title:
Dirac-like operators on the Hilbert space of differential forms on
  manifolds with boundaries

abstract:
  The problem of self-adjoint extensions of Dirac-type operators in manifolds
with boundaries is analysed. The boundaries might be regular or non-regular.
The latter situation includes point-like interactions, also called delta-like
potentials, in manifolds of dimension higher than one. Self-adjoint boundary
conditions for the case of dimension 2 are obtained explicitly.


title:
Comparison of Closed-form Solutions for the Lucas-Uzawa model via the
  Partial Hamitonian Approach and the Classical Approach

abstract:
  In this paper we derive the closed-form solutions for the Lucas-Uzawa growth
model with the aid of the partial Hamiltonian approach and then compare our
results with those derived by the classical approach \cite{chil}. The partial
Hamiltonian approach provides two first integrals \cite{naz2016} in the case
where there are no parameter restrictions and these two first integrals are
utilized to construct three sets of closed form solutions for all the variables
in the model. First two first integrals are used to find two closed form
solutions, one of which is new to the literature. We then use only one of the
first integrals to derive a third solution that is the same as that found in
the previous literature. We also show that all three solutions converge to the
same long run balance growth path.


title:
Bifurcation analysis of the Yamada model for a pulsing semiconductor
  laser with saturable absorber and delayed optical feedback

abstract:
  Semiconductor lasers exhibit a wealth of dynamics, from emission of a
constant beam of light, to periodic oscillations and excitability. Self-pulsing
regimes, where the laser periodically releases a short pulse of light, are
particularly interesting for many applications, from material science to
telecommunications. Self-pulsing regimes need to produce pulses very regularly
and, as such, they are also known to be particularly sensitive to
perturbations, such as noise or light injection.
  We investigate the effect of delayed optical feedback on the dynamics of a
self-pulsing semiconductor laser with saturable absorber (SLSA). More
precisely, we consider the Yamada model with delay -- a system of three
delay-differential equations (DDEs) for two slow and one fast variable -- which
has been shown to reproduce accurately self-pulsing features as observed in
SLSA experimentally. This model is also of broader interest because it is quite
closely related to mathematical models of other self-pulsing systems, such as
excitable spiking neurons.
  We perform a numerical bifurcation analysis of the Yamada model with delay,
where we consider both the feedback delay, the feedback strength and the
strength of pumping as bifurcation parameters. We find a rapidly increasing
complexity of the system dynamics when the feedback delay is increased from
zero. In particular, there are new feedback-induced dynamics: stable
quasi-periodic oscillations on tori, as well as a large degree of
multistability, with up to five pulse-like stable periodic solutions with
different amplitudes and repetition rates. An attractor map in the plane of
perturbations on the gain and intensity reveals a Cantor set-like, intermingled
structure of the different basins of attraction. This suggests that, in
practice, the multistable laser is extremely sensitive to small perturbations.


title:
Selective growth of epitaxial Sr2IrO4 by controlling plume dimensions in
  pulsed laser deposition

abstract:
  We report that epitaxial Sr2IrO4 thin-films can be selectively grown using
pulsed laser deposition (PLD). Due to the competition between the
Ruddlesden-Popper phases of strontium iridates (Sr_{n+1}Ir_{n}O_{3n+1}),
conventional PLD methods often result in mixed phases of Sr2IrO4 (n = 1),
Sr3Ir2O7 (n = 2), and SrIrO3 (n = infinity). We have discovered that reduced
PLD plume dimensions and slow deposition rates are the key for stabilizing pure
Sr2IrO4 phase thin-films, identified by real-time in-situ monitoring of their
optical spectra. The slow film deposition results in a thermodynamically stable
TiO2\\SrO\IrO2\SrO\SrO configuration at an interface rather than
TiO2\\SrO\SrO\IrO2\SrO between a TiO2-teminated SrTiO3 substrate and a Sr2IrO4
thin film, which is consistent with other layered oxides grown by molecular
beam epitaxy. Our approach provides an effective method for using PLD to
achieve pure phase thin-films of layered materials that are susceptible to
several energetically competing phases.


title: Amplified transduction of Planck-scale effects using quantum optics

abstract:
  The unification of quantum mechanics and gravity remains as one of the
primary challenges of present-day physics. Quantum-gravity-inspired
phenomenological models offer a window to explore potential aspects of quantum
gravity including qualitatively new behaviour that can be experimentally
tested. One such phenomenological model is the generalized uncertainty
principle (GUP), which predicts a modified Heisenberg uncertainty relation and
a deformed canonical commutator. It was recently shown that optomechanical
systems offer significant promise to put stringent experimental bounds on such
models. In this paper, we introduce a scheme to increase the sensitivity of
these experiments with an extended sequence of pulsed optomechanical
interactions. We also analyze the effects of optical phase noise and optical
loss and present a strategy to mitigate such deleterious effects.


title:
Uniqueness of the Fock quantization of scalar fields in a Bianchi I
  cosmology with unitary dynamics

abstract:
  The Fock quantization of free scalar fields is subject to an infinite
ambiguity when it comes to choosing a set of annihilation and creation
operators, choice that is equivalent to the determination of a vacuum state. In
highly symmetric situations, this ambiguity can be removed by asking vacuum
invariance under the symmetries of the system. Similarly, in stationary
backgrounds, one can demand time-translation invariance plus positivity of the
energy. However, in more general situations, additional criteria are needed.
For the case of free (test) fields minimally coupled to a homogeneous and
isotropic cosmology, it has been proven that the ambiguity is resolved by
introducing the criterion of unitary implementability of the quantum dynamics,
as an endomorphism in Fock space. This condition determines a specific
separation of the time dependence of the field, so that this splits into a very
precise background dependence and a genuine quantum evolution. Furthermore,
together with the condition of vacuum invariance under the spatial Killing
symmetries, unitarity of the dynamics selects a unique Fock representation for
the canonical commutation relations, up to unitary equivalence. In this work,
we generalize these results to anisotropic spacetimes with shear, which are
therefore not conformally symmetric, by considering the case of a free scalar
field in a Bianchi I cosmology.


title:
First numerical experiences with overlap fermions based on the Brillouin
  kernel

abstract:
  Numerical experiences are reported with overlap fermions which employ the
Brillouin action as a kernel. After discussing the dispersion relations of both
the kernel and the resulting chiral action, some of the physics features are
addressed on quenched backgrounds. We find that the overlap with Brillouin
kernel is much better localized than the overlap with Wilson kernel. Also a
preliminary account is given of the cost of the formulation, in terms of CPU
time and memory.


title:
An Analysis of Beamed Wireless Power Transfer in the Fresnel Zone Using
  a Dynamic, Metasurface Aperture

abstract:
  Wireless power transfer (WPT) has been an active topic of research, with a
number of WPT schemes implemented in the near-field (coupling) and far-field
(radiation) regimes. Here, we consider a beamed WPT scheme based on a
dynamically reconfigurable source aperture transferring power to receiving
devices within the Fresnel (near-zone) region. In this context, the dynamic
aperture resembles a reconfigurable lens capable of focusing power to a
well-defined spot, whose dimension can be related to a point spread function
(PSF). Near-zone focusing can be achieved by generating different amplitude or
phase profiles over the aperture, which can be realized using traditional
architectures, such as phased arrays. Alternatively, metasurface guided-wave
apertures can achieve dynamic focusing, with potentially lower cost
implementations. We present an initial tradeoff analysis of the near-zone WPT
concept, relating key parameters such as spot size, aperture size, wavelength,
focal distance, and availability of sources. We find that approximate design
formulas derived from the Gaussian optics approximation provide useful
estimates of system performance, including transfer efficiency and coverage
volume. The accuracy of these formulas is confirmed using numerical
calculations.


title: A positivity preserving convergent event based asynchronous PDE solver

abstract:
  A new numerical scheme for conservation equations based on evolution by
asynchronous discrete events is presented. During each event of the scheme only
two cells of the underlying Cartesian grid are active, and an event is
processed as the exact evolution of this subsystem. This naturally leads to and
adaptive scheme in space and time. Numerical results are presented which show
that the error of the asynchronous scheme decreases to zero as a control
parameter is reduced. The construction of the scheme allows it to be expressed
as repeated multiplications of matrix exponentials on an initial state vector;
thus techniques such as the Goldberg series and the Baker Campbell Hausdorff
(BCH) formula can be used to explore the theoretical properties of the scheme.
We present the framework of a convergence proof in this manner.


title: Complicial sets, an overture

abstract:
  The aim of these notes is to introduce the intuition motivating the notion of
a "complicial set", a simplicial set with certain marked "thin" simplices that
witness a composition relation between the simplices on their boundary. By
varying the marking conventions, complicial sets can be used to model
$(\infty,n)$-categories for each $n \geq 0$, including $n=\infty$. For this
reason, complicial sets present a fertile setting for thinking about weak
infinite dimensional categories in varying dimensions. This overture is
presented in three acts: the first introducing simplicial models of higher
categories; the second defining the Street nerve, which embeds strict
$\omega$-categories as "strict" complicial sets; and the third exploring an
important saturation condition on the marked simplices in a complicial set and
presenting a variety of model structures that capture their basic homotopy
theory. Scattered throughout are suggested exercises for the reader who wants
to engage more deeply with these notions.


title:
The Megamaser Cosmology Project.IX. Black hole masses for three maser
  galaxies

abstract:
  As part of the Megamaser Cosmology Project (MCP), we present VLBI maps of
nuclear water masers toward five galaxies. The masers originate in sub-parsec
circumnuclear disks. For three of the galaxies, we fit Keplerian rotation
curves to estimate their supermassive black hole (SMBH) masses, and determine
(2.9 $\pm$ 0.3) $\times~10^{6}M_\odot$ for J0437+2456, (1.7 $\pm$ 0.1)
$\times~10^{7}M_\odot$ for ESO 558$-$G009, and (1.1 $\pm$ 0.2)
$\times~10^{7}M_\odot$ for NGC 5495. In the other two galaxies, Mrk 1029 and
NGC 1320, the geometry and dynamics are more complicated and preclude robust
black hole mass estimates. Including our new results, we compiled a list of 15
VLBI-confirmed disk maser galaxies with robust SMBH mass measurements. With
this sample, we confirm the empirical relation of $R_{out} \propto 0.3
M_{SMBH}$ reported in Wardle & Yusef-Zadeh (2012). We also find a tentative
correlation between maser disk outer radii and WISE luminosity. We find no
correlations of maser disk size with X-ray 2-10 keV luminosity or [O III]
luminosity.


