title: Gyrotactic swimmer dispersion in pipe flow: testing the theory

abstract:
  Suspensions of microswimmers are a rich source of fascinating new fluid
mechanics. Recently we predicted the active pipe flow dispersion of gyrotactic
microalgae, whose orientation is biased by gravity and flow shear. Analytical
theory predicts that these active swimmers disperse in a markedly distinct
manner from passive tracers (Taylor dispersion). Dispersing swimmers display
nonzero drift and effective diffusivity that is non-monotonic with P$\'e$clet
number. Such predictions agree with numerical simulations, but hitherto have
not been tested experimentally. Here, to facilitate comparison, we obtain new
solutions of the axial dispersion theory accounting both for swimmer negative
buoyancy and a local nonlinear response of swimmers to shear, provided by two
alternative microscopic stochastic descriptions. We obtain new predictions for
suspensions of the model swimming alga $\it Dunaliella\,salina$, whose motility
and buoyant mass we parametrise using tracking video microscopy. We then
present a new experimental method to measure gyrotactic dispersion using
fluorescently stained $\it D. salina$ and provide a preliminary comparison with
predictions of a nonzero drift above the mean flow for each microscopic
stochastic description. Finally, we propose further experiments for a full
experimental characterisation of gyrotactic dispersion measures and discuss
implications of our results for algal dispersion in industrial
photobioreactors.


title: Magnetooptical determination of a topological index

abstract:
  When a Dirac fermion system acquires an energy-gap, it is said to have either
trivial (positive energy-gap) or non-trivial (negative energy-gap) topology,
depending on the parity ordering of its conduction and valence bands. The
non-trivial regime is identified by the presence of topological surface or
edge-state dispersing in the energy gap of the bulk and is attributed a
non-zero topological index. In this work, we show that such topological indices
can be determined experimentally via an accurate measurement of the effective
velocity of bulk massive Dirac fermions. We demonstrate this analytically
starting from the Bernevig-Hughes-Zhang Hamiltonian (BHZ) to show how the
topological index depends on this velocity. We then experimentally extract the
topological index in Pb1-xSnxSe and Pb1-xSnxTe using infrared magnetooptical
Landau level spectroscopy. This approach is argued to be universal to all
material classes that can be described by a BHZ-like model and that host a
topological phase transition.


title:
Nonlocal discrete diffusion equations and the fractional discrete
  Laplacian, regularity and applications

abstract:
  The analysis of nonlocal discrete equations driven by fractional powers of
the discrete Laplacian on a mesh of size $h>0$ \[ (-\Delta_h)^su=f, \] for
$u,f:\mathbb{Z}_h\to\mathbb{R}$, $0<s<1$, is performed. The pointwise nonlocal
formula for $(-\Delta_h)^su$ and the nonlocal discrete mean value property for
discrete $s$-harmonic functions are obtained. We observe that a
characterization of $(-\Delta_h)^s$ as the Dirichlet-to-Neumann operator for a
semidiscrete degenerate elliptic local extension problem is valid. Regularity
properties and Schauder estimates in discrete H\"older spaces as well as
existence and uniqueness of solutions to the nonlocal Dirichlet problem are
shown. For the latter, the fractional discrete Sobolev embedding and the
fractional discrete Poincar\'e inequality are proved, which are of independent
interest. We introduce the negative power (fundamental solution) \[
u=(-\Delta_h)^{-s}f, \] which can be seen as the Neumann-to-Dirichlet map for
the semidiscrete extension problem. We then prove the discrete
Hardy--Littlewood--Sobolev inequality for $(-\Delta_h)^{-s}$.
  As applications, the convergence of our fractional discrete Laplacian to the
(continuous) fractional Laplacian as $h\to0$ in H\"older spaces is analyzed.
Indeed, uniform estimates for the error of the approximation in terms of $h$
under minimal regularity assumptions are obtained. We finally prove that
solutions to the Poisson problem for the fractional Laplacian \[
(-\Delta)^sU=F, \] in $\mathbb{R}$, can be approximated by solutions to the
Dirichlet problem for our fractional discrete Laplacian, with explicit uniform
error estimates in terms of~$h$.


title: Fabrication of Ultrathin Single-Crystal Diamond Membranes

abstract:
  We demonstrate the fabrication of sub-micron layers of single-crystal diamond
suitable for subsequent processing as demonstrated by this test ring structure.
This method is a significant enabling technology for nanomechanical and
photonic structures incorporating colour-centres. The process uses a novel
double implant process, annealing and chemical etching to produce membranes of
diamond from single-crystal starting material, the thinnest layers achieved to
date are 210 nm thick.


title:
All-carbon multi-electrode array for real-time in vitro measurements of
  oxidizable neurotransmitters

abstract:
  We report on the ion beam fabrication of all-carbon multi electrode arrays
(MEAs) based on 16 graphitic micro-channels embedded in single-crystal diamond
(SCD) substrates. The fabricated SCD-MEAs are systematically employed for the
in vitro simultaneous amperometric detection of the secretory activity from
populations of chromaffin cells, demonstrating a new sensing approach with
respect to standard techniques. The biochemical stability and biocompatibility
of the SCD-based device combined with the parallel recording of
multi-electrodes array allow: i) a significant time saving in data collection
during drug screening and/or pharmacological tests over a large number of
cells, ii) the possibility of comparing altered cell functionality among cell
populations, and iii) the repeatition of acquisition runs over many cycles with
a fully non-toxic and chemically robust bio-sensitive substrate.


title: Optimization on fixed low latency implementation of GBT protocol in FPGA

abstract:
  In the upgrade of ATLAS experiment, the front-end electronics components are
subjected to a large radiation background. Meanwhile high speed optical links
are required for the data transmission between the on-detector and off-detector
electronics. The GBT architecture and the Versatile Link (VL) project are
designed by CERN to support the 4.8 Gbps line rate bidirectional high-speed
data transmission which is called GBT link. In the ATLAS upgrade, besides the
link with on-detector, the GBT link is also used between different off-detector
systems. The GBTX ASIC is designed for the on-detector front-end,
correspondingly for the off-detector electronics, the GBT architecture is
implemented in Field Programmable Gate Arrays (FPGA). CERN launches the
GBT-FPGA project to provide examples in different types of FPGA. In the ATLAS
upgrade framework, the Front-End LInk eXchange (FELIX) system is used to
interface the front-end electronics of several ATLAS subsystems. The GBT link
is used between them, to transfer the detector data and the timing, trigger,
control and monitoring information. The trigger signal distributed in the
down-link from FELIX to the front-end requires a fixed and low latency. In this
paper, several optimizations on the GBT-FPGA IP core are introduced, to achieve
a lower fixed latency. For FELIX, a common firmware will be used to interface
different front-ends with support of both GBT modes: the forward error
correction mode and the wide mode. The modified GBT-FPGA core has the ability
to switch between the GBT modes without FPGA reprogramming. The system clock
distribution of the multi-channel FELIX firmware is also discussed in this
paper.


title: Single-shot phase retrieval in high-energy X-ray grating interferometry

abstract:
  In X-ray phase contrast imaging, phase retrieval from intensity measurements
is the key for further quantitative analysis and tomographic reconstructions.
In this letter, we present a single-shot approach for quantitative phase
retrieval in high-energy X-ray grating interferometry. The proposed approach
makes use of the phase-attenuation duality of soft tissues when being imaged
with high-energy X-rays. The phase retrieval formula is derived and presented,
and tested by numerical experiments including photon shot noise. The good
agreement between retrieval results and theoretical values confirms the
feasibility of the presented approach.


title: Subcomputable Schnorr Randomness

abstract:
  The notion of Schnorr randomness refers to computable reals or computable
functions. We propose a version of Schnorr randomness for subcomputable classes
and characterize it in different ways: by Martin L\"of tests, martingales or
measure computable machines.


title:
Nonlinear 3-D simulation of high-intensity focused ultrasound therapy in
  the kidney

abstract:
  Kidney cancer is a severe disease which can be treated non-invasively using
high-intensity focused ultrasound (HIFU) therapy. However, tissue in front of
the transducer and the deep location of kidney can cause significant losses to
the efficiency of the treatment. The effect of attenuation, refraction and
reflection due to different tissue types on HIFU therapy of the kidney was
studied using a nonlinear ultrasound simulation model. The geometry of the
tissue was derived from a computed tomography (CT) dataset of a patient which
had been segmented for water, bone, soft tissue, fat and kidney. The combined
effect of inhomogeneous attenuation and sound-speed was found to result in an
11.0 dB drop in spatial peak-temporal average (SPTA) intensity in the kidney
compared to pure water. The simulation without refraction effects showed a 6.3
dB decrease indicating that both attenuation and refraction contribute to the
loss in focal intensity. The losses due to reflections at soft tissue
interfaces were less than 0.1 dB. Focal point shifting due to refraction
effects resulted in -1.3, 2.6 and 1.3 mm displacements in x-, y- and
z-directions respectively. Furthermore, focal point splitting into several
smaller subvolumes was observed. The total volume of the secondary focal points
was approximately 46% of the largest primary focal point. This could
potentially lead to undesired heating outside the target location and longer
therapy times.


title:
Noisy Channel-Output Feedback Capacity of the Linear Deterministic
  Interference Channel

abstract:
  In this technical report, the capacity region of the two-user linear
deterministic (LD) interference channel with noisy output feedback (IC-NOF) is
fully characterized. This result allows the identification of several
asymmetric scenarios in which implementing channel-output feedback in only one
of the transmitter-receiver pairs is as beneficial as implementing it in both
links, in terms of achievable individual rate and sum-rate improvements w.r.t.
the case without feedback. In other scenarios, the use of channel-output
feedback in any of the transmitter-receiver pairs benefits only one of the two
pairs in terms of achievable individual rate improvements or simply, it turns
out to be useless, i.e., the capacity regions with and without feedback turn
out to be identical even in the full absence of noise in the feedback links.


title: PT-symmetric quantum oscillator in an optical cavity

abstract:
  The quantum harmonic oscillator with parity-time ($\mathcal{PT}$) symmetry,
obtained from the ordinary (Hermitian) quantum harmonic oscillator by an
imaginary displacement of the spatial coordinate, provides an important and
exactly-solvable model to investigate non-Hermitian extension of the Ehrenfest
theorem. Here it is shown that transverse light dynamics in an optical
resonator with off-axis longitudinal pumping can emulate a
$\mathcal{PT}$-symmetric quantum harmonic oscillator, providing an
experimentally accessible system to investigate non-Hermitian coherent state
propagation.


