title:
Enumerating secondary structures and structural moieties for circular
  RNAs

abstract:
  A quantitative characterization of the relationship between molecular
sequence and structure is essential to improve our understanding of how
function emerges. This particular genotype-phenotype map has been often studied
in the context of RNA sequences, with the folded configurations standing as a
proxy for the phenotype. Here, we count the secondary structures of circular
RNAs of length $n$ and calculate the asymptotic distributions of different
structural moieties, such as stems or hairpin loops, by means of symbolic
combinatorics. Circular RNAs differ in essential ways from their linear
counterparts. From the mathematical viewpoint, the enumeration of the
corresponding secondary structures demands the use of combinatorial techniques
additional to those used for linear RNAs. The asymptotic number of secondary
structures for circular RNAs grows as $a^nn^{-5/2}$, with a depending on
particular constraints applied to the secondary structure. The abundance of any
structural moiety is normally distributed in the limit $n\to\infty$, with a
mean and a variance that increase linearly with $n$.

categories: q-bio.PE physics.bio-ph q-bio.BM q-bio.MN


title: A Real-Time Deep Learning Pedestrian Detector for Robot Navigation

abstract:
  A real-time Deep Learning based method for Pedestrian Detection (PD) is
applied to the Human-Aware robot navigation problem. The pedestrian detector
combines the Aggregate Channel Features (ACF) detector with a deep
Convolutional Neural Network (CNN) in order to obtain fast and accurate
performance. Our solution is firstly evaluated using a set of real images taken
from onboard and offboard cameras and, then, it is validated in a typical robot
navigation environment with pedestrians (two distinct experiments are
conducted). The results on both tests show that our pedestrian detector is
robust and fast enough to be used on robot navigation applications.


title: Search for excited spin-3/2 neutrinos at LHeC

abstract:
  We study the potential of the next $ep$ collider, namely LHeC, with two
options $\sqrt{s}=1.3$ TeV $\sqrt{s}=1.98$ TeV, to search for excited spin-1/2
and spin-3/2 neutrinos. We calculate the single production cross section of
excited spin-1/2 and spin-3/2 neutrinos according to their effective currents
describing their interactions between gauge bosons and SM leptons. We choose
the $\nu^{\star}\rightarrow eW$ decay mode of excited neutrinos and
$W\rightarrow jj$ decay mode of $W$-boson for the analysis. We put some
kinematical cuts for the final state detectable particles and plot the
invariant mass distributions for signal and the corresponding backgrounds. In
order to obtain accessible limits for excited neutrino couplings, we show the
$f-f^{\prime}$ and $c_{iV}-c_{iA}$ contour plots for excited spin-1/2 and
excited spin-3/2 neutrinos, respectively.


title:
Controlling many-body states by the electric-field effect in a
  two-dimensional material

abstract:
  To understand complex physics of a system with strong electron electron
interactions, it is ideal to control and monitor its properties while tuning an
external electric field applied to the system. Indeed, complete electric field
control of many body states in strongly correlated electron systems is
fundamental to the next generation of condensed matter research and devices.
However, the material must be thin enough to avoid shielding of the electric
field in bulk material. Two-dimensional materials do not experience electrical
screening, and their charge carrier density can be controlled by gating. 1T
TiSe2 is a prototypical 2D material that shows charge density wave(CDW) and
superconductivity in its phase diagram, presenting several similarities with
other layered systems such as copper oxides, iron pnictides, crystals of
rare-earth and actinide atoms. By studying 1T TiSe2 single crystals with
thicknesses of 10 nm or less, encapsulated in 2D layers of hexagonal boron
nitride, we achieve unprecedented control over the CDW transition temperature,
tuned from 170 K to 40 K, and over the superconductivity transition
temperature, tuned from a quantum critical point at 0 K up to 3 K. Electrically
driving TiSe2 over different ordered electronic phases allows us to study the
details of the phase transitions between many-body states. Observations of
periodic oscillations of magnetoresistance induced by the Little Parks effect
show that the appearance of superconductivity is directly correlated to the
spatial texturing of the amplitude and phase of the superconductivity order
parameter, corresponding to a 2D matrix of superconductivity. We infer that
this superconductivity matrix is supported by a matrix of incommensurate CDW
states embedded in the commensurate CDW states. Our results show that spatially
modulated electronic states are fundamental to the appearance of 2D
superconductivity.


title:
A Networked Swarm Model for UAV Deployment in the Assessment of Forest
  Environments

abstract:
  Autonomous Unmanned Aerial Vehicles (UAVs) have gained popularity due to
their many potential application fields. Alongside sophisticated sensors, UAVs
can be equipped with communication adaptors aimed for inter-UAV communication.
Inter-communication of UAVs to form a UAV swarm raises questions on how to
manage its communication structure and mobility. In this paper, we consider
therefore the problem of establishing an efficient swarm movement model and a
network topology between a collection of UAVs, which are specifically deployed
for the scenario of high-quality forest-mapping.
  The forest environment with its highly heterogeneous distribution of trees
and obstacles represents an extreme challenge for a UAV swarm. It requires the
swarm to constantly avoid possible collisions with trees, to change
autonomously the trajectory, which can lead to disconnection to the swarm, and
to reconnect to the swarm after passing the obstacle, while continue collecting
environmental data that needs to be fused and assessed efficiently.
  In this paper, we propose a novel solution to the formation flight problem
for UAV swarms. The proposed method provides an adaptive and reliable network
structure, which maintains swarm connectivity and communicability. These
characteristics are needed to achieve a detailed and accurate description of
the environment from the data acquired by the UAV swarm.
  The main characteristics of our approach are high scalability regarding the
number of UAVs in the swarm and the adaptive network topology within the swarm.


title: Search for walking technipion in four-jet sample

abstract:
  We discuss how to search for a possibe signal of the recently observed 750
GeV enhancement in the diphoton channel in the four-jet production. In the
present studies we assume that the produced state is pseudoscalar. This fact,
when combined with specificity of the corresponding amplitude, allows to
improve the signal-to-background (S/B) ratio. We discuss in detail how to
impose cuts on jets in rapidity and transverse momenta in order to find optimal
S/B ratio and not to loose too much statistics. Our study suggest a measurement
of two soft (low cut on $p_t$) large-rapidity jets and two hard (high cut on
$p_t$) mid-rapidity jets. Azimuthal correlation between the soft external jets
may be useful to further improve the situation. Several differential
distributions in rapidities and transverse momenta of jets as well as dijet
invariant mass are shown. The integrated cross sections corresponding to
different cuts are collected in a table and number of events are presented.


title:
Efficient and Robust Pedestrian Detection using Deep Learning for
  Human-Aware Navigation

abstract:
  This paper addresses the problem of Human-Aware Navigation (HAN), using multi
camera sensors to implement a vision-based person tracking system. The main
contributions of this paper are as follows: a novel and efficient Deep Learning
person detection and a standardization of human-aware constraints. In the first
stage of the approach, we propose to cascade the Aggregate Channel Features
(ACF) detector with a deep Convolutional Neural Network (CNN) to achieve fast
and accurate Pedestrian Detection (PD). Regarding the human awareness (that can
be defined as constraints associated with the robot's motion), we use a mixture
of asymmetric Gaussian functions, to define the cost functions associated to
each constraint. Both methods proposed herein are evaluated individually to
measure the impact of each of the components. The final solution (including
both the proposed pedestrian detection and the human-aware constraints) is
tested in a typical domestic indoor scenario, in four distinct experiments. The
results show that the robot is able to cope with human-aware constraints,
defined after common proxemics and social rules.


title: Approximation in Morrey spaces

abstract:
  A new subspace of Morrey spaces whose elements can be approximated by
infinitely differentiable compactly supported functions is introduced.
Consequently, we give an explicit description of the closure of the set of such
functions in Morrey spaces. A generalization of known embeddings of Morrey
spaces into weighted Lesbesgue spaces is also obtained.


title: Directed polymer in random environment and two points state space

abstract:
  We give an exact expression for the partition function of a continuous time
DPRE on a two points state space.


title: Parametric PDEs: Sparse or Low-Rank Approximations?

abstract:
  We consider adaptive approximations of the parameter-to-solution map for
elliptic operator equations depending on a large or infinite number of
parameters, comparing approximation strategies of different degrees of
nonlinearity: sparse polynomial expansions, general low-rank approximations
separating spatial and parametric variables, and hierarchical tensor
decompositions separating all variables. We describe corresponding adaptive
algorithms based on a common generic template and show their near-optimality
with respect to natural approximability assumptions for each type of
approximation. A central ingredient in the resulting bounds for the total
computational complexity are new operator compression results for the case of
infinitely many parameters. We conclude with a comparison of the complexity
estimates based on the actual approximability properties of classes of
parametric model problems, which shows that the computational costs of
optimized low-rank expansions can be significantly lower or higher than those
of sparse polynomial expansions, depending on the particular type of parametric
problem.


title: Stellar wind models of subluminous hot stars

abstract:
  Mass-loss rate is one of the most important stellar parameters. We aim to
provide mass-loss rates as a function of subdwarf parameters and to apply the
formula for individual subdwarfs, to predict the wind terminal velocities, to
estimate the influence of the magnetic field and X-ray ionization on the
stellar wind, and to study the interaction of subdwarf wind with mass loss from
Be and cool companions. We used our kinetic equilibrium (NLTE) wind models with
the radiative force determined from the radiative transfer equation in the
comoving frame (CMF) to predict the wind structure of subluminous hot stars.
Our models solve stationary hydrodynamical equations, that is the equation of
continuity, equation of motion, and energy equation and predict basic wind
parameters. We predicted the wind mass-loss rate as a function of stellar
parameters, namely the stellar luminosity, effective temperature, and
metallicity. The derived wind parameters (mass-loss rates and terminal
velocities) agree with the values derived from the observations. The radiative
force is not able to accelerate the homogeneous wind for stars with low
effective temperatures and high surface gravities. We discussed the properties
of winds of individual subdwarfs. The X-ray irradiation may inhibit the flow in
binaries with compact components. In binaries with Be components, the winds
interact with the disk of the Be star. Stellar winds exist in subluminous stars
with low gravities or high effective temperatures. Despite their low mass-loss
rates, they are detectable in the ultraviolet spectrum and cause X-ray
emission. Subdwarf stars may lose a significant part of their mass during the
evolution. The angular momentum loss in magnetic subdwarfs with wind may
explain their low rotational velocities. Stellar winds are especially important
in binaries, where they may be accreted on a compact or cool companion.
(abridged)


title: Online Grammar Compression for Frequent Pattern Discovery

abstract:
  Various grammar compression algorithms have been proposed in the last decade.
A grammar compression is a restricted CFG deriving the string
deterministically. An efficient grammar compression develops a smaller CFG by
finding duplicated patterns and removing them. This process is just a frequent
pattern discovery by grammatical inference. While we can get any frequent
pattern in linear time using a preprocessed string, a huge working space is
required for longer patterns, and the whole string must be loaded into the
memory preliminarily. We propose an online algorithm approximating this problem
within a compressed space. The main contribution is an improvement of the
previously best known approximation ratio $\Omega(\frac{1}{\lg^2m})$ to
$\Omega(\frac{1}{\lg^*N\lg m})$ where $m$ is the length of an optimal pattern
in a string of length $N$ and $\lg^*$ is the iteration of the logarithm base
$2$. For a sufficiently large $N$, $\lg^*N$ is practically constant. The
experimental results show that our algorithm extracts nearly optimal patterns
and achieves a significant improvement in memory consumption compared to the
offline algorithm.


