title:
Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino
  event

abstract:
  The discovery of extraterrestrial very-high-energy neutrinos by the IceCube
collaboration has launched a quest for the identification of their
astrophysical sources. Gamma-ray blazars have been predicted to yield a
cumulative neutrino signal exceeding the atmospheric background above energies
of 100 TeV, assuming that both the neutrinos and the gamma-ray photons are
produced by accelerated protons in relativistic jets. Since the background
spectrum falls steeply with increasing energy, the individual events with the
clearest signature of being of an extraterrestrial origin are those at PeV
energies. Inside the large positional-uncertainty fields of the first two PeV
neutrinos detected by IceCube, the integrated emission of the blazar population
has a sufficiently high electromagnetic flux to explain the detected IceCube
events, but fluences of individual objects are too low to make an unambiguous
source association. Here, we report that a major outburst of the blazar PKS
B1424-418 occurred in temporal and positional coincidence with the third
PeV-energy neutrino event (IC35) detected by IceCube. Based on an analysis of
the full sample of gamma-ray blazars in the IC35 field and assuming a
photo-hadronic emission model, we show that the long-term average gamma-ray
emission of blazars as a class is in agreement with both the measured all-sky
flux of PeV neutrinos and the spectral slope of the IceCube signal. The
outburst of PKS B1424-418 has provided an energy output high enough to explain
the observed PeV event, indicative of a direct physical association.


title: Nanodroplets Impacting on Graphene

abstract:
  The unique and remarkable properties of graphene can be exploited as the
basis to a wide range of applications. However, in spite of years of
investigations there are some important graphene properties that are not still
fully understood, as for example, its wettability. There are controversial
reported results whether graphene is really hydrophobic or hydrophilic. In
order to address this problem we have carried out classical molecular dynamics
simulations of water nanodroplets shot against graphene surface. Our results
show that the contact angle values between the nanodroplets and graphene
surfaces depend on the initial droplet velocity value and these angles can
change from 86 degrees (hydrophobic) to 35 degrees (hydrophilic). Our
preliminary results indicate that the graphene wettability can be dependent on
spreading liquid dynamics and which can explain some of the apparent
inconsistencies reported in the literature.


title:
A Density Functional Theory Investigation of Carboranethiol
  Self-Assembled Monolayer on Au(111)

abstract:
  Isolated and full monolayer adsorption of various carboranethiol
(C$_2$B$_{10}$H$_{12}$S) isomers on gold (111) surface have been investigated
using both the standard and van der Waals density functional theoretical
calculations. The effect of differing molecular dipole moment orientations on
the low energy adlayer geometries, the binding characteristics and the
electronic properties of the self-assembled monolayers of these isomers have
been studied. Specifically, the binding energy and work function changes
associated with different molecules show a correlation with their dipole
moments. The adsorption is favored for the isomers with dipole moments parallel
to the surface. Of the two possible unit cell structures, the (5$\times$5) was
found to be more stable than the ($\sqrt{19}\times\sqrt{19}$)R23.4$^o$ one.


title:
Dimension free bounds for the Hardy--Littlewood maximal operator
  associated to convex sets

abstract:
  This survey is based on a series of lectures given by the authors at the
working seminar "Convexit\'e et Probabilit\'es" at UPMC Jussieu, Paris, during
the spring 2013. It is devoted to maximal inequalities associated to symmetric
convex sets in high dimensional linear spaces, a topic mainly developed between
1982 and 1990 but recently renewed by further advances.
  The series focused on proving for these maximal functions inequalities in
$L^p(\mathbb{R}^n)$ with bounds independent of the dimension $n$, for all $p
\in (1, +\infty]$ in the best cases. This program was initiated in 1982 by
Elias Stein, who obtained the first theorem of this kind for the family of
Euclidean balls in arbitrary dimension. We present several results along this
line, proved by Bourgain, Carbery and M\"uller during the period 1986--1990,
and a new one due to Bourgain (2014) for the family of cubes in arbitrary
dimension. We complete the cube case with negative results for the weak type
$(1, 1)$ constant, due to Aldaz, Aubrun and Iakovlev--Str\"omberg between 2009
and 2013.


title: Generic solutions of equations with iterated exponentials

abstract:
  We study solutions of exponential polynomials over the complex field.
Assuming Schanuel's conjecture we prove that certain polynomials have generic
solutions in the complex field.


title: Symmetries for SM Alignment in multi-Higgs Doublet Models

abstract:
  We derive the complete set of continuous maximal symmetries for Standard
Model (SM) alignment that may occur in the tree-level scalar potential of
multi-Higgs Doublet Models, with $n > 2$ Higgs doublets. Our results generalize
the symmetries of SM alignment, without decoupling of large mass scales or
fine-tuning, previously obtained in the context of two-Higgs Doublet Models.


title: Compressive Spectral Clustering

abstract:
  Spectral clustering has become a popular technique due to its high
performance in many contexts. It comprises three main steps: create a
similarity graph between N objects to cluster, compute the first k eigenvectors
of its Laplacian matrix to define a feature vector for each object, and run
k-means on these features to separate objects into k classes. Each of these
three steps becomes computationally intensive for large N and/or k. We propose
to speed up the last two steps based on recent results in the emerging field of
graph signal processing: graph filtering of random signals, and random sampling
of bandlimited graph signals. We prove that our method, with a gain in
computation time that can reach several orders of magnitude, is in fact an
approximation of spectral clustering, for which we are able to control the
error. We test the performance of our method on artificial and real-world
network data.


title:
Cartan geometries modeled on skeletons and morphisms induced by
  extension functors

abstract:
  The extension functors between categories of Cartan geometries can be used to
define different categories of Cartan geometries with additional morphisms. The
Cartan geometries modeled on skeletons can be used for the description of such
categories of Cartan geometries and therefore we develop the theory of Cartan
geometries modeled on skeletons, in detail. In particular, we show that there
are functors from the categories of Cartan geometries with morphisms induced by
extension functors to certain categories of Cartan geometries modeled on
skeletons with the usual morphisms. We study how to compute (infinitesimal)
automorphisms of Cartan geometries modeled on skeletons and how to compute the
morphisms induced by the extension functors for particular Cartan geometries.
Some examples and applications of the morphisms induced by extension functors
are presented in the setting of the Riemannian geometries.


title: Analysis of the ensemble Kalman filter for inverse problems

abstract:
  The ensemble Kalman filter (EnKF) is a widely used methodology for state
estimation in partial, noisily observed dynamical systems, and for parameter
estimation in inverse problems. Despite its widespread use in the geophysical
sciences, and its gradual adoption in many other areas of application, analysis
of the method is in its infancy. Furthermore, much of the existing analysis
deals with the large ensemble limit, far from the regime in which the method is
typically used. The goal of this paper is to analyze the method when applied to
inverse problems with fixed ensemble size. A continuous-time limit is derived
and the long-time behavior of the resulting dynamical system is studied. Most
of the rigorous analysis is confined to the linear forward problem, where we
demonstrate that the continuous time limit of the EnKF corresponds to a set of
gradient flows for the data misfit in each ensemble member, coupled through a
common pre-conditioner which is the empirical covariance matrix of the
ensemble. Numerical results demonstrate that the conclusions of the analysis
extend beyond the linear inverse problem setting. Numerical experiments are
also given which demonstrate the benefits of various extensions of the basic
methodology.


title: Holomorphic extensions associated with series expansions

abstract:
  We study the holomorphic extension associated with power series, i.e., the
analytic continuation from the unit disk to the cut-plane $\mathbb{C} \setminus
[1,+\infty)$. Analogous results are obtained also in the study of trigonometric
series: we establish conditions on the series coefficients which are sufficient
to guarantee the series to have a KMS analytic structure. In the case of power
series we show the connection between the unique (Carlsonian) interpolation of
the coefficients of the series and the Laplace transform of a probability
distribution. Finally, we outline a procedure which allows us to obtain a
numerical approximation of the jump function across the cut starting from a
finite number of power series coefficients. By using the same methodology, the
thermal Green functions at real time can be numerically approximated from the
knowledge of a finite number of noisy Fourier coefficients in the expansion of
the thermal Green functions along the imaginary axis of the complex time plane.


title: Preoperative Volume Determination for Pituitary Adenoma

abstract:
  The most common sellar lesion is the pituitary adenoma, and sellar tumors are
approximately 10-15% of all intracranial neoplasms. Manual slice-by-slice
segmentation takes quite some time that can be reduced by using the appropriate
algorithms. In this contribution, we present a segmentation method for
pituitary adenoma. The method is based on an algorithm that we have applied
recently to segmenting glioblastoma multiforme. A modification of this scheme
is used for adenoma segmentation that is much harder to perform, due to lack of
contrast-enhanced boundaries. In our experimental evaluation, neurosurgeons
performed manual slice-by-slice segmentation of ten magnetic resonance imaging
(MRI) cases. The segmentations were compared to the segmentation results of the
proposed method using the Dice Similarity Coefficient (DSC). The average DSC
for all datasets was 75.92% +/- 7.24%. A manual segmentation took about four
minutes and our algorithm required about one second.


title: Efficient Multi-view Performance Capture of Fine-Scale Surface Detail

abstract:
  We present a new effective way for performance capture of deforming meshes
with fine-scale time-varying surface detail from multi-view video. Our method
builds up on coarse 4D surface reconstructions, as obtained with commonly used
template-based methods. As they only capture models of coarse-to-medium scale
detail, fine scale deformation detail is often done in a second pass by using
stereo constraints, features, or shading-based refinement. In this paper, we
propose a new effective and stable solution to this second step. Our framework
creates an implicit representation of the deformable mesh using a dense
collection of 3D Gaussian functions on the surface, and a set of 2D Gaussians
for the images. The fine scale deformation of all mesh vertices that maximizes
photo-consistency can be efficiently found by densely optimizing a new
model-to-image consistency energy on all vertex positions. A principal
advantage is that our problem formulation yields a smooth closed form energy
with implicit occlusion handling and analytic derivatives. Error-prone
correspondence finding, or discrete sampling of surface displacement values are
also not needed. We show several reconstructions of human subjects wearing
loose clothing, and we qualitatively and quantitatively show that we robustly
capture more detail than related methods.


