title: Gamma-rays as probes of the Universe

abstract:
  The propagation of $\gamma$ rays over very large distances provides new
insights on the intergalactic medium and on fundamental physics. On their path
to the Earth, $\gamma$ rays can annihilate with diffuse infrared or optical
photons of the intergalactic medium, producing $e^+ \, e^-$ pairs. The density
of these photons is poorly determined by direct measurements due to significant
galactic foregrounds. Studying the absorption of $\gamma$ rays from
extragalactic sources at different distances allows the density of low-energy
diffuse photons to be measured. Gamma-ray propagation may also be affected by
new phenomena predicted by extensions of the Standard Model of particle
physics. Lorentz Invariance is violated in some models of Quantum Gravity,
leading to an energy-dependent speed of light in vacuum. From differential
time-of-flight measurements of the most distant $\gamma$-ray bursts and of
flaring active galactic nuclei, lower bounds have been set on the energy scale
of Quantum Gravity. Another effect that may alter $\gamma$-ray propagation is
predicted by some models of String Theory, namely the mixing of the $\gamma$
ray with a light fundamental boson called an "axion-like particle", which does
not interact with low-energy photons. Such a mixing would make the Universe
more transparent to $\gamma$ rays than what would otherwise be, in a sense it
decreases the amount of modification to the spectrum that comes from the
extragalactic background light. The present status of the search for all these
phenomena in $\gamma$-ray astronomy is reviewed.


title:
Turbulent transport of MeV range cyclotron heated minorities as compared
  to alpha particles

abstract:
  We study the turbulent transport of an ion cyclotron resonance heated (ICRH),
MeV range minority ion species in tokamak plasmas. Such highly energetic
minorities, which can be produced in the three ion minority heating scheme [Ye.
O. Kazakov et al. (2015) Nucl. Fusion 55, 032001], have been proposed to be
used to experimentally study the confinement properties of fast ions without
the generation of fusion alphas. We compare the turbulent transport properties
of ICRH ions with that of fusion born alpha particles. Our theoretical
predictions indicate that care must be taken when conclusions are drawn from
experimental results: While the effect of turbulence on these particles is
similar in terms of transport coefficients, differences in their distribution
functions - ultimately their generation processes - make the resulting
turbulent fluxes different.


title:
Lagged and instantaneous dynamical influences related to brain
  structural connectivity

abstract:
  Contemporary neuroimaging methods can shed light on the basis of human neural
and cognitive specializations, with important implications for neuroscience and
medicine. Different MRI acquisitions provide different brain networks at the
macroscale; whilst diffusion-weighted MRI (dMRI) provides a structural
connectivity (SC) coincident with the bundles of parallel fibers between brain
areas, functional MRI (fMRI) accounts for the variations in the
blood-oxygenation-level-dependent T2* signal, providing functional connectivity
(FC).Understanding the precise relation between FC and SC, that is, between
brain dynamics and structure, is still a challenge for neuroscience. To
investigate this problem, we acquired data at rest and built the corresponding
SC (with matrix elements corresponding to the fiber number between brain areas)
to be compared with FC connectivity matrices obtained by 3 different methods:
directed dependencies by an exploratory version of structural equation modeling
(eSEM), linear correlations (C) and partial correlations (PC). We also
considered the possibility of using lagged correlations in time series; so, we
compared a lagged version of eSEM and Granger causality (GC). Our results were
two-fold: firstly, eSEM performance in correlating with SC was comparable to
those obtained from C and PC, but eSEM (not C nor PC) provides information
about directionality of the functional interactions. Second, interactions on a
time scale much smaller than the sampling time, captured by instantaneous
connectivity methods, are much more related to SC than slow directed influences
captured by the lagged analysis. Indeed the performance in correlating with SC
was much worse for GC and for the lagged version of eSEM. We expect these
results to supply further insights to the interplay between SC and functional
patterns, an important issue in the study of brain physiology and function.


title:
Conductance oscillations in quantum point contacts of InAs/GaSb
  heterostructures

abstract:
  We study quantum point contacts in two-dimensional topological insulators by
means of quantum transport simulations for InAs/GaSb heterostructures and
HgTe/(Hg,Cd)Te quantum wells. In InAs/GaSb, the density of edge states shows an
oscillatory decay as a function of the distance to the edge. This is in
contrast to the behavior of the edge states in HgTe quantum wells, which decay
into the bulk in a simple exponential manner. The difference between the two
materials is brought about by spatial separation of electrons and holes in
InAs/GaSb, which affects the magnitudes of the parameters describing the
particle-hole asymmetry and the strength of intersubband coupling within the
Bernevig-Hughes-Zhang model. We show that the character of the wave function
decay impacts directly the dependence of the point contact conductance on the
constriction width and the Fermi energy, which can be verified experimentally
and serve to determine accurately the values of relevant parameters. In the
case of InAs/GaSb heterostructures the conductance magnitude oscillates as a
function of the constriction width following the oscillations of the edge state
penetration, whereas in HgTe/(Hg,Cd)Te quantum wells a single switching from
transmitting to reflecting contact is predicted.


title:
Gap and spin texture engineering of Dirac topological states at the
  Cr-Bi$_2$Se$_3$ interface

abstract:
  The presence of an exchange field in topological insulators reveals novel
spin related phenomena derived from the combination of topology and magnetism.
In the present work we show the controlled occurrence of either metallic or
gapped topological Dirac states at the interface between ultrathin Cr films and
the Bi$_2$Se$_3$ surface. The opening and closing of the gap at the Dirac point
is caused by the spin reorientation transitions arising in the Cr films. We
find that atom thin layers of Cr adhered to Bi$_2$Se$_3$ surfaces present a
magnetic ground state with ferromagnetic planes coupled antiferromagnetically.
As the thickness of the Cr film increases stepwise from one to three atomic
layers, the direction of the magnetization changes twice from out-of-plane to
in-plane and to out-of-plane again. The out of plane magnetization drives the
gap opening and the topological surface states acquire a circular meron spin
structure. Therefore, the Cr spin reorientation leads to the metal/insulator
transition in the Bi$_2$Se$_3$ surface and to the correlated modification of
the surface state spin texture. Consequently, the thickness of the Cr film
provides an effective and controllable mechanism to modify the metallic or
gapped nature, as well as the spin texture of the topological Dirac states.


title:
An immersed boundary method for solving compressible flow with
  arbitrarily irregular and moving geometry

abstract:
  In this paper, a novel immersed boundary method is developed, validated, and
applied. Through devising a second-order three-step flow reconstruction scheme,
the proposed method is able to enforce the Dirichlet, Neumann, Robin, and
Cauchy boundary conditions in a straightforward and consistent manner. Equipped
with a fluid-solid coupling framework that integrates high-order temporal and
spatial discretization schemes, numerical experiments concerning flow involving
stationary and moving objects, convex and concave geometries, no-slip and slip
wall boundary conditions, as well as subsonic and supersonic motions are
conducted to validate the method. It is demonstrated that the proposed method
can provide efficient, accurate, and robust boundary treatment for solving flow
with arbitrarily irregular and moving geometries on Cartesian grids.


title:
Scanning Tunneling Spectroscopy of Proximity Superconductivity in
  Epitaxial Multilayer Graphene

abstract:
  We report on spatial measurements of the superconducting proximity effect in
epitaxial graphene induced by a graphene-superconductor interface.
Superconducting aluminum films were grown on epitaxial multilayer graphene on
SiC. The aluminum films were discontinuous with networks of trenches in the
film morphology reaching down to exposed graphene terraces. Scanning tunneling
spectra measured on the graphene terraces show a clear decay of the
superconducting energy gap with increasing separation from the
graphene-aluminum edges. The spectra were well described by
Bardeen-Cooper-Schrieffer (BCS) theory. The decay length for the
superconducting energy gap in graphene was determined to be greater than 400
nm. Deviations in the exponentially decaying energy gap were also observed on a
much smaller length scale of tens of nanometers.


title:
Robust stabilization loop design for gimbaled electro-optical imaging
  system

abstract:
  For electro-optical imaging systems, line-of-sight stabilization against
different disturbances created by mobile platforms is crucial property. The
development of high resolution sensors and the demand in increased operating
distances have recently increased the expectations from stabilization loops.
For that reason, higher gains and larger bandwidths become necessary. As the
stabilization loop satisfies these requirements for good disturbance
attenuation, it must also satisfy sufficient loop stability. In gimbaled
imaging systems, the main difficulties in satisfying sufficient loop stability
are structural resonances and model uncertainties. Therefore, satisfying high
stabilization performance in the presence of model uncertainties or modeling
errors requires utilization of robust control methods. In this paper, robust
LQG/LTR controller design is described for a two-axis gimbal. First, the
classical LQG/LTR method is modified such that it becomes very powerful loop
shaping method. Next, using this method, controller is synthesized. Robust
stability and robust performance of stabilization loop is investigated by using
singular value tests. The report is concluded with the experimental validation
of the designed robust controller.


title:
Denoising of gravitational-wave signal GW150914 via total-variation
  methods

abstract:
  We apply a regularized Rudin-Osher-Fatemi total variation (TV) method to
denoise the transient gravitational wave signal GW150914. We have previously
applied TV techniques to denoise numerically generated grav- itational waves
embedded in additive Gaussian noise, obtaining satisfactory results
irrespective of the signal morphology or astrophysical origin. We find that the
non-Gaussian, non-stationary noise from the gravitational wave event GW150914
can also be successfully removed with TV-denoising methods. The quality of the
de- noised waveform is comparable to that obtained with the Bayesian approach
used in the discovery paper [1]. TV-denoising techniques may thus offer an
additional viable approach for waveform reconstruction.


title: Spintronics with magnetic nanomolecules and graphene flakes

abstract:
  We show how the magnetization of nano-objects can be efficiently regulated.
Several types of nanosystems are considered: magnetics nanomolecules, magnetic
nanoclusters, polarized nanomolecules, and magnetic graphene. These
nano-objects and the structures composed of them enjoy many common properties,
with the main difference being in the type of particle interactions. The
possibility of governing spin dynamics is important for spintronics.


