title: Approaches to the sign problem in lattice field theory

abstract:
  Quantum field theories (QFTs) at finite densities of matter generically
involve complex actions. Standard Monte-Carlo simulations based upon importance
sampling, which have been producing quantitative first principle results in
particle physics for almost fourty years, cannot be applied in this case.
Various strategies to overcome this so-called Sign Problem or Complex Action
Problem were proposed during the last thirty years. We here review the sign
problem in lattice field theories, focussing on two more recent methods:
Dualization to world-line type of representations and the density-of-states
approach.


title: Power Graph and Exchange Property for Resolving Sets

abstract:
  A formula for computing the metric dimension of a simple graph, having no
singleton twin, is given. A sufficient condition for a simple graph to have the
exchange property, for resolving sets, is found. Some families of power graphs
of finite groups, having this exchange property, are identified. The metric
dimension of the power graph of a dihedral group is also computed.


title: Deterministic Income with Deterministic and Stochastic Interest Rates

abstract:
  We consider an individual or household endowed with an initial capital and an
income, modeled as a deterministic process with a continuous drift rate. At
first, we model the discounting rate as the price of a zero-coupon bond at zero
under the assumption of a short rate evolving as an Ornstein-Uhlenbeck process.
Then, a geometric Brownian motion as the preference function and an
Ornstein-Uhlenbeck process as the short rate are taken into consideration. It
is assumed that the primal interest of the economic agent is to maximise the
cumulated value of (expected) discounted consumption from a given time up to a
finite deterministic time horizon $T\in\R_+$ or, in a stochastic setting,
infinite time horizon. We find an explicit expression for the value function
and for the optimal strategy in the first two cases. In the third case, we have
to apply the viscosity ansatz.


title:
Blind Friendly Maps: Tactile Maps for the Blind as a Part of the Public
  Map Portal (Mapy.cz)

abstract:
  Blind people can now use maps located at Mapy.cz, thanks to the long-standing
joint efforts of the ELSA Center at the Czech Technical University in Prague,
the Teiresias Center at Masaryk University, and the company Seznam.cz.
Conventional map underlays are automatically adjusted so that they could be
read through touch after being printed on microcapsule paper, which opens a
whole new perspective in the use of tactile maps. Users may select an area of
their choice in the Czech Republic (only within its boundaries, for the time
being) and also the production of tactile maps, including the preparation of
the map underlays, takes no more than several minutes.


title:
Circuit design for multi-body interactions in superconducting quantum
  annealing system with applications to a scalable architecture

abstract:
  Quantum annealing provides a way of solving optimization problems by encoding
them as Ising spin models which are implemented using physical qubits. The
solution of the optimization problem then corresponds to the ground state of
the system. Quantum tunnelling is harnessed to enable the system to move to the
ground state in a potentially highly non-convex energy landscape. A major
difficulty in encoding optimization problems in physical quantum annealing
devices is the fact that many real world optimization problems require
interactions of higher connectivity as well as multi-body terms beyond the
limitations of the physical hardware. In this work we address the question of
how to implement multi-body interactions using hardware which natively only
provides two-body interactions. The main result is an efficient circuit design
of such multi-body terms using superconducting flux qubits in which effective
N-body interactions are implemented using N ancilla qubits and only two
inductive couplers. It is then shown how this circuit can be used as the unit
cell of a scalable architecture by applying it to a recently proposed embedding
technique for constructing an architecture of logical qubits with arbitrary
connectivity using physical qubits which have nearest-neighbor four-body
interactions. It is further shown that this design is robust to non-linear
effects in the coupling loops as well as mismatches in some of the circuit
parameters.


title: Image Retrieval with a Bayesian Model of Relevance Feedback

abstract:
  A content-based image retrieval system based on multinomial relevance
feedback is proposed. The system relies on an interactive search paradigm where
at each round a user is presented with k images and selects the one closest to
their ideal target. Two approaches, one based on the Dirichlet distribution and
one based the Beta distribution, are used to model the problem motivating an
algorithm that trades exploration and exploitation in presenting the images in
each round. Experimental results show that the new approach compares favourably
with previous work.


title: A multiscale method for linear elasticity reducing Poisson locking

abstract:
  We propose a generalized finite element method for linear elasticity
equations with highly varying and oscillating coefficients. The method is
formulated in the framework of localized orthogonal decomposition techniques
introduced by M{\aa}lqvist and Peterseim (Math. Comp., 83(290): 2583--2603,
2014). Assuming only $L_\infty$-coefficients we prove linear convergence in the
$H^1$-norm, also for materials with large Lam\'{e} parameter $\lambda$. The
theoretical a priori error estimate is confirmed by numerical examples.


title: Threshold Multi Secret Sharing Using Elliptic Curve and Pairing

abstract:
  Secret Sharing techniques are now the building blocks of several security
protocols. A (t;n) threshold secret sharing scheme is one in which t or more
participant can join together to retrieve the secret.Traditional single secret
sharing schemes are modified and generalized to share multiple secrets.Use of
elliptic curve and pairing in secret sharing is gaining more importance.In this
paper we propose a threshold multi secret sharing scheme where more than one
secret is shared.When the threshold number of participants collate, the multi
secret can be retrieved. The scheme make use of elliptic curve and bilinear
pairing.Verification of shares by the participants, shares consistency
checking, detection and identification of cheaters are the extended
capabilities achieved.The shared secrets are retrieved in single stage here,
unlike the multi stage secret sharing scheme.The participants can be added very
easily.The scheme is efficient and the number of public parameters are also
less compared with the existing threshold multi secret sharing scheme based on
the elliptic curve.The dealer can easily modify the secret or add additional
secret by changing the public parameters of the scheme.This is the first
proposal of a threshold multi secret sharing scheme with extended capabilities
using self pairing.


title: The inner cavity of the circumnuclear disc

abstract:
  The circumnuclear disc (CND) orbiting the Galaxy's central black hole is a
reservoir of material that can ultimately provide energy through accretion, or
form stars in the presence of the black hole, as evidenced by the stellar
cluster that is presently located at the CND's centre. In this paper, we report
the results of a computational study of the dynamics of the CND. The results
lead us to question two paradigms that are prevalent in previous research on
the Galactic Centre. The first is that the disc's inner cavity is maintained by
the interaction of the central stellar cluster's strong winds with the disc's
inner rim, and second, that the presence of unstable clumps in the disc implies
that the CND is a transient feature. Our simulations show that, in the absence
of a magnetic field, the interaction of the wind with the inner disc rim
actually leads to a filling of the inner cavity within a few orbital
time-scales, contrary to previous expectations. However, including the effects
of magnetic fields stabilizes the inner disc rim against rapid inward
migration. Furthermore, this interaction causes instabilities that continuously
create clumps that are individually unstable against tidal shearing. Thus the
occurrence of such unstable clumps does not necessarily mean that the disc is
itself a transient phenomenon. The next steps in this investigation are to
explore the effect of the magnetorotational instability on the disc evolution
and to test whether the results presented here persist for longer time-scales
than those considered here.


title: An IBE-based Signcryption Scheme for Group Key Management

abstract:
  This paper presents a new crypto scheme whose title promises it to be so
boring that no-one will bother reading past the abstract. Because of this, the
remainder of the paper is left blank.


title: Analytic pion form factor

abstract:
  The pion electromagnetic form factor and two-pion production in
electron-positron collisions are simultaneously fitted by a vector dominance
model evolving to perturbative QCD at large momentum transfer. This model was
previously successful in simultaneously fitting the nucleon electromagnetic
form factors (spacelike region) and the electromagnetic production of
nucleon-antinucleon pairs (timelike region). For this pion case dispersion
relations are used to produce the analytic connection of the spacelike and
timelike regions. The fit to all the data is good, especially for the newer
sets of time-like data. The description of high-$q^2$ data, in the time-like
region, requires one more meson with $\rho$ quantum numbers than listed in the
2014 Particle Data Group review.


title:
Why are Jupiter-family comets active and asteroids in cometary-like
  orbits inactive?

abstract:
  Context: Surveys in the visible and near-infrared spectral range have
revealed the presence of low-albedo asteroids in cometary like orbits (ACOs).
In contrast to Jupiter family comets (JFCs), ACOs are inactive, but possess
similar orbital parameters. Aims: In this work, we discuss why ACOs are
inactive, whereas JFCs show gas-driven dust activity, although both belong to
the same class of primitive solar system bodies. Methods: We hypothesize that
ACOs and JFCs have formed under the same physical conditions, namely by the
gravitational collapse of ensembles of ice and dust aggregates. We use the
memory effect of dust-aggregate layers under gravitational compression to
discuss under which conditions the gas-driven dust activity of these bodies is
possible. Results: Owing to their smaller sizes, JFCs can sustain gas-driven
dust activity much longer than the bigger ACOs, whose sub-surface regions
possess an increased tensile strength, due to gravitational compression of the
material. The increased tensile strength leads to the passivation against dust
activity after a relatively short time of activity. Conclusions: The
gravitational-collapse model of the formation of planetesimals, together with
the gravitational compression of the sub-surface material simultaneously,
explains the inactivity of ACOs and the gas-driven dust activity of JFCs. Their
initially larger sizes means that ACOs possess a higher tensile strength of
their sub-surface material, which leads to a faster termination of gas-driven
dust activity. Most objects with radii larger than $2 \, \mathrm{km}$ have
already lost their activity due to former gravitational compression of their
current surface material.


title:
The extent of mixing in stellar interiors: the open clusters Collinder
  261 and Melotte 66

abstract:
  Context: Determining carbon and nitrogen abundances in red giants provides
useful diagnostics to test mixing processes in stellar atmospheres. Aims: Our
main aim is to determine carbon-to-nitrogen and carbon isotope ratios for
evolved giants in the open clusters Collinder 261 and Melotte 66 and to compare
the results with predictions of theoretical models. Methods: High-resolution
spectra were analysed using a differential model atmosphere method. Abundances
of carbon were derived using the C_2 Swan (0,1) band head at 5635.5 A. The
wavelength interval 7940-8130 A, which contains CN features, was analysed to
determine nitrogen abundances and carbon isotope ratios. The oxygen abundances
were determined from the [O_I] line at 6300 A. Results: The mean values of the
elemental abundances in Collinder 261, as determined from seven stars, are:
[C/Fe]=-0.23 +- 0.02 (s.d.), [N/Fe]=0.18 +- 0.09, [O/Fe]=-0.03 +- 0.07. The
mean 12^C/13^C ratio is 11 +- 2, considering four red clump stars and 18 for
one star above the clump. The mean C/N ratios are 1.60 +- 0.30 and 1.74,
respectively. For the five stars in Melotte 66 we obtained: [C/Fe]=-0.21 +-
0.07 (s.d.), [N/Fe]=0.17 +- 0.07, [O/Fe]=0.16 +- 0.04. The 12^C/13^C and C/N
ratios are 8 +- 2 and 1.67 +- 0.21, respectively. Conclusions: The 12^C/13^C
and C/N ratios of stars in the investigated open clusters were compared with
the ratios predicted by stellar evolution models. The mean values of 12^C/13^C
ratios in Collinder 261 and Melotte 66 agree well with models of
thermohaline-induced extra-mixing for the corresponding stellar turn-off masses
of about 1.1 - 1.2 Msun. The mean C/N ratios are not decreased as much as
predicted by the model in which the thermohaline- and rotation-induced
extra-mixing act together.


