title: SUSY under siege from direct and indirect WIMP detection experiments

abstract:
  We examine updated prospects for detecting WIMPs in supersymmetric models via
direct and indirect dark matter search experiments. We examine several
historical and also still viable scenarios: projections for well-tempered
neutralinos (WTN), projections from the MasterCode (MC), BayesFits (BF) and
Fittino (FO) collaborations, non-thermal wino dark matter (NThW) and finally
mixed axion-higgsino dark matter from SUSY with radiatively-driven naturalness
(RNS). The WTN is ruled out by recent limits from XENON and LUX collaborations.
The NThW scenario, previously on tenuous ground due to gamma-line searches,
appears also ruled out by recent combined Fermi-LAT/MAGIC limits combined with
new HESS results from continuum gamma rays. Substantial portions of MC
parameter space and 1 TeV higgsino parameter space from BF group are ruled out.
The 100-300 GeV higgsino-like WIMP from RNS survives due to its possible
depleted local abundance (where the axion may make up the bulk of dark matter).
Projections from ton-scale noble liquid detectors should discover or rule out
WIMPs from the remaining parameter space of these surviving models.


title:
Improving and extending the testing of distributions for
  shape-restricted properties

abstract:
  Distribution testing deals with what information can be deduced about an
unknown distribution over $\{1,\ldots,n\}$, where the algorithm is only allowed
to obtain a relatively small number of independent samples from the
distribution. In the extended conditional sampling model, the algorithm is also
allowed to obtain samples from the restriction of the original distribution on
subsets of $\{1,\ldots,n\}$.
  In 2015, Canonne, Diakonikolas, Gouleakis and Rubinfeld unified several
previous results, and showed that for any property of distributions satisfying
a "decomposability" criterion, there exists an algorithm (in the basic model)
that can distinguish with high probability distributions satisfying the
property from distributions that are far from it in the variation distance.
  We present here a more efficient yet simpler algorithm for the basic model,
as well as very efficient algorithms for the conditional model, which until now
was not investigated under the umbrella of decomposable properties.
Additionally, we provide an algorithm for the conditional model that handles a
much larger class of properties.
  Our core mechanism is a way of efficiently producing an interval-partition of
$\{1,\ldots,n\}$ that satisfies a "fine-grain" quality. We show that with such
a partition at hand we can directly move forward with testing individual
intervals, instead of first searching for the "correct" partition of
$\{1,\ldots,n\}$.


title:
Control of colloidal placement by modulated molecular orientation in
  nematic cells

abstract:
  Colloids self-assemble into various organized superstructures determined by
particle interactions. There is a tremendous progress in both the scientific
understanding and applications of self-assemblies of single-type identical
particles. Forming superstructures in which the colloidal particles occupy
predesigned sites and remain in these sites despite thermal fluctuations
represents a major challenge of the current state-of-the art. Here we propose a
versatile approach to direct placement of colloids using nematic liquid
crystals with spatially varying molecular orientation pre-imposed by substrate
photoalignment. Colloidal particles in nematic environment are subject to the
long-range elastic forces originating in the orientational order of the
nematic. Gradients of the orientational order create an elastic energy
landscape that drives the colloids into locations with preferred type of
deformations. As an example, we demonstrate that colloidal spheres with
perpendicular surface anchoring are driven into the regions of maximum splay,
while spheres with tangential surface anchoring settle into the regions of
bend. Elastic forces responsible for preferential placement are measured by
exploring overdamped dynamics of the colloids. Control of colloidal
self-assembly through patterned molecular orientation opens new opportunities
for design of materials and devices in which particles should be placed in
pre-designed locations.


title: Filling-enforced Magnetic Dirac Semimetals in Two Dimensions

abstract:
  Filling-enforced Dirac semimetals, or those required at specific fillings by
the combination of crystalline and time-reversal symmetries, have been proposed
and discovered in numerous materials. However, Dirac points in these materials
are not generally robust against breaking or modifying time-reversal symmetry.
We present a new class of two-dimensional Dirac semimetal protected by the
combination of crystal symmetries and a special, antiferromagnetic
time-reversal symmetry. Systems in this class of magnetic layer groups, while
having broken time-reversal symmetry, still respect the operation of
time-reversal followed by a half-lattice translation. In contrast to 2D
time-reversal-symmetric Dirac semimetal phases, this magnetic Dirac phase is
capable of hosting just a single isolated Dirac point at the Fermi level, and
that Dirac point can be stabilized solely by symmorphic crystal symmetries. We
find that this Dirac point represents a new quantum critical point, and lives
at the boundary between Chern insulating, antiferromagnetic topological
crystalline insulating, and trivial insulating phases. We present density
functional theoretic calculations which demonstrate the presence of this 2D
magnetic Dirac semimetallic phase in FeSe monolayers and discuss the
implications for engineering quantum phase transitions in these materials.


title: Cosmological Imprints of Frozen-In Light Sterile Neutrinos

abstract:
  We investigate observable cosmological aspects of sterile neutrino dark
matter produced via the freeze-in mechanism. The study is performed in a
framework that admits many cosmologically interesting variations: high
temperature production via annihilation processes from higher dimensional
operators or low temperature production from decays of a scalar, with the
decaying scalar in or out of equilibrium with the thermal bath, in
supersymmetric or non-supersymmetric setups, thus allowing us to both extract
generic properties and highlight features unique to particular variations. We
find that while such sterile neutrinos are generally compatible with all
cosmological constraints, interesting scenarios can arise where dark matter is
cold, warm, or hot, has nontrivial momentum distributions, or provides
contributions to the effective number of relativistic degrees of freedom Neff
during Big Bang nucleosynthesis large enough to be probed by future
measurements.


title: Density Theorems for Exceptional Eigenvalues for Congruence Subgroups

abstract:
  Using the Kuznetsov formula, we prove several density theorems for
exceptional Hecke and Laplacian eigenvalues of Maass cusp forms of weight 0 or
1 for the congruence subgroups $\Gamma_0(q)$, $\Gamma_1(q)$, and $\Gamma(q)$.
These improve and extend upon results of Sarnak and Huxley, who prove similar
but slightly weaker results via the Selberg trace formula.


title:
Using CMA-ES for tuning coupled PID controllers within models of
  combustion engines

abstract:
  Proportional integral derivative (PID) controllers are important and widely
used tools in system control. Tuning of the controller gains is a laborious
task, especially for complex systems such as combustion engines. To minimize
the time of an engineer for tuning of the gains in a simulation software, we
propose to formulate a part of the problem as a black-box optimization task. In
this paper, we summarize the properties and practical limitations of tuning of
the gains in this particular application. We investigate the latest methods of
black-box optimization and conclude that the Covariance Matrix Adaptation
Evolution Strategy (CMA-ES) with bi-population restart strategy, elitist parent
selection and active covariance matrix adaptation is best suited for this task.
Details of the algorithm's experiment-based calibration are explained as well
as derivation of a suitable objective function. The method's performance is
compared with that of PSO and SHADE. Finally, its usability is verified on six
models of real engines.


title: Effects of population growth on the success of invading mutants

abstract:
  Understanding if and how mutants reach fixation in populations is an
important question in evolutionary biology. We study the impact of population
growth has on the success of mutants. To systematically understand the effects
of growth we decouple competition from reproduction; competition follows a
birth--death process and is governed by an evolutionary game, while growth is
determined by an externally controlled branching rate. In stochastic
simulations we find non-monotonic behaviour of the fixation probability of
mutants as the speed of growth is varied; the right amount of growth can lead
to a higher success rate. These results are observed in both coordination and
coexistence game scenarios, and we find that the 'one-third law' for
coordination games can break down in the presence of growth. We also propose a
simplified description in terms of stochastic differential equations to
approximate the individual-based model.


title:
Protein-protein docking by generalized Fourier transforms on 5D
  rotational manifolds

abstract:
  Energy evaluation using fast Fourier transforms enables sampling billions of
putative complex structures and hence revolutionized rigid protein-protein
docking. However, in current methods efficient acceleration is achieved only in
either the translational or the rotational subspace. Developing an efficient
and accurate docking method that expands FFT based sampling to 5 rotational
coordinates is an extensively studied but still unsolved problem. The algorithm
presented here retains the accuracy of earlier methods but yields at least
tenfold speedup. The improvement is due to two innovations. First, the search
space is treated as the product manifold $\mathbf{SO(3)x(SO(3)\setminus S^1)}$,
where $\mathbf{SO(3)}$ is the rotation group representing the space of the
rotating ligand, and $\mathbf{(SO(3)\setminus S^1)}$ is the space spanned by
the two Euler angles that define the orientation of the vector from the center
of the fixed receptor toward the center of the ligand. This representation
enables the use of efficient FFT methods developed for $\mathbf{SO(3)}$.
Second, we select the centers of highly populated clusters of docked
structures, rather than the lowest energy conformations, as predictions of the
complex, and hence there is no need for very high accuracy in energy
evaluation. Therefore it is sufficient to use a limited number of spherical
basis functions in the Fourier space, which increases the efficiency of
sampling while retaining the accuracy of docking results. A major advantage of
the method is that, in contrast to classical approaches, increasing the number
of correlation function terms is computationally inexpensive, which enables
using complex energy functions for scoring.


title: Non-parametric Regression for Spatially Dependent Data with Wavelets

abstract:
  We study non-parametric regression estimates for random fields. The data
satisfies certain strong mixing conditions and is defined on the regular
$N$-dimensional lattice structure. We show consistency and obtain rates of
convergence. The rates are optimal modulo a logarithmic factor in some cases.
As an application, we estimate the regression function with multidimensional
wavelets which are not necessarily isotropic. We simulate random fields on
planar graphs with the concept of concliques (cf. Kaiser et al. [2012]) in
numerical examples of the estimation procedure.


title:
Evolution of the magnetorotational instability on initially tangled
  magnetic fields

abstract:
  The initial magnetic field of previous magnetorotational instability (MRI)
simulations has always included a significant system-scale component, even if
stochastic. However, it is of conceptual and practical interest to assess
whether the MRI can grow when the initial field is turbulent. The ubiquitous
presence of turbulent or random flows in astrophysical plasmas generically
leads to a small-scale dynamo (SSD), which would provide initial seed turbulent
velocity and magnetic fields in the plasma that becomes an accretion disc. Can
the MRI grow from these more realistic initial conditions? To address this we
supply a standard shearing box with isotropically forced SSD generated magnetic
and velocity fields as initial conditions, and remove the forcing. We find that
if the initially supplied fields are too weak or too incoherent, they decay
from the initial turbulent cascade faster than they can grow via the MRI. When
the initially supplied fields are sufficient to allow MRI growth and
sustenance, the saturated stresses, large-scale fields, and power spectra match
those of the standard zero net flux MRI simulation with an initial large scale
vertical field.


