title: Interactions in an acoustic world

abstract:
  The present paper aims to complete an earlier paper where the acoustic world
was introduced. This is accomplished by analyzing the interactions which occur
between the inhomogeneities of the acoustic medium, which are induced by the
acoustic vibrations traveling in the medium. When a wave packet travels in a
medium, the medium becomes inhomogeneous. The spherical wave packet behaves
like an acoustic spherical lens for the acoustic plane waves. According to the
principle of causality, there is an interaction between the wave and plane wave
packet. In specific conditions the wave packet behaves as an acoustic black
hole.


title: On the monotonicity of perimeter of convex bodies

abstract:
  Let $n\ge2$ and let $\Phi\colon\mathbb{R}^n\to[0,\infty)$ be a positively
$1$-homogeneous and convex function. Given two convex bodies $A\subset B$ in
$\mathbb{R}^n$, the monotonicity of anisotropic $\Phi$-perimeters holds, i.e.
$P_\Phi(A)\le P_\Phi(B)$. In this note, we prove a quantitative lower bound on
the difference of the $\Phi$-perimeters of $A$ and $B$ in terms of their
Hausdorff distance.


title:
On the Hamiltonian and Geometric structure of the Craik-Leibovich
  equation

abstract:
  In this paper we show that the Craik-Leibovich (CL) equation in hydrodynamics
is the Euler equation on the dual of a certain central extension of the Lie
algebra of divergence-free vector fields. From this geometric viewpoint, one
can give a generalization of CL equation on any Riemannian manifold with
boundary. We also prove a stability theorem for 2-dimensional steady flows of
the Craik-Leibovich equation.


title:
Interaction and charge transfer between dielectric spheres: exact and
  approximate analytical solutions

abstract:
  We present exact analytical solutions for charge transfer reactions between
two arbitrarily charged hard dielectric spheres. These solutions, and the
corresponding exact ones for sphere-sphere interaction energies, include sums
that describe polarization effects to infinite orders in the inverse of the
distance between the sphere centers. In addition, we show that these exact
solutions may be approximated by much simpler analytical expressions that are
useful for many practical applications. This is exemplified through
calculations of Langevin type cross sections for forming a compound system of
two colliding spheres and through calculations of electron transfer cross
sections. We find that it is important to account for dielectric properties and
finite sphere sizes in such calculations, which for example may be useful for
describing the evolution, growth, and dynamics of nanometer sized dielectric
objects such as molecular clusters or dust grains in different environments
including astrophysical ones.


title: Energy Variation of Soft Matter Interfaces

abstract:
  The variation of energies associated with soft matter interfaces where
surface inhomogeneities are present. These energies include the total bending
and splay energy, the variable surface tension energy, a coupling energy
between the total curvature and an underlying surface concentration field, the
energy due to an external field, and a phase segregation energy. When
considering these energies the variation of material properties such a bending
rigidity are taken into account, which results in more general variation
expressions. These variations can be used to determine the equilibrium
interface and concentration configuration or to determine the driving forces
for non-equilibrium situations. While the focus of this work are energies
associated with multicomponent vesicles, it can easily be extended to any soft
matter interface.


title: IVOA Data Access Layer: Goals, Achievements and Current Trends

abstract:
  The IVOA Data Access Layer (DAL) working group was created in 2002 to define
protocols to homogenize data discovery, data description, data retrieval, and
data access processes. We describe its history and status today, and look at
current trends for future development of the DAL protocols.


title:
Parametrices and exact paralinearisation of semi-linear boundary
  problems

abstract:
  The subject is parametrices for semi-linear problems, based on parametrices
for linear boundary problems and on non-linearities that decompose into
solution-dependent linear operators acting on the solutions. Non-linearities of
product type are shown to admit this via exact paralinearisation. The
parametrices give regularity properties under weak conditions; improvements in
subdomains result from pseudo-locality of type $1,1$-operators. The framework
encompasses a broad class of boundary problems in H\"older and $L_p$-Sobolev
spaces (and also Besov and Lizorkin--Triebel spaces). The Besov analyses of
homogeneous distributions, tensor products and halfspace extensions have been
revised. Examples include the von Karman equation.


title:
Supersymmetric $AdS_6$ vacua in six-dimensional $N=(1,1)$ gauged
  supergravity

abstract:
  We study fully supersymmetric $AdS_6$ vacua of half-maxi\-mal $N=(1,1)$
gauged supergravity in six space-time dimensions coupled to $n$ vector
multiplets. We show that the existence of $AdS_6$ backgrounds requires that the
gauge group is of the form $G'\times G"\subset SO(4,n)$ where $G'\subset
SO(3,m)$ and $G"\subset SO(1,n-m)$. In the $AdS_6$ vacua this gauge group is
broken to its maximal compact subgroup $SO(3)\times H'\times H"$ where
$H'\subset SO(m)$ and $H"\subset SO(n-m)$. Furthermore, the $SO(3)$ factor is
the R-symmetry gauged by three of the four graviphotons. We further show that
the $AdS_6$ vacua have no moduli that preserve all supercharges. This is
precisely in agreement with the absence of supersymmetric marginal deformations
in holographically dual five-dimensional superconformal field theories.


title: Applications of multisymmetric syzygies in invariant theory

abstract:
  A presentation by generators and relations of the $n$th symmetric power $B$
of a commutative algebra $A$ over a field of characteristic zero or greater
than $n$ is given. This is applied to get information on a minimal homogeneous
generating system of $B$ (in the graded case). The known result that in
characteristic zero the algebra $B$ is isomorphic to the coordinate ring of the
scheme of $n$-dimensional representations of $A$ is also recovered. The special
case when $A$ is the two-variable polynomial algebra and $n=3$ is applied to
find generators and relations of an algebra of invariants of the symmetric
group of degree four that was studied in connection with the problem of
classifying sets of four unit vectors in the Euclidean space.


title: A theory of pictures for quasi-posets

abstract:
  The theory of pictures between posets is known to encode much of the
combinatorics of symmetric group representations and related topics such as
Young diagrams and tableaux. Many reasons, com-binatorial (e.g. since
semi-standard tableaux can be viewed as double quasi-posets) and topological
(quasi-posets identify with finite topolo-gies) lead to extend the theory to
quasi-posets. This is the object of the present article.


title: FRW Bulk Viscous Cosmology with Modified Chaplygin Gas in Flat Space

abstract:
  In this paper we study FRW bulk viscous cosmology in presence of modified
Chaplygin gas. We write modified Friedmann equations due to bulk viscosity and
Chaplygin gas and obtain time-dependent energy density for the special case of
flat space.


title:
Bayesian Body Schema Estimation using Tactile Information obtained
  through Coordinated Random Movements

abstract:
  This paper describes a computational model, called the Dirichlet process
Gaussian mixture model with latent joints (DPGMM-LJ), that can find latent tree
structure embedded in data distribution in an unsupervised manner. By combining
DPGMM-LJ and a pre-existing body map formation method, we propose a method that
enables an agent having multi-link body structure to discover its kinematic
structure, i.e., body schema, from tactile information alone. The DPGMM-LJ is a
probabilistic model based on Bayesian nonparametrics and an extension of
Dirichlet process Gaussian mixture model (DPGMM). In a simulation experiment,
we used a simple fetus model that had five body parts and performed structured
random movements in a womb-like environment. It was shown that the method could
estimate the number of body parts and kinematic structures without any
pre-existing knowledge in many cases. Another experiment showed that the degree
of motor coordination in random movements affects the result of body schema
formation strongly. It is confirmed that the accuracy rate for body schema
estimation had the highest value 84.6% when the ratio of motor coordination was
0.9 in our setting. These results suggest that kinematic structure can be
estimated from tactile information obtained by a fetus moving randomly in a
womb without any visual information even though its accuracy was not so high.
They also suggest that a certain degree of motor coordination in random
movements and the sufficient dimension of state space that represents the body
map are important to estimate body schema correctly.


title: BPS Boojums in N=2 supersymmetric gauge theories II

abstract:
  We continue our study of 1/4 Bogomol'nyi-Prasad-Sommerfield (BPS) composite
solitons of vortex strings, domain walls and boojums in N=2 supersymmetric
Abelian gauge theories in four dimensions. In this work, we numerically confirm
that a boojum appearing at an end point of a string on a thick domain wall
behaves as a magnetic monopole with a fractional charge in three dimensions. We
introduce a "magnetic" scalar potential whose gradient gives magnetic fields.
Height of the magnetic potential has a geometrical meaning that is shape of the
domain wall. We find a semi-local extension of boojum which has an additional
size moduli at an end point of a semi-local string on the domain wall. Dyonic
solutions are also studied and we numerically confirm that the dyonic domain
wall becomes an electric capacitor storing opposite electric charges on its
skins. At the same time, the boojum becomes fractional dyon whose charge
density is proportional to ${\vec E} \cdot {\vec B}$. We also study dual
configurations with an infinite number of boojums and anti-boojums on parallel
lines and analyze the ability of domain walls to store magnetic charge as
magnetic capacitors. In understanding these phenomena, the magnetic scalar
potential plays an important role. We study the composite solitons from the
viewpoints of the Nambu-Goto and Dirac-Born-Infeld actions, and find the
semi-local BIon as the counterpart of the semi-local Boojum.


title:
A Joint Analysis for Cosmology and Photometric Redshift Calculation
  Using Cross Correlations

abstract:
  We present a method of calibrating the properties of photometric redshift
bins as part of a larger Markov Chain Monte Carlo (MCMC) analysis for the
inference of cosmological parameters. The redshift bins are characterised by
their mean and variance, which are varied as free parameters and marginalised
over when obtaining the cosmological parameters. We demonstrate that the
likelihood function for cross-correlations in an angular power spectrum
framework tightly constrains the properties of bins such that they may be well
determined, reducing their influence on cosmological parameters and avoiding
the bias from poorly estimated redshift distributions. We demonstrate that even
with only three photometric and three spectroscopic bins, we can recover
accurate estimates of the mean redshift of a bin to within $\Delta\mu \approx
3-4 \times10^{-3}$ and the width of the bin to $\Delta\sigma \approx
1\times10^{-3}$ for galaxies near $z = 1$. This indicates that we may be able
to bring down the photometric redshift errors to a level which is in line with
the requirements for the next generation of cosmological experiments.


