title: Triangularizability of Families of Polynomially Compact Operators

abstract:
  A recent paper of Shemesh shows triangularizability of a pair $\{A, B\}$ of
complex matrices satisfying the condition $A [A,B]=[A,B] B=0$, or equivalently,
the matrices $A$ and $B$ commute with their product $A B$. In this paper we
extend this result to polynomially compact operators on Banach spaces. The case
when the underlying space is Hilbert and one of operators is normal is also
studied. Furthermore, we consider families of polynomially compact operators
whose iterated commutators of some fixed length are zero. We also obtain a
structure result in the special case of a finite family of algebraic operators.


title: Verification of interlocking systems using statistical model checking

abstract:
  In the railway domain, an interlocking is the system ensuring safe train
traffic inside a station by controlling its active elements such as the signals
or points. Modern interlockings are configured using particular data, called
application data, reflecting the track layout and defining the actions that the
interlocking can take. The safety of the train traffic relies thereby on
application data correctness, errors inside them can cause safety issues such
as derailments or collisions. Given the high level of safety required by such a
system, its verification is a critical concern. In addition to the safety, an
interlocking must also ensure that availability properties, stating that no
train would be stopped forever in a station, are satisfied. Most of the
research dealing with this verification relies on model checking. However, due
to the state space explosion problem, this approach does not scale for large
stations. More recently, a discrete event simulation approach limiting the
verification to a set of likely scenarios, was proposed. The simulation enables
the verification of larger stations, but with no proof that all the interesting
scenarios are covered by the simulation. In this paper, we apply an
intermediate statistical model checking approach, offering both the advantages
of model checking and simulation. Even if exhaustiveness is not obtained,
statistical model checking evaluates with a parametrizable confidence the
reliability and the availability of the entire system.


title:
Fixed Parameter Approximations for k-Center Problems in Low Highway
  Dimension Graphs

abstract:
  We consider the $k$-Center problem and some generalizations. For $k$-Center a
set of $k$ center vertices needs to be found in a graph $G$ with edge lengths,
such that the distance from any vertex of $G$ to its nearest center is
minimized. This problem naturally occurs in transportation networks, and
therefore we model the inputs as graphs with bounded highway dimension, as
proposed by Abraham et al. [SODA 2010].
  We show both approximation and fixed-parameter hardness results, and how to
overcome them using fixed-parameter approximations, where the two paradigms are
combined. In particular, we prove that for any $\varepsilon>0$ computing a
$(2-\varepsilon)$-approximation is W[2]-hard for parameter $k$ and NP-hard for
graphs with highway dimension $O(\log^2 n)$. The latter does not rule out
fixed-parameter $(2-\varepsilon)$-approximations for the highway dimension
parameter $h$, but implies that such an algorithm must have at least doubly
exponential running time in $h$ if it exists, unless the ETH fails. On the
positive side, we show how to get below the approximation factor of $2$ by
combining the parameters $k$ and $h$: we develop a fixed-parameter
$3/2$-approximation with running time $2^{O(kh\log h)}\cdot n^{O(1)}$.
Additionally we prove that, unless P=NP, our techniques cannot be used to
compute fixed-parameter $(2-\varepsilon)$-approximations for only the parameter
$h$.
  We also provide similar fixed-parameter approximations for the weighted
$k$-Center and $(k,\mathcal{F})$-Partition problems, which generalize
$k$-Center.


title: Clustering Time Series and the Surprising Robustness of HMMs

abstract:
  Suppose that we are given a time series where consecutive samples are
believed to come from a probabilistic source, that the source changes from time
to time and that the total number of sources is fixed. Our objective is to
estimate the distributions of the sources. A standard approach to this problem
is to model the data as a hidden Markov model (HMM). However, since the data
often lacks the Markov or the stationarity properties of an HMM, one can ask
whether this approach is still suitable or perhaps another approach is
required. In this paper we show that a maximum likelihood HMM estimator can be
used to approximate the source distributions in a much larger class of models
than HMMs. Specifically, we propose a natural and fairly general non-stationary
model of the data, where the only restriction is that the sources do not change
too often. Our main result shows that for this model, a maximum-likelihood HMM
estimator produces the correct second moment of the data, and the results can
be extended to higher moments.


title: HLinear: Exact Dense Linear Algebra in Haskell

abstract:
  We present an implementation in the functional programming language Haskell
of the PLE decomposition of matrices over division rings. Our benchmarks
indicate that it is competitive with the C-based implementation provided in
Flint. Describing the guiding principles of our work, we introduce the reader
to basic ideas from high-performance functional programming.


title:
Tracking of magnetic flux concentrations over a five-day observation and
  an insight into surface magnetic flux transport

abstract:
  The solar dynamo problem is the question of how the cyclic variation in the
solar magnetic field is maintained. One of the important processes is the
transport of magnetic flux by surface convection. To reveal this process, the
dependence of the squared displacement of magnetic flux concentrations upon the
elapsed time is investigated in this paper via a feature-recognition technique
and a continual five-day magnetogram. This represents the longest time scale
over which a satellite observation has ever been performed for this problem.
The dependence is found to follow a power-law and differ significantly from
that of diffusion transport. Furthermore there is a change in the behavior at a
spatial scale of 10^{3.8} km. A super-diffusion behavior with an index of 1.4
is found on smaller scales, while changing to a sub-diffusion behavior with an
index of 0.6 on larger ones. I interpret this difference in the transport
regime as coming from the network-flow pattern.


title: The strength of countable saturation

abstract:
  We determine the proof-theoretic strength of the principle of countable
saturation in the context of the systems for nonstandard arithmetic introduced
in our earlier work.


title:
Carleman estimates for elliptic operators with complex coefficients Part
  II: transmission problems

abstract:
  We consider elliptic transmission problems with complex coefficients across
an interface. Under proper transmission conditions, that extend known
conditions for well-posedness, and sub-ellipticity we derive microlocal and
local Carleman estimates near the interface. Carleman estimates are weighted a
priori estimates of the solutions of the elliptic transmission problem. The
weight is of exponential form, exp($tau$ {\phi}) where $tau$ can be taken as
large as desired. Such estimates have numerous applications in unique
continuation, inverse problems, and control theory. The proof relies on
microlocal factorizations of the symbols of the conjugated operators in
connection with the sign of the imaginary part of their roots. We further
consider weight functions where {\phi} = exp($\gamma$$\psi$), with $\gamma$
acting as a second large paremeter, and we derive estimates where the
dependency upon the two parameters, $tau$ and $\gamma$, is made explicit.
Applications to unique continuation properties are given.


title: Random Fourier Features for Operator-Valued Kernels

abstract:
  Devoted to multi-task learning and structured output learning,
operator-valued kernels provide a flexible tool to build vector-valued
functions in the context of Reproducing Kernel Hilbert Spaces. To scale up
these methods, we extend the celebrated Random Fourier Feature methodology to
get an approximation of operator-valued kernels. We propose a general principle
for Operator-valued Random Fourier Feature construction relying on a
generalization of Bochner's theorem for translation-invariant operator-valued
Mercer kernels. We prove the uniform convergence of the kernel approximation
for bounded and unbounded operator random Fourier features using appropriate
Bernstein matrix concentration inequality. An experimental proof-of-concept
shows the quality of the approximation and the efficiency of the corresponding
linear models on example datasets.


title: A Conserved Cross Helicity for Non-Barotropic MHD

abstract:
  Cross helicity is not conserved in non-barotropic magnetohydrodynamics (MHD)
(as opposed to barotropic or incompressible MHD). Here we show that variational
analysis suggests a new kind of cross helicity which is conserved in the non
barotropic case. The non barotropic cross helicity reduces to the standard
cross helicity under barotropic assumptions. The new cross helicity is
conserved even for topologies for which the variational principle does not
apply.


title:
Diophantine approximation with improvement of the simultaneous control
  of the error and of the denominator

abstract:
  In this work we proof the following theorem which is, in addition to
someother lemmas, our main result:\noindent \textbf{theorem}. Let$\ X=\{ (
x\_{1}\text{, }%t\_{1}) \text{, }( x\_{2}\text{, }t\_{2}) \text{, ...,
}(x\_{n}\text{, }t\_{n})\} $ be a finite part of $\mathbb{R}\times
\mathbb{R}^{\ast +}$, then there exist a finite part $R$ of $\mathbb{R}%^{\ast
+}$ such that for all $\varepsilon > 0$ there exists $r\in R$ such that if $0 <
\varepsilon \leq r$ then there exist rational numbers $( \dfrac{p\_{i}}{q})
\_{i=1,2,...,n}$ such that:\{c}| x\_{i}-\dfrac{p\_{i}}{q}| \leq \varepsilon
t\_{i} \varepsilon q\leq t\_{i}|\text{, }i=1,2,...,n\text{.} \tag{*}\noindent
It is clear that the condition $\varepsilon q\leq t\_{i}$ for $%i=1,2,...,n$ is
equivalent to $\varepsilon q\leq t=\underset{i=1,2,...,n}{Min%}$ $( t\_{i}) $.\
Also, we have (*) for all $\varepsilon $verifying $0 < \varepsilon \leq
\varepsilon \_{0}=\min R$.The previous theorem is the classical equivalent of
the following one whichis formulated in the context of the nonstandard analysis
($[ 2] $%, $[ 5] $, $[ 6] $, $[ 8] $).\noindent \textbf{theorem. }For every
positive infinitesimal real $\varepsilon$, there exists an unlimited integer
$q$ depending only of $\varepsilon $, such that $\forall ^{st}x \in \mathbb{R}\
\exists p_{x} \in \mathbb{Z}$ $:\{ \{ccc}x & = \& \dfrac{p_{x}}{q}+\varepsilon
\phi \varepsilon q \& \cong \& 0.$ For this reason, to prove the nonstandard
version of the main result and to get its classical version we place ourselves
in the context of the nonstandard analysis.


title:
Robust framework for quantifying the value of information in pricing and
  hedging

abstract:
  We investigate asymmetry of information in the context of robust approach to
pricing and hedging of financial derivatives. We consider two agents, one who
only observes the stock prices and another with some additional information,
and investigate when the pricing--hedging duality for the former extends to the
latter. We introduce a general framework to express the superhedging and market
model prices for an informed agent. Our key insight is that an informed agent
can be seen as a regular agent who can restrict her attention to a certain
subset of possible paths. We use results of Hou & Ob\l\'oj on robust approach
with beliefs to establish the pricing--hedging duality for an informed agent.
Our results cover number of scenarios, including information arriving before
trading starts, arriving after static position in European options is formed
but before dynamic trading starts or arriving at some point before the
maturity. For the latter we show that the superhedging value satisfies a
suitable dynamic programming principle, which is of independent interest.