title:
Phonon dispersions and Fermi surfaces nesting explaining the variety of
  charge ordering in titanium-oxypnictides superconductors

abstract:
  There has been a puzzle between experiments and theoretical predictions on
the charge ordering of layered titanium-oxypnictides superconductors.
Unconventional mechanisms to explain this discrepancy have been argued so far,
even affecting the understanding of superconductivity on the compound. We
provide a new theoretical prediction, by which the discrepancy itself is
resolved without any complicated unconventional explanation. Phonon dispersions
and changes of nesting vectors in Fermi surfaces are clarified to lead to the
variety of superlattice structures even for the common crystal structures when
without CDW, including orthorhombic $2 \times 2 \times 1$ one for
BaTi$_2$As$_2$O, which has not yet been explained successfully so far, being
different from tetragonal $\sqrt{2} \times \sqrt{2} \times 1$ for
BaTi$_2$Sb$_2$O and BaTi$_2$Bi$_2$O. The electronic structure analysis can
naturally explain experimental observations about CDW including most latest
ones without any cramped unconventional mechanisms.


title: A novel type of splayed ferromagnetic order observed in Yb2Ti2O7

abstract:
  The pyrochlore insulator Yb2Ti2O7 has attracted the attention of
experimentalists and theoreticians alike for about 15 years. Conflicting
neutron diffraction data on the possible existence of magnetic Bragg
reflections at low temperature have been published. Here we report the
observation of magnetic Bragg reflections by neutron powder diffraction at 60
mK. The magnetic diffraction pattern is analyzed using representation theory.
We find Yb2Ti2O7 to be a splayed ferromagnet as reported for Yb2Sn2O7, a
sibling compound with also dominating ferromagnetic interactions as inferred
from the positive Curie-Weiss temperature. However, the configuration of the
magnetic moment components perpendicular to the easy axis is of the
all-in--all-out type in Yb2Ti2O7 while it is two-in--two-out in Yb2Sn2O7. An
overall experimental picture of the magnetic properties emerges.


title: Graph parameters from symplectic group invariants

abstract:
  In this paper we introduce, and characterize, a class of graph parameters
obtained from tensor invariants of the symplectic group. These parameters are
similar to partition functions of vertex models, as introduced by de la Harpe
and Jones, [P. de la Harpe, V.F.R. Jones, Graph invariants related to
statistical mechanical models: examples and problems, Journal of Combinatorial
Theory, Series B 57 (1993) 207-227]. Yet they give a completely different class
of graph invariants. We moreover show that certain evaluations of the cycle
partition polynomial, as defined by Martin [P. Martin, Enum\'erations
eul\'eriennes dans les multigraphes et invariants de Tutte-Grothendieck, Diss.
Institut National Polytechnique de Grenoble-INPG; Universit\'e
Joseph-Fourier-Grenoble I, 1977], give examples of graph parameters that can be
obtained this way.


title: On the Adjoint Operator in Photoacoustic Tomography

abstract:
  Photoacoustic Tomography (PAT) is an emerging biomedical "imaging from
coupled physics" technique, in which the image contrast is due to optical
absorption, but the information is carried to the surface of the tissue as
ultrasound pulses. Many algorithms and formulae for PAT image reconstruction
have been proposed for the case when a complete data set is available. In many
practical imaging scenarios, however, it is not possible to obtain the full
data, or the data may be sub-sampled for faster data acquisition. In such
cases, image reconstruction algorithms that can incorporate prior knowledge to
ameliorate the loss of data are required. Hence, recently there has been an
increased interest in using variational image reconstruction. A crucial
ingredient for the application of these techniques is the adjoint of the PAT
forward operator, which is described in this article from physical, theoretical
and numerical perspectives. First, a simple mathematical derivation of the
adjoint of the PAT forward operator in the continuous framework is presented.
Then, an efficient numerical implementation of the adjoint using a k-space time
domain wave propagation model is described and illustrated in the context of
variational PAT image reconstruction, on both 2D and 3D examples including
inhomogeneous sound speed. The principal advantage of this analytical adjoint
over an algebraic adjoint (obtained by taking the direct adjoint of the
particular numerical forward scheme used) is that it can be implemented using
currently available fast wave propagation solvers.


title: A note on actions of some monoids

abstract:
  Smooth actions of the multiplicative monoid $(\mathbb{R},\cdot)$ of real
numbers on manifolds lead to an alternative, and for some reasons simpler,
definition of a vector bundle, a double vector bundle and related structures
like a graded bundle [Grabowski and Rotkiewicz, J. Geom. Phys. 2011]. For these
reasons it is natural to study smooth actions of certain monoids closely
related with the monoid $(\mathbb{R},\cdot)$ . Namely, we discuss geometric
structures naturally related with: smooth and holomorphic actions of the monoid
of multiplicative complex numbers, smooth actions of the monoid of second jets
of punctured maps $(\mathbb{R},0)\rightarrow (\mathbb{R},0)$, smooth action of
the monoid of real 2 by 2 matrices and smooth actions of multiplicative reals
on a supermanifold. In particular cases we recover the notions of a holomorphic
vector bundle, a complex vector bundle and a non-negatively graded manifold.


title:
High order flow harmonics of identified hadrons in 2.76 A TeV Pb+Pb
  collisions

abstract:
  Using iEBE-VISHNU hybrid model with the AMPT initial conditions, we study the
higher order flow harmonics of identified hadrons in 2.76 A TeV Pb+Pb
collisions. Comparison with the recent ALICE measurements at 20-30\% centrality
shows that our calculations nicely describe the data below 2 GeV, especially
for the $v_2$, $v_3$ and $v_4$ mass-orderings among pions, kaons and protons.
We also extended the calculations to other centrality bins, which presents
similar mass-ordering patterns for these flow harmonics as the ones observed at
20-30\% centrality. In the later part of this article, we explore the
development of $v_n$ mass ordering/splitting during the hadronic evolution
through the comparison runs from iEBE-VISHNU hybrid model and pure
hydrodynamics with different decoupling temperatures.


title:
Adaptation Logic for HTTP Dynamic Adaptive Streaming using
  Geo-Predictive Crowdsourcing

abstract:
  The increasing demand for video streaming services with high Quality of
Experience (QoE) has prompted a lot of research on client-side adaptation logic
approaches. However, most algorithms use the client's previous download
experience and do not use a crowd knowledge database generated by users of a
professional service. We propose a new crowd algorithm that maximizes the QoE.
Additionally, we show how crowd information can be integrated into existing
algorithms and illustrate this with two state-of-the-art algorithms. We
evaluate our algorithm and state-of-the-art algorithms (including our modified
algorithms) on a large, real-life crowdsourcing dataset that contains 336,551
samples on network performance. The dataset was provided by WeFi LTD. Our new
algorithm outperforms all other methods in terms of QoS (eMOS).


title:
Formulation of Liouville's Theorem for Grand Ensemble Molecular
  Simulations

abstract:
  Liouville's theorem in a grand ensemble, that is for situations where a
system is in equilibrium with a reservoir of energy and particles, is a subject
that, to our knowledge, has not been explicitly treated in literature related
to molecular simulation. Instead Liouville's theorem, a central concept for the
correct employment of molecular simulation techniques, is implicitly considered
only within the framework of systems where the total number of particles is
fixed. However the pressing demand of applied science in treating open systems
leads to the question of the existence and possible exact formulation of
Liouville's theorem when the number of particles changes during the dynamical
evolution of the system. The intention of this note is to stimulate a debate
about this crucial issue for molecular simulation.

categories: cond-mat.stat-mech math-ph math.MP physics.comp-ph


title:
Track selection in Multifunction Radars for Multi-target tracking: an
  Anti-Coordination game

abstract:
  In this paper, a track selection problem for multi-target tracking in a
multifunction radar network is studied using the concepts from game theory. The
problem is formulated as a non-cooperative game, and specifically as an
anti-coordination game, where each player aims to differ from what other
players do. The players' utilities are modeled using a proper tracking accuracy
criterion and, under different assumptions on the structure of these utilities,
the corresponding Nash equilibria are characterized. To find an equilibrium, a
distributed algorithm based on the best-response dynamics is proposed. Finally,
computer simulations are carried out to verify the effectiveness of the
proposed algorithm in a multi-target tracking scenario.


title: Developing Mathematical Creativity with Physics Invention Tasks

abstract:
  Modeling the creative mathematical sensemaking that characterizes expert
thinking in physics is typically a struggle for new learners. To help students
learn to reason this way, we created a set of supplemental activities called
Physics Invention Tasks (PITs)*. PITs engage students in quantification, the
process of mathematically generating quantities central to modeling in physics.
PITs depict a scenario in which students need to engage in decision-making
associated with creating quantities in order to resolve a problem. Students
make decisions about the arithmetic construction, the magnitude and associated
unit, and in some cases spatial direction of a new quantity. The design of PITs
is informed by Inventing with Contrasting Cases, an instructional approach
shown to foster generativity, i.e., creativity with mathematical structures. In
this paper, we describe the theoretical foundation of PITs, and their structure
and implementation. We share preliminary observations of the impact of PITs in
one course, averaged over two years, as measured by the FCI and CLASS. We see
an improvement in the FCI normalized gain corresponding to the introduction of
PITS and we see CLASS pre- to post-test gains that may be the highest reported
from a large enrollment calculus-based physics course. We discuss future
research into the learning mechanisms and instructor influence associated with
PITs.
  *available at http://inventiontasks.physics.rutgers.edu


title:
Diagnosis of interaction-driven topological phase via exact
  diagonalization

abstract:
  We propose a general scheme for diagnosing interaction-driven topological
phases in the weak interaction regime using exact diagonalization (ED). The
scheme comprises the analysis of eigenvalues of the point-group operators for
the many-body eigenstates and the correlation functions for physical
observables to extract the symmetries of the order parameters and the
topological numbers of the underlying ground states at the thermodynamic limit
from a relatively small size system afforded by ED. As a concrete example, we
investigate the interaction effects on the half-filled spinless fermions on the
checkerboard lattice with a quadratic band crossing point. Numerical results
support the existence of a spontaneous quantum anomalous Hall phase purely
driven by a nearest-neighbor weak repulsive interaction, separated from a
nematic Mott insulator phase at strong repulsive interaction by a first-order
phase transition.


title: PDFs from nucleons to nuclei

abstract:
  I review recent progress in the extraction of unpolarized parton
distributions in the proton and in nuclei from a unified point of view that
highlights how the interplay between high energy particle physics and lower
energy nuclear physics can be of mutual benefit to either field. Areas of
overlap range from the search for physics beyond the standard model at the LHC,
to the study of the non perturbative structure of nucleons and the emergence of
nuclei from quark and gluon degrees of freedom, to the interaction of colored
probes in a cold nuclear medium.