title:
On Optimizing Cooperative Cognitive User Performance under Primary QoS
  Constraints

abstract:
  We study the problem of optimizing the performance of cognitive radio users
with opportunistic real-time applications subject to primary users
quality-of-service (QoS) constraints. Two constrained optimization problems are
formulated; the first problem is maximizing the secondary user throughput while
the second problem is minimizing the secondary user average delay, subject to a
common constraint on the primary user average delay. In spite of the complexity
of the optimization problems, due to their non-convexity, we transform the
first problem into a set of linear programs and the second problem into a set
of quasiconvex optimization problems. We prove that both problems are
equivalent with identical feasible sets and optimal solutions. We show, through
numerical results, that the proposed cooperation policy represents the best
compromise between enhancing the secondary users QoS and satisfying the primary
users QoS requirements.


title: A Model-Theoretic Characterization of Constant-Depth Arithmetic Circuits

abstract:
  We study the class $\textrm{AC}^0$ of functions computed by constant-depth
polynomial-size arithmetic circuits of unbounded fan-in addition and
multiplication gates. No model-theoretic characterization for arithmetic
circuit classes is known so far. Inspired by Immerman's characterization of the
Boolean class $\textrm{AC}^0$, we remedy this situation and develop such a
characterization of $\textrm{AC}^0$. Our characterization can be interpreted as
follows: Functions in $\textrm{AC}^0$ are exactly those functions counting
winning strategies in first-order model checking games. A consequence of our
results is a new model-theoretic characterization of $\textrm{TC}^0$, the class
of languages accepted by constant-depth polynomial-size majority circuits.


title: Characterising Bounded Expansion by Neighbourhood Complexity

abstract:
  We show that a graph class $\cal G$ has bounded expansion if and only if it
has bounded $r$-neighbourhood complexity, i.e. for any vertex set $X$ of any
subgraph $H$ of $G\in\cal G$, the number of subsets of $X$ which are exact
$r$-neighbourhoods of vertices of $H$ on $X$ is linear to the size of $X$. This
is established by bounding the $r$-neighbourhood complexity of a graph in terms
of both its $r$-centred colouring number and its weak $r$-colouring number,
which provide known characterisations to the property of bounded expansion.


title: VapeTracker: Tracking Vapor Consumption to Help E-cigarette Users Quit

abstract:
  Despite current controversy over e-cigarettes as a smoking cessation aid, we
present early work based on a web survey (N=249) that shows that some
e-cigarette users (46.2%) want to quit altogether, and that behavioral feedback
that can be tracked can fulfill that purpose. Based on our survey findings, we
designed VapeTracker, an early prototype that can attach to any e-cigarette
device to track vaping activity. We discuss our future research on vaping
cessation, addressing how to improve our VapeTracker prototype, ambient
feedback mechanisms, and the future inclusion of behavior change models to
support quitting e-cigarettes.


title: Nambu bracket and M-theory

abstract:
  Nambu proposed an extension of dynamical system through the introduction of a
new bracket (Nambu bracket) in 1973. This article is a short review of the
developments after his paper. Some emphasis are put on a viewpoint that the
Nambu bracket naturally describes extended objects which appear in M-theory and
the fluid dynamics. The latter part of the paper is devoted to a review of the
studies on the Nambu bracket (Lie 3-algebra) in Bagger-Lambert-Gustavsson
theory of multiple M2-branes. This paper is a contribution to the proceedings
of Nambu memorial symposium (Osaka City University, September 29, 2015).


title:
Local search yields approximation schemes for k-means and k-median in
  Euclidean and minor-free metrics

abstract:
  We give the first polynomial-time approximation schemes (PTASs) for the
following problems: (1) uniform facility location in edge-weighted planar
graphs; (2) $k$-median and $k$-means in edge-weighted planar graphs; (3)
$k$-means in Euclidean spaces of bounded dimension. Our first and second
results extend to minor-closed families of graphs. All our results extend to
cost functions that are the $p$-th power of the shortest-path distance. The
algorithm is local search where the local neighborhood of a solution $S$
consists of all solutions obtained from $S$ by removing and adding
$1/\epsilon^{O(1)}$ centers.


title:
INDIGO-Datacloud: foundations and architectural description of a
  Platform as a Service oriented to scientific computing

abstract:
  In this paper we describe the architecture of a Platform as a Service (PaaS)
oriented to computing and data analysis. In order to clarify the choices we
made, we explain the features using practical examples, applied to several
known usage patterns in the area of HEP computing. The proposed architecture is
devised to provide researchers with a unified view of distributed computing
infrastructures, focusing in facilitating seamless access. In this respect the
Platform is able to profit from the most recent developments for computing and
processing large amounts of data, and to exploit current storage and
preservation technologies, with the appropriate mechanisms to ensure security
and privacy.


title: Will 5G See its Blind Side? Evolving 5G for Universal Internet Access

abstract:
  Internet has shown itself to be a catalyst for economic growth and social
equity but its potency is thwarted by the fact that the Internet is off limits
for the vast majority of human beings. Mobile phones---the fastest growing
technology in the world that now reaches around 80\% of humanity---can enable
universal Internet access if it can resolve coverage problems that have
historically plagued previous cellular architectures (2G, 3G, and 4G). These
conventional architectures have not been able to sustain universal service
provisioning since these architectures depend on having enough users per cell
for their economic viability and thus are not well suited to rural areas (which
are by definition sparsely populated). The new generation of mobile cellular
technology (5G), currently in a formative phase and expected to be finalized
around 2020, is aimed at orders of magnitude performance enhancement. 5G offers
a clean slate to network designers and can be molded into an architecture also
amenable to universal Internet provisioning. Keeping in mind the great social
benefits of democratizing Internet and connectivity, we believe that the time
is ripe for emphasizing universal Internet provisioning as an important goal on
the 5G research agenda. In this paper, we investigate the opportunities and
challenges in utilizing 5G for global access to the Internet for all (GAIA). We
have also identified the major technical issues involved in a 5G-based GAIA
solution and have set up a future research agenda by defining open research
problems.


title: Mountain pass solutions for the fractional Berestycki-Lions problem

abstract:
  We investigate the existence of least energy solutions and infinitely many
solutions for the following nonlinear fractional equation (-\Delta)^{s} u =
g(u) \mbox{ in } \mathbb{R}^{N}, where $s\in (0,1)$, $N\geq 2$, $(-\Delta)^{s}$
is the fractional Laplacian and $g: \mathbb{R} \rightarrow \mathbb{R}$ is an
odd $\mathcal{C}^{1, \alpha}$ function satisfying Berestycki-Lions type
assumptions. The proof is based on the symmetric mountain pass approach
developed by Hirata, Ikoma and Tanaka in \cite{HIT}. Moreover, by combining the
mountain pass approach and an approximation argument, we also prove the
existence of a positive radially symmetric solution for the above problem when
$g$ satisfies suitable growth conditions which make our problem fall in the so
called "zero mass" case.


title:
Hypersurface of a Finsler space subjected to an h-exponential change of
  metric

abstract:
  Recently we have obtained the Cartan connection for the Finsler space whose
metric is given by an exponential change with an h-vector. In this paper, we
discuss certain geometric properties of a Finslerian hyperspace subjected to an
h-exponential change of metric.


title:
LlamaFur: Learning Latent Category Matrix to Find Unexpected Relations
  in Wikipedia

abstract:
  Besides finding trends and unveiling typical patterns, modern information
retrieval is increasingly more interested in the discovery of surprising
information in textual datasets. In this work we focus on finding "unexpected
links" in hyperlinked document corpora when documents are assigned to
categories. To achieve this goal, we model the hyperlinks graph through node
categories: the presence of an arc is fostered or discouraged by the categories
of the head and the tail of the arc. Specifically, we determine a latent
category matrix that explains common links. The matrix is built using a
margin-based online learning algorithm (Passive-Aggressive), which makes us
able to process graphs with $10^{8}$ links in less than $10$ minutes. We show
that our method provides better accuracy than most existing text-based
techniques, with higher efficiency and relying on a much smaller amount of
information. It also provides higher precision than standard link prediction,
especially at low recall levels; the two methods are in fact shown to be
orthogonal to each other and can therefore be fruitfully combined.


title: From Prigogine to Raychaudhuri

abstract:
  It is highlighted by Prigogine that there are two additional universal
behaviors associated with the entropy production rate besides the four laws of
thermodynamics. One is that the entropy production rate decreases when the
system approaches the steady state, and the other is that the entropy
production rate reaches its minimal value at the steady state. Motivated by the
black hole thermodynamics and AdS/CFT correspondence, we resort to Raychaudhuri
equation to prove that these two universal behaviors are also obeyed by the
black hole entropy. In particular, our result together with the four laws of
black hole thermodynamics further indicates that the holographic gravity should
be universal, not restricted only within the context of AdS/CFT correspondence.


title: Bi-Local Fields in AdS${}_5$ Spacetime

abstract:
  Recently, the bi-local fields attract the interest in studying the duality
between $O(N)$ vector model and a higher-spin gauge theory in AdS spacetime. In
those theories, the bi-local fields are realized as collective one's of the
$O(N)$ vector fields, which are the source of higher-spin bulk fields.
Historically, the bi-local fields are introduced as a candidate of non-local
fields by Yukawa. Today, Yukawa's bi-local fields are understood from a
viewpoint of relativistic two-particle bound systems, the bi-local systems. We
study the relation between the bi-local collective fields out of higher-spin
bulk fields and the fields out of the bi-local systems embedded in AdS${}_5$
spacetime with warped metric. It is shown that the effective spring constant of
the bi-local system depends on the brane, on which the bi-local system is
located. In particular, a bi-local system with vanishing spring constant, which
is similar to the bi-local collective fields, can be realized on a low-energy
IR brane.


