title:
Study on parameter choice methods for the RFMP with respect to downward
  continuation

abstract:
  Recently, the regularized functional matching pursuit (RFMP) was introduced
as a greedy algorithm for linear ill-posed inverse problems. This algorithm
incorporates the Tikhonov-Phillips regularization which implies the necessity
of a parameter choice. In this paper, some known parameter choice methods are
evaluated with respect to their performance in the RFMP and its enhancement,
the regularized orthogonal functional matching pursuit (ROFMP). As an example
of a linear inverse problem, the downward continuation of gravitational field
data from the satellite orbit to the Earth's surface is chosen, because it is
exponentially ill-posed. For the test scenarios, different satellite heights
with several noise-to-signal ratios and kinds of noise are combined. The
performances of the parameter choice strategies in these scenarios are
analyzed. For example, it is shown that a strongly scattered set of data points
is an essentially harder challenge for the regularization than a regular grid.
The obtained results yield a first orientation which parameter choice methods
are feasible for the RFMP and the ROFMP.


title: Task-driven sampling of attributed networks

abstract:
  This paper introduces new techniques for sampling attributed networks to
support standard Data Mining tasks. The problem is important for two reasons.
First, it is commonplace to perform data mining tasks such as clustering and
classification of network attributes (attributes of the nodes, including social
media posts). Furthermore, the extraordinarily large size of real-world
networks necessitates that we work with a smaller graph sample. Second, while
random sampling will provide an unbiased estimate of content, random access is
often unavailable for many networks. Hence, network samplers such as Snowball
sampling, Forest Fire, Random Walk, Metropolis-Hastings Random Walk are widely
used; however, these attribute-agnostic samplers were designed to capture
salient properties of network structure, not node content. The latter is
critical for clustering and classification tasks. There are three contributions
of this paper. First, we introduce several attribute-aware samplers based on
Information Theoretic principles. Second, we prove that these samplers have a
bias towards capturing new content, and are equivalent to uniform sampling in
the limit. Finally, our experimental results over large real-world datasets and
synthetic benchmarks are insightful: attribute-aware samplers outperform both
random sampling and baseline attribute-agnostic samplers by a wide margin in
clustering and classification tasks.


title: DecreaseKeys are Expensive for External Memory Priority Queues

abstract:
  One of the biggest open problems in external memory data structures is the
priority queue problem with DecreaseKey operations. If only Insert and
ExtractMin operations need to be supported, one can design a comparison-based
priority queue performing $O((N/B)\lg_{M/B} N)$ I/Os over a sequence of $N$
operations, where $B$ is the disk block size in number of words and $M$ is the
main memory size in number of words. This matches the lower bound for
comparison-based sorting and is hence optimal for comparison-based priority
queues. However, if we also need to support DecreaseKeys, the performance of
the best known priority queue is only $O((N/B) \lg_2 N)$ I/Os. The big open
question is whether a degradation in performance really is necessary. We answer
this question affirmatively by proving a lower bound of $\Omega((N/B) \lg_{\lg
N} B)$ I/Os for processing a sequence of $N$ intermixed Insert, ExtraxtMin and
DecreaseKey operations. Our lower bound is proved in the cell probe model and
thus holds also for non-comparison-based priority queues.


title: Testing the hadro-quarkonium model on the lattice

abstract:
  Recently the LHCb experiment found evidence for the existence of two exotic
resonances consisting of $c\bar{c}uud$ quarks. Among the possible
interpretations is the hadro-charmonium model, in which charmonium is bound
"within" a light hadron. We test this idea on CLS $N_f$=2+1 lattices using the
static formulation for the heavy quarks. We find that the static potential is
modified by the presence of a hadron such that it becomes more attractive. The
effect is of the order of a few MeV.


title:
Effects of $Z_b$ states and bottom meson loops on $\Upsilon(4S) \to
  \Upsilon(1S,2S) \pi^+\pi^-$ transitions

abstract:
  We study the dipion transitions $\Upsilon(4S) \rightarrow \Upsilon(nS)
\pi^+\pi^-$ $(n=1,2)$. In particular, we consider the effects of the two
intermediate bottomoniumlike exotic states $Z_b(10610)$ and $Z_b(10650)$ as
well as bottom meson loops. The strong pion-pion final-state interactions,
especially including channel coupling to $K\bar{K}$ in the $S$-wave, are taken
into account model-independently by using dispersion theory. Based on a
nonrelativistic effective field theory we find that the contribution from the
bottom meson loops is comparable to those from the chiral contact terms and the
$Z_b$-exchange terms. For the $\Upsilon(4S) \rightarrow \Upsilon(2S)
\pi^+\pi^-$ decay, the result shows that including the effects of the
$Z_b$-exchange and the bottom meson loops can naturally reproduce the two-hump
behavior of the $\pi\pi$ mass spectra. Future angular distribution data are
decisive for the identification of different production mechanisms. For the
$\Upsilon(4S) \rightarrow \Upsilon(1S) \pi^+\pi^-$ decay, we show that there is
a narrow dip around 1 GeV in the $\pi\pi$ invariant mass distribution, caused
by the final-state interactions. The distribution is clearly different from
that in similar transitions from lower $\Upsilon$ states, and needs to be
verified by future data with high statistics. Also we predict the decay width
and the dikaon mass distribution of the $\Upsilon(4S) \rightarrow \Upsilon(1S)
K^+ K^-$ process.


title:
Improvements and Testing Practical Expressions for Photon Strength
  Functions of E1 Gamma-Transitions

abstract:
  Analytical expression for the E1 photon strength functions (PSF) is modified
to account for the low-energy enhancement due to nuclear structure effects
(presence of low-energy state (LES)). A closed-form expression of the E1 PSF
function includes response of two nuclear states: LES and giant diplole
resonance (GDR). Expression for the nuclear response function on
electromagnetic field is based on a model of excitation of two coupled damped
states. These approach is tested for different data sets for spherical nuclei.
Impact on PSF shape of coupling between LES and GDR excitations is considered.


title: On Parseval wavelet frames via Multiresolution Analyses

abstract:
  We give a characterization of all Parseval wavelet frames arising from a
given frame multiresolution analysis. As a consequence, we obtain a description
of all Parseval wavelet frames associated with a frame multiresolution
analysis. These results are based on a version of Unitary Extension Principle
and Oblique Extension Principle with the assumption that the origin is a point
of approximate continuity of the Fourier transform of the involved refinable
functions.


title:
Left-invariant pseudo-Riemannian metrics on four-dimensional Lie groups
  with zero Schouten-Weyl tensor

abstract:
  In the presented paper left-invariant pseudo-Riemannian metrics on
four-dimensional Lie groups with zero Schouten-Weyl tensor are investigated.
The complete classification of these metric Lie groups is obtained in terms of
the structure constants of corresponding Lie algebras.


title:
Quantum nondemolition measurement of optical field fluctuations by
  optomechanical interaction

abstract:
  According to quantum mechanics, if we keep observing a continuous variable we
generally disturb its evolution. For a class of observables, however, it is
possible to implement a so-called quantum nondemolition measurement: by
confining the perturbation to the conjugate variable, the observable is
estimated with arbitrary accuracy, or prepared in a well-known state. For
instance, when the light bounces on a movable mirror, its intensity is not
perturbed (the effect is just seen on the phase of the radiation), but the
radiation pressure allows to trace back its fluctuations by observing the
mirror motion. In this work, we implement a cavity opto-mechanical experiment
based on an oscillating micro-mirror, and we measure correlations between the
output light intensity fluctuations and the mirror motion. We demonstrate that
the uncertainty of the former is reduced below the shot-noise level determined
by the corpuscular nature of light.


title: A Dichotomy for Regular Expression Membership Testing

abstract:
  We study regular expression membership testing: Given a regular expression of
size $m$ and a string of size $n$, decide whether the string is in the language
described by the regular expression. Its classic $O(nm)$ algorithm is one of
the big success stories of the 70s, which allowed pattern matching to develop
into the standard tool that it is today.
  Many special cases of pattern matching have been studied that can be solved
faster than in quadratic time. However, a systematic study of tractable cases
was made possible only recently, with the first conditional lower bounds
reported by Backurs and Indyk [FOCS'16]. Restricted to any "type" of
homogeneous regular expressions of depth 2 or 3, they either presented a
near-linear time algorithm or a quadratic conditional lower bound, with one
exception known as the Word Break problem.
  In this paper we complete their work as follows:
  1) We present two almost-linear time algorithms that generalize all known
almost-linear time algorithms for special cases of regular expression
membership testing.
  2) We classify all types, except for the Word Break problem, into
almost-linear time or quadratic time assuming the Strong Exponential Time
Hypothesis. This extends the classification from depth 2 and 3 to any constant
depth.
  3) For the Word Break problem we give an improved $\tilde{O}(n m^{1/3} + m)$
algorithm. Surprisingly, we also prove a matching conditional lower bound for
combinatorial algorithms. This establishes Word Break as the only intermediate
problem.
  In total, we prove matching upper and lower bounds for any type of
bounded-depth homogeneous regular expressions, which yields a full dichotomy
for regular expression membership testing.


title:
Foreword with a table of contents for Special IJMPD Issue on Spacetime
  Structure and Electrodynamics

abstract:
  In the last two decades we have seen important mutual stimulations between
the community working on electrodynamics of continuous media and the community
working on spacetime structure. This is highlighted by the publication of two
important monographs from two communities: Foundations of Classical
Electrodynamics by F. W. Hehl and Yu. N. Obukhov (Birkh\"auser, Boston 2003)
and Differential Forms in Electromagnetics by I. V. Lindell (IEEE Press-Wiley,
Piscataway, NJ 2004; see also a new book "Multiforms, Dyadics, and
Electromagnetic Media" by the same author in 2015). Starting around 1960,
magnetoelectric effects and magnetoelectric media have been a focus of study.
Somewhat later, the constitutive tensor density framework was used to construct
spacetime structure theoretically and empirically. Earlier, in putting Maxwell
equations into a form compatible with general relativity, Einstein noticed that
the Maxwell equations can be formulated in a form independent of the metric
gravitational potential in 1916; only the constitutive tensor density depends
on the metric. This was followed by further stimulating and clarifying works of
Weyl in 1918, Murnaghan in 1921, Kottler in 1922 and Cartan in 1923. Year 2016
is the centennial of the start of this historical development. International
Journal of Modern Physics D of World Scientific is celebrating the occasion by
publishing this special issue on Spacetime Structure and Electrodynamics. We
have invited researchers to submit original research articles that would
contribute to a better understanding of the phenomena inherent to spacetime
structure and electrodynamic media.


