler
equations satisfying either periodic or Dirichlet boundary conditions is
examined. For smooth initial data, new blowup criteria in terms of the initial
concavity profile is presented and the effects that the boundary conditions
have on the global regularity of solutions is discussed. In particular, by
deriving a formula for a general solution along Lagrangian trajectories, we
describe how periodicity can prevent blow-up. This is as opposed to Dirichlet
boundary conditions which, as we will show, allow for the formation of
singularities in finite time. Lastly, regularity of solutions arising from
non-smooth initial data is briefly discussed.


title:
Avoided quantum criticality and magnetoelastic coupling in
  BaFe$_{2-x}$Ni$_{x}$As$_{2}$

abstract:
  We study the structural and magnetic orders in electron-doped BaFe2-xNixAs2
by high-resolution synchrotron X-ray and neutron scatterings. Upon Ni-doping x,
the nearly simultaneous tetragonal-to-orthorhombic structural T_s and
antiferromagnetic (T_N) phase transitions in BaFe2As2 are gradually suppressed
and separated, resulting in T_s>T_N with increasing x as was previously
observed. However, the temperature separation between T_s and T_N decreases
with increasing x for x> 0.065$, tending towards a quantum bi-critical point
near optimal superconductivity at x=0.1. The zero-temperature transition is
preempted by the formation of a secondary incommensurate magnetic phase in the
region 0.088< x < 0.104, resulting in a finite value of T_N \approx T_c+10$ K
above the superconducting dome around $x\approx 0.1$. Our results imply an
avoided quantum critical point, which is expected to strongly influence the
properties of both the normal and superconducting states.


title: Analysing Word Importance for Image Annotation

abstract:
  Image annotation provides several keywords automatically for a given image
based on various tags to describe its contents which is useful in Image
retrieval. Various researchers are working on text based and content based
image annotations [7,9]. It is seen, in traditional Image annotation
approaches, annotation words are treated equally without considering the
importance of each word in real world. In context of this, in this work, images
are annotated with keywords based on their frequency count and word
correlation. Moreover this work proposes an approach to compute importance
score of candidate keywords, having same frequency count.


title: Multidimensional modeling of coronal rain dynamics

abstract:
  We present the first multidimensional, magnetohydrodynamic simulations which
capture the initial formation and the long-term sustainment of the enigmatic
coronal rain phenomenon. We demonstrate how thermal instability can induce a
spectacular display of in-situ forming blob-like condensations which then start
their intimate ballet on top of initially linear force-free arcades. Our
magnetic arcades host chromospheric, transition region, and coronal plasma.
Following coronal rain dynamics for over 80 minutes physical time, we collect
enough statistics to quantify blob widths, lengths, velocity distributions, and
other characteristics which directly match with modern observational knowledge.
Our virtual coronal rain displays the deformation of blobs into $V$-shaped like
features, interactions of blobs due to mostly pressure-mediated levitations,
and gives the first views on blobs which evaporate in situ, or get siphoned
over the apex of the background arcade. Our simulations pave the way for
systematic surveys of coronal rain showers in true multidimensional settings,
to connect parametrized heating prescriptions with rain statistics, ultimately
allowing to quantify the coronal heating input.


title:
Gamma-rays from millisecond pulsar population within the central stellar
  cluster in the Galactic Center

abstract:
  It was proposed that the central dense stellar cluster in the Galactic
Center, containing the mass of $\sim$4 times larger than that of the central
black hole, had been formed as a result of a merging of several massive
globular clusters. These globular clusters are expected to provide a large
number of millisecond pulsars (MSPs) within the central parsec of the Galactic
Center. We propose that the GeV $\gamma$-ray emission observed from the
Galactic Center is in fact a cumulative effect of the emission from several
globular clusters captured by the Galactic Center black hole. Moreover, the
millisecond pulsars in globular clusters accelerate leptons in their wind zones
to energies of the order of a few tens of TeV injecting them into the dense
infrared and optical radiation region present within the central parsec. We
calculate the expected TeV $\gamma$-ray emission produced by these leptons by
the Inverse Compton Scattering process in the soft radiation field. It is shown
that this emission can be responsible for the multi-TeV $\gamma$-rays observed
by the Cherenkov telescopes from the Galactic Center for reasonable densities
of the soft radiation, diffusion models for the propagation of leptons, their
injection parameters (fluxes and spectral proprieties). If the energy
conversion efficiency from the pulsars to the relativistic leptons is of the
order of 10%, then about a thousand of MSPs have to be present in the central
cluster in the Galactic Center.


title: On The Fu\v{c}ik Spectrum Of Non-Local Elliptic Operators

abstract:
  In this article, we study the Fu\v{c}ik spectrum of fractional Laplace
operator which is defined as the set of all $(\al,\ba)\in \mb
  R^2$ such that
  \begin{equation*}
  \quad \left. \begin{array}{lr}
  \quad (-\De)^s u = \al u^{+} - \ba u^{-} \; \text{in}\; \Om
  \quad \quad \quad \quad u = 0 \; \mbox{in}\; \mb R^n \setminus\Om.\\
\end{array} \quad \right\} \end{equation*} has a non-trivial solution $u$,
where $\Om$ is a bounded domain in $\mb R^n$ with Lipschitz boundary, $n>2s$,
$s\in(0,1)$. The existence of a first nontrivial curve $\mc C$ of this
spectrum, some properties of this curve $\mc C$, e.g. Lipschitz continuous,
strictly decreasing and asymptotic behavior are studied in this article. A
variational characterization of second eigenvalue of the fractional eigenvalue
problem is also obtained. At the end, we study a nonresonance problem with
respect to Fu\v{c}ik spectrum.


title: Critical Buckling Loads of the Perfect Hollomon's Power-law Columns

abstract:
  In this work, we present analytic formulas for calculating the critical
buckling states of some plastic axial columns of constant cross-sections. The
associated critical buckling loads are calculated by Euler-type analytic
formulas and the associated deformed shapes are presented in terms of
generalized trigonometric functions. The plasticity of the material is defined
by the Hollomon's power-law equation. This is an extension of the Euler
critical buckling loads of perfect elastic columns to perfect plastic columns.
In particular, critical loads for perfect straight plastic columns with
circular and rectangular cross-sections are calculated for a list of commonly
used metals. Connections and comparisons to the classical result of the
Euler-Engesser reduced-modulus loads are also presented.


title: Topological entanglement entropy in bilayer quantum Hall systems

abstract:
  We calculate the topological entanglement entropy in bilayer quantum Hall
systems, dividing the set of quantum numbers into four parts. This topological
entanglement entropy allows us to draw a phase diagram in the parameter space
of layer separation and tunneling amplitude. We perform the finite size scaling
analysis of the topological entanglement entropy in order to see the quantum
phase transition clearly.


title: A search for b(c) quark pdf uncertainties at TeV scale ep collider

abstract:
  We discuss c\bar{c} and b\bar{b} pair productions at ep collider for studying
extremely small x(g) region. It has been shown that Large Hadron electron
Collider (LHeC) has a reach of about x(g)>10^{-6}. The aim of this work is to
show that the PDF uncertainties in the heavy flavour production. Maximum
difference of cross section between PDFs 60% has been found in the process of
ep\rightarrow eq\bar{q}X.


