title: Early warning signals: The charted and uncharted territories

abstract:
  The realization that complex systems such as ecological communities can
collapse or shift regimes suddenly and without rapid external forcing poses a
serious challenge to our understanding and management of the natural world. The
potential to identify early warning signals that would allow researchers and
managers to predict such events before they happen has therefore been an
invaluable discovery that offers a way forward in spite of such seemingly
unpredictable behavior. Research into early warning signals has demonstrated
that it is possible to define and detect such early warning signals in advance
of a transition in certain contexts. Here we describe the pattern emerging as
research continues to explore just how far we can generalize these results. A
core of examples emerges that shares three properties: the phenomenon of rapid
regime shifts, a pattern of 'critical slowing down' that can be used to detect
the approaching shift, and a mechanism of bifurcation driving the sudden
change. As research has expanded beyond these core examples, it is becoming
clear that not all systems that show regime shifts exhibit critical slowing
down, or vice versa. Even when systems exhibit critical slowing down,
statistical detection is a challenge. We review the literature that explores
these edge cases and highlight the need for (a) new early warning behaviors
that can be used in cases where rapid shifts do not exhibit critical slowing
down, (b) the development of methods to identify which behavior might be an
appropriate signal when encountering a novel system; bearing in mind that a
positive indication for some systems is a negative indication in others, and
(c) statistical methods that can distinguish between signatures of early
warning behaviors and noise.


title:
Intrinsic and extrinsic origins of low-frequency noise in GaAs/AlGaAs
  Schottky-gated nanostructures

abstract:
  We study low-frequency noise in current passing through quantum point
contacts fabricated from several GaAs/AlGaAs heterostructures with different
layer structures and fabrication processes. In contrast to previous reports,
there is no gate-dependent random telegraph noise (RTN) originating from
tunneling through a Schottky barrier in devices fabricated using the standard
low-damage process. Gate-dependent RTN appears only in devices fabricated with
a high-damage process that induces charge trap sites. We show that the
insertion of AlAs/GaAs superlattices in the AlGaAs barrier helps to suppress
trap formation. Our results enable the fabrication of damage-resistant and thus
low-noise devices.


title:
Order-from-disorder effect in the exactly solved mixed spin-(1/2, 1)
  Ising model on fully frustrated triangles-in-triangles lattices

abstract:
  The mixed spin-(1/2, 1) Ising model on two fully frustrated
triangles-in-triangles lattices is exactly solved with the help of the
generalized star-triangle transformation, which establishes a rigorous mapping
correspondence with the equivalent spin-1/2 Ising model on a triangular
lattice. It is shown that the mutual interplay between the spin frustration and
single-ion anisotropy gives rise to various spontaneously ordered and
disordered ground states, which differ mainly in an occurrence probability of
the non-magnetic spin state of the integer-valued decorating spins. We have
convincingly evidenced a possible coexistence of the spontaneous long-range
order with a partial disorder within the striking ordered-disordered ground
state, which manifest itself through a non-trivial criticality at finite
temperatures as well. A rather rich critical behaviour including the
order-from-disorder effect and reentrant phase transitions with either two or
three successive critical points is also found.


title:
Exact Ground States of Frustrated Spin-1 Ising-Heisenberg and Heisenberg
  Ladders in a Magnetic Field

abstract:
  Ground states of the frustrated spin-1 Ising-Heisenberg two-leg ladder with
Heisenberg intra-rung coupling and only Ising interaction along legs and
diagonals are rigorously found by taking advantage of local conservation of the
total spin on each rung. The constructed ground-state phase diagram of the
frustrated spin-1 Ising-Heisenberg ladder is then compared with the analogous
phase diagram of the fully quantum spin-1 Heisenberg two-leg ladder obtained by
density matrix renormalization group (DMRG) calculations. It is demonstrated
that both investigated spin models exhibit quite similar magnetization
scenarios, which involve intermediate plateaux at one-quarter, one-half and
three-quarters of the saturation magnetization.


title:
Magnetization Process and Adiabatic Demagnetization of the
  Antiferromagnetic Spin-1/2 Heisenberg Cubic Cluster

abstract:
  A full energy spectrum of the spin-1/2 Heisenberg cubic cluster is used to
investigate a low-temperature magnetization process and adiabatic
demagnetization of this zero-dimensional 2x2x2 quantum spin system. It is shown
that the antiferromagnetic spin-1/2 Heisenberg cube exhibits at low enough
temperatures a stepwise magnetization curve with four intermediate plateaux at
zero, one quarter, one half, and three quarters of the saturation
magnetization. We have also found the enhanced magnetocaloric effect close to
level-crossing fields that determine transitions between the intermediate
plateaux.


title: On Cost-Effective Incentive Mechanisms in Microtask Crowdsourcing

abstract:
  While microtask crowdsourcing provides a new way to solve large volumes of
small tasks at a much lower price compared with traditional in-house solutions,
it suffers from quality problems due to the lack of incentives. On the other
hand, providing incentives for microtask crowdsourcing is challenging since
verifying the quality of submitted solutions is so expensive that will negate
the advantage of microtask crowdsourcing. We study cost-effective incentive
mechanisms for microtask crowdsourcing in this paper. In particular, we
consider a model with strategic workers, where the primary objective of a
worker is to maximize his own utility. Based on this model, we analyze two
basic mechanisms widely adopted in existing microtask crowdsourcing
applications and show that, to obtain high quality solutions from workers,
their costs are constrained by some lower bounds. We then propose a
cost-effective mechanism that employs quality-aware worker training as a tool
to stimulate workers to provide high quality solutions. We prove theoretically
that the proposed mechanism, when properly designed, can obtain high quality
solutions with an arbitrarily low cost. Beyond its theoretical guarantees, we
further demonstrate the effectiveness of our proposed mechanisms through a set
of behavioral experiments.


title:
Rigidity of the conductance of anchored dithioazobenzene opto-mechanical
  switch

abstract:
  Reversible opto-mechanical molecular switch based on a single azobenzene
molecule suspended via thiolate links between realistic models of gold tips is
investigated. Using a combination of the transfer matrix technique and density
functional theory we focus on conductance of the nano-device in the two
(meta)stable cis and trans junction conformations. We find the conductance of
both conformations to be broadly similar. In qualitative agreement with related
experiments, we find that the same nano-device with one/two methylene linker
group(s) inserted on one/both ends of the azobenzene molecule is driven into
tunneling regime and reduces the conductances by up to two orders of magnitude,
again almost uniformly for both conformations. These results clarify the huge
differences in switching ratios found previously and indicate that this
nano-device is not particularly suited for use as a molecular switch based on
conductance change.


title: A Predictive Model of Geosynchronous Magnetopause Crossings

abstract:
  We have developed a model predicting whether or not the magnetopause crosses
geosynchronous orbit at given location for given solar wind pressure Psw, Bz
component of interplanetary magnetic field (IMF) and geomagnetic conditions
characterized by 1-min SYM-H index. The model is based on more than 300
geosynchronous magnetopause crossings (GMCs) and about 6000 minutes when
geosynchronous satellites of GOES and LANL series are located in the
magnetosheath (so-called MSh intervals) in 1994 to 2001. Minimizing of the Psw
required for GMCs and MSh intervals at various locations, Bz and SYM-H allows
describing both an effect of magnetopause dawn-dusk asymmetry and saturation of
Bz influence for very large southward IMF. The asymmetry is strong for large
negative Bz and almost disappears when Bz is positive. We found that the larger
amplitude of negative SYM-H the lower solar wind pressure is required for GMCs.
We attribute this effect to a depletion of the dayside magnetic field by a
storm-time intensification of the cross-tail current. It is also found that the
magnitude of threshold for Bz saturation increases with SYM-H index such that
for small negative and positive SYM-H the effect of saturation diminishes. This
supports an idea that enhanced thermal pressure of the magnetospheric plasma
and ring current particles during magnetic storms results in the saturation of
magnetic effect of the IMF Bz at the dayside magnetopause. A noticeable
advantage of the model prediction capabilities in comparison with other
magnetopause models makes the model useful for space weather predictions.
Supplement : a program-code of the GMC-model


title: On the fractal dimension of the Duffing attractor

abstract:
  The box counting dimension $d_C$ and the correlation dimension $d_G$ change
with the number of numerically generated points forming the attractor. At a
sufficiently large number of points the fractal dimension tends to a finite
value. The obtained values are $d_C\approx 1.43$ and $d_G\approx 1.38$.


title:
Cohomologies of deformations of solvmanifolds and closedness of some
  properties

abstract:
  We provide further techniques to study the Dolbeault and Bott-Chern
cohomologies of deformations of solvmanifolds by means of finite-dimensional
complexes. By these techniques, we can compute the Dolbeault and Bott-Chern
cohomologies of some complex solvmanifolds, and we also get explicit examples,
showing in particular that either the $\partial\overline{\partial}$-Lemma or
the property that the Hodge and Fr\"olicher spectral sequence degenerates at
the first level are not closed under deformations.


title:
Elliptical model of cutoff boundaries for the solar energetic particles
  measured by POES satellites in December 2006

abstract:
  Experimental data from a constellation of five NOAA POES satellites were used
for studying the penetration of solar energetic particles (SEP) to high
latitudes during long-lasting SEP events on December 5 to 15, 2006. We
determined cutoff latitudes for electrons with energies >100 keV and > 300 keV,
and protons with energies from 240 keV to >140 MeV. The large number of
satellites allowed us to derive snap shots of the cutoff boundaries with 1-hour
time resolution. The boundaries were fitted well by ellipses. Based on the
elliptical approach, we developed a model of cutoff latitudes for protons and
electrons in the northern and southern hemispheres. The cutoff latitude is
represented as a function of rigidity, R, of particles, MLT, geomagnetic
indices: Dst, Kp, AE, and dipole tilt angle PS. The model predicts tailward and
duskward shifting of the cutoff boundaries in relation to intensification of
the cross-tail current, field-aligned currents, and symmetrical and
asymmetrical parts of the ring current. The model was applied for prediction of
a polar cap absorption (PCA) effects observed at high latitudes by CADI network
of ionosondes. It was found that the PCA effects are related mainly to intense
fluxes of >2.5 MeV protons and >100 keV electrons, which contribute mostly to
the ionization of ionospheric D-layer at altitudes of ~75 to 85 km. This
finding was confirmed independently by FORMOSAT-3/COSMIC observations of the
SEP-associated enhancements of electron content at altitudes of ~80 km.
Supplement : a program-code of the PCap-model


title: Phase transition in an exactly solvable reaction-diffusion process

abstract:
  We study a non-conserved one-dimensional stochastic process which involves
two species of particles $A$ and $B$. The particles diffuse asymmetrically and
react in pairs as $A\emptyset\leftrightarrow AA\leftrightarrow BA
\leftrightarrow A\emptyset$ and $B\emptyset \leftrightarrow BB \leftrightarrow
AB \leftrightarrow B\emptyset$. We show that the stationary state of the model
can be calculated exactly by using matrix product techniques. The model
exhibits a phase transition at a particular point in the phase diagram which
can be related to a condensation transition in a particular zero-range process.
We determine the corresponding critical exponents and provide a heuristic
explanation for the unusually strong corrections to scaling seen in the
vicinity of the critical point.