title:
$\delta$-homogeneity in Finsler geometry and the positive curvature
  problem

abstract:
  In this paper, we explore the similarity between normal homogeneity and
$\delta$-homogeneity in Finsler geometry. They are both non-negatively curved
Finsler spaces. We show that any connected $\delta$-homogeneous Finsler space
is $G$-$\delta$-homo-geneous, for some suitably chosen connected quasi-compact
$G$. So $\delta$-homogeneous Finsler metrics can be defined by a bi-invariant
singular metric on $G$ and submersion, just as normal homogeneous metrics,
using a bi-invariant Finsler metric on $G$ instead. More careful analysis
shows, in the space of all Finsler metrics on $G/H$, the subset of all
$G$-$\delta$-homogeneous ones is in fact the closure for the subset of all
$G$-normal ones, in the local $C^0$-topology (Theorem \ref{main-thm-1}). Using
this approximation technique, the classification work for positively curved
normal homogeneous Finsler spaces can be applied to classify positively curved
$\delta$-homogeneous Finsler spaces, which provides the same classification
list. As a by-product, this argument tells more about $\delta$-homogeneous
Finsler metrics satisfying the (FP) condition (a weaker version of positively
curved condition).


title:
Phase structure analysis of CP(N-1) model using Tensor renormalization
  group

abstract:
  The phase structure of the lattice CP($N-1$) model in two dimensions is
analyzed by the tensor renormalization group (TRG) method. We focus on the case
$N=2$ and compare the numerical result of the TRG method with that of the
strong-coupling analysis in the presence of the $\theta$ term and investigate
the nature of the phase transition at $\theta=\pi$.


title:
Polynomial algorithm for exact calculation of partition function for
  binary spin model on planar graphs

abstract:
  In this paper we propose and realize (the code is publicly available at
https://github.com/Thrawn1985/2D-Partition-Function) an algorithm for exact
calculation of partition function for planar graph models with binary spins.
The complexity of the algorithm is O(N^2). Test experiments shows good
agreement with Onsager's analytical solution for two-dimensional Ising model of
infinite size.

categories: cond-mat.dis-nn cond-mat.stat-mech cs.DS physics.comp-ph


title:
Deterministic patterned growth of high-mobility large-crystal graphene:
  a path towards wafer scale integration

abstract:
  We demonstrate rapid deterministic (seeded) growth of large single-crystals
of graphene by chemical vapour deposition (CVD) utilising pre-patterned copper
substrates with chromium nucleation sites. Arrays of graphene single-crystals
as large as several hundred microns are grown with a periodicity of up to 1 mm.
The graphene is transferred to target substrates using aligned and
contamination-free semi-dry transfer. The high quality of the synthesised
graphene is confirmed by Raman spectroscopy and transport measurements,
demonstrating room-temperature carrier mobility of 21 000 cm2 / V s when
transferred on top of hexagonal boron nitride. By tailoring the nucleation of
large single-crystals according to the desired device geometry, it will be
possible to produce complex device architectures based on single-crystal
graphene, thus paving the way to the adoption of CVD graphene in wafer-scale
fabrication.


title:
Optical analogues of the Newton-Schr\"odinger equation and boson star
  evolution

abstract:
  Many gravitational phenomena that lie at the core of our understanding of the
Universe have not yet been directly observed. An example in this sense is the
boson star that has been proposed as an alternative to some compact objects
currently interpreted as being black holes. In the weak field limit, these
stars are governed by the Newton-Schrodinger equation (NSE). Here we present an
optical system that, under appropriate conditions, identically reproduces the
NSE in two dimensions. A rotating boson star is experimentally and numerically
modelled by an optical beam propagating through a medium with a positive
thermal nonlinearity and is shown to oscillate in time while also stable up to
relatively high densities. For higher densities, instabilities lead to an
apparent breakup of the star, yet coherence across the whole structure is
maintained. These results show that optical analogues can be used to shed new
light on inaccessible gravitational objects.


title: On the analytic systole of Riemannian surfaces of finite type

abstract:
  In our previous work we introduced, for a Riemannian surface $S$, the
quantity $ \Lambda(S):=\inf_F\lambda_0(F)$, where $\lambda_0(F)$ denotes the
first Dirichlet eigenvalue of $F$ and the infimum is taken over all compact
subsurfaces $F$ of $S$ with smooth boundary and abelian fundamental group. A
result of Brooks implies $\Lambda(S)\ge\lambda_0(\tilde{S})$, the bottom of the
spectrum of the universal cover $\tilde{S}$. In this paper, we discuss the
strictness of the inequality. Moreover, in the case of curvature bounds, we
relate $\Lambda(S)$ with the systole, improving a result by the last named
author.


title: Min-max theory for minimal hypersurfaces with boundary

abstract:
  In this note we propose a min-max theory for embedded hypersurfaces with a
fixed boundary and apply it to prove several theorems about the existence of
embedded minimal hypersurfaces with a given boundary. A simpler variant of
these theorems holds also for the case of the free boundary minimal surfaces.


title:
$\alpha$-scattering and $\alpha$-induced reaction cross sections of
  $^{64}$Zn at low energies

abstract:
  Background: alpha-nucleus potentials play an essential role for the
calculation of alpha-induced reaction cross sections at low energies in the
statistical model...
  Purpose: The present work studies the total reaction cross section sigma_reac
of alpha-induced reactions at low energies which can be determined from the
elastic scattering angular distribution or from the sum over the cross sections
of all open non-elastic channels.
  Method: Elastic and inelastic 64Zn(a,a)64Zn angular distributions were
measured at two energies around the Coulomb barrier at 12.1 MeV and 16.1 MeV.
Reaction cross sections of the (a,g), (a,n), and (a,p) reactions were measured
at the same energies using the activation technique. The contributions of
missing non-elastic channels were estimated from statistical model
calculations.
  Results: The total reaction cross sections from elastic scattering and from
the sum of the cross sections over all open non-elastic channels agree well
within the uncertainties. This finding confirms the consistency of the
experimental data. At the higher energy of 16.1 MeV, the predicted significant
contribution of compound-inelastic scattering to the total reaction cross
section is confirmed experimentally. As a by-product it is found that most
recent global alpha-nucleus potentials are able to describe the reaction cross
sections for 64Zn around the Coulomb barrier.
  Conclusions: Total reaction cross sections of alpha-induced reactions can be
well determined from elastic scattering angular distributions. The present
study proves experimentally that the total cross section from elastic
scattering is identical to the sum of non-elastic reaction cross sections.
Thus, the statistical model can reliably be used to distribute the total
reaction cross section among the different open channels.


title: Stability of trace theorems on the sphere

abstract:
  We prove stable versions of trace theorems on the sphere in $L^2$ with
optimal constants, thus obtaining rather precise information regarding
near-extremisers. We also obtain stability for the trace theorem into $L^q$ for
$q > 2$, by combining a refined Hardy-Littlewood-Sobolev inequality on the
sphere with a duality-stability result proved very recently by Carlen. Finally,
we extend a local version of Carlen's duality theorem to establish local
stability of certain Strichartz estimates for the kinetic transport equation.


title: Weyl-type bounds for Steklov eigenvalues

abstract:
  We present upper and lower bounds for Steklov eigenvalues for domains in
$\mathbb{R}^{N+1}$ with $C^2$ boundary compatible with the Weyl asymptotics. In
particular, we obtain sharp upper bounds on Riesz-means and the trace of
corresponding Steklov heat kernel. The key result is a comparison of Steklov
eigenvalues and Laplacian eigenvalues on the boundary of the domain by applying
Pohozaev-type identities on an appropriate tubular neigborhood of the boundary
and the min-max principle. Asymptotically sharp bounds then follow from bounds
for Riesz-means of Laplacian eigenvalues.


title:
Parallaxes of 6.7-GHz Methanol Masers towards the G305.2 High-Mass Star
  Formation Region

abstract:
  We have made measurements to determine the parallax and proper motion of the
three 6.7-GHz methanol masers G305.200$+$0.019, G305.202$+$0.208 and
G305.208$+$0.206. The combined parallax is found to be 0.25$\pm $0.05 mas,
corresponding to a distance of 4.1$^{+1.2}_{-0.7}$ kpc. This places the G305.2
star formation region in the Carina-Sagittarius spiral arm. The inclusion of
G305.2 increases the Galactic azimuth range of the sources in this arm by
40$^\circ $ from Sato et al., allowing us to determine the pitch angle of this
spiral with greater confidence to be $\psi = 19.0 \pm 2.6^\circ $. The first
VLBI spot maps of the 6.7-GHz methanol masers towards these sources show that
they have simple linear and ring-like structures, consistent with emission
expected from classII methanol masers in general.


title: Rough Set Based Color Channel Selection

abstract:
  Color channel selection is essential for accurate segmentation of sky and
clouds in images obtained from ground-based sky cameras. Most prior works in
cloud segmentation use threshold based methods on color channels selected in an
ad-hoc manner. In this letter, we propose the use of rough sets for color
channel selection in visible-light images. Our proposed approach assesses color
channels with respect to their contribution for segmentation, and identifies
the most effective ones.


title: Natural Partial Order on Rings with Involution

abstract:
  In this paper, we introduce a partial order on rings with involution, which
is a generalization of the partial order on the set of projections in a Rickart
*-ring. We prove that a *-ring with the natural partial order form a
sectionally semi-complemented poset. It is proved that every interval [0,x]
forms an orthomodular lattice in case of abelian Rickart *-rings. The concepts
of generalized comparability (GC) and partial comparability (PC) are extended
to involve all the elements of a *-ring. Further, it is proved that these
concepts are equivalent in finite abelian Rickart *-rings.


title:
Geometric properties of images of cartesian products of regular Cantor
  sets by differentiable real maps

abstract:
  We prove dimension formulas for arihmetic sums of regular Cantor sets, and,
more generally, for images of cartesian products of regular Cantor sets by
differentiable real maps.


title: Online Exploration of Rectangular Grids

abstract:
  In this paper, we consider the problem of exploring unknown environments with
autonomous agents. We model the environment as a graph with edge weights and
analyze the task of visiting all vertices of the graph at least once. The
hardness of this task heavily depends on the knowledge and the capabilities of
the agent. In our model, the agent sees the whole graph in advance, but does
not know the weights of the edges. As soon as it arrives in a vertex, it can
see the weights of all the outgoing edges. We consider the special case of two
different edge weights $1$ and $k$ and prove that the problem remains hard even
in this case. We prove a lower bound of $11/9$ on the competitive ratio of any
deterministic strategy for exploring a ladder graph and complement this result
by a $4$-competitive algorithm. All of these results hold for undirected
graphs. Exploring directed graphs, where the direction of the edges is not
known beforehand, seems to be much harder. Here, we prove that a natural greedy
strategy has a linear lower bound on the competitive ratio both in ladders and
square grids.


