title:
Design and Analysis of Deadline and Budget Constrained Autoscaling
  (DBCA) Algorithm for 5G Mobile Networks

abstract:
  In cloud computing paradigm, virtual resource autoscaling approaches have
been intensively studied recent years. Those approaches dynamically scale
in/out virtual resources to adjust system performance for saving operation
cost. However, designing the autoscaling algorithm for desired performance with
limited budget, while considering the existing capacity of legacy network
equipment, is not a trivial task. In this paper, we propose a Deadline and
Budget Constrained Autoscaling (DBCA) algorithm for addressing the
budget-performance tradeoff. We develop an analytical model to quantify the
tradeoff and cross-validate the model by extensive simulations. The results
show that the DBCA can significantly improve system performance given the
budget upper-bound. In addition, the model provides a quick way to evaluate the
budget-performance tradeoff and system design without wide deployment, saving
on cost and time.


title: On maximality of quasimonotone operators

abstract:
  We introduce the notion of quasimonotone polar of a multivalued operator, in
a similar way as the well-known monotone polar due to Martinez-Legaz and
Svaiter.
  We first recover several properties similar to the monotone polar, including
a characterization in terms of normal cones. Next, we use it to analyze certain
aspects of maximal (in the sense of graph inclusion) quasimonotonicity, and its
relation to the notion of maximal quasimonotonicity introduced by Aussel and
Eberhard.
  Furthermore, we study the connections between quasimonotonicity and Minty
Variational Inequality Problems.


title:
Hamiltonian approach to QCD in Coulomb gauge at zero and finite
  temperature

abstract:
  I report on recent results obtained within the Hamiltonian approach to QCD in
Coulomb gauge. By relating the Gribov confinement scenario to the center vortex
picture of confinement it is shown that the Coulomb string tension is tied to
the spatial string tension. For the quark sector a vacuum wave functional is
used which results in variational equations which are free of ultraviolet
divergences. The variational approach is extended to finite temperatures by
compactifying a spatial dimension. For the chiral and deconfinement phase
transition pseudo-critical temperatures of 170 MeV and 198 MeV, respectively,
are obtained.


title: In-medium properties of the phi meson with phi N resonant contributions

abstract:
  Nuclear production experiments report missing absorption processes of the
in-medium phi meson. Contributions arising from the K-bar K cloud have already
been widely studied, and therefore we investigate the phi-meson properties in
cold nuclear matter with the additional inclusion of resonant phi N
interactions. Two models are considered which dynamically generate N*-like
states close to the phi N threshold. We find that these states, together with
the non-resonant part of the amplitude, contribute to the phi self-energy with
the same order of magnitude as the K-bar K effects. At non-vanishing nuclear
density, both models lead to an additional in-medium broadening of the phi, up
to around 50 MeV. Furthermore, at least one of the models is compatible with a
mass shift to lower energies of up to 35 MeV at threshold and normal matter
density. Finally, a double-peak structure appears in the spectral function due
to the mixing of resonance-hole modes with the $\phi$ quasi-particle peak.
These results converge into the direction of the experimental findings.


title:
The Miniband Alignment Field-Effect Transistor: a superlattice-based
  steep-slope nanowire FET

abstract:
  This work investigates energy filtering in nanowires, where pass and
stopbands are obtained by including superlattices in the wire. When a pair of
such superlattices is placed in series, each being controlled by a gate, it can
act as a transistor where the (mis-)alignment of its minibands turns the device
on (off). It is shown that, in the ballistic current-regime, the transition
between the on and off state occurs in a narrow gate-bias range, giving rise to
sub-60 mV per decade switching behavior.


title:
Upper Bound for Diameter of Cosmological Black Holes and Nonexistence of
  Black Strings

abstract:
  The diameter of the apparent horizon, defined by the distance between
furthest points on the horizon, in spacetimes with a positive cosmological
constant $\varLambda$ has been investigated. It is established that the
diameter of the apparent horizon on the totally umbilic partial Cauchy surface
cannot exceed $2\pi/\sqrt{3\varLambda}$. Then, it is argued that arbitrarily
long black strings cannot be formed in our universe.


title: Spectral atoms of unimodular random trees

abstract:
  We use the Mass Transport Principle to analyze the local recursion governing
the resolvent $(A-z)^{-1}$ of the adjacency operator of unimodular random
trees. In the limit where the complex parameter $z$ approaches a given location
$\lambda$ on the real axis, we show that this recursion induces a decomposition
of the tree into finite blocks whose geometry directly determines the spectral
mass at $\lambda$. We then exploit this correspondence to obtain precise
information on the pure-point support of the spectrum, in terms of expansion
properties of the tree. In particular, we deduce that the pure-point support of
the spectrum of any unimodular random tree with minimum degree $\delta\ge 3$
and maximum degree $\Delta$ is restricted to finitely many points, namely the
eigenvalues of trees of size less than $\frac{\Delta-2}{\delta-2}$. More
generally, we show that the restriction $\delta\ge 3$ can be weakened to
$\delta\ge 2$, as long as the anchored isoperimetric constant of the tree
remains bounded away from $0$. This applies in particular to any unimodular
Galton-Watson tree without leaves, allowing us to settle a conjecture of
Bordenave, Sen and Vir\'ag (2013).


title: Symplectic fourth-order maps for the collisional N-body problem

abstract:
  We study analytically and experimentally certain symplectic and
time-reversible N-body integrators which employ a Kepler solver for each
pair-wise interaction, including the method of Hernandez & Bertschinger (2015).
Owing to the Kepler solver, these methods treat close two-body interactions
correctly, while close three-body encounters contribute to the truncation error
at second order and above. The second-order errors can be corrected to obtain a
fourth-order scheme with little computational overhead. We generalise this map
to an integrator which employs a Kepler solver only for selected interactions
and yet retains fourth-order accuracy without backward steps. In this case,
however, two-body encounters not treated via a Kepler solver contribute to the
truncation error.


title: Antennas and Receivers in Radio Interferometry

abstract:
  The primary antenna elements and receivers are two of the most important
components in a synthesis telescope. Together they are responsible for locking
onto an astronomical source in both direction and frequency, capturing its
radiation, and converting it into signals suitable for digitization and
correlation. The properties and performance of antennas and receivers can
affect the quality of the synthesized images in a number of fundamental ways.
In this lecture, their most relevant design and performance parameters are
reviewed, with emphasis on the current ALMA and VLA systems. We discuss in
detail the shape of the primary beam and the components of aperture efficiency,
and we present the basics of holography, pointing, and servo control. On
receivers, we outline the use of amplifiers and mixers both in the cryogenic
front-end and in the room temperature back-end signal path. The essential
properties of precision local oscillators (LOs), phase lock loops (PLLs), and
LO modulation techniques are also described. We provide a demonstration of the
method used during ALMA observations to measure the receiver and system
sensitivity as a function of frequency. Finally, we offer a brief derivation
and numerical simulation of the radiometer equation.


title: Gravitational wave astronomy with radio galaxy surveys

abstract:
  In the next decade, new astrophysical instruments will deliver the first
large-scale maps of gravitational waves and radio sources. Therefore, it is
timely to investigate the possibility to combine them to provide new and
complementary ways to study the Universe. Using simulated catalogues
appropriate to the planned surveys, it is possible to predict measurements of
the cross-correlation between radio sources and GW maps and the effects of a
stochastic gravitational wave background on galaxy maps. Effects of GWs on the
large scale structure of the Universe can be used to investigate the nature of
the progenitors of merging BHs, the validity of Einstein's General Relativity,
models for dark energy, and detect a stochastic background of GW. The results
obtained show that the galaxy-GW cross-correlation can provide useful
information in the near future, while the detection of tensor perturbation
effects on the LSS will require instruments with capabilities beyond the
currently planned next generation of radio arrays. Nevertheless, any
information from the combination of galaxy surveys with GW maps will help
provide additional information for the newly born gravitational wave astronomy.


title:
On convexification/optimization of functionals including an l2-misfit
  term

abstract:
  We provide theory for computing the lower semi-continuous convex envelope of
functionals of the type f(x) plus an l2 misfit, and discuss applications to
various non-convex optimization problems. The latter term is a data fit term
whereas f provides structural constraints on x. By minimizing the above
expression, possibly with additional constraints, we thus find a tradeoff
between matching the measured data and enforcing a particular structure on x,
such as sparsity or low rank. For these particular cases, the theory provides
alternatives to convex relaxation techniques such as l1 -minimization (for
vectors) and nuclear norm-minimization (for matrices). For functionals where
the l2 misfit includes a singular matrix and where the convex envelope usually
is not explicitly computable, we provide theory for how minimizers of
(explicitly computable) approximations of the convex envelope relate to
minimizers of the original functional. In particular, we give explicit
conditions on when the two coincide.


title: Nilpotent linearized polynomials over finite fields and applications

abstract:
  Let $q$ be a prime power and $\mathbb F_{q^n}$ be the finite field with $q^n$
elements, where $n>1$. We introduce the class of the linearized polynomials
$L(x)$ over $\mathbb F_{q^n}$ such that
$$L^{(t)}(x):=\underbrace{L(L(\cdots(x)\cdots))}_{t \quad\text{times}}\equiv
0\pmod {x^{q^n}-x}$$ for some $t\ge 2$, called nilpotent linearized polynomials
(NLP's). We discuss the existence and construction of NLP's and, as an
application, we show how to construct permutations of $\mathbb F_{q^n}$ from
these polynomials. For some of those permutations, we can explicitly give the
compositional inverse map and the cycle structure. This paper also contains a
method for constructing involutions over binary fields with no fixed points,
which are useful in block ciphers.


title: Testing mutual independence in high dimension via distance covariance

abstract:
  In this paper, we introduce a ${\mathcal L}_2$ type test for testing mutual
independence and banded dependence structure for high dimensional data. The
test is constructed based on the pairwise distance covariance and it accounts
for the non-linear and non-monotone dependences among the data, which cannot be
fully captured by the existing tests based on either Pearson correlation or
rank correlation. Our test can be conveniently implemented in practice as the
limiting null distribution of the test statistic is shown to be standard
normal. It exhibits excellent finite sample performance in our simulation
studies even when the sample size is small albeit dimension is high, and is
shown to successfully identify nonlinear dependence in empirical data analysis.
On the theory side, asymptotic normality of our test statistic is shown under
quite mild moment assumptions and with little restriction on the growth rate of
the dimension as a function of sample size. As a demonstration of good power
properties for our distance covariance based test, we further show that an
infeasible version of our test statistic has the rate optimality in the class
of Gaussian distribution with equal correlation.


