title:
A Polynomial-Time Algorithm for Deciding Markov Equivalence of Directed
  Cyclic Graphical Models

abstract:
  Although the concept of d-separation was originally defined for directed
acyclic graphs (see Pearl 1988), there is a natural extension of he concept to
directed cyclic graphs. When exactly the same set of d-separation relations
hold in two directed graphs, no matter whether respectively cyclic or acyclic,
we say that they are Markov equivalent. In other words, when two directed
cyclic graphs are Markov equivalent, the set of distributions that satisfy a
natural extension of the Global Directed Markov condition (Lauritzen et al.
1990) is exactly the same for each graph. There is an obvious exponential (in
the number of vertices) time algorithm for deciding Markov equivalence of two
directed cyclic graphs; simply chech all of the d-separation relations in each
graph. In this paper I state a theorem that gives necessary and sufficient
conditions for the Markov equivalence of two directed cyclic graphs, where each
of the conditions can be checked in polynomial time. Hence, the theorem can be
easily adapted into a polynomial time algorithm for deciding the Markov
equivalence of two directed cyclic graphs. Although space prohibits inclusion
of correctness proofs, they are fully described in Richardson (1994b).


title: Coherent Knowledge Processing at Maximum Entropy by SPIRIT

abstract:
  SPIRIT is an expert system shell for probabilistic knowledge bases. Knowledge
acquisition is performed by processing facts and rules on discrete variables in
a rich syntax. The shell generates a probability distribution which respects
all acquired facts and rules and which maximizes entropy. The user-friendly
devices of SPIRIT to define variables, formulate rules and create the knowledge
base are revealed in detail. Inductive learning is possible. Medium sized
applications show the power of the system.


title: Sample-and-Accumulate Algorithms for Belief Updating in Bayes Networks

abstract:
  Belief updating in Bayes nets, a well known computationally hard problem, has
recently been approximated by several deterministic algorithms, and by various
randomized approximation algorithms. Deterministic algorithms usually provide
probability bounds, but have an exponential runtime. Some randomized schemes
have a polynomial runtime, but provide only probability estimates. We present
randomized algorithms that enumerate high-probability partial instantiations,
resulting in probability bounds. Some of these algorithms are also sampling
algorithms. Specifically, we introduce and evaluate a variant of backward
sampling, both as a sampling algorithm and as a randomized enumeration
algorithm. We also relax the implicit assumption used by both sampling and
accumulation algorithms, that query nodes must be instantiated in all the
samples.


title: A Measure of Decision Flexibility

abstract:
  We propose a decision-analytical approach to comparing the flexibility of
decision situations from the perspective of a decision-maker who exhibits
constant risk-aversion over a monetary value model. Our approach is simple yet
seems to be consistent with a variety of flexibility concepts, including robust
and adaptive alternatives. We try to compensate within the model for
uncertainty that was not anticipated or not modeled. This approach not only
allows one to compare the flexibility of plans, but also guides the search for
new, more flexible alternatives.


title: Binary Join Trees

abstract:
  The main goal of this paper is to describe a data structure called binary
join trees that are useful in computing multiple marginals efficiently using
the Shenoy-Shafer architecture. We define binary join trees, describe their
utility, and sketch a procedure for constructing them.


title: Efficient Enumeration of Instantiations in Bayesian Networks

abstract:
  Over the past several years Bayesian networks have been applied to a wide
variety of problems. A central problem in applying Bayesian networks is that of
finding one or more of the most probable instantiations of a network. In this
paper we develop an efficient algorithm that incrementally enumerates the
instantiations of a Bayesian network in decreasing order of probability. Such
enumeration algorithms are applicable in a variety of applications ranging from
medical expert systems to model-based diagnosis. Fundamentally, our algorithm
is simply performing a lazy enumeration of the sorted list of all
instantiations of the network. This insight leads to a very concise algorithm
statement which is both easily understood and implemented. We show that for
singly connected networks, our algorithm generates the next instantiation in
time polynomial in the size of the network. The algorithm extends to arbitrary
Bayesian networks using standard conditioning techniques. We empirically
evaluate the enumeration algorithm and demonstrate its practicality.


title: On Separation Criterion and Recovery Algorithm for Chain Graphs

abstract:
  Chain graphs give a natural unifying point of view on Markov and Bayesian
networks and enlarge the potential of graphical models for description of
conditional independence structures. In the paper a direct graphical separation
criterion for chain graphs, called c-separation, which generalizes the
d-separation criterion for Bayesian networks is introduced (recalled). It is
equivalent to the classic moralization criterion for chain graphs and complete
in sense that for every chain graph there exists a probability distribution
satisfying exactly conditional independencies derivable from the chain graph by
the c-separation criterion. Every class of Markov equivalent chain graphs can
be uniquely described by a natural representative, called the largest chain
graph. A recovery algorithm, which on basis of the (conditional) dependency
model induced by an unknown chain graph finds the corresponding largest chain
graph, is presented.


title:
Possible World Partition Sequences: A Unifying Framework for Uncertain
  Reasoning

abstract:
  When we work with information from multiple sources, the formalism each
employs to handle uncertainty may not be uniform. In order to be able to
combine these knowledge bases of different formats, we need to first establish
a common basis for characterizing and evaluating the different formalisms, and
provide a semantics for the combined mechanism. A common framework can provide
an infrastructure for building an integrated system, and is essential if we are
to understand its behavior. We present a unifying framework based on an ordered
partition of possible worlds called partition sequences, which corresponds to
our intuitive notion of biasing towards certain possible scenarios when we are
uncertain of the actual situation. We show that some of the existing
formalisms, namely, default logic, autoepistemic logic, probabilistic
conditioning and thresholding (generalized conditioning), and possibility
theory can be incorporated into this general framework.


title:
Supply Restoration in Power Distribution Systems - A Case Study in
  Integrating Model-Based Diagnosis and Repair Planning

abstract:
  Integrating diagnosis and repair is particularly crucial when gaining
sufficient information to discriminate between several candidate diagnoses
requires carrying out some repair actions. A typical case is supply restoration
in a faulty power distribution system. This problem, which is a major concern
for electricity distributors, features partial observability, and stochastic
repair actions which are more elaborate than simple replacement of components.
This paper analyses the difficulties in applying existing work on integrating
model-based diagnosis and repair and on planning in partially observable
stochastic domains to this real-world problem, and describes the pragmatic
approach we have retained so far.


title: Real Time Estimation of Bayesian Networks

abstract:
  For real time evaluation of a Bayesian network when there is not sufficient
time to obtain an exact solution, a guaranteed response time, approximate
solution is required. It is shown that nontraditional methods utilizing
estimators based on an archive of trial solutions and genetic search can
provide an approximate solution that is considerably superior to the
traditional Monte Carlo simulation methods.


title: Testing Implication of Probabilistic Dependencies

abstract:
  Axiomatization has been widely used for testing logical implications. This
paper suggests a non-axiomatic method, the chase, to test if a new dependency
follows from a given set of probabilistic dependencies. Although the chase
computation may require exponential time in some cases, this technique is a
powerful tool for establishing nontrivial theoretical results. More
importantly, this approach provides valuable insight into the intriguing
connection between relational databases and probabilistic reasoning systems.


title: Optimal Factory Scheduling using Stochastic Dominance A*

abstract:
  We examine a standard factory scheduling problem with stochastic processing
and setup times, minimizing the expectation of the weighted number of tardy
jobs. Because the costs of operators in the schedule are stochastic and
sequence dependent, standard dynamic programming algorithms such as A* may fail
to find the optimal schedule. The SDA* (Stochastic Dominance A*) algorithm
remedies this difficulty by relaxing the pruning condition. We present an
improved state-space search formulation for these problems and discuss the
conditions under which stochastic scheduling problems can be solved optimally
using SDA*. In empirical testing on randomly generated problems, we found that
in 70%, the expected cost of the optimal stochastic solution is lower than that
of the solution derived using a deterministic approximation, with comparable
search effort.


title: Critical Remarks on Single Link Search in Learning Belief Networks

abstract:
  In learning belief networks, the single link lookahead search is widely
adopted to reduce the search space. We show that there exists a class of
probabilistic domain models which displays a special pattern of dependency. We
analyze the behavior of several learning algorithms using different scoring
metrics such as the entropy, conditional independence, minimal description
length and Bayesian metrics. We demonstrate that single link lookahead search
procedures (employed in these algorithms) cannot learn these models correctly.
Thus, when the underlying domain model actually belongs to this class, the use
of a single link search procedure will result in learning of an incorrect
model. This may lead to inference errors when the model is used. Our analysis
suggests that if the prior knowledge about a domain does not rule out the
possible existence of these models, a multi-link lookahead search or other
heuristics should be used for the learning process.


title:
Fractal algebraic and linguistic structures generated by the Laurent
  series for the Gamma function near its negative poles

abstract:
  We give closed-form expressions for the Laurent series coefficients of the
Gamma function near all its strictly negative singularities. These closed-form
expressions are clearly self-similar. We briefly describe their algebraic and
grammatical budding patterns. As the degree of the coefficient grows to
infinity its global structure becomes a fractal.


title:
Testing the Universality of the Fundamental Metallicity Relation at High
  Redshift Using Low-Mass Gravitationally Lensed Galaxies

abstract:
  We present rest-frame optical spectra for a sample of 9 low-mass star-forming
galaxies in the redshift range 1.5 < z < 3 which are gravitationally lensed by
foreground clusters. We used Triplespec, an echelle spectrograph at the Palomar
200-inch telescope that is very effective for this purpose as it samples the
entire near-infrared spectrum simultaneously. By measuring the flux of nebular
emission lines we derive gas phase metallicities and star formation rates, and
by fitting the optical to infrared spectral energy distributions we obtain
stellar masses. Taking advantage of the high magnification due to strong
lensing we are able to probe the physical properties of galaxies with stellar
masses in the range 7.8 < log M/Msun < 9.4 whose star formation rates are
similar to those of typical star-forming galaxies in the local universe. We
compare our results with the locally determined relation between stellar mass,
gas metallicity and star formation rate. Our data are in excellent agreement
with this relation, with an average offset <Delta log O/H> = 0.01 +/- 0.08,
suggesting a universal relationship. Remarkably, the scatter around the
fundamental metallicity relation is only 0.24 dex, smaller than that observed
locally at the same stellar masses, which may provide an important additional
constraint for galaxy evolution models.