title:
Green Function Approach for Calculation of the Local Density of States
  in the Graphitic Nanocone

abstract:
  Graphene and other nanostructures belong to the center of interest of today's
physics research. The local density of states of the graphitic nanocone
influenced by the spin-orbit interaction was calculated. Numerical calculations
and the Green function approach were used to solve this problem. It was proven
in the second case that the second order pproximation is not sufficient for
this purpose.


title: Simply connected latin quandles

abstract:
  A (left) quandle is connected if its left multiplication group acts
transitively. In 2014, Eisermann introduced the concept of quandle coverings,
corresponding to so-called constant quandle cocycles that form a subset of
quandle cocycles. A connected quandle is said to be \emph{simply connected} if
it has no nontrivial coverings, or, equivalently, if its second constant
cohomology groups are trivial.
  In this paper we develop a combinatorial approach to constant cohomology.
Upon applying our theory, we prove that connected quandles that are affine over
cyclic groups are simply connected (extending a result of Gra\~{n}a for
quandles of prime size) and that finite doubly transitive quandles of order
different from $4$ are simply connected.


title: Levi decomposition of nilpotent centralisers in classical groups

abstract:
  We check that the connected centralisers of nilpotent elements in the
orthogonal and symplectic groups have Levi decompositions in even
characteristic. This provides a justification for the identification of the
isomorphism classes of the reductive quotients as stated in [Liebeck, Seitz;
Unipotent and Nilpotent Classes in Simple Algebraic Groups and Lie Algebras].


title: Fast Eigenspace Approximation using Random Signals

abstract:
  We focus in this work on the estimation of the first $k$ eigenvectors of any
graph Laplacian using filtering of Gaussian random signals. We prove that we
only need $k$ such signals to be able to exactly recover as many of the
smallest eigenvectors, regardless of the number of nodes in the graph. In
addition, we address key issues in implementing the theoretical concepts in
practice using accurate approximated methods. We also propose fast algorithms
both for eigenspace approximation and for the determination of the $k$th
smallest eigenvalue $\lambda_k$. The latter proves to be extremely efficient
under the assumption of locally uniform distribution of the eigenvalue over the
spectrum. Finally, we present experiments which show the validity of our method
in practice and compare it to state-of-the-art methods for clustering and
visualization both on synthetic small-scale datasets and larger real-world
problems of millions of nodes. We show that our method allows a better scaling
with the number of nodes than all previous methods while achieving an almost
perfect reconstruction of the eigenspace formed by the first $k$ eigenvectors.


title:
Recent Advances in Transient Imaging: A Computer Graphics and Vision
  Perspective

abstract:
  Transient imaging has recently made a huge impact in the computer graphics
and computer vision fields. By capturing, reconstructing, or simulating light
transport at extreme temporal resolutions, researchers have proposed novel
techniques to show movies of light in motion, see around corners, detect
objects in highly-scattering media, or infer material properties from a
distance, to name a few. The key idea is to leverage the wealth of information
in the temporal domain at the pico or nanosecond resolution, information
usually lost during the capture-time temporal integration. This paper presents
recent advances in this field of transient imaging from a graphics and vision
perspective, including capture techniques, analysis, applications and
simulation.


title: Scale-free distribution of Dead Sea sinkholes--observations and modeling

abstract:
  There are currently more than 5500 sinkholes along the Dead Sea in Israel.
These were formed due to the dissolution of subsurface salt layers as a result
of the replacement of hypersaline groundwater by fresh brackish groundwater.
This process has been associated with a sharp decline in the Dead Sea water
level, currently more than one meter per year, resulting in a lower water table
that has allowed the intrusion of fresher brackish water. We studied the
distribution of the sinkhole sizes and found that it is scale-free with a
power-law exponent close to 2. We constructed a stochastic cellular automata
model to understand the observed scale-free behavior and the growth of the
sinkhole area in time. The model consists of a lower salt layer and an upper
soil layer in which cavities that develop in the lower layer lead to collapses
in the upper layer. The model reproduces the observed power-law distribution
without involving the threshold behavior commonly associated with criticality.


title: Geodesic completeness for Type~A surfaces

abstract:
  Type A surfaces are the locally homogeneous affine surfaces which can be
locally described by constant Christoffel symbols. We address the issue of the
geodesic completeness of these surfaces: we show that some models for Type A
surfaces are geodesically complete, that some others admit an incomplete
geodesic but model geodesically complete surfaces, and that there are also
others which do not model any complete surface. Our main result provides a way
of determining whether a given set of constant Christoffel symbols can model a
complete surface.


title: Local density approximation for the almost-bosonic anyon gas

abstract:
  We study the minimizers of an energy functional with a self-consistent
magnetic field, which describes a quantum gas of almost-bosonic anyons in the
average-field approximation. For the homogeneous gas we prove the existence of
the thermodynamic limit of the energy at fixed effective statistics parameter,
and the independence of such a limit from the shape of the domain. This result
is then used in a local density approximation to derive an effective
Thomas--Fermi-like model for the trapped anyon gas in the limit of a large
effective statistics parameter (i.e., "less-bosonic" anyons).

categories: math-ph cond-mat.mes-hall cond-mat.quant-gas math.AP math.MP


title:
Bethe Vectors for Composite Models with $\mathfrak{gl}(2|1)$ and
  $\mathfrak{gl}(1|2)$ Supersymmetry

abstract:
  Supersymmetric composite generalized quantum integrable models solvable by
the algebraic Bethe ansatz are studied. Using a coproduct in the bialgebra of
monodromy matrix elements and their action on Bethe vectors, formulas for Bethe
vectors in the composite models with supersymmetry based on the super-Yangians
$Y[\mathfrak{gl}(2|1)]$ and $Y[\mathfrak{gl}(1|2)]$ are derived.


title:
The Dirichlet problem for second order parabolic operators in divergence
  form

abstract:
  We study parabolic operators H = $\partial$t -- div $\lambda$,x A(x,
t)$\nabla$ $\lambda$,x in the parabolic upper half space R n+2 + = {($\lambda$,
x, t) : $\lambda$ > 0}. We assume that the coefficients are real, bounded,
measurable, uniformly elliptic, but not necessarily symmetric. We prove that
the associated parabolic measure is absolutely continuous with respect to the
surface measure on R n+1 in the sense defined by A$\infty$(dx dt). Our argument
also gives a simplified proof of the corresponding result for elliptic measure.


title:
Surround suppression explained by long-range recruitment of local
  competition, in a columnar V1 model

abstract:
  Although neurons in columns of visual cortex of adult carnivores and primates
share similar orientation tuning preferences, responses of nearby neurons are
surprisingly sparse and temporally uncorrelated, especially in response to
complex visual scenes. The mechanisms underlying this counter-intuitive
combination of response properties are still unknown. Here we present a
computational model of columnar visual cortex which explains experimentally
observed integration of complex features across the visual field, and which is
consistent with anatomical and physiological profiles of cortical excitation
and inhibition. In this model, sparse local excitatory connections within
columns, coupled with strong unspecific local inhibition and
functionally-specific long-range excitatory connections across columns, give
rise to competitive dynamics that reproduce experimental observations. Our
results explain surround modulation of responses to simple and complex visual
stimuli, including reduced correlation of nearby excitatory neurons, increased
excitatory response selectivity, increased inhibitory selectivity, and complex
orientation-tuning of surround modulation.


title: Architecting Time-Critical Big-Data Systems

abstract:
  - Current infrastructures for developing big-data applications are able to
process --via big-data analytics-huge amounts of data, using clusters of
machines that collaborate to perform parallel computations. However, current
infrastructures were not designed to work with the requirements of
time-critical applications; they are more focused on general-purpose
applications rather than time-critical ones. Addressing this issue from the
perspective of the real-time systems community, this paper considers
time-critical big-data. It deals with the definition of a time-critical
big-data system from the point of view of requirements, analyzing the specific
characteristics of some popular big-data applications. This analysis is
complemented by the challenges stemmed from the infrastructures that support
the applications, proposing an architecture and offering initial performance
patterns that connect application costs with infrastructure performance.


title: Runtime Template Instantiation for C++

abstract:
  Performance, genericity and flexibility are three valuable qualities for
scientific environments that tend to be antagonistic. C++ provides excellent
support for both performances and genericity thanks to its support for (class
and function) templates. However, a C++ templated library can hardly be
qualified as flexible: data of unexpected types cannot enter the system, which
hinders user interactions. This paper describes the approach that was taken in
the Vcsn platform to add flexibility on top of C++ templates, including runtime
template instantiation.


title: Mixing in modulated turbulence. Analytical results

abstract:
  Recent numerical results show that if a scalar is mixed by periodically
forced turbulence, the average mixing rate is directly affected for forcing
frequencies small compared to the integral turbulence frequency. We elucidate
this by an analytical study using simple turbulence models for spectral
transfer. Adding a large amplitude modulation to the forcing of the velocity
field enhances the energy transfer and simultaneously diminishes the scalar
transfer. Adding a modulation to a random stirring protocol will thus
negatively influence the mixing rate. We further derive the asymptotic
behaviour of the response of the passive scalar quantities in the same flow for
low and high forcing frequencies.


title: Fluctuation Theorems of work and entropy in Hamiltonian systems

abstract:
  The Fluctuation Theorems are a group of exact relations that remain valid
irrespective of how far the system has been driven away from equilibrium. Other
than having practical applications, like determination of equilibrium free
energy change from nonequilibrium processes, they help in our understanding of
the Second Law and the emergence of irreversibility from time-reversible
equations of motion at microscopic level. A vast number of such theorems have
been proposed in literature, ranging from Hamiltonian to stochastic systems,
from systems in steady state to those in transient regime, and for both open
and closed quantum systems. In this article, we discuss about a few such
relations, when the system evolves under Hamiltonian dynamics.


