title: An experimental and theoretical investigation of the C(1D) + D2 reaction

abstract:
  In a previous joint experimental and theoretical study of the barrierless
chemical reaction C(1D) + H2 at low temperatures (300-50 K) [K. M. Hickson,
J.-C. Loison, H. Guo, Y. V. Suleimanov, J. Phys. Chem. Lett., 2015, 6, 4194.],
excellent agreement was found between experimental thermal rate constants and
theoretical estimates based on ring polymer molecular dynamics (RPMD) over the
two lowest singlet potential energy surfaces (PESs). Here, we extend this work
to one of its deuterated counterparts, C(1D) + D2, over the same temperature
range. Experimental and RPMD results are in very good agreement when
contributions from both PESs to this chemical reaction are included in the RPMD
simulations. The deviation between experiment and the RPMD calculations does
not exceed 25 % and both results exhibit a slight negative temperature
dependence. The first excited 1A" PES plays a more important role than the
ground 1A' PES as the temperature is decreased, similar to our previous studies
of the C(1D) + H2 reaction but with a more pronounced effect. The small
differences in temperature dependence between the earlier and present
experimental studies of C(1D) + H2/D2 reactions are discussed in terms of the
use of non-equilibrium populations of ortho/para-H2/D2. We argue that RPMD
provides a very convenient and reliable tool to study low-temperature chemical
reactions.


title:
Neutron star-black hole coalescence rate inferred from
  macronova/kilonova observations

abstract:
  Neutron star$-$black hole (NS$-$BH) coalescences are widely believed to be
promising gravitational wave sources in the era of advanced detectors of
LIGO/Virgo but such binaries have never been directly detected yet. Evidence
for NS$-$BH coalescences have been suggested in short and hybrid GRB
observations, which are examined critically. Based on the suggested connection
between the observed macronovae/kilonovae events and NS$-$BH coalescences, we
get a fiducial lower limit of NS$-$BH coalescence rate density ${\cal R}_{\rm
nsbh} \approx 18.8^{+12.5}_{-8.6} ~{\rm Gpc^{-3}~ yr^{-1}~ (\theta_j/0.1~{\rm
rad})^{-2}}$, where $\theta_{\rm j}$ is the typical half-opening angle of the
GRB ejecta. The real value of ${\cal R}_{\rm nsbh}$ is likely at least $\sim
{\rm a~few}$ times larger, depending upon the equation of state of NS material
and the properties of the NS$-$BH system, such as the mass and spin
distribution of the black hole. If the link between macronovae/kilonovae and
NS$-$BH coalescence is valid, one can expect that at design sensitivity the
aLIGO/AdVirgo network will detect NS$-$BH coalescence signals at a rate of at
least a dozen per year, and to consequently place constraints on certain
physical properties of NS$-$BH systems.


title: High-Fidelity Model Order Reduction for Microgrids Stability Assessment

abstract:
  Proper modeling of inverter-based microgrids is crucial for accurate
assessment of stability boundaries. It has been recently realized that the
stability conditions for such microgrids are significantly different from those
known for large- scale power systems. While detailed models are available, they
are both computationally expensive and can not provide the insight into the
instability mechanisms and factors. In this paper, a computationally efficient
and accurate reduced-order model is proposed for modeling the inverter-based
microgrids. The main factors affecting microgrid stability are analyzed using
the developed reduced-order model and are shown to be unique for the
microgrid-based network, which has no direct analogy to large-scale power
systems. Particularly, it has been discovered that the stability limits for the
conventional droop-based system (omega - P/V - Q) are determined by the ratio
of inverter rating to network capacity, leading to a smaller stability region
for microgrids with shorter lines. The theoretical derivation has been provided
to verify the above investigation based on both the simplified and generalized
network configurations. More impor- tantly, the proposed reduced-order model
not only maintains the modeling accuracy but also enhances the computation
efficiency. Finally, the results are verified with the detailed model via both
frequency and time domain analyses.


title: Magneto-electric coupling in type-I multiferroic ScFeO$_3$

abstract:
  We investigate the electronic structure and the ferroelectric properties of
the recently discovered multiferroic ScFeO$_3$ by means of ab-initio
calculations. The $3d$ manifold of Fe in the half-filled configuration
naturally favors an antiferromagnetic ordering, with a theoretical estimate of
the antiferromagnetic N\'eel temperature in good agreement with the
experimental values. We find that the inversion symmetry-breaking is driven by
the off-centering of Sc atoms, which results in a large ferroelectric
polarization of $\sim$105\,$\mu$C/cm$^{2}$. Surprisingly the ferroelectric
polarization is sensitive to the local magnetization of the Fe atoms resulting
in a large negative magnetoelectric interaction. This behavior is unexpected in
type-I multiferroic materials because the magnetic and ferroelectric orders are
of different origins.


title: Nonlinear equations involving the square root of the Laplacian

abstract:
  In this paper we discuss the existence and non-existence of weak solutions to
parametric fractional equations involving the square root of the Laplacian
$A_{1/2}$ in a smooth bounded domain $\Omega\subset \mathbb{R}^n$ ($n\geq 2$)
and with zero Dirichlet boundary conditions. Namely, our simple model is the
following equation \begin{equation*} \left\{ \begin{array}{ll} A_{1/2}u=\lambda
f(u) & \mbox{ in } \Omega\\ u=0 & \mbox{ on } \partial\Omega.
\end{array}\right. \end{equation*} The existence of at least two non-trivial
$L^{\infty}$-bounded weak solutions is established for large value of the
parameter $\lambda$ requiring that the nonlinear term $f$ is continuous,
superlinear at zero and sublinear at infinity. Our approach is based on
variational arguments and a suitable variant of the Caffarelli-Silvestre
extension method.


title: Periodic solutions for a fractional asymptotically linear problem

abstract:
  We study the existence and multiplicity of periodic weak solutions for a
non-local equation involving an odd subcritical nonlinearity which is
asymptotically linear at infinity. We investigate such problem by applying the
the pseudo-index theory developed by Bartolo, Benci and Fortunato \cite{bbf}
after transforming the problem to a degenerate elliptic problem in a
half-cylinder with a Neumann boundary condition, via a Caffarelli-Silvestre
type extension in periodic setting. The periodic nonlocal case, considered
here, presents, respect to the cases studied in literature, some new additional
difficulties and a careful analysis of the fractional spaces involved is
necessary.


title: A Survey on 3D CAD model quality assurance and testing tools

abstract:
  A new taxonomy of issues related to CAD model quality is presented, which
distinguishes between explicit and procedural models. For each type of model,
morphologic, syntactic, and semantic errors are characterized. The taxonomy was
validated successfully when used to classify quality testing tools, which are
aimed at detecting and repairing data errors that may affect the
simplification, interoperability, and reusability of CAD models. The study
shows that low semantic level errors that hamper simplification are reasonably
covered in explicit representations, although many CAD quality testers are
still unaffordable for Small and Medium Enterprises, both in terms of cost and
training time. Interoperability has been reasonably solved by standards like
STEP AP 203 and AP214, but model reusability is not feasible in explicit
representations. Procedural representations are promising, as interactive
modeling editors automatically prevent most morphologic errors derived from
unsuitable modeling strategies. Interoperability problems between procedural
representations are expected to decrease dramatically with STEP AP242. Higher
semantic aspects of quality such as assurance of design intent, however, are
hardly supported by current CAD quality testers.


title:
The Galaxy Kinematics from the Cepheids with the Proper Motions from the
  GAIA DR1 Catalog

abstract:
  The sample of classic Cepheids with known distances and line-of-sight
velocities is supplemented by the proper motions from the Gaia DR1 catalog.
From spatial velocities of 260 stars the components of the peculiar Solar
velocity:
  (U,V,W)_\odot=(7.90,11.73,7.39)+/-(0.65,0.77,0.62) km/s, parameters of the
Galactic rotation curve: \Omega_0 =28.840+/-.33 km/s/kpc,
\Omega'_0=-4.05+/-0.10 km/s/kpc^2, \Omega''_0=0.805+/-0.067 km/s/kpc^3 are
obtained. For the adopted Galactocentric Solar distance R_0=8 kpc the linear
circular velocity of the Local Standard of Rest is found as V_0=231+/-6 km/s.


title: EM Algorithm and Stochastic Control in Economics

abstract:
  Generalising the idea of the classical EM algorithm that is widely used for
computing maximum likelihood estimates, we propose an EM-Control (EM-C)
algorithm for solving multi-period finite time horizon stochastic control
problems. The new algorithm sequentially updates the control policies in each
time period using Monte Carlo simulation in a forward-backward manner; in other
words, the algorithm goes forward in simulation and backward in optimization in
each iteration. Similar to the EM algorithm, the EM-C algorithm has the
monotonicity of performance improvement in each iteration, leading to good
convergence properties. We demonstrate the effectiveness of the algorithm by
solving stochastic control problems in the monopoly pricing of perishable
assets and in the study of real business cycle.


title: Nuclear symmetry energy and the role of three-body forces

abstract:
  Density dependence of nuclear symmetry energy as well as its partial wave
decomposition is studied within the framework of lowest-order constrained
variational (LOCV) method using AV18 two-body interaction supplemented by UIX
three-body force. The main focus of the present work is to introduce a revised
version of three-body force which is based on an isospin-dependent
parametrization of coefficients in the UIX force, in order to overcome the
inability to produce correct saturation-point parameters} in the framework of
LOCV method. We find that employing the new model of {\ph three-body force} in
the LOCV formalism leads to successfully reproducing the semi-empirical
parameters of cold nuclear matter, including} $E_{sym}(\rho_0)$, $L$, and
$K_{sym}$. All our models of three-body force combined with AV18 two-body force
give maximum neutron star mass higher than $2\;M_\odot$. The fraction of
protons in the nucleon cores of neutron stars strongly depends on the
three-body force parametrization.


title: LZ-End Parsing in Compressed Space

abstract:
  We present an algorithm that constructs the LZ-End parsing (a variation of
LZ77) of a given string of length $n$ in $O(n\log\ell)$ expected time and $O(z
+ \ell)$ space, where $z$ is the number of phrases in the parsing and $\ell$ is
the length of the longest phrase. As an option, we can fix $\ell$ (e.g., to the
size of RAM) thus obtaining a reasonable LZ-End approximation with the same
functionality and the length of phrases restricted by $\ell$. This modified
algorithm constructs the parsing in streaming fashion in one left to right pass
on the input string w.h.p. and performs one right to left pass to verify the
correctness of the result. Experimentally comparing this version to other
LZ77-based analogs, we show that it is of practical interest.