title:
Constraining the geometry of PSR J0855-4644: A nearby Pulsar Wind Nebula
  with Double Torus/Jet Morphology

abstract:
  Aims: PSR J0855-4644 is a fast-spinning, energetic pulsar discovered at radio
wavelengths near the south-eastern rim of the supernova remnant RX
J0852.0-4622. A follow-up observation revealed the pulsar's X-ray counterpart
and a slightly asymmetric PWN suggesting possible jet structures. PSR
J0855-4644 is a pulsar with one of the highest \dot{E}/d^{2} from which no GeV
\gamma-ray pulsations have been detected. Methods: With a dedicated Chandra
observation, we perform detailed spatial modelling to constrain the geometry of
the PWN, in particular the pulsar's line of sight \zeta_{\rm PSR}. We also
perform geometric radio and \gamma-ray light curve modelling to further
constrain \zeta_{\rm PSR} and the magnetic obliquity \alpha. Results: The
observation reveals that the compact XMM source, thought to be the X-ray
pulsar, can be further resolved into a point source surrounded by an elongated
axisymmetric nebula with a longitudinal extent of 10". The pulsar flux
represents only \sim 1\% of the XMM compact source and its spectrum is well
described by a blackbody of temperature kT=0.2 keV while the surrounding nebula
has a much harder spectrum (\Gamma=1.1 for a power-law model). Assuming the
origin of the extended emission is from a double torus yields \zeta_{\rm
PSR}=32.5\dg \pm 4.3\dg. Independent constraints from geometric light curve
modelling yield \alpha\lesssim55\dg and \zeta\lesssim55\dg, and
10\dg\lesssim|\zeta-\alpha|\lesssim30\dg. A \chi^2 fit to the radio light curve
yields a best fit at (\alpha,\zeta_{\rm PSR}) = (22\dg, 8\dg), with an
alternative fit at (\alpha,\zeta_{\rm PSR}) = (9\dg, 25\dg) within 3\sigma.
Such a geometry would explain, in the standard caustic pulsar model picture,
the radio-loud and \gamma-ray-quiet behaviour of this high \dot{E}/d^{2}
pulsar.


title: Shear yielding and shear jamming of dense hard sphere glasses

abstract:
  We investigate the response of dense hard sphere glasses to a shear strain,
in a wide range of pressures ranging from the glass transition to the
infinite-pressure jamming point. The phase diagram in the density-shear strain
plane is calculated analytically using the mean field infinite dimensional
solution. We find that just above the glass transition, the glass generically
yields at a finite shear strain. The yielding transition, in the mean field
picture, is a spinodal point in presence of disorder. At higher densities,
instead, we find that the glass generically jams at a finite shear strain: the
jamming transition prevents yielding. The shear yielding and shear jamming
lines merge in a critical point, close to which the system yields at extremely
large shear stress. Around this point, a highly non-trivial yielding dynamics
characterized by system-spanning disordered fractures is expected.


title:
Robust Markowitz mean-variance portfolio selection under ambiguous
  covariance matrix *

abstract:
  This paper studies a robust continuous-time Markowitz portfolio selection
pro\-blem where the model uncertainty carries on the covariance matrix of
multiple risky assets. This problem is formulated into a min-max mean-variance
problem over a set of non-dominated probability measures that is solved by a
McKean-Vlasov dynamic programming approach, which allows us to characterize the
solution in terms of a Bellman-Isaacs equation in the Wasserstein space of
probability measures. We provide explicit solutions for the optimal robust
portfolio strategies and illustrate our results in the case of uncertain
volatilities and ambiguous correlation between two risky assets. We then derive
the robust efficient frontier in closed-form, and obtain a lower bound for the
Sharpe ratio of any robust efficient portfolio strategy. Finally, we compare
the performance of Sharpe ratios for a robust investor and for an investor with
a misspecified model. MSC Classification: 91G10, 91G80, 60H30


title: Robust training on approximated minimal-entropy set

abstract:
  In this paper, we propose a general framework to learn a robust large-margin
binary classifier when corrupt measurements, called anomalies, caused by sensor
failure might be present in the training set. The goal is to minimize the
generalization error of the classifier on non-corrupted measurements while
controlling the false alarm rate associated with anomalous samples. By
incorporating a non-parametric regularizer based on an empirical entropy
estimator, we propose a Geometric-Entropy-Minimization regularized Maximum
Entropy Discrimination (GEM-MED) method to learn to classify and detect
anomalies in a joint manner. We demonstrate using simulated data and a real
multimodal data set. Our GEM-MED method can yield improved performance over
previous robust classification methods in terms of both classification accuracy
and anomaly detection rate.


title: Solitonic Josephson-based meminductive systems

abstract:
  Memristors, memcapacitors, and meminductors, collectively called memelements,
represent an innovative generation of circuit elements whose properties depend
on the state and history of the system. The hysteretic behavior of one of their
constituent variables, under the effect of an external time-dependent
perturbation, is their distinctive fingerprint. In turn, this feature endows
them with the ability to both store and process information on the same
physical location, a property that is expected to benefit many applications
ranging from unconventional computing to adaptive electronics to robotics, to
name just a few. For all these types of applications, it is important to find
appropriate memelements that combine a wide range of memory states (multi-state
memory), long memory retention times, and protection against unavoidable noise.
Although several physical systems belong to the general class of memelements,
few of them combine all of these important physical features in a single
component. Her we demonstrate theoretically a superconducting memory structure
based on solitonic long Josephson junctions (LJJs). We show that the Josephson
critical current of the junction behaves hysteretically as an external magnetic
field is properly swept. According to the hysteretic path displayed by the
critical current, a LJJ can be used as a multi-state memory, with a
controllable number of available states. In addition, since solitons are at the
core of its operation, this system provides an intrinsic topological protection
against external perturbations. Solitonic Josephson-based memelements may find
applications as memories, and in other emerging areas such as memcomputing,
i.e., computing directly in/by the memory.


title: Hecke operators in KK-theory and the K-homology of Bianchi groups

abstract:
  Let $\Gamma$ be a torsion-free arithmetic group acting on its associated
global symmetric space $X$. Assume that $X$ is of non-compact type and let
$\Gamma$ act on the geodesic boundary $\partial X$ of $X$. Via general
constructions in KK-theory, we endow the K-groups of the arithmetic manifold
$X/\Gamma$, of the reduced group C*-algebra of $\Gamma$ and of the boundary
crossed product algebra associated to the action of $\Gamma$ on $\partial X$,
with Hecke operators. The K-theory and K-homology groups of these C*-algebras
are related by a Gysin six-term exact sequence. In the case when $\Gamma$ is a
group of real hyperbolic isometries, we show that this Gysin sequence is Hecke
equivariant. Finally, in the case when $\Gamma$ is a subgroup of a Bianchi
group, we construct explicit Hecke-equivariant maps between the integral
cohomology of $\Gamma$ and each of these K-groups. Our methods apply to
torsion-free finite index subgroups of $PSL(2,\mathbb{Z})$ as well. These
results are achieved in the context of unbounded Fredholm modules, shedding
light on noncommutative geometric aspects of the purely infinite boundary
crossed product algebra.


title: The Anatomy of Brexit Debate on Facebook

abstract:
  Nowadays users get informed and shape their opinion through social media.
However, the disintermediated access to contents does not guarantee quality of
information. Selective exposure and confirmation bias, indeed, have been shown
to play a pivotal role in content consumption and information spreading. Users
tend to select information adhering (and reinforcing) their worldview and to
ignore dissenting information. This pattern elicits the formation of polarized
groups -- i.e., echo chambers -- where the interaction with like-minded people
might even reinforce polarization. In this work we address news consumption
around Brexit in UK on Facebook. In particular, we perform a massive analysis
on more than 1 Million users interacting with Brexit related posts from the
main news providers between January and July 2016. We show that consumption
patterns elicit the emergence of two distinct communities of news outlets.
Furthermore, to better characterize inner group dynamics, we introduce a new
technique which combines automatic topic extraction and sentiment analysis. We
compare how the same topics are presented on posts and the related emotional
response on comments finding significant differences in both echo chambers and
that polarization influences the perception of topics. Our results provide
important insights about the determinants of polarization and evolution of core
narratives on online debating.


title:
Survey on Misbehavior Detection in Cooperative Intelligent
  Transportation Systems

abstract:
  Cooperative Intelligent Transportation Systems (cITS) are a promising
technology to enhance driving safety and efficiency. Vehicles communicate
wirelessly with other vehicles and infrastructure, thereby creating a highly
dynamic and heterogeneously managed ad-hoc network. It is these network
properties that make it a challenging task to protect integrity of the data and
guarantee its correctness. A major component is the problem that traditional
security mechanisms like PKI-based asymmetric cryptography only exclude
outsider attackers that do not possess key material. However, because attackers
can be insiders within the network (i.e., possess valid key material), this
approach cannot detect all possible attacks. In this survey, we present
misbehavior detection mechanisms that can detect such insider attacks based on
attacker behavior and information analysis. In contrast to well-known intrusion
detection for classical IT systems, these misbehavior detection mechanisms
analyze information semantics to detect attacks, which aligns better with
highly application-tailored communication protocols foreseen for cITS. In our
survey, we provide an extensive introduction to the cITS ecosystem and discuss
shortcomings of PKI-based security. We derive and discuss a classification for
misbehavior detection mechanisms, provide an in-depth overview of seminal
papers on the topic, and highlight open issues and possible future research
trends.


title:
Convex Formulation for Kernel PCA and its Use in Semi-Supervised
  Learning

abstract:
  In this paper, Kernel PCA is reinterpreted as the solution to a convex
optimization problem. Actually, there is a constrained convex problem for each
principal component, so that the constraints guarantee that the principal
component is indeed a solution, and not a mere saddle point. Although these
insights do not imply any algorithmic improvement, they can be used to further
understand the method, formulate possible extensions and properly address them.
As an example, a new convex optimization problem for semi-supervised
classification is proposed, which seems particularly well-suited whenever the
number of known labels is small. Our formulation resembles a Least Squares SVM
problem with a regularization parameter multiplied by a negative sign, combined
with a variational principle for Kernel PCA. Our primal optimization principle
for semi-supervised learning is solved in terms of the Lagrange multipliers.
Numerical experiments in several classification tasks illustrate the
performance of the proposed model in problems with only a few labeled data.


title: Logarithm laws for unipotent flows on hyperbolic manifolds

abstract:
  We prove logarithm laws for unipotent flows on non-compact finite-volume
hyperbolic manifolds. Our method depends on the estimate of norms of certain
incomplete Eisenstein series.