title:
Highly responsive UV-photodetectors based on single electrospun TiO2
  nanofibres

abstract:
  In this work we study the optoelectronic properties of individual TiO2 fibres
produced through coupled sol-gel and electrospinning, by depositing them onto
pre-patterned Ti/Au electrodes on SiO2/Si substrates. Transport measurements in
the dark give a conductivity above 2*10^-5 S, which increases up to 8*10^-5 S
in vacuum. Photocurrent measurements under UV-irradiation show high sensitivity
(responsivity of 90 A/W for 375 nm wavelength) and a response time to
illumination of ~ 5 s, which is superior to state-of-the-art TiO2-based UV
photodetectors. Both responsivity and response speed are higher in air than in
vacuum, due to oxygen adsorbed on the TiO2 surface which traps photoexcited
free electrons in the conduction band, thus reducing the recombination
processes. The photodetectors are sensitive to light polarization, with an
anisotropy ratio of 12%. These results highlight the interesting combination of
large surface area and low 1D transport resistance in electrospun TiO2 fibres.
The simplicity of the sol-gel/electrospinning synthesis method, combined with a
fast response and high responsivity makes them attractive candidates for
UV-photodetection in ambient conditions. We anticipate their high (photo)
conductance is also relevant for photocatalysis and dye-sensitized solar cells.


title:
New Insight Into the Size Tuning of Monodispersed Colloidal Gold
  Obtained by Citrate Method

abstract:
  We study the effect of citrate to gold molar ratio (X) on the size of
citrated gold nanoparticles (AuNPs). This dependence is still a matter of
debate for X $\ge$ 3 where the polydispersity is yet minimized. Indeed, there
is no consensus between experiments proposed so far for comparable experimental
conditions. Nonetheless, the sole available theoretical prediction has never
been validated experimentally in this range of X. We show unambiguously using 3
techniques (UV-Vis spectroscopy, dynamic light scattering and transmission
electronic microscopy), 2 different synthetic approaches (Direct, Inverse) and
10 X values for each approach that AuNPs' size decay as a monoexponential with
X. This result is, for the first time, in agreement with the sole available
theoretical prediction by Kumar et al. on the whole studied range of X.


title: The impact of intrinsic charm on the parton distribution functions

abstract:
  In this work, we present a new investigation about the impact of intrinsic
charm (IC) on the physical observables, in particular, on the heavy structure
function $F_2^c$. Since IC distribution is dominant at large Bjorken variable
$x$, normally, it is expected that it can be explored only at large $x$. But,
by studying the correlation of the charm density in the proton with $F_2^c$, we
are going to show that the IC component can also be effective at low $x$. To
investigate further, we perform three QCD global analyses of parton
distribution functions (PDFs), by including the EMC $F_2^c$ data that are
recognized as clear evidence for existence of the intrinsic charm in the
proton, and also by considering the IC component. Although the fit of the EMC
data is extremely poor due to the data points with lower $x$ values, i.e. $x<
$0.05, but these analyses can give us new information about the impact of EMC
data and IC contribution on the behaviour of PDFs.


title: High-dimensional regression over disease subgroups

abstract:
  We consider high-dimensional regression over subgroups of observations. Our
work is motivated by biomedical problems, where disease subtypes, for example,
may differ with respect to underlying regression models, but sample sizes at
the subgroup-level may be limited. We focus on the case in which
subgroup-specific models may be expected to be similar but not necessarily
identical. Our approach is to treat subgroups as related problem instances and
jointly estimate subgroup-specific regression coefficients. This is done in a
penalized framework, combining an $\ell_1$ term with an additional term that
penalizes differences between subgroup-specific coefficients. This gives
solutions that are globally sparse but that allow information-sharing between
the subgroups. We present algorithms for estimation and empirical results on
simulated data and using Alzheimer's disease, amyotrophic lateral sclerosis and
cancer datasets. These examples demonstrate the gains our approach can offer in
terms of prediction and the ability to estimate subgroup-specific sparsity
patterns.


title:
Reply & Supply: Efficient crowdsourcing when workers do more than answer
  questions

abstract:
  Crowdsourcing works by distributing many small tasks to large numbers of
workers, yet the true potential of crowdsourcing lies in workers doing more
than performing simple tasks---they can apply their experience and creativity
to provide new and unexpected information to the crowdsourcer. One such case is
when workers not only answer a crowdsourcer's questions but also contribute new
questions for subsequent crowd analysis, leading to a growing set of questions.
This growth creates an inherent bias for early questions since a question
introduced earlier by a worker can be answered by more subsequent workers than
a question introduced later. Here we study how to perform efficient
crowdsourcing with such growing question sets. By modeling question sets as
networks of interrelated questions, we introduce algorithms to help curtail the
growth bias by efficiently distributing workers between exploring new questions
and addressing current questions. Experiments and simulations demonstrate that
these algorithms can efficiently explore an unbounded set of questions without
losing confidence in crowd answers.

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


title: Structure and computation of two-dimensional incompressible extended MHD

abstract:
  A comprehensive study of a reduced version of Lust's equations, the extended
magnetohydrodynamic (XMHD) model obtained from the two-fluid theory for
electrons and ions with the enforcement of quasineutrality, is given. Starting
from the Hamiltonian structure of the fully three-dimensional theory, a
Hamiltonian two-dimensional incompressible four-field model is derived. In this
way energy conservation along with four families of Casimir invariants are
naturally obtained. The construction facilitates various limits leading to the
Hamiltonian forms of Hall, inertial, and ideal MHD, with their conserved
energies and Casimir invariants. Basic linear theory of the four-field model is
treated, and the growth rate for collisionless reconnection is obtained.
Results from nonlinear simulations of collisionless tearing are presented and
interpreted using, in particular normal fields, a product of the Hamiltonian
theory that gives rise to simplified equations of motion.


title:
Development of frequency domain multiplexing for the X-ray Integral
  Field Unit (X-IFU) on the Athena

abstract:
  We are developing the frequency domain multiplexing (FDM) read-out of
transition-edge sensor (TES) microcalorimeters for the X-ray Integral Field
Unit (X-IFU) instrument on board of the future European X-Ray observatory
Athena. The X-IFU instrument consists of an array of $\sim$3840 TESs with a
high quantum efficiency ($>$90 \%) and spectral resolution $\Delta E$=2.5 eV
$@$ 7 keV ($E/\Delta E\sim$2800). FDM is currently the baseline readout system
for the X-IFU instrument. Using high quality factor LC filters and room
temperature electronics developed at SRON and low-noise two stage SQUID
amplifiers provided by VTT, we have recently demonstrated good performance with
the FDM readout of Mo/Au TES calorimeters with Au/Bi absorbers. An integrated
noise equivalent power resolution of about 2.0 eV at 1.7 MHz has been
demonstrated with a pixel from a new TES array from NASA/Goddard (GSFC-A2). We
have achieved X-ray energy resolutions $\sim$2.5 eV at AC bias frequency at 1.7
MHz in the single pixel read-out. We have also demonstrated for the first time
an X-ray energy resolution around 3.0 eV in a 6 pixel FDM read-out with TES
array (GSFC-A1). In this paper we report on the single pixel performance of
these microcalorimeters under MHz AC bias, and further results of the
performance of these pixels under FDM.


title:
Zeta Series Generating Function Transformations Related to Generalized
  Stirling Numbers and Partial Sums of the Hurwitz Zeta Function

abstract:
  We define a generalized class of modified zeta series transformations
generating the partial sums of the Hurwitz zeta function and series expansions
of the Lerch transcendent function. The new transformation coefficients we
define within the article satisfy expansions by generalized harmonic number
sequences, or the partial sums of the Hurwitz zeta function, which are
analogous to known properties for the Stirling numbers of the first kind and
for the known transformation coefficients employed to enumerate variants of the
polylogarithm function series. Applications of the new results we prove in the
article include new series expansions of the Dirichlet beta function, the
Legendre chi function, BBP-type series identities for special constants,
alternating and exotic Euler sum variants, alternating zeta functions with
powers of quadratic denominators, and particular series defining special cases
of the Riemann zeta function constants at the positive integers $s \geq 3$.


title:
Lagrangian Submanifolds with Constant Angle Functions of the nearly
  K\"ahler $\mathbb{S}^3\times\mathbb{S}^3$

abstract:
  We study Lagrangian submanifolds of the nearly K\"ahler
$\mathbb{S}^3\times\mathbb{S}^3$ with respect to their, so called, angle
functions. We show that if all angle functions are constant, then the
submanifold is either totally geodesic or has constant sectional curvature and
there is a classification theorem that follows from a recent paper of B. Dioos,
L. Vrancken and X. Wang (arXiv:1604.05060). Moreover, we show that if precisely
one angle function is constant, then it must be equal to $0,\frac{\pi}{3}$ or
$\frac{2\pi}{3}$. Using then two remarkable constructions together with the
classification of Lagrangian submanifolds of which the first component has
nowhere maximal rank, we obtain a classification of such Lagrangian
submanifolds.


title: On optimal stopping of multidimensional diffusions

abstract:
  This paper develops an approach for solving perpetual discounted optimal
stopping problems for multidimensional diffusions, with special emphasis on the
$d$-dimensional Wiener process. We first obtain some verification theorems for
diffusions, based on the Green kernel representation of the value function
associated with the problem. Specializing to the multidimensional Wiener
process, we apply the Martin boundary theory to obtain a set of tractable
integral equations involving only harmonic functions that characterize the
stopping region of the problem. These equations allow to formulate a
discretization scheme to obtain an approximate solution. The approach is
illustrated through the optimal stopping problem of a $d$-dimensional Wiener
process with a positive definite quadratic form reward function.


title: Adaptive mixed norm optical flow estimation

abstract:
  The pel-recursive computation of 2-D optical flow has been extensively
studied in computer vision to estimate motion from image sequences, but it
still raises a wealth of issues, such as the treatment of outliers, motion
discontinuities and occlusion. It relies on spatio-temporal brightness
variations due to motion. Our proposed adaptive regularized approach deals with
these issues within a common framework. It relies on the use of a data-driven
technique called Mixed Norm (MN) to estimate the best motion vector for a given
pixel. In our model, various types of noise can be handled, representing
different sources of error. The motion vector estimation takes into
consideration local image properties and it results from the minimization of a
mixed norm functional with a regularization parameter depending on the
kurtosis. This parameter determines the relative importance of the fourth norm
and makes the functional convex. The main advantage of the developed procedure
is that no knowledge of the noise distribution is necessary. Experiments
indicate that this approach provides robust estimates of the optical flow.