title: On conformal higher spins in curved background

abstract:
  We address the question of how to represent an interacting action for the
tower of conformal higher spin fields in a form covariant with respect to a
background metric. We use a background metric to define a star product which
plays a central role in the definition of the corresponding gauge
transformations. By an analogy with the kinetic term in the 4-derivative Weyl
gravity action expanded near an on-shell background one expects that the
kinetic term in such an action should be gauge-invariant in a Bach-flat metric.
We demonstrate this fact to first order in expansion in powers of the curvature
of the background metric. This generalizes the result of arXiv:1404.7452 for
spin 3 case to all conformal higher spins. We also comment on a possibility of
extending this claim to terms quadratic in the curvature and discuss the
appearance of background-dependent mixing terms in the quadratic part of the
conformal higher spin action.


title:
Inducing Multilingual Text Analysis Tools Using Bidirectional Recurrent
  Neural Networks

abstract:
  This work focuses on the rapid development of linguistic annotation tools for
resource-poor languages. We experiment several cross-lingual annotation
projection methods using Recurrent Neural Networks (RNN) models. The
distinctive feature of our approach is that our multilingual word
representation requires only a parallel corpus between the source and target
language. More precisely, our method has the following characteristics: (a) it
does not use word alignment information, (b) it does not assume any knowledge
about foreign languages, which makes it applicable to a wide range of
resource-poor languages, (c) it provides truly multilingual taggers. We
investigate both uni- and bi-directional RNN models and propose a method to
include external information (for instance low level information from POS) in
the RNN to train higher level taggers (for instance, super sense taggers). We
demonstrate the validity and genericity of our model by using parallel corpora
(obtained by manual or automatic translation). Our experiments are conducted to
induce cross-lingual POS and super sense taggers.


title: Collisionless loss-cone refilling: there is no final parsec problem

abstract:
  Coalescing massive black hole binaries, formed during galaxy mergers, are
expected to be a primary source of low frequency gravitational waves. Yet in
isolated gas-free spherical stellar systems, the hardening of the binary stalls
at parsec-scale separations owing to the inefficiency of relaxation-driven
loss-cone refilling. Repopulation via collisionless orbit diffusion in triaxial
systems is more efficient, but published simulation results are contradictory.
While sustained hardening has been reported in simulations of galaxy mergers
with $N \sim 10^6$ stars and in early simulations of rotating models, in
isolated non-rotating triaxial models the hardening rate continues to fall with
increasing N, a signature of spurious two-body relaxation. We present a novel
approach for studying loss cone repopulation in galactic nuclei. Since loss
cone repopulation in triaxial systems owes to orbit diffusion, it is a purely
collisionless phenomenon and can be studied with an approximated force
calculation technique, provided the force errors are well behaved and
sufficiently small. We achieve this using an accurate fast multipole method and
define a proxy for the hardening rate that depends only on stellar angular
momenta. We find that the loss cone is efficiently replenished even in very
mildly triaxial models (with axis ratios 1 : 0.9 : 0.8). Such triaxiality is
unavoidable following galactic mergers and can drive binaries into the
gravitational wave regime. We conclude that there is no final parsec problem.


title: A Lower-Bound on the Hochschild Cohomological Dimension

abstract:
  A concrete lower-bound for the Hochschild cohomological dimension of a
commutative $k$-algebra, in terms of three other homological invariants is
obtained. This result is then used to show that most $k$-algebras fail to be
quasi-free, even if they are smooth. This result generalizes a result of
\cite{cuntz1995algebra} to the case where the base-ring is no longer $\cc$ but
can be any commutative ring with unity.


title: Static critical fluctuations on the freeze-out surface

abstract:
  In this proceeding, we summarize the main results of our recent paper, which
introduces a freeze-out scheme to the dynamical models near the QCD critical
point. Within such framework of static critical fluctuations, the Beam Energy
Scan (BES) data of $C_4$ and $\kappa \sigma^2$ for net protons within different
$p_T$ ranges can be roughly described. Besides, the momentum acceptance
dependence of higher cumulants at lower collision energies can also be
qualitatively described. However, $C_2$ and $C_3$ are always over-predicted due
to the positive static critical fluctuations.


title:
Search for supersymmetry in events with one lepton and multiple jets in
  proton-proton collisions at sqrt(s) = 13 TeV

abstract:
  A search for supersymmetry is performed in events with a single electron or
muon in proton-proton collisions at a center-of-mass energy of 13 TeV. The data
were recorded by the CMS experiment at the LHC and correspond to an integrated
luminosity of 2.3 inverse femtobarns. Several exclusive search regions are
defined based on the number of jets and b-tagged jets, the scalar sum of the
jet transverse momenta, and the scalar sum of the missing transverse momentum
and the transverse momentum of the lepton. The observed event yields in data
are consistent with the expected backgrounds from standard model processes. The
results are interpreted using two simplified models of supersymmetric particle
spectra, both of which describe gluino pair production. In the first model,
each gluino decays via a three-body process to top quarks and a neutralino,
which is associated with the observed missing transverse momentum in the event.
Gluinos with masses up to 1.6 TeV are excluded for neutralino masses below 600
GeV. In the second model, each gluino decays via a three-body process to two
light quarks and a chargino, which subsequently decays to a W boson and a
neutralino. The mass of the chargino is taken to be midway between the gluino
and neutralino masses. In this model, gluinos with masses below 1.4 TeV are
excluded for neutralino masses below 700 GeV.


title:
A Theory of Intermittency Renormalization of Gaussian Multiplicative
  Chaos Measures

abstract:
  A theory of intermittency differentiation is developed for a general class of
Gaussian Multiplicative Chaos measures including the measure of Bacry and Muzy
on the interval and circle as special cases. An exact, non-local functional
equation is derived for the derivative of a general functional of the total
mass of the measure with respect to intermittency. The formal solution is given
in the form of an intermittency expansion and proved to be a renormalized
expansion in the centered moments of the total mass of the measure. The full
intermittency expansion of the Mellin transform of the total mass is computed
in terms of the corresponding expansion of log-moments. The theory is shown to
extend to the dependence structure of the measure. For application, the
intermittency expansion of the Bacry-Muzy measure on the circle is computed
exactly, and the Morris integral probability distribution is shown to reproduce
the moments of the total mass and the intermittency expansion, resulting in the
conjecture that it is the distribution of the total mass. It is conjectured in
general that the intermittency expansion captures the distribution of the total
mass uniquely.


title: Heavy-Meson Decay Constants: Isospin Breaking from QCD Sum Rules

abstract:
  Compared with lattice QCD, isospin breaking of heavy-meson decay constants
from QCD sum rules agrees for $D$ mesons but disagrees (by a factor of four)
for $B$ mesons.


title:
Unified Stochastic Geometry Modeling and Analysis of Cellular Networks
  in LOS/NLOS and Shadowed Fading

abstract:
  Statistical characterization of the signal-to-interference-plus-noise ratio
(SINR) via its cumulative distribution function (CDF) is ubiquitous in a vast
majority of technical contributions in the area of cellular networks since it
boils down to averaging the Laplace transform of the aggregate interference, a
benefit accorded at the expense of confinement to the simplistic Rayleigh
fading. In this work, to capture diverse fading channels that appear in
realistic outdoor/indoor wireless communication scenarios, we tackle the
problem differently. By exploting the moment generating function (MGF) of the
SINR, we succeed in analytically assessing cellular networks performance over
the shadowed {\kappa}-{\mu}, {\kappa}-{\mu} and {\eta}-{\mu} fading models. The
latter offer high flexibility by capturing diverse fading channels including
Rayleigh, Nakagami-m, Rician, and Rician shadow fading distributions. These
channel models have been recently praised for their capability to accurately
model dense urban environments, future femtocells and device-to-device (D2D)
shadowed channels. In addition to unifying the analysis for different channel
models, this work integrates, for the first time, the coverage, the achievable
rate, and the bit error probability (BEP), which are largely treated separately
in the literature. The developed model and analysis are validated over a broad
range of simulation setups and parameters.


title: Measurement of Sound Fields Using Moving Microphones

abstract:
  The sampling of sound fields involves the measurement of spatially dependent
room impulse responses, where the Nyquist-Shannon sampling theorem applies in
both the temporal and spatial domain. Therefore, sampling inside a volume of
interest requires a huge number of sampling points in space, which comes along
with further difficulties such as exact microphone positioning and calibration
of multiple microphones. In this paper, we present a method for measuring sound
fields using moving microphones whose trajectories are known to the algorithm.
At that, the number of microphones is customizable by trading measurement
effort against sampling time. Through spatial interpolation of the dynamic
measurements, a system of linear equations is set up which allows for the
reconstruction of the entire sound field inside the volume of interest.


title: Tuning the caloric response of BaTiO$_3$ by tensile epitaxial strain

abstract:
  We investigate the effect of epitaxial strain on the electrocaloric effect
(ECE) in BaTiO$_3$ by means of ab initio based molecular dynamics simulations.
We show that tensile strain can be used to optimize the operation range for
ferroic cooling. Strain in the range of $\leq 1$ % can be used to shift the
operation temperature by several hundreds of Kelvin both to higher and lower
temperatures, depending on the direction of the external field. In addition,
the transformation between multi-domain and mono-domain states, induced by an
in-plane electric field, results in an additional peak of the adiabatic
temperature change at lower temperatures, and a broad temperature interval
where the caloric response scales linearly with the applied field strength,
even up to very high fields.


title: Polynomial-time algorithms for the curve graph

abstract:
  We describe a polynomial-time algorithm to compute a (tight) geodesic between
two curves in the curve graph. As well as enabling us to compute the distance
between a pair of curves, this has several applications to mapping classes. For
example, we can use these geodesics to compute the asymptotic translation
length, Nielsen--Thurston type, and canonical curve system of a mapping class
in polynomial time in its word length.


title: Parametric Landau damping of space charge modes

abstract:
  Landau damping is the mechanism of plasma and beam stabilization; it arises
through energy transfer from collective modes to the incoherent motion of
resonant particles. Normally this resonance requires the resonant particle's
frequency to match the collective mode frequency. We have identified an
important new damping mechanism, {\it parametric Landau damping}, which is
driven by the modulation of the mode-particle interaction. This reveals new
possibilities for stability control through manipulation of both particle and
mode-particle coupling spectra. We demonstrate the existence of parametric
Landau damping in a simulation of transverse coherent modes of bunched
accelerator beams with space charge.


