title:
Numerical Studies of Optimization and Aberration Correction Methods for
  the Preliminary Demonstration of the Parametric Ionization Cooling (PIC)
  Principle in the Twin Helix Muon Cooling Channel

abstract:
  Muon colliders have been proposed for the next generation of particle
accelerators that study high-energy physics at the energy and intensity
frontiers. In this paper we study a possible implementation of muon ionization
cooling, Parametric-resonance Ionization Cooling (PIC), in the twin helix
channel. The resonant cooling method of PIC offers the potential to reduce
emittance beyond that achievable with ionization cooling with ordinary magnetic
focusing. We examine optimization of a variety of parameters, study the
nonlinear dynamics in the twin helix channel and consider possible methods of
aberration correction.


title: Online Clustering of Bandits

abstract:
  We introduce a novel algorithmic approach to content recommendation based on
adaptive clustering of exploration-exploitation ("bandit") strategies. We
provide a sharp regret analysis of this algorithm in a standard stochastic
noise setting, demonstrate its scalability properties, and prove its
effectiveness on a number of artificial and real-world datasets. Our
experiments show a significant increase in prediction performance over
state-of-the-art methods for bandit problems.


title: A Real-Time, GPU-Based, Non-Imaging Back-End for Radio Telescopes

abstract:
  Since the discovery of RRATs, interest in single pulse radio searches has
increased dramatically. Due to the large data volumes generated by these
searches, especially in planned surveys for future radio telescopes, such
searches have to be conducted in real-time. This has led to the development of
a multitude of search techniques and real-time pipeline prototypes. In this
work we investigated the applicability of GPUs. We have designed and
implemented a scalable, flexibile, GPU-based, transient search pipeline
composed of several processing stages, including RFI mitigation, dedispersion,
event detection and classification, as well as data quantisation and
persistence. These stages are encapsulated as a standalone framework. The
optimised GPU implementation of direct dedispersion achieves a speedup of more
than an order of magnitude when compared to an optimised CPU implementation. We
use a density-based clustering algorithm, coupled with a candidate selection
mechanism to group detections caused by the same event together and
automatically classify them as either RFI or of celestial origin. This setup
was deployed at the Medicina BEST-II array where several test observations were
conducted. Finally, we calculate the number of GPUs required to process all the
beams for the SKA1-mid non-imaging pipeline. We have also investigated the
applicability of GPUs for beamforming, where our implementation achieves more
than 50% of the peak theoretical performance. We also demonstrate that for
large arrays, and in observations where the generated beams need to be
processed outside of the GPU, the system will become PCIe bandwidth limited.
This can be alleviated by processing the synthesised beams on the GPU itself,
and we demonstrate this by integrating the beamformer to the transient
detection pipeline.


title: Nuclear Physics Review

abstract:
  Anchoring low-energy nuclear physics to the fundamental theory of strong
interactions remains an outstanding challenge. I review the current progress
and challenges of the endeavor to use lattice QCD to bridge this connection.
This is a particularly exciting time for this line of research as demonstrated
by the spike in the number of different collaborative efforts focussed on this
problem and presented at this conference. I first digress and discuss the 2013
Ken Wilson Award.


title: The Smith and critical groups of Paley graphs

abstract:
  There is a Paley graph for each prime power $q$ such that $q\equiv 1\pmod 4$.
The vertex set is the field $\mathbb Fq$ and two vertices $x$ and $y$ are
joined by an edge if and only if $x-y$ is a nonzero square of $\mathbb Fq$. We
compute the Smith normal forms of the adjacency matrix and Laplacian matrix of
a Paley graph.


title:
Infrared face recognition: a comprehensive review of methodologies and
  databases

abstract:
  Automatic face recognition is an area with immense practical potential which
includes a wide range of commercial and law enforcement applications. Hence it
is unsurprising that it continues to be one of the most active research areas
of computer vision. Even after over three decades of intense research, the
state-of-the-art in face recognition continues to improve, benefitting from
advances in a range of different research fields such as image processing,
pattern recognition, computer graphics, and physiology. Systems based on
visible spectrum images, the most researched face recognition modality, have
reached a significant level of maturity with some practical success. However,
they continue to face challenges in the presence of illumination, pose and
expression changes, as well as facial disguises, all of which can significantly
decrease recognition accuracy. Amongst various approaches which have been
proposed in an attempt to overcome these limitations, the use of infrared (IR)
imaging has emerged as a particularly promising research direction. This paper
presents a comprehensive and timely review of the literature on this subject.
Our key contributions are: (i) a summary of the inherent properties of infrared
imaging which makes this modality promising in the context of face recognition,
(ii) a systematic review of the most influential approaches, with a focus on
emerging common trends as well as key differences between alternative
methodologies, (iii) a description of the main databases of infrared facial
images available to the researcher, and lastly (iv) a discussion of the most
promising avenues for future research.


title:
Post-Markovian quantum master equations from classical environment
  fluctuations

abstract:
  In this paper we demonstrate that two commonly used phenomenological
post-Markovian quantum master equations can be derived without using any
perturbative approximation. A system coupled to an environment characterized by
self-classical configurational fluctuations, the latter obeying a Markovian
dynamics, defines the underlying physical model. Both Shabani-Lidar equation
[A. Shabani and D. A. Lidar, Phys. Rev. A 71, 020101(R) (2005)] and its
associated approximated integro-differential kernel master equation are
obtained by tracing out two different bipartite Markovian Lindblad dynamics
where the environment fluctuations are taken into account by an ancilla system.
Furthermore, conditions under which the non-Markovian system dynamics can be
unravelled in terms of an ensemble of measurement trajectories are found. In
addition, a non-Markovian quantum jump approach is formulated. Contrary to
recent analysis [L. Mazzola, E. M. Laine, H. P. Breuer, S. Maniscalco, and J.
Piilo, Phys. Rev. A 81, 062120 (2010)], we also demonstrate that these master
equations, even with exponential memory functions, may lead to non-Markovian
effects such as an environment-to-system backflow of information if the
Hamiltonian system does not commutate with the dissipative dynamics.


title:
The first Frontier Fields cluster: 4.5{\mu}m excess in a z~8 galaxy
  candidate in Abell 2744

abstract:
  We present in this letter the first analysis of a z~8 galaxy candidate found
in the Hubble and Spitzer imaging data of Abell 2744, as part of the Hubble
Frontier Fields legacy program. We applied the most commonly-used methods to
select exceptionally high-z galaxies by combining non-detection and
color-criteria using seven HST bands. We used GALFIT on IRAC images for fitting
and subtracting contamination of bright nearby sources. The physical properties
have been inferred from SED-fitting using templates with and without nebular
emission. This letter is focussed on the brightest candidate we found
(m$_{F160W}$=26.2) over the 4.9 arcmin$^2$ field of view covered by the WFC3.
It shows a non-detection in the ACS bands and at 3.6{\mu}m whereas it is
clearly detected at 4.5{\mu}m with rather similar depths. This break in the
IRAC data could be explained by strong [OIII]+H{\beta} lines at z~8 which
contribute to the 4.5{\mu}m photometry. The best photo-z is found at
z~8.0$^{+0.2}_{-0.5}$, although solutions at low-redshift (z~1.9) cannot be
completely excluded, but they are strongly disfavoured by the SED-fitting work.
The amplification factor is relatively small at {\mu}=1.49$\pm$0.02. The Star
Formation Rate in this object is ranging from 8 to 60 Mo/yr, the stellar mass
is in the order of M$_{\star}$=(2.5-10) x 10$^{9}$Mo and the size is
r~0.35$\pm$0.15 kpc. This object is one of the first z~8 LBG candidates showing
a clear break between 3.6{\mu}m and 4.5{\mu}m which is consistent with the IRAC
properties of the first spectroscopically confirmed galaxy at a similar
redshift. Due to its brightness, the redshift of this object could potentially
be confirmed by near infrared spectroscopy with current 8-10m telescopes. The
nature of this candidate will be revealed in the coming months with the arrival
of new ACS and Spitzer data, increasing the depth at optical and near-IR
wavelengths.


title:
Complex optimal transport and the pluripotential theory of
  K\"ahler-Ricci solitons

abstract:
  Let (X,L) be a (semi-) polarized complex projective variety and T a real
torus acting holomorphically on X with moment polytope P. Given a probability
density g on P we introduce a new type of Monge-Ampere measure on X, defined
for singular T-invariant metrics on the line bundle L, generalizing the
ordinary Monge-Ampere of global pluripotential theory, which corresponds to the
case when T is trivial (or g=1). In the opposite extreme case when T has
maximal rank, i.e. (X,L,T) is a toric variety, the solution of the
corresponding Monge-Ampere equation with right hand side \mu corresponds to the
convex Kantorovich potential for the optimal transport map in the
Monge-Kantorovich transport problem betweeen \mu and g (for a quadratic cost
function). Accordingly, our general setting can be seen as a complex version of
optimal transport theory. Our main complex geometric applications concern the
pluripotential study of singular (shrinking) Kahler-Ricci solitons. In
particular, we establish the uniqueness of such solitons, modulo automorphisms,
and explore their relation to a notion of modified K-stability inspired by the
work of Tian-Zhu. The quantization of this setup, in the sense of Donaldson, is
also studied.


title:
Sub-optimality of Treating Interference as Noise in the Cellular Uplink
  with Weak Interference

abstract:
  Despite the simplicity of the scheme of treating interference as noise (TIN),
it was shown to be sum-capacity optimal in the Gaussian interference channel
(IC) with very-weak (noisy) interference. In this paper, the 2-user IC is
altered by introducing an additional transmitter that wants to communicate with
one of the receivers of the IC. The resulting network thus consists of a
point-to-point channel interfering with a multiple access channel (MAC) and is
denoted PIMAC. The sum-capacity of the PIMAC is studied with main focus on the
optimality of TIN. It turns out that TIN in its naive variant, where all
transmitters are active and both receivers use TIN for decoding, is not the
best choice for the PIMAC. In fact, a scheme that combines both time division
multiple access and TIN (TDMA-TIN) strictly outperforms the naive-TIN scheme.
Furthermore, it is shown that in some regimes, TDMA-TIN achieves the
sum-capacity for the deterministic PIMAC and the sum-capacity within a constant
gap for the Gaussian PIMAC. Additionally, it is shown that, even for very-weak
interference, there are some regimes where a combination of interference
alignment with power control and treating interference as noise at the receiver
side outperforms TDMA-TIN. As a consequence, on the one hand treating
interference as noise in a cellular uplink is approximately optimal in certain
regimes. On the other hand those regimes cannot be simply described by the
strength of interference.


