title: Homology computations for complex braid groups II

abstract:
  We complete the computation of the integral homology of the generalized braid
group $B$ associated to an arbitrary irreducible complex reflection group $W$
of exceptional type. In order to do this we explicitely computed the
recursively-defined differential of a resolution of $\mathbf{Z}$ as a
$\mathbf{Z} B$-module, using parallel computing. We also deduce from this
general computation the rational homology of the Milnor fiber of the
singularity attached to most of these reflection groups.


title: Nuclear motion is classical

abstract:
  The notion from ab-initio molecular dynamics simulations that nuclear motion
is best described by classical Newton dynamics instead of the time-dependent
Schr{\"o}dinger equation is substantiated. In principle a single experiment
should bring clarity. Caution is however necessary, as temperature dependent
effects must be eliminated when trying to determine the existence of a
zero-point energy.


title:
Semi-Supervised Classification Based on Classification from Positive and
  Unlabeled Data

abstract:
  Most of the semi-supervised classification methods developed so far use
unlabeled data for regularization purposes under particular distributional
assumptions such as the cluster assumption. In contrast, recently developed
methods of classification from positive and unlabeled data (PU classification)
use unlabeled data for risk evaluation, i.e., label information is directly
extracted from unlabeled data. In this paper, we extend PU classification to
also incorporate negative data and propose a novel semi-supervised
classification approach. We establish generalization error bounds for our novel
methods and show that the bounds decrease with respect to the number of
unlabeled data without the distributional assumptions that are required in
existing semi-supervised classification methods. Through experiments, we
demonstrate the usefulness of the proposed methods.


title: Transition in the asymptotic suction boundary layer over a heated plate

abstract:
  The asymptotic suction boundary layer (ASBL) is a parallel shear flow that
becomes turbulent in a bypass transition in parameter regions where the laminar
profile is stable. We here add a temperature gradient perpendicular to the
plate and explore the interaction between convection and shear in determining
the transition. We find that the laminar state becomes unstable in a
subcritical bifurcation and that the critical Rayleigh number and wavenumber
depend strongly on the Prandtl number. We also track several secondary
bifurcations and identify states that are localized in two directions, showing
different symmetries. In the subcritical regime, transient turbulent states
which are connected to exact coherent states and follow the same transition
scenario as found in linearly stable shear flows are identified and analyzed.
The study extends the bypass transition scenario from shear flows to thermal
boundary layers and highlights the intricate interactions between thermal and
shear forces.


title: Multi-type particle layer enhanced absorption for photovoltaics

abstract:
  We discuss regular particle arrays as nanostructured front layers for 3rd
generation photovoltaic devices. A rigorous plane-wave method is used to
investigate multi-type particle layers combining different radii and
configurations. The absorbance is enhanced compared to the bare wafer and on
mixing particles we demonstrate a broadband boost in the absorbance within the
photo-active region. Efficiency enhancement in terms of short circuit current
is studied for varying geometries. Si multi-type layers achieved up to 33%
improvement without yet standard anti-reflection coatings. Metal multi-type
layers show strong parasitic absorption and boost the absorbance only in narrow
wavelength regions and no efficiency enhancement is observed.


title: Convex Hulls of Multiple Random Walks: A Large-Deviation Study

abstract:
  We study the polygons governing the convex hull of a point set created by the
steps of $n$ independent two-dimensional random walkers. Each such walk
consists of $T$ discrete time steps, where $x$ and $y$ increments are i.i.d.
Gaussian. We analyze area $A$ and perimeter $L$ of the convex hulls. We obtain
probability densities for these two quantities over a large range of the
support by using a large-deviation approach allowing us to study densities
below $10^{-900}$. We find that the densities exhibit a universal scaling
behavior as a function of $A/T$ and $L/\sqrt{T}$, respectively. As in the case
of one walker ($n=1$), the densities follow Gaussian distributions for $L$ and
$\sqrt{A}$, respectively. We also obtained the rate functions for the area and
perimeter, rescaled with the scaling behavior of their maximum possible values,
and found limiting functions for $T \rightarrow \infty$, revealing that the
densities follow the large-deviation principle. These rate functions can be
described by a power law for $n \rightarrow \infty$ as found in the $n=1$ case.
We also investigated the behavior of the averages as a function of the number
of walks $n$ and found good agreement with the predicted behavior.


title: Obliquity dependence of the tangential YORP

abstract:
  Context. Tangential YORP is a thermophysical effect that can alter the
rotation rate of asteroids and is distinct from the "normal" YORP effect, but
to date has only been studied for asteroids with zero obliquity. Aims. The
tangential YORP force produced by spherical boulders on the surface of an
asteroid with an arbitrary obliquity is studied. Methods. A finite element
method is used to simulate heat conductivity inside a boulder, to find the
recoil force experienced by it. Then an ellipsoidal asteroid uniformly covered
by such boulders is considered and the torque is numerically integrated over
its surface. Results. Tangential YORP is found to operate on non-zero
obliquities and decreases by a factor of 2 for increasing obliquity.


title:
Accretion Flow Properties of MAXI J1543-564 During 2011 Outburst from
  TCAF Solution

abstract:
  We derive accretion flow properties of the transient black hole candidate
(BHC) MAXI~J1543-564 using the RXTE data. We use Two-Component Advective Flow
(TCAF) solution to fit the data of the very initial rising phase of outburst
(from 2011 May 10 to 2011 May 15). $2.5-25$~keV spectra are fitted using the
TCAF solution {\it fits} file as a local additive table model in XSPEC. We
extract physical flow parameters such as the two component (Keplerian disk and
sub-Keplerian halo) accretion rates and size and the property of the Compton
cloud (post shock region close to a black hole). Similar to other classical
transient BHCs, monotonic evolution of low frequency quasi-periodic
oscillations (QPOs) are observed during the rising phase of the outburst, which
is fitted with the propagating oscillatory shock (POS) model which describes
how the Compton cloud properties change from day to day. From the nature of
variations of TCAF model fitted physical flow parameters and QPOs, we only
found hard-intermediate and soft-intermediate spectral states during this phase
of the outburst under study. We also calculate frequency of the dominating QPOs
from the TCAF model fitted shock parameters, and found that they roughly match
with the observed and POS model fitted values. From our spectro-temporal study
of the source with TCAF and POS models, the most probable mass of the BHC is
found to be $12.6-14.0$~$M_\odot$, or $13^{+1.0}_{-0.4}~M_\odot$.


title: Twisted Alexander invariants of complex hypersurface complements

abstract:
  We define and study twisted Alexander-type invariants of complex hypersurface
complements. We investigate torsion properties for the twisted Alexander
modules and extend classical local-to-global divisibility results to the
twisted setting. In the process, we also study the splitting fields containing
the roots of the corresponding twisted Alexander polynomials.


title: Nanoscale Superconducting Honeycomb Charge Order in IrTe2

abstract:
  Entanglement of charge orderings and other electronic orders such as
superconductivity is in the core of challenging physics issues of complex
materials including high temperature superconductivity. Here, we report on the
observation of a unique nanometer scale honeycomb charge ordering of the
cleaved IrTe2 surface, which hosts a superconducting state. IrTe2 was recently
established to exhibit an intriguing cascade of stripe charge orders. The
stripe phases coexist with a hexagonal phase, which is formed locally and falls
into a superconducting state below 3 K. The atomic and electronic structures of
the honeycomb and hexagon pattern of this phase are consistent with the charge
order nature but the superconductivity does not survive on neighboring stripe
charge order domains. The present work provides an intriguing physics issue and
a new direction of functionalization for two dimensional materials.


title:
Measurement of azimuthal correlations of D mesons and charged particles
  in pp collisions at $\sqrt{s}=7$ TeV and p-Pb collisions at $\sqrt{s_{\rm
  NN}}=5.02$ TeV

abstract:
  The azimuthal correlations of D mesons and charged particles were measured
with the ALICE detector in pp collisions at $\sqrt{s}=7$ TeV and p-Pb
collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV at the Large Hadron Collider. D$^0$,
D$^+$, and D$^{*+}$ mesons and their charge conjugates with transverse momentum
$3<p_{\rm T}<16$ GeV/$c$ and rapidity in the nucleon-nucleon centre-of-mass
system $|y_{\rm cms}|<0.5$ (pp collisions) and $-0.96<y_{\rm cms}<0.04$ (p-Pb
collisions) were correlated to charged particles with $p_{\rm T}>0.3$ Gev/$c$.
The properties of the correlation peak induced by the jet containing the D
meson, described in terms of the yield of charged particles in the peak and
peak width, are compatible within uncertainties between the two collision
systems, and described by Monte-Carlo simulations based on the PYTHIA, POWHEG
and EPOS 3 event generators.


abstract:
  A nonlinear Korn inequality based on the Green-Saint Venant strain tensor is
proved, whenever the displacement is in the Sobolev space $W^{1,p}$, $p\geq 2$,
under Dirichlet conditions on a part of the boundary. The inequality can be
useful in proving the coercivity of a nonlinear elastic energy.


title: Poynting-Robertson drag and solar wind in the space debris problem

abstract:
  We analyze the combined effect of Poynting-Robertson and solar wind drag on
space debris. We derive a model within Cartesian, Gaussian and Hamiltonian
frameworks. We focus on the geosynchronous resonance, although the results can
be easily generalized to any resonance. By numerical and analytical techniques,
we compute the drift in semi-major axis due to Poynting-Robertson and solar
wind drag. After a linear stability analysis of the equilibria, we combine a
careful investigation of the regular, resonant, chaotic behavior of the phase
space with a long-term propagation of a sample of initial conditions. The
results strongly depend on the value of the area-to-mass ratio of the debris,
which might show different dynamical behaviors: temporary capture or escape
from the geosynchronous resonance, as well as temporary capture or escape from
secondary resonances involving the rate of variation of the longitude of the
Sun. Such analysis shows that Poynting-Robertson and solar wind drag must be
taken into account, when looking at the long-term behavior of space debris.
Trapping or escape from the resonance can be used to place the debris in
convenient regions of the phase space.


