title:
What is Wrong with Topic Modeling? (and How to Fix it Using Search-based
  Software Engineering)

abstract:
  Context: Topic modeling finds human-readable structures in unstructured
textual data. A widely used topic modeler is Latent Dirichlet allocation. When
run on different datasets, LDA suffers from "order effects" i.e. different
topics are generated if the order of training data is shuffled. Such order
effects introduce a systematic error for any study. This error can relate to
misleading results;specifically, inaccurate topic descriptions and a reduction
in the efficacy of text mining classification results. Objective: To provide a
method in which distributions generated by LDA are more stable and can be used
for further analysis. Method: We use LDADE, a search-based software engineering
tool that tunes LDA's parameters using DE (Differential Evolution). LDADE is
evaluated on data from a programmer information exchange site (Stackoverflow),
title and abstract text of thousands ofSoftware Engineering (SE) papers, and
software defect reports from NASA. Results were collected across different
implementations of LDA (Python+Scikit-Learn, Scala+Spark); across different
platforms (Linux, Macintosh) and for different kinds of LDAs (VEM,or using
Gibbs sampling). Results were scored via topic stability and text mining
classification accuracy. Results: In all treatments: (i) standard LDA exhibits
very large topic instability; (ii) LDADE's tunings dramatically reduce cluster
instability; (iii) LDADE also leads to improved performances for supervised as
well as unsupervised learning. Conclusion: Due to topic instability, using
standard LDA with its "off-the-shelf" settings should now be depreciated. Also,
in future, we should require SE papers that use LDA to test and (if needed)
mitigate LDA topic instability. Finally, LDADE is a candidate technology for
effectively and efficiently reducing that instability.


title:
Comparison of spectral linewidths for quantum degenerate bosons and
  fermions

abstract:
  We observe a dramatic difference in optical line shapes of a $^4\text{He}$
Bose-Einstein condensate and a $^3\text{He}$ degenerate Fermi gas by measuring
the 1557-nm $2~^3S-2~^1S$ magnetic dipole transition ($8~\text{Hz}$ natural
linewidth) in an optical dipole trap. The $15~\text{kHz}$ FWHM condensate line
shape is only broadened by mean field interactions, whereas the degenerate
Fermi gas line shape is broadened to $75~\text{kHz}$ FWHM due to the effect of
Pauli exclusion on the spatial and momentum distributions. The asymmetric
optical line shapes are observed in excellent agreement with line shape models
for the quantum degenerate gases. For $^4$He a triplet-singlet s-wave
scattering length $a=+50(10)_{\text{stat}}(43)_{\text{syst}}~a_0$ is extracted.
The high spectral resolution reveals a doublet in the absorption spectrum of
the BEC, and this effect is understood by the presence of a weak optical
lattice in which a degeneracy of the lattice recoil and the spectroscopy photon
recoil leads to Bragg-like scattering.


title: Weierstrass semigroups on Castelnuovo curves

abstract:
  We define a class of numerical semigroups S, which we call Castelnuovo
semigroups, and study the subvariety $M^S_{g,1}$ of $M_{g,1}$ consisting of
marked smooth curves with Weierstrass semigroup S. We determine the number of
irreducible components of these loci and determine their dimensions. Curves
with these Weierstrass semigroups are always Castelnuovo curves, which provides
the basic tool for our argument. This analysis provides examples of numerical
semigroups for which $M^S_{g,1}$ is reducible and non-equidimensional.


title: Second-order accurate ensemble transform particle filters

abstract:
  Particle filters (also called sequential Monte Carlo methods) are widely used
for state and parameter estimation problems in the context of nonlinear
evolution equations. The recently proposed ensemble transform particle filter
(ETPF) (S.~Reich, {\it A non-parametric ensemble transform method for Bayesian
inference}, SIAM J.~Sci.~Comput., 35, (2013), pp. A2013--A2014) replaces the
resampling step of a standard particle filter by a linear transformation which
allows for a hybridization of particle filters with ensemble Kalman filters and
renders the resulting hybrid filters applicable to spatially extended systems.
However, the linear transformation step is computationally expensive and leads
to an underestimation of the ensemble spread for small and moderate ensemble
sizes. Here we address both of these shortcomings by developing second-order
accurate extensions of the ETPF. These extensions allow one in particular to
replace the exact solution of a linear transport problem by its Sinkhorn
approximation. It is also demonstrated that the nonlinear ensemble transform
filter (NETF) arises as a special case of our general framework. We illustrate
the performance of the second-order accurate filters for the chaotic Lorenz-63
and Lorenz-96 models and a dynamic scene-viewing model. The numerical results
for the Lorenz-63 and Lorenz-96 models demonstrate that significant accuracy
improvements can be achieved in comparison to a standard ensemble Kalman filter
and the ETPF for small to moderate ensemble sizes. The numerical results for
the scene-viewing model reveal, on the other hand, that second-order
corrections can lead to statistically inconsistent samples from the posterior
parameter distribution.


title:
Bibliometrics and Information Retrieval: Creating Knowledge through
  Research Synergies

abstract:
  This panel brings together experts in bibliometrics and information retrieval
to discuss how each of these two important areas of information science can
help to inform the research of the other. There is a growing body of literature
that capitalizes on the synergies created by combining methodological
approaches of each to solve research problems and practical issues related to
how information is created, stored, organized, retrieved and used. The session
will begin with an overview of the common threads that exist between IR and
metrics, followed by a summary of findings from the BIR workshops and examples
of research projects that combine aspects of each area to benefit IR or metrics
research areas, including search results ranking, semantic indexing and
visualization. The panel will conclude with an engaging discussion with the
audience to identify future areas of research and collaboration.


title:
Strong Lensing Analysis of the Galaxy Cluster MACS J1319.9+7003 and the
  Discovery of a Shell Galaxy

abstract:
  We present a strong-lensing (SL) analysis of the galaxy cluster MACS
J1319.9+7003 ($z=0.33$, also known as Abell 1722), as part of our ongoing
effort to analyze massive clusters with archival {\it HST} imaging. We
spectroscopically measured with Keck/MOSFIRE two galaxies multiply-imaged by
the cluster. Our analysis reveals a modest lens, with an effective Einstein
radius of $\theta_{e}(z=2)=12\pm1$", enclosing $2.1\pm0.3\times10^{13}$
$M_{\odot}$. We briefly discuss the SL properties of the cluster, using two
different modeling techniques, and make the mass models
publicly-available\footnote{ftp://wise-ftp.tau.ac.il/pub/adiz/MACS1319/}.
Independently, we identified a noteworthy, young Shell Galaxy (SG) system
forming around two likely interacting cluster members, 20" north of the BCG.
SGs are rare in galaxy clusters, and indeed, a simple estimate yields that they
are only expected in roughly one in several dozen, to several hundred, massive
galaxy clusters (the estimate can easily change by an order-of-magnitude within
a reasonable range of characteristic values relevant for the calculation).
Taking advantage of our lens model best-fit, mass-to-light scaling relation for
cluster members, we infer that the total mass of the SG system is
$\sim1.3\times10^{11}$ M$_{\odot}$, with a host-to-companion mass ratio of
about 10:1. Despite being rare in high density environments, the SG constitutes
an example to how stars of cluster galaxies are being efficiently redistributed
to the Intra Cluster Medium. Dedicated numerical simulations for the observed
shell configuration, perhaps aided by the mass model, might cast interesting
insight on the interaction history and properties of the two galaxies. An
archival HST search in galaxy cluster images can reveal more such systems.


title: Data Poisoning Attacks on Factorization-Based Collaborative Filtering

abstract:
  Recommendation and collaborative filtering systems are important in modern
information and e-commerce applications. As these systems are becoming
increasingly popular in the industry, their outputs could affect business
decision making, introducing incentives for an adversarial party to compromise
the availability or integrity of such systems. We introduce a data poisoning
attack on collaborative filtering systems. We demonstrate how a powerful
attacker with full knowledge of the learner can generate malicious data so as
to maximize his/her malicious objectives, while at the same time mimicking
normal user behavior to avoid being detected. While the complete knowledge
assumption seems extreme, it enables a robust assessment of the vulnerability
of collaborative filtering schemes to highly motivated attacks. We present
efficient solutions for two popular factorization-based collaborative filtering
algorithms: the \emph{alternative minimization} formulation and the
\emph{nuclear norm minimization} method. Finally, we test the effectiveness of
our proposed algorithms on real-world data and discuss potential defensive
strategies.


title:
Galactic Cosmic Ray Origins and OB Associations: Evidence from
  SuperTIGER Observations of Elements $_{26}$Fe through $_{40}$Zr

abstract:
  We report abundances of elements from $_{26}$Fe to $_{40}$Zr in the cosmic
radiation measured by the SuperTIGER (Trans-Iron Galactic Element Recorder)
instrument during 55 days of exposure on a long-duration balloon flight over
Antarctica. These observations resolve elemental abundances in this charge
range with single-element resolution and good statistics.
  These results support a model of cosmic-ray origin in which the source
material consists of a mixture of 19$^{+11}_{-6}$\% material from massive stars
and $\sim$81\% normal interstellar medium (ISM) material with solar system
abundances. The results also show a preferential acceleration of refractory
elements (found in interstellar dust grains) by a factor of $\sim$4 over
volatile elements (found in interstellar gas) ordered by atomic mass (A). Both
the refractory and volatile elements show a mass-dependent enhancement with
similar slopes.


title:
Robust and efficient preconditioners for the discontinuous Galerkin
  time-stepping method

abstract:
  The discontinuous Galerkin time-stepping method has many advantageous
properties for solving parabolic equations. However, it requires the solution
of a large nonsymmetric system at each time-step. This work develops a fully
robust and efficient preconditioning strategy for solving these systems.
Drawing on parabolic inf-sup theory, we first construct a left preconditioner
that transforms the linear system to a symmetric positive definite problem to
be solved by the preconditioned conjugate gradient algorithm. We then prove
that the transformed system can be further preconditioned by an ideal block
diagonal preconditioner, leading to a condition number bounded by 4 for any
time-step size, any approximation order and any positive-definite self-adjoint
spatial operators. Numerical experiments demonstrate the low condition numbers
and fast convergence of the algorithm for both ideal and approximate
preconditioners, and show the feasibility of the high-order solution of large
problems.


title: On F{\o}lner sets in topological groups

abstract:
  We extend F{\o}lner's amenability criterion to the realm of general
topological groups. Building on this, we show that a topological group $G$ is
amenable if and only if its left translation action can be approximated in a
uniform manner by amenable actions on the set $G$. As applications we obtain a
topological version of Whyte's geometric solution to the von Neumann problem
and provide an affirmative answer to a question posed by Rosendal.