title:
Carbon cluster diagnostics-I: Direct Recoil Spectroscopy (DRS) of Ar+
  and Kr+ bombarded graphite

abstract:
  Measurements of the energy spectra of multiply charged positive and negative
carbon ions recoiling from graphite surface under 100 and 150 keV argon and
krypton ion bombardment are presented. With the energy spectrometer set at
recoil angle of 79.5 degrees, direct recoil (DR) peaks have been observed with
singly as well as multiply charged carbon ions , where n = 1 to 6. These
monatomic and cluster ions have been observed recoiling with the characteristic
recoil energy E(DR) . We have observed sharp DR peaks. A collimated projectile
beam with small divergence is supplemented with a similar collimation before
the energy analyzer to reduce the background of sputtered ions due to scattered
projectiles.


title: Neutrino Astrophysics

abstract:
  We summarize the progress in neutrino astrophysics and emphasize open issues
in our understanding of neutrino flavor conversion in media. We discuss solar
neutrinos, core-collapse supernova neutrinos and conclude with ultra-high
energy neutrinos.


title: Empty smectics of hard nanorings: insights from a second-virial theory

abstract:
  Inspired by recent simulations on highly open liquid crystalline structures
formed by rigid planar nanorings we present a simple theoretical framework
explaining the prevalence of smectic over nematic ordering in systems of
ring-shaped objects. The key part of our study is a calculation of the excluded
volume of such non-convex particles in the limit of vanishing thickness to
diameter ratio. Using a simple stability analysis we then show that dilute
systems of ring-shaped particles have a strong propensity to order into smectic
structures with an unusual antinematic order while solid disks of the same
dimensions exhibit nematic order. Since our model rings have zero internal
volume these smectic structures are essential empty, resembling the strongly
porous structures found in simulation. We argue that the antinematic
intralamellar order of the rings plays an essential role in stabilizing these
novel smectic structures.


title: Hyperbolic families and coloring graphs on surfaces

abstract:
  Let $G$ be a graph embedded in a fixed surface $\Sigma$ of genus $g$ and let
$L=(L(v):v\in V(G))$ be a collection of lists such that either each list has
size at least five, or each list has size at least four and $G$ is
triangle-free, or each list has size at least three and $G$ has no cycle of
length four or less. An $L$-coloring of $G$ is a mapping $\phi$ with domain
$V(G)$ such that $\phi(v)\in L(v)$ for every $v\in V(G)$ and
$\phi(v)\ne\phi(u)$ for every pair of adjacent vertices $u,v\in V(G)$. We prove
  * if every non-null-homotopic cycle in $G$ has length $\Omega(\log g)$, then
$G$ has an $L$-coloring,
  * if $G$ does not have an $L$-coloring, but every proper subgraph does
("$L$-critical graph"), then $|V(G)|=O(g)$,
  * if every non-null-homotopic cycle in $G$ has length $\Omega(g)$, and a set
$X\subseteq V(G)$ of vertices that are pairwise at distance $\Omega(1)$ is
precolored from the corresponding lists, then the precoloring extends to an
$L$-coloring of $G$,
  * if every non-null-homotopic cycle in $G$ has length $\Omega(g)$, and the
graph $G$ is allowed to have crossings, but every two crossings are at distance
$\Omega(1)$, then $G$ has an $L$-coloring, and
  * if $G$ has at least one $L$-coloring, then it has at least
$2^{\Omega(|V(G)|)}$ distinct $L$-colorings.
  We show that the above assertions are consequences of certain isoperimetric
inequalities satisfied by $L$-critical graphs, and we study the structure of
families of embedded graphs that satisfy those inequalities. It follows that
the above assertions hold for other coloring problems, as long as the
corresponding critical graphs satisfy the same inequalities.


title: Masses of Open-Flavour Heavy-Light Hybrids from QCD Sum-Rules

abstract:
  We use QCD Laplace sum-rules to predict masses of open-flavour heavy-light
hybrids where one of the hybrid's constituent quarks is a charm or bottom and
the other is an up, down, or strange. We compute leading-order, diagonal
correlation functions of several hybrid interpolating currents, taking into
account QCD condensates up to dimension-six, and extract hybrid mass
predictions for all $J^P\in\{0^{\pm},\,1^{\pm}\}$, as well as explore possible
mixing effects with conventional quark-antiquark mesons. Within theoretical
uncertainties, our results are consistent with a degeneracy between the
heavy-nonstrange and heavy-strange hybrids in all $J^P$ channels. We find a
similar mass hierarchy of $1^+$, $1^{-}$, and $0^+$ states (a $1^{+}$ state
lighter than essentially degenerate $1^{-}$ and $0^{+}$ states) in both the
charm and bottom sectors, and discuss an interpretation for the $0^-$ states.
If conventional meson mixing is present the effect is an increase in the hybrid
mass prediction, and we estimate an upper bound on this effect.


title:
Precision measurements and test of molecular theory in highly-excited
  vibrational states of H$_2$ $(v=11)$

abstract:
  Accurate $EF{}^1\Sigma^+_g-X{}^1\Sigma^+_g$ transition energies in molecular
hydrogen were determined for transitions originating from levels with
highly-excited vibrational quantum number, $v=11$, in the ground electronic
state. Doppler-free two-photon spectroscopy was applied on vibrationally
excited H$_2^*$, produced via the photodissociation of H$_2$S, yielding
transition frequencies with accuracies of $45$ MHz or $0.0015$ cm$^{-1}$. An
important improvement is the enhanced detection efficiency by resonant
excitation to autoionizing $7p\pi$ electronic Rydberg states, resulting in
narrow transitions due to reduced ac-Stark effects. Using known $EF$ level
energies, the level energies of $X(v=11, J=1,3-5)$ states are derived with
accuracies of typically 0.002 cm$^{-1}$. These experimental values are in
excellent agreement with, and are more accurate than the results obtained from
the most advanced ab initio molecular theory calculations including
relativistic and QED contributions.


title:
The Galactic Census of High- and Medium-mass Protostars. III $^{12}$CO
  Maps and Physical Properties of Dense Clump Envelopes and their Embedding
  GMCs

abstract:
  We report the second complete molecular line data release from the {\em
Census of High- and Medium-mass Protostars} (CHaMP), a large-scale, unbiased,
uniform mapping survey at sub-parsec resolution, of mm-wave line emission from
303 massive, dense molecular clumps in the Milky Way. This release is for all
$^{12}$CO $J$=1$\rightarrow$0 emission associated with the dense gas, the first
from Phase II of the survey, which includes $^{12}$CO, $^{13}$CO, and
C$^{18}$O. The observed clump emission traced by both $^{12}$CO and HCO$^+$
(from Phase I) shows very similar morphology, indicating that, for dense
molecular clouds and complexes of all sizes, parsec-scale clumps contain $\Xi$
~ 75% of the mass, while only 25% of the mass lies in extended (>~ 10 pc) or
"low density" components in these same areas. The mass fraction of all gas
above a density 10$^9$ m$^{-3}$ is $\xi_9$ >~ 50%. This suggests that
parsec-scale clumps may be the basic building blocks of the molecular ISM,
rather than the standard GMC concept. Using $^{12}$CO emission, we derive
physical properties of these clumps in their entirety, and compare them to
properties from HCO$^+$, tracing their denser interiors. We compare the
standard X-factor converting $I_{CO}$ to $N_{H_2}$ with alternative
conversions, and show that only the latter give whole-clump properties that are
physically consistent with those of their interiors. We infer that the clump
population is systematically closer to virial equilibrium than when considering
only their interiors, with perhaps half being long-lived (10s of Myr),
pressure-confined entities which only terminally engage in vigorous massive
star formation, supporting other evidence along these lines previously
published.


title: How should we evaluate supervised hashing?

abstract:
  Hashing produces compact representations for documents, to perform tasks like
classification or retrieval based on these short codes. When hashing is
supervised, the codes are trained using labels on the training data. This paper
first shows that the evaluation protocols used in the literature for supervised
hashing are not satisfactory: we show that a trivial solution that encodes the
output of a classifier significantly outperforms existing supervised or
semi-supervised methods, while using much shorter codes. We then propose two
alternative protocols for supervised hashing: one based on retrieval on a
disjoint set of classes, and another based on transfer learning to new classes.
We provide two baseline methods for image-related tasks to assess the
performance of (semi-)supervised hashing: without coding and with unsupervised
codes. These baselines give a lower- and upper-bound on the performance of a
supervised hashing scheme.


title: Kadison's Pythagorean Theorem and essential codimension

abstract:
  Kadison's Pythagorean theorem (2002) provides a characterization of the
diagonals of projections with a subtle integrality condition. Arveson (2007),
Kaftal, Ng, Zhang (2009), and Argerami (2015) all provide different proofs of
that integrality condition. In this paper we interpret the integrality
condition in terms of the essential codimension of a pair of projections
introduced by Brown, Douglas and Fillmore (1973), or, equivalently of the index
of a Fredholm pair of projections introduced by Avron, Seiler, and Simon
(1994). The same techniques explain the integer occurring in the
characterization of diagonals of selfadjoint operators with finite spectrum by
Bownik and Jasper (2015).


title:
Analysis of Thermo-Diffusive Cellular Instabilities in Continuum
  Combustion Fronts

abstract:
  We explore numerically the morphological patterns of thermo-diffusive
instabilities in combustion fronts with a continuum fuel source, within a range
of Lewis numbers and ignition temperatures, focusing on the cellular regime.
For this purpose, we generalize the model of Brailovsky et al. to include
distinct process kinetics and reactant heterogeneity. The generalized model is
derived analytically and validated with other established models in the limit
of infinite Lewis number for zero-order and first-order kinetics. Cellular and
dendritic instabilities are found at low Lewis numbers thanks to a dynamic
adaptive mesh refinement technique that reduces finite size effects, which can
affect or even preclude the emergence of these patterns. This technique also
allows achieving very large computational domains, enabling the study of
system-size effects. Our numerical linear stability analysis is consistent with
the analytical results of Brailovsky et al. The distinct types of dynamics
found in the vicinity of the critical Lewis number, ranging from steady-state
cells to continued tip-splitting and cell-merging, are well described within
the framework of thermo-diffusive instabilities and are consistent with
previous numerical studies. These types of dynamics are classified as
"quasi-linear" and characterized by low amplitude cells and may follow the mode
selection mechanism and growth prescribed by the linear theory. Below this
range of Lewis number, highly non-linear effects become prominent and large
amplitude, complex cellular and {\it{seaweed}} dendritic morphologies emerge.