title:
Simulations of two-planet systems through all phases of stellar
  evolution: implications for the instability boundary and white dwarf
  pollution

abstract:
  Exoplanets have been observed at many stages of their host star's life,
including the main sequence (MS), subgiant and red giant branch stages. Also,
polluted white dwarfs (WDs) likely represent dynamically active systems at late
times. Here, we perform 3-body simulations which include realistic post-MS
stellar mass loss and span the entire lifetime of exosystems with two massive
planets, from the endpoint of formation to several Gyr into the WD phase of the
host star. We find that both MS and WD systems experience ejections and
star-planet collisions (Lagrange instability) even if the planet-planet
separation well-exceeds the analytical orbit-crossing (Hill instability)
boundary. Consequently, MS-stable planets do not need to be closely-packed to
experience instability during the WD phase. This instability may pollute the WD
directly through collisions, or, more likely, indirectly through increased
scattering of smaller bodies such as asteroids or comets. Our simulations show
that this instability occurs predominately between tens of Myr to a few Gyrs of
WD cooling.


title:
Isolated galaxies in hierarchical galaxy formation models - present-day
  properties and environmental histories

abstract:
  In this study, we have carried out a detailed, statistical analysis of
isolated model galaxies, taking advantage of publicly available hierarchical
galaxy formation models. To select isolated galaxies, we employ 2D methods
widely used in the observational literature, as well as a more stringent 3D
isolation criterion that uses the full 3D-real space information. In
qualitative agreement with observational results, isolated model galaxies have
larger fractions of late-type, star forming galaxies with respect to randomly
selected samples of galaxies with the same mass distribution. We also find that
the samples of isolated model galaxies typically contain a fraction of less
than 15 per cent of satellite galaxies, that reside at the outskirts of their
parent haloes where the galaxy number density is low. Projection effects cause
a contamination of 2D samples of about 18 per cent, while we estimate a typical
completeness of 65 per cent. Our model isolated samples also include a very
small (few per cent) fraction of bulge dominated galaxies (B/T > 0.8) whose
bulges have been built mainly by minor mergers. Our study demonstrates that
about 65-70 per cent of 2D isolated galaxies that are classified as isolated at
z = 0 have indeed been completely isolated since z = 1 and only 7 per cent have
had more than 3 neighbours within a comoving radius of 1 Mpc. Irrespectively of
the isolation criteria, roughly 45 per cent of isolated galaxies have
experienced at least one merger event in the past (most of the mergers are
minor, with mass ratios between 1:4 and 1:10). The latter point validates the
approximation that isolated galaxies have been mainly influenced by internal
processes.


title:
Disclination classes, fractional excitations, and the melting of quantum
  liquid crystals

abstract:
  We consider how fractional excitations bound to a dislocation evolve as the
dislocation is separated into a pair of disclinations. We show that some
dislocation-bound excitations (such as Majorana modes and half-quantum
vortices) are possible only if the elementary dislocation consists of two
inequivalent disclinations, as is the case for stripes or square lattices but
not for triangular lattices. The existence of multiple inequivalent
disclination classes governs the two-dimensional melting of quantum liquid
crystals (i.e., nematics and hexatics), determining whether superfluidity and
orientational order can simultaneously vanish at a continuous transition.


title: GALA: an automatic tool for the abundance analysis of stellar spectra

abstract:
  GALA is a freely distributed Fortran code to derive automatically the
atmospheric parameters (temperature, gravity, microturbulent velocity and
overall metallicity) and abundances for individual species of stellar spectra
using the classical method based on the equivalent widths of metallic lines.
The abundances of individual spectral lines are derived by using the WIDTH9
code developed by R. L. Kurucz. GALA is designed to obtain the best model
atmosphere, by optimizing temperature, surface gravity, microturbulent velocity
and metallicity, after rejecting the discrepant lines. Finally, it computes
accurate internal errors for each atmospheric parameter and abundance. The code
permits to obtain chemical abundances and atmospheric parameters for large
stellar samples in a very short time, thus making GALA an useful tool in the
epoch of the multi-object spectrographs and large surveys. An extensive set of
tests with both synthetic and observed spectra is performed and discussed to
explore the capabilities and robustness of the code.


title:
Mono-everything: combined limits on dark matter production at colliders
  from multiple final states

abstract:
  Searches for dark matter production at particle colliders are complementary
to direct-detection and indirect-detection experiments, and especially powerful
for small masses, $m_\chi<100$ GeV. An important collider dark matter signature
is due to the production of a pair of these invisible particles with the
initial-state radiation of a standard model particle. Currently, collider
searches use individual and nearly orthogonal final states to search for
initial-state jets, photons or massive gauge bosons. We combine these results
across final states and across experiments to give the strongest current
collider-based limits in the context of effective field theories, and map these
to limits on dark matter interactions with nuclei and to dark matter
self-annhiliation.


title: Accurate Sky Continuum Subtraction with Fibre-fed Spectrographs

abstract:
  Fibre-fed spectrographs now have throughputs equivalent to slit
spectrographs. However, the sky subtraction accuracy that can be reached has
often been pinpointed as one of the major issues associated with the use of
fibres. Using technical time observations with FLAMES-GIRAFFE, two observing
techniques, namely dual staring and cross beam-switching, were tested and the
resulting sky subtraction accuracy reached in both cases was quantified.
Results indicate that an accuracy of 0.6% on sky subtraction can be reached,
provided that the cross beam-switching mode is used. This is very encouraging
with regard to the detection of very faint sources with future fibre-fed
spectrographs, such as VLT/MOONS or E-ELT/MOSAIC.


title: GALA cookbook

abstract:
  GALA (Mucciarelli et al. 2013) is a code written in standard Fortran 77 and
aimed at finding the best atmospheric parameters and the abundance of
individual elements by using the equivalent widths (EWs) of metallic lines,
providing graphical and statistical tools to evaluate the goodness of the
solution. The derivation of the abundances is performed by using a modified
version of the WIDTH9 code(originally developed by R. L. Kurucz) in its Linux
version (Sbordone et al. 2004). In the current release, GALA can manage the
classical grid of ATLAS9 models computed by (Castelli & Kurucz, 2004), the grid
of new ATLAS9 models computed for the APOGEE survey (Mezsaros et al., 2012) and
the MARCS models with the standard composition (Gustafsson et al., 2008). When
the ATLAS9 models are used, new model atmospheres are calculated starting from
an existing guess model and according to the pre-tabulated Opacity Distribution
Functions (ODF) and Rosseland opacity tables. When MARCS are used, each new
model is obtained by interpolating within the MARCS grid.


title:
INTEGRAL/IBIS and optical observations of the Crab nebula/pulsar
  polarisation

abstract:
  Previous INTEGRAL/IBIS observations have shown that the gamma-ray radiation
of the Crab Nebula is highly polarised and remarkably aligned along the axis of
rotation of the pulsar (Forot et al. 2008). Their study was based on the first
four years of operation of the satellite. Here we present an analysis based
upon nearly ten years of operation. This new analysis allows a better
characterisation of the polarisation fraction and position angle, as well as a
measure of spectral energy distribution of the polarised component. These
results are then compared to the known optical polarisation of the pulsar and
nearby synchrotron knot. In the future we shall compare the gamma-ray
polarisation with the phase-resolved optical polarisation using instruments
such as GASP (Kyne et al. 2010).


title:
Non shifted calculus of variations on time scales with
  Nabla-differentiable Sigma

abstract:
  In calculus of variations on general time scales, an integral Euler-Lagrange
equation is usually derived in order to characterize the critical points of non
shifted Lagrangian functionals, see e.g. [R.A.C. Ferreira and co-authors,
Optimality conditions for the calculus of variations with higher-order delta
derivatives, Appl. Math. Lett., 2011].
  In this paper, we prove that the Nabla-differentiability of the forward jump
operator Sigma is a sharp assumption in order to obtain an Euler-Lagrange
equation of differential form. Furthermore, this differential form allows us to
prove a Noether-type theorem providing an explicit constant of motion for
differential Euler-Lagrange equations admitting a symmetry.


title:
Knotting of linear DNA in nano-slits and nano-channels: a numerical
  study

abstract:
  The amount and type of self-entanglement of DNA filaments is significantly
affected by spatial confinement, which is ubiquitous in biological systems.
Motivated by recent advancements in single DNA molecule experiments based on
nanofluidic devices, and by the introduction of algorithms capable of detecting
knots in open chains, we investigate numerically the entanglement of linear,
open DNA chains confined inside nano-slits. The results regard the abundance,
type and length of occurring knots and are compared with recent findings for
DNA inside nano-channels. In both cases, the width of the confining region, D,
spans the 30nm- 1\mu m range and the confined DNA chains are 1 to 4\mu m long.
It is found that the knotting probability is maximum for slit widths in the
70-100nm range. However, over the considered DNA contour lengths, the maximum
incidence of knots remains below 20%, while for channel confinement it tops
50%. Further differences of the entanglement are seen for the average contour
length of the knotted region which drops significantly below D ~100nm for
channel-confinement, while it stays approximately constant for slit-like
confinement. These properties ought to reverberate in different kinetic
properties of linear DNA depending on confinement and could be detectable
experimentally or exploitable in nano-technological applications.


title:
Pattern Formations of 2D Rayleigh-B\`enard Convection with No-Slip
  Boundary Conditions for the Velocity at the Critical Length Scales

abstract:
  We study the Rayleigh-B{\'e}nard convection in a 2-D rectangular domain with
no-slip boundary conditions for the velocity. The main mathematical challenge
is due to the no-slip boundary conditions, since the separation of variables
for the linear eigenvalue problem which works in the free-slip case is no
longer possible. It is well known that as the Rayleigh number crosses a
critical threshold $R_c$, the system bifurcates to an attractor, which is an
$(m-1)$--dimensional sphere, where $m$ is the number of eigenvalues which cross
zero as R crosses $R_c$. The main objective of this article is to derive a full
classification of the structure of this bifurcated attractor when $m=2$. More
precisely, we rigorously prove that when $m=2$, the bifurcated attractor is
homeomorphic to a one-dimensional circle consisting of exactly four or eight
steady states and their connecting heteroclinic orbits. In addition, we show
that the mixed modes can be stable steady states for small Prandtl numbers.


