title:
Max-Min Multi-Cell Aware Precoding and Power Allocation for Downlink
  Massive MIMO Systems

abstract:
  We propose a max-min multi-cell aware regularized zero-forcing (Max-Min
MCA-RZF) precoding and power allocation scheme for downlink multi-cell massive
multiple-input multiple-output (MIMO) systems. A general correlated channel
model is considered, and the adopted channel state information (CSI)
acquisition model includes the effects of estimation errors and pilot
contamination. We use results from random matrix theory to derive deterministic
equivalents for the proposed Max-Min power allocation in the large system limit
which solely depend on statistical CSI, but not on individual channel
realizations. Our numerical results show that the proposed Max-Min MCA-RZF
precoder achieves a substantially higher network-wide minimum rate than the
MCA-RZF and the conventional RZF precoders with uniform power allocation,
respectively, as well as the conventional RZF precoder with Max-Min power
allocation.


title:
Land Use Classification using Convolutional Neural Networks Applied to
  Ground-Level Images

abstract:
  Land use mapping is a fundamental yet challenging task in geographic science.
In contrast to land cover mapping, it is generally not possible using overhead
imagery. The recent, explosive growth of online geo-referenced photo
collections suggests an alternate approach to geographic knowledge discovery.
In this work, we present a general framework that uses ground-level images from
Flickr for land use mapping. Our approach benefits from several novel aspects.
First, we address the nosiness of the online photo collections, such as
imprecise geolocation and uneven spatial distribution, by performing location
and indoor/outdoor filtering, and semi- supervised dataset augmentation. Our
indoor/outdoor classifier achieves state-of-the-art performance on several
bench- mark datasets and approaches human-level accuracy. Second, we utilize
high-level semantic image features extracted using deep learning, specifically
convolutional neural net- works, which allow us to achieve upwards of 76%
accuracy on a challenging eight class land use mapping problem.


title: Convex Program Duality, Fisher Markets, and Nash Social Welfare

abstract:
  We study Fisher markets and the problem of maximizing the Nash social welfare
(NSW), and show several closely related new results. In particular, we obtain:
  -- A new integer program for the NSW maximization problem whose fractional
relaxation has a bounded integrality gap. In contrast, the natural integer
program has an unbounded integrality gap.
  -- An improved, and tight, factor 2 analysis of the algorithm of [7]; in turn
showing that the integrality gap of the above relaxation is at most 2. The
approximation factor shown by [7] was $2e^{1/e} \approx 2.89$.
  -- A lower bound of $e^{1/e}\approx 1.44$ on the integrality gap of this
relaxation.
  -- New convex programs for natural generalizations of linear Fisher markets
and proofs that these markets admit rational equilibria.
  These results were obtained by establishing connections between previously
known disparate results, and they help uncover their mathematical
underpinnings. We show a formal connection between the convex programs of
Eisenberg and Gale and that of Shmyrev, namely that their duals are equivalent
up to a change of variables. Both programs capture equilibria of linear Fisher
markets. By adding suitable constraints to Shmyrev's program, we obtain a
convex program that captures equilibria of the spending-restricted market model
defined by [7] in the context of the NSW maximization problem. Further, adding
certain integral constraints to this program we get the integer program for the
NSW mentioned above.
  The basic tool we use is convex programming duality. In the special case of
convex programs with linear constraints (but convex objectives), we show a
particularly simple way of obtaining dual programs, putting it almost at par
with linear program duality. This simple way of finding duals has been used
subsequently for many other applications.


title:
Coupled system of nonlinear Schr\"odinger and Korteweg-de Vries
  equations

abstract:
  This work is divided into two parts. First, we analyze the existence of
positive bound and ground states for a second order stationary system coming
from a coupled system of nonlinear Schr\"odinger--Korteweg-de Vries equations.
Second, we extend these results for a higher order system of nonlinear
Schr\"odinger--Korteweg-de Vries equations. Looking for "standing-traveling"
waves we arrive at a bi-harmonic stationary system, for which we prove the
existence and multiplicity of solutions under appropriate conditions on the
parameters.


title: Design of a Radial TPC for Antihydrogen Gravity Measurement with ALPHA-g

abstract:
  The gravitational interaction of antimatter and matter has never been
directly probed. ALPHA-g is a novel experiment that aims to perform the first
measurement of the antihydrogen gravitational mass. A fundamental requirement
for this new apparatus is a position sensitive particle detector around the
antihydrogen trap which provides information about antihydrogen annihilation
location. The proposed detector is a radial Time Projection Chamber, or
\textit{rTPC}, whose concept is being developed at TRIUMF. A simulation of the
detector and the development of the reconstruction software, used to determine
the antihydrogen annihilation point, is presented alongside with the expected
performance of the rTPC.


title:
The Color of the Cat is Gray: 1 Million Full-Sentences Visual Question
  Answering (FSVQA)

abstract:
  Visual Question Answering (VQA) task has showcased a new stage of interaction
between language and vision, two of the most pivotal components of artificial
intelligence. However, it has mostly focused on generating short and repetitive
answers, mostly single words, which fall short of rich linguistic capabilities
of humans. We introduce Full-Sentence Visual Question Answering (FSVQA)
dataset, consisting of nearly 1 million pairs of questions and full-sentence
answers for images, built by applying a number of rule-based natural language
processing techniques to original VQA dataset and captions in the MS COCO
dataset. This poses many additional complexities to conventional VQA task, and
we provide a baseline for approaching and evaluating the task, on top of which
we invite the research community to build further improvements.


title:
Well-posedness of the vector advection equations by stochastic
  perturbation

abstract:
  A linear stochastic vector advection equation is considered. The equation may
model a passive magnetic field in a random fluid. The driving velocity field is
a integrable to a certain power and the noise is infinite dimensional. We prove
that, thanks to the noise, the equation is well posed in a suitable sense,
opposite to what may happen without noise.


title: Fingerprints of heavy scales in electroweak effective Lagrangians

abstract:
  The couplings of the electroweak effective theory contain information on the
heavy-mass scales which are no-longer present in the low-energy Lagrangian. We
build a general effective Lagrangian, implementing the electroweak chiral
symmetry breaking $SU(2)_L\otimes SU(2)_R\to SU(2)_{L+R}$, which couples the
known particle fields to heavier states with bosonic quantum numbers
$J^P=0^\pm$ and $1^\pm$. We consider colour-singlet heavy fields that are in
singlet or triplet representations of the electroweak group. Integrating out
these heavy scales, we analyze the pattern of low-energy couplings among the
light fields which are generated by the massive states. We adopt a generic
non-linear realization of the electroweak symmetry breaking with a singlet
Higgs, without making any assumption about its possible doublet structure.
Special attention is given to the different possible descriptions of massive
spin-1 fields and the differences arising from naive implementations of these
formalisms, showing their full equivalence once a proper short-distance
behaviour is required.


title:
On the geometric convergence rate of distributed economic
  dispatch/demand response in power networks

abstract:
  Motivated by potential applications in power systems, we study a problem of
optimizing a sum of $n$ convex functions on dynamic networks of $n$ nodes when
each function is known to only a single node. The nodes' variables, while
satisfy their local constraints, are coupled through a linear constraint. Our
main contribution is to design a fully distributed primal-dual method for this
problem. Under some fairly standard assumptions on objective functions, strong
convexity and smoothness, we provide an explicit analysis for the convergence
rate of our method on different networks. In particular, the nodes variables
achieve a geometric convergence to the optimal with the associated convergence
time scales quartically in the number of nodes on any sequence of time-varying
undirected graphs satisfying a long-term connectivity condition. Moreover, this
convergence time is constant independent on the number of nodes when the
network is a b-regular simple graph with $b\geq 3$. Finally, to show the
effectiveness of our method we also simulate a number of studies on economic
dispatch problems and demand response problems in power systems.


title:
Level anti-crossing spectra of nitrogen-vacancy centers in diamond
  detected by using modulation of the external magnetic field

abstract:
  We report a study of the magnetic field dependence of the photo-luminescence
of NV$^-$ centers (negatively charged nitrogen-vacancy centers) in diamond
single crystals. In such a magnetic field dependence characteristic lines are
observed, which are coming from Level Anti-Crossings (LACs) in the coupled
electron-nuclear spin system. For enhancing the sensitivity, we used lock-in
detection to measure the photo-luminescence intensity and observed a remarkably
strong dependence of the LAC-derived lines on the modulation frequency. Upon
decreasing of the modulation frequency from 12 kHz to 17 Hz the amplitude of
the lines increases by approximately two orders of magnitude. To take a
quantitative account for such effects, we developed a theoretical model, which
describes the spin dynamics in the coupled electron-nuclear spin system under
the action of an oscillating external magnetic field. Good agreement between
experiments and theory allows us to conclude that the observed effects are
originating from coherent spin polarization exchange in the NV$^-$ center. Our
results are of great practical importance allowing one to optimize the
experimental conditions for probing LAC-derived lines in diamond defect
centers.


title:
On Efficient Computation of Shortest Dubins Paths Through Three
  Consecutive Points

abstract:
  In this paper, we address the problem of computing optimal paths through
three consecutive points for the curvature-constrained forward moving Dubins
vehicle. Given initial and final configurations of the Dubins vehicle, and a
midpoint with an unconstrained heading, the objective is to compute the
midpoint heading that minimizes the total Dubins path length. We provide a
novel geometrical analysis of the optimal path, and establish new properties of
the optimal Dubins' path through three points. We then show how our method can
be used to quickly refine Dubins TSP tours produced using state-of-the-art
techniques. We also provide extensive simulation results showing the
improvement of the proposed approach in both runtime and solution quality over
the conventional method of uniform discretization of the heading at the
mid-point, followed by solving the minimum Dubins path for each discrete
heading.


title:
The Lawrence-Krammer representation is a quantization of the symmetric
  square of the Burau representation

abstract:
  We show that the Lawrence--Krammer representation can be obtained as the
quantization of the symmetric square of the Burau representation. This
connection allows us to construct new representations of braid groups


title:
Why Johnny Can't Use Stego: a Human-oriented Perspective on the
  Application of Steganography

abstract:
  Steganography is the discipline that deals with concealing the existence of
secret communications. Existing research already provided several fundamentals
for defining steganography and presented a multitude of hiding methods and
countermeasures for this research discipline.
  We identified that no work exists that discusses the process of applying
steganography from an individual's perspective. This paper presents a phase
model that explains pre-conditions of applying steganography as well as the
decision-making process and the final termination of a steganographic
communication. The model can be used to explain whether an individual can use
steganography and to explain whether and why an individual desires to use
steganography. Moreover, the model can be used in research publications to
indicate the addressed model's phase of scientific contributions. Furthermore,
our model can be used to teach the process of steganography-application to
students.


