title: Beyond Sharing Weights for Deep Domain Adaptation

abstract:
  The performance of a classifier trained on data coming from a specific domain
typically degrades when applied to a related but different one. While
annotating many samples from the new domain would address this issue, it is
often too expensive or impractical. Domain Adaptation has therefore emerged as
a solution to this problem; It leverages annotated data from a source domain,
in which it is abundant, to train a classifier to operate in a target domain,
in which it is either sparse or even lacking altogether. In this context, the
recent trend consists of learning deep architectures whose weights are shared
for both domains, which essentially amounts to learning domain invariant
features.
  Here, we show that it is more effective to explicitly model the shift from
one domain to the other. To this end, we introduce a two-stream architecture,
where one operates in the source domain and the other in the target domain. In
contrast to other approaches, the weights in corresponding layers are related
but not shared. We demonstrate that this both yields higher accuracy than
state-of-the-art methods on several object recognition and detection tasks and
consistently outperforms networks with shared weights in both supervised and
unsupervised settings.


title:
Illumination-invariant image mosaic calculation based on logarithmic
  search

abstract:
  This technical report describes an improved image mosaicking algorithm. It is
based on Jain's logarithmic search algorithm [Jain 1981] which is coupled to
the method of Kourogi (1999} for matching images in a video sequence.
Logarithmic search has a better invariance against illumination changes than
the original optical-flow-based method of Kourogi.


title:
Probing the Interstellar Dust in Galaxies over > 10 Gyr of Cosmic
  History

abstract:
  This article is based on an invited talk given by V. P. Kulkarni at the 8th
Cosmic Dust meeting. Dust has a profound effect on the physics and chemistry of
the interstellar gas in galaxies and on the appearance of galaxies.
Understanding the cosmic evolution of dust with time is therefore crucial for
understanding the evolution of galaxies. Despite the importance of interstellar
dust, very little is known about its nature and composition in distant
galaxies. We summarize the results of our ongoing programs using observations
of distant quasars to obtain better constraints on dust grains in foreground
galaxies that happen to lie along the quasar sightlines. These observations
consist of a combination of mid-infrared data obtained with the Spitzer Space
Telescope and optical/UV data obtained with ground-based telescopes and/or the
Hubble Space Telescope. The mid-IR data target the 10 $\mu$m and 18 $\mu$m
silicate absorption features, while the optical/UV data allow determinations of
element depletions, extinction curves, 2175 {\AA} bumps, etc. Measurements of
such properties in absorption-selected galaxies with redshifts ranging from
$z\sim0$ to $z>2$ provide constraints on the evolution of interstellar dust
over the past $> 10$ Gyr. The optical depth of the 10 $\mu$m silicate
absorption feature ($\tau_{10}$) in these galaxies is correlated with the
amount of reddening along the sightline. But there are indications [e.g., based
on the $\tau_{10}$ /$E(B-V)$ ratio and possible grain crystallinity] that the
dust in these distant galaxies differs in structure and composition from the
dust in the Milky Way and the Magellanic Clouds. We briefly discuss the
implications of these results for the evolution of galaxies and their star
formation history.


title: Linear structures on locales

abstract:
  We define a notion of morphism for quotient vector bundles that yields both a
category $\textit{QVBun}$ and a contravariant global sections functor
$C:\textit{QVBun}^{\textrm{op}}\to\textit{Vect}$ whose restriction to trivial
vector bundles with fiber $F$ coincides with the contravariant functor
$\textit{Top}^{\textrm{op}}\to\textit{Vect}$ of $F$-valued continuous
functions. Based on this we obtain a linear extension of the adjunction between
the categories of topological spaces and locales: (i) a linearized topological
space is a spectral vector bundle, by which is meant a mildly restricted type
of quotient vector bundle; (ii) a linearized locale is a locale $\triangle$
equipped with both a topological vector space $A$ and a $\triangle$-valued
support map for the elements of $A$ satisfying a continuity condition relative
to the spectrum of $\triangle$ and the lower Vietoris topology on
$\operatorname{Sub} A$; (iii) we obtain an adjunction between the full
subcategory of spectral vector bundles $\textit{QVBun}_{\Sigma}$ and the
category of linearized locales $\textit{LinLoc}$, which restricts to an
equivalence of categories between sober spectral vector bundles and spatial
linearized locales. The spectral vector bundles are classified by a finer
topology on $\operatorname{Sub} A$, called the open support topology, but there
is no notion of universal spectral vector bundle for an arbitrary topological
vector space $A$.


title:
Kinetic and finite ion mass effects on the transition to relativistic
  self-induced transparency in laser-driven ion acceleration

abstract:
  We study kinetic effects responsible for the transition to relativistic
self-induced transparency in the interaction of a circularly-polarized
laser-pulse with an overdense plasma and their relation to hole-boring and ion
acceleration. It is demonstrated using particle-in-cell simulations and an
analysis of separatrices in single-electron phase-space, that ion motion can
suppress fast electron escape to the vacuum, which would otherwise lead to
transition to the relativistic transparency regime. A simple analytical
estimate shows that for large laser pulse amplitude $a_0$ the time scale over
which ion motion becomes important is much shorter than usually anticipated. As
a result, the threshold density above which hole-boring occurs decreases with
the charge-to-mass ratio. Moreover, the transition threshold is seen to depend
on the laser temporal profile, due to the effect that the latter has on
electron heating. Finally, we report a new regime in which a transition from
relativistic transparency to hole-boring occurs dynamically during the course
of the interaction. It is shown that, for a fixed laser intensity, this dynamic
transition regime allows optimal ion acceleration in terms of both energy and
energy spread.


title:
Intrinsic ultralow lattice thermal conductivity of the unfilled
  skutterudite FeSb$_3$

abstract:
  It has been generally accepted that unfilled skutterudites process high
lattice thermal conductivity ($\kappa_{l}$) that can be efficiently reduced
upon filling. Here by using first principles Boltzmann-Peierls transport
calculations, we find pure skutterudite of FeSb$_3$ with no filler in fact has
an intrinsic ultralow $\kappa_{l}$ smaller than that of CoSb$_3$ by one order
of magnitude. The value is even smaller than those of most of the fully filled
skutterudites. This finding means that with FeSb$_3$ as a reference, filling
does not necessarily lower $\kappa_{l}$. The ultralow $\kappa_{l}$ of FeSb$_3$
is a consequence of much softened optical phonon branches associated with the
weakly bonded Sb$_4$ rings. They overlap more with heat-carrying acoustic
phonons and significantly increase the phase space for three-phonon anharmonic
scattering processes. This provides an alternative non-filling related
mechanism for lowering the $\kappa_{l}$ of skutterudites.


title:
Strong coupling of the cyclotron motion of surface electrons on liquid
  helium to a microwave cavity

abstract:
  The strong coupling regime is observed in a system of two-dimensional
electrons whose cyclotron motion is coupled to an electro-magnetic mode in a
Fabry-Perot cavity resonator. The Rabi splitting of eigenfrequencies of coupled
motion is observed both in the cavity reflection spectrum and ac current of
electrons, the latter probed by measuring their bolometric photoresponse.
Despite the fact that similar observations of the Rabi splitting in
many-particle systems have been described as a quantum-mechanical effect, we
show that the observed splitting can be explained completely by a model based
on the classical electrodynamics.


title:
A Sufficient Condition of Having Independent TE and TM Modes in a
  Waveguide Filled with Homogenous Anisotropic Lossless Medium

abstract:
  Based on the idea of the Abelian group theory in mathematics,this paper finds
a sufficient condition of having independent TE and TM modes in a waveguide
filled with homogenous anisotropic lossless medium. For independent TE modes,
we prove the nonzero cut-off wavenumbers obtained from longitudinal scalar
magnetic field stimulation and transverse vector electric field stimulation are
same in theory. For independent TM modes, we also prove the nonzero cut-off
wavenumbers obtained from longitudinal scalar electric field stimulation and
transverse vector magnetic field stimulation are same in theory. Finally we
carry out several numerical experiments to verify the correctness of the
condition given by us.We hope that this condition is useful for the designs of
waveguide with homogenous anisotropic lossless medium in microwave engineering
community.


title:
Robust band gap and half-metallicity in graphene with triangular
  perforations

abstract:
  Ideal graphene antidot lattices are predicted to show promising band gap
behavior (i.e., $E_G\simeq 500$ meV) under carefully specified conditions.
However, for the structures studied so far this behavior is critically
dependent on superlattice geometry and is not robust against experimentally
realistic disorders. Here we study a rectangular array of triangular antidots
with zigzag edge geometries and show that their band gap behavior qualitatively
differs from the standard behavior which is exhibited, e.g, by rectangular
arrays of armchair-edged triangles. In the spin unpolarized case, zigzag-edged
antidots give rise to large band gaps compared to armchair-edged antidots,
irrespective of the rules which govern the existence of gaps in armchair-edged
antidot lattices. In addition the zigzag-edged antidots appear more robust than
armchair-edged antidots in the presence of geometrical disorder. The inclusion
of spin polarization within a mean-field Hubbard approach gives rise to a large
overall magnetic moment at each antidot due to the sublattice imbalance imposed
by the triangular geometry. Half-metallic behavior arises from the formation of
spin-split dispersive states near the Fermi energy, reducing the band gaps
compared to the unpolarized case. This behavior is also found to be robust in
the presence of disorder. Our results highlight the possibilities of using
triangular perforations in graphene to open electronic band gaps in systems
with experimentally realistic levels of disorder, and furthermore, of
exploiting the strong spin dependence of the system for spintronic
applications.


title: Which small reaction networks are multistationary?

abstract:
  Reaction networks taken with mass-action kinetics arise in many settings,
from epidemiology to population biology to systems of chemical reactions.
Bistable reaction networks are posited to underlie biochemical switches, which
motivates the following question: which reaction networks have the capacity for
multiple steady states? Mathematically, this asks: among certain parametrized
families of polynomial systems, which admit multiple positive roots? No
complete answer is known. This work analyzes the smallest networks, those with
only a few chemical species or reactions. For these "smallest" networks, we
completely answer the question of multistationarity and, in some cases,
multistability too, thereby extending related work of Boros. Our results
highlight the role played by the Newton polytope of a network (the convex hull
of the reactant vectors). Also, our work is motivated by recent results that
explain how a given network's capacity for multistationarity arises from that
of certain related networks which are typically smaller. Hence, we are
interested in classifying small multistationary networks, and our work forms a
first step in this direction.