title:
The Effect of Preparation Conditions on Raman and Photoluminescence of
  Monolayer WS2

abstract:
  We report on preparation dependent properties observed in monolayer WS2
samples synthesized via chemical vapor deposition (CVD) on a variety of common
substrates (Si/SiO2, sapphire, fused silica) as well as samples that were
transferred from the growth substrate onto a new substrate. The as-grown CVD
materials (as-WS2) exhibit distinctly different optical properties than
transferred WS2 (x-WS2). In the case of CVD growth on Si/SiO2, following
transfer to fresh Si/SiO2 there is a ~50 meV shift of the ground state exciton
to higher emission energy in both photoluminescence emission and optical
reflection. This shift is indicative of a reduction in tensile strain by
~0.25%. Additionally, the excitonic state in x-WS2 is easily modulated between
neutral and charged exciton by exposure to moderate laser power, while such
optical control is absent in as-WS2 for all growth substrates investigated.
Finally, we observe dramatically different laser power-dependent behavior for
as-grown and transferred WS2. These results demonstrate a strong sensitivity to
sample preparation that is important for both a fundamental understanding of
these novel materials as well as reliable reproduction of device properties.


title:
A convergent time-space adaptive dG(s) finite element method for
  parabolic problems motivated by equal error distribution

abstract:
  We shall develop a fully discrete space-time adaptive method for linear
parabolic problems based on new reliable and efficient a posteriori analysis
for higher order dG(s) finite element discretisations. The adaptive strategy is
motivated by the principle of equally distributing the a posteriori indicators
in time and the convergence of the method is guaranteed by the uniform energy
estimate from [KreuzerM\"ollerSchmidtSiebert:12] under minimal assumptions on
the regularity of the data.


title: Deep Models for Engagement Assessment With Scarce Label Information

abstract:
  Task engagement is defined as loadings on energetic arousal (affect), task
motivation, and concentration (cognition). It is usually challenging and
expensive to label cognitive state data, and traditional computational models
trained with limited label information for engagement assessment do not perform
well because of overfitting. In this paper, we proposed two deep models (i.e.,
a deep classifier and a deep autoencoder) for engagement assessment with scarce
label information. We recruited 15 pilots to conduct a 4-h flight simulation
from Seattle to Chicago and recorded their electroencephalograph (EEG) signals
during the simulation. Experts carefully examined the EEG signals and labeled
20 min of the EEG data for each pilot. The EEG signals were preprocessed and
power spectral features were extracted. The deep models were pretrained by the
unlabeled data and were fine-tuned by a different proportion of the labeled
data (top 1%, 3%, 5%, 10%, 15%, and 20%) to learn new representations for
engagement assessment. The models were then tested on the remaining labeled
data. We compared performances of the new data representations with the
original EEG features for engagement assessment. Experimental results show that
the representations learned by the deep models yielded better accuracies for
the six scenarios (77.09%, 80.45%, 83.32%, 85.74%, 85.78%, and 86.52%), based
on different proportions of the labeled data for training, as compared with the
corresponding accuracies (62.73%, 67.19%, 73.38%, 79.18%, 81.47%, and 84.92%)
achieved by the original EEG features. Deep models are effective for engagement
assessment especially when less label information was used for training.


title:
Generating functions and statistics on spaces of maximal tori in
  classical Lie groups

abstract:
  In this paper we use generating function methods to obtain new asymptotic
results about spaces of $F$-stable maximal tori in $GL_n(\overline{F_q})$,
$Sp_{2n}(\overline{F_q})$, and $SO_{2n+1}(\overline{F_q})$. We recover
stability results of Church--Ellenberg--Farb and Jim\'enez Rolland--Wilson for
"polynomial" statistics on these spaces, and we compute explicit formulas for
their stable values. We derive a double generating function for the characters
of the cohomology of flag varieties in type B/C, which we use to obtain analogs
in type B/C of results of Chen: we recover "twisted homological stability" for
the spaces of maximal tori in $Sp_{2n}(\mathbb{C})$ and
$SO_{2n+1}(\mathbb{C})$, and we compute a generating function for their "stable
twisted Betti numbers". We also give a new proof of a result of Lehrer using
symmetric function theory.


title: Fine tuning and MOND in a metamaterial multiverse

abstract:
  We consider the recently suggested model of a multiverse based on a
ferrofluid. When the ferrofluid is subjected to a modest external magnetic
field, the nanoparticles inside the ferrofluid form small hyperbolic
metamaterial domains, which from the electromagnetic standpoint behave as
individual Minkowski universes exhibiting different laws of physics, such as
different strength of effective gravity, different versions of MOND and
different radiation lifetimes. When the ferrofluid multiverse is populated with
atomic or molecular species, and these species are excited using an external
laser source, the radiation lifetimes of atoms and molecules in these universes
depend strongly on the individual physical properties of each universe via the
Purcell effect. Some universes are better fine-tuned than others to sustain the
excited states of these species. Thus, the ferrofluid-based metamaterial
multiverse may be used to study models of MOND and to illustrate the
fine-tuning mechanism in cosmology.


title: Electrical Conductivity of Quark-Gluon Plasma in Strong Magnetic Fields

abstract:
  We compute the electrical conductivity of quark-gluon plasma in a strong
magnetic field $B$ with quantum field theory at finite temperature using the
lowest Landau level approximation. We provide the one-loop result arising from
1-to-2 scattering processes whose kinematics are satisfied by the (1+1)
dimensional fermion dispersion relation. Due to the chirality conservation, the
conductivity diverges in the massless limit, and is sensitive to the value of
the current quark mass. As a result, we find that the conductivity along the
direction of the magnetic field is quite large compared with the value at
$B=0$, mainly because of the small value of the current quark mass. We show
that the resummation of the ladder diagrams for the current-current correlator
gives rise to only sub-leading contributions beyond the leading-log order, and
thus verify our one-loop result at the leading-log accuracy. We also discuss
possible implications for the relativistic heavy-ion collisions.


title:
Multiscale Abstraction, Planning and Control using Diffusion Wavelets
  for Stochastic Optimal Control Problems

abstract:
  This work presents a multiscale framework to solve a class of stochastic
optimal control problems in the context of robot motion planning and control in
a complex environment. In order to handle complications resulting from a large
decision space and complex environmental geometry, two key concepts are
adopted: (a) a diffusion wavelet representation of the Markov chain for
hierarchical abstraction of the state space; and (b) a desirability
function-based representation of the Markov decision process (MDP) to
efficiently calculate the optimal policy. In the proposed framework, a global
plan that compressively takes into account the long time/length-scale state
transition is first obtained by approximately solving an MDP whose desirability
function is represented by coarse scale bases in the hierarchical abstraction.
Then, a detailed local plan is computed by solving an MDP that considers
wavelet bases associated with a focused region of the state space, guided by
the global plan. The resulting multiscale plan is utilized to finally compute a
continuous-time optimal control policy within a receding horizon
implementation. Two numerical examples are presented to demonstrate the
applicability and validity of the proposed approach.


title:
Large blow-up sets for the prescribed Q-curvature equation in the
  Euclidean space

abstract:
  Let $m\ge 2$ be an integer. For any open domain
$\Omega\subset\mathbb{R}^{2m}$, non-positive function $\varphi\in
C^\infty(\Omega)$ such that $\Delta^m \varphi\equiv 0$, and bounded sequence
$(V_k)\subset L^\infty(\Omega)$ we prove the existence of a sequence of
functions $(u_k)\subset C^{2m-1}(\Omega)$ solving the Liouville equation of
order $2m$ $$(-\Delta)^m u_k = V_ke^{2mu_k}\quad \text{in }\Omega, \quad
\limsup_{k\to\infty} \int_\Omega e^{2mu_k}dx<\infty,$$ and blowing up exactly
on the set $S_{\varphi}:=\{x\in \Omega:\varphi(x)=0\}$, i.e.
$$\lim_{k\to\infty} u_k(x)=+\infty \text{ for }x\in S_{\varphi} \text{ and
}\lim_{k\to\infty} u_k(x)=-\infty \text{ for }x\in \Omega\setminus
S_{\varphi},$$ thus showing that a result of Adimurthi, Robert and Struwe is
sharp. We extend this result to the boundary of $\Omega$ and to the case
$\Omega=\mathbb{R}^{2m}$. Several related problems remain open.


title: The effect of surface geometry on collisions between nanoparticles

abstract:
  In this molecular dynamics study, we examine the local surface geometric
effects of the normal impact force between two approximately spherical
nanoparticles that collide in a vacuum. Three types of surface geometries,
facets, sharp crystal edges, and amorphous surfaces of nanoparticles with radii
R < 10 nm are considered, and the impact force is compared with its macroscopic
counterpart described by a nonlinear contact force, FN proportional to D with n
= 3/2 derived by Hertz (1881), where D is the overlap induced by elastic
compression. We study the surface geometry-dependent impact force. For
facet-facet impact, the mutual contact surface area does not expand due to the
large facet surface, and this in turn leads to a non-Hertz impact force, n <
3/2. A Hertz-like contact force, n = 1.5, is recovered in the edge contact and
in the amorphous surface contact, allowing expansion of the mutual contact
surface area. The results suggest that collisions of amorphous nanoparticles or
nanoparticles with sharp edges may maintain dynamic phenomena, such as
breathers and solitary waves, originating from the nonlinear contact force.


title:
Line geometry and electromagnetism IV: electromagnetic fields as
  infinitesimal Lorentz transformations

abstract:
  It is first shown that the scalar product on any orthogonal space (V, g)
allows one to define linear isomorphisms of the vector spaces of bivectors and
2-forms on V with the underlying vector spaces of the Lie algebra so(p, q) and
its dual, respectively. When those isomorphisms are applied to the
electromagnetic excitation bivector and field strength 2-form, resp., one can
associate various algebraic constructions that pertain to them as bivector
fields and 2-forms with corresponding constructions in terms of so(1, 3) and
its dual. The subsequent association with corresponding things in line geometry
will then become straightforward. In particular, the fields can be represented
by motors, such as screws and wrenches, while the Cartan-Killing form on so(1,
3) is isometric to the scalar product on bivectors that gives the Klein
quadric. When the space of bivectors (and therefore the space of 2-forms) is
given an almost-complex structure (and therefore, a complex structure), one can
also represent most of the constructions on the former and its dual in terms of
so(3; C) and its dual.


title: Asymptotic behaviors of bivariate Gaussian powered extremes

abstract:
  In this paper, joint asymptotics of powered maxima for a triangular array of
bivariate powered Gaussian random vectors are considered. Under the
H\"usler-Reiss condition, limiting distributions of powered maxima are derived.
Furthermore, the second-order expansions of the joint distributions of powered
maxima are established under the refined H\"usler-Reiss condition.


