title:
Stellar laboratories. VIII. New Zr IV - VII, Xe IV - V, and Xe VII
  oscillator strengths and the Al, Zr, and Xe abundances in the hot white
  dwarfs G191-B2B and RE0503-289

abstract:
  For the spectral analysis of high-resolution and high-signal-to-noise spectra
of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model
atmospheres are mandatory. These are strongly dependent on the reliability of
the atomic data that is used for their calculation.
  To search for Zr and Xe lines in the ultraviolet (UV) spectra of G191-B2B and
RE0503-289, new Zr IV-VII, Xe IV-V, and Xe VIII oscillator strengths were
calculated. This allows for the first time, determination of the Zr abundance
in white dwarf (WD) stars and improvement of the Xe abundance determinations.
  We calculated Zr IV-VII, Xe IV-V, and Xe VIII oscillator strengths to
consider radiative and collisional bound-bound transitions of Zr and Xe in our
NLTE stellar-atmosphere models for the analysis of their lines exhibited in UV
observations of the hot WDs G191-B2B and RE0503-289.
  We identified one new Zr IV, 14 new Zr V, and ten new Zr VI lines in the
spectrum of RE0503-289. Zr was detected for the first time in a WD. We measured
a Zr abundance of -3.5 +/- 0.2 (logarithmic mass fraction, approx. 11 500 times
solar). We dentified five new Xe VI lines and determined a Xe abundance of -3.9
+/- 0.2 (approx. 7500 times solar). We determined a preliminary photospheric Al
abundance of -4.3 +/- 0.2 (solar) in RE0503-289. In the spectra of G191-B2B, no
Zr line was identified. The strongest Zr IV line (1598.948 A) in our model gave
an upper limit of -5.6 +/- 0.3 which is about 100 times solar. No Xe line was
identified in the UV spectrum of G191-B2B and we confirmed the previously
determined upper limit of -6.8 +/- 0.3 (ten times solar).
  Precise measurements and calculations of atomic data are a prerequisite for
advanced NLTE stellar-atmosphere modeling. Observed Zr IV - VI and Xe VI - VII
line profiles in the UV spectrum of RE0503-289 were simultaneously well
reproduced.


title: Leading Neutrons From Polarized Proton-Nucleus Collisions

abstract:
  Leading neutron production on protons is known to be subject to strong
absorptive corrections, which have been under debate for a long time. On
nuclear targets these corrections are significantly enhanced and push the
partial cross sections of neutron production to the very periphery of the
nucleus. As a result, the A-dependences of inclusive and diffractive neutron
production turn out to be similar. The mechanism of \pi-a_1 interference, which
successfully explained the observed single-spin asymmetry of neutrons in
polarized pp interactions, is extended here to polarized pA collisions.
Corrected for nuclear effects it explains well the magnitude and sign of the
asymmetry A_N observed in inelastic events, resulting in a violent break up of
the nucleus. However the excessive magnitude of A_N observed in the diffractive
sample, remains a challenge.


title: Handover Management in 5G and Beyond: A Topology Aware Skipping Approach

abstract:
  Network densification is found to be a potential solution to meet 5G capacity
standards. Network densification offers more capacity by shrinking base
stations' (BSs) footprints, thus reduces the number of users served by each BS.
However, the gains in the capacity are achieved at the expense of increased
handover (HO) rates. Hence, HO rate is a key performance limiting factor that
should be carefully considered in densification planning. This paper sheds
light on the HO problem that appears in dense 5G networks and proposes an
effective solution via topology aware HO skipping. Different skipping
techniques are considered and compared with the conventional best connected
scheme. To this end, the effectiveness of the proposed schemes is validated by
studying the average user rate in the downlink single-tier and two-tier
cellular networks, which are modeled using Poisson point process and Poisson
cluster process, respectively. The proposed skipping schemes show up to 47%
gains in the average throughput that would maximize the benefit of network
densification.


title:
Gravitational waves and mass ejecta from binary neutron star mergers:
  Effect of the stars' rotation

abstract:
  We present new (3+1) dimensional numerical relativity simulations of the
binary neutron star (BNS) mergers that take into account the NS spins. We
consider different spin configurations, aligned or antialigned to the orbital
angular momentum, for equal and unequal mass BNS and for two equations of
state. All the simulations employ quasiequilibrium circular initial data in the
constant rotational velocity approach, i.e. they are consistent with Einstein
equations and in hydrodynamical equilibrium. We study the NS rotation effect on
the energetics, the gravitational waves (GWs) and on the possible
electromagnetic (EM) emission associated to dynamical mass ejecta. For
dimensionless spin magnitudes of $\chi\sim0.1$ we find that spin-orbit
interactions and also spin-induced-quadrupole deformations affect the
late-inspiral-merger dynamics. The latter is, however, dominated by finite-size
effects. Spin (tidal) effects contribute to GW phase differences up to 5 (20)
radians accumulated during the last eight orbits to merger. Similarly, after
merger the collapse time of the remnant and the GW spectrogram are affected by
the NSs rotation. Spin effects in dynamical ejecta are clearly observed in
unequal mass systems in which mass ejection originates from the tidal tail of
the companion. Consequently kilonovae and other EM counterparts are affected by
spins. We find that spin aligned to the orbital angular momentum leads to
brighter EM counterparts than antialigned spin with luminosities up to a factor
of two higher.


title:
Discretization of Maxwell's Equations for Non-inertial Observers Using
  Space-Time Algebra

abstract:
  We employ Maxwell's equations formulated in Space-Time Algebra to perform
discretization of moving geometries directly in space-time. All the derivations
are carried out without any non-relativistic assumptions, thus the application
area of the scheme is not restricted to low velocities. The 4D mesh
construction is based on a 3D mesh stemming from a conventional 3D mesh
generator. The movement of the system is encoded in the 4D mesh geometry,
enabling an easy extension of well-known 3D approaches to the space-time
setting. As a research example, we study a manifestation of Sagnac's effect in
a rotating ring resonator. In case of constant rotation, the space-time
approach enhances the efficiency of the scheme, as the material matrices are
constant for every time step, without abandoning the relativistic framework.


title: Geometry of 3D Environments and Sum of Squares Polynomials

abstract:
  Motivated by applications in robotics and computer vision, we study problems
related to spatial reasoning of a 3D environment using sublevel sets of
polynomials. These include: tightly containing a cloud of points (e.g.,
representing an obstacle) with convex or nearly-convex basic semialgebraic
sets, computation of Euclidean distances between two such sets, separation of
two convex basic semalgebraic sets that overlap, and tight containment of the
union of several basic semialgebraic sets with a single convex one. We use
algebraic techniques from sum of squares optimization that reduce all these
tasks to semidefinite programs of small size and present numerical experiments
in realistic scenarios.


title:
Finite-volume effects on phase transition in the Polyakov-loop extended
  Nambu-Jona-Lasinio model with a chiral chemical potential

abstract:
  To investigate finite-volume effects on the chiral symmetry restoration and
the deconfinement transition and some impacts of possible global topological
background for a quantum chromodynamics (QCD) system with $N_f=2$ (two quark
flavors), we apply the Polyakov-loop extended Nambu-Jona-Lasinio model by
introducing a chiral chemical potential $\mu_5$ artificially. The final
numerical results indicate that the introduced chiral chemical potential does
not change the critical exponents but shifts the location of critical end point
(CEP) significantly; the ratios for the chiral chemical potentials and
temperatures at CEP, $\mu_c/\mu_{5c}$ and $T_c/T_{5c}$, are significantly
affected by the system size $R$. The behavior is that $T_c$ increases slowly
with $\mu_5$ when $R$ is large and $T_c$ decreases first and then increases
with $\mu_5$ when $R$ is small. It is also found that for a fixed $\mu_5$,
there is a $R_{\text{min}}$, where the critical end point vanishes, and the
whole phase diagram becomes a crossover when $R<R_{\text{min}}$. Therefore, we
suggest that for the heavy-ion collision experiments, which is to study the
possible location of CEP, the finite-volume behavior should be taken into
account.


title: Lazy Local Search Meets Machine Scheduling

abstract:
  We study the restricted case of Scheduling on Unrelated Parallel Machines. In
this problem, we are given a set of jobs $J$ with processing times $p_j$ and
each job may be scheduled only on some subset of machines $S_j \subseteq M$.
The goal is to find an assignment of jobs to machines to minimize the time by
which all jobs can be processed. In a seminal paper, Lenstra, Shmoys, and
Tardos designed an elegant $2$-approximation for the problem in 1987. The
question of whether approximation algorithms with better guarantees exist for
this classic scheduling problem has since remained a source of mystery.
  In recent years, with the improvement of our understanding of Configuration
LPs, it now appears an attainable goal to design such an algorithm. Our main
contribution is to make progress towards this goal. When the processing times
of jobs are either $1$ or $\epsilon \in (0,1)$, we design an approximation
algorithm whose guarantee tends to $1 + \sqrt{3}/2 \approx 1.8660254,$ for the
interesting cases when $\epsilon \to 0$. This improves on the $2-\epsilon_0$
guarantee recently obtained by Chakrabarty, Khanna, and Li for some constant
$\epsilon_0 > 0$.


title: Mending Fences with Self-Invalidation and Self-Downgrade

abstract:
  Cache coherence protocols based on self-invalidation and self-downgrade have
recently seen increased popularity due to their simplicity, potential
performance efficiency, and low energy consumption. However, such protocols
result in memory instruction reordering, thus causing extra program behaviors
that are often not intended by the programmers. We propose a novel formal model
that captures the semantics of programs running under such protocols, and
features a set of fences that interact with the coherence layer. Using the
model, we design an algorithm to analyze the reachability and check whether a
program satisfies a given safety property with the current set of fences. We
describe a method for insertion of optimal sets of fences that ensure
correctness of the program under such protocols. The method relies on a
counter-example guided fence insertion procedure. One feature of our method is
that it can handle a variety of fences (with different costs). This diversity
makes optimization more difficult since one has to optimize the total cost of
the inserted fences, rather than just their number. To demonstrate the strength
of our approach, we have implemented a prototype and run it on a wide range of
examples and benchmarks. We have also, using simulation, evaluated the
performance of the resulting fenced programs.


title: Modular irreducibility of cuspidal unipotent characters

abstract:
  We prove a long-standing conjecture of Geck which predicts that cuspidal
unipotent characters remain irreducible after $\ell$-reduction. To this end, we
construct a progenerator for the category of representations of a finite
reductive group coming from generalised Gelfand--Graev representations. This is
achieved by showing that cuspidal representations appear in the head of
generalised Gelfand--Graev representations attached to cuspidal unipotent
classes, as defined and studied in \cite{GM96}.