title:
Coherent J/psi photoproduction in ultra-peripheral PbPb collisions at
  sqrt(s[NN]) = 2.76 TeV with the CMS experiment

abstract:
  The cross section for coherent J/psi photoproduction accompanied by at least
one neutron on one side of the interaction point and no neutron activity on the
other side, X[n]0[n], is measured with the CMS experiment in ultra-peripheral
PbPb collisions at sqrt(s[NN]) = 2.76 TeV. The analysis is based on a data
sample corresponding to an integrated luminosity of 159 inverse microbarns,
collected during the 2011 PbPb run. The J/psi mesons are reconstructed in the
dimuon decay channel, while neutrons are detected using zero degree
calorimeters. The measured cross section is dsigma[coh,X[n]0[n]] / dy(J/psi) =
0.36 +/- 0.04 (stat) +/- 0.04 (syst) mb in the rapidity interval 1.8 < abs(y) <
2.3. Using a model for the relative rate of coherent photoproduction processes,
this X[z,n,z] measurement gives a total coherent photoproduction cross section
of dsigma[coh] / dy(J/psi) = 1.82 +/- 0.22 (stat) +/- 0.20 (syst) +/- 0.19
(theo) mb. The data strongly disfavour the impulse approximation model
prediction, indicating that nuclear effects are needed to describe coherent
J/psi photoproduction in gamma + Pb interactions. The data are found to be
consistent with the leading twist approximation, which includes nuclear gluon
shadowing.


title:
Electronic Structure of FeAl Alloy Studied by Resonant Photoemission
  Spectroscopy and Ab Initio Calculations

abstract:
  Resonant photoemission spectroscopy has been used to investigate the
character of Fe 3d states in FeAl alloy. Fe 3d states have two different
character, first is of itinerant nature located very close to the Fermi level,
and second, is of less itinerant (relatively localized character), located
beyond 2 eV below the Fermi level. These distinct states are clearly
distinguishable in the resonant photoemission data. Comparison between the
results obtained from experiments and first principle based electronic
structure calculation show that the origin of the itinerant character of the Fe
3d states is due to the ordered B2 structure, whereas the relatively less
itinerant (localized) Fe 3d states are from the disorders present in the
sample. The exchange splitting of the Fe 3s core level peak confirms the
presence of local moment in this system. It is found that the itinerant
electrons arise due to the hybridization between Fe 3d and Al 3s-3p states.
Presence of hybridization is observed as a shift in the Al 2p core-level
spectra as well as in the X-ray near edge absorption spectra towards lower
binding energy. Our photoemission results are thus explained by the
co-existence of ordered and disordered phases in the system.


title: A Riemannian gossip approach to decentralized matrix completion

abstract:
  In this paper, we propose novel gossip algorithms for the low-rank
decentralized matrix completion problem. The proposed approach is on the
Riemannian Grassmann manifold that allows local matrix completion by different
agents while achieving asymptotic consensus on the global low-rank factors. The
resulting approach is scalable and parallelizable. Our numerical experiments
show the good performance of the proposed algorithms on various benchmarks.


title: Entropic Measure of Time, and Gas Expansion in Vacuum

abstract:
  The study considers advantages of the introduced measure of time based on the
entropy change under irreversible processes (entropy production). Using the
example of non-equilibrium expansion of an ideal gas in vacuum, such a measure
is introduced with the help of Boltzmann's classic entropy. It is shown that,
in the general case, this measure of time proves to be nonlinearly related to
the reference measure assumed uniform by convention. The connection between
this result and the results of other authors investigating measure of time in
some biological and cosmological problems is noted.


title: Accurate and stable time stepping in ice sheet modeling

abstract:
  In this paper we introduce adaptive time step control for simulation of
evolution of ice sheets. The discretization error in the approximations is
estimated using "Milne's device" by comparing the result from two different
methods in a predictor-corrector pair. Using a predictor-corrector pair the
expensive part of the procedure, the solution of the velocity and pressure
equations, is performed only once per time step and an estimate of the local
error is easily obtained. The stability of the numerical solution is maintained
and the accuracy is controlled by keeping the local error below a given
threshold using PI-control. Depending on the threshold, the time step $\Delta
t$ is bound by stability requirements or accuracy requirements. Our method
takes a shorter $\Delta t$ than an implicit method but with less work in each
time step and the solver is simpler. The method is analyzed theoretically with
respect to stability and applied to the simulation of a 2D ice slab and a 3D
circular ice sheet. %The automatically chosen $\Delta t$ is either restricted
by accuracy or stability depedning on an error tolerance. The stability bounds
in the experiments are explained by and agree well with the theoretical
results.


title:
Benchmark tests of a strongly constrained semilocal functional with a
  long-range dispersion correction

abstract:
  The strongly constrained and appropriately normed (SCAN) semilocal density
functional [J. Sun, A. Ruzsinszky, J. P. Perdew \textit{Phys. Rev. Lett.} {\bf
115}, 036402 (2015)] obeys all 17 known exact constraints for
meta-generalized-gradient approximations (meta-GGA) and includes some medium
range correlation effects. Long-range London dispersion interactions are still
missing, but can be accounted for via an appropriate correction scheme. In this
study, we combine SCAN with an efficient London dispersion correction and show
that lattice energies of simple organic crystals can be improved with the
applied correction by 50\%. The London-dispersion corrected SCAN meta-GGA
outperforms all other tested London-dispersion corrected meta-GGAs for
molecular geometries. Our new method delivers mean absolute deviations (MADs)
for main group bond lengths that are consistently below 1\,pm, rotational
constants with MADs of 0.2\%, and noncovalent distances with MADs below 1\%.
For a large database of general main group thermochemistry and kinetics, it
also delivers a weighted mean absolute deviation below 4 kcal/mol, one of the
lowest for long-range corrected meta-GGA functionals. We also discuss some
consequences of numerical sensitivity encountered for meta-GGAs.


title:
The Effect of Limited Sample Sizes on the Accuracy of the Estimated
  Scaling Parameter for Power-Law-Distributed Solar Data

abstract:
  Many natural processes exhibit power-law behavior. The power-law exponent is
linked to the underlying physical process and therefore its precise value is of
interest. With respect to the energy content of nanoflares, for example, a
power-law exponent steeper than 2 is believed to be a necessary condition to
solve the enigmatic coronal heating problem. Studying power-law distributions
over several orders of magnitudes requires sufficient data and appropriate
methodology. In this paper we demonstrate the shortcomings of some popular
methods in solar physics that are applied to data of typical sample sizes. We
use synthetic data to study the effect of the sample size on the performance of
different estimation methods and show that vast amounts of data are needed to
obtain a reliable result with graphical methods (where the power-law exponent
is estimated by a linear fit on a log-transformed histogram of the data). We
revisit published results on power laws for the angular width of solar coronal
mass ejections and the radiative losses of nanoflares. We demonstrate the
benefits of the maximum likelihood estimator and advocate its use.


title:
Inverse Problems for Matrix Exponential in System Identification: System
  Aliasing

abstract:
  This note addresses identification of the $A$-matrix in continuous time
linear dynamical systems on state-space form. If this matrix is partially known
or known to have a sparse structure, such knowledge can be used to simplify the
identification. We begin by introducing some general conditions for solvability
of the inverse problems for matrix exponential. Next, we introduce "system
aliasing" as an issue in the identification of slow sampled systems. Such
aliasing give rise to non-unique matrix logarithms. As we show, by imposing
additional conditions on and prior knowledge about the $A$-matrix, the issue of
system aliasing can, at least partially, be overcome. Under conditions on the
sparsity and the norm of the $A$-matrix, it is identifiable up to a finite
equivalence class.


title: Invariant measures for the two-dimensional averaged-Euler equations

abstract:
  We define a Gaussian invariant measure for the two-dimensional averaged-Euler
equation and show the existence of its solution with initial conditions on the
support of the measure. An invariant surface measure on the level sets of the
energy is also constructed, as well as the corresponding flow. Poincar\'e
recurrence theorem is used to show that the flow returns infinitely many times
in a neighbourhood of the initial state.


title: Operational definition of quantum correlations of light

abstract:
  Quantum features of correlated optical modes define a major aspect of the
nonclassicality in quantized radiation fields. However, the phase-sensitive
detection of a two-mode light field is restricted to interferometric setups and
local intensity measurements. Even the full reconstruction of the quantum state
of a single radiation mode relies on such detection layouts and the preparation
of a well-defined reference light field. In this work, we establish the notion
of the essential quantum correlations of two-mode light fields. It refers to
those quantum correlations which are measurable by a given device, i.e., the
accessible part of a nonclassical Glauber-Sudarshan phase-space distribution,
which does not depend on a global phase. Assuming a simple four-port
interferometer and photon-number-resolving detectors, we derive the
reconstruction method and nonclassicality criteria based on the
Laplace-transformed moment-generating function of the essential
quasiprobability. With this technique, we demonstrate that the essential
quantum correlations of a polarization tomography scheme are observable even if
the detectors are imperfect and cannot truly resolve the photon statistics.


title: Continuous Time Quantum Consensus & Quantum Synchronisation

abstract:
  Distributed consensus algorithm over networks of quantum systems has been the
focus of recent studies in the context of quantum computing and distributed
control. Most of the progress in this category have been on the convergence
conditions and optimizing the convergence rate of the algorithm, for quantum
networks with undirected underlying topology. This paper aims to address the
extension of this problem over quantum networks with directed underlying
graphs. In doing so, the convergence to two different stable states namely,
consensus and synchronous states have been studied. Based on the intertwining
relation between the eigenvalues, it is shown that for determining the
convergence rate to the consensus state, all induced graphs should be
considered while for the synchronous state only the underlying graph suffices.
Furthermore, it is illustrated that for the range of weights that the Aldous'
conjecture holds true, the convergence rate to both states are equal. Using the
Pareto region for convergence rates of the algorithm, the global and Pareto
optimal points for several topologies have been provided.


title:
Some Types of Linear Combinations of Weyl-Heisenberg Wave Packet Frames
  Over Local Fields of Positive Characteristic

abstract:
  In this paper, we present necessary and sufficient conditions for some types
of linear combination of frame elements (wave packet) to be a frame for
$L^2(\mathbb{K})$, where $\mathbb{K}$ is a local field of positive
characteristic.


title: The Murchison Widefield Array 21 cm Power Spectrum Analysis Methodology

abstract:
  We present the 21 cm power spectrum analysis approach of the Murchison
Widefield Array Epoch of Reionization project. In this paper, we compare the
outputs of multiple pipelines for the purpose of validating statistical limits
cosmological hydrogen at redshifts between 6 and 12. Multiple, independent,
data calibration and reduction pipelines are used to make power spectrum limits
on a fiducial night of data. Comparing the outputs of imaging and power
spectrum stages highlights differences in calibration, foreground subtraction
and power spectrum calculation. The power spectra found using these different
methods span a space defined by the various tradeoffs between speed, accuracy,
and systematic control. Lessons learned from comparing the pipelines range from
the algorithmic to the prosaically mundane; all demonstrate the many pitfalls
of neglecting reproducibility. We briefly discuss the way these different
methods attempt to handle the question of evaluating a significant detection in
the presence of foregrounds.


