title: A Perspicuous Description of the Schwarzschild Black Hole Geodesics

abstract:
  Schwarzschild black hole is the simplest black hole that is studied most in
detail. Its behavior is best understood by looking at the geodesics of the
particles under the influence of its gravitational field. In this paper, the
focus of attention is giving a perspicuous description of the Schwarzschild
geodesics by using analogue potential approach. Specifically we discuss
geodesics of light and of a massive particle in the case that their angular
momentum is non zero in the Schwarzschild spacetime. This discussion is done by
defining analogue potentials out of geodesic equations and defining relevant
dimensionless conserved quantities. Then, we designate how geodesics change in
response to the change of these quantities. Our results indicate the relation
between the particles' motion near black hole horizon and their angular
momentum. Furthermore, we make a comparison between Newtonian Physics (NP) and
General Relativity (GR) in the language of the analogue potential approach.


title: Production and interaction of the eta meson with nucleons and nuclei

abstract:
  We report on the status of the search for eta-mesic nuclei and the studies of
the interaction of the eta meson with nucleons. Recently we have completed the
analysis of the new WASA-at-COSY data on the production of the eta meson with
polarized proton beam. New results on the analyzing power for the pp->ppeta
reaction with more than an order of magnitude improved precision shed a new
light on the production mechanism of the eta meson in nucleon-nucleon
collisions. Also, the latest results of the search for eta-mesic nuclei are
discussed.


title: Solar neutrinos, helicity effects and new affine gravity with torsion II

abstract:
  The cross section for neutrino helicity spin-flip obtained from a new f(R, T)
model of gravitation with dynamic torsion field introduced by one of the
authors in [1], is phenomenologically analyzed. To this end, due to the
logarithmical energy dependence of the cross section, the relation with the
axion decay constant fa (Peccei-Quinn parameter) is used. Consequently the link
with the phenomenological energy/mass window is found from the astrophysical
and high energy viewpoints. The highest helicity spin-flip cross-sectional
values presented in this work coincide with a recent estimation on the axion
mass computed in [2] in the framework of finite temperature extended lattice
QCD and under cosmological considerations.


title: Thin II_1 factors with no Cartan subalgebras

abstract:
  It is a wide open problem to give an intrinsic criterion for a II_1 factor
$M$ to admit a Cartan subalgebra $A$. When $A \subset M$ is a Cartan
subalgebra, the $A$-bimodule $L^2(M)$ is "simple" in the sense that the left
and right action of $A$ generate a maximal abelian subalgebra of $B(L^2(M))$. A
II_1 factor $M$ that admits such a subalgebra $A$ is said to be s-thin. Very
recently, Popa discovered an intrinsic local criterion for a II_1 factor $M$ to
be s-thin and left open the question whether all s-thin II_1 factors admit a
Cartan subalgebra. We answer this question negatively by constructing s-thin
II_1 factors without Cartan subalgebras.


title: The cosmological principle is not in the sky

abstract:
  The homogeneity of matter distribution at large scales, known as the
cosmological principle, is a central assumption in the standard cosmological
model. The case is testable though, thus no longer needs to be a principle.
Here we perform a test for spatial homogeneity using the Sloan Digital Sky
Survey Luminous Red Galaxies (LRG) sample by counting galaxies within a
specified volume with the radius scale varying up to 300 Mpc/h. We directly
confront the large-scale structure data with the definition of spatial
homogeneity by comparing the averages and dispersions of galaxy number counts
with allowed ranges of the random distribution with homogeneity. The LRG sample
shows significantly larger dispersions of number counts than the random
catalogues up to 300 Mpc/h scale, and even the average is located far outside
the range allowed in the random distribution; the deviations are statistically
impossible to be realized in the random distribution. This implies that the
cosmological principle does not hold even at such large scales. The same
analysis of mock galaxies derived from the N-body simulation, however, suggests
that the LRG sample is consistent with the current paradigm of cosmology, thus
the simulation is also not homogeneous in that scale. We conclude that the
cosmological principle is not in the observed sky and nor is demanded to be
there by the standard cosmological world model. This reveals the nature of the
cosmological principle adopted in the modern cosmology paradigm, and opens new
field of research in theoretical cosmology.


title:
Effect of the orientational relaxation on the collective motion of
  patterns formed by self-propelled particles

abstract:
  We investigate the collective behavior of self-propelled particles (SPPs)
undergoing competitive processes of pattern formation and rotational relaxation
of their self-propulsion velocities. In full accordance with previous work, we
observe transitions between different steady states of the SPPs caused by the
intricate interplay among the involved effects of pattern formation,
orientational order, and coupling between the SPP density and orientation
fields. Based on rigorous analytical and numerical calculations, we prove that
the rate of the orientational relaxation of the SPP velocity field is the main
factor determining the steady states of the SPP system. Further, we determine
the boundaries between domains in the parameter plane that delineate
qualitatively different resting and moving states. In addition, we analytically
calculate the collective velocity $\vec{v}$ of the SPPs and show that it
perfectly agrees with our numerical results. We quantitatively demonstrate that
$\vec{v}$ does not vanish upon approaching the transition boundary between the
moving pattern and homogeneous steady states.


title:
Giant coronal loops dominate the quiescent X-ray emission in rapidly
  rotating M stars

abstract:
  Observations indicate that magnetic fields in rapidly rotating stars are very
strong, on both small and large scales. What is the nature of the resulting
corona? Here we seek to shed some light on this question. We use the results of
an anelastic dynamo simulation of a rapidly rotating fully-convective M-star to
drive a physics-based model for the stellar corona. We find that due to the
several kilo Gauss large-scale magnetic fields at high latitudes, the corona
and its X-ray emission are dominated by star-size large hot loops, while the
smaller, underlying colder loops are not visible much in the X-ray. Based on
this result we propose that, in rapidly rotating stars, emission from such
coronal structures dominates the quiescent, cooler but saturated X-ray
emission.


title: Logarithmic Tree Factorials

abstract:
  To any rooted tree, we associate a sequence of numbers that we call the
logarithmic factorials of the tree. This provides a generalization of
Bhargava's factorials to a natural combinatorial setting suitable for studying
questions around generalized factorials.
  We discuss several basic aspects of the framework in this paper. In
particular, we relate the growth of the sequence of logarithmic factorials
associated to a tree to the transience of the random walk and the existence of
a harmonic measure on the tree, obtain an equidistribution theorem for
factorial-determining-sequences of subsets of local fields, and provide a
factorial-based characterization of the branching number of infinite trees.
  Our treatment is based on a local weighting process in the tree which gives
an effective way of constructing the factorial sequence.


title:
A Dynamic Subgrid Scale Model for Large Eddy Simulations Based on the
  Mori-Zwanzig Formalism

abstract:
  The development of reduced models for complex multiscale problems remains one
of the principal challenges in computational physics. The optimal prediction
framework of Chorin et al., which is a reformulation of the Mori-Zwanzig (M-Z)
formalism of non-equilibrium statistical mechanics, provides a methodology for
the development of mathematically-derived reduced models of dynamical systems.
Several promising models have emerged from the optimal prediction community and
have found application in molecular dynamics and turbulent flows. In this work,
a new M-Z-based closure model that addresses some of the deficiencies of
existing methods is developed. The model is constructed by exploiting
similarities between two levels of coarse-graining via the Germano identity of
fluid mechanics and by assuming that memory effects have a finite temporal
support. The appeal of the proposed model, which will be referred to as the
`dynamic-MZ-$\tau$' model, is that it is parameter-free and has a structural
form imposed by the mathematics of the coarse-graining process (rather than the
phenomenological assumptions made by the modeler, such as in classical subgrid
scale models). To promote the applicability of M-Z models in general, two
procedures are presented to compute the resulting model form, helping to bypass
the tedious error-prone algebra that has proven to be a hindrance to the
construction of M-Z-based models for complex dynamical systems. While the new
formulation is applicable to the solution of general partial differential
equations, demonstrations are presented in the context of Large Eddy Simulation
closures for Burgers equation, decaying homogeneous turbulence, and turbulent
channel flow. The performance of the model and validity of the underlying
assumptions are investigated in detail.


title: Small-signal model for frequency analysis of thermoelectric systems

abstract:
  We show how small-signal analysis, a standard method in electrical
engineering, may be applied to thermoelectric device performance measurement by
extending a dc model to the dynamical regime. We thus provide a physical ground
to \textit{ad-hoc} models used to interpret impedance spectroscopy of
thermoelectric elements from an electrical circuit equivalent for
thermoelectric systems in the frequency domain. We particularly stress the
importance of the finite thermal impedance of the thermal contacts between the
thermoelectric system and the thermal reservoirs in the derivation of such
models. The expression for the characteristic angular frequency of the
thermoelectric system we obtain is a generalization of the expressions derived
in previous studies. In particular, it allows to envisage impedance
spectroscopy measurements beyond the restrictive case of adiabatic boundary
conditions often difficult to achieve experimentally, and hence \emph{in-situ}
characterization of thermoelectric generators.


title: Crowdsourcing in Computer Vision

abstract:
  Computer vision systems require large amounts of manually annotated data to
properly learn challenging visual concepts. Crowdsourcing platforms offer an
inexpensive method to capture human knowledge and understanding, for a vast
number of visual perception tasks. In this survey, we describe the types of
annotations computer vision researchers have collected using crowdsourcing, and
how they have ensured that this data is of high quality while annotation effort
is minimized. We begin by discussing data collection on both classic (e.g.,
object recognition) and recent (e.g., visual story-telling) vision tasks. We
then summarize key design decisions for creating effective data collection
interfaces and workflows, and present strategies for intelligently selecting
the most important data instances to annotate. Finally, we conclude with some
thoughts on the future of crowdsourcing in computer vision.


title: Eshelbian mechanics of novel materials: Quasicrystals

abstract:
  In this work, the so-called Eshelbian or configurational mechanics of
quasicrystals is presented. Quasicrystals are considered as a prototype of
novel materials. Material balance laws for quasicrystalline materials with
dislocations are derived in the framework of generalized incompatible
elasticity theory of quasicrystals. Translations, scaling transformations as
well as rotations are examined; the latter presents particular interest due to
the quasicrystalline structure. This derivation provides important quantities
of the Eshelbian mechanics, as the Eshelby stress tensor, the scaling flux
vector, the angular momentum tensor, the configurational forces (Peach-Koehler
force, Cherepanov force, inhomogeneity force or Eshelby force), the
configurational work and the configurational vector moments for dislocations in
quasicrystals. The corresponding $J$-, $M$-, and $L$-integrals for dislocation
loops and straight dislocations in quasicrystals are derived and discussed.
Moreover, the explicit formulas of the $J$-, $M$-, and $L$-integrals for
parallel screw dislocations in one-dimensional hexagonal quasicrystals are
obtained. Through this derivation, the physical interpretation of the $J$-,
$M$-, and $L$-integrals for dislocations in quasicrystals is revealed and their
connection to the Peach-Koehler force, the interaction energy and the
rotational vector moment (torque) of dislocations in quasicrystals is
established.


