title: Crowdsourcing for Bioinformatics

abstract:
  Motivation: Bioinformatics is faced with a variety of problems that require
human involvement. Tasks like genome annotation, image analysis, knowledge-base
construction and protein structure determination all benefit from human input.
In some cases people are needed in vast quantities while in others we need just
a few with very rare abilities. Crowdsourcing encompasses an emerging
collection of approaches for harnessing such distributed human intelligence.
Recently, the bioinformatics community has begun to apply crowdsourcing in a
variety of contexts, yet few resources are available that describe how these
human-powered systems work and how to use them effectively in scientific
domains. Results: Here, we provide a framework for understanding and applying
several different types of crowdsourcing. The framework considers two broad
classes: systems for solving large-volume 'microtasks' and systems for solving
high-difficulty 'megatasks'. Within these classes, we discuss system types
including: volunteer labor, games with a purpose, microtask markets and open
innovation contests. We illustrate each system type with successful examples in
bioinformatics and conclude with a guide for matching problems to crowdsourcing
solutions.


title: Finite-time consensus using stochastic matrices with positive diagonals

abstract:
  We discuss the possibility of reaching consensus in finite time using only
linear iterations, with the additional restrictions that the update matrices
must be stochastic with positive diagonals and consistent with a given graph
structure. We show that finite-time average consensus can always be achieved
for connected undirected graphs. For directed graphs, we show some necessary
conditions for finite-time consensus, including strong connectivity and the
presence of a simple cycle of even length.


title:
Continuous-time Mean-Variance Portfolio Selection with Stochastic
  Parameters

abstract:
  This paper studies a continuous-time market {under stochastic environment}
where an agent, having specified an investment horizon and a target terminal
mean return, seeks to minimize the variance of the return with multiple stocks
and a bond. In the considered model firstly proposed by [3], the mean returns
of individual assets are explicitly affected by underlying Gaussian economic
factors. Using past and present information of the asset prices, a
partial-information stochastic optimal control problem with random coefficients
is formulated. Here, the partial information is due to the fact that the
economic factors can not be directly observed. Via dynamic programming theory,
the optimal portfolio strategy can be constructed by solving a deterministic
forward Riccati-type ordinary differential equation and two linear
deterministic backward ordinary differential equations.


title: Answer to the questions of Yanyan Li and Luc Nguyen in arXiv:1302.1603

abstract:
  In this note we answer the two questions raised by Y.Y Li and L. Nguyen in
their note [LN2] below.


title: Quantum criticality in itinerant metamagnets

abstract:
  Critical thermodynamics close to a metamagnetic quantum critical endpoint
(QCEP) in a metal is discussed within the framework of spin-fluctuation theory.
We analyze the effective potential for the Ising order parameter that is
renormalized by spin-fluctuations and acquires a characteristic temperature
dependence. The resulting magnetic field, H, and temperature, T, dependence of
the magnetization, specific heat, thermal expansion, magnetostriction,
susceptibility and the Gr\"uneisen parameter are determined, and the crossover
lines in the (H,T) phase diagram are specified. We point out that the
metamagnetic QCEP is intrinsically unstable with respect to a magnetoelastic
coupling.


title: Strings attached: New light on an old problem

abstract:
  The wave equation $u_{tt} = c^2 u_{xx}$ is generally regarded as a linear
approximation to the equation describing the amplitude of a transversely
vibrating elastic string in the plane. But, as is shown in \cite{BC96}, the
assumption of transverse vibration in fact implies that the wave equation
describes the vibration precisely, with no need for approximation. We give a
simplified proof of this result, and we generalize to the case of an elastic
string vibrating (transversely or not) in a Riemannian surface $M$. In the more
general setting, the assumption of transverse vibration is replaced by the
assumption of "perfect elasticity," and we show that the wave map equation
$\nabla_{\bu_t} \bu_t = c^2 \nabla_{\bu_x} \bu_x$ gives a precise description
of the vibration of a perfectly elastic string in $M$, with no need for
approximation. Finally, we give examples describing the motion of various
vibrating strings in $\R^2$, $S^2$, and $\mathbb{H}^2$.


title: Geometrical characterization of non-Markovianity

abstract:
  We introduce a new tool for the quantitative characterisation of the
departure form Markovianity of a given dynamical process. Our tool can be
applied to a generic $N$-level system and extended straightforwardly to
Gaussian continuous-variable systems. It is linked to the change of the volume
of physical states that are dynamically accessible to a system and provides
qualitative expectations in agreement with some of the analogous tools proposed
so far. We illustrate its prediticve power by tackling a few canonical
examples.


title: Generic regular universes in higher order gravity theories

abstract:
  We review recent results on the Cauchy-Kowalevsky structure of theories with
higher derivatives in vacuum. We prove genericity of regularity of solutions
under the assumption of analyticity. Our approach is framed in the general
context of formal series expansions of the metric around a regular point.


title:
Phase transition and phase coexistence in coupled rings with driven
  exclusion process

abstract:
  We study one-dimensional exclusion processes in two coupled closed rings
consisting of a common diffusive channel and two parallel active (driven)
channels. Our model displays bulk-driven phase transition and phase coexistence
in the form of a localised domain wall (DW) in one of the active channels in a
limit where the diffusive and driven dynamics compete. By controlling a
splitting parameter which tunes the in-coming currents into the active
channels, the system can be brought to a delocalisation transition, when
delocalised DWs are formed in both the active channels. We characterise the DW
fluctuations numerically.


title: Normal forms of random braids

abstract:
  Analysing statistical properties of the normal forms of random braids, we
observe that, except for an initial and a final region whose lengths are
uniformly bounded (that is, the bound is independent of the length of the
braid), the distributions of the factors of the normal form of sufficiently
long random braids depend neither on the position in the normal form nor on the
lengths of the random braids. Moreover, when multiplying a braid on the right,
the expected number of factors in its normal form that are modified, called the
"expected penetration distance", is uniformly bounded.
  We explain these observations by analysing the growth rates of two regular
languages associated to normal forms of elements of Garside groups,
respectively to the modification of a normal form by right multiplication.
  A universal bound on the expected penetration distance in a Garside group
yields in particular an algorithm for computing normal forms that has linear
expected running time.


title:
Taming the Curse of Dimensionality: Discrete Integration by Hashing and
  Optimization

abstract:
  Integration is affected by the curse of dimensionality and quickly becomes
intractable as the dimensionality of the problem grows. We propose a randomized
algorithm that, with high probability, gives a constant-factor approximation of
a general discrete integral defined over an exponentially large set. This
algorithm relies on solving only a small number of instances of a discrete
combinatorial optimization problem subject to randomly generated parity
constraints used as a hash function. As an application, we demonstrate that
with a small number of MAP queries we can efficiently approximate the partition
function of discrete graphical models, which can in turn be used, for instance,
for marginal computation or model selection.


title:
Algorithms for singularities and real structures of weak Del Pezzo
  surfaces

abstract:
  In this paper we consider the classification of singularities (Du Val) and
real structures (Wall) of weak Del Pezzo surfaces from an algorithmic point of
view.
  It is well known that the singularities of weak Del Pezzo surfaces correspond
to root subsystems. We present an algorithm which computes the classification
of these root subsystems. We represent equivalence classes of root subsystems
by unique labels. These labels allow us to construct examples of weak Del Pezzo
surfaces with the corresponding singularity configuration.
  Equivalence classes of real structures of weak Del Pezzo surfaces are also
represented by root subsystems. We present an algorithm which computes the
classification of real structures. This leads to an alternative proof of the
known classification for Del Pezzo surfaces and extends this classification to
singular weak Del Pezzo surfaces.
  As an application we classify families of real conics on cyclides.


title:
Electron pairing and evidence of a BCS-BEC crossover in d-wave
  superconductors

abstract:
  We have demonstrated that it is possible to access a crossover scenario
starting with a weak coupling (BCS) d-wave superconductor to a strongly coupled
Bose-Einstein condensate (BEC) phase as the exchange interaction is tuned in a
two dimensional system described by a t-J-U model via numerically solving the
Bogoliubov-de Gennes (BdG) equations. While in the extreme dilute limit, the
electronic pairing phenomena is independent of the Coulomb repulsion, U, the
superconductivity depends on U, and so does the crossover. Further, the effect
of variation in the carrier density on the BCS-BEC crossover has also been
investigated. The crossover picture is illustrated by computing the chemical
potential, which when falls below the noninteracting band minimum, signals the
onset of a phase with tightly bound, shorter pairs. As an evidence of the above
feature, the Cooper pair radius is calculated which shows a significant
shortening at the emergence of a BEC-like phase. Besides, in contrast to the
previous work where a crossover was claimed only in the dilute limit, we have
demonstrated it at large densities near half filling.


title:
Enhanced ULF electromagnetic activity detected by DEMETER above
  seismogenic regions

abstract:
  In this paper we present results of a comparison between ultra low frequency
(ULF) electromagnetic (EM) radiation, recorded by an electric field instrument
(ICE) onboard the satellite DEMETER in the topside ionosphere, and the
seismicity of regions with high and lower seiismic activity. In particular we
evaluated the energy variations of the ULF Ez-electric field component during a
period of four years (2006-2009), in order to examine check the possible
relation of ULF EM radiation with seismogenic regions located in central
America, Indonesia, Eastern Mediterranean Basin and Greece. As a tool of
evaluating the ULF Ez energy variations we used Singular Spectrum Analysis
(SSA) techniques. The results of our analysis clearly show a significant
increase of the ULF EM energy emmited from regions of highest seismic activity
at the tectonic plates boundaries. We interpret these results as suggesting
that the highest ULF EM energy detected in the topside ionosphere is originated
from seismic processes within Earth's crust. We understand the results of the
present study as confirming previous evidence that the ULF EM anomalous wave
activity in the ionosphere can be considered a useful earthquake precursory
signal


title: Yau-Tian-Donaldson correspondence for K-semistable Fano manifolds

abstract:
  In this note, using the recent compactness results of Tian and
Chen-Donaldson-Sun, we prove the K-semistable version of Yau-Tian-Donaldson
correspondence for Fano manifolds.