title: Polymer Quantization of a Self-Gravitating Thin Shell

abstract:
  We study the quantum mechanics of self-gravitating thin shell collapse by
solving the polymerized Wheeler-DeWitt equation. We obtain the energy spectrum
and solve the time dependent equation using numerics. In contradistinction to
the continuum theory, we are able to consistently quantize the theory for
super-Planckian black holes, and find two choices of boundary conditions which
conserve energy and probability, as opposed to one in the continuum theory.
Another feature unique to the polymer theory is the existence of negative
energy stationary states that disappear from the spectrum as the polymer scale
goes to zero. In both theories the probability density is positive
semi-definite only for the space of positive energy stationary states.
Dynamically, we find that an initial Gaussian probability density develops
regions of negative probability as the wavepacket approaches $R=0$ and bounces.
This implies that the bouncing state is a sum of both positive and negative
eigenstates.


title:
Vote3Deep: Fast Object Detection in 3D Point Clouds Using Efficient
  Convolutional Neural Networks

abstract:
  This paper proposes a computationally efficient approach to detecting objects
natively in 3D point clouds using convolutional neural networks (CNNs). In
particular, this is achieved by leveraging a feature-centric voting scheme to
implement novel convolutional layers which explicitly exploit the sparsity
encountered in the input. To this end, we examine the trade-off between
accuracy and speed for different architectures and additionally propose to use
an L1 penalty on the filter activations to further encourage sparsity in the
intermediate representations. To the best of our knowledge, this is the first
work to propose sparse convolutional layers and L1 regularisation for efficient
large-scale processing of 3D data. We demonstrate the efficacy of our approach
on the KITTI object detection benchmark and show that Vote3Deep models with as
few as three layers outperform the previous state of the art in both laser and
laser-vision based approaches by margins of up to 40% while remaining highly
competitive in terms of processing time.


title:
Evolution of the longitudinal and azimuthal structure of the near-side
  jet peak in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV

abstract:
  In two-particle angular correlation measurements, jets give rise to a
near-side peak, formed by particles associated to a higher $p_{\mathrm{T}}$
trigger particle. Measurements of these correlations as a function of
pseudorapidity ($\Delta\eta$) and azimuthal ($\Delta\varphi$) differences are
used to extract the centrality and $p_{\mathrm{T}}$ dependence of the shape of
the near-side peak in the $p_{\mathrm{T}}$ range $1 < p_{\mathrm{T}} <$ 8 GeV/c
in Pb-Pb and pp collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. A combined
fit of the near-side peak and long-range correlations is applied to the data
and the peak shape is quantified by the variance of the distributions. While
the width of the peak in the $\Delta\varphi$ direction is almost independent of
centrality, a significant broadening in the $\Delta\eta$ direction is found
from peripheral to central collisions. This feature is prominent for the low
$p_{\mathrm{T}}$ region and vanishes above 4 GeV/c. The widths measured in
peripheral collisions are equal to those in pp in the $\Delta\varphi$ direction
and above 3 GeV/c in the $\Delta\eta$ direction. Furthermore, for the 10\% most
central collisions and $1 < p_{\mathrm{T, assoc}} <$ 2 GeV/c, $1 <
p_{\mathrm{T, trig}} <$ 3 GeV/c a departure from a Gaussian shape is found: a
depletion develops around the centre of the peak. The results are compared to
AMPT model simulations as well as other theoretical calculations indicating
that the broadening and the development of the depletion is connected to the
strength of radial and longitudinal flow.


title:
Characterization of Lung Nodule Malignancy using Hybrid Shape and
  Appearance Features

abstract:
  Computed tomography imaging is a standard modality for detecting and
assessing lung cancer. In order to evaluate the malignancy of lung nodules,
clinical practice often involves expert qualitative ratings on several criteria
describing a nodule's appearance and shape. Translating these features for
computer-aided diagnostics is challenging due to their subjective nature and
the difficulties in gaining a complete description. In this paper, we propose a
computerized approach to quantitatively evaluate both appearance distinctions
and 3D surface variations. Nodule shape was modeled and parameterized using
spherical harmonics, and appearance features were extracted using deep
convolutional neural networks. Both sets of features were combined to estimate
the nodule malignancy using a random forest classifier. The proposed algorithm
was tested on the publicly available Lung Image Database Consortium dataset,
achieving high accuracy. By providing lung nodule characterization, this method
can provide a robust alternative reference opinion for lung cancer diagnosis.


title: Fast and reliable stereopsis measurement at multiple distances with iPad

abstract:
  Purpose: To present a new fast and reliable application for iPad (ST) for
screening stereopsis at multiple distances.
  Methods: A new iPad application (app) based on a random dot stereogram was
designed for screening stereopsis at multiple distances. Sixty-five subjects
with no ocular diseases and wearing their habitual correction were tested at
two different distances: 3 m and at 0.4 m. Results were compared with other
commercial tests: TNO (at near) and Howard Dolman (at distance) Subjects were
cited one week later in order to repeat the same procedures for assessing
reproducibility of the tests.
  Results: Stereopsis at near was better with ST (40 arcsec) than with TNO (60
arcsec), but not significantly (p = 0.36). The agreement was good (k = 0.604)
and the reproducibility was better with ST (k = 0.801) than with TNO (k =
0.715), in fact median difference between days was significant only with TNO (p
= 0.02). On the other hand, poor agreement was obtained between HD and ST at
far distance (k=0.04), obtaining significant differences in medians (p = 0.001)
and poorer reliability with HD (k = 0.374) than with ST (k = 0.502).
  Conclusions: Screening stereopsis at near with a new iPad app demonstrated to
be a fast and realiable. Results were in a good agreement with conventional
tests as TNO, but it could not be compared at far vision with HD due to the
limited resolution of the iPad.


title:
Seeing is Believing: A Unified Model for Consistency and Isolation via
  States

abstract:
  This paper introduces a unified model of consistency and isolation that
minimizes the gap between how these guarantees are defined and how they are
perceived. Our approach is premised on a simple observation: applications view
storage systems as black-boxes that transition through a series of states, a
subset of which are observed by applications. For maximum clarity, isolation
and consistency guarantees should be expressed as constraints on those states.
Instead, these properties are currently expressed as constraints on operation
histories that are not visible to the application. We show that adopting a
state-based approach to expressing these guarantees brings forth several
benefits. First, it makes it easier to focus on the anomalies that a given
isolation or consistency level allows (and that applications must deal with),
rather than those that it proscribes. Second, it unifies the often disparate
theories of isolation and consistency and provides a structure for composing
these guarantees. We leverage this modularity to apply to transactions
(independently of the isolation level under which they execute) the equivalence
between causal consistency and session guarantees that Chockler et al. had
proved for single operations. Third, it brings clarity to the increasingly
crowded field of proposed consistency and isolation properties by winnowing
spurious distinctions: we find that the recently proposed parallel snapshot
isolation introduced by Sovran et al. is in fact a specific implementation of
an older guarantee, lazy consistency (or PL-2+), introduced by Adya et al.


title:
On the existence of weak solutions of semilinear elliptic equations and
  systems with Hardy potentials

abstract:
  Let $\Omega \subset \mathbb{R}^N$ ($N \geq 3$) be a bounded smooth domain and
$\delta(x)=\text{dist}(x,\partial \Omega)$. In this paper, we provide various
necessary and sufficient conditions for the existence of weak solutions to $$
-\Delta u- \frac{\mu}{\delta^2}u= u^p +\tau \quad \text{in } \Omega, \quad
\quad u=\nu \quad\text{on } \partial \Omega, $$ where $\mu \in \mathbb{R}$,
$p>0$, $\tau$ and $\nu$ are measures on $\Omega$ and $\partial \Omega$
respectively. We then establish existence results for the system $$ \left\{
\begin{aligned} &-\Delta u- \frac{\mu}{\delta^2}u = \epsilon \, v^p +\tau \quad
\text{in } \Omega, \\ &-\Delta v- \frac{\mu}{\delta^2}v = \epsilon\, u^{\tilde
p}+\tilde \tau \quad \text{in } \Omega, \\ &u=\nu, \quad v= \tilde \nu \quad
\text{on } \partial \Omega, \end{aligned} \right. $$ where $\epsilon=\pm 1$,
$p>0$, $\tilde p>0$, $\tau$ and $\tilde \tau$ are measures on $\Omega$, $\nu$
and $\tilde \nu$ are measures on $\partial \Omega$. We also deal with elliptic
systems where the nonlinearities are more general.


title: Nematicity at the Hund's metal crossover in iron superconductors

abstract:
  The theoretical understanding of the nematic state of iron-based
superconductors and especially of FeSe is still a puzzling problem. Although a
number of experiments calls for a prominent role of local correlations and
place iron superconductors at the entrance of a Hund metal state, the effect of
the electronic correlations on the nematic state has been theoretically poorly
investigated. In this work we study the nematic phase of iron superconductors
accounting for local correlations, including the effect of the Hund's coupling.
We show that Hund's physics strongly affects the nematic properties of the
system. It severely constraints the precise nature of the feasible
orbital-ordered state and induces a differentiation in the effective masses of
the zx=yz orbitals in the nematic phase. The latter effect leads to distinctive
signatures in different experimental probes, so far overlooked in the
interpretation of experiments. As notable examples the splittings between zx
and yz bands at Gamma and M points are modified, with important consequences
for ARPES measurements.


title: River-bed armoring as a granular segregation phenomenon

abstract:
  Gravel-river beds typically have an "armored" layer of coarse grains on the
surface, which acts to protect finer particles underneath from erosion. River
bed-load transport is a kind of dense granular flow, and such flows are known
to vertically segregate grains. The contribution of granular physics to
river-bed armoring, however, has not been investigated. Here we examine these
connections in a laboratory river with bimodal sediment size, by tracking the
motion of particles from the surface to deep inside the bed, and find that
armor develops by two distinct mechanisms. Bed-load transport in the
near-surface layer drives rapid segregation, with a vertical advection rate
proportional to the granular shear rate. Creeping grains beneath the bed-load
layer give rise to slow but persistent segregation, which is diffusion
dominated and insensitive to shear rate. We verify these findings with a
continuum phenomenological model and discrete element method simulations. Our
results suggest that river beds armor by granular segregation from below ---
rather than fluid-driven sorting from above --- while also providing new
insights on the mechanics of segregation that are relevant to a wide range of
granular flows.


