title:
The skeleton of the Jacobian, the Jacobian of the skeleton, and lifting
  meromorphic functions from tropical to algebraic curves

abstract:
  Let K be an algebraically closed field which is complete with respect to a
nontrivial, non-Archimedean valuation and let \Lambda be its value group. Given
a smooth, proper, connected K-curve X and a skeleton \Gamma of the Berkovich
analytification X^\an, there are two natural real tori which one can consider:
the tropical Jacobian Jac(\Gamma) and the skeleton of the Berkovich
analytification Jac(X)^\an. We show that the skeleton of the Jacobian is
canonically isomorphic to the Jacobian of the skeleton as principally polarized
tropical abelian varieties. In addition, we show that the tropicalization of a
classical Abel-Jacobi map is a tropical Abel-Jacobi map. As a consequence of
these results, we deduce that \Lambda-rational principal divisors on \Gamma, in
the sense of tropical geometry, are exactly the retractions of principal
divisors on X. We actually prove a more precise result which says that,
although zeros and poles of divisors can cancel under the retraction map, in
order to lift a \Lambda-rational principal divisor on \Gamma to a principal
divisor on X it is never necessary to add more than g extra zeros and g extra
poles. Our results imply that a continuous function F:\Gamma -> R is the
restriction to \Gamma of -log|f| for some nonzero meromorphic function f on X
if and only if F is a \Lambda-rational tropical meromorphic function, and we
use this fact to prove that there is a rational map f : X --> P^3 whose
tropicalization, when restricted to \Gamma, is an isometry onto its image.


title: The Curious Case of an Effective Theory

abstract:
  We describe an effective theory of a scalar field, motivated by some features
expected in the low energy theory of gluodynamics in 3+1 dimensions. The theory
describes two propagating massless particles in a certain limit, which we
identify with the Abelian QED limit, and has classical string solutions in the
general case. The string solutions are somewhat unusual as they are multiply
degenerate due to spontaneous breaking of diffeomorphism invariance.
Nevertheless all solutions yield identical electric field and have the same
string tension.


title:
Simulation of the nanostructure evolution under irradiation in Fe-C
  alloys

abstract:
  Neutron irradiation induces in steels nanostructural changes, which are at
the origin of the mechanical degradation that these materials experience during
operation in nuclear power plants. Some of these effects can be studied by
using as model alloy the iron-carbon system.
  The Object Kinetic Monte Carlo technique has proven capable of simulating in
a realistic and quantitatively reliable way a whole irradiation process. We
have developed a model for simulating Fe-C systems using a physical description
of the properties of vacancy and self-interstitial atom (SIA) clusters, based
on a selection of the latest data from atomistic studies and other available
experimental and theoretical work from the literature. Based on these data, the
effect of carbon on radiation defect evolution has been largely understood in
terms of formation of immobile complexes with vacancies that in turn act as
traps for SIA clusters. It is found that this effect can be introduced using
generic traps for SIA and vacancy clusters, with a binding energy that depends
on the size of the clusters, also chosen on the basis on previously performed
atomistic studies.
  The model proved suitable to reproduce the results of low (<350 K)
temperature neutron irradiation experiments, as well as the corresponding
post-irradiation annealing up to 700 K, in terms of defect cluster densities
and size distribution, when compared to available experimental data from the
literature. The use of traps proved instrumental for our model.


title: A spectral bound for graph irregularity

abstract:
  The imbalance of an edge $e=\{u,v\}$ in a graph is defined as
$i(e)=|d(u)-d(v)|$, where $d(\cdot)$ is the vertex degree. The irregularity
$I(G)$ of $G$ is then defined as the sum of imbalances over all edges of $G$.
This concept was introduced by Albertson who proved that $I(G) \leq
\frac{n^{3}}{27}$ (where $n=|V(G)|$) and obtained stronger bounds for bipartite
and triangle-free graphs. Since then a number of additional bounds were given
by various authors. In this paper we prove a new upper bound, which improves a
bound found by Zhou and Luo in 2011. Our bound involves the Laplacian spectral
radius $\lambda$.


title:
Multiplicity fluctuation analysis of target residues in nucleus-emulsion
  collisions at a few hundred MeV/nucleon

abstract:
  Multiplicity fluctuation of the target evaporated fragments emitted in 290 A
MeV 12C-AgBr, 400 A MeV 12C-AgBr, 400 A MeV 20Ne-AgBr and 500 A MeV 56Fe-AgBr
interactions is investigated using scaled factorial moment method in
two-dimensional normal phase space and cumulative variable space, respectively.
It is found that in normal phase space the scaled factorial moment (ln<Fq>)
increases linearly with increase of the divided number of phase space (lnM) for
lower q-value and increases linearly with the increase of lnM and then becomes
saturated or decreased for higher q-value, in cumulative variable space ln<Fq>
decreases linearly with increase of lnM, which indicates that no evidence of
non-statistical multiplicity fluctuation is observed in our data sets. So any
fluctuation indicated in the results of normal variable space analysis is
totally caused by non-uniformity of single-particle density distribution.


title:
The Effect of Primordial Anti-Biasing on the Local Measurement of the
  Key Cosmological Parameters

abstract:
  The best-fit values of the density parameter and the amplitude of the linear
density power spectrum obtained from the Cosmic Microwave Background (CMB)
temperature field scanned by the Planck satellite are found to notably disagree
with those estimated from the abundance of galaxy clusters observed in the
local universe. Basically, the observed cluster counts are significantly lower
than the prediction of the standard flat LambdaCDM model with the key
cosmological parameters set at the Planck best-fit values. We show that this
inconsistency between the local and the early universe can be well resolved
without failing the currently favored flat LambdaCDM cosmology if the local
universe corresponds to a region embedded in a crest of the primordial
gravitational potential field. Incorporating the condition of positive
primordial potential into the theoretical prediction for the mass function of
cluster halos, we show that the observed lower number densities of the galaxy
clusters are in fact fully consistent with the Planck universe.


title: Casimir-like forces at the percolation transition

abstract:
  Percolation and critical phenomena show common features such as scaling and
universality. Colloidal particles, immersed in a solvent close to criticality,
experience long-range effective forces, named critical Casimir forces. %These
originate from the confinement of the solvent critical fluctuations between the
colloids. Building on the analogy between critical phenomena and percolation,
we explore the possibility of observing long-range forces near a percolation
threshold. To this aim we numerically evaluate the effective potential between
two colloidal particles dispersed in a chemical sol and we show that it becomes
attractive and long-ranged on approaching the sol percolation transition. We
develop a theoretical description based on a polydisperse Asakura-Oosawa model
which captures the divergence of the interaction range, allowing us to
interpret such effect in terms of depletion interactions in a structured
solvent. Our results provide the geometric analogue of the critical Casimir
force, suggesting a novel way for tuning colloidal interactions by controlling
the clustering properties of the solvent.


title: The Real K-Theory of Compact Lie Groups

abstract:
  Let $G$ be a compact, connected, and simply-connected Lie group, equipped
with a Lie group involution $\sigma_G$ and viewed as a $G$-space with the
conjugation action. In this paper, we present a description of the ring
structure of the (equivariant) $KR$-theory of $(G, \sigma_G)$ by drawing on
previous results on the module structure of the $KR$-theory and the ring
structure of the equivariant $K$-theory.


title:
A Variational Principle for Improving 2D Triangle Meshes based on
  Hyperbolic Volume

abstract:
  In this paper, we consider the problem of improving 2D triangle meshes
tessellating planar regions. We propose a new variational principle for
improving 2D triangle meshes where the energy functional is a convex function
over the angle structures whose maximizer is unique and consists only of
equilateral triangles. This energy functional is related to hyperbolic volume
of ideal 3-simplex. Even with extra constraints on the angles for embedding the
mesh into the plane and preserving the boundary, the energy functional remains
well-behaved. We devise an efficient algorithm for maximizing the energy
functional over these extra constraints. We apply our algorithm to various
datasets and compare its performance with that of CVT. The experimental results
show that our algorithm produces the meshes with both the angles and the aspect
ratios of triangles lying in tighter intervals.


title:
Stress Evolution in Composite Silicon Electrodes during
  Lithiation/Delithiation

abstract:
  We report real-time average stress measurements on composite silicon
electrodes made with two different binders [Carboxymethyl cellulose (CMC), and
polyvinylidene fluoride (PVDF)] during electrochemical lithiation and
delithiation. During galvanostatic lithiation at very slow rates, the stress in
a CMC-based electrode becomes compressive and increases to 70 MPa, where it
reaches a plateau and increases slowly thereafter with capacity. The PVDF-based
electrode exhibits similar behavior, although with lower peak compressive
stress of about 12 MPa. These initial experiments indicate that the stress
evolution in a Si composite electrode depends strongly on the mechanical
properties of the binder. Stress data obtained from a series of
lithiation/delithiation cycles suggests plasticity induced irreversible shape
changes in contacting Si particles, and as a result, the stress response of the
system during any given lithiation/delithiation cycle depends on the cycling
history of the electrode. While these results constitute the first in-situ
stress measurements on composite Si electrodes during electrochemical cycling,
the diagnostic technique described herein can be used to assess the mechanical
response of a composite electrode made with other active material/binder
combinations.


title:
Alert-BDI: BDI Model with Adaptive Alertness through Situational
  Awareness

abstract:
  In this paper, we address the problems faced by a group of agents that
possess situational awareness, but lack a security mechanism, by the
introduction of a adaptive risk management system. The Belief-Desire-Intention
(BDI) architecture lacks a framework that would facilitate an adaptive risk
management system that uses the situational awareness of the agents. We extend
the BDI architecture with the concept of adaptive alertness. Agents can modify
their level of alertness by monitoring the risks faced by them and by their
peers. Alert-BDI enables the agents to detect and assess the risks faced by
them in an efficient manner, thereby increasing operational efficiency and
resistance against attacks.