title:
Model order reduction and sparse orthogonal expansions for random linear
  dynamical systems

abstract:
  We consider linear dynamical systems of ordinary differential equations or
differential algebraic equations. Physical parameters are substituted by random
variables for an uncertainty quantification. We expand the state variables as
well as a quantity of interest into an orthogonal system of basis functions,
which depend on the random variables. For example, polynomial chaos expansions
are applicable. The stochastic Galerkin method yields a larger linear dynamical
system, whose solution approximates the unknown coefficients in the expansions.
The Hardy norms of the transfer function provide information about the
input-output behaviour of the Galerkin system. We investigate two approaches to
construct a sparse representation of the quantity of interest, where just a low
number of coefficients is non-zero. Firstly, a standard basis is reduced by the
omission of basis functions, whose accompanying Hardy norms are relatively
small. Secondly, a projection-based model order reduction is applied to the
Galerkin system and allows for the definition of new basis functions as a
sparse representation. In both cases, we prove error bounds on the sparse
approximation with respect to Hardy norms. Numerical experiments are
demonstrated for a test example modelling a linear electric circuit.


title: Bounds on the regularity of toric ideals of graphs

abstract:
  Let $G$ be a finite simple graph. We give a lower bound for the
Castelnuovo-Mumford regularity of the toric ideal $I_G$ associated to $G$ in
terms of the sizes and number of induced complete bipartite graphs in $G$. When
$G$ is a chordal bipartite graph, we find an upper bound for the regularity of
$I_G$ in terms of the size of the bipartition of $G$. We also give a new proof
for the graded Betti numbers of the toric ideal associated to the complete
bipartite graph $K_{2,n}$.


title: A convex embedding for the rotating Kepler problem

abstract:
  In this note, we prove that below the first critical energy level, a proper
combination of the Ligon-Schaaf and Levi-Civita regularization mappings
provides a convex symplectic embedding of the energy surfaces of the planar
rotating Kepler problem into $R^4$ endowed with its standard symplectic
structure. A direct consequence is the dynamical convexity of the planar
rotating Kepler problem, which has been established by
Albers-Fish-Frauenfelder-van Koert by direct computations. This result opens up
new approaches to attack the Birkhoff conjecture about the existence of a
global surface of section in the restricted planar circular three body problem
using holomorphic curve techniques.


title:
Path integrals, SUSY QM and the Atiyah-Singer index theorem for twisted
  Dirac

abstract:
  Feynman's time-slicing construction approximates the path integral by a
product, determined by a partition of a finite time interval, of approximate
propagators. This paper formulates general conditions to impose on a short-time
approximation to the propagator in a general class of imaginary-time quantum
mechanics on a Riemannian manifold which ensure these products converge. The
limit defines a path integral which agrees pointwise with the heat kernel for a
generalized Laplacian. The result is a rigorous construction of the propagator
for supersymmetric quantum mechanics, with potential, as a path integral.
Further, the class of Laplacians includes the square of the twisted Dirac
operator, which corresponds to an extension of N=1/2 supersymmetric quantum
mechanics. General results on the rate of convergence of the approximate path
integrals suffice in this case to derive the local version of the Atiyah-Singer
index theorem.


title: Anick resolution and Koszul algebras of finite global dimension

abstract:
  We show how to study a certain associative algebra recently discovered by
Iyudu and Shkarin using the Anick resolution. This algebra is a counterexample
to the conjecture of Positselski on Koszul algebras of finite global dimension.


title: Inequalities on generalized matrix functions

abstract:
  We prove inequalities on non-integer powers of products of generalized
matrices functions on the sum of positive semi-definite matrices. For example,
for any real number $r \in \{1\} \cup [2, \infty)$, positive semi-definite
matrices $A_i,\ B_i,\ C_i\in M_{n_i}$, $i=1,2$, and generalized matrix
functions $d_\chi, d_\xi$ such as the determinant and permanent, etc., we have
\begin{eqnarray*}&&\left(d_\chi(A_1+B_1+C_1)d_\xi(A_2+B_2+C_2)\right)^r \\
&&\hskip 1in
  + \left(d_\chi(A_1)d_\xi(A_2)\right)^r
  + \left(d_\chi(B_1)d_\xi(B_2)\right)^r + \left(d_\chi(C_1)d_\xi(C_2)\right)^r
\\ & \ge &\left(d_\chi(A_1+B_1 )d_\xi(A_2+B_2 )\right)^r + \left(d_\chi(A_1+
C_1)d_\xi(A_2+ C_2)\right)^r + \left(d_\chi( B_1+C_1)d_\xi(
B_2+C_2)\right)^r\,.\end{eqnarray*} A general scheme is introduced to prove
more general inequalities involving $m$ positive semi-definite matrices for $m
\ge 3$ that extend the results of other authors.


title:
Zero sets of functions in the Nevanlinna class and the
  $\bar\partial_b$-equation on convex domains of general type in $\mathbb{C}^2$

abstract:
  The purpose of this paper is to characterize the zero sets of holomorphic
functions in the Nevanlinna class on a class of convex domains of infinite type
in $\mathbb{C}^2$. Moreover, we also obtain $L^p$ estimates, $1 \leq p \leq
\infty$, for a particular solution of the tangential Cauchy-Riemann equation on
the boundaries of these domains.


title: 1D to 3D Crossover of a Spin-Imbalanced Fermi Gas

abstract:
  We have characterized the one-dimensional (1D) to three-dimensional (3D)
crossover of a two-component spin-imbalanced Fermi gas of 6-lithium atoms in a
2D optical lattice by varying the lattice tunneling and the interactions. The
gas phase separates, and we detect the phase boundaries using in situ imaging
of the inhomogeneous density profiles. The locations of the phases are inverted
in 1D as compared to 3D, thus providing a clear signature of the crossover. By
scaling the tunneling rate with respect to the pair binding energy, we observe
a collapse of the data to a universal crossover point at a scaled tunneling
value of 0.025(7).


title: Vector lattices in synaptic algebras

abstract:
  A synaptic algebra $A$ is a generalization of the self-adjoint part of a von
Neumann algebra. We study a linear subspace $V$ of $A$ in regard to the
question of when $V$ is a vector lattice. Our main theorem states that if $V$
contains the identity element of $A$ and is closed under the formation of both
the absolute value and the carrier of its elements, then $V$ is a vector
lattice if and only if the elements of $V$ commute pairwise.


title: Entropy of a generic null surface from its associated Virasoro algebra

abstract:
  Null surfaces act as one-way membranes, blocking information from those
observers who do not cross them (e.g., in the black hole and the Rindler
spacetimes) and these observers associate an entropy (and temperature) with the
null surface. The black hole entropy can be computed from the central charge of
an appropriately defined, local, Virasoro algebra on the horizon. We show that
one can extend these ideas to a general class of null surfaces, all of which
possess a Virasoro algebra and a central charge, leading to an entropy density
(i.e., per unit area) which is just $(1/4)$. All the previously known results
of associating entropy with horizons arise as special cases of this very
general property of null surfaces demonstrated here and we believe this work
represents the derivation of the entropy-area law in the most general context.
The implications are discussed.


title:
Experimental Evaluation of Modified Decomposition Algorithm for Maximum
  Weight Bipartite Matching

abstract:
  Let $G$ be an undirected bipartite graph with positive integer weights on the
edges. We refine the existing decomposition theorem originally proposed by Kao
et al., for computing maximum weight bipartite matching. We apply it to design
an efficient version of the decomposition algorithm to compute the weight of a
maximum weight bipartite matching of $G$ in $O(\sqrt{|V|}W'/k(|V|,W'/N))$-time
by employing an algorithm designed by Feder and Motwani as a subroutine, where
$|V|$ and $N$ denote the number of nodes and the maximum edge weight of $G$,
respectively and $k(x,y)=\log x /\log(x^2/y)$. The parameter $W'$ is smaller
than the total edge weight $W,$ essentially when the largest edge weight
differs by more than one from the second largest edge weight in the current
working graph in any decomposition step of the algorithm. In best case
$W'=O(|E|)$ where $|E|$ be the number of edges of $G$ and in worst case $W'=W,$
that is, $|E| \leq W' \leq W.$ In addition, we talk about a scaling property of
the algorithm and research a better bound of the parameter $W'$. An
experimental evaluation on randomly generated data shows that the proposed
improvement is significant in general.


title:
First observation of $\Lambda_b^0 \rightarrow \Lambda K^+\pi^-$ and
  $\Lambda_b^0 \rightarrow \Lambda K^+K^-$ decays at LHCb

abstract:
  The physics potential for $b$-baryon decays has been relatively unexplored
until the advent of the LHC, and as such important questions still exist about
their fundamental properties, such as whether their decays exhibit $C\!P$
violation. Presented here are observations of the decays $\Lambda_b^0
\rightarrow \Lambda K^+\pi^-$ and $\Lambda_b^0 \rightarrow \Lambda K^+K^-$,
made at a significance level of 8.1 and 15.8 Gaussian standard deviations,
respectively, and measurements of their branching fractions. The phase-space
integrated $C\!P$ asymmetries of these decays are also measured and found to be
consistent with zero. Limits are set on the branching fractions of other
$\Lambda_b^0$ and $\Xi_b^0$ decays to $\Lambda h^+h^{\prime -}$ (where $h$ is a
kaon or pion).


title: A duality web of linear quivers

abstract:
  We show that applying the Bailey lemma to elliptic hypergeometric integrals
on the $A_n$ root system leads to a large web of dualities for $\mathcal{N} =
1$ supersymmetric linear quiver theories. The superconformal index of Seiberg's
SQCD with $SU(N_c)$ gauge group and $SU(N_f)\times SU(N_f)\times U(1)$ flavour
symmetry is equal to that of $N_f-N_c-1$ distinct linear quivers. Seiberg
duality further enlarges this web by adding new quivers. In particular, both
interacting electric and magnetic theories with arbitrary $N_c$ and $N_f$ can
be constructed by quivering an $s$-confining theory with $N_f=N_c+1$.


title: SONIK: Efficient In-situ All Item Rank Generation using Bit Operations

abstract:
  Sorting, a classical combinatorial process, forms the bedrock of numerous
algorithms with varied applications. A related problem involves efficiently
finding the corresponding ranks of all the elements - catering to rank queries,
data partitioning and allocation, etc. Although, the element ranks can be
subsequently obtained by initially sorting the elements, such procedures
involve O(n log n) computations and might not be suitable with large input
sizes for hard real-time systems or for applications with data re-ordering
constraints. This paper proposes SONIK, a non-comparison linear time and space
algorithm using bit operations inspired by radix sort for computing the ranks
of all input integer elements, thereby providing implicit sorting. The element
ranks are generated in-situ, i.e., directly at the corresponding element
position without re-ordering or recourse to any other sorting mechanism.