title: On the solution of a pairing problem in the continuum

abstract:
  We present a generalized Richardson solution for fermions interacting with
the pairing interaction in both discrete and continuum parts of the single
particle (s.p.) spectrum. The pairing Hamiltonian is based on the rational
Gaudin (RG) model which is formulated in the Berggren ensemble. We show that
solutions of the generalized Richardson equations are exact in the two limiting
situations: (i) in the pole approximation and (ii) in the s.p. continuum. If
the s.p. spectrum contains both discrete and continuum parts, then the
generalized Richardson equations provide accurate solutions for the Gamow Shell
Model.


title: Comparison Between IPv4 to IPv6 Transition Techniques

abstract:
  The IPv4 addresses exhaustion demands a protocol transition from IPv4 to
IPv6. The original transition technique, the dual stack, is not widely deployed
yet and it demanded the creation of new transition techniques to extend the
transition period. This work makes an experimental comparison of techniques
that use dual stack with a limited IPv4 address. This limited address might be
a RFC 1918 address with a NAT at the Internet Service Provider (ISP) gateway,
also known as Carrier Grade NAT (CGN), or an Address Plus Port (A+P) shared
IPv4 address. The chosen techniques also consider an IPv6 only ISP network. The
transport of the IPv4 packets through the IPv6 only networks may use IPv4
packets encapsulated on IPv6 packets or a double translation, by making one
IPv4 to IPv6 translation to enter the IPv6 only network and one IPv6 to IPv4
translation to return to the IPv4 network. The chosen techniques were DS-Lite,
464XLAT, MAP-E and MAP-T. The first part of the test is to check some of the
most common usages of the Internet by a home user and the impacts of the
transition techniques on the user experience. The second part is a measured
comparison considering bandwidth, jitter and latency introduced by the
techniques and processor usage on the network equipment.


title:
Levy Differential Operators and Gauge Invariant Equations for Dirac and
  Higgs Fields

abstract:
  We study the Levy infinite-dimensional differential operators (differential
operators defined by the analogy with the Levy Laplacian) and their
relationship to the Yang-Mills equations. We consider the parallel transport on
the space of curves as an infinite-dimensional analogue of chiral fields and
show that it is a solution to the system of differential equations if and only
if the associated curvature is a solution to the Yang-Mills equations. This
system is an analogue of the equation of motion of chiral fields and contains
the Levy divergence. The systems of infinite-dimensional equations containing
Levy differential operators, that are equivalent to the Yang-Mills-Higgs
equations and the Yang-Mills-Dirac equations (the equations of quantum
chromodinamics), are obtained. The equivalence of two ways to define the Levy
differential operators is shown.


title: 1D Classical Density Functional Theory of a Tethered Polymer Layer

abstract:
  A simple application of classical density functional theory is derived and
applied to a system of polymers grafted to a plane. The system is assumed to
have symmetry in directions parallel to the grafting plane hence it being a
'1-dimensional' problem. A quick introduction to using propagators in the
theory of chains in the presence of external fields and a numerical algorithm
for solving the modified diffusion (or Fokker-Planck) equation are presented.
Density profiles are found for hard-sphere chains which agree with results in
the literature (see Murat,.., Milner,.., Muhukumar and others) and align with
physical expectations of brush formation due to excluded volume. The linear
scaling $h \approx (\sigma)^{1/3} N$, of brush height with polymerisation $N$,
is reproduced here.


title:
Classifiers for centrality determination in proton-nucleus and
  nucleus-nucleus collisions

abstract:
  Centrality, as a geometrical property of the collision, is crucial for the
physical interpretation of nucleus-nucleus and proton-nucleus experimental
data. However, it cannot be directly accessed in event-by-event data analysis.
Common methods for centrality estimation in A-A and p-A collisions usually rely
on a single detector (either on the signal in zero-degree calorimeters or on
the multiplicity in some semi-central rapidity range). In the present work, we
made an attempt to develop an approach for centrality determination that is
based on machine-learning techniques and utilizes information from several
detector subsystems simultaneously. Different event classifiers are suggested
and evaluated for their selectivity power in terms of the number of
nucleons-participants and the impact parameter of the collision. Finer
centrality resolution may allow to reduce impact from so-called volume
fluctuations on physical observables being studied in heavy-ion experiments
like ALICE at the LHC and fixed target experiment NA61/SHINE on SPS.


title:
On metric convexity, the discrete Hahn-Banach theorem, separating
  systems and sets of points forming only acute angles

abstract:
  This text has three parts.
  The first one is largely autobiographical, hence my use of the first person.
There I recall how Gerard Cohen influenced important parts of my research.
  The second is of a more classic mathematical nature. I present a discrete
analogue of the Hahn-Banach theorem, which serves as a basis for generalizing
the notion of separating systems in the context of metric convexity.
  The third one aims at building a bridge between two communities of
researchers, those interested in separating systems, and those interested in a
certain question in combinatorial geometry --- sets of points forming only
acute angles --- who seem not to be aware of each other, while they are working
on precisely the same problem!
  Of course, these three themes are closely intertwined.


title:
Intra-wire coupling in segmented Ni/Cu nanowires deposited by
  electrodeposition

abstract:
  Segmented magnetic nanowires are a promising route for the development of
three dimensional data storage techniques. Such devices require a control of
the coercive field and the coupling mechanisms between individual magnetic
elements. In our study, we investigate electrodeposited nanomagnets within host
templates using vibrating sample magnetometry and observe a strong dependence
between nanowire length and coercive field (25 nm to 5 $\mu$m) and diameter (25
nm to 45 nm). A transition from a magnetization reversal through coherent
rotation to domain wall propagation is observed at an aspect ratio of
approximately 2. Our results are further reinforced via micromagnetic
simulations and angle dependent hysteresis loops. The found behavior is
exploited to create nanowires consisting of a fixed and a free segment in a
spin-valve like structure. The wires are released from the membrane and
electrically contacted, displaying a giant magnetoresistance effect that is
attributed to individual switching of the coupled nanomagnets. We develop a
simple analytical model to describe the observed switching phenomena and to
predict stable and unstable regimes in coupled nanomagnets of certain
geometries.


title:
Irreducible Witt modules from Weyl modules and
  $\mathfrak{gl}_{n}$-modules

abstract:
  For an irreducible module $P$ over the Weyl algebra $\mathcal{K}_n^+$ (resp.
$\mathcal{K}_n$) and an irreducible module $M$ over the general liner Lie
algebra $\mathfrak{gl}_n$, using Shen's monomorphism, we make $P\otimes M$ into
a module over the Witt algebra $W_n^+$ (resp. over $W_n$). We obtain the
necessary and sufficient conditions for $P\otimes M$ to be an irreducible
module over $W_n^+$ (resp. $W_n$), and determine all submodules of $P\otimes M$
when it is reducible. Thus we have constructed a large family of irreducible
weight modules with many different weight supports and many irreducible
non-weight modules over $W_n^+$ and $W_n$.


title: Consensus Control for Linear Systems with Optimal Energy Cost

abstract:
  In this paper, we design an optimal energy cost controller for linear systems
asymptotic consensus given the topology of the graph. The controller depends
only on relative information of the agents. Since finding the control gain for
such controller is hard, we focus on finding an optimal controller among a
classical family of controllers which is based on Algebraic Riccati Equation
(ARE) and guarantees asymptotic consensus. Through analysis, we find that the
energy cost is bounded by an interval and hence we minimize the upper bound. In
order to do that, there are two classes of variables that need to be optimized:
the control gain and the edge weights of the graph and are hence designed from
two perspectives. A suboptimal control gain is obtained by choosing $Q=0$ in
the ARE. Negative edge weights are allowed, and the problem is formulated as a
Semi-definite Programming (SDP) problem. Having negative edge weights means
that "competitions" between the agents are allowed. The motivation behind this
setting is to have a better system performance. We provide a different proof
from the angle of optimization and show that the lowest control energy cost is
reached when the graph is complete and with equal edge weights. Furthermore,
two sufficient conditions for the existence of negative optimal edge weights
realization are given.


title:
A "hidden" transition in heavy fermion compound CeB$_{6}$ at $T\sim$ 20
  K?

abstract:
  The temperature-dependent electronic structures of heavy fermion compound
CeB$_{6}$ are investigated thoroughly by means of the combination of density
functional theory and single-site dynamical mean-field theory. The band
structure, density of states, and 4$f$ valence state fluctuation of CeB$_{6}$
are calculated in a broad temperature range of 10 $\sim$ 120 K. Overall, the
4$f$ electrons remain incoherent, approximately irrespective of the
temperature. However, we find that these observables exhibit some unusual
features near 20 K. In addition, the evolution of 4$f$ orbital occupancy, total
angular momentum, and total energy with respect to temperature shows apparent
singularity around 20 K. We believe that these tantalizing characteristics are
probably related to a "hidden" electronic transition.


title:
Clustering and preferential concentration of finite-size particles in
  forced homogeneous-isotropic turbulence

abstract:
  We have performed interface-resolved direct numerical simulations of forced
homogeneous-isotropic turbulence in a dilute suspension of spherical particles
in the Reynolds number range Re-lambda=115-140. The solid-fluid density ratio
was set to 1.5, gravity was set to zero, and two particle diameters were
investigated corresponding to approximately 5 and 11 Kolmogorov lengths. Note
that these particle sizes are clearly outside the range of validity of the
point-particle approximation, as has been shown by Homann & Bec (2010). At the
present parameter points the global effect of the particles upon the fluid flow
is weak. We observe that the dispersed phase exhibits clustering with moderate
intensity. The tendency to cluster, which was quantified in terms of the
standard deviation of Voronoi cell volumes, decreases with the particle
diameter. We have analyzed the relation between particle locations and the
location of intense vortical flow structures. The results do not reveal any
significant statistical correlation. Contrarily, we have detected a small but
statistically significant preferential location of particles with respect to
the `sticky points' proposed by Goto & Vassilicos (2008), i.e. points where the
fluid acceleration field is acting such as to increase the local particle
concentration in one-way coupled point-particle models under Stokes drag. The
presently found statistical correlation between the `sticky points' and the
particle locations further increases when focusing on regions with high local
concentration. Our results suggest that small finite-size particles can be
brought together along the expansive directions of the fluid acceleration
field, as previously observed only for the simplest model for sub-Kolmogorov
particles. We further discuss the effect of density ratio and collective
particle motion upon the basic Eulerian and Lagrangian statistics.