title:
When the C in CP does not matter: anatomy of order-4 CP eigenstates and
  their Yukawa interactions

abstract:
  We explore the origin and Yukawa interactions of the scalars with peculiar
CP-properties which were recently found in a multi-Higgs model based on an
order-4 CP symmetry. We relate the existence of such scalars to the enhanced
freedom of defining CP, even beyond the well-known generalized CP symmetries,
which arises in models with several zero-charge scalar fields. We also show
that despite possessing exotic CP quantum numbers, these scalars do not have to
be inert: they can have CP-conserving Yukawa interactions provided the CP acts
on fermions by also mixing generations. This paper focuses on formal
aspects---exposed in a pedagogical manner---and includes a brief discussion of
possible phenomenological consequences.


title: Recent results on stability of planar detonations

abstract:
  We describe recent analytical and numerical results on stability and behavior
of viscous and inviscid detonation waves obtained by dynamical systems/Evans
function techniques like those used to study shock and reaction diffusion
waves. In the first part, we give a broad description of viscous and inviscid
results for 1D perturbations; in the second, we focus on inviscid
high-frequency stability in multi-D and associated questions in turning point
theory/WKB expansion.


title:
Deconstructing the glass transition through critical experiments on
  colloids

abstract:
  The glass transition is the most enduring grand-challenge problem in
contemporary condensed matter physics. Here, we review the contribution of
colloid experiments to our understanding of this problem. First, we briefly
outline the success of colloidal systems in yielding microscopic insights into
a wide range of condensed matter phenomena. In the context of the glass
transition, we demonstrate their utility in revealing the nature of spatial and
temporal dynamical heterogeneity. We then discuss the evidence from colloid
experiments in favor of various theories of glass formation that has
accumulated over the last two decades. In the next section, we expound on the
recent paradigm shift in colloid experiments from an exploratory approach to a
critical one aimed at distinguishing between predictions of competing
frameworks. We demonstrate how this critical approach is aided by the discovery
of novel dynamical crossovers within the range accessible to colloid
experiments. We also highlight the impact of alternate routes to glass
formation such as random pinning, trajectory space phase transitions and
replica coupling on current and future research on the glass transition. We
conclude our review by listing some key open challenges in glass physics such
as the comparison of growing static lengthscales and the preparation of
ultrastable glasses, that can be addressed using colloid experiments.


title: Recursive Partitioning for Personalization using Observational Data

abstract:
  We study the problem of learning to choose from m discrete treatment options
(e.g., news item or medical drug) the one with best causal effect for a
particular instance (e.g., user or patient) where the training data consists of
passive observations of covariates, treatment, and the outcome of the
treatment. The standard approach to this problem is regress and compare: split
the training data by treatment, fit a regression model in each split, and, for
a new instance, predict all m outcomes and pick the best. By reformulating the
problem as a single learning task rather than m separate ones, we propose a new
approach based on recursively partitioning the data into regimes where
different treatments are optimal. We extend this approach to an optimal
partitioning approach that finds a globally optimal partition, achieving a
compact, interpretable, and impactful personalization model. We develop new
tools for validating and evaluating personalization models on observational
data and use these to demonstrate the power of our novel approaches in a
personalized medicine and a job training application.


title: Reflected BSDEs with regulated trajectories

abstract:
  We consider reflected backward stochastic different equations with optional
barrier and so-called regulated trajectories, i.e trajectories with left and
right finite limits. We prove existence and uniqueness results. We also show
that the solution may be approximated by a modified penalization method.
Application to an optimal stopping problem is given.


title: The Generalized Smallest Grammar Problem

abstract:
  The Smallest Grammar Problem -- the problem of finding the smallest
context-free grammar that generates exactly one given sequence -- has never
been successfully applied to grammatical inference. We investigate the reasons
and propose an extended formulation that seeks to minimize non-recursive
grammars, instead of straight-line programs. In addition, we provide very
efficient algorithms that approximate the minimization problem of this class of
grammars. Our empirical evaluation shows that we are able to find smaller
models than the current best approximations to the Smallest Grammar Problem on
standard benchmarks, and that the inferred rules capture much better the
syntactic structure of natural language.


title:
Hierarchical follow-up of sub-threshold candidates of an all-sky
  Einstein@Home search for continuous gravitational waves on LIGO sixth science
  run data

abstract:
  We report results of an all-sky search for periodic gravitational waves with
frequency between 50 and 510 Hz from isolated compact objects, i.e. neutron
stars. A new hierarchical multi-stage approach is taken, supported by the
computing power of the Einstein@Home project, allowing to probe more deeply
than ever before. 16 million sub-threshold candidates from the initial search
[LVC,arXiv:1606.09619] are followed up in three stages. None of those
candidates is consistent with an isolated gravitational wave emitter, and 90%
confidence level upper limits are placed on the amplitudes of continuous waves
from the target population. Between 170.5 and 171 Hz we set the most
constraining 90% confidence upper limit on the strain amplitude h0 at 4.3x10-25
, while at the high end of our frequency range we achieve an upper limit of
7.6x10-25. These are the most constraining all-sky upper limits to date and
constrain the ellipticity of rotating compact objects emitting at 300 Hz at a
distance D to less than 6x10-7 [d/100pc].


title: Exact states and spectra of vibrationally dressed polaritons

abstract:
  Strong coupling between light and matter is possible with a variety of
organic materials. In contrast to the simpler inorganic case, organic materials
often have a complicated spectrum, with vibrationally dressed electronic
transitions. Strong coupling to light competes with this vibrational dressing,
and if strong enough, can suppress the entanglement between electronic and
vibrational degrees of freedom. By exploiting symmetries, we can perform exact
numerical diagonalization to find the polaritonic states for intermediate
numbers of molecules, and use these to define and validate accurate expressions
for the lower polariton states and strong-coupling spectrum in the
thermodynamic limit. Using this approach, we find that vibrational decoupling
occurs as a sharp transition above a critical matter-light coupling strength.
We also demonstrate how the polariton spectrum evolves with the number of
molecules, recovering classical linear optics results only at large $N$.


title: Regularity and Locality of Point Defects in Multilattices

abstract:
  We formulate a model for a point defect embedded in a homogeneous
multilattice crystal with an empirical interatomic potential interaction. Under
a natural, phonon stability assumption we quantify the decay of the long-range
elastic fields with increasing distance from the defect. These decay estimates
are an essential ingredient in quantifying approximation errors in
coarse-grained models and in the construction of optimal numerical methods for
approximating crystalline defects.


title:
Heuristic Relative Entropy Principles with Complex Measures:
  Large-Degree Asymptotics of a Family of Multi-Variate Normal Random
  Polynomials

abstract:
  We study expected values of the polynomials $P_N^{}(z)=\prod_{1\leq n\leq
N}(X_n^2+z^2)$ whose $2N$ zeros $\{\pm i X_k\}^{}_{k=1,...,N}$ are generated by
$N$ identically distributed multi-variate mean-zero normal random variables
$\{X_k\}^{N}_{k=1}$ with co-variance
${\rm{Cov}}_N^{}(X_k,X_l)=(1+\frac{\sigma^2-1}{N})\delta_{k,l}+\frac{\sigma^2-1}{N}(1-\delta_{k,l})$.
In principle these can be evaluated in closed form for arbitrary $N$, yet
commonly available computer algebra handles only $N$ up to a dozen (due to
memory constraints). A list of the first three expected polynomials shows that
the expressions become unwieldy already for moderate $N$. On the other hand,
asymptotic evaluations of the large-$N$ regime for complex $z$ have
traditionally been limited to analytic expansion techniques, several rigorous
results are proved about this regime for complex $z$. Yet if $z$ is real one
can also compute the large-$N$ asymptotics in the "infinite-degree" limit with
the help of the familiar relative entropy principle for probability measures, a
rigorous proof of this fact is supplied. Computer algebra-generated evidence is
presented in support of a conjecture that a generalization of the relative
entropy principle to *{signed and complex measures}* governs the $N\to\infty$
asymptotics of the regime of imaginary $z$. Potential generalizations, in
particular to point vortex ensembles and the prescribed Gauss curvature
problem, and to random matrix ensembles, are emphasized.


title:
The Influence of Mobility Rate on Spiral Waves in Spatial
  Rock-Paper-Scissors Games

abstract:
  We consider a two-dimensional model of three species in rock-paper-scissors
competition and study the self-organisation of the population into fascinating
spiraling patterns. Within our individual-based metapopulation formulation, the
population composition changes due to cyclic dominance (dominance-removal and
dominance-replacement), mutations, and pair-exchange of neighboring
individuals. Here, we study the influence of mobility on the emerging patterns
and investigate when the pair-exchange rate is responsible for spiral waves to
become elusive in stochastic lattice simulations. In particular, we show that
the spiral waves predicted by the system's deterministic partial equations are
found in lattice simulations only within a finite range of the mobility rate.
We also report that in the absence of mutations and dominance-replacement, the
resulting spiraling patterns are subject to convective instability and
far-field breakup at low mobility rate. Possible applications of these
resolution and far-field breakup phenomena are discussed.

categories: q-bio.PE cond-mat.stat-mech nlin.PS physics.soc-ph


title:
FEMOSAA: Feature Guided and Knee Driven Multi-Objective Optimization for
  Self-Adaptive Software

abstract:
  Self-adaptive software (SAS) can reconfigure itself to adapt to the changing
environment at runtime, aiming for continually optimizing conflicted
non-functional objectives, e.g., response time, energy consumption, throughput
and cost etc. In this paper, we present Feature guided and knEe driven
Multi-Objective optimization for Self-Adaptive softwAre (FEMOSAA), a novel
framework that automatically synergizes the feature model and Multi-Objective
Evolutionary Algorithm (MOEA), to optimize SAS at runtime. FEMOSAA operates in
two phases: at design time, FEMOSAA automatically transposes the engineers'
design of SAS, expressed as a feature model, to fit the MOEA, creating new
chromosome representation and reproduction operators. At runtime, FEMOSAA
utilizes the feature model as domain knowledge to guide the search and further
extend the MOEA, providing a larger chance for finding better solutions. In
addition, we have designed a new method to search for the knee solutions, which
can achieve a balanced trade-off. We comprehensively evaluated FEMOSAA on two
running SAS: one is a highly complex SAS with various adaptable real-world
software under the realistic workload trace, another is a service-oriented SAS
that can be dynamically composed from services. In particular, we compared the
effectiveness and overhead of FEMOSAA against four of its variants and three
other search-based frameworks for SAS under various scenarios, including three
commonly applied MOEAs, two workload patterns and diverse conflicting quality
objectives. The results reveal the effectiveness of FEMOSAA and its superiority
over the others with high statistical significance and non-trivial effect
sizes.


