title: Predictive Functional Connectivity of Real-World Systems

abstract:
  We are flooded with large-scale dynamic networked data. Analyses requiring
exact comparisons between networks are computationally intractable, so new
methodologies are sought. We extend the graphlet-based statistics to directed
networks and demonstrate that they are superior to other measures. We predict a
country's gross domestic product (GDP) solely from its wiring patterns in the
world trade network (WTN) that could inform policy makers on benefits of trade
agreements. Surprisingly, we find that it is not enough for a country to be in
a densely connected core in the WTN to have a high GDP, as was previously
believed. In addition to being in the core, a country must also trade with
peripheral countries, while only being in the core and not trading with
peripheral economies makes a country prone to debt. Furthermore, by tracking
the dynamics of a country's positioning in the WTN over years, we predict
success or failure of an emerging economy. We validate our methodology on
metabolic networks, yielding insights into preservation of enzyme function from
the network wiring patterns rather than sequence data. Overall, our methodology
enables advanced analyses of directed networked data from any area of science,
allowing domain-specific interpretation of a directed network's topology.


title:
Fourier transforms on Cantor sets: A study in non-Diophantine arithmetic
  and calculus

abstract:
  Fractals equipped with intrinsic arithmetic lead to a natural definition of
differentiation, integration and complex numbers. Applying the formalism to the
problem of a Fourier transform on fractals we show that the resulting transform
has all the expected basic properties. As an example we discuss a sawtooth
signal on the ternary middle-third Cantor set. The formalism works also for
fractals that are not self-similar.


title:
Comonotonicity and Choquet integrals of Hermitian operators and their
  applications

abstract:
  In a quantum system with d-dimensional Hilbert space, the Q-function of a
Hermitian positive semidefinite operator ?, is defined in terms of the d2
coherent states in this system. The Choquet integral CQ of the Q-function, is
introduced using a ranking of the values of the Q-function, and Mobius
transforms which remove the overlaps between coherent states. It is a figure of
merit of the quantum properties of Hermitian operators, and it provides upper
and lower bounds to various physical quantities in terms of the Q-function.
Comonotonicity is an important concept in the formalism, which is used to
formalize the vague concept of physically similar operators. Comonotonic
operators are shown to be bounded, with respect to an order based on Choquet
integrals. Applications of the formalism to the study of the ground state of a
physical system, are discussed. Bounds for partition functions, are also
derived.


title: Szegedy's quantum walk with queries

abstract:
  When searching for a marked vertex in a graph, Szegedy's usual search
operator is defined by using the transition probability matrix of the random
walk with absorbing barriers at the marked vertices. Instead of using this
operator, we analyze searching with Szegedy's quantum walk by using reflections
around the marked vertices, that is, the standard form of quantum query. We
show we can boost the probability to 1 of finding a marked vertex in the
complete graph. Numerical simulations suggests that the success probability can
be improved for other graphs, like the two-dimensional grid. We also prove
that, for a certain class of graphs, we can express Szegedy's search operator,
obtained from the absorbing walk, using the standard query model.


title: Neural Aggregation Network for Video Face Recognition

abstract:
  This paper presents a Neural Aggregation Network (NAN) for video face
recognition. The network takes a face video or face image set of a person with
a variable number of face images as its input, and produces a compact,
fixed-dimension feature representation for recognition. The whole network is
composed of two modules. The feature embedding module is a deep Convolutional
Neural Network (CNN) which maps each face image to a feature vector. The
aggregation module consists of two attention blocks which adaptively aggregate
the feature vectors to form a single feature inside the convex hull spanned by
them. Due to the attention mechanism, the aggregation is invariant to the image
order. Our NAN is trained with a standard classification or verification loss
without any extra supervision signal, and we found that it automatically learns
to advocate high-quality face images while repelling low-quality ones such as
blurred, occluded and improperly exposed faces. The experiments on IJB-A,
YouTube Face, Celebrity-1000 video face recognition benchmarks show that it
consistently outperforms naive aggregation methods and achieves the
state-of-the-art accuracy.


title:
On the analytic properties of intertwining operators I: global
  normalizing factors

abstract:
  We provide a uniform estimate for the $L^1$-norm (over any interval of
bounded length) of the logarithmic derivatives of global normalizing factors
associated to intertwining operators for the following reductive groups over
number fields: inner forms of $GL(n)$; quasi-split classical groups and their
similitude groups; the exceptional group $G_2$. This estimate is a key
ingredient in the analysis of the spectral side of Arthur's trace formula. In
particular, it is applicable to the limit multiplicity problem studied by the
authors in earlier papers.


title:
Electrical Writing of Magnetic and Resistive Multistates in CoFe Films
  Deposited onto Pb[Zr$_x$Ti$_{1-x}$]O$_3$

abstract:
  Electric control of magnetic properties is an important challenge for modern
magnetism and spintronic development. In particular, an ability to write
magnetic state electrically would be highly beneficial. Among other methods,
the use of electric field induced deformation of piezoelectric elements is a
promising low-energy approach for magnetization control. We investigate the
system of piezoelectric substrate Pb[Zr$_x$Ti$_{1-x}$]O$_3$ with CoFe
overlayers, extending the known reversible bistable electro-magnetic coupling
to surface and multistate operations, adding the initial state reset
possibility. Increasing the CoFe thickness improves the magnetoresistive
sensitivity, but at the expenses of decreasing the strain-mediated coupling,
with optimum magnetic thin film thickness of the order of 100 nm. The simplest
resistance strain gauge structure is realized and discussed as a multistate
memory cell demonstrating both resistive memory (RRAM) and magnetoresistive
memory (MRAM) functionalities in a single structure.


title:
Near-side azimuthal and pseudorapidity correlations using neutral
  strange baryons and mesons in d+Au, Cu+Cu and Au+Au collisions at
  $\sqrt{s_{NN}}$ = 200 GeV

abstract:
  We present measurements of the near-side of triggered di-hadron correlations
using neutral strange baryons ($\Lambda$, $\bar{\Lambda}$) and mesons ($K^0_S$)
at intermediate transverse momentum (3 $<$ $p_T$ $<$ 6 GeV/$c$) to look for
possible flavor and baryon/meson dependence. This study is performed in $d$+Au,
Cu+Cu and Au+Au collisions at $\sqrt{s_{{NN}}}$ = 200 GeV measured by the STAR
experiment at RHIC. The near-side di-hadron correlation contains two
structures, a peak which is narrow in azimuth and pseudorapidity consistent
with correlations due to jet fragmentation, and a correlation in azimuth which
is broad in pseudorapidity. The particle composition of the jet-like
correlation is determined using identified associated particles. The dependence
of the conditional yield of the jet-like correlation on the trigger particle
momentum, associated particle momentum, and centrality for correlations with
unidentified trigger particles are presented. The neutral strange particle
composition in jet-like correlations with unidentified charged particle
triggers is not well described by PYTHIA. However, the yield of unidentified
particles in jet-like correlations with neutral strange particle triggers is
described reasonably well by the same model.


title:
Spin wave amplification using the spin Hall effect in permalloy/platinum
  bilayers

abstract:
  We investigate the effect of an electrical current on the attenuation length
of a 900 nm wavelength spin-wave in a permalloy/Pt bilayer using propagating
spin-wave spectroscopy. The modification of the spin-wave relaxation rate is
linear in current density, reaching up to 14% for a current density of
2.3$\times10^{11} $A/m$^2$ in Pt. This change is attributed to the spin
transfer torque induced by the spin Hall effect and corresponds to an effective
spin Hall angle of 0.13, which is among the highest values reported so far. The
spin Hall effect thus appears as an efficient way of amplifying/attenuating
propagating spin waves.


title:
The VLT LEGA-C Spectroscopic Survey: The Physics of Galaxies at a
  Lookback Time of 7 Gyr

abstract:
  The Large Early Galaxy Census (LEGA-C) is a Public Spectroscopic Survey of
$\sim3200$ $K$-band selected galaxies at redshifts $z=0.6-1.0$ with stellar
masses M_star > 1e10M_sun, conducted with VIMOS on ESO's Very Large Telescope.
The survey is embedded in the COSMOS field ($R.A. = 10h00$; $Dec.=+2\deg$). The
20-hour long integrations produce high-$S/N$ continuum spectra that reveal
ages, metallicities and velocity dispersions of the stellar populations.
LEGA-C's unique combination of sample size and depth will enable us for the
first time to map the stellar content at large look-back time, across galaxies
of different types and star-formation activity. Observations started in
December 2014 and are planned to be completed by mid 2018, with early data
releases of the spectra and value-added products. In this paper we present the
science case, the observing strategy, an overview of the data reduction process
and data products, and a first look at the relationship between galaxy
structure and spectral properties, as it existed 7 Gyr ago.


title: Reconciling the ionic and covalent pictures in rare-earth nickelates

abstract:
  The properties of AMO3 perovskite oxides, where M is a 3d transition metal,
depend strongly on the level of covalency between the metal d and oxygen p
orbitals. With their complex spin orders and metal-insulator transition,
rare-earth nickelates verge between dominantly ionic and covalent characters.
Accordingly, the nature of their ground state is highly debated. Here, we
reconcile the ionic and covalent visions of the insulating state of nickelates.
Through first-principles calculations, we show that it is reminiscent of the
ionic charge disproportionation picture (with strictly low-spin 4+ and
high-spin 2+ Ni sites) while exhibiting strong covalence effects with oxygen
electrons shifted toward the depleted Ni cations, mimicking a configuration
with identical Ni sites. Our results further hint at strategies to control
electronic and magnetic phases of transition metal oxide perovskites.


title:
Existence of Strong and Nontrivial Solutions to Strongly Coupled
  Elliptic Systems

abstract:
  We establish the existence of strong solutions to a class of nonlinear
strongly coupled and uniform elliptic systems consisting of more than two
equations. The existence of of nontrivial and non constant solutions (or
pattern formations) will also be studied.


title:
Observation of the universal magnetoelectric effect in a 3D topological
  insulator

abstract:
  The electrodynamics of topological insulators (TIs) is described by modified
Maxwell's equations, which contain additional terms that couple an electric
field to a magnetization and a magnetic field to a polarization of the medium,
such that the coupling coefficient is quantized in odd multiples of $e^2 / 2 h
c $ per surface. Here, we report on the observation of this so-called
topological magnetoelectric (TME) effect. We use monochromatic terahertz (THz)
spectroscopy of TI structures equipped with a semi-transparent gate to
selectively address surface states. In high external magnetic fields, we
observe a universal Faraday rotation angle equal to the fine structure constant
$\alpha = e^2 / \hbar c$ when a linearly polarized THz radiation of a certain
frequency passes through the two surfaces of a strained HgTe 3D TI. These
experiments give insight into axion electrodynamics of TIs and may potentially
be used for a metrological definition of the three basic physical constants.


