title: Hall current effects in mean-field dynamo theory

abstract:
  The role of the Hall term on large scale dynamo action is investigated by
means of the First Order Smoothing Approximation. It is shown that the standard
$\alpha$ coefficient is altered, and is zero when a specific double Beltrami
state is attained, in contrast to the Alfv\'enic state for MHD dynamos. The
$\beta$ coefficient is no longer positive definite, and thereby enables dynamo
action even if $\alpha$-quenching were to operate. The similarities and
differences with the (magnetic) shear-current effect are pointed out, and a
mechanism that may be potentially responsible for $\beta < 0$ is advanced. The
results are compared against previous studies, and their astrophysical
relevance is also highlighted.

categories: astro-ph.GA astro-ph.IM astro-ph.SR physics.plasm-ph


title: Towards Personality-Aware Recommendation

abstract:
  In the last decade new ways of shopping online have increased the possibility
of buying products and services more easily and faster than ever. In this new
context, personality is a key determinant in the decision making of the
consumer when shopping. The two main reasons are: firstly, a person's buying
choices are influenced by psychological factors like impulsiveness, and
secondly, some consumers may be more susceptible to making impulse purchases
than others. To the best of our knowledge, the impact of personality factors on
advertisements has been largely neglected at the level of recommender systems.
This work proposes a highly innovative research which uses a personality
perspective to determine the unique associations among the consumer's buying
tendency and advert recommendations. As a matter of fact, the lack of a
publicly available benchmark for computational advertising do not allow both
the exploration of this intriguing research direction and the evaluation of
state-of-the-art algorithms. We present the ADS Dataset, a publicly available
benchmark for computational advertising enriched with Big-Five users'
personality factors and 1,200 personal users' pictures. The proposed benchmark
allows two main tasks: rating prediction over 300 real advertisements (i.e.,
Rich Media Ads, Image Ads, Text Ads) and click-through rate prediction.
Moreover, this work carries out experiments, reviews various evaluation
criteria used in the literature, and provides a library for each one of them
within one integrated toolbox.


title:
Absolute kinematics of radio-source components in the complete S5 polar
  cap sample. IV. Proper motions of the radio cores over a decade and spectral
  properties

abstract:
  We have carried out a high-precision astrometric analysis of two
very-long-baseline-interferometry (VLBI) epochs of observation of the 13
extragalactic radio sources in the complete S5 polar cap sample. The VLBI
epochs span a time baseline of 10 years and enable us to achieve precisions in
the proper motions of the source cores up to a few micro-arcseconds per year.
The observations were performed at 14.4 GHz and 43.1 GHz, and enable us to
estimate the frequency core-shifts in a subset of sources, for which the
spectral-index distributions can be computed. We study the source-position
stability by analysing the changes in the relative positions of fiducial source
points (the jet cores) over a decade. We find motions of 0.1-0.9 mas among
close-by sources between the two epochs, which imply drifts in the jet cores of
approximately a few tens of micro-as per year. These results have implications
for the standard Active Galactic Nucleus (AGN) jet model (where the core
locations are supposed to be stable in time). For one of our sources, 0615+820,
the morphological and spectral properties in year 2010, as well as the relative
astrometry between years 2000 and 2010, suggest the possibility of either a
strong parsec-scale interaction of the AGN jet with the ISM, a gravitational
lens with ~1 mas diameter, or a resolved massive binary black hole.


title:
A Study of Hardening Behavior Based on a Finite-Deformation Gradient
  Crystal-Plasticity Model

abstract:
  A systematic study on the different roles of the governing components of a
well-defined finite-deformation gradient crystal-plasticity model proposed by
(Gurtin, 2008b) is carried out, in order to visualize the capability of the
model in the prediction of a wide range of hardening behaviors as well as
rate-dependent, scale-variation and Bauschinger-like responses in a single
crystal. A function of accumulation rates of dislocations is employed and
viewed as a measure of formation of short-range interactions which impede
dislocation movements within a crystal. The model is first represented in the
reference configuration for the purpose of numerical implementation, and then
implemented in the FEM software ABAQUS via a user-defined subroutine (UEL). Our
simulation results reveal that the dissipative gradient-strengthening is also
identified as a source of isotropic-hardening behavior, which represents the
effect of cold work introduced by (Gurtin and Ohno, 2011). Moreover, plastic
flows in predefined slip systems and expansion of accumulation of GNDs are
distinctly observed in varying scales and under different loading conditions.


title:
Estimator selection: a new method with applications to kernel density
  estimation

abstract:
  Estimator selection has become a crucial issue in non parametric estimation.
Two widely used methods are penalized empirical risk minimization (such as
penalized log-likelihood estimation) or pairwise comparison (such as Lepski's
method). Our aim in this paper is twofold. First we explain some general ideas
about the calibration issue of estimator selection methods. We review some
known results, putting the emphasis on the concept of minimal penalty which is
helpful to design data-driven selection criteria. Secondly we present a new
method for bandwidth selection within the framework of kernel density density
estimation which is in some sense intermediate between these two main methods
mentioned above. We provide some theoretical results which lead to some fully
data-driven selection strategy.


title:
Microscopic Vortex Velocity in the Inner Crust and Outer Core of Neutron
  Stars

abstract:
  Treatment of the vortex motion in the superfluids of the inner crust and the
outer core of neutron stars is a key ingredient in modeling a number of pulsar
phenomena, including glitches and magnetic field evolution. After recalculating
the microscopic vortex velocity in the inner crust, we evaluate the velocity
for the vortices in the outer core for the first time. The vortex motion
between pinning sites is found to be substantially faster in the inner crust
than in the outer core, $v_0^{\rm crust} \sim 10^{7}\mbox{\cms} \gg v_0^{\rm
core} \sim 1\mbox{\cms}$. One immediate result is that vortex creep is always
in the nonlinear regime in the outer core in contrast to the inner crust, where
both nonlinear and linear regimes of vortex creep are possible. Other
implications for pulsar glitches and magnetic field evolution are also
presented.


title: A Direct Two-Dimensional Pressure Formulation in Molecular Dynamics

abstract:
  Two-dimensional (2D) pressure field estimation in molecular dynamics (MD)
simulations has been done using three-dimensional (3D) pressure field
calculations followed by averaging, which is computationally expensive due to
3D convolutions. In this work, we develop a direct 2D pressure field estimation
method which is much faster than 3D methods without losing accuracy. The method
is validated with MD simulations on two systems: a liquid film and a
cylindrical drop of argon suspended in surrounding vapor.


title:
Playing Modeling Games in the Science Classroom: The Case for
  Disciplinary Integration

abstract:
  We extend the theory of disciplinary integration of games for science
education beyond the virtual world of games, and identify two key themes of a
practice-based theoretical commitment to science learning: (1) materiality in
the classroom and (2) iterative design of multiple, complementary symbolic
inscriptions (e.g., graphs and agent-based programs). We also identify the
affordances of our proposed approach for facilitating student learning and
teacher agency.


title:
Double scattering production of two positron-electron pairs in
  ultraperipheral heavy-ion collisions

abstract:
  We present first measurable predictions for electromagnetic (two-photon)
double scattering production of two positron-electron pairs in ultraperipheral
heavy-ion collisions at LHC. Measureable cross sections are obtained with
realistic cuts on electron/positron (pseudo)rapidities and transverse momenta
for the ALICE and ATLAS or CMS experiments. The predictions for total and
differential cross sections are presented. We show also two-dimensional
distributions in rapidities of the opposite-sign (from the same or different
subcollisions) and of the same-sign ($e^+ e^+$ or $e^- e^-$) electrons and in
rapidity distance between them. Expected number of events are presented and
discussed. Our calculations strongly suggest that relevant measurements with
the help of ATLAS, CMS and ALICE detectors are possible in a near future.


title: Quaternion Fourier and Linear Canonical Inversion Theorems

abstract:
  The Quaternion Fourier transform (QFT) is one of the key tools in studying
color image processing. Indeed, a deep understanding of the QFT has created the
color images to be transformed as whole, rather than as color separated
component. In addition, understanding the QFT paves the way for understanding
other integral transform, such as the Quaternion Fractional Fourier transform
(QFRFT), Quaternion linear canonical transform (QLCT) and Quaternion
Wigner-Ville distribution. The aim of this paper is twofold: first to provide
some of the theoretical background regarding the Quaternion bound variation
function. We then apply it to derive the Quaternion Fourier and linear
canonical inversion formulas. Secondly, to provide some in tuition for how the
Quaternion Fourier and linear canonical inversion theorems work on the
absolutely integrable function space.


title: Lane formation in a driven attractive fluid

abstract:
  We investigate non-equilibrium lane formation in a generic model of a fluid
with attractive interactions, that is, a two-dimensional Lennard-Jones (LJ)
fluid composed of two particle species driven in opposite directions.
Performing Brownian Dynamics (BD) simulations for a wide range of parameters,
supplemented by a stability analysis based on dynamical density functional
theory (DDFT), we identify generic features of lane formation in presence of
attraction, including structural properties. In fact, we find a variety of
states (as compared to purely repulsive systems), as well as a close relation
between laning and long wavelength instabilities of the homogeneous phase such
as demixing and condensation.


title:
Dielectric tuning and coupling of whispering gallery modes using an
  anisotropic prism

abstract:
  Optical whispering gallery mode (WGM) resonators are a powerful and versatile
tool used in many branches of science. Fine tuning of the central frequency and
line width of individual resonances is however desirable in a number of
applications including frequency conversion, optical communications and
efficient light-matter coupling. To this end we present a detailed theoretical
analysis of dielectric tuning of WGMs supported in axisymmetric resonators.
Using the Bethe-Schwinger equation and adopting an angular spectrum field
representation we study the resonance shift and mode broadening of high $Q$
WGMs when a planar dielectric substrate is brought close to the resonator.
Particular focus is given to use of a uniaxial substrate with an arbitrarily
aligned optic axis. Competing red and blue resonance shifts ($\sim 30$ MHz),
deriving from generation of a near field material polarisation and back action
from the radiation continuum respectively, are found. Anomalous resonance
shifts can hence be observed depending on the substrate material, whereas mode
broadening on the order of $\sim 50$ MHz can also be simply realised.
Furthermore, polarisation selective coupling with extinction ratios of $> 10^4$
can be achieved when the resonator and substrate are of the same composition
and their optic axes are chosen correctly. Double refraction and properties of
out-coupled beams are also discussed.


