title: (Non)-universality of vortex reconnections in superfluids

abstract:
  An insight into vortex reconnections in superfluids is presented making use
of analytical results and numerical simulations of the Gross--Pitaevskii model.
Universal aspects of the reconnection process are investigated by considering
different initial vortex configurations and making use of a recently developed
tracking algorithm to reconstruct the vortex filaments. We show that during a
reconnection event the vortex lines approach and separate always accordingly to
the time scaling $ \delta \sim t^{1/2} $ with pre-factors that depend on the
vortex configuration. We also investigate the behavior of curvature and torsion
close to the reconnection point, demonstrating analytically that the curvature
can exhibit a self-similar behavior that might be broken by the development of
shock-like structures in the torsion.


title:
Molecular Gas in the Halo Fuels the Growth of a Massive Cluster Galaxy
  at High Redshift

abstract:
  The largest galaxies in the Universe reside in galaxy clusters. Using
sensitive observations of carbon-monoxide, we show that the Spiderweb Galaxy -a
massive galaxy in a distant protocluster- is forming from a large reservoir of
molecular gas. Most of this molecular gas lies between the protocluster
galaxies and has low velocity dispersion, indicating that it is part of an
enriched inter-galactic medium. This may constitute the reservoir of gas that
fuels the widespread star formation seen in earlier ultraviolet observations of
the Spiderweb Galaxy. Our results support the notion that giant galaxies in
clusters formed from extended regions of recycled gas at high redshift.


title: Diet2Vec: Multi-scale analysis of massive dietary data

abstract:
  Smart phone apps that enable users to easily track their diets have become
widespread in the last decade. This has created an opportunity to discover new
insights into obesity and weight loss by analyzing the eating habits of the
users of such apps. In this paper, we present diet2vec: an approach to modeling
latent structure in a massive database of electronic diet journals. Through an
iterative contract-and-expand process, our model learns real-valued embeddings
of users' diets, as well as embeddings for individual foods and meals. We
demonstrate the effectiveness of our approach on a real dataset of 55K users of
the popular diet-tracking app LoseIt\footnote{http://www.loseit.com/}. To the
best of our knowledge, this is the largest fine-grained diet tracking study in
the history of nutrition and obesity research. Our results suggest that
diet2vec finds interpretable results at all levels, discovering intuitive
representations of foods, meals, and diets.


title: Black holes in quasi-topological gravity and conformal couplings

abstract:
  Lovelock theory of gravity provides a tractable model to investigate the
effects of higher-curvature terms in the context of AdS/CFT. Yielding second
order, ghost-free field equations, this theory represents a minimal setup in
which higher-order gravitational couplings in asymptotically Anti-de Sitter
(AdS) spaces, including black holes, can be solved analytically. This however
has an obvious limitation as in dimensions lower than seven, the contribution
from cubic or higher curvature terms is merely topological. Therefore, in order
to go beyond quadratic order and study higher terms in AdS_5 analytically, one
is compelled to look for other toy models. One such model is the so-called
quasi-topological gravity, which, despite being a higher-derivative theory,
provides a tractable setup with R^3 and R^4 terms. In this paper, we
investigate AdS_5 black holes in quasi-topological gravity. We consider the
theory conformally coupled to matter and in presence of Abelian gauge fields.
We show that charged black holes in AdS_5 which, in addition, exhibit a
backreaction of the matter fields on the geometry can be found explicitly in
this theory. These solutions generalize the black hole solution of
quasi-topological gravity and exist in a region of the parameter spaces
consistent with the constraints coming from causality and other consistency
conditions. They have finite conserved charges and exhibit non-trivial
thermodynamical properties.


title:
Anomaly Detection in Video Using Predictive Convolutional Long
  Short-Term Memory Networks

abstract:
  Automating the detection of anomalous events within long video sequences is
challenging due to the ambiguity of how such events are defined. We approach
the problem by learning generative models that can identify anomalies in videos
using limited supervision. We propose end-to-end trainable composite
Convolutional Long Short-Term Memory (Conv-LSTM) networks that are able to
predict the evolution of a video sequence from a small number of input frames.
Regularity scores are derived from the reconstruction errors of a set of
predictions with abnormal video sequences yielding lower regularity scores as
they diverge further from the actual sequence over time. The models utilize a
composite structure and examine the effects of conditioning in learning more
meaningful representations. The best model is chosen based on the
reconstruction and prediction accuracy. The Conv-LSTM models are evaluated both
qualitatively and quantitatively, demonstrating competitive results on anomaly
detection datasets. Conv-LSTM units are shown to be an effective tool for
modeling and predicting video sequences.


title: Recovering the spacetime metric from a holographic dual

abstract:
  We review our recent proposal to use certain spatial cross-sections of the
boundary at infinity -- light-cone cuts -- to recover the conformal metric in
the bulk. We discuss some extensions of this work, including how to obtain the
conformal metric near the horizon of a collapsing black hole. We also show how
to obtain the conformal factor under certain conditions.


title:
Thermal Effects in Dislocation Theory II: Shear Banding and Yielding
  Transitions

abstract:
  The thermodynamic dislocation theory presented in preceding papers is used
here to describe shear-banding instabilities. Central ingredients of the theory
are a thermodynamically defined effective configurational temperature, and a
formula for the plastic deformation rate determined by thermally activated
depinning of entangled dislocations. An important feature of this paper is an
interpretation of yielding transitions in polycrystalline solids.


title:
Hypervolume-based Multi-objective Bayesian Optimization with Student-t
  Processes

abstract:
  Student-$t$ processes have recently been proposed as an appealing alternative
non-parameteric function prior. They feature enhanced flexibility and
predictive variance. In this work the use of Student-$t$ processes are explored
for multi-objective Bayesian optimization. In particular, an analytical
expression for the hypervolume-based probability of improvement is developed
for independent Student-$t$ process priors of the objectives. Its effectiveness
is shown on a multi-objective optimization problem which is known to be
difficult with traditional Gaussian processes.


title:
Definition Modeling: Learning to define word embeddings in natural
  language

abstract:
  Distributed representations of words have been shown to capture lexical
semantics, as demonstrated by their effectiveness in word similarity and
analogical relation tasks. But, these tasks only evaluate lexical semantics
indirectly. In this paper, we study whether it is possible to utilize
distributed representations to generate dictionary definitions of words, as a
more direct and transparent representation of the embeddings' semantics. We
introduce definition modeling, the task of generating a definition for a given
word and its embedding. We present several definition model architectures based
on recurrent neural networks, and experiment with the models over multiple data
sets. Our results show that a model that controls dependencies between the word
being defined and the definition words performs significantly better, and that
a character-level convolution layer designed to leverage morphology can
complement word-level embeddings. Finally, an error analysis suggests that the
errors made by a definition model may provide insight into the shortcomings of
word embeddings.


title: On the dynamics of polarons in the strong-coupling limit

abstract:
  The polaron model of H. Fr\"ohlich describes an electron coupled to the
quantized longitudinal optical modes of a polar crystal. In the strong-coupling
limit one expects that the phonon modes may be treated classically, which leads
to a coupled Schr\"odinger-Poisson system with memory. For the effective
dynamics of the electron this amounts to a nonlinear and non-local
Schr\"odinger equation. We use the Dirac-Frenkel variational principle to
derive the Schr\"odinger-Poisson system from the Fr\"ohlich model and we
present new results on the accuracy of their solutions for describing the
motion of Fr\"ohlich polarons in the strong-coupling limit. Our main result
extends to $N$-polaron systems.


title:
A dynamic stress model explains the delayed drug effect in artemisinin
  treatment of Plasmodium falciparum

abstract:
  Artemisinin resistance constitutes a major threat to the continued success of
control programs for malaria. With alternative antimalarial drugs not yet
available, improving our understanding of how artemisinin-based drugs act and
how resistance manifests is essential to enable optimisation of dosing regimens
in order to prolong the lifespan of current first-line treatment options. Here,
through introduction of a novel model of the dynamics of the parasites'
response to drug, we explore how artemisinin-based therapies may be adjusted to
maintain efficacy and how artemisinin resistance may manifest and be overcome.
We introduce a dynamic mathematical model, extending on the traditional
pharmacokinetic-pharmacodynamic framework, to capture the time-dependent
development of a stress response in parasites. We fit the model to in vitro
data and establish that the parasites' stress response explains the recently
identified complex interplay between drug concentration, exposure time and
parasite viability. Our model demonstrates that the previously reported
hypersensitivity of early ring stage parasites of the 3D7 strain to
dihydroartemisinin (DHA) is primarily due to the rapid development of stress,
rather than any change in the maximum achievable killing rate. Of direct
clinical relevance, we demonstrate that the complex temporal features of
artemisinin action observed in vitro have a significant impact on predictions
of in vivo parasite clearance using PK-PD models. Given the important role that
such models play in the design and evaluation of clinical trials for
alternative drug dosing regimens, our model contributes an enhanced predictive
platform for the continued efforts to minimise the burden of malaria.


title: Maximal Sections of Sheaves of Data over an Abstract Simplicial Complex

abstract:
  We employ techniques from topological data analysis to model sensor networks.
Our approach to sensor integration uses the topological method of sheaves over
cell complexes. The internal consistency of data from individual sensors is
determined by a set of consistency functions assigned to elements of the
complex. Using these functions we determine, for any collection of data, the
unique set of maximal sections of consistent data received from the sensors. We
offer a proof for the existence and uniqueness of these sections and illustrate
the ideas with examples.


title:
The Polar Nano Regions $\rightleftharpoons$ Relaxor Transition in
  $Pb_{1-X}(Sc_{1/2}Nb_{1/2})O_{3-X}$; $X$ = bulk concentration of nearest
  neighbor [Pb-O] divacancies

abstract:
  In previous work, molecular dynamics simulations based on a
first-principles-derived effective Hamiltonian for
$Pb_{1-X}(Sc_{1/2}Nb_{1/2})O_{3-X}$~ (PSN), with nearest-neighbor Pb-O
divacancy pairs, was used to calculate $X_{\rm [Pb-O]}$~vs.~T, phase diagrams
for PSN with: ideal rock-salt type chemical order; nanoscale chemical
short-range order; and random chemical disorder. Here, we show that the phase
diagrams should include additional regions in which a glassy relaxor-phase (or
state) is predicted. With respect to phase diagram topology, these results
strongly support the analogy between relaxors and magnetic spin-glass-systems.