title:
Explicit estimates on the torus for the sup-norm and the crest factor of
  solutions of the Modified Kuramoto-Sivashinky Equation in one and two space
  dimensions

abstract:
  We consider the Modified Kuramoto-Sivashinky Equation (MKSE) in one and two
space dimensions and we obtain explicit and accurate estimates of various
Sobolev norms of the solutions. In particular, by using the sharp constants
which appear in the functional interpolation inequalities used in the analysis
of partial differential equations, we evaluate explicitly the sup-norm of the
solutions of the MKSE. Furthermore we introduce and then compute the so-called
crest factor associated with the above solutions. The crest factor provides
information on the distortion of the solution away from its space average and
therefore, if it is large, gives evidence of strong turbulence. Here we find
that the time average of the crest factor scales like $\lambda^{(2d-1)/8}$ for
$\lambda$ large, where $\lambda$ is the bifurcation parameter of the source
term and $d=1,2$ is the space dimension. This shows that strong turbulence
cannot be attained unless the bifurcation parameter is large enough.


title: Micropolis Interdependency Modeling using Open Hybrid Automata

abstract:
  Micropolis is a virtual city that is used for various studies, such as
modeling and analyzing water networks. In this paper we model the various
interdependencies between three major infrastructures in Micropolis, the power
system, the communication network and the water network, in order to study
cascades effects between them. Specifically, we develop open hybrid automata
models for the main components of the three infrastructures and then composed
them together based on their interdependencies.


title: Sneutrino driven GUT Inflation in Supergravity

abstract:
  In this paper, we embed the model of flipped GUT sneutrino inflation -in a
flipped SU(5) or SO(10) set up- developed by Ellis et al. in a supergravity
framework. The GUT symmetry is broken by a waterfall which could happen at
early or late stage of the inflationary period. The full field dynamics is thus
studied in detail and these two main inflationary configurations are exposed,
whose cosmological predictions are both in agreement with recent astrophysical
measurements. The model has an interesting feature where the inflaton has
natural decay channels to the MSSM particles allowed by the GUT gauge symmetry.
Hence it can account for the reheating after the inflationary epoch.


title:
Magnetotransport properties and evidence of topological insulating state
  in LaSbTe

abstract:
  In this report, we present the magnetotransport and magnetization properties
of LaSbTe single crystals. Magnetic field-induced turn-on behavior and
low-temperature resistivity plateau have been observed. By adopting both
metal-semiconductor crossover and Kohler scaling analysis, we have discussed
the possible origin of the temperature and magnetic field dependence of
resistivity. At 5 K and 9 T, a large, non-saturating transverse
magnetoresistance (MR) $\sim$ 5$\times$10$^{3}$ \% has been obtained. The MR
shows considerable anisotropy, when the magnetic field is applied along
different crystallographic directions. The non-linear field dependence of the
Hall resistivity confirms the presence of two types of charge carriers. From
the semiclassical two-band fitting of Hall conductivity and longitudinal
conductivity, very high carrier mobilities and almost equal electron and hole
densities have been deduced, which result in large MR. The Fermi surface
properties have been analyzed from de Haas-van Alphen oscillation. From the
magnetization measurement, the signature of non-trivial surface state has been
detected, which confirms that LaSbTe is a topological insulator, consistent
with the earlier first-principles calculations.


title:
Analytic Solution to Geodesic Equations in Lema\^{i}tre-Tolman-Bondi
  Metric

abstract: In this paper, we use the Taylor expansion method to solve the LTB metric.


title: On the rich magnetic phase diagram of (Ni, Co)-Mn-Sn Heusler alloys

abstract:
  We put a spotlight on the exceptional magnetic properties of the metamagnetic
Heusler alloy (Ni,Co)-Mn-Sn by means of first principles simulations.
  In the energy landscape we find a multitude of local minima, which belong to
different ferrimagnetic states and are close in total magnetization and energy.
All these magnetic states correspond to the local high spin state of the Mn
atoms with different spin alignments and are related to the magnetic properties
of Mn. Compared to pure Mn, the magneto-volume coupling is reduced by Ni, Co,
and Sn atoms in the lattice and no local low-spin Mn states appear. For the
cubic phase we find a ferromagnetic ground state whereas the global energy
minimum is a tetragonal state with complicated spin structure and vanishing
magnetization which so far has been overlooked in simulations.


title: A Brief History of Gravitational Waves

abstract:
  This review describes the discovery of gravitational waves. We recount the
journey of predicting and finding those waves, since its beginning in the early
twentieth century, their prediction by Einstein in 1916, theoretical and
experimental blunders, efforts towards their detection, and finally the
subsequent successful discovery.


title:
Tan's contact and the phase distribution of repulsive Fermi gases:
  Insights from QCD noise analyses

abstract:
  Path-integral analyses originally pioneered in the study of the complex-phase
problem afflicting lattice calculations of finite-density quantum
chromodynamics are generalized to non-relativistic Fermi gases with repulsive
interactions. Using arguments similar to those previously applied to
relativistic theories, we show that the analogous problem in nonrelativistic
systems manifests itself naturally in Tan's contact as a nontrivial
cancellation between terms with varied dependence on extensive thermodynamic
quantities. We analyze that case under the assumption of gaussian phase
distribution, which is supported by our Monte Carlo calculations and
perturbative considerations. We further generalize these results to observables
other than the contact, as well as to polarized systems and systems with fixed
particle number. Our results are quite general in that they apply to repulsive
multi-component fermions, are independent of dimensionality or trapping
potential, and hold in the ground state as well as at finite temperature.

categories: cond-mat.quant-gas cond-mat.str-el hep-lat nucl-th


title:
Renormalisation Group Corrections to the Littlest Seesaw Model and
  Maximal Atmospheric Mixing

abstract:
  The Littlest Seesaw (LS) model involves two right-handed neutrinos and a very
constrained Dirac neutrino mass matrix, involving one texture zero and two
independent Dirac masses, leading to a highly predictive scheme in which all
neutrino masses and the entire PMNS matrix is successfully predicted in terms
of just two real parameters. We calculate the renormalisation group (RG)
corrections to the LS predictions, with and without supersymmetry, including
also the threshold effects induced by the decoupling of heavy Majorana
neutrinos both analytically and numerically. We find that the predictions for
neutrino mixing angles and mass ratios are rather stable under RG corrections.
For example we find that the LS model with RG corrections predicts close to
maximal atmospheric mixing, $\theta_{23}=45^\circ \pm 1^\circ$, in most
considered cases, in tension with the latest NOvA results. The techniques used
here apply to other seesaw models with a strong normal mass hierarchy.


title: The Theory of SERS on Dielectrics and Semiconductors

abstract:
  It is demonstrated that the reason of SERS on dielectric and semiconductor
substrates is the enhancement of the electric field in the regions of the tops
of the surface roughness with very small radius, or a very large curvature. The
enhancement depends on the dielectric constant of the substrate and is stronger
for a larger dielectric constant. It is indicated that the enhancement on
dielectrics and semiconductors is weaker than on metals with the same modulus
of the dielectric constant. The result obtained is confirmed by experimental
data on the enhancement coefficients obtained for various semiconductor and
dielectric substrates.


title: Energy conversion by surface-tension driven charge separation

abstract:
  In this work, the shear-induced electrokinetic streaming potential present in
free-surface electrolytic flows subjected to a gradient in surface tension is
assessed. Firstly, for a Couette flow with fully resolved electric double layer
(EDL), the streaming potential per surface stress as a function of the Debye
parameter and surface potential is analyzed. By contrast to the Smoluchowski
limit in pressure-driven channel flow, the shear-induced streaming potential
vanishes for increasing Debye parameter (infinitely thin EDL), unless the free
surface contains (induced) surface charge or the flow at the charged, solid
wall is permitted to slip. Secondly, a technical realization of surface-tension
induced streaming is proposed, with surface stress acting on the free
(slipping) surfaces of a micro-structured, superhydrophobic wall. The streaming
potential is analyzed with respect to the slip parameter and surface charge.
Finally, the surface tension is assumed to vary with temperature
(thermocapillarity) or with surfactant concentration (destillocapillarity). The
maximal thermal efficiency is derived and compared to the Carnot efficiency.
For large thermal Marangoni number, the efficiency is severely limited by the
large heat capacity of aqueous solvents. By contrast, destillocapillary flows
may reach conversion efficiencies similar to pressure-driven flow.


title: Evaluating Induced CCG Parsers on Grounded Semantic Parsing

abstract:
  We compare the effectiveness of four different syntactic CCG parsers for a
semantic slot-filling task to explore how much syntactic supervision is
required for downstream semantic analysis. This extrinsic, task-based
evaluation provides a unique window to explore the strengths and weaknesses of
semantics captured by unsupervised grammar induction systems. We release a new
Freebase semantic parsing dataset called SPADES (Semantic PArsing of
DEclarative Sentences) containing 93K cloze-style questions paired with
answers. We evaluate all our models on this dataset. Our code and data are
available at https://github.com/sivareddyg/graph-parser.


title:
A correlation between chemistry, polarization and dust properties in the
  Pipe Nebula starless core FeSt 1-457

abstract:
  Pre-stellar cores within molecular clouds provide the very initial conditions
in which stars are formed. We use the IRAM 30m telescope and the PdBI to study
the chemical and physical properties of the starless core FeSt 1-457 (Core
109), in the Pipe nebula. We fit the hyperfine structure of the N2H+(1-0) IRAM
30m data. This allow us to measure with high precision the velocity field, line
widths and opacity and derive the excitation temperature and column density in
the core. We use a modified Bonnor-Ebert sphere model adding a temperature
gradient towards the center to fit the 1.2 mm continuum emission and visual
extinction maps. Using this model, we estimate the abundances of the N2H+ and
the rest of molecular lines detected in the 30 GHz wide line survey performed
at 3 mm with IRAM 30m using ARTIST software. The core presents a rich chemistry
with emission from early (C3H2, HCN, CS) and late-time molecules (e.g., N2H+),
with a clear chemical spatial differentiation for nitrogen, oxygen and
sulphurated molecules. For most of the molecules detected (HCN, HCO+, CH3OH,
CS, SO, 13CO and C18O), abundances are best fitted with three values,
presenting a clear decrease of abundance of at least 1 or 2 orders of magnitude
towards the center of the core. The Bonnor-Ebert analysis indicates the core is
gravitationally unstable and the magnetic field is not strong enough to avoid
the collapse. Depletion of molecules onto the dust grains occurs at the
interior of the core, where dust grain growth and dust depolarization also
occurs. This suggests that these properties may be related. On the other hand,
some molecules exhibit asymmetries in their integrated emission maps, which
appear to be correlated with a previously reported submillimetre polarization
asymmetry. These asymmetries could be due to a stronger interstellar radiation
field in the western side of the core.