title:
Morphological properties of slender Ca II H fibrils observed by SUNRISE
  II

abstract:
  We use seeing-free high spatial resolution Ca II H data obtained by the
SUNRISE observatory to determine properties of slender fibrils in the lower
solar chromosphere. In this work we use intensity images taken with the SUFI
instrument in the Ca II H line during the second scientific flight of the
SUNRISE observatory to identify and track elongated bright structures. After
the identification, we analyze theses structures in order to extract their
morphological properties. We identify 598 slender Ca II H fibrils (SCFs) with
an average width of around 180 km, a length between 500 km and 4000 km, an
average lifetime of ~400 s, and an average curvature of 0.002 arcsec^-1. The
maximum lifetime of the SCFs within our time series of 57 minutes is ~2000 s.
We discuss similarities and differences of the SCFs with other small-scale,
chromospheric structures such as spicules of type I and II, or Ca II K fibrils.


title:
Synthesis of hydrogen- and methyl-capped long-chain polyynes by intense
  ultrashort laser pulse irradiation of toluene

abstract:
  Hydrogen- and methyl-capped polyynes were synthesized by irradiating pure
liquid toluene with 35 femtosecond, 300 {\mu}J laser pulses having a central
wavelength of 800 nm, generated by a regeneratively amplified Ti:sapphire
tabletop laser at a repetition rate of 1 kHz. Raman spectroscopy was used to
confirm the presence of polyynes in the irradiated samples while
high-performance liquid chromatography was used to separate hydrogen-capped
polyynes up to C18H2 and methyl-capped polyynes up to HC14CH3. These represent
the first such methyl-capped polyynes and the longest hydrogen capped chains
synthesized to date by the ultrafast laser based method. Furthermore our
results show that choice of the starting solvent molecule directly influences
the end caps of the polyynes which can be produced.


title: Anisotropic (2+1)d growth and Gaussian limits of q-Whittaker processes

abstract:
  We consider a discrete model for anisotropic (2+1)-dimensional growth of an
interface height function. Owing to a connection with q-Whittaker functions,
this system enjoys many explicit integral formulas. By considering certain
Gaussian stochastic differential equation limits of the model we are able to
prove a space-time limit to the (2+1)-dimensional additive stochastic heat
equation (or Edwards-Wilkinson equation) along characteristic directions. In
particular, the bulk height function converges to the Gaussian free field which
evolves according to this stochastic PDE.

categories: math.PR cond-mat.stat-mech math-ph math.MP


title: Integral transform methods: a critical review of various kernels

abstract:
  Some general remarks about integral transform approaches to response
functions are made. Their advantage for calculating cross sections at energies
in the continuum is stressed. In particular we discuss the class of kernels
that allow calculations of the transform by matrix diagonalization. A
particular set of such kernels, namely the wavelets, is tested in a model
study.


title:
The Tyranny of Data? The Bright and Dark Sides of Data-Driven
  Decision-Making for Social Good

abstract:
  The unprecedented availability of large-scale human behavioral data is
profoundly changing the world we live in. Researchers, companies, governments,
financial institutions, non-governmental organizations and also citizen groups
are actively experimenting, innovating and adapting algorithmic decision-making
tools to understand global patterns of human behavior and provide decision
support to tackle problems of societal importance. In this chapter, we focus
our attention on social good decision-making algorithms, that is algorithms
strongly influencing decision-making and resource optimization of public goods,
such as public health, safety, access to finance and fair employment. Through
an analysis of specific use cases and approaches, we highlight both the
positive opportunities that are created through data-driven algorithmic
decision-making, and the potential negative consequences that practitioners
should be aware of and address in order to truly realize the potential of this
emergent field. We elaborate on the need for these algorithms to provide
transparency and accountability, preserve privacy and be tested and evaluated
in context, by means of living lab approaches involving citizens. Finally, we
turn to the requirements which would make it possible to leverage the
predictive power of data-driven human behavior analysis while ensuring
transparency, accountability, and civic participation.


title: Quantum reduced loop gravity: extension to gauge vector field

abstract:
  Within the framework of Quantum Reduced Loop Gravity we quantize the
Hamiltonian for a gauge vector field. The regularization can be performed using
tools analogous to the ones adopted in full Loop Quantum Gravity, while the
matrix elements of the resulting operator between basis states are analytic
coefficients. This analysis is the first step towards deriving the full quantum
gravity corrections to the vector field semiclassical dynamics.


title:
A fast spinning magnetic white dwarf in the double-degenerate,
  super-Chandrasekhar system NLTT 12758

abstract:
  We present an analysis of the close double degenerate NLTT 12758, which is
comprised of a magnetic white dwarf with a field of about 3.1 MG and an
apparently non-magnetic white dwarf. We measured an orbital period of 1.154
days and found that the magnetic white dwarf is spinning around its axis with a
period of 23 minutes. An analysis of the atmospheric parameters has revealed
that the cooling ages of the two white dwarfs are comparable, suggesting that
they formed within a short period of time from each other. Our modelling
indicates that the non-magnetic white dwarf is more massive (M=0.83 M_sun) than
its magnetic companion (M=0.69 M_sun) and that the total mass of the system is
higher than the Chandrasekhar mass. Although the stars will not come into
contact over a Hubble time, when they do come into contact, dynamically
unstable mass transfer will take place leading to either an accretion induced
collapse into a rapidly spinning neutron star or a Type Ia supernova.


title: Geometric interpretation of Planck-scale-deformed co-products

abstract:
  For theories formulated with a maximally symmetric momentum space we propose
a general characterization for the description of interactions in terms of the
isometry group of the momentum space. The well known cases of
$\kappa$-Poincar\'e-inspired and (2+1)-dimensional gravity-inspired composition
laws both satisfy our condition. Future applications might include the proposal
of a class of models based on momenta spaces with anti-de Sitter geometry.


title:
Hadronic matter under an external magnetic field: in medium modification
  of the pion mass

abstract:
  The covariant propagator of a fermion with intrinsic magnetic moment
interacting with a uniform external magnetic field is presented for finite
temperature and baryonic density. The case of a scalar boson is also
considered. The final expressions are given in terms of a four-dimensional
momentum representation. These results, which take account of the full effect
of the magnetic field, are used to evaluate the modification of the pion mass
at zero temperature as a function of the density and the magnetic intensity.
For this purpose a self-consistent calculation, including one- and two-pion
vertices, is employed.


title: Optimal discrimination designs for semi-parametric models

abstract:
  Much of the work in the literature on optimal discrimination designs assumes
that the models of interest are fully specified, apart from unknown parameters
in some models. Recent work allows errors in the models to be non-normally
distributed but still requires the specification of the mean structures. This
research is motivated by the interesting work of Otsu (2008) to discriminate
among semi-parametric models by generalizing the KL-optimality criterion
proposed by L\'opez-Fidalgo et al. (2007) and Tommasi and L\'opez-Fidalgo
(2010). In our work we provide further important insights in this interesting
optimality criterion. In particular, we propose a practical strategy for
finding optimal discrimination designs among semi-parametric models that can
also be verified using an equivalence theorem. In addition, we study properties
of such optimal designs and identify important cases where the proposed
semi-parametric optimal discrimination designs coincide with the celebrated T
-optimal designs.


title: Sensitivity of lunar particle-detection experiments

abstract:
  The use of the Moon as a detector volume for ultra-high-energy neutrinos and
cosmic rays, by searching for the Askaryan radio pulse produced when they
interact in the lunar regolith, has been attempted by a range of projects over
the past two decades. In this contribution, I discuss some of the technical
considerations relevant to these experiments, and their consequent sensitivity
to ultra-high-energy particles. I also discuss some possible future
experiments, and highlight their potential.


title:
A controlled experiment for the empirical evaluation of safety analysis
  techniques for safety-critical software

abstract:
  Context: Today's safety critical systems are increasingly reliant on
software. Software becomes responsible for most of the critical functions of
systems. Many different safety analysis techniques have been developed to
identify hazards of systems. FTA and FMEA are most commonly used by safety
analysts. Recently, STPA has been proposed with the goal to better cope with
complex systems including software. Objective: This research aimed at comparing
quantitatively these three safety analysis techniques with regard to their
effectiveness, applicability, understandability, ease of use and efficiency in
identifying software safety requirements at the system level. Method: We
conducted a controlled experiment with 21 master and bachelor students applying
these three techniques to three safety-critical systems: train door control,
anti-lock braking and traffic collision and avoidance. Results: The results
showed that there is no statistically significant difference between these
techniques in terms of applicability, understandability and ease of use, but a
significant difference in terms of effectiveness and efficiency is obtained.
Conclusion: We conclude that STPA seems to be an effective method to identify
software safety requirements at the system level. In particular, STPA addresses
more different software safety requirements than the traditional techniques FTA
and FMEA, but STPA needs more time to carry out by safety analysts with little
or no prior experience.


title:
Pair potentials for warm dense matter and their application to x-ray
  Thomson scattering in aluminum and beryllium

abstract:
  Ultrafast laser experiments yield increasingly reliable data on warm dense
matter, but their interpretation requires theoretical models. We employ an
efficient density functional neutral-pseudoatom hypernetted-chain (NPA-HNC)
model with accuracy comparable to ab initio simulations and which provides
first-principles pseudopotentials and pair-potentials for warm-dense matter. It
avoids the use of (i) ad hoc core-repulsion models and (ii) "Yukawa screening",
and (iii) need not assume ionelectron thermal equilibrium. Computations of the
x-Ray Thomson scattering (XRTS) spectra of aluminum and beryllium are compared
with recent experiments and with density-functional-theory molecular-dynamics
(DFT-MD) simulations. The NPA-HNC structure factors, compressibilities, phonons
and conductivities agree closely with DFT-MD results, while Yukawa screening
gives misleading results. The analysis of the XRTS data for two of the
experiments, using two-temperature quasi-equilibrium models, is supported by
calculations of their temperature relaxation times.


title:
Recovering the uniform boundary observability with spectral
  Legendre-Galerkin formulations of the 1-D wave equation

abstract:
  For a Legendre-Galerkin semi-discretization of the 1-D homogeneous wave
equation, the high frequency components of the numerical solution prevent us
from obtaining the boundary observability (inequality), uniformly with regard
to the discretization parameter. A classical Fourier filtering that filters out
the high frequencies is sufficient to recover the uniform observability.
Unfortunately, this remedy needs to compute all the frequencies of the
underlying system. In this paper we present three cheaper alternative remedies,
namely a spectral filtering, a mixed formulation and Nitsche's method to append
Dirichlet type boundary conditions. Our numerical results show indeed that
uniform boundary observability inequalities may be recovered. On another hand,
surprisingly, none of them seems to provide a uniform direct (or trace)
inequality, a property which is needed in some existing general convergence
results for the adjoint boundary controllability problem. We finally show in a
numerical example that, despite this fact, convergence of the control
approximations holds whenever the uniform observability inequality is observed
numerically.