title:
Geometric construction of bases of $H_2(\overline\Omega, \partial\Omega,
  \mathbb{Z})$

abstract:
  We present an efficient algorithm for the construction of a basis of
$H_2(\overline{\Omega},\partial\Omega;\mathbb Z)$ via the Poincar\'e--Lefschetz
duality theorem. Denoting by $g$ the first Betti number of $\overline \Omega$
the idea is to find, first $g$ different $1$-boundaries of $\overline{\Omega}$
with supports contained in $\partial\Omega$ whose homology classes in $\mathbb
R^3 \setminus \Omega$ form a basis of $H_1(\mathbb R^3 \setminus \Omega;\mathbb
Z)$, and then to construct in $\overline{\Omega}$ a homological Seifert surface
of each one of these $1$-boundaries. The Poincar\'e--Lefschetz duality theorem
ensures that the relative homology classes of these homological Seifert
surfaces in $\overline\Omega$ modulo $\partial\Omega$ form a basis of
$H_2(\overline\Omega,\partial\Omega;\mathbb Z)$. We devise a simply procedure
for the construction of the required set of $1$-boundaries of
$\overline{\Omega}$ that, combined with a fast algorithm for the construction
of homological Seifert surfaces, allows the efficient computation of a basis of
$H_2(\overline{\Omega},\partial\Omega;\mathbb Z)$ via this very natural
geometrical approach. Some numerical experiments show the efficiency of the
method and its performance comparing with other algorithms.


title:
Plancherel theorem and quaternion Fourier transform for square
  integrable functions

abstract:
  The quaternion Fourier transform (QFT), a generalization of the classical 2D
Fourier transform, plays an increasingly active role in particular signal and
colour image processing. There tends to be an inordinate degree of interest
placed on the properties of QFT. The classical convolution theorem and
multiplication formula are only suitable for 2D Fourier transform of
complex-valued signal, and do not hold for QFT of quaternion-valued signal. The
purpose of this paper is to overcome these problems and establish the
Plancherel and inversion theorems of QFT in the square integrable signals space
L2. First, we investigate the behaviours of QFT in the integrable signals space
L1. Next, we deduce the energy preservation property which extends functions
from L1 to L2 space. Moreover, some other important properties such as modified
multiplication formula are also analyzed for QFT.


title: Lower bounds for areas of images of discs

abstract:
  In this article we consider Q-homeomorphisms with respect to the p-modulus on
the complex plane with p>2. It is obtained a lower area estimate for image of
discs under such mappings. We solved the extremal problem about minimization of
the area functional of images of discs.


title: Non-Isotropic Potential Theoretic Inequality

abstract:
  In this paper, the new weighted inequalities were derived by-distance which
is similar to the given inequality for the potential operator defined in [1].


title:
Universal MOND relation between the baryonic and `dynamical' central
  surface densities of disc galaxies

abstract:
  I derive a new MOND relation for pure-disc galaxies: The `dynamical' central
surface density, $\Sigma^0_D$, deduced from the measured velocities, is a
universal function of only the true, `baryonic' central surface density,
$\Sigma^0_B$: $\Sigma^0_D=\Sigma_M \mathcal{S}(\Sigma^0_B/\Sigma_M)$, where
$\Sigma_M\equiv a_0/2\pi G$ is the MOND surface density constant. This
surprising result is shown to hold in both existing, nonrelativistic MOND
theories. $\mathcal{S}(y)$ is derived: $\mathcal{S}(y)=\int_0^y\nu(y')dy'$,
with $\nu(y)$ the interpolating function of the theory. The relation aymptotes
to $\Sigma^0_D=\Sigma^0_B$ for $\Sigma^0_B\gg\Sigma_M$, and to
$\Sigma^0_D=(4\Sigma_M\Sigma^0_B)^{1/2}$ for $\Sigma^0_B\ll\Sigma_M$. This
study was prompted by the recent finding of a correlation between related
attributes of disc galaxies by Lelli et al. (2016). The MOND
central-surface-densities relation agrees very well with these results.


title:
Some Integral Inequalities For Functions Whoose Second Derivatives Are
  $\varphi$-Convex By Using Fractional Integrals

abstract:
  In this paper, we obtain new estimates on generalization of Hermite-Hadamard,
Simpson and Ostrowski type inequalities for functions whose second derivatives
is $\varphi$-convex via fractional integrals.


title:
Impact of Edge States on Device Performance of Phosphorene
  Heterojunction Tunneling Field Effect Transistors

abstract:
  Black phosphorus (BP) tunneling transistors (TFETs) using heterojunction (He)
are investigated by atomistic quantum transport simulations. It is observed
that edge states have a great impact on transport characteristics of BP
He-TFETs, which result in the potential pinning effect and deteriorate the gate
control. While, on-state current can be effectively enhanced by using hydrogen
to saturate the edge dangling bonds in BP He-TFETs, in which edge states are
quenched. By extending layered BP with a smaller band gap to the channel region
and modulating the BP thickness, device performance of BP He-TFETs can be
further optimized and fulfill the requirements of the international technology
road-map for semiconductors (ITRS) 2013 for low power applications. In 15 nm
3L-1L and 4L-1L BP He-TFETs along armchair direction on-state current can reach
above 10$^3$ $\mu$A/$\mu$m with the fixed off-state current of 10 $pA/\mu$m. It
is also found that ambipolar effect can be effectively suppressed in BP
He-TFETs.


title: Two Neumann Series Expansions for the Sine and Cosine Integrals

abstract:
  In this work, series expansions in terms of Bessel functions of the first
kind are given for the sine and cosine integrals. These representations differ
from many of the known Neumann-type series expansions for the sine and cosine
integrals, which contain non-integer order or quadratic Bessel function terms.
In addition, using the theory of Euler sums we are able to obtain some closed
form evaluations of integrals involving Bessel functions and the sine and
cosine integrals.


title: Methylbenzenes on graphene

abstract:
  We present a theory study of the physisorption of the series of
methylbenzenes (toluene, xylene and mesitylene), as well as benzene, on
graphene. This is relevant for the basic understanding of graphene used as a
material for sensors and as an idealized model for the carbon in active carbon
filters. The molecules are studied in a number of positions and orientations
relative graphene, using density functional theory with the van der Waals
functional vdW-DF. We focus on the vdW-DF1 and vdW-DF-cx functionals, and find
that the binding energy of the molecules on graphene grows linearly with the
number of methyl groups, at the rate of 0.09 eV per added methyl group.


title: Neural Machine Translation with Recurrent Attention Modeling

abstract:
  Knowing which words have been attended to in previous time steps while
generating a translation is a rich source of information for predicting what
words will be attended to in the future. We improve upon the attention model of
Bahdanau et al. (2014) by explicitly modeling the relationship between previous
and subsequent attention levels for each word using one recurrent network per
input word. This architecture easily captures informative features, such as
fertility and regularities in relative distortion. In experiments, we show our
parameterization of attention improves translation quality.


title: Exotic Topological States with Raman-Induced Spin-Orbit Coupling

abstract:
  We propose a simple experimental scheme to realize simultaneously the
one-dimensional spin-orbit coupling and the staggered spin-flip in ultracold
pseudospin-$1/2$ atomic Fermi gases trapped in square optical lattices. In the
absence of interspecies interactions, the system supports gapped Chern
insulators and gapless topological semimetal states. By turning on the $s$-wave
interactions, a rich variety of gapped and gapless inhomogeneous topological
superfluids can emerge. In particular, a gapped topological Fulde-Ferrell
superfluid, in which the chiral edge states at opposite boundaries possess the
same chirality, is predicted.


title:
Level spectroscopy in a two-dimensional quantum magnet: Linearly
  dispersing spinons at the deconfined quantum critical point

abstract:
  We study the level structure of excitations at the "deconfined" critical
point separating antiferromagnetic and valence-bond-solid phases in
two-dimensional quantum spin systems using the $J$-$Q$ model as an example.
Energy gaps in different spin ($S$) and momentum (${\bf k}$) sectors are
extracted from imaginary-time correlation functions obtained in quantum Monte
Carlo simulations. We find strong quantitative evidence for deconfined linearly
dispersing spinons with gapless points at ${\bf k}=(0,0)$, $(\pi,0)$,
$(0,\pi)$, and $(\pi,\pi)$, as inferred from two-spinon excitations ($S=0$ and
$S=1$ states) around these points. We also observe a duality between singlet
and triplet excitations at the critical point and inside the ordered phases, in
support of an enhanced symmetry, possibly SO(5).


title:
The inclination of the planetary system relative to the solar equator
  may be explained by the presence of Planet 9

abstract:
  We evaluate the effects of a distant planet, commonly known as planet 9, on
the dynamics of the giant planets of the Solar System. We find that, given the
large distance of planet 9, the dynamics of the inner giant planets can be
decomposed into a classic Lagrange-Laplace dynamics relative to their own
invariant plane (the plane orthogonal to their total angular momentum vector)
and a slow precession of said plane relative to the total angular momentum
vector of the Solar System, including planet 9. Under some specific
configurations for planet 9, this precession can explain the current tilt of
approximately 6 degrees between the invariant plane of the giant planets and
the solar equator. An analytical model is developed to map the evolution of the
inclination of the inner giant planets' invariant plane as a function of the
planet 9's mass, inclination, eccentricity and semimajor axis, and some
numerical simulations of the equations of motion of the giant planets and
planet 9 are performed to validate our analytical approach. The longitude of
the ascending node of planet 9 is found to be linked to the longitude of the
ascending node of the giant planets' invariant plane, which also constrain the
longitude of the node of planet 9 on the ecliptic. Some of the planet 9
configurations that allow explaining the current solar tilt are compatible with
those proposed to explain the orbital confinement of the most distant Kuiper
belt objects. Thus, this work on the one hand gives an elegant explanation for
the current tilt between the invariant plane of the inner giant planets and the
solar equator and, on the other hand, adds new constraints to the orbital
elements of planet 9.


title: Minimum cycle and homology bases of surface embedded graphs

abstract:
  We study the problems of finding a minimum cycle basis (a minimum weight set
of cycles that form a basis for the cycle space) and a minimum homology basis
(a minimum weight set of cycles that generates the $1$-dimensional
($\mathbb{Z}_2$)-homology classes) of an undirected graph embedded on a
surface. The problems are closely related, because the minimum cycle basis of a
graph contains its minimum homology basis, and the minimum homology basis of
the $1$-skeleton of any graph is exactly its minimum cycle basis.
  For the minimum cycle basis problem, we give a deterministic
$O(n^\omega+2^{2g}n^2+m)$-time algorithm for graphs embedded on an orientable
surface of genus $g$. The best known existing algorithms for surface embedded
graphs are those for general graphs: an $O(m^\omega)$ time Monte Carlo
algorithm and a deterministic $O(nm^2/\log n + n^2 m)$ time algorithm. For the
minimum homology basis problem, we give a deterministic $O((g+b)^3 n \log n +
m)$-time algorithm for graphs embedded on an orientable or non-orientable
surface of genus $g$ with $b$ boundary components, assuming shortest paths are
unique, improving on existing algorithms for many values of $g$ and $n$. The
assumption of unique shortest paths can be avoided with high probability using
randomization or deterministically by increasing the running time of the
homology basis algorithm by a factor of $O(\log n)$.