title:
Sine-square deformation and Mobius quantization of two-dimensional
  conformal field theory

abstract:
  Motivated by sine-square deformation (SSD) for quantum critical systems in
1+1-dimension, we discuss a Mobius quantization approach to the two-dimensional
conformal field theory (CFT), which bridges the conventional radial
quantization and the dipolar quantization recently proposed by Ishibashi and
Tada. We then find that the continuous Virasoro algebra of the dipolar
quantization can be interpreted as a continuum limit of the Virasoro algebra
for scaled generators in the SSD limit of the Mobius quantization approach.

categories: hep-th cond-mat.stat-mech math-ph math.MP


title: Upgrades of the ATLAS Muon Spectrometer with sMDT Chambers

abstract:
  With half the drift-tube diameter of the Monitored Drift Tube (MDT) chambers
of the ATLAS muon spectrometer and otherwise unchanged operating parameters,
small-diameter Muon Drift Tube (sMDT) chambers provide an order of magnitude
higher rate capability and can be installed in detector regions where MDT
chambers do not fit. The chamber assembly time has been reduced by a factor of
seven to one working day and the sense wire positioning accuracy improved by a
factor of two to better than ten microns. Two sMDT chambers have been installed
in ATLAS in 2014 to improve the momentum resolution in the barrel part of the
spectrometer. The construction of an additional twelve chambers covering the
feet regions of the ATLAS detector has started. It will be followed by the
replacement of the MDT chambers at the ends of the barrel inner layer by sMDTs
improving the Performance at the high expected background rates and providing
space for additional RPC trigger chambers.


title: Characterizing Realizability in Abstract Argumentation

abstract:
  Realizability for knowledge representation formalisms studies the following
question: given a semantics and a set of interpretations, is there a knowledge
base whose semantics coincides exactly with the given interpretation set? We
introduce a general framework for analyzing realizability in abstract
dialectical frameworks (ADFs) and various of its subclasses. In particular, the
framework applies to Dung argumentation frameworks, SETAFs by Nielsen and
Parsons, and bipolar ADFs. We present a uniform characterization method for the
admissible, complete, preferred and model/stable semantics. We employ this
method to devise an algorithm that decides realizability for the mentioned
formalisms and semantics; moreover the algorithm allows for constructing a
desired knowledge base whenever one exists. The algorithm is built in a modular
way and thus easily extensible to new formalisms and semantics. We have also
implemented our approach in answer set programming, and used the implementation
to obtain several novel results on the relative expressiveness of the
abovementioned formalisms.


title:
Influence of the different strains components on the uniaxial magnetic
  anisotropy constants for (Ga,Mn)As bulk system: a First-Principles Study

abstract:
  We present a computational study of the magnetic anisotropy energy for a
given concentration of the Mn ions in the GaAs host, in the framework of the
density functional theory. We focus on the influence of a different kind of
strains on the uniaxial magnetic anisotropy constants $K_1$ and $K_2$, which
reflect the magnetic anisotropy energy out- and in- (001) plane, respectively.
We have shown that the general trends for the applied biaxial strain on
anisotropy constants are consistent with the experimental data. We have
predicted the critical strains, for which the magnetization vector changes its
direction. Our results have shown that it is not possible to modify
considerably the uniaxial magnetic anisotropy constants, exposing (Ga,Mn)As to
hydrostatic pressure of a magnitude reasonable from experimental point of view.


title: Crucial role of Internal Collective Modes in Underdoped Cuprates

abstract:
  The enigmatic cuprate superconductors have attracted resurgent interest with
several recent reports and discussions of competing orders in the underdoped
side. Motivated by this, here we address the natural question of fragility of
the d-wave superconducting state in underdoped cuprates. Using a combination of
theoretical approaches we study t-J like models, and discover an - as yet
unexplored - instability that is brought about by an "internal" (anti-symmetric
mode) fluctuation of the d-wave state. This new theoretical result is in good
agreement with recent STM and ARPES studies of cuprates. We also suggest
experimental directions to uncover this physics.


title: An Anderson-like model of the QCD chiral transition

abstract:
  We study the problems of chiral symmetry breaking and eigenmode localisation
in finite-temperature QCD by looking at the lattice Dirac operator as a random
Hamiltonian. We recast the staggered Dirac operator into an unconventional
three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying
internal degrees of freedom, with disorder provided by the fluctuations of the
gauge links. In this framework, we identify the features relevant to chiral
symmetry restoration and localisation of the low-lying Dirac eigenmodes in the
ordering of the local Polyakov lines, and in the related correlation between
spatial links across time slices, thus tying the two phenomena to the
deconfinement transition. We then build a toy model based on QCD and on the
Dirac-Anderson approach, replacing the Polyakov lines with spin variables and
simplifying the dynamics of the spatial gauge links, but preserving the
above-mentioned relevant dynamical features. Our toy model successfully
reproduces the main features of the QCD spectrum and of the Dirac eigenmodes
concerning chiral symmetry breaking and localisation, both in the ordered
(deconfined) and disordered (confined) phases. Moreover, it allows us to study
separately the roles played in the two phenomena by the diagonal and the
off-diagonal terms of the Dirac-Anderson Hamiltonian. Our results support our
expectation that chiral symmetry restoration and localisation of the low modes
are closely related, and that both are triggered by the deconfinement
transition.


title:
Physics Goals and Experimental Challenges of the Proton-Proton
  High-Luminosity Operation of the LHC

abstract:
  The completion of Run 1 of the CERN Large Hadron Collider has seen the
discovery of the Higgs boson and an unprecedented number of precise
measurements of the Standard Model, while Run 2 operation has just started to
provide first data at higher energy. Upgrades of the LHC to high luminosity
(HL-LHC) and the experiments (ATLAS, CMS, ALICE and LHCb) will exploit the full
potential of the collider to discover and explore new physics beyond the
Standard Model. In this article, the experimental challenges and the physics
opportunities in proton-proton collisions at the HL-LHC are reviewed.


title: KK Gravitons at LHC2

abstract:
  In this work we study constraints from new searches for heavy particles at
the LHC on the allowed masses and couplings of a KK Graviton in a holographic
composite Higgs model. Keeping new electroweak states heavy such that
electroweak precision tests are satisfied, we control the mass of the lightest
KK graviton using a brane kinetic term. With this we study KK graviton masses
from 0.5-3 TeV. In our analysis we also employ Little Randall-Sundrum (RS)
Models, characterised by a lower UV scale in the 5D model which in turn implies
modified couplings to massless bulk fields. Viewing this scenario as a strongly
coupled 4D theory with a composite Higgs boson, the KK graviton is interpreted
as a composite spin-2 state and the varying UV scale corresponds to a varying
intermediate scale between the cutoff of the low energy effective theory and
the Planck scale. We find that KK gravitons with masses in the range 0.5-3 TeV
are compatible with current collider constraints, where the most promising
channels for detecting these states are the di-photon and ZZ channels. A
detection is more likely in the little RS models, in which the dual gauge
theory has a larger number of colours than in traditional RS models.


title: f(R) gravity constraints from gravitational waves

abstract:
  The recent LIGO observation sparked interest in the field of gravity wave
signals. Besides the gravity wave observation the LIGO collaboration used the
inspiraling black hole pair to constrain the graviton mass. Unlike general
relativity, $f(R)$ theories have a characteristic non-zero mass graviton. We
apply the constraint on the graviton mass to viable $f(R)$ models to find the
effects on model parameters. We find it possible to constrain the parameter
space with the gravity wave based observations. We make a case study for the
popular Hu-Sawicki model and find a parameter bracket. The result generalizes
to other $f(R)$ theories and can be used to contain the parameter space.


title: Scalar multi-wormholes

abstract:
  In 1921 Bach and Weyl derived the method of superposition to construct new
axially symmetric vacuum solutions of General Relativity. In this paper we
extend the Bach-Weyl approach to non-vacuum configurations with massless scalar
fields. Considering a phantom scalar field with the negative kinetic energy, we
construct a multi-wormhole solution describing an axially symmetric
superposition of $N$ wormholes. The solution found is static, everywhere
regular and has no event horizons. These features drastically tell the
multi-wormhole configuration from other axially symmetric vacuum solutions
which inevitably contain gravitationally inert singular structures, such as
`struts' and `membranes', that keep the two bodies apart making a stable
configuration. However, the multi-wormholes are static without any singular
struts. Instead, the stationarity of the multi-wormhole configuration is
provided by the phantom scalar field with the negative kinetic energy. Anther
unusual property is that the multi-wormhole spacetime has a complicated
topological structure. Namely, in the spacetime there exist $2^N$
asymptotically flat regions connected by throats.


title: Thermal Model Description of Collisions of Small Nuclei

abstract:
  The dependence of particle production on the size of the colliding nuclei is
analysed in terms of the thermal model using the canonical ensemble. The
concept of strangeness correlation in clusters of sub-volume $V_c$ is used to
account for the suppression of strangeness. A systematic analysis is presented
of the predictions of the thermal model for particle production in collisions
of small nuclei. The pattern of the maxima of strange-particles-to-pion ratios
as a function of beam energy is quite special, as they do not occur at the same
beam energy and are sensitive to system size. In particular, the
$\Lambda/\pi^+$ ratio shows a clear maximum even for small systems while the
maximum in the K$^+/\pi^+$ ratio is less pronounced


title:
Test for a universal behavior of Dirac eigenvalues in the complex
  Langevin method

abstract:
  We apply the complex Langevin (CL) method to a chiral random matrix theory
(ChRMT) at non-zero chemical potential and study the nearest neighbor spacing
(NNS) distribution of the Dirac eigenvalues. The NNS distribution is extracted
using an unfolding procedure for the Dirac eigenvalues obtained in the CL
method. For large quark mass, we find that the NNS distribution obeys the
Ginibre ensemble as expected. For small quark mass, the NNS distribution
follows the Wigner surmise for correct convergence case, while it follows the
Ginibre ensemble for wrong convergence case. The Wigner surmise is physically
reasonable from the chemical potential independence of the ChRMT. The Ginibre
ensemble is known to be favored in a phase quenched QCD at finite chemical
potential. Our result suggests a possibility that the originally universal
behavior of the NNS distribution is preserved even in the CL method for correct
convergence case.