title: Observed Quantization of Anyonic Heat Flow

abstract:
  The quantum of heat conductance of ballistic one-dimensional (1D) channels,
being gQ=k0T with k0=pi^2*2kB^2/3h (T - temperature, kB - Boltzmann's constant,
h - Planck's constant), is an important fundamental constant. While the
quantization of the electrical conductance of 1D ballistic conductors has long
been experimentally established, a demonstration of the quantization of thermal
conductance proved to be much harder. It has already been accomplished for
weakly interacting systems of phonons, photons, and electronic Fermi-liquids.
Theoretically, however, the quantization must also hold in strongly interacting
systems, such as the Fractional Quantum Hall effect (FQHE), where electrons
fractionalize into anyons and chargeless quasiparticles such as neutral
Majorana fermions. Since the bulk in the FQHE is incompressible, it is not
expected to contribute significantly to the heat conductance, which is
determined by chiral 1D edge modes. The thermal conductance reflects
topological properties of the FQH electronic systems to which the electrical
conductance gives no access. Here, we present results of extensive measurements
of the heat conductance in 'particle-like' (Laughlin's) and 'hole-like'
fractional states. We verify the universal value of the quantum of thermal
conductance of the charged fractional modes as well as for chargeless neutral
modes. We also prove the validity of the theoretical predictions for the more
complex (and less studied) 'hole-like' states. Heat transport measurements open
a door to ample information, not easily accessible by conductance measurements.


title:
Searches for Lepton Number Violation and resonances in the
  $K^{\pm}\rightarrow \pi \mu \mu$ decays at the NA48/2 experiment

abstract:
  The NA48/2 experiment at CERN collected a large sample of charged kaon decays
into final states with multiple charged particles in 2003--2004. A new upper
limit on the rate of the lepton number violating decay
$K^{\pm}\to\pi^{\mp}\mu^{\pm}\mu^{\pm}$ obtained from this sample is reported:
$\mathcal{B}(K^{\pm}\to\pi^{\mp}\mu^{\pm}\mu^{\pm})<8.6 \times 10^{-11}$ at
90\% CL. Searches for two-body resonances in the $K^{\pm}\to\pi\mu\mu$ decays
(including heavy neutral leptons~$N_4$ and inflatons~$\chi$) in the accessible
range of masses and lifetimes are also presented. In the absence of a signal,
upper limits are set on the products of branching
ratios~$\mathcal{B}(K^{\pm}\to\mu^{\pm}N_4)\mathcal{B}(N_4\to\pi\mu)$ and
$\mathcal{B}(K^{\pm}\to\pi^{\pm}\chi)\mathcal{B}(\chi\to\mu^+\mu^-)$ as
functions of the resonance mass and lifetime. These limits are in the
$10^{-10}-10^{-9}$ range for resonance lifetimes below 100~ps.


title:
Spiral-driven accretion in protoplanetary discs - III tri-dimensional
  simulations

abstract:
  Understanding how accretion proceeds in proto-planetary discs and more
generally their dynamics is a crucial issue for explaining the conditions in
which planets form. The role that accretion of gas from the surrounding
molecular cloud onto the disc may have on its structure needs to be quantified.
We perform tri-dimensional simulations using the Cartesian AMR code RAMSES of
an accretion disc subject to infalling material. For the aspect ratio of $H/R
\simeq 0.15$ and disk mass $M_d \simeq 10^{-2}$ M$_\odot$ used in our study, we
find that for typical accretion rates on the order of a few 10$^{-7}$ M$_\odot$
yr$^{-1}$, values of the $\alpha$ parameter as high as a few 10$^{-3}$ are
inferred. The mass that is accreted in the inner part of the disc is typically
at least $50\%$ of the total mass that has been accreted onto the disc. Our
results suggest that external accretion of gas at moderate values, onto
circumstellar discs may trigger prominent spiral arms, reminiscent of recent
observations made with various instruments, and lead to significant transport
through the disc. If confirmed from observational studies, such accretion may
therefore influence disc evolution.


title: Chiral Symmetry restoration from the hadronic regime

abstract:
  We discuss recent advances on QCD chiral symmetry restoration at finite
temperature, within the theoretical framework of Effective Theories. $U(3)$
Ward Identities are derived between pseudoscalar susceptibilities and quark
condensates, allowing to explain the behaviour of lattice meson screening
masses. Unitarized interactions and the generated $f_0(500)$ thermal state are
showed to play an essential role in the description of the transition through
the scalar susceptibility


title:
Model selection for the robust efficient signal processing observed with
  small L\'evy noise

abstract:
  We develop a new model selection method for the adaptive robust efficient
nonparametric signal estimation observed with impulse noise which is defined by
the general non Gaussian L\'evy processes. On the basis of the developed
method, we construct the estimation procedures which are analyzed in two
settings: in non asymptotic and asymptotic ones. For the first time for such
models we show non asymptotic sharp oracle inequalities for the quadratic and
for the robust risks, i.e. we show that the constructed procedures are optimal
in the sharp oracle inequalities sense. Next, by making use of the obtained
oracle inequalities, we provide the asymptotic efficiency property for the
developed estimation methods in the adaptive setting when the signal/noise
ratio goes to infinity. We apply the developed model selection methods for the
signals number detection problem in multi-path information transmission.


title: Randomized Mechanisms for Selling Reserved Instances in Cloud

abstract:
  Selling reserved instances (or virtual machines) is a basic service in cloud
computing. In this paper, we consider a more flexible pricing model for
instance reservation, in which a customer can propose the time length and
number of resources of her request, while in today's industry, customers can
only choose from several predefined reservation packages. Under this model, we
design randomized mechanisms for customers coming online to optimize social
welfare and providers' revenue.
  We first consider a simple case, where the requests from the customers do not
vary too much in terms of both length and value density. We design a randomized
mechanism that achieves a competitive ratio $\frac{1}{42}$ for both
\emph{social welfare} and \emph{revenue}, which is a improvement as there is
usually no revenue guarantee in previous works such as
\cite{azar2015ec,wang2015selling}. This ratio can be improved up to
$\frac{1}{11}$ when we impose a realistic constraint on the maximum number of
resources used by each request. On the hardness side, we show an upper bound
$\frac{1}{3}$ on competitive ratio for any randomized mechanism. We then extend
our mechanism to the general case and achieve a competitive ratio
$\frac{1}{42\log k\log T}$ for both social welfare and revenue, where $T$ is
the ratio of the maximum request length to the minimum request length and $k$
is the ratio of the maximum request value density to the minimum request value
density. This result outperforms the previous upper bound $\frac{1}{CkT}$ for
deterministic mechanisms \cite{wang2015selling}. We also prove an upper bound
$\frac{2}{\log 8kT}$ for any randomized mechanism. All the mechanisms we
provide are in a greedy style. They are truthful and easy to be integrated into
practical cloud systems.


title: Quasiminimal abstract elementary classes

abstract:
  We propose the notion of a quasiminimal abstract elementary class (AEC). This
is an AEC satisfying four semantic conditions: countable
L\"owenheim-Skolem-Tarski number, existence of a prime model, closure under
intersections, and uniqueness of the generic orbital type over every countable
model. We exhibit a correspondence between Zilber's quasiminimal pregeometry
classes and quasiminimal AECs: any quasiminimal pregeometry class induces a
quasiminimal AEC (this was known), and for any quasiminimal AEC there is a
natural functorial expansion that induces a quasiminimal pregeometry class. We
show in particular that the exchange axiom is redundant in Zilber's definition
of a quasiminimal pregeometry class.


title: Essential Signatures and Monomial Bases for $B_n$ and $D_n$

abstract:
  In the representation theory of simple Lie algebras, we consider the problem
of constructing a monomial basis in an arbitrary irreducible finite-dimensional
highest weight module. We construct a PBW-type basis in every
finite-dimensional representation of $B_n$ and $D_n$ and we describe the
associated semigroup of essential signatures. These bases are parameterized by
integer points in some polytopes. We give the inequalities defining these
polytopes.


title: Graph bisection revisited

abstract:
  The graph bisection problem is the problem of partitioning the vertex set of
a graph into two sets of given sizes such that the sum of weights of edges
joining these two sets is optimized. We present a semidefinite programming
relaxation for the graph bisection problem with a matrix variable of order $n$
- the number of vertices of the graph - that is equivalent to the currently
strongest semidefinite programming relaxation obtained by using vector lifting.
The reduction in the size of the matrix variable enables us to impose
additional valid inequalities to the relaxation in order to further strengthen
it. The numerical results confirm that our simplified and strengthened
semidefinite relaxation provides the currently strongest bound for the graph
bisection problem in reasonable time.


title:
A Non-Intrusive and Context-Based Vulnerability Scoring Framework for
  Cloud Services

abstract:
  Understanding the severity of vulnerabilities within cloud services is
particularly important for today service administrators.Although many systems,
e.g., CVSS, have been built to evaluate and score the severity of
vulnerabilities for administrators, the scoring schemes employed by these
systems fail to take into account the contextual information of specific
services having these vulnerabilities, such as what roles they play in a
particular service. Such a deficiency makes resulting scores unhelpful. This
paper presents a practical framework, NCVS, that offers automatic and
contextual scoring mechanism to evaluate the severity of vulnerabilities for a
particular service. Specifically, for a given service S, NCVS first
automatically collects S contextual information including topology,
configurations, vulnerabilities and their dependencies. Then, NCVS uses the
collected information to build a contextual dependency graph, named CDG, to
model S context. Finally, NCVS scores and ranks all the vulnerabilities in S by
analyzing S context, such as what roles the vulnerabilities play in S, and how
critical they affect the functionality of S. NCVS is novel and useful, because
1) context-based vulnerability scoring results are highly relevant and
meaningful for administrators to understand each vulnerability importance
specific to the target service; and 2) the workflow of NCVS does not need
instrumentation or modifications to any source code. Our experimental results
demonstrate that NCVS can obtain more relevant vulnerability scoring results
than comparable system, such as CVSS.


title: Fibonacci numbers and the golden ratio

abstract:
  In this expository paper written to commemorate Fibonacci Day 2016, we
discuss famous relations involving the Fibonacci sequence, the golden ratio,
continued fractions and nested radicals, and show how these fit into a more
general framework stemming from the quadratic formula.