title: On the Effectiveness of Defensive Distillation

abstract:
  We report experimental results indicating that defensive distillation
successfully mitigates adversarial samples crafted using the fast gradient sign
method, in addition to those crafted using the Jacobian-based iterative attack
on which the defense mechanism was originally evaluated.


title:
Orbital angular momentum of photons and the entanglement of
  Laguerre-Gaussian modes

abstract:
  The identification of orbital angular momentum (OAM) as a fundamental
property of a beam of light nearly twenty-five years ago has led to an
extensive body of research around this topic. The possibility that single
photons can carry OAM has made this degree of freedom an ideal candidate for
the investigation of complex quantum phenomena and their applications. Research
in this direction has ranged from experiments on complex forms of quantum
entanglement to the interaction between light and quantum states of matter.
Furthermore, the use of OAM in quantum information has generated a lot of
excitement, as it allows for encoding large amounts of information on a single
photon. Here we explain the intuition that led to the first quantum experiment
with OAM fifteen years ago. We continue by reviewing some key experiments
investigating fundamental questions on photonic OAM and the first steps into
applying these properties in novel quantum protocols. In the end, we identify
several interesting open questions that could form the subject of future
investigations with OAM.


title: Resonance Effects in Correlated Multilayer Heterostructures

abstract:
  We study the occurrence of negative differential conductance induced by
resonance effects in a model for a multilayer heterostructure. In particular,
we consider a system consisting of several correlated and non-correlated
monoatomic layers, sandwiched between two metallic leads. The geometry confines
electrons in wells within the heterostructures, which are connected to each
other and to the leads by tunneling processes. The non-equilibrium situation is
produced by applying a bias-voltage to the leads. Our results show that for
specific values of the parameters resonance tunneling takes place. We
investigate in detail its influence on the current-voltage characteristics. Our
results are obtained via non-equilibrium real-space dynamical mean-field
theory. As an impurity solver we use the so-called auxiliary master equation
approach, which addresses the impurity problem within an auxiliary system
consisting of a correlated impurity, a small number of uncorrelated bath sites,
and two Markovian environments described by a generalized master equation.


title: $C^1$ regularity of orthotropic $p-$harmonic functions in the plane

abstract:
  We prove that local weak solutions of the orthotropic $p-$harmonic equation
in $\mathbb{R}^2$ are $C^1$ functions.


title:
Effect of disorder on a pressure-induced $z=1$ magnetic quantum phase
  transition

abstract:
  Pressure-induced ordering close to a $z=1$ quantum critical point is studied
in the presence of bond disorder in the quantum spin system
(C$_4$H$_{12}$N$_2$)Cu$_2$(Cl$_{1-x}$Br$_{x}$)$_6$ (PHCX) by means of muon-spin
rotation and relaxation. As for the pure system
(C$_4$H$_{12}$N$_2$)Cu$_2$Cl$_6$, pressure allows PHCX with small levels of
disorder ($x\leq 7.5\%$) to be driven through a quantum critical point
separating a low-pressure quantum paramagnetic phase from magnetic order at
high pressures. However, the pressure-induced ordered state is highly
inhomogeneous for disorder concentrations $x>1\%$. This behavior might be
related to the formation of a quantum Griffiths phase above a critical disorder
concentration $7.5\%<x_{\rm c}<15\%$. Br-substitution increases the critical
pressure and suppresses critical temperatures and ordered moment sizes.


title: Radiative Albedo from a Linearly Fibered Half Space

abstract:
  A growing acceptance of fiber reinforced composite materials imparts some
relevance to exploring the effects which a predominantly linear scattering
lattice may have upon interior radiant transport. Indeed, a central feature of
electromagnetic wave propagation within such a lattice, if sufficiently dilute,
is ray confinement to cones whose half-angles are set by that between lattice
and the incident ray. When such propagation is subordinated to a viewpoint of
photon transport, one arrives at a somewhat simplified variant of the Boltzmann
equation with spherical scattering demoted to its cylindrical counterpart. With
a view to initiating a hopefully wider discussion of such phenomena, we follow
through in detail the half-space albedo problem. This is done first along
canonical lines that harness the Wiener-Hopf technique, and then once more in a
discrete ordinates setting via flux decomposition along the eigenbasis of the
underlying attenuation/scattering matrix. Good agreement is seen to prevail. We
further suggest that the Case singular eigenfunction apparatus could likewise
be evolved here in close analogy to its original, spherical scattering model.


title: Lipschitzian solutions to inhomogeneous linear iterative equations

abstract:
  We study the problems of the existence, uniqueness and continuous dependence
of Lipschitzian solutions $\varphi$ of equations of the form $$
\varphi(x)=\int_{\Omega}g(\omega)\varphi\big(f(x,\omega)\big)\mu(d\omega)+F(x),
$$ where $\mu$ is a measure on a $\sigma$-algebra of subsets of a set $\Omega$.


title: G\"odel Logic: from Natural Deduction to Parallel Computation

abstract:
  Propositional G\"odel logic extends intuitionistic logic with the
non-constructive principle of linearity $A\rightarrow B\ \lor\ B\rightarrow A$.
We introduce a Curry-Howard correspondence for this logic and show that a
particularly simple natural deduction calculus can be used as a typing system.
The resulting functional language enriches the simply typed lambda calculus
with a synchronous communication mechanism between parallel processes. Our
normalization proof employs original termination arguments and sophisticated
proof transformations with a meaningful computational reading. Our results
provide a computational interpretation of G\"odel logic as a logic of
communicating parallel processes, thus proving Avron's 1991 conjecture.


title:
Characterization of finite dimensional subspaces of complex functions
  that are invariant under linear differential operators

abstract:
  The method to solve inhomogeneous linear differential equations that is
usually taught at school relies on the fact that the right hand side function
is the product of a polynomial and an exponential and that the linear spaces of
those functions are invariant under differential operators (finite or
ordinary).
  This short note uses Jordan's canonical decomposition to prove that the
linear spaces spanned by products of polynomial and exponentials are the only
linear complex spaces that are invariant under differential operators,
therefore non-homogeneous linear finite difference or ordinary differential
equations can only be generically solved when the right hand side belongs to
those spaces.


title:
Partitioning a Graph into Small Pieces with Applications to Path
  Transversal

abstract:
  Given a graph $G = (V, E)$ and an integer $k$, we study $k$-Vertex Seperator
(resp. $k$-Edge Separator), where the goal is to remove the minimum number of
vertices (resp. edges) such that each connected component in the resulting
graph has at most $k$ vertices. Our primary focus is on the case where $k$ is
either a constant or a slowly growing function of $n$ (e.g. $O(\log n)$ or
$n^{o(1)}$). Our problems can be interpreted as a special case of three general
classes of problems that have been studied separately (balanced graph
partitioning, Hypergraph Vertex Cover (HVC), and fixed parameter tractability
(FPT)).
  Our main result is an $O(\log k)$-approximation algorithm for $k$-Vertex
Seperator that runs in time $2^{O(k)} n^{O(1)}$, and an $O(\log
k)$-approximation algorithm for $k$-Edge Separator that runs in time
$n^{O(1)}$. Our result on $k$-Edge Seperator improves the best previous graph
partitioning algorithm for small $k$. Our result on $k$-Vertex Seperator
improves the simple $(k+1)$-approximation from HVC. When $OPT > k$, the running
time $2^{O(k)} n^{O(1)}$ is faster than the lower bound $k^{\Omega(OPT)}
n^{\Omega(1)}$ for exact algorithms assuming the Exponential Time Hypothesis.
While the running time of $2^{O(k)} n^{O(1)}$ for $k$-Vertex Separator seems
unsatisfactory, we show that the superpolynomial dependence on $k$ may be
needed to achieve a polylogarithmic approximation ratio, based on hardness of
Densest $k$-Subgraph.
  We also study $k$-Path Transversal, where the goal is to remove the minimum
number of vertices such that there is no simple path of length $k$. With
additional ideas from FPT algorithms and graph theory, we present an $O(\log
k)$-approximation algorithm for $k$-Path Transversal that runs in time
$2^{O(k^3 \log k)} n^{O(1)}$. Previously, the existence of even $(1 -
\delta)k$-approximation algorithm for fixed $\delta > 0$ was open.


title: Imprint of thawing scalar fields on large scale galaxy overdensity

abstract:
  We investigate the observed galaxy power spectrum for the thawing class of
scalar field models taking into account various general relativistic
corrections that occur on very large scales. We consider the full general
relativistic perturbation equations for the matter as well as the dark energy
fluid. We form a single autonomous system of equations containing both the
background and perturbed equations of motion which we subsequently solve for
different scalar field potentials. First we study the percentage deviation from
$\Lambda$CDM model for different cosmological parameters as well as in the
observed galaxy power spectra on different scales in scalar field models for
various choices of scalar field potentials. Interestingly the difference in
background expansion results enhancement of power from $\Lambda$CDM on small
scales whereas the inclusion of GR corrections results the suppression of power
from $\Lambda$CDM on large scales. This can be useful to distinguish scalar
field models from $\Lambda$CDM with future optical/radio surveys. We also
compare the observed galaxy power spectra for tracking and thawing types of
scalar field using some particular choices for the scalar field potentials. We
show that thawing and tracking models can have large differences in observed
galaxy power spectra on large scales and for smaller redshifts due to different
GR effects. But on smaller scales and for larger redshifts, the difference is
small and is mainly due to difference in background expansion.