title: Multitime correlation functions in nonclassical stochastic processes

abstract:
  A general method is introduced for verifying multitime quantum correlations
through the characteristic function of the time-dependent P functional that
generalizes the Glauber-Sudarshan P function. Quantum correlation criteria are
derived which identify quantum effects for an arbitrary number of points in
time. The Magnus expansion is used to visualize the impact of the required time
ordering, which becomes crucial in situations when the interaction problem is
explicitly time dependent. We show that the latter affects the
multi-time-characteristic function and, therefore, the temporal evolution of
the nonclassicality. As an example, we apply our technique to an optical
parametric process with a frequency mismatch. The resulting
two-time-characteristic function yields full insight into the two-time quantum
correlation properties of such a system.


title: Improved bounds for Fourier coefficients of Siegel modular forms

abstract:
  The goal of this paper is to improve existing bounds for Fourier coefficients
of higher genus Siegel modular forms of small weight.


title: Chromatic number of signed graphs with bounded maximum degree

abstract:
  A signed graph $ (G, \Sigma)$ is a graph positive and negative ($\Sigma $
denotes the set of negative edges). To re-sign a vertex $v$ of a signed graph $
(G, \Sigma)$ is to switch the signs of the edges incident to $v$. If one can
obtain $ (G, \Sigma')$ by re-signing some vertices of $ (G, \Sigma)$, then
  $ (G, \Sigma) \equiv (G, \Sigma')$.
  A signed graphs $ (G, \Sigma )$ admits an homomorphism to $ (H, \Lambda )$ if
there is a sign preserving vertex mapping from $(G,\Sigma')$ to $(H, \Lambda)$
for some $ (G, \Sigma) \equiv (G, \Sigma')$.
  The signed chromatic number $\chi_{s}( (G, \Sigma))$ of the signed graph $(G,
\Sigma)$ is the minimum order (number of vertices) of a signed graph $(H,
\Lambda)$ such that $ (G, \Sigma)$ admits a homomorphism to $(H, \Lambda)$. For
a family $ \mathcal{F}$ of signed graphs $\chi_{s}(\mathcal{F}) =
\text{max}_{(G,\Sigma) \in \mathcal{F}} \chi_{s}( (G, \Sigma))$.
  We prove $2^{\Delta/2-1} \leq \chi_s(\mathcal{G}_{\Delta}) \leq (\Delta-1)^2.
2^{(\Delta-1)} +2$ for all $\Delta \geq 3$ where $\mathcal{G}_{\Delta}$ is the
family of connected signed graphs with maximum degree $\Delta$. \end{abstract}


title: Sub-pixel accuracy edge fitting by means of B-spline

abstract:
  Local perturbations around contours strongly disturb the final result of
computer vision tasks. It is common to introduce a priori information in the
estimation process. Improvement can be achieved via a deformable model such as
the snake model. In recent works, the deformable contour is modeled by means of
B-spline snakes which allows local control, concise representation, and the use
of fewer parameters. The estimation of the sub-pixel edges using a global
B-spline model relies on the contour global determination according to a
maximum likelihood framework and using the observed data likelihood. This
procedure guarantees that the noisiest data will be filtered out. The data
likelihood is computed as a consequence of the observation model which includes
both orientation and position information. Comparative experiments of this
algorithm and the classical spline interpolation have shown that the proposed
algorithm outperforms the classical approach for Gaussian and Salt & Pepper
noise.


title: Quantum limits to mass sensing in a gravitational field

abstract:
  We address the problem of estimating the mass of a quantum particle in a
gravitational field and seek the ultimate bounds to precision of
quantum-limited detection schemes. In particular, we study the effect of the
field on the achievable sensitivity and address the question of whether
quantumness of the probe state may provide a precision enhancement. The
ultimate bounds to precision are quantified in terms of the corresponding
Quantum Fisher Information. Our results show that states with no classical
limit perform better than semiclassical ones and that a non-trivial interplay
exists between the external field and the statistical model. More intense
fields generally lead to a better precision, with the exception of position
measurements in the case of freely-falling systems.


title:
Queueing Analysis of a Large-Scale Bike Sharing System through
  Mean-Field Theory

abstract:
  The bike sharing systems are fast increasing as a public transport mode in
urban short trips, and have been developed in many major cities around the
world. A major challenge in the study of bike sharing systems is that
large-scale and complex queueing networks have to be applied through
multi-dimensional Markov processes, while their discussion always suffers a
common difficulty: State space explosion. For this reason, this paper provides
a mean-field computational method to study such a large-scale bike sharing
steps: Firstly, a multi-dimensional Markov process is set up for expressing the
states of the bike sharing system, and the empirical process of the
multi-dimensional Markov process is given to partly overcome the difficulty of
state space explosion. Based on this, the mean-field equations are derived by
means of a virtual time-inhomogeneous M(t)/M(t)/1/K queue whose arrival and
service rates are determined by the mean-field computation. Secondly, the
martingale limit is employed to investigate the limiting behavior of the
empirical process, the fixed point is proved to be unique so that it can be
computed by means of a nonlinear birth-death process, the asymptotic
independence of this system is discussed simply, and specifically, these lead
to numerical computation of the steady-state probability of the problematic
(empty or full) stations. Finally, some numerical examples are given for
valuable observation on how the steady-state probability of the problematic
stations depends on some crucial parameters of the bike sharing system.


title: On a special class of boxicity 2 graphs

abstract:
  We define and study a class of graphs, called 2-stab interval graphs (2SIG),
with boxicity 2 which properly contains the class of interval graphs. A 2SIG is
an axes-parallel rectangle intersection graph where the rectangles have unit
height (that is, length of the side parallel to $Y$-axis) and intersects either
of the two fixed lines, parallel to the $X$-axis, distance $1+\epsilon$ ($0 <
\epsilon < 1$) apart. Intuitively, 2SIG is a graph obtained by putting some
edges between two interval graphs in a particular rule. It turns out that for
these kind of graphs, the chromatic number of any of its induced subgraphs is
bounded by twice of its (induced subgraph) clique number. This shows that the
graph, even though not perfect, is not very far from it. Then we prove similar
results for some subclasses of 2SIG and provide efficient algorithm for finding
their clique number. We provide a matrix characterization for a subclass of
2SIG graph.


title:
A formula for the total permutation-equivariant K-theoretic
  Gromov-Witten potential

abstract:
  We give a summation over graphs type formula for the permutation-equivariant
K-theoretic Gromov-Witten total potential of a projective manifold X in terms
of cohomological Gromov-Witten (GW) invariants of X. We achieve this by
describing combinatorially the Kawasaki strata of the moduli spaces of stable
maps to X.


title: A generalization of vortex lines

abstract:
  Helmholtz theorem states that, in ideal fluid, vortex lines move with the
fluid. Another Helmholtz theorem adds that strength of a vortex tube is
constant along the tube. The lines may be regarded as integral surfaces of a
1-dimensional integrable distribution (given by the vorticity 2-form). In
general setting of theory of integral invariants, due to Poincare and Cartan,
one can find $d$-dimensional integrable distribution whose integral surfaces
show both properties of vortex lines: they move with (abstract) fluid and, for
appropriate generalization of vortex tube, strength of the latter is constant
along the tube.


title: The origin of the UV/optical lags in NGC 5548

abstract:
  The new multi-wavelength monitoring campaign on NGC 5548 shows clearly that
the variability of the UV/optical lightcurves lags by progressively longer
times at longer wavelengths, as expected from reprocessing of an optically
thick disk, but that the timescales are longer than expected for a standard
Shakura-Sunyaev accretion disc. We build a full spectral-timing reprocessing
model to simulate the UV/optical lightcurves of NGC 5548. We show that disc
reprocessing of the observed hard X-ray lightcurve produces optical lightcurves
with too much fast variability as well as too short a lag time. Supressing the
fast variability requires an intervening structure preventing the hard X-rays
from illuminating the disc. We propose this is the disc itself, perhaps due to
atomic processes in the UV lifting the photosphere, increasing the
scale-height, making it less dense and less able to thermalise, so that it
radiates low temperature Comptonised emission as required to produce the soft
X-ray excess. The outer edge of the puffed-up Comptonised disc region emits FUV
flux, and can illuminate the outer thin blackbody disc but while this gives
reprocessed variable emission which is much closer to the observed UV and
optical lightcurves, the light travel lags are still too short to match the
data. We reverse engineer a solution to match the observations and find that
the luminosity and temperature of the lagged emission is not consistent with
material at the light travel lag distance responding to the irradiating flux
(either FUV or X-ray) from the AGN. We conclude that the UV/optical lags of NGC
5548 are not the light travel time from X-ray reprocessing, nor the light
travel time from FUV reprocessing, but instead could be the timescale for the
outer blackbody disc vertical structure to respond to the changing FUV
illumination.


title: Automorphism groups of Gabidulin-like codes

abstract:
  Let K be a cyclic Galois extension of degree f over k and T a generator of
the Galois group. For any v=(v_1,... , v_m)\in K^m such that v is linearly
independent over k, and any 0< d < m the Gabidulin-like code C(v, T , d) is a
maximum rank distance code in the space of f times m matrices over k of
dimension fd. This construction unifies the ones available in the literature.
We characterise the K-linear codes that are Gabidulin-like codes and determine
their rank-metric automorphism group.


title:
Diffusion-driven growth of nanowires by low-temperature molecular beam
  epitaxy

abstract:
  With ZnTe as an example, we use two different methods to unravel the
characteristics of the growth of nanowires by gold-catalyzed molecular beam
epitaxy at low temperature. In the first approach, CdTe insertions have been
used as markers, and the nanowires have been characterized by scanning
transmission electron microscopy, including geometrical phase analysis, and
energy dispersive electron spectrometry; the second approach uses scanning
electron microscopy and the statistics of the relationship between the length
of the tapered nanowires and their base diameter. Axial and radial growth are
quantified using a diffusion-limited model adapted to the growth conditions;
analytical expressions describe well the relationship between the NW length and
the total molecular flux (taking into account the orientation of the effusion
cells), and the catalyst-nanowire contact area. A long incubation time is
observed. This analysis allows us to assess the evolution of the diffusion
lengths on the substrate and along the nanowire sidewalls, as a function of
temperature and deviation from stoichiometric flux.


title: Non-canonical two-field inflation to order $\xi^2$

abstract:
  In non-canonical two-field inflation models, deviations from the canonical
model can be captured by a parameter $\xi$. We show this parameter is usually
one half of the slow-roll order and analytically calculate the primordial power
spectra accurate to order $\xi^2$. The super-horizon perturbations are studied
with an improved method, which gives a correction of order $\xi^2$. Three
typical examples demonstrate that our analytical formulae of power spectra fit
well with numerical simulation.


title:
Semi-positivity of logarithmic cotangent bundle and
  Shafarevich-Viehweg's conjecture, after Campana, Paun, Taji...