title:
Michel parameters for $\tau$ decays $\tau \rightarrow
  l\nu\bar{\nu}~(l=e,~\mu)$ in a general two Higgs doublet model with
  $\mu-\tau$ flavor violation

abstract:
  In a general two Higgs doublet model (2HDM), the anomaly of muon anomalous
magnetic moment (muon g-2) can be explained by $\mu-\tau$ flavor violating
Yukawa couplings, motivated by the recent CMS excess in Higgs boson decay
$h\rightarrow \mu \tau$. We study Michel parameters for $\tau$ decays $\tau
\rightarrow l \nu \bar{\nu}~(l=e,~\mu)$ in the 2HDM with the lepton flavor
violation, and show that they can be sensitive to the flavor structure as well
as the Lorentz and chiral structures of the model. We find that the correction
to the Michel parameter $\xi_\mu$ in $\tau \rightarrow \mu \nu\bar{\nu}$ is
correlated to the contribution to the muon g-2, and it can be as large as
$10^{-4}-10^{-2}$ in the parameter region where the $\mu-\tau$ flavor violating
Yukawa couplings explain the muon g-2 anomaly. Therefore the precision
measurement of the Michel parameter at the level of $10^{-4}-10^{-2}$ would
significantly probe the interesting parameter space for the solution to the
muon g-2 anomaly.


title: High Gluon Densities in Heavy Ions Collisions

abstract:
  The early stages of heavy ion collisions are dominated by high density
systems of gluons that carry each a small fraction $x$ of the momenta of the
colliding nucleons. A distinguishing feature of such systems is the phenomenon
of "saturation" which tames the expected growth of the gluon density as the
energy of the collision increases. The onset of saturation occurs at a
particular transverse momentum scale, the "saturation momentum", that emerges
dynamically and that marks the onset of non-linear gluon interactions. At high
energy, and for large nuclei, the saturation momentum is large compared to the
typical hadronic scale, making high density gluons amenable to a description
with weak coupling techniques. This paper reviews some of the challenges faced
in the study of such dense systems of small $x$ gluons, and of the progress
made in addressing them. The focus is on conceptual issues, and the
presentation is both pedagogical, and critical. Examples where high gluon
density could play a visible role in heavy ion collisions are briefly discussed
at the end, for illustration purpose.


title: Effects of scalar leptoquark on semileptonic $\Lambda_b$ decays

abstract:
  We study the scalar leptoquark effects on the rare semileptonic decays of
$\Lambda_b$ baryon, governed by the quark level transition $b \to s l^+ l^-$.
We estimate the branching ratios, forward-backward asymmetries, lepton
polarization parameters and the lepton flavour non-universality effects in
these decay channels. We find significant deviations from the corresponding
standard model predictions in some of the observables due to leptoquark
effects. We also investigate the lepton flavour violating decays $\Lambda_b \to
\Lambda l_i^- l_j^+$, the branching ratios of which are found to be ${\cal
O}(10^{-10} - 10^{-9})$.


title:
Channel Selection Algorithm for Cognitive Radio Networks with
  Heavy-Tailed Idle Times

abstract:
  We consider a multichannel Cognitive Radio Network (CRN), where secondary
users sequentially sense channels for opportunistic spectrum access. In this
scenario, the Channel Selection Algorithm (CSA) allows secondary users to find
a vacant channel with the minimal number of channel switches. Most of the
existing CSA literature assumes exponential ON-OFF time distribution for
primary users (PU) channel occupancy pattern. This exponential assumption might
be helpful to get performance bounds; but not useful to evaluate the
performance of CSA under realistic conditions. An in-depth analysis of
independent spectrum measurement traces reveals that wireless channels have
typically heavy-tailed PU OFF times. In this paper, we propose an extension to
the Predictive CSA framework and its generalization for heavy tailed PU OFF
time distribution, which represents realistic scenarios. In particular, we
calculate the probability of channel being idle for hyper-exponential OFF times
to use in CSA. We implement our proposed CSA framework in a wireless test-bed
and comprehensively evaluate its performance by recreating the realistic PU
channel occupancy patterns. The proposed CSA shows significant reduction in
channel switches and energy consumption as compared to Predictive CSA which
always assumes exponential PU ON-OFF times.Through our work, we show the impact
of the PU channel occupancy pattern on the performance of CSA in multichannel
CRN.


title: Measuring Economic Activities of China with Mobile Big Data

abstract:
  Emerging trends in smartphones, online maps, social media, and the resulting
geo-located data, provide opportunities to collect traces of people's
socio-economical activities in a much more granular and direct fashion,
triggering a revolution in empirical research. These vast mobile data offer new
perspectives and approaches for measurements of economic dynamics and are
broadening the research fields of social science and economics. In this paper,
we explore the potential of using mobile big data for measuring economic
activities of China. Firstly, We build indices for gauging employment and
consumer trends based on billions of geo-positioning data. Secondly, we advance
the estimation of store offline foot traffic via location search data derived
from Baidu Maps, which is then applied to predict revenues of Apple in China
and detect box-office fraud accurately. Thirdly, we construct consumption
indicators to track the trends of various industries in service sector, which
are verified by several existing indicators. To the best of our knowledge, we
are the first to measure the second largest economy by mining such
unprecedentedly large scale and fine granular spatial-temporal data. Our
research provides new approaches and insights on measuring economic activities.


title: The IDE as a Scriptable Information System (extended version)

abstract:
  Software engineering is extremely information-intensive. Every day developers
work with source code, version repositories, issue trackers, documentation,
web-based and other information resources. However, three key aspects of
information work lack good support: (i) combining information from different
sources; (ii) flexibly presenting collected information to enable easier
comprehension; and (iii) automatically acting on collected information, for
example to perform a refactoring. Poor support for these activities makes many
common development tasks time-consuming and error-prone. We propose an approach
that directly addresses these three issues by integrating a flexible query
mechanism into the development environment. Our approach enables diverse ways
to process and visualize information and can be extended via scripts. We
demonstrate how an implementation of the approach can be used to rapidly write
queries that meet a wide range of information needs.


title: Mean Field Games models of segregation

abstract:
  This paper introduces and analyses some models in the framework of Mean Field
Games describing interactions between two populations motivated by the studies
on urban settlements and residential choice by Thomas Schelling. For static
games, a large population limit is proved. For differential games with noise,
the existence of solutions is established for the systems of partial
differential equations of Mean Field Game theory, in the stationary and in the
evolutive case. Numerical methods are proposed, with several simulations. In
the examples and in the numerical results, particular emphasis is put on the
phenomenon of segregation between the populations.


title:
Canonical coordinates with tame estimates for the defocusing NLS
  equation on the circle

abstract:
  In a case study for integrable PDEs, we construct real analytic, canonical
coordinates for the defocusing NLS equation on the circle, specifically
taylored towards the needs in perturbation theory. They are defined in
neighbourhoods of families of finite dimensional invariant tori and are shown
to satisfy together with their derivatives tame estimates. When expressed in
these coordinates, the dNLS Hamiltonian is in normal form up to order three.


title: ${\rm P}^3$: A Practice Focused Learning Environment

abstract:
  There has been an increased focus on the integration of practices into
physics curricula, with a particular emphasis on integrating computation into
the undergraduate curriculum of scientists and engineers. In this paper, we
present a university-level, introductory physics course for science and
engineering majors at Michigan State University (MSU) called ${\rm P}^3$
(Projects and Practices in Physics) that is centered around providing
introductory physics students with the opportunity to appropriate various
science and engineering practices. The ${\rm P}^3$ design integrates
computation with analytical problem solving and is built upon a curriculum
foundation of problem-based learning, the principles of constructive alignment
and the theoretical framework of community of practice. The design includes an
innovative approach to computational physics instruction, instructional
scaffolds, and a unique approach to assessment that enables instructors to
guide students in the development of the practices of a physicist. We present
the very positive student related outcomes of the design gathered via
attitudinal and conceptual inventories and research interviews of students'
reflecting on their experiences in the ${\rm P}^3$ classroom.


title: Efficient CTL Verification via Horn Constraints Solving

abstract:
  The use of temporal logics has long been recognised as a fundamental approach
to the formal specification and verification of reactive systems. In this
paper, we take on the problem of automatically verifying a temporal property,
given by a CTL formula, for a given (possibly infinite-state) program. We
propose a method based on encoding the problem as a set of Horn constraints.
The method takes a program, modeled as a transition system, and a property
given by a CTL formula as input. It first generates a set of forall-exists
quantified Horn constraints and well-foundedness constraints by exploiting the
syntactic structure of the CTL formula. Then, the generated set of constraints
are solved by applying an off-the-shelf Horn constraints solving engine. The
program is said to satisfy the property if and only if the generated set of
constraints has a solution. We demonstrate the practical promises of the method
by applying it on a set of challenging examples. Although our method is based
on a generic Horn constraint solving engine, it is able to outperform
state-of-art methods specialised for CTL verification.


title: Hierarchical State Machines as Modular Horn Clauses

abstract:
  In model based development, embedded systems are modeled using a mix of
dataflow formalism, that capture the flow of computation, and hierarchical
state machines, that capture the modal behavior of the system. For safety
analysis, existing approaches rely on a compilation scheme that transform the
original model (dataflow and state machines) into a pure dataflow formalism.
Such compilation often result in loss of important structural information that
capture the modal behaviour of the system. In previous work we have developed a
compilation technique from a dataflow formalism into modular Horn clauses. In
this paper, we present a novel technique that faithfully compile hierarchical
state machines into modular Horn clauses. Our compilation technique preserves
the structural and modal behavior of the system, making the safety analysis of
such models more tractable.


