title: Correlations of plasticity in sheared glasses

abstract:
  In a recent paper [S. Mandal et al., Phys. Rev. E 88, 022129 (2013)] the
nature of spatial correlations of plasticity in hard sphere glasses was
addressed both via computer simulations and in experiments. It was found that
the experimentally obtained correlations obey a power law whereas the
correlations from simulations are better fitted by an exponential decay. We
here provide direct evidence--- via simulations of a hard sphere glass in
2D---that this discrepancy is a consequence of the finite system size in the 3D
simulations. By extending the study to a 2D soft disk model at zero
temperature, the robustness of the power-law decay in sheared amorphous solids
is underlined. Deviations from a power law occur when either reducing the
packing fraction towards the supercooled regime in the case of hard spheres or
changing the dissipation mechanism from contact dissipation to a mean-field
type drag for the case of soft disks.


title:
Distribution of the largest root of a matrix for Roy's test in
  multivariate analysis of variance

abstract:
  Let ${\bf X, Y} $ denote two independent real Gaussian $\mathsf{p} \times
\mathsf{m}$ and $\mathsf{p} \times \mathsf{n}$ matrices with $\mathsf{m},
\mathsf{n} \geq \mathsf{p}$, each constituted by zero mean i.i.d. columns with
common covariance. The Roy's largest root criterion, used in multivariate
analysis of variance (MANOVA), is based on the statistic of the largest
eigenvalue, $\Theta_1$, of ${\bf{(A+B)}}^{-1} \bf{B}$, where ${\bf A =X X}^T$
and ${\bf B =Y Y}^T$ are independent central Wishart matrices. We derive a new
expression and efficient recursive formulas for the exact distribution of
$\Theta_1$. The expression can be easily calculated even for large parameters,
eliminating the need of pre-calculated tables for the application of the Roy's
test.


title: A Hamiltonian Monte Carlo Method for Non-Smooth Energy Sampling

abstract:
  Efficient sampling from high-dimensional distributions is a challenging issue
which is encountered in many large data recovery problems involving Markov
chain Monte Carlo schemes. In this context, sampling using Hamiltonian dynamics
is one of the recent techniques that have been proposed to exploit the target
distribution geometry. Such schemes have clearly been shown to be efficient for
multi-dimensional sampling, but are rather adapted to the exponential families
of distributions with smooth energy function. In this paper, we address the
problem of using Hamiltonian dynamics to sample from probability distributions
having non-differentiable energy functions such as $\ell_1$. Such distributions
are being more and more used in sparse signal and image recovery applications.
The proposed technique uses a modified leapfrog transform involving a proximal
step. The resulting non-smooth Hamiltonian Monte Carlo (ns-HMC) method is
tested and validated on a number of experiments. Results show its ability to
accurately sample according to various multivariate target distributions. The
proposed technique is illustrated on synthetic examples and is applied to an
image denoising problem.


title: Chaotic behavior of a spin-glass model on a Cayley tree

abstract:
  We investigate the phase diagram of a spin--1 Ising spin-glass model on a
Cayley tree. According to early work of Thompson and collaborators, this
problem can be formulated in terms of a set of nonlinear discrete recursion
relations along the branches of the tree. Physically relevant solutions
correspond to the attractors of these mapping equations. In the limit of
infinite coordination of the tree, and for some choices of the model
parameters, we make contact with findings for the phase diagram of more
recently investigated versions of the Blume-Emery-Griffiths spin-glass model.
In addition to the anticipated phases, we numerically characterize the
existence of modulated and chaotic structures.


title: Temporal offsets among Solar activity indicators

abstract:
  Temporal offsets between the time series of solar activity indicators provide
important clues regarding the physical processes responsible for the cyclic
variability in the solar atmosphere. Hysteresis patterns generated between any
two indicators were popularly used to study their morphological features and
further to understand their inter relationships. We use time series of
different solar indicators to understand the possible cause-and-effect criteria
between their respective source regions. Sensitivity of the upper atmosphere to
the activity underneath might play an important role in introducing different
evolutionary patterns in the profiles of solar indicators and in turn cause
temporal offsets between them. Limitations in the observations may also cause
relative shifts in the time series.


title: The geometry of $\Pi$-invertible sheaves

abstract:
  Using the fact that $\Pi$-invertible sheaves can be interpreted as locally
free sheaves of modules for the super skew field $\mathbb{D}$, we give a new
construction of the $\Pi$-projective superspace $\mathbb{P}^n_{\Pi, B}$ over
affine $k$ superschemes $B$, $k$ an algebraically closed field. We characterize
morphisms into $\mathbb{P}^n_{\Pi, B}$ and give a new interpretation of the
composition of $\Pi$-invertible sheaves in terms of the algebra of
$\mathbb{D}$.


title: Classification of five-dimensional nilpotent Jordan algebras

abstract:
  The paper is devoted to classify nilpotent Jordan algebras of dimension up to
five over an algebraically closed field of characteristic not 2. We obtained a
list of 35 isolated non-isomorphic 5-dimensional nilpotent non-associative
Jordan algebras and 6 families of non-isomorphic 5-dimensional nilpotent
non-associative Jordan algebras depending either on one or two parameters over
an algebraically closed field of characteristic not 2 or 3. In addition to
these algebras we obtained two non-isomorphic 5-dimensional nilpotent
non-associative Jordan algebras over an algebraically closed field of
characteristic 3.


title: Stability in simple heteroclinic networks in $\mathbb{R}^4$

abstract:
  We describe all heteroclinic networks in $\mathbb{R}^4$ made of simple
heteroclinic cycles of types $B$ or $C$, with at least one common connecting
trajectory. For networks made of cycles of type $B$, we study the stability of
the cycles that make up the network as well as the stability of the network. We
show that even when none of the cycles has strong stability properties the
network as a whole may be quite stable. We prove, and provide illustrative
examples of, the fact that the stability of the network does not depend {\em a
priori} uniquely on the stability of the individual cycles.


title:
CCP Cleared or Bilateral CSA Trades with Initial/Variation Margins under
  credit, funding and wrong-way risks: A Unified Valuation Approach

abstract:
  The introduction of CCPs in most derivative transactions will dramatically
change the landscape of derivatives pricing, hedging and risk management, and,
according to the TABB group, will lead to an overall liquidity impact about 2
USD trillions. In this article we develop for the first time a comprehensive
approach for pricing under CCP clearing, including variation and initial
margins, gap credit risk and collateralization, showing concrete examples for
interest rate swaps. Mathematically, the inclusion of asymmetric borrowing and
lending rates in the hedge of a claim lead to nonlinearities showing up in
claim dependent pricing measures, aggregation dependent prices, nonlinear PDEs
and BSDEs. This still holds in presence of CCPs and CSA. We introduce a
modeling approach that allows us to enforce rigorous separation of the
interconnected nonlinear risks into different valuation adjustments where the
key pricing nonlinearities are confined to a funding costs component that is
analyzed through numerical schemes for BSDEs. We present a numerical case study
for Interest Rate Swaps that highlights the relative size of the different
valuation adjustments and the quantitative role of initial and variation
margins, of liquidity bases, of credit risk, of the margin period of risk and
of wrong way risk correlations.


title:
$Y$-$\Delta$ Product in 3-Way $\Delta$ and Y-Channels for Cyclic
  Interference and Signal Alignment

abstract:
  In a full-duplex 3-way $\Delta$ channel, three transceivers communicate to
each other, so that a number of six messages is exchanged. In a $Y$-channel,
however, these three transceivers are connected to an intermediate full-duplex
relay. Loop-back self-interference is suppressed perfectly. The relay forwards
network-coded messages to their dedicated users by means of interference
alignment (IA) and signal alignment. A conceptual channel model with cyclic
shifts described by a polynomial ring is considered for these two related
channels. The maximally achievable rates in terms of the degrees of freedom
measure are derived. We observe that the Y-channel and the 3-way $\Delta$
channel provide a $Y$-$\Delta$ product relationship. Moreover, we briefly
discuss how this analysis relates to spatial IA and MIMO IA.


title: Geometric Aspects of the `Deformation Method'

abstract:
  At the classical level, redefinitions of the field content of a Lagrangian
allow to rewrite an interacting model on a flat target space, in the form of a
free field model (no potential term) on a curved target space. In the present
work we extend the idea of the `deformation method' introduced in
\cite{defmet}, to show that it is possible to write an explicit correspondence
between the metrics of the curved target spaces that arise in the free versions
of distinct scalar field models. This is accomplished by obtaining an explicit
relation between the map function linking the fields and the free models'
metrics. By considering complex and even quaternionic field models, we extend
the procedure --initially proposed for models of a single scalar field-- to
systems with a content of two and four (despite constrained) real fields,
respectively, widening the range of applicability. We also analyze
supersymmetric models to illustrate more possibilities. In particular, we show
how to relate a flat Minkowskian metric to a Fubini-Study space.


title: Plasticity of Zr-Nb-Ti-Ta-Hf high-entropy alloys

abstract:
  We have investigated the plastic deformation properties of non-equiatomic
single phase Zr-Nb-Ti-Ta-Hf high-entropy alloys from room temperature up to 300
{\deg}C. Uniaxial deformation tests at a constant strain rate of 10$^{-4}$
s$^{-1}$ were performed including incremental tests such as stress-relaxations,
strain-rate- and temperature changes in order to determine the thermodynamic
activation parameters of the deformation process. The microstructure of
deformed samples was characterized by transmission electron microscopy. The
strength of the investigated Zr-Nb-Ti-Ta-Hf phase is not as high as the values
frequently reported for high-entropy alloys in other systems. We find an
activation enthalpy of about 1 eV and a stress dependent activation volume
between 0.5 and 2 nm$^3$. The measurement of the activation parameters at
higher temperatures is affected by structural changes evolving in the material
during plastic deformation.


title:
Performance Evaluation of Bit Division Multiplexing combined with
  Non-Uniform QAM

abstract:
  Broadcasting systems have to deal with channel variability in order to offer
the best spectral efficiency to the receivers. However, the transmission
parameters that maximise the spectral efficiency generally leads to a large
link unavailability. In this paper, we study analytically the trade-off between
spectral efficiency and coverage for various channel resource allocation
strategies when broadcasting two services. More precisely, we consider the
following strategies: time sharing, hierarchical modulation and bit division
multiplexing. Our main contribution is the combination of bit division
multiplexing with non-uniform QAM to improve the performance of broadcasting
systems. The results show that this scheme outperforms all the previous channel
resource allocation strategies.


