title: Dynamical evolution and chronology of the Hygiea asteroid family

abstract:
  The asteroid (10) Hygiea is the fourth largest asteroid of the Main Belt, by
volume and mass, and it is the largest member of its own family. Previous works
investigated the long-term effects of close encounters with (10) Hygiea of
asteroids in the orbital region of the family, and analyzed the taxonomical and
dynamical properties of members of this family. In this paper we apply the
high-quality SDSS-MOC4 taxonomic scheme of DeMeo and Carry (2013) to members of
the Hygiea family core and halo, we obtain an estimate of the minimum time and
number of encounter necessary to obtain a $3\sigma$ (or 99.7%) compatible
frequency distribution function of changes in proper $a$ caused by close
encounters with (10) Hygiea, we study the behavior of asteroids near secular
resonance configurations, in the presence and absence of the Yarkovsky force,
and obtain a first estimate of the age of the family based on orbital diffusion
by the Yarkovsky and YORP effects with two methods.
  The Hygiea family is at least 2 Byr old, with an estimated age of $T =
3200^{+380}_{-120}$ Myr and a relatively large initial ejection velocity field,
according to the approach of Vokrouhlick\'{y} et al. (2006a, b). Surprisingly,
we found that the family age can be shortened by $\simeq$ 25% if the dynamical
mobility caused by close encounters with (10) Hygiea is also accounted for,
which opens interesting new research lines for the dynamical evolution of
families associated with massive bodies. In our taxonomical analysis of the
Hygiea asteroid family, we also identified a new V-type candidate: the asteroid
(177904) (2005 SV5). If confirmed, this could be the fourth V-type object ever
to be identified in the outer main belt.


title: On applications of Mathematica Package "FAPT" in QCD

abstract:
  We consider computational problems in the framework of nonpower Analityc
Perturbation Theory and Fractional Analytic Perturbation Theory that are the
generalization of the standard QCD perturbation theory. The singularity-free,
finite couplings ${\cal A}_{\nu}(Q^2),{\mathfrak A}_{\nu}(s)$ appear in these
approaches as analytic images of the standard QCD coupling powers
$\alpha_s^{\nu}(Q^2)$ in the Euclidean and Minkowski domains, respectively. We
provide a package "FAPT" based on the system Mathematica for QCD calculations
of the images ${\mathcal A}_{\nu}(Q^2)$, ${\mathfrak A}_{\nu}(s)$ up to N$^3$LO
of renormalization group evolution. Application of these approaches to Bjorken
sum rule analysis and $Q^2$-evolution of higher twist $\mu_4^{p-n}$ is
considered.


title: Multipass greedy coloring of simple uniform hypergraphs

abstract:
  Let $m^*(n)$ be the minimum number of edges in an $n$-uniform simple
hypergraph that is not two colorable. We prove that
$m^*(n)=\Omega(4^n/\ln^2(n))$. Our result generalizes to $r$-coloring of
$b$-simple uniform hypergraphs. For fixed $r$ and $b$ we prove that a maximum
vertex degree in $b$-simple $n$-uniform hypergraph that is not $r$-colorable
must be $\Omega(r^n /\ln(n))$. By trimming arguments it implies that every such
graph has $\Omega((r^n /\ln(n))^{b+1/b})$ edges. For any fixed $r \geq 2$ our
techniques yield also a lower bound $\Omega(r^n/\ln(n))$ for van der Waerden
numbers $W(n,r)$.


title: Adaptive Push-Then-Pull Gossip Algorithm for Scale-free Networks

abstract:
  Real life networks are generally modelled as scale free networks. Information
diffusion in such networks in decentralised environment is a difficult and
resource consuming affair. Gossip algorithms have come up as a good solution to
this problem. In this paper, we have proposed Adaptive First Push Then Pull
gossip algorithm. We show that algorithm works with minimum cost when the
transition round to switch from Adaptive Push to Adaptive Pull is close to
Round(log(N)). Furthermore, we compare our algorithm with Push, Pull and First
Push Then Pull and show that the proposed algorithm is the most cost efficient
in Scale Free networks.


title: Quantum discord from system-environment correlations

abstract:
  In an initially uncorrelated mixed separable bi-partite system, quantum
correlations can emerge under the action of a local measurement or local noise
[A. Streltsov, H. Kampermann, and D. Bru\ss{}, Phys. Rev. Lett. 107, 170502
(2011)]. We analyze this counter-intuitive phenomenon using quantum discord as
a quantifier. We then relate changes in quantum discord to system-environment
correlations between the system in a mixed state and some purifying
environmental mode using the Koashi-Winter inequality. On this basis, we
suggest an interpretation of discord as a byproduct of transferring
entanglement and correlations around the different subsystems of a global pure
state.


title:
Quadrupole collectivity in neutron-deficient Sn nuclei: \nuc{104}{Sn}
  and the role of proton excitations

abstract:
  We report on the experimental study of quadrupole collectivity in the
neutron-deficient nucleus \nuc{104}{Sn} using intermediate-energy Coulomb
excitation. The $B(E2; 0^+_1 \rightarrow 2^+_1)$ value for the excitation of
the first $2^+$ state in \nuc{104}{Sn} has been measured to be
$0.180(37)~e^2$b$^2$ relative to the well-known $B(E2)$ value of \nuc{102}{Cd}.
This result disagrees by more than one sigma with a recently published
measurement \cite{Gua13}. Our result indicates that the most modern many-body
calculations remain unable to describe the enhanced collectivity below
mid-shell in Sn approaching $N=Z=50$. We attribute the enhanced collectivity to
proton particle-hole configurations beyond the necessarily limited shell-model
spaces and suggest the asymmetry of the $B(E2)$-value trend around mid-shell to
originate from enhanced proton excitations across $Z=50$ as $N=Z$ is
approached.


title:
Towards Applying Text Mining Techniques on Software Quality Standards
  and Models

abstract:
  Many of quality approaches are described in hundreds of textual pages. Manual
processing of information consumes plenty of resources. In this report we
present a text mining approach applied on CMMI, one well known and widely known
quality approach. The text mining analysis can provide a quick overview on the
scope of a quality approaches. The result of the analysis could accelerate the
understanding and the selection of quality approaches.


title:
Screening effect on the optical absorption in graphene and metallic
  monolayers

abstract:
  Screening is one of the fundamental concepts in solid state physics. It has a
great impact on the electronic properties of graphene where huge mobilities
were observed in spite of the large concentration of charged impurities. While
static screening has successfully explained DC mobilities, screening properties
can be significantly changed at infrared or optical frequencies. In this paper
we discuss the influence of dynamical screening on the optical absorption of
graphene and other 2D electron systems like metallic monolayers. This research
is motivated by recent experimental results which pointed out that graphene
plasmon linewidths and optical scattering rates can be much larger than
scattering rates determined by DC mobilities. Specifically we discuss a process
where a photon incident on a graphene plane can excite a plasmon by scattering
from an impurity, or surface optical phonon of the substrate.


title:
Multiplicativity of superoperator norms for some entanglement breaking
  channels

abstract:
  It is known that the minimal output entropy is additive for any product of
entanglement breaking (EB) channels. The same is true for the Renyi entropy,
where additivity is equivalent to multiplicativity of the $1 \rightarrow q$
norm for all $q \ge 1$. In this paper we consider the related question of
multiplicativity of the $2 \rightarrow q$ norm for entanglement breaking
channels. We prove that multiplicativity holds in this case for certain classes
of EB channels, including both the CQ and QC channels.


title: Gamma ray emission in Fermi bubbles and Higgs portal dark matter

abstract:
  It has been recently pointed out that the excess of the gamma ray spectrum in
the Fermi Bubbles at low latitude can be well explained by the annihilation of
dark matter particles. The best-fit candidate corresponds to the annihilation
of a dark matter with mass of around $62$ GeV into $b \bar{b}$ with the cross
section, $\sigma v \simeq 3.3 \times 10^{-26}$ cm$^3$/s, or the annihilation of
a dark matter with mass of around $10$ GeV into a tau lepton pair with the
cross section, $\sigma v \simeq 5.6 \times 10^{-27}$ cm$^3$/s. We point out
that the Higgs portal dark matter models are perfectly compatible with this
interpretation of the dark matter annihilation, satisfying other
phenomenological constraints. We also show that the parameter region which
reproduces the bet-fit values can be partly explored by the future direct dark
matter search at the XENON1T.


title: Neutrinos: Theory and Phenomenology

abstract:
  The theory and phenomenology of neutrinos will be addressed, especially that
relating to the observation of neutrino flavor transformations. The current
status and implications for future experiments will be discussed with special
emphasis on the experiments that will determine the neutrino mass ordering, the
dominant flavor content of the neutrino mass eigenstate with the smallest
electron neutrino content and the size of CP violation in the neutrino sector.
Beyond the neutrino Standard Model, the evidence for and a possible definitive
experiment to confirm or refute the existence of light sterile neutrinos will
be briefly discussed.


title: Spectral Triples and Generalized Crossed Products

abstract:
  We give a construction allowing to lift spectral triples to crossed products
by Hilbert bimodules. The spectral triple one obtains is a concrete unbounded
representative of the Kasparov product of the spectral triple and the
Pimsner-Toeplitz extension associated to the crossed product by the Hilbert
bimodule. To prove that the lifted spectral triple is the above-mentioned
Kasparov product, we rely on operator-$*$-algebras and connexions.


title: Drell-Yan processes with WINHAC

abstract:
  We present the Monte Carlo event generator WINHAC for Drell-Yan processes in
proton-proton, proton-antiproton, proton-ion and ion-ion collisions. It
features multiphoton radiation within the Yennie-Frautschi-Suura exclusive
exponentiation scheme with O(alpha) electroweak corrections for the
charged-current (W+/W-) processes and multiphoton radiation generated by PHOTOS
for neutral-current (Z+gamma) ones. For the initial-state QCD/QED parton shower
and hadronisation it is interfaced with PYTHIA. It includes several options,
e.g. for the polarized W-boson production, generation of weighted/unweighted
events, etc. WINHAC was cross-checked numerically at the per-mille level with
independent Monte Carlo programs, such as HORACE and SANC. It has been used as
a basic tool for developing and testing some new methods of precise
measurements of the Standard Model parameters at the LHC, in particular the
W-boson mass. Recently, it has been applied to simulations of double Drell-Yan
processes resulting from double-parton scattering, in order to assess their
influence on the Higgs-boson detection at the LHC in its ZZ and W+W- decay
channels.