title:
Zeroes of the spectral density of the Schroedinger operator with the
  slowly decaying Wigner-von Neumann potential

abstract:
  We consider the Schr\"odinger operator $\mathcal L_{\alpha}$ on the half-line
with a periodic background potential and a perturbation which consists of two
parts: a summable potential and the slowly decaying Wigner--von Neumann
potential $\frac{c\sin(2\omega x+\delta)}{x^{\gamma}}$, where
$\gamma\in(\frac12,1)$. The continuous spectrum of this operator has the same
band-gap structure as the continuous spectrum of the unperturbed periodic
operator. In every band there exist two points, called critical, where the
eigenfunction equation has square summable solutions. Every critical point
$\nu_{cr}$ is an eigenvalue of the operator $\mathcal L_{\alpha}$ for some
value of the boundary parameter $\alpha=\alpha_{cr}$, specific to that
particular point. We prove that for $\alpha\neq\alpha_{cr}$ the spectral
density of the operator $\mathcal L_{\alpha}$ has a zero of the exponential
type at $\nu_{cr}$.


title:
$L^p$-Wasserstein distance for stochastic differential equations driven
  by L\'{e}vy processes

abstract:
  Coupling by reflection mixed with synchronous coupling is constructed for a
class of stochastic differential equations (SDEs) driven by L\'{e}vy noises. As
an application, we establish the exponential contractivity of the associated
semigroups $(P_t)_{t\ge0}$ with respect to the standard $L^p$-Wasserstein
distance for all $p\in[1,\infty)$. In particular, consider the following SDE:
\[\mathrm{d}X_t=\mathrm{d}Z_t+b(X_t)\,\mathrm{d}t,\] where $(Z_t)_{t\ge0}$ is a
symmetric $\alpha$-stable process on $\mathbb{R}^d$ with $\alpha\in(1,2)$. We
show that if the drift term $b$ satisfies that for any $x,y\in\mathbb{R}^d$,
\[\bigl\langle b(x)-b(y),x-y\bigr\rangle\le\cases{K_1|x-y|^2,\qquad |x-y|\le
L_0;\cr -K_2|x-y|^{\theta},\qquad |x-y|>L_0}\] holds with some positive
constants $K_1$, $K_2$, $L_0>0$ and $\theta\ge2$, then there is a constant
$\lambda:=\lambda(\theta,K_1,K_2,L_0)>0$ such that for all $p\in[1,\infty)$,
$t>0$ and $x,y\in\mathbb{R}^d$, \[W_p(\delta_xP_t,\delta_yP_t)\le
C(p,\theta,K_1,K_2,L_0)\mathrm{e}^{-\lambda
t/p}\biggl[\frac{|x-y|^{1/p}\vee|x-y|}{1+|x-y|{\mathbf{1}}_{(1,\infty )\times
(2,\infty)}(t,\theta)}\biggr].\]


title: The disc origin of the Milky Way bulge

abstract:
  The Galactic bulge, that is the prominent out-of-plane over-density present
in the inner few kiloparsecs of the Galaxy, is a complex structure, as the
morphology, kinematics, chemistry and ages of its stars indicate. To understand
the nature of its main components -- those at [Fe/H] >~ -1 dex -- it is
necessary to make an inventory of the stellar populations of the Galactic
disc(s), and of their borders : the chemistry of the disc at the solar
vicinity, well known from detailed studies of stars over many years, is not
representative of the whole disc. This finding, together with the recent
revisions of the mass and sizes of the thin and thick discs, constitutes a
major step in understanding the bulge complexity. N-body models of a
boxy/peanut-shaped bulge formed from a thin disc through the intermediary of a
bar have been successful in interpreting a number of global properties of the
Galactic bulge, but they fail in reproducing the detailed chemo-kinematic
relations satisfied by its components and their morphology. It is only by
adding the thick disc to the picture that we can understand the nature of the
Galactic bulge.


title: A flexible state space model for learning nonlinear dynamical systems

abstract:
  We consider a nonlinear state-space model with the state transition and
observation functions expressed as basis function expansions. The coefficients
in the basis function expansions are learned from data. Using a connection to
Gaussian processes we also develop priors on the coefficients, for tuning the
model flexibility and to prevent overfitting to data, akin to a Gaussian
process state-space model. The priors can alternatively be seen as a
regularization, and helps the model in generalizing the data without
sacrificing the richness offered by the basis function expansion. To learn the
coefficients and other unknown parameters efficiently, we tailor an algorithm
using state-of-the-art sequential Monte Carlo methods, which comes with
theoretical guarantees on the learning. Our approach indicates promising
results when evaluated on a classical benchmark as well as real data.


title: Speeding Up Computers

abstract:
  There are two distinct approaches to speeding up large parallel computers.
The older method is the General Purpose Graphics Processing Units (GPGPU). The
newer is the Many Integrated Core (MIC) technology . Here we attempt to focus
on the MIC technology and point out differences between the two approaches to
accelerating supercomputers. This is a user perspective.


title: Quantum Vacuum Fluctuations in a Chromomagnetic-like Background

abstract:
  In this paper we study the effects associated to quantum vacuum fluctuations
of vectorial perturbations of the Abelian SU(2) Yang-Mills field in a static
and homogeneous chromomagnetic-like background field, at zero temperature. We
use periodic and antiperiodic boundary conditions in order to calculate the
Casimir energy by means of the frequency sum technique and of the
regularization method based on zeta functions, analyzing its behavior in the
weak and strong coupling regimes. We compare the obtained results with the
similar ones found for scalar and spinor fields placed in an ordinary magnetic
field background. We show that only in the weak coupling regime the non-trivial
topology of the system encoded in the antiperiodic boundary conditions changes
the nature of the Casimir force with respect to the periodic ones. Considering
the weak coupling scenario, we show that the introduction of a third
polarization state in the perturbations makes manifest the effects on the
Casimir energy due to the coupling with the chromomagnetic-like background
field, for both the boundary conditions. Finally, in the strong coupling
regime, in which the quantum vacuum is not stable due to the Nielsen-Olesen
instabilities, we evaluate the effects of a compact extra dimension on its
stabilization.


abstract:
  We present many examples of Banach spaces of linear operators and homogeneous
polynomials without the approximation property, thus improving results of
Dineen and Mujica [11] and Godefroy and Saphar [13].


title: Collision Avoidance of Two Autonomous Quadcopters

abstract:
  Traffic collision avoidance systems (TCAS) are used in order to avoid
incidences of mid-air collisions between aircraft. We present a game-theoretic
approach of a TCAS designed for autonomous unmanned aerial vehicles (UAVs). A
variant of the canonical example of game-theoretic learning, fictitious play,
is used as a coordination mechanism between the UAVs, that should choose
between the alternative altitudes to fly and avoid collision. We present the
implementation results of the proposed coordination mechanism in two
quad-copters flying in opposite directions.


title: Cosmic variance in [O/Fe] in the Galactic disk

abstract:
  We examine the distribution of the [O/Fe] abundance ratio in stars across the
Galactic disk using H-band spectra from the Apache Point Galactic Evolution
Experiment (APOGEE). We minimize systematic errors by considering groups of
stars with similar atmospheric parameters. The APOGEE measurements in the Sloan
Digital Sky Survey Data Release 12 reveal that the square root of the
star-to-star cosmic variance in the oxygen-to-iron ratio at a given metallicity
is about 0.03-0.04 dex in both the thin and thick disk. This is about twice as
high as the spread found for solar twins in the immediate solar neighborhood
and the difference is probably associated to the wider range of galactocentric
distances spanned by APOGEE stars. We quantify the uncertainties by examining
the spread among stars with the same parameters in clusters; these errors are a
function of effective temperature and metallicity, ranging between 0.005 dex at
4000 K and solar metallicity, to about 0.03 dex at 4500 K and [Fe/H]= -0.6. We
argue that measuring the spread in [O/Fe] and other abundance ratios provides
strong constraints for models of Galactic chemical evolution.


title: Active Stabilization of Ion Trap Radiofrequency Potentials

abstract:
  We actively stabilize the harmonic oscillation frequency of a laser-cooled
atomic ion confined in a rf Paul trap by sampling and rectifying the high
voltage rf applied to the trap electrodes. We are able to stabilize the 1 MHz
atomic oscillation frequency to better than 10 Hz, or 10 ppm. This represents a
suppression of ambient noise on the rf circuit by 34 dB. This technique could
impact the sensitivity of ion trap mass spectrometry and the fidelity of
quantum operations in ion trap quantum information applications.


title: Strong-field ionization of clusters using two-cycle pulses at 1.8~$\mu$m

abstract:
  The interaction of intense laser pulses with nano-scale particles leads to
the production of high-energy electrons, ions, neutral atoms, neutrons and
photons. Up to now, investigations have focused on near-infrared to X-ray laser
pulses consisting of many optical cycles. Here we study strong-field ionization
of rare-gas clusters ($10^3$ to $10^5$ atoms) using two-cycle 1.8~$\mu$m laser
pulses to access a new interaction regime in the limit where the electron
dynamics are dominated by the laser field and the cluster atoms do not have
time to move significantly. The emission of fast electrons with kinetic
energies exceeding 3keV is observed using laser pulses with a wavelength of
1.8~$\mu$m and an intensity of $1\times 10^{15}$~W/cm$^2$, whereas only
electrons below 500eV are observed at 800nm using a similar intensity and pulse
duration. Fast electrons are preferentially emitted along the laser
polarization direction, showing that they are driven out from the cluster by
the laser field. In addition to direct electron emission, an electron
rescattering plateau is observed. Scaling to even longer wavelengths is
expected to result in a highly directional current of energetic electrons on a
few-femtosecond timescale.


title: Quantum choppers

abstract:
  An optical chopper periodically interrupts a classical light beam. We propose
a realizable quantum version of the optical chopper, where the time-periodic
driving of the light-matter coupling is achieved through a nonlinear three wave
mixing element. We theoretically investigate how our scheme can be used for the
controllable shaping of few photon light. Using Floquet dynamics, we find
strong periodic modulations of the transmission and reflection envelopes in the
scattered few-photon pulses, including photon compression and blockade, as well
as dramatic changes in the quantum light statistics. Our theoretical analysis
allows us to explain these non-trivial phenomena as arising from non-adiabatic
memory effects.