title:
Understanding Galaxy Outflows as the Product of Unstable Turbulent
  Support

abstract:
  The interstellar medium is a multiphase gas in which turbulent support is as
important as thermal pressure. Sustaining this configuration requires both
continuous turbulent stirring and continuous radiative cooling to match the
decay of turbulent energy. While this equilibrium can persist for small
turbulent velocities, if the one-dimensional velocity dispersion is larger than
approximately 35 km/s, the gas moves into an unstable regime that leads to
rapid heating. I study the implications of this turbulent runaway, showing that
it causes a hot gas outflow to form in all galaxies with a gas surface density
above approximately 50 solar masses/pc^2 corresponding to a star formation rate
per unit area of 0.1$ solar masses/yr/kpc^2. For galaxies with escape
velocities above 200 km/s, the sonic point of this hot outflow should lie
interior to the region containing cold gas and stars, while for galaxies with
smaller escape velocities, the sonic point should lie outside this region. This
leads to efficient cold cloud acceleration in higher mass galaxies, while in
lower mass galaxies, clouds may be ejected by random turbulent motions rather
than accelerated by the wind. Finally, I show that energy balance cannot be
achieved at all for turbulent media above a surface density of approximately
10^5 solar masses/pc^2.


title:
Transport Theory of Monolayer Transition-Metal Dichalcogenides through
  Symmetry

abstract:
  We present a theory that elucidates the major momentum and spin relaxation
processes for electrons, holes and hot excitons in monolayer transition-metal
dichalcogenides. We expand on spin flips induced by flexural phonons and show
that the spin relaxation is ultrafast for electrons in free-standing membranes
while being mitigated in supported membranes. This behavior due to interaction
with flexural phonons is universal in two-dimensional membranes that respect
mirror symmetry and it leads to a counterintuitive inverse relation between
mobility and spin relaxation.


title: Top Quark Physics at the Tevatron

abstract:
  The heaviest known elementary particle, the top quark, was discovered in 1995
by the CDF and D0 collaborations at the Tevatron proton-antiproton collider at
Fermilab. Since its discovery, a large program was set in motion by the CDF and
D0 collaborations to characterize the production and decay properties of top
quarks, and investigate their potential for searches of new phenomena beyond
the standard model. During the past 20 years, new methods were developed and
implemented to improve the measurements and searches for new physics in the
top-quark sector. This article reviews the achievements and results obtained
through studies of the top quark at the Tevatron.


title: Partial k-Parallelisms in Finite Projective Spaces

abstract:
  In this paper we consider the following question. What is the maximum number
of pairwise disjoint $k$-spreads which exist in PG(n,q)? We prove that if k+1
divides n+1 and n>k then there exist at least two disjoint k-spreads in PG(n,q)
and there exist at least $2^{k+1}-1$ pairwise disjoint $k$-spreads in PG(n,2).
We also extend the known results on parallelism in a projective geometry from
which the points of a given subspace were removed.


title: A Non-Renormalization Theorem in Gapped Quantum Field Theory

abstract:
  We discuss the two-point functions of the U(1) current and energy-momentum
tensor in certain gapped three-dimensional field theories, and show that the
parity-odd part in both of these correlation functions is one-loop exact. In
particular, we find a new and simplified derivation of the Coleman-Hill theorem
that also clarifies several subtleties in the original argument. For the energy
momentum tensor, our result means that the gravitational Chern-Simons term for
the background metric does not receive quantum corrections


title:
The Neutral Hydrogen Content of Galaxies in Cosmological Hydrodynamic
  Simulations

abstract:
  We examine the global HI properties of galaxies in quarter-billion particle
cosmological simulations using Gadget-2, focusing on how galactic outflows
impact HI content. We consider four outflow models, including a new one (ezw)
motivated by recent interstellar medium simulations in which the wind speed and
mass loading factor scale as expected for momentum-driven outflows for larger
galaxies and energy-driven outflows for dwarfs (sigma<75 km/s). To obtain
predicted HI masses, we employ a simple but effective local correction for
particle self-shielding, and an observationally-constrained transition from
neutral to molecular hydrogen. Our ezw simulation produces an HI mass function
whose faint-end slope of -1.3 agrees well with observations from the ALFALFA
survey; other models agree less well. Satellite galaxies have a bimodal
distribution in HI fraction versus halo mass, with smaller satellites and/or
those in larger halos more often being HI-deficient. At a given stellar mass,
HI content correlates with star formation rate and inversely correlates with
metallicity, as expected if driven by stochasticity in the accretion rate. To
higher redshifts, massive HI galaxies disappear and the mass function steepens.
The global cosmic HI density conspires to remain fairly constant from z~5-0,
but the relative contribution from smaller galaxies increases with redshift.


title:
Vector-Valued Polynomials and a Matrix Weight Function with
  $B_2$-Action. II

abstract:
  This is a sequel to [SIGMA 9 (2013), 007, 23 pages, arXiv:1210.1177], in
which there is a construction of a $2\times2$ positive-definite matrix function
$K (x)$ on $\mathbb{R}^{2}$. The entries of $K(x)$ are expressed in terms of
hypergeometric functions. This matrix is used in the formula for a Gaussian
inner product related to the standard module of the rational Cherednik algebra
for the group $W(B_2)$ (symmetry group of the square) associated to the
(2-dimensional) reflection representation. The algebra has two parameters:
$k_{0}$, $k_{1}$. In the previous paper $K$ is determined up to a scalar,
namely, the normalization constant. The conjecture stated there is proven in
this note. An asymptotic formula for a sum of $_{3}F_{2}$-type is derived and
used for the proof.


title:
Inside the SU(3) quark-antiquark QCD flux tube: screening versus quantum
  widening

abstract:
  In lattice QCD, colour confinement manifests in flux tubes. We compute in
detail the quark-antiquark flux tube for pure gauge SU(3) dimension $D=3+1$ for
quark-antiquark distances R ranging from 0.4 fm to 1.4 fm. To increase the
signal over noise ratio, we apply the improved multihit and extended smearing
techniques. We detail the gauge invariant squared components of the colour
electric and colour magnetic fields both in the mediator plane between the
static quark and static antiquark and in the planes of the sources. We fit the
field densities with appropriate ansatze and we observe the screening of the
colour fields in all studied planes together with the quantum widening of the
flux tube in the mediator plane. All components squared of the colour fields
are non-vanishing and are consistent with a penetration length lambda ~ 0.22 to
0.24 fm and an effective screening mass mu ~ 0.9 to 0.8 GeV. The quantum
widening of the flux tube is well fitted with a logarithmic law in R.


title:
Radical transversal lightlike hypersurfaces of almost complex manifolds
  with Norden metric

abstract:
  In this paper we introduce radical transversal lightlike hypersurfaces of
almost complex manifolds with Norden metric. The study of these hypersurfaces
is motivated by the fact that for indefinite almost Hermitian manifolds this
class of lightlike hypersurfaces does not exist. We also establish that radical
transversal lightlike hypersurfaces of almost complex manifolds with Norden
metric have nice properties as a unique screen distribution and a symmetric
Ricci tensor of the considered hypersurfaces of Kaehler manifolds with Norden
metric. We obtain new results about lightlike hypersurfaces concerning to their
relations with non-degenerate hypersurfaces of almost complex manifolds with
Norden metric. Examples of the considered hypersurfaces are given.


title: Homological Equation for Tensor Field and Periodic Averaging

abstract:
  Homological equations of tensor type associated to periodic flows on a
manifold are studied. The Cushman intrinsic formula is generalized to the case
of multivector fields and differential forms. Some applications to normal forms
and the averaging method for perturbed Hamiltonian systems on slow-fast phase
spaces are given.


title: A Branch-and-Cut Strategy for the Manickam-Miklos-Singhi Conjecture

abstract:
  The Manickam-Miklos-Singhi Conjecture states that when n is at least 4k,
every multiset of n real numbers with nonnegative total sum has at least (n-1
choose k-1) k-subsets with nonnegative sum. We develop a branch-and-cut
strategy using a linear programming formulation to show that verifying the
conjecture for fixed values of k is a finite problem. To improve our search, we
develop a zero-error randomized propagation algorithm. Using implementations of
these algorithms, we verify a stronger form of the conjecture for all k at most
seven.


title:
Quantization and superselection sectors III: Multiply connected spaces
  and indistinguishable particles

abstract:
  We reconsider the (non-relativistic) quantum theory of indistinguishable
particles on the basis of Rieffel's notion of C*-algebraic (`strict')
deformation quantization. Using this formalism, we relate the operator approach
of Messiah and Greenberg (1964) to the configuration space approach due to
Souriau (1967), Laidlaw and DeWitt (1971), Leinaas and Myrheim (1977), and
others. The former allows parastatistics, whereas the latter apparently leaves
room for bosons and fermions only. This seems to contradict the operator
approach as far as the admissibility of parastatistics is concerned. To resolve
this, we first prove that the topologically nontrivial configuration spaces of
the second approach are quantized by the algebras of observables of the first.
Second, we show that the irreducible representations of the latter may be
realized by vector bundle constructions, which include the line bundles of the
second approach: representations on higher-dimensional bundles (which define
parastatistics) cannot be excluded a priori. However, we show that the
corresponding particle states may always be realized in terms of bosons and/or
fermions with an unobserved internal degree of freedom. Although based on
non-relativistic quantum mechanics, this conclusion is analogous to the
rigorous results of the Doplicher-Haag-Roberts analysis in algebraic quantum
field theory, as well as to the heuristic arguments which led Gell-Mann and
others to QCD.


title: Kitaev's Z_d-Codes Threshold Estimates

abstract:
  We study the quantum error correction threshold of Kitaev's toric code over
the group Z_d subject to a generalized bit-flip noise. This problem requires
novel decoding techniques, and for this purpose we generalize the
renormalization group method we previously introduced for Z_2 topological
codes.


title: A Latent Source Model for Nonparametric Time Series Classification

abstract:
  For classifying time series, a nearest-neighbor approach is widely used in
practice with performance often competitive with or better than more elaborate
methods such as neural networks, decision trees, and support vector machines.
We develop theoretical justification for the effectiveness of
nearest-neighbor-like classification of time series. Our guiding hypothesis is
that in many applications, such as forecasting which topics will become trends
on Twitter, there aren't actually that many prototypical time series to begin
with, relative to the number of time series we have access to, e.g., topics
become trends on Twitter only in a few distinct manners whereas we can collect
massive amounts of Twitter data. To operationalize this hypothesis, we propose
a latent source model for time series, which naturally leads to a "weighted
majority voting" classification rule that can be approximated by a
nearest-neighbor classifier. We establish nonasymptotic performance guarantees
of both weighted majority voting and nearest-neighbor classification under our
model accounting for how much of the time series we observe and the model
complexity. Experimental results on synthetic data show weighted majority
voting achieving the same misclassification rate as nearest-neighbor
classification while observing less of the time series. We then use weighted
majority to forecast which news topics on Twitter become trends, where we are
able to detect such "trending topics" in advance of Twitter 79% of the time,
with a mean early advantage of 1 hour and 26 minutes, a true positive rate of
95%, and a false positive rate of 4%.