title: Discrete time Dirac quantum walk in 3+1 dimensions

abstract:
  In this paper we consider quantum walks whose evolution converges to the
Dirac equation one in the limit of small wave-vectors. We show exact Fast
Fourier implementation of the Dirac quantum walks in one, two and three space
dimensions. The behaviour of particle states, defined as states smoothly peaked
in some wave-vector eigenstate of the walk, is described by an approximated
dispersive differential equation that for small wave-vectors gives the usual
Dirac particle and antiparticle kinematics. The accuracy of the approximation
is provided in terms of a lower bound on the fidelity between the exactly
evolved state and the approximated one. The jittering of the position operator
expectation value for states having both a particle and an antiparticle
component is analytically derived and observed in the numerical
implementations.


title:
A Scalable and Distributed Solution to the Inertial Motion Capture
  Problem

abstract:
  In inertial motion capture, a multitude of body segments are equipped with
inertial sensors, consisting of 3D accelerometers and 3D gyroscopes. Using an
optimization-based approach to solve the motion capture problem allows for
natural inclusion of biomechanical constraints and for modeling the connection
of the body segments at the joint locations. The computational complexity of
solving this problem grows both with the length of the data set and with the
number of sensors and body segments considered. In this work, we present a
scalable and distributed solution to this problem using tailored message
passing, capable of exploiting the structure that is inherent in the problem.
As a proof-of-concept we apply our algorithm to data from a lower body
configuration.


title: On the sign patterns of the coefficients of Hilbert polynomials

abstract:
  We show that all sign patterns of the coefficients Hilbert polynomials of
standard graded $k$-algebras are possible.


title:
Boundary concentration phenomena for the higher-dimensional Keller-Segel
  system

abstract:
  We study the existence of steady states to the Keller-Segel system with
linear chemotactical sensitivity function on a smooth bounded domain in
$\mathbb R^N,$ $N\ge3,$ having rotational symmetry. We find three different
types of chemoattractant concentration which concentrate along suitable
$(N-2)-$dimensional minimal submanifolds of the boundary. The corresponding
density of the cellular slime molds exhibit in the limit one or more Dirac
measures supported on those boundary submanifolds.


title:
Eulerian Methods for Visualizing Continuous Dynamical Systems using
  Lyapunov Exponents

abstract:
  We propose a new Eulerian numerical approach for constructing the forward
flow maps in continuous dynamical systems. The new algorithm improves the
original formulation developed in [23, 24] so that the associated partial
differential equations (PDEs) are solved forward in time and, therefore, the
forward flow map can now be determined on the fly. Due to the simplicity in the
implementations, we are now able to efficiently compute the unstable coherent
structures in the flow based on quantities like the finite time Lyapunov
exponent (FTLE), the finite size Lyapunov exponent (FSLE) and also a related
infinitesimal size Lyapunov exponent (ISLE). When applied to the ISLE
computations, the Eulerian method is in particularly computationally efficient.
For each separation factor r in the definition of the ISLE, typical Lagrangian
methods require to shoot and monitor an individual set of ray trajectories. If
the scale factor in the definition is changed, these methods have to restart
the whole computations all over again. The proposed Eulerian method, however,
requires to extract only an isosurface of a volumetric data for an individual
value of r which can be easily done using any well-developed efficient
interpolation method or simply an isosurface extraction algorithm. Moreover, we
provide a theoretical link between the FTLE and the ISLE fields which explains
the similarity in these solutions observed in various applications.


title:
On thresholdless lasing features in high-$\beta$ nitride nanobeam
  cavities: a quantum optical study

abstract:
  Exploring the limits of spontaneous emission coupling is not only one of the
central goals in the development of nanolasers, it is also highly relevant
regarding future large-scale photonic integration requiring energy-efficient
coherent light sources with a small footprint. These studies are accompanied by
a vivid debate on how to prove and interpret lasing in the high-$\beta$ regime.
We investigate close-to-ideal spontaneous emission coupling in GaN nanobeam
lasers grown on silicon. Due to their high optical quality, such nanobeam
cavities allow for efficient funneling of spontaneous emission from the quantum
well gain material into the laser mode. By performing a comprehensive optical
and quantum-optical characterization, supported by microscopic modeling of the
nanolasers, we identify high-$\beta$ lasing at room temperature and show a
lasing transition in the absence of a threshold nonlinearity at 156 K. This
peculiar characteristic is explained in terms of a temperature and excitation
power dependent interplay between 0D and 2D gain contributions.


title:
Impact of ex-situ rapid thermal annealing on the magneto-optical
  properties and the oscillator strength of In(Ga)As quantum dots

abstract:
  We discuss the influence of a rapid thermal annealing step on the
magneto-optical emission properties of In(Ga)As/GaAs quantum dots. We map out a
strong influence of the growth- and anneling parameters on the quantum
excitons' effective Land\'e g-factors and in particular on their diamagnetic
coefficients, which we directly correlate with the modification of the emitters
shape and material composition. In addition, we study the excitons' spontaneous
emission lifetime as a function of the annealing temperature and the dot
height, and observe a strong increase of the emission rate with the quantum dot
volume. The corresponding increase in oscillator strenth yields fully
consistent results with the analysis of the diamagenic behavior. In particular,
we demonstrate that a rapid thermal annealing step of 850$^\circ$ C can be
employed to increase the oscillator strength of as-grown InAs/GaAs QDs by more
than a factor of $2$.


title:
Feasibility Studies of the Diffractive Bremsstrahlung Measurement at the
  LHC

abstract:
  Feasibility studies of an observation of the exclusive diffractive
bremsstrahlung in proton-proton scattering at the LHC are reported. A
simplified approach to the photon and the scattered proton energy
reconstruction is used. The background influence is discussed.


title:
Local and doubly empirical convergence and the entropy of algebraic
  actions of sofic Groups

abstract:
  Let G be a sofic group and X a compact group that G acts on by automorphisms.
Using (and reformulating) the notion of doubly-quenched convergence developed
by Austin, we show that in many cases the topological and the measure-theoretic
entropy with respect to the Haar measure of this action agree. Our method of
proof recovers all known examples. Moreover, the proofs are direct and do not
go through explicitly computing the measure-theoretic or topological entropy.


title:
Ferrimagnetic ordering and spin entropy of field-dependent intermediate
  spins in Na0.82CoO2

abstract:
  The peculiar field-dependent magnetism of Na0.82CoO2 has been investigated
through an analysis of its DC and AC spin susceptibilities. To account for the
easily activated narrow b2g-a1g gap of the crystal field for Co in the cobalt
oxide layer, the spin-state transition of Co3+ (3d6) between the low spin (LS)
state b2g^2-a1g^0 of S=0 and the intermediate spin (IS) state b2g^1-a1g^1 of
S=1 is thus seen as thermally activated and exhibits a Boltzmann distribution.
The IS state of Co3+ within each sqrt(13a) hexagonal superlattice formed by the
S=1/2 state of the Co4+ ions appears randomly within each supercell and shows
significant temperature and field dependence. The magnetic field is found to
assist in pinning down the thermally activated state of Co3+ and swings the
Boltzmann distribution weight toward a higher fraction of the IS state. The
field dependence of the in-plane magnetic moment from the added number of S=1
spins is used to explain the origin of A-type antiferromagnetic (AF) ordering,
particularly that the ferromagnetic (FM)-like behavior below TN at low field is
actually a ferrimagnetic IS spin ordering of Co3+.


title:
Quench dynamics and relaxation in isolated integrable quantum spin
  chains

abstract:
  We review the dynamics after quantum quenches in integrable quantum spin
chains. We give a pedagogical introduction to relaxation in isolated quantum
systems, and discuss the description of the steady state by (gen- eralized)
Gibbs ensembles. When then turn to general features in the time evolution of
local observables after the quench, using a simple model of free fermions as an
example. In the second part we present an overview of recent progress in
describing quench dynamics in two key paradigms for quantum integrable models,
the transverse field Ising chain and the anisotropic spin-1/2 Heisenberg chain.


title: Mandelstam-Leibbrandt prescription

abstract:
  The light cone gauge is used frequently in string theory as well as gauge
theories and gravitation. Loop integrals however have to be infrared regulated
to remove spurious poles. The most popular and consistent of these infrared
regulators is the Mandelstam-Leibbrandt(ML) prescription. The calculations with
ML are rather cumbersome, though. In this work we show that the ML can be
replaced by a symmetry of the regulator. This symmetry simplify the
calculations, reducing them to conventional dimensional regularization
integrals.


title:
van der Waals Heterostructures of Germanene, Stanene and Silicene with
  Hexagonal Boron Nitride and Their Topological Domain Walls

abstract:
  We investigate van der Waals (vdW) heterostructures made of germanene,
stanene or silicene with hexagonal Boron Nitride (h-BN). The intriguing
topological properties of these buckled honeycomb materials can be maintained
and further engineered in the heterostructures, where the competition between
the substrate effect and external electric fields can be used to control the
tunable topological phase transitions. Using such heterostructures as building
blocks, various vdW topological domain walls (DW) are designed, along which
there exist valley polarized quantum spin Hall edge states or
valley-contrasting edge states which are protected by valley(spin)- resolved
topological charges and can be tailored by the patterning of the
heterojunctions and by external fields.


title: Online estimation of driving events and fatigue damage on vehicles

abstract:
  Driving events, such as maneuvers at slow speed and turns, are important for
durability assessments of vehicle components. By counting the number of driving
events, one can estimate the fatigue damage caused by the same kind of events.
Through knowledge of the distribution of driving events for a group of
customers, the vehicles producers can tailor the design, of vehicles, for the
group. In this article, we propose an algorithm that can be applied on-board a
vehicle to online estimate the expected number of driving events occurring, and
thus be used to estimate the distribution of driving events for a certain group
of customers. Since the driving events are not observed directly, the algorithm
uses a hidden Markov model to extract the events. The parameters of the HMM are
estimated using an online EM algorithm. The introduction of the online EM is
crucial for practical usage, on-board vehicles, due to that its complexity of
an iteration is fixed. Typically, the EM algorithm is used to find the, fixed,
parameters that maximizes the likelihood. By introducing a fixed forgetting
factor in the online EM, an adaptive algorithm is acquired. This is important
in practice since the driving conditions changes over time and a single trip
can contain different road types such as city and highway, making the
assumption of fixed parameters unrealistic. Finally, we also derive a method to
online compute the expected damage.