title: 21st Century Computer Architecture

abstract:
  Because most technology and computer architecture innovations were
(intentionally) invisible to higher layers, application and other software
developers could reap the benefits of this progress without engaging in it.
Higher performance has both made more computationally demanding applications
feasible (e.g., virtual assistants, computer vision) and made less demanding
applications easier to develop by enabling higher-level programming
abstractions (e.g., scripting languages and reusable components). Improvements
in computer system cost-effectiveness enabled value creation that could never
have been imagined by the field's founders (e.g., distributed web search
sufficiently inexpensive so as to be covered by advertising links).
  The wide benefits of computer performance growth are clear. Recently,
Danowitz et al. apportioned computer performance growth roughly equally between
technology and architecture, with architecture credited with ~80x improvement
since 1985. As semiconductor technology approaches its "end-of-the-road" (see
below), computer architecture will need to play an increasing role in enabling
future ICT innovation. But instead of asking, "How can I make my chip run
faster?," architects must now ask, "How can I enable the 21st century
infrastructure, from sensors to clouds, adding value from performance to
privacy, but without the benefit of near-perfect technology scaling?". The
challenges are many, but with appropriate investment, opportunities abound.
Underlying these opportunities is a common theme that future architecture
innovations will require the engagement of and investments from innovators in
other ICT layers.


title:
Quickest Change Detection Approach to Optimal Control in Markov Decision
  Processes with Model Changes

abstract:
  Optimal control in non-stationary Markov decision processes (MDP) is a
challenging problem. The aim in such a control problem is to maximize the
long-term discounted reward when the transition dynamics or the reward function
can change over time. When a prior knowledge of change statistics is available,
the standard Bayesian approach to this problem is to reformulate it as a
partially observable MDP (POMDP) and solve it using approximate POMDP solvers,
which are typically computationally demanding. In this paper, the problem is
analyzed through the viewpoint of quickest change detection (QCD), a set of
tools for detecting a change in the distribution of a sequence of random
variables. Current methods applying QCD to such problems only passively detect
changes by following prescribed policies, without optimizing the choice of
actions for long term performance. We demonstrate that ignoring the
reward-detection trade-off can cause a significant loss in long term rewards,
and propose a two threshold switching strategy to solve the issue. A
non-Bayesian problem formulation is also proposed for scenarios where a
Bayesian formulation cannot be defined. The performance of the proposed two
threshold strategy is examined through numerical analysis on a non-stationary
MDP task, and the strategy outperforms the state-of-the-art QCD methods in both
Bayesian and non-Bayesian settings.


title: Harmonic space analysis of pulsar timing array redshift maps

abstract:
  In this paper, we propose a new framework for treating the angular
information in the pulsar timing array response to a gravitational wave
background based on standard cosmic microwave background techniques. We
calculate the angular power spectrum of the all-sky gravitational redshift
pattern induced at the earth for both a single bright source of gravitational
radiation and a statistically isotropic, unpolarized Gaussian random
gravitational wave background. The angular power spectrum is the harmonic
transform of the Hellings & Downs curve. We use the power spectrum to examine
the expected variance in the Hellings & Downs curve in both cases. Finally, we
discuss the extent to which pulsar timing arrays are sensitive to the angular
power spectrum and find that the power spectrum sensitivity is dominated by the
quadrupole anisotropy of the gravitational redshift map.


title: Noise-Enabled Optical Ratchets

abstract:
  In this work we demonstrate single microparticle transport enabled by noise
in a one dimensional optical lattice with periodic symmetric potentials and a
small constant external force. The one dimensional lattice is implemented by
six focused beams with holographic optical tweezers, where a microparticle is
trapped in three dimensions. Transport initiates when dynamical disorder is
added to the diffracted laser power at each trap ($\pm 30\%$) at a fixed
frequency (0 to 35 Hz), while the direction of motion is set by the constant
external force. We find that transport is only achieved within a narrow noise
frequency range, which is consistent with simulations, and the predicted
behavior and observations of noise-induced energy transport in quantum and
classical systems. To our knowledge this is the first direct observation of
noise-assisted transport in a colloidal system.


title: The periplectic Brauer algebra

abstract:
  We study the periplectic Brauer algebra introduced by Moon in the study of
invariant theory for periplectic Lie superalgebras. We determine when the
algebra is quasi-hereditary and, for fields of characteristic zero, describe
the block decomposition. To achieve this, we also develop theories of
Jucys-Murphy elements, Bratteli diagrams, Murphy bases, determine when there
exist quasi-hereditary 1-covers, obtain a BGG reciprocity relation and
determine some decomposition multiplicities of cell modules. As an application,
we determine the blocks in the category of finite dimensional weight modules
over the periplectic Lie superalgebra.


title: An inhomogeneous Lax representation for the Hirota equation

abstract:
  Motivated by recent work on quantum integrable models without U(1) symmetry,
we show that the sl(2) Hirota equation admits a Lax representation with
inhomogeneous terms. The compatibility of the auxiliary linear problem leads to
a new consistent family of Hirota-like equations.


title:
Sparsity-Preserving Difference of Positive Semidefinite Matrix
  Representation of Indefinite Matrices

abstract:
  We consider the problem of writing an arbitrary symmetric matrix as the
difference of two positive semidefinite matrices. We start with simple ideas
such as eigenvalue decomposition. Then, we develop a simple adaptation of the
Cholesky that returns a difference-of-Cholesky representation of indefinite
matrices. Heuristics that promote sparsity can be applied directly to this
modification.


title:
Predicting evolutionary rescue via evolving plasticity in stochastic
  environments

abstract:
  Phenotypic plasticity and its evolution may help evolutionary rescue in a
novel and stressful environment, especially if environmental novelty reveals
cryptic genetic variation that enables the evolution of increased plasticity.
However, the environmental stochasticity ubiquitous in natural systems may
alter these predictions because high plasticity may amplify
phenotype-environment mismatches. Although previous studies have highlighted
this potential detrimental effect of plasticity in stochastic environments,
they have not investigated how it affects extinction risk in the context of
evolutionary rescue and with evolving plasticity. We investigate this question
here by integrating stochastic demography with quantitative genetic theory in a
model with simultaneous change in the mean and predictability (temporal
autocorrelation) of the environment. We develop an approximate prediction of
long-term persistence under the new pattern of environmental fluctuations, and
compare it with numerical simulations for short- and long-term extinction risk.
We find that reduced predictability increases extinction risk and reduces
persistence because it increases stochastic load during rescue. This
understanding of how stochastic demography, phenotypic plasticity, and
evolution interact when evolution acts on cryptic genetic variation revealed in
a novel environment can inform expectations for invasions, extinctions, or the
emergence of chemical resistance in pests.


title: Saturating Splines and Feature Selection

abstract:
  We extend the adaptive regression spline model by incorporating saturation,
the natural requirement that a function extend as a constant outside a certain
range. We fit saturating splines to data using a convex optimization problem
over a space of measures, which we solve using an efficient algorithm based on
the conditional gradient method. Unlike many existing approaches, our algorithm
solves the original infinite-dimensional (for splines of degree at least two)
optimization problem without pre-specified knot locations. We then adapt our
algorithm to fit generalized additive models with saturating splines as
coordinate functions and show that the saturation requirement allows our model
to simultaneously perform feature selection and nonlinear function fitting.
Finally, we briefly sketch how the method can be extended to higher order
splines and to different requirements on the extension outside the data range.


title:
The Mass Distribution of the Unusual Merging Cluster Abell 2146 from
  Strong Lensing

abstract:
  Abell 2146 consists of two galaxy clusters that have recently collided close
to the plane of the sky, and it is unique in showing two large shocks on
$\textit{Chandra X-ray Observatory}$ images. With an early stage merger,
shortly after first core passage, one would expect the cluster galaxies and the
dark matter to be leading the X-ray emitting plasma. In this regard, the
cluster Abell 2146-A is very unusual in that the X-ray cool core appears to
lead, rather than lag, the Brightest Cluster Galaxy (BCG) in their
trajectories. Here we present a strong lensing analysis of multiple image
systems identified on $\textit{Hubble Space Telescope}$ images. In particular,
we focus on the distribution of mass in Abell 2146-A in order to determine the
centroid of the dark matter halo. We use object colours and morphologies to
identify multiple image systems; very conservatively, four of these systems are
used as constraints on a lens mass model. We find that the centroid of the dark
matter halo, constrained using the strongly lensed features, is coincident with
the BCG, with an offset of $\approx$ 2 kpc between the centres of the dark
matter halo and the BCG. Thus from the strong lensing model, the X-ray cool
core also leads the centroid of the dark matter in Abell 2146-A, with an offset
of $\approx$ 30 kpc.


title: Hamiltonian formulation of teleparallel gravity

abstract:
  The Hamiltonian formulation of the teleparallel equivalent of general
relativity (TEGR) is developed from an ordinary second-order Lagrangian, which
is written as a quadratic form of the coefficients of anholonomy of the
orthonormal frames (vielbeins). We analyze the structure of eigenvalues of the
multi-index matrix entering the (linear) relation between canonical velocities
and momenta to obtain the set of primary constraints. The canonical Hamiltonian
is then built with the Moore-Penrose pseudo-inverse of that matrix. The set of
constraints, including the subsequent secondary constraints, completes a first
class algebra. This means that all of them generate gauge transformations. The
gauge freedoms are basically the diffeomorphisms, and the (local) Lorentz
transformations of the vielbein. In particular, the ADM algebra of general
relativity is recovered as a sub-algebra.


title: Adaptive Control Strategy for Constant Optical Flow Divergence Landing

abstract:
  Bio-inspired methods can provide efficient solutions to perform autonomous
landing for Micro Air Vehicles (MAVs). Flying insects such as honeybees perform
vertical landings by keeping flow divergence constant. This leads to an
exponential decay of both height and vertical velocity, and allows for smooth
and safe landings. However, the presence of noise and delay in obtaining flow
divergence estimates will cause instability of the landing when the control
gains are not adapted to the height. In this paper, we propose a strategy that
deals with this fundamental problem of optical flow control. The key to the
strategy lies in the use of a recent theory that allows the MAV to see distance
by means of its control instability. At the start of a landing, the MAV detects
the height by means of an oscillating movement and sets the control gains
accordingly. Then, during descent, the gains are reduced exponentially, with
mechanisms in place to reduce or increase the gains if the actual trajectory
deviates too much from an ideal constant divergence landing. Real-world
experiments demonstrate stable landings of the MAV in both indoor and windy
outdoor environments.