title:
Analysis of overdetermined system that describes the special class of
  two-dimensional motion of an ideal fluid

abstract:
  The paper considers the overdetermined system of PDE that describes a special
type of two-dimensional motion of an ideal fluid. The analysis of the
compatibility of the system was performed. All solutions of the system are
obtained in a closed form.


title: On the CCN [de]activation nonlinearities

abstract:
  We take into consideration the evolution of particle size in a monodisperse
aerosol population during activation and deactivation of cloud condensation
nuclei (CCN). The phase portrait of the system derived through a
weakly-nonlinear analysis reveals a saddle-node bifurcation and a cusp
catastrophe. An analytical estimate of the activation timescale is derived
through estimation of the time spent in the saddle-node bifurcation bottleneck.
Numerical integration of the system portrays two types of
activation/deactivation hystereses: one associated with the kinetic limitations
on droplet growth when the system is far from equilibrium, and one occurring
close to equilibrium and associated with the cusp catastrophe. The hysteretic
behaviour close to equilibrium imposes stringent time-resolution constraints on
numerical integration, particularly during deactivation.


title: Visual Question: Predicting If a Crowd Will Agree on the Answer

abstract:
  Visual question answering (VQA) systems are emerging from a desire to empower
users to ask any natural language question about visual content and receive a
valid answer in response. However, close examination of the VQA problem reveals
an unavoidable, entangled problem that multiple humans may or may not always
agree on a single answer to a visual question. We train a model to
automatically predict from a visual question whether a crowd would agree on a
single answer. We then propose how to exploit this system in a novel
application to efficiently allocate human effort to collect answers to visual
questions. Specifically, we propose a crowdsourcing system that automatically
solicits fewer human responses when answer agreement is expected and more human
responses when answer disagreement is expected. Our system improves upon
existing crowdsourcing systems, typically eliminating at least 20% of human
effort with no loss to the information collected from the crowd.


title: Minimal faces and Schur's Lemma for embeddings into R^U

abstract:
  In the context of N. Brown's Hom(N,R^U), we establish that given \pi: N
\rightarrow R^U, the dimension of the minimal face containing [\pi] is one less
than the dimension of the center of the relative commutant of \pi. We also show
the "convex independence" of extreme points in the sense that the convex hull
of n extreme points is an n-vertex simplex. Along the way, we establish a
version of Schur's Lemma for embeddings of II$_1$-factors.


title: Non-Euclidean Triangle Centers

abstract:
  Non-Euclidean triangle centers can be described using homogeneous coordinates
that are proportional to the generalized sines of the directed distances of a
given center from the edges of the reference triangle. Identical homogeneous
coordinates of a specific triangle center may be used for all spaces of uniform
Gaussian curvature. We also define the median point for a set of points in
non-Euclidean space and a planar center of rotation for a set of points in a
non-Euclidean plane.


title: Thermoelectric transport in monolayer phosphorene

abstract:
  We apply the generalized Boltzmann theory to describe thermoelectric
transport properties of monolayer phosphorene in the presence of short- and
long-range charged impurity interactions. First, we propose a low-energy
Hamiltonian to explore the accurate electronic band structure of phosphorene in
comparison with those results obtained by density-functional simulations. We
explain the effect of the coupling between the conduction and valence bands on
the thermoelectric properties. We show that the electric conductivity of
phosphorene is highly anisotropic, while the Seebeck coefficient and figure of
merit, without being influenced via either the presence or absence of the
coupling term, are nearly isotropic. Furthermore, we demonstrate that the
conductivity for the $n$ type of doping is more influenced by the coupling term
than that of the $p$ type. Along with thermopower sign change, profound
thermoelectric effects can be achieved.


title: Multi-fractal Geometry of Finite Networks of Spins

abstract:
  Quantum spin networks overcome the challenges of traditional charge-based
electronics by encoding the information into spin degrees of freedom. Although
beneficial for transmitting information with minimal losses when compared to
their charge-based counterparts, the mathematical formalization of the
information propagation in a spin(tronic) network is challenging due to its
complicated scaling properties. In this paper, we propose a geometric
approach---specific to finite networks---for unraveling the
information-theoretic phenomena of spin chains and rings by abstracting them as
weighted graphs, where the vertices correspond to the spin excitation states
and the edges represent the information theoretic distance between pair of
nodes. The weighted graph representation of the quantum spin network dynamics
exhibits a complex self-similar structure (where subgraphs repeat to some
extent over various space scales). To quantify this complex behavior, we
develop a new box counting inspired algorithm which assesses the mono-fractal
versus multi-fractal properties of quantum spin networks. Besides specific to
finite networks, multi-fractality is further compounded by "engineering" or
"biasing" the network for selective transfer, as selectivity makes the network
more heterogeneous. To demonstrate criticality in finite size systems, we
define a thermodynamics inspired framework for describing information
propagation and show evidence that some spin chains and rings exhibit an
informational phase transition phenomenon, akin to the metal-to-insulator phase
transition in Anderson localization in finite media.}


title:
Big Cohen-Macaulay and seed algebras in equal characteristic zero via
  ultraproducts

abstract:
  Let $R$ be a commutative, local, Noetherian ring. In a past article, the
first author developed a theory of $R$-algebras, termed seeds, that can be
mapped to balanced big Cohen-Macaulay $R$-algebras. In prime characteristic
$p$, seeds can be characterized based on the existence of certain
colon-killers, integral extensions of seeds are seeds, tensor products of seeds
are seeds, and the seed property is stable under base change between complete,
local domains. As a result, there exist directed systems of big Cohen-Macaulay
algebras over complete, local domains. In this work, we will show that these
properties can be extended to analogous results in equal characteristic zero.
The primary tool for the extension will be the notion of ultraproducts for
commutative rings as developed by Schoutens and Aschenbrenner.


title: Homogenization of Dissipative, Noisy, Hamiltonian Dynamics

abstract:
  We study the dynamics of a class of Hamiltonian systems with dissipation,
coupled to noise, in a singular (small mass) limit. We derive the homogenized
equation for the position degrees of freedom in the limit, including the
presence of a {\em noise-induced drift} term. We prove convergence to the
solution of the homogenized equation in probability and, under stronger
assumptions, in an $L^p$-norm. Applications cover the overdamped limit of
particle motion in a time-dependent electromagnetic field, on a manifold with
time-dependent metric, and the dynamics of nuclear matter.


title:
An ab initio investigation of Bi$_2$Se$_3$ topological insulator
  deposited on amorphous SiO$_2$

abstract:
  We use first-principles simulations to investigate the topological properties
of Bi$_2$Se$_3$ thin films deposited on amorphous SiO2, Bi$_2$Se$_3$/a-SiO$_2$,
which is a promising substrate for topological insulator (TI) based device
applications. The Bi$_2$Se$_3$ films are bonded to a-SiO$_2$ mediated by van
der Waals interactions. Upon interaction with the substrate, the Bi$_2$Se$_3$
topological surface and interface states remain present, however the degeneracy
between the Dirac-like cones is broken. The energy separation between the two
Dirac-like cones increases with the number of Bi$_2$Se$_3$ quintuple layers
(QLs) deposited on the substrate. Such a degeneracy breaking is caused by (i)
charge transfer from the TI to the substrate and charge redistribution along
the Bi$_2$Se$_3$ QLs, and (ii) by deformation of the QL in contact with the
a-SiO$_2$ substrate. We also investigate the role played by oxygen vacancies
(V$_O$) on the a-SiO$_2$, which increases the energy splitting between the two
Dirac-like cones. Finally, by mapping the electronic structure of
Bi$_2$Se$_3$/a-SiO$_2$, we found that the a-SiO$_2$ surface states, even upon
the presence of V$_O$, play a minor role on gating the electronic transport
properties of Bi$_2$Se$_3$.


title: Smart Policies for Artificial Intelligence

abstract:
  We argue that there already exists de facto artificial intelligence policy -
a patchwork of policies impacting the field of AI's development in myriad ways.
The key question related to AI policy, then, is not whether AI should be
governed at all, but how it is currently being governed, and how that
governance might become more informed, integrated, effective, and anticipatory.
We describe the main components of de facto AI policy and make some
recommendations for how AI policy can be improved, drawing on lessons from
other scientific and technological domains.


title:
Non-regularised Inverse Finite Element Analysis for 3D Traction Force
  Microscopy

abstract:
  The tractions that cells exert on a gel substrate from the observed
displacements is an increasingly attractive and valuable information in
biomedical experiments. The computation of these tractions requires in general
the solution of an inverse problem. Here, we resort to the discretisation with
finite elements of the associated direct variational formulation, and solve the
inverse analysis using a least square approach. This strategy requires the
minimisation of an error functional, which is usually regularised in order to
obtain a stable system of equations with a unique solution. In this paper we
show that for many common three-dimensional geometries, meshes and loading
conditions, this regularisation is unnecessary. In these cases, the
computational cost of the inverse problem becomes equivalent to a direct finite
element problem. For the non-regularised functional, we deduce the necessary
and sufficient conditions that the dimensions of the interpolated displacement
and traction fields must preserve in order to exactly satisfy or yield a unique
solution of the discrete equilibrium equations. We apply the theoretical
results to some illustrative examples and to real experimental data. Due to the
relevance of the results for biologists and modellers, the article concludes
with some practical rules that the finite element discretisation must satisfy.


title: Instabilities of Weyl-loop semi-metals

abstract:
  We study Weyl-loop semi-metals with short range interactions, focusing on the
possible interaction driven instabilities. We introduce an $\epsilon$ expansion
regularization scheme by means of which the possible instabilities may be
investigated in an unbiased manner through a controlled weak coupling
renormalization group calculation. The problem has enough structure that a
`functional' renormalization group calculation (necessary for an extended Fermi
surface) can be carried out analytically. The leading instabilities are
identified, and when there are competing degenerate instabilities a
Landau-Ginzburg calculation is performed to determine the most likely phase. In
the particle-particle channel, the leading instability is found to be to a
fully gapped chiral superconducting phase which spontaneously breaks time
reversal symmetry, in agreement with general symmetry arguments suggesting that
Weyl loops should provide natural platforms for such exotic forms of
superconductivity. In the particle hole channel, there are two potential
instabilities - to a gapless Pomeranchuk phase which spontaneously breaks
rotation symmetry, or to a fully gapped insulating phase which spontaneously
breaks mirror symmetry. The dominant instability in the particle hole channel
depends on the specific values of microscopic interaction parameters.


