title: Consistent Hashing with Bounded Loads

abstract:
  Designing algorithms for balanced allocation of clients to servers in dynamic
settings is a challenging problem for a variety of reasons. Both servers and
clients may be added and/or removed from the system periodically, and the main
objectives of allocation algorithms are: the uniformity of the allocation, and
the number of moves after adding or removing a server or a client. The most
popular solution for our dynamic settings is Consistent Hashing. However, the
load balancing of consistent hashing is no better than a random assignment of
clients to servers, so with $n$ of each, we expect many servers to be
overloaded with $\Theta(\log n/ \log\log n)$ clients. In this paper, with $n$
clients and $n$ servers, we get a guaranteed max-load of 2 while only moving an
expected constant number of clients for each update.
  We take an arbitrary user specified balancing parameter $c=1+\epsilon>1$.
With $m$ balls and $n$ bins in the system, we want no load above $\lceil
cm/n\rceil$. Meanwhile we want to bound the expected number of balls that have
to be moved when a ball or server is added or removed. Compared with general
lower bounds without capacity constraints, we show that in our algorithm when a
ball or bin is inserted or deleted, the expected number of balls that have to
be moved is increased only by a multiplicative factor $O({1\over \epsilon^2})$
for $\epsilon \le 1$ (Theorem 4) and by a factor $1+O(\frac{\log c}c)$ for
$\epsilon\ge 1$ (Theorem 3). Technically, the latter bound is the most
challenging to prove. It implies that we for superconstant $c$ only pay a
negligible cost in extra moves. We also get the same bounds for the simpler
problem where we instead of a user specified balancing parameter have a fixed
bin capacity $C$ for all bins.


title:
Multidimensional Polarization Index and its Application to an Analysis
  of the Russian State Duma

abstract:
  The multidimensional extension of the Aleskerov-Golubenko polarization index
is developed. Several versions of the polarization index are proposed based on
different distance functions. Basic properties of the index are examined.


title:
Joint Hydrogeophysical Inversion: State Estimation for Seawater
  Intrusion Models in 3D

abstract:
  Seawater intrusion (SWI) is a complex process, where 3D modeling is often
necessary in order to monitor and manage the affected aquifers. Here, we
present a synthetic study to test a joint hydrogeophysical inversion approach
aimed at solving the inverse problem of estimating initial and current
saltwater distribution. First, we use a 3D groundwater model for variable
density flow based on discretized flow and solute mass balance equations. In
addition to the groundwater model, a 3D geophysical model was developed for
direct current resistivity imaging and inversion. The objective function of the
coupled problem consists of data misfit and regularization terms as well as a
coupling term that relates groundwater and geophysical states. We present a
novel approach to solve the inverse problem using an Alternating Direction
Method of Multipliers (ADMM) to minimize this coupled objective function. The
sensitivities are derived analytically for the discretized system of equations,
which allows us to efficiently compute the gradients in the minimization
procedure and reduce the computational complexity of the problem. The method
was tested on different synthetic scenarios with groundwater and geophysical
data represented by solute mass fraction data and direct current resistivity
data. With the ADMM approach, we were able to obtain better estimates for the
solute distribution, compared to just considering each data set separately or
solving with a simple coupled approach.


title: On a question of Eliahou and a conjecture of Wilf

abstract:
  To a numerical semigroup $S$, Eliahou associated a number $E(S)$ and proved
that numerical semigroups for which the associated number is non negative
satisfy Wilf's conjecture. The search for counterexamples for the conjecture of
Wilf is therefore reduced to semigroups which have an associated negative
Eliahou number. Eliahou mentioned $5$ numerical semigroups whose Eliahou number
is $-1$. The examples were discovered by Fromentin who observed that these are
the only ones with negative Eliahou number among the over $10^{13}$ numerical
semigroups of genus up to $60$. We prove here that for any integer $n$ there
are infinitely many numerical semigroups S such that $E(S)=n$, by explicitly
giving families of such semigroups. We prove that all the semigroups in these
families satisfy Wilf's conjecture, thus providing not previously known
examples of semigroups for which the conjecture holds.


title:
Geometric measure of entanglement of symmetric d-qubits is
  polynomial-time computable

abstract:
  We give a simple formula for finding the spectral norm of d-mode symmetric
tensor in two variables over the complex or real numbers in terms of the
complex or real roots of a corresponding polynomial in one complex variable.
This result implies that the geometric measure of entanglement of symmetric
d-qubits is polynomial-time computable. We discuss a generalization to d-mode
symmetric tensor in more than two variables.


title:
Metastability of the Nonlinear Wave Equation: Insights from Transition
  State Theory

abstract:
  This paper is concerned with the long-time dynamics of the nonlinear wave
equation in one-space dimension, $$ u_{tt} - \delta^2 u_{xx} +V'(u) =0 \qquad
x\in [0,1] $$ where $\delta>0$ is a parameter and $V(u)$ is a potential bounded
from below and growing at least like $u^2$ as $|u|\to\infty$. Infinite energy
solutions of this equation preserve a natural Gibbsian invariant measure and
when the potential is double-welled, for example when $V(u) =
\tfrac14(1-u^2)^2$, there is a regime such that two small disjoint sets in the
system's phase-space concentrate most of the mass of this measure. This
suggests that the solutions to the nonlinear wave equation can be metastable
over these sets, in the sense that they spend long periods of time in these
sets and only rarely transition between them. Here we quantify this phenomenon
by calculating exactly via Transition State Theory (TST) the mean frequency at
which the solutions of the nonlinear wave equation with initial conditions
drawn from its invariant measure cross a dividing surface lying in between the
metastable sets. Numerical results suggest that the dynamics of the nonlinear
wave equation is ergodic and rapidly mixing with respect to the Gibbs invariant
measure when the parameter $\delta$ in small enough. This is a regime in which
the dynamics of the nonlinear wave equation displays a metastable behavior that
is not fundamentally different from that observed in its stochastic counterpart
in which random noise and damping terms are added to the equation. For larger
$\delta$, however, the dynamics either stops being ergodic, or its mixing time
becomes larger than the inverse of the TST frequency, indicating that
successive transitions between the metastable sets are correlated and the
coarse-graining to a Markov chain fails.


title:
Coupling a Surface Acoustic Wave to an Electron Spin in diamond via a
  Dark State

abstract:
  The emerging field of quantum acoustics explores interactions between
acoustic waves and artificial atoms and their applications in quantum
information processing. In this experimental study, we demonstrate the coupling
between a surface acoustic wave (SAW) and an electron spin in diamond by taking
advantage of the strong strain coupling of the excited states of a nitrogen
vacancy center, while avoiding the short lifetime of these states. The SAW-spin
coupling takes place through a lamda-type three-level system where two ground
spin states couple to a common excited state through a phonon-assisted as well
as a direct dipole optical transition. Both coherent population trapping and
optically-driven spin transitions have been realized. The coherent population
trapping demonstrates the coupling between a SAW and an electron spin coherence
through a dark state. The optically-driven spin transitions, which resemble the
sideband transitions in a trapped ion system, can enable the quantum control of
both spin and mechanical degrees of freedom and potentially a trapped-ion-like
solid state system for applications in quantum computing. These results
establish an experimental platform for spin-based quantum acoustic, bridging
the gap between spintronics and quantum acoustics.


title: FFT-based Computation of Polynomial Coefficients and Related Tasks

abstract:
  We present a FFT-based algorithm for the computation of a polynomial's
coefficients from its roots, and apply it to obtain the coefficients of
interpolation polynomials, to invert Vandermondians and to evaluate the
symmetric functions of a set of parameters. Analytic and numerical evidence
with problem sizes up to and beyond n=2000 confirms that it is superior over
previous algorithms for these problems in case of parameters taken from uniform
or almost uniform distributions on or near circles in the complex plane, and of
comparable performance in other cases. Its time complexity is O(n*n) and its
storage complexity for tasks other than Vandermondian inversion O(n).


title: Weakly threshold graphs

abstract:
  We define a weakly threshold sequence to be a degree sequence
$d=(d_1,\dots,d_n)$ of a graph having the property that $\sum_{i \leq k} d_i
\geq k(k-1)+\sum_{i > k} \min\{k,d_i\} - 1$ for all positive $k \leq
\max\{i:d_i \geq i-1\}$. The weakly threshold graphs are the realizations of
the weakly threshold sequences. The weakly threshold graphs properly include
the threshold graphs and satisfy pleasing extensions of many properties of
threshold graphs. We demonstrate a majorization property of weakly threshold
sequences and an iterative construction algorithm for weakly threshold graphs,
as well as a forbidden induced subgraph characterization. We conclude by
exactly enumerating weakly threshold sequences and graphs.


title:
Boundary weak Harnack estimates and quantitative strong maximum
  principles for uniformly elliptic PDE

abstract:
  We give full boundary extensions to two fundamental estimates in the theory
of elliptic PDE, the weak Harnack inequality and the quantitative strong
maximum principle, for uniformly elliptic equations in non-divergence form.


title: Mercury's gravity, tides, and spin from MESSENGER radio science data

abstract:
  We analyze radio tracking data obtained during 1311 orbits of the MESSENGER
spacecraft in the period March 2011 to April 2014. A least-squares minimization
of the residuals between observed and computed values of two-way range and
Doppler allows us to solve for a model describing Mercury's gravity, tidal
response, and spin state. We use a spherical harmonic representation of the
gravity field to degree and order 40 and report error bars corresponding to 10
times the formal uncertainties of the fit. Our estimate of the product of
Mercury's mass and the gravitational constant, $GM = (22031.87404 \pm 9 \times
10^{-4})$ km$^{3}$s$^{-2}$, is in excellent agreement with published results.
Our solution for the geophysically important second-degree coefficients
($\bar{C}_{2,0} = -2.25100 \times 10^{-5} \pm 1.3 \times 10^{-9}$,
$\bar{C}_{2,2} = 1.24973 \times 10^{-5} \pm 1.2 \times 10^{-9}$) confirms
previous estimates to better than 0.4\% and, therefore, inferences about
Mercury's moment of inertia and interior structure. Our estimate of the tidal
Love number $k_2 = 0.464 \pm 0.023$ indicates that Mercury's mantle may be
hotter and weaker than previously thought. Our spin state solution suggests
that gravity-based estimates of Mercury's spin axis orientation are marginally
consistent with previous measurements of the orientation of the crust.