title:
The renormalized superperturbation theory (SPT) approach to the Anderson
  model in and out of equilibrium

abstract:
  The properties of current-carrying steady states of strongly correlated
systems away from the linear-response regime are of topical interest. In this
article, we review the renormalized perturbation theory, or renormalized SPT of
reference [1] for the Anderson model. We present an extension to higher orders
and compare the higher-order results with NRG calculations. Finally, we
elucidate the role of Ward identities in calculating out-of-equilibrium
properties and address claims made in the literature.


title:
Managing travel demand: Location recommendation for system efficiency
  based on mobile phone data

abstract:
  Growth in leisure travel has become increasingly significant economically,
socially, and environmentally. However, flexible but uncoordinated travel
behaviors exacerbate traffic congestion. Mobile phone records not only reveal
human mobility patterns, but also enable us to manage travel demand for system
efficiency. In this paper, we propose a location recommendation system that
infers personal preferences while accounting for constraints imposed by road
capacity in order to manage travel demand. We first infer unobserved
preferences using a machine learning technique from phone records. We then
formulate an optimization method to improve system efficiency. Coupling mobile
phone data with traffic counts and road network infrastructures collected in
Andorra, this study shows that uncoordinated travel behaviors lead to longer
average travel delay, implying the opportunities in managing travel demand by
collective decisions. The interplay between congestion relief and overall
satisfied location preferences observed in extensive simulations indicate that
moderate sacrifices of individual utility lead to significant travel time
savings. Specifically, the results show that under full compliance rate, travel
delay fell by 52% at a cost of 31% less satisfaction. Under 60% compliance
rate, 41% travel delay is saved with a 17% reduction in satisfaction. This
paper highlights the effectiveness of the synergy among collective behaviors in
increasing system efficiency.


title: Update on the BINGO 21cm intensity mapping experiment

abstract:
  21cm intensity mapping is a novel approach aimed at measuring the power
spectrum of density fluctuations and deducing cosmological information, notably
from the Baryonic Acoustic Oscillations (BAO). We give an update on the
progress of BAO from Integrated Neutral Gas Observations (BINGO) which is a
single dish intensity mapping project. First we explain the basic ideas behind
intensity mapping concept before updating the instrument design for BINGO. We
also outline the survey we plan to make and its projected science output
including estimates of cosmological parameters.


title: Bounds and regularity of Solutions of Planar Div-curl Problems

abstract:
  New 2-norm bounds for solutions of planar div-curl boundary value problems on
bounded planar regions are described. Prescribed flux, tangential trace and
mixed boundary boundary are treated. A harmonic decomposition is used to
separate components of the solution due to source terms from the components due
to boundary data. Estimates for the solutions are obtained and some regularity
results are described


title:
Concurrency of anisotropy and spatial dispersion in low refractive index
  dielectric composites

abstract:
  The article demonstrates uncommon manifestation of spatial dispersion in low
refractive index contrast 3D periodic dielectric composites with periods of
about one tenth of the wavelength. First principles simulations by the well
established plane wave method reveal that spatial dispersion leads to
appearance of additional optical axes and can compensate anisotropy in certain
directions.


title:
The impacts of congestion on automobile accessibility. What happens in
  large European cities?

abstract:
  This paper analyze how congestion impact in accessibility in eight european
cities


title: $PT$ Symmetric Real Dirac Fermions and Semimetals

abstract:
  Recently Weyl fermions have attracted increasing interest in condensed matter
physics due to their rich phenomenology originated from their nontrivial
monopole charges. Here we present a theory of real Dirac points that can be
understood as real monopoles in momentum space, serving as a real
generalization of Weyl fermions with the reality being endowed by the $PT$
symmetry. The real counterparts of topological features of Weyl semimetals,
such as Nielsen-Ninomiya no-go theorem, $2$D sub topological insulators and
Fermi arcs, are studied in the $PT$ symmetric Dirac semimetals, and the
underlying reality-dependent topological structures are discussed. In
particular, we construct a minimal model of the real Dirac semimetals based on
recently proposed cold atom experiments and quantum materials about $PT$
symmetric Dirac nodal line semimetals.


title: New algorithms for radio pulsar search

abstract:
  The computational cost of searching for new pulsars is a limiting factor for
upcoming radio telescopes such as SKA. We introduce four new algorithms: an
optimal constant-period search, a coherent tree search which permits optimal
searching with O(1) cost per model, a semicoherent search which combines
information from coherent subsearches while preserving as much phase
information as possible, and a hierarchical search which interpolates between
the coherent and semicoherent limits. Taken together, these algorithms improve
the computational cost of pulsar search by several orders of magnitude. In this
paper, we consider the simple case of a constant-acceleration phase model, but
our methods should generalize to more complex search spaces.


title:
Partial Derivatives for Context-Free Languages: From $\mu$-Regular
  Expressions to Pushdown Automata

abstract:
  We extend Antimirov's partial derivatives from regular expressions to
$\mu$-regular expressions that describe context-free languages. We prove the
correctness of partial derivatives as well as the finiteness of the set of
iterated partial derivatives. The latter are used as pushdown symbols in our
construction of a nondeterministic pushdown automaton, which generalizes
Antimirov's NFA construction.


title: Vector quantile regression beyond correct specification

abstract:
  This paper studies vector quantile regression (VQR), which is a way to model
the dependence of a random vector of interest with respect to a vector of
explanatory variables so to capture the whole conditional distribution, and not
only the conditional mean. The problem of vector quantile regression is
formulated as an optimal transport problem subject to an additional
mean-independence condition. This paper provides a new set of results on VQR
beyond the case with correct specification which had been the focus of previous
work. First, we show that even under misspecification, the VQR problem still
has a solution which provides a general representation of the conditional
dependence between random vectors. Second, we provide a detailed comparison
with the classical approach of Koenker and Bassett in the case when the
dependent variable is univariate and we show that in that case, VQR is
equivalent to classical quantile regression with an additional monotonicity
constraint.


title:
A Projected Gradient and Constraint Linearization Method for Nonlinear
  Model Predictive Control

abstract:
  Projected Gradient Descent denotes a class of iterative methods for solving
optimization programs. Its applicability to convex optimization programs has
gained significant popularity for its intuitive implementation that involves
only simple algebraic operations. In fact, if the projection onto the feasible
set is easy to compute, then the method has low complexity. On the other hand,
when the problem is nonconvex, e.g. because of nonlinear equality constraints,
the projection becomes hard and thus impractical. In this paper, we propose a
projected gradient method for Nonlinear Programs (NLPs) that only requires
projections onto the linearization of the nonlinear constraints around the
current iterate, similarly to Sequential Quadratic Programming (SQP). Although
the projection is easier to compute, it makes the intermediate steps unfeasible
for the original problem. As a result, the gradient method does not fall either
into the projected gradient descent approaches, because the projection is not
performed onto the original nonlinear manifold, or into the standard SQP, since
second-order information is not used. For nonlinear smooth optimization
problems, we analyze the similarities of the proposed method with SQP and
assess its local and global convergence to a Karush-Kuhn-Tucker (KKT) point of
the original problem. Further, we show that nonlinear Model Predictive Control
(MPC) is a promising application of the proposed method, due to the sparsity of
the resulting optimization problem. We illustrate the computational efficiency
of the proposed method in a numerical example with box constraints on the
control input and a quadratic terminal constraint on the state variable.


title: On sequences of expected maxima and expected ranges

abstract:
  We investigate conditions in order to decide whether a given sequence of real
numbers represents expected maxima or expected ranges. The main result provides
a novel necessary and sufficient condition, relating an expected maxima
sequence to a translation of a Bernstein function through its
L\'{e}vy-Khintchine representation.
  Key words and phrases: expected maxima; expected ranges; Bernstein functions,
L\'{e}vy-Khintchine representation, order statistics.


title: The S.V.D. of the Poisson Kernel

abstract:
  This paper describes the singular value decomposition (SVD) of the Poisson
kernel for the Dirichlet problem for the Laplacian on bounded regions in R^N, N
>=2. This operator is a compact linear transformation from L^2 of the boundary
to L^2 of the region. These singular values and functions are related to the
eigenvalues and eigenfunctions of the Dirichlet Biharmonic Steklov
eigenproblem. The Bergman harmonic projection on L^2 is characterized and the
Reproducing kernel for the real harmonic Bergman space is described. Optimal
finite rank approximations of the Poisson kernel, with error estimates, are
found. Spectral formulae for the normal derivatives of eigenfunctions of the
Dirichlet Laplacian are found and yield bounds on a constant in an inequality
of Hassell and Tao.


title:
Computing subfields of number fields and applications to Galois group
  computations

abstract:
  A polynomial time algorithm to give a complete description of all subfields
of a given number field was given in an article by van Hoeij et al. This
article reports on a massive speedup of this algorithm. This is primary
achieved by our new concept of Galois-generating subfields. In general this is
a very small set of subfields that determine all other subfields in a
group-theoretic way. We compute them by targeted calls to the method from van
Hoeij et al. For an early termination of these calls, we give a list of
criteria that imply that further calls will not result in additional subfields.
Finally, we explain how we use subfields to get a good starting group for the
computation of Galois groups.


title:
Enhancing Cation Diffusion and Suppressing Anion Diffusion via
  Lewis-Acidic Polymer Electrolytes

abstract:
  Solid polymer electrolytes (SPE) have the potential to increase both the
energy density and stability of lithium-based batteries, but low Li-ion
conductivity remains a barrier to technological viability. SPEs are designed to
maximize Li-ion diffusivity relative to the anion, while maintaining sufficient
salt solubility. It is thus remarkable that polyethylene oxide (PEO), the most
widely used SPE, exhibits Li-ion diffusivity that is an order of magnitude
smaller than that of typical counter-ions, such as TFSI, at moderate salt
concentrations. Here, we show that Lewis-basic polymers like PEO intrinsically
favor slow cation and rapid anion diffusion while this relationship can be
reversed in Lewis-acidic polymers. Using molecular dynamics (MD) simulations,
Lewis-acidic polyboranes are identified that achieve up to a ten-fold increase
in Li-ion diffusivity and a significant decrease in anion diffusivity, relative
to PEO. The results for this new class of Lewis-acidic SPEs illustrate a
general principle for increasing Li-ion diffusivity and transference number
with polymer chemistries that exhibit weaker cation and stronger anion
coordination.