title:
Influence of long-range interactions on charge ordering phenomena on a
  square lattice

abstract:
  Usually complex charge ordering phenomena arise due to competing
interactions. We have studied how such ordered patterns emerge from the
frustration of a long-ranged interaction on a lattice. Using the lattice gas
model on a square lattice with fixed particle density, we have identified
several interesting phases; such as a generalization of Wigner crystals at low
particle densities and stripe phases at densities in between rho = 1/3 and rho
= 1/2. These stripes act as domain walls in the checkerboard phase present at
half-filling. The phases are characterised at zero temperatures using numerical
simulations, and mean field theory is used to construct a finite temperature
phase diagram.


title: Spinor norm for skew-hermitian forms over quaternion algebras

abstract:
  We complete all local spinor norm computations for quaternionic
skew-hermitian forms over the field of rational numbers. Examples of class
number computations are provided.


title:
Weak value expansion of quantum operators and its application in
  stochastic matrices

abstract:
  It is shown that any Hermitian operator can be expanded in terms of a set of
operators formed from biorthogonal basis, and the expansion coefficients are
given as products of weight functions and weak values, shedding a new light on
the physical interpretation of the weak value. The utility of our approach is
showcased with examples of spin one-half and spin one systems, where
irreversible subset of stochastic matrices describing projective measurement on
a mixed state is identified.


title: Phase estimation with weak measurement using a white light source

abstract:
  We report results of a high precision phase estimation based on a weak
measurements scheme using commercial light-emitting diode. The method is based
on a measurement of the imaginary part of the weak value of a polarization
operator. The imaginary part of the weak value appeared due to the measurement
interaction itself. The sensitivity of our method is equivalent to resolving
light pulses of order of attosecond and it is robust against chromatic
dispersion.


title:
Evolution of correlation structure of industrial indices of US equity
  markets

abstract:
  We investigate the dynamics of correlations present between pairs of industry
indices of US stocks traded in US markets by studying correlation based
networks and spectral properties of the correlation matrix. The study is
performed by using 49 industry index time series computed by K. French and E.
Fama during the time period from July 1969 to December 2011 that is spanning
more than 40 years. We show that the correlation between industry indices
presents both a fast and a slow dynamics. The slow dynamics has a time scale
longer than five years showing that a different degree of diversification of
the investment is possible in different periods of time. On top to this slow
dynamics, we also detect a fast dynamics associated with exogenous or
endogenous events. The fast time scale we use is a monthly time scale and the
evaluation time period is a 3 month time period. By investigating the
correlation dynamics monthly, we are able to detect two examples of fast
variations in the first and second eigenvalue of the correlation matrix. The
first occurs during the dot-com bubble (from March 1999 to April 2001) and the
second occurs during the period of highest impact of the subprime crisis (from
August 2008 to August 2009).


title:
Inverse scattering problem on the half-axis for a first order system of
  ordinary differential equations

abstract:
  In this article, the inverse scattering problem (ISP) of recovering the
matrix coefficient of a first order system of ordinary differential equations
on the half-axis from its scattering matrix is considered. In the case of a
triangular structure of the matrix coefficient, this system has a Volterra-type
integral transformation operator at infinity. Such type of transformation
operator allows to determine the scattering matrix on the half-axis via the
matrix Riemann-Hilbert factorization in the case, where contour is real axis,
normalization is canonical and all the partial indices are zero. The ISP on the
half-axis is solved by reducing it to ISP on the whole axis for the considered
system with the coefficients that are extended to the whole axis as zero.


title: Entropic topological invariant for a gapped one-dimensional system

abstract:
  We propose an order parameter for a general one-dimensional gapped system
with an open boundary condition. The order parameter can be computed from the
ground state entanglement entropy of some regions near one of the boundaries.
Hence, it is well-defined even in the presence of arbitrary interaction and
disorder. We also show that it is invariant under a finite-depth local quantum
circuit, suggesting its stability against an arbitrary local perturbation that
does not close the energy gap. Further, it can unambiguously distinguish
Majorana chain from a trivial chain under a global fermion parity conservation.
We argue that the order parameter can be in principle measured in an optical
lattice system.


title:
Direct and Inverse Problems for the Heat Equation with a Dynamic type
  Boundary Condition

abstract:
  This paper considers the initial-boundary value problem for the heat equation
with a dynamic type boundary condition. Under some regularity, consistency and
orthogonality conditions, the existence, uniqueness and continuous dependence
upon the data of the classical solution are shown by using the generalized
Fourier method. This paper also investigates the inverse problem of finding a
time-dependent coefficient of the heat equation from the data of integral
overdetermination condition.


title:
Performance Bounds for Multiclass FIFO in Communication Networks: A
  Deterministic Case

abstract:
  Multiclass FIFO is used in communication networks such as in input-queueing
routers/switches and in wireless networks. For the concern of providing service
guarantees in such networks, it is crucial to have analytical results, e.g.
bounds, on the performance of multi-class FIFO. Surprisingly, there are few
such results in the literature. This paper is devoted to filling the gap.
Specifically, a single hop deterministic case is studied, for which, delay and
backlog bounds are derived, in addition to guaranteed rate and service curve
characterizations that may be exploited to extend the analysis to network
cases.


title: Repair Locality with Multiple Erasure Tolerance

abstract:
  In distributed storage systems, erasure codes with locality $r$ is preferred
because a coordinate can be recovered by accessing at most $r$ other
coordinates which in turn greatly reduces the disk I/O complexity for small
$r$. However, the local repair may be ineffective when some of the $r$
coordinates accessed for recovery are also erased.
  To overcome this problem, we propose the $(r,\delta)_c$-locality providing
$\delta -1$ local repair options for a coordinate. Consequently, the repair
locality $r$ can tolerate $\delta-1$ erasures in total. We derive an upper
bound on the minimum distance $d$ for any linear $[n,k]$ code with information
$(r,\delta)_c$-locality. For general parameters, we prove existence of the
codes that attain this bound when $n\geq k(r(\delta-1)+1)$, implying tightness
of this bound. Although the locality $(r,\delta)$ defined by Prakash et al
provides the same level of locality and local repair tolerance as our
definition, codes with $(r,\delta)_c$-locality are proved to have more
advantage in the minimum distance. In particular, we construct a class of codes
with all symbol $(r,\delta)_c$-locality where the gain in minimum distance is
$\Omega(\sqrt{r})$ and the information rate is close to 1.


title: Are rigid non-inertial frames of reference really rigid?

abstract:
  In this paper the notion of the rigid frame of reference within special
relativity is analysed. Three definitions of rigidity are formulated. By using
several examples of non-inertial frames, it is shown that these definitions are
not equivalent. It is also shown that so called M\"oller rigid non-inertial
frames are locally rigid, but do not exhibit global rigidity. The physical
meaning of this phenomenon is discussed, as well as its relation to the
non-Euclidean nature of space in non-inertial frames of reference. (russian
version)


title: The exponential map of a $C^{1,1}$-metric

abstract:
  Given a pseudo-Riemannian metric of regularity $C^{1,1}$ on a smooth
manifold, we prove that the corresponding exponential map is a bi-Lipschitz
homeomorphism locally around any point. We also establish the existence of
totally normal neighborhoods in an appropriate sense. The proofs are based on
regularization, combined with methods from comparison geometry.