title:
Error-Bounded and Feature Preserving Surface Remeshing with Minimal
  Angle Improvement

abstract:
  The typical goal of surface remeshing consists in finding a mesh that is (1)
geometrically faithful to the original geometry, (2) as coarse as possible to
obtain a low-complexity representation and (3) free of bad elements that would
hamper the desired application. In this paper, we design an algorithm to
address all three optimization goals simultaneously. The user specifies desired
bounds on approximation error {\delta}, minimal interior angle {\theta} and
maximum mesh complexity N (number of vertices). Since such a desired mesh might
not even exist, our optimization framework treats only the approximation error
bound {\delta} as a hard constraint and the other two criteria as optimization
goals. More specifically, we iteratively perform carefully prioritized local
operators, whenever they do not violate the approximation error bound and
improve the mesh otherwise. In this way our optimization framework greedily
searches for the coarsest mesh with minimal interior angle above {\theta} and
approximation error bounded by {\delta}. Fast runtime is enabled by a local
approximation error estimation, while implicit feature preservation is obtained
by specifically designed vertex relocation operators. Experiments show that our
approach delivers high-quality meshes with implicitly preserved features and
better balances between geometric fidelity, mesh complexity and element quality
than the state-of-the-art.


title:
Molecular Water Lilies: Orienting Single Molecules in a Polymer Film by
  Solvent Vapor Annealing

abstract:
  The microscopic orientation and position of photoactive molecules is crucial
to the operation of optoelectronic devices such as OLEDs and solar cells. Here,
we introduce a shape-persistent macrocyclic molecule as an excellent
fluorescent probe to simply measure (i) its orientation by rotating the
excitation polarization and recording the strength of modulation in
photoluminescence (PL), and (ii) its position in a film by analyzing the
overall PL brightness at the molecular level. The unique shape, the absorption
and the fluorescence properties of this probe yields information on molecular
orientation and position. We control orientation and positioning of the probe
in a polymer film by solvent vapor annealing (SVA). During the SVA process the
molecules accumulate at the polymer/air interface, where they adopt a flat
conformation, much like water lilies on the surface of a pond. The results are
significant for OLED fabrication and single-molecule spectroscopy (SMS) in
general.


title:
The fourth dimension of the nucleon structure: spacetime analysis of the
  timelike electromagnetic proton form factors

abstract:
  As well known, spacelike proton form factors expressed in the Breit frame may
be interpreted as the Fourier transform of static space distributions of
electric charge and current. In particular, the electric form factor is simply
the Fourier transform of the charge distribution $F(q)=\int e^{i\vec q \cdot
\vec r} \rho(r)d^3r$. We don't have an intuitive interpretation of the same
level of simplicity for the proton timelike form factor appearing in the
reactions $e^+e^-\leftrightarrow \bar{p}p$. However, one may suggest that in
the center of mass (CM) frame, where $q_\mu x^\mu =qt$, a timelike electric
form factor is the Fourier transform $F(q) =\int e^{iqt} R(t)dt$ of a function
$R(t)$ expressing how the electric properties of the forming (or annihilating)
proton-antiproton pair evolve in time. Here we analyze in depth this idea, show
that the functions $\rho(r)$ and $R(t)$ can be formally written as the time and
space integrals of a unique correlation function depending on both time and
space coordinates.


title:
Predicting Solvation Free Energies and Thermodynamics in Polar Solvents
  and Mixtures Using a Solvation-Layer Interface Condition

abstract:
  We demonstrate that with two small modifications, the popular dielectric
continuum model is capable of predicting, with high accuracy, ion solvation
thermodynamics in numerous polar solvents, and ion solvation free energies in
water--co-solvent mixtures. The first modification involves perturbing the
macroscopic dielectric-flux interface condition at the solute--solvent
interface with a nonlinear function of the local electric field, giving what we
have called a solvation-layer interface condition (SLIC). The second
modification is a simple treatment of the microscopic interface potential
(static potential). We show that the resulting model exhibits high accuracy
without the need for fitting solute atom radii in a state-dependent fashion.
Compared to experimental results in nine water--co-solvent mixtures, SLIC
predicts transfer free energies to within 2.5 kJ/mol. The co-solvents include
both protic and aprotic species, as well as biologically relevant denaturants
such as urea and dimethylformamide. Furthermore, our results indicate that the
interface potential is essential to reproduce entropies and heat capacities.
The present work, together with previous studies of SLIC illustrating its
accuracy for biomolecules in water, indicates it as a promising dielectric
continuum model for accurate predictions of molecular solvation in a wide range
of conditions.


title: Bosonization of Fermionic Fields and Fermionization of Bosonic Fields

abstract:
  In this paper using the Clifford and spin-Clifford bundles formalism we show
how Weyl and Dirac equations formulated in the spin-Clifford bundle may be
written in an equivalent form as generalized Maxwell like form formulated in
the Clifford bundle. Moreover, we show how Maxwell equation formulated in the
Clifford bundle formalism can be written as an equivalent equation for a spinor
field in the spin-Cillford bundle. Investigating the details of such
equivalences this exercise shows explicitly that a fermionic field is
equivalent (in a precise sense) to an equivalence class of well defined boson
fields and that a bosonic field is equivalent to a well defined equivalence
class of fermionic fields These equivalences may be called the bosonization of
fermionic fields and the fermionization of bosonic fields.


title: Dynamics of the photosphere along the solar cycle from SDO/HMI

abstract:
  As the global magnetic field of the Sun has an activity cycle, one expects to
observe some variation of the dynamical properties of the flows visible in the
photosphere. We investigate the flow field during the solar cycle by analysing
SDO/HMI observations of continuum intensity, Doppler velocity and longitudinal
magnetic field. We first picked data at disk center during 6 years along the
solar cycle with a 48-hour time step in order to study the overall evolution of
the continuum intensity and magnetic field. Then we focused on thirty 6-hour
sequences of quiet regions without any remnant of magnetic activity separated
by 6 months, in summer and winter, when disk center latitude B0 is close to
zero. The horizontal velocity was derived from the local correlation tracking
technique over a field of view of 216.4Mm x 216.4Mm located at disk center. Our
measurements at disk center show the stability of the flow properties between
meso- and supergranular scales along the solar cycle. The network magnetic
field, produced locally at disk center independently from large scale dynamo,
together with continuum contrast, vertical and horizontal flows, seem to remain
constant during the solar cycle.


title:
Fabrication of polarization-independent waveguides deeply buried in
  crystal using aberration-corrected femtosecond laser direct writing

abstract:
  Writing optical waveguides with femtosecond laser pulses provides the
capability of forming three-dimensional photonic circuits for manipulating
light fields in both linear and nonlinear manners. To fully explore this
potential, large depths of the buried waveguides in transparent substrates are
often desirable to facilitate achieving vertical integration of waveguides in a
multi-layer configuration, which, however, is hampered by rapidly degraded
axial resolution caused by optical aberration. Here, we show that with the
correction of the spherical aberration, polarization-independent waveguides can
be inscribed in a nonlinear optical crystal lithium niobate (LN) at depths up
to 1.4 mm, which is more than one order of magnitude deeper than the waveguides
written with aberration uncorrected femtosecond laser pulses. Our technique is
beneficial for applications ranging from miniaturized nonlinear light sources
to quantum information processing.


title:
Bayesian Non-parametric model to Target Gamification Notifications Using
  Big Data

abstract:
  I suggest an approach that helps the online marketers to target their
Gamification elements to users by modifying the order of the list of tasks that
they send to users. It is more realistic and flexible as it allows the model to
learn more parameters when the online marketers collect more data. The
targeting approach is scalable and quick, and it can be used over streaming
data.


title: Spatiotemporal Residual Networks for Video Action Recognition

abstract:
  Two-stream Convolutional Networks (ConvNets) have shown strong performance
for human action recognition in videos. Recently, Residual Networks (ResNets)
have arisen as a new technique to train extremely deep architectures. In this
paper, we introduce spatiotemporal ResNets as a combination of these two
approaches. Our novel architecture generalizes ResNets for the spatiotemporal
domain by introducing residual connections in two ways. First, we inject
residual connections between the appearance and motion pathways of a two-stream
architecture to allow spatiotemporal interaction between the two streams.
Second, we transform pretrained image ConvNets into spatiotemporal networks by
equipping these with learnable convolutional filters that are initialized as
temporal residual connections and operate on adjacent feature maps in time.
This approach slowly increases the spatiotemporal receptive field as the depth
of the model increases and naturally integrates image ConvNet design
principles. The whole model is trained end-to-end to allow hierarchical
learning of complex spatiotemporal features. We evaluate our novel
spatiotemporal ResNet using two widely used action recognition benchmarks where
it exceeds the previous state-of-the-art.


title:
Effect of the final state interaction of $\eta' N$ on the $\eta'$
  photoproduction off nucleon

abstract:
  We investigate the $\eta'$ photoproduction off the nucleon with a particular
interest in the effect of the final-state interaction (FSI) of the $\eta'$
meson and nucleon $(\eta'N)$ based on three-flavor linear sigma model. We find
an enhancement in the cross section of the $\eta'$ photoproduction near the
$\eta'N$-threshold energy owing to the $\eta'N$ FSI. With the $\eta'$ meson at
forward angles, the energy dependence near the $\eta'N$ threshold is well
reproduced with the $\eta'N$ FSI. The cross section at backward angles can also
be a good probe to investigate the strength of the $\eta'N$ interaction.


title: On Statistical Properties of Jizba-Arimitsu Hybrid Entropy

abstract:
  Jizba-Arimitsu entropy (also called hybrid entropy) combines axiomatics of
R\'enyi and Tsallis entropy. It has many common properties with them, on the
other hand, some aspects as e.g., MaxEnt distributions, are completely
different from the former two entropies. In this paper, we demonstrate the
statistical properties of hybrid entropy, including the definition of hybrid
entropy for continuous distributions, its relation to discrete entropy and
calculation of hybrid entropy for some well-known distributions. Additionally,
definition of hybrid divergence and its connection to Fisher metric is also
discussed. Interestingly, the main properties of continuous hybrid entropy and
hybrid divergence are completely different from measures based on R\'enyi and
Tsallis entropy. This motivates us to introduce average hybrid entropy, which
can be understood as an average between Tsallis and R\'enyi entropy.

