title: A posteriori error estimates for the virtual element method

abstract:
  An posteriori error analysis for the virtual element method (VEM) applied to
general elliptic problems is presented. The resulting error estimator is of
residual-type and applies on very general polygonal/polyhedral meshes. The
estimator is fully computable as it relies only on quantities available from
the VEM solution, namely its degrees of freedom and element-wise polynomial
projection. Upper and lower bounds of the error estimator with respect to the
VEM approximation error are proven. The error estimator is used to drive
adaptive mesh refinement in a number of test problems. Mesh adaptation is
particularly simple to implement since elements with consecutive co-planar
edges/faces are allowed and, therefore, locally adapted meshes do not require
any local mesh post-processing.


title:
Probing the spin of the central black hole in the galactic centre with
  secondary images

abstract:
  This paper explores the possibility of determining the spin of the
supermassive black hole (SMBH) in Sgr A*, by using secondary images of stars
orbiting the SMBH. The photons propagate close to the SMBH and their
trajectories probe the space time in a region where the spin of the SMBH is
important. We find the appearance of spikes in the secondary image, which
depends on the angular momentum and spin axis of the SMBH and study the
specific case of the star S2 in detail. The spikes has a magnitude of $\sim 29$
in the K-band and the required angular resolution is of order 15-20 $\mu$as.
The combination of these two requirements poses an extreme observational
challenge, but might be possible with interferometric observations in the
sub-mm regime. The next possible time frame for observing this effect on the
star S2 is in the late 2017 and then it repeats with the period of the star.


title: Divisibility questions in commutative algebraic groups

abstract:
  Let $k$ be a number field, let ${\mathcal{A}}$ be a commutative algebraic
group defined over $k$ and let $p$ be a prime number. Let ${\mathcal{A}}[p]$
denote the $p$-torsion subgroup of ${\mathcal{A}}$. We give some sufficient
conditions for the local-global divisibility by $p$ in ${\mathcal{A}}$ and the
triviality of $Sha (k,{\mathcal{A}}[p])$. When ${\mathcal{A}}$ is an abelian
variety principally polarized, those conditions imply that the elements of the
Tate-Shafarevich group $Sha(k,{\mathcal{A}})$ are divisible by $p$ in the
Weil-Ch\^atelet group $H^1(k,{\mathcal{A}})$ and the local-global principle for
divisibility by $p$ holds in $H^r(k,{\mathcal{A}})$, for all $r\geq 0$.


title: A bridge between Dubovitskii - Federer theorems and the coarea formula

abstract:
  The Morse-Sard theorem requires that a mapping $v:R^n \to R^m$ is of class
$C^k$, $k>n-m$. In 1957 Dubovitski\u{\i} generalized this result by proving
that almost all level sets for a $C^k$ mapping have $H^s$-negligible
intersection with its critical set, where $s=\max(n-m-k+1,0)$. Here the
critical set, or $m$-critical set is defined as $Z_{v,m} = \{ x \in R^n : {\rm
rank} \nabla v(x) < m \}$. Another generalization was obtained independently by
Dubovitski\u{\i} and Federer in 1966, namely for $C^k$ mappings $v:R^n\to R^d$
and integers $m\le d$ they proved that the set of $m$-critical values
$v(Z_{v,m})$ is $H^{b}$-negligible for $b= m-1+\frac{n-m+1}{k}$. They also
established the sharpness of these results within the $C^k$ category.
  Here we prove that Dubovitski\u{\i}'s theorem can be generalized to the case
of continuous mappings of the Sobolev-Lorentz class $W^{k}_{p,1}(R^n,R^d )$,
$p=\frac{n}k$ (this is the minimal integrability assumption that guarantees the
continuity of mappings). In this situation the mappings need not be everywhere
differentiable and in order to handle the set of nondifferentiability points,
we establish for such mappings an analog of the Luzin $N$-property with respect
to lower dimensional Hausdorff content. Finally, we formulate and prove a~${\rm
bridge\ theorem}$ that includes all the above results as particular cases. This
result is new also for smooth mappings but is presented here in the general
Sobolev context. The proofs of the results are based on our previous joint
papers with J.~Bourgain (2013, 2015).
  Note, that in this paper some result concerning the Coarea formula was not
formulated accurately. Now we put an Addendum consisting of three parts: first,
we describe the accurate formulation of this result, then we give some
historical remarks, and finally its relation to other results of the paper.


title: Emergence of event cascades in inhomogeneous networks

abstract:
  There is a commonality among contagious diseases, tweets, urban crimes,
nuclear reactions, and neuronal firings that past events facilitate the future
occurrence of events. The spread of events has been extensively studied such
that the systems exhibit catastrophic chain reactions if the interaction
represented by the ratio of reproduction exceeds unity; however, their
subthreshold states for the case of the weaker interaction are not fully
understood. Here, we report that these systems are possessed by nonstationary
cascades of event-occurrences already in the subthreshold regime. Event
cascades can be harmful in some contexts, when the peak-demand causes vaccine
shortages, heavy traffic on communication lines, frequent crimes, or large
fluctuations in nuclear reactions, but may be beneficial in other contexts,
such that spontaneous activity in neural networks may be used to generate
motion or store memory. Thus it is important to comprehend the mechanism by
which such cascades appear, and consider controlling a system to tame or
facilitate fluctuations in the event-occurrences. The critical interaction for
the emergence of cascades depends greatly on the network structure in which
individuals are connected. We demonstrate that we can predict whether cascades
may emerge in a network, given information about the interactions between
individuals. Furthermore, we develop a method of reallocating connections among
individuals so that event cascades may be either impeded or impelled in a
network.


title: Quantum Spin Dynamics with Pairwise-Tunable, Long-Range Interactions

abstract:
  We present a platform for the simulation of quantum magnetism with full
control of interactions between pairs of spins at arbitrary distances in one-
and two-dimensional lattices. In our scheme, two internal atomic states
represent a pseudo-spin for atoms trapped within a photonic crystal waveguide
(PCW). With the atomic transition frequency aligned inside a band gap of the
PCW, virtual photons mediate coherent spin-spin interactions between lattice
sites. To obtain full control of interaction coefficients at arbitrary
atom-atom separations, ground-state energy shifts are introduced as a function
of distance across the PCW. In conjunction with auxiliary pump fields,
spin-exchange versus atom-atom separation can be engineered with arbitrary
magnitude and phase, and arranged to introduce non-trivial Berry phases in the
spin lattice, thus opening new avenues for realizing novel topological spin
models. We illustrate the broad applicability of our scheme by explicit
construction for several well known spin models.


title: Global flow of the Higgs potential in a Yukawa model

abstract:
  We study the renormalization flow of the Higgs potential as a function of
both field amplitude and energy scale. This overcomes limitations of
conventional techniques that rely, e.g., on an identification of field
amplitude and RG scale, or on local field expansions. Using a Higgs-Yukawa
model with discrete chiral symmetry as an example, our global flows in field
space clarify the origin of possible meta-stabilities, the fate of the
pseudo-stable phase, and provide new information about the renormalization of
the tunnel barrier. Our results confirm the relaxation of the lower bound for
the Higgs mass in the presence of more general microscopic interactions
(higher-dimensional operators) to a high quantitative accuracy.


title:
Efficient n-type Doping in Epitaxial Graphene through Strong Lateral
  Orbital Hybridization of Ti Adsorbate

abstract:
  In recent years, various doping methods for epitaxial graphene have been
demonstrated through atom substitution and adsorption. Here we observe by
angle-resolved photoemission spectroscopy (ARPES) a coupling-induced Dirac cone
renormalization when depositing small amounts of Ti onto epitaxial graphene on
SiC. We obtain a remarkably high doping efficiency and a readily tunable
carrier velocity simply by changing the amount of deposited Ti.
First-principles theoretical calculations show that a strong lateral
(non-vertical) orbital coupling leads to an efficient doping of graphene by
hybridizing the 2pz orbital of graphene and the 3d orbitals of the Ti
adsorbate, which attached on graphene without creating any trap/scattering
states. This Ti-induced hybridization is adsorbate-specific and has major
consequences for efficient doping as well as applications towards
adsorbate-induced modification of carrier transport in graphene.


title:
Duality and contravariant functors in the representation theory of artin
  algebras

abstract:
  We know that the model theory of modules leads to a way of obtaining
definable categories of modules over a ring $R$ as the kernels of certain
functors $(R\textbf{-Mod})^{\text{op}}\to\textbf{Ab}$ rather than of functors
$R\textbf{-Mod}\to\textbf{Ab}$ which are given by a pp pair. This paper will
give various algebraic characterisations of these functors in the case that $R$
is an artin algebra.
  Suppose that $R$ is an artin algebra. An additive functor
$G:(R\textbf{-Mod})^{\text{op}}\to\textbf{Ab}$ preserves inverse limits and
$G|_{(R\textbf{-mod})^{\text{op}}}:(R\textbf{-mod})^{\text{op}}\to\textbf{Ab}$
is finitely presented if and only if there is a sequence of natural
transformations $(-,A)\to(-,B)\to G\to 0$ for some $A,B\in R\textbf{-mod}$
which is exact when evaluated at any left $R$-module. Any additive functor
$(R\textbf{-Mod})^{\text{op}}\to\textbf{Ab}$ with one of these equivalent
properties has a definable kernel, and every definable subcategory of
$R\textbf{-Mod}$ can be obtained as the kernel of a family of such functors.
  In the final section a generalised setting is introduced, so that our results
apply to more categories than those of the form $R\textbf{-Mod}$ for an artin
algebra $R$. That is, our results are extended to those locally finitely
presented $K$-linear categories whose finitely presented objects form a
dualising $K$-variety, where $K$ is a commutative artinian ring.


title: Non-separability of the Gelfand space of measure algebras

abstract:
  We prove that there exists uncountably many pairwise disjoint open subsets of
the Gelfand space of the measure algebra on any locally compact non-discrete
abelian group which shows that this space is not separable (in fact, we prove
this assertion for the ideal $M_{0}(G)$ consisting of measures with
Fourier-Stieltjes transforms vanishing at infinity which is a stronger
statement). As a corollary, we obtain that the spectras of elements in the
algebra of measures cannot be recovered from the image of one countable subset
of the Gelfand space under Gelfand transform, common for all elements in the
algebra.