title:
Analysis and comparative study of non-holonomic and quasi-integrable
  deformations of the Nonlinear Schr\"odinger Equation

abstract:
  The non-holonomic deformation of the nonlinear Schr\"odinger equation,
uniquely obtained from both the Lax pair and Kupershmidt's bi-Hamiltonian
[Phys. Lett. A 372, 2634 (2008)] approaches, is compared with the
quasi-integrable deformation of the same system [Ferreira et. al. JHEP 2012,
103 (2012)]. It is found that these two deformations can locally coincide only
when the phase of the corresponding solution is discontinuous in space,
following a definite phase-modulus coupling of the non-holonomic inhomogeneity
function. These two deformations are further found to be not gauge-equivalent
in general, following the Lax formalism of the nonlinear Schr\"odinger
equation. However, asymptotically they converge for localized solutions as
expected. Similar conditional correspondence of nonholonomic deformation with a
non-integrable deformation, namely, due to local scaling of the amplitude of
the nonlinear Schr\"odinger equation is further obtained.


title: Multitask Protein Function Prediction Through Task Dissimilarity

abstract:
  Automated protein function prediction is a challenging problem with
distinctive features, such as the hierarchical organization of protein
functions and the scarcity of annotated proteins for most biological functions.
We propose a multitask learning algorithm addressing both issues. Unlike
standard multitask algorithms, which use task (protein functions) similarity
information as a bias to speed up learning, we show that dissimilarity
information enforces separation of rare class labels from frequent class
labels, and for this reason is better suited for solving unbalanced protein
function prediction problems. We support our claim by showing that a multitask
extension of the label propagation algorithm empirically works best when the
task relatedness information is represented using a dissimilarity matrix as
opposed to a similarity matrix. Moreover, the experimental comparison carried
out on three model organism shows that our method has a more stable performance
in both "protein-centric" and "function-centric" evaluation settings.


title: On the Leibniz rule for random variables

abstract:
  We prove a Leibniz-type inequality for the spread of random variables in
terms of their $L_p$-norms. The result is motivated by the Kato-Ponce
inequalities and Rieffel's strong Leibniz property.


title: Isometries, gaugings and N=2 supergravity decoupling

abstract:
  We study off-shell rigid limits for the kinetic and scalar-potential terms os
a single N=2 hypermultiplet. In the kinetic term, these rigid limits establish
relations between four-dimensional quaternion-Kahler and hyper-Kahler target
spaces with symmetry. The scalar potential is obtained by gauging the
graviphoton along an isometry of the quaternion-Kahler space. The rigid limits
unveil two distinct cases. A rigid N=2 theory on Minkowski or on AdS_4
spacetime, depending on whether the isometry is translational or rotational
respectively. We apply these results to the quaternion-Kahler space with
Heisenberg x U(1) isometry, which describes the universal hypermultiplet at
type-II string one-loop.


title: Faster ARMA maximum likelihood estimation

abstract:
  A new likelihood based AR approximation is given for ARMA models. The usual
algorithms for the computation of the likelihood of an ARMA model require
$O(n)$ flops per function evaluation. Using our new approximation, an algorithm
is developed which requires only $O(1)$ flops in repeated likelihood
evaluations. In most cases, the new algorithm gives results identical to or
very close to the exact maximum likelihood estimate (MLE). This algorithm is
easily implemented in high level Quantitative Programming Environments (QPEs)
such as {\it Mathematica\/}, MatLab and R. In order to obtain reasonable speed,
previous ARMA maximum likelihood algorithms are usually implemented in C or
some other machine efficient language. With our algorithm it is easy to do
maximum likelihood estimation for long time series directly in the QPE of your
choice. The new algorithm is extended to obtain the MLE for the mean parameter.
Simulation experiments which illustrate the effectiveness of the new algorithm
are discussed. {\it Mathematica\/} and R packages which implement the algorithm
discussed in this paper are available (McLeod and Zhang, 2007). Based on these
package implementations, it is expected that the interested researcher would be
able to implement this algorithm in other QPE's.


title: Frame Theory for Signal Processing in Psychoacoustics

abstract:
  This review chapter aims to strengthen the link between frame theory and
signal processing tasks in psychoacoustics. On the one side, the basic concepts
of frame theory are presented and some proofs are provided to explain those
concepts in some detail. The goal is to reveal to hearing scientists how this
mathematical theory could be relevant for their research. In particular, we
focus on frame theory in a filter bank approach, which is probably the most
relevant view-point for audio signal processing. On the other side, basic
psychoacoustic concepts are presented to stimulate mathematicians to apply
their knowledge in this field.


title: Quantum ferromagnet in the proximity of the tricritical point

abstract:
  Echoes of quantum phase transitions (QPTs) at finite temperatures are
theoretically and experimentally challenging and unexplored topics.
Particularly in metallic quantum ferromagnets the experimental investigations
are hampered by an intricate preparation of sufficiently pure samples and the
access to the proper coordinates in parameter space. The present study shows
that it is possible to tune a specific system at easily accessible conditions
to the vicinity of its quantum phase transition. The physics is demonstrated on
Ru-doped UCoAl, driven by pressure or substitution to and across the
tricritical point and follows the first-order transition line to the
theoretically presumed QPT. These findings open the possibilities for further
in-depth studies of classical and quantum critical phenomena at easily
reachable conditions.


title:
Overlapping Schwarz Methods with Adaptive Coarse Spaces for Multiscale
  Problems in 3D

abstract:
  We propose two variants of the overlapping additive Schwarz method for the
finite element discretiza- tion of the elliptic problem in 3D with highly
heterogeneous coefficients. The methods are efficient and simple to construct
using the abstract framework of the additive Schwarz method, and an idea of
adaptive coarse spaces. In one variant, the coarse space consists of finite
element functions associated with the wire basket nodes and functions based on
solving some generalized eigenvalue problem on the faces, and in the other
variant, it contains functions associated with the vertex nodes with functions
based on solving some generalized eigenvalue problems on subdomain faces and on
subdomain edges. The functions that are used to build the coarse spaces are
chosen adaptively, they correspond to the eigenvalues that are smaller than a
given threshold. The convergence rate of the preconditioned conjugate gradients
method in both cases, is shown to be independent of the variations in the
coefficients for sufficient number of eigenfunctions in the coarse space.
Numerical results are given to support the theory.


title:
Structural and electrical properties of electrodeposited single junction
  of cuprous (I) oxide copper

abstract:
  Cuprous (I) oxide (Cu_{2}O) based solar cells were fabricated with the use of
the electrodeposition technique at nanometre scale, and the structural,
morphological and electrical properties were investigated. The Cu_{2}O layers
were electrodeposited on crystalline and polycrystalline copper substrates. To
complete the Cu_{2}O/Cu(100) and Cu_{2}O/Cu interfaces as the solar cells the
top electrodes of silver paste were painted on the rear of Cu_{2}O. The
theoretical analysis of the current voltage curve was provided to determine the
values of electrical parameters of the most efficient solar cell of
Ag/Cu_{2}O/Cu(100) and clearly indicate presence of two Schottky barriers at
interfaces.


title:
Working Paper on Organizational Dynamics within Corporate Venture
  Capital Firms

abstract:
  Corporate venture capital is in the midst of a renaissance. The end of 2015
marked all-time highs both in the number of corporate firms participating in VC
deals and in the amount of capital being deployed by corporate VCs. This paper
explores, rather than defines, how these firms find success in the wake of this
sudden influx of corporate investors. A series of interviews was conducted in
order to capture the direct and indirect objectives, philosophies, and modes of
operation within some of these corporate VC organizations. During the course of
this exploration, numerous operational coherency issues were discovered. Many
firms were implicitly incentivizing conflicting and inconsistent behavior among
their investment team. Perhaps most surprising, the worst offenders were the
more mature corporate VCs who have been in the game for some time. As will be
discussed, fundamental evidence suggests that this misalignment is due to lack
of attention and commitment at the executive level as corporate strategy
evolves.


title:
Explicit description of jumping phenomena on moduli spaces of parabolic
  connections and Hilbert schemes of points on surfaces

abstract:
  In this paper, we investigate the apparent singularities and the dual
parameters of rank 2 parabolic connections on $\mathbb{P}^1$ and rank 2
(parabolic) Higgs bundle on $\mathbb{P}^1$. Then we obtain explicit
descriptions of Zariski open sets of the moduli space of the parabolic
connections and the moduli space of the Higgs bundles. For $n=5$, we can give
global descriptions of the moduli spaces in detail.


title: Strong inner inverses in endomorphism rings of vector spaces

abstract:
For $V$ a vector space over a field, or more generally, over a division ring,
it is well-known that every $x\in\mathrm{End}(V)$ has an inner inverse,
i.e., an element $y\in\mathrm{End}(V)$ satisfying $xyx=x.$ We show here that a
large class of such $x$ have inner inverses $y$ that satisfy with $x$ an
infinite family of additional monoid relations, making the monoid generated by
$x$ and $y$ what is known as an inverse monoid (definition recalled). We
obtain consequences of these relations, and related results.
  P. Nielsen and J. \v{S}ter, in a paper to appear, show that a much larger
class of elements $x$ of rings $R,$ including all elements of von Neumann
regular rings, have inner inverses satisfying arbitrarily large finite
subsets of the abovementioned set of relations. But we show by example that the
endomorphism ring of any infinite-dimensional vector space contains elements
having no inner inverse that simultaneously satisfies all those relations.
  A tangential result proved is a condition on an endomap $x$ of a set $S$ that
is necessary and sufficient for $x$ to belong to an inverse submonoid of the
monoid of all endomaps of $S.$


title:
Electronic Origin of Linearly Polarized Emission in CdSe/CdS Dot-in-Rod
  Heterostructures

abstract:
  Seeded CdSe/CdS nanorods exhibit intense polarized emission along the rod
main axis. The degree of linear polarization cannot be explained by dielectric
effects alone, an additional electronic contribution is present whose nature
has not been settled up to date. Using multi-band k.p theory, we analyse the
potential influence of several factors affecting excitonic emission and show
that shear strain is the main electronic mechanism promoting linear
polarization. It favors energetically light hole excitons over heavy hole ones,
via deformation potential, and makes their radiative recombination faster via
piezoelectricity. Implications of this mechanism are that linear emission can
be enhanced by growing long but thin CdS shells around large, prolate CdSe
cores, which indeed supports and rationalizes recent experimental findings.
Together with the well-known dielectric effects, these results pave the way for
controlled degree of linear polarization in dot-in-rods through dedicated
structural design.


title:
Diffusive versus displacive contact plasticity of nanoscale asperities:
  Temperature- and velocity-dependent strongest size

abstract:
  We predict a strongest size for the contact strength when asperity radii of
curvature decrease below ten nanometers. The reason for such strongest size is
found to be correlated with the competition between the dislocation plasticity
and surface diffusional plasticity. The essential role of temperature is
calculated and illustrated in a comprehensive asperity size-strengthtemperature
map taking into account the effect of contact velocity. Such a map should be
essential for various phenomena related to nanoscale contacts such as nanowire
cold welding, self-assembly of nanoparticles and adhesive nano-pillar arrays,
as well as the electrical, thermal and mechanical properties of macroscopic
interfaces.