title: Understanding ELM mitigation by resonant magnetic perturbations on MAST

abstract:
  Sustained ELM mitigation has been achieved using RMPs with a toroidal mode
number of n=4 and n=6 in lower single null and with n=3 in connected double
null plasmas on MAST. The ELM frequency increases by up to a factor of eight
with a similar reduction in ELM energy loss. A threshold current for ELM
mitigation is observed above which the ELM frequency increases approximately
linearly with current in the coils. A comparison of the filament structures
observed during the ELMs in the natural and mitigated stages shows that the
mitigated ELMs have the characteristics of type I ELMs even though their
frequency is higher, their energy loss is reduced and the pedestal pressure
gradient is decreased. During the ELM mitigated stage clear lobe structures are
observed in visible-light imaging of the X-point region. The size of these
lobes is correlated with the increase in ELM frequency observed. The RMPs
produce a clear 3D distortion to the plasma and it is likely that these
distortions explain why ELMs are destabilised and hence why ELM mitigation
occurs.


title:
Solutions for a class of quasilinear Schr\"{o}dinger equations with
  critical exponents term

abstract:
  In this paper, we study a class of quasilinear Schr\"{o}dinger equation of
the form $$-\varepsilon^2\Delta
u+V(x)u-\varepsilon^2(\Delta(|u|^{2\alpha}))|u|^{2\alpha-2}u
&=&\lambda|u|^{q-2}u+|u|^{2^*(2\alpha)-2}u,\quad\mbox{in}{\mathbb{R}}^N, $$
where $\varepsilon>0,\lambda>0,q\geq2,\alpha>1/2$ are constants, $N\geq3$. By
using change of variable and variational approach, the existence of positive
solution which has a local maximum point and decays exponentially is obtained.


title:
Impact of Facebook Usage on Undergraduate Students Performance in Irbid
  National University: Case Study

abstract:
  The aim of this study is to investigate the style of Facebook usage between
undergraduate students and the impact on their academics performance. Also,
this paper was evaluated in the view of student the using of Facebook. A
questioner was design for collecting data from a sample of 480 undergraduate
students in Irbid National University. The survey revealed that 77% of the
students have an account on Facebook. One of the main findings is that there
was a significant relationship between gender and Facebook usage. Moreover, the
survey revealed that whenever the less time spent on Facebook, the higher the
performance will be in grade point average. This was conducted by the negative
correlation between time spent on Facebook and the performance of undergraduate
student. Statistically speaking, the study has seven hypotheses; two of them
were rejecting against five acceptable hypotheses.


title: Explicit Upper Bounds for $|L(1, \chi)|$ when $\chi(3)=0$

abstract:
  Let $\chi$ be a primitive Dirichlet character of conductor $q$ and
$L(z,\chi)$ the associated L-series. In this paper we provide an explicit upper
bound for $|L(1, \chi)|$ when 3 divides $q$.


title: On restricted permutations on regular multisets

abstract:
  The extension of pattern avoidance from ordinary permutations to those on
multisets gave birth to several interesting enumerative results. We study
permutations on regular multisets, i.e., multisets in which each element occurs
the same number of times. For this case, we close a gap in the work of Heubach
and Mansour (2006) and complete the study of permutations avoiding a pair of
patterns of length three. In all studied cases, closed enumeration formulae are
given and well-known sequences appear. We conclude this paper by some remarks
on a generalization of the Stanley-Wilf conjecture to permutations on multisets
and words.


title:
Shared rewarding overcomes defection traps in generalized volunteer's
  dilemmas

abstract:
  For societies to produce or safeguard public goods, costly voluntary
contributions are often required. From the perspective of each individual,
however, it is advantageous not to volunteer such contributions, in the hope
that other individuals will carry the associated costs. This conflict can be
modeled as a volunteer's dilemma. To encourage rational individuals to make
voluntary contributions, a government or other social organizations can offer
rewards, to be shared among the volunteers. Here we apply such shared rewarding
to the generalized volunteer's dilemma, in which a threshold number of
volunteers is required for producing the public good. By means of theoretical
and numerical analyses, we show that without shared rewarding only two
evolutionary outcomes are possible: full defection or coexistence of volunteers
and non-volunteers. We show that already small rewards destabilize full
defection, stabilizing small fractions of volunteers instead. Furthermore, at
these intermediate reward levels, we find a hysteresis effect such that
increasing or decreasing group sizes can trigger different social outcomes. In
particular, when group size is increased, the fraction of volunteers first
increases gradually before jumping up abruptly; when group size is then
decreased again, the fraction of volunteers not only remains high, but even
continues to increase. As the shared reward is increased beyond a critical
level, the bi-stability underlying this hysteresis effect vanishes altogether,
and only a single social outcome remains, corresponding to the stable
coexistence of volunteers and non-volunteers. We find that this critical level
of shared rewarding is relatively small compared to the total cost of
contributing to the public good. These results show that the introduction of
shared rewarding is remarkably effective in overcoming defection traps in the
generalized volunteer's dilemma.


title: Model dependence of isospin sensitive observables at high densities

abstract:
  Within two different frameworks of isospin-dependent transport model, i.e.,
Boltzmann-Uehling-Uhlenbeck (IBUU04) and Ultrarelativistic Quantum Molecular
Dynamics (UrQMD) transport models, sensitive probes of nuclear symmetry energy
are simulated and compared. It is shown that neutron to proton ratio of free
nucleons, pi-/pi+ ratio as well as isospin-sensitive transverse and elliptic
flows given by the two transport models with their "best settings", all have
obvious differences. Discrepancy of numerical value of isospin-sensitive n/p
ratio of free nucleon from the two models mainly originates from different
symmetry potentials used and discrepancies of numerical value of charged
pi-/pi+ ratio and isospin-sensitive flows mainly originate from different
isospin-dependent nucleon-nucleon cross sections. These demonstrations call for
more detailed studies on the model inputs (i.e., the density- and
momentum-dependent symmetry potential and the isospin-dependent nucleon-nucleon
cross section in medium) of isospin-dependent transport model used. The studies
of model dependence of isospin sensitive observables can help nuclear
physicists to pin down the density dependence of nuclear symmetry energy
through comparison between experiments and theoretical simulations
scientifically.


title: Heat superdiffusion in plasmonic nanostructure networks

abstract:
  Heat-transport mechanism mediated by near-field interactions in plasmonic
nanostructures networks is shown to be analogous to a generalized random-walk
process. Existence of superdiffusive regimes is demonstrated both in linear
ordered chains and in three dimensional random networks by analyzing the
asymptotic behavior of the corresponding probability distribution function. We
show that the spread of heat in these networks is described by a type of
L\'{e}vy flight. The presence of such anomalous heat transport regimes in
plasmonic networks opens the way to the design of a new generation of composite
materials able to transport heat faster than the normal diffusion process in
solids.


