title: Arcade Implosion Caused by a Filament Eruption in a Flare

abstract:
  Coronal implosions - the convergence motion of plasmas and entrained magnetic
field in the corona due to a reduction in magnetic pressure - can help to
locate and track sites of magnetic energy release or redistribution during
solar flares and eruptions. We report here on the analysis of a well-observed
implosion in the form of an arcade contraction associated with a filament
eruption, during the C3.5 flare SOL2013-06-19T07:29. A sequence of events
including magnetic flux-rope instability and distortion, followed by filament
eruption and arcade implosion, lead us to conclude that the implosion arises
from the transfer of magnetic energy from beneath the arcade as part of the
global magnetic instability, rather than due to local magnetic energy
dissipation in the flare. The observed net contraction of the imploding loops,
which is found also in nonlinear force-free field extrapolations, reflects a
permanent reduction of magnetic energy underneath the arcade. This event shows
that, in addition to resulting in expansion or eruption of overlying field,
flux-rope instability can also simultaneously implode unopened field due to
magnetic energy transfer. It demonstrates the "partial opening of the field"
scenario, which is one of the ways in 3D to produce a magnetic eruption without
violating the Aly-Sturrock hypothesis. In the framework of this observation we
also propose a unification of three main concepts for active region magnetic
evolution, namely the metastable eruption model, the implosion conjecture, and
the standard "CSHKP" flare model.


title:
An algorithmic approach using multivariate polynomials for the
  nonlinearity of Boolean functions

abstract:
  The nonlinearity of a Boolean function is a key property in deciding its
suitability for cryptographic purposes, e.g. as a combining function in stream
ciphers, and so the nonlinearity computation is an important problem for
applications. Traditional methods to compute the nonlinearity are based on
transforms, such as the Fast Walsh Transform. In 2007 Simonetti proposed a
method to solve the above problem seen as a decision problem on the existence
of solutions for some multivariate polynomial systems. Although novel as
approach, her algorithm suffered from a direct application of Groebner bases
and was thus impractical. We now propose two more practical approaches, one
that determines the existence of solutions for Simonetti's systems in a faster
way and another that writes similar systems but over fields with a different
characteristics. For our algorithms we provide an efficient implementation in
the software package MAGMA.


title: Signature of f-electron conductance in $\alpha$-Ce single-atom contacts

abstract:
  Cerium is a fascinating element exhibiting, with its different phases,
long-range magnetic order and superconductivity in bulk form. The coupling of
the 4f electron to sd conduction electrons and to the lattice is responsible
for unique structural and electronic properties like the isostructural
first-order solid-solid transition from the cubic $\gamma$ phase to the cubic
$\alpha$ phase, which is accompanied by a huge volume collapse of 14 %. While
the $\gamma - \alpha$ phase transition has been investigated for decades,
experiments aiming at disentangling the 4f contribution to the electric
conductance of the different phases have not been performed. Here we report on
the strongly enhanced conductance of single-atom Ce contacts. By controlling
the content of $\alpha$-Ce employing different rates of cooling, we find a
strong correlation between the fraction of $\alpha$-Ce and the magnitude of the
last conductance plateau before the contact breaks. We attribute the enhanced
conductance of $\alpha$-Ce to the additional contribution of the 4f level.


title: Combinatorial Quantum Gravity: Geometry from Random Bits

abstract:
  I propose a quantum gravity model in which geometric space emerges from
random bits in a quantum phase transition driven by the combinatorial
Ollivier-Ricci curvature and corresponding to the condensation of short cycles
in random graphs. This quantum critical point defines quantum gravity
non-perturbatively. In the ordered geometric phase at large distances the
action reduces to the standard Einstein-Hilbert term.


title:
Foliations and the cohomology of moduli spaces of bounded global
  $G$-shtukas

abstract:
  For arbitrary reductive groups $G$ defined over a finite field, we decompose
Newton strata in the special fiber of moduli spaces of global $G$-shtukas into
a product of Rapoport-Zink spaces and Igusa varieties. This allows us to
compare the $\ell$-adic cohomology of these spaces together with the various
actions on them.


title:
Payload-Size and Deadline-Aware Scheduling for Time-critical Cyber
  Physical Systems

abstract:
  Compared to former mobile networks, Long Term Evolution (LTE) offers higher
transfer speeds, significantly lower latencies and a widespread availability,
qualifying LTE for a wide range of different applications and services in the
field of conventional Human-to-Human (H2H) as well as fast growing Vehicle-To-X
(V2X) and Cyber Physical Systems (CPS) communications. As a result, a steady
growth of mobile data traffic, which is reflected in an increased interaction
between different traffic classes, can be observed. In order to ensure timely
transmissions of time-critical data in the future, we propose the novel
Payload-Size and Deadline-Aware (PayDA) scheduling approach and compare its
performance regarding the compliance for deadlines with those of other common
packet scheduling mechanisms. The performance analysis is done with the complex
and open-source LTE simulation environment LTE-Sim. The results show that the
average latency can be reduced by the factor of 20 and the mean data rates can
be enhanced by a factor of about 3.5 for a high miscellaneous data traffic. In
the case of a heavy homogeneous and time-critical data traffic the mean
Deadline-Miss-Ratio (DMR) can be decreased by about 35%.


title:
Gender differences in scientific collaborations: Women are more
  egalitarian than men

abstract:
  By analyzing a unique dataset of more than 270,000 scientists, we discovered
substantial gender differences in scientific collaborations. While men are more
likely to collaborate with other men, women are more egalitarian. This is
consistently observed over all fields and regardless of the number of
collaborators a scientist has. The only exception is observed in the field of
engineering, where this gender bias disappears with increasing number of
collaborators. We also found that the distribution of the number of
collaborators follows a truncated power law with a cut-off that is gender
dependent and related to the gender differences in the number of published
papers. Considering interdisciplinary research, our analysis shows that men and
women behave similarly across fields, except in the case of natural sciences,
where women with many collaborators are more likely to have collaborators from
other fields.


title: Asymptotic formulas for general colored partition functions

abstract:
  In 1917, Hardy and Ramanujan obtained the asymptotic formula for the
classical partition function $p(n)$. The classical partition function $p(n)$
has been extensively studied. Recently, Luca and Ralaivaosaona obtained the
asymptotic formula for the square-root function. Many mathematicians have paid
much attention to congruences on some special colored partition functions. In
this paper, we investigate the general colored partition functions. Given
positive integers $1=s_1<s_2<\dots <s_k$ and $\ell_1, \ell_2,\dots , \ell_k$.
Let $g(\mathbf{s}, \mathbf{l}, n)$ be the number of $\ell$-colored partitions
of $n$ with $\ell_i$ of the colors appearing only in multiplies of $s_i\ (1\le
i\le k)$, where $\ell = \ell_1+\cdots +\ell_k$. By using the elementary method
we obtain an asymptotic formula for the partition function $g(\mathbf{s},
\mathbf{l}, n)$ with an explicit error term.


title:
Equivariant Kirchberg-Phillips-type absorption for amenable group
  actions

abstract:
  We show an equivariant Kirchberg-Phillips-type absorption theorem for
pointwise outer actions of discrete amenable groups on Kirchberg algebras with
respect to natural model actions on the Cuntz algebras $\mathcal{O}_\infty$ and
$\mathcal{O}_2$. This generalizes results known for finite groups and
poly-$\mathbb{Z}$ groups. The model actions are shown to be determined, up to
strong cocycle conjugacy, by natural abstract properties, which are verified
for some examples of actions arising from tensorial shifts. We also show the
following homotopy rigidity result, which may be understood as a precursor to a
general Kirchberg-Phillips-type classification theory: If two outer actions of
an amenable group on a unital Kirchberg algebra are equivariantly homotopy
equivalent, then they are conjugate. This marks the first C*-dynamical
classification result up to cocycle conjugacy that is applicable to actions of
all amenable groups.


title: Generalized Stefan-Boltzmann law

abstract:
  We reconsider the thermodynamic derivation by L. Boltzmann of the Stefan law
and we generalize it for various different physical systems {\it whose chemical
potential vanishes}. Being only based on classical arguments, therefore
independent of the quantum statistics, this derivation applies as well to the
saturated Bose gas in various geometries as to "compensated" Fermi gas near a
neutrality point, such as a gas of Weyl Fermions. It unifies in the same
framework the thermodynamics of many different bosonic or fermionic
non-interacting gases which were until now described in completely different
contexts.


title:
Elastic constants and thermodynamics properties of pristine PEDOT
  revealed: A first-principles PBE/PBE PAW approach

abstract:
  In this work, we report for the first time, detailed calculations of elastic
and thermodynamic properties of organic poly(3,4-ethylenedioxythiophene),
PEDOT, in an undiluted state, using PBE and PBEsol-PAW pseudopotentials within
the framework of Generalized Gradient Approximation Density Functional Theory.
Contrary to Molecular Dynamic simulations, series of PBE and PBEsol-PAW
calculations in the current work revealed the most stable state of monoclinic
structured pristine PEDOT. We determined thirteen (13) independent elastic
constants with elastic compliance which enables us to establish other elastic
properties of pristine PEDOT; the Pugh's ratio and the Vicker's hardness
calculations show small mismatches with PBE and PBEsol-PAW pseudopotentials.
The Debye temperature TD is predicted both in the PBE and PBEsol-PAW
calculations while the specific heat capacity Cv(T) follows the Dulong-Petit
curve having no mismatch with Debye model at low temperature, with PBE
predicting a higher Debye sound velocity than PBEsol-PAW. As accuracy tests
only, we performed electronic structure calculations of PEDOT and compared with
available data in the literature.