title: Primitive ideals of $\operatorname{U}(\frak{sl}(\infty))$

abstract:
  We provide an explicit description of the primitive ideals of the enveloping
algebra $\operatorname{U}(\frak{sl}(\infty))$ of the infinite-dimensional
finitary Lie algebra $\frak{sl}(\infty)$ over an uncountable algebraically
closed field of characteristic 0. Our main new result is that any primitive
ideal of $\operatorname{U}(\frak{sl}(\infty))$ is integrable. A classification
of integrable primitive ideals of $\operatorname{U}(\frak{sl}(\infty))$ has
been known previously, and relies on the pioneering work of A. Zhilinskii.


title:
Dynamical calculation of third harmonic generation in a semiconductor
  quantum well

abstract:
  Non-linear phenomena in optically excited semiconductor structures are of
high interest. We here develop a model capable of studying the dynamics of the
photoexcited carriers, including Coulomb interaction on a Hartree-Fock level,
on the same footing as the dynamics of the light field impinging on an
arbitrary photonic structure. Applying this method to calculate the third
harmonic generation in a semiconductor quantum well embedded in a Bragg mirror
structure, we find that the power-law exponent of the intensity dependence of
the third harmonic generation depends on the frequency of the exciting pulse.
Off-resonant pulses follow the expected cubic dependence, while the exponent is
smaller for resonant pulses due to saturation effects in the induced carrier
density. Our study provides a detailed understanding of the carrier and light
field dynamics during non-linear processes.


title:
Evaluation of two interaction techniques for visualization of dynamic
  graphs

abstract:
  Several techniques for visualization of dynamic graphs are based on different
spatial arrangements of a temporal sequence of node-link diagrams. Many studies
in the literature have investigated the importance of maintaining the user's
mental map across this temporal sequence, but usually each layout is considered
as a static graph drawing and the effect of user interaction is disregarded. We
conducted a task-based controlled experiment to assess the effectiveness of two
basic interaction techniques: the adjustment of the layout stability and the
highlighting of adjacent nodes and edges. We found that generally both
interaction techniques increase accuracy, sometimes at the cost of longer
completion times, and that the highlighting outclasses the stability adjustment
for many tasks except the most complex ones.


title:
Functional inequalities involving numerical differentiation formulas of
  order two

abstract:
  We write expressions connected with numerical differentiation formulas of
order $2$ in the form of Stieltjes integral, then we use Ohlin lemma and
Levin-Stechkin theorem to study inequalities connected with these expressions.
In particular, we present a new proof of the inequality \begin{equation}
\label{Dr}
  f\left(\frac{x+y}{2}\right)\leq\frac{1}{(y-x)^2}\int_x^y\hspace{-2mm}\int_x^yf\left(\frac{s+t}{2}\right)ds\:dt
\leq\frac{1}{y-x}\int_x^yf(t)dt \end{equation} satisfied by every convex
function $f:\R\to\R$ and we obtain extensions of
  \rf{Dr}.
  Then we deal with
  nonsymmetric inequalities of a similar form.


title:
Measuring out-of-time-order correlations and multiple quantum spectra in
  a trapped ion quantum magnet

abstract:
  Controllable arrays of ions and ultra-cold atoms can simulate complex
many-body phenomena and may provide insights into unsolved problems in modern
science. To this end, experimentally feasible protocols for quantifying the
buildup of quantum correlations and coherence are needed, as performing full
state tomography does not scale favorably with the number of particles. Here we
develop and experimentally demonstrate such a protocol, which uses time
reversal of the many-body dynamics to measure out-of-time-order correlation
functions (OTOCs) in a long-range Ising spin quantum simulator with more than
100 ions in a Penning trap. By measuring a family of OTOCs as a function of a
tunable parameter we obtain fine-grained information about the state of the
system encoded in the multiple quantum coherence spectrum, extract the quantum
state purity, and demonstrate the buildup of up to 8-body correlations. Future
applications of this protocol could enable studies of many-body localization,
quantum phase transitions, and tests of the holographic duality between quantum
and gravitational systems.


title: Pulsational Pair-Instability Supernovae

abstract:
  The final evolution of stars in the mass range 70 - 140 solar masses is
explored. Depending upon their mass loss history and rotation rates, these
stars will end their lives as pulsational pair-instability supernovae producing
a great variety of observational transients with total durations ranging from
weeks to millennia and luminosities from 10$^{41}$ to over 10$^{44}$ erg
s$^{-1}$. No non-rotating model radiates more than $5 \times 10^{50}$ erg of
light or has a kinetic energy exceeding $5 \times 10^{51}$ erg, but greater
energies are possible, in principle, in magnetar-powered explosions which are
explored. Many events resemble Type Ibn, Icn, and IIn supernovae, and some
potential observational counterparts are mentioned. Some PPISN can exist in a
dormant state for extended periods, producing explosions millennia after their
first violent pulse. These dormant supernovae contain bright Wolf-Rayet stars,
possibly embedded in bright x-ray and radio sources. The relevance of PPISN to
supernova impostors like Eta Carinae, to super-luminous supernovae, and to
sources of gravitational radiation is discussed. No black holes between 52 and
133 solar masses are expected from stellar evolution in close binaries.


title: Hash2Vec, Feature Hashing for Word Embeddings

abstract:
  In this paper we propose the application of feature hashing to create word
embeddings for natural language processing. Feature hashing has been used
successfully to create document vectors in related tasks like document
classification. In this work we show that feature hashing can be applied to
obtain word embeddings in linear time with the size of the data. The results
show that this algorithm, that does not need training, is able to capture the
semantic meaning of words. We compare the results against GloVe showing that
they are similar. As far as we know this is the first application of feature
hashing to the word embeddings problem and the results indicate this is a
scalable technique with practical results for NLP applications.


title: Penalised complexity priors for stationary autoregressive processes

abstract:
  The autoregressive process of order $p$ (AR($p$)) is a central model in time
series analysis. A Bayesian approach requires the user to define a prior
distribution for the coefficients of the AR($p$) model. Although it is easy to
write down some prior, it is not at all obvious how to understand and interpret
the prior, to ensure that it behaves according to the users prior knowledge. In
this paper, we approach this problem using the recently developed ideas of
penalised complexity (PC) priors. These priors have important properties like
robustness and invariance to reparameterisations, as well as a clear
interpretation. A PC prior is computed based on specific principles, where
model component complexity is penalised in terms of deviation from simple base
model formulations. In the AR(1) case, we discuss two natural base model
choices, corresponding to either independence in time or no change in time. The
latter case is illustrated in a survival model with possible time-dependent
frailty. For higher-order processes, we propose a sequential approach, where
the base model for AR($p$) is the corresponding AR($p-1$) model expressed using
the partial autocorrelations. The properties of the new prior are compared with
the reference prior in a simulation study.


title: Universal Groebner bases and Cartwright-Sturmfels ideals

abstract:
  We describe the universal Groebner basis of the ideal of maximal minors and
the ideal of $2$-minors of a multigraded matrix of linear forms. Our results
imply that the ideals are radical and provide bounds on the regularity. In
particular, the ideals of maximal minors have linear resolutions. Our main
theoretical contribution consists of introducing two new classes of ideals
named after Cartwright and Sturmfels, and proving that they are closed under
multigraded hyperplane sections. The gins of the ideals that we study enjoy
special properties.


title:
Cavity enhanced telecom heralded single photons for spin-wave solid
  state quantum memories

abstract:
  We report on a source of heralded narrowband (3MHz) single photons compatible
with solid-state spin-wave quantum memories based on praseodymium doped
crystals. Widely non-degenerate narrow-band photon pairs are generated using
cavity enhanced down conversion. One photon from the pair is at telecom
wavelengths and serves as heralding signal, while the heralded single photon is
at 606nm, resonant with an optical transition in Pr:YSO. The source offers a
heralding efficiency of 28% and a generation rate exceeding 2000 pairs/mW in a
single-mode. The single photon nature of the heralded field is confirmed by a
direct antibunching measurement, with a measured antibunching parameter down to
0.010(4). Moreover, we investigate in detail photon cross- and autocorrelation
functions proving non-classical correlations between the two photons. The
results presented in this paper represent significant improvement over the
state of the art and offer prospects for the demonstration of single photon
spin-wave storage in an on-demand solid state quantum memory, heralded by a
telecom photon.


title: Multigraded generic initial ideals of determinantal ideals

abstract:
  Let I be either the ideal of maximal minors or the ideal of 2-minors of a row
graded or column graded matrix of linear forms L. In two previous papers we
showed that I is a Cartwright-Sturmfels ideal, that is, the multigraded generic
initial ideal gin(I) of I is radical (and essentially independent of the term
order chosen). In this paper we describe generators and prime decomposition of
gin(I) in terms of data related to the linear dependences among the row or
columns of the submatrices of L. In the case of 2-minors we also give a closed
formula for its multigraded Hilbert series.


title: On the bending of light from the Newtonian point of view

abstract:
  Within the framework of modified Newtonian gravity it is shown that the
corrected Newtonian scheme can't explain both Mercury's perihelion advance and
the bending of light at the same time.


title:
Length scale of density waves in the gravitational flow of fine grains
  in pipes

abstract:
  Gravitational flow of grains in pipes is frequently encountered in industry.
When the grains and pipes are size-constrained, granular flow may result in
density waves consisting of alternate high- and low-compactness regions. This
paper discusses the length scale of density waves that appear when fine grains
fall vertically in pipes. A one-dimensional model and a linear stability
analysis of the model are presented. The analysis suggests the presence of
long-wavelength instability for the most unstable mode, moreover, a cut-off
wavenumber from which the length scale is estimated. Finally, the model results
are compared to experimental data.


title:
H, He-like recombination spectra II: $l$-changing collisions for He
  Rydberg states

abstract:
  Cosmological models can be constrained by determining primordial abundances.
Accurate predictions of the He I spectrum are needed to determine the
primordial helium abundance to a precision of $< 1$% in order to constrain Big
Bang Nucleosynthesis models. Theoretical line emissivities at least this
accurate are needed if this precision is to be achieved. In the first paper of
this series, which focused on H I, we showed that differences in $l$-changing
collisional rate coefficients predicted by three different theories can
translate into 10% changes in predictions for H I spectra. Here we consider the
more complicated case of He atoms, where low-$l$ subshells are not energy
degenerate. A criterion for deciding when the energy separation between $l$
subshells is small enough to apply energy-degenerate collisional theories is
given. Moreover, for certain conditions, the Bethe approximation originally
proposed by Pengelly & Seaton (1964) is not sufficiently accurate. We introduce
a simple modification of this theory which leads to rate coefficients which
agree well with those obtained from pure quantal calculations using the
approach of Vrinceanu et al. (2012). We show that the $l$-changing rate
coefficients from the different theoretical approaches lead to differences of
$\sim 10$% in He I emissivities in simulations of H II regions using spectral
code Cloudy.


