title: Using Self-Organizing Maps for Sentiment Analysis

abstract:
  Web 2.0 services have enabled people to express their opinions, experience
and feelings in the form of user-generated content. Sentiment analysis or
opinion mining involves identifying, classifying and aggregating opinions as
per their positive or negative polarity. This paper investigates the efficacy
of different implementations of Self-Organizing Maps (SOM) for sentiment based
visualization and classification of online reviews. Specifically, this paper
implements the SOM algorithm for both supervised and unsupervised learning from
text documents. The unsupervised SOM algorithm is implemented for sentiment
based visualization and classification tasks. For supervised sentiment
analysis, a competitive learning algorithm known as Learning Vector
Quantization is used. Both algorithms are also compared with their respective
multi-pass implementations where a quick rough ordering pass is followed by a
fine tuning pass. The experimental results on the online movie review data set
show that SOMs are well suited for sentiment based classification and sentiment
polarity visualization.


title:
H-alpha observations of the gamma-ray-emitting Be/X-ray binary
  LSI+61303: orbital modulation, disk truncation, and long-term variability

abstract:
  We report 138 spectral observations of the H-alpha emission line of the
radio- and gamma-ray-emitting Be/X-ray binary LSI+61303 obtained during the
period of September 1998 -- January 2013. From measuring various H-alpha
parameters, we found that the orbital modulation of the H-alpha is best visible
in the equivalent width ratio EW(B)/EW(R), the equivalent width of the blue
hump, and in the radial velocity of the central dip. The periodogram analysis
confirmed that the H-alpha emission is modulated with the orbital and
superorbital periods. For the past 20 years the radius of the circumstellar
disk is similar to the Roche lobe size at the periastron. It is probably
truncated by a 6:1 resonance. The orbital maximum of the equivalent width of
H-alpha emission peaks after the periastron and coincides on average with the
X-ray and gamma-ray maxima. All the spectra are available upon request from the
authors and through the CDS.


title: Rigidity of holomorphic maps between fiber spaces

abstract:
  In the study of holomorphic maps, the term "rigidity" refers to certain types
of results that give us very specific information about a general class of
holomorphic maps owing to the geometry of their domains or target spaces. Under
this theme, we begin by studying when, given two compact connected complex
manifolds $X$ and $Y$, a degree-one holomorphic map $f: Y\to X$ is a
biholomorphism. Given that the real manifolds underlying $X$ and $Y$ are
diffeomorphic, we provide a condition under which $f$ is a biholomorphism.
Using this result, we deduce a rigidity result for holomorphic self-maps of the
total space of a holomorphic fiber space. Lastly, we consider products
$X=X_1\times X_2$ and $Y=Y_1\times Y_2$ of compact connected complex manifolds.
When $X_1$ is a Riemann surface of genus $\geq 2$, we show that any
non-constant holomorphic map $F:Y\to X$ is of a special form.


title: Performance Investigation of Feature Selection Methods

abstract:
  Sentiment analysis or opinion mining has become an open research domain after
proliferation of Internet and Web 2.0 social media. People express their
attitudes and opinions on social media including blogs, discussion forums,
tweets, etc. and, sentiment analysis concerns about detecting and extracting
sentiment or opinion from online text. Sentiment based text classification is
different from topical text classification since it involves discrimination
based on expressed opinion on a topic. Feature selection is significant for
sentiment analysis as the opinionated text may have high dimensions, which can
adversely affect the performance of sentiment analysis classifier. This paper
explores applicability of feature selection methods for sentiment analysis and
investigates their performance for classification in term of recall, precision
and accuracy. Five feature selection methods (Document Frequency, Information
Gain, Gain Ratio, Chi Squared, and Relief-F) and three popular sentiment
feature lexicons (HM, GI and Opinion Lexicon) are investigated on movie reviews
corpus with a size of 2000 documents. The experimental results show that
Information Gain gave consistent results and Gain Ratio performs overall best
for sentimental feature selection while sentiment lexicons gave poor
performance. Furthermore, we found that performance of the classifier depends
on appropriate number of representative feature selected from text.


title:
Schnol's theorem and spectral properties of massless Dirac operators
  with scalar potentials

abstract:
  The spectra of massless Dirac operators are of essential interest e.g. for
the electronic properties of graphene, but fundamental questions such as the
existence of spectral gaps remain open. We show that the eigenvalues of
massless Dirac operators with suitable real-valued potentials lie inside small
sets easily characterised in terms of properties of the potentials, and we
prove a Schnol'-type theorem relating spectral points to polynomial boundedness
of solutions of the Dirac equation. Moreover, we show that, under minimal
hypotheses which leave the potential essentially unrestrained in large parts of
space, the spectrum of the massless Dirac operator covers the whole real line;
in particular, this will be the case if the potential is nearly constant in a
sequence of regions.


title: Structural Origin of Light Emission in Germanium Quantum Dots

abstract:
  The origin of visible light emission from nanostructures has been a subject
of an intense debate since the early work by L. E. Brus and A. P. Alivisatos in
1980s. The intense research that followed has paved the way towards
applications of quantum structures in optoelectronics and in bio-sensing and
contributed to the development of nanotechnology. The major new challenge is in
accessing the structural, electronic and optical properties of quantum dots on
a nanoparticle scale in order to understand complex relationships between
structural motifs and their contributions to the relevant physical (e. g.
optical and electronic) properties. Here we demonstrate that a combination of
molecular dynamics simulations and optically-detected x-ray absorption
spectroscopy shows sufficient sensitivity to distinguish between regions
contributing to the luminescence signal in oxygen and hydrogen terminated Ge
quantum dots, thus potentially providing a sub-nanoparticle resolution.


title: Calculating Ramsey numbers by partitioning coloured graphs

abstract:
  In this paper we prove a new result about partitioning coloured complete
graphs and use it to determine certain Ramsey numbers exactly. The partitioning
theorem we prove is that for k at least 1, in every edge colouring of a
complete graph with the colours red and blue, it is possible to cover all the
vertices with k disjoint red paths and a disjoint blue balanced complete
(k+1)-partite graph. When the colouring is connected in red, we prove a
stronger result - that it is possible to cover all the vertices with k red
paths and a blue balanced complete (k+2)-partite graph.
  Using these results we determine the Ramsey number of a path on n vertices,
versus a balanced complete k-partite graph, with m vertices in each part,
whenever m-1 is divisible by n-1. This generalizes a result of Erdos who proved
the m=1 case of this result. We also determine the Ramsey number of a path on n
vertices versus the power of a path on n vertices. This solves a conjecture of
Allen, Brightwell, and Skokan.


title: A Review of Privacy Essentials for Confidential Mobile Data Transactions

abstract:
  The increasingly rapid use of mobile devices for data transaction around the
world has consequently led to a new problem, and that is, how to engage in
mobile data transactions while maintaining an acceptable level of data privacy
and security. While most mobile devices engage in data transactions through a
data cloud or a set of data servers, it is still possible to apply data
confidentiality across data servers, and, as such, preserving privacy in any
mobile data transaction. Yet still, it is essential that a review of data
privacy, data utility, the techniques, and methodologies employed in the data
privacy process, is done, as the underlying data privacy principles remain the
same. In this paper, as a contribution, we present a review of data privacy
essentials that are fundamental in delivering any appropriate analysis and
specific methodology implementation for various data privacy needs in mobile
data transactions and computation.


title:
Construction of a general semilocal exchange-correlation hole model:
  Application to nonempirical meta-GGA functionals

abstract:
  Using a reverse-engineering method we construct a meta-generalized gradient
approximation (meta-GGA) angle-averaged exchange-correlation hole model which
has a general applicability. It satisfies known exact hole constraints and can
exactly recover the exchange-correlation energy density of any reasonable
meta-GGA exchange-correlation energy functional satisfying a minimal set of
exact properties. The hole model is applied to several non-empirical meta-GGA
functionals: the Tao-Perdew-Staroverov-Scuseria (TPSS), the revised TPSS
(revTPSS) and the recently Balanced LOCalization (BLOC) meta-GGA of L.A.
Constantin, E. Fabiano, and F. Della Sala, (J. Chem. Theory Comput. 9, 2256
(2013)). The empirical M06-L meta-GGA functional is also considered. Real-space
analyses of atoms and ions as well as wave-vector analyses of jellium surface
energies, show that the meta-GGA hole models, in particular the BLOC one, are
very realistic and can reproduce many features of benchmark XC holes. In
addition, the BLOC hole model can be used to estimate with good accuracy the
Coulomb hole radius of small atoms and ions. Thus, the proposed meta-GGA hole
models provide a valuable tool to validate in detail existing meta-GGA
functionals, and can be further used in the development of DFT methods beyond
the semilocal level of theory.


title:
On The {\it Fermi} -Lat Surplus of the Diffuse Galactic Gamma-Ray
  Emission

abstract:
  Recent observations of the diffuse Galactic \gr emission (DGE) by the {\it
Fermi} Large Area Telescope ({\it Fermi}-LAT) have shown significant
deviations, above a few GeV until about 100 GeV, from DGE models that use the
GALPROP code for the propagation of cosmic ray (CR) particles outside their
sources in the Galaxy and their interaction with the target distributions of
the interstellar gas and radiation fields. The surplus of radiation observed is
most pronounced in the inner Galaxy, where the concentration of CR sources is
strongest. The present study investigates this "{\it Fermi}-LAT Galactic Plane
Surplus" by estimating the \gr emission from the sources themselves, which is
disregarded in the above DGE models. It is shown that indeed the expected hard
spectrum of CRs, still confined in their sources (SCRs), can explain this
surplus. The method is based on earlier studies regarding the so-called EGRET
GeV excess which by now is generally interpreted as an instrumental effect. The
contribution from SCRs is predicted to increasingly exceed the DGE models also
above 100 GeV, up to \gr energies of about ten TeV, where the corresponding
surplus exceeds the hadronic part of the DGE by about one order of magnitude.
Above such energies the emission surplus should decrease again with energy due
to the finite life-time of the assumed supernova remnant sources. Observations
of the DGE in the inner Galaxy at 15 TeV with the Milagro \gr detector and, at
TeV energies, with the ARGO-YBJ detector are interpreted to provide
confirmation of a significant SCR contribution to the DGE.