title: Challenges in Decomposing Encodings of Verification Problems

abstract:
  Modern program verifiers use logic-based encodings of the verification
problem that are discharged by a back end reasoning engine. However, instances
of such encodings for large programs can quickly overwhelm these back end
solvers. Hence, we need techniques to make the solving process scale to large
systems, such as partitioning (divide-and-conquer) and abstraction.
  In recent work, we showed how decomposing the formula encoding of a
termination analysis can significantly increase efficiency. The analysis
generates a sequence of logical formulas with existentially quantified
predicates that are solved by a synthesis-based program analysis engine.
However, decomposition introduces abstractions in addition to those required
for finding the unknown predicates in the formula, and can hence deteriorate
precision. We discuss the challenges associated with such decompositions and
their interdependencies with the solving process.


title: Solving non-linear Horn clauses using a linear Horn clause solver

abstract:
  In this paper we show that checking satisfiability of a set of non-linear
Horn clauses (also called a non-linear Horn clause program) can be achieved
using a solver for linear Horn clauses. We achieve this by interleaving a
program transformation with a satisfiability checker for linear Horn clauses
(also called a solver for linear Horn clauses). The program transformation is
based on the notion of tree dimension, which we apply to a set of non-linear
clauses, yielding a set whose derivation trees have bounded dimension. Such a
set of clauses can be linearised. The main algorithm then proceeds by applying
the linearisation transformation and solver for linear Horn clauses to a
sequence of sets of clauses with successively increasing dimension bound. The
approach is then further developed by using a solution of clauses of lower
dimension to (partially) linearise clauses of higher dimension. We constructed
a prototype implementation of this approach and performed some experiments on a
set of verification problems, which shows some promise.


title: Removing Unnecessary Variables from Horn Clause Verification Conditions

abstract:
  Verification conditions (VCs) are logical formulas whose satisfiability
guarantees program correctness. We consider VCs in the form of constrained Horn
clauses (CHC) which are automatically generated from the encoding of (an
interpreter of) the operational semantics of the programming language. VCs are
derived through program specialization based on the unfold/fold transformation
rules and, as it often happens when specializing interpreters, they contain
unnecessary variables, that is, variables which are not required for the
correctness proofs of the programs under verification. In this paper we adapt
to the CHC setting some of the techniques that were developed for removing
unnecessary variables from logic programs, and we show that, in some cases, the
application of these techniques increases the effectiveness of Horn clause
solvers when proving program correctness.


title: Horn Binary Serialization Analysis

abstract:
  A bit layout is a sequence of fields of certain bit lengths that specifies
how to interpret a serial stream, e.g., the MP3 audio format. A layout with
variable length fields needs to include meta-information to help the parser
interpret unambiguously the rest of the stream; e.g. a field providing the
length of a following variable length field. If no such information is
available, then the layout is ambiguous. I present a linear-time algorithm to
determine whether a layout is ambiguous or not by modelling the behaviour of a
serial parser reading the stream as forward chaining reasoning on a collection
of Horn clauses.


title:
Multiplicity results for fractional Laplace problems with critical
  growth

abstract:
  This paper deals with multiplicity and bifurcation results for nonlinear
problems driven by the fractional Laplace operator $(-\Delta)^s$ and involving
a critical Sobolev term. In particular, we consider $$\begin{cases}
(-\Delta)^su=\gamma|u|^{2^*-2}u+f(x,u) & \mbox{in } \Omega u=0 & \mbox{in }
\mathbb R^n\setminus \Omega, \end{cases}$$ where $\Omega\subset\mathbb R^n$ is
an open bounded set with continuous boundary, $n>2s$ with $s\in(0,1)$, $\gamma$
is a positive real parameter, $2^*=2n/(n-2s)$ is the fractional critical
Sobolev exponent and $f$ is a Carath\'{e}odory function satisfying different
subcritical conditions.


title: Constraint-based modeling and simulation of cell populations

abstract:
  The intratumor heterogeneity has been recognized to characterize cancer cells
impairing the efficacy of cancer treatments. We here propose an extension of
constraint-based modeling approach in order to simulate metabolism of cell
populations with the aim to provide a more complete characterization of these
systems, especially focusing on the relationships among their components. We
tested our methodology by using a toy-model and taking into account the main
metabolic pathways involved in cancer metabolic rewiring. This toy-model is
used as individual to construct a population model characterized by multiple
interacting individuals, all having the same topology and stoichiometry, and
sharing the same nutrients supply. We observed that, in our population, cancer
cells cooperate with each other to reach a common objective, but without
necessarily having the same metabolic traits. We also noticed that the
heterogeneity emerging from the population model is due to the mismatch between
the objective of the individual members and the objective of the entire
population.


title:
Improvements on non-equilibrium and transport Green function techniques:
  the next-generation transiesta

abstract:
  We present novel methods implemented within the non-equilibrium Green
function code (NEGF) transiesta based on density functional theory (DFT). Our
flexible, next-generation DFT-NEGF code handles devices with one or multiple
electrodes ($N_e\ge1$) with individual chemical potentials and electronic
temperatures. We describe its novel methods for electrostatic gating, contour
opti- mizations, and assertion of charge conservation, as well as the newly
implemented algorithms for optimized and scalable matrix inversion,
performance-critical pivoting, and hybrid parallellization. Additionally, a
generic NEGF post-processing code (tbtrans/phtrans) for electron and phonon
transport is presented with several novelties such as Hamiltonian
interpolations, $N_e\ge1$ electrode capability, bond-currents, generalized
interface for user-defined tight-binding transport, transmission projection
using eigenstates of a projected Hamiltonian, and fast inversion algorithms for
large-scale simulations easily exceeding $10^6$ atoms on workstation computers.
The new features of both codes are demonstrated and bench-marked for relevant
test systems.


title:
The {\tt Mathematica} package {\tt TopoID} and its application to the
  Higgs boson production cross section

abstract:
  We present the {\tt Mathematica} package {\tt TopoID} which aims at the
automation of several steps in multiloop calculations. The algorithm which lies
at the very core of the package is described and illustrated with an example.
The main features of {\tt TopoID} are stated and some of them are briefly
demonstrated for NLO or NNLO Higgs boson production.


title: Chaotic dynamics of strings in charged black hole backgrounds

abstract:
  We study the motion of a string in the background of Reissner-Nordstrom black
hole, in both AdS as well as asymptotically flat spacetimes. We describe the
phase space of this dynamical system through largest Lyapunov exponent,
Poincare sections and basins of attractions. We observe that string motion in
these settings is particularly chaotic and comment on its characteristics.


title:
On the Minimum of a Positive Definite Quadratic Form over Non--Zero
  Lattice points. Theory and Applications

abstract:
  Let $\Sigma_d^{++}$ be the set of positive definite matrices with determinant
1 in dimension $d\ge 2$. Identifying any two $SL_d(\mathbb{Z})$-congruent
elements in $\Sigma_d^{++}$ gives rise to the space of reduced quadratic forms
of determinant one, which in turn can be identified with the locally symmetric
space $X_d:=SL_d(\mathbb{Z})\backslash SL_d(\mathbb{R})/SO_d(\mathbb{R})$.
Equip the latter space with its natural probability measure coming from a Haar
measure on $SL_d(\mathbb{R})$. In 1998, Kleinbock and Margulis established
sharp estimates for the probability that an element of $X_d$ takes a value less
than a given real number $\delta>0$ over the non--zero lattice points
$\mathbb{Z}^d\backslash\{ 0 \}$.
  In this article, these estimates are extended to a large class of probability
measures arising either from the spectral or the Cholesky decomposition of an
element of $\Sigma_d^{++}$. The sharpness of the bounds thus obtained are also
established (up to multiplicative constants) for a subclass of these measures.
  Although of an independent interest, this theory is partly developed here
with a view towards application to Information Theory. More precisely, after
providing a concise introduction to this topic fitted to our needs, we lay the
theoretical foundations of the study of some manifolds frequently appearing in
the theory of Signal Processing. This is then applied to the recently
introduced Integer-Forcing Receiver Architecture channel whose importance stems
from its expected high performance. Here, we give sharp estimates for the
probabilistic distribution of the so-called \emph{Effective Signal--to--Noise
Ratio}, which is an essential quantity in the evaluation of the performance of
this model.


title: Breathing-like excited state of the Hoyle state in ${^{12}{\rm C}}$

abstract:
  The existence of the $0_3^+$ and $0_4^+$ states around 10 MeV excitation
energy in ${^{12}{\rm C}}$ is confirmed by a fully microscopic 3$\alpha$
cluster model. Firstly, a GCM (generator coordinate method) calculation is
performed by superposing optimized 2$\alpha$+$\alpha$ THSR
(Tohsaki-Horiuchi-Schuck-R\"{o}pke) wave functions with the radius-constraint
method. The obtained two excited $0^+$ states above the Hoyle state are
consistent with the recently observed states by experiment. Secondly, a
variational calculation using the single 2$\alpha$+$\alpha$ THSR wave function
orthogonalized to the ground and Hoyle states is made and it also supports the
existence of the $0_3^+$ state obtained by the GCM calculation. The analysis of
the obtained $0_3^+$ state is made by studying its 2$\alpha$-$\alpha$ reduced
width amplitude, its 2$\alpha$ correlation function, and the large monopole
matrix element between this state and the Hoyle state, which shows that this
$0_3^+$ state is a breathing-like excited state of the Hoyle state. This
character of the $0_3^+$ state is very different from the $0_4^+$ state which
seems to have a bent-arm 3$\alpha$ structure.


title: Suppressors of selection

abstract:
  Inspired by recent works on evolutionary graph theory, an area of growing
interest in mathematical and computational biology, we present the first known
examples of undirected structures acting as suppressors of selection for any
fitness value $r > 1$. This means that the average fixation probability of an
advantageous mutant or invader individual placed at some node is strictly less
than that of this individual placed in a well-mixed population. This leads the
way to study more robust structures less prone to invasion, contrary to what
happens with the amplifiers of selection where the fixation probability is
increased on average for advantageous invader individuals. A few families of
amplifiers are known, although some effort was required to prove it. Here, we
use computer aided techniques to find an exact analytical expression of the
fixation probability for some graphs of small order (equal to $6$, $8$ and
$10$) proving that selection is effectively reduced for $r > 1$. Some numerical
experiments using Monte Carlo methods are also performed for larger graphs.