title: Extremal theory of locally sparse multigraphs

abstract:
  An $(n,s,q)$-graph is an $n$-vertex multigraph where every set of $s$
vertices spans at most $q$ edges. In this paper, we determine the maximum
product of the edge multiplicities in $(n,s,q)$-graphs if the congruence class
of $q$ modulo ${s\choose 2}$ is in a certain interval of length about $3s/2$.
The smallest case that falls outside this range is $(s,q)=(4,15)$, and here the
answer is $a^{n^2+o(n^2)}$ where $a$ is transcendental assuming Schanuel's
conjecture. This could indicate the difficulty of solving the problem in full
generality. Many of our results can be seen as extending work by Bondy-Tuza and
F\"uredi-K\"undgen about sums of edge multiplicities to the product setting.
  We also prove a variety of other extremal results for $(n,s,q)$-graphs,
including product-stability theorems. These results are of additional interest
because they can be used to enumerate and to prove logical 0-1 laws for
$(n,s,q)$-graphs. Our work therefore extends many classical enumerative results
in extremal graph theory beginning with the Erd\H{o}s-Kleitman-Rothschild
theorem to multigraphs.


title: Gerbes on $G_2$ Manifolds

abstract:
  On a projective complex manifold, the Abelian group of Divisors maps
surjectively onto that of holomorphic line bundles (the Picard group). On a
$G_2$-manifold we use coassociative submanifolds to define an analogue of the
first, and a gauge theoretical equation for a connection on a gerbe to define
an analogue of the last. Finally, we construct a map from the former to the
later. Finally, we construct some coassociative submanifolds in twisted
connected sum $G_2$-manifolds.


title:
High Electron Mobility, Quantum Hall Effect and Anomalous Optical
  Response in Atomically Thin InSe

abstract:
  A decade of intense research on two-dimensional (2D) atomic crystals has
revealed that their properties can differ greatly from those of the parent
compound. These differences are governed by changes in the band structure due
to quantum confinement and are most profound if the underlying lattice symmetry
changes. Here we report a high-quality 2D electron gas in few-layer InSe
encapsulated in hexagonal boron nitride under an inert atmosphere. Carrier
mobilities are found to exceed 1,000 and 10,000 cm2/Vs at room and
liquid-helium temperatures, respectively, allowing the observation of the
fully-developed quantum Hall effect. The conduction electrons occupy a single
2D subband and have a small effective mass. Photoluminescence spectroscopy
reveals that the bandgap increases by more than 0.5 eV with decreasing the
thickness from bulk to bilayer InSe. The band-edge optical response vanishes in
monolayer InSe, which is attributed to monolayer's mirror-plane symmetry.
Encapsulated 2D InSe expands the family of graphene-like semiconductors and, in
terms of quality, is competitive with atomically-thin dichalcogenides and black
phosphorus.


title: Importance of transient resonances in extreme-mass-ratio inspirals

abstract:
  The inspiral of stellar-mass compact objects, like neutron stars or
stellar-mass black holes, into supermassive black holes provides a wealth of
information about the strong gravitational-field regime via the emission of
gravitational waves. In order to detect and analyse these signals, accurate
waveform templates which include the effects of the compact object's
gravitational self-force are required. For computational efficiency, adiabatic
templates are often used. These accurately reproduce orbit-averaged
trajectories arising from the first-order self-force, but neglect other
effects, such as transient resonances, where the radial and poloidal
fundamental frequencies become commensurate. During such resonances the flux of
gravitational waves can be diminished or enhanced, leading to a shift in the
compact object's trajectory and the phase of the waveform. We present an
evolution scheme for studying the effects of transient resonances and apply
this to an astrophysically motivated population. We find that a large
proportion of systems encounter a low-order resonance in the later stages of
inspiral; however, the resulting effect on signal-to-noise recovery is small as
a consequence of the low eccentricity of the inspirals. Neglecting the effects
of transient resonances leads to a loss of 4% of detectable signals.


title: Computing NodeTrix Representations of Clustered Graphs

abstract:
  NodeTrix representations are a popular way to visualize clustered graphs;
they represent clusters as adjacency matrices and inter-cluster edges as curves
connecting the matrix boundaries. We study the complexity of constructing
NodeTrix representations focusing on planarity testing problems, and we show
several NP-completeness results and some polynomial-time algorithms. Building
on such algorithms we develop a JavaScript library for NodeTrix representations
aimed at reducing the crossings between edges incident to the same matrix.


title:
Dynamic Allocation of Crowd Contributions for Sentiment Analysis during
  the 2016 U.S. Presidential Election

abstract:
  Opinions about the 2016 U.S. Presidential Candidates have been expressed in
millions of tweets that are challenging to analyze automatically. Crowdsourcing
the analysis of political tweets effectively is also difficult, due to large
inter-rater disagreements when sarcasm is involved. Each tweet is typically
analyzed by a fixed number of workers and majority voting. We here propose a
crowdsourcing framework that instead uses a dynamic allocation of the number of
workers. We explore two dynamic-allocation methods: (1) The number of workers
queried to label a tweet is computed offline based on the predicted difficulty
of discerning the sentiment of a particular tweet. (2) The number of crowd
workers is determined online, during an iterative crowd sourcing process, based
on inter-rater agreements between labels.We applied our approach to 1,000
twitter messages about the four U.S. presidential candidates Clinton, Cruz,
Sanders, and Trump, collected during February 2016. We implemented the two
proposed methods using decision trees that allocate more crowd efforts to
tweets predicted to be sarcastic. We show that our framework outperforms the
traditional static allocation scheme. It collects opinion labels from the crowd
at a much lower cost while maintaining labeling accuracy.


title: Chv\'{a}tal's Conjecture and Correlation Inequalities

abstract:
  Chv\'{a}tal's conjecture in extremal combinatorics asserts that for any
decreasing family $\mathcal{F}$ of subsets of a finite set $S$, there is a
largest intersecting subfamily of $\mathcal{F}$ consisting of all members of
$\mathcal{F}$ that include a particular $x \in S$. In this paper we reformulate
the conjecture in terms of influences of variables on Boolean functions and
correlation inequalities, and study special cases and variants using tools from
discrete Fourier analysis.


title:
Weighted Hsiung-Minkowski formulas and rigidity of umbilical
  hypersurfaces

abstract:
  We use the weighted Hsiung-Minkowski integral formulas and Brendle's
inequality to show new rigidity results. First, we prove Alexandrov type
results for closed embedded hypersurfaces with radially symmetric higher order
mean curvature in a large class of Riemannian warped product manifolds,
including the Schwarzschild and Reissner-Nordstr\"{o}m spaces, where the
Alexandrov reflection principle is not available. Second, we prove that, in
Euclidean space, the only closed immersed self-expanding solitons to the
weighted generalized inverse curvature flow of codimension one are round
hyperspheres.


title: Knowledge Representation Analysis of Graph Mining

abstract:
  Many problems, especially those with a composite structure, can naturally be
expressed in higher order logic. From a KR perspective modeling these problems
in an intuitive way is a challenging task. In this paper we study the graph
mining problem as an example of a higher order problem. In short, this problem
asks us to find a graph that frequently occurs as a subgraph among a set of
example graphs. We start from the problem's mathematical definition to solve it
in three state-of-the-art specification systems. For IDP and ASP, which have no
native support for higher order logic, we propose the use of encoding
techniques such as the disjoint union technique and the saturation technique.
ProB benefits from the higher order support for sets. We compare the
performance of the three approaches to get an idea of the overhead of the
higher order support.
  We propose higher-order language extensions for IDP-like specification
languages and discuss what kind of solver support is needed. Native higher
order shifts the burden of rewriting specifications using encoding techniques
from the user to the solver itself.


title: Gonality of Expander Graphs

abstract:
  We provide lower bounds on the gonality of a graph in terms of its spectral
and edge expansion. As a consequence, we see that the gonality of a random
3-regular graph is asymptotically almost surely greater than one seventh its
genus.


title: Minimal Spin-3/2 Dark Matter in a simple $s$-channel model

abstract:
  We consider a spin~-~3/2 fermionic dark matter candidate (DM) interacting
with Standard Model fermions through a vector mediator in the $s$-channel. We
find that for pure vector couplings almost the entire parameter space of the DM
and mediator mass consistent with the observed relic density is ruled out by
the direct detection observations through DM-nucleon elastic scattering
cross-sections. In contrast, for pure axial-vector coupling, the most stringent
constraints are obtained from mono-jet searches at the Large Hadron Collider.


title: On the Origin of Earth's Moon

abstract:
  The Giant Impact is currently accepted as the leading theory for the
formation of Earth's Moon. Successful scenarios for lunar origin should be able
to explain the chemical composition of the Moon (volatile content and stable
isotope ratios), the Moon's initial thermal state, and the system's bulk
physical and dynamical properties. Hydrocode simulations of the formation of
the Moon have long been able to match the bulk properties, but recent, more
detailed work on the evolution of the protolunar disk has yielded great insight
into the origin of the Moon's chemistry, and its early thermal history. Here, I
show that the community has constructed the elements of an end-to-end theory
for lunar origin that matches the overwhelming majority of observational
constraints. In spite of the great progress made in recent years, new samples
of the Moon, clarification of processes in the impact-generated disk, and a
broader exploration of impact parameter space could yield even more insights
into this fundamental and uniquely challenging geophysical problem.


title:
Energy Rectification in Quantum Graded Spin Chains: Analysis of the XXZ
  Model

abstract:
  In this work, with focus on the energy transport properties in quantum, low
dimensional, graded materials, we address the investigation of the energy (and
spin) current in XXZ open chains with graded inner structures and driven out of
equilibrium by magnetization pumping applied at the ends. We study several
types of graded structures in different situations in order to show a
ubiquitous occurrence of energy rectification, even for the system under a
homogeneous magnetic field. Due to technical difficulties, we carry out the
computation for small chains, but we present arguments which indicate the
extension of some results to larger systems. Recalling the generic existence of
energy rectification in classical, graded materials, which are described by
anharmonic chains of oscillators, and recalling also the anharmonicity of these
XXZ models, which involve quartic terms in more transparent representation in
terms of fermionic creation and annihilation operators, we may say that our
results extend the ubiquity of energy rectification occurrence in classical
graded materials to the case of quantum systems.