title: Gravitating binaries at 5PN in the post-Minkowskian approximation

abstract:
  The energy of a compact binary system at the fifth post-Newtonian order is
explicitly computed in the post-Minkowskian approximation by means of the
Effective Field Theory approach. This result allows to determine, for the first
time beyond the test particle limit, one coefficient of the energy expression
for binary point masses on circular orbit as a function of the orbital angular
frequency.


title: Autocatalysis in Reaction Networks

abstract:
  The persistence conjecture is a long-standing open problem in chemical
reaction network theory. It concerns the behavior of solutions to coupled ODE
systems that arise from applying mass-action kinetics to a network of chemical
reactions. The idea is that if all reactions are reversible in a weak sense,
then no species can go extinct. A notion that has been found useful in thinking
about persistence is that of "critical siphon." We explore the combinatorics of
critical siphons, with a view towards the persistence conjecture. We introduce
the notions of "drainable" and "self-replicable" (or autocatalytic) siphons. We
show that: every minimal critical siphon is either drainable or
self-replicable; reaction networks without drainable siphons are persistent;
and non-autocatalytic weakly-reversible networks are persistent. Our results
clarify that the difficulties in proving the persistence conjecture are
essentially due to competition between drainable and self-replicable siphons.


title: Utilizing Noise Addition for Data Privacy, an Overview

abstract:
  The internet is increasingly becoming a standard for both the production and
consumption of data while at the same time cyber-crime involving the theft of
private data is growing. Therefore in efforts to securely transact in data,
privacy and security concerns must be taken into account to ensure that the
confidentiality of individuals and entities involved is not compromised, and
that the data published is compliant to privacy laws. In this paper, we take a
look at noise addition as one of the data privacy providing techniques. Our
endeavor in this overview is to give a foundational perspective on noise
addition data privacy techniques, provide statistical consideration for noise
addition techniques and look at the current state of the art in the field,
while outlining future areas of research.


title:
Bounded Confidence Opinion Dynamics in a Social Network of Bayesian
  Decision Makers

abstract:
  Bounded confidence opinion dynamics model the propagation of information in
social networks. However in the existing literature, opinions are only viewed
as abstract quantities without semantics rather than as part of a
decision-making system. In this work, opinion dynamics are examined when agents
are Bayesian decision makers that perform hypothesis testing or signal
detection, and the dynamics are applied to prior probabilities of hypotheses.
Bounded confidence is defined on prior probabilities through Bayes risk error
divergence, the appropriate measure between priors in hypothesis testing. This
definition contrasts with the measure used between opinions in standard models:
absolute error. It is shown that the rapid convergence of prior probabilities
to a small number of limiting values is similar to that seen in the standard
Krause-Hegselmann model. The most interesting finding in this work is that the
number of these limiting values and the time to convergence changes with the
signal-to-noise ratio in the detection task. The number of final values or
clusters is maximal at intermediate signal-to-noise ratios, suggesting that the
most contentious issues lead to the largest number of factions. It is at these
same intermediate signal-to-noise ratios at which the degradation in detection
performance of the aggregate vote of the decision makers is greatest in
comparison to the Bayes optimal detection performance.


title: Beyond substitutive dynamical systems: S-adic expansions

abstract:
  An S-adic expansion of an infinite word is a way of writing it as the limit
of an infinite product of substitutions (i.e., morphisms of a free monoid).
Such a description is related to continued fraction expansions of numbers and
vectors. A fundamental example of this relation is between Sturmian sequences
and regular continued fractions. We study S-adic words from different
perspectives, namely word combinatorics, ergodic theory, and Diophantine
approximation, by stressing the parallel with continued fraction expansions.


title: Modeling the polycentric transition of cities

abstract:
  Empirical evidence suggest that most urban systems experience a transition
from a monocentric to a polycentric organisation as they grow and expand. We
propose here a stochastic, out-of-equilibrium model of the city which explains
the appearance of subcenters as an effect of traffic congestion. We show that
congestion triggers the unstability of the monocentric regime, and that the
number of subcenters and the total commuting distance within a city scale
sublinearly with its population, predictions which are in agreement with data
gathered for around 9000 US cities between 1994 and 2010.


title:
A functional central limit theorem for a Markov-modulated
  infinite-server queue

abstract:
  The production of molecules in a chemical reaction network is modelled as a
Poisson process with a Markov-modulated arrival rate and an exponential decay
rate. We analyze the distributional properties of $M$, the number of molecules,
under specific time-scaling; the background process is sped up by $N^{\alpha}$,
the arrival rates are scaled by $N$, for $N$ large. A functional central limit
theorem is derived for $M$, which after centering and scaling, converges to an
Ornstein-Uhlenbeck process. A dichotomy depending on $\alpha$ is observed. For
$\alpha\leq1$ the parameters of the limiting process contain the deviation
matrix associated with the background process.


title: Trajectory-Based Dynamic Map Labeling

abstract:
  In this paper we introduce trajectory-based labeling, a new variant of
dynamic map labeling, where a movement trajectory for the map viewport is
given. We define a general labeling model and study the active range
maximization problem in this model. The problem is NP-complete and W[1]-hard.
In the restricted, yet practically relevant case that no more than k labels can
be active at any time, we give polynomial-time algorithms. For the general case
we present a practical ILP formulation with an experimental evaluation as well
as approximation algorithms.


title:
An Investigation of Data Privacy and Utility Preservation using KNN
  Classification as a Gauge

abstract:
  It is obligatory that organizations by law safeguard the privacy of
individuals when handling data sets containing personal identifiable
information (PII). Nevertheless, during the process of data privatization, the
utility or usefulness of the privatized data diminishes. Yet achieving the
optimal balance between data privacy and utility needs has been documented as
an NP-hard challenge. In this study, we investigate data privacy and utility
preservation using KNN machine learning classification as a gauge.


title: What's new in ALPS-II

abstract:
  This proceedings contribution gives a brief experimental update of the `Any
light particle search (ALPS) -II' at DESY which will be sensitive to sub-eV,
very weakly coupled particles beyond the Standard Model. First data on hidden
sector photon parameter space through photon-hidden photon oscillations in
vacuum is expected in 2014. Axion-like particle search (implying the
installation of superconducting HERA magnets) could be realized in 2017.


title: $\rho$ condensation and physical parameters

abstract:
  Recently we showed how a non-local Nambu-Jona-Lasinio model comes out from
QCD in the low-energy limit. In this way, it is possible to fix all the free
parameters of the model with physical ones. We use this approach to derive a
local limit to the Nambu-Jona-Lasinio model with the parameters those obtained
from QCD in order to fix the physical parameters of $\rho$ condensation. $\rho$
condensation is a consequence of the highly non-trivial behavior of the QCD
vacuum in presence a very strong magnetic field giving rising to
superconductive behavior in quark matter. Determination of the proper
parameters for this state can be an important helpful guide to identify it
experimentally.


title:
Radiative forces on macroscopic porous bodies in protoplanetary disks:
  laboratory experiments

abstract:
  In optically thin parts of protoplanetary disks photophoresis is a
significant force not just for dust grains, but also for macroscopic bodies.
The absolute strength on the supposedly highly porous objects is not known in
detail as yet. We set up a low pressure torsion balance and studied
photophoretic forces. We investigated the dependence on plate dimensions and on
ambient pressure and considered the influence of channels through the plates.
As samples for full (no channel) plates we used tissue with 2mm thickness and
circular shape with diameters of 10mm, 30mm and 50mm. The influence of channels
was probed on rectangular-shaped circuit boards of 35mm x 35mm area and 1.5mm
thickness. The number of channels was 169 and 352. At low pressure, the
absolute photophoretic force is proportional to the cross section of the
plates. At high pressure, gas flow through the channels enhances the
photophoretic force. The pressure dependence of the radiative force can
(formally) be calculated by photophoresis on particles with a characteristic
length. We derived two characteristic length scales l depending on the plate
radius r_1, the channel radius r_2, and the thickness of the plate which equals
the length of the channel d as l=r^{0.35} x d^{0.65}. The highest force is
found at a pressure p_max = 15 x l^{-1}Pa mm. In total, the photophoretic force
on a plate with channels can be well described by a superposition of the two
components: photophoresis due to the overall size and cross section of the
plate and photophoresis due to the channels, both with their characteristic
pressure dependencies. We applied these results to the transport of large
solids in protoplanetary disks and found that the influence of porosity on the
photophoretic force can reverse the inward drift of large solids, for instance
meter-sized bodies, and push them outward within the optically thin parts of
the disk.


title:
Three-loop HTLpt Pressure and Susceptibilities at Finite Temperature and
  Density

abstract:
  We present results of a three-loop hard-thermal-loop perturbation theory
calculation of the thermodynamical potential of a finite temperature and baryon
chemical potential system of quarks and gluons. We compare the resulting
pressure and diagonal quark susceptibilities with available lattice data. We
find reasonable agreement between our analytic results and lattice data at both
zero and finite chemical potential.


title: Blazhko effect in Cepheids and RR Lyrae stars

abstract:
  The Blazhko effect is the conspicuous amplitude and phase modulation of the
pulsation of RR Lyrae stars that was discovered in the early 20th century. The
field of study of this mysterious modulation has recently been invigorated
thanks to the space photometric missions providing long, uninterrupted,
ultra-precise time series data. In this paper I give a brief overview of the
new observational findings related to the Blazhko effect, like extreme
modulations, irregular modulation cycles and additional periodicities. I argue
that these findings together with dedicated ground-based efforts now provide us
with a fairly complete picture and a good starting point to theoretical
investigations. Indeed, new, unpredicted dynamical phenomena have been
discovered in Blazhko RR Lyrae stars, such as period doubling, high-order
resonances, three-mode pulsation and low-dimensional chaos. These led to the
proposal of a new explanation to this century-old enigma, namely a high-order
resonance between radial modes. Along these lines I present the latest efforts
and advances from the theoretical point of view. Lastly, amplitude variations
in Cepheids are discussed.


title: Baryonic Dark Matter

abstract:
  We investigate a simple extension of the Standard Model where the baryon
number is a local gauge symmetry and the cold dark matter in the Universe can
be described by a fermionic field with baryon number. We refer to this scenario
as "Baryonic Dark Matter''. The stability of the dark matter candidate is a
natural consequence of the spontaneous breaking of baryon number at the low
scale and there is no need to impose an extra discrete symmetry. The
constraints from the relic density and the predictions for direct detection are
discussed in detail. We briefly discuss the testability of this model using the
correlation between the Large Hadron Collider data and possible results from
dark matter experiments.