title: Polymorphic Type Inference for Machine Code

abstract:
  For many compiled languages, source-level types are erased very early in the
compilation process. As a result, further compiler passes may convert type-safe
source into type-unsafe machine code. Type-unsafe idioms in the original source
and type-unsafe optimizations mean that type information in a stripped binary
is essentially nonexistent. The problem of recovering high-level types by
performing type inference over stripped machine code is called type
reconstruction, and offers a useful capability in support of reverse
engineering and decompilation.
  In this paper, we motivate and develop a novel type system and algorithm for
machine-code type inference. The features of this type system were developed by
surveying a wide collection of common source- and machine-code idioms, building
a catalog of challenging cases for type reconstruction. We found that these
idioms place a sophisticated set of requirements on the type system, inducing
features such as recursively-constrained polymorphic types. Many of the
features we identify are often seen only in expressive and powerful type
systems used by high-level functional languages.
  Using these type-system features as a guideline, we have developed Retypd: a
novel static type-inference algorithm for machine code that supports recursive
types, polymorphism, and subtyping. Retypd yields more accurate inferred types
than existing algorithms, while also enabling new capabilities such as
reconstruction of pointer const annotations with 98% recall. Retypd can operate
on weaker program representations than the current state of the art, removing
the need for high-quality points-to information that may be impractical to
compute.


title: Gain Function Approximation in the Feedback Particle Filter

abstract:
  This paper is concerned with numerical algorithms for gain function
approximation in the feedback particle filter. The exact gain function is the
solution of a Poisson equation involving a probability-weighted Laplacian. The
problem is to approximate this solution using only particles sampled from the
probability distribution. Two algorithms are presented: a Galerkin algorithm
and a kernel-based algorithm. Both the algorithms are adapted to the samples
and do not require approximation of the probability distribution as an
intermediate step. The paper contains error analysis for the algorithms as well
as some comparative numerical results for a non-Gaussian distribution. These
algorithms are also applied and illustrated for a simple nonlinear filtering
example.


title: Allosteric control in icosahedral capsid assembly

abstract:
  During the lifecycle of a virus, viral proteins and other components
self-assemble to form a symmetric protein shell called a capsid. This assembly
process is subject to multiple competing constraints, including the need to
form a thermostable shell while avoiding kinetic traps. It has been proposed
that viral assembly satisfies these constraints through allosteric regulation,
including the interconversion of capsid proteins among conformations with
different propensities for assembly. In this article we use computational and
theoretical modeling to explore how such allostery affects the assembly of
icosahedral shells. We simulate assembly under a wide range of protein
concentrations, protein binding affinities, and two different mechanisms of
allosteric control. We find that, above a threshold strength of allosteric
control, assembly becomes robust over a broad range of subunit binding
affinities and concentrations, allowing the formation of highly thermostable
capsids. Our results suggest that allostery can significantly shift the range
of protein binding affinities that lead to successful assembly, and thus should
be accounted for in models that are used to estimate interaction parameters
from experimental data.


title:
String Stability towards Leader thanks to Asymmetric Bidirectional
  Controller

abstract:
  This paper deals with the problem of string stability of interconnected
systems with double-integrator open loop dynamics (e.g.~acceleration-controlled
vehicles). We analyze an asymmetric bidirectional linear controller, where each
vehicle is coupled solely to its immediate predecessor and to its immediate
follower with different gains in these two directions. We show that in this
setting, unlike with unidirectional or symmetric bidirectional controllers,
string stability can be recovered when disturbances act only on a small
($N$-independent) set of leading vehicles. This improves existing results from
the literature with this assumption. We also indicate that string stability
with respect to arbitrarily distributed disturbances cannot be achieved with
this controller.


title: Integral control on nonlinear spaces: two extensions

abstract:
  This paper applies the recently developed framework for integral control on
nonlinear spaces to two non-standard cases. First, we show that the property of
perfect target stabilization in presence of actuation bias holds also if this
bias is state dependent. This might not be surprising, but for practical
purposes it provides an easy way to robustly cancel nonlinear dynamics of the
uncontrolled plant. We specifically illustrate this for robust stabilization of
a pendulum at arbitrary angle, a problem posed as non-trivial by some
colleagues. Second, as previous work has been restricted to systems with as
many control inputs as configuration dimensions, we here provide results for
integral control of a non-holonomic system. More precisely, we design robust
steering control of a rigid body under velocity bias.


title: Additive noise destroys the random attractor close to bifurcation

abstract:
  We provide an example for stabilization by noise. Our approach does not rely
on monotonicity arguments due to the presence of higher order differential
operators or mixing properties of the system as the noise might be highly
degenerate. In the examples a scalar additive noise destroys a high-dimensional
random attractor of a PDE on an unbounded domain. In the presence of small
noise close to bifurcation all trajectories converge to a single stationary
solution.


title:
Leading and Subleading UV Divergences in Scattering Amplitudes for D=8
  N=1 SYM Theory in All Loops

abstract:
  We consider the leading and subleading UV divergences for the four-point
on-shell scattering amplitudes in D=8 N=1 sypersymmetric Yang-Mills theory
within the spinor-helicity and superfield formalism. This theory belongs to the
class of maximally supersymmetric gauge theories and presumably possesses
distinguished properties beyond perturbation theory. We obtain the recursive
relations that allow one to get the leading and subleading divergences in all
loops in a pure algebraic way staring from the one loop (for the leading poles)
and two loop (for the subleading ones) diagrams. As a particular example where
the recursive relations have a simple form we consider the ladder type
diagrams. The all loop summation of the leading and subleading divergences is
performed with the help of the differential equations which are the
generalization of the RG equations for non-renormalizable theories. They have
explicit solutions for the ladder type diagrams. We discuss the properties of
the obtained solutions and interpretation of the results.


title:
Revisiting the Exclusion Limits from Direct Chargino-Neutralino
  Production at the LHC

abstract:
  We revisit the existing limits on the gaugino masses in various
Supersymmetric (SUSY) scenarios derived from Run-I data of the LHC. These
limits obtained from the various final states rely heavily on the simplified
assumptions regarding the masses, compositions and decay branching ratios of
the gauginos. The most promising exclusion limits on the gaugino masses are
obtained from trilepton final states while the second lightest neutralino
($\widetilde \chi_2^0$) decaying into the SM-like Higgs and lightest SUSY
particle (LSP) results in the weakest bounds. Our aim is to assess the extent
of deviation of these exclusion limits in more realistic scenarios. After a
brief discussion on the various decay modes of the $\widetilde \chi_2^0$ and
the lightest chargino ($\widetilde \chi^{\pm}_1$), we proceed to validate the
ATLAS exclusion limits obtained from trilepton, $l\gamma\gamma$ and $lb\bar b$
final states associated with missing energy. We then consider different
combinations of the relevant branching ratios to study their impact on the
existing bounds. The results are presented alongside the existing exclusion
limits to showcase the extent of the obtained deviation. We also observe that
the three-body decay modes of $\widetilde \chi_2^0$ and $\widetilde
\chi^{\pm}_1$ via off-shell slepton decays resulting in trilepton final states
provide bounds that are far more severe in some parts of the available
parameter space than that obtained from the usual two-body decay modes of the
aforementioned gauginos.


title: Impact of sterile neutrino dark matter on core-collapse supernovae

abstract:
  We summarize the impact of sterile neutrino dark matter on core-collapse
supernova explosions. We explore various oscillations between electron
neutrinos or mixed $\mu-\tau$ neutrinos and right-handed sterile neutrinos that
may occur within a core-collapse supernova. In particular, we consider sterile
neutrino masses and mixing angles that are consistent with sterile neutrino
dark matter candidates as indicated by recent X-ray flux measurements. We find
that the interpretation of the observed 3.5 keV X-ray excess as due to a
decaying 7 keV sterile neutrino that comprises 100\% of the dark matter would
have almost no observable effect on supernova explosions. However, in the more
realistic case in which the decaying sterile neutrino comprises only a small
fraction of the total dark matter density due to the presence of other sterile
neutrino flavors, WIMPs, etc., a larger mixing angle is allowed. In this case a
7 keV sterile neutrino could have a significant impact on core-collapse
supernovae. We also consider mixing between $\mu-\tau$ neutrinos and sterile
neutrinos. We find, however, that this mixing does not significantly alter the
explosion and has no observable effect on the neutrino luminosities at early
times.


title:
X-Ray Spectra of The High-Mass X-RAY Binary 4U~1700-37 using BeppoSAX,
  Suzaku and RXTE Observations

abstract:
  We present an X-ray spectral analysis of the high-mass binary 4U~1700-37
during its hard-soft state evolution. We use the BeppoSAX, Suzaku and RXTE
(Rossi X-ray Timing Explorer), Suzaku and BeppoSAX observations for this
investigation. We argue that the X-ray broad-band spectra during all spectral
states can be adequately reproduced by a model, consisting of a low-temperature
Blackbody component, two Comptonized components both due to the presence of a
Compton cloud (CC) that up-scatters seed photons of $T_{s1}$~< 1.4 keV, and
$T_{s2}<$1 keV, and an iron-line component. We find using this model that the
photon power-law index is almost constant, $\Gamma_{1}\sim 2$ for all spectral
states. However, $\Gamma_{2}$ shows a behavior depending on the spectral state.
Namely, $\Gamma_{2}$ is quasi-constant at the level of $\Gamma_{2}\sim 2$ while
the CC plasma temperature $kT^{(2)}_e$ is less than 40 keV; on the other hand,
$\Gamma_{2}$ is in the range of $1.3<\Gamma_{2}<2$, when $kT^{(2)}_e$ is
greater than 40 keV. We explain this quasi-stability of $\Gamma$ during most of
hard-soft transitions of 4U~1700-37 in a framework of the model in which the
resulting spectrum is described by two Comptonized components. We find that
these Comptonized spectral components of the HMXB 4U~1700-37 are similar to
those previously found in NS sources. This index dependence versus both mass
accretion rate and $kT_e$ revealed in 4U~1700-37 is a universal observational
evidence for the presence of a NS in 4U 1700-37.


title: Systematics of oscillatory behavior in hadronic masses and widths

abstract:
  A systematic study of hadron masses and widths shows regular oscillations
that can be fitted by a simple cosine function. This property can be observed
when the difference between adjacent masses of each family is plotted versus
the mean mass.


title: Lepto$-$Hadronic Origin of $\gamma$-ray Outbursts of 3C 279

abstract:
  The blazar 3C 279 exhibited a giant $\gamma$-ray outburst in 2013 December
and 2014 April. Apart from the very fast $\gamma$-ray flux variability, the
spectral nature of the flares were also found to vary significantly between
these two flaring events. A prominent curvature in the $\gamma$-ray spectrum
was noticed in 2014 April flare, on the other hand, the 2013 December displayed
an extreme hardening of the spectrum. These observations, thus, put strong
constraints on our understanding of the underlying particle acceleration
mechanisms.


