title: Blue straggler formation at core collapse

abstract:
  Among the most striking feature of blue straggler stars (BSS) is the presence
of multiple sequences of BSSs in the colour-magnitude diagrams (CMDs) of
several globular clusters. It is often envisaged that such a multiple BSS
sequence would arise due a recent core collapse of the host cluster, triggering
a number of stellar collisions and binary mass transfers simultaneously over a
brief episode of time. Here we examine this scenario using direct N-body
computations of moderately massive star clusters (of order 10^4 Msun ). As a
preliminary attempt, these models are initiated with approx. 8-10 Gyr old
stellar population and King profiles of high concentrations, being "tuned" to
undergo core collapse quickly. BSSs are indeed found to form in a "burst" at
the onset of the core collapse and several of such BS-bursts occur during the
post-core-collapse phase. In those models that include a few percent primordial
binaries, both collisional and binary BSSs form after the onset of the (near)
core-collapse. However, there is as such no clear discrimination between the
two types of BSSs in the corresponding computed CMDs. We note that this may be
due to the less number of BSSs formed in these less massive models than that in
actual globular clusters.


title:
The maximum of the minimal multiplicity of eigenvalues of symmetric
  matrices whose pattern is constrained by a graph

abstract:
  In this paper we introduce a parameter $Mm(G)$, defined as the maximum over
the minimal multiplicities of eigenvalues among all symmetric matrices
corresponding to a graph $G$. We compute $Mm(G)$ for several families of
graphs.


title: Stellar populations in the outskirts of M31: the mid-infrared view

abstract:
  The mid-infrared provides a unique view of galaxy stellar populations,
sensitive to both the integrated light of old, low-mass stars and to individual
dusty mass-losing stars. We present results from an extended Spitzer/IRAC
survey of M31 with total lengths of 6.6 and 4.4 degrees along the major and
minor axes, respectively. The integrated surface brightness profile proves to
be surprisingly diffcult to trace in the outskirts of the galaxy, but we can
also investigate the disk/halo transition via a star count profile, with
careful correction for foreground and background contamination. Our
point-source catalog allows us to report on mid-infrared properties of
individual objects in the outskirts of M31, via cross-correlation with PAndAS,
WISE, and other catalogs.


title:
On the initial boundary value problem of a Navier-Stokes/$Q$-tensor
  model for liquid crystals

abstract:
  This work is concerned with the solvability of a Navier-Stokes/$Q$-tensor
coupled system modeling the nematic liquid crystal flow on a bounded domain in
three dimensional Euclidian space with strong anchoring boundary condition for
the order parameter. We prove the existence of local in time strong solution to
the system with the anisotropic elastic energy. The proof is based on mainly
two ingredients: first, we show that the Euler-Lagrange operator corresponding
to the Landau-de Gennes free energy with general elastic coefficients fulfills
the strong Legendre condition. This result together with a higher order energy
estimate leads to the well-posedness of the linearized system, and then a local
in time solution of the original system which is regular in temporal variable
follows via a fixed point argument. Secondly, the hydrodynamic part of the
coupled system can be reformulated into a quasi-stationary Stokes type equation
to which the regularity theory of the generalized Stokes system, and then a
bootstrap argument can be applied to enhance the spatial regularity of the
local in time solution.


title: LOLAS-2 : redesign of an optical turbulence profiler

abstract:
  We present the development, tests and first results of the second generation
Low Layer Scidar (LOLAS-2). This instrument constitutes a strongly improved
version of the prototype Low Layer Scidar, which is aimed at the measurement of
optical turbulence profiles close to the ground, with high altitude-resolution.
The method is based on the Generalised Scidar principle which consists in
taking double-star scintillation images on a defocused pupil plane and
calculating in real time the autocovariance of the scintillation. The main
components are an open-truss 40-cm Ritchey-Chr\'etien telescope, a german-type
equatorial mount, an Electron Multiplying CCD camera and a dedicated
acquisition and real-time data processing software. The new optical design of
LOLAS-2 is significantly simplified compared with the prototype. The
experiments carried out to test the permanence of the image within the useful
zone of the detector and the stability of the telescope focus show that LOLAS-2
can function without the use of the autoguiding and autofocus algorithms that
were developed for the prototype version. Optical turbulence profiles obtained
with the new Low Layer Scidar have the best altitude-resolution ever achieved
with Scidar-like techniques (6.3 m). The simplification of the optical layout
and the improved mechanical properties of the telescope and mount make of
LOLAS-2 a more robust instrument.


title: Linear radial Regge trajectories for mesons with any quark flavor

abstract:
  In the Regge phenomenology, the radial spectrum of light mesons is given by a
linear relation $M_n^2=a(n+b)$, where $a$ is a universal slope, the
dimensionless intercept $b$ depends on quantum numbers, and $n$ enumerates the
excited states in radial recurrences. The usual extensions of this relation to
heavy quarkonia in the framework of hadron string models typically lead to
strong nonlinearities which seem to be at variance with the available
experimental data. Introducing a radially static string picture of mesons, we
put forward a linear generalization $(M_n-m_1-m_2)^2=a(n+b)$, where $m_{1,2}$
are quark masses. The vector channel contains enough experimental states to
check this new relation and a good agreement is observed. It is shown that this
generalization leads to a simple estimate of current quark masses from the
radial spectra.


title: Generalized Weyl modules for twisted current algebras

abstract:
  We introduce the notion of generalized Weyl modules for twisted current
algebras. We study their representation-theoretic and combinatorial properties
and connection to the theory of nonsymmetric Macdonald polynomials. As an
application we compute the dimension of the classical Weyl modules in the
remaining unknown case.


title:
Magnetic Properties from the Viewpoints of Electronic Hamiltonian: Spin
  Exchange Parameters, Spin Orientation and Spin-Half Misconception

abstract:
  In this chapter we review the quantitative and qualitative aspects of
describing the properties of magnetic solids on the basis of electronic
Hamiltonian. We show that a spin Hamiltonian approach becomes consistent with
an electronic Hamiltonian approach if the spin lattice and its associated spin
exchange parameters, to be used for the spin Hamiltonian, are determined by the
energy-mapping analysis based on DFT calculations. The preferred spin
orientation (i.e., the magnetic anisotropy) of a magnetic ion is not predicted
by a spin Hamiltonian because it does not include the orbital degree of freedom
explicitly. In contrast, the magnetic anisotropy is readily predicted by
electronic structure theories employing both orbital and spin degrees of
freedom, if one takes into consideration the spin-orbit coupling (SOC). It was
shown that the preferred spin orientation of a magnetic ion can be predicted
and understood in terms of the HOMO-LUMO interactions of the magnetic ion by
taking SOC as perturbation. A spin Hamiltonian gives rise to the spin-half
misconception, namely, the blind belief that spin-half magnetic ions do not
possess magnetic anisotropy that arise from SOC. This misconception is a direct
consequence from the limitedness of a spin Hamiltonian that it lacks the
orbital degree of freedom. We show that the magnetic properties of 5d ion
oxides are better explained by the LS-coupling than by the jj-coupling scheme
of SOC, that the spin-orbital entanglement of 5d ions is not as strong as has
been assumed.


title: On the Effective Field Theory of Heterotic Vacua

abstract:
  The effective field theory of heterotic vacua that realise $\mathbb{R}^{3,1}$
preserving $\mathcal{N} =1$ supersymmetry are studied. The vacua in question
admit large radius limits taking the form $\mathbb{R}^{3,1}\times {X}$ , with
${X}$ a smooth three-fold with vanishing first Chern class and a stable
holomorphic gauge bundle $\mathcal{E}$. In a previous paper we calculated the
kinetic terms for moduli, deducing the moduli metric and Kahler potential. In
this paper, we compute the remaining couplings in the effective field theory,
correct to first order in alpha prime. In particular, we compute the
contribution of the matter sector to the Kahler potential, derive the Yukawa
couplings and other quadratic fermionic couplings. From this we write down a
Kahler potential $\mathcal{K}$ and superpotential $\mathcal{W}$ .


title:
On point interactions realised as Ter-Martirosyan-Skornyakov
  Hamiltonians

abstract:
  For quantum systems of zero-range interaction we discuss the mathematical
scheme within which modelling the two-body interaction by means of the
physically relevant ultra-violet asymptotics known as the
"Ter-Martirosyan-Skornyakov condition" gives rise to a self-adjoint realisation
of the corresponding Hamiltonian. This is done within the self-adjoint
extension scheme of Krein, Visik, and Birman. We show that the
Ter-Martirosyan-Skornyakov asymptotics is a condition of self-adjointness only
when is imposed in suitable functional spaces, and not just as a pointwise
asymptotics, and we discuss the consequences of this fact on a model of two
identical fermions and a third particle of different nature.


title: Guarded Cubical Type Theory: Path Equality for Guarded Recursion

abstract:
  This paper improves the treatment of equality in guarded dependent type
theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an
extensional type theory with guarded recursive types, which are useful for
building models of program logics, and for programming and reasoning with
coinductive types. We wish to implement GDTT with decidable type-checking,
while still supporting non-trivial equality proofs that reason about the
extensions of guarded recursive constructions. CTT is a variation of
Martin-L\"of type theory in which the identity type is replaced by abstract
paths between terms. CTT provides a computational interpretation of functional
extensionality, is conjectured to have decidable type checking, and has an
implemented type-checker. Our new type theory, called guarded cubical type
theory, provides a computational interpretation of extensionality for guarded
recursive types. This further expands the foundations of CTT as a basis for
formalisation in mathematics and computer science. We present examples to
demonstrate the expressivity of our type theory, all of which have been checked
using a prototype type-checker implementation, and present semantics in a
presheaf category.


title:
Waterfront on the Martian Planitia: Algorithmic emergent catchments on
  disordered terrain

abstract:
  Under a terraforming scenario, a reactivated hydrological cycle on Mars will
result in upwards movement of water due to evaporation and precipitation. If
Mars' embryonic fossilized catchments provide inadequate drainage, Mars'
limited supplies of water may be absorbed entirely by crater lakes and
glaciers, with negative consequences for the terraforming effort. We
demonstrate a stable, convergent algorithm for the efficient modeling of water
flow over disordered terrain. This model is applied to Mars Orbital Laser
Altimeter data and successfully predicts the formation of fossilized waterways
and canyons visible only at much higher resolution. This exploratory study
suggests that despite its impossibly rugged appearance, ancient water flows
have carved channels that provide effective drainage over the majority of Mars'
surface. We also provide one possible reconstruction of a terraformed surface
water distribution.