title:
Dancing in the Dark: New Brown Dwarf Binaries from Kernel Phase
  Interferometry

abstract:
  This paper revisits a sample of ultracool dwarfs in the Solar neighborhood
previously observed with the Hubble Space Telescope's NICMOS NIC1 instrument.
We have applied a novel high angular resolution data analysis technique based
on the extraction and fitting of kernel phases to archival data. This was found
to deliver a dramatic improvement over earlier analysis methods, permitting a
search for companions down to projected separations of $\sim$1 AU on NIC1
snapshot images. We reveal five new close binary candidates and present revised
astrometry on previously-known binaries, all of which were recovered with the
technique. The new candidate binaries have sufficiently close separation to
determine dynamical masses in a short-term observing campaign. We also present
four marginal detections of objects which may be very close binaries or high
contrast companions. Including only confident detections within 19 parsecs, we
report a binary fraction of at least $\epsilon_b = 17.2^{+5.7}_{-3.7}%$. The
results reported here provide new insights into the population of nearby
ultracool binaries, while also offering an incisive case study of the benefits
conferred by the kernel phase approach in the recovery of companions within a
few resolution elements of the PSF core.


title:
Decentralized set-valued state estimation based on non-deterministic
  chains

abstract:
  A general decentralized computational framework for set-valued state
estimation and prediction for the class of systems that accept a hybrid state
machine representation is considered in this article. The decentralized scheme
consists of a conjunction of distributed state machines that are specified by a
decomposition of the external signal space. While this is shown to produce, in
general, outer approximations of the outcomes of the original monolithic state
machine, here, specific rules for the signal space decomposition are devised by
utilizing structural properties of the underyling transition relation, leading
to a recovery of the exact state set results. By applying a suitable
approximation algorithm, we show that computational complexity in the
decentralized setting may thereby essentially reduce as compared to the
centralized estimation scheme.


title:
Families of bitangent planes of space curves and minimal non-fibration
  families

abstract:
  We define a cone curve to be a reduced sextic space curve which lies on a
quadric cone and does not go through the vertex. We classify families of
bitangent planes of cone curves. The methods we apply can be used for any space
curve with ADE singularities, though in this paper we concentrate on cone
curves.
  An embedded complex projective surface which is adjoint to a degree one weak
Del Pezzo surface contains families of minimal degree rational curves, which
cannot be defined by the fibers of a map. Such families are called minimal
non-fibration families. Families of bitangent planes of cone curves correspond
to minimal non-fibration families. The main motivation of this paper is to
classify minimal non-fibration families.
  We present algorithms wich compute all bitangent families of a given cone
curve and their geometric genera. We consider cone curves to be equivalent if
they have the same singularity configuration. For each equivalence class of
cone curves we determine the possible number of bitangent families and the
number of rational bitangent families. Finally we compute an example of a
minimal non-fibration family on an embedded weak degree one Del Pezzo surface.


title:
Consensus Seeking in Multi-Agent Systems with Multiplicative Measurement
  Noises

abstract:
  In this paper, the consensus problems of the continuous-time integrator
systems under noisy measurements are considered. The measurement noises, which
appear when agents measure their neighbors' states, are modeled to be
multiplicative. By multiplication of the noises, here, the noise intensities
are proportional to the absolute value of the relative states of agent and its
neighbor. By using known distributed protocols for integrator agent systems,
the closed-loop {system is} described in the vector form by a singular
stochastic differential equation. For the fixed and switching network
topologies cases, constant consensus gains are properly selected, such that
mean square consensus and strong consensus can be achieved. Especially,
exponential mean square convergence of agents' states to the common value is
derived for the fixed topology case. In addition, asymptotic unbiased mean
square average consensus and asymptotic unbiased strong average consensus are
also studied. Simulations shed light on the effectiveness of the proposed
theoretical results.


title:
The low-mass interacting binary system OO Aql revisited: a new quadruple
  system

abstract:
  In this study we present photometric and spectroscopic variation analysis and
orbital period study of a low-mass interacting system OO Aql. Simultaneous
solution of the light and radial velocity curves provide us a determination of
new set of stellar physical parameters for the primary and the secondary
companion as M$_{1}$ = 1.05(2) M$_{\odot}$, M$_{2}$ = 0.89(2) M$_{\odot}$,
R$_{1}$ = 1.38(2) R$_{\odot}$, R$_{2}$ = 1.28(2) R$_{\odot}$,
$\log{(L_1/L_{\odot})} = 0.258$ and $\log{(L_2/L_{\odot})} = 0.117$ and the
separation of the components were determined a = 3.333(16) R$_{\odot}$. Newly
obtained parameters yield the distance of the system as 136(8) pc. Analyses of
the mid-eclipse times indicate a period increase of $\frac{P}{\dot{P}}=4\times
10^{7}$ yr that can be interpreted in terms of the mass transfer
$\frac{dM}{dt}=5\times 10^{-8}$ M$_{\odot}$/yr from the less massive component
to the more massive component. Our new solution confirmed that OO Aql is a
multiple system in the form of AB + C + D. We found initial astrophysical
parameters for the component of the system and its current age to be 8.6 Gyr
using nonconservative stellar evolution model (EV-TWIN code).


title: Minimal families of curves on surfaces

abstract:
  A minimal family of curves on an embedded surface is defined as a
1-dimensional family of rational curves of minimal degree, which cover the
surface. We classify such minimal families using constructive methods. This
allows us to compute the minimal families of a given surface.
  The classification of minimal families of curves can be reduced to the
classification of minimal families which cover weak Del Pezzo surfaces. We
classify the minimal families of weak Del Pezzo surfaces and present a table
with the number of minimal families of each weak Del Pezzo surface up to Weyl
equivalence.
  As an application of this classification we generalize some results of
Schicho. We classify algebraic surfaces which carry a family of conics. We
determine the minimal lexicographic degree for the parametrization of a surface
which carries at least 2 minimal families.


title:
Extrinsic anomalous Hall conductivity of a topologically nontrivial
  conduction band

abstract:
  A key step towards dissipationless transport devices is the quantum anomalous
Hall effect, which is characterized by an integer quantized Hall conductance in
a ferromagnetic insulator with strong spin-orbit coupling. In this work, the
anomalous Hall effect due to the impurity scattering, namely the extrinsic
anomalous Hall effect, is studied when the Fermi energy crosses with the
topologically nontrivial conduction band of a quantum anomalous Hall system.
Two major extrinsic contributions, the side-jump and skew-scattering Hall
conductivities, are calculated using the diagrammatic techniques in which both
nonmagnetic and magnetic scattering are taken into account simultaneously. The
side-jump Hall conductivity changes its sign at a critical sheet carrier
density for the nontrivial phase, while it remains sign unchanged for the
trivial phase. The critical sheet carrier densities estimated with realistic
parameters lie in an experimentally accessible range. The results imply that a
quantum anomalous Hall system could be identified in the good-metal regime.


title:
Sputter-Induced Cross-Contaminations in Analytical AES and XPS
  Instrumentation: Utilization of the effect for the In-situ Deposition of
  Ultrathin Functional Layers

abstract:
  Cross contaminations are observed on sample surfaces by AES and XPS, if
multiple samples are mounted on one sample holder and a neighbouring sample was
sputter depth profiled. During sputter depth profiling sputtered material is
deposited on inner surfaces of the instrument. In a secondary sputter process,
which is due to species leaving the primary sputter target with higher kinetic
energy, the previously deposited material is transported from the inner
surfaces to the other samples mounted on the sample holder. This Reflective
Sputtering is utilized to deposit ultra-thin layers on sample surfaces for XPS
binding energy referencing purpose and to build up ultra-thin conductive layers
to enable AES measurements on insulating samples.


title:
Interior Models of Saturn: Including the Uncertainties in Shape and
  Rotation

abstract:
  The accurate determination of Saturn's gravitational coefficients by Cassini
could provide tighter constrains on Saturn's internal structure. Also,
occultation measurements provide important information on the planetary shape
which is often not considered in structure models. In this paper we explore how
wind velocities and internal rotation affect the planetary shape and the
constraints on Saturn's interior. We show that within the geodetic approach
(Lindal et al., 1985, ApJ, 90, 1136) the derived physical shape is insensitive
to the assumed deep rotation. Saturn's re-derived equatorial and polar radii at
100 mbar are found to be 54,445 $\pm$10 km and 60,365$\pm$10 km, respectively.
To determine Saturn's interior we use {\it 1 D} three-layer hydrostatic
structure models, and present two approaches to include the constraints on the
shape. These approaches, however, result in only small differences in Saturn's
derived composition. The uncertainty in Saturn's rotation period is more
significant: with Voyager's 10h39mns period, the derived mass of heavy elements
in the envelope is 0-7 M$_{\oplus}$. With a rotation period of 10h32mns, this
value becomes $<4$ $M_{\oplus}$, below the minimum mass inferred from
spectroscopic measurements. Saturn's core mass is found to depend strongly on
the pressure at which helium phase separation occurs, and is estimated to be
5-20 M$_{\oplus}$. Lower core masses are possible if the separation occurs
deeper than 4 Mbars. We suggest that the analysis of Cassini's radio
occultation measurements is crucial to test shape models and could lead to
constraints on Saturn's rotation profile and departures from hydrostatic
equilibrium.


title: Nonrigidity of piecewise-smooth circle maps

abstract:
  Let $f_{i},$ $i=1,2$ be piecewise-smooth $C^{1}$ circle homeomorphisms with
two break points, $\log Df_{i},$ $i=1,2$ are absolutely continuous on each
continuity intervals of $Df_{i}$ and $D\log Df_{i}\in L^{p}$ for some $p>1.$
Suppose, the jump ratios of $f_{1} $ and $f_{2} $ at their break points do not
coincide but have the same total jumps (i.e. the product of jump ratios) and
identical irrational rotation number of bounded type. Then the conjugation $h$
between $f_{1} $ and $f_{2} $ is a singular function, i.e. it is continuous on
$S^1,$ but $Dh(x)=0$ a.e. with respect to Lebesgue measure.


title: Imaging Hydrogen Bond in Real Space

abstract:
  Hydrogen bond is often assumed to be a purely electrostatic interaction
between a electron-deficient hydrogen atom and a region of high electron
density. Here, for the first time, we directly image hydrogen bond in real
space by room-temperature scanning tunneling microscopy (STM) with the
assistance of resonant tunneling effect in double barrier mode. STM
observations demonstrate that the C=O:HO hydrogen bonds lifted several angstrom
meters above metal surfaces appear shuttle-like features with a significant
contrast along the direction connected the oxygen and hydrogen atoms of a
single hydrogen bond. The off-center location of the summit and the variance of
the appearance height for the hydrogen bond with scanning bias reveal that
there are certain hybridizations between the electron orbitals of the involved
oxygen and hydrogen atoms in the C=O:HO hydrogen bond.