title: Step by Step to Peace in Syria

abstract:
  The revolution and Civil War in Syria has led to substantial death and
suffering, a massive refugee crisis, and growth of ISIS extremism and its
terror attacks globally. Conflict between disparate groups is ongoing. Complex
ethnic geography is a central reason for the large number of different groups
in conflict as this geography leads to local allegiances that do not aggregate
at the national scale. We have previously demonstrated that, where ethnic
groups exist in geographic patches of 20-60 km in diameter, there is a high
probability of conflict. We have also shown that establishing local autonomy
through subnational boundaries (as is found in Switzerland) is a means of
alleviating conflict. Our analysis suggests that providing some level of local
autonomy to the ethnic groups would reduce the impetus for local conflict and
could serve as a basis for peace and stability. Here we propose that
interventions should be pursued to stop specific individual local conflicts,
creating safe zones, that can be expanded gradually and serve as examples for
achieving a comprehensive solution for safety, peace and stable local
governance in Syria.


title: Long induced paths in graphs

abstract:
  We prove that every 3-connected planar graph on $n$ vertices contains an
induced path on $\Omega(\log n)$ vertices, which is best possible and improves
the best known lower bound by a multiplicative factor of $\log \log n$. We
deduce that any planar graph (or more generally, any graph embeddable on a
fixed surface) with a path on $n$ vertices, also contains an induced path on
$\Omega(\sqrt{\log n})$ vertices. We conjecture that for any $k$, there is a
contant $c(k)$ such that any $k$-degenerate graph with a path on $n$ vertices
also contains an induced path on $\Omega((\log n)^{c(k)})$ vertices. We provide
examples showing that this order of magnitude would be best possible (already
for chordal graphs), and prove the conjecture in the case of interval graphs.


title:
Time Reversal Invariance Violating and Parity Conserving effects in
  Proton Deuteron Scattering

abstract:
  Time reversal invariance violating parity conserving (TVPC) effects are
calculated for elastic proton deuteron scattering with proton energies up to
$2~$MeV. Distorted Wave Born Approximation is employed to estimate TVPC matrix
elements, based on hadronic wave functions, obtained by solving three-body
Faddeev-Merkuriev equations in configuration space with realistic potentials.


title: Asteroseismology with solar-like oscillations

abstract:
  Almost 100 years ago Sir Arthur Eddington noted that the interiors of stars
were inaccessible to observations. The advent of helio- and asteroseismology
has completely changed this assessment. Helioseismology has provided very
detailed information about the interior structure and dynamics of the Sun,
highlighting remaining issues in our understanding of the solar interior. In
the last decade extensive observations of stellar oscillations, in particular
from space photometry, have provided very detailed information about the global
and internal properties of stars. Here I provide an overview of these
developments, including the remarkable insight that has been obtained on the
properties of evolved stars.


title:
Effect of transverse anisotropy on inelastic tunneling spectroscopy of
  atomic-scale magnetic chains

abstract:
  We theoretically investigate the effect of transverse magnetic anisotropy on
spin-flip assisted tunneling through atomic spin chains. Using a
phenomenological approach and first-order perturbation theory, we analytically
calculate the inelastic tunneling current, differential conductance and atomic
spin transition rates. We predict the appearance of additional steps in the
differential conductance and a pronounced increase in the spin-flip transition
rate which at low voltages scale quadratically with the ratio of the transverse
anisotropy energy and the sum of the longitudinal anisotropy energy and the
exchange energy. Our results provide intuitive quantitative insight in the role
played by transverse anisotropy in inelastic tunneling spectroscopy of atomic
chains and can be observed under realistic experimental conditions.


title:
Translation-invariant and periodic Gibbs measures for Potts model on a
  Cayley tree

abstract:
  In this paper is studied ferromagnetic three states Potts model on a Cayley
tree of order three and we give explicit formulas for translation-invariant
Gibbs measures. Furthermore, we show that under some conditions on the
parameter of the antiferromagnetic Potts model with q-states with zero external
field on the Cayley tree of order $k>2$, there are exactly 2(2^q-1) periodic
(non translation-invariant) Gibbs measures.


title:
The covering dimension of a distinguished subset of the spectrum
  $M(H^\infty)$ of $H^\infty$ and the algebra of real-symmetric and continuous
  functions on $M(H^\infty)$

abstract:
  We show that the covering dimension, $\dim E$, of the closure $E$ of the
interval $]-1,1[$ in the spectrum of $H^\infty$ equals one. Using Su\'arez's
result that $\dim M(H^\infty)=2$, we then compute the Bass and topological
stable ranks of the algebra $C(M(H^\infty))_{\rm\scriptscriptstyle sym}$ of
real-symmetric continuous functions on $M(H^\infty)$.


title:
Evolution to the equilibrium in a dissipative and time dependent
  billiard

abstract:
  We study the convergence towards the equilibrium for a dissipative and
stochastic time-dependent oval billiard. The dynamics of the system is
described by using a generic four dimensional nonlinear map for the variables:
the angular position of the particle, the angle formed by the trajectory of the
article with the tangent line at the position of the collision, the absolute
velocity of the particle, and the instant of the hit with the boundary. The
dynamics of the stationary state as well as the dynamical evolution towards the
equilibrium is made by using an ensemble of non interacting particles. Finally,
we make a connection with the thermodynamic by using the energy equipartition
theorem.


title: The Riemann hypothesis and holomorphic index in complex dynamics

abstract:
  We give an interpretation of the Riemann hypothesis in terms of complex and
topological dynamics. For example, the Riemann hypothesis is affirmative and
all zeros of the Riemann zeta function are simple if and only if a certain
meromorphic function has no attracting fixed point. To obtain this, we use
holomorphic index (residue fixed point index), which characterizes local
properties of fixed points in complex dynamics.


title: Generating Realistic Synthetic Population Datasets

abstract:
  Modern studies of societal phenomena rely on the availability of large
datasets capturing attributes and activities of synthetic, city-level,
populations. For instance, in epidemiology, synthetic population datasets are
necessary to study disease propagation and intervention measures before
implementation. In social science, synthetic population datasets are needed to
understand how policy decisions might affect preferences and behaviors of
individuals. In public health, synthetic population datasets are necessary to
capture diagnostic and procedural characteristics of patient records without
violating confidentialities of individuals. To generate such datasets over a
large set of categorical variables, we propose the use of the maximum entropy
principle to formalize a generative model such that in a statistically
well-founded way we can optimally utilize given prior information about the
data, and are unbiased otherwise. An efficient inference algorithm is designed
to estimate the maximum entropy model, and we demonstrate how our approach is
adept at estimating underlying data distributions. We evaluate this approach
against both simulated data and on US census datasets, and demonstrate its
feasibility using an epidemic simulation application.


title: Nonhyperbolic step skew-products: Ergodic approximation

abstract:
  We study transitive step skew-product maps modeled over a complete shift of
$k$, $k\ge2$, symbols whose fiber maps are defined on the circle and have
intermingled contracting and expanding regions. These dynamics are genuinely
nonhyperbolic and exhibit simultaneously ergodic measures with positive,
negative, and zero exponents.
  We introduce a set of axioms for the fiber maps and study the dynamics of the
resulting skew-product. These axioms turn out to capture the key mechanisms of
the dynamics of nonhyperbolic robustly transitive maps with compact central
leaves.
  Focusing on the nonhyperbolic ergodic measures (with zero fiber exponent) of
these systems, we prove that such measures are approximated in the weak$\ast$
topology and in entropy by hyperbolic ones. We also prove that they are in the
intersection of the convex hulls of the measures with positive fiber exponent
and with negative fiber exponent. Our methods also allow us to perturb
hyperbolic measures. We can perturb a measure with negative exponent directly
to a measure with positive exponent (and vice-versa), however we lose some
amount of entropy in this process. The loss of entropy is determined by the
difference between the Lyapunov exponents of the measures.


title:
Design of broadband high-efficiency superconducting-nanowire single
  photon detectors

abstract:
  In this paper several designs to maximize the absorption efficiency of
superconducting-nanowire single-photon detectors are investigated. Using a
simple optical cavity consisting of a gold mirror and a SiO2 layer, the
absorption efficiency can be boosted to over 97%: this result is confirmed
experimentally by the realization of an NbTiN-based detector having an overall
system detection efficiency of 85% at 1.31 micrometers. Calculations show that
by sandwiching the nanowire between two dielectric Bragg reflectors, unity
absorption (> 99.9%) could be reached at the peak wavelength for optimized
structures. To achieve broadband high efficiency, a different approach is
considered: a waveguide-coupled detector. The calculations performed in this
work show that, by correctly dimensioning the waveguide and the nanowire,
polarization-insensitive detectors absorbing more than 95% of the injected
photons over a wavelength range of several hundred nm can be designed. We
propose a detector design making use of GaN/AlN waveguides, since these
materials allow lattice-matched epitaxial deposition of Nb(Ti)N films and are
transparent on a very wide wavelength range.


title:
Improving Wireless Physical Layer Security via Exploiting Co-Channel
  Interference

abstract:
  This paper considers a scenario in which a source-destination pair needs to
establish a confidential connection against an external eavesdropper, aided by
the interference generated by another source-destination pair that exchanges
public messages. The goal is to compute the maximum achievable secrecy degrees
of freedom (S.D.o.F) region of a MIMO two-user wiretap network. First, a
cooperative secrecy transmission scheme is proposed, whose feasible set is
shown to achieve all S.D.o.F. pairs on the S.D.o.F. region boundary. In this
way, the determination of the S.D.o.F. region is reduced to a problem of
maximizing the S.D.o.F. pair over the proposed transmission scheme. The maximum
achievable S.D.o.F. region boundary points are obtained in closed form, and the
construction of the precoding matrices achieving the maximum S.D.o.F. region
boundary is provided. The obtained analytical expressions clearly show the
relation between the maximum achievable S.D.o.F. region and the number of
antennas at each terminal.


title:
Scaling of Harmonic Oscillator Eigenfunctions and Their Nodal Sets
  Around the Caustic

abstract:
  We study the scaling asymptotics of the eigenspace projection kernels
$\Pi_{\hbar, E}(x,y)$ of the isotropic Harmonic Oscillator $- \hbar ^2 \Delta +
|x|^2$ of eigenvalue $E = \hbar(N + \frac{d}{2})$ in the semi-classical limit
$\hbar \to 0$. The principal result is an explicit formula for the scaling
asymptotics of $\Pi_{\hbar, E}(x,y)$ for $x,y$ in a $\hbar^{2/3}$ neighborhood
of the caustic $\mathcal C_E$ as $\hbar \to 0.$ The scaling asymptotics are
applied to the distribution of nodal sets of Gaussian random eigenfunctions
around the caustic as $\hbar \to 0$. In previous work we proved that the
density of zeros of Gaussian random eigenfunctions of $\hat{H}_{\hbar}$ have
different orders in the Planck constant $\hbar$ in the allowed and forbidden
regions: In the allowed region the density is of order $\hbar^{-1}$ while it is
$\hbar^{-1/2}$ in the forbidden region. Our main result on nodal sets is that
the density of zeros is of order $\hbar^{-\frac{2}{3}}$ in an
$\hbar^{\frac{2}{3}}$-tube around the caustic. This tube radius is the
`critical radius'. For annuli of larger inner and outer radii $\hbar^{\alpha}$
with $0< \alpha < \frac{2}{3}$ we obtain density results which interpolate
between this critical radius result and our prior ones in the allowed and
forbidden region. We also show that the Hausdorff $(d-2)$-dimensional measure
of the intersection of the nodal set with the caustic is of order $\hbar^{-
\frac{2}{3}}$.