abstract:
  Proven by A. Parshin and S. Arakelov in the early 70's, Shafaverich
hyperbolicity conjecture states that a family of curves of genus $g\ge2$
parametrized by a non hyperbolic curve (\emph{i.e.} isomorphic to
$\mathbb{P}^1$, $\mathbb{C}$, $\mathbb{C}^*$ or an elliptic curve) has to be
isotrivial : the moduli of smooth fibres are constant. In higher dimensions,
Viehweg's works on moduli of canonically polarized manifolds led him to
generalize this statement in the following way: if a family of canonically
polarized manifolds (parametrized by a quasi-projective base) has maximal
variation, the base is then of log-general type. It can be thought as an
algebraic hyperbolicity property which is expected to hold for the moduli
space.Adapting results due to Y. Miyoaka on generic semi-positivity of
cotangent bundle to the framework of pairs, F. Campana and M. P\u{a}un recently
obtained a positive answer to Viehweg's conjecture. We will also take the
opportunity of this talk to present the classification of orbifolds as
developed in Campana's works. This setting is moreover the right one to state
the optimal version of Viehweg's conjecture proven by B. Taji


title: On Jacobi Inversion Formulae for Telescopic Curves

abstract:
  For a hyperelliptic curve of genus $g$, it is well known that the symmetric
products of $g$ points on the curve are expressed in terms of their Abel-Jacobi
image by the hyperelliptic sigma function (Jacobi inversion formulae).
Matsutani and Previato gave a natural generalization of the formulae to the
more general algebraic curves defined by $y^r=f(x)$, which are special cases of
$(n,s)$ curves, and derived new vanishing properties of the sigma function of
the curves $y^r=f(x)$. In this paper we extend the formulae to the telescopic
curves proposed by Miura and derive new vanishing properties of the sigma
function of telescopic curves. The telescopic curves contain the $(n,s)$ curves
as special cases.


title: On local structures of cubicity 2 graphs

abstract:
  A 2-stab unit interval graph (2SUIG) is an axes-parallel unit square
intersection graph where the unit squares intersect either of the two fixed
lines parallel to the $X$-axis, distance $1 + \epsilon$ ($0 < \epsilon < 1$)
apart. This family of graphs allow us to study local structures of unit square
intersection graphs, that is, graphs with cubicity 2. The complexity of
determining whether a tree has cubicity 2 is unknown while the graph
recognition problem for unit square intersection graph is known to be NP-hard.
We present a polynomial time algorithm for recognizing trees that admit a 2SUIG
representation.


title:
Effects of Rashba spin-orbit coupling, Zeeman splitting and gyrotropy in
  two-dimensional cavity polaritons under the influence of the Landau
  quantization

abstract:
  GaAs-type quantum wells (QWs) with p-type valence band embedded into the
resonators. The Landau quantization of the electrons and heavy-holes (hh) was
investigated taking into account the Rashba spin-orbit coupling with
third-order chirality terms for hh and with nonparabolicity terms in their
dispersion low including the Zeeman splitting (ZS) effects. The exact solutions
for the eigenfunctions and eigenenergies were obtained using the Rashba method
[1]. We derive in the second quantization representation the Hamiltonians
describing the Coulomb electron-electron and the electron-radiation
interactions and determine the magnetoexciton energy branches and the
magnetoexciton-photon interaction. The fifth order dispersion equation
describing the energy spectrum of the cavity magnetoexciton-polariton is
investigated. It takes into account the interaction of the cavity photons with
two dipole-active and with two quadrupole-active 2D magnetoexciton energy
branches. The cavity photons have the circular polarizations oriented along
their wave vectors, which has the quantized longitudinal component. The
selection rules of the exciton-photon interaction is expressed through the
scalar products of the two-types circular polarizations and it is related with
the numbers of the LQ levels of electrons and heavy-holes. It is shown that the
Rabi frequency of the polariton branches and the magnetoexciton oscillator
strength increase in dependence on the magnetic field strength. The optical
gyrotropy effects may be revealed if changing the sign of the photon circular
polarization at a given sign of the wave vector longitudinal projection or
equivalently changing the sign of the longitudinal projection at the same
selected light circular polarization.


title:
Resolution and Efficiency of the ATLAS Muon Drift-Tube Chambers at High
  Background Rates

abstract:
  The resolution and efficiency of a precision drift-tube chamber for the ATLAS
muon spectrometer with final read-out electronics was tested at the Gamma
Irradiation Facility at CERN in a 100 GeV muon beam and at photon irradiation
rates of up to 990 Hz/square cm which corresponds to twice the highest
background rate expected in ATLAS. A silicon strip detector telescope was used
as external reference in the beam. The pulse-height measurement of the read-out
electronics was used to perform time-slewing corrections which lead to an
improvement of the average drift-tube resolution from 104 microns to 82 microns
without irradiation and from 128 microns to 108 microns at the maximum expected
rate. The measured drift-tube efficiency agrees with the expectation from the
dead time of the read-out electronics up to the maximum expected rate.


title: Magnetic field evolution of accreting neutron stars

abstract:
  The flow of a matter, accreting onto a magnetized neutron star, is
accompanied by an electric current. The closing of the electric current occurs
in the crust of a neutron stars in the polar region across the magnetic field.
But the conductivity of the crust along the magnetic field greatly exceeds the
conductivity across the field, so the current penetrates deep into the crust
down up to the super conducting core. The magnetic field, generated by the
accretion current, increases greatly with the depth of penetration due to the
Hall conductivity of the crust is also much larger than the transverse
conductivity. As a result, the current begins to flow mainly in the toroidal
direction, creating a strong longitudinal magnetic field, far exceeding an
initial dipole field. This field exists only in the narrow polar tube of $r$
width, narrowing with the depth, i.e. with increasing of the crust density
$\rho$, $r\propto \rho^{-1/4}$. Accordingly, the magnetic field $B$ in the tube
increases with the depth, $B\propto \rho^{1/2}$, and reaches the value of about
$10^{17}$ Gauss in the core. It destroys super conducting vortices in the core
of a star in the narrow region of the size of the order of ten centimeters.
Because of generated density gradient of vortices they constantly flow into
this dead zone and the number of vortices decreases, the magnetic field of a
star decreases as well. The attenuation of the magnetic field is exponential,
$B=B_0(1+t/\tau)^{-1}$. The characteristic time of decreasing of the magnetic
field $\tau$ is equal to $\tau\simeq 10^3$ years. Thus, the magnetic field of
accreted neutron stars decreases to values of $10^8 - 10^9$ Gauss during
$10^7-10^6$ years.


title:
Near-Optimal Hybrid Analog and Digital Precoding for Downlink mmWave
  Massive MIMO Systems

abstract:
  Millimeter wave (mmWave) massive MIMO can achieve orders of magnitude
increase in spectral and energy efficiency, and it usually exploits the hybrid
analog and digital precoding to overcome the serious signal attenuation induced
by mmWave frequencies. However, most of hybrid precoding schemes focus on the
full-array structure, which involves a high complexity. In this paper, we
propose a near-optimal iterative hybrid precoding scheme based on the more
realistic subarray structure with low complexity. We first decompose the
complicated capacity optimization problem into a series of ones easier to be
handled by considering each antenna array one by one. Then we optimize the
achievable capacity of each antenna array from the first one to the last one by
utilizing the idea of successive interference cancelation (SIC), which is
realized in an iterative procedure that is easy to be parallelized. It is shown
that the proposed hybrid precoding scheme can achieve better performance than
other recently proposed hybrid precoding schemes, while it also enjoys an
acceptable computational complexity.


title: Monopoles, instantons and the Helmholtz equation

abstract:
  In this work we study the dimensional reduction of smooth circle invariant
Yang-Mills instantons defined on 4-manifolds which are non-trivial circle
fibrations over hyperbolic 3-space. A suitable choice of the 4-manifold metric
within a specific conformal class gives rise to singular and smooth hyperbolic
monopoles. A large class of monopoles is obtained if the conformal factor
satisfies the Helmholtz equation on hyperbolic 3-space. We describe simple
configurations and relate our results to the JNR construction, for which we
provide a geometric interpretation.


title:
First-principles approach to the dynamic magnetoelectric couplings in
  BiFeO$_3$

abstract:
  Despite its great technological importance, the magnetoelectric (ME)
couplings in \BF are barely understood. By using a first-principles approach,
we uncover the {\it dynamic} ME couplings of the long-range spin-cycloid in
BiFeO$_3$. Based on a microscopic Hamiltonian, our first-principles approach
disentangles the hidden ME couplings due to spin-current and
exchange-striction. Beyond the spin-current polarization governed by the
inverse Dzyaloshinskii-Moriya interaction \cite{iDM}, various spin-current
polarizations derived from both ferroelectric and antiferrodistortive
distortions cooperatively produce the strong non-reciprocal directional
dichroism or the asymmetry in the absorption of counter-propagating light in
BiFeO$_3$. Our systematic approach can be generally applied to any multiferroic
material, laying the foundation for revealing hidden ME couplings on an atomic
scale and for exploiting optical ME effects in the next generation of
technological devices such as optical diodes.


title:
A general multiple-relaxation-time lattice Boltzmann model for nonlinear
  anisotropic convection-diffusion equations

abstract:
  In this paper, based on the previous work [B. Shi, Z. Guo, Lattice Boltzmann
model for nonlinear convection-diffusion equations, Phys. Rev. E 79 (2009)
016701], we develop a general multiple-relaxation-time (MRT) lattice Boltzmann
model for nonlinear anisotropic convection-diffusion equation (NACDE), and show
that the NACDE can be recovered correctly from the present model through the
Chapman-Enskog analysis. We then test the MRT model through some classic CDEs,
and find that the numerical results are in good agreement with analytical
solutions or some available results. Besides, the numerical results also show
that similar to the single-relaxation-time (SRT) lattice Boltzmann model or
so-called BGK model, the present MRT model also has a second-order convergence
rate in space. Finally, we also perform a comparative study on the accuracy and
stability of the MRT model and BGK model by using two examples. In terms of the
accuracy, both the theoretical analysis and numerical results show that a
\emph{numerical} slip on the boundary would be caused in the BGK model, and
cannot be eliminated unless the relaxation parameter is fixed to be a special
value, while the \emph{numerical} slip in the MRT model can be overcome once
the relaxation parameters satisfy some constrains. The results in terms of
stability also demonstrate that the MRT model could be more stable than the BGK
model through tuning the free relaxation parameters.