title: Efficient methods for the estimation of homogenized coefficients

abstract:
  The main goal of this paper is to define and study new methods for the
computation of effective coefficients in the homogenization of divergence-form
operators with random coefficients. The methods introduced here are proved to
have optimal computational complexity, and are shown numerically to display
small constant prefactors. In the spirit of multiscale methods, the main idea
is to rely on a progressive coarsening of the problem, which we implement via a
generalization of the Green-Kubo formula. The technique can be applied more
generally to compute the effective diffusivity of any additive functional of a
Markov process. In this broader context, we also discuss the alternative
possibility of using Monte-Carlo sampling, and show how a simple one-step
extrapolation can considerably improve the performance of this alternative
method.


title:
Bounds on the prediction error of penalized least squares estimators
  with convex penalty

abstract:
  This paper considers the penalized least squares estimator with arbitrary
convex penalty. When the observation noise is Gaussian, we show that the
prediction error is a subgaussian random variable concentrated around its
median. We apply this concentration property to derive sharp oracle
inequalities for the prediction error of the LASSO, the group LASSO and the
SLOPE estimators, both in probability and in expectation. In contrast to the
previous work on the LASSO type methods, our oracle inequalities in probability
are obtained at any confidence level for estimators with tuning parameters that
do not depend on the confidence level. This is also the reason why we are able
to establish sparsity oracle bounds in expectation for the LASSO type
estimators, while the previously known techniques did not allow for the control
of the expected risk. In addition, we show that the concentration rate in the
oracle inequalities is better than it was commonly understood before.


title:
Detecting Anomalous User Behavior Using an Extended Isolation Forest
  Algorithm: An Enterprise Case Study

abstract:
  Anomalous user behavior detection is the core component of many information
security systems, such as intrusion detection, insider threat detection and
authentication systems. Anomalous behavior will raise an alarm to the system
administrator and can be further combined with other information to determine
whether it constitutes an unauthorised or malicious use of a resource. This
paper presents an anomalous user behaviour detection framework that applies an
extended version of Isolation Forest algorithm. Our method is fast and scalable
and does not require example anomalies in the training data set. We apply our
method to an enterprise dataset. The experimental results show that the system
is able to isolate anomalous instances from the baseline user model using a
single feature or combined features.


title:
Do the Kontsevich tetrahedral flows preserve or destroy the space of
  Poisson bi-vectors?

abstract:
  From the paper "Formality Conjecture" (Ascona 1996): "I am aware of only one
such a class, it corresponds to simplest good graph, the complete graph with
$4$ vertices $($and $6$ edges$)$. This class gives a remarkable vector field on
the space of bi-vector fields on $\mathbb{R}^{d}$. The evolution with respect
to the time $t$ is described by the following non-linear partial differential
equation: ..., where $\alpha=\sum_{i,j}\alpha_{ij} {\partial}/{\partial
x_{i}}\wedge {\partial}/{\partial x_{j}}$ is a bi-vector field on
$\mathbb{R}^d$.
  It follows from general properties of cohomology that $1)$ this evolution
preserves the class of $($real-analytic$)$ Poisson structures}, ...
  In fact, I cheated a little bit. In the formula for the vector field on the
space of bivector fields which one get from the tetrahedron graph, an
additional term is present. ... It is possible to prove formally that if
$\alpha$ is a Poisson bracket, i.e. if $[{\alpha,\alpha}]=0\in
T^2(\mathbb{R}^d)$, then the additional term shown above vanishes."
  By using twelve Poisson structures with high-degree polynomial coefficients
as explicit counterexamples, we show that both the above claims are false:
neither does the first flow preserve the property of bi-vectors to be Poisson
nor does the second flow vanish identically at Poisson bi-vectors. The
counterexamples at hand suggest a correction to the formula for the "exotic"
flow on the space of Poisson bi-vectors; in fact, this flow is encoded by the
balanced sum involving both the Kontsevich tetrahedral graphs (that give rise
to the flows mentioned above). We reveal that it is only the balance $1:6$ for
which the flow does preserve the space of Poisson bi-vectors.


title:
Consistency Maintenance of State of Management Data in P2P-based
  Autonomic Network Management

abstract:
  Complex Dynamic Networks can be exploited in solving problems where
traditional solutions may not be sufficient. The increasing complexity of
computer networks imposes problems to the current network management solutions.
In this context, network management is an example of a research area that could
benefit from the use of CDNs. However, the consistency of state of management
data among the elements that build management CDNs (management nodes) is an
important challenge. Traditional mechanisms to maintain consistency of these
states are supported by some centralization which wastes some desirable
properties of CDNs (e.g., robustness). In contrast to these mechanisms, we
propose a distributed, scalable and robust mechanism to maintain the
consistency of state of management data in management CDNs. Our mechanism
introduces multi-agent truth maintenance features and communication strategies
based on dynamic process to provide consistency maintenance of state of
management data. We developed a model of a management CDN on Peersim simulator
to perform experiments. Besides, 2 case studies are presented. The result
obtained supports our scalability and robustness claims.


title:
A Neumann series of Bessel functions representation for solutions of
  perturbed Bessel equations

abstract:
  A new representation for a regular solution of the perturbed Bessel equation
of the form $Lu=-u"+\left( \frac{l(l+1)}{x^2}+q(x)\right)u=\omega^2u$ is
obtained. The solution is represented as a Neumann series of Bessel functions
uniformly convergent with respect to $\omega$. For the coefficients of the
series explicit direct formulas are obtained in terms of the systems of
recursive integrals arising in the spectral parameter power series (SPPS)
method, as well as convenient for numerical computation recurrent integration
formulas.
  The result is based on application of several ideas from the classical
transmutation (transformation) operator theory, recently discovered mapping
properties of the transmutation operators involved and a Fourier-Legendre
series expansion of the transmutation kernel. For convergence rate estimates,
asymptotic formulas, a Paley-Wiener theorem and some results from constructive
approximation theory were used.
  We show that the analytical representation obtained among other possible
applications offers a simple and efficient numerical method able to compute
large sets of eigendata with a nondeteriorating accuracy.


title:
Period estimation for sparsely-sampled quasi-periodic light curves
  applied to Miras

abstract:
  We develop a non-linear semi-parametric Gaussian process model to estimate
periods of Miras with sparsely-sampled light curves. The model uses a
sinusoidal basis for the periodic variation and a Gaussian process for the
stochastic changes. We use maximum likelihood to estimate the period and the
parameters of the Gaussian process, while integrating out the effects of other
nuisance parameters in the model with respect to a suitable prior distribution
obtained from earlier studies. Since the likelihood is highly multimodal for
period, we implement a hybrid method that applies the quasi-Newton algorithm
for Gaussian process parameters and search the period/frequency parameter over
a dense grid.
  A large-scale, high-fidelity simulation is conducted to mimic the sampling
quality of Mira light curves obtained by the M33 Synoptic Stellar Survey. The
simulated data set is publicly available and can serve as a testbed for future
evaluation of different period estimation methods. The semi-parametric model
outperforms an existing algorithm on this simulated test data set as measured
by period recovery rate and quality of the resulting Period-Luminosity
relations.


title: SPHERE IRDIS and IFS astrometric strategy and calibration

abstract:
  We present the current results of the astrometric characterization of the VLT
planet finder SPHERE over 2 years of on-sky operations. We first describe the
criteria for the selection of the astrometric fields used for calibrating the
science data: binaries, multiple systems, and stellar clusters. The analysis
includes measurements of the pixel scale and the position angle with respect to
the North for both near-infrared subsystems, the camera IRDIS and the integral
field spectrometer IFS, as well as the distortion for the IRDIS camera. The
IRDIS distortion is shown to be dominated by an anamorphism of 0.60+/-0.02%
between the horizontal and vertical directions of the detector, i.e. 6 mas at
1". The anamorphism is produced by the cylindrical mirrors in the common path
structure hence common to all three SPHERE science subsystems (IRDIS, IFS, and
ZIMPOL), except for the relative orientation of their field of view. The
current estimates of the pixel scale and North angle for IRDIS are
12.255+/-0.009 milliarcseconds/pixel for H2 coronagraphic images and
-1.75+/-0.08 deg. Analyses of the IFS data indicate a pixel scale of
7.46+/-0.02 milliarcseconds/pixel and a North angle of -102.18+/-0.13 deg. We
finally discuss plans for providing astrometric calibration to the SPHERE users
outside the instrument consortium.


title: Exceptional isomorphisms between complements of affine plane curves

abstract:
  This article describes the geometry of isomorphisms between complements of
geometrically irreducible closed curves in the affine plane $\mathbb{A}^2$,
over an arbitrary field, which do not extend to an automorphism of
$\mathbb{A}^2$.
  We show that such isomorphisms are quite exceptional. In particular, they
occur only when both curves are isomorphic to open subsets of the affine line
$\mathbb{A}^1$, with the same number of complement points, over any field
extension of the ground field. Moreover, the isomorphism is uniquely determined
by one of the curves, up to left composition with an automorphism of
$\mathbb{A}^2$, except in the case where the curve is isomorphic to the affine
line $\mathbb{A}^1$ or to the punctured line $\mathbb{A}^1 \setminus \{0\}$. If
one curve is isomorphic to $\mathbb{A}^1$, then both curves are in fact
equivalent to lines. In addition, for any positive integer $n$, we construct a
sequence of $n$ pairwise non-equivalent closed embeddings of $\mathbb{A}^1
\setminus \{0\}$ with isomorphic complements. In characteristic~$0$ we even
construct infinite sequences with this property.
  Finally, we give a geometric construction that produces a large family of
examples of non-isomorphic geometrically irreducible closed curves in
$\mathbb{A}^2$ that have isomorphic complements, answering negatively the
Complement Problem posed by Hanspeter Kraft.. This also gives a negative answer
to the holomorphic version of this problem in any dimension $n \geq 2$. The
question had been raised by Pierre-Marie Poloni.


title:
Existence of ground state solutions to Dirac equations with vanishing
  potentials at infinity

abstract:
  In this work we study the existence of ground-state solutions of Dirac
equations with potentials which are allowed to vanish at infinity. The approach
is based on minimization of the energy functional over a generalized Nehari
set. Some conditions on the potentials are given in order to overcome the lack
of compactness.