title:
Smart Library: Identifying Books in a Library using Richly Supervised
  Deep Scene Text Reading

abstract:
  Physical library collections are valuable and long standing resources for
knowledge and learning. However, managing books in a large bookshelf and
finding books on it often leads to tedious manual work, especially for large
book collections where books might be missing or misplaced. Recently, deep
neural models, such as Convolutional Neural Networks (CNN) and Recurrent Neural
Networks (RNN) have achieved great success for scene text detection and
recognition. Motivated by these recent successes, we aim to investigate their
viability in facilitating book management, a task that introduces further
challenges including large amounts of cluttered scene text, distortion, and
varied lighting conditions. In this paper, we present a library inventory
building and retrieval system based on scene text reading methods. We
specifically design our scene text recognition model using rich supervision to
accelerate training and achieve state-of-the-art performance on several
benchmark datasets. Our proposed system has the potential to greatly reduce the
amount of human labor required in managing book inventories as well as the
space needed to store book information.


title:
Generalized Radon--Nikodym Spectral Approach. Application to Relaxation
  Dynamics Study

abstract:
  Radon--Nikodym approach to relaxation dynamics, where probability density is
built first and then used to calculate observable dynamic characteristic is
developed and applied to relaxation type signals study. In contrast with $L^2$
norm approaches, such as Fourier or least squares, this new approach does not
use a norm, the problem is reduced to finding the spectrum of an operator
(virtual Hamiltonian), which is built in a way that eigenvalues represent the
dynamic characteristic of interest and eigenvectors represent probability
density. The problems of interpolation (numerical estimation of Radon--Nikodym
derivatives is developed) and obtaining the distribution of relaxation rates
from sampled timeserie are considered. Application of the theory is
demonstrated on a number of model and experimentally measured timeserie signals
of degradation and relaxation processes. Software product, implementing the
theory is developed.


title:
Tension in the inclusive versus exclusive determinations of $|V_{cb}|$:
  a possible role of new physics

abstract:
  We reconsider the possibility that the tension in the $|V_{cb}|$
determinations from inclusive and exclusive $B$ decay modes is due to a new
physics effect. We modify the Standard Model effective Hamiltonian for
semileptonic $b \to c$ transitions including a tensor operator with a lepton
flavour dependent coupling $\epsilon_T^\ell$, and investigate separately the
muon and electron modes. The interference term between SM and NP, proportional
to the lepton mass, has different impact in the inclusive and exclusive $B$
modes to muon. Moreover, even when the lepton mass is small as for the
electron, the NP effect is different in inclusive and exclusive $B$ channels.
For both $\mu$ and $e$ we find a region of $\epsilon_T^{\mu,\,e}$ where the
constraints from $B^- \to D^{(*)0} \ell^- {\bar \nu}_\ell$ and $B \to X_c \,
\ell \, \bar \nu_\ell$ are satisfied for the same $|V_{cb}|$.


title: Singularly perturbed linear programs and Markov decision processes

abstract:
  Linear programming formulations for the discounted and long-run average MDPs
have evolved along separate trajectories. In 2006, E. Altman conjectured that
the two linear programming formulations of discounted and long-run average MDPs
are, most likely, a manifestation of general properties of singularly perturbed
linear programs. In this note we demonstrate that this is, indeed, the case.


title:
Deuterium fractionation of a distant cold dark cloud along the line of
  sight of W51

abstract:
  Herschel/HIFI observations toward the compact HII region W51 has revealed the
presence of a cold dense core along its line of sight in a high-velocity stream
located just in front of W51. This detection has been made possible through
absorption measurements of low-energy transitions of HDO, NH3, and C3 against
the bright background emitted by the star-forming region. We present a
follow-up study of this core using the high sensitivity and high spectral
resolution provided by the IRAM 30-meter telescope. We report new detections of
this core in absorption for DCO+ (2-1, 3-2), H13CO+ (1-0), DNC (3-2), HN13C
(1-0), p-H2CO (202-101, 303-202), and in emission for o-NH2D. We also report
interferometric observation of this last species using the IRAM/NOEMA
telescope, revealing the fragmented nature of the source through the detection
of two cores, separated by 0.19 - 0.24 pc, with average sizes of less than 0.16
- 0.19 pc. From a non-LTE analysis, we are able to estimate the density (~2.5e4
cm-3) and temperature (~10 K) of this component, typical of what is found in
dark clouds. This component (called W51-core) has the same DCO+/HCO+ ratio
(0.02) as TMC-1 and a high DNC/HNC ratio (0.14). Detection of these deuterated
species indicates that W51-core is similar to an early-phase low-mass
star-forming region, formed from the interaction between the W51 giant
molecular cloud and the high-velocity stream in front of it. The W51 complex
being at about 5 kpc, these findings lead to what is the first detection of the
earliest phase of low-mass star-forming region at such a large distance.


title: 3D Image Reconstruction from X-Ray Measurements with Overlap

abstract:
  3D image reconstruction from a set of X-ray projections is an important image
reconstruction problem, with applications in medical imaging, industrial
inspection and airport security. The innovation of X-ray emitter arrays allows
for a novel type of X-ray scanners with multiple simultaneously emitting
sources. However, two or more sources emitting at the same time can yield
measurements from overlapping rays, imposing a new type of image reconstruction
problem based on nonlinear constraints. Using traditional linear reconstruction
methods, respective scanner geometries have to be implemented such that no rays
overlap, which severely restricts the scanner design. We derive a new type of
3D image reconstruction model with nonlinear constraints, based on measurements
with overlapping X-rays. Further, we show that the arising optimization problem
is partially convex, and present an algorithm to solve it. Experiments show
highly improved image reconstruction results from both simulated and real-world
measurements.


title: Pair Production of Beyond the Standard Model Higgs Bosons

abstract:
  Higgs pair production is not only sensitive to the trilinear Higgs
self-coupling, but it can give access to other anomolous couplings, as e.g. a
novel $hht\bar{t}$ coupling. In Composite Higgs Models, this coupling usually
leads to a large increase of the cross section. In such a framework an
interesting question is, whether it might be possible to observe new physics
for the first time in Higgs pair production. This question will be addressed by
taking into account projected sensitivities for Higgs coupling measurements and
for direct searches of new vector-like quarks. Higher order corrections to
Higgs pair production via gluon fusion are sizeable. It is hence not only
important to compute them in the Standard Model (SM) but also in its
extensions. Here, the computation of the QCD corrections in the SM with
dimension 6 operators as well as the SUSY-QCD corrections to Higgs pair
production via gluon fusion in the MSSM are presented.


title:
Call Trace and Memory Access Pattern based Runtime Insider Threat
  Detection for Big Data Platforms

abstract:
  Big data platforms such as Hadoop and Spark are being widely adopted both by
academia and industry. In this paper, we propose a runtime intrusion detection
technique that understands and works according to the properties of such
distributed compute platforms. The proposed method is based on runtime analysis
of system and library calls and memory access patterns of tasks running on the
datanodes (slaves). First, the primary datanode of a big data system creates a
behavior profile for every task it executes. A behavior profile includes (a)
trace of the system & library calls made, and (b) sequence representing the
sizes of private and shared memory accesses made during task execution. Then,
the process behavior profile is shared with other replica datanodes that are
scheduled to execute the same task on their copy of the same data. Next, these
replica datanodes verify their local tasks with the help of the information
embedded in the received behavior profiles. This is realized in two steps: (i)
comparing the system & library calls metadata, and (ii) statistical matching of
the memory access patterns. Finally, datanodes share their observations for
consensus and report an intrusion to the namenode (master) if they find any
discrepancy. The proposed solution was tested on a small hadoop cluster using
the default MapReduce examples and the results show that our approach can
detect insider attacks that cannot be detected with the traditional analysis
metrics.


title:
A distributed ADMM-like method for resource sharing over time-varying
  networks

abstract:
  We consider cooperative multi-agent resource sharing problems over
time-varying communication networks, where only local communications are
allowed. The objective is to minimize the sum of agent-specific composite
convex functions subject to a conic constraint that couples agents' decisions.
We propose a distributed primal-dual algorithm DPDA-D to solve the saddle point
formulation of the sharing problem on time-varying (un)directed communication
networks; and we show that primal-dual iterate sequence converges to a point
defined by a primal optimal solution and a consensual dual price for the
coupling constraint. Furthermore, we provide convergence rates for
suboptimality, infeasibility and consensus violation of agents' dual price
assessments; examine the effect of underlying network topology on the
convergence rates of the proposed decentralized algorithm; and compare DPDA-D
with a centralized method on the basis pursuit denoising and multi-channel
power allocation problems.


title: The Kaon identification system at the NA62 experiment at CERN

abstract:
  The NA62 experiment at CERN SPS aims to measure the branching ratio of the
ultra-rare kaon decay $K^+\to\pi^+\nu\bar{\nu}$ with 10\% precision, collecting
$\sim 100$ events, assuming the Standard Model~(SM) branching ratio of $8.4
\times 10^{-11}$, starting in 2016. The NA62 experiment uses a kaon
decay-in-flight technique and is exposed to a 750~MHz high-energy unseparated
charged hadron beam, in which kaons are a minor component (6\%). Kaon
identification is therefore mandatory to reduce the interference of the
dominant non-kaon component with the experimental measurements. The NA62 kaon
identification system and its performances are presented.


title:
Chromospheric activity on late-type star DM UMa using high-resolution
  spectroscopic observations

abstract:
  We present new 14 high-resolution echelle spectra to discuss the level of
chromospheric activity of DM UMa in {He I} D3, {Na I} D1, D2, Halpha, and {Ca
II} infrared triplet lines (IRT). It is the first time to discover the
emissions above the continuum in the {He I} D3 lines on 2015 February 9 and 10.
The emission on February 9 is the strongest one ever detected for DM UMa. We
analysed these chromospheric active indicators by employing the spectral
subtraction technique. The subtracted spectra reveal weak emissions in the {Na
I} D1, D2 lines, strong emission in the Halpha line, and clear excess emissions
in the {Ca II} IRT lines. Our values for the EW8542/EW8498 ratio are on the low
side, in the range of 1.0-1.7. There are also clear phase variations of the
level of chromospheric activity in equivalent width (EW) light curves in these
chromospheric active lines (especially the Halpha line). These phenomena might
be explained by flare events or rotational modulations of the level of
chromospheric activity.


title: La filtration canonique des $\mathcal O$-modules $p$-divisibles

abstract:
  English : In this article we associate to $G$, a truncated $p$-divisible
$\mathcal O$-module of given signature, where $\mathcal O$ is a finite
unramified extension of $\mathbb{Z}_p$, a filtration of $G$ by sub-$\mathcal
O$-modules under the conditions that his Hasse $\mu$-invariant is smaller than
an explicite bound. This filtration generalise the one given when $G$ is
$\mu$-ordinary. The construction of the filtration relies on a precise study of
the cristalline periods of a $p$-divisible $\mathcal O$-module. We then apply
this result to families of such groups, in particular to stricts neighbourhoods
of the $\mu$-ordinary locus inside some PEL Shimura varieties.
  Fran\c{c}ais : Dans cet article, \`a $G$ un groupe $p$-divisible tronqu\'e
muni d'une action d'une extension finie non ramifi\'ee $\mathcal O$ de
$\mathbb{Z}_p$, et de signature donn\'ee, on associe sous une condition
explicite sur son $\mu$-invariant de Hasse, une filtration de $G$ par des
sous-$\mathcal O$-modules qui \'etend la filtration canonique lorsque $G$ est
$\mu$-ordinaire. La construction se fait en \'etudiant les p\'eriodes
cristallines des groupes $p$-divisibles avec action de $\mathcal O$. On
applique ensuite cela aux familles de tels groupes, en particulier des
voisinages stricts du lieu $\mu$-ordinaire dans des vari\'et\'es de Shimura
PEL.


