title: Correlation and transport phenomena in topological nodal-loop semimetals

abstract:
  We study the unique physical properties of topological nodal-loop semimetals
protected by the coexistence of time-reversal and inversion symmetries with
negligible spin-orbit coupling. We argue that strong correlation effects occur
at the surface of such systems for relatively small Hubbard interaction $U$,
due to the narrow bandwidth of the "drumhead" surface states. In the
Hartree-Fock approximation, at small $U$ we obtain a surface ferromagnetic
phase through a continuous quantum phase transition characterized by the
surface-mode divergence of the spin susceptibility, while the bulk states
remain very robust against local interactions and remain non-ordered. At
slightly increased interaction strength, the system quickly changes from a
surface ferromagnetic phase to a surface charge-ordered phase through a
first-order transition. When Rashba-type spin-orbit coupling is applied to the
surface states, a canted ferromagnetic phase occurs at the surface for
intermediate values of $U$. The quantum critical behavior of the surface
ferromagnetic transition is nontrivial in the sense that the surface spin order
parameter couple to Fermi-surface excitations from both surface and bulk
states. This leads to unconventional Landau damping and consequently a na\"ive
dynamical critical exponent $z\!\approx\!1$ when the Fermi level is close to
the bulk nodal energy. We also show that, already without interactions, quantum
oscillations arise due to bulk states, despite the absence of a Fermi surface
when the chemical potential is tuned to the energy of the nodal loop. The bulk
magnetic susceptibility diverges logarithmically whenever the nodal loop
exactly overlaps with a quantized magnetic orbit in the bulk Brillouin zone.
These correlation and transport phenomena are unique signatures of nodal loop
states.


title:
Parallel Computing for Copula Parameter Estimation with Big Data: A
  Simulation Study

abstract:
  Copula-based modeling has seen rapid advances in recent years. However, in
big data applications, the lengthy computation time for estimating copula
parameters is a major difficulty. Here, we develop a novel method to speed
computation time in estimating copula parameters, using communication-free
parallel computing. Our procedure partitions full data sets into disjoint
independent subsets, performs copula parameter estimation on the subsets, and
combines the results to produce an approximation to the full data copula
parameter. We show in simulation studies that the computation time is greatly
reduced through our method, using three well-known one-parameter bivariate
copulas within the elliptical and Archimedean families: Gaussian, Frank and
Gumbel. In addition, our simulation studies find small values for estimated
bias, estimated mean squared error, and estimated relative L1 and L2 errors for
our method, when compared to the full data parameter estimates.


title: Spherical particle sedimenting in weakly viscoelastic shear flow

abstract:
  We consider the dynamics of a small spherical particle driven through an
unbounded viscoelastic shear flow by an external force. We give analytical
solutions to both the mobility problem (velocity of forced particle) and the
resistance problem (force on fixed particle), valid to second order in the
dimensionless Deborah and Weissenberg numbers, which represent the elastic
relaxation time of the fluid relative to the rate of translation and the
imposed shear rate. We find a shear-induced lift at $O({\rm Wi})$, a modified
drag at $O({\rm De}^2)$ and $O({\rm Wi}^2)$, and a second lift that is
orthogonal to the first, at $O({\rm Wi}^2)$. The relative importance of these
effects depends strongly on the orientation of the forcing relative to the
shear. We discuss how these forces affect the terminal settling velocity in an
inclined shear flow. We also describe a new basis set of symmetric Cartesian
tensors, and demonstrate how they enable general tensorial perturbation
calculations such as the present theory. In particular this scheme allows us to
write down a solution to the inhomogenous Stokes equations, required by the
perturbation expansion, by a sequence of algebraic manipulations well suited to
computer implementation.


title: Probing IrTe2 crystal symmetry by polarized Raman scattering

abstract:
  Polarized Raman scattering measurements on IrTe$_2$ single crystals carried
out over 15~K - 640~K temperature range, and across the structural phase
transition, reveal new insights regarding the crystal symmetry.\ In the high
temperature regime three Raman active modes are observed at all studied
temperatures above the structural phase transition, rather than two as
predicted by the factor group analysis for the assumed $P\bar{3}m1$ symmetry.
This indicates that the actual symmetry of the high temperature phase is lower
than previously thought.\ Observation of an additional E$_g$ mode at high
temperature can be explained by doubling of the original trigonal unit cell
along the $c$-axis and within the $P\bar{3}c1$ symmetry.\ In the low
temperature regime (below 245 K) the new Raman modes appear as a consequence of
the symmetry lowering phase transition and corresponding increase of the
primitive cell.\ All the modes observed below the phase transition temperature
can be assigned within the monoclinic crystal symmetry.\ Temperature dependence
of the Raman active phonons in both phases are mainly driven by anharmonicity
effects. The results call for reconsideration of the crystallographic phases of
IrTe$_2$.


title:
Hankel and Berezin type operators on weighted Besov spaces of
  holomorphic functions on polydiscs

abstract:
  In this paper we consider the generalized little Hankel and Berezin type
operators on Besov spaces of holomorphic functions on polydiscs and give
results about the boundedness of these operators.


title: Intracavity frequency-doubled degenerate laser

abstract:
  We develop a green light source with low spatial coherence via intracavity
frequency doubling of a solid-state degenerate laser. The second harmonic
emission supports many more transverse modes than the fundamental emission, and
exhibit lower spatial coherence. A strong suppression of speckle formation is
demonstrated for both fundamental and second harmonic beams. Using the green
emission for fluorescence excitation, we show the coherent artifacts are
removed from the full-field fluorescence images. The high power, low spatial
coherence and good directionality makes the green degenerate laser an
attractive illumination source for parallel imaging and projection display.


title: Root Parametrized Differential Equations for the classical groups

abstract:
  Let $C \langle t_1, \dots t_l\rangle$ be the differential field generated by
$l$ differential indeterminates $\boldsymbol{t}=(t_1, \dots ,t_l)$ over an
algebraically closed field $C$ of characteristic zero. We develop a lower bound
criterion for the differential Galois group $G(C)$ of a matrix parameter
differential equation
$\partial(\boldsymbol{y})=A(\boldsymbol{t})\boldsymbol{y}$ over $C \langle t_1,
\dots t_l\rangle$ and we prove that every connected linear algebraic group is
the Galois group of a linear parameter differential equation over $C\langle t_1
\rangle$. As a second application we compute explicit and nice linear parameter
differential equations over $C\langle t_1, \dots, t_l \rangle$ for the groups
$\mathrm{SL}_{l+1}(C)$, $\mathrm{SP}_{2l}(C)$, $\mathrm{SO}_{2l+1}(C)$,
$\mathrm{SO}_{2l}(C)$, i.e. for the classical groups of type $A_l$, $B_l$,
$C_l$, $D_l$, and for $\mathrm{G}_2$ (here $l=2$).


title: Learning Personalized Optimal Control for Repeatedly Operated Systems

abstract:
  We consider the problem of online learning of optimal control for repeatedly
operated systems in the presence of parametric uncertainty. During each round
of operation, environment selects system parameters according to a fixed but
unknown probability distribution. These parameters govern the dynamics of a
plant. An agent chooses a control input to the plant and is then revealed the
cost of the choice. In this setting, we design an agent that personalizes the
control input to this plant taking into account the stochasticity involved. We
demonstrate the effectiveness of our approach on a simulated system.


title: Quantum Speed-ups for Semidefinite Programming

abstract:
  We give a quantum algorithm for solving semidefinite programs (SDPs). It has
worst-case running time $n^{\frac{1}{2}} m^{\frac{1}{2}} s^2
\text{poly}(\log(n), \log(m), R, r, 1/\delta)$, with $n$ and $s$ the dimension
and row-sparsity of the input matrices, respectively, $m$ the number of
constraints, $\delta$ the accuracy of the solution, and $R, r$ a upper bounds
on the size of the optimal primal and dual solutions. This gives a square-root
unconditional speed-up over any classical method for solving SDPs both in $n$
and $m$. We prove the algorithm cannot be substantially improved (in terms of
$n$ and $m$) giving a $\Omega(n^{\frac{1}{2}}+m^{\frac{1}{2}})$ quantum lower
bound for solving semidefinite programs with constant $s, R, r$ and $\delta$.
  The quantum algorithm is constructed by a combination of quantum Gibbs
sampling and the multiplicative weight method. In particular it is based on a
classical algorithm of Arora and Kale for approximately solving SDPs. We
present a modification of their algorithm to eliminate the need for solving an
inner linear program which may be of independent interest.


title:
Exploring Damped Lyman-$\alpha$ System Host Galaxies using Gamma-ray
  Bursts

abstract:
  We present a sample of 45 Damped Lyman-$\alpha$ system (DLA, \nhi\ $ \geq 2
\times 10^{20} {\rm cm}^{-2}$) counterparts (33 detections, 12 upper limits)
which host gamma-ray bursts (GRB-DLAs) in order to investigate star-formation
and metallicity within galaxies hosting DLAs. Our sample spans $z \sim 2-6$ and
is nearly three times larger than any previously detected DLA counterparts
survey based on quasar line-of-sight searches (QSO-DLAs). We report star
formation rates (SFRs) from rest-frame UV photometry and SED modeling. We find
that DLA counterpart SFRs are not correlated with either redshift or HI column
density. Thanks to the combination of \hst\ and ground-based observations, we
also investigate DLA host star-formation efficiency. Our GRB-DLA counterpart
sample spans both higher efficiency and low efficiency star formation regions
compared to the local Kennicutt-Schmidt relation, local star formation laws,
and $z \sim 3$ cosmological simulations. We also compare the depletion times of
our DLA hosts sample to other objects in the local Universe, our sample appears
to deviate from the star formation efficiencies measured in local spiral and
dwarf galaxies. Furthermore, we find similar efficiencies as local inner disks,
SMC, and LBG outskirts. Finally, our enrichment time measurements show a spread
of systems with under- and over-abundance of metals which may suggest that
these systems had episodic star formation and a metal enrichment/depletion as a
result of strong stellar feedback and/or metal inflow/outflow.


title: On Randomized Distributed Coordinate Descent with Quantized Updates

abstract:
  In this paper, we study the randomized distributed coordinate descent
algorithm with quantized updates. In the literature, the iteration complexity
of the randomized distributed coordinate descent algorithm has been
characterized under the assumption that machines can exchange updates with an
infinite precision. We consider a practical scenario in which the messages
exchange occurs over channels with finite capacity, and hence the updates have
to be quantized. We derive sufficient conditions on the quantization error such
that the algorithm with quantized update still converge. We further verify our
theoretical results by running an experiment, where we apply the algorithm with
quantized updates to solve a linear regression problem.