title: Generation of intermittent gravitocapillary waves via parametric forcing

abstract:
  We report on the generation of an intermittent wave field driven by a
horizontally moving wave maker interacting with Faraday waves. The spectrum of
the local gravitocapillary surface wave fluctuations displays a power law in
frequency for a wide range of forcing parameters. We compute the probability
density function of the local surface height increments, which show that they
change strongly across time scales. The structure functions of these increments
are shown to display power laws as a function of the time lag, with exponents
that are nonlinear functions of the order of the structure function. We argue
that the origin of this scale-invariant intermittent spectrum is the Faraday
wave pattern breakup due to its advection by the propagating gravity waves.
Finally, some interpretations are proposed to explain the appearance of this
intermittent spectrum.


title: Orbifold Jacobian algebras for invertible polynomials

abstract:
  An important invariant of a polynomial $f$ is its Jacobian algebra defined by
its partial derivatives. Let $f$ be invariant with respect to the action of a
finite group of diagonal symmetries $G$. We axiomatically define an orbifold
Jacobian $\mathbb{Z}/2\mathbb{Z}$-graded algebra for the pair $(f,G)$ and show
its existence and uniqueness in the case, when $f$ is an invertible polynomial.
In case when $f$ defines an ADE singularity, we illustrate its geometric
meaning.


title:
SPIDERS: the spectroscopic follow-up of X-ray selected clusters of
  galaxies in SDSS-IV

abstract:
  SPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a program
dedicated to the homogeneous and complete spectroscopic follow-up of X-ray AGN
and galaxy clusters over a large area ($\sim$7500 deg$^2$) of the extragalactic
sky. SPIDERS is part of the SDSS-IV project, together with the Extended Baryon
Oscillation Spectroscopic Survey (eBOSS) and the Time-Domain Spectroscopic
Survey (TDSS). This paper describes the largest project within SPIDERS before
the launch of eROSITA: an optical spectroscopic survey of X-ray selected,
massive ($\sim 10^{14}$ to $10^{15}~M_{\odot}$) galaxy clusters discovered in
ROSAT and XMM-Newton imaging. The immediate aim is to determine precise
($\Delta_z \sim 0.001$) redshifts for 4,000-5,000 of these systems out to $z
\sim 0.6$. The scientific goal of the program is precision cosmology, using
clusters as probes of large-scale structure in the expanding Universe. We
present the cluster samples, target selection algorithms and observation
strategies. We demonstrate the efficiency of selecting targets using a
combination of SDSS imaging data, a robust red-sequence finder and a dedicated
prioritization scheme. We describe a set of algorithms and work-flow developed
to collate spectra and assign cluster membership, and to deliver catalogues of
spectroscopically confirmed clusters. We discuss the relevance of line-of-sight
velocity dispersion estimators for the richer systems. We illustrate our
techniques by constructing a catalogue of 230 spectroscopically validated
clusters ($0.031 < z < 0.658$), found in pilot observations. We discuss two
potential science applications of the SPIDERS sample: the study of the X-ray
luminosity-velocity dispersion ($L_X-\sigma$) relation and the building of
stacked phase-space diagrams.


title: An elementary inductive proof that $AB=I$ implies $BA=I$ for matrices

abstract:
  In this note we give an elementary demonstration of the fact that AB=I
implies BA=I for square matrices A,B with coefficients in a field K. By
elementary we mean that our proof follows from the very definitions of matrix
and product of a matrix, with no extra help of more sophisticated results, as
the use of dimensions of vector spaces or other ring- theoretical properties,
like being Noetherian. The proof is also elementary in the sense that it relies
on the concept and properties of the so called elementary operations on
matrices. Finally, and no less important, the proof we show can be faced by any
good student of a first year course in Mathematics, Physics or Engineering.


title: Analytic results for the Tsallis thermodynamic variables

abstract:
  We analytically investigate the thermodynamic variables of a hot and dense
system, in the framework of the Tsallis non-extensive classical statistics.
After a brief review, we start by recalling the corresponding massless limits
for all the thermodynamic variables. We then present the detail of calculation
for the exact massive result regarding the pressure -- valid for all values of
the $q$-parameter -- as well as the Tsallis $T$-, $\mu$- and $m$- parameters,
the former characterizing the non-extensivity of the system. The results for
other thermodynamic variables, in the massive case, readily follow from
appropriate differentiations of the pressure, for which we provide the
necessary formulas. For the convenience of the reader, we tabulate all of our
results. A special emphasis is put on the method used in order to perform these
computations, which happens to reduce cumbersome momentum integrals into
simpler ones. Numerical consistency between our analytic results and the
corresponding usual numerical integrals are found to be perfectly consistent.
Finally, it should be noted that our findings substantially simplify
calculations within the Tsallis framework. The latter being extensively used in
various different fields of science as for example, but not limited to,
high-energy nucleus collisions, we hope to enlighten a number of possible
applications.


title:
Interplay of projectile breakup and target excitation in reactions
  induced by weakly-bound nuclei

abstract:
  In this work, we reexamine the extension of the CDCC formalism to include
target excitation and apply it to a variety of reactions to study the effect of
breakup on inelastic cross sections. We use a transformed oscillator basis to
discretize the continuum of the projectiles in the different reactions and use
the extended CDCC method developed in this work to solve the resulting coupled
differential equations. A new code has been developed to perform the
calculations. Reactions 58Ni(d, d) 58Ni*, 24Mg(d, d) 24Mg* , 144Sm( 6Li, 6Li)
144Sm* and 9Be( 6Li, 6Li) 9Be* are studied. Satisfactory agreement is found
between experimental data and extended CDCC calculations. The studied CDCC
method is proved to be an accurate tool to describe target excitation in
reactions with weakly-bound nuclei. Moderate effects of breakup on inelastic
observables are found for the reactions studied. Cross section magnitudes are
not modified much, but angular distributions present smoothing when opposed to
calculations without breakup.


title: Robustness of classifiers: from adversarial to random noise

abstract:
  Several recent works have shown that state-of-the-art classifiers are
vulnerable to worst-case (i.e., adversarial) perturbations of the datapoints.
On the other hand, it has been empirically observed that these same classifiers
are relatively robust to random noise. In this paper, we propose to study a
\textit{semi-random} noise regime that generalizes both the random and
worst-case noise regimes. We propose the first quantitative analysis of the
robustness of nonlinear classifiers in this general noise regime. We establish
precise theoretical bounds on the robustness of classifiers in this general
regime, which depend on the curvature of the classifier's decision boundary.
Our bounds confirm and quantify the empirical observations that classifiers
satisfying curvature constraints are robust to random noise. Moreover, we
quantify the robustness of classifiers in terms of the subspace dimension in
the semi-random noise regime, and show that our bounds remarkably interpolate
between the worst-case and random noise regimes. We perform experiments and
show that the derived bounds provide very accurate estimates when applied to
various state-of-the-art deep neural networks and datasets. This result
suggests bounds on the curvature of the classifiers' decision boundaries that
we support experimentally, and more generally offers important insights onto
the geometry of high dimensional classification problems.


title: The Bayesian SLOPE

abstract:
  The SLOPE estimates regression coefficients by minimizing a regularized
residual sum of squares using a sorted-$\ell_1$-norm penalty. The SLOPE
combines testing and estimation in regression problems. It exhibits suitable
variable selection and prediction properties, as well as minimax optimality.
This paper introduces the Bayesian SLOPE procedure for linear regression. The
classical SLOPE estimate is the posterior mode in the normal regression problem
with an appropriate prior on the coefficients. The Bayesian SLOPE considers the
full Bayesian model and has the advantage of offering credible sets and
standard error estimates for the parameters. Moreover, the hierarchical
Bayesian framework allows for full Bayesian and empirical Bayes treatment of
the penalty coefficients; whereas it is not clear how to choose these
coefficients when using the SLOPE on a general design matrix. A direct
characterization of the posterior is provided which suggests a Gibbs sampler
that does not involve latent variables. An efficient hybrid Gibbs sampler for
the Bayesian SLOPE is introduced. Point estimation using the posterior mean is
highlighted, which automatically facilitates the Bayesian prediction of future
observations. These are demonstrated on real and synthetic data.


title: Domestic Axion

abstract:
  We attempt to identify a phenomenologically viable solution to the strong
$CP$ problem in which the axion is composed entirely out of Standard Model
fermion species. The axion consists predominantly of the $\eta'$ meson with a
minuscule admixture of a pseudoscalar bilinear composite of neutrinos,
$\eta_{\nu}$. The Peccei-Quinn symmetry is an axial symmetry that acts on the
up quark and the neutrino species and is spontaneously broken by the QCD
condensate of quarks as well as the condensate of neutrinos triggered by chiral
gravitational anomaly. The up-quark mass is spontaneously generated by the
neutrino condensate which plays the role of an additional composite Higgs
doublet with the compositeness scale of the order of the neutrino masses. Such
a scenario is highly economical: it solves the strong $CP$ problem, generates
the up-quark and neutrino masses from fermion condensates and simultaneously
protects the axion shift symmetry against gravitational anomaly. The
phenomenology is different from the standard hidden axion case. One of the
experimental signatures is the existence of a gravity-competing
isotope-dependent attractive force among nucleons at (sub)micron distances.


title:
J-Viz: Sibling-First Recursive Graph Drawing for Visualizing Java
  Bytecode

abstract:
  We describe a graph visualization tool for visualizing Java bytecode. Our
tool, which we call J-Viz, visualizes connected directed graphs according to a
canonical node ordering, which we call the sibling-first recursive (SFR)
numbering. The particular graphs we consider are derived from applying Shiver's
k-CFA framework to Java bytecode, and our visualizer includes helpful links
between the nodes of an input graph and the Java bytecode that produced it, as
well as a decompiled version of that Java bytecode. We show through several
case studies that the canonical drawing paradigm used in J-Viz is effective for
identifying potential security vulnerabilities and repeated use of the same
code in Java applications.


title: Quantum cosmology of scalar-tensor theories and self-adjointness

abstract:
  In this paper, the problem of the self-adjointness for the case of a quantum
minisuperspace Hamiltonian retrieved from a Brans-Dicke (BD) action is
investigated. Our matter content is presented in terms of a perfect fluid, onto
which the Schutz's formalism will be applied. We use the von Neumann theorem
and the similarity with the Laplacian operator in one of the variables to
determine the cases where the Hamiltonian is self-adjoint and if it admits
self-adjoint extensions. For the latter, we study which extension is physically
more suitable.