title:
Exact ICL maximization in a non-stationary temporal extension of the
  stochastic block model for dynamic networks

abstract:
  The stochastic block model (SBM) is a flexible probabilistic tool that can be
used to model interactions between clusters of nodes in a network. However, it
does not account for interactions of time varying intensity between clusters.
The extension of the SBM developed in this paper addresses this shortcoming
through a temporal partition: assuming interactions between nodes are recorded
on fixed-length time intervals, the inference procedure associated with the
model we propose allows to cluster simultaneously the nodes of the network and
the time intervals. The number of clusters of nodes and of time intervals, as
well as the memberships to clusters, are obtained by maximizing an exact
integrated complete-data likelihood, relying on a greedy search approach.
Experiments on simulated and real data are carried out in order to assess the
proposed methodology.


title: Mean Absolute Percentage Error for regression models

abstract:
  We study in this paper the consequences of using the Mean Absolute Percentage
Error (MAPE) as a measure of quality for regression models. We prove the
existence of an optimal MAPE model and we show the universal consistency of
Empirical Risk Minimization based on the MAPE. We also show that finding the
best model under the MAPE is equivalent to doing weighted Mean Absolute Error
(MAE) regression, and we apply this weighting strategy to kernel regression.
The behavior of the MAPE kernel regression is illustrated on simulated data.


title: "General theory of a particle mechanics" arising from a fractal surface

abstract:
  The logical line is traced of formulation of theory of mechanics founded on
the basic correlations of mathematics of hypercomplex numbers and associated
geometric images. Namely, it is shown that the physical equations of quantum,
classical and relativistic mechanics can be regarded as mathematical
consequences of a single condition of stability of exceptional algebras of
real, complex and quaternion numbers under transformations of primitive
constituents of their units and elements. In the course of the study a notion
of basic fractal surface underlying the physical three-dimensional space is
introduces, and an original geometric treatment (admitting visualization) of
some formerly considered abstract functions (mechanical action, space-time
interval) are suggested.


title: Local Scale Invariance and Inflation

abstract:
  We study the inflation and the cosmological perturbations generated during
the inflation in a local scale invariant model. The local scale invariant model
introduces a vector field $S_{\mu}$ in this theory. In this paper, for
simplicity, we consider the temporal part of the vector field $S_t$. We show
that the temporal part is associated with the slow roll parameter of scalar
field. Due to local scale invariance, we have a gauge degree of freedom. In a
particular gauge, we show that the local scale invariance provides sufficient
number of e-foldings for the inflation. Finally, we estimate the power spectrum
of scalar perturbation in terms of the parameters of the theory.


title: Factorizations of Kernels and Reproducing Kernel Hilbert Spaces

abstract:
  The paper discusses a series of results concerning reproducing kernel Hilbert
spaces, related to the factorization of their kernels. In particular, it is
proved that for a large class of spaces isometric multipliers are trivial. One
also gives for certain spaces conditions for obtaining a particular type of
dilation, as well as a classification of Brehmer type submodules.


title:
A note on "Measuring propagation speed of Coulomb fields" by R. de
  Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella

abstract:
  In connection with the discussion and the measurements fulfilled in [R. de
Sangro et al., Eur. Phys. J. C 75 (2015) 137], the full identity is
demonstrated between the Feynman formula for the field of a moving charge and
the Lienard-Wiechert potentials.


title: Reduced Quantum General Relativity in Higher Dimensions

abstract:
  The higher dimensional Quantum General Relativity of a Riemannian manifold
being an embedded space in a space-time being a Lorentzian manifold is
investigated. The model of quantum geometrodynamics, based on the
Wheeler-DeWitt equation reduced to a first order functional quantum evolution
supplemented through an additional eigenequation for the scalar curvature, is
formulated. Furthermore, making use of the objective quantum gravity and global
one-dimensional conjecture, the general wave function beyond the Feynman path
integral technique is derived. The resulting quantum gravity model creates the
opportunity of potentially new theoretical and phenomenological applications
for astrophysics, cosmology, and physics.


title: Third order variational equation for the free relativistic top

abstract:
  I proffer a development of some third order equation of motion for the free
relativistic top from the simultaneously imposed assumptions of variationality
and Lorentz symmetry.


title: Deformations of convex real projective manifolds and orbifolds

abstract:
  In this survey, we study representations of finitely generated groups into
Lie groups, focusing on the deformation spaces of convex real projective
structures on closed manifolds and orbifolds, with an excursion on projective
structures on surfaces. We survey the basics of the theory of character
varieties, geometric structures on orbifolds, and Hilbert geometry. The main
examples of finitely generated groups for us will be Fuchsian groups,
3-manifold groups and Coxeter groups.


title: X-Ray diffraction on large single crystals using a powder diffractometer

abstract:
  Information on the lattice parameter of single crystals with known
crystallographic structure allows for estimations of sample quality and
composition. In many cases it is suffcient to determine one lattice parameter
or the lattice spacing along a certain, high-symmetry direction, e.g. in order
to determine the composition in a substitution series by taking advantage of
Vegard's rule. Here we present a guide to accurate measurements of single
crystals with dimensions ranging from 200 $\mu$m up to several millimeter using
a standard powder diffractometer in Bragg-Brentano geometry. The correction of
the error introduced by the sample height and the optimization of the alignment
are discussed in detail. In particular for single crystals with a plate-like
habit, the described procedure allows for measurement of the lattice spacings
normal to the plates with high accuracy on a timescale of minutes.


title: Chaos and Stochastic Models in Physics: Ontic and Epistemic Aspects

abstract:
  There is a persistent confusion about determinism and predictability. In
spite of the opinions of some eminent philosophers (e.g., Popper), it is
possible to understand that the two concepts are completely unrelated. In few
words we can say that determinism is ontic and has to do with how Nature
behaves, while predictability is epistemic and is related to what the human
beings are able to compute. An analysis of the Lyapunov exponents and the
Kolmogorov-Sinai entropy shows how deterministic chaos, although with an
epistemic character, is non subjective at all. This should clarify the role and
content of stochastic models in the description of the physical world.


title: Axiomatics for the external numbers of nonstandard analysis

abstract:
  Neutrices are additive subgroups of a nonstandard model of the real numbers.
An external number is the algebraic sum of a nonstandard real number and a
neutrix. Due to the stability by some shifts, external numbers may be seen as
mathematical models for orders of magnitude. The algebraic properties of
external numbers gave rise to the so-called solids, which are extensions of
ordered fields, having a restricted distributivity law. However, necessary and
sufficient conditions can be given for distributivity to hold. In this article
we develop an axiomatics for the external numbers. The axioms are similar to,
but mostly somewhat weaker than the axioms for the real numbers and deal with
algebraic rules, Dedekind completeness and the Archimedean property. A
structure satisfying these axioms is called a complete arithmetical solid. We
show that the external numbers form a complete arithmetical solid, implying the
consistency of the axioms presented. We also show that the set of precise
elements (elements with minimal magnitude) has a built-in nonstandard model of
the rationals. Indeed the set of precise elements is situated between the
nonstandard rationals and the nonstandard reals whereas the set of non-precise
numbers is completely determined.


title:
How Much Cache is Needed to Achieve Linear Capacity Scaling in
  Backhaul-Limited Dense Wireless Networks?

abstract:
  Dense wireless networks are a promising solution to meet the huge capacity
demand in 5G wireless systems. However, there are two implementation issues,
namely the interference and backhaul issues. To resolve these issues, we
propose a novel network architecture called the backhaul-limited cached dense
wireless network (C-DWN), where a physical layer (PHY) caching scheme is
employed at the base stations (BSs) but only a fraction of the BSs have wired
payload backhauls. The PHY caching can replace the role of wired backhauls to
achieve both the cache-induced MIMO cooperation gain and cache-assisted
Multihopping gain. Two fundamental questions are addressed. Can we exploit the
PHY caching to achieve linear capacity scaling with limited payload backhauls?
If so, how much cache is needed? We show that the capacity of the
backhaul-limited C-DWN indeed scales linearly with the number of BSs if the BS
cache size is larger than a threshold that depends on the content popularity.
We also quantify the throughput gain due to cache-induced MIMO cooperation over
conventional caching schemes (which exploit purely the cached-assisted
multihopping). Interestingly, the minimum BS cache size needed to achieve a
significant cache-induced MIMO cooperation gain is the same as that needed to
achieve the linear capacity scaling.


title: Relative Entropy, Mixed Gauge-Gravitational Anomaly and Causality

abstract:
  In this note we explored the holographic relative entropy in the presence of
the 5d Chern-Simons term, which introduces a mixed gauge-gravity anomaly to the
dual CFT. The theory trivially satisfies an entanglement first law. However, to
quadratic order in perturbations of the stress tensor $T$ and current density
$J$, there is a mixed contribution to the relative entropy bi-linear in $T$ and
$J$, signalling a potential violation of the positivity of the relative
entropy. Miraculously, the term vanishes up to linear order in a derivative
expansion. This prompted a closer inspection on a different consistency check,
that involves time-delay of a graviton propagating in a charged background,
scattered via a coupling supplied by the Chern-Simons term. The analysis
suggests that the time-delay can take either sign, potentially violating
causality for any finite value of the CS coupling.


title:
Getting excited: Challenges in quantum-classical studies of excitons in
  polymeric systems

abstract:
  A combination of classical molecular dynamics (MM/MD) and quantum chemical
calculations based on the density functional theory (DFT) was performed to
describe conformational properties of diphenylethyne (DPE), methylated-DPE and
poly para phenylene ethynylene (PPE). DFT calculations were employed to improve
and develop force field parameters for MM/MD simulations. Many-body Green's
functions theory within the GW approximation and the Bethe-Salpeter equation
were utilized to describe excited states of the systems. Reliability of the
excitation energies based on the MM/MD conformations was examined and compared
to the excitation energies from DFT conformations. The results show an overall
agreement between the optical excitations based on MM/MD conformations and DFT
conformations. This allows for calculation of excitation energies based on
MM/MD conformations.