title:
Discovering and profiling Z' bosons using asymmetry observables in top
  quark pair production with the lepton-plus-jets final state at the LHC

abstract:
  The sensitivity of top quark pair production at the Large Hadron Collider to
the presence and nature of an underlying Z' boson is studied, accounting for
six-fermion decay with full tree-level Standard Model ttbar interference and
all intermediate particles allowed off-shell. Focus is placed on the
lepton-plus-jets final state, emulating experimental conditions, including
kinematic requirements and top quark pair reconstruction in the presence of
missing transverse energy and combinatorial ambiguity in jet-top assignment.
Considering a resonance with mass of 4 TeV, and assuming 300 inverse fb of
proton-proton collisions with a centre of mass energy of 13 TeV data, a
combination of forward-backward and top polarisation asymmetries are shown to
distinguish Z' embedded by different classes of Grand-Unified-Theory-inspired
models. In combination with the differential cross section, they may be used to
increase the significance of the signal when tested against the Standard Model,
as shown using a likelihood-based statistical test.


title:
Evidence of superconductivity-induced phonon spectra renormalization in
  alkali-doped iron selenides

abstract:
  Polarized Raman scattering spectra of superconducting K$_x$Fe$_{2-y}$Se$_2$
and nonsuperconducting K$_{0.8}$Fe$_{1.8}$Co$_{0.2}$Se$_2$ single crystals were
measured in a temperature range from 10 K up to 300 K. Two Raman active modes
from the $I4/mmm$ phase and seven from the $I4/m$ phase are observed in
frequency range from 150 to 325 cm$^{-1}$ in both compounds, suggesting that
K$_{0.8}$Fe$_{1.8}$Co$_{0.2}$Se$_2$ single crystal also has two-phase nature.
Temperature dependence of Raman mode energy is analyzed in terms of lattice
thermal expansion and phonon-phonon interaction. Temperature dependence of
Raman mode linewidth is dominated by temperature-induced anharmonic effects. It
is shown that change of Raman mode energy with temperature is dominantly driven
by thermal expansion of the crystal lattice. Abrupt change of the A$_{1g}$ mode
energy near $T_C$ was observed in K$_x$Fe$_{2-y}$Se$_2$, whereas it is absent
in non-superconducting K$_{0.8}$Fe$_{1.8}$Co$_{0.2}$Se$_2$. Phonon energy
hardening at low temperatures in the superconducting sample is a consequence of
superconductivity-induced redistribution of the electronic states below
critical temperature.


title: Public Goods Games on Adaptive Coevolutionary Networks

abstract:
  Productive societies feature high levels of cooperation and strong
connections between individuals. Public Goods Games (PGGs) are frequently used
to study the development of social connections and cooperative behavior in
model societies. In such games, contributions to the public good are made only
by cooperators, while all players, including defectors, can reap public goods
benefits. Classic results of game theory show that mutual defection, as opposed
to cooperation, is the Nash Equilibrium of PGGs in well-mixed populations,
where each player interacts with all others. In this paper, we explore the
coevolutionary dynamics of a low information public goods game on a network
without spatial constraints in which players adapt to their environment in
order to increase individual payoffs. Players adapt by changing their
strategies, either to cooperate or to defect, and by altering their social
connections. We find that even if players do not know other players' strategies
and connectivity, cooperation can arise and persist despite large short-term
fluctuations.


title: Singularities of linear systems and boundedness of Fano varieties

abstract:
  We study log canonical thresholds (also called global log canonical threshold
or $\alpha$-invariant) of $\mathbb{R}$-linear systems. We prove existence of
positive lower bounds in different settings, in particular, proving a
conjecture of Ambro. We then show that the Borisov-Alexeev-Borisov conjecture
holds, that is, given a natural number $d$ and a positive real number
$\epsilon$, the set of Fano varieties of dimension $d$ with $\epsilon$-log
canonical singularities forms a bounded family. This implies that birational
automorphism groups of rationally connected varieties are Jordan which in
particular answers a question of Serre. Next we show that if the log canonical
threshold of the anti-canonical system of a Fano variety is at most one, then
it is computed by some divisor, answering a question of Tian in this case.


title:
Robustness and convergence of fractional systems and their applications
  to adaptive systems

abstract:
  Our general aim is to give sufficient conditions for robustness behavior and
convergence to the equilibrium point of linear time-varying fractional system's
solutions. We approach this problem using as a framework a series of recent
results due to Cong et al. We establish theorems that generalize in several
ways many previous results in the specialized literature, including those of
Cong et al. We use the proposed theorems in adaptive systems, proving
convergence and robustness of such schemes, that up to date remain unsolved
problems, showing the wide scope of application of our results.


title: Patterns of authors contribution in scientific manuscripts

abstract:
  Science is becoming increasingly more interdisciplinary, giving rise to more
diversity in the areas of expertise within research labs and groups. This also
have brought changes to the role researchers in scientific works. As a
consequence, multi-authored scientific papers have now became a norm for high
quality research. Unfortunately, such a phenomenon induces bias to existing
metrics employed to evaluate the productivity and success of researchers. While
some metrics were adapted to account for the rank of authors in a paper, many
journals are now requiring a description of the specific roles of each author
in a publication. Surprisingly, the investigation of the relationship between
the rank of authors and their contributions has been limited to a few studies.
By analyzing such kind of data, here we show, quantitatively, that the
regularity in the authorship contributions decreases with the number of authors
in a paper. Furthermore, we found that the rank of authors and their roles in
papers follows three general patterns according to the nature of their
contributions, such as writing, data analysis, and the conduction of
experiments. This was accomplished by collecting and analyzing the data
retrieved from PLoS ONE and by devising an entropy-based measurement to
quantify the effective number of authors in a paper according to their
contributions. The analysis of such patterns confirms that some aspects of the
author ranking are in accordance with the expected convention, such as the fact
that the first and last authors are more likely to contribute more in a
scientific work. Conversely, such analysis also revealed that authors in the
intermediary positions of the rank contribute more in certain specific roles,
such as the task of collecting data. This indicates that the an unbiased
evaluation of researchers must take into account the distinct types of
scientific contributions.


title:
Phosphorylation-induced mechanical regulation of intrinsically
  disordered neurofilament protein assemblies

abstract:
  The biological function of protein assemblies was conventionally equated with
a unique three-dimensional protein structure and protein-specific interactions.
However, in the past 20 years it was found that some assemblies contain long
flexible regions that adopt multiple structural conformations. These include
neurofilament (NF) proteins that constitute the stress-responsive supportive
network of neurons. Herein, we show that NF networks macroscopic properties are
tuned by enzymatic regulation of the charge found on the flexible protein
regions. The results reveal an enzymatic (phosphorylation) regulation of
macroscopic properties such as orientation, stress-response and expansion in
flexible protein assemblies. Together with a model explaining the attractive
electrostatic interactions induced by enzymatically added charges, we
demonstrate that phosphorylation-regulation is far richer and versatile than
previously considered.


title: Lattice dynamics of KNi2Se2

abstract:
  We report the first principle calculations of the lattice dynamics of
KNi$_{2}$Se$_2$ together with the Raman scattering study.\ We have observed
three out of four Raman active modes predicted by the factor group analysis.
Calculated phonon frequencies are in good agreement with experimental
findings.\ Contrary to its iron counterpart (K$_x$Fe$_{2-y}$Se$_2$),
K$_{0.95}$Ni$_{1.86}$Se$_2$ does not show vacancy ordering.


title: Inflaton and dark matter in a random environment

abstract:
  We consider a Lagrangian of interacting scalar fields. We divide the
Lagrangian into two parts. The first part is to describe either the dark matter
(DM) or the inflaton (IN) depending on the choice of the self-interaction. The
second part constitutes an environment of an infinite number of scalar fields
interacting linearly with the first part. We approximate the environment by a
white noise obtaining a Langevin equation. We show that the resulting
Fokker-Planck equation has solutions determining a relation between the
diffusion constant, the cosmological constant and the temperature. As a
consequence of the Langevin approximation the energy-momentum tensor of the
dark matter and the inflaton is not conserved. The compensating energy-momentum
tensor is interpreted as the dark energy (DE). We insert the total
energy-momentum in Einstein equations. We show that under special initial
conditions Einstein equations have a solution with a constant ratio of DM/DE
and IN/DE densities.


title:
Applications of the `Ham Sandwich Theorem' to eigenvalues of the
  Laplacian

abstract:
  We apply Gromov's ham sandwich method to get
  (1) domain monotonicity (up to a multiplicative constant factor);
  (2) reverse domain monotonicity (up to a multiplicative constant factor); and
  (3) universal inequalities
  for Neumann eigenvalues of the Laplacian on bounded convex domains in a
Euclidean space.


title: On the computational complexity of detecting possibilistic locality

abstract:
  The proofs of quantum nonlocality due to GHZ and Hardy are quantitatively
different from that of Bell insofar as they rely only on a consideration of
whether events are possible or impossible, rather than relying on specific
experimental probabilities. Here, we consider the computational task of
determining whether or not a given table of possibilities constitutes a
departure from possibilistic local realism. By considering the case in which
one party has access to measurements with two outcomes and the other three, it
is possible to see at exactly which point this task becomes computationally
difficult.


title: Graphical Models for Discrete and Continuous Data

abstract:
  We introduce a general framework for undirected graphical models. It
generalizes Gaussian graphical models to a wide range of continuous, discrete,
and combinations of different types of data. The models in the framework,
called exponential trace models, are amenable to estimation based on maximum
likelihood. We introduce a sampling-based approximation algorithm for computing
the maximum likelihood estimator, and we apply this pipeline to learn
simultaneous neural activities from spike data.


title: On the completion of the mapping class group of genus two

abstract:
  In this paper, we will study the Lie algebra of the prounipotent radical of
the relative completion of the mapping class group of genus two. In particular,
we will partially determine a minimal presentation of the Lie algebra by
determining the generators and bounding the degree of the relations.


title:
Topological features of vector vortex beams perturbed with uniformly
  polarized light

abstract:
  Optical singularities manifesting at the center of vector vortex beams are
unstable, since their topological charge is higher than the lowest value
permitted by Maxwell's equations. Inspired by conceptually similar phenomena
occurring in the polarization pattern characterizing the skylight, we show how
perturbations that break the symmetry of radially symmetric vector beams lead
to the formation of a pair of fundamental and stable singularities, i.e. points
of circular polarization. We prepare a superposition of a radial (or azimuthal)
vector beam and a uniformly linearly polarized Gaussian beam; by varying the
amplitudes of the two fields, we control the formation of pairs of these
singular points and their spatial separation. We complete this study by
applying the same analysis to vector vortex beams with higher topological
charges, and by investigating the features that arise when increasing the
intensity of the Gaussian term. Our results can find application in the context
of singularimetry, where weak fields are measured by considering them as
perturbation of unstable optical beams.