title: Ultrafast tristable spin memory of a coherent polariton gas

abstract:
  Nonlinear interactions in coherent gases are not only at the origin of of
bright and dark solitons and superfluids. At the same time, they give rise to
phenomena such as multistability, which hold great promise for the development
of advanced photonic and spintronic devices. In particular, spinor
multistability in strongly-coupled semiconductor microcavities shows that the
spin of hundreds of exciton-polaritons can be coherently controlled, opening
the route to spin-optronic devices such as ultrafast spin memories, gates or
even neuronal communication schemes. Here, we demonstrate that switching
between the stable spin states of a driven polariton gas can be controlled by
ultrafast optical pulses. While such a long-lived spin memory necessarily
relies on strong and anisotropic spinor interactions within the coherent
polariton gas, we also highlight the crucial role of nonlinear losses and
formation of a non-radiative particle reservoir for ultrafast spin-switching.


title:
A new way to measure supermassive black hole spin in accretion disc
  dominated Active Galaxies

abstract:
  We show that disc continuum fitting can be used to constrain black hole spin
in a subclass of Narrow Line Seyfert 1 (NLS1) AGN as their low mass and high
mass accretion rate means that the disc peaks at energies just below the soft
X-ray bandpass. We apply the technique to the NLS1 PG1244+026, where the
optical/UV/X-ray spectrum is consistent with being dominated by a standard disc
component. This gives a best estimate for black hole spin which is low, with a
firm upper limit of $a_*<0.86$. This contrasts with the recent X-ray
determinations of (close to) maximal black hole spin in other NLS1 based on
relativistic smearing of the iron profile. While our data on PG1244+026 does
not have sufficient statistics at high energy to give a good measure of black
hole spin from the iron line profile, cosmological simulations predict that
black holes with similar masses have similar growth histories and so should
have similar spins. This suggests that there is a problem either in our
understanding of disc spectra, or/and X-ray reflection or/and the evolution of
black hole spin.


title: Route from spontaneous decay to complex multimode dynamics in cavity QED

abstract:
  We study the non-Markovian quantum dynamics of an emitter inside an open
multimode cavity, focusing on the case where the emitter is resonant with
high-frequency cavity modes. Based on a Green's function technique suited for
open photonic structures, we study the crossovers between three distinct
regimes as the coupling strength is gradually increased: (i) overdamped decay
with a time scale given by the Purcell modified decay rate, (ii) underdamped
oscillations with a time scale given by the effective vacuum Rabi frequency,
and (iii) pulsed revivals. The final multimode strong coupling regime (iii)
gives rise to quantum revivals of the atomic inversion on a time scale
associated with the cavity round-trip time. We show that the crucial parameter
to capture the crossovers between these regimes is the nonlinear Lamb shift,
accounted for exactly in our formalism.


title:
Exact study of surface critical exponents of polymer chains grafted to
  adsorbing boundary of fractal lattices embedded in three-dimensional space

abstract:
  We study the adsorption problem of linear polymers, when the container of the
polymer--solvent system is taken to be a member of the three dimensional
Sierpinski gasket (SG) family of fractals. Members of the SG family are
enumerated by an integer $b$ ($2\le b\le\infty$), and it is assumed that one
side of each SG fractal is impenetrable adsorbing boundary. We calculate the
critical exponents $\gamma_1, \gamma_{11}$, and $\gamma_s$ which, within the
self--avoiding walk model (SAW) of polymer chain, are associated with the
numbers of all possible SAWs with one, both, and no ends grafted on the
adsorbing impenetrable boundary, respectively. By applying the exact
renormalization group (RG) method, for $2\le b\le 4$, we have obtained specific
values for these exponents, for various type of polymer conformations. We
discuss their mutual relations and their relations with other critical
exponents pertinent to SAWs on the SG fractals.


title: Effects of M dwarf magnetic fields on potentially habitable planets

abstract:
  We investigate the effect of the magnetic fields of M dwarf (dM) stars on
potentially habitable Earth-like planets. These fields can reduce the size of
planetary magnetospheres to such an extent that a significant fraction of the
planet's atmosphere may be exposed to erosion by the stellar wind. We used a
sample of 15 active dM stars, for which surface magnetic-field maps were
reconstructed, to determine the magnetic pressure at the planet orbit and hence
the largest size of its magnetosphere, which would only be decreased by
considering the stellar wind. Our method provides a fast means to assess which
planets are most affected by the stellar magnetic field. We show that
hypothetical Earth-like planets with similar terrestrial magnetisation (1G)
orbiting at the inner (outer) edge of the habitable zone of these stars would
present magnetospheres that extend at most up to 6 (11.7) planetary radii. To
be able to sustain an Earth-sized magnetosphere, with the exception of only a
few cases, the terrestrial planet would either (1) need to orbit significantly
farther out than the traditional limits of the habitable zone; or else, (2) if
it were orbiting within the habitable zone, it would require at least a
magnetic field ranging from a few G to up to a few thousand G. By assuming a
magnetospheric size that is more appropriate for the young-Earth (3.4Gyr ago),
the required planetary magnetic fields are one order of magnitude weaker.
However, in this case, the polar-cap area of the planet, which is unprotected
from transport of particles to/from interplanetary space, is twice as large. As
the star becomes older and, therefore, its rotation rate and magnetic field
reduce, the interplanetary magnetic pressure decreases and the magnetosphere of
planets probably expands. Using an empirically derived
rotation-activity/magnetism relation,... (continues)


title: Distribution of the Smallest Eigenvalue in the Correlated Wishart Model

abstract:
  Wishart random matrix theory is of major importance for the analysis of
correlated time series. The distribution of the smallest eigenvalue for Wishart
correlation matrices is particularly interesting in many applications. In the
complex and in the real case, we calculate it exactly for arbitrary empirical
eigenvalues, i.e., for fully correlated Gaussian Wishart ensembles. To this
end, we derive certain dualities of matrix models in ordinary space. We thereby
completely avoid the otherwise unsurmountable problem of computing a highly
non-trivial group integral. Our results are compact and much easier to handle
than previous ones. Furthermore, we obtain a new universality for the
distribution of the smallest eigenvalue on the proper local scale.


title: Irreducible Jacobian derivations in positive characteristic

abstract:
  We prove that an irreducible polynomial derivation in positive characteristic
is a Jacobian derivation if and only if there exists an n-1-element p-basis of
its ring of constants. In the case of two variables we characterize these
derivations in terms of their divergence and some nontrivial constants.


title: Equatorial Circular Geodesics in the Hartle-Thorne Spacetime

abstract:
  We investigate the influence of the quadrupole moment of a rotating source on
the motion of a test particle in the strong field regime. For this purpose the
Hartle-Thorne metric, that is an approximate solution of vacuum Einstein field
equations that describes the exterior of any slowly rotating, stationary and
axially symmetric body, is used. The metric is given with accuracy up to the
second order terms in the body's angular momentum, and first order terms in its
quadrupole moment. We give, with the same accuracy, analytic equations for
equatorial circular geodesics in the Hartle-Thorne spacetime and integrate them
numerically.