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


title: Advection equation analysed by two-timing method

abstract:
  The aim of this paper is to study and classify the multiplicity of
distinguished limits and asymptotic solutions for the advection equation with a
general oscillating velocity field with the systematic use of the two-timing
method. Our results are:
  (i) the dimensionless advection equation contains two independent small
parameters, which represent the ratio of two characteristic time-scales and the
spatial amplitudes of oscillations; the scaling of the variables and parameters
contains Strouhal number;
  (ii) an infinite sequence of distinguished limits has been identified; this
sequence corresponds to the successive degenerations of a drift velocity;
  (iii) we have derived the averaged and oscillatory equations for the first
four distinguished limits; derivations are performed up to the forth orders in
small parameters;
  (v) we have shown, that each distinguish limit solution generates an infinite
number of parametric solutions; these solutions differ from each other by the
slow time-scale and the amplitude of prescribed velocity;
  (vi) we have discovered the inevitable appearance of pseudo-diffusion, which
appears as a Lie derivative of the averaged tensor of quadratic displacements;
we have clarified the meaning of pseudo-diffusion using a simple example;
  (vii) our main methodological result is the introduction of a logical order
into the area and classification of an infinite number of asymptotic solutions;
we hope that it can help to study the similar problems for more complex
systems;
  (viii) since in our calculations we do not employ any additional assumptions,
our study can be used as a test for the validity of the two-timing hypothesis;
  (ix) the averaged equations for five different types of oscillating velocity
fields have been considered as the examples of different drifts and
pseudo-diffusion.


title:
Comparison of theoretical elastic couple stress predictions with
  physical experiments for pure torsion

abstract:
  Several different versions of couple stress theory have appeared in the
literature, including the indeterminate Mindlin-Tiersten-Koiter couple stress
theory (MTK-CST), indeterminate symmetric modified couple stress theory (M-CST)
and determinate skew-symmetric consistent couple stress theory (C-CST). First,
the solutions within each of these theories for pure torsion of cylindrical
bars composed of isotropic elastic material are presented and found to provide
a remarkable basis for comparison with observed physical response. In
particular, recent novel physical experiments to characterize torsion of
micro-diameter copper wires in quasi-static tests show no significant size
effect in the elastic range. This result agrees with the prediction of the
skew-symmetric C-CST that there is no size effect for torsion of an elastic
circular bar in quasi-static loading, because the mean curvature tensor
vanishes in a pure twist deformation. On the other hand, solutions within the
other two theories exhibit size-dependent torsional response, which depends
upon either one or two additional material parameters, respectively, for the
indeterminate symmetric M-CST or indeterminate MTK-CST. Results are presented
to illustrate the magnitude of the expected size-dependence within these two
theories in torsion. Interestingly, if the material length scales for copper in
these two theories with size-dependent torsion is on the order of microns or
larger, then the recent physical experiments in torsion would align only with
the self-consistent skew-symmetric couple stress theory, which inherently shows
no size effect.


title:
On a possibility of observation of quantum gravitational effect by the
  cosmic laser ranging

abstract:
  Physical interpretation of Lie algebra of de Sitter group is given for Snyder
theory of quantum space-time. Feasible means of its experimental validation are
pointed out.


title:
Time and position resolution of high granularity, high counting rate
  MRPC for the inner zone of the CBM-TOF wall

abstract:
  Multi-gap RPC prototypes with readout on a multi-strip electrode were
developed for the small polar angle region of the CBM-TOF subdetector, the most
demanding zone in terms of granularity and counting rate. The prototypes are
based on low resistivity ($\sim$10$^{10}$ $\Omega$cm) glass electrodes for
performing in high counting rate environment. The strip width/pitch size was
chosen such to fulfill the impedance matching with the front-end electronics
and the granularity requirements of the innermost zone of the CBM-TOF wall. The
in-beam tests using secondary particles produced in heavy ion collisions on a
Pb target at SIS18 - GSI Darmstadt and SPS - CERN were focused on the
performance of the prototype in conditions similar to the ones expected at
SIS100/FAIR. An efficiency larger than 98\% and a system time resolution in the
order of 70~-~80~ps were obtained in high counting rate and high multiplicity
environment.


title:
Robust imaging of hippocampal inner structure at 7T: in vivo acquisition
  protocol and methodological choices

abstract:
  OBJECTIVE:Motion-robust multi-slab imaging of hippocampal inner structure in
vivo at 7T.MATERIALS AND METHODS:Motion is a crucial issue for ultra-high
resolution imaging, such as can be achieved with 7T MRI. An acquisition
protocol was designed for imaging hippocampal inner structure at 7T. It relies
on a compromise between anatomical details visibility and robustness to motion.
In order to reduce acquisition time and motion artifacts, the full slab
covering the hippocampus was split into separate slabs with lower acquisition
time. A robust registration approach was implemented to combine the acquired
slabs within a final 3D-consistent high-resolution slab covering the whole
hippocampus. Evaluation was performed on 50 subjects overall, made of three
groups of subjects acquired using three acquisition settings; it focused on
three issues: visibility of hippocampal inner structure, robustness to motion
artifacts and registration procedure performance.RESULTS:Overall, T2-weighted
acquisitions with interleaved slabs proved robust. Multi-slab registration
yielded high quality datasets in 96 % of the subjects, thus compatible with
further analyses of hippocampal inner structure.CONCLUSION:Multi-slab
acquisition and registration setting is efficient for reducing acquisition time
and consequently motion artifacts for ultra-high resolution imaging of the
inner structure of the hippocampus.


title:
Studying the brain from adolescence to adulthood through sparse
  multi-view matrix factorisations

abstract:
  Men and women differ in specific cognitive abilities and in the expression of
several neuropsychiatric conditions. Such findings could be attributed to sex
hormones, brain differences, as well as a number of environmental variables.
Existing research on identifying sex-related differences in brain structure
have predominantly used cross-sectional studies to investigate, for instance,
differences in average gray matter volumes (GMVs). In this article we explore
the potential of a recently proposed multi-view matrix factorisation (MVMF)
methodology to study structural brain changes in men and women that occur from
adolescence to adulthood. MVMF is a multivariate variance decomposition
technique that extends principal component analysis to "multi-view" datasets,
i.e. where multiple and related groups of observations are available. In this
application, each view represents a different age group. MVMF identifies latent
factors explaining shared and age-specific contributions to the observed
overall variability in GMVs over time. These latent factors can be used to
produce low-dimensional visualisations of the data that emphasise age-specific
effects once the shared effects have been accounted for. The analysis of two
datasets consisting of individuals born prematurely as well as healthy controls
provides evidence to suggest that the separation between males and females
becomes increasingly larger as the brain transitions from adolescence to
adulthood. We report on specific brain regions associated to these variance
effects.


title:
Gaussian process modeling for stochastic multi-fidelity simulators, with
  application to fire safety

abstract:
  To assess the possibility of evacuating a building in case of a fire, a
standard method consists in simulating the propagation of fire, using finite
difference methods and takes into account the random behavior of the fire, so
that the result of a simulation is non-deterministic. The mesh fineness tunes
the quality of the numerical model, and its computational cost. Depending on
the mesh fineness, one simulation can last anywhere from a few minutes to
several weeks. In this article, we focus on predicting the behavior of the fire
simulator at fine meshes, using cheaper results, at coarser meshes. In the
literature of the design and analysis of computer experiments, such a problem
is referred to as multi-fidelity prediction. Our contribution is to extend to
the case of stochastic simulators the Bayesian multi-fidelity model proposed by
Picheny and Ginsbourger (2013) and Tuo et al. (2014).


title:
The ALMA-PILS survey: First detections of deuterated formamide and
  deuterated isocyanic acid in the interstellar medium

abstract:
  Formamide (NH$_2$CHO) has previously been detected in several star-forming
regions and is thought to be a precursor for different prebiotic molecules. Its
formation mechanism is still debated, however. Observations of formamide,
related species and their isopotologues may provide useful clues to the
chemical pathways leading to their formation. The Protostellar Interferometric
Line Survey (PILS) represents an unbiased high angular resolution and
sensitivity spectral survey of the low-mass protostellar binary IRAS 16293-2422
with the Atacama Large Millimeter/submillimeter Array (ALMA). We detect for the
first time the three singly deuterated forms of NH$_2$CHO (NH$_2$CDO, cis- and
trans-NHDCHO) as well as DNCO towards the component B of this binary source.
The images reveal that the different isotopologues are all present in the same
region. Based on observations of the $^{13}$C isotopologues of formamide and a
standard $^{12}$C/$^{13}$C ratio, the deuterium fractionation is found to be
similar for the three different forms with a value of about 2%. The DNCO/HNCO
ratio is also comparable to the D/H ratio of formamide ($\sim$1%). These
results are in agreement with the hypothesis that NH$_2$CHO and HNCO are
chemically related through grain surface formation.


title:
The eigenvalues of the sample covariance matrix of a multivariate
  heavy-tailed stochastic volatility model

abstract:
  We consider a multivariate heavy-tailed stochastic volatility model and
analyze the large-sample behavior of its sample covariance matrix. We study the
limiting behavior of its entries in the infinite-variance case and derive
results for the ordered eigenvalues and corresponding eigenvectors.
Essentially, we consider two different cases where the tail behavior either
stems from the i.i.d. innovations of the process or from its volatility
sequence. In both cases, we make use of a large deviations technique for
regularly varying time series to derive multivariate $\alpha$-stable limit
distributions of the sample covariance matrix. While we show that in the case
of heavy-tailed innovations the limiting behavior resembles that of completely
independent observations, we also derive that in the case of a heavy-tailed
volatility sequence the possible limiting behavior is more diverse, i.e.
allowing for dependencies in the limiting distributions which are determined by
the structure of the underlying volatility sequence.


title:
Measurement of the Radiation Energy in the Radio Signal of Extensive Air
  Showers as a Universal Estimator of Cosmic-Ray Energy

abstract:
  We measure the energy emitted by extensive air showers in the form of radio
emission in the frequency range from 30 to 80 MHz. Exploiting the accurate
energy scale of the Pierre Auger Observatory, we obtain a radiation energy of
15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV
arriving perpendicularly to a geomagnetic field of 0.24 G, scaling
quadratically with the cosmic-ray energy. A comparison with predictions from
state-of-the-art first-principle calculations shows agreement with our
measurement. The radiation energy provides direct access to the calorimetric
energy in the electromagnetic cascade of extensive air showers. Comparison with
our result thus allows the direct calibration of any cosmic-ray radio detector
against the well-established energy scale of the Pierre Auger Observatory.