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


title:
Isentropic thermodynamics and scalar-mesons properties near the QCD
  critical end point

abstract:
  We investigate the QCD phase diagram and the location of the critical end
point (CEP) in the SU(2) Polyakov$-$Nambu$-$Jona-Lasinio model with
entanglement interaction giving special attention to the $\pi$ and
$\sigma$-mesons properties, namely the decay widths $\sigma\rightarrow\pi\pi$,
for several conditions around the CEP: we focus on the possible
$\sigma\rightarrow\pi\pi$ decay along the isentropic trajectories close to the
CEP since the hydrodynamical expansion of a heavy-ion collision fireball nearly
follows trajectories of constant entropy. It is expected that the type of
transition the dense medium goes through as it expands after the thermalization
determines the behavior of this decay. It is shown that no pions are produced
from the sigma decay in the chirally symmetric phase if the isentropic lines
approach the first order line from chemical potentials above it. Near the CEP
or above the $\sigma\rightarrow\pi\pi$ decay is possible with a high decay
width.


title: Two fundamental cosmological laws of the Local Universe

abstract:
  The Local Universe is the most detail studied part of the observable region
of space with the radius R about 100 Mpc. There are two empirical fundamental
cosmological laws directly established from observations in the Local Universe
independently from cosmological theory: first, the Hubble-Humason-Sandage
linear redshift-distance law and second, Carpenter- Karachentsev-deVaucouleurs
density-radius power-law. Review of modern state of these empirical laws and
their cosmological significance is given. Possible theoretical interpretations
of the surprising coexistence of both laws at the spatial scales from 1 Mpc to
100 Mpc are discussed. Comparison of the standard space-expansion explanation
of the cosmological redshift with possible global gravitational redshift model
is given


title: Growth of homology torsion of metabelian groups

abstract:
  We study the growth of torsion in the abelianizations of finite index
subgroups in finitely generated metabelian groups. This complements earlier
work of Kar, Kropholler and the author which covered the finitely presented
amenable groups.


title:
A multi-task learning model for malware classification with useful file
  access pattern from API call sequence

abstract:
  Based on API call sequences, semantic-aware and machine learning (ML) based
malware classifiers can be built for malware detection or classification.
Previous works concentrate on crafting and extracting various features from
malware binaries, disassembled binaries or API calls via static or dynamic
analysis and resorting to ML to build classifiers. However, they tend to
involve too much feature engineering and fail to provide interpretability. We
solve these two problems with the recent advances in deep learning: 1)
RNN-based autoencoders (RNN-AEs) can automatically learn low-dimensional
representation of a malware from its raw API call sequence. 2) Multiple
decoders can be trained under different supervisions to give more information,
other than the class or family label of a malware. Inspired by the works of
document classification and automatic sentence summarization, each API call
sequence can be regarded as a sentence. In this paper, we make the first
attempt to build a multi-task malware learning model based on API call
sequences. The model consists of two decoders, one for malware classification
and one for $\emph{file access pattern}$ (FAP) generation given the API call
sequence of a malware. We base our model on the general seq2seq framework.
Experiments show that our model can give competitive classification results as
well as insightful FAP information.


title:
Dipolar modulation in the size of galaxies: The effect of Doppler
  magnification

abstract:
  Objects falling into an overdensity appear larger on its near side and
smaller on its far side than other objects at the same redshift. This produces
a dipolar pattern of magnification, primarily as a consequence of the Doppler
effect. At low redshift this Doppler magnification completely dominates the
usual integrated gravitational lensing contribution to the lensing
magnification. We show that one can optimally observe this pattern by
extracting the dipole in the cross-correlation of number counts and galaxy
sizes. This dipole allows us to almost completely remove the contribution from
gravitational lensing up to redshift 0.5, and even at high redshift z~1 the
dipole picks up the Doppler magnification predominantly. Doppler magnification
should be easily detectable in current and upcoming optical and radio surveys;
by forecasting for telescopes such as the SKA, we show that this technique is
competitive with using peculiar velocities via redshift-space distortions to
constrain dark energy. It produces similar yet complementary constraints on the
cosmological model to those found using measurements of the cosmic shear.


title: Generalized Hardy-Ces\`aro operators between weighted spaces

abstract:
  We characterize those non-negative, measurable functions $\psi$ on $[0,1]$
and positive, continuous functions $\omega_1$ and $\omega_2$ on $\mathbb R^+$
for which the generalized Hardy-Ces\`aro operator $$(U_{\psi}f)(x)=\int_0^1
f(tx)\psi(t)\,dt$$ defines a bounded operator $U_{\psi}:L^1(\omega_1)\to
L^1(\omega_2)$. Furthermore, we extend $U_{\psi}$ to a bounded operator on
$M(\omega_1)$ with range in $L^1(\omega_2)\oplus\mathbb C\delta_0$. Finally, we
show that the zero operator is the only weakly compact generalized
Hardy-Ces\`aro operator from $L^1(\omega_1)$ to $L^1(\omega_2)$.


title: A Bayesian Approach to Estimation of Speaker Normalization Parameters

abstract:
  In this work, a Bayesian approach to speaker normalization is proposed to
compensate for the degradation in performance of a speaker independent speech
recognition system. The speaker normalization method proposed herein uses the
technique of vocal tract length normalization (VTLN). The VTLN parameters are
estimated using a novel Bayesian approach which utilizes the Gibbs sampler, a
special type of Markov Chain Monte Carlo method. Additionally the
hyperparameters are estimated using maximum likelihood approach. This model is
used assuming that human vocal tract can be modeled as a tube of uniform cross
section. It captures the variation in length of the vocal tract of different
speakers more effectively, than the linear model used in literature. The work
has also investigated different methods like minimization of Mean Square Error
(MSE) and Mean Absolute Error (MAE) for the estimation of VTLN parameters. Both
single pass and two pass approaches are then used to build a VTLN based speech
recognizer. Experimental results on recognition of vowels and Hindi phrases
from a medium vocabulary indicate that the Bayesian method improves the
performance by a considerable margin.


title: Visual-Inertial Monocular SLAM with Map Reuse

abstract:
  In recent years there have been excellent results in Visual-Inertial Odometry
techniques, which aim to compute the incremental motion of the sensor with high
accuracy and robustness. However these approaches lack the capability to close
loops, and trajectory estimation accumulates drift even if the sensor is
continually revisiting the same place. In this work we present a novel
tightly-coupled Visual-Inertial Simultaneous Localization and Mapping system
that is able to close loops and reuse its map to achieve zero-drift
localization in already mapped areas. While our approach can be applied to any
camera configuration, we address here the most general problem of a monocular
camera, with its well-known scale ambiguity. We also propose a novel IMU
initialization method, which computes the scale, the gravity direction, the
velocity, and gyroscope and accelerometer biases, in a few seconds with high
accuracy. We test our system in the 11 sequences of a recent micro-aerial
vehicle public dataset achieving a typical scale factor error of 1% and
centimeter precision. We compare to the state-of-the-art in visual-inertial
odometry in sequences with revisiting, proving the better accuracy of our
method due to map reuse and no drift accumulation.


title: Consistent Kernel Mean Estimation for Functions of Random Variables

abstract:
  We provide a theoretical foundation for non-parametric estimation of
functions of random variables using kernel mean embeddings. We show that for
any continuous function $f$, consistent estimators of the mean embedding of a
random variable $X$ lead to consistent estimators of the mean embedding of
$f(X)$. For Mat\'ern kernels and sufficiently smooth functions we also provide
rates of convergence. Our results extend to functions of multiple random
variables. If the variables are dependent, we require an estimator of the mean
embedding of their joint distribution as a starting point; if they are
independent, it is sufficient to have separate estimators of the mean
embeddings of their marginal distributions. In either case, our results cover
both mean embeddings based on i.i.d. samples as well as "reduced set"
expansions in terms of dependent expansion points. The latter serves as a
justification for using such expansions to limit memory resources when applying
the approach as a basis for probabilistic programming.


title: Solution of two level system using $3^{rd}$ order Magnus expansion

abstract:
  The solution of a two level system driven by a Laser in the adiabatic limit
is determined using third order Magnus expansion. We made the assumption that
the laser is on resonance or close to resonance with the Bohr transition. As a
consequence of which we are able to obtain a Hamiltonian which commute with
itself at different times. We solve the problem using the Sylvester Formula
where we make use of the eigenvalues.


title: Conical square functions for degenerate elliptic operators

abstract:
  The aim of this paper is to study the boundedness of different conical square
functions that arise naturally from second order divergence form degenerate
elliptic operators. More precisely, let $L_w=w^{-1}\,{\rm div}(w\,A\,\nabla)$
where $w\in A_2$ and $A$ is an $n\times n$ bounded, complex-valued, uniformly
elliptic matrix. D. Cruz-Uribe and C. Rios solved the $L^2(w)$-Kato square root
problem obtaining that $\sqrt{L_w}$ is equivalent to the gradient on $L^2(w)$.
The same authors in collaboration with the second named author of this paper
studied the $L^p(w)$-boundedness of operators that are naturally associated
with $L_w$, such as the functional calculus, Riesz transforms, or vertical
square functions. The theory developed admitted also weighted estimates (i.e.,
estimates in $L^p(v dw)$ for $v\in A_\infty(w)$), and in particular a class of
"degeneracy" weights $w$ was found in such a way that the classical $L^2$-Kato
problem can be solved. In this paper, continuing this line of research, and
also that originated in some recent results by the second and third named
authors of the current paper, we study the boundedness on $L^p(w)$ and on
$L^p(v dw)$, with $v\in A_\infty(w)$, of the conical square functions that one
can construct using the heat or Poisson semigroup associated with $L_w$. As a
consequence of our methods, we find a class of degeneracy weights $w$ for which
$L^2$-estimates for these conical square functions hold. This opens the door to
the study of weighted and unweighted Hardy spaces and of boundary value
problems associated with $L_w$.


title:
Toroidal figures of equilibrium from a 2nd-order accurate, accelerated
  SCF-method with subgrid approach

abstract:
  We compute the structure of a self-gravitating torus with polytropic
equation-of-state (EOS) rotating in an imposed centrifugal potential. The
Poisson-solver is based on isotropic multigrid with optimal covering factor
(fluid section-to-grid area ratio). We work at $2$nd-order in the grid
resolution for both finite difference and quadrature schemes. For soft EOS
(i.e. polytropic index $n \ge 1$), the underlying $2$nd-order is naturally
recovered for Boundary Values (BVs) and any other integrated quantity sensitive
to the mass density (mass, angular momentum, volume, Virial Parameter, etc.),
i.e. errors vary with the number $N$ of nodes per direction as $\sim 1/N^2$.
This is, however, not observed for purely geometrical quantities (surface area,
meridional section area, volume), unless a subgrid approach is considered (i.e.
boundary detection). Equilibrium sequences are also much better described,
especially close to critical rotation. Yet another technical effort is required
for hard EOS ($n < 1$), due to infinite mass density gradients at the fluid
surface. We fix the problem by using kernel splitting. Finally, we propose an
accelerated version of the SCF-algorithm based on a node-by-node
pre-conditionning of the mass density at each step. The computing time is
reduced by a factor $2$ typically, regardless of the polytropic index. There is
a priori no obstacle to applying these results and techniques to ellipsoidal
configurations and even to $3$D-configurations.