title: Geometric Median in Nearly Linear Time

abstract:
  In this paper we provide faster algorithms for solving the geometric median
problem: given $n$ points in $\mathbb{R}^{d}$ compute a point that minimizes
the sum of Euclidean distances to the points. This is one of the oldest
non-trivial problems in computational geometry yet despite an abundance of
research the previous fastest algorithms for computing a
$(1+\epsilon)$-approximate geometric median were $O(d\cdot
n^{4/3}\epsilon^{-8/3})$ by Chin et. al,
$\tilde{O}(d\exp{\epsilon^{-4}\log\epsilon^{-1}})$ by Badoiu et. al,
$O(nd+\mathrm{poly}(d,\epsilon^{-1})$ by Feldman and Langberg, and
$O((nd)^{O(1)}\log\frac{1}{\epsilon})$ by Parrilo and Sturmfels and Xue and Ye.
  In this paper we show how to compute a $(1+\epsilon)$-approximate geometric
median in time $O(nd\log^{3}\frac{1}{\epsilon})$ and $O(d\epsilon^{-2})$. While
our $O(d\epsilon^{-2})$ is a fairly straightforward application of stochastic
subgradient descent, our $O(nd\log^{3}\frac{1}{\epsilon})$ time algorithm is a
novel long step interior point method. To achieve this running time we start
with a simple $O((nd)^{O(1)}\log\frac{1}{\epsilon})$ time interior point method
and show how to improve it, ultimately building an algorithm that is quite
non-standard from the perspective of interior point literature. Our result is
one of very few cases we are aware of outperforming traditional interior point
theory and the only we are aware of using interior point methods to obtain a
nearly linear time algorithm for a canonical optimization problem that
traditionally requires superlinear time. We hope our work leads to further
improvements in this line of research.


title:
Calculation of thermal conductivity coefficients of electrons in
  magnetized dense matter

abstract:
  The solution of Boltzmann equation for plasma in magnetic field, with
arbitrarily degenerate electrons and non-degenerate nuclei, is obtained by
Chapman-Enskog method. Functions, generalizing Sonin polynomials are used for
obtaining an approximate solution. Fully ionized plasma is considered. The
tensor of the heat conductivity coefficients in non-quantized magnetic field is
calculated. For non-degenerate and strongly degenerate plasma the asymptotic
analytic formulas are obtained, which are compared with results of previous
authors. The Lorentz approximation, with neglecting of electron-electron
encounters, is asymptotically exact for strongly degenerate plasma.
  We obtain, for the first time, in three polynomial approximation, with
account of electron-electron collisions, analytical expressions for the heat
conductivity tensor for non-degenerate electrons, in presence of a magnetic
field. Account of the third polynomial improved substantially the precision of
results.
  In two polynomial approximation our solution coincides with the published
results. For strongly degenerate electrons we obtain, for the first time, an
asymptotically exact analytical solution for the heat conductivity tensor in
presence of a magnetic field. This solution has considerably more complicated
dependence on the magnetic field than those in previous publications, and gives
several times smaller relative value of a thermal conductivity across the
magnetic field at $\omega\tau\gtrsim 0.8$.


title: Critical slowing down and hyperuniformity on approach to jamming

abstract:
  Hyperuniformity characterizes a state of matter that is poised at a critical
point at which density or volume-fraction fluctuations are anomalously
suppressed at infinite wavelengths. Recently, much attention has been given to
the link between strict jamming and hyperuniformity in frictionless
hard-particle packings. Doing so requires one to study very large packings,
which can be difficult to jam properly. We modify the rigorous linear
programming method of Donev et al. [J. Comp. Phys. 197, 139 (2004)] in order to
test for jamming in putatively jammed packings of hard-disks in two dimensions.
We find that various standard packing protocols struggle to reliably create
packings that are jammed for even modest system sizes; importantly, these
packings appear to be jammed by conventional tests. We present evidence that
suggests that deviations from hyperuniformity in putative maximally random
jammed (MRJ) packings can in part be explained by a shortcoming in generating
exactly-jammed configurations due to a type of "critical slowing down" as the
necessary rearrangements become difficult to realize by numerical protocols.
Additionally, various protocols are able to produce packings exhibiting
hyperuniformity to different extents, but this is because certain protocols are
better able to approach exactly-jammed configurations. Nonetheless, while one
should not generally expect exact hyperuniformity for disordered packings with
rattlers, we find that when jamming is ensured, our packings are very nearly
hyperuniform, and deviations from hyperuniformity correlate with an inability
to ensure jamming, suggesting that strict jamming and hyperuniformity are
indeed linked. This raises the possibility that the ideal MRJ packings have no
rattlers. Our work provides the impetus for the development of packing
algorithms that produce large disordered strictly jammed packings that are
rattler-free.


title:
How many faces can be recognized? Performance extrapolation for
  multi-class classification

abstract:
  The difficulty of multi-class classification generally increases with the
number of classes. Using data from a subset of the classes, can we predict how
well a classifier will scale with an increased number of classes? Under the
assumption that the classes are sampled exchangeably, and under the assumption
that the classifier is generative (e.g. QDA or Naive Bayes), we show that the
expected accuracy when the classifier is trained on $k$ classes is the $k-1$st
moment of a \emph{conditional accuracy distribution}, which can be estimated
from data. This provides the theoretical foundation for performance
extrapolation based on pseudolikelihood, unbiased estimation, and
high-dimensional asymptotics. We investigate the robustness of our methods to
non-generative classifiers in simulations and one optical character recognition
example.


title:
Estimating mutual information in high dimensions via classification
  error

abstract:
  Multivariate pattern analyses approaches in neuroimaging are fundamentally
concerned with investigating the quantity and type of information processed by
various regions of the human brain; typically, estimates of classification
accuracy are used to quantify information. While a extensive and powerful
library of methods can be applied to train and assess classifiers, it is not
always clear how to use the resulting measures of classification performance to
draw scientific conclusions: e.g. for the purpose of evaluating redundancy
between brain regions. An additional confound for interpreting classification
performance is the dependence of the error rate on the number and choice of
distinct classes obtained for the classification task. In contrast, mutual
information is a quantity defined independently of the experimental design, and
has ideal properties for comparative analyses. Unfortunately, estimating the
mutual information based on observations becomes statistically infeasible in
high dimensions without some kind of assumption or prior.
  In this paper, we construct a novel classification-based estimator of mutual
information based on high-dimensional asymptotics. We show that in a particular
limiting regime, the mutual information is an invertible function of the
expected $k$-class Bayes error. While the theory is based on a large-sample,
high-dimensional limit, we demonstrate through simulations that our proposed
estimator has superior performance to the alternatives in problems of moderate
dimensionality.


title: Superconformal SU(1,1|n) mechanics

abstract:
  Recent years have seen an upsurge of interest in dynamical realizations of
the superconformal group SU(1,1|2) in mechanics. Remarking that SU(1,1|2) is a
particular member of a chain of supergroups SU(1,1|n) parametrized by an
integer n, here we begin a systematic study of SU(1,1|n) multi-particle
mechanics. A representation of the superconformal algebra su(1,1|n) is
constructed on the phase space spanned by m copies of the (1,2n,2n-1)
supermultiplet. We show that the dynamics is governed by two prepotentials V
and F, and the Witten-Dijkgraaf-Verlinde-Verlinde equation for F shows up as a
consequence of a more general fourth-order equation. All solutions to the
latter in terms of root systems reveal decoupled models only. An extension of
the dynamical content of the (1,2n,2n-1) supermultiplet by angular variables in
a way similar to the SU(1,1|2) case is problematic.


title:
Theory of the Lamb shift and Fine Structure in muonic $\mathrm{^4He}$
  ions and the muonic $\mathrm{^3He-^4He}$ Isotope Shift

abstract:
  We provide an up to date summary of the theory contributions to the 2S-2P
Lamb shift and the fine structure of the 2P state in the muonic helium ion
$(\mathrm{\mu^4He})^+$. This summary serves as the basis for the extraction of
the alpha particle charge radius from the muonic helium Lamb shift measurements
at the Paul Scherrer Institute, Switzerland. Individual theory contributions
needed for a charge radius extraction are compared and compiled into a
consistent summary. The influence of the alpha particle charge distribution on
the elastic two-photon exchange is studied to take into account possible
model-dependencies of the energy levels on the electric form factor of the
nucleus. We also discuss the theory uncertainty which enters the extraction of
the $\mathrm{^3He-^4He}$ isotope shift from the muonic measurements. The theory
uncertainty of the extraction is much smaller than a present discrepancy
between previous isotope shift measurements. This work completes our series of
$n=2$ theory compilations in light muonic atoms which we have performed already
for muonic hydrogen, deuterium, and helium-3 ions.


title:
Matters of Gravity, The Newsletter of the Division of Gravitational
  Physics of the American Physical Society, Volume 47, June 2016

abstract:
  DGRAV News:
  DGRAV
  we hear that....
  Research Briefs:
  GW150914
  Obituaries:
  Remembering Felix Pirani
  Remembering David Finkelstein
  Steve, the physicist
  Remembering Sergio Dain
  Editorial:
  Gravitational physics in the modern university


title: Learning feed-forward one-shot learners

abstract:
  One-shot learning is usually tackled by using generative models or
discriminative embeddings. Discriminative methods based on deep learning, which
are very effective in other learning scenarios, are ill-suited for one-shot
learning as they need large amounts of training data. In this paper, we propose
a method to learn the parameters of a deep model in one shot. We construct the
learner as a second deep network, called a learnet, which predicts the
parameters of a pupil network from a single exemplar. In this manner we obtain
an efficient feed-forward one-shot learner, trained end-to-end by minimizing a
one-shot classification objective in a learning to learn formulation. In order
to make the construction feasible, we propose a number of factorizations of the
parameters of the pupil network. We demonstrate encouraging results by learning
characters from single exemplars in Omniglot, and by tracking visual objects
from a single initial exemplar in the Visual Object Tracking benchmark.