title:
J$_{eff}$ description of the honeycomb Mott insulator
  ${\alpha}$-RuCl$_3$

abstract:
  Novel ground states might be realized in honeycomb lattices with strong
spin-orbit coupling. Here we study the electronic structure of
${\alpha}$-RuCl$_3$, in which the Ru ions are in a d5 configuration and form a
honeycomb lattice, by angle-resolved photoemission, x-ray photoemission and
electron energy loss spectroscopy supported by density functional theory and
multiplet calculations. We find that ${\alpha}$-RuCl$_3$ is a Mott insulator
with significant spin-orbit coupling, whose low energy electronic structure is
naturally mapped onto Jeff states. This makes ${\alpha}$-RuCl$_3$ a promising
candidate for the realization of Kitaev physics. Relevant electronic parameters
such as the Hubbard energy U, the crystal field splitting 10Dq and the charge
transfer energy are evaluated. Furthermore, we observe significant Cl
photodesorption with time, which must be taken into account when interpreting
photoemission and other surface sensitive experiments.


title:
Local Simulations of Instabilities Driven by Composition Gradients in
  the ICM

abstract:
  The distribution of Helium in the intracluster medium (ICM) permeating galaxy
clusters is not well constrained due to the very high plasma temperature.
Therefore, the plasma is often assumed to be homogeneous. A non-uniform Helium
distribution can however lead to biases when measuring key cluster parameters.
This has motivated one-dimensional models that evolve the ICM composition
assuming that the effects of magnetic fields can be parameterized or ignored.
Such models for non-isothermal clusters show that Helium can sediment in the
cluster core leading to a peak in concentration offset from the cluster center.
The resulting profiles have recently been shown to be linearly unstable when
the weakly-collisional character of the magnetized plasma is considered. In
this paper, we present a modified version of the MHD code Athena, which makes
it possible to evolve a weakly-collisional plasma subject to a gravitational
field and stratified in both temperature and composition. We thoroughly test
our implementation and confirm excellent agreement against several analytical
results. In order to isolate the effects of composition, in this initial study
we focus our attention on isothermal plasmas. We show that plasma
instabilities, feeding off gradients in composition, can induce turbulent
mixing and saturate by re-arranging magnetic field lines and alleviating the
composition gradient. Composition profiles that increase with radius lead to
instabilities that saturate by driving the average magnetic field inclination
to roughly $45^{\circ}$. We speculate that this effect may alleviate the core
insulation observed in homogeneous settings, with potential consequences for
the associated cooling flow problem.


title:
General Relativistic Considerations of the Field Shedding Model of Fast
  Radio Bursts

abstract:
  Popular models of fast radio bursts (FRBs) involve the gravitational collapse
of neutron star progenitors to black holes. It has been proposed that the
shedding of the strong neutron star magnetic field ($B$) during the collapse is
the power source for the radio emission. Previously, these models have utilized
the simplicity of the Schwarzschild metric which has the restriction that the
magnetic flux is magnetic "hair" that must be shed before final collapse. But,
neutron stars have angular momentum and charge and a fully relativistic Kerr
Newman solution exists in which $B$ has its source inside of the event horizon.
In this letter, we consider the magnetic flux to be shed as a consequence of
the electric discharge of a metastable collapsed state of a Kerr Newman black
hole. It has also been argued that the shedding model will not operate due to
pair creation. By considering the pulsar death line, we find that for a neutron
star with $B = 10^{11} - 10^{13}$ G and a long rotation period, $>1$ s this is
not a concern. We also discuss the observational evidence supporting the
plausibility of magnetic flux shedding models of FRBs that are spawned from
rapidly rotating progenitors.


title:
On King Type Modification of $(p,q)$ Baskakov Operators which preserves
  $x^2$

abstract:
  In the present paper, we construct and investigate a variant of modified
$(p,q)$-Baskakov operators, which reproduce the test function $x^2$. The order
of approximation of the operators via K-functional and second order, usual
modulus of continuity, weighted approximation properties are disscussed. In the
end some graphical results, comparison with $(p,q)$-Baskakov operators is
explained.


title:
Character relations and replication identities in 2d Conformal Field
  Theory

abstract:
  We study replication identities satisfied by conformal characters of a 2D
CFT, providing a natural framework for a physics interpretation of the famous
Hauptmodul property of Monstrous Moonshine, and illustrate the underlying ideas
in simple cases.


title: On Certain Positive Semidefinite Matrices of Special Functions

abstract:
  Special functions are often defined as a Fourier or Laplace transform of a
positive measure, and the positivity of the measure manifests as positive
definiteness of certain matrices. The purpose of this expository note is to
give a sample of such positive definite matrices to demonstrate this connection
for some well-known special functions such as Gamma, Beta, hypergeometric,
theta, elliptic, zeta and basic hypergeometric functions.


title: The geometric phase of stock trading

abstract:
  Geometric phases describe how in a continuous-time dynamical system the
displacement of a variable (called phase variable) can be related to other
variables (shape variables) undergoing a cyclic motion, according to an area
rule. The aim of this paper is to show that geometric phases can exist also for
discrete-time systems, and even when the cycles in shape space have zero area.
A context in which this principle can be applied is stock trading. A zero-area
cycle in shape space represents the type of trading operations normally carried
out by high-frequency traders (entering and exiting a position on a fast
time-scale), while the phase variable represents the cash balance of a trader.
Under the assumption that trading impacts stock prices, even zero-area cyclic
trading operations can induce geometric phases, i.e., profits or losses,
without affecting the stock quote.


title:
The on-shell effective field theory: a systematic tool to compute power
  corrections to the hard thermal loops

abstract:
  We show that effective field theory techniques can be efficiently used to
compute power corrections to the hard thermal loops (HTL) in a high temperature
T expansion. To this aim, we use the recently proposed on-shell effective field
theory (OSEFT), which describes the quantum fluctuations around on-shell
degrees of freedom. We provide the OSEFT Lagrangian up to third order in the
energy expansion for QED, and use it for the computation of power corrections
to the retarded photon polarization tensor for soft external momenta. Here soft
denotes a scale of order $eT$, where $e$ is the gauge coupling constant. We
develop the necessary techniques to perform these computations, and study the
contributions to the polarization tensor proportional to $e^2 T^2$, $e^2 T$ and
$e^2 T^0$. The first one describes the HTL contribution, the second one
vanishes, while the third one provides corrections of order $e^2$ to the soft
photon propagation. We check that the results agree with the direct calculation
from QED, up to local pieces, as expected in an effective field theory.


title: Integer Powers of Certain Complex Pentadiagonal 2-Toeplitz Matrices

abstract:
  In this study, we get a general expression for the entries of the sth power
of even order pentadiagonal 2-Toeplitz matrices.


title: The wave equation for stiff strings and piano tuning

abstract:
  We study the wave equation for a string with stiffness. We solve the equation
and provide a uniqueness theorem with suitable boundary conditions. For a
pinned string we compute the spectrum, which is slightly inharmonic. Therefore,
the widespread scale of 12 equal divisions of the just octave is not the best
choice to tune instruments like the piano. Basing on the theory of dissonance,
we provide a way to tune the piano in order to improve its consonance. A good
solution is obtained by tuning a note and its fifth by minimizing their beats.

categories: physics.class-ph math.AP math.HO physics.pop-ph


title: G-Radical Supplemented Modules

abstract:
  In this work g-radical supplemented modules are defined and investigated some
properties of this modules.


title: On connected Lie groups and the Approximation Property

abstract:
  Recently, a complete characterization of connected Lie groups with the
Approximation Property was given. The proof used of the newly introduced
property (T*). We present here a short proof of the same result avoiding the
use of property (T*). Using property (T*), however, the characterization is
extended to every almost connected group. We end with some remarks about the
impossibility of going beyond the almost connected case.


title: Towards a classification of compact quantum groups of Lie type

abstract:
  This is a survey of recent results on classification of compact quantum
groups of Lie type, by which we mean quantum groups with the same fusion rules
and dimensions of representations as for a compact connected Lie group $G$. The
classification is based on a categorical duality for quantum group actions
recently developed by De Commer and the authors in the spirit of Woronowicz's
Tannaka--Krein duality theorem. The duality establishes a correspondence
between the actions of a compact quantum group $H$ on unital C$^*$-algebras and
the module categories over its representation category Rep $H$. This is further
refined to a correspondence between the braided-commutative Yetter--Drinfeld
$H$-algebras and the tensor functors from Rep $H$. Combined with the more
analytical theory of Poisson boundaries, this leads to a classification of
dimension-preserving fiber functors on the representation category of any
coamenable compact quantum group in terms of its maximal Kac quantum subgroup,
which is the maximal torus for the $q$-deformation of $G$ if $q\ne1$. Together
with earlier results on autoequivalences of the categories Rep $G_q$, this
allows us to classify up to isomorphism a large class of quantum groups of
$G$-type for compact connected simple Lie groups $G$. In the case of $G=SU(n)$
this class exhausts all non-Kac quantum groups.


title: Improved Approximation for Node-Disjoint Paths in Planar Graphs

abstract:
  We study the classical Node-Disjoint Paths (NDP) problem: given an $n$-vertex
graph $G$ and a collection $M=\{(s_1,t_1),\ldots,(s_k,t_k)\}$ of pairs of
vertices of $G$ called demand pairs, find a maximum-cardinality set of
node-disjoint paths connecting the demand pairs. NDP is one of the most basic
routing problems, that has been studied extensively. Despite this, there are
still wide gaps in our understanding of its approximability: the best currently
known upper bound of $O(\sqrt n)$ on its approximation ratio is achieved via a
simple greedy algorithm, while the best current negative result shows that the
problem does not have a better than $\Omega(\log^{1/2-\delta}n)$-approximation
for any constant $\delta$, under standard complexity assumptions. Even for
planar graphs no better approximation algorithms are known, and to the best of
our knowledge, the best negative bound is APX-hardness. Perhaps the biggest
obstacle to obtaining better approximation algorithms for NDP is that most
currently known approximation algorithms for this type of problems rely on the
standard multicommodity flow relaxation, whose integrality gap is $\Omega(\sqrt
n)$ for NDP, even in planar graphs. In this paper, we break the barrier of
$O(\sqrt n)$ on the approximability of the NDP problem in planar graphs and
obtain an $\tilde O(n^{9/19})$-approximation. We introduce a new linear
programming relaxation of the problem, and a number of new techniques, that we
hope will be helpful in designing more powerful algorithms for this and related
problems.


title: Self-energies in itinerant magnets: A focus on Fe and Ni

abstract:
  We present a detailed study of local and non-local correlations in the
electronic structure of elemental transition metals carried out by means of the
Quasiparticle Self-consistent GW (QSGW ) and Dynamical Mean Field Theory
(DMFT). Recent high resolution ARPES and Haas-van Alphen data of two typical
transition metal systems (Fe and Ni) are used as case study. (i) We find that
the properties of Fe are very well described by QSGW. Agreement with cyclotron
and very clean ARPES measurements is excellent, provided that final-state
scattering is taken into account. This establishes the exceptional reliability
of QSGW also in metallic systems. (ii) Nonetheless QSGW alone is not able to
provide an adequate description of the Ni ARPES data due to strong local spin
fluctuations. We surmount this deficiency by combining nonlocal charge
fluctuations in QSGW with local spin fluctuations in DMFT (QSGW + 'Magnetic
DMFT'). (iii) Finally we show that the dynamics of the local fluctuations are
actually not crucial. The addition of an external static field can lead to
similarly good results if non-local correlations are included through QSGW.