title: Statistical systems with nonintegrable interaction potentials

abstract:
  Statistical systems composed of atoms interacting with each other trough
nonintegrable interaction potentials are considered. Examples of these
potentials are hard-core potentials and long-range potentials, for instance,
the Lennard-Jones and dipolar potentials. The treatment of such potentials is
known to confront several problems, e.g., the impossibility of using the
standard mean-field approximations, such as Hartree and Hartree-Fock
approximations, the impossibility of directly introducing coherent states, the
difficulty in breaking the global gauge symmetry, which is required for
describing Bose-Einstein condensed and superfluid systems, the absence of a
correctly defined Fourier transform, which hampers the description of uniform
matter as well as the use of local-density approximation for nonuniform
systems. A novel iterative procedure for describing such systems is developed,
starting from a correlated mean-field approximation, allowing for a systematic
derivation of higher orders, and meeting no problems listed above. The
procedure is applicable to arbitrary systems, whether equilibrium or
nonequilibrium. The specification for equilibrium systems is presented. The
method of extrapolating the expressions for observable quantities from weak
coupling to strong coupling is described.


title: Snowfall induced by corona discharge

abstract:
  We demonstrated for the first time the condensation and precipitation (or
snowfall) induced by a corona discharge inside a cloud chamber. Ionic wind was
found to have played a more significant role than ions as extra Cloud
Condensation Nuclei (CCN). 2.25 g of net snow enhancement was measured after
applying a 30 kV corona discharge for 25 min. In comparison with another newly
emerging femtosecond laser filamentation method, the snow precipitation induced
by the corona discharge has about 4 orders of magnitude higher wall-plug
efficiency under similar conditions.


title:
Intermittency and transition to chaos in the cubical lid-driven cavity
  flow

abstract:
  Transition from steady state to intermittent chaos in the cubical lid-driven
flow is investigated numerically. Fully three-dimensional stability analyses
have revealed that the flow experiences an Andronov-Poincar\'e-Hopf bifurcation
at a critical Reynolds number $Re_c$ = 1914. As for the 2D-periodic lid-driven
cavity flows, the unstable mode originates from a centrifugal instability of
the primary vortex core. A Reynolds-Orr analysis reveals that the unstable
perturbation relies on a combination of the lift-up and anti lift-up mechanisms
to extract its energy from the base flow. Once linearly unstable, direct
numerical simulations show that the flow is driven toward a primary limit cycle
before eventually exhibiting intermittent chaotic dynamics. Though only one
eigenpair of the linearized Navier-Stokes operator is unstable, the dynamics
during the intermittencies are surprisingly well characterized by one of the
stable eigenpairs.


title:
Near-Optimal Approximate Shortest Paths and Transshipment in Distributed
  and Streaming Models

abstract:
  We present a method for solving the transshipment problem - also known as
uncapacitated minimum cost flow - up to a multiplicative error of $1 +
\varepsilon$ in undirected graphs with non-negative edge weights using a
tailored gradient descent algorithm. Using $\tilde{O}(\cdot)$ to hide
polylogarithmic factors in $n$ (the number of nodes in the graph), our gradient
descent algorithm takes $\tilde O(\varepsilon^{-2})$ iterations, and in each
iteration it solves an instance of the transshipment problem up to a
multiplicative error of $\operatorname{polylog} n$. In particular, this allows
us to perform a single iteration by computing a solution on a sparse spanner of
logarithmic stretch. Using a randomized rounding scheme, we can further extend
the method to finding approximate solutions for the single-source shortest
paths (SSSP) problem. As a consequence, we improve upon prior work by obtaining
the following results: (1) Broadcast CONGEST model: $(1 +
\varepsilon)$-approximate SSSP using $\tilde{O}((\sqrt{n} +
D)\varepsilon^{-3})$ rounds, where $ D $ is the (hop) diameter of the network.
(2) Broadcast congested clique model: $(1 + \varepsilon)$-approximate
transshipment and SSSP using $\tilde{O}(\varepsilon^{-2})$ rounds. (3)
Multipass streaming model: $(1 + \varepsilon)$-approximate transshipment and
SSSP using $\tilde{O}(n)$ space and $\tilde{O}(\varepsilon^{-2})$ passes. The
previously fastest SSSP algorithms for these models leverage sparse hop sets.
We bypass the hop set construction; computing a spanner is sufficient with our
method. The above bounds assume non-negative edge weights that are polynomially
bounded in $n$; for general non-negative weights, running times scale with the
logarithm of the maximum ratio between non-zero weights.


title: Modeling cross-hole slug tests in an unconfined aquifer

abstract:
  A modified version of a published slug test model for unconfined aquifers is
applied to cross-hole slug test data collected in field tests conducted at the
Widen site in Switzerland. The model accounts for water-table effects using the
linearised kinematic condition. The model also accounts for inertial effects in
source and observation wells. The primary objective of this work is to
demonstrate applicability of this semi-analytical model to multi-well and
multi-level pneumatic slug tests. The pneumatic perturbation was applied at
discrete intervals in a source well and monitored at discrete vertical
intervals in observation wells. The source and observation well pairs were
separated by distances of up to 4 m. The analysis yielded vertical profiles of
hydraulic conductivity, specific storage, and specific yield at observation
well locations. The hydraulic parameter estimates are compared to results from
prior pumping and single-well slug tests conducted at the site, as well as to
estimates from particle size analyses of sediment collected from boreholes
during well installation. The results are in general agreement with results
from prior tests and are indicative of a sand and gravel aquifer. Sensitivity
analysis show that model identification of specific yield is strongest at
late-time. However, the usefulness of late-time data is limited due to the low
signal-to-noise ratios.


title: An elementary introduction to loop quantum gravity

abstract:
  An introduction to loop quantum gravity is given, focussing on the
fundamental aspects of the theory, different approaches to the dynamics, as
well as possible future directions. It is structured in five lectures,
including exercises, and requires only little prior knowledge of quantum
mechanics, gauge theory, and general relativity. The main aim of these lectures
is to provide non-experts with an elementary understanding of loop quantum
gravity and to evaluate the state of the art of the field. Technical details
are avoided wherever possible.


title:
Beamspace Channel Estimation for Millimeter-Wave Massive MIMO Systems
  with Lens Antenna Array

abstract:
  By employing the lens antenna array, beamspace MIMO can utilize beam
selection to reduce the number of required RF chains in mmWave massive MIMO
systems without obvious performance loss. However, to achieve the
capacityapproaching performance, beam selection requires the accurate
information of beamspace channel of large size, which is challenging,
especially when the number of RF chains is limited. To solve this problem, in
this paper we propose a reliable support detection (SD)-based channel
estimation scheme. Specifically, we propose to decompose the total beamspace
channel estimation problem into a series of sub-problems, each of which only
considers one sparse channel component. For each channel component, we first
reliably detect its support by utilizing the structural characteristics of
mmWave beamspace channel. Then, the influence of this channel component is
removed from the total beamspace channel estimation problem. After the supports
of all channel components have been detected, the nonzero elements of the
sparse beamspace channel can be estimated with low pilot overhead. Simulation
results show that the proposed SD-based channel estimation outperforms
conventional schemes and enjoys satisfying accuracy, even in the low SNR
region.


title:
Mesoscopic superconductivity and high spin polarization coexisting at
  metallic point contacts on the Weyl semimetal TaAs

abstract:
  A Weyl semimetal is a topologically non-trivial phase of matter that hosts
mass-less Weyl fermions, the particles that remained elusive for more than 80
years since their theoretical discovery. The Weyl semimetals exhibit unique
transport and magneto-transport properties and remarkably high surface spin
polarization. Here we show that a unique mesoscopic superconducting phase with
a critical temperature up to 7 K can be realized by forming metallic point
contacts with silver (Ag) on single crystals of TaAs, while neither Ag nor TaAs
are superconductors. The Andreev reflection spectra obtained from such point
contacts are fitted well within a modified Blonder-Tinkham-Klapwijk (BTK) model
with a superconducting energy gap up to 1.2 meV. The analysis within this model
also reveals high transport spin polarization up to 60\% indicating a spin
polarized supercurrent flowing through the point contacts on TaAs. Such point
contacts also show a large anisotropic magnetoresistance (AMR) originating from
the spin polarized current. Therefore, apart from the discovery of a novel
mesoscopic superconducting phase and it's coexistence with a large spin
polarization, our results also show that the point contacts on Weyl semimetals
are potentially important for applications in spintronics.


title:
Fully dynamic all-pairs shortest paths with worst-case update-time
  revisited

abstract:
  We revisit the classic problem of dynamically maintaining shortest paths
between all pairs of nodes of a directed weighted graph. The allowed updates
are insertions and deletions of nodes and their incident edges. We give
worst-case guarantees on the time needed to process a single update (in
contrast to related results, the update time is not amortized over a sequence
of updates).
  Our main result is a simple randomized algorithm that for any parameter $c>1$
has a worst-case update time of $O(cn^{2+2/3} \log^{4/3}{n})$ and answers
distance queries correctly with probability $1-1/n^c$, against an adaptive
online adversary if the graph contains no negative cycle. The best
deterministic algorithm is by Thorup [STOC 2005] with a worst-case update time
of $\tilde O(n^{2+3/4})$ and assumes non-negative weights. This is the first
improvement for this problem for more than a decade. Conceptually, our
algorithm shows that randomization along with a more direct approach can
provide better bounds.


title: Improved Hardness for Cut, Interdiction, and Firefighter Problems

abstract:
  We study variants of the classic $s$-$t$ cut problem and prove the following
improved hardness results assuming the Unique Games Conjecture (UGC).
  - For any constant $k \geq 2$ and $\epsilon > 0$, we show that Directed
Multicut with $k$ source-sink pairs is hard to approximate within a factor $k -
\epsilon$. This matches the trivial $k$-approximation algorithm. By a simple
reduction, our result for $k = 2$ implies that Directed Multiway Cut with two
terminals (also known as $s$-$t$ Bicut) is hard to approximate within a factor
$2 - \epsilon$, matching the trivial $2$-approximation algorithm. Previously,
the best hardness factor for these problems (for constant $k$) was $1.5 -
\epsilon$ under the UGC.
  - For Length-Bounded Cut and Shortest Path Interdiction, we show that both
problems are hard to approximate within any constant factor, even if we allow
bicriteria approximation. If we want to cut vertices or the graph is directed,
our hardness factor for Length-Bounded Cut matches the best approximation ratio
up to a constant. Previously, the best hardness factor was $1.1377$ for
Length-Bounded Cut and $2$ for Shortest Path Interdiction.
  - Assuming a variant of the UGC (implied by another variant of Bansal and
Khot), we prove that it is hard to approximate Resource Minimization Fire
Containment within any constant factor. Previously, the best hardness factor
was $2$.
  Our results are based on a general method of converting an integrality gap
instance to a length-control dictatorship test for variants of the $s$-$t$ cut
problem, which may be useful for other problems.