title:
High-power ultrafast Yb:fiber laser frequency combs using commercially
  available components and basic fiber tools

abstract:
  We present a detailed description of the design, construction, and
performance of high-power ultrafast Yb:fiber laser frequency combs in operation
in our laboratory. We discuss two such laser systems: an 87 MHz, 9 W, 85 fs
laser operating at 1060 nm and an 87 MHz, 80 W, 155 fs laser operating at 1035
nm. Both are constructed using low-cost, commercially available components, and
can be assembled using only basic tools for cleaving and splicing single-mode
fibers. We describe practical methods for achieving and characterizing
low-noise single-pulse operation and long-term stability from Yb:fiber
oscillators based on nonlinear polarization evolution. Stabilization of the
combs using a variety of transducers, including a new method for tuning the
carrier-envelope offset frequency, is discussed. High average power is achieved
through chirped-pulse amplification in simple fiber amplifiers based on
double-clad photonic crystal fibers. We describe the use of these combs in
several applications, including ultrasensitive femtosecond time-resolved
spectroscopy and cavity-enhanced high-order harmonic generation.


title:
Local geodesics between toric plurisubharmonic functions with infinite
  energy

abstract:
  Our interest is the behavior of weak geodesics between two plurisubharmonic
functions on pseudoconvex domains. We characterize the convergence condition
along the geodesic between toric psh functions with a pole at origin on a unit
ball in $\mathbb{C}^n$ by means of Lelong numbers.


title: The Schur-Horn theorem for unbounded operators with discrete spectrum

abstract:
  We characterize diagonals of unbounded self-adjoint operators on a Hilbert
space H that have only discrete spectrum, i.e., with empty essential spectrum.
Our result extends the Schur-Horn theorem from a finite dimensional setting to
an infinite dimensional Hilbert space, analogous to Kadison's theorem for
orthogonal projections, Kaftal and Weiss' results for positive compact
operators, and Bownik and Jasper's characterization for operators with finite
spectrum. Furthermore, we show that if a symmetric unbounded operator E on H
has a nondecreasing unbounded diagonal, then any sequence that weakly majorizes
this diagonal is also a diagonal of E.


title:
On well-posedness of vector-valued fractional differential-difference
  equations

abstract:
  We develop an operator-theoretical method for the analysis on well posedness
of partial differential equations that can be modeled in the form
\begin{equation*} \left\{ \begin{array}{rll} \Delta^{\alpha} u(n) &= Au(n+2) +
f(n,u(n)), \quad n \in \mathbb{N}_0, \,\, 1< \alpha \leq 2; u(0) &= u_0; u(1)
&= u_1, \end{array} \right. \end{equation*} where $A$ is an closed linear
operator defined on a Banach space $X$. Our ideas are inspired on the Poisson
distribution as a tool to sampling fractional differential operators into
fractional differences. Using our abstract approach, we are able to show
existence and uniqueness of solutions for the problem (*) on a distinguished
class of weighted Lebesgue spaces of sequences, under mild conditions on
strongly continuous sequences of bounded operators generated by $A,$ and
natural restrictions on the nonlinearity $f$. Finally we present some original
examples to illustrate our results.


title:
Estimation and Uncertainty Quantification of Yield Via Strain Recovery
  Simulations

abstract:
  In computational materials science, predicting the yield strain of
crosslinked polymers remains a challenging task. A common approach is to
identify yield via the first critical point of stress-strain curves produced by
molecular dynamics simulations. However, the simulated data can be excessively
noisy, making it difficult to extract meaningful results. In this work, we
discuss an alternate method for identifying yield on the basis of residual
strain computations. Notably, the associated raw data produce a sharper signal
for yield through a transition in their global behavior. As we show, this
transition can be analyzed in terms of simple functions (e.g. hyperbolas) that
admit straightforward uncertainty quantification techniques.


title: Dynamical Contents of Unconventional Supersymmetry

abstract:
  The Dirac Hamiltonian formalism is applied to a system in $(2+1)$-dimensions
consisting of a Dirac field $\psi$ minimally coupled to Chern-Simons $U(1)$ and
$SO(2,1)$ connections, $A$ and $\omega$, respectively. This theory is connected
to a supersymmetric Chern-Simons form in which the gravitino has been projected
out (unconventional supersymmetry) and, in the case of a flat background,
corresponds to the low energy limit of graphene. The separation between
first-class and second-class constraints is performed explicitly, and both the
field equations and gauge symmetries of the Lagrangian formalism are fully
recovered. The degrees of freedom of the theory in generic sectors shows that
the propagating states correspond to fermionic modes in the background
determined by the geometry of the graphene sheet and the nondynamical
electromagnetic field. This is shown for the following canonical sectors: i) a
conformally invariant generic description where the spinor field and the
dreibein are locally rescaled; ii) a specific configuration for the Dirac
fermion consistent with its spin, where Weyl symmetry is exchanged by time
reparametrizations; iii) the vacuum sector $\psi=0$, which is of interest for
perturbation theory. For the latter the analysis is adapted to the case of
manifolds with boundary, and the corresponding Dirac brackets together with the
centrally extended charge algebra are found. Finally, the $SU(2)$
generalization of the gauge group is briefly treated, yielding analogous
conclusions for the degrees of freedom.


title:
A linear time algorithm for a variant of the max cut problem in series
  parallel graphs

abstract:
  Given a graph $G=(V, E)$, a connected sides cut $(U, V\backslash U)$ or
$\delta (U)$ is the set of edges of E linking all vertices of U to all vertices
of $V\backslash U$ such that the induced subgraphs $G[U]$ and $G[V\backslash
U]$ are connected. Given a positive weight function $w$ defined on $E$, the
maximum connected sides cut problem (MAX CS CUT) is to find a connected sides
cut $\Omega$ such that $w(\Omega)$ is maximum. MAX CS CUT is NP-hard. In this
paper, we give a linear time algorithm to solve MAX CS CUT for series parallel
graphs. We deduce a linear time algorithm for the minimum cut problem in the
same class of graphs without computing the maximum flow.


title: The Mondrian Kernel

abstract:
  We introduce the Mondrian kernel, a fast random feature approximation to the
Laplace kernel. It is suitable for both batch and online learning, and admits a
fast kernel-width-selection procedure as the random features can be re-used
efficiently for all kernel widths. The features are constructed by sampling
trees via a Mondrian process [Roy and Teh, 2009], and we highlight the
connection to Mondrian forests [Lakshminarayanan et al., 2014], where trees are
also sampled via a Mondrian process, but fit independently. This link provides
a new insight into the relationship between kernel methods and random forests.


title:
Sentiment Aggregate Functions for Political Opinion Polling using
  Microblog Streams

abstract:
  The automatic content analysis of mass media in the social sciences has
become necessary and possible with the raise of social media and computational
power. One particularly promising avenue of research concerns the use of
sentiment analysis in microblog streams. However, one of the main challenges
consists in aggregating sentiment polarity in a timely fashion that can be fed
to the prediction method. We investigated a large set of sentiment aggregate
functions and performed a regression analysis using political opinion polls as
gold standard. Our dataset contains nearly 233 000 tweets, classified according
to their polarity (positive, negative or neutral), regarding the five main
Portuguese political leaders during the Portuguese bailout (2011-2014). Results
show that different sentiment aggregate functions exhibit different feature
importance over time while the error keeps almost unchanged.


title:
Orthogonality of divisorial Zariski decompositions for classes with
  volume zero

abstract:
  We show that the orthogonality conjecture for divisorial Zariski
decompositions on compact Kahler manifolds holds for pseudoeffective (1,1)
classes with volume zero.


title: Notes on heat engines and negative temperatures

abstract:
  We show that a Carnot cycle operating between a positive
canonical-temperature bath and a negative canonical-temperature bath has
efficiency equal to unity. It follows that a negative canonical-temperature
cannot be identified with an absolute temperature. We illustrate this with a
spin in a varying magnetic field.


title: Networked Control under Random and Malicious Packet Losses

abstract:
  We study cyber security issues in networked control of a linear dynamical
system. Specifically, the dynamical system and the controller are assumed to be
connected through a communication channel that face malicious attacks as well
as random packet losses due to unreliability of transmissions. We provide a
probabilistic characterization for the link failures which allows us to study
combined effects of malicious and random packet losses. We first investigate
almost sure stabilization under an event-triggered control law, where we
utilize Lyapunov-like functions to characterize the triggering times at which
the plant and the controller attempt to exchange state and control data over
the network. We then provide a look at the networked control problem from the
attacker's perspective and explore malicious attacks that cause instability.
Finally, we demonstrate the efficacy of our results with numerical examples.


title: Development of n-in-p pixel modules for the ATLAS Upgrade at HL-LHC

abstract:
  Thin planar pixel modules are promising candidates to instrument the inner
layers of the new ATLAS pixel detector for HL-LHC, thanks to the reduced
contribution to the material budget and their high charge collection efficiency
after irradiation. 100-200 $\mu$m thick sensors, interconnected to FE-I4
read-out chips, have been characterized with radioactive sources and beam tests
at the CERN-SPS and DESY. The results of these measurements are reported for
devices before and after irradiation up to a fluence of $14\times10^{15}$
n$_{eq}$/cm$^2$. The charge collection and tracking efficiency of the different
sensor thicknesses are compared. The outlook for future planar pixel sensor
production is discussed, with a focus on sensor design with the pixel pitches
(50x50 and 25x100 $\mu$m$^2$) foreseen for the RD53 Collaboration read-out chip
in 65 nm CMOS technology. An optimization of the biasing structures in the
pixel cells is required to avoid the hit efficiency loss presently observed in
the punch-through region after irradiation. For this purpose the performance of
different layouts have been compared in FE-I4 compatible sensors at various
fluence levels by using beam test data. Highly segmented sensors will represent
a challenge for the tracking in the forward region of the pixel system at
HL-LHC. In order to reproduce the performance of 50x50 $\mu$m$^2$ pixels at
high pseudo-rapidity values, FE-I4 compatible planar pixel sensors have been
studied before and after irradiation in beam tests at high incidence angle
(80$^\circ$) with respect to the short pixel direction. Results on cluster
shapes, charge collection and hit efficiency will be shown.


title:
Search for giant planets in M67 III: excess of hot Jupiters in dense
  open clusters

abstract:
  Since 2008 we used high-precision radial velocity (RV) measurements obtained
with different telescopes to detect signatures of massive planets around
main-sequence and evolved stars of the open cluster (OC) M67. We aimed to
perform a long-term study on giant planet formation in open clusters and
determine how this formation depends on stellar mass and chemical composition.
A new hot Jupiter (HJ) around the main-sequence star YBP401 is reported in this
work. An update of the RV measurements for the two HJ host-stars YBP1194 and
YBP1514 is also discussed. Our sample of 66 main-sequence and turnoff stars
includes 3 HJs, which indicates a high rate of HJs in this cluster (~5.6% for
single stars and ~4.5% for the full sample ). This rate is much higher than
what has been discovered in the field, either with RV surveys or by transits.
High metallicity is not a cause for the excess of HJs in M67, nor can the
excess be attributed to high stellar masses. When combining this rate with the
non-zero eccentricity of the orbits, our results are qualitatively consistent
with a HJ formation scenario dominated by strong encounters with other stars or
binary companions and subsequent planet-planet scattering, as predicted by
N-body simulations.