title:
Effect of long range spatial correlations on the lifetime statistics of
  an emitter in a two-dimensional disordered lattice

abstract:
  The effect of spatial correlations on the Purcell effect in a bidimensional
dispersion of resonant nanoparticles is analyzed. We perform extensive
calculations on the fluorescence decay rate of a point emitter embedded in a
system of nanoparticles statistically distributed according to a simple 2D
lattice-gas model near the critical point. For short-range correlations (high
temperature thermalization) the Purcell factors present a long-tailed statistic
which evolves towards a bimodal distribution when approaching the critical
point where the spatial correlation length diverges. Our results suggest
long-range correlations as a possible origin of the large fluctuations of
experimental decay rates in disordered metal films.


title: A new cold sub-Saturnian candidate planet orbiting GJ 221

abstract:
  We re-analyse the recently published HARPS and PFS velocities of the nearby K
dwarf GJ 221 that have been reported to contain the signatures of two planets
orbiting the star. Our goal is to see whether the earlier studies discussing
the system fell victims of false negative detections. We perform the analyses
by using an independent statistical method based on posterior samplings and
model comparisons in the Bayesian framework that is known to be more sensitive
to weak signals of low-mass planets. According to our analyses, we find strong
evidence in favour of a third candidate planet in the system corresponding to a
cold sub-Saturnian planet with an orbital period of 500 days and a minimum mass
of 29 $M_{\oplus}$. Application of sub-optimal signal detection methods can
leave low-amplitude signals undetected in radial velocity time-series. Our
results suggest that the estimated statistical properties of low-mass planets
can thus be biased because several signals corresponding to low-mass candidate
planets may have gone unnoticed. This also suggests that the occurrence rates
of such planets based on radial velocity surveys might be underestimated.


title:
Structure of polymer layers grafted to nanoparticles in
  silica-polystyrene nanocomposites

abstract:
  The structural features of polystyrene brushes grafted on spherical silica
nanoparticles immersed in polystyrene are investigated by means of a Monte
Carlo methodology based on polymer mean field theory. The nanoparticle radii
(either 8 nm or 13 nm) are held constant, while the grafting density and the
lengths of grafted and matrix chains are varied systematically in a series of
simulations. The primary objective of this work is to simulate realistic
nanocomposite systems of specific chemistry at experimentally accessible length
scales and study the structure and scaling of the grafted brush. The profiles
of polymer density around the particles are examined; based on them, the brush
thickness of grafted chains is estimated and its scaling behavior is compared
against theoretical models and experimental findings. Then, neutron scattering
spectra are predicted both from single grafted chains and from the entire
grafted corona. It is found that increasing both the grafting density and the
grafted chain molar mass drastically alters the brush dimensions, affecting the
wetting behavior of the polymeric brush. On the contrary, especially for
particles dispersed in high molecular weight matrix, variation of the matrix
chain length causes an almost imperceptible change of the density around the
particle surface.


title: Circular Proofs for G\"odel-L\"ob Logic

abstract:
  We present a sequent-style proof system for provability logic GL that admits
so-called circular proofs. For these proofs, the graph underlying a proof is
not a finite tree but is allowed to contain cycles. As an application, we
establish Lindon interpolation for GL syntactically.


title:
The ($NUV-r$) vs. $M_r$ as a tracer of early-type galaxies evolution in
  USGC U376 and LGG 225 groups

abstract:
  With the aim of tracing back the evolution of galaxies in nearby groups we
use smooth particle hydrodynamical (SPH) simulations with chemo-photometric
implementation. Here we focus on the evolution of the early-type members (Es
and S0s, ETGs hereafter) in two groups, USGC U376 and LGG 225, both in the Leo
cloud. We use the near-UV (NUV)-optical rest-frame $NUV-r$ versus $M_r$ color
magnitude diagram to follow their evolution, from the blue cloud (BC) to the
red sequence (RS), through the green valley (GV). ETGs brighter than $M_r=-21$
mag are older than 13 Gyr and spend up to 10 Gyr of their overall evolutionary
time in the BC before they reach the RS migrating through the GV. Fainter ETGs
are younger, of about 2 Gyr on average, and evolve for about 7-8 Gyr along the
BC. The turn-off occurs at z ~ 0.3-0.4. Therefore these ETGs spend up to 3-5
Gyr crossing the GV; UGC 06324, the faintest ETG in the sample, still is in the
GV. The mechanism driving their evolution is gravitational, due to merging
and/or interaction. Our SPH simulations suggest that ETG members of these
groups evolved toward the RS before and during the group collapse phase. This
result is consistent with the dynamical analysis of both groups showing that
they are not yet virialized.


title:
Fluctuating local moments, itinerant electrons and the magnetocaloric
  effect: the compositional hypersensitivity of FeRh

abstract:
  We describe an ab-initio Disordered Local Moment Theory for materials with
quenched static compositional disorder traversing first order magnetic phase
transitions. It accounts quantitatively for metamagnetic changes and the
magnetocaloric effect. For perfect stoichiometric B2-ordered FeRh, we calculate
the transition temperature of the ferromagnetic-antiferromagnetic transition to
be $T_t =$ 495K and a maximum isothermal entropy change in 2 Tesla of $|\Delta
S|= 21.1$ J~K$^{-1}$~kg$^{-1}$. A large (40\%) component of $|\Delta S|$ is
electronic. The transition results from a fine balance of competing electronic
effects which is disturbed by small compositional changes - e.g. swapping just
2\% Fe of `defects' onto the Rh sublattice makes $T_t$ drop by 290K. This
hypersensitivity explains the narrow compositional range of the transition and
impurity doping effects.


title:
Studying the SINR process of the typical user in Poisson networks by
  using its factorial moment measures

abstract:
  Based on a stationary Poisson point process, a wireless network model with
random propagation effects (shadowing and/or fading) is considered in order to
examine the process formed by the signal-to-interference-plus-noise ratio
(SINR) values experienced by a typical user with respect to all base stations
in the down-link channel. This SINR process is completely characterized by
deriving its factorial moment measures, which involve numerically tractable,
explicit integral expressions. This novel framework naturally leads to
expressions for the k-coverage probability, including the case of random SINR
threshold values considered in multi-tier network models. While the k-coverage
probabilities correspond to the marginal distributions of the order statistics
of the SINR process, a more general relation is presented connecting the
factorial moment measures of the SINR process to the joint densities of these
order statistics. This gives a way for calculating exact values of the coverage
probabilities arising in a general scenario of signal combination and
interference cancellation between base stations. The presented framework
consisting of mathematical representations of SINR characteristics with respect
to the factorial moment measures holds for the whole domain of SINR and is
amenable to considerable model extension.


title:
Attaining sub-classical metrology in lossy systems with entangled
  coherent states

abstract:
  Quantum mechanics allows entanglement enhanced measurements to be performed,
but loss remains an obstacle in constructing realistic quantum metrology
schemes. However, recent work has revealed that entangled coherent states
(ECSs) have the potential to perform robust sub-classical measurements [J. Joo
et. al., Phys. Rev. Lett. 107, 83601 (2011)]. Up to now no read out scheme has
been devised which exploits this robust nature of ECSs, but we present here an
experimentally accessible method of achieving precision close to the
theoretical bound, even with loss. We show substantial improvements over
unentangled "classical" states and highly-entangled NOON states for a wide
range of loss values, elevating quantum metrology to a realizable technology in
the near future.


title:
Inference of weighted $V$-statistics for nonstationary time series and
  its applications

abstract:
  We investigate the behavior of Fourier transforms for a wide class of
nonstationary nonlinear processes. Asymptotic central and noncentral limit
theorems are established for a class of nondegenerate and degenerate weighted
$V$-statistics through the angle of Fourier analysis. The established theory
for $V$-statistics provides a unified treatment for many important time and
spectral domain problems in the analysis of nonstationary time series, ranging
from nonparametric estimation to the inference of periodograms and spectral
densities.


title: Inelastic neutrino scattering off hot nuclei in supernova environments

abstract:
  We study inelastic neutrino scattering off hot nuclei for temperatures
relevant under supernova conditions. The method we use is based on the
quasiparticle random phase approximation extended to finite temperatures within
the thermo field dynamics (TQRPA). The method allows a transparent treatment of
upward and downward transitions in hot nuclei, avoiding the application of
Brink's hypothesis. For the sample nuclei $^{56}$Fe and $^{82}$Ge we perform a
detailed analysis of thermal effects on the strength distributions of allowed
Gamow-Teller (GT) transitions which dominate the scattering process at low
neutrino energies. For $^{56}$Fe and $^{82}$Ge the finite temperature
cross-sections are calculated by taking into account the contribution of
allowed and forbidden transitions. The observed enhancement of the
cross-section at low neutrino energies is explained by considering thermal
effects on the GT strength. For $^{56}$Fe we compare the calculated
cross-sections to those obtained earlier from a hybrid approach that combines
large-scale shell-model and RPA calculations.


title: A dynamic method for charging-up calculations: the case of GEM

abstract:
  The simulation of Micro Pattern Gaseous Detectors (MPGDs) signal response is
an important and powerful tool for the design and optimization of such
detectors. However, several attempts to simulate exactly the effective charge
gain have not been completely successful. Namely, the gain stability over time
has not been fully understood. Charging-up of the insulator surfaces have been
pointed as one of the responsible for the difference between experimental and
Monte Carlo results. This work describes two iterative methods to simulate the
charging-up in one MPGD device, the Gas Electron Multiplier (GEM). The first
method uses a constant step for avalanches time evolution, very detailed, but
slower to compute. The second method uses a dynamic step that improves the
computing time. Good agreement between both methods was reached. Despite of
comparison with experimental results shows that charging-up plays an important
role in detectors operation, should not be the only responsible for the
difference between simulated and measured effective gain, but explains the time
evolution in the effective gain.


title:
Size-independent Young's modulus of inverted conical GaAs nanowire
  resonators

abstract:
  We explore mechanical properties of top down fabricated, singly clamped
inverted conical GaAs nanowires. Combining nanowire lengths of 2-9 $\mu$m with
foot diameters of 36-935 nm yields fundamental flexural eigenmodes spanning two
orders of magnitude from 200 kHz to 42 MHz. We extract a size-independent value
of Young's modulus of (45$\pm$3) GPa. With foot diameters down to a few tens of
nanometers, the investigated nanowires are promising candidates for
ultra-flexible and ultra-sensitive nanomechanical devices.