title:
Electronic spectroscopy of a cold SiO$^+$ sample: Implications for
  optical pumping

abstract:
  The dispersed fluorescence following pulsed dye laser excitation of the
$\textrm{B}_2 \Sigma^+ - \textrm{X}^2 \Sigma^+(0,0)$ band of a cold sample of
SiO$^+$ has been recorded and analyzed. The branching ratios for $\textrm{B}_2
\Sigma^+ (v=0) \rightarrow \textrm{X}^2 \Sigma^+(v)$ and $\textrm{B}_2 \Sigma^+
(v=0) \rightarrow \textrm{A}^2 \Pi_i(v)$ emission were determined and compared
with values predicted based upon existing experimental and theoretical data.
The experimentally determined branching ratios show that the $\textrm{B}_2
\Sigma^+ (v=0) \rightarrow \textrm{X}^2 \Sigma^+(v)$ transitions are somewhat
less diagonal than predicted. The implications for laser cooling of a trapped
sample of SiO$^+$ using broadband laser excitation are discussed.


title:
Two-loop planar master integrals for Higgs$\to 3$ partons with full
  heavy-quark mass dependence

abstract:
  We present the analytic computation of all the planar master integrals which
contribute to the two-loop scattering amplitudes for Higgs$\to 3$ partons, with
full heavy-quark mass dependence. These are relevant for the NNLO corrections
to fully inclusive Higgs production and to the NLO corrections to Higgs
production in association with a jet, in the full theory. The computation is
performed using the differential equations method. Whenever possible, a basis
of master integrals that are pure functions of uniform weight is used. The
result is expressed in terms of one-fold integrals of polylogarithms and
elementary functions up to transcendental weight four. Two integral sectors are
expressed in terms of elliptic functions. We show that by introducing a
one-dimensional parametrization of the integrals the relevant second order
differential equation can be readily solved, and the solution can be expressed
to all orders of the dimensional regularization parameter in terms of iterated
integrals over elliptic kernels. We express the result for the elliptic sectors
in terms of two and three-fold iterated integrals, which we find suitable for
numerical evaluations. This is the first time that four-point multiscale
Feynman integrals have been computed in a fully analytic way in terms of
elliptic functions.


title:
Character-level and Multi-channel Convolutional Neural Networks for
  Large-scale Authorship Attribution

abstract:
  Convolutional neural networks (CNNs) have demonstrated superior capability
for extracting information from raw signals in computer vision. Recently,
character-level and multi-channel CNNs have exhibited excellent performance for
sentence classification tasks. We apply CNNs to large-scale authorship
attribution, which aims to determine an unknown text's author among many
candidate authors, motivated by their ability to process character-level
signals and to differentiate between a large number of classes, while making
fast predictions in comparison to state-of-the-art approaches. We extensively
evaluate CNN-based approaches that leverage word and character channels and
compare them against state-of-the-art methods for a large range of author
numbers, shedding new light on traditional approaches. We show that
character-level CNNs outperform the state-of-the-art on four out of five
datasets in different domains. Additionally, we present the first application
of authorship attribution to reddit.


title: Heegner points at Eisenstein primes and twists of elliptic curves

abstract:
  Given an elliptic curve $E$ over $\mathbb{Q}$, a celebrated conjecture of
Goldfeld asserts that a positive proportion of its quadratic twists should have
analytic rank 0 (resp. 1). We show this conjecture holds whenever $E$ has a
rational 3-isogeny. We also prove the analogous result for the sextic twists of
$j$-invariant 0 curves (Mordell curves). To prove these results, we establish a
general criterion for the non-triviality of the $p$-adic logarithm of Heegner
points at an Eisenstein prime $p$, in terms of the relative $p$-class numbers
of certain number fields and then apply this criterion to the special case
$p=3$. As a by-product, we also prove the 3-part of the Birch and
Swinnerton-Dyer conjecture for many elliptic curves of $j$-invariant 0.


title:
Analysis of nucleon electromagnetic form factors from light-front
  holographic QCD : The spacelike region

abstract:
  We present a comprehensive analysis of the spacelike nucleon electromagnetic
form factors and their flavor decomposition within the framework of light-front
holographic QCD. We show that the inclusion of the higher Fock components $\ket
{qqqq\bar{q}}$ has a significant effect on the spin-flip elastic Pauli form
factor and almost zero effect on the spin-conserving Dirac form factor. We
present light-front holographic QCD results for the proton and neutron form
factors at any momentum transfer range, including asymptotic predictions, and
show that our results agree with the available experimental data with high
accuracy. In order to correctly describe the Pauli form factor we need an
admixture of a five quark state of about 30$\%$ in the proton and about 40$\%$
in the neutron. We also extract the nucleon charge and magnetic radii and
perform a flavor decomposition of the nucleon electromagnetic form factors. The
free parameters needed to describe the experimental nucleon form factors are
very few: two parameters for the probabilities of higher Fock states for the
spin-flip form factor and a phenomenological parameter $r$, required to account
for possible SU(6) spin-flavor symmetry breaking effects in the neutron,
whereas the Pauli form factors are normalized to the experimental values of the
anomalous magnetic moments. The covariant spin structure for the Dirac and
Pauli nucleon form factors prescribed by AdS$_5$ semiclassical gravity
incorporates the correct twist scaling behavior from hard scattering and also
leads to vector dominance at low energy.


title:
Dynamical Formation of Low-Mass Merging Black Hole Binaries like
  GW151226

abstract:
  Using numerical models for star clusters spanning a wide range in ages and
metallicities (Z) we study the masses of binary black holes (BBHs) produced
dynamically and merging in the local universe ($z\lesssim0.2$). After taking
into account cosmological constraints on star-formation rate and metallicity
evolution, which realistically relate merger delay times obtained from models
with merger redshifts, we show here for the first time that while old,
metal-poor globular clusters can naturally produce merging BBHs with heavier
components, as observed in GW150914, lower-mass BBHs like GW151226 are easily
formed dynamically in younger, higher-metallicity clusters.More specifically,
we show that the mass of GW151226 is well within $1\sigma$ of the mass
distribution obtained from our models for clusters with Z/Zsun$\gtrsim0.5$.
Indeed dynamical formation of a system like GW151226 likely requires a cluster
that is younger and has a higher metallicity than typical Galactic globular
clusters. The LVT151012 system, if real, could have been created in any cluster
with Z/Zsun$\lesssim0.25$. On the other hand, GW150914 is more massive (beyond
$1\sigma$) than typical BBHs from even the lowest-metallicity (Z/Zsun=0.005)
clusters we consider, but is within $2\sigma$ of the intrinsic mass
distribution from our cluster models with Z/Zsun$\lesssim0.05$; of course
detection biases also push the observed distributions towards higher masses.


title: Localization C*-algebras and K-theoretic duality

abstract:
  Based on the localization algebras of Yu, and their subsequent analysis by
Qiao and Roe, we give a new picture of KK-theory in terms of time-parametrized
families of (locally) compact operators that asymptotically commute with
appropriate representations.


title: Quantum Observables and Effect Algebras

abstract:
  We study observables on monotone $\sigma$-complete effect algebras. We find
conditions when a spectral resolution implies existence of the corresponding
observable. The set of sharp elements of a monotone $\sigma$-complete
homogeneous effect algebra is a monotone $\sigma$-complete subalgebra. In
addition, we study compatibility in orthoalgebras.


title:
Larkin-Ovchinnikov superfluidity in a two-dimensional imbalanced atomic
  Fermi gas

abstract:
  We present an extensive study of two-dimensional Larkin-Ovchinnikov (LO)
superfluidity in a spin-imbalanced two-component atomic Fermi gas. In the
context of Fulde-Ferrell-Larkin- Ovchinnikov (FFLO) phase, we explore a wide
and generic class of pairing gap functions with ex- plicit spatial dependency.
The mean-field theory of such phases is applied through the Bogoliubov-de
Gennes equations in which the pairing gap can be determined self-consistently.
In order to systemat- ically explore the configuration space we consider both
the canonical and grand canonical ensembles where we control the polarization
or chemical potentials of the system, respectively. The mean-field calculations
enable us to understand the nature of the phase transitions in the fully paired
Bardeen- Cooper-Schrieffer (BCS) state, exotic LO phase, and partially
polarized free Fermi gas. The order of the phase transitions has been examined
and in particular we find a weak first-order phase transition between the
exotic inhomogeneous LO phase and the BCS phase. In comparison to the
three-dimensional case, where the phase diagram is dominated by a generic
separation phase, we predict a broader parameter space for the spatially
inhomogeneous LO phase. By computing the superfluid density of the LO phase at
different polarization, we show how the superfluidity of the system is
suppressed with increasing spin polarization.


title:
SoftTarget Regularization: An Effective Technique to Reduce Over-Fitting
  in Neural Networks

abstract:
  Deep neural networks are learning models with a very high capacity and
therefore prone to over-fitting. Many regularization techniques such as
Dropout, DropConnect, and weight decay all attempt to solve the problem of
over-fitting by reducing the capacity of their respective models (Srivastava et
al., 2014), (Wan et al., 2013), (Krogh & Hertz, 1992). In this paper we
introduce a new form of regularization that guides the learning problem in a
way that reduces over-fitting without sacrificing the capacity of the model.
The mistakes that models make in early stages of training carry information
about the learning problem. By adjusting the labels of the current epoch of
training through a weighted average of the real labels, and an exponential
average of the past soft-targets we achieved a regularization scheme as
powerful as Dropout without necessarily reducing the capacity of the model, and
simplified the complexity of the learning problem. SoftTarget regularization
proved to be an effective tool in various neural network architectures.


title: PixelNet: Towards a General Pixel-level Architecture

abstract:
  We explore architectures for general pixel-level prediction problems, from
low-level edge detection to mid-level surface normal estimation to high-level
semantic segmentation. Convolutional predictors, such as the
fully-convolutional network (FCN), have achieved remarkable success by
exploiting the spatial redundancy of neighboring pixels through convolutional
processing. Though computationally efficient, we point out that such approaches
are not statistically efficient during learning precisely because spatial
redundancy limits the information learned from neighboring pixels. We
demonstrate that (1) stratified sampling allows us to add diversity during
batch updates and (2) sampled multi-scale features allow us to explore more
nonlinear predictors (multiple fully-connected layers followed by ReLU) that
improve overall accuracy. Finally, our objective is to show how a architecture
can get performance better than (or comparable to) the architectures designed
for a particular task. Interestingly, our single architecture produces
state-of-the-art results for semantic segmentation on PASCAL-Context, surface
normal estimation on NYUDv2 dataset, and edge detection on BSDS without
contextual post-processing.