title: Stellar Filaments in Self-Interacting Brans-Dicke Gravity

abstract:
  This paper is devoted to study cylindrically symmetric stellar filaments in
self-interacting Brans-Dicke gravity. For this purpose, we construct polytropic
filamentary models through generalized Lane-Emden equation in Newtonian regime.
The resulting models depend upon the values of cosmological constant (due to
scalar field) along with polytropic index and represent a generalization of the
corresponding models in general relativity. We also investigate fragmentation
of filaments by exploring the radial oscillations through stability analysis.
This stability criteria depends only upon the adiabatic index.


title:
Origin of Hinge-Like Mechanism in Single-Layer Black Phosphorus: the
  Angle-Angle Cross Interaction

abstract:
  The single-layer black phosphorus is characteristic for its puckered
configuration that possesses the hinge-like mechanism, which leads to the
highly anisotropic in-plane Poisson's ratios and the negative out-of-plane
Poisson's ratio. We reveal that the hinge-like mechanism can be attributed to
the angle-angle cross interaction, which, combined with the bond stretching and
angle bending interactions, is able to provide a good description of the
mechanical properties in the single-layer black phosphorus. We also propose a
nonlinear angle-angle cross interaction, which follows the form of the
Stillinger-Weber potential and is advantageous for molecular dynamics
simulations of single-layer black phosphorous under large deformations.


title: A note on Gekeler's h-function

abstract:
  We give a brief introduction to Drinfeld modular forms, concentrating on the
many equivalent constructions of the form h of weight q+1 and type 1, to which
we contribute some new characterizations involving Moore determinants, and an
application to the Weil pairing on Drinfeld modules. We also define Drinfeld
modular functions of non-zero type and provide a moduli interpretation of
these.


title: The Rubber band and the Ruler

abstract:
  In this short presentation, we address two somewhat separate issues. The
first one deals with the establishment (vs discovery) of what we call "physical
laws". The discussion runs on a "successive approximations" approach, suited to
our own thinking process, and aiming at the "simplest \emph{possible}
formulation ", as opposed to the idea of pre-existing laws to be discovered. In
the second part, we review briefly an approach to the (observed) metric
originating from a short distance fractal structure, and remind how a
symmetrical situation can arise from mere re-summations.


title:
Characterization and Inference of Graph Diffusion Processes from
  Observations of Stationary Signals

abstract:
  Many tools from the field of graph signal processing exploit knowledge of the
underlying graph's structure (e.g., as encoded in the Laplacian matrix) to
process signals on the graph. Therefore, in the case when no graph is
available, graph signal processing tools cannot be used anymore. Researchers
have proposed approaches to infer a graph topology from observations of signals
on its nodes. Since the problem is ill-posed, these approaches make
assumptions, such as smoothness of the signals on the graph, or sparsity
priors. In this paper, we propose a characterization of the space of valid
graphs, in the sense that they can explain stationary signals. To simplify the
exposition in this paper, we focus here on the case where signals were i.i.d.
at some point back in time and were observed after diffusion on a graph. We
show that the set of graphs verifying this assumption has a strong connection
with the eigenvectors of the covariance matrix, and forms a convex set. Along
with a theoretical study in which these eigenvectors are assumed to be known,
we consider the practical case when the observations are noisy, and
experimentally observe how fast the set of valid graphs converges to the set
obtained when the exact eigenvectors are known, as the number of observations
grows. To illustrate how this characterization can be used for graph recovery,
we present two methods for selecting a particular point in this set under
chosen criteria, namely graph simplicity and sparsity. Additionally, we
introduce a measure to evaluate how much a graph is adapted to signals under a
stationarity assumption. Finally, we evaluate how state-of-the-art methods
relate to this framework through experiments on a dataset of temperatures.


title: On Causality in Dynamical Systems

abstract:
  Discovery of causal relations is fundamental for understanding the dynamics
of complex systems. While causal interactions are well defined for acyclic
systems that can be separated into causally effective subsystems, a
mathematical definition of gradual causal interaction is still lacking for
nonseparable dynamical systems. The solution proposed here is analytically
tractable for time discrete chaotic maps and is shown to fulfill basic
requirements for causality measures. It implies a method for determination of
directed effective influences using pairs of measurements from dynamical
systems. Applications to time series from systems of coupled differential
equations and linear stochastic systems demonstrate its general utility.


title:
Variations of selective separability and tightness in function spaces
  with set open topologies

abstract:
  We study tightness properties and selective versions of separability in
bitopological function spaces endowed with set-open topologies.


title:
Application of the Principle of Maximum Conformality to the
  Hadroproduction of the Higgs Boson at the LHC

abstract:
  We present improved pQCD predictions for Higgs boson hadroproduction at the
Large Hadronic Collider (LHC) by applying the Principle of Maximum Conformality
(PMC), a procedure which resums the pQCD series using the renormalization group
(RG), thereby eliminating the dependence of the predictions on the choice of
the renormalization scheme while minimizing sensitivity to the initial choice
of the renormalization scale. In previous pQCD predictions for Higgs boson
hadroproduction, it has been conventional to assume that the renormalization
scale $\mu_r$ of the QCD coupling $\alpha_s(\mu_r)$ is the Higgs mass, and then
to vary this choice over the range $1/2 m_H < \mu_r < 2 m_H $ in order to
estimate the theory uncertainty. However, this error estimate is only sensitive
to the non-conformal $\beta$ terms in the pQCD series, and thus it fails to
correctly estimate the theory uncertainty in cases where pQCD series has large
higher order contributions, as is the case for Higgs boson hadroproduction.
Furthermore, this \mbox{\it ad hoc} choice of scale and range gives pQCD
predictions which depend on the renormalization scheme being used, in
contradiction to basic RG principles. In contrast, after applying the PMC, we
obtain next-to-next-to-leading order RG resummed pQCD predictions for Higgs
boson hadroproduction which are renormalization-scheme independent and have
minimal sensitivity to the choice of the initial renormalization scale. Taking
$m_H=125$ GeV, the PMC predictions for the $p p \to H X$ Higgs inclusive
hadroproduction cross-sections for various LHC center-of-mass energies and the
fiducial cross section $\sigma_{\rm fid}(pp\to H\to\gamma\gamma)$ are
presented...... The PMC predictions show better agreement with the ATLAS
measurements than the LHC-XS predictions which are based on conventional
renormalization scale-setting.


title: Cosmological perturbation theory and quantum gravity

abstract:
  It is shown how cosmological perturbation theory arises from a fully
quantized perturbative theory of quantum gravity. Central for the derivation is
a non-perturbative concept of gauge-invariant local observables by means of
which perturbative invariant expressions of arbitrary order are generated. In
particular, in the linearised theory, first order gauge-invariant observables
familiar from cosmological perturbation theory are recovered. Explicit
expressions of second order quantities are presented as well.


title: Bipolar rings from jet-inflated bubbles around evolved binary stars

abstract:
  We show that a fast wind that expands into a bipolar nebula composed of two
opposite jet-inflated bubbles can form a pair of bipolar rings around giant
stars. Our model assumes three mass loss episodes: a spherical slow and dense
shell, two opposite jets, and a spherical fast wind. We use the FLASH
hydrodynamical code in three-dimensions to simulate the flow, and obtain the
structure of the nebula. We assume that the jets are launched from an accretion
disk around a stellar companion to the giant star. The accretion disk is
assumed to be formed when the primary giant star and the secondary star suffer
a strong interaction accompanied by a rapid mass transfer process from the
primary to the secondary star, mainly a main sequence star. Later in the
evolution the primary star is assumed to shrink and blow a fast tenuous wind
that interacts with the dense gas on the surface of the bipolar structure. We
assume that the dense mass loss episode before the jets are launched is
spherically symmetric. Our results might be applicable to some planetary
nebulae, and further emphasize the large variety of morphological features that
can be formed by jets. But we could not reproduce some of the properties of the
outer rings of SN1987A. It seems that some objects, like SN1987A, require a
pre-jets mass loss episode with a mass concentration at mid-latitudes.


title: One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

abstract:
  A combination of variable-temperature neutron scattering, reverse Monte Carlo
analysis and direct Monte Carlo simulation is used to characterise the
emergence of magnetic order in the metal--organic framework (MOF) Tb(HCOO)$_3$
over the temperature range 100 K to 1.6 K $=T_{\rm N}$. We show that the
magnetic transition at $T_{\rm N}$ involves one-dimensional ferromagnetic
ordering to a partially-ordered state related to the triangular Ising
antiferromagnet. In this phase, the direction of magnetisation of ferromagnetic
chains tends to alternate between neighbouring chains but this alternation is
frustrated and is not itself ordered. In neutron scattering measurements this
partial order gives rise to Bragg-like peaks, which cannot be interpreted using
conventional magnetic crystallography without resort to unphysical spin models.
The existence of low-dimensional magnetic order in Tb(HCOO)$_3$ is stabilised
by the contrasting strength of inter- and intra-chain magnetic coupling, itself
a consequence of the underlying MOF architecture. Our results demonstrate how
MOFs may provide an attractive if as yet under-explored platform for the
realisation and investigation of low-dimensional physics.


title:
Stable pairs with descendents on local surfaces I: the vertical
  component

abstract:
  We study the full stable pair theory --- with descendents --- of the
Calabi-Yau 3-fold $X=K_S$, where $S$ is a surface with a smooth canonical
divisor $C$.
  By both $\mathbb C^*$-localisation and cosection localisation we reduce to
stable pairs supported on thickenings of $C$ indexed by partitions. We show
that only strict partitions contribute, and give a complete calculation for
length-1 partitions. The result is a surprisingly simple closed product formula
for these "vertical" thickenings.
  This gives all contributions for the curve classes $[C]$ and $2[C]$ (and
those which are not an integer multiple of the canonical class). Here the
result verifies, via the descendent-MNOP correspondence, a conjecture of
Maulik-Pandharipande, as well as various results about the Gromov-Witten theory
of $S$ and spin Hurwitz numbers.


title:
Proofs of the Technical Results Justifying an Algorithm of Reactive 3D
  Navigation for a Surface Scan by a Nonholonomic Mobile Robot

abstract:
  A single nonholonomic under-actuated mobile robot with a bounded control
range travels in a 3D workspace. This workspace also hosts a compact unknown
domain with a smooth boundary. The robot has access to the horizontal distance
to this domain and to a certain direction (typically, vertical) in the space,
along with its coordinate (typically, altitude) in this direction. We present a
new navigation law that drives the robot to the desired distance to the domain
and ensures subsequent full scan of its surface within a desired range of
"altitudes". The proposed strategy is computationally inexpensive and achieves
full scan at the lowest control level via generating the current control as a
simple, reflex-like reaction to the current observation. The paper presents and
proves key technical facts underlying mathematically rigorous analysis and
justification of the proposed guidance approach.