title: Squarefree Doubly Primitive Divisors in Dynamical Sequences

abstract:
  Let K be a number field or a function field of characteristic 0, let f be a
K-rational function of degree greater than 1, and let a be an element of K. Let
S be a finite set of places of K containing all the archimedean ones and the
primes where f has bad reduction. After excluding all the natural
counter-examples, we define a subset A(f,a) of pairs of integers (m,n) with m
nonnegative and n positive, and show that for all but finitely many (m,n) in
A(f,a) there is a prime p of K which is not in S such that the p-adic valuation
of f^{m+n}(a)-f^m(a) is precisely equal to 1, and moreover a has portrait (m,n)
under the action of f modulo p. This latter condition implies that the p-adic
valuation of f^{u+v}(a)-f^u(a) is not positive if u is a nonnegative integer
and v is a positive integer with u<m or v<n. Our proof assumes a conjecture of
Vojta in the number field case and is unconditional in the function field case
thanks to a deep theorem of Yamanoi. This paper extends earlier work of
Ingram-Silverman, Faber-Granville, and of the authors.


title: Making Caches Work for Graph Analytics

abstract:
  Modern hardware systems are heavily underutilized when running large-scale
graph applications. While many in-memory graph frameworks have made substantial
progress in optimizing these applications, we show that it is still possible to
achieve up to 4 $\times$ speedups over the fastest frameworks by greatly
improving cache utilization. Previous systems have applied out-of-core
processing techniques from the memory/disk boundary to the cache/DRAM boundary.
However, we find that blindly applying such techniques is ineffective because
of the much smaller performance gap between DRAM and cache. We present two
techniques that take advantage of the cache with minimal or no instruction
overhead. The first, frequency based clustering, groups together frequently
accessed vertices to improve the utilization of each cache line with no runtime
overhead. The second, CSR segmenting, partitions the graph to restrict all
random accesses to the cache, makes all DRAM access sequential, and merges
partition results using a very low overhead cache-aware merge. Both techniques
can be easily implemented on top of optimized graph frameworks. Our techniques
combined give speedups of up to 4 $\times$ for PageRank, Label Propagation and
Collaborative Filtering, and 2 $\times$ for Betweenness Centrality over the
best published results


title: On $\mathfrak F$-hypercentral modules and character clusters

abstract:
  Let $\mathfrak F$ be a saturated formation of soluble Lie algebras over a
field $F$ of characteristic $p > 0$ and let ${\mathbb F}_p$ denote the field of
$p$ elements. Let $(L,[p])$ be a restricted Lie algebra over $F$ with
$z^{$\scriptstyle [p]$}=0$ for all $z$ in the centre of $L$. Let $S \in
\mathfrak F$, $S\ne 0$ be a subnormal subalgebra of $L$. Let $V, W$ be
$L$-modules. Suppose that the character cluster of $W$ is contained in the set
of ${\mathbb F}_p$-linear combinations of the characters in the character
cluster of $V$. Suppose that $V$, regarded as $S$-module, is $\mathfrak
F$-hypercentral. Then $W$, regarded as $S$-module, is also $\mathfrak
F$-hypercentral.


title: Adaptive Estimation of Nonparametric Functionals

abstract:
  We provide general adaptive upper bounds for estimating nonparametric
functionals based on second order U-statistics arising from finite dimensional
approximation of the infinite dimensional models. We then provide examples of
functionals for which the theory produces rate optimally matching adaptive
upper and lower bounds. Our results are automatically adaptive in both
parametric and nonparametric regimes of estimation and are automatically
adaptive and semiparametric efficient in the regime of parametric convergence
rate.


title: Multifactor CES General Equilibrium: Models and Applications

abstract:
  Sector specific multifactor CES elasticity of substitution and the
corresponding productivity growths are jointly measured by regressing the
growths of factor-wise cost shares against the growths of factor prices. We use
linked input-output tables for Japan and the Republic of Korea as the data
source for factor price and cost shares in two temporally distant states. We
then construct a multi-sectoral general equilibrium model using the system of
estimated CES unit cost functions, and evaluate the economy-wide propagation of
an exogenous productivity stimuli, in terms of welfare. Further, we examine the
differences between models based on a priori elasticity such as Leontief and
Cobb-Douglas.


title:
Accelerated atomistic simulation study on the stability and mobility of
  carbon tri-interstitial cluster in cubic SiC

abstract:
  Using a combination of kinetic Activation Relaxation Technique with empirical
potential and ab initio based climbing image nudged elastic band method, we
perform an extensive search of the migration and rotation paths of the most
stable carbon tri-interstitial cluster in cubic SiC. Our research reveals paths
with the lowest energy barriers to migration, rotation, and dissociation of the
most stable cluster. The kinetic properties of the most stable cluster,
including its mobility, rotation behavior at different temperatures and
stability against high temperature annealing, are discussed based on the
calculated transition barriers. In addition to fundamental insights, our study
provides a methodology for investigation of other extended defects in a
technologically important material.


title: Casimir effect via a generalized Matsubara formalism

abstract:
  We investigate the Casimir effect in the context of a nontrivial topology by
means of a generalized Matsubara formalism. This is performed in the context of
a scalar field in $D$ Euclidean spatial dimensions with $d$ compactified
dimensions. The procedure gives us the advantage of considering simultaneously
spatial constraints and thermal effects. In this sense, the Casimir pressure in
a heated system between two infinite planes is obtained and the results are
compared with those found in the literature.


title:
Tailoring magnetic energies to form dipole skyrmions and skyrmion
  lattices

abstract:
  The interesting physics and potential memory technologies resulting from
topologically protected spin textures such as skyrmions, has prompted efforts
to discover new material systems that can host these kind of magnetic
structures. Here we use the highly tunable magnetic properties of amorphous
Fe/Gd multilayer films to explore the magnetic properties that lead to
dipole-stabilized skyrmions and skyrmion lattices that form from the
competition of dipolar field and exchange energy. Using both real space imaging
and reciprocal space scattering techniques we determined the range of material
properties and magnetic fields where skyrmions form. Micromagnetic modeling
closely matches our observation of small skyrmion features (~50 to 70nm) and
suggests these class of skyrmions have a rich domain structure that is Bloch
like in the center of the film and more N\'eel like towards each surface. Our
results provide a pathway to engineer the formation and controllability of
dipole skyrmion phases in a thin film geometry at different temperatures and
magnetic fields.


title: Dressed Active Particles in Spherical Crystals

abstract:
  We investigate the dynamics of an active particle in two-dimensional
spherical crystals, which provide an ideal environment to illustrate the
interplay of active particle and crystallographic defects. A moving active
particle is observed to be surrounded by localized topological defects,
becoming a dressed active particle. Such a physical picture characterizes both
the lattice distortion around the moving particle and the healing of the
distorted lattice in its trajectory. We find that the dynamical behaviors of an
active particle in both random and ballistic motions uniformly conform to this
featured scenario, whether the particle is initially a defect or not. We
further observe that the defect pattern around a dressed ballistic active
particle randomly oscillates between two well-defined wing-like defect motifs
regardless of its speed. The established physical picture of dressed active
particles in this work partially deciphers the complexity of the intriguing
nonequilibrium behaviors in active crystals, and opens the promising
possibility of introducing the activity to engineer defects, which has strong
connections with the design of materials.


title: Feedback by AGN Jets and Wide-Angle Winds on a Galactic Scale

abstract:
  To investigate the differences in mechanical feedback from radio-loud and
radio-quiet Active Galactic Nuclei (AGN) on the host galaxy, we perform 3D AMR
hydrodynamic simulations of wide angle, radio-quiet winds with different
inclinations on a single, massive, gas-rich disk galaxy at a redshift of 2-3.
We compare our results to hydrodynamic simulations of the same galaxy but with
a jet. The jet has an inclination of 0 degrees (perpendicular to the galactic
plane), and the winds have inclinations of 0, 45, and 90 degrees. We analyze
the impact on the host's gas, star formation, and circum-galactic medium. We
find that jet feedback is energy-driven and wind feedback is momentum-driven.
In all the simulations, the jet or wind creates a cavity mostly devoid of dense
gas in the nuclear region where star formation is then quenched, but we find
strong positive feedback in all the simulations at radii greater than 3 kpc.
All four simulations have similar SFRs and stellar velocities with large radial
and vertical components. However, the wind at an inclination of 90 degrees
creates the highest density regions through ram pressure and generates the
highest rates of star formation due to its ongoing strong interaction with the
dense gas of the galactic plane. With increased wind inclination, we find
greater asymmetry in gas distribution and resulting star formation. Our model
generates an expanding ring of triggered star formation with typical velocity
of order 1/3 of the circular velocity, superimposed on the older stellar
population. This should result in a potentially detectable blue asymmetry in
stellar absorption features at kpc scales.


title:
Local-global principles for Weil-Ch\^atelet divisibility in positive
  characteristic

abstract:
  We extend existing results characterizing Weil-Ch\^atelet divisibility of
locally trivial torsors over number fields to global fields of positive
characteristic. Building on work of Gonz\'alez-Avil\'es and Tan, we
characterize when local-global divisibility holds in such contexts, providing
examples showing that these results are optimal. We give an example of an
elliptic curve over a global field of characteristic $2$ containing a rational
point which is locally divisible by $8$, but is not divisible by $8$ as well as
examples showing that the analogous local-global principle for divisibility in
the Weil-Ch\^atelet group can also fail.


title: Permutation NMF

abstract:
  Nonnegative Matrix Factorization(NMF) is a common used technique in machine
learning to extract features out of data such as text documents and images
thanks to its natural clustering properties. In particular, it is popular in
image processing since it can decompose several pictures and recognize common
parts if they're located in the same position over the photos. This paper's aim
is to present a way to add the translation invariance to the classical NMF,
that is, the algorithms presented are able to detect common features, even when
they're shifted, in different original images.