title: Unfolding Semantics of the Untyped {\lambda}-Calculus with letrec

abstract:
  We investigate the relationship between finite terms in {\lambda}-letrec, the
{\lambda}-calculus with letrec, and the infinite {\lambda}-terms they express.
We say that a lambda-letrec term expresses a lambda-term if the latter can be
obtained as an infinite unfolding of the former. Unfolding is the process of
substituting occurrences of function variables by the right-hand side of their
definition.
  We consider the following questions: (i) How can we characterise those
infinite {\lambda}-terms that are {\lambda}-letrec-expressible? (ii) Given two
{\lambda}-letrec terms, how can we determine whether they have the same
unfolding? (iii) Given a {\lambda}-letrec term, can we find a more compact
version of the term with the same unfolding? To tackle these questions we
introduce and study the following formalisms: (i) a rewriting system for
unfolding {\lambda}-letrec terms into {\lambda}-terms (ii) a rewriting system
for `observing' {\lambda}-terms by dissecting their term structure (iii)
higher-order and first-order graph formalisms together with translations
between them as well as translations from and to {\lambda}-letrec.
  We identify a first-order term graph formalism on which bisimulation
preserves and reflects the unfolding semantics of {\lambda}-letrec and which is
closed under functional bisimulation. From this we derive efficient methods to
determine whether two terms are equivalent under infinite unfolding and to
compute the maximally shared form of a given {\lambda}-letrec term.


title: Note on a one-dimensional system of annihilating particles

abstract:
  We consider a system of annihilating particles where particles start from the
points of a Poisson process on either the full-line or positive half-line and
move at constant i.i.d. speeds until collision. When two particles collide,
they annihilate. We assume the law of speeds to be symmetric. We prove almost
sure annihilation of positive-speed particles started from the positive
half-line, and existence of a regime of survival of zero-speed particles on the
full-line in the case when speeds can only take 3 values.


title: Clustering by connection center evolution

abstract:
  The determination of cluster centers generally depends on the scale that we
use to analyze the data to be clustered. Inappropriate scale usually leads to
unreasonable cluster centers and thus unreasonable results. In this study, we
first consider the similarity of elements in the data as the connectivity of
nodes in an undirected graph, then present the concept of a connection center
and regard it as the cluster center of the data. Based on this definition, the
determination of cluster centers and the assignment of class are very simple,
natural and effective. One more crucial finding is that the cluster centers of
different scales can be obtained easily by the different powers of a similarity
matrix and the change of power from small to large leads to the dynamic
evolution of cluster centers from local (microscopic) to global (microscopic).
Further, in this process of evolution, the number of categories changes
discontinuously, which means that the presented method can automatically skip
the unreasonable number of clusters, suggest appropriate observation scales and
provide corresponding cluster results.


title:
Two-photon-exchange effects in the unpolarized $\mu p$ scattering within
  the hadronic model

abstract:
  In this work, the two-photon-exchange (TPE) effects in the unpolarized $\mu
p$ scattering are discussed within the hadronic model where the intermediate
states $N,\Delta$ and $\sigma$ are considered. The contribution from the $N$
intermediate is close to the results given by Ref. \cite{Tomalak2014} at the
small $Q$ and there is a sizeable difference when $Q>0.25$GeV (where $Q^2$ is
the four momentum transfer). The contributions from the $\Delta$ and the
$\sigma$ intermediate states are much smaller than that from the $N$
intermediate at the small $Q$. In the kinematic region with $k_i\subseteq
[0.01,0.3]$ GeV and $Q \leq0.4$GeV (where $k_i$ is the three momentum of
initial muon at Lab frame), a naive expression for the TPE contributions is
given, which can be used directly for other analysis.


title: A one parameter class of Fractional Maxwell-like models

abstract:
  In this paper we discuss a one parameter modification of the well known
fractional Maxwell model of viscoelasticity. Such models appear to be
particularly interesting because they describe the short time asymptotic limit
of a more general class of viscoelastic models known in the literature as
Bessel models.

categories: math-ph cond-mat.mtrl-sci math.CV math.MP


title: Quantifying the dynamical complexity of time series

abstract:
  A powerful tool is developed for the characterization of chaotic signals. The
approach is based on the symbolic encoding of time series (according to their
ordinal patterns) combined with the ensuing characterization of the
corresponding cylinder sets. Quantitative estimates of the Kolmogorov-Sinai
entropy are obtained by introducing a modified permutation entropy which takes
into account the average width of the cylinder sets. The method works also in
hyperchaotic systems and allows estimating the fractal dimension of the
underlying attractors.


title: Performance analysis of polling systems with retrials and glue periods

abstract:
  We consider gated polling systems with two special features: (i) retrials,
and (ii) glue or reservation periods. When a type-$i$ customer arrives, or
retries, during a glue period of station $i$, it will be served in the next
visit period of the server to that station. Customers arriving at station $i$
in any other period join the orbit of that station and retry after an
exponentially distributed time. Such polling systems can be used to study the
performance of certain switches in optical communication systems.
  For the case of exponentially distributed glue periods, we present an
algorithm to obtain the moments of the number of customers in each station. For
generally distributed glue periods, we consider the distribution of the total
workload in the system, using it to derive a pseudo conservation law which in
its turn is used to obtain accurate approximations of the individual mean
waiting times. We also consider the problem of choosing the lengths of the glue
periods, under a constraint on the total glue period per cycle, so as to
minimize a weighted sum of the mean waiting times.


title: Proximity-Aware Balanced Allocations in Cache Networks

abstract:
  We consider load balancing in a network of caching servers delivering
contents to end users. Randomized load balancing via the so-called power of two
choices is a well-known approach in parallel and distributed systems that
reduces network imbalance. In this paper, we propose a randomized load
balancing scheme which simultaneously considers cache size limitation and
proximity in the server redirection process.
  Since the memory limitation and the proximity constraint cause correlation in
the server selection process, we may not benefit from the power of two choices
in general. However, we prove that in certain regimes, in terms of memory
limitation and proximity constraint, our scheme results in the maximum load of
order $\Theta(\log\log n)$ (here $n$ is the number of servers and requests),
and at the same time, leads to a low communication cost. This is an exponential
improvement in the maximum load compared to the scheme which assigns each
request to the nearest available replica. Finally, we investigate our scheme
performance by extensive simulations.


title:
Neutrino oscillations from warped flavor symmetry: predictions for long
  baseline experiments T2K, NOvA and DUNE

abstract:
  Here we study the pattern of neutrino oscillations emerging from a previously
proposed warped model construction incorporating $\Delta(27)$ flavor symmetry.
In addition to a complete description of fermion masses, the model predicts the
lepton mixing matrix in terms of two parameters. The good measurement of
$\theta_{13}$ makes these two parameters nearly proportional, leading to an
approximate one-parameter description of neutrino oscillations. There is a
sharp fourfold degenerate correlation between $\delta_{CP}$ and the atmospheric
mixing angle $\theta_{23}$, so that maximal $\theta_{23}$ also implies maximal
leptonic CP violation. The predicted electron neutrino and anti-neutrino
appearance probabilities indicate that the model should be tested at the T2K,
NO$\nu$A and DUNE long baseline oscillation experiments.


title:
Generating end modes in a superconducting wire by periodic driving of
  the hopping

abstract:
  We show that harmonic driving of either the magnitude or the phase of the
nearest-neighbor hopping amplitude in a p-wave superconducting wire can
generate modes localized near the ends of the wire. The Floquet eigenvalues of
these modes can either be equal to $\pm 1$ (which is known to occur in other
models) or can lie near other values in complex conjugate pairs which is
unusual; we call the latter anomalous end modes. All the end modes have equal
probabilities of particles and holes. If the amplitude of driving is small, we
observe an interesting bulk-boundary correspondence: the Floquet eigenvalues
and the peaks of the Fourier transform of the end modes lie close to the
Floquet eigenvalues and momenta at which the Floquet eigenvalues of the bulk
system have extrema.


title:
Diophantine approximation in Kleinian groups: singular, extremal, and
  bad limit points

abstract:
  The overall aim of this note is to initiate a "manifold" theory for metric
Diophantine approximation on the limit sets of Kleinian groups. We investigate
the notions of singular and extremal limit points within the geometrically
finite Kleinian group framework. Also, we consider the natural analogue of
Davenport's problem regarding badly approximable limit points in a given subset
of the limit set. Beyond extremality, we discuss potential Khintchine-type
statements for subsets of the limit set. These can be interpreted as the
conjectural "manifold" strengthening of Sullivan's logarithmic law for
geodesics.


title: Vacuum $ f(R)$ thick brane solution with a Gaussian warp function

abstract:
  This work deals with $f(R)$ modified gravity in five dimensional space-time.
The Gaussian thick brane is shown to be an exact solution in the frame work of
$f(R)$ gravity in five dimensions with a bulk cosmological constant. Response
of the brane to gravitational fluctuations and concordance with the Starobinsky
model is addressed. It is shown that the matter which supports the Starobinsky
$f(R)$ solution with the background geometry being flat FLRW with a Gaussian
warp function, behaves like a radiation dominated era of universe, gradually
changing to a dark energy dominated era.


title: Slow electrostatic fluctuations generated by beam-plasma interaction

abstract:
  Eulerian simulations of the Vlasov-Poisson equations have been employed to
analyze the excitation of slow electrostatic fluctuations (with phase speed
close to the electron thermal speed), due to a beam-plasma interaction, and
their propagation in linear and nonlinear regime. In 1968, O'Neil and Malmberg
[Phys. Fluids {\bf 11}, 1754 (1968)] dubbed these waves "beam modes". In the
present paper, it is shown that, in the presence of a cold and low density
electron beam, these beam modes can become unstable and then survive Landau
damping unlike the Langmuir waves. When an electron beam is launched in a
plasma of Maxwellian electrons and motionless protons and this initial
equilibrium is perturbed by a monochromatic density disturbance, the electric
field amplitude grows exponentially in time and then undergoes nonlinear
saturation, associated with the kinetic effects of particle trapping and phase
space vortex generation. Moreover, if the initial density perturbation is setup
in the form of a low amplitude random phase noise, once the most unstable mode
has reached its nonlinear saturation amplitude after the linear growth, the
whole Fourier spectrum of wavenumbers is excited. As a result, the electric
field profile appears as a train of isolated pulses, each of them being
associated with a phase space vortex in the electron distribution function. At
later times, these vortical structures tend to merge and, correspondingly, the
electric pulses collapse, showing the tendency towards a time asymptotic
configuration with a single phase space structure associated to an electric
soliton-like pulse. This dynamical evolution is driven by purely kinetic
processes, possibly at work in many space and laboratory plasma environments.