title: CHIRON - A Fiber Fed Spectrometer for Precise Radial Velocities

abstract:
  The CHIRON optical high-resolution echelle spectrometer was commissioned at
the 1.5m telescope at CTIO in 2011. The instrument was designed for high
throughput and stability, with the goal of monitoring radial velocities of
bright stars with high precision and high cadence for the discovery of low-mass
exoplanets. Spectral resolution of R=79,000 is attained when using a slicer
with a total (including telescope and detector) efficiency of 6% or higher,
while a resolution of R=136,000 is available for bright stars. A fixed spectral
range of 415 to 880 nm is covered. The echelle grating is housed in a vacuum
enclosure and the instrument temperature is stabilized to +-0.2deg. Stable
illumination is provided by an octagonal multimode fiber with excellent
light-scrambling properties. An iodine cell is used for wavelength calibration.
We describe the main optics, fiber feed, detector, exposure-meter, and other
aspects of the instrument, as well as the observing procedure and data
reduction.


title: Synchronization in a semiclassical Kuramoto model

abstract:
  Synchronization is a ubiquitous phenomenon occurring in social, biological,
and technological systems when the internal rhythms of their constituents are
adapted to be in unison as a result of their coupling. This natural tendency
towards dynamical consensus has spurred a large body of theoretical and
experimental research in recent decades. The Kuramoto model constitutes the
most studied and paradigmatic framework in which to study synchronization. In
particular, it shows how synchronization appears as a phase transition from a
dynamically disordered state at some critical value for the coupling strength
between the interacting units. The critical properties of the synchronization
transition of this model have been widely studied and many variants of its
formulations have been considered to address different physical realizations.
However, the Kuramoto model has been studied only within the domain of
classical dynamics, thus neglecting its applications for the study of quantum
synchronization phenomena. Based on a system-bath approach and within the
Feynman path-integral formalism, we derive equations for the Kuramoto model by
taking into account the first quantum fluctuations. We also analyze its
critical properties, the main result being the derivation of the value for the
synchronization onset. This critical coupling increases its value as
quantumness increases, as a consequence of the possibility of tunneling that
quantum fluctuations provide.


title:
Simulation study on origin of multi-core events in cosmic rays extensive
  air showers

abstract:
  Some experiments have found multi-core events in cosmic rays extensive air
showers which should be interpreted by hadronic interaction theory. In this
paper, the multi-core events are reproduced by Monte Carlo simulation with
CORSIKA. The origin of each sub-cores is tracked back from the observation
level. The interaction mechanism and original particles of sub-core are studied
in this paper.


title: Competition of spin and charge excitations in the Hubbard model

abstract:
  Motivated by recent experiments with ultracold fermionic atoms in optical
lattices, we study finite temperature magnetic correlations, as singlet and
triplet correlations, and the double occupancy in the one-dimensional Hubbard
model. We point out that for intermediate interaction strengths the double
occupancy has an intriguing doubly non-monotonic temperature dependence due to
the competition between spin and charge modes, related to the Pomeranchuk
effect. Furthermore, we determine properties of magnetic correlations in the
temperature regimes relevant for current cold atom experiments and discuss
effects of the trap on spatially integrated observables. We estimate the
entropy and the temperature reached in the experiment by Greif et al., Science
340, 1307 (2013).


title: Problem Complexity Research from Energy Perspective

abstract:
  Computational complexity is a particularly important objective. The idea of
Landauer principle was extended through mapping three classic problems
(sorting,ordered searching and max of N unordered numbers) into Maxwell demon
thought experiment in this paper. The problems'complexity is defined on the
entropy basis and the minimum energy required to solve them are rigorous
deduced from the perspective of energy (entropy) and the second law of
thermodynamics. Then the theoretical energy consumed by real program and basic
operators of classical computer are both analyzed, the time complexity lower
bounds of three problems'all possible algorithms are derived in this way. The
lower bound is also deduced for the two n*n matrix multiplication problem. In
the end, the reason why reversible computation is impossible and the
possibility of super-linear energy consumption capacity which may be the power
behind quantum computation are discussed, a conjecture is proposed which may
prove NP!=P. The study will bring fresh and profound understanding of
computation complexity.


title: Chiral behavior of vector meson self energies

abstract:
  We employ a chiral Lagrangian framework with three dynamical flavors to
calculate the masses of the lowest-lying vector mesons to one loop accuracy,
and use the resulting formulae to extrapolate recent QCDSF lattice data on
vector meson masses and mass ratios to the physical point. Our representation
for the vector meson self energies also enables us to discuss loop corrections
to the $\omega\phi$ mixing amplitude.


title:
Collapse of a self-similar cylindrical scalar field with non-minimal
  coupling II: strong cosmic censorship

abstract:
  We investigate self-similar scalar field solutions to the Einstein equations
in whole cylinder symmetry. Imposing self-similarity on the spacetime gives
rise to a set of single variable functions describing the metric. Furthermore,
it is shown that the scalar field is dependent on a single unknown function of
the same variable and that the scalar field potential has exponential form. The
Einstein equations then take the form of a set of ODEs. Self-similarity also
gives rise to a singularity at the scaling origin. We extend the work of [1],
which determined the global structure of all solutions in the causal past of
the singularity. We identified a class of solutions that evolves through the
past null cone of the singularity. We give the global structure of these
solutions and show that the singularity is censored in all cases.


title: Stability of persistent currents in spinor Bose-Einstein condensates

abstract:
  Motivated by a recent experiment [S. Beattie, S. Moulder, R. J. Fletcher, and
Z. Hadzibabic, PRL 110, 025301 (2013)] we study the superflow of atomic spinor
Bose-Einstein condensates optically trapped in a ring-shaped geometry. Within a
dissipative mean-field approach we simulate a two-component condensate in
conditions adapted to the experiment. In qualitative agreement with the
experimental findings, we observe persistent currents, if the spin-population
imbalance is above some well-defined `critical' value. The triply charged
vortices decay in quantized steps. The vortex lines escape from the center of
the ring through dynamically created regions in the condensate annulus with
reduced density of one component filled by atoms of the other component. The
vortices then leave the ring-shaped high density region of the condensate and
finally decay into elementary excitations.


title:
Kinetic theory of equilibrium axisymmetric collisionless plasmas in
  off-equatorial tori around compact objects

abstract:
  The possible occurrence of equilibrium off-equatorial tori in the
gravitational and electromagnetic fields of astrophysical compact objects has
been recently proved based on non-ideal MHD theory. These stationary structures
can represent plausible candidates for the modelling of coronal plasmas
expected to arise in association with accretion discs. However, accretion disc
coronae are formed by a highly diluted environment, and so the fluid
description may be inappropriate. The question is posed of whether similar
off-equatorial solutions can be determined also in the case of collisionless
plasmas for which treatment based on kinetic theory, rather than fluid one, is
demanded. In this paper the issue is addressed in the framework of the
Vlasov-Maxwell description for non-relativistic multi-species axisymmetric
plasmas subject to an external dominant spherical gravitational and dipolar
magnetic field. Equilibrium configurations are investigated and explicit
solutions for the species kinetic distribution function are constructed, which
are expressed in terms of generalized Maxwellian functions characterized by
isotropic temperature and non-uniform fluid fields. The conditions for the
existence of off-equatorial tori are investigated. It is proved that these
levitating systems are admitted under general conditions when both
gravitational and magnetic fields contribute to shaping the spatial profiles of
equilibrium plasma fluid fields. Then, specifically-kinetic effects carried by
the equilibrium solution are explicitly provided and identified here with
diamagnetic, energy-correction and electrostatic contributions. It is shown
that these kinetic terms characterize the plasma equation of state by
introducing non-vanishing deviations from the assumption of thermal pressure.


title: Stability of the linearized MHD-Maxwell free interface problem

abstract:
  We consider the free boundary problem for the plasma-vacuum interface in
ideal compressible magnetohydrodynamics (MHD). In the plasma region, the flow
is governed by the usual compressible MHD equations, while in the vacuum region
we consider the Maxwell system for the electric and the magnetic fields, in
order to investigate the well-posedness of the problem, in particular in
relation with the electric field in vacuum. At the free interface, driven by
the plasma velocity, the total pressure is continuous and the magnetic field on
both sides is tangent to the boundary.
  Under suitable stability conditions satisfied at each point of the
plasma-vacuum interface, we derive a basic a priori estimate for solutions to
the linearized problem. The proof follows by a suitable secondary
symmetrization of the Maxwell equations in vacuum and the energy method.
  An interesting novelty is represented by the fact that the interface is
characteristic with variable multiplicity, so that the problem requires a
different number of boundary conditions, depending on the direction of the
front velocity (plasma expansion into vacuum or viceversa). To overcome this
difficulty, we recast the vacuum equations in terms of a new variable which
makes the interface characteristic of constant multiplicity. In particular, we
don't assume that plasma expands into vacuum.


title:
Growth and order of automorphisms of free groups and free Burnside
  groups

abstract:
  We prove that an outer automorphism of the free group is exponentially
growing if and only if it induces an outer automorphism of infinite order of
free Burnside groups with sufficiently large odd exponent.


title:
Desingularization of complex multiple zeta-functions, fundamentals of
  $p$-adic multiple $L$-functions, and evaluation of their special values

abstract:
  This paper deals with a multiple version of zeta- and L-functions both in the
complex case and in the p-adic case: [I] Our motivation in the complex case is
to find suitable rigorous meaning of the values of multivariable multiple
zeta-functions (MZFs) at non-positive integer points. (a) We reveal that MZFs
turn to be entire on the whole space after taking the desingularization.
Further we show that the desingularized function is given by a suitable finite
linear combination of MZFs with some arguments shifted. It is also shown that
specific combinations of Bernoulli numbers attain the special values at their
non-positive integers of the desingularized ones. (b) Twisted MZFs can be
continued to entire functions and their special values at non-positive integer
points can be explicitly calculated. [II] Our work in the p-adic case is to
develop the study on analytic side of the Kubota-Leopoldt p-adic L-functions
(pLFs) into the multiple setting. We construct p-adic multiple L-functions
(pMLFs), multivariable versions of their pLFs, by using a specific p-adic
measure. We establish their various fundamental properties: (a) We establish
their intimate connection with the above complex MZFs by showing that the
special values of pMLFs at non-positive integers are expressed by the twisted
multiple Bernoulli numbers, the special values of the complex MZFs at
non-positive integers. (b) We extend Kummer congruence for Bernoulli numbers to
congruences for the twisted multiple Bernoulli numbers. (c) We extend the
vanishing property of the Kubota-Leopoldt pLFs with odd characters to our
pMLFs. (d) We establish their close relationship with the p-adic twisted
multiple polylogarithms (pTMPLs) by showing that the special values of pMLFs at
positive integers are described by those of pTMPLs at roots of unity, which
generalizes the previous result of Coleman in the single variable case.