categories: cond-mat.stat-mech math-ph math.MP stat.AP


title:
Phase matching alters spatial multiphoton processes in dense atomic
  ensembles

abstract:
  Multiphoton processes in dense atomic vapors such as four-wave mixing or
coherent blue light generation are typically viewed from single-atom
perspective. Here we study the surprisingly important effect of phase matching
near two-photon resonances that arises due to spatial extent of the atomic
medium within which the multiphoton process occurs. The non-unit refractive
index of the atomic vapor may inhibit generation of light in nonlinear
processes, significantly shift the efficiency maxima in frequencies and
redirect emitted beam. We present these effects on an example of four-wave
mixing in dense rubidium vapors in a double-ladder configuration. By deriving a
simple theory that takes into account essential spatial properties of the
process, we give precise predictions and confirm their validity in the
experiment. The model allows us to improve on the geometry of the experiment
and engineer more efficient four-wave mixing.


title:
A high numerical aperture (NA = 0.92) objective lens for imaging and
  addressing of cold atoms

abstract:
  We have designed, built, and characterized a high-resolution objective lens
that is compatible with an ultra-high vacuum environment. The lens system
exploits the principle of the Weierstrass-sphere solid immersion lens to reach
a numerical aperture (NA) of 0.92. Tailored to the requirements of optical
lattice experiments, the objective lens features a relatively long working
distance of 150 micrometers. Our two-lens design is remarkably insensitive to
mechanical tolerances in spite of the large NA. Additionally, we demonstrate
the application of a tapered optical fiber tip, as used in scanning near-field
optical microscopy, to measure the point spread function of a high NA optical
system. From the point spread function, we infer the wavefront aberration for
the entire field of view of about 75 micrometers. Pushing the NA of an optical
system to its ultimate limit enables novel applications in quantum technologies
such as quantum control of atoms in optical microtraps with an unprecedented
spatial resolution and photon collection efficiency.


title: Characterization of pinched Ricci curvature by functional inequalities

abstract:
  In this article, functional inequalities for diffusion semigroups on
Riemannian manifolds (possibly with boundary) are established, which are
equivalent to pinched Ricci curvature, along with gradient estimates,
$L^p$-inequalities and log-Sobolev inequalities. These results are further
extended to differential manifolds carrying geometric flows. As application, it
is shown that they can be used in particular to characterize general geometric
flow and Ricci flow by functional inequalities.


title:
The BRITE-Constellation Nanosatellite Space Mission And Its First
  Scientific Results

abstract:
  The BRIght Target Explorer (BRITE) Constellation is the first nanosatellite
mission applied to astrophysical research. Five satellites in low-Earth orbits
perform precise optical two-colour photometry of the brightest stars in the
night sky. BRITE is naturally well suited for variability studies of hot stars.
This contribution describes the basic outline of the mission and some initial
problems that needed to be overcome. Some information on BRITE data products,
how to access them, and how to join their scientific exploration is provided.
Finally, a brief summary of the first scientific results obtained by BRITE is
given.


title:
METAPHOR: A machine learning based method for the probability density
  estimation of photometric redshifts

abstract:
  A variety of fundamental astrophysical science topics require the
determination of very accurate photometric redshifts (photo-z's). A wide
plethora of methods have been developed, based either on template models
fitting or on empirical explorations of the photometric parameter space.
Machine learning based techniques are not explicitly dependent on the physical
priors and able to produce accurate photo-z estimations within the photometric
ranges derived from the spectroscopic training set. These estimates, however,
are not easy to characterize in terms of a photo-z Probability Density Function
(PDF), due to the fact that the analytical relation mapping the photometric
parameters onto the redshift space is virtually unknown. We present METAPHOR
(Machine-learning Estimation Tool for Accurate PHOtometric Redshifts), a method
designed to provide a reliable PDF of the error distribution for empirical
techniques. The method is implemented as a modular workflow, whose internal
engine for photo-z estimation makes use of the MLPQNA neural network (Multi
Layer Perceptron with Quasi Newton learning rule), with the possibility to
easily replace the specific machine learning model chosen to predict photo-z's.
We present a summary of results on SDSS-DR9 galaxy data, used also to perform a
direct comparison with PDF's obtained by the Le Phare SED template fitting. We
show that METAPHOR is capable to estimate the precision and reliability of
photometric redshifts obtained with three different self-adaptive techniques,
i.e. MLPQNA, Random Forest and the standard K-Nearest Neighbors models.


title: Unrolled Generative Adversarial Networks

abstract:
  We introduce a method to stabilize Generative Adversarial Networks (GANs) by
defining the generator objective with respect to an unrolled optimization of
the discriminator. This allows training to be adjusted between using the
optimal discriminator in the generator's objective, which is ideal but
infeasible in practice, and using the current value of the discriminator, which
is often unstable and leads to poor solutions. We show how this technique
solves the common problem of mode collapse, stabilizes training of GANs with
complex recurrent generators, and increases diversity and coverage of the data
distribution by the generator.


title:
Numerical methods for the deterministic second moment equation of
  parabolic stochastic PDEs

abstract:
  Numerical methods for stochastic partial differential equations typically
estimate moments of the solution from sampled paths. Instead, we shall directly
target the deterministic equations satisfied by the first and second moments,
as well as the covariance.
  In the first part, we focus on stochastic ordinary differential equations.
For the canonical examples with additive noise (Ornstein-Uhlenbeck process) or
multiplicative noise (geometric Brownian motion) we derive these deterministic
equations in variational form and discuss their well-posedness in detail.
Notably, the second moment equation in the multiplicative case is naturally
posed on projective-injective tensor product spaces as trial-test spaces. We
construct Petrov-Galerkin discretizations based on tensor product piecewise
polynomials and analyze their stability and convergence in these natural norms.
  In the second part, we proceed with parabolic stochastic partial differential
equations with affine multiplicative noise. We prove well-posedness of the
deterministic variational problem for the second moment, improving an earlier
result. We then propose conforming space-time Petrov-Galerkin discretizations,
which we show to be stable and quasi-optimal.
  In both parts, the outcomes are illustrated by numerical examples.


title: Spectral gap on Riemannian path space over static and evolving manifolds

abstract:
  In this article, we continue the discussion of Fang-Wu (2015) to estimate the
spectral gap of the Ornstein-Uhlenbeck operator on path space over a Riemannian
manifold of pinched Ricci curvature. Along with explicit estimates we study the
short-time asymptotics of the spectral gap. The results are then extended to
the path space of Riemannian manifolds evolving under a geometric flow. Our
paper is strongly motivated by Naber's recent work (2015) on characterizing
bounded Ricci curvature through stochastic analysis on path space.


title:
Micromachined integrated quantum circuit containing a superconducting
  qubit

abstract:
  We present a device demonstrating a lithographically patterned transmon
integrated with a micromachined cavity resonator. Our two-cavity, one-qubit
device is a multilayer microwave integrated quantum circuit (MMIQC), comprising
a basic unit capable of performing circuit-QED (cQED) operations. We describe
the qubit-cavity coupling mechanism of a specialized geometry using an electric
field picture and a circuit model, and finally obtain specific system
parameters using simulations. Fabrication of the MMIQC includes lithography,
etching, and metallic bonding of silicon wafers. Superconducting wafer bonding
is a critical capability that is demonstrated by a micromachined storage cavity
lifetime $34.3~\mathrm{\mu s}$, corresponding to a quality factor of 2 million
at single-photon energies. The transmon coherence times are
$T_1=6.4~\mathrm{\mu s}$, and $T_2^{Echo}= 11.7~\mathrm{\mu s}$. We measure
qubit-cavity dispersive coupling with rate $\chi_{q\mu}/2\pi=-1.17~$MHz,
constituting a Jaynes-Cummings system with an interaction strength
$g/2\pi=49~$MHz. With these parameters we are able to demonstrate cQED
operations in the strong dispersive regime with ease. Finally, we highlight
several improvements and anticipated extensions of the technology to complex
MMIQCs.


title: Designing Neural Network Architectures using Reinforcement Learning

abstract:
  At present, designing convolutional neural network (CNN) architectures
requires both human expertise and labor. New architectures are handcrafted by
careful experimentation or modified from a handful of existing networks. We
introduce MetaQNN, a meta-modeling algorithm based on reinforcement learning to
automatically generate high-performing CNN architectures for a given learning
task. The learning agent is trained to sequentially choose CNN layers using
$Q$-learning with an $\epsilon$-greedy exploration strategy and experience
replay. The agent explores a large but finite space of possible architectures
and iteratively discovers designs with improved performance on the learning
task. On image classification benchmarks, the agent-designed networks
(consisting of only standard convolution, pooling, and fully-connected layers)
beat existing networks designed with the same layer types and are competitive
against the state-of-the-art methods that use more complex layer types. We also
outperform existing meta-modeling approaches for network design on image
classification tasks.


title:
Observation of spin-polarized bands and domain-dependent Fermi arcs in
  polar Weyl semimetal MoTe$_2$

abstract:
  We investigate the surface electronic structures of polar 1T'-MoTe2, the Weyl
semimetal candidate realized through the nonpolar-polar structural phase
transition, by utilizing the laser angle-resolved photoemission spectroscopy
(ARPES) combined with first-principles calculations. Two kinds of domains with
different surface band dispersions are observed from a single-crystalline
sample. The spin-resolved measurements further reveal that the spin
polarizations of the surface and the bulk-derived states show the different
domain-dependences, indicating the opposite bulk polarity. For both domains,
some segment-like band features resembling the Fermi arcs are clearly observed.
The patterns of the arcs present the marked contrast between the two domains,
respectively agreeing well with the slab calculation of (0 0 1) and (0 0 -1)
surfaces. The present result strongly suggests that the Fermi arc connects the
identical pair of Weyl nodes on one side of the polar crystal surface, whereas
it connects between the different pairs of Weyl nodes on the other side.