title: Leadership Network and Team Performance in Interactive Contests

abstract:
  Over the years, the concept of leadership has experienced a paradigm shift -
from solitary leader (centralized leadership) to de-centralized leadership or
distributed leadership. This paper explores the idea that centralized
leadership, as earlier suggested, negatively impacts team performance. I
applied the hypothesis to cricket, a sport in which leaders play an important
role in team's success. I generated batting partnership network and evaluated
the central-most player in the team, applying tools of social network analysis.
Analyzing 3420 matches in one day international cricket and 1979 Test matches
involving 10 teams, I examined the impact of centralized leadership in outcome
of a contest. I observed that the odds for winning a one day international
match under centralized leadership is 30% higher than the odds for winning
under de-centralized leadership. In both forms of cricket (Test and one day
international ), I failed to find evidence that distributed leadership is
associated with higher team performance. These results suggest important
implications for cricket administrators in development and management of
working teams.


title:
The Nature and Frequency of the Gas Outbursts in Comet
  67P/Churyumov-Gerasimenko observed by the Alice Far-ultraviolet Spectrograph
  on Rosetta

abstract:
  Alice is a far-ultraviolet imaging spectrograph onboard Rosetta that, amongst
multiple objectives, is designed to observe emissions from various atomic and
molecular species from within the coma of comet 67P/Churyumov-Gerasimenko. The
initial observations, made following orbit insertion in August 2014, showed
emissions of atomic hydrogen and oxygen spatially localized close to the
nucleus and attributed to photoelectron impact dissociation of H2O vapor.
Weaker emissions from atomic carbon were subsequently detected and also
attributed to electron impact dissociation, of CO2, the relative H I and C I
line intensities reflecting the variation of CO2 to H2O column abundance along
the line-of-sight through the coma. Beginning in mid-April 2015, Alice
sporadically observed a number of outbursts above the sunward limb
characterized by sudden increases in the atomic emissions, particularly the
semi-forbidden O I 1356 multiplet, over a period of 10-30 minutes, without a
corresponding enhancement in long wavelength solar reflected light
characteristic of dust production. A large increase in the brightness ratio O I
1356/O I 1304 suggests O2 as the principal source of the additional gas. These
outbursts do not correlate with any of the visible images of outbursts taken
with either OSIRIS or the navigation camera. Beginning in June 2015 the nature
of the Alice spectrum changed considerably with CO Fourth Positive band
emission observed continuously, varying with pointing but otherwise fairly
constant in time. However, CO does not appear to be a major driver of any of
the observed outbursts.


title: SQuAD: 100,000+ Questions for Machine Comprehension of Text

abstract:
  We present the Stanford Question Answering Dataset (SQuAD), a new reading
comprehension dataset consisting of 100,000+ questions posed by crowdworkers on
a set of Wikipedia articles, where the answer to each question is a segment of
text from the corresponding reading passage. We analyze the dataset to
understand the types of reasoning required to answer the questions, leaning
heavily on dependency and constituency trees. We build a strong logistic
regression model, which achieves an F1 score of 51.0%, a significant
improvement over a simple baseline (20%). However, human performance (86.8%) is
much higher, indicating that the dataset presents a good challenge problem for
future research.
  The dataset is freely available at https://stanford-qa.com


title: On The Fourier And Wavelet Analysis Of Coronal Time Series

abstract:
  Using Fourier and wavelet analysis, we critically re-assess the significance
of our detection of periodic pulsations in coronal loops. We show that the
proper identification of the frequency dependence and statistical properties of
the different components of the power spectra provies a strong argument against
the common practice of data detrending, which tends to produce spurious
detections around the cut-off frequency of the filter. In addition, the white
and red noise models built into the widely used wavelet code of Torrence &
Compo cannot, in most cases, adequately represent the power spectra of coronal
time series, thus also possibly causing false positives. Both effects suggest
that several reports of periodic phenomena should be re-examined. The Torrence
& Compo code nonetheless effectively computes rigorous confidence levels if
provided with pertinent models of mean power spectra, and we describe the
appropriate manner in which to call its core routines. We recall the meaning of
the default confidence levels output from the code, and we propose new
Monte-Carlo-derived levels that take into account the total number of degrees
of freedom in the wavelet spectra. These improvements allow us to confirm that
the power peaks that we detected have a very low probability of being caused by
noise.


title: Division by 2 on hyperelliptic curves and jacobians

abstract:
  Let $K$ be an algebraically closed field of characteristic different from 2,
$g$ a positive integer, $f(x)$ a degree $(2g+1)$ polynomial with coefficients
in $K$ and without multiple roots, $C: y^2=f(x)$ the corresponding genus $g$
hyperelliptic curve over $K$ and $J$ the jacobian of $C$. We identify $C$ with
the image of its canonical embedding into $J$ (the infinite point of $C$ goes
to the zero point of $J$). For each point $P=(a,b)\in C(K)$ there are $2^{2g}$
points $\frac{1}{2}P \in J(K)$. We describe explicitly the Mumford
represesentations of all $\frac{1}{2}P$. The rationality questions for
$\frac{1}{2}P$ are also discussed.


title: Universal criterion for designability of heteropolymers

abstract:
  Proteins are an example of heteropolymers able to self-assemble in specific
target structures. The self-assembly of designed artificial heteropolymers is
still, to the best of our knowledge, not possible with control over the single
chain self-assembling properties comparable to what natural proteins can
achieve. What artificial heteropolymers lacks compared to bio-heteropolymers
that grants the latter such a versatility? Is the geometry of the protein
skeleton the only a particular choice to be designable? Here we introduce a
general criteria to discriminate which polymer backbones can be designed to
adopt a predetermined structure. With our approach we can explore different
polymer backbones and different amino acids alphabets. By comparing the radial
distribution functions of designable and not-designable scenarios we identify
as designability criteria the presence of a particular peak in the radial
distribution function that dominates over the random packing of the
heteropolymer. We show that the peak is a universal feature of all designable
heteropolymers, as it is dominating also the radial distribution function of
natural proteins. Our finding can help in understanding the key features that
make proteins a highly designable system. The criteria that we present can be
applied to engineer new types of self-assembling modular polymers that will
open new applications for polymer based material science.


title:
Recent advancement in Next Generation Sequencing techniques and its
  computational analysis

abstract:
  Next Generation Sequencing (NGS), a recently evolved technology, have served
a lot in the research and development sector of our society. This novel
approach is a newbie and has critical advantages over the traditional Capillary
Electrophoresis (CE) based Sanger Sequencing. The advancement of NGS has led to
numerous important discoveries, which could have been costlier and time taking
in case of traditional CE based Sanger sequencing. NGS methods are highly
parallelized enabling to sequence thousands to millions of molecules
simultaneously. This technology results into huge amount of data, which need to
be analysed to conclude valuable information. Specific data analysis algorithms
are written for specific task to be performed. The algorithms in group, act as
a tool in analysing the NGS data. Analysis of NGS data unravels important clues
in quest for the treatment of various life-threatening diseases; improved crop
varieties and other related scientific problems related to human welfare. In
this review, an effort was made to address basic background of NGS
technologies, possible applications, computational approaches and tools
involved in NGS data analysis, future opportunities and challenges in the area.


title: 3D zigzag for multislicing, multiband and video processing

abstract:
  We present a 3D zigzag rafter (first in literature) which allows us to obtain
the exact sequence of spectral components after application of Discrete Cosine
Transform 3D (DCT-2D) over a cube. Such cube represents part of a video or
eventually a group of images such as multislicing (e.g., Magnetic Resonance or
Computed Tomography imaging) and multi or hyperspectral imagery (optical
satellites). Besides, we present a new version of the traditional 2D zigzag,
including the case of rectangular blocks. Finally, all the attached code is
done in MATLAB, and that code serves both blocks of pixels or blocks of blocks.


title:
Effects of Spatial Heterogeneity in Rainfall and Vegetation Type on Soil
  Moisture and Evapotranspiration

abstract:
  Nonlinear plant-scale interactions controlling the soil-water balance are
generally not valid at larger spatial scales due to spatial heterogeneity in
rainfall and vegetation type. The relationships between spatially averaged
variables are hysteretic even when unique relationships are imposed at the
plant scale. The characteristics of these hysteretic relationships depend on
the size of the averaging area and the spatial properties of the soil,
vegetation, and rainfall. We upscale the plant-scale relationships to the scale
of a regional land-surface model based on simulation data obtained through
explicit representation of spatial heterogeneity in rainfall and vegetation
type. The proposed upscaled function improves predictions of spatially averaged
soil moisture and evapotranspiration relative to the effective-parameter
approach for a water-limited Texas shrubland. The degree of improvement is a
function of the scales of heterogeneity and the size of the averaging area. We
also find that single-valued functions fail to predict spatially averaged
leakage accurately. Furthermore, the spatial heterogeneity results in
scale-dependent hysteretic relationships for the statistical-dynamic and
Montaldo & Albertson approaches.


title: DNA brick self-assembly with an off-lattice potential

abstract:
  We report Monte Carlo simulations of a simple off-lattice patchy-particle
model for DNA `bricks'. We relate the parameters that characterise this model
with the binding free energy of pairs of single-stranded DNA molecules. We
verify that an off-lattice potential parameterised in this way reproduces much
of the behaviour seen with a simpler lattice model we introduced previously,
although the relaxation of the geometric constraints leads to a more
error-prone self-assembly pathway. We investigate the self-assembly process as
a function of the strength of the non-specific interactions. We show that our
off-lattice model for DNA bricks results in robust self-assembly into a variety
of target structures.