title:
Enhanced sensitivity to Lorentz invariance violations in short-range
  gravity experiments

abstract:
  Recently, first limits on putative Lorentz invariance violation coefficients
in the pure gravity sector were determined by the reanalysis of short-range
gravity experiments. Such experiments search for new physics at sidereal
frequencies. They are not, however, designed to optimize the signal strength of
a Lorentz invariance violation force; in fact the Lorentz violating signal is
suppressed in the planar test mass geometry employed in those experiments. We
describe a short-range torsion pendulum experiment with enhanced sensitivity to
possible Lorentz violating signals. A periodic, striped test mass geometry is
used to augment the signal. Careful arrangement of the phases of the striped
patterns on opposite ends of the pendulum further enhances the signal while
simultaneously suppressing the Newtonian background.


title: An Equilibrium Model with Computationally Constrained Agents

abstract:
  We study a large economy in which firms cannot compute exact solutions to the
non-linear equations that characterize the equilibrium price at which they can
sell future output. Instead, firms use polynomial expansions to approximate
prices. The precision with which they can compute prices is endogenous and
depends on the overall level of supply. At the same time, firms' individual
supplies, and thus aggregate supply, depend on the precision with which they
approximate prices. This interrelation between supply and price forecast
induces multiple equilibria, with inefficiently low output, in economies that
otherwise have a unique, efficient equilibrium. Moreover, exogenous parameter
changes, which would increase output were there no computational frictions, can
diminish agents' ability to approximate future prices, and reduce output. Our
model therefore accommodates the intuition that interventions, such as
unprecedented quantitative easing, can put agents into "uncharted territory".


title:
Hyperelastic bodies under homogeneous Cauchy stress induced by
  three-dimensional non-homogeneous deformations

abstract:
  In isotropic finite elasticity, unlike in the linear elastic theory, a
homogeneous Cauchy stress may be induced by non-homogeneous strains. To
illustrate this, we identify compatible non-homogeneous three-dimensional
deformations producing a homogeneous Cauchy stress on a cuboid geometry, and
provide an example of an isotropic hyperelastic material, which is not rank-one
convex, and for which the homogeneous stress and the associated non-homogeneous
strains on a domain similar to those analysed are given explicitly.


title:
The Shallow End: Empowering Shallower Deep-Convolutional Networks
  through Auxiliary Outputs

abstract:
  Depth is one of the key factors behind the success of convolutional neural
networks (CNNs). Since ResNet, we are able to train very deep CNNs as the
gradient vanishing issue has been largely addressed by the introduction of skip
connections. However, we observe that, when the depth is very large, the
intermediate layers (especially shallow layers) may fail to receive sufficient
supervision from the loss due to the severe transformation through a long
backpropagation path. As a result, the representation power of intermediate
layers can be very weak and the model becomes very redundant with limited
performance. In this paper, we first investigate the supervision vanishing
issue in existing backpropagation (BP) methods. And then, we propose to address
it via an effective method, called Multi-way BP (MW-BP), which relies on
multiple auxiliary losses added to the intermediate layers of the network. The
proposed MW-BP method can be applied to most deep architectures with slight
modifications, such as ResNet and MobileNet. Our method often gives rise to
much more compact models (denoted by "Mw+Architecture") than existing methods.
For example, MwResNet-44 with 44 layers performs better than ResNet-110 with
110 layers on CIFAR-10 and CIFAR-100. More critically, the resultant models
even outperform the light models obtained by state-of-the-art model compression
methods. Last, our method inherently produces multiple compact models with
different depths at the same time, which is helpful for model selection.


title:
Three-dimensional label-free imaging and quantification of lipid
  droplets in live hepatocytes

abstract:
  Lipid droplets (LDs) are subcellular organelles with important roles in lipid
storage and metabolism and involved in various diseases including cancer,
obesity, and diabetes. Conventional methods, however, have limited ability to
provide quantitative information on individual LDs and have limited capability
for three-dimensional (3-D) imaging of LDs in live cells especially for fast
acquisition of 3-D dynamics. Here, we present an optical method based on 3-D
quantitative phase imaging to measure the 3-D structural distribution and
biochemical parameters (concentration and dry mass) of individual LDs in live
cells without using exogenous labelling agents. The biochemical change of LDs
under oleic acid treatment was quantitatively investigated, and 4-D tracking of
the fast dynamics of LDs revealed the intracellular transport of LDs in live
cells.


title: Magnetohydrodynamic Simulation Code CANS+: Assessments and Applications

abstract:
  We present a new magnetohydrodynamic (MHD) simulation code with the aim of
providing accurate numerical solutions to astrophysical phenomena where
discontinuities, shock waves, and turbulence are inherently important. The code
implements the HLLD approximate Riemann solver, the
fifth-order-monotonicity-preserving interpolation (MP5) scheme, and the
hyperbolic divergence cleaning method for a magnetic field. This choice of
schemes significantly improved numerical accuracy and stability, and saved
computational costs in multidimensional problems. Numerical tests of one- and
two-dimensional problems showed the advantages of using the high-order scheme
by comparing with results from a standard second-order TVD MUSCL scheme. The
present code enabled us to explore long-term evolution of a three-dimensional
accretion disk around a black hole, in which compressible MHD turbulence caused
continuous mass accretion via nonlinear growth of the magneto-rotational
instability (MRI). Numerical tests with various computational cell sizes
exhibited a convergent picture of the early nonlinear growth of the MRI in a
global model, and indicated that the MP5 scheme has more than twice the
resolution of the MUSCL scheme in practical applications.

categories: astro-ph.IM astro-ph.HE physics.comp-ph physics.plasm-ph physics.space-ph


title:
Topology optimization of anisotropic elastic metamaterial with broadband
  double-negative index

abstract:
  Aiming at the promising superlensing for the medical ultrasonic and
detection, the double-negative metamaterials which possess the negative mass
density and elastic modulus simultaneously can be acted as the ideal superlens
for breaking the diffraction limit. In this paper, we use topology optimization
to design the two-dimensional single-phase anisotropic elastic metamaterials
with broadband double-negative indices and numerically demonstrate the
superlensing at the deep-subwavelength scale. We also discuss the impact of
several parameters adopted in the objective function and constraints on the
optimized results. Unlike all previous reported mechanisms, our optimized
structures exhibit the new quadrupolar or multipolar resonances for the
negative mass density, negative longitudinal and shear moduli. In addition, we
observe the negative refraction of transverse waves in a single-phase material.
Most structures can serve as the anisotropic zero-index metamaterials for the
longitudinal or transverse wave at a certain frequency. The cloaking effect is
demonstrated for both the longitudinal and transverse waves. Moreover, with the
particular constraints in optimization, we design a super-anisotropic
metamaterial exhibiting the double-negative and hyperbolic dispersions along
two principal directions, respectively. Our optimization work provides a robust
computational approach to negative index engineering in elastic metamaterials
and guides design of other kinds of metamaterials, including the
electromagnetic and acoustic metamaterials. The unusual properties of our
optimized structures are likely to inspire new ideas and novel applications
including the low-frequency vibration attenuation, flat lens and
ultrasonography for elastic waves in the future.


title: Conserved currents in the Cartan formulation of general relativity

abstract:
  We derive the expressions for the local, on-shell closed co-dimension 2 forms
in the Cartan formulation of general relativity and explicitly show their
equivalence to those of the metric formulation.


title:
A Simpler and Faster Strongly Polynomial Algorithm for Generalized Flow
  Maximization

abstract:
  We present a new strongly polynomial algorithm for generalized flow
maximization that is significantly simpler and faster than the previous
strongly polynomial algorithm [V\'egh16]. For the uncapacitated problem
formulation, the complexity bound $O(mn(m+n\log n)\log (n^2/m))$ improves on
the previous estimate by almost a factor $O(n^2)$. Even for small numerical
parameter values, our running time bound is comparable to the best weakly
polynomial algorithms. The key new technical idea is relaxing the primal
feasibility conditions. This allows us to work almost exclusively with integral
flows, in contrast to all previous algorithms for the problem.


title: Learning to Act by Predicting the Future

abstract:
  We present an approach to sensorimotor control in immersive environments. Our
approach utilizes a high-dimensional sensory stream and a lower-dimensional
measurement stream. The cotemporal structure of these streams provides a rich
supervisory signal, which enables training a sensorimotor control model by
interacting with the environment. The model is trained using supervised
learning techniques, but without extraneous supervision. It learns to act based
on raw sensory input from a complex three-dimensional environment. The
presented formulation enables learning without a fixed goal at training time,
and pursuing dynamically changing goals at test time. We conduct extensive
experiments in three-dimensional simulations based on the classical
first-person game Doom. The results demonstrate that the presented approach
outperforms sophisticated prior formulations, particularly on challenging
tasks. The results also show that trained models successfully generalize across
environments and goals. A model trained using the presented approach won the
Full Deathmatch track of the Visual Doom AI Competition, which was held in
previously unseen environments.


title:
The Oka principle for holomorphic Legendrian curves in $\mathbb
  C^{2n+1}$

abstract:
  Let $M$ be a connected open Riemann surface. We prove that the space
$\mathscr L(M,\mathbb C^{2n+1})$ of all holomorphic Legendrian immersions of
$M$ into $\mathbb C^{2n+1}$, $n\geq 1$, endowed with the standard holomorphic
contact structure, is weakly homotopy equivalent to the space $\mathscr
C(M,\mathbb S^{4n-1})$ of continuous maps from $M$ to the sphere $\mathbb
S^{4n-1}$. If $M$ has finite topological type, then these spaces are homotopy
equivalent. We determine the homotopy groups of $\mathscr L(M,\mathbb
C^{2n+1})$ in terms of the homotopy groups of $\mathbb S^{4n-1}$. It follows
that $\mathscr L(M,\mathbb C^{2n+1})$ is $(4n-3)$-connected.