title:
Signature of surface state coupling in thin films of the topological
  Kondo insulator SmB$_6$ from anisotropic magnetoresistance

abstract:
  The temperature and thickness dependencies of the in-plane anisotropic
magnetoresistance (AMR) of SmB$_6$ thin films are reported. We find that the
AMR changes sign from negative ($\rho_{||}<\rho_{\perp}$) at high temperatures
to positive ($\rho_{||}>\rho_{\perp}$) at low temperatures. The temperature,
T$_s$, at which this sign change occurs, decreases with increasing film
thickness $t$ and T$_s$ vanishes for $t$ $>$ 30 nm. We interpret our results in
the framework of a competition between two components: a negative bulk
contribution and a positive surface AMR.


title:
The Search for Multiple Populations in Magellanic Cloud Clusters II: The
  Detection of Multiple Populations in Three Intermediate-Age SMC Clusters

abstract:
  This is the second paper in our series about the search for multiple
populations in Magellanic Cloud star clusters using the Hubble Space Telescope.
Here we report the detection of multiple stellar populations in the
colour-magnitude diagrams of the intermediate-age clusters Lindsay 1, NGC 416
and NGC 339. With ages between 6.0 and 7.5 Gyr, these clusters are the youngest
ones in which chemical abundance spreads have been detected so far. This
confirms that the appearance of multiple populations is not restricted to only
ancient globular clusters, but may also be a common feature in clusters as
young as 6 Gyr. Our results are in agreement with a recent spectroscopic study
of Lindsay 1. We found that the fraction of enriched stars in NGC 416 is ~45%
whereas it is ~25% in NGC 339 and ~36% in Lindsay 1. Similar to NGC 121, these
fractions are lower than the average value for globular clusters in the Milky
Way.


title: Almost all quantum channels are equidistant

abstract:
  In this work we analyze properties of generic quantum channels in the case of
large system size. We use random matrix theory and free probability to show
that the distance between two independent random channels converges to a
constant value as the dimension of the system grows larger. As a measure of the
distance we use the diamond norm. In the case of a flat Hilbert-Schmidt
distribution on quantum channels, we obtain that the distance converges to
$\frac12 + \frac{2}{\pi}$, giving also an estimate for the maximum success
probability for distinguishing the channels. We also consider the problem of
distinguishing two random unitary rotations.


title:
Reduced Order Models for Pricing European and American Options under
  Stochastic Volatility and Jump-Diffusion Models

abstract:
  European options can be priced by solving parabolic partial(-integro)
differential equations under stochastic volatility and jump-diffusion models
like Heston, Merton, and Bates models. American option prices can be obtained
by solving linear complementary problems (LCPs) with the same operators. A
finite difference discretization leads to a so-called full order model (FOM).
Reduced order models (ROMs) are derived employing proper orthogonal
decomposition (POD). The early exercise constraint of American options is
enforced by a penalty on subset of grid points. The presented numerical
experiments demonstrate that pricing with ROMs can be orders of magnitude
faster within a given model parameter variation range.


title:
Exponential reduction of finite volume effects with twisted boundary
  conditions

abstract:
  Flavor-twisted boundary conditions can be used for exponential reduction of
finite volume artifacts in flavor-averaged observables in lattice QCD
calculations with $SU(N_f)$ light quark flavor symmetry. Finite volume artifact
reduction arises from destructive interference effects in a manner closely
related to the phase averaging which leads to large $N_c$ volume independence.
With a particular choice of flavor-twisted boundary conditions, finite volume
artifacts for flavor-singlet observables in a hypercubic spacetime volume are
reduced to the size of finite volume artifacts in a spacetime volume with
periodic boundary conditions that is four times larger.


title: Learning Shape Abstractions by Assembling Volumetric Primitives

abstract:
  We present a learning framework for abstracting complex shapes by learning to
assemble objects using 3D volumetric primitives. In addition to generating
simple and geometrically interpretable explanations of 3D objects, our
framework also allows us to automatically discover and exploit consistent
structure in the data. We demonstrate that using our method allows predicting
shape representations which can be leveraged for obtaining a consistent parsing
across the instances of a shape collection and constructing an interpretable
shape similarity measure. We also examine applications for image-based
prediction as well as shape manipulation.


title:
Accurate Pre-Eruption and Post-Eruption Orbital Periods for the
  Dwarf/Classical Nova V1017 Sgr

abstract:
  V1017 Sgr is a classical nova (in 1919) that displayed an earlier dwarf nova
eruption (in 1901), and two more dwarf nova events (in 1973 and 1991). Previous
work on this bright system in quiescence (V=13.5) has only been a few isolated
magnitudes, a few spectra, and an ambiguous claim for an orbital period of
5.714 days as based on nine radial velocities. To test this period, we have
collected 2896 magnitudes (plus 53 in the literature) in the UBVRIJHKL bands
from 1897 to 2016, making an essentially complete photometric history of this
unique cataclysmic variable. We find that the light curve in all bands is
dominated by the ellipsoidal modulations of a G giant companion star, with a
post-eruption (after the 1919 nova event) orbital period of 5.786290 +-
0.000032 days. This is the longest period for any classical nova, the accretion
must be powered by the nuclear evolution of the companion star, and the dwarf
nova events occur only because the outer parts of the large disk are cool
enough to be unstable. Furthermore, we measure the pre-eruption orbital period
(from 1907 to 1916), and there is a small steady period change in quiescence.
The orbital period has decreased by 273 +- 61 parts-per-million across the 1919
eruption, with the significance of the period change being at the 5.7-sigma
confidence level. This is startling and mystifying for nova-theory, because the
three known period change effects cannot account for a period decrease in V1017
Sgr, much less one of such a large size.


title: Connectivity properties of Branching Interlacements

abstract:
  We consider connectivity properties of the Branching Interlacements model in
$\mathbb{Z}^d,~d\ge5$, recently introduced by Angel, R\'ath and Zhu in 2016.
Using stochastic dimension techniques we show that every two vertices visited
by the branching interlacements are connected via at most $\lceil d/4\rceil$
conditioned critical branching random walks from the underlying Poisson
process, and that this upper bound is sharp. In particular every such two
branching random walks intersect if and only if $5\le d\le 8$. The stochastic
dimension of branching random walk result is of independent interest. We
additionally obtain heat kernel bounds for branching random walks conditioned
on survival.


title: Optimizing Governed Blockchains for Financial Process Authentications

abstract:
  We propose the formal study of governed blockchains that are owned and
controlled by organizations and that neither create cryptocurrencies nor
provide any incentives to solvers of cryptographic puzzles. We view such
approaches as frameworks in which system parts, such as the cryptographic
puzzle, may be instantiated with different technology. Owners of such a
blockchain procure puzzle solvers as resources they control, and use a
mathematical model to compute optimal parameters for the cryptographic puzzle
mechanism or other parts of the blockchain. We illustrate this approach with a
use case in which blockchains record hashes of financial process transactions
to increase their trustworthiness and that of their audits. For Proof of Work
as cryptographic puzzle, we develop a detailed mathematical model to derive
MINLP optimization problems for computing optimal Proof of Work configuration
parameters that trade off potentially conflicting aspects such as availability,
resiliency, security, and cost in this governed setting. We demonstrate the
utility of such a mining calculus by solving some instances of this problem.
This experimental validation is strengthened by statistical experiments that
confirm the validity of random variables used in formulating our mathematical
model. We hope that our work may facilitate the creation of domain-specific
blockchains for a wide range of applications such as trustworthy information in
Internet of Things systems and bespoke improvements of legacy financial
services.


title:
Computerized Multiparametric MR image Analysis for Prostate Cancer
  Aggressiveness-Assessment

abstract:
  We propose an automated method for detecting aggressive prostate cancer(CaP)
(Gleason score >=7) based on a comprehensive analysis of the lesion and the
surrounding normal prostate tissue which has been simultaneously captured in
T2-weighted MR images, diffusion-weighted images (DWI) and apparent diffusion
coefficient maps (ADC). The proposed methodology was tested on a dataset of 79
patients (40 aggressive, 39 non-aggressive). We evaluated the performance of a
wide range of popular quantitative imaging features on the characterization of
aggressive versus non-aggressive CaP. We found that a group of 44
discriminative predictors among 1464 quantitative imaging features can be used
to produce an area under the ROC curve of 0.73.


title:
Dimensionally compactified Chern-Simon theory in 5D as a gravitation
  theory in 4D

abstract:
  We propose a gravitation theory in 4 dimensional space-time obtained by
compacting to 4 dimensions the five dimensional topological Chern-Simons theory
with the gauge group SO(1,5) or SO(2,4) -- the de Sitter or anti-de Sitter
group of 5-dimensional space-time. In the resulting theory, torsion, which is
solution of the field equations as in any gravitation theory in the first order
formalism, is not necessarily zero. However, a cosmological solution with zero
torsion exists, which reproduces the Lambda-CDM cosmological solution of
General Relativity. A realistic solution with spherical symmetry is also
obtained.


title: Deep Variational Information Bottleneck

abstract:
  We present a variational approximation to the information bottleneck of
Tishby et al. (1999). This variational approach allows us to parameterize the
information bottleneck model using a neural network and leverage the
reparameterization trick for efficient training. We call this method "Deep
Variational Information Bottleneck", or Deep VIB. We show that models trained
with the VIB objective outperform those that are trained with other forms of
regularization, in terms of generalization performance and robustness to
adversarial attack.


title:
Powers of generic ideals and the weak Lefschetz property for powers of
  some monomial complete intersections

abstract:
  Given an ideal $I=(f_1,\ldots,f_r)$ in $\mathbb C[x_1,\ldots,x_n]$ generated
by forms of degree $d$, and an integer $k>1$, how large can the ideal $I^k$ be,
i.e., how small can the Hilbert function of $\mathbb C[x_1,\ldots,x_n]/I^k$ be?
If $r\le n$ the smallest Hilbert function is achieved by any complete
intersection, but for $r>n$, the question is in general very hard to answer. We
study the problem for $r=n+1$, where the result is known for $k=1$. We also
study a closely related problem, the Weak Lefschetz property, for $S/I^k$,
where $I$ is the ideal generated by the $d$'th powers of the variables.


title:
Improvement in the accuracy of flux measurement of radio sources by
  exploiting an arithmetic pattern in photon bunching noise

abstract:
  A hierarchy of statistics of increasing sophistication and accuracy is
proposed, to exploit an interesting and fundamental arithmetic structure in the
photon bunching noise of incoherent light of large photon occupation number,
with the purpose of suppressing the noise and rendering a more reliable and
unbiased measurement of the light intensity. The method does not require any
new hardware, rather it operates at the software level, with the help of high
precision computers, to reprocess the intensity time series of the incident
light to create a new series with smaller bunching noise coherence length. The
ultimate accuracy improvement of this method of flux measurement is limited by
the timing resolution of the detector and the photon occupation number of the
beam (the higher the photon number the better the performance). The principal
application is accuracy improvement in the bolometric flux measurement of a
radio source.