title: Wireless Coverage Area Computation and Optimization

abstract:
  A wireless network's design must include the optimization of the area of
coverage of its wireless transmitters - mobile and base stations in cellular
networks, wireless access points in WLANs, or nodes on a transmit schedule in a
wireless ad-hoc network. Typically, the coverage optimization for the common
channels is solved by spatial multiplexing, i.e. keeping the access networks
far apart. However, with increasing densities of wireless network deployments
(including the Internet-of-Things) and paucity of spectrum, and new
developments like whitespace devices and self-organizing, cognitive networks,
there is a need to manage interference and optimize coverage by efficient
algorithms that correctly set the transmit powers to ensure that transmissions
only use the power necessary.
  In this work we study methods for computing and optimizing
interference-limited coverage maps of a set of transmitters. We progress
successively through increasingly realistic network scenarios. We begin with a
disk model with a fixed set of transmitters and present an optimal algorithm
for computing the coverage map. We then enhance the model to include updates to
the network, in the form of addition or deletion of one transmitter. In this
dynamic setting, we present an optimal algorithm to maintain updates to the
coverage map. We then move to a more realistic interference model - the SINR
model. For the SINR model we first show geometric bases for coverage maps. We
then present a method to approximate the measure of the coverage area. Finally,
we present an algorithm that uses this measure to optimize the coverage area
with minimum total transmit power.


title:
An inequality concerning the growth bound of a discrete evolution family
  on a complex Banach space

abstract:
  We prove that the uniform growth bound $\omega_0(\mathcal{U})$ of a discrete
evolution family $\mathcal{U}$ of bounded linear operators acting on a complex
Banach space $X$ satisfies the inequality
$$\omega_0(\mathcal{U})c_{\mathcal{U}}(\mathcal{X})\le -1;$$ here
$c_{\mathcal{U}}(\mathcal{X})$ is the operator norm of a convolution operator
which acts on a certain Banach space $\mathcal{X}$ of $X$-valued sequences.


title:
Charge transfer of edge states in zigzag silicene nanoribbons with
  Stone-Wales defects

abstract:
  Stone-Wales (SW) defects are favorably existed in graphenelike materials with
honeycomb lattice structure and potentially employed to change the electronic
properties in band engineering. In this paper, we investigate structural and
electronic properties of SW defects in bulk silicene and its nanoribbons as a
function of their concentration using the methods of periodic boundary
conditions with first-principles calculations. We first calculate the formation
energy, structural properties, and electronic band structures of SW defects in
bulk silicene, with dependence on the concentration of SW defects. Our results
show a good agreement with available values from the previous first-principles
calculations. The energetics, structural aspects, and electronic properties of
SW defects with dependence on defect concentration and location in
edge-hydrogenated zigzag silicene nanoribbons are obtained. For all calculated
concentrations, the SW defects prefer to locate at the edge due to the lower
formation energy. The SW defects at the center of silicene nanoribbons slightly
influence on the electronic properties, whereas the SW defects at the edge of
silicene nanoribbons split the degenerate edge states and induce a sizable gap,
which depends on the concentration of defects. It is worth to find that the SW
defects produce a perturbation repulsive potential, which leads the decomposed
charge of edge states at the side with defect to transfer to the other side
without defect.


title:
Global-in-time regularity via duality for congestion-penalized Mean
  Field Games

abstract:
  After a brief introduction to one of the most typical problems in Mean Field
Games, the congestion case (where agents pay a cost depending on the density of
the regions they visit), and to its variational structure, we consider the
question of the regularity of the optimal solutions. A duality argument, used
for the first time in a paper by Y. Brenier on incompressible fluid mechanics,
and recently applied to MFG with density constraints, allows to easily get some
Sobolev regularity, locally in space and time. In the paper we prove that a
careful analysis of the behaviour close to the final time allows to extend the
same result including t = T .


title:
A Homogenization Technique for Obtaining Generalized Sheet Transition
  Conditions (GSTCs) for a Metafilm Embedded in a Magneto-Dielectric Interface

abstract:
  Using the multiple-scale homogenization method, we derive generalized sheet
transition conditions (GSTCs) for electromagnetic fields at the surface of a
metafilm. The scatterers that compose the metafilm are of arbitrary shape and
are embedded between two different magneto-dielectric media. The parameters in
these boundary conditions are interpreted as effective electric and magnetic
surface susceptibilities, which themselves are related to the geometry of the
scatterers that constitute the metafilm.


title: Comment on "Unraveling the 'Pressure Effect' in Nucleation"

abstract:
  In a 2008 Letter, Wedekind et al. discussed the influence of an inert carrier
gas on the vapor-liquid nucleation rate. They found an additional
"pressure-volume work" that is performed against the carrier gas, and also
quantified the nonisothermal effects arising from the carrier gas. We argue
that the pressure-volume work term represents the influence of the carrier gas
on phase equilibrium itself. This term will not appear explicitly when a
definition of the supersaturation is used that is appropriate for high-pressure
nucleation.


title:
Sparse Representation of Multivariate Extremes with Applications to
  Anomaly Ranking

abstract:
  Extremes play a special role in Anomaly Detection. Beyond inference and
simulation purposes, probabilistic tools borrowed from Extreme Value Theory
(EVT), such as the angular measure, can also be used to design novel
statistical learning methods for Anomaly Detection/ranking. This paper proposes
a new algorithm based on multivariate EVT to learn how to rank observations in
a high dimensional space with respect to their degree of 'abnormality'. The
procedure relies on an original dimension-reduction technique in the extreme
domain that possibly produces a sparse representation of multivariate extremes
and allows to gain insight into the dependence structure thereof, escaping the
curse of dimensionality. The representation output by the unsupervised
methodology we propose here can be combined with any Anomaly Detection
technique tailored to non-extreme data. As it performs linearly with the
dimension and almost linearly in the data (in O(dn log n)), it fits to large
scale problems. The approach in this paper is novel in that EVT has never been
used in its multivariate version in the field of Anomaly Detection.
Illustrative experimental results provide strong empirical evidence of the
relevance of our approach.


title: On Cartwright's theorem

abstract:
  We present a characterization of sets for which Cartwright's theorem holds
true. The connection is discussed between these sets and sampling sets for
entire functions of exponential type.


title:
Singularity Degree of the Positive Semidefinite Matrix Completion
  Problem

abstract:
  The singularity degree of a semidefinite programming problem is the smallest
number of facial reduction steps to make the problem strictly feasible. We
introduce two new graph parameters, called the singularity degree and the
nondegenerate singularity degree, based on the singularity degree of the
positive semidefinite matrix completion problem. We give a characterization of
the class of graphs whose parameter value is equal to one for each parameter.
Specifically, we show that the singularity degree of a graph is equal to one if
and only if the graph is chordal, and the nondegenerate singularity degree of a
graph is equal to one if and only if the graph is the clique sum of chordal
graphs and $K_4$-minor free graphs. We also show that the singularity degree is
bounded by two if the treewidth is bounded by two, and exhibit a family of
graphs with treewidth three, whose singularity degree grows linearly in the
number of vertices.


title: On the number of lattice convex chains

abstract:
  An asymptotic formula is presented for the number of planar lattice convex
polygonal lines joining the origin to a distant point of the diagonal. The
formula involves the non-trivial zeros of the zeta function and leads to a
necessary and sufficient condition for the Riemann Hypothesis to hold.


title:
A Quantitative Central Limit Theorem for the Euler-Poincar\'e
  Characteristic of Random Spherical Eigenfunctions

abstract:
  We establish here a Quantitative Central Limit Theorem (in Wasserstein
distance) for the Euler-Poincar\'{e} Characteristic of excursion sets of random
spherical eigenfunctions in dimension 2. Our proof is based upon a
decomposition of the Euler-Poincar\'{e} Characteristic into different
Wiener-chaos components: we prove that its asymptotic behaviour is dominated by
a single term, corresponding to the chaotic component of order two. As a
consequence, we show how the asymptotic dependence on the threshold level $u$
is fully degenerate, i.e., the Euler-Poincar\'{e} Characteristic converges to a
single random variable times a deterministic function of the threshold. This
deterministic function has a zero at the origin, where the variance is thus
asymptotically of smaller order. Our results can be written as an asymptotic
second-order Gaussian Kinematic Formula for the excursion sets of Gaussian
spherical harmonics.


title:
Poset edge densities, nearly reduced words, and barely set-valued
  tableaux

abstract:
  In certain finite posets, the expected down-degree of their elements is the
same whether computed with respect to either the uniform distribution or the
distribution weighting an element by the number of maximal chains passing
through it. We show that this coincidence of expectations holds for Cartesian
products of chains, connected minuscule posets, weak Bruhat orders on finite
Coxeter groups, certain lower intervals in Young's lattice, and certain lower
intervals in the weak Bruhat order below dominant permutations. Our tools
involve formulas for counting nearly reduced factorizations in 0-Hecke
algebras; that is, factorizations that are one letter longer than the Coxeter
group length.


title:
An unexpected new explanation of seasonality in suicide attempts: Grey's
  Anatomy broadcasting

abstract:
  Seasonality is one of the oldest and most elucidation-resistant issues in
suicide epidemiological research. Despite winter depression (also known as
Seasonal Affective Disorder, SAD) is known and treated since many years,
worldwide cross-sectional data from 28 countries show a lower frequency of
suicide attempts around the equinoxes and a higher frequency in spring (both in
Northern and Southern Hemisphere). This peak is not compatible with the SAD
explanation. However, in recent years epidemiological research has yielded new
results, which provide new perspectives on the matter. In fact, the discovery
of a new pathology called Post-Series Depression (PSD) could provide an
explanation of the suicide attempts pattern. The aim of this study is to
analyse weekly data in order to compare them with the TV series broadcasting.
Since medical observations in our sample are distributed over many years, in
order to compare them as best as we can with the television programming, Grey's
Anatomy series was chosen. This medical drama has been in the top 10 of most
viewed TV series since 12 years and it is broadcast all over the world, so that
it can be considered a universal and homogeneous phenomenon. A full season of
the series is split into two separate units with a hiatus around the end of the
calendar year, and it runs from September through May. Data analysis was made
in order to prove the correlation between PSD and the increase of suicide
attempts. Surprisingly, the data analysis shows that the increase of rate of
suicide attempts does not coincide with the breaks in Grey's Anatomy
scheduling, but with the series broadcasting. This therefore suggests that it
is the series itself to increase the viewer's depression.