title: New Asymptotically Lifshitz Black Holes in Horava gravity

abstract:
  We study asymptotically Lifshitz solutions with critical exponent $z \neq 1$
in Horava gravity in three and four spacetime dimensions. For $z=2$ and
$z=3/2$, we find a novel class of numerical solutions with regular universal
horizon, but are characterized by non-analytic behavior near infinity. In the
interior, inside the universal horizon, the unit timelike vector field
associated with the preferred time foliation exhibits oscillatory behavior,
qualitatively similar to that found earlier in asymptotically flat solutions.
For $z>2$ no solutions of this type appear to exist. We comment on potential
applications to holographic Lifshitz dualities.


title: How Fermat found extrema

abstract:
  We present a short elementary proof of the well-known criterion for a cubic
polynomial to have three real roots. The proof is based on Fermat's approach to
calculus for polynomials. This approach illustrates the idea of a derivative
rigorously but without technical $\varepsilon$-$\delta$ language. The note is
accessible to high-school students. An English version is followed by a more
detailed Russian version.


title:
Dynamical Bulk Scaling limit of Gaussian Unitary Ensembles and
  Stochastic Differential Equation gaps

abstract:
  The distributions of $ N $-particle systems of Gaussian unitary ensembles
converge to Sine$_2$ point processes under bulk-scaling limits. These scalings
are parameterized by a macro-position $ \theta $ in the support of the
semicircle distribution. The limits are always Sine$_{2}$ point processes and
independent of the macro-position $ \theta $ up to the dilations of
determinantal kernels. We prove a dynamical counter part of this fact. We prove
that the solution of the $ N $-particle systems given by stochastic
differential equations (SDEs) converges to the solution of the
infinite-dimensional Dyson model. We prove the limit infinite-dimensional SDE
(ISDE), referred to as Dyson's model, is independent of the macro-position $
\theta $, whereas the $ N $-particle SDEs depend on $ \theta $ and are
different from the ISDE in the limit whenever $ \theta \not= 0 $.


title:
Relation between Functional Complexity, Scalability and Energy
  Efficiency in WSNs

abstract:
  In order to understand the underlying mechanisms that lead to certain network
properties (i.e. scalability, energy efficiency) we apply a complex systems
science approach to analyze clustering in Wireless Sensor Networks (WSN). We
represent different implementations of clustering in WSNs with a functional
topology graph. Different characteristics of the functional topology provide
insight into the relationships between system parts that result in certain
properties of the whole system. Moreover, we employ a complexity metric -
functional complexity (C_F) - to explain how local interactions give rise to
the global behavior of the network. Our analysis shows that higher values of
C_F indicate higher scalability and lower energy efficiency.


title: Security Testbed for the Internet of Things

abstract:
  The Internet of Things (IoT) is a global ecosystem of information and
communication technologies aimed at connecting any type of object (thing), at
any time and in any place, to each other and to the Internet. One of the major
problems associated with the IoT is maintaining security; the heterogeneous
nature of such deployments poses a challenge to many aspects of security,
including security testing and analysis. In addition, there is no existing
mechanism that performs security testing for IoT devices in different contexts.
In this paper, we propose an innovative security testbed framework targeted at
IoT devices. The security testbed supports both standard and context-based
security testing, with a set of security tests conducted under the different
environmental conditions in which IoT devices operate. The requirements and
architectural design of the proposed testbed are discussed, and the testbed
operation is demonstrated in several testing scenarios.


title:
Sparse Bayesian Inference and the Temperature Structure of the Solar
  Corona

abstract:
  Measuring the temperature structure of the solar atmosphere is critical to
understanding how it is heated to high temperatures. Unfortunately, the
temperature of the upper atmosphere cannot be observed directly, but must be
inferred from spectrally resolved observations of individual emission lines
that span a wide range of temperatures. Such observations are "inverted" to
determine the distribution of plasma temperatures along the line of sight. This
inversion is ill-posed and, in the absence of regularization, tends to produce
wildly oscillatory solutions. We introduce the application of sparse Bayesian
inference to the problem of inferring the temperature structure of the solar
corona. Within a Bayesian framework a preference for solutions that utilize a
minimum number of basis functions can be encoded into the prior and many ad hoc
assumptions can be avoided. We demonstrate the efficacy of the Bayesian
approach by considering a test library of 40 assumed temperature distributions.


title: Towards generalized prehomogeneous zeta integrals

abstract:
  Let $X$ be a prehomogeneous vector space under a connected reductive group
$G$ over $\mathbb{R}$. Assume that the open $G$-orbit $X^+$ admits a finite
covering by a symmetric space. We study certain zeta integrals involving (i)
Schwartz functions on $X$, and (ii) generalized matrix coefficients on
$X^+(\mathbb{R})$ of Casselman-Wallach representations of $G(\mathbb{R})$, upon
a twist by complex powers of relative invariants. This merges representation
theory with prehomogeneous zeta integrals of Igusa et al. We show their
convergence in some shifted cone, and prove their meromorphic continuation via
the machinery of $b$-function together with V. Ginzburg's results on admissible
$D$-modules. This provides some evidences for a broader theory of zeta
integrals associated to affine spherical embeddings.


title: Hamiltonian extensions in quantum metrology

abstract:
  We study very generally to what extent the uncertainty with which a phase
shift can be estimated in quantum metrology can be reduced by extending the
Hamiltonian that generates the phase shift to an ancilla system with a Hilbert
space of arbitrary dimension, and allowing arbitrary interactions between the
original system and the ancilla. Such Hamiltonian extensions provide a general
framework for open quantum systems, as well as for "non-linear metrology
schemes" that have been investigated over the last few years. We prove that
such Hamiltonian extensions cannot improve the sensitivity of the phase shift
measurement when considering the quantum Fisher information optimized over
input states.


title:
New scenario of turbulence theory and wall-bounded turbulence:
  Theoretical significance

abstract:
  General scenario of turbulence theory is proposed and applied to streaky
wall-bounded turbulence. This scenario introduces a new field of transverse
waves. Significance of the theory rests on a mathematical theorem associated
with the conservation law of current flux, expressed in a form of 4d physical
space-time representation, which predicts a system of Maxwell-type equation and
supports transverse waves traveling with a phase speed c_t. In regard to the
streaky wall flows, there exist both dynamical mechanism and energy channel
which excite transverse waves and exchange energy between flow field and wave
field. Energy is supplied from the flow field to the wave field if wavelengths
are sufficiently large. The waves are accompanied with a new mechanism of
energy dissipation, an internal friction analogous to the Ohm's effect. Some
part of the energy is dissipated into heat. Thus, there exists a sustaining
mechanism, which implies that the streaky structure of wall-bounded turbulence
is a dissipative structure.
  The predictions are consistent with experimental observations of wall
turbulence: (i) Existence of traveling waves: The waves are characterized by
two scales of wavelength and a damping-length d. (ii) Existence of two large
scales (LSM and VLSM) observed in turbulent shear flows: Those are interpreted
by the waves amplified with the transient growth mechanism and maintained by
interaction with the new transverse wave field. The waves are robust since they
have their own energy and momentum. (iii) Enhanced energy dissipation in wavy
turbulence. Its bulk rate of energy dissipation takes a form resembling the
models of eddy-viscosity, and its coefficient \nu_D is estimated to be of the
order of c_t d and much larger than the molecular viscosity.
  No self-contradiction is incurred by the new field introduced.


title: A product formula for the higher rank Drinfeld discriminant function

abstract:
  We give a product expansion for the Drinfeld discriminant function in
arbitrary rank $r$, which generalizes the formula obtained by Gekeler for the
rank 2 Drinfeld discriminant function. This enables one to compute the Fourier
expansion of this function much more efficiently.
  The formula in this article uses an $r-1$-dimensional parameter and as such
provides a nice counterpoint to the formula previously obtained by Hamahata,
which is written in terms of several 1-dimensional parameters.


title:
Analysis of a Triple-cavity Photonic Molecule Based on Coupled Mode
  Theory

abstract:
  In this paper, we analyze a chain-linked triple-cavity photonic molecule
(TCPM) with controllable coupling strengths between the cavities on their
spectral properties and field (energy) distributions by solving eigenvalues and
eigenvectors of the Hamiltonian matrix based on coupled mode theory. Phase
transition is extended from double-cavity photonic molecules (DCPMs) to TCPMs,
and evolutions of the supermode frequencies and linewidths are analyzed, which
have synchronous relations with the degree of coherence between adjacent
optical microcavities and energy distributions in the three cavities,
respectively. We develop a superposition picture for the three supermodes of
the TCPM, as interferences between supermodes of sub-DCPMs. In particular, we
demonstrate the abnormal properties of the central supermode in TCPMs, such as
dark state in middle cavity and phase shift when energy flowing between side
cavities, which are promising in information processing and remote control of
energy. General properties of TCPMs are summarized and limitation on linewidths
are given. Finally, we make an interesting analog to intracavity
electromagnetically induced transparency in multi-level atomic systems using
the flexible TCPM platform under appropriate conditions.


title:
Near-infrared spectroscopy of nearby Seyfert galaxies: Is there evidence
  for the shock excitation in narrow-line regions?

abstract:
  One of the unsettled, important problems in active galactic nuclei (AGNs) is
the major ionization mechanism of gas clouds in their narrow-line regions
(NLRs). In order to investigate this issue, we present our $J$-band
spectroscopic observations for a sample of 26 nearby Seyfert galaxies. In our
study, we use the flux ratio of the following two forbidden emission lines, [Fe
II]1.257$\mu$m and [P II]1.188$\mu$m because it is known that this ratio is
sensitive to the ionization mechanism. We obtain the [Fe II]/[P II] flux ratio
or its lower limit for 19 objects. In addition to our data, we compile this
flux ratio (or its lower limit) of 23 nearby Seyfert galaxies from the
literature. Based on the collected data, we find that three Seyfert galaxies
show very large lower limits of [Fe II]/[P II] flux ratios ($\gtrsim$10); NGC
2782, 5005, and Mrk 463. It is thus suggested that the contribution of the fast
shock in the gas excitation is significantly large for them. However, more than
half of Seyfert galaxies in our sample show moderate [Fe II]/[P II] flux ratios
($\sim$2), that is consistent to the pure photoionization by power-law ionizing
continuum emission. We also find that the [Fe II]/[P II] flux ratio shows no
clear correlation with the radio loudness, suggesting that the radio jet is not
the primary origin of shocks in NLRs of Seyfert galaxies.