title: Detection of a diffusive cloak via second-order statistics

abstract:
  We propose a scheme to detect the diffusive cloak proposed by Schittny et al
[Science 345, 427 (2014)]. We exploit the fact that diffusion of light is an
approximation that disregards wave interference. The long-range contribution to
intensity correlation is sensitive to locations of paths crossings and the
interference inside the medium, allowing one to detect the size and position,
including the depth, of the diffusive cloak. Our results also suggest that it
is possible to separately manipulate the first- and the second-order statistics
of wave propagation in turbid media.


title: Three-Boson Bound States in Two Dimensions

abstract:
  We investigate the possible existence of the bound state in the system of
three bosons interacting with each other via zero-radius potentials in two
dimensions (it can be atoms confined in two dimensions or tri-exciton states in
heterostructures or dihalogenated materials). The bosons are classified in two
species (a,b) such that a-a and b-b pairs repel each other and a-b attract each
other, forming the two-particle bound state with binding energy
$\epsilon_b^{(2)}$ (such as bi-exciton). We developed an efficient routine
based on the proper choice of basis for analytic and numerical calculations.
For zero-angular momentum we found the energies of the three-particle bound
states $\epsilon^{(3)}_b$ for wide ranges of the scattering lengths, and found
a universal curve of $\epsilon^{(3)}_b/\epsilon^{(2)}_b$ which depends only on
the scattering lengths but not the microscopic details of the interactions,
this is in contrast to the three-dimensional Efimov effect, where a
non-universal three-body parameter is needed.


title: Confidence distributions from likelihoods by median bias correction

abstract:
  By the modified directed likelihood, higher order accurate confidence limits
for a scalar parameter are obtained from the likelihood. They are conveniently
described in terms of a confidence distribution, that is a sample dependent
distribution function on the parameter space. In this paper we explore a
different route to accurate confidence limits via tail-symmetric confidence
curves, that is curves that describe equal tailed intervals at any level.
Instead of modifying the directed likelihood, we consider inversion of the
log-likelihood ratio when evaluated at the median of the maximum likelihood
estimator. This is shown to provide equal tailed intervals, and thus an exact
confidence distribution, to the third-order of approximation in regular
one-dimensional models. Median bias correction also provides an alternative
approximation to the modified directed likelihood which holds up to the second
order in exponential families.


title: Periodically Driven Three-Level Systems

abstract:
  We study the dynamics of a three-level system (ThLS) sinusoidally driven in
both longitudinal and transverse directions and in the presence of a uniaxial
anisotropy $D$ entering the generic Hamiltonian through the zero-energy
splitting term $D(S^{z})^{2}$ where $S^{z}$ is the projection of the spin
vector along the quantization direction. As a consequence of the addition of
this term, the order of the symmetry group of the Hamiltonian is increased by a
unit and we observe a sequence of cascaded $SU(3)$
Landau-Zener-St\"uckelberg-Majorana (LZSM) interferometers. The study is
carried out by analytically and numerically calculating the probabilities of
non-adiabatic and adiabatic evolutions. For non-adiabatic evolutions, two main
approximations based on the weak and strong driving limits are discussed by
comparing the characteristic frequency of the longitudinal drive with the
amplitudes of driven fields. For each of the cases discussed, our analytical
results quite well reproduce the gross temporal profile of the exact numerical
probabilities. This allows us to check the range of validity of analytical
results and confirm our assumptions. For adiabatic evolutions, a general theory
is constructed allowing for the description of adiabatic passages in arbitrary
ThLSs in which direct transitions between states with extremal spin projections
are forbidden. A compact formula for adiabatic evolutions is derived and
numerically tested for some illustrative cases. Interference patterns
demonstrating multiple LZSM transitions are reported. Applications of our
results to the Nitrogen Vacancy Center (NVC) in diamond are discussed.


title: On the structure of flat chains modulo $p$

abstract:
  In this paper, we prove that every equivalence class in the quotient group of
integral $1$-currents modulo $p$ in Euclidean space contains an integral
current, with quantitative estimates on its mass and the mass of its boundary.
Moreover, we show that the validity of this statement for $m$-dimensional
integral currents modulo $p$ implies that the family of $(m-1)$-dimensional
flat chains of the form $pT$, with $T$ a flat chain, is closed with respect to
the flat norm. In particular, we deduce that such closedness property holds for
$0$-dimensional flat chains, and, using a proposition from "The structure of
minimizing hypersurfaces mod $4$" by Brian White, also for flat chains of
codimension $1$.


title: SBBA: a Strongly-Budget-Balanced Double-Auction Mechanism

abstract:
  In a seminal paper, McAfee (1992) presented the first dominant strategy
truthful mechanism for double auction. His mechanism attains nearly optimal
gain-from-trade when the market is sufficiently large. However, his mechanism
may leave money on the table, since the price paid by the buyers may be higher
than the price paid to the sellers. This money is included in the
gain-from-trade and in some cases it accounts for almost all the
gain-from-trade, leaving almost no gain-from-trade to the traders. We present
SBBA: a variant of McAfee's mechanism which is strongly budget-balanced. There
is a single price, all money is exchanged between buyers and sellers and no
money is left on the table. This means that all gain-from-trade is enjoyed by
the traders. We generalize this variant to spatially-distributed markets with
transit costs.


title: Learning to Hash with Binary Deep Neural Network

abstract:
  This work proposes deep network models and learning algorithms for
unsupervised and supervised binary hashing. Our novel network design constrains
one hidden layer to directly output the binary codes. This addresses a
challenging issue in some previous works: optimizing non-smooth objective
functions due to binarization. Moreover, we incorporate independence and
balance properties in the direct and strict forms in the learning. Furthermore,
we include similarity preserving property in our objective function. Our
resulting optimization with these binary, independence, and balance constraints
is difficult to solve. We propose to attack it with alternating optimization
and careful relaxation. Experimental results on three benchmark datasets show
that our proposed methods compare favorably with the state of the art.


title: Rescuing Complementarity With Little Drama

abstract:
  The AMPS paradox challenges black hole complementarity by apparently
constructing a way for an observer to bring information from the outside of the
black hole into its interior if there is no drama at its horizon, making
manifest a violation of monogamy of entanglement. We propose a new resolution
to the paradox: this violation cannot be explicitly checked by an infalling
observer in the finite proper time they have to live after crossing the
horizon. Our resolution depends on a weak relaxation of the no-drama condition
(we call it "little drama") which is the "complementarity dual" of scrambling
of information on the stretched horizon. When translated to the description of
the black hole interior, this implies that the fine-grained quantum information
of infalling matter is rapidly diffused across the entire interior while
classical observables and coarse-grained geometry remain unaffected. Under the
assumption that information has diffused throughout the interior, we consider
the difficulty of the information-theoretic task that an observer must perform
after crossing the event horizon of a Schwarzschild black hole in order to
verify a violation of monogamy of entanglement. We find that the time required
to complete a necessary subroutine of this task, namely the decoding of Bell
pairs from the interior and the late radiation, takes longer than the maximum
amount of time that an observer can spend inside the black hole before hitting
the singularity. Therefore, an infalling observer cannot observe monogamy
violation before encountering the singularity.


title: Joint Event Detection and Entity Resolution: a Virtuous Cycle

abstract:
  Clustering web documents has numerous applications, such as aggregating news
articles into meaningful events, detecting trends and hot topics on the Web,
preserving diversity in search results, etc. At the same time, the importance
of named entities and, in particular, the ability to recognize them and to
solve the associated co-reference resolution problem are widely recognized as
key enabling factors when mining, aggregating and comparing content on the Web.
  Instead of considering these two problems separately, we propose in this
paper a method that tackles jointly the problem of clustering news articles
into events and cross-document co-reference resolution of named entities. The
co-occurrence of named entities in the same clusters is used as an additional
signal to decide whether two referents should be merged into one entity. These
refined entities can in turn be used as enhanced features to re-cluster the
documents and then be refined again, entering into a virtuous cycle that
improves simultaneously the performances of both tasks. We implemented a
prototype system and report results using the TDT5 collection of news articles,
demonstrating the potential of our approach.


title: Congestion Games with Mixed Objectives

abstract:
  We study a new class of games which generalizes congestion games and its
bottleneck variant. We introduce congestion games with mixed objectives to
model network scenarios in which players seek to optimize for latency and
bandwidths alike. We characterize the existence of pure Nash equilibria (PNE)
and the convergence of improvement dynamics. For games that do not possess PNE
we give bounds on the approximation ratio of approximate pure Nash equilibria.


title:
SALZA: Soft algorithmic complexity estimates for clustering and
  causality inference

abstract:
  A complete set of practical estimators for the conditional, simple and joint
algorihmic complexities is presented, from which a semi-metric is derived.
Also, new directed information estimators are proposed that are applied to
causality inference on Directed Acyclic Graphs. The performances of these
estimators are investigated and shown to compare well with respect to the
state-of-the-art Normalized Compression Distance (NCD).


title:
Entanglement manipulation of multipartite pure states with finite rounds
  of classical communication

abstract:
  We studied pure state transformations using local operations assisted by
finitely many rounds of classical communication ($LOCC_{\mathbb{N}}$) in C.
Spee, J.I. de Vicente, D. Sauerwein, B. Kraus, arXiv:1606.04418 (2016). Here,
we first of all present the details of some of the proofs and generalize the
construction of examples of state transformations via $LOCC_{\mathbb{N}}$ which
require a probabilistic step. However, we also present explicit examples of
SLOCC classes where any separable transformation can be realized by a protocol
in which each step is deterministic (all-det-$LOCC_{\mathbb{N}}$). Such
transformations can be considered as natural generalizations of bipartite
transformations. Furthermore, we provide examples of pure state transformations
which are possible via separable transformations, but not via
$LOCC_{\mathbb{N}}$. We also analyze an interesting genuinely multipartite
effect which we call locking or unlocking the power of other parties. This
means that one party can prevent or enable the implementation of LOCC
transformations by other parties. Moreover, we investigate the maximally
entangled set restricted to $LOCC_{\mathbb{N}}$ and show how easily computable
bounds on some entanglement measures can be derived by restricting to
$LOCC_{\mathbb{N}}$.