title:
An analytical model for the evolution of starless cores I: The
  constant-mass case

abstract:
  We propose an analytical model for the quasistatic evolution of starless
cores confined by a constant external pressure, assuming that cores are
isothermal and obey a spherically-symmetric density distribution. We model core
evolution for Plummer-like and Gaussian density distributions in the adiabatic
and isothermal limits, assuming Larson-like dissipation of turbulence. We model
the variation in the terms in the virial equation as a function of core
characteristic radius, and determine whether cores are evolving toward virial
equilibrium or gravitational collapse. We ignore accretion onto cores in the
current study. We discuss the different behaviours predicted by the isothermal
and adiabatic cases, and by our choice of index for the size-linewidth
relation, and suggest a means of parameterising the magnetic energy term in the
virial equation. We model the evolution of the set of cores observed by Pattle
et al. (2015) in the L1688 region of Ophiuchus in the 'virial plane'. We find
that not all virially-bound and pressure-confined cores will evolve to become
gravitationally bound, with many instead contracting to virial equilibrium with
their surroundings, and find an absence of gravitationally-dominated and
virially-unbound cores. We hypothesise a 'starless core desert' in this
quadrant of the virial plane, which may result from cores initially forming as
pressure-confined objects. We conclude that a virially-bound and
pressure-confined core will not necessarily evolve to become gravitationally
bound, and thus cannot be considered prestellar. A core can only be
definitively considered prestellar (collapsing to form an individual stellar
system) if it is gravitationally unstable.


title: Black supernovae and black holes in non-local gravity

abstract:
  In a previous paper, we studied the interior solution of a collapsing body in
a non-local theory of gravity super-renormalizable at the quantum level. We
found that the classical singularity is replaced by a bounce, after which the
body starts expanding. A black hole, strictly speaking, never forms. The
gravitational collapse does not create an event horizon but only an apparent
one for a finite time. In this paper, we solve the equations of motion assuming
that the exterior solution is static. With such an assumption, we are able to
reconstruct the solution in the whole spacetime, namely in both the exterior
and interior regions. Now the gravitational collapse creates an event horizon
in a finite comoving time, but the central singularity is approached in an
infinite time. We argue that these black holes should be unstable, providing a
link between the scenarios with and without black holes. Indeed, we find a non
catastrophic ghost-instability of the metric in the exterior region.
Interestingly, under certain conditions, the lifetime of our black holes
exactly scales as the Hawking evaporation time.


title: Supernova Feedback in Molecular Clouds: Global Evolution and Dynamics

abstract:
  We use magnetohydrodynamical simulations of converging warm neutral medium
flows to analyse the formation and global evolution of magnetised and turbulent
molecular clouds subject to supernova feedback from massive stars. We show that
supernova feedback alone fails to disrupt entire, gravitationally bound,
molecular clouds, but is able to disperse small--sized (~10 pc) regions on
timescales of less than 1 Myr. Efficient radiative cooling of the supernova
remnant as well as strong compression of the surrounding gas result in
non-persistent energy and momentum input from the supernovae. However, if the
time between subsequent supernovae is short and they are clustered, large hot
bubbles form that disperse larger regions of the parental cloud. On longer
timescales, supernova feedback increases the amount of gas with moderate
temperatures (T~300-3000 K). Despite its inability to disrupt molecular clouds,
supernova feedback leaves a strong imprint on the star formation process. We
find an overall reduction of the star formation efficiency by a factor of 2 and
of the star formation rate by roughly factors of 2-4.


title:
Velocity-resolved hot water emission detected toward HL Tau with the
  Submillimeter Array

abstract:
  Using the Submillimeter Array (SMA) on Mauna Kea, the H2-16O 10_2,9-9_3,6
transition (E_up=1863K) at 321.2 GHz has been detected toward the embedded
low-mass protostar HL Tau. The line centroid is blue-shifted by 15 km/s with
respect to the source velocity, and it has a FWHM of 20 km/s. The emission is
tentatively resolved and extends ~3-4" over the sky (~2 beams), or ~500 AU at
the distance of Taurus. The velocity offset, and to a lesser degree the spatial
extent of the emission, shows that the line originates in the protostellar jet
or wind. This result suggests that at least some water emission observed toward
embedded sources, and perhaps also disk sources, with Herschel and Spitzer
contains a wind or jet component, which is crucial for interpreting these data.
These pathfinder observations done with the SMA opens a new window to studying
the origin of water emission with e.g. ALMA, thus providing new insights into
where water is in protostellar systems.


title: A Note on Non-Degenerate Integer Programs with Small Sub-Determinants

abstract:
  The intention of this note is two-fold. First, we study integer optimization
problems in standard form defined by $A \in\mathbb{Z}^{m\times{}n}$ and present
an algorithm to solve such problems in polynomial-time provided that both the
largest absolute value of an entry in $A$ and $m$ are constant. Then, this is
applied to solve integer programs in inequality form in polynomial-time, where
the absolute values of all maximal sub-determinants of $A$ lie between $1$ and
a constant.


title:
High-dimensional approximate nearest neighbor: k-d Generalized
  Randomized Forests

abstract:
  We propose a new data-structure, the generalized randomized kd forest, or
kgeraf, for approximate nearest neighbor searching in high dimensions. In
particular, we introduce new randomization techniques to specify a set of
independently constructed trees where search is performed simultaneously, hence
increasing accuracy. We omit backtracking, and we optimize distance
computations, thus accelerating queries. We release public domain software
geraf and we compare it to existing implementations of state-of-the-art methods
including BBD-trees, Locality Sensitive Hashing, randomized kd forests, and
product quantization. Experimental results indicate that our method would be
the method of choice in dimensions around 1,000, and probably up to 10,000, and
pointsets of cardinality up to a few hundred thousands or even one million;
this range of inputs is encountered in many critical applications today. For
instance, we handle a real dataset of $10^6$ images represented in 960
dimensions with a query time of less than $1$sec on average and 90\% responses
being true nearest neighbors.


title:
Flow- and Context-Sensitive Points-to Analysis using Generalized
  Points-to Graphs

abstract:
  Computing precise (fully flow-sensitive and context-sensitive) and exhaustive
points-to information is computationally expensive. Many practical tools
approximate the points-to information trading precision for efficiency. This
has adverse impact on computationally intensive analyses such as model
checking. Past explorations in top-down approaches of fully flow- and
context-sensitive points-to analysis (FCPA) have not scaled. We explore the
alternative of bottom-up interprocedural approach which constructs summary flow
functions for procedures to represent the effect of their calls. This approach
has been effectively used for many analyses. However, it is computationally
expensive for FCPA which requires modelling unknown locations accessed
indirectly through pointers. Such accesses are commonly handled by using
placeholders to explicate unknown locations or by using multiple call-specific
summary flow functions.
  We generalize the concept of points-to relations by using the counts of
indirection levels leaving the unknown locations implicit. This allows us to
create summary flow functions in the form of generalized points-to graphs
(GPGs) without the need of placeholders. By design, GPGs represent both memory
(in terms of classical points-to facts) and memory transformers (in terms of
generalized points-to facts). We perform FCPA by progressively reducing
generalized points-to facts to classical points-to facts. GPGs distinguish
between may and must pointer updates thereby facilitating strong updates within
calling contexts.
  The size of GPG is linearly bounded by the number of variables and is
independent of the number of statements in the procedure. Empirical
measurements on SPEC benchmarks show that GPGs are indeed compact in spite of
large procedure sizes. This allows us to scale FCPA to 158 kLoC using GPGs
(compared to 35 kLoC reported by liveness-based FCPA).


title:
SciChallenge: Using Student-Generated Content and Contests to Enhance
  the Interest for Science Education and Careers

abstract:
  Science education will play a vital role in shaping the present and future of
modern societies. Thus, Europe needs all its talents to increase creativity and
competitiveness. Young boys and girls especially have to be engaged to pursue
careers in Science, Technology, Engineering and Mathematics (STEM). However,
statistics still show that enrolment rates in STEM-based degree programs are
decreasing. This will lead to a workforce problem in the industrial sector as
well as in research and development, especially in many of the new member
countries. This paper highlights a recently funded EU-research project
SciChallenge (www.scichallenge.eu), which focuses on the development of novel
concepts to get young people excited about science education. It uses a
contest-based approach towards self-produced digital education materials from
young people for young people. In cooperation with partner schools, teachers,
and other youth-oriented institutions, the contest participants (individuals or
groups) between the ages of 10 and 20 years generate creative digital materials
(videos, slides, or infographics). The participants upload their content in
social media channels and the submissions are aggregated on the SciChallenge
Web Platform. The winners receive prizes funded by science-oriented industry
and other stakeholders. Intelligent cross-sectoral positioning of various
awareness modules on the SciChallenge Open Information Hub is expected to
increase awareness on science careers. Through a strong involvement of related
organizations and industries, we expect to open new opportunities for young
people in regards to internships or taster days in STEM disciplines.
Additionally, aggregated information on science events (such as, slams, nights,
festivals) is shared. With this multi-level approach, SciChallenge may boost
the attractiveness of science education and careers among young people.


title: Total Variation Applications in Computer Vision

abstract:
  The objectives of this chapter are: (i) to introduce a concise overview of
regularization; (ii) to define and to explain the role of a particular type of
regularization called total variation norm (TV-norm) in computer vision tasks;
(iii) to set up a brief discussion on the mathematical background of TV
methods; and (iv) to establish a relationship between models and a few existing
methods to solve problems cast as TV-norm. For the most part, image-processing
algorithms blur the edges of the estimated images, however TV regularization
preserves the edges with no prior information on the observed and the original
images. The regularization scalar parameter {\lambda} controls the amount of
regularization allowed and it is an essential to obtain a high-quality
regularized output. A wide-ranging review of several ways to put into practice
TV regularization as well as its advantages and limitations are discussed.


title:
Recovery of time-dependent damping coefficients and potentials appearing
  in wave equations from partial data

abstract:
  We consider the inverse problem of determining a time-dependent damping
coefficient $a$ and a time-dependent potential $q$, appearing in the wave
equation $\partial_t^2u-\Delta_x u+a(t,x)\partial_tu+q(t,x)u=0$ in
$Q=(0,T)\times\Omega$, with $T>0$ and $\Omega$ a $ \mathcal C^2$ bounded domain
of $\mathbb R^n$, $n\geq2$, from partial observations of the solutions on
$\partial Q$. More precisely, we look for observations on $\partial Q$ that
allow to determine uniquely a large class of time-dependent damping
coefficients $a$ and time-dependent potentials $q$ without involving an
important set of data. We prove global unique determination of $a\in
W^{1,p}(Q)$, with $p>n+1$, and $q\in L^\infty(Q)$ from partial observations on
$\partial Q$.