title:
Unconventional height functions in simultaneous Diophantine
  approximation

abstract:
  Simultaneous Diophantine approximation is concerned with the approximation of
a point $\mathbf x\in\mathbb R^d$ by points $\mathbf r\in\mathbb Q^d$, with a
view towards jointly minimizing the quantities $\|\mathbf x - \mathbf r\|$ and
$H(\mathbf r)$. Here $H(\mathbf r)$ is the so-called "standard height" of the
rational point $\mathbf r$. In this paper the authors ask: What changes if we
replace the standard height function by a different one? As it turns out, this
change leads to dramatic differences from the classical theory and requires the
development of new methods. We discuss three examples of nonstandard height
functions, computing their exponents of irrationality as well as giving more
precise results. A list of open questions is also given.


title:
Phase Imprinting in Equilibrating Fermi Gases: The Transience of Vortex
  Rings and Other Defects

abstract:
  We present numerical simulations of phase imprinting experiments in ultracold
trapped Fermi gases which are in good agreement with recent, independent
experimental results. Our focus is on the sequence and evolution of defects
using the fermionic time-dependent Ginzburg-Landau equation, which contains
dissipation necessary for equilibration. In contrast to other simulations we
introduce small, experimentally unavoidable symmetry breaking, particularly
that associated with thermal fluctuations and with the phase imprinting tilt
angle, and illustrate their dramatic effects. The former causes vortex rings in
confined geometries to move to the trap surface and rapidly decay into more
stable vortex lines, as appears consistent with recent experimental claims. The
latter aligns the precessing and relatively long-lived vortex filaments,
rendering them difficult to distinguish from solitons.


title:
On the similarity of meshless discretizations of Peridynamics and
  Smooth-Particle Hydrodynamics

abstract:
  This paper discusses the similarity of meshless discretizations of
Peridynamics and Smooth-Particle-Hydrodynamics (SPH), if Peridynamics is
applied to classical material models based on the deformation gradient. We show
that the discretized equations of both methods coincide if nodal integration is
used. This equivalence implies that Peridynamics reduces to an old meshless
method and all instability problems of collocation-type particle methods apply.
These instabilities arise as a consequence of the nodal integration scheme,
which causes rank-deficiency and leads to spurious zero-energy modes. As a
result of the demonstrated equivalence to SPH, enhanced implementations of
Peridynamics should employ more accurate integration schemes.


title: Experiments with Three Approaches to Recognizing Lexical Entailment

abstract:
  Inference in natural language often involves recognizing lexical entailment
(RLE); that is, identifying whether one word entails another. For example,
"buy" entails "own". Two general strategies for RLE have been proposed: One
strategy is to manually construct an asymmetric similarity measure for context
vectors (directional similarity) and another is to treat RLE as a problem of
learning to recognize semantic relations using supervised machine learning
techniques (relation classification). In this paper, we experiment with two
recent state-of-the-art representatives of the two general strategies. The
first approach is an asymmetric similarity measure (an instance of the
directional similarity strategy), designed to capture the degree to which the
contexts of a word, a, form a subset of the contexts of another word, b. The
second approach (an instance of the relation classification strategy)
represents a word pair, a:b, with a feature vector that is the concatenation of
the context vectors of a and b, and then applies supervised learning to a
training set of labeled feature vectors. Additionally, we introduce a third
approach that is a new instance of the relation classification strategy. The
third approach represents a word pair, a:b, with a feature vector in which the
features are the differences in the similarities of a and b to a set of
reference words. All three approaches use vector space models (VSMs) of
semantics, based on word-context matrices. We perform an extensive evaluation
of the three approaches using three different datasets. The proposed new
approach (similarity differences) performs significantly better than the other
two approaches on some datasets and there is no dataset for which it is
significantly worse. Our results suggest it is beneficial to make connections
between the research in lexical entailment and the research in semantic
relation classification.


title: Expansion and rupture of charged microcapsules

abstract:
  We study the deformations of pH-responsive spherical microcapsules --
micrometer-scale liquid drops surrounded by thin, solid shells -- under the
influence of electrostatic forces. When exposed to a large concentration of
NaOH, the microcapsules become highly charged, and expand isotropically. We
find that the extent of this expansion can be understood by coupling
electrostatics with shell theory; moreover, the expansion dynamics is well
described by Darcy's law for fluid flow through the microcapsule shell.
Unexpectedly, however, below a threshold NaOH concentration, the microcapsules
begin to disintegrate, and eventually rupture; they then expand non-uniformly,
ultimately forming large, jellyfish-like structures. Our results highlight the
fascinating range of behaviors exhibited by pH-responsive microcapsules, driven
by the interplay between electrostatic and mechanical forces.

categories: cond-mat.soft cond-mat.mes-hall cond-mat.mtrl-sci physics.flu-dyn


title: Hedging Expected Losses on Derivatives in Electricity Futures Markets

abstract:
  We investigate the problem of pricing and hedging derivatives of Electricity
Futures contract when the underlying asset is not available. We propose to use
a cross hedging strategy based on the Futures contract covering the larger
delivery period. A quick overview of market data shows a basis risk for this
market incompleteness. For that purpose we formulate the pricing problem in a
stochastic target form along the lines of Bouchard and al. (2008), with a
moment loss function. Following the same techniques as in the latter, we avoid
to demonstrate the uniqueness of the value function by comparison arguments and
explore convex duality methods to provide a semi-explicit solution to the
problem. We then propose numerical results to support the new hedging strategy
and compare our method to the Black-Scholes naive approach.


title:
The works of Charles Ehresmann on connections: from Cartan connections
  to connections on fibre bundles

abstract:
  Around 1923, Elie Cartan introduced affine connections on manifolds and
definedthe main related concepts: torsion, curvature, holonomy groups. He
discussed applications of these concepts in Classical and Relativistic
Mechanics; in particular he explained how parallel transport with respect to a
connection can be related to the principle of inertia in Galilean Mechanics
and, more generally, can be used to model the motion of a particle in a
gravitational field. In subsequent papers, Elie Cartan extended these concepts
for other types of connections on a manifold: Euclidean, Galilean and
Minkowskian connections which can be considered as special types of affine
connections, the group of affine transformations of the affine tangent space
being replaced by a suitable subgroup; and more generally, conformal and
projective connections, associated to a group which is no more a subgroup of
the affine group. Around 1950, Charles Ehresmann introduced connections on a
fibre bundle and, when the bundle has a Lie group as structure group,
connection forms on the associated principal bundle, with values in the Lie
algebra of the structure group. He called Cartan connections the various types
of connections on a manifold previously introduced by E. Cartan, and explained
how they can be considered as special cases of connections on a fibre bundle
with a Lie group G as structure group: the standard fibre of the bundle is then
an homogeneous space G/G' ; its dimension is equal to that of the base
manifold; a Cartan connection determines an isomorphism of the vector bundle
tangent to the the base manifold onto the vector bundle of vertical vectors
tangent to the fibres of the bundle along a global section. These works are
reviewed and some applications of the theory of connections are sketched.


title:
Molecular Dynamics Simulation of Coherent Interfaces in Fluorite
  Heterostructures

abstract:
  The standard model of enhanced ionic conductivities in solid electrolyte
heterostructures follows from a continuum mean-field description of defect
distributions that makes no reference to crystalline structure. To examine
ionic transport and defect distributions while explicitly accounting for
ion-ion correlations and lattice effects, we have performed molecular dynamics
simulations of a model coherent fluorite heterostructure without any extrinsic
defects, with a difference in standard chemical potentials of mobile fluoride
ions between phases induced by an external potential. Increasing the offset in
fluoride ion standard chemical potentials across the internal interfaces
decreases the activation energies for ionic conductivity and diffusion and
strongly enhances fluoride ion mobilities and defect concentrations near the
heterostructure interfaces. Non-charge-neutral "space-charge" regions, however,
extend only a few atomic spacings from the interface, suggesting a continuum
model may be inappropriate. Defect distributions are qualitatively inconsistent
with the predictions of the continuum mean-field model, and indicate strong
lattice-mediated defect-defect interactions. We identify an atomic-scale
"Frenkel polarisation" mechanism for the interfacial enhancement in ionic
mobility, where preferentially oriented associated Frenkel pairs form at the
interface and promote local ion mobility via concerted diffusion processes.


title:
Empirical Bayes unfolding of elementary particle spectra at the Large
  Hadron Collider

abstract:
  We consider the so-called unfolding problem in experimental high energy
physics, where the goal is to estimate the true spectrum of elementary
particles given observations distorted by measurement error due to the limited
resolution of a particle detector. This an important statistical inverse
problem arising in the analysis of data at the Large Hadron Collider at CERN.
Mathematically, the problem is formalized as one of estimating the intensity
function of an indirectly observed Poisson point process. Particle physicists
are particularly keen on unfolding methods that feature a principled way of
choosing the regularization strength and allow for the quantification of the
uncertainty inherent in the solution. Though there are many approaches that
have been considered by experimental physicists, it can be argued that few --
if any -- of these deal with these two key issues in a satisfactory manner. In
this paper, we propose to attack the unfolding problem within the framework of
empirical Bayes estimation: we consider Bayes estimators of the coefficients of
a basis expansion of the unknown intensity, using a regularizing prior; and
employ a Monte Carlo expectation-maximization algorithm to find the marginal
maximum likelihood estimate of the hyperparameter controlling the strength of
the regularization. Due to the data-driven choice of the hyperparameter,
credible intervals derived using the empirical Bayes posterior lose their
subjective Bayesian interpretation. Since the properties and meaning of such
intervals are poorly understood, we explore instead the use of bootstrap
resampling for constructing purely frequentist confidence bands for the true
intensity. The performance of the proposed methodology is demonstrated using
both simulations and real data from the Large Hadron Collider.


title:
Two-loop top-Yukawa-coupling corrections to the Higgs boson masses in
  the complex MSSM

abstract:
  Results for the leading two-loop corrections of
$\mathcal{O}{\left(\alpha_t^2\right)}$ from the Yukawa sector to the
Higgs-boson masses of the MSSM with complex parameters are presented. The
corresponding self-energies and their renormalization have been obtained in a
Feynman-diagrammatic approach. A numerical analysis of the new contributions is
performed for the mass of the lightest Higgs boson, supplemented by the full
one-loop result and the $\mathcal{O}{\left(\alpha_t \alpha_s\right)}$ terms
including complex phases. In the limit of the real MSSM a previous result is
confirmed.