title: The Anderson model with missing sites

abstract:
  In the present note we show dynamical localization for an Anderson model with
missing sites in a discrete setting at the bottom of the spectrum in arbitrary
dimension $d$. In this model, the random potential is defined on a relatively
dense subset of $\mathbb Z^d$, not necessarily periodic, i.e., a Delone set in
$\mathbb Z^d$. To work in the lower band edge we need no further assumption on
the geometric complexity of the Delone set. We use a spatial averaging argument
by Bourgain-Kenig to obtain a uniform Wegner estimate and an initial length
scale estimate, which yields localization through the Multiscale Analysis for
non ergodic models. This argument gives an explicit dependence on the maximal
distance parameter of the Delone set for the Wegner estimate. We discuss the
case of the upper spectral band edge and the arising need of imposing the
(complexity) condition of strict uniform pattern frequency on the Delone set.


title: Majorana Fermions: The race continues

abstract:
  A critical overview is given, aimed at non-specialist audience, of the recent
efforts to detect and manipulate Majorana fermions in solid state devices. It
is argued that the experiments on semiconductor quantum wires proximity coupled
to superconducting leads present tantalizing hints but not a definitive
evidence for these elusive particles.


title: From Nobel Prize to Project Management: Getting Risks Right

abstract:
  A major source of risk in project management is inaccurate forecasts of
project costs, demand, and other impacts. The paper presents a promising new
approach to mitigating such risk, based on theories of decision making under
uncertainty which won the 2002 Nobel prize in economics. First, the paper
documents inaccuracy and risk in project management. Second, it explains
inaccuracy in terms of optimism bias and strategic misrepresentation. Third,
the theoretical basis is presented for a promising new method called "reference
class forecasting," which achieves accuracy by basing forecasts on actual
performance in a reference class of comparable projects and thereby bypassing
both optimism bias and strategic misrepresentation. Fourth, the paper presents
the first instance of practical reference class forecasting, which concerns
cost forecasts for large transportation infrastructure projects. Finally,
potentials for and barriers to reference class forecasting are assessed.


title: Can magnetar spin-down power extended emission in some short GRBs?

abstract:
  Extended emission gamma-ray bursts are a subset of the `short' class of burst
which exhibit an early time rebrightening of gamma emission in their light
curves. This extended emission arises just after the initial emission spike,
and can persist for up to hundreds of seconds after trigger. When their light
curves are overlaid, our sample of 14 extended emission bursts show a
remarkable uniformity in their evolution, strongly suggesting a common central
engine powering the emission. One potential central engine capable of this is a
highly magnetized, rapidly rotating neutron star, known as a magnetar.
Magnetars can be formed by two compact objects coallescing, a scenario which is
one of the leading progenitor models for short bursts in general. Assuming a
magnetar is formed, we gain a value for the magnetic field and late time spin
period for 9 of the extended emission bursts by fitting the magnetic dipole
spin-down model of Zhang & Meszaros (2001). Assuming the magnetic field is
constant, and the observed energy release during extended emission is entirely
due to the spin-down of this magnetar, we then derive the spin period at birth
for the sample. We find all birth spin periods are in good agreement with those
predicted for a newly born magnetar.


title: Optical Observations of the Transiting Exoplanet GJ 1214b

abstract:
  We observed nine primary transits of the super-Earth exoplanet GJ 1214b in
several optical photometric bands from March to August 2012, with the goal of
constraining the short-wavelength slope of the spectrum of GJ 1214b. Our
observations were conducted on the Kuiper 1.55 m telescope in Arizona and the
STELLA-I robotic 1.2 m telescope in Tenerife, Spain. From the derived light
curves we extracted transit depths in R (0.65 {\mu}m), V (0.55 {\mu}m), and g'
(0.475 {\mu}m) bands. Most previous observations of this exoplanet suggest a
flat spectrum varying little with wavelength from the near-infrared to the
optical, corresponding to a low-scale-height, high-molecular-weight atmosphere.
However, a handful of observations around Ks band (~2.15 {\mu}m) and g-band
(~0.46 {\mu}m) are inconsistent with this scenario and suggest a variation on a
hydrogen- or water-dominated atmosphere that also contains a haze layer of
small particles. In particular, the g-band observations of de Mooij et al.
(2012), consistent with Rayleigh scattering, limit the potential atmosphere
compositions of GJ 1214b due to the increasing slope at optical wavelengths
(Howe & Burrows 2012). We find that our results overlap within errors the
short-wavelength observations of de Mooij et al. (2012), but are also
consistent with a spectral slope of zero in GJ 1214b in the optical wavelength
region. Our observations thus allow for a larger suite of possible atmosphere
compositions, including those with a high-molecular-weight and/or hazes.


title: Aharony Dualities for 3d Theories with Adjoint Matter

abstract:
  We study Aharony dualities for 3d N=2 gauge theories of classical gauge group
with one adjoint and fundamental matters. We work out the 3d superconformal
index for the dual pairs to find the perfect matchings. Along with it, we
enumerate the independent monopole operators parametrizing the Coulomb branches
and confirm the nonperturbative truncation of the chiral rings, consistent with
the proposed dualities.


title:
Effects of Minijets on Common Observables in Heavy-Ion Collisions with
  Uncommon Implications

abstract:
  In this brief review of the observable effects of minijets in heavy-ion
collisions the main points emphasized are that the quadruple moment
$v_2(p_T,b)$ and the hadronic ($\pi$ and $p$) spectra at low $p_T$ can both be
reproduced by minijet contributions to the recombination of thermal and shower
partons. Without using hydrodynamics the minijet approach does not trace the
evolution of the expanding system. The thermal distribution of the medium
partons at the time of hadronization is assumed, but rapid thermalization
initially is not required so as to allow minijets to leave their footprints on
the system in the final state. Azimuthal anisotropy due to minijets is directly
calculated in the momentum space without any fluid assumption relating the
spatial eccentricity to $v_2$. There are no more parameters used, compared to
the hydro approach in fitting the data on $v_2$ and $p_T$ spectra. Thus both
approaches satisfy the sufficiency condition for a viable description of the
dynamical process involved.


title: Phase transitions and equilibrium measures in random matrix models

abstract:
  The paper is devoted to a study of phase transitions in the Hermitian random
matrix models with a polynomial potential. In an alternative equivalent
language, we study families of equilibrium measures on the real line in a
polynomial external field. The total mass of the measure is considered as the
main parameter, which may be interpreted also either as temperature or time.
Our main tools are differentiation formulas with respect to the parameters of
the problem, and a representation of the equilibrium potential in terms of a
hyperelliptic integral. Using this combination we introduce and investigate a
dynamical system (system of ODE's) describing the evolution of families of
equilibrium measures. On this basis we are able to systematically derive a
number of new results on phase transitions, such as the local behavior of the
system at all kinds of phase transitions, as well as to review a number of
known ones.


title:
Causality and non-equilibrium second-order phase transitions in
  inhomogeneous systems

abstract:
  When a second-order phase transition is crossed at fine rate, the evolution
of the system stops being adiabatic as a result of the critical slowing down in
the neighborhood of the critical point. In systems with a topologically
nontrivial vacuum manifold, disparate local choices of the ground state lead to
the formation of topological defects. The universality class of the transition
imprints a signature on the resulting density of topological defects: It obeys
a power law in the quench rate, with an exponent dictated by a combination of
the critical exponents of the transition. In inhomogeneous systems the
situation is more complicated, as the spontaneous symmetry breaking competes
with bias caused by the influence of the nearby regions that already chose the
new vacuum. As a result, the choice of the broken symmetry vacuum may be
inherited from the neighboring regions that have already entered the new phase.
This competition between the inherited and spontaneous symmetry breaking
enhances the role of causality, as the defect formation is restricted to a
fraction of the system where the front velocity surpasses the relevant sound
velocity and phase transition remains effectively homogeneous. As a
consequence, the overall number of topological defects can be substantially
suppressed. When the fraction of the system is small, the resulting total
number of defects is still given by a power law related to the universality
class of the transition, but exhibits a more pronounced dependence on the
quench rate. This enhanced dependence complicates the analysis but may also
facilitate experimental test of defect formation theories.


title: Ruderman-Kittel-Kasuya-Yosida interaction in biased bilayer graphene

abstract:
  We study the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two
contact magnetic impurities placed on bilayer graphene (BLG). We compute the
interaction mediated by the carriers of the pristine and biased BLG as well as
the conduction electrons of the doped system. The results are obtained from the
linear-response expression for the susceptibility written in terms of the
integral over lattice Green's functions. For the unbiased system, we obtain
some analytical expressions in terms of the Meijer G-functions, which consist
of the product of two oscillatory terms, one coming from the interference
between the two Dirac points and the second coming from the Fermi momentum. In
particular, for the undoped BLG, the system exhibits the RKKY interaction
commensurate with its bipartite nature as expected from the particle-hole
symmetry of the system. Furthermore, we explore a beating pattern of
oscillations of the RKKY interaction in a highly doped BLG system within the
four-band continuum model. Besides, we discuss the discrepancy between the
short-range RKKY interaction calculated from the two-band model and that
obtained from the four-band continuum model. The final results for the applied
gate voltage are obtained numerically and are fitted with the functional forms
based on the results for the unbiased case. In this case, we show that the
long-range behavior is scaled with a momentum that depends on Fermi energy and
gate voltage, allowing the possibility of tuning of the RKKY interaction by
gate voltage.


title: Curvature properties of 3-quasi-Sasakian manifolds

abstract:
  We find some curvature properties of 3-quasi-Sasakian manifolds which are
similar to some well-known identities holding in the Sasakian case. As an
application, we prove that any 3-quasi-Sasakian manifold of constant horizontal
sectional curvature is necessarily either 3-\alpha-Sasakian or 3-cosymplectic.


title:
Large-scale neural network model for functional networks of the human
  cortex

abstract:
  We investigate the influence of indirect connections, interregional distance
and collective effects on the large-scale functional networks of the human
cortex. We study topologies of empirically derived resting state networks
(RSNs), extracted from fMRI data, and model dynamics on the obtained networks.
The RSNs are calculated from mean time-series of blood-oxygen-level-dependent
(BOLD) activity of distinct cortical regions via Pearson correlation
coefficients. We compare functional-connectivity networks of simulated BOLD
activity as a function of coupling strength and correlation threshold. Neural
network dynamics underpinning the BOLD signal fluctuations are modelled as
excitable FitzHugh-Nagumo oscillators subject to uncorrelated white Gaussian
noise and time-delayed interactions to account for the finite speed of the
signal propagation along the axons. We discuss the functional connectivity of
simulated BOLD activity in dependence on the signal speed and correlation
threshold and compare it to the empirical data.