title:
Initial results from a laboratory emulation of weak gravitational
  lensing measurements

abstract:
  Weak gravitational lensing observations are a key science driver for the NASA
Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of
the WFIRST infrared detectors, we have performed a laboratory emulation of weak
gravitational lensing measurements. Our experiments used a custom precision
projector system to image a target mask composed of a grid of pinholes,
emulating stellar point sources, onto a 1.7 micron cut-off Teledyne HgCdTe/H2RG
detector. We used a 880nm LED illumination source and f/22 pupil stop to
produce undersampled point spread functions similar to those expected from
WFIRST. We also emulated the WFIRST image reconstruction strategy, using the
IMage COMbination (IMCOM) algorithm to derive oversampled images from dithered,
undersampled input images. We created shear maps for this data and computed
shear correlation functions to mimic a real weak lensing analysis. After
removing only 2nd order polynomial fits to the shear maps, we found that the
correlation functions could be reduced to O(10^-6). This places a conservative
upper limit on the detector-induced bias to the correlation function (under our
test conditions). This bias is two orders of magnitude lower than the expected
weak lensing signal. Restricted to scales relevant to dark energy analyses (sky
separations > 0.5 arcmin), the bias is O(10^-7): comparable to the requirement
for future weak lensing missions to avoid biasing cosmological parameter
estimates. Our experiment will need to be upgraded and repeated under different
configurations to fully characterize the shape measurement performance of
WFIRST IR detectors.


title:
Detection and Filtering of Collaborative Malicious Users in Reputation
  System using Quality Repository Approach

abstract:
  Online reputation system is gaining popularity as it helps a user to be sure
about the quality of a product/service he wants to buy. Nonetheless online
reputation system is not immune from attack. Dealing with malicious ratings in
reputation systems has been recognized as an important but difficult task. This
problem is challenging when the number of true user's ratings is relatively
small and unfair ratings plays majority in rated values. In this paper, we have
proposed a new method to find malicious users in online reputation systems
using Quality Repository Approach (QRA). We mainly concentrated on anomaly
detection in both rating values and the malicious users. QRA is very efficient
to detect malicious user ratings and aggregate true ratings. The proposed
reputation system has been evaluated through simulations and it is concluded
that the QRA based system significantly reduces the impact of unfair ratings
and improve trust on reputation score with lower false positive as compared to
other method used for the purpose.


title:
Influence of periodically modulated cavity field on the generation of
  atomic-squeezed states

abstract:
  We investigate the influence of periodically time-modulated cavity frequency
on the generation of atomic squeezed states for a collection of N two-level
atoms confined in a non-stationary cavity with a moving mirror. We show that
the two-photon character of the field generated from the vacuum state of field
plays a significant role in producing the atomic or spin squeezed states. We
further show that the maximum amount of persistent atomic squeezing is obtained
for the initial cavity field prepared in the vacuum state.


title:
Identifying Non-Abelian Topological Order through Minimal Entangled
  States

abstract:
  The topological order is equivalent to the pattern of long-range quantum
entanglements, which cannot be measured by any local observable. Here we
perform an exact diagonalization study to establish the non-Abelian topological
order through entanglement entropy measurement. We focus on the quasiparticle
statistics of the non-Abelian Moore-Read and Read-Rezayi states on the lattice
boson models. We identify multiple independent minimal entangled states (MESs)
in the groundstate manifold on a torus. The extracted modular $\mathcal{S}$
matrix from MESs faithfully demonstrates the Majorana quasiparticle or
Fibonacci quasiparticle statistics, including the quasiparticle quantum
dimensions and the fusion rules for such systems. These findings support that
MESs manifest the eigenstates of quasiparticles for the non-Abelian topological
states and encode the full information of the topological order.


title:
Measurement of the W-boson helicity in top-quark decays from ttbar
  production in lepton+jets events in pp collisions at sqrt(s) = 7 TeV

abstract:
  The W-boson helicity fractions in top-quark decays are measured with ttbar
events in the lepton+jets final state, using proton-proton collisions at a
centre-of-mass energy of 7 TeV, collected in 2011 with the CMS detector at the
LHC. The data sample corresponds to an integrated luminosity of 5.0 inverse
femtobarns. The measured fractions of longitudinal, left-, and right-handed
helicity are F0 = 0.682 +/- 0.030 (stat.) +/- 0.033 (syst.), FL = 0.310 +/-
0.022 (stat.) +/- 0.022 (syst.), and FR = 0.008 +/- 0.012 (stat.) +/- 0.014
(syst.), consistent with the standard model predictions. The measured fractions
are used to probe the existence of anomalous Wtb couplings. Exclusion limits on
the real components of the anomalous couplings gL, gR are also derived.


title:
Nonlocal and relativistic behavior from a mutual physical base: a toy
  model

abstract:
  Classical objects have been excluded as subjects of the observed quantum
properties, and the related problem of the nature of quantum objects has been
suspended since the early days of Quantum Theory. Recent experiments show that
the problem could be reasonably revisited. The presented model indicates new
issues which could result from exploring a specific kind of objects:
topological defects in solids.


title: Bounded variation and the strength of Helly's selection theorem

abstract:
  We analyze the strength of Helly's selection theorem HST, which is the most
important compactness theorem on the space of functions of bounded variation.
For this we utilize a new representation of this space intermediate between
$L_1$ and the Sobolev space W1,1, compatible with the, so called, weak*
topology. We obtain that HST is instance-wise equivalent to the
Bolzano-Weierstra\ss\ principle over RCA0. With this HST is equivalent to ACA0
over RCA0. A similar classification is obtained in the Weihrauch lattice.


title: Toward Better Physics Labs for Future Biologists

abstract:
  We have developed a set of laboratories and hands on activities to accompany
a new two-semester interdisciplinary physics course that has been successfully
developed and tested in two small test classes of students at the University of
Maryland, College Park (UMD) in 2012-2013. We have designed the laboratories to
be taken accompanying a reformed course in the student's second year, with
calculus, biology, and chemistry as prerequisites. This permits the
laboratories to include significant content on physics relevant to cellular
scales, from chemical interactions to random motion and charge screening in
fluids. We also introduce the students to research-grade equipment and modern
physics analysis tools in contexts relevant to biology, while maintaining the
pedagogically valuable open-ended laboratory structure of reformed
laboratories. Preliminary student results from these two small test classes are
discussed.


title:
Efficient sum-of-exponentials approximations for the heat kernel and
  their applications

abstract:
  In this paper, we show that efficient separated sum-of-exponentials
approximations can be constructed for the heat kernel in any dimension. In one
space dimension, the heat kernel admits an approximation involving a number of
terms that is of the order $O(\log(\frac{T}{\delta})
(\log(\frac{1}{\epsilon})+\log\log(\frac{T}{\delta})))$ for any $x\in\bbR$ and
$\delta \leq t \leq T$, where $\epsilon$ is the desired precision. In all
higher dimensions, the corresponding heat kernel admits an approximation
involving only $O(\log^2(\frac{T}{\delta}))$ terms for fixed accuracy
$\epsilon$. These approximations can be used to accelerate integral
equation-based methods for boundary value problems governed by the heat
equation in complex geometry. The resulting algorithms are nearly optimal. For
$N_S$ points in the spatial discretization and $N_T$ time steps, the cost is
$O(N_S N_T \log^2 \frac{T}{\delta})$ in terms of both memory and CPU time for
fixed accuracy $\epsilon$. The algorithms can be parallelized in a
straightforward manner. Several numerical examples are presented to illustrate
the accuracy and stability of these approximations.


title: Enhanced index of refraction in four-wave mixing media

abstract:
  Refractive index enhancement accompanied by vanishing absorption in a
four-level atomic system interacting with two control and two probe fields in a
regime of four-wave mixing (FWM) has been predicted and studied in the present
work. We analyzed the maximal index enhancement in the four-level FWM system
and gave index estimates for a real atomic gas of $^{40}$K, taking into account
its multilevel structure and collisional and Doppler broadenings at large
atomic densities. We also discussed how vanishing absorption with no nearby
amplification can be realized in a two species system, consisting of a
four-level FWM and a two-level system, where the latter provides additional
absorption for one of the probe fields. We numerically estimated the index
change in a system composed of $^{40}$K and $^{39}$K gases.


title: Reliable multicast in large enterprise networks

abstract:
  In this work, we have presented a complete end-end architecture to employ the
rate-less codes. We have developed a new architecture Rate-less Codes Multicast
(RCNC). This architecture is shown to provide high throughput gains,
reliability and near optimal throughput performance.


title: Length scales and self-organization in dense suspension flows

abstract:
  Dense non-Brownian suspension flows of hard particles display mystifying
properties: as the jamming threshold is approached, the viscosity diverges, as
well as a length scale that can be identified from velocity correlations. To
unravel the microscopic mechanism governing dissipation and its connection to
the observed long-range correlations, we develop an analogy between suspension
flows and the rigidity transition occurring when floppy networks are pulled --
a transition believed to be associated to the stress-stiffening of certain
gels. After deriving the critical properties near the rigidity transition, we
show numerically that suspensions flows lie close to it. We find that this
proximity causes a decoupling between viscosity and the correlation length of
velocities \xi, which scales as the length l_c characterizing the response of
the velocity in flow to a local perturbation, previously predicted to follow
l_c\sim 1/\sqrt{z_c-z}\sim p^{0.18} where p is the dimensionless particle
pressure, z the coordination of the contact network made by the particles and
z_c is twice the spatial dimension. We confirm these predictions numerically,
predict the existence of a larger length scale l_r\sim 1/\sqrt{p} with mild
effects on velocity correlation and the existence of a vanishing strain \delta
\gamma\sim 1/p that characterizes de-correlation in flow.


title:
Impurity-induced sub-gap bound gap states in alkali doped iron
  chalcogenide superconductors

abstract:
  Measurements of the local density of states near impurities can be useful for
identifying the superconducting gap structure in alkali doped iron chalcogenide
superconductors K_xFe_{2-y}Se_2. Here, we study the effects of nonmagnetic and
magnetic impurities within a nearest neighbor d-wave and next-nearest neighbor
s-wave superconducting state. For both repulsive and attractive nonmagnetic
impurities, it is shown that sub-gap bound states exist only for d-wave
superconductors with the positions of these bound states depending rather
sensitively on the electron doping level. Further, for such disorder Coulomb
interactions can lead to local impurity-induced magnetism in the case of d-wave
superconductivity. For magnetic impurities, both s-wave and d-wave
superconducting states support sub-gap bound states. The above results can be
explained by a simple analytic model that provides a semi-quantitative
understanding of the variation of the impurity bound states energies as a
function of impurity potential and chemical doping level.