title: Wrinkling of a thin circular sheet bonded to a spherical substrate

abstract:
  We consider a disk-shaped thin elastic sheet bonded to a compliant sphere.
(Our sheet can slip along the sphere; the bonding controls only its normal
displacement.) If the bonding is stiff (but not too stiff), the geometry of the
sphere makes the sheet wrinkle to avoid azimuthal compression. The total energy
of this system is the elastic energy of the sheet plus a (Winkler-type)
substrate energy. Treating the thickness of the sheet $h$ as a small parameter,
we determine the leading-order behavior of the energy as $h$ tends to zero, and
give (almost matching) upper and lower bounds for the next-order correction.
Our analysis of the leading-order behavior determines the macroscopic
deformation of the sheet; in particular it determines the extent of the
wrinkled region, and predicts the (nontrivial) radial strain of the sheet. The
leading-order behavior also provides insight about the length scale of the
wrinkling, showing that it must be approximately independent of the distance
$r$ from the center of the sheet (so that the number of wrinkles must increase
with $r$). Our results on the next-order correction provide insight about how
the wrinkling pattern should vary with $r$. Roughly speaking, they suggest that
the length scale of wrinkling should {\it not} be exactly constant -- rather,
it should vary a bit, so that the number of wrinkles at radius $r$ can be
approximately piecewise constant in its dependence on $r$, taking values that
are integer multiples of $h^{-\alpha}$ with $\alpha \approx 1/2$.

categories: math.AP cond-mat.mtrl-sci cond-mat.soft math.DG


title: Clique colouring of binomial random graphs

abstract:
  A clique colouring of a graph is a colouring of the vertices so that no
maximal clique is monochromatic (ignoring isolated vertices). The smallest
number of colours in such a colouring is the clique chromatic number.
  In this paper, we study the asymptotic behaviour of the clique chromatic
number of the random graph G(n,p) for a wide range of edge-probabilities
p=p(n). We see that the typical clique chromatic number, as a function of the
average degree, forms an intriguing step function.


title: Domain Adaptation For Formant Estimation Using Deep Learning

abstract:
  In this paper we present a domain adaptation technique for formant estimation
using a deep network. We first train a deep learning network on a small read
speech dataset. We then freeze the parameters of the trained network and use
several different datasets to train an adaptation layer that makes the obtained
network universal in the sense that it works well for a variety of speakers and
speech domains with very different characteristics. We evaluated our adapted
network on three datasets, each of which has different speaker characteristics
and speech styles. The performance of our method compares favorably with
alternative methods for formant estimation.


title:
Calculating Galois groups of third order linear differential equations
  with parameters

abstract:
  Motivated by developing algorithms that decide hypertranscendence of
solutions of extensions of the Bessel differential equation, algorithms
computing the unipotent radical of a parameterized differential Galois group
have been recently developed. Extensions of Bessel's equation, such as the
Lommel equation, can be viewed as homogeneous parameterized linear differential
equations of the third order. In the present paper, we give the first known
algorithm that calculates the differential Galois group of a third order
parameterized linear differential equation.


title: Leggett-Garg Inequalities for Squeezed States

abstract:
  Temporal Bell inequalities, or Leggett-Garg Inequalities (LGI), are studied
for continuous-variable systems placed in a squeezed state. The importance of
those systems lies in their broad applicability which allows the description of
many different physical settings in various branches of physics, ranging from
cosmology to condensed matter physics and from optics to quantum information
theory. LGI violations are explored and systematically mapped in squeezing
parameter space. Configurations for which LGI violation occurs are found but it
is shown that no violation can be obtained if all squeezing angles vanish,
contrary to what happens for the spatial Bell inequalities. We also assess the
effect of decoherence on the detectability of such violations. Our study opens
up the possibility of new experimental designs for the observation of LGI
violation.


title:
Energy-Efficient Resource Allocation for Multi-User Mobile Edge
  Computing

abstract:
  To increase mobile batteries' lifetime and improve quality of experience for
computation-intensive and latency-sensitive applications, mobile edge computing
has received significant interest. Designing energy-efficient mobile edge
computing systems requires joint optimization of communication and computation
resources. In this paper, we consider energy-efficient resource allocation for
a multi-user mobile edge computing system. First, we establish on two
computation-efficient models with negligible and non-negligible base station
(BS) executing durations, respectively. Then, under each model, we formulate
the overall weighted sum energy consumption minimization problem by optimally
allocating communication and computation resources. The optimization problem
for negligible BS executing duration is convex, and we obtain the optimal
solution in closed-form to this problem. The optimization problem for
non-negligible BS executing duration is NP-hard in general, and we obtain a
sub-optimal solution with low-complexity to this problem, by connecting it to a
three-stage flow-shop scheduling problem and wisely utilizing Johnson's
algorithm. Finally, numerical results show that the proposed solutions
outperform some baseline schemes.


title: Learning to superoptimize programs

abstract:
  Code super-optimization is the task of transforming any given program to a
more efficient version while preserving its input-output behaviour. In some
sense, it is similar to the paraphrase problem from natural language processing
where the intention is to change the syntax of an utterance without changing
its semantics. Code-optimization has been the subject of years of research that
has resulted in the development of rule-based transformation strategies that
are used by compilers. More recently, however, a class of stochastic search
based methods have been shown to outperform these strategies. This approach
involves repeated sampling of modifications to the program from a proposal
distribution, which are accepted or rejected based on whether they preserve
correctness, and the improvement they achieve. These methods, however, neither
learn from past behaviour nor do they try to leverage the semantics of the
program under consideration. Motivated by this observation, we present a novel
learning based approach for code super-optimization. Intuitively, our method
works by learning the proposal distribution using unbiased estimators of the
gradient of the expected improvement. Experiments on benchmarks comprising of
automatically generated as well as existing ("Hacker's Delight") programs show
that the proposed method is able to significantly outperform state of the art
approaches for code super-optimization.


title: Local Picard Group of Binoids and Their Algebras

abstract:
  We begin by introducing schemes of binoids, invertible $\mathcal{O}_M$-sets
and cohomology of sheaves of abelian groups defined on schemes of binoids. We
define the so-called punctured combinatorial \v{C}ech-Picard complex, whose
first cohomology computes $\mathrm{Pic}^{\mathrm{loc}}(M)$, the local Picard
group of a binoid. We look then at simplicial binoids, whose spectrum presents
very nice combinatorial properties. We prove that the cohomology of a constant
sheaf on this punctutured spectra can be computed entirely in terms of
simplicial cohomology. Through some other results, we prove that we can compute
cohomology of the sheaf of units (and thus the local Picard group) by meaning
of reduced simplicial cohomology. We move from combinatorics to algebra and we
try to use these tools to understand binoid algebras and cohomology of their
sheaf of units. We introduce a new topology, that we call combinatorial
topology on $\mathrm{Spec}\mathbb{K}[M]$. In this topology, if $M$ is a
reduced, torsion-free and cancellative binoid, we can decompose the sheaf of
units of its algebra in a direct sum of a constant part $\mathbb{K}^*$ and of
the pushforward of the combinatorial units. We specialize to the case of the
Stanley-Reisner rings, for which we are able to prove a vanishing result for
the affine case. By meaning of the combinatorial topology we then prove that we
can compute the Zariski cohomology of the sheaf of units entirely in terms of
simplicial cohomology, both usual and reduced. This ultimately leads to a
generalization to any monomial ideal, thus yielding us some purely
combinatorial non-vanishing results for
$\mathrm{Pic}^{\mathrm{loc}}(\mathbb{K}[M])$ in the last Corollary.


title: Test of the Brink-Axel hypothesis for the pygmy dipole resonance

abstract:
  The gamma strength function and level density of 1- states in 96Mo have been
extracted from a high-resolution study of the (p,p') reaction at 295 MeV and
extreme forward angles. By comparison with compound nucleus $\gamma$ decay
experiments, this allows a test of the generalized Brink-Axel hypothesis in the
energy region of the Pygmy Dipole Resonance. The Brink-Axel hypothesis is
commonly assumed in astrophysical reaction network calculations and states that
the gamma strength function in nuclei is independent of the structure of
initial and final state. The present results validiate the Brink-Axel
hypothesis for 96Mo and provide independent confirmation of the methods used to
separate gamma strength function and level density in $\gamma$ decay
experiments.


title: Motion magnification in coronal seismology

abstract:
  We introduce a new method for the investigation of low-amplitude transverse
oscillations of solar plasma non-uniformities, such as coronal loops,
individual strands in coronal arcades, jets, prominence fibrils, polar plumes,
and other contrast features, observed with imaging instruments. The method is
based on the two-dimensional dual tree complex wavelet transform
(DT$\mathbb{C}$WT). It allows us to magnify transverse, in the
plane-of-the-sky, quasi-periodic motions of contrast features in image
sequences. The tests performed on the artificial data cubes imitating
exponentially decaying, multi-periodic and frequency-modulated kink
oscillations of coronal loops showed the effectiveness, reliability and
robustness of this technique. The algorithm was found to give linear scaling of
the magnified amplitudes with the original amplitudes provided they are
sufficiently small. Also, the magnification is independent of the oscillation
period in a broad range of the periods. The application of this technique to
SDO/AIA EUV data cubes of a non-flaring active region allowed for the improved
detection of low-amplitude decay-less oscillations in the majority of loops.


title:
Solar Flare Prediction Model with Three Machine-Learning Algorithms
  Using Ultraviolet Brightening and Vector Magnetogram

abstract:
  We developed a flare prediction model using machine learning, which is
optimized to predict the maximum class of flares occurring in the following 24
h. Machine learning is used to devise algorithms that can learn from and make
decisions on a huge amount of data. We used solar observation data during the
period 2010-2015, such as vector magnetogram, ultraviolet (UV) emission, and
soft X-ray emission taken by the Solar Dynamics Observatory and the
Geostationary Operational Environmental Satellite. We detected active regions
from the full-disk magnetogram, from which 60 features were extracted with
their time differentials, including magnetic neutral lines, the current
helicity, the UV brightening, and the flare history. After standardizing the
feature database, we fully shuffled and randomly separated it into two for
training and testing. To investigate which algorithm is best for flare
prediction, we compared three machine learning algorithms: the support vector
machine (SVM), k-nearest neighbors (k-NN), and extremely randomized trees
(ERT). The prediction score, the true skill statistic (TSS), was higher than
0.9 with a fully shuffled dataset, which is higher than that for human
forecasts. It was found that k-NN has the highest performance among the three
algorithms. The ranking of the feature importance showed that the previous
flare activity is most effective, followed by the length of magnetic neutral
lines, the unsigned magnetic flux, the area of UV brightening, and the time
differentials of features over 24 h, all of which are strongly correlated with
the flux emergence dynamics in an active region.