title: A note on the existence of non-monotone non-oscillating wavefronts

abstract:
  In this note, we present a monostable delayed reaction-diffusion equation
with the unimodal birth function which admits only non-monotone wavefronts.
Moreover, these fronts are either eventually monotone (in particular, such is
the minimal wave) or slowly oscillating. Hence, for the Mackey-Glass type
diffusive equations, we answer affirmatively the question about the existence
of non-monotone non-oscillating wavefronts. As it was recently established by
Hasik {\it et al.} and Ducrot {\it et al.}, the same question has a negative
answer for the KPP-Fisher equation with a single delay.


title: Quantum black holes in Loop Quantum Gravity

abstract:
  We study the quantization of spherically symmetric vacuum spacetimes within
loop quantum gravity. In particular, we give additional details about our
previous work in which we showed that one could complete the quantization the
model and that the singularity inside black holes is resolved. Moreover, we
consider an alternative quantization based on a slightly different kinematical
Hilbert space. The ambiguity in kinematical spaces stems from how one treats
the periodicity of one of the classical variables in these models. The
corresponding physical Hilbert spaces solve the diffeomorphism and Hamiltonian
constraint but their intrinsic structure is radically different depending on
the kinematical Hilbert space one started from. In both cases there are quantum
observables that do not have a classical counterpart. However, one can show
that at the end of the day, by examining Dirac observables, both quantizations
lead to the same physical predictions.


title: Critical behavior of 3D Z(N) lattice gauge theories at zero temperature

abstract:
  Three-dimensional $Z(N)$ lattice gauge theories at zero temperature are
studied for various values of $N$. Using a modified phenomenological
renormalization group, we explore the critical behavior of the generalized
$Z(N)$ model for $N=2,3,4,5,6,8$. Numerical computations are used to simulate
vector models for $N=2,3,4,5,6,8,13,20$ for lattices with linear extension up
to $L=96$. We locate the critical points of phase transitions and establish
their scaling with $N$. The values of the critical indices indicate that the
models with $N>4$ belong to the universality class of the three-dimensional
$XY$ model. However, the exponent $\alpha$ derived from the heat capacity is
consistent with the Ising universality class. We discuss a possible resolution
of this puzzle. We also demonstrate the existence of a rotationally symmetric
region within the ordered phase for all $N\geq 5$ at least in the finite
volume.


title:
Electron sampling depth and saturation effects in perovskite films
  investigated by soft x-ray absorption spectroscopy

abstract:
  Knowledge of the electron sampling depth and related saturation effects is
important for quantitative analysis of X-ray absorption spectroscopy data, yet
for oxides with the perovskite structure no quantitative values are so far
available. Here we study absorption saturation in films of two of the
most-studied perovskites, LCMO and YBCO, at the L2,3 edge of Mn and Cu,
respectively. By measuring the electron-yield intensity as a function of photon
incidence angle and film thickness, the sampling depth d, photon attenuation
length, lambda, and the ratio lambda/d have been independently determined
between 50 and 300 K. The extracted sampling depth dLCMO=3 nm for LCMO at high
temperatures in its polaronic insulator state (150-300K) is not much larger
than values reported for pure transition metals (d Co or Ni=2-2.5nm) at room
temperature, but it is smaller than dYBCO=3.9 nm for metallic YBCO that is in
turn smaller than the value reported for Fe3O4 (d=4.5 nm) The measured dLCMO
increases to 4.5 nm when LCMO is in the metallic state at low temperatures.
These results indicate that a universal rule of thumb for the sampling depth in
oxides cannot be assumed, and that it can be measurably influenced by
electronic phase transitions that derive from strong correlations.


title:
Improvement of Automatic Hemorrhages Detection Methods Using Shapes
  Recognition

abstract:
  Diabetic Retinopathy is a medical condition where the retina is damaged
because fluid leaks from blood vessels into the retina. The presence of
hemorrhages in the retina is the earliest symptom of diabetic retinopathy. The
number and shape of hemorrhages is used to indicate the severity of the
disease. Early automated hemorrhage detection can help reduce the incidence of
blindness. This paper introduced new method depending on the hemorrhage shape
to detect the dot hemorrhage (DH), its number, and size at early stage, this
can be achieved by reducing the retinal image details. Detection and recognize
the DH by following three sequential steps, removing the fovea, removing the
vasculature and recognize DH by determining the circularity for all the objects
in the image, finally determine the shape factor which is related to DH
recognition, this stage strengthens the recognition process. The proposed
method recognizes and separates all the DH.


title: Conduction of spin currents through insulating oxides

abstract:
  Spintronics is a field of electronics based on using the electron spin
instead of its charge. The recent advance in the manipulation of pure spin
currents, i.e. angular momentum transfer not associated to conventional charge
currents, has opened new opportunities to build spin based devices with low
energy consumption. It has also allowed to integrate ferromagnetic insulators
in spintronic devices, either as spin sources or spin conductors using their
magnetic excitations to propagate a spin signal. Antiferromagnetic insulators
belong to another class of materials that can also sustain magnetic
excitations, even with a higher group velocity. Hence, they have potential as
angular momentum conductors, possibly making faster spin devices. At the
opposite end, angular momentum insulators are also required in spintronic
circuits. The present letter underlines some essential features relevant for
spin current conduction, based on measurements of angular momentum transmission
in antiferromagnetic NiO and in the non-magnetic light element insulator
SiO$_2$.


title: Diagrammatics for Bose condensation in anyon theories

abstract:
  Phase transitions in anyon models in (2+1)-dimensions can be driven by
condensation of bosonic particle sectors. We study such condensates in a
diagrammatic language and explicitly establish the relation between the states
in the fusion spaces of the theory with the condensate, to the states in the
parent theory using a new set of mathematical quantities called vertex lifting
coefficients (VLCs). These allow one to calculate the full set of topological
data ($S$-, $T$-, $R$- and $F$-matrices) in the condensed phase. We provide
closed form expressions of the topological data in terms of the VLCs and
provide a method by which one can calculate the VLCs for a wide class of
bosonic condensates. We furthermore furnish a concrete recipe to lift arbitrary
diagrams directly from the condensed phase to the original phase, such that
they can be evaluated using the data of the original theory and a limited
number of VLCs. Some representative examples are worked out in detail.


title: Weak Values with Remote Postselection and Shared Entanglement

abstract:
  We propose a new protocol for the weak measurement of any observable with
remote pre and postselections. We show that if two parties share a pure
entangled state, then by using local operations and classical communication
they can preselect and postselect at distant locations leading to the weak
value of an observable as a shift in the pointer of the apparatus at one
location in the process of the weak measurement. This can be achieved with
either sharing of a pure maximally or non-maximally entangled state. We
generalize the protocol for realizing the weak value of any observable with
remote pre and postselection of mixed states. Finally, we show how the weak
value is modified in the remote pre and postselection setting if Alice and Bob
share a mixed entangled state.


title:
Maximum Efficiency of Heat Engines Based on a Small System: Carnot Cycle
  at the Nanoscale

abstract:
  We study the maximum efficiency of a Carnot cycle heat engine based on a
small system. It is revealed that due to the finiteness of the system,
irreversibility may arise when the working substance contacts with a heat bath.
As a result, there is a working-substance-dependent correction to the usual
Carnot efficiency, which is valid only when the working substance is in the
thermodynamic limit. We derives a general and simple expression for the maximum
efficiency of a Carnot cycle heat engine in terms of the relative entropy. This
maximum efficiency approaches the usual Carnot efficiency asymptotically when
the size of the working substance increases to the thermodynamic limit. Our
study extends the Carnot's result to cases with arbitrary size working
substance and demonstrates the subtlety of thermodynamics in small systems.


title:
Analysis of explicit and implicit discrete-time equivalent-control based
  sliding mode controllers

abstract:
  Different time-discretization methods for equivalent-control based sliding
mode control (ECB-SMC) are presented. A new discrete-time sliding mode control
scheme is proposed for linear time-invariant (LTI) systems. It is error-free in
the discretization of the equivalent part of the control input. Results from
simulations using the various discretized SMC schemes are shown, with and
without perturbations. They illustrate the different behaviours that can be
observed. Stability results for the proposed scheme are derived.


title: A Numerical Study on the Weak Galerkin Method for the Helmholtz Equation

abstract:
  A weak Galerkin (WG) method is introduced and numerically tested for the
Helmholtz equation. This method is flexible by using discontinuous piecewise
polynomials and retains the mass conservation property. At the same time, the
WG finite element formulation is symmetric and parameter free. Several test
scenarios are designed for a numerical investigation on the accuracy,
convergence, and robustness of the WG method in both inhomogeneous and
homogeneous media over convex and non-convex domains. Challenging problems with
high wave numbers are also examined. Our numerical experiments indicate that
the weak Galerkin is a finite element technique that is easy to implement, and
provides very accurate and robust numerical solutions for the Helmholtz problem
with high wave numbers.


title: Multivariate Residues and Maximal Unitarity

abstract:
  We extend the maximal unitarity method to amplitude contributions whose cuts
define multidimensional algebraic varieties. The technique is valid to all
orders and is explicitly demonstrated at three loops in gauge theories with any
number of fermions and scalars in the adjoint representation. Deca-cuts
realized by replacement of real slice integration contours by
higher-dimensional tori encircling the global poles are used to factorize the
planar triple box onto a product of trees. We apply computational algebraic
geometry and multivariate complex analysis to derive unique projectors for all
master integral coefficients and obtain compact analytic formulae in terms of
tree-level data.


title: Efficient Optimization for Sparse Gaussian Process Regression

abstract:
  We propose an efficient optimization algorithm for selecting a subset of
training data to induce sparsity for Gaussian process regression. The algorithm
estimates an inducing set and the hyperparameters using a single objective,
either the marginal likelihood or a variational free energy. The space and time
complexity are linear in training set size, and the algorithm can be applied to
large regression problems on discrete or continuous domains. Empirical
evaluation shows state-of-art performance in discrete cases and competitive
results in the continuous case.


title: Computing in permutation groups without memory

abstract:
  Memoryless computation is a new technique to compute any function of a set of
registers by updating one register at a time while using no memory. Its aim is
to emulate how computations are performed in modern cores, since they typically
involve updates of single registers. The memoryless computation model can be
fully expressed in terms of transformation semigroups, or in the case of
bijective functions, permutation groups. In this paper, we consider how
efficiently permutations can be computed without memory. We determine the
minimum number of basic updates required to compute any permutation, or any
even permutation. The small number of required instructions shows that very
small instruction sets could be encoded on cores to perform memoryless
computation. We then start looking at a possible compromise between the size of
the instruction set and the length of the resulting programs. We consider
updates only involving a limited number of registers. In particular, we show
that binary instructions are not enough to compute all permutations without
memory when the alphabet size is even. These results, though expressed as
properties of special generating sets of the symmetric or alternating groups,
provide guidelines on the implementation of memoryless computation.