title: Polychromatic Colorings on the Hypercube

abstract:
  Given a subgraph G of the hypercube Q_n, a coloring of the edges of Q_n such
that every embedding of G contains an edge of every color is called a
G-polychromatic coloring. The maximum number of colors with which it is
possible to G-polychromatically color the edges of any hypercube is called the
polychromatic number of G. To determine polychromatic numbers, it is only
necessary to consider a structured class of colorings, which we call simple.
The main tool for finding upper bounds on polychromatic numbers is to translate
the question of polychromatically coloring the hypercube so every embedding of
a graph G contains every color into a question of coloring the 2-dimensional
grid so that every so-called shape sequence corresponding to G contains every
color. After surveying the tools for finding polychromatic numbers, we apply
these techniques to find polychromatic numbers of a class of graphs called
punctured hypercubes. We also consider the problem of finding polychromatic
numbers in the setting where larger subcubes of the hypercube are colored. We
exhibit two new constructions which show that this problem is not a
straightforward generalization of the edge coloring problem.


title: An Innovative Workspace for The Cherenkov Telescope Array

abstract:
  The Cherenkov Telescope Array (CTA) is an initiative to build the next
generation, ground-based gamma-ray observatories. We present a prototype
workspace developed at INAF that aims at providing innovative solutions for the
CTA community. The workspace leverages open source technologies providing web
access to a set of tools widely used by the CTA community. Two different user
interaction models, connected to an authentication and authorization
infrastructure, have been implemented in this workspace. The first one is a
workflow management system accessed via a science gateway (based on the Liferay
platform) and the second one is an interactive virtual desktop environment. The
integrated workflow system allows to run applications used in astronomy and
physics researches into distributed computing infrastructures (ranging from
clusters to grids and clouds). The interactive desktop environment allows to
use many software packages without any installation on local desktops
exploiting their native graphical user interfaces. The science gateway and the
interactive desktop environment are connected to the authentication and
authorization infrastructure composed by a Shibboleth identity provider and a
Grouper authorization solution. The Grouper released attributes are consumed by
the science gateway to authorize the access to specific web resources and the
role management mechanism in Liferay provides the attribute-role mapping.


title: Optimal regularized inverse matrices for inverse problems

abstract:
  In this paper, we consider optimal low-rank regularized inverse matrix
approximations and their applications to inverse problems. We give an explicit
solution to a generalized rank-constrained regularized inverse approximation
problem, where the key novelties are that we allow for updates to existing
approximations and we can incorporate additional probability distribution
information. Since computing optimal regularized inverse matrices under rank
constraints can be challenging, especially for problems where matrices are
large and sparse or are only accessable via function call, we propose an
efficient rank-update approach that decomposes the problem into a sequence of
smaller rank problems. Using examples from image deblurring, we demonstrate
that more accurate solutions to inverse problems can be achieved by using
rank-updates to existing regularized inverse approximations. Furthermore, we
show the potential benefits of using optimal regularized inverse matrix updates
for solving perturbed tomographic reconstruction problems.


title:
On strain measures and the geodesic distance to $\text{SO}_n$ in the
  general linear group

abstract:
  We consider various notions of strains; quantitative measures for the
deviation of a linear transformation from an isometry. The main approach, which
is motivated by physical applications and follows the work of Patrizio Neff and
co-workers , is to select a Riemannian metric on $\text{GL}_n$, and use its
induced geodesic distance to measure the distance of a linear transformation
from the set of isometries. We give a short geometric derivation of the formula
for the strain measure for the case where the metric is
left-$\text{GL}_n$-invariant and right-$\text{O}_n$-invariant. We proceed to
investigate alternative distance functions on $\text{GL}_n$, and the properties
of their induced strain measures. We start by analyzing Euclidean distances,
both intrinsic and extrinsic. Next, we prove that there are no bi-invariant
distances on $\text{GL}_n$. Lastly, we investigate strain measures induced by
inverse-invariant distances.


title:
Magnons in Sr$_2$CuO$_3$: possible evidence for Goldstone-Higgs
  interaction in a weakly ordered spin-1/2 chain antiferromagnet

abstract:
  The Goldstone theorem mandates that a spontaneous symmetry breaking entails
the emergence of gap(mass)less excitations. In the case where a rotational
invariance of a system of spin magnetic moments is broken by an
antiferromagnetic order, these are well-known transverse spin waves. The
interaction of such Goldstone magnons with the Higgs amplitude mode of the
order parameter is usually discarded, even though glimpses of Higgs physics
have recently been reported in a quantum magnet, a topological insulator, and
ferroelectric and disordered superconductor systems. The Goldstone-Higgs
interactions could be expected to grow in importance near a quantum critical
point (QCP), where the symmetry-breaking order is weak, and its amplitude
fluctuations are significant. Here we report an electron spin resonance (ESR)
study of a nearly one-dimensional spin-1/2 chain system, Sr$_2$CuO$_3$, which
presents exactly such a case. The ESR spectra at $T > T_N$, in the disordered
Luttinger-spin-liquid phase with unconfined spinons reveal ideal
Heisenberg-chain behavior with only very small, field-independent linewidth,
$\sim 1/T$. In the ordered state, below $T_N$, we identify antiferromagnetic
resonance (AFMR) modes, which are well described by pseudo-Goldstone magnons in
the model of a collinear biaxial antiferromagnet with two gaps, $\Delta_1 =
23.0$ GHz and $\Delta_2 = 13.3$ GHz. Additionally, we observe a major resonant
response of special nature, which we attribute to magnon interaction with the
Higgs amplitude mode in a weakly ordered antiferromagnet. Its unusual field
dependence indicates the presence of a quantum phase transition at $\mu_0 H
\simeq 9.4$ T.


title: An alternative measure of solar activity from detailed sunspot datasets

abstract:
  The sunspot number is analyzed by using detailed sunspot data, including
aspects of observability, sunspot sizes, and proper identification of sunspot
groups as discrete entities of the solar activity. The tests show that besides
the subjective factors there are also objective causes of the ambiguities in
the series of sunspot numbers. To introduce an alternative activity measure the
physical meaning of the sunspot number has to be reconsidered. It contains two
components whose numbers are governed by different physical mechanisms, this is
one source of the ambiguity. This article suggests an activity index, which is
the amount of emerged magnetic flux. The only long-term proxy measure is the
detailed sunspot area dataset with proper calibration to the magnetic flux
amount. The Debrecen sunspot databases provide an appropriate source for the
establishment of the suggested activity index.


title: Impact on floating membranes

abstract:
  When impacted by a rigid object, a thin elastic membrane with negligible
bending rigidity floating on a liquid pool deforms. Two axisymmetric waves
radiating from the impact point propagate. In the first place, a longitudinal
wave front -- associated with in-plane deformation of the membrane and
traveling at constant speed -- separates an outward stress free domain with a
stretched but flat domain. Then, in the stretched domain a dispersive
transverse wave travels at a wave speed that depends on the local stretching
rate. We study the dynamics of this fluid-body system and we show that the wave
dynamics is similar to the capillary waves that propagate at a liquid-gas
interface but with a surface tension coefficient that depends on impact speed.
We emphasize the role of the stretching in the membrane in the wave dynamics
but also in the development of a buckling instability that give rise to radial
wrinkles.


title: A distribution-function-valued SPDE and its applications

abstract:
  In this paper we further study the stochastic partial differential equation
first proposed by Xiong (2013). Under localized conditions on the coefficients
we show that the solution is in fact distribution-function-valued and we
establish the pathwise uniqueness of the solution. As applications we obtain
the well-posedness of the martingale problems for two classes of measure-valued
diffusions: interacting super-Brownian motions and interacting Fleming-Viot
processes. Properties of the two superprocesses such as the existence of
density fields and the extinction behaviors are also studied.


title: Milnor invariants of covering links

abstract:
  We consider Milnor invariants for certain covering links as a generalization
of covering linkage invariants formulated by R. Hartley and K. Murasugi. A set
of Milnor invariants for covering links is a cobordism invariant of a link, and
that this invariant can distinguish some links for which the ordinary Milnor
invariants coincide. Moreover, for a Brunnian link $L$, the first non-vanishing
Milnor invariants of $L$ is modulo-$2$ congruent to a sum of Milnor invariants
of covering links. As a consequence, a sum of linking numbers of ' iterated'
covering links gives the first non-vanishing Milnor invariant of $L$ modulo
$2$.


title: On a calculus of variations problem

abstract:
  The paper is of scientific-methodical character. The classical soap film
shape (minimal surface) problem is considered, the film being stretched between
two parallel coaxial rings. An analytical approach based on relations to the
Sturm-Liouville problem is proposed. An energy terms interpretation of the
classical Goldschmidt condition is discussed. Appearance of the soliton
potential in course of the second variation analysis is noticed.


title:
Approximated Robust Principal Component Analysis for Improved General
  Scene Background Subtraction

abstract:
  The research reported in this paper addresses the fundamental task of
separation of locally moving or deforming image areas from a static or globally
moving background. It builds on the latest developments in the field of robust
principal component analysis, specifically, the recently reported practical
solutions for the long-standing problem of recovering the low-rank and sparse
parts of a large matrix made up of the sum of these two components. This
article addresses a few critical issues including: embedding global motion
parameters in the matrix decomposition model, i.e., estimation of global motion
parameters simultaneously with the foreground/background separation task,
considering matrix block-sparsity rather than generic matrix sparsity as
natural feature in video processing applications, attenuating background
ghosting effects when foreground is subtracted, and more critically providing
an extremely efficient algorithm to solve the low-rank/sparse matrix
decomposition task. The first aspect is important for background/foreground
separation in generic video sequences where the background usually obeys global
displacements originated by the camera motion in the capturing process. The
second aspect exploits the fact that in video processing applications the
sparse matrix has a very particular structure, where the non-zero matrix
entries are not randomly distributed but they build small blocks within the
sparse matrix. The next feature of the proposed approach addresses removal of
ghosting effects originated from foreground silhouettes and the lack of
information in the occluded background regions of the image. Finally, the
proposed model also tackles algorithmic complexity by introducing an extremely
efficient "SVD-free" technique that can be applied in most
background/foreground separation tasks for conventional video processing.


title:
Generalized support vector regression: duality and tensor-kernel
  representation

abstract:
  In this paper we study the variational problem associated to support vector
regression in Banach function spaces. Using the Fenchel-Rockafellar duality
theory, we give explicit formulation of the dual problem as well as of the
related optimality conditions. Moreover, we provide a new computational
framework for solving the problem which relies on a tensor-kernel
representation. This analysis overcomes the typical difficulties connected to
learning in Banach spaces. We finally present a large class of tensor-kernels
to which our theory fully applies: power series tensor kernels. This type of
kernels describe Banach spaces of analytic functions and include
generalizations of the exponential and polynomial kernels as well as, in the
complex case, generalizations of the Szeg\"o and Bergman kernels.