title: 3D printed beam splitter for polar neutral molecules

abstract:
  We describe a macroscopic beam splitter for polar neutral molecules. A
complex electrode structure is required for the beam splitter which would be
very difficult to produce with traditional manufacturing methods. Instead, we
make use of a nascent manufacturing technique: 3D printing of a plastic piece,
followed by electroplating. This fabrication method opens a plethora of avenues
for research, since 3D printing imposes practically no limitations on possible
shapes, and the plating produces chemically robust, conductive construction
elements with an almost free choice of surface material; it has the added
advantage of dramatically reduced production cost and time. Our beam splitter
is an electrostatic hexapole guide that smoothly transforms into two bent
quadrupoles. We demonstrate the correct functioning of this device by
separating a supersonic molecular beam of ND3 into two correlated fractions. It
is shown that this device can be used to implement experiments with
differential detection wherein one of the fractions serves as a probe and the
other as a reference. Reverse operation would allow to merging of two beams of
neutral polar molecules.

categories: physics.chem-ph physics.atm-clus physics.atom-ph physics.ins-det


title: Squeezing in a nonlocal photon fluid

abstract:
  Quantum fluids of light are an emerging tool employed in quantum many-body
physics. Their amazing properties and versatility allow using them in a wide
variety of fields including gravitation, quantum information and simulation.
However the implications of the quantum nature of light in the nonlinear
optical propagation are still missing many features. We theoretically predict
classical spontaneous squeezing of a photon fluid in a nonlocal nonlinear
medium. By using the so called Gamow vectors, we show that the quadratures of a
coherent state get squeezed and that a maximal squeezing power exists. Our
analysis holds true for temporal and spatial optical propagation in highly
nonlocal regime. These results open a new scenario in quantum photon fluids and
may lead to novel applications in fields like metrology and analogues of
quantum gravity.


title:
Ultra-wide frequency response measurement of an optical system with a DC
  photo-detector

abstract:
  Precise knowledge of an optical device's frequency response is crucial for it
to be useful in most applications. Traditional methods for determining the
frequency response of an optical system (e.g. optical cavity or waveguide
modulator) usually rely on calibrated broadband photo-detectors or complicated
RF mixdown operations. As the bandwidths of these devices continue to increase,
there is a growing need for a characterization method that does not have
bandwidth limitations, or require a previously calibrated device. We
demonstrate a new calibration technique on an optical system (consisting of an
optical cavity and a high-speed waveguide modulator) that is free from
limitations imposed by detector bandwidth, and does not require a calibrated
photo-detector or modulator. We use a low-frequency (DC) photo-detector to
monitor the cavity's optical response as a function of modulation frequency,
which is also used to determine the modulator's frequency response. Knowledge
of the frequency-dependent modulation depth allows us to more precisely
determine the cavity's characteristics (free spectral range and linewidth). The
precision and repeatability of our technique is demonstrated by measuring the
different resonant frequencies of orthogonal polarization cavity modes caused
by the presence of a non-linear crystal. Once the modulator has been
characterized using this simple method, the frequency response of any passive
optical element can be determined.


title: Effect of body deformability on microswimming

abstract:
  In this work we consider the following question: given a mechanical
microswimming mechanism, does increased deformability of the swimmer body
hinder or promote the motility of the swimmer? To answer this we study a
microswimmer model composed of deformable beads connected with springs. We
determine the velocity of the swimmer analytically, starting from the forces
driving the motion and assuming that the oscillations in the effective radii of
the beads are known and are much smaller than the radii themselves. We find
that to the lowest order, only the driving frequency mode of the surface
oscillations contributes to the swimming velocity, and that this velocity may
both rise and fall with the deformability of the beads depending on the spring
constant. To test these results, we run immersed boundary lattice Boltzmann
simulations of the swimmer, and show that they reproduce both the
velocity-promoting and velocity-hindering effects of bead deformability
correctly in the predicted parameter ranges. Our results mean that for a
general swimmer, its elasticity determines whether passive deformations of the
swimmer body, induced by the fluid flow, aid or oppose the motion.


title: Modular Multitask Reinforcement Learning with Policy Sketches

abstract:
  We describe a framework for multitask deep reinforcement learning guided by
policy sketches. Sketches annotate tasks with sequences of named subtasks,
providing information about high-level structural relationships among tasks but
not how to implement them---specifically not providing the detailed guidance
used by much previous work on learning policy abstractions for RL (e.g.
intermediate rewards, subtask completion signals, or intrinsic motivations). To
learn from sketches, we present a model that associates every subtask with a
modular subpolicy, and jointly maximizes reward over full task-specific
policies by tying parameters across shared subpolicies. Optimization is
accomplished via a decoupled actor--critic training objective that facilitates
learning common behaviors from multiple dissimilar reward functions. We
evaluate the effectiveness of our approach in three environments featuring both
discrete and continuous control, and with sparse rewards that can be obtained
only after completing a number of high-level subgoals. Experiments show that
using our approach to learn policies guided by sketches gives better
performance than existing techniques for learning task-specific or shared
policies, while naturally inducing a library of interpretable primitive
behaviors that can be recombined to rapidly adapt to new tasks.


title: Born-Oppenheimer Approximation for a Simple Renormalizable System

abstract:
  We discuss a simple singular system in two dimension, two heavy particles
interacting with a light particle via an attractive contact interaction.
Although intuitively clear the actual application of the Born-Oppenheimer
approximation to this problem is quite subtle. Nevertheless, with due care we
show that this can be done, as a result we calculate the leading term of the
Born-Oppenheimer approximation and indicate how to get the higher order
corrections.


title:
A "Rosetta Stone" for protoplanetary disks: The synergy of
  multi-wavelength observations

abstract:
  The recent progress in instrumentation and telescope development has brought
us different ways to observe protoplanetary disks, including interferometers,
space missions, adaptive optics, polarimetry, and time- and spectrally-resolved
data. While the new facilities have changed the way we can tackle the existing
open problems in disk structure and evolution, there is a substantial lack of
interconnection between different observing techniques and their user
communities. Here, we explore the complementarity of some of the
state-of-the-art observing techniques, and how they can be brought together in
a collective effort to understand how disks evolve and disperse at the time of
planet formation.
  This paper was born at the "Protoplanetary Discussions" meeting in Edinburgh,
2016. Its goal is to clarify where multi-wavelength observations of disks
converge in unveiling disk structure and evolution, and where they diverge and
challenge our current understanding. We discuss caveats that should be
considered when linking results from different observations, or when drawing
conclusions based on limited datasets (in terms of wavelength or sample). We
focus on disk properties that are currently being revolutionized by
multi-wavelength observations. Specifically: the inner disk radius, holes and
gaps and their link to large-scale disk structures, the disk mass, and the
accretion rate. We discuss how the links between them, as well as the apparent
contradictions, can help us to disentangle the disk physics and to learn about
disk evolution.


title:
Generative Adversarial Networks as Variational Training of Energy Based
  Models

abstract:
  In this paper, we study deep generative models for effective unsupervised
learning. We propose VGAN, which works by minimizing a variational lower bound
of the negative log likelihood (NLL) of an energy based model (EBM), where the
model density $p(\mathbf{x})$ is approximated by a variational distribution
$q(\mathbf{x})$ that is easy to sample from. The training of VGAN takes a two
step procedure: given $p(\mathbf{x})$, $q(\mathbf{x})$ is updated to maximize
the lower bound; $p(\mathbf{x})$ is then updated one step with samples drawn
from $q(\mathbf{x})$ to decrease the lower bound. VGAN is inspired by the
generative adversarial networks (GANs), where $p(\mathbf{x})$ corresponds to
the discriminator and $q(\mathbf{x})$ corresponds to the generator, but with
several notable differences. We hence name our model variational GANs (VGANs).
VGAN provides a practical solution to training deep EBMs in high dimensional
space, by eliminating the need of MCMC sampling. From this view, we are also
able to identify causes to the difficulty of training GANs and propose viable
solutions. \footnote{Experimental code is available at
https://github.com/Shuangfei/vgan}


title:
Callias-type operators in $C^\ast$-algebras and positive scalar
  curvature on noncompact manifolds

abstract:
  A Dirac-type operator on a complete Riemannian manifold is of Callias-type if
its square is a Schr\"{o}dinger-type operator with a potential uniformly
positive outside of a compact set. We develop the theory of Callias-type
operators twisted with Hilbert $C^\ast$-module bundles and prove an index
theorem for such operators. As an application, we derive an obstruction to the
existence of complete Riemannian metrics of positive scalar curvature on
noncompact spin manifolds in terms of closed submanifolds of codimension-one.


title: Activity Recognition Based on Micro-Doppler Signature with In-Home Wi-Fi

abstract:
  Device free activity recognition and monitoring has become a promising
research area with increasing public interest in pattern of life monitoring and
chronic health conditions. This paper proposes a novel framework for in-home
Wi-Fi signal-based activity recognition in e-healthcare applications using
passive micro-Doppler (m-D) signature classification. The framework includes
signal modeling, Doppler extraction and m-D classification. A data collection
campaign was designed to verify the framework where six m-D signatures
corresponding to typical daily activities are sucessfully detected and
classified using our software defined radio (SDR) demo system. Analysis of the
data focussed on potential discriminative characteristics, such as maximum
Doppler frequency and time duration of activity. Finally, a sparsity induced
classifier is applied for adaptting the method in healthcare application
scenarios and the results are compared with those from the well-known Support
Vector Machine (SVM) method.


title: Self-Wiring Question Answering Systems

abstract:
  Question answering (QA) has been the subject of a resurgence over the past
years. The said resurgence has led to a multitude of question answering (QA)
systems being developed both by companies and research facilities. While a few
components of QA systems get reused across implementations, most systems do not
leverage the full potential of component reuse. Hence, the development of QA
systems is currently still a tedious and time-consuming process. We address the
challenge of accelerating the creation of novel or tailored QA systems by
presenting a concept for a self-wiring approach to composing QA systems. Our
approach will allow the reuse of existing, web-based QA systems or modules
while developing new QA platforms. To this end, it will rely on QA modules
being described using the Web Ontology Language. Based on these descriptions,
our approach will be able to automatically compose QA systems using a
data-driven approach automatically.


title: Proca Q Tubes and their Coupling to Gravity

abstract:
  The Einstein-Proca system is studied in the case of a complex vector-field
self-interacting through an appropriate potential with a global U(1) symmetry.
The corresponding equations for a static, cylindrically symmetric metric and
matter fields are then constructed and solved. In the probe limit (no gravity),
it is shown that the equations admit at least two classes of regular solutions
distinguished by the asymptotic behavior of the matter fields. One of these
classes corresponds to lumps of vector fields localized in a cylindrical
region, we naturally call these solutions "Proca-Q-tubes". They constitute the
cylindrical counterparts of spherical Proca-Q-balls constructed recently, they
can be characterized by finite mass and charge per unit-length of the tube. The
domain of existence of these Proca-Q-tubes with respect to the coupling
constants determining the potential is studied in detail. Finally, the
gravitating Proca-Q-tubes are constructed and studied.


