title:
Reflections at infinity of time changed RBMs on a domain with Liouville
  branches

abstract:
  Let $Z$ be the transient reflecting Brownian motion on the closure of an
unbounded domain $D\subset {\mathbb R}^d$ with $N$ number of Liouville
branches. We consider a diffusion $X$ on $\overline D$ having finite lifetime
obtained from $Z$ by a time change. We show that $X$ admits only a finite
number of possible symmetric conservative diffusion extensions $Y$ beyond its
lifetime characterized by possible partitions of the collection of $N$ ends and
we identify the family of the extended Dirichlet spaces of all $Y$ (which are
independent of time change used) as subspaces of the space ${\rm BL}(D)$
spanned by the extended Sobolev space $H_e^1(D)$ and the approaching
probabilities of $Z$ to the ends of Liouville branches.


title:
The Spherical Hecke algebra, partition functions, and motivic
  integration

abstract:
  This article gives a proof of the Langlands-Shelstad fundamental lemma for
the spherical Hecke algebra for every unramified p-adic reductive group G in
large positive characteristic. The proof is based on the transfer principle for
constructible motivic integration. To carry this out, we introduce a general
family of partition functions attached to the complex L-group of the unramified
p-adic group G. Our partition functions specialize to Kostant's q-partition
function for complex connected groups and also specialize to the Langlands
L-function of a spherical representation. These partition functions are used to
extend numerous results that were previously known only when the L-group is
connected (that is, when the p-adic group is split). We give explicit formulas
for branching rules, the inverse of the weight multiplicity matrix, the
Kato-Lusztig formula for the inverse Satake transform, the Plancherel measure,
and Macdonald's formula for the spherical Hecke algebra on a non-connected
complex group (that is, non-split unramified p-adic group).


title: What Do Recurrent Neural Network Grammars Learn About Syntax?

abstract:
  Recurrent neural network grammars (RNNG) are a recently proposed
probabilistic generative modeling family for natural language. They show
state-of-the-art language modeling and parsing performance. We investigate what
information they learn, from a linguistic perspective, through various
ablations to the model and the data, and by augmenting the model with an
attention mechanism (GA-RNNG) to enable closer inspection. We find that
explicit modeling of composition is crucial for achieving the best performance.
Through the attention mechanism, we find that headedness plays a central role
in phrasal representation (with the model's latent attention largely agreeing
with predictions made by hand-crafted head rules, albeit with some important
differences). By training grammars without nonterminal labels, we find that
phrasal representations depend minimally on nonterminals, providing support for
the endocentricity hypothesis.


title:
Explicit (Polynomial!) Expressions for the Expectation, Variance and
  Higher Moments of the Size of a (2n + 1, 2n + 3)-core partition with Distinct
  Parts

abstract:
  Inspired by Armin Straub's conjecture (arXiv:1601.07161) about the number and
maximal size of (2n+1, 2n+3)-core partitions with distinct parts, we develop
relatively efficient, symbolic-computational algorithms, based on non-linear
functional recurrences, to generate the generating functions, according to
size, of the set of such partitions. By computing these polynomials for
n=1,...21, we are able to rigorously derive explicit expressions for the
expectation, variance, and third through seventh moments of the random variable
"size of a (2n+1, 2n+3)-core partition with distinct parts." In particular, we
find that this random variable is not asymptotically normal as n goes to
infinity.


title: A note on FC-nilpotency

abstract:
  The notion of bounded FC-nilpotent group is introduced and it is shown that
any such group is nilpotent-by-finite, generalizing a result of Neumann on
bounded FC-groups.


title:
DeeperBind: Enhancing Prediction of Sequence Specificities of DNA
  Binding Proteins

abstract:
  Transcription factors (TFs) are macromolecules that bind to
\textit{cis}-regulatory specific sub-regions of DNA promoters and initiate
transcription. Finding the exact location of these binding sites (aka motifs)
is important in a variety of domains such as drug design and development. To
address this need, several \textit{in vivo} and \textit{in vitro} techniques
have been developed so far that try to characterize and predict the binding
specificity of a protein to different DNA loci. The major problem with these
techniques is that they are not accurate enough in prediction of the binding
affinity and characterization of the corresponding motifs. As a result,
downstream analysis is required to uncover the locations where proteins of
interest bind. Here, we propose DeeperBind, a long short term recurrent
convolutional network for prediction of protein binding specificities with
respect to DNA probes. DeeperBind can model the positional dynamics of probe
sequences and hence reckons with the contributions made by individual
sub-regions in DNA sequences, in an effective way. Moreover, it can be trained
and tested on datasets containing varying-length sequences. We apply our
pipeline to the datasets derived from protein binding microarrays (PBMs), an
in-vitro high-throughput technology for quantification of protein-DNA binding
preferences, and present promising results. To the best of our knowledge, this
is the most accurate pipeline that can predict binding specificities of DNA
sequences from the data produced by high-throughput technologies through
utilization of the power of deep learning for feature generation and positional
dynamics modeling.


title:
Towards the Modeling of Behavioral Trajectories of Users in Online
  Social Media

abstract:
  In this paper, we introduce a methodology that allows to model behavioral
trajectories of users in online social media. First, we illustrate how to
leverage the probabilistic framework provided by Hidden Markov Models (HMMs) to
represent users by embedding the temporal sequences of actions they performed
online. We then derive a model-based distance between trained HMMs, and we use
spectral clustering to find homogeneous clusters of users showing similar
behavioral trajectories. To provide platform-agnostic results, we apply the
proposed approach to two different online social media --- i.e. Facebook and
YouTube. We conclude discussing merits and limitations of our approach as well
as future and promising research directions.

categories: cs.CY cs.SI physics.soc-ph stat.AP stat.ML


title:
Two-dimensional Shannon type expansions via one-dimensional affine and
  wavelet lattice actions

abstract:
  It is rather unexpected, but true, that it is possible to construct
reproducing formulae and orthonormal bases of $L^2 (\mathbb{R}^2)$ just by
applying the standard one dimensional wavelet action of translations and
dilations to the first variable $x_1$ of the generating function
$\psi(x_1,x_2)$, $\psi \in L^2 (\mathbb{R}^2)$, i.e., by making use of building
blocks $$\psi_{u,s}(x_1,x_2)=s^{-1/2}\psi\left(\frac{x_1-u}{s},x_2\right),
\text{where } u\in \mathbb{R}, s>0,$$ in the case of reproducing formulae, and
$$\psi_{k,m}(x_1,x_2)=2^{-k/2} \psi\left(\frac{x_1-2^k m}{2^k},x_2 \right),
\text{where } k,m\in \mathbb{Z},$$ in the case of orthonormal bases. It is
possible to compensate the fact, that the second variable $x_2$ is not acted
upon, by a careful selection of the generating function $\psi$. Shannon wavelet
tiling of the time-frequency plane $\mathbb{R}^2$, a standard illustration of
orthogonality and completeness phenomena corresponding to the Shannon wavelet,
$$ \chi_{(2^km,2^k(m+1)]}(x) \chi_{2^{-k}I}(\xi),\, k,m\in \mathbb{Z}, \,I=-
(1/2,1]\cup (1/2,1], $$ with $x$ representing time and $\xi$ frequency, is
substituted by a phase space tiling of $\mathbb{R}^4$ with unbounded,
hyperboloid type blocks of the form $$
\chi_{(2^km,2^k(m+1)]}(x_1)\sum_{n,l}\chi_{2^{-k}I_{D(n,l)}}(\xi_1)
\chi_{(n,n+1]}(x_2)\chi_{(l,l+1]}(\xi_2),\, k,m\in \mathbb{Z} $$ where
$I_r=2^{-r}I$, $ r\ge 1$, and $D:\mathbb{Z} \times \mathbb{Z} \rightarrow
\mathbb{N}$ is a bijection, an additional parameter of the generating function,
needed for the lift from $L^2(\mathbb{R})$ to $L^2(\mathbb{R}^2)$. Variables
$x_1,x_2$ are coordinates of position and variables $\xi_1,\xi_2$ of momentum.


title: Gap Safe screening rules for sparsity enforcing penalties

abstract:
  In high dimensional regression settings, sparsity enforcing penalties have
proved useful to regularize the data-fitting term. A recently introduced
technique called screening rules propose to ignore some variables in the
optimization leveraging the expected sparsity of the solutions and consequently
leading to faster solvers. When the procedure is guaranteed not to discard
variables wrongly the rules are said to be safe. In this work, we propose a
unifying framework for generalized linear models regularized with standard
sparsity enforcing penalties such as $\ell_1$ or $\ell_1/\ell_2$ norms. Our
technique allows to discard safely more variables than previously considered
safe rules, particularly for low regularization parameters. Our proposed Gap
Safe rules (so called because they rely on duality gap computation) can cope
with any iterative solver but are particularly well suited to (block)
coordinate descent methods. Applied to many standard learning tasks, Lasso,
Sparse-Group Lasso, multi-task Lasso, binary and multinomial logistic
regression, etc., we report significant speed-ups compared to previously
proposed safe rules on all tested data sets.


title:
Geometric Resonance of Composite Fermions near Bilayer Quantum Hall
  States

abstract:
  Via the application of parallel magnetic field, we induce a single-layer to
bilayer transition in two-dimensional electron systems confined to wide GaAs
quantum wells, and study the geometric resonance of composite fermions (CFs)
with a periodic density modulation in our samples. The measurements reveal that
CFs exist close to bilayer quantum Hall states, formed at Landau level filling
factors $\nu=1$ and 1/2. Near $\nu=1$, the geometric resonance features are
consistent with half the total electron density in the bilayer system, implying
that CFs prefer to stay in separate layers and exhibit a two-component
behavior. In contrast, close to $\nu=1/2$, CFs appear single-layer-like
(single-component) as their resonance features correspond to the total density.


title: Chiral Surface Waves for Enhanced Circular Dichroism

abstract:
  We present a novel chiral sensing platform that combines a one-dimensional
photonic crystal design with a birefringent surface defect. The platform
sustains simultaneous transverse electric and transverse magnetic surface
modes, which are exploited to generate chiral surface waves. The present design
provides homogeneous and superchiral fields of both handednesses over
arbitrarily large areas in a wide spectral range, resulting in the enhancement
of the circular dichroism signal by two orders of magnitude, thus paving the
road toward the successful combination of surface-enhanced spectroscopies and
electromagnetic superchirality.