title:
Poisson and near-symplectic structures on generalized wrinkled
  fibrations in dimension 6

abstract:
  We show that generalized broken fibrations in arbitrary dimensions admit
rank-2 Poisson structures compatible with the fibration structure. After
extending the notion of wrinkled fibration to dimension 6 we prove that these
wrinkled fibrations also admit compatible rank-2 Poisson structures. In the
cases with indefinite singularities we can provide these wrinkled fibrations in
dimension 6 with near-symplectic structures.


title: A statistical state dynamics approach to wall-turbulence

abstract:
  This paper reviews results from the study of wall-bounded turbulent flows
using statistical state dynamics (SSD) that demonstrate the benefits of
adopting this perspective for understanding turbulence in wall-bounded shear
flows. The SSD approach used in this work employs a second-order closure which
isolates the interaction between the streamwise mean and the equivalent of the
perturbation covariance. This closure restricts nonlinearity in the SSD to that
explicitly retained in the streamwise constant mean together with nonlinear
interactions between the mean and the perturbation covariance. This dynamical
restriction, in which explicit perturbation-perturbation nonlinearity is
removed from the perturbation equation, results in a simplified dynamics
referred to as the restricted nonlinear (RNL) dynamics. RNL systems in which an
ensemble of a finite number of realizations of the perturbation equation share
the same mean flow provide tractable approximations to the equivalently
infinite ensemble RNL system. The infinite ensemble system, referred to as the
S3T, introduces new analysis tools for studying turbulence. The RNL with a
single ensemble member can be alternatively viewed as a realization of RNL
dynamics. RNL systems provide computationally efficient means to approximate
the SSD, producing self-sustaining turbulence exhibiting qualitative features
similar to those observed in direct numerical simulations (DNS) despite its
greatly simplified dynamics. Finally, we show that RNL turbulence can be
supported by as few as a single streamwise varying component interacting with
the streamwise constant mean flow and that judicious selection of this
truncated support, or "band-limiting", can be used to improve quantitative
accuracy of RNL turbulence. The results suggest that the SSD approach provides
new analytical and computational tools allowing new insights into
wall-turbulence.


title: Rigidity of quadratic Poisson tori

abstract:
  We prove a rigidity theorem for the Poisson automorphisms of the function
fields of tori with quadratic Poisson structures over fields of characteristic
0. It gives an effective method for classifying the full Poisson automorphism
groups of ${\mathbb{N}}$-graded connected cluster algebras equipped with
Gekhtman-Shapiro-Vainshtein Poisson structures. Based on this, we classify the
groups of algebraic Poisson automorphisms of the open Schubert cells of the
full flag varieties of semisimple algebraic groups over fields of
characteristic 0, equipped with the standard Poisson structures. Their
coordinate rings can be identified with the semiclassical limits of the
positive parts $U_q({\mathfrak{n}}_+)$ of the quantized universal enveloping
algebras of semisimple Lie algebras, and the last result establishes a Poisson
version of the Andruskiewitsch-Dumas conjecture on ${\mathrm{Aut}}
U_q({\mathfrak{n}}_+)$.


title: Simulation of the IEEE 1588 Precision Time Protocol in OMNeT++

abstract:
  Real-time systems rely on a distributed global time base. As any physical
clock device suffers from noise, it is necessary to provide some kind of clock
synchronization to establish such a global time base. Different clock
synchronization methods have been invented for individual application domains.
The Precision Time Protocol (PTP), which is specified in IEEE 1588, is another
interesting option. It targets local networks, where it is acceptable to assume
small amounts of hardware support, and promises sub-microsecond precision. PTP
provides many different implementation and configuration options, and thus the
Design Space Exploration (DSE) is challenging. In this paper we discuss the
implementation of realistic clock noise and its synchronization via PTP in
OMNeT++. The components presented in this paper are intended to assist
engineers with the configuration of PTP networks.


title: Spatio-Temporal Sentiment Hotspot Detection Using Geotagged Photos

abstract:
  We perform spatio-temporal analysis of public sentiment using geotagged photo
collections. We develop a deep learning-based classifier that predicts the
emotion conveyed by an image. This allows us to associate sentiment with place.
We perform spatial hotspot detection and show that different emotions have
distinct spatial distributions that match expectations. We also perform
temporal analysis using the capture time of the photos. Our spatio-temporal
hotspot detection correctly identifies emerging concentrations of specific
emotions and year-by-year analyses of select locations show there are strong
temporal correlations between the predicted emotions and known events.


title:
Joint CTC-Attention based End-to-End Speech Recognition using Multi-task
  Learning

abstract:
  Recently, there has been an increasing interest in end-to-end speech
recognition that directly transcribes speech to text without any predefined
alignments. One approach is the attention-based encoder-decoder framework that
learns a mapping between variable-length input and output sequences in one step
using a purely data-driven method. The attention model has often been shown to
improve the performance over another end-to-end approach, the Connectionist
Temporal Classification (CTC), mainly because it explicitly uses the history of
the target character without any conditional independence assumptions. However,
we observed that the performance of the attention has shown poor results in
noisy condition and is hard to learn in the initial training stage with long
input sequences. This is because the attention model is too flexible to predict
proper alignments in such cases due to the lack of left-to-right constraints as
used in CTC. This paper presents a novel method for end-to-end speech
recognition to improve robustness and achieve fast convergence by using a joint
CTC-attention model within the multi-task learning framework, thereby
mitigating the alignment issue. An experiment on the WSJ and CHiME-4 tasks
demonstrates its advantages over both the CTC and attention-based
encoder-decoder baselines, showing 5.4-14.6% relative improvements in Character
Error Rate (CER).


title: Competing Structures in (In,Ga)Se and (In,Ga)2Se3 Semiconductors

abstract:
  The electronic structure of four polytypes (beta, gamma, delta and epsilon)
of hexagonal GaSe and InSe is calculated from first principles, using the
WIEN2k and VASP codes and PBEsol prescription for the exchange-correlation
potential, aiming specifically at elucidating the crystallographic parameters
and comparing the energy placement of corresponding competing structures.
Further on, the compounds with different composition of the same constituents,
namely the ordered-vacancies systems Ga2Se3 and In2Se3, were subject to a
similar study, of which the relaxed crystal structure data for three different
phases is reported. Comparison is done with the nomi- nal wurtzite structure
over which the cation vacancies are introduced, and the relaxation pattern
discussed.


title: Homoclinical structure of SICNNs with rectangular input currents

abstract:
  Shunting inhibitory cellular neural networks (SICNNs) with continuous as well
as discontinuous external inputs are investigated. The descriptions of
homoclinic and heteroclinic motions are provided in the functional sense for
the multidimensional dynamics of SICNNs, and it is demonstrated that the
networks under investigation exhibit such motions. Homoclinic and heteroclinic
outputs that are asymptotic to quasi-periodic outputs are illustrated.


title:
BTW model with probabilistically nonuniform distribution of particles
  from the unstable sites

abstract:
  The two dimensional BTW model of SOC, with probabilistically nonuniform
distribution of particles among the nearest neighbouring sites, is studied by
computer simulation. When the value of height variable of a particular site
reaches the critical value (z c = 4), the value of height variable of that site
is reduced by four units by distributing four particles among the four nearest
neighbouring sites. In this paper, it is considered that, two particles are
distributed equally among the two nearest neighbouring sites along X-axis.
However, the distribution of other two particles along Y- axis, is
probabilistically nonuniform. The variation of spatial average of the height
variable with time is studied. In the SOC state, the distribution of avalanche
sizes and durations is obtained. The total number of topplings occured during
the stipulated time of evolution is also calculated.


title: Can the Sierpinski graph be embedded in the Hamming graph?

abstract:
  The (generalized & expanded) Sierpinski graph, S(n,m), and the Hamming graph
have the same set of vertices (n-tuples from the set {0,1,...,m-1}. The edges
of both are (unordered) pairs of vertices. Each set of edges is defined by a
different property so that neither is contained in the other. We ask if there
is a subgraph of the Hamming graph isomorphic to the Sierpinski graph and show
that the answer is yes. The embedding map leads to number of variations and
ramifications. Among them is a simple algebraic formula for the solution of the
Tower of Hanoi puzzle.


title: Proper Orientations of Planar Bipartite Graphs

abstract:
  An orientation of a graph $G$ is proper if any two adjacent vertices have
different indegrees. The proper orientation number $\overrightarrow{\chi}(G)$
of a graph $G$ is the minimum of the maximum indegree, taken over all proper
orientations of $G$. In this paper, we show that a connected bipartite graph
may be properly oriented even if we are only allowed to control the orientation
of a specific set of edges, namely, the edges of a spanning tree and all the
edges incident to one of its leaves. As a consequence of this result, we prove
that 3-connected planar bipartite graphs have proper orientation number at most
6. Additionally, we give a short proof that $\overrightarrow{\chi}(G) \leq 4$,
when $G$ is a tree and this proof leads to a polynomial-time algorithm to
proper orient trees within this bound.


title:
A Novel GPU-based Parallel Implementation Scheme and Performance
  Analysis of Robot Forward Dynamics Algorithms

abstract:
  We propose a novel unifying scheme for parallel implementation of articulated
robot dynamics algorithms. It is based on a unified Lie group notation for
deriving the equations of motion of articulated robots, where various
well-known forward algorithms differ only by their joint inertia matrix
inversion strategies. This new scheme leads to a unified abstraction of
state-of-the-art forward dynamics algorithms into combinations of block
bi-diagonal and/or block tri-diagonal systems, which may be efficiently solved
by parallel all-prefix-sum operations (scan) and parallel odd-even elimination
(OEE) respectively. We implement the proposed scheme on a Nvidia CUDA GPU
platform for the comparative study of three algorithms, namely the hybrid
articulated-body inertia algorithm (ABIA), the parallel joint space inertia
inversion algorithm (JSIIA) and the constrained force algorithm (CFA), and the
performances are analyzed.


title: A zero-one Law for improvements to Dirichlet's Theorem

abstract:
  We give an integrability condition on a function $\psi$ guaranteeing that for
almost all (or almost no) $x\in\mathbb{R}$, the system $|qx-p|\leq \psi(t)$,
$|q|<t$ is solvable in $p\in \mathbb{Z}$, $q\in \mathbb{Z}\smallsetminus \{0\}$
for sufficiently large $t$. Along the way, we characterize such $x$ in terms of
the growth of their continued fraction entries, and we establish that
Dirichlet's Approximation Theorem is sharp in a very strong sense.
Higher-dimensional generalizations are discussed at the end of the paper.