title:
Possible nodal superconducting gap emerging at the Lifshitz transition
  in heavily hole-doped Ba0.1K0.9Fe2As2

abstract:
  We performed a high energy resolution ARPES investigation of over-doped
Ba0.1K0.9Fe2As2 with T_c= 9 K. The Fermi surface topology of this material is
similar to that of KFe2As2 and differs from that of slightly less doped
Ba0.3K0.7Fe2As2, implying that a Lifshitz transition occurred between x=0.7 and
x=0.9. Albeit for a vertical node found at the tip of the emerging
off-M-centered Fermi surface pocket lobes, the superconducting gap structure is
similar to that of Ba0.3K0.7Fe2As2, suggesting that the paring interaction is
not driven by the Fermi surface topology.


title:
Exponential convergence to equilibrium for the homogeneous Landau
  equation with hard potentials

abstract:
  This paper deals with the long time behaviour of solutions to the spatially
homogeneous Landau equation with hard potentials . We prove an exponential in
time convergence towards the equilibrium with the optimal rate given by the
spectral gap of the associated linearized operator. This result improves the
polynomial in time convergence obtained by Desvillettes and Villani
\cite{DesVi2}. Our approach is based on new decay estimates for the semigroup
generated by the linearized Landau operator in weighted (polynomial or
stretched exponential) $L^p$-spaces, using a method develloped by Gualdani,
Mischler and Mouhot \cite{GMM}.


title:
On estimation of the noise variance in high-dimensional probabilistic
  principal component analysis

abstract:
  In this paper, we develop new statistical theory for probabilistic principal
component analysis models in high dimensions. The focus is the estimation of
the noise variance, which is an important and unresolved issue when the number
of variables is large in comparison with the sample size. We first unveil the
reasons of a widely observed downward bias of the maximum likelihood estimator
of the variance when the data dimension is high. We then propose a
bias-corrected estimator using random matrix theory and establish its
asymptotic normality. The superiority of the new (bias-corrected) estimator
over existing alternatives is first checked by Monte-Carlo experiments with
various combinations of $(p, n)$ (dimension and sample size). In order to
demonstrate further potential benefits from the results of the paper to general
probability PCA analysis, we provide evidence of net improvements in two
popular procedures (Ulfarsson and Solo, 2008; Bai and Ng, 2002) for determining
the number of principal components when the respective variance estimator
proposed by these authors is replaced by the bias-corrected estimator. The new
estimator is also used to derive new asymptotics for the related
goodness-of-fit statistic under the high-dimensional scheme.


title: Energy barriers govern glassy dynamics in tissues

abstract:
  Recent observations demonstrate that densely packed tissues exhibit features
of glassy dynamics, such as caging behavior and dynamical heterogeneities,
although it has remained unclear how single-cell properties control this
behavior. Here we develop numerical and theoretical models to calculate energy
barriers to cell rearrangements, which help govern cell migration in cell
monolayers. In contrast to work on sheared foams, we find that energy barrier
heights are exponentially distributed and depend systematically on the cell's
number of neighbors. Based on these results, we predict glassy two-time
correlation functions for cell motion, with a timescale that increases rapidly
as cell activity decreases. These correlation functions are used to construct
simple random walks that reproduce the caging behavior observed for cell
trajectories in experiments. This work provides a theoretical framework for
predicting collective motion of cells in wound-healing, embryogenesis and
cancer tumorigenesis.


title:
Do the rich get richer? An empirical analysis of the BitCoin transaction
  network

abstract:
  The possibility to analyze everyday monetary transactions is limited by the
scarcity of available data, as this kind of information is usually considered
highly sensitive. Present econophysics models are usually employed on presumed
random networks of interacting agents, and only macroscopic properties (e.g.
the resulting wealth distribution) are compared to real-world data. In this
paper, we analyze BitCoin, which is a novel digital currency system, where the
complete list of transactions is publicly available. Using this dataset, we
reconstruct the network of transactions, and extract the time and amount of
each payment. We analyze the structure of the transaction network by measuring
network characteristics over time, such as the degree distribution, degree
correlations and clustering. We find that linear preferential attachment drives
the growth of the network. We also study the dynamics taking place on the
transaction network, i.e. the flow of money. We measure temporal patterns and
the wealth accumulation. Investigating the microscopic statistics of money
movement, we find that sublinear preferential attachment governs the evolution
of the wealth distribution. We report a scaling relation between the degree and
wealth associated to individual nodes.


title: Short dynamic fibrils in sunspot chromospheres

abstract:
  Sunspot chromospheres display vigorous oscillatory signature when observed in
chromospheric diagnostics like the strong Ca II lines and H-alpha. New
high-resolution sunspot observations from the Swedish 1-m Solar Telescope show
the ubiquitous presence of small-scale periodic jet-like features that move up
and down. This phenomenon has not been described before. Their typical width is
about 0.3 arcsec and they display clear parabolic trajectories in space-time
diagrams. The maximum extension of the top of the jets is lowest in the umbra,
a few 100 km, and progressively longer further away from the umbra in the
penumbra, with the longest more than 1000 km. These jets resemble dynamic
fibrils found in plage regions but at smaller extensions. LTE inversion of
spectro-polarimetric Ca II 8542 observations enabled for a comparison of the
magnetic field inclination and the properties of these short jets. We find that
the most extended of these jets also have longer periods and tend to be located
in regions with more horizontal magnetic fields. This is a direct observational
confirmation of the mechanism of long-period waves propagating along inclined
magnetic fields into the solar chromosphere. This mechanism was identified
earlier as the driver of dynamic fibrils in plage, part of the mottles in quiet
Sun, and type I spicules at the limb. The sunspot dynamic fibrils that we
report here represent a new class of manifestation of this mechanism. They are
not the same as the transient penumbral and umbral micro-jets reported earlier.


title:
(In-)Stability and Stabilisation of QNL-Type Atomistic-to-Continuum
  Coupling Methods

abstract:
  We study the stability of ghost force-free energy-based
atomistic-to-continuum coupling methods. In 1D we essentially complete the
theory by introducing a universally stable a/c coupling as well as a
stabilisation mechanism for unstable coupling schemes.
  We then present a comprehensive study of a two-dimensional scalar planar
interface setting, as a step towards a general 2D/3D vectorial analysis. Our
results point out various new challenges. For example, we find that none of the
ghost force-free methods known to us are universally stable (i.e., stable under
general interaction and general loads). We then explore to what extent our 1D
stabilisation mechanism can be extended.


title:
Focusing Quantum Many-body Dynamics: The Rigorous Derivation of the 1D
  Focusing Cubic Nonlinear Schr\"odinger Equation

abstract:
  We consider the dynamics of N bosons in one dimension. We assume that the
pair interaction is attractive and given by N^{\beta -1}V(N^{\beta}\cdot) where
\int V\leqslant 0. We develop new techniques in treating the N-body Hamiltonian
so that we overcome the difficulties generated by the attractive interaction
and establish new energy estimates. We also prove the optimal 1D collapsing
estimate which reduces the regularity requirement in the uniqueness argument by
half a derivative. We derive rigorously the one dimensional focusing cubic NLS
with a quadratic trap as the N->\infty limit of the N-body dynamic and hence
justify the mean-field limit and prove the propagation of chaos for the
focusing quantum many-body system.


title: Cross Number Invariants of Finite Abelian Groups

abstract:
  The cross number of a sequence over a finite abelian group $G$ is the sum of
the inverse orders of the terms of that sequence. We study two group
invariants, the maximal cross number of a zero-sum free sequence over $G$,
called $\mathsf{k}(G)$, introduced by Krause, and the maximal cross number of a
unique factorization sequence over $G$, called $K_{1}(G)$, introduced by Gao
and Wang. Conjectured formulae for $\mathsf{k}(G)$ and $\mathsf{K}_{1}(G)$ are
known, but only some special cases are proved for either. We show structural
results about maximal cross number sequences that allow us to prove an
inductive theorem giving conditions under which the conjectured values of
$\mathsf{k}$ and $\mathsf{K}_{1}$ must be correct for $G\oplus C_{p^{\alpha}}$
if they are correct for a group $G$. As a corollary of this result we prove the
conjectured values of $\mathsf{k}(G)$ and $\mathsf{K}_{1}(G)$ for cyclic groups
$C_{n}$, given that the prime factors of $n$ are far apart. Our methods also
prove the $\mathsf{K}_{1}(G)$ conjecture for rank two groups of the form
$C_{n}\oplus C_{q}$, where $q$ is the largest or second largest prime dividing
$n$, and the prime factors of $n$ are far apart, and the $\mathsf{k}(G)$
conjecture for groups of the form $C_{n}\oplus H_{q}$, where the prime factors
of $n$ are far apart, $q$ is the largest prime factor of $n$, and $H_{q}$ is an
arbitrary finite abelian $q$-group. Finally, we pose a conjecture about the
structure of maximal-length unique factorization sequences over elementary
$p$-groups, which is a major roadblock to extending the $\mathsf{K}_{1}$
conjecture to groups of higher rank, and formulate a general question about the
structure of maximal zero-sum free and unique factorization sequences with
respect to arbitrary weighting functions.


title: The Ax-Kochen Theorem: an application of model theory to algebra

abstract:
  The Ax-Kochen Theorem is a purely algebraic statement about the zeros of
homogeneous polynomials over the p-adic numbers, but it was originally proved
using techniques from mathematical logic. This document, the author's
undergraduate honors thesis, provides an exposition of the theorem and its
proof via model theory, assuming no previous experience with logic.


title: Firefly Algorithm: Recent Advances and Applications

abstract:
  Nature-inspired metaheuristic algorithms, especially those based on swarm
intelligence, have attracted much attention in the last ten years. Firefly
algorithm appeared in about five years ago, its literature has expanded
dramatically with diverse applications. In this paper, we will briefly review
the fundamentals of firefly algorithm together with a selection of recent
publications. Then, we discuss the optimality associated with balancing
exploration and exploitation, which is essential for all metaheuristic
algorithms. By comparing with intermittent search strategy, we conclude that
metaheuristics such as firefly algorithm are better than the optimal
intermittent search strategy. We also analyse algorithms and their implications
for higher-dimensional optimization problems.