title: Multi-stage quantum absorption heat pumps

abstract:
  It is well known that heat pumps, while being all limited by the same basic
thermodynamic laws, may find realization on systems as "small" and "quantum" as
a three-level maser. In order to quantitatively assess how the performance of
these devices scales with their size, we design generalized $N$-dimensional
ideal heat pumps by merging $N-2$ elementary three-level stages. We set them to
operate in the absorption chiller mode between given hot and cold baths, and
study their maximum achievable cooling power and the corresponding efficiency
as a function of $N$. While the efficiency at maximum power is roughly
size-independent, the power itself slightly increases with the dimension,
quickly saturating to a constant. Thus, interestingly, scaling up autonomous
quantum heat pumps does not render a significant enhancement beyond the optimal
double-stage configuration.


title:
Towards a Cellular Automata Based Network Intrusion Detection System
  with Power Level Metric in Wireless Adhoc Networks (IDFADNWCA)

abstract:
  Adhoc wireless network with their changing topology and distributed nature
are more prone to intruders. The efficiency of an Intrusion detection system in
the case of an adhoc network is not only determined by its dynamicity in
monitoring but also in its flexibility in utilizing the available power in each
of its nodes. In this paper we propose a hybrid intrusion detection system,
based on a power level metric for potential adhoc hosts, which is used to
determine the duration for which a particular node can support a
network-monitoring node. The detection of intrusions in the network is done
with the help of Cellular Automata (CA). IDFADNWCA (Intrusion Detection for
Adhoc Networks with Cellular Automata) focuses on the available power level in
each of the nodes and determines the network monitors. Power Level Metric in
the network results in maintaining power for network monitoring, with monitors
changing often, since it is an iterative power optimal solution to identify
nodes for distributed agent based intrusion detection. The advantage of this
approach entails is the inherent flexibility it provides, by means of
considering only fewer nodes for reestablishing network monitors.


title: Equivalent Circuit Analysis of Super-Planckian Emission into Far Field

abstract:
  Using our recently developed equivalent circuit model of radiative heat
transfer we analyze the far-field thermal emission from bodies of constrained
dimensions. We prove that the power radiated by a hypothetical metamaterial
emitter which is conjugate matched with all the harmonics of the emitted field
at a given wavelength can be infinitely higher than the power emitted by an
ideal black body of the same radius. However, for optically large bodies,
fulfilling the conjugate match conditions for higher-order harmonics is not a
trivial task, which effectively limits the far-field radiated power by the
well-known Planck law.


title:
Cancellation of Singularities in SAR for Curved Flight Paths and
  Non-Flat Topography

abstract:
  We consider a mathematical model of synthetic aperture radar (SAR) with a
known, possibly non-flat, topography. In this context we consider the problem
of recovering the wavefront set of the ground reflectivity, given radar data
measured along a curved flight path. We show that if singularities are located
at "mirror points," then the resulting data may be smooth; in effect, the
singularities "cancel." With a flat topography, these mirror points are always
discrete, but we show that in a non-flat topography there may be infinite
families of mirror points.


title: Some notes on Gorenstein projective modules

abstract:
  Let $R$ be a ring. It is proved that $(\mathcal{GP}(R),
\mathcal{GP}(R)^\bot)$ is a complete hereditary cotorsion pair, where
$\mathcal{GP}(R)$ denotes the class of the Gorenstein projective left
$R$-modules. Then we get that each left $R$-module has a special Gorenstein
projective precover. As an application, we prove that all Gorenstein projective
left $R$-modules are Gorenstein flat over left noetherian rings.


title:
A Density Dependence for Protostellar Luminosity in Class I Sources:
  Collaborative Accretion

abstract:
  Class I protostars in three high-mass star-forming regions are found to have
correlations among the local projected density of other Class I protostars, the
summed flux from these other protostars, and the protostellar luminosity in the
WISE 22 micron band. Brighter Class I sources form in higher-density and
higher-flux regions, while low luminosity sources form anywhere. These
correlations depend slightly on the number of neighbors considered (from 2 to
20) and could include a size-of-sample effect from the initial mass function
(i.e., larger numbers include rarer and more massive stars). Luminosities seem
to vary by neighborhood with nearby protostars having values proportional to
each other and higher density regions having higher values. If Class I
luminosity is partially related to the accretion rate, then this luminosity
correlation is consistent with the competitive accretion model, although it is
more collaborative than competitive. The correlation is also consistent with
primordial mass segregation, and could explain why the stellar initial mass
function resembles the dense core mass function even when cores form multiple
stars.


title: Anti-helium from Dark Matter annihilations

abstract:
  Galactic Dark Matter (DM) annihilations can produce cosmic-ray anti-nuclei
via the nuclear coalescence of the anti-protons and anti-neutrons originated
directly from the annihilation process. Since anti-deuterons have been shown to
offer a distinctive DM signal, with potentially good prospects of detection in
large portions of the DM-particle parameter space, we explore here the
production of heavier anti-nuclei, specifically anti-helium. Even more than for
anti-deuterons, the DM-produced anti-He flux can be mostly prominent over the
astrophysical anti-He background at low kinetic energies, typically below 3-5
GeV/n. However, the larger number of anti-nucleons involved in the formation
process makes the anti-He flux extremely small. We therefore explore, for a few
DM benchmark cases, whether the yield is sufficient to allow for anti-He
detection in current-generation experiments, such as AMS-02. We account for the
uncertainties due to the propagation in the Galaxy and to the uncertain details
of the coalescence process, and we consider the constraints already imposed by
anti-proton searches. We find that only for very optimistic configurations it
might be possible to achieve detection with current generation detectors. We
estimate that, in more realistic configurations, an increase in experimental
sensitivity at low-kinetic energies of about a factor of 500-1000 would allow
to start probing DM through the rare cosmic anti-He production.


title: A JVLA 10~degree^2 deep survey

abstract:
  (Abridged)One of the fundamental challenges for astrophysics in the 21st
century is finding a way to untangle the physical processes that govern galaxy
formation and evolution. Given the importance and scope of this problem, the
multi-wavelength astronomical community has used the past decade to build up a
wealth of information over specific extragalactic deep fields to address key
questions in galaxy formation and evolution. These fields generally cover at
least 10square degrees to facilitate the investigation of the rarest, typically
most massive, galaxies and AGN. Furthermore, such areal coverage allows the
environments to be fully accounted for, thereby linking the single halo to the
two-halo terms in the halo occupation distribution. Surveys at radio
wavelengths have begun to lag behind those at other wavelengths, especially in
this medium-deep survey tier. However, the survey speed offered by the JVLA
means that we can now reach a point where we can begin to obtain commensurate
data at radio wavelengths to those which already exists from the X-ray through
to the far-infrared over ~10 square degrees.
  We therefore present the case for a 10 square degree survey to 1.5uJy at
L-band in A or B Array, requiring ~4000 hours to provide census of
star-formation and AGN-accretion activity in the Universe. For example, the
observations will allow galaxies forming stars at 10Msolar/yr to be detected
out to z~1 and luminous infrared galaxies (1000Msolar/yr to be found out to
z~6. Furthermore, the survey area ensures that we will have enough cosmic
volume to find these rare sources at all epochs. The bandwidth will allow us to
determine the polarisation properties galaxies in the high-redshift Universe as
a function of stellar mass, morphology and redshift.


title:
Phase asymmetry effect in longitudinal offset coupled resonator optical
  waveguides

abstract:
  We show that the implementation of the longitudinal displacement technique
for adjusting the coupling coefficients in microring waveguides is subject to a
phase asymmetry effect. This issue is shown to substantially alter the system
response in apodized filters and cannot be ignored in the design stage.


title: Robust Recursive State Estimation with Random Measurements Droppings

abstract:
  A recursive state estimation procedure is derived for a linear time varying
system with both parametric uncertainties and stochastic measurement droppings.
This estimator has a similar form as that of the Kalman filter with
intermittent observations, but its parameters should be adjusted when a plant
output measurement arrives. A new recursive form is derived for the
pseudo-covariance matrix of estimation errors, which plays important roles in
analyzing its asymptotic properties. Based on a Riemannian metric for positive
definite matrices, some necessary and sufficient conditions have been obtained
for the strict contractiveness of an iteration of this recursion. It has also
been proved that under some controllability and observability conditions, as
well as some weak requirements on measurement arrival probability, the gain
matrix of this recursive robust state estimator converges in probability one to
a stationary distribution. Numerical simulation results show that estimation
accuracy of the suggested procedure is more robust against parametric modelling
errors than the Kalman filter.


title: A thermodynamic theory for thermal-gradient-driven domain wall motion

abstract:
  Spin waves (or magnons) interact with magnetic domain walls (DWs) in a
complicated way that a DW can propagate either along or against magnon flow.
However, thermally activated magnons always drive a DW to the hotter region of
a nanowire of magnetic insulators under a temperature gradient. We
theoretically illustrate why it is surely so by showing that DW entropy is
always larger than that of a domain as long as material parameters do not
depend on spin textures. Equivalently, the total free energy of the wire can be
lowered when the DW moves to the hotter region. The larger DW entropy is
related to the increase of magnon density of states at low energy originated
from the gapless magnon bound states.


title: Elements of $\mu$-calculus and thermodynamics of $\mu$-Bose gas model

abstract:
  We review on and give some further details about the thermodynamical
properties of the \mu-Bose gas model (arXiv:1309.1363) introduced by us
recently. This model was elaborated in connection with \mu-deformed
oscillators. Here, we present the necessary concepts and tools from the
so-called \mu-calculus. For the high temperatures, we obtain the virial
expansion of the equation of state, as well as five virial coefficients. In the
regime of low temperatures, the critical temperature of condensation is
inferred. We also obtain the specific heat, internal energy, and entropy for a
\mu-Bose gas for both low and high temperatures. All thermodynamical functions
depend on the deformation parameter \mu. The dependences of the entropy and the
specific heat on the deformation parameter are visualized.