title:
The Validity of the Weizsacker-Williams Approximation and the Analysis
  of Beam Dump Experiments: Production of a New Scalar Boson

abstract:
  Beam dump experiments have been used to search for new particles with null
results interpreted in terms of limits on masses $m_\phi$ and coupling
constants $\epsilon$. However these limits have been obtained by using
approximations [including the Weizs\"{a}cker-Williams (WW) approximation] or
Monte-Carlo simulations. We display methods, using a new scalar boson as an
example, to obtain the cross section and the resulting particle production
numbers without using approximations or Monte-Carlo simulations. We show that
the approximations cannot be used to obtain accurate values of cross sections.
The corresponding exclusion plots differ by substantial amounts when seen on a
linear scale. In the event of a discovery, we generate pseudodata (assuming
given values of $m_\phi$ and $\epsilon$) in the currently allowed regions of
parameter space. The use of approximations to analyze the pseudodata for the
future experiments is shown to lead to considerable errors in determining the
parameters. Furthermore, a new region of parameter space can be explored
without using one of the common approximations, $m_\phi\gg m_e$. Our method can
be used as a consistency check for Monte-Carlo simulations.


title: Deep Learning for Video Classification and Captioning

abstract:
  Accelerated by the tremendous increase in Internet bandwidth and storage
space, video data has been generated, published and spread explosively,
becoming an indispensable part of today's big data. In this paper, we focus on
reviewing two lines of research aiming to stimulate the comprehension of videos
with deep learning: video classification and video captioning. While video
classification concentrates on automatically labeling video clips based on
their semantic contents like human actions or complex events, video captioning
attempts to generate a complete and natural sentence, enriching the single
label as in video classification, to capture the most informative dynamics in
videos. In addition, we also provide a review of popular benchmarks and
competitions, which are critical for evaluating the technical progress of this
vibrant field.


title:
Nonparametric Bayesian Topic Modelling with the Hierarchical Pitman-Yor
  Processes

abstract:
  The Dirichlet process and its extension, the Pitman-Yor process, are
stochastic processes that take probability distributions as a parameter. These
processes can be stacked up to form a hierarchical nonparametric Bayesian
model. In this article, we present efficient methods for the use of these
processes in this hierarchical context, and apply them to latent variable
models for text analytics. In particular, we propose a general framework for
designing these Bayesian models, which are called topic models in the computer
science community. We then propose a specific nonparametric Bayesian topic
model for modelling text from social media. We focus on tweets (posts on
Twitter) in this article due to their ease of access. We find that our
nonparametric model performs better than existing parametric models in both
goodness of fit and real world applications.


title:
Multisource thermal model to the transverse momentum spectra in pp
  collisions at RHIC and LHC energies

abstract:
  In this paper, an improved multi-source thermal model is used to analyze the
transverse momentum spectra in $pp$ collisions at high energies ranging from
$\sqrt{\mathrm{\it s_{NN}}}$ = 62.4 GeV to 7 TeV. We give a detailed comparison
between the theoretical results and experimental data at RHIC and LHC energies.
It is shown that the excitation factors of emission sources depend linearly on
ln$\sqrt{\mathrm{\it s_{NN}}}$ in the framework. Based on the variation
regularity of the source-excitation factors, transverse momentum spectra are
predicted in $pp$ collisions at higher energies, potential future $pp$
colliders operating at $\sqrt{\mathrm{\it s_{NN}}}$ = 33 and 100 TeV.


title: An Elmendorf-Piacenza type Theorem for Actions of Monoids

abstract:
  Let $M$ be a monoid and $G:\mathbf{Mon} \to \mathbf{Grp}$ be the group
completion functor from monoids to groups. Given a collection $\mathcal{Z}$ of
submonoids of $M$ and for each $N\in \mathcal{Z}$ a collection $\mathcal{Y}_N$
of subgroups of $G(N)$, we construct a model structure on the category of
$M$-spaces and $M$-equivariant maps, in which weak equivalences and fibrations
are determined by the standard $\mathcal{Y}_N$-model structures on
$G(N)$-spaces for all $N\in \mathcal{Z}$. We also show that there is a small
category $\mathsf{O}_(\mathcal{Z},\mathcal{Y})$ such that, under mild
conditions on $\mathcal{Z}$ and $\mathcal{Y}_N$'s, the projective model
structure on the category of contravariant
$\mathsf{O}_(\mathcal{Z},\mathcal{Y})$-diagrams of spaces is Quillen equivalent
to our model structure. In particular, we prove a theorem generalizing
Elmendorf-Piacenza Theorem to actions of monoids.


title: Five-loop massive tadpoles

abstract:
  We provide an update on a long-term project that aims at evaluating massive
vacuum integrals at the five-loop frontier, with high precision and in various
space-time dimensions. A number of applications are sketched, mainly concerning
the determination of anomalous dimensions, for quantum field theories in four,
three and two dimensions.


title:
Observation of Magnetic reconnection at a 3D null point associated with
  a solar eruption

abstract:
  Magnetic null has long been recognized as a special structure serving as a
preferential site for magnetic reconnection (MR). However, the direct
observational study of MR at null-points is largely lacking. Here, we show the
observations of MR around a magnetic null associated with an eruption that
resulted in an M1.7 flare and a coronal mass ejection. The GOES X- ray profile
of the flare exhibited two peaks at 02:23 UT and 02:40 UT on 2012 November 8,
respectively. Based on the imaging observations, we find that the first and
also primary X- ray peak was originated from MR in the current sheet underneath
the erupting magnetic flux rope (MFR). On the other hand, the second and also
weaker X-ray peak was caused by MR around a null-point located above the
pre-eruption MFR. The interaction of the null-point and the erupting MFR can be
described as a two-step process. During the first step, the erupting and fast
expanding MFR passed through the null-point, resulting in a significant
displacement of the magnetic field surrounding the null. During the second
step, the displaced magnetic field started to move back, resulting in a
converging inflow and subsequently the MR around the null. The null-point
reconnection is a different process from the current sheet reconnection in this
flare; the latter is the cause of the main peak of the flare, while the former
is the cause of the secondary peak of the flare and the conspicuous high-lying
cusp structure.


title: Modules close to SSP- and SIP-modules

abstract:
  In this paper, we investigate some properties of SIP, SSP and CS-Rickart
modules. We give equivalent conditions for SIP and SSP modules; establish
connections between the class of semisimple artinian rings and the class of SIP
rings. It shows that $R$ is a semisimple artinian ring if and only if $R_R$ is
SIP and every right $R$-module has a SIP-cover. We also prove that $R$ is a
semiregular ring and $J(R) = Z(R_R)$ if only if every finitely generated
projective module is a SIP-CS module which is also a $C2$ module.


title: Krigings Over Space and Time Based on Latent Low-Dimensional Structures

abstract:
  We propose a new approach to represent nonparametrically the linear
dependence structure of a spatio-temporal process in terms of latent common
factors. Though it is formally similar to the existing reduced rank
approximation methods (Section 7.1.3 of Cressie and Wikle, 2011), the
fundamental difference is that the low-dimensional structure is completely
unknown in our setting, which is learned from the data collected irregularly
over space but regularly over time. Furthermore a graph Laplacian is
incorporated in the learning in order to take the advantage of the continuity
over space, and a new aggregation method via randomly partitioning space is
introduced to improve the efficiency. We do not impose any stationarity
conditions over space either, as the learning is facilitated by the
stationarity in time. Krigings over space and time are carried out based on the
learned low-dimensional structure, which is scalable to the cases when the data
are taken over a large number of locations and/or over a long time period.
Asymptotic properties of the proposed methods are established. Illustration
with both simulated and real data sets is also reported.


title:
Gallium Bismuth Halides GaBi-X2 (X= I, Br, Cl) Monolayers with Distorted
  Hexagonal Framework: Novel Room-Temperature Quantum Spin Hall Insulators

abstract:
  Quantum Spin Hall (QSH) insulators with a large topologically nontrivial bulk
gap are crucial for future applications of the QSH effect. Among these, group
III-V monolayers and their halides with chair structure (regular hexagonal
framework, RHF) were widely studied. Using first-principles calculations, we
propose a new structure model for the functionalized group III-V monolayers,
which consist of rectangular GaBi-X2 (X=I, Br, Cl) monolayers with a distorted
hexagonal framework (DHF). These structures have a much lower energy than the
GaBi-X2 monolayers with chair structure. Remarkably, the DHF GaBi-X2 monolayers
are all QSH insulators, which exhibit sizeable nontrivial band gaps ranging
from 0.17 eV to 0.39 eV. Those band gaps can be widely tuned by applying
different spin-orbit coupling (SOC) strengths, resulting in a distorted Dirac
cone.


title:
Twitter-Network Topic Model: A Full Bayesian Treatment for Social
  Network and Text Modeling

abstract:
  Twitter data is extremely noisy -- each tweet is short, unstructured and with
informal language, a challenge for current topic modeling. On the other hand,
tweets are accompanied by extra information such as authorship, hashtags and
the user-follower network. Exploiting this additional information, we propose
the Twitter-Network (TN) topic model to jointly model the text and the social
network in a full Bayesian nonparametric way. The TN topic model employs the
hierarchical Poisson-Dirichlet processes (PDP) for text modeling and a Gaussian
process random function model for social network modeling. We show that the TN
topic model significantly outperforms several existing nonparametric models due
to its flexibility. Moreover, the TN topic model enables additional informative
inference such as authors' interests, hashtag analysis, as well as leading to
further applications such as author recommendation, automatic topic labeling
and hashtag suggestion. Note our general inference framework can readily be
applied to other topic models with embedded PDP nodes.


title:
Central Runge-Kutta discontinuous Galerkin methods for the special
  relativistic hydrodynamics

abstract:
  This paper developes Runge-Kutta $P^K$-based central discontinuous Galerkin
(CDG) methods with WENO limiter to the one- and two-dimensional special
relativistic hydrodynamical (RHD) equations, $K=1,2,3$. Different from the
non-central DG methods, the \CDG{} have to find two approximate solutions
defined on mutually dual meshes. For each mesh, the CDG approximate solutions
on its dual mesh are used to calculate the flux values in the cell and on the
cell boundary so that the approximate solutions on mutually dual meshes are
coupled with each other, and the use of numerical flux may be avoided. The WENO
limiter is adaptively implemented via two steps: the "troubled" cells are first
identified by using a modified TVB minmod function, and then the WENO technique
is used to locally reconstruct new polynomials of degree $(2K+1)$ replacing the
CDG solutions inside the "troubled' cells by the cell average values of the CDG
solutions in the neighboring cells as well as the original cell averages of the
"troubled" cells. Because the WENO limiter is only employed for finite
"troubled" cells, the computational cost can be as little as possible. The
accuracy of the CDG without the numerical dissipation is analyzed and
calculation of the flux integrals over the cells is also addressed. Several
test problems in one and two dimensions are solved by using our \CDG{} with
WENO limiter. The computations demonstrate that our methods are stable,
accurate, and robust in solving complex RHD problems.