title:
Fundamental costs in the production and destruction of persistent
  polymer copies

abstract:
  Living cells use readout molecules to record the state of receptor proteins,
similar to measurements or copies in typical computational devices. But is this
analogy rigorous? Can cells be optimally efficient, and if not, why? We show
that, as in computation, a canonical biochemical readout network generates
correlations; extracting no work from these correlations sets a lower bound on
dissipation. For general input, the biochemical network cannot reach this
bound, even with arbitrarily slow reactions or weak thermodynamic driving. It
faces an accuracy-dissipation trade-off that is qualitatively distinct from and
worse than implied by the bound, and more complex steady-state copy processes
cannot perform better. Nonetheless, the cost remains close to the thermodynamic
bound unless accuracy is extremely high. Additionally, we show that
biomolecular reactions could be used in thermodynamically optimal devices under
exogenous manipulation of chemical fuels, suggesting an experimental system for
testing computational thermodynamics.


title: Conditional steering under von-Neumann scenario

abstract:
  In
[\href{http://www.sciencedirect.com/science/article/pii/037596019290711T}{Phys.
Lett. A {\bf 166}, 293 (1992)}] Popescu characterized nonlocality of pure
$n$-partite entangled systems by studying bipartite violation of local realism
when $n-2$ number of parties perform projective measurements on their
particles. A pertinent question in this scenario is whether similar
characterization is possible for $n$-partite mixed entangled states also. In
the present work we have followed an analogous approach so as to explore
whether given a tripartite mixed entangled state the conditional bipartite
states obtained by performing projective measurement on the third party,
demonstrate a weaker form of nonlocality, quantum steering. We also compare
this new phenomenon of conditional steering with existing notions of tripartite
correlations. Interestingly the tripartite state need not be genuinely
entangled to demonstrate conditional steering.


title: Compactness and existence results for the $p$-Laplace equation

abstract:
  Given $1<p<N$ and two measurable functions $V\left( r\right) \geq 0$ and
$K\left( r\right) >0$, $r>0$, we define the weighted spaces \[ W=\left\{ u\in
D^{1,p}(\mathbb{R}^{N}):\int_{\mathbb{R}^{N}}V\left( \left| x\right| \right)
\left| u\right| ^{p}dx<\infty \right\} ,\quad
L_{K}^{q}=L^{q}(\mathbb{R}^{N},K\left( \left| x\right| \right) dx) \] and study
the compact embeddings of the radial subspace of $W$ into
$L_{K}^{q_{1}}+L_{K}^{q_{2}}$, and thus into $L_{K}^{q}$
($=L_{K}^{q}+L_{K}^{q}$) as a particular case. We consider exponents
$q_{1},q_{2},q$ that can be greater or smaller than $p$. Our results do not
require any compatibility between how the potentials $V$ and $K$ behave at the
origin and at infinity, and essentially rely on power type estimates of their
relative growth, not of the potentials separately. We then apply these results
to the investigation of existence and multiplicity of finite energy solutions
to nonlinear $p$-Laplace equations of the form \[ -\triangle _{p}u+V\left(
\left| x\right| \right) |u|^{p-1}u=g\left( \left| x\right| ,u\right) \quad
\text{in }\mathbb{R}^{N},\ 1<p<N, \] where $V$ and $g\left( \left| \cdot
\right| ,u\right) $ with $u$ fixed may be vanishing or unbounded at zero or at
infinity. Both the cases of $g$ super and sub $p$-linear in $u$ are studied
and, in the sub $p$-linear case, nonlinearities with $g\left( \left| \cdot
\right| ,0\right) \neq 0$ are also considered.


title: Multiple polylogarithms in weight 4

abstract:
  We clarify the relationship between different multiple polylogarithms in
weight~4 by writing suitable linear combinations of a given type of iterated
integral I_{n_1,...,n_d}(z_1,...,z_d), in depth d>1 and weight \sum_i n_i=4 in
terms of the classical tetralogarithm Li_4. In the process, we prove a
statement conjectured by Goncharov which can be rephrased as writing the sum of
iterated integrals I_{3,1}(V(x,y),z), where V(x,y) denotes a formal version of
the five term relation for the dilogarithm, in terms of Li_4-terms (we need 122
such).


title:
Face-to-diagonal reduction of Kramers-Wannier approximation for cubic
  lattice particle systems with nearest neighbour exclusion

abstract:
  The paper is concerned with interacting particle systems on the simple cubic
lattice obeying the nearest neighbour exclusion (NNE). This constraint forbids
any two neighbouring sites of the lattice to be simultaneously occupied, thus
reducing the set of admissible configurations for the cubic cell and its
subclusters such as edges and faces. This reduction extends applicability of
Kikuchi's Cluster Variation Method (CVM) with higher-order clusters to systems
with complex site configurations and short-range ordering, which would be
impractical beyond the NNE framework because of the "curse of dimensionality".
For edges of the cubic cell, which are the operational clusters of the
Bethe-Peierls entropy approximation in the CVM hierarchy, the edge-to-site
reduction of the entropy cumulants was studied previously. In extending the
earlier results, we develop a face-to-diagonal reduction of the Kramers-Wannier
entropy approximation of the CVM in the NNE setting. We also outline an
application of the resulting approximation to thermodynamic modeling of
disordered condensed media, such as liquid silicates, and discuss combinatorial
and numerical aspects of the implementation of this approach.


title: Opponent Modeling in Deep Reinforcement Learning

abstract:
  Opponent modeling is necessary in multi-agent settings where secondary agents
with competing goals also adapt their strategies, yet it remains challenging
because strategies interact with each other and change. Most previous work
focuses on developing probabilistic models or parameterized strategies for
specific applications. Inspired by the recent success of deep reinforcement
learning, we present neural-based models that jointly learn a policy and the
behavior of opponents. Instead of explicitly predicting the opponent's action,
we encode observation of the opponents into a deep Q-Network (DQN); however, we
retain explicit modeling (if desired) using multitasking. By using a
Mixture-of-Experts architecture, our model automatically discovers different
strategy patterns of opponents without extra supervision. We evaluate our
models on a simulated soccer game and a popular trivia game, showing superior
performance over DQN and its variants.


title: Slowly decaying averages and fat towers

abstract:
  Let $(X,\Sigma,m,\tau)$ be an ergodic system, that is, $(X, \Sigma, m)$ is a
probability space and $\tau: X \to X$ is an invertible ergodic $m$-preserving
transformation. For a function $f:X\to\mathbb R$, let $A_Nf$ denote the $N$th
ergodic average, $A_Nf(x)=\frac{1}{N}\cdot (f(x)+\dots+\tau^ {N-1}f(x))$.
Martin Barlow (personal communication) asked the following question, which
arose from the work of a student (Zichun Ye) on interface models. Question: If
$f(x) \ge 0$ is integrable, and $N(x) = \min \{n: A_kf(x) \le 2 \int f
\text{for all} k \ge n\}$, is it the case that $N(x)$ is also integrable? In
this note we show that the answer to this Question is no in general, even for
bounded functions. In so doing we discover that every ergodic system has a
special sort of Kakutani tower which we call a fat tower.


title: From Multiview Image Curves to 3D Drawings

abstract:
  Reconstructing 3D scenes from multiple views has made impressive strides in
recent years, chiefly by correlating isolated feature points, intensity
patterns, or curvilinear structures. In the general setting - without
controlled acquisition, abundant texture, curves and surfaces following
specific models or limiting scene complexity - most methods produce unorganized
point clouds, meshes, or voxel representations, with some exceptions producing
unorganized clouds of 3D curve fragments. Ideally, many applications require
structured representations of curves, surfaces and their spatial relationships.
This paper presents a step in this direction by formulating an approach that
combines 2D image curves into a collection of 3D curves, with topological
connectivity between them represented as a 3D graph. This results in a 3D
drawing, which is complementary to surface representations in the same sense as
a 3D scaffold complements a tent taut over it. We evaluate our results against
truth on synthetic and real datasets.


title: Alkali-induced rich properties in graphene nanoribbons: Chemical bonding

abstract:
  The alkali-adsorbed graphene nanoribbons exhibit the feature-rich electronic
and magnetic properties. From the first-principles calculations, there are only
few adatom-dominated conduction bands, and the other conduction and valence
bands are caused by carbon atoms. A lot of free electrons are revealed in the
occupied alkali- and carbon-dependent conduction bands. Energy bands are
sensitive to the concentration, distribution and kind of adatom and the edge
structure, while the total linear free carrier density only relies on the first
one. These mainly arise from a single $s-2p_z$ orbital hybridization in the
adatom-carbon bond. Specifically, zigzag systems can present the
anti-ferromagnetic ordering across two edges, ferromagnetic ordering along one
edge and non-magnetism, being reflected in the edge-localized energy bands with
or without spin splitting. The diverse energy dispersions contribute many
special peaks in density of states. The critical chemical bonding and the
distinct spin configuration could be verified from the experimental
measurements.


title: Negative Results for Software Effort Estimation

abstract:
  Context:More than half the literature on software effort estimation (SEE)
focuses on comparisons of new estimation methods. Surprisingly, there are no
studies comparing state of the art latest methods with decades-old approaches.
Objective:To check if new SEE methods generated better estimates than older
methods. Method: Firstly, collect effort estimation methods ranging from
"classical" COCOMO (parametric estimation over a pre-determined set of
attributes) to "modern" (reasoning via analogy using spectral-based clustering
plus instance and feature selection, and a recent "baseline method" proposed in
ACM Transactions on Software Engineering).Secondly, catalog the list of
objections that lead to the development of post-COCOMO estimation
methods.Thirdly, characterize each of those objections as a comparison between
newer and older estimation methods.Fourthly, using four COCOMO-style data sets
(from 1991, 2000, 2005, 2010) and run those comparisons experiments.Fifthly,
compare the performance of the different estimators using a Scott-Knott
procedure using (i) the A12 effect size to rule out "small" differences and
(ii) a 99% confident bootstrap procedure to check for statistically different
groupings of treatments). Results: The major negative results of this paper are
that for the COCOMO data sets, nothing we studied did any better than Boehm's
original procedure. Conclusions: When COCOMO-style attributes are available, we
strongly recommend (i) using that data and (ii) use COCOMO to generate
predictions. We say this since the experiments of this paper show that, at
least for effort estimation,how data is collected is more important than what
learner is applied to that data.


