title: Quantitative recovery conditions for tree-based compressed sensing

abstract:
  As shown in [Blumensath and Davies 2009, Baraniuk et al. 2010], signals whose
wavelet coefficients exhibit a rooted tree structure can be recovered using
specially-adapted compressed sensing algorithms from just n=O(k) measurements,
where k is the sparsity of the signal. Motivated by these results, we introduce
a simplified proportional-dimensional asymptotic framework which enables the
quantitative evaluation of recovery guarantees for tree-based compressed
sensing. In the context of Gaussian matrices, we apply this framework to
existing worst-case analysis of the Iterative Tree Projection (ITP) algorithm
which makes use of the tree-based Restricted Isometry Property (RIP). Within
the same framework, we then obtain quantitative results based on a new method
of analysis, recently introduced in [Cartis and Thompson, 2015], which
considers the fixed points of the algorithm. By exploiting the realistic
average-case assumption that the measurements are statistically independent of
the signal, we obtain significant quantitative improvements when compared to
the tree-based RIP analysis. Our results have a refreshingly simple
interpretation, explicitly determining a bound on the number of measurements
that are required as a multiple of the sparsity. For example we prove that
exact recovery of binary tree-based signals from noiseless Gaussian
measurements is asymptotically guaranteed for ITP with constant stepsize
provided n>50k. All our results extend to the more realistic case in which
measurements are corrupted by noise.


title: Sampling BSSRDFs with non-perpendicular incidence

abstract:
  Sub-surface scattering is key to our perception of translucent materials.
Models based on diffusion theory are used to render such materials in a
realistic manner by evaluating an approximation of the material BSSRDF at any
two points of the surface. Under the assumption of perpendicular incidence,
this BSSRDF approximation can be tabulated over 2 dimensions to provide fast
evaluation and importance sampling. However, accounting for non-perpendicular
incidence with the same approach would require to tabulate over 4 dimensions,
making the model too large for practical applications. In this report, we
present a method to efficiently evaluate and importance sample the
multi-scattering component of diffusion based BSSRDFs for non-perpendicular
incidence. Our approach is based on tabulating a compressed angular model of
Photon Beam Diffusion. We explain how to generate, evaluate and sample our
model. We show that 1 MiB is enough to store a model of the multi-scattering
BSSRDF that is within $0.5\%$ relative error of Photon Beam Diffusion. Finally,
we present a method to use our model in a Monte Carlo particle tracer and show
results of our implementation in PBRT.


title: Second-order nonlinear optical response of graphene

abstract:
  Although massless Dirac fermions in graphene constitute a centrosymmetric
medium for in-plane excitations, their second-order nonlinear optical response
is nonzero if the effects of spatial dispersion are taken into account. Here we
present a rigorous quantum-mechanical theory of the second-order nonlinear
response of graphene beyond the electric dipole approximation, which includes
both intraband and interband transitions. The resulting nonlinear
susceptibility tensor satisfies all symmetry and permutation properties, and
can be applied to all three-wave mixing processes. We obtain useful analytic
expressions in the limit of a degenerate electron distribution, which reveal
quite strong second-order nonlinearity at long wavelengths, Fermi-edge
resonances, and unusual polarization properties.


title:
Nesting statistics in the $O(n)$ loop model on random maps of arbitrary
  topologies

abstract:
  We pursue the analysis of nesting statistics in the $O(n)$ loop model on
random maps, initiated for maps with the topology of disks and cylinders in
math-ph/1605.02239, here for arbitrary topologies. For this purpose we rely on
the topological recursion results of math-ph/0910.5896 and math-ph/1303.5808
for the enumeration of maps in the $O(n)$ model. We characterize the generating
series of maps of genus $g$ with $k'$ marked points and $k$ boundaries and
realizing a fixed nesting graph. These generating series are amenable to
explicit computations in the loop model with bending energy on triangulations,
and we characterize their behavior at criticality in the dense and in the
dilute phase.


title: The Social Dynamics of Language Change in Online Networks

abstract:
  Language change is a complex social phenomenon, revealing pathways of
communication and sociocultural influence. But, while language change has long
been a topic of study in sociolinguistics, traditional linguistic research
methods rely on circumstantial evidence, estimating the direction of change
from differences between older and younger speakers. In this paper, we use a
data set of several million Twitter users to track language changes in
progress. First, we show that language change can be viewed as a form of social
influence: we observe complex contagion for phonetic spellings and "netspeak"
abbreviations (e.g., lol), but not for older dialect markers from spoken
language. Next, we test whether specific types of social network connections
are more influential than others, using a parametric Hawkes process model. We
find that tie strength plays an important role: densely embedded social ties
are significantly better conduits of linguistic influence. Geographic locality
appears to play a more limited role: we find relatively little evidence to
support the hypothesis that individuals are more influenced by geographically
local social ties, even in their usage of geographical dialect markers.


title:
Accurate calculation of the geometric measure of entanglement for
  multipartite quantum states

abstract:
  This article proposes an efficient way of calculating the geometric measure
of entanglement using tensor decomposition methods. The connection between
these two concepts is explored using the tensor representation of the
wavefunction. Numerical examples are benchmarked and compared. Furthermore, we
search for highly entangled qubit states to show the applicability of this
method.


title: Visual Saliency Detection Based on Multiscale Deep CNN Features

abstract:
  Visual saliency is a fundamental problem in both cognitive and computational
sciences, including computer vision. In this paper, we discover that a
high-quality visual saliency model can be learned from multiscale features
extracted using deep convolutional neural networks (CNNs), which have had many
successes in visual recognition tasks. For learning such saliency models, we
introduce a neural network architecture, which has fully connected layers on
top of CNNs responsible for feature extraction at three different scales. The
penultimate layer of our neural network has been confirmed to be a
discriminative high-level feature vector for saliency detection, which we call
deep contrast feature. To generate a more robust feature, we integrate
handcrafted low-level features with our deep contrast feature. To promote
further research and evaluation of visual saliency models, we also construct a
new large database of 4447 challenging images and their pixelwise saliency
annotations. Experimental results demonstrate that our proposed method is
capable of achieving state-of-the-art performance on all public benchmarks,
improving the F- measure by 6.12% and 10.0% respectively on the DUT-OMRON
dataset and our new dataset (HKU-IS), and lowering the mean absolute error by
9% and 35.3% respectively on these two datasets.


title:
Ferromagnetic layer thickness dependence of the Dzyaloshinskii-Moriya
  interaction and spin-orbit torques in Pt\Co\AlOx

abstract:
  We report the thickness dependence of Dzyaloshinskii-Moriya interaction (DMI)
and spin-orbit torques (SOTs) in Pt\Co(t)\AlOx, studied by current-induced
domain wall (DW) motion and second-harmonic experiments. From the DW motion
study, a monotonous decay of the effective DMI strength with an increasing Co
thickness is observed, in agreement with a DMI originating at the Pt\Co
interface. The study of the ferromagnetic thickness dependence of spin-orbit
torques reveals a more complex behavior. The effective SOT-field driving the DW
motion is found to initially increase and then saturate with an increasing
ferromagnetic thickness, while the effective SOT-fields acting on a saturated
magnetic state exhibit a non-monotonic behavior with increasing Co-thickness.
The observed thickness dependence suggests the spin-Hall effect in Pt as the
main origin of the SOTs, with the measured SOT amplitudes resulting from the
interplay between the varying thickness and the transverse spin diffusion
length of the Co layer.


title:
Vertex coloring of graphs via phase dynamics of coupled oscillatory
  networks

abstract:
  While Boolean logic has been the backbone of digital information processing,
there are classes of computationally hard problems wherein this conventional
paradigm is fundamentally inefficient. Vertex coloring of graphs, belonging to
the class of combinatorial optimization represents such a problem; and is well
studied for its wide spectrum of applications in data sciences, life sciences,
social sciences and engineering and technology. This motivates alternate, and
more efficient non-Boolean pathways to their solution. Here, we demonstrate a
coupled relaxation oscillator based dynamical system that exploits the
insulator-metal transition in vanadium dioxide (VO2), to efficiently solve the
vertex coloring of graphs. By harnessing the natural analogue between
optimization, pertinent to graph coloring solutions, and energy minimization
processes in highly parallel, interconnected dynamical systems, we harness the
physical manifestation of the latter process to approximate the optimal
coloring of k-partite graphs. We further indicate a fundamental connection
between the eigen properties of a linear dynamical system and the spectral
algorithms that can solve approximate graph coloring. Our work not only
elucidates a physics-based computing approach but also presents tantalizing
opportunities for building customized analog co-processors for solving hard
problems efficiently.


title: Proof mining in $L^p$ spaces

abstract:
  We obtain an equivalent implicit characterization of $L^p$ Banach spaces that
is amenable to a logical treatment. Using that, we obtain an axiomatization for
such spaces into a higher-order logical system, the kind of which is used in
proof mining, a research program that aims to obtain the hidden computational
content of mathematical proofs using tools from mathematical logic. As an
aside, we obtain a concrete way of formalizing $L^p$ spaces in positive-bounded
logic. The axiomatization is followed by a corresponding metatheorem in the
style of proof mining. We illustrate its use with the derivation for this class
of spaces of the standard modulus of uniform convexity.


title:
An Investigation into the Mathematical Nature of Electrophysiological
  Signals with Applications

abstract:
  In this work we have proposed a rigorous mathematical definition for the one
dimensional time domain electrophysiological signals and established its
relationship with two of the three Dirichlet's conditions. We have argues that
any such signal can be represented as the trajectory of a particle moving in a
force field with one degree of freedom. At point on the trajectory, that is, on
the signal, the kinetic energy dissipated by the particle embeds semantic
information into the trajectory or the signal in terms of giving its shape. We
have shown that the rate of kinetic energy dissipation operator or the power
operator P is of importance in shape analysis of the signal by considering its
sign changes. Operating the P-operator on digital signals we have
mathematically proved that its sign change can induce 13 different shapes to a
three successive point configuration. In other words, semantic information at
each point in a digital signal can be embedded by a syllable of 13 different
letters. We have shown some preliminary applications.


title:
An improved uncertainty decoding scheme with weighted samples for
  DNN-HMM hybrid systems

abstract:
  In this paper, we advance a recently-proposed uncertainty decoding scheme for
DNN-HMM (deep neural network - hidden Markov model) hybrid systems. This
numerical sampling concept averages DNN outputs produced by a finite set of
feature samples (drawn from a probabilistic distortion model) to approximate
the posterior likelihoods of the context-dependent HMM states. As main
innovation, we propose a weighted DNN-output averaging based on a minimum
classification error criterion and apply it to a probabilistic distortion model
for spatial diffuseness features. The experimental evaluation is performed on
the 8-channel REVERB Challenge task using a DNN-HMM hybrid system with
multichannel front-end signal enhancement. We show that the recognition
accuracy of the DNN-HMM hybrid system improves by incorporating uncertainty
decoding based on random sampling and that the proposed weighted DNN-output
averaging further reduces the word error rate scores.