title: Galaxy clusters, type Ia supernovae and the fine structure constant

abstract:
  As is well known, measurements of the Sunyaev-Zeldovich effect can be
combined with observations of the X-ray surface brightness of galaxy clusters
to estimate the angular diameter distance to these structures. In this paper,
we show that this technique depends on the fine structure constant, $\alpha$.
Therefore, if $\alpha$ is a time-dependent quantity, e.g., $\alpha=\alpha_0
\phi(z)$, where $\phi$ is a function of redshift, we argue that current data do
not provide the real angular diameter distance, $D_{\rm{A}}(z)$, to the cluster
but instead $D_A^{data}(z) = \phi(z)^2 D_{\rm{A}}(z)$. We use this result to
derive constraints on a possible variation of $\alpha$ for a class of dilaton
runaway models considering a sample of 25 measurements of $D_A^{data}(z)$ in
redshift range $0.023 < z < 0.784$ and estimates of $D_{\rm{A}}(z)$ from
current type Ia supernovae observations. We find no significant indication of
variation of $\alpha$ with the present data.


title: Automorphisms of Deitmar schemes, I. Functoriality and Trees

abstract:
  In a recent paper [3], the authors introduced a map $\mathcal{F}$ which
associates a Deitmar scheme (which is defined over the field with one element,
denoted by $\mathbb{F}_1$) with any given graph $\Gamma$. By base extension, a
scheme $\mathcal{X}_k = \mathcal{F}(\Gamma) \otimes_{\mathbb{F}_1} k$ over any
field $k$ arises. In the present paper, we will show that all these mappings
are functors, and we will use this fact to study automorphism groups of the
schemes $\mathcal{X}_k$. Several automorphism groups are considered:
combinatorial, topological, and scheme-theoretic groups, and also groups
induced by automorphisms of the ambient projective space. When $\Gamma$ is a
finite tree, we will give a precise description of the combinatorial and
projective groups, amongst other results.


title:
Educational multi-touch applications, number sense, and the homogenizing
  role of the educator

abstract:
  As part of an educational project proposed in Italian preschools, an educator
followed a tested protocol proposing two chosen iPad apps to children of ages 5
to 6. Though her interventions were supposedly aimed at strengthening the
number sense of the children, the result was a homogenization of their schemes,
in various cases seemingly inhibiting development of number sense.


title: On homogeneous Besov spaces for $1D$ Hamiltonians without zero resonance

abstract:
  We consider 1-D Laplace operator with short range potential V(x), such that
$$(1+|x|)^\gamma V(x) \in L^1(R), \ \ \gamma > 1.$$ We study the equivalence of
classical homogeneous Besov type spaces $\dot{B}^s_p(R)$, $p \in (1,\infty)$
and the corresponding perturbed homogeneous Besov spaces associated with the
perturbed Hamiltonian $\mathcal{H}= -\partial_x^2 + V(x)$ on the real line. It
is shown that the assumptions $1/p < \gamma -1$ and zero is not a resonance
guarantee that the perturbed and unperturbed homogeneous Besov norms of order
$s \in [0,1/p)$ are equivalent. As a corollary, the corresponding wave
operators leave classical homogeneous Besov spaces of order $s \in [0,1/p)$
invariant.


title:
Maintaining dragging and the pivot invariant in processes of conjecture
  generation

abstract:
  In this paper, we analyze processes of conjecture generation in the context
of open problems proposed in a dynamic geometry environment, when a particular
dragging modality, maintaining dragging, is used. This involves dragging points
while maintaining certain properties, controlling the movement of the figures.
Our results suggest that the pragmatic need of physically controlling the
simultaneous movements of the different parts of figures can foster the
production of two chains of successive properties, hinged together by an
invariant that we will call pivot invariant. Moreover, we show how the
production of these chains is tied to the production of conjectures and to the
processes of argumentation through which they are generated.


title: From conjecture generation by maintaining dragging to proof

abstract:
  In this paper we propose a hypothesis about how different uses of maintaining
dragging, either as a physical tool in a dynamic geometry environment or as a
psychological tool for generating conjectures can influence subsequent
processes of proving. Through two examples we support the hypothesis that using
maintaining dragging as a physical tool may foster cognitive rupture between
the conjecturing phase and the proof, while using it as a psychological tool
may foster cognitive unity between them.


title: Stability for line solitary waves of Zakharov-Kuznetsov equation

abstract:
  In this paper, we consider the stability for line solitary waves of the two
dimensional Zakharov-Kuznetsov equation on $\mathbb{R}\times\mathbb{T}_L$ which
is one of a high dimensional generalization of Korteweg-de Vries equation ,
where $\mathbb{T}_L$ is the torus with the period $2\pi L$. The orbital and
asymptotic stability of the one soliton of Korteweg-de Vries equation on the
energy space has been proved by Benjamin, Pego and Weinstein and Martel and
Merle. We regard the one soliton of Korteweg-de Vries equation as a line
solitary wave of Zakharov-Kuznetsov equation on $\mathbb{R}\times\mathbb{T}_L$.
We prove the stability and the transverse instability of the line solitary
waves of Zakharov-Kuznetsov equation by applying Evans' function method and the
argument of Rousset and Tzvetkov. Moreover, we prove the asymptotic stability
for the orbitally stable line solitary wave of Zakharov-Kuznetsov equation by
using the argument of Martel and Merle, a Liouville type theorem and a
corrected virial type estimate.


title: System Intelligence: Model, Bounds and Algorithms

abstract:
  We present a general framework for understanding system intelligence, i.e.,
the level of system smartness perceived by users, and propose a novel metric
for measuring intelligence levels of dynamical human-in-the-loop systems,
defined to be the maximum average reward obtained by proactively serving user
demands, subject to a resource constraint. Our metric captures two important
elements of smartness, i.e., being able to know what users want and pre-serve
them, and achieving good resource management while doing so. We provide an
explicit characterization of the system intelligence, and show that it is
jointly determined by user demand volume (opportunity to impress), demand
correlation (user predictability), and system resource and action costs
(flexibility to pre-serve).
  We then propose an online learning-aided control algorithm called
Learning-aided Budget-limited Intelligent System Control (\mtt{LBISC}). We show
that \lbisc{} achieves an intelligence level that is within
$O(N(T)^{-\frac{1}{2}}+\epsilon)$ of the highest level, where $N(T)$ represents
the number of data samples collected within a learning period $T$ and is
proportional to the user population size in the system, while guaranteeing an
$O(\max( N(T)^{-\frac{1}{2}}/\epsilon, \log(1/\epsilon)^2))$ average resource
deficit. Moreover, we show that \lbisc{} possesses an $O(\max(
N(T)^{-\frac{1}{2}}/\epsilon$, $ \log(1/\epsilon)^2)+T)$ convergence time,
which is much smaller compared to the $\Theta(1/\epsilon)$ time required for
non-learning based algorithms. The analysis of \lbisc{} rigorously quantifies
the impacts of data and user population (captured by $N(T)$), learning
(captured by our learning method), and control (captured by \lbisc) on
achievable system intelligence, and provides novel insight and guideline into
designing future smart systems.


title:
Whitney Smooth Families of Invariant Tori within the Reversible Context
  2 of KAM Theory

abstract:
  We prove a general theorem on the persistence of Whitney infinitely smooth
families of invariant tori in the reversible context 2 of KAM theory. This
context refers to the situation where dim Fix G < (codim T)/2 where Fix G is
the fixed point manifold of the reversing involution G and T is the invariant
torus in question. Our result is obtained as a corollary of the theorem by
H.W.Broer, M.-C.Ciocci, H.Hanssmann, and A.Vanderbauwhede of 2009 concerning
quasi-periodic stability of invariant tori with singular "normal" matrices in
reversible systems.


title:
Nodal sets of Laplace eigenfunctions: polynomial upper estimates of the
  Hausdorff measure

abstract:
  Let $\mathbb{M}$ be a compact $C^\infty$-smooth Riemannian manifold of
dimension $n$, $n\geq 3$, and let $\varphi_\lambda: \Delta_M \varphi_\lambda +
\lambda \varphi_\lambda = 0$ denote the Laplace eigenfunction on $\mathbb{M}$
corresponding to the eigenvalue $\lambda$. We show that $$H^{n-1}(\{
\varphi_\lambda=0\}) \leq C \lambda^{\alpha},$$ where $\alpha>1/2$ is a
constant, which depends on $n$ only, and $C>0$ depends on $\mathbb{M}$ . This
result is a consequence of our study of zero sets of harmonic functions on
$C^\infty$-smooth Riemannian manifolds. We develop a technique of propagation
of smallness for solutions of elliptic PDE that allows us to obtain local
bounds from above for the volume of the nodal sets in terms of the frequency
and the doubling index.


title: A Vizing-like theorem for union vertex-distinguishing edge coloring

abstract:
  We introduce a variant of the vertex-distinguishing edge coloring problem,
where each edge is assigned a subset of colors. The label of a vertex is the
union of the sets of colors on edges incident to it. In this paper we
investigate the problem of finding a coloring with the minimum number of colors
where every vertex receives a distinct label. Finding such a coloring
generalizes several other well-known problems of vertex-distinguishing
colorings in graphs.We show that for any graph (without connected component
reduced to an edge or a single vertex), the minimum number of colors for which
such a coloring exists can only take 3possible values depending on the order of
the graph. Moreover, we provide the exact value for paths, cycles and complete
binary trees.


title:
Nodal sets of Laplace eigenfunctions: proof of Nadirashvili's conjecture
  and of the lower bound in Yau's conjecture

abstract:
  Let $u$ be a harmonic function in the unit ball $B(0,1) \subset
\mathbb{R}^n$, $n \geq 3$, such that $u(0)=0$. Nadirashvili conjectured that
there exists a positive constant $c$, depending on the dimension $n$ only, such
that $H^{n-1}(\{u=0 \}\cap B) \geq c$. We prove Nadirashvili's conjecture as
well as its counterpart on $C^\infty$-smooth Riemannian manifolds. The latter
yields the lower bound in Yau's conjecture. Namely, we show that for any
compact $C^\infty$-smooth Riemannian manifold $M$ (without boundary) of
dimension $n$ there exists $c>0$ such that for any Laplace eigenfunction
$\varphi_\lambda$ on $M$, which corresponds to the eigenvalue $\lambda$, the
following inequality holds: $c \sqrt \lambda \leq H^{n-1}(\{\varphi_\lambda
=0\})$.