title: Homogeneous fibrations on log Calabi-Yau varieties

abstract:
  We prove a structure theorem for the Albanese maps of varieties with
Q-linearly trivial log canonical divisors. Our start point is the action of a
nonlinear algebraic group on a projective variety.


title: Algorithmic Discrepancy Beyond Partial Coloring

abstract:
  The partial coloring method is one of the most powerful and widely used
method in combinatorial discrepancy problems. However, in many cases it leads
to sub-optimal bounds as the partial coloring step must be iterated a
logarithmic number of times, and the errors can add up in an adversarial way.
We give a new and general algorithmic framework that overcomes the limitations
of the partial coloring method and can be applied in a black-box manner to
various problems. Using this framework, we give new improved bounds and
algorithms for several classic problems in discrepancy. In particular, for
Tusnady's problem, we give an improved $O(\log^2 n)$ bound for discrepancy of
axis-parallel rectangles and more generally an $O_d(\log^dn)$ bound for
$d$-dimensional boxes in $\mathbb{R}^d$. Previously, even non-constructively,
the best bounds were $O(\log^{2.5} n)$ and $O_d(\log^{d+0.5}n)$ respectively.
Similarly, for the Steinitz problem we give the first algorithm that matches
the best known non-constructive bounds due to Banaszczyk [Banaszczyk 2012] in
the $\ell_\infty$ case, and improves the previous algorithmic bounds
substantially in the $\ell_2$ case. Our framework is based upon a substantial
generalization of the techniques developed recently in the context of the
Koml\'os discrepancy problem [BDG16].


title: Inverse Participation Ratios in the XX spin chain

abstract:
  We continue the study of the Inverse Participation Ratios (IPRs) of the XXZ
Heisenberg spin chain initiated by Misguich, Pasquier and Luck (2016) by
focusing on the case of the XX Heisenberg Spin Chain. For the ground state,
Misguich et al. note that calculating the IPR is equivalent to Dyson's constant
term ex-conjecture. We express the IPRs of excited states as an apparently new
"discrete" Hall inner product. We analyze this inner product using the theory
of symmetric functions (Jack polynomials, Schur polynomials, the standard Hall
inner product and $\omega_{q,t}$) to determine some exact expressions and
asymptotics for IPRs. We show that IPRs can be indexed by partitions, and
asymptotically the IPR of a partition is equal to that of the conjugate
partition. We relate the IPRs to two other models from physics, namely, the
circular symplectic ensemble of Dyson and the Dyson-Gaudin two-dimensional
Coulomb lattice gas. Finally, we provide a description of the IPRs in terms of
a signed count of diagonals of permutohedra.


title: Topological properties of spaces admitting a coaxial homeomorphism

abstract:
  Wright showed that, if a 1-ended simply connected locally compact ANR Y with
pro-monomorphic fundamental group at infinity admits a proper Z-action, then
that fundamental group at infinity can be represented by an inverse sequence of
finitely generated free groups. Geoghegan and Guilbault strengthened that
result, proving that Y also satisfies the crucial "semistability" condition.
  Here we get a stronger theorem with weaker hypotheses. We drop the
pro-monomorphic hypothesis and simply assume that the Z-action is generated by
what we call a "coaxial" homeomorphism. In the pro-monomorphic case every
proper Z-action is generated by a coaxial homeomorphism, but coaxials occur in
far greater generality (often embedded in a cocompact action). When the
generator is coaxial, we obtain the sharp conclusion: Y is proper 2-equivalent
to the product of a locally finite tree with a line. Even in the
pro-monomorphic case this is new: it says that, from the viewpoint of
fundamental group at infinity, the end of Y looks like the suspension of a
totally disconnected compact set.


title: Anti-gravity \`a la Carlotto-Schoen

abstract:
  We review the Carlotto-Schoen construction of general relativistic initial
data sets which are trivial outside of cones, discuss the context, the
implications, and some further developments.


title: Ample tangent bundle on smooth projective stacks

abstract:
  We study ample vector bundles on smooth projective stacks. In particular, we
prove that the tangent bundle for the weighted projective stack
$\mathbb{P}(a_0,...,a_n)$ is ample. A result of Mori shows that the only smooth
projective varieties with ample vector bundle are isomorphic to $\mathbb{P}^N$
for some $N$. Extending our geometric spaces from varieties to projective
stacks, we are able to provide a new example. This leaves the open question of
knowing if the only smooth projective stacks are the weighted projective
stacks.


title: Asymptotic symmetry algebra of conformal gravity

abstract:
  We compute asymptotic symmetry algebras of conformal gravity. Due to more
general boundary conditions allowed in conformal gravity in comparison to those
in Einstein gravity, we can classify the corresponding algebras. The highest
algebra for non-trivial boundary conditions is five dimensional and it leads to
global geon solution with non-vanishing charges.


title: Destroying extremal magnetized black holes

abstract:
  The gedanken experiment by Wald to destroy a black hole using a test particle
in the equatorial plane is adopted to the case of extremal magnetized black
holes. We find the presence of external magnetic fields resulting from the
"Ernst magnetization" permits a test particle to have strong enough energy to
destroy the black hole. However, the corresponding effective potentials show
that such particles would never reach the horizon.


title: On the unique predual problem for Lipschitz spaces

abstract:
  For any metric space X, the predual of Lip(X) is unique. If X has finite
diameter or is complete and convex --- in particular, if it is a Banach space
--- then the predual of Lip_0(X) is unique.


title: Symmetric Potentials Beget Symmetric Ground States

abstract:
  Using an unusual type of symmetric average, we show that for several common
equations involving quite general potentials possessing symmetry, the ground
state, if it exists, must also be symmetric.


title:
Terahertz-frequency magnon-phonon-polaritons in the strong coupling
  regime

abstract:
  Strong coupling between light and matter occurs when the two interact
strongly enough to form new hybrid modes called polaritons. Here we report on
the strong coupling of both the electric and magnetic degrees of freedom to an
ultrafast terahertz (THz) frequency electromagnetic wave. In our system,
optical phonons in a slab of ferroelectric lithium niobate (LiNbO$_3$) are
strongly coupled to a THz electric field to form phonon-polaritons, which are
simultaneously strongly coupled to magnons in an adjacent slab of canted
antiferromagnetic erbium orthoferrite (ErFeO$_3$) via the THz magnetic field.
The strong coupling leads to the formation of new magnon-phonon-polariton
modes, which we experimentally observe in the wavevector-frequency dispersion
curve as an avoided crossing and in the time-domain as a normal-mode beating.
Our simple yet versatile on-chip waveguide platform provides a promising avenue
by which to explore both ultrafast THz spintronics applications and the quantum
nature of the interaction.


title:
Periods and motives in the spectral action of Robertson-Walker
  spacetimes

abstract:
  We show that, when considering the scaling factor as an affine variable, the
coefficients of the asymptotic expansion of the spectral action on a
(Euclidean) Robertson-Walker spacetime are periods of mixed Tate motives,
involving relative motives of complements of unions of hyperplanes and quadric
hypersurfaces and divisors given by unions of coordinate hyperplanes.


title: Small covers of graph-associahedra and realization of cycles

abstract:
  An oriented connected closed manifold $M^n$ is called a URC-manifold if for
any oriented connected closed manifold $N^n$ of the same dimension there exists
a nonzero degree mapping of a finite-fold covering $\widehat{M}^n$ of $M^n$
onto $N^n$. This condition is equivalent to the following: For any
$n$-dimensional integral homology class of any topological space $X$, a
multiple of it can be realized as the image of the fundamental class of a
finite-fold covering $\widehat{M}^n$ of $M^n$ under a continuous mapping
$f\colon \widehat{M}^n\to X$. In 2007 the author gave a constructive proof of
the classical result by Thom that a multiple of any integral homology class can
be realized as an image of the fundamental class of an oriented smooth
manifold. This construction yields the existence of URC-manifolds of all
dimensions. For an important class of manifolds, the so-called small covers of
graph-associahedra corresponding to connected graphs, we prove that either they
or their two-fold orientation coverings are URC-manifolds. In particular, we
obtain that the two-fold covering of the small cover of the usual Stasheff
associahedron is a URC-manifold. In dimensions 4 and higher, this manifold is
simpler than all previously known URC-manifolds.


title:
Exploring the Pathways of Adaptation an Avatar 3D Animation Procedures
  and Virtual Reality Arenas in Research of Human Courtship Behaviour and
  Sexual Reactivity in Psychological Research

abstract:
  There are many reasons for utilising 3D animation and virtual reality in
sexuality research. Apart from providing a mean with which to (re)experience
certain situations there are four main advantages: a) bespoke animated stimuli
can be created and customized, which is especially important when researching
paraphilia and sexual preferences, b) stimulus production is less expensive and
easier to produce compared to real world stimuli, c) virtual reality allows us
to capture data such as physiological reasons to stimuli, that we would not be
able to otherwise (without resorting to self-report measures which are
especially problematic in this research domain), d) ethical, legal, and health
and safety issues are less complex since neither physical nor psychological
harm is caused to animated characters allowing for the safe presentation of
stimuli involving vulnerable targets. The animation sub-group has been
exploring so far several production quality levels and various animation
procedures in a number of available software. The aim is to develop static as
well as dynamic, interactive sexual stimuli for sexual diagnostic and
therapeutic purposes. We are aware of number of ethical issues related to the
use of virtual reality in proposed research are analysed in this chapter.


title: A note on the positive semidefinitness of $A_\alpha (G)$

abstract:
  Let $G$ be a graph with adjacency matrix $A(G)$ and let $D(G)$ be the
diagonal matrix of the degrees of $G$. For every real $\alpha\in\left[
0,1\right] $, write $A_{\alpha}\left( G\right) $ for the matrix \[
A_{\alpha}\left( G\right) =\alpha D\left( G\right) +(1-\alpha)A\left( G\right)
. \] Let $\alpha_{0}\left( G\right) $ be the smallest $\alpha$ for which
$A_{\alpha}(G)$ is positive semidefinite. It is known that $\alpha_{0}\left(
G\right) \leq1/2$. The main results of this paper are:
  (1) if $G$ is $d$-regular then \[
\alpha_{0}=\frac{-\lambda_{\min}(A(G))}{d-\lambda_{\min}(A(G))}, \] where
$\lambda_{\min}(A(G))$ is the smallest eigenvalue of $A(G)$;
  (2) $G$ contains a bipartite component if and only if $\alpha_{0}\left(
G\right) =1/2$;
  (3) if $G$ is $r$-colorable, then $\alpha_{0}\left( G\right) \geq1/r$.