title: Searching for Gene Sets with Mutually Exclusive Mutations

abstract:
  Cancer cells evolve through random somatic mutations. "Beneficial" mutations
which disrupt key pathways (e.g. cell cycle regulation) are subject to natural
selection. Multiple mutations may lead to the same "beneficial" effect, in
which case there is no selective advantage to having more than one of these
mutations. Hence we are interested in finding sets of genes whose mutations are
approximately mutually exclusive (anti-co-occurring) within the TCGA Pancancer
dataset. In principle, finding the best set is NP Hard. Nevertheless, we will
show how a new Mutation anti-co-OCcurrence Algorithm (MOCA) provides an
effective greedy search and testing algorithm with guaranteed control of the
familywise error rate or false discovery rate, by combining some
under-appreciated ideas from frequentist hypothesis testing. These ideas
include: (a) A novel exact conditional test for the tendency of multiple sets
to have a large/small union/intersection, which generalises Fisher's exact test
of 2x2 tables. (b) Randomised hypothesis tests for discrete distributions. (c)
Stouffer's method for combining p-values. (d) Weighted multiple hypothesis
testing. A new approach to setting a-priori weights which generates additional
implicit hypothesis tests is suggested, and allows us to preserve almost all
statistical power when testing pairs despite introducing a combinatorially
large number of additional hypotheses.


title:
Invariant measures and measurable projective factors for actions of
  higher-rank lattices on manifolds

abstract:
  We consider smooth actions of lattices in higher-rank semisimple Lie groups
on manifolds. We define two numbers $r(G)$ and $m(G)$ associated with the roots
system of the Lie algebra of a Lie group $G$. If the dimension of the manifold
is smaller than $r(G)$, then we show the action preserves a Borel probability
measure. If the dimension of the manifold is at most $m(G)$, we show there is a
quasi-invariant measure on the manifold such that the action is measurable
isomorphic to a relatively measure preserving action over a standard boundary
action.


title:
Label-Free Supervision of Neural Networks with Physics and Domain
  Knowledge

abstract:
  In many machine learning applications, labeled data is scarce and obtaining
more labels is expensive. We introduce a new approach to supervising neural
networks by specifying constraints that should hold over the output space,
rather than direct examples of input-output pairs. These constraints are
derived from prior domain knowledge, e.g., from known laws of physics. We
demonstrate the effectiveness of this approach on real world and simulated
computer vision tasks. We are able to train a convolutional neural network to
detect and track objects without any labeled examples. Our approach can
significantly reduce the need for labeled training data, but introduces new
challenges for encoding prior knowledge into appropriate loss functions.


title: Is Feynman's Analysis of Electrostatic Screening Correct?

abstract:
  In a recent paper on electrostatic shielding, Chapman, Hewett and Trefethen
present arguments that the analysis of this effect by Feynman is incorrect.
Feynman analyzed shielding by a row of infinitesimally thin wires. They claim
that Feynman used the wrong boundary conditions invalidating his analysis. In
this paper we emphasize that Feynman's solution is a Green's function through
which behavior of the potential due to finite thickness wires of arbitrary
cross-section with appropriate boundary condition can be understood. This shows
that the main conclusions of Feynman's treatment are indeed correct. Analogy to
a parallel plate capacitor with one of the plates replaced by a row of wires
provides a more intuitive understanding of Feynman's argument. The case of a
finite number of wires arranged in a ring (not treated by Feynman), as a model
of Faraday cage, is different. The structure of the solution in radial
coordinates already suggests that one should not expect exponential behavior
and further analysis confirms this. There appear to be contradictory results in
the literature for its screening behavior in the presence of external charges
or fields.


title: Q-holes

abstract:
  We consider localized soliton-like solutions in the presence of a stable
scalar condensate background. By the analogy with classical mechanics, it can
be shown that there may exist solutions of the nonlinear equations of motion
that describe dips or rises in the spatially-uniform charge distribution. We
also present explicit analytical solutions for some of such objects and examine
their properties.


title: Improved error bounds for the Fermat primality test on random inputs

abstract:
  We investigate the probability that a random odd composite number passes a
random Fermat primality test, improving on earlier estimates in moderate
ranges. For example, with random numbers to $2^{200}$, our results improve on
prior estimates by close to 3 orders of magnitude.


title:
Automated Proof (or Disproof) of Linear Recurrences Satisfied by Pisot
  Sequences

abstract:
  Pisot sequences (sequences $a_n$ with initial terms $a_0=x, a_1=y$, and
defined for $n>1$ by $a_n= \lfloor a_{n-1}^2/a_{n-2} + \frac{1}{2} \rfloor$)
often satisfy linear recurrences with constant coefficients that are valid for
all $n \geq 0$, but there are also cautionary examples where there is a linear
recurrence that is valid for an initial range of values of $n$ but fails to be
satisfied beyond that point, providing further illustrations of Richard Guy's
celebrated "Strong Law of Small Numbers". In this paper we present a decision
algorithm, fully implemented in an accompanying Maple program ({\tt
Pisot.txt}), that first searches for a putative linear recurrence and then
decides whether or not it holds for all values of $n$. We also explain why the
failures happen (in some cases the `fake' linear recurrence may be valid for
thousands of terms). We conclude by defining, and studying, higher-order
analogs of Pisot sequences, and point out that similar phenomena occur there,
albeit far less frequently. This article is dedicated to Richard K. Guy (b.
Sept. 30, 1916) on his 100th birthday.


title: Evolution as a coexistence mechanism: Does genetic architecture matter?

abstract:
  Species sharing a prey or a predator species may go extinct due to
exploitative or apparent competition. We examine whether evolution of the
shared species acts as a coexistence mechanism and to what extent the answer
depends on the genetic architecture underlying trait evolution. In our models
of exploitative and apparent competition, the shared species evolves its
defense or prey use. Evolving species are either haploid or diploid. A single
locus pleiotropically determines prey nutritional quality and predator attack
rates. When pleiotropy is sufficiently antagonistic (e.g. nutritional prey are
harder to capture), eco-evolutionary assembly culminates in one of two stable
states supporting only two species. When pleiotropy is weakly antagonistic or
synergistic, assembly is intransitive: species-genotype pairs are cyclically
displaced by rare invasions of the missing genotypes or species. This
intransitivity allows for coexistence if, along its equilibria, the geometric
mean of recovery rates exceeds the geometric mean of loss rates of the rare
genotypes or species. By affecting these rates, synergistic pleiotropy can
mediate coexistence, while antagonistic pleiotropy does not. For diploid
populations experiencing weak antagonistic pleiotropy, superadditive allelic
contributions to fitness can mitigate coexistence via an eco-evolutionary
storage effect. Density-dependence and mutations also promote coexistence.
These results highlight how the efficacy of evolution as a coexistence
mechanism may depend on the underlying genetic architecture.


title: The Bootstrap and von Neumann algebras: The Maximal Intersection Lemma

abstract:
  Given a suitably nested family $Z = \langle Z(m,k,\gamma) \rangle_{m,k \in
\mathbb N, \gamma >0}$ of Borel subsets of matrices, and associated Borel
measures and rate function, $\mu$, an entropy, $\chi^{\mu}(Z)$, is introduced
which generalizes the microstates free entropy in free probability theory.
Under weak regularity conditions there exists a finite tuple of operators $X$
in a tracial von Neumann algebra such that \begin{eqnarray*} \chi^{\mu}(X) &
\geq & \chi^{\mu}(X \cap Z)
  & = & \chi^{\mu}(Z)\\ \end{eqnarray*} where $X \cap Z = \langle
\Gamma(X;m,k,\gamma) \cap Z(m,k,\gamma) \rangle_{m, k \in \mathbb N, \gamma
>0}$. This observation can be used to establish the existence of finite tuples
of operators with finite $\chi^{\mu}$-entropy. The intuition and proof come
from the bootstrap in statistical inference.


title:
Optimality and Sub-optimality of PCA for Spiked Random Matrices and
  Synchronization

abstract:
  A central problem of random matrix theory is to understand the eigenvalues of
spiked random matrix models, in which a prominent eigenvector is planted into a
random matrix. These distributions form natural statistical models for
principal component analysis (PCA) problems throughout the sciences. Baik, Ben
Arous and P\'ech\'e showed that the spiked Wishart ensemble exhibits a sharp
phase transition asymptotically: when the signal strength is above a critical
threshold, it is possible to detect the presence of a spike based on the top
eigenvalue, and below the threshold the top eigenvalue provides no information.
Such results form the basis of our understanding of when PCA can detect a
low-rank signal in the presence of noise.
  However, not all the information about the spike is necessarily contained in
the spectrum. We study the fundamental limitations of statistical methods,
including non-spectral ones. Our results include:
  I) For the Gaussian Wigner ensemble, we show that PCA achieves the optimal
detection threshold for a variety of benign priors for the spike. We extend
previous work on the spherically symmetric and i.i.d. Rademacher priors through
an elementary, unified analysis.
  II) For any non-Gaussian Wigner ensemble, we show that PCA is always
suboptimal for detection. However, a variant of PCA achieves the optimal
threshold (for benign priors) by pre-transforming the matrix entries according
to a carefully designed function. This approach has been stated before, and we
give a rigorous and general analysis.
  III) For both the Gaussian Wishart ensemble and various synchronization
problems over groups, we show that inefficient procedures can work below the
threshold where PCA succeeds, whereas no known efficient algorithm achieves
this. This conjectural gap between what is statistically possible and what can
be done efficiently remains open.

categories: math.ST cs.DS cs.IT math.IT math.PR stat.ML stat.TH


title:
Matrix representations of frame and lifted-graphic matroids correspond
  to gain functions

abstract:
  Let $M$ be a 3-connected matroid and let $\mathbb F$ be a field. Let $A$ be a
matrix over $\mathbb F$ representing $M$ and let $(G,\mathcal B)$ be a biased
graph representing $M$. We characterize the relationship between $A$ and
$(G,\mathcal B)$, settling four conjectures of Zaslavsky. We show that for each
matrix representation $A$ and each biased graph representation
$(G,\mathcal{B})$ of $M$, $A$ is projectively equivalent to a canonical matrix
representation arising from $G$ as a gain graph over $\mathbb F^+$ or $\mathbb
F^\times$ realizing $\mathcal{B}$. Further, we show that the projective
equivalence classes of matrix representations of $M$ are in one-to-one
correspondence with the switching equivalence classes of gain graphs arising
from $(G,\mathcal B)$, except in one degenerate case.