categories: physics.chem-ph cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.soft


title:
Longitudinal Conductivity in Strong Magnetic Field in Perturbative QCD:
  Complete Leading Order

abstract:
  We compute the longitudinal electrical conductivity in the presence of strong
background magnetic field in complete leading order of perturbative QCD, based
on the assumed hierarchy of scales $\alpha_s eB\ll (m_q^2,T^2)\ll eB$. We
formulate an effective kinetic theory of lowest Landau level quarks with the
leading order QCD collision term arising from 1-to-2 processes that become
possible due to 1+1 dimensional Landau level kinematics. In small $m_q/T\ll 1$
regime, the longitudinal conductivity behaves as $\sigma_{zz}\sim
e^2(eB)T/(\alpha_s m_q^2\log(m_q/T))$, where the quark mass dependence can be
understood from the chiral anomaly with the axial charge relaxation provided by
a finite quark mass $m_q$. We also present parametric estimates for the
longitudinal and transverse "color conductivities" in the presence of strong
magnetic field, by computing dominant damping rates for quarks and gluons that
are responsible for color charge transportation. We observe that the
longitudinal color conductivity is enhanced by strong magnetic field, which
implies that the sphaleron transition rate in perturbative QCD is suppressed by
strong magnetic field due to the enhanced Lenz's law in color field dynamics.


title: Numerical Evidence for Thermally Induced Monopoles

abstract:
  Electrical charges are conserved. The same would be expected to hold for
magnetic charges, yet magnetic monopoles have never been observed. It is
therefore surprising that the laws of non-equilibrium thermodynamics, combined
with Maxwell's equations, suggest that colloidal particles heated or cooled in
certain polar or paramagnetic solvents may behave as if they carry an
electrical/magnetic charge [J. Phys. Chem. B $\textbf{120}$, 5987 (2016)]. Here
we present numerical simulations that show that the field distribution around a
pair of such heated/cooled colloidal particles agrees quantitatively with the
theoretical predictions for a pair of oppositely charged electrical or magnetic
monopoles. However, in other respects, the non-equilibrium colloids do not
behave as monopoles: they cannot be moved by a homogeneous applied field. The
numerical evidence for the monopole-like fields around heated/cooled colloids
is crucial because the experimental and numerical determination of forces
between such colloids would be complicated by the presence of other effects,
such as thermophoresis.


title:
Modular Dedekind symbols associated to Fuchsian groups and higher-order
  Eisenstein series

abstract:
  Let $E(z,s)$ be the non-holomorphic Eisenstein series for the modular group
$SL(2,{\mathbb Z})$. The classical Kronecker limit formula shows that the
second term in the Laurent expansion at $s=1$ of $E(z,s)$ is essentially the
logarithm of the Dedekind eta function. This eta function is a weight $1/2$
modular form and Dedekind expressed its multiplier system in terms of Dedekind
sums. Building on work of Goldstein, we extend these results from the modular
group to more general Fuchsian groups $\Gamma$. The analogue of the eta
function has a multiplier system that may be expressed in terms of a map
$S:\Gamma \to {\mathbb R}$ which we call a modular Dedekind symbol. We obtain
detailed properties of these symbols by means of the limit formula.
  Twisting the usual Eisenstein series with powers of additive homomorphisms
from $\Gamma$ to ${\mathbb C}$ produces higher-order Eisenstein series. These
series share many of the properties of $E(z,s)$ though they have a more
complicated automorphy condition. They satisfy a Kronecker limit formula and
produce higher-order Dedekind symbols $S^*:\Gamma \to {\mathbb R}$. As an
application of our general results, we prove that higher-order Dedekind symbols
associated to genus one congruence groups $\Gamma_0(N)$ are rational.


title: Non-abelian factorisation for next-to-leading-power threshold logarithms

abstract:
  Soft and collinear radiation is responsible for large corrections to many
hadronic cross sections, near thresholds for the production of heavy final
states. There is much interest in extending our understanding of this radiation
to next-to-leading power (NLP) in the threshold expansion. In this paper, we
generalise a previously proposed all-order NLP factorisation formula to include
non-abelian corrections. We define a non-abelian radiative jet function,
organising collinear enhancements at NLP, and compute it for quark jets at one
loop. We discuss in detail the issue of double counting between soft and
collinear regions. Finally, we verify our prescription by reproducing all NLP
logarithms in Drell-Yan production up to NNLO, including those associated with
double real emission. Our results constitute an important step in the
development of a fully general resummation formalism for NLP threshold effects.


title:
Possibility of Systematic Study of Supernova Explosions by Nuclear
  Imaging Spectroscopy

abstract:
  An all-sky monitor with nuclear imaging spectroscopy is a promising tool for
the systematic study of supernova explosions. In particular, progenitor
scenarios of type-Ia supernovae, which are not yet well understood, can be
resolved using light curves in the nuclear gamma-ray band. Here we report an
expected result of an all-sky monitor with imaging spectroscopy using
electron-tracking Compton camera, which will enable us to observe nuclear
gamma-ray lines from type-Ia supernovae.

categories: astro-ph.IM astro-ph.CO astro-ph.HE physics.ins-det


title: An optimal approximation formula for functions with singularities

abstract:
  We propose an optimal approximation formula for analytic functions that are
defined on a complex region containing the real interval $(-1,1)$ and possibly
have algebraic singularities at the endpoints of the interval. As a space of
such functions,we consider a Hardy space with the weight given by $w_{\mu}(z) =
(1-z^{2})^{\mu/2}$ for $\mu > 0$, and formulate the optimality of an
approximation formula for the functions in the space. Then, we propose an
optimal approximation formula for the space for any $\mu > 0$ as opposed to
existing results with the restriction $0 < \mu < \mu_{\ast}$ for a certain
constant $\mu_{\ast}$. We also provide the results of numerical experiments to
show the performance of the proposed formula.


title: A Polynomial-Time Algorithm for Pliable Index Coding

abstract:
  In pliable index coding, we consider a server with $m$ messages and $n$
clients where each client has as side information a subset of the messages. We
seek to minimize the number of broadcast transmissions, so that each client can
recover any one unknown message she does not already have. Previous work has
shown that the pliable index coding problem is NP-hard and requires at most
$\mathcal{O}(\log^2(n))$ broadcast transmissions, which indicates exponential
savings over the conventional index coding that requires in the worst case
$\mathcal{O}(n)$ transmissions. In this work, building on a decoding criterion
that we propose, we first design a deterministic polynomial-time algorithm that
can realize the exponential benefits, by achieving, in the worst case, a
performance upper bounded by $\mathcal{O}(\log^2(n))$ broadcast transmissions.
We extend our algorithm to the $t$-requests case, where each client requires
$t$ unknown messages that she does not have, and show that our algorithm
requires at most $\mathcal{O}(t\log(n)+\log^2(n))$ broadcast transmissions. We
construct lower bound instances that require at least $\Omega(\log(n))$
transmissions for linear pliable index coding and at least $\Omega(t+\log(n))$
transmissions for the $t$-requests case, indicating that both our upper and
lower bounds are polynomials of $\log(n)$ and differ within a factor of
$\mathcal{O}(\log(n))$. Finally, we provide a probabilistic analysis and show
that the required number of transmissions is almost surely $\Theta(\log(n))$,
as compared to $\Theta(n/\log(n))$ for index coding. Our numerical experiments
show that our algorithm outperforms existing algorithms for pliable index
coding by up to $50\%$ less transmissions.


title:
Stochastic Geometric Analysis of Energy-Efficient Dense Cellular
  Networks

abstract:
  Dense cellular networks (DenseNets) are fast becoming a reality with the
rapid deployment of base stations (BSs) aimed at meeting the explosive data
traffic demand. In legacy systems however this comes with the penalties of
higher network interference and energy consumption. In order to support network
densification in a sustainable manner, the system behavior should be made
'load-proportional' thus allowing certain portions of the network to activate
on-demand. In this work, we develop an analytical framework using tools from
stochastic geometry theory for the performance analysis of DenseNets where
load-awareness is explicitly embedded in the design. The model leverages on a
flexible cellular network architecture where there is a complete separation of
the data and signaling communication functionalities. Using the proposed model,
we identify the most energy- efficient deployment solution for meeting certain
minimum service criteria and analyze the corresponding power savings through
dynamic sleep modes. Based on state-of-the-art system parameters, a homogeneous
pico deployment for the data plane with a separate layer of signaling
macro-cells is revealed to be the most energy-efficient solution in future
dense urban environments.


title:
Phase-Retrieved Tomography enables imaging of a Tumor Spheroid in
  Mesoscopy Regime

abstract:
  Optical tomographic imaging of biological specimen bases its reliability on
the combination of both accurate experimental measures and advanced
computational techniques. In general, due to high scattering and absorption in
most of the tissues, multi view geometries are required to reduce diffuse halo
and blurring in the reconstructions. Scanning processes are used to acquire the
data but they inevitably introduces perturbation, negating the assumption of
aligned measures. Here we propose an innovative, registration free, imaging
protocol implemented to image a human tumor spheroid at mesoscopic regime. The
technique relies on the calculation of autocorrelation sinogram and object
autocorrelation, finalizing the tomographic reconstruction via a three
dimensional Gerchberg Saxton algorithm that retrieves the missing phase
information. Our method is conceptually simple and focuses on single image
acquisition, regardless of the specimen position in the camera plane. We
demonstrate increased deep resolution abilities, not achievable with the
current approaches, rendering the data alignment process obsolete.


title: An Efficient Minibatch Acceptance Test for Metropolis-Hastings

abstract:
  We present a novel Metropolis-Hastings method for large datasets that uses
small expected-size minibatches of data. Previous work on reducing the cost of
Metropolis-Hastings tests yield variable data consumed per sample, with only
constant factor reductions versus using the full dataset for each sample. Here
we present a method that can be tuned to provide arbitrarily small batch sizes,
by adjusting either proposal step size or temperature. Our test uses the
noise-tolerant Barker acceptance test with a novel additive correction
variable. The resulting test has similar cost to a normal SGD update. Our
experiments demonstrate several order-of-magnitude speedups over previous work.


title: Differential equations satisfied by modular forms of level 5

abstract:
  This paper describes the derivation of the level 5 versions of Ramanujan's
system of ordinary differential equations satisfied by the Eisenstein series,
$E_2(q),E_4(q)$, and $E_6(q).$


title: Note on some theorem of Farkas and Kra

abstract:
  In this paper, we apply high level versions of Jacobi's derivative formula to
number theory such as quarternary quadratic forms and convolution sums of some
arithmetical functions.


title:
Polynomial interpolation in higher dimension: from simplicial complexes
  to GC sets

abstract:
  Geometrically characterized (GC) sets were introduced by Chung-Yao in their
work on polynomial interpolation in R^d. Conjectures on the structure of GC
sets have been proposed by Gasca-Maeztu for the planar case, and in higher
dimension by de Boor and Apozyan-Hakopian. We investigate GC sets in dimension
three or more, and show that one way to obtain such sets is from the
combinatorics of simplicial complexes.