title: Non-linear Barrier Coverage using Mobile Wireless Sensors

abstract:
  A belt region is said to be k-barrier covered by a set of sensors if all
paths crossing the width of the belt region intersect the sensing regions of at
least k sensors. Barrier coverage can be achieved from a random initial
deployment of mobile sensors by suitably relocating the sensors to form a
barrier. Reducing the movement of the sensors is important in such scenarios
due to the energy constraints of sensor devices. In this paper, we propose a
centralized algorithm which achieves 1-barrier coverage by forming a non-linear
barrier from a random initial deployment of sensors in a belt. The algorithm
uses a novel idea of physical behavior of chains along with the concept of
virtual force. Formation of non-linear barrier reduces the movement of the
sensors needed as compared to linear barriers. Detailed simulation results are
presented to show that the proposed algorithm achieves barrier coverage with
less movement of sensors compared to other existing algorithms in the
literature.


title: Geodesic motion of test particles in Korkina-Grigoryev metric

abstract:
  We study the geodesic structure of the Korkina-Grigoryev spacetime. The
corresponding metric is a generalization of the Schwarzschild geometry to the
case involving a massless scalar field. We investigate the relation between the
angular momentum of the test particle and the charge of the field, which
determines the shape of the effective-potential curves. The ratio for angular
momentum of the particle, the charge of the scalar field and the dimensionless
spatial parameter is found, under which the finite motion of particles occurs.
From the behavior of the potential curves the radii of both stable and unstable
circular orbits around a black hole are found, as well as the corresponding
energies of the test particles. The effective-potential curves for the
Korkina-Grigoryev, the Schwarzschild and the Reissner-Nordstrom fields are
compared. It is shown, that in the case of the Korkina-Grigoryev metric the
stable orbits eventually vanish with increasing charge.


title:
A Robust Force Control Approach for Underwater Vehicle Manipulator
  Systems

abstract:
  In various interaction tasks using Underwater Vehicle Manipulator Systems
(UVMSs) (e.g. sampling of the sea organisms, underwater welding), important
factors such as: i) uncertainties and complexity of UVMS dynamic model ii)
external disturbances (e.g. sea currents and waves) iii) imperfection and
noises of measuring sensors iv) steady state performance as well as v) inferior
overshoot of interaction force error, should be addressed during the force
control design. Motivated by the above factors, this paper presents a
model-free control protocol for force controlling of an Underwater Vehicle
Manipulator System which is in contact with a compliant environment, without
incorporating any knowledge of the UVMS's dynamic model, exogenous disturbances
and sensor's noise model. Moreover, the transient and steady state response as
well as reduction of overshooting force error are solely determined by certain
designer-specified performance functions and are fully decoupled by the UVMS's
dynamic model, the control gain selection, as well as the initial conditions.
Finally, a simulation study clarifies the proposed method and verifies its
efficiency.


title:
A Deep Learning Based DDoS Detection System in Software-Defined
  Networking (SDN)

abstract:
  Distributed Denial of Service (DDoS) is one of the most prevalent attacks
that an organizational network infrastructure comes across nowadays. We propose
a deep learning based multi-vector DDoS detection system in a software-defined
network (SDN) environment. SDN provides flexibility to program network devices
for different objectives and eliminates the need for third-party
vendor-specific hardware. We implement our system as a network application on
top of an SDN controller. We use deep learning for feature reduction of a large
set of features derived from network traffic headers. We evaluate our system
based on different performance metrics by applying it on traffic traces
collected from different scenarios. We observe high accuracy with a low
false-positive for attack detection in our proposed system.


title: Music and astronomy. II. unitedsoundsofcosmos

abstract:
  We have been congratulated on the stage by a Nobel laureate (he was our
curtain raiser), played our music in planetariums, museums, observatories
throughout Spain and at the end of the meeting of the ESO telescopes time
allocation committee, shocked audiences in rock concerts, written monthly on
Musica Universalis, made the second concert in 3D in Spain after Kraftwerk and
broadcasted it live in Radio 3, mixed our music with poetry read aloud by
scientists, composed the soundtracks of CARMENES, QUIJOTE, ESTRACK and the Gaia
first data release, made a videoclip on how computer simulates the formation of
stars... All those moments will not be lost in time like tears in rain, but put
together in Bilbao during the 2016 meeting of the Spanish Astronomical Society.


title: A model violating the Boltzmann distribution

abstract:
  We study a model of an ionic conductor having interstitial ions that jump
from site to site. The conductor is subject to an external electric field.
According to classical mechanics, the ion number density follows the Boltzmann
distribution. But according to quantum mechanics, we show that the Boltzmann
distribution is violated by a factor of 2. And the violation provides a
mechanism to explain the Haven ratio observed in some experiments.


title:
Low-Dimensional Stochastic Modeling of the Electrical Properties of
  Biological Tissues

abstract:
  Uncertainty quantification plays an important role in biomedical engineering
as measurement data is often unavailable and literature data shows a wide
variability. Using state-of-the-art methods one encounters difficulties when
the number of random inputs is large. This is the case, e.g., when using
composite Cole-Cole equations to model random electrical properties. It is
shown how the number of parameters can be significantly reduced by the
Karhunen-Loeve expansion. The low-dimensional random model is used to quantify
uncertainties in the axon activation during deep brain stimulation. Numerical
results for a Medtronic 3387 electrode design are given.


title:
Partition-free theory of time-dependent current correlations in
  nanojunctions in response to an arbitrary time-dependent bias

abstract:
  Working within the Nonequilibrium Green's Function (NEGF) formalism, a
formula for the two-time current correlation function is derived for the case
of transport through a nanojunction in response to an arbitrary time-dependent
bias. The one-particle Hamiltonian and the Wide Band Limit Approximation (WBLA)
are assumed, enabling us to extract all necessary Green's functions and self
energies for the system, extending the analytic work presented previously
[Ridley et al. Phys. Rev. B (2015)]. We show that our new expression for the
two-time correlation function generalises the B\"uttiker theory of shot and
thermal noise on the current through a nanojunction to the time-dependent bias
case including the transient regime following the switch-on. Transient terms in
the correlation function arise from an initial state that does not assume (as
is usually done) that the system is initially uncoupled, i.e. our approach is
partition-free. We show that when the bias loses its time-dependence, the long
time-limit of the current correlation function depends on the time difference
only, as in this case an ideal steady state is reached. This enables derivation
of known results for the single frequency power spectrum and for the zero
frequency limit of this power spectrum. In addition, we present a technique
which for the first time facilitates fast calculations of the transient quantum
noise, valid for arbitrary temperature, time and voltage scales. We apply this
to the quantum dot and molecular wire systems for both DC and AC biases, and
find a novel signature of the traversal time for electrons crossing the wire in
the time-dependent cross-lead current correlations.


title:
Modulation of bandgap in bilayer armchair graphene ribbons by tuning
  vertical and transverse electric fields

abstract:
  We investigate the effects of external electric fields on the electronic
properties of bilayer armchair graphene nano-ribbons. Using atomistic
simulations with Tight Binding calculations and the Non-equilibrium Green
function formalism, we demonstrate that (i) in semi-metallic structures,
vertical fields impact more effectively than transverse fields in terms of
opening larger bandgap, showing a contrary phenomenon compared to that
demonstrated in previous studies in bilayer zigzag graphene nano-ribbons; (ii)
in some semiconducting structures, if transverse fields just show usual effects
as in single layer armchair graphene nano-ribbons where the bandgap is
suppressed when varying the applied potential, vertical fields exhibit an
anomalous phenomenon that the bandgap can be enlarged, i.e., for a structure of
width of 16 dimer lines, the bandgap increases from 0.255 eV to the maximum
value of 0.40 eV when a vertical bias equates 0.96 V applied. Although the
combined effect of two fields does not enlarge the bandgap as found in bilayer
zigzag graphene nano-ribbons, it shows that the mutual effect can be useful to
reduce faster the bandgap in semiconducting bilayer armchair graphene
nano-ribbons. These results are important to fully understand the effects of
electric fields on bilayer graphene nano-ribbons (AB stacking) and also suggest
appropriate uses of electric gates with different edge orientations.


title:
Spin and recombination dynamics of excitons and free electrons in p-type
  GaAs : effect of carrier density

abstract:
  Carrier and spin recombination are investigated in p-type GaAs of acceptor
concentration NA = 1.5 x 10^(17) cm^(-3) using time-resolved photoluminescence
spectroscopy at 15 K. At low pho- tocarrier concentration, acceptors are mostly
neutral and photoelectrons can either recombine with holes bound to acceptors
(e-A0 line) or form excitons which are mostly trapped on neutral acceptors
forming the (A0X) complex. It is found that the spin lifetime is shorter for
electrons that recombine through the e-A0 transition due to spin relaxation
generated by the exchange scattering of free electrons with either trapped or
free holes, whereas spin flip processes are less likely to occur once the
electron forms with a free hole an exciton bound to a neutral acceptor. An
increase of exci- tation power induces a cross-over to a regime where the
bimolecular band-to-band (b-b) emission becomes more favorable due to screening
of the electron-hole Coulomb interaction and ionization of excitonic complexes
and free excitons. Then, the formation of excitons is no longer possible, the
carrier recombination lifetime increases and the spin lifetime is found to
decrease dramatically with concentration due to fast spin relaxation with free
photoholes. In this high density regime, both the electrons that recombine
through the e-A0 transition and through the b-b transition have the same spin
relaxation time.


title: A matrix description of weakly bipartitive and bipartitive families

abstract:
  The notions of weakly bipartitive and bipartitive families were introduced by
Montgolfier (2003) as a general tool for studying some decomposition of graphs
and other combinatorial structures. In this paper, we give a matrix description
of these notions.