title:
Investigation of Nuclear Phase Transition by Solvababe supersymmetric
  algebraic model and its application in Ru-Rh and Zn-Cu Isotopes

abstract:
  Solvable supersymmetric algebraic model for descriptions of the spherical to
gama unstable shape- phase transition in even and odd mass nuclei is proposed.
This model is based on dual algebraic structure and Richardson - Gaudin method,
where the duality relations between the unitary and quasispin algebraic
structures for the boson and fermion systems are extended to mixed boson-
fermion system. The structure of two type of nuclear supersymmetry schemes,
based on the U(6/2) and U(6/4) supergroups, is discussed. We investigate the
change in level structure induced by the phase transition by doing a quantal
analysis. By using the generalized quasispin algebra, it is shown that the
nuclear supersymmetry concept can be also used for transitional regions in
addition to dynamical symmetry limits. Experimental evidence for the U(5)-O(6)
transition in Ru-Rh and Zn- Cu supermultiplets is presented. The low-states
energy spectra and B(E2)values for these nuclei have been calculated and
compared with the experimental data.


title:
Close-Form Expression of One-Tap Normalized LMS Carrier Phase Recovery
  in Optical Communication Systems

abstract:
  The performance of long-haul high speed coherent optical fiber communication
systems is significantly degraded by the laser phase noise and the equalization
enhanced phase noise (EEPN). In this paper, the analysis of the one-tap
normalized least-mean-square (LMS) carrier phase recovery (CPR) is carried out
and the close-form expression is investigated for quadrature phase shift keying
(QPSK) coherent optical fiber communication systems, in compensating both laser
phase noise and equalization enhanced phase noise. Numerical simulations have
also been implemented to verify the theoretical analysis. It is found that the
one-tap normalized least-mean-square algorithm gives the same analytical
expression for predicting CPR bit-error-rate (BER) floors as the traditional
differential carrier phase recovery, when both the laser phase noise and the
equalization enhanced phase noise are taken into account.


title: Calculation of 2D electronic band structure using matrix mechanics

abstract:
  We extend previous work applying elementary matrix mechanics to
one-dimensional periodic arrays (to generate energy bands) to two-dimensional
arrays. We generate band structures for the square lattice "2D Kronig-Penney
model" (square wells), muffin-tin potential (cylindrical wells), and Gaussian
wells. We then apply the method to periodic arrays of more than one atomic site
in a unit cell, in particular, the case of materials with hexagonal lattices
like graphene. These straightforward extensions of undergraduate-level
calculations allow students to readily determine band structures of current
research interest.


title: Energy cascade in internal wave attractors

abstract:
  One of the pivotal questions in the dynamics of the oceans is related to the
cascade of mechanical energy in the abyss and its contribution to mixing. Here,
we propose internal wave attractors in the large amplitude regime as a unique
self-consistent experimental and numerical setup that models a cascade of
triadic interactions transferring energy from large-scale monochro-matic input
to multi-scale internal wave motion. We also provide signatures of a discrete
wave turbulence framework for internal waves. Finally, we show how beyond this
regime, we have a clear transition to a regime of small-scale high-vorticity
events which induce mixing. Introduction.


title: Non-linear vorticity upsurge in Burgers' flow

abstract:
  We demonstrate that numerical solutions of Burgers' equation can be obtained
by a scale-totality algorithm for fluids of small viscosity (down to one
billionth). Two sets of initial data, modelling simple shears and wall boundary
layers, are chosen for our computations. Most of the solutions are carried out
well into the fully turbulent regime over finely-resolved scales in space and
in time. It is found that an abrupt spatio-temporal concentration in shear
constitutes an essential part during the flow evolution. The vorticity surge
has been instigated by the non-linearity complying with instantaneous enstrophy
production, while ad hoc disturbances play no role in the process. In
particular, the present method predicts the precipitous vorticity
re-distribution and accumulation, predominantly over localised regions of
minute dimension. The growth rate depends on viscosity and is a strong function
of initial data. Nevertheless, the long-time energy decay is
history-independent and is inversely proportional to time. Our results provide
direct evidence of the vorticity proliferation embedded in the equations of
motion. The non-linear intensification is a robust feature, and is ultimately
responsible for the drastic succession in boundary layer profiles over the
intrinsic laminar-turbulent transition (Schubauer and Klebanoff 1955). The
dynamical inception of turbulence can be decrypted by solving the full
time-dependent Navier-Stokes equations which ascribe no instability stages.


title: Computer-generated visual morphology catalog of ~3,000,000 SDSS galaxies

abstract:
  We applied computer analysis to classify the broad morphological type of
~3,000,000 SDSS galaxies. The catalog provides for each galaxy the DR8 object
ID, right ascension, declination, and the certainty of the automatic
classification to spiral or elliptical. The certainty of the classification
allows controlling the accuracy of a subset of galaxies by sacrificing some of
the least certain classifications. The accuracy of the catalog was tested using
galaxies that were classified by the manually annotated Galaxy Zoo catalog. The
results show that the catalog contains ~900,000 spiral galaxies and ~600,000
elliptical galaxies with classification certainty that has a statistical
agreement rate of ~98% with Galaxy Zoo debiased 'superclean' dataset. That also
demonstrates the ability of computers to turn large datasets of galaxy images
into structured catalogs of galaxy morphology. The catalog can be downloaded at
http://vfacstaff.ltu.edu/lshamir/data/morph_catalog , and can be accessed
through public tables on CAS: public.broadMorph.LargeGM,
public.broadMorph.LargeWnnGM, and public.broadMorph.SpectraGM. The image
analysis software that was used to create the catalog is also publicly
available.


title: Tsallis statistics in the income distribution of Brazil

abstract:
  This paper discusses the empirical evidence of Tsallis statistical functions
in the personal income distribution of Brazil. Yearly samples from 1978 to 2014
were linearized by the q-logarithm and straight lines were fitted to the entire
range of the income data in all samples, producing a two-parameters-only single
function representation of the whole distribution in every year. The results
showed that the time evolution of the parameters is periodic and plotting one
in terms of the other reveals a cycle mostly clockwise. It was also found that
the empirical data oscillate periodically around the fitted straight lines with
the amplitude growing as the income values increase. Since the entire income
data range can be fitted by a single function, this raises questions on
previous results claiming that the income distribution is constituted by a well
defined two-classes-base income structure, since such a division in two very
distinct income classes might not be an intrinsic property of societies, but a
consequence of an a priori fitting-choice procedure that may leave aside
possibly important income dynamics at the intermediate levels.

categories: q-fin.EC nlin.AO physics.data-an physics.soc-ph


title:
Long time semiclassical Egorov theorem for $\hbar$-pseudodifferential
  systems

abstract:
  In the Heisenberg picture, we study the semiclassical time evolution of a
bounded quantum observable $Q^w(x,\hbar D_x)$ associated to a $(m\times m)$
matrix-valued symbol $Q$ generated by a semiclassical matrix-valued Hamiltonian
$H\sim H_0+\hbar H_1$. Under a non-crossing assumption on the eigenvalues of
the principal symbol $H_0$ that ensures the existence of almost invariant
subspaces of $L^{2}(\mathbb R^n)\otimes \mathbb C^m$, and for a class of
observables that are semiclassically block-diagonal with respect to the
projections onto these almost invariants subspaces, we establish a long time
matrix-valued version for the semiclassical Egorov theorem valid in a large
time interval of Ehrenfest type $T(\hbar)\simeq log(\hbar^{-1})$.


title: Physics case for a polarised target for AFTER@LHC

abstract:
  We review a number of ideas put forward in favour of the use of a polarised
target along with the proposed idea of a fixed-target experiment using the LHC
beams -- AFTER@LHC. A number of recent studies have shown that single
transverse-spin asymmetries (STSAs) are large enough to be precisely measured
in the region accessible with AFTER@LHC, in particular as regards the Drell-Yan
process as well as single-pion, isolated-photon and jet production. AFTER@LHC
with a polarised target would also be the ideal experimental set-up to measure
the gluon Sivers effect via a number of original quarkonium STSA studies. We
discuss first figures-of-merit based on simulations for AFTER@LHC with a
polarised target.


title: Demonstrating Martian Gravity

abstract:
  The surface gravity on Mars is smaller than the surface gravity on Earth,
resulting in longer falling times. This effect can be simulated on Earth by
taking advantage of air resistance and buoyancy, which cause low density
objects to fall slowly enough to approximate objects falling on the surface of
Mars. We describe a computer simulation based on an experiment that
approximates Martian gravity, and verify our numerical results by performing
the experiment.


title:
Autocrine signaling and quorum sensing: Extreme ends of a common
  spectrum

abstract:
  "Secrete-and-sense cells" can communicate by secreting a signaling molecule
while also producing a receptor that detects the molecule. The cell can
potentially "talk" to itself ("self-communication") or talk to neighboring
cells with the same receptor ("neighbor-communication"). The predominant forms
of secrete-and-sense cells are self-communicating "autocrine cells" that are
largely found in animals, and neighbor-communicating "quorum sensing cells"
that are mostly associated with bacteria. While assumed to function independent
of one another, recent studies have discovered quorum sensing organs and
autocrine signaling microbes. Moreover, similar types of genetic circuits
control many autocrine and quorum sensing cells. We outline these recent
findings and explain how autocrine and quorum sensing are two sides of a
many-sided "dice" created by the versatile secrete-and-sense cell.