title: Phil Anderson's Magnetic Ideas in Science

abstract:
  In Philip W. Anderson's research, magnetism has always played a special role,
providing a prism through which other more complex forms of collective behavior
and broken symmetry could be examined. I discuss his work on magnetism from the
1950s, where his early work on antiferromagnetism led to the pseudospin
treatment of superconductivity - to the 70s and 80s, highlighting his
contribution to the physics of local magnetic moments. Phil's interest in the
mechanism of moment formation, and screening evolved into the modern theory of
the Kondo effect and heavy fermions.

categories: cond-mat.str-el cond-mat.stat-mech cond-mat.supr-con physics.hist-ph


title:
Reflections on works by I.S.Shklovsky regarding the nature of radio
  galaxies

abstract:
  The paper is a brief overview of the works by Iosif S. Shklovsky
(1916--1985), carried out over almost 30 years (1955--1985), on the nature of
activity (primarily in the radio frequency range) in nuclei of some galaxies.
  Worthy of note is Shklovsky's pioneering work of 1962, in which he made an
attempt to consider possible evolutionary tracks of extragalactic radio sources
by constructing an analog of the Herzsprung--Russel diagram for stars (radio
luminosity at 160 MHz was taken instead of optical luminosity; total radio size
at the same frequency, as the other parameter). Later works by other authors
are also discussed, where similar diagrams were plotted using a larger
observational material.
  Special attention is paid to the evolution of Shklovsky's views regarding the
possible ways of gas getting into radio galaxies' central regions, followed by
high-velocity ejections of magnetized plasmons from their nuclei. In his
assumptions, Shklovsky was mainly based on the observational data for the
properties of the closest radio galaxy, NGC 4486 (Virgo A, M87), which he
believed to be the same reference standard for extragalactic radio astronomy as
the Crab Nebula for galactic radio astronomy.
  Shklovsky's approach to the recurrence of the activity phenomenon in galactic
nuclei and the one-sided character of radio ejections from them is discussed.
  Modern views on these issues are also briefly considered.


title: DP-EM: Differentially Private Expectation Maximization

abstract:
  The iterative nature of the expectation maximization (EM) algorithm presents
a challenge for privacy-preserving estimation, as each iteration increases the
amount of noise needed. We propose a practical private EM algorithm that
overcomes this challenge using two innovations: (1) a novel moment perturbation
formulation for differentially private EM (DP-EM), and (2) the use of two
recently developed composition methods to bound the privacy "cost" of multiple
EM iterations: the moments accountant (MA) and zero-mean concentrated
differential privacy (zCDP). Both MA and zCDP bound the moment generating
function of the privacy loss random variable and achieve a refined tail bound,
which effectively decrease the amount of additive noise. We present empirical
results showing the benefits of our approach, as well as similar performance
between these two composition methods in the DP-EM setting for Gaussian mixture
models. Our approach can be readily extended to many iterative learning
algorithms, opening up various exciting future directions.


title: Extracting Higher-Order Goals from the Mizar Mathematical Library

abstract:
  Certain constructs allowed in Mizar articles cannot be represented in
first-order logic but can be represented in higher-order logic. We describe a
way to obtain higher-order theorem proving problems from Mizar articles that
make use of these constructs. In particular, higher-order logic is used to
represent schemes, a global choice construct and set level binders. The
higher-order automated theorem provers Satallax and LEO-II have been run on
collections of these problems and the results are discussed.


title: Multiple Dirac cones at the surface of the topological metal LaBi

abstract:
  The rare-earth monopnictide LaBi exhibits exotic magneto-transport properties
including an extremely large and anisotropic magnetoresistance. Experimental
evidence for topological surface states is still missing although band
inversions have been postulated to induce a topological phase in LaBi. By
employing angle-resolved photoemission spectroscopy (ARPES) in conjunction with
$ab~initio$ calculations, we have revealed the existence of surface states of
LaBi through the observation of three Dirac cones: two coexist at the corners
and one appears at the center of the Brillouin zone. The odd number of surface
Dirac cones is a direct consequence of the odd number of band inversions in the
bulk band structure, thereby proving that LaBi is a topological, compensated
semi-metal, which is equivalent to a time-reversal invariant topological
insulator. Our findings provide insight into the topological surface states of
LaBi's semi-metallicity and related magneto-transport properties.


title: Onset of exciton-exciton annihilation in single layer black phosphorus

abstract:
  The exciton dynamics in monolayer black phosphorus is investigated over a
very wide range of photoexcited exciton densities using time resolved
photoluminescence. At low excitation densities, the exciton dynamics is
successfully described in terms of a double exponential decay. With increasing
exciton population, a fast, non-exponential component develops as
exciton-exciton annihilation takes over as the dominant recombination mechanism
under high excitation conditions. Our results identify an upper limit for the
injection density, after which exciton-exciton annihilation reduces the quantum
yield, which will significantly impact the performance of light emitting
devices based on single layer black phosphorus.


title:
A Tale of Three Galaxies: A "Clumpy" View of the Spectroscopically
  Anomalous Galaxies IRAS F10398+1455, IRAS F21013-0739 and SDSS J0808+3948

abstract:
  We investigate the dust properties in three spectroscopically anomalous
galaxies (IRAS F10398+1455, IRAS F21013-0739 and SDSS J0808+3948). Their
Spitzer/IRS spectra are characterized by a steep ~5-8 micron emission
continuum, strong emission bands from polycyclic aromatic hydrocarbon (PAH)
molecules, and prominent 10 micron silicate emission. The steep ~5-8 micron
continuum and strong PAH emission features suggest the presence of starbursts,
while the silicate emission is indicative of significant heating from AGNs. The
simultaneous detection of these two observational properties has rarely been
reported on galactic scale. We employ the PAHFIT software to estimate their
starlight contributions, and the CLUMPY model for the components contributed by
the AGN tori. We find that the CLUMPY model is generally successful in
explaining the overall dust infrared emission, although it appears to emit too
flat at the ~5-8 micron continuum to be consistent with that observed in IRAS
F10398+1455 and IRAS F21013-0739. The flat ~5-8 micron continuum calculated
from the CLUMPY model could arise from the adopted specific silicate opacity of
Ossenkopf et al. (1992) which exceeds that of the Draine & Lee (1984)
"astronomical silicate" by a factor up to 2 in the ~5-8 micron wavelength
range. Future models with a variety of dust species incorporated in the CLUMPY
radiation transfer regime are needed for a thorough understanding of the dust
properties of these spectroscopically anomalous galaxies.


title: The role of ices in star-forming clouds

abstract:
  Ices play a critical role during the evolution of interstellar clouds. Their
presence is ubiquitous in the dense molecular medium and their impact is not
only limited to chemistry. Species adsorbed onto dust grains also affect cloud
thermodynamics. It all depends on the interstellar conditions, the chemical
parameters, and the composition of ice layers. In this work, I study the
formation of ices by focusing on the interplay between gas and solid phase to
determine their role on cloud evolution and star formation. I show that while
the formation of ices greatly impacts the cloud chemistry, their role on the
thermodynamics is more conservative, and their influence on star formation is
only marginal.


title:
A deep Chandra observation of the interacting star-forming galaxy Arp
  299

abstract:
  We present results from a 90 ks Chandra ACIS-S observation of the X-ray
luminous interacting galaxy system Arp 299 (NGC 3690/IC 694). We detect 25
discrete X-ray sources with luminosities above 4.0x10^38 erg s^-1 covering the
entire Ultra Luminous X-ray source (ULX) regime. Based on the hard X-ray
spectra of the non-nuclear discrete sources identified in Arp 299, and their
association with young, actively star-forming region of Arp 299 we identify
them as HMXBs. We find in total 20 off-nuclear sources with luminosities above
the ULX limit, 14 of which are point-like sources. Furthermore we observe a
marginally significant deficit in the number of ULXs, with respect to the
number expected from scaling relations of X-ray binaries with the star
formation rate (SFR). Although the high metalicity of the galaxy could result
in lower ULX numbers, the good agreement between the observed total X-ray
luminosity of ULXs, and that expected from the relevant scaling relation
indicates that this deficit could be the result of confusion effects. The
integrated spectrum of the galaxy shows the presence of a hot gaseous component
with kT = 0.72+-0.03 keV, contributing 20% of the soft (0.1-2.0 keV) unabsorbed
luminosity of the galaxy. A plume of soft X-ray emission in the west of the
galaxy indicates a large scale outflow. We find that the AGN in NGC 3690
contributes only 22% of the observed broad-band X-ray luminosity of Arp 299.


title: Bootstrap Percolation on Degenerate Graphs

abstract:
  In this paper we focus on $r$-neighbor bootstrap percolation, which is a
process on a graph where initially a set $A_0$ of vertices gets infected. Now
subsequently, an uninfected vertex becomes infected if it is adjacent to at
least $r$ infected vertices. Call $A_f$ the set of vertices that is infected
after the process stops. More formally set $A_t:=A_{t-1}\cup \{v\in V:
|N(v)\cap A_{t-1}|\geq r\}$, where $N(v)$ is the neighborhood of $v$. Then
$A_f=\bigcup_{t>0} A_t$. We deal with finite graphs only and denote by $n$ the
number of vertices. We are mainly interested in the size of the final set
$A_f$. We present a theorem for degenerate graphs that bounds the size of the
final infected set. More precisely for a $d$-degenerate graph, if $r>d$, we
bound the size set $A_f$ from above by $(1+\tfrac{d}{r-d})|A_0|$.


title: Image Restoration with Locally Selected Class-Adapted Models

abstract:
  State-of-the-art algorithms for imaging inverse problems (namely deblurring
and reconstruction) are typically iterative, involving a denoising operation as
one of its steps. Using a state-of-the-art denoising method in this context is
not trivial, and is the focus of current work. Recently, we have proposed to
use a class-adapted denoiser (patch-based using Gaussian mixture models) in a
so-called plug-and-play scheme, wherein a state-of-the-art denoiser is plugged
into an iterative algorithm, leading to results that outperform the best
general-purpose algorithms, when applied to an image of a known class (e.g.
faces, text, brain MRI). In this paper, we extend that approach to handle
situations where the image being processed is from one of a collection of
possible classes or, more importantly, contains regions of different classes.
More specifically, we propose a method to locally select one of a set of
class-adapted Gaussian mixture patch priors, previously estimated from clean
images of those classes. Our approach may be seen as simultaneously performing
segmentation and restoration, thus contributing to bridging the gap between
image restoration/reconstruction and analysis.