title:
Comment on "Breakdown of Interference Rules in Azulene, a Nonalternant
  Hydrocarbon"

abstract:
  Quantum interference (QI) effects in molecular systems are a topic of
emerging interest in electron transport studies of single molecule junctions.
In a recent Letter, Xia et al. employed a graphical scheme introduced by my
colleagues and myself that enables to distinguish between molecular topologies
in conjugated pi systems which exhibit QI effects in their conductance from
those who do not. They claimed that this scheme is not applicable for
nonalternant hydrocarbons, in particular Azulenes (Az), whose transport
properties were studied both theoretically and experimentally by connecting the
electrodes at Az's 1,3-, 2,6-, 4,7-, and 5,7-positions, respectively. An
apparent disagreement has been identified between the predictions of our scheme
referred to as "atom- or bond-counting model" and theoretical simulations for
featureless, wide band electrodes in the GW approximation as well as for the
tight-binding (TB) model our method was originally derived from.
  In the following I would like to clarify that this apparent disagreement
vanishes if the graphical scheme is applied correctly, providing a different
result for the 1,3 Az compound than claimed by Xia et al. It will further be
argued that the graphical scheme is completely general for any molecular
topology in conjugated pi systems regardless of whether they are alternant or
non-alternant hydrocarbons as long as the basic assumptions of its derivation
are fulfilled.


title:
Molecular dynamics simulations and photoluminescence measurements of
  annealed ZnO surfaces

abstract:
  The effect of thermal annealing on wurtzite ZnO, terminated by two surfaces,
(0 0 0 $\bar 1$) (which is oxygen-terminated) and (0 0 0 1) (which is
Zn-terminated), is investigated via molecular dynamics simulation using
reactive force field (ReaxFF). As a result of annealing at a threshold
temperature range of 700~K $ < T_{\mbox{\small t}} \leq 800$~K, surface oxygen
atoms begin to sublimate from the (0 0 0 $\bar 1$) surface, while no atom
leaves the (0 0 0 1) surface. The ratio of oxygen leaving the surface increases
with temperature $T$ (for $T \geq T_{\mbox{\small t}}$). The relative
luminescence intensity of the secondary peak in the photoluminescence (PL)
spectra, interpreted as a measurement of amount of vacancies on the sample
surfaces, qualitatively agrees with the threshold behavior as found in the MD
simulations. Our simulations have also revealed the formation of oxygen dimers
on the surface and evolution of partial charge distribution during the
annealing process. Our MD simulation based on the ReaxFF is consistent with
experimental observations.


title:
Electronic structure contribution to hydrogen bonding interaction of a
  water dimer

abstract:
  Hydrogen bond (H-bond) covalency has recently been observed in ice and liquid
water, while the penetrating molecular orbitals (MOs) in the H-bond region of
most typical water dimer system, (H2O)2, have also been discovered. However,
obtaining the quantitative contribution of these MOs to the H-bond interaction
is still problematic. In this work, we introduced the orbital-resolved electron
density projected integral (EDPI) along the H-bond to approach this problem.
The calculations show that, surprisingly, the electronic occupied orbital
(HOMO-4) of (H2O)2 accounts for about 40% of the electron density at the bond
critical point. Moreover, the charge transfer analysis visualizes the electron
accumulating effect of the orbital interaction within the H-bond between water
molecules, supporting its covalent-like character. Our work expands the
classical understanding of H-bond with specific contributions from certain MOs,
and will also advance further research into such covalency and offer
quantitative electronic structure insights into intermolecular systems.


title: Next-to-soft corrections to high energy scattering in QCD and gravity

abstract:
  We examine the Regge (high energy) limit of 4-point scattering in both QCD
and gravity, using recently developed techniques to systematically compute all
corrections up to next-to-leading power in the exchanged momentum i.e. beyond
the eikonal approximation. We consider the situation of two scalar particles of
arbitrary mass, thus generalising previous calculations in the literature. In
QCD, our calculation describes power-suppressed corrections to the Reggeisation
of the gluon. In gravity, we confirm a previous conjecture that next-to-soft
corrections correspond to two independent deflection angles for the incoming
particles. Our calculations in QCD and gravity are consistent with the
well-known double copy relating amplitudes in the two theories.


title:
Time-reversal and rotation symmetry breaking superconductivity in Dirac
  materials

abstract:
  We consider mixed symmetry superconducting phases in Dirac materials in the
odd parity channel, where pseudoscalar and vector order parameters can coexist
due to their similar critical temperatures when attractive interactions are of
finite range. We show that the coupling of these order parameters to unordered
magnetic dopants favors the condensation of novel time-reversal symmetry
breaking (TRSB) phases, characterized by a condensate magnetization, rotation
symmetry breaking, and simultaneous ordering of the dopant moments. We find a
rich phase diagram of mixed TRSB phases characterized by peculiar bulk
quasiparticles, with Weyl nodes and nodal lines, and distinctive surface
states. These findings are consistent with recent experiments on
Nb$_x$Bi$_2$Se$_3$ that report evidence of point nodes, nematicity, and TRSB
superconductivity induced by Nb magnetic moments.


title:
Parse Geometry from a Line: Monocular Depth Estimation with Partial
  Laser Observation

abstract:
  Many standard robotic platforms are equipped with at least a fixed 2D laser
range finder and a monocular camera. Although those platforms do not have
sensors for 3D depth sensing capability, knowledge of depth is an essential
part in many robotics activities. Therefore, recently, there is an increasing
interest in depth estimation using monocular images. As this task is inherently
ambiguous, the data-driven estimated depth might be unreliable in robotics
applications. In this paper, we have attempted to improve the precision of
monocular depth estimation by introducing 2D planar observation from the
remaining laser range finder without extra cost. Specifically, we construct a
dense reference map from the sparse laser range data, redefining the depth
estimation task as estimating the distance between the real and the reference
depth. To solve the problem, we construct a novel residual of residual neural
network, and tightly combine the classification and regression losses for
continuous depth estimation. Experimental results suggest that our method
achieves considerable promotion compared to the state-of-the-art methods on
both NYUD2 and KITTI, validating the effectiveness of our method on leveraging
the additional sensory information. We further demonstrate the potential usage
of our method in obstacle avoidance where our methodology provides
comprehensive depth information compared to the solution using monocular camera
or 2D laser range finder alone.


title:
Neutron-capture element abundances in the planetary nebula NGC 5315 from
  deep high-resolution optical and near-IR spectrophotometry

abstract:
  We have done a spectroscopical analysis of the type I planetary nebula (PN)
NGC 5315, through high-resolution (R$\sim$40000) optical spectroscopy with UVES
at the 8.2m Very Large Telescope, and medium-resolution (R$\sim$4800) near-IR
spectroscopy with FIRE at the 6.5m Magellan Baade telescope, covering a wide
spectral range from 0.31 $\mu$m to 2.50 $\mu$m. The main aim of this work is to
investigate the slow neutron(n)-capture process (the s-process) in the
Asymptotic Giant Branch (AGB) star progenitor of a type I PNe. We detected and
identified about 700 features, including lines from the n-capture elements Kr,
Se, and possibly Br and Xe. We compute physical conditions using line ratios of
common ions. Ionic abundances are computed for the species with available
atomic data. We calculate total abundances using recent ionization correction
factors (ICFs) or by summing ionic abundances. Our results for common elements
are in good agreement with previous works on the same object. We do not find a
substantial s-process enrichment in NGC 5315, which is typical for type I PNe.


title: Randomness in Quantum Mechanics: Philosophy, Physics and Technology

abstract:
  This progress report covers recent developments in the area of quantum
randomness, which is an extraordinarily interdisciplinary area that belongs not
only to physics, but also to philosophy, mathematics, computer science, and
technology. For this reason the article contains three parts that will be
essentially devoted to different aspects of quantum randomness, and even
directed, although not restricted, to various audiences: a philosophical part,
a physical part, and a technological part. For these reasons the article is
written on an elementary level, combining very elementary and non-technical
descriptions with a concise review of more advanced results. In this way
readers of various provenances will be able to gain while reading the article.


title:
A Markov Decision Process Model to Guide Treatment of Abdominal Aortic
  Aneurysms

abstract:
  An abdominal aortic aneurysm (AAA) is an enlargement of the abdominal aorta
which, if left untreated, can progressively widen and may rupture with fatal
consequences. In this paper, we determine an optimal treatment policy using
Markov decision process modeling. The policy is optimal with respect to the
number of quality adjusted life-years (QALYs) that are expected to be
accumulated during the remaining life of a patient. The new policy takes into
account factors that are ignored by the current clinical policy (e.g. the
life-expectancy and the age-dependent surgical mortality). The resulting
optimal policy is structurally different from the current policy. In
particular, the policy suggests that young patients with small aneurysms should
undergo surgery. The robustness of the policy structure is demonstrated using
simulations. A gain in the number of expected QALYs is shown, which indicates a
possibility of improved care for patients with AAAs.


title:
Nonequilibrium dynamics of a pure dry friction model subjected to
  coloured noise

abstract:
  We investigate the impact of noise on a two-dimensional simple paradigmatic
piecewise-smooth dynamical system. For that purpose we consider the motion of a
particle subjected to dry friction and coloured noise. The finite correlation
time of the noise provides an additional dimension in phase space, a nontrivial
probability current, and thus establishes a proper nonequilibrium regime.
Furthermore, the finite noise correlation time allows for the study of
stick-slip phenomena which show up as a singular component in the stationary
probability density. Analytic insight can be provided by application of the
unified coloured noise approximation, developed by Jung and H\"anggi (Phys.
Rev. A 35, 4464 (R) (1987)). The analysis of probability currents and a closer
look at power spectral densities underpin the observed stick-slip transitions
which are related with a critical value of the noise correlation time.


title: 6d Dual Conformal Symmetry and Minimal Volumes in AdS

abstract:
  The S-matrix of a theory often exhibits symmetries which are not manifest
from the viewpoint of its Lagrangian. For instance, powerful constraints on
scattering amplitudes are imposed by the dual conformal symmetry of planar 4d
$\mathcal{N}=4$ super Yang-Mills theory and the ABJM theory. Motivated by this,
we investigate the consequences of dual conformal symmetry in six dimensions,
which may provide useful insight into the worldvolume theory of M5-branes (if
it enjoys such a symmetry). We find that 6d dual conformal symmetry uniquely
fixes the integrand of the one-loop 4-point amplitude, and its structure
suggests a Lagrangian with more than two derivatives. On integrating out the
loop momentum in $6-2 \epsilon$ dimensions, the result is very similar to the
corresponding amplitude of $\mathcal{N}=4$ super Yang-Mills theory. We confirm
this result holographically by generalizing the Alday-Maldacena solution for a
minimal area string in Anti-de Sitter space to a minimal volume M2-brane ending
on pillow-shaped Wilson surface in the boundary whose seams correspond to a
null-polygonal Wilson loop. This involves careful treatment of a prefactor
which diverges as $1/\epsilon$, and we comment on its possible interpretation.
We also study 2-loop 4-point integrands with 6d dual conformal symmetry and
speculate on the existence of an all-loop formula for the 4-point amplitude.