title: Magnitudes and Timescales of Total Solar Irradiance Variability

abstract:
  The Sun's net radiative output varies on timescales of minutes to gigayears.
Direct measurements of the total solar irradiance (TSI) show changes in the
spatially- and spectrally-integrated radiant energy on timescales as short as
minutes to as long as a solar cycle. Variations of ~0.01 % over a few minutes
are caused by the ever-present superposition of convection and oscillations
with very large solar flares on rare occasion causing slightly-larger
measureable signals. On timescales of days to weeks, changing photospheric
magnetic activity affects solar brightness at the ~0.1 % level. The 11-year
solar cycle shows variations of comparable magnitude with irradiances peaking
near solar maximum. Secular variations are more difficult to discern, being
limited by instrument stability and the relatively short duration of the
space-borne record. Historical reconstructions of the Sun's irradiance based on
indicators of solar-surface magnetic activity, such as sunspots, faculae, and
cosmogenic isotope records, suggest solar brightness changes over decades to
millennia, although the magnitudes of these variations have high uncertainties
due to the indirect historical records on which they rely. Stellar evolution
affects yet longer timescales and is responsible for the greatest solar
variabilities. In this manuscript I summarize the Sun's variability magnitudes
over different temporal regimes and discuss the irradiance record's relevance
for solar and climate studies as well as for detections of exo-solar planets
transiting Sun-like stars.


title: Stokes Soliton in Optical Microcavities

abstract:
  Solitons are wavepackets that resist dispersion through a self-induced
potential well. They are studied in many fields, but are especially well known
in optics on account of the relative ease of their formation and control in
optical fiber waveguides. Besides their many interesting properties, solitons
are important to optical continuum generation, in mode-locked lasers and have
been considered as a natural way to convey data over great distances. Recently,
solitons have been realized in microcavities thereby bringing the power of
microfabrication methods to future applications. This work reports a soliton
not previously observed in optical systems, the Stokes soliton. The Stokes
soliton forms and regenerates by optimizing its Raman interaction in space and
time within an optical-potential well shared with another soliton. The Stokes
and the initial soliton belong to distinct transverse mode families and benefit
from a form of soliton trapping that is new to microcavities and soliton lasers
in general. The discovery of a new optical soliton can impact work in other
areas of photonics including nonlinear optics and spectroscopy.


title:
The Heisenberg algebra as near horizon symmetry of the black flower
  solutions of Chern-Simons-like theories of gravity

abstract:
  In this paper we study the near horizon symmetry algebra of the non-extremal
black hole solutions of the Chern-Simons-like theories of gravity, which are
stationary but are not necessarily spherically symmetric. We define the
extended off-shell ADT current which is an extension of the generalized ADT
current. We use the extended off-shell ADT current to define quasi-local
conserved charges such that they are conserved for Killing vectors and
asymptotically Killing vectors which depend on dynamical fields of the
considered theory. We apply this formalism to the Generalized Minimal Massive
Gravity( GMMG) and obtain conserved charges of a spacetime which describes near
horizon geometry of non-extremal black holes. Eventually, we find the algebra
of conserved charges in Fourier modes. It is interesting that, similar to the
Einstein gravity in the presence of negative cosmological constant, for the
GMMG model also we obtain the Heisenberg algebra as the near horizon symmetry
algebra of the black flower solutions. Also the vacuum state and all
descendants of the vacuum have the same energy. Thus these zero energy
excitations on the horizon appear as soft hairs on the black hole.


title:
Suppression of electron thermal conduction in the high $\beta$
  intracluster medium of galaxy clusters

abstract:
  Understanding the thermodynamic state of the hot intracluster medium (ICM) in
a galaxy cluster requires a knowledge of the plasma transport processes,
especially thermal conduction. The basic physics of thermal conduction in
plasmas with ICM-like conditions has yet to be elucidated, however. We use
particle-in-cell simulations and analytic models to explore the dynamics of an
ICM-like plasma (with small gyroradius, large mean-free-path, and strongly
sub-dominant magnetic pressure) driven by the diffusive heat flux associated
with thermal conduction. Lin- ear theory reveals that whistler waves are driven
unstable electron heat flux, even when the heat flux is weak. The resonant
interaction of electrons with these waves then plays a critical role in
scattering electrons and suppressing the heat flux. In a 1D model where only
whistler modes that are parallel to the magnetic field are captured, the only
resonant electrons are moving in the opposite direction to the heat flux and
the electron heat flux suppression is small. In 2D or more, oblique whistler
modes also resonate with electrons moving in the direction of the heat flux.
The overlap of resonances leads to effective symmetrization of the electron
distribution function and a strong suppression of heat flux. The results
suggest that thermal conduction in the ICM might be strongly suppressed,
possibly to negligible levels.

categories: astro-ph.HE astro-ph.CO astro-ph.GA physics.plasm-ph


title: Convolutional Residual Memory Networks

abstract:
  Very deep convolutional neural networks (CNNs) yield state of the art results
on a wide variety of visual recognition problems. A number of state of the the
art methods for image recognition are based on networks with well over 100
layers and the performance vs. depth trend is moving towards networks in excess
of 1000 layers. In such extremely deep architectures the vanishing or exploding
gradient problem becomes a key issue. Recent evidence also indicates that
convolutional networks could benefit from an interface to explicitly
constructed memory mechanisms interacting with a CNN feature processing
hierarchy. Correspondingly, we propose and evaluate a memory mechanism enhanced
convolutional neural network architecture based on augmenting convolutional
residual networks with a long short term memory mechanism. We refer to this as
a convolutional residual memory network. To the best of our knowledge this
approach can yield state of the art performance on the CIFAR-100 benchmark and
compares well with other state of the art techniques on the CIFAR-10 and SVHN
benchmarks. This is achieved using networks with more breadth, much less depth
and much less overall computation relative to comparable deep ResNets without
the memory mechanism. Our experiments and analysis explore the importance of
the memory mechanism, network depth, breadth, and predictive performance.


title: Anomalous precession of planets on a Weyl conformastatic solution

abstract:
  In this paper, we investigate the anomalous planets precession in the
nearly-newtonian gravitational regime. This limit is obtained from the
application of the slow motion condition to the geodesic equations without
altering the geodesic deviation equations. Using a non-standard expression for
the perihelion advance from the Weyl conformastatic vacuum solution as a model,
we can describe the anomaly in planets precession compared with different
observational data from Ephemerides of the Planets and the Moon (EPM2008 and
EPM2011) and Planetary and Lunar Ephemeris (INPOP10a). As a result, using the
Levenberg-Marquardt algorithm and calculating the related Chi-squared
statistic, we find that the anomaly is statistical irrelevant in accordance
with INPOP10a observations. As a complement to this work, we also do an
application to the relativistic precession of giant planets using observational
data calibrated with the EPM2011.


title:
On a holographic dark energy model with a Nojiri-Odintsov cut-off in
  general relativity

abstract:
  In this paper we consider the models of the accelerated expanding large scale
universe~(according to general relativity) containing a generalized holographic
dark energy with a Nojiri - Odintsov cut - off. The second component of the
darkness is assumed to be the pressureless cold dark matter according to
observed symmetries of the large scale universe. Moreover, we assume specific
forms of the interaction between these two components and besides the
cosmographic analysis, we discuss appropriate results from $Om$ and $Om3$
analysis and organize a closer look to the models via the statefinder hierarchy
analysis, too. In this way we study mainly impact of the interaction on the
dynamics of the background of our universe~(within specific forms of
interaction). To complete the cosmographic analysis, the present day values of
the statefinder parameters $(r,s)$ and $(\omega^{\prime}_{de}, \omega_{de})$
has been estimated for all cases and the validity of the generalized second law
of thermodynamics is demonstrated. Our study showed that theoretical results
from considered phenomenological models are consistent with the available
observational data and symmetries.


title: Viscous Generalized Chaplygin Gas Interacting with f(R,T) gravity

abstract:
  In this paper, we study in Friedmann-Robertson-Walker universe the
interaction between the viscous generalized Chaplygin gas with $f(R,T)$
gravity, which is an arbitrary function of the Ricci scalar $R$ and the trace
$T$ of the energy-momentum tensor. Assuming that the contents of universe is
dominated by a generalized Chaplygin gas and dark energy, we obtained the
modified Friedmann equations and also the time dependent energy density and
pressure of dark energy due to the shear and bulk viscosities for three
interacting models depending on an input parameter $Q$. Within the simple form
of scale factor (power-law), we discuss the graphical representation of dark
energy density parameter and investigate the shear and bulk viscosities effects
on the accelerating expansion of the universe for each interacting model.


title:
Formation and evolution of heavy sub-structures in the centre of galaxy
  clusters: the local effect of dark energy

abstract:
  We discuss how the centres of galaxy clusters evolve in time, showing the
results of a series of direct N-body simulations. In particular, we followed
the evolution of a galaxy cluster with a mass $M_{clus} \simeq 10^{14}
$M$_{\odot}$ in different configurations. The dynamical evolution of the system
leads in all the cases to the formation of dense and massive sub-structures in
the cluster centre, that form in consequence of a series of collisions and
merging among galaxies travelling in the cluster core. We investigate how the
structural properties of the main merging product depends on the
characteristics of those galaxies that contributed to its formation.


title: Can dark energy explain the observed outflow in galaxy clusters?

abstract:
  Recent observations of the Virgo cluster and the Local Group suggested that
some galaxies are flowing out from their parent cluster. This may be the
signature that dark energy (DE) acts significantly also on small cosmological
scales. By means of direct N-body simulations we performed several simulations,
in which the effect of DE and gravity are taken into account, aiming to
determine whether DE can produce an outflow of galaxies compatible with
observations. Comparing the different simulations, our results suggest that the
observed outflow of galaxies is likely due to the local effect of DE.


title: Isometry Groups of Combinatorial Codes

abstract:
  Two isometry groups of combinatorial codes are described: the group of
automorphisms and the group of monomial automorphisms, which is the group of
those automorphisms that extend to monomial maps. Unlike the case of classical
linear codes, where these groups are the same, it is shown that for
combinatorial codes the groups can be arbitrary different. Particularly, there
exist codes with the full automorphism group and the trivial monomial
automorphism group. In the paper the two groups are characterized and codes
with predefined isometry groups are constructed.


title: Evolution of spherical domain walls in solitonic symmetron models

abstract:
  In this work, inspired by the symmetron model, we analyse the evolution of
spherical domain walls by considering specific potentials that ensure symmetry
breaking and the occurrence of degenerate vacua that are necessary for the
formation of domain walls. By considering a simple analytical model of
spherical domain wall collapse in vacuum, it is shown that this model fits the
more accurate numerical results very well until full collapse, after which
oscillations and scalar radiation take place. Furthermore, we explore the
effect of a central non-relativistic matter lump on the evolution of a
spherical domain wall and show that the central lump can prevent the full
collapse and annihilation of the domain wall bubble, due to the repulsion
between the domain wall and matter over-density within the adopted symmetron
inspired model.