title:
Heritability maps of human face morphology through large-scale automated
  three-dimensional phenotyping

abstract:
  The human face is a complex trait under strong genetic control, as evidenced
by the striking visual similarity between twins. Nevertheless, heritability
estimates of facial traits have often been surprisingly low or difficult to
replicate. Furthermore, the construction of facial phenotypes that correspond
to naturally perceived facial features remains largely a mystery. We present
here a large-scale heritability study of face geometry that aims to address
these issues. High-resolution, three-dimensional facial models have been
acquired on a cohort of $952$ twins recruited from the TwinsUK registry, and
processed through a novel landmarking workflow, GESSA (Geodesic Ensemble
Surface Sampling Algorithm). The algorithm places thousands of landmarks
throughout the facial surface and automatically establishes point-wise
correspondence across faces. These landmarks enabled us to intuitively
characterize facial geometry at a fine level of detail through curvature
measurements, yielding accurate heritability maps of the human face
(www.heritabilitymaps.info).


title: Bloch oscillations in the absence of a lattice

abstract:
  We experimentally investigate the quantum motion of an impurity atom that is
immersed in a strongly interacting one-dimensional Bose liquid and is subject
to an external force. We find that the momentum distribution of the impurity
exhibits characteristic Bragg reflections at the edge of an emergent Brillouin
zone. While Bragg reflections are typically associated with lattice structures,
in our strongly correlated quantum liquid they result from the interplay of
short-range crystalline order and kinematic constraints on the many-body
scattering processes in the one-dimensional system. As a consequence, the
impurity exhibits periodic dynamics that we interpret as Bloch oscillations,
which arise even though the quantum liquid is translationally invariant. Our
observations are supported by large-scale numerical simulations.


title:
Zonal Flow Patterns: How Toroidal Coupling Induces Phase Jumps and Shear
  Layers

abstract:
  A new, frequency modulation mechanism for zonal flow pattern formation is
presented. The model predicts the probability distribution function of the flow
strength as well as the evolution of the characteristic spatial scale. Magnetic
toroidicity-induced global phase dynamics is shown to determine the spatial
structure of the flow. A key result is the observation that global phase
patterning can lead to zonal flow formation in the absence of turbulence
inhomogeneity.


title: A coin vibrational motor swimming at low Reynolds number

abstract:
  Low-cost coin vibrational motors, used in haptic feedback, exhibit rotational
internal motion inside a rigid case. Because the motor case motion exhibits
rotational symmetry, when placed into a fluid such as glycerin, the motor does
not swim even though its vibrations induce steady streaming in the fluid.
However, a piece of rubber foam stuck to the curved case and giving the motor
neutral buoyancy also breaks the rotational symmetry allowing it to swim. We
measured a 1 cm diameter coin vibrational motor swimming in glycerin at a speed
of a body length in 3 seconds or at 3 mm/s. The swim speed puts the vibrational
motor in a low Reynolds number regime similar to bacterial motility, but
because of the vibration it is not analogous to biological organisms. Rather
the swimming vibrational motor may inspire small inexpensive robotic swimmers
that are robust as they contain no external moving parts. A time dependent
Stokes equation planar sheet model suggests that the swim speed depends on a
steady streaming velocity $V_{stream} \sim Re_s^{1/2} U_0$ where $U_0$ is the
velocity of surface vibrations, and streaming Reynolds number $Re_s =
U_0^2/(\omega \nu)$ for angular vibrational frequency $\omega$ and fluid
kinematic viscosity $\nu$.


title: Invariance principles for tree-valued Cannings chains

abstract:
  We consider sequences of tree-valued Markov chains that describe evolving
genealogies in Cannings models, and we show their convergence in distribution
to tree-valued Fleming-Viot processes. Under the conditions of M\"ohle and
Sagitov, this convergence holds for all tree-valued Fleming-Viot processes
under consideration in the dust-free case, and for the Fleming-Viot processes
with values in the space of distance matrix distributions in the case with
dust. Convergence to Fleming-Viot processes with values in the space of marked
metric measure spaces in the case with dust is ensured by an additional
assumption on the probability that a randomly sampled individual belongs to a
non-singleton family.


title:
Non-local functionals related to the total variation and connections
  with Image Processing

abstract:
  We present new results concerning the approximation of the total variation,
$\int_{\Omega} |\nabla u|$, of a function $u$ by non-local, non-convex
functionals of the form $$ \Lambda_\delta u = \int_{\Omega} \int_{\Omega}
\frac{\delta \varphi \big( |u(x) - u(y)|/ \delta\big)}{|x - y|^{d+1}} \, dx \,
dy, $$ as $\delta \to 0$, where $\Omega$ is a domain in $\mathrm{R}^d$ and
$\varphi: [0, + \infty) \to [0, + \infty)$ is a non-decreasing function
satisfying some appropriate conditions. The mode of convergence is extremely
delicate and numerous problems remain open. De Giorgi's concept of
Gamma-convergence illuminates the situation, but also introduces mysterious
novelties. The original motivation of our work comes from Image Processing.


title:
Accessing the real part of the forward $J/\psi$-p scattering amplitude
  from $J/\psi$ photo-production on protons around threshold

abstract:
  We provide an updated analysis of the forward $J/\psi$-p scattering
amplitude, relating its imaginary part to $\gamma p \to J/\psi p$ and $\gamma p
\to c \bar c X$ cross section data, and calculating its real part through a
once-subtracted dispersion relation. From a global fit to both differential and
total cross section data, we extract a value for the spin-averaged $J/\psi$-p
s-wave scattering length $a_{\psi p} = 0.046 \pm 0.005$ fm, which can be
translated into a $J/\psi$ binding energy in nuclear matter of $B_\psi = 2.7
\pm 0.3$ MeV. We estimate the forward-backward asymmetry to the $\gamma p \to
e^- e^+ p$ process around the $J/\psi$ resonance, which results from
interchanging the leptons in the interference between the $J/\psi$ production
and the Bethe-Heitler mechanisms. We show that to good approximation this
asymmetry depends linearly on $a_{\psi p}$, and can reach values around -25%
for forthcoming $J/\psi$ threshold production experiments at Jefferson Lab. Its
measurement can thus provide a very sensitive observable for a refined
extraction of $a_{\psi p}$.


title: Frustrated magnetism and bicollinear antiferromagnetic order in FeTe

abstract:
  Iron chalcogenides display a rich variety of electronic orders in their phase
diagram. A particularly enigmatic case is FeTe, a metal which possesses
co-existing hole and electron Fermi surfaces as in the iron pnictides but has a
distinct ($\pi$/2,$\pi/2$) bicollinear antiferromagnetic order in the Fe square
lattice. While local-moment physics has been recognized as essential for
understanding the electronic order, it has been a long-standing challenge to
understand how the bicollinear antiferromagnetic ground state emerges in a
proper quantum spin model. We show here that a bilinear-biquadratic spin-$1$
model on a square lattice with nonzero ring-exchange interactions exhibits the
bicollinear antiferromagnetic order over an extended parameter space in its
phase diagram. Our work shows that frustrated magnetism in the quantum spin
model provides a unified description of the electronic orders in the iron
chalcogenides and iron pnictides.


title: Uniformly rotating neutron stars

abstract:
  In this chapter we review the recent results on the equilibrium
configurations of static and uniformly rotating neutron stars within the Hartle
formalism. We start from the Einstein-Maxwell-Thomas-Fermi equations formulated
and extended by Belvedere et al. (2012, 2014). We demonstrate how to conduct
numerical integration of these equations for different central densities ${\it
\rho}_c$ and angular velocities $\Omega$ and compute the static $M^{stat}$ and
rotating $M^{rot}$ masses, polar $R_p$ and equatorial $R_{\rm eq}$ radii,
eccentricity $\epsilon$, moment of inertia $I$, angular momentum $J$, as well
as the quadrupole moment $Q$ of the rotating configurations. In order to
fulfill the stability criteria of rotating neutron stars we take into
considerations the Keplerian mass-shedding limit and the axisymmetric secular
instability. Furthermore, we construct the novel mass-radius relations,
calculate the maximum mass and minimum rotation periods (maximum frequencies)
of neutron stars. Eventually, we compare and contrast our results for the
globally and locally neutron star models.


title: Polarization Control by Using Anisotropic 3D Chiral Structures

abstract:
  Due to the mirror symmetry breaking, chiral structures show fantastic
electromagnetic (EM) properties involving negative refraction, giant optical
activity, and asymmetric transmission. Aligned electric and magnetic dipoles
excited in chiral structures contribute to extraordinary properties. However,
the chiral structures that exhibit n-fold rotational symmetry show limited
tuning capability. In this paper, we proposed a compact, light, and highly
tunable anisotropic chiral structure to overcome this limitation and realize a
linear-to-circular polarization conversion. The anisotropy is due to
simultaneous excitations of two different pairs of aligned electric and
magnetic dipoles. The 3D omega-like structure, etched on two sides of one PCB
board and connected by metallic vias, achieves 60% of linearto- circular
conversion (transmission) efficiency at the operating frequency of 9.2 GHz. The
desired 90-degree phase shift between the two orthogonal linear polarization
components is not only from the finite-thickness dielectric substrate but also
from the anisotropic chiral response slightly off the resonance. The work
enables elegant and practical polarization control of EM waves.


title: The quantization of a black hole

abstract:
  We apply our model of quantum gravity to an AdS black hole resulting in a
wave equation in a quantum spacetime which has a sequence of solutions that can
be expressed as a product of stationary and temporal eigenfunctions. The
stationary eigenfunctions can be interpreted as radiation and the temporal as
gravitational waves. The event horizon corresponds in the quantum model to a
Cauchy hypersurface that can be crossed by causal curves in both directions
such that the information paradox does not occur.


title:
What is the Contribution of Intra-household Inequality to Overall Income
  Inequality? Evidence from Global Data, 1973-2013

abstract:
  Intra-household inequality continues to remain a neglected corner despite
renewed focus on income and wealth inequality. Using the LIS micro data, we
present evidence that this neglect is equivalent to ignoring up to a third of
total inequality. For a wide range of countries and over four decades, we show
that at least 30 per cent of total inequality is attributable to inequality
within the household. Using a simple normative measure of inequality, we
comment on the welfare implications of these trends.


title:
Einstein@Home discovery of a Double-Neutron Star Binary in the PALFA
  Survey

abstract:
  We report here the Einstein@Home discovery of PSR J1913+1102, a 27.3-ms
pulsar found in data from the ongoing Arecibo PALFA pulsar survey. The pulsar
is in a 4.95-hr double neutron star (DNS) system with an eccentricity of 0.089.
From radio timing with the Arecibo 305-m telescope, we measure the rate of
advance of periastron to be 5.632(18) deg/yr. Assuming general relativity
accurately models the orbital motion, this corresponds to a total system mass
of 2.875(14) solar masses, similar to the mass of the most massive DNS known to
date, B1913+16, but with a much smaller eccentricity. The small eccentricity
indicates that the second-formed neutron star (the companion of PSR J1913+1102)
was born in a supernova with a very small associated kick and mass loss. In
that case this companion is likely, by analogy with other systems, to be a
light (1.2 solar mass) neutron star; the system would then be highly
asymmetric. A search for radio pulsations from the companion yielded no
plausible detections, so we can't yet confirm this mass asymmetry. By the end
of 2016, timing observations should permit the detection of two additional
post-Keplerian parameters: the Einstein delay, which will enable precise mass
measurements and a verification of the possible mass asymmetry of the system,
and the orbital decay due to the emission of gravitational waves, which will
allow another test of the radiative properties of gravity. The latter effect
will cause the system to coalesce in ~0.5 Gyr.