title: Generic free resolutions and root systems

abstract:
  In this paper I give an explicit construction of the generic ring R_{gen} for
finite free resolutions of length 3. The corresponding problem for resolutions
of length 2 was solved in 1970'ies by Hochster and Huneke. The key role is
played by the defect Lie algebra introduced in my old work on the subject. The
defect Lie algebra turns out to be a parabolic Lie algebra in a Kac-Moody Lie
algebra associated to the graph T_{p,q,r} corresponding to the format of the
resolution. The ring R_{gen} is Noetherian if and only if the graph T_{p.q.r}
is a Dynkin graph.


title: Carbon membranes for efficient water-ethanol separation

abstract:
  We demonstrate, on the basis of molecular dynamics simulations, the
possibility of an efficient water-ethanol separation using nanoporous carbon
membranes, namely carbon nanotube membranes, nanoporous graphene sheets, and
multilayer graphene membranes. While these carbon membranes are in general
permeable to both pure liquids, they exhibit a counter-intuitive
"self-semi-permeability" to water in the presence of water-ethanol mixtures.
This originates in a preferred ethanol adsorption in nanoconfinement that
prevents water molecules from entering the carbon nanopores. An osmotic
pressure is accordingly expressed across the carbon membranes for the
water-ethanol mixture, which agrees with the classic van't Hoff type
expression. This suggests a robust and versatile membrane-based separation,
built on a pressure-driven reverse-osmosis process across these carbon-based
membranes. In particular, the recent development of large-scale
'graphene-oxide' like membranes then opens an avenue for a versatile and
efficient ethanol dehydration using this separation process, with possible
application for bio-ethanol fabrication.


title:
Magnetic fields in protoplanetary disks: from MHD simulations to ALMA
  observations

abstract:
  Magnetic fields significantly influence the evolution of protoplanetary disks
and the formation of planets, following the predictions of numerous
magnetohydrodynamic (MHD) simulations. However, these predictions are yet
observationally unconstrained. To validate the predictions on the influence of
magnetic fields on protoplanetary disks, we apply 3D radiative transfer
simulations of the polarized emission of aligned aspherical dust grains that
directly link 3D global non-ideal MHD simulations to ALMA observations. Our
simulations show that it is feasible to observe the predicted toroidal
large-scale magnetic field structures, not only in the ideal observations but
also with high-angular resolution ALMA observations. Our results show further
that high angular resolution observations by ALMA are able to identify vortices
embedded in outer magnetized disk regions.


title:
Stability of higher-dimensional interval decomposable persistence
  modules

abstract:
  The algebraic stability theorem for $\mathbb{R}$-persistence modules is a
fundamental result in topological data analysis. We present a stability theorem
for $n$-dimensional rectangle decomposable persistence modules up to a constant
$(2n-1)$ that is a generalization of the algebraic stability theorem, and also
has connections to the complexity of calculating the interleaving distance. The
proof given reduces to a new proof of the algebraic stability theorem with
$n=1$. We give an example to show that the bound cannot be improved for $n=2$.
We apply the same technique to prove stability results for zigzag modules and
Reeb graphs, reducing the previously known bounds to a constant that cannot be
improved, settling these questions.


title:
Clearing the Skies: A deep network architecture for single-image rain
  removal

abstract:
  We introduce a deep network architecture called DerainNet for removing rain
streaks from an image. Based on the deep convolutional neural network (CNN), we
directly learn the mapping relationship between rainy and clean image detail
layers from data. Because we do not possess the ground truth corresponding to
real-world rainy images, we synthesize images with rain for training. In
contrast to other common strategies that increase depth or breadth of the
network, we use image processing domain knowledge to modify the objective
function and improve deraining with a modestly-sized CNN. Specifically, we
train our DerainNet on the detail (high-pass) layer rather than in the image
domain. Though DerainNet is trained on synthetic data, we find that the learned
network translates very effectively to real-world images for testing. Moreover,
we augment the CNN framework with image enhancement to improve the visual
results. Compared with state-of-the-art single image de-raining methods, our
method has improved rain removal and much faster computation time after network
training.


title: One-loop effective actions and higher spins

abstract:
  The idea we advocate in this paper is that the one-loop effective action of a
free (massive) field theory coupled to external sources (via conserved
currents) contains complete information about the classical dynamics of such
sources. We show many explicit examples of this fact for (scalar and fermion)
free field theories in various dimensions $d=3,4,5,6$ coupled to (bosonic,
completely symmetric) sources with a number of spins. In some cases we also
provide compact formulas for any dimension. This paper is devoted to two-point
correlators, so the one-loop effective action we construct contains only the
quadratic terms and the relevant equations of motion for the sources we obtain
are the linearized ones.


title: Exceptionally simple exceptional models

abstract:
  We discuss models with no dynamical vector fields in various dimensions which
we claim might have exceptional symmetry on some loci of their parameter space.
In particular we construct theories with four supercharges flowing to theories
with global symmetry enhancing to $F_4$, $E_6$, and $E_7$. The main evidence
for these claims is based on extracting information about the symmetry
properties of the theories from their supersymmetric partition functions.


title: A variant of Waring's Problem for the ring of integers modulo n

abstract:
  We study a variant of Waring's problem for $\mathbb{Z}_n$, the ring of
integers modulo $n$: For a fixed integer $k \geq 2$, what is the minimum number
$m$ of $k$th powers necessary such that $x \equiv x_1^k + \dots + x_m^k
\pmod{n}$ has a solution for every $x \in \mathbb{Z}_n$? Using only elementary
methods, we answer fully this question for exponents $k \leq 10$, and we
further discuss some intermediary cases such as categorizing the values of $n$
such that every element in $\mathbb{Z}_n$ can be written as a sum of three
squares. Hensel's Theorem for $p$-adic integers plays a key role. Finally, we
give an application of this problem to the Erd\H os-Falconer distance problem
for rings $\mathbb{Z}_n^d$.


title: A note on Brill--Noether existence for graphs of low genus

abstract:
  In an influential 2008 paper, Baker proposed a number of conjectures relating
the divisor theory of algebraic curves with an analogous combinatorial theory
on finite graphs. In this note, we examine Baker's Brill--Noether existence
conjecture for special divisors. For $g\leq 5$ and $\rho(g,r,d)$ non-negative,
every graph of genus $g$ is shown to admit a divisor of rank $r$ and degree at
most $d$. Moreover, the conjecture is shown to hold in rank $1$ for a number of
families of highly connected combinatorial types of graphs of arbitrarily high
genus. In the relevant genera, our arguments give the first combinatorial proof
of the Brill--Noether existence theorem for metric graphs, giving a partial
answer to a related question of Baker.


title: Unruh acceleration effect on the precision of parameter estimation

abstract:
  The dynamics of Fisher information for an accelerated system initially
prepared in the $X$-state is discussed. An analytical solution, which consists
of three parts: classical, the average over all pure states and a mixture of
pure states is derived for the general state and for Werner state. It is shown
that, the Unruh acceleration has a depleting effect on the Fisher information.
This depletion depends on the degree of entanglement of the initial state
settings. For the $X$-state, for some intervals of Unruh acceleration, the
Fisher information remains constant, irrespective to the Unruh acceleration. In
general, the possibility of estimating the state's parameters decreases as the
acceleration increases. However, the precision of estimation can be maximized
for certain values of the Unruh acceleration. We also investigate the
contribution of the different parts of the Fisher information on the dynamics
of the total Fisher information.


title: Dynamical complexity and controlled operator K-theory

abstract:
  In this paper, we introduce a property of topological dynamical systems that
we call finite dynamical complexity. For systems with this property, one can in
principle compute the $K$-theory of the associated crossed product
$C^*$-algebra by splitting it up into simpler pieces and using the methods of
controlled $K$-theory. The main part of the paper illustrates this idea by
giving a new proof of the Baum-Connes conjecture for actions with finite
dynamical complexity.
  We have tried to keep the paper as self-contained as possible: we hope the
main part will be accessible to someone with the equivalent of a first course
in operator $K$-theory. In particular, we do not assume prior knowledge of
controlled $K$-theory, and use a new and concrete model for the Baum-Connes
conjecture with coefficients that requires no bivariant $K$-theory to set up.


title: Optimality of the Johnson-Lindenstrauss Lemma

abstract:
  For any integers $d, n \geq 2$ and $1/({\min\{n,d\}})^{0.4999} <
\varepsilon<1$, we show the existence of a set of $n$ vectors $X\subset
\mathbb{R}^d$ such that any embedding $f:X\rightarrow \mathbb{R}^m$ satisfying
$$ \forall x,y\in X,\ (1-\varepsilon)\|x-y\|_2^2\le \|f(x)-f(y)\|_2^2 \le
(1+\varepsilon)\|x-y\|_2^2 $$ must have $$ m = \Omega(\varepsilon^{-2} \lg n).
$$ This lower bound matches the upper bound given by the Johnson-Lindenstrauss
lemma [JL84]. Furthermore, our lower bound holds for nearly the full range of
$\varepsilon$ of interest, since there is always an isometric embedding into
dimension $\min\{d, n\}$ (either the identity map, or projection onto
$\mathop{span}(X)$).
  Previously such a lower bound was only known to hold against linear maps $f$,
and not for such a wide range of parameters $\varepsilon, n, d$ [LN16]. The
best previously known lower bound for general $f$ was $m =
\Omega(\varepsilon^{-2}\lg n/\lg(1/\varepsilon))$ [Wel74, Lev83, Alo03], which
is suboptimal for any $\varepsilon = o(1)$.


title: Mid-infrared time-resolved photoconduction in black phosphorus

abstract:
  Black phosphorus has attracted interest as a material for use in
optoelectronic devices due to many favorable properties such as a high carrier
mobility, field-effect, and a direct bandgap that can range from 0.3 eV in its
bulk crystalline form to 2 eV for a single atomic layer. The low bandgap energy
for bulk black phosphorus allows for direct transition photoabsorption that
enables detection of light out to mid-infrared frequencies. In this work we
characterize the room temperature optical response of a black phosphorus
photoconductive detector at wavelengths ranging from 1.56 $\mu$m to 3.75
$\mu$m. Pulsed autocorrelation measurements in the near-infrared regime reveal
a strong, sub-linear photocurrent nonlinearity with a response time of 1 ns,
indicating that gigahertz electrical bandwidth is feasible. Time resolved
photoconduction measurements covering near- and mid-infrared frequencies show a
fast 65 ps rise time, followed by a carrier relaxation with a time scale that
matches the intrinsic limit determined by autocorrelation. The sublinear
photoresponse is shown to be caused by a reduction in the carrier relaxation
time as more energy is absorbed in the black phosphorus flake and is well
described by a carrier recombination model that is nonlinear with excess
carrier density. The device exhibits a measured noise-equivalent power of 530
pW/$\sqrt{\text{Hz}}$ which is the expected value for Johnson noise limited
performance. The fast and sensitive room temperature photoresponse demonstrates
that black phosphorus is a promising new material for mid-infrared
optoelectronics.