title: On the combinatorics of commutators of Lie algebras

abstract:
  Motivated by the combinatorial properties of products in Lie algebras, we
investigate the subset of permutations that naturally appears when we write the
long commutator $[x_1, x_2, ..., x_m]$ as a sum of associative monomials. We
characterize this subset and find some useful equivalences. Moreover, we
explore properties concerning the action of this subset on sequences of m
elements. In particular we describe sequences that share some special
symmetries which can be useful in the study of combinatorial properties in
graded Lie algebras.


title: Cooperative Training of Descriptor and Generator Networks

abstract:
  This paper studies the cooperative training of two generative models for
image modeling and synthesis. Both models are parametrized by convolutional
neural networks (ConvNets). The first model is a deep energy-based model, whose
energy function is defined by a bottom-up ConvNet, which maps the observed
image to the energy. We call it the descriptor network. The second model is a
generator network, which is a non-linear version of factor analysis. It is
defined by a top-down ConvNet, which maps the latent factors to the observed
image. The maximum likelihood learning algorithms of both models involve MCMC
sampling such as Langevin dynamics. We observe that the two learning algorithms
can be seamlessly interwoven into a cooperative learning algorithm that can
train both models simultaneously. Specifically, within each iteration of the
cooperative learning algorithm, the generator model generates initial
synthesized examples to initialize a finite-step MCMC that samples and trains
the energy-based descriptor model. After that, the generator model learns from
how the MCMC changes its synthesized examples. That is, the descriptor model
teaches the generator model by MCMC, so that the generator model accumulates
the MCMC transitions and reproduces them by direct ancestral sampling. We call
this scheme MCMC teaching. We show that the cooperative algorithm can learn
highly realistic generative models.


title: Variations of the total mixed scalar curvature of a distribution

abstract:
  We examine the total mixed scalar curvature of a fixed distribution as a
functional of a pseudo-Riemannian metric. We develop variational formulas for
quantities of extrinsic geometry of the distribution to find the critical
points of this action. Together with the arbitrary variations of the metric, we
consider also variations that preserve the volume of the manifold or partially
preserve the metric (e.g. on the distribution). For each of those cases we
obtain the Euler-Lagrange equation and its several solutions. The examples of
critical metrics that we find are related to various fields of geometry such as
contact and 3-Sasakian manifolds, geodesic Riemannian flows and codimension-one
foliations of interesting geometric properties (e.g. totally umbilical,
minimal).


title:
Homogenization and Non-Homogenization of certain Non-Convex
  Hamilton-Jacobi Equations

abstract:
  We continue the study of the homogenization of coercive non-convex
Hamilton-Jacobi equations in random media identifying two general classes of
Hamiltonians with very distinct behavior. For the first class there is no
homogenization in a particular environment while for the second homogenization
takes place in environments with finite range dependence. Motivated by the
recent counter-example of Ziliotto, who constructed a coercive but non-convex
Hamilton-Jacobi equation with stationary ergodic random potential field for
which homogenization does not hold, we show that same happens for coercive
Hamiltonians which have a strict saddle-point, a very local property. We also
identify, based on the recent work of Armstrong and Cardaliaguet on the
homogenization of positively homogeneous random Hamiltonians in environments
with finite range dependence, a new general class Hamiltonians, namely
equations with uniformly strictly star-shaped sub-level sets, which homogenize.


title:
Seismic collapse prediction of frame structures by means of genetic
  algorithms

abstract:
  This paper presents an automatic approach for the evaluation of the plastic
load and failure modes of planar frames. The method is based on the generation
of elementary collapse mechanisms and on their linear combination aimed at
minimizing the collapse load factor. The minimization procedure is efficiently
performed by means of genetic algorithms which allow to compute an approximate
collapse load factor, and the correspondent failure mode, with sufficient
accuracy in a very short computing time. A user-friendly original software in
the agent-based programming language Netlogo, here employed for the first time
with structural engineering purposes, has been developed showing its great
versatility and advantages. Many applications have been performed both with
reference to the classical plastic analysis approach, in which all the loads
increase proportionally, and with a seismic point of view considering a system
of horizontal forces whose magnitude increases while the vertical loads are
assumed to be constant. In this latter case a parametric study has been
performed aiming at evaluating the influence of some geometric, mechanical and
load distribution parameters on the ultimate collapse load of planar frames.


title: Experimental Measurement of the Berry Curvature from Anomalous Transport

abstract:
  Geometrical properties of energy bands underlie fascinating phenomena in a
wide-range of systems, including solid-state materials, ultracold gases and
photonics. Most famously, local geometrical characteristics like the Berry
curvature can be related to global topological invariants such as those
classifying quantum Hall states or topological insulators. Regardless of the
band topology, however, any non-zero Berry curvature can have important
consequences, such as in the semi-classical evolution of a wave packet. Here,
we experimentally demonstrate for the first time that wave packet dynamics can
be used to directly map out the Berry curvature. To this end, we use optical
pulses in two coupled fibre loops to study the discrete time-evolution of a
wave packet in a 1D geometrical "charge" pump, where the Berry curvature leads
to an anomalous displacement of the wave packet under pumping. This is both the
first direct observation of Berry curvature effects in an optical system, and,
more generally, the proof-of-principle demonstration that semi-classical
dynamics can serve as a high-resolution tool for mapping out geometrical
properties.


title:
Clean up or mess up: the effect of sampling biases on measurements of
  degree distributions in mobile phone datasets

abstract:
  Mobile phone data have been extensively used in the recent years to study
social behavior. However, most of these studies are based on only partial data
whose coverage is limited both in space and time. In this paper, we point to an
observation that the bias due to the limited coverage in time may have an
important influence on the results of the analyses performed. In particular, we
observe significant differences, both qualitatively and quantitatively, in the
degree distribution of the network, depending on the way the dataset is
pre-processed and we present a possible explanation for the emergence of Double
Pareto LogNormal (DPLN) degree distributions in temporal data.


title:
Core-halo mass relation of ultralight axion dark matter from merger
  history

abstract:
  In the context of structure formation with ultralight axion dark matter, we
offer an alternative explanation for the mass relation of solitonic cores and
their host halos observed in numerical simulations. Our argument is based
entirely on the mass gain that occurs during major mergers of binary cores and
largely independent of the initial core-halo mass relation assigned to hosts
that have just collapsed. We find a relation between the halo mass $M_h$ and
corresponding core mass $M_c$, $M_c\propto M_h^{2\beta-1}$, where $(1-\beta)$
is the core mass loss fraction. Following the evolution of core masses in
stochastic merger trees, we find empirical evidence for our model. Our results
are useful for statistically modeling the effects of dark matter cores on the
properties of galaxies and their substructures in axion dark matter
cosmologies.


title:
Solutions of the fractional Schr\"odinger equation with sign-changing
  nonlinearity

abstract:
  We look for a solutions to a nonlinear, fractional Schr\"odinger equation
$$(-\Delta)^{\alpha / 2}u + V(x)u = f(x,u)-\Gamma(x)|u|^{q-2}u\hbox{ on
}\mathbb{R}^N,$$ where potential $V$ is coercive or $V=V_{per} + V_{loc}$ is a
sum of periodic in $x$ potential $V_{per}$ and localized potential $V_{loc}$,
$\Gamma\in L^{\infty}(\mathbb{R}^N)$ is periodic in $x$, $\Gamma(x)\geq 0$ for
a.e. $x\in\mathbb{R}^N$ and $2<q<2^*_\alpha$. If $f$ has the subcritical
growth, but higher than $\Gamma(x)|u|^{q-2}u$, then we find a ground state
solution being a minimizer on the Nehari manifold. Moreover we show that if $f$
is odd in $u$ and $V$ is periodic, this equation admits infinitely many
solutions, which are pairwise geometrically distinct. Finally, we obtain the
existence result in the case of coercive potential $V$.


title: Arbitrarily Accurate Pulse Sequences for Robust Dynamical Decoupling

abstract:
  We introduce universally robust sequences for dynamical decoupling, which
simultaneously compensate pulse imperfections and the detrimental effect of a
dephasing environment to an arbitrary order, work with any pulse shape, and
improve performance for any initial condition. Moreover, the number of pulses
in a sequence grows only linearly with the order of error compensation. Our
sequences outperform the state-of-the-art robust sequences for dynamical
decoupling. Beyond the theoretical proposal, we also present convincing
experimental data for dynamical decoupling of atomic coherences in a
solid-state optical memory.


title:
Supercritical instability of Dirac electrons in the field of two
  oppositely charged nuclei

abstract:
  The Dirac equation for an electron in a finite dipole potential has been
studied within the method of linear combination of atomic orbitals (LCAO). The
Coulomb potential of the nuclei that compose a dipole is regularized, by
considering the finite nuclear size. It is shown that if the dipole momentum
reaches a certain critical value, the novel type of supercriticality occurs;
namely, the wave function of the highest occupied electron bound state changes
its localization from the negatively charged nucleus to the positively charged
one. This phenomenon can be interpreted as a spontaneous creation of an
electron-positron pair in vacuum, with each of the created particles being in
the bound state with the corresponding nucleus and partially screening it.


title:
Infrequent social interaction can accelerate the spread of a persuasive
  idea

abstract:
  We study the spread of a persuasive new idea through a population of
continuous-time random walkers in one dimension. The idea spreads via social
gatherings involving groups of nearby walkers who act according to a biased
"majority rule": After each gathering, the group takes on the new idea if more
than a critical fraction $\frac{1-\varepsilon}{2} < \frac{1}{2}$ of them
already hold it; otherwise they all reject it. The boundary of a domain where
the new idea has taken hold expands as a traveling wave in the density of new
idea holders. Our walkers move by L\'{e}vy motion, and we compute the wave
velocity analytically as a function of the frequency of social gatherings and
the exponent of the jump distribution. When this distribution is sufficiently
heavy tailed, then, counter to intuition, the idea can propagate faster if
social gatherings are held less frequently. When jumps are truncated, a
critical gathering frequency can emerge which maximizes propagation velocity.
We explore our model by simulation, confirming our analytical results.