title:
Large scale flow visualization and anemometry applied to lab on chip
  models of porous media

abstract:
  The following is a report on an experimental technique allowing to quantify
and map the velocity field with a very high resolution and a simple equipment
in large 2D devices. A simple Shlieren technique is proposed to reinforce the
contrast in the images and allow you to detect seeded particles that are
pixel-sized or even inferior to it. The velocimetry technique that we have
reported on is based on auto-correlation functions of the pixel intensity,
which we have shown are directly related to the magnitude of the local average
velocity. The characteristic time involved in the decorrelation of the signal
is proportional to the tracer size and inversely proportional to the average
velocity. We have reported on a detailed discussion about the optimization of
relevant involved parameters, the spatial resolution and the accuracy of the
method. The technique is then applied to a model porous media made of a random
channel network. We show that it is highly efficient to determine the magnitude
of the flow in each of the channels of the network, opening the road to the
fundamental study of the flows of complex fluids. The latter is illustrated
with yield stress fluid, in which the flow becomes highly heterogeneous at
small flow rates.


title:
From plane waves to local Gaussians for the simulation of correlated
  periodic systems

abstract:
  We present a simple, robust and black-box approach to the implementation and
use of local, periodic, atom-centered Gaussian basis functions within a plane
wave code, in a computationally efficient manner. The procedure outlined is
based on the representation of the Gaussians within a finite bandwidth by their
underlying plane wave coefficients. The core region is handled within the
projected augment wave framework, by pseudizing the Gaussian functions within a
cut-off radius around each nucleus, smoothing the functions so that they are
faithfully represented by a plane wave basis with only moderate kinetic energy
cutoff. To mitigate the effects of the basis set superposition error and
incompleteness at the mean-field level introduced by the Gaussian basis, we
also propose a hybrid approach, whereby the complete occupied space is first
converged within a large plane wave basis, and the Gaussian basis used to
construct a complementary virtual space for the application of correlated
methods. We demonstrate that these pseudized Gaussians yield compact and
systematically improvable spaces with an accuracy comparable to their
non-pseudized Gaussian counterparts. A key advantage of the described method is
its ability to efficiently capture and describe electronic correlation effects
of weakly bound and low-dimensional systems, where plane waves are not
sufficiently compact or able to be truncated without unphysical artefacts. We
investigate the accuracy of the pseudized Gaussians for the water dimer
interaction, neon solid and water adsorption on a LiH surface, at the level of
second-order M\{o}ller--Plesset perturbation theory.


title: Numerical methods for the sign problem in Lattice Field Theory

abstract:
  The great majority of algorithms employed in the study of lattice field
theory are based on Monte Carlo's importance sampling method, i.e. on
probability interpretation of the Boltzmann weight. Unfortunately in many
theories of interest one cannot associated a real and positive weight to every
configuration, that is because their action is explicitly complex or because
the weight is multiplied by some non positive term. In this cases one says that
the theory on the lattice is affected by the sign problem. An outstanding
example of sign problem preventing a quantum field theory to be studied, is QCD
at finite chemical potential. Whenever the sign problem is present, standard
Monte Carlo methods are problematic to apply and, in general, new approaches
are needed to explore the phase diagram of the complex theory. Here we will
review three of the main candidate methods to deal with the sign problem,
namely complex Langevin dynamics, Lefschetz thimbles and density of states
method. We will first study complex Langevin dynamics, combined with the gauge
cooling method, on the one-dimensional Polyakov line model, and then we will
apply it to pure gauge Yang-Mills theory with a topological theta-term. It
follows a comparison between complex Langevin dynamics and the Lefschetz
thimbles method on three toy models, which are the quartic model, the U(1)
one-link model with a mu dependent determinant, and the SU(2) non abelian
one-link model with complex beta parameter. Lastly, we introduce the density of
state method, based on the LLR algorithm, and we will employ it in the study of
the relativistic Bose gas at finite chemical potential.


title:
Characterization of neighborhood behaviours in a multi-neighborhood
  local search algorithm

abstract:
  We consider a multi-neighborhood local search algorithm with a large number
of possible neighborhoods. Each neighborhood is accompanied by a weight value
which represents the probability of being chosen at each iteration. These
weights are fixed before the algorithm runs, and are considered as parameters
of the algorithm. Given a set of instances, off-line tuning of the algorithm's
parameters can be done by automated algorithm configuration tools (e.g., SMAC).
However, the large number of neighborhoods can make the tuning expensive and
difficult even when the number of parameters has been reduced by some
intuition. In this work, we propose a systematic method to characterize each
neighborhood's behaviours, representing them as a feature vector, and using
cluster analysis to form similar groups of neighborhoods. The novelty of our
characterization method is the ability of reflecting changes of behaviours
according to hardness of different solution quality regions. We show that using
neighborhood clusters instead of individual neighborhoods helps to reduce the
parameter configuration space without misleading the search of the tuning
procedure. Moreover, this method is problem-independent and potentially can be
applied in similar contexts.


title: Right Amenable Left Group Sets and the Tarski-F{\o}lner Theorem

abstract:
  We introduce right amenability, right F{\o}lner nets, and right paradoxical
decompositions for left homogeneous spaces and prove the Tarski-F{\o}lner
theorem for left homogeneous spaces with finite stabilisers. It states that
right amenability, the existence of right F{\o}lner nets, and the non-existence
of right paradoxical decompositions are equivalent.


title:
Remote Antenna Unit Selection Assisted Seamless Handover for High-Speed
  Railway Communications with Distributed Antennas

abstract:
  To attain seamless handover and reduce the han- dover failure probability for
high-speed railway (HSR) com- munication systems, this paper proposes a remote
antenna unit (RAU) selection assisted handover scheme where two antennas are
installed on high speed train (HST) and distributed antenna system (DAS) cell
architecture on ground is adopted. The RAU selection is used to provide high
quality received signals for trains moving in DAS cells and the two HST
antennas are employed on trains to realize seamless handover. Moreover, to
efficiently evaluate the system performance, a new met- ric termed as handover
occurrence probability is defined for describing the relation between handover
occurrence position and handover failure probability. We then analyze the
received signal strength, the handover trigger probability, the handover
occurrence probability, the handover failure probability and the communication
interruption probability. Numerical results are provided to compare our
proposed scheme with the current existing ones. It is shown that our proposed
scheme achieves better performances in terms of handover failure probability
and communication interruption probability.


title: Marginalized Bayesian filtering with Gaussian priors and posteriors

abstract:
  Marginalization techniques are presented for the Bayesian filtering problem
under the assumption of Gaussian priors and posteriors and a set of
sequentially more constraining state space model assumptions. The techniques
provide the capabilities to 1) reduce the filtering problem to essential
marginal moment integrals, 2) combine model and numerical approximations to the
moment integrals, and 3) decouple modelling and system composition. Closed-form
expressions of the posterior means and covariances are developed as functions
of subspace projection matrices, subsystem models, and the marginal moment
integrals. Finally, we review prior work and how the results relate to Kalman
and marginalized particle filtering techniques.


title:
Controlling Explanatory Heatmap Resolution and Semantics via
  Decomposition Depth

abstract:
  We present an application of the Layer-wise Relevance Propagation (LRP)
algorithm to state of the art deep convolutional neural networks and Fisher
Vector classifiers to compare the image perception and prediction strategies of
both classifiers with the use of visualized heatmaps. Layer-wise Relevance
Propagation (LRP) is a method to compute scores for individual components of an
input image, denoting their contribution to the prediction of the classifier
for one particular test point. We demonstrate the impact of different choices
of decomposition cut-off points during the LRP-process, controlling the
resolution and semantics of the heatmap on test images from the PASCAL VOC 2007
test data set.


title: Character density in central subalgebras of compact quantum groups

abstract:
  We investigate quantum group generalizations of various density results from
Fourier analysis on compact groups. In particular, we establish the density of
characters in the space of fixed points of the conjugation action on
$L^2(\mathbb{G})$, and use this result to show the weak* density and norm
density of characters in $ZL^{\infty}(\mathbb{G})$ and $ZC(\mathbb{G})$,
respectively. As a corollary, we partially answer an open question of
Woronowicz. At the level of $L^1(\mathbb{G})$, we show that the center
$\mathcal{Z}(L^1(\mathbb{G}))$ is precisely the closed linear span of the
quantum characters for a large class of compact quantum groups, including
arbitrary compact Kac algebras. In the latter setting, we show, in addition,
that $\mathcal{Z}(L^1(\mathbb{G}))$ is a completely complemented
$\mathcal{Z}(L^1(\mathbb{G}))$-submodule of $L^1(\mathbb{G})$.


title:
On noise-induced synchronization and consensus of nonlinear network
  systems under input disturbances

abstract:
  This paper is concerned with the study of synchronization and consensus
phenomena in complex networks of diffusively-coupled nodes subject to external
disturbances. Specifically, we make use of stochastic Lyapunov functions to
provide conditions for synchronization and consensus for networks of nonlinear,
diffusively coupled nodes, where noise diffusion is not just additive but it
depends on the nodes' state. The sufficient condition we provide, wich links
together network topology, coupling strength and noise diffusion, offers two
interesting interpretations. First, as suggested by {\em intuition}, in order
for a network to achieve synchronization/consensus, its nodes need to be
sufficiently well connected together. The second implication might seem,
instead, counter-intuitive: if noise diffusion is {\em properly} designed, then
it can drive an unsynchronized network towards synchronization/consensus.
Motivated by our current research in Smart Cities and Internet of Things, we
illustrate the effectiveness of our approach by showing how our results can be
used to control certain collective decision processes.


title:
Development and prospect of Very Small Angle Neutron Scattering (VSANS)
  Techniques

abstract:
  Very Small Angle Neutron Scattering (VSANS) is an upgrade of the traditional
Small Angle Neutron Scattering (SANS) technique which can cover three orders of
magnitude of length scale from one nanometer to one micrometer. It is a
powerful tool for structure calibration in polymer science, biology, material
science and condensed matter physics. Since the first VSANS instrument, D11 in
Grenoble, was built in 1972, new collimation techniques, focusing optics
(multi-beam converging apertures, material or magnetic lenses, and focusing
mirrors) and higher resolution detectors combined with the long flight paths
and long incident neutron wavelengths have been developed. In this paper, a
detailed review is given of the development, principles and application
conditions of various VSANS techniques. Then, beam current gain factors are
calculated to evaluate those techniques. A VSANS design for the China
Spallation Neutron Source (CSNS) is thereby presented.