title:
The motion of chondrules and other particles in a protoplanetary disc
  with temperature fluctuations

abstract:
  We consider the mechanism of photophoretic transport in protoplanetary disks
that are optically thick to radiation. Here, photophoresis is not caused by the
central star but by temperature fluctuations that subject suspended solid
particles, including chondrules, to non-isotropic thermal radiation within the
disk. These short-lived temperature fluctuations can explain time-of-flight
size sorting and general number density enhancements. The same mechanism will
also lead to velocity fluctuations of dust aggregates beyond
$100\,\mathrm{m\,s^{-1}}$ for mm-sized particles in protoplanetary disks.
Applying this in future research will change our understanding of the early
phases of collisional dust evolution and aggregate growth as particles cross
the bouncing barrier and as mass transfer rates are altered.


title:
A Fourier dimensionality reduction model for big data interferometric
  imaging

abstract:
  Data dimensionality reduction in radio interferometry can provide savings of
computational resources for image reconstruction through reduced memory
footprints and lighter computations per iteration, which is important for the
scalability of imaging methods to the big data setting of the next-generation
telescopes. This article sheds new light on dimensionality reduction from the
perspective of compressed sensing theory and studies its interplay with imaging
algorithms designed in the context of convex optimization. We propose a
post-gridding linear data embedding to the space spanned by the left singular
vectors of the measurement operator, providing a dimensionality reduction below
image size. This embedding preserves the null space of the measurement operator
and hence also its sampling properties as per compressed sensing theory. We
show that this can be approximated by first computing the dirty image and then
applying a weighted subsampled discrete Fourier transform to obtain the final
reduced data vector. This Fourier dimensionality reduction model ensures a fast
implementation of the full measurement operator, essential for any iterative
image reconstruction method. The proposed reduction also preserves the i.i.d.
Gaussian properties of the original measurement noise. For convex
optimization-based imaging algorithms, this is key to justify the use of the
standard L2-norm as the data fidelity term. Our simulations confirm that this
dimensionality reduction approach can be leveraged by convex optimization
algorithms with no loss in imaging quality relative to reconstructing the image
from the complete visibility data set. Reconstruction results in simulation
settings with no direction dependent effects or calibration errors show
promising performance of the proposed dimensionality reduction. MATLAB code
implementing the proposed reduction method is available on GitHub.


title: The isometry group of an $\mathsf{RCD}^*$-space is Lie

abstract:
  We give necessary and sufficient conditions that show that both the group of
isometries and the group of measure-preserving isometries are Lie groups for a
large class of metric measure spaces. In addition we study, among other
examples, whether spaces having a generalized lower Ricci curvature bound
fulfill these requirements. The conditions are satisfied by RCD*-spaces and,
under extra assumptions, by CD-spaces, CD*-spaces, and MCP-spaces. However, we
show that the MCP-condition by itself is not enough to guarantee a smooth
behavior of these automorphism groups. More generally we show that spaces with
good optimal transport properties meet as well the hypotheses.


title:
The Gauss map on translational Riemannian manifolds and the topology of
  hypersurfaces

abstract:
  We introduce the notion of translational Riemannian manifolds and define a
Gauss map for orientable immersed hypersurfaces lying in these ambients, an
associated translational curvature and prove a Gauss-Bonnet theorem. We also
use this Gauss map to prove that if $M^{n}$ is a compact, connected and
oriented immersed hypersurface of the unit sphere $\mathbb{S}^{n+1}$ ($n\geq2$)
contained in a geodesic ball of radius $R$ and whose principal curvatures are
strictly bigger than $\tan\left( R/2 \right)$, then $M$ is diffeomorphic to
$\mathbb{S}^{n}$. Additionally, we show that for any
$\varepsilon\in(0,\sqrt{2}-1)$ there exists a compact, connected and oriented
immersed hypersurface $M_{\varepsilon}$ of $\mathbb{S}^{n+1}$ whose principal
curvatures are strictly bigger than $\varepsilon \tan \left( R/2 \right)$ but
$M_{\varepsilon}$ is not homeomorphic to a sphere. Finally, using this previous
result, we reobtain a theorem of Qiaoling Wang and Changyu Xia (see [4]) which
asserts that if a compact and oriented hypersurface of $\mathbb{S}^{n+1}$ is
contained in an open hemisphere and has nowhere zero Gauss-Kronecker curvature,
then it is diffeomorphic to $\mathbb{S}^n$.


title:
An introduction to integrable techniques for one-dimensional quantum
  systems

abstract:
  This monograph introduces the reader to basic notions of integrable
techniques for one-dimensional quantum systems. In a pedagogical way, a few
examples of exactly solvable models are worked out to go from the coordinate
approach to the Algebraic Bethe Ansatz, with some discussion on the finite
temperature thermodynamics. The aim is to provide the instruments to approach
more advanced books or to allow for a critical reading of research articles and
the extraction of useful information from them. We describe the solution of the
anisotropic XY spin chain; of the Lieb-Liniger model of bosons with contact
interaction at zero and finite temperature; and of the XXZ spin chain, first in
the coordinate and then in the algebraic approach. To establish the connection
between the latter and the solution of two dimensional classical models, we
also introduce and solve the 6-vertex model. Finally, the low energy physics of
these integrable models is mapped into the corresponding conformal field
theory. Through its style and the choice of topics, this book tries to touch
all fundamental ideas behind integrability and is meant for students and
researchers interested either in an introduction to later delve in the advance
aspects of Bethe Ansatz or in an overview of the topic for broadening their
culture.


title:
KSbOSiO$_4$ microcrystallites as a source of corrosion of blue-green
  lead-potassium glass beads of the 19th century

abstract:
  Presently, deterioration of glass beads is a significant problem in
conservation and restoration of beaded exhibits in museums. Glass corrosion
affects nearly all kinds of beads but cloudy blue-green ones are more than
others subjected to disastrous destruction. However, physical and chemical
mechanisms of this phenomenon have not been understood thus far. This article
presents results of a study of elemental and phase composition of glass of the
blue-green beads of the 19th century obtained from exhibits kept in Russian
museums. Using scanning electron microscopy, X-ray microanalysis and X-ray
powder analysis we have detected and investigated Sb-rich microinclusions in
the glass matrix of these beads and found them to be micro crystallites of
KSbSiO$_5$. These crystallites were not detected in other kinds of beads which
are much less subjected to corrosion than the blue-green ones and deteriorate
in a different way. We belive that individual precipitates of KSbSiO$_5$ and
especially their clusters play a major role in the blue-green bead
deterioration giving rise to slow internal corrosion of the bead glass.


title: Noise induces rare events in granular media

abstract:
  The granular Leidenfrost effect (B. Meerson et al, Phys. Rev. Lett. {\bf 91},
024301 (2003), P. Eshuis et al, Phys. Rev. Lett. {\bf 95}, 258001 (2005)) is
the levitation of a mass of granular matter when a wall below the grains is
vibrated giving rise to a hot granular gas below the cluster. We find by
simulation that for a range of parameters the system is bistable: the levitated
cluster can occasionally break and give rise to two clusters and a hot granular
gas above and below. We use techniques from the theory of rare events to
compute the mean transition time for breaking to occur. This requires the
introduction of a two-component reaction coordinate.


title:
The method of shifted partial derivatives cannot separate the permanent
  from the determinant

abstract:
  The method of shifted partial derivatives was used to prove a
super-polynomial lower bound on the size of depth four circuits needed to
compute the permanent. We show that this method alone cannot prove that the
padded permanent $\ell^{n-m} perm_m$ cannot be realized inside the
$GL_{n^2}$-orbit closure of the determinant $ det_n$ when $n>2m^2+2m$. Our
proof relies on several simple degenerations of the determinant polynomial,
Macaulay's theorem that gives a lower bound on the growth of an ideal, and a
lower bound estimate from Gupta et. al. regarding the shifted partial
derivatives of the determinant.


title: A Consumer-Centric Market for Database Computation in the Cloud

abstract:
  The availability of public computing resources in the cloud has
revolutionized data analysis, but requesting cloud resources often involves
complex decisions for consumers. Under the current pricing mechanisms, cloud
service providers offer several service options and charge consumers based on
the resources they use. Before they can decide which cloud resources to
request, consumers have to estimate the completion time and cost of their
computational tasks for different service options and possibly for different
service providers. This estimation is challenging even for expert cloud users.
We propose a new market-based framework for pricing computational tasks in the
cloud. Our framework introduces an agent between consumers and cloud providers.
The agent takes data and computational tasks from users, estimates time and
cost for evaluating the tasks, and returns to consumers contracts that specify
the price and completion time. Our framework can be applied directly to
existing cloud markets without altering the way cloud providers offer and price
services. In addition, it simplifies cloud use for consumers by allowing them
to compare contracts, rather than choose resources directly. We present design,
analytical, and algorithmic contributions focusing on pricing computation
contracts, analyzing their properties, and optimizing them in complex
workflows. We conduct an experimental evaluation of our market framework over a
real-world cloud service and demonstrate empirically that our market ensures
three key properties: competitiveness, fairness, and resilience. Finally, we
present a fine-grained pricing mechanism for complex workflows and show that it
can increase agent profits by more than an order of magnitude in some cases.


title:
Rotational Symmetry of Asymptotically Conical Mean Curvature Flow
  Self-Expanders

abstract:
  In this article, we examine complete, mean-convex self-expanders for the mean
curvature flow whose ends have decaying principal curvatures. We prove a
Liouville-type theorem associated to this class of self-expanders. As an
application, we show that mean-convex self-expanders which are asymptotic to
$O(n)$-invariant cones are rotationally symmetric.


title: Isolating the young stellar population in the outer disk of NGC 300

abstract:
  The recent star formation history (SFH) in the outer disk of NGC 300 is
presented through the analysis of color magnitude diagrams (CMDs). We analyze
resolved stellar photometry by creating CMDs from four Hubble Space Telescope
fields containing a combination of images from the Advanced Camera for Surveys
and the UVIS imager aboard the Wide Field Camera 3. From the best models of
these CMDs, we derive the SFH in order to extract the young stellar component
for the past 200 Myrs. We find that the young stellar disk of NGC 300 is
unbroken out to at least ${\sim}$8 scale lengths (including an upper limit out
to ${\sim}$10 scale lengths) with $r{_s}$ = 1.4 ${\pm}$ 0.1 kpc, which is
similar to the total stellar surface brightness profile. This unbroken profile
suggests that NGC 300 is undisturbed, similar to the isolated disk galaxy NGC
2403. We compare the environments of NGC 300, NGC 2403, and M33 along with the
properties of the gas and stellar disks. We find that the disturbed HI outer
disk morphology is not accompanied by a break in the young stellar disk. This
may indicate that processes which affect the outer HI morphology may not leave
an imprint on the young stellar disk.