title: Classical capacities of quantum channels with environment assistance

abstract:
  A quantum channel physically is a unitary interaction between the information
carrying system and an environment, which is initialized in a pure state before
the interaction. Conventionally, this state, as also the parameters of the
interaction, is assumed to be fixed and known to the sender and receiver. Here,
following the model introduced by us earlier [Karumanchi et al.,
arXiv[quant-ph]:1407.8160], we consider a benevolent third party, i.e. a
helper, controlling the environment state, and how the helper's presence
changes the communication game. In particular, we define and study the
classical capacity of a unitary interaction with helper, indeed two variants,
one where the helper can only prepare separable states across many channel
uses, and one without this restriction. Furthermore, the two even more powerful
scenarios of pre-shared entanglement between helper and receiver, and of
classical communication between sender and helper (making them conferencing
encoders) are considered.


title: A Class of Integrable Metrics

abstract:
  In four dimensions, the most general metric admitting two Killing vectors and
a rank-two Killing tensor can be parameterized by ten arbitrary functions of a
single variable. We show that picking a special vierbien, reducing the system
to eight functions, implies the existence of two geodesic and share-free, null
congruences, generated by two principal null directions of the Weyl tensor.
Thus, if the spacetime is an Einstein manifold, the Goldberg-Sachs theorem
implies it is Petrov type D, and by explicit construction, is in the Carter
class. Hence, our analysis provide an straightforward connection between the
most general integrable structure and the Carter family of spacetimes.


title:
Correlation functions of three-dimensional Yang-Mills theory from
  Dyson-Schwinger equations

abstract:
  The two- and three-point functions and the four-gluon vertex of
three-dimensional Yang-Mills theory are calculated from their Dyson-Schwinger
equations and the 3PI effective action. Within a self-contained truncation
various effects of truncating Dyson-Schwinger equations are studied. Estimates
for the errors induced by truncations are derived from comparisons between
results from different equations, comparisons with lattice results, and varying
higher Green functions. The results indicate that the two-loop diagrams are
important in the gluon propagator, where they are explicitly calculated, but
not for the vertices. Furthermore, the influence of the four-gluon vertex on
lower Green functions is found to be small.


title: Holographic Construction of Excited CFT States

abstract:
  We present a systematic construction of bulk solutions that are dual to CFT
excited states. The bulk solution is constructed perturbatively in bulk fields.
The linearised solution is universal and depends only on the conformal
dimension of the primary operator that is associated with the state via the
operator-state correspondence, while higher order terms depend on detailed
properties of the operator, such as its OPE with itself and generally involve
many bulk fields. We illustrate the discussion with the holographic
construction of the universal part of the solution for states of two
dimensional CFTs, either on $R \times S^1$ or on $R^{1,1}$. We compute the
1-point function both in the CFT and in the bulk, finding exact agreement. We
comment on the relation with other reconstruction approaches.


title:
Efficient and Scalable Distributed Autonomous Spatial Aloha Networks via
  Local Leader Election

abstract:
  This paper uses a spatial Aloha model to describe a distributed autonomous
wireless network in which a group of transmit-receive pairs (users) shares a
common collision channel via slotted-Aloha-like random access. The objective of
this study is to develop an intelligent algorithm to be embedded into the
transceivers so that all users know how to self-tune their medium access
probability (MAP) to achieve overall Pareto optimality in terms of network
throughput under spatial reuse while maintaining network stability. While the
optimal solution requires each user to have complete information about the
network, our proposed algorithm only requires users to have local information.
The fundamental of our algorithm is that the users will first self-organize
into a number of non-overlapping neighborhoods, and the user with the maximum
node degree in each neighborhood is elected as the local leader (LL). Each LL
then adjusts its MAP according to a parameter R which indicates the radio
intensity level in its neighboring region, whereas the remaining users in the
neighborhood simply follow the same MAP value. We show that by ensuring R less
than or equal to 2 at the LLs, the stability of the entire network can be
assured even when each user only has partial network information. For practical
implementation, we propose each LL to use R=2 as the constant reference signal
to its built-in proportional and integral controller. The settings of the
control parameters are discussed and we validate through simulations that the
proposed method is able to achieve close-to-Pareto-front throughput.


title:
Analysis of Network Coding in a Slotted ALOHA-based Two-Way Relay
  Network

abstract:
  This paper deals with a two-way relay network (TWRN) based on a slotted ALOHA
protocol which utilizes network coding to exchange the packets. We proposed an
analytical approach to study the behavior of such networks and the effects of
network coding on the throughput, power, and queueing delay of the relay node.
In addition, when end nodes are not saturated, our approach enables us to
achieve the stability region of the network in different situations. Finally,
we carry out some simulation to confirm the validity of the proposed analytical
approach.


title:
Exact solution of the trigonometric SU(3) spin chain with generic
  off-diagonal boundary reflections

abstract:
  The nested off-diagonal Bethe ansatz is generalized to study the quantum spin
chain associated with the $SU_q(3)$ R-matrix and generic integrable
non-diagonal boundary conditions. By using the fusion technique, certain closed
operator identities among the fused transfer matrices at the inhomogeneous
points are derived. The corresponding asymptotic behaviors of the transfer
matrices and their values at some special points are given in detail. Based on
the functional analysis, a nested inhomogeneous T-Q relations and Bethe ansatz
equations of the system are obtained. These results can be naturally
generalized to cases related to the $SU_q(n)$ algebra.

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


title: A Bivariant Theory for the Cuntz Semigroup

abstract:
  We introduce a bivariant version of the Cuntz semigroup as equivalence
classes of order zero maps generalizing the ordinary Cuntz semigroup. The
theory has many properties formally analogous to KK-theory including a
composition product. We establish basic properties, like additivity, stability
and continuity, and study categorical aspects in the setting of local
C*-algebras. We determine the bivariant Cuntz semigroup for numerous examples
such as when the second algebra is a Kirchberg algebra, and Cuntz homology for
compact Hausdorff spaces which provides a complete invariant. Moreover, we
establish identities when tensoring with strongly self-absorbing C*-algebras.
Finally, we show that the bivariant Cuntz semigroup of the present work can be
used to classify all unital and stably finite C*-algebras.


title:
Recursive Starlight and Bias Estimation for High-Contrast Imaging with
  an Extended Kalman Filter

abstract:
  For imaging faint exoplanets and disks, a coronagraph-equipped observatory
needs focal plane wavefront correction to recover high contrast. The most
efficient correction methods iteratively estimate the stellar electric field
and suppress it with active optics. The estimation requires several images from
the science camera per iteration. To maximize the science yield, it is
desirable both to have fast wavefront correction and to utilize all the
correction images for science target detection. Exoplanets and disks are
incoherent with their stars, so a nonlinear estimator is required to estimate
both the incoherent intensity and the stellar electric field. Such techniques
assume a high level of stability found only on space-based observatories and
possibly ground-based telescopes with extreme adaptive optics. In this paper,
we implement a nonlinear estimator, the iterated extended Kalman filter (IEKF),
to enable fast wavefront correction and a recursive, nearly-optimal estimate of
the incoherent light. In Princeton's High Contrast Imaging Laboratory we
demonstrate that the IEKF allows wavefront correction at least as fast as with
a Kalman filter and provides the most accurate detection of a faint companion.
The nonlinear IEKF formalism allows us to pursue other strategies such as
parameter estimation to improve wavefront correction.


title:
Fuzzy Logic Control of a Hybrid Energy Storage Module for Naval Pulsed
  Power Applications

abstract:
  There is need for an energy storage device capable of transferring high power
in transient situations aboard naval vessels. Currently, batteries are used to
accomplish this task, but previous research has shown that when utilized at
high power rates, these devices deteriorate over time causing a loss in
lifespan. It has been shown that a hybrid energy storage configuration is
capable of meeting such a demand while reducing the strain placed on individual
components. While designing a custom converter capable of controlling the power
to and from a battery would be ideal for this application, it can be costly to
develop when compared to purchasing commercially available products.
Commercially available products offer limited controllability in exchange for
their proven performance and lower cost point - often times only allowing a
system level control input without any way to interface with low level controls
that are frequently used in controller design. This paper proposes the use of
fuzzy logic control in order to provide a system level control to the
converters responsible for limiting power to and from the battery. A system
will be described mathematically, modeled in MATLAB/Simulink, and a fuzzy logic
controller will be compared with a typical controller.


title: MyAdChoices: Bringing Transparency and Control to Online Advertising

abstract:
  The intrusiveness and the increasing invasiveness of online advertising have,
in the last few years, raised serious concerns regarding user privacy and Web
usability. As a reaction to these concerns, we have witnessed the emergence of
a myriad of ad-blocking and anti-tracking tools, whose aim is to return control
to users over advertising. The problem with these technologies, however, is
that they are extremely limited and radical in their approach: users can only
choose either to block or allow all ads. With around 200 million people
regularly using these tools, the economic model of the Web ---in which users
get content free in return for allowing advertisers to show them ads--- is at
serious peril. In this paper, we propose a smart Web technology that aims at
bringing transparency to online advertising, so that users can make an informed
and equitable decision regarding ad blocking. The proposed technology is
implemented as a Web-browser extension and enables users to exert fine-grained
control over advertising, thus providing them with certain guarantees in terms
of privacy and browsing experience, while preserving the Internet economic
model. Experimental results in a real environment demonstrate the suitability
and feasibility of our approach, and provide preliminary findings on behavioral
targeting from real user browsing profiles.


title:
Utiliza\c{c}\~ao de Grafos e Matriz de Similaridade na Sumariza\c{c}\~ao
  Autom\'atica de Documentos Baseada em Extra\c{c}\~ao de Frases

abstract:
  The internet increased the amount of information available. However, the
reading and understanding of this information are costly tasks. In this
scenario, the Natural Language Processing (NLP) applications enable very
important solutions, highlighting the Automatic Text Summarization (ATS), which
produce a summary from one or more source texts. Automatically summarizing one
or more texts, however, is a complex task because of the difficulties inherent
to the analysis and generation of this summary. This master's thesis describes
the main techniques and methodologies (NLP and heuristics) to generate
summaries. We have also addressed and proposed some heuristics based on graphs
and similarity matrix to measure the relevance of judgments and to generate
summaries by extracting sentences. We used the multiple languages (English,
French and Spanish), CSTNews (Brazilian Portuguese), RPM (French) and DECODA
(French) corpus to evaluate the developped systems. The results obtained were
quite interesting.