title: Computing in matrix groups without memory

abstract:
  Memoryless computation is a novel means of computing any function of a set of
registers by updating one register at a time while using no memory. We aim to
emulate how computations are performed on modern cores, since they typically
involve updates of single registers. The computation model of memoryless
computation can be fully expressed in terms of transformation semigroups, or in
the case of bijective functions, permutation groups. In this paper, we view
registers as elements of a finite field and we compute linear permutations
without memory. We first determine the maximum complexity of a linear function
when only linear instructions are allowed. We also determine which linear
functions are hardest to compute when the field in question is the binary field
and the number of registers is even. Secondly, we investigate some matrix
groups, thus showing that the special linear group is internally computable but
not fast. Thirdly, we determine the smallest set of instructions required to
generate the special and general linear groups. These results are important for
memoryless computation, for they show that linear functions can be computed
very fast or that very few instructions are needed to compute any linear
function. They thus indicate new advantages of using memoryless computation.


title:
Richtmyer-Meshkov Instability of a Liquid-Gas Interface Driven by a
  Cylindrical Imploding Pressure Wave

abstract:
  The compression of a cylindrical gas bubble by an imploding molten lead (Pb)
shell may be accompanied by the development of the Richtmyer-Meshkov (RM)
instability at the liquid-gas interface due to the initial imperfection of the
interface. A converging pressure wave impinging upon the interface causes a
shell of liquid to detach and continue to travel inwards, compressing the gas
bubble. The efficiency of compression and collapse evolution can be affected by
development of the RM instability. Investigations have been performed in the
regime of extreme Atwood number $A=-1$ with the additional complexity of
modeling liquid cavitation in the working fluid. Simulations have been carried
out using the open source CFD software OpenFOAM on a set of parameters relevant
to the prototype compression system under development at General Fusion Inc.
for use as a Magnetized Target Fusion (MTF) driver.
  After validating the numerical setup in planar geometry, simulations have
been carried out in 2D cylindrical geometry for both initially smooth and
perturbed interfaces. Where possible, results have been validated against
existing theoretical models and very good agreement has been found. While our
main focus is on the effects of initial perturbation amplitude and azimuthal
mode number, we also address differences between this problem and those usually
considered, such as RM instability at an interface between two gases with a
moderate density ratio. One important difference is the formation of narrow
molten lead jets rapidly propagating inwards during the final stages of the
collapse. Jet behaviour has been observed for a range of azimuthal mode numbers
and perturbation amplitudes.


title: On Sparse Representation in Fourier and Local Bases

abstract:
  We consider the classical problem of finding the sparse representation of a
signal in a pair of bases. When both bases are orthogonal, it is known that the
sparse representation is unique when the sparsity $K$ of the signal satisfies
$K<1/\mu(D)$, where $\mu(D)$ is the mutual coherence of the dictionary.
Furthermore, the sparse representation can be obtained in polynomial time by
Basis Pursuit (BP), when $K<0.91/\mu(D)$. Therefore, there is a gap between the
unicity condition and the one required to use the polynomial-complexity BP
formulation. For the case of general dictionaries, it is also well known that
finding the sparse representation under the only constraint of unicity is
NP-hard.
  In this paper, we introduce, for the case of Fourier and canonical bases, a
polynomial complexity algorithm that finds all the possible $K$-sparse
representations of a signal under the weaker condition that $K<\sqrt{2}
/\mu(D)$. Consequently, when $K<1/\mu(D)$, the proposed algorithm solves the
unique sparse representation problem for this structured dictionary in
polynomial time. We further show that the same method can be extended to many
other pairs of bases, one of which must have local atoms. Examples include the
union of Fourier and local Fourier bases, the union of discrete cosine
transform and canonical bases, and the union of random Gaussian and canonical
bases.


title: Evolution of swarming behavior is shaped by how predators attack

abstract:
  Animal grouping behaviors have been widely studied due to their implications
for understanding social intelligence, collective cognition, and potential
applications in engineering, artificial intelligence, and robotics. An
important biological aspect of these studies is discerning which selection
pressures favor the evolution of grouping behavior. In the past decade,
researchers have begun using evolutionary computation to study the evolutionary
effects of these selection pressures in predator-prey models. The selfish herd
hypothesis states that concentrated groups arise because prey selfishly attempt
to place their conspecifics between themselves and the predator, thus causing
an endless cycle of movement toward the center of the group. Using an
evolutionary model of a predator-prey system, we show that how predators attack
is critical to the evolution of the selfish herd. Following this discovery, we
show that density-dependent predation provides an abstraction of Hamilton's
original formulation of ``domains of danger.'' Finally, we verify that
density-dependent predation provides a sufficient selective advantage for prey
to evolve the selfish herd in response to predation by coevolving predators.
Thus, our work corroborates Hamilton's selfish herd hypothesis in a digital
evolutionary model, refines the assumptions of the selfish herd hypothesis, and
generalizes the domain of danger concept to density-dependent predation.


title: Matchings and Hamilton Cycles with Constraints on Sets of Edges

abstract:
  The aim of this paper is to extend and generalise some work of Katona on the
existence of perfect matchings or Hamilton cycles in graphs subject to certain
constraints. The most general form of these constraints is that we are given a
family of sets of edges of our graph and are not allowed to use all the edges
of any member of this family. We consider two natural ways of expressing
constraints of this kind using graphs and using set systems.
  For the first version we ask for conditions on regular bipartite graphs $G$
and $H$ for there to exist a perfect matching in $G$, no two edges of which
form a $4$-cycle with two edges of $H$.
  In the second, we ask for conditions under which a Hamilton cycle in the
complete graph (or equivalently a cyclic permutation) exists, with the property
that it has no collection of intervals of prescribed lengths whose union is an
element of a given family of sets. For instance we prove that the smallest
family of $4$-sets with the property that every cyclic permutation of an
$n$-set contains two adjacent pairs of points has size between $(1/9+o(1))n^2$
and $(1/2-o(1))n^2$. We also give bounds on the general version of this problem
and on other natural special cases.
  We finish by raising numerous open problems and directions for further study.


title: Higher algebraic structures in Hamiltonian Floer theory I

abstract:
  This is the first of two papers devoted to showing how the rich algebraic
formalism of Eliashberg-Givental-Hofer's symplectic field theory (SFT) can be
used to define higher algebraic structures on the symplectic cohomology of open
symplectic manifolds. Using the SFT of Hamiltonian mapping tori we show how to
define a homotopy extension of the well-known Lie bracket on symplectic
cohomology. Apart from discussing applications to the existence of closed Reeb
orbits, we outline how the $L_{\infty}$-structure is conjecturally related via
mirror symmetry to the extended deformation theory of complex structures.


title:
A High Order Time Splitting Method Based on Integral Deferred Correction
  for Semi-Lagrangian Vlasov Simulations

abstract:
  Semi-Lagrangian schemes with various splitting methods, and with different
reconstruction/interpolation strategies have been applied to kinetic
simulations. For example, the order of spatial accuracy of the algorithms
proposed in {[Qiu and Christlieb, J. Comp. Phys., 2010]} is very high (as high
as ninth order). However, the temporal error is dominated by the operator
splitting error, which is second order for Strang splitting. It is therefore
important to overcome such low order splitting error, in order to have
numerical algorithms that achieve higher orders of accuracy in both space and
time. In this paper, we propose to use the integral deferred correction (IDC)
method to reduce the splitting error. Specifically, the temporal order accuracy
is increased by $r$ with each correction loop in the IDC framework, where
$r=1,\,2$ for coupling the first order splitting and the Strang splitting,
respectively. The proposed algorithm is applied to the Vlasov-Poisson system,
the guiding center model, and two dimensional incompressible flow simulations
in the vorticity stream-function formulation. We show numerically that the IDC
procedure can automatically increase the order of accuracy in time. We also
investigate numerical stability of the proposed algorithm via performing
Fourier analysis to a linear model problem.


title:
Large Hadron Collider constraints on a light baryon number violating
  sbottom coupling to a top and a light quark

abstract:
  We investigate a model of R-parity violating (RPV) supersymmetry in which the
right-handed sbottom is the lightest supersymmetric particle, and a baryon
number violating coupling involving a top is the only non-negligible RPV
coupling. This model evades proton decay and flavour constraints. We consider
in turn each of the couplings lambda"_{313} and lambda"_{323} as the only
non-negligible RPV coupling, and we recast two recent Large Hadron Collider
(LHC) measurements and searches (CMS top transverse momentum p_T(t) spectrum
and ATLAS multiple jet resonance search) in the form of constraints on the
mass-coupling parameter planes. We delineate a large region in the parameter
space of the mass of the sbottom (m_{b_R}) and the lambda"_{313} coupling that
is ruled out by the measurements, as well as a smaller region in the parameter
space of m_{b_R} and lambda"_{323}. A certain region of the
m_{b_R}-lambda"_{313} parameter space was previously found to successfully
explain the anomalously large ttbar forward backward asymmetry measured by
Tevatron experiments. The entire region is excluded at the 95% CL by CMS
measurements of the top p_T spectrum. We also present p_T(ttbar) distributions
of the forward-backward asymmetry for this model.


title: Strong approximation of fractional Sobolev maps

abstract:
  Brezis and Mironescu have announced several years ago that for a compact
manifold $N^n \subset \mathbb{R}^\nu$ and for real numbers $0 < s < 1$ and $1
\le p < \infty$ the class $C^\infty(\overline{Q}^m; N^n)$ of smooth maps on the
cube with values into $N^n$ is dense with respect to the strong topology in the
Sobolev space $W^{s, p}(Q^m; N^n)$ when the homotopy group $\pi_{\lfloor sp
\rfloor}(N^n)$ of order $\lfloor sp \rfloor$ is trivial. The proof of this
beautiful result is long and rather involved. Under the additional assumption
that $N^n$ is $\lfloor sp \rfloor$ simply connected, we give a shorter proof of
their result. Our proof for $sp \ge 1$ is based on the existence of a
retraction of $\mathbb{R}^\nu$ onto $N^n$ except for a small subset in the
complement of $N^n$ and on the Gagliardo-Nirenberg interpolation inequality for
maps in $W^{1, q} \cap L^\infty$. In contrast, the case $sp < 1$ relies on the
density of step functions on cubes in $W^{s, p}$.