title:
Control and Local Measurement of the Spin Chemical Potential in a
  Magnetic Insulator

abstract:
  The spin chemical potential characterizes the tendency of spins to diffuse.
Probing the spin chemical potential could provide insight into materials such
as magnetic insulators and spin liquids and aid optimization of spintronic
devices. Here, we introduce single-spin magnetometry as a generic platform for
non-perturbative, nanoscale characterization of spin chemical potentials. We
use this platform to investigate magnons in a magnetic insulator, surprisingly
finding that the magnon chemical potential can be efficiently controlled by
driving the system's ferromagnetic resonance. We introduce a symmetry-based
two-fluid theory describing the underlying magnon processes, realize the first
experimental determination of the local thermomagnonic torque, and illustrate
the detection sensitivity using electrically controlled spin injection. Our
results open the way for nanoscale control and imaging of spin transport in
mesoscopic spin systems.


title: A Metric for Performance Portability

abstract:
  The term "performance portability" has been informally used in computing to
refer to a variety of notions which generally include: 1) the ability to run
one application across multiple hardware platforms; and 2) achieving some
notional level of performance on these platforms. However, there has been a
noticeable lack of consensus on the precise meaning of the term, and authors'
conclusions regarding their success (or failure) to achieve performance
portability have thus been subjective. Comparing one approach to performance
portability with another has generally been marked with vague claims and
verbose, qualitative explanation of the comparison. This paper presents a
concise definition for performance portability, along with a simple metric that
accurately captures the performance and portability of an application across
different platforms. The utility of this metric is then demonstrated with a
retroactive application to previous work.


title:
[Ultra] Luminous Infrared Galaxies selected at 90 $\mu$m in the AKARI
  deep field: a study of AGN types contributing to their infrared emission

abstract:
  The aim of this work is to characterize physical properties of Ultra Luminous
Infrared Galaxies (ULIRGs) and Luminous Infrared Galaxies (LIRGs) detected in
the far-infrared (FIR) 90um band in the AKARI Deep Field-South (ADF-S) survey.
In particular, we want to estimate the AGN contribution to the [U]LIRGs'
infrared emission and which types of AGNs are related to their activity. We
examined 69 galaxies at z>0.05 detected at 90um by the AKARI satellite in the
ADF-S, with optical counterparts and spectral coverage from the ultraviolet to
the FIR. We used two independent spectral energy distribution fitting codes:
one fitting the SED from FIR to FUV (CIGALE) and gray-body + power spectrum fit
for the infrared part of the spectra (CMCIRSED) in order to identify a
subsample of [U]LIRGs, and to estimate their properties. Based on the CIGALE
SED fitting, we have found that [U]LIRGs selected at the 90um AKARI band
compose ~56% of our sample (we found 17 ULIRGs and 22 LIRGs, spanning over the
redshift range 0.06<z<1.23). Their physical parameters, such as stellar mass,
star formation rate (SFR), and specific SFR are consistent with the ones found
for other samples selected at IR wavelengths. We have detected a significant
AGN contribution to the MIR luminosity for 63% of LIRGs and ULIRGs. Our LIRGs
contain Type 1, Type 2, and intermediate types of AGN, whereas for ULIRGs, a
majority (more than 50%) of AGN emission originates from Type 2 AGNs. The
temperature--luminosity and temperature--mass relations for the dust component
of ADF--S LIRGs and ULIRGs indicate that these relations are shaped by the dust
mass and not by the increased dust heating. We conclude that LIRGs contain Type
1, Type 2, and intermediate types of AGNs, with an AGN contribution to the MIR
emission at the median level of 13+/-3%, whereas the majority of ULIRGs contain
Type 2 AGNs, with a median AGN fraction equal to 19+/-8%.


title:
Decay constants $f_B$ and $f_{B_s}$ and quark masses $m_b$ and $m_c$
  from HISQ simulations

abstract:
  We present a progress report on our calculation of the decay constants $f_B$
and $f_{B_s}$ from lattice-QCD simulations with highly-improved staggered
quarks. Simulations are carried out with several heavy valence-quark masses on
$(2+1+1)$-flavor ensembles that include charm sea quarks. We include data at
six lattice spacings and several light sea-quark masses, including an
approximately physical-mass ensemble at all but the smallest lattice spacing,
0.03 fm. This range of parameters provides excellent control of the continuum
extrapolation to zero lattice spacing and of heavy-quark discretization errors.
Finally, using the heavy-quark effective theory expansion we present a method
of extracting from the same correlation functions the charm- and bottom-quark
masses as well as some low-energy constants appearing in the heavy-quark
expansion.


title:
Statistical Methods for Thermal Index Estimation Based on Accelerated
  Destructive Degradation Test Data

abstract:
  Accelerated destructive degradation test (ADDT) is a technique that is
commonly used by industries to access material's long-term properties. In many
applications, the accelerating variable is usually the temperature. In such
cases, a thermal index (TI) is used to indicate the strength of the material.
For example, a TI of 200C may be interpreted as the material can be expected to
maintain a specific property at a temperature of 200C for 100,000 hours. A
material with a higher TI possesses a stronger resistance to thermal damage. In
literature, there are three methods available to estimate the TI based on ADDT
data, which are the traditional method based on the least-squares approach, the
parametric method, and the semiparametric method. In this chapter, we provide a
comprehensive review of the three methods and illustrate how the TI can be
estimated based on different models. We also conduct comprehensive simulation
studies to show the properties of different methods. We provide thorough
discussions on the pros and cons of each method. The comparisons and discussion
in this chapter can be useful for practitioners and future industrial
standards.


title: Trojan capture by terrestrial planets

abstract:
  The paper is devoted to investigate the capture of asteroids by Venus, Earth
and Mars into the 1:1 mean motion resonance especially into Trojan orbits.
Current theoretical studies predict that Trojan asteroids are a frequent
by-product of the planet formation. This is not only the case for the outer
giant planets, but also for the terrestrial planets in the inner Solar System.
By using numerical integrations, we investigated the capture efficiency and the
stability of the captured objects. We found out that the capture efficiency is
larger for the planets in the inner Solar System compared to the outer ones,
but most of the captured Trojan asteroids are not long term stable. This
temporary captures caused by chaotic behaviour of the objects were investigated
without any dissipative forces. They show an interesting dynamical behaviour of
mixing like jumping from one Lagrange point to the other one.


title: The Heterogeneous Capacitated $k$-Center Problem

abstract:
  In this paper we initiate the study of the heterogeneous capacitated
$k$-center problem: given a metric space $X = (F \cup C, d)$, and a collection
of capacities. The goal is to open each capacity at a unique facility location
in $F$, and also to assign clients to facilities so that the number of clients
assigned to any facility is at most the capacity installed; the objective is
then to minimize the maximum distance between a client and its assigned
facility. If all the capacities $c_i$'s are identical, the problem becomes the
well-studied uniform capacitated $k$-center problem for which constant-factor
approximations are known. The additional choice of determining which capacity
should be installed in which location makes our problem considerably different
from this problem, as well the non-uniform generalizations studied thus far in
literature. In fact, one of our contributions is in relating the heterogeneous
problem to special-cases of the classical Santa Claus problem. Using this
connection, and by designing new algorithms for these special cases, we get the
following results: (a)A quasi-polynomial time $O(\log
n/\epsilon)$-approximation where every capacity is violated by $1+\varepsilon$,
(b) A polynomial time $O(1)$-approximation where every capacity is violated by
an $O(\log n)$ factor. We get improved results for the {\em soft-capacities}
version where we can place multiple facilities in the same location.


title: Commutative algebra and the linear diophantine problem of Frobenius

abstract:
  Let $A$ be a finite set of relatively prime positive integers, and let $S(A)$
be the set of all nonnegative integral linear combinations of elements of $A$.
The set $S(A)$ is a semigroup that contains all sufficiently large integers.
The largest integer not in $S(A)$ is the Frobenius number of $A$, and the
number of positive integers not in $S(A)$ is the genus of $A$. Sharp and
Sylvester proved in 1884 that the Frobenius number of the set $A = \{a,b\}$ is
$ab-a-b$, and that the genus of $A$ is $(a-1)(b-1)/2$. Graded rings and a
simple form of Hilbert's syzygy theorem are used to give a commutative algebra
proof of this result.


title:
A WISE-based search for debris discs amongst M-dwarfs in nearby, young,
  moving groups

abstract:
  We present a search for debris discs amongst M-dwarf members of nearby, young
(5-150 Myr) moving groups (MGs) using infrared (IR) photometry, primarily from
the Wide Infrared Survey Explorer (WISE). A catalogue of 100 MG M-dwarfs that
have suitable WISE data is compiled and 19 of these are found to have
significant IR excess emission at 22$\mu$m. Our search is likely to be complete
for discs where the ratio of flux from the disc to flux from the star $f_{\rm
d}/f_{*} > 10^{-3}$. The spectral energy distributions are supplemented with
2MASS photometry and data at longer wavelengths and fitted with simple disc
models to characterise the IR excesses. There is a bimodal distribution --
twelve targets have $W1-W4 > 3$, corresponding to $f_{\rm d}/f_{*} > 0.02$ and
are likely to be gas-rich, primordial discs. The remaining seven targets have
$W1-W4 < 1$ ($f_{\rm d}/f_{*} \lesssim 10^{-3}$) and include three objects with
previously known or suspected debris discs and four new debris disc candidates
that are all members of the Beta Pic MG. All of the IR excesses are identified
in stars that are likely members of MGs with age $< 30$ Myr. The detected
debris disc frequency falls from 13 to 5 per cent to $< 7$ per cent (at 95 per
cent confidence) for objects younger or older than 30 Myr respectively. This
provides evidence for the evolution of debris discs on this timescale and does
not support models where the maximum of debris disc emission occurs much later
in lower-mass stars.


title:
ADDT: An R Package for Analysis of Accelerated Destructive Degradation
  Test Data

abstract:
  Accelerated destructive degradation tests (ADDT) are often used to collect
necessary data for assessing the long-term properties of polymeric materials.
Based on the data, a thermal index (TI) is estimated. The TI can be useful for
material rating and comparisons. The R package ADDT provides the
functionalities of performing the traditional method based on the least-squares
method, the parametric method based on maximum likelihood estimation, and the
semiparametric method based on spline methods for analyzing ADDT data, and then
estimating the TI for polymeric materials. In this chapter, we provide a
detailed introduction to the ADDT package. We provide a step-by-step
illustration for the use of functions in the package. Publicly available
datasets are used for illustrations.


title:
Partial estimators and application to covariance estimation of gaussian
  and elliptical distributions

abstract:
  Robustness to outliers is often a desirable property of statistical
estimators. Indeed many well known estimators offer very good optimal
performance in theory but are unusable in applied contexts because of their
sensitivity to outliers. Of particular interest to the authors is the case of
covariance estimators in adaptive matched filtering schemes in signal
processing applications such as RADAR and SONAR detection, for which a
contamination by outliers of the estimated noise covariance can lead to a great
impact on performances, in particular when these outliers are similar to the
target signal of the matched filter.
  This paper presents a generic method for building partial estimators from
known estimators, which aim at avoiding these issues; the resulting algorithms
are shown for a few chosen cases.