title: The combinatorial Chow ring of products of graphs

abstract:
  We prove results describing the structure of a Chow ring associated to a
product of graphs, which arises from the Gross-Schoen desingularization of a
product of regular proper semi-stable curves over discrete valuation rings. By
the works of Johannes Kolb and Shou-Wu Zhang, this ring controls the behavior
of the non-Archimedean height pairing on products of smooth proper curves over
non-Archimedean fields. We provide a complete description of the degree map,
and prove vanishing results affirming a conjecture of Kolb, which, combined
with his work, leads to an analytic formula for the arithmetic intersection
number of adelic metrized line bundles on products of curves over complete
discretely valued fields.


title: SIMEX: Simulation of Experiments at Advanced Light Sources

abstract:
  Realistic simulations of experiments at large scale photon facilities, such
as optical laser laboratories, synchrotrons, and free electron lasers, are of
vital importance for the successful preparation, execution, and analysis of
these experiments investigating ever more complex physical systems, e.g.
biomolecules, complex materials, and ultra-short lived states of highly excited
matter. Traditional photon science modelling takes into account only isolated
aspects of an experiment, such as the beam propagation, the photon-matter
interaction, or the scattering process, making idealized assumptions about the
remaining parts, e.g.\ the source spectrum, temporal structure and coherence
properties of the photon beam, or the detector response. In SIMEX, we have
implemented a platform for complete start-to-end simulations, following the
radiation from the source, through the beam transport optics to the sample or
target under investigation, its interaction with and scattering from the
sample, and its registration in a photon detector, including a realistic model
of the detector response to the radiation. Data analysis tools can be hooked up
to the modelling pipeline easily. This allows researchers and facility
operators to simulate their experiments and instruments in real life scenarios,
identify promising and unattainable regions of the parameter space and
ultimately make better use of valuable beamtime.
  This work is licensed under the Creative Commons Attribution 3.0 Unported
License: http://creativecommons.org/licenses/by/3.0/.


title:
Entropy production in photovoltaic-thermoelectric nanodevices from the
  non-equilibrium Green's function formalism

abstract:
  We derive the expressions of photon energy and particle currents inside an
open nanosystem interacting with light using non-equilibrium Green's functions.
The model allows different temperatures for the electron reservoirs, which
basically defines a photovoltaic-thermoelectric hybrid. Thanks to these
expressions, we formulate the steady-state entropy production rate to assess
the efficiency of reversible photovoltaic-thermoelectric nanodevices. Next,
quantum dot based nanojunctions are closely examined. We show that entropy
production is always positive when one considers spontaneous emission of
photons with a specific energy, while in general the emission spectrum is
broadened, notably for strong coupling to reservoirs. In this latter case, when
the emission is integrated over all the energies of the spectrum, we find that
entropy production can reach negative values. This result provides matter to
question the second law of thermodynamics for interacting nanosystems beyond
the assumption of weak coupling.


title: The temporal evolution of the central fixation bias in scene viewing

abstract:
  When watching the image of a natural scene on a computer screen, observers
initially move their eyes towards the center of the image --- a reliable
experimental finding termed central fixation bias. This systematic tendency in
eye guidance likely masks attentional selection driven by image properties and
top-down cognitive processes. Here we show that the central fixation bias can
be reduced by delaying the initial saccade relative to image onset. In four
scene-viewing experiments we manipulated observers' initial gaze position and
delayed their first saccade by a specific time interval relative to the onset
of an image. We analyzed the distance to image center over time and show that
the central fixation bias of initial fixations was significantly reduced after
delayed saccade onsets. We additionally show that selection of the initial
saccade target strongly depended on the first saccade latency. Processes
influencing the time course of the central fixation bias were investigated by
comparing simulations of several dynamic and statistical models. Model
comparisons suggest that the central fixation bias is generated by a default
activation as a response to the sudden image onset and that this default
activation pattern decreases over time. Our results suggest that it may often
be preferable to use a modified version of the scene viewing paradigm that
decouples image onset from the start signal for scene exploration and
explicitly controls the central fixation bias. In general, the initial fixation
location and the latency of the first saccade need to be taken into
consideration when investigating eye movements during scene viewing.


title:
Tidal Frequencies in the Time Series Measurements of Atmospheric Muon
  Flux from Cosmic Rays

abstract:
  Tidal frequencies are detected in time series muon flux measurements
performed over a period of eight years. Meson production and subsequent decay
produce the muons that are observed at ground level. We interpret the periodic
behavior as a consequence of high altitude density variations at the point of
meson production. These variations are driven by solar thermal cycles. The
detected frequencies are in good agreement with published tidal frequencies and
suggest that muons can be a complementary probe to the study of atmospheric
tides at altitudes between 20 to 60 km.


title:
Particle Swarm Optimization for Generating Interpretable Fuzzy
  Reinforcement Learning Policies

abstract:
  Fuzzy controllers are efficient and interpretable system controllers for
continuous state and action spaces. To date, such controllers have been
constructed manually or trained automatically either using expert-generated
problem-specific cost functions or incorporating detailed knowledge about the
optimal control strategy. Both requirements for automatic training processes
are not found in most real-world reinforcement learning (RL) problems. In such
applications, online learning is often prohibited for safety reasons because
online learning requires exploration of the problem's dynamics during policy
training. We introduce a fuzzy particle swarm reinforcement learning (FPSRL)
approach that can construct fuzzy RL policies solely by training parameters on
world models that simulate real system dynamics. These world models are created
by employing an autonomous machine learning technique that uses previously
generated transition samples of a real system. To the best of our knowledge,
this approach is the first to relate self-organizing fuzzy controllers to
model-based batch RL. Therefore, FPSRL is intended to solve problems in domains
where online learning is prohibited, system dynamics are relatively easy to
model from previously generated default policy transition samples, and it is
expected that a relatively easily interpretable control policy exists. The
efficiency of the proposed approach with problems from such domains is
demonstrated using three standard RL benchmarks, i.e., mountain car, cart-pole
balancing, and cart-pole swing-up. Our experimental results demonstrate
high-performing, interpretable fuzzy policies.


title: Learning Robust Video Synchronization without Annotations

abstract:
  Aligning video sequences is a fundamental yet still unsolved component for a
broad range of applications in computer graphics and vision. Most classical
image processing methods cannot be directly applied to related video problems
due to the high amount of underlying data and their limit to small changes in
appearance. We present a scalable and robust method for computing a non-linear
temporal video alignment. The approach autonomously manages its training data
for learning a meaningful representation in an iterative procedure each time
increasing its own knowledge. It leverages on the nature of the videos
themselves to remove the need for manually created labels. While previous
alignment methods similarly consider weather conditions, season and
illumination, our approach is able to align videos from data recorded months
apart.


title: Natural lifts of Dorfman brackets

abstract:
  In this note we prove that, for a vector bundle $E$ over a manifold $M$, a
Dorfman bracket on $TM\oplus E^*$ anchored by $\operatorname{pr}_{TM}$ and with
$E$ a vector bundle over $M$, is equivalent to a lift from $\Gamma(TM\oplus
E^*)$ to linear sections of $TE\oplus T^*E\to E$, that intertwines the given
Dorfman bracket with the Courant-Dorfman bracket on sections of $TE\oplus
T^*E$. This shows a universality of the Courant-Dorfman bracket, and allows us
to caracterise twistings and symmetries of transitive Dorfman brackets via the
corresponding lifts.


title: Curvature-controlled defect dynamics in active systems

abstract:
  We have studied the collective motion of polar active particles confined to
ellipsoidal surfaces. The geometric constraints lead to the formation of
vortices that encircle surface points of constant curvature (umbilics). We have
found that collective motion patterns are particularly rich on ellipsoids, with
four umbilics where vortices tend to be located near pairs of umbilical points
to minimize their interaction energy. Our results provide a new perspective on
the migration of living cells, which most likely use the information provided
from the curved substrate geometry to guide their collective motion.


title: On a new kind of Ansatz Spaces for Matrix Polynomials

abstract:
  In this paper, we introduce a new family of equations for matrix pencils that
may be utilized for the construction of strong linearizations for any square or
rectangluar matrix polynomial. We provide a comprehensive characterization of
the resulting vector spaces and show that almost every matrix pencil therein is
a strong lineariza- tion regardless whether the matrix polynomial under
consideration is regular or sin- gular. These novel "ansatz spaces" cover all
block-Kronecker pencils as a subset and therefore contain all Fiedler pencils
modulo permutations. The important case of square matrix polynomials is
examined in greater depth. We prove that the intersection of any number of
block-Kronecker ansatz spaces is never empty and construct large subspaces of
blocksymmetric matrix pencils among which still almost every pencil is a strong
linearization. Moreover, we show that the original ansatz spaces L1 and L2 may
essentially be recovered from block-Kronecker ansatz spaces via pre- and
postmultiplication, respectively, of certain constant matrices.


title: Radiative charge transfer in collisions of C with He+

abstract:
  Radiative charge exchange collisions between a carbon atom C(${}^3$P) and a
helium ion He+, both in their ground state, are investigated theoretically.
Detailed quantum chemistry calculations are carried out to obtain potential
energy curves and transition dipole matrix elements for doublet and quartet
molecular states of the HeC+ cation. Radiative charge transfer cross sections
and rate coefficients are calculated and are found at thermal and lower
energies to be large compared to those for direct charge transfer. The present
results might be applicable to modelling the complex interplay of [C II] (or
C+), C, and CO at the boundaries of interstellar photon dominated regions
(PDRs) and in xray dominated regions (XDRs), where the abundance of He+ affects
the abundance of CO.


title: Testing stellar evolution models with the retired A star HD 185351

abstract:
  The physical parameters of the retired A star HD 185351 were analysed in
great detail by Johnson et al. (2014) using interferometry, spectroscopy and
asteroseismology. Results from all independent methods are consistent with HD
185351 having a mass in excess of $1.5\mathrm{M}_{\odot}$. However, the study
also showed that not all observational constraints could be reconciled in
stellar evolutionary models, leading to mass estimates ranging from $\sim
1.6-1.9\mathrm{M}_{\odot}$ and casting doubts on the accuracy of stellar
properties determined from asteroseismology. Here we solve this discrepancy and
construct a theoretical model in agreement with all observational constraints
on the physical parameters of HD 185351. The effects of varying input physics
are examined as well as considering the additional constraint of the observed
g-mode period spacing. This quantity is found to be sensitive to the inclusion
of additional mixing from the convective core during the main sequence, and can
be used to calibrate the overshooting efficiency using low-luminosity red giant
stars. A theoretical model with metallicity
$\left[\mathrm{Fe/H}\right]=0.16$dex, mixing-length parameter
$\alpha_{\mathrm{MLT}}=2.00$, and convective overshooting efficiency parameter
$f=0.030$ is found to be in complete agreement with all observational
constraints for a stellar mass of $M\simeq1.60\mathrm{M}_{\odot}$.