title:
Local instabilities in magnetized rotational flows: A short-wavelength
  approach

abstract:
  We perform a local stability analysis of rotational flows in the presence of
a constant vertical magnetic field and an azimuthal magnetic field with a
general radial dependence. Employing the short-wavelength approximation we
develop a unified framework for the investigation of the standard, the helical,
and the azimuthal version of the magnetorotational instability, as well as of
current-driven kink-type instabilities. Considering the viscous and resistive
setup, our main focus is on the case of small magnetic Prandtl numbers which
applies, e.g., to liquid metal experiments but also to the colder parts of
accretion disks. We show that the inductionless versions of MRI that were
previously thought to be restricted to comparably steep rotation profiles
extend well to the Keplerian case if only the azimuthal field slightly deviates
from its current-free (in the fluid) profile. We find an explicit criterion
separating the pure azimuthal inductionless magnetorotational instability from
the regime where this instability is mixed with the Tayler instability. We
further demonstrate that for particular parameter configurations the azimuthal
MRI originates as a result of a dissipation-induced instability of the
Chandrasekhar's equipartition solution of ideal magnetohydrodynamics.

categories: physics.flu-dyn astro-ph.SR math.DS physics.plasm-ph


title: Modeling Electronic Quantum Transport with Machine Learning

abstract:
  We present a Machine Learning approach to solve electronic quantum transport
equations of one-dimensional nanostructures. The transmission coefficients of
disordered systems were computed to provide training and test datasets to the
machine. The system's representation encodes energetic as well as geometrical
information to characterize similarities between disordered configurations,
while the Euclidean norm is used as a measure of similarity. Errors for
out-of-sample predictions systematically decrease with training set size,
enabling the accurate and fast prediction of new transmission coefficients. The
remarkable performance of our model to capture the complexity of interference
phenomena lends further support to its viability in dealing with transport
problems of undulatory nature.


title:
Space charge impedances of a rectangular beam with longitudinal density
  modulations inside a rectangular chamber

abstract:
  This paper studies the space charge impedances of a rectangular beam inside a
rectangular chamber, and the limiting case, e.g., a rectangular beam between
parallel plates, respectively. The charged beam has uniform density in vertical
direction and arbitrary distribution in horizontal direction. The method of
separation of variables is used to calculate the space charge potentials,
fields, and impedances which are valid in the whole perturbation wavelength
spectrum. Comparisons between the theoretical calculations and the numerical
simulations are also provided and they match quite well. It is shown that the
rectangular beam shape may help to reduce the longitudinal space charge
impedances.


title:
Asteroseismology of eclipsing binary stars using Kepler and the HERMES
  spectrograph

abstract:
  We introduce our PhD project in which we focus on pulsating stars in
eclipsing binaries. The combination of high-precision Kepler photometry with
high-resolution HERMES spectroscopy allows for detailed descriptions of our
sample of target stars. We report here the detection of three false positives
by radial velocity measurements.


title: The CCAT Software System

abstract:
  CCAT will be a 25-meter telescope for sub millimeter astronomy located at
5600m altitude on Cerro Chajnantor in northern Chile. CCAT will combine high
sensitivity, a wide field of view, and a broad wavelength range (0.35 to 2.1mm)
to provide an unprecedented capability for deep, large-area multicolor
submillimeter surveys. It is planned to have a suite of instruments including
large format KID cameras, a large heterodyne array and a KID-based direct
detection multi-object spectrometer. The remote location drives a desire for
fully autonomous observing coupled with data reduction pipelines and fast
feedback to principal investigators.


title: MLS110213:022733+130617: A new eclipsing polar above the period gap

abstract:
  We present new data that confirm MLS110213:022733+130617 as a new eclipsing
polar. Some system properties were estimated.


title: Thim's Experiment and Exact Rotational Space-Time Transformations

abstract:
  Thim measured the transverse Doppler shift using a system consisting of a
stationary antenna and pickup, in addition to a number of intermediate antennas
mounted on the rim of a rotating disk. No such shift was detected, although the
experiment should have had enough sensitivity to measure it, as predicted by
the Lorentz transformations. However, using the Lorentz transformations to
analyze the results of experiments involving circular motion, while commonly
done, is inappropriate because such an analysis involves non-inertial frames,
which are outside the range of validity of special relativity. In this paper,
we re-analyze Thim's experiment using exact rotational space-time
transformations, finding that his null result is consistent with theoretical
predictions.


title:
The generalized second law of thermodynamics for the interacting in
  $f(T)$ gravity

abstract:
  We study the validity of the generalized second law (GSL) of gravitational
thermodynamics in a non-flat FRW universe containing the interacting in $f(T)$
gravity. We consider that the boundary of the universe to be confined by the
dynamical apparent horizon in FRW universe. In general, we discuss the
effective equation of state, deceleration parameter and GLS in this framewok.
Also, we find that the interacting-term $Q$ modifies these quantities and in
particular, the evolution of the total entropy, results in an increases on the
GLS of thermodynamic, by a factor $4\pi\,R_A^3\,Q/3$. By using a viable $f(T)$
gravity with an exponential dependence on the torsion, we develop a model where
the interaction term is related to the total energy density of matter. Here, we
find that a crossing of phantom divide line is possible for the
interacting-$f(T)$ model.


title: The mass-metallicity relation of galaxies up to redshift 0.35

abstract:
  Our research on the age-metallicity and mass-metallicity relations of
galaxies is presented and compared to the most recent investigations in the
field. We have been able to measure oxygen abundances using the direct method
for objects spanning four orders of magnitude in mass, and probing the last 4
Gyr of galaxy evolution. We have found preliminary evidence that the
metallicity evolution is consistent with expectations based on age-metallicity
relations obtained with low resolution stellar spectra of resolved Local Group
galaxies.


title: Semi-classical weights and equivariant spectral theory

abstract:
  We prove inverse spectral results for differential operators on manifolds and
orbifolds invariant under a torus action. These inverse spectral results
involve the asymptotic equivariant spectrum, which is the spectrum itself
together with "very large" weights of the torus action on eigenspaces. More
precisely, we show that the asymptotic equivariant spectrum of the Laplace
operator of any toric metric on a generic toric orbifold determines the
equivariant biholomorphism class of the orbifold; we also show that the
asymptotic equivariant spectrum of a T^n-invariant Schrodinger operator on R^n
determines its potential in some suitably convex cases. In addition, we prove
that the asymptotic equivariant spectrum of an S^1-invariant metric on S^2
determines the metric itself in many cases. Finally, we obtain an asymptotic
equivariant inverse spectral result for weighted projective spaces. As a
crucial ingredient in these inverse results, we derive a surprisingly simple
formula for the asymptotic equivariant trace of a family of semi-classical
differential operators invariant under a torus action.


title: Real polynomial maps and singular open books at infinity

abstract:
  We provide significant conditions under which we prove the existence of
stable open book structures at infinity, i.e. on spheres $S^{m-1}_R$ of large
enough radius $R$. We obtain new classes of real polynomial maps $\mathbb R^m
\to \mathbb R^p$ which induce such structures.


title: Observing dark photon with dark matter detectors

abstract:
  Motivated by various kinds of new physics models, a new light neutral vector
boson (the dark photon) connected to the Standard Model of particle physics
only through the kinetic mixing with the U(1)_Y factor has been studied
extensively. Various kinds of experiments are proposed to detect it. For the
dark photon with a mass smaller than 10 keV, it can be copiously produced
inside the Sun, and then be detected by the detectors on the earth. We show
that with the S2 only analysis, the result from XENON10 experiment provides the
up-to-date most stringent limit on the region 10^{-5} eV < m_V < 10^3 eV: kappa
m_V < 3 times 10^{-12} eV for the Stueckelberg dark photon model, where kappa
is the kinetic mixing and m_V is the mass of the dark photon. If there is a
light Higgs boson accompanied with the dark photon, the sensitivity of XENON10
experiment is kappa times e' < 10^{-13}, which is still second to the
constraints from the lifetime of horizontal branch starts which dictates kappa
times e' < 3 times10^{-14}.


title: A Scalable Hybrid FPGA/GPU FX Correlator

abstract:
  Radio astronomical imaging arrays comprising large numbers of antennas,
O(10^2-10^3) have posed a signal processing challenge because of the required
O(N^2) cross correlation of signals from each antenna and requisite signal
routing. This motivated the implementation of a Packetized Correlator
architecture that applies Field Programmable Gate Arrays (FPGAs) to the O(N)
"F-stage" transforming time domain to frequency domain data, and Graphics
Processing Units (GPUs) to the O(N^2) "X-stage" performing an outer product
among spectra for each antenna. The design is readily scalable to at least
O(10^3) antennas. Fringes, visibility amplitudes and sky image results obtained
during field testing are presented.


title:
Spherically symmetric static solutions in a non-local infrared
  modification of General Relativity

abstract:
  We discuss static spherically symmetric solutions in a recently proposed
non-local infrared modification of Einstein equations induced by a term
$m^2g_{\mu\nu}\Box^{-1} R$, where $m$ is a mass scale. We find that, contrary
to what happens in usual theories of massive gravity, in this non-local theory
there is no vDVZ discontinuity and classical non-linearities do not become
large below a Vainshtein radius parametrically larger than the Schwarzschild
radius $r_S$. Rather on the contrary, in the regime $r\ll m^{-1}$ the
corrections to the metric generated by a static body in GR are of the form
$1+{\cal O}(m^2r^2)$ and become smaller and smaller toward smaller values of
$r$. The modification to the GR solutions only show up at $r > m^{-1}$. For
$m={\cal O}(H_0)$, as required for having interesting cosmological
consequences, the non-local theory therefore recovers all successes of GR at
the solar system and lab scales.


title:
Control of asymmetric Hopfield networks and application to cancer
  attractors

abstract:
  The asymmetric Hopfield model is used to simulate signaling dynamics in
gene/transcription factor networks. The model allows for a direct mapping of a
gene expression pattern into attractor states. We analyze different control
strategies aiming at disrupting attractor patterns using selective local fields
representing therapeutic interventions. The control strategies are based on the
identification of signaling $bottlenecks$, which are single nodes or strongly
connected clusters of nodes that have a large impact on the signaling. We
provide a theorem with bounds on the minimum number of nodes that guarantee
controllability of bottlenecks consisting of strongly connected components. The
control strategies are applied to the identification of sets of proteins that,
when inhibited, selectively disrupt the signaling of cancer cells while
preserving the signaling of normal cells. We use an experimentally validated
non-specific network and a specific B cell interactome reconstructed from gene
expression data to model cancer signaling in lung and B cells, respectively.
This model could help in the rational design of novel robust therapeutic
interventions based on our increasing knowledge of complex gene signaling
networks.