title: Geodesics and compression bodies

abstract:
  We consider hyperbolic structures on the compression body C with genus 2
positive boundary and genus 1 negative boundary. Note that C deformation
retracts to the union of the torus boundary and a single arc with its endpoints
on the torus. We call this arc the core tunnel of C. We conjecture that, in any
geometrically finite structure on C, the core tunnel is isotopic to a geodesic.
By considering Ford domains, we show this conjecture holds for many
geometrically finite structures. Additionally, we give an algorithm to compute
the Ford domain of such a manifold, and a procedure which has been implemented
to visualize many of these Ford domains. Our computer implementation gives
further evidence for the conjecture.


title: A note on interface solutions in higher-spin gravity

abstract:
  In this paper we construct holographic interface solutions in the
Chern-Simons formulation of higher-spin gravity. It is shown that the global
regularity of the gauge connection imposes conditions on the conserved currents
consistent with interface being totally transmissive or topological. An
interface solution connecting the $W_3$ and $W_3^{(2)}$ vacuum is constructed
in the $SL(3,R)$ higher spin gravity. An interface solution corresponding to
turning on relevant deformations in higher spin $SL(4,R)$ gravity is presented.


title: Pricing Corporate Defaultable Bond using Declared Firm Value

abstract:
  We study the pricing problem for corporate defaultable bond from the
viewpoint of the investors outside the firm that could not exactly know about
the information of the firm. We consider the problem for pricing of corporate
defaultable bond in the case when the firm value is only declared in some fixed
discrete time and unexpected default intensity is determined by the declared
firm value. Here we provide a partial differential equation model for such a
defaultable bond and give its pricing formula. Our pricing model is derived to
solving problems of partial differential equations with random constants (de-
fault intensity) and terminal values of binary types. Our main method is to use
the solving method of a partial differential equation with a random constant in
every subinterval and to take expectation to remove the random constants.


title:
Evidence for a Snow Line Beyond the Transitional Radius in the TW Hya
  Protoplanetary Disk

abstract:
  We present an observational reconstruction of the radial water vapor content
near the surface of the TW Hya transitional protoplanetary disk, and report the
first localization of the snow line during this phase of disk evolution. The
observations are comprised of Spitzer-IRS, Herschel-PACS, and Herschel-HIFI
archival spectra. The abundance structure is retrieved by fitting a
two-dimensional disk model to the available star+disk photometry and all
observed H2O lines, using a simple step-function parameterization of the water
vapor content near the disk surface. We find that water vapor is abundant
(~10^{-4} per H2) in a narrow ring, located at the disk transition radius some
4AU from the central star, but drops rapidly by several orders of magnitude
beyond 4.2 AU over a scale length of no more than 0.5AU. The inner disk
(0.5-4AU) is also dry, with an upper limit on the vertically averaged water
abundance of 10^{-6} per H2. The water vapor peak occurs at a radius
significantly more distant than that expected for a passive continuous disk
around a 0.6 Msun star, representing a volatile distribution in the TW Hya disk
that bears strong similarities to that of the solar system. This is
observational evidence for a snow line that moves outward with time in passive
disks, with a dry inner disk that results either from gas giant formation or
gas dissipation and a significant ice reservoir at large radii. The amount of
water present near the snow line is sufficient to potentially catalyze the
(further) formation of planetesimals and planets at distances beyond a few AU.


title: Geometrical CP violation in the N-Higgs-doublet model

abstract:
  Geometrical CP violation is a particular type of spontaneous CP violation in
which the vacuum expectation values have phases which are calculable, i.e.
stable against the variation of the free parameters of the scalar potential.
Although originally suggested within a specific version of the
three-Higgs-doublet model, it is a generic phenomenon. We investigate its
viability and characteristic features in models with several Higgs doublets.
Our work contains both general results and illustrative examples.


title: Some Remarks on Graphical Sequences for Graphs and Bipartite Graphs

abstract:
  For finite sequence $\underbar{\em d}$ of positive integers, we consider
graphs that have $\underbar{\em d}$ as their list of vertex degrees, and
bipartite graphs for which each part has $\underbar{\em d}$ as its list of
vertex degrees. In particular, we make a connection between a result for
bipartite graphs by Alon, Ben-Shimon and Krivelevich and a result of Zverovich
and Zverovich for graphs, and we give an improvement of a result of Zverovich
and Zverovich. We show that the bipartite graphs with vertex degree sequences
$(\underbar{\em d},\underbar{\em d}\,)$ are in one to one correspondence with
graphs with loops with reduced degree sequence $\underbar{\em d}$, where the
reduced degree of a vertex is defined to be the number of edges incident to the
vertex, with loops counted only once. We also give two Erd\H{o}s--Gallai type
theorems for graphs with loops.


title: Effect of n- and p-type Doping on Coherent Phonons in GaN

abstract:
  Effect of doping on the carrier-phonon interaction in wurtzite GaN is
investigated by pump-probe reflectivity measurements using 3.1 eV light in near
resonance with the fundamental band gap of 3.39 eV. Coherent modulations of the
reflectivity due to the E2 and the A1(LO) modes, as well as the 2A1(LO)
overtone are observed. Doping of acceptor and more so for donor atoms enhances
the dephasing of the polar A1(LO) phonon via coupling with plasmons, with the
effect of donors being stronger. Doping also enhances the relative amplitude of
the coherent A1(LO) phonon with respect to that of the high-frequency E2
phonon, though it does not affect the relative intensity in Raman spectroscopic
measurements. This enhanced coherent amplitude indicates that transient
depletion field screening (TDFS), in addition to impulsive stimulated Raman
scattering (ISRS), contribute to generation of the coherent polar phonons even
for sub-band gap excitation. Because the TDFS mechanism requires
photoexcitation of carriers, we argue that the interband transition is made
possible at the surface with photon energies below the bulk band gap through
the Franz-Keldysh effect.


title: Quaternionic CR Geometry

abstract:
  Modelled on a real hypersurface in a quaternionic manifold, we introduce a
quaternionic analogue of CR structure, called quaternionic CR structure. We
define the strong pseudoconvexity of this structure as well as the notion of
quaternionic pseudohermitian structure. Following the construction of the
Tanaka-Webster connection in complex CR geometry, we construct a canonical
connection associated with a quaternionic pseudohermitian structure, when the
underlying quaternionic CR structure satisfies the ultra-pseudoconvexity which
is stronger than the strong pseudoconvexity. Comparison to Biquard's
quaternionic contact structure is also made.


title: On Zero Delay Source-Channel Coding

abstract:
  In this paper, we study the zero-delay source-channel coding problem, and
specifically the problem of obtaining the vector transformations that optimally
map between the m-dimensional source space and the k-dimensional channel space,
under a given transmission power constraint and for the mean square error
distortion. We first study the functional properties of this problem and show
that the objective is concave in the source and noise densities and convex in
the density of the input to the channel. We then derive the necessary
conditions for optimality of the encoder and decoder mappings. A well known
result in information theory pertains to the linearity of optimal encoding and
decoding mappings in the scalar Gaussian source and channel setting, at all
channel signal-to-noise ratios (CSNRs). In this paper, we study this result
more generally, beyond the Gaussian source and channel, and derive the
necessary and sufficient condition for linearity of optimal mappings, given a
noise (or source) distribution, and a specified power constraint. We also prove
that the Gaussian source-channel pair is unique in the sense that it is the
only source-channel pair for which the optimal mappings are linear at more than
one CSNR values. Moreover, we show the asymptotic linearity of optimal mappings
for low CSNR if the channel is Gaussian regardless of the source and, at the
other extreme, for high CSNR if the source is Gaussian, regardless of the
channel. Our numerical results show strict improvement over prior methods. The
numerical approach is extended to the scenario of source-channel coding with
decoder side information. The resulting encoding mappings are shown to be
continuous relatives of, and in fact subsume as special case, the Wyner-Ziv
mappings encountered in digital distributed source coding systems.


title: Magnetoelectric Effect driven by Magnetic Domain Modification in LuFe2O4

abstract:
  Magneto-capacitance effect was investigated using the impedance spectroscopy
on single crystals of LuFe2O4. The intrinsic impedance response could be
separated from the interfacial response and showed a clear hysteresis loop
below TFerri ~ 240 K under the magnetic field. The neutron diffraction
experiment under the magnetic field proves the origin of dielectric property
related to the motion of nano-sized ferromagnetic domain boundary. These
results imply that the modification of the microscopic domain structure is
responsible for the magnetoelectric effect in LuFe2O4.


title:
Orbital reformation with vanadium trimerization in $d^2$ triangular
  lattice LiVO$_2$ revealed by $^{51}$V NMR

abstract:
  LiVO$_2$ is a model system of the valence bond solid (VBS) in $3d^2$
triangular lattice. The origin of the VBS formation has remained controversial.
We investigate the microscopic mechanism by elucidating the $d$ orbital
character via on-site $^{51}$V NMR measurements in a single crystal up to 550 K
across a structural transition temperature $T_c$. The Knight shift, $K$, and
nuclear quadrupole frequency, $\delta \nu$, show that the 3d orbital with local
trigonal symmetry are reconstructed into a $d_{yz}d_{zx}$ orbital order below
$T_c$. Together with the NMR spectra with three-fold rotational symmetry, we
confirm a vanadium trimerization with $d$-$d$ $\sigma$ bonds. The Knight shift
extracts the large Van-Vleck orbital susceptibility, $\chi^{\rm VV} = 3.6
\times 10^{-4}$, in a paramagnetic state above $T_c$, which is comparable to
the spin susceptibility. The results suggest that orbitally induced Peierls
transition in the proximity of the frustrated itinerant state is the dominant
driving force of the trimerization transition.