title: Evolving Boolean Regulatory Networks with Epigenetic Control

abstract:
  The significant role of epigenetic mechanisms within natural systems has
become increasingly clear. This paper uses a recently presented abstract,
tunable Boolean genetic regulatory network model to explore aspects of
epigenetics. It is shown how dynamically controlling transcription via a DNA
methylation-inspired mechanism can be selected for by simulated evolution under
various single and multiple cell scenarios. Further, it is shown that the
effects of such control can be inherited without detriment to fitness.


title: Heat transport of nitrogen in helium atmospheric pressure microplasma

abstract:
  Stable DC atmospheric pressure normal glow discharges in ambient air were
produced between the water surface and the metallic capillary coupled with
influx of helium gas. Multiple independent repeated trials indicated that
vibrational temperature of nitrogen rises from 3200 to 4622 K, and rotational
temperature of nitrogen decreases from 1270 to 570 K as gas flux increasing
from 20 to 80 sccm and discharge current decreasing from 11 to 3 mA.
Furthermore, it was found that the vibrational degree of the nitrogen molecule
has priority to gain energy than the rotational degree of nitrogen molecule in
nonequilibrium helium microplasma.


title: Stiff directed lines in random media

abstract:
  We investigate the localization of stiff directed lines with bending energy
by a short-range random potential. We apply perturbative arguments, Flory
scaling arguments, a variational replica calculation, and functional
renormalization to show that a stiff directed line in 1+d dimensions undergoes
a localization transition with increasing disorder for d > 2=3. We demonstrate
that this transition is accessible by numerical transfer matrix calculations in
1+1 dimensions and analyze the properties of the disorder dominated phase in
detail. On the basis of the two-replica problem, we propose a relation between
the localization of stiff directed lines in 1+d dimensions and of directed
lines under tension in 1+3d dimensions, which is strongly supported by
identical free energy distributions. This shows that pair interactions in the
replicated Hamiltonian determine the nature of directed line localization
transitions with consequences for the critical behavior of the
Kardar-Parisi-Zhang (KPZ) equation. We support the proposed relation to
directed lines via multifractal analysis revealing an analogous Anderson
transition-like scenario and a matching correlation length exponent.
Furthermore, we quantify how the persistence length of the stiff directed line
is reduced by disorder.


title: Effects of Berry Curvature on the Collective Modes of Ultracold Gases

abstract:
  Topological energy bands have important geometrical properties described by
the Berry curvature. We show that the Berry curvature changes the hydrodynamic
equations of motion for a trapped Bose-Einstein condensate, and causes
significant modifications to the collective mode frequencies. We illustrate our
results for the case of two-dimensional Rashba spin-orbit coupling in a Zeeman
field. Using an operator approach, we derive the effects of Berry curvature on
the dipole mode in very general settings. We show that the sizes of these
effects can be large and readily detected in experiment. Collective modes
therefore provide a sensitive way to measure geometrical properties of energy
bands.


title:
Nonlinear charge transport in redox molecular junctions: a Marcus
  perspective

abstract:
  Redox molecular junctions are molecular conduction junctions that involve
more than one oxidation state of the molecular bridge. This property is derived
from the ability of the molecule to transiently localize transmitting
electrons, implying relatively weak molecule-leads coupling and, in many cases,
the validity of the Marcus theory of electron transfer. Here we study the
implications of this property on the non-linear transport properties of such
junctions. We obtain an analytical solution of the integral equations that
describe molecular conduction in the Marcus kinetic regime and use it in
different physical limits to predict some important features of nonlinear
transport in metal-molecule-metal junctions. In particular, conduction,
rectification and negative differential resistance can be obtained in different
regimes of interplay between two different conduction channels associated with
different localization properties of the excess molecular charge, without
specific assumptions about the electronic structure of the molecular bridge.
The predicted behaviors show temperature dependences typically observed in the
experiment. The validity of the proposed model and ways to test its predictions
and implement the implied control strategies are discussed


title: Symmetric Graphs and their Quotients

abstract:
  In this expository paper we describe a group theoretic characterization of
arc-transitive graphs and their quotients. When passing from a symmetric graph
to its quotient, much information is lost, but some of this information may be
recovered from a certain combinatorial design on the blocks, as well as a
bipartite graph between the blocks. We address the "extention problem" which
asks, when is this additional information sufficient to recover the original
graph?


title:
From Clarkia to Escherichia and Janus: the physics of natural and
  synthetic active colloids

abstract:
  An active colloid is a suspension of particles that transduce free energy
from their environment and use the energy to engage in intrinsically
non-equilibrium activities such as growth, replication and self-propelled
motility. An obvious example of active colloids is a suspension of bacteria
such as Escherichia coli, their physical dimensions being almost invariably in
the colloidal range. Synthetic self-propelled particles have also become
available recently, such as two-faced, or Janus, particles propelled by
differential chemical reactions on their surfaces driving a self-phoretic
motion. In these lectures, I give a pedagogical introduction to the physics of
single-particle and collective properties of active colloids, focussing on self
propulsion. I will compare and contrast phenomena in suspensions of `swimmers'
with the behaviour of suspensions of passive particles, where only Brownian
motion (discovered by Robert Brown in granules from the pollen of the wild
flower {\it Clarkia pulchella}) is relevant. I will pay particular attention to
issues that pertain to performing experiments using these active particle
suspensions, such as how to characterise the suspension's swimming speed
distribution, and include an appendix to guide physicists wanting to start
culturing motile bacteria.


title:
From local force-flux relationships to internal dissipations and their
  impact on heat engine performance: The illustrative case of a thermoelectric
  generator

abstract:
  We present an in-depth analysis of the sometimes understated role of the
principle of energy conservation in linear irreversible thermodynamics. Our
case study is that of a thermoelectric generator (TEG), which is a heat engine
of choice in irreversible thermodynamics, owing to the coupling between the
electrical and heat fluxes. We show why Onsager's reciprocal relations must be
considered locally and how internal dissipative processes emerge from the
extension of these relations to a global scale: the linear behavior of a heat
engine at the local scale is associated with a dissipation process that must
partake in the global energy balance. We discuss the consequences of internal
dissipations on the so-called efficiency at maximum power, in the light of our
comparative analyses of exoreversibility and endoreversibility on the one hand,
and of two classes of heat engines, autonomous and periodically-driven, on the
other hand. Finally, basing our analysis on energy conservation, we also
discuss recent works which claim the possibility to overcome the traditional
boundaries on efficiency imposed by finite-time thermodynamics in
thermoelectric systems with broken time-reversal symmetry; this we do by
introducing a "thermal" thermopower and an "electrical" thermopower which
permits an analysis of the thermoelectric response of the TEG considering a
possible dissymmetry between the electrical/thermal and the thermal/electrical
couplings.