title: The price of being SM-like in SUSY

abstract:
  We compute the tuning in supersymmetric models associated with the
constraints from collider measurements of the Higgs couplings to fermions and
gauge bosons. In supersymmetric models, a CP-even state with SM Higgs couplings
mixes with additional, heavier CP-even states, causing deviations in the Higgs
couplings from SM values. These deviations are reduced as the heavy states are
decoupled with large soft masses, thereby exacerbating the tuning associated
with the electroweak scale. This new source of tuning is different from that
derived from collider limits on stops, gluinos and Higgsinos. It can be offset
with large tan beta in the MSSM, however this compensating effect is limited in
the NMSSM with a large Higgs-singlet coupling due to restrictions on large tan
beta from electroweak precision tests. We derive a lower bound on this tuning
and show that the level of precision of Higgs coupling measurements at the LHC
will probe naturalness in the NMSSM at the few-percent level. This is
comparable to the tuning derived from superpartner limits in models with a low
messenger scale and split families. Instead the significant improvement in
sensitivity of Higgs coupling measurements at the ILC will allow naturalness in
these models to be constrained at the per-mille level, beyond any tuning
derived from direct superpartner limits.


title:
Fragmentation of massive dense cores down to ~1000 AU: Relation between
  fragmentation and density structure

abstract:
  In order to shed light on the main physical processes controlling
fragmentation of massive dense cores, we present a uniform study of the density
structure of 19 massive dense cores, selected to be at similar evolutionary
stages, for which their relative fragmentation level was assessed in a previous
work. We inferred the density structure of the 19 cores through a simultaneous
fit of the radial intensity profiles at 450 and 850 micron (or 1.2 mm in two
cases) and the Spectral Energy Distribution, assuming spherical symmetry and
that the density and temperature of the cores decrease with radius following
power-laws. We find a weak (inverse) trend of fragmentation level and density
power-law index, with steeper density profiles tending to show lower
fragmentation, and vice versa. In addition, we find a trend of fragmentation
increasing with density within a given radius, which arises from a combination
of flat density profile and high central density and is consistent with Jeans
fragmentation. We considered the effects of rotational-to-gravitational energy
ratio, non-thermal velocity dispersion, and turbulence mode on the density
structure of the cores, and found that compressive turbulence seems to yield
higher central densities. Finally, a possible explanation for the origin of
cores with concentrated density profiles, which are the cores showing no
fragmentation, could be related with a strong magnetic field, consistent with
the outcome of radiation magnetohydrodynamic simulations.


title: Jet (de)coherence in Pb-Pb collisions at the LHC

abstract:
  We study the modifications of jets created in heavy-ion collisions at LHC
energies. The inherent hierarchy of scales governing the jet evolution allows
to distinguish a leading jet structure, which interacts coherently with the
medium as a single color charge, from softer sub-structures that will be
sensitive to effects of color decoherence. We argue how this separation comes
about and show that this picture is consistent with experimental data on
reconstructed jets at the LHC, providing a quantitative description
simultaneously of the jet nuclear modification factor, the missing energy in
di-jet events and the modification of the fragmentation functions. In
particular, we demonstrate that effects due to color decoherence are manifest
in the excess of soft particles measured in fragmentation functions in Pb-Pb
compared to proton-proton collisions.


title: Evolution of extortion in structured populations

abstract:
  Extortion strategies can dominate any opponent in an iterated prisoner's
dilemma game. But if players are able to adopt the strategies performing
better, extortion becomes widespread and evolutionary unstable. It may
sometimes act as a catalyst for the evolution of cooperation, and it can also
emerge in interactions between two populations, yet it is not the evolutionary
stable outcome. Here we revisit these results in the realm of spatial games. We
find that pairwise imitation and birth-death dynamics return known evolutionary
outcomes. Myopic best response strategy updating, on the other hand, reveals
new counterintuitive solutions. Defectors and extortioners coarsen
spontaneously, which allows cooperators to prevail even at prohibitively high
temptations to defect. Here extortion strategies play the role of a Trojan
horse. They may emerge among defectors by chance, and once they do, cooperators
become viable as well. These results are independent of the interaction
topology, and they highlight the importance of coarsening, checkerboard
ordering, and best response updating in evolutionary games.


title:
Spin liquid versus dimer phases in an anisotropic J1-J2 frustrated
  square antiferromagnet

abstract:
  The spin-1/2 J1-J2 antiferromagnet is a prototypical model for frustrated
magnetism and one possible candidate for a realization of a spin liquid phase.
The generalization of this system on the anisotropic square lattice is given by
the J1-J2-J1'-J2' Heisenberg model, which can be treated by a renormalization
group (RG) analysis of coupled frustrated chains. The J1-J2-J1'-J2'-model shows
an interesting interplay of N\'eel order, dimerization, and spin liquid
behavior. The analytical findings supported by numerical results indicate that
for the isotropic model the phase at intermediate coupling strength 0.4 J1 < J2
< 0.6 J1 is not a spin liquid, but has instead a spontaneously staggered dimer
order.


title: 3D simulations of disc-winds extending radially self-similar MHD models

abstract:
  Disc-winds originating from the inner parts of accretion discs are considered
as the basic component of magnetically collimated outflows. The only available
analytical MHD solutions to describe disc-driven jets are those characterized
by the symmetry of radial self-similarity. However, radially self-similar MHD
jet models, in general, have three geometrical shortcomings, (i) a singularity
at the jet axis, (ii) the necessary assumption of axisymmetry, and (iii) the
non-existence of an intrinsic radial scale, i.e. the jets formally extend to
radial infinity. Hence, numerical simulations are necessary to extend the
analytical solutions towards the axis, by solving the full three-dimensional
equations of MHD and impose a termination radius at finite radial distance. We
focus here on studying the effects of relaxing the (ii) assumption of
axisymmetry, i.e. of performing full 3D numerical simulations of a disc-wind
crossing all magnetohydrodynamic critical surfaces. We compare the results of
these runs with previous axisymmetric 2.5D simulations. The structure of the
flow in all simulations shows strong similarities. The 3D runs reach a steady
state and stay close to axisymmetry for most of the physical quantities, except
for the poloidal magnetic field and the toroidal velocity which slightly
deviate from axisymmetry. The latter quantities show signs of instabilities,
which, however, are confined to the region inside the fast magnetosonic
separatrix surface. The forces present in the flow, both of collimating and
accelerating nature, are in good agreement in both the 2.5D and the 3D runs. We
conclude that the analytical solution behaves well also after relaxing the
basic assumption of axisymmetry.


title:
The Progenitors of Local Ultra-massive Galaxies Across Cosmic Time: from
  Dusty Star-bursting to Quiescent Stellar Populations

abstract:
  Using the UltraVISTA catalogs, we investigate the evolution in the 11.4~Gyr
since $z=3$ of the progenitors of local ultra-massive galaxies ($\log{(M_{\rm
star}/M_{\odot})}\approx11.8$; UMGs), providing a complete and consistent
picture of how the most massive galaxies at $z=0$ have assembled. By selecting
the progenitors with a semi-empirical approach using abundance matching, we
infer a growth in stellar mass of 0.56$^{+0.35}_{-0.25}$ dex,
0.45$^{+0.16}_{-0.20}$~dex, and 0.27$^{+0.08}_{-0.12}$ dex from $z=3$, $z=2$,
and $z=1$, respectively, to $z=0$. At $z<1$, the progenitors of UMGs constitute
a homogeneous population of only quiescent galaxies with old stellar
populations. At $z>1$, the contribution from star-forming galaxies
progressively increases, with the progenitors at $2<z<3$ being dominated by
massive ($M_{\rm star} \approx 2 \times 10^{11}$M$_{\odot}$), dusty ($A_{\rm
V}\sim$1--2.2 mag), star-forming (SFR$\sim$100--400~M$_{\odot}$ yr$^{-1}$)
galaxies with a large range in stellar ages. At $z=2.75$, $\sim$15\% of the
progenitors are quiescent, with properties typical of post-starburst galaxies
with little dust extinction and strong Balmer break, and showing a large
scatter in color. Our findings indicate that at least half of the stellar
content of local UMGs was assembled at $z>1$, whereas the remaining was
assembled via merging from $z\sim 1$ to the present. Most of the quenching of
the star-forming progenitors happened between $z=2.75$ and $z=1.25$, in good
agreement with the typical formation redshift and scatter in age of $z=0$ UMGs
as derived from their fossil records. The progenitors of local UMGs, including
the star-forming ones, never lived on the blue cloud since $z=3$. We propose an
alternative path for the formation of local UMGs that refines previously
proposed pictures and that is fully consistent with our findings.


title:
X-ray spectral modelling of the AGN obscuring region in the CDFS:
  Bayesian model selection and catalogue

abstract:
  AGN are known to have complex X-ray spectra that depend on both the
properties of the accreting SMBH (e.g. mass, accretion rate) and the
distribution of obscuring material in its vicinity ("torus"). Often however,
simple and even unphysical models are adopted to represent the X-ray spectra of
AGN. In the case of blank field surveys in particular, this should have an
impact on e.g. the determination of the AGN luminosity function, the inferred
accretion history of the Universe and also on our understanding of the relation
between AGN and their host galaxies. We develop a Bayesian framework for model
comparison and parameter estimation of X-ray spectra. We take into account
uncertainties associated with X-ray data and photometric redshifts. We also
demonstrate how Bayesian model comparison can be used to select among ten
different physically motivated X-ray spectral models the one that provides a
better representation of the observations. Despite the use of low-count
spectra, our methodology is able to draw strong inferences on the geometry of
the torus. For a sample of 350 AGN in the 4 Ms Chandra Deep Field South field,
our analysis identifies four components needed to represent the diversity of
the observed X-ray spectra: (abridged). Simpler models are ruled out with
decisive evidence in favour of a geometrically extended structure with
significant Compton scattering. Regarding the geometry of the obscurer, there
is strong evidence against both a completely closed or entirely open toroidal
geometry, in favour of an intermediate case. The additional Compton reflection
required by data over that predicted by toroidal geometry models, may be a sign
of a density gradient in the torus or reflection off the accretion disk.
Finally, we release a catalogue with estimated parameters such as the accretion
luminosity in the 2-10 keV band and the column density, $N_{H}$, of the
obscurer.