title:
Impedance spectroscopy, dielectric and magnetic study of M-type
  Strontium hexaferrite and its modified systems by Cobalt (Co) and Titanium
  (Ti)

abstract:
  Polycrystalline M-type hexagonal Strontium hexaferrite and its modified
systems by Cobalt (Co) and Titanium (Ti) were successfully prepared by the
solid state reaction method. The single phase formation of all the systems and
well grain growth of micrometer range was confirmed by X-ray diffraction
pattern and Scanning Electron Microscopic image respectively. The impedance
spectroscopy and dielectric properties were investigated in a selected
frequency & temperature range. The room temperature M-H loop study for
Strontium hexaferrite and Cobalt modified Strontium hexaferrite was carried out
by Vibrate Sample Magnetometer. From the investigation it was found that, the
grain, grain boundary and electrode polarization have significant effect on
dielectric relaxation and conduction mechanism for all the systems. From M-H
loop study it was found that Co modified system has drastic reduction of
coercive field.


title: Finite reflection groups and graph norms

abstract:
  Given a graph $H$ on vertex set $\{1,2,\cdots, n\}$ and a function $f:[0,1]^2
\rightarrow \mathbb{R}$, define \begin{align*} \|f\|_{H}:=\left\vert\int
\prod_{ij\in E(H)}f(x_i,x_j)d\mu^{|V(H)|}\right\vert^{1/|E(H)|}, \end{align*}
where $\mu$ is the Lebesgue measure on $[0,1]$. We say that $H$ is norming if
$\|\cdot\|_H$ is a semi-norm. A similar notion $\|\cdot\|_{r(H)}$ is defined by
$\|f\|_{r(H)}:=\||f|\|_{H}$ and $H$ is said to be weakly norming if
$\|\cdot\|_{r(H)}$ is a norm. Classical results show that weakly norming graphs
are necessarily bipartite. In the other direction, Hatami showed that even
cycles, complete bipartite graphs, and hypercubes are all weakly norming. We
demonstrate that any graph whose edges percolate in an appropriate way under
the action of a certain natural family of automorphisms is weakly norming. This
result includes all previously known examples of weakly norming graphs, but
also allows us to identify a much broader class arising from finite reflection
groups. We include several applications of our results. In particular, we
define and compare a number of generalisations of Gowers' octahedral norms and
we prove some new instances of Sidorenko's conjecture.


title: Bol loops and Bruck loops of order $pq$

abstract:
  Right Bol loops are loops satisfying the identity $((zx)y)x = z((xy)x)$, and
right Bruck loops are right Bol loops satisfying the identity $(xy)^{-1} =
x^{-1}y^{-1}$. Let $p$ and $q$ be odd primes such that $p>q$. Advancing the
research program of Niederreiter and Robinson from $1981$, we classify right
Bol loops of order $pq$. When $q$ does not divide $p^2-1$, the only right Bol
loop of order $pq$ is the cyclic group of order $pq$. When $q$ divides $p^2-1$,
there are precisely $(p-q+4)/2$ right Bol loops of order $pq$ up to
isomorphism, including a unique nonassociative right Bruck loop $B_{p,q}$ of
order $pq$.
  Let $Q$ be a nonassociative right Bol loop of order $pq$. We prove that the
right nucleus of $Q$ is trivial, the left nucleus of $Q$ is normal and is equal
to the unique subloop of order $p$ in $Q$, and the right multiplication group
of $Q$ has order $p^2q$ or $p^3q$. When $Q=B_{p,q}$, the right multiplication
group of $Q$ is isomorphic to the semidirect product of $\mathbb{Z}_p\times
\mathbb{Z}_p$ with $\mathbb{Z}_q$. Finally, we offer computational results as
to the number of right Bol loops of order $pq$ up to isotopy.


title:
Linking Light Scalar Modes with A Small Positive Cosmological Constant
  in String Theory

abstract:
  Based on the studies in Type IIB string theory phenomenology, we conjecture
that a good fraction of the meta-stable de Sitter vacua in the cosmic stringy
landscape tend to have a very small cosmological constant $\Lambda$ when
compared to either the string scale $M_S$ or the Planck scale $M_P$, i.e.,
$\Lambda \ll M_S^4 \ll M_P^4$. These low lying de Sitter vacua tend to be
accompanied by very light scalar bosons/axions. Here we illustrate this
phenomenon with the bosonic mass spectra in a set of Type IIB string theory
flux compactification models. We conjecture that small $\Lambda$ with light
bosons is generic among de Sitter solutions in string theory; that is, the
smallness of $\Lambda$ and the existence of very light bosons (may be even the
Higgs boson) are results of the statistical preference for such vacua in the
landscape. We also discuss a scalar field $\phi^3/\phi^4$ model to illustrate
how this statistical preference for a small $\Lambda$ remains when quantum loop
corrections are included, thus bypassing the radiative instability problem.


title:
FPGA Implementation of a Scalable and Run-Time Adaptable Multi-Standard
  Packet Detector

abstract:
  This paper describes a step by step approach for implementing a scalable and
run-time adaptable multi-standard packet detector for orthogonal frequency
divisional multiplexing (OFDM) based communication standards. The paper briefly
describes considerations and design choices in making a modular system block
with generic control supporting rapid prototyping and implementation of
preamble-based packet detectors. The results were generated through
implementation on a Xilinx Virtex-6 FPGA with a MicroBlaze processor
instantiated to provide run-time control and adaptability.


title:
Data Science in Service of Performing Arts: Applying Machine Learning to
  Predicting Audience Preferences

abstract:
  Performing arts organizations aim to enrich their communities through the
arts. To do this, they strive to match their performance offerings to the taste
of those communities. Success relies on understanding audience preference and
predicting their behavior. Similar to most e-commerce or digital entertainment
firms, arts presenters need to recommend the right performance to the right
customer at the right time. As part of the Michigan Data Science Team (MDST),
we partnered with the University Musical Society (UMS), a non-profit performing
arts presenter housed in the University of Michigan, Ann Arbor. We are
providing UMS with analysis and business intelligence, utilizing historical
individual-level sales data. We built a recommendation system based on
collaborative filtering, gaining insights into the artistic preferences of
customers, along with the similarities between performances. To better
understand audience behavior, we used statistical methods from customer-base
analysis. We characterized customer heterogeneity via segmentation, and we
modeled customer cohorts to understand and predict ticket purchasing patterns.
Finally, we combined statistical modeling with natural language processing
(NLP) to explore the impact of wording in program descriptions. These ongoing
efforts provide a platform to launch targeted marketing campaigns, helping UMS
carry out its mission by allocating its resources more efficiently. Celebrating
its 138th season, UMS is a 2014 recipient of the National Medal of Arts, and it
continues to enrich communities by connecting world-renowned artists with
diverse audiences, especially students in their formative years. We aim to
contribute to that mission through data science and customer analytics.


title:
Applying Software Craftsmanship Practices to a Scrum Project: an
  Experience Report

abstract:
  The Software Craftsmanship manifesto has defined values and principles that
software development teams should follow to deliver quality software that
fulfills functional and non-functional requirements without dealing with high
amounts of technical debt. Software craftsmanship approach to software
development prioritizes technical practices in order to provide a clean code
base. This work analyzes a set of practices that can be applied to a Scrum
project that aims to incorporate Software Craftsmanship values. The process
implementation described may be a useful contribution for software development
teams who also intend to implement Software Craftsmanship on their projects.


title: Chains of semidualizing modules

abstract:
  Let $(R, \mathfrak{m}, k)$ be a commutative Noetherian local ring. We study
the suitable chains of semidualizing $R$-modules. We prove that when $R$ is
Artinian, the existence of a suitable chain of semidualizing modules of length
$n=\mathrm{max}\,\{\,i\geqslant 0\ |\ \mathfrak{m}^{i}\neq 0\,\}$ implies that
the the Poincar$\acute{\mathrm{e}}$ series of $k$ and the Bass series of $R$
have very specific forms. Also, in this case we show that the Bass numbers of
$R$ are strictly increasing. This gives an insight into the question of Huneke
about the Bass numbers of $R$.


title:
Search for new phenomena in events containing a same-flavour
  opposite-sign dilepton pair, jets, and large missing transverse momentum in
  $\sqrt{s}=13$ TeV pp collisions with the ATLAS detector

abstract:
  Two searches for new phenomena in final states containing a same-flavour
opposite-lepton (electron or muon) pair, jets, and large missing transverse
momentum are presented. These searches make use of proton--proton collision
data, collected during 2015 and 2016 at a centre-of-mass energy $\sqrt{s}=13$
TeV by the ATLAS detector at the Large Hadron Collider, which correspond to an
integrated luminosity of 14.7 fb$^{-1}$. Both searches target the pair
production of supersymmetric particles, squarks or gluinos, which decay to
final states containing a same-flavour opposite-sign lepton pair via one of two
mechanisms: a leptonically decaying Z boson in the final state, leading to a
peak in the dilepton invariant-mass distribution around the Z boson mass; and
decays of neutralinos (e.g. $\tilde{\chi}_2^0 \rightarrow \ell^+\ell^-
\tilde{\chi}_1^0$), yielding a kinematic endpoint in the dilepton
invariant-mass spectrum. The data are found to be consistent with the Standard
Model expectation. Results are interpreted in simplified models of gluino-pair
(squark-pair) production, and provide sensitivity to gluinos (squarks) with
masses as large as 1.70 TeV (980 GeV).


title: Low Energy Background Spectrum in CDMSlite

abstract:
  One trend in dark matter direct detection is the development of techniques
which will lower experimental thresholds and achieve sensitivity to light mass
dark matter particles. In doing so, it is necessary to have an understanding of
the low energy spectrum of the major background components. Geant4 has a number
of specialized low energy physics processes that can be implemented when
simulating an experimental geometry. To understand this low energy region for
the Super Cryogenic Dark Matter Search (SuperCDMS), a variety of these models
have been simulated and compared against theoretical calculations and SuperCDMS
calibration data. Most of the low energy processes include a more complete
description of the atomic structure, allowing us to observe the phenomenon of
Compton steps in the simulation. An important application of this low energy
background modeling is for the SuperCDMS low ionization threshold experiment
(CDMSlite). CDMSlite has reached world-leading sensitivities in the search for
low mass weakly interacting massive particle (WIMP) dark matter. Using
Neganov-Trofinov-Luke phonon amplification, CDMSlite has achieved a threshold
of less than 60 eV for electron recoils. The dark matter sensitivity of the
CDMSlite-Soudan data can be improved by understanding and modeling the
experimental backgrounds down to this threshold. Development of the machinery
for creating a low energy background model will also be useful in the future
SuperCDMS-SNOLAB experiment which will run multiple high voltage detectors in
CDMSlite mode.