title: $tbW$ Anomalous Couplings in the Two Higgs Doublet Model

abstract:
  We make a complete one loop calculation of the $tbW$ couplings in the Two
Higgs Doublet Model. We evaluate both the anomalous couplings $g_L$ and $g_R$
as well as left handed and right handed component of $tbW$. The computation is
done in the Feynman gauge using the on-shell scheme renormalization for the
Standard Model wave functions and parameters. We first show that the relative
corrections to these anomalous couplings are rather small in most regions of
the parameter space. We then analyze the effects of these anomalous couplings
on certain observables such as top quark polarization in single top production
through $t-$channel as well as $W^\pm$ boson helicity fractions in top decay.


title: A Carlitz-von Staudt type theorem for finite rings

abstract:
  We compute the $k$th power-sums (for all $k>0$) over an arbitrary finite
unital ring $R$. This unifies and extends the work of Brawley, Carlitz, and
Levine for matrix rings [Duke Math. J. 1974], with folklore results for finite
fields and finite cyclic groups, and more general recent results of Grau and
Oller-Marcen for commutative rings [Finite Fields Appl. 2017]. As an
application, we resolve a conjecture by Fortuny Ayuso, Grau, Oller-Marcen, and
Rua on zeta values for matrix rings over finite commutative rings [Internat. J.
Algebra Comput. 2017]. We further recast our main result via zeta values over
polynomial rings, and end by classifying the translation-invariant polynomials
over a large class of finite commutative rings.


title: Dynamic Collective Choice: Social Optima

abstract:
  We consider a dynamic collective choice problem where a large number of
players are cooperatively choosing between multiple destinations while being
influenced by the behavior of the group. For example, in a robotic swarm
exploring a new environment, a robot might have to choose between multiple
sites to visit, but at the same time it should remain close to the group to
achieve some coordinated tasks. We show that to find a social optimum for our
problem, one needs to solve a set of Linear Quadratic Regulator problems, whose
number increases exponentially with the size of the population. Alternatively,
we develop via the Mean Field Games methodology a set of decentralized
strategies that are independent of the size of the population. When the number
of agents is sufficiently large, these strategies qualify as approximately
socially optimal. To compute the approximate social optimum, each player needs
to know its own state and the statistical distributions of the players' initial
states and problem parameters. Finally, we give a numerical example where the
cooperative and noncooperative cases have opposite behaviors. Whereas in the
former the size of the majority increases with the social effect, in the
latter, the existence of a majority is disadvantaged.


title: The Effect of Heteroscedasticity on Regression Trees

abstract:
  Regression trees are becoming increasingly popular as omnibus predicting
tools and as the basis of numerous modern statistical learning ensembles. Part
of their popularity is their ability to create a regression prediction without
ever specifying a structure for the mean model. However, the method implicitly
assumes homogeneous variance across the entire explanatory-variable space. It
is unknown how the algorithm behaves when faced with heteroscedastic data. In
this study, we assess the performance of the most popular regression-tree
algorithm in a single-variable setting under a very simple step-function model
for heteroscedasticity. We use simulation to show that the locations of splits,
and hence the ability to accurately predict means, are both adversely
influenced by the change in variance. We identify the pruning algorithm as the
main concern, although the effects on the splitting algorithm may be meaningful
in some applications.


title:
New non-linear equations and modular form expansion for double-elliptic
  Seiberg-Witten prepotential

abstract:
  Integrable N-particle systems have an important property that the associated
Seiberg-Witten prepotentials satisfy the WDVV equations. However, this does not
apply to the most interesting class of elliptic and double-elliptic systems.
Studying the commutativity conjecture for theta-functions on the families of
associated spectral curves, we derive some other non-linear equations for the
perturbative Seiberg-Witten prepotential, which turn out to have exactly the
double-elliptic system as their generic solution. In contrast with the WDVV
equations, the new equations acquire non-perturbative corrections which are
straightforwardly deducible from the commutativity conditions. We obtain such
corrections in the first non-trivial case of N=3 and describe the structure of
non-perturbative solutions as expansions in powers of the flat moduli with
coefficients that are (quasi)modular forms of the elliptic parameter.


title:
Designing Intelligent Automation based Solutions for Complex Social
  Problems

abstract:
  Deciding effective and timely preventive measures against complex social
problems affecting relatively low income geographies is a difficult challenge.
There is a strong need to adopt intelligent automation based solutions with low
cost imprints to tackle these problems at larger scales. Starting with the
hypothesis that analytical modelling and analysis of social phenomena with high
accuracy is in general inherently hard, in this paper we propose design
framework to enable data-driven machine learning based adaptive solution
approach towards enabling more effective preventive measures. We use survey
data collected from a socio-economically backward region of India about
adolescent girls to illustrate the design approach.


title: Positivity of Shimura operators

abstract:
  In [16] G. Shimura introduced a family of invariant differential operators
that play a key role in the study of nearly holomorphic automorphic forms, and
he asked for a determination of their \textquotedblleft domain of
positivity\textquotedblright. In this paper we relate the eigenvalues of
Shimura operators to certain polynomials introduced by A. Okounkov, which leads
to an explicit answer to Shimura's questions.


title: Stochastic blockmodels for exchangeable collections of networks

abstract:
  We construct a novel class of stochastic blockmodels using Bayesian
nonparametric mixtures. These model allows us to jointly estimate the structure
of multiple networks and explicitly compare the community structures underlying
them, while allowing us to capture realistic properties of the underlying
networks. Inference is carried out using MCMC algorithms that incorporates
sequentially allocated split-merge steps to improve mixing. The models are
illustrated using a simulation study and a variety of real-life examples.


title:
Pulse Sequences for Efficient Multi-Cycle Terahertz Generation in
  Periodically Poled Lithium Niobate

abstract:
  The use of laser pulse sequences to drive the cascaded difference frequency
generation of high energy, high peak-power and multi-cycle terahertz pulses in
cryogenically cooled periodically poled lithium niobate is proposed. Detailed
simulations considering the coupled nonlinear interaction of terahertz and
optical waves show that unprecedented optical-to-terahertz energy conversion
efficiencies > 5%, peak electric fields of hundred(s) of Mega volts/meter at
terahertz pulse durations of hundred(s) of picoseconds can be achieved. The
proposed methods are shown to circumvent laser-induced damage at Joule-level
pumping by 1$\mu$m lasers to enable multi-cycle terahertz sources with pulse
energies >> 10 milli-joules. Various pulse sequence formats are proposed and
analyzed. Numerical calculations for periodically poled structures accounting
for cascaded difference frequency generation, self-phase-modulation, cascaded
second harmonic generation and laser induced damage are introduced.
Unprecedented studies of the physics governing terahertz generation in this
high conversion efficiency regime, limitations and practical considerations are
discussed. Varying the poling period along the crystal length and further
reduction of absorption is shown to lead to even higher energy conversion
efficiencies >>10%. An analytic formulation valid for arbitrary pulse formats
and closed-form expressions for important cases are presented. Parameters
optimizing conversion efficiency in the 0.1-1 THz range, the corresponding peak
electric fields, crystal lengths and terahertz pulse properties are furnished.


title:
Causal Inference in Rebuilding and Extending the Recondite Bridge
  between Finite Population Sampling and Experimental Design

abstract:
  This article considers causal inference for treatment contrasts from a
randomized experiment using potential outcomes in a finite population setting.
Adopting a Neymanian repeated sampling approach that integrates such causal
inference with finite population survey sampling, an inferential framework is
developed for general mechanisms of assigning experimental units to multiple
treatments. This framework extends classical methods by allowing the
possibility of randomization restrictions and unequal replications. Novel
conditions that are "milder" than strict additivity of treatment effects, yet
permit unbiased estimation of the finite population sampling variance of any
treatment contrast estimator, are derived. The consequences of departures from
such conditions are also studied under the criterion of minimax bias, and a new
justification for using the Neymanian conservative sampling variance estimator
in experiments is provided. The proposed approach can readily be extended to
the case of treatments with a general factorial structure.


title:
ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: The Infrared
  Excess of UV-selected z=2-10 galaxies as a function of UV-continuum Slope and
  Stellar Mass

abstract:
  We make use of deep 1.2mm-continuum observations (12.7microJy/beam RMS) of a
1 arcmin^2 region in the Hubble Ultra Deep Field to probe dust-enshrouded star
formation from 330 Lyman-break galaxies spanning the redshift range z=2-10 (to
~2-3 Msol/yr at 1sigma over the entire range). Given the depth and area of
ASPECS, we would expect to tentatively detect 35 galaxies extrapolating the
Meurer z~0 IRX-beta relation to z>~2 (assuming T_d~35 K). However, only 6
tentative detections are found at z>~2 in ASPECS, with just three at >3sigma.
Subdividing z=2-10 galaxies according to stellar mass, UV luminosity, and
UV-continuum slope and stacking the results, we only find a significant
detection in the most massive (>10^9.75 Msol) subsample, with an infrared
excess (IRX=L_{IR}/L_{UV}) consistent with previous z~2 results. However, the
infrared excess we measure from our large selection of sub-L* (<10^9.75 Msol)
galaxies is 0.11(-0.42)(+0.32) and 0.14(-0.14)(+0.15) at z=2-3 and z=4-10,
respectively, lying below even an SMC IRX-beta relation (95% confidence). These
results demonstrate the relevance of stellar mass for predicting the IR
luminosity of z>~2 galaxies. We furthermore find that the evolution of the
IRX-stellar mass relationship depends on the evolution of the dust temperature.
If the dust temperature increases monotonically with redshift (as (1+z)^0.32)
such that T_d~44-50 K at z>=4, current results are suggestive of little
evolution in this relationship to z~6. We use these results to revisit recent
estimates of the z>~3 SFR density. One less obvious implication is in
interpreting the high Halpha EWs seen in z~5 galaxies: our results imply that
star-forming galaxies produce Lyman-continuum photons at twice the efficiency
(per unit UV luminosity) as implied in conventional models. Star-forming
galaxies can then reionize the Universe, even if the escape fraction is <10%.