title:
Discovery of a low-mass companion inside the debris ring surrounding the
  F5V star HD206893

abstract:
  Uncovering the ingredients and the architecture of planetary systems is a
very active field of research that has fuelled many new theories on giant
planet formation, migration, composition, and interaction with the
circumstellar environment. We aim at discovering and studying new such systems,
to further expand our knowledge of how low-mass companions form and evolve. We
obtained high-contrast H-band images of the circumstellar environment of the
F5V star HD206893, known to host a debris disc never detected in scattered
light. These observations are part of the SPHERE High Angular Resolution Debris
Disc Survey (SHARDDS) using the InfraRed Dual-band Imager and Spectrograph
(IRDIS) installed on VLT/SPHERE. We report the detection of a source with a
contrast of 3.6x10^{-5} in the H-band, orbiting at a projected separation of
270 milliarcsecond or 10 au, corresponding to a mass in the range 24 to 73 Mjup
for an age of the system in the range 0.2 to 2 Gyr. The detection was confirmed
ten months later with VLT/NaCo, ruling out a background object with no proper
motion. A faint extended emission compatible with the disc scattered light
signal is also observed. The detection of a low-mass companion inside a massive
debris disc makes this system an analog of other young planetary systems such
as beta Pictoris, HR8799 or HD95086 and requires now further characterisation
of both components to understand their interactions.


title:
A Theoretical Framework for Robustness of (Deep) Classifiers against
  Adversarial Examples

abstract:
  Most machine learning classifiers, including deep neural networks, are
vulnerable to adversarial examples. Such inputs are typically generated by
adding small but purposeful modifications that lead to incorrect outputs while
imperceptible to human eyes. The goal of this paper is not to introduce a
single method, but to make theoretical steps towards fully understanding
adversarial examples. By using concepts from topology, our theoretical analysis
brings forth the key reasons why an adversarial example can fool a classifier
($f_1$) and adds its oracle ($f_2$, like human eyes) in such analysis. By
investigating the topological relationship between two (pseudo)metric spaces
corresponding to predictor $f_1$ and oracle $f_2$, we develop necessary and
sufficient conditions that can determine if $f_1$ is always robust
(strong-robust) against adversarial examples according to $f_2$. Interestingly
our theorems indicate that just one unnecessary feature can make $f_1$ not
strong-robust, and the right feature representation learning is the key to
getting a classifier that is both accurate and strong-robust.


title:
Single-shot measurement of the orbital-angular-momentum spectrum of
  light

abstract:
  The existing methods for measuring the orbital-angular-momentum (OAM)
spectrum suffer from issues such as poor efficiency, strict interferometric
stability requirements, and too much loss. Furthermore, most techniques
inevitably discard part of the field and measure only a post-selected portion
of the true spectrum. Here, we propose and demonstrate an interferometric
technique for measuring the true OAM spectrum of optical fields in a
single-shot manner. Our technique directly encodes the OAM-spectrum information
in the azimuthal intensity profile of the output interferogram. In the absence
of noise, the spectrum can be fully decoded using a single acquisition of the
output interferogram, and, in the presence of noise, acquisition of two
suitable interferograms is sufficient for the purpose. As an important
application of our technique, we demonstrate measurements of the angular
Schmidt spectrum of the entangled photons produced by parametric
down-conversion and report a broad spectrum with the angular Schmidt number
82.1.


title: Some remarks on 'superradiant' phase transitions in light-matter systems

abstract:
  In this paper we analyze properties of the phase transition that appears in a
set of quantum optical models; Dicke, Tavis-Cummings, quantum Rabi, and finally
the Jaynes-Cummings model. As the light-matter coupling is increased into the
deep strong coupling regime, the ground state turns from vacuum to become a
superradiant state characterized by both atomic and photonic excitations. It is
pointed out that all four transitions are of the mean-field type, that quantum
fluctuations are negligible, and hence these fluctuations cannot be responsible
for the corresponding vacuum instability. In this respect, these are not
quantum phase transitions. In the case of the Tavis-Cummings and
Jaynes-Cummings models, the continuous symmetry of these models implies that
quantum fluctuations are not only negligible, but strictly zero. However, all
models possess a non-analyticity in the ground state in agreement with a
continuous quantum phase transition. As such, it is a matter of taste whether
the transitions should be termed quantum or not. In addition, we also consider
the modifications of the transitions when photon losses are present. For the
Dicke and Rabi models these non-equilibrium steady states remain critical,
while the criticality for the open Tavis-Cummings and Jaynes-Cummings models is
completely lost, i.e. in realistic settings one cannot expect a true critical
behaviour for the two last models.


title: The AAA algorithm for rational approximation

abstract:
  We introduce a new algorithm for approximation by rational functions on a
real or complex set of points, implementable in 40 lines of Matlab and
requiring no user input parameters. Even on a disk or interval the algorithm
may outperform existing methods, and on more complicated domains it is
especially competitive. The core ideas are (1) representation of the rational
approximant in barycentric form with interpolation at certain support points
and (2) greedy selection of the support points to avoid exponential
instabilities. The name AAA stands for "adaptive Antoulas--Anderson" in honor
of the authors who introduced a scheme based on (1). We present the core
algorithm with a Matlab code and nine applications and describe variants
targeted at problems of different kinds. Comparisons are made with vector
fitting, RKFIT, and other existing methods for rational approximation.


title:
Hippocampus Temporal Lobe Epilepsy Detection using a Combination of
  Shape-based Features and Spherical Harmonics Representation

abstract:
  Most of the temporal lobe epilepsy detection approaches are based on
hippocampus deformation and use complicated features, resulting, detection is
done with complicated features extraction and pre-processing task. In this
paper, a new detection method based on shape-based features and spherical
harmonics is proposed which can analysis the hippocampus shape anomaly and
detection asymmetry. This method consisted of two main parts; (1) shape feature
extraction, and (2) image classification. For evaluation, HFH database is used
which is publicly available in this field. Nine different geometry and 256
spherical harmonic features are introduced then selected Eighteen of them that
detect the asymmetry in hippocampus significantly in a randomly selected subset
of the dataset. Then a support vector machine (SVM) classifier was employed to
classify the remaining images of the dataset to normal and epileptic images
using our selected features. On a dataset of 25 images, 12 images were used for
feature extraction and the rest 13 for classification. The results show that
the proposed method has accuracy, specificity and sensitivity of, respectively,
84%, 100%, and 80%. Therefore, the proposed approach shows acceptable result
and is straightforward also; complicated pre-processing steps were omitted
compared to other methods.


title: Anomalous diffusion on a fractal mesh

abstract:
  An exact analytical analysis of anomalous diffusion on a fractal mesh is
presented. The fractal mesh structure is a direct product of two fractal sets
which belong to a main branch of backbones and side branch of fingers. The
fractal sets of both backbones and fingers are constructed on the entire
(infinite) $y$ and $x$ axises. To this end we suggested a special algorithm of
this special construction. The transport properties of the fractal mesh is
studied, in particular, subdiffusion along the backbones is obtained with the
dispersion relation $\langle x^2(t)\rangle\sim t^{\beta}$, where the transport
exponent $\beta<1$ is determined by the fractal dimensions of both backbone and
fingers. Superdiffusion with $\beta>1$ has been observed as well when the
environment is controlled by means of a memory kernel.


title:
Statistical link between the structure of molecular clouds and their
  density distribution

abstract:
  We introduce the concept of a class of equivalence of molecular clouds
represented by an abstract spherically symmetric, isotropic object. This object
is described by use of abstract scales in respect to a given mass density
distribution. Mass and average density are ascribed to each scale and thus are
linked to the density distribution: a power-law type and an arbitrary
continuous one. In the latter case, we derive a differential relationship
between the mean density at a given scale and the structure parameter which
defines the mass-density relationship. The two-dimensional (2D) projection of
the cloud along the line of sight is also investigated. Scaling relations of
mass and mean density are derived in the considered cases of power-law and
arbitrary continuous distributions. We obtain relations between scaling
exponents in the 2D and 3D cases. The proposed classes of equivalence are
representative for the general structure of real clouds with various types of
column-density distributions: power law, lognormal or combination of both.


title: A Compositional Object-Based Approach to Learning Physical Dynamics

abstract:
  We present the Neural Physics Engine (NPE), a framework for learning
simulators of intuitive physics that naturally generalize across variable
object count and different scene configurations. We propose a factorization of
a physical scene into composable object-based representations and a neural
network architecture whose compositional structure factorizes object dynamics
into pairwise interactions. Like a symbolic physics engine, the NPE is endowed
with generic notions of objects and their interactions; realized as a neural
network, it can be trained via stochastic gradient descent to adapt to specific
object properties and dynamics of different worlds. We evaluate the efficacy of
our approach on simple rigid body dynamics in two-dimensional worlds. By
comparing to less structured architectures, we show that the NPE's
compositional representation of the structure in physical interactions improves
its ability to predict movement, generalize across variable object count and
different scene configurations, and infer latent properties of objects such as
mass.


title:
Atmospheric Retrieval for Direct Imaging Spectroscopy of Gas Giants In
  Reflected Light II: Orbital Phase and Planetary Radius

abstract:
  Future space-based telescopes, such as the Wide-Field Infrared Survey
Telescope (WFIRST), will observe the reflected-light spectra of directly imaged
extrasolar planets. Interpretation of such data presents a number of novel
challenges, including accounting for unknown planet radius and uncertain
stellar illumination phase angle. Here we report on our continued development
of Markov Chain Monte Carlo retrieval methods for addressing these issues in
the interpretation of such data. Specifically we explore how the unknown planet
radius and potentially poorly known observer-planet-star phase angle impacts
retrievals of parameters of interest such as atmospheric methane abundance,
cloud properties and surface gravity. As expected, the uncertainty in retrieved
values is a strong function of signal-to-noise ratio (SNR) of the observed
spectra, particularly for low metallicity atmospheres, which lack deep
absorption signatures. Meaningful results may only be possible above certain
SNR thresholds; for cases across a metallicity range of 1-50 times solar, we
find that only an SNR of 20 systematically reproduces close to the correct
methane abundance at all phase angles. However, even in cases where the phase
angle is poorly known we find that the planet radius can be constrained to
within a factor of two. We find that uncertainty in planet radius decreases at
phase angles past quadrature, as the highly forward scattering nature of the
atmosphere at these geometries limits the possible volume of phase space that
relevant parameters can occupy. Finally, we present an estimation of possible
improvement that can result from combining retrievals against observations at
multiple phase angles.