title:
How Lock-free Data Structures Perform in Dynamic Environments: Models
  and Analyses

abstract:
  In this paper we present two analytical frameworks for calculating the
performance of lock-free data structures. Lock-free data structures are based
on retry loops and are called by application-specific routines. In contrast to
previous work, we consider in this paper lock-free data structures in dynamic
environments. The size of each of the retry loops, and the size of the
application routines invoked in between, are not constant but may change
dynamically. The new frameworks follow two different approaches. The first
framework, the simplest one, is based on queuing theory. It introduces an
average-based approach that facilitates a more coarse-grained analysis, with
the benefit of being ignorant of size distributions. Because of this
independence from the distribution nature it covers a set of complicated
designs. The second approach, instantiated with an exponential distribution for
the size of the application routines, uses Markov chains, and is tighter
because it constructs stochastically the execution, step by step.
  Both frameworks provide a performance estimate which is close to what we
observe in practice. We have validated our analysis on (i) several fundamental
lock-free data structures such as stacks, queues, deques and counters, some of
them employing helping mechanisms, and (ii) synthetic tests covering a wide
range of possible lock-free designs. We show the applicability of our results
by introducing new back-off mechanisms, tested in application contexts, and by
designing an efficient memory management scheme that typical lock-free
algorithms can utilize.


title:
Sensitivity of quantum walks to boundary of two-dimensional lattices:
  approaches from the CGMV method and topological phases

abstract:
  In this paper, we treat quantum walks in a two-dimensional lattice with
cutting edges along a straight boundary introduced by Asboth and Edge (2015
Phys.Rev. A 91 022324) in order to study one-dimensional edge states
originating from topological phases of matter and to obtain collateral evidence
of how a quantum walker reacts to the boundary. Firstly, we connect this model
to the CMV matrix, which provides a 5-term recursion relation of the Laurent
polynomial associated with spectral measure on the unit circle. Secondly,we
explicitly derive the spectra of bulk and edge states of the quantum walk with
the boundary using spectral analysis of the CMV matrix. Thirdly, while
topological numbers of the model studied so far are well-defined only when gaps
in the bulk spectrum exist, we find a new topological number defined only when
there are no gaps in the bulk spectrum. We confirm that the existence of the
spectrum for edge states derived from the CMV matrix is consistent with the
prediction from a bulk-edge correspondence using topological numbers calculated
in the cases where gaps in the bulk spectrum do or do not exist. Finally, we
show how the edge states contribute to the asymptotic behavior of the quantum
walk through limit theorems of the finding probability. Conversely, we also
propose a differential equation using this limit distribution whose solution is
the underlying edge state.


title:
A Fast Stable Discretization of the
  Constant-Convection-Diffusion-Reaction Equations of Kinetic Capillary
  Electrophoresis (KCE)

abstract:
  A discretization scheme is introduced for a set of convection-diffusion
equations with a non-linear reaction term, where the convection velocity is
constant for each reactant. This constancy allows a transformation to new
spatial variables, which ensures the global stability of discretization.
Convection-diffusion equations are notorious for their lack of stability,
arising from the algebraic interaction of the convection and diffusion terms.
Unexpectedly, our implemented numerical algorithm proves to be faster than
computing exact solutions derived for a special case, while remaining
reasonably accurate, as demonstrated in our runtime and error analysis.


title: Imprecise Continuous-Time Markov Chains

abstract:
  Continuous-time Markov chains are mathematical models that are used to
describe the state-evolution of dynamical systems under stochastic uncertainty,
and have found widespread applications in various fields. In order to make
these models computationally tractable, they rely on a number of assumptions
that may not be realistic for the domain of application; in particular, the
ability to provide exact numerical parameter assessments, and the applicability
of time-homogeneity and the eponymous Markov property. In this work, we extend
these models to imprecise continuous-time Markov chains (ICTMC's), which are a
robust generalisation that relaxes these assumptions while remaining
computationally tractable.
  More technically, an ICTMC is a set of "precise" continuous-time finite-state
stochastic processes, and rather than computing expected values of functions,
we seek to compute lower expectations, which are tight lower bounds on the
expectations that correspond to such a set of "precise" models. Note that, in
contrast to e.g. Bayesian methods, all the elements of such a set are treated
on equal grounds; we do not consider a distribution over this set.
  The first part of this paper develops a formalism for describing
continuous-time finite-state stochastic processes that does not require the
aforementioned simplifying assumptions. Next, this formalism is used to
characterise ICTMC's and to investigate their properties. The concept of lower
expectation is then given an alternative operator-theoretic characterisation,
by means of a lower transition operator, and the properties of this operator
are investigated as well. Finally, we use this lower transition operator to
derive tractable algorithms (with polynomial runtime complexity w.r.t. the
maximum numerical error) for computing the lower expectation of functions that
depend on the state at any finite number of time points.


title: On the linearity of Regge trajectory at large transfer energy

abstract:
  In this note we consider the four-point function of identical scalar
operators in its Mellin representation. For CFTs, taking the large scaling
dimension limit of the Mellin amplitude yields the flat-space S-matrix. Using
this correspondence, and assuming that the Regge-limit of the Mellin amplitude
vanishes, we prove that the resulting flat space S-matrix must have string-like
linear Regge trajectory in the limit |s|>>|t|>>1. We also show that the Regge
limit of Mellin amplitude is captured by the three-point coefficient of two
scalars and one double trace operator in the large-spin limit. Using this, we
can see that vanishing Regge behaviour occurs at small t'Hooft limit.


title:
Inductive detection of field-like and damping-like AC inverse spin-orbit
  torques in ferromagnet/normal metal bilayers

abstract:
  Functional spintronic devices rely on spin-charge interconversion effects,
such as the reciprocal processes of electric field-driven spin torque and
magnetization dynamics-driven spin and charge flow. Both damping-like and
field-like spin-orbit torques have been observed in the forward process of
current-driven spin torque and damping-like inverse spin-orbit torque has been
well-studied via spin pumping into heavy metal layers. Here we demonstrate that
established microwave transmission spectroscopy of ferromagnet/normal metal
bilayers under ferromagnetic resonance can be used to inductively detect the AC
charge currents driven by the inverse spin-charge conversion processes. This
technique relies on vector network analyzer ferromagnetic resonance (VNA-FMR)
measurements. We show that in addition to the commonly-extracted spectroscopic
information, VNA-FMR measurements can be used to quantify the magnitude and
phase of all AC charge currents in the sample, including those due to spin
pumping and spin-charge conversion. Our findings reveal that
Ni$_{80}$Fe$_{20}$/Pt bilayers exhibit both damping-like and field-like inverse
spin-orbit torques. While the magnitudes of both the damping-like and
field-like inverse spin-orbit torque are of comparable scale to prior reported
values for similar material systems, we observed a significant dependence of
the damping-like magnitude on the order of deposition. This suggests interface
quality plays an important role in the overall strength of the damping-like
spin-to-charge conversion.


title: The Freiburg Groceries Dataset

abstract:
  With the increasing performance of machine learning techniques in the last
few years, the computer vision and robotics communities have created a large
number of datasets for benchmarking object recognition tasks. These datasets
cover a large spectrum of natural images and object categories, making them not
only useful as a testbed for comparing machine learning approaches, but also a
great resource for bootstrapping different domain-specific perception and
robotic systems. One such domain is domestic environments, where an autonomous
robot has to recognize a large variety of everyday objects such as groceries.
This is a challenging task due to the large variety of objects and products,
and where there is great need for real-world training data that goes beyond
product images available online. In this paper, we address this issue and
present a dataset consisting of 5,000 images covering 25 different classes of
groceries, with at least 97 images per class. We collected all images from
real-world settings at different stores and apartments. In contrast to existing
groceries datasets, our dataset includes a large variety of perspectives,
lighting conditions, and degrees of clutter. Overall, our images contain
thousands of different object instances. It is our hope that machine learning
and robotics researchers find this dataset of use for training, testing, and
bootstrapping their approaches. As a baseline classifier to facilitate
comparison, we re-trained the CaffeNet architecture (an adaptation of the
well-known AlexNet) on our dataset and achieved a mean accuracy of 78.9%. We
release this trained model along with the code and data splits we used in our
experiments.


title: Splitting schemes for unsteady problems involving the grad-div operator

abstract:
  In this paper we consider various splitting schemes for unsteady problems
containing the grad-div operator. The fully implicit discretization of such
problems would yield at each time step a linear problem that couples all
components of the solution vector. In this paper we discuss various
possibilities to decouple the equations for the different components that
result in unconditionally stable schemes. If the spatial discretization uses
Cartesian grids, the resulting schemes are Locally One Dimensional (LOD). The
stability analysis of these schemes is based on the general stability theory of
additive operator-difference schemes developed by Samarskii and his
collaborators. The results of the theoretical analysis are illustrated on a 2D
numerical example with a smooth manufactured solution.


title:
Automatic continuity of abstract homomorphisms between locally compact
  and Polish groups

abstract:
  We are concerned with questions of the following type. Suppose that $G$ and
$K$ are topological groups belonging to a certain class $\cal K$ of spaces, and
suppose that $\phi:K \to G$ is an abstract (i.e. not necessarily continuous)
surjective group homomorphism. Under what conditions on the group $G$ and the
kernel is the homomorphism $\phi$ automatically continuous and open? Questions
of this type have a long history and were studied in particular for the case
that $G$ and $K$ are Lie groups, compact groups, or Polish groups. We develop
an axiomatic approach, which allows us to resolve the question uniformly for
different classes of topological groups. In this way we are able to extend the
classical results about automatic continuity to a much more general setting.


title:
Hund interaction, spin-orbit coupling and the mechanism of
  superconductivity in strongly hole-doped iron pnictides

abstract:
  We present a novel mechanism of s-wave pairing in Fe-based superconductors.
The mechanism involves holes near dxz/dyz pockets only and is applicable
primarily to strongly hole doped materials. We argue that as long as the
renormalized Hund's coupling J exceeds the renormalized inter-orbital Hubbard
repulsion U', any finite spin-orbit coupling gives rise to s-wave
superconductivity. This holds even at weak coupling and regardless of the
strength of the intra-orbital Hubbard repulsion U. The transition temperature
grows as the hole density decreases. The pairing gaps are four-fold symmetric,
but anisotropic, with the possibility of eight accidental nodes along the
larger pocket. The resulting state is consistent with the experiments on
KFe2As2.