title:
What a single snapshot reveals about the future and the past of
  turbulent flow

abstract:
  We develop an analytic formalism and derive new exact relations that express
the short-time dispersion of fluid particles via the single-time velocity
correlation functions in homogeneous isotropic and incompressible turbulence.
The formalism establishes a bridge between single-time Eulerian and long-time
Lagrangian pictures of turbulent flows. In particular, we derive an exact
formula for a short-term analog of the long-time Richardson law, and we
identify a conservation law of turbulent dispersion which is true even in
non-stationary turbulence.

categories: nlin.CD cond-mat.stat-mech hep-th physics.flu-dyn


title: Numerical study of unitary fermions in one spatial dimension

abstract:
  I perform lattice Monte Carlo studies of universal four-component fermion
systems in one spatial dimension. Continuum few-body observables (i.e.,
ground-state energies and integrated contact densities) are determined for both
unpolarized and polarized systems of up to eight fermions confined to a
harmonic trap. Estimates of the continuum energies for four and five trapped
fermions show agreement with exact analytic calculations to within
approximately one percent statistical uncertainties. Continuum many-body
observables are determined for unpolarized systems of up to 88 fermions
confined to a finite box, and 56 fermions confined to a harmonic trap. Results
are reported for universal quantities such as the Bertsch parameter, defined as
the energy of the untrapped many-body system in units of the corresponding
free-gas energy, and its subleading correction at large but finite scattering
length. Two independent estimates of these quantities are obtained from
thermodynamic limit extrapolations of continuum extrapolated observables. A
third estimate of the Bertsch parameter is obtained by combining estimates of
the untrapped and trapped integrated contact densities with additional
theoretical input from a calculation based on Thomas-Fermi theory. All
estimates of the Bertsch parameter and its subleading correction are found to
be consistent to within approximately one percent statistical uncertainties.
Finally, the continuum restoration of virial theorems is verified for both few-
and many-body systems confined to a trap.


title: Complexity vs Energy: Theory of Computation and Theoretical Physics

abstract:
  This paper is a survey dedicated to the analogy between the notions of {\it
complexity} in theoretical computer science and {\it energy} in physics. This
analogy is not metaphorical: I describe three precise mathematical contexts,
suggested recently, in which mathematics related to (un)computability is
inspired by and to a degree reproduces formalisms of statistical physics and
quantum field theory.

categories: cs.CC cond-mat.stat-mech math-ph math.MP


title: On the heat redistribution of the hot transiting exoplanet WASP-18b

abstract:
  The energy deposition and redistribution in hot Jupiter atmospheres is not
well understood currently, but is a major factor for their evolution and
survival. We present a time dependent radiative transfer model for the
atmosphere of WASP-18b which is a massive (10 MJup) hot Jupiter (Teq ~ 2400 K)
exoplanet orbiting an F6V star with an orbital period of only 0.94 days. Our
model includes a simplified parametrisation of the day-to-night energy
redistribution by a modulation of the stellar heating mimicking a solid body
rotation of the atmosphere. We present the cases with either no rotation at all
with respect to the synchronously rotating reference frame or a fast
differential rotation. The results of the model are compared to previous
observations of secondary eclipses of Nymeyer et al. (2011) with the Spitzer
Space Telescope. Their observed planetary flux suggests that the efficiency of
heat distribution from the day-side to the night-side of the planet is
extremely inefficient. Our results are consistent with the fact that such large
day-side fluxes can be obtained only if there is no rotation of the atmosphere.
Additionally, we infer light curves of the planet for a full orbit in the two
Warm Spitzer bandpassses for the two cases of rotation and discuss the
observational differences.


title:
Optimization of the yttrium iron garnet/platinum interface for spin
  pumping-based applications

abstract:
  The dependence of the spin pumping efficiency and the spin mixing conductance
on the surface processing of yttrium iron garnet (YIG) before the platinum (Pt)
deposition has been investigated quantitatively. The ferromagnetic resonance
driven spin pumping injects a spin polarized current into the Pt layer, which
is transformed into an electromotive force by the inverse spin Hall effect. Our
experiments show that the spin pumping effect indeed strongly depends on the
YIG/Pt interface condition. We measure an enhancement of the inverse spin Hall
voltage and the spin mixing conductance of more than two orders of magnitude
with improved sample preparation.


title: Compact Bell inequalities for multipartite experiments

abstract:
  A method for construction of the multipartite Clauser-Horne-Shimony-Holt
(CHSH) type Bell inequalities, for the case of local binary observables, is
presented. The standard CHSH-type Bell inequalities can be obtained as special
cases. A unified framework to establish all kinds of CHSH-type Bell
inequalities by increasing step by step the number of observers is given. As an
application, compact Bell inequalities, for eight observers, involving just
four correlation functions are proposed. They require much less experimental
effort than standard methods and thus is experimentally friendly in
multi-photon experiments.


title: Note on the Unruh Effect

abstract:
  It was suggested by Unruh that a uniformly accelerated detector in vacuum
would perceive a noise with a thermal distribution. We obtain a representation
of solutions of the wave equation in two dimensions suitable for the Rindler
regions. The representation includes the dependence on a parameter. The Unruh
field corresponds to a singular limit of the representation.


title: Refine Predictions Ad Infinitum?

abstract:
  We study how standard auction objectives in sponsored search markets change
with refinements in the prediction of the relevance (click-through rates) of
ads. We study mechanisms that optimize for a convex combination of efficiency
and revenue. We show that the objective function of such a mechanism can only
improve with refined (improved) relevance predictions, i.e., the search engine
has no disincentive to perform these refinements. More interestingly, we show
that under assumptions, refinements to relevance predictions can only improve
the efficiency of any such mechanism. Our main technical contribution is to
study how relevance refinements affect the similarity between ranking by
virtual-value (revenue ranking) and ranking by value (efficiency ranking).
Finally, we discuss implications of our results to the literature on signaling.


title:
Fluctuation-electromagnetic interaction of a small particle with
  evanescent modes of the surface: impact of translational motion and rotation

abstract:
  Based on the fluctuation-electromagnetic theory, we have calculated
tangential (frictional) and normal forces, radiation heat flux and frictional
torque on a small rotating particle moving at a nonrelativistic velocity close
to a smooth featureless surface. The particle and surface are characterized by
different temperatures corresponding to the local thermodynamic equilibrium in
their own reference frames.


title: Andrews Style Partition Identities

abstract:
  We propose a method to construct a variety of partition identities at once.
The main application is an all-moduli generalization of some of Andrews'
results in [5]. The novelty is that the method constructs solutions to
functional equations which are satisfied by the generating functions. In
contrast, the conventional approach is to show that a variant of well-known
series satisfies the system of functional equations, thus reconciling two
separate lines of computations.


title: Compressive Sensing for Spread Spectrum Receivers

abstract:
  With the advent of ubiquitous computing there are two design parameters of
wireless communication devices that become very important power: efficiency and
production cost. Compressive sensing enables the receiver in such devices to
sample below the Shannon-Nyquist sampling rate, which may lead to a decrease in
the two design parameters. This paper investigates the use of Compressive
Sensing (CS) in a general Code Division Multiple Access (CDMA) receiver. We
show that when using spread spectrum codes in the signal domain, the CS
measurement matrix may be simplified. This measurement scheme, named
Compressive Spread Spectrum (CSS), allows for a simple, effective receiver
design. Furthermore, we numerically evaluate the proposed receiver in terms of
bit error rate under different signal to noise ratio conditions and compare it
with other receiver structures. These numerical experiments show that though
the bit error rate performance is degraded by the subsampling in the CS-enabled
receivers, this may be remedied by including quantization in the receiver
model. We also study the computational complexity of the proposed receiver
design under different sparsity and measurement ratios. Our work shows that it
is possible to subsample a CDMA signal using CSS and that in one example the
CSS receiver outperforms the classical receiver.


title:
Decentralized set-valued state estimation and prediction for hybrid
  systems: A symbolic approach

abstract:
  A symbolic approach to decentralized set-valued state estimation and
prediction for systems that admit a hybrid state machine representations is
proposed. The decentralized computational scheme represents a conj unction of a
finite number of distributed state machines, which are specified by an
appropriate decomposition of the external signal space. It aims at a
distribution of computational tasks into smaller ones, allocated to individual
distributed state machines, leading to a potentially significant reduction in
the overall space/time computational complexity. We show that, in general, such
a scheme outerapproximates the state set estimates and predictions of the
original monolithic state machine. By utilizing structural properties of the
transition relation of the latter, in a next step, we propose constructive
decomposition algorithms for a recovery of the exact state set outcomes.


title:
Optical properties of a disordered metallic film: local vs. collective
  phenomena

abstract:
  We apply the dual-varibles approach to the problem of the optical response of
an disordered film of metal particles with dipole-dipole interaction. Long
range dipole-dipole interaction makes the effect of spatial correlations
significant, so that dual-variables technique provides a desirable improvement
of the coherent-potential results. It is shown that the effect of nonlocality
is more pronounced for a medium-range concentration of the particles. The
result is compared with the non-local cluster approach. It is shown that
short-range correlations accounted in the cluster method reveal themselves in
the spectral properties of the response, whereas long-range phenomena kept in
the dual technique are more pronounced in the k-dependence of the Green's
function.


title: Complete intersections in simplicial toric varieties

abstract:
  Given a set $\mathcal A = \{a_1,\ldots,a_n\} \subset \mathbb{N}^m$ of nonzero
vectors defining a simplicial toric ideal $I_{\mathcal A} \subset
k[x_1,...,x_n]$, where $k$ is an arbitrary field, we provide an algorithm for
checking whether $I_{\mathcal A}$ is a complete intersection. This algorithm
does not require the explicit computation of a minimal set of generators of
$I_{\mathcal A}$. The algorithm is based on the application of some new results
concerning toric ideals to the simplicial case. For homogenous simplicial toric
ideals, we provide a simpler version of this algorithm. Moreover, when $k$ is
an algebraically closed field, we list all ideal-theoretic complete
intersection simplicial projective toric varieties that are either smooth or
have one singular point.