title:
Weak field approximation in a model of de Sitter gravity:
  Schwarzschild-de Sitter solutions

abstract:
  The weak field approximation in a model of de Sitter gravity is investigated
in the static and spherically symmetric case, under the assumption that the
vacuum spacetime without perturbations from matter fields is a torsion-free de
Sitter spacetime. It is shown on one hand that any solution should be singular
at the center of the matter field, if the exterior is described by a
Schwarzschild-de Sitter spacetime and is smoothly connected to the interior. On
the other, all the regular solutions are obtained, which might be used to
explain the galactic rotation curves without involving dark matter.


title:
All-electrical manipulation of electron spin by the spin-orbit
  interaction in a semiconductor nanotube: analytical results

abstract:
  A possibility of controlled manipulation of electron spin states has been
investigated for a cylindrical two-dimensional electron gas confined in a
semiconductor nanotube/cylindrical nanowire with the Rashba spin-orbit
interaction. We present analytical solutions for the two limiting cases, in
which the spin-orbit interaction results from (A) the radial electric field and
(B) the electric field applied along the axis z of the nanotube. In case (A),
the superposition of the two lowest-energy bands corresponding to the opposite
spins leads to the precession of electron spin around the nanowire axis. We
have found that the direction of the spin precession changes from clockwise to
counterclockwise if the energy of the injected electron achieves the value
corresponding to the crossing of energy levels associated with the two
components of the superposition state. In case (B), we have obtained the damped
oscillations of the z spin component with the period that changes as a function
of the coordinate z. We have also shown that the damped oscillations of the
average value of the z spin component form beats localized along the nanowire
axis.


title: Geometric temperature and entropy of quantum isolated horizons

abstract:
  By reintroducing Lorentz invariance in canonical loop quantum gravity, we
define a geometrical notion of temperature for quantum isolated horizons. This
is done by demanding that the horizon state satisfying the boundary conditions
be a Kubo-Martin-Schwinger state. The exact formula for the temperature can be
derived by imposing the reality conditions in the form of the linear simplicity
constraints for an imaginary Barbero-Immirzi parameter. Thus, our analysis
reveals the connection between the analytic continuation to the Ashtekar
self-dual variables and the thermality of the horizon. The horizon thermal
equilibrium state can then be used to compute both the entanglement and the
Boltzmann entropies. We show that the two provide the same finite answer, which
allows us to recover the Bekenstein-Hawking formula in the semi-classical
limit. In this way, we shed new light on the microscopic origin of black hole
entropy by revealing the equivalence between the near-horizon degrees of
freedom entanglement proposal and the state-counting interpretation. The
connection with the Connes-Rovelli thermal time proposal for a general
relativistic statistical mechanics is worked out.


title: The minimum number of disjoint pairs in set systems and related problems

abstract:
  Let F be a set system on [n] with all sets having k elements and every pair
of sets intersecting. The celebrated theorem of Erdos-Ko-Rado from 1961 says
that any such system has size at most ${n-1 \choose k-1}$. A natural question,
which was asked by Ahlswede in 1980, is how many disjoint pairs must appear in
a set system of larger size. Except for the case k=2, solved by Ahlswede and
Katona, this problem has remained open for the last three decades.
  In this paper, we determine the minimum number of disjoint pairs in small
k-uniform families, thus confirming a conjecture of Bollobas and Leader in
these cases. Moreover, we obtain similar results for two well-known extensions
of the Erdos-Ko-Rado theorem, determining the minimum number of matchings of
size q and the minimum number of t-disjoint pairs that appear in set systems
larger than the corresponding extremal bounds. In the latter case, this
provides a partial solution to a problem of Kleitman and West.


title: Neutron-rich hypernuclei: Lambda-6H and beyond

abstract:
  Recent experimental evidence presented by the FINUDA Collaboration for a
particle-stable Lambda-6H has stirred renewed interest in charting domains of
particle-stable neutron-rich Lambda hypernuclei, particularly for unbound
nuclear cores. We have studied within a shell-model approach several
neutron-rich Lambda hypernuclei in the nuclear p shell that could be formed in
(pi-,K+) or in (K-,pi+) reactions on stable nuclear targets. Hypernuclear
shell-model input is taken from a theoretically inspired successful fit of
gamma-ray transitions in p-shell Lambda hypernuclei which includes also
Lambda-N <-> Sigma-N coupling (Lambda<->Sigma coupling). The particle stability
of Lambda-6H is discussed and predictions are made for binding energies of
Lambda-9He, Lambda-10Li, Lambda-12Be, Lambda-14B. None of the large effects
conjectured by some authors to arise from Lambda<->Sigma coupling is borne out,
neither by these realistic p-shell calculations, nor by quantitative estimates
outlined for heavier hypernuclei with substantial neutron excess.


title: Dyanamics of Social Queues

abstract:
  Queues formed by social wasps to inherit the dominant position in the nest
are analyzed by using a transient quasi-birth-and-death process. We show that
the extended nest life time due to division of labor between queen and helpers
has a big impact for the nest productivity.


title:
Exploring the water and carbon monoxide shell around Betelgeuse with
  VLTI/AMBER

abstract:
  We present the results of the analysis of our recent interferometric
observations of Betelgeuse, using the AMBER instrument of the VLTI. Using the
medium spectral resolution mode ($R \sim 1500$) we detected the presence of the
water vapour and carbon monoxide (CO) molecules in the H and K bands. We also
derived the photospheric angular diameter in the continuum. By analysing the
depth of the molecular lines and the interferometric visibilities, we derived
the column densities of the molecules, as well as the temperature and the size
of the corresponding regions in the atmosphere of Betelgeuse (the MOLsphere)
using a single shell model around the photosphere. Our results confirm the
findings by Perrin \et al\ (\cite{Perrin2004}) and Ohnaka \et al\
(\cite{Ohnaka2011}) that the H$_2$O and CO molecules are distributed around
Betelgeuse in a MOLsphere extending to approximately 1.3 times the star's
photospheric radius.


title:
Phonon anomalies and lattice dynamics in superconducting oxychlorides
  Ca$_{2-x}$CuO$_2$Cl

abstract:
  We present a comprehensive study of the phonon dispersion in an underdoped,
superconducting Ca$_{2-x}$CuO$_2$Cl$_2$ crystal. We interpret the results using
lattice dynamical calculations based on a shell model, and we compare the
results, to other hole-doped cuprates, in particular to the ones isomorphic to
La$_{2-x}$Sr$_x$CuO$_4$ (LSCO). We found that an anomalous dip in the Cu-O bond
stretching dispersion develops in oxychlorides with a simultaneous marked
broadening of the mode. The broadening is maximum at $\approx (\pi / (2a) ~ 0 ~
0)$ that corresponds to the charge-modulations propagation vector. Our analysis
also suggests that screening effects in calculations may cause an apparent
cosine-shaped bending of the Cu-O bond-stretching dispersion along both the
($q$ 0 0) and ($q$ $q$ 0) directions, that is not observed on the data close to
optimal doping. This observation suggests that the discrepancy between
experimental data and \textit{ab-initio} calculations on this mode originates
from an overestimation of the doping effects on the mode.


title: Quasilinear elliptic Hamilton-Jacobi equations on complete manifolds

abstract:
  Let (M^n,g) be a n-dimensional complete, non-compact and connected Riemannian
manifold, with Ricci tensor Ricc_g and sectional curvature Sec_g. Assume
Ricc_g\geq (1-n)B^2, and either p>2 and Sec_g(x)=o(dist^2(x,a)) when
dist^2(x,a)\to\infty for a\in M, or 1<p<2 and Sec_g(x)\leq 0. If q>p-1> 0, any
C^1 solution of (E) -\Gd_pu+\abs{\nabla u}^q=0 on M satisfies \abs{\nabla
u(x)}\leq c_{n,p,q}B^{\frac{1}{q+1-p}} for some constant c_{n,p,q}>0. As a
consequence there exists c_{n,p}>0 such that any positive p-harmonic function v
on M satisfies v(a)e^{-c_{n,p}B\dist (x,a)}\leq v(x)\leq v(a)e^{c_{n,p}B\dist
(x,a)} for any (a,x)\in M\times M.


title: Type-based Dependency Analysis for JavaScript

abstract:
  Dependency analysis is a program analysis that determines potential data flow
between program points. While it is not a security analysis per se, it is a
viable basis for investigating data integrity, for ensuring confidentiality,
and for guaranteeing sanitization. A noninterference property can be stated and
proved for the dependency analysis. We have designed and implemented a
dependency analysis for JavaScript. We formalize this analysis as an
abstraction of a tainting semantics. We prove the correctness of the tainting
semantics, the soundness of the abstraction, a noninterference property, and
the termination of the analysis.


title:
Detection of a large sample of Gamma Dor stars from Kepler space
  photometry and high-resolution ground-based spectroscopy

abstract:
  The space-missions MOST, CoRoT, and Kepler deliver a huge amount of
high-quality photometric data suitable to study numerous pulsating stars.
  Our ultimate goal is a detection and analysis of an extended sample of Gamma
Dor-type pulsating stars with the aim to search for observational evidence of
non-uniform period spacings and rotational splittings of gravity modes in
main-sequence stars typically twice as massive as the Sun.
  We applied an automated supervised photometric classification method to
select a sample of 69 Gamma Doradus candidate stars. We used an advanced method
to extract the Kepler light curves from the pixel data information using custom
masks. For 36 of the stars, we obtained high-resolution spectroscopy with the
HERMES spectrograph installed at the Mercator telescope.
  We find that all stars for which spectroscopic estimates of Teff and logg are
available fall into the region of the HR diagram where the Gamma Dor and Delta
Sct instability strips overlap. The stars cluster in a 700 K window in
effective temperature, logg measurements suggest luminosity class IV-V. From
the Kepler photometry, we identify 45 Gamma Dor-type pulsators, 14 Gamma
Dor/Delta Sct hybrids, and 10 stars which are classified as "possibly Gamma
Dor/Delta Sct hybrid pulsators".
  The results of photometric and spectroscopic classifications according to the
type of variability are in perfect agreement. We find a clear correlation
between the spectroscopically derived vsini and the frequencies of independent
pulsation modes and show that it has nothing to do with rotational modulation
of the stars but is related to their stellar pulsations. Our sample and
frequency determinations offer a good starting point for seismic modelling of
slow to moderately rotating Gamma Dor stars.


