title: Lie bialgebra structures on 2-step nilpotent graph algebras

abstract:
  We generalize a result on the Heisenberg Lie algebra that gives restrictions
to possible Lie bialgebra cobrackets on 2-step nilpotent algebras with some
additional properties. For the class of 2-step nilpotent Lie algebras coming
from graphs, we describe these extra properties in a very easy
graph-combinatorial way. We exhibit applications for $\mathfrak f_n$, the free
2-step nilpotent Lie algebra.


title: A time-stepping DPG scheme for the heat equation

abstract:
  We introduce and analyze a discontinuous Petrov-Galerkin method with optimal
test functions for the heat equation. The scheme is based on the backward Euler
time stepping and uses an ultra-weak variational formulation at each time step.
We prove the stability of the method for the field variables (the original
unknown and its gradient weighted by the square root of the time step) and
derive a C\'ea-type error estimate. For low-order approximation spaces this
implies certain convergence orders when time steps are not too small in
comparison with mesh sizes. Some numerical experiments are reported to support
our theoretical results.


title:
Observation of the quantum paradox of separation of a single photon from
  one of its properties

abstract:
  We report an experimental realization of the quantum paradox of the
separation of a single photon from one of its properties (the so-called
"quantum Cheshire cat"). We use a modified Sagnac interferometer with displaced
paths to produce appropriately pre- and postselected states of heralded single
photons. Weak measurements of photon presence and circular polarization are
performed in each arm of the interferometer by introducing weak absorbers and
small polarization rotations and analyzing changes in the postselected signal.
The absorber is found to have an appreciable effect only in one arm of the
interferometer, while the polarization rotation significantly affects the
signal only when performed in the other arm. We carry out both sequential and
simultaneous weak measurements and find good agreement between measured and
predicted weak values. In the language of Aharonov et al. and in the sense of
the ensemble averages described by weak values, the experiment establishes the
separation of a particle from one its properties during the passage through the
interferometer.


title: Performance analysis for the new G-2 experiment

abstract:
  The new g-2 experiment at Fermilab aims to measure the muon anomalous
magnetic moment by a fourfold improvement in precision compared to the BNL
experiment. Achieving this goal requires the delivery of highly polarized 3.094
GeV/c muons with a narrow +-0.5% {\Delta}p/p acceptance to the storage ring. In
this study, we describe a muon capture and transport scheme that should meet
this requirement. First, we present the conceptual design of our proposed
scheme wherein we describe its basic features. Then, we detail our numerical
model and present a complete end-to-end simulation of all g-2 beamlines.


title: Public Naming of Planets and Planetary Satellites

abstract:
  While one of the IAU's missions is to "serve as the internationally
recognized authority for assigning designations to celestial bodies and surface
features on them", the participation of the public in the naming of celestial
objects has been a little-known, but decade-long tradition of the IAU. While
reiterating its opposition to having the public pay to give a name to an
exoplanet, the IAU Executive Committee nonetheless recognized the right of
organizations to invite public, international exoplanet naming or voting
campaigns. To this end, clear selection rules were to be defined by the IAU,
inviting mutual collaboration, the goal being to sanction the campaign and
officially approve the resulting names, for the sake of boosting the public's
interest in astronomy and at the same time reaffirm the authority of the IAU.
In no way were these names supposed to supersede the designations in use by
professional astronomers. Since the field of exoplanet research was still
"virgin" for naming but is now becoming scientifically mature (with hundreds of
well-characterized, confirmed objects) and so appealing to the public's
interest and imagination, IAU decided to organize a naming contest as the
leader of a new project with a potentially high worldwide impact, the first
since the International Year of Astronomy in 2009, called "NameExoWorlds".


title:
The Representation Dimension of a Selfinjective Algebra of Wild Tilted
  Type

abstract:
  We prove that the representation dimension of a selfinjective algebra of wild
tilted type is equal to three, and give an explicit construction of an
Auslander generator of its module category. We also show that if a connected
selfinjective algebra admits an acyclic generalised standard Auslander-Reiten
component then its representation dimension is equal to three.


title:
Multi-wavelength Study of Transition Region Penumbral Subarcsecond
  Bright Dots Using IRIS and NST

abstract:
  Using high-resolution transition region (TR) observations taken by the
Interface Region Imaging Spectrograph (IRIS) mission, Tian et al. (2014b)
revealed numerous short-lived subarcsecond bright dots (BDs) above sunspots
(mostly located in the penumbrae), which indicate yet unexplained small-scale
energy releases. Moreover, whether these subarcsecond TR brightenings have any
signature in the lower atmosphere and how they are formed are still not fully
resolved. This paper presents a multi-wavelength study of the TR penumbral BDs
using a coordinated observation of a near disk-center sunspot with IRIS and the
1.6 m New Solar Telescope (NST) at the Big Bear Solar Observatory. NST provides
high-resolution chromospheric and photospheric observations with narrow-band
H-alpha imaging spectroscopy and broad-band TiO images, respectively,
complementary to IRIS TR observations. A total of 2692 TR penumbral BDs are
identified from a 37-minute time series of IRIS 1400 A slitjaw images. Their
locations tend to be associated more with downflowing and darker fibrils in the
chromosphere, and weakly associated with bright penumbral features in the
photosphere. However, temporal evolution analyses of the BDs show that there is
no consistent and convincing brightening response in the chromosphere. These
results are compatible with a formation mechanism of the TR penumbral BDs by
falling plasma from coronal heights along more vertical and dense magnetic
loops. The BDs may also be produced by small-scale impulsive magnetic
reconnection taking place sufficiently high in the atmosphere that has no
energy release in the chromosphere.


title:
Optimal Tree Hash Modes: the Case of Trees Having their Leaves at All
  the Levels

abstract:
  A recent work shows how we can optimize a tree based mode of operation for a
hash function where the sizes of input message blocks and digest are the same,
subject to the constraint that the involved tree structure has all its leaves
at the same depth. In this work, we show that we can further optimize the
running time of such a mode by using a tree having leaves at all its levels. We
make the assumption that the input message block has a size a multiple of that
of the digest and denote by $d$ the ratio block size over digest size. The
running time is evaluated in terms of number of operations performed by the
hash function, i.e. the number of calls to its underlying function. It turns
out that a digest can be computed in $\lceil \log_{d+1} (l/2) \rceil+2$
evaluations of the underlying function using $\lceil l/2 \rceil$ processors,
where $l$ is the number of blocks of the message. Other results of interest are
discussed, such as the optimization of the parallel running time for a tree of
restricted height.


title:
Mechanical stability study for Integrable Optics Test Accelerator at
  Fermilab

abstract:
  The Integrable Optics Test Accelerator (IOTA) is proposed for operation at
Fermilab. The goal of IOTA is to create practical nonlinear accelerator
focusing systems with a large frequency spread and stable particle motion. The
IOTA is a 40 m circumference, 150 MeV (e-), 2.5 MeV (p+) diagnostic test ring.
A heavy low frequency steel floor girder is proposed as the primary tier for
IOTA device component support. Two design lengths; (8) 3.96 m and (2) 3.1 m
long girders with identical cross section completely encompass the ring. This
study focuses on the 3.96 m length girder and the development of a working
prototype. Hydrostatic Level Sensor (HLS), temperature, metrology and fast
motion measurements characterize the anticipated mechanical stability of the
IOTA ring.


title:
Full Monte-Carlo description of the Moscow State University Extensive
  Air Shower experiment

abstract:
  The Moscow State University Extensive Air Shower (EAS-MSU) array studied
high-energy cosmic rays with primary energies ~(1-500) PeV in the Northern
hemisphere. The EAS-MSU data are being revisited following recently found
indications to an excess of muonless showers, which may be interpreted as the
first observation of cosmic gamma rays at ~100 PeV. In this paper, we present a
complete Monte-Carlo model of the surface detector which results in a good
agreement between data and simulations. The model allows us to study the
performance of the detector and will be used to obtain physical results in
further studies.


title: A WENO-based Method of Line Transpose Approach for Vlasov Simulations

abstract:
  In this paper, a high order implicit Method of Line Transpose (MOL$^T$ )
method based on a weighted essentially non-oscillatory (WENO) methodology is
developed for one-dimensional linear transport equations and further applied to
the Vlasov-Poisson (VP) simulations via dimensional splitting. In the MOL$^T$
framework, the time variable is first discretized by a diagonally implicit
strong-stability-preserving Runge-Kutta method, resulting in a boundary value
problem (BVP) at the discrete time levels. Then an integral formulation coupled
with a high order WENO methodology is employed to solve the BVP. As a result,
the proposed scheme is high order accurate in both space and time and free of
oscillations even though the solution is discontinuous or has sharp gradients.
Moreover, the scheme is able to take larger time step evolution compared with
an explicit MOL WENO scheme with the same order of accuracy. The desired
positivity-preserving (PP) property of the scheme is further attained by
incorporating a newly proposed high order PP limiter. We perform numerical
experiments on several benchmarks including linear advection, solid body
rotation problem; and on the Landau damping, two-stream instabilities,
bump-on-tail, and plasma sheath by solving the VP system. The efficacy and
efficiency of the proposed scheme is numerically verified.


title: Local integrands for two-loop QCD amplitudes

abstract:
  In this talk we review the recent computation of the five- and six-gluon
two-loop amplitudes in Yang-Mills theory using local integrands which make the
infrared pole structure manifest. We make some remarks on the connection with
BCJ relations and the all-multiplicity structure.


title:
Hamburger Sternwarte plate archives: Historic long-term variability
  study of active galaxies based on digitized photographic plates

abstract:
  At the Hamburger Sternwarte an effort was started in 2010 with the aim of
digitizing its more than 45000 photographic plates and films stored in its
plate archives. At the time of writing, more than 31000 plates have already
been made available on the Internet for researchers, historians, as well as for
the interested public. The digitization process and the Internet presentation
of the plates and accompanying hand written material (plate envelopes,
logbooks, observer notes) are presented here. To fully exploit the unique
photometric and astrometric data, stored on the plates, further processing
steps are required including registering the plate to celestial coordinates,
masking of the plates, and a calibration of the photo-emulsion darkening curve.
To demonstrate the correct functioning of these procedures, historical light
curves of two bright BL Lac type active galactic nuclei are extracted. The
resulting light curve of the blazar 1ES 1215+303 exhibits a large decrease in
the magnitude from $14.25^{+0.07}_{-0.12}$ to $15.94^{+0.09}_{-0.13}$ in about
300 days, which proves the variability in the optical region. Furthermore, we
compare the measured magnitudes for the quasar 3C~273 with contemporaneous
measurements.