title:
Confinement of dislocations inside a crystal with a prescribed external
  strain

abstract:
  A system of $n$ screw dislocations in an isotropic crystal undergoing
antiplane shear is studied in the framework of linear elasticity. Imposing a
suitable boundary condition for the strain, namely requesting the non-vanishing
of its boundary integral, results in a confinement effect. More precisely, in
the presence of an external strain with circulation equal to n times the
lattice spacing, it is energetically convenient to have n distinct dislocations
lying inside the crystal. The result is obtained by formulating the problem via
the core radius approach and by studying the asymptotics as the core size
vanishes. An iterative scheme is devised to prove the main result. This work
sets the basis for studying the upscaling problem, i.e., the limit as
$n\to\infty$, which is treated in [17].


title: Spark Level Sparsity and the $\ell_1$ Tail Minimization

abstract:
  Solving compressed sensing problems relies on the properties of sparse
signals. It is commonly assumed that the sparsity s needs to be less than one
half of the spark of the sensing matrix A, and then the unique sparsest
solution exists, and recoverable by $\ell_1$-minimization or related
procedures. We discover, however, a measure theoretical uniqueness exists for
nearly spark-level sparsity from compressed measurements Ax = b. Specifically,
suppose A is of full spark with m rows, and suppose $\frac{m}{2}$ < s < m. Then
the solution to Ax = b is unique for x with $\|x\|_0 \leq s$ up to a set of
measure 0 in every s-sparse plane. This phenomenon is observed and confirmed by
an $\ell_1$-tail minimization procedure, which recovers sparse signals uniquely
with s > $\frac{m}{2}$ in thousands and thousands of random tests. We further
show instead that the mere $\ell_1$-minimization would actually fail if s >
$\frac{m}{2}$ even from the same measure theoretical point of view.


title:
Probing single-photon state tomography using phase-randomized coherent
  states

abstract:
  Quantum processes involving single-photon states are of broad interest in
particular for quantum communication. Extending to continuous values a recent
proposal by Yuan et al \cite{YUAN16}, we show that single-photon quantum
processes can be characterized using phase randomized coherent states (PRCS) as
inputs. As a proof of principle, we present the experimental investigation of
single-photon tomography using PRCS. The probability distribution of field
quadratures measurements for single-photon states can be accurately derived
from the PRCS data. As a consequence, the Wigner function and the density
matrix of single-photon states are reconstructed with good precision. The
sensitivity of the reconstruction to experimental errors and the number of PRCS
used is addressed.


title: Big Data: Perspektiven fuer Smart Grids und Smart Buildings

abstract:
  This paper gives a short survey of recent trends in the emerging field of big
data. It explains the definitions and useful methods. In addition, application
fields of smart buildings and smart grids are discussed.


title: Automated Big Text Security Classification

abstract:
  In recent years, traditional cybersecurity safeguards have proven ineffective
against insider threats. Famous cases of sensitive information leaks caused by
insiders, including the WikiLeaks release of diplomatic cables and the Edward
Snowden incident, have greatly harmed the U.S. government's relationship with
other governments and with its own citizens. Data Leak Prevention (DLP) is a
solution for detecting and preventing information leaks from within an
organization's network. However, state-of-art DLP detection models are only
able to detect very limited types of sensitive information, and research in the
field has been hindered due to the lack of available sensitive texts. Many
researchers have focused on document-based detection with artificially labeled
"confidential documents" for which security labels are assigned to the entire
document, when in reality only a portion of the document is sensitive. This
type of whole-document based security labeling increases the chances of
preventing authorized users from accessing non-sensitive information within
sensitive documents. In this paper, we introduce Automated Classification
Enabled by Security Similarity (ACESS), a new and innovative detection model
that penetrates the complexity of big text security classification/detection.
To analyze the ACESS system, we constructed a novel dataset, containing
formerly classified paragraphs from diplomatic cables made public by the
WikiLeaks organization. To our knowledge this paper is the first to analyze a
dataset that contains actual formerly sensitive information annotated at
paragraph granularity.


title:
Diffuse Interstellar Bands and the Ultraviolet Extinction Curves: The
  Missing Link Revisited

abstract:
  A large number of interstellar absorption features at ~ 4000\AA\ -- 1.8
{\mu}m, known as the "diffuse interstellar bands" (DIBs), remains unidentified.
Most recent works relate them to large polycyclic aromatic hydrocarbon (PAH)
molecules or ultrasmall carbonaceous grains which are also thought to be
responsible for the 2175 \AA\ extinction bump and/or the far ultraviolet (UV)
extinction rise at $\lambda^{-1} > 5.9\ {\mu}m^{-1}$. Therefore, one might
expect some relation between the UV extinction and DIBs. Such a relationship,
if established, could put important constraints on the carrier of DIBs. Over
the past four decades, whether DIBs are related to the shape of the UV
extinction curves has been extensively investigated. However, the results are
often inconsistent, partly due to the inconsistencies in characterizing the UV
extinction. Here we re-examine the connection between the UV extinction curve
and DIBs. We compile the extinction curves and the equivalent widths of 40 DIBs
along 97 slightlines. We decompose the extinction curve into three Drude-like
functions composed of the visible/near-infrared component, the 2175 \AA\ bump,
and the far-UV extinction at $\lambda^{-1} > 5.9\ {\mu}m^{-1}$. We argue that
the wavelength-integrated far-UV extinction derived from this decomposition
technique best measures the strength of the far-UV extinction. No correlation
is found between the far-UV extinction and most (~90\%) of the DIBs. We have
also shown that the color excess E(1300-1700), the extinction difference at
1300 \AA\ and 1700 \AA\ often used to measure the strength of the far-UV
extinction, does not correlate with DIBs. Finally, we confirm the earlier
findings of no correlation between the 2175 \AA\ bump and DIBs or between the
2175 \AA\ bump and the far-UV extinction.


title: Characterization methods dedicated to nanometer-thick hBN layers

abstract:
  Hexagonal boron nitride (hBN) regains interest as a strategic component in
graphene engineering and in van der Waals heterostructures built with two
dimensional materials. It is crucial then, to handle reliable characterization
techniques capable to assess the quality of structural and electronic
properties of the hBN material used. We present here characterization
procedures based on optical spectroscopies, namely cathodoluminescence and
Raman, with the additional support of structural analysis conducted by
transmission electron microscopy. We show the capability of optical
spectroscopies to investigate and benchmark the optical and structural
properties of various hBN thin layers sources.


title:
Evaluating the stoichiometric and energetic constraints of
  cyanobacterial diurnal growth

abstract:
  Cyanobacteria are an integral part of the Earth's biogeochemical cycles and a
promising resource for the synthesis of renewable bioproducts from atmospheric
CO2 . Growth and metabolism of cyanobacteria are inherently tied to the diurnal
rhythm of light availability. As yet, however, insight into the stoichiometric
and energetic constraints of cyanobacterial diurnal growth is limited. Here, we
develop a computational platform to evaluate the optimality of diurnal
phototrophic growth using a high-quality genome-scale metabolic reconstruction
of the cyanobacterium Synechococcus elongatus PCC 7942. We formulate
phototrophic growth as a self-consistent autocatalytic process and evaluate the
resulting time-dependent resource allocation problem using constraint-based
analysis. Based on a narrow and well defined set of parameters, our approach
results in an ab initio prediction of growth properties over a full diurnal
cycle. In particular, our approach allows us to study the optimality of
metabolite partitioning during diurnal growth. The cyclic pattern of glycogen
accumulation, an emergent property of the model, has timing characteristics
that are shown to be a trade-off between conflicting cellular objectives. The
approach presented here provides insight into the time-dependent resource
allocation problem of phototrophic diurnal growth and may serve as a general
framework to evaluate the optimality of metabolic strategies that evolved in
photosynthetic organisms under diurnal conditions.


title:
Spatio-temporal adaptive penalized splines with application to
  Neuroscience

abstract:
  Data analysed here derive from experiments conducted to study neurons'
activity in the visual cortex of behaving monkeys. We consider a
spatio-temporal adaptive penalized spline (P-spline) approach for modelling the
firing rate of visual neurons. To the best of our knowledge, this is the first
attempt in the statistical literature for locally adaptive smoothing in three
dimensions. Estimation is based on the Separation of Overlapping Penalties
(SOP) algorithm, which provides the stability and speed we look for.


title: Fast estimation of multidimensional adaptive P-spline models

abstract:
  A fast and stable algorithm for estimating multidimensional adaptive P-spline
models is presented. We call it as Separation of Overlapping Penalties (SOP) as
it is an extension of the \textit{Separation of Anisotropic Penalties} (SAP)
algorithm. SAP was originally derived for the estimation of the smoothing
parameters of a multidimensional tensor product P-spline model with anisotropic
penalties.


title: General parabolic initial-boundary value problems in H\"ormander spaces

abstract:
  We investigate a general nonhomogeneous parabolic initial-boundary value
problem in some anisotropic H\"ormander inner product spaces. We prove that the
operators corresponding to this problem are isomorphisms between appropriate
H\"ormander spaces. As an application of this result, we establish a theorem on
the local increase in regularity of solutions to the problem.


title: Convergence Rate Estimates for Consensus over Random Graphs

abstract:
  Multi-agent coordination algorithms with randomized interactions have seen
use in a variety of settings in the multi-agent systems literature. In some
cases, these algorithms can be random by design, as in a gossip-like algorithm,
and in other cases they are random due to external factors, as in the case of
intermittent communications. Targeting both of these scenarios, we present
novel convergence rate estimates for consensus problems solved over random
graphs. Established results provide asymptotic convergence in this setting, and
we provide estimates of the rate of convergence in two forms. First, we
estimate decreases in a quadratic Lyapunov function over time to bound how
quickly the agents' disagreement decays, and second we bound the probability of
being at least a given distance from the point of agreement. Both estimates
rely on (approximately) computing eigenvalues of the expected matrix
exponential of a random graph's Laplacian, which we do explicitly in terms of
the network's size and edge probability, without assuming that any relationship
between them holds. Simulation results are provided to support the theoretical
developments made.


title:
A note on the acylindrical hyperbolicity of groups acting on CAT(0) cube
  complexes

abstract:
  We study the acylindrical hyperbolicity of groups acting by isometries on
CAT(0) cube complexes, and obtain simple criteria formulated in terms of
stabilisers for the action. Namely, we show that a group acting essentially and
non-elementarily on a finite dimensional irreducible CAT(0) cube complex is
acylindrically hyperbolic if there exist two hyperplanes whose stabilisers
intersect along a finite subgroup. We also give further conditions on the
geometry of the complex so that the result holds if we only require the
existence of a single pair of points whose stabilisers intersect along a finite
subgroup.