title:
Spatially Heterogeneous Biofilm Simulations using an Immersed Boundary
  Method with Lagrangian Nodes Defined by Bacterial Locations

abstract:
  In this work we consider how surface-adherent bacterial biofilm communities
respond in flowing systems. We simulate the fluid-structure interaction and
separation process using the immersed boundary method. In these simulations we
model and simulate different density and viscosity values of the biofilm than
that of the surrounding fluid. The simulation also includes breakable springs
connecting the bacteria in the biofilm. This allows the inclusion of erosion
and detachment into the simulation. We use the incompressible Navier-Stokes
(N-S) equations to describe the motion of the flowing fluid. We discretize the
fluid equations using finite differences and use a geometric multigrid method
to solve the resulting equations at each time step. The use of multigrid is
necessary because of the dramatically different densities and viscosities
between the biofilm and the surrounding fluid. We investigate and simulate the
model in both two and three dimensions.
  Our method differs from previous attempts of using IBM for modeling
biofilm/flow interactions in the following ways: the density and viscosity of
the biofilm can differ from the surrounding fluid, and the Lagrangian node
locations correspond to experimentally measured bacterial cell locations from
3D images taken of Staphylococcus epidermidis in a biofilm.


title:
A novel magnetic phase prior to a saturation moment in frustrated spinel
  oxides in ultra-high magnetic fields

abstract:
  We have investigated the magnetic-field induced phases of a typical
three-dimensional frustrated magnet, CdCr$_2$O$_4$, in magnetic fields of up to
120 T that is generated by the single-turn coil techniques. We focused on
magnetic phase transitions in proximity of a saturated magnetization moment. We
utilized both the electromagnetic induction method using magnetic pick-up coils
and magneto-optical spectroscopies of the $d$-$d$ transitions and the
exciton-magnon-phonon transitions to study the magnetic properties subjected to
ultra-high magnetic fields. Anomalies were observed in magneto-optical
absorption intensity as well as differential magnetization prior to a fully
polarized magnetic phase (a vacuum state in the magnon picture), revealing a
novel magnetic phase associated with changes in both crystal and magnetic
structures accompanied by the first order phase transition. Magnetic superfluid
state such as an umbrella-like magnetic structure or a spin nematic state, is
proposed as a candidate for the novel magnetic phase, which is found universal
in the series of chromium spinel oxides, $A$Cr$_2$O$_4$ ($A$ = Zn, Cd, Hg).


title:
Construction of topologies, filters and uniformities for a product of
  sets

abstract:
  Starting from filters over the set of indices, we introduce structures in a
product of sets where the coordinate sets have the given structures.


title: Simulations of micrometeoroid interactions with the Earth atmosphere

abstract:
  Micrometeoroids (cosmic dust with size between a few $\mu$m and $\sim$1 mm)
dominate the annual extraterrestrial mass flux to the Earth. We investigate the
range of physical processes occurring when micrometeoroids traverse the
atmosphere. We compute the time (and altitude) dependent mass loss, energy
balance, and dynamics to identify which processes determine their survival for
a range of entry conditions. We develop a general numerical model for the
micrometeoroid-atmosphere interaction. The equations of motion, energy, and
mass balance are simultaneously solved for different entry conditions (e.g.
initial radii, incident speeds and angles). Several different physical
processes are taken into account in the equation of energy and in the mass
balance, in order to understand their relative roles and evolution during the
micrometeoroid-atmosphere interaction. In particular, to analyze the
micrometeoroid thermal history we include in the energy balance: collisions
with atmospheric particles, micrometeoroid radiation emission, evaporation,
melting, sputtering and kinetic energy of the ablated mass. Low entry
velocities and grazing incidence angles favor micrometeoroid survival. Among
those that survive, our model distinguishes (1) micrometeoroids who reach the
melting temperature and for which melting is the most effective mass loss
mechanism, and (2) micrometeoroids for which ablation due to evaporation causes
most of the the mass loss. Melting is the most effective cooling mechanism.
Sputtering-induced mass loss is negligible.


title:
Gauge Independence of Magnetic Moment and Vanishing Charge of Dirac
  Neutrinos: an Exact One-loop Demonstration

abstract:
  The magnetic moment and vanishing charge of a Dirac neutrino are physically
observable quantities and must not depend on the choice of gauge in a
consistent quantum field theory. We verify this statement explicitly at the one
loop level in both R_xi and unitary gauges of the minimally extended standard
model. We accomplish this by manipulating directly the integrands of loop
integrals and employing simple algebraic identities and integral relations. Our
result generally applies for any masses of the relevant particles and unitary
neutrino mixing.


title: Bio-inspired data mining: Treating malware signatures as biosequences

abstract:
  The application of machine learning to bioinformatics problems is well
established. Less well understood is the application of bioinformatics
techniques to machine learning and, in particular, the representation of
non-biological data as biosequences. The aim of this paper is to explore the
effects of giving amino acid representation to problematic machine learning
data and to evaluate the benefits of supplementing traditional machine learning
with bioinformatics tools and techniques. The signatures of 60 computer viruses
and 60 computer worms were converted into amino acid representations and first
multiply aligned separately to identify conserved regions across different
families within each class (virus and worm). This was followed by a second
alignment of all 120 aligned signatures together so that non-conserved regions
were identified prior to input to a number of machine learning techniques.
Differences in length between virus and worm signatures after the first
alignment were resolved by the second alignment. Our first set of experiments
indicates that representing computer malware signatures as amino acid sequences
followed by alignment leads to greater classification and prediction accuracy.
Our second set of experiments indicates that checking the results of data
mining from artificial virus and worm data against known proteins can lead to
generalizations being made from the domain of naturally occurring proteins to
malware signatures. However, further work is needed to determine the advantages
and disadvantages of different representations and sequence alignment methods
for handling problematic machine learning data.


title:
On a numerical algorithm for computing topological characteristics of
  three-dimensional bodies

abstract:
  We present an algorithm for computing the main topological characteristics of
three-dimensional bodies. The algorithm is based on a discretization of Morse
theory and uses discrete analogs of smooth functions with only nondegenerate
(Morse) and the simplest degenerate critical points.


title: Graph $C^\ast$-algebras with a $T_1$ primitive ideal space

abstract:
  We give necessary and sufficient conditions which a graph should satisfy in
order for its associated $C^\ast$-algebra to have a $T_1$ primitive ideal
space. We give a description of which one-point sets in such a primitive ideal
space are open, and use this to prove that any purely infinite graph
$C^\ast$-algebra with a $T_1$ (in particular Hausdorff) primitive ideal space,
is a $c_0$-direct sum of Kirchberg algebras. Moreover, we show that graph
$C^\ast$-algebras with a $T_1$ primitive ideal space canonically may be given
the structure of a $C(\widetilde{\mathbb N})$-algebra, and that isomorphisms of
their $\widetilde{\mathbb N}$-filtered $K$-theory (without coefficients) lift
to $E(\widetilde{\mathbb N})$-equivalences, as defined by Dadarlat and Meyer.


title:
The Fluctuations of Blocked Ionic Current Reveal the Instantaneous
  Statuses of DNA in Graphene Nanopore

abstract:
  Extracting the sequence information of DNA from the blocked ionic current is
the crucial step of the ionic current-based nanopore sequencing approaches. The
thinnest graphene nanopore, which contained only one layer of carbon atoms,
potentially has ultra-high DNA sequencing sensitivity. However, the dynamical
translocation information of DNA contained in the blocked ionic current has not
been well understood to date. In this letter, an assessment to the sensitivity
of ionic current-based graphene nanopore DNA sensing approach was carried out
using molecular dynamics simulations. By filtering the molecular thermal motion
induced noise of ionic current, we found that the instantaneous conformational
variations of DNA in graphene nanopore could be revealed from the fluctuations
of the denoised ionic current. However, the blockage of ionic current which
induced by the proximity of the DNA base-pairs to the nanopore (within 1.5 nm)
was also observed. Although the expected single-base resolution of graphene
nanopore should be enhanced by further studies, our findings indicated that the
ionic current-based graphene nanopore sensing approach has high sensitivity to
the instantaneous translocation status of DNA.


title:
A Polynomial Time Algorithm for Finding Area-Universal Rectangular
  Layouts

abstract:
  A rectangular layout $\mathcal{L}$ is a rectangle partitioned into disjoint
smaller rectangles so that no four smaller rectangles meet at the same point.
Rectangular layouts were originally used as floorplans in VLSI design to
represent VLSI chip layouts. More recently, they are used in graph drawing as
rectangular cartograms. In these applications, an area $a(r)$ is assigned to
each rectangle $r$, and the actual area of $r$ in $\mathcal{L}$ is required to
be $a(r)$. Moreover, some applications require that we use combinatorially
equivalent rectangular layouts to represent multiple area assignment functions.
$\mathcal{L}$ is called {\em area-universal} if any area assignment to its
rectangles can be realized by a layout that is combinatorially equivalent to
$\mathcal{L}$.
  A basic question in this area is to determine if a given plane graph $G$ has
an area-universal rectangular layout or not. A fixed-parameter-tractable
algorithm for solving this problem was obtained in \cite{EMSV12}. Their
algorithm takes $O(2^{O(K^2)}n^{O(1)})$ time (where $K$ is the maximum number
of degree 4 vertices in any minimal separation component), which is exponential
time in general case. It is an open problem to find a true polynomial time
algorithm for solving this problem. In this paper, we describe such a
polynomial time algorithm.
  This paper has been revised for many versions. For previous versions,
referrers who are familiar with area-universal rectangular layouts always have
the same doubt for the correctness of our algorithm. They doubt that our
algorithm will give a wrong output which combine two \emph{conflicting} REL
together.
  In the current version, we realize this critical issue for the previous
algorithm and we will provide two subsections 5.3 and 5.4 to solve this issue.
(A backtracking algorithm to detect wrong outputs.)


title: Global Optimal Solutions to General Sensor Network Localization Problem

abstract:
  Sensor network localization problem is to determine the position of the
sensor nodes in a network given pairwise distance measurements. Such problem
can be formulated as a polynomial minimization via the least squares method.
This paper presents a canonical duality theory for solving this challenging
problem. It is shown that the nonconvex minimization problem can be
reformulated as a concave maximization dual problem over a convex set in a
symmetrical matrix space, and hence can be solved efficiently by combining a
general (linear or quadratic) perturbation technique with existing optimization
techniques. Applications are illustrated by solving some relatively large-scale
problems. Our results show that the general sensor network localization problem
is not NP-hard unless its canonical dual problem has no solution.