title:
Quadrature Amplitude Modulation Division for Multiuser MISO Broadcast
  Channels

abstract:
  This paper considers a discrete-time multiuser multiple-input single-output
(MISO) Gaussian broadcast channel~(BC), in which channel state information
(CSI) is available at both the transmitter and the receivers. The flexible and
explicit design of a uniquely decomposable constellation group (UDCG) is
provided based on pulse amplitude modulation (PAM) and rectangular quadrature
amplitude modulation (QAM) constellations. With this, a modulation division
(MD) transmission scheme is developed for the MISO BC. The proposed MD scheme
enables each receiver to uniquely and efficiently detect their desired signals
from the superposition of mutually interfering cochannel signals in the absence
of noise. In our design, the optimal transmitter beamforming problem is solved
in a closed-form for two-user MISO BC using max-min fairness as a design
criterion. Then, for a general case with more than two receivers, we develop a
user-grouping-based beamforming scheme, where the grouping method, beamforming
vector design and power allocation problems are addressed by using weighted
max-min fairness. It is shown that our proposed approach has a lower
probability of error compared with the zero-forcing (ZF) method when the
Hermitian angle between the two channel vectors is small in a two-user case. In
addition, simulation results also reveal that for the general channel model
with more than two users, our user-grouping-based scheme significantly
outperforms the ZF, time division (TD), minimum mean-square error (MMSE) and
signal-to-leakage-and-noise ratio (SLNR) based techniques in moderate and high
SNR regimes when the number of users approaches to the number of base station
(BS) antennas and it degrades into the ZF scheme when the number of users is
far less than the number of BS antennas in Rayleigh fading channels.


title: The characteristic function of rough Heston models

abstract:
  It has been recently shown that rough volatility models, where the volatility
is driven by a fractional Brownian motion with small Hurst parameter, provide
very relevant dynamics in order to reproduce the behavior of both historical
and implied volatilities. However, due to the non-Markovian nature of the
fractional Brownian motion, they raise new issues when it comes to derivatives
pricing. Using an original link between nearly unstable Hawkes processes and
fractional volatility models, we compute the characteristic function of the
log-price in rough Heston models. In the classical Heston model, the
characteristic function is expressed in terms of the solution of a Riccati
equation. Here we show that rough Heston models exhibit quite a similar
structure, the Riccati equation being replaced by a fractional Riccati
equation.


title: On the Impact of Time-Synchronization in Molecular Timing Channels

abstract:
  This work studies the impact of time- synchronization in molecular timing
(MT) channels by analyzing three different modulation techniques. The first
requires transmitter-receiver synchronization and is based on modulating
information on the release timing of information particles. The other two are
asynchronous and are based on modulating information on the relative time
between two consecutive releases of information particles using
indistinguishable or distinguishable particles. All modulation schemes result
in a system that relate the transmitted and the received signals through an
additive noise, which follows a stable distribution. As the common notion of
the variance of a signal is not suitable for defining the power of stable
distributed signals (due to infinite variance), we derive an expression for the
geometric power of a large class of stable distributions, and then use this
result to characterize the geometric signal-to-noise ratio (G-SNR) for each of
the modulation techniques. In addition, for binary communication, we derive the
optimal detection rules for each modulation technique. Numerical evaluations
indicate that the bit error rate (BER) is constant for a given G-SNR, and the
performance gain obtained by using synchronized communication is significant.
Yet, it is also shown that by using two distinguishable particles per bit
instead of one, the BER of the asynchronous technique can approach that of the
synchronous one.


title:
Constructing balanced equations of motion for particles in general
  relativistic theories: the general case

abstract:
  We present a general approach for the formulation of equations of motion for
compact objects in general relativistic theories. The particle is assumed to be
moving in a geometric background which in turn is asymptotically flat. Our
approach defines a model for particle like objects which emphasizes different
aspects of a set of gravitating objects; by concentrating in the main
contributions coming from back reaction effects due to gravitational radiation.


title: Anisotropic dependence of tune-out wavelength near Dy 741-nm transition

abstract:
  We report the first measurement of a tune-out wavelength for ground-state
bosonic Dy and linearly polarized light. The tune-out wavelength measured is
near the narrow-line 741-nm transition in $^{162}$Dy, and is the wavelength at
which the total Stark shift of the ground state vanishes. We find that it
strongly depends on the relative angle between the optical field and
quantization axis due to Dy's large tensor polarizability. This anisotropy
provides a wide, 22-GHz tunability of the tune-out frequency for linearly
polarized light, in contrast to Rb and Cs whose near-infrared tune-out
wavelengths do not exhibit large anisotropy. The measurements of the total
light shift are performed by measuring the contrast of multipulse Kapitza-Dirac
diffraction. The calculated wavelengths are within a few GHz of the measured
values using known Dy electronic transition data. The lack of hyperfine
structure in bosonic Dy implies that the tune-out wavelengths for the other
bosonic Dy isotopes should be related to this $^{162}$Dy measurement by the
known isotope shifts.


title:
Studentized sensitivity analysis for the sample average treatment effect
  in paired observational studies

abstract:
  A fundamental limitation of causal inference in observational studies is that
perceived evidence for an effect might instead be explained by factors not
accounted for in the primary analysis. Methods for assessing the sensitivity of
a study's conclusions to unmeasured confounding have been established under the
assumption that the treatment effect is constant across all individuals. In the
potential presence of unmeasured confounding, it has been argued that certain
patterns of effect heterogeneity may conspire with unobserved covariates to
render the performed sensitivity analysis inadequate. We present a new method
for conducting a sensitivity analysis for the sample average treatment effect
in the presence of effect heterogeneity in paired observational studies. Our
recommended procedure, called the studentized sensitivity analysis, represents
an extension of recent work on studentized permutation tests to the case of
observational studies, where randomizations are no longer drawn uniformly. The
method naturally extends conventional tests for the sample average treatment
effect in paired experiments to the case of unknown, but bounded, probabilities
of assignment to treatment. In so doing, we illustrate that concerns about
certain sensitivity analyses operating under the presumption of constant
effects are largely unwarranted.


title: Uniqueness of Embeddings of the Affine Line into Algebraic Groups

abstract:
  Let $Y$ be the underlying variety of a connected affine algebraic group. We
prove that two embeddings of the affine line $\mathbb{C}$ into $Y$ are the same
up to an automorphism of $Y$ provided that $Y$ is not isomorphic to a product
of a torus $(\mathbb{C}^\ast)^k$ and one of the three varieties $\mathbb{C}^3$,
$\operatorname{SL}_2$, and $\operatorname{PSL}_2$.


title:
Damage to white matter bottlenecks contributes to language impairments
  after left hemispheric stroke

abstract:
  Damage to the white matter underlying the left posterior temporal lobe leads
to deficits in multiple language functions. The posterior temporal white matter
may correspond to a bottleneck where both dorsal and ventral language pathways
are vulnerable to simultaneous damage. Damage to a second putative white matter
bottleneck in the left deep prefrontal white matter involving projections
associated with ventral language pathways and thalamo-cortical projections has
recently been proposed as a source of semantic deficits after stroke. However,
the effects of damage to a priori identified white matter bottlenecks on
language function have not been directly investigated. Here, we first used
white matter atlases to identify the previously described white matter
bottlenecks in the posterior temporal and deep prefrontal white matter. We then
assessed the effects of damage to each region on measures of category fluency,
picture naming, and auditory semantic decision-making in 43 patients with
chronic aphasia. Damage to the posterior temporal bottleneck predicted deficits
on all language measures, while damage to the anterior bottleneck only
predicted deficits in category fluency. Importantly, the effects of damage to
the bottleneck regions were not attributable to lesion volume, lesion loads on
the tracts traversing the bottlenecks, or damage to nearby cortical language
areas. Multivariate lesion-symptom mapping and fiber tracking analyses
corroborated these findings. Together, our results provide strong support for
the proposal that spatially specific white matter damage affecting white matter
bottlenecks, particularly in the posterior temporal lobe, contribute to chronic
language deficits after left hemispheric stroke. Our results suggest that
damage to this area is likely to simultaneously disrupt signaling via the
simultaneous disruption of dorsal and ventral language processing streams.


title: Formation and Evolution of Blue Stragglers in 47 Tucanae

abstract:
  Blue stragglers (BSS) are stars whose position in the Color-Magnitude Diagram
(CMD) places them above the main sequence turn-off (TO) point of a star
cluster. Using data from the core of 47 Tuc in the ultraviolet (UV), we have
identified various stellar populations in the CMD, and used their radial
distributions to study the evolution and origin of BSS, and obtain a dynamical
estimate of the mass of BSS systems. When we separate the BSS into two samples
by their magnitude, we find that the bright BSS show a much more centrally
concentrated radial distribution and thus higher mass estimate (over twice the
TO mass for these BSS systems), suggesting an origin involving triple or
multiple stellar systems. In contrast, the faint BSS are less concentrated,
with a radial distribution similar to the main sequence (MS) binaries, pointing
to the MS binaries as the likely progenitors of these BSS. Putting our data
together with available photometric data in the visible and using MESA
evolutionary models, we calculate the expected number of stars in each
evolutionary stage for the normal evolution of stars and the number of stars
coming from the evolution of BSS. The results indicate that BSS have a post-MS
evolution comparable to that of a normal star of the same mass and a MS BSS
lifetime of about 200-300 Myr. We also find that the excess population of
asymptotic giant branch (AGB) stars in 47 Tuc is due to evolved BSS.


title: Ask the GRU: Multi-Task Learning for Deep Text Recommendations

abstract:
  In a variety of application domains the content to be recommended to users is
associated with text. This includes research papers, movies with associated
plot summaries, news articles, blog posts, etc. Recommendation approaches based
on latent factor models can be extended naturally to leverage text by employing
an explicit mapping from text to factors. This enables recommendations for new,
unseen content, and may generalize better, since the factors for all items are
produced by a compactly-parametrized model. Previous work has used topic models
or averages of word embeddings for this mapping. In this paper we present a
method leveraging deep recurrent neural networks to encode the text sequence
into a latent vector, specifically gated recurrent units (GRUs) trained
end-to-end on the collaborative filtering task. For the task of scientific
paper recommendation, this yields models with significantly higher accuracy. In
cold-start scenarios, we beat the previous state-of-the-art, all of which
ignore word order. Performance is further improved by multi-task learning,
where the text encoder network is trained for a combination of content
recommendation and item metadata prediction. This regularizes the collaborative
filtering model, ameliorating the problem of sparsity of the observed rating
matrix.