categories: quant-ph cond-mat.quant-gas hep-ph hep-th math-ph math.MP


title:
Asymptotic Behavior of the Pseudo-Covariance Matrix of a Robust State
  Estimator with Intermittent Measurements

abstract:
  Ergodic properties and asymptotic stationarity are investigated in this paper
for the pseudo-covariance matrix (PCM) of a recursive state estimator which is
robust against parametric uncertainties and is based on plant output
measurements that may be randomly dropped. When the measurement dropping
process is described by a Markov chain and the modified plant is both
controllable and observable, it is proved that if the dropping probability is
less than 1, this PCM converges to a stationary distribution that is
independent of its initial values. A convergence rate is also provided. In
addition, it has also been made clear that when the initial value of the PCM is
set to the stabilizing solution of the algebraic Riccati equation related to
the robust state estimator without measurement dropping, this PCM converges to
an ergodic process. Based on these results, two approximations are derived for
the probability distribution function of the stationary PCM, as well as a bound
of approximation errors. A numerical example is provided to illustrate the
obtained theoretical results.


title: The Null Energy Condition and its violation

abstract:
  We give a mini-review of scalar field theories with second-derivative
Lagrangians, whose field equations are second order. Some of these theories
admit solutions violating the Null Energy Condition and having no obvious
pathologies. We give a few examples of using these theories in cosmological
setting and also in the context of the creation of a universe in the
laboratory.


title: Unambiguous Buchi is weak

abstract:
  A non-deterministic automaton running on infinite trees is unambiguous if it
has at most one accepting run on every tree. The class of languages
recognisable by unambiguous tree automata is still not well-understood. In
particular, decidability of the problem whether a given language is
recognisable by some unambiguous automaton is open. Moreover, there are no
known upper bounds on the descriptive complexity of unambiguous languages among
all regular tree languages.
  In this paper we show the following complexity collapse: if a
non-deterministic parity tree automaton $A$ is unambiguous and its priorities
are between $i$ and $2n$ then the language recognised by $A$ is in the class
$Comp(i+1,2n)$. A particular case of this theorem is for $i=n=1$: if $A$ is an
unambiguous Buchi tree automaton then $L(A)$ is recognisable by a weak
alternating automaton (or equivalently definable in weak MSO). The main
motivation for this result is a theorem by Finkel and Simonnet stating that
every unambiguous Buchi automaton recognises a Borel language.
  The assumptions of the presented theorem are syntactic (we require one
automaton to be both unambiguous and of particular parity index). However, to
the authors' best knowledge this is the first theorem showing a collapse of the
parity index that exploits the fact that a given automaton is unambiguous.


title: Sparse Learning of Markovian Population Models in Random Environments

abstract:
  Markovian population models are suitable abstractions to describe well-mixed
interacting particle systems in situation where stochastic fluctuations are
significant due to the involvement of low copy particles. In molecular biology,
measurements on the single-cell level attest to this stochasticity and one is
tempted to interpret such measurements across an isogenic cell population as
different sample paths of one and the same Markov model. Over recent years
evidence built up against this interpretation due to the presence of
cell-to-cell variability stemming from factors other than intrinsic
fluctuations. To account for this extrinsic variability, Markovian models in
random environments need to be considered and a key emerging question is how to
perform inference for such models. We model extrinsic variability by a random
parametrization of all propensity functions. To detect which of those
propensities have significant variability, we lay out a sparse learning
procedure captured by a hierarchical Bayesian model whose evidence function is
iteratively maximized using a variational Bayesian expectation-maximization
algorithm.


title:
Data-Driven Combined State and Parameter Reduction for Extreme-Scale
  Inverse Problems

abstract:
  In this contribution we present an accelerated optimization-based approach
for combined state and parameter reduction of a parametrized linear control
system which is then used as a surrogate model in a Bayesian inverse setting.
Following the basic ideas presented in [Lieberman, Willcox, Ghattas. Parameter
and state model reduction for large-scale statistical inverse settings, SIAM J.
Sci. Comput., 32(5):2523-2542, 2010], our approach is based on a generalized
data-driven optimization functional in the construction process of the
surrogate model and the usage of a trust-region-type solution strategy that
results in an additional speed-up of the overall method. In principal, the
model reduction procedure is based on the offline construction of appropriate
low-dimensional state and parameter spaces and an online inversion step based
on the resulting surrogate model that is obtained through projection of the
underlying control system onto the reduced spaces. The generalization and
enhancements presented in this work are shown to decrease overall computational
time and increase accuracy of the reduced order model and thus allow an
application to extreme-scale problems. Numerical experiments for a generic
model and a fMRI connectivity model are presented in order to compare the
computational efficiency of our improved method with the original approach.


title:
Compton scattering from 12C using tagged photons in the energy range 65
  - 115 MeV

abstract:
  Elastic scattering of photons from 12C has been investigated using
quasi-monoenergetic tagged photons with energies in the range 65 - 115 MeV at
laboratory angles of 60 deg, 120 deg, and 150 deg at the Tagged-Photon Facility
at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed
to provide an estimate of the sensitivity of the 12C(g,g)12C cross section to
the bound-nucleon polarizabilities.


title: Weakly nonadditive Polychronakos statistics

abstract:
  A two-parametric fractional statistics is proposed, which can be used to
model a weakly-interacting Bose-system. It is shown that the parameters of the
introduced weakly nonadditive Polychronakos statistics can be linked to effects
of interactions as well as finite-size corrections. The calculations of the
specific heat and condensate fraction of the model system corresponding to
harmonically trapped Rb-87 atoms are made. The behavior of the specific heat of
three-dimensional isotropic harmonic oscillators with respect to the values of
the statistics parameters is studied in the temperature domain including the
BEC-like phase transition point.


title:
Measurement Method for Evaluating the Probability Distribution of the
  Quality Factor of Mode-Stirred Reverberation Chambers

abstract:
  An original experimental method for determining the empirical probability
distribution function (PDF) of the quality factor (Q) of a mode-stirred
reverberation chamber is presented. Spectral averaging of S-parameters across a
relatively narrow frequency interval at a single pair of locations for the
transmitting and receiving antennas is applied to estimate the stored and
dissipated energy in the cavity, avoiding the need for spatial scanning to
obtain spatial volume or surface averages. The effective number of
simultaneously excited cavity modes per stir state, M, can be estimated by
fitting the empirical distribution to the parametrized theoretical
distribution. The measured results support a previously developed theoretical
model for the PDF of Q and show that spectral averaging over a bandwidth as
small as a few hundred kHz is sufficient to obtain accurate results.


title:
Extension of Grimus-Stockinger formula from operator expansion of free
  Green function

abstract:
  The operator expansion of free Green function of Helmholtz equation for
arbitrary N- dimension space leads to asymptotic extension of 3- dimension
Grimus-Stockinger formula closely related to multipole expansion. Analytical
examples inspired by neutrino oscillation and neutrino deficit problems are
considered for relevant class of wave packets


title: Spectral curve for gamma-deformed AdS/CFT

abstract:
  We construct the spectral curve of gamma-deformed AdS/CFT from the strong
coupling scaling limit of the T-system. As we interpret the twisted T-functions
in the classical limit as characters of the highest weight representations of
the psu(2,2|4) symmetry group, we compute the twisted quasimomenta which
characterize classical integrability and analyze their analytic and asymptotic
properties. These twisted quasimomenta are compared to Beisert-Roiban Bethe
ansatz equations and classical string solutions.


title: High-quality multi-terminal suspended graphene devices

abstract:
  We introduce a new scheme to realize suspended, multi-terminal graphene
structures that can be current annealed successfully to obtain uniform, very
high quality devices. A key aspect is that the bulky metallic contacts are not
connected directly to the part of graphene probed by transport measurements,
but only through etched constriction, which prevents the contacts from acting
invasively. The device high quality and uniformity is demonstrated by a
reproducibly narrow (delta_n ~ 10^9 cm^-2) resistance peak around charge
neutrality, by carrier mobility values exceeding 10^6 cm^2/V/s, by the
observation of integer quantum Hall plateaus starting at 30 mT and of symmetry
broken states at about 200 mT, and by the occurrence of a negative
multi-terminal resistance directly proving the occurrence of ballistic
transport. As these multi-terminal devices enable measurements that cannot be
done in a simpler two-terminal configuration, we anticipate that their use in
future studies of graphene-based systems will be particularly relevant.


title:
From First Principles of QED to an Application: Hyperfine Structure of P
  States of Muonic Hydrogen

abstract:
  The purpose of this article is twofold. First, we attempt to give a brief
overview of the different application areas of quantum electrodynamics (QED).
These include fundamental physics (prediction of atomic energy levels), where
the atom may be exposed to additional external fields (hyperfine splitting and
g factor). We also mention QED processes in highly intense laser fields, and
more applied areas like Casimir and Casimir--Polder interactions. Both the
unifying aspects as well as the differences in the the theoretical treatment
required by these application areas (such as the treatment of infinities) are
highlighted. Second, we discuss an application of the formalism in the
fundamentally interesting area of the prediction of energy levels, namely, the
hyperfine structure of P states of muonic hydrogen.


title: PICARD: A novel code for the Galactic Cosmic Ray propagation problem

abstract:
  In this manuscript we present a new approach for the numerical solution of
the Galactic Cosmic Ray propagation problem. We introduce a method using
advanced contemporary numerical algorithms while retaining the general
complexity of other established codes. In this paper we present the underlying
numerical scheme in conjunction with tests showing the correctness of the
scheme. Finally we show the solution of a first example propagation problem
using the new code to show its applicability to Galactic Cosmic Ray
propagation.


title: Sequences of Laplacian cut-off functions

abstract:
  We derive several new applications of the concept of sequences of Laplacian
cut-off functions on Riemannian manifolds (which we prove to exist on
geodesically complete Riemannian manifolds with nonnegative Ricci curvature):
In particular, we prove that this existence implies $\mathsf{L}^q$-estimates of
the gradient, a new density result of smooth compactly supported functions in
Sobolev spaces on the whole $\mathsf{L}^q$-scale, and a slightly weaker and
slightly stronger variant of the conjecture of Braverman, Milatovic and Shubin
on the nonnegativity of $\mathsf{L}^2$-solutions $f$ of $(-\Delta+1)f\geq 0$.
The latter fact is proved within a new notion of positivity preservation for
Riemannian manifolds which is related to stochastic completeness.


