title:
Photoionization of multishell fullerenes studied by ab initio and model
  approaches

abstract:
  Photoionization of two buckyonions, C$_{60}$@C$_{240}$ and C$_{20}$@C$_{60}$,
is investigated by means of time-dependent density-functional theory (TDDFT).
The TDDFT-based photoabsorption spectrum of C$_{60}$@C$_{240}$, calculated in a
broad photon energy range, resembles the sum of spectra of the two isolated
fullerenes, thus illustrating the absence of strong plasmonic coupling between
the fullerenes which was proposed earlier. The calculated spectrum of the
smaller buckyonion, C$_{20}$@C$_{60}$, differs significantly from the sum of
the cross sections of the individual fullerenes because of strong geometrical
distortion of the system. The contribution of collective electron excitations
arising in individual fullerenes is evaluated by means of plasmon resonance
approximation (PRA). An extension of the PRA formalism is presented, which
allows for the study of collective electron excitations in multishell
fullerenes under photon impact. An advanced analysis of photoionization of
buckyonions, performed using modern computational and analytical approaches,
provides valuable information on the response of complex molecular systems to
the external electromagnetic field.


title: Update on nuclear structure effects in light muonic atoms

abstract:
  We present calculations of the nuclear structure corrections to the Lamb
shift in light muonic atoms, using state-of-the-art nuclear potentials. We
outline updated results on finite nucleon size contributions.


title:
Rapid Circumstellar Disk Evolution and an Accelerating Star Formation
  Rate in the Infrared Dark Cloud M17 SWex

abstract:
  We present a catalog of 840 X-ray sources and first results from a 100 ks
Chandra X-ray Observatory imaging study of the filamentary infrared dark cloud
G014.225$-$00.506, which forms the central regions of a larger cloud complex
known as the M17 southwest extension (M17 SWex). In addition to the rich
population of protostars and young stellar objects with dusty circumstellar
disks revealed by Spitzer Space Telescope archival data, we discover a
population of X-ray-emitting, intermediate-mass pre--main-sequence stars (IMPS)
that lack infrared excess emission from circumstellar disks. We model the
infrared spectral energy distributions of this source population to measure its
mass function and place new constraints on the inner dust disk destruction
timescales for 2-8 $M_{\odot}$ stars. We also place a lower limit on the star
formation rate (SFR) and find that it is quite high ($\dot{M}\ge
0.007~M_{\odot}$ yr$^{-1}$), equivalent to several Orion Nebula Clusters in
G14.225$-$0.506 alone, and likely accelerating. The cloud complex has not
produced a population of massive, O-type stars commensurate with its SFR. This
absence of very massive (${\ge}20~M_{\odot}$) stars suggests that either (1)
M17 SWex is an example of a distributed mode of star formation that will
produce a large OB association dominated by intermediate-mass stars but
relatively few massive clusters, or (2) the massive cores are still in the
process of accreting sufficient mass to form massive clusters hosting O stars.


title: Stabilized Sparse Online Learning for Sparse Data

abstract:
  Stochastic gradient descent (SGD) is commonly used for optimization in
large-scale machine learning problems. Langford et al. (2009) introduce a
sparse online learning method to induce sparsity via truncated gradient. With
high-dimensional sparse data, however, the method suffers from slow convergence
and high variance due to the heterogeneity in feature sparsity. To mitigate
this issue, we introduce a stabilized truncated stochastic gradient descent
algorithm. We employ a soft-thresholding scheme on the weight vector where the
imposed shrinkage is adaptive to the amount of information available in each
feature. The variability in the resulted sparse weight vector is further
controlled by stability selection integrated with the informative truncation.
To facilitate better convergence, we adopt an annealing strategy on the
truncation rate, which leads to a balanced trade-off between exploration and
exploitation in learning a sparse weight vector. Numerical experiments show
that our algorithm compares favorably with the original algorithm in terms of
prediction accuracy, achieved sparsity and stability.


title: Regular polyhedra in the 3-torus

abstract:
  In this paper we discuss the classification rank $3$ lattices preserved by
finite orthogonal groups of isometries and derive from it the classification of
regular polyhedra in the $3$-dimensional torus. This classification is highly
related to the classification of regular polyhedra in the $3$-space.