title:
Fundamental fields around compact objects: Massive spin-2 fields,
  Superradiant instabilities and Stars with dark matter cores

abstract:
  Fundamental bosonic fields of arbitrary spin are predicted by generic
extensions of the Standard Model and of General Relativity, and are
well-motivated candidates to explain the dark components of the Universe. One
of most promising channels to look for their presence is through their
gravitational interaction with compact objects. Within this context, in this
thesis I study several mechanisms by which bosonic fields may affect the
dynamics and structure of black holes and neutron stars. The first part of the
thesis is devoted to the study of massive spin-2 fields around spherically
symmetric black-hole spacetimes. Massive spin-2 fields can be consistently
described within theories of massive gravity, making it possible to perform a
systematic study of the propagation of these fields in curved spacetimes. In
particular, I show that due to the presence of additional degrees of freedom in
these theories, the structure of black-hole solutions is richer than in General
Relativity. In the second part of the thesis, I discuss in detail superradiant
instabilities in the context of black-hole physics. I show that several
mechanisms, such as massive bosonic fields and magnetic fields, can turn
spinning black holes unstable against superradiant modes, which has important
implications for astrophysics and for physics beyond the Standard Model. In the
last part of this thesis, I present a study of how bosonic dark matter
condensates interact gravitationally with compact stars. In particular, I show
that stable stellar configurations formed by a perfect fluid and a bosonic
condensate exist and can describe the late stages of dark matter accretion onto
stars, in dark matter rich environments.

categories: gr-qc astro-ph.CO astro-ph.SR hep-ph hep-th


title:
Superlattice-induced insulating states and valley-protected orbits in
  twisted bilayer graphene

abstract:
  Twisted bilayer graphene (TwBLG) is one of the simplest van der Waals
heterostructures, yet it yields a complex electronic system with intricate
interplay between moir\'{e} physics and interlayer hybridization effects. We
report on electronic transport measurements of high mobility small angle TwBLG
devices showing clear evidence for insulating states at the superlattice band
edges, with thermal activation gaps several times larger than theoretically
predicted. Moreover, Shubnikov-de Haas oscillations and tight binding
calculations reveal that the band structure consists of two intersecting Fermi
contours whose crossing points are effectively unhybridized. We attribute this
to exponentially suppressed interlayer hopping amplitudes for momentum
transfers larger than the moir\'{e} wavevector.


title:
Frobenius algebras and homotopy fixed points of group actions on
  bicategories

abstract:
  We explicitly show that symmetric Frobenius structures on a
finite-dimensional, semi-simple algebra stand in bijection to homotopy fixed
points of the trivial SO(2)-action on the bicategory of finite-dimensional,
semi-simple algebras, bimodules and intertwiners. The results are motivated by
the 2-dimensional Cobordism Hypothesis for oriented manifolds, and can hence be
interpreted in the realm of Topological Quantum Field Theory.


title:
Multiple scattering of polarized light in disordered media exhibiting
  short-range structural correlations

abstract:
  We develop a model based on a multiple scattering theory to describe the
diffusion of polarized light in disordered media exhibiting short-range
structural correlations. Starting from exact expressions of the average field
and the field spatial correlation function, we derive a radiative transfer
equation for the polarization-resolved specific intensity that is valid for
weak disorder and we solve it analytically in the diffusion limit. A
decomposition of the specific intensity in terms of polarization eigenmodes
reveals how structural correlations, represented via the standard anisotropic
scattering parameter $g$, affect the diffusion of polarized light. More
specifically, we find that propagation through each polarization eigenchannel
is described by its own transport mean free path that depends on $g$ in a
specific and non-trivial way.


title:
Statistical Methods in Topological Data Analysis for Complex,
  High-Dimensional Data

abstract:
  The utilization of statistical methods an their applications within the new
field of study known as Topological Data Analysis has has tremendous potential
for broadening our exploration and understanding of complex, high-dimensional
data spaces. This paper provides an introductory overview of the mathematical
underpinnings of Topological Data Analysis, the workflow to convert samples of
data to topological summary statistics, and some of the statistical methods
developed for performing inference on these topological summary statistics. The
intention of this non-technical overview is to motivate statisticians who are
interested in learning more about the subject.


title: Path Integrals on Manifolds with Boundary

abstract:
  We give time-slicing path integral formulas for solutions to the heat
equation corresponding to a self-adjoint Laplace type operator acting on
sections of a vector bundle over a compact Riemannian manifold with boundary.
More specifically, we show that such a solution can be approximated by
integrals over finite-dimensional path spaces of piecewise geodesics
subordinated to increasingly fine partitions of the time interval. We consider
a subclass of mixed boundary conditions which includes standard Dirichlet and
Neumann boundary conditions.


title:
Strong Short Time Asymptotics and Convolution Approximation of the Heat
  Kernel

abstract:
  We give a short proof of a strong version of the short time asymptotic
expansion of heat kernels associated to Laplace type operators acting on
sections of vector bundles over compact Riemannian manifolds, including
exponential decay of the difference of the approximate heat kernel and the true
heat kernel. We use this to show that repeated convolution of the approximate
heat kernels can be used to approximate the heat kernel on all of $M$, which is
related to expressing the heat kernel as a path integral. This scheme is then
applied to obtain a short-time asymptotic expansion of the heat kernel at the
cut locus.


title:
Half-period Aharonov-Bohm oscillations in disordered rotating optical
  ring cavities

abstract:
  There exists an analogy between Maxwell equations in a rotating frame and
Schr\"odinger equation for a charged particle in the presence of a magnetic
field. We exploit this analogy to point out that electromagnetic phenomena in
the rotating frame, under appropriate conditions, can exhibit periodicity with
respect to the angular velocity of rotation. In particular, in disordered ring
cavities one finds the optical analog of the Al'tshuler-Aronov-Spivak effect
well known in mesoscopic physics of disordered metals.


title:
On the Application of Support Vector Machines to the Prediction of
  Propagation Losses at 169 MHz for Smart Metering Applications

abstract:
  Recently, the need of deploying new wireless networks for smart gas metering
has raised the problem of radio planning in the169 MHz band. Unluckily,
software tools commonly adopted for radio planning in cellular communication
systems cannot be employed to solve this problem because of the substantially
lower transmission frequencies characterizing this application. In this
manuscript a novel data-centric solution, based on the use of support vector
machine techniques for classification and regression, is proposed. Our method
requires the availability of a limited set of received signal strength
measurements and the knowledge of a three-dimensional map of the propagation
environment of interest, and generates both an estimate of the coverage area
and a prediction of the field strength within it. Numerical results referring
to different Italian villages and cities evidence that our method is able to
achieve good accuracy at the price of an acceptable computational cost and of a
limited effort for the acquisition of measurements in the considered
environments.


title:
Quantum mutual information and quantumness vectors for multi-qubit
  systems

abstract:
  We introduce a new information theoretic measure of quantum correlations for
multiparticle systems. We use a form of multivariate mutual information -- the
interaction information and generalize it to multiparticle quantum systems.
There are a number of different possible generalizations. We consider two of
them. One of them is related to the notion of quantum discord and the other to
the concept of quantum dissension. This new measure, called dissension vector,
is a set of numbers -- quantumness vector. This can be thought of as a
fine-grained measure, as opposed to measures that quantify some average quantum
properties of a system. These quantities quantify/characterize the correlations
present in multiparticle states. We consider some multiqubit states and find
that these quantities are responsive to different aspects of quantumness, and
correlations present in a state. We find that different dissension vectors can
track the correlations (both classical and quantum), or quantumness only. As
physical applications, we find that these vectors might be useful in several
information processing tasks. We consider the role of dissension vectors -- (a)
in deciding the security of BB84 protocol against an eavesdropper and (b) in
determining the possible role of correlations in the performance of Grover
search algorithm. Especially, in the Grover search algorithm, we find that
dissension vectors can detect the correlations and show the maximum
correlations when one expects.


title: Adaptive Integrand Decomposition

abstract:
  We present a simplified variant of the integrand reduction algorithm for
multiloop scattering amplitudes in $d = 4 - 2\epsilon$ dimensions, which
exploits the decomposition of the integration momenta in parallel and
orthogonal subspaces, $d=d_\parallel+d_\perp$, where $d_\parallel$ is the
dimension of the space spanned by the legs of the diagrams. We discuss the
advantages of a lighter polynomial division algorithm and how the orthogonality
relations for Gegenbauer polynomilas can be suitably used for carrying out the
integration of the irreducible monomials, which eliminates spurious integrals.
Applications to one- and two-loop integrals, for arbitrary kinematics, are
discussed.


title: Multi-view pattern matching

abstract:
  We introduce the \textit{multi-view pattern matching} problem, where a text
can have multiple views. Each view is a string of the same size and drawn from
disjoint alphabets. The pattern is drawn from the union of all alphabets.
  The algorithm we present is an extension of the Horspool algorithm, and in
our experiments on synthetic data it shows an $3 \times$ improvement over the
naive baseline.


title:
Resonant enhancement of second harmonic generation in the mid-infrared
  using localized surface phonon polaritons in sub-diffractional nanostructures

abstract:
  We report on strong enhancement of mid-infrared second harmonic generation
(SHG) from SiC nanopillars due to the resonant excitation of localized surface
phonon-polaritons within the Reststrahlen band. The magnitude of the SHG peak
at the monopole mode experiences a strong dependence on the resonant frequency
beyond that described by the field localization degree and the dispersion of
linear and nonlinear-optical SiC properties. Comparing the results for the
identical nanostructures made of 4H and 6H SiC polytypes, we demonstrate the
interplay of localized surface phonon polaritons with zone-folded weak phonon
modes of the anisotropic crystal. Tuning the monopole mode in and out of the
region where the zone-folded phonon is excited in 6H-SiC, we observe a
prominent increase of the already monopole-enhanced SHG output when the two
modes are coupled. Envisioning this interplay as one of the showcase features
of mid-infrared nonlinear nanophononics, we discuss its prospects for the
effective engineering of nonlinear-optical materials with desired properties in
the infrared spectral range.


title: Optimal Consistent Network Updates in Polynomial Time

abstract:
  Software-defined networking (SDN) allows operators to control the behavior of
a network by programatically managing the forwarding rules installed on
switches. However, as is common in distributed systems, it can be difficult to
ensure that certain consistency properties are preserved during periods of
reconfiguration. The widely-accepted notion of PER-PACKET CONSISTENCY requires
every packet to be forwarded using the new configuration or the old
configuration, but not a mixture of the two. If switches can be updated in some
(partial) order which guarantees that per-packet consistency is preserved, we
call this order a CONSISTENT ORDER UPDATE. In particular, switches that are
incomparable in this order can be updated in parallel. We call a consistent
order update OPTIMAL if it allows maximal parallelism. This paper presents a
polynomial-time algorithm for finding an optimal consistent order update. This
contrasts with other recent results in the literature, which show that for
other classes of properties (e.g., loop-freedom and waypoint enforcement), the
optimal update problem is NP-complete.