title:
Flavor origin of dark matter and its relation with leptonic nonzero
  $\theta_{13}$ and Dirac CP phase $\delta$

abstract:
  We propose a minimal extension of the standard model by including a $U(1)$
flavor symmetry to establish a correlation between the relic abundance of dark
matter, measured by WMAP and PLANCK satellite experiments and non-zero value of
$\sin \theta_{13}$ observed at DOUBLE CHOOZ, Daya Bay, RENO and T2K. The
flavour symmetry is allowed to be broken at a high scale to a remnant
$\mathcal{Z}_2$ symmetry, which not only ensures the stability to the dark
matter, but also gives rise to a modification to the existing $A_4$-based
tri-bimaximal neutrino mixing. This deviation in turn suggests the required
non-zero value of $\sin \theta_{13}$. We assume the dark matter to be neutral
under the existing $A_4$ symmetry while charged under the $U(1)$ flavor
symmetry. Hence in this set-up, the non-zero value of $\sin \theta_{13}$
predicts the dark matter charge under $U(1)$, which can be tested at various
ongoing and future direct and collider dark matter search experiments. We also
point out the involvement of nonzero leptonic CP phase $\delta$, which plays an
important role in the analysis.


title: SMCL - Stochastic Model Checker for Learning in Games

abstract:
  A stochastic model checker is presented for analysing the performance of
game-theoretic learning algorithms. The method enables the comparison of
short-term behaviour of learning algorithms intended for practical use. The
procedure of comparison is automated and it can be tuned for accuracy and
speed. Users can choose from among various learning algorithms to select a
suitable one for a given practical problem. The powerful performance of the
method is enabled by a novel behaviour-similarity-relation, which compacts
large state spaces into small ones. The stochastic model checking tool is
tested on a set of examples classified into four categories to demonstrate the
effectiveness of selecting suitable algorithms for distributed decision making.


title: Reduction-Based Creative Telescoping for Fuchsian D-finite Functions

abstract:
  Continuing a series of articles in the past few years on creative telescoping
using reductions, we adapt Trager's Hermite reduction for algebraic functions
to fuchsian D-finite functions and develop a reduction-based creative
telescoping algorithm for this class of functions, thereby generalizing our
recent reduction-based algorithm for algebraic functions, presented at ISSAC
2016.


title: Deep Learning Approximation for Stochastic Control Problems

abstract:
  Many real world stochastic control problems suffer from the "curse of
dimensionality". To overcome this difficulty, we develop a deep learning
approach that directly solves high-dimensional stochastic control problems
based on Monte-Carlo sampling. We approximate the time-dependent controls as
feedforward neural networks and stack these networks together through model
dynamics. The objective function for the control problem plays the role of the
loss function for the deep neural network. We test this approach using examples
from the areas of optimal trading and energy storage. Our results suggest that
the algorithm presented here achieves satisfactory accuracy and at the same
time, can handle rather high dimensional problems.


title: Nodal Curves on K3 Surfaces

abstract:
  In this paper, we study the Severi variety $V_{L,g}$ of genus $g$ curves in
$|L|$ on a general polarized K3 surface $(X,L)$. We show that the closure of
every component of $V_{L,g}$ contains a component of $V_{L,g-1}$. As a
consequence, we see that the general members of every component of $V_{L,g}$
are nodal.


title: Evolution of the Fermi surface of the nematic superconductors FeSe1-xSx

abstract:
  We investigate the evolution of the Fermi surfaces and electronic
interactions across the nematic phase transition in single crystals of
FeSe1-xSx using Shubnikov-de Haas oscillations in high magnetic fields up to 45
tesla in the low temperature regime. The unusually small and strongly elongated
Fermi surface of FeSe increases monotonically with chemical pressure, x, due to
the suppression of the in-plane anisotropy except for the smallest orbit which
suffers a Lifshitz-like transition once nematicity disappears. Even outside the
nematic phase the Fermi surface continues to increase, in stark contrast to the
reconstructed Fermi surface detected in FeSe under applied external pressure.
We detect signatures of orbital-dependent quasiparticle mass renomalization
suppressed for those orbits with dominant dxz=yz character, but unusually
enhanced for those orbits with dominant dxy character. The lack of enhanced
superconductivity outside the nematic phase in FeSe1-xSx suggest that
nematicity may not play the essential role in enhancing Tc in these systems.


title:
Non-Orthogonal Multiple Access (NOMA) for Downlink Multiuser MIMO
  Systems: User Clustering, Beamforming, and Power Allocation

abstract:
  We investigate the application of non-orthogonal multiple access (NOMA) with
successive interference cancellation (SIC) in downlink multiuser multiple-input
multiple-output (MIMO) cellular systems, where the total number of receive
antennas at user equipment (UE) ends in a cell is more than the number of
transmit antennas at the base station (BS). We first dynamically group the UE
receive antennas into a number of clusters equal to or more than the number of
BS transmit antennas. A single beamforming vector is then shared by all the
receive antennas in a cluster. We propose a linear beamforming technique in
which all the receive antennas can significantly cancel the inter-cluster
interference. On the other hand, the receive antennas in each cluster are
scheduled on power domain NOMA basis with SIC at the receiver ends. For
inter-cluster and intra-cluster power allocation, we provide dynamic power
allocation solutions with an objective to maximizing the overall cell capacity.
An extensive performance evaluation is carried out for the proposed MIMO-NOMA
system and the results are compared with those for conventional orthogonal
multiple access (OMA)-based MIMO systems and other existing MIMO-NOMA
solutions. The numerical results quantify the capacity gain of the proposed
MIMO-NOMA model over MIMO-OMA and other existing MIMO-NOMA solutions.


title:
Kinematics of Extremely Metal-poor Galaxies: Evidence for Stellar
  Feedback

abstract:
  The extremely metal-poor (XMP) galaxies analyzed in a previous paper have
large star-forming regions with a metallicity lower than the rest of the
galaxy. Such a chemical inhomogeneity reveals the external origin of the
metal-poor gas fueling star formation, possibly indicating accretion from the
cosmic web. This paper studies the kinematic properties of the ionized gas in
these galaxies. Most XMPs have rotation velocity around a few tens of km/s. The
star-forming regions appear to move coherently. The velocity is constant within
each region, and the velocity dispersion sometimes increases within the
star-forming clump towards the galaxy midpoint, suggesting inspiral motion
toward the galaxy center. Other regions present a local maximum in velocity
dispersion at their center, suggesting a moderate global expansion. The Halpha
line wings show a number of faint emission features with amplitudes around a
few percent of the main Halpha component, and wavelength shifts between 100 and
400 km/s. The components are often paired, so that red and blue emission
features with similar amplitudes and shifts appear simultaneously. Assuming the
faint emission to be produced by expanding shell-like structures, the inferred
mass loading factor (mass loss rate divided by star formation rate) exceeds 10.
Since the expansion velocity exceeds by far the rotational and turbulent
velocities, the gas may eventually escape from the galaxy disk. The observed
motions involve energies consistent with the kinetic energy released by
individual core-collapse supernovae. Alternative explanations for the faint
emission have been considered and discarded.


title:
Infrared properties of a prototype model for beyond-Standard Model
  physics

abstract:
  We construct a prototype BSM model based on the SU(3) color gauge group and a
combination of 4 light (massless) and 8 heavy flavors. In the infrared, the
SU(4) flavor chiral symmetry is spontaneously broken, while in the ultraviolet
this model exhibits the properties of the $N_f=12$ conformal fixed point.
Renormalization group considerations predict the spectrum of such a system to
show hyperscaling, i.e. dimensionless ratios of hadron masses or decay
constants are independent of the heavy mass. Hyperscaling is present for bound
states of light, heavy, or a combination of heavy and light flavors and leads
to a strongly predictive model. Despite chiral symmetry breaking, this system
features a spectrum exhibiting a very non-QCD like behavior. Furthermore, the
gauge coupling becomes an irrelevant parameter. We support these expectations
by presenting numerical results based on four different values of the heavy
quark mass $am_h$, up to six different values of the light quark mass
$am_\ell$, and include, for the first time, preliminary data at a second value
of the gauge coupling $\beta$. Our model can be embedded in scenarios
describing the Higgs boson either as a pseudo Nambu-Goldstone boson or a
dilaton-like particle.


title:
Differences between radio-loud and radio-quiet gamma-ray pulsars as
  revealed by Fermi

abstract:
  By comparing the properties of non-recycled radio-loud $\gamma-$ray pulsars
and radio-quiet $\gamma-$ray pulsars, we have searched for the differences
between these two populations. We found that the $\gamma-$ray spectral
curvature of radio-quiet pulsars can be larger than that of radio-loud pulsars.
Based on the full sample of non-recycled $\gamma-$ray pulsars, their
distributions of the magnetic field strength at the light cylinder are also
found to be different. We notice that this might be resulted from the
observational bias. In re-examining the previously reported difference of
$\gamma-$ray-to-X-ray flux ratios, we found the significance can be hampered by
their statistical uncertainties. In the context of outer gap model, we discuss
the expected properties of these two populations and compare with the possible
differences identified in our analysis.


title:
TreeView: Peeking into Deep Neural Networks Via Feature-Space
  Partitioning

abstract:
  With the advent of highly predictive but opaque deep learning models, it has
become more important than ever to understand and explain the predictions of
such models. Existing approaches define interpretability as the inverse of
complexity and achieve interpretability at the cost of accuracy. This
introduces a risk of producing interpretable but misleading explanations. As
humans, we are prone to engage in this kind of behavior \cite{mythos}. In this
paper, we take a step in the direction of tackling the problem of
interpretability without compromising the model accuracy. We propose to build a
Treeview representation of the complex model via hierarchical partitioning of
the feature space, which reveals the iterative rejection of unlikely class
labels until the correct association is predicted.


title: A new approach to unramified descent in Bruhat-Tits theory

abstract:
  The purpose of the paper is to present an alternative approach to unramified
descent in Bruhat-Tits theory of reductive groups over nonarchimedean local
fields. This approach appears to be conceptually simpler than the approach in
the papers of Bruhat and Tits.


title:
Upgrades for the Precision Proton Spectrometer at the LHC: Precision
  Timing and Tracking Detectors

abstract:
  The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) is an approved project
to add tracking and timing information at approximately $\pm$210~m from the
interaction point around the CMS detector. It is designed to operate at high
luminosity with up to 50 interactions per 25~ns bunch crossing to perform
measurements of e.g. the quartic gauge couplings and search for rare exclusive
processes. During 2016, CT-PPS took data in normal high-luminosity
proton-proton LHC collisions. In the coming years, high radiation doses and
large multiple-vertex interactions will represent difficult challenges that
resemble those of the high-luminosity LHC program. A coordinated effort of
detector upgrades with the goal of reaching the physics goals while mitigating
the degradation effects is under way. Upgrades to the tracking and timing
detectors are discussed.