title:
Homogeneous limit of Cd(1-x)Mn(x)GeAs(2) alloy: electrical and magnetic
  properties

abstract:
  We present the studies of structural, electrical, and magnetic properties of
bulk Cd$_{1\textrm{-}x}$Mn$_{x}$GeAs$_{2}$ crystals with low Mn content, $x$,
varying from 0 to 0.037. The studied samples have excellent crystallographic
quality indicated by the presence of diffraction patterns never before observed
experimentally for this compound. The electrical transport in our samples is
dominated by thermal activation of conducting holes from the impurity states to
the valence band with activation energy of about 200$\;$meV. The defect states
acting as ionic scattering centers with concentration in the range from 6 to
15$\times$10$^{17}$$\;$cm$^{-3}$ are observed. The effective Mn content in our
samples, $\bar{x}_{\theta}$, determined from fit of the susceptibility data to
the Curie-Weiss law, is very close to the average chemical content, $x$. It
indicates that the Mn ions are distributed randomly, substituting the Cd sites
in the host CdGeAs$_{2}$ lattice. We observe a negative Curie-Weiss
temperature, $|\theta|$$\,$$\leq$$\,$3.1$\;$K, increasing as a function of $x$.
This indicates the significance of the short-range interactions between the Mn
ions.


title: The index of symmetry of a flag manifold

abstract:
  We study the index of symmetry of a compact generalized flag manifold M=G/H
endowed with an invariant Kaehler structure. When the group G is simple we show
that the leaves of symmetry are irreducible Hermitian symmetric spaces and we
estimate their dimension.


title: Coupling Extraction From Off-Shell Cross-sections

abstract:
  In this note, we present a novel method of extracting the couplings of a new
heavy particle to the Standard Model states. Contrary to the usual discovery
process which involves studying the on-shell production, we look at regions
away from resonance to take advantage of the simple scaling of the
cross-section with the couplings. We apply the procedure to the case of a heavy
quark as an illustration.


title: A Wright-Fisher model with indirect selection

abstract:
  We study a generalization of the Wright--Fisher model in which some
individuals adopt a behavior that is harmful to others without any direct
advantage for themselves. This model is motivated by studies of spiteful
behavior in nature, including several species of parasitoid hymenoptera in
which sperm-depleted males continue to mate de- spite not being fertile. We
first study a single reproductive season, then use it as a building block for a
generalized Wright--Fisher model. In the large population limit, for
male-skewed sex ratios, we rigorously derive the convergence of the
renormalized process to a diffusion with a frequency-dependent selection and
genetic drift. This allows a quantitative comparison of the indirect selective
advantage with the direct one classically considered in the Wright--Fisher
model. From the mathematical point of view, each season is modeled by a mix
between samplings with and without replacement, and analyzed by a sort of
"reverse numerical analysis", viewing a key recurrence relation as a
discretization scheme for a PDE. The diffusion approximation is then obtained
by classical methods.


title: Quantum Analogs of Classical Wakes in Bose-Einstein Condensates

abstract:
  We show that an elliptical obstacle moving through a Bose-Einstein condensate
generates wakes of quantum vortices which resemble those of classical viscous
flow past a cylinder or sphere. The role of ellipticity is to facilitate the
interaction of the vortices nucleated by the obstacle. Initial steady symmetric
wakes lose their symmetry and form clusters of like-signed vortices, in analogy
to the classical B\'enard-von K\'arm\'an vortex street. Our findings,
demonstrated numerically in both two and three dimensions, confirm the
intuition that a sufficiently large number of quanta of circulation reproduce
classical physics.


title:
Ultrafast structural and electronic dynamics of the metallic phase in a
  layered manganite

abstract:
  The transition between different states in manganites can be driven by
various external stimuli. Controlling these transitions with light opens the
possibility to investigate the microscopic path through which they evolve. We
performed femtosecond (fs) transmission electron microscopy on a bi-layered
manganite to study its response to ultrafast photoexcitation. We show that a
photoinduced temperature jump launches a pressure wave that provokes coherent
oscillations of the lattice parameters, detected via ultrafast electron
diffraction. Their impact on the electronic structure are monitored via
ultrafast electron energy loss spectroscopy (EELS), revealing the dynamics of
the different orbitals in response to specific structural distortions.


title: Causality and phase transitions in PT-symmetrical optical systems

abstract:
  We discuss phase transitions in PT-symmetric optical systems. We show that
due to frequency dispersion of the dielectric permittivity, an optical system
can have PT-symmetry at isolated frequency points only. An assumption of the
existence of a PT-symmetric system in a continuous frequency interval violates
the causality principle. Therefore, the ideal symmetry-breaking transition
cannot be observed by simply varying the frequency.


title:
Interplay between electronic topology and crystal symmetry:
  Dislocation-line modes in topological band-insulators

abstract:
  We elucidate the general rule governing the response of dislocation lines in
three-dimensional topological band insulators. According to this ${\bf
K}\text{-}{\bf b}\text{-}{\bf t}$ rule, the lattice topology, represented by
dislocation lines oriented in direction ${\bf t}$ with Burgers vector ${\bf
b}$, combines with the electronic-band topology, characterized by the
band-inversion momentum ${\bf K}_{\rm inv}$, to produce gapless propagating
modes when the plane orthogonal to the dislocation line features a band
inversion with a nontrivial ensuing flux $\Phi={\bf K}_{\rm inv}\cdot {\bf
b}\,\, ({\rm mod\,\,2\pi})$. Although it has already been discovered by Y. Ran
{\it et al.}, Nature Phys. {\bf 5}, 298 (2009), that dislocation lines host
propagating modes, the exact mechanism of their appearance in conjunction with
the crystal symmetries of a topological state is provided by the ${\bf
K}\text{-}{\bf b}\text{-}{\bf t}$ rule . Finally, we discuss possible
experimentally consequential examples in which the modes are oblivious for the
direction of propagation, such as the recently proposed
topologically-insulating state in electron-doped BaBiO$_3$.


title:
Theoretical grounds for the propagation of uncertainties in Monte Carlo
  particle transport

abstract:
  We introduce a theoretical framework for the calculation of uncertainties
affecting observables produced by Monte Carlo particle transport, which derive
from uncertainties in physical parameters input into simulation. The
theoretical developments are complemented by a heuristic application, which
illustrates the method of calculation in a streamlined simulation environment.

categories: physics.data-an hep-ex nucl-ex physics.comp-ph


title: Critical k-Very Ampleness for Abelian Surfaces

abstract:
  Let $(S,L)$ be a polarized abelian surface of Picard rank one and let $\phi$
be the function which takes each ample line bundle $L'$ to the least integer
$k$ such that $L'$ is $k$-very ample but not $(k+1)$-very ample. We use
Bridgeland's stability conditions and Fourier-Mukai techniques to give a closed
formula for $\phi(L^n)$ as a function of $n$ showing that it is linear in $n$
for $n>1$. As a byproduct, we calculate the walls in the Bridgeland stability
space for certain Chern characters.


title: Gamma-Ray Burst Pulse Shapes: Evidence for Embedded Shock Signatures?

abstract:
  A study of a set of well-isolated pulses in Long and Intermediate gamma ray
burst light curves indicates that simple pulse models having smooth and
monotonic pulse rise and decay regions are inadequate. Examining the residuals
of fits of pulses to such models suggests the following patterns of departure
from smooth pulses: three separate wavelike peaks found in the residuals of
each pulse (the precursor peak, the central peak, and the decay peak) combine
with the underlying Norris et al. (2005) pulse model to produce five distinct
regions in the temporal evolution of each pulse. The Precursor Shelf occurs
prior to or concurrent with the exponential Rapid Rise. The pulse reaches
maximum intensity at the Peak Plateau, then undergoes a Rapid Decay. The decay
gradually slows into an Extended Tail. Despite these distinct temporal
segments, the pulses studied are almost universally characterized by hard to
soft spectral evolution, arguing that the new pulse features reflect a single
evolution, rather than being artifacts of pulse overlap. The fluctuations can
give a single pulse the appearance of having up to three distinct localized
peaks, leading to ambiguities in pulse-fitting if an incorrect pulse model is
used. The approach demonstrates that complex GRBs may be composed of fewer
pulses than indicated by the number of peaks. The large degree of similar
spectro-temporal behavior within gamma-ray burst pulses indicates that a single
process is responsible for producing pulses spanning a tremendous range of
durations, luminosities, and spectral hardnesses, and the correlated
characteristics of the wavelike peaks are related to the pulse asymmetry,
suggesting kinematic origins that seem supportive of relativistic shocks.


title: The inner product on exterior powers of a complex vector space

abstract:
  We give a formula for the inner product of forms on a Hermitian vector space
in terms of linear combinations of iterates of the adjoint of the Lefschetz
operator. As an application, we reprove the Kobayashi-Lubke inequality for
Hermite-Einstein bundles.


title:
On some strengthening of the global implicit function theorem with an
  application to a Cauchy problem for an integro-differential Volterra system

abstract:
  In the paper, we improve our earlier results concerning the existence,
uniqueness and differentiability of a global implicit function. Some
application to a Cauchy problem for an integro-differential Volterra system of
nonconvolution type, is given.


title: Molecular orbital tomography beyond the plane wave approximation

abstract:
  The use of plane wave approximation in molecular orbital tomography via
high-order harmonic generation has been questioned since it was proposed, owing
to the fact that it ignores the essential property of the continuum wave
function. To address this problem, we develop a theory to retrieve the valence
molecular orbital directly utilizing molecular continuum wave function which
takes into account the influence of the parent ion field on the continuum
electrons. By transforming this wave function into momentum space, we show that
the mapping from the relevant molecular orbital to the high-order harmonic
spectra is still invertible. As an example, the highest orbital of
$\mathrm{N_2}$ is successfully reconstructed and it shows good agreement with
the \emph{ab initio} orbital. Our work clarifies the long-standing controversy
and strengthens the theoretical basis of molecular orbital tomography.


title: Do lattice data constrain the vector interaction strength of QCD?

abstract:
  We show how repulsive interactions of deconfined quarks as well as confined
hadrons have an influence on the baryon number susceptibilities and the
curvature of the chiral pseudo critical line in effective models of QCD. We
discuss implications and constraints for the vector interaction strength from
comparisons to lattice QCD and comment on earlier constraints, extracted from
the curvature of the transition line of QCD and compact star observables. Our
results clearly point to a strong vector repulsion in the hadronic phase and
near-zero repulsion in the deconfined phase.