title:
Scaling limit of the path leading to the leftmost particle in a
  branching random walk

abstract:
  We consider a discrete-time branching random walk defined on the real line,
which is assumed to be supercritical and in the boundary case. It is known that
its leftmost position of the $n$-th generation behaves asymptotically like
$\frac{3}{2}\ln n$, provided the non-extinction of the system. The main goal of
this paper, is to prove that the path from the root to the leftmost particle,
after a suitable normalizatoin, converges weakly to a Brownian excursion in
$D([0,1],\r)$.


title:
Towards a theory of extremely intermittent pulsars I: Does something
  orbits PSR B1931 + 24 ?

abstract:
  We investigate whether one or many companions are orbiting the extremely
intermittent pulsar PSR B1931+24. We constrained our analysis on previous
observations of eight fundamental properties of PSR B1931+24. The most puzzling
properties are the intermittent nature of the pulsar's activity, with active
and quiet phases that alternate quasi-periodically; the variation of the
slowing-down rate of its period between active and quiet phases; and because
there are no timing residuals, it is highly unlikely that the pulsar has a
massive companion. Here, we examine the effects that one putative companion
immersed in the magnetospheric plasma or the wind of the pulsar might have, as
well as the associated electric current distribution. We analysed several
possibilities for the distance and orbit of this hypothetical companion and the
nature of its interaction with the neutron star. We show that if the
quasi-periodic behaviour of PSR B1931+24 was caused by a companion orbiting the
star with a period of 35 or 70 days, the radio emissions, usually considered to
be those of the pulsar would in that specific case be emitted in the
companion's environment. We analysed four possible configurations and conclude
that none of them would explain the whole set of peculiar properties of PSR
1931+24. We furthermore considered a period 70 days for the precession of the
periastron associated to an orbit very close to the neutron star. This
hypothesis is analysed in a companion paper.


title:
Asymptotic equivalence of jumps L\'evy processes and their discrete
  counterpart

abstract:
  We establish the global asymptotic equivalence between a pure jumps L\'evy
process $\{X_t\}$ on the time interval $[0,T]$ with unknown L\'evy measure
$\nu$ belonging to a non-parametric class and the observation of $2m^2$ Poisson
independent random variables with parameters linked with the L\'evy measure
$\nu$. The equivalence result is asymptotic as $m$ tends to infinity. The time
$T$ is kept fixed and the sample path is continuously observed. This result
justifies the idea that, from a statistical point of view, knowing how many
jumps fall into a grid of intervals gives asymptotically the same amount of
information as observing $\{X_t\}$.


title:
Towards a theory of extremely intermittent pulsars II: Asteroids at a
  close distance

abstract:
  We investigate whether there may be one or many companions orbiting at close
distance to the light cylinder around the extremely intermittent pulsars PSR
B1931+24 and PSR J1841-0500. These pulsars, behaving in a standard way when
they are active, also "switch off" for durations of several days, during which
their magnetospheric activity is interrupted or reduced. We constrained our
analysis on eight fundamental properties of PSR B1931+24 that summarise the
observations. We considered that the disruption/activation of the
magnetospheric activity would be caused by the direct interaction of the star
with the Alfv\'en wings emanating from the companions. We also considered the
recurrence period of 70 days to be the period of precession of the periastron
of the companions orbit. We analysed in which way the time scale of the
"on/off" pseudo-cycle would be conditioned by the precession of the periastron
and not by the orbital time scale, and we derived a set of orbital constraints
that we solved. We then compared the model, based on PSR 1931+24, with the
known properties of PSR 1841+0500. We conclude that PSR B1931+24 may be
surrounded at a close distance to the star by a stream of small bodies of
kilometric or sub-kilometric sizes that could originate from the tidal
disruption of a body of moderate size that fell at a close distance to the
neutron star on an initially very eccentric orbit. This scenario is also
compatible with the properties of PSR J1841-0500, although the properties of
PSR J1841-0500 are, by now, less constrained. These results raise new
questions. Why are the asteroids not yet evaporated ? What kind of interaction
can explain the disruption of the magnetospheric activity ? These questions are
the object of two papers in preparation that will complete the present
analysis.


title: Optical pumping of a lithium atomic beam for atom interferometry

abstract:
  We apply optical pumping to prepare the lithium beam of our atom
interferometer in a single hyperfine-Zeeman sublevel: we use two components of
the D1-line for pumping the 7Li atoms in a dark state F,mF=+2 (or -2) sublevel.
The optical pumping efficiency has been characterized by two techniques:
state-selective laser atom deflection or magnetic dephasing of the atom
interferometer signals. The first technique has not achieved a high
sensitivity, because of a limited signal to noise ratio, but magnetic dephasing
signals have shown that about 95% of the population has been transferred in the
aimed sublevel, with similar results for three mean velocities of the atomic
beam covering the range 744-1520m/s.


title:
Smooth multisoliton solutions and their peakon limit of Novikov's
  Camassa-Holm type equation with cubic nonlinearity

abstract:
  We consider Novikov's Camassa-Holm type equation with cubic nonlinearity. In
particular, we present a compact parametric representation of the smooth bright
multisolution solutions on a constant background and investigate their
structure. We find that the tau-functions associated with the solutions are
closely related to those of a model equation for shallow-water waves (SWW)
introduced by Hirota and Satsuma. This novel feature is established by applying
the reciprocal transformation to the Novikov equation. We also show by
specifying a complex phase parameter that the smooth soliton is converted to a
novel singular soliton with single cusp and double peaks. We demonstrate that
both the smooth and singular solitons converge to a peakon as the background
field tends to zero whereby we employ a method that has been developed for
performing the similar limiting procedure for the multisoliton solutions of the
Camassa-Holm equation. In the subsequent asymptotic analysis of the two- and
$N$-soliton solutions, we confirm their solitonic behaviour. Remarkably, the
formulas for the phase shifts of solitons as well as their peakon limits
coincide formally with those of the Degasperis-Procesi equation. Last, we
derive an infinite number of conservation laws of the Novikov equation by using
a relation between solutions of the Novikov equation and those of the SWW
equation. In appendix, we prove various bilinear identities associated with the
tau-functions of the multisoliton solutions of the SWW equation.


title: The Cramer Varieties Cr(r,r+s,s)

abstract:
  In this paper we study quasi-homogeneous affine algebraic varieties, that is,
varieties obtained as closures of orbits of suitable group representations. We
also discuss one interesting case that has links with the Orthogonal
Grassmannian OGr(5,10). The main aim is to write the tangent bundle and the
canonical class of quasi-homogeneous affine algebraic varieties in terms of
group representations.


title:
Conductance fluctuation and shot noise in disordered graphene systems, a
  perturbation expansion approach

abstract:
  We report the investigation of conductance fluctuation and shot noise in
disordered graphene systems with two kinds of disorder, Anderson type
impurities and random dopants. To avoid the brute-force calculation which is
time consuming and impractical at low doping concentration, we develop an
expansion method based on the coherent potential approximation (CPA) to
calculate the average of four Green's functions and the results are obtained by
truncating the expansion up to 6th order in terms of "single-site-T-matrix".
Since our expansion is with respect to "single-site-T-matrix" instead of
disorder strength $W$, good result can be obtained at 6th order for finite $W$.
We benchmark our results against brute-force method on disordered graphene
systems as well as the two dimensional square lattice model systems for both
Anderson disorder and the random doping. The results show that in the regime
where the disorder strength $W$ is small or the doping concentration is low,
our results agree well with the results obtained from the brute-force method.
Specifically, for the graphene system with Anderson impurities, our results for
conductance fluctuation show good agreement for $W$ up to $0.4t$, where $t$ is
the hopping energy. While for average shot noise, the results are good for $W$
up to $0.2t$. When the graphene system is doped with low concentration 1%, the
conductance fluctuation and shot noise agrees with brute-force results for
large $W$ which is comparable to the hopping energy $t$. At large doping
concentration 10%, good agreement can be reached for conductance fluctuation
and shot noise for $W$ up to $0.4t$. We have also tested our formalism on
square lattice with similar results. Our formalism can be easily combined with
linear muffin-tin orbital first-principles transport calculations for light
doping nano-scaled systems, making prediction on variability of nano-devices.


title:
Thermodynamic Properties of the Anisotropic Frustrated Spin-chain
  Compound Linarite PbCuSO$_4$(OH)$_2$

abstract:
  We present a comprehensive macroscopic thermodynamic study of the
quasi-one-dimensional (1D) $s = \tfrac{1}{2}$ frustrated spin-chain system
linarite. Susceptibility, magnetization, specific heat, magnetocaloric effect,
magnetostriction, and thermal-expansion measurements were performed to
characterize the magnetic phase diagram. In particular, for magnetic fields
along the b axis five different magnetic regions have been detected, some of
them exhibiting short-range-order effects. The experimental magnetic entropy
and magnetization are compared to a theoretical modelling of these quantities
using DMRG and TMRG approaches. Within the framework of a purely 1D isotropic
model Hamiltonian, only a qualitative agreement between theory and the
experimental data can be achieved. Instead, it is demonstrated that a
significant symmetric anisotropic exchange of about 10% is necessary to account
for the basic experimental observations, including the 3D saturation field, and
which in turn might stabilize a triatic (three-magnon) multipolar phase.


title:
Comparison of the atomic level structure of the plastic crystalline and
  the liquid phases of CBr2Cl2: neutron diffraction and Reverse Monte Carlo
  modeling

abstract:
  Neutron diffraction results obtained for plastic crystalline
dichlorodibromomethane (CBr2Cl2) have been modelled by means of the Reverse
Monte Carlo method. Comparison with its liquid phase is provided at several
levels of the atomic structure (total scattering structure factors, partial
radial distribution functions, orientational and dipole-dipole correlations).
Results reveal that the relative orientation of neighbouring molecules largely
depends on the steric effect. The small dipole moment has not as strong
influence as the steric effect on the short range order. Our observations fit
well with earlier findings presented for the series CBrnCl4-n (n=0, 1, 2, 4).


title:
Entropy production and information fluctuations along quantum
  trajectories

abstract:
  Employing the stochastic wave function method, we study quantum features of
stochastic entropy production in nonequilibrium processes of open systems. It
is demonstarted that continuous measurements on the environment introduce an
additional, non-thermal contribution to the entropy flux, which is shown to be
a direct consequence of quantum fluctuations. These features lead to a quantum
definition of single trajectory entropy contributions, which accounts for the
difference between classical and quantum trajectories and results in a quantum
correction to the standard form of the integral fluctuation theorem.