title: Self-interacting dark matter cusps around massive black holes

abstract:
  We adopt the conduction fluid approximation to model the steady-state
distribution of matter around a massive black hole at the center of a weakly
collisional cluster of particles. By "`weakly collisional" we mean a cluster in
which the mean free time between particle collisions is much longer than the
characteristic particle crossing (dynamical) time scale, but shorter than the
cluster lifetime. When applied to a star cluster, we reproduce the familiar
Bahcall-Wolf power-law cusp solution for the stars bound to the black hole.
Here the star density scales with radius as $r^{-7/4}$ and the velocity
dispersion as $r^{-1/2}$ throughout most of the gravitational well of the black
hole. When applied to a relaxed, self-interacting dark matter (SIDM) halo with
a velocity-dependent cross section $\sigma \sim v^{-a}$, the gas again forms a
power-law cusp, but now the SIDM density scales as $r^{-\beta}$, where $\beta =
(a+3)/4$, while its velocity dispersion again varies as $r^{-1/2}$. Results are
obtained first in Newtonian theory and then in full general relativity.
Although the conduction fluid model is a simplification, it provides a
reasonable first approximation to the matter profiles and is much easier to
implement than a full Fokker-Planck treatment or an $N$-body simulation of the
Boltzmann equation with collisional perturbations.

categories: astro-ph.CO astro-ph.GA astro-ph.HE gr-qc


title:
The total infrared luminosity may significantly overestimate the star
  formation rate of recently quenched galaxies

abstract:
  The total infrared (IR) luminosity is very useful for estimating the star
formation rate (SFR) of galaxies, but converting the IR luminosity into an SFR
relies on assumptions that do not hold for all galaxies. We test the
effectiveness of the IR luminosity as an SFR indicator by applying it to
synthetic spectral energy distributions generated from three-dimensional
hydrodynamical simulations of isolated disc galaxies and galaxy mergers. In
general, the SFR inferred from the IR luminosity agrees well with the true
instantaneous SFR of the simulated galaxies. However, for the major mergers in
which a strong starburst is induced, the SFR inferred from the IR luminosity
can overestimate the instantaneous SFR during the post-starburst phase by
greater than two orders of magnitude. Even though the instantaneous SFR
decreases rapidly after the starburst, the stars that were formed in the
starburst remain dust-obscured and thus produce significant IR luminosity.
Consequently, use of the IR luminosity as an SFR indicator may cause one to
conclude that post-starburst galaxies are still star-forming, whereas in
reality, star formation was recently quenched.


title: Higher spin entanglement entropy from CFT

abstract:
  We consider free fermion and free boson CFTs in two dimensions, deformed by a
chemical potential $\mu$ for the spin-three current. For the CFT on the
infinite spatial line, we calculate the finite temperature entanglement entropy
of a single interval perturbatively to second order in $\mu$ in each of the
theories. We find that the result in each case is given by the same non-trivial
function of temperature and interval length. Remarkably, we further obtain the
same formula using a recent Wilson line proposal for the holographic
entanglement entropy, in holomorphically factorized form, associated to the
spin-three black hole in SL(3, R) x SL(3, R) Chern-Simons theory. Our result
suggests that the order $\mu^2$ correction to the entanglement entropy may be
universal for W-algebra CFTs with spin-three chemical potential, and
constitutes a check of the holographic entanglement entropy proposal for higher
spin theories of gravity in AdS_3.


title:
Energy-conserving Discontinuous Galerkin Methods for the Vlasov-Maxwell
  System

abstract:
  In this paper, we generalize the idea in our previous work for the
Vlasov-Amp\`{e}re (VA) system \cite{cheng_va} and develop energy-conserving
discontinuous Galerkin (DG) methods for the Vlasov-Maxwell (VM) system. The VM
system is a fundamental model in the simulation of collisionless magnetized
plasmas. Compared to \cite{cheng_va}, additional care needs to be taken for
both the temporal and spatial discretizations to achieve similar type of
conservation when the magnetic field is no longer negligible. Our proposed
schemes conserve the total particle number and the total energy at the same
time, and therefore can obtain accurate, yet physically relevant solutions. The
main components of our methods include second order and above, explicit or
implicit energy-conserving temporal discretizations, and DG methods for Vlasov
and Maxwell's equations with carefully chosen numerical fluxes. Benchmark
numerical tests such as the streaming Weibel instability are provided to
validate the accuracy and conservation of the schemes.


title: Qualitative Relational Mapping and Navigation for Planetary Rovers

abstract:
  This paper presents a novel method for qualitative mapping of large scale
spaces. The proposed framework makes use of a graphical representation of the
world in order to build a map consisting of qualitative constraints on the
geometric relationships between landmark triplets. A novel measurement method
based on camera imagery is presented which extends previous work from the field
of Qualitative Spatial Reasoning. Measurements are fused into the map using a
deterministic, iterative graph update. A Branch-and-Bound approach is taken to
solve a set of non-convex feasibility problems required for generating on-line
measurements and off-line operator lookup tables. A navigation approach for
travel between distant landmarks is developed, using estimates of the Relative
Neighborhood Graph extracted from the qualitative map in order to generate a
sequence of landmark objectives based on proximity. Average and asymptotic
performance of the mapping algorithm is evaluated using Monte Carlo tests on
randomly generated maps, and data-driven simulation results are presented for a
robot traversing the Jet Propulsion Laboratory Mars Yard while building a
relational map. Simulation results demonstrate an initial rapid convergence of
qualitative state estimates for visible landmarks, followed by a slow tapering
as the remaining ambiguous states are removed from the map.


title: Firehose and Mirror Instabilities in a Collisionless Shearing Plasma

abstract:
  Hybrid-kinetic numerical simulations of firehose and mirror instabilities in
a collisionless plasma are performed in which pressure anisotropy is driven as
the magnetic field is changed by a persistent linear shear $S$. For a
decreasing field, it is found that mostly oblique firehose fluctuations grow at
ion Larmor scales and saturate with energies $\sim$$S^{1/2}$; the pressure
anisotropy is pinned at the stability threshold by particle scattering off
microscale fluctuations. In contrast, nonlinear mirror fluctuations are large
compared to the ion Larmor scale and grow secularly in time; marginality is
maintained by an increasing population of resonant particles trapped in
magnetic mirrors. After one shear time, saturated order-unity magnetic mirrors
are formed and particles scatter off their sharp edges. Both instabilities
drive sub-ion-Larmor--scale fluctuations, which appear to be
kinetic-Alfv\'{e}n-wave turbulence. Our results impact theories of momentum and
heat transport in astrophysical and space plasmas, in which the stretching of a
magnetic field by shear is a generic process.


title:
Dissipation through localised loss in bosonic systems with long-range
  interactions

abstract:
  In recent years, controlled dissipation has proven to be a useful tool for
probing of a quantum system in the ultracold setup. In this paper we consider
dynamics of bosons induced by a dissipative local defect. We address superfluid
and supersolid phases close to half-filling that are ground states of an
extended Bose-Hubbard Hamiltonian. To this end, we solve the master equation
using the Gutzwiller approximation and find that in the superfluid phase
repulsive nearest neighbour interactions can lead to enhanced dissipation
processes. On the other hand, our mean-field approach indicates that the
effective loss rates are significantly suppressed deep in the supersolid phase
where repulsive nearest neighbour interactions play a dominant role. Our
numerical results are explained by analytical arguments and in particular, in
the limit of strong dissipation we recover the quantum Zeno effect.


title:
Roaming dynamics in ion-molecule reactions: phase space reaction
  pathways and geometrical interpretation

abstract:
  A model Hamiltonian for the reaction CH$_4^+ \rightarrow$ CH$_3^+$ + H,
parametrized to exhibit either early or late inner transition states, is
employed to investigate the dynamical characteristics of the roaming mechanism.
Tight/loose transition states and conventional/roaming reaction pathways are
identified in terms of time-invariant objects in phase space. These are
dividing surfaces associated with normally hyperbolic invariant manifolds
(NHIMs). For systems with two degrees of freedom NHIMS are unstable periodic
orbits which, in conjunction with their stable and unstable manifolds,
unambiguously define the (locally) non-recrossing dividing surfaces assumed in
statistical theories of reaction rates. By constructing periodic orbit
continuation/bifurcation diagrams for two values of the potential function
parameter corresponding to late and early transition states, respectively, and
using the total energy as another parameter, we dynamically assign different
regions of phase space to reactants and products as well as to conventional and
roaming reaction pathways. The classical dynamics of the system are
investigated by uniformly sampling trajectory initial conditions on the
dividing surfaces. Trajectories are classified into four different categories:
direct reactive and non reactive trajectories,which lead to the formation of
molecular and radical products respectively, and roaming reactive and non
reactive orbiting trajectories, which represent alternative pathways to form
molecular and radical products. By analysing gap time distributions at several
energies we demonstrate that the phase space structure of the roaming region,
which is strongly influenced by non-linear resonances between the two degrees
of freedom, results in nonexponential (nonstatistical) decay.

categories: physics.chem-ph cond-mat.stat-mech math.DS nlin.CD


title: Classifying Latent Infection States in Complex Networks

abstract:
  Algorithms for identifying the infection states of nodes in a network are
crucial for understanding and containing infections. Often, however, only a
relatively small set of nodes have a known infection state. Moreover, the
length of time that each node has been infected is also unknown. This missing
data -- infection state of most nodes and infection time of the unobserved
infected nodes -- poses a challenge to the study of real-world cascades.
  In this work, we develop techniques to identify the latent infected nodes in
the presence of missing infection time-and-state data. Based on the likely
epidemic paths predicted by the simple susceptible-infected epidemic model, we
propose a measure (Infection Betweenness) for uncovering these unknown
infection states. Our experimental results using machine learning algorithms
show that Infection Betweenness is the most effective feature for identifying
latent infected nodes.


title:
PIC Simulations of Continuously Driven Mirror and Ion Cyclotron
  Instabilities in High Beta Astrophysical and Heliospheric Plasmas

abstract:
  We use particle-in-cell (PIC) simulations to study the nonlinear evolution of
ion velocity space instabilities in an idealized problem in which a background
velocity shear continuously amplifies the magnetic field. We simulate the
astrophysically relevant regime where the shear timescale is long compared to
the ion cyclotron period, and the plasma beta is ~ 1-100. The background field
amplification in our calculation is meant to mimic processes such as turbulent
fluctuations or MHD-scale instabilities. The field amplification continuously
drives a pressure anisotropy with the perpendicular pressure larger than the
parallel pressure, and the plasma becomes unstable to the mirror and ion
cyclotron instabilities. In all cases, the nonlinear state is dominated by the
mirror instability, not the ion cyclotron instability, and the plasma pressure
anisotropy saturates near the threshold for the linear mirror instability. The
magnetic field fluctuations initially undergo exponential growth but saturate
in a secular phase in which the fluctuations grow on the same timescale as the
background magnetic field (with \delta B ~ 0.3 <B> in the secular phase). At
early times, the ion magnetic moment is well-conserved but once the fluctuation
amplitudes exceed \delta B ~ 0.1 <B>, the magnetic moment is no longer
conserved but instead changes on a timescale comparable to that of the mean
magnetic field. We discuss the implications of our results for
low-collisionality astrophysical plasmas, including the near-Earth solar wind
and low-luminosity accretion disks around black holes.