title:
Unified Theory of Activated Relaxation in Liquids over 14 Decades in
  Time

abstract:
  We formulate a predictive theory at the level of forces of activated
relaxation in hard sphere fluids and thermal liquids that covers in a unified
manner the apparent Arrhenius, crossover and deeply supercooled regimes. The
alpha relaxation event involves coupled cage-scale hopping and a long range
collective elastic distortion of the surrounding liquid, which results in two
inter-related, but distinct, barriers. The strongly temperature and density
dependent collective barrier is associated with a growing length scale, the
shear modulus and density fluctuations. Thermal liquids are mapped to an
effective hard sphere fluid based on matching long wavelength density
fluctuation amplitudes, resulting in a zeroth order quasi-universal
description. The theory is devoid of fit parameters, has no divergences at
finite temperature nor below jamming, and captures the key features of the
alpha time of molecular liquids from picoseconds to hundreds of seconds.


title: Graph Clustering with Surprise: Complexity and Exact Solutions

abstract:
  Clustering graphs based on a comparison of the number of links within
clusters and the expected value of this quantity in a random graph has gained a
lot of attention and popularity in the last decade. Recently, Aldecoa and Marin
proposed a related, but slightly different approach leading to the quality
measure surprise, and reported good behavior in the context of synthetic and
real world benchmarks. We show that the problem of finding a clustering with
optimum surprise is NP-hard. Moreover, a bicriterial view on the problem
permits to compute optimum solutions for small instances by solving a small
number of integer linear programs, and leads to a polynomial time algorithm on
trees.


title:
Chow groups of intersections of quadrics via homological projective
  duality and (Jacobians of) noncommutative motives

abstract:
  The Beilinson-Bloch type conjectures predict that the low degree rational
Chow groups of intersections of quadrics are one dimensional. This conjecture
was proved by Otwinowska. Making use of homological projective duality and the
recent theory of (Jacobians of) noncommutative Chow motives, we give an
alternative proof of this conjecture in the case of a complete intersection of
either two quadrics or three odd-dimensional quadrics. Moreover, without the
use of the powerful Lefschetz theorem, we prove that in these cases the unique
non-trivial algebraic Jacobian is the middle one. As an application, making use
of Vial's work, we describe the rational Chow motives of these complete
intersections and show that smooth fibrations in such complete intersections
over small dimensional bases S verify Murre's conjecture (dim(S) less or equal
to 1), Grothendieck's standard conjectures (dim(S) less of equal to 2), and
Hodge's conjecture (dim(S) less or equal to 3).


title: Closure operators on algebras

abstract:
  We study connections between closure operators on an algebra $(A,\Om)$ and
congruences on the extended power algebra defined on the same algebra. We use
these connections to give an alternative description of the lattice of all
subvarieties of semilattice ordered algebras.


title: Quantum curves for Hitchin fibrations and the Eynard-Orantin theory

abstract:
  We generalize the topological recursion of Eynard-Orantin (2007) to the
family of spectral curves of Hitchin fibrations. A spectral curve in the
topological recursion, which is defined to be a complex plane curve, is
replaced with a generic curve in the cotangent bundle $T^*C$ of an arbitrary
smooth base curve $C$. We then prove that these spectral curves are
quantizable, using the new formalism. More precisely, we construct the
canonical generators of the formal $\hbar$-deformation family of $D$-modules
over an arbitrary projective algebraic curve $C$ of genus greater than $1$,
from the geometry of a prescribed family of smooth Hitchin spectral curves
associated with the $SL(2,\mathbb{C})$-character variety of the fundamental
group $\pi_1(C)$. We show that the semi-classical limit through the WKB
approximation of these $\hbar$-deformed $D$-modules recovers the initial family
of Hitchin spectral curves.


title:
Scaling limits for conditional diffusion exit problems, Doob's
  h-transform, and asymptotics for nonlinear elliptic equations

abstract:
  The goal of this paper is to supplement the large deviation principle of the
Freidlin--Wentzell theory on exit problems for diffusion processes with results
of classical central limit theorem kind. We describe a class of situations
where conditioning on exit through unlikely locations leads to a Gaussian
scaling limit for the exit distribution. Our results are based on Doob's
h-transform and new asymptotic convergence gradient estimates for elliptic
nonlinear equations that allow to reduce the problem to the Levinson case. We
devote a separate section to a rigorous and general discussion of h-transform.


title: Primitive Idempotents of Schur Rings

abstract:
  In this paper, we explore the nature of central idempotents of Schur rings
over finite groups. We introduce the concept of a lattice Schur ring and
explore properties of these kinds of Schur rings. In particular, the primitive,
central idempotents of lattice Schur rings are completely determined. For a
general Schur ring $S$, $S$ contains a maximal lattice Schur ring, whose
central, primitive idempotents form a system of pairwise orthogonal, central
idempotents in $S$. We show that if $S$ is a Schur ring with rational
coefficients over a cyclic group, then these idempotents are always primitive
and are spanned by the normal subgroups contained in $S$. Furthermore, a
Wedderburn decomposition of Schur rings over cyclic groups is given. Some
examples of Schur rings over non-cyclic groups will also be explored.


title:
An optimal three-way stable and monotonic spectrum of bounds on
  quantiles: a spectrum of coherent measures of financial risk and economic
  inequality

abstract:
  A certain spectrum, indexed by a\in[0,\infty], of upper bounds P_a(X;x) on
the tail probability P(X\geq x), with P_0(X;x)=P(X\geq x) and P_\infty(X;x)
being the best possible exponential upper bound on P(X\geq x), is shown to be
stable and monotonic in a, x, and X, where x is a real number and X is a random
variable. The bounds P_a(X;x) are optimal values in certain minimization
problems. The corresponding spectrum, also indexed by a\in[0,\infty], of upper
bounds Q_a(X;p) on the (1-p)-quantile of X is stable and monotonic in a, p, and
X, with Q_0(X;p) equal the largest (1-p)-quantile of X. In certain sense, the
quantile bounds Q_a(X;p) are usually close enough to the true quantiles
Q_0(X;p). Moreover, Q_a(X;p) is subadditive in X if a\geq 1, as well as
positive-homogeneous and translation-invariant, and thus is a so-called
coherent measure of risk. A number of other useful properties of the bounds
P_a(X;x) and Q_a(X;p) are established. In particular, quite similarly to the
bounds P_a(X;x) on the tail probabilities, the quantile bounds Q_a(X;p) are the
optimal values in certain minimization problems. This allows for a
comparatively easy incorporation of the bounds P_a(X;x) and Q_a(X;p) into more
specialized optimization problems. It is shown that the minimization problems
for which P_a(X;x) and Q_a(X;p) are the optimal values are in a certain sense
dual to each other; in the case a=\infty this corresponds to the bilinear
Legendre--Fenchel duality. In finance, the (1-p)-quantile Q_0(X;p) is known as
the value-at-risk (VaR), whereas the value of Q_1(X;p) is known as the
conditional value-at-risk (CVaR) and also as the expected shortfall (ES),
average value-at-risk (AVaR), and expected tail loss (ETL). It is shown that
the quantile bounds Q_a(X;p) can be used as measures of economic inequality.
The spectrum parameter, a, may be considered an index of sensitivity to
risk/inequality.

categories: math.PR math.OC math.ST q-fin.RM stat.TH


title: Effective Field Theory of Dark Energy: a Dynamical Analysis

abstract:
  The effective field theory (EFT) of dark energy relies on three functions of
time to describe the background dynamics. The viability of these functions is
investigated here by means of a thorough dynamical analysis. While the system
is underdetermined, and one can always find a set of functions reproducing any
expansion history, we are able to determine general compatibility conditions
for these functions by requiring a viable background cosmology. In particular,
we identify a set of variables that allows us to transform the non-autonomous
system of equations into an infinite-dimensional one characterized by a
significant recursive structure. We then analyze several autonomous
sub-systems, obtained truncating the original one at increasingly higher
dimension, that correspond to increasingly general models of dark energy and
modified gravity. Furthermore, we exploit the recursive nature of the system to
draw some general conclusions on the different cosmologies that can be
recovered within the EFT formalism and the corresponding compatibility
requirements for the EFT functions. The machinery that we set up serves
different purposes. It offers a general scheme for performing dynamical
analysis of dark energy and modified gravity models within the model
independent framework of EFT; the general results, obtained with this
technique, can be projected into specific models, as we show in one example. It
also can be used to determine appropriate ansatze for the three EFT background
functions when studying the dynamics of cosmological perturbations in the
context of large scale structure tests of gravity.


title: Cross-Polarized Microwave Surface-State Anti-Resonance

abstract:
  We propose a polarization-sensitive measurement of microwave electromagnetic
resonances in a magnetic field to detect the metallic surface state of a bulk
insulator. A quantitative model is used to demonstrate that a unique,
unambiguous signature of the dissipative but conducting surface can be seen in
the orthogonally polarized transmission spectra.


title: A stochastic model for quantum measurement

abstract:
  We develop a statistical model of microscopic stochastic deviation from
classical mechanics based on a stochastic processes with a transition
probability that is assumed to be given by an exponential distribution of
infinitesimal stationary action. We apply the statistical model to
stochastically modify a classical mechanical model for the measurement of
physical quantities reproducing the prediction of quantum mechanics. The
system+apparatus always have a definite configuration all the time as in
classical mechanics, fluctuating randomly following a continuous trajectory. On
the other hand, the wave function and quantum mechanical Hermitian operator
corresponding to the physical quantity arise formally as artificial
mathematical constructs. During a single measurement, the wave function of the
whole system+apparatus evolves according to a Schr\"odinger equation and the
configuration of the apparatus acts as the pointer of the measurement so that
there is no wave function collapse. We will also show that while the result of
each single measurement event does not reveal the actual value of the physical
quantity prior to measurement, its average in an ensemble of identical
measurement is equal to the average of the actual value of the physical
quantity prior to measurement over the distribution of the configuration of the
system.