title: Trace Preserving Homomorphisms on SL(2,C)

abstract:
  Let G a be subgroup of SL(2,C), the group of 2x2 matrices of determinant 1
with complex entries. Let h map onto h(G) be a homomorphism. We call h a trace
preserving homomorphism if tr(h(g))=tr(g) for all g in G,where tr(g) is the
trace of g. We solve the question of when a trace invariant homomorphism is a
conjugation by some A in SL(2,R). Moreover, if the group G is finitely
presented, this paper determines which traces of the generators and products of
the generators determine the group up to conjugation. Incomplete solutions are
known from the study of Fuchsian groups. Our theorems in this paper will expand
the results in the literature to include Fuchsian Groups with elliptic
elements, which have not been considered before. Moreover, they will be
applicable to any class of subgroups of SL(2,C). The methods used will be
relatively elementary and will indicate how many traces are needed, and the
role that any relator equation plays in the parameterization by traces of a
class of groups.


title: Vanishing of the negative homotopy K-theory of quotient singularities

abstract:
  Making use of Gruson-Raynaud's technique of "platification par eclatement",
Kerz and Strunk proved that the negative homotopy K-theory groups of a
Noetherian scheme X of Krull dimension d vanish below -d. In this note, making
use of noncommutative algebraic geometry, we improve this result in the case of
quotient singularities by proving that the negative homotopy K-theory groups
vanish below -1. Furthermore, in the case of cyclic quotient singularities, we
provide an explicit "upper bound" for the first negative homotopy K-theory
group.


title:
Possible evolution of a bouncing universe in cosmological models with
  non-minimally coupled scalar fields

abstract:
  We explore dynamics of cosmological models with bounce solutions evolving on
a spatially flat Friedmann-Lemaitre-Robertson-Walker background. We consider
cosmological models that contain the Hilbert-Einstein curvature term, the
induced gravity term with a negative coupled constant, and even polynomial
potentials of the scalar field. Bounce solutions with non-monotonic Hubble
parameters have been obtained and analyzed. The case when the scalar field has
the conformal coupling and the Higgs-like potential with an opposite sign is
studied in detail. In this model the evolution of the Hubble parameter of the
bounce solution essentially depends on the sign of the cosmological constant.


title: Coxeter Pairs, Ammann Patterns and Penrose-like Tilings

abstract:
  We identify a precise geometric relationship between: (i) certain natural
pairs of irreducible reflection groups ("Coxeter pairs"); (ii) self-similar
quasicrystalline patterns formed by superposing sets of 1D
quasi-periodically-spaced lines, planes or hyper-planes ("Ammann patterns");
and (iii) the tilings dual to these patterns ("Penrose-like tilings"). We use
this relationship to obtain all irreducible Ammann patterns and their dual
Penrose-like tilings, along with their key properties in a simple, systematic
and unified way, expanding the number of known examples from four to infinity.
For each symmetry, we identify the minimal Ammann patterns (those composed of
the fewest 1d quasiperiodic sets) and construct the associated Penrose-like
tilings: 11 in 2D, 9 in 3D and one in 4D. These include the original Penrose
tiling, the four other previously known Penrose-like tilings, and sixteen that
are new. We also complete the enumeration of the quasicrystallographic space
groups corresponding to the irreducible non-crystallographic reflection groups,
by showing that there is a unique such space group in 4D (with nothing beyond
4D).

categories: math-ph cond-mat.mtrl-sci hep-th math.MG math.MP


title:
Raining on black holes and massive galaxies: the top-down multiphase
  condensation model

abstract:
  The atmospheres filling massive galaxies, groups, and clusters display
remarkable similarities with rainfalls. Such plasma halos are shaped by AGN
heating and subsonic turbulence (~150 km/s), as probed by Hitomi. The new 3D
high-resolution simulations show the soft X-ray (< 1 keV) plasma cools rapidly
via radiative emission at the high-density interface of the turbulent eddies,
stimulating a top-down condensation cascade of warm, $10^4$ K filaments. The
ionized (optical/UV) filaments extend up to several kpc and form a skin
enveloping the neutral filaments (optical/IR/21-cm). The peaks of the warm
filaments further condense into cold molecular clouds (<50 K; radio) with total
mass up to several $10^7$ M$_\odot$, i.e., 5/50$\times$ the neutral/ionized
masses. The multiphase structures inherit the chaotic kinematics and are
dynamically supported. In the inner 500 pc, the clouds collide in inelastic
way, mixing angular momentum and leading to chaotic cold accretion (CCA). The
BHAR can be modeled via quasi-spherical viscous accretion with collisional mean
free path ~100 pc. Beyond the inner kpc region pressure torques drive the
angular momentum transport. In CCA, the BHAR is recurrently boosted up to 2 dex
compared with the disc evolution, which arises as turbulence is subdominant.
The CCA BHAR distribution is lognormal with pink noise power spectrum
characteristic of fractal phenomena. The rapid self-similar CCA variability can
explain the light curve variability of AGN and HMXBs. An improved criterium to
trace thermal instability is proposed. The 3-phase CCA reproduces crucial
observations of cospatial multiphase gas in massive galaxies, as Chandra X-ray
images, SOAR H$\alpha$ warm filaments and kinematics, Herschel [C$^+$]
emission, and ALMA giant molecular associations. CCA plays key role in AGN
feedback, AGN unification/obscuration, the evolution of BHs, galaxies, and
clusters.

categories: astro-ph.GA astro-ph.CO astro-ph.HE physics.comp-ph physics.flu-dyn


title:
The spectral evolution of the first Galaxies. III. Simulated James Webb
  Space Telescope spectra of reionization-epoch galaxies with Lyman continuum
  leakage

abstract:
  Using four different suites of cosmological simulations, we generate
synthetic spectra for galaxies with different Lyman continuum escape fractions
(fesc) at redshifts z=7-9, in the rest-frame wavelength range relevant for the
James Webb Space Telescope (JWST) NIRSpec instrument. By investigating the
effects of realistic star formation histories and metallicity distributions on
the EW(Hb)-beta diagram (previously proposed as a tool for identifying galaxies
with very high fesc), we find that neither of these effects are likely to
jeopardize the identification of galaxies with extreme Lyman continuum leakage.
Based on our models, we expect essentially all z=7-9 galaxies that exhibit
rest-frame EW(Hb)< 30 {\AA} to have fesc>0.5. Incorrect assumptions concerning
the ionizing fluxes of stellar populations or the dust properties of z>6
galaxies can in principle bias the selection, but substantial model
deficiencies of this type will at the same time reveal themselves as an offset
between the observed and simulated distribution of z>6 galaxies in the
EW(Hb)-beta diagram. Such offsets would thereby allow JWST/NIRSpec measurements
of these observables to serve as input for further model refinement.


title:
The origin of scatter in the stellar mass - halo mass relation of
  central galaxies in the EAGLE simulation

abstract:
  We use the hydrodynamical EAGLE simulation to study the magnitude and origin
of the scatter in the stellar mass - halo mass relation for central galaxies.
We separate cause and effect by correlating stellar masses in the baryonic
simulation with halo properties in a matched dark matter only (DMO) simulation.
The scatter in stellar mass increases with redshift and decreases with halo
mass. At $z = 0.1$ it declines from 0.25 dex at $M_{200, \rm DMO} \approx
10^{11}$ M$_{\odot}$ to 0.12 dex at $M_{200, \rm DMO} \approx 10^{13}$
M$_{\odot}$, but the trend is weak above $10^{12}$ M$_{\odot}$. For $M_{200,
\rm DMO} < 10^{12.5}$ M$_{\odot}$ up to 0.04 dex of the scatter is due to
scatter in the halo concentration. At fixed halo mass, a larger stellar mass
corresponds to a more concentrated halo. This is likely because higher
concentrations imply earlier formation times and hence more time for accretion
and star formation, and/or because feedback is less efficient in haloes with
higher binding energies. The maximum circular velocity, $V_{\rm max, DMO}$, and
binding energy are therefore more fundamental properties than halo mass,
meaning that they are more accurate predictors of stellar mass, and we provide
fitting formulae for their relations with stellar mass. However, concentration
alone cannot explain the total scatter in the $M_{\rm star} - M_{200, \rm DMO}$
relation, and it does not explain the scatter in $M_{\rm star} -V_{\rm max,
DMO}$. Halo spin, sphericity, triaxiality, substructure and environment are
also not responsible for the remaining scatter, which thus could be due to more
complex halo properties or non-linear/stochastic baryonic effects.


title: NoFAQ: Synthesizing Command Repairs from Examples

abstract:
  Command-line tools are confusing and hard to use for novice programmers due
to their cryptic error messages and lack of documentation. Novice users often
resort to online help-forums for finding corrections to their buggy commands,
but have a hard time in searching precisely for posts that are relevant to
their problem and then applying the suggested solutions to their buggy command.
  We present a tool, NoFAQ, that uses a set of rules to suggest possible fixes
when users write buggy commands that trigger commonly occurring errors. The
rules are expressed in a language called FixIt and each rule pattern-matches
against the user's buggy command and the corresponding error message, and uses
these inputs to produce a possible fixed command. Our main contribution is an
algorithm based on lazy VSA for synthesizing FixIt rules from examples of buggy
and repaired commands. The algorithm allows users to add new rules in NoFAQ
without having to manually encode them. We present the evaluation of NoFAQ on
92 benchmark problems and show that NoFAQ is able to instantly synthesize rules
for 81 benchmark problems in real time using just 2 to 5 input-output examples
for each rule.