title:
The Complexity of Holant Problems over Boolean Domain with Non-negative
  Weights

abstract:
  Holant problem is a general framework to study the computational complexity
of counting problems. We prove a complexity dichotomy theorem for Holant
problems over Boolean domain with non-negative weights. It is the first
complete Holant dichotomy where constraint functions are not necessarily
symmetric.
  Holant problems are indeed read-twice $\#$CSPs. Intuitively, some $\#$CSPs
that are $\#$P-hard become tractable when restricting to read-twice instances.
To capture them, we introduce the Block-rank-one condition. It turns out that
the condition leads to a clear separation. If a function set $\mathcal{F}$
satisfies the condition, then $\mathcal{F}$ is of affine type or product type.
Otherwise (a) $\mathrm{Holant}(\mathcal{F})$ is $\#$P-hard; or (b) every
function in $\mathcal{F}$ is a tensor product of functions of arity at most 2;
or (c) $\mathcal{F}$ is transformable to a product type by some real orthogonal
matrix. Holographic transformations play an important role in both the hardness
proof and the characterization of tractability.


title: Good Hilbert functors

abstract:
  We introduce the good Hilbert functor and prove that it is algebraic. This
functor generalizes various versions of the Hilbert moduli problem, such as the
multigraded Hilbert scheme and the invariant Hilbert scheme. Moreover, we
generalize a result concerning formal GAGA for good moduli spaces.


title:
Higher dimensional communication complexity problems: classical
  protocols vs quantum ones based on Bell's Theorem or prepare-transmit-measure
  schemes

abstract:
  Communication complexity problems (CCPs) are tasks in which separated parties
attempt to compute a function whose inputs are distributed among the parties.
Their communication is limited so that not all inputs can be sent. We show that
broad classes of Bell inequalities can be mapped to CCPs and that a quantum
violation of a Bell inequality is a necessary and sufficient condition for an
enhancement of the related CCP beyond its classical limitation. However, one
can implement CCPs by transmitting a quantum system, encoding no more
information than is allowed in the CCP, and extract information by performing
measurements. We show that for a large class of Bell inequalities, the
improvement of the CCP associated to a quantum violation of a Bell inequality
can be no greater than the improvement obtained from quantum
prepare-transmit-measure strategies.


title:
Nonmodal analysis of helical and azimuthal magnetorotational
  instabilities

abstract:
  Helical and azimuthal magnetorotational instabilities operate in rotating
magnetized flows with relatively steep negative or extremely steep positive
shear. The corresponding lower and upper Liu limits of the shear, which
determine the threshold of modal growth of these instabilities, are
continuously connected when some axial electrical current is allowed to pass
through the rotating fluid. We investigate the nonmodal dynamics of these
instabilities arising from the non-normality of shear flow in the local
approximation, generalizing the results of the modal approach. It is
demonstrated that moderate transient/nonmodal amplification of both types of
magnetorotational instability occurs within the Liu limits, where the system is
stable according to modal analysis. We show that for the helical
magnetorotational instability this magnetohydrodynamic behavior is closely
connected with the nonmodal growth of the underlying purely hydrodynamic
problem.

categories: physics.plasm-ph astro-ph.SR physics.flu-dyn physics.space-ph


title:
Conservative and Stable Degree Preserving SBP Operators for
  Non-Conforming Meshes

abstract:
  Non-conforming numerical approximations offer increased flexibility for
applications that require high resolution in a localized area of the
computational domain or near complex geometries. Two key properties for
non-conforming methods to be applicable to real world applications are
conservation and energy stability. The summation-by-parts (SBP) property, which
certain finite-difference and discontinuous Galerkin methods have, finds
success for the numerical approximation of hyperbolic conservation laws,
because the proofs of energy stability and conservation can discretely mimic
the continuous analysis of partial differential equations. In addition, SBP
methods can be developed with high-order accuracy, which is useful for
simulations that contain multiple spatial and temporal scales. However,
existing non-conforming SBP schemes result in a reduction of the overall degree
of the scheme, which leads to a reduction in the order of the solution error.
This loss of degree is due to the particular interface coupling through a
simultaneous-approximation-term (SAT). We present in this work a novel class of
SBP-SAT operators that maintain conservation, energy stability, and have no
loss of the degree of the scheme for non-conforming approximations. The new
\emph{degree preserving} discretizations require an ansatz that the norm matrix
of the SBP operator is of a degree $\geq 2p$, in contrast to, for example,
existing finite difference SBP operators, where the norm matrix is $2p-1$
accurate. We demonstrate the fundamental properties of the new scheme with
rigorous mathematical analysis as well as numerical verification.


title: Sampling methods for multistage robust convex optimization problems

abstract:
  In this paper, probabilistic guarantees for constraint sampling of multistage
robust convex optimization problems are derived. The dynamic nature of these
problems is tackled via the so-called scenario-with-certificates approach. This
allows to avoid the conservative use of explicit parametrizations through
decision rules, and provides a significant reduction of the sample complexity
to satisfy a given level of reliability. An explicit bound on the probability
of violation is also given. Numerical results dealing with a multistage
inventory management problem show the efficacy of the proposed approach.


title: Tur\'an numbers for disjoint paths

abstract:
  The Tur\'{a}n number of a graph $H$, $ex(n,H)$, is the maximum number of
edges in any graph of order $n$ which does not contain $H$ as a subgraph.
Lidick\'{y}, Liu and Palmer determined $ex(n, F_m)$ for $n$ sufficiently large
and proved that the extremal graph is unique, where $F_m$ is disjoint paths of
$P_{k_1}, \ldots, P_{k_m}$ [Lidick\'{y},B., Liu,H. and Palmer,C. (2013). On the
Tur\'{a}n number of forests. Electron. J. Combin. 20(2) Paper 62, 13 pp]. In
this paper, by mean of a different approach, we determine $ex(n, F_m)$ for all
integers $n$ with minor conditions, which extends their partial results.
Furthermore, we partly confirm the conjecture proposed by Bushaw and Kettle for
$ex(n, k\cdot P_l)$ [Bushaw,N. and Kttle,N. (2011) Tur\'{a}n numbers of
multiple paths and equibipartite forests. Combin. Probab. Comput. 20 837-853].
Moreover, we show that there exist two family graphs $F_m$ and $F_m^{\prime}$
such that $ex(n, F_m)=ex(n, F_m^{\prime})$ for all integers $n$, which is
related to an old problem of Erd\H{o}s and Simonovits.


title:
Realizations and properties of $3$-spherical Curtis-Tits Groups and Phan
  groups

abstract:
  In this note we establish the existence of all Curtis-Tits groups and Phan
groups with $3$-spherical diagram as classified previously and investigate some
of their geometric and group theoretic properties. Whereas it is known that
orientable Curtis-Tits groups with spherical or non-spherical and non-affine
diagram are almost simple, we show that non-orientable Curtis-Tits groups are
acylindrically hyperbolic and therefore have infinitely many infinite-index
normal subgroups. However, we also provide concrete examples of non-orientable
Curtis-Tits groups whose quotients are finite simple groups of Lie type.


title:
Convergence of the Finite Volume Method for scalar conservation laws
  with multiplicative noise: an approach by kinetic formulation

abstract:
  We prove the convergence of the explicit-in-time Finite Volume method with
monotone fluxes for the approximation of scalar first-order conservation laws
with multiplicative, compactly supported noise.


title: Convergence of approximations to stochastic scalar conservation laws

abstract:
  We develop a general framework for the analysis of approximations to
stochastic scalar conservation laws. Our aim is to prove, under minimal
consistency properties and bounds, that such approximations are converging to
the solution to a stochastic scalar conservation law. The weak probabilistic
convergence mode is convergence in law, the most natural in this context. We
use also a kinetic formulation and martingale methods. Our result is applied to
the convergence of the Finite Volume Method in the companion paper [15].


title:
Dynamic coherent backscattering of ultrasound in three-dimensional
  strongly-scattering media

abstract:
  We present measurements of the diffusion coefficient of ultrasound in
strongly scattering three-dimensional (3D) disordered media using the dynamic
coherent backscattering (CBS) effect. Our experiments measure the CBS of
ultrasonic waves using a transducer array placed in the far-field of a 3D slab
sample of brazed aluminum beads surrounded by vacuum. We extend to 3D media the
general microscopic theory of CBS that was developed initially for acoustic
waves in 2D. This theory is valid in the strong scattering, but still diffuse,
regime that is realized in our sample, and is evaluated in the diffuse far
field limit encountered in our experiments. By comparing our theory with the
experimental data, we obtain an accurate measurement of the diffusion
coefficient of ultrasound in our sample. We find that the value of $D$ is quite
small, $0.74 \pm 0.03$ mm$^2/\mu$s, and comment on the implications of this
slow transport for the energy velocity.


title: The dynamics of linarite: Observations of magnetic excitations

abstract:
  Here we present inelastic neutron scattering measurements from the
frustrated, quantum spin-1/2 chain material linarite, PbCuSO_4(OH)_2. Time of
flight data, taken at 0.5K and zero applied magnetic field reveals low-energy
dispersive spin wave excitations below 1.5meV both parallel and perpendicular
to the Cu-chain direction. From this we confirm that the interchain couplings
within linarite are around 10% of the nearest neighbour intrachain
interactions. We analyse the data within both linear spin-wave theory and
density matrix renormalisation group theories and establish the main magnetic
exchange interactions and the simplest realistic Hamiltonian for this material.


title:
Spherical arc-length as a global conformal parameter for analytic curves
  in the Riemann sphere

abstract:
  We prove that for every analytic curve in the complex plane, Euclidean and
spherical arc-lengths are global conformal parameters. We also prove that for
any analytic curve in the hyperbolic plane, hyperbolic arc-length is also a
global parameter. We generalize some of these results to the case of analytic
curves in Euclidean n-space and complex n-space and we discuss the situation of
curves in the Riemann sphere.