title:
Experimental bit commitment based on quantum communication and special
  relativity

abstract:
  Bit commitment is a fundamental cryptographic primitive in which Bob wishes
to commit a secret bit to Alice. Perfectly secure bit commitment has been
proven impossible through asynchronous exchange of classical and quantum
information. Perfect security is however possible by restraining the exchange
of classical and quantum information to suitably chosen relativistic
constraints. This requires Alice (and Bob) to split into two remote agents
performing space-like separated classical communication, and in one agent
exchanging quantum bits with the other party. The duration of the commitment is
given by the distance between the two remote agents. The original protocol
requires the quantum communication to happen at a precise location and time
with respect to the classical communication. We show how the protocol can be
modified to relax this constraint such that the quantum part of the protocol
can be performed at any time before the actual commitment, making it much more
practical. Finally, we present an experimental demonstration of this protocol
realized with a commercial quantum key distribution system and with
synchronized classical agents located in Geneva and Singapore, yielding a
commitment time of 15 ms. Our work includes a complete security analysis,
accounting for experimental imperfections (multi-photon emission, transmission
loss, detector inefficiency and dark counts) and finite statistics.


title:
The Variable Stars from the OGLE-III Shallow Survey in the Large
  Magellanic Cloud

abstract:
  We describe variable stars found in the data collected during the OGLE-III
Shallow Survey covering the I-band magnitude range from 9.7 mag to 14.5 mag.
The main result is the extension of period--luminosity relations for Cepheids
up to 134 days. We also detected 82 binary systems and 110 long-period
variables not present in the main OGLE catalogs. Additionally 558 objects were
selected as candidates for miscellaneous variables.


title: Tidal indicators in the spacetime of a rotating deformed mass

abstract:
  Tidal indicators are commonly associated with the electric and magnetic parts
of the Riemann tensor (and its covariant derivatives) with respect to a given
family of observers in a given spacetime. Recently, observer-dependent tidal
effects have been extensively investigated with respect to a variety of special
observers in the equatorial plane of the Kerr spacetime. This analysis is
extended here by considering a more general background solution to include the
case of matter which is also endowed with an arbitrary mass quadrupole moment.
Relation with curvature invariants and Bel-Robinson tensor, i.e.,
observer-dependent super-energy density and super-Poynting vector, are
investigated too.


title: Pseudo spin torque induced by strain field of Dirac fermions in graphene

abstract:
  In contrast to recent description [Phys. Rev. Lett. 106 (2011)116803], we
show that pseudo spin in graphene is not completely a real angular momentum.
The pseudo spin only in the direction perpendicular to graphene sheet is real
angular momentum, while the pseudo spin parallel to graphene plane is still not
real angular momentum. Interestingly, it is also shown that the Newtonian-like
force and pseudo spin torque of massive Dirac electrons in graphene under
strain field mimic gravitomagnetic force and gravitomagnetic spin torque,
respectively. This is due to the equivalence of pseudo spin and velocity
operators of 2+1 dimensional massive electrons in graphene, different from that
in real 3+1 dimensional Dirac fields. This work reveals new physical property
of graphene as a pseudo gravitomagnetic material.


title: Convex Relaxations for Permutation Problems

abstract:
  Seriation seeks to reconstruct a linear order between variables using
unsorted, pairwise similarity information. It has direct applications in
archeology and shotgun gene sequencing for example. We write seriation as an
optimization problem by proving the equivalence between the seriation and
combinatorial 2-SUM problems on similarity matrices (2-SUM is a quadratic
minimization problem over permutations). The seriation problem can be solved
exactly by a spectral algorithm in the noiseless case and we derive several
convex relaxations for 2-SUM to improve the robustness of seriation solutions
in noisy settings. These convex relaxations also allow us to impose structural
constraints on the solution, hence solve semi-supervised seriation problems. We
derive new approximation bounds for some of these relaxations and present
numerical experiments on archeological data, Markov chains and DNA assembly
from shotgun gene sequencing data.


title: Symplectic form on hyperpolygon spaces

abstract:
  In [GM], a family of parabolic Higgs bundles on $CP^1$ has been constructed
and identified with a moduli space of hyperpolygons. Our aim here is to give a
canonical alternative construction of this family. This enables us to compute
the Higgs symplectic form for this family and show that the isomorphism of [GM]
is a symplectomorphism.


title: Nonlinear continuous integral-derivative observer

abstract:
  In this paper, a high-order nonlinear continuous integral-derivative observer
is presented based on finite-time stability and singular perturbation
technique. The proposed integral-derivative observer can not only obtain the
multiple integrals of a signal, but can also estimate the derivatives.
Conditions are given ensuring finite-time stability for the presented
integral-derivative observer, and the stability and robustness in time domain
are analysed. The merits of the presented integral-derivative observer include
its synchronous estimation of integrals and derivatives, finite-time stability,
ease of parameters selection, sufficient stochastic noises rejection and almost
no drift phenomenon. The theoretical results are confirmed by computational
analysis and simulations.


title: Observational Constraints on Modified Chaplygin Gas from Cosmic Growth

abstract:
  We investigate the linear growth function for the large scale structures of
the universe considering modified Chaplygin gas as dark energy. Taking into
account observational growth data for a given range of redshift from the
Wiggle-Z measurements and rms mass fluctuations from Ly-$\alpha$ measurements
we numerically analyze cosmological models to constrain the parameters of the
MCG. The observational data of Hubble parameter with redshift ($Z$) is also
considered. The Wang-Steinhardt ansatz for growth index $\gamma$ and growth
function $f$ (defined as $f=\Omega_{m}^{\gamma} (a)$) are considered for the
numerical analysis. The best-fit values of the equation of state parameters
obtained here is employed to study the growth function $(f)$, growth index
($\gamma$) and state parameter ($\omega$) with redshift $z$. We note that MCG
satisfactorily accommodates an accelerating phase followed by a matter
dominated universe.


title:
Hygrothermal effects on free vibration and buckling of laminated
  composites with cutouts

abstract:
  The effect of moisture concentration and the thermal gradient on the free
flexural vibration and buckling of laminated composite plates are investigated.
The effect of a centrally located cutout on the global response is also
studied. The analysis is carried out within the framework of the extended
finite element method. A Heaviside function is used to capture the jump in the
displacement and an enriched shear flexible 4-noded quadrilateral element is
used for the spatial discretization. The formulation takes into account the
transverse shear deformation and accounts for the lamina material properties at
elevated moisture concentrations and temperature. The influence of the plate
geometry, the geometry of the cutout, the moisture concentration, the thermal
gradient and the boundary conditions on the free flexural vibration is
numerically studied.


title:
A matrix differential Harnack estimate for a class of ultraparabolic
  equations

abstract:
  Let $u$ be a positive solution of the ultraparabolic equation
\begin{equation*} \partial_t u=\sum_{i=1}^n \partial_{x_i}^2 u+\sum_{i=1}^k
x_i\partial_{x_{n+i}}u \hspace{8mm} \mbox{on} \hspace{4mm}
\mathbb{R}^{n+k}\times (0,T), \end{equation*} where $1\leq k\leq n$ and $0<T
\leq +\infty$. Assume that $u$ and its derivatives (w.r.t. the space variables)
up to the second order are bounded on any compact subinterval of $(0,T)$. Then
the difference $H(\log u)- H(\log f)$ of the Hessian matrices of $\log u$ and
of $\log f$ (both w.r.t. the space variables) is non-negatively definite, where
$f$ is the fundamental solution of the above equation with pole at the origin
$(0,0)$. The estimate in the case $n=k=1$ is due to Hamilton. As a corollary we
get that $\Delta l+\frac{n+3k}{2t}+\frac{6k}{t^3}\geq 0$, where $l=\log u$, and
$\Delta=\sum_{i=1}^{n+k} \partial_{x_i}^2 $.