title: Self-Similar One-Dimensional Quasilattices

abstract:
  We study 1D quasilattices, especially self-similar ones that can be used to
generate two-, three- and higher-dimensional quasicrystalline tesselations that
have matching rules and invertible self-similar substitution rules (also known
as inflation rules) analogous to the rules for generating Penrose tilings. The
lattice positions can be expressed in a closed-form expression we call
\emph{floor form}: $x_{n} = S (n-\alpha) + (L-S) \lfloor \kappa (n-\beta)
\rfloor$, where $L > S > 0$ and $0 < \kappa < 1$ is an irrational number. We
describe three equivalent geometric constructions of these quasilattices and
show how they can be subdivided into various types of equivalence classes: (i)
\emph{lattice equivalent}, where any two quasilattices in the same lattice
equivalence class may be derived from one another by a local decoration/gluing
rule; (ii) \emph{self-similar}, a proper subset of lattice equivalent where, in
addition, the two quasilattices are locally isomorphic; and (iii)
\emph{self-same}, a proper subset of self-similar where, in addition, the two
quasilattices are globally isomorphic (i.e. identical up to rescaling). For all
three types of equivalence class, we obtain the explicit transformation law
between the floor form expression for two quasilattices in the same class. We
tabulate (in Table 1 and Figure 5) the ten special self-similar 1D
quasilattices relevant for constructing Ammann patterns and Penrose-like
tilings in two dimensions and higher, and we explicitly construct and catalog
the corresponding self-same quasilattices. Finally, we sketch the extension of
our results from degree two to degree $N$ (i.e to 1D quasilattices built from
$N$ different intervals).

categories: math-ph cond-mat.mtrl-sci hep-th math.MP


title: Robust symmetry-protected metrology with the Haldane phase

abstract:
  We propose a metrology scheme that is made robust to a wide range of noise
processes by using the passive, error-preventing properties of
symmetry-protected topological phases. The so-called fractionalized edge mode
of an antiferromagnetic Heisenberg spin-1 chain in a rotationally-symmetric
Haldane phase can be used to measure the direction of an unknown electric
field, by exploiting the way in which the field direction reduces the symmetry
of the chain. Specifically, the direction of the field is registered in the
holonomy under an adiabatic sensing protocol, and the degenerate fractionalized
edge mode is protected through this process by the remaining reduced symmetry.
We illustrate the scheme with respect to a potential realization by Rydberg
dressed atoms.


title:
A Hard Ionizing Spectrum in z=3-4 Ly-alpha Emitters with Intense [OIII]
  Emission: Analogs of Galaxies in the Reionization Era?

abstract:
  We present Keck/MOSFIRE spectra of the diagnostic nebular emission lines
[OIII]5007,4959, [OII]3727, and H-beta for a sample of 15 redshift z=3.1-3.7
Ly-alpha emitters (LAEs) and Lyman break galaxies (LBGs). In conjunction with
spectra from other surveys, we confirm earlier indications that LAEs have a
much higher [OIII]/[OII] line ratio than is seen in similar redshift LBGs. By
comparing their distributions on a [OIII]/[OII] versus R23 diagram, we
demonstrate that this difference cannot arise solely because of their lower
metallicities but most likely is due to a harder ionizing spectrum. Using
measures of H-beta and recombination theory, we demonstrate, for a subset of
our LAEs, that xi_ion - the number of Lyman continuum photons per UV luminosity
- is indeed 0.2-0.5 dex larger than for typical LBGs at similar redshifts.
Using photoionization models we estimate the effect this would have on both
[OIII]/[OII] and R23 and conclude such a hard spectrum can only partially
explain such intense line emission. The additional possibility is that such a
large [OIII]/[OII] ratio is in part due to density rather than ionization bound
nebular regions, which would imply a high escape fraction of ionizing photons.
We discuss how further observations could confirm this possibility. Clearly
LAEs with intense [OIII] emission represent a promising analog of those z>7
sources with similarly strong lines which are thought to be an important
contributor to cosmic reionization.


title: Model-independent inference on compact-binary observations

abstract:
  The recent advanced LIGO detections of gravitational waves from merging
binary black holes enhance the prospect of exploring binary evolution via
gravitational-wave observations of a population of compact-object binaries. In
the face of uncertainty about binary formation models, model-independent
inference provides an appealing alternative to comparisons between observed and
modelled populations. We describe a procedure for clustering in the
multi-dimensional parameter space of observations that are subject to
significant measurement errors. We apply this procedure to a mock data set of
population-synthesis predictions for the masses of merging compact binaries
convolved with realistic measurement uncertainties, and demonstrate that we can
accurately distinguish subpopulations of binary neutron stars, binary black
holes, and mixed neutron star -- black hole binaries with tens of observations.


title:
Long-Term X-ray Variability of Typical Active Galactic Nuclei in the
  Distant Universe

abstract:
  We perform long-term ($\approx 15$ yr, observed-frame) X-ray variability
analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6
Ms $Chandra$ Deep Field-South (CDF-S) survey; the majority are in the redshift
range of $0.6-3.1$, providing access to penetrating rest-frame X-rays up to
$\approx 10-30$ keV. Twenty-four of the 68 sources are optical spectral type I
AGNs, and the rest (44) are type II AGNs. The time scales probed in this work
are among the longest for X-ray variability studies of distant AGNs.
Photometric analyses reveal widespread photon-flux variability: $90\%$ of AGNs
are variable above a 95% confidence level, including many X-ray obscured AGNs
and several optically classified type II quasars. We characterize the intrinsic
X-ray luminosity ($L_{\rm{X}}$) and absorption ($N_{\rm{H}}$) variability via
spectral fitting. Most (74%) sources show $L_{\rm{X}}$ variability; the
variability amplitudes are generally smaller for quasars. A Compton-thick
candidate AGN shows variability of its high-energy X-ray flux, indicating the
size of reflecting material to be $\lesssim 0.3$ pc. $L_{\rm{X}}$ variability
is also detected in a broad absorption line (BAL) quasar. The $N_{\rm{H}}$
variability amplitude for our sample appears to rise as time separation
increases. About 16% of sources show $N_{\rm{H}}$ variability. One source
transitions from an X-ray unobscured to obscured state while its optical
classification remains type I; this behavior indicates the X-ray eclipsing
material is not large enough to obscure the whole broad-line region.


title: Why does deep and cheap learning work so well?

abstract:
  We show how the success of deep learning could depend not only on mathematics
but also on physics: although well-known mathematical theorems guarantee that
neural networks can approximate arbitrary functions well, the class of
functions of practical interest can frequently be approximated through "cheap
learning" with exponentially fewer parameters than generic ones. We explore how
properties frequently encountered in physics such as symmetry, locality,
compositionality, and polynomial log-probability translate into exceptionally
simple neural networks. We further argue that when the statistical process
generating the data is of a certain hierarchical form prevalent in physics and
machine-learning, a deep neural network can be more efficient than a shallow
one. We formalize these claims using information theory and discuss the
relation to the renormalization group. We prove various "no-flattening
theorems" showing when efficient linear deep networks cannot be accurately
approximated by shallow ones without efficiency loss, for example, we show that
$n$ variables cannot be multiplied using fewer than 2^n neurons in a single
hidden layer.


title:
The Observer's Ghost: a field-space connection-form and its application
  to gauge theories and general relativity

abstract:
  We introduce a functional covariant differential as a tool for studying field
space geometry in a manifestly covariant way. We then touch upon its role in
gauge theories and general relativity over bounded regions, and in BRST
symmetry. Due to the Gribov problem, we argue that our formalism ---allowing
for a non-vanishing functional curvature---is necessary for a global treatment
of gauge-invariance in field space. We conclude by suggesting that the
structures we introduce satisfactorily implement the notion of a
(non-asymptotic) observer in gauge theories and general relativity.


title: The insulating phases of vanadium dioxide are Mott-Hubbard insulators

abstract:
  We present the first comprehensive broadband optical spectroscopy data on two
insulating phases of vanadium dioxide (VO2): monoclinic M2 and triclinic. The
main result of our work is that the energy gap and the electronic structure are
essentially unaltered by the first-order structural phase transition between
the M2 and triclinic phases. Moreover, the optical interband features in the M2
and triclinic phases are remarkably similar to those observed in the
well-studied monoclinic M1 insulating phase of VO2. As the energy gap is
insensitive to the different lattice structures of the three insulating phases,
we rule out Peierls effects as the dominant contributor to the opening of the
gap. Rather, the energy gap arises from intra-atomic Coulomb correlations.


title:
High-Threshold Low-Overhead Fault-Tolerant Classical Computation and the
  Replacement of Measurements with Unitary Quantum Gates

abstract:
  Von Neumann's classic "multiplexing" method is unique in achieving
high-threshold fault-tolerant classical computation (FTCC), but has several
significant barriers to implementation: i) the extremely complex circuits
required by randomized connections, ii) the difficulty of calculating its
performance in practical regimes of both code size and logical error rate, and
iii) the (perceived) need for large code sizes. Here we present numerical
results indicating that the third assertion is false, and introduce a novel
scheme that eliminates the two remaining problems while retaining a threshold
very close to von Neumann's ideal of 1/6. We present a simple, highly ordered
wiring structure that vastly reduces the circuit complexity, demonstrates that
randomization is unnecessary, and provides a feasible method to calculate the
performance. This in turn allows us to show that the scheme requires only
moderate code sizes, vastly outperforms concatenation schemes, and under a
standard error model a unitary implementation realizes universal FTCC with an
accuracy threshold of p < 5.5%, in which p is the error probability for 3-qubit
gates. FTCC is a key component in realizing measurement-free protocols for
quantum information processing. In view of this we use our scheme to show that
all-unitary quantum circuits can reproduce any measurement-based feedback
process in which the asymptotic error probabilities for the measurement and
feedback are 0.51p and 1.51p, respectively.


title: Pretty good measures in quantum information theory

abstract:
  Quantum generalizations of Renyi's entropies are a useful tool to describe a
variety of operational tasks in quantum information processing. Two families of
such generalizations turn out to be particularly useful: the Petz quantum Renyi
divergence $\bar{D}_{\alpha}$ and the minimal quantum Renyi divergence
$\tilde{D}_{\alpha}$. In this paper, we prove a reverse Araki-Lieb-Thirring
inequality that implies a new relation between these two families of
divergences, namely that $\alpha \bar{D}_{\alpha}(\rho \| \sigma) \leq
\tilde{D}_{\alpha}(\rho \| \sigma)$ for $\alpha \in [0,1]$ and where $\rho$ and
$\sigma$ are density operators. This bound suggests defining a "pretty good
fidelity", whose relation to the usual fidelity implies the known relations
between the optimal and pretty good measurement as well as the optimal and
pretty good singlet fraction. We also find a new necessary and sufficient
condition for optimality of the pretty good measurement and singlet fraction.


title: Interferometric Measurement of Acceleration at Relativistic Speeds

abstract:
  We show that an interferometer moving at a relativistic speed relative to a
point source of light offers a sensitive probe of acceleration. Such an
accelerometer contains no moving parts, and is thus more robust than
conventional "mass-on-a-spring" accelerometers. In an interstellar mission to
Alpha-Centauri, such an accelerometer could be used to measure the masses of
planets around other stars as well as the mass distribution of the Milky Way
Galaxy.