title: Tracial stability for C*-algebras

abstract:
  We consider tracial stability, which requires that tuples of elements of a
C*-algebra with a trace that nearly satisfy the relation are close to tuples
that actually satisfy the relation. Here both "near" and "close" are in terms
of the associated 2-norm from the trace, e.g., the Hilbert-Schmidt norm for
matrices. Precise definitions are stated in terms of liftings from tracial
ultraproducts of C*-algebras. We completely characterize matricial tracial
stability for nuclear C*-algebras in terms of certain approximation properties
for traces. For non-nuclear $C^{\ast}$-algebras we find new obstructions for
stability by relating it to Voiculescu's free entropy dimension. We show that
the class of C*-algebras that are stable with respect to tracial norms on
real-rank-zero C*-algebras is closed under tensoring with commutative
C*-algebras. We show that $C(X)$ is tracially stable with respect to tracial
norms on all $C^{\ast}$-algebras if and only if $X$ is approximately
path-connected.


title: KAWA 2015: Dynamical moduli spaces and elliptic curves

abstract:
  In these lecture notes, we present a connection between the complex dynamics
of a family of rational functions $f_t: \mathbb{P}^1\to \mathbb{P}^1$,
parameterized by $t$ in a Riemann surface $X$, and the arithmetic dynamics of
$f_t$ on rational points $\mathbb{P}^1(k)$ where $k = \mathbb{C}(X)$ or
$\bar{\mathbb{Q}}(X)$. An explicit relation between stability and canonical
height is explained, with a proof that contains a piece of the Mordell-Weil
theorem for elliptic curves over function fields. Our main goal is to pose some
questions and conjectures about these families, guided by the principle of
"unlikely intersections" from arithmetic geometry, as in [Zannier 2012]. We
also include a proof that the hyperbolic postcritically-finite maps are Zariski
dense in the moduli space of rational maps of any given degree $d>1$. These
notes are based on four lectures at KAWA 2015, in Pisa, Italy, designed for an
audience specializing in complex analysis, expanding upon the main results of
[Baker-DeMarco 2013, DeMarco 2016, DeMarco-Wang-Ye 2016].


title:
Representations of *-algebras by unbounded operators: C*-hulls,
  local-global principle, and induction

abstract:
  We define a C*-hull for a *-algebra, given a notion of integrability for its
representations on Hilbert modules. We establish a local-global principle
which, in many cases, characterises integrable representations on Hilbert
modules through the integrable representations on Hilbert spaces. The induction
theorem constructs a C*-hull for a certain class of integrable representations
of a graded *-algebra, given a C*-hull for its unit fibre.


title:
(Anti-) de Sitter Electrically Charged Black Hole Solutions in
  Higher-Derivative Gravity

abstract:
  In this paper, static electrically charged black hole solutions with
cosmological constant are investigated in an Einstein-Hilbert theory of gravity
with additional quadratic curvature terms. Beside the analytic Schwarzschild
(Anti-) de Sitter solutions, non-Schwarzschild (Anti-) de Sitter solutions are
also obtained numerically by employing the shooting method. The results show
that there exist two groups of asymptotically (Anti-) de Sitter spacetimes for
both charged and uncharged black holes. In particular, it was found that for
uncharged black holes the first group can be reduced to the Schwarzschild
(Anti-) de Sitter solution, while the second group is intrinsically different
from a Schwarzschild (Anti-) de Sitter solution even when the charge and the
cosmological constant become zero.


title: The Influence of Canalization on the Robustness of Boolean Networks

abstract:
  Time- and state-discrete dynamical systems are frequently used to model
molecular networks. This paper provides a collection of mathematical and
computational tools for the study of robustness in Boolean network models. The
focus is on networks governed by $k$-canalizing functions, a recently
introduced class of Boolean functions that contains the well-studied class of
nested canalizing functions. The activities and sensitivity of a function
quantify the impact of input changes on the function output. This paper
generalizes the latter concept to $c$-sensitivity and provides formulas for the
activities and $c$-sensitivity of general $k$-canalizing functions as well as
canalizing functions with more precisely defined structure. A popular measure
for the robustness of a network, the Derrida value, can be expressed as a
weighted sum of the $c$-sensitivities of the governing canalizing functions,
and can also be calculated for a stochastic extension of Boolean networks.
These findings provide a computationally efficient way to obtain Derrida values
of Boolean networks, deterministic or stochastic, that does not involve
simulation.


title: Moufang Twin Trees of prime order

abstract:
  We prove that the unipotent horocyclic group of a Moufang twin tree of prime
order is nilpotent of class at most 2.


title: Dirac-graphene in slow-light

abstract:
  We obtained exact solutions for the wave function and the Green function in
the slow light pulse with the group velocity, consistent with the Fermi
velocity in graphene.


title:
Rederivation of the Casimir force under the completeness relation of
  continuum operator

abstract:
  Casimir effects manifests that, the two closely paralleled plates, generally
produce a macroscopic attractive force due to the quantum vacuum fluctuations
of the electromagnetic fields. The derivation of the force requires an {\it
artificial} regulator by removing the divergent summation. By including
naturally a spectrum density factor, based on the observation that an
incomplete eigenvectors of observable, such as the eigenstates for the photons
in the free field, can form a complete set of eigenvectors by introducing a
unique spectrum transformation, an alternative way is presented to rederive the
force, without using a regulator. As a result, the Casimir forces are obtained
with the first term $-\pi^2 \hbar c/(240 a^4)$ attractive, and the second one,
$-\pi^4 \hbar c^3 \sigma^2/(1008 a^6)$, also attractive but smaller, with $a$
the plate separation, and $\sigma$ a to-be-determined small constant number in
the spectrum density factor.


title:
Viscosity and effective temperature of an active dense system of
  self-propelled particles

abstract:
  We obtain a nonequilibrium theory for a simple model of a generic class of
active dense systems consisting of self-propelled particles with a
self-propulsion force, $f_0$, and persistence time, $\tau_p$, of their motion.
We consider two models of activity and find the system is characterized by an
evolving effective temperature $T_{eff}(\tau)$, defined through a generalized
fluctuation-dissipation theorem. $T_{eff}(\tau)$ is equal to the equilibrium
temperature at very short time $\tau$ and saturates to
$T_{eff}=T_{eff}(\tau\to\infty)$ at long times; The transition time $t_{trans}$
when $T_{eff}(\tau)$ goes to the long-time limit depends on $\tau_p$ alone and
$t_{trans}\sim \tau_p^{0.85}$ for both models. $f_0$ reduces the viscosity with
increasing activity, $\tau_p$ on the other hand, may increase or decrease
viscosity depending on the details of how the activity is included. However, as
a function of $T_{eff}$, viscosity shows the same behavior for different models
of activity and $\eta\sim (T_{eff}-T)^{-\gamma}$ with $\gamma=1.74$. Our theory
gives reasonable agreement when compared with experimental data and is
consistent with several experiments on diverse systems.


title:
Partition functions 1: Improved partition functions and thermodynamic
  quantities for normal, equilibrium, and ortho and para molecular hydrogen

abstract:
  Aims. In this work we rigorously show the shortcomings of various
simplifications that are used to calculate the total internal partition
function. These shortcomings can lead to errors of up to 40 percent or more in
the estimated partition function. These errors carry on to calculations of
thermodynamic quantities. Therefore a more complicated approach has to be
taken.
  Methods. Seven possible simplifications of various complexity are described,
together with advantages and disadvantages of direct summation of experimental
values. These were compared to what we consider the most accurate and most
complete treatment (case 8). Dunham coefficients were determined from
experimental and theoretical energy levels of a number of electronically
excited states of H$_2$ . Both equilibrium and normal hydrogen was taken into
consideration.
  Results. Various shortcomings in existing calculations are demonstrated, and
the reasons for them are explained. New partition functions for equilibrium,
normal, and ortho and para hydrogen are calculated and thermodynamic quantities
are reported for the temperature range 1 - 20000 K. Our results are compared to
previous estimates in the literature. The calculations are not limited to the
ground electronic state, but include all bound and quasi-bound levels of
excited electronic states. Dunham coefficients of these states of H$_2$ are
also reported.
  Conclusions. For most of the relevant astrophysical cases it is strongly
advised to avoid using simplifications, such as a harmonic oscillator and rigid
rotor or ad hoc summation limits of the eigenstates to estimate accurate
partition functions and to be particularly careful when using polynomial fits
to the computed values. Reported internal partition functions and thermodynamic
quantities in the present work are shown to be more accurate than previously
available data.


title:
Influence of grain size and exchange interaction on the LLB modeling
  procedure

abstract:
  Reliably predicting bit-error rates in realistic heat-assisted magnetic
recording simulations is a challenging task. Integrating the
Landau-Lifshitz-Bloch (LLB) equation can reduce the computational effort to
determine the magnetization dynamics in the vicinity of the Curie temperature.
If one aims that these dynamics coincide with trajectories calculated from the
atomistic Landau-Lifshitz-Gilbert equation, one has to carefully model required
temperature dependent material functions such as the zero-field equilibrium
magnetization as well as the parallel and normal susceptibilities. We present
an extensive study on how these functions depend on grain size and exchange
interactions. We show that, if the size or the exchange constant of a reference
grain is modified, the material functions can be scaled, according to the
changed Curie temperature, yielding negligible errors. This is shown to be
valid for volume changes of up to $\pm 40$ % and variations of the exchange
constant of up to $\pm10$ %. Besides the temperature dependent material curves,
computed switching probabilities also agree well with probabilities separately
determined for each system. Our study suggest that there is no need to
recalculate the required LLB input functions for each particle. Within the
presented limits it is sufficient to scale them to the Curie temperature of the
altered system.


title:
Big-bounce cosmology from quantum gravity: The case of a cyclical
  Bianchi I universe

abstract:
  We analyse the classical and quantum dynamics of a Bianchi I model in the
presence of a small negative cosmological constant characterizing its evolution
in term of the dust-time dualism. We demonstrate that in a canonical metric
approach, the cosmological singularity is removed in correspondence to a
positive defined value of the dust energy density. Furthermore, the quantum
Big-Bounce is connected to the Universe turning point via a well-defined
semiclassical limit. Then we can reliably infer that the proposed scenario is
compatible with a cyclical Universe picture. We also show how, when the
contribution of the dust energy density is sufficiently high, the proposed
scenario can be extended to the Bianchi IX cosmology and therefore how it can
be regarded as a paradigm for the generic cosmological model. Finally, we
investigate the origin of the observed cut-off on the cosmological dynamics,
demonstrating how the Big-Bounce evolution can be mimicked by the same
semiclassical scenario, where the negative cosmological constant is replaced
via a polymer discretization of the Universe volume. A direct proportionality
law between such two parameters is then established.