title: Optimized parameter estimation in the presence of collective phase noise

abstract:
  We investigate phase and frequency estimation with different measurement
strategies under the effect of collective phase noise. First, we consider the
standard linear estimation scheme and present an experimentally realisable
optimization of the initial probe states by collective rotations. We identify
the optimal rotation angle for different measurement times. Second, we show
that sub-shot noise sensitivity - up to the Heisenberg limit - can be reached
in presence of collective phase noise by using differential interferometry,
where one part of the system is used to monitor the noise. For this, not only
GHZ states but also symmetric Dicke states are suitable. We investigate the
optimal splitting for a general symmetric Dicke state at both inputs and
discuss possible experimental realisations of differential interferometry.


title: Conic optimization and complementarity problems

abstract:
  Although the Karush-Kuhn-Tucker conditions suggest a connection between a
conic optimization problem and a complementarity problem, it is difficult to
find an accessible explicit form of this relationship in the literature. This
note will present such a relationship.


title:
Progressive Analytics: A Computation Paradigm for Exploratory Data
  Analysis

abstract:
  Exploring data requires a fast feedback loop from the analyst to the system,
with a latency below about 10 seconds because of human cognitive limitations.
When data becomes large or analysis becomes complex, sequential computations
can no longer be completed in a few seconds and data exploration is severely
hampered. This article describes a novel computation paradigm called
Progressive Computation for Data Analysis or more concisely Progressive
Analytics, that brings at the programming language level a low-latency
guarantee by performing computations in a progressive fashion. Moving this
progressive computation at the language level relieves the programmer of
exploratory data analysis systems from implementing the whole analytics
pipeline in a progressive way from scratch, streamlining the implementation of
scalable exploratory data analysis systems. This article describes the new
paradigm through a prototype implementation called ProgressiVis, and explains
the requirements it implies through examples.


title: Anisotropic composite fermions and fractional quantum Hall effect

abstract:
  We study the role of anisotropy on the transport properties of composite
fermions near Landau level filling factor $\nu=1/2$ in two-dimensional holes
confined to a GaAs quantum well. By applying a parallel magnetic field, we tune
the composite fermion Fermi sea anisotropy and monitor the relative change of
the transport scattering time at $\nu=1/2$ along the principal directions.
Interpreted in a simple Drude model, our results suggest that the scattering
time is longer along the longitudinal direction of the composite fermion Fermi
sea. Furthermore, the measured energy gap for the fractional quantum Hall state
at $\nu=2/3$ decreases when anisotropy becomes significant. The decrease,
however, might partly stem from the charge distribution becoming bilayer-like
at very large parallel magnetic fields.


title:
Evidence for a magnetic field-induced unconventional nematic state in
  the frustrated and anisotropic spin-chain cuprate LiCuSbO$_4$

abstract:
  Modern theories of quantum magnetism predict exotic multipolar states in
weakly interacting strongly frustrated spin-1/2 Heisenberg chains with
ferromagnetic nearest neighbor (NN) inchain exchange in high magnetic fields.
Experimentally these states remained elusive so far. Here we report the
evidence for a long-sought magnetic field-induced nematic state arising above a
field of $\sim 13$ T in the edge-sharing chain cuprate LiSbCuO$_4$ $\equiv$
LiCuSbO$_4$. This interpretation is based on the observation of a field induced
spin-gap in the measurements of the $^7$Li NMR spin relaxation rate $T_1^{-1}$
as well as a contrasting field-dependent power-law behavior of $T_1^{-1}$ vs.
$T$ and is further supported by static magnetization and ESR data. An
underlying theoretical microscopic approach favoring a nematic scenario is
based essentially on the NN XYZ exchange anisotropy within a model for
frustrated spin-1/2 chains. It is investigated by the DMRG technique. The
employed exchange parameters are justified qualitatively by electronic
structure calculations for LiCuSbO$_4$.


title:
Towards a Universal Approach for Monotonic Searchability in
  Self-Stabilizing Overlay Networks

abstract:
  For overlay networks, the ability to recover from a variety of problems like
membership changes or faults is a key element to preserve their functionality.
In recent years, various self-stabilizing overlay networks have been proposed
that have the advantage of being able to recover from any illegal state.
However, the vast majority of these networks cannot give any guarantees on its
functionality while the recovery process is going on. We are especially
interested in searchability, i.e., the functionality that search messages for a
specific identifier are answered successfully if a node with that identifier
exists in the network. We investigate overlay networks that are not only
self-stabilizing but that also ensure that monotonic searchability is
maintained while the recovery process is going on, as long as there are no
corrupted messages in the system. More precisely, once a search message from
node $u$ to another node $v$ is successfully delivered, all future search
messages from $u$ to $v$ succeed as well. Monotonic searchability was recently
introduced in OPODIS 2015, in which the authors provide a solution for a simple
line topology.
  We present the first universal approach to maintain monotonic searchability
that is applicable to a wide range of topologies. As the base for our approach,
we introduce a set of primitives for manipulating overlay networks that allows
us to maintain searchability and show how existing protocols can be transformed
to use theses primitives.
  We complement this result with a generic search protocol that together with
the use of our primitives guarantees monotonic searchability.
  As an additional feature, searching existing nodes with the generic search
protocol is as fast as searching a node with any other fixed routing protocol
once the topology has stabilized.


title:
Solutions and stability of generalized Kannappan's and Van Vleck's
  functional equations

abstract:
  We study the solutions of the integral Kannappan's and Van Vleck's functional
equations $$\int_{S}f(xyt)d\mu(t)+\int_{S}f(x\sigma(y)t)d\mu(t) = 2f(x)f(y),
\;x,y\in S;$$ $$\int_{S}f( x\sigma(y)t)d\mu(t)-\int_{S}f(xyt)d\mu(t) =
2f(x)f(y), \;x,y\in S,$$ where $S$ is a semigroup, $\sigma$ is an involutive
automorphism of $S$ and $\mu$ is a linear combination of Dirac measures
$(\delta_{z_{i}})_{i\in I}$, such that for all $i\in I$, $z_{i}$ is contained
in the center of $S$. We show that the solutions of these equations are closely
related to the solutions of the d'Alembert's classic functional equation with
an involutive automorphism. Furthermore, we obtain the superstability theorems
that these functional equations are superstable in the general case, where
$\sigma$ is an involutive morphism.


title:
Two-step wavelet-based estimation for mixed Gaussian fractional
  processes

abstract:
  A mixed Gaussian fractional process $\{Y(t)\}_{t \in {\Bbb R}} = \{PX(t)\}_{t
\in {\Bbb R}}$ is a multivariate stochastic process obtained by pre-multiplying
a vector of independent, Gaussian fractional process entries $X$ by a
nonsingular matrix $P$. It is interpreted that $Y$ is observable, while $X$ is
a hidden process occurring in an (unknown) system of coordinates $P$. Mixed
processes naturally arise as approximations to solutions of physically relevant
classes of multivariate fractional SDEs under aggregation. We propose a
semiparametric two-step wavelet-based method for estimating both the demixing
matrix $P^{-1}$ and the memory parameters of $X$. The asymptotic normality of
the estimators is established both in continuous and discrete time. Monte Carlo
experiments show that the finite sample estimation performance is comparable to
that of parametric methods, while being very computationally efficient. As
applications, we model a bivariate time series of annual tree ring width
measurements, and establish the asymptotic normality of the eigenstructure of
sample wavelet matrices.


title: Evaluation of Spectral Zeta-Functions with the Renormalization Group

abstract:
  We evaluate spectral zeta-functions of certain network Laplacians that can be
treated exactly with the renormalization group. As specific examples we
consider a class of Hanoi networks and those hierarchical networks obtained by
the Migdal-Kadanoff bond moving scheme from regular lattices. As possible
applications of these results we mention quantum search algorithms as well as
synchronization, which we discuss in more detail.


title:
Sparse Estimation of Generalized Linear Models (GLM) via Approximated
  Information Criteria

abstract:
  We propose a new sparse estimation method, termed MIC (Minimum approximated
Information Criterion), for generalized linear models (GLM) in fixed
dimensions. What is essentially involved in MIC is the approximation of the
$\ell_0$-norm with a continuous unit dent function. Besides, a
reparameterization step is devised to enforce sparsity in parameter estimates
while maintaining the smoothness of the objective function. MIC yields superior
performance in sparse estimation by optimizing the approximated information
criterion without reducing the search space and is computationally advantageous
since no selection of tuning parameters is required. Moreover, the
reparameterization tactic leads to valid significance testing results that are
free of post-selection inference. We explore the asymptotic properties of MIC
and illustrate its usage with both simulated experiments and empirical
examples.


title: Natural guide-star processing for wide-field laser-assisted AO systems

abstract:
  Sky-coverage in laser-assisted AO observations largely depends on the
system's capability to guide on the faintest natural guide-stars possible. Here
we give an up-to-date status of our natural guide-star processing tailored to
the European-ELT's visible and near-infrared (0.47 to 2.45 {\mu}m) integral
field spectrograph - Harmoni. We tour the processing of both the isoplanatic
and anisoplanatic tilt modes using the spatio-angular approach whereby the
wave-front is estimated directly in the pupil plane avoiding a cumbersome
explicit layered estimation on the 35-layer profiles we're currently using.
Taking the case of Harmoni, we cover the choice of wave-front sensors, the
number and field location of guide-stars, the optimised algorithms to beat down
angular anisoplanatism and the performance obtained with different temporal
controllers under split high-order/low-order tomography or joint tomography. We
consider both atmospheric and far greater telescope wind buffeting
disturbances. In addition we provide the sky-coverage estimates thus obtained.


title:
LTE security, protocol exploits and location tracking experimentation
  with low-cost software radio

abstract:
  The Long Term Evolution (LTE) is the latest mobile standard being implemented
globally to provide connectivity and access to advanced services for personal
mobile devices. Moreover, LTE networks are considered to be one of the main
pillars for the deployment of Machine to Machine (M2M) communication systems
and the spread of the Internet of Things (IoT). As an enabler for advanced
communications services with a subscription count in the billions, security is
of capital importance in LTE. Although legacy GSM (Global System for Mobile
Communications) networks are known for being insecure and vulnerable to rogue
base stations, LTE is assumed to guarantee confidentiality and strong
authentication. However, LTE networks are vulnerable to security threats that
tamper availability, privacy and authentication. This manuscript, which
summarizes and expands the results presented by the author at ShmooCon 2016
\cite{jover2016lte}, investigates the insecurity rationale behind LTE protocol
exploits and LTE rogue base stations based on the analysis of real LTE radio
link captures from the production network. Implementation results are discussed
from the actual deployment of LTE rogue base stations, IMSI catchers and
exploits that can potentially block a mobile device. A previously unknown
technique to potentially track the location of mobile devices as they move from
cell to cell is also discussed, with mitigations being proposed.