title:
Exact Finite-Difference Time-Domain Modelling of Broadband Huygens'
  Metasurfaces with Lorentz Dispersions

abstract:
  An explicit time-domain finite-difference technique for modelling
zero-thickness Huygens' metasurfaces based on Generalized Sheet Transition
Conditions (GSTCs), is proposed and demonstrated using full-wave simulations.
The Huygens' metasurface is modelled using electric and magnetic surface
susceptibilities, which are found to follow a double-Lorentz dispersion
profile. To solve zero-thickness Huygens' metasurface problems for general
broadband excitations, the double-Lorentz dispersion profile is combined with
GSTCs, leading to a set of first-order differential fields equations in
time-domain. Identifying the exact equivalence between Huygens' metasurfaces
and coupled RLC oscillator circuits, the field equations are then subsequently
solved using standard circuit modelling techniques based on a finite-difference
formulation. Several examples including generalized refraction are shown to
illustrate the temporal evolution of scattered fields from the Huygens'
metasurface under plane-wave normal incidence, in both harmonic steady-state
and broadband regimes. In particular, due to its inherent time-domain
formulation, a significant strength of the methodology is its ability to model
time-varying metasurfaces, which is demonstrated with a simple example of a
pumped metasurface leading to new frequency generation and wave amplification.


title: Homogeneity for a Class of Riemannian Quotient Manifolds

abstract:
  We study riemannian coverings $\varphi: \widetilde{M} \to \Gamma\backslash
\widetilde{M}$ where $\widetilde{M}$ is a normal homogeneous space $G/K_1$
fibered over another normal homogeneous space $M = G/K$ and $K$ is locally
isomorphic to a nontrivial product $K_1\times K_2$. The most familiar such
fibrations $\pi: \widetilde{M} \to M$ are the natural fibrations of Stieffel
manifolds $SO(n_1 + n_2)/SO(n_1)$ over Grassmann manifolds $SO(n_1 +
n_2)/[SO(n_1)\times SO(n_2)]$ and the twistor space bundles over quaternionic
symmetric spaces (= quaternion-Kaehler symmetric spaces = Wolf spaces). The
most familiar of these coverings $\varphi: \widetilde{M} \to \Gamma\backslash
\widetilde{M}$ are the universal riemannian coverings of spherical space forms.
When $M = G/K$ is reasonably well understood, in particular when $G/K$ is a
riemannian symmetric space or when $K$ is a connected subgroup of maximal rank
in $G$, we show that the Homogeneity Conjecture holds for $\widetilde{M}$. In
other words we show that $\Gamma\backslash \widetilde{M}$ is homogeneous if and
only if every $\gamma \in \Gamma$ is an isometry of constant displacement. In
order to find all the isometries of constant displacement on $\widetilde{M}$ we
work out the full isometry group of $\widetilde{M}$, extending Elie Cartan's
determination of the full group of isometries of a riemannian symmetric space.
We also discuss some pseudo-riemannian extensions of our results.


title: Conformal QED in two-dimensional topological insulators

abstract:
  It has been shown recently that local four-fermion interactions on the edges
of two-dimensional time-reversal-invariant topological insulators give rise to
a new non-Fermi-liquid phase, called helical Luttinger liquid (HLL). In this
work, we provide a first-principle derivation of this non-Fermi-liquid phase
based on the gauge-theory approach. Firstly, we derive a gauge theory for the
edge states by simply assuming that the interactions between the Dirac fermions
at the edge are mediated by a quantum dynamical electromagnetic field. Here,
the massless Dirac fermions are confined to live on the one-dimensional
boundary, while the (virtual) photons of the U(1) gauge field are free to
propagate in all the three spatial dimensions that represent the physical space
where the topological insulator is embedded. We then determine the effective
1+1-dimensional conformal field theory (CFT) given by the conformal quantum
electrodynamics (CQED). By integrating out the gauge field in the corresponding
partition function, we show that the CQED gives rise to a 1+1-dimensional
Thirring model. The bosonized Thirring Hamiltonian describes exactly a HLL with
a parameter K and a renormalized Fermi velocity that depend on the value of the
fine-structure constant $\alpha$.


title:
The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS):
  Survey design, data catalogue and GAMA/WiggleZ spectroscopy

abstract:
  We present the Large Area Radio Galaxy Evolution Spectroscopic Survey
(LARGESS), a spectroscopic catalogue of radio sources designed to include the
full range of radio AGN populations out to redshift z = 0.8. The catalogue
covers roughly 800 square degrees of sky, and provides optical identifications
for 19,179 radio sources from the 1.4 GHz Faint Images of the Radio Sky at
Twenty-cm (FIRST) survey down to an optical magnitude limit of i_mod < 20.5 in
Sloan Digital Sky Survey (SDSS) images. Both galaxies and point-like objects
are included, and no colour cuts are applied. In collaboration with the WiggleZ
and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have
obtained new spectra for over 5,000 objects in the LARGESS sample. Combining
these new spectra with data from earlier surveys provides spectroscopic data
for 12,329 radio sources in the survey area, of which 10,856 have reliable
redshifts. 85% of the LARGESS spectroscopic sample are radio AGN (median
redshift z = 0.44), and 15% are nearby star-forming galaxies (median z = 0.08).
Low-excitation radio galaxies (LERGs) comprise the majority (83%) of LARGESS
radio AGN at z < 0.8, with 12% being high-excitation radio galaxies (HERGs) and
5% radio-loud QSOs. Unlike the more homogeneous LERG and QSO sub-populations,
HERGs are a heterogeneous class of objects with relatively blue optical colours
and a wide dispersion in mid-infrared colours. This is consistent with a
picture in which most HERGs are hosted by galaxies with recent or ongoing star
formation as well as a classical accretion disk.


title: Simultaneous construction of hyperbolic isometries

abstract:
  Given isometric actions by a group G on finitely many \delta-hyperbolic
metric spaces, we provide a sufficient condition that guarantees the existence
of a single element in G that is hyperbolic for each action. As an application
we prove a conjecture of Handel and Mosher regarding relatively fully
irreducible subgroups and elements in the outer automorphism group of a free
group.


title: Abelian Squares and Their Progenies

abstract:
  A polynomial $P \in \mathbb{C}[z_1, \ldots, z_d]$ is strongly
$\mathbb{D}^d$-stable if $P$ has no zeroes in the closed unit polydisc
$\overline{\mathbb{D}}^d.$ For such a polynomial define its spectral density
function as $\mathcal{S}_P(\mathbf{z}) =
\left(P(\mathbf{z})\overline{P(1/\overline{\mathbf{z}})}\right)^{-1}.$ An
abelian square is a finite string of the form $ww'$ where $w'$ is a
rearrangement of $w.$
  We examine a polynomial-valued operator whose spectral density function's
Fourier coefficients are all generating functions for combinatorial classes of
constrained finite strings over a $d$-character alphabet. These classes
generalize the notion of an abelian square, and their associated generating
functions are the Fourier coefficients of one, and essentially only one,
$L^2(\mathbb{T}^d)$-valued operator. Integral representations, divisibility
properties, and recurrent and asymptotic behavior of the coefficients of these
generating functions are given as consequences. Tools in the derivations of our
asymptotic formulas include a version of Laplace's method for sums over lattice
point translations due to Greenhill, Janson, and Ruci\'{n}ski, a version of
stationary phase method for oscillatory integrals with complex phase due to
Pemantle and Wilson, and various polynomial identities related to powers of
modified Bessel functions of the first kind due to Moll and Vignat.


title: Exact solution of the two-axis countertwisting Hamiltonian

abstract:
  It is shown that the two-axis countertwisting Hamiltonian is exactly solvable
when the quantum number of the total angular momentum of the system is an
integer after the Jordan-Schwinger (differential) boson realization of the
SU(2) algebra. Algebraic Bethe ansatz is used to get the exact solution with
the help of the SU(1,1) algebraic structure, from which a set of Bethe ansatz
equations of the problem is derived. It is shown that solutions of the Bethe
ansatz equations can be obtained as zeros of the Heine-Stieltjes polynomials.
The total number of the four sets of the zeros equals exactly to $2J+1$ for a
given integer angular momentum quantum number $J$, which proves the
completeness of the solutions. It is also shown that double degeneracy in level
energies may also occur in the $J\rightarrow\infty$ limit for integer $J$ case
except a unique non-degenerate level with zero excitation energy.


title:
Design and Analysis of Initial Access in Millimeter Wave Cellular
  Networks

abstract:
  Initial access is the process which allows a mobile user to first connect to
a cellular network. It consists of two main steps: cell search (CS) on the
downlink and random access (RA) on the uplink. Millimeter wave (mmWave)
cellular systems typically must rely on directional beamforming (BF) in order
to create a viable connection. The beamforming direction must therefore be
learned-as well as used-in the initial access process for mmWave cellular
networks. This paper considers four simple but representative initial access
protocols that use various combinations of directional beamforming and
omnidirectional transmission and reception at the mobile and the BS, during the
CS and RA phases. We provide a system-level analysis of the success probability
for CS and RA for each one, as well as of the initial access delay and
user-perceived downlink throughput (UPT). For a baseline exhaustive search
protocol, we find the optimal BS beamwidth and observe that in terms of initial
access delay it is decreasing as blockage becomes more severe, but is
relatively constant (about $\pi/12$) for UPT. Of the considered protocols, the
best trade-off between initial access delay and UPT is achieved under a fast
cell search protocol.


title:
Color: A Crucial Factor for Aesthetic Quality Assessment in a Subjective
  Dataset of Paintings

abstract:
  Computational aesthetics is an emerging field of research which has attracted
different research groups in the last few years. In this field, one of the main
approaches to evaluate the aesthetic quality of paintings and photographs is a
feature-based approach. Among the different features proposed to reach this
goal, color plays an import role. In this paper, we introduce a novel dataset
that consists of paintings of Western provenance from 36 well-known painters
from the 15th to the 20th century. As a first step and to assess this dataset,
using a classifier, we investigate the correlation between the subjective
scores and two widely used features that are related to color perception and in
different aesthetic quality assessment approaches. Results show a
classification rate of up to 73% between the color features and the subjective
scores.


title: Continuous and discontinuous transitions to synchronization

abstract:
  We describe how the transition to synchronization in a system of globally
coupled Stuart-Landau oscillators changes from continuous to discontinuous when
the nature of the coupling is moved from diffusive to reactive. We explain this
drastic qualitative change as resulting from the co-existence of a particular
synchronized macrostate together with the trivial incoherent macrostate, in a
range of parameter values for which the later is linearly stable. In contrast
to the paradigmatic Kuramoto model, this particular state observed at the
synchronization transition contains a finite, non-vanishing number of
synchronized oscillators, which results in a discontinuous transition. We
consider successively two situations where either a fully synchronized state or
a partially synchronized state exist at the transition. Thermodynamic limit and
finite size effects are briefly discussed, as well as connections with recently
observed discontinuous transitions.