title:
Electric-field dependent g-factor anisotropy in Ge-Si core-shell
  nanowire quantum dots

abstract:
  We present angle-dependent measurements of the effective g-factor g* in a
Ge-Si core-shell nanowire quantum dot. g* is found to be maximum when the
magnetic field is pointing perpendicular to both the nanowire and the electric
field induced by local gates. Alignment of the magnetic field with the electric
field reduces g* significantly. g* is almost completely quenched when the
magnetic field is aligned with the nanowire axis. These findings confirm recent
calculations, where the obtained anisotropy is attributed to a Rashba-type
spin-orbit interaction induced by heavy-hole light-hole mixing. In principle,
this facilitates manipulation of spin-orbit qubits by means of a continuous
high-frequency electric field.


title: Matching universal behavior with potential models

abstract:
  Two-, three-, and four-boson systems are studied close to the unitary limit
using potential models constructed to reproduce the minimal information given
by the two-body scattering length $a$ and the two-body binding energy or
virtual state energy $E_2$. The particular path used to reach the unitary limit
is given by varying the potential strength. In this way the energy spectrum in
the three- and four-boson systems is computed. The lowest energy states show
finite-range effects absorbed in the construction of level functions that can
be used to study real systems. Higher energy levels are free from finite-range
effects, therefore the corresponding level functions tend to the zero-range
universal function. Using this property a zero-range equation for the
four-boson system is proposed and the four-boson universal function is
computed.


title:
Symmetry breaking in spin spirals and skyrmions by in-plane and canted
  magnetic fields

abstract:
  The influence of in-plane and canted magnetic fields on spin spirals and
skyrmions in atomic bilayer islands of palladium and iron on an Ir(111)
substrate is investigated by scanning tunnelling microscopy at low
temperatures. It is shown that the spin spiral propagation direction is
determined by the island's border which can be explained by equilibrium state
calculations on a triangular lattice. By application of in-plane fields, the
spin spiral reorientates its propagation direction and becomes distorted,
thereby allowing a proof for its cycloidal nature. Furthermore, it is
demonstrated that the skyrmions' shape is distorted in canted fields which
allows to determine the sense of magnetisation rotation as enforced by the
interfacial Dzyaloshinskii-Moriya interaction.


title:
How Violent are the Collisions of Different Sized Droplets in a
  Turbulent Flow?

abstract:
  We study the typical collisional velocities in a polydisperse suspension of
droplets in two and three-dimensional turbulent flow and obtain precise
theoretical estimates of the dependence of the impact velocity of
particles-pairs on their relative sizes. These analytical results are validated
against data from our direct numerical simulations. We show that the impact
velocity saturates exponentially with the inverse of the particle-size ratios.
Our results are important to model coalescence or fragmentation (depending on
the impact velocities) and will be crucial, for example, in obtaining precise
coalescence kernels to describe the growth of water droplets which trigger rain
in warm clouds.


title:
Gas Dynamics and Outflow in the Barred Starburst Galaxy NGC 1808
  Revealed with ALMA

abstract:
  NGC 1808 is a nearby barred starburst galaxy with an outflow from the nuclear
region. To study the inflow and outflow processes related to star formation and
dynamical evolution of the galaxy, we have carried out \(^{12}\)CO (\(J=1-0\))
mapping observations of the central \(r\sim4\) kpc of NGC 1808 using the
Atacama Large Millimeter/submillimeter Array (ALMA). Four distinct components
of molecular gas are revealed at high spatial resolution of 2\arcsec
(\(\sim100\) pc): (1) a compact (\(r<200\) pc) circumnuclear disk (CND), (2)
\(r\sim500\) pc ring, (3) gas-rich galactic bar, and (4) spiral arms. Basic
geometric and kinematic parameters are derived for the central 1-kpc region
using tilted-ring modeling. The derived rotation curve reveals multiple mass
components that include (1) a stellar bulge, (2) nuclear bar and molecular CND,
and (3) unresolved massive (\(\sim10^7~M_\sun\)) core. Two systemic velocities,
998 km s\(^{-1}\) for the CND and 964 km s\(^{-1}\) for the 500-pc ring, are
revealed, indicating a kinematic offset. The pattern speed of the primary bar,
derived by using a cloud-orbit model, is \(56\pm11\) km s\(^{-1}\)
kpc\(^{-1}\). Non-circular motions are detected associated with a nuclear
spiral pattern and outflow in the central 1-kpc region. The ratio of the mass
outflow rate to the star formation rate is \(\dot{M}_\mathrm{out}/SFR\sim0.2\)
in the case of optically thin CO (1-0) emission in the outflow, suggesting low
efficiency of star formation quenching.


title: Bayesian Constrained-Model Selection for Factor Analytic Modeling

abstract:
  My dissertation revolves around Bayesian approaches towards constrained
statistical inference in the factor analysis (FA) model. Two interconnected
types of restricted-model selection are considered. These types have a natural
connection to selection problems in the exploratory FA (EFA) and confirmatory
FA (CFA) model and are termed Type I and Type II model selection. Type I
constrained-model selection is taken to mean the determination of the
appropriate dimensionality of a model. This type of constrained-model selection
connects with EFA in the sense of selecting the optimal dimensionality of the
latent vector. Type II model selection is taken to mean the determination of
appropriate inequality, order or shape restrictions on the parameter space. The
dissertation connects Type II constrained-model selection to CFA by focusing on
the determination of linear inequality constraints as expressions of the
direction and (relative) strength of factor loadings. The figures accompanying
this article are taken from the slides of my Division 5 Awards Symposium
Invited address at the APA 2015 Annual Convention in Toronto. These slides can
be retrieved from \url{https://github.com/CFWP/ConventionTalk}.


title:
High-scale validity of a two Higgs doublet scenario: metastability
  included

abstract:
  We make an attempt to identify regions in a Type II Two-Higgs Doublet Model,
which correspond to a metastable electroweak vacuum with lifetime larger than
the age of the universe. We analyse scenarios which retain perturbative
unitarity up to Grand unification and Planck scales. Each point in the
parameter space is restricted using Data from the Large Hadron Collider (LHC)
as well as flavor and precision electroweak constraints. We find that
substantial regions of the parameter space are thus identified as corresponding
to metastability, which compliment the allowed regions for absolute stability,
for top quark mass at the high as well as low end of its currently allowed
range. Thus, a two-Higgs doublet scenario with the electroweak vacuum, either
stable or metastable, can sail through all the way up to the Planck scale
without facing any contradictions.


title: The end of the nucleon-spin crisis

abstract:
  The small fraction of the quark polarization of the nucleon obtained in deep
inelastic lepton scattering is a consequence of a wrong assumption on the flux
of polarized virtual photons in the analysis of the data. The true flux of
polarized photons is due to fluctuations into strongly interacting
quark-antiquarks at least 20\% smaller than assumed and, therefore, the quark
polarization is larger. Realizing this peculiarity the quark polarization
agrees with that given by the Ellis-Jaffe sum rule, i.e. is consistent with the
prediction derived from the experimentally determined weak coupling constants.
It also solves the problem with the under-exhaustion of the fundamental
Bjorken-sum rule. However, it has to be realized that the fluctuations render
it impossible to measure the quark spin with credibility.


title:
The role of SiO as a tracer of past star-formation events: The case of
  the high-mass protocluster NGC 2264-C

abstract:
  NGC 2264-C is a high-mass protocluster where several star-formation events
are known to have occurred. To investigate whether past protostellar activity
has left a chemical imprint in this region, we mapped it in SiO($J = 2-1$), a
shock tracer, and several other molecular lines with the Nobeyama 45 m
telescope. Our observations show the presence of a complex network of
protostellar outflows. The strongest SiO emission lies beyond a radius of $\sim
0.1$ pc with respect to the center of the clump, and is characterized by broad
($> 10$ km s$^{-1}$) lines and abundances of $\sim 1.4 \times 10^{-8}$ with
respect to H$_2$. Interestingly, SiO appears relatively depleted
($\chi_\mathrm{SiO} \sim 4 \times 10^{-9}$) within this radius, despite it
being affected by molecular outflow activity. We attribute this to fast
condensation of SiO back onto dust grains and/or rapid gas-phase destruction of
SiO, favored by the high density present in this area ($> 10^6$ cm$^{-3}$).
Finally, we identify a peripheral, narrow-line ($\sim 2$ km s$^{-1}$)
component, where SiO has an abundance of a few times 10$^{-11}$. After
considering different options, we conclude that this weak emission may be
tracing protostellar shocks from the star formation episode that preceded the
current one, which have decelerated over time and eventually resulted in SiO
being largely depleted/destroyed. Alternatively, a population of unresolved
low-mass protostars may be responsible for the narrow SiO emission.
High-angular resolution observations are necessary to distinguish between these
two possibilities and thus understand the role of SiO as a chemical tracer of
past star-formation episodes in massive protoclusters.


title: Ultra High Energy Cosmic Rays and Neutrinos

abstract:
  We discuss the production of ultra high energy neutrinos coming from the
propagation of ultra high energy cosmic rays and in the framework of top-down
models for the production of these extremely energetic particles. We show the
importance of the detection of ultra high energy neutrinos that can be a
fundamental diagnostic tool to solve the discrepancy in the observed chemical
composition of ultra high energy cosmic rays and, at the extreme energies, can
unveil new physics in connection with the recent cosmological observations of
the possible presence of tensor modes in the fluctuation pattern of the cosmic
microwave background.


title: Adjoint-based Optimal Flow Control for Compressible DNS

abstract:
  A novel adjoint-based framework oriented to optimal flow control in
compressible direct numerical simulations is presented. Also, a new formulation
of the adjoint characteristic boundary conditions is introduced, which enhances
the stability of the adjoint simulations. The flow configuration chosen as a
case study consists of a two dimensional open cavity flow with aspect ratio
$L/H=3$ and Reynolds number $Re=5000$. This flow configuration is of particular
interest, as the turbulent and chaotic nature of separated flows pushes the
adjoint approach to its limit. The target of the flow actuation, defined as
cost, is the reduction of the pressure fluctuations at the sensor location. To
exploit the advantages of the adjoint method, a large number of control
parameters is used. The control consists of an actuating sub-domain where a
two-dimensional body force is applied at every point within the sub-volume.
This results in a total of $2.256 \cdot 10^6$ control parameters. The final
actuation achieved a successful reduction of the cost of $79.6\%$, by altering
the directivity of the sound radiated by the trailing edge of the cavity and
breaking up the large shear layer instabilities into smaller structures.