title:
Crystal growth and electronic properties of a 3D Rashba material, BiTeI,
  with adjusted carrier concentrations

abstract:
  3D Rashba materials can be a leading player in spin-related novel phenomena,
ranging from the metallic extreme (unconventional superconductivity) to the
transport intermediate (spin Hall effects) to the novel insulating variant (3D
topological insulating states). As the essential backbone for both fundamental
and applied research of such a 3D Rashba material, this study established the
growth of sizeable single crystals of a candidate compound BiTeI with adjusted
carrier concentrations. Three techniques (standard vertical Bridgman, modified
horizontal Bridgman, and vapour transport) were employed, and BiTeI crystals (>
1 * 1 * 0.2 mm3) with fundamentally different electronic states from metallic
to insulating were successfully grown by the chosen techniques. The 3D Rashba
electronic states, including the Fermi surface topology, for the corresponding
carrier concentrations of the obtained BiTeI crystals were revealed by
relativistic first-principles calculations.


title: Mariner 2 and its Legacy: 50 Years on

abstract:
  Fifty years ago, NASA's Jet Propulsion Laboratory (JPL) built and flew the
first successful spacecraft to another planet: Mariner 2 to Venus. This paper
discusses the context of this mission at a crucial phase in the space race
between the USA and USSR and its results and legacy. As its first major
success, Mariner 2 helped to cement JPL's position as a centre for robotic
planetary exploration. Mariner 2 successfully solved the scientific problem of
the high temperature observed for Venus by ground-based radio telescopes. It
also pioneered new techniques for observing the atmosphere of a planet from
space, which were subsequently developed into the microwave sounding and
infrared sounding techniques for observing the Earth atmosphere. Today these
techniques provide some of the most important data for constraining weather
forecasting models, as well as a key series of data on the Earth's changing
climate.


title: Wilson Theorems for Double-, Hyper-, Sub- and Super-factorials

abstract:
  We present generalisations of Wilson's theorem for double factorials,
hyperfactorials, subfactorials and superfactorials.


title:
Microscopic theory of ultrafast dynamics of carriers photoexcited by THz
  and near-infrared linearly-polarized laser pulses in graphene

abstract:
  We investigate the dynamics of photoexcited carriers and nonequilibrium
phonons in graphene by solving the microscopic kinetic Bloch equations. The
pump and drift effects from the laser field as well as the relevant scatterings
(including the Coulomb scattering with dynamic screening) are explicitly
included. When the pump-photon energy is high enough, the influence of the
drift term is shown to be negligible and the isotropic hot-electron Fermi
distribution is established under the scattering during the linearly polarized
laser pulse investigated here. However, in the case with low pump-phonon
energy, the drift term is important and leads to a net momentum transfer from
the electric field to electrons. Due to this net momentum and the dominant
Coulomb scattering, a drifted Fermi distribution different from the one
established under static electric field is found to be established in several
hundred femtoseconds. We also show that the Auger process investigated in the
literature involving only the diagonal terms of density matrices is forbidden
by the dynamic screening. However, we propose an Auger process involving the
interband coherence and show that it contributes to the dynamics of carriers
when the pump-photon energy is low. In addition, the anisotropically
momentum-resolved hot-phonon temperatures due to the linearly polarized light
are also investigated, with the underlying physics revealed.


title:
Morley's other miracle: $\displaystyle 4^{p-1}\equiv\pm (\smallmatrix
  p-1 \frac{p-1}{2} \endsmallmatrix) \pmod {p^3} $

abstract:
  Frank Morley is famous for his theorem concerning the angle trisectors of a
triangle. This note gives an elementary proof of another result of Morley's,
which relates the middle binomial coefficient to a certain power of two. The
striking thing about Morley's congruence is that it is valid modulo the third
power of the prime being considered.


title:
Metallicity Distribution Functions, Radial Velocities, and Alpha Element
  Abundances in Three Off-Axis Bulge Fields

abstract:
  We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe],
[Si/Fe], and [Ca/Fe] for 264 red giant branch (RGB) stars in three Galactic
bulge off-axis fields located near (l,b)=(-5.5,-7), (-4,-9), and (+8.5,+9). The
results are based on equivalent width and spectrum synthesis analyses of
moderate resolution (R~18,000), high signal-to-noise ratio (S/N~75-300) spectra
obtained with the Hydra spectrographs on the Blanco 4m and WIYN 3.5m
telescopes. The targets were selected from the blue side of the giant branch to
avoid cool stars that would be strongly affected by CN and TiO; however, a
comparison of the color-metallicity distribution in literature samples suggests
our selection of bluer targets should not present a significant bias against
metal-rich stars. We find a full range in metallicity that spans
[Fe/H]\approx-1.5 to +0.5, and that, in accordance with the previously observed
minor-axis vertical metallicity gradient, the median [Fe/H] also declines with
increasing Galactic latitude in off-axis fields. The off-axis vertical [Fe/H]
gradient in the southern bulge is estimated to be ~0.4 dex/kpc. The (+8.5,+9)
field exhibits a higher than expected metallicity, with a median [Fe/H]=-0.23,
that might be related to a stronger presence of the X--shaped bulge structure
along that line-of-sight. All fields exhibit an identical, strong decrease in
velocity dispersion with increasing metallicity that is consistent with
observations in similar minor-axis outer bulge fields. Additionally, the
[O/Fe], [Si/Fe], and [Ca/Fe] versus [Fe/H] trends are identical among our three
fields, and are in good agreement with past bulge studies. [abridged]


title: Quantum Gravity on a Quantum Computer?

abstract:
  EPR-type measurements on spatially separated entangled spin qubits allow one,
in principle, to detect curvature. Also the entanglement of the vacuum state is
affected by curvature. Here, we ask if the curvature of spacetime can be
expressed entirely in terms of the spatial entanglement structure of the
vacuum. This would open up the prospect that quantum gravity could be simulated
on a quantum computer and that quantum information techniques could be fully
employed in the study of quantum gravity.


title: On Weak Dress Codes for Cloud Storage

abstract:
  In a distributed storage network, reliability and bandwidth optimization can
be provided by regenerating codes. Recently table based regenerating codes viz.
DRESS (Distributed Replication-based Exact Simple Storage) codes has been
proposed which also optimizes the disk I/O. Dress codes consists of an outer
MDS code with an inner fractional repetition (FR) code with replication degree
$\rho$. Several constructions of FR codes based on regular graphs, resolvable
designs and bipartite graphs are known. This paper presents a simple modular
construction of FR codes. We also generalize the concept of FR codes to weak
fractional repetition (WFR) codes where each node has different number of
packets. We present a construction of WFR codes based on partial regular graph.
Finally we present a simple generalized ring construction of both strong and
weak fractional repetition codes.


title:
Kink during the formation of the Kondo resonance band in the heavy
  fermion system

abstract:
  We have investigated the formation of the Kondo resonance (KR) band and the
hybridization gap (HG) in the heavy fermion compound CeCoGe2, using a combined
approach of the density functional theory (DFT) and the dynamical mean field
theory (DMFT). Low temperature (T) spec-tral functions show dispersive KR
states, similarly to the recent experimental observation. During the evolution
from the nonf conduction band state at high T to the dispersive KR band state
at low T, which have topologically different band shapes, we have found the
existence of kinks in the spectral function near EF . The observation of kink
is clearly in correspondence with the multiple temperature scale of the
formation of the KR band. We suggest that the detailed analysis on the abrupt
change of electron velocity and the scattering rate near the Fermi level will
provide crucial information for the heavy fermion system.


title: The Cherenkov radiation in the galaxy halo of dark matter

abstract:
  The effect of light refraction in a galaxy halo of dark matter, described by
profiles of Navarro-Frenk-White and Burkett, was considered. Powers of the
Cherenkov radiation for the refractive indexes of gravitational fields with
these profiles were calculated. It was shown that correspondent radiation
temperature in the X-rays range have the magnitude about some microKelvins. It
was also marked that its detection may be the criteria on choosing the
preferable dark matter density distribution in a galaxy.


title: Homotopy Probability Theory I

abstract:
  This is the first of two papers that introduce a deformation theoretic
framework to explain and broaden a link between homotopy algebra and
probability theory. In this paper, cumulants are proved to coincide with
morphisms of homotopy algebras. The sequel paper outlines how the framework
presented here can assist in the development of homotopy probability theory,
allowing the principles of derived mathematics to participate in classical and
noncommutative probability theory.


title:
Count-based differential expression analysis of RNA sequencing data
  using R and Bioconductor

abstract:
  RNA sequencing (RNA-seq) has been rapidly adopted for the profiling of
transcriptomes in many areas of biology, including studies into gene
regulation, development and disease. Of particular interest is the discovery of
differentially expressed genes across different conditions (e.g., tissues,
perturbations), while optionally adjusting for other systematic factors that
affect the data collection process. There are a number of subtle yet critical
aspects of these analyses, such as read counting, appropriate treatment of
biological variability, quality control checks and appropriate setup of
statistical modeling. Several variations have been presented in the literature,
and there is a need for guidance on current best practices. This protocol
presents a "state-of-the-art" computational and statistical RNA-seq
differential expression analysis workflow largely based on the free open-source
R language and Bioconductor software and in particular, two widely-used tools
DESeq and edgeR. Hands-on time for typical small experiments (e.g., 4-10
samples) can be <1 hour, with computation time <1 day using a standard desktop
PC.


title: Logic Blog 2012

abstract:
  The 2012 logic blog has focussed on the following: Randomness and computable
analysis/ergodic theory; Systematizing algorithmic randomness notions;
Traceability; Higher randomness; Calibrating the complexity of equivalence
relations from computability theory and algebra.


title: Confronting Cold Dark Matter Predictions with Observed Galaxy Rotations

abstract:
  The rich statistics of galaxy rotations as captured by the velocity function
(VF) provides invaluable constraints on galactic baryon physics and the nature
of dark matter (DM). However, the comparison of observed galaxy rotations
against cosmological models is prone to subtle caveats that can easily lead to
misinterpretations. Our analysis reveals full statistical consistency between
~5000 galaxy rotations, observed in line-of-sight projection, and predictions
based on the standard cosmological model (LCDM) at the mass-resolution of the
Millennium simulation (HI line-based circular velocities above ~50 km/s).
Explicitly, the HI linewidths in the HI Parkes All Sky Survey (HIPASS) are
found consistent with those in S3-SAX, a post-processed semi-analytic model for
the Millennium simulation. Previously found anomalies in the VF can be
plausibly attributed to (1) the mass-limit of the Millennium simulation, (2)
confused sources in HIPASS, (3) inaccurate inclination measurements for
optically faint sources, and (4) the non-detectability of gas-poor early-type
galaxies. These issues can be bypassed by comparing observations and models
using linewidth source counts rather than VFs. We investigate if and how well
such source counts can constrain the temperature of DM.