title:
The Gibbons--Tsarev equation: symmetries, invariant solutions, and
  applications

abstract:
  In this paper we present the full classification of the symmetry-invariant
solutions for the Gibbons--Tsarev equation. Then we use these solutions to
construct explicit expressions for reductions of Benney's moments equations, to
get solutions of Pavlov's equation, and to find integrable reductions of the
Ferapontov--Huard--Zhang system, which describes implicit two-phase solutions
of the dKP equation.


title:
A fast, deterministic algorithm for computing a Hermite Normal Form of a
  polynomial matrix

abstract:
  Given a square, nonsingular matrix of univariate polynomials $\mathbf{F} \in
\mathbb{K}[x]^{n \times n}$ over a field $\mathbb{K}$, we give a fast,
deterministic algorithm for finding the Hermite normal form of $\mathbf{F}$
with complexity $O^{\sim}\left(n^{\omega}d\right)$ where $d$ is the degree of
$\mathbf{F}$. Here soft-$O$ notation is Big-$O$ with log factors removed and
$\omega$ is the exponent of matrix multiplication. The method relies of a fast
algorithm for determining the diagonal entries of its Hermite normal form,
having as cost $O^{\sim}\left(n^{\omega}s\right)$ operations with $s$ the
average of the column degrees of $\mathbf{F}$.


title:
Recovery rate affects the effective epidemic threshold with synchronous
  updating

abstract:
  Accurate identification of effective epidemic threshold is essential for
understanding epidemic dynamics on complex networks. The existing studies on
the effective epidemic threshold of the susceptible-infected-removed (SIR)
model generally assume that all infected nodes immediately recover after the
infection process, which more or less does not conform to the realistic
situation of disease. In this paper, we systematically study the effect of
arbitrary recovery rate on the SIR spreading dynamics on complex networks. We
derive the theoretical effective epidemic threshold and final outbreak size
based on the edge-based compartmental theory. To validate the proposed
theoretical predictions, extensive numerical experiments are implemented by
using asynchronous and synchronous updating methods. When asynchronous updating
method is used in simulations, recovery rate does not affect the final state of
spreading dynamics. But with synchronous updating, we find that the effective
epidemic threshold decreases with recovery rate, and final outbreak size
increases with recovery rate. A good agreement between the theoretical
predictions and numerical results are observed on both synthetic and real-world
networks. Our results extend the existing theoretical studies, and help us to
understand the phase transition with arbitrary recovery rate.


title: Frustrated polaritons

abstract:
  Artificially engineered light-matter systems constitute a novel, versatile
architecture for the quantum simulation of driven, dissipative phase
transitions and non-equilibrium quantum many-body systems. Here, we review
recent experimental as well as theoretical works on the simulation of
geometrical frustration in interacting photonic systems out of equilibrium. In
particular, we discuss two recent discoveries at the interface of quantum
optics and condensed matter physics: (i) the experimental achievement of
bosonic condensation into a flat energy band and (ii) the theoretical
prediction of crystalline phases of light in a frustrated qubit-cavity array.
We show that this new line of research leads to novel and unique tools for the
experimental investigation of frustrated systems and holds the potential to
create new phases of light and matter with interesting spatial structure.

categories: cond-mat.mes-hall cond-mat.quant-gas cond-mat.str-el physics.optics quant-ph


title: A Comparison of 10 Sampling Algorithms for Configurable Systems

abstract:
  Almost every software system provides configuration options to tailor the
system to the target platform and application scenario. Often, this
configurability renders the analysis of every individual system configuration
infeasible. To address this problem, researchers have proposed a diverse set of
sampling algorithms. We present a comparative study of 10 state-of-the-art
sampling algorithms regarding their fault-detection capability and size of
sample sets. The former is important to improve software quality and the latter
to reduce the time of analysis. In a nutshell, we found that sampling
algorithms with larger sample sets are able to detect higher numbers of faults,
but simple algorithms with small sample sets, such as most-enabled-disabled,
are the most efficient in most contexts. Furthermore, we observed that the
limiting assumptions made in previous work influence the number of detected
faults, the size of sample sets, and the ranking of algorithms. Finally, we
have identified a number of technical challenges when trying to avoid the
limiting assumptions, which questions the practicality of certain sampling
algorithms.


title: Instability in electromagnetically driven flows Part I

abstract:
  The MHD flow driven by a travelling magnetic field (TMF) in an annular
channel is investigated numerically. For sufficiently large magnetic Reynolds
number Rm, or if a large enough pressure gradient is externally applied, the
system undergoes an instability in which the flow rate in the channel
dramatically drops from synchronism with the wave to much smaller velocities.
This transition takes the form of a saddle-node bifurcation for the
time-averaged quantities. In this first paper, we characterize the bifurcation,
and study the stability of the flow as a function of several parameters. We
show that the bifurcation of the flow involves a bistability between
Poiseuille-like and Hartman-like regimes, and relies on magnetic flux
expulsion. Based on this observation, new predictions are made for the
occurrence of this stalling instability.


title:
Competing collinear magnetic structures in superconducting FeSe by first
  principles quantum Monte Carlo calculations

abstract:
  Resolving the interplay between magnetic interactions and structural
properties in strongly correlated materials through a quantitatively accurate
approach has been a major challenge in condensed matter physics. Here we apply
highly accurate first principles quantum Monte Carlo (QMC) techniques to obtain
structural and magnetic properties of the iron selenide (FeSe) superconductor
under pressure. Where comparable, the computed properties are very close to the
experimental values. Of potential ordered magnetic configurations, collinear
spin configurations are the most energetically favorable over the explored
pressure range. They become nearly degenerate in energy with bicollinear spin
orderings at around 7 GPa, when the experimental critical temperature $T_c$ is
the highest. On the other hand, ferromagnetic, checkerboard, and staggered
dimer configurations become relatively higher in energy as the pressure
increases. The behavior under pressure is explained by an accurate analysis of
the charge compressibility and the orbital occupation as described by the QMC
many-body wave function, which reveals how spin, charge and orbital degrees of
freedom are strongly coupled in this compound. This remarkable pressure
evolution suggests that stripe-like magnetic fluctuations may be responsible
for the enhanced $T_c$ in FeSe and that higher T$_c$ is associated with
nearness to a crossover between collinear and bicollinear ordering.


title: Bayesian aggregation of average data: An application in drug development

abstract:
  Throughout the different phases of a drug development program, randomized
trials are used to establish the tolerability, safety, and efficacy of a
candidate drug. At each stage one aims to optimize the design of future studies
by extrapolation from the available evidence at the time. This includes
collected trial data and relevant external data. However, relevant external
data are typically available as averages only, for example from trials on
alternative treatments reported in the literature. Here we report on such an
example from a drug development for wet age-related macular degeneration. This
disease is the leading cause of severe vision loss in the elderly. While
current treatment options are efficacious, they are also a substantial burden
for the patient. Hence, new treatments are under development which need to be
compared against existing treatments. The general statistical problem this
leads to is meta-analysis, which addresses the question of how we can combine
datasets collected under different conditions. Bayesian methods have long been
used to achieve partial pooling. Here we consider the challenge when the model
of interest is complex (hierarchical and nonlinear) and one dataset is given as
raw data while the second dataset is given as averages only. In such a
situation, common meta-analytic methods can only be applied when the model is
sufficiently simple for analytic approaches. When the model is too complex, for
example nonlinear, an analytic approach is not possible. We provide a Bayesian
solution by using simulation to approximately reconstruct the likelihood of the
external summary and allowing the parameters in the model to vary under the
different conditions. We first evaluate our approach using fake-data
simulations and then report results for the drug development program that
motivated this research.


title:
Two-channel Kondo effect and renormalization flow with macroscopic
  quantum charge states

abstract:
  Many-body correlations and macroscopic quantum behaviors are fascinating
condensed matter problems. A powerful test-bed for the many-body concepts and
methods is the Kondo model which entails the coupling of a quantum impurity to
a continuum of states. It is central in highly correlated systems and can be
explored with tunable nanostructures. Although Kondo physics is usually
associated with the hybridization of itinerant electrons with microscopic
magnetic moments, theory predicts that it can arise whenever degenerate quantum
states are coupled to a continuum. Here we demonstrate the previously elusive
`charge' Kondo effect in a hybrid metal-semiconductor implementation of a
single-electron transistor, with a quantum pseudospin-1/2 constituted by two
degenerate macroscopic charge states of a metallic island. In contrast to other
Kondo nanostructures, each conduction channel connecting the island to an
electrode constitutes a distinct and fully tunable Kondo channel, thereby
providing an unprecedented access to the two-channel Kondo effect and a clear
path to multi-channel Kondo physics. Using a weakly coupled probe, we reveal
the renormalization flow, as temperature is reduced, of two Kondo channels
competing to screen the charge pseudospin. This provides a direct view of how
the predicted quantum phase transition develops across the symmetric quantum
critical point. Detuning the pseudospin away from degeneracy, we demonstrate,
on a fully characterized device, quantitative agreement with the predictions
for the finite-temperature crossover from quantum criticality.


title: A Generalised Differential Framework for Measuring Signal Sparsity

abstract:
  The notion of signal sparsity has been gaining increasing interest in
information theory and signal processing communities. As a consequence, a
plethora of sparsity metrics has been presented in the literature. The
appropriateness of these metrics is typically evaluated against a set of
objective criteria that has been proposed for assessing the credibility of any
sparsity metric. In this paper, we propose a Generalised Differential Sparsity
(GDS) framework for generating novel sparsity metrics whose functionality is
based on the concept that sparsity is encoded in the differences among the
signal coefficients. We rigorously prove that every metric generated using GDS
satisfies all the aforementioned criteria and we provide a computationally
efficient formula that makes GDS suitable for high-dimensional signals. The
great advantage of GDS is its flexibility to offer sparsity metrics that can be
well-tailored to certain requirements stemming from the nature of the data and
the problem to be solved. This is in contrast to current state-of-the-art
sparsity metrics like Gini Index (GI), which is actually proven to be only a
specific instance of GDS, demonstrating the generalisation power of our
framework. In verifying our claims, we have incorporated GDS in a stochastic
signal recovery algorithm and experimentally investigated its efficacy in
reconstructing randomly projected sparse signals. As a result, it is proven
that GDS, in comparison to GI, both loosens the bounds of the assumed sparsity
of the original signals and reduces the minimum number of projected dimensions,
required to guarantee an almost perfect reconstruction of heavily compressed
signals. The superiority of GDS over GI in conjunction with the fact that the
latter is considered as a standard in numerous scientific domains, prove the
great potential of GDS as a general purpose framework for measuring sparsity.