title: The smallest matrix black hole model in the classical limit

abstract:
  We study the smallest non-trivial matrix model that can be considered to be a
(toy) model of a black hole. The model consists of a pair of $2\times 2$
traceless hermitian matrices with a commutator squared potential and an $SU(2)$
gauge symmetry, plus an $SO(2)$ rotation symmetry. We show that using the
symmetries of the system, all but two of the variables can be separated. The
two variables that remain display chaos and a transition from chaos to
integrability when a parameter related to an $SO(2)$ angular momentum is tuned
to a critical value. We compute the Lyapunov exponents near this transition and
study the critical exponent of the Lyapunov exponents near the critical point.
We compare this transition to extremal rotating black holes.


title:
Detection relic gravitational waves in thermal case by using Adv.LIGO
  data of GW150914

abstract:
  The thermal spectrum of relic gravitational waves causes the new amplitude
that called `modified amplitude'. Our analysis shows that, there exist some
chances for detection of the thermal spectrum in addition to the usual spectrum
by Adv.LIGO data of GW150914 and detector based on the maser light (Dml). The
behavior of the inflation and reheating stages are often known as power law
expansion like $ S(\eta)\propto \eta^{1+\beta}$, $S(\eta)\propto
\eta^{1+\beta_s}$ respectively. The $\beta$ and $\beta_s$ have an unique effect
on the shape of the spectrum. We find some upper bounds on the $\beta$ and
$\beta_s$ by comparison the usual and the thermal spectrum with the Adv.LIGO
and Dml. As this result modifies our information about the nature of the
evolution of inflation and reheating stages.


title:
Towards Transparent AI Systems: Interpreting Visual Question Answering
  Models

abstract:
  Deep neural networks have shown striking progress and obtained
state-of-the-art results in many AI research fields in the recent years.
However, it is often unsatisfying to not know why they predict what they do. In
this paper, we address the problem of interpreting Visual Question Answering
(VQA) models. Specifically, we are interested in finding what part of the input
(pixels in images or words in questions) the VQA model focuses on while
answering the question. To tackle this problem, we use two visualization
techniques -- guided backpropagation and occlusion -- to find important words
in the question and important regions in the image. We then present qualitative
and quantitative analyses of these importance maps. We found that even without
explicit attention mechanisms, VQA models may sometimes be implicitly attending
to relevant regions in the image, and often to appropriate words in the
question.


title:
Improved accuracy for time-splitting methods for the numerical solution
  of parabolic equations

abstract:
  In this work, we study time-splitting strategies for the numerical
approximation of evolutionary reaction-diffusion problems. In particular, we
formulate a family of domain decomposition splitting methods that overcomes
some typical limitations of classical alternating direction implicit (ADI)
schemes. The splitting error associated with such methods is observed to be
$\mathcal{O}(\tau^2)$ in the time step $\tau$. In order to decrease the size of
this splitting error to $\mathcal{O}(\tau^3)$, we add a correction term to the
right-hand side of the original formulation. This procedure is based on the
improved initialization technique proposed by Douglas and Kim in the framework
of ADI methods. The resulting non-iterative schemes reduce the global system to
a collection of uncoupled subdomain problems that can be solved in parallel.
Computational results comparing the newly derived algorithms with the
Crank-Nicolson scheme and certain ADI methods are presented.


title: High-precision spectroscopy of the HD+ molecule at the 1-p.p.b. level

abstract:
  Recently we reported a high precision optical frequency measurement of the
(v,L):(0,2)->(8,3) vibrational overtone transition in trapped deuterated
molecular hydrogen (HD+) ions at 10 mK temperature. Achieving a resolution of
0.85 parts-per-billion (p.p.b.) we found the experimental value ($\nu_0=
383,407,177.38(41)$ MHz) to be in agreement with the value from molecular
theory ($\nu_\text{th}=383,407,177.150(15)$ MHz) within 0.6(1.1) p.p.b.
[Biesheuvel et al., Nat. Commun. 7, 10385 (2016)]. This enabled an improved
test of molecular theory (including QED), new constraints on the size of
possible effects due to 'new physics', and the first determination of the
proton-electron mass ratio from a molecule. Here, we provide the details of the
experimental procedure, spectral analysis, and the assessment of systematic
frequency shifts. Our analysis focuses in particular on deviations of the HD+
velocity distribution from thermal (Gaussian) distributions under the influence
of collisions with fast ions produced during (laser-induced) chemical
reactions, as such deviations turn out to significantly shift the
hyperfine-less vibrational frequency as inferred from the saturated and
Doppler-broadened spectrum, which contains partly unresolved hyperfine
structure.


title: A CFT Perspective on Gravitational Dressing and Bulk Locality

abstract:
  We revisit the construction of local bulk operators in AdS/CFT with special
focus on gravitational dressing and its consequences for bulk locality.
Specializing to 2+1-dimensions, we investigate these issues via the proposed
identification between bulk operators and cross-cap boundary states. We obtain
explicit expressions for correlation functions of bulk fields with boundary
stress tensor insertions, and find that they are free of non-local branch cuts
but do have non-local poles. We recover the HKLL recipe for restoring bulk
locality for interacting fields as the outcome of a natural CFT crossing
condition. We show that, in a suitable gauge, the cross-cap states solve the
bulk wave equation for general background geometries, and satisfy a conformal
Ward identity analogous to a soft graviton theorem, Virasoro symmetry, the
large N conformal bootstrap and the uniformization theorem all play a key role
in our derivations.


title:
The NuSTAR X-ray Spectrum of Hercules X-1: A Radiation-Dominated
  Radiative Shock

abstract:
  We report new spectral modeling of the accreting X-ray pulsar Hercules X- 1.
Our radiation-dominated radiative shock model is an implementation of the
analytic work of Becker & Wolff on Comptonized accretion flows onto magnetic
neutron stars. We obtain a good fit to the spin-phase averaged 4 to 78 keV
X-ray spectrum observed by the Nuclear Spectroscopic Telescope Array during a
main- on phase of the Her X-1 35-day accretion disk precession period. This
model allows us to estimate the accretion rate, the Comptonizing temperature of
the radiating plasma, the radius of the magnetic polar cap, and the average
scattering opacity parameters in the accretion column. This is in contrast to
previous phenomenological models that characterized the shape of the X-ray
spectrum but could not determine the physical parameters of the accretion flow.
We describe the spectral fitting details and discuss the interpretation of the
accretion flow physical parameters.


title:
Effects of autoionization in electron loss from helium-like highly
  charged ions in collisions with photons and fast atomic particles

abstract:
  We study theoretically single electron loss from helium-like highly charged
ions involving excitation and decay of autoionizing states of the ion. Electron
loss is caused by either photo absorption or the interaction with a fast atomic
particle (a bare nucleus, a neutral atom, an electron). The interactions with
the photon field and the fast particles are taken into account in the first
order of perturbation theory. Two initial states of the ion are considered:
$1s^2$ and $(1s2s)_{J=0}$. We analyze in detail how the shape of the emission
pattern depends on the atomic number $Z_{I}$ of the ion discussing, in
particular, the inter-relation between electron loss via photo absorption and
due to the impact of atomic particles in collisions at modest relativistic and
extreme relativistic energies. According to our results, in electron loss from
the $1s^2$ state autoionization may substantially influence the shape of the
emission spectra only up to $Z_{I} \approx 35-40$. A much more prominent role
is played by autoionization in electron loss from $(1s2s)_{J=0}$ where it not
only strongly affect the shape of the emission pattern but also may
substantially increase the total loss cross section.


title:
Enhancing Chaotic Behavior at room temperature in GaAs/(Al,Ga)As
  Superlattices

abstract:
  Previous theoretical and experimental work has put forward 50-period
semiconductor superlattices as fast, true random number generators at room
temperature. Their randomness stems from feedback between nonlinear electronic
dynamics and stochastic processes that are intrinsic to quantum transitions.
This work theoretically demonstrates that shorter superlattices with higher
potential barriers contain fully chaotic dynamics over several intervals of the
applied bias voltage compared to the 50-periods device which presented a much
weaker chaotic behavior. The chaos arises from deterministic dynamics, hence it
persists even in the absence of additional stochastic processes. Moreover, the
frequency of the chaotic current oscillations is higher for shorter
superlattices. These features should allow for faster and more robust
generation of true random numbers.


title: Disentangling the Virgo Overdensity with RR Lyrae stars

abstract:
  We use a combination of spatial distribution and radial velocity to search
for halo sub-structures in a sample of 412 RR Lyrae stars (RRLS) that covers a
$\sim 525$ square degrees region of the Virgo Overdensity (VOD) and spans
distances from the Sun from 4 to 75 kpc. With a friends-of-friends algorithm we
identified six high significance groups of RRLS in phase space, which we
associate mainly with the VOD and with the Sagittarius stream. Four other
groups were also flagged as less significant overdensities. Three high
significance and 3 lower significance groups have distances between $\sim 10$
and 20 kpc, which places them with the distance range attributed by others to
the VOD. The largest of these is the Virgo Stellar Stream (VSS) at 19 kpc,
which has 18 RRLS, a factor of 2 increase over the number known previously.
While these VOD groups are distinct according to our selection cirteria, their
overlap in position and distance, and, in a few cases, similarity in radial
velocity are suggestive that they may not all stem separate accretion events.
Even so, the VOD appears to be caused by more than one overdensity. The Sgr
stream is a very obvious feature in the background of the VOD at a mean
distance of 44 kpc. Two additional high significant groups were detected at
distances $>40$ kpc. Their radial velocities and locations differ from the
expected path of the Sgr debris in this part of the sky, and they are likely to
be remnants of other accretion events.


title:
Four-loop QCD $\beta$-function with different fermion representations of
  the gauge group

abstract:
  We present analytical results at four-loop level for the $\beta$-function of
the coupling of a generic gauge group and any number of different quark
representations. From this we can directly derive the gluino contribution to
the strong coupling $\beta$-function of supersymmetric extensions of the
Standard Model.