title: Effective Genericity and Differentiability

abstract:
  We prove that a real x is 1-generic if and only if every differentiable
computable function has continuous derivative at x. This provides a counterpart
to recent results connecting effective notions of randomness with
differentiability. We also consider multiply differentiable computable
functions and polynomial time computable functions.


title: Stochastic Optimization of Service Provision with Selfish Users

abstract:
  We develop a computationally efficient technique to solve a fairly general
distributed service provision problem with selfish users and imperfect
information. In particular, in a context in which the service capacity of the
existing infrastructure can be partially adapted to the user load by activating
just some of the service units, we aim at finding the configuration of active
service units that achieves the best trade-off between maintenance (e.g.\
energetic) costs for the provider and user satisfaction. The core of our
technique resides in the implementation of a belief-propagation (BP) algorithm
to evaluate the cost configurations. Numerical results confirm the
effectiveness of our approach.


title:
The ADI iteration for Lyapunov equations implicitly performs H2
  pseudo-optimal model order reduction

abstract:
  Two approaches for approximating the solution of large-scale Lyapunov
equations are considered: the alternating direction implicit (ADI) iteration
and projective methods by Krylov subspaces. A link between them is presented by
showing that the ADI iteration can always be identified by a Petrov-Galerkin
projection with rational block Krylov subspaces. Then a unique Krylov-projected
dynamical system can be associated with the ADI iteration, which is proven to
be an H2 pseudo-optimal approximation. This includes the generalization of
previous results on H2 pseudo-optimality to the multivariable case.
Additionally, a low-rank formulation of the residual in the Lyapunov equation
is presented, which is well-suited for implementation, and which yields a
measure of the "obliqueness" that the ADI iteration is associated with.


title: Time resolved spin Seebeck effect experiments

abstract:
  In this Letter, we present the results of transient thermopower experiments,
performed at room temperature on yttrium iron garnet/platinum bilayers. Upon
application of a time-varying thermal gradient, we observe a characteristic
low-pass frequency response of the ensuing thermopower voltage with cutoff
frequencies of up to 37 MHz. We interpret our results in terms of the spin
Seebeck effect, and argue that small wavevector magnons are of minor importance
for the spin Seebeck effect in our thin film hybrid structures.


title: Extending the nuclear chart by continuum: from oxygen to titanium

abstract:
  Nuclear masses ranging from O to Ti isotopes are systematically investigated
with relativistic continuum Hartree-Bogoliubov (RCHB) theory, which can provide
a proper treatment of pairing correlations in the presence of the continuum.
From O to Ti isotopes, there are 402 nuclei predicted to be bound by the
density functional PC-PK1. For the 234 nuclei with mass measured, the root mean
square (rms) deviation is 2.23 MeV. It is found that the proton drip-lines
predicted with various mass models are roughly the same and basically agree
with the observation. The neutron drip-lines predicted, however, are quite
different. Due to the continuum couplings, the neutron drip-line nuclei
predicted are extended further neutron-rich than other mass models. By
comparison with finite-range droplet model (FRDM), the neutron drip-line
nucleus predicted by RCHB theory has respectively 2(O), 10(Ne), 10(Na), 6(Mg),
8(Al), 6(Si), 8(P), 6(S), 14(K), 10(Ca), 10(Sc), and 12(Ti) more neutrons.


title: The Redshift Distribution of the TOUGH Survey

abstract:
  We present the redshift results from a Very Large Telescope program aimed at
optimizing the legacy value of the Swift mission: to characterize a
homogeneous, X-ray selected, sample of 69 GRB host galaxies. 19 new redshifts
have been secured, resulting in a 83% (57/69) redshift completion, making the
survey the most comprehensive in terms of redshift completeness of any sample
to the full Swift depth, available to date. We present the cumulative redshift
distribution and derive a conservative, yet small, associated uncertainty. We
constrain the fraction of Swift GRBs at high redshift to a maximum of 10% (5%)
for z > 6 (z > 7). The mean redshift of the host sample is assessed to be <z> >
2.2. Using this more complete sample, we confirm previous findings that the GRB
rate at high redshift (z > 3) appears to be in excess of predictions based on
assumptions that it should follow conventional determinations of the star
formation history of the universe, combined with an estimate of its likely
metallicity dependence. This suggests that either star formation at high
redshifts has been significantly underestimated, for example due to a dominant
contribution from faint, undetected galaxies, or that GRB production is
enhanced in the conditions of early star formation, beyond those usually
ascribed to lower metallicity.


title:
Approximation properties of random polytopes associated with Poisson
  hyperplane processes

abstract:
  We consider a stationary Poisson hyperplane process with given directional
distribution and intensity in $d$-dimensional Euclidean space. Generalizing the
zero cell of such a process, we fix a convex body $K$ and consider the
intersection of all closed halfspaces bounded by hyperplanes of the process and
containing $K$. We study how well these random polytopes approximate $K$
(measured by the Hausdorff distance) if the intensity increases, and how this
approximation depends on the directional distribution in relation to properties
of $K$.


title:
Nanoscale temperature measurements using non-equilibrium Brownian
  dynamics of a levitated nanosphere

abstract:
  Einstein realised that the fluctuations of a Brownian particle can be used to
ascertain properties of its environment. A large number of experiments have
since exploited the Brownian motion of colloidal particles for studies of
dissipative processes, providing insight into soft matter physics, and leading
to applications from energy harvesting to medical imaging. Here we use
optically levitated nanospheres that are heated to investigate the
non-equilibrium properties of the gas surrounding them. Analysing the sphere's
Brownian motion allows us to determine the temperature of the centre-of-mass
motion of the sphere, its surface temperature and the heated gas temperature in
two spatial dimensions. We observe asymmetric heating of the sphere and gas,
with temperatures reaching the melting point of the material. This method
offers new opportunities for accurate temperature measurements with spatial
resolution on the nanoscale, and a new means for testing non-equilibrium
thermodynamics

categories: cond-mat.soft cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.stat-mech quant-ph


title: The magnetic moment of the \rho-meson

abstract:
  The magnetic moment of the \rho-meson is calculated in the framework of a
low-energy effective field theory of the strong interactions. We find that the
complex-valued strong interaction corrections to the gyromagnetic ratio are
small leading to a value close to the real leading tree level result, g_\rho =
2. This is in a reasonably good agreement with the available lattice QCD
calculations for this quantity.


title: ArDM: first results from underground commissioning

abstract:
  The Argon Dark Matter experiment is a ton-scale double phase argon Time
Projection Chamber designed for direct Dark Matter searches. It combines the
detection of scintillation light together with the ionisation charge in order
to discriminate the background (electron recoils) from the WIMP signals
(nuclear recoils). After a successful operation on surface at CERN, the
detector was recently installed in the underground Laboratorio Subterr\'aneo de
Canfranc, and the commissioning phase is ongoing. We describe the status of the
installation and present first results from data collected underground with the
detector filled with gas argon at room temperature.


title: Inadmissible Class of Boolean Functions under Stuck-at Faults

abstract:
  Many underlying structural and functional factors that determine the fault
behavior of a combinational network, are not yet fully understood. In this
paper, we show that there exists a large class of Boolean functions, called
root functions, which can never appear as faulty response in irredundant
two-level circuits even when any arbitrary multiple stuck-at faults are
injected. Conversely, we show that any other Boolean function can appear as a
faulty response from an irredundant realization of some root function under
certain stuck-at faults. We characterize this new class of functions and show
that for n variables, their number is exactly equal to the number of
independent dominating sets (Harary and Livingston, Appl. Math. Lett., 1993) in
a Boolean n-cube. We report some bounds and enumerate the total number of root
functions up to 6 variables. Finally, we point out several open problems and
possible applications of root functions in logic design and testing.


title: Quantum estimation of magnetic-field gradient using W-state

abstract:
  We study the precision limits of detecting a linear magnetic-field gradient
by using W-states in the presence of different types of noises. We consider to
use an atomic spin chain for probing the magnetic-field gradient, where a
W-state is prepared. We compare this method with the measurement of using two
uncorrelated atoms. For pure states, W-states can provide an improvement over
uncorrelated states in determining the magnetic-field gradient up to four
particles. We examine the effects of local dephasing and dissipations on the
performances of detections. In presence of dephasing, the uncorrelated atoms
can give a higher precision than using W-states. But W-states provide a better
performance in the presence of dissipation for a few particles. We briefly
discuss the implementation of the detection methods with cold atoms and trapped
ions.


title: Bisector analysis of RR Lyrae: atmosphere dynamics at different phases

abstract:
  This article reports some preliminary results on an analysis of line
bisectors of metal absorption lines of RR Lyrae, the prototype of its class of
pulsators. The extensive data set used for this study consists of a time series
of spectra obtained at various pulsation phases as well as different Blazhko
phases. This setup should allow a comparison of the atmospheric behavior,
especially of the function of radial velocity versus depth at differing Blazhko
phases, but (almost) identical pulsation phase, making it possible to
investigate whether the modulation causes a change in the atmospheric motion of
RR Lyrae. While the nature of the Blazhko modulation has often been
investigated photometrically and described as a change in the light curve,
studies on time series of high resolution spectra are rare. We present for the
first time work on line bisectors at different phases of RR Lyr.


title:
Cosmological Fluid Mechanics with Adaptively Refined Large Eddy
  Simulations

abstract:
  We investigate turbulence generated by cosmological structure formation by
means of large eddy simulations using adaptive mesh refinement. In contrast to
the widely used implicit large eddy simulations, which resolve a limited range
of length scales and treat the effect of turbulent velocity fluctuations below
the grid scale solely by numerical dissipation, we apply a subgrid-scale model
for the numerically unresolved fraction of the turbulence energy. For
simulations with adaptive mesh refinement, we utilize a new methodology that
allows us to adjust the scale-dependent energy variables in such a way that the
sum of resolved and unresolved energies is globally conserved. We test our
approach in simulations of randomly forced turbulence, a gravitationally bound
cloud in a wind, and the Santa Barbara cluster. To treat inhomogeneous
turbulence, we introduce an adaptive Kalman filtering technique that separates
turbulent velocity fluctuations on resolved length scales from the
non-turbulent bulk flow. From the magnitude of the fluctuating component and
the subgrid-scale turbulence energy, a total turbulent velocity dispersion of
several 100 km/s is obtained for the Santa Barbara cluster, while the
low-density gas outside the accretion shocks is nearly devoid of turbulence.
The energy flux through the turbulent cascade and the dissipation rate
predicted by the subgrid-scale model correspond to dynamical time scales around
5 Gyr, independent of numerical resolution.