title:
Time resolution of the plastic scintillator strips with matrix
  photomultiplier readout for J-PET tomograph

abstract:
  Recent tests of a single module of the Jagiellonian Positron Emission
Tomography system (J-PET) consisting of 30 cm long plastic scintillator strips
have proven its applicability for the detection of annihilation quanta (0.511
MeV) with a coincidence resolving time (CRT) of 0.266 ns. The achieved
resolution is almost by a factor of two better with respect to the current
TOF-PET detectors and it can still be improved since, as it is shown in this
article, the intrinsic limit of time resolution for the determination of time
of the interaction of 0.511 MeV gamma quanta in plastic scintillators is much
lower. As the major point of the article, a method allowing to record
timestamps of several photons, at two ends of the scintillator strip, by means
of matrix of silicon photomultipliers (SiPM) is introduced. As a result of
simulations, conducted with the number of SiPM varying from 4 to 42, it is
shown that the improvement of timing resolution saturates with the growing
number of photomultipliers, and that the 2 x 5 configuration at two ends
allowing to read twenty timestamps, constitutes an optimal solution. The
conducted simulations accounted for the emission time distribution, photon
transport and absorption inside the scintillator, as well as quantum efficiency
and transit time spread of photosensors, and were checked based on the
experimental results. Application of the 2 x 5 matrix of SiPM allows for
achieving the coincidence resolving time in positron emission tomography of
$\approx$ 0.170 ns for 15 cm axial field-of-view (AFOV) and $\approx$ 0.365 ns
for 100 cm AFOV. The results open perspectives for construction of a
cost-effective TOF-PET scanner with significantly better TOF resolution and
larger AFOV with respect to the current TOF-PET modalities.


title:
Exponential extinction time of the contact process on rank-one
  inhomogeneous random graphs

abstract:
  We show that the contact process on the rank-one inhomogeneous random graphs
and Erdos-R{\'e}nyi graphs with mean degree large enough survives a time
exponential in the size of these graphs for any positive infection rate. In
addition, a metastable result for the extinction time is also proved.


title: A proof of the Kazdan-Warner identity via the Minkowski spacetime

abstract:
  Any 2-dim Riemannian manifold with spherical topology can be embedded
isometrically into a lightcone of the Minkowski spacetime. We apply this fact
to give a proof of the Kazdan-Warner identity.


title: Instability in electromagnetically driven flows Part II

abstract:
  In a previous paper, we have reported numerical simulations of the MHD flow
driven by a travelling magnetic field (TMF) in an annular channel, at low
Reynolds number. It was shown that the stalling of such induction pump is
strongly related to magnetic flux expulsion. In the present article, we show
that for larger hydrodynamic Reynolds number, and with more realistic boundary
conditions, this instability takes the form of a large axisymmetric vortex flow
in the (r,z)-plane, in which the fluid is locally pumped in the direction
opposite to the one of the magnetic field. Close to the marginal stability of
this vortex flow, a low-frequency pulsation is generated. Finally, these
results are compared to theoretical predictions and are discussed within the
framework of experimental annular linear induction electromagnetic pumps.


title:
On the uncertainty estimates of the $\sigma$-pole determination by
  Pad\'e approximants

abstract:
  We discuss the determination of the $f_0(500)$ (or $\sigma$) resonance by
analytic continuation through Pad\'e approximants of the $\pi\pi$-scattering
amplitude from the physical region to the pole in the complex energy plane. The
aim is to analyze the uncertainties of the method, having in view the fact that
analytic continuation is an ill-posed problem in the sense of Hadamard. Using
as input a class of admissible parameterizations of the scalar-isoscalar
$\pi\pi$ partial wave, which satisfy with great accuracy the same set of
dispersive constraints, we find that the Roy-type integral representations lead
to almost identical pole positions for all of them, while the predictions of
the Pad\'e approximants have a larger spread, being sensitive to features of
the input parameterization that are not controlled by the dispersive
constraints. Our conservative conclusion is that the $\sigma$-pole
determination by Pad\'e approximants is consistent with the prediction of
Roy-type equations, but has an uncertainty almost a factor two larger.


title: On the power of dominated players in team competitions

abstract:
  We investigate multi-round team competitions between two teams, where each
team selects one of its players simultaneously in each round and each player
can play at most once. The competition defines an extensive-form game with
perfect recall and can be solved efficiently by standard methods. We are
interested in the properties of the subgame perfect equilibria of this game.
  We first show that uniformly random strategy is a subgame perfect equilibrium
strategy for both teams when there are no redundant players (i.e., the number
of players in each team equals to the number of rounds of the competition).
Secondly, a team can safely abandon its weak players if it has redundant
players and the strength of players is transitive.
  We then focus on the more interesting case where there are redundant players
and the strength of players is not transitive. In this case, we obtain several
counterintuitive results. First of all, a player might help improve the payoff
of its team, even if it is dominated by the entire other team. We give a
necessary condition for a dominated player to be useful. We also study the
extent to which the dominated players can increase the payoff.
  These results bring insights into playing and designing general team
competitions.


title: Skyrmions in thin films with easy-plane magnetocrystalline anisotropy

abstract:
  We demonstrate that chiral skyrmionic magnetization configurations can be
found as the minimum energy state in B20 thin film materials with easy-plane
magnetocrystalline anisotropy with an applied magnetic field perpendicular to
the film plane. Our observations contradict results from prior analytical work,
but are compatible with recent experimental investigations. The size of the
observed skyrmions increases with the easy-plane magnetocrystalline anisotropy.
We use a full micromagnetic model including demagnetization and a
three-dimensional geometry to find local energy minimum (metastable)
magnetization configurations using numerical damped time integration. We
explore the phase space of the system and start simulations from a variety of
initial magnetization configurations to present a systematic overview of
anisotropy and magnetic field parameters for which skyrmions are metastable and
global energy minimum (stable) states.


title:
Deterministic Joint Remote Preparation of a Four-qubit Cluster-type
  State via GHZ states

abstract:
  A scheme for the deterministic joint remote preparation of a four- qubit
cluster-type state using only two Greenberger-Horne-Zeilinger (GHZ) states as
quantum channels is presented. In this scheme, the first sender per- forms a
two-qubit projective measurement according to the real coefficient of the
desired state. Then, the other sender utilizes the measurement result and the
complex coefficient to perform another projective measurement. To obtain the
desired state, the receiver applies appropriate unitary operations to his/her
own two qubits and two CNOT operations to the two ancillary ones. Most
interestingly, our scheme can achieve unit success probability, i.e., Psuc=1.
Furthermore, comparison reveals that the efficiency is higher than that of most
other analogous schemes.


title:
Distributed Fictitious Play for Optimal Behavior of Multi-Agent Systems
  with Incomplete Information

abstract:
  A multi-agent system operates in an uncertain environment about which agents
have different and time varying beliefs that, as time progresses, converge to a
common belief. A global utility function that depends on the realized state of
the environment and actions of all the agents determines the system's optimal
behavior. We define the asymptotically optimal action profile as an equilibrium
of the potential game defined by considering the expected utility with respect
to the asymptotic belief. At finite time, however, agents have not entirely
congruous beliefs about the state of the environment and may select conflicting
actions. This paper proposes a variation of the fictitious play algorithm which
is proven to converge to equilibrium actions if the state beliefs converge to a
common distribution at a rate that is at least linear. In conventional
fictitious play, agents build beliefs on others' future behavior by computing
histograms of past actions and best respond to their expected payoffs
integrated with respect to these histograms. In the variations developed here
histograms are built using knowledge of actions taken by nearby nodes and best
responses are further integrated with respect to the local beliefs on the state
of the environment. We exemplify the use of the algorithm in coordination and
target covering games.


title:
Criterion for the occurrence of many body localization in the presence
  of a single particle mobility edge

abstract:
  Non-interacting fermions in one dimension can undergo a
localization-delocalization transition in the presence of a quasi-periodic
potential as a function of that potential. In the presence of interactions,
this transition transforms into a Many-Body Localization (MBL) transition.
Recent studies have suggested that this type of transition can also occur in
models with quasi-periodic potentials that possess single particle mobility
edges. Two such models were studied in PRL 115,230401(2015) but only one was
found to exhibit an MBL transition in the presence of interactions while the
other one did not. In this work we investigate the occurrence of MBL in the
presence of weak interactions in five different models with single particle
mobility edges in one dimension with a view to obtaining a criterion for the
same. We find that not all such models undergo a thermal-MBL phase transition
in presence of weak interactions. We propose a criterion to determine whether
MBL is likely to occur in presence of interaction based only on the properties
of the non-interacting models. The relevant quantity $\epsilon$ is a measure of
how localized the localized states are relative to how delocalized the
delocalized states are in the non-interacting model. We also study various
other features of the non-interacting models such as the divergence of the
localization length at the mobility edge and the presence or absence of
`ergodicity' and localization in their many-body eigenstates. However, we find
that these features cannot be used to predict the occurrence of MBL upon the
introduction of weak interactions.


title:
From Softmax to Sparsemax: A Sparse Model of Attention and Multi-Label
  Classification

abstract:
  We propose sparsemax, a new activation function similar to the traditional
softmax, but able to output sparse probabilities. After deriving its
properties, we show how its Jacobian can be efficiently computed, enabling its
use in a network trained with backpropagation. Then, we propose a new smooth
and convex loss function which is the sparsemax analogue of the logistic loss.
We reveal an unexpected connection between this new loss and the Huber
classification loss. We obtain promising empirical results in multi-label
classification problems and in attention-based neural networks for natural
language inference. For the latter, we achieve a similar performance as the
traditional softmax, but with a selective, more compact, attention focus.