title:
COOLL: Controlled On/Off Loads Library, a Public Dataset of High-Sampled
  Electrical Signals for Appliance Identification

abstract:
  This paper gives a brief description of the Controlled On/Off Loads Library
(COOLL) dataset. This latter is a dataset of high-sampled electrical current
and voltage measurements representing individual appliances consumption. The
measurements were taken in June 2016 in the PRISME laboratory of the University
of Orl\'eans, France. The appliances are mainly controllable appliances (i.e.
we can precisely control their turn-on/off time instants). 42 appliances of 12
types were measured at a 100 kHz sampling frequency.


title:
Existence of quasicrystals and universal stable sampling and
  interpolation in LCA groups

abstract:
  We characterize all the locally compact abelian (LCA) groups that contain
quasicrystals (a class of model sets). Moreover, we describe all possible
quasicrystals in the group constructing an appropriate lattice associated with
the cut and project scheme that produces it. On the other hand, if an LCA group
G admits a simple quasicrystal, we prove that recent results of Meyer and Matei
for the case of the n-dimensional Euclidean space can be extended to G. More
precisely, we prove that simple quasicrystals are universal sets of stable
sampling and universal sets of stable interpolation in generalized Paley-Wiener
spaces.


title: Phylogenetic trees

abstract:
  We introduce the package PhylogeneticTrees for Macaulay2 which allows users
to compute phylogenetic invariants for group-based tree models. We provide some
background information on phylogenetic algebraic geometry and show how the
package PhylogeneticTrees can be used to calculate a generating set for a
phylogenetic ideal as well as a lower bound for its dimension. Finally, we show
how methods within the package can be used to compute a generating set for the
join of any two ideals.


title:
Filling the gaps: Gaussian mixture models from noisy, truncated or
  incomplete samples

abstract:
  Astronomical data often suffer from noise and incompleteness. We extend the
common mixtures-of-Gaussians density estimation approach to account for
situations with a known sample incompleteness by simultaneous imputation from
the current model. The method, called GMMis, generalizes existing
Expectation-Maximization techniques for truncated data to arbitrary truncation
geometries and probabilistic rejection processes, as long as they can be
specified and do not depend on the density itself. The method accounts for
independent multivariate normal measurement errors for each of the observed
samples and recovers an estimate of the error-free distribution from which both
observed and unobserved samples are drawn. It can perform a separation of a
mixtures-of-Gaussian signal from a specified background distribution whose
amplitude may be unknown. We compare GMMis to the standard Gaussian mixture
model for simple test cases with different types of incompleteness, and apply
it to observational data from the NASA Chandra X-ray telescope. The python code
is released as an open-source package at https://github.com/pmelchior/pyGMMis

categories: astro-ph.IM astro-ph.HE physics.data-an stat.ME


title: Singular Values of the Attenuated Photoacoustic Imaging Operator

abstract:
  We analyse the ill-posedness of the photoacoustic imaging problem in the case
of an attenuating medium. To this end, we introduce an attenuated photoacoustic
operator and determine the asymptotic behaviour of its singular values.
Dividing the known attenuation models into strong and weak attenuation classes,
we show that for strong attenuation, the singular values of the attenuated
photoacoustic operator decay exponentially, and in the weak attenuation case
the singular values of the attenuated photoacoustic operator decay with the
same rate as the singular values of the non-attenuated photoacoustic operator.


title: Holography with a Landau pole

abstract:
  Holography for UV-incomplete gauge theories is important but poorly
understood. A paradigmatic example is $d=4$, $\mathcal{N}=4$ super Yang-Mills
coupled to $N_f$ quark flavors, which possesses a Landau pole at a UV scale
$\Lambda_{LP}$. The dual gravity solution exhibits a UV singularity at a finite
proper distance along the holographic direction. Despite this, holographic
renormalization can be fully implemented via analytic continuation to an AdS
solution. The presence of a UV cut-off manifests itself in several interesting
ways. At energies $E \ll \Lambda_{LP}$ no pathologies appear, as expected from
effective field theory. In contrast, at scales $E \lesssim \Lambda_{LP}$ the
gravitational potential becomes repulsive, and at temperatures $T \lesssim
\Lambda_{LP}$ the specific heat becomes negative. Although we focus on
$\mathcal{N}=4$ super Yang-Mills with flavor, our qualitative results apply to
a much more general class of theories, since they only depend on the fact that
the metric near the UV singularity is a hyper-scaling violating metric with
exponent $\theta > d-1$.


title:
Dynamical contribution to the heat conductivity in stochastic energy
  exchanges of locally confined gases

abstract:
  We present a systematic computation of the heat conductivity of the Markov
jump process modeling the energy exchanges in an array of locally confined hard
spheres at the conduction threshold. Based on a variational formula [Sasada M.
2016, {\it Thermal conductivity for stochastic energy exchange models},
arXiv:1611.08866], explicit upper bounds on the conductivity are derived, which
exhibit a rapid power-law convergence towards an asymptotic value. We thereby
conclude that the ratio of the heat conductivity to the energy exchange
frequency deviates from its static contribution by a small negative correction,
its dynamic contribution, evaluated to be $-0.000\,373$ in dimensionless units.
This prediction is corroborated by kinetic Monte Carlo simulations which were
substantially improved compared to earlier results.


title:
Noncommutative geometrical origin of the energy-momentum dispersion
  relation

abstract:
  We investigate a link between the energy-momentum dispersion relation and the
spectral distance in the context of a Lorentzian almost-commutative spectral
geometry, defined by the product of Minkowski spacetime and an internal
discrete noncommutative space. Using the causal structure, the
almost-commutative manifold can be identified with a pair of four-dimensional
Minkowski spacetimes embedded in a five-dimensional Minkowski geometry.
Considering fermions travelling within the light cone of the ambient
five-dimensional spacetime, we then derive the energy-momentum dispersion
relation.


title: Intermediate planar algebra revisited

abstract:
  In this paper, we explicitly work out the subfactor planar algebra $P^{(N
\subset Q)}$ for an intermediate subfactor $N \subset Q \subset M$ of an
irreducible subfactor $N \subset M$ of finite index. We do this in terms of the
subfactor planar algebra $P^{(N \subset M)}$ by showing that if $T$ is any
planar tangle, the associated operator $Z^{(N \subset Q)}_T$ can be read off
from $Z^{(N \subset M)}_T$ by a formula involving the so-called {\em
biprojection} corresponding to the intermediate subfactor $N \subset Q \subset
M$ and a scalar $\alpha(T)$ carefully chosen so as to ensure that the formula
defining $Z^{(N \subset Q)}_T$ is multiplicative with respect to composition of
tangles. Also, the planar algebra of $Q \subset M$ can be obtained by applying
these results to $M \subset M_1$. We also apply our result to the example of a
semi-direct product subgroup-subfactor.


title: Infinite S-Expansion with Ideal Subtraction and Some Applications

abstract:
  According to the literature, the S-expansion procedure involving a finite
semigroup is valid no matter what the structure of the original Lie
(super)algebra is; However, when something about the structure of the starting
(super)algebra is known and when certain particular conditions are met, the
S-expansion method (with its features of resonance and reduction) is able not
only to lead to several kinds of expanded (super)algebras, but also to
reproduce the effects of the standard as well as the generalized
In\"on\"u-Wigner contraction. In the present paper, we propose a new
prescription for S-expansion, involving an infinite abelian semigroup
$S^{(\infty)}$ and the subtraction of an infinite ideal subalgebra. We show
that the subtraction of the infinite ideal subalgebra corresponds to a
reduction. Our approach is a generalization of the finite S-expansion procedure
presented in the literature, and it offers an alternative view of the
generalized In\"on\"u-Wigner contraction. We then show how to write the
invariant tensors of the target (super)algebras in terms of those of the
starting ones in the infinite S-expansion context presented in this work. We
also give some interesting examples of application on algebras and
superalgebras.


title: Large bipolarons and oxide superconductivity

abstract:
  Large-bipolaron superconductivity is plausible with carrier densities well
below those of conventional metals. Bipolarons form when carriers self-trap in
pairs. Coherently moving large-bipolarons require extremely large ratios of
static to optical dielectric-constants. The mutual Coulomb repulsion of a
planar large-bipolarons paired carriers drives it to a four-lobed shape. A
phonon-mediated attraction among large-bipolarons propels their condensation
into a liquid. This liquids excitations move slowly with a huge effective mass.
Excitations concomitant weak scattering by phonons produces a moderate
low-temperature dc resistivity that increases linearly with rising temperature.
With falling temperature an energy gap opens between large-bipolarons
excitations and those of their self-trapped electronic carriers.


title:
Balancing specificity, sensitivity and speed of ligand discrimination by
  zero-order ultraspecificity

abstract:
  Specific interactions between receptors and their target ligands in the
presence of non-target ligands are crucial for biological processes such as T
cell ligand discrimination. To discriminate between the target and non-target
ligands, cells have to increase specificity by amplifying the small differences
in affinity among ligands. In addition, sensitivity to ligand concentration and
quick discrimination are also important to detect low amounts of target ligands
and facilitate fast cellular decision making after ligand recognition. In this
work, we find that ultraspecificity is naturally derived from a well-known
mechanism for zero-order ultrasensitivity to concentration. We also show that
this mechanism can produce an optimal balance of specificity, sensitivity, and
quick discrimination. Furthermore, we show that a model for insensitivity to
large number of non-terget ligands can be naturally derived from the
ultraspecificity model. Zero-order ultraspecificity may provide alternative way
to understand ligand discrimination from the viewpoint of the nonlinear
properties of biochemical reactions.


title:
MHD boundary layers theory in Sobolev spaces without monotonicity. I.
  well-posedness theory

abstract:
  We study the well-posedness theory for the MHD boundary layer. The boundary
layer equations are governed by the Prandtl type equations that are derived
from the incompressible MHD system with non-slip boundary condition on the
velocity and perfectly conducting condition on the magnetic field. Under the
assumption that the initial tangential magnetic field is not zero, we establish
the local-in-time existence, uniqueness of solution for the nonlinear MHD
boundary layer equations. Compared with the well-posedness theory of the
classical Prandtl equations for which the monotonicity condition of the
tangential velocity plays a crucial role, this monotonicity condition is not
needed for MHD boundary layer. This justifies the physical understanding that
the magnetic field has a stabilizing effect on MHD boundary layer in rigorous
mathematics.


