title:
An SQP Method Combined with Gradient Sampling for Small-Signal Stability
  Constrained OPF

abstract:
  Small-Signal Stability Constrained Optimal Power Flow (SSSC-OPF) can provide
additional stability measures and control strategies to guarantee the system to
be small-signal stable. However, due to the nonsmooth property of the spectral
abscissa function, existing algorithms solving SSSC-OPF cannot guarantee
convergence. To tackle this computational challenge of SSSC-OPF, we propose a
Sequential Quadratic Programming (SQP) method combined with Gradient Sampling
(GS) for SSSCOPF.At each iteration of the proposed SQP, the gradient of the
spectral abscissa unction is randomly sampled at the current iterate and
additional nearby points to make the search direction computation effective in
nonsmooth regions. The method can guarantee SSSC-OPF is globally and
efficiently convergent to stationary points with probability one. The
effectiveness of the proposed method is tested and validated on WSCC 3-machine
9-bus system, New England 10-machine 39-bus system, and IEEE 54-machine 118-bus
system.


title: Laser-driven recollisions under the Coulomb barrier

abstract:
  Photoelectron spectra obtained from the ab initio solution of the
time-dependent Schr\"odinger equation can be in striking disagreement with
predictions by the strong-field approximation (SFA) not only at low energy but
also around twice the ponderomotive energy where the transition from the direct
to the rescattered electrons is expected. In fact, the relative enhancement of
the ionization probability compared to the SFA in this regime can be several
orders of magnitude. We show for which laser and target parameters such an
enhancement occurs and for which the SFA prediction is qualitatively good. The
enhancement is analyzed in terms of the Coulomb-corrected action along analytic
quantum orbits in the complex-time plane, taking soft recollisions under the
Coulomb barrier into account. These recollisions in complex time and space
prevent a separation into sub-barrier motion up to the "tunnel exit" and
subsequent classical dynamics. Instead, the entire quantum path up to the
detector determines the ionization probability.


title: Traversing Environments Using Possibility Graphs for Humanoid Robots

abstract:
  Locomotion for legged robots poses considerable challenges when confronted by
obstacles and adverse environments. Footstep planners are typically only
designed for one mode of locomotion, but traversing unfavorable environments
may require several forms of locomotion to be sequenced together, such as
walking, crawling, and jumping. Multi-modal motion planners can be used to
address some of these problems, but existing implementations tend to be
time-consuming and are limited to quasi-static actions. This paper presents a
motion planning method to traverse complex environments using multiple
categories of actions. We introduce the concept of the "Possibility Graph",
which uses high-level approximations of constraint manifolds to rapidly explore
the "possibility" of actions, thereby allowing lower-level single-action motion
planners to be utilized more efficiently. We show that the Possibility Graph
can quickly find paths through several different challenging environments which
require various combinations of actions in order to traverse.


title: Automation of 2-loop Amplitude Calculations

abstract:
  Some of the tools and techniques that have recently been used to compute
Higgs boson pair production at NLO in QCD are discussed. The calculation relies
on the use of integral reduction, to reduce the number of integrals which must
be computed, and expressing the amplitude in terms of a quasi-finite basis,
which simplifies their numeric evaluation. Emphasis is placed on sector
decomposition and Quasi-Monte Carlo (QMC) integration which are used to
numerically compute the master integrals.


title: Measuring and correcting wobble in large-scale transmission radiography

abstract:
  Large-scale transmission radiography scanners are used to image vehicles and
cargo containers. Acquired images are inspected for threats by a human operator
or a computer algorithm. To make accurate detections, it is important that
image values are precise. However, due to the scale of such systems, they can
be mechanically unstable, causing the imaging array to wobble during a scan.
This leads to an effective loss of precision in the captured image. We consider
the measurement of wobble and amelioration of the consequent loss of image
precision. Following our previous work, we use Beam Position Detectors (BPDs)
to measure the cross-sectional profile of the X-ray beam, allowing for
estimation, and thus correction of wobble. We propose: (i) a model of image
formation with a wobbling detector array; (ii) a method of wobble correction
derived from this model; (iii) methods for calibrating sensor sensitivities and
relative offsets; (iv) a Random Regression Forest based method for
instantaneous estimation of detector wobble, and (v) using these estimates to
apply corrections to captured images of difficult scenes. We show that these
methods are able to correct for $87\%$ of image error due wobble, and when
applied to difficult images, a significant visible improvement in the
intensity-windowed image quality is observed. The method improves the precision
of wobble affected images, which should help improve detection of threats and
the identification of different materials in the image.


title: Influence of excitonic effects on luminescence quantum yield in silicon

abstract:
  Nonradiative exciton lifetime in silicon is determined by comparison of the
experimental and theoretical curves of bulk minority charge carriers lifetime
on doping and excitation levels. This value is used to analyze the influence of
excitonic effects on internal luminescence quantum yield at room temperature,
taking into account both nonradiative and radiative exciton lifetimes. A range
of Shockley-Hall-Reed lifetimes is found, where excitonic effects lead to an
increase of internal luminescence quantum yield.


title: Proposal of Readout Electronics for CSNS-WNS BaF2 Detector

abstract:
  BaF2 (Barium fluoride) detector is one of the experiment facilities at the
under construction CSNS-WNS (White Neutron Source at China Spallation Neutron
Source). It is designed for precisely measuring (n,gamma) cross section with
total 92 crystal elements and completely 4 pi steradian coverage. In this
proposal for readout electronics, waveform digitizing technique with 1GSps
sampling rate and 12-bit resolution is adopted to precisely capture the
detector signal. To solve the problem of massive data readout and processing,
the readout electronics system is designed into a distributed architecture with
4 PXIe crates. The digitized detector's signal is concentrated to PXIe crate
controller through PCIe bus on backplane and transmitted to data acquisition
system over Gigabit Ethernet in parallel. Besides, clock and trigger can be
fanned out synchronously to each electronic channel over a high-precision
distributing network. Test results showed that the prototype of the readout
electronics system achieved good performance and cooperated well.


title:
On the completeness of orbits of a Pommiez operator in weighted
  (LF)-spaces of entire functions

abstract:
  We describe cyclic vectors for a Pommiez operator on a weighted (LF)-space E
of entire functions. The full description is obtained where $E$ is the Laplace
transform of the strong dual of the space of all germs of holomorphic functions
on a convex locally closed set in the complex plane.


title:
Next-to-Leading Order Corrections to Higgs Boson Pair Production in
  Gluon Fusion

abstract:
  We present a calculation of the next-to-leading order QCD corrections to the
production of Higgs boson pairs in gluon fusion keeping the full dependence on
the mass of the top quark. The virtual corrections, involving two-loop
integrals with up to four mass scales, have been calculated numerically and we
present an efficient algorithm to obtain accurate results of the virtual
amplitude using numerical integrations. Taking the top quark mass into account
we obtain significant differences compared to results obtained in the heavy top
limit.


title:
A LOFAR mini-survey for low-frequency radio emission from the nearest
  brown dwarfs

abstract:
  We have conducted a mini-survey for low-frequency radio emission from some of
the closest brown dwarfs to the Sun with rapid rotation rates: SIMP
J013656.5+093347, WISEPC J150649.97+702736.0, and WISEPA J174124.26+255319.5.
We have placed robust 3-sigma upper limits on the flux density in the 111 - 169
MHz frequency range for these targets: WISE 1506: < 0.72 mJy; WISE 1741: < 0.87
mJy; SIMP 0136: < 0.66 mJy. At 8 hours of integration per target to achieve
these limits, we find that systematic and detailed study of this class of
object at LOFAR frequencies will require a substantial dedication of resources.


title: Analytical formulation of lunar cratering asymmetries

abstract:
  We formulate the lunar cratering distribution and verify the cratering
asymmetries generated by the main-belt asteroids (MBAs) as well as the
near-Earth objects (NEOs).
  Based on a planar model that excludes the terrestrial and lunar gravitations
on the impactors and assuming the impactor encounter speed with Earth
$v_{\rm{enc}}$ is higher than the lunar orbital speed $v_{\rm{M}}$, we
rigorously integrated the lunar cratering distribution, and derived its
approximation to the first order of $v_{\rm{M}}/v_{\rm{enc}}$. Numerical
simulations of lunar bombardment by the MBAs during the late heavy bombardment
were performed with an Earth-Moon distance $a_{\rm{M}}$ = 20--60 Earth radii in
five cases.
  The analytical model directly proves the existence of a leading/trailing
asymmetry and the absence of near/far asymmetry. The approximate form of the
leading/trailing asymmetry is $(1 + A_1 \cos\beta)$, which decreases as the
apex distance $\beta$ increases. The numerical simulations show evidence of a
pole/equator asymmetry as well as the leading/trailing asymmetry, and the
former is empirically described as $(1 + A_2 \cos2\varphi)$, which decreases as
the latitude modulus $|\varphi|$ increases. The amplitudes $A_{1,2}$ are
reliable measurements of asymmetries. Our analysis explicitly indicates the
quantitative relations between cratering distribution and bombardment
conditions (impactor properties and the lunar orbital status) like $A_1 \propto
v_{\rm{M}}/v_{\rm{enc}}$, resulting in a method for reproducing the bombardment
conditions through measuring the asymmetry. Mutual confirmation between
analytical model and numerical simulations is found in terms of the cratering
distribution and its variation with $a_{\rm{M}}$. Estimates of $A_1$ for crater
density distributions generated by the MBAs and the NEOs are 0.101--0.159 and
0.117, respectively.


title: Spin-orbit coupled fermions in an optical lattice clock

abstract:
  Engineered spin-orbit coupling (SOC) in cold atom systems can aid in the
study of novel synthetic materials and complex condensed matter phenomena.
Despite great advances, alkali atom SOC systems are hindered by heating from
spontaneous emission, which limits the observation of many-body effects,
motivating research into potential alternatives. Here we demonstrate that SOC
can be engineered to occur naturally in a one-dimensional fermionic 87Sr
optical lattice clock (OLC). In contrast to previous SOC experiments, in this
work the SOC is both generated and probed using a direct ultra-narrow optical
clock transition between two electronic orbital states. We use clock
spectroscopy to prepare lattice band populations, internal electronic states,
and quasimomenta, as well as to produce SOC dynamics. The exceptionally long
lifetime of the excited clock state (160 s) eliminates decoherence and atom
loss from spontaneous emission at all relevant experimental timescales,
allowing subsequent momentum- and spin-resolved in situ probing of the SOC band
structure and eigenstates. We utilize these capabilities to study Bloch
oscillations, spin-momentum locking, and Van Hove singularities in the
transition density of states. Our results lay the groundwork for the use of
OLCs to probe novel SOC phases of matter.