title:
Tracking multiple moving objects in images using Markov Chain Monte
  Carlo

abstract:
  A new Bayesian state and parameter learning algorithm for multiple target
tracking (MTT) models with image observations is proposed. Specifically, a
Markov chain Monte Carlo algorithm is designed to sample from the posterior
distribution of the unknown number of targets, their birth and death times,
states and model parameters, which constitutes the complete solution to the
tracking problem. The conventional approach is to pre-process the images to
extract point observations and then perform tracking. We model the image
generation process directly to avoid potential loss of information when
extracting point observations. Numerical examples show that our algorithm has
improved tracking performance over commonly used techniques, for both synthetic
examples and real florescent microscopy data, especially in the case of dim
targets with overlapping illuminated regions.


title: Quantitative combinatorial geometry for continuous parameters

abstract:
  We prove variations of Carath\'eodory's, Helly's and Tverberg's theorems
where the sets involved are measured according to continuous functions such as
the volume or diameter. Among our results, we present continuous quantitative
versions of Lov\'asz's colorful Helly theorem, B\'ar\'any's colorful
Carath\'eodory's theorem, and the colorful Tverberg theorem.


title:
Renormalisation of the low-energy constants of chiral perturbation
  theory from loops with dynamical vector mesons

abstract:
  Starting from a relativistic Lagrangian for pseudoscalar Goldstone bosons and
vector mesons in the antisymmetric tensor representation, a one-loop
calculation is performed to pin down the divergent structures that appear for
the effective low-energy action at chiral orders Q^2 and Q^4. The corresponding
renormalisation-scale dependences of all low-energy constants up to chiral
order Q^4 are determined. Calculations are carried out for both the
pseudoscalar octet and the pseudoscalar nonet, the latter in the framework of
chiral perturbation theory in the limit of a large number of colours.


title: Quantitative Tverberg theorems over lattices and other discrete sets

abstract:
  This paper presents a new variation of Tverberg's theorem. Given a discrete
set $S$ of $R^d$, we study the number of points of $S$ needed to guarantee the
existence of an $m$-partition of the points such that the intersection of the
$m$ convex hulls of the parts contains at least $k$ points of $S$. The proofs
of the main results require new quantitative versions of Helly's and
Carath\'eodory's theorems.


title: Destructibility of the tree property at $\aleph_{\omega+1}$

abstract:
  We construct a model in which the tree property holds in $\aleph_{\omega +
1}$ and it is destructible under $\text{Col}(\omega, \omega_1)$. On the other
hand we discuss some cases in which the tree property is indestructible under
small or closed forcings.


title: Pseudo-real multiplication and an application to Teichm\"uller curves

abstract:
  In this paper, we classify three-dimensional complex Abelian varieties
isogenous to a product $A_1 \times A_2$, where one of the factors admits real
multiplication by a real quadratic order $\mathcal{O}_D$ of discriminant $D$.
We show that the moduli space $X_D^{(3)}$ of these varieties essentially is the
disjoint union of certain Hilbert modular varieties $X_{\mathfrak{a}}$, each
component depending on the choice of an ideal $\mathfrak{a}$ of
$\mathcal{O}_D$. We give an explicit construction of these varieties.
  We show that the boundary of the eigenform locus for pseudo-real
multiplication by an order $\mathcal{O}$ in $\mathbb{Q}(\sqrt{D}) \oplus
\mathbb{Q}$ over geometric genus zero stable curves is contained in the union
of subvarieties defined by equations involving cross-ratios of projective
coordinates. Moreover, restricted to certain topological types of stable curves
relevant to the classification of primitive Teichm\"uller curves, we show that
the boundary of the eigenform locus coincides with the subspace cut out by
these cross-ratio equations. We compute these equations for the example of
genus three Prym Teichm\"uller curves.


title:
Electrostatic trapping and in situ detection of Rydberg atoms above
  chip-based transmission lines

abstract:
  Beams of helium atoms in Rydberg-Stark states with principal quantum number
$n=48$ and electric dipole moments of 4600~D have been decelerated from a mean
initial longitudinal speed of 2000~m/s to zero velocity in the laboratory-fixed
frame-of-reference in the continuously moving electric traps of a
transmission-line decelerator. In this process accelerations up to
$-1.3\times10^{7}$~m/s$^2$ were applied, and changes in kinetic energy of
$\Delta E_{\mathrm{kin}}=1.3\times10^{-20}$~J ($\Delta E_{\mathrm{kin}}/e =
83$~meV) per atom were achieved. Guided and decelerated atoms, and those
confined in stationary electrostatic traps, were detected in situ by pulsed
electric field ionisation. The results of numerical calculations of particle
trajectories within the decelerator have been used to characterise the observed
deceleration efficiencies, and aid in the interpretation of the experimental
data.


title: Photoelectron spectra with Qprop and t-SURFF

abstract:
  Calculating strong-field, momentum-resolved photoelectron spectra (PES) from
numerical solutions of the time-dependent Schr\"odinger equation (TDSE) is a
very demanding task due to the large spatial excursions and drifts of electrons
in intense laser fields. The time-dependent surface flux (t-SURFF) method for
the calculation of PES [L. Tao, A. Scrinzi, New Journal of Physics 14, 013021
(2012)] allows to keep the numerical grid much smaller than the space over
which the wavefunction would be spread at the end of the laser pulse. We
present an implementation of the t-SURFF method in the well established
TDSE-solver Qprop [D. Bauer, P. Koval, Comput. Phys. Commun. 174, 396 (2006)].
Qprop efficiently propagates wavefunctions for single-active electron systems
with spherically symmetric binding potentials in classical, linearly (along
$z$) or elliptically (in the $xy$-plane) polarized laser fields in dipole
approximation. Its combination with t-SURFF makes the simulation of PES
feasible in cases where it is just too expensive to keep the entire
wavefunction on the numerical grid, e.g., in the long-wavelength or long-pulse
regime.


title: The complex Dirac Delta, Plemelj formula, and integral representations

abstract:
  The extension of the Dirac Delta distribution (DD) to the complex field is
needed for dealing with the complex-energy solutions of the Schr\"odinger
equation, typically when calculating their inner products. In quantum
scattering theory the DD usually arises as an integral representation involving
plane waves of real momenta. We deal with the complex extension of these
representations by using a Gaussian regularization. Their interpretation as
distributions requires prescribing the integration path and a corresponding
space of test functions. An extension of the Sokhotski-Plemelj formula is
obtained. This definition of distributions is alternative to the historic one
referred to surface integrations on the complex plane.


title: Local asymptotics for the first intersection of two independent renewals

abstract:
  We study the intersection of two independent renewal processes,
$\rho=\tau\cap\sigma$. Assuming that $\mathbf{P}(\tau_1 = n ) = \varphi(n)\,
n^{-(1+\alpha)}$ and $\mathbf{P}(\sigma_1 = n ) = \tilde\varphi(n)\, n^{-(1+
\tilde\alpha)} $ for some $\alpha,\tilde \alpha \geq 0$ and some slowly varying
$\varphi,\tilde\varphi$, we give the asymptotic behavior first of
$\mathbf{P}(\rho_1>n)$ (which is straightforward except in the case of
$\min(\alpha,\tilde\alpha)=1$) and then of $\mathbf{P}(\rho_1=n)$. The result
may be viewed as a kind of reverse renewal theorem, as we determine
probabilities $\mathbf{P}(\rho_1=n)$ while knowing asymptotically the renewal
mass function
$\mathbf{P}(n\in\rho)=\mathbf{P}(n\in\tau)\mathbf{P}(n\in\sigma)$. Our results
can be used to bound coupling-related quantities, specifically the increments
$|\mathbf{P}(n\in\tau)-\mathbf{P}(n-1\in\tau)|$ of the renewal mass function.


title: The Wilson Flow and the finite temperature phase transition

abstract:
  We consider the determination of the finite temperature phase transition in
the Yang--Mills SU(3) gauge theory. We compute the difference of the spatial
and temporal energy density at a physical Wilson flow time. This difference is
zero in the confined phase and becomes non zero in the deconfined phase. We
locate the phase transition by using a new technique based on an exponential
smoothing spline. This method is an alternative to the determination of the
phase transition based on the Polyakov loop susceptibility and can also be used
with dynamical fermions.


title: Compressed sensing of data with a known distribution

abstract:
  Compressed sensing is a technique for recovering an unknown sparse signal
from a small number of linear measurements. When the measurement matrix is
random, the number of measurements required for perfect recovery exhibits a
phase transition: there is a threshold on the number of measurements after
which the probability of exact recovery quickly goes from very small to very
large. In this work we are able to reduce this threshold by incorporating
statistical information about the data we wish to recover. Our algorithm works
by minimizing a suitably weighted $\ell_1$-norm, where the weights are chosen
so that the expected statistical dimension of the corresponding descent cone is
minimized. We also provide new discrete-geometry-based Monte Carlo algorithms
for computing intrinsic volumes of such descent cones, allowing us to bound the
failure probability of our methods.


title:
On Existence of $L^2$-solutions of Coupled Boltzmann Continuous Slowing
  Down Transport Equation System

abstract:
  The paper considers a coupled system of linear Boltzmann transport equations
(BTE), and its Continuous Slowing Down Approximation (CSDA). This system can be
used to model the relevant transport of particles used e.g. in dose calculation
in radiation therapy. The evolution of charged particles (e.g. electrons and
positrons) are in practice often modelled using the CSDA version of BTE because
of the so-called forward peakedness of scattering events contributing to the
particle fluencies (or particle densities), which causes severe problems in
numerical methods. We shall find, after the preliminary treatments, that for
some interactions CSDA-type modelling is actually necessary due to
hyper-singularities in the differential cross-sections of certain interactions,
that is, first or second order partial derivatives with respect to energy and
angle must be included into the transport part of charged particles. The
existence and uniqueness of (weak) solutions is shown, under sufficient
criteria and in appropriate $L^2$-based spaces, for a single (particle)
CSDA-equation by using three techniques, the Lions-Lax-Milgram Theorem
(variational approach), the theory of $m$-dissipative operators and the theory
evolution operators (semigroup approach). The due a priori estimates are
derived and the positivity of solutions are retrieved. In addition, we prove
the corresponding results and estimates for the system of coupled transport
equations. The related existence results are given for the adjoint problem as
well. We also give some computational points (e.g. certain explicit formulas),
and we outline a related inverse problem at the end of the paper.