title: Spin-dependent optical response of multiferroic EuO

abstract:
  Using first-principles density functional calculations, electronic and
optical properties of ferromagnetic semiconductor EuO are investigated. In
particular, we have developed a way to obtain the spin-dependent optical
response of the magnetic materials, which is helpful to verify the
spin-dependent band structure of EuO. Significantly different optical responses
from spin-up and spin-down channels are obtained in both linear and nonlinear
cases, making it possible to distinguish contributions from different
spin-channels in the optical absorption spectra if spin-flip process can be
neglected. In addition, the red-shift of the absorption edge from paramagnetic
to ferromagnetic ordering is explained by exchange interactions. Using such
method, we have also compared the optical properties of multiferroic EuO which
is induced by strong epitaxial strain. Our results show that from tensile to
compressive strain, the blue-shift of the leading absorption peaks in the
optical spectra, the red-shift of the optical band gap in spin-up state can be
observed, consistent to the energy difference between spin-splitting orbits.
The spin-dependent nonlinear optical properties reveal that in the infrared and
visible light region, the contributions to second-harmonic generation (SHG)
susceptibilities are mainly from spin-majority channels. In addition, the
strain effect is also discussed. With the increase of epitaxial strain, the
larger energy shift of the leading absorption peaks, and the more remarkable
nonlinear optical response can be obtained.


title:
Evaluation of an ensemble-based incremental variational data
  assimilation

abstract:
  In this work, we aim at studying ensemble based optimal control strategies
for data assimilation. Such formulation nicely combines the ingredients of
ensemble Kalman filters and variational data assimilation (4DVar). In the same
way as variational assimilation schemes, it is formulated as the minimization
of an objective function, but similarly to ensemble filter, it introduces in
its objective function an empirical ensemble-based background-error covariance
and works in an off-line smoothing mode rather than sequentially like
sequential filters. These techniques have the great advantage to avoid the
introduction of tangent linear and adjoint models, which are necessary for
standard incremental variational techniques. They also allow handling a time
varying background covariance matrix representing the error evolution between
the estimated solution and a background solution. As this background error
covariance matrix -- of reduced rank in practice -- plays a key role in the
variational process, our study particularly focuses on the generation of the
analysis ensemble state with localization techniques. Besides, to clarify well
the differences between the different methods and to highlight the potential
pitfall and advantages of the different methods, we present key theoretical
properties associated to different choices involved in their setup. We compared
experimentally the performances of several variations of an ensemble technique
of interest with an incremental 4DVar method. The comparisons have been leaded
on the basis of a Shallow Water model and have been carried out both with
synthetic data and through a close experimental setup. The cases where the
system's components are either fully observed or only partially have been in
particular addressed.


title: Classification and Spectral Evolution of Outbursts of Aql X-1

abstract:
  We present a broad classification of all outbursts detected with the All-Sky
Monitor (ASM) on the Rossi X-Ray Timing Explorer (RXTE) and the Monitor of All
Sky X-Ray Image (MAXI) of Aql X-1. We identify three types of outbursts;
long-high, medium-low, and short-low, based on the duration and maximum flux.
We analyse the trends in the "phase-space" of flux-derivative versus flux to
demonstrate the differences in the three identified outburst types. We present
a spectral analysis of the observations of Aql X-1 performed by the
Proportional Counter Array (PCA) onboard RXTE during the 2000 and 2011
outbursts of the long-high class and the 2010 outburst of the medium-low class.
We model the source spectrum with a hybrid thermal/non-thermal hot plasma
emission model (EQPAIR in XSPEC, Coppi 2000) together with a Gaussian component
to model the Fe K_alpha emission line. We construct time histories of the
source flux, the optical depth of the corona (tau), the seed photon temperature
(kT_bb) and the hard state compactness (l_h) for these three outbursts. We show
that the physical parameters of either classes reach the same values throughout
the outbursts, the only difference being the maximum flux. We discuss our
results in the terms of modes of interaction of the star with the disc and size
of the disc kept hot by irradiation. We conclude that irradiation is the
dominant physical process leading to the different classes of outbursts.


title: Universality splitting in distribution of number of miRNA co-targets

abstract:
  In a recent work [arXiv:1307.1382] it was pointed out that the link-weight
distribution of microRNA (miRNA) co-target network of a wide class of species
are universal up to scaling. The number cell types, widely accepted as a
measure of complexity, turns out to be proportional to these scale-factor. In
this article we discuss additional universal features of these networks and
show that, this universality splits if one considers distribution of number of
common targets of three or more number of miRNAs. These distributions for
different species can be collapsed onto two distinct set of universal
functions, revealing the fact that the species which appeared in early
evolution have different complexity measure compared to those appeared late.


title:
Anomalous Post-Newtonian terms and the secular increase of the
  Astronomical Unit

abstract:
  In the last decade a major debate has emerged on the astrophysics community
concerning the anomalous behaviour of the astronomical unit, the fundamental
scale of distances in the Solar system. Several independent studies have
combined radar ranging and optical data from the last four decades to come to
the conclusion that the astronomical unit is increasing by several meters per
century. It is abundantly clear that General Relativity cannot account for this
new effect, although an still undefined angular momentum transfer mechanism
could provide the simpler and more conventional explanation. Here we
investigate several anomalous post-newtonian terms containing only the product
of the mass and angular momentum of the Sun as well as its Schwarzschild radius
in order to determine if they could explain the secular increase of the
astronomical unit and the recently reported increase of Lunar eccentricity. If
these anomalies are confirmed, searching for a modification of General
Relativity predicting these terms could have far-reaching consequences.


title:
Observations of supra-arcade fans: instabilities at the head of
  reconnection jets

abstract:
  Supra-arcade fans are bright, irregular regions of emission that develop
during eruptive flares, above flare arcades. The underlying flare arcades are
thought to be a consequence of magnetic reconnection along a current sheet in
the corona. At the same time, theory predicts plasma jets from the reconnection
site which would be extremely difficult to observe directly because of their
low density. It has been suggested that the dark supra-arcade downflows (SADs)
seen falling through supra-arcade fans may be low density jet plasma. The head
of a low density jet directed towards higher density plasma would be
Rayleigh-Taylor unstable, and lead to the development of rapidly growing low
and high density fingers along the interface. Using SDO/AIA 131A images, we
show details of SADs seen from three different orientations with respect to the
flare arcade and current sheet, and highlight features that have been
previously unexplained, such as the splitting of SADs at their heads, but are a
natural consequence of instabilities above the arcade. Comparison with 3-D
magnetohydrodynamic simulations suggests that supra-arcade downflows are the
result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of
reconnection jets.


title: Doubly Heavy Tetraquarks and Baryons

abstract:
  During the last three years strong experimental evidence from $B$ and charm
factories has been accumulating for the existence of exotic hadronic quarkonia,
narrow resonances which cannot be made from a quark and an antiquark. Their
masses and decay modes show that they contain a heavy quark-antiquark pair, but
their quantum numbers are such that they must also contain a light
quark-antiquark pair. The theoretical challenge has been to determine the
nature of these resonances. The main possibilities are that they are either
"genuine tetraquarks", i.e. two quarks and two antiquarks within one
confinement volume, or "hadronic molecules" of two heavy-light mesons. In the
last few months there as been more and more evidence in favor of the latter. I
discuss the experimental data and its interpretation and provide fairly precise
predictions for masses and quantum numbers of the additional exotic states
which are naturally expected in the molecular picture but have yet to be
observed. In addition, I provide arguments in favor of the existence of an even
more exotic state - a hypothetical deuteron-like bound state of two heavy
baryons. I also consider "baryon-like" states $Q Q' \bar q\bar q'$, which if
found will be direct evidence not just for near-threshold binding of two heavy
mesons, but for genuine tetraquarks with novel color networks. I stress the
importance of experimental search for doubly-heavy baryons in this context.


title:
Effect of Structural Transition on Magnetic Properties of Ca and Mn
  co-substituted BiFeO3 Ceramics

abstract:
  Composition-driven structural transitions in Bi1-xCaxFe1-xMnxO3 ceramics
prepared by the tartaric acid modified sol-gel technique have been studied to
analyze its effect on the magnetic properties of bismuth ferrite (BiFeO3). It
was observed that the co-substitution of Ca & Mn at Bi & Fe sites in BiFeO3
(BFO) significantly suppress the impurity phases. The quantitative
crystallographic phase analysis has been carried out by double phase Rietveld
analysis of all the XRD patterns which indicates the existence of compositional
driven crystal structure transformation from rhombohederal (R3c space group,
lower crystal symmetry) to the orthorhombic (Pbnm space group, higher crystal
symmetry) with the increase in substitution concentration due to excess
chemical pressure (lattice strain). Magnetic measurements reveal that
co-substituted BFO nanoparticles for x = 0.15 have enhanced remnant
magnetization about 14 times that of pure one due to the suppression of cycloid
spin structure which could be explained in terms of field induced spin
reorientation and weak ferromagnetism. However, at the morphological phase
boundary (x = 0.15), the remnant and maximum magnetization at 8 T reaches a
maximum which indicates almost broken spin cycloid structure and further
increase in substitution results in the reduction of both magnetizations due to
the appearance of complete antiferromagnetic ordering in the orthorhombic
structure because of the significant contribution from the crystallographic
phase of Pbnm space group (as obtained from double phase Rietveld analysis).


title:
Dynamo action in thick disks around Kerr black holes: high-order
  resistive GRMHD simulations

abstract:
  We present the first kinematic study of an $\alpha\Omega$-dynamo in the
General Relativistic Magneto-HydroDynamics (GRMHD) regime, applied to thick
disks orbiting around Kerr black holes and using a fully covariant mean field
dynamo closure for the Ohm law. We show that the $\alpha\Omega$-dynamo
mechanism leads to a continuous exponential growth of the magnetic field within
the disk and to the formation of dynamo waves drifting away or toward the
equatorial plane. Since the evolution of the magnetic field occurs
qualitatively in the same fashion as in the Sun, we present also butterfly
diagrams that characterize our models and show the establishment of an
additional timescale, which depends on the microscopic properties of the
turbulent motions, possibly providing an alternative explanation to
periodicities observed in many high-energy astrophysical sources where
accretion onto a rotating black hole is believed to operate.


title: Proximity Effects in Topological Insulator Heterostructures

abstract:
  Topological insulators (TIs) are bulk insulators that possess robust helical
conducting states along their interfaces with conventional insulators. A
tremendous research effort has recently been devoted to TI-based
heterostructures, in which conventional proximity effects give rise to a series
of exotic physical phenomena. This paper reviews our recent works on the
potential existence of topological proximity effects at the interface between a
topological insulator and a normal insulator or other topologically trivial
systems. Using first-principles approaches, we have established the tunability
of the vertical location of the topological helical state via intriguing
dual-proximity effects. To further elucidate the control parameters of this
effect, we have used the graphene-based heterostructures as prototypical
systems to reveal a more complete phase diagram. On the application side of the
topological helical states, we have presented a catalysis example, where the
topological helical state plays an essential role in facilitating surface
reactions by serving as an effective electron bath. These discoveries lay the
foundation for accurate manipulation of the real space properties of the
topological helical state in TI-based heterostructures and pave the way for
realization of the salient functionality of topological insulators in future
device applications.