title:
Bayesian inferences of the thermal properties of a wall using
  temperature and heat flux measurements

abstract:
  The assessment of the thermal properties of walls is essential for accurate
building energy simulations that are needed to make effective energy-saving
policies. These properties are usually investigated through in-situ
measurements of temperature and heat flux over extended time periods. The
one-dimensional heat equation with unknown Dirichlet boundary conditions is
used to model the heat transfer process through the wall. In [F. Ruggeri, Z.
Sawlan, M. Scavino, R. Tempone, A hierarchical Bayesian setting for an inverse
problem in linear parabolic PDEs with noisy boundary conditions, Bayesian
Analysis 12 (2) (2017) 407--433], it was assessed the uncertainty about the
thermal diffusivity parameter using different synthetic data sets. In this
work, we adapt this methodology to an experimental study conducted in an
environmental chamber, with measurements recorded every minute from temperature
probes and heat flux sensors placed on both sides of a solid brick wall over a
five-day period. The observed time series are locally averaged, according to a
smoothing procedure determined by the solution of a criterion function
optimization problem, to fit the required set of noise model assumptions.
Therefore, after preprocessing, we can reasonably assume that the temperature
and the heat flux measurements have stationary Gaussian noise and we can avoid
working with full covariance matrices. The results show that our technique
reduces the bias error of the estimated parameters when compared to other
approaches. Finally, we compute the information gain under two experimental
setups to recommend how the user can efficiently determine the duration of the
measurement campaign and the range of the external temperature oscillation.


title: First Order Feynman-Kac Formula

abstract:
  We study the parabolic integral kernel associated with the weighted Laplacian
and the Feynman-Kac kernels. For manifold with a pole we deduce formulas and
estimates for them and for their derivatives, given in terms of a Gaussian term
and the semi-classical bridge. Assumptions are on the Riemannian data.


title: The sharp threshold for making squares

abstract:
  Consider a random sequence of $N$ integers, each chosen uniformly and
independently from the set $\{1,\dots,x\}$. Motivated by applications to
factorisation algorithms such as Dixon's algorithm, the quadratic sieve, and
the number field sieve, Pomerance in 1994 posed the following problem: how
large should $N$ be so that, with high probability, this sequence contains a
subsequence, the product of whose elements is a perfect square? Pomerance
determined asymptotically the logarithm of the threshold for this event, and
conjectured that it in fact exhibits a sharp threshold in $N$. More recently,
Croot, Granville, Pemantle and Tetali determined the threshold up to a factor
of $4/\pi + o(1)$ as $x \to \infty$, and made a conjecture regarding the
location of the sharp threshold.
  In this paper we prove both of these conjectures, by determining the sharp
threshold for making squares. Our proof combines techniques from combinatorics,
probability and analytic number theory; in particular, we use the so-called
method of self-correcting martingales in order to control the size of the
2-core of the random hypergraph that encodes the prime factors of our random
numbers. Our method also gives a new (and completely different) proof of the
upper bound in the main theorem of Croot, Granville, Pemantle and Tetali.


title: In-Medium Pion Valence Distributions in a Light-Front Model

abstract:
  Pion valence distributions in nuclear medium and vacuum are studied in a
light-front constituent quark model. The in-medium input for studying the pion
properties is calculated by the quark-meson coupling model. We find that the
in-medium pion valence distribution, as well as the in-medium pion valence wave
function, are substantially modified at normal nuclear matter density, due to
the reduction in the pion decay constant.


title:
A Simulated Annealing based Inexact Oracle for Wasserstein Loss
  Minimization

abstract:
  Learning under a Wasserstein loss, a.k.a. Wasserstein loss minimization
(WLM), is an emerging research topic for gaining insights from a large set of
structured objects. Despite being conceptually simple, WLM problems are
computationally challenging because they involve minimizing over functions of
quantities (i.e. Wasserstein distances) that themselves require numerical
algorithms to compute. In this paper, we introduce a stochastic approach based
on simulated annealing for solving WLMs. Particularly, we have developed a
Gibbs sampler to approximate effectively and efficiently the partial gradients
of a sequence of Wasserstein losses. Our new approach has the advantages of
numerical stability and readiness for warm starts. These characteristics are
valuable for WLM problems that often require multiple levels of iterations in
which the oracle for computing the value and gradient of a loss function is
embedded. We applied the method to optimal transport with Coulomb cost and the
Wasserstein non-negative matrix factorization problem, and made comparisons
with the existing method of entropy regularization.


title: Model-free consistency of graph partitioning

abstract:
  In this paper, we exploit the theory of dense graph limits to provide a new
framework to study the stability of graph partitioning methods, which we call
structural consistency. Both stability under perturbation as well as asymptotic
consistency (i.e., convergence with probability $1$ as the sample size goes to
infinity under a fixed probability model) follow from our notion of structural
consistency. By formulating structural consistency as a continuity result on
the graphon space, we obtain robust results that are completely independent of
the data generating mechanism. In particular, our results apply in settings
where observations are not independent, thereby significantly generalizing the
common probabilistic approach where data are assumed to be i.i.d.
  In order to make precise the notion of structural consistency of graph
partitioning, we begin by extending the theory of graph limits to include
vertex colored graphons. We then define continuous node-level statistics and
prove that graph partitioning based on such statistics is consistent. Finally,
we derive the structural consistency of commonly used clustering algorithms in
a general model-free setting. These include clustering based on local graph
statistics such as homomorphism densities, as well as the popular spectral
clustering using the normalized Laplacian.
  We posit that proving the continuity of clustering algorithms in the graph
limit topology can stand on its own as a more robust form of model-free
consistency. We also believe that the mathematical framework developed in this
paper goes beyond the study of clustering algorithms, and will guide the
development of similar model-free frameworks to analyze other procedures in the
broader mathematical sciences.


title:
Another look at the fast iterative shrinkage/thresholding algorithm
  (FISTA)

abstract:
  This paper provides a new way of developing the fast iterative
shrinkage/thresholding algorithm (FISTA) that is widely used for minimizing
composite convex functions with a nonsmooth term such as the $\ell_1$
regularizer. In particular, this paper shows that FISTA corresponds to an
optimized approach to accelerating the proximal gradient method with respect to
a worst-case bound of the cost function. This paper then proposes a new
algorithm that is derived by instead optimizing the step coefficients of the
proximal gradient method with respect to a worst-case bound of the composite
gradient mapping. The proof is based on the worst-case analysis called
Performance Estimation Problem.


title:
A Bayesian Perspective on Residential Demand Response Using Smart Meter
  Data

abstract:
  The widespread deployment of Advanced Metering Infrastructure has made
granular data of residential electricity consumption available on a large
scale. Smart meters enable a two way communication between residential
customers and utilities. One field of research that relies on such granular
consumption data is Residential Demand Response, where individual users are
incentivized to temporarily reduce their consumption during periods of high
marginal cost of electricity. To quantify the economic potential of Residential
Demand Response, it is important to estimate the reductions during Demand
Response hours, taking into account the heterogeneity of electricity users. In
this paper, we incorporate latent variables representing behavioral archetypes
of electricity users into the process of short term load forecasting with
Machine Learning methods, thereby differentiating between varying levels of
energy consumption. The latent variables are constructed by fitting Conditional
Mixture Models of Linear Regressions and Hidden Markov Models on smart meter
readings of a Residential Demand Response program in the western United States.
We observe a notable increase in the accuracy of short term load forecasts
compared to the case without latent variables. We then estimate the reductions
during Demand Response events conditional on the latent variables, and discover
a higher DR reduction among users with automated smart home devices compared to
those without.


title:
Large deviations for high-dimensional random projections of
  $\ell_p^n$-balls

abstract:
  The paper provides a description of the large deviation behavior for the
Euclidean norm of projections of $\ell_p^n$-balls to high-dimensional random
subspaces. More precisely, for each integer $n\geq 1$, let
$k_n\in\{1,\ldots,n-1\}$, $E^{(n)}$ be a uniform random $k_n$-dimensional
subspace of $\mathbb R^n$ and $X^{(n)}$ be a random point that is uniformly
distributed in the $\ell_p^n$-ball of $\mathbb R^n$ for some $p\in[1,\infty]$.
Then the Euclidean norms $\|P_{E^{(n)}}X^{(n)}\|_2$ of the orthogonal
projections are shown to satisfy a large deviation principle as the space
dimension $n$ tends to infinity. Its speed and rate function are identified,
making thereby visible how they depend on $p$ and the growth of the sequence of
subspace dimensions $k_n$. As a key tool we prove a probabilistic
representation of $\|P_{E^{(n)}}X^{(n)}\|_2$ which allows us to separate the
influence of the parameter $p$ and the subspace dimension $k_n$.


title: A geometrical look at MOSPA Estimation using Transportation Theory

abstract:
  It was shown in [6] that the Wasserstein distance is equivalent to the Mean
Optimal Sub-Pattern Assignment (MOSPA) measure for empirical probability
density functions. A more recent paper [7], extends on it by drawing new
connections between the MOSPA concept, which is getting a foothold in the
multi-target tracking community, and the Wasserstein distance, a metric widely
used in theoretical statistics. However, the comparison between the two
concepts has been overlooked. In this letter we prove that the equivalence of
Wasserstein distance with the MOSPA measure holds for general types of
probability density function. This non trivial result allows us to leverage one
recent finding in the computational geometry literature to show that the
Minimum MOPSA (MMOSPA) estimates are the centroids of additive weighted Voronoi
regions with a specific choice of the weights.


title:
Determining proportions of lunar crater populations by fitting crater
  size distribution

abstract:
  We determine the proportions of two mixed crater populations distinguishable
by size distributions on the Moon. A "multiple power-law" model is built to
formulate crater size distribution $N(D) \propto D^{-\alpha}$ whose slope
$\alpha$ varies with crater diameter $D$. Fitted size distribution of lunar
highland craters characterized by $\alpha = 1.17 \pm 0.04$, $1.88 \pm 0.07$,
$3.17 \pm 0.10$ and $1.40 \pm 0.15$ for consecutive $D$ intervals divided by
49, 120 and 251 km and that of lunar Class 1 craters with a single slope
$\alpha = 1.96 \pm 0.14$, are taken as Population 1 and 2 crater size
distribution respectively, whose sum is then fitted to the size distribution of
global lunar craters with $D$ between 10 and 100 km. Estimated crater densities
of Population 1 and 2 are $44 \times 10^{-5}$ and $5 \times 10^{-5}$ km$^{-2}$
respectively, leading to the proportion of the latter $10 \%$. The results
underlines the need for considering the Population 1 craters and the relevant
impactors, the primordial main-belt asteroids which dominated the late heavy
bombardment.