title:
On the possible triple central star system of PN SuWt 2: No m\'enage \`a
  trois at the heart of the Wedding Ring

abstract:
  SuWt 2 is a planetary nebula consisting of a bright ring-like waist from
which protrude faint extended lobes - a morphology believed to be typical of
progenitors which have experienced a close-binary evolution. Previous
observations of NSV 19992, the star at the projected centre of SuWt 2, have
found it to comprise two A-type stars in a 4.9 day eclipsing orbit, neither of
which could be the nebular progenitor. Radial velocity studies provided a hint
that the systemic velocity of this double A-type binary might be varying over
time, suggesting the presence of a third component hypothesised to be the
nebular progenitor. Here, we present an extensive radial velocity monitoring
study of NSV 19992, performed with the high-resolution echelle spectrograph
UVES mounted on ESO's VLT, in order to constrain the possible variation in the
systemic velocity of the A-type binary and its relation to the progenitor of
SuWt 2. The observations, acquired over a period of approximately one year,
show no evidence of variability in the systemic velocity of NSV 19992.
Combining these new observations with previous high-resolution spectroscopy
demonstrates that the systemic velocity is also stable over much longer periods
and, moreover, is distinct from that of SuWt 2, strongly indicating that the
two are not associated. We conclude that NSV 19992 is merely a field star
system, by chance lying in the same line of sight as the nebular centre, and
that it bares no relation to SuWt 2 or its, as yet unidentified, central
star(s).


title:
A Semi-Automatic Approach for Detecting Dataset References in Social
  Science Texts

abstract:
  Today, full-texts of scientific articles are often stored in different
locations than the used datasets. Dataset registries aim at a closer
integration by making datasets citable but authors typically refer to datasets
using inconsistent abbreviations and heterogeneous metadata (e.g. title,
publication year). It is thus hard to reproduce research results, to access
datasets for further analysis, and to determine the impact of a dataset.
Manually detecting references to datasets in scientific articles is
time-consuming and requires expert knowledge in the underlying research
domain.We propose and evaluate a semi-automatic three-step approach for finding
explicit references to datasets in social sciences articles.We first extract
pre-defined special features from dataset titles in the da|ra registry, then
detect references to datasets using the extracted features, and finally match
the references found with corresponding dataset titles. The approach does not
require a corpus of articles (avoiding the cold start problem) and performs
well on a test corpus. We achieved an F-measure of 0.84 for detecting
references in full-texts and an F-measure of 0.83 for finding correct matches
of detected references in the da|ra dataset registry.


title:
Bounded weight modules of the Lie algebra of vector fields on ${\mathbb
  C}^2$

abstract:
  We study weight modules of the Lie algebra $W_2$ of vector fields on
${\mathbb C}^2$. A classification of all simple weight modules of $W_2$ with a
uniformly bounded set of weight multiplicities is provided. To achieve this
classification we introduce a new family of generalized tensor $W_n$-modules.
Our classification result is an important step in the classification of all
simple weight $W_n$-modules with finite weight multiplicities.


title:
Quantum critical local spin dynamics near the Mott metal-insulator
  transition in infinite dimensions

abstract:
  Finding microscopic models for metallic states that exhibit quantum critical
properties such as $\omega/T$ scaling is a major theoretical challenge. We
calculate the local dynamical spin susceptibility $\chi(T,\omega)$ for a
Hubbard model at half filling using Dynamical Mean-Field Theory, which is exact
in infinite dimensions. Qualitatively distinct behavior is found in the
different regions of the phase diagram: Mott insulator, Fermi liquid metal, bad
metal, and a quantum critical region above the finite temperature critical
point. The signature of the latter is $\omega/T$ scaling where $T$ is the
temperature. Our results are consistent with previous results showing scaling
of the dc electrical conductivity and are relevant to experiments on organic
charge transfer salts.


title: Parameterized counting of trees, forests and matroid bases

abstract:
  We investigate the complexity of counting trees, forests and bases of
matroids from a parameterized point of view. It turns out that the problems of
computing the number of trees and forests with $k$ edges are $\# W[1]$-hard
when parameterized by $k$. Together with the recent algorithm for deterministic
matrix truncation by Lokshtanov et al. (ICALP 2015), the hardness result for
$k$-forests implies $\# W[1]$-hardness of the problem of counting bases of a
matroid when parameterized by rank or nullity, even if the matroid is
restricted to be representable over a field of characteristic $2$. We
complement this result by pointing out that the problem becomes fixed parameter
tractable for matroids represented over a fixed finite field.


title:
Robust Distance-Based Formation Control of Multiple Rigid Bodies with
  Orientation Alignment

abstract:
  This paper addresses the problem of distance- and orientation-based formation
control of a class of second-order nonlinear multi-agent systems in 3D space,
under static and undirected communication topologies. More specifically, we
design a decentralized model-free control protocol in the sense that each agent
uses only local information from its neighbors to calculate its own control
signal, without incorporating any knowledge of the model nonlinearities and
exogenous disturbances. Moreover, the transient and steady state response is
solely determined by certain designer-specified performance functions and is
fully decoupled by the agents' dynamic model, the control gain selection, the
underlying graph topology as well as the initial conditions. Additionally, by
introducing certain inter-agent distance constraints, we guarantee collision
avoidance and connectivity maintenance between neighboring agents. Finally,
simulation results verify the performance of the proposed controllers.


title:
Robust State-Feedback H-infinity Control For Discrete-Time Descriptor
  Systems With Norm-Bounded Parametric Uncertainties

abstract:
  This paper deals with a state feedback H-infinity control problem for linear
time-invariant discrete-time descriptor systems with norm-bounded parametric
uncertainties. To this end, bounded real lemma (BRL) is extended on the class
of uncertain descriptor systems. The control design procedure based on the
conditions of BRL for uncertain descriptor systems is proposed. Numerical
example is included to illustrate the effectiveness of the present result.


title:
A Decade of Developing Radio-Astronomy Instrumentation using CASPER
  Open-Source Technology

abstract:
  The Collaboration for Astronomy Signal Processing and Electronics Research
(CASPER) has been working for a decade to reduce the time and cost of
designing, building and deploying new digital radio-astronomy instruments.
Today, CASPER open-source technology powers over 45 scientific instruments
worldwide, and is used by scientists and engineers at dozens of academic
institutions. In this paper we catalog the current offerings of the CASPER
collaboration, and instruments past and present built by CASPER users and
developers. We describe the ongoing state of software development, as CASPER
looks to support a broader range of programming environments and hardware and
ensure compatibility with the latest vendor tools.


title: Information Performance Tradeoffs in Control

abstract:
  We focus our attention on the most common scenario in networked control
systems where the measured output from the observer is transmitted via a
communication channel to the controller. Using information theoretic results,
we studied the tradeoff between the performance and the accuracy of
observations due to communication constraints for such a scenario. We focused
on three important cases in the communication channel, the additive white
Gaussian noise (AWGN), limited data rate and systems with multiplicative
uncertainty in the system parameters. Using known theoretical results for a
rate limited communication channel, we showed the effect of entropy of the
output of quantizer on the control performance. The same was done for the case
of multiplicative uncertainty in the system . For an AWGN channel, we showed
the effect of channel SNR on the performance. For the analog joint source
channel coding approach (which works only for Gaussian disturbances in the
system), we showed that the known lower bound is tight even for non Gaussian
system disturbances. We also compared the simulated performance of a system
with known upper and lower rate distortion bounds for all the three cases. The
lower bound on the rate is closely approached by a simple uniform quantization
scheme, hence demonstrating its tightness.


title: Fast ADMM for homogeneous self-dual embedding of sparse SDPs

abstract:
  We propose an efficient first-order method, based on the alternating
direction method of multipliers (ADMM), to solve the homogeneous self-dual
embedding problem for a primal-dual pair of semidefinite programs (SDPs) with
chordal sparsity. Using a series of block eliminations, the per-iteration cost
of our method is the same as applying a splitting method to the primal or dual
alone. Moreover, our approach is more efficient than other first-order methods
for generic sparse conic programs since we work with smaller semidefinite
cones. In contrast to previous first-order methods that exploit chordal
sparsity, our algorithm returns both primal and dual solutions when available,
and a certificate of infeasibility otherwise. Our techniques are implemented in
the open-source MATLAB solver CDCS. Numerical experiments on three sets of
benchmark problems from the library SDPLIB show speed-ups compared to some
common state-of-the-art software packages.


title: Monotone and Pseudo-Monotone Equilibrium Problems in Hadamard Spaces

abstract:
  We study equilibrium problems in Hadamard spaces, which extend variational
inequalities and many other problems in nonlinear analysis. In this paper,
first we study the existence of solutions of equilibrium problems associated
with pseudo-monotone bifunctions with suitable conditions on the bifunctions in
Hadamard spaces. Then to approximate of an equilibrium point, we consider the
proximal point algorithm for pseudo-monotone bifunctions. We prove existence of
the sequence generated by the algorithm in several cases in Hadamard spaces.
Next, we introduce the resolvent of a bifunction in Hadamard spaces. We prove
convergence of the resolvent to an equilibrium point. We also prove
$\bigtriangleup$-convergence of the sequence generated by the proximal point
algorithm to an equilibrium point of the pseudo-monotone bifunction and also
the strong convergence with additional assumptions on the bifunction. Finally,
we study a regularization of Halpern type and prove the strong convergence of
the generated sequence to an equilibrium point without any additional
assumption on the pseudo-monotone bifunction. Some examples in fixed point
theory and convex minimization are also presented.


title:
Proximal Point Algorithm for Quasi-convex Minimization Problems in
  metric spaces

abstract:
  In this paper, the proximal point algorithm for quasi-convex minimization
problem in nonpositive curvature metric spaces is studied. We prove
$\Delta$-convergence of the generated sequence to a critical point (which is
defined in the text) of an objective convex, proper and lower semicontinuous
function with at least a minimum point as well as some strong convergence
results to a minimum point with some additional conditions. The results extend
the recent results of the proximal point algorithm in Hadamard manifolds and
CAT(0) spaces.