title:
Exploring the cylindrical photo-bending shape in polydomain nematic
  glass

abstract:
  This paper explores different photo-bending shapes in polydomain nematic
glass. The motivation is to explain the phenomenon in experiment [1] under
polarized light in which a nematic film curls into an circular arc, like part
of a cylindrical surface. Polarized light triggers photo-isomerization and
therefore makes liquid crystals (LCs) contract along their directors. We apply
the Sachs limit to homogenize the deformation of polydomain LC glass.
Photo-strain can be either contraction or expansion through the material.
Bending shapes can be anticlastic, bowl-shaped and cylindrical affected by
Poisson ratio and illumination intensity. An explanation for the cylindrical
bend and ways to observe other shapes are given in a parameter plane.


title:
Finite-size scaling analysis of localization transition for scalar waves
  in a 3D ensemble of resonant point scatterers

abstract:
  We use the random Green's matrix model to study the scaling properties of the
localization transition for scalar waves in a three-dimensional (3D) ensemble
of resonant point scatterers. We show that the probability density $p(g)$ of
normalized decay rates of quasi-modes $g$ is very broad at the transition and
in the localized regime and that it does not obey a single-parameter scaling
law for finite system sizes that we can access. The single-parameter scaling
law holds, however, for the small-$g$ part of $p(g)$ which we exploit to
estimate the critical exponent $\nu$ of the localization transition.
Finite-size scaling analysis of small-$q$ percentiles $g_q$ of $p(g)$ yields an
estimate $\nu \simeq 1.55 \pm 0.07$. This value is consistent with previous
results for Anderson transition in the 3D orthogonal universality class and
suggests that the localization transition under study belongs to the same
class.


title: Extremes and Recurrence in Dynamical Systems

abstract:
  This book provides a comprehensive introduction for the study of extreme
events in the context of dynamical systems. The introduction provides a broad
overview of the interdisciplinary research area of extreme events, underlining
its relevance for mathematics, natural sciences, engineering, and social
sciences. After exploring the basics of the classical theory of extreme events,
the book presents a careful examination of how a dynamical system can serve as
a generator of stochastic processes, and explores in detail the relationship
between the hitting and return time statistics of a dynamical system and the
possibility of constructing extreme value laws for given observables. Explicit
derivation of extreme value laws are then provided for selected dynamical
systems. The book then discusses how extreme events can be used as probes for
inferring fundamental dynamical and geometrical properties of a dynamical
system and for providing a novel point of view in problems of physical and
geophysical relevance. A final summary of the main results is then presented
along with a discussion of open research questions. Finally, an appendix with
software in Matlab programming language allows the readers to develop further
understanding of the presented concepts.

categories: math.DS cond-mat.stat-mech math-ph math.MP math.PR nlin.CD


title:
Non-Uniform Code Concatenation for Universal Fault-Tolerant Quantum
  Computing

abstract:
  Using transversal gates is a straightforward and efficient technique for
fault-tolerant quantum computing. Since transversal gates alone cannot be
computationally universal, they must be combined with other approaches such as
magic state distillation, code switching or code concatenation in order to
achieve universality. In this paper we propose an alternative approach for
universal fault-tolerant quantum computing mainly based on the code
concatenation approach proposed in [PRL 112, 010505 (2014)] but in a
non-uniform fashion. The proposed approach is described based on non-uniform
concatenation of the 7-qubit Steane code with the 15-qubit Reed-Muller code as
well as the 5-qubit code with the 15-qubit Reed-Muller code, which lead to two
49-qubit and 47-qubit codes, respectively. These codes can correct any
arbitrary single physical error with the ability to perform a universal set of
fault-tolerant gates, without using magic state distillation.


title: madmom: a new Python Audio and Music Signal Processing Library

abstract:
  In this paper, we present madmom, an open-source audio processing and music
information retrieval (MIR) library written in Python. madmom features a
concise, NumPy-compatible, object oriented design with simple calling
conventions and sensible default values for all parameters, which facilitates
fast prototyping of MIR applications. Prototypes can be seamlessly converted
into callable processing pipelines through madmom's concept of Processors,
callable objects that run transparently on multiple cores. Processors can also
be serialised, saved, and re-run to allow results to be easily reproduced
anywhere. Apart from low-level audio processing, madmom puts emphasis on
musically meaningful high-level features. Many of these incorporate machine
learning techniques and madmom provides a module that implements some in MIR
commonly used methods such as hidden Markov models and neural networks.
Additionally, madmom comes with several state-of-the-art MIR algorithms for
onset detection, beat, downbeat and meter tracking, tempo estimation, and piano
transcription. These can easily be incorporated into bigger MIR systems or run
as stand-alone programs.


title: BMOBench: Black-Box Multi-Objective Optimization Benchmarking Platform

abstract:
  This document briefly describes the Black-Box Multi-Objective Optimization
Benchmarking (BMOBench) platform. It presents the test problems, evaluation
procedure, and experimental setup. To this end, the BMOBench is demonstrated by
comparing recent multi-objective solvers from the literature, namely SMS-EMOA,
DMS, and MO-SOO.


title: Hypergroups Related to a Pair of Compact Hypergroups

abstract:
  The purpose of the present paper is to investigate a hypergroup associated
with irreducible characters of a compact hypergroup $H$ and a closed
subhypergroup $H_0$ of $H$ with $|H/H_0|< +\infty$. The convolution of this
hypergroup is introduced by inducing irreducible characters of $H_0$ to $H$ and
by restricting irreducible characters of $H$ to $H_0$. The method of proof
relies on the notion of an induced character and an admissible hypergroup pair.


title:
Infrared refractive index dispersion of PMMA spheres from synchrotron
  extinction spectra

abstract:
  We performed high-resolution Fourier-transform infrared (FTIR) spectroscopy
of a polymethyl methacrylate (PMMA) sphere of unknown size in the Mie
scattering region. Apart from a slow, oscillatory structure (wiggles), which is
due to an interference effect, the measured FTIR extinction spectrum exhibits a
ripple structure, which is due to electromagnetic resonances. We fully
characterize the underlying electromagnetic mode structure of the spectrum by
assigning two mode numbers to each of the ripples in the measured spectrum. We
show that analyzing the ripple structure in the spectrum in the wavenumber
region from about $3000\,$cm$^{-1}$ to $8000\,$cm$^{-1}$ allows us to both
determine the unknown radius of the sphere and the PMMA index of refraction,
which shows a strong frequency dependence in this near-infrared spectral
region. While in this paper we focus on examining a PMMA sphere as an example,
our method of determining the refractive index and its dispersion from
synchrotron infrared extinction spectra is generally applicable for the
determination of the index of refraction of any transparent substance that can
be shaped into micron-sized spheres.


title: Completing the nuclear reaction puzzle of the nucleosynthesis of 92Mo

abstract:
  One of the greatest questions for modern physics to address is how elements
heavier than iron are created in extreme, astrophysical environments. A
particularly challenging part of that question is the creation of the so-called
p-nuclei, which are believed to be mainly produced in some types of supernovae.
The lack of needed nuclear data presents an obstacle in nailing down the
precise site and astrophysical conditions. In this work, we present for the
first time measurements on the nuclear level density and average strength
function of $^{92}$Mo. State-of-the-art p-process calculations systematically
underestimate the observed solar abundance of this isotope. Our data provide
stringent constraints on the $^{91}$Nb$(p,{\gamma})^{92}$Mo reaction rate,
which is the last unmeasured reaction in the nucleosynthesis puzzle of
$^{92}$Mo. Based on our results, we conclude that the $^{92}$Mo abundance
anomaly is not due to the nuclear physics input to astrophysical model
calculations.


title: Time lag in transient cosmic accreting sources

abstract:
  We develop models for time lag between maxima of the source brightness in
different wavelengths during a transient flash of luminosity connected with a
short period of increase of the mass flux onto the central compact object.
  We derive a simple formula for finding the time delay among events in
different wavelengths, valid in general for all disk accreting cosmic sources,
and discuss quantitatively a model for time lag formation in AGNs.
  In close binaries with accretion disks the time lag is connected with effects
of viscosity defining a radial motion of matter in the accretion disk. In AGN
flashes, the falling matter has a low angular momentum, and the time lag is
defined by the free fall time to the gravitating center.
  We show the validity of these models by means of several examples of galactic
and extragalactic accreting sources.


title:
Optical fingerprint of dark 2p-states in transition metal
  dichalcogenides

abstract:
  We present a microscopic study on higher excitonic states in transition metal
dichalcogenides in the presence of disorder. We show that the geometric phase
cancels the degeneration of 2s and 2p states and that a significant
disorder-induced coupling of bright and dark states offers a strategy to
circumvent optical selection rules. As a prove, we show a direct fingerprint of
dark 2p states in absorption spectra of WS$_2$. The predicted softening of
optical selection rules through exciton-disorder coupling is of general nature
and therefore applicable to related two-dimensional semiconductors.


title: Boson Stars in a Theory of Complex Scalar Field coupled to Gravity

abstract:
  We study boson stars in a theory of complex scalar field coupled to Einstein
gravity with the potential: $V(|\Phi|) := m^{2} |\Phi|^2 +2 \lambda |\Phi|$
(where $m^2$ and $\lambda$ are positive constant parameters). This could be
considered either as a theory of massive complex scalar field coupled to
gravity in a conical potential or as a theory in the presence of a potential
which is an overlap of a parabolic and a conical potential. We study our theory
with positive as well as negative values of the cosmological constant
$\Lambda$. Boson stars are found to come in two types, having either ball-like
or shell-like charge density. We have studied the properties of these solutions
and have also determined their domains of existence for some specific values of
the parameters of the theory. Similar solutions have also been obtained by
Hartmann, Kleihaus, Kunz, and Schaffer, in a V-shaped scalar potential.


title:
Distinguishing number and distinguishing index of some operations on
  graphs

abstract:
  The distinguishing number (index) $D(G)$ ($D'(G)$) of a graph $G$ is the
least integer $d$ such that $G$ has an vertex labeling (edge labeling) with $d$
labels that is preserved only by a trivial automorphism. We examine the effects
on $D(G)$ and $D'(G)$ when $G$ is modified by operations on vertex and edge of
$G$. Let $G$ be a connected graph of order $n\geq 3$. We show that $-1\leq
D(G-v)-D(G)\leq D(G)$, where $G-v$ denotes the graph obtained from $G$ by
removal of a vertex $v$ and all edges incident to $v$ and these inequalities
are true for the distinguishing index. Also we prove that $|D(G-e)-D(G)|\leq 2$
and $-1 \leq D'(G-e)-D'(G)\leq 2$, where $G-e$ denotes the graph obtained from
$G$ by simply removing the edge $e$. Finally we consider the vertex contraction
and the edge contraction of $G$ and prove that the edge contraction decrease
the distinguishing number (index) of $G$ by at most one and increase by at most
$3D(G)$ ($3D'(G)$).