title: Extremal metrics on blowups along submanifolds

abstract:
  We give conditions under which the blowup of an extremal K\"ahler manifold
along a submanifold of codimension greater than two admits an extremal metric.
This generalizes work of Arezzo-Pacard-Singer, who considered blowups in
points.


title: Relativistic Magnetic Reconnection in the Laboratory

abstract:
  Magnetic reconnection is a fundamental plasma process involving an exchange
of magnetic energy to plasma kinetic energy through changes in the magnetic
field topology. In many astrophysical plasmas magnetic reconnection plays a key
role in the release of large amounts of energy \cite{hoshino1}, although making
direct measurements is challenging in the case of high-energy astrophysical
systems such as pulsar wind emissions \cite{lyubarsky1}, gamma-ray bursts
\cite{thompson1}, and jets from active galactic nuclei \cite{liu1}. Therefore,
laboratory studies of magnetic reconnection provide an important platform for
testing theories and characterising different regimes. Here we present
experimental measurements as well as numerical modeling of relativistic
magnetic reconnection driven by short-pulse, high-intensity lasers that produce
relativistic plasma along with extremely strong magnetic fields. Evidence of
magnetic reconnection was identified by the plasma's X-ray emission patterns,
changes to the electron energy spectrum, and by measuring the time over which
reconnection occurs. Accessing these relativistic conditions in the laboratory
allows for further investigation that may provide insight into unresolved areas
in space and astro-physics.


title:
Quench-induced resonant tunneling mechanisms of bosons in an optical
  lattice with harmonic confinement

abstract:
  The non-equilibrium dynamics of small boson ensembles in a one-dimensional
optical lattice is explored upon a sudden quench of an additional harmonic trap
from strong to weak confinement. We find that the competition between the
initial localization and the repulsive interaction leads to a resonant response
of the system for intermediate quench amplitudes, corresponding to avoided
crossings in the many-body eigenspectrum with varying final trap frequency. In
particular, we show that these avoided crossings can be utilized to prepare the
system in a desired state. The dynamical response is shown to depend on both
the interaction strength as well as the number of atoms manifesting the
many-body nature of the tunneling dynamics.


title:
Mobility-limited polyarylamine biscarbonate ester (PABC) /[6,6]-phenyl
  $C_{61}$ butyric acid methyl ester (PCBM) bulk heterojunction photovoltaic
  device

abstract:
  Photovoltaic (PV) devices made from blends of a polyarylamine biscarbonate
ester (PABC) and [6,6]-phenyl $C_{61}$ butyric acid methyl ester (PCBM) have
been fabricated and characterized. PABC is a hole transporting co-polymer
prepared from reacting
N,N'diphenyl-N,N'bis(3-hydroxyphenyl)1,1;biphenyl(4,4'diamine), diethylene
glycol bischloroformate, and triethylemine. By varying the polymer loading in
the blend, optimal power conversion efficiency (PCE) of approximately 0.45\%
has been achieved for a blend consisting of 25 wt\% PABC, which is an order of
magnitude higher than the PCE for a 45 wt\% blend. The optimal ratio is at
about 0.44:0.56 molar ratio of the active hole transporting to electron
transporting moieties. Results of mobility studies suggest that blends with
higher PABC loading have efficiencies limited by 'hole' transport. Also
responsible for the lower efficiency at higher PABC concentrations was optical
filtering. The efficiency does not appear to be limited by deep charge
trapping. Density functional theory calculations conducted pointed toward a
strong localization of the frontier orbitals, which might offer an explanation
for the low PABC hole mobility. Calculated frontier orbital energy levels found
band gap to be consistent with the $V_{OC}$ measured.


title:
A Stability Result for a Family of Sharp Gagliardo-Nirenberg
  Inequalities

abstract:
  In a recent paper, E. Carlen and A. Figalli prove a stability estimate - also
known as a quantitative inequality - for a sharp Gagliardo-Nirenberg inequality
and use this result to solve a Keller-Segal Equation. The Gagliardo-Nirenberg
Inequality that Carlen and Figalli prove their stability estimate for is part
of a larger family of sharp Gagliardo-Nirenberg inequalities, for which the
sharp constants and extremals were identified in some cases by Carrillo and
Toscani, and then for the remaining cases by Del Pino and Dolbeault. We prove a
stability estimate for the entire family of sharp Gagliardo-Nirenberg
inequalities for which Del Pino and Dolbeault calculated the sharp constants
and extremals. Establishing stability estimates of inequalities is an active
topic. A key piece of our proof is the application of a continuous dimension
generalization of the Bianchi-Egnell Stability Estimate proven by the author.


title:
The Kodaira dimension of contact 3-manifolds and geography of symplectic
  fillings

abstract:
  We introduce the Kodaira dimension of contact 3-manifolds and establish some
basic properties. In particular, contact 3-manifolds with distinct Kodaria
dimensions behave differently when it comes to the geography of various kinds
of fillings. On the other hand, we also prove that, given any contact
3-manifold, there is a lower bound of $2\chi+3\sigma$ for all its minimal
symplectic fillings. This is motivated by the bound of Stipsicz for Stein
fillings. Finally, we discuss various aspects of exact self cobordisms of
fillable 3-manifolds.


title: The Morel-Voevodsky localization theorem in spectral algebraic geometry

abstract:
  We prove an analogue of the Morel-Voevodsky localization theorem over
spectral algebraic spaces. As a corollary we deduce a "derived nilpotent
invariance" result which, informally speaking, says that A^1-homotopy
invariance kills all higher homotopy groups of a connective commutative ring
spectrum.


title:
A thorough analysis of the short- and mid-term activity-related
  variations in the solar acoustic frequencies

abstract:
  The frequencies of the solar acoustic oscillations vary over the activity
cycle. The variations in other activity proxies are found to be well correlated
with the variations in the acoustic frequencies. However, each proxy has a
slightly different time behaviour. Our goal is to characterize the differences
between the time behaviour of the frequency shifts and of two other activity
proxies, namely, the area covered by sunspots and the 10.7cm flux. We define a
new observable that is particularly sensitive to the short-term frequency
variations. We then compare the observable when computed from model frequency
shifts and from observed frequency shifts obtained with the Global Oscillation
Network Group (GONG) for cycle 23. Our analysis shows that on the shortest
time-scales the variations in the frequency shifts seen in the GONG
observations are strongly correlated with the variations in the area covered by
sunspots. However, a significant loss of correlation is still found. We verify
that the times when the frequency shifts and the sunspot area do not vary in a
similar way tend to coincide with the times of the maxima of the quasi-biennial
variations seen in the solar seismic data. A similar analysis of the relation
between the 10.7cm flux and the frequency shifts reveals that the short-time
variations in the frequency shifts follow even more closely those of the 10.7cm
flux than those of the sunspot area. However, a loss of correlation between
frequency shifts and 10.7cm flux variations is still found around the same
times.


title: Topological sound in active-liquid metamaterials

abstract:
  Liquids composed of self-propelled particles have been experimentally
realized using molecular, colloidal, or macroscopic constituents. These active
liquids can flow spontaneously even in the absence of an external drive. Unlike
spontaneous active flow, the propagation of density waves in confined active
liquids is not well explored. Here, we exploit a mapping between density waves
on top of a chiral flow and electrons in a synthetic gauge field to lay out
design principles for artificial structures termed topological active
metamaterials. We design metamaterials that break time-reversal symmetry using
lattices composed of annular channels filled with a spontaneously flowing
active liquid. Such active metamaterials support topologically protected sound
modes that propagate unidirectionally, without backscattering, along either
sample edges or domain walls and despite overdamped particle dynamics. Our work
illustrates how parity-symmetry breaking in metamaterial structure combined
with microscopic irreversibility of active matter leads to novel
functionalities that cannot be achieved using only passive materials.


title: Beyond complex Langevin equations

abstract:
  A simple integral relation between a complex weight and the corresponding
positive distribution is derived by introducing a second complex variable.
Together with the positivity and normalizability conditions, this sum rule
allows to construct explicitly equivalent pairs of distributions in simple
cases. In particular the well known solution for a complex gaussian
distribution is generalized to an arbitrary complex slope. This opens a
possibility of positive representation of Feynman path integrals directly in
the Minkowski time. Such construction is then explicitly carried through in the
second part of this presentation. The continuum limit of the new representation
exists only if some of the additional couplings tend to infinity and are tuned
in a specific way. The approach is then successfully applied to three quantum
mechanical examples including a particle in a constant magnetic field -- a
simplest prototype of a Wilson line. Further generalizations are shortly
discussed and an amusing interpretation of new variables is briefly mentioned.


title: Efficient Large Eddy Simulation for the Discontinuous Galerkin Method

abstract:
  In this paper we present a new technique for efficiently implementing Large
Eddy Simulation with the Discontin- uous Galerkin method on unstructured
meshes. In particular, we will focus upon the approach to overcome the
computational complexity that the additional degrees of freedom in
Discontinuous Galerkin methods entail. The turbulence algorithms have been
implemented within Fluidity, an open-source computational fluid dynamics
solver. The model is tested with the well known backward-facing step problem,
and is shown to concur with published results.


title: Finite-key-size effect in commercial plug-and-play QKD system

abstract:
  A security evaluation against the finite-key-size effect was performed for a
commercial plug-and-play quantum key distribution (QKD) system. We demonstrate
the ability of an eavesdropper to force the system to distill key from a
smaller length of sifted-key. We also derive a key-rate equation that is
specific for this system. This equation provides bounds above the upper bound
of secure key under finite-key-size analysis. From this equation and our
experimental data, we show that the keys that have been distilled from the
smaller sifted-key size fall above our bound. Thus, their security is not
covered by finite-key-size analysis. Experimentally, we could consistently
force the system to generate the key outside of the bound. We also test
manufacturer's software update. Although all the keys after the patch fall
under our bound, their security cannot be guaranteed under this analysis. Our
methodology can be used for security certification and standardization of QKD
systems.