title: A statistical analysis of circumstellar material in Type Ia supernovae

abstract:
  A key tracer of the elusive progenitor systems of Type Ia supernovae (SNe Ia)
is the detection of narrow blueshifted time-varying Na I D absorption lines,
interpreted as evidence of circumstellar material (CSM) surrounding the
progenitor system. The origin of this material is controversial, but the
simplest explanation is that it results from previous mass loss in a system
containing a white dwarf and a non-degenerate companion star. We present new
single-epoch intermediate-resolution spectra of 17 low-redshift SNe Ia taken
with XShooter on the ESO Very Large Telescope. Combining this sample with
events from the literature, we confirm an excess (~20 per cent) of SNe Ia
displaying blueshifted narrow Na I D absorption features compared to
non-blueshifted Na I D features. The host galaxies of SNe Ia displaying
blueshifted absorption profiles are skewed towards later-type galaxies,
compared to SNe Ia that show no Na I D absorption, and SNe Ia displaying
blueshifted narrow Na I D absorption features have broader light curves. The
strength of the Na I D absorption is stronger in SNe Ia displaying blueshifted
Na I D absorption features than those without blueshifted features, and the
strength of the blueshifted Na I D is correlated with the B-V colour of the SN
at maximum light. This strongly suggests the absorbing material is local to the
SN. In the context of the progenitor systems of SNe Ia, we discuss the
significance of these findings and other recent observational evidence on the
nature of SN Ia progenitors. We present a summary that suggests there are at
least two distinct populations of normal, cosmologically useful SNe Ia.


title: Bat Algorithm: Literature Review and Applications

abstract:
  Bat algorithm (BA) is a bio-inspired algorithm developed by Yang in 2010 and
BA has been found to be very efficient. As a result, the literature has
expanded significantly in the last 3 years. This paper provides a timely review
of the bat algorithm and its new variants. A wide range of diverse applications
and case studies are also reviewed and summarized briefly here. Further
research topics are also discussed.


title:
Population of SOHO/STEREO Kreutz Sungrazers and the Arrival of Comet
  C/2011 W3 (Lovejoy)

abstract:
  We examine properties of the population of SOHO/STEREO (dwarf) Kreutz
sungrazing comets from 2004 to 2013, including the arrival rates, peculiar
gaps, and a potential relationship to the spectacular comet C/2011 W3
(Lovejoy). Selection effects, influencing the observed distribution, are
largely absent among bright dwarf sungrazers, whose temporal sequence implies
the presence of a swarm, with the objects brighter at maximum than apparent
magnitude 3 arriving at a peak rate of about 4.6 per year in late 2010, while
those brighter than magnitude 2 at a peak rate of about 4.3 per year in early
2011, both a few times the pre-swarm rate. The entire population of SOHO/STEREO
Kreutz sungrazers also peaked about one year before the appearance of C/2011
W3. Orbital data show, however, that all bright dwarf sungrazers moved in paths
similar to that of comet C/1843 D1, deviating 10 deg or more from the orbit of
C/2011 W3 in the angular elements. The evidence from the swarm and the overall
elevated arrival rates suggests the existence of a fragmented sizable sungrazer
that shortly preceded C/2011 W3 but was independent of it. On the other hand,
these findings represent another warning signal that the expected 21st-century
cluster of spectacular Kreutz comets is on its way to perihelion, to arrive
during the coming decades. It is only in this sense that we find a parallel
link between C/2011 W3 and the spikes in the population of SOHO/STEREO Kreutz
sungrazers.


title: Free algebras arising from positive-entropy automorphisms of surfaces

abstract:
  Let X be a smooth projective surface defined over an uncountable
algebraically closed field k and let k(X) be its field of rational functions.
Let s be an automorphism of X. This paper proves there is a non-negative
integer n and elements a and b in k(X) such that the subalgebra of the skew
Laurent extension k(X)[t, t^{-1};s] generated by at^n and bt^n is a free
algebra if and only if the spectral radius for the action of s^* on the
Neron-Severi group of X is >1. Thus, when s is an automorphism of a smooth
complex projective surface X, C(X)[t,t^{-1};s] has a free subalgebra on >1
variables if and only if the topological entropy of s is positive. Furthermore,
if s is an automorphism of k(X), then k(X)[t,t^{-1};s] contains a free
subalgebra if and only if the dynamical degree of s is >1; in this situation, s
might not be induced by an automorphism of any smooth projective surface. These
results are used to show that certain twisted homogeneous coordinate rings of
smooth projective surfaces contain free subalgebras.


title:
Sensitivity of an Upgraded LHC to R-Parity Violating Signatures of the
  MSSM

abstract:
  We present a sensitivity study for the pair-production of supersymmetric
particles which decay through R-parity violating channels. As the scope of
possible RPV signatures is very broad, the reach of several selected signatures
spanning a representative variety of possible final states is considered.
Preference in representation is given to spectra motivated by naturalness, i.e.
light higgsinos, stops and gluinos. The sensitivity studies are presented for
proton-proton collisions at 14 TeV with an integrated luminosity of 300 and
3000 fb^-1, as well as at 33 TeV with an integrated luminosity of 3000 fb^-1.


title:
The existence of two closed characteristics on every compact star-shaped
  hypersurface in ${\bf R}^4$

abstract:
  Recently, Cristofaro-Gardiner and Hutchings proved that there exist at least
two closed characteristics on every compact star-shaped hypersuface in ${\bf
R}^4$. Then Ginzburg, Hein, Hryniewicz, and Macarini gave this result a second
proof. In this paper, we give it a third proof by using index iteration theory,
resonance identities of closed characteristics and a remarkable theorem of
Ginzburg et al.


title:
One-step iterative reconstruction of conductivity inclusion via the
  concept of topological derivative

abstract:
  We consider an inverse problem of location identification of small
conductivity inhomogeneity inside a conductor via boundary measurements which
occurs in the EIT (Electrical Impedance Tomography). For this purpose, we
derive topological derivative by applying the asymptotic formula for steady
state voltage potentials in the existence of conductivity inclusion of small
diameter. Using this derivative, we design only one-step iterative location
search algorithm of small conductivity inhomogeneity completely embedded in the
homogeneous domain by solving an adjoint problem. Numerical experiments
presented for showing the feasibility of proposed algorithm.


title:
Structure and properties of linear sampling method for perfectly
  conducting, arc-like cracks

abstract:
  We consider the imaging of arbitrary shaped, arc-like perfectly conducting
cracks located in the two-dimensional homogeneous space via linear sampling
method. Based on the structure of eigenvectors of so-called Multi Static
Response (MSR) matrix, we discover the relationship between imaging functional
adopted in the linear sampling method and Bessel function of integer order of
the first kind. This relationship tells us that why linear sampling method
works for imaging of perfectly conducting cracks in either Transverse Magnetic
(Dirichlet boundary condition) and Transverse Electric (Neumann boundary
condition), and explains its certain properties. Furthermore, we suggest
multi-frequency imaging functional, which improves traditional linear sampling
method. Various numerical experiments are performed for supporting our
explores.


title: Unstable Schwarzschild-Tangherlini black holes in fourth-order gravity

abstract:
  We study the stability of Schwarzschild-Tangherlini (ST) black holes in
fourth-order gravity which provides a higher dimensional linearized massive
equation. The linearized-Ricci tensor perturbation is employed to exhibit
unstable modes featuring the Gregory-Laflamme (GL) instability of higher
dimensional black strings, in comparison to the stable ST black holes in
Einstein gravity. It turns out that the GL instability of the ST black holes in
the fourth-order gravity originates from the massiveness, but not a nature of
fourth-order derivative theories giving ghost states.


title:
Absolute light yield measurements on SrF$_{2}$ and BaF$_{2}$ doped with
  rare earth ions

abstract:
  Results of absolute light output measurements on strontium and barium
fluoride doped with PrF$_3$ and CeF$_3$ are presented and compared with
scintillators having well-known light output (NaI-Tl, CsI-Tl, BGO). For pure
SrF$_2$ crystal we obtain a value of about 28600 photons/MeV.


title: Existence of Smooth Solutions of the Navier-Stokes Equations

abstract:
  In this paper, we prove existence of smooth solutions of the Navier-Stokes
equations that gives a positive answer to the problem proposed by Fefferman
[3].


title: Exact cosmological solutions from Hojman conservation quantities

abstract:
  We present a new approach to find exact solutions for cosmological models. By
requiring the existence of a symmetry transformation vector for the equations
of motion of the given cosmological model (without using either Lagrangian or
Hamiltonian), one can find corresponding Hojman conserved quantities. With the
help of these conserved quantities, the analysis of the cosmological model can
be simplified. In the case of quintessence scalar-tensor models, we show that
the Hojman conserved quantities exist for a wide range of V(\phi)-potentials
and allow to find exact solutions for the cosmic scale factor and the scalar
field. Finally, we investigate the general cosmological behavior of solutions
by adopting a phase-space view.


title: Oersted Lecture 2013: How should we think about how our students think?

abstract:
  Physics Education Research (PER) applies a scientific approach to the
question, "How do our students think about and learn physics?" PER allows us to
explore such intellectually engaging questions as, "What does it mean to
understand something in physics?" and, "What skills and competencies do we want
our students to learn from our physics classes?" To address questions like
these, we need to do more than observe student difficulties and build
curricula. We need a theoretical framework -- a structure for talking about,
making sense of, and modeling how one thinks about, learns, and understands
physics. In this paper, I outline some aspects of the Resources Framework, a
structure that some of us are using to create a phenomenology of physics
learning that ties closely to modern developments in neuroscience, psychology,
and linguistics. As an example of how this framework gives new insights, I
discuss epistemological framing -- the role of students' perceptions of the
nature of the knowledge they are learning and what knowledge is appropriate to
bring to bear on a given task. I discuss how this foothold idea fits into our
theoretical framework, show some classroom data on how it plays out in the
classroom, and give some examples of how my awareness of the resources
framework influences my approach to teaching.


title:
A finite element approximation for the stochastic
  Landau-Lifshitz-Gilbert equation

abstract:
  The stochastic Landau--Lifshitz--Gilbert (LLG) equation describes the
behaviour of the magnetization under the influence of the effective field
consisting of random fluctuations. We first reformulate the equation into an
equation the unknown of which is differentiable with respect to the time
variable. We then propose a convergent $\theta$-linear scheme for the numerical
solution of the reformulated equation. As a consequence, we show the existence
of weak martingale solutions to the stochastic LLG equation. A salient feature
of this scheme is that it does not involve a nonlinear system, and that no
condition on time and space steps is required when $\theta\in(\frac{1}{2},1]$.
Numerical results are presented to show the applicability of the method.