title: Longitudinal Dynamic Functional Regression

abstract:
  This article develops flexible methodology to study the association between
scalar outcomes and functional predictors observed over time, at many
instances, in longitudinal studies. We propose a parsimonious modeling
framework to study time-varying regression that leads to superior prediction
properties and allows to reconstruct full trajectories of the response. The
idea is to model the time-varying functional predictors using orthogonal basis
functions and expand the time-varying regression coefficient using the same
basis. Numerical investigation through simulation studies and data analysis
show excellent performance in terms of accurate prediction and efficient
computations, when compared with existing alternatives. The methods are
inspired and applied to an animal science application, where of interest is to
study the association between the feed intake of lactating sows and the
minute-by-minute {temperature} throughout the 21st days of their lactation
period. R code and an R illustration are provided at
http://www4.stat.ncsu.edu/~staicu/software


title: Spin filtering in all-electrical three-terminal interferometers

abstract:
  Unlike the two-terminal device, in which the time-reversal invariant
spin-orbit interaction alone cannot polarize the spins, such a polarization can
be generated when electrons from one source reservoir flow into two (or more)
separate drain reservoirs. We present analytical solutions for two examples.
First, we demonstrate that the electrons transmitted through a "diamond"
interferometer into two drains can be simultaneously fully spin-polarized along
different tunable directions, even when the two arms of the interferometer are
not identical. Second, we show that a single helical molecule attached to more
than one drain can induce a significant spin polarization in electrons passing
through it. The average polarization remains non-zero even when the electrons
outgoing into separate leads are eventually mixed incoherently into one
absorbing reservoir. This may explain recent experiments on spin selectivity of
certain helical-chiral molecules.


title: Number of particles absorbed in a BBM on the extinction event

abstract:
  We consider a branching Brownian motion which starts from $0$ with drift $\mu
\in \mathbb{R}$ and we focus on the number $Z_x$ of particles killed at $-x$,
where $x>0$. Let us call $\mu_0$ the critical drift such that there is a
positive probability of survival if and only if $\mu>-\mu_0$. Maillard
\cite{maillard2013number} and Berestycki et al. \cite{berestycki2015branching}
have study $Z_x$ in the case $\mu \leq -\mu_0$ and $\mu\geq \mu_0$
respectively. We complete the picture by considering the case where
$\mu>-\mu_0$ on the extinction event. More precisely we study the asymptotic of
$q_i(x):=\mathbb{P}\left(Z_x=i,\zeta_x<\infty\right)$. We show that the radius
of convergence $R(\mu)$ of the corresponding power series increases as $\mu$
increases, up until $\mu=\mu_c\in [-\mu_0,+\infty]$ after which it is constant.
We also give a necessary and sufficient condition for $\mu_c<+\infty$. In
addition, finer asymptotics are also obtained, which highlight three different
regimes depending on $\mu<\mu_c$, $\mu=\mu_c$ or $\mu>\mu_c$.


title:
Steady-state distributions of ideal active Brownian particles under
  confinement and forcing

abstract:
  We develop a formally exact technique for obtaining steady-state
distributions of non-interacting active Brownian particles in a variety of
systems. Our technique draws on results from the theory of two-way diffusion
equations to solve the steady-state Smoluchowski equation for the 1-particle
distribution function. The methods are employed to study in detail three
scenarios: 1) confinement in a channel, 2) a constant flux steady state, and 3)
sedimentation in a uniform external field. In each scenario, known behaviors
are reproduced and precisely quantified, and new results are presented. In
particular, in the constant flux state we derive an effective diffusivity which
interpolates between the ballistic behavior of particle trajectories at short
distances and their diffusive behavior at large distances. We also calculate
the sedimentation profile of active Brownian particles near a wall, which
complements earlier studies on the part far from the wall. Our techniques
easily generalize to other active models, including systems whose activity is
modeled in terms of Gaussian colored noise.


title: Compressed Dynamic Range Majority and Minority Data Structures

abstract:
  In the range $\alpha$-majority query problem, we are given a sequence
$S[1..n]$ and a fixed threshold $\alpha \in (0, 1)$, and are asked to
preprocess $S$ such that, given a query range $[i..j]$, we can efficiently
report the symbols that occur more than $\alpha (j-i+1)$ times in $S[i..j]$,
which are called the range $\alpha$-majorities. In this article we first
describe a dynamic data structure that represents $S$ in compressed space ---
$nH_k+ o(n\lg \sigma)$ bits for any $k = o(\log_{\sigma} n)$, where $\sigma$ is
the alphabet size and $H_k \le H_0 \le \lg\sigma $ is the $k$-th order
empirical entropy of $S$ --- and answers queries in $O \left(\frac{\log
n}{\alpha \log \log n} \right)$ time while supporting insertions and deletions
in $S$ in $O \left( \frac{\lg n}{\alpha} \right)$ amortized time. We then show
how to modify our data structure to receive some $\beta \ge \alpha$ at query
time and report the range $\beta$-majorities in $O \left( \frac{\log n}{\beta
\log \log n} \right)$ time, without increasing the asymptotic space or
update-time bounds. The best previous dynamic solution has the same query and
update times as ours, but it occupies $O(n)$ words and cannot take advantage of
being given a larger threshold $\beta$ at query time.
  [ABSTRACT CLIPPED DUE TO LENGTH.]


title: Ancestry in adapting, spatially-extended populations

abstract:
  Selective sweeps affect neutral genetic diversity through hitchhiking. While
this effect is limited to the local genomic region of the sweep in panmictic
populations, we find that in spatially-extended populations the combined
effects of many unlinked sweeps can affect patterns of ancestry (and therefore
neutral genetic diversity) across the whole genome. Even low rates of sweeps
can be enough to skew the spatial locations of ancestors such that neutral
mutations that occur in an individual living outside a small region in the
center of the range have virtually no chance of fixing in the population.


title: Singular vector distribution of sample covariance matrices

abstract:
  We consider a class of sample covariance matrices of the form $Q=TXX^{*}T^*,$
where $X=(x_{ij})$ is an $M \times N$ rectangular matrix consisting of i.i.d
entries and $T$ is a deterministic matrix satisfying $T^*T$ is diagonal.
Assuming $M$ is comparable to $N$, we prove that the distribution of the
components of the singular vectors close to the edge singular values agrees
with that of Gaussian ensembles provided the first two moments of $x_{ij}$
coincide with the Gaussian random variables. For the singular vectors
associated with the bulk singular values, the same conclusion holds if the
first four moments of $x_{ij}$ match with those of Gaussian random variables.
Similar results have been proved for Wigner matrices by Knowles and Yin.


title: Entropy-SGD: Biasing Gradient Descent Into Wide Valleys

abstract:
  This paper proposes a new optimization algorithm called Entropy-SGD for
training deep neural networks that is motivated by the local geometry of the
energy landscape. Local extrema with low generalization error have a large
proportion of almost-zero eigenvalues in the Hessian with very few positive or
negative eigenvalues. We leverage upon this observation to construct a
local-entropy-based objective function that favors well-generalizable solutions
lying in large flat regions of the energy landscape, while avoiding
poorly-generalizable solutions located in the sharp valleys. Conceptually, our
algorithm resembles two nested loops of SGD where we use Langevin dynamics in
the inner loop to compute the gradient of the local entropy before each update
of the weights. We show that the new objective has a smoother energy landscape
and show improved generalization over SGD using uniform stability, under
certain assumptions. Our experiments on convolutional and recurrent networks
demonstrate that Entropy-SGD compares favorably to state-of-the-art techniques
in terms of generalization error and training time.


title: Hierarchical Question Answering for Long Documents

abstract:
  We present a framework for question answering that can efficiently scale to
longer documents while maintaining or even improving performance of
state-of-the-art models. While most successful approaches for reading
comprehension rely on recurrent neural networks (RNNs), running them over long
documents is prohibitively slow because it is difficult to parallelize over
sequences. Inspired by how people first skim the document, identify relevant
parts, and carefully read these parts to produce an answer, we combine a
coarse, fast model for selecting relevant sentences and a more expensive RNN
for producing the answer from those sentences. We treat sentence selection as a
latent variable trained jointly from the answer only using reinforcement
learning. Experiments demonstrate the state of the art performance on a
challenging subset of the Wikireading and on a new dataset, while speeding up
the model by 3.5x-6.7x.


title:
Effective magnetic interactions in spin-orbit coupled $d^4$ Mott
  insulators

abstract:
  Transition metal compounds with the $(t_{2g})^4$ electronic configuration are
expected to be nonmagnetic atomic singlets both in the weakly interacting
regime due to spin-orbit coupling, as well as in the Coulomb dominated regime
with oppositely aligned $L=1$ and $S=1$ angular momenta. However, starting with
the full multi-orbital electronic Hamiltonian, we show the low energy effective
magnetic Hamiltonian contains isotropic superexchange spin interactions but
anisotropic orbital interactions. By tuning the ratio of superexchange to
spin-orbit coupling $J_\mathrm{SE}/\lambda$, we obtain a phase transition from
nonmagnetic atomic singlets to novel magnetic phases depending on the strength
of Hund's coupling, the crystal structure and the number of active orbitals.
Spin-orbit coupling plays a non-trivial role in generating a triplon condensate
of weakly interacting excitations at antiferromagnetic ordering vector $\vec
k=\vec \pi$, regardless of whether the local spin interactions are
ferromagnetic or antiferromagnetic. In the large $J_\mathrm{SE} / \lambda$
regime, the localized spin and orbital moments produce anisotropic orbital
interactions that are frustrated or constrained even in the absence of
geometric frustration. Orbital frustration leads to frustration in the spin
channel opening up the possibility of spin-orbital liquids with both spin and
orbital entanglement.


title: Gr\"obner theory and tropical geometry on spherical varieties

abstract:
  Let $G$ be a connected reductive algebraic group. We develop a Gr\"obner
theory for multiplicity-free $G$-algebras, as well as a tropical geometry for
subschemes in a spherical homogeneous space $G/H$. We define the notion of a
spherical tropical variety and prove a fundamental theorem of tropical geometry
in this context. We also propose a definition for a spherical amoeba in $G/H$.
Our work partly builds on the previous work of Vogiannou on spherical
tropicalization and in some ways is complementary.