title: Matching Community Structure Across Online Social Networks

abstract:
  The discovery of community structure in networks is a problem of considerable
interest in recent years. In online social networks, often times, users are
simultaneously involved in multiple social media sites, some of which share
common social relationships. It is of great interest to uncover a shared
community structure across these networks. However, in reality, users typically
identify themselves with different usernames across social media sites. This
creates a great difficulty in detecting the community structure. In this paper,
we explore several approaches for community detection across online social
networks with limited knowledge of username alignment across the networks. We
refer to the known alignment of usernames as seeds. We investigate strategies
for seed selection and its impact on networks with a different fraction of
overlapping vertices. The goal is to study the interplay between network
topologies and seed selection strategies, and to understand how it affects the
detected community structure. We also propose several measures to assess the
performance of community detection and use them to measure the quality of the
detected communities in both Twitter-Twitter networks and Twitter-Instagram
networks.


title:
Discovery of Rapidly Moving Partial X-ray Absorbers within gamma
  Cassiopeiae

abstract:
  Gamma Cassiopeiae is an enigmatic Be star with unusually strong hard X-ray
emission. The Suzaku observatory detected six rapid X-ray spectral hardening
events called "softness dips" in a ~100 ksec duration observation in 2011. All
the softness dip events show symmetric softness ratio variations, and some of
them have flat bottoms apparently due to saturation. The softness dip spectra
are best described by either ~40% or ~70% partial covering absorption to kT ~12
keV plasma emission by matter with a neutral hydrogen column density of ~2-8e21
cm-2, while the spectrum outside of these dips is almost free of absorption.
This result suggests the presence of two distinct X-ray emitting spots in the
gamma Cas system, perhaps on a white dwarf companion with dipole mass
accretion. The partial covering absorbers may be blobs in the Be stellar wind,
the Be disk, or rotating around the white dwarf companion. Weak correlations of
the softness ratios to the hard X-ray flux suggest the presence of stable
plasmas at kT ~0.9 and 5 keV, which may originate from the Be or white dwarf
winds. The formation of a Be star and white dwarf binary system requires mass
transfer between two stars; gamma Cas may have experienced such activity in the
past.


title:
Braking Index of Isolated Pulsars II: A novel two-dipole model of pulsar
  magnetism

abstract:
  The magnetic dipole radiation (MDR) model is currently the best approach we
have to explain pulsar radiation. However a most characteristic parameter of
the observed radiation, the braking index n$_{\rm obs}$ shows deviations for
all the eight best studied isolated pulsars, from the simple model prediction
n$_{\rm dip}$ = 3. The index depends upon the rotational frequency and its
first and second time derivatives, but also on the assumption of that the
magnetic dipole moment and inclination angle, and the moment of inertia of the
pulsar are constant in time. In a recent paper [Phys. Rev. D 91, 063007 (2015)]
we showed conclusively that changes in the moment of inertia with frequency
alone, cannot explain the observed braking indices.
  Possible observational evidence for the magnetic dipole moment migrating away
from the rotational axis at a rate $\dot\alpha$ $\sim$ 0.6$^{\circ}$ per 100
years over the life time of the Crab pulsar has been recently suggested by Lyne
et al. In this paper, we explore the MDR model with constant moment of inertia
and magnetic dipole moment but variable inclination angle $\alpha$. We first
discuss the effect of the variation of $\alpha$ on the observed braking indices
and show they all can be understood. However, no explanation for the origin of
the change in $\alpha$ is provided.
  After discussion of the possible source(s) of magnetism in pulsars we propose
a simple mechanism for the change in $\alpha$ based on a toy model in which the
magnetic structure in pulsars consists of two interacting dipoles. We show that
such a system can explain the Crab observation and the measured braking
indices.


title: Moir\'e-free ultrathin iron oxide film: FeO(111) on Ag(111)

abstract:
  Ultrathin iron oxide films epitaxially grown on the (111)- and
(0001)-oriented metal single crystal supports exhibit unique electronic,
catalytic and magnetic properties not observed for the corresponding bulk
oxides. These properties originate mainly from the presence of Moir\'e
superstructures which, in turn, disqualify ultrathin films as model systems
imitating bulk materials. We present a route for the preparation of a
close-packed Moir\'e-free ultrathin iron oxide film, namely FeO(111) on
Ag(111). Experimental scanning tunneling microscopy (STM), low energy electron
diffraction (LEED) and x-ray photoelectron spectroscopy (XPS) results confirm
perfect structural order in the film. Density functional theory (DFT)-based
calculations suggest full relaxation of the oxide layer that adopts the atomic
lattice of the crystalline support and exhibits properties similar to those of
a free-standing FeO. The results open new pathways for model-type studies of
electronic, catalytic and magnetic properties of fully-relaxed iron oxide films
and related systems.


title: D-STREAMON - a NFV-capable distributed framework for network monitoring

abstract:
  Many reasons make NFV an attractive paradigm for IT security: lowers costs,
agile operations and better isolation as well as fast security updates,
improved incident responses and better level of automation. At the same time,
the network threats tend to be increasingly complex and distributed, implying
huge traffic scale to be monitored and increasingly strict mitigation delay
requirements. Considering the current trend of the networking and the
requirements to counteract to the evolution of cyber-threats, it is expected
that also network monitoring will move towards NFV based solutions. In this
paper, we present Distributed StreaMon (D-StreaMon) an NFV-capable distributed
framework for network monitoring. D-StreaMon has been designed to face the
above described challenges. It relies on the StreaMon platform, a solution for
network monitoring originally designed for traditional middleboxes. An
evolution path which migrates StreaMon from middleboxes to Virtual Network
Functions (VNFs) is described. The paper reports a performance evaluation of
the realized NFV based solution and discusses potential benefits in monitoring
tenants' VMs for Service Providers.


title:
Analysis of the Bayesian Cramer-Rao lower bound in astrometry: Studying
  the impact of prior information in the location of an object

abstract:
  Context. The best precision that can be achieved to estimate the location of
a stellar-like object is a topic of permanent interest in the astrometric
community.
  Aims. We analyse bounds for the best position estimation of a stellar-like
object on a CCD detector array in a Bayesian setting where the position is
unknown, but where we have access to a prior distribution. In contrast to a
parametric setting where we estimate a parameter from observations, the
Bayesian approach estimates a random object (i.e., the position is a random
variable) from observations that are statistically dependent on the position.
  Methods. We characterize the Bayesian Cramer-Rao (CR) that bounds the minimum
mean square error (MMSE) of the best estimator of the position of a point
source on a linear CCD-like detector, as a function of the properties of
detector, the source, and the background.
  Results. We quantify and analyse the increase in astrometric performance from
the use of a prior distribution of the object position, which is not available
in the classical parametric setting. This gain is shown to be significant for
various observational regimes, in particular in the case of faint objects or
when the observations are taken under poor conditions. Furthermore, we present
numerical evidence that the MMSE estimator of this problem tightly achieves the
Bayesian CR bound. This is a remarkable result, demonstrating that all the
performance gains presented in our analysis can be achieved with the MMSE
estimator.
  Conclusions The Bayesian CR bound can be used as a benchmark indicator of the
expected maximum positional precision of a set of astrometric measurements in
which prior information can be incorporated. This bound can be achieved through
the conditional mean estimator, in contrast to the parametric case where no
unbiased estimator precisely reaches the CR bound.


title:
On the Kunz-Souillard approach to localization for the discrete one
  dimensional generalized Anderson model

abstract:
  We prove dynamical and spectral localization at all energies for the discrete
generalized Anderson model via the Kunz-Souillard approach to localization.
This is an extension of the original Kunz-Souillard approach to localization
for Schr\"odinger operators, to the case where a single random variable
determines the potential on a block of an arbitrary, but fixed, size $\alpha$.
For this model, we also give a description of the almost sure spectrum as a set
and prove uniform positivity of the Lyapunov exponents. In fact, regarding
positivity of the Lyapunov exponents, we prove a stronger statement where we
also allow finitely supported distributions. We also show that for any size
$\alpha$ {\it generalized Anderson model}, there exists some finitely supported
distribution $\nu$ for which the Lyapunov exponent will vanish for at least one
energy. Moreover, restricting to the special case $\alpha=1$, we describe a
pleasant consequence of this modified technique to the original Kunz-Souillard
approach to localization. In particular, we demonstrate that actually the
single operator $T_1$ is a strict contraction in $L^2(\mathbb{R})$, whereas
before it was only shown that the second iterate of $T_1$ is a strict
contraction.


title: Ultra-Low Dissipation Superfluid Micromechanical Resonator

abstract:
  Micro and nanomechanical resonators with ultra-low dissipation have great
potential as useful quantum resources. The superfluid micromechanical
resonators presented here possess several advantageous characteristics:
straightforward thermalization, dissipationless flow, and in situ tunability.
We identify and quantitatively model the various dissipation mechanisms in two
resonators, one fabricated from borosilicate glass and one from single crystal
quartz. As the resonators are cryogenically cooled into the superfluid state,
the damping from thermal effects and from the normal fluid component are
strongly suppressed. At our lowest temperatures, damping is limited solely by
internal dissipation in the substrate materials, and reach quality factors up
to 913,000 at 13 mK. By lifting this limitation through substrate material
choice and resonator design, modelling suggests that the resonators should
reach quality factors as high as 10$^8$ at 100 mK, putting this architecture in
an ideal position to harness mechanical quantum effects.


title: The A-polynomial 2-tuple of twisted Whitehead links

abstract:
  We compute the A-polynomial 2-tuple of twisted Whitehead links. As
applications, we determine canonical components of twisted Whitehead links and
give a formula for the volume of twisted Whitehead link cone-manifolds.


title:
K-shell spectroscopy in hot plasmas: Stark effect, Breit interaction and
  QED corrections

abstract:
  The broadening of lines by Stark effect is widely used for inferring electron
density and temperature in plasmas. Stark-effect calculations often rely on
atomic data (transition rates, energy levels,...) not always exhaustive and/or
valid only for isolated atoms. In this work, we first present a recent
development in the detailed opacity code SCO-RCG for K-shell spectroscopy. The
approach is adapted from the work of Gilles and Peyrusse. Neglecting
non-diagonal terms in dipolar and collision operators, the line profile is
expressed as a sum of Voigt functions associated to the Stark components. The
formalism relies on the use of parabolic coordinates and the relativistic
fine-structure of Lyman lines is included by diagonalizing the hamiltonian
matrix associated to quantum states having the same principal quantum number n.
The SCO-RCG code enables one to investigate plasma environment effects, the
impact of the microfield distribution, the decoupling between electron and ion
temperatures and the role of satellite lines (such as Li-like 1s nl n'l' - 1s2
nl, Be-like, etc.). Atomic-structure calculations have reached levels of
accuracy which require evaluation of Breit interaction and many-electron
quantum electro-dynamics (QED) contributions. Although much work was done for
QED effects (self-energy and vacuum polarization) in hydrogenic atoms, the case
of an arbitrary number of electrons is more complicated. Since exact analytic
solutions do not exist, a number of heuristic methods have been used to
approximate the screening of additional \'electrons in the self-energy part. We
compare different ways of including such effects in atomic-structure codes
(Slater-Condon, Multi-Configuration Dirac-Fock, etc.).