title: Global Minimum for a Finsler Elastica Minimal Path Approach

abstract:
  In this paper, we propose a novel curvature-penalized minimal path model via
an orientation-lifted Finsler metric and the Euler elastica curve. The original
minimal path model computes the globally minimal geodesic by solving an Eikonal
partial differential equation (PDE). Essentially, this first-order model is
unable to penalize curvature which is related to the path rigidity property in
the classical active contour models. To solve this problem, we present an
Eikonal PDE-based Finsler elastica minimal path approach to address the
curvature-penalized geodesic energy minimization problem. We were successful at
adding the curvature penalization to the classical geodesic energy. The basic
idea of this work is to interpret the Euler elastica bending energy via a novel
Finsler elastica metric that embeds a curvature penalty. This metric is
non-Riemannian, anisotropic and asymmetric, and is defined over an
orientation-lifted space by adding to the image domain the orientation as an
extra space dimension. Based on this orientation lifting, the proposed minimal
path model can benefit from both the curvature and orientation of the paths.
Thanks to the fast marching method, the global minimum of the
curvature-penalized geodesic energy can be computed efficiently. We introduce
two anisotropic image data-driven speed functions that are computed by
steerable filters. Based on these orientation-dependent speed functions, we can
apply the proposed Finsler elastica minimal path model to the applications of
closed contour detection, perceptual grouping and tubular structure extraction.
Numerical experiments on both synthetic and real images show that these
applications of the proposed model indeed obtain promising results.


title:
Peccei-Quinn Transformations and Black Holes : Orbit Transmutations and
  Entanglement Generation

abstract:
  In a recent paper [Mod. Phys. Lett. A30 (2015) 1550104], the black-hole/qubit
correspondence (BHQC) was exploited to define "black hole quantum circuits"
allowing for a change of the supersymmetry-preserving features of
electromagnetic charge configurations supporting the black hole solution, thus
switching from one U-duality orbit to another, or - equivalently - from an
element of the corresponding Freudenthal Triple System with a definite rank, to
another one. On the supergravity side of BHQC, such quantum gates relate to
particular symplectic transformations acting on the black hole charges; namely,
such transformations cannot belong to the U-duality group, otherwise switching
among orbits would be impossible. In this paper, we consider a particular class
of such symplectic transformations, namely the ones belonging to the so-called
Peccei-Quinn symplectic group, introduced some time ago within the study of
very special Kaehler geometries of the vector multiplets' scalar manifolds in N
= 2 supergravity in D = 4 space-time dimensions.


title: Holographic Dark Energy

abstract:
  We review the paradigm of holographic dark energy (HDE), which arises from a
theoretical attempt of applying the holographic principle (HP) to the dark
energy (DE) problem. Making use of the HP and the dimensional analysis, we
derive the general formula of the energy density of HDE. Then, we describe the
properties of HDE model, in which the future event horizon is chosen as the
characteristic length scale. We also introduce the theoretical explorations and
the observational constraints for this model. Next, in the framework of HDE, we
discuss various topics, such as spatial curvature, neutrino, instability of
perturbation, time-varying gravitational constant, inflation, black hole and
big rip singularity. In addition, from both the theoretical and the
observational aspects, we introduce the interacting holographic dark energy
scenario, where the interaction between dark matter and HDE is taken into
account. Furthermore, we discuss the HDE scenario in various modified gravity
(MG) theories, such as Brans-Dicke theory, braneworld theory, scalar-tensor
theory, Horava-Lifshitz theory, and so on. Besides, we introduce the attempts
of reconstructing various scalar-field DE and MG models from HDE. Moreover, we
introduce other DE models inspired by the HP, in which different characteristic
length scales are chosen. Finally, we make comparisons among various
HP-inspired DE models, by using cosmological observations and diagnostic tools.


title: Stringy bounces and gradient instabilities

abstract:
  Bouncing solutions are obtained from a generally covariant action
characterized by a potential which is a nonlocal functional of the dilaton
field at two separated space-time points. Gradient instabilities are shown to
arise in this context but they are argued to be nongeneric. After performing a
gauge-invariant and frame-invariant derivation of the evolution equations of
the fluctuations, a heuristic criterion for the avoidance of pathological
instabilities is proposed and corroborated by a number of explicit examples
that turn out to be compatible with a quasi-flat spectrum of curvature
inhomogeneities for typical wavelengths larger than the Hubble radius.


title:
Bootstrapping incremental dialogue systems: using linguistic knowledge
  to learn from minimal data

abstract:
  We present a method for inducing new dialogue systems from very small amounts
of unannotated dialogue data, showing how word-level exploration using
Reinforcement Learning (RL), combined with an incremental and semantic grammar
- Dynamic Syntax (DS) - allows systems to discover, generate, and understand
many new dialogue variants. The method avoids the use of expensive and
time-consuming dialogue act annotations, and supports more natural
(incremental) dialogues than turn-based systems. Here, language generation and
dialogue management are treated as a joint decision/optimisation problem, and
the MDP model for RL is constructed automatically. With an implemented system,
we show that this method enables a wide range of dialogue variations to be
automatically captured, even when the system is trained from only a single
dialogue. The variants include question-answer pairs, over- and
under-answering, self- and other-corrections, clarification interaction,
split-utterances, and ellipsis. This generalisation property results from the
structural knowledge and constraints present within the DS grammar, and
highlights some limitations of recent systems built using machine learning
techniques only.


title:
Irregular Conformal States and Spectral Curve: Irregular Matrix Model
  Approach

abstract:
  We present recent developments of irregular conformal conformal states.
Irregular vertex operators and their adjoint in a new formalism are used to
define the irregular conformal states and their inner product instead of using
the colliding limit procedure. Free field formalism can be augmented by
screening operators which provide more degrees of freedom. The inner product is
conveniently given as the partition function of an irregular matrix model.
(Deformed) spectral curve is the loop equation of the matrix model at
Nekrasov-Shatashivili limit. We present the details of analytic structure of
the spectral curve for Virasoso symmetry and its extensions, $W$-symmetry and
super-symmetry.


title: Broken-Symmetry Quantum Hall States in Twisted Bilayer Graphene

abstract:
  Twisted bilayer graphene offers a unique bilayer two-dimensional-electron
system where the layer separation is only in sub-nanometer scale. Unlike
Bernal-stacked bilayer, the layer degree of freedom is disentangled from spin
and valley, providing eight-fold degeneracy in the low energy states. We have
investigated broken-symmetry quantum Hall (QH) states and their transitions due
to the interplay of the relative strength of valley, spin and layer
polarizations in twisted bilayer graphene. The energy gaps of the
broken-symmetry QH states show an electron-hole asymmetric behaviour, and their
dependence on the induced displacement field are opposite between even and odd
filling factor states. These results strongly suggest that the QH states with
broken valley and spin symmetries for individual layer become hybridized via
interlayer tunnelling, and the hierarchy of the QH states is sensitive to both
magnetic field and displacement field due to charge imbalance between layers.


title: $ND$ and $NB$ systems in quark delocalization color screening model

abstract:
  The $ND$ and $NB$ systems with $I=0$ and $1$, $J^{P}=\frac{1}{2}^{\pm}$,
$\frac{3}{2}^{\pm}$, and $\frac{5}{2}^{\pm}$ are investigated within the
framework of quark delocalization color screening model. The results show that
all the positive parity states are unbound. By coupling to the $ND^{*}$
channel, the state $ND$ with $I=0,~J^{P}=\frac{1}{2}^{-}$ can form a bound
state, which can be invoked to explain the observed $\Sigma(2800)$ state. The
mass of the $ND^{*}$ with $I=0,~J^{P}=\frac{3}{2}^{-}$ is close to that of the
reported $\Lambda_{c}(2940)^{+}$, which indicates that $\Lambda_{c}(2940)^{+}$
can be explained as a $ND^{*}$ molecular state in QDCSM. Besides, the $\Delta
D^{*}$ with $I=1,~J^{P}=\frac{5}{2}^{-}$ is also a possible resonance state.
The results of the bottom case of $NB$ system are similar to those of the $ND$
system. Searching for these states will be a challenging subject of
experiments.


title: Simple recipe for holographic Weyl anomaly

abstract:
  We propose a recipe - arguably the simplest - to compute the holographic
type-B Weyl anomaly for general higher-derivative gravity in asymptotically AdS
spacetimes. In 5 and 7 dimensions we identify a suitable basis of curvature
invariants that allows to read off easily, without any further computation, the
Weyl anomaly coefficients of the dual CFT. We tabulate the contributions from
quadratic, cubic and quartic purely algebraic curvature invariants and also
from terms involving derivatives of the curvature. We provide few examples,
where the anomaly coefficients have been obtained by other means, to illustrate
the effectiveness of our prescription.


title: Performance Evaluation of Caching Policies in NDN - an ICN Architecture

abstract:
  Information Centric Networking (ICN) advocates the philosophy of accessing
the content independent of its location. Owing to this location independence in
ICN, the routers en-route can be enabled to cache the content to serve the
future requests for the same content locally. Several ICN architectures have
been proposed in the literature along with various caching algorithms for
caching and cache replacement at the routers en-route. The aim of this paper is
to critically evaluate various caching policies using Named Data Networking
(NDN), an ICN architecture proposed in literature. We have presented the
performance comparison of different caching policies naming First In First Out
(FIFO), Least Recently Used (LRU), and Universal Caching (UC) in two network
models; Watts-Strogatz (WS) model (suitable for dense short link networks such
as sensor networks) and Sprint topology (better suited for large Internet
Service Provider (ISP) networks) using ndnSIM, an ns3 based discrete event
simulator for NDN architecture. Our results indicate that UC outperforms other
caching policies such as LRU and FIFO and makes UC a better alternative for
both sensor networks and ISP networks.