title: On Escaping a Galaxy Cluster in an Accelerating Universe

abstract:
  We derive the escape velocity profile for an Einasto density field in an
accelerating universe and demonstrate its physical viability by comparing
theoretical expectations to both light-cone data generated from N-body
simulations and archival data on 20 galaxy clusters. We demonstrate that the
projection function ($g(\beta )$) is deemed physically viable only for the
theoretical expectation that includes a cosmology-dependent term. Using
simulations, we show that the inferred velocity anisotropy is more than
6{\sigma} away from the expected value for the theoretical profile that ignores
the acceleration of the universe. In the archival data, we constrain the
average velocity anisotropy parameter of a sample of 20 clusters to be $\beta
={0.248}_{-0.360}^{+0.164}$ at the 68% confidence level. Lastly, we briefly
discuss how our analytic model may be used as a novel cosmological probe based
on galaxy clusters.


title:
Nothing Else Matters: Model-Agnostic Explanations By Identifying
  Prediction Invariance

abstract:
  At the core of interpretable machine learning is the question of whether
humans are able to make accurate predictions about a model's behavior. Assumed
in this question are three properties of the interpretable output: coverage,
precision, and effort. Coverage refers to how often humans think they can
predict the model's behavior, precision to how accurate humans are in those
predictions, and effort is either the up-front effort required in interpreting
the model, or the effort required to make predictions about a model's behavior.
  In this work, we propose anchor-LIME (aLIME), a model-agnostic technique that
produces high-precision rule-based explanations for which the coverage
boundaries are very clear. We compare aLIME to linear LIME with simulated
experiments, and demonstrate the flexibility of aLIME with qualitative examples
from a variety of domains and tasks.


title: The random members of a $\Pi^0_1$ class

abstract:
  We examine several notions of randomness for elements in a given $\Pi^0_1$
class $\mathcal{P}$. Such an effectively closed subset $\mathcal{P}$ of
$2^\omega$ may be viewed as the set of infinite paths through the tree
$T_{\mathcal{P}}$ of extendible nodes of $\mathcal{P}$, i.e., those finite
strings that extend to a member of $\mathcal{P}$, so one approach to defining a
random member of $\mathcal{P}$ is to randomly produce a path through
$T_{\mathcal{P}}$ using a sufficiently random oracle for advice. In addition,
this notion of randomness for elements of $\mathcal{P}$ may be induced by a map
from $2^\omega$ onto $\mathcal{P}$ that is computable relative to
$T_{\mathcal{P}}$, and the notion even has a characterization in term of
Kolmogorov complexity. Another approach is to define a relative measure on
$\mathcal{P}$ by conditionalizing the Lebesgue measure on $\mathcal{P}$, which
becomes interesting if $\mathcal{P}$ has Lebesgue measure 0. Lastly, one can
alternatively define a notion of incompressibility for members of $\mathcal{P}$
in terms of the amount of branching at levels of $T_{\mathcal{P}}$. We explore
some notions of homogeneity for $\Pi^0_1$ classes, inspired by work of van
Lambalgen. A key finding is that in a specific class of sufficiently
homogeneous $\Pi^0_1$ classes $\mathcal{P}$, each of these approaches
coincides. We conclude with a discussion of random members of $\Pi^0_1$ classes
of positive measure.


title: Kolmogorov complexity and generalized length functions

abstract:
  Kolmogorov complexity measures the algorithmic complexity of a finite binary
string $\sigma$ in terms of the length of the shortest description $\sigma^*$
of $\sigma$. Traditionally, the length of a string is taken to measure the
amount of information contained in the string. However, we may also view the
length of $\sigma$ as a measure of the cost of producing $\sigma$, which
permits one to generalize the notion of length, wherein the cost of producing a
0 or a 1 can vary in some prescribed manner.
  In this article, we initiate the study of this generalization of length based
on the above information cost interpretation. We also modify the definition of
Kolmogorov complexity to use such generalized length functions instead of
standard length. We further investigate conditions under which the notion of
complexity defined in terms of a given generalized length function preserves
some essential properties of Kolmogorov complexity. We focus on a specific
class of generalized length functions that are intimately related to a specific
subcollection of Bernoulli $p$-measures, namely those corresponding to the
unique computable real $p\in(0,1)$ such that $p^k=1-p$, for integers $k\geq 1$.
We then study randomness with respect to such measures, by proving a
generalization version of the classic Levin-Schnorr theorem that involves
$k$-length functions and then proving subsequent results that involve effective
dimension and entropy.


title:
On-line detection of qualitative dynamical changes in nonlinear systems:
  the resting-oscillation case

abstract:
  Motivated by neuroscience applications, we introduce the concept of
qualitative detection, that is, the problem of determining on-line the current
qualitative dynamical behavior (e.g., resting, oscillating, bursting, spiking
etc.) of a nonlinear system. The approach is thought for systems characterized
by i) large parameter variability and redundancy, ii) a small number of
possible robust, qualitatively different dynamical behaviors and, iii) the
presence of sharply different characteristic timescales. These properties are
omnipresent in neurosciences and hamper quantitative modeling and fitting of
experimental data. As a result, novel control theoretical strategies are needed
to face neuroscience challenges like on-line epileptic seizure detection. The
proposed approach aims at detecting the current dynamical behavior of the
system and whether a qualitative change is likely to occur without
quantitatively fitting any model nor asymptotically estimating any parameter.
We talk of qualitative detection. We rely on the qualitative properties of the
system dynamics, extracted via singularity and singular perturbation theories,
to design low dimensional qualitative detectors. We introduce this concept on a
general class of singularly perturbed systems and then solve the problem for an
analytically tractable class of two-dimensional systems with a single unknown
sigmoidal nonlinearity and two sharply separated timescales. Numerical results
are provided to show the performance of the designed qualitative detector.


title: Universal Limit on Communication

abstract:
  I derive a universal upper bound on the capacity of any communication channel
between two distant systems. The Holevo quantity, and hence the mutual
information, is at most of order $E \Delta t / \hbar$, where $E$ is the average
energy of the signal, and $\Delta t$ is the amount of time for which detectors
operate. The bound does not depend on the size or mass of the emitting and
receiving systems, nor on the nature of the signal. No restrictions on
preparing and processing the signal are imposed.
  As an example, I consider the encoding of information in the transverse or
angular position of a signal emitted and received by systems of arbitrarily
large cross-section. In the limit of a large message space, quantum effects
become important even if individual signals are classical, and the bound is
upheld.


title: Charmed Meson Scattering from Lattice QCD

abstract:
  State-of-the-art lattice QCD calculations of scattering amplitudes in
coupled-channel $D\pi$, $D\eta$ and $D_{s}\bar{K}$ scattering, as well elastic
$DK$ scattering are discussed. The methodology employed allows a determination
of the relevant poles in the scattering matrix, while also providing a measure
of the coupling of each channel to a given pole. By investigating $S$, $P$ and
$D$ wave interactions, the nature of states with $J^{P} = 0^{+}$, relevant for
the $D^{*}_{0}(2400)$ and $D^{*}_{s0}(2317)$, as well as states with $J^{P} =
1^{-}, 2^{+}$ are discussed.


title:
Characterization of projective spaces and $\mathbb P^r$-bundles as ample
  divisors

abstract:
  Let $X$ be a projective manifold of dimension $n$. Suppose that $T_X$
contains an ample subsheaf. We show that $X$ is isomorphic to $\mathbb{P}^n$.
As an application, we derive the classification of projective manifolds
containing a $\mathbb{P}^r$-bundle as an ample divisor by the recent work of
D.~Litt.


title: HDG methods for elastodynamics

abstract:
  We derive and analyze a hybridizable discontinuous Galerkin (HDG) method for
approximating weak solutions to the equations of time-harmonic linear
elasticity on a bounded Lipschitz domain in three dimensions. The real symmetry
of the stress tensor is strongly enforced and its coefficients as well as those
of the displacement vector field are approximated simultaneously at optimal
convergence with respect to the choice of approximating spaces, wavenumber, and
mesh size. Sufficient conditions are given so that the system is indeed
transferable onto a global hybrid variable that, for larger polynomial degrees,
may be approximated via a smaller-dimensional space than the original
variables. We construct several variants of this method and discuss their
advantages and disadvantages, and give a systematic approach to the error
analysis for these methods. We touch briefly on the application of this error
analysis to the time-dependent problem, and finally, we examine two different
implementations of the method over various polynomial degrees and numerically
demonstrate the convergence properties proven herein.


title: Monte Carlo Glauber wounded nucleon model with meson cloud

abstract:
  We study the effect of the nucleon meson cloud on predictions of the Monte
Carlo Glauber wounded nucleon model for $AA$, $pA$, and $pp$ collisions. From
the analysis of the data on the charged multiplicity density in $AA$ collisions
we find that the meson-baryon Fock component reduces the required fraction of
binary collisions by a factor of $\sim 2$ for Au+Au collisions at
$\sqrt{s}=0.2$ TeV and $\sim 1.5$ for Pb+Pb collisions at $\sqrt{s}=2.76$ TeV.
For central $AA$ collisions the meson cloud can increase the multiplicity
density by $\sim 16-18$\%. We give predictions for the midrapidity charged
multiplicity density in Pb+Pb collisions at $\sqrt{s}=5.02$ TeV for the future
LHC run 2. We find that the meson cloud has a weak effect on the centrality
dependence of the ellipticity $\epsilon_2$ in $AA$ collisions. For collisions
of the deformed uranium nuclei at $\sqrt{s}=0.2$ TeV we find that the meson
cloud may improve somewhat agreement with the data on the dependence of the
elliptic flow on the charged multiplicity for very small centralities defined
via the ZDCs signals. We find that the meson cloud may lead to a noticeable
reduction of $\epsilon_2$ and the size of the fireball in $pA$ and $pp$
collisions.


title: Eccentricity distribution in the main asteroid belt

abstract:
  The observationally complete sample of the main belt asteroids now spans more
than two orders of magnitude in size and numbers more than 64,000 (excluding
collisional family members). We undertook an analysis of asteroids'
eccentricities and their interpretation with simple physical models. We find
that Plummer's (1916) conclusion that the asteroids' eccentricities follow a
Rayleigh distribution holds for the osculating eccentricities of large
asteroids, but the proper eccentricities deviate from a Rayleigh distribution:
there is a deficit of eccentricities smaller than $\sim0.1$ and an excess of
larger eccentricities. We further find that the proper eccentricities do not
depend significantly on asteroid size but have strong dependence on
heliocentric distance: the outer asteroid belt follows a Rayleigh distribution,
but the inner belt is strikingly different. Eccentricities in the inner belt
can be modeled as a vector sum of a primordial eccentricity vector of random
orientation and magnitude drawn from a Rayleigh distribution of parameter
$\sim0.06$, and an excitation of random phase and magnitude $\sim0.13$. These
results imply that a late dynamical excitation of the asteroids occurred, it
was independent of asteroid size, it was stronger in the inner belt than in the
outer belt. We discuss implications for the primordial asteroid belt and
suggest that the observationally complete sample size of main belt asteroids is
large enough that more sophisticated model-fitting of the eccentricities is
warranted and could serve to test alternative theoretical models of the
dynamical excitation history of asteroids and its links to the migration
history of the giant planets.