title:
When does an old nova become a dwarf nova? Kinematics and age of the
  nova shell of the dwarf nova AT Cnc

abstract:
  The Z Cam-type dwarf nova AT Cnc displays a classical nova (CN) shell,
demonstrating that mass transfer in cataclysmic binaries decreases
substantially after a CN eruption. The hibernation scenario of cataclysmic
binaries predicts such a decrease, on a timescale of a few centuries. In order
to measure the time since AT Cnc's last CN eruption, we have measured the
radial velocities of a hundred clumps in its ejecta with SITELLE, CFHT's
recently commissioned imaging Fourier transform spectrometer. These range from
-455 to +490 km/s. Coupled with the known distance to AT Cnc of 460 pc (Shara
2012), the size of AT Cnc's shell, and a simple model of nova ejecta
deceleration, we determine that the last CN eruption of this system occurred
$330_{-90}^{+135}$ years ago. This is the most rapid transition from a high
mass transfer rate, novalike variable to a low mass transfer rate, dwarf nova
yet measured, and in accord with the hibernation scenario of cataclysmic
binaries. We conclude by noting the similarity in deduced outburst date (within
a century of 1686 CE) of AT Cnc with a "guest star" reported in the
constellation Cancer by Korean observers in 1645 CE.


title:
Counting fixed points and rooted closed walks of the singular map $x
  \mapsto x^{x^n}$ modulo powers of a prime

abstract:
  The "self-power" map $x \mapsto x^x$ modulo $m$ and its generalized form $x
\mapsto x^{x^n}$ modulo $m$ are of considerable interest for both theoretical
reasons and for potential applications to cryptography. In this paper, we use
$p$-adic methods, primarily $p$-adic interpolation, Hensel's lemma, and lifting
singular points modulo $p$, to count fixed points and rooted closed walks of
equations related to these maps when $m$ is a prime power. In particular, we
introduce a new technique for lifting singular solutions of several congruences
in several unknowns using the left kernel of the Jacobian matrix.


title:
On the estimation of parameters of a spheroid distribution from planar
  sections

abstract:
  We study two different methods for inferring the parameters of a spheroid
distribution from planar sections of a stationary spatial system of spheroids:
one method first unfolds non-parametrically the joint size-shape-orientation
distribution of the observable ellipses in the plane into the joint
size-shape-orientation distribution of the spheroids followed by a maximum
likelihood estimation of the parameters; the second method directly estimates
these parameters based on statistics of the observable ellipses using a
quasi-likelihood approach. As an application we consider a metal-matrix
composite with ceramic particles as reinforcing inclusions, model the
inclusions as prolate spheroids and estimate the parameters of their
distribution from planar sections.


title:
Pulling back stability with applications to Out($F_n$) and relatively
  hyperbolic groups

abstract:
  We prove that stability -- a strong quasiconvexity property -- pulls back
under proper actions on proper metric spaces. This result has several
applications, including that convex cocompact subgroups of both mapping class
groups and outer automorphism groups of free groups are stable. We also
characterize stability in relatively hyperbolic groups whose parabolic
subgroups have linear divergence.


title:
Accurate Least-Squares P$_N$ Scaling based on Problem Optical Thickness
  for solving Neutron Transport Problems

abstract:
  In this paper, we present an accurate and robust scaling operator based on
material optical thickness (OT) for the least-squares spherical harmonics
(LSP$_N$) method for solving neutron transport problems. LSP$_N$ without proper
scaling is known to be erroneous in highly scattering medium, if the optical
thickness of the material is large. A previously presented scaling developed by
Manteuffel, et al.\ does improve the accuracy of LSP$_N$, in problems where the
material is optically thick. With the method, however, essentially no scaling
is applied in optically thin materials, which can lead to an erroneous solution
with presence of highly scattering medium. Another scaling approach, called the
reciprocal-removal (RR) scaled LSP$_N$, which is equivalent to the self-adjoint
angular flux (SAAF) equation, has numerical issues in highly-scattering
materials due to a singular weighting. We propose a scaling based on optical
thickness that improves the solution in optically thick media while avoiding
the singularity in the SAAF formulation.


title: Resilient Operation of Transportation Networks via Variable Speed Limits

abstract:
  In this paper, we investigate the use of variable speed limits for resilient
operation of transportation networks, which are modeled as dynamical flow
networks under local routing decisions. In such systems, some external inflow
is injected to the so-called origin nodes of the network. The total inflow
arriving at each node is routed to its operational outgoing links based on
their current particle densities. The density on each link has first order
dynamics driven by the difference of its incoming and outgoing flows. A link
irreversibly fails if it reaches its jam density. Such failures may propagate
in the network and cause a systemic failure. We show that larger link
capacities do not necessarily help in preventing systemic failures under local
routing. Accordingly, we propose the use of variable speed limits to operate
the links below their capacities, when necessary, to compensate for the lack of
global information and coordination in routing decisions. Our main result shows
that systemic failures under feasible external inflows can always be averted
through a proper selection of speed limits if the routing decisions are
sufficiently responsive to local congestion and the network is initially
uncongested. This is an attractive feature as it is much easier in practice to
adjust the speed limits than to build more physical capacity or to alter
routing decisions that are determined by social behavior.


title: Laws of Large Numbers for Supercritical Branching Gaussian Processes

abstract:
  A general class of non-Markov, supercritical Gaussian branching particle
systems is introduced and its long-time asymptotics is studied. Both weak and
strong laws of large numbers are developed with the limit object being
characterized in terms of particle motion/mutation. Long memory processes, like
branching fractional Brownian motion and fractional Ornstein-Uhlenbeck
processes with large Hurst parameters, as well as rough processes, like
fractional processes with with smaller Hurst parameter, are included as
important examples. General branching with second moments is allowed and moment
measure techniques are utilized.


title:
NMR Investigation of antiferromagnetism and coherence in
  URu$_2$Si$_{2-x}$P$_x$

abstract:
  We report $^{31}$P and $^{29}$Si NMR in single crystals of
URu$_2$Si$_{2-x}$P$_x$ for $x=0.09$ and $x=0.33$. The spectra in the $x=0.33$
sample are consistent with a homogenous commensurate antiferromagnetic phase
below $T_N \sim 37$ K. The Knight shift exhibits an anomaly at the coherence
temperature, $T^*$, that is slightly enhanced with P doping. Spin lattice
relaxation rate data indicate that the density of states is suppressed for
$x=0.09$ below 30 K, similar to the undoped compound, but there is no evidence
of long range order at this concentration. Our results suggest that Si
substitution provides chemical pressure without inducing electronic
inhomogeneity.


title:
Potential cooling of an accretion-heated neutron star crust in the
  low-mass X-ray binary 1RXS J180408.9-342058

abstract:
  We have monitored the transient neutron star low-mass X-ray binary 1RXS
J180408.9-342058 in quiescence after its ~4.5 month outburst in 2015. The
source has been observed using Swift and XMM-Newton. Its X-ray spectra were
dominated by a thermal component. The thermal evolution showed a gradual X-ray
luminosity decay from ~18 x 10^32 to ~4 x 10^32 (D/5.8 kpc)^2 erg s^{-1}
between ~8 and ~379 d in quiescence, and the inferred neutron star surface
temperature (for an observer at infinity; using a neutron star atmosphere
model) decreased from ~100 to ~71 eV. This can be interpreted as cooling of an
accretion-heated neutron star crust. Modelling the observed temperature curve
(using NSCOOL) indicated that the source required ~1.9 MeV per accreted nucleon
of shallow heating in addition to the standard deep crustal heating to explain
its thermal evolution. Alternatively, the decay could also be modelled without
the presence of deep crustal heating, only having a shallow heat source (again
~1.9 MeV per accreted nucleon was required). However, the XMM-Newton data
statistically required an additional power-law component. This component
contributed ~30 per cent of the total unabsorbed flux in 0.5-10 keV energy
range. The physical origin of this component is unknown. One possibility is
that it arises from low-level accretion. The presence of this component in the
spectrum complicates our cooling crust interpretation because it might indicate
that the smooth luminosity and temperature decay curves we observed may not be
due to crust cooling but due to some other process.


title:
Autonomous quantum clocks: does thermodynamics limit our ability to
  measure time?

abstract:
  Time remains one of the least well understood concepts in physics, most
notably in quantum mechanics. A central goal is to find the fundamental limits
of measuring time. One of the main obstacles is the fact that time is not an
observable and thus has to be measured indirectly. Here we explore these
questions by introducing a model of time measurements that is complete and
autonomous. Specifically, our autonomous quantum clock consists of a system out
of thermal equilibrium --- a prerequisite for any system to function as a clock
--- powered by minimal resources, namely two thermal baths at different
temperatures. Through a detailed analysis of this specific clock model, we find
that the laws of thermodynamics dictate a trade-off between the amount of
dissipated heat and the clock's performance in terms of its accuracy and
resolution. Our results furthermore imply that a fundamental entropy production
is associated with the operation of any autonomous quantum clock, assuming that
quantum machines cannot achieve perfect efficiency at finite power. More
generally, autonomous clocks provide a natural framework for the exploration of
fundamental questions about time in quantum theory and beyond.


title: Orientation effects on spectral emission features of quasars

abstract:
  We present an analysis of the orientation effects in SDSS quasar composite
spectra. In a previous work we have shown that the equivalent width EW of the
[OIII] {\lambda}5008{\AA} line is a reliable indicator of the inclination of
the accretion disk. Here, we have selected a sample of ~15,000 quasars from the
SDSS 7th Data Release and divided it in sub-samples with different values of
EW([OIII]). We find inclination effects both on broad and narrow quasars
emission lines, among which an increasing broadening from low to high EW for
the broad lines and a decreasing importance of the blue component for the
narrow lines. These effects are naturally explained with a variation of source
inclination from nearly face-on to edge-on, confirming the goodness of
EW([OIII]) as an orientation indicator. Moreover, we suggest that orientation
effects could explain, at least partially, the origin of the anticorrelation
between [OIII] and FeII intensities, i.e. the well known Eigenvector 1.


title:
Diffusions on a space of interval partitions with Poisson-Dirichlet
  stationary distributions

abstract:
  We construct a pair of related diffusions on a space of interval partitions
of the unit interval $[0,1]$ that are stationary with the Poisson-Dirichlet
laws with parameters (1/2,0) and (1/2,1/2) respectively. These are two
particular cases of a general construction of such processes obtained by
decorating the jumps of a spectrally positive L\'evy process with independent
squared Bessel excursions. The processes of ranked interval lengths of our
partitions are members of a two parameter family of diffusions introduced by
Ethier and Kurtz (1981) and Petrov (2009). The latter diffusions are continuum
limits of up-down Markov chains on Chinese restaurant processes. Our
construction is also a step towards describing a diffusion on the space of real
trees whose existence has been conjectured by Aldous.