title:
Distributed Optimization for Client-Server Architecture with Negative
  Gradient Weights

abstract:
  Availability of both massive datasets and computing resources have made
machine learning and predictive analytics extremely pervasive. In this work we
present a synchronous algorithm and architecture for distributed optimization
motivated by privacy requirements posed by applications in machine learning. We
present an algorithm for the recently proposed multi-parameter-server
architecture. We consider a group of parameter servers that learn a model based
on randomized gradients received from clients. Clients are computational
entities with private datasets (inducing a private objective function), that
evaluate and upload randomized gradients to the parameter servers. The
parameter servers perform model updates based on received gradients and share
the model parameters with other servers. We prove that the proposed algorithm
can optimize the overall objective function for a very general architecture
involving $C$ clients connected to $S$ parameter servers in an arbitrary time
varying topology and the parameter servers forming a connected network.


title:
Correlations of the density and of the current in non-equilibrium
  diffusive systems

abstract:
  We use fluctuating hydrodynamics to analyze the dynamical properties in the
non-equilibrium steady state of a diffusive system coupled with reservoirs. We
derive the two-time correlations of the density and of the current in the
hydrodynamic limit in terms of the diffusivity and the mobility. Within this
hydrodynamic framework we discuss a generalization of the fluctuation
dissipation relation in a non-equilibrium steady state where the response
function is expressed in terms of the two-time correlations. We compare our
results to an exact solution of the symmetric exclusion process. This exact
solution also allows one to directly verify the fluctuating hydrodynamics
equation.


title: Quotients of mapping class groups from $\text{Out}(F_n)$

abstract:
  We give a short proof of Masbaum and Reid's result that mapping class groups
involve any finite group, appealing to free quotients of surface groups and a
result of Gilman, following Dunfield-Thurston.


title: Record Dynamics: Direct Experimental Evidence from Jammed Colloids

abstract:
  In a broad class of complex materials a quench leads to a multi-scaled
relaxation process known as aging. To explain its commonality and the
astounding insensitivity to most microscopic details, record dynamics (RD)
posits that a small set of increasingly rare and irreversible events, so called
quakes, controls the dynamics. While key predictions of RD are known to concur
with a number of experimental and simulational results, its basic assumption on
the nature of quake statistics has proven extremely difficult to verify
experimentally. The careful distinction of rare ("record") cage-breaking events
from in-cage rattle accomplished in previous experiments on jammed colloids,
enables us to extract the first direct experimental evidence for the
fundamental hypothesis of RD that the rate of quakes decelerates with the
inverse of the system age. The resulting description shows the predicted growth
of the particle mean square displacement and of a mesoscopic lengthscale with
the logarithm of time.


title:
Test of Lorentz invariance in $\beta$ decay of polarized
  $^{20}\text{Na}$

abstract:
  We search for a dependence of the lifetime of $^{20}\text{Na}$ nuclei on the
nuclear spin direction. Such a directional dependence would be evidence for
Lorentz-invariance violation in weak interactions. A difference in lifetime
between nuclei that are polarized in the east and west direction is searched
for. This difference is maximally sensitive to the rotation of the Earth, while
the sidereal dependence is free from most systematic errors. The experiment
sets a limit of $2\times 10^{-4}$ at 90 % C.L. on the amplitude of the sidereal
variation of the relative lifetime differences, an improvement by a factor 15
compared to an earlier result.


title:
Application of Polynomial Optimization to Electricity Transmission
  Networks

abstract:
  Transmission system operators need to adapt their decision-making tools to
the technological evolutions of the twenty first century. A computation
inherent to most tools seeks to find alternating-current power flows that
minimize power loss or generation cost. Mathematically, it consists in an
optimization problem that can be described using only addition and
multiplication of complex numbers (i.e. complex polynomial optimization). The
objective of this thesis is to find feasible points that are globally optimal.
One of the outcomes of this collaborative doctoral project is to transpose the
Lasserre hierarchy to complex numbers. We use it to compute globally optimal
power flows in the European high-voltage transmission network. It consist in a
sparse non-convex quadratically-constrained quadratic program with several
thousand variables and constraints. The complex hierarchy is generally more
tractable than the Lasserre hierarchy when applied to the optimal power flow
problem.


title: Common Origin of Neutrino Mass, Dark Matter and Dirac Leptogenesis

abstract:
  We study the possibility of generating tiny Dirac neutrino masses at one loop
level through the \textit{scotogenic} mechanism such that one of the particles
going inside the loop can be a stable cold dark matter (DM) candidate. Majorana
mass terms of singlet fermions as well as tree level Dirac neutrino masses are
prevented by incorporating the presence of additional discrete symmetries in a
minimal fashion, which also guarantee the stability of the dark matter
candidate. Due to the absence of total lepton number violation, the observed
baryon asymmetry of the Universe is generated through the mechanism of Dirac
leptogenesis where an equal and opposite amount of leptonic asymmetry is
generated in the left and right handed sectors which are prevented from
equilibration due to tiny Dirac Yukawa couplings. Dark matter relic abundance
is generated through its usual freeze-out at a temperature much below the scale
of leptogenesis. We constrain the relevant parameter space from neutrino mass,
baryon asymmetry, Planck bound on dark matter relic abundance, and latest LUX
bound on spin independent DM-nucleon scattering cross section. We also discuss
the charged lepton flavour violation $(\mu \rightarrow e \gamma)$ and electric
dipole moment of electron in this model in the light of the latest experimental
data and constrain the parameter space of the model.


title: New Properties of the Zeros of Krall Polynomials

abstract:
  We identify a class of remarkable algebraic relations satisfied by the zeros
of the Krall orthogonal polynomials that are eigenfunctions of linear
differential operators of order higher than two. Given an orthogonal polynomial
family {p_n(x)}, we relate the zeros of the polynomial p_N with the zeros of
p_m for each m <= N (the case m=N corresponding to the relations that involve
the zeros of p_N only). These identities are obtained by exacting the
similarity transformation that relates the spectral and the (interpolatory)
pseudospectral matrix representations of linear differential operators, while
using the zeros of the polynomial p_N as the interpolation nodes. The proposed
framework generalizes known properties of classical orthogonal polynomials to
the case of nonclassical polynomial families of Krall type. We illustrate the
general result by proving new remarkable identities satisfied by the
Krall-Legendre, the Krall-Laguerre and the Krall-Jacobi orthogonal polynomials.


title: LDPC Lattice Codes for Full-Duplex Relay Channels

abstract:
  Low density parity check (LDPC) lattices are obtained from Construction D'
and a family of nested binary LDPC codes. We consider an special case of these
lattices with one binary LDPC code as underlying code. This special case of
LDPC lattices can be obtained by lifting binary LDPC codes using Construction A
lattices. The LDPC lattices were the first family of lattices which have
efficient decoding in high dimensions. We employ the encoding and decoding of
the LDPC lattices in a cooperative transmission framework. We establish two
efficient shaping methods based on hypercube shaping and Voronoi shaping, to
obtain LDPC lattice codes. Then, we propose the implementation of block Markov
encoding for one-way and two-way relay networks using LDPC lattice codes. This
entails owning an efficient method for decomposing full-rate codebook into
lower rate codebooks. We apply different decomposition schemes for one-way and
two-way relay channels which are the altered versions of the decomposition
methods of low density lattice codes (LDLCs). Due to the lower complexity of
the decoding for LDPC lattices comparing to LDLCs, the complexity of our
schemes are significantly lower than the ones proposed for LDLCs. The
efficiency of the proposed schemes are presented using simulation results.


title:
Sensor Selection and Power Allocation Strategies for Energy Harvesting
  Wireless Sensor Networks

abstract:
  In this paper, we investigate the problem of jointly selecting a predefined
number of energy-harvesting (EH) sensors and computing the optimal power
allocation. The ultimate goal is to minimize the reconstruction distortion at
the fusion center. This optimization problem is, unfortunately, non-convex. To
circumvent that, we propose two suboptimal strategies: (i) a joint sensor
selection and power allocation (JSS-EH) scheme that, we prove, is capable of
iteratively finding a stationary solution of the original problem from a
sequence of surrogate convex problems; and (ii) a separate sensor selection and
power allocation (SS-EH) scheme, on which basis we can identify a sensible
sensor selection and analytically find a power allocation policy by solving a
convex problem. We also discuss the interplay between the two strategies.
Performance in terms of reconstruction distortion, impact of initialization,
actual subsets of selected sensors and computed power allocation policies,
etc., is assessed by means of computer simulations. To that aim, an EH-agnostic
sensor selection strategy, a lower bound on distortion, and an online version
of the SS-EH and JSS-EH schemes are derived and used for benchmarking.


title:
New Fourier Transform Containing a Pair of Complex Euler Gamma Functions
  With a Monomial: Mathematical and Physical Applications

abstract:
  One of the goals of the present paper is to propose an elementary method to
find a general formula for the Fourier transform containing a pair of complex
gamma functions with a monomial sm in terms of Gauss's hypergeometric functions
2F1. We further collect some mathematical results that follow by means of this
transform. Physical applications requiring the expectation values of position
and momentum operators for a quantum system endowed with position-dependent
effective mass are presented.


title:
Product lambda-doublet ratios for the O(3P) + D2 reaction: A mechanistic
  imprint

abstract:
  In the last decade, the development of theoretical methods have allowed
chemists to reproduce and explain almost all of the experimental data
associated with elementary atom plus diatom collisions. However, there are
still a few examples where theory cannot account yet for experimental results.
This is the case for the preferential population of one of the
$\Lambda$-doublet states produced by chemical reactions. In particular, recent
measurements of the OD($^2\Pi$) product of the O($^3$P) + D$_2$ reaction have
shown a clear preference for the $\Pi(A')$ $\Lambda$-doublet states, in
apparent contradiction with {\em ab initio} calculations, which predict a
larger reactivity on the $A"$ potential energy surface. Here we present a
method to calculate the $\Lambda$-doublet ratio when concurrent potential
energy surfaces participate in the reaction. It accounts for the experimental
$\Lambda$-doublet populations via explicit consideration of the stereodynamics
of the process. Furthermore, our results demonstrate that the propensity of the
$\Pi(A')$ state is a consequence of the different mechanisms of the reaction on
the two concurrent potential energy surfaces.


title: The Weighted Ambrosio - Tortorelli Approximation Scheme

abstract:
  The Ambrosio-Tortorelli approximation scheme with weighted underlying metric
is investigated. It is shown that it {\Gamma}-converges to a Mumford-Shah image
segmentation functional depending on the weight $\omega dx$, where $\omega\in
SBV(\Omega)$, and on its value $\omega^-$.


title:
Magnetotransport signatures of the proximity exchange and spin-orbit
  couplings in graphene

abstract:
  Graphene on an insulating ferromagnetic substrate---ferromagnetic insulator
or ferromagnetic metal with a tunnel barrier---is expected to exhibit giant
proximity exchange and spin-orbit couplings. We use a realistic transport model
of charge-disorder scattering and solve the linearized Boltzmann equation
numerically exactly for the anisotropic Fermi contours of modified Dirac
electrons to find magnetotransport signatures of these proximity effects:
proximity anisotropic magnetoresistance, inverse spin-galvanic effect, and the
planar Hall resistivity. We establish the corresponding anisotropies due to the
exchange and spin-orbit couplings, with respect to the magnetization
orientation. We also present parameter maps guiding towards optimal regimes for
observing transport magnetoanisotropies in proximity graphene.