title:
A numerical point of view at the Gurov-Reshetnyak inequality on the real
  line

abstract:
  A "norm" of power function in the Gurov-Reshetnyak class on the real line is
computed. Moreover, a lower bound for the norm of the operator of even
extension from the semi-axis to the whole real line in the Gurov-Reshetnyak
class is obtained from numerical experiments.


title: Modeling and Analysis for Cache-Enabled Networks with Dynamic Traffic

abstract:
  Instead of assuming fully loaded cells in the analysis on cache-enabled
networks with tools of stochastic geometry, we focus on the dynamic traffic in
this letter. With modeling traffic dynamics of request arrivals and departures,
probabilities of full-, free-, and modest-load cells in the large-scale
cache-enabled network are elaborated based on the traffic queue state.
Moreover, we propose to exploit the packets cached at cache-enabled users as
side information to cancel the incoming interference. Then the packet loss
rates for both the cache-enabled and cache-untenable users are investigated.
The simulation results verify our analysis.


title:
Tensor Completion by Alternating Minimization under the Tensor Train
  (TT) Model

abstract:
  Using the matrix product state (MPS) representation of tensor train
decompositions, in this paper we propose a tensor completion algorithm which
alternates over the matrices (tensors) in the MPS representation. This
development is motivated in part by the success of matrix completion algorithms
which alternate over the (low-rank) factors. We comment on the computational
complexity of the proposed algorithm and numerically compare it with existing
methods employing low rank tensor train approximation for data completion as
well as several other recently proposed methods. We show that our method is
superior to existing ones for a variety of real settings.


title: On time change equivalence of Borel flows

abstract:
  This paper addresses the notion of time change equivalence for Borel
multidimensional flows. We show that all free flows are time change equivalent
up to a compressible set. An appropriate version of this result for non-free
flows is also given.


title: Minimal Mirror Twin Higgs

abstract:
  In a Mirror Twin World with a maximally symmetric Higgs sector the little
hierarchy of the Standard Model can be significantly mitigated, perhaps
displacing the cutoff scale above the LHC reach. We show that consistency with
observations requires that the Z2 parity exchanging the Standard Model with its
mirror be broken in the Yukawa couplings. A minimal such effective field
theory, with this sole Z2 breaking, can generate the Z2 breaking in the Higgs
sector necessary for the Twin Higgs mechanism. The theory has constrained and
correlated signals in Higgs decays, direct Dark Matter Detection and Dark
Radiation, all within reach of foreseen experiments, over a region of parameter
space where the fine-tuning for the electroweak scale is 10-50%. For dark
matter, both mirror neutrons and a variety of self-interacting mirror atoms are
considered. Neutrino mass signals and the effects of a possible additional Z2
breaking from the vacuum expectation values of B-L breaking fields are also
discussed.


title: Fast Single Shot Detection and Pose Estimation

abstract:
  For applications in navigation and robotics, estimating the 3D pose of
objects is as important as detection. Many approaches to pose estimation rely
on detecting or tracking parts or keypoints [11, 21]. In this paper we build on
a recent state-of-the-art convolutional network for slidingwindow detection
[10] to provide detection and rough pose estimation in a single shot, without
intermediate stages of detecting parts or initial bounding boxes. While not the
first system to treat pose estimation as a categorization problem, this is the
first attempt to combine detection and pose estimation at the same level using
a deep learning approach. The key to the architecture is a deep convolutional
network where scores for the presence of an object category, the offset for its
location, and the approximate pose are all estimated on a regular grid of
locations in the image. The resulting system is as accurate as recent work on
pose estimation (42.4% 8 View mAVP on Pascal 3D+ [21] ) and significantly
faster (46 frames per second (FPS) on a TITAN X GPU). This approach to
detection and rough pose estimation is fast and accurate enough to be widely
applied as a pre-processing step for tasks including high-accuracy pose
estimation, object tracking and localization, and vSLAM.


title:
Monte Carlo Simulation of Evaporation Driven Self-Assembly in Suspension
  of Colloidal Rods

abstract:
  The vertical drying of a colloidal film containing rod-like particles was
studied by means of kinetic Monte Carlo (MC) simulation. The problem was
approached using a two-dimensional square lattice and the rods were represented
as linear $k$-mers (i.e., particles occupying $k$ adjacent sites). The initial
state before drying was produced using a model of random sequential adsorption
(RSA) with isotropic orientations of the $k$-mers (orientation of the $k$-mers
along horizontal $x$ and vertical $y$ directions are equiprobable). In the RSA
model, overlapping of the $k$-mers is forbidden. During the evaporation, an
upper interface falls with a linear velocity of $u$ in the vertical direction
and the $k$-mers undergo translation Brownian motion. The MC simulations were
run at different initial concentrations, $p_i$, ($p_i \in [0, p_j]$, where
$p_j$ is the jamming concentration), lengths of $k$-mers ($k \in [1, 12]$), and
solvent evaporation rates, $u$. For completely dried films, the spatial
distributions of $k$-mers and their electrical conductivities in both $x$ and
$y$ directions were examined. Significant evaporation-driven self-assembly and
orientation stratification of the $k$-mers oriented along the $x$ and $y$
directions were observed. The extent of stratification increased with
increasing value of $k$. The anisotropy of the electrical conductivity of the
film can be finely regulated by changes in the values of $p_i$, $k$ and $u$.


title: Conley Conjecture Revisited

abstract:
  We show that whenever a closed symplectic manifold admits a Hamiltonian
diffeomorphism with finitely many simple periodic orbits, the manifold has a
spherical homology class of degree two with positive symplectic area and
positive integral of the first Chern class. This theorem encompasses all known
cases of the Conley conjecture (symplectic CY and negative monotone manifolds)
and also some new ones (e.g., weakly exact symplectic manifolds with
non-vanishing first Chern class).
  The proof hinges on a general Lusternik-Schnirelmann type result that, under
some natural additional conditions, the sequence of mean spectral invariants
for the iterations of a Hamiltonian diffeomorphism never stabilizes. We also
show that for the iterations of a Hamiltonian diffeomorphism with finitely many
periodic orbits the sequence of action gaps between the "largest" and the
"smallest" spectral invariants remains bounded and, as consequence, establish
some new cases of the $C^\infty$-generic existence of infinitely many simple
periodic orbits.


title:
Symmetrical broken and nonlinear response of Weyl semimetal TaAs
  influenced by the topological surface states and Weyl nodes

abstract:
  A Weyl semimetal (WSM) features Weyl fermions in its bulk and topological
surface states on surfaces, and is novel material hosting Weyl fermions, a kind
of fundamental particles. The WSM was regarded as a three-dimensional version
of "graphene" under the illusion. In order to explore its promising
photoelectric properties and applications in photonics and photoelectronics,
here, we study the anisotropic linear and nonlinear optical responses of a WSM
TaAs, which are determined by the relationship and balance between its
topological surface states and Weyl nodes. We demonstrate that topological
surface states which break the bulk symmetry are responsible for the anisotropy
of the mobility, and the anisotropic nonlinear response shows saturable
characteristic with extremely large saturable intensity. We also find that the
mobility is anisotropic with the magnitude of 104 cm2V-1s-1 at room temperature
and can be accelerated by the optical field. By analyzing the symmetry, the
nonlinear response is mainly contributed by the fermions close to the Weyl
nodes, and is related to the Pauli's blocking of fermions, electron-electron
interaction. This work experimentally discovers the anisotropic ultrahigh
mobility of WSMs in the optical field and may start the field for the
applications of WSMs in photonics and photoelectronics.


title: Geometric classification of nilpotent Jordan algebras of dimension five

abstract:
  The variety $JorN_{5}$ of five-dimensional nilpotent Jordan algebras
structures over an algebraically closed field is investigated. We show that
$JorN_{5}$ is the union of five irreducible components, four of them correspond
to the Zariski closure of the $GL_5$-orbits of four rigid algebras and the
other one is the Zariski closure of an union of orbits of infinite family of
algebras, none of them being rigid.


title:
Audio-band Coating Thermal Noise Measurement for Advanced LIGO with a
  Multi-mode Optical Resonator

abstract:
  In modern high precision optical instruments, such as in gravitational wave
detectors or frequency references, thermally induced fluctuations in the
reflective coatings can be a limiting noise source. This noise, known as
coating thermal noise, can be reduced by choosing materials with low mechanical
loss. Examination of new materials becomes a necessity in order to further
minimize the coating thermal noise and thus improve sensitivity of next
generation instruments. We present a novel approach to directly measure coating
thermal noise using a high finesse folded cavity in which multiple
Hermite-Gaussian modes co-resonate. This method is used to probe surface
fluctuations on the order 10^-17 m\rtHz in the frequency range 30-400 Hz. We
applied this technique to measure thermal noise and loss angle of the coating
used in Advanced LIGO.


title:
$J/\psi$ Production in Polarized and Unpolarized $ep$ Collision and
  Sivers and $\cos2\phi$ Asymmetries

abstract:
  We calculate the Sivers and $\cos2\phi$ azimuthal asymmetries in $J/\psi$
production in polarized and unpolarized semi-inclusive $ep$ collision
respectively, using the formalism based on transverse momentum dependent parton
distributions (TMDs). Non-relativistic QCD based color octet model is employed
for calculating the $J/\psi$ production rate. The Sivers asymmetry in this
process directly probes the gluon Sivers function. The estimated Sivers
asymmetry at $z=1$ is negative which is in good agreement with COMPASS data. We
also investigate the effect of TMD evolution on the Sivers asymmetry. The
$\cos2\phi$ asymmetry is sizable and probes the linearly polarized gluon
distribution in an unpolarized proton.


title: Proton-proton hollowness at the LHC from inverse scattering

abstract:
  Parameterizations of the pp scattering data at the LHC collision energies
indicate a hollow in the inelasticity profile of the pp interaction, with less
absorption for head-on collisions than at a non-zero impact parameter. We show
that some qualitatively unnoticed features may be unveiled by a judicious
application of the inverse scattering problem in the eikonal approximation and
interpre- tation within an optical potential model. The hollowness effect is
magnifed in a 3D picture of the optical potential, and will presumably be
enhanced at yet higher energies. Moreover, in 3D it sets in at much smaller
energies than at the LHC. We argue that hollowness in the impact parameter is a
quantum effect, relying on the build-up of the real part of the eikonal
scattering phase and its possible passage through $\pi/2$. We also show that it
precludes models of inelastic collisions where inelasticity is obtained by
naive folding of partonic densities.