title:
A comparative study on defect estimation using XPS and Raman
  spectroscopy in few layer nanographitic structures

abstract:
  Defects in planar and vertically oriented nanographitic structures (NGSs)
synthesized by plasma enhanced chemical vapor deposition (PECVD) has been
investigated using Raman and X-ray photoelectron spectroscopy. While Raman
spectra reveal the dominance of vacancy and boundary type defects respectively
in vertical and planar NGSs, XPS provides additional information on vacancy
related defect peaks at C 1s spectrum that originate from non-conjugated carbon
atoms in hexagonal lattice. Although an excellent correlation prevails between
these two techniques, our results show that estimation of surface defects by
XPS is more accurate than Raman analysis. Nuances of these techniques are
discussed in the context of assessing defects in nanographitic structures.


title:
Modeling of Reduced Effective Secondary Electron Emission Yield from a
  Velvet Surface

abstract:
  Complex structures on a material surface can significantly reduce total
secondary electron emission from that surface. A velvet is a surface that
consists of an array of vertically standing whiskers. The reduction occurs due
to the capture of low-energy, true secondary electrons emitted at the bottom of
the structure and on the sides of the velvet whiskers. We performed numerical
simulations and developed an approximate analytical model that calculates the
net secondary electron emission yield from a velvet surface as a function of
the velvet whisker length and packing density, and the angle of incidence of
primary electrons. We found that to suppress secondary electrons, the following
condition on dimensionless parameters must be met: {\pi}/2 DA tan {\theta} >> 1
where {\theta} is the angle of incidence of the primary electron from the
normal, D is the fraction of surface area taken up by the velvet whisker bases,
and A is the aspect ratio, A {\equiv} h/r, the ratio of height to radius of the
velvet whiskers. We find that velvets available today can reduce the secondary
electron yield by 90% from the value of a flat surface. The values of optimal
velvet whisker packing density that maximally suppresses secondary electron
emission yield are determined as a function of velvet aspect ratio and electron
angle of incidence.


title: The Oxford Olympics Study 2016: Cost and Cost Overrun at the Games

abstract:
  Given that Olympic Games held over the past decade each have cost USD 8.9
billion on average, the size and financial risks of the Games warrant study.
The objectives of the Oxford Olympics study are to (1) establish the actual
outturn costs of previous Olympic Games in a manner where cost can consistently
be compared across Games; (2) establish cost overruns for previous Games, i.e.,
the degree to which final outturn costs reflect projected budgets at the bid
stage, again in a way that allows comparison across Games; (3) test whether the
Olympic Games Knowledge Management Program has reduced cost risk for the Games,
and, finally, (4) benchmark cost and cost overrun for the Rio 2016 Olympics
against previous Games. The main contribution of the Oxford study is to
establish a phenomenology of cost and cost overrun at the Olympics, which
allows consistent and systematic comparison across Games. This has not been
done before. The study concludes that for a city and nation to decide to stage
the Olympic Games is to decide to take on one of the most costly and
financially most risky type of megaproject that exists, something that many
cities and nations have learned to their peril.


title: Control of Recoil Losses in Nanomechanical SiN Membrane Resonators

abstract:
  In the context of a recoil damping analysis, we have designed and produced a
membrane resonator equipped with a specific on-chip structure working as a
"loss shield" for a circular membrane. In this device the vibrations of the
membrane, with a quality factor of $10^7$, reach the limit set by the intrinsic
dissipation in silicon nitride, for all the modes and regardless of the modal
shape, also at low frequency. Guided by our theoretical model of the loss
shield, we describe the design rationale of the device, which can be used as
effective replacement of commercial membrane resonators in advanced
optomechanical setups, also at cryogenic temperatures.


title: A variant of Harish-Chandra functors

abstract:
  Harish-Chandra induction and restriction functors play a key role in the
representation theory of reductive groups over finite fields. In this paper,
extending earlier work of Dat, we introduce and study generalisations of these
functors which apply to a wide range of finite and profinite groups, typical
examples being compact open subgroups of reductive groups over non-archimedean
local fields. We prove that these generalisations are compatible with two of
the tools commonly used to study the (smooth, complex) representations of such
groups, namely Clifford theory and the orbit method. As a test case, we examine
in detail the induction and restriction of representations from and to the
Siegel Levi subgroup of the symplectic group Sp(4) over a finite local
principal ideal ring of length two. We obtain in this case a Mackey-type
formula for the composition of these induction and restriction functors which
is a perfect analogue of the well-known formula for the composition of
Harish-Chandra functors. In a different direction, we study representations of
the Iwahori subgroup I(n) of GL(n,F), where F is a non-archimedean local field.
We establish a bijection between the set of irreducible representations of I(n)
and tuples of primitive irreducible representations of smaller Iwahori
subgroups, where primitivity is defined by the vanishing of suitable
restriction functors.


title: The Quiescent Intracluster Medium in the Core of the Perseus Cluster

abstract:
  Clusters of galaxies are the most massive gravitationally-bound objects in
the Universe and are still forming. They are thus important probes of
cosmological parameters and a host of astrophysical processes. Knowledge of the
dynamics of the pervasive hot gas, which dominates in mass over stars in a
cluster, is a crucial missing ingredient. It can enable new insights into
mechanical energy injection by the central supermassive black hole and the use
of hydrostatic equilibrium for the determination of cluster masses. X-rays from
the core of the Perseus cluster are emitted by the 50 million K diffuse hot
plasma filling its gravitational potential well. The Active Galactic Nucleus of
the central galaxy NGC1275 is pumping jetted energy into the surrounding
intracluster medium, creating buoyant bubbles filled with relativistic plasma.
These likely induce motions in the intracluster medium and heat the inner gas
preventing runaway radiative cooling; a process known as Active Galactic
Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus
cluster core, which reveal a remarkably quiescent atmosphere where the gas has
a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from
the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s
is found across the 60 kpc image of the cluster core. Turbulent pressure
support in the gas is 4% or less of the thermodynamic pressure, with large
scale shear at most doubling that estimate. We infer that total cluster masses
determined from hydrostatic equilibrium in the central regions need little
correction for turbulent pressure.


title: Hedging under generalized good-deal bounds and model uncertainty

abstract:
  We study a notion of good-deal hedging, that corresponds to good-deal
valuation for generalized good-deal constraints. Under model uncertainty about
the market prices of risk of hedging assets, a robust approach leads to a
reduction or even elimination of a speculative component in good-deal hedging,
which is shown to be equivalent to a global risk-minimization in the sense of
F\"ollmer and Sondermann (1986) if uncertainty is sufficiently large.
Constructive results on hedges and valuations are derived from backward
stochastic differential equations, including new examples with explicit
formulas.


title:
Procedure for measuring particle's circular polarization variation with
  respect to the reaction plane in relativistic heavy-ion collisions

abstract:
  The EM field pattern created by spectators in relativistic heavy-ion
collisions plants a seed of positive (negative) magnetic helicity in the
hemisphere above (below) the reaction plane. Owing to the chiral anomaly, the
magnetic helicity interacts with the fermionic helicity of the collision
system, and causes photons emitted in upper- and lower-hemispheres to have
different preferences in the circular polarization. In this paper, we lay down
a procedure to measure the variation of the circular polarization w.r.t the
reaction plane in relativistic heavy-ion collisions for massless photons, as
well as similar polarization patterns for vector mesons decaying into two
daughters. We propose to study the yield differentially and compare the yield
between upper- and lower-hemispheres in order to identify and quantify such
effects.


title:
Asymptotic results for a multivariate version of the alternative
  fractional Poisson process

abstract:
  A multivariate fractional Poisson process was recently defined in Beghin and
Macci (2016) by considering a common independent random time change for a
finite dimensional vector of independent (non-fractional) Poisson processes;
moreover it was proved that, for each fixed $t\geq 0$, it has a suitable
multinomial conditional distribution of the components given their sum. In this
paper we consider another multivariate process
$\{\underline{M}^\nu(t)=(M_1^\nu(t),\ldots,M_m^\nu(t)):t\geq 0\}$ with the same
conditional distributions of the components given their sums, and different
marginal distributions of the sums; more precisely we assume that the
one-dimensional marginal distributions of the process
$\left\{\sum_{i=1}^mM_i^\nu(t):t\geq0\right\}$ coincide with the ones of the
alternative fractional (univariate) Poisson process in Beghin and Macci (2013).
We present large deviation results for
$\{\underline{M}^\nu(t)=(M_1^\nu(t),\ldots,M_m^\nu(t)):t\geq 0\}$, and this
generalizes the result in Beghin and Macci (2013) concerning the univariate
case. We also study moderate deviations and we present some statistical
applications concerning the estimation of the fractional parameter $\nu$.


title: Non-commutativity in polar coordinates

abstract:
  We reconsider the fundamental commutation relations for non-commutative
$\mathbb{R}^{2}$ described in polar coordinates with non-commutativity
parameter $\theta$. Previous analysis found that the natural transition from
Cartesian coordinates to polars led to a representation of $\left[\hat{r},
\hat{\varphi}\right]$ as an everywhere diverging series. We compute the Borel
resummation of this series, showing that it can subsequently be extended
throughout parameter space and hence provide an interpretation of this
commutator. Our analysis provides a complete solution for arbitrary $r$ and
$\theta$ that reproduces the earlier calculations at lowest order. We compare
our results to previous literature in the (pseudo-)commuting limit, finding a
surprising spatial dependence for the coordinate commutator when $\theta \gg
r^{2}$. We raise some questions for future study in light of this progress.


title: Neural Tree Indexers for Text Understanding

abstract:
  Recurrent neural networks (RNNs) process input text sequentially and model
the conditional transition between word tokens. In contrast, the advantages of
recursive networks include that they explicitly model the compositionality and
the recursive structure of natural language. However, the current recursive
architecture is limited by its dependence on syntactic tree. In this paper, we
introduce a robust syntactic parsing-independent tree structured model, Neural
Tree Indexers (NTI) that provides a middle ground between the sequential RNNs
and the syntactic treebased recursive models. NTI constructs a full n-ary tree
by processing the input text with its node function in a bottom-up fashion.
Attention mechanism can then be applied to both structure and node function. We
implemented and evaluated a binarytree model of NTI, showing the model achieved
the state-of-the-art performance on three different NLP tasks: natural language
inference, answer sentence selection, and sentence classification,
outperforming state-of-the-art recurrent and recursive neural networks.