title: Broadband illumination of superconducting pair breaking photon detectors

abstract:
  Understanding the detailed behaviour of superconducting pair breaking photon
detectors such as Kinetic Inductance Detectors requires knowledge of the
nonequilibrium quasiparticle energy distributions. We have previously
calculated the steady state distributions resulting from uniform absorption of
monochromatic sub gap and above gap frequency radiation by thin films. In this
work, we use the same methods to calculate the effect of illumination by
broadband sources, such as thermal radiation from astrophysical phenomena or
from the readout system. Absorption of photons at multiple above gap
frequencies is shown to not change the structure of the quasiparticle energy
distribution close to the superconducting gap. Hence for typical absorbed
powers, we find the effects of absorption of broadband pair breaking radiation
can simply be considered as the sum of the effects of absorption of many
monochromatic sources. Distribution averaged quantities, like quasiparticle
generation effciency $\eta$, match exactly a weighted average over the
bandwidth of the source of calculations assuming a monochromatic source. For
sub gap frequencies, however, distributing the absorbed power across multiple
frequencies does change the low energy quasiparticle distribution. For moderate
and high absorbed powers, this results in a significantly larger $\eta$ - a
higher number of excess quasiparticles for a broadband source compared to a
monochromatic source of equal total absorbed power. Typically in KIDs the
microwave power absorbed has a very narrow bandwidth, but in devices with broad
resonance characteristics (low quality factors), this increase in $\eta$ may be
measurable.


title: Nonlocal conservation laws of the constant astigmatism equation

abstract:
  For the constant astigmatism equation, we construct a system of nonlocal
conservation laws (an abelian covering) closed under the reciprocal
transformations. We give functionally independent potentials modulo a Wronskian
type relation.


title:
Noise-resilient Quantum Computing with a Nitrogen-Vacancy Center and
  Nuclear Spins

abstract:
  Selective control of qubits in a quantum register for the purposes of quantum
information processing represents a critical challenge for dense spin ensembles
in solid state systems. Here we present a protocol that achieves a complete set
of selective single and two-qubit gates on nuclear spins in such an ensemble in
diamond facilitated by a nearby NV center. The protocol suppresses internuclear
interactions as well as unwanted coupling between the NV center and other spins
of the ensemble to achieve quantum gate fidelities well exceeding 99% .
Notably, our method can be applied to weakly coupled, distant, spins and
therefore represents a scalable procedure that exploits the exceptional
properties of nuclear spins in diamond as robust quantum memories.


title: Higher-Order Low-Rank Regression

abstract:
  This paper proposes an efficient algorithm (HOLRR) to handle regression tasks
where the outputs have a tensor structure. We formulate the regression problem
as the minimization of a least square criterion under a multilinear rank
constraint, a difficult non convex problem. HOLRR computes efficiently an
approximate solution of this problem, with solid theoretical guarantees. A
kernel extension is also presented. Experiments on synthetic and real data show
that HOLRR outperforms multivariate and multilinear regression methods and is
considerably faster than existing tensor methods.


title:
Discrete maximal regularity and the finite element method for parabolic
  equations

abstract:
  Maximal regularity is a fundamental concept in the theory of partial
differential equations. In this paper, we establish a fully discrete version of
maximal regularity for a parabolic equation. We derive various stability
results in $L^p(0,T;L^q(\Omega))$ norm, $p,q\in (1,\infty)$ for the finite
element approximation with the mass-lumping to the linear heat equation. Our
method of analysis is an operator theoretical one using pure imaginary powers
of operators and might be a discrete version of G.~Dore and A.~Venni (On the
closedness of the sum of two closed operators. \emph{Math.\ Z.},
196(2):189--201, 1987). As an application, optimal order error estimates in
that norm are proved. Furthermore, we study the finite element approximation
for semilinear heat equations with locally Lipschitz continuous nonlinearity
and offer a new method for deriving optimal order error estimates. Some
interesting auxiliary results including discrete Gagliardo-Nirenberg and
Sobolev inequalities are also presented.


title: An Empirical Study on Computing Equilibria in Polymatrix Games

abstract:
  The Nash equilibrium is an important benchmark for behaviour in systems of
strategic autonomous agents. Polymatrix games are a succinct and expressive
representation of multiplayer games that model pairwise interactions between
players. The empirical performance of algorithms to solve these games has
received little attention, despite their wide-ranging applications. In this
paper we carry out a comprehensive empirical study of two prominent algorithms
for computing a sample equilibrium in these games, Lemke's algorithm that
computes an exact equilibrium, and a gradient descent method that computes an
approximate equilibrium. Our study covers games arising from a number of
interesting applications. We find that Lemke's algorithm can compute exact
equilibria in relatively large games in a reasonable amount of time. If we are
willing to accept (high-quality) approximate equilibria, then we can deal with
much larger games using the descent method. We also report on which games are
most challenging for each of the algorithms.


title: Forecasting the Flu: Designing Social Network Sensors for Epidemics

abstract:
  Early detection and modeling of a contagious epidemic can provide important
guidance about quelling the contagion, controlling its spread, or the effective
design of countermeasures. A topic of recent interest has been to design social
network sensors, i.e., identifying a small set of people who can be monitored
to provide insight into the emergence of an epidemic in a larger population. We
formally pose the problem of designing social network sensors for flu epidemics
and identify two different objectives that could be targeted in such sensor
design problems. Using the graph theoretic notion of dominators we develop an
efficient and effective heuristic for forecasting epidemics at lead time. Using
six city-scale datasets generated by extensive microscopic epidemiological
simulations involving millions of individuals, we illustrate the practical
applicability of our methods and show significant benefits (up to twenty-two
days more lead time) compared to other competitors. Most importantly, we
demonstrate the use of surrogates or proxies for policy makers for designing
social network sensors that require from nonintrusive knowledge of people to
more information on the relationship among people. The results show that the
more intrusive information we obtain, the longer lead time to predict the flu
outbreak up to nine days.


title: Lower bound for the Complexity of the Boolean Satisfiability Problem

abstract:
  This paper depicts algorithms for solving the decision Boolean Satisfiability
Problem. An extreme problem is formulated to analyze the complexity of
algorithms and the complexity for solving it. A novel and easy reformulation as
a lottery for an extreme case is presented to determine a stable complexity
around $2^n$. The reformulation point out that the decision Boolean
Satisfiability Problem can only be solved in exponential time. This implies
there is not an efficient algorithm for the NP Class.


title: Does a phase shift occur in an AC arc?

abstract:
  This is a translation of a classic paper in German showing that the apparent
power in an AC arc is larger than the active power although no phase shift
exists between the voltage and the current, indicating that the reactive power
vanishes. The phenomenon studied in this paper gave rise to a variety of
mutually conflicting "power triangle" models relating the active, reactive, and
apparent powers P, Q, and S whose merits are still under debate today.


title:
On direct Arbitrary-Lagrangian-Eulerian ADER-WENO finite volume schemes
  for the HPR model of nonlinear hyperelasticity

abstract:
  This paper is concerned with the numerical solution of the unified first
order hyperbolic formulation of continuum mechanics proposed by Peshkov &
Romenski (HPR model), which is based on the theory of nonlinear hyperelasticity
of Godunov & Romenski . Notably, the governing PDE system is symmetric
hyperbolic and fully consistent with the first and the second principle of
thermodynamics. The nonlinear system of governing equations of the HPR model is
large and includes stiff source terms as well as non-conservative products. In
this paper we solve this model for the first time on moving unstructured meshes
in multiple space dimensions by employing high order accurate one-step
ADER-WENO finite volume schemes in the context of cell-centered direct
Arbitrary-Lagrangian-Eulerian (ALE) algorithms.
  The numerical method is based on a WENO polynomial reconstruction operator on
moving unstructured meshes, a fully-discrete one-step ADER scheme that is able
to deal with stiff sources, a nodal solver with relaxation to determine the
mesh motion, and a path-conservative technique of Castro & Par\`es for the
treatment of non-conservative products. We present numerical results obtained
by solving the HPR model with ADER-WENO-ALE schemes in the stiff relaxation
limit, showing that fluids (Euler or Navier-Stokes limit), as well as purely
elastic or elasto-plastic solids can be simulated in the framework of nonlinear
hyperelasticity with the same system of governing PDE. The obtained results are
in good agreement when compared to exact or numerical reference solutions
available in the literature.


title:
Comment on "Loophole-free Bell inequality violation using electron spins
  separated by 1.3 kilometers"

abstract:
  In a recent article Hensen et al. [Nature 526, 682 (2015)] report on a
sophisticated Bell experiment, simultaneously closing, for the first time,
loopholes for local hidden-variable theories (HVTs). The authors claim that
'local realism' has been refuted, under certain natural assumptions. The aim of
the present Comment is twofold. First, it is urged that the class of local HVTs
that is eliminated by the reported experiment should be specified in greater
detail than is done by the authors. Second, it is argued that the class of
local HVTs that still survives is wide and natural. For instance, hidden
variables describing a 'background' field can exploit the freedom-of-choice
loophole, which cannot be closed for this type of hidden variables. The
dynamics of such background-based theories can be illustrated by existing
systems, e.g. from fluid mechanics.


title:
Application Location Based Service (LBS) Location Search Palembang
  Nature-Based Android

abstract:
  With the development of information systems to make the operating system more
diverse mobile devices, the emergence of the Android operating system that is
open allows users to search for and acquire various information easily and
quickly. Application Search Nature Places is an application that can help bring
information on nearby Places Nature is all around. Can be used in the Android
Operating System and Global Positioning System (GPS). To be able to use this
application, users must be connected to the Internet because it requires data
taken from Google Maps. The main facilities contained in this application is a
feature that makes it Map and Route users in finding the intended location.
With the LBS application is expected to provide information that is accurate,
clear and precise to determine location points Nature Palembang, and can
facilitate local and foreign tourists and the public, especially the city of
Palembang.


title: Principal Component Projection Without Principal Component Analysis

abstract:
  We show how to efficiently project a vector onto the top principal components
of a matrix, without explicitly computing these components. Specifically, we
introduce an iterative algorithm that provably computes the projection using
few calls to any black-box routine for ridge regression.
  By avoiding explicit principal component analysis (PCA), our algorithm is the
first with no runtime dependence on the number of top principal components. We
show that it can be used to give a fast iterative method for the popular
principal component regression problem, giving the first major runtime
improvement over the naive method of combining PCA with regression.
  To achieve our results, we first observe that ridge regression can be used to
obtain a "smooth projection" onto the top principal components. We then sharpen
this approximation to true projection using a low-degree polynomial
approximation to the matrix step function. Step function approximation is a
topic of long-term interest in scientific computing. We extend prior theory by
constructing polynomials with simple iterative structure and rigorously
analyzing their behavior under limited precision.