title:
Hydrodynamic theory of coupled current and magnetization dynamics in
  spin-textured antiferromagnets

abstract:
  Antiferromagnets with vanishingly small (or zero) magnetization are
interesting candidates for spintronics applications. In the present paper we
propose two models for description of the current-induced phenomena in
antiferromagnetic textures. We show that the magnetization that originates from
rotation or oscillations of antiferromagnetic vector can, via $sd$-exchange
coupling, polarize the current and give rise to adiabatic and nonadiabatic spin
torques. Due to the Lorentz-type dynamics of antiferromagnetic moments (unlike
the Galilenian-like dynamics in ferromagnets), the adiabatic spin torque
affects the characteristic lengthscale of the moving texture. Nonadiabatic spin
torque contributes to the energy pumping and can induce the stable motion of
antiferromagnetic texture, but, in contrast to ferromagnets, has pure dynamic
origin. We also consider the current-induced phenomena in artificial
antiferromagnets where the current maps the staggered magnetization of the
structure. In this case the effect of nonadiabatic spin torque is similar to
that in ferromagnetic constituents of the structure. In particular, the current
can remove degeneracy of the translational antiferromagnetic domains
indistinguishable in the external magnetic field and thus can set into motion
the 180$^\circ$ domain wall.


title: Random walks maximizing the probability to visit an interval

abstract:
  We consider random walks, say $W_n=(M_0, M_1,\dots, M_n)$, of length $n$
starting at 0 and based on the martingale sequence $M_k$ with differences
$X_m=M_m-M_{m-1}$. Assuming that the differences are bounded, $|X_m|\leq 1$, we
solve the problem \begin{equation} D_n(x)\=\sup P \left\{W_n \ \text{visits an
interval}\ [x,\infty)\right\},\qquad x\in R, \label{piirma} \end{equation}
where $\sup$ is taken over all possible $W_n$. In particular, we describe
random walks which maximize the probability in $\eqref{piirma}$. We also extend
the result to super-martingales.


title: An Adaptive Sequential Monte Carlo Algorithm for Computing Permanents

abstract:
  We consider the computation of the permanent of a binary n by n matrix. It is
well- known that the exact computation is a #P complete problem. A variety of
Markov chain Monte Carlo (MCMC) computational algorithms have been introduced
in the literature whose cost, in order to achieve a given level of accuracy, is
O(n^7 log^4(n)). These algorithms use a particular collection of probability
distributions, the `ideal' of which, (in some sense) are not known and need to
be approximated. In this paper we propose an adaptive sequential Monte Carlo
(SMC) algorithm that can both estimate the permanent and the ideal sequence of
probabilities on the fly, with little user input. We provide theoretical
results associated to the SMC estimate of the permanent, establishing its
convergence and analyzing the relative variance of the estimate, in particular
computating explicit bounds on the relative variance which depend upon n. Using
this latter result, we provide a lower-bound on the computational cost, in
order to achieve an arbitrarily small relative variance; we find that this cost
is O(n^4 log^4(n)). Some numerical simulations are also given.


title: Newton-Cartan Supergravity

abstract:
  We construct a supersymmetric extension of three-dimensional Newton-Cartan
gravity by gauging a super-Bargmann algebra. In order to obtain a non-trivial
supersymmetric extension of the Bargmann algebra one needs at least two
supersymmetries leading to a N=2 super-Bargmann algebra. Due to the fact that
there is a universal Newtonian time, only one of the two supersymmetries can be
gauged. The other supersymmetry is realized as a fermionic Stueckelberg
symmetry and only survives as a global supersymmetry. We explicitly show how,
in the frame of a Galilean observer, the system reduces to a supersymmetric
extension of the Newton potential. The corresponding supersymmetry rules can
only be defined, provided we also introduce a `dual Newton potential'. We
comment on the four-dimensional case.


title: Using GPU Simulation to Accurately Fit to the Power-Law Distribution

abstract:
  This article describes a methodology for fitting experimental data to the
discrete power-law distribution and provides the results of a detailed
simulation exercise used to calculate accurate cutoff values used to assess the
fit to a power-law distribution when using the maximum likelihood estimation
for the exponent of the distribution. Using massively parallel programming
computing, we were able to accelerate by a factor of 60 the computational time
required for these calculations across a range of parameters and construct a
series of detailed tables containing the test values to be used in a
Kolmogorov-Smirnov goodness-of-fit test, allowing for an accurate assessment of
the power-law fit from empirical data.

categories: stat.CO cs.DC physics.comp-ph physics.data-an stat.AP


title: Commutation relations for truncated Toeplitz operators

abstract:
  For truncated Toeplitz operators, which are compressions of multiplication
operators to model subspaces of the Hardy space $H^2$, we obtain criteria for
commutation relations. The results show an analogy to the case of Toeplitz
matrices, and they extend the theory of Sedlock algebras.


title: Holographic entanglement entropy in imbalanced superconductors

abstract:
  We study the behavior of holographic entanglement entropy (HEE) for
imbalanced holographic superconductors. We employ a numerical approach to
consider the robust case of fully back-reacted gravity system. The hairy black
hole solution is found by using our numerical scheme. Then it is used to
compute the HEE for the superconducting case. The cases we study show that in
presence of a mismatch between two chemical potentials, below the critical
temperature, superconducting phase has a lower HEE in comparison to the
AdS-Reissner-Nordstrom black hole phase. Interestingly, the effects of chemical
imbalance are different in the contexts of black hole and superconducting
phases. For black hole, HEE increases with increasing imbalance parameter while
it behaves oppositely for the superconducting phase. The implications of these
results are discussed.


title: Finite Quantum Gravity

abstract:
  We hereby present a class of multidimensional higher derivative theories of
gravity that realizes an ultraviolet completion of Einstein general relativity.
This class is marked by a "non-polynomal" entire function (form factor), which
averts extra degrees of freedom (including ghosts) and improves the high energy
behavior of the loop amplitudes. By power counting arguments, it is proved that
the theory is super-renormalizable in any dimension, i.e. only one-loop
divergences survive. Furthermore, in odd dimensions there are no counter terms
for pure gravity and the theory turns out to be "finite." Finally, considering
the infinite tower of massive states coming from dimensional reduction, quantum
gravity is finite in even dimension as well.


title: Positronium decay in a circular polarized laser field

abstract:
  We calculate the lifetime of both the o-Ps and the p-Ps positronium
annihilation decay $ Ps\to\gamma\gamma$ in the strong circular polarized laser
field. We take a strategy of the factorization to separate the effects caused
by the Coulomb interaction and the strong laser field interaction. It is
factorized in the time direction but not in the space direction. Our results
show that in the laser with long wavelength and high intensity, the lifetimes
of those Ps states are dramatically increased. For $\rm CO_2$ laser with $10\,
\mu m$ wavelength and $10^{13} W/cm^2$ intensity, lifetime of the spin-single
positronium is increased by $10^8$ times. Our result is consistent with those
obtained by solving the Sch{\"{o}}dinger equation. This effect may be useful
for the high harmonic generation(HHG) effects provided with the
Ps\cite{keitel2004}.


title: Contractively included subspaces of Pick spaces

abstract:
  Pick spaces are a class of reproducing kernel Hilbert spaces that generalize
the classical Hardy space and the Drury--Arveson reproducing kernel spaces. We
give characterizations of certain contractively included subspaces of Pick
spaces. These generalize the characterization of closed invariant subspaces of
Trent and McCullough, as well as results for the Drury--Arveson space obtained
by Ball, Bolotnikov and Fang.


title:
Analytical continuum mechanics \`a la Hamilton-Piola: least action
  principle for second gradient continua and capillary fluids

abstract:
  In this paper a stationary action principle is proven to hold for capillary
fluids, i.e. fluids for which the deformation energy has the form suggested,
starting from molecular arguments, for instance by Cahn and Hilliard. Remark
that these fluids are sometimes also called Korteweg-de Vries or Cahn-Allen. In
general continua whose deformation energy depend on the second gradient of
placement are called second gradient (or Piola-Toupin or Mindlin or
Green-Rivlin or Germain or second gradient) continua. In the present paper, a
material description for second gradient continua is formulated. A Lagrangian
action is introduced in both material and spatial description and the
corresponding Euler-Lagrange bulk and boundary conditions are found. These
conditions are formulated in terms of an objective deformation energy volume
density in two cases: when this energy is assumed to depend on either C and
grad C or on C^-1 and grad C^-1 ; where C is the Cauchy-Green deformation
tensor. When particularized to energies which characterize fluid materials, the
capillary fluid evolution conditions (see e.g. Casal or Seppecher for an
alternative deduction based on thermodynamic arguments) are recovered. A
version of Bernoulli law valid for capillary fluids is found and, in the
Appendix B, useful kinematic formulas for the present variational formulation
are proposed. Historical comments about Gabrio Piola's contribution to
continuum analytical mechanics are also presented. In this context the reader
is also referred to Capecchi and Ruta.


title: On the Concept of Variable Roles and its Use in Software Analysis

abstract:
  Human written source code in imperative programming languages exhibits
typical patterns for variable use such as flags, loop iterators, counters,
indices, bitvectors etc. Although it is widely understood by practitioners that
these variable roles are important for automated software analysis tools, they
are not systematically studied by the formal methods community, and not well
documented in the research literature. In this paper, we study the notion of
variable roles on the example of basic types (int, float, char) in C. We
propose a classification of the variables in a program by variable roles, and
demonstrate that classical data flow analysis lends itself naturally both as a
specification formalism and an analysis paradigm for this classification
problem. We demonstrate the practical applicability of our method by predicting
membership of source files to the different categories of the software
verification competition SVCOMP 2013.


title: Asymptotic properties of Arnold tongues and Josephson effect

abstract:
  A three-parametrical family of ODEs on a torus arises from a model of
Josephson effect in a resistive case when a Josephson junction is biased by a
sinusoidal microwave current. We study asymptotics of Arnold tongues of this
family on the parametric plane (the third parameter is fixed) and prove that
the boundaries of the tongues are asymptotically close to Bessel functions.


title: Weak and strong solutions of general stochastic models

abstract:
  Typically, a stochastic model relates stochastic "inputs" and, perhaps,
controls to stochastic "outputs". A general version of the Yamada-Watanabe and
Engelbert theorems relating existence and uniqueness of weak and strong
solutions of stochastic equations is given in this context. A notion of {\em
compatibility} between inputs and outputs is critical in relating the general
result to its classical forebears. The relationship between the compatibility
condition and the usual formulation of stochastic differential equations driven
by semimartingales is discussed.