title: The thermal state of KS 1731-260 after 14.5 years in quiescence

abstract:
  Crustal cooling of accretion-heated neutron stars provides insight into the
stellar interior of neutron stars. The neutron star X-ray transient,
KS~1731$-$260, was in outburst for 12.5 years before returning to quiescence in
2001. We have monitored the cooling of this source since then through {\it
Chandra} and {\it XMM-Newton} observations. Here, we present a 150 ks {\it
Chandra} observation of KS~1731$-$260 taken in August 2015, about 14.5 years
into quiescence, and 6 years after the previous observation. We find that the
neutron star surface temperature is consistent with the previous observation,
suggesting that crustal cooling has likely stopped and the crust has reached
thermal equilibrium with the core. Using a theoretical crust thermal evolution
code, we fit the observed cooling curves and constrain the core temperature
(T$_c = 9.35\pm0.25\times10^7$ K), composition (Q$_{imp} = 4.4^{+2.2}_{-0.5}$)
and level of extra shallow heating required (Q$_{sh} = 1.36\pm0.18$
MeV/nucleon). We find that the presence of a low thermal conductivity layer, as
expected from nuclear pasta, is not required to fit the cooling curve well, but
cannot be excluded either.


title: Ruelle Operator for Continuous Potentials and DLR-Gibbs Measures

abstract:
  In this work we study the Ruelle Operator associated to a continuous
potential defined on a countable product of a compact metric space. We prove a
generalization of Bowen's criterion for the uniqueness of the eigenmeasures.
One of the main results of the article is to show that a probability is
DLR-Gibbs (associated to a continuous translation invariant specification), if
and only if, is an eigenprobability for the transpose of the Ruelle operator.
Bounded extensions of the Ruelle operator to the Lebesgue space of integrable
functions, with respect to the eigenmeasures, are studied and the problem of
existence of maximal positive eigenfunctions for them is considered. One of our
main results in this direction is the existence of such positive eigenfunctions
for Bowen's potential in the setting of a compact and metric alphabet. We also
present

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


title:
Milnor numbers of deformations of semi-quasi-homogeneous plane curve
  singularities II

abstract:
  We show the possible Milnor numbers of deformations of semi-quasi-homogeneous
isolated plane curve singularities. In Theorem 1.1 we list integers can be
attained as Milnor numbers of a given semi-quasi-homogeneous singularity.


title: On the weak and pointwise topologies in function spaces II

abstract:
  For a compact space $K$ we denote by $C_w(K)$ ($C_p(K)$) the space of
continuous real-valued functions on $K$ endowed with the weak (pointwise)
topology. In this paper we discuss the following basic question which seems to
be open: Let $K$ and $L$ be infinite compact spaces. Can it happen that
$C_w(K)$ and $C_p(L)$ are homeomorphic?
  M. Krupski proved that the above problem has a negative answer when $K=L$ and
$K$ is finite-dimensional and metrizable. We extend this result to the class of
finite-dimensional Valdivia compact spaces $K$.


title:
Off-axis QEPAS using a pulsed nanosecond Mid-Infrared Optical Parametric
  Oscillator

abstract:
  A trace gas sensor, based on quartz-enhanced photoacoustic spectroscopy
(QEPAS), consisting of two acoustically coupled micro-resonators (mR) with an
off-axis 20 kHz quartz tuning fork (QTF) is demonstrated. The complete
acoustically coupled mR system is optimized based on finite element simulations
and experimentally verified. The QEPAS sensor is pumped resonantly by a
nanosecond pulsed single-mode mid-infrared optical parametric oscillator (MIR
OPO). The sensor is used for spectroscopic measurements on methane in the 3.1
um to 3.5 um wavelength region with a resolution bandwidth of 1 cm^-1 and a
detection limit of 0.8 ppm. An Allan deviation analysis shows that the
detection limit at optimum integration time for the QEPAS sensor is 32
ppbv@190s and that the background noise is solely due to the thermal noise of
the QTF.


title:
Dual bases in Temperley-Lieb algebras, quantum groups, and a question of
  Jones

abstract:
  We derive a Laurent series expansion for the structure coefficients appearing
in the dual basis corresponding to the Kauffman diagram basis of the
Temperley-Lieb algebra $\text{TL}_k(d)$, converging for all complex loop
parameters $d$ with $|d| > 2\cos\big(\frac{\pi}{k+1}\big)$. In particular, this
yields a new formula for the structure coefficients of the Jones-Wenzl
projection in $\text{TL}_k(d)$. The coefficients appearing in each Laurent
expansion are shown to have a natural combinatorial interpretation in terms of
a certain graph structure we place on non-crossing pairings, and these
coefficients turn out to have the remarkable property that they either always
positive integers or always negative integers. As an application, we answer
affirmatively a question of Vaughan Jones, asking whether every Temperley-Lieb
diagram appears with non-zero coefficient in the expansion of each dual basis
element in $\text{TL}_k(d)$ (when $d \in \mathbb R \backslash
[-2\cos\big(\frac{\pi}{k+1}\big),2\cos\big(\frac{\pi}{k+1}\big)]$).
Specializing to Jones-Wenzl projections, this result gives a new proof of a
result of Ocneanu, stating that every Temperley-Lieb diagram appears with
non-zero coefficient in a Jones-Wenzl projection. Our methods establish a
connection with the Weingarten calculus on free quantum groups, and yield as a
byproduct improved asymptotics for the free orthogonal Weingarten function.


title: On the Rotation Speed of the Milky Way Determined from HI Emission

abstract:
  The circular rotation speed of the Milky Way at the solar radius, Theta_o,
has been estimated to be 220 km/s by fitting the maximum velocity of HI
emission as a function of Galactic longitude. This result is in tension with a
recent estimate of Theta_o=240 km/s, based on VLBI parallaxes and proper
motions from the BeSSeL and VERA surveys for large numbers of high-mass star
forming regions across the Milky Way. We find that the rotation curve best
fitted to the VLBI data is slightly curved, and that this curvature results in
a biased estimate of Theta_o from the HI data when a flat rotation curve is
assumed. This relieves the tension between the methods and favors Theta_o=240
km/s.


title: Stable random fields indexed by finitely generated free groups

abstract:
  In this work, we investigate the extremal behaviour of left-stationary
symmetric $\alpha$-stable (S$\alpha$S) random fields indexed by finitely
generated free groups. We begin by studying the rate of growth of a sequence of
partial maxima obtained by varying the indexing parameter of the field over
balls of increasing size. This leads to a phase-transition that depends on the
ergodic properties of the underlying nonsingular action of the free group but
is different from what happens in the case of S$\alpha$S random fields indexed
by $\mathbb{Z}^d$. The presence of this new dichotomy is confirmed by the study
of a stable random field induced by the canonical action of the free group on
its Furstenberg-Poisson boundary with the measure being Patterson-Sullivan.
This field is generated by a conservative action but its maxima sequence grows
as fast as the i.i.d. case contrary to what happens in the case of
$\mathbb{Z}^d$. When the action of the free group is dissipative, we also
establish that the scaled extremal point process sequence converges weakly to a
novel class of point processes that we have termed as randomly thinned cluster
Poisson processes. This limit too is very different from that in the case of a
lattice.


title:
Origin of central abundances in the hot intra-cluster medium - II.
  Chemical enrichment and supernova yield models

abstract:
  The hot intra-cluster medium (ICM) is rich in metals, which are synthesised
by supernovae (SNe) and accumulate over time into the deep gravitational
potential well of clusters of galaxies. Since most of the elements visible in
X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae,
measuring their abundances gives us direct information on the nucleosynthesis
products of billions of SNe since the epoch of the star formation peak (z~2-3).
In this study, we compare the most accurate average X/Fe abundance ratios
(compiled in a previous work from XMM-Newton EPIC and RGS observations of 44
galaxy clusters, groups, and ellipticals), representative of the chemical
enrichment in the nearby ICM, to various SNIa and SNcc nucleosynthesis models
found in the literature. The use of a SNcc model combined to any favoured
standard SNIa model (deflagration or delayed-detonation) fails to reproduce our
abundance pattern. In particular, the Ca/Fe and Ni/Fe ratios are significantly
underestimated by the models. We show that the Ca/Fe ratio can be reproduced
better, either by taking a SNIa delayed-detonation model that matches the
observations of the Tycho supernova remnant, or by adding a contribution from
the Ca-rich gap transient SNe, whose material should easily mix into the hot
ICM. On the other hand, the Ni/Fe ratio can be reproduced better by assuming
that both deflagration and delayed-detonation SNIa contribute in similar
proportions to the ICM enrichment. In either case, the fraction of SNIa over
the total number of SNe (SNIa+SNcc) contributing to the ICM enrichment ranges
within 29-45%. This fraction is found to be systematically higher than the
corresponding SNIa/SNe fraction contributing to the enrichment of the
proto-solar environnement (15-25%). We also discuss and quantify two useful
constraints on both SNIa and SNcc that can be inferred from the ICM abundance
ratios.

categories: astro-ph.GA astro-ph.CO astro-ph.HE astro-ph.SR


title: Interactive and Iterative Discovery of Entity Network Subgraphs

abstract:
  Graph mining to extract interesting components has been studied in various
guises, e.g., communities, dense subgraphs, cliques. However, most existing
works are based on notions of frequency and connectivity and do not capture
subjective interestingness from a user's viewpoint. Furthermore, existing
approaches to mine graphs are not interactive and cannot incorporate user
feedbacks in any natural manner. In this paper, we address these gaps by
proposing a graph maximum entropy model to discover surprising connected
subgraph patterns from entity graphs. This model is embedded in an interactive
visualization framework to enable human-in-the-loop, model-guided data
exploration. Using case studies on real datasets, we demonstrate how
interactions between users and the maximum entropy model lead to faster and
explainable conclusions.