title: Spectral properties of cographs and $P_5$-free graphs

abstract:
  A cograph is a simple graph which contains no path on 4 vertices as an
induced subgraph. We consider the eigenvalues of adjacency matrices of cographs
and prove that a graph $G$ is a cograph if and only if no induced subgraph of
$G$ has an eigenvalue in the interval $(-1,0)$. It is also shown that the
multiplicity of any eigenvalue of a cograph $G$ does not exceed the sum of
multiplicities of $0$ and $-1$ as eigenvalues of $G$. We introduce a partial
order on the vertex set of graphs $G$ in terms of inclusions among the open and
closed neighborhoods of vertices, and conjecture that the multiplicity of any
eigenvalue of a cograph $G$ except for $0,-1$ does not exceed the maximum size
of an antichain with respect to that partial order. In two extreme cases (in
particular for threshold graphs), the conjecture is shown to be true. Finally,
we give a simple proof for the result that bipartite $P_5$-free graphs have no
eigenvalue in the intervals $(-1/2,0)$ and $(0,1/2)$.


title: Compressive PCA for Low-Rank Matrices on Graphs

abstract:
  We introduce a novel framework for an approxi- mate recovery of data matrices
which are low-rank on graphs, from sampled measurements. The rows and columns
of such matrices belong to the span of the first few eigenvectors of the graphs
constructed between their rows and columns. We leverage this property to
recover the non-linear low-rank structures efficiently from sampled data
measurements, with a low cost (linear in n). First, a Resrtricted Isometry
Property (RIP) condition is introduced for efficient uniform sampling of the
rows and columns of such matrices based on the cumulative coherence of graph
eigenvectors. Secondly, a state-of-the-art fast low-rank recovery method is
suggested for the sampled data. Finally, several efficient, parallel and
parameter-free decoders are presented along with their theoretical analysis for
decoding the low-rank and cluster indicators for the full data matrix. Thus, we
overcome the computational limitations of the standard linear low-rank recovery
methods for big datasets. Our method can also be seen as a major step towards
efficient recovery of non- linear low-rank structures. For a matrix of size n X
p, on a single core machine, our method gains a speed up of $p^2/k$ over Robust
Principal Component Analysis (RPCA), where k << p is the subspace dimension.
Numerically, we can recover a low-rank matrix of size 10304 X 1000, 100 times
faster than Robust PCA.


title: The Wild Bootstrap for Multivariate Nelson-Aalen Estimators

abstract:
  We rigorously extend the widely used wild bootstrap resampling technique to
the multivariate Nelson-Aalen estimator under Aalen's multiplicative intensity
model. Aalen's model covers general Markovian multistate models including
competing risks subject to independent left-truncation and right-censoring.
This leads to various statistical applications such as asymptotically valid
confidence bands or tests for equivalence and proportional hazards. This is
exemplified in a data analysis examining the impact of ventilation on the
duration of intensive care unit stay. The finite sample properties of the new
procedures are investigated in a simulation study.


title:
Stability analysis of pressure correction schemes for the Navier-Stokes
  equations with traction boundary conditions

abstract:
  We present a stability analysis for two different rotational pressure
correction schemes with open and traction boundary conditions. First, we
provide a stability analysis for a rotational version of the grad-div
stabilized scheme of [A. Bonito, J.-L. Guermond, and S. Lee. Modified
pressure-correction projection methods: Open boundary and variable time
stepping. In Numerical Mathematics and Advanced Applications - ENUMATH 2013,
volume 103 of Lecture Notes in Computational Science and Engineering, pages
623-631. Springer, 2015]. This scheme turns out to be unconditionally stable,
provided the stabilization parameter is suitably chosen. We also establish a
conditional stability result for the boundary correction scheme presented in
[E. Bansch. A finite element pressure correction scheme for the Navier-Stokes
equations with traction boundary condition. Comput. Methods Appl. Mech. Engrg.,
279:198-211, 2014]. These results are shown by employing the equivalence
between stabilized gauge Uzawa methods and rotational pressure correction
schemes with traction boundary conditions.


title: On mod p local-global compatibility for GL_3 in the ordinary case

abstract:
  Suppose that F/F+ is a CM extension of number fields in which the prime p
splits completely and every other prime is unramified. Fix a place w|p of F.
Suppose that rbar : Gal(F-bar/F) -> GL_3(Fp-bar) is a continuous irreducible
Galois representation such that rbar|_{Gal(F_w-bar/F_w)} is upper-triangular,
maximally non-split, and generic. If rbar is automorphic, and some suitable
technical conditions hold, we show that rbar|_{\Gal(F_w-bar/F_w)} can be
recovered from the GL_3(F_w)-action on a space of mod p automorphic forms on a
compact unitary group. On the way we prove results about weights in Serre's
conjecture for rbar, show the existence of an ordinary lifting of rbar, and
prove the freeness of certain Taylor-Wiles patched modules in this context. We
also show the existence of many Galois representations rbar to which our main
theorem applies.


title: Newton-Okounkov bodies sprouting on the valuative tree

abstract:
  Given a smooth projective algebraic surface X, a point O in X and a big
divisor D on X, we consider the set of all Newton-Okounkov bodies of D with
respect to valuations of the field of rational functions of X centred at O, or,
equivalently, with respect to a flag (E,p) which is infinitely near to O, in
the sense that there is a sequence of blowups mapping the smooth, irreducible
rational curve E to O. The main objective of this paper is to start a
systematic study of the variation of these infinitesimal Newton-Okounkov bodies
as (E, p) varies, focusing on the case X = P2.


title:
Experiment Investigating the Connection between Weak Values and
  Contextuality

abstract:
  Weak value measurements have recently given rise to a large interest for both
the possibility of measurement amplification and the chance of further quantum
mechanics foundations investigation. In particular, a question emerged about
weak values being proof of the incompatibility between Quantum Mechanics and
Non-Contextual Hidden Variables Theories (NCHVT). A test to provide a
conclusive answer to this question was given in [M. Pusey, Phys. Rev. Lett.
113, 200401 (2014)], where a theorem was derived showing the NCHVT
incompatibility with the observation of anomalous weak values under specific
conditions. In this paper we realize this proposal, clearly pointing out the
strict connection between weak values and the contextual nature of Quantum
Mechanics.


title: Blow-ups in generalized complex geometry

abstract:
  We study blow-ups in generalized complex geometry. To that end we introduce
the concept of holomorphic ideal, which allows one to define a blow-up in the
category of smooth manifolds. We then investigate which generalized complex
submanifolds are suitable for blowing up. Two classes naturally appear;
generalized Poisson submanifolds and generalized Poisson transversals,
submanifolds which look complex, respectively symplectic in transverse
directions. We show that generalized Poisson submanifolds carry a canonical
holomorphic ideal and give a necessary and sufficient condition for the
corresponding blow-up to be generalized complex. For the generalized Poisson
transversals we give a normal form for a neighborhood of the submanifold, and
use that to define a generalized complex blow-up, which is up to deformation
independent of choices.


title: Cancer and electromagnetic radiation therapy: Quo Vadis?

abstract:
  In oncology, treating cancer with a beam of photons is a well established
therapeutic technique, developed over 100 years, and today over 50% of cancer
patients will undergo traditional X-ray radiotherapy. However, ionizing
radiation therapy is not the only option, as the high-energy photons delivering
their cell-killing radiation energy into cancerous tumor can lead to
significant damage to healthy tissues surrounding the tumor, located throughout
the beam's path. Therefore, in nowadays, advances in ionizing radiation therapy
are competitive to non-ionizing ones, as for example the laser light based
therapy, resulting in a synergism that has revolutionized medicine. The use of
non-invasive or minimally invasive (e.g. through flexible endoscopes)
therapeutic procedures in the management of patients represents a very
interesting treatment option. Moreover, as the major breakthrough in cancer
management is the individualized patient treatment, new biophotonic techniques,
e.g. photo-activated drug carriers, help the improvement of treatment efficacy
and/or normal tissue toxicity. Additionally, recent studies support that laser
technology progresses could revolutionize cancer proton therapy, by reducing
the cost of the needed installations. The aim of this review is to present some
laser-based future objectives for cancer radiation therapy, aiming to address
the relevant advances in the ionizing and non-ionizing radiation therapy, i.e.
protons and heavy ions therapy, as well as photodynamic targeted and molecular
therapies.


title: Accurate multireference study of Si3 electronic manifold

abstract:
  Since it has been shown that the silicon trimer has a highly multi-reference
character, accurate multi-reference configuration interaction calculations are
performed to elucidate its electronic manifold. Emphasis is given to the long
range part of the potential, aiming to understand the atom-diatom collisions
dynamical aspects, to describe conical intersections and important saddle
points along the reactive path. Potential energy surface main features analysis
are performed for benchmarking, and highly accurate values for structures,
vibrational constants and energy gaps are reported, as well as the unpublished
spin-orbit coupling magnitude. The results predict that inter-system crossings
will play an important role in dynamical simulations, specially in triplet
state quenching, making the problem of constructing a precise potential energy
surface more complicated and multi-layer dependent. The ground state is
predicted to be the singlet one, but since the singlet-triplet gap is rather
small (2.448 kJ/mol) both of them are expected to be populated at room
temperature.


title: Tachyonic approach to neutrino dark matter

abstract:
  We apply a new approach based on three relativistic groups (bradyon, tachyon
and instanton) forming the `Lorentz groupoid' which allows, in particular, to
consider tachyons without introducing imaginary masses and negative energies
(related, as known, to violation of causality and unitarity). This leads to
effectively scalar conglomerate composed of tachyonic neutrino and antineutrino
spinor wave functions as a viable model for stationary dark matter. We also
briefly discuss a relevant early non-stationary high-energy stage of the
universe evolution.


title:
Irreversible Rapid Changes of Magnetic Field Associated with the 2012
  October 23 Circular Near-limb X1.8 Flare

abstract:
  It has been found that photospheric magnetic fields can change in accordance
with the three-dimensional magnetic field restructuring following solar
eruptions. Previous studies mainly use vector magnetic field data taken for
events near the disk center. In this paper, we analyze the magnetic field
evolution associated with the 2012 October 23 X1.8 flare in NOAA AR 11598 that
is close to the solar limb, using both the 45 s cadence line-of-sight and 12
minute cadence vector magnetograms from the Helioseismic and Magnetic Imager on
board Solar Dynamic Observatory. This flare is classified as a circular-ribbon
flare with spine-fan type magnetic topology containing a null point. In the
line-of-sight magnetograms, there are two apparent polarity inversion lines
(PIL). The PIL closer to the limb is affected more by the projection effect.
Between these two PILs there lie positive polarity magnetic fields, which are
surrounded by negative polarity fields outside the PILs. We find that after the
flare, both the apparent limb-ward and disk-ward negative fluxes decrease,
while the positive flux in-between increases. We also find that the horizontal
magnetic fields have a significant increase along the disk-ward PIL, while in
surrounding area, they decrease. Synthesizing the observed field changes, we
conclude that the magnetic fields collapse toward the surface above the
disk-ward PIL as depicted in the coronal implosion scenario, while the
peripheral field turns to a more vertical configuration after the flare. We
also suggest that this event is an asymmetric circular-ribbon flare: a flux
rope is likely present above the disk-ward PIL. Its eruption causes the
instability of the entire fan-spine structure and the implosion near that PIL.