title:
Measuring the CP property of Higgs coupling to tau leptons in the VBF
  channel at the LHC

abstract:
  We study the prospects of measuring the CP property of the Higgs ($h$)
coupling to tau leptons using the vector boson fusion (VBF) production mode at
the high-luminosity LHC. Utilizing the previously proposed angle between the
planes spanned by the momentum vectors of the $(\pi^+\pi^0)$ and $(\pi^-
\pi^0)$ pairs originating in $\tau^\pm$ decays as the CP-odd observable, we
perform a detailed Monte Carlo analysis, taking into account the relevant
standard model backgrounds, as well as detector resolution effects. We find
that excluding a pure CP-odd coupling hypothesis requires $\mathcal{O}(400
{~\rm fb}^{-1})$ luminosity at the 14 TeV LHC, and values of the CP-mixing
angle larger than about $25^\circ$ can be excluded at $95\%$ confidence level
using $3 {~\rm ab}^{-1}$ data. It is observed that the uncertainty in the
angular resolution of the neutral pion momenta does not constitute a
significant hurdle. Achieving a signal to background ratio ($S/B$) close to
one, while keeping a high enough signal yield required to study the angular
distributions selects out VBF as a promising mode to probe the CP nature of the
$h\tau\tau$ coupling, with gluon fusion suffering from a low $S/B$, and the
$W^\pm h/Zh$ mode (with leptonically decaying $W^\pm /Z$) having a much smaller
signal rate.


title:
Distributed Nash Equilibrium Seeking via the Alternating Direction
  Method of Multipliers

abstract:
  In this paper, the problem of finding a Nash equilibrium of a multi-player
game is considered. The players are only aware of their own cost functions as
well as the action space of all players. We develop a relatively fast algorithm
within the framework of inexact-ADMM. It requires a communication graph for the
information exchange between the players as well as a few mild assumptions on
cost functions. The convergence proof of the algorithm to a Nash equilibrium of
the game is then provided. Moreover, the convergence rate is investigated via
simulations.


title: Asymptotic expansions of the largest eigenvalues

abstract:
  In this paper, we provide a rigorous derivation of asymptotic formula for the
largest eigenvalues using the convergence estimation of the eigenvalues of a
sequence of self-adjoint compact operators of perturbations resulting from the
presence of small inhomogeneities.


title: Weyl Semimetals, Fermi Arcs and Chiral Anomalies (A Short Review)

abstract:
  Physicists have discovered a novel topological semimetal, the Weyl semimetal,
whose surface features a non-closed Fermi surface while the low energy
quasiparticles in the bulk emerge as Weyl fermions. Here they share a brief
review of the development and present perspectives on the next step forward.


title: New Relations for Gauge-Theory and Gravity Amplitudes at Loop Level

abstract:
  In this letter, we extend the tree-level Kawai--Lewellen--Tye (KLT) and
Bern--Carrasco--Johansson (BCJ) amplitude relations to loop integrands of gauge
theory and gravity. By rearranging the propagators of gauge and gravity loop
integrands, we propose the first manifestly gauge- and diffeomorphism invariant
formulation of their double-copy relations. The one-loop KLT formula expresses
gravity integrands in terms of more basic gauge invariant building blocks for
gauge-theory amplitudes, dubbed partial integrands. The latter obey a one-loop
analogue of the BCJ relations, and both KLT and BCJ relations are universal to
bosons and fermions in any number of spacetime dimensions and independent on
the amount of supersymmetry. Also, one-loop integrands of Einstein--Yang--Mills
(EYM) theory are related to partial integrands of pure gauge theories.


title:
A historical overview of pro cdh descent in algebraic $K$-theory and its
  relation to rigid analytic varieties

abstract:
  This note was prepared after the workshop on cdh descent and algebraic
$K$-theory in Hara-mura, Japan (1 - 5 Sept. 2016), to complement the author's
talk on the history and applications of pro cdh descent. In the final section
pro cdh descent is used to define $K$-groups of rigid analytic varieties. This
note was revised and released in light of Kerz, Strunk, and Tamme establishing
pro cdh descent in general (arXiv:1611.08466).


title:
Restructuring and destruction of hydrocarbon dust in the interstellar
  medium

abstract:
  A model of key processes influencing the evolution of a hydrocarbon grain of
an arbitrary size under astrophysical conditions corresponding to ionized
hydrogen regions (HII regions) and supernova remnants is presented. The
considered processes include aromatization and photodestruction, sputtering by
electrons and ions, and shattering due to collisions between grains. The model
can be used to simulate the grain size distribution and the aromatization
degree during the evolution of HII regions and supernova remnants for a
specified radiation field, relative velocity of gas and dust, etc. The
contribution of various processes to the evolution of hydrocarbon dust grains
for parameters typical for the interstellar medium of our Galaxy is presented.
Small grains (less than 50 carbon atoms) should be fully aromatized in the
general interstellar medium. If larger grains initially have an aliphatic
structure, it is preserved to a substantial extent. Variations in the size
distribution of the grains due to their mutual collisions depend appreciably on
the adopted initial size distribution. For the MRN initial distribution a
significant redistribution of grain sizes is obtained, which increases the mass
fraction of smaller grains. Characteristic for an initial distribution from the
work of Jones et al. (2013), with high initial fraction of small grains, is a
general decrease in the number of grains of all sizes.


title:
The evolution of hydrocarbon dust grains in the interstellar medium and
  its influence on the infrared spectra of dust

abstract:
  We present evolutionary calculations for the size and aromatization degree
distributions of interstellar dust grains, driven by their destruction by
radiation, collisions with gas particles, and shattering due to grain-grain
collisions. Based on these calculations we model dust emission spectra. The
initial grain size distribution play the important role in the evolution of an
ensemble of dust particles. Radiation in the considered intensity range mostly
aromatizes grains. The smallest grains are mainly destructed via sputtering by
collisions with gas particles. There are no grains smaller than 20~\AA\ in the
medium at relative gas-dust velocities more than 50~km/s, which is typical for
shocks in supernova remnants. The IR emission spectrum changes significantly
due to the dust evolution depending on the adopted grain properties, in
particular, on the energy of the C--C bonds ($E_0$). Aromatic bands in the
near-IR (2--15~$\mu$m) are absent, if $E_0$ is low, even when the medium
properties correspond to the average interstellar medium in our Galaxy. As in
reality these bands are observed, high $E_0$ values are more preferable. We
consider dependence of the emission intensity ratios for various photometric
bands on the medium properties. The aromatization degree of small grains shows
up most strongly in the $I_{3.4}/I_{11.3}$ intensity ratio while the fraction
of aromatic grains in the total dust mass influences the $I_{3.3}/I_{70+160}$
ratio.


title: Bulk Universality for Generalized Wigner Matrices With Few Moments

abstract:
  In this paper we consider $N \times N$ real generalized Wigner matrices whose
entries are only assumed to have finite $(2 + \varepsilon)$-th moment for some
fixed, but arbitrarily small, $\varepsilon > 0$. We show that the Stieltjes
transforms $m_N (z)$ of these matrices satisfy a weak local semicircle law on
the nearly smallest possible scale, when $\eta = \Im (z)$ is almost of order
$N^{-1}$. As a consequence, we establish bulk universality for local spectral
statistics of these matrices at fixed energy levels, both in terms of
eigenvalue gap distributions and correlation functions, meaning that these
statistics converge to those of the Gaussian Orthogonal Ensemble (GOE) in the
large $N$ limit.


title:
Factorization of differential expansion for non-rectangular
  representations

abstract:
  Factorization of the differential expansion coefficients for HOMFLY-PT
polynomials of double braids, discovered in arXiv:1606.06015 in the case of
rectangular representations $R$, is extended to the first non-rectangular
representations $R=[2,1]$ and $R=[3,1]$. This increases chances that such
factorization will take place for generic $R$, thus fixing the shape of the DE.
We illustrate the power of the method by conjecturing the DE-induced expression
for double-braid polynomials for all $R=[r,1]$. In variance with rectangular
case, the knowledge for double braids is not fully sufficient to deduce the
exclusive Racah matrix $\bar S$ -- the entries in the sectors with non-trivial
multiplicities sum up and remain unseparated. Still a considerable piece of the
matrix is extracted directly and its other elements can be found by solving the
unitarity constraints.


title: TorontoCity: Seeing the World with a Million Eyes

abstract:
  In this paper we introduce the TorontoCity benchmark, which covers the full
greater Toronto area (GTA) with 712.5 $km^2$ of land, 8439 $km$ of road and
around 400,000 buildings. Our benchmark provides different perspectives of the
world captured from airplanes, drones and cars driving around the city.
Manually labeling such a large scale dataset is infeasible. Instead, we propose
to utilize different sources of high-precision maps to create our ground truth.
Towards this goal, we develop algorithms that allow us to align all data
sources with the maps while requiring minimal human supervision. We have
designed a wide variety of tasks including building height estimation
(reconstruction), road centerline and curb extraction, building instance
segmentation, building contour extraction (reorganization), semantic labeling
and scene type classification (recognition). Our pilot study shows that most of
these tasks are still difficult for modern convolutional neural networks.


title:
Doubly robust matching estimators for high dimensional confounding
  adjustment

abstract:
  Valid estimation of treatment effects from observational data requires proper
control of confounding. If the number of covariates is large relative to the
number of observations, then controlling for all available covariates is
infeasible. In cases where a sparsity condition holds, variable selection or
penalization can reduce the dimension of the covariate space in a manner that
allows for valid estimation of treatment effects. In this article, we propose
matching on both the estimated propensity score and the estimated prognostic
scores when the number of covariates is large relative to the number of
observations. We derive asymptotic results for the matching estimator and show
that it is doubly robust, in the sense that only one of the two score models
need be correct to obtain a consistent estimator. We show via simulation its
effectiveness in controlling for confounding and highlight its potential to
address nonlinear confounding. Finally, we apply the proposed procedure to
analyze the effect of gender on prescription opioid use using insurance claims
data.