title: Chaplygin-gas Solutions of f(R) Gravity

abstract:
  We explore exact f(R) gravity solutions that mimic Chaplygin-gas inspired
LCDM cosmology. Starting with the original and modified Chaplygin gas equations
of state, we reconstruct the forms of f(R) Lagrangians. The resulting solutions
are generally quadratic in the Ricci scalar, but have appropriate LCDM
solutions in limiting cases. These solutions, given appropriate initial
conditions, can be potential candidates for scalar field-driven early universe
expansion (inflation) and dark energy-driven late-time cosmic acceleration.


title: Local limit theorems and renewal theory with no moments

abstract:
  We study i.i.d. sums $\tau_k$ of nonnegative variables with index $0$: this
means $\mathbf{P}(\tau_1=n) = \varphi(n) n^{-1}$, with $\varphi(\cdot)$ slowly
varying, so that $\mathbf{E}(\tau_1^\varepsilon)=\infty$ for all
$\varepsilon>0$. We prove a local limit and local (upward) large deviation
theorem, giving the asymptotics of $\mathbf{P}(\tau_k=n)$ when $n$ is at least
the typical length of $\tau_k$. A recent renewal theorem by Nagaev [21] is an
immediate consequence: $\mathbf{P}(n\in\tau) \sim
\mathbf{P}(\tau_1=n)/\mathbf{P}(\tau_1 > n)^2$ as $n\to\infty$. If instead we
only assume regular variation of $\mathbf{P}(n\in\tau)$ and slow variation of
$U_n:= \sum_{k=0}^n \mathbf{P}(k\in\tau)$, we obtain a similar equivalence but
with $\mathbf{P}(\tau_1=n)$ replaced by its average over a short interval. We
give an application to the local asymptotics of the distribution of the first
intersection of two independent renewals. We further derive downward moderate
and large deviations estimates, that is, the asymptotics of $\mathbf{P}(\tau_k
\leq n)$ when $n$ is much smaller than the typical length of $\tau_k$.


title: Spotting deviations from R^2 inflation

abstract:
  We discuss the soundness of inflationary scenarios in theories beyond the
Starobinsky model, namely a class of theories described by arbitrary functions
of the Ricci scalar and the K-essence field. We discuss the pathologies
associated with higher-order equations of motion which will be shown to
constrain the stability of this class of theories. We provide a general
framework to calculate the slow-roll parameters and the corresponding mappings
to the theory parameters. For paradigmatic gravitational models within the
class of theories under consideration we illustrate the power of the
Planck/Bicep2 latest results to constrain such gravitational Lagrangians.
Finally, bounds for potential deviations from Starobinsky-like inflation are
derived.


title:
Inference for dynamics of continuous variables: the Extended Plefka
  Expansion with hidden nodes

abstract:
  We consider the problem of a subnetwork of observed nodes embedded into a
larger bulk of unknown (i.e. hidden) nodes, where the aim is to infer these
hidden states given information about the subnetwork dynamics. The biochemical
networks underlying many cellular and metabolic processes are important
realizations of such a scenario as typically one is interested in
reconstructing the time evolution of unobserved chemical concentrations
starting from the experimentally more accessible ones. We present an
application to this problem of a novel dynamical mean field approximation, the
Extended Plefka Expansion, which is based on a path integral description of the
stochastic dynamics. As a paradigmatic model we study the stochastic linear
dynamics of continuous degrees of freedom interacting via random Gaussian
couplings. The resulting joint distribution is known to be Gaussian and this
allows us to fully characterize the posterior statistics of the hidden nodes.
In particular the equal-time hidden-to-hidden variance -- conditioned on
observations -- gives the expected error at each node when the hidden time
courses are predicted based on the observations. We assess the accuracy of the
Extended Plefka Expansion in predicting these single node variances as well as
error correlations over time, focussing on the role of the system size and the
number of observed nodes.


title: Symplectic $n$-level densities with restricted support

abstract:
  In this paper we demonstrate that the alternative form, derived by us in an
earlier paper, of the $n$-level densities for eigenvalues of matrices from the
classical compact group $USp(2N)$ is far better suited for comparison with
derivations of the $n$-level densities of zeros in the family of Dirichlet
$L$-functions associated with real quadratic characters than the traditional
determinantal random matrix formula. Previous authors have found ingenious
proofs that the leading order term of the $n$-level density of the zeros agrees
with the determinantal random matrix result under certain conditions, but here
we show that comparison is more straightforward if the more suitable form of
the random matrix result is used. For the support of the test function in
$[1,-1]$ and in $[-2,2]$ we compare with existing number theoretical results.
For support in $[-3,3]$ no rigorous number theoretical result is known for the
$n$-level densities, but we derive the densities here using random matrix
theory in the hope that this may make the path to a rigorous number theoretical
result clearer.


title:
Conferencing in Wyner's Asymmetric Interference Network: Effect of
  Number of Rounds

abstract:
  Our goal is to study the effect of the number of conferencing rounds on the
capacity of large interference networks. We do this at hand of the per-user
multiplexing gain (MG) of Wyner's soft-handoff model with dedicated
conferencing links between neighbouring transmitters and receivers. We present
upper and lower bounds on the per-user MG of this network, which depend on the
capacities of the transmitter- and receiver-conferencing links and on the
number of allowed conferencing rounds. The bounds are tight when: the prelogs
of the conferencing links are small or high; there is only transmitter
conferencing or only receiver conferencing; or some symmetry conditions between
transmitter-conferencing and receiver-conferencing hold. We also determine the
per-user MG of the network when the number of conferencing rounds is unlimited.
Our results show that for small conferencing prelogs around 1/6, a single
conferencing round suffices to attain the maximum per-user MG when the number
of conferencing rounds is unconstrained. In contrast, when the prelogs are
large, then every additional conferencing round increases the maximum per-user
MG.


title: A 15-vertex triangulation of the quaternionic projective plane

abstract:
  In 1992, Brehm and K\"uhnel constructed a 8-dimensional simplicial complex
$M^8_{15}$ with 15 vertices as a candidate to be a minimal triangulation of the
quaternionic projective plane. They managed to prove that it is a manifold
"like a projective plane" in the sense of Eells and Kuiper. However, it was not
known until now if this complex is PL homeomorphic (or at least homeomorphic)
to $\mathbb{H}P^2$. This problem was reduced to the computation of the first
rational Pontryagin class of this combinatorial manifold. Realizing an
algorithm due to Gaifullin, we compute the first Pontryagin class of
$M^8_{15}$. As a result, we obtain that it is indeed a minimal triangulation of
$\mathbb{H}P^2$.


title:
The ultraluminous X-ray source NGC 5643 ULX1: a large stellar mass black
  hole accreting at super-Eddington rates?

abstract:
  A sub-set of the brightest ultraluminous X-ray sources (ULXs), with X-ray
luminosities well above $10^{40}$ erg s$^{-1}$, typically have energy spectra
which can be well described as hard power-laws, and short-term variability in
excess of $\sim10\%$. This combination of properties suggests that these ULXs
may be some of the best candidates to host intermediate mass black holes
(IMBHs), which would be accreting at sub-Eddington rates in the hard state seen
in Galactic X-ray binaries. In this work, we present a temporal and spectral
analysis of all of the available XMM-Newton data from one such ULX, the
previously poorly studied 2XMM J143242.1$-$440939, located in NGC 5643. We
report that its high quality EPIC spectra can be better described by a broad,
thermal component, such as an advection dominated disc or an optically thick
Comptonising corona. In addition, we find a hint of a marginal change in the
short-term variability which does not appear to be clearly related to the
source unabsorbed luminosity. We discuss the implications of these results,
excluding the possibility that the source may be host an IMBH in a low state,
and favouring an interpretation in terms of super-Eddington accretion on to a
black hole of stellar origin. The properties of NGC 5643 ULX1 allow us to
associate this source to the population of the hard/ultraluminous ULX class.


title: On irrationality of surfaces in $\mathbb{P}^3$

abstract:
  The degree of irrationality $irr(X)$ of a $n$-dimensional complex projective
variety $X$ is the least degree of a dominant rational map $X\dashrightarrow
\mathbb{P}^n$. It is a well-known fact that given a product $X\times
\mathbb{P}^m$ or a $n$-dimensional variety $Y$ dominating $X$, their degrees of
irrationality may be smaller than the degree of irrationality of $X$. In this
paper, we focus on smooth surfaces $S\subset\mathbb{P}^3$ of degree $d\geq 5$,
and we prove that $irr(S\times\mathbb{P}^{m})=irr(S)$ for any positive integer
$m$, whereas $irr(Y)<irr(S)$ occurs for some $Y$ dominating $S$ if and only if
$S$ contains a rational curve.


title:
Accelerating Deep Neural Network Training with Inconsistent Stochastic
  Gradient Descent

abstract:
  SGD is the widely adopted method to train CNN. Conceptually it approximates
the population with a randomly sampled batch; then it evenly trains batches by
conducting a gradient update on every batch in an epoch. In this paper, we
demonstrate Sampling Bias, Intrinsic Image Difference and Fixed Cycle Pseudo
Random Sampling differentiate batches in training, which then affect learning
speeds on them. Because of this, the unbiased treatment of batches involved in
SGD creates improper load balancing. To address this issue, we present
Inconsistent Stochastic Gradient Descent (ISGD) to dynamically vary training
effort according to learning statuses on batches. Specifically ISGD leverages
techniques in Statistical Process Control to identify a undertrained batch.
Once a batch is undertrained, ISGD solves a new subproblem, a chasing logic
plus a conservative constraint, to accelerate the training on the batch while
avoid drastic parameter changes. Extensive experiments on a variety of datasets
demonstrate ISGD converges faster than SGD. In training AlexNet, ISGD is
21.05\% faster than SGD to reach 56\% top1 accuracy under the exactly same
experiment setup. We also extend ISGD to work on multiGPU or heterogeneous
distributed system based on data parallelism, enabling the batch size to be the
key to scalability. Then we present the study of ISGD batch size to the
learning rate, parallelism, synchronization cost, system saturation and
scalability. We conclude the optimal ISGD batch size is machine dependent.
Various experiments on a multiGPU system validate our claim. In particular,
ISGD trains AlexNet to 56.3% top1 and 80.1% top5 accuracy in 11.5 hours with 4
NVIDIA TITAN X at the batch size of 1536.


title: Optimal probe states for the estimation of Gaussian unitary channels

abstract:
  We construct a practical method for finding optimal Gaussian probe states for
the estimation of parameters encoded by Gaussian unitary channels. This method
can be used for finding all optimal probe states, rather than focusing on the
performance of specific states as shown in previous studies. As an example, we
apply this method to find optimal probes for the channel that combines the
phase-change and squeezing channels, and for generalized two-mode squeezing and
mode-mixing channels. The method enables a comprehensive study of temperature
effects in Gaussian parameter estimation. It has been shown that the precision
in parameter estimation using single mode states can be enhanced by increasing
the temperature of the probe. We show that not only higher temperature, but
also larger temperature differences between modes of a Gaussian probe state can
enhance the estimation precision.