title: Time in quantum cosmology

abstract:
  A cosmological model with two global internal times shows that time
reparameterization invariance, and therefore covariance, is not guaranteed by
deparameterization. In particular, it is impossible to derive proper-time
effective equations from a single deparameterized model if quantum corrections
from fluctuations and higher moments are included. The framework of effective
constraints shows how proper-time evolution can consistently be defined in
quantum cosmological systems, such that it is time reparameterization invariant
when compared with other choices of coordinate time. At the same time, it
allows transformations of moment corrections in different deparameterizations
of the same model, indicating partial time reparameterization of internal-time
evolution. However, in addition to corrections from moments such as quantum
fluctuations, also factor ordering corrections may appear. The latter
generically break covariance in internal-time formulations. Fluctuation effects
in quantum cosmology are therefore problematic, in particular if derivations
are made with a single choice of internal time or a fixed physical Hilbert
space.


title: On the equatorial Dehn twist of a Lagrangian nodal sphere

abstract:
  Let $(M^4,\omega)$ be a geometrically bounded symplectic manifold, and
$L\subset M$ a Lagrangian nodal sphere such that $\omega\mid_{\pi_2(M,L)}=0$.
We show that an equatorial Dehn twist of $L$ does not extend to a Hamiltonian
diffeomorphism of $M$. We also confirm a mirror symmetry prediction about the
action of a symplectomorphism extending an equatorial Dehn twist on the Floer
theory of the nodal sphere. We present analogues of the equatorial Dehn twist
for more singular Lagrangians, and make concrete conjectures about them.


title: Atlas as solution of Sincov's inequality

abstract:
  We find a solution of Sincov's inequality. Further, we prove that in the
differentiable case we can interpret such solution as a differentiable manifold
in the original sense of Lang. This allows to generalize the notion of atlas
and transition map for non-differentiable and discontinuous case.


title:
A Large Deformation Diffeomorphic Approach to Registration of CLARITY
  Images via Mutual Information

abstract:
  CLARITY is a method for converting biological tissues into translucent and
porous hydrogel-tissue hybrids. This facilitates interrogation with light sheet
microscopy and penetration of molecular probes while avoiding physical slicing.
In this work, we develop a pipeline for registering CLARIfied mouse brains to
an annotated brain atlas. Due to the novelty of this microscopy technique it is
impractical to use absolute intensity values to align these images to existing
standard atlases. Thus we adopt a large deformation diffeomorphic approach for
registering images via mutual information matching. Furthermore we show how a
cascaded multi-resolution approach can improve registration quality while
reducing algorithm run time. As acquired image volumes were over a terabyte in
size, they were far too large for work on personal computers. Therefore the
NeuroData computational infrastructure was deployed for multi-resolution
storage and visualization of these images and aligned annotations on the web.


title:
Influence of the external pressure on the quantum correlations of
  molecular magnets

abstract:
  The study of quantum correlations in solid state systems is a large avenue
for research and their detection and manipulation are an actual challenge to
overcome. In this context, we show by using first-principles calculations on
the prototype material KNaCuSi$_{4}$O$_{10}$ that the degree of quantum
correlations in this spin cluster system can be managed by external hydrostatic
pressure. Our results open the doors for research in detection and manipulation
of quantum correlations in magnetic systems with promising applications in
quantum information science.


title: A Study of a Nonlinear Schr\"odinger Equation for Optical Fibers

abstract:
  Non linear fiber optics concerns with the non linear optical phenomena
occurring inside optical fibers. The propagation of light in single-mode fibers
is governed by the one-dimensional nonlinear Schr\"odinger equation (NLS) in
the presence of attenuation, dispersion, and non linear effects. In this NLS
the role of space and time is exchanged with respect to the standard NLS as
introduced in the almost entire mathematical literature. Such an exchange is
far from being only formal as it enters in the interpretation of basic ideas as
well-posedness and stability, as well as in the phenomenological meaning of the
predictions formulated by such model. In this dissertation, the physical bases
of the optical fibers are provided, and a derivation of the NLS from the
Maxwell's equations is reviewed. Furthermore, problems of local nature (local
existence of solutions, uniqueness) and problems of global nature (global
existence) are studied by the Kato's method based on a fixed point argument and
Strichartz's estimates. Moreover, tools usually employed to study global
problems connected with finite-time blow up of solutions, are here used to show
a closeness result between the NLS for optical fibers and an integrable NLS.
Integrability is pursued by means of the Painlev\'e analysis that allows to
describe quite a large class of integrable equations like the transformed
equation from the standard NLS. Among these functions, one can be described as
a standard NLS with an additional linear harmonic oscillator term. This
equation is showed to be close in $L^2$-norm to the NLS for single-mode fibers.
Finally, the dissertation focuses on two kinds of stationary solutions: the
so-called time-homogenous, that is given by a stationary wave oscillating in
space, and the soliton-like solution. Results are obtained about stability
properties of them.


title: The Weyl-Heisenberg ensemble: hyperuniformity and higher Landau levels

abstract:
  Weyl-Heisenberg ensembles are a class of determinantal point processes
associated with the Schr\"odinger representation of the Heisenberg group.
Hyperuniformity characterizes a state of matter for which (scaled) density
fluctuations diminish towards zero at the largest length scales. We will prove
that Weyl-Heisenberg ensembles are hyperuniform. Weyl-Heisenberg ensembles
include as a special case a multi-layer extension of the Ginibre ensemble
modeling the distribution of electrons in higher Landau levels, which has
recently been object of study in the realm of the Ginibre-type ensembles
associated with polyanalytic functions. In addition, the family of
Weyl-Heisenberg ensembles includes new structurally anisotropic processes,
where point-statistics depend on the different spatial directions, and thus
provide a first means to study directional hyperuniformity.


title:
On the approximation of electronic wavefunctions by anisotropic Gauss
  and Gauss-Hermite functions

abstract:
  The electronic Schr\"odinger equation describes the motion of N electrons
under Coulomb interaction forces in a field of clamped nuclei. The solutions of
this equation, the electronic wavefunctions, depend on 3N variables, three
spatial dimensions for each electron. We study the approximability of these
wavefunctions by linear combinations of anisotropic Gauss functions, or more
precisely Gauss-Hermite functions, products of polynomials and anisotropic
Gauss functions in the narrow sense. We show that the original, singular
wavefunctions can up to given accuracy and a negligibly small residual error be
approximated with only insignificantly more such terms than their convolution
with a Gaussian kernel of sufficiently small width and that basically arbitrary
orders of convergence can be reached. This is a fairly surprising result, since
it essentially means that by this type of approximation, the intricate
hierarchies of non-smooth cusps in electronic wavefunctions have almost no
impact on the convergence, once the global structure is resolved.


title: Inverse-phase Rabi oscillations in semiconductor microcavities

abstract:
  We study experimentally the oscillations of a non stationary transient signal
of a semiconductor microcavity with embedded InGaAs quantum wells. The
oscillations occur as a result of quantum beats between the upper and lower
polariton modes due to the strong exciton-photon coupling in the microcavity
sample (Rabi oscillations). The registration of spectrally resolved signal has
allowed for separate observation of oscillations at the eigenfrequencies of two
polariton modes. Surprisingly, the observed oscillations measured at the lower
and upper polariton modes have opposite phases. We demonstrate theoretically
that the opposite-phase oscillations are caused by the pump-induced
modification of polariton Hopfield coefficients, which govern the ratio of
exciton and photon components in each of the polartion modes. Such a behaviour
is a fundamental feature of the quantum beats of coupled light-matter states.
In contrast, the reference pump-probe experiment performed for the pure
excitonic states in a quantum well heterostructure with no microcavity revealed
the in-phase oscillations of the pump-probe signals measured at different
excitonic levels.


title: Metrizable topologies and admissible algebras

abstract:
  We provide a necessary and sufficient condition for the embeddability of a
metrizable group into semigroup compactifications associated to uniformly
continuous functions. Our result employs a technique used by I. Ben Yaacov, A.
Berenstein and S. Ferri, and generalizes a theorem by them. This paper is part
of the author's Ph.D. dissertation written under the supervision of Stefano
Ferri and Jorge Galindo at Universidad de los Andes (Bogot\'a-Colombia).


title: Ice grains grow by dissolution, ripening and grain boundary migration

abstract:
  Despite the exponential growth in computing resources and the availability of
a myriad of different theoretical water models, an accurate, yet
computationally efficient molecular level description of mesoscopic grain
growth remains a grand challenge. The underlying phase transitions and
dynamical processes in deeply supercooled systems are often rendered
inaccessible due to limitations imposed by system sizes and timescales, which
is further compounded by their sluggish kinetics. Here, we introduce a
machine-learned, bond-order-based potential model (BOP) that more accurately
describes the anomalous behavior, as well as structural and thermodynamical
properties of both liquid water and ice, with at least two orders of magnitude
cheaper computational cost than existing atomistic water models. In a
significant departure from conventional force-field fitting, we use a
multilevel evolutionary strategy that trains the BOP model against not just
energetics but temperature dependent properties inferred from on-the-fly
molecular dynamics simulations as well. We use the BOP model to probe the
homogeneous ice nucleation and growth process by performing molecular dynamics
on multi-million molecule systems for up to microsecond time scales. These
massively parallel, long-time simulations naturally capture the competition
between cubic, hexagonal, and stacking disordered ice phases during nucleation
and early stages of growth leading to the formation of nanometer sized grains.
Subsequently, we elucidate the hitherto elusive mechanism of grain coarsening
of the crystallized mixed ice phases, which occur through grain dissolution and
Ostwald ripening followed by grain boundary migration.


title:
Radial measurements of IMF-sensitive absorption features in two massive
  ETGs

abstract:
  We make radial measurements of stellar initial mass function (IMF) sensitive
absorption features in the two massive early-type galaxies NGC 1277 and IC 843.
Using the Oxford Short Wavelength Integral Field SpecTrogaph (SWIFT), we obtain
resolved measurements of the NaI0.82 and FeH0.99 indices, among others, finding
both galaxies show strong gradients in NaI absorption combined with flat FeH
profiles at $\sim0.4$\AA. We find these measurements may be explained by radial
gradients in the IMF, appropriate abundance gradients in [Na/Fe] and [Fe/H], or
a combination of the two, and our data is unable to break this degeneracy. We
also use full spectral fitting to infer global properties from an integrated
spectrum of each object, deriving a unimodal IMF slope consistent with Salpeter
in IC 843 ($x=2.27\pm0.17$) but steeper than Salpeter in NGC 1277
($x=2.69\pm0.11$), despite their similar FeH equivalent widths. Independently,
we fit the strength of the FeH feature and compare to the E-MILES and CvD12
stellar population libraries, finding agreement between the models. The IMF
values derived in this way are in close agreement with those from spectral
fitting in NGC 1277 ($x_{\mathrm{CvD}}=2.59^{+0.25}_{-0.48}$ ,
$x_{\mathrm{E-MILES}}=2.77\pm0.31$), but are less consistent in IC 843, with
the IMF derived from FeH alone leading to steeper slopes than when fitting the
full spectrum ($x_{\mathrm{CvD}}=2.57^{+0.30}_{-0.41}$,
$x_{\mathrm{E-MILES}}=2.72\pm0.25$). This work highlights the importance of a
large wavelength coverage for breaking the degeneracy between abundance and IMF
variations, and may bring into doubt the use of the Wing-Ford band as an IMF
index if used without other spectral information.