title:
Towards a Mathematical Understanding of the Difficulty in Learning with
  Feedforward Neural Networks

abstract:
  Training deep neural networks for solving machine learning problems is one
great challenge in the field, mainly due to its associated optimisation problem
being highly non-convex. Recent developments have suggested that many training
algorithms do not suffer from undesired local minima under certain scenario,
and consequently led to great efforts in pursuing mathematical explanations for
such observations. This work provides an alternative mathematical understanding
of the challenge from a smooth optimisation perspective. By assuming exact
learning of finite samples, sufficient conditions are identified via a critical
point analysis to ensure any local minimum to be globally minimal as well.
Furthermore, a state of the art algorithm, known as the Generalised
Gauss-Newton (GGN) algorithm, is rigorously revisited as an approximate
Newton's algorithm, which shares the property of being locally quadratically
convergent to a global minimum under the condition of exact learning.


title: Absorption and Photoluminescence in Organic Cavity QED

abstract:
  Organic microcavities can be engineered to reach exotic quantum regimes of
strong and ultrastrong light-matter coupling. However, the microscopic
interpretation of their spectroscopic signals can be challenging due to the
competition between coherent and dissipative processes involving electrons,
vibrations and cavity photons. We develop here a theoretical framework based on
the Holstein-Tavis-Cummings model and a Markovian treatment of dissipation to
account for previously unexplained spectroscopic features of organic
microcavities consistently. We identify conditions for the formation of dark
vibronic polaritons, a new class of light-matter excitations that are not
visible in absorption but lead to strong photoluminescence lines. We show that
photon leakage from dark vibronic polaritons can be responsible for enhancing
photoluminescence at the lower polariton frequency, and also explain the
apparent breakdown of reciprocity between absorption and emission in the
vicinity of the bare molecular transition frequency. Successful comparison with
experimental data demonstrates the applicability of our theory.


title: An active particle in a complex fluid

abstract:
  In this work, we study active particles with prescribed surface velocities in
non-Newtonian fluids. We employ the reciprocal theorem to obtain the velocity
of an active spherical particle with an arbitrary axisymmetric slip-velocity in
an otherwise quiescent second-order fluid. We then determine how the motion of
a diffusiophoretic Janus particle is affected by complex fluid rheology, namely
viscoelasticity and shear-thinning viscosity, compared to a Newtonian fluid,
assuming a fixed slip-velocity. We find that a Janus particle may go faster or
slower in a viscoelastic fluid, but is always slower in a shear-thinning fluid
as compared to a Newtonian fluid.


title:
A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC
  6273 (M 19)

abstract:
  Recent observations have shown that a growing number of the most massive
Galactic globular clusters contain multiple populations of stars with different
[Fe/H] and neutron-capture element abundances. NGC 6273 has only recently been
recognized as a member of this "iron-complex" cluster class, and we provide
here a chemical and kinematic analysis of > 300 red giant branch (RGB) and
asymptotic giant branch (AGB) member stars using high resolution spectra
obtained with the Magellan-M2FS and VLT-FLAMES instruments. Multiple lines of
evidence indicate that NGC 6273 possesses an intrinsic metallicity spread that
ranges from about [Fe/H] = -2 to -1 dex, and may include at least three
populations with different [Fe/H] values. The three populations identified here
contain separate first (Na/Al-poor) and second (Na/Al-rich) generation stars,
but a Mg-Al anti-correlation may only be present in stars with [Fe/H] > -1.65.
The strong correlation between [La/Eu] and [Fe/H] suggests that the s-process
must have dominated the heavy element enrichment at higher metallicities. A
small group of stars with low [alpha/Fe] is identified and may have been
accreted from a former surrounding field star population. The cluster's large
abundance variations are coupled with a complex, extended, and multimodal blue
horizontal branch (HB). The HB morphology and chemical abundances suggest that
NGC 6273 may have an origin that is similar to omega Cen and M 54.


title: Generalized LR parsing and the shuffle operator

abstract:
  We adapt Tomita's Generalized LR algorithm to languages generated by
context-free grammars enriched with a shuffle operator. The change involves
extensions to the underlying handle-finding finite automaton, construction of
parser tables, and the necessary optimizations in constructing a deterministic
parser. Our system is motivated by an application from artificial intelligence
plan recognition. We argue for the correctness of the system, and discuss
future extensions of this work.


title:
Geometrical models for the study of astrophysical systems with
  spheroidal symmetry imbedded in a standard cosmology: The case of cosmic
  voids

abstract:
  We present a class of general prolate and oblate spheroidal spacetimes for
the description of cosmic structures in the Universe. They are exact geometries
which represent, in an appropriated way, the imbedding of spheroidal
matter-energy distributions within a standard cosmological scenario, and
therefore they allow for an improved description of a wider class of
astrophysical systems from a more accurate point of view. These spacetimes can
be used to describe overdensity or underdensity regions; in this work we
consider the last case, that is, the description of cosmic voids. We introduce
and study a model of void which is a generalization of a simpler one in
spherical symmetry and we use it for the calculation of weak lensing optical
scalars as a non-trivial and interesting application. In this particular
example we show the rich observable features that can be found in such models.


title: Dark Energy and Inflation with Volume Normalized Action

abstract:
  In the theories described by a volume normalized action functional, an
arbitrary cosmological constant is eliminated from the physical picture of our
Universe, and dynamical alternatives must be responsible for today's
accelerated expansion as well as for the conjectured early-time inflation in
the Universe. A few well-known such scenarios realized by a single homogeneous
scalar field are examined in this new context, and their diverse fates are
elucidated. Typical inflationary models are not affected at the level of the
background evolution, and also give rise to the scalar perturbations equivalent
to those obtained in the standard General Relativity; however, the primordial
quantum tensor fluctuations are absent in the new framework, irrespective of
the inflationary model. As a consequence, our proposal would be ruled out
should the primordial tensor modes, or their indirect consequences, be
discovered in observations.


title: Chimera states in uncoupled neurons induced by a multilayer structure

abstract:
  Spatial coexistence of coherent and incoherent dynamics in network of coupled
oscillators is called a chimera state. We study such chimera states in a
network of neurons without any direct interactions but connected through
another medium of neurons, forming a multilayer structure. The upper layer is
thus made up of uncoupled neurons and the lower layer plays the role of a
medium through which the neurons in the upper layer share information among
each other. Hindmarsh-Rose neurons with square wave bursting dynamics are
considered as nodes in both layers. In addition, we also discuss the existence
of chimera states in presence of inter layer heterogeneity. The neurons in the
bottom layer are globally connected through electrical synapses, while across
the two layers chemical synapses are formed. According to our research, the
competing effects of these two types of synapses can lead to chimera states in
the upper layer of uncoupled neurons. Remarkably, we find a density-dependent
threshold for the emergence of chimera states in uncoupled neurons, similar to
the quorum sensing transition to a synchronized state. Finally, we examine the
impact of both homogeneous and heterogeneous inter-layer information
transmission delays on the observed chimera states over a wide parameter space.


title: A Socio-geographic Perspective on Human Activities in Social Media

abstract:
  Location-based social media make it possible to understand social and
geographic aspects of human activities. However, previous studies have mostly
examined these two aspects separately without looking at how they are linked.
The study aims to connect two aspects by investigating whether there is any
correlation between social connections and users' check-in locations from a
socio-geographic perspective. We constructed three types of networks: a
people-people network, a location-location network, and a city-city network
from former location-based social media Brightkite and Gowalla in the U.S.,
based on users' check-in locations and their friendships. We adopted some
complexity science methods such as power-law detection and head/tail breaks
classification method for analysis and visualization. Head/tail breaks
recursively partitions data into a few large things in the head and many small
things in the tail. By analyzing check-in locations, we found that users'
check-in patterns are heterogeneous at both the individual and collective
levels. We also discovered that users' first or most frequent chec-in locations
can be the representatives of users' spatial information. The constructed
networks based on these locations are very heterogeneous, as indicated by the
high ht-index. Most importantly, the node degree of the networks correlates
highly with the population at locations (mostly with R-square being 0.7) or
cities (above 0.9). This correlation indicates that the geographic
distributions of the social media users relate highly to their online social
connections.
  Keywords: social networks, check-in locations, natural cities, power law,
head/tail breaks, ht-index


title:
Temperature dependence of the polaronic band structure in strongly
  correlated electron systems with strong electron-phonon interaction

abstract:
  In this work we investigate temperature dependence of electronic structure of
system with strong electronic correlations and strong electron-phonon
interaction modeling cuprates in the frameworks of the three-band p-d-Holstein
model by a polaronic version of the generalized tight binding (GTB) method.
Within this approach the electronic structure is formed by polaronic
quasiparticles constructed as excitations between initial and final polaronic
multielectron states. Temperature effect is taken into account by occupation
numbers of local excited polaronic states and variations in the magnitude of
spin-spin correlation functions and it is manifested in the redistribution of
the spectral weight over the Hubbard polaron subbands, and the temperature
dependent band structure. Temperature increasing leads to broadening of the
spectral function peak at the top of the valence band, shift of the peak, the
decreasing of the peak intensity, the growth of bandwidth and reduction of the
insulator energy gap. These effects are in a qualitative agreement to the
temperature dependence of the ARPES spectra observed in the undoped HTSC
cuprates.


title: AutoScaler: Scale-Attention Networks for Visual Correspondence

abstract:
  Finding visual correspondence between local features is key to many computer
vision problems. While defining features with larger contextual scales usually
implies greater discriminativeness, it could also lead to less spatial accuracy
of the features. We propose AutoScaler, a scale-attention network to explicitly
optimize this trade-off in visual correspondence tasks. Our network consists of
a weight-sharing feature network to compute multi-scale feature maps and an
attention network to combine them optimally in the scale space. This allows our
network to have adaptive receptive field sizes over different scales of the
input. The entire network is trained end-to-end in a siamese framework for
visual correspondence tasks. Our method achieves favorable results compared to
state-of-the-art methods on challenging optical flow and semantic matching
benchmarks, including Sintel, KITTI and CUB-2011. We also show that our method
can generalize to improve hand-crafted descriptors (e.g Daisy) on general
visual correspondence tasks. Finally, our attention network can generate
visually interpretable scale attention maps.