title:
Quantitative imaging of flux vortices in type-II superconductor MgB$_2$
  using Cryo-Lorentz Transmission Electron Microscopy

abstract:
  Imaging of flux vortices in high quality MgB$_2$ single crystals has been
successfully performed in a commercial Field Emission Gun-based Transmission
Electron Microscope. In Cryo-Lorentz Microscopy, the sample quality and the
vortex lattice can be monitored simultaneously, allowing one to relate
microscopically the surface quality and the vortex dynamics. Such a vortex
motion ultimately determines the flow resistivity, $\rho_{f}$, the knowledge of
which is indispensable for practical applications such as superconducting
magnets or wires for Magnetic Resonance Imaging. The observed patterns have
been analyzed and compared with other studies by Cryo-Lorentz Microscopy or
Bitter decoration. We find that the vortex lattice arrangement depends strongly
on the surface quality obtained during the specimen preparation, and tends to
form an hexagonal Abrikosov lattice at a relatively low magnetic field. Stripes
or gossamer-like patterns, recently suggested as potential signatures of an
unconventional behavior of MgB$_2$, were not observed.


title: Towards Autotuning of OpenMP Applications on Multicore Architectures

abstract:
  In this paper we describe an autotuning tool for optimization of OpenMP
applications on highly multicore and multithreaded architectures. Our work was
motivated by in-depth performance analysis of scientific applications and
synthetic benchmarks on IBM Power 775 architecture. The tool provides an
automatic code instrumentation of OpenMP parallel regions. Based on measurement
of chosen hardware performance counters the tool decides on the number of
parallel threads that should be used for execution of chosen code fragments.


title:
Improved cosmological constraints from a joint analysis of the SDSS-II
  and SNLS supernova samples

abstract:
  We present cosmological constraints from a joint analysis of type Ia
supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations.
The data set includes several low-redshift samples (z<0.1), all 3 seasons from
the SDSS-II (0.05 < z < 0.4), and 3 years from SNLS (0.2 <z < 1) and totals
\ntotc spectroscopically confirmed type Ia supernovae with high quality light
curves. We have followed the methods and assumptions of the SNLS 3-year data
analysis except for the following important improvements: 1) the addition of
the full SDSS-II spectroscopically-confirmed SN Ia sample in both the training
of the SALT2 light curve model and in the Hubble diagram analysis (\nsdssc
SNe), 2) inter-calibration of the SNLS and SDSS surveys and reduced systematic
uncertainties in the photometric calibration, performed blindly with respect to
the cosmology analysis, and 3) a thorough investigation of systematic errors
associated with the SALT2 modeling of SN Ia light-curves. We produce
recalibrated SN Ia light-curves and associated distances for the SDSS-II and
SNLS samples. The large SDSS-II sample provides an effective, independent,
low-z anchor for the Hubble diagram and reduces the systematic error from
calibration systematics in the low-z SN sample. For a flat LCDM cosmology we
find Omega_m=0.295+-0.034 (stat+sys), a value consistent with the most recent
CMB measurement from the Planck and WMAP experiments. Our result is 1.8sigma
(stat+sys) different than the previously published result of SNLS 3-year data.
The change is due primarily to improvements in the SNLS photometric
calibration. When combined with CMB constraints, we measure a constant
dark-energy equation of state parameter w=-1.018+-0.057 (stat+sys) for a flat
universe. Adding BAO distance measurements gives similar constraints:
w=-1.027+-0.055.


title:
Cosmological Parameter Uncertainties from SALT-II Type Ia Supernova
  Light Curve Models

abstract:
  We use simulated SN Ia samples, including both photometry and spectra, to
perform the first direct validation of cosmology analysis using the SALT-II
light curve model. This validation includes residuals from the light curve
training process, systematic biases in SN Ia distance measurements, and the
bias on the dark energy equation of state parameter w. Using the SN-analysis
package SNANA, we simulate and analyze realistic samples corresponding to the
data samples used in the SNLS3 analysis: 120 low-redshift (z < 0.1) SNe Ia, 255
SDSS SNe Ia (z < 0.4), and 290 SNLS SNe Ia (z <= 1). To probe systematic
uncertainties in detail, we vary the input spectral model, the model of
intrinsic scatter, and the smoothing (i.e., regularization) parameters used
during the SALT-II model training. Using realistic intrinsic scatter models
results in a slight bias in the ultraviolet portion of the trained SALT-II
model, and w biases (winput - wrecovered) ranging from -0.005 +/- 0.012 to
-0.024 +/- 0.010. These biases are indistinguishable from each other within
uncertainty; the average bias on w is -0.014 +/- 0.007.


title: Spectral enclosure and superconvergence for eigenvalues in gaps

abstract:
  We consider the problem of how to compute eigenvalues of a self-adjoint
operator when a direct application of the Galerkin (finite-section) method is
unreliable. The last two decades have seen the development of the so-called
quadratic methods for addressing this problem. Recently a new perturbation
approach has emerged, the idea being to perturb eigenvalues off the real line
and, consequently, away from regions where the Galerkin method fails. We
propose a simplified perturbation method which requires no \'a priori
information and for which we provide a rigorous convergence analysis. The
latter shows that, in general, our approach will significantly outperform the
quadratic methods. We also present a new spectral enclosure for operators of
the form $A+iB$ where $A$ is self-adjoint, $B$ is self-adjoint and bounded.
This enables us to control, very precisely, how eigenvalues are perturbed from
the real line. The main results are demonstrated with examples including
magnetohydrodynamics, Schr\"odinger and Dirac operators.


title:
Odd and Even Partial Waves of \eta\pi^- and \eta'\pi^- in 191 GeV/c
  \pi^-p

abstract:
  In the year 2008 COMPASS recorded diffractive events of the signature
\pi^-(191 GeV) p --> X_fast p. We present results of the analysis of the
subsystems X = \eta(')\pi^-. Besides the known resonances a_2(1320), a_4(2040),
we study the properties of the spin-exotic P+ wave, and all other
natural-exchange partial waves up to spin J = 6. We find a striking difference
between the two final states: whereas the even partial waves J = 2, 4, 6 in the
two systems are related by phase-space factors, the odd partial waves are
relatively suppressed in the \eta\pi^- system. The relative phases between the
even waves appear identical whereas the phase between the D and P waves behave
quite differently, suggesting different resonant and non-resonant contributions
in the two odd-angular-momentum systems. Branching ratios and parameters of the
well-known resonances a_2 and a_4 are measured.


title: Efficient transfer entropy analysis of non-stationary neural time series

abstract:
  Information theory allows us to investigate information processing in neural
systems in terms of information transfer, storage and modification. Especially
the measure of information transfer, transfer entropy, has seen a dramatic
surge of interest in neuroscience. Estimating transfer entropy from two
processes requires the observation of multiple realizations of these processes
to estimate associated probability density functions. To obtain these
observations, available estimators assume stationarity of processes to allow
pooling of observations over time. This assumption however, is a major obstacle
to the application of these estimators in neuroscience as observed processes
are often non-stationary. As a solution, Gomez-Herrero and colleagues
theoretically showed that the stationarity assumption may be avoided by
estimating transfer entropy from an ensemble of realizations. Such an ensemble
is often readily available in neuroscience experiments in the form of
experimental trials. Thus, in this work we combine the ensemble method with a
recently proposed transfer entropy estimator to make transfer entropy
estimation applicable to non-stationary time series. We present an efficient
implementation of the approach that deals with the increased computational
demand of the ensemble method's practical application. In particular, we use a
massively parallel implementation for a graphics processing unit to handle the
computationally most heavy aspects of the ensemble method. We test the
performance and robustness of our implementation on data from simulated
stochastic processes and demonstrate the method's applicability to
magnetoencephalographic data. While we mainly evaluate the proposed method for
neuroscientific data, we expect it to be applicable in a variety of fields that
are concerned with the analysis of information transfer in complex biological,
social, and artificial systems.


title: Binary Scientific Star Coauthors Core Size

abstract:
  It is examined whether the relationship $ J \propto A/r^{\alpha}$, and the
subsequent coauthor core notion (Ausloos 2013), between the number ($J$) of
joint publications (JP) by a "main scientist" (LI) with her/his coauthors (CAs)
can be extended to a team-like system. This is done by considering that each
coauthor can be so strongly tied to the LI that they are forming {\it binary
scientific star} (BSS) systems with respect to their other collaborators.
Moreover, publications in peer review journals and in "proceedings", both often
thought to be of "different quality", are separetely distinguished. The role of
a time interval for measuring $J$ and $\alpha$ is also examined. New indirect
measures are also introduced.
  For making the point, two LI cases with numerous CAs are studied. It is found
that only a few BSS need to be usefully examined. The exponent $\alpha$ turns
out to be "second scientist" weakly dependent, but still "size" and
"publication type" dependent, according to the number of CAs or JP. The CA core
value is found to be (CA or JP) size and publication type dependent, but
remains in an understandable range. Somewhat unexpectedly, no special
qualitative difference on the binary scientific star CA core value is found
between publications in peer review journals and in proceedings.
  In conclusion, some remark is made on partner cooperation in BSS teams. It is
suggested that such measures can serve as criteria for distinguishing the role
of scientists in a team.


title: Incorporating Streams into Milky Way Models

abstract:
  We develop a framework for modelling the Milky Way using stellar streams and
a wide range of photometric and kinematic observations. Through the use of mock
data we demonstrate that a standard suite of Galactic observations leads to
degeneracies in the inferred halo parameters. We then incorporate a GD-1-like
stream into this suite using the orbit-fitting technique and show that the
streams reduces the uncertainties in these parameters provided all observations
are fit simultaneously. We also explore how the assumption of a disk-halo
alignment can lead unphysical models. Our results may explain why some studies
based on the Sagittarius stream find that the halo's intermediate axis is
parallel to the disk spin axis even though such a configuration is highly
unstable. Finally we show that both longer streams and multiple streams lead to
improvements in our ability to infer the shape of our dark halo.