title: Weak and strong wave turbulence spectra for elastic thin plate

abstract:
  Variety of statistically steady energy spectra in elastic wave turbulence
have been reported in numerical simulations, experiments, and theoretical
studies. Focusing on the energy levels of the system, we have performed direct
numerical simulations according to the F\"{o}ppl--von K\'{a}rm\'{a}n equation,
and successfully reproduced the variability of the energy spectra by changing
the magnitude of external force systematically. When the total energies in wave
fields are small, the energy spectra are close to a statistically steady
solution of the kinetic equation in the weak turbulence theory. On the other
hand, in large-energy wave fields, another self-similar spectrum is found.
Coexistence of the weakly nonlinear spectrum in large wavenumbers and the
strongly nonlinear spectrum in small wavenumbers are also found in moderate
energy wave fields.


title:
Effect of inter-particle interaction in a free oscillation atomic
  interferometer

abstract:
  We investigate the dynamics of two interacting bosons repeatedly scattering
off a beam-splitter in a free oscillation atom interferometer. Using the
inter-particle scattering length and the beam splitter probabilites as our
control parameters, we show that even in a simple setup like this a wide range
of strongly correlated quantum states can be created. This in particular
includes the NOON state, which maximizes the quantum Fisher information and is
a foremost state in quantum metrology.


title: Nonperturbative quantization and turbulence: the comparison

abstract:
  The comparison of calculations methods in nonperturbative quantum fields
theory and turbulence theory is made. The main result is that in both cases
there is an infinite equations set. In the first case it is the equations set
for Green's functions and in the second case it is the equations set for
cumulants. It allows us to use similar mathematical methods to solve problems
in nonperturbative quantum field theory and turbulence modeling. A closure
problem of truncation of the infinite equations set is discussed.


title: Cohomology bounds for sheaves of dimension one

abstract:
  We find the sharp bounds on $h^0(F)$ for one-dimensional semistable sheaves
$F$ on a projective variety $X$ by using the spectrum of semistable sheaves.
The result generalizes the Clifford theorem. When $X$ is the projective plane
$\mathbb{P}^2$, we study the stratification of the moduli space by the spectrum
of sheaves. We show that the deepest stratum is isomorphic to a subscheme of a
relative Hilbert scheme. This provides an example of a family of semistable
sheaves having the biggest dimensional global section space.


title:
An innovative approach of structural instabilities in tetragonal
  tungsten bronze crystals through the concept of rigid unit modes

abstract:
  Tetragonal tungsten bronze (TTB) oxides are one of the most important classes
of ferroelectrics. Many of these framework structures undergo ferroelastic
transformations related to octahedron tilting deformations. Such tilting
deformations are closely related to the Rigid Unit Modes (RUMs). This paper
discusses the whole set of RUMs in an ideal TTB lattice and possible crystal
structures which can emerge owing to the condensation of some of them. Analysis
of available experimental data for the TTB-like niobates lends credence to the
obtained theoretical predictions.


title: Arithmetic properties of the $\ell$-regular partitions

abstract:
  For a given prime $p$, we study the properties of the $p$-dissection
identities of Ramanujan's theta functions $\psi(q)$ and $f(-q)$, respectively.
Then as applications, we find many infinite family of congruences modulo 2 for
some $\ell$-regular partition functions, especially, for $\ell=2,4,5,8,13,16$.
Moreover, based on the classical congruences for $p(n)$ given by Ramanujan, we
obtain many more congruences for some $\ell$-regular partition functions.


title:
Search for a light charged Higgs boson in the decay channel H+->csbar in
  ttbar events using pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

abstract:
  A search for a charged Higgs boson (H+) in ttbar decays is presented, where
one of the top quarks decays via t->H+b, followed by H+->two jets (csbar). The
other top quark decays to Wb, where the W boson then decays into a lepton
(e/mu) and a neutrino. The data were recorded in pp collisions at sqrt(s) =
7TeV by the ATLAS detector at the LHC in 2011, and correspond to an integrated
luminosity of 4.7 fb-1. With no observation of a signal, 95% confidence level
(CL) upper limits are set on the decay branching ratio of top quarks to charged
Higgs bosons varying between 5% and 1% for H+ masses between 90 GeV and 150
GeV, assuming Br(H+->csbar)=100%.


title: Limit curves for zeros of sections of exponential integrals

abstract:
  We are interested in studying the asymptotic behavior of the zeros of partial
sums of power series for a family of entire functions defined by exponential
integrals. The zeros grow on the order of O(n), and after rescaling we
explicitly calculate their limit curve. We find that the rate that the zeros
approach the curve depends on the order of the singularities/zeros of the
integrand in the exponential integrals. As an application of our findings we
derive results concerning the zeros of partial sums of power series for Bessel
functions of the first kind.


title:
Anomalous scaling behavior in a mixed-state Hall effect of a
  cobalt-doped BaFe2As2 epitaxial film with a high critical current density
  over 1 MA/cm2

abstract:
  The mixed-state Hall effect was examined in a Ba(Fe1-xCox)2As2 epitaxial film
with a high critical current density. The transverse resistivity {\rho}xy and
the longitudinal resistivity {\rho}xx follow power law scaling {\rho}xy =
A{\rho}xx{\beta}. In the temperature-sweep with a fixed field (T sweep), all of
the {\beta} values are independent of magnetic field up to 9 T, and are lower
than 2.0 (around 1.8). In contrast, the {\beta} values in the magnetic-field
sweep with a fixed temperature (H sweep) change from 1.8 to 2.0 as the
temperature increases from 13 to 16 K even in the T/H region that overlaps with
the T sweep measurements. These results indicate that the vortices introduced
at low temperatures are trapped by strong pinning centers, but a portion of the
vortices introduced at high temperatures are not strongly trapped by the
pinning centers. The sign of {\rho}xy is negative, and a sign reversal is not
detected. These distinct scaling behaviors, which sharply contrast cuprates and
MgB2, are explained by high-density c-axis pinning centers in the
Ba(Fe1-xCox)2As2 epitaxial film and are consistent with a wider vortex liquid
phase.


title:
How to evaluate individual researchers working in the natural and life
  sciences meaningfully? A proposal of methods based on percentiles of
  citations

abstract:
  Although bibliometrics has been a separate research field for many years,
there is still no uniformity in the way bibliometric analyses are applied to
individual researchers. Therefore, this study aims to set up proposals how to
evaluate individual researchers working in the natural and life sciences. 2005
saw the introduction of the h index, which gives information about a
researcher's productivity and the impact of his or her publications in a single
number (h is the number of publications with at least h citations); however, it
is not possible to cover the multidimensional complexity of research
performance and to undertake inter-personal comparisons with this number. This
study therefore includes recommendations for a set of indicators to be used for
evaluating researchers. Our proposals relate to the selection of data on which
an evaluation is based, the analysis of the data and the presentation of the
results.


title: Search for FCNC in top-quark events in ATLAS

abstract:
  Searches for flavor changing neutral current (FCNC) processes in top-quark
production and decays by the ATLAS Collaboration are presented. Data collected
from $pp$ collisions at the LHC at a centre-of-mass energy of 7 TeV during
2011, corresponding to an integrated luminosity of 2.05/fb, are used. In a
first analysis single top-quarks produced via FCNC are searched for. Candidate
events with a semileptonic top-quark decay signature are classified as signal
or background-like events by using several kinematic variables as input to a
neural network. No signal is observed in the neural network output distribution
and a Bayesian upper limit is placed on the production cross-section. The
observed upper limit is converted using a model-independent approach into upper
limits on the coupling strengths k_{ugt}/Lambda < 6.9x10^{-3}/TeV and
k_{cgt}/Lambda < 1.6x10^{-2}/TeV, where Lambda is the new physics scale, and on
the branching fractions BF(t-->ug) < 5.7x10^{-5} and BF(t-->cg) < 2.7x10^{-4}.
A second search is performed for top-quark pair-production events, with one top
quark decaying through the t-->Zq FCNC (q=u,c) channel, and the other through
the Standard Model dominant mode t-->Wb. Only the decays of the Z boson to
charged leptons and leptonic W-boson decays are considered as signal. No
evidence for an FCNC signal is found and thus an upper limit on the t-->Zq
branching ratio of BF(t-->Zq)<0.73% is set at the 95% confidence level.


title: SM single-top production at hadron colliders

abstract:
  We give an overview of the status of theoretical predictions for single-top
production in the Standard Model. We focus in particular on recent
developments, including calculations of off-shell effects at next-to-leading
order beyond the narrow-width approximation, all-order resummation of soft
corrections and matching of next-to-leading order parton-level results to Monte
Carlo parton showers.


title: Density Ratio Hidden Markov Models

abstract:
  Hidden Markov models and their variants are the predominant sequential
classification method in such domains as speech recognition, bioinformatics and
natural language processing. Being generative rather than discriminative
models, however, their classification performance is a drawback. In this paper
we apply ideas from the field of density ratio estimation to bypass the
difficult step of learning likelihood functions in HMMs. By reformulating
inference and model fitting in terms of density ratios and applying a fast
kernel-based estimation method, we show that it is possible to obtain a
striking increase in discriminative performance while retaining the
probabilistic qualities of the HMM. We demonstrate experimentally that this
formulation makes more efficient use of training data than alternative
approaches.


title:
Spin-flop and antiferromagnetic phases of the ferromagnetic half-twist
  ladder compounds Ba3Cu3In4O12 and Ba3Cu3Sc4O12

abstract:
  The title compounds have dominant ferromagnetic (FM) exchange interactions
within one-dimensional (1D) half-twist ladders of s =1/2 Cu2^{+} ions and
antiferromagnetic(AFM) interactions between ladders, leading to ordered 3D
phases at temperatures below 20K. Here we show that a microscopic 1D model of
the paramagnetic (PM) phase combined with a phenomenological model based on
sublattice magnetization describes the observed temperature and field dependent
magnetism. The model identifies AFM, spin-flop (SF) and PM phases whose
boundaries have sharp features in the experimental magnetization M(T,H) and
specific heat CP(T,H). Exact diagonalization (ED) of the 1D model, possible for
24 spins due to special structural features of half-twist ladders, yields the
magnetization and spin susceptibility of the PM phase. AFM interactions between
ladders are included at the mean-field level using the field, HAF, obtained
from modeling the ordered phases. Isotropic exchange J1 = -135K and g-tensor g
= 2.1 within ladders, plus exchange and anisotropy fields HAF and HA, describe
the ordered phases, and are almost quantitative for the PM phase.