title: Teleparallel loop quantum cosmology in a system of intersecting branes

abstract:
  Recently, some authors have removed the big bang singularity in teleparallel
Loop Quantum Cosmology (LQC) and have shown that the universe may undergo a
number of oscillations. We investigate the origin of this type of teleparallel
theory in a system of intersecting branes in M-theory in which the angle
between them changes with time. This system is constructed by two intersecting
anti-D8-branes, one compacted D4-brane and the other a D3-brane. These branes
are built by joining M0-branes which develop in decaying fundamental strings.
The compacted D4-brane is located between two intersecting anti-D8 branes and
glues to one of them. Our universe is located on the D3 brane which wraps the
D4 brane from one end and sticks to one of the anti-D8 branes from another one.
In this system, there are three types of fields, corresponding to compacted D4
branes, intersecting branes and D3-branes. These fields interact with each
other and make the angle between branes oscillate. By decreasing this angle and
approaching the intersecting anti-D8 branes towards each other, the D4 brane
rolls, the D3 brane wraps around the D4 brane, and t he universe contracts. By
separating the intersecting branes and increasing the angle, the D4 brane rolls
in the opposite direction, the D3 brane separates from it and the expansion
branch begins. Also, the interaction between branes in this system gives us the
exact form of the relevant Lagrangian for teleparallel LQC.


title: Self-Duality and Self-Similarity of Little String Orbifolds

abstract:
  We study a class of ${\cal N}=(1,0)$ little string theories obtained from
orbifolds of M-brane configurations. These are realised in two different ways
that are dual to each other: either as $M$ parallel M5-branes probing a
transverse $A_{N-1}$ singularity or $N$ M5-branes probing an $A_{M-1}$
singularity. These backgrounds can further be dualised into toric, non-compact
Calabi-Yau threefolds $X_{N,M}$ which have double elliptic fibrations and thus
give a natural geometric description of T-duality of the little string
theories. The little string partition functions are captured by the topological
string partition function of $X_{N,M}$. We analyse in detail the free energies
$\Sigma_{N,M}$ associated with the latter in a special region in the K\"ahler
moduli space of $X_{N,M}$ and discover a remarkable property: in the
Nekrasov-Shatashvili-limit, $\Sigma_{N,M}$ is identical to $NM$ times
$\Sigma_{1,1}$. This entails that the BPS degeneracies for any $(N,M)$ can
uniquely be reconstructed from the $(N,M)=(1,1)$ configuration, a property we
refer to as self-similarity. Moreover, as $\Sigma_{1,1}$ is known to display a
number of recursive structures, BPS degeneracies of little string
configurations for arbitrary $(N,M)$ as well acquire additional symmetries.
These symmetries suggest that in this special region the two little string
theories described above are self-dual under T-duality.


title: GLEU Without Tuning

abstract:
  The GLEU metric was proposed for evaluating grammatical error corrections
using n-gram overlap with a set of reference sentences, as opposed to
precision/recall of specific annotated errors (Napoles et al., 2015). This
paper describes improvements made to the GLEU metric that address problems that
arise when using an increasing number of reference sets. Unlike the originally
presented metric, the modified metric does not require tuning. We recommend
that this version be used instead of the original version.


title: Generalized-Seniority Pattern and Thermal Properties in Even Sn Isotopes

abstract:
  Even tin isotopes of mass number $A = 108 \sim 124$ are calculated with
realistic interactions in the generalized-seniority approximation of the
nuclear shell model. For each nucleus, we compute the lowest ten thousand
states ($5000$ of each parity) up to around $8$ MeV in excitation energy, by
allowing as many as four broken pairs. The lowest fifty eigen energies of each
parity are compared with the exact results of the large-scale shell-model
calculation. The wavefunctions of the mid-shell nuclei show a clear pattern of
the stepwise breakup of condensed coherent pairs with increasing excitation
energy. We also compute in the canonical ensemble the thermal properties --
level density, entropy, and specific heat -- in relation to the thermal pairing
phase transition.


title: Storage-ring Electron Cooler for Relativistic Ion Beams

abstract:
  Application of electron cooling at ion energies above a few GeV has been
limited due to reduction of electron cooling efficiency with energy and
difficulty in producing and accelerating a high-current high-quality electron
beam. A high-current storage-ring electron cooler offers a solution to both of
these problems by maintaining high cooling beam quality through
naturally-occurring synchrotron radiation damping of the electron beam.
However, the range of ion energies where storage-ring electron cooling can be
used has been limited by low electron beam damping rates at low ion energies
and high equilibrium electron energy spread at high ion energies. This paper
reports a development of a storage ring based cooler consisting of two sections
with significantly different energies: the cooling and damping sections. The
electron energy and other parameters in the cooling section are adjusted for
optimum cooling of a stored ion beam. The beam parameters in the damping
section are adjusted for optimum damping of the electron beam. The necessary
energy difference is provided by an energy recovering SRF structure. A
prototype linear optics of such storage-ring cooler and initial tracking
simulations are presented and some potential issues such as coherent
synchrotron radiation and beam break up are discussed.


title:
Nodal sets of Laplace eigenfunctions: estimates of the Hausdorff measure
  in dimension two and three

abstract:
  Let $\Delta_M$ be the Laplace operator on a compact $n$-dimensional
Riemannian manifold without boundary. We study the zero sets of its
eigenfunctions $u:\Delta u + \lambda u =0$. In dimension $n=2$ we refine the
Donnelly-Fefferman estimate by showing that $H^1(\{u=0 \})\le
C\lambda^{3/4-\beta}$, $\beta \in (0,1/4)$. The proof employs the
Donnelli-Fefferman estimate and a combinatorial argument, which also gives a
lower (non-sharp) bound in dimension $n=3$: $H^2(\{u=0\})\ge c\lambda^\alpha$,
$\alpha \in (0,1/2)$. The positive constants $c,C$ depend on the manifold,
$\alpha$ and $\beta$ are universal.


title: Quantum Information Approach to Dynamical Diffraction Theory

abstract:
  We present a simplified model for dynamical diffraction of particles through
a periodic thick perfect crystal based on repeated application of a coherent
beam splitting unitary at coarse-grained lattice sites. By demanding
translational invariance and a computationally tractable number of sites in the
coarse-graining we show how this approach reproduces many results typical of
dynamical diffraction theory and experiments. This approach has the benefit of
being applicable in the thick, thin, and intermediate crystal regimes. The
method is applied to a three-blade neutron interferometer to predict the output
beam profiles, interference patterns, and contrast variation.


title: Fundamental Limits of Spectrum Sharing Full-Duplex Multicell Networks

abstract:
  This paper studies the degrees of freedom of full-duplex multicell networks
that share the spectrum among multiple cells in a non-orthogonal setting. In
the considered network, we assume that {\em full-duplex} base stations with
multiple transmit and receive antennas communicate with multiple single-antenna
mobile users. By spectrum sharing among multiple cells and (simultaneously)
enabling full-duplex radio, the network can utilize the spectrum more flexibly,
but, at the same time, the network is subject to multiple sources of
interference compared to a network with separately dedicated bands for distinct
cells and uplink--downlink traffic. Consequently, to take advantage of the
additional freedom in utilizing the spectrum, interference management is a
crucial ingredient. In this work, we propose a novel strategy based on
interference alignment which takes into account inter-cell interference and
intra-cell interference caused by spectrum sharing and full-duplex to establish
a general achievability result on the sum degrees of freedom of the considered
network. Paired with an upper bound on the sum degrees of freedom, which is
tight under certain conditions, we demonstrate how spectrum sharing and
full-duplex can significantly improve the throughput over conventional cellular
networks, especially for a network with large number of users and/or cells.


title:
Hydrogen atom in a quantum plasma environment under the influence of
  Aharonov-Bohm flux and electric and magnetic fields

abstract:
  This study presents the confinement influences of Aharonov-Bohm-flux
(AB-flux), electric and magnetic fields directed along $z$-axis and encircled
by quantum plasmas, on the hydrogen atom. The all-inclusive effects result to a
strongly attractive system while the localizations of quantum levels change and
the eigenvalues decrease. We find that, the combined effect of the fields is
stronger than solitary effect and consequently, there is a substantial shift in
the bound state energy of the system. We also find that to perpetuate a
low-energy medium for hydrogen atom in quantum plasmas, strong electric field
and weak magnetic field are required, where AB-flux field can be used as a
regulator. The application of perturbation technique utilized in this paper is
not restricted to plasma physics, it can also be applied in molecular physics.


title: A new approach for strong-field ionization

abstract:
  A model describing the electronic transitions in an atom subject to a strong
high frequency laser pulse is proposed in the velocity gauge. The model
accounts for the initial state coupling with the the remaining discrete and
continuum spectra. Continuum-continuum transitions are also taken into account
following well known strong-field approximation. A single integro-differential
equation for the initial state amplitude has been obtained. Exact numerical
solutions of this equation are computed and compared with the full time
dependent Schr{\"o}dinger equation solution for Hydrogen atoms. The initial
state amplitude is well described by two versions of the model: with and
without the continuum-continuum coupling model. However the electron energy
spectrum is only well described when the model accounts for the coupling
between continuum states. Improvement on SFA arise from using Coulomb final
wave function as well as regarding the initial state probability depletion.


title: Twisted Fock Representations of Noncommutative K\"ahler Manifolds

abstract:
  We introduce twisted Fock representations of noncommutative K\"ahler
manifolds and give their explicit expressions. The twisted Fock representation
is a representation of the Heisenberg like algebra whose states are constructed
by acting creation operators on a vacuum state. "Twisted" means that creation
operators are not hermitian conjugate of annihilation operators in this
representation. In deformation quantization of K\"ahler manifolds with
separation of variables formulated by Karabegov, local complex coordinates and
partial derivatives of the K\"ahler potential with respect to coordinates
satisfy the commutation relations between the creation and annihilation
operators. Based on these relations, we construct the twisted Fock
representation of noncommutative K\"ahler manifolds and give a dictionary to
translate between the twisted Fock representations and functions on
noncommutative K\"ahler manifolds concretely.