title: A new photopolymer based VPHG for astronomy: The case of SN 2013fj

abstract:
  The spectroscopic studies of near infrared emission arising from supernovae
allow to derive crucial quantities that could better characterise physical
conditions of the expanding gas, such as the CaII IR HVF spectral feature. For
this reason is mandatory to have Diffractive Optical Elements (DOEs) with a
spectral coverage in the range 8000 - 10000 Angstroms (for low z sources)
combined with a reasonable Signal to Noise Ratio (S/N) and medium-low
resolution. In order to cope with all of those requirements we developed a
Volume Phase Holographic Grating (VPHG) based on an innovative photosensitive
material, developed by Bayer MaterialScience. We demonstrated the capabilities
of this new DOE through observation of SN 2013fj as case study at Asiago
Copernico Telescope where AFOSC spectrograph is available.


title: Mirror Symmetry in Three Dimensions via Gauged Linear Quivers

abstract:
  Starting from mirror pairs consisting only of linear (framed A-type) quivers,
we demonstrate that a wide class of three-dimensional quiver gauge theories
with N=4 supersymmetry and their mirror duals can be obtained by suitably
gauging flavor symmetries. Infinite families of mirror pairs including various
quivers of D and E-type and their affine extensions, star-shaped quivers, and
quivers with symplectic gauge groups may be generated in this fashion. We
present two different computational strategies to perform the aforementioned
gauging procedure - one of them involves N=2* classical parameter space
description, while the other one uses partition functions of the N=4 theories
on S^3. The partition function, in particular, turns out to be an extremely
efficient tool for implementing this gauging procedure as it readily
generalizes to arbitrary size of the quiver and arbitrary rank of the gauge
group at each node. For most examples of mirror pairs obtained via this
procedure, we perform additional checks of mirror symmetry using the Hilbert
series.


title:
Capacity of Binary State Symmetric Channel with and without Feedback and
  Transmission Cost

abstract:
  We consider a unit memory channel, called Binary State Symmetric Channel
(BSSC), in which the channel state is the modulo2 addition of the current
channel input and the previous channel output. We derive closed form
expressions for the capacity and corresponding channel input distribution, of
this BSSC with and without feedback and transmission cost. We also show that
the capacity of the BSSC is not increased by feedback, and it is achieved by a
first order symmetric Markov process.


title: Symmetry-projected Wave Functions in Quantum Monte Carlo Calculations

abstract:
  We consider symmetry-projected Hartree--Fock trial wave functions in
constrained-path Monte Carlo (CPMC) calculations. Previous CPMC calculations
have mostly employed Hartree--Fock (HF) trial wave functions, restricted or
unrestricted. The symmetry-projected HF approach results in a hierarchy of wave
functions with increasing quality: the more symmetries that are broken and
restored in a self-consistent manner, the higher the quality of the trial wave
function. This hierarchy is approximately maintained in CPMC calculations: the
accuracy in the energy increases and the statistical variance decreases when
further symmetries are broken and restored. Significant improvement is achieved
in CPMC with the best symmetry-projected trial wave functions over those from
simple HF. We analyze and quantify the behavior using the two-dimensional
repulsive Hubbard model as an example. In the sign-problem-free region, where
CPMC can be made exact but a constraint is deliberately imposed here,
spin-projected wave functions remove the constraint bias. Away from
half-filling, spatial symmetry restoration in addition to that of the spin lead
to highly accurate results from CPMC. Since the computational cost of
symmetry-projected HF trial wave functions in CPMC can be made to scale
algebraically with system size, this provides a potentially general approach
for accurate calculations in many-fermion systems.


title: BPS solitons in a Dirac-Born-Infeld action

abstract:
  We present several classes of solitons in ($1+1$)-dimensional models where
the standard canonical kinetic term is replaced by a Dirac-Born-Infeld (DBI)
one. These are static solutions with finite energy and different properties,
namely, they can have compact support, or be kink or lump-like, according to
the type of potential chosen, which depend on the DBI parameter $\beta$.
Through a combination of numerical and analytical arguments, by which the
equation of motion is seen as that corresponding to \emph{another} canonical
model with a new $\beta$-dependent potential and a $\beta$-deformed energy
density, we construct models in which increasing smoothly the DBI parameter
both the compacton radius, the thickness of the kink and the width of the lump
get modified until each soliton reaches its standard canonical shape as $\beta
\rightarrow \infty$. In addition we present compacton solutions whose canonical
counterparts are not compact.


title: On Zeilberger Conjecture

abstract:
  We prove a conjecture by D. Zeilberger on the determinant of a certain matrix
and relate it to a problem of non-existence of 1-cycles in this note.


title:
Kinematic structure of massive star-forming regions - I. Accretion along
  filaments

abstract:
  The mid- and far-infrared view on high-mass star formation, in particular
with the results from the Herschel space observatory, has shed light on many
aspects of massive star formation. However, these continuum studies lack
kinematic information.
  We study the kinematics of the molecular gas in high-mass star-forming
regions.
  We complemented the PACS and SPIRE far-infrared data of 16 high-mass
star-forming regions from the Herschel key project EPoS with N2H+ molecular
line data from the MOPRA and Nobeyama 45m telescope. Using the full N2H+
hyperfine structure, we produced column density, velocity, and linewidth maps.
These were correlated with PACS 70micron images and PACS point sources. In
addition, we searched for velocity gradients.
  For several regions, the data suggest that the linewidth on the scale of
clumps is dominated by outflows or unresolved velocity gradients. IRDC18454 and
G11.11 show two velocity components along several lines of sight. We find that
all regions with a diameter larger than 1pc show either velocity gradients or
fragment into independent structures with distinct velocities. The velocity
profiles of three regions with a smooth gradient are consistent with gas flows
along the filament, suggesting accretion flows onto the densest regions.
  We show that the kinematics of several regions have a significant and complex
velocity structure. For three filaments, we suggest that gas flows toward the
more massive clumps are present.


title:
Generalized particle/hole cumulant approximation for the electron
  Green's function

abstract:
  The cumulant expansion is a powerful approach for including correlation
effects in electronic structure calculations beyond the GW approximation.
However, current implementations are incomplete since they ignore terms that
lead to partial occupation numbers and satellites both above and below the
Fermi energy. These limitations are corrected here with a generalized cumulant
approximation that includes both particle and hole contributions within a
retarded Green's function formalism. The computational effort is still
comparable to GW, and the method can be extended easily to finite temperature.
The approach is illustrated with calculations for the homogeneous electron gas
and comparisons to experiment and other methods.


title: Chern-Simons and Born-Infeld gravity theories and Maxwell algebras type

abstract:
  Recently was shown that standard odd and even-dimensional General Relativity
can be obtained from a $(2n+1)$-dimensional Chern-Simons Lagrangian invariant
under the $B_{2n+1}$ algebra and from a $(2n)$-dimensional Born-Infeld
Lagrangian invariant under a subalgebra $\cal{L}^{B_{2n+1}}$ respectively. Very
Recently, it was shown that the generalized In\"on\"u-Wigner contraction of the
generalized AdS-Maxwell algebras provides Maxwell algebras types $\cal{M}_{m}$
which correspond to the so called $B_{m}$ Lie algebras. In this article we
report on a simple model that suggests a mechanism by which standard
odd-dimensional General Relativity may emerge as a weak coupling constant limit
of a $(2p+1)$-dimensional Chern-Simons Lagrangian invariant under the Maxwell
algebra type $\cal{M}_{2m+1}$, if and only if $m\geq p$. Similarly, we show
that standard even-dimensional General Relativity emerges as a weak coupling
constant limit of a $(2p)$-dimensional Born-Infeld type Lagrangian invariant
under a subalgebra $\cal{L}^{\cal{M}_{2m}}$ of the Maxwell algebra type, if and
only if $m\geq p$. It is shown that when $m<p$ this is not possible for a
$(2p+1)$-dimensional Chern-Simons Lagrangian invariant under the
$\cal{M}_{2m+1}$ and for a $(2p)$-dimensional Born-Infeld type Lagrangian
invariant under $\cal{L}^{\cal{M}_{2m}}$ algebra.


title:
Polynomial time recognition of squares of ptolemaic graphs and
  3-sun-free split graphs

abstract:
  The square of a graph $G$, denoted $G^2$, is obtained from $G$ by putting an
edge between two distinct vertices whenever their distance is two. Then $G$ is
called a square root of $G^2$. Deciding whether a given graph has a square root
is known to be NP-complete, even if the root is required to be a chordal graph
or even a split graph.
  We present a polynomial time algorithm that decides whether a given graph has
a ptolemaic square root. If such a root exists, our algorithm computes one with
a minimum number of edges.
  In the second part of our paper, we give a characterization of the graphs
that admit a 3-sun-free split square root. This characterization yields a
polynomial time algorithm to decide whether a given graph has such a root, and
if so, to compute one.


title:
Mechanism of the enhanced conductance of a molecular junction under
  tensile stress

abstract:
  Despite its fundamental importance for nano physics and chemistry and
potential device applications, the relationship between atomic structure and
electronic transport in molecular nanostructures is not well understood. Thus
the experimentally observed increase of the conductance of some molecular nano
junctions when they are stretched continues to be counterintuitive and
controversial. Here we explore this phenomenon in propanedithiolate molecules
bridging gold electrodes by means of {\em ab initio} computations and
semi-empirical modeling. We show that in this system it is due to changes in
Au-S-C bond angles and strains in the gold electrodes, rather than to the
previously proposed mechanisms of Au-S bond stretching and an associated energy
shift of the highest occupied molecular orbital and/or Au atomic chain
formation. Our findings indicate that conductance enhancement in response to
the application of tensile stress should be a generic property of molecular
junctions in which the molecule is thiol-bonded in a similar way to gold
electrodes.