title:
Towards Resolving Landauer's Paradox Through Direct Observation of
  Multiscale Ferroelastic-Ferroelectric Interplay

abstract:
  Electric-polarization reversibility in nano-ferroelectric structures renders
them as a convenient platform for exploring phase transitions and developing
energy-efficient switching devices. However, the fundamental question of how
ferroic domains switch, i.e. how the polarization changes from one state to
another, is yet to be answered fully. There are contradicting models and a wide
body of accumulated data which disagree as to whether the switching requires
domain nucleation. Moreover, ferroelectric domains switch under electric fields
that are supposedly too weak to form nucleation sites, indicating that the
level of disorder seen in real systems plays an important role. This
longstanding so-called Landauer's paradox is the ferroelectric equivalent to
the absence of raindrop formation in a dust-free vacuum, leading to
supersaturated vapors that cannot exist otherwise, e.g. in spinodal
decompositions or inhomogeneous nucleation environments. Here we show that
polarization switching in ferroelectric-ferroelastic systems comprises domain
types that differ by symmetry, lengthscale and switching energy. These domains
switch simultaneously thanks to intermediate-range order of organized pinning
sites, supporting the previously-unexplained coexistence of
nucleation-and-growth and nucleation-frustrated mechanisms. Our treatment is
applicable to other Kolmogorov-Avrami systems with multi-scale phase
transitions. Finally, we demonstrate augmented electromechanical coupling based
on the collective motion of pinning sites, which is promising for nano
electro-mechanical and low-power switching devices.


title: Could Cirrus Clouds Have Warmed Early Mars?

abstract:
  The presence of the ancient valley networks on Mars indicates that the
climate at 3.8 Ga was warm enough to allow substantial liquid water to flow on
the martian surface for extended periods of time. However, the mechanism for
producing this warming continues to be debated. One hypothesis is that Mars
could have been kept warm by global cirrus cloud decks in a CO2-H2O atmosphere
containing at least 0.25 bar of CO2 (Urata and Toon, 2013). Initial warming
from some other process, e.g., impacts, would be required to make this model
work. Those results were generated using the CAM 3-D global climate model.
Here, we use a single-column radiative-convective climate model to further
investigate the cirrus cloud warming hypothesis. Our calculations indicate that
cirrus cloud decks could have produced global mean surface temperatures above
freezing, but only if cirrus cloud cover approaches ~75 - 100% and if other
cloud properties (e.g., height, optical depth, particle size) are chosen
favorably. However, at more realistic cirrus cloud fractions, or if cloud
parameters are not optimal, cirrus clouds do not provide the necessary warming,
suggesting that other greenhouse mechanisms are needed.


title:
Major mergers are not significant drivers of star formation or
  morphological transformation around the epoch of peak cosmic star formation

abstract:
  We investigate the contribution of major mergers (mass ratios $>1:5$) to
stellar mass growth and morphological transformations around the epoch of peak
cosmic star formation ($z\sim2$). We visually classify a complete sample of
massive (M $>$ 10$^{10}$M$_{\odot}$) galaxies at this epoch, drawn from the
CANDELS survey, into late-type galaxies, major mergers, spheroids and disturbed
spheroids which show morphological disturbances. Given recent simulation work,
which indicates that recent ($<$0.3-0.4 Gyr) major-merger remnants exhibit
clear tidal features in such images, we use the fraction of disturbed spheroids
to probe the role of major mergers in driving morphological transformations.
The percentage of blue spheroids (i.e. with ongoing star formation) that show
morphological disturbances is only 21 $\pm$ 4%, indicating that major mergers
are not the dominant mechanism for spheroid creation at $z\sim2$ - other
processes, such as minor mergers or cold accretion are likely to be the main
drivers of this process. We also use the rest-frame U-band luminosity as a
proxy for star formation to show that only a small fraction of the star
formation budget ($\sim$3%) is triggered by major mergers. Taken together, our
results show that major mergers are not significant drivers of galaxy evolution
at $z\sim2$.


title: A Low-Mass Black Hole in the Nearby Seyfert Galaxy UGC 06728

abstract:
  We present the results of a recent reverberation mapping campaign for UGC
06728, a nearby low-luminosity Seyfert 1 in a late-type galaxy. Nightly
monitoring in the spring of 2015 allowed us to determine an H$\beta$ time delay
of $\tau = 1.4 \pm 0.8$ days. Combined with the width of the variable H$\beta$
line profile, we determine a black hole mass of $M_{\rm BH} = (7.1 \pm 4.0)
\times 10^5$ M$_{\odot}$. We also constrain the bulge stellar velocity
dispersion from higher-resolution long slit spectroscopy along the galaxy minor
axis and find $\sigma_{\star} = 51.6 \pm 4.9$ km s$^{-1}$. The measurements
presented here are in good agreement with both the $R_{\rm BLR} - L$
relationship and the $M_{\rm BH}-\sigma_{\star}$ relationship for AGNs.
Combined with a previously published spin measurement, our mass determination
for UGC 06728 makes it the lowest-mass black hole that has been fully
characterized, and thus an important object to help anchor the low-mass end of
black hole evolutionary models.


title:
Dirac dark matter and $b \to s \ell^+ \ell^-$ with $\mathrm{U(1)}$ gauge
  symmetry

abstract:
  We revisit the possibility of a Dirac fermion dark matter candidate in the
light of current $b \to s \ell^+ \ell^-$ anomalies by investigating a minimal
extension of the Standard Model with a horizontal $\mathrm{U(1)}^{\prime}$
local symmetry. Dark matter stability is protected by a remnant $\mathcal{Z}_2$
symmetry arising after spontaneous symmetry breaking of
$\mathrm{U(1)}^{\prime}$. The associated $Z^{\prime}$ gauge boson can
accommodate current hints of new physics in $b \to s \ell^+ \ell^-$ decays, and
acts as a vector portal between dark matter and the visible sector. We find
that the model is severely constrained by a combination of precision
measurements at flavour factories, LHC searches for dilepton resonances, as
well as direct and indirect dark matter searches. Despite this, viable regions
of the parameter space accommodating the observed dark matter relic abundance
and the $b \to s \ell^+ \ell^-$ anomalies still persist for dark matter and
$Z^{\prime}$ masses in the TeV range.


title:
The evolution of Red Supergiants to supernova in the LMC cluster NGC
  2100

abstract:
  The mass loss rates of red supergiants (RSGs) govern their evolution towards
supernova and dictate the appearance of the resulting explosion. To study how
mass-loss rates change with evolution we measure the mass-loss rates (\mdot)
and extinctions of 19 red supergiants in the young massive cluster NGC2100 in
the Large Magellanic Cloud. By targeting stars in a coeval cluster we can study
the mass-loss rate evolution whilst keeping the variables of mass and
metallicity fixed. Mass-loss rates were determined by fitting DUSTY models to
mid-IR photometry from WISE and Spitzer/IRAC. We find that the \mdot\ in red
supergiants increases as the star evolves, and is well described by \mdot\
prescription of de Jager, used widely in stellar evolution calculations. We
find the extinction caused by the warm dust is negligible, meaning the warm
circumstellar material of the inner wind cannot explain the higher levels of
extinction found in the RSGs compared to other cluster stars. We discuss the
implications of this work in terms of supernova progenitors and stellar
evolution theory. We argue there is little justification for substantially
increasing the \mdot\ during the RSG phase, as has been suggested recently in
order to explain the absence of high mass Type IIP supernova progenitors. We
also argue that an increase in reddening towards the end of the RSG phase, as
observed for the two most evolved cluster stars, may provide a solution to the
red supergiant problem.


title: On Helium Mixing in Quasi-global Simulations of the Intracluster Medium

abstract:
  The assumption of a spatially uniform helium distribution in the intracluster
medium can lead to biases in the estimates of key cluster parameters if
composition gradients are present. The helium concentration profile in galaxy
clusters is unfortunately not directly observable. Current models addressing
the putative sedimentation are one-dimensional and parametrize the presence of
magnetic fields in a crude way, ignoring the weakly-collisional, magnetized
nature of the medium. When these effects are considered, a wide variety of
instabilities can play an important role in the plasma dynamics. In a series of
recent papers, we have developed the local, linear theory of these
instabilities and addressed their non-linear development with a modified
version of Athena. Here, we extend our study by developing a quasi-global
approach that we use to simulate the mixing of helium as induced by
generalizations of the heat-flux-driven buoyancy instability (HBI) and the
magneto-thermal instability (MTI), which feed off thermal and composition
gradients. In the inner region of the ICM, mixing can occur on few Gyrs, after
which the average magnetic field inclination angle is $\sim 45^{\circ}$
resulting in an averaged Spitzer parameter higher by about 20 % than the value
obtained in homogeneous simulations. In the cluster outskirts the instabilities
are rather inefficient, due to the shallow gradients. This suggests that
compositions gradients in cluster cores might be shallower than one-dimensional
models predict. More quantitative statements demand more refined models that
can incorporate the physics driving the sedimentation process and
simultaneously account for the weakly-collisional nature of the plasma.


title:
Chandra and Swift X-ray Observations of the X-ray Pulsar SMC X-2 During
  the Outburst of 2015

abstract:
  We report the Chandra/HRC-S and Swift/XRT observations for the 2015 outburst
of the high-mass X-ray binary (HMXB) pulsar in the Small Magellanic Cloud, SMC
X-2. While previous studies suggested that either an O star or a Be star in the
field is the high-mass companion of SMC X-2, our Chandra/HRC-S image
unambiguously confirms the O-type star as the true optical counterpart. Using
the Swift/XRT observations, we extracted accurate orbital parameters of the
pulsar binary through a time of arrivals (TOAs) analysis. In addition, there
were two X-ray dips near the inferior conjunction, which are possibly caused by
eclipses or an ionized high-density shadow wind near the companion's surface.
Finally, we propose that an outflow driven by the radiation pressure from day
~10 played an important role in the X-ray/optical evolution of the outburst.


title: Curvature transformation

abstract:
  A transformation based on mean curvature is introduced which morphs
triangulated surfaces into round spheres.


title:
NMR study of nematic spin fluctuations in a detwinned single crystal of
  underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$

abstract:
  We report the experimental details of how mechanical detwinning can be
implemented in tandem with high sensitivity nuclear magnetic resonance
measurements and use this setup to measure the in-plane anisotropy of the
spin-lattice relaxation rate in underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$
with $x=0.048$. The anisotropy reaches a maximum of 30\% at $T_{N}$, and the
recovery data reveal that the glassy behavior of the spin fluctuations present
in the twinned state persist in the fully detwinned crystal. A theoretical
model is presented to describe the spin-lattice relaxation rate in terms of
anisotropic nematic spin fluctuations.


title:
Tunneling transport of mono- and few-layers magnetic van der Waals
  MnPS$_3$

abstract:
  We have investigated the tunneling transport of mono- and few-layers of MnPS3
by using conductive atomic force microscopy. Due to the band alignment of
indium tin oxide/MnPS3/Pt-Ir tip junction, the key features of both Schottky
junction and Fowler-Nordheim tunneling (FNT) were observed for all the samples
with varying thickness. Using the FNT model and assuming the effective electron
mass (0.5 me) of MnPS3, we estimate the tunneling barrier height to be 1.31 eV
and the dielectric breakdown strength as 5.41 MV/cm.