title:
Stress Transfer Mechanisms at the Submicron Level for Graphene/Polymer
  Systems

abstract:
  The stress transfer mechanism from a polymer substrate to a nano-inclusion,
such as a graphene flake, is of extreme interest for the production of
effective nanocomposites. Previous work conducted mainly at the micron scale
has shown that the intrinsic mechanism of stress transfer is shear at the
interface. However, since the interfacial shear takes its maximum value at the
very edge of the nano-inclusion it is of extreme interest to assess the effect
of edge integrity upon axial stress transfer at the submicron scale. Here, we
conduct a detailed Raman line mapping near the edges of a monolayer graphene
flake which is simply supported onto an epoxy based photoresist
(SU8)/poly(methyl methacrylate) (PMMA) matrix at steps as small as 100 nm. We
show for the first time that, the distribution of axial strain (stress) along
the flake deviates somewhat from the classical shear-lag prediction for a
region of about 2 um from the edge. This behavior is mainly attributed to the
presence of residual stresses, unintentional doping and/or edge effects
(deviation from the equilibrium values of bond lengths and angles, as well as
different edge chiralities). By considering a simple balance of shear-to-normal
stresses at the interface we are able to directly convert the strain (stress)
gradient to values of interfacial shear stress for all the applied tensile
levels without assuming classical shear-lag behavior. For large flakes a
maximum value of interfacial shear stress (ISS) of 0.4 MPa is obtained prior to
flake slipping.


title: Mobility-Aware Caching in D2D Networks

abstract:
  Caching at mobile devices can facilitate device-to-device (D2D)
communications, which may significantly improve spectrum efficiency and
alleviate the heavy burden on backhaul links. However, most previous works
ignored user mobility, thus having limited practical applications. In this
paper, we take advantage of the user mobility pattern by the inter-contact
times between different users, and propose a mobility-aware caching placement
strategy to maximize the data offloading ratio, which is defined as the
percentage of the requested data that can be delivered via D2D links rather
than through base stations (BSs). Given the NP-hard caching placement problem,
we first propose an optimal dynamic programming (DP) algorithm to obtain a
performance benchmark, but with much lower complexity than exhaustive search.
We will then prove that the problem falls in the category of monotone
submodular maximization over a matroid constraint, and propose a time-efficient
greedy algorithm, which achieves an approximation ratio as 1/2. Simulation
results with real-life data-sets will validate the effectiveness of our
proposed mobility-aware caching placement strategy. We observe that users
moving at either a very low or very high speed should cache the most popular
files, while users moving at a medium speed should cache less popular files to
avoid duplication.


title: Entanglement and deterministic quantum computing with one qubit

abstract:
  The role of entanglement and quantum correlations in complex physical systems
and quantum information processing devices has become a topic of intense study
in the past two decades. In this work we present new tools for learning about
entanglement and quantum correlations in dynamical systems where the quantum
states are mixed and the eigenvalue spectrum is highly degenerate. We apply
these results to the Deterministic quantum computing with one qubit (DQC1)
computation model and show that the states generated in a DQC1 circuit have an
eigenvalue structure that makes them difficult to entangle, even when they are
relatively far from the completely mixed state. Our results strengthen the
conjecture that it may be possible to find quantum algorithms that do not
generate entanglement and yet still have an exponential advantage over their
classical counterparts.


title: Cyclicity of the left regular representation of a locally compact group

abstract:
  We combine harmonic analysis and operator algebraic techniques to give a
concise argument that the left regular representation of a locally compact
group is cyclic if and only if the group is first countable, a result first
proved by Greenleaf and Moskowitz.


title: A Primer on the Differential Calculus of 3D Orientations

abstract:
  The proper handling of 3D orientations is a central element in many
optimization problems in engineering. Unfortunately many researchers and
engineers struggle with the formulation of such problems and often fall back to
suboptimal solutions. The existence of many different conventions further
complicates this issue, especially when interfacing multiple differing
implementations. This document discusses an alternative approach which makes
use of a more abstract notion of 3D orientations. The relative orientation
between two coordinate systems is primarily identified by the coordinate
mapping it induces. This is combined with the standard exponential map in order
to introduce representation-independent and minimal differentials, which are
very convenient in optimization based methods.


title:
Spectral decomposition method of dialog state tracking via collective
  matrix factorization

abstract:
  The task of dialog management is commonly decomposed into two sequential
subtasks: dialog state tracking and dialog policy learning. In an end-to-end
dialog system, the aim of dialog state tracking is to accurately estimate the
true dialog state from noisy observations produced by the speech recognition
and the natural language understanding modules. The state tracking task is
primarily meant to support a dialog policy. From a probabilistic perspective,
this is achieved by maintaining a posterior distribution over hidden dialog
states composed of a set of context dependent variables. Once a dialog policy
is learned, it strives to select an optimal dialog act given the estimated
dialog state and a defined reward function. This paper introduces a novel
method of dialog state tracking based on a bilinear algebric decomposition
model that provides an efficient inference schema through collective matrix
factorization. We evaluate the proposed approach on the second Dialog State
Tracking Challenge (DSTC-2) dataset and we show that the proposed tracker gives
encouraging results compared to the state-of-the-art trackers that participated
in this standard benchmark. Finally, we show that the prediction schema is
computationally efficient in comparison to the previous approaches.


title: Almost automorphic distributions

abstract:
  This work deals with almost automorphy of distributions. We give
characterizations and main properties of these distributions. We also study the
existence of distributional almost automorphic solutions of linear
difference-differential equations.


title:
Non-Gaussian chain statistics and finite extensibility in liquid crystal
  elastomers

abstract:
  In this work we will derive an anisotropic generalisation of the finitely
extensible chain model, due to Kuhn and Gr\"un, which is well known in rubber
elasticity. This provides a chain energy that couples elastic behaviour to a
probability distribution describing the orientations of liquid crystal monomers
within a main chain elastomer. The key point is to invoke a maximum relative
entropy assumption on the distribution of bond angles in an observed chain. The
chain energy's fourth order Taylor expansion is also given, which couples to
the second and fourth moments of the nematic distribution function only.


title: TSSort: Probabilistic Noise Resistant Sorting

abstract:
  In this paper we present TSSort, a probabilistic, noise resistant, quickly
converging comparison sort algorithm based on Microsoft TrueSkill. The
algorithm combines TrueSkill's updating rules with a newly developed next item
pair selection strategy, enabling it to beat standard sorting algorithms w.r.t.
convergence speed and noise resistance, as shown in simulations. TSSort is
useful if comparisons of items are expensive or noisy, or if intermediate
results shall be approximately ordered.


title:
Common Fixed Points of Weakly Commuting Multivalued Mappings on Domain
  of Sets Endowed with Directed Graph

abstract:
  In this paper, the existence of coincidence points and common fixed points
for multivalued mappings satisfying certain graphic {\psi}-contraction
contractive conditions with set-valued domain endowed with a graph, without
appealing to continuity, is established. Some examples are presented to support
the results proved herein. Our results unify, generalize and extend various
results in the existing literature.


title: On the spectrum of a Robin Laplacian in a planar waveguide

abstract:
  We consider the Laplace operator in a planar waveguide, i.e., an infinite
two-dimensional straight strip of constant width, with particular types of
Robin boundary conditions. We study the essential spectrum of the corresponding
Laplacian when the boundary coupling function has a limit at infinity.
Furthermore, we derive sufficient conditions for the existence of discrete
spectrum.


title: The Field White Dwarf Mass Distribution

abstract:
  We revisit the properties and astrophysical implications of the field white
dwarf mass distribution in preparation of Gaia applications. Our study is based
on the two samples with the best established completeness and most precise
atmospheric parameters, the volume-complete survey within 20 pc and the Sloan
Digital Sky Survey (SDSS) magnitude-limited sample. We explore the modelling of
the observed mass distributions with Monte Carlo simulations, but find that it
is difficult to constrain independently the initial mass function (IMF), the
initial-to-final-mass relation (IFMR), the stellar formation history (SFH), the
variation of the Galactic disk vertical scale height as a function of stellar
age, and binary evolution. Each of these input ingredients has a moderate
effect on the predicted mass distributions, and we must also take into account
biases owing to unidentified faint objects (20 pc sample), as well as unknown
masses for magnetic white dwarfs and spectroscopic calibration issues (SDSS
sample). Nevertheless, we find that fixed standard assumptions for the above
parameters result in predicted mean masses that are in good qualitative
agreement with the observed values. It suggests that derived masses for both
studied samples are consistent with our current knowledge of stellar and
Galactic evolution. Our simulations overpredict by 40-50% the number of massive
white dwarfs (M > 0.75 Msun) for both surveys, although we can not exclude a
Salpeter IMF when we account for all biases. Furthermore, we find no evidence
of a population of double white dwarf mergers in the observed mass
distributions.


title: A Comparison of Big Data Frameworks on a Layered Dataflow Model

abstract:
  In the world of Big Data analytics, there is a series of tools aiming at
simplifying programming applications to be executed on clusters. Although each
tool claims to provide better programming, data and execution models, for which
only informal (and often confusing) semantics is generally provided, all share
a common underlying model, namely, the Dataflow model. The Dataflow model we
propose shows how various tools share the same expressiveness at different
levels of abstraction. The contribution of this work is twofold: first, we show
that the proposed model is (at least) as general as existing batch and
streaming frameworks (e.g., Spark, Flink, Storm), thus making it easier to
understand high-level data-processing applications written in such frameworks.
Second, we provide a layered model that can represent tools and applications
following the Dataflow paradigm and we show how the analyzed tools fit in each
level.


title:
Can Machine Learn Steganography? - Implementing LSB Substitution and
  Matrix Coding Steganography with Feed-Forward Neural Networks

abstract:
  In recent years, due to the powerful abilities to deal with highly complex
tasks, the artificial neural networks (ANNs) have been studied in the hope of
achieving human-like performance in many applications. Since the ANNs have the
ability to approximate complex functions from observations, it is
straightforward to consider the ANNs for steganography. In this paper, we aim
to implement the well-known LSB substitution and matrix coding steganography
with the feed-forward neural networks (FNNs). Our experimental results have
shown that, the used FNNs can achieve the data embedding operation of the LSB
substitution and matrix coding steganography. For steganography with the ANNs,
though there may be some challenges to us, it would be very promising and
valuable to pay attention to the ANNs for steganography, which may be a new
direction for steganography.