title: Flocking dynamics with voter-like interactions

abstract:
  We study the collective motion of a large set of self-propelled particles
subject to voter-like interactions. Each particle moves on a two-dimensional
space at a constant speed in a direction that is randomly assigned initially.
Then, at every step of the dynamics, each particle adopts the direction of
motion of a randomly chosen neighboring particle. We investigate the time
evolution of the global alignment of particles measured by the order parameter
$\varphi$, until complete order $\varphi=1.0$ is reached (polar consensus). We
find that $\varphi$ increases as $t^{1/2}$ for short times and approaches
exponentially fast to $1.0$ for long times. Also, the mean time to consensus
$\tau$ varies non-monotonically with the density of particles $\rho$, reaching
a minimum at some intermediate density $\rho_{\tiny \mbox{min}}$. At
$\rho_{\tiny \mbox{min}}$, the mean consensus time scales with the system size
$N$ as $\tau_{\tiny \mbox{min}} \sim N^{0.765}$, and thus the consensus is
faster than in the case of all-to-all interactions (large $\rho$) where
$\tau=2N$. We show that the fast consensus, also observed at intermediate and
high densities, is a consequence of the segregation of the system into clusters
of equally-oriented particles which breaks the balance of transitions between
directional states in well mixed systems.


title: Bulk-boundary correspondence from the inter-cellular Zak phase

abstract:
  The Zak phase $\gamma$, the generalization of the Berry phase to Bloch wave
functions in solids, is often used to characterize inversion-symmetric 1D
topological insulators; however, since its value can depend on the choice of
real-space origin and unit cell, only the difference between the Zak phase of
two regions is believed to be relevant. Here, we show that one can extract an
origin-independent part of $\gamma$, the so-called inter-cellular Zak phase
$\gamma^{\mathrm{inter}}$, which can be used as a bulk quantity to predict the
number of surface modes as follows: a neutral finite 1D tight-binding system
has $n_s = \gamma^{\mathrm{inter}}/\pi$ (mod 2) number of in-gap surface modes
below the Fermi level if there exists a commensurate bulk unit cell that
respects inversion symmetry. We demonstrate this by first verifying that $\pm
e\gamma^{\mathrm{inter}}/2\pi$ (mod $e$) is equal to the extra charge
accumulation in the surface region for a general translationally invariant 1D
insulator, while the remnant part of $\gamma$, the intra-cellular Zak phase
$\gamma^{\mathrm{intra}}$, corresponds to the electronic part of the dipole
moment of the bulk's unit cell. Second, we show that the extra charge
accumulation can be related to the number of surface modes when the unit cell
is inversion symmetric. This bulk-boundary correspondence using
$\gamma^{\mathrm{inter}}$ reduces to the conventional one using $\gamma$ when
the real-space origin is at the inversion center. Our work thereby clarifies
the usage of $\gamma$ in the bulk-boundary correspondence. We study several
tight binding models to quantitatively check the relation between the extra
charge accumulation and the inter-cellular Zak phase as well as the
bulk-boundary correspondence using the inter-cellular Zak phase.


title:
$\mathbf{\alpha}$-induced reaction cross sections in the mass range
  $\mathbf{A \approx 20 - 50}$: a critical review

abstract:
  In a recent review it was shown that the cross sections of $\alpha$-induced
reactions in the $A \approx 20 - 50$ mass range follow a general and smooth
trend in most cases. For comparison of cross sections of different targets at
various energies the method of reduced cross sections $\sigma_{\rm{red}}$ and
reduced energies $E_{\rm{red}}$ was used. Four outliers were identified:
$^{36}$Ar and $^{40}$Ar with unusally small cross sections and $^{23}$Na and
$^{33}$S with unusually large cross sections. New data for $^{23}$Na were
presented at this NPA-7 conference; contrary to the previous data, these new
data fit into the general systematics. In addition, a relation between the most
effective energy $E_0$ for astrophysical reaction rates (the so-called Gamow
window) and the reduced energy $E_{\rm{red}}$ is presented.


abstract:
  The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array
designed to characterize relic primordial gravitational waves from inflation
and the optical depth to reionization through a measurement of the polarized
cosmic microwave background (CMB) on the largest angular scales. The
frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one
dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high
atmospheric emission and span the minimum of the polarized Galactic
foregrounds: synchrotron emission at lower frequencies and dust emission at
higher frequencies. Low-noise transition edge sensor detectors and a rapid
front-end polarization modulator provide a unique combination of high
sensitivity, stability, and control of systematics. The CLASS site, at 5200 m
in the Chilean Atacama desert, allows for daily mapping of up to 70\% of the
sky and enables the characterization of CMB polarization at the largest angular
scales. Using this combination of a broad frequency range, large sky coverage,
control over systematics, and high sensitivity, CLASS will observe the
reionization and recombination peaks of the CMB E- and B-mode power spectra.
CLASS will make a cosmic variance limited measurement of the optical depth to
reionization and will measure or place upper limits on the tensor-to-scalar
ratio, $r$, down to a level of 0.01 (95\% C.L.).


title:
Nowhere differentiable functions of analytic type on products of
  finitely connected planar domains

abstract:
  Using Laurent decomposition and Mergelyan's theorem combined with Baire's
category theorem, we prove generic nowhere differentiability on the
distinguished boundary of functions of analytic type on products of planar
domains bounded by finitely many disjoint Jordan curves. The parametrization of
the boundaries are those induced by the natural Riemann maps.


title: Extending the rigidity of general relativity

abstract:
  We give the most general conditions to date which lead to uniqueness of the
general relativistic Hamiltonian. Namely, we show that all spatially covariant
generalizations of the scalar constraint which extend the standard one while
remaining quadratic in the momenta are second class. Unlike previous
investigations along these lines, we do not require a specific Poisson bracket
algebra, and the quadratic dependence on the momenta is completely general,
with an arbitrary local operator as the kinetic term.


title:
Clustering determines the dynamics of complex contagions in multiplex
  networks

abstract:
  We present the mathematical analysis of generalized complex contagions in
clustered multiplex networks for susceptible-infected-recovered (SIR)-like
dynamics. The model is intended to understand diffusion of influence, or any
other spreading process implying a threshold dynamics, in setups of
interconnected networks with significant clustering. The contagion is assumed
to be general enough to account for a content-dependent linear threshold model,
where each link type has a different weight (for spreading influence) that may
depend on the content (e.g., product, rumor, political view) that is being
spread. Using the generating functions formalism, we determine the conditions,
probability, and expected size of the emergent global cascades. This analysis
provides a generalization of previous approaches and is specially useful in
problems related to spreading and percolation. The results present non trivial
dependencies between the clustering coefficient of the networks and its average
degree. In particular, several phase transitions are shown to occur depending
on these descriptors. Generally speaking, our findings reveal that increasing
clustering decreases the probability of having global cascades and their size,
however this tendency changes with the average degree. There exists a certain
average degree from which on clustering favours the probability and size of the
contagion. By comparing the dynamics of complex contagions over multiplex
networks and their monoplex projections, we demonstrate that ignoring link
types and aggregating network layers may lead to inaccurate conclusions about
contagion dynamics, particularly when the correlation of degrees between layers
is high.


title:
A discrete chemo-dynamical model of the giant elliptical galaxy NGC
  5846: dark matter fraction, internal rotation and velocity anisotropy out to
  six effective radii

abstract:
  We construct a suite of discrete chemo-dynamical models of the giant
elliptical galaxy NGC 5846. These models are a powerful tool to constrain both
the mass distribution and internal dynamics of multiple tracer populations. We
use Jeans models to simultaneously fit stellar kinematics within the effective
radius $R_{\rm e}$, planetary nebula (PN) radial velocities out to $3\, R_{\rm
e}$, and globular cluster (GC) radial velocities and colours out to $6\,R_{\rm
e}$. The best-fitting model is a cored DM halo which contributes $\sim 10\%$ of
the total mass within $1\,R_{\rm e}$, and $67\% \pm 10\%$ within $6\,R_{\rm
e}$, although a cusped DM halo is also acceptable. The red GCs exhibit mild
rotation with $v_{\rm max}/\sigma_0 \sim 0.3$ in the region $R > \,R_{\rm e}$,
aligned with but counter-rotating to the stars in the inner parts, while the
blue GCs and PNe kinematics are consistent with no rotation. The red GCs are
tangentially anisotropic, the blue GCs are mildly radially anisotropic, and the
PNe vary from radially to tangentially anisotropic from the inner to the outer
region. This is confirmed by general made-to-measure models. The tangential
anisotropy of the red GCs in the inner regions could stem from the preferential
destruction of red GCs on more radial orbits, while their outer tangential
anisotropy -- similar to the PNe in this region -- has no good explanation. The
mild radial anisotropy of the blue GCs is consistent with an accretion
scenario.


title:
A discrete chemo-dynamical model of the dwarf spheroidal galaxy
  Sculptor: mass profile, velocity anisotropy and internal rotation

abstract:
  We present a new discrete chemo-dynamical axisymmetric modeling technique,
which we apply to the dwarf spheroidal galaxy Sculptor. The major improvement
over previous Jeans models is that realistic chemical distributions are
included directly in the dynamical modelling of the discrete data. This avoids
loss of information due to spatial binning and eliminates the need for hard
cuts to remove contaminants and to separate stars based on their chemical
properties. Using a combined likelihood in position, metallicity and
kinematics, we find that our models naturally separate Sculptor stars into a
metal-rich and a metal-poor population. Allowing for non-spherical symmetry,
our approach provides a central slope of the dark matter density of $\gamma =
0.5 \pm 0.3$. The metal-rich population is nearly isotropic (with
$\beta_r^{red} = 0.0\pm0.1$) while the metal-poor population is tangentially
anisotropic (with $\beta_r^{blue} = -0.2\pm0.1$) around the half light radius
of $0.26$ kpc. A weak internal rotation of the metal-rich population is
revealed with $v_{max}/\sigma_0 = 0.15 \pm 0.15$. We run tests using mock data
to show that a discrete dataset with $\sim 6000$ stars is required to
distinguish between a core ($\gamma = 0$) and cusp ($\gamma = 1$), and to
constrain the possible internal rotation to better than $1\,\sigma$ confidence
with our model. We conclude that our discrete chemo-dynamical modelling
technique provides a flexible and powerful tool to robustly constrain the
internal dynamics of multiple populations, and the total mass distribution in a
stellar system.