title:
Berry-Esseen's bound and Cram\'er's large deviation expansion for a
  supercritical branching process in a random environment

abstract:
  Let $(Z_n)$ be a supercritical branching process in a random environment $\xi
= (\xi_n)$. We establish a Berry-Esseen bound and a Cram\'er's type large
deviation expansion for $\log Z_n$ under the annealed law $\mathbb P$. We also
improve some earlier results about the harmonic moments of the limit variable
$W=lim_{n\to \infty} W_n$, where $W_n =Z_n/ \mathbb{E}_{\xi} Z_n$ is the
normalized population size.


title:
Low energy anomalies in electron tunneling through strongly asymmetric
  Majorana nanowire

abstract:
  Electron transport through Majorana nanowire with strongly asymmetric
couplings to normal metal leads is considered. In three terminal geometry
(electrically grounded nanowire) it is shown that the presence of unbiased
electrode restores zero-bias anomaly even for strong Majorana energy splitting.
For effectively two-terminal geometry we show that electrical current through
asymmetric Majorana junction is qualitatively different from the analogous
current through a resonant (Breit-Wigner) level.


title:
Genome-inspired molecular identification in organic matter via Raman
  spectroscopy

abstract:
  Rapid, non-destructive characterization of molecular level chemistry for
organic matter (OM) is experimentally challenging. Raman spectroscopy is one of
the most widely used techniques for non-destructive chemical characterization,
although it currently does not provide detailed identification of molecular
components in OM, due to the combination of diffraction-limited spatial
resolution and poor applicability of peak-fitting algorithms. Here, we develop
a genome-inspired collective molecular structure fingerprinting approach, which
utilizes ab initio calculations and data mining techniques to extract molecular
level chemistry from the Raman spectra of OM. We illustrate the power of such
an approach by identifying representative molecular fingerprints in OM, for
which the molecular chemistry is to date inaccessible using non-destructive
characterization techniques. Chemical properties such as aromatic cluster size
distribution and H/C ratio can now be quantified directly using the identified
molecular fingerprints. Our approach will enable non-destructive identification
of chemical signatures with their correlation to the preservation of
biosignatures in OM, accurate detection and quantification of environmental
contamination, as well as objective assessment of OM with respect to their
chemical contents.


title: On two weight estimates for dyadic operators

abstract:
  We provide a quantitative two weight estimate for the dyadic paraproduct
$\pi_b$ under certain conditions on a pair of weights $(u;v)$ and $b$ in
$Carl_{u,v}$, a new class of functions that we show coincides with BMO when $u
= v \in A^d_2$. We obtain quantitative two weight estimates for the dyadic
square function and the martingale transforms under the assumption that the
maximal function is bounded from $L_2(u)$ into $L_2(v)$ and $v \in RH^d_1$.
Finally we obtain a quantitative two weight estimate from $L_2(u)$ into
$L_2(v)$ for the dyadic square function under the assumption that the pair $(u;
v)$ is in joint $A^d_2$ and $u^{-1} \in RH^d_1$, this is sharp in the sense
that when $u = v$ the conditions reduce to $u \in A^d_2$ and the estimate is
the known linear mixed estimate.


title: A short conceptual proof of Narayana's path-counting formula

abstract:
  We deduce Narayana's formula for the number of lattice paths that fit in a
Young diagram as a direct consequence of the Gessel-Viennot theorem on
non-intersecting lattice paths.


title: Region Based Approximation for High Dimensional Bayesian Network Models

abstract:
  Performing efficient inference on Bayesian Networks (BNs), with large numbers
of densely connected variables is challenging. With exact inference methods,
such as the Junction Tree algorithm, clustering complexity can grow
exponentially with the number of nodes and so computation becomes intractable.
This paper presents a general purpose approximate inference algorithm called
Triplet Region Construction (TRC) that reduces the clustering complexity for
factorized models from worst case exponential to polynomial. We employ graph
factorization to reduce connection complexity and produce clusters of limited
size. Unlike MCMC algorithms TRC is guaranteed to converge and we present
experiments that show that TRC achieves accurate results when compared with
exact solutions.


title:
Comment on "Nonlocal quartic interactions and universality classes in
  perovskite manganites"

abstract:
  In a recent paper [Phys. Rev. E \textbf{92}, 012123 (2015)] a modified
$d$-dimensional $\Phi^4$ model was investigated which differs from the standard
one in that the $\Phi^4$ term was replaced by a nonlocal one with a potential
$u(\bm{x}-\bm{x}')$ that depends on a parameter $\sigma$ and decays
exponentially as $|\bm{x}-\bm{x}'|\to\infty$ on a scale $|m|^{-1}<\infty$. The
authors claim the upper critical dimension of this model to be
$d_\sigma=4+2\sigma$. Performing a one-loop calculation they arrive at
expansions in powers of $\epsilon_\sigma=d_\sigma-d$ for critical exponents
such as $\eta$ and related ones to $O(\epsilon_\sigma)$ whose
$O(\epsilon_\sigma)$ coefficients depend on $\sigma$ and the ratio
$w=m^2/\Lambda^2$, where $\Lambda$ is the UV cutoff. We show that these claims
are unfounded and based on misjudgments and an ill-conceived renormalization
group calculation.


title:
Simulation of Macromolecular Liquids with the Adaptive Resolution
  Molecular Dynamics Technique

abstract:
  We extend the application of the adaptive resolution technique (AdResS) to
liquid systems composed of alkane chains of different lengths. The aim of the
study is to develop and test the modifications of AdResS required in order to
handle the change of representation of large molecules. The robustness of the
approach is shown by calculating several relevant structural properties and
comparing them with the results of full atomistic simulations. The extended
scheme represents a robust prototype for the simulation of macromolecular
systems of interest in several fields, from material science to biophysics.

categories: cond-mat.soft physics.bio-ph physics.chem-ph physics.comp-ph


title: Harmonic Grammar in a DisCo Model of Meaning

abstract:
  The model of cognition developed in (Smolensky and Legendre, 2006) seeks to
unify two levels of description of the cognitive process: the connectionist and
the symbolic. The theory developed brings together these two levels into the
Integrated Connectionist/Symbolic Cognitive architecture (ICS). Clark and
Pulman (2007) draw a parallel with semantics where meaning may be modelled on
both distributional and symbolic levels, developed by Coecke et al, 2010 into
the Distributional Compositional (DisCo) model of meaning. In the current work,
we revisit Smolensky and Legendre (S&L)'s model. We describe the DisCo
framework, summarise the key ideas in S&L's architecture, and describe how
their description of harmony as a graded measure of grammaticality may be
applied in the DisCo model.


title: The inner structure of the TW Hya Disk as revealed in scattered light

abstract:
  We observe a significant change in the TW Hya disk interior to 40~AU via
archival unpolarized multi-wavelength Hubble Space Telescope/STIS and NICMOS
images with an inner working angle (IWA) of 0\farcs4 (22~AU). Our images show
the outer edge of a clearing at every wavelength with similar behavior,
demonstrating that the feature is structural, rather than due to some property
of polarized light in the disk. We compare our observations to those taken by
Akiyama et al. (2015) and Rapson et al. (2015), and discuss the spectral
evolution of the disk interior to 80~AU. We construct a model with two gaps:
one at 30~AU and one at 80~AU that fit the observed surface brightness profile
but overpredicts the absolute brightness of the disk. Our models require an
additional dimming to be consistent with observations, which we tentatively
ascribe to shadowing. The gap structures seen in scattered light are spatially
coincident with sub-mm detections of CO and N$_2$H$^+$, and are near expected
condensation fronts of these molecular species, providing tentative evidence
that the structures seen in scattered light may be correlated with chemical
changes in the disk.


title: Towards Innovative Physical Layer Design for Mobile WSN Platforms

abstract:
  We today live in the era of dynamic and mobile wireless enabled platforms.
This kind of stringent communication capability in the face of volatile and
turbulent mobility demands a fresh look at physical layer in general and
antenna design in particular. The dimension of the antenna is 30x35x1.6 mm^3.
Multiplicity of bands is very useful for compatibility purposes where legacy
robotic platforms generally operate in MHz range while latest robotic platforms
are capable to handle GHz communication regimes and can pump data very at much
greater speeds. Seven frequency bands are obtained at 700 MHz, 2.4 GHz, 3.6
GHz, 4.37 GHz, 5.8 GHz, 6.93 GHz and 7.7 GHz with bandwidth of 1.1 GHz, 0.7
GHz, 0.8 GHz, 0.23 GHz, 0.90 GHz, 0.19 GHz and 0.12 GHz respectively.


title:
Large deviations and concentration inequalities for the
  Ornstein-Uhlenbeck process without tears

abstract:
  Our goal is to establish large deviations and concentration inequalities for
the maximum likelihood estimator of the drift parameter of the
Ornstein-Uhlenbeck process without tears. We propose a new strategy to
establish large deviation results which allows us, via a suitable
transformation, to circumvent the classical difficulty of non-steepness. Our
approach holds in the stable case where the process is positive recurrent as
well as in the unstable and explosive cases where the process is respectively
null recurrent and transient. Notwithstanding of this trichotomy, we also
provide new concentration inequalities for the maximum likelihood estimator.


title: Universality and scaling in a charge two-channel Kondo device

abstract:
  We study a charge two-channel Kondo model, demonstrating that recent
experiments [Iftikhar et al, Nature 526, 233 (2015)] realize an essentially
perfect quantum simulation -- not just of its universal physics, but also
nonuniversal effects away from the scaling limit. Numerical renormalization
group (NRG) calculations yield conductance lineshapes encoding RG flow to a
critical point involving a free Majorana fermion. By mimicking the experimental
protocol, the experimental curve is reproduced quantitatively over 9 orders of
magnitude, although we show that far greater bandwidth/temperature separation
is required to obtain the universal result. Fermi liquid instabilities are also
studied: In particular, our exact analytic results for non-linear conductance
provide predictions away from thermal equilibrium, in the regime of existing
experiments.