title:
Finite-temperature properties of non-magnetic transition metals:
  Comparison of the performance of constraint-based semi and nonlocal
  functionals

abstract:
  We assess the performance of nonempirical, truly nonlocal and semi-local
functionals with regard to structural and thermal properties of $3d$, $4d$, and
$5d$ non-magnetic transition metals. We focus on constraint-based functionals
and consider the new consistent-exchange van der Waals density functional
version vdW-DF-cx [Phys. Rev. B 89, 035412 (2014)], the semi-local PBE [Phys.
Rev. Lett. 77, 3865 (1996)] and PBEsol functionals [Phys. Rev. Lett. 100,
136406 (2008)] as well as the AM05 meta-functional [Phys. Rev. B 72, 085108
(2005)]. Using the quasi-harmonic approximation structural parameters, elastic
response, and thermal expansion at finite temperatures are computed and
compared to experimental data. We also compute cohesive energies explicitly
including zero-point vibrations. It is shown that overall vdW-DF-cx provides an
accurate description of thermal properties and retains a level of
transferability and accuracy that is comparable to or better than some of the
best constraint-based semi-local functionals. Especially, with regard to the
cohesive energies the consistent inclusion of spin polarization effects in the
atoms turns out to be crucial and it is important to use the rigorous
spin-vdW-DF-cx formulation [Phys. Rev. Lett. 115, 136402 (2015)]. This
demonstrates that vdW-DF-cx has general-purpose character and can be used to
study systems that have both sparse and dense electron distributions.


title: On some Euler-Mahonian distributions

abstract:
  We prove that the pair of statistics (des,maj) on multiset permutations is
equidistributed with the pair (stc,inv) on certain quotients of the symmetric
group. We define the analogue of the statistic stc on multiset permutations,
whose joint distribution with the inversions equals that of (des,maj). We
extend the definition of the statistic stc to hyperoctahedral and even
hyperoctahedral groups. Such functions, together with the Coxeter length, are
equidistributed, respectively, with (ndes,nmaj) and (ddes,dmaj).


title: DBI from Gravity

abstract:
  We study the dynamics of gravitational lumps. By a lump, we mean a metric
configuration that asymptotes to a flat space-time. Such lumps emerge in string
theory as strong coupling descriptions of D-branes. We provide a physical
argument that the broken global symmetries of such a background, generated by
certain large diffeomorphisms, constrain the dynamics of localized modes. These
modes include the translation zero modes and any localized tensor modes. The
constraints we find are gravitational analogues of those found in brane
physics. For the example of a Taub-NUT metric in eleven-dimensional
supergravity, we argue that a critical value for the electric field arises from
standard gravity without higher derivative interactions.


title: Immersions of the circle into a surface

abstract:
  We classify immersions $f$ of $S^1$ in a $2$-manifold $M$ in terms of
elementary invariants: the parity $S(f)$ of the number of double points of a
self-transverse $C^1$-approximation of $f$, and the turning number $T(e\bar f)$
of the immersion $e\bar f:S^1\to M_f\subset\Bbb R^2$, where $\bar f$ is a lift
of $f$ to the cover $M_f$ of $M$ corresponding to the subgroup
$\left<[f]\right>\subset\pi_1(M)$. Namely, immersions $f,g:S^1\to M$ are
regular homotopic if and only if they are homotopic, and if $M=S^2$ or $\Bbb R
P^2$ or the normal bundle $\nu(f)$ is non-orientable, then $S(f)=S(g)$, whereas
if $M\not= S^2,\Bbb R P^2$ and $\nu(f)$, $\nu(g)$ have orientations $o$, $o'$,
compatible with respect to the homotopy, then $T(e_o\bar f)=T(e_{o'}\bar g)$,
where $e_o$ is a standard embedding of the oriented surface $M_f$ (an annulus
or a plane) in $\Bbb R^2$. In fact, for homotopic immersions $f$, $g$ both
$S(f)-S(g)$ and $T(e_o\bar f)-T(e_{o'}\bar g)$ boil down to the turning number
of a lift of a null-homotopic immersion $f\# g^*$ to the universal cover of
$M$. Here "immersions" $S^1\to M$ are either smooth or topological; we include
a smoothing theorem, which shows that there is no difference. We also classify
immersions of a graph in $M$ up to regular homotopy in terms of the invariants
$S(f)$ and $T(e_o\bar f)$ of immersed $S^1$'s. The proofs are based on the
h-principle. The point of this unsophisticated note is to simplify [10] and
[11], where a classification of immersions of a graph in $M$ was obtained for
$M\ne\Bbb R P^2$ in terms of a rather laboriously defined "winding number" of a
pair of homotopic immersions $S^1\to M$ (rather than of an individual
immersion) with respect to a given vector field with zeroes on $M$.


title: Generalizing Skills with Semi-Supervised Reinforcement Learning

abstract:
  Deep reinforcement learning (RL) can acquire complex behaviors from low-level
inputs, such as images. However, real-world applications of such methods
require generalizing to the vast variability of the real world. Deep networks
are known to achieve remarkable generalization when provided with massive
amounts of labeled data, but can we provide this breadth of experience to an RL
agent, such as a robot? The robot might continuously learn as it explores the
world around it, even while deployed. However, this learning requires access to
a reward function, which is often hard to measure in real-world domains, where
the reward could depend on, for example, unknown positions of objects or the
emotional state of the user. Conversely, it is often quite practical to provide
the agent with reward functions in a limited set of situations, such as when a
human supervisor is present or in a controlled setting. Can we make use of this
limited supervision, and still benefit from the breadth of experience an agent
might collect on its own? In this paper, we formalize this problem as
semisupervised reinforcement learning, where the reward function can only be
evaluated in a set of "labeled" MDPs, and the agent must generalize its
behavior to the wide range of states it might encounter in a set of "unlabeled"
MDPs, by using experience from both settings. Our proposed method infers the
task objective in the unlabeled MDPs through an algorithm that resembles
inverse RL, using the agent's own prior experience in the labeled MDPs as a
kind of demonstration of optimal behavior. We evaluate our method on
challenging tasks that require control directly from images, and show that our
approach can improve the generalization of a learned deep neural network policy
by using experience for which no reward function is available. We also show
that our method outperforms direct supervised learning of the reward.


title: A Microfilament-Eruption Mechanism for Solar Spicules

abstract:
  Recent investigations indicate that solar coronal jets result from eruptions
of small-scale chromospheric filaments, called minifilaments; that is, the jets
are produced by scaled-down versions of typical-sized filament eruptions. We
consider whether solar spicules might in turn be scaled-down versions of
coronal jets, being driven by eruptions of "microfilaments." Assuming a
microfilament's size is about a spicule's width ($\sim$300~km), the estimated
occurrence number plotted against the estimated size of erupting filaments,
minifilaments, and microfilaments approximately follows a power-law
distribution (based on counts of CMEs, coronal jets, and spicules), suggesting
that many or most spicules could result from microfilament eruptions. Observed
spicule-base Ca II brightenings plausibly result from such microfilament
eruptions. By analogy with coronal jets, microfilament eruptions might produce
spicules with many of their observed characteristics, including smooth rise
profiles, twisting motions, and EUV counterparts. The postulated microfilament
eruptions are presumably eruptions of twisted-core micro magnetic bipoles that
are $\sim$1$".0$ wide. These explosive bipoles might be built and destabilized
by merging and cancelation of magnetic-flux elements of $\sim$few$\times 100$~G
and of size <~$0".5$---$1".0$. If however spicules are relatively more numerous
than indicated by our extrapolated distribution, then only a fraction of
spicules might result from this proposed mechanism.


title: Properties of J-fusion frames in Krein space

abstract:
  In this paper we characterize $\sqrt{2}$-1-uniform $J$-Parseval fusion frames
in a Krein space $\mathbb{K}$. We provide a few results regarding construction
of new $J$-tight fusion frame from given $J$-tight fusion frames. We also
characterize any uniformly $J$-definite subspace of a Krein space $\mathbb{K}$
in terms of a $J$-fusion frame inequality. Finally we generalize the
fundamental identity of frames in Krein space $J$-fusion frame setting.


title: Magnus pairs in, and free conjugacy separability of, limit groups

abstract:
  There are limit groups having non-conjugate elements whose images are
conjugate in every free quotient. Towers over free groups are freely conjugacy
separable.


title: Comments on Holographic Complexity

abstract:
  We study two recent conjectures for holographic complexity: the
complexity=action conjecture and the complexity=volume conjecture. In
particular, we examine the structure of the UV divergences appearing in these
quantities, and show that the coefficients can be written as local integrals of
geometric quantities in the boundary. We also consider extending these
conjectures to evaluate the complexity of the mixed state produced by reducing
the pure global state to a specific subregion of the boundary time slice. The
UV divergences in this subregion complexity have a similar geometric structure,
but there are also new divergences associated with the geometry of the surface
enclosing the boundary region of interest. We discuss possible implications
arising from the geometric nature of these UV divergences.


title: Stationary coalescing walks on the lattice

abstract:
  We consider translation invariant measures on families of nearest-neighbor
semi-infinite walks on the integer lattice. We assume that once walks meet,
they coalesce. In $2d$, we classify the collective behavior of these walks
under mild assumptions: they either coalesce almost surely or form bi-infinite
trajectories. Bi-infinite trajectories form measure-preserving dynamical
systems, have a common asymptotic direction in $2d$, and possess other nice
properties. We use our theory to classify the behavior of compatible families
of semi-infinite geodesics in stationary first- and last-passage percolation.
We also partially answer a question raised by C. Hoffman about the limiting
empirical measure of weights seen by geodesics. We construct several examples:
our main example is a standard first-passage percolation model where geodesics
coalesce almost surely, but have no asymptotic direction or average weight.


title: Blocking duality for $p$-modulus on networks and applications

abstract:
  This paper explores the implications of blocking duality---pioneered by
Fulkerson et al.---in the context of $p$-modulus on networks. Fulkerson's
blocking duality is an analogue on networks to the method of conjugate families
of curves in the plane. The technique presented here leads to a general
framework for studying families of objects on networks; each such family has a
corresponding dual family whose $p$-modulus is essentially the reciprocal of
the original family's. As an application, we give a modulus-based proof for the
fact that effective resistance is a metric on graphs. This proof immediately
generalizes to yield a family of graph metrics, depending on the parameter $p$,
that continuously interpolates among the shortest-path metric, the effective
resistance metric, and the mincut ultrametric. In a second application, we
establish a connection between Fulkerson's blocking duality and the
probabilistic interpretation of modulus. This connection, in turn, provides a
straightforward proof of several monotonicity properties of modulus that
generalize known monotonicity properties of effective resistance. Finally, we
use this framework to expand on a result of Lov\'asz in the context of randomly
weighted graphs.