title: Sidorenko's conjecture, colorings and independent sets

abstract:
  Let $\hom(H,G)$ denote the number of homomorphisms from a graph $H$ to a
graph $G$. Sidorenko's conjecture asserts that for any bipartite graph $H$, and
a graph $G$ we have $$\hom(H,G)\geq
v(G)^{v(H)}\left(\frac{\hom(K_2,G)}{v(G)^2}\right)^{e(H)},$$ where $v(H),v(G)$
and $e(H),e(G)$ denote the number of vertices and edges of the graph $H$ and
$G$, respectively. In this paper we prove Sidorenko's conjecture for certain
special graphs $G$: for the complete graph $K_q$ on $q$ vertices, for a $K_2$
with a loop added at one of the end vertices, and for a path on $3$ vertices
with a loop added at each vertex. These cases correspond to counting colorings,
independent sets and Widom-Rowlinson colorings of a graph $H$. For instance,
for a bipartite graph $H$ the number of $q$-colorings $\textrm{ch}(H,q)$
satisfies $$\textrm{ch}(H,q)\geq q^{v(H)}\left(\frac{q-1}{q}\right)^{e(H)}.$$
In fact, we will prove that in the last two cases (independent sets and
Widom-Rowlinson colorings) the graph $H$ does not need to be bipartite. In all
cases, we first prove a certain correlation inequality which implies
Sidorenko's conjecture in a stronger form.


title:
Quasi-Stationary Asymptotics for Perturbed Semi-Markov Processes in
  Discrete Time

abstract:
  We consider a discrete time semi-Markov process where the characteristics
defining the process depend on a small perturbation parameter. It is assumed
that the state space consists of one finite communicating class of states and,
in addition, one absorbing state. Our main object of interest is the asymptotic
behaviour of the joint probabilities of the position of the semi-Markov process
and the event of non-absorption as time tends to infinity and the perturbation
parameter tends to zero. The main result gives exponential expansions of these
probabilities together with an recursive algorithm for computing the
coefficients in the expansions.


title:
The ExoMol database: molecular line lists for exoplanet and other hot
  atmospheres

abstract:
  The ExoMol database (www.exomol.com) provides extensive line lists of
molecular transitions which are valid over extended temperatures ranges. The
status of the current release of the database is reviewed and a new data
structure is specified. This structure augments the provision of energy levels
(and hence transition frequencies) and Einstein $A$ coefficients with other key
properties, including lifetimes of individual states, temperature-dependent
cooling functions, Land\'e $g$-factors, partition functions, cross sections,
$k$-coefficients and transition dipoles with phase relations. Particular
attention is paid to the treatment of pressure broadening parameters. The new
data structure includes a definition file which provides the necessary
information for utilities accessing ExoMol through its application programming
interface (API). Prospects for the inclusion of new species into the database
are discussed.


title:
Asymptotic Expansions for Moment Functionals of Perturbed Discrete Time
  Semi-Markov Processes

abstract:
  In this paper, we study mixed power-exponential moment functionals of
nonlinearly perturbed semi-Markov processes in discrete time. Conditions under
which the moment functionals of interest can be expanded in asymptotic power
series with respect to the perturbation parameter are given. We show how the
coefficients in these expansions can be computed from explicit recursive
formulas. In particular, the results of the present paper have applications for
studies of quasi-stationary distributions.


title:
Beyond Poisson-Boltzmann: Numerical sampling of charge density
  fluctuations

abstract:
  We present a method aimed at sampling charge density fluctuations in Coulomb
systems. The derivation follows from a functional integral representation of
the partition function in terms of charge density fluctuations. Starting from
the mean-field solution given by the Poisson-Boltzmann equation, an original
approach is proposed to numerically sample fluctuations around it, through the
propagation of a Langevin like stochastic partial differential equation (SPDE).
The diffusion tensor of the SPDE can be chosen so as to avoid the numerical
complexity linked to long-range Coulomb interactions, effectively rendering the
theory completely local. A finite-volume implementation of the SPDE is
described, and the approach is illustrated with preliminary results on the
study of a system made of two like-charge ions immersed in a bath of
counter-ions.


title: Subsurface characterization of 67P/Churyumov-Gerasimenko's Abydos site

abstract:
  On November 12, 2014, the ESA/Rosetta descent module Philae landed on the
Abydos site of comet 67P/Churyumov-Gerasimenko. Aboard this module, the Ptolemy
mass spectrometer measured a CO/CO2 ratio of 0.07 +/- 0.04 which differs
substantially from the value obtained in the coma by the Rosetta/ROSINA
instrument, suggesting a heterogeneity in the comet nucleus. To understand this
difference, we investigated the physico-chemical properties of the Abydos
subsurface leading to CO/CO2 ratios close to that observed by Ptolemy at the
surface of this region. We used a comet nucleus model that takes into account
different water ice phase changes (amorphous ice, crystalline ice and
clathrates), as well as diffusion of molecules throughout the pores of the
matrix. The input parameters of the model were optimized for the Abydos site
and the ROSINA CO/CO2 measured ratio is assumed to correspond to the bulk value
in the nucleus. We find that all considered structures of water ice are able to
reproduce the Ptolemy observation with a time difference not exceeding ~50
days, i.e. lower than ~2% on 67P/Churyumov-Gerasimenko's orbital period. The
suspected heterogeneity of 67P/Churyumov-Gerasimenko's nucleus is also found
possible only if it is constituted of crystalline ices. If the icy phase is
made of amorphous ice or clathrates, the difference between Ptolemy and
ROSINA's measurements would rather originate from the spatial variations in
illumination on the nucleus surface. An eventual new measurement of the CO/CO2
ratio at Abydos by Ptolemy could be decisive to distinguish between the three
water ice structures.


title: On cyclic DNA codes over $\mathbb{F}_2+u\mathbb{F}_2+u^2\mathbb{F}_2$

abstract:
  In the present paper we study the structure of cyclic DNA codes of even
lenght over the ring $\mathbb{F}_2+u\mathbb{F}_2+u^2\mathbb{F}_2$ where
$u^3=0$. We investigate two presentations of cyclic codes of even lenght over
$\mathbb{F}_2+u\mathbb{F}_2+u^2\mathbb{F}_2$ satisfying the reverse constraint
and reverse-complement constraint.


title:
Asymptotics for Quasi-Stationary Distributions of Perturbed Discrete
  Time Semi-Markov Processes

abstract:
  In this paper, we study quasi-stationary distributions of nonlinearly
perturbed semi-Markov processes in discrete time. This type of distributions is
of interest for the analysis of stochastic systems which have finite lifetimes,
but are expected to persist for a long time. We obtain asymptotic power series
expansions for quasi-stationary distributions and it is shown how the
coefficients in these expansions can be computed from a recursive algorithm. As
an illustration of this algorithm, we present a numerical example for a
discrete time Markov chain.


title: Ultrafiltration of charge-stabilized dispersions at low salinity

abstract:
  We present a comprehensive study of cross-flow ultrafiltration (UF) of
charge-stabilized suspensions, under low-salinity conditions of
electrostatically strongly repelling colloidal particles. The axially varying
permeate flux, near-membrane concentration-polarization (CP) layer and osmotic
pressure profiles are calculated using a macroscopic diffusion-advection
boundary layer method, and are compared with filtration experiments on aqueous
suspensions of charge-stabilized silica particles. The theoretical description
based on the one-component macroion fluid model (OCM) accounts for the strong
influence of surface-released counterions on the renormalized colloid charge
and suspension osmotic compressibility, and for the influence of the colloidal
hydrodynamic interactions and electric double layer repulsion on the
concentration-dependent suspension viscosity $\eta$, and collective diffusion
coefficient $D_c$. A strong electro-hydrodynamic enhancement of $D_c$ and
$\eta$, and likewise of the osmotic pressure is predicted theoretically, as
compared with their values for a hard-sphere suspension. We also point to the
failure of generalized Stokes-Einstein relations describing reciprocal
relations between $D_c$ and $\eta$. According to our filtration model, $D_c$ is
of dominant influence, giving rise to an only weakly developed CP layer having
practically no effect on the permeate flux. This prediction is quantitatively
confirmed by our UF measurements of the permeate flux using an aqueous
suspension of charged silica spheres as the feed system. The experimentally
detected fouling for the largest considered transmembrane pressure values is
shown not to be due to filter cake formation by crystallization or
vitrification.


title: Mapping multiplex hubs in human functional brain network

abstract:
  Typical brain networks consist of many peripheral regions and a few highly
central ones, i.e. hubs, playing key functional roles in cerebral
inter-regional interactions. Studies have shown that networks, obtained from
the analysis of specific frequency components of brain activity, present
peculiar architectures with unique profiles of region centrality. However, the
identification of hubs in networks built from different frequency bands
simultaneously is still a challenging problem, remaining largely unexplored.
Here we identify each frequency component with one layer of a multiplex network
and face this challenge by exploiting the recent advances in the analysis of
multiplex topologies. First, we show that each frequency band carries unique
topological information, fundamental to accurately model brain functional
networks. We then demonstrate that hubs in the multiplex network, in general
different from those ones obtained after discarding or aggregating the measured
signals as usual, provide a more accurate map of brain's most important
functional regions, allowing to distinguish between healthy and schizophrenic
populations better than conventional network approaches.

categories: q-bio.NC cond-mat.dis-nn physics.bio-ph physics.med-ph


title: The conjugacy action of $S_n$ and modules induced from centralisers

abstract:
  We establish, for the character table of the symmetric group, the positivity
of the row sums indexed by irreducible characters, when restricted to various
subsets of the conjugacy classes. A notable example is that of partitions with
all parts odd. More generally, we study representations related to the
conjugacy action of the symmetric group. These arise as sums of submodules
induced from centraliser subgroups, and their Frobenius characteristics have
elegant descriptions, often as a multiplicity-free sum of power-sum symmetric
functions. We describe a general framework in which such representations, and
consequently such linear combinations of power-sums, can be analysed. The
conjugacy action for the symmetric group, and more generally for a large class
of groups, is known to contain every irreducible. We find other representations
of dimension $n!$ with this property, including a twisted analogue of the
conjugacy action.