title:
Search for Blazar Flux-Correlated TeV Neutrinos in IceCube 40-String
  Data

abstract:
  We present a targeted search for blazar flux-correlated high-energy
($\varepsilon_\nu > 1$ TeV) neutrinos from six bright northern blazars, using
the public database of northern-hemisphere neutrinos detected during "IC40"
40-string operations of the IceCube neutrino observatory (April 2008 to May
2009). Our six targeted blazars are subjects of long-term monitoring campaigns
by the VERITAS TeV gamma-ray observatory. We use the publicly-available VERITAS
lightcurves to identify periods of excess and flaring emission. These
predefined intervals serve as our "active temporal windows" in a search for an
excess of neutrinos, relative to Poisson fluctuations of the near-isotropic
atmospheric neutrino background which dominates at these energies. After
defining the parameters of an optimized search, we confirm the expected Poisson
behavior with Monte Carlo simulations prior to testing for excess neutrinos in
the actual data. We make two searches: One for excess neutrinos associated with
the bright flares of Mrk 421 that occurred during the IC40 run, and one for
excess neutrinos associated with the brightest emission periods of five other
blazars (Mrk 501, 1ES 0805+524, 1ES 1218+304, 3C66A, and W Comae), all
significantly fainter than the Mrk 421 flares. We find no significant excess of
neutrinos from the preselected blazar directions during the selected temporal
windows. We derive 90%-confidence upper limits on the number of expected
flux-associated neutrinos from each search. These limits are consistent with
previous point-source searches and Fermi GeV flux-correlated searches. Our
upper limits are sufficiently close to the physically-interesting regime that
we anticipate future analyses using already-collected data will either
constrain models or yield discovery of the first blazar-associated high-energy
neutrinos.


title:
Towards Competitive Classifiers for Unbalanced Classification Problems:
  A Study on the Performance Scores

abstract:
  Although a great methodological effort has been invested in proposing
competitive solutions to the class-imbalance problem, little effort has been
made in pursuing a theoretical understanding of this matter.
  In order to shed some light on this topic, we perform, through a novel
framework, an exhaustive analysis of the adequateness of the most commonly used
performance scores to assess this complex scenario. We conclude that using
unweighted H\"older means with exponent $p \leq 1$ to average the recalls of
all the classes produces adequate scores which are capable of determining
whether a classifier is competitive.
  Then, we review the major solutions presented in the class-imbalance
literature. Since any learning task can be defined as an optimisation problem
where a loss function, usually connected to a particular score, is minimised,
our goal, here, is to find whether the learning tasks found in the literature
are also oriented to maximise the previously detected adequate scores. We
conclude that they usually maximise the unweighted H\"older mean with $p = 1$
(a-mean).
  Finally, we provide bounds on the values of the studied performance scores
which guarantee a classifier with a higher recall than the random classifier in
each and every class.


title:
Controlling mode competition by tailoring the spatial pump distribution
  in a laser: A resonance-based approach

abstract:
  We introduce a simplified version of the steady-state ab initio laser theory
for calculating the effects of mode competition in continuous wave lasers using
the passive cavity resonances. This new theory harnesses widely available
numerical methods that can efficiently calculate the passive cavity resonances,
with negligible additional computational overhead. Using this theory, we
demonstrate that the pump profile of the laser cavity can be optimized both for
highly multi-mode and single-mode emission. An open source implementation of
this method has been made available.


title:
ALFALFA and WSRT Imaging of Extended HI Features in the Leo Cloud of
  Galaxies

abstract:
  We present ALFALFA HI observations of a well studied region of the Leo Cloud,
which includes the NGC 3227 group and the NGC 3190 group. We detect optically
dark HI tails and plumes with extents potentially exceeding 600 kpc, well
beyond the field of view of previous observations. These HI features contain
approximately 40% of the total HI mass in the NGC~3227 group and 10% in the
NGC~3190 group. We also present WSRT maps which show the complex morphology of
the extended emission in the NGC~3227 group. We comment on previously proposed
models of the interactions in these groups and the implications for the scale
of group processing through interactions. Motivated by the extent of the HI
plumes, we place the HI observations in the context of the larger loose group,
demonstrating the need for future sensitive, wide field HI surveys to
understand the role of group processing in galaxy evolution.


title: Iterative Mechanisms for Electricity Markets

abstract:
  In order to deal with market power that sporadically results from
contingencies (e.g., severe weather, plant outages) most electricity markets
have institutions in charge of monitoring market performance and mitigating
market power. The latter task is often achieved by producing estimates of
marginal costs (also referred to as "reference levels") that may replace the
actual bids by generators with market power. In this paper, we propose an
iterative mechanism that constitutes an alternative to outright regulatory
intervention in those sporadic situations in which market power is a
significant concern. The iterative mechanism proposed is based upon relatively
simple information exchange between the market maker and market participants
and is equipped to handle general non-linear (convex) constraints related to
technical and/or reliability requirements. We show the mechanism proposed has
many desirable properties (approximately): incentive compatibility, efficiency,
individual rationality and (weak) budget balance. In addition, we show it is
robust to imperfect information regarding costs. To illustrate we consider its
application to the joint clearing of day ahead dispatch and reserves, an
approach that has been proposed for the large-scale integration of renewable
generation. In this context, we relax the assumption that each generator has
perfect information on its own expected marginal costs of adjustment and show
the mechanism retains most of its properties.


title: A democratic suggestion

abstract:
  Within the framework of quark mass matrices with a democratic texture, the
unitary rotation matrices that diagonalize the quark matrices are obtained by a
specific parametrization of the Cabibbo-Kobayashi-Maskawa mixing matrix.
Different forms of democratic quark mass matrices are derived from slightly
different parametrizations.


title:
Even-primitive vectors in induced supermodules for general linear
  supergroups and in costandard supermodules for Schur superalgebras

abstract:
  Let $G=GL(m|n)$ be the general linear supergroup over an algebraically closed
field $K$ of characteristic zero and let $G_{ev}=GL(m)\times GL(n)$ be its even
subsupergroup. The induced supermodule $H^0_G(\lambda)$, corresponding to a
dominant weight $\lambda$ of $G$, can be represented as
$H^0_{G_{ev}}(\lambda)\otimes \Lambda(Y)$, where $Y=V_m^*\otimes V_n$ is a
tensor product of the dual of the natural $GL(m)$-module $V_m$ and the natural
$GL(n)$-module $V_n$, and $\Lambda(Y)$ is the exterior algebra of $Y$. For a
dominant weight $\lambda$ of $G$, we construct explicit $G_{ev}$-primitive
vectors in $H^0_G(\lambda)$. Related to this, we give explicit formulas for
$G_{ev}$-primitive vectors of the supermodules $H^0_{G_{ev}}(\lambda)\otimes
\otimes^k Y$. Finally, we describe a basis of $G_{ev}$-primitive vectors in the
largest polynomial subsupermodule $\nabla(\lambda)$ of $H^0_G(\lambda)$ (and
therefore in the costandard supermodule of the corresponding Schur superalgebra
$S(m|n)$). This yields a description of a basis of $G_{ev}$-primitive vectors
in arbitrary induced supermodule $H^0_G(\lambda)$.


title:
The structure of typical eye-free graphs and a Turan-type result for two
  weighted colours

abstract:
  The $(a,b)$-eye is the graph $I_{a,b} = K_{a+b}-K_b$ obtained by deleting the
edges of a clique of size $b$ from a clique of size $a+b$. We show that for any
$a,b \ge 2$ and $p \in (0,1)$, if we condition the random graph $G \sim G(n,p)$
on having no induced copy of $I_{a,b}$, then with high probability $G$ is close
to an $a$-partite graph or the complement of a $(b-1)$-partite graph. Our proof
uses the recently developed theory of hypergraph containers, and a stability
result for an extremal problem with two weighted colours. We also apply the
stability method to obtain an exact Tur\'an-type result for this extremal
problem.


title:
Modelling resonances and orbital chaos in disk galaxies. Application to
  a Milky Way spiral model

abstract:
  Context: Resonances in the stellar orbital motion under perturbations from
spiral arms structure play an important role in the evolution of the disks of
spiral galaxies. The epicyclic approximation allows the determination of the
corresponding resonant radii on the equatorial plane (for nearly circular
orbits), but is not suitable in general.
  Aims: We expand the study of resonant orbits by analysing stellar motions
perturbed by spiral arms with Gaussian-shaped profiles without any restriction
on the stellar orbital configurations, and we expand the concept of Lindblad
(epicyclic) resonances for orbits with large radial excursions.
  Methods: We define a representative plane of initial conditions, which covers
the whole phase space of the system. Dynamical maps on representative planes
are constructed numerically, in order to characterize the phase-space structure
and identify the precise location of resonances. The study is complemented by
the construction of dynamical power spectra, which provide the identification
of fundamental oscillatory patterns in the stellar motion.
  Results: Our approach allows a precise description of the resonance chains in
the whole phase space, giving a broader view of the dynamics of the system when
compared to the classical epicyclic approach, even for objects in retrograde
motion. The analysis of the solar neighbourhood shows that, depending on the
current azimuthal phase of the Sun with respect to the spiral arms, a star with
solar kinematic parameters may evolve either inside the stable co-rotation
resonance or in a chaotic zone.
  Conclusions: Our approach contributes to quantifying the domains of resonant
orbits and the degree of chaos in the whole Galactic phase-space structure. It
may serve as a starting point to apply these techniques to the investigation of
clumps in the distribution of stars in the Galaxy, such as kinematic moving
groups.


title:
Associative Yang-Baxter equation and Fukaya categories of square-tiled
  surfaces

abstract:
  We show that all strongly non-degenerate trigonometric solutions of the
associative Yang-Baxter equation (AYBE) can be obtained from triple Massey
products in the Fukaya category of square-tiled surfaces. Along the way, we
give a classification result for cyclic $A_\infty$-algebra structures on a
certain Frobenius algebra associated with a pair of 1-spherical objects in
terms of the equivalence classes of the corresponding solutions of the AYBE. As
an application, combining our results with homological mirror symmetry for
punctured tori (cf. arXiv:1601.06141), we prove that any two simple vector
bundles on a cycle of projective lines are related by a sequence of 1-spherical
twists and their inverses.


title:
Transmission spectroscopy of the inflated exoplanet WASP-52b, and
  evidence for a bright region on the stellar surface

abstract:
  We have measured the transmission spectrum of the extremely inflated hot
Jupiter WASP-52b using simultaneous photometric observations in SDSS u', g' and
a filter centred on the sodium doublet (NaI) with the ULTRACAM instrument
mounted on the 4.2m William Herschel Telescope. We find that Rayleigh
scattering is not the dominant source of opacity within the planetary
atmosphere and find a transmission spectrum more consistent with
wavelength-independent opacity such as from clouds. We detect an in-transit
anomaly that we attribute to the presence of stellar activity and find that
this feature can be more simply modelled as a bright region on the stellar
surface akin to Solar faculae rather than spots. A spot model requires a
significantly larger planet/star radius ratio than that found in previous
studies. Our results highlight the precision that can be achieved by
ground-based photometry with errors in the scaled planetary radii of less than
one atmospheric scale height, comparable to HST observations.