title:
Theory of Multiwave Mixing within the Superconducting Kinetic-Inductance
  Traveling-Wave Amplifier

abstract:
  We present a theory of parametric mixing within the coplanar waveguide (CPW)
of a superconducting nonlinear kinetic-inductance traveling-wave (KIT)
amplifier engineered with periodic dispersion loadings. This is done by first
developing a metamaterial band theory of the dispersion-engineered KIT using a
Floquet-Bloch construction and then applying it to the description of mixing of
the nonlinear RF traveling waves. Our theory allows us to calculate signal gain
vs. signal frequency in the presence of a frequency stop gap, based solely on
loading design. We present results for both three-wave mixing (3WM), with
applied DC bias, and four-wave mixing (4WM), without DC. Our theory predicts an
intrinsic and deterministic origin to undulations of 4WM signal gain with
signal frequency, apart from extrinsic sources, such as impedance mismatch, and
shows that such undulations are absent from 3WM signal gain achievable with DC.
Our theory is extensible to amplifiers based on Josephson junctions in a lumped
LC transmission line (TWPA).


title:
Electrically Driven Bose-Einstein Condensation of Magnons in
  Antiferromagnets

abstract:
  We explore routes to realize electrically driven Bose-Einstein condensation
of magnons in insulating antiferromagnets. Even in insulating antiferromagnets,
the localized spins can strongly couple to itinerant spins in adjacent metals
via spin-transfer torque and spin pumping. We describe the formation of
steady-state magnon condensates controlled by a spin accumulation polarized
along the staggered field in an adjacent normal metal. Two types of magnons
exist in antiferromagnets, which carry opposite magnetic moments. Consequently,
and in contrast to ferromagnets, Bose-Einstein condensation can occur for
either sign of the spin accumulation. This condensation may occur even at room
temperature when the interaction with the normal metal is fast compared to the
relaxation processes within the antiferromagnet. In antiferromagnets, the
operating frequencies of the condensate are orders of magnitude faster than in
ferromagnets.


title: Large-scale Validation of Counterfactual Learning Methods: A Test-Bed

abstract:
  The ability to perform effective off-policy learning would revolutionize the
process of building better interactive systems, such as search engines and
recommendation systems for e-commerce, computational advertising and news.
Recent approaches for off-policy evaluation and learning in these settings
appear promising. With this paper, we provide real-world data and a
standardized test-bed to systematically investigate these algorithms using data
from display advertising. In particular, we consider the problem of filling a
banner ad with an aggregate of multiple products the user may want to purchase.
This paper presents our test-bed, the sanity checks we ran to ensure its
validity, and shows results comparing state-of-the-art off-policy learning
methods like doubly robust optimization, POEM, and reductions to supervised
learning using regression baselines. Our results show experimental evidence
that recent off-policy learning methods can improve upon state-of-the-art
supervised learning techniques on a large-scale real-world data set.


title:
An explicit two step quantization of Poisson structures and Lie
  bialgebras

abstract:
  We develop a new approach to deformation quantizations of Lie bialgebras and
Poisson structures which goes in two steps.
  In the first step one associates to any Poisson (resp. Lie bialgebra)
structure a so called quantizable Poisson (resp. Lie bialgebra) structure. We
show explicit transcendental formulae for this correspondence.
  In the second step one deformation quantizes a quantizable Poisson (resp. Lie
bialgebra) structure. We show again explicit transcendental formulae for this
second step correspondence (as a byproduct we obtain configuration space models
for biassociahedron and bipermutohedron).
  In the Poisson case the first step is the most non-trivial one and requires a
choice of an associator while the second step quantization is essentially
unique, it is independent of a choice of an associator and can be done by a
trivial induction. We conjecture that similar statements hold true in the case
of Lie bialgebras.
  The main new result is a surprisingly simple explicit universal formula
(which uses only smooth differential forms) for universal quantizations of
finite-dimensional Lie bialgebras.


title: New Ideas for Brain Modelling 3

abstract:
  This paper considers a process for the creation and subsequent firing of
sequences of neuronal patterns, as might be found in the human brain. The scale
is one of larger patterns emerging from an ensemble mass, possibly through some
type of energy equation and a reduction procedure. The links between the
patterns can be formed naturally, as a residual effect of the pattern creation
itself. This paper follows-on closely from the earlier research, including two
earlier papers in the series and uses the ideas of entropy and cohesion. With a
small addition, it is possible to show how the inter-pattern links can be
determined. A compact Grid form of an earlier Counting Mechanism is also
demonstrated and may be a new clustering technique. It is possible to explain
how a very basic repeating structure can form the arbitrary patterns and
activation sequences between them, and a key question of how nodes synchronise
may even be answerable.


title: Improved Image Captioning via Policy Gradient optimization of SPIDEr

abstract:
  Current image captioning methods are usually trained via (penalized) maximum
likelihood estimation. However, the log-likelihood score of a caption does not
correlate well with human assessments of quality. Standard syntactic evaluation
metrics, such as BLEU, METEOR and ROUGE, are also not well correlated. The
newer SPICE and CIDEr metrics are better correlated, but have traditionally
been hard to optimize for. In this paper, we show how to use a policy gradient
(PG) method to directly optimize a linear combination of SPICE and CIDEr (a
combination we call SPIDEr): the SPICE score ensures our captions are
semantically faithful to the image, while CIDEr score ensures our captions are
syntactically fluent. The PG method we propose improves on the prior MIXER
approach, by using Monte Carlo rollouts instead of mixing MLE training with PG.
We show empirically that our algorithm leads to easier optimization and
improved results compared to MIXER. Finally, we show that using our PG method
we can optimize any of the metrics, including the proposed SPIDEr metric which
results in image captions that are strongly preferred by human raters compared
to captions generated by the same model but trained to optimize MLE or the COCO
metrics.


title:
Microscopic description of fission in nobelium isotopes with the
  Gogny-D1M energy density functional

abstract:
  Constrained mean-field calculations, based on the Gogny-D1M energy density
functional, have been carried out to describe fission in the isotopes
$^{250-260}$No. The even-even isotopes have been considered within the standard
Hartree-Fock-Bogoliobov (HFB) framework while for the odd-mass ones the Equal
Filling Approximation (HFB-EFA) has been employed. Ground state quantum numbers
and deformations, pairing energies, one-neutron separation energies, inner and
outer barrier heights as well as fission isomer excitation energies are given.
Fission paths, collective masses and zero-point quantum vibrational and
rotational corrections are used to compute the systematic of the spontaneous
fission half-lives t$_\mathrm{SF}$ both for even-even and odd-mass nuclei.
Though there exists a strong variance of the predicted fission rates with
respect to the details involved in their computation, it is shown that both the
specialization energy and the pairing quenching effects, taken into account
within the self-consistent HFB-EFA blocking procedure, lead to larger
t$_\mathrm{SF}$ values in odd-mass nuclei as compared with their even-even
neighbors. Alpha decay lifetimes have also been computed using a
parametrization of the Viola-Seaborg formula. The high quality of the Gogny-D1M
functional regarding nuclear masses leads to a very good reproduction of
$Q_{\alpha}$ values and consequently of lifetimes.


title: The inertia operator on the motivic Hall algebra

abstract:
  We study the action of the inertia operator on the motivic Hall algebra, and
prove that it is diagonalizable. This leads to a filtration of the Hall
algebra, whose associated graded algebra is commutative. In particular, the
degree 1 subspace forms a Lie algebra, which we call the Lie algebra of
virtually indecomposable elements, following Joyce. We prove that the integral
of virtually indecomposable elements admits an Euler characteristic
specialization. In order to take advantage of the fact that our inertia groups
are unit groups in algebras, we introduce the notion of algebroid.


title: Equilibration in one-dimensional quantum hydrodynamic systems

abstract:
  We study quench dynamics and equilibration in one-dimensional quantum
hydrodynamics, which provides effective descriptions of the density and
velocity fields in gapless quantum gases. We show that the information content
of the large time steady state is inherently connected to the presence of
ballistically moving localised excitations. When such excitations are present,
the system retains memory of initial correlations up to infinite times, thus
evading decoherence. We demonstrate this connection in the context of the
Luttinger model, the simplest quantum hydrodynamic model, and in the quantum
KdV equation. In the standard Luttinger model, memory of all initial
correlations is preserved throughout the time evolution up to infinitely large
times, as a result of the purely ballistic dynamics. However nonlinear
dispersion or interactions, when separately present, lead to spreading and
delocalisation that suppress the above effect by eliminating the memory of
non-Gaussian correlations. We show that, for any initial state that satisfies
sufficient clustering of correlations, the steady state is Gaussian in terms of
the bosonised or fermionised fields in the dispersive or interacting case
respectively. On the other hand, when dispersion and interaction are
simultaneously present, a semiclassical approximation suggests that
localisation is restored as the two effects compensate each other and solitary
waves are formed. Solitary waves, or simply solitons, are experimentally
observed in quantum gases and theoretically predicted based on semiclassical
approaches, but the question of their stability at the quantum level remains to
a large extent an open problem. We give a general overview on the subject and
discuss the relevance of our findings to general out of equilibrium problems.

categories: cond-mat.stat-mech cond-mat.quant-gas math-ph math.MP


title: Spatial Decompositions for Large Scale SVMs

abstract:
  Although support vector machines (SVMs) are theoretically well understood,
their underlying optimization problem becomes very expensive, if, for example,
hundreds of thousands of samples and a non-linear kernel are considered.
Several approaches have been proposed in the past to address this serious
limitation. In this work we investigate a decomposition strategy that learns on
small, spatially defined data chunks. Our contributions are two fold: On the
theoretical side we establish an oracle inequality for the overall learning
method using the hinge loss, and show that the resulting rates match those
known for SVMs solving the complete optimization problem with Gaussian kernels.
On the practical side we compare our approach to learning SVMs on small,
randomly chosen chunks. Here it turns out that for comparable training times
our approach is significantly faster during testing and also reduces the test
error in most cases significantly. Furthermore, we show that our approach
easily scales up to 10 million training samples: including hyper-parameter
selection using cross validation, the entire training only takes a few hours on
a single machine. Finally, we report an experiment on 32 million training
samples. All experiments used liquidSVM (Steinwart and Thomann, 2017).