title: "Chaos" in energy and commodity markets: a controversial matter

abstract:
  We test whether the futures prices of some commodity and energy markets are
determined by stochastic rules or exhibit nonlinear deterministic endogenous
fluctuations. As for the methodologies, we use the maximal Lyapunov exponents
(MLE) and a determinism test, both based on the reconstruction of the phase
space. In particular, employing a recent methodology, we estimate a coefficient
$\kappa$ that describes the determinism rate of the analyzed time series. We
find that the underlying system for futures prices shows a reliability level
$\kappa$ near to $1$ while the MLE is positive for all commodity futures
series. Thus, the empirical evidence suggests that commodity and energy futures
prices are the measured footprint of a nonlinear deterministic, rather than a
stochastic, system.


title: Picard groups of moduli spaces of curves with symmetry

abstract:
  We study the Picard groups of moduli spaces of smooth complex projective
curves that have a group of automorphisms with a prescribed topological action.
One of our main tools is the theory of symmetric mapping class groups. In the
first part of the paper, we show that, under mild restrictions, the moduli
spaces of smooth curves with an abelian group of automorphisms of a fixed
topological type have finitely generated Picard groups. In certain special
cases, we are able to compute them exactly. In the second part of the paper, we
show that finite abelian level covers of the hyperelliptic locus in the moduli
space of smooth curves have finitely generated Picard groups. We also compute
the Picard groups of the moduli spaces of hyperelliptic curves of compact type.


title: Invariants of Classical Braids Valued in $G_{n}^{2}$

abstract:
  The aim of the present note is to construct invariants of the Artin braid
group valued in $G_{N}^{2}$, and further study of groups related to
$G_{n}^{3}$. In the groups $G_{n}^{2}$, the word problem is solved; these
groups are much simpler than $G_{n}^{3}$.


title:
Genetic optimization of training sets for improved machine learning
  models of molecular properties

abstract:
  The training of molecular models of quantum mechanical properties based on
statistical machine learning requires large datasets which exemplify the map
from chemical structure to molecular property. Intelligent a priori selection
of training examples is often difficult or impossible to achieve as prior
knowledge may be sparse or unavailable. Ordinarily representative selection of
training molecules from such datasets is achieved through random sampling. We
use genetic algorithms for the optimization of training set composition
consisting of tens of thousands of small organic molecules. The resulting
machine learning models are considerably more accurate with respect to small
randomly selected training sets: mean absolute errors for out-of-sample
predictions are reduced to ~25% for enthalpies, free energies, and zero-point
vibrational energy, to ~50% for heat-capacity, electron-spread, and
polarizability, and by more than ~20% for electronic properties such as
frontier orbital eigenvalues or dipole-moments. We discuss and present
optimized training sets consisting of 10 molecular classes for all molecular
properties studied. We show that these classes can be used to design improved
training sets for the generation of machine learning models of the same
properties in similar but unrelated molecular sets.


title:
Symplectic $(-2)$ spheres and the symplectomorphism group of small
  rational 4-manifolds, I

abstract:
  Let $(X,\omega)$ be a symplectic rational 4 manifold. We study the space of
tamed almost complex structures $\mathcal{J}_{\omega}$ using a fine
decomposition via smooth rational curves and a relative version of the
infinite-dimensional Alexander duality. This decomposition provides new
understandings of both the variation and stability of the symplectomorphism
group $Symp(X,\omega)$ when deforming $\omega$. In particular, we compute the
rank of $\pi_1(Symp(X,\omega))$ with Euler number $\chi(X)\leq 7$ in terms of
the number $N$ of -2 symplectic sphere classes.


title: The first law of cubology for the Rubik's Revenge

abstract:
  We state and prove the first law of cubology of the Rubik's Revenge and
provide necessary and sufficient conditions for a randomly assembled Rubik's
Revenge to be solvable.


title: Achieving non-discrimination in data release

abstract:
  Discrimination discovery and prevention/removal are increasingly important
tasks in data mining. Discrimination discovery aims to unveil discriminatory
practices on the protected attribute (e.g., gender) by analyzing the dataset of
historical decision records, and discrimination prevention aims to remove
discrimination by modifying the biased data before conducting predictive
analysis. In this paper, we show that the key to discrimination discovery and
prevention is to find the meaningful partitions that can be used to provide
quantitative evidences for the judgment of discrimination. With the support of
the causal graph, we present a graphical condition for identifying a meaningful
partition. Based on that, we develop a simple criterion for the claim of
non-discrimination, and propose discrimination removal algorithms which
accurately remove discrimination while retaining good data utility. Experiments
using real datasets show the effectiveness of our approaches.


title: An approach to the Jacobian Conjecture in terms of irreducibility

abstract:
  We present some motivations and discuss various aspects of an approach to the
Jacobian Conjecture in terms of irreducible elements and square-free elements.


title:
Spectral properties of polynomials in independent Wigner and
  deterministic matrices

abstract:
  On the one hand, we prove that almost surely, for large dimension, there is
no eigenvalue of a Hermitian polynomial in independent Wigner and deterministic
matrices, in any interval lying at some distance from the supports of a
sequence of deterministic probability measures, which is computed with the
tools of free probability. On the other hand, we establish the strong
asymptotic freeness of independent Wigner matrices and any family of
deterministic matrices with strong limiting distribution.


title: An integration approach to the Toeplitz square peg problem

abstract:
  The "square peg problem" or "inscribed square problem" of Toeplitz asks if
every simple closed curve in the plane inscribes a (non-degenerate) square, in
the sense that all four vertices of that square lie on the curve. By a variety
of arguments of a "homological" nature, it is known that the answer to this
question is positive if the curve is sufficiently regular. The regularity
hypotheses are needed to rule out the possibility of arbitrarily small squares
that are inscribed or almost inscribed on the curve; because of this, these
arguments do not appear to be robust enough to handle arbitrarily rough curves.
  In this paper we augment the homological approach by introducing certain
integrals associated to the curve. This approach is able to give positive
answers to the square peg problem in some new cases, for instance if the curve
is the union of two Lipschitz graphs $f, g \colon [t_0,t_1] \to \mathbf{R}$
that agree at the endpoints, and whose Lipschitz constants are strictly less
than one. We also present some simpler variants of the square problem which
seem particularly amenable to this integration approach, including a a periodic
version of the problem that is not subject to the problem of arbitrarily small
squares (and remains open even for regular curves), as well as an almost purely
combinatorial conjecture regarding the sign patterns of sums $y_1+y_2+y_3$ for
$y_1,y_2,y_3$ ranging in finite sets of real numbers.


title:
On the symplectic covariance and interferences of time-frequency
  distributions

abstract:
  We study the covariance property of quadratic time-frequency distributions
with respect to the action of the extended symplectic group. We show how
covariance is related, and in fact in competition, with the possibility of
damping the interferences which arise due to the quadratic nature of the
distributions. We also show that the well known fully covariance property of
the Wigner distribution in fact characterizes it (up to a constant factor)
among the quadratic distributions $L^{2}(\mathbb{R}^{n})\rightarrow C_{0}({
\mathbb{R}^{2n}})$. A similar characterization for the closely related Weyl
transform is given as well. The results are illustrated by several numerical
experiments for the Wigner and Born-Jordan distributions of the sum of four
Gaussian functions in the so-called "diamond configuration".


title:
Mapping chemical performance on molecular structures using locally
  interpretable explanations

abstract:
  In this work, we present an application of Locally Interpretable
Machine-Agnostic Explanations to 2-D chemical structures. Using this framework
we are able to provide a structural interpretation for an existing black-box
model for classifying biologically produced fuel compounds with regard to
Research Octane Number. This method of "painting" locally interpretable
explanations onto 2-D chemical structures replicates the chemical intuition of
synthetic chemists, allowing researchers in the field to directly accept,
reject, inform and evaluate decisions underlying inscrutably complex
quantitative structure-activity relationship models.


title: Singular TQFTs, foams and type D arc algebras

abstract:
  We combinatorially describe the $2$-category of singular cobordisms, called
(rank one) foams, which governs the functorial version of Khovanov homology. As
an application we topologically realize the type $\mathrm{D}$ arc algebra using
this singular cobordism construction.


title: First-principles spin-transfer torque in CuMnAs$|$GaP$|$CuMnAs junctions

abstract:
  We demonstrate that an all-antiferromagnetic tunnel junction with current
perpendicular to the plane geometry can be used as an efficient spintronics
device with potential high frequency operation. By using state-of-the-art
density functional theory combined with quantum transport, we show that the
N\'eel vector of the electrodes can be manipulated by spin-transfer torque.
This is staggered over the two different magnetic sublattices and can generate
dynamics and switching. At the same time the different magnetization states of
the junction can be read by standard tunnelling magnetoresistance. Calculations
are performed for CuMnAs$|$GaP$|$CuMnAs junctions with different surface
terminations between the anti-ferromagnetic CuMnAs electrodes and the
insulating GaP spacer. In particular we find that the torque remains staggered
regardless of the termination, while the magnetoresistance depends on the
microscopic details of the interface.


title:
Quark horizontal flavor symmetry and two-Higgs doublet in
  (7+1)-dimensional extended spin space

abstract:
  An extended spin-space model in $7+1$ dimensions is presented that describes
the standard-model electroweak quark sector. Up to four generations of massless
and massive quarks and two-Higgs doublets derive from the associated
representation space, in addition to the W- and Z-vector bosons. Other mass
operators are obtained that put restrictions on additional non-Higgs scalars
and their vacuum expectation value. After symmetry breaking, the scalar
components give rise to a hierarchy effect vertically (within doublets)
associated to the Higgs fields, and horizontally (within generations)
associated to the non-Higgs elements.


title:
Electron transport parameters in CO$_2$: scanning drift tube
  measurements and kinetic computations

abstract:
  This work presents transport coefficients of electrons (bulk drift velocity,
longitudinal diffusion coefficient, and effective ionization frequency) in CO2
measured under time-of-flight conditions over a wide range of the reduced
electric field, 15Td <= E/N <= 2660Td in a scanning drift tube apparatus. The
data obtained in the experiments are also applied to determine the effective
steady-state Townsend ionization coefficient. These parameters are compared to
the results of previous experimental studies, as well as to results of various
kinetic computations: solutions of the electron Boltzmann equation under
different approximations (multiterm and density gradient expansions) and Monte
Carlo simulations. The experimental data extend the range of E/N compared with
previous measurements and are consistent with most of the transport parameters
obtained in these earlier studies. The computational results point out the
range of applicability of the respective approaches to determine the different
measured transport properties of electrons in CO2. They demonstrate as well the
need for further improvement of the electron collision cross section data for
CO2 taking into account the present experimental data.