title:
The Quantum Pinch Effect in Semiconducting Quantum Wires: A Bird's-Eye
  View

abstract:
  Those who measure success with culmination do not seem to be aware that life
is a journey not a destination. This spirit is best reflected in the unceasing
failures in efforts for solving the problem of controlled thermonuclear fusion
for even the simplest pinches for over decades; and the nature keeps us
challenging with examples. However, these efforts have permitted researchers
the obtention of a dense plasma with a lifetime that, albeit short, is
sufficient to study the physics of the pinch effect, to create methods of
plasma diagnostics, and to develop a modern theory of plasma processes. Most
importantly, they have impregnated the solid state plasmas, particularly the
electron-hole plasmas in semiconductors, which do not suffer from the issues
related with the confinement and which have demonstrated their potential not
only for the fundamental physics but also for the device physics. Here, we
report on a two-component, cylindrical, quasi-one-dimensional quantum plasma
subjected to a {\em radial} confining harmonic potential and an applied
magnetic field in the symmetric gauge. It is demonstrated that such a system as
can be realized in semiconducting quantum wires offers an excellent medium for
observing the quantum pinch effect at low temperatures. An exact analytical
solution of the problem allows us to make significant observations:
surprisingly, in contrast to the classical pinch effect, the particle density
as well as the current density display a {\em determinable} maximum before
attaining a minimum at the surface of the quantum wire. The effect will persist
as long as the equilibrium pair density is sustained. Therefore, the
technological promise that emerges is the route to the precise electronic
devices that will control the particle beams at the nanoscale.


title: The dynamics of starvation and recovery

abstract:
  The eco-evolutionary dynamics of species are fundamentally linked to the
energetic constraints of its constituent individuals. Of particular importance
is the interplay between reproduction and the dynamics of starvation and
recovery. To elucidate this interplay, we introduce a nutritional
state-structured model that incorporates two classes of consumer: nutritionally
replete, reproducing consumers, and undernourished, non-reproducing consumers.
We obtain strong constraints on starvation and recovery rates by deriving
allometric scaling relationships and find that population dynamics are
typically driven to a steady state. Moreover, these rates fall within a
'refuge' in parameter space, where the probability of population extinction is
minimized. We also show that our model provides a natural framework to predict
maximum mammalian body size by determining the relative stability of an
otherwise homogeneous population to a competing population with altered percent
body fat. This framework provides a principled mechanism for a selective driver
of Cope's rule.


title: Classical and quantum shortcuts to adiabaticity in a tilted piston

abstract:
  Adiabatic quantum state evolution can be accelerated through a variety of
shortcuts to adiabaticity. In one approach, a counterdiabatic quantum
Hamiltonian $\hat H_{CD}$ is constructed to suppress nonadiabatic excitations.
In the analogous classical problem, a counterdiabatic classical Hamiltonian
$H_{CD}$ ensures that the classical action remains constant even under rapid
driving. Both the quantum and classical versions of this problem have been
solved for the special case of scale-invariant driving, characterized by linear
expansions, contractions or translations of the system. Here we investigate an
example of a non-scale-invariant system -- a tilted piston. We solve exactly
for the classical counterdiabatic Hamiltonian $H_{CD}(q,p,t)$, which we then
quantize to obtain a Hermitian operator $\hat H_{CD}(t)$. Using numerical
simulations, we find that $\hat H_{CD}$ effectively suppresses non-adiabatic
excitations under rapid driving. These results offer a proof of principle --
beyond the special case of scale-invariant driving -- that quantum shortcuts to
adiabaticity can successfully be constructed from their classical counterparts.


title:
Existence results for Isaacs equations with local conditions and related
  semilinear Cauchy problems

abstract:
  Our goal is to prove existence results for classical solutions to some
general nondegenerate Cauchy problems which are natural generalizations of
Isaacs equations. For the latter we are able to extend our results by admitting
local conditions for coefficients. Such equations appear naturally for instance
in robust control theory. Using our general results, we can solve not only
Isaacs equations, but also equations for other sophisticated control problems,
for instance models with state dependent constraints on the control set.


title:
Critical Current Oscillations of Elliptical Josephson Junctions with
  Single-Domain Ferromagnetic Layers

abstract:
  Josephson junctions containing ferromagnetic layers are of considerable
interest for the development of practical cryogenic memory and superconducting
qubits. Such junctions exhibit a phase shift of $\pi$ for certain ranges of
ferromagnetic layer thickness. We present studies of Nb based micron-scale
elliptically-shaped Josephson junctions containing ferromagnetic barriers of
Ni$_{81}$Fe$_{19}$ or Ni$_{65}$Co$_{20}$Fe$_{15}$. By applying an external
magnetic field, the critical current of the junctions are found to follow
characteristic Fraunhofer patterns, and display sharp switching behavior
suggestive of single-domain magnets. The high quality of the Fraunhofer
patterns enables us to extract the maximum value of the critical current even
when the peak is shifted significantly outside the range of the data due to the
magnetic moment of the ferromagnetic layer. The maximum value of the critical
current oscillates as a function of the ferromagnetic barrier thickness,
indicating transitions in the phase difference across the junction between
values of zero and $\pi$. We compare the data to previous work and to models of
the 0-$\pi$ transitions based on existing theories.


title: Credit default prediction and parabolic potential theory

abstract:
  We consider an approach to credit risk in which the information about the
time of bankruptcy is modelled using a Brownian bridge that starts at zero and
is conditioned to equal zero when the default occurs. This raises the question
whether the default can be foreseen by observing the evolution of the bridge
process. Unlike in most standard models for credit risk, we allow the
distribution of the default time to be singular. Using a well known fact from
parabolic potential theory, we provide a sufficient condition for its
predictability.


title: Learning Syntactic Program Transformations from Examples

abstract:
  IDEs, such as Visual Studio, automate common transformations, such as Rename
and Extract Method refactorings. However, extending these catalogs of
transformations is complex and time-consuming. A similar phenomenon appears in
intelligent tutoring systems where instructors have to write cumbersome code
transformations that describe "common faults" to fix similar student
submissions to programming assignments. We present REFAZER, a technique for
automatically generating program transformations. REFAZER builds on the
observation that code edits performed by developers can be used as examples for
learning transformations. Example edits may share the same structure but
involve different variables and subexpressions, which must be generalized in a
transformation at the right level of abstraction. To learn transformations,
REFAZER leverages state-of-the-art programming-by-example methodology using the
following key components: (a) a novel domain-specific language (DSL) for
describing program transformations, (b) domain-specific deductive algorithms
for synthesizing transformations in the DSL, and (c) functions for ranking the
synthesized transformations. We instantiate and evaluate REFAZER in two
domains. First, given examples of edits used by students to fix incorrect
programming assignment submissions, we learn transformations that can fix other
students' submissions with similar faults. In our evaluation conducted on 4
programming tasks performed by 720 students, our technique helped to fix
incorrect submissions for 87% of the students. In the second domain, we use
repetitive edits applied by developers to the same project to synthesize a
program transformation that applies these edits to other locations in the code.
In our evaluation conducted on 59 scenarios of repetitive edits taken from 3 C#
open-source projects, REFAZER learns the intended program transformation in 83%
of the cases.


title: Complex Perspective for the Projective Heat Map Acting on Pentagons

abstract:
  We place Schwartz's work on the real dynamics of the projective heat map $H$
into the complex perspective by computing its first dynamical degree and
gleaning some corollaries about the dynamics of $H$.


title: Mining Half a Billion Topical Experts Across Multiple Social Networks

abstract:
  Mining topical experts on social media is a problem that has gained
significant attention due to its wide-ranging applications. Here we present the
first study that combines data from four major social networks -- Twitter,
Facebook, Google+ and LinkedIn, along with the Wikipedia graph and internet
webpage text and metadata, to rank topical experts across the global population
of users. We perform an in-depth analysis of 37 features derived from various
data sources such as message text, user lists, webpages, social graphs and
wikipedia. This large-scale study includes more than 12 billion messages over a
90-day sliding window and 58 billion social graph edges. Comparison reveals
that features derived from Twitter Lists, Wikipedia, internet webpages and
Twitter Followers are especially good indicators of expertise. We train an
expertise ranking model using these features on a large ground truth dataset
containing almost 90,000 labels. This model is applied within a production
system that ranks over 650 million experts in more than 9,000 topical domains
on a daily basis. We provide results and examples on the effectiveness of our
expert ranking system, along with empirical validation. Finally, we make the
topical expertise data available through open REST APIs for wider use.


title: Initial state dependence of a quantum-resonance ratchet

abstract:
  We demonstrate quantum resonance ratchets created with Bose-Einstein
condensates exposed to pulses of an off-resonant standing light wave. We show
how some of the basic properties of the ratchets are controllable through the
creation of different initial states of the system. In particular, our results
prove that through an appropriate choice of initial state it is possible to
reduce the extent to which the ratchet state changes with respect to time. We
develop a simple theory to explain our results and indicate how ratchets might
be used as part of a matter wave interferometer or quantum-random walk
experiment.


title:
On subexponential tails for the maxima of negatively driven compound
  renewal and L\'evy processes

abstract:
  We study subexponential tail asymptotics for the distribution of the maximum
$M_t:=\sup_{u\in[0,t]}X_u$ of a process $X_t$ with negative drift for the
entire range of $t>0$. We consider compound renewal processes with linear drift
and L\'evy processes. For both we also formulate and prove the principle of a
single big jump for their maxima. The class of compound renewal processes
particularly includes Cram\'er-Lundberg risk process.


title: Measuring the Quality of Exercises

abstract:
  This work explores the problem of exercise quality measurement since it is
essential for effective management of diseases like cerebral palsy (CP). This
work examines the assessment of quality of large amplitude movement (LAM)
exercises designed to treat CP in an automated fashion. Exercise data was
collected by trained participants to generate ideal examples to use as a
positive samples for machine learning. Following that, subjects were asked to
deliberately make subtle errors during the exercise, such as restricting
movements, as is commonly seen in cases of patients suffering from CP. The
quality measurement problem was then posed as a classification to determine
whether an example exercise was either "good" or "bad". Popular machine
learning techniques for classification, including support vector machines
(SVM), single and doublelayered neural networks (NN), boosted decision trees,
and dynamic time warping (DTW), were compared. The AdaBoosted tree performed
best with an accuracy of 94.68% demonstrating the feasibility of assessing
exercise quality.