title:
DoF Analysis in a Two-Layered Heterogeneous Wireless Interference
  Network

abstract:
  Degrees of freedom (DoF) is studied in the downlink of a heterogenous
wireless network modeled as a two-layered interference network. The first layer
of the interference network is the backhaul layer between macro base stations
(MB) and small cell base stations (SB), which is modeled as a Wyner type linear
network. The second layer is the transmission layer between SBs and mobile
terminals (MTs), which is modeled as a linear Wyner $L_T$ network, i.e., each
MT is connected to $L_T+1$ SBs. The SBs are assumed to be half-duplex, thus
restricting the per user degrees of freedom (puDoF) in the system to $1/2$. The
puDoF can be further restricted by the number of antennas at the MB. For $L_T
\in \{1,2\}$, the optimal puDoF can be achieved by using simple interference
avoidance schemes. The increase in the connectivity of transmission layer
beyond $L_T=2$ limits the achievable puDoF using only zero-forcing schemes to
less than 1/2, even in the presence of large number of antennas at each MB but
the optimal puDoF can be achieved by making each message available at multiple
SBs. This is done by sending an appropriate linear combination to the SB to
zero-force interference at the intended user. The maximum per user DoF of 1/2
can be achieved in the linear network with sufficient number of antennas using
only interference avoidance schemes. These results are also extended to a more
realistic hexagonal cellular model as well.


title:
Hirzebruch $\chi_y$-genera modulo $8$ of fiber bundles for odd integers
  $y$

abstract:
  I. Hambleton, A. Korzeniewski and A. Ranicki proved that the signature of a
fibre bundle of closed, connected, compatibly oriented PL manifolds is always
multiplicative modulo 4. In this paper, we consider the Hirzebruch
$\chi_y$-genera for odd integers $y$ for a smooth fiber bundle such that the
base, fibre, and total space are compact complex algebraic manifolds (in the
complex analytic topology, not in the Zariski topology). We show that the
Hirzebruch $\chi_y$-genera of such a fibre bundle are always multiplicative
modulo 4. We also investigate multiplicativity modulo 8 and show that if $y$ is
congruent to 3 modulo 4, then the $\chi_y$-genera are multiplicative modulo 8.
We also show that when $y$ is congruent to 1 modulo 4, the Hirzebruch
$\chi_y$-genera of such a fiber bundle are multiplicative modulo 8 if and only
if the signature is multiplicative modulo 8, and that the non-multiplicativity
modulo 8, in this case, is identified with an Arf-Kervaire invariant.


title: Degeneration of Dynamical Degrees in Families of Maps

abstract:
  The dynamical degree of a dominant rational map
$f:\mathbb{P}^N\rightarrow\mathbb{P}^N$ is the quantity
$\delta(f):=\lim(\text{deg} f^n)^{1/n}$. We study the variation of dynamical
degrees in 1-parameter families of maps $f_T$. We make a conjecture and ask two
questions concerning, respectively, the set of $t$ such that: (1)
$\delta(f_t)\le\delta(f_T)-\epsilon$; (2) $\delta(f_t)<\delta(f_T)$; (3)
$\delta(f_t)<\delta(f_T)$ and $\delta(g_t)<\delta(g_T)$ for "independent"
families of maps. We give a sufficient condition for our conjecture to hold and
prove that it is true for monomial maps. We describe non-trivial families of
maps for which our questions have affirmative and negative answers.


title: Time-changes of stochastic processes associated with resistance forms

abstract:
  Given a sequence of resistance forms that converges with respect to the
Gromov-Hausdorff-vague topology and satisfies a uniform volume doubling
condition, we show the convergence of corresponding Brownian motions and local
times. As a corollary of this, we obtain the convergence of time-changed
processes. Examples of our main results include scaling limits of Liouville
Brownian motion, the Bouchaud trap model and the random conductance model on
trees and self-similar fractals. For the latter two models, we show that under
some assumptions the limiting process is a FIN diffusion on the relevant space.


title: Generating realistic scaled complex networks

abstract:
  Research on generative models is a central project in the emerging field of
network science, and it studies how statistical patterns found in real networks
could be generated by formal rules. Output from these generative models is then
the basis for designing and evaluating computational methods on networks, and
for verification and simulation studies. During the last two decades, a variety
of models has been proposed with an ultimate goal of achieving comprehensive
realism for the generated networks. In this study, we (a) introduce a new
generator, termed ReCoN; (b) explore how ReCoN and some existing models can be
fitted to an original network to produce a structurally similar replica, (c)
use ReCoN to produce networks much larger than the original exemplar, and
finally (d) discuss open problems and promising research directions. In a
comparative experimental study, we find that ReCoN is often superior to many
other state-of-the-art network generation methods. We argue that ReCoN is a
scalable and effective tool for modeling a given network while preserving
important properties at both micro- and macroscopic scales, and for scaling the
exemplar data by orders of magnitude in size.


title:
Entropy, topological transitivity, and dimensional properties of unique
  $q$-expansions

abstract:
  Let $M$ be a positive integer and $q \in(1,M+1].$ We consider expansions of
real numbers in base $q$ over the alphabet $\{0,\ldots, M\}$. In particular, we
study the set $\mathcal{U}_{q}$ of real numbers with a unique $q$-expansion,
and the set $\mathbf{U}_q$ of corresponding sequences.
  It was shown in (Komornik et al, 2017 Adv. Math.) that the function $H$,
which associates to each $q\in(1, M+1]$ the topological entropy of
$\mathcal{U}_q$, is a Devil's staircase. In this paper we explicitly determine
the plateaus of $H$, and characterize the bifurcation set $\mathcal E$ of $q$'s
where the function $H$ is not locally constant. Moreover, we show that
$\mathcal E$ is a Cantor set of full Hausdorff dimension. We also investigate
the topological transitivity of a naturally occurring subshift $(\mathbf{V}_q,
\sigma),$ which has a close connection with open dynamical systems. Finally, we
prove that the Hausdorff dimension and box dimension of $\mathcal{U}_q$
coincide for all $q\in(1,M+1]$.


title:
Time Series Analysis of fMRI Data: Spatial Modelling and Bayesian
  Computation

abstract:
  Time series analysis of fMRI data is an important area of medical statistics
for neuroimaging data. The neuroimaging community has embraced mean-field
variational Bayes (VB) approximations, which are implemented in Statistical
Parametric Mapping (SPM) software. While computationally efficient, the quality
of VB approximations remains unclear even though they are commonly used in the
analysis of neuroimaging data. For reliable statistical inference, it is
important that these approximations be accurate and that users understand the
scenarios under which they may not be accurate.
  We consider this issue for a particular model that includes spatially-varying
coefficients. To examine the accuracy of the VB approximation we derive
Hamiltonian Monte Carlo (HMC) for this model and conduct simulation studies to
compare its performance with VB. As expected we find that the computation time
required for VB is considerably less than that for HMC. In settings involving a
high or moderate signal-to-noise ratio (SNR) we find that the two approaches
produce very similar results suggesting that the VB approximation is useful in
this setting. On the other hand, when one considers a low SNR, substantial
differences are found, suggesting that the approximation may not be accurate in
such cases and we demonstrate that VB produces Bayes estimators with larger
mean squared error (MSE). A real application related to face perception is also
carried out. Overall, our work clarifies the usefulness of VB for the
spatiotemporal analysis of fMRI data, while also pointing out the limitation of
VB when the SNR is low and the utility of HMC in this case.


title: Gauge Mediation Models with Adjoint Messengers

abstract:
  We present a class of models in the framework of gauge mediation
supersymmetry breaking where the messenger fields transform in the adjoint
representation of the Standard Model gauge symmetry. To avoid unacceptably
light right-handed sleptons in the spectrum we introduce a non-zero U(1)_B-L
D-term. This leads to an additional contribution to the soft supersymmetry
breaking mass terms which makes the right-handed slepton masses compatible with
the current experimental bounds. We show that in this framework the observed
125 GeV Higgs boson mass can be accommodated with the sleptons accessible at
the LHC, while the squarks and gluinos lie in the multi-TeV range. We also
discuss the issue of the fine-tuning and show that the desired relic dark
matter abundance can also be accommodated.


title:
Bifurcations observed in the spectra of coupled electron-phonon modes in
  multiferroic $PrFe_3(BO_3)_4$ subjected to a magnetic field

abstract:
  We report on bifurcations effect mediated by the electron-phonon coupling in
a concentrated rare-earth-containing antiferromagnet, observed in the spectra
of coupled $4f$-electron-phonon modes under the influence of an external
magnetic field. The effect was observed in the low-temperature far-infrared
(terahertz) reflection spectra of a multiferroic easy-axis antiferromagnet
$PrFe_3(BO_3)_4$ in magnetic fields $\textbf{B}_{ext}||c$. Both paramagnetic
and magnetically ordered phases (including a spin-flop one) were studied in
magnetic fields up to 30 T. We show that the field behavior of the coupled
modes can be successfully explained and modeled on the base of the equation
derived in the frame of the theory of coupled electron-phonon modes, with the
same field-independent electron-phonon interaction constant $|W| = 14.8
cm^{-1}$.


title:
Order statistics of vectors with dependent coordinates, and the
  Karhunen-Lo\`eve basis

abstract:
  Let $X$ be an $n$-dimensional random centered Gaussian vector with
independent but not identically distributed coordinates and let $T$ be an
orthogonal trasformation of $\mathbb R^n$. We show that the random vector
$Y=T(X)$ satisfies $$\mathbb E\sum\limits_{j=1}^k j\mbox{-}\min_{i\leq
n}{X_{i}}^2 \leq C\mathbb E\sum\limits_{j=1}^k j\mbox{-}\min_{i\leq
n}{Y_{i}}^2$$ for all $k<n$, where "$j\mbox{-}\min$" denotes the $j$-th
smallest component of corresponding vector and $C>0$ is a universal constant.
This resolves (up to a multiplicative constant) an old question of S.Mallat and
O.Zeitouni regarding optimality of the Karhunen-Loeve basis for the nonlinear
signal approximation. As a by-product we obtain some relations for order
statistics of random vectors (not only Gaussian) which are of independent
interest.