title: Nonlinear plasmonic amplification via dissipative soliplasmons

abstract:
  In this contribution we introduce a new strategy for the compensation of
plasmonic losses based on a recently proposed nonlinear mechanism: the resonant
interaction between surface plasmon polaritons and spatial solitons propagating
in parallel along a metal/dielectric/Kerr structure. This mechanism naturally
leads to the generation of a quasi-particle excitation, the so-called
soliplasmon resonance. We analyze the role played by the effective nonlinear
coupling inherent to this system and how this can be used to provide a new
mechanism of quasi-resonant nonlinear excitation of surface plasmon polaritons.
We will pay particular attention to the introduction of asymmetric linear gain
in the Kerr medium. The unique combination of nonlinear propagation, nonlinear
coupling and gain give rise to a new scenario for the excitation of long- range
surface plasmon polaritons with distinguishing characteristics. The connection
between plasmonic losses and soliplasmon resonances in the presence of gain
will be discussed.


title:
Using Social Dynamics to Make Individual Predictions: Variational
  Inference with a Stochastic Kinetic Model

abstract:
  Social dynamics is concerned primarily with interactions among individuals
and the resulting group behaviors, modeling the temporal evolution of social
systems via the interactions of individuals within these systems. In
particular, the availability of large-scale data from social networks and
sensor networks offers an unprecedented opportunity to predict state-changing
events at the individual level. Examples of such events include disease
transmission, opinion transition in elections, and rumor propagation. Unlike
previous research focusing on the collective effects of social systems, this
study makes efficient inferences at the individual level. In order to cope with
dynamic interactions among a large number of individuals, we introduce the
stochastic kinetic model to capture adaptive transition probabilities and
propose an efficient variational inference algorithm the complexity of which
grows linearly --- rather than exponentially --- with the number of
individuals. To validate this method, we have performed epidemic-dynamics
experiments on wireless sensor network data collected from more than ten
thousand people over three years. The proposed algorithm was used to track
disease transmission and predict the probability of infection for each
individual. Our results demonstrate that this method is more efficient than
sampling while nonetheless achieving high accuracy.


title:
Diffusion and Clustering of Carbon Dioxide on non-porous Amorphous Solid
  Water

abstract:
  Observations by ISO and Spitzer towards young stellar objects (YSOs) showed
that CO$_2$ segregates in the icy mantles covering dust grains. Thermal
processing of ice mixture was proposed as responsible for the segregation.
Although several laboratory studied thermally induced segregation, a satisfying
quantification is still missing. We propose that the diffusion of CO$_2$ along
pores inside water ice is the key to quantify segregation. We combined
Temperature Programmed Desorption (TPD) and Reflection Absorption InfraRed
Spectroscopy (RAIRS) to study how CO$_2$ molecules interact on a non-porous
amorphous solid water (np-ASW) surface. We found that CO$_2$ diffuses
significantly on a np-ASW surface above 65~K and clusters are formed at well
below one monolayer. A simple rate equation simulation finds that the diffusion
energy barrier of CO$_2$ on np-ASW is 2150$\pm$50 K, assuming a diffusion
pre-exponential factor of 10$^{12}$ s$^{-1}$. This energy should also apply to
the diffusion of CO$_2$ on wall of pores. The binding energy of CO$_2$ from
CO$_2$ clusters and CO$_2$ from H$_2$O ice have been found to be $2415\pm20$
and $2250\pm20$~K, respectively, assuming the same prefactor for desorption.
CO$_2$-CO$_2$ interaction is stronger than CO$_2$-H$_2$O interaction, in
agreement with the experimental finding that CO$_2$ does not wet np-ASW
surface. For comparison, we carried out similar experiments with CO on np-ASW,
and found that the CO-CO interaction is always weaker than CO-H$_2$O. As a
result, CO wets np-ASW surface. This study should be of help to uncover the
thermal history of CO$_2$ on the icy mantles of dust grains.


title:
Observational Evidence Linking Interstellar UV Absorption to PAH
  Molecules

abstract:
  The 2175 \AA\ UV extinction feature was discovered in the mid-1960s, yet its
physical origin remains poorly understood. One suggestion is absorption by
Polycyclic Aromatic Hydrocarbons (PAH) molecules, which is supported by
theoretical molecular structure computations and by laboratory experiments.
PAHs are positively detected by their 3.3, 6.2, 7.7 8.6, 11.3 & 12.7 $\mu$m IR
emission bands, which are specified by their modes of vibration. A definitive
empirical link between the 2175 \AA\ UV extinction, and the PAH IR emission
bands, however, is still missing. We present a new sample of hot stars that
have both 2175 \AA\ absorption and PAH IR emission. We find significant shifts
of the central wavelength of the UV absorption feature, up to 2350 \AA, but
predominantly in stars that also have IR PAH emission. These UV shifts depend
on stellar temperature in a fashion that is similar to the shifts of the 6.2
and 7.7$\mu$m PAH IR bands, namely the features are increasingly more
red-shifted as the stellar temperature decreases, but only below $\sim 15$ kK.
Above 15 kK both UV and IR features retain their nominal values. Moreover, we
find a suggestive correlation between the UV and IR shifts. We hypothesize that
these similar dependences of both the UV and IR features on stellar temperature
hint to a common origin of the two in PAH molecules and may establish the
missing link between the UV and IR observations. We further suggest that the
shifts depend on molecular size, and that the critical temperature of $\sim 15$
kK above which no shifts are observed is related to the onset of UV driven
hot-star winds and their associated shocks.


title: A single strontium Rydberg ion confined in a Paul trap

abstract:
  Trapped Rydberg ions are a promising new system for quantum information
processing. They have the potential to join the precise quantum operations of
trapped ions and the strong, long-range interactions between Rydberg atoms.
Technically, the ion trap will need to stay active while exciting the ions into
the Rydberg state, else the strong Coulomb repulsion will quickly push the ions
apart. Thus, a thorough understanding of the trap effects on Rydberg ions is
essential for future applications. Here we report the observation of two
fundamental trap effects. First, we investigate the interaction of the Rydberg
electron with the quadrupolar electric trapping field. This effect leads to
Floquet sidebands in the spectroscopy of Rydberg D-states whereas Rydberg
S-states are unaffected due to their symmetry. Second, we report on the
modified trapping potential in the Rydberg state compared to the ground state
which results from the strong polarizability of the Rydberg ion. We observe the
resultant energy shifts as a line broadening which can be suppressed by cooling
the ion to the motional ground state in the directions orthogonal to the
excitation laser.


title: Trusting SVM for Piecewise Linear CNNs

abstract:
  We present a novel layerwise optimization algorithm for the learning
objective of Piecewise-Linear Convolutional Neural Networks (PL-CNNs), a large
class of convolutional neural networks. Specifically, PL-CNNs employ piecewise
linear non-linearities such as the commonly used ReLU and max-pool, and an SVM
classifier as the final layer. The key observation of our approach is that the
problem corresponding to the parameter estimation of a layer can be formulated
as a difference-of-convex (DC) program, which happens to be a latent structured
SVM. We optimize the DC program using the concave-convex procedure, which
requires us to iteratively solve a structured SVM problem. This allows to
design an optimization algorithm with an optimal learning rate that does not
require any tuning. Using the MNIST, CIFAR and ImageNet data sets, we show that
our approach always improves over the state of the art variants of
backpropagation and scales to large data and large network settings.


title:
CEPC Precision of Electroweak Oblique Parameters and Weakly Interacting
  Dark Matter: the Fermionic Case

abstract:
  Future electroweak precision measurements in the Circular Electron Positron
Collider (CEPC) project would significantly improve the precision of
electroweak oblique parameters. We evaluate the expected precision through
global fits, and study the corresponding sensitivity to weakly interacting
fermionic dark matter. Three models with electroweak multiplets in the dark
sector are investigated as illuminating examples. We find that the CEPC data
can probe up to TeV scales and explore some regions where direct detection
cannot reach, especially when the models respect the custodial symmetry.


title:
Classifying spaces for the family of virtually cyclic subgroups of braid
  groups

abstract:
  We prove that, for $n\geq 3$, the minimal dimension of a model of the
classifying space of the full braid group $B_n$, and of the pure braid group
$P_n$, with respect to the family of virtually cyclic groups is $n$.


title: Descriptive characterizations of the integral by seminorms

abstract:
  In this paper, we first define the concept of the limit average range of a
function defined on $[0,1]$ and taking values in a Hausdorff locally convex
topological vector space (locally convex space) $X$. Then, we present
characterizations of the primitive $F:[0,1] \to X$ of an integrable by
seminorms function $f:[0,1] \to X$ in terms of the limit average range of $F$.
It is shown that the limit average range characterizes the integral by
seminorms better then the usual differential.


title:
CoCoA: A General Framework for Communication-Efficient Distributed
  Optimization

abstract:
  The scale of modern datasets necessitates the development of efficient
distributed optimization methods for machine learning. We present a
general-purpose framework for distributed computing environments, CoCoA, that
has an efficient communication scheme and is applicable to a wide variety of
problems in machine learning and signal processing. We extend the framework to
cover general non-strongly-convex regularizers, including L1-regularized
problems like lasso, sparse logistic regression, and elastic net
regularization, and show how earlier work can be derived as a special case. We
provide convergence guarantees for the class of convex regularized loss
minimization objectives, leveraging a novel approach in handling
non-strongly-convex regularizers and non-smooth loss functions. The resulting
framework has markedly improved performance over state-of-the-art methods, as
we illustrate with an extensive set of experiments on real distributed
datasets.


title:
Lattice calculation of the pion transition form factor $\pi^0 \to
  \gamma^* \gamma^*$

abstract:
  We calculate the pion transition form factor ${\cal
F}_{\pi^0\gamma^*\gamma^*}(q_1^2,q_2^2)$, which describe the interaction of an
on-shell pion with two off-shell photons, using lattice QCD simulations with
two degenerate flavors of dynamical quarks. This form factor is the main
ingredient in the calculation of the pion-pole contribution to hadronic
light-by-light scattering in the muon $g-2$, $a_\mu^{\mathrm{HLbL}; \pi^0}$. We
focus our study on the spacelike region with photon virtualities up to
$1.5~\mathrm{GeV}^2$, not yet measured experimentally. Several lattice spacings
and pion masses are used to extrapolate the results to the physical point and a
comparison with different phenomenological models is performed. Finally, we use
our extrapolated form factor to provide a lattice determinaiton of
$a_\mu^{\mathrm{HLbL}; \pi^0}$.