title: Notes on S-folds and $\mathcal{N}=3$ theories

abstract:
  We consider D3 branes in presence of an S-fold plane. The latter is a non
perturbative object, arising from the combined projection of an S-duality twist
and a discrete orbifold of the R-symmetry group. This construction naively
gives rise to 4d $\mathcal{N}=3$ SCFTs. Nevertheless it has been observed that
in some cases supersymmetry is enhanced to $\mathcal{N}=4$. In this paper we
study the explicit counting of degrees of freedom arising from vector
multiplets associated to strings suspended between the D3 branes probing the
S-fold. We propose that, for trivial discrete torsion, there is no vector
multiplet associated to $(1,0)$ strings stretched between a brane and its
image. We then focus on the case of rank 2 $\mathcal{N}=3$ theory that enhances
to $SU(3)$ $\mathcal{N}=4$ SYM, explicitly spelling out the isomorphism between
the BPS-spectrum of the manifestly $\mathcal{N}=3$ theory and that of three D3
branes in flat spacetime. Subsequently, we consider 3-pronged strings in these
setups and show how wall-crossing in the S-fold background implies wall
crossing in the flat geometry. This can be considered a consistency check of
the \emph{conjectured} SUSY enhancement. We also find that the above
isomorphism implies that a $(1,0)$ string, suspended between a brane and its
image in the S-fold, corresponds to a 3-string junction in the flat geometry.
This is in agreement with our claim on the absence of a vector multiplet
associated to such $(1,0)$ strings. This is because the 3-string junction in
flat geometry gives rise to a $1/4$-th BPS multiplet of the $\mathcal{N}=4$
algebra. Such multiplets always include particles with spin $>1$ as opposed to
a vector multiplet which is restricted by the requirement that the spins must
be $\leq 1$.


title: HOMFLY-PT homology for general link diagrams and braidlike isotopy

abstract:
  Khovanov and Rozansky's categorification of the HOMFLY-PT polynomial is
invariant under braidlike isotopies for any link diagram and Markov moves for
braid closures. To define HOMFLY-PT homology, they required a link to be
presented as a braid closure, because they did not prove invariance under the
other oriented Reidemeister moves. In this text we prove that the Reidemeister
IIb move fails in HOMFLY-PT homology by using virtual crossing filtrations of
the author and Rozansky. The decategorification of HOMFLY-PT homology for
general link diagrams gives a deformed version of the HOMFLY-PT polynomial,
$P^{b}(D)$, which can be used to detect nonbraidlike isotopies. Finally, we
will use $P^{b}(D)$ to prove that HOMFLY-PT homology is not an invariant of
virtual links, even when virtual links are presented as virtual braid closures.


title:
A multilevel framework for sparse optimization with application to
  inverse covariance estimation and logistic regression

abstract:
  Solving l1 regularized optimization problems is common in the fields of
computational biology, signal processing and machine learning. Such l1
regularization is utilized to find sparse minimizers of convex functions. A
well-known example is the LASSO problem, where the l1 norm regularizes a
quadratic function. A multilevel framework is presented for solving such l1
regularized sparse optimization problems efficiently. We take advantage of the
expected sparseness of the solution, and create a hierarchy of problems of
similar type, which is traversed in order to accelerate the optimization
process. This framework is applied for solving two problems: (1) the sparse
inverse covariance estimation problem, and (2) l1-regularized logistic
regression. In the first problem, the inverse of an unknown covariance matrix
of a multivariate normal distribution is estimated, under the assumption that
it is sparse. To this end, an l1 regularized log-determinant optimization
problem needs to be solved. This task is challenging especially for large-scale
datasets, due to time and memory limitations. In the second problem, the
l1-regularization is added to the logistic regression classification objective
to reduce overfitting to the data and obtain a sparse model. Numerical
experiments demonstrate the efficiency of the multilevel framework in
accelerating existing iterative solvers for both of these problems.


title:
Influences of transversely-isotropic rheology and translational
  diffusion on the stability of active suspensions

abstract:
  Suspensions of self-motile, elongated particles are a topic of significant
current interest, exemplifying a form of `active matter'. Examples include
self-propelling bacteria, algae and sperm, and artificial swimmers. Ericksen's
model of a transversely-isotropic fluid [J. L. Ericksen, Colloid Polym. Sci.
173(2):117-122 (1960)] treats suspensions of non-motile particles as a
continuum with an evolving preferred direction; this model describes fibrous
materials as diverse as extracellular matrix, textile tufts and plant cell
walls. Director-dependent effects are incorporated through a modified stress
tensor with four viscosity-like parameters. By making fundamental connections
with recent models for active suspensions, we propose a modification to
Ericksen's model, mainly the inclusion of self motility; this can be considered
the simplest description of an oriented suspension including
transversely-isotropic effects. Motivated by the fact that
transversely-isotropic fluids exhibit modified flow stability, we conduct a
linear stability analysis of two distinct cases, aligned and isotropic
suspensions of elongated active particles. Novel aspects include the
anisotropic rheology and translational diffusion. In general anisotropic
effects increase the instability of small perturbations, whilst translational
diffusion stabilises a range of wave-directions and, in some cases, a finite
range of wave-numbers, thus emphasising that both anisotropy and translational
diffusion can have important effects in these systems.


title:
Phosphorene as an Anode Material for High Performance Lithium-Ion
  Battery: First Principle Study and Experimental Measurement

abstract:
  The prospects of phosphorene as an anode material for high performance Li-ion
battery was systematically investigated from the first principle calculations
and experimental measurements. The diffusion energy barriers of a Li atom
moving along various orientations on phosphorene layer were calculated from the
Li adsorption energy landscape. It was found that the diffusion mobility of a
Li atom along the zigzag direction in the valley of phosphorene could be about
7 to 11 orders of magnitude faster than that along the other directions,
indicating its ultrafast and anisotropic diffusivity. The lithium insertion in
phosphorene was studied considering various LinP16 configurations (n=1~16). It
was found that phosphorene could accommodate up to one Li per P atom (i.e.,
Li16P16), and the predicted theoretical value of the Li capacity for a single
layered phosphorene can reach about 865 mAh/g. Our experimental measurement on
the Li capacity for a network of a few layered phosphorene can reach a
reversible stable value of ~ 453 mAh/g even after 50 cycles. In particular, it
was found that, even at the high Li concentration (e.g., x = 1 in LixP), there
was no Li clustering and the structure of phosphorene is reversible during the
lithium intercalation. Our results clearly show that phosphorene has promise as
a novel anode material for high performance Li-ion batteries.


title: The Evolution of Sex through the Baldwin Effect

abstract:
  This paper suggests that the fundamental haploid-diploid cycle of eukaryotic
sex exploits a rudimentary form of the Baldwin effect. With this explanation
for the basic cycle, the other associated phenomena can be explained as
evolution tuning the amount and frequency of learning experienced by an
organism. Using the well-known NK model of fitness landscapes it is shown that
varying landscape ruggedness varies the benefit of the haploid-diploid cycle,
whether based upon endomitosis or syngamy. The utility of pre-meiotic doubling
and recombination during the cycle are also shown to vary with landscape
ruggedness. This view is suggested as underpinning, rather than contradicting,
many existing explanations for sex.


title: Quantum smoothing for classical mixtures

abstract:
  In quantum mechanics, wave functions and density matrices represent our
knowledge about a quantum system and give probabilities for the outcomes of
measurements. If the combined dynamics and measurements on a system lead to a
density matrix $\rho(t)$ with only diagonal elements in a given basis
$\{|n\rangle\}$, it may be treated as a classical mixture, i.e., a system which
randomly occupies the basis states $|n\rangle$ with probabilities
$\rho_{nn}(t)$. Fully equivalent to so-called smoothing in classical
probability theory, subsequent probing of the occupation of the states
$|n\rangle$ improves our ability to retrodict what was the outcome of a
projective state measurement at time $t$. Here, we show with experiments on a
superconducting qubit that the smoothed probabilities do not, in the same way
as the diagonal elements of $\rho$, permit a classical mixture interpretation
of the state of the system at the past time $t$.


title:
Probing Intergalactic Magnetic Fields with Simulations of
  Electromagnetic Cascades

abstract:
  We determine the effect of intergalactic magnetic fields on the distribution
of high energy gamma rays by performing three-dimensional Monte Carlo
simulations of the development of gamma-ray-induced electromagnetic cascades in
the magnetized intergalactic medium. We employ the so-called 'Large Sphere
Observer' method to efficiently simulate blazar gamma ray halos. We study
magnetic fields with a Batchelor spectrum and with maximal left- and
right-handed helicities. We also consider the case of sources whose jets are
tilted with respect to the line of sight. We verify the formation of extended
gamma ray halos around the source direction, and observe spiral-like patterns
if the magnetic field is helical. We apply the $Q$-statistics to the simulated
halos to extract their spiral nature and also propose an alternative method,
the $S$-statistics. Both methods provide a quantative way to infer the helicity
of the intervening magnetic fields from the morphology of individual blazar
halos for magnetic field strengths $B \gtrsim 10^{-15}\,{\rm G}$ and magnetic
coherence lengths $L_{\rm c} \gtrsim 100\,{\rm Mpc}$. We show that the
$S$-statistics has a better performance than the $Q$-statistics when assessing
magnetic helicity from the simulated halos.


title: Formal Definition of QoE Metrics

abstract:
  This technical report formally defines the QoE metrics which are introduced
and discussed in the article "QoE Beyond the MOS: An In-Depth Look at QoE via
Better Metrics and their Relation to MOS" by Tobias Ho{\ss}feld, Poul E.
Heegaard, Martin Varela, Sebastian M\"oller, accepted for publication in the
Springer journal "Quality and User Experience". Matlab scripts for computing
the QoE metrics for given data sets are available in GitHub.