title:
Partially reduced formulation of scalar Yukawa model:
  Poincare-invariance and unitarity

abstract:
  We consider a scalar Yukawa-like model in the framework of partially reduced
quantum field theory. The reduced Lagrangian of the model consists of free
scalar field terms and nonlocal current interaction term. Hamiltonian
expressions for conserved quantities arose from a Lorentz-invariance of the
model in the momentum representation have been found in the first-order
approximation with respect to a coupling constant squared. Canonical
quantization of the system is performed. It is shown that the obtained
conserved quantities and previously founded the Hamiltonian and the momentum of
the system satisfy the commutational relations of the Poincare group. The
expression for S-matrix in the current approximation is found. Unitarity of
this operator is proven by direct calculation.


title:
The inversion number and the major index are asymptotically jointly
  normally distributed on words

abstract:
  In a recent paper, Baxter and Zeilberger show that the two most important
Mahonian statistics, the inversion number and the major index, are
asymptotically independently normally distributed on permutations. In another
recent paper, Canfield, Janson and Zeilberger prove the result, already known
to statisticians, that the Mahonian distribution is asymptotically normal on
words. This leaves one question unanswered: What, asymptotically, is the joint
distribution of the inversion number and the major index on words? We answer
this question by establishing convergence to a bivariate normal distribution.


title: Topological properties of positively curved manifolds with symmetry

abstract:
  Manifolds admitting positive sectional curvature are conjectured to have
rigid homotopical structure and, in particular, comparatively small Euler
charateristics.
  In this article, we obtain upper bounds for the Euler characteristic of a
positively curved Riemannian manifold that admits a large isometric torus
action. We apply our results to prove obstructions to symmetric spaces,
products of manifolds, and connected sums admitting positively curved metrics
with symmetry.


title: Surfaces that are covered by two pencils of circles

abstract:
  We list up to M\"obius equivalence all possible degrees and embedding
dimensions of real surfaces that are covered by at least two pencils of
circles, together with the number of such pencils. In addition, we classify
incidences between the contained circles, complex lines and isolated
singularities. Such geometric characteristics are encoded in the N\'eron-Severi
lattices of such surfaces and is of potential interest to geometric modelers
and architects. As an application we confirm Blum's conjecture in higher
dimensional space and we address the Blaschke-Bol problem by classifying
surfaces that are covered by hexagonal webs of circles. In particular, we find
new examples of such webs that cannot be embedded in 3-dimensional space.


title:
Multiple exciton generation in nano-crystals revisited: Consistent
  calculation of the yield based on pump-probe spectroscopy

abstract:
  Multiple exciton generation (MEG) is a process in which more than one exciton
is generated upon the absorption of a high energy photon, typically higher than
two times the band gap, in semiconductor nanocrystals. It can be observed
experimentally using time resolved spectroscopy such as the transient
absorption measurements. Quantification of the MEG yield is usu- ally done by
assuming that the bi-exciton signal is twice the signal from a single exciton.
Herein we show that this assumption is not always justified and may lead to
significant errors in the estimated MEG yields. We develop a methodology to
determine proper scaling factors to the signals from the transient absorption
experiments. Using the methodology we find modest MEG yields in lead
chalcogenide nanocrystals including the nanorods.


title: The Elliptic Function in Statistical Integrable Models II

abstract:
  Two dimensional statistical integrable models, such as the Ising model, the
chiral Potts model and the Belavin model, becomes integrable. Because of the
SU(2) symmetry of these models, these models become integrable. The integral
models are often parameterized by the elliptic function or the elliptic theta
function. In this paper, we study the Ising model, and we show that the
Yang-Baxter equation of the Ising model can be written as the integrability
condition of SU(2), and we gives the natural explanation why the Ising model
can be parameterized by the elliptic function by connecting the spherical
trigonometry relation and the elliptic function. Addition formula of the
elliptic function is the secret of the exact solvability of the Ising model.


title: Quantum Transport and Electroweak Baryogenesis

abstract:
  We review the mechanism of electroweak baryogenesis. Our focus is on the
derivation of quantum transport equations from first principles within the
Schwinger-Keldysh formalism. We emphasize the importance of the semiclassical
force approach, which provides reliable predictions in most models. In the
light of recent electric dipole moment measurements and given the results on
new physics searches from collider experiments, the status of electroweak
baryogenesis is discussed in a variety of models.


title:
On signals faint and sparse: the ACICA algorithm for blind de-trending
  of Exoplanetary transits with low signal-to-noise

abstract:
  Independent Component Analysis (ICA) has recently been shown to be a
promising new path in data analysis and de-trending of exoplanetary time series
signals. Such approaches do not require or assume any prior or auxiliary
knowledge on the data or instrument in order to de-convolve the astrophysical
light curve signal from instrument or stellar systematic noise. These methods
are often known as 'blind source separation' (BSS) algorithms. Unfortunately
all BSS methods suffer from a amplitude and sign ambiguity of their
de-convolved components which severely limits these methods in low
signal-to-noise (S/N) observations where their scalings cannot be determined
otherwise. Here we present a novel approach to calibrate ICA using sparse
wavelet calibrators. The Amplitude Calibrated Independent Component Analysis
(ACICA) allows for the direct retrieval of the independent components' scalings
and the robust de-trending of low S/N data. Such an approach gives us an unique
and unprecedented insight in the underlying morphology of a data set, making
this method a powerful tool for exoplanetary data de-trending and signal
diagnostics.


title: Bruhat strata and F-zips with additional structures

abstract:
  In this paper we study the Bruhat decomposition of not necessarily connected
reductive quasi-split groups $G$ with respect to not necessarily connected
parabolic subgroups. If $G$ is defined over a finite field, we construct a
smooth morphism from the stack classifying $F$-zips with $G$-structure to the
stack classifying the generalized Bruhat cells and study the relation between
the resulting stratifications. We apply these general results to the twisted
orthogonal $F$-zip given by the second De Rham cohomology of a relative
surface, focussing on K3-surfaces.


title:
"Quantum" linearization of Painlev\'{e} equations as a component of
  their $L,A$ pairs

abstract:
  The procedure of the "quantum" linearization of the Hamiltonian ordinary
differential equations with one degree of freedom is introduced. It is offered
to be used for the classification of integrable equations of the Painleve type.
By this procedure and all natural numbers $n$ we construct the solutions
$\Psi(\hbar,t,x,n)$ to the non-stationary Shr\"{o}dinger equation with the
Hamiltonian $H = (p^2+q^2)/2$ which tend to zero as $x\to\pm\infty$. On the
curves $x=q_n (\hbar, t) $ defined by the old Bohr-Sommerfeld quantization rule
the solutions satisfy the relation $i\hbar \Psi '_x\equiv p_n (\hbar, t) \Psi
$, where $p_n (\hbar, t) = (q_n (\hbar, t)) '_t $ is the classical momentum
corresponding to the harmonic $q_n (\hbar, t) $.

categories: nlin.SI hep-th math-ph math.CA math.MP quant-ph


title: Back-Reaction in Relativistic Cosmology

abstract:
  We introduce the concept of back-reaction in relativistic cosmological
modeling. Roughly speaking, this can be thought of as the difference between
the large-scale behaviour of an inhomogeneous cosmological solution of
Einstein's equations, and a homogeneous and isotropic solution that is a
best-fit to either the average of observables or dynamics in the inhomogeneous
solution. This is sometimes paraphrased as `the effect that structure has of
the large-scale evolution of the universe'. Various different approaches have
been taken in the literature in order to try and understand back-reaction in
cosmology. We provide a brief and critical summary of some of them,
highlighting recent progress that has been made in each case.


title:
Coordination-driven magnetic-to-nonmagnetic transition in manganese
  doped silicon clusters

abstract:
  The interaction of a single manganese impurity with silicon is analyzed in a
combined experimental and theoretical study of the electronic, magnetic, and
structural properties of manganese-doped silicon clusters. The structural
transition from exohedral to endohedral doping coincides with a quenching of
high-spin states. For all geometric structures investigated, we find a similar
dependence of the magnetic moment on the manganese coordination number and
nearest neighbor distance. This observation can be generalized to manganese
point defects in bulk silicon, whose magnetic moments fall within the observed
magnetic-to-nonmagnetic transition, and which therefore react very sensitively
to changes in the local geometry. The results indicate that high spin states in
manganese-doped silicon could be stabilized by an appropriate lattice
expansion.


title:
X-ray luminosity functions of different morphological and X-ray type AGN
  populations

abstract:
  Luminosity functions are one of the most important observational clues when
studying galaxy evolution over cosmic time. In this paper we present the X-ray
luminosity functions of X-ray detected AGN in the SXDS and GWS fields. The
limiting fluxes of our samples are 9.0x10^(-15) and 4.8x10^(-16)
erg/cm^2/sec^(-1) in the 0.5 - 7.0 keV band in the two fields, respectively. We
carried out analysis in three X-ray bands and in two redshift intervals up to z
< 1.4. Moreover, we derive the luminosity functions for different optical
morphologies and X-ray types. We confirm strong luminosity evolution in all
three bands, finding the most luminous objects at higher redshift. However, no
signs of density evolution are found in any tested X-ray band. We obtain
similar results for compact and early-type objects. Finally, we observe the
`Steffen effect', where X-ray type-1 sources are more numerous at higher
luminosities in comparison with type-2 sources.


title: Sterile Neutrinos: Cosmology vs Short-BaseLine Experiments

abstract:
  Cosmology and short baseline neutrino oscillation data both hint at the
existence of light sterile neutrinos with masses in the 1 eV range. Here we
perform a detailed analysis of the sterile neutrino scenario using both
cosmological and SBL data. We have additionally considered the possibility that
the extra neutrino degrees of freedom are not fully thermalised in the early
universe. Even when analyzing only cosmological data we find a preference for
the existence of massive sterile neutrinos in both (3+1) and (3+2) scenarios,
and with the inclusion of SBL data the evidence is formally at the 3.3sigma
level in the case of a (3+1) model. Interestingly, cosmological and SBL data
both point to the same mass scale of approximately 1 eV. In the (3+1) framework
WMAP9+SPT provide a value of the sterile mass eigenstate m_4 = (1.72 \pm 0.65)
eV: this result is strenghtened by adding the prior from SBL posterior to m_4 =
(1.27 \pm 0.12) eV (m_4 = (1.23 \pm 0.13) eV when SDSS is also considered in
the cosmological analysis). In the (3+2) scheme, two additional, non--fully
thermalized, neutrinos are compatible with the whole set of cosmological and
SBL data, leading to mass values of m_4 = (0.95 \pm 0.30) eV and m_5 = (1.59
\pm 0.49) eV. The inclusion of Planck data does not change our considerations
about the mass scale; concerning the extra neutrino degrees of freedom,
invoking a partial thermalisation the 3+1 model is still consistent with the
latest data.