title: Uniform control of local times of spectrally positive stable processes

abstract:
  We establish two results about local times of spectrally positive stable
processes. The first is a general approximation result, uniform in space and on
compact time intervals, in a model where each jump of the stable process may be
marked by a random path. The second gives moment control on the H\"older
constant of the local times, uniformly across a compact spatial interval and in
certain random time intervals. For the latter, we introduce the notion of a
L\'evy process restricted to a compact interval, which is a variation of
Lambert's L\'evy process confined in a finite interval and of Pistorius' doubly
reflected process. We use the results of this paper to exhibit a class of
path-continuous branching processes of Crump-Mode-Jagers type with continuum
genealogical structure. A further motivation for this study lies in the
construction of diffusion processes in spaces of interval partitions and
R-trees, which we explore in forthcoming articles.


title:
A gas density drop in the inner 6 AU of the transition disk around the
  Herbig Ae star HD 139614: Further evidence for a giant planet inside the
  disk?

abstract:
  Context: Quantifying the gas content inside the dust gaps of transition disks
is important to establish their origin. Aims: We seek to constrain the surface
density of warm gas in the disk of HD 139614, a Herbig Ae star with a
transition disk exhibiting a dust gap from 2.3 to 6 AU. Methods: We have
obtained ESO/VLT CRIRES high-resolution spectra of CO ro-vibrational emission.
We derived constraints on the disk's structure by modeling the line-profiles,
the spectroastrometric signal, and the rotational diagrams using flat Keplerian
disk models. Results: We detected v=1-0 12CO, 2-1 12CO, 1-0 13CO, 1-0 C18O, and
1-0 C17O ro-vibrational lines. 12CO v=1-0 lines have an average width of 14
km/s, Tgas of 450 K and an emitting region from 1 to 15 AU. 13CO and C18O lines
are on average 70 and 100 K colder, 1 and 4 km/s narrower, and are dominated by
emission at R>6 AU. The 12CO v=1-0 line-profile indicates that if there is a
gap in the gas it must be narrower than 2 AU. We find that a drop in the gas
surface density (delta_gas) at R<5-6 AU is required to simultaneously reproduce
the line-profiles and rotational diagrams of the three CO isotopologs.
Delta_gas can range from 10^-2 to 10^-4 depending on the gas-to-dust ratio of
the outer disk. We find that at 1<R<6 AU the gas surface density profile is
flat or increases with radius. We derive a gas column density at 1<R<6 AU of
NH=3x10^19 - 10^21 cm^-2. We find a 5sigma upper limit on NCO at R<1 AU of
5x10^15 cm^-2 (NH<5x10^19 cm^-2). Conclusions: The dust gap in the disk of HD
139614 has gas. The gas surface density in the disk at R<6 AU is significantly
lower than the surface density expected from HD 139614's accretion rate
assuming a viscous alpha-disk model. The gas density drop, the non-negative
density gradient of the gas inside 6 AU, and the absence of a wide (>2 AU) gas
gap suggest the presence of an embedded <2 MJ planet at around 4 AU.


title:
Evolutionary Multi-Objective Optimisation of Colour Pixels based on
  Dielectric Nano-Antennas

abstract:
  The rational design of photonic nanostructures consists in anticipating their
optical response from simple models or as variations of reference systems. This
strategy is limited when different objectives are simultaneously targeted.
Inspired from biology, evolutionary approaches drive the morphology of a
nano-object towards an optimum through several cycles of selection, mutation
and cross-over, mimicking the process of natural selection. However, their
extension to scenarii with multiple objectives demands efficient computational
schemes. We present a numerical technique to design photonic nanostructures
with optical properties optimized along several arbitrary objectives. This
combination of evolutionary multi-objective algorithms with frequency-domain
electro-dynamical simulations is used to design silicon nanostructures resonant
at user-defined, polarization-dependent wavelengths. The spectra of pixels
fabricated by electron beam lithography following the optimized design show
excellent agreement with the targeted objectives. The method is self-adaptive
to arbitrary constraints, and therefore particularly interesting for the design
of complex structures within technological limits.


title:
Neutrini in profondit\`a: Vita, morte e miracoli dei neutrini rivelati
  sotto terra, sotto i ghiacci o in fondo al mare

abstract:
  The neutrino is the most elusive particle that we know and for many years
physicists doubted that neutrinos might never be revealed. Today we know and we
reveal neutrinos produced by different astrophysical objects and by
interactions of cosmic rays (natural neutrinos) or produced by nuclear reactors
and as secondary particles in accelerators (artificial neutrinos). This paper
focus on naturally occurring neutrinos, the disclosure of which requires
enormous experimental apparatus in underground laboratories, under water or
under the ice of the South Pole. They have allowed huge advances in
understanding of neutrino properties with the discovery of the oscillation
mechanism. And at the same time they opened new frontiers for the study of
astrophysics of the processes that produce energy inside the Sun; on the
mechanisms leading to stellar gravitational collapses; on astrophysical objects
that produce cosmic rays up to extreme energies.


title:
Quantum and random walks as universal generators of probability
  distributions

abstract:
  Quantum walks and random walks bear similarities and divergences. One of the
most remarkable disparities affects the probability of finding the particle at
a given location: typically, almost a flat function in the first case and a
bell-shaped one in the second case. Here I show how one can impose any desired
stochastic behavior (compatible with the continuity equation for the
probability function) on both systems by the appropriate choice of time- and
site-dependent coins. This implies, in particular, that one can devise quantum
walks that show diffusive spreading without loosing coherence, as well as
random walks that exhibit the characteristic fast propagation of a quantum
particle driven by a Hadamard coin.

categories: quant-ph cond-mat.stat-mech math-ph math.MP


title:
Design, characterization and visual performance of a new multizone
  contact lens

abstract:
  Objectives: To analyze the whole process involved in the production of a new
bifocal Multizone Contact Lens (MCL) for presbyopia.
  Methods: The optical quality of a new MCL was evaluated by ray tracing
software in a model eye with pupil different diameters with the lens centered
and decentered. A stock of low addition (+1.5 D) MCL for presbyopia was ordered
for manufacturing. Power profiles were measured with a contact lens power
mapper, processed with a custom software and compared with the theoretical
design. Nine lenses from the stock were fitted to presbyopic subjects and the
visual performance was evaluated with new APPs for iPad Retina.
  Results: Numerical simulations showed that the trough the focus curve
provided by MCL has an extended depth of focus. The optical quality was not
dependent on pupil size and only decreased for lens decentered with a pupil
diameter of 4.5 mm. The manufactured MCL showed a smoothed power profile with a
less-defined zones. The bias between experimental and theoretical zone sizes
was uniform along the optical zone unless for the most central area. Eyes
fitted with the manufactured MCL showed an improvement in near Visual Acuity
(VA) and near stereopsis. Althouh Contrast Sensitivity (CS) at distance
decreased, the defocus curve for contrast showed an extended depth of focus
correlated to the ray tracing results.
  Conclusions: The understanding of vision with MCL requires a process that
involves design and characterization for detecting any defect that may have
impact in the final visual performance. Keywords: Multifocal contact lenses,
design, characterization, visual performance


title: Testing Endogeneity with High Dimensional Covariates

abstract:
  Modern, high dimensional data has renewed investigation on instrumental
variables (IV) analysis, primarily focusing on estimation of effects of
endogenous variables and putting little attention towards specification tests.
This paper studies in high dimensions the Durbin-Wu-Hausman (DWH) test, a
popular specification test for endogeneity in IV regression. We show,
surprisingly, that the DWH test maintains its size in high dimensions, but at
an expense of power. We propose a new test that remedies this issue and has
better power than the DWH test. Simulation studies reveal that our test
achieves near-oracle performance to detect endogeneity.


title: Parafermionic wires at the interface of chiral topological states

abstract:
  We explore a scenario where local interactions form one-dimensional gapped
interfaces between a pair of distinct chiral two-dimensional topological states
- referred to as phases 1 and 2 - such that each gapped region terminates at a
domain wall separating the chiral gapless edge states of these phases. We show
that this type of T-junction supports point-like fractionalized excitations
obeying parafermion statistics, thus implying that the one-dimensional gapped
interface forms an effective topological parafermionic wire possessing a
non-trivial ground state degeneracy. The physical properties of the anyon
condensate that gives rise to the gapped interface are investigated.
Remarkably, this condensate causes the gapped interface to behave as a type of
anyon "Andreev reflector" in the bulk, whereby anyons from one phase, upon
hitting the interface, can be transformed into a combination of reflected
anyons and outgoing anyons from the other phase. Thus, we conclude that while
different topological orders can be connected via gapped interfaces, the
interfaces are themselves topological.


title:
The effects of host galaxy properties on merging compact binaries
  detectable by LIGO

abstract:
  Cosmological simulations of galaxy formation can produce present-day galaxies
with a large range of assembly and star formation histories. A detailed study
of the metallicity evolution and star formation history of such simulations can
assist in predicting LIGO-detectable compact object binary mergers. Recent
simulations of compact binary evolution suggest the compact object merger rate
depends sensitively on the progenitor's metallicity. Rare low-metallicity star
formation during galaxy assembly can produce more detected compact binaries
than typical star formation. Using detailed simulations of galaxy and chemical
evolution, we determine how sensitively the compact binary populations of
galaxies with similar present-day appearance depend on the details of their
assembly. We also demonstrate by concrete example the extent to which dwarf
galaxies overabundantly produce compact binary mergers, particularly binary
black holes, relative to more massive galaxies. We discuss the implications for
transient multimessenger astronomy with compact binary sources.


abstract:
  Standard accretion disk theory (Shakura & Sunyaev 1973) predicts that the
total pressure in disks at typical (sub-)Eddington accretion rates becomes
radiation pressure dominated. However, radiation pressure dominated disks are
thermally unstable. Since these disks are observed in approximate steady state
over the instability time-scale, our accretion models in the radiation pressure
dominated regime (i.e. inner disk) need to be modified. Here, we present a
modification to the SS model, where radiation pressure is in equipartition with
gas pressure in the inner region. We call these flows Accretion in Radiative
Equipartition (AiRE) Disks. We introduce the basic features of AiRE disks and
show how they modify disk properties such as the Toomre parameter and central
temperature. We then show that the accretion rate of AiRE disks is limited from
above and below, by Toomre and nodal sonic point instabilities, respectively.
The former leads to a strict upper limit on the mass of supermassive black
holes as a function of cosmic time (and spin), while the latter could explain
the transition between hard and soft states of X-ray binaries.