title:
D-OAMP: A Denoising-based Signal Recovery Algorithm for Compressed
  Sensing

abstract:
  Approximate message passing (AMP) is an efficient iterative signal recovery
algorithm for compressed sensing (CS). For sensing matrices with independent
and identically distributed (i.i.d.) Gaussian entries, the behavior of AMP can
be asymptotically described by a scaler recursion called state evolution.
Orthogonal AMP (OAMP) is a variant of AMP that imposes a divergence-free
constraint on the denoiser. In this paper, we extend OAMP to incorporate
generic denoisers, hence the name D-OAMP. Our numerical results show that state
evolution predicts the performance of D-OAMP well for generic denoisers when
i.i.d. Gaussian or partial orthogonal sensing matrices are involved. We compare
the performances of denosing-AMP (D-AMP) and D-OAMP for recovering natural
images from CS measurements. Simulation results show that D-OAMP outperforms
D-AMP in both convergence speed and recovery accuracy for partial orthogonal
sensing matrices.


title: Negative spontaneous emission by a moving two-level atom

abstract:
  In this paper we investigate how the dynamics of a two-level atom is affected
by its interaction with the quantized near field of a plasmonic slab in
relative motion. We demonstrate that for small separation distances and a
relative velocity greater than a certain threshold, this interaction can lead
to a population inversion, such that the probability of the excited state
exceeds the probability of the ground state, corresponding to a negative
spontaneous emission rate. It is shown that the developed theory is intimately
related to a classical problem. The problem of quantum friction is analyzed and
the differences with respect to the corresponding classical effect are
highlighted.


title: Maxwell Quasiparticles Emerged in Optical Lattices

abstract:
  We construct a two-dimensional tight-binding model of an optical lattice,
where the low energy excitations should be described by the spin-1 Maxwell
equations in the Hamiltonian form, and such linear dispersion excitations with
pesudospin-1 are so called as the Maxwell quasiparticles. The system has rich
topological features, for examples, the threefold degeneracy points called
Maxwell points may have nontrivial $\pm 2\pi$ Berry phases and the anomalous
quantum Hall effect with spin-momentum locking may appear in topological
Maxwell insulators. We propose realistic schemes for realizing the Maxwell
metals/insulators and detecting the intrinsic properties of the topological
Maxwell quasiparticles with ultracold atoms in optical lattices.


title: Parallel Construction of Wavelet Trees on Multicore Architectures

abstract:
  The wavelet tree has become a very useful data structure to efficiently
represent and query large volumes of data in many different domains, from
bioinformatics to geographic information systems. One problem with wavelet
trees is their construction time. In this paper, we introduce two algorithms
that reduce the time complexity of a wavelet tree's construction by taking
advantage of nowadays ubiquitous multicore machines.
  Our first algorithm constructs all the levels of the wavelet in parallel in
$O(n)$ time and $O(n\lg\sigma + \sigma\lg n)$ bits of working space, where $n$
is the size of the input sequence and $\sigma$ is the size of the alphabet. Our
second algorithm constructs the wavelet tree in a domain-decomposition fashion,
using our first algorithm in each segment, reaching $O(\lg n)$ time and
$O(n\lg\sigma + p\sigma\lg n/\lg\sigma)$ bits of extra space, where $p$ is the
number of available cores. Both algorithms are practical and report good
speedup for large real datasets.


title:
Transferring arbitrary d-dimensional quantum states of a superconducting
  qudit in circuit QED

abstract:
  A qudit ($d$-level quantum systems) has a large Hilbert space and thus can be
used to achieve many quantum information and communication tasks. Here, we
propose a method to transfer arbitrary $d$-dimensional quantum states (known or
unknown) between two superconducting qudits coupled to a single cavity. The
state transfer can be performed fast because of employing resonant interactions
only. In addition, quantum states can be deterministically transferred without
measurement. Numerical simulations show that high-fidelity transfer of quantum
states between two superconducting transmon qudits ($d\leq5$) is feasible with
current circuit QED technology. This proposal is quite general and can be
applied to accomplish the same task with various superconducting qudits,
quantum dots, or natural atoms coupled to a cavity or resonator.


title: Penalized Variable Selection for Multi-center Competing Risks Data

abstract:
  We consider variable selection in competing risks regression for multi-center
data. Our research is motivated by deceased donor kidney transplants, from
which recipients would experience graft failure, death with functioning graft
(DWFG), or graft survival. The occurrence of DWFG precludes graft failure from
happening and therefore is a competing risk. Data within a transplant center
may be correlated due to a latent center effect, such as varying patient
populations, surgical techniques, and patient management. The proportional
subdistribution hazard (PSH) model has been frequently used in the regression
analysis of competing risks data. Two of its extensions, the stratified and the
marginal PSH models, can be applied to multi-center data to account for the
center effect. In this paper, we propose penalization strategies for the two
models, primarily to select important variables and estimate their effects
whereas correlations within centers serve as a nuisance. Simulations
demonstrate good performance and computational efficiency for the proposed
methods. It is further assessed using an analysis of data from the United
Network of Organ Sharing.


title:
Coherent diffractive imaging of single helium nanodroplets with a high
  harmonic generation source

abstract:
  Coherent diffractive imaging of individual free nanoparticles has opened
novel routes for the in-situ analysis of their transient structural, optical,
and electronic properties. So far, single-shot single-particle diffraction was
assumed to be feasible only at extreme ultraviolet (XUV) and X-ray
free-electron lasers, restricting this research field to large-scale
facilities. Here we demonstrate single-shot imaging of isolated helium
nanodroplets using XUV pulses from a femtosecond-laser driven high harmonic
source. We obtain bright wide-angle scattering patterns, that allow us to
uniquely identify hitherto unresolved prolate shapes of superfluid helium
droplets. Our results mark the advent of single-shot gas-phase nanoscopy with
lab-based short-wavelength pulses and pave the way to ultrafast coherent
diffractive imaging with phase-controlled multicolor fields and attosecond
pulses.


title: Dimension of the moduli space of a curve in the complex plane

abstract:
  We give a formula to compute the dimension of the generic component of the
moduli space of an irreducible germ of curve in the complex plane.


title: Yang-Baxter operators in symmetric categories

abstract:
  We introduce non-degenerate solutions of the Yang-Baxter equation in the
setting of symmetric monoidal categories. Our theory includes non-degenerate
set-theoretical solutions as basic examples. However, infinite families of
non-degenerate solutions (that are not of set-theoretical type) appear. As in
the classical theory of Etingof, Schedler and Soloviev, non-degenerate
solutions are classified in terms of invertible 1-cocycles. Braces and matched
pairs of cocommutative Hopf algebras (or braiding operators) are also
generalized to the context of symmetric monoidal categories and turn out to be
equivalent to invertible 1-cocycles.


title: Exceptional times of the critical dynamical Erd\H{o}s-R\'enyi graph

abstract:
  In this paper we introduce a network model which evolves in time, and study
its largest connected component. We consider a process of graphs $(G_t:t\in
[0,1])$, where initially we start with a critical Erd\H{o}s-R\'enyi graph ER(n,
1/n), and then evolve forwards in time by resampling each edge independently at
rate 1. We show that the size of the largest connected component that appears
during the time interval $[0, 1]$ is of order $n^{2/3} log^{1/3} n$ with high
probability. This is in contrast to the largest component in the static
critical Erd\H{o}s-R\'enyi graph, which is of order $n^{2/3}$.


title: Gauge covariance of the fermion Schwinger-Dyson equation in QED

abstract:
  Any practical application of the Schwinger-Dyson equations to the study of
$n$-point Green's functions of a field theory requires truncations, the best
known being finite order perturbation theory. Strong coupling studies require a
different approach. In the case of QED, gauge covariance is a powerful
constraint. By using a spectral representation for the massive fermion
propagator in QED, we are able to show that the constraints imposed by the
Landau-Khalatnikov-Fradkin transformations are linear operations on the
spectral densities. Here we formally define these group operations and show
with a couple of examples how in practice they provide a straightforward way to
test the gauge covariance of any viable truncation of the Schwinger-Dyson
equation for the fermion 2-point function.


title: Schlesinger foliation for deformations of foliations

abstract:
  In this article, we show that for any deformation of analytic foliations,
there exists a maximal analytic singular foliation on the space of parameters
along the leaves of which the deformation is integrable.


title:
Zooming into the Cosmic Horseshoe: new insights on the lens profile and
  the source shape

abstract:
  The gravitational lens SDSS J1148+1930, also known as the Cosmic Horseshoe,
is one of the biggest and of the most detailed Einstein rings ever observed. We
use the forward reconstruction method implemented in the lens fitting code
Lensed to investigate with great detail the properties of the lens and of the
background source. We model the lens with different mass distributions,
focusing in particular on the determination of the slope of the dark matter
component. The inherent degeneracy between the lens slope and the source size
can be broken when we can isolate separate components of each lensed image, as
in this case. For an elliptical power law model, $\kappa(r) \sim r^{-t}$, the
results favour a flatter-than-isothermal slope with a maximum-likelihood value
t = 0.08. Instead, when we consider the contribution of the baryonic matter
separately, the maximum-likelihood value of the slope of the dark matter
component is t = 0.31 or t = 0.44, depending on the assumed Initial Mass
Function. We discuss the origin of this result by analysing in detail how the
images and the sources change when the slope t changes. We also demonstrate
that these slope values at the Einstein radius are not inconsistent with recent
forecast from the theory of structure formation in the LambdaCDM model.


title:
Robust unidirectional transport in a one-dimensional metacrystal with
  long-range hopping

abstract:
  In two- and three-dimensional structures, topologically-protected chiral edge
modes offer a powerful mean to realize robust light transport. However, little
attention has been paid so far to robust one-way transport in one-dimensional
systems. Here it is shown that unidirectional transport, which is immune to
disorder and backscattering, can occur in certain one-dimensional metacrystals
with long-range hopping without resorting to topological protection. Such
metacrystals are described by an effective Hermitian Hamiltonian with broken
time reversal symmetry, and transport does not require adiabatic (Thouless)
pumping. A simple implementation in optics of such one-dimensional
metacrystals, based on transverse light dynamics in a self-imaging optical
cavity with phase gratings, is suggested


title: On the topology of Diophantine approximation Spectra

abstract:
  Fix an integer $n\ge 2$. To each non-zero point $\mathbf{u}$ in
$\mathbb{R}^n$, one attaches several numbers called exponents of Diophantine
approximation. However, as Khintchine first observed, these numbers are not
independent of each other. This raises the problem of describing the set of all
possible values that a given family of exponents can take by varying the point
$\mathbf{u}$. To avoid trivialities, one restricts to points $\mathbf{u}$ whose
coordinates are linearly independent over $\mathbb{Q}$. The resulting set of
values is called the spectrum of these exponents. We show that, in an
appropriate setting, any such spectrum is a compact connected set. In the case
$n=3$, we prove moreover that it is a semi-algebraic set closed under
component-wise minimum. For $n=3$, we also obtain a description of the spectrum
of a family of six exponents recently introduced by Schmidt and Summerer.