title:
On the theory of firm in nonlinear dynamic financial and economic
  systems

abstract:
  The new business paradigms originate a strong necessity to re-think the
theory of the firm with the aim to get a better understanding on the
organizational and functional principles of the firm, operating in the
investment economies in the prosperous societies. In this connection, we make
the innovative research to advance our scientific knowledge on the theory of
firm in the conditions of the nonlinear dynamic financial and economic systems.
We propose that the nonlinearities have to be taken to the consideration and
the nonlinear differential equation have to be used to model the firm in the
modern theories of the firm in the nonlinear dynamic financial and economic
systems. We apply the econophysical approach with the dynamic regimes modeling
on the bifurcation diagram as in the dynamic chaos theory with the purpose to
accurately characterize the nonlinearities in the economic theory of the firm.
We introduce the Ledenyov firm stability theorem, based on the Lyapunov
stability criteria, to precisely characterize the stability of the firm in the
nonlinear dynamic financial and economic systems in the time of globalization.


title:
The effects of flattening and rotation on the temperature of the X-ray
  halos of elliptical galaxies

abstract:
  Elliptical galaxies have hot coronae with X-ray luminosities and mean gas
temperatures that span over wide ranges. This variation can be partially due to
the energy budget of the hot gas, that depends on the host galaxy structure and
internal kinematics. With the aid of realistic axisymmetric galaxy models, we
performed a diagnostic study focussed on the effects of galaxy flattening and
rotational support on the hot gas temperature.


title:
Next-to-next-to-leading order post-Newtonian linear-in-spin binary
  Hamiltonians

abstract:
  The next-to-next-to-leading order post-Newtonian spin-orbit and
spin(1)-spin(2) Hamiltonians for binary compact objects in general relativity
are derived. The Arnowitt-Deser-Misner canonical formalism and its
generalization to spinning compact objects in general relativity are presented
and a fully reduced matter-only Hamiltonian is obtained. Several
simplifications using integrations by parts are discussed. Approximate
solutions to the constraints and evolution equations of motion are provided.
Technical details of the integration procedures are given including an analysis
of the short-range behavior of the integrands around the sources. The
Hamiltonian of a test-spin moving in a stationary Kerr spacetime is obtained by
rather simple approach and used to check parts of the mentioned results.
Kinematical consistency checks by using the global (post-Newtonian approximate)
Poincar\'e algebra are applied. Along the way a self-contained overview for the
computation of the 3PN ADM point-mass Hamiltonian is provided, too.


title: Filiform Lie algebras of order 3

abstract:
  The aim of this work is to generalize a very important type of Lie algebras
and superalgebras, i.e. filiform Lie (super)algebras, into the theory of Lie
algebras of order F$. Thus, the concept of filiform Lie algebras of order F is
obtained. In particular, for F=3 it has been proved that by using infinitesimal
deformations of the associated model elementary Lie algebra it can be obtained
families of filiform elementary lie algebras of order 3, analogously as that
occurs into the theory of Lie algebras (Vergne, 1970). Also we give the
dimension, using an adaptation of the sl(2,C)-module Method, and a basis of
such infinitesimal deformations in some generic cases.


title: Disk dynamics and the X-ray emission of S0 and flat early-type galaxies

abstract:
  With 2D hydrodynamical simulations, we study the evolution of the hot gas
flows in early-type galaxies, focussing on the effects of galaxy rotation on
the thermal and dynamical status of the ISM. The galaxy is modelled as a
two-component axisymmetric system (stars and dark matter), with a variable
amount of azimuthal velocity dispersion and rotational support; the presence of
a counter rotating stellar disk is also considered. It is found that the ISM of
the rotationally supported (isotropic) model is more prone to thermal
instabilities than the fully velocity dispersion counterpart, while its ISM
temperature and X-ray luminosity are lower. The model with counter rotation
shows an intermediate behaviour.


title:
Relativistic corrections to \eta_c-pair production in high energy
  proton-proton collisions

abstract:
  On the basis of perturbative QCD and the relativistic quark model we
calculate relativistic corrections to the double $\eta_c$ meson production in
proton-proton interactions at LHC energies. Relativistic terms in the
production amplitude connected with the relative motion of heavy quarks and the
transformation law of the bound state wave functions to the reference frame of
moving charmonia are taken into account. For the gluon and quark propagators
entering the amplitude we use a truncated expansion in relative quark momenta
up to the second order. Relativistic corrections to the quark bound state wave
functions are considered by means of the Breit-like potential. It turns out
that the examined effects decrease total nonrelativistic cross section more
than two times and on 20 percents in the rapidity region of LHCb detector.


title: Frozen percolation in two dimensions

abstract:
  Aldous introduced a modification of the bond percolation process on the
binary tree where clusters stop growing (freeze) as soon as they become
infinite. We investigate the site version of this process on the triangular
lattice where clusters freeze as soon as they reach L infinity diameter at
least N for some parameter N. We show that, informally speaking, in the limit N
goes to infinity, the clusters only freeze in the critical window of site
percolation on the triangular lattice. Hence the fraction of vertices that
eventually (i. e. at time 1) are in a frozen cluster tends to 0 as N goes to
infinity. We also show that the diameter of the open cluster at time 1 of a
given vertex is, with high probability, smaller than N but of order N. This
shows that the process on the triangular lattice has a behaviour quite
different from Aldous' process. We also indicate which modifications have to be
made to adapt the proofs to the case of the N-parameter frozen bond percolation
process on the square lattice. This extends our results to the square lattice,
and answers the questions posed by van den Berg, de Lima and Nolin in an
earlier paper.


title:
Estimations of the low dimensional homology of Lie algebras with large
  abelian ideals

abstract:
  A Lie algebra $L$ of dimension $n \ge1 $ may be classified, looking for
restrictions of the size on its second integral homology Lie algebra
$H_2(L,\mathbb{Z})$, denoted by $M(L)$ and often called Schur multiplier of
$L$. In case $L$ is nilpotent, we proved that $\mathrm{dim} \ M(L) \leq
\frac{1}{2}(n+m-2)(n-m-1)+1$, where $\mathrm{dim} \ L^2=m \ge 1$, and worked on
this bound under various perspectives. In the present paper, we estimate the
previous bound for $\mathrm{dim} \ M(L) $ with respect to other inequalities of
the same nature. Finally, we provide new upper bounds for the Schur multipliers
of pairs and triples of nilpotent Lie algebras, by means of certain exact
sequences due to Ganea and Stallings in their original form.


title:
Analogue Special and General Relativity by Optical Multilayer Thin
  Films: The Rindler Space Case

abstract:
  In this paper, to obtain an analogy between the curved spaces and the linear
optics, we expand the idea of Ref.[1, 2] to the multilayer films. We
investigate efects of thickness and index of refraction of the films on the
Lorentzian transformations. In addition, by using the multilayer films, we
suggest very simple experimental set-up which can serve as an analogue computer
for testing special relativity. Finally, we draw an analogy between the Rindler
space, as an example of the curved spaces, and a suitable multilayer film.


title: Sufficient conditions for sampling and interpolation on the sphere

abstract:
  We obtain sufficient conditions for arrays of points,
$\mathcal{Z}=\{\mathcal{Z}(L) \}_{L\ge 1},$ on the unit sphere
$\mathcal{Z}(L)\subset \mathbb{S}^d,$ to be Marcinkiewicz-Zygmund and
interpolating arrays for spaces of spherical harmonics. The conditions are in
terms of the mesh norm and the separation radius of $\mathcal{Z}(L)$.


title:
Properties of modified Bessel functions and completely monotonic degrees
  of differences between exponential and trigamma functions

abstract:
  In the paper, the author establishes inequalities, monotonicity, convexity,
and unimodality for functions concerning the modified Bessel functions of the
first kind and compute the completely monotonic degrees of differences between
the exponential and trigamma functions.


title: Velocity Correlations in an Active Nematic

abstract:
  The flow properties of a continuum model for an active nematic is studied and
compared with recent experiments on suspensions of microtubule bundles and
molecular motors. The velocity correlation length is found to be independent of
the strength of the activity while the characteristic velocity scale increases
monotonically as the activity is increased, both in agreement with the
experimental observations. We interpret our results in terms of the creation
and annihilation dynamics of a gas of topological defects.

categories: cond-mat.soft cond-mat.mes-hall physics.bio-ph physics.flu-dyn


title:
Focusing, Power Tunneling and Rejection from Chiral and/or Chiral
  Nihility/Nihility Metamaterials Layers

abstract:
  Focusing of electromagnetic plane wave from a large size paraboloidal
reflector, composed of layers of chiral and/or chiral nihility metamaterials,
has been studied us- ing Maslov's method. First, the transmission and
reflection of electromagnetic plane wave from two parallel layers of chiral
and/or chiral nihility metamaterials are cal- culated using transfer matrix
method. The effects of change of angle of incidence, chirality parameters and
impedances of layers are noted and discussed. Special cases by taking very
large and small values of permittivity of second layer, while assuming value of
corresponding chirality equal to zero, are also treated. These special cases
are equivalent to reflection from a perfect electric conductor backed chiral
layer and nihility backed chiral layer, respectively. Results of reflection
from parallel layers have been utilized to study focusing from a large size
paraboloidal reflector. The present study, on focusing from a paraboloidal
re{\deg}ector, not only unifies several published works conducted by different
researchers but also provides better understanding of new cases.


title: Jet-induced jammed states of granular jet impacts

abstract:
  The impacts of granular jets for both frictional and frictionless grains in
two dimensions are numerically investigated. A dense flow with a dead zone
emerges during the impact. From our two-dimensional simulation, we evaluate the
equations of state and the con- stitutive equations of the flow. The asymptotic
divergences of pressure and shear stress similar to the situation near the
jamming transition appear for the frictionless case, while their exponents are
smaller than those of the sheared granular systems, and are close to the
extrapolation from the kinetic theoretical regime. In a similar manner to the
jam- ming for frictional grains, the critical density decreases as the friction
constant of grains increases. For bi-disperse systems, the effective friction
constant defined as the ratio of shear stress to normal stress, monotonically
increases from near zero, as the strain rate increases. On the other hand, the
effective friction constant has two metastable branches for mono-disperse
systems because of the coexistence of a crystallized state and a liquid state.