title:
Continuum limit of the $D$ meson, $D_s$ meson and charmonium spectrum
  from $N_f=2+1+1$ twisted mass lattice QCD

abstract:
  We compute masses of $D$ meson, $D_s$ meson and charmonium states using
$N_f=2+1+1$ Wilson twisted mass lattice QCD. All results are extrapolated to
physical light quark masses, physical strange and charm quark masses and to the
continuum. Our analysis includes states with spin $J = 0,1,2$, parity
$\mathcal{P} = -,+$ and in case of charmonium also charge conjugation
$\mathcal{C} = -,+$. Computations are based on a large set of quark-antiquark
meson creation operators. We investigate and quantify all sources of systematic
errors, including fitting range uncertainties, finite volume effects, isospin
breaking effects and the choice of the fitting ansatz for the combined chiral
and continuum extrapolation such that the resulting meson masses can be
compared directly and in a meaningful way to experimental results. Within
combined statistical and systematic errors, which are between below two per
mille and three percent, our results agree with available experimental results
for most of the states. In the few cases where we observe discrepancies, we
discuss possible reasons.


title:
Modeling and Optimal Operation of Distributed Battery Storage in Low
  Voltage Grids

abstract:
  Due to high power in-feed from photovoltaics, it can be expected that more
battery systems will be installed in the distribution grid in near future to
mitigate voltage violations and thermal line and transformer overloading. In
this paper, we present a two-stage centralized model predictive control scheme
for distributed battery storage that consists of a scheduling entity and a
real-time control entity. To guarantee secure grid operation, we solve a robust
multi-period optimal power flow (OPF) for the scheduling stage that minimizes
battery degradation and maximizes photovoltaic utilization subject to grid
constraints. The real-time controller solves a real-time OPF taking into
account storage allocation profiles from the scheduler, a detailed battery
model, and real-time measurements. To reduce the computational complexity of
the controllers, we present a linearized OPF that approximates the nonlinear
AC-OPF into a linear programming problem. Through a case study, we show, for
two different battery technologies, that we can substantially reduce battery
degradation when we incorporate a battery degradation model. A further finding
is that we can reduce battery losses by 30% by using the detailed battery model
in the real-time control stage.


title: Cyclic uniform 2-factorizations of the complete multipartite graph

abstract:
  The generalization of the Oberwolfach Problem, proposed by J. Liu in 2000,
asks for a uniform $2$-factorization of the complete multipartite graph
$K_{m\times n}$. Here we focus our attention on $2$-factorizations regular
under the cyclic group $Z_{mn}$, whose $2$-factors are disjoint union of cycles
all of even length $\ell$. In particular, we present a complete solution for
the extremal cases $\ell=4$ and $\ell=mn$.


title: Frankenstein: Learning Deep Face Representations using Small Data

abstract:
  Deep convolutional neural networks have recently proven extremely effective
for difficult face recognition problems in uncontrolled settings. To train such
networks, very large training sets are needed with millions of labeled images.
For some applications, such as near-infrared (NIR) face recognition, such large
training datasets are not publicly available and difficult to collect. In this
work, we propose a method to generate very large training datasets of synthetic
images by compositing real face images in a given dataset. We show that this
method enables to learn models from as few as 10,000 training images, which
perform on par with models trained from 500,000 images. Using our approach we
also obtain state-of-the-art results on the CASIA NIR-VIS2.0 heterogeneous face
recognition dataset.


title:
Rashba semiconductor as spin Hall material: Experimental demonstration
  of spin pumping in wurtzite $n$-GaN:Si

abstract:
  Pure spin currents in semiconductors are essential for implementation in the
next generation of spintronic elements. Heterostructures of III- nitride
semiconductors are currently employed as central building-blocks for lighting
and high-power devices. Moreover, the long relaxation times and the spin-orbit
coupling (SOC) in these materials indicate them as privileged hosts for spin
currents and related phenomena. Spin pumping is an efficient mechanism for the
inception of spin current and its conversion into charge current in
non-magnetic metals and semiconductors with Rashba SOC $via$ spin Hall effects.
We report on the generation in $n$-GaN:Si\,--\,at room temperature and through
spin pumping\,--\,of pure spin current, fundamental for the understanding of
the spin dynamics in these non-centrosymmetric Rashba systems. We find for
$n$-GaN:Si a spin Hall angle $\theta_{\mathrm{SH}}$=$3.03\times10^{-3}$,
exceeding by one order of magnitude those reported for other semiconductors,
pointing at III-nitrides as particularly efficient spin current generators.


title: Programmable atom-photon quantum interface

abstract:
  We present the implementation of a programmable atom-photon quantum
interface, employing a single trapped $^{40}$Ca$^+$ ion and single photons.
Depending on its mode of operation, the interface serves as a bi-directional
atom-photon quantum-state converter, as a source of entangled atom-photon
states, or as a quantum frequency converter of single photons. The interface
lends itself particularly to interfacing ions with single or entangled photons
in hybrid quantum networks.


title:
Singular ferromagnetic susceptibility of the transverse-field Ising
  antiferromagnet on the triangular lattice

abstract:
  A transverse magnetic field $\Gamma$ is known to induce antiferromagnetic
three-sublattice order of the Ising spins $\sigma^z$ in the triangular lattice
Ising antiferromagnet at low enough temperature. This low-temperature order is
known to melt on heating in a two-step manner, with a power-law ordered
intermediate temperature phase characterized by power-law correlations at the
three-sublattice wavevector ${\bf Q}$: $\langle \sigma^z(\vec{R})
\sigma^z(0)\rangle \sim \cos({\mathbf Q}\cdot \vec{R}) /|\vec{R}|^{\eta(T)}$
with the temperature-dependent power-law exponent $\eta(T) \in (1/9,1/4)$.
  Here, we use a newly developed quantum cluster algorithm to study the {\em
ferromagnetic} easy-axis susceptibility $\chi_{u}(L)$ of an $L \times L$ sample
in this power-law ordered phase. Our numerical results are consistent with a
recent prediction of a singular $L$ dependence $\chi_{u}(L)\sim L^{2- 9 \eta}$
when $\eta(T)$ is in the range $(1/9,2/9)$. This finite-size result implies,
via standard scaling arguments, that the ferromagnetic susceptibility
$\chi_{u}(B)$ to a uniform field $B$ along the easy axis is singular at
intermediate temperatures in the small $B$ limit, $\chi_{u}(B) \sim
|B|^{-\frac{4 - 18 \eta}{4-9\eta}}$ for $\eta(T) \in (1/9, 2/9)$, although
there is no ferromagnetic long-range order in the low temperature state.


title:
Robert Dicke and the naissance of experimental gravity physics,
  1957-1967

abstract:
  The experimental study of gravity became much more active in the late 1950s,
a change pronounced enough be termed the birth, or naissance, of experimental
gravity physics. I present a review of developments in this subject since 1915,
through the broad range of new approaches that commenced in the late 1950s, and
up to the transition of experimental gravity physics to what might be termed a
normal and accepted part of physical science in the late 1960s. This review
shows the importance of advances in technology, here as in all branches of
natural science. The role of contingency is illustrated by Robert Dicke's
decision in the mid-1950s to change directions in mid-career, to lead a
research group dedicated to the experimental study of gravity. The review also
shows the power of nonempirical evidence. Some in the 1950s felt that general
relativity theory is so logically sound as to be scarcely worth the testing.
But Dicke and others argued that a poorly tested theory is only that, and that
other nonempirical arguments, based on Mach's Principle and Dirac's Large
Numbers hypothesis, suggested it would be worth looking for a better theory of
gravity. I conclude by offering lessons from this history, some peculiar to the
study of gravity physics during the naissance, some of more general relevance.
The central lesson, which is familiar but not always well advertised, is that
physical theories can be empirically established, sometimes with surprising
results.


title:
Diffuse-Interface Two-Phase Flow Models with Different Densities: A New
  Quasi-Incompressible Form and a Linear Energy-Stable Method

abstract:
  While various phase-field models have recently appeared for two-phase fluids
with different densities, only some are known to be thermodynamically
consistent, and practical stable schemes for their numerical simulation are
lacking. In this paper, we derive a new form of thermodynamically-consistent
quasi-incompressible diffuse-interface Navier-Stokes Cahn-Hilliard model for a
two-phase flow of incompressible fluids with different densities. The
derivation is based on mixture theory by invoking the second law of
thermodynamics and Coleman-Noll procedure. We also demonstrate that our model
and some of the existing models are equivalent and we provide a unification
between them. In addition, we develop a linear and energy-stable
time-integration scheme for the derived model. Such a linearly-implicit scheme
is nontrivial, because it has to suitably deal with all nonlinear terms, in
particular those involving the density. Our proposed scheme is the first linear
method for quasi-incompressible two-phase flows with nonsolenoidal velocity
that satisfies discrete energy dissipation independent of the time-step size,
provided that the mixture density remains positive. The scheme also preserves
mass. Numerical experiments verify the suitability of the scheme for two-phase
flow applications with high density ratios using large time steps by
considering the coalescence and break-up dynamics of droplets including
pinching due to gravity.


title:
Dynamic Prediction for Multiple Repeated Measures and Event Time Data:
  An Application to Parkinson's Disease

abstract:
  In many clinical trials studying neurodegenerative diseases such as
Parkinson's disease (PD), multiple longitudinal outcomes are collected to fully
explore the multidimensional impairment caused by this disease. If the outcomes
deteriorate rapidly, patients may reach a level of functional disability
sufficient to initiate levodopa therapy for ameliorating disease symptoms. An
accurate prediction of the time to functional disability is helpful for
clinicians to monitor patients' disease progression and make informative
medical decisions. In this article, we first propose a joint model that
consists of a semiparametric multilevel latent trait model (MLLTM) for the
multiple longitudinal outcomes, and a survival model for event time. The two
submodels are linked together by an underlying latent variable. We develop a
Bayesian approach for parameter estimation and a dynamic prediction framework
for predicting target patients' future outcome trajectories and risk of a
survival event, based on their multivariate longitudinal measurements. Our
proposed model is evaluated by simulation studies and is applied to the DATATOP
study, a motivating clinical trial assessing the effect of deprenyl among
patients with early PD.