title: An $SU(2)_L$ Septet Scalar Linking to Radiative Neutrino Model

abstract:
  We study a radiative neutrino model with a SU(2) septet scalar with
hypercharge $Y=2$ where active neutrino mass is induced at a one-loop level.
Calculating a one-loop diagram, mass matrices for active neutrino is derived.
We also analyze lepton flavor violations, anomalous magnetic moment of muon and
the flavor violating Higgs decay $h \to \mu \tau$. Then sizable muon $g-2$ and
$\sim 1 \%$ of $BR(h \to \mu \tau)$ could be obtained in our set up.
Furthermore, the collider signature of the septet is discussed where we focus
on quadratically charged scalar at the LHC 14 TeV. We find that it could be
discovered up to $1.5$ TeV mass by searching multi charged lepton signal
events.


title: Super-biderivations of Lie superalgebras

abstract:
  In this paper we attempt to investigate the super-biderivations of Lie
superalgebras. Furthermore, we prove that all super-biderivations on the
centerless super-Virasoro algebras are inner super-biderivations. Finally, we
study the linear super commuting maps on the centerless super-Virasoro
algebras.


title:
The WSRT ZoA Perseus-Pisces Filament wide-field HI imaging survey I. HI
  catalogue and atlas

abstract:
  We present results of a blind 21cm HI-line imaging survey of a galaxy
overdensity located behind the Milky Way at $\ell,b$ $\approx$ 160 deg, 0.5
deg. The overdensity corresponds to a Zone-of-Avoidance crossing of the
Perseus-Pisces Supercluster filament. Although it is known that this filament
contains an X-ray galaxy cluster (3C129) hosting two strong radio galaxies,
little is known about galaxies associated with this potentially rich cluster
because of the high Galactic dust extinction. We mapped a sky area of $\sim$9.6
sq.deg using the Westerbork Synthesis Radio Telescope in a hexagonal mosaic of
35 pointings observed for 12 hours each, in the radial velocity range $cz =
2400 - 16600$ km/s. The survey has a sensitivity of 0.36 mJy/beam rms at a
velocity resolution of 16.5 km/s. We detected 211 galaxies, 62% of which have a
near-infrared counterpart in the UKIDSS Galactic Plane Survey. We present a
catalogue of the HI properties and an HI atlas containing total intensity maps,
position-velocity diagrams, global HI profiles and UKIDSS counterpart images.
For the resolved galaxies we also present HI velocity fields and radial HI
surface density profiles. A brief analysis of the structures outlined by these
galaxies finds that 87 of them lie at the distance of the Perseus-Pisces
Supercluster ($cz \sim 4000 - 8000$ km/s) and seem to form part of the 3C129
cluster. Further 72 detections trace an overdensity at a velocity of $cz
\approx$ 10000 km/s and seem to coincide with a structure predicted from mass
density reconstructions in the first 2MASS Redshift Survey.


title: On a mollifier of the perturbed Riemann zeta-function

abstract:
  The mollification $\zeta(s) + \zeta'(s)$ put forward by Feng is computed by
analytic methods coming from the techniques of the ratios conjectures of
$L$-functions. The current situation regarding the percentage of non-trivial
zeros of the Riemann zeta-function on the critical line is then clarified.


title: Efficient Reversible Data Hiding Algorithms Based on Dual Prediction

abstract:
  In this paper, a new reversible data hiding (RDH) algorithm that is based on
the concept of shifting of prediction error histograms is proposed. The
algorithm extends the efficient modification of prediction errors (MPE)
algorithm by incorporating two predictors and using one prediction error value
for data embedding. The motivation behind using two predictors is driven by the
fact that predictors have different prediction accuracy which is directly
related to the embedding capacity and quality of the stego image. The key
feature of the proposed algorithm lies in using two predictors without the need
to communicate additional overhead with the stego image. Basically, the
identification of the predictor that is used during embedding is done through a
set of rules. The proposed algorithm is further extended to use two and three
bins in the prediction errors histogram in order to increase the embedding
capacity. Performance evaluation of the proposed algorithm and its extensions
showed the advantage of using two predictors in boosting the embedding capacity
while providing competitive quality for the stego image.


title: On the 5G Wireless Communications at the Low Terahertz Band

abstract:
  Initiation of fourth generation (4G) mobile telecommunication system rollouts
fires the starting pistol for beyond 4G research activities. Whereas
technologies enhancing spectral efficiency have traditionally been the solution
to data rate and network capacity increase demands, due to the already advanced
techniques, returns of the even more complicated algorithms hardly worth the
complexity increase any longer. In addition, surging number of connected
devices now enables operative use of short-range communication methods. Also
considering the recently approved standards for the 60 gigahertz (GHz)
industrial, scientific and medical radio band, in this paper the transmission
windows around 300 GHz is proposed to be utilized for the fifth generation
wireless communication systems. Motivations for the low end of the terahertz
(THz) band are provided in accordance with market trends, and standardization
activities in higher frequencies are listed. Unified mathematical expressions
of the electromagnetic wave propagation mechanisms in the low-THz band are
presented. THz band device technologies are outlined and a complete survey of
the state-of-the-art low-THz band circuit blocks which are suitable for mass
market production is given. Future research directions are specified before the
conclusion of the paper.


title: Convolutive superposition for multicarrier cognitive radio systems

abstract:
  Recently, we proposed a spectrum-sharing paradigm for single-carrier
cognitive radio (CR) networks, where a secondary user (SU) is able to maintain
or even improve the performance of a primary user (PU) transmission, while also
obtaining a low-data rate channel for its own communication. According to such
a scheme, a simple multiplication is used to superimpose one SU symbol on a
block of multiple PU symbols.The scope of this paper is to extend such a
paradigm to a multicarrier CR network, where the PU employs an orthogonal
frequency-division multiplexing (OFDM) modulation scheme. To improve its
achievable data rate, besides transmitting over the subcarriers unused by the
PU, the SU is also allowed to transmit multiple block-precoded symbols in
parallel over the OFDM subcarriers used by the primary system. Specifically,
the SU convolves its block-precoded symbols with the received PU data in the
time-domain, which gives rise to the term convolutive superposition. An
information-theoretic analysis of the proposed scheme is developed, which
considers different amounts of network state information at the secondary
transmitter, as well as different precoding strategies for the SU. Extensive
simulations illustrate the merits of our analysis and designs, in comparison
with conventional CR schemes, by considering as performance indicators the
ergodic capacity of the considered systems.


title: Quartic amplitudes for Minkowski higher spin

abstract:
  The problem of finding general quartic interaction terms between fields of
higher helicities on the light-front is discussed from the point of view of
calculating the corresponding amplitudes directly from the cubic vertices using
BCFW recursion. Amplitude based no-go results that has appeared in the
literature are reviewed and discussed and it is pointed out how they may
perhaps be circumvented.


title: Dynamic Decomposition of Spatiotemporal Neural Signals

abstract:
  Neural signals are characterized by rich temporal and spatiotemporal dynamics
that reflect the organization of cortical networks. Theoretical research has
shown how neural networks can operate at different dynamic ranges that
correspond to specific types of information processing. Here we present a data
analysis framework that uses a linearized model of these dynamic states in
order to decompose the measured neural signal into a series of components that
capture both rhythmic and non-rhythmic neural activity. The method is based on
stochastic differential equations and Gaussian process regression. Through
computer simulations and analysis of magnetoencephalographic data, we
demonstrate the efficacy of the method in identifying meaningful modulations of
oscillatory signals corrupted by structured temporal and spatiotemporal noise.
These results suggest that the method is particularly suitable for the analysis
and interpretation of complex temporal and spatiotemporal neural signals.


title: A local and BRST-invariant Yang-Mills theory within the Gribov horizon

abstract:
  We present a local setup for the recently introduced BRST-invariant
formulation of Yang-Mills theories for linear covariant gauges that takes into
account the existence of gauge copies \`a la Gribov and Zwanziger. Through the
convenient use of auxiliary fields, including one of the Stueckelberg type, it
is shown that both the action and the associated nilpotent BRST operator can be
put in local form. Direct consequences of this fully local and BRST-symmetric
framework are drawn from its Ward identities: (i) an exact prediction for the
longitudinal part of the gluon propagator in linear covariant gauges that is
compatible with recent lattice results and (ii) a proof of the gauge-parameter
independence of all correlation functions of local BRST-invariant operators.


title:
Matrix Product Operators, Matrix Product States, and ab initio Density
  Matrix Renormalization Group algorithms

abstract:
  Current descriptions of the ab initio DMRG algorithm use two superficially
different languages: an older language of the renormalization group and
renormalized operators, and a more recent language of matrix product states and
matrix product operators. The same algorithm can appear dramatically different
when written in the two different vocabularies. In this work, we carefully
describe the translation between the two languages in several contexts. First,
we describe how to efficiently implement the ab-initio DMRG sweep using a
matrix product operator based code, and the equivalence to the original
renormalized operator implementation. Next we describe how to implement the
general matrix product operator/matrix product state algebra within a pure
renormalized operator-based DMRG code. Finally, we discuss two improvements of
the ab initio DMRG sweep algorithm motivated by matrix product operator
language: Hamiltonian compression, and a sum over operators representation that
allows for perfect computational parallelism. The connections and
correspondences described here serve to link the future developments with the
past, and are important in the efficient implementation of continuing advances
in ab initio DMRG and related algorithms.


title:
Direct optical interfacing of CVD diamond for deported NV-based sensing
  experiments

abstract:
  Nitrogen-vacancy (NV) defect in diamond is a very promising tool for numerous
sensing applications like magnetometry or thermometry. In this paper, we
demonstrate a compact and convenient device for magnetic field imaging where a
commercial single mode photonic crystal fibre is directly coupled to a
commercial CVD ppm diamond. We managed to excite and detect efficiently the
luminescence from an ensemble of NV centres and also to perform Electron Spin
Resonance (ESR) experiments where the NV hyperfine structure is perfectly
resolved under continuous excitation and measurement.


title:
Effective field theory for large logarithms in radiative corrections to
  electron proton scattering

abstract:
  Radiative corrections to elastic electron-proton scattering are analyzed in
effective field theory. A new factorization formula identifies all sources of
large logarithms in the limit of large momentum transfer, $Q^2\gg m_e^2$.
Explicit matching calculations are performed through two-loop order. A
renormalization analysis in soft-collinear effective theory is performed to
systematically compute and resum large logarithms. Implications for the
extraction of charge radii and other observables from scattering data are
discussed. The formalism may be applied to other lepton-nucleon scattering and
$e^+e^-$ annihilation processes.