title: A smooth transition from Wishart to GOE

abstract:
  It is well known that an $n \times n$ Wishart matrix with $d$ degrees of
freedom is close to the appropriately centered and scaled Gaussian Orthogonal
Ensemble (GOE) if $d$ is large enough. Recent work of Bubeck, Ding, Eldan, and
Racz, and independently Jiang and Li, shows that the transition happens when $d
= \Theta ( n^{3} )$. Here we consider this critical window and explicitly
compute the total variation distance between the Wishart and GOE matrices when
$d / n^{3} \to c \in (0, \infty)$. This shows, in particular, that the phase
transition from Wishart to GOE is smooth.


title:
Maximizing the minimum achievable secrecy rate of two-way relay networks
  using the null space beamforming method

abstract:
  This paper concerns maximizing the minimum achievable secrecy rate of a
two-way relay network in the presence of an eavesdropper, in which two nodes
aim to exchange messages in two hops, using a multi-antenna relay. Throughout
the first hop, the two nodes simultaneously transmit their messages to the
relay. In the second hop, the relay broadcasts a combination of the received
information to the users such that the transmitted signal lies in the null
space of the eavesdropper's channel; this is called null space beamforming
(NSBF). The best NSBF matrix for maximizing the minimum achievable secrecy rate
is studied, showing that the problem is not convex in general. To address this
issue, the problem is divided into three sub-problems: a close-to-optimal
solution is derived by using the semi-definite relaxation (SDR) technique.
Simulation results demonstrate the superiority of the proposed method w.r.t.
the most well-known method addressed in the literature.


title:
Nonuniform dependence on initial data for compressible gas dynamics: The
  periodic Cauchy problem

abstract:
  We start with the classic result that the Cauchy problem for ideal
compressible gas dynamics is locally well posed in time in the sense of
Hadamard; there is a unique solution that depends continuously on initial data
in Sobolev space $H^s$ for $s>d/2+1$ where $d$ is the space dimension. We prove
that the data to solution map for periodic data in two dimensions although
continuous is not uniformly continuous on any bounded subset of Sobolev class
functions.


title:
Living on the Edge: A Toy Model for Holographic Reconstruction of
  Algebras with Centers

abstract:
  We generalize the Pastawski-Yoshida-Harlow-Preskill (HaPPY) holographic
quantum error-correcting code to provide a toy model for bulk gauge fields or
linearized gravitons. The key new elements are the introduction of degrees of
freedom on the links (edges) of the associated tensor network and their
connection to further copies of the HaPPY code by an appropriate isometry. The
result is a model in which boundary regions allow the reconstruction of bulk
algebras with central elements living on the interior edges of the (greedy)
entanglement wedge, and where these central elements can also be reconstructed
from complementary boundary regions. In addition, the entropy of boundary
regions receives both Ryu-Takayanagi-like contributions and further corrections
that model the $\frac{\delta \text{Area}}{4G_N}$ term of Faulkner, Lewkowycz,
and Maldacena. Comparison with Yang-Mills theory then suggests that this
$\frac{\delta \text{Area}}{4G_N}$ term can be reinterpreted as a part of the
bulk entropy of gravitons under an appropriate extension of the physical bulk
Hilbert space.


title:
Video Processing from Electro-optical Sensors for Object Detection and
  Tracking in Maritime Environment: A Survey

abstract:
  We present a survey on maritime object detection and tracking approaches,
which are essential for the development of a navigational system for autonomous
ships. The electro-optical (EO) sensor considered here is a video camera that
operates in the visible or the infrared spectra, which conventionally
complement radar and sonar and have demonstrated effectiveness for situational
awareness at sea has demonstrated its effectiveness over the last few years.
This paper provides a comprehensive overview of various approaches of video
processing for object detection and tracking in the maritime environment. We
follow an approach-based taxonomy wherein the advantages and limitations of
each approach are compared. The object detection system consists of the
following modules: horizon detection, static background subtraction and
foreground segmentation. Each of these has been studied extensively in maritime
situations and has been shown to be challenging due to the presence of
background motion especially due to waves and wakes. The main processes
involved in object tracking include video frame registration, dynamic
background subtraction, and the object tracking algorithm itself. The
challenges for robust tracking arise due to camera motion, dynamic background
and low contrast of tracked object, possibly due to environmental degradation.
The survey also discusses multisensor approaches and commercial maritime
systems that use EO sensors. The survey also highlights methods from computer
vision research which hold promise to perform well in maritime EO data
processing. Performance of several maritime and computer vision techniques is
evaluated on newly proposed Singapore Maritime Dataset.


title:
Contributed Discussion to Bayesian Solution Uncertainty Quantification
  for Differential Equations

abstract:
  We begin by introducing the main ideas of the paper under discussion, and we
give a brief description of the method proposed. Next, we discuss an
alternative approach based on B-spline expansion, and lastly we make some
comments on the method's convergence rate.


title: Irreducible components of exotic Springer fibres

abstract:
  Kato introduced the exotic nilpotent cone to be a substitute for the ordinary
nilpotent cone of type C with cleaner properties. Here we describe the
irreducible components of exotic Springer fibres (the fibres of the resolution
of the exotic nilpotent cone), and prove that they are naturally in bijection
with standard bitableaux. As a result, we deduce the existence of an exotic
Robinson-Schensted bijection, which is a variant of the type C
Robinson-Schensted bijection between pairs of same-shape standard bitableaux
and elements of the Weyl group; this bijection is described explicitly in the
sequel to this paper. Note that this is in contrast with ordinary type C
Springer fibres, where the parametrisation of irreducible components, and the
resulting geometric Robinson-Schensted bijection, are more complicated. As an
application, we explicitly describe the structure in the special cases where
the irreducible components of the exotic Springer fibre have dimension 2, and
show that in those cases one obtains Hirzebruch surfaces.


title:
Infinite dimensional optimistic optimisation with applications on
  physical systems

abstract:
  This paper presents a novel numerical optimisation method for infinite
dimensional optimisation. The functional optimisation makes minimal assumptions
about the functional and without any specific knowledge on the derivative of
the functional. The algorithm has been tested on several physical systems
(brachistochrone and catenary problems) and it is shown that the solutions
obtained are close to the actual solutions in one thousand functional
evaluations. It is also shown that for the tested cases, the new algorithm
provides better convergence to the optimum value compared to the tested
existing algorithms.


title: The WA105-3x1x1 m3 dual phase LAr-TPC demonstrator

abstract:
  The dual phase Liquid Argon Time Projection Chamber (LAr TPC) is the
state-of-art technology for neutrino detection thanks to its superb 3D tracking
and calorimetry performance. Its main feature is the charge amplification in
gas argon which provides excellent signal-to-noise ratio. Electrons produced in
the liquid argon are extracted in the gas phase. Here, a readout plane based on
Large Electron Multiplier detectors provides amplification of the charges
before its collection onto an anode with strip readout. The charge
amplification enables constructing fully homoge- nous giant LAr-TPCs with
tuneable gain, excellent charge imaging performance and increased sensitivity
to low energy events. Following a staged approach the WA105 collaboration is
con- structing a dual phase LAr-TPC with an active volume of 3x1x1m3 that will
soon be tested with cosmic rays. Its construction and operation aims to test
scalable solutions for the crucial aspects of this technology: ultra high argon
purity in non-evacuable tank, large area dual phase charge readout system in
several square meter scale, and accessible cold front-end electronics. A mile-
stone was achieved last year in the completion of the 24 m3 cryostat that hosts
the TPC. This is the first cryostat based on membrane technology to be
constructed at CERN and is therefore also an important step towards the
realisation of the upcoming protoDUNE detectors. The 3x1x1m3 dual phase LAr-TPC
will be described in and we will report on the latest construction progress.


title: An elastic two-sphere swimmer in Stokes flow

abstract:
  Swimming at low Reynolds number in Newtonian fluids is only possible through
non-reciprocal body deformations due to the kinematic reversibility of the
Stokes equations. We consider here a model swimmer consisting of two linked
spheres, wherein one sphere is rigid and the other an incompressible
neo-Hookean solid. The two spheres are connected by a rod which changes its
length periodically. We show that the deformations of the body are
non-reciprocal despite the reversible actuation and hence, the elastic
two-sphere swimmer propels forward. Our results indicate that even weak elastic
deformations of a body can affect locomotion and may be exploited in designing
artificial microswimmers.


title: The Conformal Spectrum of Non-Abelian Anyons

abstract:
  We study the spectrum of multiple non-Abelian anyons in a harmonic trap. The
system is described by Chern-Simons theory, coupled to either bosonic or
fermionic non-relativistic matter, and has an SO(2,1) conformal invariance. We
describe a number of special properties of the spectrum, focussing on a class
of protected states whose energies are dictated by their angular momentum. We
show that the angular momentum of a bound state of non-Abelian anyons is
determined by the quadratic Casimirs of their constituents.


title: Codimension one holomorphic distributions on the projective three-space

abstract:
  We study codimension one holomorphic distributions on the projective
three-space, analyzing the properties of their singular schemes and tangent
sheaves. In particular, we provide a classification of codimension one
distributions of degree at most 2 with locally free tangent sheaves, and show
that codimension one distributions of arbitrary degree with only isolated
singularities have stable tangent sheaves. Furthermore, we describe the moduli
space of distributions in terms of Grothendieck's Quot-scheme for the tangent
bundle. In certain cases, we show that the moduli space of codimension one
distributions on the projective space is an irreducible, nonsingular
quasi-projective variety. Finally, we prove that every rational foliation, and
certain logarithmic foliations have stable tangent sheaves.