title:
Anomalous 3D bulk AC conduction within the Kondo gap of SmB$_6$ single
  crystals

abstract:
  The Kondo insulator SmB$_6$ has long been known to display anomalous
transport behavior at low temperatures, T$<5$ K. In this temperatures range, a
plateau is observed in the dc resistivity, contrary to the exponential
divergence expected for a gapped system. Recent theoretical calculations
suggest that SmB$_6$ may be the first topological Kondo insulator (TKI) and
propose that the residual conductivity is due to topological surface states
which reside within the Kondo gap. Since the TKI prediction many experiments
have claimed to observe high mobility surface states within a perfectly
insulating hybridization gap. Here, we investigate the low energy optical
conductivity within the hybridization gap of single crystals of SmB$_6$ via
time domain terahertz spectroscopy. Samples grown by both optical floating zone
and aluminum flux methods are investigated to probe for differences originating
from sample growth techniques. We find that both samples display significant 3D
bulk conduction originating within the Kondo gap. Although SmB$_6$ may be a
bulk dc insulator, it shows significant bulk ac conduction that is many orders
of magnitude larger than any known impurity band conduction. The nature of
these in-gap states and their coupling with the low energy spin excitons of
SmB$_6$ is discussed. Additionally, the well defined conduction path geometry
of our optical experiments allows us to show that any surface states, which lie
below our detection threshold if present, must have a sheet resistance of
R$/\square \ge$ 1000 $\Omega$.


title:
Rapid Classification of Crisis-Related Data on Social Networks using
  Convolutional Neural Networks

abstract:
  The role of social media, in particular microblogging platforms such as
Twitter, as a conduit for actionable and tactical information during disasters
is increasingly acknowledged. However, time-critical analysis of big crisis
data on social media streams brings challenges to machine learning techniques,
especially the ones that use supervised learning. The Scarcity of labeled data,
particularly in the early hours of a crisis, delays the machine learning
process. The current state-of-the-art classification methods require a
significant amount of labeled data specific to a particular event for training
plus a lot of feature engineering to achieve best results. In this work, we
introduce neural network based classification methods for binary and
multi-class tweet classification task. We show that neural network based models
do not require any feature engineering and perform better than state-of-the-art
methods. In the early hours of a disaster when no labeled data is available,
our proposed method makes the best use of the out-of-event data and achieves
good results.


title:
Local disorder, topological ground state degeneracy and entanglement
  entropy, and discrete anyons

abstract:
  In this comprehensive study of Kitaev's abelian models defined on a graph
embedded on a closed orientable surface, we provide complete proofs of the
topological ground state degeneracy, the absence of local order parameters,
compute the entanglement entropy exactly and characterise the elementary
anyonic excitations. The homology and cohomolgy groups of the cell complex play
a central role and allow for a rigorous understanding of the relations between
the above characterisations of topological order.


title: Elastic Microplane Formulation for Transversely Isotropic Materials

abstract:
  This contribution investigates the extension of the microplane formulation to
the description of transversely isotropic materials such as shale rock, foams,
unidirectional composites, and ceramics. Two possible approaches are
considered: 1) the spectral decomposition of the stiffness tensor to define the
microplane constitutive laws in terms of energetically orthogonal eigenstrains
and eigenstresses; and 2) the definition of orientation-dependent microplane
elastic moduli. It is shown that the first approach provides a rigorous way to
tackle anisotropy within the microplane framework whereas the second approach
represents an approximation which, however, makes the formulation of nonlinear
constitutive equations much simpler. The efficacy of the second approach in
modeling the macroscopic elastic behavior is compared to the thermodynamic
restrictions of the anisotropic parameters showing that a significant range of
elastic properties can be modeled with excellent accuracy. Further, it is shown
that it provides a very good approximation of the microplane stresses provided
by the first approach, with the advantage of a simpler formulation.
  It is concluded that the spectral stiffness decomposition represents the best
approach in such cases as for modeling unidirectional composites, in which
accurately capturing the elastic behavior is important. The introduction of
orientation-dependent microplane elastic moduli provides a simpler framework
for the modeling of transversely isotropic materials with remarked inelastic
behavior, as in the case, for example, of shale rock.


title:
Using Centroids of Word Embeddings and Word Mover's Distance for
  Biomedical Document Retrieval in Question Answering

abstract:
  We propose a document retrieval method for question answering that represents
documents and questions as weighted centroids of word embeddings and reranks
the retrieved documents with a relaxation of Word Mover's Distance. Using
biomedical questions and documents from BIOASQ, we show that our method is
competitive with PUBMED. With a top-k approximation, our method is fast, and
easily portable to other domains and languages.


title:
Solutions and stability of a variant of Van Vleck's and d'Alembert's
  functional equations

abstract:
  In this paper. (1) We determine the complex-valued solutions of the following
variant of Van Vleck's functional equation
$$\int_{S}f(\sigma(y)xt)d\mu(t)-\int_{S}f(xyt)d\mu(t) = 2f(x)f(y), \;x,y\in
S,$$ where $S$ is a semigroup, $\sigma$ is an involutive morphism of $S$, and
$\mu$ is a complex measure that is linear combinations of Dirac measures
$(\delta_{z_{i}})_{i\in I}$, such that for all $i\in I$, $z_{i}$ is contained
in the center of $S$. (2) We determine the complex-valued continuous solutions
of the following variant of d'Alembert's functional equation
$$\int_{S}f(xty)d\upsilon(t)+\int_{S}f(\sigma(y)tx)d\upsilon(t) = 2f(x)f(y),
\;x,y\in S,$$ where $S$ is a topological semigroup, $\sigma$ is a continuous
involutive automorphism of $S$, and $\upsilon$ is a complex measure with
compact support and which is $\sigma$-invariant. (3) We prove the
superstability theorems of the first functional equation.


title: Temporal Registration in In-Utero Volumetric MRI Time Series

abstract:
  We present a robust method to correct for motion and deformations for
in-utero volumetric MRI time series. Spatio-temporal analysis of dynamic MRI
requires robust alignment across time in the presence of substantial and
unpredictable motion. We make a Markov assumption on the nature of deformations
to take advantage of the temporal structure in the image data. Forward message
passing in the corresponding hidden Markov model (HMM) yields an estimation
algorithm that only has to account for relatively small motion between
consecutive frames. We demonstrate the utility of the temporal model by showing
that its use improves the accuracy of the segmentation propagation through
temporal registration. Our results suggest that the proposed model captures
accurately the temporal dynamics of deformations in in-utero MRI time series.


title: Implementing robust neuromodulation in neuromorphic circuits

abstract:
  We introduce a methodology to implement the physiological transition {between
distinct neuronal spiking modes} in electronic circuits composed of resistors,
capacitors and transistors. The result is a simple neuromorphic device
organized by the same geometry {and exhibiting the same input--output
properties as} high-dimensional electrophysiological neuron models.
{Preliminary} experimental results highlight the robustness of the approach in
real-world applications.


title: The Far-Infrared Surveyor Mission Study: Paper I, the Genesis

abstract:
  This paper describes the beginning of the Far-Infrared Surveyor mission study
for NASA's Astrophysics Decadal 2020. We describe the scope of the study, and
the open process approach of the Science and Technology Definition Team. We are
currently developing the science cases and provide some preliminary highlights
here. We note key areas for technological innovation and improvements necessary
to make a Far-Infrared Surveyor mission a reality.


title:
Hinode and IRIS observations of the magnetohydrodynamic waves
  propagating from the photosphere to the chromosphere in a sunspot

abstract:
  Magnetohydrodynamic (MHD) waves have been considered as energy sources for
heating the solar chromosphere and the corona. Although MHD waves have been
observed in the solar atmosphere, there are a lack of quantitative estimates on
the energy transfer and dissipation in the atmosphere. We performed
simultaneous Hinode and IRIS observations of a sunspot umbra to derive the
upward energy fluxes at two different atmospheric layers (photosphere and lower
transition region) and estimate the energy dissipation. The observations
revealed some properties of the observed periodic oscillations in physical
quantities, such as their phase relations, temporal behaviors, and power
spectra, making a conclusion that standing slow-mode waves are dominant at the
photosphere with their high-frequency leakage, which is observed as upward
waves at the chromosphere and the lower transition region. Our estimates of
upward energy fluxes are $2.0\times10^7$ erg cm$^{-2}$ s$^{-1}$ at the
photospheric level and $8.3\times10^4$ erg cm$^{-2}$ s$^{-1}$ at the lower
transition region level. The difference between the energy fluxes is larger
than the energy required to maintain the chromosphere in the sunspot umbrae,
suggesting that the observed waves can make a crucial contribution to the
heating of the chromosphere in the sunspot umbrae. In contrast, the upward
energy flux derived at the lower transition region level is smaller than the
energy flux required for heating the corona, implying that we may need another
heating mechanism. We should, however, note a possibility that the energy
dissipated at the chromosphere might be overestimated because of the opacity
effect.


title:
Growth of ultra thin vanadium dioxide thin films using magnetron
  sputtering

abstract:
  In this work, the results of fabricating ultra thin VO$_2$ films on the
technologically relevant amorphous SiO$_2$ surface using reactive DC magnetron
sputtering are presented. Results indicate that a post deposition anneal in low
partial pressures of oxygen is an effective way at stabilizing the
VO$_2$(M$_{1}$) phase on the SiO$_2$ surface. VO$_2$ films with a thickness of
42nm show a continuous microstructure, and undergo a resistivity change of more
than a factor of 200 as the temperature of the film increases above 72$^{o}C$.
The film shows hysteresis in the metal-insulator transition temperature upon
heating and cooling with a width of approximately 8$^o$C. The resistivity of
the low temperature semiconducting phase is found to be thermally activated
with an activation energy 0.16$\pm$0.03 $ev$. Stress measurements using X-ray
diffraction indicate that the ultra thin VO$_2$ film has a large tensile stress
of 2.0$\pm$0.2 $GPa$. This value agrees well with the calculated thermal stress
due to differential thermal expansion between the VO$_2$ thin film and silicon
substrate. The stress leads to a shift of the metal-insulator transition
temperature by approximately 4$^{o}C$.