title: Lattice-motivated holomorphic nearly perturbative QCD

abstract:
  Newer lattice results indicate that, in the Landau gauge at low spacelike
momenta, the gluon propagator and the ghost dressing function are finite
nonzero. This leads to a definition of the QCD running coupling, in a specific
scheme, that goes to zero at low spacelike momenta. We construct a running
coupling which fulfills these conditions, and at the same time reproduces to a
high precision the perturbative behavior at high momenta. The coupling is
constructed in such a way that it reflects qualitatively correctly the
holomorphic (analytic) behavior of spacelike observables in the complex plane
of the squared momenta, as dictated by the general principles of Quantum Field
Theories. Further, we require the coupling to reproduce correctly the
nonstrange semihadronic decay rate of tau lepton which is the best measured
low-momentum QCD observable with small higher-twist effects. Subsequent
application of the Borel sum rules to the V+A spectral functions of tau lepton
decays, as measured by OPAL Collaboration, determines the values of the gluon
condensate and of the V+A 6-dimensional condensate, and reproduces the data to
a significantly higher precision than the usual MSbar running coupling.


title:
DYNAMO-HST Survey: Clumps in Nearby Massive Turbulent Disks and the
  Effects of Clump Clustering on Kiloparsec Scale Measurements of Clumps

abstract:
  We present $\sim$100 pc resolution Hubble Space Telescope H$\alpha$ images of
10 galaxies from the DYnamics of Newly-Assembled Massive Objects (DYNAMO)
survey of low-$z$ turbulent disk galaxies, and use these to undertake the first
detailed systematic study of the effects of resolution and clump clustering on
observations of clumps in turbulent disks. In the DYNAMO-{\em HST} sample we
measure clump diameters spanning the range $d_{clump} \sim 100-800$~pc, and
individual clump star formation rates as high as $\sim5$~M$_{\odot}$~yr$^{-1}$.
DYNAMO clumps have very high SFR surface densities, $\Sigma_{SFR}\sim
15$~M$_{\odot}$~yr$^{-1}$~kpc$^{-2}$, $\sim100\times$ higher than in H{\sc ii}
regions of nearby spirals. Indeed, SFR surface density provides a simple
dividing line between massive star forming clumps and local star forming
regions, where massive star forming clumps have $\Sigma_{SFR}>
0.5$~M$_{\odot}$~yr$^{-1}$~kpc$^{-2}$. When degraded to match the observations
of galaxies in $z\sim 1-3$ surveys, DYNAMO galaxies are similar in morphology
and measured clump properties to clumpy galaxies observed in the high-$z$
Universe. Emission peaks in the simulated high-redshift maps typically
correspond to multiple clumps in full resolution images. This clustering of
clumps systematically increases the apparent size and SFR of clumps in 1~kpc
resolution maps, and decreases the measured SFR surface density of clumps by as
much as a factor of 20$\times$. From these results we can infer that clump
clustering is likely to strongly effect the measured properties of clumps in
high-$z$ galaxies, which commonly have kiloparsec scale resolution.


title:
Temporal Convolutional Networks: A Unified Approach to Action
  Segmentation

abstract:
  The dominant paradigm for video-based action segmentation is composed of two
steps: first, for each frame, compute low-level features using Dense
Trajectories or a Convolutional Neural Network that encode spatiotemporal
information locally, and second, input these features into a classifier that
captures high-level temporal relationships, such as a Recurrent Neural Network
(RNN). While often effective, this decoupling requires specifying two separate
models, each with their own complexities, and prevents capturing more nuanced
long-range spatiotemporal relationships. We propose a unified approach, as
demonstrated by our Temporal Convolutional Network (TCN), that hierarchically
captures relationships at low-, intermediate-, and high-level time-scales. Our
model achieves superior or competitive performance using video or sensor data
on three public action segmentation datasets and can be trained in a fraction
of the time it takes to train an RNN.


title: Bell nonlocality in the turbulent atmosphere

abstract:
  Violations of Bell inequalities are better preserved by turbulent atmospheric
channels than by comparable optical fibers in the scenario of copropagating
entangled photons [A.A. Semenov and W. Vogel, Phys. Rev. A 81, 023835 (2010);
arXiv:0909.2492]. Here we reexamine this result for the case of
counterpropagation also considering the fact that each receiver registers
so-called double-click events, which are caused by dark counts, stray light,
and multi-photon entangled pairs. We show that advantages of the atmospheric
links are feasible only for the copropagation scenario in the case of strong
fluctuations of losses. For counterpropagation, the violations of Bell
inequalities can be improved with an additional postselection procedure testing
the channel transmittance.


title:
On the spatio-temporal behavior of magnetohydrodynamic turbulence in a
  magnetized plasma

abstract:
  Using direct numerical simulations of three-dimensional magnetohydrodynamic
(MHD) turbulence the spatio-temporal behavior of magnetic field fluctuations is
analyzed. Cases with relatively small, medium and large values of a mean
background magnetic field are considered. The (wavenumber) scale dependent time
correlation function is directly computed for different simulations, varying
the mean magnetic field value. From this correlation function the time
decorrelation is computed and compared with different theoretical times,
namely, the local non-linear time, the random sweeping time, and the Alfv\'enic
time, the latter being a wave effect. It is observed that time decorrelations
are dominated by sweeping effects, and only at large values of the mean
magnetic field and for wave vectors mainly aligned with this field time
decorrelations are controlled by Alfv\'enic effects.


title: An Exploration of Sequence A000975

abstract:
  Sequence A000975 in the Online Encyclopedia of Integer Sequences (OEIS)
starts out 1, 2, 5, 10, 21, 42, 85, ... . As of July 1, 2016, the description
in the OEIS lists several characterizations of this sequence and numerous
examples of instances where this sequence occurs. It also presents a "not yet
proved" result, a conjecture, and an unanswered question concerning this
sequence. In this paper we show that all of these proposed results are in fact
true.


title: Relations between randomness deficiencies

abstract:
  The notion of random sequence was introduced by Martin-Loef in 1966. At the
same time he defined the so-called randomness deficiency function that shows
how close are random sequences to non-random (in some natural sense). Other
deficiency functions can be obtained from the Levin-Schnorr theorem, that
describes randomness in terms of Kolmogorov complexity. The difference between
all of these deficiencies is bounded by a logarithmic term. In this paper we
show that the difference between some deficiencies can be as large as possible.


title: Efficient Relaxations for Joint Chance Constrained AC Optimal Power Flow

abstract:
  Evolving power systems with increasing levels of stochasticity call for a
need to solve optimal power flow problems with large quantities of random
variables. Weather forecasts, electricity prices, and shifting load patterns
introduce higher levels of uncertainty and can yield optimization problems that
are difficult to solve in an efficient manner. Efficient solution methods for
single chance constraints in optimal power flow problems have been considered
in the literature; however, joint chance constraints have predominantly been
solved via scenario-based approaches or by utilizing the overly conservative
Boole's inequality as an upper bound. In this paper, joint chance constraints
are used to solve an AC optimal power flow problem which maintain desired
levels of voltage magnitude in distribution grids under high penetrations of
photovoltaic systems. A tighter version of Boole's inequality is derived and
used to provide a new upper bound on the joint chance constraint, and
simulation results are shown demonstrating the benefit of the proposed upper
bound.


title: Simulating a slow bar in the low surface brightness galaxy UGC 628

abstract:
  We present a disc-halo N-body model of the low surface brightness galaxy UGC
628, one of the few systems that harbours a "slow" bar with a ratio of
corotation radius to bar length of $\mathcal{R} \equiv R_c/a_b \sim 2$. We
select our initial conditions using SDSS DR10 photometry, a physically
motivated radially variable mass-to-light ratio profile, and rotation curve
data from the literature. A global bar instability grows in our submaximal disc
model, and the disc morphology and dynamics agree broadly with the photometry
and kinematics of UGC 628 at times between peak bar strength and the onset of
buckling. Prior to bar formation, the disc and halo contribute roughly equally
to the potential in the galaxy's inner region, giving the disc enough self
gravity for bar modes to grow. After bar formation there is significant mass
redistribution, creating a baryon dominated inner and dark matter dominated
outer disc. This implies that, unlike most other low surface brightness
galaxies, UGC 628 is not dark matter dominated everywhere. Our model
nonetheless implies that UGC 628 falls on same the relationship between dark
matter fraction and rotation velocity found for high surface brightness
galaxies, and lends credence to the argument that the disc mass fraction
measured at the location where its contribution to the potential peaks is not a
reliable indicator of its dynamical importance at all radii.


title:
Topological quantum phase transition in strongly correlated Kondo
  insulators in 1D

abstract:
  We investigate, by means of a field-theory analysis combined with the
density-matrix renormalization group (DMRG) method, a theoretical model for a
strongly correlated quantum system in one dimension realizing a
topologically-ordered Haldane phase ground state. The model consists of a
spin-1/2 Heisenberg chain coupled to a tight-binding chain via two competing
Kondo exchange couplings of different type: a "s-wave" Kondo coupling
($J^s_{K}$), and a less common "p-wave" ($J^p_{K}$) Kondo coupling. While the
first coupling is the standard Kondo interaction studied in many
condensed-matter systems, the latter has been recently introduced by Alexandrov
and Coleman [Phys. Rev. B 90, 115147 (2014)] as a possible mechanism leading to
a topological Kondo-insulating ground state in one dimension. As a result of
this competition, a topological quantum phase transition (TQPT) occurs in the
system for a critical value of the ratio $J^s_{K}/J^p_{K}$, separating a
(Haldane-type) topological phase from a topologically trivial ground state
where the system can be essentially described as a product of local singlets.
We study and characterize the TQPT by means for the magnetization profile, the
entanglement entropy and the full entanglement spectrum of the ground state.
Our results might be relevant to understand how topologically-ordered phases of
fermions emerge in strongly interacting quantum systems.


title: A metric for wettability at the nanoscale

abstract:
  Wettability is the affinity of a liquid for a solid surface. For energetic
reasons, macroscopic drops of liquid are nearly spherical away from interfaces
with solids, and any local deformations due to molecular-scale surface
interactions are negligible. Studies of wetting phenomena, therefore, typically
assume that a liquid on a surface adopts the shape of a spherical cap. The
degree of wettability is then captured by the contact angle where the
liquid-vapor interface meets the solid-liquid interface. As droplet volumes
shrink to the scale of attoliters, however, surface interactions become
significant, and droplets gradually assume distorted shapes that no longer
comply with our conventional, macroscopic conception of a drop. In this regime,
the contact angle becomes ambiguous, and it is unclear how to parametrize a
liquid's affinity for a surface. A scalable metric for quantifying wettability
is needed, especially given the emergence of technologies exploiting
liquid-solid interactions at the nanoscale. Here we combine nanoscale
experiments with molecular-level simulation to study the breakdown of spherical
droplet shapes at small length scales. We demonstrate how measured droplet
topographies increasingly reveal non-spherical features as volumes shrink, in
agreement with theoretical predictions. Ultimately, the nanoscale liquid
flattens out to form layer-like molecular assemblies, instead of droplets, at
the solid surface. For the lack of a consistent contact angle at small scales,
we introduce a droplet's adsorption energy density as a new metric for a
liquid's affinity for a surface. We discover that extrapolating the macroscopic
idealization of a drop to the nanoscale, though it does not geometrically
resemble a realistic droplet, can nonetheless recover its adsorption energy if
line tension is properly included.