title: Minimal-assumption inference from population-genomic data

abstract:
  Samples of multiple complete genome sequences contain vast amounts of
information about the evolutionary history of populations, much of it in the
associations among polymorphisms at different loci. Current methods that take
advantage of this linkage information rely on models of recombination and
coalescence, limiting the sample sizes and populations that they can analyze.
We introduce a method, Minimal-Assumption Genomic Inference of Coalescence
(MAGIC), that reconstructs key features of the evolutionary history, including
the distribution of coalescence times, by integrating information across
genomic length scales without using an explicit model of recombination,
demography or selection. Using simulated data, we show that MAGIC's performance
is comparable to PSMC' on single diploid samples generated with standard
coalescent and recombination models. More importantly, MAGIC can also analyze
arbitrarily large samples and is robust to changes in the coalescent and
recombination processes. Using MAGIC, we show that the inferred coalescence
time histories of samples of multiple human genomes exhibit inconsistencies
with a description in terms of an effective population size based on
single-genome data.


title: Learning to Perform Physics Experiments via Deep Reinforcement Learning

abstract:
  When encountering novel objects, humans are able to infer a wide range of
physical properties such as mass, friction and deformability by interacting
with them in a goal driven way. This process of active interaction is in the
same spirit as a scientist performing experiments to discover hidden facts.
Recent advances in artificial intelligence have yielded machines that can
achieve superhuman performance in Go, Atari, natural language processing, and
complex control problems; however, it is not clear that these systems can rival
the scientific intuition of even a young child. In this work we introduce a
basic set of tasks that require agents to estimate properties such as mass and
cohesion of objects in an interactive simulated environment where they can
manipulate the objects and observe the consequences. We found that state of art
deep reinforcement learning methods can learn to perform the experiments
necessary to discover such hidden properties. By systematically manipulating
the problem difficulty and the cost incurred by the agent for performing
experiments, we found that agents learn different strategies that balance the
cost of gathering information against the cost of making mistakes in different
situations.

categories: stat.ML cs.AI cs.CV cs.LG cs.NE physics.soc-ph


title:
The (dark) halo-to-stellar mass ratio in the Spitzer Survey of Stellar
  Structure in Galaxies (S$^4$G)

abstract:
  We use 3.6 $\mu$m photometry for 1154 disk galaxies ($i<65^{\circ}$) in the
Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G, Sheth et al. 2010)
to obtain the stellar component of the circular velocity. By combining the
disk+bulge rotation curves with HI line width measurements from the literature,
we estimate the ratio of the halo-to-stellar mass ($M_{\rm halo}/M_{\ast}$)
within the optical disk, and compare it to the total stellar mass ($M_{\ast}$).
We find the $M_{\rm halo}/M_{\ast}$-$M_{\ast}$ relation in good agreement with
the best-fit model at z$\approx$0 in $\Lambda$CDM cosmological simulations
(e.g. Moster et al. 2010), assuming that the dark matter halo within the
optical radius comprises a constant fraction ($\sim4\%$) of its total mass.


title: Urban MV and LV Distribution Grid Topology Estimation via Group Lasso

abstract:
  The increasing penetration of distributed energy resources poses numerous
reliability issues to the urban distribution grid. The topology estimation is a
critical step to ensure the robustness of distribution grid operation. However,
the bus connectivity and grid topology estimation are usually hard in
distribution grids. For example, it is technically challenging and costly to
monitor the bus connectivity in urban grids, e.g., underground lines. It is
also inappropriate to use the radial topology assumption exclusively because
the grids of metropolitan cities and regions with dense loads could be with
many mesh structures. To resolve these drawbacks, we propose a data-driven
topology estimation method for MV and LV distribution grids by only utilizing
the historical smart meter measurements. Particularly, a probabilistic
graphical model is utilized to capture the statistical dependencies amongst bus
voltages. We prove that the bus connectivity and grid topology estimation
problems, in radial and mesh structures, can be formulated as a linear
regression with a least absolute shrinkage regularization on grouped variables
(\textit{group lasso}). Simulations show highly accurate results in eight MV
and LV distribution networks at different sizes and 22 topology configurations
using PG\&E residential smart meter data.


title: Holographic torus entanglement and its RG flow

abstract:
  We study the universal contributions to the entanglement entropy (EE) of 2+1d
and 3+1d holographic conformal field theories (CFTs) on topologically
non-trivial manifolds, focusing on tori. The holographic bulk corresponds to
AdS-soliton geometries. We characterize the properties of these
regulator-independent EE terms as a function of both the size of the
cylindrical entangling region, and the shape of the torus. In 2+1d, in the
simple limit where the torus becomes a thin 1d ring, the EE reduces to a
shape-independent constant $2\gamma$. This is twice the EE obtained by
bipartitioning an infinite cylinder into equal halves. We study the RG flow of
$\gamma$ by defining a renormalized EE that 1) is applicable to general QFTs,
2) resolves the failure of the area law subtraction, and 3) is inspired by the
F-theorem. We find that the renormalized $\gamma$ decreases monotonically when
the holographic CFT is deformed by a relevant operator for all allowed scaling
dimensions. We also discuss the question of non-uniqueness of such renormalized
EEs both in 2+1d and 3+1d.


title: Two-cylinder entanglement entropy under a twist

abstract:
  We study the von Neumann and R\'enyi entanglement entropy (EE) of
scale-invariant theories defined on tori in 2+1 and 3+1 spacetime dimensions.
We focus on spatial bi-partitions of the torus into two cylinders, and allow
for twisted boundary conditions along the non-contractible cycles. Various
analytical and numerical results are obtained for the universal EE of the
relativistic boson and Dirac fermion conformal field theories (CFTs), and for
the fermionic quadratic band touching and the boson with $z=2$ Lifshitz
scaling. The shape dependence of the EE clearly distinguishes these theories,
although intriguing similarities are found in certain limits. We also study the
evolution of the EE when a mass is introduced to detune the system from its
scale-invariant point, by employing a renormalized EE that goes beyond a naive
subtraction of the area law. In certain cases we find non-monotonic behavior of
the torus EE under RG flow, which distinguishes it from the EE of a disk.


title: Scattering of ultrarelativistic electrons in ultrathin crystals

abstract:
  Quantum theory is proposed of high energy electrons scattering in ultrathin
crystals. This theory is based upon a special representation of the scattering
amplitude in the form of the integral over the surface surrounding the crystal,
and on the spectral method of determination of the wave function. The
comparison is performed of quantum and classical differential scattering
cross-sections in the transitional range of crystal thicknesses, from those at
which the channeling phenomenon is not developed up to those at which it is
realized. It is shown that in this thickness range the quantum scattering
cross-section, unlike the classical one, contains sharp peaks corresponding to
some specific scattering angles, that is connected with the diffraction of the
incident plane wave onto the periodically distributed crystal atomic strings.
It is shown that the value of the scattering cross-section in the peaks varies
periodically with the change of the target thickness. We note that this must
lead to a new interference effect in radiation that is connected with the
rearrangement of incident wave packet in transitional area of crystal
thicknesses.


title:
Universal structural estimator and dynamics approximator for complex
  networks

abstract:
  Revealing the structure and dynamics of complex networked systems from
observed data is of fundamental importance to science, engineering, and
society. Is it possible to develop a universal, completely data driven
framework to decipher the network structure and different types of dynamical
processes on complex networks, regardless of their details? We develop a Markov
network based model, sparse dynamical Boltzmann machine (SDBM), as a universal
network structural estimator and dynamics approximator. The SDBM attains its
topology according to that of the original system and is capable of simulating
the original dynamical process. We develop a fully automated method based on
compressive sensing and machine learning to find the SDBM. We demonstrate, for
a large variety of representative dynamical processes on model and real world
complex networks, that the equivalent SDBM can recover the network structure of
the original system and predicts its dynamical behavior with high precision.


title: On High-Resolution Adaptive Sampling of Deterministic Signals

abstract:
  In this work we study the topic of high-resolution adaptive sampling of a
given deterministic signal and establish a connection with classic approaches
to high-rate quantization. Specifically, we formulate solutions for the task of
optimal high-resolution sampling, counterparts of well-known results for
high-rate quantization. Our results reveal that the optimal high-resolution
sampling structure is determined by the density of the signal-gradient energy,
just as the probability-density-function defines the optimal high-rate
quantization form. This paper has three main contributions: the first is
establishing a fundamental paradigm bridging the topics of sampling and
quantization. The second is a theoretical analysis of nonuniform sampling
relevant to the emerging field of high-resolution signal processing. The third
is a new practical approach to nonuniform sampling of one-dimensional signals
that enables reconstruction based only on the sampling time-points and the
signal extrema locations and values. Experiments for signal sampling and coding
showed that our method outperforms an optimized tree-structured sampling
technique.


title:
Bayesian Optimisation with Prior Reuse for Motion Planning in Robot
  Soccer

abstract:
  We integrate learning and motion planning for soccer playing differential
drive robots using Bayesian optimisation. Trajectories generated using
end-slope cubic Bezier splines are first optimised globally through Bayesian
optimisation for a set of candidate points with obstacles. The optimised
trajectories along with robot and obstacle positions and velocities are stored
in a database. The closest planning situation is identified from the database
using k-Nearest Neighbour approach. It is further optimised online through
reuse of prior information from previously optimised trajectory. Our approach
reduces computation time of trajectory optimisation considerably. Velocity
profiling generates velocities consistent with robot kinodynamoic constraints,
and avoids collision and slipping. Extensive testing is done on developed
simulator, as well as on physical differential drive robots. Our method shows
marked improvements in mitigating tracking error, and reducing traversal and
computational time over competing techniques under the constraints of
performing tasks in real time.


title: MSSM fits to the ATLAS 1 lepton excess

abstract:
  We use the framework of the p19MSSM to perform a fit to the mild excesses
over the Standard Model background recently observed in three bins of the ATLAS
1-lepton + (b-)jets + MET search. We find a few types of spectra that can fit
the emerging signal and at the same time are not excluded by other LHC
searches. They can be grouped roughly in two categories. The first class is
characterized by the presence of one stop or stop and sbottoms with mass in the
ballpark of 700-800 GeV and a neutralino LSP of mass around 400 GeV, with or
without the additional presence of an intermediate chargino. In the second type
of scenarios the stop, lightest chargino, sbottom if present, and the
neutralino are about or heavier than ~650 GeV and the signal originates from
cascade decays of squarks of the 1st and 2nd generation, which should have a
mass of 1.1-1.2 TeV. For the best-fit scenarios, we compare the global
chi-squared with respect to several ATLAS and CMS searches with the
corresponding chi-squared of the Standard Model expectation, showing that the
putative signal is also favored globally with respect to the background only
hypothesis. We point out that if the observed excess persists in the next round
of data, it should be accompanied by associated significant excesses in
all-hadronic final state searches.