title: Locally quasi-nilpotent elementary operators

abstract:
  Let $A$ be a unital dense algebra of linear mappings on a complex vector
space $X$. Let $\phi=\sum_{i=1}^n M_{a_i,b_i}$ be a locally quasi-nilpotent
elementary operator of length $n$ on $A$. We show that, if $\{a_1,\ldots,a_n\}$
is locally linearly independent, then the local dimension of
$V(\phi)=\spa\{b_ia_j: 1 \leq i,j \leq n\}$ is at most $\frac{n(n-1)}{2}$. If
$\lDim V(\phi)=\frac{n(n-1)}{2} $, then there exists a representation of $\phi$
as $\phi=\sum_{i=1}^n M_{u_i,v_i}$ with $v_iu_j=0$ for $i\geq j$. Moreover, we
give a complete characterization of locally quasi-nilpotent elementary
operators of length 3.


title: Exceptional geometry and tensor fields

abstract:
  We present a tensor calculus for exceptional generalised geometry.
Expressions for connections, torsion and curvature are given a unified
formulation for different exceptional groups E_n(n). We then consider "tensor
gauge fields" coupled to the exceptional generalised gravity. Many of the
properties of forms on manifolds are carried over to these fields.


title: Non-gravitational exceptional supermultiplets

abstract:
  We examine non-gravitational minimal supermultiplets which are based on the
tensor gauge fields appearing as matter fields in exceptional generalised
geometry. When possible, off-shell multiplets are given. The fields in the
multiplets describe non-gravitational parts of the internal dynamics of
compactifications of M-theory. In flat backgrounds, they enjoy a global
U-duality symmetry, but also provide multiplets with a possibility of coupling
to a generalised exceptional geometry.


title: Finding overlapping communities in networks using evolutionary method

abstract:
  Community structure is a typical property of many real-world networks, and
has become a key to understand the dynamics of the networked systems. In these
networks most nodes apparently lie in a community while there often exists a
few nodes straddling several communities. An ideal algorithm for community
detection is preferable which can identify the overlapping communities in such
networks. To represent an overlapping division we develop a encoding schema
composed of two segments, the first one represents a disjoint partition and the
second one represents a extension of the partition that allows of multiple
memberships. We give a measure for the informativeness of a node, and present
an evolutionary method for detecting the overlapping communities in a network.


title:
Specific heat and thermal conductivity of ferromagnetic magnons in
  Yttrium Iron Garnet

abstract:
  The specific heat and thermal conductivity of the insulating ferrimagnet
Y$_3$Fe$_5$O$_{12}$ (Yttrium Iron Garnet, YIG) single crystal were measured
down to 50 mK. The ferromagnetic magnon specific heat $C$$_m$ shows a
characteristic $T^{1.5}$ dependence down to 0.77 K. Below 0.77 K, a downward
deviation is observed, which is attributed to the magnetic dipole-dipole
interaction with typical magnitude of 10$^{-4}$ eV. The ferromagnetic magnon
thermal conductivity $\kappa_m$ does not show the characteristic $T^2$
dependence below 0.8 K. To fit the $\kappa_m$ data, both magnetic defect
scattering effect and dipole-dipole interaction are taken into account. These
results complete our understanding of the thermodynamic and thermal transport
properties of the low-lying ferromagnetic magnons.


title:
Spectral description of fluctuating electromagnetic fields of solids
  including a self consistency

abstract:
  Another way to evaluate the spectral-correlation properties of thermal fields
of solids is suggested. Such a method takes into account detailed structure of
the interface transition layer separating one bulk region from those of the
vacuum region. The principal element here is the surface linear response
function of an arbitrary inhomogeneous electron subsystem of solids. Along with
straightforward using the known response functions, for example in a
hydrodynamic approach, the suggested method allows calculating the response
functions self-consistently based on the time dependent density functional
theory. The self-consistent calculation of the linear response function
followed by an application of the fluctuation-dissipation theorem yield in the
spectral power densities of the fluctuating charge and current correlation
functions. The final step of this sequence of actions aiming in obtaining the
spectral-correlation properties of thermal fields of solids at any distances.


title:
Variable transformation to obtain geometric ergodicity in the
  random-walk Metropolis algorithm

abstract:
  A random-walk Metropolis sampler is geometrically ergodic if its equilibrium
density is super-exponentially light and satisfies a curvature condition
[Stochastic Process. Appl. 85 (2000) 341-361]. Many applications, including
Bayesian analysis with conjugate priors of logistic and Poisson regression and
of log-linear models for categorical data result in posterior distributions
that are not super-exponentially light. We show how to apply the
change-of-variable formula for diffeomorphisms to obtain new densities that do
satisfy the conditions for geometric ergodicity. Sampling the new variable and
mapping the results back to the old gives a geometrically ergodic sampler for
the original variable. This method of obtaining geometric ergodicity has very
wide applicability.


title:
The evolution of cooperation through institutional incentives and
  optional participation

abstract:
  Rewards and penalties are common practical tools that can be used to promote
cooperation in social institutions. The evolution of cooperation under reward
and punishment incentives in joint enterprises has been formalized and
investigated, mostly by using compulsory public good games. Recently, Sasaki et
al. (2012, Proc Natl Acad Sci USA 109:1165-1169) considered optional
participation as well as institutional incentives and described how the
interplay between these mechanisms affects the evolution of cooperation in
public good games. Here, we present a full classification of these evolutionary
dynamics. Specifically, whenever penalties are large enough to cause the
bi-stability of both cooperation and defection in cases in which participation
in the public good game is compulsory, these penalties will ultimately result
in cooperation if participation in the public good game is optional. The global
stability of coercion-based cooperation in this optional case contrasts
strikingly with the bi-stability that is observed in the compulsory case. We
also argue that optional participation is not so effective at improving
cooperation under rewards.


title:
Deposition of model chains on surfaces: anomalous relation between flux
  and stability

abstract:
  Model chains are studied via Monte Carlo simulations which are deposited with
a fixed flux on a substrate. They may represent, e.g., stiff lipophilic chains
with an head group and tail groups mimicking the alkyl chain. After some
subsequent fixed simulation time we determine the final energy as a function of
flux and temperature. Surprisingly, in some range of temperature and flux the
final energy increases with decreasing flux. The physical origin of this
counterintuitive observation is elucidated. In contrast, when performing
equivalent cooling experiments no such anomaly is observed. Furthermore, it is
elaborated whether flux experiments give rise to configurations with lower
energies as compared to cooling experiments. These results are related to
recent experiments by the Ediger group where very stable configurations of
glass-forming systems have been generated via flux experiments.


title: Injection locking at zero field in two free layer spin-valves

abstract:
  This paper predicts the possibility to achieve synchronization (via injection
locking to a microwave current) of spin-transfer torque oscillators based on
hybrid spin-valves composed by two free layers and two perpendicular polarizers
at zero bias field. The locking regions are attained for microwave frequency
near 0.5f0, f0, and 2f0 where f0 is the input oscillator frequency. Those
properties make this system promising for applications, such as high-speed
frequency dividers and multipliers, and phase-locked-loop demodulators.


title: The Redner - Ben-Avraham - Kahng cluster system

abstract:
  We consider a coagulation model first introduced by Redner, Ben-Avraham and
Krapivsky in [Redner, Ben-Avraham, Kahng: Kinetics of 'cluster eating', J.
Phys. A: Math. Gen., 20 (1987), 1231-1238], the main feature of which is that
the reaction between a j-cluster and a k-cluster results in the creation of a
|j-k|-cluster, and not, as in Smoluchowski's model, of a (j+k)-cluster. In this
paper we prove existence and uniqueness of solutions under reasonably general
conditions on the coagulation coefficients, and we also establish
differenciability properties and continuous dependence of solutions. Some
interesting invariance properties are also proved. Finally, we study the
long-time behaviour of solutions, and also present a preliminary analysis of
their scaling behaviour.


title:
Improved multivariate normal mean estimation with unknown covariance
  when p is greater than n

abstract:
  We consider the problem of estimating the mean vector of a p-variate normal
$(\theta,\Sigma)$ distribution under invariant quadratic loss,
$(\delta-\theta)'\Sigma^{-1}(\delta-\theta)$, when the covariance is unknown.
We propose a new class of estimators that dominate the usual estimator
$\delta^0(X)=X$. The proposed estimators of $\theta$ depend upon X and an
independent Wishart matrix S with n degrees of freedom, however, S is singular
almost surely when p>n. The proof of domination involves the development of
some new unbiased estimators of risk for the p>n setting. We also find some
relationships between the amount of domination and the magnitudes of n and p.


title: On a family of complex algebraic surfaces of degree 3n

abstract:
  We study a class of algebraic surfaces of degree 3n in the complex projective
space with only ordinary double points. They are obtained by using bivariate
polynomials with complex coefficients related to the generalized cosine
associated to the affine Weyl group of the root system A2.


title:
A code arithmetic approach for quaternary code designs and its
  application to (1/64)th-fractions

abstract:
  The study of good nonregular fractional factorial designs has received
significant attention over the last two decades. Recent research indicates that
designs constructed from quaternary codes (QC) are very promising in this
regard. The present paper aims at exploring the fundamental structure and
developing a theory to characterize the wordlengths and aliasing indexes for a
general $(1/4)^p$th-fraction QC design. Then the theory is applied to
(1/64)th-fraction QC designs. Examples are given, indicating that there exist
some QC designs that have better design properties, and are thus more
cost-efficient, than the regular fractional factorial designs of the same size.
In addition, a result about the periodic structure of (1/64)th-fraction QC
designs regarding resolution is stated.


title: Spatially resolved H_2 emission from a very low-mass star

abstract:
  Molecular outflows from very low-mass stars (VLMSs) and brown dwarfs have
been studied very little. So far, only a few CO outflows have been observed,
allowing us to map the immediate circumstellar environment. We present the
first spatially resolved H2 emission around IRS54 (YLW52), a ~0.1-0.2 Msun
Class I source. By means of VLT SINFONI K-band observations, we probed the H2
emission down to the first ~50 AU from the source. The molecular emission shows
a complex structure delineating a large outflow cavity and an asymmetric
molecular jet. Thanks to the detection of several H2 transitions, we are able
to estimate average values along the jet-like structure (from source position
to knot D) of Av~28 mag, T~2000-3000 K, and H2 column density N(H2)~1.7x10^17
cm^-2. This allows us to estimate a mass loss rate of ~2x10^-10 Msun/yr for the
warm H2 component . In addition, from the total flux of the Br Gamma line, we
infer an accretion luminosity and mass accretion rate of 0.64 Lsun and ~3x10^-7
Msun/yr, respectively. The outflow structure is similar to those found in
low-mass Class I and CTTS. However, the Lacc/Lbol ratio is very high (~80%),
and the mass accretion rate is about one order of magnitude higher when
compared to objects of roughly the same mass, pointing to the young nature of
the investigated source.