title:
Gradient Projection Iterative Sketch for Large-Scale Constrained
  Least-Squares

abstract:
  We propose a randomized first order optimization algorithm Gradient
Projection Iterative Sketch (GPIS) and an accelerated variant for efficiently
solving large scale constrained Least Squares (LS). We provide theoretical
convergence analysis for both proposed algorithms and demonstrate our methods'
computational efficiency compared to classical accelerated gradient method, and
the state of the art variance-reduced stochastic gradient methods through
numerical experiments in various large synthetic/real data sets.


title: Finding the magnetic center of sextupole using vibrating wire technique

abstract:
  In order to obtain stable and high-quality synchrotron radiation photon, the
magnets in the storage ring of High Energy Photon Source(HEPS) need to have a
stable support and precise positioning. The vibrating wire technique can be
used to pre-align the quadrupoles and sextupoles on one girder with high
precision to meet the extremely low emittance requirement of HEPS. This thesis
introduces the measurement of magnetic center of sextupole using vibrating
wire. According to the measurement results, the magnetic field distribution is
consistent with theoretical expectation. And vibrating wire has achieved the
purpose of measuring the magnetic center and has reached a certain precision.


title:
Physical paradigm of Life as a generalization of biochemical conception.
  A Physical law governing life origin and development

abstract:
  The present view of biological phenomena is based on a biomolecular paradigm
that development of living organisms is entirely defined by information stored
in a molecular form as some genetic code. However, new facts and discoveries
indicate that biological phenomena cannot be reduced to a biomolecular realm
alone, but are also governed by mechanisms of other nature. These mechanisms,
acting in tight cooperation with biochemical mechanisms, define life cycles of
individual organisms, and, through this, the origin and evolution of the living
world. Here, we present such a physical mechanism (General growth law), which
represents a new physical law of nature acting at cellular, organ, system and
whole organism levels, directing growth and reproduction together with
biomolecular mechanisms. It imposes uniquely defined constraints on
distribution of nutrients between biomass production and maintenance, thus
defining the composition of biochemical reactions, their change and
irreversibility during the organismal life cycle. Mathematically, this law is
represented by the growth equation. Using this equation, we introduce growth
models and explain division mechanisms for unicellular organisms. High adequacy
of obtained results to experiments proves validity of the General growth law
and of the new physical paradigm of Life based on this law.


title: Jet formation in solar atmosphere due to magnetic reconnection

abstract:
  Using numerical simulations, we show that jets with features of type II
spicules and cold coronal jets corresponding to temperatures $10^{4}$ K can be
formed due to magnetic reconnection in a scenario in presence of magnetic
resistivity. For this we model the low chromosphere-corona region using the C7
equilibrium solar atmosphere model and assuming Resistive MHD rules the
dynamics of the plasma. The magnetic filed configurations we analyze correspond
to two neighboring loops with opposite polarity. The separation of the loops'
feet determines the thickness of a current sheet that triggers a magnetic
reconnection process, and the further formation of a high speed and sharp
structure. We analyze the cases where the magnetic filed strength of the two
loops is equal and different. In the first case, with a symmetric configuration
the spicules raise vertically whereas in an asymmetric configuration the
structure shows an inclination. With a number of simulations carried out under
a 2.5D approach, we explore various properties of excited jets, namely, the
morphology, inclination and velocity. The parameter space involves magnetic
field strength between 20 and 40 G, and the resistivity is assumed to be
uniform with a constant value of the order $10^{-2}\Omega\cdot m$


title:
An application of approach theory to the relative Hausdorff measure of
  non-compactness for the Wasserstein metric

abstract:
  After shortly reviewing the fundamentals of approach theory as introduced by
R. Lowen in 1989, we show that this theory is intimately related with the
well-known Wasserstein metric on the space of probability measures with a
finite first moment on a complete and separable metric space. More precisely,
we introduce a canonical approach structure, called the contractive approach
structure, and prove that it is metrized by the Wasserstein metric. The key
ingredients of the proof of this result are Dini's Theorem, Ascoli's Theorem,
and the fact that the class of real-valued contractions on a metric space has
some nice stability properties. We then combine the obtained result with
Prokhorov's Theorem to establish inequalities between the relative Hausdorff
measure of non-compactness for the Wasserstein metric and a canonical measure
of non-uniform integrability.


title:
Probing gluon saturation with next-to-leading order photon production at
  central rapidities in proton-nucleus collisions

abstract:
  We compute the cross section for photons emitted from sea quarks in
proton-nucleus collisions at collider energies. The computation is performed
within the dilute-dense kinematics of the Color Glass Condensate (CGC)
effective field theory. Albeit the result obtained is formally at
next-to-leading order in the CGC power counting, it provides the dominant
contribution for central rapidities. We observe that the inclusive photon cross
section is proportional to all-twist Wilson line correlators in the nucleus.
These correlators also appear in quark-pair production; unlike the latter,
photon production is insensitive to hadronization uncertainties and therefore
more sensitive to multi-parton correlations in the gluon saturation regime of
QCD. We demonstrate that $k_\perp$ and collinear factorized expressions for
inclusive photon production are obtained as leading twist approximations to our
result. In particular, the collinearly factorized expression is directly
sensitive to the nuclear gluon distribution at small $x$. Other results of
interest include the realization of the Low-Burnett-Kroll soft photon theorem
in the CGC framework and a comparative study of how the photon amplitude is
obtained in Lorenz and light-cone gauges.


title: On the Singular Neumann Problem in Linear Elasticity

abstract:
  The Neumann problem of linear elasticity is singular with a kernel formed by
the rigid motions of the body. There are several tricks that are commonly used
to obtain a non-singular linear system. However, they often cause reduced
accuracy or lead to poor convergence of the iterative solvers. In this paper,
different well-posed formulations of the problem are studied through
discretization by the finite element method, and preconditioning strategies
based on operator preconditioning are discussed. For each formulation we derive
preconditioners that are independent of the discretization parameter.
Preconditioners that are robust with respect to the first Lam\'e constant are
constructed for the pure displacement formulations, while a preconditioner that
is robust in both Lam\'e constants is constructed for the mixed formulation. It
is shown that, for convergence in the first Sobolev norm, it is crucial to
respect the orthogonality constraint derived from the continuous problem. Based
on this observation a modification to the conjugate gradient method is proposed
that achieves optimal error convergence of the computed solution.


title: Relativistic quantum clocks

abstract:
  The conflict between quantum theory and the theory of relativity is
exemplified in their treatment of time. We examine the ways in which their
conceptions differ, and describe a semiclassical clock model combining elements
of both theories. The results obtained with this clock model in flat spacetime
are reviewed, and the problem of generalizing the model to curved spacetime is
discussed, before briefly describing an experimental setup which could be used
to test of the model. Taking an operationalist view, where time is that which
is measured by a clock, we discuss the conclusions that can be drawn from these
results, and what clues they contain for a full quantum relativistic theory of
time.


title:
Kerr/CFT correspondence in a 4D extremal rotating regular black hole
  with a non-linear magnetic monopole

abstract:
  We carry out the Kerr/CFT correspondence in a four-dimensional extremal
rotating regular black hole with a non-linear magnetic monopole (NLMM). One
problem in this study would be whether our geometry can be a solution or not.
We search for the way making our rotating geometry into a solution based on the
fact that the Schwarzschild regular black hole geometry with a NLMM can be a
solution. However, in the attempt to extend the Schwarzschild case that we can
naturally consider, it turns out that it is impossible to construct a model in
which our geometry can be a exact solution. We manage this problem by making
use of the fact that our geometry can be a solution approximately in the whole
space-time except for the black hole's core region. As a next problem, it turns
out that the equation to obtain the horizon radii is given by a fifth-order
equation due to the regularization effect. We overcome this problem by treating
the regularization effect perturbatively. As a result, we can obtain the
near-horizon extremal Kerr (NHEK) geometry with the correction of the
regularization effect. Once obtaining the NHEK geometry, we can obtain the
central charge and the Frolov-Thorne temperature in the dual CFT. Using these,
we compute its entropy through the Cardy formula, which agrees with the one
computed from the Bekenstein-Hawking entropy.


title:
The Crisis in Astrophysics and Planetary Science: How Commercial Space
  and Program Design Principles will let us Escape

abstract:
  Astrophysics and planetary science are in crisis. The large missions we need
for the next generation of observations cost too much to let us do more than
one at a time. This spreads the science out onto a generational timescale,
inhibiting progress in both fields. There are two escape paths. In the long
run, but still well within our planning horizon, commercial space will bring
mission costs down substantially allowing parallel missions at multiple
wavelengths or to multiple destinations. In the short run, adopting prudent
principles for designing a research program will let us maintain vitality in
the field by retaining breadth at a modest cost in depth.


title:
Visualizing Dependence in High-Dimensional Data: An Application to S&P
  500 Constituent Data

abstract:
  The notion of a zenpath and a zenplot is introduced to search and detect
dependence in high-dimensional data for model building and statistical
inference. By using any measure of dependence between two random variables
(such as correlation, Spearman's rho, Kendall's tau, tail dependence etc.), a
zenpath can construct paths through pairs of variables in different ways, which
can then be laid out and displayed by a zenplot. The approach is illustrated by
investigating tail dependence and model fit in constituent data of the S&P 500
during the financial crisis of 2007-2008. The corresponding Global Industry
Classification Standard (GICS) sector information is also addressed.
  Zenpaths and zenplots are useful tools for exploring dependence in
high-dimensional data, for example, from the realm of finance, insurance and
quantitative risk management. All presented algorithms are implemented using
the R package zenplots and all examples and graphics in the paper can be
reproduced using the accompanying demo SP500.


title: CNN Architectures for Large-Scale Audio Classification

abstract:
  Convolutional Neural Networks (CNNs) have proven very effective in image
classification and show promise for audio. We use various CNN architectures to
classify the soundtracks of a dataset of 70M training videos (5.24 million
hours) with 30,871 video-level labels. We examine fully connected Deep Neural
Networks (DNNs), AlexNet [1], VGG [2], Inception [3], and ResNet [4]. We
investigate varying the size of both training set and label vocabulary, finding
that analogs of the CNNs used in image classification do well on our audio
classification task, and larger training and label sets help up to a point. A
model using embeddings from these classifiers does much better than raw
features on the Audio Set [5] Acoustic Event Detection (AED) classification
task.