title: Injectivity of generalized Wronski maps

abstract:
  We study linear projections on Pluecker space whose restriction to the
Grassmannian is a non-trivial branched cover. When an automorphism of the
Grassmannian preserves the fibers, we show that the Grassmannian is necessarily
of m-dimensional linear subspaces in a symplectic vector space of dimension 2m,
and the linear map is the Lagrangian involution. The Wronski map for a
self-adjoint linear differential operator and pole placement map for symmetric
linear systems are natural examples.


title: Black Hole Quantum Vacuum Polarization in Higher Dimensions

abstract:
  The goal of this paper is to extend to higher dimensionality the methods and
computations of vacuum polarization effects in black hole spacetimes. We focus
our attention on the case of five dimensional Schwarzschild-Tangherlini black
holes, for which we adapt the general method initially developed by Candelas
and later refined by Anderson and others. We make use of point splitting
regularization and of the WKB approximation to extract the divergences occuring
in the coincidence limit of the Green function and, after calculating the
counter-terms using the Schwinger - De Witt expansion, we explicitly prove the
cancellation of the divergences and the regularity of the vacuum polarization
once counter-terms are added up. We finally handle numerically the renormalized
expression of the vacuum polarization. As a check on the method we also prove
the regularity of the vacuum polarization in the six dimensional case in the
large mass limit.


title:
Particle-Filter-Enabled Real-Time Sensor Fault Detection Without a Model
  of Faults

abstract:
  We are experiencing an explosion in the amount of sensors measuring our
activities and the world around us. These sensors are spread throughout the
built environment and can help us perform state estimation and control of
related systems, but they are often built and/or maintained by third parties or
system users. As a result, by outsourcing system measurement to third parties,
the controller must accept their measurements without being able to directly
verify the sensors' correct operation. Instead, detection and rejection of
measurements from faulty sensors must be done with the raw data only. Towards
this goal, we present a method of detecting possibly faulty behavior of
sensors. The method does not require that the control designer have any model
of faulty sensor behavior. As we discuss, it turns out that the widely-used
particle filter state estimation algorithm provides the ingredients necessary
for a hypothesis test against all ranges of correct operating behavior,
obviating the need for a fault model to compare measurements. We demonstrate
the applicability of our method by demonstrating its ability to reject faulty
measurements and improve state estimation accuracy in a nonlinear vehicle
traffic model without information of generated faulty measurements'
characteristics. In our test, we correctly identify nearly 90% of measurements
as faulty or non-faulty without having any fault model. This leads to only a 3%
increase in state estimation error over a theoretical 100%-accurate fault
detector.


title:
Dispersive Jaynes-Cummings Hamiltonian describing a two-level atom
  interacting with a two-level single mode field

abstract:
  We investigate the time evolution of statistical properties of a single mode
radiation field after its interaction with a two-level atom. The entire system
is described by a dispersive Jaynes-Cummings Hamiltonian assuming the atomic
state evolving from an initial superposition of its excited and ground states,
$\vert e\rangle +\vert g\rangle ,$ and the field evolving from an initial
superposition of two excited levels, $\vert n_{1}\rangle+ \vert n_{2}\rangle$.
It is found that the field evolution is periodic, the period depending on the
ratio $n_{2}/n_{1}.$ The energy excitation oscillates between these two states
and the statististics can be either sub- or super-Poissonian, depending on the
values $n_{1},$ $n_{2}$.


title: Manipulation of magnetic Skyrmions with a Scanning Tunneling Microscope

abstract:
  The dynamics of a single magnetic Skyrmion in an atomic spin system under the
influence of Scanning Tunneling Microscope is investigated by computer
simulations solving the Landau-Lifshitz-Gilbert equation. Two possible
scenarios are described: manipulation with aid of a spin-polarized tunneling
current and by an electric field created by the scanning tunneling microscope.
The dynamics during the creation and annihilation process is studied and the
possibility to move single Skyrmions is showed.


title: Environment-Protected Solid State Based Distributed Charge Qubit

abstract:
  A novel solid state based charge qubit is presented. The system consists of a
one-dimensional wire with a pair of qubits embedded at its center. It is shown
that the system supports collective states localized in the left and right
sides of the wire and therefore, as a whole, performs as a single qubit. The
couplings between the ground and excited states of the two central qubits are
inversely proportional making them fully asynchronized and allowing for
coherent manipulation and gate operations. Initialization and measurement
devices, such as leads and charge detectors, connected to the edges of the wire
are modeled by a continuum of energy states. The coupling to the continuum is
discussed using the effective non-Hermitian Hamiltonian. At weak continuum
coupling, all internal states uniformly acquire small decay widths. This
changes dramatically as the coupling strength increases: the width distribution
undergoes a sharp restructuring and is no longer uniformly divided among the
eigenstates. Two broad resonances localized at the ends of the wire are formed.
These superradiant states (analogous to Dicke states in quantum optics),
effectively protect the remaining internal states from decaying into the
continuum and hence increase the lifetime of the qubit. Environmental noise is
introduced by considering random Gaussian fluctuations of electronic energies.
The interplay between decoherence and superradiance is studied by solving the
stochastic Liouville equation. In addition to increasing the lifetime, the
emergence of the superradiant states increases the qubit coherence.


title: Simulating single photons with realistic photon sources

abstract:
  Quantum information processing provides remarkable advantages over its
classical counterpart. Quantum optical systems are proved to be sufficient for
realizing general quantum tasks, which however often rely on single photon
sources. In practice, imperfect single photon sources, such as weak coherent
state source, are used instead, which will inevitably limit the power in
demonstrating quantum effects. For instance, with imperfect photon sources, the
key rate of the BB84 quantum key distribution protocol will be very low, which
fortunately can be resolved by utilizing the decoy state method. As a
generalization, we investigate an efficient way to simulate single photons with
imperfect ones to an arbitrary desired accuracy when the number of photonic
inputs is small. Based on this simulator, we can thus replace the tasks that
involve only a few single photon inputs with the ones that only make use of
imperfect photon sources. In addition, our method also provides a quantum
simulator to quantum computation based on quantum optics. In the main context,
we take phase randomized coherent state as an example for analysis. A general
photon source applies similarly and may provide some further advantages for
certain tasks.


title: Non-formality of the odd dimensional framed little balls operads

abstract:
  We prove that the chain operad of the framed little balls (or disks) operad
is not formal as a non-symmetric operad over the rationals if the dimension of
their balls is odd and greater than 4.


title:
Numerical search for a potential planet sculpting the young disc of HD
  115600

abstract:
  Radial and azimuthal features (such as disc offsets and eccentric rings) seen
in high resolution images of debris discs, provide us with the unique
opportunity of finding potential planetary companions which betray their
presence by gravitationally sculpting such asymmetric features. The young
debris disc around HD 115600, imaged recently by the Gemini Planet Imager, is
such a disc with an eccentricity 0.1<e<0.2 and a projected offset from the star
of 4 AU. Using our modified N-body code which incorporates radiation forces, we
firstly aim to determine the orbit of a hidden planetary companion potentially
responsible for shaping the disc. We run a suite of simulations covering a
broad range of planetary parameters using a Monte Carlo Markov Chain sampling
method and create synthetic images from which we extract the geometric disc
parameters to be compared with the observed and model-derived quantities. We
then repeat the study using a traditional grid to explore the planetary
parameter space and aim secondly to compare the efficiency of both sampling
methods. We find a planet of 7.8 Jupiter mass orbiting at 30 AU with an
eccentricity of e = 0.2 to be the best fit to the observations of HD 115600.
Technically, such planet has a contrast detectable by direct imaging, however
the system's orientation does not favour such detection. In this study, at
equal number of explored planetary configurations, the Monte Carlo Markov Chain
not only converges faster but provides a better fit than a traditional grid.


title: Measurement of the B^0 -> D^*- pi^+ pi^- pi^+ branching fraction

abstract:
  Using a sample of (470.9 +- 2.8) x 10^6 BB-bar pairs, we measure the decay
branching fraction B(B^0 -> D^*- pi^+ pi^- pi^+) = (7.26 +- 0.11 +- 0.31) x
10^-3, where the first uncertainty is statistical and the second is systematic.
Our measurement will be helpful in studies of lepton universality by measuring
B(B^0 -> D^*- tau^+ nu_tau) using tau^+ -> pi^+ pi^- pi^+ nu-bar_tau decays,
normalized to B(B^0 -> D^*- pi^+ pi^- pi^+.


title:
Fully pseudospectral solution of the conformally invariant wave equation
  near the cylinder at spacelike infinity. II: Schwarzschild background

abstract:
  It has recently been demonstrated (Class. Quantum Grav. 31, 085010, 2014)
that the conformally invariant wave equation on a Minkowski background can be
solved with a fully pseudospectral numerical method. In particular, it is
possible to include spacelike infinity into the numerical domain, which is
appropriately represented as a cylinder, and highly accurate numerical
solutions can be obtained with a moderate number of gridpoints. In this paper,
we generalise these considerations to the spherically-symmetric wave equation
on a Schwarzschild background. In the Minkowski case, a logarithmic singularity
at the future boundary is present at leading order, which can easily be removed
to obtain completely regular solutions. An important new feature of the
Schwarzschild background is that the corresponding solutions develop
logarithmic singularities at infinitely many orders. This behaviour seems to be
characteristic for massive space-times. In this sense this work is indicative
of properties of the solutions of the Einstein equations near spatial infinity.
The use of fully pseudospectral methods allows us to still obtain very accurate
numerical solutions, and the convergence properties of the spectral
approximations reveal details about the singular nature of the solutions on
spacelike and null infinity. These results seem to be impossible to achieve
with other current numerical methods. Moreover, we describe how to impose
conditions on the asymptotic behaviour of initial data so that the
leading-order logarithmic terms are avoided, which further improves the
numerical accuracy.