title:
Discontinuities of the minimizers of the weighted or anisotropic total
  variation for image reconstruction

abstract:
  The study of the regularity of the minimizer of the weighted anisotropic
total variation with a general fidelity term is at the heart of this paper. We
generalized some recent results on the inclusion of the discontinuities of the
minimizer of the image denoising problem. In particular, we proved that for
well-chosen weights and anisotropies, it is actually possible to create
discontinuities that were not contained in the original image. We also observed
a reduced jump property at the discontinuities of the minimizer. To prove these
results we used some regularity theorems for minimal surfaces that we had to
adapt to our setting. We also illustrated our theoretical results with several
numerical simulations.


title: Uniform bounds for strongly $F$-regular surfaces

abstract:
  We show that if $(X,B)$ is a two dimensional Kawamata log terminal pair
defined over an algebraically closed field of characteristic $p$, and $p$ is
sufficiently large, depending only on the coefficients of $B$, then $(X,B)$ is
also strongly $F$-regular.


title:
Breaking the Crowther Limit: Combining Depth-Sectioning and Tilt
  Tomography for High-Resolution, Wide-Field 3D Reconstructions

abstract:
  To date, high-resolution (< 1 nm) imaging of extended objects in
three-dimensions (3D) has not been possible. A restriction known as the
Crowther criterion forces a tradeoff between object size and resolution for 3D
reconstructions by tomography. Further, the sub-Angstrom resolution of
aberration-corrected electron microscopes is accompanied by a greatly
diminished depth of field, causing regions of larger specimens (> 6 nm) to
appear blurred or missing. Here we demonstrate a three-dimensional imaging
method that overcomes both these limits by combining through-focal depth
sectioning and traditional tilt-series tomography to reconstruct extended
objects, with high-resolution, in all three dimensions. The large convergence
angle in aberration corrected instruments now becomes a benefit and not a
hindrance to higher quality reconstructions. A through-focal reconstruction
over a 390 nm 3D carbon support containing over one hundred dealloyed and
nanoporous PtCu catalyst particles revealed with sub-nanometer detail the
extensive and connected interior pore structure that is created by the
dealloying instability.


title:
Fuzzy Decision Analysis in Negotiation between the System of Systems
  Agent and the System Agent in an Agent-Based Model

abstract:
  Previous papers have described a computational approach to System of Systems
(SoS) development using an Agent-Based Model (ABM). This paper describes the
Fuzzy Decision Analysis used in the negotiation between the SoS agent and a
System agent in the ABM of an Acknowledged SoS development. An Acknowledged SoS
has by definition a limited influence on the development of the individual
Systems. The individual Systems have their own priorities, pressures, and
agenda which may or may not align with the goals of the SoS. The SoS has some
funding and deadlines which can be used to negotiate with the individual System
in order to illicit the required capability from that System. The Fuzzy
Decision Analysis determines how the SoS agent will adjust the funding and
deadlines for each of the Systems in order to achieve the desired SoS
architecture quality. The Fuzzy Decision Analysis has inputs of performance,
funding, and deadlines as well as weights for each capability. The performance,
funding, and deadlines are crisp values which are fuzzified. The fuzzified
values are then used with a Fuzzy Inference Engine to get the fuzzy outputs of
funding adjustment and deadline adjustment which must then be defuzzified
before being passed to the System agent. The first contribution of this paper
is the fuzzy decision analysis that represents the negotiation between the SoS
agent and the System agent. A second contribution of this paper is the method
of implementing the fuzzy decision analysis which provides a generalized fuzzy
decision analysis.


title: Neural Variational Inference and Learning in Belief Networks

abstract:
  Highly expressive directed latent variable models, such as sigmoid belief
networks, are difficult to train on large datasets because exact inference in
them is intractable and none of the approximate inference methods that have
been applied to them scale well. We propose a fast non-iterative approximate
inference method that uses a feedforward network to implement efficient exact
sampling from the variational posterior. The model and this inference network
are trained jointly by maximizing a variational lower bound on the
log-likelihood. Although the naive estimator of the inference model gradient is
too high-variance to be useful, we make it practical by applying several
straightforward model-independent variance reduction techniques. Applying our
approach to training sigmoid belief networks and deep autoregressive networks,
we show that it outperforms the wake-sleep algorithm on MNIST and achieves
state-of-the-art results on the Reuters RCV1 document dataset.


title:
The geometric sieve and the density of squarefree values of invariant
  polynomials

abstract:
  We develop a method for determining the density of squarefree values taken by
certain multivariate integer polynomials that are invariants for the action of
an algebraic group on a vector space. The method is shown to apply to the
discriminant polynomials of various prehomogeneous and coregular
representations where generic stabilizers are finite. This has applications to
a number of arithmetic distribution questions, e.g., to the density of small
degree number fields having squarefree discriminant, and the density of certain
unramified nonabelian extensions of quadratic fields. In separate works, the
method forms an important ingredient in establishing lower bounds on the
average orders of Selmer groups of elliptic curves.


title: Minimal Projections with respect to Numerical Radius

abstract:
  In this paper we survey some results on minimality of projections with
respect to numerical radius. We note that in the cases $L^p$, $p=1,2,\infty$,
there is no difference between the minimality of projections measured either
with respect to operator norm or with respect to numerical radius. However, we
give an example of a projection from $l^p_3$ onto a two-dimensional subspace
which is minimal with respect to norm, but not with respect to numerical radius
for $p\neq 1,2,\infty$. Furthermore, utilizing a theorem of Rudin and motivated
by Fourier projections, we give a criterion for minimal projections, measured
in numerical radius. Additionally, some results concerning strong unicity of
minimal projections with respect to numerical radius are given.


title: Generalized Quantifiers on Dependent Types: A System for Anaphora

abstract:
  We propose a system for the interpretation of anaphoric relationships between
unbound pronouns and quantifiers. The main technical contribution of our
proposal consists in combining generalized quantifiers with dependent types.
Empirically, our system allows a uniform treatment of all types of unbound
anaphora, including the notoriously difficult cases such as quantificational
subordination, cumulative and branching continuations, and 'donkey anaphora'.


title: On convex optimization problems in quantum information theory

abstract:
  Convex optimization problems arise naturally in quantum information theory,
often in terms of minimizing a convex function over a convex subset of the
space of hermitian matrices. In most cases, finding exact solutions to these
problems is usually impossible. As inspired by earlier investigations into the
relative entropy of entanglement [Phys. Rev. A 78 032310 (2008)], we introduce
a general method to solve the converse problem rather than find explicit
solutions. That is, given a matrix in a convex set, we determine a family of
convex functions that are minimized at this point. This method allows us find
explicit formulae for the relative entropy of entanglement and the Rains bound,
two well-known upper bounds on the distillable entanglement, and yields
interesting information about these quantities, such as the fact that they
coincide in the case where at least one subsystem of a multipartite state is a
qubit.


title: The Relativistic Inverse Stellar Structure Problem

abstract:
  The observable macroscopic properties of relativistic stars (whose equations
of state are known) can be predicted by solving the stellar structure equations
that follow from Einstein's equation. For neutron stars, however, our knowledge
of the equation of state is poor, so the direct stellar structure problem can
not be solved without modeling the highest density part of the equation of
state in some way. This talk will describe recent work on developing a model
independent approach to determining the high-density neutron-star equation of
state by solving an inverse stellar structure problem. This method uses the
fact that Einstein's equation provides a deterministic relationship between the
equation of state and the macroscopic observables of the stars which are
composed of that material. This talk illustrates how this method will be able
to determine the high-density part of the neutron-star equation of state with
few percent accuracy when high quality measurements of the masses and radii of
just two or three neutron stars become available. This talk will also show that
this method can be used with measurements of other macroscopic observables,
like the masses and tidal deformabilities, which can (in principle) be measured
by gravitational wave observations of binary neutron-star mergers.


title:
The Dirichlet boundary problem for second order parabolic operators
  satisfying Carleson condition

abstract:
  We establish $L^p$, $2\le p\le\infty$ solvability of the Dirichlet boundary
value problem for a parabolic equation $u_t-\mbox{div}(A\nabla u)=0$ on
time-varying domains with coefficient matrix $A=(a_{ij})$ that satisfy a small
Carleson condition. The result is motivated by similar results for the elliptic
equation $\mbox{div}(A\nabla u)=0$ that were established previously.


title: Formation of the Moon: a new mechanism

abstract:
  Understanding the Moon's formation mechanism is necessary for studying not
only the Moon itself, but also the evolution, formation, habitability, and
structure of other planets and the moons in the Solar system and in extrasolar
planetary systems. In this paper, I suggest a mechanism of the Moon formation.
I posit that the Moon came into existence from the same gaseous cloud that the
Earth originated from. The paper concludes that the moons can only form at the
time of planet formation in a parallel and simultaneous process, and the new
moons cannot form in a grown up Solar system. The Earth-Moon system is not a
special exception in nature; rather it evolved following the same laws that
other planets or moons have evolved from. This perspective successfully
elucidates what happened between the disk formation and the accumulation of the
Moon from the disk.


title: Sensitivity and Entanglement in the Avian Chemical Compass

abstract:
  The Radical Pair Mechanism can help to explain avian orientation and
navigation. Some evidence indicates that the intensity of external magnetic
fields plays an important role in avian navigation. In this paper, based on a
two-stage strategy, we demonstrate that birds could reasonably detect the
directions of geomagnetic fields and gradients of these fields using a
yield-based chemical compass that is sensitive enough for navigation. Also, we
find that the lifetime of entanglement in this proposed compass is
angle-dependent and long enough to allow adequate electron transfer between
molecules.


title: Linking Rigid Bodies Symmetrically

abstract:
  The mathematical theory of rigidity of body-bar and body-hinge frameworks
provides a useful tool for analyzing the rigidity and flexibility of many
articulated structures appearing in engineering, robotics and biochemistry. In
this paper we develop a symmetric extension of this theory which permits a
rigidity analysis of body-bar and body-hinge structures with point group
symmetries. The infinitesimal rigidity of body-bar frameworks can naturally be
formulated in the language of the exterior (or Grassmann) algebra. Using this
algebraic formulation, we derive symmetry-adapted rigidity matrices to analyze
the infinitesimal rigidity of body-bar frameworks with Abelian point group
symmetries in an arbitrary dimension. In particular, from the patterns of these
new matrices, we derive combinatorial characterizations of infinitesimally
rigid body-bar frameworks which are generic with respect to a point group of
the form $\mathbb{Z}/2\mathbb{Z}\times \dots \times \mathbb{Z}/2\mathbb{Z}$.
Our characterizations are given in terms of packings of bases of signed-graphic
matroids on quotient graphs. Finally, we also extend our methods and results to
body-hinge frameworks with Abelian point group symmetries in an arbitrary
dimension. As special cases of these results, we obtain combinatorial
characterizations of infinitesimally rigid body-hinge frameworks with
$\mathcal{C}_2$ or $\mathcal{D}_2$ symmetry - the most common symmetry groups
found in proteins.