title:
General considerations on the nature of $Z_b(10610)$ and $Z_b(10650)$
  from their pole positions

abstract:
  The nature of the bottomonium-like states $Z_b(10610)$ and $Z_b(10650)$ is
studied by calculating the $B^{(*)}\overline B^{*}$ compositeness ($X$) in
those resonances. We first consider uncoupled isovector $S$-wave scattering of
$B^{(*)}\overline B^{*}$ within the framework of effective-range expansion
(ERE). Expressions for the scattering length ($a$) and effective range ($r$)
are derived exclusively in terms of the masses and widths of the two $Z_b$
states. We then develop compositeness within ERE for the resonance case and
deduce the expression $X=1/\sqrt{2r/a-1}$, which is then applied to the systems
of interest. Finally, the actual compositeness parameters are calculated in
terms of resonance pole positions and their experimental branching ratios into
$B^{(*)}\overline{B}^*$ by using the method of Ref.[1]. We find the values
$X=0.66\pm 0.11$ and $0.51\pm 0.10$ for the $Z_b(10610)$ and $Z_b(10650)$,
respectively. We also compare the ERE with Breit-Wigner and Flatt\'e
parameterizations to discuss the applicability of the last two ones for
near-threshold resonances with explicit examples.


title: A complete overhaul of the EELS and XAS database: eelsdb.eu

abstract:
  The Electron Energy-Loss Spectroscopy (EELS) and X-ray Absorption
Spectroscopy (XAS) database has been completely rewritten, with an improved
design, user interface and a number of new tools. The database is accessible at
https://eelsdb.eu/ and can now be used without registration. The submission
process has been streamlined to encourage spectrum submissions and the new
design gives greater emphasis on contributors original work by highlighting
their papers. With numerous new filters and a powerful search function, it is
now simple to explore the database of several hundred of EELS and XAS spectra.
Interactive plots allow spectra to be overlaid, facilitating online comparison.
An application-programming interface has been created, allowing external tools
and software to easily access the information held within the database. In
addition to the database itself, users can post and manage job adverts and read
the latest news and events regarding the EELS and XAS communities. In
accordance with the ongoing drive towards open access data increasingly
demanded by funding bodies, the database will facilitate open access data
sharing of EELS and XAS spectra.


title: Conformality and $Q$-harmonicity in sub-Riemannian manifolds

abstract:
  We prove the equivalence of several natural notions of conformal maps between
sub-Riemannian manifolds. Our main contribution is in the setting of those
manifolds that support a suitable regularity theory for subelliptic
$p$-Laplacian operators. For such manifolds we prove a Liouville-type theorem,
i.e., 1-quasiconformal maps are smooth. In particular, we prove that contact
manifolds support the suitable regularity. The main new technical tools are a
sub-Riemannian version of p-harmonic coordinates and a technique of propagation
of regularity from horizontal layers.


title:
Quantification of Uncertainties in Turbulence Modeling: A Comparison of
  Physics-Based and Random Matrix Theoretic Approaches

abstract:
  Numerical models based on Reynolds-Averaged Navier-Stokes (RANS) equations
are widely used in engineering turbulence modeling. However, the RANS
predictions have large model-form uncertainties for many complex flows.
Quantification of these large uncertainties originating from the modeled
Reynolds stresses has attracted attention in turbulence modeling community.
Recently, a physics-based Bayesian framework for quantifying model-form
uncertainties has been proposed with successful applications to several flows.
Nonetheless, how to specify proper priors without introducing unwarranted,
artificial information remains challenging to the current form of the
physics-based approach. Another recently proposed method based on random matrix
theory provides the prior distributions with the maximum entropy, which is an
alternative for model-form uncertainty quantification in RANS simulations. In
this work, we utilize the random matrix theoretic approach to assess and
possibly improve the specification of priors used in the physics-based
approach. The numerical results show that, to achieve maximum entropy in the
prior of Reynolds stresses, the perturbations of shape parameters in
Barycentric coordinates are normally distributed. Moreover, the perturbations
of the turbulence kinetic energy should conform to log-normal distributions.
Finally, it sheds light on how large the variance of each physical variable
should be compared with each other to achieve the approximate maximum entropy
prior. The conclusion can be used as a guidance for specifying proper priors in
the physics-based, Bayesian uncertainty quantification framework.


title: On spectral cover equations in Simpson integrable systems

abstract:
  Following Simpson we consider the integrable system structure on the moduli
spaces of Higgs bundles on a compact K\"ahler manifold $X$. We propose a
description of the corresponding spectral cover of $X$ as the fiberwise
projective dual to a hypersurface in the projectivization
$\mathbb{P}(\mathcal{T}_{X} \oplus \mathcal{O}_X)$ of the tangent bundle
$\mathcal{T}_X$ to $X$. The defining equation of the hypersurface dual to the
Simpson spectral cover is explicitly constructed in terms of the Higgs fields.


title:
Projectors and seed conformal blocks for traceless mixed-symmetry
  tensors

abstract:
  In this paper we derive the projectors to all irreducible SO(d)
representations (traceless mixed-symmetry tensors) that appear in the partial
wave decomposition of a conformal correlator of four stress-tensors in d
dimensions. These projectors are given in a closed form for arbitrary length
$l_1$ of the first row of the Young diagram. The appearance of Gegenbauer
polynomials leads directly to recursion relations in $l_1$ for seed conformal
blocks. Further results include a differential operator that generates the
projectors to traceless mixed-symmetry tensors and the general normalization
constant of the shadow operator.


title: Radial expansion for spinning conformal blocks

abstract:
  This paper develops a method to compute any bosonic conformal block as a
series expansion in the optimal radial coordinate introduced by Hogervorst and
Rychkov. The method reduces to the known result when the external operators are
all the same scalar operator, but it allows to compute conformal blocks for
external operators with spin. Moreover, we explain how to write closed form
recursion relations for the coefficients of the expansions. We study three
examples of four point functions in detail: one vector and three scalars; two
vectors and two scalars; two spin 2 tensors and two scalars. Finally, for the
case of two external vectors, we also provide a more efficient way to generate
the series expansion using the analytic structure of the blocks as a function
of the scaling dimension of the exchanged operator.


title: Non-backtracking random walks and a weighted Ihara's theorem

abstract:
  We study the mixing rate of non-backtracking random walks on graphs by
looking at non-backtracking walks as walks on the directed edges of a graph. A
result known as Ihara's Theorem relates the adjacency matrix of a graph to a
matrix related to non-backtracking walks on the directed edges. We prove a
weighted version of Ihara's Theorem which relates the transition probability
matrix of a non-backtracking walk to the transition matrix for the usual random
walk. This allows us to determine the spectrum of the transition probability
matrix of a non-backtracking random walk in the case of regular graphs and
biregular graphs. As a corollary, we obtain a result of Alon et. al. that in
most cases, a non-backtracking random walk on a regular graph has a faster
mixing rate than the usual random walk. In addition, we obtain an analogous
result for biregular graphs.


title:
Multiplicity results and sign changing solutions of non-local equations
  with concave-convex nonlinearities

abstract:
  In this paper we prove the existence of infinitely many nontrivial solutions
of the following equations driven by a nonlocal integro-differential operator
$L_K$ with concave-convex nonlinearities and homogeneous Dirichlet boundary
conditions \begin{eqnarray*}
  \mathcal{L}_{K} u + \mu\, |u|^{q-1}u + \lambda\,|u|^{p-1}u &=& 0
\quad\text{in}\quad \Omega, \\[2mm]
  u&=&0 \quad\mbox{in}\quad\mathbb{R}^N\setminus\Omega,
  \end{eqnarray*} where $\Omega$ is a smooth bounded domain in $\mathbb{R}^N$,
$N>2s$, $s\in(0, 1)$, $0<q<1<p\leq \frac{N+2s}{N-2s}$. Moreover, when $L_K$
reduces to the fractional laplacian operator $-(-\Delta)^s $,
$p=\frac{N+2s}{N-2s}$, $\frac{1}{2}(\frac{N+2s}{N-2s})<q<1$, $N>6s$,
$\lambda=1$, we find $\mu^*>0$ such that for any $\mu\in(0,\mu^*)$, there
exists at least one sign changing solution.


title: The Wide-Angle Outflow of the Lensed z = 1.51 AGN HS 0810+2554

abstract:
  We present results from X-ray observations of the gravitationally lensed z =
1.51 AGN HS 0810+2554 performed with the Chandra X-ray Observatory and
XMM-Newton. Blueshifted absorption lines are detected in both observations at
rest-frame energies ranging between ~1-12 keV at > 99% confidence. The inferred
velocities of the outflowing components range between ~0.1c and ~0.4c. A strong
emission line at ~6.8 keV accompanied by a significant absorption line at ~7.8
keV is also detected in the Chandra observation. The presence of these lines is
a characteristic feature of a P-Cygni profile supporting the presence of an
expanding outflowing highly ionized iron absorber in this quasar. Modeling of
the P-Cygni profile constrains the covering factor of the wind to be > 0.6,
assuming disk shielding. A disk-reflection component is detected in the
XMM-Newton observation accompanied by blueshifted absorption lines. The
XMM-Newton observation constrains the inclination angle to be < 45 degrees at
90% confidence, assuming the hard excess is due to blurred reflection from the
accretion disk. The detection of an ultrafast and wide-angle wind in an AGN
with intrinsic narrow absorption lines (NALs) would suggest that quasar winds
may couple efficiently with the intergalactic medium and provide significant
feedback if ubiquitous in all NAL and BAL quasars. We estimate the mass-outflow
rate of the absorbers to lie in the range of 1.5 and 3.4 Msolar/yr for the two
observations. We find the fraction of kinetic to electromagnetic luminosity
released by HS 0810+2554 is large (epsilon = 9 (-6,+8)) suggesting that
magnetic driving is likely a significant contributor to the acceleration of
this outflow.


title: Simultaneous stationary reflection and square sequences

abstract:
  We investigate the relationship between weak square principles and
simultaneous reflection of stationary sets.