title: Callias-type operators in von Neumann algebras

abstract:
  We study differential operators on complete Riemannian manifolds which act on
sections of a bundle of finite type modules over a von Neumann algebra with a
trace. We prove a relative index and a Callias-type index theorems for von
Neumann indexes of such operators. We apply these results to obtain a version
of Atiyah's $L^2$-index theorem, which states that the index of a Callias-type
operator on a non-compact manifold $M$ is equal to the $\Gamma$-index of its
lift to a Galois cover of $M$. We also prove the cobordism invariance of the
index of Callias-type operators. In particular, we give a new proof of the
cobordism invariance of the von Neumann index of operators on compact
manifolds.


title:
Cosmological model with fermion and tachyon fields interacting via
  Yukawa-type potential

abstract:
  A model for the universe with tachyonic and fermionic fields interacting
through a Yukawa-type potential is investigated. It is shown that the tachyonic
field answers for the initial accelerated regime and for the subsequent
decelerated regime so that it behaves as an inflaton at early times and as a
matter field at intermediate times, while the fermionic field has the role of a
dark energy constituent, since it leads to an accelerated regime at later
times. The interaction between the fields via a Yukawa-type potential controls
the duration of the decelerated era, since a stronger coupling makes a shorter
decelerated period.


title:
Giant Optical Polarization Rotation Induced by Spin-Orbit Coupling in
  Polarons

abstract:
  We have uncovered a giant gyrotropic magneto-optical response for doped
ferromagnetic manganite La2/3Ca1/3MnO3 around the near room-temperature
paramagnetic-to-ferromagnetic transition. At odds with current wisdom, where
this response is usually assumed to be fundamentally fixed by the electronic
band structure, we point to the presence of small polarons as the driving force
for this unexpected phenomenon. We explain the observed properties by the
intricate interplay of mobility, Jahn-Teller effect and spin-orbit coupling of
small polarons. As magnetic polarons are ubiquitously inherent to many strongly
correlated systems, our results provide an original, general pathway towards
the generation of gigantic gyrotropic responses that can be harnessed for
nonreciprocal devices that exploit the polarization of light.


title: The Push the button algorithm for contragredient Lie superalgebras

abstract:
  The purpose of the present paper is to explain how the push the button
algorithm can be successfully applied to the Vogan superdiagram associated to a
contragredient Lie superalgebra, so to obtain the equivalent super version of
the Borel-De Siebenthal Theorem.


title:
Anharmonic effects in atomic hydrogen: superconductivity and lattice
  dynamical stability

abstract:
  We present first-principles calculations of metallic atomic hydrogen in the
400-600 GPa pressure range in a tetragonal structure with space group
$I4_1/amd$, which is predicted to be its first atomic phase. Our calculations
show a band structure close to the free-electron-like limit due to the high
electronic kinetic energy induced by pressure. Bands are properly described
even in the independent electron approximation fully neglecting the
electron-electron interaction. Linear-response harmonic calculations show a
dynamically stable phonon spectrum with marked Kohn anomalies. Even if the
electron-electron interaction has a minor role in the electronic bands, the
inclusion of electronic ex- change and correlation in the density response is
essential to obtain a dynamically stable structure. Anharmonic effects, which
are calculated within the stochastic self-consistent harmonic approxima- tion,
harden high-energy optical modes and soften transverse acoustic modes up to a
20% in energy. Despite a large impact of anharmonicity has been predicted in
several high-pressure hydrides, here the superconducting critical temperature
is barely affected by anharmonicity, as it is lowered from its harmonic 318 K
value only to 300 K at 500 GPa. We atribute the small impact of anharmoncity on
superconductivity to the absence of softened optical modes and the fairly
uniform distribution of the electron-phonon coupling among the vibrational
modes.


title:
Conservation Law for Massive Scale-Invariant Photons in Weyl-Invariant
  Gravity

abstract:
  It is demonstrated that a Stueckelberg-type gauge theory, coupled to the
scalar-tensor theory of gravity, is invariant under both gauge and Weyl
transformations. Unlike the pure Stueckelberg theory, this coupled Lagrangian
has a genuine Weyl symmetry, with a non-vanishing current. The above is true in
the Jordan frame, whereas in the Einstein frame, the same theory manifests as
Proca theory in presence of pure gravity. It is found that broken scale
invariance leads to simultaneous spontaneous breaking of the gauge symmetry.


title:
A generalized sampling and preconditioning scheme for sparse
  approximation of polynomial chaos expansions

abstract:
  In this paper we propose an algorithm for recovering sparse orthogonal
polynomials using stochastic collocation. Our approach is motivated by the
desire to use generalized polynomial chaos expansions (PCE) to quantify
uncertainty in models subject to uncertain input parameters. The standard
sampling approach for recovering sparse polynomials is to use Monte Carlo (MC)
sampling of the density of orthogonality. However MC methods result in poor
function recovery when the polynomial degree is high. Here we propose a general
algorithm that can be applied to any admissible weight function on a bounded
domain and a wide class of exponential weight functions defined on unbounded
domains. Our proposed algorithm samples with respect to the weighted
equilibrium measure of the parametric domain, and subsequently solves a
preconditioned $\ell^1$-minimization problem, where the weights of the diagonal
preconditioning matrix are given by evaluations of the Christoffel function. We
present theoretical analysis to motivate the algorithm, and numerical results
that show our method is superior to standard Monte Carlo methods in many
situations of interest. Numerical examples are also provided that demonstrate
that our proposed Christoffel Sparse Approximation algorithm leads to
comparable or improved accuracy even when compared with Legendre and Hermite
specific algorithms.


title: Helicity, Topology and Kelvin Waves in reconnecting quantum knots

abstract:
  Helicity is a topological invariant that measures the linkage and knottedness
of lines, tubes and ribbons. As such, it has found myriads of applications in
astrophysics and solar physics, in fluid dynamics, in atmospheric sciences, and
in biology. In quantum flows, where topology-changing reconnection events are a
staple, helicity appears as a key quantity to study. However, the usual
definition of helicity is not well posed in quantum vortices, and its
computation based on counting links and crossings of vortex lines can be
downright impossible to apply in complex and turbulent scenarios. We present a
new definition of helicity which overcomes these problems. With it, we show
that only certain reconnection events conserve helicity. In other cases
helicity can change abruptly during reconnection. Furthermore, we show that
these events can also excite Kelvin waves, which slowly deplete helicity as
they interact nonlinearly, thus linking the theory of vortex knots with
observations of quantum turbulence.


title:
Topological energy transfer in an optomechanical system with exceptional
  points

abstract:
  Topological operations have the merit of achieving certain goals without
requiring accurate control over local operational details. To date, topological
operations have been used to control geometric phases, and have been proposed
as a means for controlling the state of certain systems within their degenerate
subspaces[1-8]. More recently, it was predicted that topological operations can
be extended to transfer energy between normal modes, provided that the system
possesses a specific type of degeneracy known as an exceptional point
(EP)[9-11]. Here we demonstrate the transfer of energy between two modes of a
cryogenic optomechanical device by topological operations. We show that this
transfer arises from the presence of an EP in the device's spectrum. We also
show that this transfer is non-reciprocal[12-14]. These results open new
directions in system control; they also open the possibility of exploring other
dynamical effects related to EPs[15,16], as well as the behavior of thermal and
quantum fluctuations in the vicinity of EPs.


title:
Matrix Sturm-Liouville equation with a Bessel-type singularity on a
  finite interval

abstract:
  The matrix Sturm-Liouville equation on a finite interval with a Bessel-type
singularity in the end of the interval is studied. Special fundamental systems
of solutions for this equation are constructed: analytic Bessel-type solutions
with the prescribed behavior at the singular point and Birkhoff-type solutions
with the known asymptotics for large values of the spectral parameter. The
asymptotic formulas for Stokes multipliers, connecting these two fundamental
systems of solutions, are derived. We also set boundary conditions and obtain
asymptotic formulas for the spectral data (the eigenvalues and the weight
matrices) of the boundary value problem. Our results will be useful in the
theory of direct and inverse spectral problems.


title:
Heating and Acceleration of the Fast Solar Wind by Alfv\'{e}n Wave
  Turbulence

abstract:
  We present numerical simulations of reduced magnetohydrodynamic (RMHD)
turbulence in a magnetic flux tube at the center of a polar coronal hole. The
model for the background atmosphere is a solution of the momentum equation, and
includes the effects of wave pressure on the solar wind outflow. Alfv\'{e}n
waves are launched at the coronal base, and reflect at various heights due to
variations in Alfv\'{e}n speed and outflow velocity. The turbulence is driven
by nonlinear interactions between the counter-propagating Alfv\'{e}n waves.
Results are presented for two models of the background atmosphere. In the first
model the plasma density and Alfv\'{e}n speed vary smoothly with height,
resulting in minimal wave reflections and low energy dissipation rates. We find
that the dissipation rate is insufficient to maintain the temperature of the
background atmosphere. The standard phenomenological formula for the
dissipation rate significantly overestimates the rate derived from our RMHD
simulations, and a revised formula is proposed. In the second model we
introduce additional density variations along the flux tube with a correlation
length of 0.04 $R_\odot$ and with relative amplitude of $10 \%$. These density
variations simulate the effects of compressive MHD waves on the Alfv\'{e}n
waves. We find that such variations significantly enhance the wave reflection
and thereby the turbulent dissipation rates, producing enough heat to maintain
the background atmosphere. We conclude that interactions between Alfv\'{e}n-
and compressive waves may play an important role in the turbulent heating of
the fast solar wind.


title: Electromagnetic instability induced by neutrino interaction

abstract:
  We consider the generation and evolution of magnetic field in a primordial
plasma at temperature T < 1 MeV in presence of asymmetric neutrino background
i.e. the number densities of right- handed and left-handed neutrinos are not
same. Semi-classical equations of motion of a charged fermion are derived using
the effective low-energy Lagrangian. It is shown that the spin degree of
freedom of the charged fermion couples with the neutrino background. Using this
kinetic equation we study the collective modes of the plasma. We find that
there exist an unstable mode. This instability is closely related with the
instability induced by chiral-anomaly in high temperature T > 80 TeV plasma
where right and left-handed electrons are out of equilibrium. We find that at
the temperatures below the neutrino decoupling the instability can produce
magnetic field of 10 Gauss in the Universe. We discuss cosmological
implications of the results.