title:
Near-degeneracy of extended $s + d_{x^2-y^2}$ and $d_{xy}$ order
  parameters in quasi-two-dimensional organic superconductors

abstract:
  The symmetry of the superconducting order parameter in quasi-two-dimensional
BEDT-TTF organic superconductors is a subject of ongoing debate. We report ab
initio density functional theory calculations for a number of organic
superconductors containing $\kappa$-type layers. Using projective Wannier
functions we derive parameters of a common low-energy Hamiltonian based on
individual BEDT-TTF molecular orbitals. In a random phase approximation
spin-fluctuation approach we investigate the evolution of the superconducting
pairing symmetry within this model and point out a phase-transition between
extended $s + d_{x^2-y^2}$ and $d_{xy}$ symmetry. We discuss the origin of the
mixed order parameter and the relation between the realistic molecule
description and the widely used dimer approximation. Based on our ab initio
calculations we position the investigated materials in the obtained molecule
model phase diagram and simulate scanning tunneling spectroscopy experiments
for selected cases. Our calculations show that many $\kappa$-type materials lie
close to the phase transition line between the two pairing symmetry types found
in our calculation, possibly explaining the multitude of contradictory
experiments in this field.


title: Online Learning with Feedback Graphs Without the Graphs

abstract:
  We study an online learning framework introduced by Mannor and Shamir (2011)
in which the feedback is specified by a graph, in a setting where the graph may
vary from round to round and is \emph{never fully revealed} to the learner. We
show a large gap between the adversarial and the stochastic cases. In the
adversarial case, we prove that even for dense feedback graphs, the learner
cannot improve upon a trivial regret bound obtained by ignoring any additional
feedback besides her own loss. In contrast, in the stochastic case we give an
algorithm that achieves $\widetilde \Theta(\sqrt{\alpha T})$ regret over $T$
rounds, provided that the independence numbers of the hidden feedback graphs
are at most $\alpha$. We also extend our results to a more general feedback
model, in which the learner does not necessarily observe her own loss, and show
that, even in simple cases, concealing the feedback graphs might render a
learnable problem unlearnable.


title: Role of interactions in a dissipative many-body localized system

abstract:
  Recent experimental and theoretical efforts have focused on the effect of
dissipation on quantum many-body systems in their many-body localized (MBL)
phase. While in the presence of dephasing noise such systems reach a unique
ergodic state, their dynamics is characterized by slow relaxation manifested in
non-exponential decay of self-correlations. Here we shed light on a currently
much debated issue, namely the role of interactions for this relaxation
dynamics. We focus on the experimentally relevant situation of the evolution
from an initial charge density wave in the presence of strong dephasing noise.
We find a crossover from a regime dominated by disorder to a regime dominated
by interactions, with a concomitant change of time correlators from stretched
exponential to compressed exponential form. The strongly interacting regime can
be explained in terms of nucleation and growth dynamics of relaxing regions -
reminiscent of the kinetics of crystallization in soft matter systems - and
should be observable experimentally. This interaction-driven crossover suggests
that the competition between interactions and noise give rise to a much richer
structure of the MBL phase than anticipated so far.

categories: cond-mat.str-el cond-mat.dis-nn cond-mat.quant-gas quant-ph


title: The Delicate Balance of Static and Dynamic Electron Correlation

abstract:
  Multi-configurational approaches yield universal wave function
parameterizations that can qualitatively well describe electronic structures
along reaction pathways. For quantitative results, multi-reference perturbation
theory is required to capture dynamic electron correlation from the otherwise
neglected virtual orbitals. Still, the overall accuracy suffers from the finite
size and choice of the active orbital space and peculiarities of the
perturbation theory. Fortunately, the electronic wave functions at equilibrium
structures of reactants and products can often be well described by
single-reference methods and hence are accessible to accurate coupled cluster
calculations. Here, we calculate the heterolytic double dissociation energy of
four 3d-metallocenes with the complete active space self-consistent field
method and compare to highly accurate coupled cluster data. Our coupled cluster
data are well within the experimental error bars. This accuracy can also be
approached by complete active space calculations with an orbital selection
based on information entropy measures. The entropy based active space selection
is discussed in detail. We find a very subtle balance between static and
dynamic electron correlation effects that emphasizes the need for algorithmic
active space selection and that differs significantly from restricted active
space results for identical active spaces reported in the literature.

categories: physics.chem-ph cond-mat.str-el physics.atom-ph physics.comp-ph quant-ph


title:
More on Non-supersymmetric Asymmetric Orbifolds with Vanishing
  Cosmological Constant

abstract:
  We explore various non-supersymmetric type II string vacua constructed based
on asymmetric orbifolds of tori with vanishing cosmological constant at the one
loop. The string vacua we present are modifications of the models studied in
arXiv:1512.05155[hep-th], of which orbifold group is just generated by a single
element. We especially focus on two types of modifications: (i) the orbifold
twists include different types of chiral reflections not necessarily removing
massless Rarita-Schwinger fields in the 4-dimensional space-time, (ii) the
orbifold twists do not include the shift operator. We further discuss the
unitarity and stability of constructed non-supersymmetric string vacua, with
emphasizing the common features of them.


title:
Analysis of electro-osmotic flow in a microchannel with undulated
  surfaces

abstract:
  The electro-osmotic flow through a channel between two undulated surfaces
induced by an external electric field is investigated. The gap of the channel
is very small and comparable to the thickness of the electrical double layers.
A lattice Boltzmann simulation is carried out on the model consisting of the
Poisson equation for electrical potential, the Nernst--Planck equation for ion
concentration, and the Navier--Stokes {\color{black}equations} for flows of the
electrolyte solution. An analytical model that predicts the flow rate is also
derived under the assumption that the channel width is very small compared with
the characteristic length of the variation along the channel. The analytical
results are compared with the numerical results obtained by using the lattice
Boltzmann method. In the case of a constant surface charge density along the
channel, the variation of the channel width reduces the electro-osmotic flow,
and the flow rate is smaller than that of a straight channel. In the case of a
surface charge density distributed in homogeneously, one-way flow occurs even
under the restriction of a zero net surface charge along the channel.

categories: cond-mat.soft cond-mat.mes-hall physics.comp-ph physics.flu-dyn


title: Faster GPU-based convolutional gridding via thread coarsening

abstract:
  Convolutional gridding is a processor-intensive step in interferometric
imaging. While it is possible to use graphics processing units (GPUs) to
accelerate this operation, existing methods use only a fraction of the
available flops. We apply thread coarsening to improve the efficiency of an
existing algorithm, and observe performance gains of up to $3.2\times$ for
single-polarization gridding and $1.9\times$ for quad-polarization gridding on
a GeForce GTX 980, and smaller but still significant gains on a Radeon R9 290X.


title:
A functional renormalization group approach to electronic structure
  calculations for systems without translational symmetry

abstract:
  A formalism for electronic-structure calculations is presented that is based
on the functional renormalization group (FRG). The traditional FRG has been
formulated for systems that exhibit a translational symmetry with an associated
Fermi surface, which can provide the organization principle for the
renormalization group (RG) procedure. We here advance an alternative
formulation, where the RG-flow is organized in the energy-domain rather than in
k-space. This has the advantage that it can also be applied to inhomogeneous
matter lacking a band-structure, such as disordered metals or molecules. The
energy-domain FRG ({\epsilon}FRG) presented here accounts for Fermi-liquid
corrections to quasi-particle energies and particle-hole excitations. It goes
beyond the state of the art GW-BSE, because in {\epsilon}FRG the Bethe-Salpeter
equation (BSE) is solved in a self-consistent manner. An efficient
implementation of the approach that has been tested against exact
diagonalization calculations and calculations based on the density matrix
renormalization group is presented.
  Similar to the conventional FRG, also the {\epsilon}FRG is able to signalize
the vicinity of an instability of the Fermi-liquid fixed point via runaway flow
of the corresponding interaction vertex. Embarking upon this fact, in an
application of {\epsilon}FRG to the spinless disordered Hubbard model we
calculate its phase-boundary in the plane spanned by the interaction and
disorder strength. Finally, an extension of the approach to finite temperatures
and spin S = 1/2 is also given.

categories: cond-mat.mtrl-sci cond-mat.dis-nn cond-mat.str-el physics.comp-ph


title:
Collaborative Filtering with Side Information: a Gaussian Process
  Perspective

abstract:
  We tackle the problem of collaborative filtering (CF) with side information,
through the lens of Gaussian Process (GP) regression. Driven by the idea of
using the kernel to explicitly model user-item similarities, we formulate the
GP in a way that allows the incorporation of low-rank matrix factorisation,
arriving at our model, the Tucker Gaussian Process (TGP). Consequently, TGP
generalises classical Bayesian matrix factorisation models, and goes beyond
them to give a natural and elegant method for incorporating side information,
giving enhanced predictive performance for CF problems. Moreover we show that
it is a novel model for regression, especially well-suited to grid-structured
data and problems where the dependence on covariates is close to being
separable.


title: Spontaneous vs. Posed smiles - can we tell the difference?

abstract:
  Smile is an irrefutable expression that shows the physical state of the mind
in both true and deceptive ways. Generally, it shows happy state of the mind,
however, `smiles' can be deceptive, for example people can give a smile when
they feel happy and sometimes they might also give a smile (in a different way)
when they feel pity for others. This work aims to distinguish spontaneous
(felt) smile expressions from posed (deliberate) smiles by extracting and
analyzing both global (macro) motion of the face and subtle (micro) changes in
the facial expression features through both tracking a series of facial
fiducial markers as well as using dense optical flow. Specifically the eyes and
lips features are captured and used for analysis. It aims to automatically
classify all smiles into either `spontaneous' or `posed' categories, by using
support vector machines (SVM). Experimental results on large database show
promising results as compared to other relevant methods.