title:
Construction of Convex Sets on Quadrilateral Ordered Tiles or Graphs
  with Propagation Neighborhood Operations. Dales, Concavity Structures.
  Application to Gray Image Analysis of Human-Readable Shapes

abstract:
  An effort has been made to show mathematicians some new ideas applied to
image analysis. Gray images are presented as tilings. Based on topological
properties of the tiling, a number of gray convex hulls: maximal, minimal, and
oriented ones are constructed and some are proved. They are constructed with
only one operation. Two tilings are used in the Constraint and Allowance types
of operations. New type of concavity described: a dale. All operations are
parallel, possible to realize clock-less. Convexities define what is the
background. They are treated as separate gray objects. There are multiple
relations among them and their descendants. Via that, topological size of
concavities is proposed. Constructed with the same type of operations, Rays and
Angles in a tiling define possible spatial relations. Notions like "strokes"
are defined through concavities. Unusual effects on levelized gray objects are
shown. It is illustrated how alphabet and complex hieroglyphs can be described
through concavities and their relations. A hypothesis of living organisms image
analysis is proposed. A number of examples with symbols and a human face are
calculated with new Asynchwave C++ software library.


title: Business Process Deviance Mining: Review and Evaluation

abstract:
  Business process deviance refers to the phenomenon whereby a subset of the
executions of a business process deviate, in a negative or positive way, with
respect to its expected or desirable outcomes. Deviant executions of a business
process include those that violate compliance rules, or executions that
undershoot or exceed performance targets. Deviance mining is concerned with
uncovering the reasons for deviant executions by analyzing business process
event logs. This article provides a systematic review and comparative
evaluation of deviance mining approaches based on a family of data mining
techniques known as sequence classification. Using real-life logs from multiple
domains, we evaluate a range of feature types and classification methods in
terms of their ability to accurately discriminate between normal and deviant
executions of a process. We also analyze the interestingness of the rule sets
extracted using different methods. We observe that feature sets extracted using
pattern mining techniques only slightly outperform simpler feature sets based
on counts of individual activity occurrences in a trace.


title:
A Stackelberg Game Approach for Two-Level Distributed Energy Management
  in Smart Grids

abstract:
  The pursuit of sustainability motivates microgrids that depend on distributed
resources to produce more renewable energies. An efficient operation and
planning relies on a holistic framework that takes into account the
interdependent decision-making of the generators of the existing power grids
and the distributed resources of the microgrid in the integrated system. To
this end, we use a Stackelberg game-theoretic framework to study the
interactions between generators (leaders) and microgrids (followers). Entities
on both sides make strategic decisions on the amount of power generation to
maximize their payoffs. Our framework not only takes into account the economic
factors but also incorporates the stability and efficiency of the smart grid,
such as the power flow constraints and voltage angle regulations. We develop
three update schemes for both generators and microgrids, respectively, and
among which a fully distributed algorithm enabled by phasor measurement units
is presented. The distributed algorithm merely requires the information of
voltage angles at local buses for updates, and its convergence to the unique
equilibrium is shown. We further develop the implementation architectures of
the update schemes in the smart grid. Finally, case studies are used to
corroborate the effectiveness of the proposed algorithms.


title:
Comment on "Matter-Wave Interferometry of a Levitated Thermal
  Nano-Oscillator Induced and Probed by a Spin"

abstract:
  In this comment, we agree with the formulas derived in Refs. [1,2] but show
that the results are not due to "interference between spatially separated
states of the center of mass of a mesoscopic harmonic oscillator".


title:
Resonant optical spectroscopy and coherent control of Cr4+ spin
  ensembles in SiC and GaN

abstract:
  Spins bound to point defects are increasingly viewed as an important resource
for solid-state implementations of quantum information technologies. In
particular, there is a growing interest in the identification of new classes of
defect spin that can be controlled optically. Here we demonstrate ensemble
optical spin polarization and optically detected magnetic resonance (ODMR) of
the S = 1 electronic ground state of chromium (Cr4+) impurities in silicon
carbide (SiC) and gallium nitride (GaN). Spin polarization is made possible by
the narrow optical linewidths of these ensembles (< 8.5 GHz), which are similar
in magnitude to the ground state zero-field spin splitting energies of the ions
at liquid helium temperatures. We therefore are able to optically resolve
individual spin sublevels within the ensembles at low magnetic fields using
resonant excitation from a cavity-stabilized, narrow-linewidth laser.
Additionally, these near-infrared emitters possess exceptionally weak phonon
sidebands, ensuring that > 73% of the overall optical emission is contained
with the defects zero-phonon lines. These characteristics make this
semiconductor-based, transition metal impurity system a promising target for
further study in the ongoing effort to integrate optically active quantum
states within common optoelectronic materials.


title:
Aspects of Perturbation theory in Quantum Mechanics: The BenderWu
  Mathematica package

abstract:
  We discuss a general setup which allows the study of the perturbation theory
of an arbitrary, locally harmonic 1D quantum mechanical potential as well as
its multi-variable (many-body) generalization. The latter may form a prototype
for regularized quantum field theory. We first generalize the method of
Bender-Wu, and derive exact recursion relations which allow the determination
of the perturbative wave-function and energy corrections to an arbitrary order,
at least in principle. For 1D systems, we implement these equations in an easy
to use Mathematica package we call BenderWu. Our package enables quick
home-computer computation of high orders of perturbation theory (about 100
orders in 10-30 seconds, and 250 orders in 1-2h) and enables practical study of
a large class of problems in Quantum Mechanics. We have two hopes concerning
the BenderWu package. One is that due to resurgence, large amount of
non-perturbative information, such as non-perturbative energies and
wave-functions (e.g. WKB wave functions), can in principle be extracted from
the perturbative data. We also hope that the package may be used as a teaching
tool, providing an effective bridge between perturbation theory and
non-perturbative physics in textbooks. Finally, we show that for the
multi-variable case, the recursion relation acquires a geometric character, and
has a structure which allows easy parallelization to computer clusters.


title:
Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS
  southern sample

abstract:
  Massive, Main-Sequence AF-type stars have so far remained unexplored in past
radial velocity surveys, due to their small number of spectral lines and their
high rotational velocities that prevent the classic RV computation method. Our
aim was to search for giant planets around AF MS stars, to get first
statistical information on their occurrence rate and to compare the results
with evolved stars and lower-mass MS stars. We used the HARPS spectrograph
located on the 3.6m telescope at ESO La Silla Observatory to observe 108 AF MS
stars with B-V in the -0.04 to 0.58 range and masses in the range 1.1-3.6 Msun.
We used our SAFIR software specifically developed to compute the radial
velocities of these early-type stars. We report the new detection of a mpsini =
4.51 Mjup companion with a ~826-day period to the F6V dwarf HD111998. We
present new data on the 2-planet system around the F6IV-V dwarf HD60532. We
also report the detection of 14 binaries with long-term RV trends. 70% of our
targets show detection limits between 0.1 and 10 Mjup in the 1 to 10^3-day
range. We derive brown dwarf (13 < mpsini < 80 Mjup) occurrence rates in the 1
to 10^3-day range of $2_{-2}^{+5}$% and $2.6_{-2.6}^{+6.7}$% for stars with
masses in the ranges 1.1-1.5 and 1.5-3 Msun, respectively. As for Jupiter-mass
companions (1 < mpsini < 13 Mjup), we get occurrence rates in the 1 to 10^3-day
range of $4_{-0.9}^{+5.9}$% and $6.3_{-6.3}^{+15.9}$% respectively for the same
stellar mass ranges. When considering the same Jupiter-mass companions but
periods in the 1 to 100-day range only, we get occurrence rates of
$2_{-2}^{+5.2}$% and $3.9_{-3.9}^{+9.9}$%. Given the present error bars, these
results do not show a significant difference with companion frequencies derived
for solar-like stars.


title: Reenactment for Read-Committed Snapshot Isolation

abstract:
  Provenance for transactional updates is critical for many applications such
as auditing and debugging of transactions. Recently, we have introduced
MV-semirings, an extension of the semiring provenance model that supports
updates and transactions. Furthermore, we have proposed reenactment, a
declarative form of replay with provenance capture, as an efficient and
non-invasive method for computing this type of provenance. However, this
approach is limited to the snapshot isolation (SI) concurrency control protocol
while many real world applications apply the read committed version of snapshot
isolation (RC-SI) to improve performance at the cost of consistency. We present
non-trivial extensions of the model and reenactment approach to be able to
compute provenance of RC-SI transactions efficiently. In addition, we develop
techniques for applying reenactment across multiple RC-SI transactions. Our
experiments demonstrate that our implementation in the GProM system supports
efficient re-construction and querying of provenance.


title:
BANYAN. VIII. New Low-Mass Stars and Brown Dwarfs with Candidate
  Circumstellar Disks

abstract:
  We present the results of a search for new circumstellar disks around
low-mass stars and brown dwarfs with spectral types >K5 that are confirmed or
candidate members of nearby young moving groups. Our search input sample was
drawn from the BANYAN surveys of Malo et al. and Gagn\'e et al. Two-Micron
All-Sky Survey and Wide-field Infrared Survey Explorer data were used to detect
near- to mid-infrared excesses that would reveal the presence of circumstellar
disks. A total of 13 targets with convincing excesses were identified: four are
new and nine were already known in the literature. The new candidates are 2MASS
J05010082$-$4337102 (M4.5), J08561384$-$1342242 (M8$\,\gamma$),
J12474428$-$3816464 (M9$\,\gamma$) and J02265658$-$5327032 (L0$\,\delta$), and
are candidate members of the TW Hya ($\sim10\pm 3\,$Myr), Columba ($\sim
42^{+6}_{-4}\,$Myr) and Tucana-Horologium ($\sim 45\pm 4\,$Myr) associations,
with masses of $120$ and $13-18\,M_{\mathrm{Jup}}$. The M8$-$L0 objects in
Columba and Tucana-Horologium are potentially among the first substellar disk
systems aged $\sim 40\,$Myr. Estimates of the new candidates' mean disk
temperatures and fractional luminosities are in the ranges $\sim 135-520\,$K
and $0.021-0.15$, respectively. New optical spectroscopy of J0501$-$4337
reveals strong H$\alpha$ emission, possibly indicating ongoing accretion,
provides a detection of lithium absorption and a radial velocity measurement
that is consistent with a membership to Columba. We also present a
near-infrared spectrum of J0226$-$5327 that reveals Paschen $\beta$ emission
and shows signs of low surface gravity, consistent with accretion from a disk
and a young age.