title: Discussion for the Solutions of Dyson-Schwinger Equations at m>0 in QED3

abstract:
  In the case of nonzero fermion mass, within a range of Ansatze for the full
fermion-boson vertex, we show that Dyson-Schwinger equation for the fermion
propagator in QED3 has two qualitatively distinct dynamical chiral symmetry
breaking solutions. As the fermion mass increases and reaches to a critical
value mc, one solution disappears, and the dependence of mc on the number of
fermion flavors is also given.


title: Rapid Decay of Color Gauge Fields by Production of Magnetic Monopoles

abstract:
  It has been argued that the rapid decay of coherent color gauge fields
generated immediately after high energy heavy ion collisions produces quark
gluon plasma. But there are no convincing mechanisms for the rapid decay of the
gauge fields which satisfy phenomenological constraints on their life time. We
show by using classical statistical field theory that the production of
magnetic monopoles cause the rapid decay of the gauge fields. The monopoles are
unstable modes just like Nielsen-Olesen modes and are enormously produced by
dual Schwinger mechanism.


title: Bayes Regularized Graphical Model Estimation in High Dimensions

abstract:
  There has been an intense development of Bayes graphical model estimation
approaches over the past decade - however, most of the existing methods are
restricted to moderate dimensions. We propose a novel approach suitable for
high dimensional settings, by decoupling model fitting and covariance
selection. First, a full model based on a complete graph is fit under novel
class of continuous shrinkage priors on the precision matrix elements, which
induces shrinkage under an equivalence with Cholesky-based regularization while
enabling conjugate updates of entire precision matrices. Subsequently, we
propose a post-fitting graphical model estimation step which proceeds using
penalized joint credible regions to perform neighborhood selection sequentially
for each node. The posterior computation proceeds using straightforward fully
Gibbs sampling, and the approach is scalable to high dimensions. The proposed
approach is shown to be asymptotically consistent in estimating the graph
structure for fixed $p$ when the truth is a Gaussian graphical model.
Simulations show that our approach compares favorably with Bayesian competitors
both in terms of graphical model estimation and computational efficiency. We
apply our methods to high dimensional gene expression and microRNA datasets in
cancer genomics.


title:
Robust Supervisory Control for Uniting Two Output-Feedback Hybrid
  Controllers with Different Objectives

abstract:
  The problem of robustly, asymptotically stabilizing a point (or a set) with
two output-feedback hybrid controllers is considered. These control laws may
have different objectives, e.g., the closed-loop systems resulting with each
controller may have different attractors. We provide a control algorithm that
combines the two hybrid controllers to accomplish the stabilization task. The
algorithm consists of a hybrid supervisor that, based on the values of plant's
outputs and (norm) state estimates, selects the hybrid controller that should
be applied to the plant. The accomplishment of the stabilization task relies on
an output-to-state stability property induced by the controllers, which enables
the construction of an estimator for the norm of the plant's state. The
algorithm is motivated by and applied to robust, semi-global stabilization
problems uniting two controllers.


title: Medial Meshes for Volume Approximation

abstract:
  Volume approximation is an important problem found in many applications of
computer graphics, vision, and image processing. The problem is about computing
an accurate and compact approximate representation of 3D volumes using some
simple primitives. In this study, we propose a new volume representation,
called medial meshes, and present an efficient method for its computation.
Specifically, we use the union of a novel type of simple volume primitives,
which are spheres and the convex hulls of two or three spheres, to approximate
a given 3D shape. We compute such a volume approximation based on a new method
for medial axis simplification guided by Hausdorff errors. We further
demonstrate the superior efficiency and accuracy of our method over existing
methods for medial axis simplification.


title:
Ionospheric effects during first 2 hours after the Chelyabinsk meteorite
  impact

abstract:
  This paper presents the analysis of ionospheric effects in the region close
to the Chelyabinsk meteorite explosion at 03:20UT 2013 February 15 from the
Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of
Sciences (ISTP SB RAS) EKB radar data, and from the Institute of Geophysics of
Ural Branch of Russian Academy of Sciences (IG UB RAS) PARUS ionosonde data.
Both instruments are located within the IG UB RAS Arti Observatory
approximately 200 km northward from the estimated explosion site. According to
the data obtained, the ionospheric disturbance caused by the meteorite flyby,
explosion, and impact had high dynamics and amplitude. However, it obviously
did not lead to a variation in the ionosphere mean parameters in the region
above the disturbance center during the first 2 hours. Essential effects,
however, were observed at more than 100-200 km from the explosion site and
farther up to 1500 km.


title: The Superfluid Glass Phase of 3He-A

abstract:
  It is established theoretically that an ordered state with continuous
symmetry is inherently unstable to arbitrarily small amounts of disorder [1,
2]. This principle is of central importance in a wide variety of condensed
systems including superconducting vortices [3, 4], Ising spin models [5] and
their dynamics [6], and liquid crystals in porous media [7, 8], where some
degree of disorder is ubiquitous, although its experimental observation has
been elusive. Based on these ideas it was predicted [9] that 3He in high
porosity aerogel would become a superfluid glass. We report here our nuclear
magnetic resonance measurements on 3He in aerogel demonstrating destruction of
long range orientational order of the intrinsic superfluid orbital angular
momentum, confirming the existence of a superfluid glass. In contrast, 3He-A
generated by warming from superfluid 3He-B has perfect long-range orientational
order providing a mechanism for switching off this effect.


title:
Galois representations attached to moments of Kloosterman sums and
  conjectures of Evans

abstract:
  Kloosterman sums for a finite field arise as Frobenius trace functions of
certain local systems defined over $\Gm$. The moments of Kloosterman sums
calculate the Frobenius traces on the cohomology of tensor powers (or symmetric
powers, exterior powers, etc.) of these local systems. We show that when $p$
ranges over all primes, the moments of the corresponding Kloosterman sums for
$\mathbb{F}_{p}$ arise as Frobenius traces on a continuous $\ell$-adic Galois
representation that comes from geometry. We also give bounds on the
ramification of these Galois representations. All this is done in the
generality of Kloosterman sheaves attached to reductive groups introduced in
\cite{HNY}. As an application, we give proofs of conjectures of R. Evans
(\cite{Evans0}, \cite{Evans}) expressing the seventh and eighth symmetric power
moments of the classical Kloosterman sum in terms of Fourier coefficients of
explicit modular forms. The proof for the eighth symmetric power moment
conjecture relies on the computation done in Appendix B by C.Vincent.


title: Wave, Particle, or a Third Possibility?

abstract:
  This paper presents an alternative quantum theory, the Theory of Discrete
Extension, which avoids many of the conceptual problems of standard quantum
mechanics. It is a deterministic, dynamic collapse theory with a well-defined
primitive ontology.
  In place of the dual, classical concepts of wave and particle, the unitary,
non-classical concept of a discretely extended object emerges directly from the
theory's dynamic equations as a primitive ontology. Because this ontology is
unitary, the theory avoids the dilemmas of wave-particle dualism and
complementarity.
  Furthermore, the theory's dynamic equations generate correct, quasi-discrete
values of action increments and energy levels without recourse to the operator
formalism and eigenvalue postulate of standard quantum mechanics. Quantization
of the harmonic oscillator provides a simple illustration.
  The theory provides insight into the nature of a number of quantum effects
such as the zero-point energy of the harmonic oscillator. It also makes a
number of predictions that distinguish it from standard quantum mechanics and
from Bohmian mechanics.


title:
Lagrangian study of surface transport in the Kuroshio Extension area
  based on simulation of propagation of Fukushima-derived radionuclides

abstract:
  Lagrangian approach is applied to study near-surface large-scale transport in
the Kuroshio Extension area using a simulation with synthetic particles
advected by AVISO altimetric velocity field. A material line technique is
applied to find the origin of water masses in cold-core cyclonic rings pinched
off from the jet in summer 2011. Tracking and Lagrangian maps provide the
evidence of cross-jet transport. Fukushima derived caesium isotopes are used as
Lagrangian tracers to study transport and mixing in the area a few months after
the March of 2011 tsunami that caused a heavy damage of the Fukushima nuclear
power plant (FNPP). Tracking maps are computed to trace the origin of water
parcels with measured levels of Cs-134 and Cs-137 concentrations collected in
two R/V cruises in June and July 2011 in the large area of the Northwest
Pacific. It is shown that Lagrangian simulation is useful to finding the
surface areas that are potentially dangerous due to the risk of radioactive
contamination. The results of simulation are supported by tracks of the surface
drifters which were deployed in the area.


title:
Efficient Approximation of Well-Founded Justification and Well-Founded
  Domination (Corrected and Extended Version)

abstract:
  Many native ASP solvers exploit unfounded sets to compute consequences of a
logic program via some form of well-founded negation, but disregard its
contrapositive, well-founded justification (WFJ), due to computational cost.
However, we demonstrate that this can hinder propagation of many relevant
conditions such as reachability. In order to perform WFJ with low computational
cost, we devise a method that approximates its consequences by computing
dominators in a flowgraph, a problem for which linear-time algorithms exist.
Furthermore, our method allows for additional unfounded set inference, called
well-founded domination (WFD). We show that the effect of WFJ and WFD can be
simulated for a important classes of logic programs that include reachability.
This paper is a corrected and extended version of a paper published at the 12th
International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMR
2013). It has been adapted to exclude Theorem 10 and its consequences, but
provides all missing proofs.


title:
Analysis and Synthesis of a Subsystem of the Manual Control Loop for
  Manned Spacecraft

abstract:
  A salient feature of the manned spacecraft is the predominance of discrete
information in the manual control loop of the onboard systems. Specifically,
command-signaling control panels (CSCP) as a subsystem of the manual control
loop are widely used in the Russian manned spacecraft. In this paper CSCP are
classified into four types: a) control panels based on multi-channel control;
b) control panels based on command-information compression; c) control panels
based on command and signaling information compression; d) integrated control
consoles (ICC) based on computer and information technology. It is shown that
ICC underlies modern information display systems (IDS). ICC first appeared in
the Russian manned space program in the IDS of the Soyuz-TMA spacecraft and the
Russian modules of the International Space Station. Results of engineering and
psychological studies of different types of panels are produced.