title: Braking Index of Isolated Pulsars

abstract:
  Isolated pulsars are rotating neutron stars with accurately measured angular
velocities $\Omega$, and their time derivatives that show unambiguously that
the pulsars are slowing down. The commonly accepted view is that it arises
through emission of magnetic dipole radiation (MDR) from a rotating magnetized
body. The calculated energy loss by a rotating pulsar with a constant moment of
inertia is assumed proportional to a model dependent power of $\Omega$. This
relation leads to the power law $\dot{\Omega}$ = -K $\Omega^{\rm n}$ where $n$
is called the braking index. The MDR model predicts $n$ exactly equal to 3.
Selected observations of isolated pulsars provide rather precise values of $n$,
individually accurate to a few percent or better, in the range 1$ <$ n $ < $
2.8, which is consistently less than the predictions of the MDR model. In spite
of an extensive investigation of various modifications of the MDR model, no
satisfactory explanation of observation has been found yet.
  The aim of this work is to determine the deviation of the value of $n$ from
the canonical $n = 3$ for a star with a frequency dependent moment of inertia
in the region of frequencies from zero to the Kepler velocity (onset of mass
shedding by a rotating deformed star), in the macroscopic MDR model. For the
first time, we use microscopic realistic equations of state (EoS) of the star
to determine its behavior and structure. In addition, we examine the effects of
the baryonic mass M$_{\rm B}$ of the star, and possible core superfluidity, on
the value of the braking index within the MDR model.


title: Censored symmetric L\'evy processes

abstract:
  We examine three equivalent constructions of a censored symmetric purely
discontinuous L\'evy process on an open set $D$; via the corresponding
Dirichlet form, through the Feynman-Kac transform of the L\'evy process killed
outside of $D$ and from the same killed process by the Ikeda-Nagasawa-Watanabe
piecing together procedure. By applying the trace theorem on $n$-sets for
Besov-type spaces of generalized smoothness associated with complete Bernstein
functions satisfying certain scaling conditions, we analyze the boundary
behaviour of the corresponding censored L\'evy process and determine conditions
under which the process approaches the boundary $\partial D$ in finite time.
Furthermore, we prove a stronger version of the 3G inequality and its
generalized version for Green functions of purely discontinuous L\'evy
processes on $\kappa$-fat open sets. Using this result, we obtain the scale
invariant Harnack inequality for the corresponding censored process.


title:
Improving Predictions with Reliable Extrapolation Schemes and Better
  Understanding of Factorization

abstract:
  We investigate two distinct sources of uncertainty in low-energy nuclear
physics calculations and develop ways to account for them.
  Harmonic oscillator basis expansions are widely used in ab-initio nuclear
structure calculations. Finite computational resources usually require that the
basis be truncated before observables are fully converged, necessitating
reliable extrapolation schemes. We show that a finite oscillator basis
effectively imposes a hard-wall boundary condition. We accurately determine the
position of the hard-wall as a function of oscillator space parameters, derive
extrapolation formulas for the energy and other observables, and discuss the
extension of this approach to higher angular momentum.
  Nucleon knockout reactions have been widely used to study and understand
nuclear properties. Such an analysis implicitly assumes that the effects of the
probe can be separated from the physics of the target nucleus. This
factorization between nuclear structure and reaction components depends on the
renormalization scale and scheme, and has not been well understood. But it is
potentially critical for interpreting experiments and for extracting
process-independent nuclear properties. We use similarity renormalization group
(SRG) transformations to systematically study the scale dependence of
factorization for the simplest knockout process of deuteron
electrodisintegration. We find that the extent of scale dependence depends
strongly on kinematics, but in a systematic way. Based on examination of the
relevant overlap matrix elements, we are able to qualitatively explain and even
predict the nature of scale dependence based on the kinematics under
consideration.


title: Cross-Domain Entity Resolution in Social Media

abstract:
  The challenge of associating entities across multiple domains is a key
problem in social media understanding. Successful cross-domain entity
resolution provides integration of information from multiple sites to create a
complete picture of user and community activities, characteristics, and trends.
In this work, we examine the problem of entity resolution across Twitter and
Instagram using general techniques. Our methods fall into three categories:
profile, content, and graph based. For the profile-based methods, we consider
techniques based on approximate string matching. For content-based methods, we
perform author identification. Finally, for graph-based methods, we apply novel
cross-domain community detection methods and generate neighborhood-based
features. The three categories of methods are applied to a large graph of users
in Twitter and Instagram to understand challenges, determine performance, and
understand fusion of multiple methods. Final results demonstrate an equal error
rate less than 1%.


title:
Minimal Ingredients for Orbital Texture Switches at Dirac Points in
  Strong Spin-Orbit Coupled Materials

abstract:
  Recent angle resolved photoemission spectroscopy measurements on strong
spin-orbit coupled materials have shown an in-plane orbital texture switch at
their respective Dirac points, regardless of whether they are topological
insulators or "trivial" Rashba materials. This feature has also been
demonstrated in a few materials ($\text{Bi}_2\text{Se}_3$,
$\text{Bi}_2\text{Te}_3$, and $\text{BiTeI}$) though DFT calculations. Here we
present a minimal orbital-derived tight binding model to calculate the electron
wave-function in a two-dimensional crystal lattice. We show that the orbital
components of the wave-function demonstrate an orbital-texture switch in
addition to the usual spin switch seen in spin polarized bands. This orbital
texture switch is determined by the existence of three main properties: local
or global inversion symmetry breaking, strong spin-orbit coupling, and
non-local physics (the electrons are on a lattice). Using our model we
demonstrate that the orbital texture switch is ubiquitous and to be expected in
many real systems. The orbital hybridization of the bands is the key aspect for
understanding the unique wave function properties of these materials, and this
minimal model helps to establish the quantum perturbations that drive these
hybridizations.


title: Observation of Multimode Solitons in Few-Mode Fiber

abstract:
  We experimentally isolate and directly observe multimode solitons in few-mode
graded-index fiber. By varying the input energy and modal composition of the
launched pulse, we observe a continuous variation of multimode solitons with
different spatiotemporal properties. They exhibit an energy-volume relation
that is distinct from those of single-mode and fully spatiotemporal solitons.


title:
The bending of the proton plus helium flux in primary cosmic rays
  measured by the ARGO-YBJ experiment in the energy range from 20 TeV to 5 PeV

abstract:
  The measurement of proton plus helium and all-particle energy spectra in the
range $20\,$ TeV to $5 \,$PeV and $80 \,$TeV to $5 \,$PeV respectively are
presented. Data taken by the ARGO-YBJ detector in the 2010 year have been
analyzed. The ARGO-YBJ experiment (Tibet, P. R. China) has been taking data for
more than five years by means of a full-coverage array of RPC detectors. The
discrimination between showers produced by light and heavy primaries has been
performed by looking at the lateral particle density close to the core region.
A Bayesian unfolding technique was therefore applied to the measured quantities
in order to evaluate the cosmic ray energy spectrum. The proton plus helium
spectrum clearly shows a bending at about $1 \,$PeV, while the all-particle
spectrum is consistent with previous observations.


title:
Extensions of CM elliptic curves and orbit counting on the projective
  line

abstract:
  There are several formulas for the number of orbits of the projective line
under the action of subgroups of $GL_2$. We give an interpretation of two such
formulas in terms of the geometry of elliptic curves, and prove a more general
formula for a large class of congruence subgroups of Bianchi groups. Our
formula involves the number of walks on a certain graph called an isogeny
volcano. Underlying our results is a complete description of the group of
extensions of a pair of CM elliptic curves, and of a pair of lattices in a
quadratic field.


title:
Language free character recognition using character sketch and center of
  gravity shifting

abstract:
  In this research, we present a heuristic method for character recognition.
For this purpose, a sketch is constructed from the image that contains the
character to be recognized. This sketch contains the most important pixels of
image that are representatives of original image. These points are the most
probable points in pixel-by-pixel matching of image that adapt to target image.
Furthermore, a technique called gravity shifting is utilized for taking over
the problem of elongation of characters. The consequence of combining sketch
and gravity techniques leaded to a language free character recognition method.
This method can be implemented independently for real-time uses or in
combination of other classifiers as a feature extraction algorithm. Low
complexity and acceptable performance are the most impressive features of this
method that let it to be simply implemented in mobile and battery-limited
computing devices. Results show that in the best case 86% of accuracy is
obtained and in the worst case 28% of recognized characters are accurate.


title: A phenomenological dislocation mobility law for bcc metals

abstract:
  Dislocation motion in body centered cubic (bcc) metals displays a number of
specific features that result in a strong temperature dependence of the flow
stress, and in shear deformation asymmetries relative to the loading direction
as well as crystal orientation. Here we develop a generalized dislocation
mobility law in bcc metals, and demonstrate its use in discrete Dislocation
Dynamics (DD) simulations of plastic flow in tungsten (W) micro pillars. We
present the theoretical background for dislocation mobility as a motivating
basis for the developed law. Analytical theory, molecular dynamics (MD)
simulations, and experimental data are used to construct a general
phenomenological description. The usefulness of the mobility law is
demonstrated through its application to modeling the plastic deformation of W
micro pillars. The model is consistent with experimental observations of
temperature and orientation dependence of the flow stress and the corresponding
dislocation microstructure.


title: Affine Monotonic and Risk-Sensitive Models in Dynamic Programming

abstract:
  In this paper we consider a broad class of infinite horizon discrete-time
optimal control models that involve a nonnegative cost function and an affine
mapping in their dynamic programming equation. They include as special cases
classical models such as stochastic undiscounted nonnegative cost problems,
stochastic multiplicative cost problems, and risk-sensitive problems with
exponential cost. We focus on the case where the state space is finite and the
control space has some compactness properties. We assume that the affine
mapping has a semicontractive character, whereby for some policies it is a
contraction, while for others it is not. In one line of analysis, we impose
assumptions that guarantee that the latter policies cannot be optimal. Under
these assumptions, we prove strong results that resemble those for discounted
Markovian decision problems, such as the uniqueness of solution of Bellman's
equation, and the validity of forms of value and policy iteration. In the
absence of these assumptions, the results are weaker and unusual in character:
the optimal cost function need not be a solution of Bellman's equation, and an
optimal policy may not be found by value or policy iteration. Instead the
optimal cost function over just the contractive policies solves Bellman's
equation, and can be computed by a variety of algorithms.