title: Formation of a solar Ha filament from orphan penumbrae

abstract:
  The formation of an Ha filament in active region (AR) 10953 is described.
Observations from the Solar Optical Telescope (SOT) aboard the Hinode satellite
starting on 27th April 2007 until 1st May 2007 were analysed. 20 scans of the
6302A Fe I line pair recorded by SOT/SP were inverted using the SPINOR code.
The inversions were analysed together with SOT/BFI G-band and Ca II H and
SOT/NFI Ha observations. Following the disappearance of an initial Ha filament
aligned along the polarity inversion line (PIL) of the AR, a new Ha filament
formed in its place some 20 hours later, which remained stable for at least 1.5
days. The creation of the new Ha filament was driven by the ascent of
horizontal magnetic fields from the photosphere into the chromosphere at three
separate locations along the PIL. The magnetic fields at two of these locations
were situated directly underneath the initial Ha filament and formed orphan
penumbrae already aligned along the Ha filament channel. The 700 G orphan
penumbrae were stable and trapped in the photosphere until the disappearance of
the overlying initial Ha filament, after which they started to ascend into the
chromosphere at 10pm5 m/s. Each ascent was associated with a simultaneous
magnetic flux reduction of up to 50% in the photosphere. The ascended orphan
penumbrae formed dark 'seed' structures in Ha in parallel with the PIL, which
elongated and merged to form an Ha filament. The filament channel featured
horizontal magnetic fields of on average 260 G at log(tau)=-2 suspended above
the nearly field-free lower photosphere. The fields took on an 'inverse'
configuration at log(tau)=-2 suggesting a flux rope for the new Ha filament.
The orphan penumbral fields ascend into the chromosphere 9-24 hours before the
Ha filament is fully formed. The destruction of the initial Ha filament was
likely caused by the flux emergence at the third location along the PIL.


title:
Convexity of a stochastic control functional related to importance
  sampling of It\^o diffusions

abstract:
  We consider the problem of rare event importance sampling, where the random
variable of interest is a path functional of an It\^o diffusion computed up to
the first exit from a $d$-dimensional bounded domain. Dupuis and Wang
(\textit{Ann. Appl. Probab.}, 15 (2005), pp. 1-38) studied the importance
sampling problem by formulating it as a stochastic optimal control problem,
where the value function is related to the conditional cumulant generating
function of the random variable. In this paper, we show that the sufficient
conditions for the value function to be twice-differentiable and
$\alpha$-uniformly H\"older continuous on the closure of the domain are also
sufficient conditions for positive definiteness of the second variation of the
control functional on the space of differentiable, $\alpha$-uniformly H\"older
continuous $\mathbb{R}^d$-valued feedback controls. We derive an expression for
the second variation using Kazamaki's sufficient condition for
$L^q$-boundedness of exponential martingales, and using Fredholm theory to
prove the finiteness of the moment generating function of the first exit time
over any bounded interval containing the origin. The strict convexity result
suggests that one may be able to solve the corresponding
Hamilton-Jacobi-Bellman boundary value problem in a dimension-robust way, by
combining convex optimisation and Monte Carlo methods. We apply the result to
analyse a gradient descent algorithm proposed by Hartmann and Sch\"utte
(\textit{J. Stat. Mech. Theor. Exp.} (2012), P11004) for efficient rare event
simulation.


title: Emotion Classification from Noisy Speech - A Deep Learning Approach

abstract:
  This paper investigates the performance of Deep Learning for speech emotion
classification when the speech is compounded with noise. It reports on the
classification accuracy and concludes with the future directions for achieving
greater robustness for emotion recognition from noisy speech.


title: Intrinsic Time Quantum Gravity

abstract:
  Correct identification of the true gauge symmetry of General Relativity being
3d spatial diffeomorphism invariant(3dDI) (not the conventional infinite tensor
product group with principle fibre bundle structure), together with intrinsic
time extracted from clean decomposition of the canonical structure yields a
self-consistent theory of quantum gravity. A new set of fundamental commutation
relations is also presented. The basic variables are the eight components of
the unimodular part of the spatial dreibein and eight SU(3) generators which
correspond to Klauder's momentric variables that characterize a free theory of
quantum gravity. The commutation relations are not canonical, but have well
defined group theoretical meanings. All fundamental entities are dimensionless;
and the quantum wave functionals are preferentially in the dreibein
representation. The successful quantum theory of gravity involves only broad
spectrum of knowledge and deep insights but no exotic idea.


title:
Assessing reliable human mobility patterns from higher-order memory in
  mobile communications

abstract:
  Understanding how people move within a geographic area, e.g. a city, a
country or the whole world, is fundamental in several applications, from
predicting the spatio-temporal evolution of an epidemics to inferring migration
patterns. Mobile phone records provide an excellent proxy of human mobility,
showing that movements exhibit a high level of memory. However, the precise
role of memory in widely adopted proxies of mobility, as mobile phone records,
is unknown. Here we use 560 millions of call detail records from Senegal to
show that standard Markovian approaches, including higher-order ones, fail in
capturing real mobility patterns and introduce spurious movements never
observed in reality. We introduce an adaptive memory-driven approach to
overcome such issues. At variance with Markovian models, it is able to
realistically model conditional waiting times, i.e. the probability to stay in
a specific area depending on individual's historical movements. Our results
demonstrate that in standard mobility models the individuals tend to diffuse
faster than what observed in reality, whereas the predictions of the adaptive
memory approach significantly agree with observations. We show that, as a
consequence, the incidence and the geographic spread of a disease could be
inadequately estimated when standard approaches are used, with crucial
implications on resources deployment and policy making during an epidemic
outbreak.

categories: physics.soc-ph cond-mat.dis-nn cs.SI physics.data-an


title:
Michelson-Morley experiment, Doppler effect, aberration of light and the
  aether concept

abstract:
  After an overview of various citations relevant in the context of photon
propagation, the relativistic Doppler effect and the addition theorem of
velocities are first derived taking into account momentum and energy
conservation. Clocks and the aberration of light are treated next, before the
lengths of rods and the Lorentz transformations are discussed. The
Michelson-Morley experiment is described at rest and in motion with respect to
a preferred aether system, first under the assumption of an operation in
vacuum. It is concluded that the aether concept is fully consistent with the
formal application of the Special Theory of Relativity (STR). Whether a
determination of the speed of the laboratory system relative to the aether is
possible, is considered next either for an operation of the experiment in
vacuum or in a medium with an index of refraction not equal to one. In both
cases, the answer appears to be negative.


title:
Three Formulations of the Kuramoto Model as a System of Polynomial
  Equations

abstract:
  We compare three formulations of stationary equations of the Kuramoto model
as systems of polynomial equations. In the comparison, we present bounds on the
numbers of real equilibria based on the work of Bernstein, Kushnirenko, and
Khovanskii, and performance of methods for the optimisation over the set of
equilibria based on the work of Lasserre, both of which could be of independent
interest.


title:
Plasma observations during the Mars atmospheric "plume" event of
  March-April 2012

abstract:
  We present initial analysis and conclusions from plasma observations made
during the reported "Mars plume event" of March - April 2012. During this
period, multiple independent amateur observers detected a localized,
high-altitude "plume" over the Martian dawn terminator [Sanchez-Lavega et al.,
Nature, 2015, doi:10.1038/nature14162], the cause of which remains to be
explained. The estimated brightness of the plume exceeds that expected for
auroral emissions, and its projected altitude greatly exceeds that at which
clouds are expected to form. We report on in-situ measurements of ionospheric
plasma density and solar wind parameters throughout this interval made by Mars
Express, obtained over the same surface region, but at the opposing terminator.
Measurements in the ionosphere at the corresponding location frequently show a
disturbed structure, though this is not atypical for such regions with intense
crustal magnetic fields. We tentatively conclude that the formation and/or
transport of this plume to the altitudes where it was observed could be due in
part to the result of a large interplanetary coronal mass ejection (ICME)
encountering the Martian system. Interestingly, we note that the only similar
plume detection in May 1997 may also have been associated with a large ICME
impact at Mars.


title:
Threshold of auroral intensification reduced by electron precipitation
  effect

abstract:
  It has been known that discrete aurora suddenly intensifies and deforms from
an arc-like to a variety of wavy/vortex structures, especially during a
substorm period. The instability of Alfv$\acute{\rm e}$n waves reflected from
the ionosphere has been analyzed in order to comprehend the ignition process of
auroral intensification. It was presented that the prime key is an enhancement
of plasma convection, and the convection electric field has a threshold. This
study examined effects of auroral electron precipitation, causing the
ionization of neutral atmosphere, on the linear instability of Alfv$\acute{\rm
e}$n waves. It was found that the threshold of convection electric fields is
significantly reduced by increasing the ionization rate, the realistic range of
which could be estimated from observed electron energy spectra.


title:
Investigating the Maximum Number of Real Solutions to the Power Flow
  Equations: Analysis of Lossless Four-Bus Systems

abstract:
  The power flow equations model the steady-state relationship between the
power injections and voltage phasors in an electric power system. By separating
the real and imaginary components of the voltage phasors, the power flow
equations can be formulated as a system of quadratic polynomials. Only the real
solutions to these polynomial equations are physically meaningful. This paper
focuses on the maximum number of real solutions to the power flow equations. An
upper bound on the number of real power flow solutions commonly used in the
literature is the maximum number of complex solutions. There exist two- and
three-bus systems for which all complex solutions are real. It is an open
question whether this is also the case for larger systems. This paper
investigates four-bus systems using techniques from numerical algebraic
geometry and conjectures a negative answer to this question. In particular,
this paper studies lossless, four-bus systems composed of PV buses connected by
lines with arbitrary susceptances. Computing the Galois group, which is
degenerate, enables conversion of the problem of counting the number of real
solutions to the power flow equations into counting the number of positive
roots of a univariate sextic polynomial. From this analysis, it is conjectured
that the system has at most 16 real solutions, which is strictly less than the
maximum number of complex solutions, namely 20. We also provide explicit
parameter values where this system has 16 real solutions so that the
conjectured upper bound is achievable.


title:
Acylindrical hyperbolicity, non simplicity and SQ-universality of groups
  splitting over Z

abstract:
  We show, using acylindrical hyperbolicity, that a finitely generated group
splitting over $\Z$ cannot be simple. We also obtain SQ-universality in most
cases, for instance a balanced group (one where if two powers of an infinite
order element are conjugate then they are equal or inverse) which is finitely
generated and splits over $\Z$ must either be SQ-universal or it is one of
exactly seven virtually abelian exceptions.


title:
Reconstruction of the Higgs mass in events with Higgs bosons decaying
  into a pair of tau leptons using matrix element techniques

abstract:
  We present an algorithm for the reconstruction of the Higgs mass in events
with Higgs bosons decaying into a pair of tau leptons. The algorithm is based
on matrix element (ME) techniques and achieves a relative resolution on the
Higgs boson mass of typically 15-20%. A previous version of the algorithm has
been used in analyses of Higgs boson production performed by the CMS
collaboration during LHC Run 1. The algorithm is described in detail and its
performance on simulated events is assessed. The development of techniques to
handle tau decays in the ME formalism represents an important result of this
paper.