title:
Distance Correlation Methods for Discovering Associations in Large
  Astrophysical Databases

abstract:
  High-dimensional, large-sample astrophysical databases of galaxy clusters,
such as the Chandra Deep Field South COMBO-17 database, provide measurements on
many variables for thousands of galaxies and a range of redshifts. Current
understanding of galaxy formation and evolution rests sensitively on
relationships between different astrophysical variables; hence an ability to
detect and verify associations or correlations between variables is important
in astrophysical research. In this paper, we apply a recently defined
statistical measure called the distance correlation coefficient which can be
used to identify new associations and correlations between astrophysical
variables. The distance correlation coefficient applies to variables of any
dimension; it can be used to determine smaller sets of variables that provide
equivalent astrophysical information; it is zero only when variables are
independent; and it is capable of detecting nonlinear associations that are
undetectable by the classical Pearson correlation coefficient. Hence, the
distance correlation coefficient provides more information than the Pearson
coefficient. We analyze numerous pairs of variables in the COMBO-17 database
with the distance correlation method and with the maximal information
coefficient. We show that the Pearson coefficient can be estimated with higher
accuracy from the corresponding distance correlation coefficient than from the
maximal information coefficient. For given values of the Pearson coefficient,
the distance correlation method has a greater ability than the maximal
information coefficient to resolve astrophysical data into highly concentrated
V-shapes, which enhances classification and pattern identification. These
results are observed over a range of redshifts beyond the local universe and
for galaxies from elliptical to spiral.

categories: astro-ph.CO math.ST stat.AP stat.ML stat.TH


title: Aztec Castles and the dP3 Quiver

abstract:
  Bipartite, periodic, planar graphs known as brane tilings can be associated
to a large class of quivers. This paper will explore new algebraic properties
of the well-studied del Pezzo 3 quiver and geometric properties of its
corresponding brane tiling. In particular, a factorization formula for the
cluster variables arising from a large class of mutation sequences (called
$\tau-$mutation sequences) is proven; this factorization also gives a recursion
on the cluster variables produced by such sequences. We can realize these
sequences as walks in a triangular lattice using a correspondence between the
generators of the affine symmetric group $\tilde{A_2}$ and the mutations which
generate $\tau-$mutation sequences. Using this bijection, we obtain explicit
formulae for the cluster that corresponds to a specific alcove in the lattice.
With this lattice visualization in mind, we then express each cluster variable
produced in a $\tau$-mutation sequence as the sum of weighted perfect matchings
of a new family of subgraphs of the dP3 brane tiling, which we call Aztec
castles. Our main result generalizes previous work on a certain mutation
sequence on the dP3 quiver in [Zha12], and forms part of the emerging story in
combinatorics and theoretical high energy physics relating cluster variables to
subgraphs of the associated brane tiling.


title: SN 2009ip and SN 2010mc as dual-shock Quark-Novae

abstract:
  In recent years a number of double-humped supernovae have been discovered.
This is a feature predicted by the dual-shock Quark-Nova model where a SN
explosion is followed (a few days to a few weeks later) by a Quark-Nova
explosion. SN 2009ip and SN 2010mc are the best observed examples of
double-humped SNe. Here, we show that the dual-shock Quark-Nova model naturally
explains their lightcurves including the late time emission, which we attribute
to the interaction between the mixed SN and QN ejecta and the surrounding CSM.
Our model applies to any star (O-stars, LBVs, WRs etc.) provided that the SN
explosion mass is ~ 20M_sun which point to the conditions for forming a
Quark-Nova.


title: Specialization orders on atom spectra of Grothendieck categories

abstract:
  We introduce systematic methods to construct Grothendieck categories from
colored quivers and develop a theory of the specialization orders on the atom
spectra of Grothendieck categories. We show that any partially ordered set is
realized as the atom spectrum of some Grothendieck category, which is an analog
of Hochster's result in commutative ring theory. We also show that there exists
a Grothendieck category which has empty atom spectrum but has nonempty
injective spectrum.


title:
Numerical conformal mapping via a boundary integral equation with the
  adjoint generalized Neumann kernel

abstract:
  This paper presents a new uniquely solvable boundary integral equation for
computing the conformal mapping, its derivative and its inverse from bounded
multiply connected regions onto the five classical canonical slit regions. The
integral equation is derived by reformulating the conformal mapping as an
adjoint Riemann-Hilbert problem. From the adjoint Riemann-Hilbert problem, we
derive a boundary integral equation with the adjoint generalized Neumann kernel
for the derivative of the boundary correspondence function $\theta'$. Only the
right-hand side of the integral equation is different from a canonical region
to another. The function $\theta'$ is integrated to obtain the boundary
correspondence function $\theta$. The integration constants as well as the
parameters of the canonical region are computed using the same uniquely
solvable integral equation.
  A numerical example is presented to illustrate the accuracy of the proposed
method.


title: Optimal values of bipartite entanglement in a tripartite system

abstract:
  For a general tripartite system in some pure state, an observer possessing
any two parts will see them in a mixed state. By the consequence of
Hughston-Jozsa-Wootters theorem, each basis set of local measurement on the
third part will correspond to a particular decomposition of the bipartite mixed
state into a weighted sum of pure states. It is possible to associate an
average bipartite entanglement ($\bar{\mathcal{S}}$) with each of these
decompositions. The maximum value of $\bar{\mathcal{S}}$ is called the
entanglement of assistance ($E_A$) while the minimum value is called the
entanglement of formation ($E_F$). An appropriate choice of the basis set of
local measurement will correspond to an optimal value of $\bar{\mathcal{S}}$;
we find here a generic optimality condition for the choice of the basis set. In
the present context, we analyze the tripartite states $W$ and $GHZ$ and show
how they are fundamentally different.


title:
Evidence of Contribution of Intervening Clouds to GRB's X-ray Column
  Density

abstract:
  The origin of excess of X-ray column density with respect to optical
extinction in Gamma-ray bursts (GRBs) is still a puzzle. A proposed explanation
of the excess is the photoelectric absorption due to the intervening clouds
along a GRB's line-of-sight. We here test this scenario by using the
intervening \ion{Mg}{2} absorption as a tracer of the neutral hydrogen column
density of the intervening clouds. We identify a connection between large X-ray
column density (and large column density ratio of
$\mathrm{\log(N_{H,X}/N_{HI})}\sim0.5$) and large neutral hydrogen column
density probed by the \ion{Mg}{2} doublet ratio (DR). In addition, GRBs with
large X-ray column density (and large ratio of
$\mathrm{\log(N_{H,X}/N_{HI})}>0$) tend to have multiple saturated intervening
absorbers with $\mathrm{DR<1.2}$. These results therefore indicate an
additional contribution of the intervening system to the observed X-ray column
density in some GRBs, although the contribution of the host galaxy alone cannot
be excluded based on this study.


title:
A Closed Algebra of Clebsch Forms Derived from Whittaker
  Super-potentials and applications in electromagnetic research

abstract:
  A type of closed exterior algebra in R3 under the cross product is revealed
to hold between differential forms from the three Whittaker scalar potentials,
associated with the fields of a moving electron. A special algebraic structure
is revealed in the context of Clebsch reparametrization of these scalars, and a
special prescription for the construction of permutation invariant
electromagnetic fields is given as well as a superposition with parallel
electric and magnetic components.


title: A characterization of BMO self-maps of a metric measure space

abstract:
  This paper studies functions of bounded mean oscillation (BMO) on metric
spaces equipped with a doubling measure. The main result gives
characterizations for mappings that preserve BMO. This extends the
corresponding Euclidean results by Gotoh to metric measure spaces. The argument
is based on a generalizations Uchiyama's construction of certain extremal
BMO-functions and John-Nirenberg's lemma.


title: An extension of the pair-correlation conjecture and applications

abstract:
  We study an extension of Montgomery's pair-correlation conjecture and its
relevance in some problems on the distribution of prime numbers.


title:
Massive Quiescent Cores in Orion: V. The Physical Structures on
  Sub-Jeans Scale and the Chemical Properties in Two Extremely Dense Cores

abstract:
  We present a high-resolution $1.5"$ observational study towards two massive
dust-and-gas cores, ORI8nw\_2 and ORI2\_6 in Orion Molecular Cloud using the
Combined Array for Research in Millimeter-wave Astronomy (CARMA). In both
regions the 3.2 mm continuum emission reveals a dense and compact dust core of
1 to 3 solar masses. The cores are estimated to have number densities more than
$10^9$ cm$^{-3}$, which are among the highest volume density ever published for
the star-forming cores. In both regions the ${\rm N_2H^+}$ shows multiple gas
clumps which are spatially displaced from the dense gas traced by the 3.2 mm
continuum as well as the ${\rm HCO^+}$. The ${\rm N_2H^+}$ clumps in ORI8nw\_2
are gravitationally unbound. The clumps have masses comparable to the thermal
Jeans mass, and are separated with intervals comparable with the Jeans length,
thus likely result from thermal Jeans fragmentation. The fragmentation may have
prohibited the high-mass star formation in the two cores which originally have
larger total masses. In both regions the abundance ratio of ${\rm
[N_2H^+]/[HCO^+]}$ appears to be higher than those in infrared dark clouds as a
result of CO depletion. The extreme high central density in these Orion cores
implies a very small Jeans scale ($<500$ AU). To further reveal the evolution
of such dense cores requires higher resolution and sensitivity.


title: Particle Production at CBM in a Thermal Model Approach

abstract:
  The Compressed Baryonic Matter (CBM) experiment planned at Facility for
Antiproton and Ion Research (FAIR) will provide a major scientific effort for
exploring the properties of strongly interacting matter in the high baryon
density regime. One of the important goal behind such experiment is to
precisely determine the equation of state (EOS) for the strongly interacting
matter at extreme baryon density. In this paper, we have used a thermal model
EOS incorporating excluded volume description for the hot and dense hadron gas
(HG). We then predict different particle ratios and the total multiplicity of
various hadrons in the CBM energy range i.e. from $10$ A GeV to $40$ A GeV lab
energies, which corresponds to $4.43$ A GeV and $8.71$ A GeV center-of-mass
energies. Our main emphasis is to estimate the strange particles enhancement as
well as increase in the net baryon density in CBM experiment. We have also
compared our results with the results obtained from various other theoretical
approaches existing in the literature such as hadron string dynamics (HSD)
model and ultra-relativistic quantum molecular dynamics (UrQMD) etc.


title: Compiling Finite Domain Constraints to SAT with BEE: the Director's Cut

abstract:
  BEE is a compiler which facilitates solving finite domain constraints by
encoding them to CNF and applying an underlying SAT solver. In BEE constraints
are modeled as Boolean functions which propagate information about equalities
between Boolean literals. This information is then applied to simplify the CNF
encoding of the constraints. We term this process equi-propagation. A key
factor is that considering only a small fragment of a constraint model at one
time enables to apply stronger, and even complete reasoning to detect
equivalent literals in that fragment. Once detected, equivalences propagate to
simplify the entire constraint model and facilitate further reasoning on other
fragments. BEE is described in several recent papers. In this paper, after a
quick review of BEE, we elaborate on two undocumented details of the
implementation: the hybrid encoding of cardinality constraints and complete
equi-propagation. We thendescribe on-going work aimed to extend BEE to consider
binary representation of numbers.