title: Improving Bandwidth Efficiency in E-band Communication Systems

abstract:
  The allocation of a large amount of bandwidth by regulating bodies in the
70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges
for providing affordable and reliable Gigabit per second wireless
point-to-point links. This article first reviews the available bandwidth and
licensing regulations in the E-band. Subsequently, different propagation
models, e.g., the ITU-R and Cane models, are compared against measurement
results and it is concluded that to meet specific availability requirements,
E-band wireless systems may need to be designed with larger fade margins
compared to microwave systems. A similar comparison is carried out between
measurements and models for oscillator phase noise. It is confirmed that phase
noise characteristics, that are neglected by the models used for narrowband
systems, need to be taken into account for the wideband systems deployed in the
E-band. Next, a new multi-input multi-output (MIMO) transceiver design, termed
continuous aperture phased (CAP)-MIMO, is presented. Simulations show that
CAP-MIMO enables E-band systems to achieve fiber-optic like throughputs.
Finally, it is argued that full-duplex relaying can be used to greatly enhance
the coverage of E-band systems without sacrificing throughput, thus,
facilitating their application in establishing the backhaul of heterogeneous
networks.


title: Local tensor valuations

abstract:
  The local Minkowski tensors are valuations on the space of convex bodies in
Euclidean space with values in a space of tensor measures. They generalize at
the same time the intrinsic volumes, the curvature measures and the isometry
covariant Minkowski tensors that were introduced by McMullen and characterized
by Alesker. In analogy to the characterization theorems of Hadwiger and
Alesker, we give here a complete classification of all locally defined tensor
measures on convex bodies that share with the local Minkowski tensors the basic
geometric properties of isometry covariance and weak continuity.


title: The measure matters

abstract:
  We adopt a framework where quantum-gravity's dynamical dimensional reduction
of spacetime at short distances is described in terms of modified dispersion
relations. We observe that by subjecting such models to a momentum-space
diffeomorphism one obtains a "dual picture" with unmodified dispersion
relations, but a modified measure of integration over momenta. We then find
that the UV {\it Hausdorff} dimension of momentum space which can be inferred
from this modified integration measure coincides with the short-distance {\it
spectral} dimension of spacetime. This result sheds light into why
scale-invariant fluctuations are obtained if the original model for two UV
spectral dimensions is combined with Einstein gravity. By studying the
properties of the inner product we derive the result that it is only in 2
energy-momentum dimensions that microphysical vacuum fluctuations are
scale-invariant. This is true ignoring gravity, but then we find that if
Einstein gravity is postulated in the original frame, in the dual picture
gravity switches off, since all matter becomes conformally coupled. We argue
that our findings imply that the following concepts are closely connected:
scale-invariance of vacuum quantum fluctuations, conformal invariance of the
gravitational coupling, UV reduction to spectral dimension 2 in position space
and UV reduction to Hausdorff dimension 2 in energy-momentum space.


title: Modeling of Nonlinear Signal Distortion in Fiber-Optical Networks

abstract:
  A low-complexity model for signal quality prediction in a nonlinear
fiber-optical network is developed. The model, which builds on the Gaussian
noise model, takes into account the signal degradation caused by a combination
of chromatic dispersion, nonlinear signal distortion, and amplifier noise. The
center frequencies, bandwidths, and transmit powers can be chosen independently
for each channel, which makes the model suitable for analysis and optimization
of resource allocation, routing, and scheduling in large-scale optical networks
applying flexible-grid wavelength-division multiplexing.


title:
The impact range for smooth wall-liquid interactions in nanoconfined
  liquids

abstract:
  Bulk and nanoconfined liquids have initially very different physics; for
instance, nanoconfined liquids show stratification and position-dependent
relaxation processes. A number of similarities between bulk and nanoconfined
liquids have nevertheless been reported in computer simulations during the last
decade. Inspired by these observations, we present results from molecular
dynamics computer simulations of three nanoconfined liquids (i.e.,
single-component Lennard-Jones (LJ) liquid, Kob-Andersen binary LJ mixture, and
an asymmetric dumbbell model) demonstrating also a microscopic similarity
between bulk and nanoconfined liquids. The results show that the interaction
range for the wall-liquid and liquid-liquid interactions of the nanoconfined
liquid are identical to the bulk liquid as long as the liquid remains "Roskilde
simple" in nanoconfinement, i.e., the liquid has strong correlations between
virial and potential energy equilibrium fluctuations in the NVT ensemble.


title: Parabolic type semigroups: asymptotics and order of contact

abstract:
  We study the asymptotic behavior of parabolic type semigroups acting on the
unit disk as well as those acting on the right half-plane. We use the
asymptotic behavior to investigate the local geometry of the semigroup
trajectories near the boundary Denjoy--Wolff point. The geometric content
includes, in particular, the asymptotes to trajectories, the so-called limit
curvature, the order of contact, and so on. We then establish asymptotic
rigidity properties for a broad class of semigroups of parabolic type.


title: Entanglement Entropies in One-Dimensional Systems

abstract:
  Entanglement entropies have revealed, in the last years, to be a powerful
tool to extract information about the physics of condensed-matter systems. In
the first part of this thesis, we show how to extract essential details about
the quasi-long-range order of a one-dimensional critical systems by means of
entanglement entropies. In the second part we show how to derive analytically
the scaling of such quantities for critical systems, whose low-energy physics
is described by a conformal field theory, in presence of general open boundary
conditions that preserve the conformal invariance.


title:
The Development of High-Performance Alkali-Hybrid Polarized
  $^3\mathrm{He}$ Targets for Electron Scattering

abstract:
  We present the development of high-performance polarized $^3\mathrm{He}$
targets for use in electron scattering experiments that utilize the technique
of alkali-hybrid spin-exchange optical pumping. We include data obtained during
the characterization of 24 separate target cells, each of which was constructed
while preparing for one of four experiments at Jefferson Laboratory in Newport
News, Virginia. The results presented here document dramatic improvement in the
performance of polarized $^3\mathrm{He}$ targets, as well as the target
properties and operating parameters that made those improvements possible.
Included in our measurements were determinations of the so-called $X$-factors
that quantify a temperature-dependent and as-yet poorly understood
spin-relaxation mechanism that limits the maximum achievable $^3\mathrm{He}$
polarization to well under 100%. The presence of this spin-relaxation mechanism
was clearly evident in our data. We also present results from a simulation of
the alkali-hydrid spin-exchange optical pumping process that was developed to
provide guidance in the design of these targets. Good agreement with actual
performance was obtained by including details such as off-resonant optical
pumping. Now benchmarked against experimental data, the simulation is useful
for the design of future targets. Included in our results is a measurement of
the $\mathrm{K}$-$^3\mathrm{He}$ spin-exchange rate coefficient
$k^\mathrm{K}_\mathrm{se} = \left ( 7.46 \pm 0.62 \right )\!\times\!10^{-20}\
\mathrm{cm^3/s}$ over the temperature range 503 K to 563 K.

categories: physics.atom-ph hep-ex nucl-ex physics.ins-det


title: Magnetic Phase Transition in the Low Dimensional Compound BaMn2Si2O7

abstract:
  The structural and magnetic properties of BaMn2Si2O7 have been investigated.
The magnetic susceptibility and specific heat, measured using single crystals,
suggest that the quasi-one-dimensional magnetism originating from the loosely
coupled Mn2+ chain carrying S=5/2 is present at high temperatures, which is
similar to the other quasi-one-dimensional barium silicates, BaM2Si2O7 (M: Cu
and Co). The Neel temperature (TN=26 K) is high compared to the magnetic
interaction along the chain (J = -6 K). The neutron powder diffraction study
has revealed that the magnetic structure is long-ranged with antiferromagnetic
arrangement along the chain (c) direction and ferromagnetic arrangement along
the a and b axes. The detailed structural analysis suggests that the interchain
interaction via Mn-O-Mn bond along the a axis is relatively large, which makes
the system behave more two-dimensionally in the ac plane and enhances TN.


title: Properly discontinuous actions on Hilbert manifolds

abstract:
  In this article we study properly discontinuous actions on Hilbert manifolds
giving new examples of complete Hilbert manifolds with nonnegative,
respectively nonpositive, sectional curvature with infinite fundamental group.
We also get examples of complete infinite dimensional K\"ahler manifolds with
positive holomorphic sectional curvature and infinite fundamental group in
contrast with the finite dimensional case and we classify abelian groups acting
linearly, isometrically and properly discontinuously on Stiefel manifolds.
Finally, we classify homogeneous Hilbert manifolds with constant sectional
curvature.


title: A Clifford Bundle Approach to the Differential Geometry of Branes

abstract:
  The Clifford bundle formalism (CBF) of differential forms and the theory of
extensors acting on $\mathcal{C\ell}(M,g)$ is first used for a fomulation of
the intrinsic geometry of a differential manifold $M$ equipped with a metric
field $\boldsymbol{g}$ of signature $(p,q)$ and an arbitrary metric compatible
connection $\nabla$ introducing the torsion (2-1)-extensor field $\tau$, the
curvature $(2-2)$ extensor field $\mathfrak{R}$ and (once fixing a gauge) the
connection $(1-2)$-extensor $\omega$ and the Ricci operator
$\boldsymbol{\partial}\wedge\boldsymbol{\partial}$ (where
$\boldsymbol{\partial}$ is the Dirac operator acting on sections of
$\mathcal{C\ell}(M,g)$) which plays an important role in this paper. Next,
using the CBF we give a thoughtful presentation the Riemann or the Lorentzian
geometry of an orientable submanifold $M$ ($\dim M=m$) living in a manifold
$\mathring{M}$ (such that $\mathring{M}\simeq\mathbb{R}^{n}$ is equipped with a
semi-Riemannian metric $\boldsymbol{\mathring{g}}$ with signature
$(\mathring{p},\mathring{q})$ and \ $\mathring{p}+\mathring{q}=n$ and its
Levi-Civita connection $\mathring{D}$) and where there is defined a metric
$\boldsymbol{g=i}^{\ast}\mathring{g}$, where $\boldsymbol{i}:$ $M\rightarrow
\mathring{M}$ is the inclusion map. We prove several equivalent forms for the
curvature operator $\mathfrak{R}$ of $M$. It is shown that the Ricci operator
of $M$ is the (negative) square of the shape operator $\mathbf{S}$ of $M$. Also
we disclose the relationship between the connection (1-2%)-extensor $\omega$
and the shape biform $\mathcal{S}$ (an object related to $\mathbf{S}$). We hope
that our presentation will be useful for differential geometers and theoretical
physists interested, e.g, in string and brane theories and relativity theory.