title:
Gate-tunable Kondo resistivity and dephasing rate in graphene studied by
  numerical renormalization group calculations

abstract:
  We investigate the resistivity and dephasing rate in the Kondo regime due to
magnetic impurities in graphene with different chemial potentials ($\mu$). The
Kondo effect due to either carbon vacancies or magnetic adatoms in graphene is
described by the single-orbital pseudo-gap asymmetric Anderson impurity model.
We find that although the Anderson impurity model considered here is a mixed
valence system, it can be drived into either the Kondo [$\mu > \mu_c$ (critical
value) $>0$] or mixed valency ($\mu \approx \mu_c$) or empty orbital ($\mu <
\mu_c$) regime by a gate voltage, giving rise to characteristic features in
resistivity and dephasing rate in each regime. Specifically, in the case of
$\mu < \mu_c$, the shapes of the resistivity (dephasing rate) curves for
different $\mu$ are nearly identical. However, as temperature decreases, they
start to increase to their maxima at a lower $T/T_K$ but more rapidly [as
$(T_K/T)^{3/2}$] than in normal metals [here $T$ ($T_K$) denotes the (Kondo)
temperature]. As $T$ further decreases, after reaching the maximum, the
dephasing rate drops more quickly than in normal metals, behaving as
$(T/T_K)^3$ instead of $(T/T_K)^2$. Furthermore, the resistivity has a distinct
peak above the saturation value near $T_K$. In the case of $\mu > \mu_c$, in
contrast, the resistivity curve has an additional broad shoulder above 10$T_K$
and the dephasing rate exhibits an interesting shoulder-peak shape. In the
narrow boundary region ($\mu \approx \mu_c$), both the resistivity and
dephasing rate curves are similar to the corresponding ones in normal metals.
This explains the conventional Kondo like resistivity from recent experiments
on graphene with defects. The resistivity and dephasing rate are analysized in
terms of the calculated $T$-dependent spectral function, correlation
self-energy and renormalized impurity level.


title: Collective behaviour of large number of vortices in the plane

abstract:
  We investigate the dynamics of $N$ point vortices in the plane, in the limit
of large $N$. We consider {\em relative equilibria}, which are rigidly rotating
lattice-like configurations of vortices. These configurations were observed in
several recent experiments [Durkin and Fajans, Phys. Fluids (2000) 12, 289-293;
Grzybowski {\em et.al} PRE (2001)64, 011603]. We show that these solutions and
their stability are fully characterized via a related {\em aggregation model}
which was recently investigated in the context of biological swarms [Fetecau
{\em et.al.}, Nonlinearity (2011) 2681; Bertozzi {\em et.al.}, M3AS (2011)]. By
utilizing this connection, we give explicit analytic formulae for many of the
configurations that have been observed experimentally. These include
configurations of vortices of equal strength; the $N+1$ configurations of $N$
vortices of equal strength and one vortex of much higher strength; and more
generally, $N+K$ configurations. We also give examples of configurations that
have not been studied experimentally, including $N+2$ configurations where $N$
vortices aggregate inside an ellipse. Finally, we introduce an artificial
``damping'' to the vortex dynamics, in an attempt to explain the phenomenon of
crystalization that is often observed in real experiments. The diffusion breaks
the conservative structure of vortex dynamics so that any initial conditions
converge to the lattice-like relative equilibrium.

categories: cond-mat.quant-gas math.AP math.DS nlin.PS physics.flu-dyn


title:
motifDiverge: a model for assessing the statistical significance of gene
  regulatory motif divergence between two DNA sequences

abstract:
  Next-generation sequencing technology enables the identification of thousands
of gene regulatory sequences in many cell types and organisms. We consider the
problem of testing if two such sequences differ in their number of binding site
motifs for a given transcription factor (TF) protein. Binding site motifs
impart regulatory function by providing TFs the opportunity to bind to genomic
elements and thereby affect the expression of nearby genes. Evolutionary
changes to such functional DNA are hypothesized to be major contributors to
phenotypic diversity within and between species; but despite the importance of
TF motifs for gene expression, no method exists to test for motif loss or gain.
Assuming that motif counts are Binomially distributed, and allowing for
dependencies between motif instances in evolutionarily related sequences, we
derive the probability mass function of the difference in motif counts between
two nucleotide sequences. We provide a method to numerically estimate this
distribution from genomic data and show through simulations that our estimator
is accurate. Finally, we introduce the R package {\tt motifDiverge} that
implements our methodology and illustrate its application to gene regulatory
enhancers identified by a mouse developmental time course experiment. While
this study was motivated by analysis of regulatory motifs, our results can be
applied to any problem involving two correlated Bernoulli trials.


title: Recent Progress on D$^3$ -- The Directional Dark Matter Detector

abstract:
  Direction-sensitive WIMP dark matter searches may help overcome the
challenges faced by direct dark matter detection experiments. In particular,
directional detectors should be able to clearly differentiate a dark matter
signal from background sources. We are developing a Directional Dark Matter
Detector (D$^3$) based on a gas Time Projection Chamber (TPC) using Gas
Electron Multipliers (GEMs) for charge amplification and pixel electronics for
readout. This approach allows the three-dimensional reconstruction of nuclear
recoils in a room-temperature detector with low energy threshold and low noise.
We present an overview of our past and ongoing work developing this technology,
including the performance measurements of small prototypes, as well as our
planned future work constructing a m$^3$-scale detector to clearly determine
whether the signals seen by DAMA, CoGeNT, and CRESST-II are due to low-mass
WIMPs or background.


title: Topological Complexities of Surfaces

abstract:
  The sphere $S^2$ and the torus $T^2$ are the only closed connected surfaces
for which higher topological complexities are known (for each
$n\in\{2,3,...\}\subset\mathbb{N}$, $\mathrm{TC}_n(S^2)=n$ and
$\mathrm{TC}_n(T^2)=2n-2$). This text aims to find topological complexities for
most other closed connected surfaces. For all but $S^2$, $T^2$, the projective
plane ($\mathbb{R}\mathbb{P}^2$) and the Klein bottle the $n$-th topological
complexity is $2n$.


title:
Pilot Optimization and Channel Estimation for Multiuser Massive MIMO
  Systems

abstract:
  This paper proposes novel pilot optimization and channel estimation algorithm
for the downlink multiuser massive multiple input multiple output (MIMO) system
with $K$ decentralized single antenna mobile stations (MSs), and time division
duplex (TDD) channel estimation which is performed by utilizing $N$ pilot
symbols. The proposed algorithm is explained as follows. First, we formulate
the channel estimation problem as a weighted sum mean square error (WSMSE)
minimization problem containing pilot symbols and introduced variables. Second,
for fixed pilot symbols, the introduced variables are optimized using minimum
mean square error (MMSE) and generalized Rayleigh quotient methods. Finally,
for $N=1$ and $N=K$ settings, the pilot symbols of all MSs are optimized using
semi definite programming (SDP) convex optimization approach, and for the other
settings of $N$ and $K$, the pilot symbols of all MSs are optimized by applying
simple iterative algorithm. When $N=K$, it is shown that the latter iterative
algorithm gives the optimal pilot symbols achieved by the SDP method.
Simulation results confirm that the proposed algorithm achieves less WSMSE
compared to that of the conventional semi-orthogonal pilot symbol and MMSE
channel estimation algorithm which creates pilot contamination.


title:
Carbon nanomaterials for electronics, optoelectronics, photovoltaics,
  and sensing

abstract:
  In the last three decades, zero-dimensional, one-dimensional, and
two-dimensional carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and
graphene, respectively) have attracted significant attention from the
scientific community due to their unique electronic, optical, thermal,
mechanical, and chemical properties. While early work showed that these
properties could enable high performance in selected applications, issues
surrounding structural inhomogeneity and imprecise assembly have impeded robust
and reliable implementation of carbon nanomaterials in widespread technologies.
However, with recent advances in synthesis, sorting, and assembly techniques,
carbon nanomaterials are experiencing renewed interest as the basis of numerous
scalable technologies. Here, we present an extensive review of carbon
nanomaterials in electronic, optoelectronic, photovoltaic, and sensing devices
with a particular focus on the latest examples based on the highest purity
samples. Specific attention is devoted to each class of carbon nanomaterial,
thereby allowing comparative analysis of the suitability of fullerenes, carbon
nanotubes, and graphene for each application area. In this manner, this article
will provide guidance to future application developers and also articulate the
remaining research challenges confronting this field.


title:
Emerging Device Applications for Semiconducting Two-Dimensional
  Transition Metal Dichalcogenides

abstract:
  With advances in exfoliation and synthetic techniques, atomically thin films
of semiconducting transition metal dichalcogenides have recently been isolated
and characterized. Their two-dimensional structure, coupled with a direct band
gap in the visible portion of the electromagnetic spectrum, suggests
suitability for digital electronics and optoelectronics. Towards that end,
several classes of high-performance devices have been reported along with
significant progress in understanding their physical properties. Here, we
present a review of the architecture, operating principles, and physics of
electronic and optoelectronic devices based on ultrathin transition metal
dichalcogenide semiconductors. By critically assessing and comparing the
performance of these devices with competing technologies, the merits and
shortcomings of this emerging class of electronic materials are identified,
thereby providing a roadmap for future development.


title: Improved determination of $B_K$ with staggered quarks

abstract:
  We present results for the kaon mixing parameter $B_K$ obtained using
improved staggered fermions on a much enlarged set of MILC asqtad lattices.
Compared to our previous publication, which was based largely on a single
ensemble at each of the three lattice spacings $a\approx 0.09\;$fm, $0.06\;$fm
and $0.045\;$fm, we have added seven new fine and four new superfine ensembles,
with a range of values of the light and strange sea-quark masses. We have also
increased the number of measurements on one of the original ensembles. This
allows us to do controlled extrapolations in the light and strange sea-quark
masses, which we do simultaneously with the continuum extrapolation. This
reduces the extrapolation error and improves the reliability of our error
estimates. Our final result is $\hat{B}_K = 0.7379 \pm 0.0047 (\text{stat}) \pm
0.0365 (\text{sys})$.