title: Joint ML calibration and DOA estimation with separated arrays

abstract:
  This paper investigates parametric direction-of-arrival (DOA) estimation in a
particular context: i) each sensor is characterized by an unknown complex gain
and ii) the array consists of a collection of subarrays which are substantially
separated from each other leading to a structured noise covariance matrix. We
propose two iterative algorithms based on the maximum likelihood (ML)
estimation method adapted to the context of joint array calibration and DOA
estimation. Numerical simulations reveal that the two proposed schemes, the
iterative ML (IML) and the modified iterative ML (MIML) algorithms for joint
array calibration and DOA estimation, outperform the state of the art methods
and the MIML algorithm reaches the Cram\'er-Rao bound for a low number of
iterations.


title:
Clustering with a Reject Option: Interactive Clustering as Bayesian
  Prior Elicitation

abstract:
  A good clustering can help a data analyst to explore and understand a data
set, but what constitutes a good clustering may depend on domain-specific and
application-specific criteria. These criteria can be difficult to formalize,
even when it is easy for an analyst to know a good clustering when she sees
one. We present a new approach to interactive clustering for data exploration,
called \ciif, based on a particularly simple feedback mechanism, in which an
analyst can choose to reject individual clusters and request new ones. The new
clusters should be different from previously rejected clusters while still
fitting the data well. We formalize this interaction in a novel Bayesian prior
elicitation framework. In each iteration, the prior is adapted to account for
all the previous feedback, and a new clustering is then produced from the
posterior distribution. To achieve the computational efficiency necessary for
an interactive setting, we propose an incremental optimization method over data
minibatches using Lagrangian relaxation. Experiments demonstrate that \ciif can
produce accurate and diverse clusterings.


title: Van Est isomorphism for homogeneous cochains

abstract:
  VB-groupoids define a special class of Lie groupoids which carry a compatible
linear structure. In this paper, we show that their differentiable cohomology
admits a refinement by considering the complex of cochains which are
k-homogeneous on the linear fiber. Our main result is a Van Est theorem for
such cochains. We also work out two applications to the general theory of
representations of Lie groupoids and algebroids. The case k=1 yields a Van Est
map for representations up to homotopy on 2-term graded vector bundles.
Arbitrary k-homogeneous cochains on suitable VB-groupoids lead to a novel Van
Est theorem for differential forms on Lie groupoids with values in a
representation.


title:
The Matsu Wheel: A Cloud-based Framework for Efficient Analysis and
  Reanalysis of Earth Satellite Imagery

abstract:
  Project Matsu is a collaboration between the Open Commons Consortium and NASA
focused on developing open source technology for the cloud-based processing of
Earth satellite imagery. A particular focus is the development of applications
for detecting fires and floods to help support natural disaster detection and
relief. Project Matsu has developed an open source cloud-based infrastructure
to process, analyze, and reanalyze large collections of hyperspectral satellite
image data using OpenStack, Hadoop, MapReduce, Storm and related technologies.
  We describe a framework for efficient analysis of large amounts of data
called the Matsu "Wheel." The Matsu Wheel is currently used to process incoming
hyperspectral satellite data produced daily by NASA's Earth Observing-1 (EO-1)
satellite. The framework is designed to be able to support scanning queries
using cloud computing applications, such as Hadoop and Accumulo. A scanning
query processes all, or most of the data, in a database or data repository.
  We also describe our preliminary Wheel analytics, including an anomaly
detector for rare spectral signatures or thermal anomalies in hyperspectral
data and a land cover classifier that can be used for water and flood
detection. Each of these analytics can generate visual reports accessible via
the web for the public and interested decision makers. The resultant products
of the analytics are also made accessible through an Open Geospatial Compliant
(OGC)-compliant Web Map Service (WMS) for further distribution. The Matsu Wheel
allows many shared data services to be performed together to efficiently use
resources for processing hyperspectral satellite image data and other, e.g.,
large environmental datasets that may be analyzed for many purposes.


title:
Solving Resource Recharging Station Location-routing Problem through a
  Resource-space-time Network Representation

abstract:
  The resource recharging station location routing problem is a generalization
of the location routing problem with sophisticated and critical resource
consumption and recharging constraints. Based on a representation of
discretized acyclic resource-space-time networks, we propose a generic
formulation to optimize dynamic infrastructure location and routes decisions.
The proposed integer linear programming formulation could greatly simplify the
modeling representation of time window, resource change, and sub-tour
constraints through a well-structured multi-dimensional network. An
approximation solution framework based on the Lagrangian relaxation is
developed to decompose the problem to a knapsack sub-problem for selecting
recharging stations and a vehicle routing sub-problem in a space-time network.
Both sub-problems can be solved through dynamic programming algorithms to
obtain optimal solution. A number of experiments are used to demonstrate the
Lagrangian multiplier adjustment-based location routing decision making, as
well as the effectiveness of the developed algorithm in large-scale networks.


title: Bi-scalar modified gravity and cosmology with conformal invariance

abstract:
  We investigate the cosmological applications of a bi-scalar modified gravity
that exhibits partial conformal invariance, which could become full conformal
invariance in the absence of the usual Einstein-Hilbert term and introducing
additionally either the Weyl derivative or properly rescaled fields. Such a
theory is constructed by considering the action of a non-minimally
conformally-coupled scalar field, and adding a second scalar allowing for a
nonminimal derivative coupling with the Einstein tensor and the energy-momentum
tensor of the first field. At a cosmological framework we obtain an effective
dark-energy sector constituted from both scalars. In the absence of an explicit
matter sector we extract analytical solutions, which for some parameter regions
correspond to an effective matter era and/or to an effective radiation era,
thus the two scalars give rise to "mimetic dark matter" or to "dark radiation"
respectively. In the case where an explicit matter sector is included we obtain
a cosmological evolution in agreement with observations, that is a transition
from matter to dark energy era, with the onset of cosmic acceleration.
Furthermore, for particular parameter regions, the effective dark-energy
equation of state can transit to the phantom regime at late times. These
behaviours reveal the capabilities of the theory, since they arise purely from
the novel, bi-scalar construction and the involved couplings between the two
fields.


title: Suprema of continuous functions on connected spaces

abstract:
  Let $K$ be a compact Hausdorff space and let $(f_n)_{n\in \N}$ be a pairwise
disjoint sequence of continuous functions from $K$ into $[0,1]$. We say that a
compact space $L$ \emph{adds supremum} of $(f_n)_{n\in \N}$ in $K$ if there
exists a continuous surjection $\pi:L\longrightarrow K$ such that there exists
$sup\{f_n\circ\pi:n\in \N\}$ in $C(L)$. Moreover, we expect that $L$ preserves
suprema of disjoint continuous functions which already existed in $C(K)$.
Namely, if $sup\{g_n:n\in \N\}$ exists in $C(K)$, we must have
$sup\{g_n\circ\pi:n\in \N\}$ in $C(L)$.
  This paper studies the preservation of connectedness in extensions by
continuous functions -- a technique developed by Piotr Koszmider to add suprema
of continuous functions on Hausdorff connected compact spaces -- proving the
following results:
  (1) If $K$ is a metrizable and locally connected compactum, then any
extension of $K$ by continuous functions is connected (but it may be not
locally connected).
  (2) There exists a disconnected extension of a metrizable connected compactum
$K$.
  (3) For any metrizable compactum $K$ there exists a disconnected $L$ which is
obtained from $K$ by finitely many extensions by continuous functions.


title: Reducing the fine-tuning of gauge-mediated SUSY breaking

abstract:
  Despite their appealing features, models with gauge-mediated supersymmetry
breaking (GMSB) typically present a high degree of fine-tuning, due to the
initial absence of the top trilinear scalar couplings, $A_t=0$. In this paper,
we carefully evaluate such a tuning, showing that is worse than per mil in the
minimal model. Then, we examine some existing proposals to generate $A_t\neq 0$
term in this context. We find that, although the stops can be made lighter,
usually the tuning does not improve (it may be even worse), with some
exceptions, which involve the generation of $A_t$ at one loop or tree level. We
examine both possibilities and propose a conceptually simplified version of the
latter; which is arguably the optimum GMSB setup (with minimal matter content),
concerning the fine-tuning issue. The resulting fine-tuning is better than one
per mil, still severe but similar to other minimal supersymmetric standard
model constructions. We also explore the so-called "little $A_t^2/m^2$
problem", i.e. the fact that a large $A_t$-term is normally accompanied by a
similar or larger sfermion mass, which typically implies an increase in the
fine-tuning. Finally, we find the version of GMSB for which this ratio is
optimized, which, nevertheless, does not minimize the fine-tuning.


title:
Family-joining: A fast distance-based method for constructing generally
  labeled trees

abstract:
  The widely used model for evolutionary relationships is a bifurcating tree
with all taxa/observations placed at the leaves. This is not appropriate if the
taxa have been densely sampled across evolutionary time and may be in a direct
ancestral relationship, or if there is not enough information to fully resolve
all the branching points in the evolutionary tree. In this paper, we present a
fast distance-based agglomeration method called family-joining (FJ) for
constructing so-called generally labeled trees in which taxa may be placed at
internal vertices and the tree may contain polytomies. FJ constructs such trees
on the basis of pairwise distances and a distance threshold. We tested three
methods for threshold selection, FJ-AIC, FJ-BIC and FJ-CV, which minimize
Akaike information criterion, Bayesian information criterion, and
cross-validation error, respectively. When compared with related methods on
simulated data, FJ-BIC was among the best at reconstructing the correct tree
across a wide range of simulation scenarios. FJ-BIC was applied to HIV
sequences sampled from individuals involved in a known transmission chain. The
FJ-BIC tree was found to be compatible with almost all transmission events. On
average, internal branches in the FJ-BIC tree have higher bootstrap support
than branches in the leaf-labeled bifurcating tree constructed using RAxML.
$36\%$ and $25\%$ of the internal branches in the FJ-BIC tree and RAxML tree,
respectively, have bootstrap support greater than $70\%$. To the best of our
knowledge the method presented here is the first attempt at modeling
evolutionary relationships using generally labeled trees.


title: Extension complexity of polytopes with few vertices or facets

abstract:
  We study the extension complexity of polytopes with few vertices or facets.
On the one hand, we provide a complete classification of $d$-polytopes with at
most $d+4$ vertices according to their extension complexity: Out of the
super-exponentially many $d$-polytopes with $d+4$ vertices, all have extension
complexity $d+4$ except for some families of size $\theta(d^2)$. On the other
hand, we show that generic realizations of simplicial/simple $d$-polytopes with
$d+1+\alpha$ vertices/facets have extension complexity at least $2
\sqrt{d(d+\alpha)} -d + 1$, which shows that for all $d>(\frac{\alpha-1}{2})^2$
there are $d$-polytopes with $d+1+\alpha$ vertices or facets and extension
complexity $d+1+\alpha$.