title:
Multi-wavelength Diagnostics of the Precursor and Main phases of an M1.8
  Flare on 2011 April 22

abstract:
  We study the temporal, spatial and spectral evolution of the M1.8 flare,
which occurred in NOAA AR 11195 (S17E31) on 22 April 2011, and explore the
underlying physical processes during the precursors and their relation to the
main phase. The study of the source morphology using the composite images in
131 {\deg}A wavelength observed by the SDO/AIA and 6-14 keV revealed a
multiloop system that destabilized systematically during the precursor and main
phases. In contrast, HXR emission (20-50 keV) was absent during the precursor
phase, appearing only from the onset of the impulsive phase in the form of
foot-points of emitting loop/s. This study has also revealed the heated
loop-top prior to the loop emission, although no accompanying foot-point
sources were observed during the precursor phase. We estimate the flare plasma
parameters viz. T, EM, power-law index, and photon turn-over energy by forward
fitting RHESSI spectral observations. The energy released in the precursor
phase was thermal and constituted ~1 per cent of the total energy released
during the flare. The study of morphological evolution of the filament in
conjunction with synthesized T and EM maps has been carried out which reveals
(a) Partial filament eruption prior to the onset of the precursor emission, (b)
Heated dense plasma over the polarity inversion line and in the vicinity of the
slowly rising filament during the precursor phase. Based on the implications
from multi-wavelength observations, we propose a scheme to unify the energy
release during the precursor and main phase emissions in which, the precursor
phase emission has been originated via conduction front formed due to the
partial filament eruption. Next, the heated leftover S-shaped filament has
undergone slow rise and heating due to magnetic reconnection and finally
erupted to produce emission during the impulsive and gradual phases.


title:
Frustrating antiferromagnetic exchange interactions enhance specific
  valence-bond-pair motifs

abstract:
  We present variational results for the ground state of the antiferromagnetic
quantum Heisenberg model with frustrating next-nearest-neighbour interactions.
The trial wave functions employed are of resonating-valence-bond type,
elaborated to account for various geometric motifs of adjacent bond pairs. The
calculation is specialized to a square-lattice cluster consisting of just
sixteen sites, large enough that the system can accommodate nontrivial singlet
dimer correlations but small enough that exhaustive enumeration of states in
the total spin zero sector is still feasible. A symbolic computation approach
allows us to generate an algebraic expression for the expectation value of any
observable and hence to carry out the energy optimization exactly. While we
have no measurements that could unambiguously identify a spin liquid state in
the controversial region at intermediate frustration, we can say that the
bond-bond correlation factors that emerge do not appear to be consistent with
the existence of a columnar valence bond crystal. Furthermore, our results
suggest that the magnetically disordered region may accommodate two distinct
phases.


title:
A Rapidly Star-forming Galaxy 700 Million Years After the Big Bang at
  z=7.51

abstract:
  Out of several dozen z > 7 candidate galaxies observed spectroscopically,
only five have been confirmed via Lyman-alpha emission, at z=7.008, 7.045,
7.109, 7.213 and 7.215. The small fraction of confirmed galaxies may indicate
that the neutral fraction in the intergalactic medium (IGM) rises quickly at z
> 6.5, as Lyman-alpha is resonantly scattered by neutral gas. However, the
small samples and limited depth of previous observations makes these
conclusions tentative. Here we report the results of a deep near-infrared
spectroscopic survey of 43 z > 6.5 galaxies. We detect only a single galaxy,
confirming that some process is making Lyman-alpha difficult to detect. The
detected emission line at 1.0343 um is likely to be Lyman-alpha emission,
placing this galaxy at a redshift z = 7.51, an epoch 700 million years after
the Big Bang. This galaxy's colors are consistent with significant metal
content, implying that galaxies become enriched rapidly. We measure a
surprisingly high star formation rate of 330 Msol/yr, more than a factor of 100
greater than seen in the Milky Way. Such a galaxy is unexpected in a survey of
our size, suggesting that the early universe may harbor more intense sites of
star-formation than expected.


title: (0,2) Dynamics From Four Dimensions

abstract:
  We study (0,2) supersymmetric two-dimensional theories obtained by
compactifying four-dimensional N=1 supersymmetric theories on a two-torus, with
a magnetic field for a global U(1) symmetry, and present evidence that Seiberg
duality in four dimensions leads to an identification of different models of
this type.


title: Simple numerical implementation of general dark energy models

abstract:
  We present a formalism for the numerical implementation of general theories
of dark energy, combining the computational simplicity of the equation of state
for perturbations approach with the generality of the effective field theory
approach. An effective fluid description is employed, based on a general action
describing single-scalar field models. The formalism is developed from first
principles, and constructed keeping the goal of a simple implementation into
CAMB in mind. Benefits of this approach include its straightforward
implementation, the generality of the underlying theory, the fact that the
evolved variables are physical quantities, and that model-independent
phenomenological descriptions may be straightforwardly investigated. We hope
this formulation will provide a powerful tool for the comparison of theoretical
models of dark energy with observational data.


title: Buckets of Higgs and Tops

abstract:
  We show that associated production of a Higgs with a top pair can be observed
in purely hadronic decays. Reconstructing the top quarks in the form of jet
buckets allows us to control QCD backgrounds as well as signal combinatorics.
The background can be measured from side bands in the reconstructed Higgs mass.
We back up our claims with a detailed study of the QCD event simulation, both
for the signal and for the backgrounds.


title: Probing the Higgs Portal at the LHC Through Resonant di-Higgs Production

abstract:
  We investigate resonant di-Higgs production as a means of probing extended
scalar sectors that include a 125 GeV Standard Model-like Higgs boson. For
concreteness, we consider a gauge singlet Higgs portal scenario leading to two
mixed doublet-singlet states, h_1,2. For m_h_2 > 2 m_h_1, the resonant di-Higgs
production process p p -> h_2 -> h_1 h_1 will lead to final states associated
with the decaying pair of Standard Model-like Higgs scalars. We focus on h_2
production via gluon fusion and on the b b tau^+ tau^- final state. We find
that discovery of the h_2 at the LHC may be achieved with ~ 100 fb^-1 of
integrated luminosity for benchmark parameter choices relevant to cosmology.
Our analysis directly maps onto the decoupling limits of the Next-to-Minimal
Supersymmetric Standard Model (NMSSM) and more generically onto extensions of
the Standard Model Higgs sector in which a heavy scalar produced through gluon
fusion decays to a pair of Standard Model-like Higgs bosons.


title: Hydrodynamics of charge fluctuations and balance functions

abstract:
  We apply stochastic hydrodynamics to the study of charge density fluctuations
in QCD matter undergoing Bjorken expansion. We find that the charge density
correlations are given by a time integral over the history of the system, with
the dominant contribution coming from the QCD crossover region where the change
of susceptibility per entropy, chi T/s, is most significant. We study the
rapidity and azimuthal angle dependence of the resulting charge balance
function using a simple analytic model of heavy-ion collision evolution. Our
results are in agreement with experimental measurements, indicating that
hydrodynamic fluctuations contribute significantly to the measured charge
correlations in high energy heavy-ion collisions. The sensitivity of the
balance function to the value of the charge diffusion coefficient D allows us
to estimate the typical value of this coefficient in the crossover region to be
rather small, of the order of 1/(2pi T), characteristic of a strongly coupled
plasma.


title:
H$\alpha$ Star Formation Rates of $z$ > 1 Galaxy Clusters in the IRAC
  Shallow Cluster Survey

abstract:
  We present Hubble Space Telescope near-IR spectroscopy for 18 galaxy clusters
at 1.0 < $z$ < 1.5 in the IRAC Shallow Cluster Survey. We use Wide Field Camera
3 grism data to spectroscopically identify H$\alpha$ emitters in both the cores
of galaxy clusters as well as in field galaxies. We find a large
cluster-to-cluster scatter in the star formation rates within a projected
radius of 500 kpc, and many of our clusters (~60%) have significant levels of
star formation within a projected radius of 200 kpc. A stacking analysis
reveals that dust reddening in these star-forming galaxies is positively
correlated with stellar mass and may be higher in the field than the cluster at
a fixed stellar mass. This may indicate a lower amount of gas in star-forming
cluster galaxies than in the field population. Also, H$\alpha$ equivalent
widths of star-forming galaxies in the cluster environment are still suppressed
below the level of the field. This suppression is most significant for lower
mass galaxies (log M$_{*}$ < 10.0 M$_{\odot}$). We therefore conclude that
environmental effects are still important at 1.0 < $z$ < 1.5 for star-forming
galaxies in galaxy clusters with log M$_{*}$ < 10.0 M$_{\odot}$.


title: Sufficient observables for large scale structure in galaxy surveys

abstract:
  Beyond the linear regime, the power spectrum and higher order moments of the
matter field no longer capture all cosmological information encoded in density
fluctuations. While non-linear transforms have been proposed to extract this
information lost to traditional methods, up to now, the way to generalize these
techniques to discrete processes was unclear; ad hoc extensions had some
success. We pointed out in Carron and Szapudi (2013) that the logarithmic
transform approximates extremely well the optimal "sufficient statistics",
observables that extract all information from the (continuous) matter field.
Building on these results, we generalize optimal transforms to discrete galaxy
fields. We focus our calculations on the Poisson sampling of an underlying
lognormal density field. We solve and test the one-point case in detail, and
sketch out the sufficient observables for the multi-point case. Moreover, we
present an accurate approximation to the sufficient observables in terms of the
mean and spectrum of a non-linearly transformed field. We find that the
corresponding optimal non-linear transformation is directly related to the
maximum a posteriori Bayesian reconstruction of the underlying continuous field
with a lognormal prior as put forward in Kitaura et al (2010). Thus simple
recipes for realizing the sufficient observables can be built on previously
proposed algorithms that have been successfully implemented and tested in
simulations.


title: The Era of Star Formation in Galaxy Clusters

abstract:
  We analyze the star formation properties of 16 infrared-selected,
spectroscopically confirmed galaxy clusters at $1 < z < 1.5$ from the
Spitzer/IRAC Shallow Cluster Survey (ISCS). We present new spectroscopic
confirmation for six of these high-redshift clusters, five of which are at
$z>1.35$. Using infrared luminosities measured with deep Spitzer/MIPS
observations at 24 $\mu$m, along with robust optical+IRAC photometric redshifts
and SED-fitted stellar masses, we present the dust-obscured star-forming
fractions, star formation rates and specific star formation rates in these
clusters as functions of redshift and projected clustercentric radius. We find
that $z\sim 1.4$ represents a transition redshift for the ISCS sample, with
clear evidence of an unquenched era of cluster star formation at earlier times.
Beyond this redshift the fraction of star-forming cluster members increases
monotonically toward the cluster centers. Indeed, the specific star formation
rate in the cores of these distant clusters is consistent with field values at
similar redshifts, indicating that at $z>1.4$ environment-dependent quenching
had not yet been established in ISCS clusters. Combining these observations
with complementary studies showing a rapid increase in the AGN fraction, a
stochastic star formation history, and a major merging episode at the same
epoch in this cluster sample, we suggest that the starburst activity is likely
merger-driven and that the subsequent quenching is due to feedback from
merger-fueled AGN. The totality of the evidence suggests we are witnessing the
final quenching period that brings an end to the era of star formation in
galaxy clusters and initiates the era of passive evolution.