title:
HATS-19b, HATS-20b, HATS-21b: Three Transiting Hot-Saturns Discovered by
  the HATSouth Survey

abstract:
  We report the discovery by the HATSouth exoplanet survey of three hot-Saturn
transiting exoplanets: HATS-19b, HATS-20b, and HATS-21b. The planet host
HATS-19 is a slightly evolved V = 13.0 G0 star with [Fe/H] = 0.240, a mass of
1.303 Msun, and a radius of 1.75 Rsun. HATS-19b is in an eccentric orbit (e =
0.30) around this star with an orbital period of 4.5697 days and has a mass of
0.427 Mjup and a highly inflated radius of 1.66 Rjup. The planet HATS-20b has a
Saturn-like mass and radius of 0.273 Mjup and 0.776 Rjup respectively. It
orbits the V = 13.8 G9V star HATS-20 (Ms = 0.910 Msun; Rs = 0.892 Rsun) with a
period of 3.7993 days. Finally, HATS-21 is a V = 12.2 G4V star with [Fe/H] =
0.300, a mass of 1.080 Msun, and a radius of 1.021 Rsun. Its accompanying
planet HATS-21b has a 3.5544-day orbital period, a mass of 0.332 Mjup, and a
moderately inflated radius of 1.123 Rjup. With the addition of these three very
different planets to the growing sample of hot-Saturns, we re-examine the
relations between the observed giant planet radii, stellar irradiation, and
host metallicity. We find a significant positive correlation between planet
equilibrium temperature and radius, and a weak negative correlation between
host metallicity and radius. To assess the relative influence of various
physical parameters on observed planet radii, we train and fit models using
Random Forest regression. We find that for hot-Saturns (0.1 < Mp < 0.5 Mjup),
the planetary mass and equilibrium temperature play dominant roles in
determining radii. For hot-Jupiters (0.5 < Mp < 2.0 Mjup), the most important
parameter is equilibrium temperature alone. Finally, for irradiated higher-mass
planets (Mp > 2.0 Mjup), we find that equilibrium temperature dominates in
influence, with smaller contributions from planet mass and host metallicity.


title:
Rotationally-Driven Fragmentation for the Formation of the Binary
  Protostellar System L1551 IRS 5

abstract:
  Either bulk rotation or local turbulence is widely invoked to drive
fragmentation in collapsing cores so as to produce multiple star systems. Even
when the two mechanisms predict different manners in which the stellar spins
and orbits are aligned, subsequent internal or external interactions can drive
multiple systems towards or away from alignment thus masking their formation
process. Here, we demonstrate that the geometrical and dynamical relationship
between the binary system and its surrounding bulk envelope provide the crucial
distinction between fragmentation models. We find that the circumstellar disks
of the binary protostellar system L1551 IRS 5 are closely parallel not just
with each other but also with their surrounding flattened envelope.
Measurements of the relative proper motion of the binary components spanning
nearly 30 yr indicate an orbital motion in the same sense as the envelope
rotation. Eliminating orbital solutions whereby the circumstellar disks would
be tidally truncated to sizes smaller than are observed, the remaining
solutions favor a circular or low-eccentricity orbit tilted by up to
$\sim$25$^\circ$ from the circumstellar disks. Turbulence-driven fragmentation
can generate local angular momentum to produce a coplanar binary system, but
which bears no particular relationship with its surrounding envelope. Instead,
the observed properties conform with predictions for rotationally-driven
fragmentation. If the fragments were produced at different heights or on
opposite sides of the midplane in the flattened central region of a rotating
core, the resulting protostars would then exhibit circumstellar disks parallel
with the surrounding envelope but tilted from the orbital plane as is observed.


title: Finite-energy pseudoholomorphic planes with multiple asymptotic limits

abstract:
  It's known from from work of Hofer, Wysocki, and Zehnder [1996] and Bourgeois
[2002] that in a contact manifold equipped with either a nondegenerate or
Morse-Bott contact form, a finite-energy pseudoholomorphic curve will be
asymptotic at each of its non removable punctures to a single periodic orbit of
the Reeb vector field and that the convergence is exponential. We provide
examples here to show that this need not be the case if the contact form is
degenerate. More specifically, we show that on any contact manifold $(M, \xi)$
with cooriented contact structure one can choose a contact form $\lambda$ with
$\ker\lambda=\xi$ and a compatible complex structure $J$ on $\xi$ so that for
the associated $\mathbb{R}$-invariant almost complex structure $\tilde J$ on
$\mathbb{R}\times M$ there exist families of embedded finite-energy $\tilde
J$-holomorphic cylinders and planes having embedded tori as limit sets.


title:
Permutation Invariant Training of Deep Models for Speaker-Independent
  Multi-talker Speech Separation

abstract:
  We propose a novel deep learning model, which supports permutation invariant
training (PIT), for speaker independent multi-talker speech separation,
commonly known as the cocktail-party problem. Different from most of the prior
arts that treat speech separation as a multi-class regression problem and the
deep clustering technique that considers it a segmentation (or clustering)
problem, our model optimizes for the separation regression error, ignoring the
order of mixing sources. This strategy cleverly solves the long-lasting label
permutation problem that has prevented progress on deep learning based
techniques for speech separation. Experiments on the equal-energy mixing setup
of a Danish corpus confirms the effectiveness of PIT. We believe improvements
built upon PIT can eventually solve the cocktail-party problem and enable
real-world adoption of, e.g., automatic meeting transcription and multi-party
human-computer interaction, where overlapping speech is common.


title: Evaluating linear response in active systems with no perturbing field

abstract:
  We present a method for the evaluation of time-dependent linear response
functions for systems of active Ornstein-Uhlenbeck particles from unperturbed
simulations. The method is inspired by the Malliavin weights sampling method
proposed by Warren and Allen [Phys. Rev. Lett. 109, 250601 (2012)] for systems
of Brownian particles. We illustrate our method by evaluating a linear response
function for a single active particle in an external harmonic potential. As an
application, we calculate the time-dependent mobility function and an effective
temperature, defined through the Einstein relation between the self-diffusion
and mobility coefficients, for a system of active particles interacting via a
screened-Coulomb potential. We find that this effective temperature decreases
with increasing persistence time of the self-propulsion. Initially, for not too
large persistence times, it changes rather slowly, but then it decreases
markedly when the persistence length of the self-propelled motion becomes
comparable with the particle size.


title:
The field and Killing spinor equations of M-theory and type IIA/IIB
  supergravity in coordinate-free notation

abstract:
  We review the actions of the supergravity theory in eleven dimensions as well
as the type IIA and IIB supergravities in ten dimensions and derive the bosonic
equations of motion in a coordinate-free notation. We also consider the
existence of supersymmetries and the associated generalized Killing spinor
equations. The aim of this note is to serve as a formulary and make the
equations of supergravity more easily accessible to mathematicians.


title: Amenability of coarse spaces and K-algebras

abstract:
  In this article we analyze the notions of amenability and paradoxical
decomposition from an algebraic perspective. We consider this dichotomy for
locally finite extended metric spaces and for general algebras over commutative
fields. In the context of algebras we also study the relation of amenability
with proper infiniteness. We apply our general analysis to two important
classes of algebras: the unital Leavitt path algebras and the translation
algebras on locally finite extended metric spaces. In particular, we show that
the amenability of a metric space is equivalent to the algebraic amenability of
the corresponding translation algebra.


title:
Proactive Location-Based Scheduling of Delay-Constrained Traffic Over
  Fading Channels

abstract:
  In this paper, proactive resource allocation based on user location for
point-to-point communication over fading channels is introduced, whereby the
source must transmit a packet when the user requests it within a deadline of a
single time slot. We introduce a prediction model in which the source predicts
the request arrival $T_p$ slots ahead, where $T_p$ denotes the prediction
window (PW) size. The source allocates energy to transmit some bits proactively
for each time slot of the PW with the objective of reducing the transmission
energy over the non-predictive case. The requests are predicted based on the
user location utilizing the prior statistics about the user requests at each
location. We also assume that the prediction is not perfect. We propose
proactive scheduling policies to minimize the expected energy consumption
required to transmit the requested packets under two different assumptions on
the channel state information at the source. In the first scenario, offline
scheduling, we assume the channel states are known a-priori at the source at
the beginning of the PW. In the second scenario, online scheduling, it is
assumed that the source has causal knowledge of the channel state. Numerical
results are presented showing the gains achieved by using proactive scheduling
policies compared with classical (reactive) networks. Simulation results also
show that increasing the PW size leads to a significant reduction in the
consumed transmission energy even with imperfect prediction.


title: Beyond LCDM: Bits join the Dark Side

abstract:
  We are encouraged to look beyond LambdaCDM as there are no satisfactory
explanations for dark energy or dark matter. An evidence based approach applies
two foundational principles of information theory to show dark energy and dark
matter may be Holographic Dark Information Energy, HDIE. HDIE explains many
effects attributed separately to Lambda and CDM. HDIE mimics Lambda with
sufficient energy and an equation of state parameter, w= -1.03+-0.05 at
redshifts z<1.35 to account for accelerating expansion. HDIE is clumped around
galaxies at densities that distort space-time, explaining many CDM attributed
effects. The present ratio of HDIE:baryons ~2.15, required for observed
expansion history, is equivalent to a dark matter fraction ~68%, consistent
with several galaxy surveys. The HDIE/baryon model is based largely on proven
physics, provides a common explanation for dark energy and dark matter, and
solves the cosmological coincidence problem. At earlier times, z > ~1.35, HDIE
was phantom, w = -1.82+-0.08, enabling the model to be falsified. HDIE fits
Planck dark energy wo-wa plots at least as well as Lambda, and is consistent
with other results that suggest dark energy was phantom at earlier times. A new
w-parameterisation is proposed, as the usual CPL parameterisation is unsuitable
for distinguishing between HDIE/baryon and LambdaCDM models.


title: Machine-based Multimodal Pain Assessment Tool for Infants: A Review

abstract:
  Bedside caregivers assess infants' pain at constant intervals by observing
specific behavioral and physiological signs of pain. This standard has two main
limitations. The first limitation is the intermittent assessment of pain, which
might lead to missing pain when the infants are left unattended. Second, it is
inconsistent since it depends on the observer's subjective judgment and differs
between observers. The intermittent and inconsistent assessment can induce poor
treatment and, therefore, cause serious long-term consequences. To mitigate
these limitations, the current standard can be augmented by an automated system
that monitors infants continuously and provides quantitative and consistent
assessment of pain. Several automated methods have been introduced to assess
infants' pain automatically based on analysis of behavioral or physiological
pain indicators. This paper comprehensively reviews the automated approaches
(i.e., approaches to feature extraction) for analyzing infants' pain and the
current efforts in automatic pain recognition. In addition, it reviews the
databases available to the research community and discusses the current
limitations of the automated pain assessment.


title:
Short-Pulse Amplification by Strongly-Coupled Stimulated Brillouin
  Scattering

abstract:
  We examine the feasibility of strongly-coupled stimulated Brillouin
scattering as a mechanism for the plasma-based amplification of sub-picosecond
pulses. In particular, we use fluid theory and particle-in-cell simulations to
compare the relative advantages of Raman and Brillouin amplification over a
broad range of achievable parameters.