title: Nonequilibrium spin-boson model: from weak to strong coupling

abstract:
  We present a general theory to explore energy transfer in nonequilibrium
spin-boson models within the framework of nonequilibrium Green's function
(NEGF). In contrast to conventionally used NEGF methods based on a perturbation
expansion in the system-bath coupling, we adopt the polaron transformation to
the Hamiltonian and identify the tunneling term as a perturbation with the
system-bath coupling being treated nonperturbatively, herein termed the
polaron-transformed NEGF method. To evaluate terms in the Dyson series, we
further utilize the Majorana-fermion representation. The proposed method not
only allows us to deal with weak as well as strong coupling regime, but also
enables an investigation on the role of bias. As an application of the method,
we study the energy transfer between two Ohmic bosonic baths mediated by a
spin. For a unbiased spin system, our energy current result smoothly bridges
predictions of two benchmarks, namely, the quantum master equation and the
nonequilibrium non-interacting blip approximation, thus our method is beyond
existing theories. In case of a biased spin system, we reveal a bias-induced
nonmomotonic behavior of the energy conductance in the intermediate coupling
regime, due to the resonant character of the energy transfer. This finding may
offer a nontrivial quantum control knob over energy transfer at the nanoscale.


title:
Search for a dark vector gauge boson decaying to $\pi^+ \pi^-$ using
  $\eta \rightarrow \pi^+\pi^- \gamma$ decays

abstract:
  We report a search for a dark vector gauge boson $U^\prime$ that couples to
quarks in the decay chain $D^{*+} \to D^0 \pi^+, D^0 \to K^0_S \eta, \eta \to
U^\prime \gamma$, $U^\prime \to \pi^+ \pi^-$. No signal is found and we set a
mass-dependent limit on the baryonic fine structure constant of $10^{-3} -
10^{-2}$ in the $U^\prime$ mass range of 290 to 520 MeV/$c^2$. This analysis is
based on a data sample of 976 fb$^{-1}$ collected by the Belle experiment at
the KEKB asymmetric-energy $e^+e^-$ collider.


title: Graph-Structured Representations for Visual Question Answering

abstract:
  This paper proposes to improve visual question answering (VQA) with
structured representations of both scene contents and questions. A key
challenge in VQA is to require joint reasoning over the visual and text
domains. The predominant CNN/LSTM-based approach to VQA is limited by
monolithic vector representations that largely ignore structure in the scene
and in the form of the question. CNN feature vectors cannot effectively capture
situations as simple as multiple object instances, and LSTMs process questions
as series of words, which does not reflect the true complexity of language
structure. We instead propose to build graphs over the scene objects and over
the question words, and we describe a deep neural network that exploits the
structure in these representations. This shows significant benefit over the
sequential processing of LSTMs. The overall efficacy of our approach is
demonstrated by significant improvements over the state-of-the-art, from 71.2%
to 74.4% in accuracy on the "abstract scenes" multiple-choice benchmark, and
from 34.7% to 39.1% in accuracy over pairs of "balanced" scenes, i.e. images
with fine-grained differences and opposite yes/no answers to a same question.


title: Idology and Its Applications in Public Security and Network Security

abstract:
  Fraud (swindling money, property, or authority by fictionizing,
counterfeiting, forging, or imitating things, or by feigning other persons
privately) forms its threats against public security and network security.
Anti-fraud is essentially the identification of a person or thing. In this
paper, the authors first propose the concept of idology - a systematic and
scientific study of identifications of persons and things, and give the
definitions of a symmetric identity and an asymmetric identity. Discuss the
converting symmetric identities (e.g., fingerprints) to asymmetric identities.
Make a comparison between a symmetric identity and an asymmetric identity, and
emphasize that symmetric identities cannot guard against inside jobs. Compare
asymmetric RFIDs with BFIDs, and point out that a BFID is lightweight,
economical, convenient, and environmentalistic, and more suitable for the
anti-counterfeiting and source tracing of consumable merchandise such as foods,
drugs, and cosmetics. The authors design the structure of a united verification
platform for BFIDs and the composition of an identification system, and discuss
the wide applications of BFIDs in public security and network security -
antiterrorism and dynamic passwords for example.


title: Emergence of singularities from decoherence: Quantum catastrophes

abstract:
  We use a master equation to study the dynamics of two coupled macroscopic
quantum systems (e.g.\ a Josephson junction made of two Bose-Einstein
condensates or two spin states of an ensemble of trapped ions) subject to a
weak continuous measurement. If the coupling between the two systems is
suddenly switched on the resulting dynamics leads to caustics (fold and cusp
catastrophes) in the number-difference probability distribution, and at the
same time the measurement gradually induces a quantum-to-classical transition.
Decoherence is often invoked to help resolve paradoxes associated with
macroscopic quantum mechanics, but here, on the contrary, caustics are
well-behaved in the quantum (many-particle) theory and divergent in the
classical (mean-field) theory. Caustics thus represent a breakdown of the
classical theory towards which decoherence seems to inevitably lead. We find
that measurement backaction plays a crucial role in softening the resulting
singularities and calculate the modification to the Arnol'd index which governs
the scaling of the caustic's amplitude with the number of atoms. The Arnol'd
index acts as a critical exponent for the formation of singularities during
quantum dynamics and its modification by the open nature of the system is
analogous to the modification of the critical exponents of phase transitions
occurring in open systems.


title: Effective indirect multi-site spin-spin interactions in the s-d(f) model

abstract:
  Using the diagram technique for Matsubara Green's functions it is shown that
the dynamics of the localized spin subsystem in the s-d(f) model can be
described in terms of an effective spin model with multi-site spin-spin
interactions. An exact representation of the action for the effective purely
spin model is derived as an infinite series in powers of s-d(f) exchange
interaction $J$. The indirect interactions of the 2-nd, 3-rd and 4-th order are
discussed.


title:
A Database of Phase Calibration Sources and their Radio Spectra for the
  Giant Metrewave Radio Telescope

abstract:
  We are pursuing a project to build a database of phase calibration sources
suitable for Giant Metrewave Radio Telescope (GMRT). Here we present the first
release of 45 low frequency calibration sources at 235 MHz and 610 MHz. These
calibration sources are broadly divided into quasars, radio galaxies and
unidentified sources. We provide their flux densities, models for calibration
sources, (u,v) plots, final deconvolved restored maps and clean-component
lists/files for use in the Astronomical Image Processing System (AIPS) and the
Common Astronomy Software Applications (CASA). We also assign a quality factor
to each of the calibration sources. These data products are made available
online through the GMRT observatory website. In addition we find that (i) these
45 low frequency calibration sources are uniformly distributed in the sky and
future efforts to increase the size of the database should populate the sky
further, (ii) spectra of these calibration sources are about equally divided
between straight, curved and complex shapes, (iii) quasars tend to exhibit
flatter radio spectra as compared to the radio galaxies or the unidentified
sources, (iv) quasars are also known to be radio variable and hence possibly
show complex spectra more frequently, and (v) radio galaxies tend to have
steeper spectra, which are possibly due to the large redshifts of distant
galaxies causing the shift of spectrum to lower frequencies.


title: Skyrme-Faddeev Lagrangian from reformulated Georgi-Glashow model

abstract:
  Recently we proposed a decomposition for fields of the Georgi-Glashow model
and interpreted Cho's decomposition as a result of some constraints on
Georgi-Glashow's fields. Now, using the decomposition form that Faddeev and
Niemi proposed, we introduce a simple and novel method to derive the
Skyrme-Faddeev Lagrangian from the reformulation of the Georgi-Glashow model
with an extra constraint. As we showed before, this extra constraint leads to
appearance of both vortices and monopoles.


title:
The effect of distributed time-delays on the synchronization of neuronal
  networks

abstract:
  Here we investigate the synchronization of networks of FitzHugh-Nagumo
neurons coupled in scale-free, small-world and random topologies, in the
presence of distributed time delays in the coupling of neurons. We explore how
the synchronization transition is affected when the time delays in the
interactions between pairs of interacting neurons are non-uniform. We find that
the presence of distributed time-delays does not change the behavior of the
synchronization transition significantly, vis-a-vis networks with constant
time-delay, where the value of the constant time-delay is the mean of the
distributed delays. We also notice that a normal distribution of delays gives
rise to a transition at marginally lower coupling strengths, vis-a-vis
uniformly distributed delays. These trends hold across classes of networks and
for varying standard deviations of the delay distribution, indicating the
generality of these results. So we conclude that distributed delays, which may
be typically expected in real-world situations, do not have a notable effect on
synchronization. This allows results obtained with constant delays to remain
relevant even in the case of randomly distributed delays.


title: Initial behavior of solutions to the Yang-Mills heat equation

abstract:
  We explore the small-time behavior of solutions to the Yang-Mills heat
equation with rough initial data. We consider solutions $A(t)$ with initial
value $A_0\in H_{1/2}(M)$, where $M$ is a bounded convex region in
$\mathbb{R}^3$ or all of $\mathbb{R}^3$. The behavior, as $t\downarrow 0$, of
the $L^p(M)$ norms of the time derivatives of $A(t)$ and its curvature $B(t)$
will be determined for $p=2$ and $6$, along with the $H_1(M)$ norm of these
derivatives.


title:
Carbon cluster diagnostics-III: Direct Recoil Spectroscopy (DRS) versus
  ExB Velocity Analysis

abstract:
  A comparative study is being reported on the identification of heavy carbon
clusters using two different techniques namely the Direct Recoil Spectroscopy
(DRS) and velocity spectrometry using a Wien ExB velocity filter. In both the
techniques carbon clusters are formed in situ either under energetic heavy ion
bombardment of graphite surfaces for which DRS is employed or these are emitted
from the regenerative sooting discharges and analyzed using ExB velocity
analysis.


title: Selective sampling after solving a convex problem

abstract:
  We consider the problem of selective inference after solving a (randomized)
convex statistical learning program in the form of a penalized or constrained
loss function. Our first main result is a change-of-measure formula that
describes many conditional sampling problems of interest in selective
inference. Our approach is model-agnostic in the sense that users may provide
their own statistical model for inference, we simply provide the modification
of each distribution in the model after the selection.
  Our second main result describes the geometric structure in the Jacobian
appearing in the change of measure, drawing connections to curvature measures
appearing in Weyl-Steiner volume-of-tubes formulae. This Jacobian is necessary
for problems in which the convex penalty is not polyhedral, with the
prototypical example being group LASSO or the nuclear norm. We derive explicit
formulae for the Jacobian of the group LASSO.
  To illustrate the generality of our method, we consider many examples
throughout, varying both the penalty or constraint in the statistical learning
problem as well as the loss function, also considering selective inference
after solving multiple statistical learning programs. Penalties considered
include LASSO, forward stepwise, stagewise algorithms, marginal screening and
generalized LASSO. Loss functions considered include squared-error, logistic,
and log-det for covariance matrix estimation.
  Having described the appropriate distribution we wish to sample from through
our first two results, we outline a framework for sampling using a projected
Langevin sampler in the (commonly occuring) case that the distribution is
log-concave.