title:
Recurrence and transience of contractive autoregressive processes and
  related Markov chains

abstract:
  We characterize recurrence and transience of nonnegative multivariate
autoregressive processes of order one with random contractive coefficient
matrix, of subcritical multitype Galton-Watson branching processes in random
environment with immigration, and of the related max-autoregressive processes
and general random exchange processes. Our criterion is given in terms of the
maximal Lyapunov exponent of the coefficient matrix and the cumulative
distribution function of the innovation/immigration component.


title: Harmonic measure on sets of codimension larger than one

abstract:
  We introduce a new notion of a harmonic measure for a $d$-dimensional set in
$\R^n$ with $d<n-1$, that is, when the codimension is strictly bigger than 1.
Our measure is associated to a degenerate elliptic PDE, it gives rise to a
comprehensive elliptic theory, and, most notably, it is absolutely continuous
with respect to the $d$-dimensional Hausdorff measure on reasonably nice sets.
This note provides general strokes of the proof of the latter statement for
Lipschitz graphs with small Lipschitz constant.


title: Quasimetric embeddings and their applications

abstract:
  We study generalizations of classical metric embedding results to the case of
quasimetric spaces; that is, spaces that do not necessarily satisfy symmetry.
Quasimetric spaces arise naturally from the shortest-path distances on directed
graphs. Perhaps surprisingly, very little is known about low-distortion
embeddings for quasimetric spaces.
  Random embeddings into ultrametric spaces are arguably one of the most
successful geometric tools in the context of algorithm design. We extend this
to the quasimetric case as follows. We show that any $n$-point quasimetric
space supported on a graph of treewidth $t$ admits a random embedding into
quasiultrametric spaces with distortion $O(t \log^2 n)$, where
quasiultrametrics are a natural generalization of ultrametrics. This result
allows us to obtain $t\log^{O(1)} n$-approximation algorithms for the Directed
Non-Bipartite Sparsest-Cut and the Directed Multicut problems on $n$-vertex
graphs of treewidth $t$, with running time polynomial in both $n$ and $t$.
  The above results are obtained by considering a generalization of random
partitions to the quasimetric case, which we refer to as random
quasipartitions. Using this definition and a construction of [Chuzhoy and
Khanna 2009] we derive a polynomial lower bound on the distortion of random
embeddings of general quasimetric spaces into quasiultrametric spaces. Finally,
we establish a lower bound for embedding the shortest-path quasimetric of a
graph $G$ into graphs that exclude $G$ as a minor. This lower bound is used to
show that several embedding results from the metric case do not have natural
analogues in the quasimetric setting.


title:
Role of Electron Inertia and Reconnection Dynamics in a Stressed X-point
  Collapse with a Guide-Field

abstract:
  In previous simulations of collisionless 2D magnetic reconnection it was
consistently found that the term in the generalised Ohm's law that breaks the
frozen-in condition is the divergence of the electron pressure tensor's
non-gyrotropic components. A fully relativistic particle-in-cell (PIC) code was
used to model $X$-point collapse with a guide-field in two and three spatial
dimensions. We show that in a 2D $X$-point collapse with a guide-field close to
the strength of the in-plane field, the increased induced shear flows along the
diffusion region lead to a new reconnection regime in which electron inertial
terms play a dominant role at the $X$-point. This transition is marked by the
emergence of a magnetic island - and hence a second reconnection site - as well
as electron flow vortices moving along the current sheet. The reconnection
electric field at the $X$-point is shown to exceed all lower guide-field cases
for a brief period, indicating a strong burst in reconnection. By extending the
simulation to three spatial dimensions it is shown that the locations of
vortices along the current sheet (visualised by their $Q$-value) vary in the
out-of-plane direction, producing tilted vortex tubes. The vortex tubes on
opposite sides of the diffusion region are tilted in opposite directions,
similarly to bifurcated current sheets in oblique tearing-mode reconnection.
The tilt angles of vortex tubes were compared to a theoretical estimation and
were found to be a good match. Particle velocity distribution functions for
different guide-field runs, for 2.5D and 3D simulations, are analysed and
compared.


title:
Iterative Hard Thresholding for Model Selection in Genome-Wide
  Association Studies

abstract:
  A genome-wide association study (GWAS) correlates marker variation with trait
variation in a sample of individuals. Each study subject is genotyped at a
multitude of SNPs (single nucleotide polymorphisms) spanning the genome. Here
we assume that subjects are unrelated and collected at random and that trait
values are normally distributed or transformed to normality. Over the past
decade, researchers have been remarkably successful in applying GWAS analysis
to hundreds of traits. The massive amount of data produced in these studies
present unique computational challenges. Penalized regression with LASSO or MCP
penalties is capable of selecting a handful of associated SNPs from millions of
potential SNPs. Unfortunately, model selection can be corrupted by false
positives and false negatives, obscuring the genetic underpinning of a trait.
This paper introduces the iterative hard thresholding (IHT) algorithm to the
GWAS analysis of continuous traits. Our parallel implementation of IHT
accommodates SNP genotype compression and exploits multiple CPU cores and
graphics processing units (GPUs). This allows statistical geneticists to
leverage commodity desktop computers in GWAS analysis and to avoid
supercomputing. We evaluate IHT performance on both simulated and real GWAS
data and conclude that it reduces false positive and false negative rates while
remaining competitive in computational time with penalized regression. Source
code is freely available at https://github.com/klkeys/IHT.jl.


title:
Few paths, fewer words: model selection with automatic structure
  functions

abstract:
  We consider the problem of finding an optimal statistical model for a given
binary string. Following Kolmogorov, we use structure functions. In order to
get concrete results, we replace Turing machines by finite automata and
Kolmogorov complexity by Shallit and Wang's automatic complexity.
  The $p$-value of a model for given data $x$ is the probability that there
exists a model with as few states, accepting as few words, fitting uniformly
randomly selected data $y$.
  Deterministic and nondeterministic automata can give different optimal
models. For $x=011\, 110\, 110\, 11$, the best deterministic model has
$p$-value $0.3$, whereas the best nondeterministic model has $p$-value $0.04$.
  In the nondeterministic case, counting paths and counting words can give
different optimal models. For $x=01100\, 01000$, the best path-counting model
has $p$-value $0.79$, whereas the best word-counting model has $p$-value
$0.60$.


title: Anderson-Witting transport coefficients for flows in general relativity

abstract:
  The transport coefficients induced by the Anderson-Witting approximation of
the collision term in the relativistic Boltzmann equation are derived for close
to equilibrium flows in general relativity. Using the tetrad formalism, it is
shown that the expression for these coefficients is the same as that obtained
on flat space-time, in agreement with the generalized equivalence principle.


title: Dual Density Operators and Natural Language Meaning

abstract:
  Density operators allow for representing ambiguity about a vector
representation, both in quantum theory and in distributional natural language
meaning. Formally equivalently, they allow for discarding part of the
description of a composite system, where we consider the discarded part to be
the context. We introduce dual density operators, which allow for two
independent notions of context. We demonstrate the use of dual density
operators within a grammatical-compositional distributional framework for
natural language meaning. We show that dual density operators can be used to
simultaneously represent: (i) ambiguity about word meanings (e.g. queen as a
person vs. queen as a band), and (ii) lexical entailment (e.g. tiger ->
mammal). We provide a proof-of-concept example.


title: Interacting Conceptual Spaces

abstract:
  We propose applying the categorical compositional scheme of [6] to conceptual
space models of cognition. In order to do this we introduce the category of
convex relations as a new setting for categorical compositional semantics,
emphasizing the convex structure important to conceptual space applications. We
show how conceptual spaces for composite types such as adjectives and verbs can
be constructed. We illustrate this new model on detailed examples.


title: Words, Concepts, and the Geometry of Analogy

abstract:
  This paper presents a geometric approach to the problem of modelling the
relationship between words and concepts, focusing in particular on analogical
phenomena in language and cognition. Grounded in recent theories regarding
geometric conceptual spaces, we begin with an analysis of existing static
distributional semantic models and move on to an exploration of a dynamic
approach to using high dimensional spaces of word meaning to project subspaces
where analogies can potentially be solved in an online, contextualised way. The
crucial element of this analysis is the positioning of statistics in a
geometric environment replete with opportunities for interpretation.


title: Quantifier Scope in Categorical Compositional Distributional Semantics

abstract:
  In previous work with J. Hedges, we formalised a generalised quantifiers
theory of natural language in categorical compositional distributional
semantics with the help of bialgebras. In this paper, we show how quantifier
scope ambiguity can be represented in that setting and how this representation
can be generalised to branching quantifiers.


title: Entailment Relations on Distributions

abstract:
  In this paper we give an overview of partial orders on the space of
probability distributions that carry a notion of information content and serve
as a generalisation of the Bayesian order given in (Coecke and Martin, 2011).
We investigate what constraints are necessary in order to get a unique notion
of information content. These partial orders can be used to give an ordering on
words in vector space models of natural language meaning relating to the
contexts in which words are used, which is useful for a notion of entailment
and word disambiguation. The construction used also points towards a way to
create orderings on the space of density operators which allow a more
fine-grained study of entailment. The partial orders in this paper are directed
complete and form domains in the sense of domain theory.


title: Quantum Algorithms for Compositional Natural Language Processing

abstract:
  We propose a new application of quantum computing to the field of natural
language processing. Ongoing work in this field attempts to incorporate
grammatical structure into algorithms that compute meaning. In (Coecke,
Sadrzadeh and Clark, 2010), the authors introduce such a model (the CSC model)
based on tensor product composition. While this algorithm has many advantages,
its implementation is hampered by the large classical computational resources
that it requires. In this work we show how computational shortcomings of the
CSC approach could be resolved using quantum computation (possibly in addition
to existing techniques for dimension reduction). We address the value of
quantum RAM (Giovannetti,2008) for this model and extend an algorithm from
Wiebe, Braun and Lloyd (2012) into a quantum algorithm to categorize sentences
in CSC. Our new algorithm demonstrates a quadratic speedup over classical
methods under certain conditions.