title:
Lithium antineutrino source in the tandem scheme of the accelerator and
  neutron producting tungsten target

abstract:
  The antineutrinos of the neutron rich 8Li isotope is characterized by hard
and good defined spectrum - averaged energy is 6.5 MeV and maximal - up to 13
MeV. An intensive antineutrino source with such parameters can be unique
instrument for neutrino investigations and especially for search of sterile
neutrinos. The 8Li can be produced by (n,gamma)-activation of 7Li isotope. The
proposed scheme of the antineutrino source is based on the lithium blanket
around the accelerator neutron producting target. We propose to use heavy water
solution of the lithium hydroxide instead of lithium in metallic state. Such
solution for lithium blanket substance ensure the large perspectives in real
steps for creation of this installation. An analyses of neutron fields in the
blanket and distribution of 8Li creation allows to propose the next principal
steps in the construction of the lithium blanket. We propose to enclose the
blanket volume isolating it's central part with more high 8Li production. This
solution allows to decrease the necessary mass of very pure 7Li isotope (with
admixture of 6Li - 0.0001) up to 120-130 kg (i.e., to decrease in ~ 150 times
compare to variant of lithium blanket in metallic state). The source become
more compact - the linear dimension is decreased in 2.5 times (up to 1.3 m) and
this is very essential for sterile neutrino search taking in mind the
indication on difference ~1 eV2 between squared mass of sterile and active
neutrinos.


title:
Performance of Edgeless Silicon Pixel Sensors on p-type substrate for
  the ATLAS High-Luminosity Upgrade

abstract:
  In view of the LHC upgrade phases towards the High Luminosity LHC (HL-LHC),
the ATLAS experiment plans to upgrade the Inner Detector with an all-silicon
system. The n-on-p silicon technology is a promising candidate to achieve a
large area instrumented with pixel sensors, since it is radiation hard and cost
effective. The paper reports on the performance of novel n-on-p edgeless planar
pixel sensors produced by FBK-CMM, making use of the active trench for the
reduction of the dead area at the periphery of the device. After discussing the
sensor technology an overview of the first beam test results will be given.


title: Dynamic Control of Topological Defects in Artificial Colloidal Ice

abstract:
  We demonstrate the use of an external field to stabilize and control defect
lines connecting topological monopoles in spin ice. For definiteness we perform
Brownian dynamics simulations with realistic units mimicking experimentally
realized artificial colloidal spin ice systems, and show how defect lines can
grow, shrink or move under the action of direct and alternating fields.
Asymmetric alternating biasing fields can cause the defect line to ratchet in
either direction, making it possible to precisely position the line at a
desired location. Such manipulation could be employed to achieve fast, dense,
and mobile information storage in these metamaterials.


title: Affine surfaces and their Veech groups

abstract:
  We introduce a class of objects which we call 'affine surfaces'. These
provide families of foliations on surfaces whose dynamics we are interested in.
We present and analyze a couple of examples, and we define concepts related to
these in order to motivate several questions and open problems. In particular
we generalise the notion of Veech group to affine surfaces, and we prove a
structure result about these Veech groups.


title: A lower bound for the dimension of Bernoulli convolutions

abstract:
  Let $\beta\in(1,2)$ and let $H_\beta$ denote Garsia's entropy for the
Bernoulli convolution $\mu_\beta$ associated with $\beta$. In the present paper
we show that $H_\beta>0.82$ for all $\beta \in (1, 2)$ and improve this bound
for certain ranges. Combined with recent results by Hochman and
Breuillard-Varj\'u, this yields $\dim (\mu_\beta)\ge0.82$ for all
$\beta\in(1,2)$. In addition, we show that if an algebraic $\beta$ is such that
$[\mathbb{Q}(\beta): \mathbb{Q}(\beta^k)] = k$ for some $k \geq 2$, then
$\dim(\mu_\beta)=1$. Such is, for instance, any root of a Pisot number which is
not a Pisot number itself.


title:
UberNet: Training a `Universal' Convolutional Neural Network for Low-,
  Mid-, and High-Level Vision using Diverse Datasets and Limited Memory

abstract:
  In this work we introduce a convolutional neural network (CNN) that jointly
handles low-, mid-, and high-level vision tasks in a unified architecture that
is trained end-to-end. Such a universal network can act like a `swiss knife'
for vision tasks; we call this architecture an UberNet to indicate its
overarching nature.
  We address two main technical challenges that emerge when broadening up the
range of tasks handled by a single CNN: (i) training a deep architecture while
relying on diverse training sets and (ii) training many (potentially unlimited)
tasks with a limited memory budget. Properly addressing these two problems
allows us to train accurate predictors for a host of tasks, without
compromising accuracy.
  Through these advances we train in an end-to-end manner a CNN that
simultaneously addresses (a) boundary detection (b) normal estimation (c)
saliency estimation (d) semantic segmentation (e) human part segmentation (f)
semantic boundary detection, (g) region proposal generation and object
detection. We obtain competitive performance while jointly addressing all of
these tasks in 0.7 seconds per frame on a single GPU. A demonstration of this
system can be found at http://cvn.ecp.fr/ubernet/.


title: Mitochondrial network complexity emerges from fission/fusion dynamics

abstract:
  Mitochondrial networks exhibit a variety of complex behaviors, including
coordinated cell-wide oscillations of energy states as well as a phase
transition (depolarization) in response to oxidative stress. Since functional
and structural properties are often interwinded, here we characterize the
structure of mitochondrial networks in mouse embryonic fibroblasts using
network tools and percolation theory. Subsequently we perturbed the system
either by promoting the fusion of mitochondrial segments or by inducing
mitochondrial fission. Quantitative analysis of mitochondrial clusters revealed
that the structural parameters of healthy mitochondria lay in between the
extremes of highly fragmented and completely fusioned networks. We confirmed
our results by contrasting our emprirical findings with the predictions of a
recently described computational model of mitochondrial network emergence based
on fission-fusion kinetics. Altogether these results not only offer an
objective methodology to parametrize the complexity of this organelle but add
weight to the idea that mitochondrial networks behave as critical systems and
undergo structural phase transitions.


title:
Observational Constraints on First-Star Nucleosynthesis. II.
  Spectroscopy of an Ultra Metal-Poor CEMP-no Star

abstract:
  We report on the first high-resolution spectroscopic analysis of HE0020-1741,
a bright (V=12.9), ultra metal-poor ([Fe/H] = -4.1), carbon-enhanced ([C/Fe] =
+1.7) star selected from the Hamburg/ESO Survey. This star exhibits low
abundances of neutron-capture elements ([Ba/Fe] = -1.1), and an absolute carbon
abundance A(C) = 6.1; based on either criterion, HE0020-1741 is sub-classified
as a CEMP-no star. We show that the light-element abundance pattern of
HE0020-1741 is consistent with predicted yields from a massive (M = 21.5 Mo),
primordial composition, supernova (SN) progenitor. We also compare the
abundance patterns of other ultra metal-poor stars from the literature with
available measures of C, N, Na, Mg, and Fe abundances with an extensive grid of
SN models (covering the mass range 10 Mo - 100 Mo), in order to probe the
nature of their likely stellar progenitors. Our results suggest that at least
two classes of progenitors are required at [Fe/H] < -4.0, as the abundance
patterns for more than half of the sample studied in this work (7 out of 12
stars) cannot be easily reproduced by the predicted yields.


title:
Optimizing Codes for Source Separation in Color Image Demosaicing and
  Compressive Video Recovery

abstract:
  There exist several applications in image processing (eg: video compressed
sensing [Hitomi, Y. et al, "Video from a single coded exposure photograph using
a learned overcomplete dictionary"] and color image demosaicing [Moghadam, A.
A. et al, "Compressive Framework for Demosaicing of Natural Images"]) which
require separation of constituent images given measurements in the form of a
coded superposition of those images. Physically practical code patterns in
these applications are non-negative, systematically structured, and do not
always obey the nice incoherence properties of other patterns such as Gaussian
codes, which can adversely affect reconstruction performance. The contribution
of this paper is to design code patterns for video compressed sensing and
demosaicing by minimizing the mutual coherence of the matrix $\boldsymbol{\Phi
\Psi}$ where $\boldsymbol{\Phi}$ represents the sensing matrix created from the
code, and $\boldsymbol{\Psi}$ is the signal representation matrix. Our main
contribution is that we explicitly take into account the special structure of
those code patterns as required by these applications: (1)~non-negativity,
(2)~block-diagonal nature, and (3)~circular shifting. In particular, the last
property enables for accurate and seamless patch-wise reconstruction for some
important compressed sensing architectures.


title:
Quantum Cloning of Binary Coherent States - Optimal Transformations and
  Practical Limits

abstract:
  The notions of qubits and coherent states correspond to different physical
systems and are described by specific formalisms. Qubits are associated with a
two-dimensional Hilbert space and can be illustrated on the Bloch sphere. In
contrast, the underlying Hilbert space of coherent states is
infinite-dimensional and the states are typically represented in phase space.
For the particular case of binary coherent state alphabets these otherwise
distinct formalisms can equally be applied. We capitalize this formal
connection to analyse the properties of optimally cloned binary coherent
states. Several practical and near-optimal cloning schemes are discussed and
the associated fidelities are compared to the performance of the optimal
cloner.


title: Tracking Algorithm for Microscopic Flow Data Collection

abstract:
  Various methods to automate traffic data collection have recently been
developed by many researchers. A macroscopic data collection through image
processing has been proposed. For microscopic traffic flow data, such as
individual speed and time or distance headway, tracking of individual movement
is needed. The tracking algorithms for pedestrian or vehicle have been
developed to trace the movement of one or two pedestrians based on sign
pattern, and feature detection. No research has been done to track many
pedestrians or vehicles at once. This paper describes a new and fast algorithm
to track the movement of many individual vehicles or pedestrians


title:
Understanding General Relativity after 100 years: A matter of
  perspective

abstract:
  This is the centenary year of general relativity, it is therefore natural to
reflect on what perspective we have evolved in 100 years. I wish to share here
a novel perspective, and the insights and directions that ensue from it.


title:
Random Shuffling and Resets for the Non-stationary Stochastic Bandit
  Problem

abstract:
  We consider a non-stationary formulation of the stochastic multi-armed bandit
where the rewards are no longer assumed to be identically distributed. For the
best-arm identification task, we introduce a version of Successive Elimination
based on random shuffling of the $K$ arms. We prove that under a novel and mild
assumption on the mean gap $\Delta$, this simple but powerful modification
achieves the same guarantees in term of sample complexity and cumulative regret
than its original version, but in a much wider class of problems, as it is not
anymore constrained to stationary distributions. We also show that the original
{\sc Successive Elimination} fails to have controlled regret in this more
general scenario, thus showing the benefit of shuffling. We then remove our
mild assumption and adapt the algorithm to the best-arm identification task
with switching arms. We adapt the definition of the sample complexity for that
case and prove that, against an optimal policy with $N-1$ switches of the
optimal arm, this new algorithm achieves an expected sample complexity of
$O(\Delta^{-2}\sqrt{NK\delta^{-1} \log(K \delta^{-1})})$, where $\delta$ is the
probability of failure of the algorithm, and an expected cumulative regret of
$O(\Delta^{-1}{\sqrt{NTK \log (TK)}})$ after $T$ time steps.