title:
Dynamic Modularity Approach to Adaptive Inner/Outer Loop Control of
  Robotic Systems

abstract:
  Modern applications of robotics typically involve a robot control system with
an inner PI (proportional-integral) or PID (proportional-integral-derivative)
control loop and an outer user-specified control loop. The existing outer loop
controllers, however, do not take into consideration the dynamic effects of
robots and their effectiveness relies on the ad hoc assumption that the inner
PI or PID control loop is fast enough, and other torque-based control
algorithms cannot be implemented in robotics with closed architecture. This
paper investigates the adaptive control of robotic systems with an inner/outer
loop structure, taking into full account the effects of the dynamics and the
system uncertainties, and both the task-space control and joint-space control
are considered. We propose a dynamic modularity approach to resolve this issue,
and a class of adaptive outer loop control schemes is proposed and their role
is to dynamically generate the joint velocity (or position) command for the
low-level joint servoing loop. Without relying on the ad hoc assumption that
the joint servoing is fast enough or the modification of the low-level joint
controller structure, we rigorously show that the proposed outer loop
controllers can ensure the stability and convergence of the closed-loop system.
We also propose the outer loop versions of several standard joint-space
direct/composite adaptive controllers for rigid or flexible-joint robots, and a
promising conclusion may be that most torque-based adaptive controllers for
robots can be designed to fit the inner/outer loop structure by using the new
definition of the joint velocity (or position) command. Simulation results are
provided to show the performance of various adaptive outer loop controllers,
using a three-DOF (degree-of-freedom) manipulator, and experiment results using
the UR10 robotic system are also presented.


title:
Observation of charge density wave order in 1D mirror twin boundaries of
  single-layer MoSe2

abstract:
  Properties of two-dimensional transition metal dichalcogenides are highly
sensitive to the presence of defects in the crystal structure. A detailed
understanding of defect structure may lead to control of material properties
through defect engineering. Here we provide direct evidence for the existence
of isolated, one-dimensional charge density waves at mirror twin boundaries in
single-layer MoSe2. Our low-temperature scanning tunneling
microscopy/spectroscopy measurements reveal a substantial bandgap of 60 - 140
meV opening at the Fermi level in the otherwise one dimensional metallic
structure. We find an energy-dependent periodic modulation in the density of
states along the mirror twin boundary, with a wavelength of approximately three
lattice constants. The modulations in the density of states above and below the
Fermi level are spatially out of phase, consistent with charge density wave
order. In addition to the electronic characterization, we determine the atomic
structure and bonding configuration of the one-dimensional mirror twin boundary
by means of high-resolution non-contact atomic force microscopy. Density
functional theory calculations reproduce both the gap opening and the
modulations of the density of states.


title:
Representations of Gaussian random fields and approximation of elliptic
  PDEs with lognormal coefficients

abstract:
  Approximation of elliptic PDEs with random diffusion coefficients typically
requires a representation of the diffusion field in terms of a sequence
$y=(y_j)_{j\geq 1}$ of scalar random variables. One may then apply
high-dimensional approximation methods to the solution map $y\mapsto u(y)$.
Although Karhunen-Lo\`eve representations are commonly used, it was recently
shown, in the relevant case of lognormal diffusion fields, that they do not
generally yield optimal approximation rates. Motivated by these results, we
construct wavelet-type representations of stationary Gaussian random fields
defined on bounded domains. The size and localization properties of these
wavelets are studied, and used to obtain polynomial approximation results for
the related elliptic PDE which outperform those achievable when using
Karhunen-Lo\`eve representations. Our construction is based on a periodic
extension of the random field, and the expansion on the domain is then obtained
by simple restriction. This makes the approach easily applicable even when the
computational domain of the PDE has a complicated geometry. In particular, we
apply this construction to the class of Gaussian processes defined by the
family of Mat\'ern covariances.


title: Discovery of molecular hydrogen in SN 1987A

abstract:
  Both CO and SiO have been observed at early and late phases in SN 1987A. H_2
was predicted to form at roughly the same time as these molecules, but was not
detected at early epochs. Here we report the detection of NIR lines from H_2 at
2.12 mu and 2.40 mu in VLT/SINFONI spectra obtained between days 6489 and
10,120. The emission is concentrated to the core of the supernova in contrast
to H-alpha and approximately coincides with the [Si I]/[Fe II] emission
detected previously in the ejecta. Different excitation mechanisms and power
sources of the emission are discussed. From the nearly constant H_2
luminosities we favour excitation resulting from the 44Ti decay.


title:
Weak and strong convergence of derivations and stability of flows with
  respect to MGH convergence

abstract:
  This paper is devoted to the study of weak and strong convergence of
derivations, and of the flows associated to them, when dealing with a sequence
of metric measure structures (X,d,m_n), m_n weakly convergent to m. In
particular, under curvature assumptions, either only on the limit metric
structure (X,d,m) or on the whole sequence of metric measure spaces, we provide
several stability results.


title: Monolayer MoSe2: A candidate for room temperature polaritonics

abstract:
  Monolayered MoSe2 is a promising new material to investigate advanced
light-matter coupling as it hosts stable and robust excitons with comparably
narrow optical resonances. In this work, we investigate the evolution of the
lowest lying excitonic transition, the so-called A-valley exciton, with
temperature. We find a strong, phonon-induced temperature broadening of the
resonance, and more importantly, a reduction of the oscillator strength for
increased temperatures. Based on these experimentally extracted, temperature
dependent parameters, we apply a coupled oscillator model to elucidate the
possibility to observe the strong coupling regime between the A-exciton and a
microcavity resonance in three prototypical photonic architectures with varying
mode volumes. We find that the formation of exciton-polaritons up to ambient
conditions in short, monolithic dielectric and Tamm-based structures seems
feasible. In contrast, a temperature-induced transition into the weak coupling
regime can be expected for structures with extended effective cavity length.
Based on these findings, we calculate and draw the phase diagram of polariton
Bosonic condensation in a MoSe2 cavity.


title:
TI tether rig for solving secular spinrate change problem of electric
  sail

abstract:
  The electric solar wind sail (E-sail) is a way to propel a spacecraft by
using the natural solar wind as a thrust source. The problem of secular
spinrate change was identified earlier which is due to the orbital Coriolis
effect and tends to slowly increase or decrease the sail's spinrate, depending
on which way the sail is inclined with respect to the solar wind. Here we
present an E-sail design and its associated control algorithm which enable
spinrate control during propulsive flight by the E-sail effect itself. In the
design, every other maintether ("T-tether") is galvanically connected through
the remote unit with the two adjacent auxtethers, while the other maintethers
("I-tethers") are insulated from the tethers. This enables one to effectively
control the maintether and auxtether voltages separately, which in turn enables
spinrate control. We use a detailed numerical simulation to show that the
algorithm can fully control the E-sail's spin state in real solar wind. The
simulation includes a simple and realistic set of controller sensors: an imager
to detect remote unit angular positions and a vector accelerometer. The imager
resolution requirement is modest and the accelerometer noise requirement is
feasible to achieve. The TI tether rig enables building E-sails that are able
to control their spin state fully and yet are actuated by pure tether voltage
modulation from the main spacecraft and requiring no functionalities from the
remote units during flight.


title: Phase field modeling of partially saturated deformable porous media

abstract:
  A poromechanical model of partially saturated deformable porous media is
proposed based on a phase field approach at modeling the behavior of the
mixture of liquid water and wet air, which saturates the pore space, the phase
field being the saturation (ratio). While the standard retention curve is
expected still to provide the intrinsic retention properties of the porous
skeleton, depending on the porous texture, an enhanced description of surface
tension between the wetting (liquid water) and the non-wetting (wet air) fluid,
occupying the pore space, is stated considering a regularization of the phase
field model based on an additional contribution to the overall free energy
depending on the saturation gradient. The aim is to provide a more refined
description of surface tension interactions.
  An enhanced constitutive relation for the capillary pressure is established
together with a suitable generalization of Darcy's law, in which the gradient
of the capillary pressure is replaced by the gradient of the so-called
generalized chemical potential, which also accounts for the \lq\lq
force\rq\rq\, associated to the local free energy of the phase field model. A
micro-scale heuristic interpretation of the novel constitutive law of capillary
pressure is proposed, in order to compare the envisaged model with that one
endowed with the concept of average interfacial area.
  The considered poromechanical model is formulated within the framework of
strain gradient theory in order to account for possible effects, at laboratory
scale, of the micro-scale hydro-mechanical couplings between highly-localized
flows (fingering) and localized deformations of the skeleton (fracturing).


title:
Fractional differentiability for solutions of nonlinear elliptic
  equations

abstract:
  We study nonlinear elliptic equations in divergence form
$${\operatorname{div}}{\mathcal A}(x,Du)={\operatorname{div}}G.$$ When
${\mathcal A}$ has linear growth in $Du$, and assuming that $x\mapsto{\mathcal
A}(x,\xi)$ enjoys $B^\alpha_{\frac{n}\alpha, q}$ smoothness, local
well-posedness is found in $B^\alpha_{p,q}$ for certain values of
$p\in[2,\frac{n}{\alpha})$ and $q\in[1,\infty]$. In the particular case
${\mathcal A}(x,\xi)=A(x)\xi$, $G=0$ and $A\in B^\alpha_{\frac{n}\alpha,q}$,
$1\leq q\leq\infty$, we obtain $Du\in B^\alpha_{p,q}$ for each
$p<\frac{n}\alpha$. Our main tool in the proof is a more general result, that
holds also if ${\mathcal A}$ has growth $s-1$ in $Du$, $2\leq s\leq n$, and
asserts local well-posedness in $L^q$ for each $q>s$, provided that
$x\mapsto{\mathcal A}(x,\xi)$ satisfies a locally uniform $VMO$ condition.


title: Growing networks of overlapping communities with internal structure

abstract:
  We introduce an intuitive model that describes both the emergence of
community structure and the evolution of the internal structure of communities
in growing social networks. The model comprises two complementary mechanisms:
One mechanism accounts for the evolution of the internal link structure of a
single community, and the second mechanism coordinates the growth of multiple
overlapping communities. The first mechanism is based on the assumption that
each node establishes links with its neighbors and introduces new nodes to the
community at different rates. We demonstrate that this simple mechanism gives
rise to an effective maximal degree within communities. This observation is
related to the anthropological theory known as Dunbar's number, i.e., the
empirical observation of a maximal number of ties which an average individual
can sustain within its social groups. The second mechanism is based on a
recently proposed generalization of preferential attachment to community
structure, appropriately called structural preferential attachment (SPA). The
combination of these two mechanisms into a single model (SPA+) allows us to
reproduce a number of the global statistics of real networks: The distribution
of community sizes, of node memberships and of degrees. The SPA+ model also
predicts (a) three qualitative regimes for the degree distribution within
overlapping communities and (b) strong correlations between the number of
communities to which a node belongs and its number of connections within each
community. We present empirical evidence that support our findings in real
complex networks.


title:
Search for QCD Instanton-Induced Processes at HERA in the High-$Q^2$
  Domain

abstract:
  Signals of QCD instanton-induced processes are searched for in neutral
current deep-inelastic scattering at the electron-proton collider HERA in the
kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the
inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$
GeV$^2$. The search is performed using H1 data corresponding to an integrated
luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD
instanton-induced events is observed. Upper limits on the cross section for
instanton-induced processes between $1.5$~pb and $6$~pb, at $95\%$~ confidence
level, are obtained depending on the kinematic domain in which instantons could
be produced. Compared to earlier publications, the limits are improved by an
order of magnitude and for the first time are challenging theory predictions.