title: Some questions on subgroups of 3-dimensional Poincar\'e duality groups

abstract:
  We state a number of open questions on 3-dimensional Poincar\'e duality
groups and their subgroups, motivated by considerations from 3-manifold
topology.


title: Variable Packet-Error Coding

abstract:
  We consider a problem in which a source is encoded into N packets, an unknown
number of which are subject to adversarial errors en route to the decoder. We
seek code designs for which the decoder is guaranteed to be able to reproduce
the source subject to a certain distortion constraint when there are no packets
errors, subject to a less stringent distortion constraint when there is one
error, etc. Focusing on the special case of the erasure distortion measure, we
introduce a code design based on the polytope codes of Kosut, Tong, and Tse.
The resulting designs are also applied to a separate problem in distributed
storage.


title: Faster CNNs with Direct Sparse Convolutions and Guided Pruning

abstract:
  Phenomenally successful in practical inference problems, convolutional neural
networks (CNN) are widely deployed in mobile devices, data centers, and even
supercomputers. The number of parameters needed in CNNs, however, are often
large and undesirable. Consequently, various methods have been developed to
prune a CNN once it is trained. Nevertheless, the resulting CNNs offer limited
benefits. While pruning the fully connected layers reduces a CNN's size
considerably, it does not improve inference speed noticeably as the compute
heavy parts lie in convolutions. Pruning CNNs in a way that increase inference
speed often imposes specific sparsity structures, thus limiting the achievable
sparsity levels.
  We present a method to realize simultaneously size economy and speed
improvement while pruning CNNs. Paramount to our success is an efficient
general sparse-with-dense matrix multiplication implementation that is
applicable to convolution of feature maps with kernels of arbitrary sparsity
patterns. Complementing this, we developed a performance model that predicts
sweet spots of sparsity levels for different layers and on different computer
architectures. Together, these two allow us to demonstrate 3.1--7.3$\times$
convolution speedups over dense convolution in AlexNet, on Intel Atom, Xeon,
and Xeon Phi processors, spanning the spectrum from mobile devices to
supercomputers. We also open source our project at
https://github.com/IntelLabs/SkimCaffe.


title: Bayesian Kernel and Mutual $k$-Nearest Neighbor Regression

abstract:
  We propose Bayesian extensions of two nonparametric regression methods which
are kernel and mutual $k$-nearest neighbor regression methods. Derived based on
Gaussian process models for regression, the extensions provide distributions
for target value estimates and the framework to select the hyperparameters. It
is shown that both the proposed methods asymptotically converge to kernel and
mutual $k$-nearest neighbor regression methods, respectively. The simulation
results show that the proposed methods can select proper hyperparameters and
are better than or comparable to the former methods for an artificial data set
and a real world data set.


title:
Heat accumulation and all-optical switching by domain wall motion in
  Co/Pd superlattices

abstract:
  All-optical switching by domain wall motion has been observed in Co/Pd
superlattices. Heat accumulation is part of the switching process for our
experimental conditions. Numerical calculations point to a connection between
domain wall motion and in-plane heat diffusion.


title:
Sum formulas of mltiple zeta values with arguments are multiple of a
  positive integer

abstract:
  For $k\leq n$, let $E(mn,k)$ be the sum of all multiple zeta values of depth
$k$ and weight $mn$ with arguments are multiples of $m\geq 2$. More precisely,
$E(mn,k)=\sum_{|\boldsymbol{\alpha}|=n}\zeta(m\alpha_1,m\alpha_2,\ldots,
m\alpha_k)$. In this paper, we develop a formula to express $E(mn,k)$ in terms
of $\zeta(\{m\}^p)$ and $\zeta^\star(\{m\}^q)$, $0\leq p,q\leq n$. In
particular, we settle Gen\v{c}ev's conjecture on the evaluation of $E(4n,k)$
and also evaluate $E(mn,k)$ explicitly for small even $m\leq 8$.


title: Solving General Arithmetic Word Problems

abstract:
  This paper presents a novel approach to automatically solving arithmetic word
problems. This is the first algorithmic approach that can handle arithmetic
problems with multiple steps and operations, without depending on additional
annotations or predefined templates. We develop a theory for expression trees
that can be used to represent and evaluate the target arithmetic expressions;
we use it to uniquely decompose the target arithmetic problem to multiple
classification problems; we then compose an expression tree, combining these
with world knowledge through a constrained inference framework. Our classifiers
gain from the use of {\em quantity schemas} that supports better extraction of
features. Experimental results show that our method outperforms existing
systems, achieving state of the art performance on benchmark datasets of
arithmetic word problems.


title: Properties of the Extended Graph Permanent

abstract:
  Previously, the graph permanent was introduced as a single-valued invariant
for graphs $G$ with $|E(G)| = k(|V(G)|-1)$ for some $k \in \mathbb{Z}_{>0}$.
Herein, we construct the extended graph permanent, an infinite sequence for all
graphs. We prove that, like the graph permanent, the extended graph permanent
is invariant under the graph operations that are known to preserve the period.
Further, the original construction and extension arise from permanents of
matrices, but we construct a novel graph polynomial such that the sequence can
be generated from the point count of this polynomial, as a residue over
prime-order finite fields.


title:
Shadow prices, fractional Brownian motion, and portfolio optimisation
  under transaction costs

abstract:
  We continue the analysis of our previous paper (Czichowsky/Schachermayer/Yang
2014) pertaining to the existence of a shadow price process for portfolio
optimisation under proportional transaction costs. There, we established a
positive answer for a continuous price process $S=(S_t)_{0\leq t\leq T}$
satisfying the condition $(NUPBR)$ of "no unbounded profit with bounded risk".
This condition requires that $S$ is a semimartingale and therefore is too
restrictive for applications to models driven by fractional Brownian motion. In
the present paper, we derive the same conclusion under the weaker condition
$(TWC)$ of "two way crossing", which does not require $S$ to be a
semimartingale. Using a recent result of R.~Peyre, this allows us to show the
existence of a shadow price for exponential fractional Brownian motion and
$all$ utility functions defined on the positive half-line having reasonable
asymptotic elasticity. Prime examples of such utilities are logarithmic or
power utility.


title: A Computational Workflow for Designing Silicon Donor Qubits

abstract:
  Developing devices that can reliably and accurately demonstrate the
principles of superposition and entanglement is an on-going challenge for the
quantum computing community. Modeling and simulation offer attractive means of
testing early device designs and establishing expectations for operational
performance. However, the complex integrated material systems required by
quantum device designs are not captured by any single existing computational
modeling method. We examine the development and analysis of a multi-staged
computational workflow that can be used to design and characterize silicon
donor qubit systems with modeling and simulation. Our approach integrates
quantum computational chemistry calculations with electrostatic field solvers
to perform detailed simulations of a phosphorus dopant in silicon. We show how
atomistic details can be synthesized into an operational model for the logical
gates that define quantum computation in this particular technology. The
resulting computational workflow realizes a design tool for silicon donor
qubits that can help verify and validate current and near-term experimental
devices.


title: The Ursa Major cluster redefined as a `supergroup'

abstract:
  We identify gravitationally bound structures in the Ursa Major region using
positions, velocities and photometry from the Sloan Digital Sky Survey (SDSS
DR7) and the Third Reference Catalogue of Bright Galaxies (RC3). A
friends-of-friends algorithm is extensively tested on mock galaxy lightcones
and then implemented on the real data to determine galaxy groups whose members
are likely to be physically and dynamically associated with one another. We
find several galaxy groups within the region that are likely bound to one
another and in the process of merging. We classify 6 galaxy groups as the Ursa
Major `supergroup', which are likely to merge and form a poor cluster with a
mass of ~8x10^13 Msun. Furthermore, the Ursa Major supergroup as a whole is
likely bound to the Virgo cluster, which will eventually form an even larger
system in the context of hierarchical structure formation. [abridged]


title: Collatz Numbers

abstract:
  In this article we present set of infinite natural numbers which satisfies
the conjecture $3n+1$.


title:
Systems-level approach to uncovering diffusive states and their
  transitions from single particle trajectories

abstract:
  The stochastic motions of a diffusing particle contain information concerning
the particle's interactions with binding partners and with its local
environment. However, accurate determination of the underlying diffusive
properties, beyond normal diffusion, has remained challenging when analyzing
particle trajectories on an individual basis. Here, we introduce the maximum
likelihood estimator (MLE) for confined diffusion and fractional Brownian
motion. We demonstrate that this MLE yields improved estimation over
traditional mean square displacement analyses. We also introduce a model
selection scheme (that we call mleBIC) that classifies individual trajectories
to a given diffusion mode. We demonstrate the statistical limitations of
classification via mleBIC using simulated data. To overcome these limitations,
we introduce a new version of perturbation expectation-maximization (pEMv2),
which simultaneously analyzes a collection of particle trajectories to uncover
the system of interactions which give rise to unique normal and/or non-normal
diffusive states within the population. We test and evaluate the performance of
pEMv2 on various sets of simulated particle trajectories, which transition
among several modes of normal and non-normal diffusion, highlighting the key
considerations for employing this analysis methodology.


title: Modeling the early afterglow in the short and hard GRB 090510

abstract:
  The bright, short and hard GRB 090510 was detected by all instruments aboard
Fermi and Swift satellites. The multiwavelength observations of this burst
presented similar features with the Fermi-LAT-detected gamma-ray bursts. In the
framework of the external shock model of early afterglow, a leptonic scenario
that evolves in a homogeneous medium is proposed to revisit GRB 090510 and
explain the multiwavelength light curve observations presented in this burst.
These observations are consistent with the evolution of a jet before and after
the jet break. The long-lasting LAT, X-ray and optical fluxes are explained in
the synchrotron emission from the adiabatic forward shock. Synchrotron
self-Compton emission from the reverse shock is consistent with the bright LAT
peak provided that progenitor environment is entrained with strong magnetic
fields. It could provide compelling evidence of magnetic field amplification in
the neutron star merger.