title:
Early onset of structural inequality in the formation of collaborative
  knowledge, Wikipedia

abstract:
  We perform an in-depth analysis on the inequality in 863 Wikimedia projects.
We take the complete editing history of 267,304,095 Wikimedia items until 2016,
which not only covers every language edition of Wikipedia, but also embraces
the complete versions of Wiktionary, Wikisource, Wikivoyage, etc. Our findings
of common growth pattern described by the interrelations between four
characteristic growth yardsticks suggest a universal law of communal data
formation. In this encyclopaedic data set, we observe the interplay between the
number of edits and the degree of inequality. In particular, the rapid increase
in the Gini coefficient suggests that this entrenched inequality stems from the
nature of such open-editing communal data sets, namely the abiogenesis of the
supereditors' oligopoly. We show that these supereditor groups were created at
the early stages of these open-editing media and are still active. Furthermore,
our model considers both short-term and long-term memories to successfully
elucidate the underlying mechanism of the establishment of oligarchy in
Wikipedia. Our results anticipate a noticeable prospect of such communal
databases in the future: the disparity will not be resolved spontaneously.


title:
Localization, quantum resonances and ratchet acceleration in a
  periodically-kicked $\mathcal{PT}$-symmetric quantum rotator

abstract:
  We consider wave transport phenomena in a $\mathcal{PT}$-symmetric extension
of the periodically-kicked quantum rotator model and reveal that dynamical
localization assists the unbroken $\mathcal{PT}$ phase. In the delocalized
(quantum resonance) regime, $\mathcal{PT}$ symmetry is always in the broken
phase and ratchet acceleration arises as a signature of unidirectional
non-Hermitian transport. An optical implementation of the periodically-kicked
$\mathcal{PT}$-symmetric Hamiltonian, based on transverse beam propagation in a
passive optical resonator with combined phase and loss gratings, is suggested
to visualize acceleration modes in fractional Talbot cavities.


title: K-clique-graphs for Dense Subgraph Discovery

abstract:
  Finding dense subgraphs in a graph is a fundamental graph mining task, with
applications in several fields. Algorithms for identifying dense subgraphs are
used in biology, in finance, in spam detection, etc. Standard formulations of
this problem such as the problem of finding the maximum clique of a graph are
hard to solve. However, some tractable formulations of the problem have also
been proposed, focusing mainly on optimizing some density function, such as the
degree density and the triangle density. However, maximization of degree
density usually leads to large subgraphs with small density. In this paper, we
introduce the k-clique-graph densest subgraph problem, k >= 3, a novel
formulation for the discovery of dense subgraphs. Given an input graph, its
k-clique-graph is a new graph created from the input graph where each vertex of
the new graph corresponds to a k-clique of the input graph and two vertices are
connected with an edge if they share a common (k-1)-clique. We define a simple
density function, the k-clique-graph density, which gives compact and at the
same time dense subgraphs, and we project its resulting subgraphs back to the
input graph. In this paper we focus on the triangle-graph densest subgraph
problem obtained for k=3. To optimize the proposed function, we present an
efficient greedy approximation algorithm that scales well to larger graphs. We
evaluate the proposed algorithm on real datasets and compare it with other
algorithms in terms of the size and the density of the extracted subgraphs. The
results verify the ability of the proposed algorithm in finding high-quality
subgraphs in terms of size and density. Finally, we apply the proposed method
to the important problem of keyword extraction from textual documents.


title:
Constrained Cohort Intelligence using Static and Dynamic Penalty
  Function Approach for Mechanical Components Design

abstract:
  Most of the metaheuristics can efficiently solve unconstrained problems;
however, their performance may degenerate if the constraints are involved. This
paper proposes two constraint handling approaches for an emerging metaheuristic
of Cohort Intelligence (CI). More specifically CI with static penalty function
approach (SCI) and CI with dynamic penalty function approach (DCI) are
proposed. The approaches have been tested by solving several constrained test
problems. The performance of the SCI and DCI have been compared with algorithms
like GA, PSO, ABC, d-Ds. In addition, as well as three real world problems from
mechanical engineering domain with improved solutions. The results were
satisfactory and validated the applicability of CI methodology for solving real
world problems.


title:
Regularity of complex geodesics and (non)-Gromov hyperbolicity of convex
  tube domains

abstract:
  We deliver examples of non-Gromov hyperbolic tube domains with convex bases
(equipped with the Kobayashi distance). This is shown by providing a criterion
on non-Gromov hyperbolicity of (non-smooth) domains.The results show the
similarity of geometry of the bases of non-Gromov hyperbolic tube domains with
the geometry of non-Gromov hyperbolic convex domains. A connection between the
Hilbert metric of a convex domain $\Omega$ in $\mathbb R^n$ with the Kobayashi
distance of the tube domain over the domain $\Omega$ is also shown. Moreover,
continuity properties up to the boundary of complex geodesics in tube domains
with a smooth convex bounded base are also studied in detail.


title: Pasta phases within the QMC model

abstract:
  In this work the low density regions of nuclear and neutron star matter are
studied. The search for the existence of pasta phases in this region is
performed within the context of the quark-meson coupling (QMC) model, which
incorporates quark degrees of freedom. Fixed proton fractions are considered,
as well as nuclear matter in beta equilibrium at zero temperature. We discuss
the recent attempts to better understand the surface energy in the coexistence
phases regime and we present results that show the existence of the pasta
phases subject to some choices of the surface energy coefficient. We also
analyze the influence of the nuclear pasta on some neutron star properties. The
equation of state containing the pasta phase will be part of a complete grid
for future use in supernova simulations.


title: Omnithermal Perfect Simulation for Multi-server Queues

abstract:
  A number of perfect simulation algorithms for multi-server First Come First
Served queues have recently been developed. Those of Connor and Kendall (2015)
and Blanchet, Pei, and Sigman (2015) use dominated Coupling from the Past
(domCFTP) to sample from the equilibrium distribution of the Kiefer-Wolfowitz
workload vector for stable M/G/c and GI/GI/c queues respectively, using Random
Assignment queues as dominating processes. In this note we answer a question
posed by Connor and Kendall (2015), by demonstrating how these algorithms may
be modified in order to carry out domCFTP simultaneously for a range of values
of c (the number of servers).


title: On the width of N-Delta and Delta-Delta states

abstract:
  It is seen by a coupled-channel calculation that in the two-baryon N-Delta or
Delta-Delta system the width of the state is greatly diminished due to the
relative kinetic energy of the two baryons, since the internal energy of the
particles, available for pionic decay, is smaller. A similar state dependent
effect arises from the centrifugal barrier in N-Delta or Delta-Delta systems
with non-zero orbital angular momentum. The double-Delta width can become even
smaller than the free width of a single Delta. This has some bearing to the
interpretation of the d'(2380) resonance recently discovered at COSY.


title: Collision of two Hopfions

abstract:
  We study the collision of two hopfions or Hopf-Ra\~nada electromagnetic
fields. The superposition of two of such fields, travelling in opposite
directions, yields different topology for the electric and magnetic field
lines. Controlling the angular momentum of such fields, we can control the
topology of the flow associated to the field lines, and the energy
distribution. The concept of electromagnetic helicity and the exchange between
its magnetic and electric components are used to explain the different
behaviours observed when the angular momentum is reversed.


title: Making of a nonlinear optical cavity

abstract:
  In the article we explain in detail how to build a photorefractive oscillator
(PRO), which is a laser-pumped nonlinear optical cavity containing a
photorefractive crystal. The specific PRO whose construction we describe
systematically, is based on a Fabry-Perot optical cavity working in a
non-degenerate four wave-mixing configuration. This particular PRO has the
property that the generated beam exhibits laser-like phase invariance and, as
an application, we show how a suitably modulated injected beam converts the
output field from phase-invariant into phase-bistable. While the emphasis is
made on the making of the experimental device and on the way measurements are
implemented, some introduction to the photorefractive effect as well as to the
necessary concepts of nonlinear dynamics are also given, so that the article is
reasonably self-contained.

categories: physics.ins-det nlin.PS physics.ed-ph physics.optics


title:
The effect of tangential drifts on neoclassical transport in
  stellarators close to omnigeneity

abstract:
  In general, the orbit-averaged radial magnetic drift of trapped particles in
stellarators is non-zero due to the three-dimensional nature of the magnetic
field. Stellarators in which the orbit-averaged radial magnetic drift vanishes
are called omnigeneous, and they exhibit neoclassical transport levels
comparable to those of axisymmetric tokamaks. However, the effect of deviations
from omnigeneity cannot be neglected in practice. For sufficiently low
collision frequencies (below the values that define the $1/\nu$ regime), the
components of the drifts tangential to the flux surface become relevant. This
article focuses on the study of such collisionality regimes in stellarators
close to omnigeneity when the gradient of the non-omnigeneous perturbation is
small. First, it is proven that closeness to omnigeneity is required to
preserve radial locality in the drift-kinetic equation for collisionalities
below the $1/\nu$ regime. Then, it is shown that neoclassical transport is
determined by two layers in phase space. One of the layers corresponds to the
$\sqrt{\nu}$ regime and the other to the superbanana-plateau regime. The
importance of the superbanana-plateau layer for the calculation of the
tangential electric field is emphasized, as well as the relevance of the latter
for neoclassical transport in the collisionality regimes considered in this
paper. In particular, the tangential electric field is essential for the
emergence of a new subregime of superbanana-plateau transport when the radial
electric field is small. A formula for the ion energy flux that includes the
$\sqrt{\nu}$ regime and the superbanana-plateau regime is given. The energy
flux scales with the square of the size of the deviation from omnigeneity.
Finally, it is explained why below a certain collisionality value the
formulation presented in this article ceases to be valid.


title: Rapidly rotating pulsar radiation in vacuum nonlinear electrodynamics

abstract:
  In this paper we investigate vacuum nonlinear electrodynamics corrections on
rapidly rotating pulsar radiation and spin-down in the perturbative QED
approach (post-Maxwellian approximation). An analytical expression for the
pulsar's radiation intensity has been obtained and analyzed.