title: Enhancing LambdaMART Using Oblivious Trees

abstract:
  Learning to rank is a machine learning technique broadly used in many areas
such as document retrieval, collaborative filtering or question answering. We
present experimental results which suggest that the performance of the current
state-of-the-art learning to rank algorithm LambdaMART, when used for document
retrieval for search engines, can be improved if standard regression trees are
replaced by oblivious trees. This paper provides a comparison of both variants
and our results demonstrate that the use of oblivious trees can improve the
performance by more than $2.2\%$. Additional experimental analysis of the
influence of a number of features and of a size of the training set is also
provided and confirms the desirability of properties of oblivious decision
trees.


title: Stability phenomena in the homology of tree braid groups

abstract:
  For a tree $G$, we study the changing behaviors in the homology groups
$H_i(B_nG)$ as $n$ varies, where $B_nG := \pi_1($UConf$_n(G))$. We prove that
the ranks of these homologies can be described by a single polynomial for all
$n$, and construct this polynomial explicitly in terms of invariants of the
tree $G$. To accomplish this we prove that the group $\bigoplus_n H_i(B_nG)$
can be endowed with the structure of a finitely generated graded module over an
integral polynomial ring, and further prove that it naturally decomposes as a
direct sum of graded shifts of squarefree monomial ideals. Following this, we
spend time considering how our methods might be generalized to braid groups of
arbitrary graphs, and make various conjectures in this direction.


title:
Experimental study of the astrophysical gamma-process reaction
  124Xe(alpha,gamma)128Ba

abstract:
  The synthesis of heavy, proton rich isotopes in the astrophysical
gamma-process proceeds through photodisintegration reactions. For the improved
understanding of the process, the rates of the involved nuclear reactions must
be known. The reaction 128Ba(g,a)124Xe was found to affect the abundance of the
p nucleus 124Xe. Since the stellar rate for this reaction cannot be determined
by a measurement directly, the aim of the present work was to measure the cross
section of the inverse 124Xe(a,g)128Ba reaction and to compare the results with
statistical model predictions. Of great importance is the fact that data below
the (a,n) threshold was obtained. Studying simultaneously the 124Xe(a,n)127Ba
reaction channel at higher energy allowed to further identify the source of a
discrepancy between data and prediction. The 124Xe + alpha cross sections were
measured with the activation method using a thin window 124Xe gas cell. The
studied energy range was between E = 11 and 15 MeV close above the
astrophysically relevant energy range. The obtained cross sections are compared
with statistical model calculations. The experimental cross sections are
smaller than standard predictions previously used in astrophysical
calculations. As dominating source of the difference, the theoretical alpha
width was identified. The experimental data suggest an alpha width lower by at
least a factor of 0.125 in the astrophysical energy range. An upper limit for
the 128Ba(g,a)124Xe stellar rate was inferred from our measurement. The impact
of this rate was studied in two different models for core-collapse supernova
explosions of 25 solar mass stars. A significant contribution to the 124Xe
abundance via this reaction path would only be possible when the rate was
increased above the previous standard value. Since the experimental data rule
this out, they also demonstrate the closure of this production path.


title:
Inhomogeneous relativistic Boltzmann equation near vacuum in the
  Robertson-Walker space-time

abstract:
  In this paper, we consider the Cauchy problem for the relativistic Boltzmann
equation with near vacuum initial data where the distribution function depends
on the time, the position and the impulsion. The collision kernel considered
here is for the hard potentials case and the background space-time in which the
study is done is the Robertson-Walker space-time. Unique global (in time) mild
solution is obtained in a suitable weighted space.


title: Quantum software for linear photonic simulations

abstract:
  The search for new, application-specific quantum computers designed to
outperform any classical computer is driven by the ending of Moore's law and
the quantum advantages potentially obtainable. Photonic networks are promising
examples, with experimental demonstrations and potential for obtaining a
quantum computer to solve problems believed classically impossible. This
introduces a challenge: how does one design or understand such photonic
networks? We develop novel complex phase-space software for simulating these
photonic networks, and apply this to boson sampling experiments. Our techniques
give sampling errors orders of magnitude lower than experimental measurements
of correlations, for the same number of samples. We show that these techniques
remove systematic errors in previous algorithms for estimating correlations,
with order of magnitude improvements in errors in some cases. In addition to
that, we obtain a scalable channel-combination strategy for assessment of boson
sampling devices.


title:
Discussion of "Fast Approximate Inference for Arbitrarily Large
  Semiparametric Regression Models via Message Passing"

abstract:
  Discussion paper on "Fast Approximate Inference for Arbitrarily Large
Semiparametric Regression Models via Message Passing" by Wand
[arXiv:1602.07412].


title:
Preorder-Based Triangle: A Modified Version of Bilattice-Based Triangle
  for Belief Revision in Nonmonotonic Reasoning

abstract:
  Bilattice-based triangle provides an elegant algebraic structure for
reasoning with vague and uncertain information. But the truth and knowledge
ordering of intervals in bilattice-based triangle can not handle repetitive
belief revisions which is an essential characteristic of nonmonotonic
reasoning. Moreover the ordering induced over the intervals by the
bilattice-based triangle is not sometimes intuitive. In this work, we construct
an alternative algebraic structure, namely preorder-based triangle and we
formulate proper logical connectives for this. It is also demonstrated that
Preorder-based triangle serves to be a better alternative to the
bilattice-based triangle for reasoning in application areas, that involve
nonmonotonic fuzzy reasoning with uncertain information.


title: On the scaling limits of weakly asymmetric bridges

abstract:
  We consider a discrete bridge from $(0,0)$ to $(2N,0)$ evolving according to
the corner growth dynamics, where the jump rates are subject to an upward
asymmetry of order $N^{-\alpha}$ with $\alpha \in (0,\infty)$. We provide a
classification of the asymptotic behaviours - invariant measure, hydrodynamic
limit and fluctuations - of this model according to the value of the parameter
$\alpha$.


title:
$K$-band integral field spectroscopy and optical spectroscopy of massive
  young stellar objects in the Small Magellanic Cloud

abstract:
  We present $K$-band integral field spectroscopic observations towards 17
massive young stellar objects (YSOs) in the low metallicity Small Magellanic
Cloud (SMC) and two YSO candidates in the compact H ii regions N81 and N88 A
(also in the SMC). These sources, originally identified using $Spitzer$
photometry and/or spectroscopy, have been resolved into 29 $K$-band continuum
sources. By comparing Br$\gamma$ emission luminosities with those presented for
a Galactic sample of massive YSOs, we find tentative evidence for increased
accretion rates in the SMC. Around half of our targets exhibit emission line
(Br$\gamma$, He i and H$_2$) morphologies which extend significantly beyond the
continuum source and we have mapped both the emission morphologies and the
radial velocity fields. This analysis also reveals evidence for the existence
of ionized low density regions in the centre outflows from massive YSOs.
Additionally we present an analysis of optical spectra towards a similar sample
of massive YSOs in the SMC, revealing that the optical emission is
photo-excited and originates near the outer edges of molecular clouds, and is
therefore consistent with a high mean-free path of UV photons in the
interstellar medium (ISM) of the SMC. Finally, we discuss the sample of YSOs in
an evolutionary context incorporating the results of previous infrared and
radio observations, as well as the near-infrared and optical observations
presented in this work. Our spectroscopic analysis in both the $K$-band and the
optical regimes, combined with previously obtained infrared and radio data,
exposes differences between properties of massive YSOs in our own Galaxy and
the SMC, including tracers of accretion, discs and YSO--ISM interactions.


title:
Coarse-to-fine Surgical Instrument Detection for Cataract Surgery
  Monitoring

abstract:
  The amount of surgical data, recorded during video-monitored surgeries, has
extremely increased. This paper aims at improving existing solutions for the
automated analysis of cataract surgeries in real time. Through the analysis of
a video recording the operating table, it is possible to know which instruments
exit or enter the operating table, and therefore which ones are likely being
used by the surgeon. Combining these observations with observations from the
microscope video should enhance the overall performance of the systems. To this
end, the proposed solution is divided into two main parts: one to detect the
instruments at the beginning of the surgery and one to update the list of
instruments every time a change is detected in the scene. In the first part,
the goal is to separate the instruments from the background and from irrelevant
objects. For the second, we are interested in detecting the instruments that
appear and disappear whenever the surgeon interacts with the table. Experiments
on a dataset of 36 cataract surgeries validate the good performance of the
proposed solution.


title: High quality-factor mechanical resonators based on WSe2 monolayers

abstract:
  Suspended monolayer transition metal-dichalcogenides (TMD) are membranes that
combine ultra-low mass and exceptional optical properties, making them
intriguing materials for opto-mechanical applications. However, the low
measured quality factor of TMD resonators has been a roadblock so far. Here, we
report an ultrasensitive optical readout of monolayer TMD resonators that
allows us to reveal their mechanical properties at cryogenic temperatures. We
find that the quality factor of monolayer WSe2 resonators greatly increases
below room temperature, reaching values as high as 1.6E^4 at liquid nitrogen
temperature and 4.7E^4 at liquid helium temperature. This surpasses the quality
factor of monolayer graphene resonators with similar surface areas. Upon
cooling the resonator, the resonant frequency increases significantly due to
the thermal contraction of the WSe2 lattice. These measurements allow us to
experimentally study the thermal expansion coefficient of WSe2 monolayers for
the first time. High Q-factors are also found in resonators based on MoS2 and
MoSe2 monolayers. The high quality-factor found in this work opens new
possibilities for coupling mechanical vibrational states to two-dimensional
excitons, valley pseudospins, and single quantum emitters, and for quantum
opto-mechanical experiments based on the Casimir interaction.


title:
Extending Unification in $\mathcal{EL}$ to Disunification: The Case of
  Dismatching and Local Disunification

abstract:
  Unification in Description Logics has been introduced as a means to detect
redundancies in ontologies. We try to extend the known decidability results for
unification in the Description Logic $\mathcal{EL}$ to disunification since
negative constraints can be used to avoid unwanted unifiers. While decidability
of the solvability of general $\mathcal{EL}$-disunification problems remains an
open problem, we obtain NP-completeness results for two interesting special
cases: dismatching problems, where one side of each negative constraint must be
ground, and local solvability of disunification problems, where we consider
only solutions that are constructed from terms occurring in the input problem.
More precisely, we first show that dismatching can be reduced to local
disunification, and then provide two complementary NP-algorithms for finding
local solutions of disunification problems.