title:
Emergent Momentum-Space Skyrmion Texture on the Surface of Topological
  Insulators

abstract:
  The quantum anomalous Hall effect has been theoretically predicted and
experimentally verified in magnetic topological insulators. In addition, the
surface states of these materials exhibit a hedgehog-like "spin" texture in
momentum space. Here, we apply the previously formulated low-energy model for
Bi$_2$Se$_3$, a parent compound for magnetic topological insulators, to a slab
geometry in which an exchange field acts only within one of the surface layers.
In this sample set up, the hedgehog transforms into a skyrmion texture beyond a
critical exchange field. This critical field marks a transition between two
topologically distinct phases. The topological phase transition takes place
without energy gap closing at the Fermi level and leaves the transverse Hall
conductance unchanged and quantized to $e^2/2h$. The momentum-space skyrmion
texture persists in a finite field range. It may find its realization in hybrid
heterostructures with an interface between a three-dimensional topological
insulator and a ferromagnetic insulator.


title: Stokes Phenomena in Discrete Painlev\'e II

abstract:
  We consider the asymptotic behaviour of the second discrete Painlev\'{e}
equation in the limit as the independent variable becomes large. Using
asymptotic power series, we find solutions that are asymptotically pole-free
within some region of the complex plane. These asymptotic solutions exhibit
Stokes phenomena, which is typically invisible to classical power series
methods. We subsequently apply exponential asymptotic techniques to investigate
such phenomena, and obtain mathematical descriptions of the rapid switching
behaviour associated with Stokes curves. Through this analysis, we determine
the regions of the complex plane in which the asymptotic approximations are
valid, and find that the behaviour of these asymptotic solutions shares a
number of features with the tronqu\'{e}e and tri-tronqu\'{e}e solutions of the
second continuous Painlev\'{e} equation.


title: In-situ spectroscopic studies of viologen based electrochromic device

abstract:
  Fabrication and operation of simple solid state electrochromic devices using
ethyl viologen diperchlorate in a polymer matrix is presented here. In-situ
Raman and transmission/absorption studies have been done to establish the
origin of bias induced color change, between a transparent and navy blue color,
in the electrochromic device. The origin of bias induced color change has been
attributed to the bias induced redox switching between its viologen dication
and free redicle forms. Fundamental reason behind colour changes of viologen
molecule has been established. In-situ UV-Vis spectra reveals that the navy
blue color of the device under biased condition is not due to increase in the
transparency corresponding to blue wavelength but due to suppression of the
transparency corresponding to the complementary colors. Absorption modulation
has been reported from the device with good ON/OFF contrast of the device.


title: Resonance production in Pomeron-Pomeron collisions at the LHC

abstract:
  A model for Pomeron-Pomeron total cross section in the resonance region
$\sqrt{M^{2}} \le$ 5 GeV is presented. This model is based on Regge poles from
the Pomeron and two different $f$ trajectories, and includes the isolated
f$_{0}(500)$ resonance in the region $\sqrt{M^{2}}\lesssim 1$ GeV. A slowly
varying background is included. The presented Pomeron-Pomeron cross section is
not directly measurable, but is an essential ingredient for calculating
exclusive resonance production at the LHC.


title:
One-Loop Radiative Correction to the Triple Higgs Coupling in the Higgs
  Singlet Model

abstract:
  Though the 125 GeV Higgs boson is consistent with the standard model (SM)
prediction until now, the triple Higgs coupling can deviate from the SM value
in the physics beyond the SM (BSM). In this paper, the radiative correction to
the triple Higgs coupling is investigated in the minimal extension of the SM by
adding a real gauge singlet scalar. In this model there are two scalars $h$ and
$H$, and both of them are mixing states of the doublet and singlet. Provided
that the mixing angle is set to be zero, namely the SM limit, $h$ is the pure
left-over of the doublet and its behaviour is the same as that of the SM at the
tree level. However the loop corrections can alter $h$-related couplings. In
this SM limit case, the effect of the singlet $H$ may show up in the
$h$-related couplings, especially the triple $h$ coupling. Our numerical
results show that the deviation is sizable. For $\lambda_{\Phi{S}}=1$ (see the
text for definition), the deviation $\delta_{hhh}^{(1)}$ around threshold can
be more than $20\%$ if mass of the new scalar is light. For
$\lambda_{\Phi{S}}=1.5,3$, the deviation $\delta_{hhh}^{(1)}$ can reach above
$30\%$ in the vicinity of threshold. For $\lambda_{\Phi{S}}=-1$, $m_H$ can be
light. The deviation $\delta_{hhh}^{(1)}$ is negative in this case and can be
even $-50\%$ in the threshold enhanced region. The radiative correction for the
$hZZ$ coupling is from the counter-term, which is universal in this model and
always with negative sign. $\delta_{hZZ}^{(1)}$ is independent of the sign of
$\lambda_{\Phi{S}}$ and its typical size is $-0.2\%\sim-2\%$. When combining
$hhh$ and $hZZ$ precision measurements together, parameter space of this model
can be probed well including the sign and size of $\lambda_{\Phi{S}}$.


title:
Chemical and physical parameters from X-ray high resolution spectra of
  the Galactic nova V959 Mon

abstract:
  Two observations of V959 Mon, done using the Chandra X-ray gratings during
the late outburst phases (2012 September and December), offer extraordinary
insight into the physics and chemistry of this Galactic ONe nova. the X-ray
flux was 1.7 x 10(-11) erg/cm(2)/s and 8.6 x 10(-12) erg/cm(2)/s, respectively
at the two epochs. The first result, coupled with electron density diagnostics
and compared with published optical and ultraviolet observations, indicates
that most likely in 2012 September the X-rays originate from a very small
fraction of the ejecta, concentrated in very dense clumps. We obtained a fairly
good fit to the September spectrum with a model of plasma in collisional
ionization equilibrium (CIE) with two components; one at a temperature of 0.78
keV, blueshifted by 710-930 km/s, the other at a temperature of 4.5 keV, mostly
contributing to the high-energy continuum. However, we cannot rule out a range
of plasma temperatures between these two extremes. In December, the central
white dwarf (WD) became visible in X-rays. We estimate an effective temperature
of about 680,000 K, consistent with a WD mass ~1.1 M(sol). The WD flux is
modulated with the orbital period, indicating high inclination, and two
quasi-periodic modulations with hour timescales were also observed. No hot
plasma component with temperature above 0.5 keV was observed in December, and
the blue-shifted component cooled to kT~0.45 keV. Additionally, new emission
lines due to a much cooler plasma appeared, which were not observed two months
earlier. We estimate abundances and yields of elements in the nova wind that
cannot be measured in the optical spectra and confirm the high Ne abundance
previously derived for this nova. We also find high abundance of Al, 230 times
the solar value, consistently with the prediction that ONe novae contribute to
at least 1/3rd of the Galactic yield of Al(26).


title:
Selecting Algorithms for Black Box Matrices: Checking for Matrix
  Properties That Can Simplify Computations

abstract:
  Processes to automate the selection of appropriate algorithms for various
matrix computations are described. In particular, processes to check for, and
certify, various matrix properties of black box matrices are presented. These
include sparsity patterns and structural properties that allow "superfast"
algorithms to be used in place of black-box algorithms. Matrix properties that
hold generically, and allow the use of matrix preconditioning to be reduced or
eliminated, can also be checked for and certified - notably including in the
small-field case, where this presently has the greatest impact on the
efficiency of the computation.


title: Number representations and term rewriting

abstract:
  In this paper we examine a number of term rewriting system for integer number
representations, building further upon the datatype defining systems described
in [2]. In particular, we look at automated methods for proving confluence and
termination in binary and decimal term rewriting systems for both append and
tree constructor functions. We find that some of these term rewriting systems
are not strongly terminating, which we resolve with minor changes to these
systems. Moreover, most of the term rewriting systems discussed do not exhibit
the confluence property, which seems more difficult to resolve.


title: Coupling any number of balls in the infinite-bin model

abstract:
  The infinite-bin model, introduced by Foss and Konstantopoulos, describes the
Markovian evolution of configurations of balls placed inside bins, obeying
certain transition rules. We prove that we can couple the behaviour of any
finite number of balls, provided at least two different transition rules are
allowed. This coupling makes it possible to define the regeneration events
needed by Foss and Zachary to prove convergence results for the distribution of
the balls.


title: Stem Cell Networks

abstract:
  We present a general computational theory of stem cell networks and their
developmental dynamics. Stem cell networks are special cases of developmental
control networks. Our theory generates a natural classification of all possible
stem cell networks based on their network architecture. Each stem cell network
has a unique topology and semantics and developmental dynamics that result in
distinct phenotypes. We show that the ideal growth dynamics of multicellular
systems generated by stem cell networks have mathematical properties related to
the coefficients of Pascal's Triangle. The relationship to cancer stem cells
and their control networks is indicated. The theory lays the foundation for a
new research paradigm for understanding and investigating stem cells. The
theory of stem cell networks implies that new methods for generating and
controlling stem cells will become possible.


title: Formal gluing along non-linear flags

abstract:
  In this paper we prove formal glueing along an arbitrary closed substack $Z$
of an arbitrary Artin stack $X$ (locally of finite type over a field $k$), for
the stacks of (almost) perfect complexes , and of $G$-bundles on $X$ (for $G$ a
smooth affine algebraic $k$-group scheme). By iterating this result, we get a
decomposition of these stacks along an arbitrary nonlinear flag of closed
substacks in $X$. By taking points over the base field, we deduce from this
both a formal glueing, and a flag-related decomposition formula for the
corresponding symmetric monoidal derived $\infty$-categories of (almost)
perfect modules. When $X$ is a quasi-compact and quasi-separated scheme, we
also prove a localization theorem for almost perfect complexes on $X$, which
parallels Thomason's localization results for perfect complexes. This is one of
the main ingredients we need to provide a global characterization of the
category of almost perfect complexes on the punctured formal neighbourhood. We
then extend all of the previous results - i.e. the formal glueing and
flag-decomposition formulas - to the case when $X$ is a derived Artin stack
(locally almost of finite type over a field $k$), for the derived versions of
the stacks of (almost) perfect modules, and of $G$-bundles on $X$. We close the
paper by highlighting some expected progress in the subject matter of this
paper, related to a Geometric Langlands program for higher dimensional
varieties. In an Appendix (for $X$ a variety), we give a precise comparison
between our formal glueing results and the rigid-analytic approach of
Ben-Bassat and Temkin.