title: Jacobi-Maupertuis-Eisenhart metric and geodesic flows

abstract:
  The Jacobi metric derived from the line element by one of the authors is
shown to reduce to the standard formulation in the non-relativistic
approximation. We obtain the Jacobi metric for various stationary metrics.
Finally, the Jacobi-Maupertuis metric is formulated for time-dependent metrics
by including the Eisenhart-Duval lift, known as the Jacobi-Eisenhart metric.


title: Long-lived neighbors determine the rheological response of glasses

abstract:
  Glasses exhibit a liquid-like structure but a solid-like rheological response
with plastic deformations only occurring beyond yielding. Thus, predicting the
rheological behavior from the microscopic structure is difficult, but important
for materials science. Here, we consider colloidal suspensions and propose to
supplement the static structural information with the local dynamics, namely
the rearrangement and breaking of the cage of neighbors. This is quantified by
the mean squared nonaffine displacement and the number of particles that remain
nearest neighbors for a long time, i.e. long-lived neighbors, respectively.
Both quantities are followed under shear using confocal microscopy and are the
basis to calculate the affine and nonaffine contributions to the elastic
stress, which is complemented by the viscous stress to give the total stress.
During start-up of shear, the model predicts three transient regimes that
result from the interplay of affine, nonaffine and viscous contributions. Our
prediction quantitatively agrees with rheological data and their dependencies
on volume fraction and shear rate.


title: Piecewise Latent Variables for Neural Variational Text Processing

abstract:
  Advances in neural variational inference have facilitated the learning of
powerful directed graphical models with continuous latent variables, such as
variational autoencoders. The hope is that such models will learn to represent
rich, multi-modal latent factors in real-world data, such as natural language
text. However, current models often assume simplistic priors on the latent
variables - such as the uni-modal Gaussian distribution - which are incapable
of representing complex latent factors efficiently. To overcome this
restriction, we propose the simple, but highly flexible, piecewise constant
distribution. This distribution has the capacity to represent an exponential
number of modes of a latent target distribution, while remaining mathematically
tractable. Our results demonstrate that incorporating this new latent
distribution into different models yields substantial improvements in natural
language processing tasks such as document modeling and natural language
generation for dialogue.


title:
Landau parameters for energy density functionals generated by local
  finite-range pseudopotentials

abstract:
  In Landau theory of Fermi liquids, the particle-hole interaction near the
Fermi energy in different spin-isospin channels is probed in terms of an
expansion over the Legendre polynomials. This provides a useful and efficient
way to constrain properties of nuclear energy density functionals in symmetric
nuclear matter and finite nuclei. In this study, we present general expressions
for Landau parameters corresponding to a two-body central local regularized
pseudopotential. We also show results obtained for two recently adjusted NLO
and N$^2$LO parametrizations. Such pseudopotentials will be used to determine
mean-field and beyond-mean-field properties of paired nuclei across the entire
nuclear chart.


title:
Spin anisotropy due to spin-orbit coupling in optimally hole-doped
  Ba$_{0.67}$K$_{0.33}$Fe$_{2}$As$_{2}$

abstract:
  We use polarized inelastic neutron scattering to study the temperature and
energy dependence of spin space anisotropies in the optimally hole-doped iron
pnictide Ba$_{0.67}$K$_{0.33}$Fe$_{2}$As$_{2}$ ($T_{{\rm c}}=38$ K). In the
superconducting state, while the high-energy part of the magnetic spectrum is
nearly isotropic, the low-energy part displays a pronouced anisotropy,
manifested by a $c$-axis polarized resonance. We also observe that the spin
anisotropy in superconducting Ba$_{0.67}$K$_{0.33}$Fe$_{2}$As$_{2}$ extends to
higher energies compared to electron-doped BaFe$_{2-x}TM_{x}$As$_{2}$ ($TM=$Co,
Ni) and isovalent-doped BaFe$_{2}$As$_{1.4}$P$_{0.6}$, suggesting a connection
between $T_{\rm c}$ and the energy scale of the spin anisotropy. In the normal
state, the low-energy spin anisotropy for optimally hole- and electron-doped
iron pnictides onset at temperatures similar to the temperatures at which the
elastoresistance deviate from Curie-Weiss behavior, pointing to a possible
connection between the two phenomena. Our results highlight the relevance of
the spin-orbit coupling to the superconductivity of the iron pnictides.


title: Playing Doom with SLAM-Augmented Deep Reinforcement Learning

abstract:
  A number of recent approaches to policy learning in 2D game domains have been
successful going directly from raw input images to actions. However when
employed in complex 3D environments, they typically suffer from challenges
related to partial observability, combinatorial exploration spaces, path
planning, and a scarcity of rewarding scenarios. Inspired from prior work in
human cognition that indicates how humans employ a variety of semantic concepts
and abstractions (object categories, localisation, etc.) to reason about the
world, we build an agent-model that incorporates such abstractions into its
policy-learning framework. We augment the raw image input to a Deep Q-Learning
Network (DQN), by adding details of objects and structural elements
encountered, along with the agent's localisation. The different components are
automatically extracted and composed into a topological representation using
on-the-fly object detection and 3D-scene reconstruction.We evaluate the
efficacy of our approach in Doom, a 3D first-person combat game that exhibits a
number of challenges discussed, and show that our augmented framework
consistently learns better, more effective policies.


title:
Using Random Boundary Conditions to simulate disordered quantum spin
  models in 2D-systems

abstract:
  Disordered quantum antiferromagnets in two-dimensional compounds have been a
focus of interest in the last years due to their exotic properties. However,
with very few exceptions, the ground states of the corresponding Hamiltonians
are notoriously difficult to simulate making their characterization and
detection very elusive, both, theoretically and experimentally. Here we propose
a method to signal quantum disordered antiferromagnets by doing exact
diagonalization in small lattices using random boundary conditions and
averaging the observables of interest over the different disorder realizations.
We apply our method to study a Heisenberg spin-1/2 model in an anisotropic
triangular lattice. In this model, the competition between frustration and
quantum fluctuations might lead to some spin liquid phases as predicted from
different methods ranging from spin wave mean field theory to 2D-DMRG or PEPS.
Our method accurately reproduces the ordered phases expected of the model and
signals disordered phases by the presence of a large number of quasi degenerate
ground states together with the absence of a local order parameter. The method
presents a weak dependence on finite size effects.

categories: cond-mat.quant-gas cond-mat.dis-nn cond-mat.str-el quant-ph


title: Evenly Divisible Rational Approximations of Quadratic Irrationalities

abstract:
  In a recent paper of Blomer, Bourgain, Radziwi{\l}{\l} and Rudnick, the
authors proved the existence of small gaps between eigenvalues of the Laplacian
in a rectangular billiard with sides $\pi$ and $\pi/\sqrt\alpha$, i.e. numbers
of the form $\alpha m^2+ n^2$, whenever $\alpha$ is a quadratic irrationality
of certain types. In this note, we extend their results to all positive
quadratic irrationalities $\alpha$.


title:
Tuning the Scheduling of Distributed Stochastic Gradient Descent with
  Bayesian Optimization

abstract:
  We present an optimizer which uses Bayesian optimization to tune the system
parameters of distributed stochastic gradient descent (SGD). Given a specific
context, our goal is to quickly find efficient configurations which
appropriately balance the load between the available machines to minimize the
average SGD iteration time. Our experiments consider setups with over thirty
parameters. Traditional Bayesian optimization, which uses a Gaussian process as
its model, is not well suited to such high dimensional domains. To reduce
convergence time, we exploit the available structure. We design a probabilistic
model which simulates the behavior of distributed SGD and use it within
Bayesian optimization. Our model can exploit many runtime measurements for
inference per evaluation of the objective function. Our experiments show that
our resulting optimizer converges to efficient configurations within ten
iterations, the optimized configurations outperform those found by generic
optimizer in thirty iterations by up to 2X.


title: A strongly truncated inner accretion disk in the Rapid Burster

abstract:
  The neutron star (NS) low-mass X-ray binary (LMXB) the Rapid Burster (RB; MXB
1730-335) uniquely shows both Type-I and Type-II X-ray bursts. The origin of
the latter is ill-understood but has been linked to magnetospheric gating of
the accretion flow. We present a spectral analysis of simultaneous Swift,
NuSTAR and XMM-Newton observations of the RB during its 2015 outburst. Although
a broad Fe-K line has been observed before, the high quality of our
observations allows us to model this line using relativistic reflection models
for the first time. We find that the disk is strongly truncated at
$41.8^{+6.7}_{-5.3}$ gravitational radii ($\sim 87$ km), which supports
magnetospheric Type-II burst models and strongly disfavors models involving
instabilities at the innermost stable circular orbit. Assuming that the RB
magnetic field indeed truncates the disk, we find $B = (6.2 \pm 1.5) \times
10^8$ G, larger than typically inferred for NS LMXBs. In addition, we find a
low inclination ($i = 29\pm2^{\rm o}$). Finally, we comment on the origin of
the Comptonized and thermal components in the RB spectrum.


title: Temporal Attention-Gated Model for Robust Sequence Classification

abstract:
  Typical techniques for sequence classification are designed for
well-segmented sequences which have been edited to remove noisy or irrelevant
parts. Therefore, such methods cannot be easily applied on noisy sequences
expected in real-world applications. In this paper, we present the Temporal
Attention-Gated Model (TAGM) which integrates ideas from attention models and
gated recurrent networks to better deal with noisy or unsegmented sequences.
Specifically, we extend the concept of attention model to measure the relevance
of each observation (time step) of a sequence. We then use a novel gated
recurrent network to learn the hidden representation for the final prediction.
An important advantage of our approach is interpretability since the temporal
attention weights provide a meaningful value for the salience of each time step
in the sequence. We demonstrate the merits of our TAGM approach, both for
prediction accuracy and interpretability, on three different tasks: spoken
digit recognition, text-based sentiment analysis and visual event recognition.