title:
Invasion fronts on graphs: the Fisher-KPP equation on homogeneous trees
  and Erd\H{o}s-R\'eyni graphs

abstract:
  We study the dynamics of the Fisher-KPP equation on the infinite homogeneous
tree and Erd\H{o}s-R\'eyni random graphs. We assume initial data that is zero
everywhere except at a single node. For the case of the homogeneous tree, the
solution will either form a traveling front or converge pointwise to zero. This
dichotomy is determined by the linear spreading speed and we compute critical
values of the diffusion parameter for which the spreading speed is zero and
maximal and prove that the system is linearly determined. We also study the
growth of the total population in the network and identify the exponential
growth rate as a function of the diffusion coefficient, $\alpha$. Finally, we
make predictions for the Fisher-KPP equation on Erd\H{o}s-R\'enyi random graphs
based upon the results on the homogeneous tree. When $\alpha$ is small we
observe via numerical simulations that mean arrival times are linearly related
to distance from the initial node and the speed of invasion is well
approximated by the linear spreading speed on the tree. Furthermore, we observe
that exponential growth rates of the total population on the random network can
be bounded by growth rates on the homogeneous tree and provide an explanation
for the sub-linear exponential growth rates that occur for small diffusion.


title:
On the Enumeration of Irreducible Polynomials over $\text{GF}(q)$ with
  Prescribed Coefficients

abstract:
  We present an efficient deterministic algorithm which outputs exact
expressions in terms of $n$ for the number of monic degree $n$ irreducible
polynomials over $\mathbb{F}_{q}$ of characteristic $p$ for which the first $l
< p$ coefficients are prescribed, provided that $n$ is coprime to $p$. Each of
these counts is $\frac{1}{n}(q^{n-l} + \mathcal{O}(q^{n/2}))$. The main idea
behind the algorithm is to associate to an equivalent problem a set of
Artin-Schreier curves defined over $\mathbb{F}_q$ whose number of
$\mathbb{F}_{q^n}$-rational affine points must be combined. This is
accomplished by computing their zeta functions using a $p$-adic algorithm due
to Lauder and Wan. Using the computational algebra system Magma one can, for
example, compute the zeta functions of the arising curves for $q=5$ and $l=4$
very efficiently, and we detail a proof-of-concept demonstration. Due to the
failure of Newton's identities in positive characteristic, the $l \ge p$ cases
are seemingly harder. Nevertheless, we use an analogous algorithm to compute
example curves for $q = 2$ and $l \le 7$, and for $q = 3$ and $l = 3$. Again
using Magma, for $q = 2$ we computed the relevant zeta functions for $l = 4$
and $l = 5$, obtaining explicit formulae for these open problems for $n$ odd,
as well as for subsets of these problems for all $n$, while for $q = 3$ we
obtained explicit formulae for $l = 3$ and $n$ coprime to $3$. We also discuss
some of the computational challenges and theoretical questions arising from
this approach in the general case and propose some natural open problems.


title: On the connected components of affine Deligne-Lusztig varieties

abstract:
  We study the set of connected components of certain unions of affine
Deligne-Lusztig varieties arising from the study of Shimura varieties. We
determine the set of connected components for basic $\s$-conjugacy classes. As
an application, we verify the Axioms in \cite{HR} for certain PEL type Shimura
varieties. We also show that for any nonbasic $\s$-conjugacy class in a
residually split group, the set of connected components is "controlled" by the
set of straight elements associated to the $\s$-conjugacy class, together with
the obstruction from the corresponding Levi subgroup. Combined with
\cite{Zhou}, this allows one to verify in the residually split case, the
description of the mod-$p$ isogeny classes on Shimura varieties conjectured by
Langland and Rapoport. Along the way, we determine the Picard group of the Witt
vector affine Grassmannian of \cite{BS} and \cite{Zhu} which is of independent
interest.


title: A dominance maximization approach to portfolio selection

abstract:
  In the portfolio multiobjective optimization framework, we propose to compare
and choose, among all feasible asset portfolios of a given market, the one that
maximizes the product of the distances between its values of risk and gain and
those of a suitable reference point (e.g., the so-called nadir). We show that
this approach has distinctive and remarkable features. While being not
influenced by how the objectives are scaled, it provides one with an efficient
(Pareto) portfolio that "dominates the most" with respect to the reference
point. Furthermore, although our no-preference strategy generally requires the
solution of a nonconvex (constrained) single-objective problem, we show how the
resulting (global) optimal portfolio can be easily and efficiently computed. We
also perform numerical tests based on some publicly available benchmark data
sets often used in the literature, highlighting the nice properties of our
approach.


title:
Enhancing light transmission through a random medium with inhomogeneous
  scattering and loss

abstract:
  We enhanced the total transmission of light through a disordered waveguide
with spatially inhomogeneous scattering and loss by shaping the incident
wavefront of a laser beam. Using an on-chip tapered lead, we were able to
access all input modes in the waveguide with a spatial light modulator. The
adaptive wavefront shaping resulted in selective coupling of input light to
high transmission channels, which bypassed the regions of higher scattering and
loss in the waveguide. The spatial inhomogeneity of scattering and loss led to
redirecting of energy flux to optical paths with less scattering and loss to
maximize total energy transported through the system. This work demonstrated
the power of wavefront shaping in coherent control of light transport in
inhomogeneous scattering media, which are common in real applications.


title: Neutron Stars in the Laboratory

abstract:
  Neutron stars are astrophysical laboratories of many extremes of physics.
Their rich phenomenology provides insights into the state and composition of
matter at densities which cannot be reached in terrestrial experiments. Since
the core of a mature neutron star is expected to be dominated by superfluid and
superconducting components, observations also probe the dynamics of large-scale
quantum condensates. The testing and understanding of the relevant theory tends
to focus on the interface between the astrophysics phenomenology and nuclear
physics. The connections with low-temperature experiments tend to be ignored.
However, there has been dramatic progress in understanding laboratory
condensates (from the different phases of superfluid helium to the entire range
of superconductors and cold atom condensates). In this review, we provide an
overview of these developments, compare and contrast the mathematical
descriptions of laboratory condensates and neutron stars and summarise the
current experimental state-of-the-art. This discussion suggests novel ways that
we may make progress in understanding neutron star physics using
low-temperature laboratory experiments.

categories: astro-ph.HE cond-mat.other cond-mat.supr-con physics.flu-dyn


title: Many-particle entanglement criterion for superradiant-like states

abstract:
  We derive a many-particle inseparability criterion for mixed states using the
relation between single-mode and many-particle nonclassicalities. It works very
well not only in the vicinity of the Dicke states, but also for the
superposition of them: superradiant ground state of finite/infinite number of
particles and time evolution of single-photon superradiance. We also obtain a
criterion for ensemble-field entanglement which works fine for such kind of
states. Even though the collective excitations of the many-particle system is
sub-Poissonian --which results in entanglement-- the wave function displays
bunching.


title: Electrokinetic flows in liquid crystal thin films with fixed anchoring

abstract:
  We study ionic and mass transport in a liquid crystalline fluid film in its
nematic phase under an applied electrostatic field. Both analytic and numerical
solutions are given for some prototypical configurations of interest in
electrokinetics: Thin films with spatially nonuniform nematic director that are
either periodic or comprise a set of isolated disclinations. We present a
quantitative description of the mechanisms inducing spatial charge separation
in the nematic, and of the structure and magnitude of the resulting flows. The
fundamental solutions for the charge distribution and flow velocities induced
by disclinations of topological charge $m=-1/2, 1/2$ and $1$ are given. These
solutions allow the analysis of several designer flows, such as "pusher" flows
created by three colinear disclinations, the flow induced by an immersed
spherical particle (equivalent to an $m=1$ defect) and its accompanying $m=-1$
hyperbolic hedgehog defect, and the mechanism behind nonlinear ionic mobilities
when the imposed field is perpendicular to the line joining the defects.


title:
Constructing oxide interfaces and heterostructures by atomic
  layer-by-layer laser molecular beam epitaxy

abstract:
  Advancements in nanoscale engineering of oxide interfaces and
heterostructures have led to discoveries of emergent phenomena and new
artificial materials. Combining the strengths of reactive molecular-beam
epitaxy and pulsed-laser deposition, we show here, with examples of
Sr1+xTi1-xO3+delta, Ruddlesden-Popper phase Lan+1NinO3n+1 (n = 4), and
LaAl1+yO3(1+0.5y)/SrTiO3 interfaces, that atomic layer-by-layer laser
molecular-beam epitaxy (ALL-Laser MBE) significantly advances the state of the
art in constructing oxide materials with atomic layer precision and control
over stoichiometry. With ALL-Laser MBE we have produced conducting
LaAlO3/SrTiO3 interfaces at high oxygen pressures that show no evidence of
oxygen vacancies, a capability not accessible by existing techniques. The
carrier density of the interfacial two-dimensional electron gas thus obtained
agrees quantitatively with the electronic reconstruction mechanism.


title:
Noise-Robust Modes of the Retinal Population Code have the Geometry of
  "Ridges" and Correspond with Neuronal Communities

abstract:
  An appealing new principle for neural population codes is that correlations
among neurons organize neural activity patterns into a discrete set of
clusters, which can each be viewed as a noise-robust population "codeword".
Previous studies assumed that these codewords corresponded geometrically with
local peaks in the probability landscape of neural population responses. Here,
we analyze multiple datasets of the responses of ~150 retinal ganglion cells
and show that local probability peaks are absent under broad, non-repeated
stimulus ensembles, which are characteristic of natural behavior. However, we
find that neural activity still forms noise-robust clusters in this regime,
albeit clusters with a different geometry. We start by defining a soft local
maximum, which is a local probability maximum when constrained to a fixed spike
count. Next, we show that soft local maxima are robustly present, and can
moreover be linked across different spike count levels in the probability
landscape to form a "ridge". We found that these ridges are comprised of
combinations of spiking and silence in the neural population such that all of
the spiking neurons are members of the same neuronal community, a notion from
network theory. We argue that a neuronal community shares many of the
properties of Donald Hebb's classic cell assembly, and show that a simple,
biologically plausible decoding algorithm can recognize the presence of a
specific neuronal community.


title: The Evolution of Meson Masses in a Strong Magnetic Field

abstract:
  Spectra of $q \bar{q}$ hadrons are investigated in the framework of the
Hamiltonian obtained from the relativistic path integral in external
homogeneous magnetic field. The spectra of all 12 spin-isospin s-wave states,
generated by $\pi$ and $\rho$ mesons with different spin projections, are
studied both analytically and numerically on the lattice as functions of
(magnetic field) $eB$. Results are in agreement and demonstrate three types of
behavior, with characteristic splittings predicted by the theory.


title: A model for vortex nucleation in the Ginzburg-Landau equations

abstract:
  This paper studies questions related to the dynamic transition between local
and global minimizers in the Ginzburg-Landau theory of superconductivity. We
derive a heuristic equation governing the dynamics of vortices that are close
to the boundary, and of dipoles with small inter vortex separation. We consider
a small random perturbation of this equation, and study the asymptotic regime
under which vortices nucleate.