title: The Haagerup property is stable under graph products

abstract:
  The Haagerup property, which is a strong converse of Kazhdan's property
$(T)$, has translations and applications in various fields of mathematics such
as representation theory, harmonic analysis, operator K-theory and so on.
Moreover, this group property implies the Baum-Connes conjecture and related
Novikov conjecture. The Haagerup property is not preserved under arbitrary
group extensions and amalgamated free products over infinite groups, but it is
preserved under wreath products and amalgamated free products over finite
groups. In this paper, we show that it is also preserved under graph products.
We moreover give bounds on the equivariant and non-equivariant
$L_p$-compressions of a graph product in terms of the corresponding
compressions of the vertex groups. Finally, we give an upper bound on the
asymptotic dimension in terms of the asymptotic dimensions of the vertex
groups. This generalizes a result from Dranishnikov on the asymptotic dimension
of right-angled Coxeter groups.


title: Creation of excitations from a uniform impurity motion in the condensate

abstract:
  We investigate a phenomenon of creation of excitations in the homogenous
Bose-Einstein condensate due to an impurity moving with a constant velocity. A
simple model is considered to take into account dynamical effects due to
motions of the impurity. Based on this model, we show that there can be a
finite amount of excitations created even if velocity of the impurity is below
Landau's critical velocity. We also show that the total number of excitations
scales differently for large time across the speed of sound. Thus, our result
dictates the critical behavior across Landau's one and validates Landau's
institution to the problem. We discuss how Landau's critical velocity emerges
and its validity within our model.


title: Equilateral sets in uniformly smooth Banach spaces

abstract:
  Let $X$ be an infinite dimensional uniformly smooth Banach space. We prove
that $X$ contains an infinite equilateral set. That is, there exists a constant
$\lambda>0$ and an infinite sequence $(x_i)_{i=1}^\infty\subset X$ such that
$\|x_i-x_j\|=\lambda$ for all $i\neq j$.


title:
Hamiltonian Analysis of Minimal Massive Gravity Coupled to Galileon
  Tadpole Term

abstract:
  We perform the Hamiltonian analysis of minimal massive gravity coupled to the
Galileon tadpole term. We determine all constraints and we argue that the
physical degrees of freedom correspond to ten modes of the massive gravity
together with 2(D-3) Galileons so that given model is ghost free.


title:
The problem of small angular scale structure in the cosmic ray
  anisotropy data

abstract:
  Recent observations have revealed structure on small angular scales in the
anisotropy data of cosmic rays at multi TeV energies. Even though the absolute
amplitudes are very small, these effects are somewhat surprising and a wide
range of possible causes have been discussed. A possible origin associated with
heliospheric electric fields is proposed.


title:
Majority-vote model on (3,12^2), (4,6,12) and (4,8^2) Archimedean
  lattices

abstract:
  On ($3,12^2$), ($4,6,12$) and ($4,8^2$) Archimedean lattices, the critical
properties of majority-vote model are considered and studied using the Glauber
transition rate proposed by Kwak {\it et all.} [Phys. Rev. E, {\bf 75}, 061110
(2007)] rather than the traditional majority-vote with noise [Jos\'e M\'ario de
Oliveira, J. Stat. Phys. {\bf 66}, 273 (1992)]. The critical temperature and
the critical exponents for this transition rate are obtained from extensive
Monte Carlo simulations and with a finite size scaling analysis. The calculated
values of the critical temperatures Binder cumulant are $T_c=0.363(2)$ and
$U_4^*=0.577(4)$; $T_c=0.651(3)$ and $U_4^*=0.612(5)$; and $T_c=0.667(2)$ and
$U_4^*=0.613(5)$ for ($3,12^2$), ($4,6,12$) and ($4,8^2$) lattices,
respectively. The critical exponents $\beta/\nu$, $\gamma/\nu$ and $1/\nu$ for
this model are $0.237(6)$, $0.73(10)$, and $ 0.83(5)$; $0.105(8)$, $1.28(11)$,
and $1.16(5)$; $0.113(2)$, $1.60(4)$, and $0.84(6)$ for ($3,12^2$), ($4,6,12$)
and ($4,8^2$) lattices, respectively. These results differ from the usual Ising
model results and the majority-vote model on so-far studied regular lattices or
complex networks.


title:
Structure, dynamics and bifurcations of discrete solitons in trapped ion
  crystals

abstract:
  We study discrete solitons (kinks) accessible in state-of-the-art trapped ion
experiments, considering zigzag crystals and quasi-3D configurations, both
theoretically and experimentally. We first extend the theoretical understanding
of different phenomena predicted and recently experimentally observed in the
structure and dynamics of these topological excitations. Employing tools from
topological degree theory, we analyze bifurcations of crystal configurations in
dependence on the trapping parameters, and investigate the formation of kink
configurations and the transformations of kinks between different structures.
This allows us to accurately define and calculate the effective potential
experienced by solitons within the Wigner crystal, and study how this
(so-called Peierls-Nabarro) potential gets modified to a nonperiodic globally
trapping potential in certain parameter regimes. The kinks' rest mass (energy)
and spectrum of modes are computed and the dynamics of linear and nonlinear
kink oscillations are analyzed. We also present novel, experimentally observed,
configurations of kinks incorporating a large-mass defect realized by an
embedded molecular ion, and of pairs of interacting kinks stable for long
times, offering the perspective for exploring and exploiting complex collective
nonlinear excitations, controllable on the quantum level.


title: Josephson effect and slow-fast systems

abstract:
  In order to model the processes taking place in systems with Josephson
contacts, a differential equation on a torus with three parameters is used. One
of the parameters of the system can be considered small and the methods of the
fast--slow systems theory can be applied. The properties of the phase--lock
areas -- the subsets in the parameter space, in which the changing of a current
doesn't affect the voltage -- are important in practical applications. The
phase-lock areas coincide with the Arnold tongues of a Poincare map along the
period. A description of the limit properties of Arnold tongues is given. It is
shown that the parameter space is split into certain areas, where the tongues
have different geometrical structures due to fast--slow effects. An efficient
algorithm for the calculation of tongue borders is elaborated. The statement
concerning the asymptotic approximation of borders by Bessel functions is
proven.


title: Moduli Spaces of Planar Pentagonal Linkages: Combinatorial Description

abstract:
  Moduli spaces of planar polygonal linkages admit a cell structure which can
be realized as a surgery on the permutohedron. We present a 3D visualization of
the result of the surgery for all types of non-degenerate pentagonal linkages.


title: Auto-similarity in rational base number systems

abstract:
  This work is a contribution to the study of set of the representations of
integers in a rational base number system. This prefix-closed subset of the
free monoid is naturally represented as a highly non regular tree whose nodes
are the integers and whose subtrees are all distinct. With every node of that
tree is then associated a minimal infinite word. The main result is that a
sequential transducer which computes for all n the minimal word associated with
n+1 from the one associated with n, has essentially the same underlying graph
as the tree itself. These infinite words are then interpreted as
representations of real numbers; the difference between the numbers represented
by these two consecutive minimal words is the called the span of a node of the
tree. The preceding construction allows to characterise the topological closure
of the set of spans.


title: Multipath Metropolis Simulation of Classical Heisenberg Model

abstract:
  Processor cores are becoming less expensive and thus more accessible. To
utilize increasing number of available computing elements, good parallel
algorithms are necessary. In light of these changes in contemporary computing,
multipath Metropolis simulation of classical Heisenberg model is explored. In
contrast to the original single-path algorithm, multipath simulation approach
is inherently parallel because different random-walk paths are mutually
independent. This independence enables easy and efficient harnessing of
numerous cores' computing power in embarrassingly parallel algorithms. Aside
form being inherently parallel, multipath simulation approach results in
independent and normally distributed simulation output. Normal distribution
enables simple and straightforward statistical processing. Thus, multipath
simulation results can be easily computed with arbitrary and statistically
known precision.


title: Advanced Methods in Black-Hole Perturbation Theory

abstract:
  Black-hole perturbation theory is a useful tool to investigate issues in
astrophysics, high-energy physics, and fundamental problems in gravity. It is
often complementary to fully-fledged nonlinear evolutions and instrumental to
interpret some results of numerical simulations. Several modern applications
require advanced tools to investigate the linear dynamics of generic small
perturbations around stationary black holes. Here, we present an overview of
these applications and introduce extensions of the standard semianalytical
methods to construct and solve the linearized field equations in curved
spacetime. Current state-of-the-art techniques are pedagogically explained and
exciting open problems are presented.


title:
SOAPdenovo-Trans: De novo transcriptome assembly with short RNA-Seq
  reads

abstract:
  Motivation: Transcriptome sequencing has long been the favored method for
quickly and inexpensively obtaining the sequences for a large number of genes
from an organism with no reference genome. With the rapidly increasing
throughputs and decreasing costs of next generation sequencing, RNA-Seq has
gained in popularity; but given the typically short reads (e.g. 2 x 90 bp
paired ends) of this technol- ogy, de novo assembly to recover complete or
full-length transcript sequences remains an algorithmic challenge. Results: We
present SOAPdenovo-Trans, a de novo transcriptome assembler designed
specifically for RNA-Seq. Its performance was evaluated on transcriptome
datasets from rice and mouse. Using the known transcripts from these
well-annotated genomes (sequenced a decade ago) as our benchmark, we assessed
how SOAPdenovo- Trans and two other popular software handle the practical
issues of alternative splicing and variable expression levels. Our conclusion
is that SOAPdenovo-Trans provides higher contiguity, lower redundancy, and
faster execution. Availability and Implementation: Source code and user manual
are at http://sourceforge.net/projects/soapdenovotrans/ Contact:
xieyl@genomics.cn or bgi-soap@googlegroups.com


title:
Theoretical assessment on the possibility of constraining point defect
  energetics by pseudo-phase transition pressures

abstract:
  Making use of the energetics and equations of state of defective uranium
dioxide that calculated with first-principles method, we demonstrate a
possibility of constraining the formation energy of point defects by measuring
the transition pressures of the corresponding pseudo-phase of defects. The
mechanically stable range of fluorite structure of UO2, which dictates the
maximum possible pressure of relevant pseudo-phase transitions, gives rise to
defect formation energies that span a wide band and overlap with the existing
experimental estimates. We reveal that the knowledge about pseudo-phase
boundaries can not only provide important information of energetics that is
helpful for reducing the scattering in current estimates, but also be valuable
for guiding theoretical assessments, even to validate or disprove a theory. In
order to take defect interactions into account and to extrapolate the physical
quantities at finite stoichiometry deviations to that near the stoichiometry,
we develop a general formalism to describe the thermodynamics of a defective
system. We also show that it is possible to include interactions among defects
in a simple expression of point defect model (PDM) by introducing an auxiliary
constant mean-field. This generalization of the simple PDM leads to great
versatility that allows one to study nonlinear effects of stoichiometry
deviation on materials' behavior. It is a powerful tool to extract the defect
energetics from finite defect concentrations to the dilute limit. Besides
these, the full content of the theoretical formalism and some relevant and
interesting issues, including reentrant pseudo-transition, multi-defect
coexistence, charged defects, and possible consequence of instantaneous
defective response in a quantum crystal, are explored and discussed.