title: Commutative rings whose finitely generated ideals are quasi-flat

abstract:
  A definition of quasi-flat left module is proposed and it is shown that any
left module which is either quasi-projective or flat is quasi-flat. A
characterization of local commutative rings for which each ideal is quasi-flat
(resp. quasi-projective) is given. It is also proven that each commutative ring
R whose finitely generated ideals are quasi-flat is of $\lambda$-dimension
$\le$ 3, and this dimension $\le$ 2 if R is local. This extends a former result
about the class of arithmetical rings. Moreover, if R has a unique minimal
prime ideal then its finitely generated ideals are quasi-projective if they are
quasi-flat. In [1] Abuhlail, Jarrar and Kabbaj studied the class of commutative
fqp-rings (finitely generated ideals are quasi-projective). They proved that
this class of rings strictly contains the one of arithmetical rings and is
strictly contained in the one of Gaussian rings. It is also shown that the
property for a commutative ring to be fqp is preserved by localization. It is
known that a commutative ring R is arithmetical (resp. Gaussian) if and only if
R M is arithmetical (resp. Gaussian) for each maximal ideal M of R. But an
example given in [6] shows that a commutative ring which is a locally fqp-ring
is not necessarily a fqp-ring. So, in this cited paper the class of fqf-rings
is introduced. Each local commutative fqf-ring is a fqp-ring, and a commutative
ring is fqf if and only if it is locally fqf. These fqf-rings are defined in
[6] without a definition of quasi-flat modules. Here we propose a definition of
these modules and another definition of fqf-ring which is equivalent to the one
given in [6]. We also introduce the module property of self-flatness. Each
quasi-flat module is self-flat but we do not know if the converse holds. On the
other hand, each flat module is quasi-flat and any finitely generated module is
quasi-flat if and only if it is flat modulo its annihilator. In Section 2 we
give a complete characterization of local commutative rings for which each
ideal is self-flat. These rings R are fqp and their nilradical N is the subset
of zerodivisors of R. In the case where R is not a chain ring for which N = N 2
and R N is not coherent every ideal is flat modulo its annihilator. Then in
Section 3 we deduce that any ideal of a chain ring (valuation ring) R is
quasi-projective if and only if it is almost maximal and each zerodivisor is
nilpotent. This complete the results obtained by Hermann in [11] on valuation
domains. In Section 4 we show that each commutative fqf-ring is of
$\lambda$-dimension $\le$ 3. This extends the result about arithmetical rings
obtained in [4]. Moreover it is shown that this $\lambda$-dimension is $\le$ 2
in the local case. But an example of a local Gaussian ring R of
$\lambda$-dimension $\ge$ 3 is given.


title:
Lagragian methods for a general inhomogeneous incompressible
  Navier-Stokes-Korteweg system with variable capillarity and viscosity
  coefficients

abstract:
  We study the inhomogeneous incompressible Navier-Stokes system endowed with a
general capillary term. Thanks to recent methods based on Lagrangian change of
variables, we obtain local well-posedness in critical Besov spaces (even if the
integration index p is different from 2) and for variable viscosity and
capillary terms. In the case of constant coefficients and for initial data that
are perturbations of a constant state, we are able to prove that the lifespan
goes to infinity as the capillary coefficient goes to zero, connecting our
result to the global existence result obtained by Danchin and Mucha for the
incompressible Navier-Stokes system with constant coefficients.


title:
Geometrical Convergence Rate for Distributed Optimization with
  Time-Varying Directed Graphs and Uncoordinated Step-Sizes

abstract:
  This paper studies a class of distributed optimization algorithms by a set of
agents, where each agent has only access to its own local convex objective
function, and jointly minimizes the sum of the functions. The communications
among agents are described by a sequence of time-varying directed graphs which
are assumed to be uniformly strongly connected. A column stochastic mixing
matrices is employed in the algorithm, which also exactly steers all the agents
to asymptotically converge to a global and consensual optimal solution even
under the assumption that the step-sizes are uncoordinated. Two fairly standard
conditions for achieving the geometrical convergence rate are established under
the assumption that the objective functions are strong convexity and have
Lipschitz continuous gradient. The theoretical analysis shows that the
distributed algorithm is capable of driving the whole network to geometrically
converge to an optimal solution of the convex optimization problem as long as
the uncoordinated step-sizes do not exceed some upper bounds. We also give an
explicit analysis for the convergence rate of our algorithm through a different
approach. Finally, simulation results illustrate the feasibility of the
proposed algorithm and the theoretical analysis throughout this paper.


title: Mesoscopic fluctuations for the thinned Circular Unitary Ensemble

abstract:
  In this paper we study the asymptotic behavior of mesoscopic fluctuations for
the thinned Circular Unitary Ensemble. The effect of thinning is that the
eigenvalues start to decorrelate. The decorrelation is stronger on the larger
scales than on the smaller scales. We investigate this behavior by studying
mesoscopic linear statistics. There are two regimes depending on the scale
parameter and the thinning parameter. In one regime we obtain a CLT of a
classical type and in the other regime we retrieve the CLT for CUE. The two
regimes are separated by a critical line. On the critical line the limiting
fluctuations are no longer Gaussian, but described by infinitely divisible
laws. We argue that this transition phenomenon is universal by showing that the
same transition and their laws appear for fluctuations of the thinned sine
process in a growing box. The proofs are based on a Riemann-Hilbert problem for
integrable operators.


title:
Fully polynomial time approximation schemes (FPTAS) for some counting
  problems

abstract:
  In this thesis we develop FPTASs for the counting problems of m-tuples,
contingency tables with two rows, and 0/1 knapsack. For the problem of counting
m-tuples, we design two algorithms, one is strongly polynomial. As far as we
know, these are the first FPTASs for this problem. For the problem of counting
contingency tables we improve significantly over the running time of existing
algorithms. For the problem of counting 0/1 knapsack solutions, we design a
simple strongly polynomial algorithm, with similar running times to the
existing algorithms. Our results are derived by using, as well as expanding,
the method of K-approximation sets and functions.


title: Controllability of a bent 3-link magnetic microswimmer

abstract:
  - In this paper, we focus on a variant of a 3-link magnetic microswimmer
which consists of three rigid magnetized segments connected by two torsional
springs. In particular, we assume that one of the springs is twisted so that
the swimmer is not aligned at rest. By acting on it with an external magnetic
field, the swimmer twists and moves through the surrounding fluid. By
considering the external magnetic field as a control function, we state a local
partial controllability result around the equilibrium states. Then, we propose
a constructive method to find the magnetic field that allows the swimmer to
move along a prescribed trajectory. Finally, we show numerical simulations in
which the swimmer moves along a prescribed path.


title:
Velocity fluctuations and boundary layer structure in a rough
  Rayleigh-B{\'e}nard cell filled with water

abstract:
  We report Particle Image Velocimetry of the Large Scale Circulation and the
viscous boundary layer in turbulent thermal convection. We use two
parallelepipedic Rayleigh-B{\'e}nard cells with a top smooth plate. The first
one has a rough bottom plate and the second one has a smooth one so we compare
the rough-smooth and the smooth-smooth configurations. The dimensions of the
cell allow to consider a bi-dimensional mean flow. Lots of previous heat flux
measurements have shown a Nusselt--Rayleigh regime transition corresponding to
an increase of the heat flux in presence of roughness which is higher than the
surface increase. Our velocity measurements show that if the mean velocity
field is not clearly affected by the roughness, the velocity fluctuations rise
dramatically. It is accompanied by a change of the longitudinal velocity
structure functions scaling. Moreover, we show that the boundary layer becomes
turbulent close to roughness, as it was observed recently in the air [Liot et
al., JFM, vol. 786, pp. 275-293]. Finally we discuss the link between the
change of the boundary layer structure and the ones observed on the Large Scale
Circulation.


title: An empirical study for Vietnamese dependency parsing

abstract:
  This paper presents an empirical comparison of different dependency parsers
for Vietnamese, which has some unusual characteristics such as copula drop and
verb serialization. Experimental results show that the neural network-based
parsers perform significantly better than the traditional parsers. We report
the highest parsing scores published to date for Vietnamese with the labeled
attachment score (LAS) at 73.53% and the unlabeled attachment score (UAS) at
80.66%.


title: Thresholds of Prox-Boundedness of PLQ functions

abstract:
  Introduced in the 1960s, the Moreau envelope has grown to become a key tool
in non\-smooth analysis and optimization. Essentially an infimal convolution
with a parametrized norm squared, the Moreau envelope is used in many
applications and optimization algorithms. An important aspect in applying the
Moreau envelope to nonconvex functions is determining if the function is
prox-bounded, that is, if there exists a point $x$ and a parameter $r$ such
that the Moreau envelope is finite. The infimum of all such $r$ is called the
threshold of prox-boundedness (prox-threshold) of the function $f.$ In this
paper, we seek to understand the prox-thresholds of piecewise linear-quadratic
(PLQ) functions. (A PLQ function is a function whose domain is a union of
finitely many polyhedral sets, and that is linear or quadratic on each piece.)
The main result provides a computational technique for determining the
prox-threshold for a PLQ function, and further analyzes the behavior of the
Moreau envelope of the function using the prox-threshold. We provide several
examples to illustrate the techniques and challenges.


title: LQG for portfolio optimization

abstract:
  We introduce a generic solver for dynamic portfolio allocation problems when
the market exhibits return predictability, price impact and partial
observability. We assume that the price modeling can be encoded into a linear
state-space and we demonstrate how the problem then falls into the LQG
framework. We derive the optimal control policy and introduce analytical tools
that preserve the intelligibility of the solution. Furthermore, we link the
existence and uniqueness of the optimal controller to a dynamical non-arbitrage
criterion. Finally, we illustrate our method using a synthetic portfolio
allocation problem.


title:
Hybrid scheme for factorization: Factoring 551 using a 3-qubit NMR
  quantum adiabatic processor

abstract:
  Quantum processors are potentially superior to their classical counterparts
for many computational tasks including factorization. Circuit methods as well
as adiabatic methods have already been proposed and implemented for finding the
factors of a given composite number. The main challenge in scaling it to larger
numbers is the unavailability of large number of qubits. Here we propose a
hybrid scheme that involves both classical and quantum computation, which
reduces the number of qubits required for factorization. The classical part
involves setting up and partially simplifying a set of bit-wise factoring
equations and the quantum part involves solving these coupled equations using a
quantum adiabatic process. We demonstrate the hybrid scheme by factoring 551
using a three qubit NMR quantum register.