title:
Efficiently Retrieving Function Dependencies in the Linux Kernel Using
  XSB

abstract:
  In this paper we investigate XSB-Prolog as a static analysis engine for data
represented by medium-sized graphs. We use XSB-Prolog to automatically identify
function dependencies in the Linux Kernel---queries that are difficult to
implement efficiently in a commodity database and that developers often have to
identify manually. This project illustrates that Prolog systems are ideal for
building tools for use in other disciplines that require sophisticated
inferences, because Prolog is both declarative and can efficiently implement
complex problem specifications through tabling and indexing.


title:
Implementing Constraint Handling Rules as a Domain-Specific Language
  Embedded in Java

abstract:
  Programming languages and techniques based on logic and constraints, such as
the Constraint Handling Rules (CHR), can support many common programming tasks
that can be expressed in the form of a search for feasible or optimal
solutions. Developing new constraint solvers using CHR is especially
interesting in configuration management for large scale, distributed and
dynamic cloud applications, where dynamic configuration and component selection
is an integral part of the programming environment. Writing CHR-style
constraint solvers in a domain-specific language which is a subset of Java --
instead of using a separate language layer -- solves many integration,
development cycle disruption, testing and debugging problems that discourage or
make difficult the adoption of the CHR-based approach in the mainstream
programming environments. Besides, the prototype implementation exposes a
well-defined API that supports transactional store behavior, safe termination,
and debugging via event notifications.


title:
Towards an Abstract Domain for Resource Analysis of Logic Programs Using
  Sized Types

abstract:
  We present a novel general resource analysis for logic programs based on
sized types.Sized types are representations that incorporate structural (shape)
information and allow expressing both lower and upper bounds on the size of a
set of terms and their subterms at any position and depth. They also allow
relating the sizes of terms and subterms occurring at different argument
positions in logic predicates. Using these sized types, the resource analysis
can infer both lower and upper bounds on the resources used by all the
procedures in a program as functions on input term (and subterm) sizes,
overcoming limitations of existing analyses and enhancing their precision. Our
new resource analysis has been developed within the abstract interpretation
framework, as an extension of the sized types abstract domain, and has been
integrated into the Ciao preprocessor, CiaoPP. The abstract domain operations
are integrated with the setting up and solving of recurrence equations for
both, inferring size and resource usage functions. We show that the analysis is
an improvement over the previous resource analysis present in CiaoPP and
compares well in power to state of the art systems.


title: Why It's Nice to be Quoted: Quasiquoting for Prolog

abstract:
  Prolog's support for dynamic programming, meta programming and text
processing using context free grammars make the language highly suitable for
defining domain specific languages (DSL) as well as analysing, refactoring or
generating expression states in other (programming) languages. Well known DSLs
are the DCG (Definite Clause Grammar) notation and constraint languages such as
CHR. These extensions use Prolog operator declarations and the {...} notation
to realise a good syntax. When external languages, such as HTML, SQL or
JavaScript enter the picture, operators no longer satisfy for embedding
snippets of these languages into a Prolog source file. In addition, Prolog has
poor support for quoting long text fragments.
  Haskell introduced quasi quotationsto resolve this problem. In this paper we
`ported' the Haskell mechanism for quasi quoting to Prolog. We show that this
can be done cleanly and that quasi quoting can solve the above mentioned
problems.


title:
Nonparametric independence screening and structure identification for
  ultra-high dimensional longitudinal data

abstract:
  Ultra-high dimensional longitudinal data are increasingly common and the
analysis is challenging both theoretically and methodologically. We offer a new
automatic procedure for finding a sparse semivarying coefficient model, which
is widely accepted for longitudinal data analysis. Our proposed method first
reduces the number of covariates to a moderate order by employing a screening
procedure, and then identifies both the varying and constant coefficients using
a group SCAD estimator, which is subsequently refined by accounting for the
within-subject correlation. The screening procedure is based on working
independence and B-spline marginal models. Under weaker conditions than those
in the literature, we show that with high probability only irrelevant variables
will be screened out, and the number of selected variables can be bounded by a
moderate order. This allows the desirable sparsity and oracle properties of the
subsequent structure identification step. Note that existing methods require
some kind of iterative screening in order to achieve this, thus they demand
heavy computational effort and consistency is not guaranteed. The refined
semivarying coefficient model employs profile least squares, local linear
smoothing and nonparametric covariance estimation, and is semiparametric
efficient. We also suggest ways to implement the proposed methods, and to
select the tuning parameters. An extensive simulation study is summarized to
demonstrate its finite sample performance and the yeast cell cycle data is
analyzed.


title: Hamiltonian and Phase-Space Representation of Spatial Solitons

abstract:
  We use Hamiltonian ray tracing and phase-space representation to describe the
propagation of a single spatial soliton and soliton collisions in a Kerr
nonlinear medium. Hamiltonian ray tracing is applied using the iterative
nonlinear beam propagation method, which allows taking both wave effects and
Kerr nonlinearity into consideration. Energy evolution within a single spatial
soliton and the exchange of energy when two solitons collide are interpreted
intuitively by ray trajectories and geometrical shearing of the Wigner
distribution functions.


title:
Adsorbate Migration Effects on Continuous and Discontinuous
  Temperature-Dependent Transitions in the Quality Factors of Graphene
  Nanoresonators

abstract:
  We perform classical molecular dynamics simulation to investigate the
mechanisms underpinning the unresolved, experimentally-observed
temperature-dependent scaling transition in the quality factors of graphene
nanomechanical resonators (GNMR). Our simulations reveal that the mechanism
underlying this temperature scaling phenomenon is the out-of-plane migration of
adsorbates on GNMRs. Specifically, the migrating adsorbate undergoes frequent
collisions with the GNMR, which strongly influences the resulting mechanical
oscillation, and thus the quality factors. We also predict a discontinuous
transition in the quality factor at a lower critical temperature, which results
from the in-plane migration of the adsorbate. Overall, our work clearly
demonstrates the strong effect of adsorbate migration on the quality factors of
GNMRs.


title: Ordering Families using Lusztig's symbols in type B: the integer case

abstract:
  Let $\Irr(W)$ be the set of irreducible representations of a finite Weyl
group $W$. Following an idea from Spaltenstein, Geck has recently introduced a
preorder $\leq_L$ on $\Irr(W)$ in connection with the notion of Lusztig
families. In a later paper with Iancu, they have shown that in type $B$ (in the
asymptotic case and in the equal parameter case) this order coincides with the
order on Lusztig symbols as defined by Geck and the second author in \cite{GJ}.
In this paper, we show that this caracterisation extends to the so-called
integer case, that is when the ratio of the parameters is an integer.


title: Optimal Algorithms for Testing Closeness of Discrete Distributions

abstract:
  We study the question of closeness testing for two discrete distributions.
More precisely, given samples from two distributions $p$ and $q$ over an
$n$-element set, we wish to distinguish whether $p=q$ versus $p$ is at least
$\eps$-far from $q$, in either $\ell_1$ or $\ell_2$ distance. Batu et al. gave
the first sub-linear time algorithms for these problems, which matched the
lower bounds of Valiant up to a logarithmic factor in $n$, and a polynomial
factor of $\eps.$
  In this work, we present simple (and new) testers for both the $\ell_1$ and
$\ell_2$ settings, with sample complexity that is information-theoretically
optimal, to constant factors, both in the dependence on $n$, and the dependence
on $\eps$; for the $\ell_1$ testing problem we establish that the sample
complexity is $\Theta(\max\{n^{2/3}/\eps^{4/3}, n^{1/2}/\eps^2 \}).$


title:
Momentum-space dynamics of Dirac quasiparticles in correlated random
  potentials: Interplay between dynamical and Berry phases

abstract:
  We consider Dirac quasi-particles, as realized with cold atoms loaded in a
honeycomb lattice or in a $\pi$-flux square lattice, in the presence of a weak
correlated disorder such that the disorder fluctuations do not couple the two
Dirac points of the lattices. We numerically and theoretically investigate the
time evolution of the momentum distribution of such quasi-particles when they
are initially prepared in a quasi-monochromatic wave packet with a given mean
momentum. The parallel transport of the pseudo-spin degree of freedom along
scattering paths in momentum space generates a geometrical phase which alters
the interference associated with reciprocal scattering paths. In the massless
case, a well-known dip in the momentum distribution develops at backscattering
(respective to the Dirac point considered) around the transport mean free time.
This dip later vanishes in the honeycomb case because of trigonal warping. In
the massive case, the dynamical phase of the scattering paths becomes crucial.
Its interplay with the geometrical phase induces an additional transient broken
reflection symmetry in the momentum distribution. The direction of this
asymmetry is a property of the Dirac point considered, independent of the
energy of the wave packet. These Berry phase effects could be observed in
current cold atom lattice experiments.


title: Quantum phases in circuit QED with a superconducting qubit array

abstract:
  Circuit QED on a chip has become a powerful platform for simulating complex
many-body physics. In this report, we realize a Dicke-Ising model with an
antiferromagnetic nearest-neighbor spin-spin interaction in circuit QED with a
superconducting qubit array. We show that this system exhibits a competition
between the collective spin-photon interaction and the antiferromagnetic
nearest-neighbor spin-spin interaction, and then predict four quantum phases,
including: a paramagnetic normal phase, an antiferromagnetic normal phase, a
paramagnetic superradiant phase, and an antiferromagnetic superradiant phase.
The antiferromagnetic normal phase and the antiferromagnetic superradiant phase
are new phases in many-body quantum optics. In the antiferromagnetic
superradiant phase, both the antiferromagnetic and superradiant orders can
coexist, and thus the system possesses $Z_{2}^{z}\otimes Z_{2}$\ symmetry.
Moreover, we find an unconventional photon signature in this phase. In future
experiments, these predicted quantum phases could be distinguished by detecting
both the mean-photon number and the magnetization.