title:
Generalized rank weights of reducible codes, optimal cases and related
  properties

abstract:
  Reducible codes for the rank metric were introduced for cryptographic
purposes. They have fast encoding and decoding algorithms, include maximum rank
distance (MRD) codes and can correct many rank errors beyond half of their
minimum rank distance, which makes them suitable for error-correction in
network coding. In this paper, we study their security behaviour against
information leakage on networks when applied as coset coding schemes, giving
the following main results: 1) we give lower and upper bounds on their
generalized rank weights (GRWs), which measure worst-case information leakage
to the wire-tapper, 2) we find new parameters for which these codes are MRD
(meaning that their first GRW is optimal), and use the previous bounds to
estimate their higher GRWs, 3) we show that all linear (over the extension
field) codes whose GRWs are all optimal for fixed packet and code sizes but
varying length are reducible codes up to rank equivalence, and 4) we show that
the information leaked to a wire-tapper when using reducible codes is often
much less than the worst case given by their (optimal in some cases) GRWs. We
conclude with some secondary related properties: Conditions to be rank
equivalent to cartesian products of linear codes, conditions to be rank
degenerate, duality properties and MRD ranks.


title: Hard-Clustering with Gaussian Mixture Models

abstract:
  Training the parameters of statistical models to describe a given data set is
a central task in the field of data mining and machine learning. A very popular
and powerful way of parameter estimation is the method of maximum likelihood
estimation (MLE). Among the most widely used families of statistical models are
mixture models, especially, mixtures of Gaussian distributions. A popular
hard-clustering variant of the MLE problem is the so-called complete-data
maximum likelihood estimation (CMLE) method. The standard approach to solve the
CMLE problem is the Classification-Expectation-Maximization (CEM) algorithm.
Unfortunately, it is only guaranteed that the algorithm converges to some
(possibly arbitrarily poor) stationary point of the objective function.
  In this paper, we present two algorithms for a restricted version of the CMLE
problem. That is, our algorithms approximate reasonable solutions to the CMLE
problem which satisfy certain natural properties. Moreover, they compute
solutions whose cost (i.e. complete-data log-likelihood values) are at most a
factor $(1+\epsilon)$ worse than the cost of the solutions that we search for.
Note the CMLE problem in its most general, i.e. unrestricted, form is not well
defined and allows for trivial optimal solutions that can be thought of as
degenerated solutions.


title:
Positive clusters for smooth perturbations of a critical elliptic
  equation in dimensions four and five

abstract:
  We construct clustering positive solutions for a perturbed critical elliptic
equation on a closed manifold of dimension $n=4,5$. Such a construction is
already available in the literature in dimensions $n\ge 6$ (see for instance
[8,12,27,29,33]) and not possible in dimension $3$ by [25]. This also provides
new patterns for the Lin--Ni [21] problem on closed manifolds and completes
results by Br\'ezis and Li [6] about this problem.


title: Spatial discretizations of generic dynamical systems

abstract:
  How is it possible to read the dynamical properties (ie when the time goes to
infinity) of a system on numerical simulations? To try to answer this question,
we study in this manuscript a model reflecting what happens when the orbits of
a discrete time system $f$ (for example an homeomorphism) are computed
numerically . The computer working in finite numerical precision, it will
replace $f$ by a spacial discretization of $f$, denoted by $f_N$ (where the
order $N$ of discretization stands for the numerical accuracy). In particular,
we will be interested in the dynamical behaviour of the finite maps $f_N$ for a
generic system $f$ and $N$ going to infinity, where generic will be taken in
the sense of Baire (mainly among sets of homeomorphisms or
$C^1$-diffeomorphisms).
  The first part of this manuscript is devoted to the study of the dynamics of
the discretizations $f_N$, when $f$ is a generic conservative/dissipative
homeomorphism of a compact manifold. We show that it would be mistaken to try
to recover the dynamics of $f$ from that of a single discretization $f_N$ : its
dynamics strongly depends on the order $N$. To detect some dynamical features
of $f$, we have to consider all the discretizations $f_N$ when $N$ goes through
$\mathbf N$.
  The second part deals with the linear case, which plays an important role in
the study of $C^1$-generic diffeomorphisms, discussed in the third part of this
manuscript. Under these assumptions, we obtain results similar to those
established in the first part, though weaker and harder to prove.


title:
Lensing convergence and the neutrino mass scale in galaxy redshift
  surveys

abstract:
  We demonstrate the importance of including the lensing contribution in galaxy
clustering analyses with large galaxy redshift surveys. It is well known that
radial cross-correlations between different redshift bins of galaxy surveys are
dominated by lensing. But we show here that also neglecting lensing in the
autocorrelations within one bin severely biases cosmological parameter
estimation with redshift surveys. It leads to significant shifts for several
cosmological parameters, most notably the scalar spectral index and the
neutrino mass scale. Especially the latter parameter is one of the main targets
of future galaxy surveys.


title: Spectroscopic evidence for type II Weyl semimetal state in MoTe2

abstract:
  In a type I Dirac or Weyl semimetal, the low energy states are squeezed to a
single point in momentum space when the chemical potential Ef is tuned
precisely to the Dirac/Weyl point. Recently, a type II Weyl semimetal was
predicted to exist, where the Weyl states connect hole and electron bands,
separated by an indirect gap. This leads to unusual energy states, where hole
and electron pockets touch at the Weyl point. Here we present the discovery of
a type II topological Weyl semimetal (TWS) state in pure MoTe2, where two sets
of WPs (W2+-, W3+-) exist at the touching points of electron and hole pockets
and are located at different binding energies above Ef. Using ARPES, modeling,
DFT and calculations of Berry curvature, we identify the Weyl points and
demonstrate that they are connected by different sets of Fermi arcs for each of
the two surface terminations. We also find new surface "track states" that form
closed loops and are unique to type II Weyl semimetals. This material provides
an exciting, new platform to study the properties of Weyl fermions.


title: Qualitative stability of nonlinear networked systems

abstract:
  In many large systems, such as those encountered in biology or economics, the
dynamics are nonlinear and are only known very coarsely. It is often the case,
however, that the signs (excitation or inhibition) of individual interactions
are known. This paper extends to nonlinear systems the classical criteria of
linear sign stability introduced in the 70's, yielding simple sufficient
conditions to determine stability using only the sign patterns of the
interactions.


title: Turbulent drag in a rotating frame

abstract:
  What is the turbulent drag force experienced by an object moving in a
rotating fluid? This open and fundamental question can be addressed by
measuring the torque needed to drive an impeller at constant angular velocity
$\omega$ in a water tank mounted on a platform rotating at a rate $\Omega$. We
report a dramatic reduction in drag as $\Omega$ increases, down to values as
low as $12$\% of the non-rotating drag. At small Rossby number $Ro =
\omega/\Omega$, the decrease in drag coefficient $K$ follows the approximate
scaling law $K \sim Ro$, which is predicted in the framework of nonlinear
inertial wave interactions and weak-turbulence theory. However, stereoscopic
particle image velocimetry measurements indicate that this drag reduction
rather originates from a weakening of the turbulence intensity in line with the
two-dimensionalization of the large-scale flow.


title:
A System for Probabilistic Linking of Thesauri and Classification
  Systems

abstract:
  This paper presents a system which creates and visualizes probabilistic
semantic links between concepts in a thesaurus and classes in a classification
system. For creating the links, we build on the Polylingual Labeled Topic Model
(PLL-TM). PLL-TM identifies probable thesaurus descriptors for each class in
the classification system by using information from the natural language text
of documents, their assigned thesaurus descriptors and their designated
classes. The links are then presented to users of the system in an interactive
visualization, providing them with an automatically generated overview of the
relations between the thesaurus and the classification system.


title: Discovery of a very weak magnetic field on the Am star Alhena

abstract:
  Alhena ($\gamma$ Gem) was observed in the frame of the BRITE (BRIght Target
Explorer) spectropolarimetric survey, which gathers high resolution, high
signal-to-noise, high sensitivity, spectropolarimetric observations of all
stars brighter than V=4 to combine seismic and spectropolarimetric studies of
bright stars.
  We present here the discovery of a very weak magnetic field \textbf{on} the
Am star Alhena, thanks to very high signal-to-noise spectropolarimetric data
obtained with Narval at T\'elescope Bernard Lyot (TBL). All previously studied
Am stars show the presence of ultra-weak (sub-Gauss) fields with Zeeman
signatures with an unexpected prominent positive lobe. However, Alhena presents
a slightly stronger (but still very weak, only a few Gauss) field with normal
Zeeman signatures with a positive and negative lobe, as found in stronger field
(hundreds or thousands of Gauss) stars. It is the first detection of a normal
magnetic signature in an Am star.
  Alhena is thus a very interesting object, which might provide the clue to
understanding the peculiar shapes of the magnetic signatures of the other Am
stars.


title:
Selection of direction of the ordered moments in Na$_2$IrO$_3$ and
  $\alpha-$RuCl$_3$

abstract:
  The magnetic orders in Na$_2$IrO$_3$ and $\alpha-$RuCl$_3$, honeycomb systems
with strong spin-orbit coupling and correlations, have been recently described
by models with the dominant Kitaev interactions. In this work we discuss how
the orientation of magnetic order parameter is selected in this class of
models. We show that while the order-by-disorder mechanism in the models with
solely Kitaev anisotropies always select cubic axes as easy axes for magnetic
ordering, the additional effect of other small bond-dependent anisotropies,
such as, e.g., $\Gamma$-terms, lead to a deviation of the order parameter from
the cubic directions. We show that both the zigzag ground state and the
face-diagonal orientation of magnetic moments in Na$_2$IrO$_3$ can be obtained
within the $J_1-K_1-J_2-K_2-J_3$ model in the presence of perturbatively small
$\Gamma$-terms. We also show that the zigzag phase found in the nearest
neighbor Kitaev-Heisenberg model, relevant for $\alpha-$RuCl$_3$, has some
stability against the $\Gamma$-term.


title: Ultra Short Period Planets in K2: SuPerPiG Results for Campaigns 0-5

abstract:
  We have analyzed data from Campaigns 0-5 of the K2 mission and report 19
ultra-short-period candidate planets with orbital periods of less than 1 day
(nine of which have not been previously reported). Planet candidates range in
size from 0.7-16 Earth radii and in orbital period from 4.2 to 23.5 hours. One
candidate (EPIC 203533312, Kp=12.5) is among the shortest-period planet
candidates discovered to date (P=4.2 hours), and, if confirmed as a planet,
must have a density of at least rho=8.9 g/cm^3 in order to not be tidally
disrupted. Five candidates have nominal radius values in the sub-Jovian desert
(R_P=3-11 R_E and P<=1.5 days) where theoretical models do not favor their
long-term stability; the only confirmed planet in this range is in fact thought
to be disintegrating (EPIC 201637175). In addition to the planet candidates, we
report on four objects which may not be planetary, including one with
intermittent transits (EPIC 211152484) and three initially promising candidates
that are likely false positives based on characteristics of their light curves
and on radial velocity follow-up. A list of 91 suspected eclipsing binaries
identified at various stages in our vetting process is also provided. Based on
an assessment of our survey's completeness, we estimate an occurrence rate for
ultra-short period planets among K2 target stars that is about half that
estimated from the Kepler sample, raising questions as to whether K2 systems
are intrinsically different from Kepler systems, possibly as a result of their
different galactic location.