title:
Microwave dynamics of high aspect ratio superconducting nanowires
  studied using self-resonance

abstract:
  We study the microwave impedance of extremely high aspect ratio (length/width
~ 5,000) superconducting niobium nitride nanowires. The nanowires are
fabricated in a compact meander geometry that is in series with the center
conductor of a 50 ohm coplanar waveguide transmission line. The transmission
coefficient of the sample is measured up to 20 GHz. At high frequency, a peak
in the transmission coefficient is seen. Numerical simulations show that this
is a half-wave resonance along the length of the nanowire, where the nanowire
acts as a high impedance, slow wave transmission line. This resonance sets the
upper frequency limit for these nanowires as inductive elements. Fitting
simulations to the measured resonance enables a precise determination of the
nanowire's complex sheet impedance at the resonance frequency. The real part is
a measure of dissipation, while the imaginary part is dominated by kinetic
inductance. We characterize the dependence of the sheet resistance and sheet
inductance on both temperature and current and compare the results to recent
theoretical predictions for disordered superconductors. These results can aid
in the understanding of high frequency devices based on superconducting
nanowires. They may also lead to the development of novel superconducting
devices such as ultra-compact resonators and slow-wave structures.


title: Sharp detection in PCA under correlations: all eigenvalues matter

abstract:
  Principal component analysis (PCA) is a widely used method for dimension
reduction. In high dimensional data, the "signal" eigenvalues corresponding to
weak principal components (PCs) do not necessarily separate from the bulk of
the "noise" eigenvalues. Therefore, popular tests based on the largest
eigenvalue have little power to detect weak PCs. In the special case of the
spiked model, certain tests asymptotically equivalent to linear spectral
statistics (LSS)---averaging effects over all eigenvalues---were recently shown
to achieve some power.
  We consider a nonparametric, non-Gaussian generalization of the spiked model
to the setting of Marchenko and Pastur (1967). This allows a general bulk of
the noise eigenvalues, accomodating correlated variables even under the null
hypothesis of no significant PCs.
  We develop new tests based on LSS to detect weak PCs in this model. We show
using the CLT for LSS that the optimal LSS satisfy a Fredholm integral equation
of the first kind. We develop algorithms to solve it, building on our recent
method for computing the limit empirical spectrum. In contrast to the standard
spiked model, we find that under "widely spread" null eigenvalue distributions,
the new tests have a lot of power.


title: Enablers and Inhibitors in Causal Justifications of Logic Programs

abstract:
  To appear in Theory and Practice of Logic Programming (TPLP). In this paper
we propose an extension of logic programming (LP) where each default literal
derived from the well-founded model is associated to a justification
represented as an algebraic expression. This expression contains both causal
explanations (in the form of proof graphs built with rule labels) and terms
under the scope of negation that stand for conditions that enable or disable
the application of causal rules. Using some examples, we discuss how these new
conditions, we respectively call "enablers" and "inhibitors", are intimately
related to default negation and have an essentially different nature from
regular cause-effect relations. The most important result is a formal
comparison to the recent algebraic approaches for justifications in LP:
"Why-not Provenance" (WnP) and "Causal Graphs" (CG). We show that the current
approach extends both WnP and CG justifications under the Well-Founded
Semantics and, as a byproduct, we also establish a formal relation between
these two approaches.


title:
A unified concept of effective one component plasma for hot dense
  plasmas

abstract:
  Orbital-free molecular dynamics simulations are used to benchmark two popular
models for hot dense plasmas: the one component plasma (OCP) and the Yukawa
model. A unified concept emerges where an effective OCP (eOCP) is constructed
from the short-range structure of the plasma. An unambiguous ionization and the
screening length can be defined and used for a Yukawa system, which reproduces
the long range structure with finite compressibility. Similarly, the dispersion
relation of longitudinal waves is consistent with the screened model at
vanishing wavenumber but merges with the OCP at high wavenumber. Additionally,
the eOCP reproduces the overall relaxation timescales of the correlation
functions associated with ionic motion. In the hot dense regime, this unified
concept of eOCP can be fruitfully applied to deduce properties such as the
equation of state, ionic transport coefficients, and the ion feature in x-ray
Thomson scattering experiments.


title: Relative p-adic Hodge theory, II: Imperfect period rings

abstract:
  In a previous paper, we constructed a category of (phi, Gamma)-modules
associated to any adic space over Q_p with the property that the etale (phi,
Gamma)-modules correspond to etale Q_p-local systems; these involve sheaves of
period rings for Scholze's pro-etale topology. In this paper, we first extend
Kiehl's theory of coherent sheaves on rigid analytic spaces to a theory of
pseudocoherent sheaves on adic spaces, then construct a corresponding theory of
pseudocoherent (phi, Gamma)-modules. We then relate these objects to a more
explicit construction in case the space comes equipped with a suitable infinite
etale cover; in this case, one can decomplete the period sheaves and establish
an analogue of the theorem of Cherbonnier-Colmez on the overconvergence of
p-adic Galois representations. As an application, we show that relative (phi,
Gamma)-modules in our sense coincide with the relative (phi, Gamma)-modules
constructed by Andreatta and Brinon in the geometric setting where the latter
can be constructed. As another application, we establish that the category of
pseudocoherent (phi, Gamma)-modules on an arbitrary rigid analytic space over a
p-adic field is abelian, satisfies the ascending chain condition, and is stable
under various natural derived functors (including Hom, tensor product, and
pullback). Applications to the etale cohomology of pro-etale local systems will
be given in a subsequent paper.


title: Bound collective modes in nonuniform superconductors

abstract:
  We study dynamics of a superconducting condensate in the presence of a domain
wall defect in the order parameter. We find that broken translation and
reflection symmetries result in new collective excitations, bound to the domain
wall region. Two additional amplitude/Higgs modes lie below the bulk
pairbreaking edge $2\Delta$; one of them is a Goldstone mode with vanishing
excitation energy. Spectrum of bound collective modes is related to the
topological structure and stability of the domain wall. The `unbound' bulk
collective modes and transverse gauge field mostly propagate across the domain
wall, but the longitudinal component of the gauge field is completely
reflected. Softening of the amplitude mode suggests reduced damping and
possible route to its detection in geometrically confined superfluids or in
superconductor-ferromagnetic heterostructures.


title: Symbol Length of $p$-Algebras of Prime Exponent

abstract:
  We prove that if the maximal dimension of an anisotropic homogeneous
polynomial form of prime degree $p$ over a field $F$ with
$\operatorname{char}(F)=p$ is a finite integer $d$ greater than 1 then the
symbol length of $p$-algebras of exponent $p$ over $F$ is bounded from above by
$\left \lceil \frac{d-1}{p} \right \rceil-1$, and show that every two tensor
products of symbol algebras of lengths $k$ and $\ell$ with $(k+\ell) p \geq
d-1$ can be modified so that they share a common slot. For $p=2$, we obtain an
upper bound of $\frac{u(F)}{2}-1$ for the symbol length, which is sharp when
$I_q^3 F=0$.


title: Lossy Compression with Near-uniform Encoder Outputs

abstract:
  It is well known that lossless compression of a discrete memoryless source
with near-uniform encoder output is possible at a rate above its entropy if and
only if the encoder is randomized. This work focuses on deriving conditions for
near-uniform encoder output(s) in the Wyner-Ziv and the distributed lossy
compression problems. We show that in the Wyner-Ziv problem, near-uniform
encoder output and operation close to the WZ-rate limit is simultaneously
possible, whereas in the distributed lossy compression problem, jointly
near-uniform outputs is achievable in the interior of the distributed lossy
compression rate region if the sources share non-trivial G\'{a}cs-K\"{o}rner
common information.


title: Cosmological dynamics of extended chameleons

abstract:
  We investigate the cosmological dynamics of the recently proposed extended
chameleon models at both background and linear perturbation levels. Dynamical
systems techniques are employed to fully characterize the evolution of the
universe at the largest distances, while structure formation is analysed at
sub-horizon scales within the quasi-static approximation. The late time
dynamical transition from dark matter to dark energy domination can be well
described by almost all extended chameleon models considered, with no
deviations from $\Lambda$CDM results at both background and perturbation
levels. The results obtained in this work confirm the cosmological viability of
extended chameleons as alternative dark energy models.


title: Structured illumination microscopy image reconstruction algorithm

abstract:
  Structured illumination microscopy (SIM) is a very important super-resolution
microscopy technique, which provides high speed super-resolution with about
two-fold spatial resolution enhancement. Several attempts aimed at improving
the performance of SIM reconstruction algorithm have been reported. However,
most of these highlight only one specific aspect of the SIM reconstruction --
such as the determination of the illumination pattern phase shift accurately --
whereas other key elements -- such as determination of modulation factor,
estimation of object power spectrum, Wiener filtering frequency components with
inclusion of object power spectrum information, translocating and the merging
of the overlapping frequency components -- are usually glossed over
superficially. In addition, most of the work reported lie scattered throughout
the literature and a comprehensive review of the theoretical background is
found lacking. The purpose of the present work is two-fold: 1) to collect the
essential theoretical details of SIM algorithm at one place, thereby making
them readily accessible to readers for the first time; and 2) to provide an
open source SIM reconstruction code (named OpenSIM), which enables users to
interactively vary the code parameters and study it's effect on reconstructed
SIM image.


title: Constant slope maps and the Vere-Jones classification

abstract:
  We study continuous countably piecewise monotone interval maps, and formulate
conditions under which these are conjugate to maps of constant slope,
particularly when this slope is given by the topological entropy of the map. We
confine our investigation to the Markov case and phrase our conditions in the
terminology of the Vere-Jones classification of infinite matrices.


title: Localization, Whitehead groups, and the Atiyah Conjecture

abstract:
  Let Wh^w(G) be the K_1-group of square matrices over the integral group ring
ZG which are not necessarily invertible but induce weak isomorphisms after
passing to Hilbert space completions. Let D(G) be the division closure of ZG in
the algebra U(G) of operators affiliated to the group von Neumann algebra. Let
C be the smallest class of groups which contains all free groups and is closed
under directed unions and extensions with elementary amenable quotients. Let G
be a torsionfree group which belongs to C. Then we prove that Wh^w(G) is
isomorphic to K_1(D(G)). Furthermore we show that D(G) is a skew field and henc
K_1(\D(G)) is the abelianization of the multiplicative group of units in D(G).