title:
Rubidium-traced white-light etalon calibrator for radial velocity
  measurements at the cm/s level

abstract:
  We report on the construction and testing of a vacuum-gap Fabry-P\'erot
etalon calibrator for high precision radial velocity spectrographs. Our etalon
is traced against a rubidium frequency standard to provide a cost effective,
yet ultra-precise wavelength reference. We describe here a turn-key system
working at 500 nm to 900 nm, ready to be installed at any current and next
generation radial velocity spectrograph that requires calibration over a wide
spectral bandpass. Where appropriate, we have used off-the-shelf, commercial
components with demonstrated long-term performance to accelerate the
development timescale of this instrument. Our system combines for the first
time the advantages of passively stabilized etalons for optical and
near-infrared wavelengths with the laser-locking technique demonstrated for
single-mode fiber etalons. We realize uncertainties in the position of one
etalon line at the 10 cm/s level in individual measurements taken at 4 Hz. When
binning the data over 10 s, we are able to trace the etalon line with a
precision of better than 3 cm/s . We present data obtained during a week of
continuous operation where we detect (and correct for) the predicted, but
previously unobserved shrinking of the etalon Zerodur spacer corresponding to a
shift of 13 cm/s per day.


title:
An empirical study on the impact of IDE tool support in pair and solo
  programming

abstract:
  Agile software development has been widespread adopted. One well-known agile
approach is eXtreme Programming (XP) where pair programming (PP) is a relevant
practice. Although various aspects of PP have been studied, we have not found,
under a traditional model of PP, studies that examine the impact of using an
IDE tool support. In an attempt to obtain a better understanding of the impact
of using an IDE, we present the results of a controlled experiment that expose
the influence on quality, measured as the number of defects injected per hour,
and cost, measured as the time necessary to complete programming assignments,
of pair and solo programming with and without the use of an IDE. For quality,
our findings suggest that the use of an IDE results in significantly higher
defect injection rates (for both pairs and solos) when the programming
assignment is not very complicated. Nevertheless, defect injection rates seem
to decrease when pairs work on more complicated programming assignments
irrespective of the tool support used. For cost, the programming assignment
significantly affects the time necessary to complete the assignment. Finally,
both aspects (quality and cost) are affected in a similar manner when either
pair or solo programming is used.


title:
Is spoken language all-or-nothing? Implications for future speech-based
  human-machine interaction

abstract:
  Recent years have seen significant market penetration for voice-based
personal assistants such as Apple's Siri. However, despite this success, user
take-up is frustratingly low. This position paper argues that there is a
habitability gap caused by the inevitable mismatch between the capabilities and
expectations of human users and the features and benefits provided by
contemporary technology. Suggestions are made as to how such problems might be
mitigated, but a more worrisome question emerges: "is spoken language
all-or-nothing"? The answer, based on contemporary views on the special nature
of (spoken) language, is that there may indeed be a fundamental limit to the
interaction that can take place between mismatched interlocutors (such as
humans and machines). However, it is concluded that interactions between native
and non-native speakers, or between adults and children, or even between humans
and dogs, might provide critical inspiration for the design of future
speech-based human-machine interaction.


title:
Inferring habitat quality and habitat selection using static site
  occupancy models

abstract:
  When evaluating the ecological value of land use within a landscape,
investigators typically rely on measures of habitat selection and habitat
quality. Traditional measures of habitat selection and habitat quality require
data from resource intensive study designs (e.g., telemetry or mark-recapture).
Often, managers must evaluate ecological value despite only having data from
less resource intensive study designs. In this paper, we use occupancy data to
measure habitat quality and habitat selection response for the Puerto Rican
Vireo, an endemic songbird whose population growth is depressed by brood
parasitism from the Shiny Cowbird. We were interested in how vireo habitat
quality and vireo habitat selection varied among three land uses (forest,
shaded coffee plantations, and sun coffee) in Puerto Rico. We estimated vireo
occupancy probability as a measure of habitat selection, and the probability of
cowbird occurrence given vireo presence as a measure of habitat quality. To
estimate the latter, we explored different ways of modeling the occurrence of
the two species jointly, and compared these models to independent models using
measures of predictive performance. Vireos preferentially selected forested
sites and shaded coffee sites over sun coffee sites. By our measure of habitat
quality, either type of coffee plantation was poor quality, and the forested
sites were high quality. This suggests that shade coffee may be an ecological
trap for the vireo in our study area. One joint model performed best by our
measures of predictive ability, thus showing that the cowbird may not occur
independently of the vireo. Vireo population dynamics in our study area may
benefit from having large amounts of forest relative to coffee plantations.
Incorporating species interactions into occupancy models has the potential to
improve monitoring for conservation.


title:
Relative equilibria with holes for the surface quasi-geostrophic
  equations

abstract:
  We study the existence of doubly connected rotating patches for the inviscid
surface quasi- geostrophic equation left open in \cite{HHH}. By using the
approach proposed by \cite{CCGS} we also prove that close to the annulus the
boundaries are actually analytic curves.


title: Query-Focused Extractive Video Summarization

abstract:
  Video data is explosively growing. As a result of the "big video data",
intelligent algorithms for automatic video summarization have re-emerged as a
pressing need. We develop a probabilistic model, Sequential and Hierarchical
Determinantal Point Process (SH-DPP), for query-focused extractive video
summarization. Given a user query and a long video sequence, our algorithm
returns a summary by selecting key shots from the video. The decision to
include a shot in the summary depends on the shot's relevance to the user query
and importance in the context of the video, jointly. We verify our approach on
two densely annotated video datasets. The query-focused video summarization is
particularly useful for search engines, e.g., to display snippets of videos.


title:
Towards Designing Cost-Optimal Policies to Utilize IaaS Clouds under
  Online Learning

abstract:
  Many businesses possess a small infrastructure that they can use for their
computing tasks, but also often buy extra computing resources from clouds.
Cloud vendors such as Amazon EC2 offer two types of purchase options: on-demand
and spot instances. As tenants have limited budgets to satisfy their computing
needs, it is crucial for them to determine how to purchase different options
and utilize them (in addition to possible self-owned instances) in a
cost-effective manner while respecting their response-time targets. In this
paper, we propose a framework to design policies to allocate self-owned,
on-demand and spot instances to arriving jobs. In particular, we propose a
near-optimal policy to determine the number of self-owned instance and an
optimal policy to determine the number of on-demand instances to buy and the
number of spot instances to bid for at each time unit. Our policies rely on a
small number of parameters and we use an online learning technique to infer
their optimal values. Through numerical simulations, we show the effectiveness
of our proposed policies, in particular that they achieve a cost reduction of
up to 64.51% when spot and on-demand instances are considered and of up to
43.74% when self-owned instances are considered, compared to previously
proposed or intuitive policies.


title: Scanning the IPv6 Internet: Towards a Comprehensive Hitlist

abstract:
  Active network measurements constitute an impor- tant part in gaining a
better understanding of the Internet. Although IPv4-wide scans are now easily
possible, random active probing is infeasible in the IPv6 Internet. Therefore,
we propose a hybrid approach to generate a hitlist of IPv6 addresses for
scanning: First, we extract IPv6 addresses from passive flow data. Second, we
leverage publicly available resources such as rDNS data to gather further IPv6
addresses. Third, we conduct traceroute measurements from several vantage
points to obtain additional addresses. We perform multiple active measurements
on gathered IPv6 addresses and evaluate response rates over time. We
extensively compare all IPv6 address sources. In total we found 150M unique
IPv6 addresses over the course of four weeks. Our hitlist covers 72% of
announced prefixes and 84% of Autonomous Systems. Finally, we give concrete
recommendations to maximize source efficiency for different scan types.


title: Hamiltonian Tomography of Photonic Lattices

abstract:
  In this letter we introduce a novel approach to Hamiltonian tomography of
non-interacting tight-binding photonic lattices. To begin with, we prove that
the matrix element of the low-energy effective Hamiltonian between sites $i$
and $j$ may be obtained directly from $S_{ij}(\omega)$, the (suitably
normalized) two-port measurement between sites $i$ and $j$ at frequency
$\omega$. This general result enables complete characterization of both on-site
energies and tunneling matrix elements in arbitrary lattice networks by
spectroscopy, and suggests that coupling between lattice sites is actually a
topological property of the two-port spectrum. We further provide extensions of
this technique for measurement of band-projectors in finite, disordered systems
with good flatness ratios, and apply the tool to direct real-space measurement
of the Chern number. Our approach demonstrates the extraordinary potential of
microwave quantum circuits for exploration of exotic synthetic materials,
providing a clear path to characterization and control of single-particle
properties of Jaynes-Cummings-Hubbard lattices. More broadly, we provide a
robust, unified method of spectroscopic characterization of linear networks
from photonic crystals to microwave lattices and everything in-between.


title:
On stability of asymptotic property C for products and some group
  extensions

abstract:
  We show that Dranishnikov's asymptotic property C is preserved by direct
products and the free product of discrete metric spaces. In particular, if $G$
and $H$ are groups with asymptotic property C, then both $G \times H$ and $G *
H$ have asymptotic property C. We also prove that a group~$G$ has asymptotic
property C if $1\to K\to G\to H\to 1$ is exact, if $\operatorname{asdim}
K<\infty$, and if $H$ has asymptotic property C. The groups are assumed to have
left-invariant proper metrics and need not be finitely generated. These results
settle questions of Dydak and Virk, of Bell and Moran, and an open problem in
topology from the Lviv Topological Seminar.


title: Dynamical moderate deviations for the Curie-Weiss model

abstract:
  We derive moderate deviation principles for the trajectory of the empirical
magnetization of the standard Curie-Weiss model via a general analytic approach
based on convergence of generators and uniqueness of viscosity solutions for
associated Hamilton-Jacobi equations. The moderate asymptotics depend crucially
on the phase under consideration.


title: Diurnal and Weekly Cycles in IPv6 Traffic

abstract:
  IPv6 activity is commonly reported as a fraction of network traffic per day.
Within this traffic, however, are daily and weekly characteristics, driven by
non-uniform IPv6 deployment across ISPs and regions. This paper discusses some
of the more apparent patterns we observe today.