title:
Maximal intensity higher-order Akhmediev breathers of the nonlinear
  Schrodinger equation and their systematic generation

abstract:
  It is well known that Akhmediev breathers of the nonlinear cubic Schrodinger
equation can be superposed nonlinearly via the Darboux transformation to yield
breathers of higher order. Surprisingly, we find that the peak height of each
Akhmediev breather only adds {\it linearly} to form the peak height of the
final breather. Using this new peak-height formula, we show that at any given
periodicity, there exist a unique high-order breather of maximal intensity.
Moreover, these high-order breathers form a continuous hierarchy, growing in
intensity with increasing periodicity. For any such higher-order breather, a
simple initial wave function can be extracted from the Darboux transformation
to dynamically generate that breather from the nonlinear Schrodinger equation.


title:
Unified treatment of a class of spherically symmetric potentials:
  quasi-exact solution

abstract:
  In this paper, we investigate the Schr\"odinger equation for a class of
spherically symmetric potentials in a simple and unified manner using the Lie
algebraic approach within the framework of quasi-exact solvability. We
illustrate that all models give rise to the same basic differential equation,
which is expressible as an element of the universal enveloping algebra of
sl(2). Then, we obtain the general exact solutions of the problem by employing
the representation theory of sl(2) Lie algebra.


title: Partial orders and immunity in reverse mathematics

abstract:
  We identify computability-theoretic properties enabling us to separate
various statements about partial orders in reverse mathematics. We obtain
simpler proofs of existing separations, and deduce new compound ones. This work
is part of a larger program of unification of the separation proofs of various
Ramsey-type theorems in reverse mathematics in order to obtain a better
understanding of the combinatorics of Ramsey's theorem and its consequences. We
also answer a question of Murakami, Yamazaki and Yokoyama about pseudo Ramsey's
theorem for pairs.


title:
Two impurities in a Bose-Einstein condensate: from Yukawa to Efimov
  attracted polarons

abstract:
  The well-known Yukawa and Efimov potentials are two different mediated
interaction potentials. The first one arises in quantum field theory from the
exchange of virtual particles. The second one is mediated by a real particle
resonantly interacting with two other particles. This Letter shows how two
impurities immersed in a Bose-Einstein condensate can exhibit both phenomena.
For a weak impurity-boson attractive interactionattraction with the condensate,
the two impurities form two polarons that interact through a weak Yukawa
attraction mediated by virtual excitations. For a resonant attraction with the
condensate, the exchanged excitation becomes a real boson and the mediated
interaction changes to a strong Efimov attraction that can bind the two
polarons. The resulting bipolarons turn into in-medium Efimov trimers made of
the two impurities and one boson. Evidence of this physics could be seen in
ultracold mixtures of atoms.


title: Spatio-Orientational Decoherence of Nanoparticles

abstract:
  Motivated by trapping and cooling experiments with non-spherical
nanoparticles, we discuss how their combined rotational and translational
quantum state is affected by the interaction with a gaseous environment. Based
on the quantum master equation in terms of orientation-dependent scattering
amplitudes, we evaluate the localization rate for gas collisions off an
anisotropic van der Waals-type potential and for photon scattering off an
anisotropic dielectric. We also show how pure angular momentum diffusion arises
from these open quantum dynamics in the limit of weak anisotropies.


title:
Optimizing Synchronization Stability of the Kuramoto Model in Complex
  Networks and Power Grids

abstract:
  Maintaining the stability of synchronization state is crucial for the
functioning of many natural and artificial systems. In this study, we develop
methods to optimize the synchronization stability of the Kuramoto model by
minimizing the dominant Lyapunov exponent. With the help of the recently
proposed cut-set space approximation of the steady states, we greatly simplify
the objective function, and further derive its gradient and Hessian with
respect to natural frequencies, which leads to an efficient algorithm with the
quasi-Newton's method. The optimized systems are demonstrated to achieve better
synchronization stability for the Kuramoto model with or without inertia in
certain regimes. Hence our method is applicable in improving the stability of
power grids. It is also viable to adjust the coupling strength of each link to
improve the stability of the system. Various operational constraints can also
be easily integrated into our scope by employing the interior point method in
convex optimization. The properties of the optimized networks are also
discussed.


title:
Existence of positive solution for a system of elliptic equations via
  bifurcation theory

abstract:
  In this paper we study the existence of solution for the following class of
system of elliptic equations $$
  \left\{
  \begin{array}{lcl}
  -\Delta u=\left(a-\int_{\Omega}K(x,y)f(u,v)dy\right)u+bv,\quad \mbox{in}
\quad \Omega
  -\Delta v=\left(d-\int_{\Omega}\Gamma(x,y)g(u,v)dy\right)v+cu,\quad \mbox{in}
\quad \Omega u=v=0,\quad \mbox{on} \quad \partial\Omega
  \end{array}
  \right.
  \eqno{(P)}
  $$ where $\Omega\subset\R^N$ is a smooth bounded domain, $N\geq1$, and
$K,\Gamma:\Omega\times\Omega\rightarrow\R$ is a nonnegative function checking
some hypotheses and $a,b,c,d\in\R$. The functions $f$ and $g$ satisfy some
conditions which permit to use Bifurcation Theory to prove the existence of
solution for $(P)$.


title: Radio emissions from double RHESSI TGFs

abstract:
  A detailed analysis of Reuven Ramaty High Energy Solar Spectroscopic Imager
(RHESSI) terrestrial gamma ray flashes (TGFs) is performed in association with
World Wide Lightning Location Network (WWLLN) sources and very low frequency
(VLF) sferics recorded at Duke University. RHESSI clock offset is evaluated and
found to experience changes on the 5 August 2005 and 21 October 2013, based on
the analysis of TGF-WWLLN matches. The clock offsets were found for all three
periods of observations with standard deviations less than 100 {\mu}s. This
result opens the possibility for the precise comparative analyses of RHESSI
TGFs with the other types of data (WWLLN, radio measurements, etc.) In case of
multiple-peak TGFs, WWLLN detections are observed to be simultaneous with the
last TGF peak for all 16 cases of multipeak RHESSI TGFs simultaneous with WWLLN
sources. VLF magnetic field sferics were recorded for two of these 16 events at
Duke University. These radio measurements also attribute VLF sferics to the
second peak of the double TGFs, exhibiting no detectable radio emission during
the first TGF peak. Possible scenarios explaining these observations are
proposed. Double (multipeak) TGFs could help to distinguish between the VLF
radio emission radiated by the recoil currents in the +IC leader channel and
the VLF emission from the TGF producing electrons.


title:
THz Discrimination of materials: demonstration of a bioinspired
  apparatus based on metasurfaces selective filters

abstract:
  We present an apparatus for terahertz fingerprint discrimination of materials
designed to be fast, simple, compact and economical in order to be suitable for
preliminary on-field analysis. The system working principles, bioinspired by
the human vision of colors, are based on the use of microfabricated
metamaterials selective filters and of a very compact optics based on metallic
ellipsoidal mirrors in air. We experimentally demonstrate the operation of the
apparatus in discriminating simple substances such as salt, staple foods and
grease in an accurate and reproducible manner. We present the system and the
obtained results and discuss issues and possible developments.


title: Projective spaces over $\mathbb{F}_{1^{\ell}}$

abstract:
  In this essay we study various notions of projective space (and other
schemes) over $\mathbb{F}_{1^\ell}$, with $\mathbb{F}_1$ denoting the field
with one element. Our leading motivation is the "Hiden Points Principle," which
shows a huge deviation between the set of rational points as closed points
defined over $\mathbb{F}_{1^\ell}$, and the set of rational points defined as
morphisms $\texttt{Spec}(\mathbb{F}_{1^\ell}) \mapsto \mathcal{X}$. We also
introduce, in the same vein as Kurokawa [13], schemes of
$\mathbb{F}_{1^\ell}$-type, and consider their zeta functions.


title:
Black Box Linear Algebra: Extending Wiedemann's Analysis of a Sparse
  Matrix Preconditioner for Computations over Small Fields

abstract:
  Wiedemann's paper, introducing his algorithm for sparse and structured matrix
computations over arbitrary fields, also presented a pair of matrix
preconditioners for computations over small fields. The analysis of the second
of these is extended in order to provide more explicit statements of the
expected number of nonzero entries in the matrices obtained as well as bounds
on the probability that such matrices have maximal rank.
  This is part of ongoing work to establish that this matrix preconditioner can
also be used to bound the number of nontrivial nilpotent blocks in the Jordan
normal form of a preconditioned matrix, in such a way that one can also sample
uniformly from the null space of the originally given matrix. If successful
this will result in a black box algorithm for the type of matrix computation
required when using the number field sieve for integer factorization that is
provably reliable and - by a small factor - asymptotically more efficient than
alternative techniques that make use of other matrix preconditioners or require
computations over field extensions.


title: Multi-body Non-rigid Structure-from-Motion

abstract:
  Conventional structure-from-motion (SFM) research is primarily concerned with
the 3D reconstruction of a single, rigidly moving object seen by a static
camera, or a static and rigid scene observed by a moving camera --in both cases
there are only one relative rigid motion involved. Recent progress have
extended SFM to the areas of {multi-body SFM} (where there are {multiple rigid}
relative motions in the scene), as well as {non-rigid SFM} (where there is a
single non-rigid, deformable object or scene). Along this line of thinking,
there is apparently a missing gap of "multi-body non-rigid SFM", in which the
task would be to jointly reconstruct and segment multiple 3D structures of the
multiple, non-rigid objects or deformable scenes from images. Such a multi-body
non-rigid scenario is common in reality (e.g. two persons shaking hands,
multi-person social event), and how to solve it represents a natural
{next-step} in SFM research. By leveraging recent results of subspace
clustering, this paper proposes, for the first time, an effective framework for
multi-body NRSFM, which simultaneously reconstructs and segments each 3D
trajectory into their respective low-dimensional subspace. Under our
formulation, 3D trajectories for each non-rigid structure can be well
approximated with a sparse affine combination of other 3D trajectories from the
same structure (self-expressiveness). We solve the resultant optimization with
the alternating direction method of multipliers (ADMM). We demonstrate the
efficacy of the proposed framework through extensive experiments on both
synthetic and real data sequences. Our method clearly outperforms other
alternative methods, such as first clustering the 2D feature tracks to groups
and then doing non-rigid reconstruction in each group or first conducting 3D
reconstruction by using single subspace assumption and then clustering the 3D
trajectories into groups.