title:
Families of rational curves on holomorphic symplectic varieties and
  applications to 0-cycles

abstract:
  We study families of rational curves on certain irreducible holomorphic
symplectic varieties. In particular, we prove that any ample linear system on a
projective holomorphic symplectic variety of K3[n]-type contains a uniruled
divisor. As an application we provide a generalization of the Beauville-Voisin
result on the Chow group of 0-cycles on such varieties.


title:
Temperature-dependent electron-phonon coupling in
  La$_{2-x}$Sr$_x$CuO$_4$ probed by femtosecond X-ray diffraction

abstract:
  The strength of the electron-phonon coupling parameter and its evolution
throughout a solid's phase diagram often determines phenomena such as
superconductivity, charge- and spin-density waves. Its experimental
determination relies on the ability to distinguish thermally activated phonons
from those emitted by conduction band electrons, which can be achieved in an
elegant way by ultrafast techniques. Separating the electronic from the
out-of-equilibrium lattice subsystems, we probed their re-equilibration by
monitoring the transient lattice temperature through femtosecond X-ray
diffraction in La$_{2-x}$Sr$_x$CuO$_4$ single crystals with $x$=0.1 and 0.21.
The temperature dependence of the electron-phonon coupling is obtained
experimentally and shows similar trends to what is expected from the
\textit{ab-initio} calculated shape of the electronic density-of-states near
the Fermi energy. This study evidences the important role of band effects in
the electron-lattice interaction in solids, in particular in superconductors.


title: Floer cohomology of the Chiang Lagrangian

abstract:
  We study holomorphic discs with boundary on a Lagrangian submanifold $L$ in a
Kaehler manifold admitting a Hamiltonian action of a group $K$ which has $L$ as
an orbit. We prove various transversality and classification results for such
discs which we then apply to the case of a particular Lagrangian in
$\mathbf{CP}^3$ first noticed by Chiang. We prove that this Lagrangian has
non-vanishing Floer cohomology if and only if the coefficient ring has
characteristic 5, in which case it generates the split-closed derived Fukaya
category as a triangulated category.


title:
Generalized belief propagation for the magnetization of the simple cubic
  Ising model

abstract:
  A new approximation of the cluster variational method is introduced for the
three-dimensional Ising model on the simple cubic lattice. The maximal cluster
is, as far as we know, the largest ever used in this method. A message-passing
algorithm, generalized belief propagation, is used to minimize the variational
free energy. Convergence properties and performance of the algorithm are
investigated. The approximation is used to compute the spontaneous
magnetization, which is then compared to previous results. Using the present
results as the last step in a sequence of three cluster variational
approximations, an extrapolation is obtained which captures the leading
critical behaviour with a good accuracy.


title:
Mott transition and Antiferromagnetic Metal on Shastry-Sutherland
  Lattice

abstract:
  The Shastry-Sutherland lattice, one of the simplest systems with geometric
frustration, which has an exact eigenstate by putting singlets on diagonal
bonds, can be realized in a group of layered compounds and rises both
theoretical and experimental interest. Most of the previous studies on the
Shastry-Sutherland lattice are focusing on the Heisenberg model. Here we opt
for the Hubbard model to calculate phase diagrams over a wide range of
interaction parameters, and show the competing effects of interaction,
frustration and temperature. At low temperature, frustration is shown to favor
a paramagnetic metallic ground state, while interaction drives the system to an
antiferromagnetic insulator phase. Between these two phases, there are an
antiferromagnetic metal phase and a paramagnetic insulator (which should be a
valence bond solid) phase resulting from the competition of the frustration and
the interaction. Our results may shed light on more exhaustive studies about
quantum phase transitions in this lattice.


title:
Application of the parallel multicanonical method to lattice gas
  condensation

abstract:
  We present the speedup from a novel parallel implementation of the
multicanonical method on the example of a lattice gas in two and three
dimensions. In this approach, all cores perform independent equilibrium runs
with identical weights, collecting their sampled histograms after each
iteration in order to estimate consecutive weights. The weights are then
redistributed to all cores. These steps are repeated until the weights are
converged. This procedure benefits from a minimum of communication while
distributing the necessary amount of statistics efficiently.
  Using this method allows us to study a broad temperature range for a variety
of large and complex systems. Here, a gas is modeled as particles on the
lattice, which interact only with their nearest neighbors. For a fixed density
this model is equivalent to the Ising model with fixed magnetization. We
compare our results to an analytic prediction for equilibrium droplet
formation, confirming that a single macroscopic droplet forms only above a
critical density.


title:
Fresnel versus Kummer surfaces: geometrical optics in dispersionless
  linear (meta)materials and vacuum

abstract:
  Geometrical optics describes, with good accuracy, the propagation of
high-frequency plane waves through an electromagnetic medium. Under such
approximation, the behaviour of the electromagnetic fields is characterised by
just three quantities: the temporal frequency $\omega$, the spatial wave
(co)vector $k$, and the polarisation (co)vector $a$. Numerous key properties of
a given optical medium are determined by the Fresnel surface, which is the
visual counterpart of the equation relating $\omega$ and $k$. For instance, the
propagation of electromagnetic waves in a uniaxial crystal, such as calcite, is
represented by two light-cones. Kummer, whilst analysing quadratic line
complexes as models for light rays in an optical apparatus, discovered in the
framework of projective geometry a quartic surface that is linked to the
Fresnel one. Given an arbitrary dispersionless linear (meta)material or vacuum,
we aim to establish whether the resulting Fresnel surface is equivalent to, or
is more general than, a Kummer surface.


title:
Linear-optical simulation of the cooling of a cluster-state Hamiltonian
  system

abstract:
  A measurement-based quantum computer could consist of a local-gapped
Hamiltonian system, whose thermal states --at sufficiently low temperature--
are universal resources for the computation. Initialization of the computer
would correspond to cooling the system. We perform an experimental quantum
simulation of such cooling process with entangled photons. We prepare
three-qubit thermal cluster states exploiting the equivalence between local
dephasing and thermalisation for these states. This allows us to tune the
system's temperature by changing the dephasing strength. We monitor the
entanglement as the system cools down and observe the transitions from
separability to bound entanglement, and then to free entanglement. We also
analyze the performance of the system for measurement-based single-qubit state
preparation. These studies constitute a basic characterisation of experimental
cluster-state computation under imperfect conditions.


title: Decay Phase Cooling and Inferred Heating of M- and X-class Solar Flares

abstract:
  In this paper, the cooling of 72 M- and X-class flares is examined using
GOES/XRS and SDO/EVE. The observed cooling rates are quantified and the
observed total cooling times are compared to the predictions of an analytical
0-D hydrodynamic model. It is found that the model does not fit the
observations well, but does provide a well defined lower limit on a flare's
total cooling time. The discrepancy between observations and the model is then
assumed to be primarily due to heating during the decay phase. The decay phase
heating necessary to account for the discrepancy is quantified and found be
~50% of the total thermally radiated energy as calculated with GOES. This decay
phase heating is found to scale with the observed peak thermal energy. It is
predicted that approximating the total thermal energy from the peak is
minimally affected by the decay phase heating in small flares. However, in the
most energetic flares the decay phase heating inferred from the model can be
several times greater than the peak thermal energy.


title:
Noncommutative Topological Quantum Field Theory, Noncommutative Floer
  Homology, Noncommutative Hodge Theory

abstract:
  We present some ideas for a possible Noncommutative Topological Quantum Field
Theory (NCTQFT) and Noncommutative Floer Homology (NCFH). Our motivation is
two-fold and it comes both from physics and mathematics: On the one hand we
argue that NCTQFT is the correct mathematical framework for a quantum field
theory of all known interactions in nature (including gravity). On the other
hand we hope that a possible NCFH will apply to practically every 3-manifold
(and not only to homology 3-spheres as ordinary Floer Homology currently does).
The two motivations are closely related since, at least in the commutative
case, Floer Homology Groups constitute the space of quantum observables of
(3+1)-dim Topological Quantum Field Theory. Towards this goal we present some
"Noncommutative" Versions of Hodge Theory for noncommutative differentail forms
and tangential cohomology for foliations.


title:
Stable determination of a scattered wave from its far-field pattern: the
  high frequency asymptotics

abstract:
  We deal with the stability issue for the determination of outgoing
time-harmonic acoustic waves from their far-field patterns. We are especially
interested in keeping as explicit as possible the dependence of our stability
estimates on the wavenumber of the corresponding Helmholtz equation and in
understanding the high wavenumber, that is frequency, asymptotics.
  Applications include stability results for the determination from far-field
data of solutions of direct scattering problems with sound-soft obstacles and
an instability analysis for the corresponding inverse obstacle problem.
  The key tool consists of establishing precise estimates on the behavior of
Hankel functions with large argument or order.


title:
Stochastic Backpropagation and Approximate Inference in Deep Generative
  Models

abstract:
  We marry ideas from deep neural networks and approximate Bayesian inference
to derive a generalised class of deep, directed generative models, endowed with
a new algorithm for scalable inference and learning. Our algorithm introduces a
recognition model to represent approximate posterior distributions, and that
acts as a stochastic encoder of the data. We develop stochastic
back-propagation -- rules for back-propagation through stochastic variables --
and use this to develop an algorithm that allows for joint optimisation of the
parameters of both the generative and recognition model. We demonstrate on
several real-world data sets that the model generates realistic samples,
provides accurate imputations of missing data and is a useful tool for
high-dimensional data visualisation.


title:
Large Dimensional Analysis and Optimization of Robust Shrinkage
  Covariance Matrix Estimators

abstract:
  This article studies two regularized robust estimators of scatter matrices
proposed (and proved to be well defined) in parallel in (Chen et al., 2011) and
(Pascal et al., 2013), based on Tyler's robust M-estimator (Tyler, 1987) and on
Ledoit and Wolf's shrinkage covariance matrix estimator (Ledoit and Wolf,
2004). These hybrid estimators have the advantage of conveying (i) robustness
to outliers or impulsive samples and (ii) small sample size adequacy to the
classical sample covariance matrix estimator. We consider here the case of
i.i.d. elliptical zero mean samples in the regime where both sample and
population sizes are large. We demonstrate that, under this setting, the
estimators under study asymptotically behave similar to well-understood random
matrix models. This characterization allows us to derive optimal shrinkage
strategies to estimate the population scatter matrix, improving significantly
upon the empirical shrinkage method proposed in (Chen et al., 2011).