categories: cond-mat.mtrl-sci cond-mat.dis-nn cond-mat.stat-mech physics.comp-ph quant-ph


title: Hedging without sweat: a genetic programming approach

abstract:
  Hedging in the presence of transaction costs leads to complex optimization
problems. These problems typically lack closed-form solutions, and their
implementation relies on numerical methods that provide hedging strategies for
specific parameter values. In this paper we use a genetic programming algorithm
to derive explicit formulas for near-optimal hedging strategies under nonlinear
transaction costs. The strategies are valid over a large range of parameter
values and require no information about the structure of the optimal hedging
strategy.


title: Homogenization of the nonlinear bending theory for plates

abstract:
  We carry out the spatially periodic homogenization of nonlinear bending
theory for plates. The derivation is rigorous in the sense of
Gamma-convergence. In contrast to what one naturally would expect, our result
shows that the limiting functional is not simply a quadratic functional of the
second fundamental form of the deformed plate as it is the case in nonlinear
plate theory. It turns out that the limiting functional discriminates between
whether the deformed plate is locally shaped like a "cylinder" or not. For the
derivation we investigate the oscillatory behavior of sequences of second
fundamental forms associated with isometric immersions, using two-scale
convergence. This is a non-trivial task, since one has to treat two-scale
convergence in connection with a nonlinear differential constraint.


title: Light scattering from coupled plasmonic nanospheres on a substrate

abstract:
  An efficient numerical method based on half-space Green function and
spherical harmonics expansion is used to study the light scattering from
coupled multiple nanospheres on a substrate. The ellipsometric spectra for
various geometries of coupled Au nanospheres are calculated and analyzed to
realize the effects of plasmonic coupling of closely-spaced nanospheres. With
only a few parameters to describe the distribution of various coupled
nanosphere clusters embedded in a random distribution of nanospheres, the
calculated ellipsometric spectra can fit the experimental data very well. This
illustrates that our realistic model calculations can be used for determination
of the distribution of nanospheres on a substrate or embedded in multilayer
structures such as biological samples.


title:
Marginal density expansions for diffusions and stochastic volatility,
  part II: Applications [to the Stein--Stein model]

abstract:
  In the compagnion paper [Marginal density expansions for diffusions and
stochastic volatility, part I] we discussed density expansions for
multidimensional diffusions $(X^1,...,X^d)$, at fixed time $T$ and projected to
their first $l$ coordinates, in the small noise regime. Global conditions were
found which replace the well-known "not-in-cutlocus" condition known from
heat-kernel asymptotics. In the present paper we discuss financial
applications; these include tail and implied volatility asymptotics in some
correlated stochastic volatility models. In particular, we solve a problem left
open by A. Gulisashvili and E.M. Stein (2009).


title: In Search of H-theorem for Ulam's Redistribution Problem

abstract:
  We discuss the possibility of deriving an H-theorem for the nonlinear
discrete time evolution known as Ulam's redistribution of energy problem. In
this model particles are paired at random and then their total energy is
redistributed between them according to some probability law. It appears
possible to obtain the proper H-function which always increases during the
relaxation only for a special set of redistribution laws, given by symmetric
beta distributions. This H-function differs from the usual entropy by an
additional term that vanishes only for the uniform redistribution law. But for
arbitrary redistribution the evolution has some features of relaxation to a
non-equilibrium steady state and the H-function is still unknown.


title: Note on generalized gravitational entropy in Lovelock gravity

abstract:
  The recently proposed gravitational entropy generalize the usual black hole
entropy to Euclidean solutions without U(1) symmetry in the framework of
Einstein gravity. The entropy of such smooth configuration is given by the area
of minimal surface, therefore explaining the Ryu-Takayanagi formula of
holographic entanglement entropy. In this note we investigate the generalized
gravitational entropy for general Lovelock gravity in arbitrary dimensions. We
use the replica trick and consider the Euclidean bulk spacetime with conical
singularity localized at a codimension two surface. We obtain a constraint
equation for the surface by requiring the bulk equation of motion to be of good
behavior. When the bulk spacetime is maximally symmetric, the constraints show
that the traces of the extrinsic curvatures of the surface are vanishing, i.e.
the surface has to be geometrically a minimal surface. However the constraint
equation cannot be obtained by the variation of the known functional for
holographic entanglement entropy in Lovelock gravity.


title: Dynamical analysis of the Gliese-876 Laplace resonance

abstract:
  The existence of multiple planetary systems involved in mean motion
conmensurabilities has increased significantly since the Kepler mission.
Although most correspond to 2-planet resonances, multiple resonances have also
been found. The Laplace resonance is a particular case of a three-body
resonance where the period ratio between consecutive pairs is n_1/n_2 near to
n_2/n_3 near to 2/1. It is not clear how this triple resonance can act in order
to stabilize (or not) the systems.
  The most reliable extrasolar system located in a Laplace resonance is GJ876
because it has two independent confirmations. However best-fit parameters were
obtained without previous knowledge of resonance structure and no exploration
of all the possible stable solutions for the system where done.
  In the present work we explored the different configurations allowed by the
Laplace resonance in the GJ876 system by varying the planetary parameters of
the third outer planet. We find that in this case the Laplace resonance is a
stabilization mechanism in itself, defined by a tiny island of regular motion
surrounded by (unstable) highly chaotic orbits. Low eccentric orbits and mutual
inclinations from -20 to 20 degrees are compatible with the observations. A
definite range of mass ratio must be assumed to maintain orbital stability.
Finally we give constrains for argument of pericenters and mean anomalies in
order to assure stability for this kind of systems.


title:
Optimising the use of detector arrays for measuring intensity
  correlations of photon pairs

abstract:
  Intensity correlation measurements form the basis of many experiments based
on spontaneous parametric down-conversion. In the most common situation, two
single-photon avalanche diodes and coincidence electronics are used in the
detection of the photon pairs, and the coincidence count distributions are
measured by making use of some scanning procedure. Here we analyse the
measurement of intensity correlations using multi-element detector arrays. By
considering the detector parameters such as the detection and noise
probabilities, we found that the mean number of detected photons that maximises
the visibility of the two photon correlations is approximately equal to the
mean number of noise events in the detector array. We provide expressions
predicting the strength of the measured intensity correlations as a function of
the detector parameters and on the mean number of detected photons. We
experimentally test our predictions by measuring far-field intensity
correlations of spontaneous parametric down-conversion with an electron
multiplying CCD camera, finding excellent agreement with the theoretical
analysis.


title:
Structure of neutron, quark and exotic stars in Eddington-inspired
  Born-Infeld gravity

abstract:
  We consider the structure and physical properties of specific classes of
neutron, quark and "exoti"' stars in Eddington-inspired Born-Infeld (EiBI)
gravity. The latter reduces to standard general relativity in vacuum, but
presents a different behavior of the gravitational field in the presence of
matter. The equilibrium equations for a spherically symmetric configuration
(mass continuity and Tolman-Oppenheimer-Volkoff) are derived, and their
solutions are obtained numerically for different equations of state of neutron
and quark matter. More specifically, stellar models, described by the stiff
fluid, radiation-like, polytropic and the bag model quark equations of state
are explicitly constructed in both general relativity and EiBI gravity, thus
allowing a comparison between the predictions of these two gravitational
models. As a general result it turns out that for all the considered equations
of state, EiBI gravity stars are more massive than their general relativistic
counterparts. Furthermore, an exact solution of the spherically symmetric field
equations in EiBI gravity, describing an "exotic" star, with decreasing
pressure but increasing energy density, is also obtained. As a possible
astrophysical application of the obtained results we suggest that stellar mass
black holes, with masses in the range of $3.8M_{\odot}$ and $6M_{\odot}$,
respectively, could be in fact EiBI neutron or quark stars.


title:
Decomposing the dynamics of heterogeneous delayed networks with
  applications to connected vehicle systems

abstract:
  Delay-coupled networks are investigated with nonidentical delay times and the
effects of such heterogeneity on the emergent dynamics of complex systems are
characterized. A simple decomposition method is presented that decouples the
dynamics of the network into node-size modal equations in the vicinity of
equilibria. The resulting independent components contain distributed delays
that map the spatiotemporal complexity of the system to the time domain. We
demonstrate that this new approach can be used to reveal new physical phenomena
in heterogenous vehicular traffic when vehicles are linked via
vehicle-to-vehicle (V2V) communication.


title: Quarks and leptons which might be composite

abstract:
  An option of composite quarks and leptons is briefly outlined, where
elementary color-triplet quark-like fermions are bound with an elementary
color-triplet isoscalar scalar boson due to the color coupling 3* x 3* -> 3 and
3* x 3 -> 1, respectively.


title: Dynamics of topological defects in ion Coulomb crystals

abstract:
  We study experimentally and theoretically the properties of structural
defects (kink solitons) in two-dimensional ion Coulomb crystals. We show how
different types of kink solitons with different physical properties can be
realized, and transformed from one type into another by varying the aspect
ratio of the trap confinement. Further, we discuss how impurities in ion
Coulomb crystals, such as mass defects, can modify the dynamics of kink
creation and their stability. For both pure and impure crystals, the
experimentally observed kink dynamics are analyzed in detail and explained
theoretically by numerical simulations and calculations of the Peierls-Nabarro
potential. Finally, we show that static electric fields provide a handle to
vary the influence of mass defects on kinks in a controlled way and allow for
deterministic manipulation and creation of kinks.


title: Neutrino mixing with revamped A4 flavour symmetry

abstract:
  We suggest a minimal extension of the simplest A4 flavour model that can
induce a nonzero theta13 value, as required by recent neutrino oscillation data
from reactors and accelerators. The predicted correlation between the
atmospheric mixing angle theta23 and the magnitude of theta13 leads to an
allowed region substantially smaller than indicated by neutrino oscillation
global fits. Moreover, the scheme correlates CP violation in neutrino
oscillations with the octant of the atmospheric mixing parameter theta23 in
such a way that, for example, maximal mixing necessarily violates CP. We
briefly comment on other phenomenological features of the model.