title: Cosmological wormholes in $f(R)$ theories of gravity

abstract:
  Motivated by recent proposals of possible wormhole existence in galactic
halos, we analyse the cosmological evolution of wormhole solutions in modified
$f(R)$ gravity. We construct a dynamical wormhole that asymptotically
approaches FLRW universe, with supporting material going to the perfect
isotropic fluid described by the equation of state for radiation and matter
dominated universe respectively. Our analysis is based on an approximation of a
small wormhole - a wormhole that can be treated as matched with the FLRW metric
at some radial coordinate much smaller than the Hubble radius, so that
cosmological boundary conditions are satisfied. With a special interest in
viable wormhole solutions, we refer to the results of reconstruction procedure
and use $f(R)$ functions which lead to the experimentally confirmed
$\Lambda$CDM expansion history of the Universe. Solutions we find imply no need
for exotic matter near the throat of considered wormholes, while in the limit
of $f(R)=R$ this need is always present during radiation and matter dominated
epoch.


title:
Constraining new physics with collider measurements of Standard Model
  signatures

abstract:
  A new method providing general consistency constraints for
Beyond-the-Standard-Model (BSM) theories, using measurements at particle
colliders, is presented. The method, `Constraints On New Theories Using Rivet',
Contur, exploits the fact that particle-level differential measurements made in
fiducial regions of phase-space have a high degree of model-independence. These
measurements can therefore be compared to BSM physics implemented in Monte
Carlo generators in a very generic way, allowing a wider array of final states
to be considered than is typically the case. The Contur approach should be seen
as complementary to the discovery potential of direct searches, being designed
to eliminate inconsistent BSM proposals in a context where many (but perhaps
not all) measurements are consistent with the Standard Model. We demonstrate,
using a competitive simplified dark matter model, the power of this approach.
The Contur method is highly scaleable to other models and future measurements.


title: Exact eigenfunctions and the open topological string

abstract:
  Mirror curves to toric Calabi-Yau threefolds can be quantized and lead to
trace class operators on the real line. The eigenvalues of these operators are
encoded in the BPS invariants of the underlying threefold, but much less is
known about their eigenfunctions. In this paper we first develop methods in
spectral theory to compute these eigenfunctions. We also provide a matrix
integral representation which allows to study them in a 't Hooft limit, where
they are described by standard topological open string amplitudes. Based on
these results, we propose a conjecture for the exact eigenfunctions which
involves both the WKB wavefunction and the standard topological string
wavefunction. This conjecture can be made completely explicit in the maximally
supersymmetric, or self-dual case, which we work out in detail for local P1xP1.
In this case, our conjectural eigenfunctions turn out to be closely related to
Baker-Akhiezer functions on the mirror curve, and they are in full agreement
with first-principle calculations in spectral theory.


title: Fractals of generalized F- Hutchinson operator in b-metric spaces

abstract:
  The aim of this paper is to construct a fractal with the help of a finite
family of generalized F-contraction mappings, a class of mappings more general
than contraction mappings, defined in the setup of b-metric space.
Consequently, we obtain a variety of results for iterated function system
satisfying a different set of contractive conditions. Our results unify,
generalize and extend various results in the existing literature.


title:
Common Fixed Point Results for Family of Generalized Multivalued
  F-contraction Mappings in Ordered Metric Spaces

abstract:
  In this paper, we study the existence of common fixed points of family of
multivalued mappings satisfying generalized F-contractive conditions in ordered
metric spaces. These results establish some of the general common fixed point
theorems for family of multivalued maps.


title: Sharp convergence rates for averaged nonexpansive maps

abstract:
  We establish sharp estimates for the convergence rate of the
Kranosel'ski\v{\i}-Mann fixed point iteration in general normed spaces, and we
use them to show that the asymptotic regularity bound recently proved in [11]
(Israel Journal of Mathematics 199(2), 757-772, 2014) with constant
$1/\sqrt{\pi}$ is sharp and cannot be improved. To this end we consider the
recursive bounds introduced in [3] (Proceedings of the 2nd International
Conference on Fixed Point Theory and Applications, World Scientific Press,
London, 27-66, 1992) which we reinterpret in terms of a nested family of
optimal transport problems. We show that these bounds are tight by building a
nonexpansive map $T:[0,1]^{\mathbb N}\to[0,1]^{\mathbb N}$ that attains them
with equality, settling the main conjecture in [3]. The recursive bounds are in
turn reinterpreted as absorption probabilities for an underlying Markov chain
which is used to establish the tightness of the constant $1/\sqrt{\pi}$.


title: Spectra of quantum KdV Hamiltonians, Langlands duality, and affine opers

abstract:
  We prove a system of relations in the Grothendieck ring of the category O of
representations of the Borel subalgebra of an untwisted quantum affine algebra
U_q(g^) introduced in [HJ]. This system was discovered in [MRV1, MRV2], where
it was shown that solutions of this system can be attached to certain affine
opers for the Langlands dual affine Kac-Moody algebra of g^, introduced in
[FF5]. Together with the results of [BLZ3, BHK], which enable one to associate
quantum g^-KdV Hamiltonians to representations from the category O, this
provides strong evidence for the conjecture of [FF5] linking the spectra of
quantum g^-KdV Hamiltonians and affine opers for the Langlands dual affine
algebra. As a bonus, we obtain a direct and uniform proof of the Bethe Ansatz
equations for a large class of quantum integrable models associated to
arbitrary untwisted quantum affine algebras, under a mild genericity condition.
We also conjecture analogues of these results for the twisted quantum affine
algebras and elucidate the notion of opers for twisted affine algebras, making
a connection to twisted opers introduced in [FG].


title: Generalized Direct Change Estimation in Ising Model Structure

abstract:
  We consider the problem of estimating change in the dependency structure
between two $p$-dimensional Ising models, based on respectively $n_1$ and $n_2$
samples drawn from the models. The change is assumed to be structured, e.g.,
sparse, block sparse, node-perturbed sparse, etc., such that it can be
characterized by a suitable (atomic) norm. We present and analyze a
norm-regularized estimator for directly estimating the change in structure,
without having to estimate the structures of the individual Ising models. The
estimator can work with any norm, and can be generalized to other graphical
models under mild assumptions. We show that only one set of samples, say $n_2$,
needs to satisfy the sample complexity requirement for the estimator to work,
and the estimation error decreases as $\frac{c}{\sqrt{\min(n_1,n_2)}}$, where
$c$ depends on the Gaussian width of the unit norm ball. For example, for
$\ell_1$ norm applied to $s$-sparse change, the change can be accurately
estimated with $\min(n_1,n_2)=O(s \log p)$ which is sharper than an existing
result $n_1= O(s^2 \log p)$ and $n_2 = O(n_1^2)$. Experimental results
illustrating the effectiveness of the proposed estimator are presented.


title: Classification of finite-growth contragredient Lie superalgebras

abstract:
  A contragredient Lie superalgebra is a superalgebra defined by a Cartan
matrix. In general, a contragredient Lie superalgebra is not finite
dimensional, however it has a natural Z-grading by finite dimensional
components. A contragredient Lie superalgebra has finite growth if the
dimensions of these graded components depend polynomially on the degree. We
discuss the classification of finite-growth contragredient Lie superalgebras.
(Joint work with Vera Serganova)


title: Tannaka-Krein reconstruction for coactions of finite quantum groupoids

abstract:
  We study coactions of finite quantum groupoids on unital $C^*$-algebras and
obtain the Tannaka-Krein reconstruction theorem for them.


title: On good Z-gradings of basic Lie superalgebras

abstract:
  We discuss the classification of good Z-gradings of basic Lie superalgebras.
This problem arose in connection to W-algebras, where good Z-gradings play a
role in their construction.


title: Exact Recovery of Discrete Measures from Wigner D-Moments

abstract:
  In this paper, we show the possibility of recovering a sum of Dirac measures
on the rotation group $SO(3)$ from its low degree moments with respect to
Wigner D-functions only. The main Theorem of the paper states, that exact
recovery from moments up to degree $N$ is possible, if the support set of the
measure obeys a separation distance of $\frac{36}{N+1}$. In this case, the
sought measure is the unique solution of a total variation minimization. The
proof of the uniqueness requires localization estimates for interpolation
kernels and corresponding derivatives on the rotation group $SO(3)$ with
explicit constants.


title:
Broadband X-ray emission and the reality of the broad iron line from the
  Neutron Star - White Dwarf X-ray binary 4U 1820-30

abstract:
  Broad relativistic iron lines from neutron star X-ray binaries are important
probes of the inner accretion disk. The X-ray reflection features can be
weakened due to strong magnetic fields or very low iron abundances such as is
possible in X-ray binaries with low mass, first generation stars as companions.
Here we investigate the reality of the broad iron line detected earlier from
the neutron star low mass X-ray binary 4U~1820--30 with a degenerate helium
dwarf companion. We perform a comprehensive, systematic broadband spectral
study of the atoll source using \suzaku{} and simultaneous \nustar{} \&
\swift{} observations. We have used different continuum models involving
accretion disk emission, thermal blackbody and thermal Comptonization of either
disk or blackbody photons. The \suzaku{} data show positive and negative
residuals in the region of iron K band. These features are well described by
two absorption edges at $7.67\pm0.14\kev$ and $6.93\pm0.07\kev$ or partial
covering photoionized absorption or by blurred reflection. Though, the
simultaneous \swift{} and \nustar{} data do not clearly reveal the emission or
absorption features, the data are consistent with the presence of either
absorption or emission features. Thus, the absorption based models provide an
alternative to the broad iron line or reflection model. The absorption features
may arise in winds from the inner accretion disk. The broadband spectra appear
to disfavour continuum models in which the blackbody emission from the neutron
star surface provides the seed photons for thermal Comptonization. Our results
suggest emission from a thin accretion disk ($kT_{disk} \sim 1\kev$),
Comptonization of disk photons in a boundary layer most likely covering a large
fraction of the neutron star surface and innermost parts of the accretion disk,
and blackbody emission ($kT_{bb} \sim 2\kev$) from the polar regions.


title: Broken scale invariance, $\alpha$-attractors and vector impurity

abstract:
  We show that if the $\alpha$-attractor model is realized by the spontaneous
breaking of the scale symmetry, then the stability and the dynamics of the
vector field that gauges the scale symmetry can severely constrain the
$\alpha$-parameter as $5/6 < \alpha < 1$ restricting the inflationary
predictions in a very tiny region in the $n_s - r$ plane that are in great
agreement with the latest Planck data. Although the different values of
$\alpha$ do not make a tangible difference for $n_s$ and $r$, they provide
radically different scenarios for the post-inflationary dynamics which
determines the standard BBN processes and the large scale isotropy of the
universe.