title:
Standing on the shoulders of Dwarfs: the $Kepler$ asteroseismic LEGACY
  sample I - oscillation mode parameters

abstract:
  The advent of space-based missions like $Kepler$ has revolutionized the study
of solar-type stars, particularly through the measurement and modeling of their
resonant modes of oscillation. Here we analyze a sample of 66 $Kepler$
main-sequence stars showing solar-like oscillations as part of the $Kepler$
seismic LEGACY project. We use $Kepler$ short-cadence data, of which each star
has at least 12 months, to create frequency power spectra optimized for
asteroseismology. For each star we identify its modes of oscillation and
extract parameters such as frequency, amplitude, and line width using a
Bayesian Markov chain Monte Carlo `peak-bagging' approach. We report the
extracted mode parameters for all 66 stars, as well as derived quantities such
as frequency difference ratios, the large and small separations $\Delta\nu$ and
$\delta\nu_{02}$; the behavior of line widths with frequency and line widths at
$\nu_{\rm max}$ with $T_{\rm eff}$, for which we derive parametrizations; and
behavior of mode visibilities. These average properties can be applied in
future peak-bagging exercises to better constrain the parameters of the stellar
oscillation spectra. The frequencies and frequency ratios can tightly constrain
the fundamental parameters of these solar-type stars, and mode line widths and
amplitudes can test models of mode damping and excitation.


title: Efficient Pose and Cell Segmentation using Column Generation

abstract:
  We study the problems of multi-person pose segmentation in natural images and
instance segmentation in biological images with crowded cells. We formulate
these distinct tasks as integer programs where variables correspond to
poses/cells. To optimize, we propose a generic relaxation scheme for solving
these combinatorial problems using a column generation formulation where the
program for generating a column is solved via exact optimization of very small
scale integer programs. This results in efficient exploration of the spaces of
poses and cells.


title: Hydrogen Axion Star: Metallic Hydrogen Bound to a QCD Axion BEC

abstract:
  As a cold dark matter candidate, the QCD axion may form Bose-Einstein
condensates, called axion stars, with masses around $10^{-11}\,M_{\odot}$. In
this paper, we point out that a brand new astrophysical object, a Hydrogen
Axion Star (HAS), may well be formed by ordinary baryonic matter becoming
gravitationally bound to an axion star. We study the properties of the HAS and
find that the hydrogen cloud has a high pressure and temperature in the center
and is likely in the liquid metallic hydrogen state. Because of the high
particle number densities for both the axion star and the hydrogen cloud, the
feeble interaction between axion and hydrogen can still generate enough
internal power, around $10^{13}~\mbox{W}\times(m_a/5~\mbox{meV})^4$, to make
these objects luminous point sources. High resolution ultraviolet, optical and
infrared telescopes can discover HAS via black-body radiation.


title:
Topology and complex structures of leaves of foliations by Riemann
  surfaces

abstract:
  We study conformal structure and topology of leaves of singular foliations by
Riemann surfaces.


title: Modelling Wt and tWZ production at NLO for ATLAS analyses

abstract:
  The generation of single top production in the $Wt$ channel at NLO gives rise
to doubly-resonant diagrams that overlap with $t \bar t$, and similarly for
associated production with a $Z$ or Higgs boson. Several methods exist to
remove this overlap, thus avoiding double counting and separating the two
processes. In Diagram Removal 1, the amplitudes of doubly-resonant diagrams are
set to zero, which also removes the interference of $Wt$ with $t \bar t$. If a
measurement is performed in a region where this interference is not negligible,
it would be of interest to take it into account. Another method, Diagram
Subtraction, preserves the interference. However, it relies upon momentum
reshuffling, which introduces uncertainties to the prediction. An alternative
method, Diagram Removal 2, does not involve reshuffling and preserves the
interference by subtracting the amplitude squared of the doubly-resonant
diagrams from the total. The predictions of Diagram Removal 2 from MG5_aMC@NLO
are compared with other predictions for $Wt$ and $tWZ$ production in the
context of analyses at the ATLAS experiment. Implications of using Diagram
Removal 2 are discussed, both for measurements of single top processes and when
$Wt$ or $tWZ$ are treated as a background. Differential distributions are
shown, investigating in what regions the predictions differ the most.


title: Diffraction from static potential in QED

abstract:
  We model a wire as a cylindrical potential barrier and calculate diffraction
from that potential using quantum electrodynamics. We compare our results with
classical Fraunhofer diffraction. We find general agreement between the quantum
and the classical results; however, we find that the classical approach
overestimates the wire radius. We consider an incoming electron beam
diffracting from the potential. We also consider the case of an incoming photon
beam. For the photon case we only indicate the amplitudes that need to be
evaluated numerically. We also study the case of two beams in phase that
interfere and diffract from the wire-like potential.


title: Protection of entanglement between two two-level atoms

abstract:
  The dynamical evolution of entanglement between two polarizable two-level
atoms in weak interaction with electromagnetic vacuum fluctuations is
investigated. We find that, for initial Bell state $\psi^{\pm}$, the decay rate
of entanglement between atoms is just the superradiant spontaneous emission
rate, which depends not only on the spontaneous emission rate of atom but also
on the modulation of the spontaneous emission rate due to the presence of
another atom. It is shown that, with the presence of a boundary, the
entanglement between transversely polarizable atoms can be protected for a very
long time. It is pointed out that when the two atoms in initial Bell state
$\psi^{-}$ are put close enough , the entanglement between them can also be
protected.


title:
Detection of Dangerous Magnetic Field Ranges from Tablets by Clustering
  Analysis

abstract:
  The paper considers the problem of the extremely low frequency magnetic field
radiation generated by the tablet computers. Accordingly, the measurement of
the magnetic field radiation from a set of tablets is carried out. Furthermore,
the measurement results are analyzed and clustered according to the K-Medians
algorithm to obtain different magnetic field ranges. The obtained cluster
ranges are evaluated according to the reference level proposed by the TCO
standard in order to define dangerous areas in the neighborhood of tablet,
which are established during the typical work with tablet computers. Analysis
shows that dangerous areas correspond to specific inner components of tablet,
and gives suggestions to users for a safe usage of tablet and to companies
producing tablet components for limiting the risk of magnetic field exposure.


title:
Production of quarkonia and doubly heavy baryons in $pp$-collisions with
  duality approach

abstract:
  In present work we discuss the production of heavy quarkonia and diquarks in
$pp$-interactions. The aim is to take into account the production of bound
states of quarks originating from independent parton scatterings. This
production is regulated by constraints on the invariant mass of constituents.
Such an approach leads to larger value of the diquark production cross section
than traditional consideration in single parton scattering. This production
mechanism of doubly heavy baryons can sooner be verified by modern experiments
(e.g. LHCb). We also discuss related contributions to double and associated
quarkonium production.


title: Near-Memory Address Translation

abstract:
  Memory and logic integration on the same chip is becoming increasingly cost
effective, creating the opportunity to offload data-intensive functionality to
processing units placed inside memory chips. The introduction of memory-side
processing units (MPUs) into conventional systems faces virtual memory as the
first big showstopper: without efficient hardware support for address
translation MPUs have highly limited applicability. Unfortunately, conventional
translation mechanisms fall short of providing fast translations as
contemporary memories exceed the reach of TLBs, making expensive page walks
common.
  In this paper, we are the first to show that the historically important
flexibility to map any virtual page to any page frame is unnecessary in today's
servers. We find that while limiting the associativity of the
virtual-to-physical mapping incurs no penalty, it can break the
translate-then-fetch serialization if combined with careful data placement in
the MPU's memory, allowing for translation and data fetch to proceed
independently and in parallel. We propose the Distributed Inverted Page Table
(DIPTA), a near-memory structure in which the smallest memory partition keeps
the translation information for its data share, ensuring that the translation
completes together with the data fetch. DIPTA completely eliminates the
performance overhead of translation, achieving speedups of up to 3.81x and
2.13x over conventional translation using 4KB and 1GB pages respectively.


title: How Bright are Planet-Induced Spiral Arms in Scattered Light?

abstract:
  Recently, high angular resolution imaging instruments such as SPHERE and GPI
have discovered many spiral-arm-like features in near-infrared scattered light
images of protoplanetary disks. Theory and simulations have suggested that
these arms are most likely excited by planets forming in the disks; however, a
quantitative relation between the arm-to-disk brightness contrast and planet
mass is still missing. Using 3D hydrodynamics and radiative transfer
simulations, we examine the morphology and contrast of planet-induced arms in
disks. We find a power-law relation for the face-on arm contrast ($\delta_{\rm
max}$) as a function of planet mass ($M_{\rm p}$) and disk aspect ratio
($h/r$): $\delta_{\rm max}\approx((M_{\rm p}/M_{\rm J})/(h/r)^{1.38})^{0.22}$.
With current observational capability, at a 30 AU separation, the minimum
planet mass for driving detectable arms in a disk around a 1 Myr 1$M_\odot$
star at 140 pc at low inclinations is around Saturn mass. For planets more
massive than Neptune masses, they typically drive multiple arms. Therefore in
observed disks with spirals, it is unlikely that each spiral arm originates
from a different planet. We also find only massive perturbers with at least
multi-Jupiter masses are capable of driving bright arms with $\delta_{\rm
max}\gtrsim2$ as found in SAO 206462, MWC 758, and LkH$\alpha$~330, and these
arms do not follow linear wave propagation theory. Additionally, we find the
morphology and contrast of the primary and secondary arms are largely
unaffected by a modest level of viscosity with $\alpha\lesssim0.01$. Finally,
the contrast of the arms in the SAO 206462 disk suggests that the perturber SAO
206462 b at $\sim100$ AU is about $5-10M_{\rm J}$ in mass.


title:
SINFONI-HiZELS: The dynamics, merger rates & metallicity gradients of
  `typical' star-forming galaxies at $z$ = 0.8-2.2

abstract:
  We present adaptive optics (AO) assisted SINFONI integral field unit (IFU)
spectroscopy of eleven H$\alpha$ emitting galaxies selected from the High-Z
Emission Line Survey (HiZELS). We obtain spatially resolved dynamics on
~kpc-scales of star-forming galaxies (stellar mass M$_\star$ = 10$^{9.5-10.5}$
M$_\odot$ and star formation rate SFR = 2-30 M$_\odot$ yr$^{-1}$) near the peak
of the cosmic star-formation rate history. Combining these observations with
our previous SINFONI-HiZELS campaign, we construct a sample of twenty
homogeneously selected galaxies with IFU AO-aided observations -- the `SHiZELS'
survey, with roughly equal number of galaxies per redshift slice, at $z$ = 0.8,
1.47, and 2.23. We measure the dynamics and identify the major kinematic axis
by modelling their velocity fields to extract rotational curves and infer their
inclination-corrected rotational velocities. We explore the stellar mass
Tully-Fisher relationship, finding that galaxies with higher velocity
dispersions tend to deviate from this relation. Using kinemetry analyses we
find that galaxy interactions might be the dominant mechanism controlling the
star-formation activity at $z$ = 2.23 but they become gradually less important
down to $z$ = 0.8. Metallicity gradients derived from the [NII]/H$\alpha$
emission line ratio show a median negative gradient for the SHiZELS survey of
$\Delta$log(O/H)/$\Delta$R = -0.026$\pm$0.008 dex kpc$^{-1}$. We find that
metal-rich galaxies tend to show negative gradients, whereas metal-poor
galaxies tend to exhibit positive metallicity gradients. This result suggests
that the accretion of pristine gas in the periphery of galaxies plays an
important role in replenishing the gas in `typical' star-forming galaxies.