title: $L^p$-bounds for pseudo-differential operators on compact Lie groups

abstract:
  Given a compact Lie group $G$, in this paper we establish $L^p$-bounds for
pseudo-differential operators in $L^p(G)$. The criteria here are given in terms
of the concept of matrix symbols defined on the non-commutative analogue of the
phase space $G\times\widehat{G}$, where $\widehat{G}$ is the unitary dual of
$G$. We obtain two different types of $L^p$ bounds: first for finite regularity
symbols and second for smooth symbols. The conditions for smooth symbols are
formulated using $\mathscr{S}_{\rho,\delta}^m(G)$ classes which are a suitable
extension of the well known $(\rho,\delta)$ ones on the Euclidean space. The
results herein extend classical $L^p$ bounds established by C. Fefferman on
$\mathbb R^n$. While Fefferman's results have immediate consequences on general
manifolds for $\rho>\max\{\delta,1-\delta\}$, our results do not require the
condition $\rho>1-\delta$. Moreover, one of our results also does not require
$\rho>\delta$. Examples are given for the case of SU(2)$\cong\mathbb S^3$ and
vector fields/sub-Laplacian operators when operators in the classes
$\mathscr{S}_{0,0}^m$ and $\mathscr{S}_{\frac12,0}^m$ naturally appear, and
where conditions $\rho>\delta$ and $\rho>1-\delta$ fail, respectively.


title: Measurement of Baryon Electromagnetic Form Factors at BESIII

abstract:
  The Beijing $e^+e^-$-collider (BEPCII) is a double-ring symmetric collider
running at center-of-mass energies between 2.0 and 4.6 GeV. This energy range
allows the BESIII-experiment to measure baryon electromagnetic form factors in
direct $e^+e^-$-annihilation and in initial state radiation processes. In this
paper, results on $e^+e^-\rightarrow p\bar{p}$ and $e^+e^-\rightarrow \Lambda
\bar{\Lambda}$ based on data collected by BESIII in 2011 and 2012 are
presented. Expectations from the BESIII high luminosity energy scan from 2015
and from radiative return at different center-of-mass energies are also
reported.


title: $q$-Virasoro modular double and 3d partition functions

abstract:
  We study partition functions of 3d $\mathcal{N}=2$ U(N) gauge theories on
compact manifolds which are $S^1$ fibrations over $S^2$. We show that the
partition functions are free field correlators of vertex operators and
screening charges of the $q$-Virasoro modular double, which we define. The
inclusion of supersymmetric Wilson loops in arbitrary representations allows us
to show that the generating functions of Wilson loop vacuum expectation values
satisfy two SL(2,$\mathbb{Z}$)-related commuting sets of $q$-Virasoro
constraints. We generalize our construction to 3d $\mathcal{N}=2$ unitary
quiver gauge theories and as an example we give the free boson realization of
the ABJ(M) model.


title: Isotropic Dynamic Hierarchical Clustering

abstract:
  We face a need of discovering a pattern in locations of a great number of
points in a high-dimensional space. Goal is to group the close points together.
We are interested in a hierarchical structure, like a B-tree. B-Trees are
hierarchical, balanced, and they can be constructed dynamically. B-Tree
approach allows to determine the structure without any supervised learning or a
priori knowlwdge. The space is Euclidean and isotropic. Unfortunately, there
are no B-Tree implementations processing indices in a symmetrical and
isotropical way. Some implementations are based on constructing compound
asymmetrical indices from point coordinates; and the others split the nodes
along the coordinate hyper-planes. We need to process tens of millions of
points in a thousand-dimensional space. The application has to be scalable.
Ideally, a cluster should be an ellipsoid, but it would require to store O(n2)
ellipse axes. So, we are using multi-dimensional balls defined by the centers
and radii. Calculation of statistical values like the mean and the average
deviation, can be done in an incremental way. While adding a point to a tree,
the statistical values for nodes recalculated in O(1) time. We support both,
brute force O(2n) and greedy O(n2) split algorithms. Statistical and aggregated
node information also allows to manipulate (to search, to delete) aggregated
sets of closely located points. Hierarchical information retrieval. When
searching, the user is provided with the highest appropriate nodes in the tree
hierarchy, with the most important clusters emerging in the hierarchy
automatically. Then, if interested, the user may navigate down the tree to more
specific points. The system is implemented as a library of Java classes
representing Points, Sets of points with aggregated statistical information,
B-tree, and Nodes with a support of serialization and storage in a MySQL
database.


title:
An adaptive non-symmetric finite volume and boundary element coupling
  method for a fluid mechanics interface problem

abstract:
  We consider an interface problem often arising in transport problems: a
coupled system of partial differential equations with one (elliptic) transport
equation on a bounded domain and one equation (in this case the Laplace
problem) on the complement, an unbounded domain. Based on the non-symmetric
coupling of the finite volume method and boundary element method of [Erath et
al., arXiv:1509.00440, 2015] we introduce a robust residual error estimator.
The upper bound of the error in an energy (semi)norm is robust against
variation of the model data. The lower bound, however, additionally depends on
the Peclet number. In several examples we use the local contributions of the
a~posteriori error estimator to steer an adaptive mesh-refining algorithm. The
adaptive FVM-BEM coupling turns out to be an efficient method especially to
solve problems from fluid mechanics, mainly because of the local flux
conservation and the stable approximation of convection dominated problems.


title:
Do #ifdefs Influence the Occurrence of Vulnerabilities? An Empirical
  Study of the Linux Kernel

abstract:
  Preprocessors support the diversification of software products with #ifdefs,
but also require additional effort from developers to maintain and understand
variable code. We conjecture that #ifdefs cause developers to produce more
vulnerable code because they are required to reason about multiple features
simultaneously and maintain complex mental models of dependencies of
configurable code.
  We extracted a variational call graph across all configurations of the Linux
kernel, and used configuration complexity metrics to compare vulnerable and
non-vulnerable functions considering their vulnerability history. Our goal was
to learn about whether we can observe a measurable influence of configuration
complexity on the occurrence of vulnerabilities.
  Our results suggest, among others, that vulnerable functions have higher
variability than non-vulnerable ones and are also constrained by fewer
configuration options. This suggests that developers are inclined to notice
functions appear in frequently-compiled product variants. We aim to raise
developers' awareness to address variability more systematically, since
configuration complexity is an important, but often ignored aspect of software
product lines.


title: Invariant slow-roll parameters in scalar-tensor theories

abstract:
  A general scalar-tensor theory can be formulated in different
parametrizations that are related by a conformal rescaling of the metric and a
scalar field redefinition. We compare formulations of slow-roll regimes in the
Einstein and Jordan frames using quantities that are invariant under the
conformal rescaling of the metric and transform as scalar functions under the
reparametrization of the scalar field. By comparing spectral indices,
calculated up to second order, we find that the frames are equivalent up to
this order, due to the underlying assumptions.


title: Entanglement in the Born-Oppenheimer Approximation

abstract:
  The role of electron-nuclear entanglement on the validity of the
Born-Oppenheimer (BO) approximation is investigated. While nonadiabatic
couplings generally lead to entanglement and to a failure of the BO
approximation, surprisingly the degree of electron-nuclear entanglement is
found to be uncorrelated with the degree of validity of the BO approximation.
This is because while the degree of entanglement of BO states is determined by
their deviation from the corresponding states in the crude BO approximation,
the accuracy of the BO approximation is dictated, instead, by the deviation of
the BO states from the exact electron-nuclear states. In fact, in the context
of a minimal avoided crossing model, extreme cases are identified where an
adequate BO state is seen to be maximally entangled, and where the BO
approximation fails but the associated BO state remains approximately
unentangled. Further, the BO states are found to not preserve the entanglement
properties of the exact electron-nuclear eigenstates, and to be completely
unentangled only in the limit in which the BO approximation becomes exact.


title: The graded product of real spectral triples

abstract:
  Forming the product of two geometric spaces is one of the most basic
operations in geometry, but in the spectral-triple formulation of
non-commutative geometry, the standard prescription for taking the product of
two real spectral triples is problematic: among other drawbacks, it is
non-commutative, non-associative, does not transform properly under unitaries,
and often fails to define a proper spectral triple. In this paper, we explain
that these various problems result from using the ungraded tensor product; by
switching to the graded tensor product, we obtain a new prescription where all
of the earlier problems are neatly resolved: in particular, the new product is
commutative, associative, transforms correctly under unitaries, and always
forms a well defined spectral triple.


title: Progress on VLBI Ecliptic Plane Survey

abstract:
  We launched the VLBI Ecliptic Plane Survey program in 2015. The goal of this
program is to find all compact sources within 7.5 degrees of the ecliptic plane
which are suitable as phase calibrators for anticipated phase referencing
observations of spacecrafts. We planned to observe a complete sample of the
sources brighter than 50 mJy at 5 GHz listed in the PMN and GB6 catalogues that
have not yet been observed with VLBI. By April 2016, eight 24-hour sessions
have been performed and processed. Among 2227 observed sources, 435 sources
were detected in three or more observations. We have also run three 8-hour
segments with VLBA for improving positions of 71 ecliptic sources.


title: Friction and Nonlinear Dynamics

abstract:
  The nonlinear dynamics associated with sliding friction forms a broad
interdisciplinary research field that involves complex dynamical processes and
patterns covering a broad range of time and length scales. Progress in
experimental techniques and computational resources has stimulated the
development of more refined and accurate mathematical and numerical models,
capable of capturing many of the essentially nonlinear phenomena involved in
friction.


title:
Spacetimes foliated by non-expanding and Killing horizons: higher
  dimension

abstract:
  The theory of non-expanding horizons (NEH) geometry and the theory of near
horizon geometries (NHG) are two mathematical relativity frameworks
generalizing the black hole theory. From the point of view of the NEHs theory,
a NHG is just a very special case of a spacetime containing an NEH of many
extra symmetries. It can be obtained as the Horowitz limit of a neighborhood of
an arbitrary extremal Killing horizon. An unexpected relation between the two
of them, was discovered in the study of spacetimes foliated by a family of
NEHs. The class of 4-dimensional NHG solutions (either vacuum or coupled to a
Maxwell field) was found as a family of examples of spacetimes admitting a NEH
foliation. In the current paper we systematically investigate geometries of the
NEHs foliating a spacetime for arbitrary matter content and in arbitrary
spacetime dimension. We find that each horizon belonging to the foliation
satisfies a condition that may be interpreted as an invitation for a
transversal extremal Killing horizon to exist. Assuming the existence of a
transversal extremal Killing horizon, we derive all the spacetime metrics
satisfying the vacuum Einstein's equations.


title:
A phase transition in the coming down from infinity of simple
  exchangeable fragmentation-coagulation processes

abstract:
  We consider the class of exchangeable fragmentation-coagulation (EFC)
processes where coagulations are multiple and not simultaneous, as in a
$\Lambda$-coalescent, and fragmentation dislocates at finite rate an individual
block into sub-blocks of infinite size. We call these partition-valued
processes, simple EFC processes, and study the question whether such a process,
when started with infinitely many blocks, can visit partitions with a finite
number of blocks or not. When this occurs, one says that the process comes down
from infinity. We introduce two sharp parameters $\theta_{\star}\leq
\theta^{\star}\in [0,\infty]$, so that if $\theta^{\star}<1$, the process comes
down from infinity and if $\theta_\star>1$, then it stays infinite. We
illustrate our result with regularly varying coagulation and fragmentation
measures. In this case, the parameters $\theta_{\star},\theta^{\star}$ coincide
and are explicit.