title: Solar Obliquity Induced by Planet Nine: Simple Calculation

abstract:
  Bailey et al.~(2016) and Gomes et al.~(2016) recently suggested that the 6
degree misalignment between the Sun's rotational equator and the orbital plane
of the major planets may be produced by the forcing from the hypothetical
Planet Nine on an inclined orbit. Here we present a simple but accurate
calculation of the effect, which provides a clear description of how the Sun's
spin orientation depends on the property of Planet Nine in this scenario.


title: Turning Around along the Cosmic Web

abstract:
  A bound-violation designates a case that the turn-around radius of a bound
object exceeds the upper limit put by the spherical collapse model based on the
standard $\Lambda$CDM paradigm. Given that the turn-around radius of a bound
object is a stochastic quantity and that the spherical model overly simplifies
the true gravitational collapse which actually proceeds anisotropically along
the cosmic web, the rarity of the occurrence of a bound violation may depend on
the web environment. Assuming a Planck cosmology, we numerically construct the
bound-zone peculiar velocity profiles along the cosmic web (filaments and
sheets) around the isolated groups with virial mass $M_{\rm v}\ge 3\times
10^{13}\,h^{-1}M_{\odot}$ identified in the Small MultiDark Planck simulations
and determine the radial distances at which their peculiar velocities equal the
Hubble expansion speed as the turn-around radii of the groups. It is found that
although the average turn-around radii of the isolated groups are well below
the spherical bound-limit on all mass scales, the bound violations are not
forbidden for individual groups and that the cosmic web has an effect of
reducing the rarity of the occurrence of a bound violation. Explaining that the
spherical bound limit on the turn-around radius in fact represents the
threshold distance up to which the intervention of the external gravitational
field in the bound-zone peculiar velocity profiles around the non-isolated
groups stays negligible, we discuss the possibility of using the threshold
distance scale to constrain locally the equation of state of dark energy .


title: Multiplicaton formulas and canonical basis for quantum affine gl_n

abstract:
  We will give a representation-theoretic proof for the multiplication formula
in the Ringel-Hall algebra ${\frak H}_\Delta(n)$ of a cyclic quiver $\Delta(n)$
given in \cite[Thm~4.5]{DuFu2015quantum}. As a first application, we see
immediately the existence of Hall polynomials for cyclic quivers, a fact
established in \cite{Guo1995hallpoly} and \cite{Ringel1993composition}, and
derive a recursive formula to compute them. We will further use the formula and
the construction of certain monomial base for ${\mathfrak H}_\Delta(n)$ given
in \cite{DengDuXiao2007generic}, together with the double Ringel--Hall algebra
realisation of the quantum loop algebra $U_v(\hat{gl}_n)$ in
\cite{DengDuFu2012double}, to develop some algorithms and to compute the
canonical basis for $U_v(\hat{gl}_n)^+$. As examples, we will show explicitly
the part of the canonical basis associated with modules of Lowey length at most
$2$ for the quantum group $U_v(\hat{gl}_n)$.


title: Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

abstract:
  Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O$_2$
and N$_2$, which for low doses chemisorb only on defect sites or vacancies of
the SWCNTs at the ppm level. However, very low doping has a major effect on the
electronic properties and conductivity of the SWCNTs. Already at low O$_2$
doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes
saturated, indicating nearly all the SWCNT's vacancies have been oxidized. As a
result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather
low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that,
even under these conditions, the first principles density functional theory
calculated Kohn-Sham O 1s binding energies may be used to assign the XPS O 1s
spectra for oxidized vacancies on SWCNTs into its individual components. This
allows one to determine the specific functional groups or bonding environments
measured. We find the XPS O 1s signal is mostly due to three O-containing
functional groups on SWCNT vacancies: epoxy (C$_2$$>$O), carbonyl
(C$_2$$>$C$=$O), and ketene (C$=$C$=$O), as ordered by abundance. Upon
oxidation of nearly all the SWCNT's vacancies, the central peak's intensity for
the metallic SWCNT sample is 60\% greater than for the semiconducting SWCNT
sample. This suggests a greater abundance of O-containing defect structures on
the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find
O$_2$ does not contribute to the measured XPS O~1s spectra.


title: Commutators in the Endomorphism Ring of a Complex

abstract:
  According to an old result of Albert and Muckenhoupt, the commutators in the
endomorphism ring of a finite dimensional vector space are precisely the
elements of trace zero. We replace the finite dimensional vector space with a
complex of finite dimensional vector spaces, and characterize commutators and
other elements with commutator-like properties in terms of appropriately
defined traces.


title: Solving Laplacian Systems in Logarithmic Space

abstract:
  We investigate the space complexity of solving linear systems of equations.
While all known deterministic or randomized algorithms solving a square system
of $n$ linear equations in $n$ variables require $\Omega(\log^2 n)$ space,
Ta-Shma (STOC 2013) recently showed that on a quantum computer an approximate
solution can be computed in logarithmic space, giving the first explicit
computational task for which quantum computation seems to outperform classical
computation with respect to space complexity. In this paper we show that for
systems of linear equations in the Laplacian matrix of graphs, the same
logarithmic space complexity can actually be achieved by a classical (i.e.,
non-quantum) algorithm. More precisely, given a system of linear equations
$Lx=b$, where $L$ is the (normalized) Laplacian matrix of a graph on $n$
vertices and $b$ is a unit-norm vector, our algorithm outputs a vector $\tilde
x$ such that $\left\lVert\tilde x -x\right\rVert\le 1/\mathrm{poly}(n)$ and
uses only $O(\log n)$ space if the underlying graph has polynomially bounded
weights. We also show how to estimate, again in logarithmic space, the smallest
non-zero eigenvalue of $L$.


title: Higher-dimensional contact manifolds with infinitely many Stein fillings

abstract:
  For any integer $n\geq 2$, we construct an infinite family of Stein fillable
contact $(4n-1)$-manifolds each of which admits infinitely many pairwise
homotopy inequivalent Stein fillings.


title: Effects of Longitudinal Asymmetry in Heavy-Ion Collisions

abstract:
  In collisions of identical nuclei at a given impact parameter, the number of
nucleons participating in the overlap region of each nucleus can be unequal due
to nuclear density fluctuations. The asymmetry due to the unequal number of
participating nucleons, referred to as longitudinal asymmetry, causes a shift
in the center of mass rapidity of the participant zone. The information of the
event asymmetry allows us to isolate and study the effect of longitudinal
asymmetry on rapidity distribution of final state particles. In a Monte Carlo
Glauber model the average rapidity-shift is found to be almost linearly related
to the asymmetry. Using toy models, as well as Monte Carlo data for Pb-Pb
collisions at 2.76 TeV generated with HIJING, two different versions of AMPT
and DPMJET models, we demonstrate that the effect of asymmetry on final state
rapidity distribution can be quantitatively related to the average rapidity
shift via a third-order polynomial with a dominantly linear term. The
coefficients of the polynomial are proportional to the rapidity shift with the
dependence being sensitive to the details of the rapidity
distribution.Experimental estimates of the spectator asymmetry through the
measurement of spectator nucleons in a Zero Degree Calorimeter may hence be
used to further constrain the initial conditions in ultra-relativistic
heavy-ion collisions.


title: Distributed Observers for LTI Systems

abstract:
  We consider the problem of distributed state estimation of a linear
time-invariant (LTI) system by a network of sensors. We develop a distributed
observer that guarantees asymptotic reconstruction of the state for the most
general class of LTI systems, sensor network topologies and sensor measurement
structures. Our analysis builds upon the following key observation - a given
node can reconstruct a portion of the state solely by using its own
measurements and constructing appropriate Luenberger observers; hence it only
needs to exchange information with neighbors (via consensus dynamics) for
estimating the portion of the state that is not locally detectable. This
intuitive approach leads to a new class of distributed observers with several
appealing features. Furthermore, by imposing additional constraints on the
system dynamics and network topology, we show that it is possible to construct
a simpler version of the proposed distributed observer that achieves the same
objective while admitting a fully distributed design phase. Our general
framework allows extensions to time-varying networks that result from
communication losses, and scenarios including faults or attacks at the nodes.


title:
Demand Control Management in Micro-grids: The Impact of Different
  Policies and Communication Network Topologies

abstract:
  This work studies how the communication network between proactive consumers
affects the power utilization and fairness in a simplified direct-current
micro-grid model, composed by three coupled layers: physical (an electric
circuit that represents a micro-grid), communication (a peer-to-peer network
within the micro-grid) and regulatory (individual decision strategies). Our
results show that, for optimal power utilization and fairness, a global
knowledge about the system is needed, demonstrating the importance of a
micro-grid aggregator to inform about the power consumption for different time
periods.


title: An efficient iterative thresholding method for image segmentation

abstract:
  We proposed an efficient iterative thresholding method for multi-phase image
segmentation. The algorithm is based on minimizing piecewise constant
Mumford-Shah functional in which the contour length (or perimeter) is
approximated by a non-local multi-phase energy. The minimization problem is
solved by an iterative method. Each iteration consists of computing simple
convolutions followed by a thresholding step. The algorithm is easy to
implement and has the optimal complexity $O(N \log N)$ per iteration. We also
show that the iterative algorithm has the total energy decaying property. We
present some numerical results to show the efficiency of our method.


title:
Decision Error Probability in a Two-stage Communication Network for
  Smart Grids with Imperfect Data Links

abstract:
  This paper analyzes a scenario where the distribution system operator needs
to estimate whether the average power demand in a given period is above a
predetermined threshold using an 1-bit memoryless scheme. Specifically,
individual smart-meters periodically monitor the average power demand of their
respective households to inform the system operator if it is above a
predetermined level using only a 1-bit signal. The communication link between
the meters and the operator occurs in two hops and is modeled as binary
symmetric channels. The first hop connects individual smart meters to their
corresponding aggregator, while the second connects different aggregators to
the system operator. A decision about the power demand also happens in two
stages based on the received information bit. We consider here three decision
rules: AND, OR and MAJORITY. Our analytical results indicate the circumstances
(i.e. how frequent the meters experience the consumption above the defined
threshold) and the design setting (i.e. decision rules) that a low error
probability can be attained. We illustrate our approach with numerical results
from actual daily consumption from 12 households and 3 aggregators.