title: Fe K and ejecta emission in SNR G15.9+0.2 with XMM-Newton

abstract:
  Aims: We present a study of the Galactic supernova remnant SNR G15.9+0.2 with
archival XMM-Newton observations. Methods: EPIC data are used to investigate
the morphological and spectral properties of the remnant, searching in
particular for supernova ejecta and Fe K line emission. By comparing the SNR's
X-ray absorption column density with the atomic and molecular gas distribution
along the line of sight, we attempt to constrain the distance to the SNR.
Results: Prominent line features reveal the presence of ejecta. Abundance
ratios of Mg, Si, S, Ar, and Ca strongly suggest that the progenitor of SNR
G15.9+0.2 was a massive star with a main sequence mass likely in the range
20-25 $M_{\odot}$, strengthening the physical association with a candidate
central compact object detected with Chandra. Using EPIC's collective power, Fe
K line emission from SNR G15.9+0.2 is detected for the first time. We measure
the line properties and find evidence for spatial variations. We discuss how
the source fits within the sample of SNRs with detected Fe K emission and find
that it is the core-collapse SNR with the lowest Fe K centroid energy. We also
present some caveats regarding the use of Fe K line centroid energy as a typing
tool for SNRs. Only a lower limit of 5 kpc is placed on the distance to SNR
G15.9+0.2, constraining its age to $t_{SNR} \gtrsim 2$ kyr.


title: Di-J/psi production at the Tevatron and the LHC

abstract:
  We briefly review recent results which we have obtained in the study of
J/psi-pair production at the Tevatron and the LHC. We claim that the existing
data set from CMS and D0 point at a significant double-parton-scattering
contribution with an effective cross section smaller than that for jet-related
observables. We have also derived simple relations involving feed-down
fractions from excited states which can help in disentangling the single from
the double scatterings.


title: Liouville field theory and log-correlated Random Energy Models

abstract:
  An exact mapping is established between the $c\geq25$ Liouville field theory
(LFT) and the Gibbs measure statistics of a thermal particle in a 2D Gaussian
Free Field plus a logarithmic confining potential. The probability distribution
of the position of the minimum of the energy landscape is obtained exactly by
combining the conformal bootstrap and one-step replica symmetry breaking
methods. Operator product expansions in LFT allow to unveil novel universal
behaviours of the log-correlated Random Energy class. High precision numerical
tests are given.

categories: cond-mat.stat-mech cond-mat.dis-nn hep-th math-ph math.MP


title: Mean Field Model for Collective Motion Bistability

abstract:
  We consider the Czir\'ok model for collective motion of locusts along a
one-dimensional torus. In the model, each agent's velocity locally interacts
with other agents' velocities in the system, and there is also exogenous
randomness to each agent's velocity. The interaction tends to create the
alignment of collective motion. By analyzing the associated nonlinear
Fokker-Planck equation, we obtain the condition for the existence of stationary
order states and the conditions for their linear stability. These conditions
depend on the noise level, which should be strong enough, and on the
interaction between the agent's velocities, which should be neither too small,
nor too strong. We carry out the fluctuation analysis of the interacting system
and describe the large deviation principle to calculate the transition
probability from one order state to the other. Numerical simulations confirm
our analytical findings.


title: An epidemic model for cholera with optimal control treatment

abstract:
  We propose a mathematical model for cholera with treatment through
quarantine. The model is shown to be both epidemiologically and mathematically
well posed. In particular, we prove that all solutions of the model are
positive and bounded; and that every solution with initial conditions in a
certain meaningful set remains in that set for all time. The existence of
unique disease-free and endemic equilibrium points is proved and the basic
reproduction number is computed. Then, we study the local asymptotic stability
of these equilibrium points. An optimal control problem is proposed and
analyzed, whose goal is to obtain a successful treatment through quarantine. We
provide the optimal quarantine strategy for the minimization of the number of
infectious individuals and bacteria concentration, as well as the costs
associated with the quarantine. Finally, a numerical simulation of the cholera
outbreak in the Department of Artibonite (Haiti), in 2010, is carried out,
illustrating the usefulness of the model and its analysis.


title:
Inner mean-motion resonances with eccentric planets: A possible origin
  for exozodiacal dust clouds

abstract:
  High levels of dust have been detected in the immediate vicinity of many
stars, both young and old. A promising scenario to explain the presence of this
short-lived dust is that these analogues to the Zodiacal cloud (or exozodis)
are refilled in situ through cometary activity and sublimation. As the
reservoir of comets is not expected to be replenished, the presence of these
exozodis in old systems has yet to be adequately explained.
  It was recently suggested that mean-motion resonances (MMR) with exterior
planets on moderately eccentric ($\mathrm{e_p}\gtrsim 0.1$) orbits could
scatter planetesimals on to cometary orbits with delays of the order of several
100 Myr. Theoretically, this mechanism is also expected to sustain continuous
production of active comets once it has started, potentially over
Gyr-timescales.
  We aim here to investigate the ability of this mechanism to generate
scattering on to cometary orbits compatible with the production of an exozodi
on long timescales. We combine analytical predictions and complementary
numerical N-body simulations to study its characteristics.
  We show, using order of magnitude estimates, that via this mechanism, low
mass discs comparable to the Kuiper Belt could sustain comet scattering at
rates compatible with the presence of the exozodis which are detected around
Solar-type stars, and on Gyr timescales. We also find that the levels of dust
detected around Vega could be sustained via our proposed mechanism if an
eccentric Jupiter-like planet were present exterior to the system's cold debris
disc.


title: Limit sets of Weil-Petersson geodesics

abstract:
  In this paper we prove that the limit set of any Weil-Petersson geodesic ray
with uniquely ergodic ending lamination is a single point in the Thurston
compactification of Teichm\"uller space. On the other hand, we construct
examples of Weil-Petersson geodesics with minimal nonuniquely ergodic ending
laminations and limit set a circle in the Thurston compactification.


title:
Acceleration of spin-orbit coupled Bose-Einstein condensates: analytical
  description of the emergence of Landau-Zener transitions

abstract:
  We analytically study the effect of gravitational and harmonic forces on
ultra-cold atoms with synthetic spin-orbit coupling (SOC). In particular, we
focus on the recently observed transitions between internal states induced by
acceleration of the external modes. Our description corresponds to a
generalized version of the Landau-Zener (LZ) model: the dimensionality is
enlarged to combine the quantum treatment of the external variables with the
internal-state characterization; additionally, atomic-interaction effects are
considered. The emergence of the basic model is analytically traced. Namely, by
using a sequence of unitary transformations and a subsequent reduction to the
spin space, the SOC Hamiltonian, with the gravitational potential incorporated,
is exactly converted into the primary LZ scenario. Moreover, the transitions
induced by harmonic acceleration are approximately cast into the framework of
the basic LZ model through a complete analytical procedure. We evaluate how the
validity of our picture depends on the system preparation and on the magnitude
of atomic-interaction effects. The identification of the regime of
applicability and the rigorous characterization of the parameters of the
effective model provide elements to control the transitions.


title:
Inference for Additive Models in the Presence of Possibly Infinite
  Dimensional Nuisance Parameters

abstract:
  A framework for estimation and hypothesis testing of functional restrictions
against general alternatives is proposed. The parameter space is a reproducing
kernel Hilbert space (RKHS). The null hypothesis does not necessarily define a
parametric model. The test allows us to deal with infinite dimensional nuisance
parameters. The methodology is based on a moment equation similar in spirit to
the construction of the efficient score in semiparametric statistics. The
feasible version of such moment equation requires to consistently estimate
projections in the space of RKHS and it is shown that this is possible using
the proposed approach. This allows us to derive some tractable asymptotic
theory and critical values by fast simulation. Simulation results show that the
finite sample performance of the test is consistent with the asymptotics and
that ignoring the effect of nuisance parameters highly distorts the size of the
tests.


title: Unsupervised Cross-Domain Image Generation

abstract:
  We study the problem of transferring a sample in one domain to an analog
sample in another domain. Given two related domains, S and T, we would like to
learn a generative function G that maps an input sample from S to the domain T,
such that the output of a given function f, which accepts inputs in either
domains, would remain unchanged. Other than the function f, the training data
is unsupervised and consist of a set of samples from each domain. The Domain
Transfer Network (DTN) we present employs a compound loss function that
includes a multiclass GAN loss, an f-constancy component, and a regularizing
component that encourages G to map samples from T to themselves. We apply our
method to visual domains including digits and face images and demonstrate its
ability to generate convincing novel images of previously unseen entities,
while preserving their identity.


title: Holographic c-Function

abstract:
  We propose a simple and generic holographic $c$-function that is defined
purely from geometry by using the non-affine expansion for null congruences. We
examined the proposal for BPS black solutions in $\mathcal{N}=2$ gauged
supergravity that interpolate between two different dimensional AdS spacetimes
and also for domain wall solutions. Moreover, we commented on the relation of
this geometric proposal with the one from the holographic entanglement entropy.


title:
Efficient polar convolution based on the discrete Fourier-Bessel
  transform for application in computational biophotonics

abstract:
  We discuss efficient algorithms for the accurate forward and reverse
evaluation of the discrete Fourier-Bessel transform (dFBT) as numerical tools
to assist in the 2D polar convolution of two radially symmetric functions,
relevant, e.g., to applications in computational biophotonics. In our survey of
the numerical procedure we account for the circumstance that the objective
function might result from a more complex measurement process and is, in the
worst case, known on a finite sequence of coordinate values, only. We contrast
the performance of the resulting algorithms with a procedure based on a
straight forward numerical quadrature of the underlying integral transform and
asses its efficienty for two benchmark Fourier-Bessel pairs. An application to
the problem of finite-size beam-shape convolution in polar coordinates,
relevant in the context of tissue optics and optoacoustics, is used to
illustrate the versatility and computational efficiency of the numerical
procedure.