title:
Joint Millimeter-Wave Fronthaul and OFDMA Resource Allocation in
  Ultra-Dense CRAN

abstract:
  Ultra-dense (UD) wireless networks and cloud radio access networks (CRAN) are
two promising network architectures for the emerging fifth-generation (5G)
wireless communication systems. By jointly employing them, a new appealing
network solution is proposed in this paper, termed UD-CRAN. In a UD-CRAN,
millimeter-wave (mmWave) wireless fronthaul is preferred for information
exchange between the central processor and the distributed remote radio heads
(RRHs), due to its lower cost and higher flexibility in deployment, compared to
fixed optical links. This motivates our study in this paper on the downlink
transmission in a mmWave fronthaul enabled, orthogonal frequency division
multiple access (OFDMA) based UD-CRAN. In particular, the fronthaul is shared
among the RRHs via time division multiple access (TDMA), while the RRHs jointly
transmit to the users on orthogonal frequency subchannels using OFDMA. The
joint resource allocation over the TDMA-based mmWave fronthaul and OFDMA-based
wireless transmission is investigated to maximize the weighted sum rate of all
users. Although the problem is non-convex, we propose a Lagrange duality based
solution, which can be efficiently computed with good accuracy. To further
reduce the complexity, we also propose a greedy search based heuristic, which
achieves close to optimal performance under practical setups. Finally, we show
the significant throughput gains of the proposed joint resource allocation
approach compared to other benchmark schemes by simulations.


title:
Statistical investigation and thermal properties for a 1-D impact system
  with dissipation

abstract:
  The behavior of the average velocity, its deviation and average squared
velocity are characterized using three techniques for a 1-D dissipative impact
system. The system -- a particle, or an ensemble of non interacting particles,
moving in a constant gravitation field and colliding with a varying platform --
is described by a nonlinear mapping. The average squared velocity allows to
describe the temperature for an ensemble of particles as a function of the
parameters using: (i) straightforward numerical simulations; (ii) analytically
from the dynamical equations; (iii) using the probability distribution
function. Comparing analytical and numerical results for the three techniques,
one can check the robustness of the developed formalism, where we are able to
estimate numerical values for the statistical variables, without doing
extensive numerical simulations. Also, extension to other dynamical systems is
immediate, including time dependent billiards.


title: Volume bounds of conic 2-spheres

abstract:
  We obtain sharp volume bound for a conic 2-sphere in terms of its Gaussian
curvature bound. We also give the geometric models realizing the extremal
volume. In particular, when the curvature is bounded in absolute value by $1$,
we compute the minimal volume of a conic sphere in the sense of Gromov. In
order to apply the level set analysis and iso-perimetric inequality as in our
previous works, we develop some new analytical tools to treat regions with
vanishing curvature.


title:
Dynamical spin properties of confined Fermi and Bose systems in presence
  of spin-orbit coupling

abstract:
  Due to the recent experimental progress, tunable spin-orbit (SO) interactions
represent ideal candidates for the control of polarization and dynamical spin
properties in both quantum wells and cold atomic systems. A detailed
understanding of spin properties in SO coupled systems is thus a compelling
prerequisite for possible novel applications or improvements in the context of
spintronics and quantum computers. Here we analyze the case of equal Rashba and
Dresselhaus couplings in both homogeneous and laterally confined
two-dimensional systems. Starting from the single-particle picture and
subsequently introducing two-body interactions we observe that periodic spin
fluctuations can be induced and maintained in the system. Through an analytical
derivation we show that the two-body interaction does not involve decoherence
effects in the bosonic dimer, and, in the repulsive homogeneous Fermi gas it
may be even exploited in combination with the SO coupling to induce and tune
standing currents. By further studying the effects of a harmonic lateral
confinement --a particularly interesting case for Bose condensates-- we
evidence the possible appearance of non-trivial {\it spin textures}, whereas
the further application of a small Zeeman-type interaction can be exploited to
fine-tune the system polarizability.


title:
Disentangling the origins of torque enhancement through wall roughness
  in Taylor-Couette turbulence

abstract:
  Direct numerical simulations (DNSs) are performed to analyze the global
transport properties of turbulent Taylor-Couette flow with inner rough wall up
to Taylor number $Ta=10^{10}$. The dimensionless torque $Nu_\omega$ shows an
effective scaling of $Nu_\omega \propto Ta^{0.42\pm0.01}$, which is steeper
than the ultimate regime effective scaling $Nu_\omega \propto Ta^{0.38}$ seen
for smooth inner and outer walls. It is found that at the inner rough wall, the
dominant contribution to the torque comes from the pressure forces on the
radial faces of the rough elements; while viscous shear stresses on the rough
surfaces contribute little to $Nu_\omega$. Thus, the log layer close to the
rough wall depends on the roughness length scale, rather than on the viscous
length scale. We then separate the torque contributed from the smooth inner
wall and the rough outer wall. It is found that the smooth wall torque scaling
follows $Nu_s \propto Ta_s^{0.38\pm0.01}$, in excellent agreement with the case
where both walls are smooth. In contrast, the rough wall torque scaling follows
$Nu_r \propto Ta_r^{0.47\pm0.03}$, very close to the pure ultimate regime
scaling $Nu_\omega \propto Ta^{1/2}$. The energy dissipation rate at the wall
of inner rough cylinder decreases significantly as a consequence of the wall
shear stress reduction caused by the flow separation at the rough elements. On
the other hand, the latter shed vortices in the bulk that are transported
towards the outer cylinder and dissipated. Compared to the purely smooth case,
the inner wall roughness renders the system more bulk dominated and thus
increases the effective scaling exponent.


title:
Energetic, electronic and magnetic properties of Mn-dimers on
  reconstructed (001) GaAs surfaces

abstract:
  We study energetic, magnetic, and electronic properties of diluted
substitutional Mn-pairs on the reconstructed $(001)$ GaAs surfaces. The studies
are based on first-principles calculations in the framework of the density
functional theory. We demonstrate that the stability of the systems strongly
depends on the position, orientation, and the distance between the Mn-atoms
constituting the pair. Independently of the considered surface reconstruction
pattern, the Mn-pairs with Mn-atoms being the nearest neighbors (NN) on
cationic sublattice turn out to be energetically more favorable than the pairs
with the larger distance between the Mn-atoms. However, the preferential
build-up orientation of the Mn-NN-pair depends on the surface reconstruction
and is parallel either to $[110]$ or $[1\bar{1}0]$ crystallographic direction.
We reveal also the mechanisms of the magnetic ordering of Mn-NN-pairs. The
Mn-NN-pairs along the $[110]$ crystallographic direction exhibit always
ferromagnetic alignment of Mn spins, whereas the spins in the Mn-NN-pairs along
$[1\bar{1}0]$ direction are mostly anti-ferromagnetically aligned. In the
electronic structure of the systems containing Mn-pairs with ferromagnetically
aligned spins, we observe the valence band hole states in the neighborhood of
Fermi energy. This indicates that the surface ferromagnetism in this prototype
of dilute magnetic semiconductors can be explained in terms of the $p$-$d$
Zener model.


title: Cavity quantum interferences with three-level atoms

abstract:
  We discuss quantum interference phenomena in a system consisting from a laser
driven three-level ladder-type emitter possessing orthogonal transition dipoles
and embedded in a leaking optical resonator. The cavity mean-photon number
vanishes due to the destructive nature of the interference phenomena. The
effect occurs for some particular parameter regimes which were identified.
Furthermore, upper bare-state population inversion occurs as well.


title:
Robust multicolor single photon emission from point defects in hexagonal
  boron nitride

abstract:
  Hexagonal boron nitride (hBN) is an emerging two dimensional material for
quantum photonics owing to its large bandgap and hyperbolic properties. Here we
report a broad range of multicolor room temperature single photon emissions
across the visible and the near infrared spectral ranges from point defects in
hBN multilayers. We show that the emitters can be categorized into two general
groups, but most likely possess similar crystallographic structure. We further
show two approaches for engineering of the emitters using either electron beam
irradiation or annealing, and characterize their photophysical properties. The
emitters exhibit narrow line widths of sub 10 nm at room temperature, and a
short excited state lifetime with high brightness. Remarkably, the emitters are
extremely robust and withstand aggressive annealing treatments in oxidizing and
reducing environments. Our results constitute the first step towards
deterministic engineering of single emitters in 2D materials and hold great
promise for the use of defects in boron nitride as sources for quantum
information processing and nanophotonics.


title: Strong Morita equivalence of operator spaces

abstract:
  We introduce and examine the notions of strong $\Delta$-equivalence and
strong TRO equivalence for operator spaces. We show that they behave in an
analogous way to how strong Morita equivalence does for the category of
C*-algebras. In particular, we prove that strong $\Delta$-equivalence coincides
with stable isomorphism under the expected countability hypothesis, and that
strongly TRO equivalent operator spaces admit a correspondence between
particular representations. Furthermore we show that strongly
$\Delta$-equivalent operator spaces have stably isomorphic second duals and
strongly $\Delta$-equivalent TRO envelopes. In the case of unital operator
spaces, strong $\Delta$-equivalence implies stable isomorphism of the
C*-envelopes.


title:
A machine-learning approach to measuring the escape of ionizing
  radiation from galaxies in the reionization epoch

abstract:
  Recent observations of galaxies at $z \gtrsim 7$, along with the low value of
the electron scattering optical depth measured by the Planck mission, make
galaxies plausible as dominant sources of ionizing photons during the epoch of
reionization. However, scenarios of galaxy-driven reionization hinge on the
assumption that the average escape fraction of ionizing photons is
significantly higher for galaxies in the reionization epoch than in the local
Universe. The NIRSpec instrument on the James Webb Space Telescope (JWST) will
enable spectroscopic observations of large samples of reionization-epoch
galaxies. While the leakage of ionizing photons will not be directly measurable
from these spectra, the leakage is predicted to have an indirect effect on the
spectral slope and the strength of nebular emission lines in the rest-frame
ultraviolet and optical. Here, we apply a machine learning technique known as
lasso regression on mock JWST/NIRSpec observations of simulated $z=7$ galaxies
in order to obtain a model that can predict the escape fraction from
JWST/NIRSpec data. Barring systematic biases in the simulated spectra, our
method is able to retrieve the escape fraction with a mean absolute error of
$\Delta f_{\mathrm{esc}} \approx 0.12$ for spectra with $S/N\approx 5$ at a
rest-frame wavelength of 1500 {\AA} for our fiducial simulation. This
prediction accuracy represents a significant improvement over previous similar
approaches.