title:
Elliptic regularity and quantitative homogenization on percolation
  clusters

abstract:
  We establish quantitative homogenization, large-scale regularity and
Liouville results for the random conductance model on a supercritical
(Bernoulli bond) percolation cluster. The results are also new in the case that
the conductivity is constant on the cluster. The argument passes through a
series of renormalization steps: first, we use standard percolation results to
find a large scale above which the geometry of the percolation cluster behaves
(in a sense made precise) like that of Euclidean space. Then, following the
work of Barlow, we find a succession of larger scales on which certain
functional and elliptic estimates hold. This gives us the analytic tools to
adapt the quantitative homogenization program of Armstrong and Smart to
estimate the yet larger scale on which solutions on the cluster can be
well-approximated by harmonic functions on $\mathbb{R}^d$. This is the first
quantitative homogenization result in a porous medium and the harmonic
approximation allows us to estimate the scale on which a higher-order
regularity theory holds. The size of each of these random scales is shown to
have at least a stretched exponential moment. As a consequence of this
regularity theory, we obtain a Liouville-type result that states that, for each
$k\in\mathbb{N}$, the vector space of solutions growing at most like
$o(|x|^{k+1})$ as $|x|\to \infty$ has the same dimension as the set of harmonic
polynomials of degree at most $k$, generalizing a result of Benjamini,
Duminil-Copin, Kozma, and Yadin from $k\le1$ to $k\in\mathbb{N}$.


title:
A Searchlight Factor Model Approach for Locating Shared Information in
  Multi-Subject fMRI Analysis

abstract:
  There is a growing interest in joint multi-subject fMRI analysis. The
challenge of such analysis comes from inherent anatomical and functional
variability across subjects. One approach to resolving this is a shared
response factor model. This assumes a shared and time synchronized stimulus
across subjects. Such a model can often identify shared information, but it may
not be able to pinpoint with high resolution the spatial location of this
information. In this work, we examine a searchlight based shared response model
to identify shared information in small contiguous regions (searchlights)
across the whole brain. Validation using classification tasks demonstrates that
we can pinpoint informative local regions.


title:
Maximizing the Strong Triadic Closure in Split Graphs and Proper
  Interval Graphs

abstract:
  In social networks the {\sc Strong Triadic Closure} is an assignment of the
edges with strong or weak labels such that any two vertices that have a common
neighbor with a strong edge are adjacent. The problem of maximizing the number
of strong edges that satisfy the strong triadic closure was recently shown to
be NP-complete for general graphs. Here we initiate the study of graph classes
for which the problem is solvable. We show that the problem admits a
polynomial-time algorithm for two unrelated classes of graphs: proper interval
graphs and trivially-perfect graphs. To complement our result, we show that the
problem remains NP-complete on split graphs, and consequently also on chordal
graphs. Thus we contribute to define the first border between graph classes on
which the problem is polynomially solvable and on which it remains NP-complete.


title:
Understanding the Strain-Dependent Dielectric Behavior of Carbon Black
  Reinforced Natural Rubber: An interfacial or bulk phenomenon?

abstract:
  Filler-polymer interactions are one of the keys to understanding the physical
properties of polymer composites. These interactions give rise to an interface
with specific properties that may have a nontrivial effect on the macroscopic
properties of composites. Direct measurement of the interface properties at
nanometer scale is usually unavailable. Thus, interface properties are often
back calculated from the bulk response using a computational model. However, if
the model does not take into account the morphology of the filler dispersion,
the results can be misleading. Recently it has been found that the dielectric
response of a carbon black filled natural rubber film can change dramatically
upon stretching [Huang, Macromolecules 49, 2339 (2016)]1. In this paper, we
will show that this phenomenon can be largely explained by changes in filler
cluster connectivity due to strain and is probably not caused by changes in the
interfacial interactions. To support the argument, the polarization mechanism
of the composites in the measured frequency range is analyzed and numerical
models are developed to virtually reproduce the physical phenomenon as a
function of strain. As a result, a power-law dependence of dielectric
permittivity with strain is derived, which matches closely with the
experimental results.


title:
On the statistical properties of viral misinformation in online social
  media

abstract:
  The massive diffusion of online social media allows for the rapid and
uncontrolled spreading of conspiracy theories, hoaxes, unsubstantiated claims,
and false news. Such an impressive amount of misinformation can influence
policy preferences and encourage behaviors strongly divergent from recommended
practices. In this paper, we study the statistical properties of viral
misinformation in online social media. By means of methods belonging to Extreme
Value Theory, we show that the number of extremely viral posts over time
follows a homogeneous Poisson process, and that the interarrival times between
such posts are independent and identically distributed, following an
exponential distribution. Moreover, we characterize the uncertainty around the
rate parameter of the Poisson process through Bayesian methods. Finally, we are
able to derive the predictive posterior probability distribution of the number
of posts exceeding a certain threshold of shares over a finite interval of
time.


title: Composably secure time-frequency quantum key distribution

abstract:
  We present a composable security proof, valid against arbitrary attacks and
including finite-size effects, for a high dimensional time-frequency quantum
key distribution (TFQKD) protocol based upon spectrally entangled photons.
Previous works have focused on TFQKD schemes as it combines the impressive loss
tolerance of single-photon QKD with the large alphabets of continuous variable
(CV) schemes, which enables the potential for more than one bit of secret key
per transmission. However, the finite-size security of such schemes has only
been proven under the assumption of collective Gaussian attacks. Here, by
combining recent advances in entropic uncertainty relations for CVQKD with
decoy state analysis, we derive a composable security proof that predicts key
rates on the order of Mbits/s over metropolitan distances (40km or less) and
maximum transmission distances of up to 140km.


title:
Stability of Integral Delay Equations and Stabilization of
  Age-Structured Models

abstract:
  We present bounded dynamic (but observer-free) output feedback laws that
achieve global stabilization of equilibrium profiles of the partial
differential equation (PDE) model of a simplified, age-structured chemostat
model. The chemostat PDE state is positive-valued, which means that our global
stabilization is established in the positive orthant of a particular function
space-a rather non-standard situation, for which we develop non-standard tools.
Our feedback laws do not employ any of the (distributed) parametric knowledge
of the model. Moreover, we provide a family of highly unconventional Control
Lyapunov Functionals (CLFs) for the age-structured chemostat PDE model. Two
kinds of feedback stabilizers are provided: stabilizers with continuously
adjusted input and sampled-data stabilizers. The results are based on the
transformation of the first-order hyperbolic partial differential equation to
an ordinary differential equation (one-dimensional) and an integral delay
equation (infinite-dimensional). Novel stability results for integral delay
equations are also provided; the results are of independent interest and allow
the explicit construction of the CLF for the age-structured chemostat model.


title: Higher dimensional generalizations of twistor spaces

abstract:
  We construct a generalization of twistor spaces of hypercomplex manifolds and
hyper-Kahler manifolds $M$, by generalizing the twistor $\mathbb{P}^{1}$ to a
more general complex manifold $Q$. The resulting manifold $X$ is complex if and
only if $Q$ admits a holomorphic map to $\mathbb{P}^1$. We make branched double
covers of these manifolds. Some class of these branched double covers can give
rise to non-Kahler Calabi-Yau manifolds. We show that these manifolds $X$ and
their branched double covers are non-Kahler. In the cases that $Q$ is a
balanced manifold, the resulting manifold $X$ and its special branched double
cover have balanced Hermitian metrics.


title: A note on shadowing properties

abstract:
  Let $\mathfrak{X}^{1}(M)$ be the space of $C^{1}$-vector fields on $M$
endowed with the $C^{1}$-topology and let $\Lambda$ be an isolated set for a
$X\in\mathfrak{X}^{1}(M)$. In this paper, we directly prove that every
$X\in\mathfrak{X}^{1}(M)$ having the (asymptotic) average shadowing property in
$\Lambda$ has no proper attractor in $\Lambda$. Our proof is a direct version
of the results by Gu and Ribeiro. We also show that every
$X\in\mathfrak{X}^{1}(M)$ having the (two-sided) limit shadowing property with
a gap in $\Lambda$ is topologically transitive and has the shadowing property
in $\Lambda$.


title: A Quantum Information Geometric Approach to Renormalization

abstract:
  This essay constitutes a review of the information geometric approach to
renormalization developed in the recent works of B\'eny and Osborne as well as
a detailed work-through of some of their contents. A noncommutative
generalization of information geometry allows one to treat quantum state
distinguishability in geometric terms with an intuitive empirical
interpretation, allowing for an information theoretic prescription of
renormalization which incorporates both the condensed matter and quantum field
theoretic approaches.


title:
Fast dual proximal gradient algorithms with rate $O(1/k^{1.5})$ for
  convex minimization

abstract:
  We consider minimizing the composite function that consists of a strongly
convex function and a convex function. The fast dual proximal gradient (FDPG)
method decreases the dual function with a rate $O(1/k^2)$, leading to a rate
$O(1/k)$ for decreasing the primal function. We propose a generalized FDPG
method that guarantees an $O(1/k^{1.5})$ rate for the dual proximal gradient
norm decrease. By relating this to the primal function decrease, the proposed
approach decreases the primal function with the improved $O(1/k^{1.5})$ rate.


title:
Modeling Orbital Gamma-Ray Spectroscopy Experiments at Carbonaceous
  Asteroids

abstract:
  To evaluate the feasibility of measuring differences in bulk composition
among carbonaceous meteorite parent bodies from an asteroid or comet orbiter,
we present the results of a performance simulation of an orbital gamma-ray
spectroscopy ("GRS") experiment in a Dawn-like orbit around spherical model
asteroids with a range of carbonaceous compositions. The orbital altitude was
held equal to the asteroid radius for 4.5 months. Both the asteroid gamma-ray
spectrum and the spacecraft background flux were calculated using the MCNPX
Monte-Carlo code. GRS is sensitive to depths below the optical surface (to
~20--50 cm depth depending on material density). This technique can therefore
measure underlying compositions beneath a sulfur-depleted (e.g., Nittler et al.
2001) or desiccated surface layer. We find that 3\sigma\ uncertainties of under
1 wt% are achievable for H, C, O, Si, S, Fe, and Cl for five carbonaceous
meteorite compositions using the heritage Mars Odyssey GRS design in a
spacecraft- deck-mounted configuration at the Odyssey end-of-mission energy
resolution, FWHM = 5.7 keV at 1332 keV. The calculated compositional
uncertainties are smaller than the compositional differences between
carbonaceous chondrite subclasses.