title:
Spin-valley dynamics of electrically driven ambipolar carbon-nanotube
  quantum dots

abstract:
  An ambipolar $n$-$p$ double quantum dot defined by potential variation along
a semiconducting carbon-nanotube is considered. We focus on the (1e,1h) charge
configuration with a single excess electron in the conduction band state
confined in the $n$-type dot and a single missing electron in the valence band
state of the $p$-dot for which lifting of the Pauli blockade of the current was
observed in the electric-dipole spin resonance [E. A. Laird et al. Nat.
Nanotech. 8 , 565 (2013)]. The dynamics of the system driven by periodic
electric field is studied with the Floquet theory and the time-dependent
configuration interaction method with the single-electron spin-valley-orbitals
determined for atomistic tight-binding Hamiltonian. We find that the
transitions lifting the Pauli blockade are strongly influenced by coupling to a
vacuum state with an empty $n$ dot and a fully filled $p$ dot. The coupling
shifts the transition energies and strongly modifies the effective $g$ factors
for axial magnetic field. The coupling is modulated by the bias between the
dots but it appears effective for surprisingly large energy splitting between
the (1e,1h) ground state and the vacuum (0e,0h) state. Multiphoton transitions
and high harmonic generation effects are also discussed.


title: Hyperfiniteness and Borel combinatorics

abstract:
  We study the relationship between hyperfiniteness and problems in Borel graph
combinatorics by adapting game-theoretic techniques introduced by Marks to the
hyperfinite setting. We compute the possible Borel chromatic numbers and edge
chromatic numbers of bounded degree acyclic hyperfinite Borel graphs and use
this to answer a question of Kechris and Marks about the relationship between
Borel chromatic number and measure chromatic number. We also show that for
every $d > 1$ there is a $d$-regular acyclic hyperfinite Borel bipartite graph
with no Borel perfect matching. These techniques also give examples of
hyperfinite bounded degree Borel graphs for which the Borel local lemma fails,
in contrast to the recent results of Cs\'oka, Grabowski, M\'ath\'e, Pikhurko,
and Tyros.
  Related to the Borel Ruziewicz problem, we show there is a continuous
paradoxical action of $(\mathbb{Z}/2\mathbb{Z})^{*3}$ on a Polish space that
admits a finitely additive invariant Borel probability measure, but admits no
countably additive invariant Borel probability measure. In the context of
studying ultrafilters on the quotient space of equivalence relations under
$\mathrm{AD}$, we also construct an ultrafilter $U$ on the quotient of $E_0$
which has surprising complexity. In particular, Martin's measure is
Rudin-Kiesler reducible to $U$.
  We end with a problem about whether every hyperfinite bounded degree Borel
graph has a witness to its hyperfiniteness which is uniformly bounded below in
size.


title: Playing SNES in the Retro Learning Environment

abstract:
  Mastering a video game requires skill, tactics and strategy. While these
attributes may be acquired naturally by human players, teaching them to a
computer program is a far more challenging task. In recent years, extensive
research was carried out in the field of reinforcement learning and numerous
algorithms were introduced, aiming to learn how to perform human tasks such as
playing video games. As a result, the Arcade Learning Environment (ALE)
(Bellemare et al., 2013) has become a commonly used benchmark environment
allowing algorithms to train on various Atari 2600 games. In many games the
state-of-the-art algorithms outperform humans. In this paper we introduce a new
learning environment, the Retro Learning Environment --- RLE, that can run
games on the Super Nintendo Entertainment System (SNES), Sega Genesis and
several other gaming consoles. The environment is expandable, allowing for more
video games and consoles to be easily added to the environment, while
maintaining the same interface as ALE. Moreover, RLE is compatible with Python
and Torch. SNES games pose a significant challenge to current algorithms due to
their higher level of complexity and versatility.


title: Group theoretical methods to construct the graphene

abstract:
  In this paper, the tiling of the Euclidean plane with regular hexagons whose
vertices are occupied by carbon atoms is called the graphene. We describe six
different ways to generate the graphene by the means of group theory. There are
two ways starting from the triangular lattice of Lie algebra $A_2$ and $G_2$,
and one way for each of the Lie algebras $B_3$, $C_3$ and $A_3$, by projecting
the weight system of their lowest representation to the hexagons of $A_2$.
Colouring of the graphene is presented. Changing from one colouring to another
is called phase transition. Multistep refinements of the graphene are
described.


title:
Heat transfer in laminar Couette flow laden with rigid spherical
  particles

abstract:
  We study heat transfer in plane Couette flow laden with rigid spherical
particles by means of direct numerical simulations using a direct-forcing
immersed boundary method to account for the dispersed phase. A volume of fluid
approach is employed to solve the temperature field inside and outside of the
particles.
  We focus on the variation of the heat transfer with the particle Reynolds
number, total volume fraction (number of particles) and the ratio between the
particle and fluid thermal diffusivity, quantified in terms of an effective
suspension diffusivity. We show that, when inertia at the particle scale is
negligible, the heat transfer increases with respect to the unladen case
following an empirical correlation recently proposed. In addition, an average
composite diffusivity can be used to predict the effective diffusivity of the
suspension the inertialess regime when varying the molecular diffusion in the
two phases. At finite particle inertia, however, the heat transfer increase is
significantly larger, saturating at higher volume fractions. By phase-ensemble
averaging we identify the different mechanisms contributing to the total heat
transfer and show that the increase of the effective conductivity observed at
finite inertia is due to the increase of the transport associated to fluid and
particle velocity. We also show that the heat conduction in the solid phase
reduces when increasing the particle Reynolds number and so that particles of
low thermal diffusivity weakly alter the total heat flux in the suspension at
finite particle Reynolds numbers. On the other hand, a higher particle thermal
diffusivity significantly increase the total heat transfer.


title:
Moments and Cumulants in Infinite Dimensions with Applications to
  Poisson, Gamma and Dirichlet-Ferguson Random Measures

abstract:
  We show that the chaos representation of some Compound Poisson Type processes
displays an underlying intrinsic combinatorial structure, partly independent of
the chosen process. From the computational viewpoint, we solve the arising
combinatorial complexity by means of the moments/cumulants duality for the laws
of the corresponding processes, themselves measures on distributional spaces,
and provide a combinatorial interpretation of the associated 'extended' Fock
spaces. From the theoretical viewpoint, in the case of the Gamma measure, we
trace back such complexity to its 'simplicial part', i.e. the
Dirichlet-Ferguson measure, hence to the Dirichlet distribution on the
finite-dimensional simplex. We thoroughly explore the combinatorial and
algebraic properties of the latter distribution, arising in connection with
cycle index polynomials of symmetric groups and dynamical symmetry algebras of
confluent Lauricella functions.


title:
Prime II$_1$ factors arising from irreducible lattices in products of
  rank one simple Lie groups

abstract:
  We prove that if $\Gamma$ is an icc irreducible lattice in a product of
connected non-compact rank one simple Lie groups with finite center, then the
II$_1$ factor $L(\Gamma)$ is prime. In particular, we deduce that the II$_1$
factors associated to the arithmetic groups $\text{PSL}_2(\mathbb Z[\sqrt{d}])$
and $\text{PSL}_2(\mathbb Z[S^{-1}])$ are prime, for any square-free integer
$d\geq 2$ with $d\not\equiv 1 mod{4}$ and any finite non-empty set of primes
$S$. This provides the first examples of prime II$_1$ factors arising from
lattices in higher rank semisimple Lie groups. More generally, we describe all
tensor product decompositions of $L(\Gamma)$ for icc countable groups $\Gamma$
that are measure equivalent to a product of non-elementary hyperbolic groups.
In particular, we show that $L(\Gamma)$ is prime, unless $\Gamma$ is a product
of infinite groups, in which case we prove a unique prime factorization result
for $L(\Gamma)$.


title: Categorical geometric symmetric Howe duality

abstract:
  We provide a natural geometric setting for symmetric Howe duality. This is
realized as a (loop) sl(n) action on derived categories of coherent sheaves on
certain varieties arising in the geometry of the Beilinson-Drinfeld
Grassmannian.
  The main construction parallels our earlier work on categorical sl(n) actions
and skew Howe duality. In that case the varieties involved arose in the
geometry of the affine Grassmannian. We discuss some relationships between the
two actions.


title: Topos points of quasi-coherent sheaves over monoid schemes

abstract:
  Let $X$ be a monoid scheme. We will show that the stalk at any point of $X$
defines a point of the topos $\Qc(X)$ of quasi-coherent sheaves over $X$. As it
turns out, every topos point of $\Qc(X)$ is of this form if $X$ satisfies some
finiteness conditions. In particular, it suffices for $M/M^\times$ to be
finitely generated when $X$ is affine, where $M^\times$ is the group of
invertible elements.
  This allows us to prove that two quasi-projective monoid schemes $X$ and $Y$
are isomorphic if and only if $\Qc(X)$ and $\Qc(Y)$ are equivalent.
  The finiteness conditions are essential, as one can already conclude by the
work of A. Connes and C. Consani \cite{cc1}. We will study the topos points of
free commutative monoids and show that already for $\mathbb{N}^\infty$, there
are `hidden' points. That is to say, there are topos points which are not
coming from prime ideals. This observation reveals that there might be a more
interesting `geometry of monoids'.


title:
Destruction of Magnetic Long-Range Order by Hole-Induced Skyrmions in
  Two-Dimensional Heisenberg Model

abstract:
  Motivated by the rapid destruction of antiferromagnetic long-range order in
hole-doped cuprate high-temperature superconductors, we study the effect of
skyrmions on the magnetic long-range order (MLRO). Here we assume that either a
skyrmion or antiskyrmion is introduced by a doped hole. Our numerical
simulation indicates that in the case of isolated skyrmions, there is an abrupt
disappearance of MLRO for doping concentration $x < 1.0\times 10^{-4}$. In the
case of skyrmion-antiskyrmion pairs, the critical doping concentration $x_c$
for the suppression of MLRO is given as a function of the separation of the
pairs. For a moderate separation of $3 - 4$ lattice constants, we find that the
critical doping is consistent with the experimental value.


title:
A Low-rank Control Variate for Multilevel Monte Carlo Simulation of
  High-dimensional Uncertain Systems

abstract:
  Multilevel Monte Carlo (MLMC) is a recently proposed variation of Monte Carlo
(MC) simulation that achieves variance reduction by simulating the governing
equations on a series of spatial (or temporal) grids with increasing
resolution. Instead of directly employing the fine grid solutions, MLMC
estimates the expectation of the quantity of interest from the coarsest grid
solutions as well as differences between each two consecutive grid solutions.
When the differences corresponding to finer grids become smaller, hence less
variable, fewer MC realizations of finer grid solutions are needed to compute
the difference expectations, thus leading to a reduction in the overall work.
This paper presents an extension of MLMC, referred to as multilevel control
variates (MLCV), where a low-rank approximation to the solution on each grid,
obtained primarily based on coarser grid solutions, is used as a control
variate for estimating the expectations involved in MLMC. Cost estimates as
well as numerical examples are presented to demonstrate the advantage of this
new MLCV approach over the standard MLMC when the solution of interest admits a
low-rank approximation and the cost of simulating finer grids grows fast.