title: Surprises in astrophysical gasdynamics

abstract:
  Much of astrophysics consists of the study of ionised gas under the influence
of gravitational and magnetic fields. Thus, it is not possible to understand
the astrophysical universe without a detailed knowledge of the dynamics of
magnetised fluids. Fluid dynamics is, however, a notoriously tricky subject, in
which it is all too easy for one's a priori intuition to go astray. In this
review, we seek to guide the reader through a series of illuminating yet
deceptive problems, all with an enlightening twist. We cover a broad range of
topics including the instabilities acting in accretion discs, the hydrodynamics
governing the convective zone of the Sun, the magnetic shielding of a cooling
galaxy cluster, and the behaviour of thermal instabilities and evaporating
clouds. The aim of this review is to surprise and intrigue even veteran
astrophysical theorists with an idiosynchratic choice of problems and
counterintuitive results. At the same time, we endeavour to bring forth the
fundamental ideas, to set out important assumptions, and to describe carefully
whatever novel techniques may be appropriate to the problem at hand. By
beginning at the beginning, and analysing a wide variety of astrophysical
settings, we seek not only to make this review suitable for fluid dynamic
veterans, but to engage novice recruits as well with what we hope will be an
unusual and instructive introduction to the subject.


title:
Derived categories of quasi-hereditary algebras and their derived
  composition series

abstract:
  We study composition series of derived module categories in the sense of
Angeleri H\"ugel, K\"onig & Liu for quasi-hereditary algebras. More precisely,
we show that having a composition series with all factors being derived
categories of vector spaces does not characterise derived categories of
quasi-hereditay algebras. This gives a negative answer to a question of Liu &
Yang and the proof also confirms part of a conjecture of Bobi\'nski & Malicki.
In another direction, we show that derived categories of quasi-hereditary
algebras can have composition series with lots of different lengths and
composition factors. In other words, there is no Jordan-H\"older property for
composition series of derived categories of quasi-hereditary algebras.


title: On the regularity of fractional integrals of modular forms

abstract:
  In this paper we study some local and global regularity properties of Fourier
series obtained as fractional integrals of modular forms. In particular we
characterize the differentiability at rational points, determine their H\"older
exponent everywhere (using several definitions) and compute the associated
spectrum of singularities. We also show that these functions satisfy an
approximate functional equation, and use it to discuss the graphs of "Riemann's
example" and of fractional integrals of cusp forms for $\Gamma_0(N)$. We
include some computer plots.


title:
Photoproduction of $\Lambda$ and $\Sigma^0$ hyperons using linearly
  polarized photons

abstract:
  Background: Measurements of polarization observables for the reactions
$\vec{\gamma} p \rightarrow K^+ \Lambda$ and $\vec{\gamma} p \rightarrow K^+
\Sigma^0$ have been performed. This is part of a programme of measurements
designed to study the spectrum of baryon resonances.
  Purpose: The accurate measurement of several polarization observables
provides tight constraints for phenomenological fits. Beam-recoil observables
for the $\vec{\gamma} p \rightarrow K^+ \Sigma^0$ reaction have not been
reported before now.
  Method: The measurements were carried out using linearly polarized photon
beams and the CLAS detector at the Thomas Jefferson National Accelerator
Facility. The energy range of the results is 1.71\,GeV $<W<$ 2.19\,GeV, with an
angular range $-0.75 < \cos\theta^{\star}_K < +0.85$.
  Results: The observables extracted for both reactions are beam asymmetry
$\Sigma$, target asymmetry $T$, and the beam-recoil double polarization
observables $O_x$ and $O_z$.
  Conclusions: Comparison with theoretical fits indicates that in the regions
where no previous data existed, the new data contain significant new
information, and strengthen the evidence for the set of resonances used in the
latest Bonn-Gatchina fit.


title: A new multicomponent Poincar\'e-Beckner inequality

abstract:
  We prove a new vectorial functional inequality of Poincar\'{e}-Beckner type.
The inequality may be interpreted as an entropy-entropy production one for a
gradient flow in the metric space of Radon measures. The proof uses subtle
analysis of combinations of related super- and sub-level sets employing the
coarea formula and the relative isoperimetric inequality.


title:
Enriching Ontologies with Encyclopedic Background Knowledge for Document
  Indexing

abstract:
  The rapidly increasing number of scientific documents available publicly on
the Internet creates the challenge of efficiently organizing and indexing these
documents. Due to the time consuming and tedious nature of manual
classification and indexing, there is a need for better methods to automate
this process. This thesis proposes an approach which leverages encyclopedic
background knowledge for enriching domain-specific ontologies with textual and
structural information about the semantic vicinity of the ontologies' concepts.
The proposed approach aims to exploit this information for improving both
ontology-based methods for classifying and indexing documents and methods based
on supervised machine learning.


title: Topological hard-core bosons on the honeycomb lattice

abstract:
  This paper presents a connection between the topological properties of
hardcore bosons and that of magnons in quantum spin magnets. We utilize the
Haldane-like hardcore bosons on the honeycomb lattice as an example. We show
that this system maps to a spin-$1/2$ quantum XY model with a
next-nearest-neighbour Dzyaloshinsky-Moriya interaction. We obtain the magnon
excitations of the quantum spin model and compute the edge states, Berry
curvature, thermal and spin Nernst conductivities. Due to the mapping from spin
variables to bosons, the hardcore bosons possess the same nontrivial
topological properties as those in quantum spin system. These results are
important in the study of magnetic excitations in quantum magnets and they are
also useful for understanding the control of ultracold bosonic quantum gases in
honeycomb optical lattices, which is experimentally accessible.


title:
Instance Influence Estimation for Hyperspectral Target Signature
  Characterization using Extended Functions of Multiple Instances

abstract:
  The Extended Functions of Multiple Instances (eFUMI) algorithm is a
generalization of Multiple Instance Learning (MIL). In eFUMI, only bag level
(i.e. set level) labels are needed to estimate target signatures from mixed
data. The training bags in eFUMI are labeled positive if any data point in a
bag contains or represents any proportion of the target signature and are
labeled as a negative bag if all data points in the bag do not represent any
target. From these imprecise labels, eFUMI has been shown to be effective at
estimating target signatures in hyperspectral subpixel target detection
problems. One motivating scenario for the use of eFUMI is where an analyst
circles objects/regions of interest in a hyperspectral scene such that the
target signatures of these objects can be estimated and be used to determine
whether other instances of the object appear elsewhere in the image collection.
The regions highlighted by the analyst serve as the imprecise labels for eFUMI.
Often, an analyst may want to iteratively refine their imprecise labels. In
this paper, we present an approach for estimating the influence on the
estimated target signature if the label for a particular input data point is
modified. This "instance influence estimation" guides an analyst to focus on
(re-)labeling the data points that provide the largest change in the resulting
estimated target signature and, thus, reduce the amount of time an analyst
needs to spend refining the labels for a hyperspectral scene. Results are shown
on real hyperspectral sub-pixel target detection data sets.


title: A disorder-enhanced quasi-one-dimensional superconductor

abstract:
  A powerful approach to analysing quantum systems with dimensionality $d>1$
involves adding a weak coupling to an array of one-dimensional (1D) chains. The
resultant quasi-one-dimensional (q1D) systems can exhibit long-range order at
low temperature, but are heavily influenced by interactions and disorder due to
their large anisotropies. Real q1D materials are therefore ideal candidates not
only to provoke, test and refine theories of strongly correlated matter, but
also to search for unusual emergent electronic phases. Here we report the
unprecedented enhancement of a superconducting instability by disorder in
single crystals of Na$_{2-\delta}$Mo$_6$Se$_6$, a q1D superconductor comprising
MoSe chains weakly coupled by Na atoms. We argue that disorder-enhanced Coulomb
pair-breaking (which usually destroys superconductivity) may be averted due to
a screened long-range Coulomb repulsion intrinsic to disordered q1D materials.
Our results illustrate the capability of disorder to tune and induce new
correlated electron physics in low-dimensional materials.


title: Optimal Liquidation under Stochastic Liquidity

abstract:
  We solve explicitly a two-dimensional singular control problem of finite fuel
type for infinite time horizon. The problem stems from the optimal liquidation
of an asset position in a financial market with multiplicative and transient
price impact. Liquidity is stochastic in that the volume effect process, which
determines the inter-temporal resilience of the market in spirit of Predoiu,
Shaikhet and Shreve (2011), is taken to be stochastic, being driven by own
random noise. The optimal control is obtained as the local time of a diffusion
process reflected at a non-constant free boundary. To solve the HJB variational
inequality and prove optimality, we need a combination of probabilistic
arguments and calculus of variations methods, involving Laplace transforms of
inverse local times for diffusions reflected at elastic boundaries.


title: Symmetries of second order differential equations on Lie algebroids

abstract:
  In this paper we investigate the relations between semispray, nonlinear
connection, dynamical covariant derivative and Jacobi endomorphism on Lie
algebroids. Using these geometric structures, we study the symmetries of second
order differential equations in the general framework of Lie algebroids.


title:
Galactic cosmic rays on extrasolar Earth-like planets: II. Atmospheric
  implications

abstract:
  (abridged abstract) Theoretical arguments indicate that close-in terrestial
exoplanets may have weak magnetic fields. As described in the companion article
(Paper I), a weak magnetic field results in a high flux of galactic cosmic rays
to the top of the planetary atmosphere. We investigate effects that may result
from a high flux of galactic cosmic rays both throughout the atmosphere and at
the planetary surface. Using an air shower approach, we calculate how the
atmospheric chemistry and temperature change under the influence of galactic
cosmic rays for Earth-like (N_2-O_2 dominated) atmospheres. We evaluate the
production and destruction rate of atmospheric biosignature molecules. We
derive planetary emission and transmission spectra to study the influence of
galactic cosmic rays on biosignature detectability. We then calculate the
resulting surface UV flux, the surface particle flux, and the associated
equivalent biological dose rates. We find that up to 20% of stratospheric ozone
is destroyed by cosmic-ray protons. The reduction of the planetary ozone layer
leads to an increase in the weighted surface UV flux by two orders of magnitude
under stellar UV flare conditions. The resulting biological effective dose rate
is, however, too low to strongly affect surface life. We also examine the
surface particle flux: For a planet with a terrestrial atmosphere, a reduction
of the magnetic shielding efficiency can increase the biological radiation dose
rate by a factor of two. For a planet with a weaker atmosphere (with a surface
pressure of 97.8 hPa), the planetary magnetic field has a much stronger
influence on the biological radiation dose, changing it by up to two orders of
magnitude.