title:
Analysis of functionally graded material plates using triangular
  elements with cell-based smoothed discrete shear gap method

abstract:
  In this paper, a cell based smoothed finite element method with discrete
shear gap technique is employed to study the static bending, free vibration,
mechanical and thermal buckling behaviour of functionally graded material (FGM)
plates. The plate kinematics is based on the first order shear deformation
theory and the shear locking is suppressed by a discrete shear gap method. The
shear correction factors are evaluated by employing the energy equivalence
principle. The material property is assumed to be temperature dependent and
graded only in the thickness direction. The effective properties are computed
by using the Mori-Tanaka homogenization method. The accuracy of the present
formulation is validated against available solutions. A systematic parametric
study is carried out to examine the influence the gradient index, the plate
aspect ratio, skewness of the plate and the boundary conditions on the global
response of the FGM plates. The effect of a centrally located circular cutout
on the global response is also studied.


title: Irreversibility and hysteresis in redox molecular conduction junctions

abstract:
  In this work we present and discuss theoretical models of redox molecular
junctions that account for recent observations of nonlinear charge transport
phenomena, such as hysteresis and hysteretic negative differential resistance
(NDR). A defining feature in such models is the involvement of at least two
conduction channels - a slow channel that determines transitions between charge
states of the bridge and a fast channel that dominates its conduction. Using
Marcus theory of heterogeneous electron transfer (ET) at metal-molecule
interfaces we identify and describe different regimes of nonlinear conduction
through redox molecular bridges, where the transferring charge can be highly
localized around the redox moiety. This localization and its stabilization by
polarization of the surrounding medium and/or conformational changes can lead
to decoupling of the current response dynamics from the timescale of the
voltage sweep (that is, the current does not adiabatically follow the voltage),
hence to the appearance of memory (thermodynamic irreversibility) in this
response that is manifested by hysteresis in current-voltage cycles. In
standard voltammetry such irreversibility leads to relative shift of the
current peaks along the forward and backward voltage sweeps. The common origin
of these behaviors is pointed out and expressions of the threshold voltage
sweep rates are provided. In addition, the theory is extended (a) to analyze
the different ways by which such phenomena are manifested in single sweep
cycles and in ensemble averages of such cycles, and (b) to examine quantum
effects in the fast transport channel.


title:
Optical IFU observations of gas pillars surrounding the super star
  cluster NGC 3603

abstract:
  We present optical integral field unit (IFU) observations of two gas pillars
surrounding the Galactic young massive star cluster NGC 3603. The high S/N and
spectral resolution of these data have allowed us to accurately quantify the
H-alpha, [NII] and [SII] emission line shapes, and we find a mixture of broad
(FWHM~70-100 km/s) and narrow (<50 km/s) components. The broad components are
found close to the edges of both pillars, suggesting that they originate in
turbulent mixing layers (TMLs) driven by the effect of the star cluster wind.
Both pillars exhibit surprisingly high ionized gas densities of >10000 cm-3. In
one pillar we found that these high densities are only found in the narrow
component, implying it must originate from deeper within the pillar than the
broad component. From this, together with our kinematical data, we conclude
that the narrow component traces a photoevaporation flow, and that the TML
forms at the interface with the hot wind. On the pillar surfaces we find a
consistent offset in radial velocity between the narrow (brighter) components
of H-alpha and [NII] of ~5-8 km/s, for which we were unable to find a
satisfactory explanation. We urge the theoretical community to simulate
mechanical and radiative cloud interactions in more detail to address the many
unanswered questions raised by this study.


title:
Gr\"obner bases and some immersion theorems for Grassmann manifolds
  G_{3,n}

abstract:
  A Gr\"obner basis for the ideal determining mod 2 cohomology of Grassmannian
G_{3,n} is obtained. This is used, along with the method of obstruction theory,
to establish some new immersion results for these manifolds.


title:
Prediction of thermomagnetic and thermoelectric properties for novel
  materials and systems

abstract:
  We express the link between conductivity and coefficients of Seebeck,
Nernst-Ettingshausen, Peltier, and Thompson and Reghi-Leduc via the temperature
derivative of the chemical potential of a system. These general expressions are
applied to three-, two- and one-dimensional systems of charge carriers having a
parabolic or Dirac spectrum. The method allows for predicting thermoelectric
and thermomagnetic properties of novel materials and structures.


title:
On differentiability of stochastic flow for a multidimensional SDE with
  discontinuous drift

abstract:
  We consider a $d$-dimensional SDE with an identity diffusion matrix and a
drift vector being a vector function of bounded variation. We give a
representation for the derivative of the solution with respect to the initial
data.


title: Scaling forms for Relaxation Times of the Fiber Bundle model

abstract:
  Using extensive numerical analysis of the Fiber Bundle Model with Equal Load
Sharing dynamics we studied the finite-size scaling forms of the relaxation
times against the deviations of applied load per fiber from the critical point.
Our most crucial result is we have not found any $\ln (N)$ dependence of the
average relaxation time $\langle T(\sigma,N) \rangle$ in the precritical state.
The other results are: (i) The critical load $\sigma_c(N)$ for the bundle of
size $N$ approaches its asymptotic value $\sigma_c(\infty)$ as $\sigma_c(N) =
\sigma_c(\infty) + AN^{-1/\nu}$. (ii) Right at the critical point the average
relaxation time $\langle T(\sigma_c(N),N) \rangle$ scales with the bundle size
$N$ as: $\langle T(\sigma_c(N),N) \rangle \sim N^{\eta}$ and this behavior
remains valid within a small window of size $|\Delta \sigma| \sim N^{-\zeta}$
around the critical point. (iii) When $1/N < |\Delta \sigma| < 100N^{-\zeta}$
the finite-size scaling takes the form: $\langle T(\sigma,N) \rangle / N^{\eta}
\sim {\cal G}[\{\sigma_c(N)-\sigma\}N^{\zeta}]$ so that in the limit of $N \to
\infty$ one has $\langle T(\sigma) \rangle \sim (\sigma - \sigma_c)^{-\tau}$.
  The high precision of our numerical estimates led us to verify that $\nu =
3/2$, conjecture that $\eta = 1/3$, $\zeta = 2/3$ and therefore $\tau = 1/2$.


title: On the chromatic number of a simplicial complex

abstract:
  In [Ho] A.J. Hoffman proved a lower bound on the chromatic number of a graph
in the terms of the largest and the smallest eigenvalues of its adjacency
matrix. In this paper, we prove a higher dimensional version of this result and
give a lower bound on the chromatic number of a pure $d$-dimensional simplicial
complex in the terms of the spectra of the higher Laplacian operators.


title: A note on a residual subset of Lipschitz functions on metric spaces

abstract:
  Let (X, d) be a quasi-convex, complete and separable metric space with
reference probability measure m. We prove that the set of of real valued
Lipschitz function with non zero point-wise Lipschitz constant m-almost
everywhere is residual, and hence dense, in the Banach space of Lipschitz and
bounded functions. The result is the metric analogous of a result proved for
real valued Lipschitz maps defined on R2 by Alberti, Bianchini and Crippa in
[1].