title: Simulation tests of galaxy cluster constraints on chameleon gravity

abstract:
  We use two new hydrodynamical simulations of $\Lambda$CDM and $f(R)$ gravity
to test the methodology used by Wilcox et al. 2015 (W15) in constraining the
effects of a fifth force on the profiles of clusters of galaxies. We construct
realistic simulated stacked weak lensing and X-ray surface brightness cluster
profiles from these cosmological simulations, and then use these data projected
along various lines-of-sight to test the spherical symmetry of our stacking
procedure. We also test the applicability of the NFW profile to model weak
lensing profiles of clusters in $f(R)$ gravity. Finally, we test the validity
of the analytical model developed in W15 against the simulated profiles.
Overall, we find our methodology is robust and broadly agrees with these
simulated data. We also apply our full Markov Chain Monte Carlo (MCMC) analysis
from W15 to our simulated X-ray and lensing profiles, providing consistent
constraints on the modified gravity parameters as obtained from the real
cluster data, e.g. for our $\Lambda$CDM simulation we obtain $|f_{\rm{R}0}| <
8.3 \times 10^{-5}$ (95% CL), which is in good agreement with the W15
measurement of $|f_{\rm{R}0}| < 6 \times 10^{-5}$. Overall, these tests confirm
the power of our methodology which can now be applied to larger cluster samples
available with the next generation surveys.


title:
Representations of Rota-Baxter algebras and regular singular
  decompositions

abstract:
  There is a Rota-Baxter algebra structure on the field $A=\mathbf{k}((t))$
with $ P$ being the projection map $A=\mathbf{k}[[t]]\oplus
t^{-1}\mathbf{k}[t^{-1}]$ onto $ \mathbf{k}[[ t]]$. We study the representation
theory and regular-singular decompositions of any finite dimensional $A$-vector
space. The main result shows that the category of finite dimensional
representations is semisimple and consists of exactly three isomorphism classes
of irreducible representations which are all one-dimensional. As a consequence,
the number of $GL_A(V)$-orbits in the set of all regular-singular
decompositions of an $n$-dimensional $ A$-vector space $V$ is $(n+2)(n+1)/2$.
We also use the result to compute the generalized class number, i.e., the
number of the $GL_n(A)$-isomorphism classes of finitely generated
$\mathbf{k}[[t]]$-submodules of $A^n$.


title:
Suzaku Observation of the High-Inclination Binary EXO 0748-676 in the
  Hard State

abstract:
  Utilizing an archived Suzaku data acquired on 2007 December 25 for 46 ks,
X-ray spectroscopic properties of the dipping and eclipsing low-mass X-ray
binary EXO 0748$-$676 were studied. At an assumed distance of 7.1 kpc, the data
gave a persistent unabsorbed luminosity of $3.4\times10^{36}$ erg cm$^{-2}$
s$^{-1}$ in 0.6 $-$ 55 keV. The source was in a relatively bright low/hard
state, wherein the 0.6 $-$ 55 keV spectrum can be successfully explained by a
"double-seed" Comptonization model, incorporating a common corona with an
electron temperature of $\sim13$ keV. The seed photons are thought to be
supplied from both the neutron star surface, and a cooler truncated disk.
Compared to a sample of non-dipping low-mass X-ray binaries in the low/hard
state, the spectrum is subject to stronger Comptonization, with a relatively
larger Comptonizing $y$-parameter of $\sim1.4$ and a larger coronal optical
depth of $\sim5$. This result, when attributed to the high inclination of EXO
0748$-$676, suggests that the Comptonizing corona may elongate along the disk
plane, and give a longer path for the seed photons when viewed from edge-on
inclinations.


title: Statistically validated network of portfolio overlaps and systemic risk

abstract:
  Common asset holding by financial institutions, namely portfolio overlap, is
nowadays regarded as an important channel for financial contagion with the
potential to trigger fire sales and thus severe losses at the systemic level.
In this paper we propose a method to assess the statistical significance of the
overlap between pairs of heterogeneously diversified portfolios, which then
allows us to build a validated network of financial institutions where links
indicate potential contagion channels due to realized portfolio overlaps. The
method is implemented on a historical database of institutional holdings
ranging from 1999 to the end of 2013, but can be in general applied to any
bipartite network where the presence of similar sets of neighbors is of
interest. We find that the proportion of validated network links (i.e., of
statistically significant overlaps) increased steadily before the 2007-2008
global financial crisis and reached a maximum when the crisis occurred. We
argue that the nature of this measure implies that systemic risk from fire
sales liquidation was maximal at that time. After a sharp drop in 2008,
systemic risk resumed its growth in 2009, with a notable acceleration in 2013,
reaching levels not seen since 2007. We finally show that market trends tend to
be amplified in the portfolios identified by the algorithm, such that it is
possible to have an informative signal about financial institutions that are
about to suffer (enjoy) the most significant losses (gains).


title:
MSIQ: Joint Modeling of Multiple RNA-seq Samples for Accurate Isoform
  Quantification

abstract:
  Next-generation RNA sequencing (RNA-seq) technology has been widely used to
assess full-length RNA isoform abundance in a high-throughput manner. RNA-seq
data offer insight into gene expression levels and transcriptome structures,
enabling us to better understand the regulation of gene expression and
fundamental biological processes. Accurate isoform quantification from RNA-seq
data is challenging due to the information loss in sequencing experiments. A
recent accumulation of multiple RNA-seq data sets from the same tissue or cell
type provides new opportunities to improve the accuracy of isoform
quantification. However, existing statistical or computational methods for
multiple RNA-seq samples either pool the samples into one sample or assign
equal weights to the samples when estimating isoform abundance. These methods
ignore the possible heterogeneity in the quality of different samples and could
result in biased and unrobust estimates. In this article, we develop a method,
which we call "joint modeling of multiple RNA-seq samples for accurate isoform
quantification" (MSIQ), for more accurate and robust isoform quantification by
integrating multiple RNA-seq samples under a Bayesian framework. Our method
aims to (1) identify a consistent group of samples with homogeneous quality and
(2) improve isoform quantification accuracy by jointly modeling multiple
RNA-seq samples by allowing for higher weights on the consistent group. We show
that MSIQ provides a consistent estimator of isoform abundance, and we
demonstrate the accuracy and effectiveness of MSIQ compared with alternative
methods through simulation studies on D. melanogaster genes. We justify MSIQ's
advantages over existing approaches via application studies on real RNA-seq
data from human embryonic stem cells, brain tissues, and the HepG2 immortalized
cell line.


title: Riemannian geometry of the space of volume preserving immersions

abstract:
  Given a compact manifold $M$ and a Riemannian manifold $N$ of bounded
geometry, we consider the manifold ${\rm Imm} (M,N)$ of immersions from $M$ to
$N$ and its subset ${\rm Imm}_\mu (M,N)$ of those immersions with the property
that the volume-form of the pull-back metric equals $\mu$. We first show that
the non-minimal elements of ${\rm Imm}_\mu (M,N) $ form a splitting
submanifold. On this submanifold we consider the Levi-Civita connection for
various natural Sobolev metrics write down the geodesic equation and show local
well-posedness in many cases. The question is a natural generalization of the
corresponding well-posedness question for the group of volume-preserving
diffeomorphisms, which is of great importance in fluid mechanics.


title: On the set of wild points of attracting surfaces in $\mathbb{R}^3$

abstract:
  Suppose that a closed surface $S \subseteq \mathbb{R}^3$ is an attractor, not
necessarily global, for a discrete dynamical system. Assuming that its set of
wild points $W$ is totally disconnected, we prove that (up to an ambient
homeomorphism) it has to be contained in a straight line. Using this result and
a modification of the classical construction of a wild sphere due to Antoine we
show that there exist uncountably many different $2$--spheres in $\mathbb{R}^3$
none of which can be realized as an attractor for a homeomorphism.


title: Work Fluctuations in Bosonic Josephson Junctions

abstract:
  We calculate the first two moments and full probability distribution of the
work performed on a system of bosonic particles in a two-mode Bose-Hubbard
Hamiltonian when the self-interaction term is varied instantaneously or with a
finite-time ramp. In the instantaneous case, we show how the irreversible work
scales differently depending on whether the system is driven to the Josephson
or Fock regime of the bosonic Josephson junction. In the finite-time case, we
use optimal control techniques to substantially decrease the irreversible work
to negligible values. Our analysis can be implemented in present-day
experiments with ultracold atoms and we show how to relate the work statistics
to that of the population imbalance of the two modes.


title: The Distributional Zeta-Function in Disordered Field Theory

abstract:
  In this paper we present a new mathematical rigorous technique for computing
the average free energy of a disordered system with quenched randomness, using
the replicas. The basic tool of this technique is a distributional
zeta-function, a complex function whose derivative at the origin yields the
average free energy of the system as the sum of two contributions: the first
one is a series in which all the integer moments of the partition function of
the model contribute; the second one, which can not be written as a series of
the integer moments, can be made as small as desired. This result supports the
use of integer moments of the partition function, computed via replicas, for
expressing the average free energy of the system. One advantage of the proposed
formalism is that it does not require the understanding of the properties of
the permutation group when the number of replicas goes to zero. Moreover, the
symmetry is broken using the saddle-point equations of the model. As an
application for the distributional zeta-function technique, we obtain the
average free energy of the disordered $\lambda\varphi^{4}$ model defined in a
$d$-dimensional Euclidean space.


title:
Partial and Total Dielectronic Recombination rate coefficients for W73+
  to W56+

abstract:
  Dielectronic recombination (DR) is a key atomic process which affects the
spectroscopic diagnostic modelling of tungsten, most of whose ionization stages
will be found somewhere in the ITER fusion reactor: in the edge, divertor, or
core plasma. Accurate DR data is sparse while complete DR coverage is
unsophisticated (e.g. average-atom or Burgess General Formula) as illustrated
by the large uncertainties which currently exist in the tungsten ionization
balance. To this end, we present a series of partial final state-resolved and
total DR rate coefficients for W73+ to W56+ Tungsten ions. This is part of a
wider effort within The Tungsten Project to calculate accurate dielectronic
recombination rate coefficients for the tungsten isonuclear sequence for use in
collisional-radiative modelling of finite-density tokamak plasmas. The
recombination rate coefficients have been calculated with autostructure using
kappa-averaged relativistic wavefunctions in level resolution (intermediate
coupling) and configuration resolution (configuration average). The results are
available from OPEN-ADAS according to the adf09 and adf48 standard formats.
Comparison with previous calculations of total DR rate coefficients for W63+
and W56+ yield agreement to within 20% and 10%, respectively, at peak
temperature. It is also seen that the Juttner correction to the Maxwell
distribution has a significant effect on the ionization balance of tungsten at
the highest charge states, changing both the peak abundance temperatures and
the ionization fractions of several ions.