title:
The evolution of dust-obscured star formation activity in galaxy
  clusters relative to the field over the last 9 billion years

abstract:
  We compare the star formation (SF) activity in cluster galaxies to the field
from z=0.3-1.5 using $Herschel$ SPIRE 250$\mu$m imaging. We utilize 274
clusters from the IRAC Shallow Cluster Survey (ISCS) selected as rest-frame
near-infrared overdensities over the 9 square degree Bootes field . This
analysis allows us to quantify the evolution of SF in clusters over a long
redshift baseline without bias against active cluster systems. Using a stacking
analysis, we determine the average star formation rates (SFRs) and
specific-SFRs (SSFR=SFR/M$_{\star}$) of stellar mass-limited (M>1.3x10$^{10}$
M$_{\odot}$), statistical samples of cluster and field galaxies, probing both
the star forming and quiescent populations. We find a clear indication that the
average SF in cluster galaxies is evolving more rapidly than in the field, with
field SF levels at z>1.2 in the cluster cores (r<0.5 Mpc), in good agreement
with previous ISCS studies. By quantifying the SF in cluster and field galaxies
as an exponential function of cosmic time, we determine that cluster galaxies
are evolving ~2 times faster than the field. Additionally, we see enhanced SF
above the field level at z~1.4 in the cluster outskirts (r>0.5 Mpc). These
general trends in the cluster cores and outskirts are driven by the lower mass
galaxies in our sample. Blue cluster galaxies have systematically lower SSFRs
than blue field galaxies, but otherwise show no strong differential evolution
with respect to the field over our redshift range. This suggests that the
cluster environment is both suppressing the star formation in blue galaxies on
long time-scales and rapidly transitioning some fraction of blue galaxies to
the quiescent galaxy population on short time-scales. We argue that our results
are consistent with both strangulation and ram pressure stripping acting in
these clusters, with merger activity occurring in the cluster outskirts.


title: Using the UM dynamical cores to reproduce idealised 3D flows

abstract:
  We demonstrate that both the current (New Dynamics), and next generation
(ENDGame) dynamical cores of the UK Met Office global circulation model, the
UM, reproduce consistently, the long-term, large-scale flows found in several
published idealised tests. The cases presented are the Held-Suarez test, a
simplified model of Earth (including a stratosphere), and a hypothetical
tidally locked Earth. Furthermore, we show that using simplifications to the
dynamical equations, which are expected to be justified for the physical
domains and flow regimes we have studied, and which are supported by the
ENDGame dynamical core, also produces matching long-term, large-scale flows.
Finally, we present evidence for differences in the detail of the planetary
flows and circulations resulting from improvements in the ENDGame formulation
over New Dynamics.


title: The Rapid Decline in Metallicity of Damped Ly-alpha Systems at z~5

abstract:
  We present evidence that the cosmological mean metallicity of neutral atomic
hydrogen gas shows a sudden decrease at z>4.7 down to <Z>=-2.03(+0.09-0.11),
which is 6 sigma deviant from that predicted by a linear fit to the data at
lower redshifts. This measurement is made possible by the chemical abundance
measurements of 8 new damped Ly-alpha (DLA) systems at z>4.7 observed with the
Echellette Spectrograph and Imager on the Keck II telescope, doubling the
number of measurements at z>4.7 to 16. Possible explanations for this sudden
decrease in metallicity include a change in the physical processes that enrich
the neutral gas within disks, or an increase of the covering factor of neutral
gas outside disks due to a lower ultra-violet radiation field and higher
density at high redshift. The later possibility would result in a new
population of presumably lower metallicity DLAs, with an increased contribution
to the DLA population at higher redshifts resulting in a reduced mean
metallicity. Furthermore, we provide evidence of a possible decrease at z>4.7
in the comoving metal mass density of DLAs, which is flat out to z~4.3. Such a
decrease is expected, as otherwise most of the metals from star-forming
galaxies would reside in DLAs by z~6. While the metallicity is decreasing at
high redshift, the contribution of DLAs to the total metal budget of the
universe increases with redshift, with DLAs at z~4.3 accounting for ~20% as
many metals as produced by Lyman break galaxies.


title: Heisenberg-limited atom clocks based on entangled qubits

abstract:
  We present a quantum-enhanced atomic clock protocol based on groups of
sequentially larger Greenberger-Horne-Zeilinger (GHZ) states, that achieves the
best clock stability allowed by quantum theory up to a logarithmic correction.
The simultaneous interrogation of the laser phase with such a cascade of GHZ
states realizes an incoherent version of the phase estimation algorithm that
enables Heisenberg-limited operation while extending the Ramsey interrogation
time beyond the laser noise limit. We compare the new protocol with state of
the art interrogation schemes, and show that entanglement allow a significant
quantum gain in the stability for short averaging time.


title:
Eccentricity growth and orbit flip in coplanar hierarchical three body
  systems

abstract:
  The dynamical evolution of a hierarchical three body system is well
characterized by the eccentric Kozai-Lidov mechanism, where the inner orbit can
undergo large eccentricity and inclination oscillations. It was shown before
that starting with a circular inner orbit, large mutual inclination (40-140
degree) can produce long timescale modulations that drives the eccentricity to
extremely large value and can flip the orbit. Here, we demonstrate that
starting with an almost coplanar configuration, for eccentric inner and outer
orbits, the eccentricity of the inner orbit can still be excited to high
values, and the orbit can flip by ~180 degree, rolling over its major axis. The
~180 degree flip criterion and the flip timescale are described by simple
analytic expressions that depend on the initial orbital parameters. With tidal
dissipation, this mechanism can produce counter-orbiting exo-planetary systems.
In addition, we also show that this mechanism has the potential to enhance the
tidal disruption or collision rates for different systems.


title: A quantum network of clocks

abstract:
  The development of precise atomic clocks has led to many scientific and
technological advances that play an increasingly important role in modern
society. Shared timing information constitutes a key resource for positioning
and navigation with a direct correspondence between timing accuracy and
precision in applications such as the Global Positioning System (GPS). By
combining precision metrology and quantum networks, we propose here a quantum,
cooperative protocol for the operation of a network consisting of
geographically remote optical atomic clocks. Using non-local entangled states,
we demonstrate an optimal utilization of the global network resources, and show
that such a network can be operated near the fundamental limit set by quantum
theory yielding an ultra-precise clock signal. Furthermore, the internal
structure of the network, combined with basic techniques from quantum
communication, guarantees security both from internal and external threats.
Realization of such a global quantum network of clocks may allow construction
of a real-time single international time scale (world clock) with unprecedented
stability and accuracy.


title: PyGFit: A Tool for Extracting PSF Matched Photometry

abstract:
  We present PyGFit, a program designed to measure PSF-matched photometry from
images with disparate pixel scales and PSF sizes. While PyGFit has a number of
uses, its primary purpose is to extract robust spectral energy distributions
(SEDs) from crowded images. It does this by fitting blended sources in crowded,
low resolution images with models generated from a higher resolution image.
This approach minimizes the impact of crowding and also yields consistently
measured fluxes in different filters, minimizing systematic uncertainty in the
final SEDs. We present an example of applying PyGFit to real data and perform
simulations to test its fidelity. The uncertainty in the best-fit flux rises
sharply as a function of nearest-neighbor distance for objects with a neighbor
within 60% of the PSF size. Similarly, the uncertainty increases quickly for
objects blended with a neighbor more than four times brighter. For all other
objects the fidelity of PyGFit's results depends only on flux, and the
uncertainty is primarily limited by sky noise.


title:
Gamma-ray constraints on dark-matter annihilation to electroweak gauge
  and Higgs bosons

abstract:
  Dark-matter annihilation into electroweak gauge and Higgs bosons results in
$\gamma$-ray emission. We use observational upper limits on the fluxes of both
line and continuum $\gamma$-rays from the Milky Way Galactic Center and from
Milky Way dwarf companion galaxies to set exclusion limits on allowed
dark-matter masses. (Generally, Galactic Center $\gamma$-ray line search limits
from the Fermi-LAT and the H.E.S.S. experiments are most restrictive.) Our
limits apply under the following assumptions: a) the dark matter species is a
cold thermal relic with present mass density equal to the measured dark-matter
density of the universe; b) dark-matter annihilation to standard-model
particles is described in the non-relativistic limit by a single effective
operator ${\cal O} \propto J_{DM}\cdot J_{SM}$, where $J_{DM}$ is a
standard-model singlet current consisting of dark-matter fields (Dirac fermions
or complex scalars), and $J_{SM}$ is a standard-model singlet current
consisting of electroweak gauge and Higgs bosons; and c) the dark-matter mass
is in the range 5 GeV to 20 TeV. We consider, in turn, the 34 possible
operators with mass dimension 8 or lower with non-zero s-wave annihilation
channels satisfying the above assumptions. Our limits are presented in a large
number of figures, one for each of the 34 possible operators; these limits can
be grouped into 13 classes determined by the field content and structure of the
operators. We also identify three classes of operators (coupling to the Higgs
and $SU(2)_L$ gauge bosons) that can supply a 130 GeV line with the desired
strength to fit the putative line signal in Fermi data, while saturating the
relic density and satisfying all other indirect constraints we consider.


title: A Ground-based Optical Transmission Spectrum of WASP-6b

abstract:
  We present a ground based optical transmission spectrum of the inflated
sub-Jupiter mass planet WASP-6b. The spectrum was measured in twenty spectral
channels from 480 nm to 860nm using a series of 91 spectra over a complete
transit event. The observations were carried out using multi-object
differential spectrophotometry with the IMACS spectrograph on the Baade
telescope at Las Campanas Observatory. We model systematic effects on the
observed light curves using principal component analysis on the comparison
stars, and allow for the presence of short and long memory correlation
structure in our Monte Carlo Markov Chain analysis of the transit light curves
for WASP-6. The measured transmission spectrum presents a general trend of
decreasing apparent planetary size with wavelength and lacks evidence for broad
spectral features of Na and K predicted by clear atmosphere models. The
spectrum is consistent with that expected for scattering that is more efficient
in the blue, as could be caused by hazes or condensates in the atmosphere of
WASP-6b. WASP-6b therefore appears to be yet another massive exoplanet with
evidence for a mostly featureless transmission spectrum, underscoring the
importance that hazes and condensates can have in determining the transmission
spectra of exoplanets.