title:
Lower and upper bounds on the mass of light quark-antiquark scalar
  resonance in the SVZ sum rules

abstract:
  The calculation of the mass of light scalar isosinglet meson within the
Shifman-Vainshtein-Zakharov (SVZ) sum rules is revisited. We develop simple
analytical methods for estimation of hadron masses in the SVZ approach and try
to reveal the origin of their numerical values. The calculations of hadron
parameters in the SVZ sum rules are known to be heavily based on a choice of
the perturbative threshold. This choice requires some important ad hoc
information. We show analytically that the scalar mass under consideration has
a lower and upper bound which are independent of this choice: $0.78\lesssim
m_s\lesssim1.28$ GeV.


title:
Leveraging percolation theory to single out influential spreaders in
  networks

abstract:
  Among the consequences of the disordered interaction topology underlying many
social, techno- logical and biological systems, a particularly important one is
that some nodes, just because of their position in the network, may have a
disproportionate effect on dynamical processes mediated by the complex
interaction pattern. For example, the early adoption by an opinion leader in a
social network may change the fate of a commercial product, or just a few
super-spreaders may determine the virality of a meme in social media. Despite
many recent efforts, the formulation of an accurate method to optimally
identify influential nodes in complex network topologies remains an unsolved
challenge. Here, we present the exact solution of the problem for the specific,
but highly relevant, case of the Susceptible-Infected-Removed (SIR) model for
epidemic spreading at criticality. By exploiting the mapping between bond
percolation and the static properties of SIR, we prove that the recently
introduced Non-Backtracking centrality is the optimal criterion for the
identification of influential spreaders in locally tree-like networks at
criticality. By means of simulations on synthetic networks and on a very
extensive set of real-world networks, we show that the Non-Backtracking
centrality is a highly reliable metric to identify top influential spreaders
also in generic graphs not embedded in space, and for noncritical spreading.


title:
Product-form stationary distributions for deficiency zero networks with
  non-mass action kinetics

abstract:
  In many applications, for example when computing statistics of fast
subsystems in a multiscale setting, we wish to find the stationary
distributions of systems of continuous time Markov chains. Here we present a
class of models that appears naturally in certain averaging approaches whose
stationary distributions can be computed explicitly. In particular, we study
continuous time Markov chain models for biochemical interaction systems with
non-mass action kinetics whose network satisfies a certain constraint.
Analogous with previous related results, the distributions can be written in
product form.


title:
Maxwell-Juttner distribution for rigidly-rotating flows in spherically
  symmetric spacetimes using the tetrad formalism

abstract:
  We consider rigidly rotating states in thermal equilibrium on static
spherically symmetric spacetimes. Using the Maxwell-Juttner equilibrium
distribution function, onstructed as a solution of the relativistic Boltzmann
equation, the equilibrium particle flow four-vector, stress-energy tensor and
the transport coefficients in the Marle model are computed. Their properties
are discussed in view of the topology of the speed-of-light surface induced by
the rotation for two classes of spacetimes: maximally symmetric (Minkowski, de
Sitter and anti-de Sitter) and charged (Reissner-Nordstrom) black-hole
spacetimes. To facilitate our analysis, we employ a non-holonomic comoving
tetrad field, obtained unambiguously by applying a Lorentz boost on a fixed
background tetrad.


title:
Direct measurement of interfacial Dzyaloshinskii-Moriya interaction in
  X/CoFeB/MgO heterostructures with a scanning-NV magnetometer

abstract:
  The Dzyaloshinskii-Moriya Interaction (DMI) has recently attracted
considerable interest owing to its fundamental role in the stabilization of
chiral spin textures in ultrathin ferromagnets, which are interesting
candidates for future spintronic technologies. Here we employ a scanning
nano-magnetometer based on a single nitrogen-vacancy (NV) defect in diamond to
locally probe the strength of the interfacial DMI in CoFeB/MgO ultrathin films
grown on different heavy metal underlayers X=Ta,TaN, and W. By measuring the
stray field emanating from DWs in micron-long wires of such materials, we
observe deviations from the Bloch profile for TaN and W underlayers that are
consistent with a positive DMI value favoring right-handed chiral spin
structures. Moreover, our measurements suggest that the DMI constant might vary
locally within a single sample, illustrating the importance of local probes for
the study of magnetic order at the nanoscale.


title:
A family of non-split topologically slice links with arbitrarily large
  smooth slice genus

abstract:
  We construct an infinite family of topologically slice 2--component boundary
links $\ell_i$, none of which is smoothly concordant to a split link, such that
$g_4(\ell_i)=i$.


title: Phase retrieval from multiple-window short-time Fourier measurements

abstract:
  In this paper, we introduce two symmetric directed graphs depending on
supports of signals and windows, and we show that the connectivity of those
graphs provides either necessary and sufficient conditions to phase retrieval
of a signal from magnitude measurements of its multiple-window short-time
Fourier transform. Also we propose an algebraic reconstruction algorithm, and
provide an error estimate to our algorithm when magnitude measurements are
corrupted by deterministic/random noises.


title: Li-Yorke chaos for invertible mappings on compact metric spaces

abstract:
  In this paper, we construct a homeomorphism on the unit closed disk to show
that an invertible mapping on a compact metric space is Li-Yorke chaotic does
not imply its inverse being Li-Yorke chaotic.


title: The role of Alfv\'en wave heating in solar prominences

abstract:
  Observations have shown that magnetohydrodynamic waves over a large frequency
range are ubiquitous in solar prominences. The waves are probably driven by
photospheric motions and may transport energy up to prominences suspended in
the corona. Dissipation of wave energy can lead to heating of the cool
prominence plasma, so contributing to the local energy balance within the
prominence. Here we discuss the role of Alfv\'en wave dissipation as a heating
mechanism for the prominence plasma. We consider a slab-like quiescent
prominence model with a transverse magnetic field embedded in the solar corona.
The prominence medium is modelled as a partially ionized plasma composed of a
charged ion-electron single fluid and two separate neutral fluids corresponding
to neutral hydrogen and neutral helium. Friction between the three fluids acts
as a dissipative mechanism for the waves. The heating caused by
externally-driven Alfv\'en waves incident on the prominence slab is
analytically explored. We find that the dense prominence slab acts as a
resonant cavity for the waves. The fraction of incident wave energy that is
channelled into the slab strongly depends upon the wave period, $P$. Using
typical prominence conditions, we obtain that wave energy trapping and
associated heating are negligible when $P \gtrsim 100$ s, so that it is
unlikely that those waves have a relevant influence on prominence energetics.
When $1$ s $\lesssim P \lesssim 100$ s the energy absorption into the slab
shows several sharp and narrow peaks, that can reach up to 100%, when the
incident wave frequency matches a cavity resonance of the slab. Wave heating is
enhanced at those resonant frequencies. Conversely, when $P \lesssim 1$ s
cavity resonances are absent, but the waves are heavily damped by the strong
dissipation. We estimate that wave heating may compensate for about 10% of
radiative losses of the prominence plasma.


title: $2$--hyperreflexivity and hyporeflexivity of power partial isometries

abstract:
  Power partial isometries are not always hyperreflexive neither reflexive. In
the present paper it will be shown that power partial isometries are always
hyporeflexive and $2$--hyperreflexive.


title: Valence Characterization of Surface and Subsurface Region in SmB6

abstract:
  Samarium hexaboride (SmB6), which lies in the mixed valence regime in the
Anderson model, has been predicted to possess topologically protected surface
states. The intensive investigations on SmB6 have brought up the long standing
questions about the discrepancy between the surface and bulk electronic
properties in rare-earth compounds in general. Here, we investigate and
eventually clarify this discrepancy in the particular case of SmB6 by the
photoemission core-level spectra. We focus on the change in both Sm and B
states depending on time, temperature, probing depth, and surface termination
on the cleaved (100) surface. Our spectra show that the unusual time-dependent
change in the Sm valence occurs within a period of hours, which is not related
to the adsorption of residual gases. Moreover, we observe a reduction of the
surface feature in the B and Sm states on the same timescale accompanied by the
formation of a subsurface region. Thus, it indicates the relatively slow charge
redistribution between the surface and subsurface regions. Our findings
demonstrate that the f states is strongly involved in the surface relaxation.


title:
Convergence Analysis for Rectangular Matrix Completion Using
  Burer-Monteiro Factorization and Gradient Descent

abstract:
  We address the rectangular matrix completion problem by lifting the unknown
matrix to a positive semidefinite matrix in higher dimension, and optimizing a
nonconvex objective over the semidefinite factor using a simple gradient
descent scheme. With $O( \mu r^2 \kappa^2 n \max(\mu, \log n))$ random
observations of a $n_1 \times n_2$ $\mu$-incoherent matrix of rank $r$ and
condition number $\kappa$, where $n = \max(n_1, n_2)$, the algorithm linearly
converges to the global optimum with high probability.


title: Genetic recombination as DNA repair

abstract:
  Maintenance of sexual reproduction and genetic recombination imposes
physiological costs when compared to parthenogenic reproduction, most
prominently: for maintaining the corresponding (molecular) machinery, for
finding a mating partner, and through the decreased fraction of females in a
population, which decreases the reproductive capacity. Based on principles from
information theory, we have previously developed a new population genetic
model, and applying it in simulations, we have recently hypothesized that all
species maintain the maximum genomic complexity that is required by their niche
and allowed by their mutation rate and selection intensity. Applying this idea
to the complexity overhead of recombination maintenance, its costs must be more
than compensated by an additional capacity for complexity in recombining
populations. Here, we show a simple mechanism, where recombination helps to
maintain larger biases of alleles frequencies in a population, so the
advantageous alleles can have increased frequency. This allows recombining
populations to maintain higher fitness and phenotypic efficiency in comparison
with asexual populations with the same parameters. Random mating alone already
significantly increases the ability to maintain genomic and phenotypic
complexity. Sexual selection provides additional capacity for this complexity.
The model can be considered as a unifying synthesis of previous hypotheses
about the roles of recombination in Muller's ratchet, mutation purging and Red
Queen dynamics, because the introduction of recombination both increases
population frequencies of beneficial alleles and decreases detrimental ones. In
addition, we suggest simple explanations for niche-dependent prevalence of
transient asexuality and the exceptional asexual lineage of Bdelloid rotifers.