title:
On SPDE and backward filtering equations for SDE systems (direct
  approach)

abstract:
  A direct approach to linear backward filtering equations for SDE systems is
proposed. This preprint is a corrected version of the paper 1995 in the LMS
Lecture Notes combined with another paper by the author on the direct approach
to linear SPDEs for SDEs.


title: Massive scalar field evolution in de Sitter

abstract:
  The behaviour of a massive, non-interacting and non-minimally coupled
quantised scalar field in an expanding de Sitter background is investigated by
solving the field evolution for an arbitrary initial state. In this approach
there is no need to choose a vacuum in order to provide a definition for
particle states. We conclude that the expanding de Sitter space is a stable
equilibrium configuration under small perturbations of the initial conditions.
Depending on the initial state, the energy density can approach its asymptotic
value from above or below, the latter of which implies a violation of the weak
energy condition. The backreaction of the quantum corrections can therefore
lead to a phase of super-acceleration also in the non-interacting massive case.


title:
Understanding the pseudocapacitance of RuO2 from joint density
  functional theory

abstract:
  Pseudocapacitors have been experimentally studied for many years in electric
energy storage. However, first principles understanding of the pseudocapacitive
behavior is still not satisfactory due to the complexity involved in modeling
electrochemistry. In this paper, we applied a novel simulation technique called
Joint Density Functional Theory (JDFT) to simulate the pseudocapacitive
behavior of RuO2, a prototypical material, in a model electrolyte. We obtained
from JDFT a capacitive curve which showed a redox peak position comparable to
that in the experimental cyclic voltammetry (CV) curve. We found that the
experimental turning point from double-layer to pseudocapacitive charge storage
at low scan rates could be explained by the hydrogen adsorption at low
coverage. As the electrode voltage becomes more negative, H coverage increases
and causes the surface structure change, leading to bended OH bonds at the
on-top oxygen atoms and large capacitance. This H coverage-dependent
capacitance can explain the high pseudocapacitance of hydrous RuO2. Our work
here provides a first principles understanding of the pseudocapacitance for
RuO2 in particular and for transition-metal oxides in general.


title:
Two problems from the Polishchuk and Positselski book on Quadratic
  algebras

abstract:
  In the book 'Quadratic algebras' by Polishchuk and Positselski [23] algebras
with a small number of generators (n=2,3) are considered. For some number r of
relations possible Hilbert series are listed, and those appearing as series of
Koszul algebras are specified. The first case, where it was not possible to do,
namely the case of three generators n=3 and six relations r=6 is formulated as
an open problem. We give here a complete answer to this question, namely for
quadratic algebras with dim A_1=dim A_2=3, we list all possible Hilbert series,
and find out which of them can come from Koszul algebras, and which can not.
  As a consequence of this classification, we found an algebra, which serves as
a counterexample to another problem from the same book [23] (Chapter 7, Sec. 1,
Conjecture 2), saying that Koszul algebra of finite global homological
dimension d has dim A_1 >= d. Namely, the 3-generated algebra A given by
relations xx+yx=xz=zy=0 is Koszul and its Koszul dual algebra A^! has Hilbert
series of degree 4: H_{A^!}(t)= 1+3t+3t^2+2t^3+t^4, hence A has global
homological dimension 4.


title: Late Time Emission of Prompt Fission Gamma Rays

abstract:
  The emission of prompt fission $\gamma$ rays within a few nanoseconds to a
few microseconds following the scission point is studied in the Hauser-Feshbach
formalism applied to the deexcitation of primary excited fission fragments.
Neutron and $\gamma$-ray evaporations from fully accelerated fission fragments
are calculated in competition at each stage of the decay, and the role of
isomers in the fission products, before $\beta$-decay, is analyzed. The time
evolution of the average total $\gamma$-ray energy, average total $\gamma$-ray
multiplicity, and fragment-specific $\gamma$-ray spectra, is presented in the
case of neutron-induced fission reactions of $^{235}$U and $^{239}$Pu, as well
as spontaneous fission of $^{252}$Cf. The production of specific isomeric
states is calculated and compared to available experimental data. About 7% of
all prompt fission $\gamma$ rays are predicted to be emitted between 10 nsec
and 5 $\mu$sec following fission, in the case of $^{235}$U and $^{239}$Pu
$(n_{\rm th},f)$ reactions, and up to 3% in the case of $^{252}$Cf spontaneous
fission. The cumulative average total $\gamma$-ray energy increases by 2 to 5%
in the same time interval. Finally, those results are shown to be robust
against significant changes in the model input parameters.


title:
Convergence properties of $\eta\to 3\pi$ decays in chiral perturbation
  theory

abstract:
  Theoretical efforts to describe and explain the $\eta\to 3\pi$ decays reach
far back in time. Even today, the convergence of the decay widths and some of
the Dalitz plot parameters seems problematic in low energy QCD. In the
framework of resummed CHPT, we explore the question of compatibility of
experimental data with a reasonable convergence of a carefully defined chiral
series, where NNLO remainders are assumed to be small. By treating the
uncertainties in the higher orders statistically, we numerically generate a
large set of theoretical predictions, which are then confronted with
experimental information. In the case of the decay widths, the experimental
values can be reconstructed for a reasonable range of the free parameters and
thus no tension is observed, in spite of what some of the traditional
calculations suggest. The Dalitz plot parameters $a$ and $d$ can be described
very well too. When the parameters $b$ and $\alpha$ are concerned, we find a
mild tension for the whole range of the free parameters, at less than 2$\sigma$
C.L. This can be interpreted in two ways - either some of the higher order
corrections are indeed unexpectedly large or there is a specific configuration
of the remainders, which is, however, not completely improbable. Also, the
distribution of the theoretical uncertainties is found to be significantly
non-gaussian, so the consistency cannot be simply judged by the 1$\sigma$ error
bars.


title: Orbit Portraits in non-Autonomous Iteration

abstract:
  We extend the definition of an orbit portrait to the context of
non-autonomous iteration, both for the combinatorial version involving
collections of angles and for the dynamic version involving external rays where
combinatorial portraits can be realized by the dynamics associated with
sequences of polynomials with suitably uniformly bounded degrees and
coefficients. We show that, in the case of sequences of polynomials of constant
degree, the portraits which arise are eventually periodic which is somewhat
similar to the classical theory of polynomial iteration. However, if the
degrees of the polynomials in the sequence are allowed to vary, one can obtain
portraits with complementary arcs of irrational length which are fundamentally
different from the classical ones.


title: Elastic Graphs

abstract:
  An elastic graph is a graph with an elasticity associated to each edge. It
may be viewed as a network made out of ideal rubber bands. If the rubber bands
are stretched on a target space there is an elastic energy. We characterize
when a homotopy class of maps from one elastic graph to another is loosening,
i.e., decreases this elastic energy for all possible targets. This fits into a
more general framework of energies for maps between graphs.


title:
Role of spin-transfer torques on synchronization and resonance phenomena
  in stochastic magnetic oscillators

abstract:
  A theoretical study on how synchronization and resonance-like phenomena in
superparamagnetic tunnel junctions can be driven by spin-transfer torques is
presented. We examine the magnetization of a superparamagnetic free layer that
reverses randomly between two well-defined orientations due to thermal
fluctuations, acting as a stochastic oscillator. When subject to an external ac
forcing this system can present stochastic resonance and noise-enhanced
synchronization. We focus on the roles of the mutually perpendicular
damping-like and field-like torques, showing that the response of the system is
very different at low and high-frequencies. We also demonstrate that the
field-like torque can increase the efficiency of the current-driven forcing,
specially at sub-threshold electric currents. These results can be useful for
possible low-power, more energy efficient, applications.


title: Beyond the standard gauging: gauge symmetries of Dirac Sigma Models

abstract:
  In this paper we study the general conditions that have to be met for a
gauged extension of a two-dimensional bosonic sigma-model to exist. In an
inversion of the usual approach of identifying a global symmetry and then
promoting it to a local one, we focus directly on the gauge symmetries of the
theory. This allows for action functionals which are gauge invariant for rather
general background fields in the sense that their invariance conditions are
milder than the usual case. In particular, the vector fields that control the
gauging need not be Killing. The relaxation of isometry for the background
fields is controlled by two connections on a Lie algebroid L in which the gauge
fields take values, in a generalization of the common Lie-algebraic picture.
Here we show that these connections can always be determined when L is a Dirac
structure in the H-twisted Courant algebroid. This also leads us to a
derivation of the general form for the gauge symmetries of a wide class of
two-dimensional topological field theories called Dirac sigma-models, which
interpolate between the G/G Wess-Zumino-Witten model and the (Wess-Zumino-term
twisted) Poisson sigma model.


title:
NuSTAR Observations of the Black Hole GS 1354-645: Evidence of Rapid
  Black Hole Spin

abstract:
  We present the results of a NuSTAR study of the dynamically confirmed
stellar-mass black hole GS 1354-645. The source was observed during its 2015
"hard" state outburst; we concentrate on spectra from two relatively bright
phases. In the higher-flux observation, the broadband NuSTAR spectra reveal a
clear, strong disk reflection spectrum, blurred by a degree that requires a
black hole spin of a = cJ/GM^2 > 0.98 (1 sigma statistical limits only). The
fits also require a high inclination: theta = 75(2) degrees. Strong "dips" are
sometimes observed in the X-ray light curves of sources viewed at such an
angle; these are absent, perhaps indicating that dips correspond to flared disk
structures that only manifest at higher accretion rates. In the lower-flux
observation, there is evidence of radial truncation of the thin accretion disk.
We discuss these results in the context of spin in stellar-mass black holes,
and inner accretion flow geometries at moderate accretion rates.


title:
Today a Duo, But Once a Trio? The Double White Dwarf HS 2220$+$2146 May
  Be A Post-Blue Straggler Binary

abstract:
  For sufficiently wide orbital separations {\it a}, the two members of a
stellar binary evolve independently. This implies that in a wide double white
dwarf (DWD), the more massive WD should always be produced first, when its more
massive progenitor ends its main-sequence life, and should therefore be older
and cooler than its companion. The bound, wide DWD HS 2220$+$2146
($a\approx500$ AU) does not conform to this picture: the more massive WD is the
younger, hotter of the pair. We show that this discrepancy is unlikely to be
due to past mass-transfer phases or to the presence of an unresolved companion.
Instead, we propose that HS 2220$+$2146 formed through a new wide DWD
evolutionary channel involving the merger of the inner binary in a hierarchical
triple system. The resulting blue straggler and its wide companion then evolved
independently, forming the WD pair seen today. Although we cannot rule out
other scenarios, the most likely formation channel has the inner binary merging
while both stars are still on the main sequence. This provides us with the
tantalizing possibility that Kozai-Lidov oscillations may have played a role in
the inner binary's merger. {\it Gaia} may uncover hundreds more wide DWDs,
leading to the identification of other systems like HS 2220$+$2146. There are
already indications that other WD systems may have been formed through
different, but related, hierarchical triple evolutionary scenarios.
Characterizing these populations may allow for thorough testing of the
efficiency with which KL oscillations induce stellar mergers.