title:
$\alpha_s$ and $\rm V_{cs}$ determination, and CKM unitarity test, from
  W decays at NNLO

abstract:
  The hadronic ($\Gamma^{\rm W}_{\rm had}$) and total ($\Gamma^{\rm W}_{\rm
tot}$) widths of the W boson, computed at least at
next-to-next-to-leading-order (NNLO) accuracy, are combined to derive a new
precise prediction for the hadronic W branching ratio ${\cal B}^{\rm W}_{\rm
had} \equiv \Gamma^{\rm W}_{\rm had}/\Gamma^{\rm W}_{\rm tot}$ = $0.682 \pm
0.011_{\rm par}$, using the experimental Cabibbo-Kobayashi-Maskawa (CKM) matrix
elements, or ${\cal B}^{\rm W}_{\rm had} = 0.6742 \pm 0.0002_{\rm th} \pm
0.0001_{\rm par}$ assuming CKM unitarity, with uncertainties dominated by the
input parameters of the calculations. Comparing the theoretical predictions and
experimental measurements for various W decay observables, the NNLO strong
coupling constant at the Z pole, $\alpha_s(m_Z) = 0.117 \pm 0.042_{\rm exp} \pm
0.004_{\rm th} \pm 0.001_{\rm par}$, as well as the charm-strange CKM element,
$\rm V_{cs}$ = 0.973 $\pm$ 0.004$_{\rm exp}$ $\pm$ 0.002$_{\rm par}$, can be
extracted under different assumptions. We also show that W decays provide today
the most precise test of CKM unitarity for the 5 quarks lighter than $m_{\rm
W}$, $\sum_{ u,c,d,s,b} |V_{ ij}|^2 = 1.999 \pm 0.008_{\rm exp} \pm 0.001_{\rm
th}$. Perspectives for $\alpha_s$ and $\rm V_{cs}$ extractions from W decays
measurements at the LHC and future $e^+e^-$ colliders are presented.


title:
Spectral characterization and differential rotation study of active
  CoRoT stars

abstract:
  The CoRoT space telescope observed nearly 160 000 light curves. Among the
most outstanding is that of the young, active planet host star CoRoT-2A. In
addition to deep planetary transits, the light curve of CoRoT-2A shows strong
rotational variability and a superimposed beating pattern. To study the stars
that produce such an intriguing pattern of photometric variability, we
identified a sample of eight stars with rotation periods between 0.8 and 11
days and photometric variability amplitudes of up to 7.5 %, showing a similar
CoRoT light curve. We also obtained high-resolution follow-up spectroscopy with
TNG/SARG and carried out a spectral analysis with SME and MOOG. We find that
the color dependence of the light curves is consistent with rotational
modulation due to starspots and that latitudinal differential rotation provides
a viable explanation for the light curves, although starspot evolution is also
expected to play an important role. Our MOOG and SME spectral analyses provide
consistent results, showing that the targets are dwarf stars with spectral
types between F and mid-K. Detectable Li i absorption in four of the targets
confirms a low age of 100-400 Myr also deduced from gyrochronology. Our study
indicates that the photometric beating phenomenon is likely attributable to
differential rotation in fast-rotating stars with outer convection zones.


title: Static and Dynamic Feature Selection in Morphosyntactic Analyzers

abstract:
  We study the use of greedy feature selection methods for morphosyntactic
tagging under a number of different conditions. We compare a static ordering of
features to a dynamic ordering based on mutual information statistics, and we
apply the techniques to standalone taggers as well as joint systems for tagging
and parsing. Experiments on five languages show that feature selection can
result in more compact models as well as higher accuracy under all conditions,
but also that a dynamic ordering works better than a static ordering and that
joint systems benefit more than standalone taggers. We also show that the same
techniques can be used to select which morphosyntactic categories to predict in
order to maximize syntactic accuracy in a joint system. Our final results
represent a substantial improvement of the state of the art for several
languages, while at the same time reducing both the number of features and the
running time by up to 80% in some cases.


title: Quantum correlations for the metric

abstract:
  We discuss the correlation function for the metric for homogeneous and
isotropic cosmologies. The exact propagator equation determines the correlation
function as the inverse of the second functional derivative of the quantum
effective action. This formulation relates the metric correlation function
employed in quantum gravity computations to cosmological observables as the
graviton power spectrum. In the Einstein-Hilbert approximation for the
effective action the on-shell graviton correlation function can be obtained
equivalently from a product of mode functions which solve the linearized
Einstein equations. In contrast, the product of mode functions, often employed
in the context of cosmology, does not yield the correlation function for the
vector and scalar components of the metric fluctuations. We divide the metric
fluctuations into "physical fluctuations", which couple to a conserved energy
momentum tensor, and gauge fluctuations. On the subspace of physical metric
fluctuations the relation to physical sources becomes invertible, such that the
effective action and its relation to correlation functions no longer needs to
involve a gauge fixing term. The physical metric fluctuations have a similar
status as the Bardeen potentials, while being formulated in a covariant way. We
compute the effective action for the physical metric fluctuations for
geometries corresponding to realistic cosmologies.


title:
Characterizations of symmetrically partial Boolean functions with exact
  quantum query complexity

abstract:
  We give and prove an optimal exact quantum query algorithm with complexity
$k+1$ for computing the promise problem (i.e., symmetric and partial Boolean
function) $DJ_n^k$ defined as: $DJ_n^k(x)=1$ for $|x|=n/2$, $DJ_n^k(x)=0$ for
$|x|$ in the set $\{0, 1,\ldots, k, n-k, n-k+1,\ldots,n\}$, and it is undefined
for the rest cases, where $n$ is even, $|x|$ is the Hamming weight of $x$. The
case of $k=0$ is the well-known Deutsch-Jozsa problem. We outline all symmetric
(and partial) Boolean functions with degrees 1 and 2, and prove their exact
quantum query complexity. Then we prove that any symmetrical (and partial)
Boolean function $f$ has exact quantum 1-query complexity if and only if $f$
can be computed by the Deutsch-Jozsa algorithm. We also discover the optimal
exact quantum 2-query complexity for distinguishing between inputs of Hamming
weight $\{ \lfloor n/2\rfloor, \lceil n/2\rceil \}$ and Hamming weight in the
set $\{ 0, n\}$ for all odd $n$. In addition, a method is provided to determine
the degree of any symmetrical (and partial) Boolean function.


title: A new type of diagrams for modules

abstract:
  We introduce a new type of diagrams and prove the existence of a particular
one, the "central tuned diagram", with some optimal features, for finitely
generated modules of certain categories. This is achieved by getting to the
idea of "the virtual category" of a module. Important applications are
specifically suggested to the modular representations of finite groups of Lie
type.


title: Energy-Aware Cooperative Wireless Networks with Multiple Cognitive Users

abstract:
  In this paper, we study and analyze cooperative cognitive radio networks with
arbitrary number of secondary users (SUs). Each SU is considered a prospective
relay for the primary user (PU) besides having its own data transmission
demand. We consider a multi-packet transmission framework which allows multiple
SUs to transmit simultaneously thanks to dirty-paper coding. We propose power
allocation and scheduling policies that optimize the throughput for both PU and
SU with minimum energy expenditure. The performance of the system is evaluated
in terms of throughput and delay under different opportunistic relay selection
policies. Towards this objective, we present a mathematical framework for
deriving stability conditions for all queues in the system. Consequently, the
throughput of both primary and secondary links is quantified. Furthermore, a
moment generating function (MGF) approach is employed to derive a closed-form
expression for the average delay encountered by the PU packets. Results reveal
that we achieve better performance in terms of throughput and delay at lower
energy cost as compared to equal power allocation schemes proposed earlier in
literature. Extensive simulations are conducted to validate our theoretical
findings.


title:
On Relationship of Koopman Eigenvalues and Frequencies in Dynamic Mode
  Decomposition

abstract:
  The frequency estimation from the Koopman eigenvalues (phase angles) obtained
via Dynamic Mode Decomposition (DMD) is addressed. Since the calculations of
the frequencies from the phase angles are nonunique, the modifications of DMD
for uniqueness restoration are considered. The nonlinear oscillating mode of
supersonic jet, impinging the flat plate, is used as a toy problem.


title: Quantum work and the thermodynamic cost of quantum measurements

abstract:
  Quantum work is usually determined from two projective measurements of the
energy at the beginning and at the end of a thermodynamic process. However,
this paradigm cannot be considered thermodynamically consistent as it does not
account for the thermodynamic cost of these measurements. To remedy this
conceptual inconsistency we introduce a novel paradigm that relies only on the
expected change of the average energy given the initial energy eigenbasis. In
particular, we completely omit quantum measurements in the definition of
quantum work, and hence quantum work is identified as a thermodynamic quantity
of only the system. As main results we derive a modified quantum Jarzynski
equality and a sharpened maximum work theorem in terms of the information free
energy. Comparison of our results with the standard approach allows to quantify
the informational cost of projective measurements.


title:
Measurement and tricubic interpolation of the magnetic field for the
  OLYMPUS experiment

abstract:
  The OLYMPUS experiment used a 0.3 T toroidal magnetic spectrometer to measure
the momenta of outgoing charged particles. In order to accurately determine
particle trajectories, knowledge of the magnetic field was needed throughout
the spectrometer volume. For that purpose, the magnetic field was measured at
over 36,000 positions using a three-dimensional Hall probe actuated by a system
of translation tables. We used these field data to fit a numerical magnetic
field model, which could be employed to calculate the magnetic field at any
point in the spectrometer volume. Calculations with this model were
computationally intensive; for analysis applications where speed was crucial,
we pre-computed the magnetic field and its derivatives on an evenly spaced grid
so that the field could be interpolated between grid points. We developed a
spline-based interpolation scheme suitable for SIMD implementations, with a
memory layout chosen to minimize space and optimize the cache behavior to
quickly calculate field values. This scheme requires only one-eighth of the
memory needed to store necessary coefficients compared with a previous scheme
[1]. This method was accurate for the vast majority of the spectrometer volume,
though special fits and representations were needed to improve the accuracy
close to the magnet coils and along the toroid axis.