title: Profiling Web Archive Coverage for Top-Level Domain and Content Language

abstract:
  The Memento aggregator currently polls every known public web archive when
serving a request for an archived web page, even though some web archives focus
on only specific domains and ignore the others. Similar to query routing in
distributed search, we investigate the impact on aggregated Memento TimeMaps
(lists of when and where a web page was archived) by only sending queries to
archives likely to hold the archived page. We profile twelve public web
archives using data from a variety of sources (the web, archives' access logs,
and full-text queries to archives) and discover that only sending queries to
the top three web archives (i.e., a 75% reduction in the number of queries) for
any request produces the full TimeMaps on 84% of the cases.


title: Access Patterns for Robots and Humans in Web Archives

abstract:
  Although user access patterns on the live web are well-understood, there has
been no corresponding study of how users, both humans and robots, access web
archives. Based on samples from the Internet Archive's public Wayback Machine,
we propose a set of basic usage patterns: Dip (a single access), Slide (the
same page at different archive times), Dive (different pages at approximately
the same archive time), and Skim (lists of what pages are archived, i.e.,
TimeMaps). Robots are limited almost exclusively to Dips and Skims, but human
accesses are more varied between all four types. Robots outnumber humans 10:1
in terms of sessions, 5:4 in terms of raw HTTP accesses, and 4:1 in terms of
megabytes transferred. Robots almost always access TimeMaps (95% of accesses),
but humans predominately access the archived web pages themselves (82% of
accesses). In terms of unique archived web pages, there is no overall
preference for a particular time, but the recent past (within the last year)
shows significant repeat accesses.


title:
Limits on Alpha Particle Temperature Anisotropy and Differential Flow
  from Kinetic Instabilities: Solar Wind Observations

abstract:
  Previous studies have shown that the observed temperature anisotropies of
protons and alpha particles in the solar wind are constrained by theoretical
thresholds for pressure-anisotropy-driven instabilities such as the
Alfv\'en/ion-cyclotron (A/IC) and fast-magnetosonic/whistler (FM/W)
instabilities. In this letter, we use a long period of in-situ measurements
provided by the {\em Wind} spacecraft's Faraday cups to investigate the
combined constraint on the alpha-proton differential flow velocity and the
alpha-particle temperature anisotropy due to A/IC and FM/W instabilities. We
show that the majority of the data are constrained to lie within the region of
parameter space in which A/IC and FM/W waves are either stable or have
extremely low growth rates. In the minority of observed cases in which the
growth rate of the A/IC (FM/W) instability is comparatively large, we find
relatively higher values of $T_{\perp\alpha}/T_{\perp p}$
($T_{\parallel\alpha}/T_{\parallel p}$) when alpha-proton differential flow
velocity is small, where $T_{\perp\alpha}$ and $T_{\perp p}$
($T_{\parallel\alpha}$ and $T_{\parallel p}$) are the perpendicular (parallel)
temperatures of alpha particles and protons. We conjecture that this observed
feature might arise from preferential alpha-particle heating which can drive
the alpha particles beyond the instability thresholds.


title: Tropical compactification in log-regular varieties

abstract:
  In this article we define a natural tropicalization procedure for closed
subsets of log-regular varieties in the case of constant coefficients and study
its basic properties. This framework allows us to generalize some of Tevelev's
results on tropical compactification as well as Hacking's result on the
cohomology of the link of a tropical variety to log-regular varieties.


title:
Nonlinear optics from an ab-initio approach by means of the dynamical
  Berry phase: Application to second- and third-harmonic generation in
  semiconductors

abstract:
  We present an ab-initio real-time-based computational approach to study
nonlinear optical properties in condensed matter systems that is especially
suitable for crystalline solids and periodic nanostructures. The equations of
motion and the coupling of the electrons with the external electric field are
derived from the Berry-phase formulation of the dynamical polarization [Souza
et al., Phys. Rev. B 69, 085106 (2004)]. Many-body effects are introduced by
adding single-particle operators to the independent-particle Hamiltonian. We
add a Hartree operator to account for crystal local effects and a scissor
operator to correct the independent particle band structure for quasiparticle
effects. We also discuss the possibility of accurately treating excitonic
effects by adding a screened Hartree-Fock self-energy operator. The approach is
validated by calculating the second-harmonic generation of SiC and AlAs bulk
semiconductors: an excellent agreement is obtained with existing ab initio
calculations from response theory in frequency domain [Luppi et al., Phys. Rev.
B 82, 235201 (2010)]. We finally show applications to the second-harmonic
generation of CdTe and the third-harmonic generation of Si.


title: The resolved structure of the extragalactic supernova remnant SNR 4449-1

abstract:
  We present very long baseline interferometry (VLBI) observations of the
milliarcsecond-scale radio structure of the supernova remnant SNR 4449$-$1 in
the galaxy NGC 4449. This young and superluminous remnant was observed at 1.6
GHz ($\lambda = 18$\,cm) with the European VLBI Network. The observations
confirm earlier identifications of this object with a supernova remnant (SNR)
while revealing a somewhat different morphology compared with the structure
reported by Bietenholz et al. from VLBI observations at 1.4 GHz. This
difference is discussed here in the context of structural sensitivity of both
observations. The 1.6 GHz image yields accurate estimates of the size (0.0422
arcsec $\times$ 0.0285 arcsec and 0.8 $\times$ 0.5 pc) and age ($\sim$55 yr) of
SNR 4449$-$1. With a total flux of 6.1 $\pm$ 0.6 mJy measured in the VLBI
image, the historical lightcurve of the source can be well represented by a
power-law decay with a power index of $-$1.19 $\pm$ 0.07. The SNR exhibits a
decline rate of the radio emission of 2.2$%$ $\pm$ 0.1$%$ yr$^{-1}$ and a radio
luminosity of 1.74 $\times$ 10$^{35}$ erg s$^{-1}$.


title: Automatic quantitative morphological analysis of interacting galaxies

abstract:
  The large number of galaxies imaged by digital sky surveys reinforces the
need for computational methods for analyzing galaxy morphology. While the
morphology of most galaxies can be associated with a stage on the Hubble
sequence, morphology of galaxy mergers is far more complex due to the
combination of two or more galaxies with different morphologies and the
interaction between them. Here we propose a computational method based on
unsupervised machine learning that can quantitatively analyze morphologies of
galaxy mergers and associate galaxies by their morphology. The method works by
first generating multiple synthetic galaxy models for each galaxy merger, and
then extracting a large set of numerical image content descriptors for each
galaxy model. These numbers are weighted using Fisher discriminant scores, and
then the similarities between the galaxy mergers are deduced using a variation
of Weighted Nearest Neighbor analysis such that the Fisher scores are used as
weights. The similarities between the galaxy mergers are visualized using
phylogenies to provide a graph that reflects the morphological similarities
between the different galaxy mergers, and thus quantitatively profile the
morphology of galaxy mergers.


title:
Isoparametric functions and harmonic unit vector fields in K-contact
  geometry

abstract:
  We provide some examples of harmonic unit vector fields as normalized
gradients of isoparametric functions from a K-contact geometry setting.


title: Who and What Links to the Internet Archive

abstract:
  The Internet Archive's (IA) Wayback Machine is the largest and oldest public
web archive and has become a significant repository of our recent history and
cultural heritage. Despite its importance, there has been little research about
how it is discovered and used. Based on web access logs, we analyze what users
are looking for, why they come to IA, where they come from, and how pages link
to IA. We find that users request English pages the most, followed by the
European languages. Most human users come to web archives because they do not
find the requested pages on the live web. About 65% of the requested archived
pages no longer exist on the live web. We find that more than 82% of human
sessions connect to the Wayback Machine via referrals from other web sites,
while only 15% of robots have referrers. Most of the links (86%) from websites
are to individual archived pages at specific points in time, and of those 83%
no longer exist on the live web.


title:
Search for dark matter in events with a hadronically decaying W or Z
  boson and missing transverse momentum in pp collisions at sqrt(s)=8 TeV with
  the ATLAS detector

abstract:
  A search is presented for dark matter pair production in association with a W
or Z boson in pp collisions representing 20.3 fb-1 of integrated luminosity at
sqrt(s)=8 TeV using data recorded with the ATLAS detector at the Large Hadron
Collider. Events with a hadronic jet with the jet-mass consistent with a W or Z
boson, and with large missing transverse momentum are analyzed. The data are
consistent with the Standard Model expectations, and limits are set on the mass
scale in effective field theories that describe the interaction of dark matter
and Standard Model particles.


title:
A biomolecular electrostatics solver using Python, GPUs and boundary
  elements that can handle solvent-filled cavities and Stern layers

abstract:
  The continuum theory applied to bimolecular electrostatics leads to an
implicit-solvent model governed by the Poisson-Boltzmann equation. Solvers
relying on a boundary integral representation typically do not consider
features like solvent-filled cavities or ion-exclusion (Stern) layers, due to
the added difficulty of treating multiple boundary surfaces. This has hindered
meaningful comparisons with volume-based methods, and the effects on accuracy
of including these features has remained unknown. This work presents a solver
called PyGBe that uses a boundary-element formulation and can handle multiple
interacting surfaces. It was used to study the effects of solvent-filled
cavities and Stern layers on the accuracy of calculating solvation energy and
binding energy of proteins, using the well-known APBS finite-difference code
for comparison. The results suggest that if required accuracy for an
application allows errors larger than about 2%, then the simpler,
single-surface model can be used. When calculating binding energies, the need
for a multi-surface model is problem-dependent, becoming more critical when
ligand and receptor are of comparable size. Comparing with the APBS solver, the
boundary-element solver is faster when the accuracy requirements are higher.
The cross-over point for the PyGBe code is in the order of 1-2% error, when
running on one GPU card (NVIDIA Tesla C2075), compared with APBS running on six
Intel Xeon CPU cores. PyGBe achieves algorithmic acceleration of the boundary
element method using a treecode, and hardware acceleration using GPUs via
PyCuda from a user-visible code that is all Python. The code is open-source
under MIT license.