title:
First search for neutrinos in correlation with gamma-ray bursts with the
  ANTARES neutrino telescope

abstract:
  A search for neutrino-induced muons in correlation with a selection of 40
gamma-ray bursts that occurred in 2007 has been performed with the ANTARES
neutrino telescope. During that period, the detector consisted of 5 detection
lines. The ANTARES neutrino telescope is sensitive to TeV--PeV neutrinos that
are predicted from gamma-ray bursts. No events were found in correlation with
the prompt photon emission of the gamma-ray bursts and upper limits have been
placed on the flux and fluence of neutrinos for different models.


title:
Proposed imaging of the ultrafast electronic motion in samples using
  x-ray phase-contrast

abstract:
  Tracing the motion of electrons has enormous relevance to understanding
ubiquitous phenomena in ultrafast science, such as the dynamical evolution of
the electron density during complex chemical and biological processes.
Scattering of ultrashort x-ray pulses from an electronic wavepacket would
appear to be the most obvious approach to image the electronic motion in
real-time and real-space with the notion that such scattering patterns, in the
far-field regime, encode the instantaneous electron density of the wavepacket.
However, recent results by Dixit {\em et al.} [Proc. Natl. Acad. Sci. U.S.A.,
{\bf 109}, 11636 (2012)] have put this notion into question and shown that the
scattering in the far-field regime probes spatio-temporal density-density
correlations. Here, we propose a possible way to image the instantaneous
electron density of the wavepacket via ultrafast x-ray {\em phase contrast
imaging}. Moreover, we show that inelastic scattering processes, which plague
ultrafast scattering in the far-field regime, do not contribute in ultrafast
x-ray phase contrast imaging as a consequence of an interference effect. We
illustrate our general findings by means of a wavepacket that lies in the time
and energy range of the dynamics of valence electrons in complex molecular and
biological systems. This present work offers a potential to image not only
instantaneous snapshots of non-stationary electron dynamics, but also the
Laplacian of these snapshots which provide information about the complex
bonding and topology of the charge distributions in the systems.

categories: physics.atom-ph cond-mat.mes-hall physics.atm-clus physics.chem-ph


title:
The Shifting Technique for Computing the Extreme Solutions of $X +
  A^\top X^{-1} A = Q$

abstract:
  We propose a new way for speeding up the search of the maximal solution $X_+$
of $X + A^\top X^{-1} A = Q$. It is known that the speed of convergence of
traditional approaches for solving this problem depends highly on the spectral
radius $\rho(X_+^{-1}A)$. If $\rho(X_+^{-1}A)$ is close to one or equal to one,
the iterations of traditional approaches converges very slowly or does not
converge. Our goal is to come up with a shifting tactic to remove the
singularities embedded in $\rho(X_+^{-1}A)$. Finally, an example is used to
demonstrate the capacity of our method.


title:
L^2-Betti numbers of locally compact groups and their cross section
  equivalence relations

abstract:
  We prove that the L^2-Betti numbers of a unimodular locally compact group G
coincide, up to a natural scaling constant, with the L^2-Betti numbers of the
countable equivalence relation induced on a cross section of any essentially
free ergodic probability measure preserving action of G. As a consequence, we
obtain that the reduced and un-reduced L^2-Betti numbers of G agree and that
the L^2-Betti numbers of a lattice Gamma in G equal those of G up to scaling by
the covolume of Gamma in G. We also deduce several vanishing results, including
the vanishing of the reduced L^2-cohomology for amenable locally compact
groups.


title: Linear magnetoresistance in HgTe quantum wells

abstract:
  We report magnetotransport measurements in a HgTe quantum well with an
inverted band structure, which is expected to be a two-dimensional (2D)
topological insulator. A small magnetic field perpendicular the 2D layer breaks
the time reversal symmetry and thereby, suppresses the edge state transport. A
linear magnetoresistance is observed in low magnetic fields, when the chemical
potential moves through the the bulk gap. That magnetoresistance is well
described by numerical calculations of the edge states magnetotransport in the
presence of nonmagnetic disorder. With magnetic field increasing the
resistance, measured both in the local and nonlocal configurations first
sharply decreases and then increases again in disagreement with the existing
theories.


title: Magnetic relaxation in uranium ferromagnetic superconductors

abstract:
  There is proposed a phenomenological theory of quasi-elastic neutron
scattering in the itinerant ferromagnets UGe$_2$ and UCoGe based on their
property that magnetization supported by the moments located at uranium atoms
is not conserved quantity relaxing to equilibrium by the interaction with
itinerant electrons subsystem. As result the line width of quasi elastic
neutron scattering at $q\to 0$ acquires nonvanishing value at all temperatures
but the Curie temperature.


title:
Band widths and gaps from the Tran-Blaha functional : Comparison with
  many-body perturbation theory

abstract:
  For a set of ten crystalline materials (oxides and semiconductors), we
compute the electronic band structures using the Tran-Blaha [Phys. Rev. Lett.
102, 226401 (2009)] (TB09) functional. The band widths and gaps are compared
with those from the local-density approximation (LDA) functional, many-body
perturbation theory (MBPT), and experiments. At the density-functional theory
(DFT) level, TB09 leads to band gaps in much better agreement with experiments
than LDA. However, we observe that it globally underestimates, often strongly,
the valence (and conduction) band widths (more than LDA). MBPT corrections are
calculated starting from both LDA and TB09 eigenenergies and wavefunctions.
They lead to a much better agreement with experimental data for band widths.
The band gaps obtained starting from TB09 are close to those from
quasi-particle self-consistent GW calculations, at a much reduced cost.
Finally, we explore the possibility to tune one of the semi-empirical
parameters of the TB09 functional in order to obtain simultaneously better band
gaps and widths. We find that these requirements are conflicting.


title:
An extension of Paulsen-Gjessing's risk model with stochastic return on
  investments

abstract:
  We consider in this paper a general two-sided jump-diffusion risk model that
allows for risky investments as well as for correlation between the two
Brownian motions driving insurance risk and investment return. We first
introduce the model and then find the integro-differential equations satisfied
by the Gerber-Shiu functions as well as the expected discounted penalty
functions at ruin caused by a claim or by oscillation; We also study the
dividend problem for the threshold and barrier strategies, the moments and
moment-generating function of the total discounted dividends until ruin are
discussed. Some examples are given for special cases.


title: Is the Sulphur Anomaly in Planetary Nebulae Caused by the s-Process?

abstract:
  Motivated by unexplained observations of low sulphur abundances in planetary
nebulae (PNe) and the PG1159 class of post asymptotic giant branch (AGB) stars,
we investigate the possibility that sulphur may be destroyed by nucleosynthetic
processes in low-to-intermediate mass stars during stellar evolution. We use a
3 Msun, Z=0.01 evolutionary sequence to examine the consequences of high and
low reaction rate estimates of neutron captures onto sulphur and neighbouring
elements. In addition, we have tested high and low rates for the neutron
producing reactions C13(alpha,n)O16 and Ne22(alpha,n)Mg25. We vary the mass
width of a partially mixed zone (PMZ), which is responsible for the formation
of a C13 pocket and is the site of the C13(alpha,n)O16 neutron source. We test
PMZ masses from zero up to an extreme upper limit of the entire He-intershell
mass at 10^-2 Msun. We find that the alternative reaction rates and variations
to the partially mixed zone have almost no effect on surface sulphur abundances
and do not reproduce the anomaly. To understand the effect of initial mass on
our conclusions, 1.8 Msun and 6 Msun evolutionary sequences are also tested
with similar results for sulphur abundances. We are able to set a constraint on
the size of the PMZ, as PMZ sizes that are greater than half of the
He-intershell mass (in the 3 Msun model) are excluded by comparison with neon
abundances in planetary nebulae. We compare the 1.8 Msun model's intershell
abundances with observations of PG1159-035, whose surface abundances are
thought to reflect the intershell composition of a progenitor AGB star. We find
general agreement between the patterns of F, Ne, Si, P, and Fe abundances and a
very large discrepancy for sulphur where our model predicts abundances that are
30-40 times higher than is observed in the star.


title: Voltage tunability of single spin-states in a quantum dot

abstract:
  Single spins in the solid-state offer a unique opportunity to store and
manipulate quantum information, and to perform quantum-enhanced sensing of
local fields and charges. Optical control of these systems using techniques
developed in atomic physics has yet to exploit all the advantages of the
solid-state. We demonstrate voltage tunability of the spin energy levels in a
single quantum dot by modifying how spins sense magnetic field. We find the
in-plane g-factor varies discontinuously for electrons, as more holes are
loaded onto the dot. In contrast, the in-plane hole g-factor varies
continuously. The device can change the sign of the in-plane g-factor of a
single hole, at which point an avoided crossing is observed in the two spin
eigenstates. This is exactly what is required for universal control of a single
spin with a single electrical gate.


title:
Modified wave operators without loss of regularity for some long range
  Hartree equations. II

abstract:
  We continue the study of the theory of scattering for some long range Hartree
equations with potential |x|^-gamma, performed in a previous paper, denoted as
I, in the range 1/2 < gamma < 1. Here we extend the results to the range 1/3 <
gamma < 1/2. More precisely, we study the local Cauchy problem with infinite
initial time, which is the main step in the construction of the modified wave
operators. We solve that problem without loss of regularity between the
asymptotic state and the solution, as in I, but in contrast to I, we are no
longer able to cover the entire subcritical range of regularity of the
solutions. The method is an extension of that of I, using a better asymptotic
form of the solutions, obtained as the next step of a natural procedure of
successive approximations.