title: Semi-supervised Speech Enhancement in Envelop and Details Subspaces

abstract:
  In this study, we propose a modulation decoupling based single channel speech
enhancement subspace framework, in which the spectrogram of noisy speech is
decoupled as the product of a spectral envelop subspace and a spectral details
subspace. This decoupling approach provides a method to specifically work on
elimination of those noises that greatly affect the intelligibility. Two
supervised low-rank and sparse decomposition schemes are developed in the
spectral envelop subspace to obtain a robust recovery of speech components. A
Bayesian formulation of non-negative factorization is used to learn the speech
dictionary from the spectral envelop subspace of clean speech samples. In the
spectral details subspace, a standard robust principal component analysis is
implemented to extract the speech components. The validation results show that
compared with four speech enhancement algorithms, including MMSE-SPP, NMF-RPCA,
RPCA, and LARC, the proposed MS based algorithms achieve satisfactory
performance on improving perceptual quality, and especially speech
intelligibility.


title: Contextual RNN-GANs for Abstract Reasoning Diagram Generation

abstract:
  Understanding, predicting, and generating object motions and transformations
is a core problem in artificial intelligence. Modeling sequences of evolving
images may provide better representations and models of motion and may
ultimately be used for forecasting, simulation, or video generation.
Diagrammatic Abstract Reasoning is an avenue in which diagrams evolve in
complex patterns and one needs to infer the underlying pattern sequence and
generate the next image in the sequence. For this, we develop a novel
Contextual Generative Adversarial Network based on Recurrent Neural Networks
(Context-RNN-GANs), where both the generator and the discriminator modules are
based on contextual history (modeled as RNNs) and the adversarial discriminator
guides the generator to produce realistic images for the particular time step
in the image sequence. We evaluate the Context-RNN-GAN model (and its variants)
on a novel dataset of Diagrammatic Abstract Reasoning, where it performs
competitively with 10th-grade human performance but there is still scope for
interesting improvements as compared to college-grade human performance. We
also evaluate our model on a standard video next-frame prediction task,
achieving improved performance over comparable state-of-the-art.


title:
Tables of experimental branching ratios of Auger-type post collisional
  ionization of rare gases

abstract:
  When an electron is emitted from a sub-valence shell, a vacancy is created
and there is a not-null probability for different post collisional ionization
(PCI) processes giving rise to a higher target charge state. It is reasonable
to consider that PCI is a time-delayed electron emission and, therefore,
independent of the projectile. We include the tables of the branching ratios of
$0-6$ post-collisionally emitted electrons after single ionization of Ne, Ar,
Kr and Xe in different inner shells. These values have already been employed
with good results in previous calculations of multiple ionization of rare gases
by electrons, positron, protons, antiprotons and different positive ions (see
the text and references therein). These tables and explanation is included in
[Montanari C C and Miraglia J E 2014, \textit{J. Phys. B: At. Mol. Opt. Phys.}
{\bf 45}, 105203].


title: Hamiltonian identifiability assisted by single-probe measurement

abstract:
  We study the Hamiltonian identifiability of a many-body spin-1/2 system
assisted by the measure- ment on a single quantum probe based on the
eigensystem realization algorithm (ERA) approach employed in Phys. Rev. Lett.
113, 080401 (2014). We demonstrate a potential application of Gr\"obner basis
to the identifiability test of the Hamiltonian, and provide the necessary
experimental resources, such as the lower bound in the number of the required
measurement points, the upper bound in total required evolution time, and thus
the total measurement time. Focusing on the examples of the identifiability in
the spin chain model with nearest-neighboring interaction, we classify the
spin-chain Hamiltonian based on its identifiability, and provide the control
protocols to engineer the nonidentifiable Hamiltonian to be an identifiable
Hamiltonian.


title: Local and Union Boxicity

abstract:
  The boxicity $\operatorname{box}(H)$ of a graph $H$ is the smallest integer
$d$ such that $H$ is the intersection of $d$ interval graphs, or equivalently,
that $H$ is the intersection graph of axis-aligned boxes in $\mathbb{R}^d$.
These intersection representations can be interpreted as covering
representations of the complement $H^c$ of $H$ with co-interval graphs, that
is, complements of interval graphs. We follow the recent framework of global,
local and folded covering numbers (Knauer and Ueckerdt, Discrete Mathematics
339 (2016)) to define two new parameters: the local boxicity
$\operatorname{box}_\ell(H)$ and the union boxicity
$\overline{\operatorname{box}}(H)$ of $H$. The union boxicity of $H$ is the
smallest $d$ such that $H^c$ can be covered with $d$ vertex-disjoint unions of
co-interval graphs, while the local boxicity of $H$ is the smallest $d$ such
that $H^c$ can be covered with co-interval graphs, at most $d$ at every vertex.
  We show that for every graph $H$ we have $\operatorname{box}_\ell(H) \leq
\overline{\operatorname{box}}(H) \leq \operatorname{box}(H)$ and that each of
these inequalities can be arbitrarily far apart. Moreover, we show that local
and union boxicity are also characterized by intersection representations of
appropriate axis-aligned boxes in $\mathbb{R}^d$. We demonstrate with a few
striking examples, that in a sense, the local boxicity is a better indication
for the complexity of a graph, than the classical boxicity.


title:
Hierarchical Multistage Gaussian Signaling Games in Noncooperative
  Communication and Control Systems

abstract:
  We analyze in this paper finite horizon hierarchical signaling games between
(information provider) senders and (decision maker) receivers in a dynamic
environment. The underlying information evolves in time while sender and
receiver interact repeatedly. Different from the classical communication
(control) models, however, the sender (sensor) and the receiver (controller)
have different objectives and there is a hierarchy between the players such
that the sender leads the game by announcing his policies beforehand. He needs
to anticipate the reaction of the receiver and the impact of the actions on the
horizon while controlling the transparency of the disclosed information at each
interaction. With quadratic cost functions and multivariate Gaussian processes,
evolving according to first order auto-regressive models, we show that
memoryless "linear" sender signaling rules are optimal (in the sense of
game-theoretic hierarchical equilibrium) within the general class of measurable
policies in the noncooperative communication context. In the noncooperative
control context, we also analyze the hierarchical equilibrium for linear
signaling rules and provide an algorithm to compute the optimal linear
signaling rules numerically with global optimality guarantees.


title:
A Cross Entropy based Stochastic Approximation Algorithm for
  Reinforcement Learning with Linear Function Approximation

abstract:
  In this paper, we provide a new algorithm for the problem of prediction in
Reinforcement Learning, \emph{i.e.}, estimating the Value Function of a Markov
Reward Process (MRP) using the linear function approximation architecture, with
memory and computation costs scaling quadratically in the size of the feature
set. The algorithm is a multi-timescale variant of the very popular Cross
Entropy (CE) method which is a model based search method to find the global
optimum of a real-valued function. This is the first time a model based search
method is used for the prediction problem. The application of CE to a
stochastic setting is a completely unexplored domain. A proof of convergence
using the ODE method is provided. The theoretical results are supplemented with
experimental comparisons. The algorithm achieves good performance fairly
consistently on many RL benchmark problems. This demonstrates the
competitiveness of our algorithm against least squares and other
state-of-the-art algorithms in terms of computational efficiency, accuracy and
stability.


title: Compressed Sensing for Finite-Valued Signals

abstract:
  The need of reconstructing discrete-valued sparse signals from few
measurements, that is solving an undetermined system of linear equations,
appears frequently in science and engineering. Whereas classical compressed
sensing algorithms do not incorporate the additional knowledge of the discrete
nature of the signal, classical lattice decoding approaches such as the sphere
decoder do not utilize sparsity constraints.
  In this work, we present an approach that incorporates a discrete values
prior into basis pursuit. In particular, we address unipolar binary and bipolar
ternary sparse signals, i.e., sparse signals with entries in $\{0,1\}$,
respectively in $\{-1,0,1\}$. We will show that phase transition takes place
earlier than when using the classical basis pursuit approach and that,
independently of the sparsity of the signal, at most $N/2$, respectively
$3N/4$, measurements are necessary to recover a unipolar binary, and a bipolar
ternary signal uniquely, where $N$ is the dimension of the ambient space. We
will further discuss robustness of the algorithm and generalizations to signals
with entries in larger alphabets.


title: Redefining Binarization and the Visual Archetype

abstract:
  Although binarization is considered passe, it still remains a highly popular
research topic. In this paper we propose a rethinking of what binarization is.
We introduce the notion of the visual archetype as the ideal form of any one
document. Binarization can be defined as the restoration of the visual
archetype for a class of images. This definition broadens the scope of what
binarization means but also suggests ground-truth should focus on the
foreground.


title: Free orbits for minimal actions on the circle

abstract:
  We prove that if $\Gamma$ is a countable group without a subgroup isomorphic
to $\mathbb{Z}^2$ that acts faithfully and minimally by orientation preserving
homeomorphisms on the circle, then it has a free orbit. We give examples
showing that this does not hold for actions by homeomorphisms of the line.


title: Connective C*-algebras

abstract:
  Connectivity is a homotopy invariant property of separable C*-algebras which
has three notable consequences: absence of nontrivial projections,
quasidiagonality and a more geometric realization of KK-theory for nuclear
C*-algebras using asymptotic morphisms. The purpose of this paper is to further
explore the class of connective C*-algebras. We give new characterizations of
connectivity for exact and for nuclear separable C*-algebras and show that an
extension of connective separable nuclear C*-algebras is connective. We
establish connectivity or lack of connectivity for C*-algebras associated to
certain classes of groups: virtually abelian groups, linear connected nilpotent
Lie groups and linear connected semisimple Lie groups.