title: Computing the Homology of Real Projective Sets

abstract:
  We describe and analyze a numerical algorithm for computing the homology
(Betti numbers and torsion coefficients) of real projective varieties. Here
numerical means that the algorithm is numerically stable (in a sense to be made
precise). Its cost depends on the condition of the input as well as on its size
and is singly exponential in the number of variables (the dimension of the
ambient space) and polynomial in the condition and the degrees of the defining
polynomials. In addition, we show that outside of an exceptional set of measure
exponentially small in the size of the data, the algorithm takes exponential
time.


title: Stochastic series expansion simulation of the $t$-$V$ model

abstract:
  We present an algorithm for the efficient simulation of the half-filled
spinless $t$-$V$ model on bipartite lattices, which combines the stochastic
series expansion method with determinantal quantum Monte Carlo techniques
widely used in fermionic simulations. The algorithm scales linearly in the
inverse temperature, cubically with the system size and is free from the
time-discretization error. We use it to map out the finite temperature phase
diagram of the spinless $t$-$V$ model on the honeycomb lattice and observe a
suppression of the critical temperature of the charge density wave phase in the
vicinity of a fermionic quantum critical point.


title:
Thermal Ising transitions in the vicinity of two-dimensional quantum
  critical points

abstract:
  The scaling of the transition temperature into an ordered phase close to a
quantum critical point as well as the order parameter fluctuations inside the
quantum critical region provide valuable information about universal properties
of the underlying quantum critical point. Here, we employ quantum Monte Carlo
simulations to examine these relations in detail for two-dimensional quantum
systems that exhibit a finite-temperature Ising-transition line in the vicinity
of a quantum critical point that belongs to the universality class of either
(i) the three-dimensional Ising model for the case of the quantum Ising model
in a transverse magnetic field on the square lattice or (ii) the ${\it chiral}$
Ising transition for the case of a half-filled system of spinless fermions on
the honeycomb lattice with nearest-neighbor repulsion. While the first case
allows large-scale simulations to assess the scaling predictions to a high
precision in terms of the known values for the critical exponents at the
quantum critical point, for the later case we extract values of the critical
exponents $\nu$ and $\eta$, related to the order parameter fluctuations, which
we discuss in relation to other recent estimates from ground state quantum
Monte Carlo calculations as well as analytical approaches.


title:
Fast AC Power Flow Optimization using Difference of Convex Functions
  Programming

abstract:
  An effective means for analyzing the impact of novel operating schemes on
power systems is time domain simulation, for example for investigating
optimization-based curtailment of renewables to alleviate voltage violations.
Traditionally, interior-point methods are used for solving the non-convex AC
optimal power flow (OPF) problems arising in this type of simulation. This
paper presents an alternative algorithm that better suits the simulation
framework, because it can more effectively be warm-started, has linear
computational and memory complexity in the problem size per iteration and
globally converges to Karush-Kuhn-Tucker (KKT) points with a linear rate if
they exist. The algorithm exploits a difference-of-convex-functions
reformulation of the OPF problem, which can be performed effectively. Numerical
results are presented comparing the method to state-of-the-art OPF solver
implementations in MATPOWER, leading to significant speedups compared to the
latter.


title:
Continuous opinions and discrete actions in social networks: a
  multi-agent system approach

abstract:
  This paper proposes and analyzes a novel multi-agent opinion dynamics model
in which agents have access to actions which are quantized version of the
opinions of their neighbors. The model produces different behaviors observed in
social networks such as disensus, clustering, oscillations, opinion
propagation, even when the communication network is connected. The main results
of the paper provides the characterization of preservation and diffusion of
actions under general communication topologies. A complete analysis allowing
the opinion forecasting is given in the particular cases of complete and ring
communication graphs. Numerical examples illustrate the main features of this
model.


title:
Entanglement Detection with Fewer Measurements based on the Geometric
  Criterion

abstract:
  We present a new technique to reduce the expected number of measurements to
declare an unknown quantum state as entangled. Our method is based on the
geometric criterion and so requires only local Pauli measurements. Using
concentration of measure, we provide a heuristic which allows us to reinterpret
a previous decision tree algorithm due to Laskowski et al and that forms the
basis for our new algorithm. Numerical simulations show that for three to six
qubits we use fewer measurements than either the trivial algorithm or the
decision tree algorithm. In addition, our method is easy to construct, assumes
no prior knowledge of the system and works for any number of qubits.


title:
Higgs vacuum metastability in primordial inflation, preheating, and
  reheating

abstract:
  Current measurements of the Higgs boson mass and top Yukawa coupling suggest
that the effective Higgs potential develops an instability below the Planck
scale. If the energy scale of inflation is as high as the GUT scale,
inflationary quantum fluctuations of the Higgs field can easily destabilize the
standard electroweak vacuum and produce a lot of AdS domains. This
destabilization during inflation can be avoided if a relatively large
nonminimal Higgs-gravity or inflaton-Higgs coupling is introduced. Such
couplings generate a large effective mass term for the Higgs, which can raise
the effective Higgs potential and suppress the vacuum fluctuation of the Higgs
field. After primordial inflation, however, such effective masses drops rapidly
and the nonminimal Higgs-gravity or inflaton-Higgs coupling can cause large
fluctuations of the Higgs field to be generated via parametric resonance, thus
producing AdS domains in the preheating stage. Furthermore, thermal
fluctuations of the Higgs field cannot be neglected in the proceeding reheating
epoch. We discuss the Higgs vacuum fluctuations during inflation, preheating,
and reheating, and show that the Higgs metastability problem is severe unless
the energy scale of the inflaton potential is much lower than the GUT scale.


title: Variance-Reduced and Projection-Free Stochastic Optimization

abstract:
  The Frank-Wolfe optimization algorithm has recently regained popularity for
machine learning applications due to its projection-free property and its
ability to handle structured constraints. However, in the stochastic learning
setting, it is still relatively understudied compared to the gradient descent
counterpart. In this work, leveraging a recent variance reduction technique, we
propose two stochastic Frank-Wolfe variants which substantially improve
previous results in terms of the number of stochastic gradient evaluations
needed to achieve $1-\epsilon$ accuracy. For example, we improve from
$O(\frac{1}{\epsilon})$ to $O(\ln\frac{1}{\epsilon})$ if the objective function
is smooth and strongly convex, and from $O(\frac{1}{\epsilon^2})$ to
$O(\frac{1}{\epsilon^{1.5}})$ if the objective function is smooth and
Lipschitz. The theoretical improvement is also observed in experiments on
real-world datasets for a multiclass classification application.


title: The Spacey Random Walk: a Stochastic Process for Higher-order Data

abstract:
  Random walks are a fundamental model in applied mathematics and are a common
example of a Markov chain. The limiting stationary distribution of the Markov
chain represents the fraction of the time spent in each state during the
stochastic process. A standard way to compute this distribution for a random
walk on a finite set of states is to compute the Perron vector of the
associated transition matrix. There are algebraic analogues of this Perron
vector in terms of transition probability tensors of higher-order Markov
chains. These vectors are nonnegative, have dimension equal to the dimension of
the state space, and sum to one and are derived by making an algebraic
substitution in the equation for the joint-stationary distribution of a
higher-order Markov chains. Here, we present the spacey random walk, a
non-Markovian stochastic process whose stationary distribution is given by the
tensor eigenvector. The process itself is a vertex-reinforced random walk, and
its discrete dynamics are related to a continuous dynamical system. We analyze
the convergence properties of these dynamics and discuss numerical methods for
computing the stationary distribution. Finally, we provide several applications
of the spacey random walk model in population genetics, ranking, and clustering
data, and we use the process to analyze taxi trajectory data in New York. This
example shows definite non-Markovian structure.


title:
First evidence of running cosmic vacuum: challenging the concordance
  model

abstract:
  Despite the fact that a rigid $\Lambda$-term is a fundamental building block
of the concordance $\Lambda$CDM model, we show that a large class of
cosmological scenarios with dynamical vacuum energy density $\rho_{\Lambda}$
and/or gravitational coupling $G$, together with a possible non-conservation of
matter, are capable of seriously challenging the traditional phenomenological
success of the $\Lambda$CDM. In this paper, we discuss these "running vacuum
models" (RVM's), in which $\rho_{\Lambda}=\rho_{\Lambda}(H)$ consists of a
nonvanishing constant term and a series of powers of the Hubble rate. Such
generic structure is potentially linked to the quantum field theoretical
description of the expanding Universe. By performing an overall fit to the
cosmological observables $SNIa+BAO+H(z)+LSS+BBN+CMB$ (in which the WMAP9,
Planck 2013 and Planck 2015 data are taken into account), we find that the
class of RVM's appears significantly more favored than the $\Lambda$CDM, namely
at an unprecedented level of $\gtrsim4.2\sigma$. Furthermore, the Akaike and
Bayesian information criteria confirm that the dynamical RVM's are strongly
preferred as compared to the conventional rigid $\Lambda$-picture of the cosmic
evolution.


title:
Time-dependent renormalized-natural-orbital theory applied to
  laser-driven H$_2^+$

abstract:
  Recently introduced time-dependent renormalized-natural orbital theory
(TDRNOT) is extended towards a multi-component approach in order to describe
H$_2^+$ beyond the Born-Oppenheimer approximation. Two kinds of natural
orbitals, describing the electronic and the nuclear degrees of freedom are
introduced, and the exact equations of motion for them are derived. The theory
is benchmarked by comparing numerically exact results of the time-dependent
Schr\"odinger equation for a H$_2^+$ model system with the corresponding TDRNOT
predictions. Ground state properties, linear response spectra, fragmentation,
and high-order harmonic generation are investigated.


title: Calibration of the Liverpool Telescope RINGO3 polarimeter

abstract:
  We present an analysis of polarimetric observations of standard stars
performed over the period of more than three years with the RINGO3 polarimeter
mounted on the Liverpool Telescope. The main objective was to determine the
instrumental polarisation of the RINGO3 polarimeter in three spectral energy
ranges: blue (350--640~nm), green (650--760~nm) and red (770--1000~nm). The
observations were conducted between 2012 and 2016. The total time span of 1126
days was split into five epochs due to the hardware changes to the observing
system. Our results should be applied to calibrate all polarimetric
observations performed with the RINGO3 polarimeter.