title:
Upper bound on the center-of-mass energy of the collisional Penrose
  process

abstract:
  Following the interesting work of Ba\~nados, Silk, and West [Phys. Rev. Lett.
{\bf 103}, 111102 (2009)], it is repeatedly stated in the physics literature
that the center-of-mass energy, ${\cal E}_{\text{c.m}}$, of two colliding
particles in a maximally rotating black-hole spacetime can grow unboundedly.
For this extreme scenario to happen, the particles have to collide at the
black-hole horizon. In this paper we show that Thorne's famous hoop conjecture
precludes this extreme scenario from occurring in realistic black-hole
spacetimes. In particular, it is shown that a new (and larger) horizon is
formed {\it before} the infalling particles reach the horizon of the original
black hole. As a consequence, the center-of-mass energy of the collisional
Penrose process is {\it bounded} from above by the simple scaling relation
${\cal E}^{\text{max}}_{\text{c.m}}/2\mu\propto(M/\mu)^{1/4}$, where $M$ and
$\mu$ are respectively the mass of the central black hole and the proper mass
of the colliding particles.


title:
Exocometary gas structure, origin and physical properties around $\beta$
  Pictoris through ALMA CO multi-transition observations

abstract:
  Recent ALMA observations unveiled the structure of CO gas in the 23 Myr-old
$\beta$ Pictoris planetary system, a component that has been discovered in many
similarly young debris disks. We here present ALMA CO J=2-1 observations, at an
improved spectro-spatial resolution and sensitivity compared to previous CO
J=3-2 observations. We find that 1) the CO clump is radially broad, favouring
the resonant migration over the giant impact scenario for its dynamical origin,
2) the CO disk is vertically tilted compared to the main dust disk, at an angle
consistent with the scattered light warp. We then use position-velocity
diagrams to trace Keplerian radii in the orbital plane of the disk. Assuming a
perfectly edge-on geometry, this shows a CO scale height increasing with radius
as $R^{0.75}$, and an electron density (derived from CO line ratios through
NLTE analysis) in agreement with thermodynamical models. Furthermore, we show
how observations of optically thin line ratios can solve the primordial versus
secondary origin dichotomy in gas-bearing debris disks. As shown for $\beta$
Pictoris, subthermal (NLTE) CO excitation is symptomatic of H$_2$ densities
that are insufficient to shield CO from photodissociation over the system's
lifetime. This means that replenishment from exocometary volatiles must be
taking place, proving the secondary origin of the disk. In this scenario,
assuming steady state production/destruction of CO gas, we derive the CO+CO$_2$
ice abundance by mass in $\beta$ Pic's exocomets to be at most $\sim$6%,
consistent with comets in our own Solar System and in the coeval HD181327
system.


title: Anisotropy in the all-sky distribution of galaxy morphological types

abstract:
  We present the first study of the isotropy of the distribution of
morphological types of galaxies in the Local Universe out to around 200 Mpc
using more than 60,000 galaxies from the HyperLeda database. We divide the sky
into two opposite hemispheres and compare the abundance distribution of the
morphological types, $T$, using the Kolmogorov-Smirnov (KS) test. This is
repeated for different directions in the sky and the KS statistic as a function
of sky coordinates is obtained. For three samples of galaxies within around
100, 150, and 200 Mpc, we find a significant hemispherical asymmetry with a
vanishingly small chance of occurring in an isotropic distribution.
Astonishingly, regardless of this extreme significance, the hemispherical
asymmetry is aligned with the Celestial Equator at the 97.1-99.8% and with the
Ecliptic at the 94.6-97.6% confidence levels, estimated using a Monte Carlo
analysis. Shifting $T$ values randomly within their uncertainties has a
negligible effect on this result. When a magnitude limit of $B\leq 15$ mag is
applied, the sample within 100 Mpc shows no significant anisotropy after random
shifting of $T$. However, the direction of the asymmetry in the samples within
150 and 200 Mpc and $B\leq 15$ mag is found to be within an angular separation
of 32 degrees from $(l,b)=(123.7, 24.6)$ with 97.2% and 99.9% confidence
levels, respectively. This direction is only 2.6 degrees away from the
Celestial North Pole. Unless the Local Universe has a significant anisotropic
distribution of galaxy types aligned with the orientation or the orbit of the
Earth (which would be a challenge for the Cosmological Principle), our results
show that there seems to be a systematic bias in the classification of galaxy
morphological types between the data from the Northern and the Southern
Equatorial sky. Further studies are absolutely needed to find out the exact
source of this anisotropy.


title:
The First Circumbinary Planet Found by Microlensing:
  OGLE-2007-BLG-349L(AB)c

abstract:
  We present the analysis of the first circumbinary planet microlensing event,
OGLE-2007-BLG-349. This event has a strong planetary signal that is best fit
with a mass ratio of $q \approx 3.4\times10^{-4}$, but there is an additional
signal due to an additional lens mass, either another planet or another star.
We find acceptable light curve fits with two classes of models: 2-planet models
(with a single host star) and circumbinary planet models. The light curve also
reveals a significant microlensing parallax effect, which constrains the mass
of the lens system to be $M_L \approx 0.7 M_\odot$. Hubble Space Telescope
images resolve the lens and source stars from their neighbors and indicate
excess flux due to the star(s) in the lens system. This is consistent with the
predicted flux from the circumbinary models, where the lens mass is shared
between two stars, but there is not enough flux to be consistent with the
2-planet, 1-star models. So, only the circumbinary models are consistent with
the HST data. They indicate a planet of mass $m_c = 80\pm 13\,M_\oplus$,
orbiting a pair of M-dwarfs with masses of $M_A = 0.41\pm 0.07 M_\odot$ and
$M_B = 0.30\pm 0.07 M_\oplus$, which makes this the lowest mass circumbinary
planet system known. The ratio of the separation between the planet and the
center-of-mass to the separations of the two stars is $\sim 40$, so unlike most
of the circumbinary planets found by Kepler, the planet does not orbit near the
stability limit.


title:
Mid-Infrared Colors of Dwarf Galaxies: Young Starbursts Mimicking Active
  Galactic Nuclei

abstract:
  Searching for active galactic nuclei (AGN) in dwarf galaxies is important for
our understanding of the seed black holes that formed in the early Universe.
Here, we test infrared selection methods for AGN activity at low galaxy masses.
Our parent sample consists of ~18,000 nearby dwarf galaxies (M*< 3 x 10^9 Msun,
$z<0.055$) in the Sloan Digital Sky Survey with significant detections in the
first three bands of the AllWISE data release from the Wide-field Infrared
Survey Explorer (WISE). First, we demonstrate that the majority of
optically-selected AGNs in dwarf galaxies are not selected as AGNs using WISE
infrared color diagnostics and that the infrared emission is dominated by the
host galaxies. We then investigate the infrared properties of
optically-selected star-forming dwarf galaxies, finding that the galaxies with
the reddest infrared colors are the most compact, with blue optical colors,
young stellar ages and large specific star formation rates. These results
indicate that great care must be taken when selecting AGNs in dwarf galaxies
using infrared colors, as star-forming dwarf galaxies are capable of heating
dust in such a way that mimics the infrared colors of more luminous AGNs. In
particular, a simple $\mathrm{W1}-\mathrm{W2}$ color cut alone should not be
used to select AGNs in dwarf galaxies. With these complications in mind, we
present a sample of 41 dwarf galaxies worthy of follow-up observations that
fall in WISE infrared color space typically occupied by more luminous AGNs.


title:
On the pi pi continuum in the nucleon form factors and the proton radius
  puzzle

abstract:
  We present an improved determination of the $\pi\pi$ continuum contribution
to the isovector spectral functions of the nucleon electromagnetic form
factors. Our analysis includes the most up-to-date results for the
$\pi\pi\to\bar N N$ partial waves extracted from Roy-Steiner equations,
consistent input for the pion vector form factor, and a thorough discussion of
isospin-violating effects and uncertainty estimates. As an application, we
consider the $\pi\pi$ contribution to the isovector electric and magnetic radii
by means of sum rules, which, in combination with the accurately known neutron
electric radius, are found to slightly prefer a small proton charge radius.

categories: hep-ph hep-lat nucl-ex nucl-th physics.atom-ph


title: A Modern Approach to Superradiance

abstract:
  In this paper, we provide a simple and modern discussion of rotational
superradiance based on quantum field theory. We work with an effective theory
valid at scales much larger than the size of the spinning object responsible
for superradiance. Within this framework, the probability of absorption by an
object at rest completely determines the superradiant amplification rate when
that same object is spinning. We first discuss in detail superradiant
scattering of spin 0 particles with orbital angular momentum $\ell=1$, and then
extend our analysis to higher values of orbital angular momentum and spin.
Along the way, we provide a simple derivation of vacuum friction---a "quantum
torque" acting on spinning objects in empty space. Our results apply not only
to black holes but to arbitrary spinning objects. We also discuss superradiant
instability due to formation of bound states and, as an illustration, we
calculate the instability rate $\Gamma$ for bound states with massive spin 1
particles. For a black hole with mass $M$ and angular velocity $\Omega$, we
find $\Gamma \sim (G M \mu)^7 \Omega$ when the particle's Compton wavelength
$1/\mu$ is much greater than the size $GM$ of the spinning object. This rate is
parametrically much larger than the instability rate for spin 0 particles,
which scales like $(GM \mu)^9 \Omega$. This enhanced instability rate can be
used to constrain the existence of ultralight particles beyond the Standard
Model.


title: A tale of two cones: the Higgs Branch of Sp(n) theories with 2n flavours

abstract:
  The purpose of this short note is to highlight a particular phenomenon which
concerns the Higgs branch of a certain family of 4d N = 2 theories with SO(2N)
flavour symmetry. By studying the Higgs branch as an algebraic variety through
Hilbert series techniques we find that it is not a single hyperkahler cone but
rather the union of two cones with intersection a hyperkahler subvariety which
we specify. This remarkable phenomenon is not only interesting per se but plays
a crucial role in understanding the structure of all Higgs branches that are
generated by mesons.


title:
Fractional charge and emergent mass hierarchy in diagonal two-leg t-J
  cylinders

abstract:
  We define a new class of "diagonal" t-J ladders rotated by $\pi$/4 relative
to the canonical lattice directions of the square lattice, and study it using
density matrix renormalization group (DMRG). Here, we focus on the two-leg
cylinder with a doped hole concentration near x = 1/4. At exactly x = 1/4, the
system forms a period 4 charge density wave (CDW) and exhibits spin-charge
separation. Slightly away from 1/4 doping we observe several topologically
distinct types of solitons with well defined fractionalized quantum numbers.
Remarkably, given the absence of any obvious small parameter, the effective
masses of the emergent solitons differ by several orders of magnitude.