title:
Observational Diagnostics of Gas Flows: Insights from Cosmological
  Simulations

abstract:
  Galactic accretion interacts in complex ways with gaseous halos, including
galactic winds. As a result, observational diagnostics typically probe a range
of intertwined physical phenomena. Because of this complexity, cosmological
hydrodynamic simulations have played a key role in developing observational
diagnostics of galactic accretion. In this chapter, we review the status of
different observational diagnostics of circumgalactic gas flows, in both
absorption (galaxy pair and down-the-barrel observations in neutral hydrogen
and metals; kinematic and azimuthal angle diagnostics; the cosmological column
density distribution; and metallicity) and emission (Lya; UV metal lines; and
diffuse X-rays). We conclude that there is no simple and robust way to identify
galactic accretion in individual measurements. Rather, progress in testing
galactic accretion models is likely to come from systematic, statistical
comparisons of simulation predictions with observations. We discuss specific
areas where progress is likely to be particularly fruitful over the next few
years.


title: Gas Accretion onto the Milky Way

abstract:
  The Milky Way is surrounded by large amounts of gaseous matter that are
slowly being accreted over cosmic timescales to support star formation in the
disk. The corresponding gas-accretion rate represents a key parameter for the
past, present, and future evolution of the Milky Way. In this article, I
discuss our current understanding of gas accretion processes in the Galaxy by
reviewing past and recent observational and theoretical studies. The first part
of this review deals with the spatial distribution of the different gas phases
in the Milky Way halo, the origin of the gas, and its total mass. The second
part discusses the gas dynamics and the physical processes that regulate the
gas flow from the outer Galactic halo to the disk. From the most recent studies
follows that the present-day gas accretion rate of the Milky Way is a few solar
masses per year, which is sufficient to maintain the Galaxy's star-formation
rate at its current level.


title: Subleading Power Corrections for N-Jettiness Subtractions

abstract:
  The $N$-jettiness observable $\mathcal{T}_N$ provides a way of describing the
leading singular behavior of the $N$-jet cross section in the $\tau
=\mathcal{T}_N/Q \to 0$ limit, where $Q$ is a hard interaction scale. We
consider subleading power corrections in the $\tau \ll 1$ expansion, and employ
soft-collinear effective theory to obtain analytic results for the dominant
$\alpha_s \tau \ln\tau$ and $\alpha_s^2 \tau\ln^3\tau$ subleading terms for
thrust in $e^+e^-$ collisions and $0$-jettiness for $q\bar q$-initiated
Drell-Yan-like processes at hadron colliders. These results can be used to
significantly improve the numerical accuracy and stability of the $N$-jettiness
subtraction technique for performing fixed-order calculations at NLO and NNLO.
They reduce the size of missing power corrections in the subtractions by an
order of magnitude. We also point out that the precise definition of
$N$-jettiness has an important impact on the size of the power corrections and
thus the numerical accuracy of the subtractions. The sometimes employed
definition of $N$-jettiness in the hadronic center-of-mass frame suffers from
power corrections that grow exponentially with rapidity, causing the power
expansion to deteriorate away from central rapidity. This degradation does not
occur for the original $N$-jettiness definition, which explicitly accounts for
the boost of the Born process relative to the frame of the hadronic collision,
and has a well-behaved power expansion throughout the entire phase space.
Integrated over rapidity, using this $N$-jettiness definition in the
subtractions yields another order of magnitude improvement compared to
employing the hadronic-frame definition.


title: Gas Accretion in Star-Forming Galaxies

abstract:
  Cold-mode gas accretion onto galaxies is a direct prediction of LCDM
simulations and provides galaxies with fuel that allows them to continue to
form stars over the lifetime of the Universe. Given its dramatic influence on a
galaxy's gas reservoir, gas accretion has to be largely responsible for how
galaxies form and evolve. Therefore, given the importance of gas accretion, it
is necessary to observe and quantify how these gas flows affect galaxy
evolution. However, observational data have yet to conclusively show that gas
accretion ubiquitously occurs at any epoch. Directly detecting gas accretion is
a challenging endeavor and we now have obtained a significant amount of
observational evidence to support it. This chapter reviews the current
observational evidence of gas accretion onto star-forming galaxies.


title:
$\boldsymbol{\mu^-}$- $\boldsymbol{e^+}$ Conversion from Short-Range
  Operators

abstract:
  We present a detailed discussion of the lepton flavour and number violating
conversion of bound muons into positrons. This process is a viable alternative
to neutrinoless double beta decay and, given that experiments on ordinary
$\mu^-$- $e^-$ conversion are expected to improve their sensitivities by
several orders of magnitude in the coming years, we can also assume the limit
on $\mu^-$- $e^+$ conversion to improve by roughly the same factor. We discuss
how new physics at a high scale can lead to short-range contributions to this
conversion process and we present one explicit case in great detail (the single
one for which the corresponding nuclear matrix element is presently known). The
main goal of our discussion is to make the respective computation accessible to
the particle physics community, so that promising models can be investigated
while the nuclear physics community can simultaneously advance the computation
of nuclear matrix elements. Given the progress to be expected on the
experimental side, it may even be possible that lepton number violation in the
$e\mu$-sector is discovered by $\mu^-$- $e^+$ conversion before neutrinoless
double beta decay can show its existence in the $ee$-sector.


title:
A Universe Without Dark Energy: Cosmic Acceleration from Dark
  Matter-Baryon Interactions

abstract:
  Cosmic acceleration is widely believed to require either a source of negative
pressure (i.e., dark energy), or a modification of gravity, which necessarily
implies new degrees of freedom beyond those of Einstein gravity. In this paper
we present a third possibility, using only dark matter and ordinary matter. The
mechanism relies on the coupling between dark matter and ordinary matter
through an effective metric. Dark matter couples to an Einstein-frame metric,
and experiences a matter-dominated, decelerating cosmology up to the present
time. Ordinary matter couples to an effective metric that depends also on the
DM density, in such a way that it experiences late-time acceleration. Linear
density perturbations are stable and propagate with arbitrarily small sound
speed, at least in the case of `pressure' coupling. Assuming a simple
parametrization of the effective metric, we show that our model can
successfully match a set of basic cosmological observables, including
luminosity distance, BAO measurements, angular-diameter distance to last
scattering {\it etc.} For the growth history of density perturbations, we find
an intriguing connection between the growth factor and the Hubble constant. To
get a growth history similar to the $\Lambda$CDM prediction, our model predicts
a higher $H_0$, closer to the value preferred by direct estimates. On the flip
side, we tend to overpredict the growth of structures whenever $H_0$ is
comparable to the Planck preferred value. The model also tends to predict
larger redshift-space distortions at low redshift than $\Lambda$CDM.


title: Two New Calcium-Rich Gap Transients in Group and Cluster Environments

abstract:
  We present the Palomar Transient Factory discoveries and the photometric and
spectroscopic observations of PTF11kmb and PTF12bho. We show that both
transients have properties consistent with the class of calcium-rich gap
transients, specifically lower peak luminosities and rapid evolution compared
to ordinary supernovae, and a nebular spectrum dominated by [Ca II] emission. A
striking feature of both transients is their host environments: PTF12bho is an
intra-cluster transient in the Coma Cluster, while PTF11kmb is located in a
loose galaxy group, at a physical offset ~150 kpc from the most likely host
galaxy. Deep Subaru imaging of PTF12bho rules out an underlying host system to
a limit of $M_R > -8.0$ mag, while Hubble Space Telescope imaging of PTF11kmb
reveals a marginal counterpart that, if real, could be either a background
galaxy or a globular cluster. We show that the offset distribution of Ca-rich
gap transients is significantly more extreme than that seen for Type Ia
supernovae or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets
are caused by a kick, they require larger kick velocities and/or longer merger
times than sGRBs. We also show that almost all Ca-rich gap transients found to
date are in group and cluster environments with elliptical host galaxies,
indicating a very old progenitor population; the remote locations could
partially be explained by these environments having the largest fraction of
stars in the intra-group/intra-cluster light following galaxy-galaxy
interactions.


title:
Efficient computation of the gravitational wave spectrum emitted by
  eccentric massive black hole binaries in stellar environments

abstract:
  We present a fast and versatile method to calculate the characteristic
spectrum $h_c$ of the gravitational wave background (GWB) emitted by a
population of eccentric massive black hole binaries (MBHBs). We fit the
spectrum of a reference MBHB with a simple analytic function and show that the
spectrum of any other MBHB can be derived from this reference spectrum via
simple scalings of mass, redshift and frequency. We then apply our calculation
to a realistic population of MBHBs evolving via 3-body scattering of stars in
galactic nuclei. We demonstrate that our analytic prescription satisfactorily
describes the signal in the frequency band relevant to pulsar timing array
(PTA) observations. Finally we model the high frequency steepening of the GWB
to provide a complete description of the features characterizing the spectrum.
For typical stellar distributions observed in massive galaxies, our calculation
shows that 3-body scattering alone is unlikely to affect the GWB in the PTA
band and a low frequency turnover in the spectrum is caused primarily by high
eccentricities.


title:
Characterising radio telescope software with the Workload
  Characterisation Framework

abstract:
  We present a modular framework, the Workload Characterisation Framework
(WCF), that is developed to reproducibly obtain, store and compare key
characteristics of radio astronomy processing software. As a demonstration, we
discuss the experiences using the framework to characterise a LOFAR calibration
and imaging pipeline.


title: Searching for Primordial Black Holes in the radio and X-ray sky

abstract:
  We model the accretion of gas onto a population of massive primordial black
holes in the Milky Way, and compare the predicted radio and X-ray emission with
observational data. We show that under conservative assumptions on the
accretion process, the possibility that ${\cal O}(10) \, M_\odot$ primordial
black holes can account for all of the dark matter in the Milky Way is excluded
at $5\sigma$ by a comparison with a VLA radio catalog at $1.4$ GHz, and at
$\simeq 40\sigma$ by a comparison with a Chandra X-ray catalog ($0.5 - 8$ keV).
We argue that this method can be used to identify such a population of
primordial black holes with more sensitive future radio and X-ray surveys.