title: Mckay Correspondence in Quasitoric Orbifolds

abstract:
  We show Mckay correspondence of Betti numbers of Chen-Ruan coho- mology for
omnioriented quasitoric orbifolds. In previous articles with M. Poddar [8],
[9], we proved the correspondence for four dimension and six dimensions. Here
we deal with the general case.


title:
An Electronically Non-Adiabatic Generalization of Ring Polymer Molecular
  Dynamics

abstract:
  In this thesis I generalize Ring Polymer Molecular Dynamics (RPMD) rate
theory to electronically non-adiabatic systems, followed by application to two
one-dimensional curve crossing models and a multidimensional spin-boson model.


title: Formality theorem for gerbes

abstract:
  We extend the formality theorem of Maxim Kontsevich from deformations of the
structure sheaf on a manifold to deformations of gerbes on smooth and complex
manifolds.


title:
Automorphisms of surfaces of general type with q=1 acting trivially in
  cohomology

abstract:
  Let S be a complex minimal surface of general type with irregularity q(S)=1
and Aut_0(S) the subgroup of automorphisms acting trivially on the cohomology
ring with rational coefficients. In this paper we show that |Aut_0(S)|<=4, and
if the equality holds then $S$ is a surface isogenous to a product of unmixed
type. Moreover, examples of surfaces with |Aut_0(S)|=4 and all possible values
of the geometric genus are provided.


title:
Density of States Scaling at the Semimetal to Metal Transition in Three
  Dimensional Topological Insulators

abstract:
  The quantum phase transition between the three dimensional Dirac semimetal
and the diffusive metal can be induced by increasing disorder. Taking the
system of disordered $\mathbb{Z}_2$ topological insulator as an important
example, we compute the single particle density of states by the kernel
polynomial method. We focus on three regions: the Dirac semimetal at the phase
boundary between two topologically distinct phases, the tricritical point of
the two topological insulator phases and the diffusive metal, and the diffusive
metal lying at strong disorder. The density of states obeys a novel single
parameter scaling, collapsing onto two branches of a universal scaling
function, which correspond to the Dirac semimetal and the diffusive metal. The
diverging length scale critical exponent $\nu$ and the dynamical critical
exponent $z$ are estimated, and found to differ significantly from those for
the conventional Anderson transition. Critical behavior of experimentally
observable quantities near and at the tricritical point is also discussed.


title: New Integral Inequalities through generalized convex functions

abstract:
  In this paper, we establish various inequalities for some mappings that are
linked with the illustrious Hermite-Hadamard integral inequality for mappings
whose absolute values belong to the class K?;s m;1 and K?;s m;2.


title: On the finitely separability of subgroups of generalized free products

abstract:
  It is proved that all finitely generated subgroups of generalized free
product of two groups are finitely separable provided that free factors have
this property and amalgamated subgroups are normal in corresponding factors and
satisfy the maximum condition for subgroups.


title:
Target Assignment in Robotic Networks: Distance Optimality Guarantees
  and Hierarchical Strategies

abstract:
  We study the problem of multi-robot target assignment to minimize the total
distance traveled by the robots until they all reach an equal number of static
targets. In the first half of the paper, we present a necessary and sufficient
condition under which true distance optimality can be achieved for robots with
limited communication and target-sensing ranges. Moreover, we provide an
explicit, non-asymptotic formula for computing the number of robots needed to
achieve distance optimality in terms of the robots' communication and
target-sensing ranges with arbitrary guaranteed probabilities. The same bounds
are also shown to be asymptotically tight.
  In the second half of the paper, we present suboptimal strategies for use
when the number of robots cannot be chosen freely. Assuming first that all
targets are known to all robots, we employ a hierarchical communication model
in which robots communicate only with other robots in the same partitioned
region. This hierarchical communication model leads to constant approximations
of true distance-optimal solutions under mild assumptions. We then revisit the
limited communication and sensing models. By combining simple rendezvous-based
strategies with a hierarchical communication model, we obtain decentralized
hierarchical strategies that achieve constant approximation ratios with respect
to true distance optimality. Results of simulation show that the approximation
ratio is as low as 1.4.


title:
Iterative Multiuser Detection and Decoding with Spatially Coupled
  Interleaving

abstract:
  Spatially coupled (SC) interleaving is proposed to improve the performance of
iterative multiuser detection and decoding (MUDD) for quasi-static fading
multiple-input multiple-output systems. The linear minimum mean-squared error
(LMMSE) demodulator is used to reduce the complexity and to avoid error
propagation. Furthermore, sliding window MUDD is proposed to circumvent an
increase of the decoding latency due to SC interleaving. Theoretical and
numerical analyses show that SC interleaving can improve the performance of the
iterative LMMSE MUDD for regular low-density parity-check codes.


title:
Unusual Low Temperature Reactivity of Water. The CH + H2O Reaction as a
  Source of Interstellar Formaldehyde?

abstract:
  Water is an important reservoir species for oxygen in interstellar space and
plays a key role in the physics of star formation through cooling by
far-infrared emission. Whilst water vapour is present at high abundances in the
outflows of protostars, its contribution to the chemical evolution of these
regions is a minor one due to its limited low temperature reactivity in the
gas-phase. Here, we performed kinetic experiments on the barrierless CH + H2O
reaction in a supersonic flow reactor down to 50 K. The measured rate increases
rapidly below room temperature, confirming and extending the predictions of
earlier statistical calculations. The open product channels for this reaction
suggest that this process could be an important gas-phase route for
formaldehyde formation in protostellar envelopes.


title: Spontaneous breaking of rotational symmetry in the presence of defects

abstract:
  We prove a strong form of spontaneous breaking of rotational symmetry for a
simple model of two-dimensional crystals with random defects in thermal
equilibrium at low temperature. The defects consist of isolated missing atoms.


abstract:
  N=6 conformal supergravity in three dimensions is studied in an off-shell
component field formulation. We obtain local symmetry transformation laws and a
Lagrangian of the conformal supergravity multiplet. We then couple it to the
ABJM theory and obtain local transformation laws and a Lagrangian of the
coupled theory.


title:
Portfolio return distributions: Sample statistics with non-stationary
  correlations

abstract:
  We consider random vectors drawn from a multivariate normal distribution and
compute the sample statistics in the presence of non-stationary correlations.
For this purpose, we construct an ensemble of random correlation matrices and
average the normal distribution over this ensemble. The resulting distribution
contains a modified Bessel function of the second kind whose behavior differs
significantly from the multivariate normal distribution, in the central part as
well as in the tails. This result is then applied to asset returns. We compare
with empirical return distributions using daily data from the Nasdaq Composite
Index in the period from 1992 to 2012. The comparison reveals good agreement,
the average portfolio return distribution describes the data well especially in
the central part of the distribution. This in turn confirms our ansatz to model
the non-stationarity by an ensemble average.


title: Majorana modes in smooth normal-superconductor nanowire junctions

abstract:
  A numerical method to obtain the spectrum of smooth normal-superconductor
junctions in nanowires, able to host Majorana zero modes, is presented.
Softness in the potential and superconductor interfaces yields opposite effects
on the protection of Majorana modes. While a soft potential is a hindrance for
protection, a soft superconductor gap transition greatly favors it. Our method
also points out the possibility of extended Majorana states when propagating
modes are active far from the junction, although this requires equal incident
fluxes in all open channels.


title: An astronomical survey conducted in Belgium

abstract:
  This article presents the results of the first survey conducted in Belgium
about the interest and knowledge in astronomy. Two samples were studied, the
public at large (667 questionnaires) and students (2589 questionnaires), but
the results are generally similar in both samples. We evaluated people's
interest, main information source, and attitudes towards astronomy, as well as
their supposed and actual knowledge of the subject. The main conclusion is
that, despite a poor self-confidence, people do know the basic astronomical
concepts. However, that knowledge is not deeply rooted, as reasoning questions
show well-spread misconceptions and/or misunderstandings.


title: What Is Armchair-Zigzag Grain Boundary Structure in Graphene?

abstract:
  We have developed a new global optimization method for the determination of
interface structure based on the differential evolution algorithm. Here, we
applied this method to search for the ground state atomic structures of the
grain boundary between the armchair and zigzag oriented graphene. We find two
new grain boundary structures with considerably lower formation energy of about
1 eV/nm than that of the previously widely used structural models. These newly
predicted structures show better mechanical property under external uniaxial
strain, and distinguishable scanning tunneling microscope features, compared
with the previous structural models. Our results provide important new
information for the determination of grain boundary structures and henceforth
the electronic properties of defected graphene.


title:
Electronic band gaps and transport properties in aperiodic bilayer
  graphene superlattices of Thue-Morse sequence

abstract:
  We investigate electronic band structure and transport properties in bilayer
graphene superlattices of Thue-Morse sequence. It is interesting to find that
the zero-$\bar{k}$ gap center is sensitive to interlayer coupling $t'$, and the
centers of all gaps shift versus $t'$ at a linear way. Extra Dirac points may
emerge at $k_{y}\ne$0, and when the extra Dirac points are generated in pairs,
the electronic conductance obeys a diffusive law, and the Fano factor tends to
be 1/3 as the order of Thue-Morse sequence increases. Our results provide a
flexible and effective way to control the transport properties in graphene.


title:
Analyzing Herd Behavior in Global Stock Markets: An Intercontinental
  Comparison

abstract:
  Herd behavior is an important economic phenomenon, especially in the context
of the recent financial crises. In this paper, herd behavior in global stock
markets is investigated with a focus on intercontinental comparison. Since most
existing herd behavior indices do not provide a comparative method, we propose
a new herd behavior index and demonstrate its desirable properties through
simple theoretical models. As for empirical analysis, we use global stock
market data from Morgan Stanley Capital International to study herd behavior
especially during periods of financial crises in detail.


title:
Steady state properties of a driven atomic ensemble with non-local
  dissipation

abstract:
  The steady state of a driven dense ensemble of two-level atoms is determined
from the competition of coherent laser excitation and decay that acts in a
correlated way on several atoms simultaneously. We show that the presence of
this non-local dissipation lifts the direct link between the density of excited
atoms and the photon emission rate which is typically present when atoms decay
independently. The non-locality disconnects these static and dynamic
observables so that a dynamical transition in one does not necessarily imply a
transition in the other. Furthermore, the collective nature of the quantum jump
operators governing the non-local decay results in the formation of spatial
coherence in the steady state which can be measured by analyzing solely global
quantities - the photon emission rate and the density of excited atoms. The
experimental realization of the system with strontium atoms in a lattice is
discussed.