title:
Structural and Magnetic Characterization of Large Area, Free-Standing
  Thin Films of Magnetic Ion Intercalated Dichalcogenides Mn0.25TaS2 and
  Fe0.25TaS2

abstract:
  Free-standing thin films of magnetic ion intercalated transition metal
dichalcogenides are produced using ultramicrotoming techniques. Films of
thicknesses ranging from 30nm to 250nm were achieved and characterized using
transmission electron diffraction and X-ray magnetic circular dichroism.
Diffraction measurements visualize the long range crystallographic ordering of
the intercalated ions, while the dichroism measurements directly assess the
orbital contributions to the total magnetic moment. We thus verify the
unquenched orbital moment in Fe0.25TaS2 and measure the fully quenched orbital
contribution in Mn0.25TaS2. Such films can be used in a wide variety of
ultrafast X-ray and electron techniques that benefit from transmission
geometries, and allow measurements of ultrafast structural, electronic, and
magnetization dynamics in space and time.


title:
Empirical Evaluation of a Thread-Safe Dynamic Range Min-Max Tree using
  HTM

abstract:
  Succinct trees, such as wavelet trees and those based on, for instance, range
Min-Max trees (RMMTs), are a family of practical data structures that store
information close to their information-theoretic space lower bound. These
structures are often static; meaning that once they are built, nodes cannot be
added, deleted or modified. This read-only property simplifies concurrency.
However, newer versions of these data structures allow for a fair degree of
dynamism. Parallel programming using Hardware Transactional Memory(HTM), has
been available in mainstream microprocessors since a few years ago. One
limitation of HTM is still on the size of each transaction. This is why HTM's
use, for the moment, is limited to operations that involve few memory addresses
that need to be updated atomically, or where the level of concurrency is low.
We provide the first available implementation of a concurrent, dynamic RMMT
based on HTM, and we compare empirically how well HTM performs compared to a
naive implementation using locks. We have shown that because of the formal
properties of RMMTs, HTM is a good fit for adding concurrency to otherwise slow
lock-based alternatives. We have also shown that HTM performs better than locks
when the number of write operations increase, making it a practical structure
to use in several write-intensive contexts. This is, as far as we know, the
only practical implementation of RMMTs thoroughly tested using HTM.


title: Uncertainty Estimates for Theoretical Atomic and Molecular Data

abstract:
  Sources of uncertainty are reviewed for calculated atomic and molecular data
that are important for plasma modeling: atomic and molecular structure and
cross sections for electron-atom, electron-molecule, and heavy particle
collisions. We concentrate on model uncertainties due to approximations to the
fundamental many-body quantum mechanical equations and we aim to provide
guidelines to estimate uncertainties as a routine part of computations of data
for structure and scattering.


title: Rydberg polaritons in a thermal vapor

abstract:
  We present a pulsed four-wave mixing (FWM) scheme via a Rydberg state to
create, store and retrieve collective Rydberg polaritons. The storage medium
consists of a gas of thermal Rb atoms confined in a 220 {\mu}m thick cell,
which are heated above room temperature. The experimental sequence consists of
a pulsed excitation of Rydberg polaritons via the D1 line, a variable delay or
storage time, and a final retrieval pulse via the D2 line. The lifetime of the
Rydberg polaritons is around 1.2 ns, almost entirely limited by the excitation
bandwidth and the corresponding motional dephasing of the atoms. The presented
scheme combined with a tightly confined atomic ensemble is a good candidate for
a deterministic single-photon source, as soon as strong interactions in terms
of a Rydberg blockade are added.


title:
The joint distribution of the Parisian ruin time and the number of
  claims until Parisian ruin in the classical risk model

abstract:
  In this paper we propose new iterative algorithm of calculating the joint
distribution of the Parisian ruin time and the number of claims until Parisian
ruin for the classical risk model. Examples are provided when the generic claim
size is exponentially distributed.


title: Terahertz properties of Dirac fermions in HgTe films with optical doping

abstract:
  Terahertz properties of mercury telluride (HgTe) films with critical
thickness are presented and discussed. The density of the charge carriers is
controlled using contact-free optical doping by visible light. In the
magneto-optical response of HgTe the contribution of two types of carriers
(electrons and holes) can be identified. The density of the electrons can be
modified by light illumination by more than one order of magnitude. As the hole
density is roughly illuminationindependent, the terahertz response of the
illuminated samples becomes purely electronic. In some cases, light
illumination may switch the qualitative electrodynamic response from hole-like
to the electron-like. The cyclotron mass of the electrons could be extracted
from the data and shows a square root dependence upon the charge concentration
in the broad range of parameters. This can be interpreted as a clear proof of a
linear dispersion relations, i.e. Dirac-type charge carriers.


title:
Shaken not stirred: Creating exotic angular momentum states by shaking
  an optical lattice

abstract:
  We propose a method to create higher orbital states of ultracold atoms in the
Mott regime of an optical lattice. This is done by periodically modulating the
position of the trap minima (known as shaking) and controlling the interference
term of the lasers creating the lattice. These methods are combined with
techniques of shortcuts to adiabaticity. As an example of this, we show
specifically how to create an anti-ferromagnetic type ordering of angular
momentum states of atoms. The specific pulse sequences are designed using
Lewis-Riesenfeld invariants and a four-level model for each well. The results
are compared with numerical simulations of the full Schroedinger equation.


title: Monoidal supercategories

abstract:
  In the literature, one finds several competing notions for the super (i.e.,
Z/2-graded) analog of a monoidal category. The goal of this paper is to clarify
these definitions and the connections between them. We also discuss in detail
the example of the odd Temperley-Lieb supercategory. In a forthcoming article,
we will exploit the formalism developed here in order to define super analogs
of the Kac-Moody 2-categories of Khovanov-Lauda and Rouquier.


title: Entanglement Entropy of the N=4 SYM spin chain

abstract:
  We present a detailed study of the Entanglement Entropy (EE) of excited
states in all closed rank one subsectors of N=4 SYM, namely SU(2), SU(1|1) and
SL(2). Exploiting the techniques of the Coordinate and the Algebraic Bethe
Ansatz we obtain the EE for spin chains with up to seven magnons, at leading
order in the coupling expansion but exact in the length of the spin chain and
of the part of it that we cut. Focusing on the superconformal primary operator
with two magnons in the BMN limit, we derive analytic and exact, in the
coupling $\lambda'$, expressions for the Renyi and the EE. The interpolating
functions for the Renyi and the EE monotonically increase as the coupling
increases from the weak coupling $\lambda' \rightarrow 0$ regime to the strong
coupling $\lambda' \rightarrow \infty$ regime. This results to a violation of a
certain bound for the EE that is present at weak coupling and confirms the
physical intuition that entanglement increases when the coupling increases.


title: Geometric Hypergraph Learning for Visual Tracking

abstract:
  Graph based representation is widely used in visual tracking field by finding
correct correspondences between target parts in consecutive frames. However,
most graph based trackers consider pairwise geometric relations between local
parts. They do not make full use of the target's intrinsic structure, thereby
making the representation easily disturbed by errors in pairwise affinities
when large deformation and occlusion occur. In this paper, we propose a
geometric hypergraph learning based tracking method, which fully exploits
high-order geometric relations among multiple correspondences of parts in
consecutive frames. Then visual tracking is formulated as the mode-seeking
problem on the hypergraph in which vertices represent correspondence hypotheses
and hyperedges describe high-order geometric relations. Besides, a
confidence-aware sampling method is developed to select representative vertices
and hyperedges to construct the geometric hypergraph for more robustness and
scalability. The experiments are carried out on two challenging datasets
(VOT2014 and Deform-SOT) to demonstrate that the proposed method performs
favorable against other existing trackers.


title:
Kinetic control of the coverage of oil droplets by DNA-functionalised
  colloids

abstract:
  We report a study of reversible adsorption of DNA-coated colloids on
complementary functionalized oil droplets. We show that it is possible to
control the surface coverage of oil droplets by colloidal particles, by
exploiting the fact that during slow adsorption, compositional arrest takes
place well before structural arrest occurs. As a consequence, we can prepare
colloid-coated oil droplets with a `frozen' degree of loading, but with fully
ergodic colloidal dynamics on the droplets. We illustrate the equilibrium
nature of the adsorbed colloidal phase by exploring the quasi two-dimensional
(2d) phase behaviour of the adsorbed colloids under the influence of depletion
interactions. We present simulations of a simple model that illustrates the
nature of the compositional arrest and the structural ergodicity.


title:
Elastic vector and axial scattering of weakly interacting particles off
  nuclei

abstract:
  We analyze the elastic scattering of particles interacting with nuclei
through vector and axial currents with overall couplings of the order of the
Standard Model weak interaction, or smaller; the dominant contribution to the
elastic cross section is identified as the coherent component and is therefore
spin-independent. Differential and integrated cross sections are obtained for a
wide range of incident particle masses and velocities and for nuclear targets
with different masses; vector, axial and overall couplings of the incident
particle and of the hadronic target to the massive exchanged boson are also
kept general. This study naturally encompasses several kinds of possible dark
matter components, including active and sterile neutrinos or neutralinos, and
addresses the prospects for their direct detection through elastic scattering
off nuclei.


title: Distributed Iterative Learning Control for a Team of Quadrotors

abstract:
  The goal of this work is to enable a team of quadrotors to learn how to
accurately track a desired trajectory while holding a given formation. We solve
this problem in a distributed manner, where each vehicle has only access to the
information of its neighbors. The desired trajectory is only available to one
(or few) vehicles. We present a distributed iterative learning control (ILC)
approach where each vehicle learns from the experience of its own and its
neighbors' previous task repetitions, and adapts its feedforward input to
improve performance. Existing algorithms are extended in theory to make them
more applicable to real-world experiments. In particular, we prove stability
for any causal learning function with gains chosen according to a simple scalar
condition. Previous proofs were restricted to a specific learning function that
only depends on the tracking error derivative (D-type ILC). Our extension
provides more degrees of freedom in the ILC design and, as a result, better
performance can be achieved. We also show that stability is not affected by a
linear dynamic coupling between neighbors. This allows us to use an additional
consensus feedback controller to compensate for non-repetitive disturbances.
Experiments with two quadrotors attest the effectiveness of the proposed
distributed multi-agent ILC approach. This is the first work to show
distributed ILC in experiment.