title:
Exploiting vibrational strong coupling to make an optical parametric
  oscillator out of a Raman laser

abstract:
  When the collective coupling of the rovibrational states in organic molecules
and confined electromagnetic modes is sufficiently strong, the system enters
into vibrational strong coupling, leading to the formation of hybrid
light-matter quasiparticles. In this work we demonstrate theoretically how this
hybridization in combination with stimulated Raman scattering can be utilized
to widen the capabilities of Raman laser devices. We explore the conditions
under which the lasing threshold can be diminished and the system can be
transformed into an optical parametric oscillator. Finally, we show how the
dramatic reduction of the many final molecular states into two collective
excitations can be used to create an all-optical switch with output in the
mid-infrared.


title:
Critical-angle x-ray transmission grating spectrometer with extended
  bandpass and resolving power > 10,000

abstract:
  Several high priority subjects in astrophysics can be addressed by a
state-of-the-art soft x-ray grating spectrometer (XGS). An Explorer-scale,
large-area (> 1,000 cm2), high resolving power (R > 3,000) XGS is highly
feasible based on Critical-Angle Transmission (CAT) gratings, even for
telescopes with angular resolution of 5-10 arcsec. Significantly higher
performance can be provided by a CAT XGS on an X-ray-Surveyor-type mission. CAT
gratings combine the advantages of blazed reflection gratings (high efficiency,
use of higher diffraction orders) with those of transmission gratings (low
mass, relaxed alignment and temperature requirements, transparent at high
energies) with minimal mission resource demands. They are high-efficiency
blazed transmission gratings that consist of freestanding, ultra-high
aspect-ratio grating bars made from SOI wafers using anisotropic dry and wet
etch techniques. Blazing is achieved through reflection off grating bar
sidewalls. Silicon is well matched to the soft x-ray band, and existing silicon
CAT gratings exceed 30% absolute diffraction efficiency, with clear paths for
improvement. CAT gratings coated with heavier elements allow extension of the
CAT grating principle to higher energies and larger angles, enabling higher
resolving power at shorter wavelengths. We show x-ray data from CAT gratings
coated with platinum using atomic layer deposition, and demonstrate blazing to
higher energies and much larger blaze angles than possible with silicon. We
measure resolving power of a CAT XGS consisting of a Wolter-I focusing mirror
pair from GSFC and CAT gratings, performed at the MSFC SLF. Measurement of the
Al Ka doublet in 18th order shows resolving power > 10,000, based on
preliminary analysis. This demonstrates that currently fabricated CAT gratings
are compatible with the most advanced XGS designs for future soft x-ray
spectroscopy missions.


title:
Empirical study of the influence of social groups in evacuation
  scenarios

abstract:
  The effects of social groups on pedestrian dynamics, especially in evacuation
scenarios, have attracted some interest recently. However, due to the lack of
reliable empirical data, most of the studies focussed on modelling aspects. It
was shown that social groups can have a considerable effect, e.g. on evacuation
times. In order to test the model predictions we have performed laboratory
experiments of evacuations with different types and sizes of the social groups.
The experiments have been performed with pupils of different ages. Parameters
that have been considered are (1) group size, (2) strength of intra-group
interactions, and (3) composition of the groups (young adults, children, and
mixtures). For all the experiments high-quality trajectories for all
participants have been obtained using the PeTrack software. This allows for a
detailed analysis of the group effects. One surprising observation is a
decrease of the evacuation time with increasing group size.


title: Mirror and cavity formations by chains of collectively radiating atoms

abstract:
  We search for mirror and cavity-like features of a linear chain of atoms in
which one of the atoms is specially chosen as a probe atom that is initially
prepared in its excited state or is continuously driven by a laser field. Short
chains are considered, composed of only three and five atoms. The analysis
demonstrate the importance of the inter atomic dipole-dipole interaction which
may lead to a collective ordering of the emission along some specific
directions. We examine the conditions under which the radiative modes available
for the emission are only those contained inside a cone centered about the
inter atomic axis. Particular interest is in achieving the one-way emission
along the inter atomic axis, either into left (backward) or right (forward)
direction, which is referred to as a mirror-like behavior of the atomic chain.
A direction dependent quantity called the directivity function, which
determines how effective the system is in concentrating the radiation into a
given direction, is introduced. We show that the function depends crucially on
the distance between the atoms and find that there is a threshold for the inter
atomic distances above which a strongly directional emission can be achieved.
The one-sided emission as a manifestation of the mirror-like behavior and a
highly focused emission along the inter atomic axis as a characteristic of a
single-mode cavity are demonstrated to occur in the stationary field. Below the
threshold the directivity function is spherically symmetric. However, we find
that the population can be trapped in one of the atoms, and sometimes in all
atoms indicating that at these small distances the system decays to a state for
which there are no radiative modes available for emission.


title:
Normalized bound states for the nonlinear Schrodinger equation in
  bounded domains

abstract:
  Given $\rho>0$, we study the elliptic problem \[ \text{find } (U,\lambda)\in
H^1_0(\Omega)\times \mathbb{R} \text{ such that } \begin{cases} -\Delta
U+\lambda U=|U|^{p-1}U \int_{\Omega} U^2\, dx=\rho, \end{cases} \] where
$\Omega\subset\mathbb{R}^N$ is a bounded domain and $p>1$ is
Sobolev-subcritical, searching for conditions (about $\rho$, $N$ and $p$) for
the existence of solutions. By the Gagliardo-Nirenberg inequality it follows
that, when $p$ is $L^2$-subcritical, i.e. $1<p\leq1+4/N$, the problem admits
solution for every $\rho>0$. In the $L^2$-critical and supercritical case, i.e.
when $1+4/N \leq p < 2^*-1$, we show that, for any $k\in\mathbb{N}$, the
problem admits solutions having Morse index bounded above by $k$ only if $\rho$
is sufficiently small. Next we provide existence results for certain ranges of
$\rho$, which can be estimated in terms of the Dirichlet eigenvalues of
$-\Delta$ in $H^1_0(\Omega)$, extending to general domains and to changing sign
solutions some results obtained in [Noris, Tavares, Verzini, Analysis & PDE,
2014] for positive solutions in the ball.


title: Yamabe type equations on graphs

abstract:
  Let $G=(V,E)$ be a locally finite graph, $\Omega\subset V$ be a bounded
domain, $\Delta$ be the usual graph Laplacian, and $\lambda_1(\Omega)$ be the
first eigenvalue of $-\Delta$ with respect to Dirichlet boundary condition.
Using the mountain pass theorem due to Ambrosetti-Rabinowitz, we prove that if
$\alpha<\lambda_1(\Omega)$, then for any $p>2$, there exists a positive
solution to $-\Delta u-\alpha u=|u|^{p-2}u$ in $\Omega^\circ$, $u=0$ on
$\partial\Omega$, where $\Omega^\circ$ and $\partial\Omega$ denote the interior
and the boundary of $\Omega$ respectively. Also we consider similar problems
involving the $p$-Laplacian and poly-Laplacian by the same method. Such
problems can be viewed as discrete versions of the Yamabe type equations on
Euclidean space or compact Riemannian manifolds.


title:
Modelling high-dimensional time series efficiently by means of
  constrained spatio--temporal models

abstract:
  Many econometric analyses involve spatio--temporal data. A considerable
amount of literature has addressed spatio--temporal models, with Spatial
Dynamic Panel Data (SDPD) being widely investigated and applied. In real data
applications, checking the validity of the theoretical assumptions underlying
the SDPD models is essential but sometimes difficult. At other times, the
assumptions are clearly violated. For example, the spatial matrix is assumed to
be known but it may actually be unknown and needs to be estimated. In such
cases, the performance of the SDPD model's estimator is generally affected.
Motivated by such considerations, we propose a new model (called stationary
SDPD) and a new estimation procedure based on simple and clear assumptions that
can be easily checked with real data. The new model is highly adaptive, and the
estimation procedure has a rate of convergence that is not affected by the
dimension of the time series (under general assumptions), notwithstanding the
relatively high number of parameters to be estimated. The new model may be used
to represent a wide class of multivariate time series, not necessarily
spatio-temporal. So, it can be used as a valid alternative to vector
autoregressive (VAR) models with two immediate advantages: i) a faster rate of
convergence of the estimation procedure and ii) the possibility of estimating
the model even when the dimension is higher than the time series length,
overcoming the curse of dimensionality typical of the VAR models. The
simulation study shows that the new estimation procedure performs well compared
with the classic alternative procedure, even when the spatial matrix is unknown
and therefore estimated.


title: Highly Itinerant Atomic Vacancies in Phosphorene

abstract:
  Using detailed first-principles calculations, we investigate the hopping rate
of vacancies in phosphorene, an emerging elemental 2D material besides
graphene. Our work predicts that a direct observation of these mono-vacancies
(MVs), showing a highly mobile and anisotropic motion, is possible only at low
temperatures around 70 K or below where the thermal activity is greatly
suppressed. At room temperature, the motion of a MV is sixteen orders faster
than that in graphene, because of the low diffusion barrier of 0.3 eV. Built-in
strain associated with the vacancies extends far along the zigzag direction
while attenuating rapidly along the armchair direction. We reveal new features
of the motion of di-vacancies (DVs) in phosphorene via multiple
dissociation-recombination processes of vacancies owing to a small energy cost
of ~ 1.05 eV for the splitting of a DV into two MVs. Furthermore, we find that
uniaxial tensile strain along the zigzag direction can promote the motion of
MVs, while the tensile strain along the armchair direction has the opposite
effect. These itinerant features of vacancies, rooted in the unique puckering
structure facilitating bond reorganization, enable phosphorene to be a bright
new opportunity to broaden the knowledge of the evolution of vacancies, and a
proper control of the exceedingly active and anisotropic movement of the
vacancies should be critical for applications based on phosphorene.


title: Tachyon inflation in an AdS braneworld with back-reaction

abstract:
  We analyze the inflationary scenario based on the tachyon field coupled with
the radion of the second Randall-Sundrum model (RSII). The tachyon Lagrangian
is derived from the dynamics of a 3-brane moving in the five dimensional bulk.
The AdS$_5$ geometry of the bulk is extended to include the radion. Using the
Hamiltonian formalism we find four nonlinear field equations supplemented by
the modified Friedmann equations of the RSII braneworld cosmology. After a
suitable rescaling we reduce the parameters of our model to only one free
parameter related to the brane tension and the AdS$_5$ curvature. We solve the
equations numerically assuming a reasonably wide range of initial conditions
determined by physical considerations. Varying the free parameter and initial
conditions we confront our results with the Planck 2015 data.