title:
On the study of solutions for a non linear differential equation on
  compact Riemannian Manifolds

abstract:
  In this paper we study the existence of solutions for a class of non-linear
differential equation on compact Riemannian manifolds. We establish a lower and
upper solutions' method to show the existence of a smooth positive solution for
the equation (EQ1) \begin{equation}
  \label{E4} \Delta u \ + \ a(x)u \ = \ f(x)F(u) \ + \ h(x)H(u), (EQ1)
\end{equation} where \ $a, \ f, \ h$ \ are positive smooth functions on $M^n$,
a $n-$dimensional compact Riemannian manifold, and \ $ F, \ H$ \ are
non-decreasing smooth functions on $\mathbb{R}$. In \cite{djadli} the equation
(EQ1) was studied when $F(u)=u^{2^{\ast}-1} $ and $H(u)=u^q$ in the Riemannian
context, i.e., \begin{equation} \label{E3} \Delta u \ + \ a(x)u \ = \
f(x)u^{2^{\ast}-1} \ + \ h(x)u^q, (EQ2) \end{equation} \nd where \ $0 \ < \ q \
< 1$. In \cite{correa} Corr\^ea, Gon\c{c}alves and Melo studied an equation of
the type equation (EQ2), in the Euclidean context.


title: Geometry of isolated horizons

abstract:
  While the formalism of isolated horizons is known for some time, only quite
recently the near horizon solution of Einstein's equations has been found in
the Bondi-like coordinates by Krishnan in 2012. In this framework, the
space-time is regarded as the characteristic initial value problem with the
initial data given on the horizon and another null hypersurface. It is not
clear, however, what initial data reproduce the simplest physically relevant
black hole solution, namely that of Kerr-Newman which describes stationary,
axisymmetric black hole with charge. Moreover, Krishnan's construction employs
the non-twisting null geodesic congruence and the tetrad which is parallelly
propagated along this congruence. While the existence of such tetrad can be
easily established in general, its explicit form can be very difficult to find
and, in fact it has not been provided for the Kerr-Newman metric. The goal of
this thesis was to fill this gap and provide a full description of the
Kerr-Newman metric in the framework of isolated horizons. In the theoretical
part of the thesis we review the spinor and Newman-Penrose formalism, basic
geometry of isolated horizons and then present our results. Thesis is
complemented by several appendices.


title:
Characterization and linear-time detection of minimal obstructions to
  concave-round graphs and the circular-ones property

abstract:
  A graph is concave-round if its vertices can be circularly enumerated so that
the closed neighbourhood of each vertex is an interval in the enumeration. In
this work, we give a minimal forbidden induced subgraph characterization for
the class of concave-round graphs, solving a problem posed by Bang-Jensen,
Huang, and Yeo [SIAM J Discrete Math, 13:179--193, 2000]. In addition, we show
that it is possible to find one such forbidden induced subgraph in linear time
in any given graph that is not concave-round. As part of the analysis, we
obtain characterizations by minimal forbidden submatrices for the circular-ones
property for rows and for the circular-ones property for rows and columns and
show that, also for both variants of the property, one of the corresponding
forbidden submatrices can be found (if present) in any given matrix in linear
time. We make some final remarks regarding connections to some classes of
circular-arc graphs.


title: Wronskians of theta functions and series for $1/\pi$

abstract:
  In this article, we define functions analogous to Ramanujan's function $f(n)$
defined in his famous paper "Modular equations and approximations to $\pi$". We
then use these new functions to study Ramanujan's series for $1/\pi$ associated
with the classical, cubic and quartic bases.


title: Self-Similar Polygonal Tiling

abstract:
  The purpose of this paper is to give the flavor of the subject of
self-similar tilings in a relatively elementary setting, and to provide a novel
method for the construction of such polygonal tilings.


title:
Stabilization of (G)EIM in presence of measurement noise: application to
  nuclear reactor physics

abstract:
  The Empirical Interpolation Method (EIM) and its generalized version (GEIM)
can be used to approximate a physical system by combining data measured from
the system itself and a reduced model representing the underlying physics. In
presence of noise, the good properties of the approach are blurred in the sense
that the approximation error no longer converges but even diverges. We propose
to address this issue by a least-squares projection with constrains involving a
some a priori knowledge of the geometry of the manifold formed by all the
possible physical states of the system. The efficiency of the approach, which
we will call Constrained Stabilized GEIM (CS-GEIM), is illustrated by numerical
experiments dealing with the reconstruction of the neutron flux in nuclear
reactors. A theoretical justification of the procedure will be presented in
future works.


title:
Room Temperature Formation of Carbon Onions via Ultrasonic Agitation of
  MoS2 in Isopropanol

abstract:
  Ultrasonic agitation is a proven method for breaking down layered materials
such as MoS2 into single or few layer nanoparticles. In this experiment, MoS2
powder is sonicated in isopropanol for an extended period of time in an attempt
to create particles of the smallest possible size. As expected, the process
yielded a significant quantity of nanoscale MoS2 in the form of finite layer
sheets with lateral dimensions as small as a few tens of nanometers. Although
no evidence was found to indicate a larger the longer sonication times resulted
in a significant increase in yield of single layer MoS2, the increased
sonication did result in the formation of several types of carbon allotropes in
addition to the sheets of MoS2. These carbon structures appear to originate
from the breakdown of the isopropanol and consist of finite layer graphite
platelets as well as a large number of multi-walled fullerenes, also known as
carbon onions. Both the finite layer graphite and MoS2 nanoplatelets were both
found to be heavily decorated with carbon onions. However, isolated clusters of
carbon onions could also be found. Our results show that liquid exfoliation of
MoS2 is not only useful for forming finite layer MoS2, but also creating carbon
onions at room temperature as well.


title: Minimax-optimal semi-supervised regression on unknown manifolds

abstract:
  We consider semi-supervised regression when the predictor variables are drawn
from an unknown manifold. A simple two step approach to this problem is to: (i)
estimate the manifold geodesic distance between any pair of points using both
the labeled and unlabeled instances; and (ii) apply a k nearest neighbor
regressor based on these distance estimates. We prove that given sufficiently
many unlabeled points, this simple method of geodesic kNN regression achieves
the optimal finite-sample minimax bound on the mean squared error, as if the
manifold were known. Furthermore, we show how this approach can be efficiently
implemented, requiring only O(k N log N) operations to estimate the regression
function at all N labeled and unlabeled points. We illustrate this approach on
two datasets with a manifold structure: indoor localization using WiFi
fingerprints and facial pose estimation. In both cases, geodesic kNN is more
accurate and much faster than the popular Laplacian eigenvector regressor.


title:
Surface stress effects on the electrostatic pull-in instability of
  nanomechanical systems

abstract:
  The electrostatic pull-in instability (EPI), within the framework of the
nanoelectromechanical systems (NEMS) has been shown as a robust and versatile
method for characterizing mechanical properties of nanocantilevers. This paper
aims to investigate the surface effects, specifically residual surface stress
and surface elasticity, on the EPI of micro and nano-scale cantilevers as well
as double clamped beams. Since the cantilever has one end free, it has no
residual stress, thus the strain-independent component of the surface stress or
intrinsic surface stress has no influence on the EPI, as long as it has small
deformation. The strain-dependent component of the surface stress or surface
elasticity changes the bending stiffness of the cantilever and, consequently,
induces shifts in the EPI. For double clamped beams, the effective residual
surface stress comes into play and modifies the effective residual stress of
the beam. The nonlinear electromechanical coupled equations, which take into
account the surface effects are solved numerically. The theoretical results
presented in this paper indicate that the EPI is very sensitive to the surface
effects, especially when a double clamped beam is employed. The results show
that the influence of surface effects on the EPI of cantilevers become more
profound when the thickness is below 50 nm, while the influence on double
clamped beams is significant even at sub-micron scale. The present study can
provide helpful insights for the design and characterization of NEMS switches.
Moreover, the results can be used to provide the proof of concepts of a new
surface stress sensing method using EPI in nanomechanical sensor systems.


title: On the Hardy space theory of compensated compactness quantities

abstract:
  We make progress on a problem of R. Coifman, P.-L. Lions, Y. Meyer, and S.
Semmes from 1993 by showing that the Jacobian operator $J$ does not map
$W^{1,n}(\mathbb R^n,\mathbb R^n)$ onto the Hardy space $\mathcal{H}^1(\mathbb
R^n)$ for any $n \ge 2$. The related question about surjectivity of $J \colon
\dot{W}^{1,n}(\mathbb R^n,\mathbb R^n) \to \mathcal{H}^1(\mathbb R^n)$ is still
open.
  The second main result and its variants reduce the proof of $\mathcal{H}^1$
regularity of a large class of compensated compactness quantities to an
integration by parts or easy arithmetic, and applications are presented.
Furthermore, we exhibit a class of nonlinear partial differential operators in
which weak sequential continuity is a strictly stronger condition than
$\mathcal{H}^1$ regularity, shedding light on another problem of Coifman,
Lions, Meyer, and Semmes.


title:
Measurement of neutral-current $K^+$ production by neutrinos using
  MINERvA

abstract:
  Neutral-current production of $K^{+}$ by atmospheric neutrinos is a
background in searches for the proton decay $p \rightarrow K^{+} \bar{\nu}$.
Reactions such as $\nu p \rightarrow \nu K^{+} \Lambda$ are indistinguishable
from proton decays when the decay products of the $\Lambda$ are below detection
threshold. Events with $K^{+}$ are identified in MINERvA by reconstructing the
timing signature of a $K^{+}$ decay at rest. A sample of 201 neutrino-induced
neutral-current $K^{+}$ events is used to measure differential cross sections
with respect to the $K^{+}$ kinetic energy, and the non-$K^{+}$ hadronic
visible energy. An excess of events at low hadronic visible energy is observed
relative to the prediction of the NEUT event generator. Good agreement is
observed with the cross section prediction of the GENIE generator. A search for
photons from $\pi^{0}$ decay, which would veto a neutral-current $K^{+}$ event
in a proton decay search, is performed, and a 2$\sigma$ deficit of detached
photons is observed relative to the GENIE prediction.