title: Topology optimization of microwave waveguide filters

abstract:
  We present a density based topology optimization approach for the design of
metallic microwave insert filters. A two-phase optimization procedure is
proposed in which we, starting from a uniform design, first optimize to obtain
a set of spectral varying resonators followed by a band gap optimization for
the desired filter characteristics. This is illustrated through numerical
experiments and comparison to a standard band pass filter design. It is seen
that the carefully optimized topologies can sharpen the filter characteristics
and improve performance. Furthermore, the obtained designs share little
resemblance to standard filter layouts and hence the proposed design method
offers a new design tool in microwave engineering.


title: Correlations in Usage Frequencies and Shannon Entropy for Codons

abstract:
  The usage frequencies for codons belonging to quartets are analized, over the
whole exonic region, for 92 biological species. Correlation is put into
evidence, between the usage frequencies of synonymous codons with third
nucleotide A and C and between the usage frequencies of non synonymous codons,
belonging to suitable subsets of the quartets, with the same third nucleotide.
A correlation is pointed out between amino acids belonging to subsets of the
set encoded by quartets of codons. It is remarked that the computed Shannon
entropy for quartets is weakly dependent on the biological species. The
observed correlations well fit in the mathematical scheme of the crystal basis
model of the genetic code.


title:
Beyond Jcrit: a critical curve for suppression of H2-cooling in
  protogalaxies

abstract:
  Suppression of H2-cooling in early protogalaxies has important implications
for the formation of supermassive black holes seeds, the first generation of
stars, and the epoch of reionization. This suppression can occur via
photodissociation of H2 (by ultraviolet Lyman-Werner [LW] photons) or by
photodetachment of H-, a precursor in H2 formation (by infrared [IR] photons).
Previous studies have typically adopted idealised spectra, with a blackbody or
a power-law shape, in modeling the chemistry of metal-free protogalaxies, and
utilised a single parameter, the critical UV flux, or Jcrit, to determine
whether H2-cooling is prevented. This can be misleading, and that independent
of the spectral shape, there is a critical curve in the (kLW , kH^- ) plane,
where kLW and kH^- are the H2-dissocation rates by LW and IR photons, which
determines whether a protogalaxy can cool below ~1000 Kelvin. We use a one-zone
model to follow the chemical and thermal evolution of gravitationally
collapsing protogalactic gas, to compute this critical curve, and provide an
accurate analytical fit for it. We improve on previous works by considering a
variety of more realistic Pop III or Pop II-type spectra from population
synthesis models and perform fully frequency-dependent calculations of the
H2-photodissociation rates for each spectrum. We compute the ratio kLW/kH^- for
each spectrum, as well as the minimum stellar mass M_star, for various IMFs and
metallicities, required to prevent cooling in a neighboring halo a distance d
away. We provide critical M_star/d2 values for suppression of H2-cooling, with
analytic fits, which can be used in future studies.


title: Efficiency of Planetesimal Ablation in Giant Planetary Envelopes

abstract:
  Observations of exoplanetary spectra are leading to unprecedented constraints
on their atmospheric elemental abundances, particularly O/H, C/H, and C/O
ratios. Recent studies suggest that elemental ratios could provide important
constraints on formation and migration mechanisms of giant exoplanets. A
fundamental assumption in such studies is that the chemical composition of the
planetary envelope represents the sum-total of compositions of the accreted gas
and solids during the formation history of the planet. We investigate the
efficiency with which accreted planetesimals ablate in a giant planetary
envelope thereby contributing to its composition rather than sinking to the
core. From considerations of aerodynamic drag causing `frictional ablation' and
the envelope temperature structure causing `thermal ablation', we compute mass
ablations for impacting planetesimals of radii 30 m to 1 km for different
compositions (ice to iron) and a wide range of velocities and impact angles,
assuming spherical symmetry. Icy impactors are fully ablated in the outer
envelope for a wide range of parameters. Even for Fe impactors substantial
ablation occurs in the envelope for a wide range of sizes and velocities. For
example, iron impactors of sizes below ~0.5 km and velocities above ~30 km/s
are found to ablate by ~60-80% within the outer envelope at pressures below
10^3 bar due to frictional ablation alone. For deeper pressures (~10^7 bar),
substantial ablation happens over a wider range of parameters. Therefore, our
exploratory study suggests that atmospheric abundances of volatile elements in
giant planets reflect their accretion history during formation.


title:
Taming outliers in pulsar-timing datasets with hierarchical likelihoods
  and Hamiltonian sampling

abstract:
  Pulsar-timing datasets have been analyzed with great success using
probabilistic treatments based on Gaussian distributions, with applications
ranging from studies of neutron-star structure to tests of general relativity
and searches for nanosecond gravitational waves. As for other applications of
Gaussian distributions, outliers in timing measurements pose a significant
challenge to statistical inference, since they can bias the estimation of
timing and noise parameters, and affect reported parameter uncertainties. We
describe and demonstrate a practical end-to-end approach to perform Bayesian
inference of timing and noise parameters robustly in the presence of outliers,
and to identify these probabilistically. The method is fully consistent (i.e.,
outlier-ness probabilities vary in tune with the posterior distributions of the
timing and noise parameters), and it relies on the efficient sampling of the
hierarchical form of the pulsar-timing likelihood. Such sampling has recently
become possible with a "no-U-turn" Hamiltonian sampler coupled to a highly
customized reparametrization of the likelihood; this code is described
elsewhere, but it is already available online. We recommend our method as a
standard step in the preparation of pulsar-timing-array datasets: even if
statistical inference is not affected, follow-up studies of outlier candidates
can reveal unseen problems in radio observations and timing measurements;
furthermore, confidence in the results of gravitational-wave searches will only
benefit from stringent statistical evidence that datasets are clean and
outlier-free.


title:
Star Formation in Nearby Early-Type Galaxies: The Radio Continuum
  Perspective

abstract:
  We present a 1.4 GHz Karl G. Jansky Very Large Array (VLA) study of a sample
of early-type galaxies (ETGs) from the volume- and magnitude-limited ATLAS-3D
survey. The radio morphologies of these ETGs at a resolution of 5" are diverse
and include sources that are compact on sub-kpc scales, resolved structures
similar to those seen in star-forming spiral galaxies, and kpc-scale radio
jets/lobes associated with active nuclei. We compare the 1.4 GHz, molecular
gas, and infrared (IR) properties of these ETGs. The most CO-rich ATLAS-3D ETGs
have radio luminosities consistent with extrapolations from H_2-mass-derived
star formation rates from studies of late-type galaxies. These ETGs also follow
the radio-IR correlation. However, ETGs with lower molecular gas masses tend to
have less radio emission relative to their CO and IR emission compared to
spirals. The fraction of galaxies in our sample with high IR-radio ratios is
much higher than in previous studies, and cannot be explained by a systematic
underestimation of the radio luminosity due to the presence extended,
low-surface-brightness emission that was resolved-out in our VLA observations.
In addition, we find that the high IR-radio ratios tend to occur at low IR
luminosities, but are not associated with low dynamical mass or metallicity.
Thus, we have identified a population of ETGs that have a genuine shortfall of
radio emission relative to both their IR and molecular gas emission. A number
of mechanisms may conspire to cause this radio deficiency, including a
bottom-heavy stellar initial mass function, weak magnetic fields, a higher
prevalence of environmental effects compared to spirals and enhanced cosmic ray
losses.


title: Emergence of supersymmetric quantum electrodynamics

abstract:
  Supersymmetric (SUSY) gauge theories such as the Minimal Supersymmetric
Standard Model play a fundamental role in modern particle physics, but have not
been verified so far in nature. Here, we show that a SUSY gauge theory with
dynamical gauge bosons and fermionic gauginos emerges naturally at the
pair-density-wave (PDW) quantum phase transition on the surface of a correlated
topological insulator (TI) hosting three Dirac cones, such as the topological
Kondo insulator SmB$_6$. At the quantum tricritical point between the surface
Dirac semimetal and nematic PDW phases, three massless bosonic Cooper pair
fields emerge as the superpartners of three massless surface Dirac fermions.
The resulting low-energy effective theory is the supersymmetric XYZ model,
which is dual by mirror symmetry to $\mathcal{N}=2$ supersymmetric quantum
electrodynamics (SQED) in 2+1 dimensions, providing a first example of emergent
supersymmetric gauge theory in condensed matter systems. Supersymmetry allows
us to determine exactly certain critical exponents and the optical conductivity
of the surface states at the strongly coupled tricritical point, which may be
measured in future experiments.


title: Impeded Dark Matter

abstract:
  We consider dark matter models in which the mass splitting between the dark
matter particles and their annihilation products is tiny. Compared to the
previously proposed Forbidden Dark Matter scenario, the mass splittings we
consider are much smaller, and are allowed to be either positive or negative.
To emphasize this modification, we dub our scenario "Impeded Dark Matter". We
demonstrate that Impeded Dark Matter can be easily realized without requiring
tuning of model parameters. For negative mass splitting, we demonstrate that
the annihilation cross-section for Impeded Dark Matter depends linearly on the
dark matter velocity or may even be kinematically forbidden, making this
scenario almost insensitive to constraints from the cosmic microwave background
and from observations of dwarf galaxies. Accordingly, it may be possible for
Impeded Dark Matter to yield observable signals in clusters or the Galactic
center, with no corresponding signal in dwarfs. For positive mass splitting, we
show that the annihilation cross-section is suppressed by the small mass
splitting, which helps light dark matter to survive increasingly stringent
constraints from indirect searches. As specific realizations for Impeded Dark
Matter, we introduce a model of vector dark matter from a hidden $SU(2)$
sector, and a composite dark matter scenario based on a QCD-like dark sector.


title:
An Ultra-Faint Galaxy Candidate Discovered in Early Data from the
  Magellanic Satellites Survey

abstract:
  We report a new ultra-faint stellar system found in Dark Energy Camera data
from the first observing run of the Magellanic Satellites Survey (MagLiteS).
MagLiteS J0644-5953 (Pictor II or Pic II) is a low surface brightness ({\mu} =
28.5 mag arcsec$^{-2}$ within its half-light radius) resolved overdensity of
old and metal-poor stars located at a heliocentric distance of 45 kpc. The
physical size (r$_{1/2}$ = 46 pc) and low luminosity (Mv = -3.2 mag) of this
satellite are consistent with the locus of spectroscopically confirmed
ultra-faint galaxies. MagLiteS J0644-5953 (Pic II) is located 11.3 kpc from the
Large Magellanic Cloud (LMC), and comparisons with simulation results in the
literature suggest that this satellite was likely accreted with the LMC. The
close proximity of MagLiteS J0644-5953 (Pic II) to the LMC also makes it the
most likely ultra-faint galaxy candidate to still be gravitationally bound to
the LMC.