title:
Fast radio bursts and their gamma-ray or radio afterglows as Kerr-Newman
  black hole binaries

abstract:
  Fast radio bursts (FRBs) are radio transients lasting only about a few
milliseconds. They seem to occur at cosmological distances. We propose that
these events can be originated in the collapse of the magnetosphere of
Kerr-Newman black holes (KNBHs). We show that the closed orbits of charged
particles in the magnetosphere of these objects are unstable. After examining
the dependencies on the specific charge of the particle and the spin and charge
of the KNBH, we conclude that the resulting timescale and radiation mechanism
fit well with the extant observations of FRBs. Furthermore, we argue that the
merger of a KNBH binary is one of the plausible central engines for potential
gamma-ray or radio afterglow following a certain FRBs, and can also account for
gravitational wave (GW) events like GW 150914. Our model leads to predictions
that can be tested by combined multi-wavelength electromagnetic and GW
observations.


title:
Emergence of correlated optics in one-dimensional waveguides for
  classical and quantum atomic gases

abstract:
  We analyze the emergence of correlated optical phenomena in the transmission
of light through a waveguide that confines classical or ultracold quantum
degenerate atomic ensembles. The conditions of the correlated collective
response are identified in terms of atom density, thermal broadening, and
photon losses by using stochastic Monte-Carlo simulations and transfer matrix
methods of transport theory. We also calculate the "cooperative Lamb shift" for
the waveguide transmission resonance, and discuss line shifts that are specific
to effectively one-dimensional waveguide systems.

categories: quant-ph cond-mat.quant-gas physics.atom-ph physics.optics


title:
Hubbard band or oxygen vacancy states in the correlated electron metal
  SrVO$_3$?

abstract:
  We study the effect of oxygen vacancies on the electronic structure of the
model strongly correlated metal SrVO$_3$. By means of angle-resolved
photoemission (ARPES) synchrotron experiments, we investigate the systematic
effect of the UV dose on the measured spectra. We observe the onset of a
spurious dose-dependent prominent peak at an energy range were the lower
Hubbard band has been previously reported in this compound, raising questions
on its previous interpretation. By a careful analysis of the dose dependent
effects we succeed in disentangling the contributions coming from the oxygen
vacancy states and from the lower Hubbard band. We obtain the intrinsic ARPES
spectrum for the zero-vacancy limit, where a clear signal of a lower Hubbard
band remains. We support our study by means of state-of-the-art ab initio
calculations that include correlation effects and the presence of oxygen
vacancies. Our results underscore the relevance of potential spurious states
affecting ARPES experiments in correlated metals, which are associated to the
ubiquitous oxygen vacancies as extensively reported in the context of a
two-dimensional electron gas (2DEG) at the surface of insulating $d^0$
transition metal oxides.


title: Prime Factoring and The Complexity Of

abstract:
  A difference equation based method of determining two factors of a composite
is presented. The feasibility of P-complexity is shown. Presentation of
material is non-theoretical; intended to be accessible to a broader audience of
non academic and theoretical practitioners.


title: Obstruction theory for coincidences of multiple maps

abstract:
  Let $f_1,..., f_k:X\to N$ be maps from a complex $X$ to a compact manifold
$N$, $k\ge 2$. In previous works \cite{BLM,MS}, a Lefschetz type theorem was
established so that the non-vanishing of a Lefschetz type coincidence class
$L(f_1,...,f_k)$ implies the existence of a coincidence $x\in X$ such that
$f_1(x)=...=f_k(x)$. In this paper, we investigate the converse of the
Lefschetz coincidence theorem for multiple maps. In particular, we study the
obstruction to deforming the maps $f_1,...,f_k$ to be coincidence free. We
construct an example of two maps $f_1,f_2:M\to T$ from a sympletic $4$-manifold
$M$ to the $2$-torus $T$ such that $f_1$ and $f_2$ cannot be homotopic to
coincidence free maps but for {\it any} $f:M\to T$, the maps $f_1,f_2,f$ are
deformable to be coincidence free.


title: Exact solutions for hydrodynamic interactions of two squirming spheres

abstract:
  We provide exact solutions of the Stokes equations for a squirming sphere
close to a no-slip surface, both planar and spherical, and for the interactions
between two squirmers, in three dimensions. These allow the hydrodynamic
interactions of swimming microscopic organisms with confining boundaries, or
each other, to be determined for arbitrary separation and, in particular, in
the close proximity regime where approximate methods based on point singularity
descriptions cease to be valid. We give a detailed description of the circular
motion of an arbitrary squirmer moving parallel to a no-slip spherical boundary
or flat free surface at close separation, finding that the circling generically
has opposite sense at free surfaces and at solid boundaries. While the
asymptotic interaction is symmetric under head-tail reversal of the swimmer, in
the near field microscopic structure can result in significant asymmetry. We
also find the translational velocity towards the surface for a simple model
with only the lowest two squirming modes. By comparing these to asymptotic
approximations of the interaction we find that the transition from near- to
far-field behaviour occurs at a separation of about two swimmer diameters.
These solutions are for the rotational velocity about the wall normal, or
common diameter of two spheres, and the translational speed along that same
direction, and are obtained using the Lorentz reciprocal theorem for Stokes
flows in conjunction with known solutions for the conjugate Stokes drag
problems, the derivations of which are demonstrated here for completeness. The
analogous motions in the perpendicular directions, i.e. parallel to the wall,
currently cannot be calculated exactly since the relevant Stokes drag solutions
needed for the reciprocal theorem are not available.


title:
Robust AN-Aided Beamforming and Power Splitting Design for Secure MISO
  Cognitive Radio With SWIPT

abstract:
  A multiple-input single-output cognitive radio downlink network is studied
with simultaneous wireless information and power transfer. In this network, a
secondary user coexists with multiple primary users and multiple energy
harvesting receivers. In order to guarantee secure communication and energy
harvesting, the problem of robust secure artificial noise-aided beamforming and
power splitting design is investigated under imperfect channel state
information (CSI). Specifically, the transmit power minimization problem and
the max-min fairness energy harvesting problem are formulated for both the
bounded CSI error model and the probabilistic CSI error model. These problems
are non-convex and challenging to solve. A one-dimensional search algorithm is
proposed to solve these problems based on ${\cal S}\text{-Procedure} $ under
the bounded CSI error model and based on Bernstein-type inequalities under the
probabilistic CSI error model. It is shown that the optimal robust secure
beamforming can be achieved under the bounded CSI error model, whereas a
suboptimal beamforming solution can be obtained under the probabilistic CSI
error model. A tradeoff is elucidated between the secrecy rate of the secondary
user receiver and the energy harvested by the energy harvesting receivers under
a max-min fairness criterion.


title: Moduli spaces of stable sheaves on Enriques surfaces

abstract:
  We shall study the existence condition of slope stable sheaves on Enriques
surfaces. We also gives a different proof of the irreducibility of the moduli
spaces of rank 2 stable sheaves.


title: Periodicity in Rectangular Arrays

abstract:
  We discuss several two-dimensional generalizations of the familiar
Lyndon-Schutzenberger periodicity theorem for words. We consider the notion of
primitive array (as one that cannot be expressed as the repetition of smaller
arrays). We count the number of m x n arrays that are primitive. Finally, we
show that one can test primitivity and compute the primitive root of an array
in linear time.


title: Sparse Linear Regression via Generalized Orthogonal Least-Squares

abstract:
  Sparse linear regression, which entails finding a sparse solution to an
underdetermined system of linear equations, can formally be expressed as an
$l_0$-constrained least-squares problem. The Orthogonal Least-Squares (OLS)
algorithm sequentially selects the features (i.e., columns of the coefficient
matrix) to greedily find an approximate sparse solution. In this paper, a
generalization of Orthogonal Least-Squares which relies on a recursive relation
between the components of the optimal solution to select L features at each
step and solve the resulting overdetermined system of equations is proposed.
Simulation results demonstrate that the generalized OLS algorithm is
computationally efficient and achieves performance superior to that of existing
greedy algorithms broadly used in the literature.


title:
Andreev Bound States in Superconducting Films and Confined Superfluid
  He-3

abstract:
  This paper reviews the confinement-driven phase transitions, and the
prediction of superfluid phases with broken time-reversal or translational
symmetry in thin films. The new phases are a result of particle-hole coherent
Andreev scattering processes that create quasiparticle states with energies
inside the superconducting gap. These states cause profound restructuring of
the low-energy spectrum in the surface region of several coherence lengths
$\xi_0$ with large spatial variations of the superconducting order parameter.
In confined geometry, such as slabs, films, pores, or nano-dots, with one or
more physical dimensions $D \sim 10\xi_0$, Andreev bound states can dominate
properties of the superfluid phases, leading to modified experimental
signatures. They can dramatically change the energy landscape, and drive
transitions into new superfluid phases, that are typically unstable in the bulk
superfluid. On the examples of single-component singlet d-wave superconductor,
and triplet multi-component superfluid $^3$He I show how properties of
condensed phases in restricted geometry depend on the order parameter
structure. I will highlight the connection between Andreev bound states and
confinement-stabilized phases with additional broken symmetries, describe
recent progress and open questions in theoretical and experimental
investigation of superfluids in confined geometry.


title: On equicontinuity of Orlicz--Sobolev class in s closure of a domain

abstract:
  A behavior of homeomorphisms of Orlicz--Sobolev classes in a closure of a
domain is investigated. There are obtained theorems about equicontinuity of
classes mentioned above in terms of prime ends of regular domains. In
particular, it is proved that above classes are equicontinuous in domains with
some restrictions on it's boundaries provided that the corresponding inner
dilatation of order $p$ has a majorant of finite mean oscillation at every
point.


title: Asymptotic analysis for the Lane-Emden problem in dimension two

abstract:
  We consider the Lane-Emden Dirichlet problem \begin{equation}\tag{1}
\left\{\begin{array}{lr}-\Delta u= |u|^{p-1}u\qquad \mbox{ in }\Omega
u=0\qquad\qquad\qquad\mbox{ on }\partial \Omega \end{array}\right.
\end{equation} when $p>1$ and $\Omega\subset\mathbb R^2$ is a smooth bounded
domain. The aim of the paper is to survey some recent results on the asymptotic
behavior of solutions of (1) as the exponent $p\rightarrow \infty $.