title: Free parafermions

abstract:
  The spectrum of the quantum Ising chain can be found by expressing the spins
in terms of free fermions. An analogous transformation exists for clock chains
with $Z_n$ symmetry, but is of less use because the resulting parafermionic
operators remain interacting. Nonetheless, Baxter showed that a certain
non-hermitian (but PT-symmetric) clock Hamiltonian is "free", in the sense that
the entire spectrum is found in terms of independent energy levels, with the
striking feature that there are $n$ possibilities for occupying each level.
Here I show this directly explicitly finding shift operators obeying a $Z_n$
generalization of the Clifford algebra. I also find higher Hamiltonians that
commute with Baxter's and prove their spectrum comes from the same set of
energy levels. This thus provides an explicit notion of a "free parafermion". A
byproduct is an elegant method for the solution of the Ising/Kitaev chain with
spatially varying couplings.

categories: cond-mat.stat-mech cond-mat.str-el hep-th math-ph math.MP


title: Quark gap equation in an external magnetic field

abstract:
  The nonperturbative quark gap equation under the rainbow truncation and with
two versions of a phenomenological one-gluon exchange interaction is studied in
the presence of a uniform external magnetic field, with emphasis on the small
field limit. The chiral quark condensate, magnetic moment and susceptibility
are calculated and compared to recent lattice data.


title: Equivalence Principle in Chameleon Models: first approach

abstract:
  Most theories that predict time and/or space variation of fundamental
constants also predict violations of the Weak Equivalence Principle (WEP).
Khoury and Weltmann proposed the chameleon model in 2004 and claimed that this
model avoids experimental bounds on WEP. We present a contrasting view based on
an approximate calculation of the two body problem for the chameleon field and
show that the force depends on the test body composition. Furthermore, we
compare the prediction of the force on a test body with E\"otv\"os type
experiments and find that the chameleon field effect cannot account for current
bounds.


title: Holographic Space-time and Newton's Law

abstract:
  We derive Newton's Law from the formalism of Holographic Space-Time (HST).
More precisely, we show that for a large class of Hamiltonians of the type
proposed previously for the HST description of a geodesic in Minkowski space,
the eikonal for scattering of two massless particles at large impact parameter
scales as expected with the impact parameter and the energies of the particles
in the center of mass (CM) frame. We also discuss the criteria for black hole
production in this collision, and find an estimate, purely within the HST
framework, for the impact parameter at which it sets in, which coincides with
the estimate based on general relativity.


title:
Measurement- and comparison-based sizes of Schr\"{o}dinger cat states of
  light

abstract:
  We extend several measurement-based definitions of effective "cat-size" to
coherent state superpositions with branches composed of either single coherent
states or tensor products of coherent states. These effective cat-size measures
depend on determining the maximal quantum distinguishability of certain states
associated with the superposition state: e.g., in one measure, the maximal
distinguishability of the branches of the superposition is considered as in
quantum binary decision theory; in another measure, the maximal
distinguishability of the initial superposition and its image after a
one-parameter evolution generated by a local Hermitian operator is of interest.
The cat-size scaling with the number of modes and mode intensity (i.e., photon
number) is compared to the scaling derived directly from the Wigner function of
the superposition and to that estimated experimentally from decoherence. We
also apply earlier comparison-based methods for determining macroscopic
superposition size that require a reference GHZ state. The case of a
hierarchical Schr\"{o}dinger cat state with branches composed of smaller
superpositions is also analyzed from a measurement-based perspective.


title: How does a magnetic trap work?

abstract:
  Magnetic trapping is a cornerstone for modern ultracold physics and its
applications (e.g., quantum information processing, quantum metrology, quantum
optics, or high-resolution spectroscopies). Here a comprehensive analysis and
discussion of the basic physics behind the most commonly used magnetic traps in
Bose-Einstein condensation is presented. This analysis includes the quadrupole
trap, the time-averaged orbiting potential trap, and the Ioffe-Pritchard trap.
It is shown how the trapping conditions and efficiency of these devices can be
determined from simple derivations based on classical electromagnetism, even
though they operate on quantum objects.

categories: cond-mat.quant-gas physics.atom-ph physics.chem-ph quant-ph


title: Multirate generalized additive Runge Kutta methods

abstract:
  This work constructs a new class of multirate schemes based on the recently
developed generalized additive Runge-Kutta (GARK) methods (Sandu and Guenther,
2013). Multirate schemes use different step sizes for different components and
for different partitions of the right-hand side based on the local activity
levels. We show that the new multirate GARK family includes many well-known
multirate schemes as special cases. The order conditions theory follows
directly from the GARK accuracy theory. Nonlinear stability and monotonicity
investigations show that these properties are inherited from the base schemes
provided that additional coupling conditions hold.


title:
On the number of representations of integers by quadratic forms with
  congruence conditions

abstract:
  We characterize the generating function of the number of representations
described in the title in terms of the theory of modular forms. Appealing to
this characterization we obtain explicit formulas for the representation
numbers as examples.


title:
Upper bounds for the Euclidean minima of abelian fields of odd prime
  power conductor

abstract:
  The aim of this paper is to give upper bounds for the Euclidean minima of
abelian fields of odd prime conductor. In particular, these bounds imply
Minkowski's conjecture for totally real number fields of conductor p^r, where p
is an odd prime and r is at least 2.


title: Isotope Spectroscopy

abstract:
  The measurement of isotopic ratios provides a privileged insight both into
nucleosynthesis and into the mechanisms operating in stellar envelopes, such as
gravitational settling. In this article, we give a few examples of how isotopic
ratios can be determined from high-resolution, high-quality stellar spectra. We
consider examples of the lightest elements, H and He, for which the isotopic
shifts are very large and easily measurable, and examples of heavier elements
for which the determination of isotopic ratios is more difficult. The presence
of 6Li in the stellar atmospheres causes a subtle extra depression in the red
wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the
highest quality. But even with the best spectra, the derived $^6$Li abundance
can only be as good as the synthetic spectra used for their interpretation. It
is now known that 3D non-LTE modelling of the lithium spectral line profiles is
necessary to account properly for the intrinsic line asymmetry, which is
produced by convective flows in the atmospheres of cool stars, and can mimic
the presence of 6Li. We also discuss briefly the case of the carbon isotopic
ratio in metal-poor stars, and provide a new determination of the nickel
isotopic ratios in the solar atmosphere.


title:
Many-body quantum chemistry for the electron gas: convergent
  perturbative theories

abstract:
  We investigate the accuracy of a number of wavefunction based methods at the
heart of quantum chemistry for metallic systems. Using Hartree-Fock as a
reference, perturbative (M{\o}ller-Plesset, MP) and coupled cluster (CC)
theories are used to study the uniform electron gas model. Our findings suggest
that non-perturbative coupled cluster theories are acceptable for modelling
electronic interactions in metals whilst perturbative coupled cluster theories
are not. Using screened interactions, we propose a simple modification to the
widely-used coupled-cluster singles and doubles plus perturbative triples
method (CCSD(T)) that lifts the divergent behaviour and is shown to give very
accurate correlation energies for the homogeneous electron gas.

categories: physics.chem-ph cond-mat.mtrl-sci cond-mat.other cond-mat.quant-gas


title: Tight Bounds for the Entanglement of Formation of Gaussian States

abstract:
  We establish tight upper and lower bounds for the Entanglement of Formation
of an arbitrary two-mode Gaussian state employing necessary properties of
Gaussian channels. Both bounds are strictly given by the Entanglement of
Formation of symmetric Gaussian states, which are simply constructed from the
reduced states obtained by partial trace of the original one.


title:
Cosmological Constraints on Bose-Einstein-Condensed Scalar Field Dark
  Matter

abstract:
  (Abridged) Despite the success of Cold Dark Matter (CDM) in explaining a wide
range of observations, the microscopic nature of dark matter is still unknown.
Attempts to detect WIMPs, the most commonly studied form, have not yet
succeeded. Some predictions are even in apparent conflict with observations
(e.g. cuspy-cored halos and `missing satellite problem'). Therefore, it is
important to consider different forms of CDM. We focus on dark matter comprised
of ultralight bosons that form a Bose-Einstein Condensate (BEC), described by a
complex scalar field, and solve the Klein-Gordon and Einstein field equations
to evolve the Friedmann-Robertson-Walker universe. We find, in addition to
phases of radiation-, matter- and \Lambda-domination, an earlier phase of
scalar-field-domination. Moreover, while WIMP CDM is non-relativistic at all
times after it decouples, BEC scalar field dark matter (SFDM) is relativistic
at early times, evolving from stiff to radiation-like, before it becomes
non-relativistic (CDM-like) at late times. The timing of transitions between
these phases yields fundamental constraints on SFDM model parameters, particle
mass m and self-interaction coupling strength \lambda. We derive the range of
particle parameters required to match observations of the evolving background
universe, including the CMB and abundances of light elements produced by BBN,
characterized by N_eff, the effective number of neutrino species, and the epoch
of matter-radiation equality z_eq. This yields m >= 2.4*10^{-21} eV/c^2 and
9.5*10^{-19} eV^{-1}cm^3 <= \lambda/(mc^2)^2 <= 4*10^{-17} eV^{-1}cm^3. Our
model accommodates current observations in which N_eff at BBN is higher than at
z_eq, as probed by the CMB, otherwise unexplained by WIMP CDM. SFDM without
self-interaction (`Fuzzy Dark Matter') cannot satisfy current BBN constraints
within 68% confidence and is therefore disfavored.


title:
Combined l_1 and greedy l_0 penalized least squares for linear model
  selection

abstract:
  We introduce a computationally effective algorithm for a linear model
selection consisting of three steps: screening--ordering--selection (SOS).
Screening of predictors is based on the thresholded Lasso that is l_1 penalized
least squares. The screened predictors are then fitted using least squares (LS)
and ordered with respect to their t statistics. Finally, a model is selected
using greedy generalized information criterion (GIC) that is l_0 penalized LS
in a nested family induced by the ordering. We give non-asymptotic upper bounds
on error probability of each step of the SOS algorithm in terms of both
penalties. Then we obtain selection consistency for different (n, p) scenarios
under conditions which are needed for screening consistency of the Lasso. For
the traditional setting (n >p) we give Sanov-type bounds on the error
probabilities of the ordering--selection algorithm. Its surprising consequence
is that the selection error of greedy GIC is asymptotically not larger than of
exhaustive GIC. We also obtain new bounds on prediction and estimation errors
for the Lasso which are proved in parallel for the algorithm used in practice
and its formal version.