title: Stashing the stops in multijet events at the LHC

abstract:
  While the presence of a light stop is increasingly disfavored by the
experimental limits set on R-parity conserving scenarios, the naturalness of
supersymmetry could still be safely concealed in the more challenging final
states predicted by the existence of non-null R-parity violating couplings.
Although R-parity violating signatures are extensively looked for at the Large
Hadron Collider, these searches always assume 100\% branching ratios for the
direct decays of supersymmetric particles into Standard Model ones. In this
paper we scrutinize the implications of relaxing this assumption by focusing on
one motivated scenario where the lightest stop is heavier than a chargino and a
neutralino. Considering a class of R-parity baryon number violating couplings,
we show on general grounds that while the direct decay of the stop into
Standard Model particles is dominant for large values of these couplings,
smaller values give rise, instead, to the dominance of a plethora of longer
decay chains and richer final states that have not yet been analyzed at the
LHC, thus weakening the impact of the present experimental stop mass limits. We
characterize the case for R-parity baryon number violating couplings in the
$10^{-7} - 10^{-1}$ range, in two different benchmark points scenarios within
the model-independent setting of the low-energy phenomenological Minimal
Supersymmetric Standard Model. We identify the different relevant experimental
signatures, estimate the corresponding proton--proton cross sections at
$\sqrt{s}=14$ TeV and discuss signal versus background issues.


title:
Spectral dynamics of THz pulses generated by two-color laser filaments
  in air: The role of Kerr nonlinearities and pump wavelength

abstract:
  We theoretically and numerically study the influence of both instantaneous
and Raman-delayed Kerr nonlinearities as well as a long-wavelength pump in the
terahertz (THz) emissions produced by two-color femtosecond filaments in air.
Although the Raman-delayed nonlinearity induced by air molecules weakens THz
generation, four-wave mixing is found to impact the THz spectra accumulated
upon propagation via self-, cross-phase modulations and self-steepening.
Besides, using the local current theory, we show that the scaling of
laser-to-THz conversion efficiency with the fundamental laser wavelength
strongly depends on the relative phase between the two colors, the pulse
duration and shape, rendering a universal scaling law impossible. Scaling laws
in powers of the pump wavelength may only provide a rough estimate of the
increase in the THz yield. We confront these results with comprehensive
numerical simulations of strongly focused pulses and of filaments propagating
over meter-range distances.


title: Stellar cooling bounds on new light particles: plasma mixing effects

abstract:
  Strong constraints on the coupling of new light particles to the Standard
Model (SM) arise from their production in the hot cores of stars, and the
effects of this on stellar cooling. For new light particles which have an
effective in-medium mixing with the photon, plasma effects can result in
parametrically different production rates to those obtained from a naive
calculation. Taking these previously-neglected contributions into account, we
make updated estimates for the stellar cooling bounds on light scalars and
vectors with a variety of SM couplings. In particular, we improve the bounds on
light (m <~ keV) scalars coupling to electrons or nucleons by up to 3 orders of
magnitude in the coupling squared, significantly revise the supernova cooling
bounds on dark photon couplings, and qualitatively change the mass dependence
of stellar bounds on new vectors. Scalars with mass <~ 2 keV that couple
through the Higgs portal are constrained to mixing angle <~ 3*10^-10, which
gives the dominant bound for scalar masses above ~ 0.2 eV.


title:
Bubble nucleation and growth in very strong cosmological phase
  transitions

abstract:
  Strongly first-order phase transitions, i.e., those with a large order
parameter, are characterized by a considerable supercooling and high velocities
of phase transition fronts. A very strong phase transition may have important
cosmological consequences due to the departures from equilibrium caused in the
plasma. In general, there is a limit to the strength, since the metastability
of the old phase may prevent the transition to complete. Near this limit, the
bubble nucleation rate achieves a maximum and thus departs from the widely
assumed behavior in which it grows exponentially with time. We study the
dynamics of this kind of phase transitions. We show that in some cases a
gaussian approximation for the nucleation rate is more suitable, and in such a
case we solve analytically the evolution of the phase transition. We compare
the gaussian and exponential approximations with realistic cases and we
determine their ranges of validity. We also discuss the implications for cosmic
remnants such as gravitational waves.


title:
Biodiversity in models of cyclic dominance is preserved by heterogeneity
  in site-specific invasion rates

abstract:
  Global, population-wide oscillations in models of cyclic dominance may result
in the collapse of biodiversity due to the accidental extinction of one species
in the loop. Previous research has shown that such oscillations can emerge if
the interaction network has small-world properties, and more generally, because
of long-range interactions among individuals or because of mobility. But
although these features are all common in nature, global oscillations are
rarely observed in actual biological systems. This begets the question what is
the missing ingredient that would prevent local oscillations to synchronize
across the population to form global oscillations. Here we show that, although
heterogeneous species-specific invasion rates fail to have a noticeable impact
on species coexistence, randomness in site-specific invasion rates successfully
hinders the emergence of global oscillations and thus preserves biodiversity.
Our model takes into account that the environment is often not uniform but
rather spatially heterogeneous, which may influence the success of microscopic
dynamics locally. This prevents the synchronization of locally emerging
oscillations, and ultimately results in a phenomenon where one type of
randomness is used to mitigate the adverse effects of other types of randomness
in the system.

categories: q-bio.PE nlin.AO physics.bio-ph physics.soc-ph


title: Type II intermediate-luminosity optical transients (ILOTs)

abstract:
  We propose that in a small fraction of intermediate luminosity optical
transients (ILOTs) powered by a strongly interacting binary system, the ejected
mass in the equatorial plane can block the central source from our line of
sight. We can therefore observe only radiation that is reprocessed by polar
outflow, much as in type~II active galactic nuclei (AGN). An ejection of
$M_{\rm ej,e}=10^{-4} ~\rm{M_\odot} ~ (1 ~\rm{M_\odot})$ at 30 degrees from the
equatorial plane and at a velocity of $v_{\rm e} = 100 ~\rm{km~s^{-1}}$ will
block the central source in the NIR for about 5 years (500 years). During that
period of time the object might disappear in the visible band, and be detected
only in the IR band due to polar dust. We raise the possibility that the
recently observed disappearance of a red giant in the visible, designated
N6946-BH1, is a type~II ILOT rather than a failed supernova. For this case we
estimate that the ejected mass in the polar direction was $M_{\rm ej,p}\approx
10^{-3} ~\rm{M_\odot}$. Our scenario predicts that this event should reinstate
its visible emission in several decades.


title: Generalized gravity from modified DFT

abstract:
  Recently, generalized equations of type IIB supergravity have been derived
from the requirement of classical kappa-symmetry of type IIB superstring theory
in the Green-Schwarz formulation. These equations are covariant under
generalized T-duality transformations and hence one may expect a formulation
similar to double field theory (DFT). In this paper, we consider a modification
of the DFT equations of motion by relaxing a condition for the generalized
covariant derivative with an extra generalized vector. In this modified double
field theory (mDFT), we show that the flatness condition of the modified
generalized Ricci tensor leads to the NS-NS part of the generalized equations
of type IIB supergravity. In particular, the extra vector fields appearing in
the generalized equations correspond to the extra generalized vector in mDFT.
We also discuss duality symmetries and a modification of the string charge in
mDFT.


title: Perturbed Yukawa Textures in the Minimal Seesaw Model

abstract:
  \noindent We revisit the \textit{minimal seesaw model}, i.e., the type-I
seesaw mechanism involving only two right-handed neutrinos. % This model
represents an important minimal benchmark scenario for future experimental
updates on neutrino oscillations. % It features four real parameters that
cannot be fixed by the current data: two $CP$-violating phases, $\delta$ and
$\sigma$, as well as one complex parameter, $z$, that is experimentally
inaccessible at low energies. % The parameter $z$ controls the structure of the
neutrino Yukawa matrix at high energies, which is why it may be regarded as a
label or index for all UV completions of the minimal seesaw model. % The fact
that $z$ encompasses only two real degrees of freedom allows us to
systematically scan the minimal seesaw model over all of its possible UV
completions. % In doing so, we address the following question: Suppose $\delta$
and $\sigma$ should be measured at particular values in the future---to what
extent is one then still able to realize approximate textures in the neutrino
Yukawa matrix? % Our analysis, thus, generalizes previous studies of the
minimal seesaw model based on the assumption of exact texture zeros. % In
particular, our study allows us to assess the theoretical uncertainty inherent
to the common texture ansatz. % One of our main results is that a normal
light-neutrino mass hierarchy is, in fact, still consistent with a two-zero
Yukawa texture, provided that the two texture zeros receive corrections at the
level of $\mathcal{O}\left(\textrm{10}\,\%\right)$. % While our numerical
results pertain to the minimal seesaw model only, our general procedure appears
to be applicable to other neutrino mass models as well.


title:
On the measurements of numerical viscosity and resistivity in Eulerian
  MHD codes

abstract:
  We propose a simple ansatz for estimating the value of the numerical
resistivity and the numerical viscosity of any Eulerian MHD code. We test this
ansatz with the help of simulations of the propagation of (magneto)sonic waves,
Alfven waves, and the tearing mode instability using the MHD code Aenus. By
comparing the simu- lation results with analytical solutions of the
resistive-viscous MHD equations and an empirical ansatz for the growth rate of
tearing modes we measure the numerical viscosity and resistivity of Aenus. The
comparison shows that the fast-magnetosonic speed and wavelength are the
characteristic velocity and length, respectively, of the aforementioned
(relatively simple) systems. We also determine the dependance of the numerical
viscosity and resistivity on the time integration method, the spatial
reconstruction scheme and (to a lesser extent) the Riemann solver employed in
the simulations. From the measured results we infer the numerical resolution
(as a function of the spatial reconstruction method) required to properly
resolve the growth and saturation level of the magnetic field amplified by the
magnetorotational instability in the post-collapsed core of massive stars. Our
results show that it is to the best advantage to resort to ultra-high order
methods (e.g., 9th-order Monotonicity Preserving method) to tackle this problem
properly, in particular in three dimensional simulations.


title: Crucial Physical Dependencies of the Core-Collapse Supernova Mechanism

abstract:
  We explore with self-consistent 2D F{\sc{ornax}} simulations the dependence
of the outcome of collapse on many-body corrections to neutrino-nucleon cross
sections, the nucleon-nucleon bremsstrahlung rate, electron capture on heavy
nuclei, pre-collapse seed perturbations, and inelastic neutrino-electron and
neutrino-nucleon scattering. Importantly, proximity to criticality amplifies
the role of even small changes in the neutrino-matter couplings, and such
changes can together add to produce outsized effects. When close to the
critical condition the cumulative result of a few small effects (including
seeds) that individually have only modest consequence can convert an anemic
into a robust explosion, or even a dud into a blast. Such sensitivity is not
seen in one dimension and may explain the apparent heterogeneity in the
outcomes of detailed simulations performed internationally. A natural
conclusion is that the different groups collectively are closer to a realistic
understanding of the mechanism of core-collapse supernovae than might have
seemed apparent.