title: Gas Accretion via Lyman Limit Systems

abstract:
  In cosmological simulations, a large fraction of the partial Lyman limit
systems (pLLSs; 16<log N(HI)<17.2) and LLSs (17.2log N(HI)<19) probes
large-scale flows in and out of galaxies through their circumgalactic medium
(CGM). The overall low metallicity of the cold gaseous streams feeding galaxies
seen in these simulations is the key to differentiating them from metal rich
gas that is either outflowing or being recycled. In recent years, several
groups have empirically determined an entirely new wealth of information on the
pLLSs and LLSs over a wide range of redshifts. A major focus of the recent
research has been to empirically determine the metallicity distribution of the
gas probed by pLLSs and LLSs in sizable and representative samples at both low
(z<1) and high (z>2) redshifts. Here I discuss unambiguous evidence for
metal-poor gas at all z probed by the pLLSs and LLSs. At z<1, all the pLLSs and
LLSs so far studied are located in the CGM of galaxies with projected distances
<100-200 kpc. Regardless of the exact origin of the low-metallicity pLLSs/LLSs,
there is a significant mass of cool, dense, low-metallicity gas in the CGM that
may be available as fuel for continuing star formation in galaxies over cosmic
time. As such, the metal-poor pLLSs and LLSs are currently among the best
observational evidence of cold, metal-poor gas accretion onto galaxies.


title: Dense Gas in the Outer Spiral Arm of M51

abstract:
  There is a linear relation between the mass of dense gas, traced by the
HCN(1-0) luminosity, and the star formation rate (SFR), traced by the
far-infrared luminosity. Recent observations of galactic disks have shown some
systematic variations. In order to explore the SFR-dense gas link at high
resolution ($\sim 4"$, $\sim 150$ pc) in the outer disk of an external galaxy,
we have mapped a region about 5 kpc from the center along the northern spiral
arm of M51 in the HCN(1-0), HCO$^+$(1-0) and HNC(1-0) emission lines using the
Northern Extended Millimeter Array (NOEMA) interferometer. The HCN and HCO$^+$
lines were detected in 6 giant molecular associations (GMAs) while HNC emission
was only detected in the two brightest GMAs. One of the GMAs hosts a powerful
HII region and HCN is stronger than HCO$^+$ there. Comparing with observations
of GMAs in the disks of M31 and M33 at similar angular resolution ($\sim 100$
pc), we find that GMAs in the outer disk of M51 are brighter in both HCN and
HCO$^+$ lines by a factor of 3 on average. However, the $I_{HCN}/I_{CO}$ and
$I_{HCO^+}/I_{CO}$ ratios are similar to the ratios in nearby galactic disks
and the Galactic plane. Using the Herschel 70 $\mu$m data to trace the total IR
luminosity at the resolution of the GMAs, we find that both the
L$_{IR}$-L$_{HCN}$ and L$_{IR}$-L$_{HCO^+}$ relations in the outer disk GMAs
are consistent with the proportionality between the L$_{IR}$ and the dense gas
mass established globally in galaxies within the scatter. The IR/HCN and
IR/HCO$^+$ ratios of the GMAs vary by a factor of 3, probably depending on
whether massive stars are forming or not.


title:
Low-mass neutralino dark matter in supergravity scenarios: phenomenology
  and naturalness

abstract:
  The latest experimental results from the LHC and dark matter (DM) searches
suggest that the parameter space allowed in supersymmetric theories is subject
to strong reductions. These bounds are especially constraining for scenarios
entailing light DM particles. Previous studies have shown that light neutralino
DM in the Minimal Supersymmetric Standard Model (MSSM), with parameters defined
at the electroweak scale, is still viable when the low energy spectrum of the
model features light sleptons, in which case, the relic density constraint can
be fulfilled. In view of this, we have investigated the viability of light
neutralinos as DM candidates in the MSSM, with parameters defined at the grand
unification scale. We have analysed the optimal choices of non-universalities
in the soft supersymmetry-breaking parameters for both, gauginos and scalars,
in order to avoid the stringent experimental constraints. We show that light
neutralinos, with a mass as low as 25 GeV, are viable in supergravity scenarios
if the gaugino mass parameters at high energy are very non universal, while the
scalar masses can remain of the same order. These scenarios typically predict a
very small cross section of neutralinos off protons and neutrons, thereby being
very challenging for direct detection experiments. However, a potential
detection of smuons and selectrons at the LHC, together with a hypothetical
discovery of a gamma-ray signal from neutralino annihilations in dwarf
spheroidal galaxies could shed light on this kind of solutions. Finally, we
have investigated the naturalness of these scenarios, taking into account all
the potential sources of tuning. Besides the electroweak fine-tuning, we have
found that the tuning to reproduce the correct DM relic abundance and that to
match the measured Higgs mass can also be important when estimating the total
degree of naturalness.


title: An Introduction to Gas Accretion onto Galaxies

abstract:
  Evidence for gas accretion onto galaxies can be found throughout the
universe. In this chapter, I summarize the direct and indirect signatures of
this process and discuss the primary sources. The evidence for gas accretion
includes the star formation rates and metallicities of galaxies, the evolution
of the cold gas content of the universe with time, numerous indirect indicators
for individual galaxies, and a few direct detections of inflow. The primary
sources of gas accretion are the intergalactic medium, satellite gas and
feedback material. There is support for each of these sources from observations
and simulations, but the methods with which the fuel ultimately settles in to
form stars remain murky.


title: A robust generalization of the Legendre transform for QFT

abstract:
  Although perturbative quantum field theory is highly successful, it possesses
a number of well-known analytic problems, from ultraviolet and infrared
divergencies to the divergence of the perturbative expansion itself. As a
consequence, it has been difficult, for example, to prove with full rigor that
the Legendre transform of the quantum effective action is the generating
functional of connected graphs. Here, we give a rigorous proof of this central
fact. To this end, we show that the Legendre transform can be re-defined purely
combinatorially and that it ultimately reduces to a simple homological
relation, the Euler characteristic for tree graphs. This result suggests that,
similarly, also the quantum field theoretic path integral, being a Fourier
transform, may be reducible to an underlying purely algebraic structure.


title: Chaos in the Y-chromosome evolution?

abstract:
  The Y-chromosome degeneration is still an intriguing mechanism and comprises
the very origin of sex. We present a coupled version of the well known logistic
map and the logistic equation describing the evolution of XY chromosomes.
Although chaos was found in X, Y chromosomes do not evolve chaotically. A
mathematical constraint is shown as the responsible for this behaviour. In
addition, analytical solutions are presented for the differential equations
herein.


title: Analytical halo model of galactic conformity

abstract:
  We present a fully analytical halo model of colour-dependent clustering that
incorporates the effects of galactic conformity in a halo occupation
distribution (HOD) framework. The model, based on our previous numerical work,
describes conformity through a correlation between the colour of a galaxy and
the concentration of its parent halo, leading to a correlation between central
and satellite galaxy colours at fixed halo mass. The strength of the
correlation is set by a tunable `group quenching efficiency', and the model can
separately describe group-level correlations between galaxy colour (1-halo
conformity) and large scale correlations induced by assembly bias (2-halo
conformity). We validate our analytical results using clustering measurements
in mock galaxy catalogs, finding that the model is accurate at the 10-20
percent level for a wide range of luminosities and length scales. We apply the
formalism to interpret the colour-dependent clustering of galaxies in the Sloan
Digital Sky Survey (SDSS). We find good overall agreement between the data and
a model that has 1-halo conformity at a level consistent with previous results
based on an SDSS group catalog, although the clustering data require satellites
to be redder than suggested by the group catalog. Within our modelling
uncertainties, however, we do not find strong evidence of 2-halo conformity
driven by assembly bias in SDSS clustering.


title:
The occurrence of Binary Evolution Pulsators in the classical
  instability strip of RR Lyrae and Cepheid variables

abstract:
  Single star evolution does not allow extremely low-mass stars to cross the
classical instability strip (IS) during the Hubble time. However, within binary
evolution framework low-mass stars can appear inside the IS once the mass
transfer (MT) is taken into account. Triggered by a discovery of low-mass 0.26
Msun RR Lyrae-like variable in a binary system, OGLE-BLG-RRLYR-02792, we
investigate the occurrence of similar binary components in the IS, which set up
a new class of low-mass pulsators. They are referred to as Binary Evolution
Pulsators (BEPs) to underline the interaction between components, which is
crucial for substantial mass loss prior to the IS entrance. We simulate a
population of 500 000 metal-rich binaries and report that 28 143 components of
binary systems experience severe MT (loosing up to 90% of mass), followed by at
least one IS crossing in luminosity range of RR Lyrae (RRL) or Cepheid
variables. A half of these systems enter the IS before the age of 4 Gyr. BEPs
display a variety of physical and orbital parameters, with the most important
being the BEP mass in range 0.2-0.8 Msun, and the orbital period in range
10-2500 d. Based on the light curve only, BEPs can be misclassified as genuine
classical pulsators, and as such they would contaminate genuine RRL and
classical Cepheid variables at levels of 0.8% and 5%, respectively. We state
that the majority of BEPs will remain undetected and we discuss relevant
detection limitations.


title: Thermal Resummation and Phase Transitions

abstract:
  The consequences of phase transitions in the early universe are becoming
testable in a variety of manners, from colliders physics to gravitational wave
astronomy. In particular one phase transition we know of, the Electroweak Phase
Transition (EWPT), could potentially be first order in BSM scenarios and
testable in the near future. If confirmed this could provide a mechanism for
Baryogenesis, which is one of the most important outstanding questions in
physics. To reliably make predictions it is necessary to have full control of
the finite temperature scalar potentials. However, as we show the standard
methods used in BSM physics to improve phase transition calculations, resumming
hard thermal loops, introduces significant errors into the scalar potential. In
addition, the standard methods make it impossible to match theories to an EFT
description reliably. In this paper we define a thermal resummation procedure
based on Partial Dressing (PD) for general BSM calculations of phase
transitions beyond the high-temperature approximation. Additionally, we
introduce the modified Optimized Partial Dressing (OPD) procedure, which is
numerically nearly as efficient as old incorrect methods, while yielding
identical results to the full PD calculation. This can be easily applied to
future BSM studies of phase transitions in the early universe. As an example,
we show that in unmixed singlet scalar extensions of the SM, the (O)PD
calculations make new phenomenological predictions compared to previous
analyses. An important future application is the study of EFTs at finite
temperature.