title: Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

abstract:
  We describe some of the first polarized neutron scattering measurements
performed at HYSPEC spectrometer at the Spallation Neutron Source, Oak Ridge
National Laboratory. We discuss details of the instrument setup and the
experimental procedures in the mode with full polarization analysis. Examples
of polarized neutron diffraction and polarized inelastic neutron data obtained
on single crystal samples are presented.


title:
New algorithms for identifying the flavour of $B^0$ mesons using pions
  and protons

abstract:
  Two new algorithms for use in the analysis of $pp$ collision are developed to
identify the flavour of $B^0$ mesons at production using pions and protons from
the hadronization process. The algorithms are optimized and calibrated on data,
using $B^0 \rightarrow D^- \pi^+$ decays from $pp$ collision data collected by
LHCb at centre-of-mass energies of 7 and 8 TeV. The tagging power of the new
pion algorithm is 60 % greater than the previously available one; the algorithm
using protons to identify the flavour of a $B^0$ meson is the first of its
kind.


title: Gravitation at the Josephson Junction

abstract:
  A geometric potential from the kinetic term of a constrained to a curved
hyperplane of space-time quantum superconducting condensate is derived. An
energy conservation relation involving the geometric field at every material
point in the superconductor is demonstrated. At a Josephson junction the energy
conservation relation implies the possibility of transforming electric energy
into geometric field energy, that is, curvature of space-time. Experimental
procedures to verify that the Josephson junction can act as a
voltage-to-curvature converter are discussed.


title: Graphs of kei and their diameters

abstract:
  A kei on $[n]$ can be thought of as a set of maps $(f_x)_{x \in [n]}$, where
each $f_x$ is an involution on $[n]$ such that $(x)f_x = x$ for all $x$ and
$f_{(x)f_y} = f_yf_xf_y$ for all $x$ and $y$. We can think of kei as loopless,
edge-coloured multigraphs on $[n]$ where we have an edge of colour $y$ between
$x$ and $z$ if and only if $(x)f_y = z$; in this paper we show that any
component of diameter $d$ in such a graph must have at least $2^d$ vertices and
contain at least $2^{d-1}$ edges of the same colour. We also show that these
bounds are tight for each value of $d$.


title: From Malware Signatures to Anti-Virus Assisted Attacks

abstract:
  Although anti-virus software has significantly evolved over the last decade,
classic signature matching based on byte patterns is still a prevalent concept
for identifying security threats. Anti-virus signatures are a simple and fast
detection mechanism that can complement more sophisticated analysis strategies.
However, if signatures are not designed with care, they can turn from a
defensive mechanism into an instrument of attack. In this paper, we present a
novel method for automatically deriving signatures from anti-virus software and
demonstrate how the extracted signatures can be used to attack sensible data
with the aid of the virus scanner itself. We study the practicability of our
approach using four commercial products and exemplarily discuss a novel attack
vector made possible by insufficiently designed signatures. Our research
indicates that there is an urgent need to improve pattern-based signatures if
used in anti-virus software and to pursue alternative detection approaches in
such products.


title:
Practical estimation of rotation distance and induced partial order for
  binary trees

abstract:
  Tree rotations (left and right) are basic local deformations allowing to
transform between two unlabeled binary trees of the same size. Hence, there is
a natural problem of practically finding such transformation path with low
number of rotations, the optimal minimal number is called the rotation
distance. Such distance could be used for instance to quantify similarity
between two trees for various machine learning problems, for example to compare
hierarchical clusterings or arbitrarily chosen spanning trees of two graphs,
like in SMILES notation popular for describing chemical molecules.
  There will be presented inexpensive practical greedy algorithm for finding a
short rotation path, optimality of which has still to be determined. It uses
introduced partial order for binary trees of the same size: $t_1 \leq t_2$ iff
$t_2$ can be obtained from $t_1$ by a sequence of only right rotations.
Intuitively, the shortest rotation path should go through the least upper bound
or the greatest lower bound for this partial order. The algorithm finds a path
through candidates for both points in representation of binary tree as stack
graph: describing evolution of content of stack while processing a formula
described by a given binary tree. The article is accompanied with Mathematica
implementation of all used procedures (Appendix).


title:
$H_{u,d}$-messenger Couplings Address the $\mu/B_\mu$ \& $A_t/m_{H_u}^2$
  Problem and $(g-2)_\mu$ Puzzle

abstract:
  Gauge mediated supersymmetry (SUSY)-breaking (GMSB) furnishes the best idea
to overcome the flavor problem in SSMs, supersymmetric stand models (SM).
However, implemented in the minimal SSM (MSSM), a very serious fine-tuning
problem arises, owing to the absence of a large $A_t$ term in the stop sector
to radiatively enhance the SM-like Higgs boson mass. In the extended GMSB
coupling $H_u$ to messengers can alleviate this problem but encounters the
$A_t/m_{H_u}^2$ problem, i.e., at the same time a large $m_{H_u}^2$ is
generated, rendering radiative electroweak spontaneously breaking (EWSB)
problematic. This issue shows similarity to another long-standing problem of
GMSB, the $\mu/{B_\mu }$ problem, and, of great interest, we find that they may
admit the same solution, nonradiative EWSB. Such a solution is naturally
accommodated when both $H_u$ and $H_d$ couple to messengers. As a bonus of
nonradiative EWSB, the sleptons tend to be very light due to the significant
renormalization group equation effect and they are able to account for the
$(g-2)_\mu$ puzzle. As a concrete example, we investigate a hidden sector with
$(10,\overline {10})$ messengers.


title:
The maximal existence region of the analytic solutions for a class of
  characteristic Einstein vacuum equations

abstract:
  The main goal of this work consists in showing that the analytic solutions
for a class of characteristic problems for the Einstein vacuum equations have
an existence region larger than the one provided by the Cauchy-Kowalevski
theorem, due to the intrinsic hyperbolicity of the Einstein equations. The
magnitude of this region depends only on suitable $H_s$ Sobolev norms of the
initial data for a fixed $s\leq 7$ and if the initial data are sufficiently
small the analytic solution is global. In a previous paper, hereafter "I", we
have described a geometric way of writing the vacuum Einstein equations for the
characteristic problems we are considering and a local solution in a suitable
"double null cone gauge" characterized by the use of a double null cone
foliation of the spacetime.


title: Least squares estimation in the monotone single index model

abstract:
  We study the monotone single index model where a real response variable $Y $
is linked to a $d$-dimensional covariate $X$ through the relationship $E[Y | X]
= \Psi_0(\alpha^T_0 X)$ almost surely. Both the ridge function, $\Psi_0$, and
the index parameter, $\alpha_0$, are unknown and the ridge function is assumed
to be monotone on its interval of support. Under some regularity conditions,
without imposing a particular distribution on the regression error, we show the
$n^{-1/3}$ rate of convergence in the $\ell_2$-norm for the least squares
estimator of the bundled function $\psi_0({\alpha}^T_0 \cdot),$ and also that
of the ridge function and the index separately. Furthermore, we show that the
least squares estimator is nearly parametrically rate-adaptive to piecewise
constant ridge functions.


title:
B\"uchi automata recognizing sets of reals definable in first-order
  logic with addition and order

abstract:
  This work considers weak deterministic B\"uchi automata reading encodings of
non-negative reals in a fixed base. A Real Number Automaton is an automaton
which recognizes all encoding of elements of a set of reals. It is explained
how to decide in linear time whether a set of reals recognized by a given
minimal weak deterministic RNA is ${FO}[\mathbb R;+,<,1]$-definable.
Furthermore, it is explained how to compute in quasi-quadratic (respectively,
quasi-linear) time an existential (respectively, existential-universal)
${FO}[\mathbb R;+,<,1]$-formula which defines the set of reals recognized by
the automaton. It is also shown that techniques given by Muchnik and by Honkala
for automata over vector of natural numbers also works on vector of real
numbers. It implies that some problems such as deciding whether a set of tuples
of reals $R\subseteq\mathbb R^{d}$ is a subsemigroup of $(\mathbb R^{d},+)$ or
is ${FO}[\mathbb R;+,<,1]$-definable is decidable.


title:
On the splitting method for the nonlinear Schr\"odinger equation with
  initial data in $H^1$

abstract:
  In this paper, we establish a convergence result for the operator splitting
scheme $Z_{\tau}$ introduced by Ignat, with initial data in $H^1$, for the
nonlinear Schr\"odinger equation :
  $$
  \partial_t u = i \Delta u + i\lambda |u|^{p} u,\qquad u (x,0) =\phi (x),
  $$ where $(x,t) \in \mathbb{R}^d \times [0,\infty)$, with $0< p < 4/(d-2)$
for $d\geq3$ and $0< p<\infty$ for $d=1,2$. We prove the $L^2$ convergence of
order $\mathcal{O}(\tau^{1/2})$ for this scheme with initial data in the space
$H^1 (\mathbb{R}^d)$.


title:
Swimming at small Reynolds number of a collinear assembly of spheres in
  an incompressible viscous fluid

abstract:
  Swimming at small Reynolds number of a linear assembly of identical spheres
immersed in a viscous fluid is studied on the basis of a set of equations of
motion for the individual spheres. The motion of the spheres is caused by
actuating forces and forces derived from a direct interaction potential, as
well as hydrodynamic forces exerted by the fluid as frictional and added mass
hydrodynamic interactions. The swimming velocity is deduced from the momentum
balance equation for the assembly of spheres, and the mean power required
during a period is calculated from an instantaneous power equation. Expressions
are derived for the mean swimming velocity and the mean power, valid to second
order in the amplitude of displacements from the relative equilibrium
positions. Hence these quantities can be evaluated in terms of prescribed
periodic displacements. Explicit calculations are performed for a linear chain
of three identical spheres.


title:
Optimal convergence rate of nonrelativistic limit for the nonlinear
  pseudo-relativistic equations

abstract:
  In this paper, we are concerned with the nonrelativistic limit of the
following pseudo-relativistic equation with Hartree nonlinearity or power type
nonlinearity \[ \left(\sqrt{-\hbar^2c^2 \Delta +m^2c^4} - mc^2 \right) u + \mu
u = \mathcal{N}(u), \] where $c$ denotes the speed of light. We prove that the
ground states of this equation converges to the ground state of its
nonrelativistic counterpart \[ -\frac{\hbar^2}{2m}\Delta u + \mu u =
\mathcal{N}(u) \] with an explicit convergence rate $1/c^2$ in arbitrary order
as $c \to \infty$. Moreover, we show that this rate is optimal.