title: An Atlas of subgroup lattices of finite almost simple groups

abstract:
  We announce an atlas of subgroup lattices of almost simple groups and present
two algorithms that were used to produce the atlas.


title: A class of representations of Hecke algebras

abstract:
  A type of directed multigraph called a W-digraph is introduced to model the
structure of certain representations of Hecke algebras, including those
constructed by Lusztig and Vogan from involutions in a Weyl group. Building on
results of Lusztig, a complete characterization of W-digraphs is given in terms
of subdigraphs for dihedral parabolic subgroups. Graph-theoretic properties of
W-digraphs are established including, under certain assumptions, acyclicity. In
case the Coxeter system is finite, a bound on the number of vertices of a
connected W-digraph is obtained, and a graph-theoretic version of the usual
duality operation is obtained.


title: Photospheric emission from stratified jets

abstract:
  We explore photospheric emissions from stratified two-component jets, wherein
a highly relativistic spine outflow is surrounded by a wider and less
relativistic sheath outflow. Thermal photons are injected in regions of high
optical depth and propagated until they escape at the photosphere. Due to the
presence of shear in velocity (Lorentz factor) at the boundary of the spine and
sheath region, a fraction of the injected photons are accelerated via a
Fermi-like acceleration mechanism such that a high energy power-law tail is
formed in the resultant spectrum. We show, in particular, that if a velocity
shear with a considerable variance in the bulk Lorentz factor is present, the
high energy part of observed Gamma-ray Bursts (GRBs) photon spectrum can be
explained by this photon acceleration mechanism. We also show that the
accelerated photons may also account for the origin of the extra hard power-law
component above the bump of the thermal-like peak seen in some peculiar bursts
(e.g., GRB 090510, 090902B, 090926A). It is demonstrated that time-integrated
spectra can also reproduce the low energy spectrum of GRBs consistently due to
a multi-temperature effect when time evolution of the outflow is considered.
Finally, we show that the empirical Ep-Lp relation can be explained by
differences in the outflow properties of individual sources.


title: RF field-attenuation formulae for the multilayer coating model

abstract:
  Formulae that describe the RF electromagnetic field attenuation for the
multilayer coating model with a single superconductor layer and a single
insulator layer deposited on a bulk superconductor are derived from a rigorous
calculation with the Maxwell equations and the London equation.


title:
Fluctuational-electrodynamic theory and dynamics of heat transfer in
  multiple dipolar systems

abstract:
  A general fluctuational-electrodynamic theory is developed to investigate
radiative heat exchanges between objects which are assumed small compared with
their thermal wavelength (dipolar approximation) in N-body systems immersed in
a thermal bath. This theoretical framework is applied to study the dynamic of
heating/cooling of three-body systems. We show that many-body interactions
allow to tailor the temperature field distribution and to drastically change
the time scale of thermal relaxation processes.


title: A bright ultraluminous X-ray source in NGC 5907

abstract:
  We present a multi-mission X-ray analysis of a bright (peak observed 0.3-10
keV luminosity of ~ 6x10^{40} erg s^{-1}), but relatively highly absorbed ULX
in the edge-on spiral galaxy NGC 5907. The ULX is spectrally hard in X-rays
(Gamma ~ 1.2-1.7, when fitted with an absorbed power-law), and has a
previously-reported hard spectral break consistent with it being in the
ultraluminous accretion state. It is also relatively highly absorbed for a ULX,
with a column of ~ 0.4-0.9x10^{22} atom cm^{-2} in addition to the
line-of-sight column in our Galaxy. Although its X-ray spectra are well
represented by accretion disc models, its variability characteristics argue
against this interpretation. The ULX spectra instead appear dominated by a
cool, optically-thick Comptonising corona. We discuss how the measured 9 per
cent rms variability and a hardening of the spectrum as its flux diminishes
might be reconciled with the effects of a very massive, radiatively-driven
wind, and subtle changes in the corona respectively. We speculate that the cool
disc-like spectral component thought to be produced by the wind in other ULXs
may be missing from the observed spectrum due to a combination of a low
temperature (~ 0.1 keV), and the high column to the ULX. We find no evidence,
other than its extreme X-ray luminosity, for the presence of an intermediate
mass black hole (~ 10^2 - 10^4 Msun) in this object. Rather, the observations
can be consistently explained by a massive (greater than ~ 20 Msun) stellar
remnant black hole in a super-Eddington accretion state.


title: Embeddings for solutions of Einstein equations

abstract:
  We study isometric embeddings of some solutions of the Einstein equations
with suffciently high symmetries into a flat ambient space. We briefly describe
a method for constructing surfaces with a given symmetry. We discuss all
minimal embeddings of the Schwarzschild metric obtained using this method and
show how the method can be used to construct all minimal embeddings for the
Friedmann models. We classify all the embeddings in terms of realizations of
symmetries of the corresponding solutions.


title: Primitive Groups Synchronize Non-uniform Maps of Extreme Ranks

abstract:
  Let $\Omega$ be a set of cardinality $n$, $G$ a permutation group on
$\Omega$, and $f:\Omega\to\Omega$ a map which is not a permutation. We say that
$G$ synchronizes $f$ if the semigroup $\langle G,f\rangle$ contains a constant
map.
  The first author has conjectured that a primitive group synchronizes any map
whose kernel is non-uniform. Rystsov proved one instance of this conjecture,
namely, degree $n$ primitive groups synchronize maps of rank $n-1$ (thus, maps
with kernel type $(2,1,\ldots,1)$). We prove some extensions of Rystsov's
result, including this: a primitive group synchronizes every map whose kernel
type is $(k,1,\ldots,1)$. Incidentally this result provides a new
characterization of imprimitive groups. We also prove that the conjecture above
holds for maps of extreme ranks, that is, ranks 3, 4 and $n-2$.
  These proofs use a graph-theoretic technique due to the second author: a
transformation semigroup fails to contain a constant map if and only if it is
contained in the endomorphism semigroup of a non-null (simple undircted) graph.
  The paper finishes with a number of open problems, whose solutions will
certainly require very delicate graph theoretical considerations.


title: ESPOON: Enforcing Encrypted Security Policies in Outsourced Environments

abstract:
  The enforcement of security policies in outsourced environments is still an
open challenge for policy-based systems. On the one hand, taking the
appropriate security decision requires access to the policies. However, if such
access is allowed in an untrusted environment then confidential information
might be leaked by the policies. Current solutions are based on cryptographic
operations that embed security policies with the security mechanism. Therefore,
the enforcement of such policies is performed by allowing the authorised
parties to access the appropriate keys. We believe that such solutions are far
too rigid because they strictly intertwine authorisation policies with the
enforcing mechanism.
  In this paper, we want to address the issue of enforcing security policies in
an untrusted environment while protecting the policy confidentiality. Our
solution ESPOON is aiming at providing a clear separation between security
policies and the enforcement mechanism. However, the enforcement mechanism
should learn as less as possible about both the policies and the requester
attributes.