title:
Decoupled Asynchronous Proximal Stochastic Gradient Descent with
  Variance Reduction

abstract:
  In the era of big data, optimizing large scale machine learning problems
becomes a challenging task and draws significant attention. Asynchronous
optimization algorithms come out as a promising solution. Recently, decoupled
asynchronous proximal stochastic gradient descent (DAP-SGD) is proposed to
minimize a composite function. It is claimed to be able to off-loads the
computation bottleneck from server to workers by allowing workers to evaluate
the proximal operators, therefore, server just need to do element-wise
operations. However, it still suffers from slow convergence rate because of the
variance of stochastic gradient is nonzero. In this paper, we propose a faster
method, decoupled asynchronous proximal stochastic variance reduced gradient
descent method (DAP-SVRG). We prove that our method has linear convergence for
strongly convex problem. Large-scale experiments are also conducted in this
paper, and results demonstrate our theoretical analysis.


title: Most recent changepoint detection in Panel data

abstract:
  Detecting recent changepoints in time-series can be important for short-term
prediction, as we can then base predictions just on the data since the
changepoint. In many applications we have panel data, consisting of many
related univariate time-series. We present a novel approach to detect sets of
most recent changepoints in such panel data which aims to pool information
across time-series, so that we preferentially infer a most recent change at the
same time-point in multiple series. Our approach is computationally efficient
as it involves analysing each time-series independently to obtain a profile
likelihood like quantity that summarises the evidence for the series having
either no change or a specific value for its most recent changepoint. We then
post-process this output from each time-series to obtain a potentially small
set of times for the most recent changepoints, and, for each time, the set of
series which has their most recent changepoint at that time. We demonstrate the
usefulness of this method on two data sets: forecasting events in a
telecommunications network and inference about changes in the net asset ratio
for a panel of US firms.


title:
Asymptotic properties of adaptive group Lasso for sparse reduced rank
  regression

abstract:
  This paper studies the asymptotic properties of the penalized least squares
estimator using an adaptive group Lasso penalty for the reduced rank
regression. The group Lasso penalty is defined in the way that the regression
coefficients corresponding to each predictor are treated as one group. It is
shown that under certain regularity conditions, the estimator can achieve the
minimax optimal rate of convergence. Moreover, the variable selection
consistency can also be achieved, that is, the relevant predictors can be
identified with probability approaching one. In the asymptotic theory, the
number of response variables, the number of predictors, and the rank number are
allowed to grow to infinity with the sample size.


title:
Correctness Guarantees for the Composition of Lane Keeping and Adaptive
  Cruise Control

abstract:
  This paper develops a control approach with correctness guarantees for the
simultaneous operation of lane keeping and adaptive cruise control. The safety
specifications for these driver assistance modules are expressed in terms of
set invariance. Control barrier functions are used to design a family of
control solutions that guarantee the forward invariance of a set, which implies
satisfaction of the safety specifications. The control barrier functions are
synthesized through a combination of sum-of-squares program and physics-based
modeling and optimization. A real-time quadratic program is posed to combine
the control barrier functions with the performance-based controllers, which can
be either expressed as control Lyapunov function conditions or as black-box
legacy controllers. In both cases, the resulting feedback control guarantees
the safety of the composed driver assistance modules in a formally correct
manner. Importantly, the quadratic program admits a closed-form solution that
can be easily implemented. The effectiveness of the control approach is
demonstrated by simulations in the industry-standard vehicle simulator Carsim.


title:
Neumann problem for p-Laplace equation in metric spaces using a
  variational approach: existence, boundedness, and boundary regularity

abstract:
  We employ a variational approach to study the Neumann boundary value problem
for the $p$-Laplacian on bounded smooth-enough domains in the metric setting,
and show that solutions exist and are bounded. The boundary data considered are
Borel measurable bounded functions. We also study boundary continuity
properties of the solutions. One of the key tools utilized is the trace theorem
for Newton-Sobolev functions, and another is an analog of the De Giorgi
inequality adapted to the Neumann problem.


title: An infinite family of vertex-primitive 2-arc-transitive digraphs

abstract:
  We solve the long-standing existence problem of vertex-primitive
2-arc-transitive digraphs by constructing an infinite family of such digraphs.


abstract:
  In this paper we confirm several conjectures of Z.-W. Sun on Hankel-type
determinants for some combinatorial sequences including Franel numbers, Domb
numbers and Ap\'ery numbers. For any nonnegative integer $n$, define
\begin{gather*}f_n:=\sum_{k=0}^n\binom nk^3,\ D_n:=\sum_{k=0}^n\binom
nk^2\binom{2k}k\binom{2(n-k)}{n-k}, b_n:=\sum_{k=0}^n\binom nk^2\binom{n+k}k,\
A_n:=\sum_{k=0}^n\binom nk^2\binom{n+k}k^2. \end{gather*} For $n=0,1,2,\ldots$,
we show that $6^{-n}|f_{i+j}|_{0\leq i,j\leq n}$ and $12^{-n}|D_{i+j}|_{0\le
i,j\le n}$ are positive odd integers, and $10^{-n}|b_{i+j}|_{0\leq i,j\leq n}$
and $24^{-n}|A_{i+j}|_{0\leq i,j\leq n}$ are always integers.


title:
A lower bound of the distortion of the Torelli group in the mapping
  class group with boundary components

abstract:
  We prove that each Torelli group of an orientable surface with any number of
boundary components is at least exponentially distorted in the mapping class
group by using Broaddus-Farb-Putman's techniques. Further we show that the
distortion of each Torelli group in the level $d$ mapping class group is the
same as that of in the mapping class group.


title: Bottom crossing probability for symmetric jump processes (full version)

abstract:
  We determine the decay rate of the bottom crossing probability for symmetric
jump processes under the condition on heat kernel estimates. Our results are
applicable to symmetric stable-like processes and stable-subordinated diffusion
processes on a class of (unbounded) fractals and fractal-like spaces.


title: Complexity of virtual 3-manifolds

abstract:
  Virtual $3$-manifolds were introduced by S.V. Matveev in 2009 as natural
generalizations of the classical $3$-manifolds. In this paper, we introduce a
notion of complexity of a virtual $3$-manifold. We investigate the values of
the complexity for virtual 3-manifolds presented by special polyhedra with one
or two $2$-components. On the basis of these results, we establish the exact
values of the complexity for a wide class of hyperbolic $3$-manifolds with
totally geodesic boundary.


title: Escape rate of the Brownian motions on hyperbolic spaces

abstract:
  We discuss the escape rate of the Brownian motion on a hyperbolic space. We
point out that the escape rate is determined by using the Brownian expression
of the radial part and a generalized Kolmogorov's test for the one dimensional
Brownian motion.


title: How correlated is the FeSe/SrTiO$_3$ system ?

abstract:
  Recent observation of $\sim$ 10 times higher critical temperature in FeSe
monolayer compared with its bulk phase has drawn a great deal of attention
because the electronic structure in the monolayer phase appears to be different
than bulk FeSe. Using a combination of density functional theory and dynamical
mean field theory, we find electronic correlations have important effects on
the predicted atomic-scale geometry and the electronic structure of the
monolayer FeSe on SrTiO$_3$. The electronic correlations are dominantly
controlled by the Se-Fe-Se angle either in the bulk phase or the monolayer
phase. But the angle sensitivity increases and the orbital differentiation
decreases in the monolayer phase compared to the bulk phase. The correlations
are more dependent on Hund's J than Hubbard U. The observed orbital selective
incoherence to coherence crossover with temperature confirms the Hund's
metallic nature of the monolayer FeSe. We also find electron doping by oxygen
vacancies in SrTiO$_3$ increases the correlation strength, especially in the
$d_{xy}$ orbital by reducing the Se-Fe-Se angle.


title:
Ultrafast generation of skyrmionic defects with vortex beams: printing
  laser profiles on magnets

abstract:
  Controlling electric and magnetic properties of matter by laser beams is
actively explored in the broad region of condensed matter physics, including
spintronics and magneto-optics. Here we theoretically propose an application of
optical and electron vortex beams carrying intrinsic orbital angular momentum
to chiral ferro- and antiferro- magnets. We analyze the time evolution of spins
in chiral magnets under irradiation of vortex beams, by using the stochastic
Landau-Lifshitz-Gilbert equation. We show that beam-driven nonuniform
temperature lead to a class of ring-shaped magnetic defects, what we call
skyrmion multiplex, as well as conventional skyrmions. We discuss the proper
beam parameters and the optimal way of applying the beams for the creation of
these topological defects. Our findings provide an ultrafast scheme of
generating topological magnetic defects in a way applicable to both metallic
and insulating chiral (anti-) ferromagnets.


title:
Fast Evolution and Waveform Generator for Extreme-Mass-Ratio Inspirals
  in Equatorial-Circular Orbits

abstract:
  In this paper we discuss the development of a fast and accurate waveform
model for the quasi-circular orbital evolution of extreme-mass-ratio-inspirals
(EMRIs). This model simply employs the data of a few numerical Teukoulsky-based
energy fluxes and waveforms to fit out a set of polynomials for the entire
fluxes and waveforms. These obtained polynomials are accurate enough in the
entire evolution domain, and much more accurate than the resummation
post-Newtonian (PN) energy fluxes and waveforms, especially when the spin of a
black hole becomes large. The dynamical equation we adopted for orbital
revolution is the effective-one-body (EOB) formalism. Because of the simplified
expressions, the efficiency of calculating the orbital evolution with our
polynomials is also better than the traditional method which uses the resummed
PN analytical fluxes. Our model should be useful in calculation of waveform
templates of EMRIs for the gravitational wave detectors such as the evolved
Laser Interferometer Space Antenna (eLISA).


title:
Computing the monodromy and pole order filtration on Milnor fiber
  cohomology of plane curves

abstract:
  We describe an algorithm computing the monodromy and the pole order
filtration on the Milnor fiber cohomology of any reduced projective plane curve
$C$. The relation to the zero set of Bernstein-Sato polynomial of the defining
homogeneous polynomial for $C$ is also discussed. When $C$ has some non
weighted homogeneous singularities, then we have to assume that a conjecture
holds in order to get some of our results. In all the examples computed so far
this conjecture holds.


title:
Preliminary Test and Shrinkage Estimations of Scale Parameters for Two
  Exponential Distributions based on Record Values

abstract:
  The exponential distribution is applied in a very wide variety of statistical
procedures. Among the most prominent applications are those in the field of
life testing and reliability theory. When there are two record samples
available for estimating the scale parameter, a preliminary test is usually
used to determine whether to pool the samples or use the individual sample. In
this paper, the preliminary test estimator and shrinkage estimator are studied.
The optimum level of significance for preliminary test estimation and the
optimum values of shrinkage coefficient are obtained based on minimax regret
criterion under the weighted square error loss function.