title:
Neural Document Embeddings for Intensive Care Patient Mortality
  Prediction

abstract:
  We present an automatic mortality prediction scheme based on the unstructured
textual content of clinical notes. Proposing a convolutional document embedding
approach, our empirical investigation using the MIMIC-III intensive care
database shows significant performance gains compared to previously employed
methods such as latent topic distributions or generic doc2vec embeddings. These
improvements are especially pronounced for the difficult problem of
post-discharge mortality prediction.


title:
Energetics and Birth Rates of Supernova Remnants in the Large Magellanic
  Cloud

abstract:
  Published X-ray emission properties for a sample of 50 supernova remnants
(SNRs) in the LMC are used as input for SNR evolution modelling calculations.
The forward shock emission is modelled to obtain the initial explosion energy,
age, and circumstellar medium density for each SNR in the sample. The resulting
age distribution yields a SNR birthrate of 1/(500 yr) for the LMC. The
explosion energy distribution is well fit by a log-normal distribution, with
most-probable explosion energy of $0.5\times10^{51}$erg, with a 1-$\sigma$
dispersion by factor 3 in energy. The circumstellar medium density distribution
is broader than the explosion energy distribution, with most-probable density
of $\sim$0.1 cm$^{-3}$. The shape of the density distribution can be fit with a
log-normal distribution, with incompleteness at high density caused by shorter
evolution times of SNRs.


title:
Electron and hole transport in disordered monolayer MoS2: atomic
  vacancy-induced short-range and Coulomb disorder scattering

abstract:
  Atomic disorder is a common limiting factor for the low-temperature mobility
in monolayer transition-metal dichalcogenides (TMDs; MX2). Here, we study the
effect of often occurring atomic vacancies on carrier scattering and transport
in p- and n-type monolayer MoS2. Due to charge trapping in vacancy-induced
in-gap states, both neutral and charged vacancies resembling, respectively,
short-range and combined short-range and long-range Coulomb scatterers, must be
considered. Using the T-matrix formalism, we demonstrate a strong
renormalization of the Born description of short-range scattering, manifested
in a pronounced reduction and a characteristic energy dependence of the
scattering rate. As a consequence, carrier scattering in TMDs with charged
vacancies is dominated by the long-range Coulomb-disorder scattering, giving
rise to a strong screening-induced temperature and density dependence of the
low-temperature carrier mobility. For TMDs with neutral vacancies, the absence
of intrinsic Coulomb disorder results in significantly higher mobilities as
well as an unusual density dependence of the mobility which decreases with the
carrier density. Our work illuminates the transport-limiting effects of
atomic-vacancy scattering relevant for high-mobility TMD devices.


title:
Spatially modulated instabilities of holographic gauge-gravitational
  anomaly

abstract:
  We performed a study of the perturbative instabilities in
Einstein-Maxwell-Chern-Simons theory with a gravitational Chern-Simons term,
which is dual to a strongly coupled field theory with both chiral and mixed
gauge-gravitational anomaly. With an analysis of the fluctuations in the near
horizon regime at zero temperature, we found that there might be two possible
sources of instabilities. The first one corresponds to a real mass-squared
which is below the BF bound of AdS$_2$, and it leads to the bell-curve phase
diagram at finite temperature. The effect of mixed gauge-gravitational anomaly
is emphasised. Another source of instability is independent of gauge
Chern-Simons coupling and exists for any finite gravitational Chern-Simons
coupling. There is a singular momentum close to which unstable mode appears.
The possible implications of this singular momentum are discussed. Our analysis
suggests that the theory with a gravitational Chern-Simons term around
Reissner-Nordstr\"om black hole is unreliable unless the gravitational
Chern-Simons coupling is treated as a small perturbative parameter.


title: Large subgraphs in rainbow-triangle free colorings

abstract:
  Fox--Grinshpun--Pach showed that every $3$-coloring of the complete graph on
$n$ vertices without a rainbow triangle contains a clique of size
$\Omega\left(n^{1/3}\log^2 n\right)$ which uses at most two colors, and this
bound is tight up to the constant factor. We show that if instead of looking
for large cliques one only tries to find subgraphs of large chromatic number,
one can do much better. We show that every such coloring contains a $2$-colored
subgraph with chromatic number at least $n^{2/3}$, and this is best possible.
We further show that for fixed positive integers $s,r$ with $s\leq r$, every
$r$-coloring of the edges of the complete graph on $n$ vertices without a
rainbow triangle contains a subgraph that uses at most $s$ colors and has
chromatic number at least $n^{s/r}$, and this is best possible.
Fox--Grinshpun--Pach previously showed a clique version of this result.
  As a direct corollary of our result we obtain a generalisation of the
celebrated theorem of Erd\H{o}s-Szekeres, which states that any sequence of $n$
numbers contains a monotone subsequence of length at least $\sqrt{n}$. We prove
that if an $r$-coloring of the edges of an $n$-vertex tournament does not
contain a rainbow triangle then there is an $s$-colored directed path on
$n^{s/r}$ vertices, which is best possible. This gives a partial answer to a
question of Loh.


title: Understanding image motion with group representations

abstract:
  Motion is an important signal for agents in dynamic environments, but
learning to represent motion from unlabeled video is a difficult and
underconstrained problem. We propose a model of motion based on elementary
group properties of transformations and use it to train a representation of
image motion. While most methods of estimating motion are based on pixel-level
constraints, we use these group properties to constrain the abstract
representation of motion itself. We demonstrate that a deep neural network
trained using this method captures motion in both synthetic 2D sequences and
real-world sequences of vehicle motion, without requiring any labels. Networks
trained to respect these constraints implicitly identify the image
characteristic of motion in different sequence types. In the context of vehicle
motion, this method extracts information useful for localization, tracking, and
odometry. Our results demonstrate that this representation is useful for
learning motion in the general setting where explicit labels are difficult to
obtain.


title: Charmed mesons at finite temperature and chemical potential

abstract:
  We compute the masses of the pseudoscalar mesons $\pi^+$ , $K^0$ and $D^+$ at
finite temperature and baryon chemical potential. The computations are based on
a symmetry- preserving Dyson-Schwinger equation treatment of a vector-vector
four quark contact interaction. The results found for the temperature
dependence of the meson masses are in qualitative agreement with lattice QCD
data and QCD sum rules calculations. The chemical potential dependence of the
masses provide a novel prediction of the present computation.


title: Brownian Dynamics of Confined Suspensions of Active Microrollers

abstract:
  We develop efficient numerical methods for performing many-body Brownian
dynamics simulations of a recently-observed fingering instability in an active
suspension of colloidal rollers sedimented above a wall [M. Driscoll, B.
Delmotte, M. Youssef, S. Sacanna, A. Donev and P. Chaikin, Nature Physics,
2016, doi:10.1038/nphys3970]. We present a stochastic Adams-Bashforth
integrator for the equations of Brownian dynamics, which has the same cost as
but is more accurate than the widely-used Euler-Maruyama scheme, and uses a
random finite difference to capture the stochastic drift proportional to the
divergence of the configuration-dependent mobility matrix. We generate the
Brownian increments using a Krylov method, and show that for particles confined
to remain in the vicinity of a no-slip wall by gravity or active flows the
number of iterations is independent of the number of particles. Our numerical
experiments with active rollers show that the thermal fluctuations set the
characteristic height of the colloids above the wall, both in the initial
condition and the subsequent evolution dominated by active flows. The
characteristic height in turn controls the timescale and wavelength for the
development of the fingering instability.


title:
Transfer Learning Across Patient Variations with Hidden Parameter Markov
  Decision Processes

abstract:
  Due to physiological variation, patients diagnosed with the same condition
may exhibit divergent, but related, responses to the same treatments. Hidden
Parameter Markov Decision Processes (HiP-MDPs) tackle this transfer-learning
problem by embedding these tasks into a low-dimensional space. However, the
original formulation of HiP-MDP had a critical flaw: the embedding uncertainty
was modeled independently of the agent's state uncertainty, requiring an
unnatural training procedure in which all tasks visited every part of the state
space---possible for robots that can be moved to a particular location,
impossible for human patients. We update the HiP-MDP framework and extend it to
more robustly develop personalized medicine strategies for HIV treatment.


title:
Extensive Large-Scale Study of Error in Samping-Based Distinct Value
  Estimators for Databases

abstract:
  The problem of distinct value estimation has many applications. Being a
critical component of query optimizers in databases, it also has high
commercial impact. Many distinct value estimators have been proposed, using
various statistical approaches. However, characterizing the errors incurred by
these estimators is an open problem: existing analytical approaches are not
powerful enough, and extensive empirical studies at large scale do not exist.
We conduct an extensive large-scale empirical study of 11 distinct value
estimators from four different approaches to the problem over families of
Zipfian distributions whose parameters model real-world applications. Our study
is the first that \emph{scales to the size of a billion-rows} that today's
large commercial databases have to operate in. This allows us to characterize
the error that is encountered in real-world applications of distinct value
estimation. By mining the generated data, we show that estimator error depends
on a key latent parameter --- the average uniform class size --- that has not
been studied previously. This parameter also allows us to unearth error
patterns that were previously unknown. Importantly, ours is the first approach
that provides a framework for \emph{visualizing the error patterns} in distinct
value estimation, facilitating discussion of this problem in enterprise
settings. Our characterization of errors can be used for several problems in
distinct value estimation, such as the design of hybrid estimators. This work
aims at the practitioner and the researcher alike, and addresses questions
frequently asked by both audiences.


title: Gas Accretion via Condensation and Fountains

abstract:
  For most of their lives, galaxies are surrounded by large and massive coronae
of hot gas, which constitute vast reservoirs for gas accretion. This Chapter
describes a mechanism that allows star-forming disc galaxies to extract gas
from their coronae. Stellar feedback powers a continuous circulation (galactic
fountain) of gas from the disc into the halo, producing mixing between
metal-rich disc material and metal-poor coronal gas. This mixing causes a
dramatic reduction of the cooling time of the corona making it condense and
accrete onto the disc. This fountain- driven accretion model makes clear
predictions for the kinematics of the extraplanar cold/warm gas in disc
galaxies, which are in good agreement with a number of independent
observations. The amount of gas accretion predicted by the model is of the
order of what is needed to sustain star formation. Accretion is expected to
occur preferentially in the outer parts of discs and its efficiency drops for
higher coronal temperatures. Thus galaxies are able to gather new gas as long
as they do not become too massive nor fall into large halos and maintain their
star-forming gaseous discs.