title: Nonsupersymmetric dualities from mirror symmetry

abstract:
  We study supersymmetry breaking perturbations of the simplest dual pair of
2+1-dimensional N = 2 supersymmetric field theories -- the free chiral
multiplet and N = 2 super-QED with a single flavor. We find dual descriptions
of a phase diagram containing four distinct massive phases. The equivalence of
the intervening critical theories gives rise to several non-supersymmetric
avatars of mirror symmetry: we find dualities relating scalar QED to a free
fermion and Wilson-Fisher theories to both scalar and fermionic QED. Thus,
mirror symmetry can be viewed as the multicritical parent duality from which
these non-supersymmetric dualities directly descend.


title:
Boosting Lya and HeII 1640A Line Fluxes from Pop III Galaxies:
  Stochastic IMF Sampling and Departures from Case-B

abstract:
  We revisit calculations of nebular hydrogen Lya and HeII 1640A line strengths
for population III galaxies, undergoing continuous and bursts of star
formation. We focus on initial mass functions (IMFs) motivated by recent
theoretical studies, which generally span a lower range of stellar masses than
earlier works. We also account for case-B departures and the stochastic
sampling of the IMF. In agreement with previous works, we find that departures
from case-B can enhance the Lya flux by a factor of a few, but we argue that
this enhancement is driven mainly by collisional excitation and ionization, and
not due to photoionization from the n = 2 state of atomic hydrogen. The
increased sensitivity of the Lya flux to the high-energy end of the galaxy
spectrum makes it more subject to stochastic sampling of the IMF. The latter
introduces a dispersion in the predicted nebular line fluxes around the
deterministic value by as much as a factor of ~4. In contrast, the stochastic
sampling of the IMF has less impact on the emerging Lyman Werner (LW) photon
flux. When case-B departures and stochasticity effects are combined, nebular
line emission from population III galaxies can be up to one order of magnitude
brighter than predicted by 'standard' calculations that do not include these
effects. This enhances the prospects for detection with future facilities such
as JWST and large, groundbased telescopes.


title: String Theory and the Dark Glueball Problem

abstract:
  We study cosmological constraints on dark pure Yang-Mills sectors. Dark
glueballs are overproduced for large regions of ultraviolet parameter space.
The problem may be alleviated in two ways: via a large preferential reheating
into the visible sector, motivating certain inflation or modulus decay models,
or via decays into axions or moduli, which are strongly constrained by
nucleosynthesis and $\Delta N_{\text{eff}}$ bounds. String models frequently
have multiple hidden Yang-Mills sectors, which are subject to even stronger
constraints due to the existence of multiple dark glueballs.


title:
Ultra-deep GEMINI near-infrared observations of the bulge globular
  cluster NGC 6624

abstract:
  We used ultra-deep $J$ and $K_s$ images secured with the near-infrared GSAOI
camera assisted by the multi-conjugate adaptive optics system GeMS at the
GEMINI South Telescope in Chile, to obtain a ($K_s$, $J-K_s$) color-magnitude
diagram (CMD) for the bulge globular cluster NGC 6624. We obtained the deepest
and most accurate near-infrared CMD from the ground for this cluster, by
reaching $K_s$ $\sim$ 21.5, approximately 8 magnitudes below the horizontal
branch level. The entire extension of the Main Sequence (MS) is nicely sampled
and at $K_s$ $\sim$ 20 we detected the so-called MS "knee" in a purely
near-infrared CMD. By taking advantage of the exquisite quality of the data, we
estimated the absolute age of NGC 6624 ($t_{age}$ = 12.0 $\pm$ 0.5 Gyr), which
turns out to be in good agreement with previous studies in the literature. We
also analyzed the luminosity and mass functions of MS stars down to M $\sim$
0.45 M$_{\odot}$ finding evidence of a significant increase of low-mass stars
at increasing distances from the cluster center. This is a clear signature of
mass segregation, confirming that NGC 6624 is in an advanced stage of dynamical
evolution.


title:
Photochemical-dynamical models of externally FUV irradiated
  protoplanetary discs

abstract:
  There is growing theoretical and observational evidence that protoplanetary
disc evolution may be significantly affected by the canonical levels of far
ultraviolet (FUV) radiation found in a star forming environment, leading to
substantial stripping of material from the disc outer edge even in the absence
of nearby massive stars. In this paper we perform the first full radiation
hydrodynamic simulations of the flow from the outer rim of protoplanetary discs
externally irradiated by such intermediate strength FUV fields, including
direct modelling of the photon dominated region (PDR) which is required to
accurately compute the thermal properties. We find excellent agreement between
our models and the semi-analytic models of Facchini et al. (2016) for the
profile of the flow itself, as well as the mass loss rate and location of their
"critical radius". This both validates their results (which differed
significantly from prior semi-analytic estimates) and our new numerical method,
the latter of which can now be applied to elements of the problem that the
semi--analytic approaches are incapable of modelling. We also obtain the
composition of the flow, but given the simple geometry of our models we can
only hint at some diagnostics for future observations of externally irradiated
discs at this stage. We also discuss the potential for these models as
benchmarks for future photochemical-dynamical codes.


title: The First-Order Euler-Lagrange equations and some of their uses

abstract:
  In many nonlinear field theories, relevant solutions may be found by reducing
the order of the original Euler-Lagrange equations, e.g., to first order
equations (Bogomolnyi equations, self-duality equations, etc.). Here we
generalise, further develop and apply one particular method for the order
reduction of nonlinear field equations which, despite its systematic and
versatile character, is not widely known.


title:
SDSS-IV MaNGA: A serendipitous observation of a potential gas accretion
  event

abstract:
  The nature of warm, ionized gas outside of galaxies may illuminate several
key galaxy evolutionary processes. A serendipitous observation by the MaNGA
survey has revealed a large, asymmetric H$\alpha$ complex with no optical
counterpart that extends $\approx8"$ ($\approx6.3$ kpc) beyond the effective
radius of a dusty, starbursting galaxy. This H$\alpha$ extension is
approximately three times the effective radius of the host galaxy and displays
a tail-like morphology. We analyze its gas-phase metallicities, gaseous
kinematics, and emission-line ratios, and discuss whether this H$\alpha$
extension could be diffuse ionized gas, a gas accretion event, or something
else. We find that this warm, ionized gas structure is most consistent with gas
accretion through recycled wind material, which could be an important process
that regulates the low-mass end of the galaxy stellar mass function.


title:
The binary fraction, separation distribution, and merger rate of white
  dwarfs from SPY

abstract:
  From a sample of spectra of 439 white dwarfs (WDs) from the ESO-VLT
Supernova-Ia Progenitor surveY (SPY), we measure the maximal changes in
radial-velocity (DRVmax) between epochs (generally two epochs, separated by up
to 470d), and model the observed DRVmax statistics via Monte-Carlo simulations,
to constrain the population characteristics of double WDs (DWDs). The DWD
fraction among WDs is fbin=0.100+/-0.020 (1-sigma, random) +0.02 (systematic),
in the separation range ~<4AU within which the data are sensitive to binarity.
Assuming the distribution of binary separation, a, is a power-law, dN/da ~
a^alpha, at the end of the last common-envelope phase and the start of solely
gravitational-wave-driven binary evolution, the constraint by the data is
alpha=-1.3+/-0.2 (1-sigma) +/-0.2 (systematic). If these parameters extend to
small separations, the implied Galactic WD merger rate per unit stellar mass is
R_merge=(1-80)e-13 /yr/Msun (2-sigma), with a likelihood-weighted mean of
R_merge=(7+/-2)e-13 /yr/Msun (1-sigma). The Milky Way's specific Type-Ia
supernova (SN Ia) rate is likely R_Ia~1.1e-13 /yr/Msun and therefore, in terms
of rates, a possibly small fraction of all merging DWDs (e.g. those with
massive-enough primary WDs) could suffice to produce most or all SNe Ia.


title:
Out-of-equilibrium protocol for R\'enyi entropies via the Jarzynski
  equality

abstract:
  In recent years entanglement measures, such as the von Neumann and the
R\'enyi entropies, provided a unique opportunity to access elusive feature of
quantum many-body systems. However, extracting entanglement properties
analytically, experimentally, or in numerical simulations can be a formidable
task. Here, by combining the replica trick and the Jarzynski equality we devise
a new effective out-of-equilibrium protocol for measuring the equilibrium
R\'enyi entropies. The key idea is to perform a quench in the geometry of the
replicas. The R\'enyi entropies are obtained as the exponential average of the
work performed during the quench. We illustrate an application of the method in
classical Monte Carlo simulations, although it could be useful in different
contexts, such as in Quantum Monte Carlo, or experimentally in cold-atom
systems. The method is most effective in the quasi-static regime, i.e., for a
slow quench, where it allows to obtain the R\'enyi entropies in a single
realization of the protocol. As a benchmark, we present results for the R\'enyi
entropies in the Ising universality class in $1$$+$$1$ dimensions, which are
found in perfect agreement with the well-known Conformal Field Theory (CFT)
predictions.

categories: cond-mat.str-el cond-mat.quant-gas cond-mat.stat-mech hep-lat hep-th


title: The Hodge-elliptic genus, spinning BPS states, and black holes

abstract:
  We perform a refined count of BPS states in the compactification of M-theory
on $K3 \times T^2$, keeping track of the information provided by both the
$SU(2)_L$ and $SU(2)_R$ angular momenta in the $SO(4)$ little group.
Mathematically, this four variable counting function may be expressed via the
motivic Donaldson-Thomas counts of $K3 \times T^2$, simultaneously refining
Katz, Klemm, and Pandharipande's motivic Donaldson-Thomas counts on $K3$ and
Oberdieck-Pandharipande's Gromov-Witten counts on $K3 \times T^2$. This
provides the first full answer for motivic curve counts of a compact Calabi-Yau
threefold. Along the way, we develop a Hodge-elliptic genus for Calabi-Yau
manifolds -- a new counting function for BPS states that interpolates between
the Hodge polynomial and the elliptic genus of a Calabi-Yau.


title: Quantum-gravity phenomenology with primordial black holes

abstract:
  Quantum gravity may allow black holes to tunnel into white holes. If so, the
lifetime of a black hole could be shorter than the one given by Hawking
evaporation, solving the information paradox. More interestingly, this could
open to a new window for quantum-gravity phenomenology, in connection with the
existence of primordial black holes. We discuss in particular the power of the
associated explosion and the possibility to observe an astrophysical signal in
the radio and in the gamma wavelengths.