title: Convergence Rate of Frank-Wolfe for Non-Convex Objectives

abstract:
  We give a simple proof that the Frank-Wolfe algorithm obtains a stationary
point at a rate of $O(1/\sqrt{t})$ on non-convex objectives with a Lipschitz
continuous gradient. Our analysis is affine invariant and is the first, to the
best of our knowledge, giving a similar rate to what was already proven for
projected gradient methods (though on slightly different measures of
stationarity).


title: Distributed-memory Hierarchical Interpolative Factorization

abstract:
  The hierarchical interpolative factorization (HIF) offers an efficient way
for solving or preconditioning elliptic partial differential equations. By
exploiting locality and low-rank properties of the operators, the HIF achieves
quasi-linear complexity for factorizing the discrete positive definite elliptic
operator and linear complexity for solving the associated linear system. In
this paper, the distributed-memory HIF (DHIF) is introduced as a parallel and
distributed-memory implementation of the HIF. The DHIF organizes the processes
in a hierarchical structure and keep the communication as local as possible.
The computation complexity is $O\left(\frac{N\log N}{P}\right)$ and
$O\left(\frac{N}{P}\right)$ for constructing and applying the DHIF,
respectively, where $N$ is the size of the problem and $P$ is the number of
processes. The communication complexity is $O\left(\sqrt{P}\log^3
P\right)\alpha + O\left(\frac{N^{2/3}}{\sqrt{P}}\right)\beta$ where $\alpha$ is
the latency and $\beta$ is the inverse bandwidth. Extensive numerical examples
are performed on the NERSC Edison system with up to 8192 processes. The
numerical results agree with the complexity analysis and demonstrate the
efficiency and scalability of the DHIF.


title:
Colorful simplicial depth, Minkowski sums, and generalized Gale
  transforms

abstract:
  The colorful simplicial depth of a collection of d+1 finite sets of points in
Euclidean d-space is the number of choices of a point from each set such that
the origin is contained in their convex hull. We use methods from combinatorial
topology to prove a tight upper bound on the colorful simplicial depth. This
implies a conjecture of Deza et al. (2006). Furthermore, we introduce colorful
Gale transforms as a bridge between colorful configurations and Minkowski sums.
Our colorful upper bound then yields a tight upper bound on the number of
totally mixed facets of certain Minkowski sums of simplices. This resolves a
conjecture of Burton (2003) in the theory of normal surfaces.


title:
Gauged B-L Number and Neutron--Antineutron Oscillation: Long-range
  Forces Mediated by Baryophotons

abstract:
  Transformation of neutron to antineutron is a small effect that has not yet
been experimentally observed. %\cite{Phillips:2014fgb}. In principle, it can
occur with free neutrons in the vacuum or with bound neutrons inside the
nuclear environment different for neutrons and antineutrons and for that reason
in the latter case it is heavily suppressed. Free neutron transformation also
can be suppressed if environmental vector field exists destinguishing neutron
from antineutron. We consider here the case of a vector field coupled to $B-L$
charge of the particles ($B-L$ photons) and study a possibility of this to lead
to the observable suppression of neutron to antineutron transformation. The
suppression effect however can be removed by applying external magnetic field.
If the neutron--antineutron oscillation will be discovered in free neutron
oscillation experiments, this will imply limits on $B-L$ photon coupling
constant and interaction radius few order of magnitudes stronger than present
limits form the tests of the equivalence principle. If $n-\bar n$ oscillation
will be discovered via nuclear instability, but not in free neutron
oscillations in corresponding level, this would indicate to the presence of
fifth-forces mediated by such baryophotons.


title:
Painlev\'e analysis for two 1D parabolic-parabolic models of chemotaxis;
  some travelling wave solutions

abstract:
  In this paper we study the Painlev\'e analysis for two models of chemotaxis.
We find that in some cases the reductions of these models in terms of
travelling wave variable allow exact analytical solutions.


title: Quantum solvable models with nonlocal one point interactions

abstract:
  Within the framework of quantum mechanics working with one-dimensional,
manifestly non-Hermitian Hamiltonians $H=T+V$ the traditional class of the
exactly solvable models with local point interactions $V=V(x)$ is generalized.
The consequences of the use of the nonlocal point interactions such that $(V
f)(x) = \int K(x,s) f(s) ds$ are discussed using the suitably adapted formalism
of boundary triplets.


title:
A Comparison of Preconditioned Krylov Subspace Methods for Large-Scale
  Nonsymmetric Linear Systems

abstract:
  Preconditioned Krylov subspace (KSP) methods are widely used for solving
large-scale sparse linear systems arising from numerical solutions of partial
differential equations (PDEs). These linear systems are often nonsymmetric due
to the nature of the PDEs, boundary or jump conditions, or discretization
methods. While implementations of preconditioned KSP methods are usually
readily available, it is unclear to users which methods are the best for
different classes of problems. In this work, we present a comparison of some
KSP methods, including GMRES, TFQMR, BiCGSTAB, and QMRCGSTAB, coupled with
three classes of preconditioners, namely Gauss-Seidel, incomplete LU
factorization (including ILUT, ILUTP, and multilevel ILU), and algebraic
multigrid (including BoomerAMG and ML). Theoretically, we compare the
mathematical formulations and operation counts of these methods. Empirically,
we compare the convergence and serial performance for a range of benchmark
problems from numerical PDEs in 2D and 3D with up to millions of unknowns and
also assess the asymptotic complexity of the methods as the number of unknowns
increases. Our results show that GMRES tends to deliver better performance when
coupled with an effective multigrid preconditioner, but it is less competitive
with an ineffective preconditioner due to restarts. BoomerAMG with proper
choice of coarsening and interpolation techniques typically converges faster
than ML, but both may fail for ill-conditioned or saddle-point problems while
multilevel ILU tends to succeed. We also show that right preconditioning is
more desirable. This study helps establish some practical guidelines for
choosing preconditioned KSP methods and motivates the development of more
effective preconditioners.


title:
Minimizing statistical and systematic bias in transverse momentum
  correlations for relativistic heavy-ion collisions

abstract:
  Two-particle correlation measurements and analysis are an important component
of the relativistic heavy-ion physics program. In particular, particle
pair-number correlations on two-dimensional transverse momentum ($p_t$) allow
unique access to soft, semi-hard and hard-scattering processes in these
collisions. Precise measurements of this type of correlation are essential for
understanding the dynamics in heavy-ion collisions. However, transverse
momentum correlation measurements are especially vulnerable to statistical and
systematic biases. In this paper the origins of these large bias effects are
explained and mathematical correlation forms are derived from mean-$p_t$
fluctuation quantities in the literature. Monte Carlo simulations are then used
to determine the conditions, e.g. multiplicity and collision centrality bin
widths, where each correlation form is minimally biased. The ranges of
applicability for each correlation quantity are compared. Several are found to
reproduce the assumed input correlations with reasonable fidelity over a wide
range of conditions encountered in practical analysis of data.


title: To fission or not to fission

abstract:
  The fission-fragments mass-yield of 236U is obtained by an approximate
solution of the eigenvalue problem of the collective Hamiltonian that describes
the dynamics of the fission process whose degrees of freedom are: the fission
(elongation), the neck and the mass-asymmetry mode. The macroscopic-microscopic
method is used to evaluate the potential energy surface. The macroscopic energy
part is calculated using the liquid drop model and the microscopic corrections
are obtained using the Woods-Saxon single-particle levels. The four dimensional
modified Cassini ovals shape parametrization is used to describe the shape of
the fissioning nucleus. The mass tensor is taken within the cranking-type
approximation. The final fragment mass distribution is obtained by weighting
the adiabatic density distribution in the collective space with the
neck-dependent fission probability. The neck degree of freedom is found to play
a significant role in determining that final fragment mass distribution.


title: STAM: A Framework for Spatio-Temporal Affordance Maps

abstract:
  Affordances have been introduced in literature as action opportunities that
objects offer, and used in robotics to semantically represent their
interconnection. However, when considering an environment instead of an object,
the problem becomes more complex due to the dynamism of its state. To tackle
this issue, we introduce the concept of Spatio-Temporal Affordances (STA) and
Spatio-Temporal Affordance Map (STAM). Using this formalism, we encode action
semantics related to the environment to improve task execution capabilities of
an autonomous robot. We experimentally validate our approach to support the
execution of robot tasks by showing that affordances encode accurate semantics
of the environment.


title:
A note on some inequalities used in channel polarization and polar
  coding

abstract:
  We give a unified treatment of some inequalities that are used in the proofs
of channel polarization theorems involving a binary-input discrete memoryless
channel.


title:
Design of Robust, Protograph Based LDPC Codes for Rate-Adaptation via
  Probabilistic Shaping

abstract:
  In this work, the design of robust, protograph-based low-density parity-check
(LDPC) codes for rate-adaptive communication via probabilistic shaping is
considered. Recently, probabilistic amplitude shaping (PAS) by B\"ocherer et
al. has been introduced for capacity approaching and rate-adaptive
communication with a bitwise-demapper and binary decoder. Previous work by the
authors considered the optimization of protograph based LDPC codes for PAS and
specific spectral efficiencies (SEs) to jointly optimize the LDPC code node
degrees and the mapping of the coded bits to the bit-interleaved coded
modulation (BICM) bit-channels. We show that these codes tend to perform poor
when operated at other rates and propose the design of robust LDPC codes by
employing a min-max approach in the search for good protograph ensembles via
differential evolution. The considered design uses a single 16
amplitude-shift-keying (ASK) constellation and a robust 13/16 rate LDPC code to
operate between 0.7 to 2.7 bits per channel use. For a blocklength of 16224
bits and a target frame error rate of 1e-3 the proposed code operates within
1.32 dB of continuous AWGN capacity for 0.7 to 1.3 bpcu and within 1.05 dB for
1.3 bpcu to 2.7 bpcu.