title:
Hard X-ray optics simulation using the coherent mode decomposition of
  Gaussian Schell model

abstract:
  The propagation of hard X ray beam from partially coherent synchrotron source
is simulated by using the novel method based on the coherent mode decomposition
of Gaussian Schell model and wave front propagation. We investigate how the
coherency properties and intensity distributions of the beam are changed by
propagation through optical elements. Here, we simulate and analyze the
propagation of the partially coherent radiation transmitted through an ideal
slit. We present the first simulations for focusing partially coherent
synchrotron hard X ray beams using this novel method. And when compared with
the traditional method which assumes the source is a totally coherent point
source or completely incoherent, this method is proved to be more reasonable
and can also demonstrate the coherence properties of the focusing beam. We also
simulate the double slit experiment and the simulated results validate the
academic analysis.


title:
Differential Photoproduction Cross Sections of the Sigma0(1385),
  Lambda(1405), and Lambda(1520)

abstract:
  We report the exclusive photoproduction cross sections for the Sigma(1385),
Lambda(1405), and Lambda(1520) in the reactions gamma + p -> K+ + Y* using the
CLAS detector for energies from near the respective production thresholds up to
a center-of-mass energy W of 2.85 GeV. The differential cross sections are
integrated to give the total exclusive cross sections for each hyperon.
Comparisons are made to current theoretical models based on the effective
Lagrangian approach and fitted to previous data. The accuracy of these models
is seen to vary widely. The cross sections for the Lambda(1405) region are
strikingly different for the Sigma+pi-, Sigma0 pi0, and Sigma- pi+ decay
channels, indicating the effect of isospin interference, especially at W values
close to the threshold.


title:
Existence of positive solutions for nonlinear Kirchhoff type problems in
  R^3 with critical Sobolev exponent and sign-changing nonlinearities

abstract:
  In this paper, we study the following nonlinear problem of Kirchhoff type
with critical Sobolev exponent: -\left(a+b\ds\int_{\R^3}|D u|^2\right)\Delta
u+u=f(x,u)+u^{5}, u\in H^1(\R^3), u>0, $x\in \R^3$ where a,b>0 are constants.
Under certain assumptions on the sign-changing function $f(x,u)$, we prove the
existence of positive solutions by variational methods. Our main results can be
viewed as a partial extension of a recent result of He and Zou in [17]
concerning the existence of positive solutions to the nonlinear Kirchhoff
problem \left(\varepsilon^2a+\varepsilon b\ds\int_{\R^3}|D u|^2\right)\Delta
u+V(x)u=f(u), u\in H^1(\R^3), u>0, $x\in \R^3$, where $\varepsilon>0$ is a
parameter, $V(x)$ is a positive continuous potential and $f(u)\thicksim
|u|^{p-2}u$ with $4<p<6$ and satisfies the Ambrosetti-Rabinowitz type
condition.


title: Algebraic differential equations associated to some polynomials

abstract:
  We compute the Gauss-Manin differential equation for any period of a
polynomial in \ $\C[x_{0},\dots, x_{n}]$ \ with \ $(n+2)$ \ monomials. We give
two general factorizations theorem in the algebra \ $\C< z,
(\frac{\partial}{\partial z})^{-1}>$ \ for such a differential equations.


title: Introduction to the STANDARD MODEL of the Electro-Weak Interactions

abstract:
  These are the notes of a set of four lectures which I gave at the 2012 CERN
Summer School of Particle Physics. They cover the basic ideas of gauge
symmetries and the phenomenon of spontaneous symmetry breaking which are used
in the construction of the Standard Model of the Electro-Weak Interactions.


title: Three Dimensional Dirac Semimetal and Quantum Transports in Cd3As2

abstract:
  Based on the first-principles calculations, we recover the silent topological
nature of Cd3As2, a well known semiconductor with high carrier mobility. We
find that it is a symmetry-protected topological semimetal with a single pair
of three-dimensional (3D) Dirac points in the bulk and non-trivial Fermi arcs
on the surfaces. It can be driven into a topological insulator and a Weyl
semi-metal state by symmetry breaking, or into a quantum spin Hall insulator
with gap more than 100meV by reducing dimensionality. We propose that the 3D
Dirac cones in the bulk of Cd3As2 can support sizable linear quantum
magnetoresistance even up to room temperature.


title: Generators for abelian extensions of number fields

abstract:
  Let $U/L$ be a finite abelian extension of number fields. We first construct
a universal primitive generator of $U$ over $L$ whose relative trace to any
intermediate field $F$ becomes a generator of $F$ over $L$, too. We also
develop a similar argument in terms of norm. As its examples we investigate
towers of ray class fields over imaginary quadratic fields. And, we further
present a new method of finding a normal element for the extension $U/L$.


title: Analytical eigenstates for the quantum Rabi model

abstract:
  We develop a method to find analytical solutions for the eigenstates of the
quantum Rabi model. These include symmetric, anti-symmetric and asymmetric
analytic solutions given in terms of the confluent Heun functions. Both regular
and exceptional solutions are given in a unified form. In addition, the
analytic conditions for determining the energy spectrum are obtained. Our
results show that conditions proposed by Braak [Phys. Rev. Lett. \textbf{107},
100401 (2011)] are a type of sufficiency condition for determining the regular
solutions. The well-known Judd isolated exact solutions appear naturally as
truncations of the confluent Heun functions.


title:
Low-Rate Machine-Type Communication via Wireless Device-to-Device (D2D)
  Links

abstract:
  Wireless cellular networks feature two emerging technological trends. The
first is the direct Device-to-Device (D2D) communications, which enables direct
links between the wireless devices that reutilize the cellular spectrum and
radio interface. The second is that of Machine-Type Communications (MTC), where
the objective is to attach a large number of low-rate low-power devices, termed
Machine-Type Devices (MTDs) to the cellular network. MTDs pose new challenges
to the cellular network, one if which is that the low transmission power can
lead to outage problems for the cell-edge devices. Another issue imminent to
MTC is the \emph{massive access} that can lead to overload of the radio
interface. In this paper we explore the opportunity opened by D2D links for
supporting MTDs, since it can be desirable to carry the MTC traffic not through
direct links to a Base Station, but through a nearby relay. MTC is modeled as a
fixed-rate traffic with an outage requirement. We propose two network-assisted
D2D schemes that enable the cooperation between MTDs and standard cellular
devices, thereby meeting the MTC outage requirements while maximizing the rate
of the broadband services for the other devices. The proposed schemes apply the
principles Opportunistic Interference Cancellation and the Cognitive Radio's
underlaying. We show through analysis and numerical results the gains of the
proposed schemes.


title: Ramanujan graphings and correlation decay in local algorithms

abstract:
  Let $G$ be a large-girth $d$-regular graph and $\mu$ be a random process on
the vertices of $G$ produced by a randomized local algorithm. We prove the
upper bound $(k+1-2k/d)\Bigl(\frac{1}{\sqrt{d-1}}\Bigr)^k$ for the (absolute
value of the) correlation of values on pairs of vertices of distance $k$ and
show that this bound is optimal. The same results hold automatically for factor
of i.i.d processes on the $d$-regular tree. In that case we give an explicit
description for the (closure) of all possible correlation sequences. Our proof
is based on the fact that the Bernoulli graphing of the infinite $d$-regular
tree has spectral radius $2\sqrt{d-1}$. Graphings with this spectral gap are
infinite analogues of finite Ramanujan graphs and they are interesting on their
own right.


title:
On Timing and Spectral Characteristics of the X-ray Pulsar 4U 0115+63:
  Evolution of the Pulsation Period and the Cyclotron Line Energy

abstract:
  An overview of the results of observations for the transient X-ray pulsar 4U
0115+63, a member of a binary system with a Be star, since its discovery to the
present day (~40 years) based on data from more than dozen observatories and
instruments is presented. A overall light curve and the history of change in
the spin frequency of the neutron star over the entire history of its
observations, which also includes the results of recent measurements made by
the INTEGRAL observatory during the 2004, 2008, and 2011 outbursts, are
provided. The source's energy spectra have also been constructed from the
INTEGRAL data obtained during the 2011 outburst for a dynamic range of its
luminosities (~10^{37} - 7 x 10^{37} erg/s). We show that apart from the
fundamental harmonic of the cyclotron absorption line at energy ~11 keV, its
four higher harmonics at energies ~24, 35.6, 48.8, and 60.7 keV are detected in
the spectrum. We have performed a detailed analysis of the source's spectra in
the 4-28 keV energy band based on all of the available RXTE archival data
obtained during bright outbursts in 1995-2011. We have confirmed that modifying
the source's continuum model can lead to the disappearance of the observed
anticorrelation between the energy of the fundamental harmonic of the cyclotron
absorption line and the source's luminosity. Thus, the question about the
evolution of the cyclotron absorption line energy with the luminosity of the
X-ray pulsar 4U 0115+63 remains open and a physically justified radiation model
for X-ray pulsars is needed to answer it.


title:
Kinetic simulation of the sheath dynamics in the intermediate
  radio-frequency regime

abstract:
  The dynamics of temporally modulated plasma boundary sheaths is studied in
the intermediate radio frequency regime where the applied radio frequency and
the ion plasma frequency are comparable. Two kinetic simulation codes are
employed and their results are compared. The first code is a realization of the
well-known scheme, Particle-In-Cell with Monte Carlo collisions (PIC/MCC) and
simulates the entire discharge, a planar radio frequency capacitively coupled
plasma (RF-CCP) with an additional heating source. The second code is based on
the recently published scheme Ensemble-in-Spacetime (EST); it resolves only the
sheath and requires the time resolved voltage across and the ion flux into the
sheath as input. Ion inertia causes a temporal asymmetry (hysteresis) of the
sheath charge-voltage relation; also other ion transit time effects are found.
The two codes are in good agreement, both with respect to the spatial and
temporal dynamics of the sheath and with respect to the ion energy
distributions at the electrodes. It is concluded that the EST scheme may serve
as an efficient post-processor for fluid or global simulations and for
measurements: It can rapidly and accurately calculate ion distribution
functions even when no genuine kinetic information is available.


title: Compact narrow-band THz radiation source based on photocathode rf gun

abstract:
  Narrow-band THz coherent Cherenkov radiation can be driven by a subpicosecond
electron bunch traveling along the axis of a hollow cylindrical
dielectric-lined waveguide. We present a scheme of compact THz radiation source
based on the photocathode rf gun. On the basis of our analytic result, the
subpicosecond electron bunch with high charge (800pC) can be generated directly
in the photocathode rf gun. A narrow emission spectrum peaked at 0.24 THz with
2 megawatt (MW) peak power is expected to gain in the proposed scheme (the
length of the facility is about 1.2 m), according to the analytical and
simulated results.