title:
Assessing the Performance of a 60-GHz Dense Small-Cell Network
  Deployment from Ray-Based Simulations

abstract:
  Future dense small-cell networks are one key 5G candidates to offer outdoor
high access data rates, especially in millimeter wave (mmWave) frequency bands.
At those frequencies, the free space propagation loss and shadowing (from
buildings, vegetation or any kind of obstacles) are far stronger than in the
traditional radio cellular spectrum. Therefore, the cell range is expected to
be limited to 50 - 100 meters, and directive high gain antennas are required at
least for the base stations. This paper investigates the kind of topology that
is required to serve a suburban area with a small-cell network operating at 60
GHz and equipped with beam-steering antennas. A real environment is considered
to introduce practical deployment and propagation constraints. The analysis
relies on Monte-Carlo system simulations with non-full buffer, and ray-based
predictions. The ray-tracing techniques are today identified as a relevant
solution to capture the main channel properties impacting the beam-steering
performance (angular dispersion, inter-link correlation); and the one involved
in the present study was specifically enhanced to deal with detailed vegetation
modeling. In addition to the user outage, the paper evaluates the evolution of
the inter-cell interference along with the user density, and investigates the
network behavior in case of local strong obstructions.


title:
Low Power Wide Area Networks (LPWANs) for Internet of Things (IoT)
  Applications: Research Challenges and Future Trends

abstract:
  Internet of things (IoT) changes significantly the requirements for
connectivity, mainly with regards to long battery life, low device cost, low
deployment cost, extended coverage and support for a massive number of devices.
Driven from these requirements, several different cellular and non-cellular low
power wide area network (LPWAN) solutions are emerging and competing for IoT
business and the overall connectivity market. Motivated by this, in this paper,
we review and compare the design specifications of different LPWAN solutions,
as well as, we discuss their suitability for different IoT applications.
Finally, we present the challenges, future trends, and potential research
directions for LPWANs.


title: Grad-CAM: Why did you say that?

abstract:
  We propose a technique for making Convolutional Neural Network (CNN)-based
models more transparent by visualizing input regions that are 'important' for
predictions -- or visual explanations. Our approach, called Gradient-weighted
Class Activation Mapping (Grad-CAM), uses class-specific gradient information
to localize important regions. These localizations are combined with existing
pixel-space visualizations to create a novel high-resolution and
class-discriminative visualization called Guided Grad-CAM. These methods help
better understand CNN-based models, including image captioning and visual
question answering (VQA) models. We evaluate our visual explanations by
measuring their ability to discriminate between classes, to inspire trust in
humans, and their correlation with occlusion maps. Grad-CAM provides a new way
to understand CNN-based models.
  We have released code, an online demo hosted on CloudCV, and a full version
of this extended abstract.


title: Sampling Random Spanning Trees Faster than Matrix Multiplication

abstract:
  We present an algorithm that, with high probability, generates a random
spanning tree from an edge-weighted undirected graph in
$\tilde{O}(n^{4/3}m^{1/2}+n^{2})$ time (The $\tilde{O}(\cdot)$ notation hides
$\operatorname{polylog}(n)$ factors). The tree is sampled from a distribution
where the probability of each tree is proportional to the product of its edge
weights. This improves upon the previous best algorithm due to Colbourn et al.
that runs in matrix multiplication time, $O(n^\omega)$. For the special case of
unweighted graphs, this improves upon the best previously known running time of
$\tilde{O}(\min\{n^{\omega},m\sqrt{n},m^{4/3}\})$ for $m \gg n^{5/3}$ (Colbourn
et al. '96, Kelner-Madry '09, Madry et al. '15).
  The effective resistance metric is essential to our algorithm, as in the work
of Madry et al., but we eschew determinant-based and random walk-based
techniques used by previous algorithms. Instead, our algorithm is based on
Gaussian elimination, and the fact that effective resistance is preserved in
the graph resulting from eliminating a subset of vertices (called a Schur
complement). As part of our algorithm, we show how to compute
$\epsilon$-approximate effective resistances for a set $S$ of vertex pairs via
approximate Schur complements in $\tilde{O}(m+(n + |S|)\epsilon^{-2})$ time,
without using the Johnson-Lindenstrauss lemma which requires $\tilde{O}(
\min\{(m + |S|)\epsilon^{-2}, m+n\epsilon^{-4} +|S|\epsilon^{-2}\})$ time. We
combine this approximation procedure with an error correction procedure for
handing edges where our estimate isn't sufficiently accurate.


title:
Isovector charges of the nucleon from 2+1-flavor QCD with clover
  fermions

abstract:
  We present high-statistics estimates of the isovector charges of the nucleon
from four 2+1-flavor ensembles generated using Wilson-clover fermions with
stout smearing and tree-level tadpole improved Symanzik gauge action at lattice
spacings $a=0.114$ and $0.080$ fm and with $M_\pi \approx 315$ and 200 MeV. The
truncated solver method with bias correction and the coherent source sequential
propagator construction are used to cost-effectively achieve $O(10^5)$
measurements on each ensemble. Using these data, the analysis of two-point
correlation functions is extended to include four states in the fits and of
three-point functions to three states. Control over excited-state contamination
in the calculation of the nucleon mass, the mass gaps between excited states,
and in the matrix elements is demonstrated by the consistency of estimates
using this multistate analysis of the spectral decomposition of the correlation
functions and from simulations of the three-point functions at multiple values
of the source-sink separation. The results for all three charges, $g_A$, $g_S$
and $g_T$, are in good agreement with calculations done using the
clover-on-HISQ lattice formulation with similar values of the lattice
parameters.


title: On distortion of normal subgroups

abstract:
  We examine distortion of finitely generated normal subgroups. We show a
connection between subgroup distortion and group divergence. We suggest a
method computing the distortion of normal subgroups by decomposing the whole
group into smaller subgroups. We apply our work to compute the distortion of
normal subgroups of graph of groups and normal subgroups of right-angled Artin
groups that induce infinite cyclic quotient groups. We construct normal
subgroups of $\CAT(0)$ groups introduced by Macura and introduce a collection
of normal subgroups of right-angled Artin groups. These groups provide a rich
source to study the connection between subgroup distortion and group divergence
on $\CAT(0)$ groups.


title:
An Agent-Based Model of Message Propagation in the Facebook Electronic
  Social Network

abstract:
  A large scale agent-based model of common Facebook users was designed to
develop an understanding of the underlying mechanism of information diffusion
within online social networks at a micro-level analysis. The agent-based model
network structure is based on a sample from Facebook. Using an erased
configuration model and the idea of common neighbours, a new correction
procedure was investigated to overcome the problem of missing graph edges to
construct a representative sample of the Facebook network graph. The model
parameters are based on assumptions and general activity patterns (such as
posting rate, time spent on Facebook etc.) taken from general data on Facebook.
Using the agent-based model, the impact of post length, post score and
publisher's friend count on the spread of wall posts in several scenarios was
analyzed. Findings indicated that post content has the highest impact on the
success of post propagation. However, amusing and absorbing but lengthy posts
(e.g. a funny video) do not spread as well as short but unremarkable ones (e.g.
an interesting photo). In contrast to product adoption and disease spread
propagation models, the absence of a similar "epidemic" threshold in Facebook
post diffusion is observed.


title: Reexamination of strong subadditivity: A quantum-correlation approach

abstract:
  The strong subadditivity inequality of von Neumann entropy relates the
entropy of subsystems of a tripartite state $\rho_{ABC}$ to that of the
composite system. Here, we define $\boldsymbol{T}^{(a)}(\rho_{ABC})$ as the
extent to which $\rho_{ABC}$ fails to satisfy the strong subadditivity
inequality $S(\rho_{B})+S(\rho_{C}) \le S(\rho_{AB})+S(\rho_{AC})$ with
equality and investigate its properties. In particular, by introducing
auxiliary subsystem $E$, we consider any purification $|\psi_{ABCE}\rangle$ of
$\rho_{ABC}$ and formulate $\boldsymbol{T}^{(a)}(\rho_{ABC})$ as the extent to
which the bipartite quantum correlations of $\rho_{AB}$ and $\rho_{AC}$,
measured by entanglement of formation and quantum discord, change under the
transformation $B\rightarrow BE$ and $C\rightarrow CE$. Invariance of quantum
correlations of $\rho_{AB}$ and $\rho_{AC}$ under such transformation is shown
to be a necessary and sufficient condition for vanishing
$\boldsymbol{T}^{(a)}(\rho_{ABC})$. Our approach allows one to characterize,
intuitively, the structure of states for which the strong subadditivity is
saturated. Moreover, along with providing a conservation law for quantum
correlations of states for which the strong subadditivity inequality is
satisfied with equality, we find that such states coincides with those that the
Koashi-Winter monogamy relation is saturated.


title: Helium atom excitations by the GW and Bethe-Salpeter many-body formalism

abstract:
  Helium atom is the simplest many-body electronic system provided by nature.
The exact solution to the Schr\"odinger equation is known for helium ground and
excited states, and represents a workbench for any many-body methodology. Here,
we check the ab initio many-body GW approximation and Bethe-Salpeter equation
(BSE) against the exact solution for helium. Starting from Hartree-Fock, we
show that GW and BSE yield impressively accurate results on excitation energies
and oscillator strength, systematically improving time-dependent Hartree-Fock.
These findings suggest that the accuracy of BSE and GW approximations is not
significantly limited by self-interaction and self-screening problems even in
this few electron limit. We further discuss our results in comparison to those
obtained by time-dependent density-functional theory.


title: Continuous-time limit of topological quantum walks

abstract:
  We derive the continuous-time limit of discrete quantum walks with
topological phases. We show the existence of a continuous-time limit that
preserves their topological phases. We consider both simple-step and split-step
walks, and derive analytically equations of motion governing their behavior. We
obtain simple analytical solutions showing the existence of bound states at the
boundary of two phases, and solve the equations of motion numerically in the
bulk.


title:
A problem of Beelen, Garcia and Stichtenoth on an Artin-Schreier tower
  in characteristic two

abstract:
  We study a tower of function fields of Artin-Schreier type over a finite
field with $2^s$ elements. The study of the asymptotic behavior of this tower
was left as an open problem by Beelen, Garc\'ia and Stichtenoth in $2006$. We
prove that this tower is asymptotically good for $s$ even and asymptotically
bad for $s$ odd.