title:
Triangles bridge the scales: Quantifying cellular contributions to
  tissue deformation

abstract:
  In this article, we propose a general framework to study the dynamics and
topology of cellular networks that capture the geometry of cell packings in
two-dimensional tissues. Such epithelia undergo large-scale deformation during
morphogenesis of a multicellular organism. Large-scale deformations emerge from
many individual cellular events such as cell shape changes, cell
rearrangements, cell divisions, and cell extrusions. Using a triangle-based
representation of cellular network geometry, we obtain an exact decomposition
of large-scale material deformation. Interestingly, our approach reveals
contributions of correlations between cellular rotations and elongation as well
as cellular growth and elongation to tissue deformation. Using this Triangle
Method, we discuss tissue remodeling in the developing pupal wing of the fly
Drosophila melanogaster.


title:
Investigation of thermal acoustic effects on SRF cavities within CM1 at
  Fermilab

abstract:
  Radio Frequency (RF) power studies are in progress following the cryogenic
commissioning of Cryomodule #1 (CM1) at Fermilab's Superconducting Radio
Frequency (SRF) Accelerator Test Facility. These studies are complemented by
the characterization of thermal acoustic effects on cavity microphonics
manifested by apparent noisy boiling of helium involving vapor bubble and
liquid vibration. The thermal acoustic measurements also consider pressure and
temperature spikes which drive the phenomenon at low and high frequencies.


title: Moving Toward High Precision Dynamical Modelling in Hidden Markov Models

abstract:
  Hidden Markov Model (HMM) is often regarded as the dynamical model of choice
in many fields and applications. It is also at the heart of most
state-of-the-art speech recognition systems since the 70's. However, from
Gaussian mixture models HMMs (GMM-HMM) to deep neural network HMMs (DNN-HMM),
the underlying Markovian chain of state-of-the-art models did not changed much.
The "left-to-right" topology is mostly always employed because very few other
alternatives exist. In this paper, we propose that finely-tuned HMM topologies
are essential for precise temporal modelling and that this approach should be
investigated in state-of-the-art HMM system. As such, we propose a
proof-of-concept framework for learning efficient topologies by pruning down
complex generic models. Speech recognition experiments that were conducted
indicate that complex time dependencies can be better learned by this approach
than with classical "left-to-right" models.


title: A scaled Bregman theorem with applications

abstract:
  Bregman divergences play a central role in the design and analysis of a range
of machine learning algorithms. This paper explores the use of Bregman
divergences to establish reductions between such algorithms and their analyses.
We present a new scaled isodistortion theorem involving Bregman divergences
(scaled Bregman theorem for short) which shows that certain "Bregman
distortions'" (employing a potentially non-convex generator) may be exactly
re-written as a scaled Bregman divergence computed over transformed data.
Admissible distortions include geodesic distances on curved manifolds and
projections or gauge-normalisation, while admissible data include scalars,
vectors and matrices.
  Our theorem allows one to leverage to the wealth and convenience of Bregman
divergences when analysing algorithms relying on the aforementioned Bregman
distortions. We illustrate this with three novel applications of our theorem: a
reduction from multi-class density ratio to class-probability estimation, a new
adaptive projection free yet norm-enforcing dual norm mirror descent algorithm,
and a reduction from clustering on flat manifolds to clustering on curved
manifolds. Experiments on each of these domains validate the analyses and
suggest that the scaled Bregman theorem might be a worthy addition to the
popular handful of Bregman divergence properties that have been pervasive in
machine learning.


title: MuSim, a graphical user interface for multiple simulation programs

abstract:
  MuSim is a new user-friendly program designed to interface to many different
particle simulation codes, regardless of their data formats or geometry
descriptions. It presents the user with a compelling graphical user interface
that includes a flexible 3-D view of the simulated world plus powerful editing
and drag-and-drop capabilities. All aspects of the design can be parameterized
so that parameter scans and optimizations are easy. It is simple to create
plots and display events in the 3-D viewer (with a slider to vary the
transparency of solids), allowing for an effortless comparison of different
simulation codes. Simulation codes: G4beamline 3.02 and MCNP 6.1; more are
coming. Many accelerator design tools and beam optics codes were written long
ago, with primitive user interfaces by today's standards. MuSim is specifically
designed to make it easy to interface to such codes, providing a common user
experience for all, and permitting the construction and exploration of models
with very little overhead. For today's technology-driven students, graphical
interfaces meet their expectations far better than text based tools, and
education in accelerator physics is one of our primary goals.


title: The spectrogram expansion of Wigner functions

abstract:
  Wigner functions generically attain negative values and hence are not
probability densities. We prove an asymptotic expansion of Wigner functions in
terms of Hermite spectrograms, which are probability densities. The expansion
provides exact formulas for the quantum expectations of polynomial observables.
In the high frequency regime it allows to approximate quantum expectation
values up to any order of accuracy in the high frequency parameter. We present
a Markov Chain Monte Carlo method to sample from the new densities and
illustrate our findings by numerical experiments.


title:
Using smartphone pressure sensors to measure vertical velocities of
  elevators, stairways, and drones

abstract:
  We measure the vertical velocities of elevators, pedestrians climbing stairs,
and drones (flying unmanned aerial vehicles), by means of smartphone pressure
sensors. The barometric pressure obtained with the smartphone is related to the
altitude of the device via the hydrostatic approximation. From the altitude
values, vertical velocities are derived. The approximation considered is valid
in the first hundred meters of the inner layers of the atmosphere. In addition
to pressure, acceleration values were also recorded using the built-in
accelerometer. Numerical integration was performed, obtaining both vertical
velocity and altitude. We show that data obtained using the pressure sensor is
significantly less noisy than that obtained using the accelerometer. Error
accumulation is also evident in the numerical integration of the acceleration
values. In the proposed experiments, the pressure sensor also outperforms GPS,
because this sensor does not receive satellite signals indoors and, in general,
the operating frequency is considerably lower than that of the pressure sensor.
In the cases in which it is possible, comparison with reference values taken
from the architectural plans of buildings validates the results obtained using
the pressure sensor. This proposal is ideally performed as an external or
outreach activity with students to gain insight about fundamental questions in
mechanics, fluids, and thermodynamics.


title: Quantum Gravity Effects around Sagittarius A*

abstract:
  Recent VLBI observations have resolved Sagittarius A* at horizon scales. The
Event Horizon Telescope is expected to provide increasingly good images of the
region around the Schwarzschild radius $r_S$ of Sgr A* soon. A number of
authors have recently pointed out the possibility that non-perturbative quantum
gravitational phenomena could affect the space surrounding a black hole. Here
we point out that the existence of a region around $\frac76 r_S$ where these
effects should be maximal.


title: Exploring new horizons of the Gribov problem in Yang-Mills theories

abstract:
  The understanding of the non-perturbative regime of YM theories remains a
challenging open problem in theoretical physics. Notably, a satisfactory
description of the confinement of gluons is not at our disposal so far. In this
thesis, the RGZ framework, designed to provide a proper quantization of YM
theories by taking into account the existence of the so-called Gribov copies is
explored. Successfully introduced in the Landau gauge, the RGZ set up does not
extend easily to different gauges. The main reason is that a clear formulation
of the analogue of the Gribov horizon in the Landau gauge is obstructed by
technical difficulties when more sophisticated gauges are chosen. Moreover, the
RGZ action breaks BRST symmetry explicitly, making the task of extracting gauge
invariant results even more difficult. The main goal of the present thesis is
precisely to provide a consistent framework to extend the RGZ action to gauges
that are connected to Landau gauge via a gauge parameter. Our main result is
the reformulation of the theory in the Landau gauge with appropriate variables
such that a non-perturbative BRST symmetry is constructed. This symmetry
corresponds to a deformation of the standard BRST symmetry by taking into
account non-perturbative effects. This opens a toolbox which allow us to
explore what would be the Gribov horizon in different gauges as linear
covariant and Curci-Ferrari gauges. Consistency with gauge independence of
physical quantities as well as the computation of the gluon propagator in these
gauges is provided. Remarkably, when lattice or functional methods results are
available, we verify very good agreement with our analytical proposal giving
support that it could provide some insights about the non-perturbative regime
of YM theories. A positivity violating gluon propagator in the infrared seems
to be a general feature of the formalism.


title:
Gradient of the Value Function in Parametric Convex Optimization
  Problems

abstract:
  We investigate the computation of the gradient of the value function in
parametric convex optimization problems. We derive general expression for the
gradient of the value function in terms of the cost function, constraints and
Lagrange multipliers. In particular, we show that for the strictly convex
parametric quadratic program the value function is continuously differentiable
at every point in the interior of feasible space for which the Linear
Independent Constraint Qualification holds.


title: Riemannian Geometry of Two Families of Tangent Lie Groups

abstract:
  Using vertical and complete lifts, any left invariant Riemannian metric on a
Lie group induces a left invariant Riemannian metric on the tangent Lie group.
In the present article we study the Riemannian geometry of tangent bundle of
two families of Lie groups. The first one is the family of special Lie groups
considered by J. Milnor and the second one is the class of Lie groups with
one-dimensional commutator groups. The Levi-Civita connection, sectional and
Ricci curvatures have been investigated.


title: An Application of ParaExp to Electromagnetic Wave Problems

abstract:
  Recently, ParaExp was proposed for the time integration of hyperbolic
problems. It splits the time interval of interest into sub-intervals and
computes the solution on each sub-interval in parallel. The overall solution is
decomposed into a particular solution defined on each sub-interval with zero
initial conditions and a homogeneous solution propagated by the matrix
exponential applied to the initial conditions. The efficiency of the method
results from fast approximations of this matrix exponential using tools from
linear algebra. This paper deals with the application of ParaExp to
electromagnetic wave problems in time-domain. Numerical tests are carried out
for an electric circuit and an electromagnetic wave problem discretized by the
Finite Integration Technique.


title: Complementarity and Stability Conditions

abstract:
  We discuss the issue of complementarity between the confining phase and the
Higgs phase for gauge theories in which there are no light particles below the
scale of confinement or spontaneous symmetry breaking. We show with a number of
examples that even though the low energy effective theories are the same (and
trivial), discontinuous changes in the structure of heavy stable particles can
signal a phase transition and thus we can sometimes argue that two phases which
have different structures of heavy particles cannot be continuously connected
and thus the phases cannot be complementary. We discuss what this means and
suggest that such "stability conditions" can be a useful physical check for
complementarity.