title:
In Defense of an Accelerating Universe: Model Insensitivity of the
  Hubble Diagram

abstract:
  A recently published paper by Nielsen, Guffanti and Sarkar argues that the
evidence for cosmic acceleration is marginal and that a coasting universe - the
Milne Universe - fits the same supernovae data in a Hubble diagram nearly as
well. The Milne Universe has negative spatial curvature. Nevertheless, we
confirm that the Milne model fits the data just as well as LCDM. We show that
this unexpected result points to a weakness in the Hubble diagram rather than
to a flaw in LCDM. It seems the Hubble diagram is insensitive to spatial
curvature. Here we present the data and both models in a scale factor vs.
cosmological time plot.This plot is exquisitely sensitive to spatial curvature
because one of three unique transformations, for each of curvatures 0,+1,-1, is
applied to transform from the Hubble diagram. Although the Milne negative
curvature did not matter much in the Hubble diagram, it matters critically in
the scale factor plot. Given that space is flat as measured by precise CMB
observations, we find that when the SNe data, the LCDM model and the Milne
model are plotted as scale factor vs. cosmological time the two resulting
curves separate at 2 sigma above the noise- ten times their separation above
the noise in the Hubble diagram. The transformed data fit to the LCDM model
confirms, at a 95% confidence level, that the universe is accelerating and the
Milne coasting universe is ruled out.


title: Structure of twisted and buckled bilayer graphene

abstract:
  We study the atomic structure of twisted bilayer graphene, with very small
mismatch angles ($\theta \sim 0.28^0$), a topic of intense recent interest. We
use simulations, in which we combine a recently presented semi-empirical
potential for single-layer graphene, with a new term for out-of-plane
deformations, [Jain et al., J. Phys. Chem. C, 119, 2015] and an often-used
interlayer potential [Kolmogorov et al., Phys. Rev. B, 71, 2005]. This
combination of potentials is computationally cheap but accurate and precise at
the same time, allowing us to study very large samples, which is necessary to
reach very small mismatch angles in periodic samples. By performing large scale
atomistic simulations, we show that the vortices appearing in the Moir\'e
pattern in the twisted bilayer graphene samples converge to a constant size in
the thermodynamic limit. Furthermore, the well known sinusoidal behavior of
energy no longer persists once the misorientation angle becomes very small
($\theta<1^0$). We also show that there is a significant buckling after the
relaxation in the samples, with the buckling height proportional to the system
size. These structural properties have direct consequences on the electronic
and optical properties of bilayer graphene.


title: Trans-cis molecular photoswitching in interstellar Space

abstract:
  As many organic molecules, formic acid (HCOOH) has two conformers (trans and
cis). The energy barrier to internal conversion from trans to cis is much
higher than the thermal energy available in molecular clouds. Thus, only the
most stable conformer (trans) is expected to exist in detectable amounts. We
report the first interstellar detection of cis-HCOOH. Its presence in
ultraviolet (UV) irradiated gas exclusively (the Orion Bar photodissociation
region), with a low trans-to-cis abundance ratio of 2.8+-1.0, supports a
photoswitching mechanism: a given conformer absorbs a stellar photon that
radiatively excites the molecule to electronic states above the interconversion
barrier. Subsequent fluorescent decay leaves the molecule in a different
conformer form. This mechanism, which we specifically study with ab initio
quantum calculations, was not considered in Space before but likely induces
structural changes of a variety of interstellar molecules submitted to UV
radiation.


title: On the quasi-ergodic distribution of absorbing Markov processes

abstract:
  In this paper, we give a sufficient condition for the existence of a
quasi-ergodic distribution for absorbing Markov processes. Using an
orthogonal-polynomial approach, we prove that the previous main result is valid
for the birth-death process on the nonnegative integers with 0 an absorbing
boundary and $\infty$ an entrance boundary. We also show that the quasi-ergodic
distribution is stochastically larger than the unique quasi-stationary
distribution in the sense of monotone likelihood-ratio ordering for the
birth-death process.


title: The Commutation Relation for Cavity Mode Operators

abstract:
  We have obtained the commutation relation for a cavity mode driven by
coherent light and interacting with a two-level atom. We have found that the
commutation relation for a free cavity mode with or without photons is just the
usual commutation relation. However, the commutation relation for a cavity
mode, which is interacting with a two-level atom, turns out to be different
from the usual one.


title: Half-integral linkages in highly connected directed graphs

abstract:
  We study the half-integral $k$-Directed Disjoint Paths Problem
($\tfrac12$kDDPP) in highly strongly connected digraphs. The integral kDDPP is
NP-complete even when restricted to instances where $k=2$, and the input graph
is $L$-strongly connected, for any $L\geq 1$. We show that when the integrality
condition is relaxed to allow each vertex to be used in two paths, the problem
becomes efficiently solvable in highly connected digraphs (even with $k$ as
part of the input). Specifically, we show that there is an absolute constant
$c$ such that for each $k\geq 2$ there exists $L(k)$ such that $\tfrac12$kDDPP
is solvable in time $O(|V(G)|^c)$ for a $L(k)$-strongly connected directed
graph $G$. As the function $L(k)$ grows rather quickly, we also show that
$\tfrac12$kDDPP is solvable in time $O(|V(G)|^{f(k)})$ in $(36k^3+2k)$-strongly
connected directed graphs. We also show that for each $\epsilon<1$ deciding
half-integral feasibility of kDDPP instances is NP-complete when $k$ is given
as part of the input, even when restricted to graphs with strong connectivity
$\epsilon k$.


title: Module production of the one-arm AFP 3D pixel tracker

abstract:
  The ATLAS Forward Proton (AFP) detector is designed to identify events in
which one or two protons emerge intact from the LHC collisions. AFP will
consist of a tracking detector, to measure the momentum of the protons, and a
time of flight system to reduce the background from multiple proton-proton
interactions. Following an extensive qualification period, 3D silicon pixel
sensors were selected for the AFP tracker. The sensors were produced at CNM
(Barcelona) during 2014. The tracker module assembly and quality control was
performed at IFAE during 2015. The assembly of the first AFP arm and the
following installation in the LHC tunnel took place in February 2016. This
paper reviews the fabrication process of the AFP tracker focusing on the pixel
modules.


title: Bayesian Heuristics for Group Decisions

abstract:
  We propose a model of inference and heuristic decision-making in groups that
is rooted in the Bayes rule but avoids the complexities of rational inference
in partially observed environments with incomplete information, which are
characteristic of group interactions. Our model is also consistent with a
dual-process psychological theory of thinking: the group members behave
rationally at the initiation of their interactions with each other (the slow
and deliberative mode); however, in the ensuing decision epochs, they rely on a
heuristic that replicates their experiences from the first stage (the fast
automatic mode). We specialize this model to a group decision scenario where
private observations are received at the beginning, and agents aim to take the
best action given the aggregate observations of all group members. We study the
implications of the information structure together with the properties of the
probability distributions which determine the structure of the so-called
"Bayesian heuristics" that the agents follow in our model. We also analyze the
group decision outcomes in two classes of linear action updates and log-linear
belief updates and show that many inefficiencies arise in group decisions as a
result of repeated interactions between individuals, leading to overconfident
beliefs as well as choice-shifts toward extremes. Nevertheless, balanced
regular structures demonstrate a measure of efficiency in terms of aggregating
the initial information of individuals. These results not only verify some
well-known insights about group decision-making but also complement these
insights by revealing additional mechanistic interpretations for the group
declension-process, as well as psychological and cognitive intuitions about the
group interaction model.

categories: cs.MA cs.SI cs.SY math.ST stat.AP stat.TH


title:
Unified theory to describe and engineer conservation laws in
  light-matter interactions

abstract:
  We present a unified theory to treat conservation laws in light-matter
interactions. It can be used to describe and engineer the transfer of any
measurable property from the electromagnetic field to any object. The theory
allows to explicitly characterize and separately compute the transfer due to
asymmetry of the object and the transfer due to field absorption by the object.
It also allows to compute the upper bound of the transfer rate of any given
property to any given object, together with the corresponding most efficient
illumination which achieves the bound. Due to its algebraic nature, the
approach is inherently suited for computer implementation.


title: Helical Kink Instability in the confined Solar Eruption on 2002 May 27

abstract:
  This paper presents an improved MHD modeling of the confined filament
eruption in solar active region NOAA~9957 on 2002 May~27 by extending the
parametric studies of the event in Torok & Kliem 2005 and Hassanin & Kliem
2016. Here the initial flux rope equilibrium is chosen to possess a small apex
height identical to the observed initial filament height, which implies a more
realistic inclusion of the photospheric line tying. The model matches the
observations as closely as in the preceding studies, with the closest agreement
again being obtained for an initial average flux rope twist of about $4\pi$.
Thus, the model for strongly writhing confined solar eruptions, which assumes
that a kink-unstable flux rope in the stability domain of the torus instability
exists at the onset of the eruption's main acceleration phase, is further
substantiated.


title:
Phase Shift Keying on the Hypersphere: Peak Power-Efficient MIMO
  Communications

abstract:
  Phase Shift Keying on the Hypersphere (PSKH), a generalization of
conventional Phase Shift Keying (PSK) for Multiple-Input Multiple-Output (MIMO)
systems, is introduced. In PSKH, constellation points are distributed on a
multidimensional hypersphere. The use of such constellations with a
Peak-To-Average-Sum-Power-Ratio (PASPR) of 1 allows to use load-modulated
transmitters which can cope with a small backoff, which in turn results in a
high power efficiency. In this paper, we discuss several methods how to
generate PSKH constellations and compare their performance. After applying
conventional Pulse-Amplitude Modulation (PAM), the PASPR of the continuous time
PSKH signal depends on the choice of the pulse shaping method. This choice also
influences bandwidth and power efficiency of a PSKH system. In order to reduce
the PASPR of the continuous transmission signal, we use spherical interpolation
to generate a smooth signal over the hypersphere and present corresponding
receiver techniques. Additionally, complexity reduction techniques are proposed
and compared. Finally, we discuss the methods presented in this paper regarding
their trade-offs with respect to PASPR, bandwidth, power efficiency and
receiver complexity.


title: Even and odd plane labelled bipartite trees

abstract:
  Let $T(n,m)$ be the set of all plane labelled bipartite trees with $n$ white
vertices and $m$ black. If the number $n+m$ of vertices is even, then the set
$T(n,m)$ is a union of two disjoint subsets --- subset od "even" trees and
subset of "odd" trees. This partition has a clear geometric meaning.


title: Periods of Mixed Tate Motives over Real Quadratic Number Rings

abstract:
  Recently, the author defined multiple Dedekind zeta values \cite{MDZF}
associated to a number $K$ field and a cone $C$. In this paper we construct
explicitly non-trivial examples of mixed Tate motives over the ring of integers
in $K$, for a real quadratic number field $K$ and a particular cone C. The
period of such a motive is a multiple Dedekind zeta values at
$(s_1,s_2)=(1,2)$, associated to the pair $(K;C)$, times a nonzero element of
$K$.