title: Quasi-Gorensteinness of extended Rees algebras

abstract:
  Let $R$ be a Noetherian local ring and $I$ an $R$-ideal. It is well-known
that if the associated graded ring $\gr_I(R)$ is Cohen-Macaulay (Gorenstein),
then so is $R$, but the converse is not true in general. In this paper we
investigate the Cohen-Macaulayness and Gorensteinness of the associated graded
ring $\gr_I(R)$ under the hypothesis of the extended Rees algebra
$R[It,t^{-1}]$ is quasi-Gorenstein or the associated graded ring $\gr_I(R)$ is
a domain.


title:
Recurrence Relations for Graph Polynomials on Bi-iterative Families of
  Graphs

abstract:
  We show that any graph polynomial from a wide class of graph polynomials
yields a recurrence relation on an infinite class of families of graphs. The
recurrence relations we obtain have coefficients which themselves satisfy
linear recurrence relations. We give explicit applications to the Tutte
polynomial and the independence polynomial. Furthermore, we get that for any
sequence $a_{n}$ satisfying a linear recurrence with constant coefficients, the
sub-sequence corresponding to square indices $a_{n^{2}}$ and related
sub-sequences satisfy recurrences with recurrent coefficients.


title: The 11-years solar cycle as the manifestation of the dark Universe

abstract:
  The solar luminosity in the visible changes at the 10-3 level, following an
11 years period. In X-rays, which should not be there, the amplitude varies
100000 times stronger, making their mysterious origin since the discovery in
1938 even more puzzling, and inspiring. We suggest that the multifaceted
mysterious solar cycle is due to some kind of dark matter streams hitting the
Sun. Planetary gravitational lensing enhances (occasionally) slow moving flows
of dark constituents towards the Sun, giving rise to the periodic behaviour.
Jupiter provides the driving oscillatory force, though its 11.8 years orbital
period appears slightly decreased, just as 11 years, if the lensing impact of
other planets is included. Then, the 11 years solar clock may help to decipher
(overlooked) signatures from the dark sector in laboratory experiments or
observations in space.


title: Exploring Subexponential Parameterized Complexity of Completion Problems

abstract:
  Let ${\cal F}$ be a family of graphs. In the ${\cal F}$-Completion problem,
we are given a graph $G$ and an integer $k$ as input, and asked whether at most
$k$ edges can be added to $G$ so that the resulting graph does not contain a
graph from ${\cal F}$ as an induced subgraph. It appeared recently that special
cases of ${\cal F}$-Completion, the problem of completing into a chordal graph
known as Minimum Fill-in, corresponding to the case of ${\cal
F}=\{C_4,C_5,C_6,\ldots\}$, and the problem of completing into a split graph,
i.e., the case of ${\cal F}=\{C_4, 2K_2, C_5\}$, are solvable in parameterized
subexponential time $2^{O(\sqrt{k}\log{k})}n^{O(1)}$. The exploration of this
phenomenon is the main motivation for our research on ${\cal F}$-Completion.
  In this paper we prove that completions into several well studied classes of
graphs without long induced cycles also admit parameterized subexponential time
algorithms by showing that:
  - The problem Trivially Perfect Completion is solvable in parameterized
subexponential time $2^{O(\sqrt{k}\log{k})}n^{O(1)}$, that is ${\cal
F}$-Completion for ${\cal F} =\{C_4, P_4\}$, a cycle and a path on four
vertices.
  - The problems known in the literature as Pseudosplit Completion, the case
where ${\cal F} = \{2K_2, C_4\}$, and Threshold Completion, where ${\cal F} =
\{2K_2, P_4, C_4\}$, are also solvable in time $2^{O(\sqrt{k}\log{k})}
n^{O(1)}$.
  We complement our algorithms for ${\cal F}$-Completion with the following
lower bounds:
  - For ${\cal F} = \{2K_2\}$, ${\cal F} = \{C_4\}$, ${\cal F} = \{P_4\}$, and
${\cal F} = \{2K_2, P_4\}$, ${\cal F}$-Completion cannot be solved in time
$2^{o(k)} n^{O(1)}$ unless the Exponential Time Hypothesis (ETH) fails.
  Our upper and lower bounds provide a complete picture of the subexponential
parameterized complexity of ${\cal F}$-Completion problems for ${\cal
F}\subseteq\{2K_2, C_4, P_4\}$.


title:
Absence of splash singularities for SQG sharp fronts and the Muskat
  problem

abstract:
  In this paper for either the sharp front Surface Quasi-Geostrophic equation
or the Muskat problem we rule out the "splash singularity" blow-up scenario; in
other words we prove that the contours evolving from either of these systems
can not intersect at a single point while the free boundary remains smooth.
Splash singularities have been shown to hold for the free boundary
incompressible Euler equation in the form of the water waves contour evolution
problem \cite{ADCPJ}. Our result confirms the numerical simulations in
\cite{CFMR} where it is shown that the curvature blows up due to the contours
collapsing at a point. Here we prove that maintaining control of the curvature
will remove the possibility of pointwise interphase collapse. Another
conclusion that we provide is a better understanding of the work \cite{DP3} in
which squirt singularities are ruled out; here a positive volume of fluid
between the contours can not be ejected in finite time.


title:
The Cyborg Astrobiologist: Matching of Prior Textures by Image
  Compression for Geological Mapping and Novelty Detection

abstract:
  (abridged) We describe an image-comparison technique of Heidemann and Ritter
that uses image compression, and is capable of: (i) detecting novel textures in
a series of images, as well as of: (ii) alerting the user to the similarity of
a new image to a previously-observed texture. This image-comparison technique
has been implemented and tested using our Astrobiology Phone-cam system, which
employs Bluetooth communication to send images to a local laptop server in the
field for the image-compression analysis. We tested the system in a field site
displaying a heterogeneous suite of sandstones, limestones, mudstones and
coalbeds. Some of the rocks are partly covered with lichen. The image-matching
procedure of this system performed very well with data obtained through our
field test, grouping all images of yellow lichens together and grouping all
images of a coal bed together, and giving a 91% accuracy for similarity
detection. Such similarity detection could be employed to make maps of
different geological units. The novelty-detection performance of our system was
also rather good (a 64% accuracy). Such novelty detection may become valuable
in searching for new geological units, which could be of astrobiological
interest. The image-comparison technique is an unsupervised technique that is
not capable of directly classifying an image as containing a particular
geological feature; labeling of such geological features is done post facto by
human geologists associated with this study, for the purpose of analyzing the
system's performance. By providing more advanced capabilities for similarity
detection and novelty detection, this image-compression technique could be
useful in giving more scientific autonomy to robotic planetary rovers, and in
assisting human astronauts in their geological exploration and assessment.


title: On stable lattices and the diagonal group

abstract:
  Inspired by work of McMullen, we show that any orbit for the action of the
diagonal group on the space of lattices, accumulates on a stable lattice. We
use this to settle a conjecture of Ramharter about Mordell's constant, get new
proofs of Minkowski's conjecture in dimensions up to seven, and answer a
question of Harder on the volume of stable lattices.


title:
Secure Degrees of Freedom of MIMO X-Channels with Output Feedback and
  Delayed CSIT

abstract:
  We investigate the problem of secure transmission over a two-user multi-input
multi-output (MIMO) X-channel in which channel state information is provided
with one-unit delay to both transmitters (CSIT), and each receiver feeds back
its channel output to a different transmitter. We refer to this model as MIMO
X-channel with asymmetric output feedback and delayed CSIT. The transmitters
are equipped with M-antennas each, and the receivers are equipped with
N-antennas each. For this model, accounting for both messages at each receiver,
we characterize the optimal sum secure degrees of freedom (SDoF) region. We
show that, in presence of asymmetric output feedback and delayed CSIT, the sum
SDoF region of the MIMO X-channel is same as the SDoF region of a two-user MIMO
BC with 2M-antennas at the transmitter, N-antennas at each receiver and delayed
CSIT. This result shows that, upon availability of asymmetric output feedback
and delayed CSIT, there is no performance loss in terms of sum SDoF due to the
distributed nature of the transmitters. Next, we show that this result also
holds if only output feedback is conveyed to the transmitters, but in a
symmetric manner, i.e., each receiver feeds back its output to both
transmitters and no CSIT. We also study the case in which only asymmetric
output feedback is provided to the transmitters, i.e., without CSIT, and derive
a lower bound on the sum SDoF for this model. Furthermore, we specialize our
results to the case in which there are no security constraints. In particular,
similar to the setting with security constraints, we show that the optimal sum
DoF region of the (M,M,N,N)--MIMO X-channel with asymmetric output feedback and
delayed CSIT is same as the DoF region of a two-user MIMO BC with 2M-antennas
at the transmitter, N-antennas at each receiver, and delayed CSIT. We
illustrate our results with some numerical examples.


title:
Gravitational waves from known pulsars: results from the initial
  detector era

abstract:
  We present the results of searches for gravitational waves from a large
selection of pulsars using data from the most recent science runs (S6, VSR2 and
VSR4) of the initial generation of interferometric gravitational wave detectors
LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do
not see evidence for gravitational wave emission from any of the targeted
sources but produce upper limits on the emission amplitude. We highlight the
results from seven young pulsars with large spin-down luminosities. We reach
within a factor of five of the canonical spin-down limit for all seven of
these, whilst for the Crab and Vela pulsars we further surpass their spin-down
limits. We present new or updated limits for 172 other pulsars (including both
young and millisecond pulsars). Now that the detectors are undergoing major
upgrades, and, for completeness, we bring together all of the most up-to-date
results from all pulsars searched for during the operations of the
first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195
pulsars including the most recent results described in this paper.


title: Degenerations of invariant lagrangian manifolds

abstract:
  We consider a pair (H,I) where I is an involutive ideal of a Poisson algebra
and H lies in I. We show that if I defines a 2n-gon singularity then, under
arithmetical conditions on H, any deformation of H can "integrated" as a
deformation of (H,I).