title: Cluster Gutzwiller method for bosonic lattice systems

abstract:
  A versatile and numerically inexpensive method is presented allowing the
accurate calculation of phase diagrams for bosonic lattice models. By treating
clusters within the Gutzwiller theory, a surprisingly good description of
quantum fluctuations beyond the mean-field theory is achieved approaching
quantum Monte-Carlo predictions for large clusters. Applying this powerful
method to the Bose-Hubbard model, we demonstrate that it yields precise results
for the superfluid to Mott-insulator transition in square, honeycomb, and cubic
lattices. Due to the exact treatment within a cluster, the method can be
effortlessly adapted to more complicated Hamiltonians in the fast progressing
field of optical lattice experiments. This includes state- and site-dependent
superlattices, large confined atomic systems and disordered potentials, as well
as various types of extended Hubbard models. Furthermore, the approach allows
an excellent treatment of systems with arbitrary filling factors. We discuss
the perspectives that allow for the computation of large, spatially-varying
lattices, low-lying excitations, and time evolution.


title:
The first passage time problem for mixed-exponential jump processes with
  applications in insurance and finance

abstract:
  This paper stidies the first passage times to constant boundaries for
mixed-exponential jump diffusion processes. Explicit solutions of the Laplace
transforms of the distribution of the first passage times, the joint
distribution of the first passage times and undershoot (overshoot) are
obtained. As applications, we present explicit expression of the Gerber-Shiu
functions for surplus processes with two-sided jumps, present the analytical
solutions for popular path-dependent options such as lookback and barrier
options in terms of Laplace transforms and give a closed-form expression on the
price of the zero-coupon bond under a structural credit risk model with jumps.


title: Modules with irrational slope over tubular algebras

abstract:
  Let $A$ be a tubular algebra and let $r$ be a positive irrational. Let
${\mathcal D}_r$ be the definable subcategory of $A$-modules of slope $r$. Then
the width of the lattice of pp formulas for ${\mathcal D}_r$ is $\infty$. It
follows that if $A$ is countable then there is a superdecomposable
pure-injective module of slope $r$.


title:
Categorizing Bugs with Social Networks: A Case Study on Four Open Source
  Software Communities

abstract:
  Efficient bug triaging procedures are an important precondition for
successful collaborative software engineering projects. Triaging bugs can
become a laborious task particularly in open source software (OSS) projects
with a large base of comparably inexperienced part-time contributors. In this
paper, we propose an efficient and practical method to identify valid bug
reports which a) refer to an actual software bug, b) are not duplicates and c)
contain enough information to be processed right away. Our classification is
based on nine measures to quantify the social embeddedness of bug reporters in
the collaboration network. We demonstrate its applicability in a case study,
using a comprehensive data set of more than 700,000 bug reports obtained from
the Bugzilla installation of four major OSS communities, for a period of more
than ten years. For those projects that exhibit the lowest fraction of valid
bug reports, we find that the bug reporters' position in the collaboration
network is a strong indicator for the quality of bug reports. Based on this
finding, we develop an automated classification scheme that can easily be
integrated into bug tracking platforms and analyze its performance in the
considered OSS communities. A support vector machine (SVM) to identify valid
bug reports based on the nine measures yields a precision of up to 90.3% with
an associated recall of 38.9%. With this, we significantly improve the results
obtained in previous case studies for an automated early identification of bugs
that are eventually fixed. Furthermore, our study highlights the potential of
using quantitative measures of social organization in collaborative software
engineering. It also opens a broad perspective for the integration of social
awareness in the design of support infrastructures.

categories: cs.SE cs.LG cs.SI nlin.AO physics.soc-ph


title: Evolution and dynamics of cusped light-like Wilson loops

abstract:
  We discuss the possible relation between the singular structure of TMDs on
the light-cone and the geometrical behaviour of rectangular Wilson loops.


title: A bag-of-paths framework for network data analysis

abstract:
  This work develops a generic framework, called the bag-of-paths (BoP), for
link and network data analysis. The central idea is to assign a probability
distribution on the set of all paths in a network. More precisely, a
Gibbs-Boltzmann distribution is defined over a bag of paths in a network, that
is, on a representation that considers all paths independently. We show that,
under this distribution, the probability of drawing a path connecting two nodes
can easily be computed in closed form by simple matrix inversion. This
probability captures a notion of relatedness between nodes of the graph: two
nodes are considered as highly related when they are connected by many,
preferably low-cost, paths. As an application, two families of distances
between nodes are derived from the BoP probabilities. Interestingly, the second
distance family interpolates between the shortest path distance and the
resistance distance. In addition, it extends the Bellman-Ford formula for
computing the shortest path distance in order to integrate sub-optimal paths by
simply replacing the minimum operator by the soft minimum operator.
Experimental results on semi-supervised classification show that both of the
new distance families are competitive with other state-of-the-art approaches.
In addition to the distance measures studied in this paper, the bag-of-paths
framework enables straightforward computation of many other relevant network
measures.


title: Topology optimization of robust superhydrophobic surfaces

abstract:
  In this paper we apply topology optimization to micro-structured
superhydrophobic surfaces for the first time. It has been experimentally
observed that a droplet suspended on a brush of micrometric posts shows a high
static contact angle and low roll-off angle. To keep the fluid from penetrating
the space between the posts, we search for an optimal post cross section, that
minimizes the vertical displacement of the liquid-air interface at the base of
the drop when a pressure difference is applied. Topology optimisation proves
effective in this framework, showing that posts with a branching cross-section
are optimal, which is consistent with several biologic strategies to achieve
superhydrophobicity. Through a filtering technique, we can also control the
characteristic length scale of the optimal design, thus obtaining feasible
geometries


title: Missing Entries Matrix Approximation and Completion

abstract:
  We describe several algorithms for matrix completion and matrix approximation
when only some of its entries are known. The approximation constraint can be
any whose approximated solution is known for the full matrix. For low rank
approximations, similar algorithms appears recently in the literature under
different names. In this work, we introduce new theorems for matrix
approximation and show that these algorithms can be extended to handle
different constraints such as nuclear norm, spectral norm, orthogonality
constraints and more that are different than low rank approximations. As the
algorithms can be viewed from an optimization point of view, we discuss their
convergence to global solution for the convex case. We also discuss the optimal
step size and show that it is fixed in each iteration. In addition, the derived
matrix completion flow is robust and does not require any parameters. This
matrix completion flow is applicable to different spectral minimizations and
can be applied to physics, mathematics and electrical engineering problems such
as data reconstruction of images and data coming from PDEs such as Helmholtz
equation used for electromagnetic waves.


title:
Dynamic phase diagrams of the Blume-Capel model in an oscillating field
  by the path probability method

abstract:
  We calculate the dynamic phase transition (DPT) temperatures and present the
dynamic phase diagrams in the Blume-Capel model under the presence of a
time-dependent oscillating external magnetic field by using the path
probability method. We study the time variation of the average order parameters
to obtain the phases in the system and the paramagnetic (P), ferromagnetic (F)
and the F + P mixed phases are found. We also investigate the thermal behavior
of the dynamic order parameters to analyze the nature (continuous and
discontinuous) of transitions and to obtain the DPT points. We present the
dynamic phase diagrams in three planes, namely (T, h), (d, T) and (k2/k1, T),
where T is the reduced temperature, h the reduced magnetic field amplitude, d
the reduced crystal-field interaction and the k2, k1 rate constants. The phase
diagrams exhibit dynamic tricritical and reentrant behaviors as well as a
double critical end point and triple point, strongly depending on the values of
the interaction parameters and the rate constants. We compare and discuss the
dynamic phase diagrams with dynamic phase diagrams that are obtained within the
Glauber-type stochastic dynamics based on the mean-field theory and the
effective field theory.


title: Total communicability as a centrality measure

abstract:
  We examine a node centrality measure based on the notion of total
communicability, defined in terms of the row sums of the exponential of the
adjacency matrix of the network. We argue that this is a natural metric for
ranking nodes in a network, and we point out that it can be computed very
rapidly even in the case of large networks. Furthermore, we propose the total
sum of node communicabilities as a useful measure of network connectivity.
Extensive numerical studies are conducted in order to compare this centrality
measure with the closely related ones of subgraph centrality [E. Estrada and J.
A. Rodriguez-Velazquez, Phys. Rev. E, 71 (2005), 056103] and Katz centrality
[L. Katz, Psychometrica, 18 (1953), pp. 39-43]. Both synthetic and real-world
networks are used in the computations.


title:
Rate of adaptation in sexuals and asexuals: A solvable model of the
  Fisher-Muller effect

abstract:
  The adaptation of large asexual populations is hampered by the competition
between independently arising beneficial mutations in different individuals,
which is known as clonal interference. Fisher and Muller proposed that
recombination provides an evolutionary advantage in large populations by
alleviating this competition. Based on recent progress in quantifying the speed
of adaptation in asexual populations undergoing clonal interference, we present
a detailed analysis of the Fisher-Muller mechanism for a model genome
consisting of two loci with an infinite number of beneficial alleles each and
multiplicative fitness effects. We solve the infinite population dynamics
exactly and show that, for a particular, natural mutation scheme, the speed of
adaptation in sexuals is twice as large as in asexuals. Guided by the infinite
population result and by previous work on asexual adaptation, we postulate an
expression for the speed of adaptation in finite sexual populations that agrees
with numerical simulations over a wide range of population sizes and
recombination rates. The ratio of the sexual to asexual adaptation speed is a
function of population size that increases in the clonal interference regime
and approaches 2 for extremely large populations. The simulations also show
that the imbalance between the numbers of accumulated mutations at the two loci
is strongly suppressed even by a small amount of recombination. The
generalization of the model to an arbitrary number $L$ of loci is briefly
discussed. If each offspring samples the alleles at each locus from the gene
pool of the whole population rather than from two parents, the ratio of the
sexual to asexual adaptation speed is approximately equal to $L$ in large
populations. A possible realization of this scenario is the reassortment of
genetic material in RNA viruses with $L$ genomic segments.


title:
Robustness of spin filtering against current leakage in a
  Rashba-Dresselhaus-Aharonov-Bohm interferometer

abstract:
  In an earlier paper [Phys. Rev. B 84, 035323 (2011)], we proposed a spin
filter which was based on a diamond-like interferometer, subject to both an
Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Here
we show that the full polarization of the outgoing electron spins remains the
same even when one allows leakage of electrons from the branches of the
interferometer. Once the gate voltage on one of the branches is tuned to
achieve an effective symmetry between them, this polarization can be controlled
by the electric and/or magnetic fields which determine the spin-orbit
interaction strength and the Aharonov-Bohm flux.