categories: hep-ph hep-ex nucl-ex nucl-th physics.atom-ph


title:
Global Strong $L^p$ Well-Posedness of the 3D Primitive Equations with
  Heat and Salinity Diffusion

abstract:
  Consider the full primitive equations, i.e. the three dimensional primitive
equations coupled to the equation for temperature and salinity, and subject to
outer forces. It is shown that this set of equations is globally strongly
well-posed for arbitrary large initial data lying in certain interpolation
spaces, which are explicitly characterized as subspaces of $H^{2/p,p}$,
$1<p<\infty$, satisfying certain boundary conditions. In particular, global
well-posedeness of the full primitive equations is obtained for initial data
having less differentiability properties than $H^1$, hereby generalizing by
result by Cao and Titi (Ann. of Math. (2) 166 (2007), no. 1, 245-267) to the
case of non-smooth data. In addition, it is shown that the solutions are
exponentially decaying provided the outer forces possess this property.


title: A Non-Convex Blind Calibration Method for Randomised Sensing Strategies

abstract:
  The implementation of computational sensing strategies often faces
calibration problems typically solved by means of multiple, accurately chosen
training signals, an approach that can be resource-consuming and cumbersome.
Conversely, blind calibration does not require any training, but corresponds to
a bilinear inverse problem whose algorithmic solution is an open issue. We here
address blind calibration as a non-convex problem for linear random sensing
models in which we aim to recover an unknown signal from its projections on
sub-Gaussian random vectors, each of which is subject to an unknown
multiplicative factor (gain). To solve this optimisation problem we resort to
projected gradient descent starting from a suitable initialisation. An analysis
of this algorithm allows us to show that it converges to the global optimum
provided a sample complexity requirement is met, i.e., relating convergence to
the amount of information collected during the sensing process. Finally, we
present some numerical experiments in which our algorithm allows for a simple
solution to blind calibration of sensor gains in computational sensing
applications.


title: Consistent systems of linear differential and difference equations

abstract:
  We consider systems of linear differential and difference equations
\begin{eqnarray*} \partial Y(x) =A(x)Y(x), \sigma Y(x) =B(x)Y(x)
\end{eqnarray*} with $\partial = \frac{d}{dx}$, $\sigma$ a shift operator
$\sigma(x) = x+a$, $q$-dilation operator $\sigma(x) = qx$ or Mahler operator
$\sigma(x) = x^p$ and systems of two linear difference equations
\begin{eqnarray*} \sigma_1 Y(x) =A(x)Y(x), \sigma_2 Y(x) =B(x)Y(x)
\end{eqnarray*} with $(\sigma_1,\sigma_2)$ a sufficiently independent pair of
shift operators, pair of $q$-dilation operators or pair of Mahler operators.
Here $A(x)$ and $B(x)$ are $n\times n$ matrices with rational function entries.
Assuming a consistency hypothesis, we show that such system can be reduced to a
system of a very simple form. Using this we characterize functions satisfying
two linear scalar differential or difference equations with respect to these
operators. We also indicate how these results have consequences both in the
theory of automatic sets, leading to a new proof of Cobham's Theorem, and in
the Galois theories of linear difference and differential equations, leading to
hypertranscendence results.


title:
Epitaxial growth and thermodynamic stability of SrIrO3/SrTiO3
  heterostructures

abstract:
  Obtaining high-quality thin films of 5d transition metal oxides is essential
to explore the exotic semimetallic and topological phases predicted to arise
from the combination of strong electron correlations and spin-orbit coupling.
Here, we show that the transport properties of SrIrO3 thin films, grown by
pulsed laser deposition, can be optimized by considering the effect of
laser-induced modification of the SrIrO3 target surface. We further demonstrate
that bare SrIrO3 thin films are subject to degradation in air and are highly
sensitive to lithographic processing. A crystalline SrTiO3 cap layer deposited
in-situ is effective in preserving the film quality, allowing us to measure
metallic transport behavior in films with thicknesses down to 4 unit cells. In
addition, the SrTiO3 encapsulation enables the fabrication of devices such as
Hall bars without altering the film properties, allowing precise
(magneto)transport measurements on micro- and nanoscale devices.


title: The descent statistic on signed simsun permutations

abstract:
  In this paper we study the generating polynomials obtained by enumerating
signed simsun permutations by number of the descents. Properties of the
polynomials, including the recurrence relations and generating functions are
studied.


title: On the Emergence of Shortest Paths by Reinforced Random Walks

abstract:
  The co-evolution between network structure and functional performance is a
fundamental and challenging problem whose complexity emerges from the intrinsic
interdependent nature of structure and function. Within this context, we
investigate the interplay between the efficiency of network navigation (i.e.,
path lengths) and network structure (i.e., edge weights). We propose a simple
and tractable model based on iterative biased random walks where edge weights
increase over time as function of the traversed path length. Under mild
assumptions, we prove that biased random walks will eventually only traverse
shortest paths in their journey towards the destination. We further
characterize the transient regime proving that the probability to traverse
non-shortest paths decays according to a power-law. We also highlight various
properties in this dynamic, such as the trade-off between exploration and
convergence, and preservation of initial network plasticity. We believe the
proposed model and results can be of interest to various domains where biased
random walks and decentralized navigation have been applied.


title: Universality of (2+1)-dimensional restricted solid-on-solid models

abstract:
  Extensive dynamical simulations of Restricted Solid on Solid models in
$D=2+1$ dimensions have been done using parallel multisurface algorithms
implemented on graphics cards. Numerical evidence is presented that these
models exhibit KPZ surface growth scaling, irrespective of the step heights
$N$. We show that by increasing $N$ the corrections to scaling increase, thus
smaller step-sized models describe better the asymptotic, long-wave-scaling
behavior.

categories: cond-mat.stat-mech cond-mat.mtrl-sci cs.DC physics.comp-ph


title: Power variations and testing for co-jumps: the small noise approach

abstract:
  In this paper we study the effects of noise on the bipower variation (BPV),
realized volatility (RV) and testing for co-jumps in high-frequency data under
the small noise framework. We first establish asymptotic properties of the BPV
in this framework. In the presence of the small noise, the RV is asymptotically
biased and the additional asymptotic conditional variance term appears in its
limit distribution. We also give feasible estimation methods of the asymptotic
conditional variances of the RV. Second, we derive the asymptotic distribution
of the test statistic proposed in Jacod and Todorov(2009) under the presence of
small noise for testing the presence of co-jumps in two dimensional It\^o
semimartingale. In contrast to the setting in Jacod and Todorov(2009), we show
that the additional conditional asymptotic variance terms appear, and give
consistent estimation procedures for the asymptotic conditional variances in
order to make the test feasible. Simulation experiments show that our
asymptotic results give reasonable approximations in the finite sample cases.


title: Pulsation-triggered mass loss from AGB stars: the 60-day critical period

abstract:
  Low- and intermediate-mass stars eject much of their mass during the late,
red giant branch (RGB) phase of evolution. The physics of their strong stellar
winds is still poorly understood. In the standard model, stellar pulsations
extend the atmosphere, allowing a wind to be driven through radiation pressure
on condensing dust particles. Here we investigate the onset of the wind, using
nearby RGB stars drawn from the Hipparcos catalogue. We find a sharp onset of
dust production when the star first reaches a pulsation period of 60 days. This
approximately co-incides with the point where the star transitions to the first
overtone pulsation mode. Models of the spectral energy distributions show
stellar mass-loss rate suddenly increases at this point, by a factor of ~10
over the existing (chromospherically driven) wind. The dust emission is
strongly correlated with both pulsation period and amplitude, indicating
stellar pulsation is the main trigger for the strong mass loss, and determines
the mass-loss rate. Dust emission does not strongly correlate with stellar
luminosity, indicating radiation pressure on dust has little effect on the
mass-loss rate. RGB stars do not normally appear to produce dust, whereas dust
production by asymptotic giant branch stars appears commonplace, and is
probably ubiquitous above the RGB-tip luminosity. We conclude that the strong
wind begins with a step change in mass-loss rate, and is triggered by stellar
pulsations. A second rapid mass-loss-rate enhancement is suggested when the
star transitions to the fundamental pulsation mode, at a period of ~300 days.


title: Rayleigh scattering in the atmospheres of hot stars

abstract:
  Rayleigh scattering is a result of an interaction of photons with bound
electrons. Rayleigh scattering is mostly neglected in calculations of hot star
model atmospheres because most of the hydrogen atoms are ionized and the
heavier elements have a lower abundance than hydrogen. In atmospheres of some
chemically peculiar stars, helium overabundant regions containing singly
ionized helium are present and Rayleigh scattering can be a significant opacity
source.
  We evaluate the contribution of Rayleigh scattering by neutral hydrogen and
singly ionized helium in the atmospheres of hot stars with solar composition
and in the atmospheres of helium overabundant stars. We computed several series
of model atmospheres using the TLUSTY code and emergent fluxes using the
SYNSPEC code. These models describe atmospheres of main sequence B-type stars
with different helium abundance. We used an existing grid of models for
atmospheres with solar chemical composition and we calculated an additional
grid for helium-rich stars with $N$(He)/$N$(H)=10.
  Rayleigh scattering by neutral hydrogen can be neglected in atmospheres of
hot stars, while Rayleigh scattering by singly ionized helium can be a
non-negligible opacity source in some hot stars, especially in helium-rich
stars.


title:
Paracontrolled calculus and Funaki-Quastel approximation for the KPZ
  equation

abstract:
  In this paper, we consider the approximating KPZ equation introduced by
Funaki and Quastel [2], which is suitable for studying invariant measures. They
showed that the stationary solution of the approximating equation converges to
the Cole-Hopf solution of the KPZ equation with extra term $(1/24)t$. On the
other hand, Gubinelli and Perkowski [5] gave a pathwise meaning to the KPZ
equation as an application of the paracontrolled calculus. We show that Funaki
and Quastel's result is extended to nonstationary solutions by using the
paracontrolled calculus.


title: Drell-Yan lepton angular distributions in perturbative QCD

abstract:
  We present a comprehensive comparison of the available experimental data for
the Drell-Yan lepton angular coefficients $\lambda$ and $\nu$ to calculations
at leading and next-to-leading order of perturbative QCD. To obtain the
next-to-leading order corrections, we make use of publicly available numerical
codes that allow us to compute the Drell-Yan cross section at second order in
perturbation theory and from which the contributions we need can be extracted.
Our comparisons reveal that perturbative QCD is able to describe the
experimental data overall rather well, especially at colliders, but also in the
fixed-target regime. On the basis of the angular coefficients alone, there
appears to be little (if any) convincing evidence for effects that go beyond
fixed-order collinear factorized perturbation theory, although the presence of
such effects is not ruled out.