title: Parabolic subalgebras, parabolic buildings and parabolic projection

abstract:
  Reductive (or semisimple) algebraic groups, Lie groups and Lie algebras have
a rich geometry determined by their parabolic subgroups and subalgebras, which
carry the structure of a building in the sense of J. Tits. We present herein an
elementary approach to the geometry of parabolic subalgebras, over an arbitrary
field of characteristic zero, which does not rely upon the structure theory of
semisimple Lie algebras. Indeed we derive such structure theory, from root
systems to the Bruhat decomposition, from the properties of parabolic
subalgebras. As well as constructing the Tits building of a reductive Lie
algebra, we establish a "parabolic projection" process which sends parabolic
subalgebras of a reductive Lie algebra to parabolic subalgebras of a Levi
subquotient. We indicate how these ideas may be used to study geometric
configurations and their moduli.


title:
Measurement of the $e^+e^- \to \omega\eta$ cross section below
  $\sqrt{s}=2$ GeV

abstract:
  The cross section for the process $e^+e^- \to \omega\eta$ is measured in the
center-of-mass energy range 1.34--2.00 GeV. The analysis is based on data
collected with the SND detector at the VEPP-2000 $e^+e^-$ collider. The
measured $e^+e^- \to \omega\eta$ cross section is the most accurate to date. A
significant discrepancy is observed between our data and previous BABAR
measurement.


title: Efficient Timeout Synthesis in Fixed-Delay CTMC Using Policy Iteration

abstract:
  We consider the fixed-delay synthesis problem for continuous-time Markov
chains extended with fixed-delay transitions (fdCTMC). The goal is to
synthesize concrete values of the fixed-delays (timeouts) that minimize the
expected total cost incurred before reaching a given set of target states. The
same problem has been considered and solved in previous works by computing an
optimal policy in a certain discrete-time Markov decision process (MDP) with a
huge number of actions that correspond to suitably discretized values of the
timeouts.
  In this paper, we design a symbolic fixed-delay synthesis algorithm which
avoids the explicit construction of large action spaces. Instead, the algorithm
computes a small sets of "promising" candidate actions on demand. The candidate
actions are selected by minimizing a certain objective function by computing
its symbolic derivative and extracting a univariate polynomial whose roots are
precisely the points where the derivative takes zero value. Since roots of high
degree univariate polynomials can be isolated very efficiently using modern
mathematical software, we achieve not only drastic memory savings but also
speedup by three orders of magnitude compared to the previous methods.


title: On the Supersymmetric Extension of Gauss-Bonnet like Gravity

abstract:
  We explore the supersymmetry invariance of a supergravity theory in the
presence of a non-trivial boundary. The explicit construction of a bulk
Lagrangian based on an enlarged superalgebra, known as $AdS$-Lorentz, is
presented. Using a geometric approach we show that the supersymmetric extension
of a Gauss-Bonnet like gravity is required in order to restore the
supersymmetry invariance of the theory.


title: The Spectrum of Darkonium in the Sun

abstract:
  Dark matter that gets captured in the Sun may form positronium-like bound
states if it self-interacts via light dark photons. In this case, dark matter
can either annihilate to dark photons or recombine in bound states which
subsequently also decay to dark photons. The fraction of the dark photons that
leave the Sun without decaying to Standard Model particles have a
characteristic energy spectrum which is a mixture of the direct annihilation
process, the decays of ortho- and para- bound states and the recombination
process. The ultimate decay of these dark photons to positron-electron pairs
(via kinetic mixing) outside the Sun creates a distinct signal that can either
identify or set strict constraints on dark photon models.


title:
The chemistry of interstellar argonium and other probes of the molecular
  fraction in diffuse clouds

abstract:
  We present a general parameter study, in which the abundance of interstellar
argonium (ArH$^+$) is predicted using a model for the physics and chemistry of
diffuse interstellar gas clouds. Results have been obtained as a function of UV
radiation field, cosmic-ray ionization rate, and cloud extinction. No single
set of cloud parameters provides an acceptable fit to the typical ArH$^+$,
OH$^+$ and $\rm H_2O^+$ abundances observed in diffuse clouds within the
Galactic disk. Instead, the observed abundances suggest that ArH$^+$ resides
primarily in a separate population of small clouds of total visual extinction
of at most 0.02 mag per cloud, within which the column-averaged molecular
fraction is in the range $10^{-5} - 10^{-2}$, while OH$^+$ and $\rm H_2O^+$
reside primarily in somewhat larger clouds with a column-averaged molecular
fraction $\sim 0.2$. This analysis confirms our previous suggestion that the
argonium molecular ion is a unique tracer of almost purely atomic gas.


title:
Men Set Their Own Cites High: Gender and Self-citation across Fields and
  over Time

abstract:
  How common is self-citation in scholarly publication, and does the practice
vary by gender? Using novel methods and a data set of 1.5 million research
papers in the scholarly database JSTOR published between 1779 and 2011, the
authors find that nearly 10 percent of references are self-citations by a
paper's authors. The findings also show that between 1779 and 2011, men cited
their own papers 56 percent more than did women. In the last two decades of
data, men self-cited 70 percent more than women. Women are also more than 10
percentage points more likely than men to not cite their own previous work at
all. While these patterns could result from differences in the number of papers
that men and women authors have published rather than gender-specific patterns
of self-citation behavior, this gender gap in self-citation rates has remained
stable over the last 50 years, despite increased representation of women in
academia. The authors break down self-citation patterns by academic field and
number of authors and comment on potential mechanisms behind these
observations. These findings have important implications for scholarly
visibility and cumulative advantage in academic careers.


title:
On global well-posedness for Klein-Gordon equation with concentrated
  nonlinearity

abstract:
  We prove global well-posedness for the 3D Klein-Gordon equation with a
concentrated nonlinearity.


title: Want Drugs? Use Python

abstract:
  We describe how Python can be leveraged to streamline the curation, modelling
and dissemination of drug discovery data as well as the development of
innovative, freely available tools for the related scientific community. We
look at various examples, such as chemistry toolkits, machine-learning
applications and web frameworks and show how Python can glue it all together to
create efficient data science pipelines.


title: Probabilistic Programming and PyMC3

abstract:
  In recent years sports analytics has gotten more and more popular. We propose
a model for Rugby data - in particular to model the 2014 Six Nations
tournament. We propose a Bayesian hierarchical model to estimate the
characteristics that bring a team to lose or win a game, and predict the score
of particular matches. This is intended to be a brief introduction to
Probabilistic Programming in Python and in particular the powerful library
called PyMC3.


title: High-energy neutrinos from sources in clusters of galaxies

abstract:
  High-energy cosmic rays can be accelerated in clusters of galaxies, by
mega-parsec scale shocks induced by accretion of gas during the formation of
large-scale structure, or by powerful sources harbored in clusters. Once
accelerated, the highest energy particles leave the cluster via almost
rectilinear trajectories, while lower energy ones can be confined by the
cluster magnetic field up to cosmological time and interact with the
intracluster gas. Using a realistic model of the baryon distribution and the
turbulent magnetic field in clusters, we studied the propagation and hadronic
interaction of high-energy protons in the intracluster medium. We report the
cumulative cosmic ray and neutrino spectra generated by galaxy clusters
including embedded sources, and demonstrate that clusters can contribute a
significant fraction of the observed IceCube neutrinos above 30 TeV while
remaining undetected in high-energy cosmic rays and $\gamma$ rays for
reasonable choices of parameters and source scenarios.


title: Spacetime Dynamics of a Higgs Vacuum Instability During Inflation

abstract:
  A remarkable prediction of the Standard Model is that, in the absence of
corrections lifting the energy density, the Higgs potential becomes negative at
large field values. If the Higgs field samples this part of the potential
during inflation, the negative energy density may locally destabilize the
spacetime. We use numerical simulations of the Einstein equations to study the
evolution of inflation-induced Higgs fluctuations as they grow towards the true
(negative-energy) minimum. These simulations show that forming a single patch
of true vacuum in our past light cone during inflation is incompatible with the
existence of our Universe; the boundary of the true vacuum region grows outward
in a causally disconnected manner from the crunching interior, which forms a
black hole. We also find that these black hole horizons may be arbitrarily
elongated---even forming black strings---in violation of the hoop conjecture.
By extending the numerical solution of the Fokker-Planck equation to the
exponentially suppressed tails of the field distribution at large field values,
we derive a rigorous correlation between a future measurement of the
tensor-to-scalar ratio and the scale at which the Higgs potential must receive
stabilizing corrections in order for the Universe to have survived inflation
until today.


title:
H0LiCOW II. Spectroscopic survey and galaxy-group identification of the
  strong gravitational lens system HE0435-1223

abstract:
  Galaxies located in the environment or on the line of sight towards
gravitational lenses can significantly affect lensing observables, and can lead
to systematic errors on the measurement of $H_0$ from the time-delay technique.
We present the results of a systematic spectroscopic identification of the
galaxies in the field of view of the lensed quasar HE0435-1223, using the W. M.
Keck, Gemini and ESO-Very Large telescopes. Our new catalog triples the number
of known galaxy redshifts in the vicinity of the lens, expanding to 102 the
number of measured redshifts for galaxies separated by less than 3 arcmin from
the lens. We complement our catalog with literature data to gather redshifts up
to 15 arcmin from the lens, and search for galaxy groups or clusters projected
towards HE0435-1223. We confirm that the lens is a member of a small group that
includes at least 12 galaxies, and find 8 other group candidates near the line
of sight of the lens. The flexion shift, namely the shift of lensed images
produced by high order perturbation of the lens potential, is calculated for
each galaxy/group and used to identify which objects produce the largest
perturbation of the lens potential. This analysis demonstrates that i) at most
three of the five brightest galaxies projected within 12 arcsec of the lens
need to be explicitly used in the lens models, and ii) the groups can be
treated in the lens model as an external tidal field (shear) contribution.


title:
Correcting cosmological parameter biases for all redshift surveys
  induced by estimating and reweighting redshift distributions

abstract:
  Photometric redshift uncertainties are a major source of systematic error for
ongoing and future photometric surveys. We study different sources of redshift
error caused by choosing a suboptimal redshift histogram bin width and propose
methods to resolve them. The selection of a too large bin width is shown to
oversmooth small scale structure of the radial distribution of galaxies. This
systematic error can significantly shift cosmological parameter constraints by
up to $6 \, \sigma$ for the dark energy equation of state parameter $w$.
Careful selection of bin width can reduce this systematic by a factor of up to
6 as compared with commonly used current binning approaches. We further discuss
a generalised resampling method that can correct systematic and statistical
errors in cosmological parameter constraints caused by uncertainties in the
redshift distribution. This can be achieved without any prior assumptions about
the shape of the distribution or the form of the redshift error. Our
methodology allows photometric surveys to obtain unbiased cosmological
parameter constraints using a minimum number of spectroscopic calibration data.
For a DES-like galaxy clustering forecast we obtain unbiased results with
respect to errors caused by suboptimal histogram bin width selection, using
only 5k representative spectroscopic calibration objects per tomographic
redshift bin.