title:
Keyless authentication in the presence of a simultaneously transmitting
  adversary

abstract:
  If Alice must communicate with Bob over a channel shared with the adversarial
Eve, then Bob must be able to validate the authenticity of the message. In
particular we consider the model where Alice and Eve share a discrete
memoryless multiple access channel with Bob, thus allowing simultaneous
transmissions from Alice and Eve. By traditional random coding arguments, we
demonstrate an inner bound on the rate at which Alice may transmit, while still
granting Bob the ability to authenticate. Furthermore this is accomplished in
spite of Alice and Bob lacking a pre-shared key, as well as allowing Eve prior
knowledge of both the codebook Alice and Bob share and the messages Alice
transmits.


title:
Intruder penetration into granular matter studied by Lock-in
  Accelerometry

abstract:
  Understanding the penetration dynamics of intruders in granular beds is
relevant not only for fundamental physics, but also for geophysical processes
and construction on sediments or granular soils in areas potentially affected
by earthquakes. In this work, we use Lock-in accelerometry to study the
penetration of intruders into quasi-2D granular matter fluidized by lateral
shaking. We observed that there are two well-defined stages in the penetration
dynamics as the intruder sinks into the granular material.


title:
Magnetically elevated accretion disks in active galactic nuclei: broad
  emission line regions and associated star formation

abstract:
  We propose that the accretion disks fueling active galactic nuclei are
supported vertically against gravity by a strong toroidal ($\phi-$direction)
magnetic field that develops naturally as the result of an accretion disk
dynamo. The magnetic pressure elevates most of the gas carrying the accretion
flow at $R$ to large heights $z > 0.1 R$ and low densities, while leaving a
thin dense layer containing most of the mass --- but contributing very little
accretion --- around the equator. We show that such a disk model leads
naturally to the formation of a broad emission line region through thermal
instability. Extrapolating to larger radii, we demonstrate that local
gravitational instability and associated star formation are strongly suppressed
compared to standard disk models for AGN, although star formation in the
equatorial zone is predicted for sufficiently high mass supply rates. This new
class of accretion disk models thus appears capable of resolving two
longstanding puzzles in the theory of AGN fueling: the formation of broad
emission line regions and the suppression of fragmentation thought to inhibit
accretion at the required rates. We show that the disk of stars that formed in
the Galactic Center a few million years ago could have resulted from an episode
of magnetically elevated accretion at $> 0.1$ of the Eddington limit.


title:
From arteries to boreholes: Steady-state response of a poroelastic
  cylinder to fluid injection

abstract:
  The radially outward flow of fluid into a porous medium occurs in many
practical problems, from transport across vascular walls to the pressurisation
of boreholes. As the driving pressure becomes non-negligible relative to the
stiffness of the solid structure, the poromechanical coupling between the fluid
and the solid has an increasingly strong impact on the flow. For very large
pressures or very soft materials, as is the case for hydraulic fracturing and
arterial flows, this coupling can lead to large deformations and, hence, to
strong deviations from a classical, linear-poroelastic response. Here, we study
this problem by analysing the steady-state response of a poroelastic cylinder
to fluid injection. We consider the qualitative and quantitative impacts of
kinematic and constitutive nonlinearity, highlighting the strong impact of
deformation-dependent permeability. We show that the wall thickness (thick vs.
thin) and the outer boundary condition (free vs. constrained) play a central
role in controlling the mechanics.


title:
Wind-invariant saltation heights imply linear scaling of aeolian
  saltation flux with shear stress

abstract:
  Wind-driven sand transport generates atmospheric dust, forms dunes, and
sculpts landscapes. However, it remains unclear how the sand flux scales with
wind speed, largely because models do not agree on how particle speed changes
with wind shear velocity. Here, we present comprehensive measurements from
three new field sites and three published studies, showing that characteristic
saltation layer heights, and thus particle speeds, remain approximately
constant with shear velocity. This result implies a linear dependence of
saltation flux on wind shear stress, which contrasts with the nonlinear 3/2
scaling used in most aeolian process predictions. We confirm the linear flux
law with direct measurements of the stress-flux relationship occurring at each
site. Models for dust generation, dune migration, and other processes driven by
wind-blown sand on Earth, Mars, and several other planetary surfaces should be
modified to account for linear stress-flux scaling.


title: Drying of agarose gels monitored by in-situ interferometry

abstract:
  Hydrogels behave as viscoelastic soft solids and display a porous
microstructure filled with water with typical amounts of 90\%~w/w or more. As
such, these materials are highly sensitive to water loss through evaporation,
which impacts their mechanical properties. Yet, aside from scattered empirical
observations, little is known about the gel drying kinetics for which there is
a lack of temporally and spatially resolved measurements. Here we report a
benchmark study of the slow drying of agarose gels cast in cylindrical Petri
dishes. The weak adhesion of the gel to the lateral wall of the dish guarantees
that the gel diameter remains constant during the drying process and that the
gel shrinkage is purely vertical. The thinning rate is monitored by in-situ
interferometry using a Michelson interferometer. The displacement of
interference fringes are analyzed using an original spatiotemporal filtering
method, which allows us to measure local thinning rates of about 10~nm/s with
high accuracy. Experiments conducted at different positions along the gel
radius show that the gel thins locally with a constant velocity before
experiencing a sudden collapse at the end of the drying process. We further use
the thinning rate measured at the center of the dish during the early stage of
the drying process as a robust observable to quantify the role of additives on
the gel drying kinetics and compare gels of different compositions. Our work
exemplifies interferometry as a powerful tool to quantify the impact of minute
amounts of additives on the drying of biopolymer gels.


title:
The Bartnik-Bray outer mass of small metric spheres in time-symmetric
  3-slices

abstract:
  Given a sphere with Bartnik data close to that of a round sphere in Euclidean
3-space, we compute its Bartnik-Bray outer mass to first order in the data's
deviation from the standard sphere. The Hawking mass gives a well-known lower
bound, and an upper bound is obtained by estimating the mass of a static vacuum
extension. As an application we confirm that in a time-symmetric slice
concentric geodesic balls shrinking to a point have mass-to-volume ratio
converging to the energy density at their center, in accord with physical
expectation and the behavior of other quasilocal masses. For balls shrinking to
a flat point we can also compute the outer mass to fifth order in the
radius---the term is proportional to the Laplacian of the scalar curvature at
the center---but our estimate is not refined enough to identify this term at a
point which is merely scalar flat. In particular it cannot discern
gravitational contributions to the mass.


title:
Bianchi I cosmology in the presence of a causally regularized viscous
  fluid

abstract:
  We analyze the dynamics of a Bianchi I cosmology in the presence of a viscous
fluid, causally regularized according to the Lichnerowicz approach. We show how
the effect induced by shear viscosity is still able to produce a matter
creation phenomenon, meaning that also in the regularized theory we address,
the Universe is emerging from a singularity with a vanishing energy density
value. We discuss the structure of the singularity in the isotropic limit, when
bulk viscosity is the only retained contribution. We see that, as far as
viscosity is not a dominant effect, the dynamics of the isotropic Universe
possesses the usual inviscid power-law behavior but in correspondence of
aneffective equation of state, depending on the bulk viscosity coefficient.
Finally, we show that, in the limit of a strong non-thermodynamical equilibrium
of the Universe mimicked by a dominant contribution of the effective viscous
pressure, a power-law inflation behavior of the Universe appears, the
cosmological horizons are removed and a significant amount of entropy is
produced.


title:
Principles and simulations of high-resolution STM imaging with flexible
  tip apex

abstract:
  We present a robust but still efficient simulation approach for
high-resolution scanning tunneling microscopy with a flexible tip apex showing
sharp submolecular features. The approach takes into account the electronic
structure of sample and tip and relaxation of the tip apex. We validate our
model by achieving good agreement with various experimental images which allows
us to explain the origin of several observed features. Namely, we have found
that high-resolution STM mechanism consists of the standard STM imaging,
convolving electronic states of the sample and the tip apex orbital structure,
with the contrast heavily distorted by the relaxation of the flexible apex
caused by interaction with the substrate.


title: Distributed Navigation of Multi-Robot Systems For Sensing Coverage

abstract:
  This research investigates decentralized control of mobile robots
specifically for coverage problems. There are different approaches associated
with decentralized control strategy for coverage control problems. We perform a
comparative review of these approaches and use the approach based on simple
local coordination rules. We investigate this extensively used nearest
neighbour rule based approach for developing coverage control algorithms. In
this approach, a mobile robot gives an equal importance to every neighbour
robot coming under its communication range. We develop our control approach by
making some of the mobile robots playing a more influential role than other
members in the team. The approach based on this control strategy becomes
efficient in terms of achieving a consensus on control inputs, say heading
angle, velocity, etc. The decentralized control of mobile robots can also
exhibit a cyclic behaviour under some physical constraints like a quantized
orientation of mobile robot. We further investigate the cyclic behaviour
appearing due to the quantized control of mobile robots under some conditions.
Our nearest neighbour rule based approach offers a biased strategy in case of
cyclic behaviour appearing in the team of mobile robots. We consider a
clustering technique inside the team of mobile robots. Our decentralized
control strategy calculates the similarity measure among the neighbours of a
mobile robot. The team of mobile robots with the similarity measure based
approach becomes efficient in achieving a fast consensus like on heading angle
or velocity. We perform a rigorous mathematical analysis of our developed
approach. We also develop a condition based on relaxed criteria for achieving
consensus on velocity or heading angle of the mobile robots. Our validation
approach is based on mathematical arguments and extensive computer simulations.


title: A note on square-free factorizations

abstract:
  We analyze properties of various square-free factorizations in greatest
common divisor domains and domains satisfying the ascending chain condition for
principal ideals.


title: A rigidity result for some parabolic germs

abstract:
  The goal of this article is to prove a rigidity result for unicritical
polynomials with parabolic cycles. More precisely, we show that if two
unicritical polynomials have conformally conjugate parabolic germs, then the
polynomials are affinely conjugate.


title:
MASTER OT J190519.41+301524.4: New Eclipsing Cataclysmic Variable of VY
  Scl Type

abstract:
  MASTER OT J190519.41+301524.4 was discovered as an optical transient of 15.7m
by the Mobile Astronomical System of TElescope-Robots in March 2014. We report
the results of photometric observations of this variable performed at Lajatico
Astronomical Center in June-July 2015. The light curve is showing deep V-shaped
eclipses with an amplitude of two magnitudes. The orbital period was determined
to be 0.129694 d (3.113 h). Based on the archival observations and the shape of
the orbital curve we suggest that MASTER OT J190519.41+301524.4 is a new
cataclysmic variable of VY Scl type ("anti-nova") with an inclination angle
close to 90 deg.