title:
Entanglement dynamics for uniformly accelerated two-level atoms coupled
  with electromagnetic vacuum fluctuations

abstract:
  We investigate the entanglement dynamics of two uniformly accelerated atoms
with the same acceleration perpendicular to their separation. The two-atom
system is treated as an open system coupled with fluctuating electromagnetic
fields in the Minkowski vacuum, and in the Born-Markov approximation the master
equation that describes the completely positive time evolution of the two-atom
system is derived. In particular, we investigate the phenomena of entanglement
degradation, generation, revival and enhancement. As opposed to the
scalar-field case, the entanglement dynamics is crucially dependent on the
polarization directions of the atoms. For the two-atom system with certain
acceleration and separation, the polarization directions of the atoms may
determine whether entanglement generation, revival or enhancement happens,
while for entanglement degradation, they affect the decay rate of entanglement.
A comparison between the entanglement evolution of accelerated atoms and that
of static ones immersed in a thermal bath at the Unruh temperature shows that
they are the same only when the acceleration is extremely small.


title: An Exponential Inequality for U-Statistics under Mixing Conditions

abstract:
  The family of U-statistics plays a fundamental role in statistics. This paper
proves a novel exponential inequality for U-statistics under the time series
setting. Explicit mixing conditions are given for guaranteeing fast
convergence, the bound proves to be analogous to the one under independence,
and extension to non-stationary time series is straightforward. The proof
relies on a novel decomposition of U-statistics via exploiting the temporal
correlatedness structure. Such results are of interest in many fields where
high dimensional time series data are present. In particular, applications to
high dimensional time series inference are discussed.


title:
Effect of adding nanometre-sized heterogeneities on the structural
  dynamics and the excess wing of a molecular glass former

abstract:
  We present the relaxation dynamics of glass-forming glycerol mixed with 1.1
nm sized polyhedral oligomeric silsesquioxane (POSS) molecules using dielectric
spectroscopy (DS) and two different neutron scattering (NS) techniques. Both,
the reorientational dynamics as measured by DS and the density fluctuations
detected by NS reveal a broadening of the alpha relaxation when POSS molecules
are added. Moreover, we find a significant slowing down of the alpha-relaxation
time. These effects are in accord with the heterogeneity scenario considered
for the dynamics of glasses and supercooled liquids. The addition of POSS also
affects the excess wing in glycerol arising from a secondary relaxation
process, which seems to exhibit a dramatic increase in relative strength
compared to the alpha-relaxation.


title: Strategic Seeding of Rival Opinions

abstract:
  We present a network influence game that models players strategically seeding
the opinions of nodes embedded in a social network. A social learning dynamic,
whereby nodes repeatedly update their opinions to resemble those of their
neighbors, spreads the seeded opinions through the network. After a fixed
period of time, the dynamic halts and each player's utility is determined by
the relative strength of the opinions held by each node in the network
vis-a-vis the other players. We show that the existence of a pure Nash
equilibrium cannot be guaranteed in general. However, if the dynamics are
allowed to progress for a sufficient amount of time so that a consensus among
all of the nodes is obtained, then the existence of a pure Nash equilibrium can
be guaranteed. The computational complexity of finding a pure strategy best
response is shown to be NP-complete, but can be efficiently approximated to
within a (1 - 1/e) factor of optimal by a simple greedy algorithm.


title:
Convex PBW-type Lyndon Bases and Restricted Two-Parameter Quantum Group
  of Type $F_4$

abstract:
  We determine convex PBW-type Lyndon bases for two-parameter quantum groups
$U_{r,s}(F_4)$ with detailed commutation relations. We construct a
finite-dimensional Hopf algebra $\mathfrak u_{r,s}(F_4)$, as a quotient of
$U_{r,s}(F_4)$ by a Hopf ideal generated by certain central elements, which is
pointed, and of a Drinfel'd double structure under a certain condition. All of
Hopf isomorphisms of $\mathfrak u_{r,s}(F_4)$ are determined which are
important for seeking the possible new pointed objects in low order with
$(\ell, 210)\ne 1$. Finally, necessary and sufficient conditions for $\mathfrak
u_{r,s}(F_4)$ to be a ribbon Hopf algebra are singled out by describing the
left and right integrals.


title: Algorithmic Persuasion with No Externalities

abstract:
  We study the algorithmics of information structure design -- a.k.a.
persuasion or signaling -- in a fundamental special case introduced by Arieli
and Babichenko: multiple agents, binary actions, and no inter-agent
externalities. Unlike prior work on this model, we allow many states of nature.
We assume that the principal's objective is a monotone set function, and study
the problem both in the public signal and private signal models, drawing a
sharp contrast between the two in terms of both efficacy and computational
complexity.
  When private signals are allowed, our results are largely positive and quite
general. First, we show polynomial-time equivalence between optimal signaling
and the problem of maximizing the objective function plus an additive function.
This yields an efficient implementation of the optimal scheme when the
objective is supermodular or anonymous. Second, we exhibit a
(1-1/e)-approximation of the optimal private signaling scheme, modulo an
additive loss of $\epsilon$, when the objective function is submodular. These
two results simplify, unify, and generalize results of [Arieli and Babichenko,
2016] and [Babichenko and Barman, 2016], extending them from a binary state of
nature to many states (modulo the additive loss in the latter result). Third,
we consider the binary-state case with a submodular objective, and simplify and
slightly strengthen the result of [Babichenko and Barman, 2016] to obtain a
(1-1/e)-approximation via an explicitly constructed scheme.
  When only a public signal is allowed, our results are negative. First, we
show that it is NP-hard to approximate the optimal public scheme, within any
constant factor, even when the objective is additive. Second, we show that the
optimal private scheme can outperform the optimal public scheme, in terms of
maximizing the sender's objective, by a polynomial factor.


title: Bibliographic Analysis with the Citation Network Topic Model

abstract:
  Bibliographic analysis considers author's research areas, the citation
network and paper content among other things. In this paper, we combine these
three in a topic model that produces a bibliographic model of authors, topics
and documents using a non-parametric extension of a combination of the Poisson
mixed-topic link model and the author-topic model. We propose a novel and
efficient inference algorithm for the model to explore subsets of research
publications from CiteSeerX. Our model demonstrates improved performance in
both model fitting and a clustering task compared to several baselines.


title:
On embeddings of the Grassmannian $Gr(2,m)$ into the Grassmannian
  $Gr(2,n)$

abstract:
  In this {paper}, we consider holomorphic embeddings of $Gr(2,m)$ into
$Gr(2,n)$. We study such embeddings by finding all possible total Chern classes
of the pull-back of the universal bundles under these embeddings. Using the
relations between Chern classes of the universal bundles and Schubert cycles,
together with properties of holomorphic vector bundles of rank $2$ on complex
Grassmannians, we find conditions on $m$ and $n$ for which any holomorphic
embedding of $Gr(2,m)$ into $Gr(2,n)$ is linear.


title:
Six-wave mixing induced by free-carrier plasma in silicon nanowire
  waveguides

abstract:
  Nonlinear wave mixing in mesoscopic silicon structures is a fundamental
nonlinear process with broad impact and applications. Silicon nanowire
waveguides, in particular, have large third-order Kerr nonlinearity, enabling
salient and abundant four-wave-mixing dynamics and functionalities. Besides the
Kerr effect, in silicon waveguides two-photon absorption generates high
free-carrier densities, with corresponding fifth-order nonlinearity in the
forms of free-carrier dispersion and free-carrier absorption. However, whether
these fifth-order free-carrier nonlinear effects can lead to six-wave-mixing
dynamics still remains an open question until now. Here we report the
demonstration of free-carrier-induced six-wave mixing in silicon nanowires.
Unique features, including inverse detuning dependence of six-wave-mixing
efficiency and its higher sensitivity to pump power, are originally observed
and verfied by analytical prediction and numerical modeling. Additionally,
asymmetric sideband generation is observed for different laser detunings,
resulting from the phase-sensitive interactions between free-carrier
six-wave-mixing and Kerr four-wave-mixing dynamics. These discoveries provide a
new path for nonlinear multi-wave interactions in nanoscale platforms.


title: Summation identities and transformations for hypergeometric series

abstract:
  We find summation identities and transformations for the McCarthy's $p$-adic
hypergeometric series by evaluating certain Gauss sums which appear while
counting points on the family $$Z_{\lambda}: x_1^d+x_2^d=d\lambda
x_1x_2^{d-1}$$ over a finite field $\mathbb{F}_p$. A. Salerno expresses the
number of points over a finite field $\mathbb{F}_p$ on the family $Z_{\lambda}$
in terms of quotients of $p$-adic gamma function under the condition that
$d|p-1$. In this paper, we first express the number of points over a finite
field $\mathbb{F}_p$ on the family $Z_{\lambda}$ in terms of McCarthy's
$p$-adic hypergeometric series for any odd prime $p$ not dividing $d(d-1)$, and
then deduce two summation identities for the $p$-adic hypergeometric series. We
also find certain transformations and special values of the $p$-adic
hypergeometric series. We finally find a summation identity for the Greene's
finite field hypergeometric series.


title: Nonparametric Density Estimation for Spatial Data with Wavelets

abstract:
  Nonparametric density estimators are studied for $d$-dimensional, strongly
spatial mixing data which is defined on a general $N$-dimensional lattice
structure. We consider linear and nonlinear hard thresholded wavelet estimators
which are derived from a $d$-dimensional multiresolution analysis. We give
sufficient criteria for the consistency of these estimators and derive rates of
convergence in $L^{p'}$ for $p'\in [1,\infty)$. For this reason, we study
density functions which are elements of a $d$-dimensional Besov space
$B^s_{p,q}(\mathbb{R}^d)$. We also verify the analytic correctness of our
results in numerical simulations.


title: Hawkes Processes with Stochastic Excitations

abstract:
  We propose an extension to Hawkes processes by treating the levels of
self-excitation as a stochastic differential equation. Our new point process
allows better approximation in application domains where events and intensities
accelerate each other with correlated levels of contagion. We generalize a
recent algorithm for simulating draws from Hawkes processes whose levels of
excitation are stochastic processes, and propose a hybrid Markov chain Monte
Carlo approach for model fitting. Our sampling procedure scales linearly with
the number of required events and does not require stationarity of the point
process. A modular inference procedure consisting of a combination between
Gibbs and Metropolis Hastings steps is put forward. We recover expectation
maximization as a special case. Our general approach is illustrated for
contagion following geometric Brownian motion and exponential Langevin
dynamics.