title:
The Grism Lens-Amplified Survey from Space (GLASS). IX. The dual origin
  of low-mass cluster galaxies as revealed by new structural analyses

abstract:
  Using deep Hubble Frontier Fields imaging and slitless spectroscopy from the
Grism Lens-Amplified Survey from Space, we analyze 2200 cluster and 1748 field
galaxies at $0.2\leq z\leq0.7$ to determine the impact of environment on galaxy
size and structure at $\log M_*/M_\odot>7.8$, an unprecedented limit at these
redshifts. Based on simple assumptions-$r_e=f(M_*)$-we find no significant
differences in half-light radii ($r_e$) between equal-mass cluster or field
systems. More complex analyses-$r_e=f(M_*,U-V,n,z,\Sigma$)-reveal local density
$(\Sigma$) to induce only a $7\% \pm 3\%$ ($95\%$ confidence) reduction in
$r_e$ beyond what can be accounted for by $U-V$ color, Sersic index ($n$), and
redshift ($z$) effects.Almost any size difference between galaxies in high- and
low-density regions is thus attributable to their different distributions in
properties other than environment. Indeed, we find a clear color-$r_e$
correlation in low-mass passive cluster galaxies ($\log M_*/M_\odot<9.8$) such
that bluer systems have larger radii, with the bluest having sizes consistent
with equal-mass star-forming galaxies. We take this as evidence that
large-$r_e$ low-mass passive cluster galaxies are recently acquired systems
that have been environmentally quenched without significant structural
transformation (e.g., by ram pressure stripping or starvation).Conversely,
$\sim20\%$ of small-$r_e$ low-mass passive cluster galaxies appear to have been
in place since $z\sim3$. Given the consistency of the small-$r_e$ galaxies'
stellar surface densities (and even colors) with those of systems more than ten
times as massive, our findings suggest that clusters mark places where galaxy
evolution is accelerated for an ancient base population spanning most masses,
with late-time additions quenched by environment-specific mechanisms are mainly
restricted to the lowest masses.


title:
A Model for (Quasi-)Periodic Multi-wavelength Photometric Variability in
  Young Stellar Objects

abstract:
  We present radiation transfer models of rotating young stellar objects (YSOs)
with hotspots in their atmospheres, inner disk warps and other 3-D effects in
the nearby circumstellar environment. Our models are based on the geometry
expected from the magneto-accretion theory, where material moving inward in the
disk flows along magnetic field lines to the star and creates stellar hotspots
upon impact. Due to rotation of the star and magnetosphere, the disk is
variably illuminated. We compare our model light curves to data from the
Spitzer YSOVAR project (Morales-Calderon et al. 2014, Cody et al. 2014) to
determine if these processes can explain the variability observed at optical
and mid-infrared wavelengths in young stars. We focus on those variables
exhibiting "dipper" behavior that may be periodic, quasi-periodic, or
aperiodic. We find that the stellar hotspot size and temperature affects the
optical and near-infrared light curves, while the shape and vertical extent of
the inner disk warp affects the mid-IR light curve variations. Clumpy disk
distributions with non-uniform fractal density structure produce more
stochastic light curves. We conclude that the magneto-accretion theory is
consistent with certain aspects of the multi-wavelength photometric variability
exhibited by low-mass YSOs. More detailed modeling of individual sources can be
used to better determine the stellar hotspot and inner disk geometries of
particular sources.


title:
The Global 21-cm Signal in the Context of the High-z Galaxy Luminosity
  Function

abstract:
  Motivated by recent progress in studies of the high-$z$ Universe, we build a
new model for the global 21-cm signal that is explicitly calibrated to
measurements of the galaxy luminosity function (LF) and further tuned to match
the Thomson scattering optical depth of the cosmic microwave background,
$\tau_e$. Assuming that the $z \lesssim 8$ galaxy population can be smoothly
extrapolated to higher redshifts, the recent decline in best-fit values of
$\tau_e$ and the inefficient heating induced by X-ray binaries (HMXBs; the
presumptive sources of the X-ray background at high-$z$) imply that the
entirety of cosmic reionization and reheating occurs at redshifts $z \lesssim
12$. In contrast to past global 21-cm models, whose $z \sim 20$ ($\nu \sim 70$
MHz) absorption features and strong $\sim 25$ mK emission features were driven
largely by the assumption of efficient early star-formation and X-ray heating,
our new fiducial model peaks in absorption at $\nu \sim 110$ MHz at a depth of
$\sim -160$ mK and has a negligible emission component. As a result, a strong
emission signal would provide convincing evidence that HMXBs are not the only
drivers of cosmic reheating. Shallow absorption troughs should accompany strong
heating scenarios, but could also be caused by a low escape fraction of
Lyman-Werner photons. Generating signals with troughs at $\nu \lesssim 95$ MHz
requires a floor in the star-formation efficiency in halos below $\sim 10^{9}
M_{\odot}$, which is equivalent to steepening the faint-end of the galaxy LF.
These findings demonstrate that the global 21-cm signal is a powerful
complement to current and future galaxy surveys and efforts to better
understand the interstellar medium in high-$z$ galaxies.


title:
Investigating dust trapping in transition disks with millimeter-wave
  polarization

abstract:
  Spatially resolved polarized (sub-)mm emission has been observed for example
in the protoplanetary disk around HL Tau. Magnetically aligned grains are
commonly interpreted as the source of polarization. However, self-scattering by
large dust grains with a high enough albedo is another polarization mechanism,
becoming a compelling method independent of the spectral index to constrain the
dust grain size in protoplanetary disks. We study the dust polarization at mm
wavelength in the dust trapping scenario proposed for transition disks, when a
giant planet opens a gap in the disk. We investigate the characteristic
polarization patterns and their dependence on disk inclination, dust size
evolution, planet position, and observing wavelength. We combine
two-dimensional hydrodynamical simulations of planet-disk interactions with
self-consistent dust growth models. These size-dependent dust density
distributions are used for follow-up three-dimensional radiative transfer
calculations to predict the polarization degree at ALMA bands due to scattered
thermal emission. We find that the polarization pattern of a disk with a
planetary gap after 1 Myr of dust evolution shows a distinctive three ring
structure. Two narrow inner rings are located at the planet gap edges. For
increasing observing wavelengths all three rings slightly change their
position, where the innermost and outermost rings move inward. This distance is
detectable comparing the results at ALMA bands 3, 6 and 7. Within the highest
polarized intensity regions the polarization vectors are oriented in the
azimuthal direction. For an inclined disk there is an interplay between
polarization originating from a flux gradient and inclination-induced
quadrupole polarization. For intermediate inclined transition disks the
polarization degree is as high as ~ 2% at band 3, which is well above the
detection limit of future ALMA observations.


title:
The eigenstate thermalization hypothesis in constrained Hilbert spaces:
  a case study in non-Abelian anyon chains

abstract:
  Many phases of matter, including superconductors, fractional quantum Hall
fluids and spin liquids, are described by gauge theories with constrained
Hilbert spaces. However, thermalization and the applicability of quantum
statistical mechanics has primarily been studied in unconstrained Hilbert
spaces. In this article, we investigate whether constrained Hilbert spaces
permit local thermalization. Specifically, we explore whether the eigenstate
thermalization hypothesis (ETH) holds in a pinned Fibonacci anyon chain, which
serves as a representative case study. We first establish that the constrained
Hilbert space admits a notion of locality, by showing that the influence of a
measurement decays exponentially in space. This suggests that the constraints
are no impediment to thermalization. We then provide numerical evidence that
ETH holds for the diagonal and off-diagonal matrix elements of various local
observables in a generic disorder-free non-integrable model. We also find that
certain non-local observables obey ETH.


title: Higgs production in bottom-quark fusion: matching beyond leading order

abstract:
  We compute the total cross-section for Higgs boson production in bottom-quark
fusion using the so-called FONLL method for the matching of a scheme in which
the $b$-quark is treated as a massless parton to that in which it is treated as
a massive final-state particle, and extend our previous results to the case in
which the next-to-next-to-leading-log five-flavor scheme result is combined
with the next-to-leading-order O(as^3) four-flavor scheme computation.


title: The g-theorem and quantum information theory

abstract:
  We study boundary renormalization group flows between boundary conformal
field theories in $1+1$ dimensions using methods of quantum information theory.
We define an entropic $g$-function for theories with impurities in terms of the
relative entanglement entropy, and we prove that this $g$-function decreases
along boundary renormalization group flows. This entropic $g$-theorem is valid
at zero temperature, and is independent from the $g$-theorem based on the
thermal partition function. We also discuss the mutual information in boundary
RG flows, and how it encodes the correlations between the impurity and bulk
degrees of freedom. Our results provide a quantum-information understanding of
(boundary) RG flow as increase of distinguishability between the UV fixed point
and the theory along the RG flow.


title: Master symmetry in the $AdS_5\times S^5$ pure spinor string

abstract:
  We lift the set of classical non-local symmetries recently studied by Klose,
Loebbert, and M\"unkler in the context of $\mathbb Z_2$ cosets to the pure
spinor description of the superstring in the $AdS_5\times S^5$ background.


title:
Antiferromagnetic correlations in two-dimensional fermionic
  Mott-insulating and metallic phases

abstract:
  Near zero temperature, quantum magnetism can non-trivially arise from
short-range interactions, but the occurrence of magnetic order depends
crucially on the interplay of interactions, lattice geometry, dimensionality
and doping. Even though the consequences of this interplay are not yet fully
understood, quantum magnetism is believed to be connected to a range of complex
phenomena in the solid state, for example, in the context of high-$T_c$
superconductivity and spin liquids in frustrated lattices. Ultracold atomic
Fermi gases in optical lattices constitute an experimental system with
unrivalled tunability and detection capabilities to explore quantum magnetism
by analog quantum simulation. In this work, we study the emergence of
antiferromagnetic correlations between ultracold fermionic atoms in two
dimensions with decreasing temperature. We determine the magnetic
susceptibility of the Hubbard model from simultaneous measurements of the
in-situ density of both spin components. At half-filling and strong
interactions our data approach the Heisenberg model of localized spins with
antiferromagnetic correlations. Moreover, we observe the disappearance of
magnetic correlations when the system is doped away from half-filling. Our
observation of the dependence of quantum magnetism on doping paves the way for
future studies on the emergence of pseudogap and pairing phenomena away from
half-filling.