title: Discrete gauge symmetries from (closed string) tachyon condensation

abstract:
  The study of discrete gauge symmetries in field theory and string theory is
often carried out by embedding them into continuous symmetries. Many symmetries
however do not seem to admit such embedding, for instance discrete isometries
given by large diffeomorphisms in compactifications. We show that in the
context of string theory even those symmetries can be embedded into continuous
ones. This requires extending the system to a supercritical string theory
configuration with extra dimensions, on which the continuous symmetry acts. The
extra dimensions are subsequently removed by closed string tachyon
condensation, which breaks the continuous symmetry but preserves a discrete
subgroup. The construction is explicit and the tachyon condensation can even be
followed quantitatively for lightlike tachyon profiles. The embedding of
discrete into continuous symmetries allows a realization of charged topological
defects as closed string tachyon solitons, in tantalizing reminiscence of the
construction of D-branes as open tachyon solitons.


title: Second-Order Coding Rates for Channels with State

abstract:
  We study the performance limits of state-dependent discrete memoryless
channels with a discrete state available at both the encoder and the decoder.
We establish the epsilon-capacity as well as necessary and sufficient
conditions for the strong converse property for such channels when the sequence
of channel states is not necessarily stationary, memoryless or ergodic. We then
seek a finer characterization of these capacities in terms of second-order
coding rates. The general results are supplemented by several examples
including i.i.d. and Markov states and mixed channels.


title: Fibonacci sequence related to a combinatorial problem on binary matrices

abstract:
  We discuss an equivalence relation on the set of square binary matrices with
the same number of 1's in each row and each column. Each binary matrix is
represented using ordered n-tuples of natural numbers. We give a few starting
values of integer sequences related to the discussed problem. The obtained
sequences are new and they are not described in the On-Line Encyclopedia of
Integer Sequences (OEIS). We show a relationship between some particular values
of the parameters and the Fibonacci sequence.


title:
Existence of positive ground state solutions for the nonlinear Kirchhoff
  type equations in $R^3$

abstract:
  In this paper, we study the following nonlinear problem of Kirchhoff type
with pure power nonlinearities: (a+b\ds\int_{\R^3}|D u|^2\right)\Delta
u+V(x)u=|u|^{p-1}u, u\in H^1(\R^3), u>0, $x\in \R^3, where $a,$ $b>0$ are
constants, $2<p<5$ and $V:\R^3\rightarrow\R$. Under certain assumptions on $V$,
we prove that \eqref{0.1} has a positive ground state solution by using a
monotonicity trick and a new version of global compactness lemma. Our main
results can be viewed as a partial extension of a recent result of He and Zou
in [16] concerning the existence of positive solutions to the nonlinear
Kirchhoff problem (\varepsilon^2a+\varepsilon b\ds\int_{\R^3}|D
u|^2\right)\Delta u+V(x)u=f(u), u\in H^1(\R^3), u>0, $x\in \R^3$, where
$\varepsilon>0$ is a parameter, $V(x)$ is a positive continuous potential and
$f(u)\thicksim |u|^{p-1}u$ with $3<p<5$ and satisfies the Ambrosetti-Rabinowitz
type condition. Our main results extend also the arguments used in [7,36],
which deal with Schr\"{o}dinger-Poisson system with pure power nonlinearities,
to the Kirchhoff type problem.


title:
Spin Conductance of Diffusive Graphene Nanoribbons: a Probe of Zigzag
  Edge Magnetization

abstract:
  We investigate spin transport in diffusive graphene nanoribbons with both
clean and rough zigzag edges, and long-range potential fluctuations. The
long-range fields along the ribbon edges cause the local doping to come close
to the charge neutrality point forming $p$-$n$ junctions with localized
magnetic moments, similar to the predicted magnetic edge of clean zigzag
graphene nanoribbons. The resulting random edge magnetization polarizes charge
currents and causes sample-to-sample fluctuations of the spin currents obeying
universal predictions. We show furthermore that, although the average spin
conductance vanishes, an applied transverse in-plane electric field can
generate a finite spin conductance. A similar effect can also be achieved by
aligning the edge magnetic moments through an external magnetic field.


title: Entropy production along nonequilibrium quantum jump trajectories

abstract:
  For classical nonequilibrium systems, the separation of the total entropy
production into the adiabatic and nonadiabatic contributions is useful for
understanding irreversibility in nonequilibrium thermodynamics. In this
article, we formulate quantum analogs for driven open quantum systems
describable by quantum jump trajectories by applying a quantum stochastic
thermodynamics. Our main conclusions are based on a quantum formulation of the
local detailed balance condition.


title: What makes a multi-complex exact?

abstract:
  In this paper, we give a sufficient condition which makes the total complex
of a cube exact. This can be regarded as a variant of the Buchsbaum-Eisenbud
theorem which gives a characterization of what makes a complex of finitely
generated free modules exact in terms of the grade of the Fitting ideals of
boundary maps of the complex.


title:
On the Effects of Lag-Times in Networks Constructed from Similarities of
  Monthly Fluctuations of Climate Fields

abstract:
  The complex network framework has been successfully applied to the analysis
of climatological data, providing, for example, a better understanding of the
mechanisms underlying reduced predictability during El Ni\~no or La Ni\~na
years. Despite the large interest that climate networks have attracted, several
issues remain to be investigated. Here we focus in the influence of the
periodic solar forcing in climate networks constructed via similarities of
monthly averaged surface air temperature (SAT) anomalies. We shift the time
series in each pair of nodes such as to superpose their seasonal cycles. In
this way, when two nodes are located in different hemispheres we are able to
quantify the similarity of SAT anomalies during the winters and during the
summers. We find that data time-shifting does not significantly modify the
network area weighted connectivity (AWC), which is the fraction of the total
area of the Earth to which each node is con- nected. This unexpected network
property can be understood in terms of how data time-shifting modifies the
strength of the links connecting geographical regions in different hemispheres,
and how these modifications are washed out by averaging the AWC.


title: Extraterrestrial sink dynamics in granular matter

abstract:
  A loosely packed bed of sand sits precariously on the fence between
mechanically stable and flowing states. This has especially strong implications
for animals or vehicles needing to navigate sandy environments, which can sink
and become stuck in a "dry quicksand" if their weight exceeds the yield stress
of this fragile matter. While it is known that the contact stresses in these
systems are loaded by gravity, very little is known about the sinking dynamics
of objects into loose granular systems under gravitational accelerations
different from the Earth's (g). A fundamental understanding of how objects sink
in different gravitational environments is not only necessary for successful
planetary navigation and engineering, but it can also improve our understanding
of celestial impact dynamics and crater geomorphology. Here we perform and
explain the first systematic experiments of the sink dynamics of objects into
granular media in different gravitational accelerations. By using an
accelerating experimental apparatus, we explore gravitational conditions
ranging from 0.4g to 1.2g. With the aid of discrete element modeling
simulations, we reproduce these results and extend this range to include
objects as small as asteroids and as large as Jupiter. Surprisingly, we find
that the final sink depth is independent of the gravitational acceleration, an
observation with immediate relevance to the design of future extraterrestrial
structures land-roving spacecraft. Using a phenomenological equation of motion
that includes a gravity-loaded frictional term, we are able to quantitatively
explain the experimental and simulation results.


title:
Continuous-Time Random Walk with multi-step memory: An application to
  market dynamics

abstract:
  A novel version of the Continuous-Time Random Walk (CTRW) model with memory
is developed. This memory means the dependence between arbitrary number of
successive jumps of the process, while waiting times between jumps are
considered as i.i.d. random variables. The dependence was found by analysis of
empirical histograms for the stochastic process of a single share price on a
market within the high frequency time scale, and justified theoretically by
considering bid-ask bounce mechanism containing some delay characteristic for
any double-auction market. Our model turns out to be exactly analytically
solvable, which enables a direct comparison of its predictions with their
empirical counterparts, for instance, with empirical velocity autocorrelation
function. Thus this paper significantly extends the capabilities of the CTRW
formalism.


title: Equation of State of the Fermionic 2D Hubbard Model

abstract:
  We present results for the equation of state of the two-dimensional Hubbard
model on an isotropic square lattice as obtained from a controlled and
numerically exact large-cluster dynamical mean field simulation. Our results
are obtained for large but finite systems and are extrapolated to infinite
system size using a known finite size scaling relation. We present the energy,
entropy, double occupancy and nearest-neighbour spin correlations extrapolated
to the thermodynamic limit and discuss the implications of these calculations
on pseudogap physics of the 2D-Hubbard model away from half filling. We find a
strong behavioural shift in energy below a temperature $T^*$ which becomes more
pronounced for larger clusters. Finally, we provide reference calculations and
tables for the equation of state for values of doping away from half filling
which are of interest to cold atom experiments.


title: X-Ray Observations of Black Widow Pulsars

abstract:
  We describe the first X-ray observations of five short orbital period ($P_B <
1$ day), $\gamma$-ray emitting, binary millisecond pulsars. Four of these, PSRs
J0023+0923, J1124$-$3653, J1810+1744, and J2256$-$1024 are `black-widow'
pulsars, with degenerate companions of mass $\ll0.1 M_{\odot}$, three of which
exhibit radio eclipses. The fifth source, PSR J2215+5135, is an eclipsing
`redback' with a near Roche-lobe filling $\sim$0.2 solar mass non-degenerate
companion. Data were taken using the \textit{Chandra X-Ray Observatory} and
covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and
J2256$-$1024, show significant orbital variability while PSR J1124$-$3653 shows
marginal orbital variability. The lightcurves for these three pulsars have
X-ray flux minima coinciding with the phases of the radio eclipses. This
phenomenon is consistent with an intrabinary shock emission interpretation for
the X-rays. The other two pulsars, PSRs J0023+0923 and J1810+1744, are fainter
and do not demonstrate variability at a level we can detect in these data. All
five spectra are fit with three separate models: a power-law model, a blackbody
model, and a combined model with both power-law and blackbody components. The
preferred spectral fits yield power-law indices that range from 1.3 to 3.2 and
blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135
shows a significant hard X-ray component, with a large number of counts above 2
keV, which is additional evidence for the presence of intrabinary shock
emission and is similar to what has been detected in the low-mass X-ray binary
to millisecond pulsar transition object PSR J1023+0038.


title: Ovopub: Modular data publication with minimal provenance

abstract:
  With the growth of the Semantic Web as a medium for creating, consuming,
mashing up and republishing data, our ability to trace any statement(s) back to
their origin is becoming ever more important. Several approaches have now been
proposed to associate statements with provenance, with multiple applications in
data publication, attribution and argumentation. Here, we describe the ovopub,
a modular model for data publication that enables encapsulation, aggregation,
integrity checking, and selective-source query answering. We describe the
ovopub RDF specification, key design patterns and their application in the
publication and referral to data in the life sciences.