title: Assertion-based Analysis via Slicing with ABETS (System Description)

abstract:
  We present ABETS, an assertion-based, dynamic analyzer that helps diagnose
errors in Maude programs. ABETS uses slicing to automatically create reduced
versions of both a run's execution trace and executed program, reduced versions
in which any information that is not relevant to the bug currently being
diagnosed is removed. In addition, ABETS employs runtime assertion checking to
automate the identification of bugs so that whenever an assertion is violated,
the system automatically infers accurate slicing criteria from the failure. We
summarize the main services provided by ABETS, which also include a novel
assertion-based facility for program repair that generates suitable program
fixes when a state invariant is violated. Finally, we provide an experimental
evaluation that shows the performance and effectiveness of the system. This
paper is under consideration for publication in TPLP.


title:
Decoupling Jupiter's deep and atmospheric flows using the upcoming Juno
  gravity measurements and a dynamical inverse model

abstract:
  Observations of the flow on Jupiter exists essentially only for the
cloud-level, which is dominated by strong east-west jet-streams. These have
been suggested to result from dynamics in a superficial thin weather-layer, or
alternatively be a manifestation of deep interior cylindrical flows. However,
it is possible that the observed winds are indeed superficial, yet there exists
deep flow that is completely decoupled from it. To date, all models linking the
wind, via the induced density anomalies, to the gravity field, to be measured
by Juno, consider only flow that is a projection of the observed could-level
wind. Here we explore the possibility of complex wind dynamics that include
both the shallow weather-layer wind, and a deep flow that is decoupled from the
flow above it. The upper flow is based on the observed cloud-level flow and is
set to decay with depth. The deep flow is constructed to produce cylindrical
structures with variable width and magnitude, thus allowing for a wide range of
possible scenarios for the unknown deep flow. The combined flow is then related
to the density anomalies and gravitational moments via a dynamical model. An
adjoint inverse model is used for optimizing the parameters controlling the
setup of the deep and surface-bound flows, so that these flows can be
reconstructed given a gravity field. We show that the model can be used for
examination of various scenarios, including cases in which the deep flow is
dominating over the surface wind. We discuss extensively the uncertainties
associated with the model solution. The flexibility of the adjoint method
allows for a wide range of dynamical setups, so that when new observations and
physical understanding will arise, these constraints could be easily
implemented and used to better decipher Jupiter flow dynamics.


title:
Isotopic enrichment of forming planetary systems from supernova
  pollution

abstract:
  Heating by short-lived radioisotopes (SLRs) such as aluminum-26 and iron-60
fundamentally shaped the thermal history and interior structure of Solar System
planetesimals during the early stages of planetary formation. The subsequent
thermo-mechanical evolution, such as internal differentiation or rapid volatile
degassing, yields important implications for the final structure, composition
and evolution of terrestrial planets. SLR-driven heating in the Solar System is
sensitive to the absolute abundance and homogeneity of SLRs within the
protoplanetary disk present during the condensation of the first solids. In
order to explain the diverse compositions found for extrasolar planets, it is
important to understand the distribution of SLRs in active planet formation
regions (star clusters) during their first few Myr of evolution. By
constraining the range of possible effects, we show how the imprint of SLRs can
be extrapolated to exoplanetary systems and derive statistical predictions for
the distribution of aluminum-26 and iron-60 based on N-body simulations of
typical to large clusters (1000-10000 stars) with a range of initial
conditions. We quantify the pollution of protoplanetary disks by supernova
ejecta and show that the likelihood of enrichment levels similar to or higher
than the Solar System can vary considerably, depending on the cluster
morphology. Furthermore, many enriched systems show an excess in radiogenic
heating compared to Solar System levels, which implies that the formation and
evolution of planetesimals could vary significantly depending on the birth
environment of their host stars.


title: Non-geometric Five-branes in Heterotic Supergravity

abstract:
  We study T-duality chains of five-branes in heterotic supergravity where the
first order $\alpha'$-corrections are present. By performing the
$\alpha'$-corrected T-duality transformations of the heterotic NS5-brane
solutions, we obtain the KK5-brane and the exotic $5^2_2$-brane solutions
associated with the symmetric, the neutral and the gauge NS5-branes. We find
that the Yang-Mills gauge field in these solutions satisfies the self-duality
condition in the three- and two-dimensional transverse spaces to the brane
world-volumes. The $O(2,2)$ monodromy structures of the $5^2_2$-brane solutions
are investigated by the $\alpha'$-corrected generalized metric. Our analysis
shows that the symmetric $5^2_2$-brane solution, which satisfies the standard
embedding condition, is a T-fold and it exhibits the non-geometric nature. We
also find that the neutral $5^2_2$-brane solution is a T-fold at least at
$\mathcal{O} (\alpha')$. On the other hand, the gauge $5^2_2$-brane solution is
not a T-fold but show unusual structures of space-time.


title:
A New Energy Conservation Law for Time-Harmonic Electromagnetic Fields
  and Its Applications

abstract:
  We report a new energy conservation law for time-harmonic electromagnetic
fields, which is valid for an arbitrary medium. In contrast to the
well-established Poynting theorem for time-harmonic fields, the real part of
the new energy conservation law gives an equation for the sum of stored
electric and magnetic field energies and the imaginary part involves an
equation related to the difference between the dissipated electric and magnetic
energies. Universally applicable expressions for both the electric and magnetic
field energies have been obtained and demonstrated to be valuable in
characterizing the energy storage and transport properties in complex media.
For a lossless isotropic and homogeneous medium, the new energy conservation
law implies that the stored electromagnetic field energy of a radiating system
enclosed by a surface is equal to the total field energy inside the surface
subtracted by the energy flowing out of the surface.


title: Three friendly walkers

abstract:
  More than 15 years ago Guttmann and V\"oge [J. Statist. Plann. Inference,
{\bf 101}, 107 (2002)], introduced a model of friendly walkers. Since then it
has remained unsolved. In this paper we provide the exact solution to a closely
allied model, originally introduced by Tsuchiya and Katori [J. Phys. Soc. Japan
{\bf 67}, 1655 (1988)], which essentially only differs in the boundary
conditions. The exact solution is expressed in terms of the reciprocal of the
generating function for vicious walkers which is a D-finite function. However,
ratios of D-finite functions are inherently not D-finite and in this case we
prove that the friendly walkers generating function is the solution to a
non-linear differential equation with polynomial coefficients, it is in other
words D-algebraic. We then show via numerically exact calculations that the
generating function of the original model can also be expressed as a D-finite
function times the reciprocal of the generating function for vicious walkers.
We obtain an expression for this D-finite function in terms of a ${}_{2}F_{1}$
hypergeometric function with a rational pullback and its first and second
derivatives.

categories: math-ph cond-mat.stat-mech math.CA math.CO math.MP


title:
Re-appraisal and extension of the Gratton-Vargas two-dimensional
  analytical snowplow model of plasma focus - Part II: Looking at the
  singularity

abstract:
  The Gratton-Vargas snowplow model, recently revisited and expanded (S K H
Auluck, Physics of Plasmas, 20, 112501 (2013)), has given rise to significant
new insights into some aspects of the Dense Plasma Focus (DPF), in spite of
being a purely kinematic description having no reference to plasma phenomena.
It is able to provide a good fit to the experimental current waveforms in at
least 4 large facilities. It has been used for construction of a local
curvilinear frame of reference, in which conservation laws for mass, momentum
and energy can be reduced to effectively-one-dimensional hyperbolic
conservation law equations. Its utility in global parameter optimization of
device parameters has been demonstrated. These features suggest that the
Gratton-Vargas model deserves a closer look at its supposed limitations near
the singular phase of the DPF. This paper presents a discussion of its
development near the device axis, based on the original work of Gratton and
Vargas, with some differences. It is shown that the Gratton-Vargas partial
differential equation has solutions for times after the current singularity,
which exhibit an expanding bounded volume, (which can serve as model of an
expanding plasma column) and decreasing dynamic inductance of the discharge, in
spite of having no built-in hydrodynamics. This enables the model to
qualitatively reproduce the characteristic shape of the current derivative in
DPF experiments without reference to any plasma phenomena such as
instabilities, anomalous resistance or reflection of hydrodynamic shock wave
from the axis. The axial propagation of the solution exhibits a power-law
dependence on the dimensionless time starting from the time of singularity,
which is similar to the power-law relations predicted by theory of point
explosions in ideal gases and which has also been observed experimentally.


title:
Anopheles number prediction on environmental and climate variables using
  Lasso and stratified two levels cross validation

abstract:
  This paper deals with prediction of anopheles number using environmental and
climate variables. The variables selection is performed by an automatic machine
learning method based on Lasso and stratified two levels cross validation.
Selected variables are debiased while the predictionis generated by simple GLM
(Generalized linear model). Finally, the results reveal to be qualitatively
better, at selection, the prediction,and the CPU time point of view than those
obtained by B-GLM method.


title:
Improving Multi-label Learning with Missing Labels by Structured
  Semantic Correlations

abstract:
  Multi-label learning has attracted significant interests in computer vision
recently, finding applications in many vision tasks such as multiple object
recognition and automatic image annotation. Associating multiple labels to a
complex image is very difficult, not only due to the intricacy of describing
the image, but also because of the incompleteness nature of the observed
labels. Existing works on the problem either ignore the label-label and
instance-instance correlations or just assume these correlations are linear and
unstructured. Considering that semantic correlations between images are
actually structured, in this paper we propose to incorporate structured
semantic correlations to solve the missing label problem of multi-label
learning. Specifically, we project images to the semantic space with an
effective semantic descriptor. A semantic graph is then constructed on these
images to capture the structured correlations between them. We utilize the
semantic graph Laplacian as a smooth term in the multi-label learning
formulation to incorporate the structured semantic correlations. Experimental
results demonstrate the effectiveness of the proposed semantic descriptor and
the usefulness of incorporating the structured semantic correlations. We
achieve better results than state-of-the-art multi-label learning methods on
four benchmark datasets.


title: Janus Waves

abstract:
  We show the existence of a family of waves that share a common interesting
property affecting the way they propagate and focus. These waves are a
superposition of twin waves, which are conjugate to each other under inversion
of the propagation direction. In analogy to holography, these twin "real" and
"virtual" waves are related respectively to the converging and the diverging
part of the beam and can be clearly visualized in real space at two distinct
foci under the action of a focusing lens. Analytic formulas for the intensity
distribution after focusing are derived, while numerical and experimental
demonstrations are given for some of the most interesting members of this
family, the accelerating Airy and ring-Airy beams