title:
Mathematical modeling of T-cells activation dynamics for CD3 molecules
  recycling process

abstract:
  The down regulation of CD3 protein present on the surface of a T-cell
triggers the process of activation. A rapid decrease of CD3 from the surface is
required to reach the threshold that is necessary for the continuation of the
activation process. By flow cytometry technique, it is well established that an
amount of down regulated CD3 proteins recycle and may come on the surface of
T-cell. This article is dedicated to study the impact of recycled CD3 protein
that is recruited into the immune synapse at different rates. The population
density of T-cells is distributed over surface protein (CD3) concentration
under the framework of population balance models by using coupled system of
PDEs. Such problems need non-conventional population balance modeling so that
classical numerical technique can be applied. A recently developed efficient
numerical method is validated against the analytical and numerical solutions.


title: Field Theory of the Eulerian Perfect Fluid

abstract:
  The Eulerian perfect-fluid theory is reformulated from its action principle
in a pure field-theoretic manner. Conservation of the convective current is no
longer imposed by Lin's constraints, but rather adopted as the central idea of
the theory. Our formulation, for the first time, successfully reduces redundant
degrees of freedom promoting one half of the Clebsch variables as the true
dynamical fields. Interactions on these fields allow for the exchange of the
convective current of quantities such as mass and charge, which are uniformly
understood as the breaking of the underlying symmetry of the force-free fluid.
The Clebsch fields play the essential role in the exchange of angular momentum
with the force field producing vorticity.


title:
Near field asymptotic behavior for the porous medium equation on the
  half-line

abstract:
  Kamin and V\'azquez proved in 1991 that solutions to the Cauchy-Dirichlet
problem for the porous medium equation $u_t=(u^m)_{xx}$ on the half line with
zero boundary data and nonnegative compactly supported integrable initial data
behave for large times as a dipole type solution to the equation having the
same first moment as the initial data, with an error which is $o(t^{-1/m})$.
However, on sets of the form $0<x<g(t)$, with $g(t)=o(t^{1/(2m)})$ as
$t\to\infty$, in the so called near field, the dipole solution is
$o(t^{-1/m})$, and their result does not give neither the right rate of decay
of the solution, nor a nontrivial asymptotic profile. In this paper we will
show that the error is $o\big(t^{-(2m+1)/(2m^2)}(1+x)^{1/m}\big)$. This allows
in particular to obtain a nontrivial asymptotic profile in the near field
limit, which is a multiple of $x^{1/m}$, thus improving in this scale the
results of Kamin and V\'azquez.


title: How to Combine a Billion Alphas

abstract:
  We give an explicit algorithm and source code for computing optimal weights
for combining a large number N of alphas. This algorithm does not cost O(N^3)
or even O(N^2) operations but is much cheaper, in fact, the number of required
operations scales linearly with N. We discuss how in the absence of binary or
quasi-binary clustering of alphas, which is not observed in practice, the
optimization problem simplifies when N is large. Our algorithm does not require
computing principal components or inverting large matrices, nor does it require
iterations. The number of risk factors it employs, which typically is limited
by the number of historical observations, can be sizably enlarged via using
position data for the underlying tradables.


title:
Efficient and powerful familywise error control in genome-wide
  association studies using generalized linear models

abstract:
  In genetic association studies, detecting phenotype-genotype association is a
primary goal. We assume that the relationship between the data -phenotype,
genetic markers and environmental covariates - can be modelled by a generalized
linear model (GLM). The inclusion of environmental covariates makes it possible
to account for important confounding factors, such as sex and population
substructure. A multivariate score statistic, which under the complete null
hypothesis of no phenotype-genotype association asymptotically has a
multivariate normal distribution with a covariance matrix that can be estimated
from the data, is used to test a large number of genetic markers for
association with the phenotype. We stress the importance of controlling the
familywise error rate (FWER), and use the asymptotic distribution of the
multivariate score test statistic to find a local significance level for the
individual test. Using real data (from one study on schizophrenia and bipolar
disorder and one on maximal oxygen uptake) and constructed correlated
structures, we show that our method is a powerful alternative to the popular
Bonferroni and Sidak methods. For GLMs without environmental covariates, we
show that our method is an efficient alternative to permutation methods for
multiple testing. Further, we show that if environmental covariates and genetic
markers are uncorrelated, the estimated covariance matrix of the score test
statistic can be approximated by the estimated correlation matrix for just the
genetic markers. As byproducts of our method, an effective number of
independent tests can be defined, and FWER-adjusted $p$-values can be
calculated as an alternative to using a local significance level.


title: Online Distributed Scheduling on a Fault-prone Parallel System

abstract:
  We consider a parallel system of $m$ identical machines prone to
unpredictable crashes and restarts, trying to cope with the continuous arrival
of tasks to be executed. Tasks have different computational requirements (i.e.,
processing time or size). The flow of tasks, their size, and the crash and
restart of the machines are assumed to be controlled by an adversary. Then, we
focus on the study of online distributed algorithms for the efficient
scheduling of the tasks. We use competitive analysis, considering as efficiency
metric the completed-load, i.e., the aggregated size of the completed tasks. We
first present optimal completed-load competitiveness algorithms when the number
of different task sizes that can be injected by the adversary is bounded. (It
is known that, if it is not bounded, competitiveness is not achievable.) We
first consider only two different task sizes, and then proceed to $k$ different
ones, showing in both cases that the optimal completed-load competitiveness can
be achieved. Then, we consider the possibility of having some form of resource
augmentation, allowing the scheduling algorithm to run with a speedup $s \geq
1$. In this case, we show that the competitiveness of all work-conserving
scheduling algorithms can be increased by using a large enough speedup.


title:
Current of interacting particles inside a channel of exponential
  cavities: Application of a modified Fick--Jacobs equation

abstract:
  The Fick--Jacobs equation has been widely studied, because of its
applications in the diffusion and transport of non-interacting particles in
narrow channels. It is also known that a modified version of this equation can
be used to describe the same system with particles interacting through a
hard-core potential. In this work we present a system that can be exactly
solved using the Fick--Jacobs equation. The exact results of the particle
concentration profile along the channel $n$, the current, $J$, and the
mobility, $\mu$, of particles as a function of an external force are contrasted
with Monte Carlo simulations results of non-interacting particles. For
interacting particles the behavior of $n$, $J$ and $\mu$, obtained from the
modified Fick--Jacobs equation are in agreement with numerical simulations,
where the hard-core interaction is taken into account. Even more, for
interacting particles the modified Fick--Jacobs equation gives comparatively
more accurate results of the current difference (when a force is applied in
opposite directions) than the exact result for the non-interacting ones.


title:
Uplink FBMC/OQAM-based Multiple Access Channel: Distortion Analysis
  under Strong Frequency Selectivity

abstract:
  This paper computes the distortion power at the receiver side of an
FBMC/OQAM-based OFDMA uplink channel under strong frequency selectivity and/or
user timing errors. More precisely, it provides a distortion expression that is
valid for a wide class of prototype pulses (not necessarily
perfect-reconstruction ones) when the number of subcarriers is sufficiently
large. This result is a valuable instrument for analyzing how users interfere
to one another and to justify, formally, the common choice of placing an empty
guard band between adjacent users. Interestingly, the number of out-band
subcarriers contaminated by each user only depends on the prototype pulses and
not on the channel nor on the equalizer. To conclude, the distortion analysis
presented in this paper, together with some simulation results for a realistic
scenario, also provide convincing evidence that FBMC/OQAM-based OFDMA is
superior to classic circular-prefix OFDMA in the case of asynchronous users.


title: Report on the Poblacion Flotante of Bogota (D.C.)

abstract:
  In this document we describe the size of the Poblacion Flotante of Bogota
(D.C.). The Poblacion Flotante is composed by people who live outside Bogota
(D.C.), but who rely on the city for performing their job. We estimate the
Poblacion Flotante impact relying on a new data source provided by
telecommunications operators in Colombia, which enables us to estimate how many
people commute daily from every municipality of Colombia to a specific area of
Bogota (D.C.). We estimate that the size of the Poblacion Flotante could
represent a 5.4% increase of Bogota (D.C.)'s population. During weekdays, the
commuters tend to visit the city center more.


title:
Nanbu-Goto action and qubit theory in any signature and higher
  dimensions

abstract:
  We perform an extension of the relation between the Nambu-Goto action and
qubit theory. Of course, the Cayley hyperdeterminant is the key mathematical
tool in such generalization. Using the Wick rotation we find that in four
dimensions such a relation can be established no only in (2+2)-dimensions but
also in any signature. We generalize our result to a curved space-time of
(2$^{2n}$+2$^{2n}$)-dimensions and (2$^{2n+1}$+2$^{2n+1}$)-dimensions.


title: Lower Bounds for Graph Exploration Using Local Policies

abstract:
  We give lower bounds for various natural node- and edge-based local
strategies for exploring a graph. We consider this problem both in the setting
of an arbitrary graph as well as the abstraction of a geometric exploration of
a space by a robot, both of which have been extensively studied. We consider
local exploration policies that use time-of-last- visit or alternatively
least-frequently-visited local greedy strategies to select the next step in the
exploration path. Both of these strategies were previously considered by Cooper
et al. (2011) for a scenario in which counters for the last visit or visit
frequency are attached to the edges. In this work we consider the case in which
the counters are associated with the nodes, which for the case of dual graphs
of geometric spaces could be argued to be intuitively more natural and likely
more efficient. Surprisingly, these alternate strategies give worst-case
superpolynomial/ exponential time for exploration, whereas the least-frequently
visited strategy for edges has a polynomially bounded exploration time, as
shown by Cooper et al. (2011).


title:
Parameterized vertex deletion problems for hereditary graph classes with
  a block property

abstract:
  For a class of graphs $\mathcal{P}$, the Bounded $\mathcal{P}$-Block Vertex
Deletion problem asks, given a graph $G$ on $n$ vertices and positive integers
$k$ and $d$, whether there is a set $S$ of at most $k$ vertices such that each
block of $G-S$ has at most $d$ vertices and is in $\mathcal{P}$. We show that
when $\mathcal{P}$ satisfies a natural hereditary property and is recognizable
in polynomial time, Bounded $\mathcal{P}$-Block Vertex Deletion can be solved
in time $2^{O(k \log d)}n^{O(1)}$. When $\mathcal{P}$ contains all split
graphs, we show that this running time is essentially optimal unless the
Exponential Time Hypothesis fails. On the other hand, if $\mathcal{P}$ consists
of only complete graphs, or only cycle graphs and $K_2$, then Bounded
$\mathcal{P}$-Block Vertex Deletion admits a $c^{k}n^{O(1)}$-time algorithm for
some constant $c$ independent of $d$. We also show that Bounded
$\mathcal{P}$-Block Vertex Deletion admits a kernel with $O(k^2 d^7)$ vertices.