title:
Characterization of Image Spaces of Riemann-Liouville Fractional
  Integral Operators on Sobolev Spaces $W^{m,p}(\Omega)$

abstract:
  Fractional operators are widely used in mathematical models describing
abnormal and nonlocal phenomena. Although there are extensive numerical methods
for solving the corresponding model problems, theoretical analysis such as the
regularity result, or the relationship between the left-side and right-side
fractional operators are seldom mentioned. In stead of considering the
fractional derivative spaces, this paper starts from discussing the image
spaces of Riemann-Liouville fractional integrals of $L_p(\Omega)$ functions,
since the fractional derivative operators that often used are all
pseudo-differential. Then high regularity situation---the image spaces of
Riemann-Liouville fractional integral operators on $W^{m,p}(\Omega)$ space are
considered. Equivalent characterizations of the defined spaces, as well as of
the intersection of the left-side and right-side spaces are given. The behavior
of the functions in the defined spaces at both the nearby boundary point/ponits
and the points in the domain are demonstrated in a clear way. Besides, tempered
fractional operators show to be reciprocal to the corresponding
Riemann-Liouville fractional operators, which is expected to make some efforts
on theoretical support for relevant numerical methods. Last, we also provide
some instructions on how to take advantage of the introduced spaces when
numerically solving fractional equations.


title:
Conjecture and improved extension theorems for paraboloids in the finite
  field setting

abstract:
  We study the extension estimates for paraboloids in d-dimensional vector
spaces over finite fields F_q with q elements. We use the connection between
L^2 based restriction estimates and L^p\to L^r extension estimates for
paraboloids. As a consequence, we improve the L^2\to L^r extension results
obtained by A. Lewko and M. Lewko in even dimensions d\ge 6 and odd dimensions
d=4\ell+3 for \ell \in \mathbb N. Our results extend the consequences for 3-D
paraboloids due to M. Lewko to higher dimensions. We also clarifies conjectures
on finite field extension problems for paraboloids.


title: Coning-off CAT(0) cube complexes

abstract:
  In this paper, we study the geometry of cone-offs of CAT(0) cube complexes
over a family of combinatorially convex subcomplexes, with an emphasis on their
Gromov-hyperbolicity. A first application gives a direct cubical proof of the
characterization of the (strong) relative hyperbolicity of right-angled Coxeter
groups, which is a particular case of a result due to Behrstock, Caprace and
Hagen. A second application gives the acylindrical hyperbolicity of
$C'(1/4)-T(4)$ small cancellation quotients of free products.


title: Exact results for one dimensional fluids through functional integration

abstract:
  We review some of the exactly solvable one dimensional continuum fluid models
of equilibrium classical statistical mechanics under the unified setting of
functional integration in one dimension. We make some further developments and
remarks concerning fluids with non pairwise-additive interaction. We then apply
our developments to the study of a particular non pairwise-additive Gaussian
model for which we are unable to find a well defined thermodynamics.

categories: physics.class-ph cond-mat.stat-mech math-ph math.MP


title: Collisionless Encounters and the Origin of the Lunar Inclination

abstract:
  The Moon is generally thought to have formed from the debris ejected by the
impact of a planet-sized object with the proto-Earth towards the end of
planetary accretion. Modeling of the impact process predicts that the lunar
material was disaggregated into a circumplanetary disk and that lunar accretion
subsequently placed the Moon in a near equatorial orbit. Forward integration of
the lunar orbit from this initial state predicts a modern inclination at least
an order of magnitude smaller than the lunar value, a long-standing discrepancy
known as the lunar inclination problem. Here we show that the modern lunar
orbit provides a sensitive record of gravitational interactions with
Earth-crossing planetesimals not yet accreted at the time of the Moon-forming
event. The excited lunar orbit can naturally be reproduced via interaction with
a small quantity of mass (corresponding to 0.0075-0.015 ME eventually accreted
to the Earth) carried by a few bodies, consistent with constraints and models
of late accretion. While the process has a stochastic element, the observed
value of the lunar inclination is among the most likely outcomes for a wide
range of parameters. The excitation of the lunar orbit is most readily
reproduced via collisionless encounters with strong tidal dissipation on the
early Earth. This mechanism obviates the necessity of previously proposed (but
idealized) excitation mechanisms and can constrain the planet formation context
of the Moon-forming event and the pristineness of the dynamical state of the
Earth-Moon system.


title:
Experimental study of the initial growth of a localized turbulent patch
  in a stably stratified fluid

abstract:
  We present a laboratory experiment of the growth of a turbulent patch in a
stably stratified fluid, due to a localized source of turbulence, generated by
an oscillating grid. Synchronized and overlapping particle image velocimetry
and planar laser induced fluorescence measurements have been conducted
capturing the evolution of the patch through its initial growth until it
reached a maximum size, followed by its collapse. The simultaneous measurements
of density and velocity fields allow for a direct quantification of the degree
of mixing within the patch, the propagation speed of the
turbulent/non-turbulent interface and its thickness. The velocity measurements
indicate significant non-equilibrium effects inside the patch which are not
consistent with the classical used grid-action model. A local analysis of the
turbulent/non-turbulent interface provides direct measurements of the
entrainment velocity $w_{e}$ as compared to the local vertical velocity and
turbulent intensity at the proximity of the interface. It is found that the
entrainment rate $E$ is constrained in the range of $0{\div}0.1$ and that the
local, gradient Richardson number at the interface is $\mathcal{O} (100)$.
Finally, we show that the mean flow is responsible for the patch collapse.


title: A saturation phenomenon for a nonlinear nonlocal eigenvalue problem

abstract:
  Given $1\le q \le 2$ and $\alpha\in\mathbb R$, we study the properties of the
solutions of the minimum problem \[
\lambda(\alpha,q)=\min\left\{\dfrac{\displaystyle\int_{-1}^{1}|u'|^{2}dx+\alpha\left|\int_{-1}^{1}|u|^{q-1}u\,
dx\right|^{\frac2q}}{\displaystyle\int_{-1}^{1}|u|^{2}dx}, u\in
H_{0}^{1}(-1,1),\,u\not\equiv 0\right\}. \] In particular, depending on
$\alpha$ and $q$, we show that the minimizers have constant sign up to a
critical value of $\alpha=\alpha_{q}$, and when $\alpha>\alpha_{q}$ the
minimizers are odd.


title: The sphere packing problem in dimension 24

abstract:
  Building on Viazovska's recent solution of the sphere packing problem in
eight dimensions, we prove that the Leech lattice is the densest packing of
congruent spheres in twenty-four dimensions and that it is the unique optimal
periodic packing. In particular, we find an optimal auxiliary function for the
linear programming bounds, which is an analogue of Viazovska's function for the
eight-dimensional case.


title:
Reconstructing WIMP properties through an interplay of signal
  measurements in direct detection, Fermi-LAT, and CTA searches for dark matter

abstract:
  We examine the projected ability to reconstruct the mass, scattering, and
annihilation cross section of dark matter in the new generation of large
underground detectors, XENON-1T, SuperCDMS, and DarkSide-G2, in combination
with diffuse gamma radiation from expected 15 years of data from Fermi-LAT
observation of 46 local spiral dwarf galaxies and projected CTA sensitivity to
a signal from the Galactic Center. To this end we consider several benchmark
points spanning a wide range of WIMP mass, different annihilation final states,
and large enough event rates to warrant detection in one or more experiments.
As previously shown, below some 100 GeV only direct detection experiments will
in principle be able to reconstruct the WIMP mass well. This may, in case a
signal at Fermi-LAT is also detected, additionally help restricting \sigma v
and the allowed decay branching rates. In the intermediate range between some
100 GeV and up a few hundred GeV, direct and indirect detection experiments can
be used in complementarity to ameliorate the respective determinations, which
in individual experiments can at best be rather poor, thus making the WIMP
reconstruction in this mass range very challenging. At large WIMP mass, ~1 TeV,
CTA will have the ability to reconstruct mass, annihilation cross section, and
the allowed decay branching rates to very good precision for the $\tau^+\tau^-$
or purely leptonic final state, good for the $W^+W^-$ case, and rather poor for
$b\bar{b}$. A substantial improvement can potentially be achieved by reducing
the systematic uncertainties, increasing exposure, or by an additional
measurement at Fermi-LAT that would help reconstruct the annihilation cross
section and the allowed branching fractions to different final states.


title: Finding Planet Nine: a Monte Carlo approach

abstract:
  Planet Nine is a hypothetical planet located well beyond Pluto that has been
proposed in an attempt to explain the observed clustering in physical space of
the perihelia of six extreme trans-Neptunian objects or ETNOs. The predicted
approximate values of its orbital elements include a semimajor axis of 700 au,
an eccentricity of 0.6, an inclination of 30 degrees, and an argument of
perihelion of 150 degrees. Searching for this putative planet is already under
way. Here, we use a Monte Carlo approach to create a synthetic population of
Planet Nine orbits and study its visibility statistically in terms of various
parameters and focusing on the aphelion configuration. Our analysis shows that,
if Planet Nine exists and is at aphelion, it might be found projected against
one out of four specific areas in the sky. Each area is linked to a particular
value of the longitude of the ascending node and two of them are compatible
with an apsidal anti-alignment scenario. In addition and after studying the
current statistics of ETNOs, a cautionary note on the robustness of the
perihelia clustering is presented.


title:
Amplification phenomena of Casimir force fluctuations on close
  scatterers coupled via a coherent fermionic fluid

abstract:
  We study the mechanical actions affecting close scatterers immersed in a
coherent fermionic fluid. Using a scattering field theory, we theoretically
analyse the single-scatterer and the two-scatterer case. Concerning the
single-scatterer case, we find that a net force affects the scatterer dynamics
only in non-equilibrium condition, i.e. imposing the presence of a
non-vanishing particle current flowing through the system. The force
fluctuation (variance) is instead not negligible both in equilibrium and in
non-equilibrium conditions. Concerning the two-scatterer case, an attractive
fluid-mediated Casimir force is experienced by the scatterers at small spatial
separation, while a decaying attractive/repulsive behavior as a function of the
scatterer separation is found. Furthermore, the Casimir force fluctuations
acting on a given scatterer in close vicinity of the other present an
oscillating behavior reaching a long distance limit comparable to the value of
the single-scatterer case. The relevance of these findings is discussed in
connection with fluctuation phenomena in low-dimensional nanostructures and
cold atoms systems.