title:
A Hiking Trip Through the Orders of Magnitude: Deriving Efficient
  Generators for Closed Simply-Typed Lambda Terms and Normal Forms

abstract:
  Contrary to several other families of lambda terms, no closed formula or
generating function is known and none of the sophisticated techniques devised
in analytic combinatorics can currently help with counting or generating the
set of {\em simply-typed closed lambda terms} of a given size.
  Moreover, their asymptotic scarcity among the set of closed lambda terms
makes counting them via brute force generation and type inference quickly
intractable, with previous published work showing counts for them only up to
size 10.
  By taking advantage of the synergy between logic variables, unification with
occurs check and efficient backtracking in today's Prolog systems, we climb 4
orders of magnitude above previously known counts by deriving progressively
faster Horn Clause programs that generate and/or count the set of closed
simply-typed lambda terms of sizes up to 14. A similar count for {\em closed
simply-typed normal forms} is also derived up to size 14.
  {\em {\bf Keywords:} logic programming transformations, type inference,
combinatorics of lambda terms, simply-typed lambda calculus, simply-typed
normal forms. }


title:
Bayesian mode and maximum estimation and accelerated rates of
  contraction

abstract:
  We study the problem of estimating the mode and maximum of an unknown
regression function in the presence of noise. We adopt the Bayesian approach by
using tensor-product B-splines and endowing the coefficients with Gaussian
priors. In the usual fixed-in-advanced sampling plan, we establish posterior
contraction rates for mode and maximum and show that they coincide with the
minimax rates for this problem. To quantify estimation uncertainty, we
construct credible sets for these two quantities that have high coverage
probabilities with optimal sizes. If one is allowed to collect data
sequentially, we further propose a Bayesian two-stage estimation procedure,
where a second stage posterior is built based on samples collected within a
credible set constructed from a first stage posterior. Under appropriate
conditions on the radius of this credible set, we can accelerate optimal
contraction rates from the fixed-in-advanced setting to the minimax sequential
rates. A simulation experiment shows that our Bayesian two-stage procedure
outperforms single-stage procedure and also slightly improves upon a
non-Bayesian two-stage procedure.


title: When was that made?

abstract:
  In this paper, we explore deep learning methods for estimating when objects
were made. Automatic methods for this task could potentially be useful for
historians, collectors, or any individual interested in estimating when their
artifact was created. Direct applications include large-scale data organization
or retrieval. Toward this goal, we utilize features from existing deep networks
and also fine-tune new networks for temporal estimation. In addition, we create
two new datasets of 67,771 dated clothing items from Flickr and museum
collections. Our method outperforms both a color-based baseline and previous
state of the art methods for temporal estimation. We also provide several
analyses of what our networks have learned, and demonstrate applications to
identifying temporal inspiration in fashion collections.


title:
The action of $\rm{GL}_2(\mathbb{F}_q)$ on irreducible polynomials over
  $\F_q$

abstract:
  Let $\F_q$ be the finite field with $q$ elements, $p=\Char \F_q$. The group
$\GL_2(\F_q)$ acts naturally in the set of irreducible polynomials over $\F_q$
of degree at least $2$. In this paper we are interested in the characterization
and number of the irreducible polynomials that are fixed by the elements of a
subgroup $H$ of $\GL_2(\F_q)$. We make a complete characterization of the fixed
polynomials in the case when $H$ has only elements of the form
$\left(\begin{matrix} 1&b\\ 0&1 \end{matrix}\right)$, corresponding to
translations $x\mapsto x+b$ and, as a consequence, the case when $H$ is a
$p-$subgroup of $\GL_2(\F_q)$. This paper also contains alternative solutions
for the cases when $H$ is generated by an element of the form
$\left(\begin{matrix} a&0\\ 0&1 \end{matrix}\right)$, obtained by Garefalakis
(2010) and $H=\rm{PGL}$$_2(\F_q)$, obtained by Stichtenoth and Topuzoglu
(2011).


title: Brownian motion of solitons in a Bose-Einstein Condensate

abstract:
  For the first time, we observed and controlled the Brownian motion of
solitons. We launched solitonic excitations in highly elongated $^{87}\rm{Rb}$
BECs and showed that a dilute background of impurity atoms in a different
internal state dramatically affects the soliton. With no impurities and in
one-dimension (1-D), these solitons would have an infinite lifetime, a
consequence of integrability. In our experiment, the added impurities scatter
off the much larger soliton, contributing to its Brownian motion and decreasing
its lifetime. We describe the soliton's diffusive behavior using a quasi-1-D
scattering theory of impurity atoms interacting with a soliton, giving
diffusion coefficients consistent with experiment.


title:
The Age and Distance of the Kepler Open Cluster NGC 6811 from an
  Eclipsing Binary, Turnoff Star Pulsation, and Giant Asteroseismology

abstract:
  We present the analysis of an eccentric, partially eclipsing long-period
($P=19.23$ d) binary system KIC 9777062 that contains main sequence stars near
the turnoff of the intermediate age open cluster NGC 6811. The primary is a
metal-lined Am star with a possible convective blueshift to its radial
velocities, and one star (probably the secondary) is likely to be a $\gamma$
Dor pulsator. The component masses are $1.603\pm0.006$(stat.)$\pm0.016$(sys.)
and $1.419\pm0.003\pm0.008 M_\odot$, and the radii are $1.744\pm0.004\pm0.002$
and $1.544\pm0.002\pm0.002 R_\odot$. The isochrone ages of the stars are mildly
inconsistent: the age from the mass-radius combination for the primary
($1.05\pm0.05\pm0.09$ Gyr, where the last quote was systematic uncertainty from
models and metallicity) is smaller than that from the secondary
($1.21\pm0.05\pm0.15$ Gyr) and is consistent with the inference from the
color-magnitude diagram ($1.00\pm0.05$ Gyr).
  We have improved the measurements of the asteroseismic parameters $\Delta
\nu$ and $\nu_{\rm max}$ for helium-burning stars in the cluster. The masses of
the stars appear to be larger (or alternately, the radii appear to be smaller)
than predicted from isochrones using the ages derived from the eclipsing stars.
  The majority of stars near the cluster turnoff are pulsating stars: we
identify a sample of 28 $\delta$ Sct, 15 $\gamma$ Dor, and 5 hybrid types. We
used the period-luminosity relation for high-amplitude $\delta$ Sct stars to
fit the ensemble of the strongest frequencies for the cluster members, finding
$(m-M)_V = 10.37\pm0.03$. This is larger than most previous determinations, but
smaller than values derived from the eclipsing binary ($10.47\pm0.05$).


title: Scalar-Tensor Teleparallel Wormholes by Noether Symmetries

abstract:
  A gravitational theory of a scalar field non-minimally coupled with torsion
and boundary term is considered with the aim to construct Lorentzian wormholes.
Geometrical parameters including shape and redshift functions are obtained for
these solutions. We adopt the formalism of Noether Gauge Symmetry Approach in
order to find symmetries, Lie brackets and invariants (conserved quantities).
Furthermore by imposing specific forms of potential function, we are able to
calculate metric coefficients and discuss their geometrical behavior.


title: 6d strings from new chiral gauge theories

abstract:
  We study the 6d $\mathcal{N}=(1,0)$ superconformal field theory with smallest
non-Higgsable gauge symmetry $SU(3)$. In particular, we propose new 2d gauge
theory descriptions of its self-dual strings in the tensor branch. We use our
gauge theories to compute the elliptic genera of the self-dual strings, which
completely agree with the partial data known from topological strings. We
further study the strings of the $(E_6,E_6)$ conformal matter by generalizing
our 2d gauge theories. We also show that anomalies of all our gauge theories
agree with the self-dual string anomalies computed by inflows from 6d.


title: Perovskite-perovskite tandem photovoltaics with optimized bandgaps

abstract:
  We demonstrate four and two-terminal perovskite-perovskite tandem solar cells
with ideally matched bandgaps. We develop an infrared absorbing 1.2eV bandgap
perovskite, $FA_{0.75}Cs_{0.25}Sn_{0.5}Pb_{0.5}I_3$, that can deliver 14.8 %
efficiency. By combining this material with a wider bandgap
$FA_{0.83}Cs_{0.17}Pb(I_{0.5}Br_{0.5})_3$ material, we reach monolithic two
terminal tandem efficiencies of 17.0 % with over 1.65 volts open-circuit
voltage. We also make mechanically stacked four terminal tandem cells and
obtain 20.3 % efficiency. Crucially, we find that our infrared absorbing
perovskite cells exhibit excellent thermal and atmospheric stability,
unprecedented for Sn based perovskites. This device architecture and materials
set will enable 'all perovskite' thin film solar cells to reach the highest
efficiencies in the long term at the lowest costs.


title:
Hector - a new massively multiplexed IFS instrument for the
  Anglo-Australian Telescope

abstract:
  Hector will be the new massively-multiplexed integral field spectroscopy
(IFS) instrument for the Anglo-Australian Telescope (AAT) in Australia and the
next main dark-time instrument for the observatory. Based on the success of the
SAMI instrument, which is undertaking a 3400-galaxy survey, the integral field
unit (IFU) imaging fibre bundle (hexabundle) technology under-pinning SAMI is
being improved to a new innovative design for Hector. The distribution of
hexabundle angular sizes is matched to the galaxy survey properties in order to
image 90% of galaxies out to 2 effective radii. 50-100 of these IFU imaging
bundles will be positioned by 'starbug' robots across a new 3-degree field
corrector top end to be purpose-built for the AAT. Many thousand fibres will
then be fed into new replicable spectrographs. Fundamentally new science will
be achieved compared to existing instruments due to Hector's wider field of
view (3 degrees), high positioning efficiency using starbugs, higher
spectroscopic resolution (R~3000-5500 from 3727-7761A, with a possible redder
extension later) and large IFUs (up to 30 arcsec diameter with 61-217 fibre
cores). A 100,000 galaxy IFS survey with Hector will decrypt how the accretion
and merger history and large-scale environment made every galaxy different in
its morphology and star formation history. The high resolution, particularly in
the blue, will make Hector the only instrument to be able to measure
higher-order kinematics for galaxies down to much lower velocity dispersion
than in current large IFS galaxy surveys, opening up a wealth of new nearby
galaxy science.


title: Sedimentation analysis of small ice crystals by Lattice Boltzmann Method

abstract:
  Lattice Boltzmann Method (LBM) is used to simulate and analyze the
sedimentation of small ($15-80 \,\mu m$) columnar ice particles in the
atmosphere. We are specially interested in evaluating the terminal falling
velocity of columnar ice crystals with hexagonal cross section. The main
objective is to apply the LBM to solve ice crystal sedimentation problems. This
numerical method is evaluated as a powerful numerical tool to solve ice crystal
sedimentation problems in a variety of sizes. LBM results are presented in
comparison with laboratory experimental results and theoretical approaches well
known in the literature. The numerical results show good agreement with
experimental and theoretical results for the analyzed geometrical
configurations.


title:
Fluid nonlinear frequency shift of nonlinear ion acoustic waves in
  multi-ion species plasmas in small wave number region

abstract:
  The properties of the nonlinear frequency shift (NFS) especially the fluid
NFS from the harmonic generation of the ion-acoustic wave (IAW) in multi-ion
species plasmas have been researched by Vlasov simulation. The pictures of the
nonlinear frequency shift from harmonic generation and particles trapping are
shown to explain the mechanism of NFS qualitatively. The theoretical model of
the fluid NFS from harmonic generation in multi-ion species plasmas is given
and the results of Vlasov simulation are consistent to the theoretical result
of multi-ion species plasmas. When the wave number $k\lambda_{De}$ is small,
such as $k\lambda_{De}=0.1$, the fluid NFS dominates in the total NFS and will
reach as large as nearly $15\%$ when the wave amplitude $|e\phi/T_e|\sim0.1$,
which indicates that in the condition of small $k\lambda_{De}$, the fluid NFS
dominates in the saturation of stimulated Brillouin scattering especially when
the nonlinear IAW amplitude is large.