title:
Word Spotting in Cursive Handwritten Documents using Modified Character
  Shape Codes

abstract:
  There is a large collection of Handwritten English paper documents of
Historical and Scientific importance. But paper documents are not recognized
directly by computer. Hence the closest way of indexing these documents is by
storing their document digital image. Hence a large database of document images
can replace the paper documents. But the document and data corresponding to
each image cannot be directly recognized by the computer.
  This paper applies the technique of word spotting using Modified Character
Shape Code to Handwritten English document images for quick and efficient query
search of words on a database of document images. It is different from other
Word Spotting techniques as it implements two level of selection for word
segments to match search query. First based on word size and then based on
character shape code of query. It makes the process faster and more efficient
and reduces the need of multiple pre-processing.


title:
The characterization of topological properties in Quantum Monte Carlo
  simulations of the Kane-Mele-Hubbard model

abstract:
  Topological insulators present a bulk gap, but allow for dissipationless spin
transport along the edges. These exotic states are characterized by the $Z_2$
topological invariant and are protected by time-reversal symmetry. The
Kane-Mele model is one model to realize this topological class in two
dimensions, also called the quantum spin Hall state. In this review, we provide
a pedagogical introduction to the influence of correlation effects in the
quantum spin Hall states, with special focus on the half-filled
Kane-Mele-Hubbard model, solved by means of unbiased determinant quantum Monte
Carlo (QMC) simulations. We explain the idea of identifying the topological
insulator via $\pi$-flux insertion, the $Z_2$ invariant and the associated
behavior of the zero-frequency Green's function, as well as the spin Chern
number in parameter-driven topological phase transitions. The examples
considered are two descendants of the Kane-Mele-Hubbard model, the generalized
and dimerized Kane-Mele-Hubbard model. From the $Z_2$ index, spin Chern numbers
and the Green's function behavior, one can observe that correlation effects
induce shifts of the topological phase boundaries. Although the implementation
of these topological quantities has been successfully employed in QMC
simulations to describe the topological phase transition, we also point out
their limitations as well as suggest possible future directions in using
numerical methods to characterize topological properties of strongly correlated
condensed matter systems.


title:
Vector Bremsstrahlung by Ultrarelativistic Collisions in Higher
  Dimensions

abstract:
  A classical computation of vector bremsstrahlung in ultrarelativistic
gravitational-force collisions of massive point particles is presented in an
arbitrary number d of extra dimensions. Our method adapts the post-linear
formalism of General Relativity to the multidimensional case. The total emitted
energy, as well as its angular and frequency distribution and characteristic
values, are discussed in detail.
  For an electromagnetic mediation propagated in the bulk, the emitted energy
$E_{em}$ of scattering with impact parameter b has magnitude $E_{em} \sim e^4
e'^2 \gamma^{d+2}/(m^2 b^{3d+3})$, with dominant frequency $\omega_{em} \sim
\gamma^2/b$. For the gravitational force the charge emits via vector field,
propagated in the bulk, energy $E_{rad}\sim[G_D m' e]^2 \gamma^{d+2}/b^{3d+3}$
for $d \geq 2$, with dominant frequency $\omega\sim\gamma^2/b$ and energy
$E_{rad}\sim[G_5 m' e]^2\gamma^{3}\ln \gamma/b^{6}$ for $d=1$, with most of the
energy coming from a wide frequency region $\omega \in [\gamma/b),\gamma^2/b]
$. For the UED model with extra space volume $V=(2\pi R)^d$ the emitted energy
is $E_{UED}\sim (b^{d}/V)^2 E_{rad}$. Finally, for the ADD model, including
four dimensions, the electromagnetic field living on 3-brane, loses on emission
the energy $E_{ADD}\sim[G_D m'e]^2\gamma^{3}/(V b^{2d+3})$, with characteristic
frequency $\omega_{ADD}\sim\gamma/b$.
  The contribution of the low frequency part of the radiation (soft photons) to
the total radiated energy is shown to be negligible for all values of d. The
domain of validity of the classical result is discussed. The result is analyzed
from the viewpoint of the deWitt - Brehme - Hobbs equation (and corresponding
equations in higher dimensions).


title:
Skin Segmentation based Elastic Bunch Graph Matching for efficient
  multiple Face Recognition

abstract:
  This paper is aimed at developing and combining different algorithms for face
detection and face recognition to generate an efficient mechanism that can
detect and recognize the facial regions of input image. For the detection of
face from complex region, skin segmentation isolates the face-like regions in a
complex image and following operations of morphology and template matching
rejects false matches to extract facial region. For the recognition of the
face, the image database is now converted into a database of facial segments.
Hence, implementing the technique of Elastic Bunch Graph matching (EBGM) after
skin segmentation generates Face Bunch Graphs that acutely represents the
features of an individual face enhances the quality of the training set. This
increases the matching probability significantly.


title: Multiple Kernel Learning for Brain-Computer Interfacing

abstract:
  Combining information from different sources is a common way to improve
classification accuracy in Brain-Computer Interfacing (BCI). For instance, in
small sample settings it is useful to integrate data from other subjects or
sessions in order to improve the estimation quality of the spatial filters or
the classifier. Since data from different subjects may show large variability,
it is crucial to weight the contributions according to importance. Many
multi-subject learning algorithms determine the optimal weighting in a separate
step by using heuristics, however, without ensuring that the selected weights
are optimal with respect to classification. In this work we apply Multiple
Kernel Learning (MKL) to this problem. MKL has been widely used for feature
fusion in computer vision and allows to simultaneously learn the classifier and
the optimal weighting. We compare the MKL method to two baseline approaches and
investigate the reasons for performance improvement.


title:
Gas signatures of Herbig Ae/Be disks probed with Herschel SPIRE
  spectroscopy

abstract:
  Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are
seen to form a stable circumstellar disk which is initially gas-rich and could
ultimately form a planetary system. We present Herschel SPIRE 460-1540 GHz
spectra of five targets out of a sample of 13 young disk sources, showing line
detections mainly due to warm CO gas.


title: Bubble Universe Dynamics After Free Passage

abstract:
  We consider bubble collisions in single scalar field theories with multiple
vacua. Recent work has argued that at sufficiently high impact velocities,
collisions between such bubble vacua are governed by 'free passage' dynamics in
which field interactions can be ignored during the collision, providing a
systematic process for populating local minima without quantum nucleation. We
focus on the time period that follows the bubble collision and provide evidence
that, for certain potentials, interactions can drive significant deviations
from the free-passage bubble profile, thwarting the production of bubbles with
different field values.


title: Kinetic Density Functional Theory of Freezing

abstract:
  A theory of freezing of a dense hard sphere gas is presented. Starting from a
revised Enskog theory, hydrodynamic equations that account for non-local
variations in the density but local variations in the flow field are derived
using a modified Chapman Enskog procedure. These hydrodynamic equations, which
retain structural correlations, are shown to be effectively a time dependent
density functional theory. The ability of this theory to capture the solid
liquid phase transition is established through analysis and numerical
simulations.


title: Large low-temperature magnetoresistance in SrFe2As2 single crystals

abstract:
  We present the first report on a large low-temperature magnetoresistance (MR)
of more than 1600% in a SrFe2As2 single crystal and 1300% in a low-energy Ca
ion-implanted SrFe2As2 single crystal that occurs before the emergence of
crystallographic strain-induced bulk superconductivity arising from a sample
aging effect. In accordance to band structure calculations from literature,
which consitently show more than 2 bands are involved in the transport, we have
modeled this large MR at high fields using a 3-carrier scenario rather than
solely on quantum linear MR model generally used to explain the MR in
iron-pnictides. At and below 20 K the large MR may be due to 3-carrier
transport in an inhomogeneous state where there are superconducting and
metallic regions.


title: Gate-tunable carbon nanotube-MoS2 heterojunction p-n diode

abstract:
  The p-n junction diode and field-effect transistor (FET) are the two most
ubiquitous building blocks of modern electronics and optoelectronics. In recent
years, the emergence of reduced dimensionality materials has suggested that
these components can be scaled down to atomic thicknesses. Although high
performance field-effect devices have been achieved from monolayered materials
and their heterostructures, a p-n heterojunction diode derived from ultrathin
materials is notably absent and constrains the fabrication of complex
electronic and optoelectronic circuits. Here, we demonstrate a gate-tunable p-n
heterojunction diode using semiconducting single-walled carbon nanotubes
(s-SWCNTs) and single-layer molybdenum disulfide (SL-MoS2) as p-type and n-type
semiconductors, respectively. The vertical stacking of these two direct band
gap semiconductors forms a heterojunction with electrical characteristics that
can be tuned with an applied gate bias to achieve a wide range of charge
transport behavior ranging from insulating to rectifying with
forward-to-reverse bias current ratios exceeding 10^4. This heterojunction
diode also responds strongly to optical irradiation with an external quantum
efficiency (EQE) of 25% and fast photoresponse < 15 {\mu}s. Since SWCNTs have a
diverse range of electrical properties as a function of chirality, and since an
increasing number of atomically thin 2D nanomaterials are being isolated, the
gate-tunable p-n heterojunction concept presented here should be widely
generalizable to realize diverse ultrathin, high-performance electronics and
optoelectronics.


title: Two Vignettes On Full Rook Placements

abstract:
  Using bijections between pattern-avoiding permutations and certain full rook
placements on Ferrers boards, we give short proofs of two enumerative results.
The first is a simplified enumeration of the 3124, 1234-avoiding permutations,
obtained recently by Callan via a complicated decomposition. The second is a
streamlined bijection between 1342-avoiding permutations and permutations which
can be sorted by two increasing stacks in series, originally due to Atkinson,
Murphy, and Ru\v{s}kuc.


title:
Stein factors for negative binomial approximation in Wasserstein
  distance

abstract:
  The paper gives the bounds on the solutions to a Stein equation for the
negative binomial distribution that are needed for approximation in terms of
the Wasserstein metric. The proofs are probabilistic, and follow the approach
introduced in Barbour and Xia (Bernoulli 12 (2006) 943-954). The bounds are
used to quantify the accuracy of negative binomial approximation to parasite
counts in hosts. Since the infectivity of a population can be expected to be
proportional to its total parasite burden, the Wasserstein metric is the
appropriate choice.


title:
Renormalization of the momentum density on the lattice using shifted
  boundary conditions

abstract:
  In order to extract transport quantities from energy-momentum-tensor (EMT)
correlators in Lattice QCD there is a strong need for a non-perturbative
renormalization of these operators. This is due to the fact that the lattice
regularization explicitly breaks translational invariance, invalidating the
non-renormalization-theorem. Here we present a non-perturbative calculation of
the renormalization constant of the off-diagonal components of the EMT in SU(3)
pure gauge theory using lattices with shifted boundary conditions. This allows
us to induce a non-zero momentum in the system controlled by the shift
parameter and to determine the normalization of the momentum density operator.