title: Concentration inequalities for sampling without replacement

abstract:
  Concentration inequalities quantify the deviation of a random variable from a
fixed value. In spite of numerous applications, such as opinion surveys or
ecological counting procedures, few concentration results are known for the
setting of sampling without replacement from a finite population. Until now,
the best general concentration inequality has been a Hoeffding inequality due
to Serfling [Ann. Statist. 2 (1974) 39-48]. In this paper, we first improve on
the fundamental result of Serfling [Ann. Statist. 2 (1974) 39-48], and further
extend it to obtain a Bernstein concentration bound for sampling without
replacement. We then derive an empirical version of our bound that does not
require the variance to be known to the user.


title: Perfect powers expressible as sums of two fifth or seventh powers

abstract:
  We show that the generalized Fermat equations with signatures (5,5,7),
(5,5,19), and (7,7,5) (and unit coefficients) have no non-trivial primitive
integer solutions. Assuming GRH, we also prove the nonexistence of non-trivial
primitive integer solutions for the signatures (5,5,11), (5,5,13), and
(7,7,11). The main ingredients for obtaining our results are descent
techniques, the method of Chabauty-Coleman, and the modular approach to
Diophantine equations.


title:
Epitaxial Growth of Spinel Cobalt Ferrite Films on MgAl$_2$O$_4$
  Substrates by Direct Liquid Injection Chemical Vapor Deposition

abstract:
  The direct liquid injection chemical vapor deposition (DLI-CVD) technique has
been used for the growth of cobalt ferrite (CFO) films on (100)-oriented
MgAl$_2$O$_4$ (MAO) substrates. Smooth and highly epitaxial cobalt ferrite thin
films, with the epitaxial relationship $\mathrm{MAO} (100)\:[001] \parallel
\mathrm{CFO} (100)\:[001]$, are obtained under optimized deposition conditions.
The films exhibit bulk-like structural and magnetic properties with an
out-of-plane lattice constant of $8.370\;\mathrm{\AA}$ and a saturation
magnetization of $420\;\mathrm{kA/m}$ at room temperature. The Raman spectra of
films on MgAl$_2$O$_4$ support the fact that the Fe$^{3+}$- and the
Co$^{2+}$-ions are distributed in an ordered fashion on the B-site of the
inverse spinel structure. The DLI-CVD technique has been extended for the
growth of smooth and highly oriented cobalt ferrite thin films on a variety of
other substrates, including MgO, and piezoelectric lead magnesium niobate-lead
titanate and lead zinc niobate-lead titanate substrates.


title: Maps preserving the spectrum of certain products of operators

abstract:
  Let H be a complex Hilbert space, B(H) and S(H) be the spaces of all bounded
operators and all self-adjoint operators on H, respectively. We give the
concrete forms of the maps on B(H) and also S(H) which preserve the spectrum of
certain products of operators.


title: The complexity of parity graph homomorphism: an initial investigation

abstract:
  Given a graph G, we investigate the question of determining the parity of the
number of homomorphisms from G to some other fixed graph H. We conjecture that
this problem exhibits a complexity dichotomy, such that all parity graph
homomorphism problems are either polynomial-time solvable or parityP-complete,
and provide a conjectured characterisation of the easy cases.
  We show that the conjecture is true for the restricted case in which the
graph H is a tree, and provide some tools that may be useful in further
investigation into the parity graph homomorphism problem, and the problem of
counting homomorphisms for other moduli.


title:
The Weighted Sum Rate Maximization in MIMO Interference Networks: The
  Minimax Lagrangian Duality and Algorithm

abstract:
  We take a new perspective on the weighted sum-rate maximization in
multiple-input multiple-output (MIMO) interference networks, by formulating an
equivalent max-min problem. This seemingly trivial reformulation has
significant implications: the Lagrangian duality of the equivalent max-min
problem provides an elegant way to establish the sum-rate duality between an
interference network and its reciprocal when such a duality exists, and more
importantly, suggests a novel iterative minimax algorithm for the weighted
sum-rate maximization. Moreover, the design and convergence proof of the
algorithm use only general convex analysis. They apply and extend to any
max-min problems with similar structure, and thus provide a general class of
algorithms for such optimization problems. This paper presents a promising step
and lends hope for establishing a general framework based on the minimax
Lagrangian duality for characterizing the weighted sum-rate and developing
efficient algorithms for general MIMO interference networks.


title:
Domain and Function: A Dual-Space Model of Semantic Relations and
  Compositions

abstract:
  Given appropriate representations of the semantic relations between carpenter
and wood and between mason and stone (for example, vectors in a vector space
model), a suitable algorithm should be able to recognize that these relations
are highly similar (carpenter is to wood as mason is to stone; the relations
are analogous). Likewise, with representations of dog, house, and kennel, an
algorithm should be able to recognize that the semantic composition of dog and
house, dog house, is highly similar to kennel (dog house and kennel are
synonymous). It seems that these two tasks, recognizing relations and
compositions, are closely connected. However, up to now, the best models for
relations are significantly different from the best models for compositions. In
this paper, we introduce a dual-space model that unifies these two tasks. This
model matches the performance of the best previous models for relations and
compositions. The dual-space model consists of a space for measuring domain
similarity and a space for measuring function similarity. Carpenter and wood
share the same domain, the domain of carpentry. Mason and stone share the same
domain, the domain of masonry. Carpenter and mason share the same function, the
function of artisans. Wood and stone share the same function, the function of
materials. In the composition dog house, kennel has some domain overlap with
both dog and house (the domains of pets and buildings). The function of kennel
is similar to the function of house (the function of shelters). By combining
domain and function similarities in various ways, we can model relations,
compositions, and other aspects of semantics.


title:
The Spectrum Of Hypercubes Quotiented By Doubly Even Codewords And The
  Thermodynamics Of Adinkras

abstract:
  In a previous paper, a solution to the problem of determining isomorphism
classes of Lie algebra representations was explored using graphs called
adinkras and subgraphs called baobabs arXiv:1306.0550[math-ph] In this paper, I
show that adinkras contain Shannon entropy and a latent heat from the
information stored in their associated baobabs. In Garden algebra, both
properties are closely related to the spectrum of hypercubes quotiented by
doubly even codewords, which is introduced in this paper.


title:
Statistical distribution of the reversible gates: what percentage of
  them are self-inverse?

abstract:
  It is well known that most of the frequently used reversible logic gates
(e.g., NOT, CNOT, SWAP, Toffoli, Fredkin) are self-inverse and are represented
by square matrices that are unitary and Hermitian. However, with a simple
minded argument, it is established that the most of the allowed reversible
gates are non-self-inverse (unitary but non-Hermitian) in nature. It is also
shown that the % of non-Hermitian gates increases with the dimension. For
example, 58.33% of the 2-bit gates, 98.10% of the 3-bit gates and 99.99% of the
4-bit gates are non-Hermitian. As classical reversible gates are essentially
permutation gates, above statistics is strictly valid for classical reversible
gates, but the argument can be easily extended to include quantum gates and to
establish that the majority of the quantum gates are also non-self-inverse.
Further, the % of genuinely 2-bit reversible gates (i.e., 2-bit gates that
cannot be decomposed as a product of two single bit gates) among all possible
gates has been computed as 83.3%, and the applicability of this analysis in the
optimization of circuit cost is discussed.


title: Operators in Rigged Hilbert spaces: some spectral properties

abstract:
  A notion of resolvent set for an operator acting in a rigged Hilbert space
$\D \subset \H\subset \D^\times$ is proposed. This set depends on a family of
intermediate locally convex spaces living between $\D$ and $\D^\times$, called
interspaces. Some properties of the resolvent set and of the corresponding
multivalued resolvent function are derived and some examples are discussed.


title: Evolving networks in the human epileptic brain

abstract:
  Network theory provides novel concepts that promise an improved
characterization of interacting dynamical systems. Within this framework,
evolving networks can be considered as being composed of nodes, representing
systems, and of time-varying edges, representing interactions between these
systems. This approach is highly attractive to further our understanding of the
physiological and pathophysiological dynamics in human brain networks. Indeed,
there is growing evidence that the epileptic process can be regarded as a
large-scale network phenomenon. We here review methodologies for inferring
networks from empirical time series and for a characterization of these
evolving networks. We summarize recent findings derived from studies that
investigate human epileptic brain networks evolving on timescales ranging from
few seconds to weeks. We point to possible pitfalls and open issues, and
discuss future perspectives.


title:
Demonstration of spectral correlation control in a source of
  polarization entangled photon pairs at telecom wavelength

abstract:
  Spectrally correlated photon pairs can be used to improve performance of long
range fiber based quantum communication protocols. We present a source based on
spontaneous parametric down-conversion producing polarization entangled photons
without spectral filtering. In addition, the spectral correlation within the
photon pair can be controlled by changing the pump pulse duration or coupled
spatial modes characteristics. The spectral and polarization correlations were
characterized. The generated photon pairs feature both positive spectral
correlations, no correlations, or negative correlations and polarization
entanglement with the fidelity as high as 0.97 (no background subtraction) with
the expected Bell state.


title: Anomalous Hall effect arising from noncollinear antiferromagnetism

abstract:
  In most conductors current flow perpendicular to electric field direction
(Hall current) can be explained in terms of the Lorentz forces present when
charged particles flow in an external magnetic field. However, as established
in the very early work of Edwin Hall, ferromagnetic conductors such as Fe, Co,
and Ni have an anomalous Hall conductivity contribution that cannot be
attributed to Lorentz forces and therefore survives in the absence of a
magnetic field. Although the anomalous Hall effect is experimentally strong, it
has stood alone among metallic transport effects for much of the last century
because it lacked a usefully predictive, generally accepted theory. Progress
over the past decade has explained why. It is now clear that the anomalous Hall
effect in ferromagnets has contributions from both extrinsic scattering
mechanisms similar to those that determine most transport coefficients, and
from an intrinsic mechanism that is independent of scattering. The anomalous
Hall effect is also observed in paramagnets, which have nonzero magnetization
induced by an external magnetic field. Although no explicit relationship has
been established, the anomalous Hall effect in a particular material is usually
assumed to be proportional to its magnetization. In this work we point out that
it is possible to have an anomalous Hall effect in a noncollinear
antiferromagnet with zero net magnetization provided that certain common
symmetries are absent, and predict that Mn3Ir, a technologically important
antiferromagnetic material with noncollinear order that survives to very high
temperatures, has a surprisingly large anomalous Hall effect comparable in size
to those of the elemental transition metal ferromagnets.