title:
Cluster and field elliptical galaxies at z~1.3. The marginal role of the
  environment and the relevance of the galaxy central regions

abstract:
  We compared the properties of 56 elliptical galaxies selected from three
clusters at $1.2<z<1.4$ with those of field galaxies in the GOODS-S (~30),
COSMOS (~180) and CANDELS (~220) fields. We studied the relationships among
effective radius, surface brightness, stellar mass, stellar mass density
$\Sigma_{Re}$ and central mass density $\Sigma_{1kpc}$ within 1 kpc radius. We
find that cluster ellipticals do not differ from field ellipticals: they share
the same structural parameters at fixed mass and the same scaling relations. On
the other hand, the population of field ellipticals at $z\sim1.3$ shows a
significant lack of massive ($M_*> 2\times 10^{11}$ M$_\odot$) and large (R$_e
> 4-5$ kpc) ellipticals with respect to the cluster. Nonetheless, at
$M*<2\times 10^{11}$ M$_\odot$, the two populations are similar. The size-mass
relation of ellipticals at z~1.3 defines two different regimes, above and below
a transition mass $m_t\sim 2-3\times10^{10}$ M$_\odot$: at lower masses the
relation is nearly flat (R$_e\propto M_*^{-0.1\pm 0.2}$), the mean radius is
constant at ~1 kpc and $\Sigma_{Re}\sim \Sigma_{1kpc}$ while, at larger masses,
the relation is R$_e\propto M*^{0.64\pm0.09}$. The transition mass marks the
mass at which galaxies reach the maximum $\Sigma_{Re}$. Also the
$\Sigma_{1kpc}$-mass relation follows two different regimes,
$\Sigma_{1kpc}\propto M*^{0.64\ >m_t}_{1.07\ <m_t}$, defining a transition mass
density $\Sigma_{1kpc}\sim 2-3\times10^3$ M$_\odot$ pc$^{-2}$. The mass density
$\Sigma_{Re}$ does not correlate with mass, dense/compact galaxies can be
assembled over a wide mass regime, independently of the environment. The
central mass density, $\Sigma_{1kpc}$, besides to be correlated with the mass,
is correlated to the age of the stellar population: the higher the central
stellar mass density, the higher the mass, the older the age of the stellar
population. [Abridged]


title: Black hole clustering and duty cycles in the Illustris simulation

abstract:
  We use the high-resolution cosmological simulation Illustris to investigate
the clustering of supermassive black holes across cosmic time, the link between
black hole clustering and host halo masses, and the implications for black hole
duty cycles. Our predicted black hole correlation length and bias match the
observational data very well across the full redshift range probed. Black hole
clustering is strongly luminosity-dependent on small, 1-halo scales, with some
moderate dependence on larger scales of a few Mpc at intermediate redshifts. We
find black hole clustering to evolve only weakly with redshift, initially
following the behaviour of their hosts. However below z ~ 2 black hole
clustering increases faster than that of their hosts, which leads to a
significant overestimate of the clustering-predicted host halo mass. The full
distribution of host halo masses is very wide, including a low-mass tail
extending up to an order of magnitude below the naive prediction for minimum
host mass. Our black hole duty cycles follow a power-law dependence on black
hole mass and decrease with redshift, and we provide accurate analytic fits to
these. The increase in clustering amplitude at late times, however, means that
duty cycle estimates based on black hole clustering can overestimate duty
cycles substantially, by more than two orders of magnitude. We find the best
agreement when the minimum host mass is assumed to be $10^{11.2} M_\odot$ ,
which provides an accurate measure across all redshifts and luminosity ranges
probed by our simulation.


title:
ASTErIsM - Application of topometric clustering algorithms in automatic
  galaxy detection and classification

abstract:
  We present a study on galaxy detection and shape classification using
topometric clustering algorithms. We first use the DBSCAN algorithm to extract,
from CCD frames, groups of adjacent pixels with significant fluxes and we then
apply the DENCLUE algorithm to separate the contributions of overlapping
sources. The DENCLUE separation is based on the localization of pattern of
local maxima, through an iterative algorithm which associates each pixel to the
closest local maximum. Our main classification goal is to take apart elliptical
from spiral galaxies. We introduce new sets of features derived from the
computation of geometrical invariant moments of the pixel group shape and from
the statistics of the spatial distribution of the DENCLUE local maxima
patterns. Ellipticals are characterized by a single group of local maxima,
related to the galaxy core, while spiral galaxies have additional ones related
to segments of spiral arms. We use two different supervised ensemble
classification algorithms, Random Forest, and Gradient Boosting. Using a sample
of ~ 24000 galaxies taken from the Galaxy Zoo 2 main sample with spectroscopic
redshifts, and we test our classification against the Galaxy Zoo 2 catalog. We
find that features extracted from our pipeline give on average an accuracy of ~
93%, when testing on a test set with a size of 20% of our full data set, with
features deriving from the angular distribution of density attractor ranking at
the top of the discrimination power.


title: Physical stress, mass, and energy for non-relativistic matter

abstract:
  For theories of relativistic matter fields there exist two possible
definitions of the stress-energy tensor, one defined by a variation of the
action with the coframes at fixed connection, and the other at fixed torsion.
These two stress-energy tensors do not necessarily coincide and it is the
latter that corresponds to the Cauchy stress measured in the lab. In this note
we discuss the corresponding issue for non-relativistic matter theories. We
point out that while the physical non-relativistic stress, momentum, and mass
currents are defined by a variation of the action at fixed torsion, the energy
current does not admit such a description and is naturally defined at fixed
connection. Any attempt to define an energy current at fixed torsion results in
an ambiguity which cannot be resolved from the background spacetime data or
conservation laws. We also provide computations of these quantities for some
simple non-relativistic actions.


title:
Generalized Pseudopotentials for the Anisotropic Fractional Quantum Hall
  Effect

abstract:
  We generalize the notion of Haldane pseudopotentials to anisotropic
fractional quantum Hall (FQH) systems which are physically realized, e.g., in
tilted magnetic field experiments or anisotropic band structures. This
formalism allows us to expand any translation-invariant interaction over a
complete basis, and directly reveals the intrinsic metric of incompressible FQH
fluids. We show that purely anisotropic pseudopotentials give rise to new types
of bound states for small particle clusters in the infinite plane, and can be
used as a diagnostic of FQH nematic order. We also demonstrate that generalized
pseudopotentials quantify the anisotropic contribution to the effective
interaction potential, which can be particularly large in models of fractional
Chern insulators.


title:
Two New Theories for the Current Charge Relativity and the Electric
  Origin of the Magnetic Force Between Two Filamentary Current Elements

abstract:
  This paper presents two new theories and a new current representation to
explain the magnetic force between two filamentary current elements as a result
of electric force interactions between current charges. The first theory states
that a current has an electric charge relative to its moving observer. The
second theory states that the magnetic force is an electric force in origin.
The new current representation characterizes a current as equal amounts of
positive and negative point charges moving in opposite directions at the speed
of light. Previous work regarded electricity and magnetism as different aspects
of the same subject. One effort was made by Johnson to unify the origin of
electricity and magnetism, but this effort yielded a formula that is unequal to
the well-known magnetic force law. The explanation provided for the magnetic
force depends on three factors: 1) representing the electric current as charges
moving at the speed of light, 2) considering the relative velocity between
moving charges, and 3) analyzing the electric field spreading in the space due
to the movement of charges inside current elements. The electric origin of the
magnetic force is proved by deriving the magnetic force law and Biot-Savart law
using the electric force law. This paper is helpful for unifying the concepts
of magnetism and electricity.


title:
Dynamical symmetry breaking and phase transitions in driven diffusive
  systems

abstract:
  We study the probability distribution of a current flowing through a
diffusive system connected to a pair of reservoirs at its two ends. Sufficient
conditions for the occurrence of a host of possible phase transitions both in
and out of equilibrium are derived. These transitions manifest themselves as
singularities in the large deviation function, resulting in enhanced current
fluctuations. Microscopic models which implement each of the scenarios are
presented, with possible experimental realizations. Depending on the model, the
singularity is associated either with a particle-hole symmetry breaking, which
leads to a continuous transition, or in the absence of the symmetry with a
first-order phase transition. An exact Landau theory which captures the
different singular behaviors is derived.


title:
A note on Wall's modification of the Schur algorithm and linear pencils
  of Jacobi matrices

abstract:
  In this note we revive a transformation that was introduced by H. S. Wall and
that establishes a one-to-one correspondence between continued fraction
representations of Schur, Carath\'eodory, and Nevanlinna functions. This
transformation can be considered as an analog of the Szeg\H{o} mapping but it
is based on the Cayley transform, which relates the upper half-plane to the
unit disc. For example, it will be shown that, when applying the Wall
transformation, instead of OPRL, we get a sequence of orthogonal rational
functions that satisfy three-term recurrence relation of the form $(H-\lambda
J)u=0$, where $u$ is a semi-infinite vector, whose entries are the rational
functions. Besides, $J$ and $H$ are Hermitian Jacobi matrices for which a
version of the Denisov-Rakhmanov theorem holds true. Finally we will
demonstrate how pseudo-Jacobi polynomials (aka Routh-Romanovski polynomials)
fit into the picture.


title:
The Distribution of Dark and Luminous Matter in the Unique Galaxy
  Cluster Merger Abell 2146

abstract:
  Abell 2146 ($z$ = 0.232) consists of two galaxy clusters undergoing a major
merger. The system was discovered in previous work, where two large shock
fronts were detected using the $\textit{Chandra X-ray Observatory}$, consistent
with a merger close to the plane of the sky, caught soon after first core
passage. A weak gravitational lensing analysis of the total gravitating mass in
the system, using the distorted shapes of distant galaxies seen with ACS-WFC on
$\textit{Hubble Space Telescope}$, is presented. The highest peak in the
reconstruction of the projected mass is centred on the Brightest Cluster Galaxy
(BCG) in Abell 2146-A. The mass associated with Abell 2146-B is more extended.
Bootstrapped noise mass reconstructions show the mass peak in Abell 2146-A to
be consistently centred on the BCG. Previous work showed that BCG-A appears to
lag behind an X-ray cool core; although the peak of the mass reconstruction is
centred on the BCG, it is also consistent with the X-ray peak given the
resolution of the weak lensing mass map. The best-fit mass model with two
components centred on the BCGs yields $M_{200}$ =
1.1$^{+0.3}_{-0.4}$$\times$10$^{15}$M$_{\odot}$ and
3$^{+1}_{-2}$$\times$10$^{14}$M$_{\odot}$ for Abell 2146-A and Abell 2146-B
respectively, assuming a mass concentration parameter of $c=3.5$ for each
cluster. From the weak lensing analysis, Abell 2146-A is the primary halo
component, and the origin of the apparent discrepancy with the X-ray analysis
where Abell 2146-B is the primary halo is being assessed using simulations of
the merger.