title: Linear finite difference operators preserving Laguerre-P\'olya class

abstract:
  We completely describe all finite difference operators of the form $$
\Delta_{M_1, M_2, h}(f)(z)=M_1(z) f(z+h) + M_2(z) f(z-h) $$ preserving the
Laguerre-P\'olya class of entire functions. Here $M_1$ and $M_2$ are some
complex functions and $h$ is a nonzero complex number.


title: Generating positive geometric entropy from recurrent leaves

abstract:
  In this paper we introduce a new $C^r-$perturbation procedure, with respect
to the $C^r$-Epstein topology, for $C^r$-foliations by surfaces. Using this
perturbation procedure we show how one can use the existence of recurrent
leaves of certain $C^r-$foliation $\mathcal F$ to obtain a foliation $\mathcal
G$, $C^r-$close to $\mathcal F$ in the $C^r-$Epstein topology, which has a
resilient leaf. In particular, one can take advantage of recurrence property to
construct examples of $C^r-$foliations by surfaces, $C^r-$close to each other
and such that one of them has a resilient leaf while the other is Riemannian
(therefore has trivial dynamics).


title: The Moon as a Recorder of Nearby Supernovae

abstract:
  The lunar geological record is expected to contain a rich record of the
galactic environment of the Solar System, including records of nearby (i.e.
less than a few tens of parsecs) supernova explosions. This record will be
composed of two principal components: (i) cosmogenic nuclei produced within, as
well as radiation damage to, surface materials caused by increases in the
galactic cosmic ray flux resulting from nearby supernovae; and (ii) the direct
collection of supernova ejecta, likely enriched in a range of unusual and
diagnostic isotopes, on the lunar surface. Both aspects of this potentially
very valuable astrophysical archive will be best preserved in currently buried,
but nevertheless near-surface, layers that were directly exposed to the space
environment at known times in the past and for known durations. Suitable
geological formations certainly exist on the Moon, but accessing them will
require a greatly expanded programme of lunar exploration.

categories: astro-ph.EP astro-ph.HE astro-ph.IM astro-ph.SR


title:
Four-dimensional Painlev\'e-type equations associated with ramified
  linear equations I: Matrix Painlev\'e systems

abstract:
  As a sequel to Kawakami-Nakamura-Sakai (arXiv:1209.3836), this series of
papers constructs the complete degeneration scheme of four-dimensional
Painlev\'e-type equations which includes the Painlev\'e-type equations
associated with linear systems of ramified type. In the present paper, we
consider the degeneration of Painlev\'e-type equations which we call the matrix
Painlev\'e systems.


title:
Hybrid Jacobian and Gauss-Seidel proximal block coordinate update
  methods for linearly constrained convex programming

abstract:
  Recent years have witnessed the rapid development of block coordinate update
(BCU) methods, which are particularly suitable for problems involving
large-sized data and/or variables. In optimization, BCU first appears as the
coordinate descent method that works well for smooth problems or those with
separable nonsmooth terms and/or separable constraints. As nonseparable
constraints exist, BCU can be applied under primal-dual settings.
  In the literature, it has been shown that for weakly convex problems with
nonseparable linear constraint, BCU with fully Gauss-Seidel updating rule may
fail to converge and that with fully Jacobian rule can converge sublinearly.
However, empirically the method with Jacobian update is usually slower than
that with Gauss-Seidel rule. To maintain their advantages, we propose a hybrid
Jacobian and Gauss-Seidel BCU method for solving linearly constrained
multi-block structured convex programming, where the objective may have a
nonseparable quadratic term and separable nonsmooth terms. At each primal block
variable update, the method approximates the augmented Lagrangian function at
an affine combination of the previous two iterates, and the affinely mixing
matrix with desired nice properties can be chosen through solving a
semidefinite programming. We show that the hybrid method enjoys the theoretical
convergence guarantee as Jacobian BCU. In addition, we numerically demonstrate
that the method can perform as well as Gauss-Seidel method and better than a
recently proposed randomized primal-dual BCU method.


abstract:
  In this manuscript, I introduce and describe the work of mathematicians and
mathematics educators in the group Transforming Post-Secondary Education in
Mathematics (TPSE Math or TPSE, pronounced "tipsy", for short). TPSE aims to
coordinate and drive constructive change in education in the mathematical
sciences at two-year colleges, four-year colleges, and universities across the
nation. It seeks to build on the successes of the entire mathematical sciences
community.
  This manuscript reviews the events that led to the founding of TPSE Math and
articulates its vision and mission. In its first phase with national events,
TPSE found broad consensus with the mathematical sciences community on the
challenges facing the community. Learning from educational transformations
experiences in other scientific fields, and with the support of the
Mathematical Advisory Group of 34 mathematical sciences department chairs and
leaders, TPSE moves into a second phase focused on action. This is a snapshot
in time, and TPSE's ongoing activities will continue to be documented and
disseminated. The piece concludes with a reflection of the impact that my
involvement in this work has had on my career.


title:
On the origin of the scatter broadening of fast radio burst pulses and
  astrophysical implications

abstract:
  Fast radio bursts (FRBs) have been identified as extragalactic sources which
can make a probe of turbulence in the intergalactic medium (IGM) and their host
galaxies. To account for the observed millisecond pulses caused by scatter
broadening, we examine a variety of possible models of electron density
fluctuations in both the IGM and the host galaxy medium. We find that a
short-wave-dominated power-law spectrum of density, which may arise in highly
supersonic turbulence with pronounced local dense structures of
shock-compressed gas in the host interstellar medium (ISM), can produce the
required density enhancements at sufficiently small scales to interpret the
scattering timescale of FRBs. It implies that an FRB residing in a galaxy with
efficient star formation in action tends to have a broadened pulse. The scaling
of the scattering time with dispersion measure (DM) in the host galaxy varies
in different turbulence and scattering regimes. The host galaxy can be the
major origin of scatter broadening, but contribute to a small fraction of the
total DM. We also find that the sheet-like structure of density in the host ISM
associated with folded magnetic fields in a viscosity-dominated regime of
magnetohydrodynamic (MHD) turbulence cannot give rise to strong scattering.
Furthermore, valuable insights into the IGM turbulence concerning the detailed
spatial structure of density and magnetic field can be gained from the observed
scattering timescale of FRBs. Our results are in favor of the suppression of
micro-plasma instabilities and the validity of collisional-MHD description of
turbulence properties in the collisionless IGM.


title:
Superiorized iteration based on proximal point method and its
  application to XCT image reconstruction

abstract:
  In this paper, we investigate how to determine a better perturbation for
superiorized iteration. We propose to seek the perturbation by proximal point
method. In our method, the direction and amount of perturbation are computed
simultaneously. The convergence conditions are also discussed for bounded
perterbation resilence iteration. Numerical experiments on simulated XCT
projection data show that the proposed method improves the convergence rate and
the image quality.


title:
Human Pose Estimation from Depth Images via Inference Embedded
  Multi-task Learning

abstract:
  Human pose estimation (i.e., locating the body parts / joints of a person) is
a fundamental problem in human-computer interaction and multimedia
applications. Significant progress has been made based on the development of
depth sensors, i.e., accessible human pose prediction from still depth images
[32]. However, most of the existing approaches to this problem involve several
components/models that are independently designed and optimized, leading to
suboptimal performances. In this paper, we propose a novel inference-embedded
multi-task learning framework for predicting human pose from still depth
images, which is implemented with a deep architecture of neural networks.
Specifically, we handle two cascaded tasks: i) generating the heat (confidence)
maps of body parts via a fully convolutional network (FCN); ii) seeking the
optimal configuration of body parts based on the detected body part proposals
via an inference built-in MatchNet [10], which measures the appearance and
geometric kinematic compatibility of body parts and embodies the dynamic
programming inference as an extra network layer. These two tasks are jointly
optimized. Our extensive experiments show that the proposed deep model
significantly improves the accuracy of human pose estimation over other several
state-of-the-art methods or SDKs. We also release a large-scale dataset for
comparison, which includes 100K depth images under challenging scenarios.


title: Improved Dynamic Regret for Non-degenerate Functions

abstract:
  Recently, there has been a growing research interest in the analysis of
dynamic regret, which measures the performance of an online learner against a
sequence of local minimizers. By exploiting the strong convexity, previous
studies have shown that the dynamic regret can be upper bounded by the
path-length of the comparator sequence. In this paper, we illustrate that the
dynamic regret can be further improved by allowing the learner to query the
gradient of the function multiple times, and meanwhile the strong convexity can
be weakened to other non-degenerate conditions. Specifically, we introduce the
squared path-length, which could be much smaller than the path-length, as a new
regularity of the comparator sequence. When multiple gradients are accessible
to the learner, we first demonstrate that the dynamic regret of strongly convex
functions can be upper bounded by the minimum of the path-length and the
squared path-length. We then extend our theoretical guarantee to functions that
are semi-strongly convex or self-concordant. To the best of our knowledge, this
is the first time that semi-strong convexity and self-concordance are utilized
to tighten the dynamic regret.


title:
Gorenstein properties and integer decomposition properties of lecture
  hall polytopes

abstract:
  Though much is known about ${\bf s}$-lecture hall polytopes, there are still
many unanswered questions. In this paper, we show that ${\bf s}$-lecture hall
polytopes satisfy the integer decomposition property (IDP) in the case of
monotonic ${\bf s}$-sequences. Given restrictions on a monotonic ${\bf
s}$-sequence, we discuss necessary and sufficient conditions for the Fano,
reflexive and Gorenstein properties. Additionally, we give a construction for
producing Gorenstein/IDP lecture hall polytopes.


title: Minkowski's theorem on independent conjugate units

abstract:
  We call a unit $\beta$ in a Galois extension $l/\mathbb{Q}$ a Minkowski unit
if the subgroup generated by $\beta$ and its conjugates over $\mathbb{Q}$ has
maximum rank in the unit group of $l$. Minkowski showed the existence of such
units in every Galois extension. We will give a new proof to Minkowski's
theorem and show that there exists a Minkowski unit $\beta \in l$ such that the
Weil height of $\beta$ is comparable with the sum of the heights of a
fundamental system of units of $l$. Our proof implies a bound on the index of
the subgroup generated by the algebraic conjugates of $\beta$ in the unit group
of $l$.
  If $k$ is an intermediate field such that \begin{equation*} \mathbb{Q}
\subseteq k \subseteq l, \end{equation*} and $l/\mathbb{Q}$ and $k/\mathbb{Q}$
are Galois extensions, we prove an analogous bound for the subgroup of relative
units.