title:
Numerical approximation of a coagulation-Fragmentation Model for Animal
  Group Size Statistics

abstract:
  We study numerically a coagulation-fragmentation model derived by Niwa and
further elaborated by Degond et al., where a unique equilibrium distribution of
group sizes is shown to exist in both cases of continuous and discrete group
size distributions. We provide a numerical investigation of these equilibria
using three different methods to approximate the equilibrium: a recursive
algorithm based on the work of Ma et. al., a Newton method and the resolution
of the time-dependent problem. All three schemes are validated by showing that
they approximate the predicted small and large size asymptotic behaviour of the
equilibrium accurately. The recursive algorithm is used to investigate the
transition from discrete to continuous size distributions and the time
evolution scheme is exploited to show uniform convergence to equilibrium in
time and to determine convergence rates.


title: Modelocked mid-infrared frequency combs in a silicon microresonator

abstract:
  Mid-infrared (mid-IR) frequency combs have broad applications in molecular
spectroscopy and chemical/biological sensing. Recently developed
microresonator-based combs in this wavelength regime could enable portable and
robust devices using a single-frequency pump field. Here, we report the first
demonstration of a modelocked microresonator-based frequency comb in the mid-IR
spanning 2.4 {\mu}m to 4.3 {\mu}m. We observe high pump-to-comb conversion
efficiency, in which 40% of the pump power is converted to the output comb
power. Utilizing an integrated PIN structure allows for tuning the silicon
microresonator and controling modelocking and cavity soliton formation,
simplifying the generation, monitoring and stabilization of mid-IR frequency
combs via free-carrier detection and control. Our results significantly advance
microresonator-based comb technology towards a portable and robust mid-IR
spectroscopic device that operates at low pump powers.


title: Spin Transport at Interfaces with Spin-Orbit Coupling: Phenomenology

abstract:
  This paper presents the boundary conditions needed for drift-diffusion models
to treat interfaces with spin-orbit coupling. Using these boundary conditions
for heavy metal/ferromagnet bilayers, solutions of the drift-diffusion
equations agree with solutions of the spin-dependent Boltzmann equation and
allow for a much simpler interpretation of the results. A key feature of these
boundary conditions is their ability to capture the role that in-plane electric
fields have on the generation of spin currents that flow perpendicularly to the
interface. The generation of these spin currents is a direct consequence of the
effect of interfacial spin-orbit coupling on interfacial scattering. In heavy
metal/ferromagnet bilayers, these spin currents provide an important mechanism
for the creation of damping-like and field-like torques; they also lead to
possible reinterpretations of experiments in which interfacial contributions to
spin torques are thought to be suppressed.


title:
A Linear-Time Branching-Time Spectrum for Behavioral Specification
  Theories

abstract:
  We propose behavioral specification theories for most equivalences in the
linear-time--branching-time spectrum. Almost all previous work on specification
theories focuses on bisimilarity, but there is a clear interest in
specification theories for other preorders and equivalences. We show that
specification theories for preorders cannot exist and develop a general scheme
which allows us to define behavioral specification theories, based on
disjunctive modal transition systems, for most equivalences in the
linear-time--branching-time spectrum.


title: The chromatic number of the square of subcubic planar graphs

abstract:
  Wegner conjectured in 1977 that the square of every planar graph with maximum
degree at most $3$ is $7$-colorable. We prove this conjecture using the
discharging method and computational techniques to verify reducible
configurations.


title: Entangled photon added coherent states

abstract:
  We study the degree of entanglement of arbitrary superpositions of $m,n$
photon-added coherent states (PACS) $|\psi\rangle \propto u |{\alpha},m\rangle
|{\beta},n \rangle+ v |{\beta},n\rangle |{\alpha},m\rangle$ using the
concurrence, and obtain the general conditions for maximal entanglement. We
show that photon addition process can be identified as an entanglement enhancer
operation for superpositions of coherent states (SCS). Specifically for the
known bipartite positive SCS: $|\psi\rangle \propto |\alpha\rangle_a
|-\alpha\rangle_b + |-\alpha\rangle_a |\alpha\rangle_b $ whose entanglement
tends to zero for $\alpha \to 0$, can be maximal if al least one photon is
added in a subsystem. A full family of maximally entangled PACS is also
presented. We also analyzed the decoherence effects in the entangled PACS
induced by a simple depolarizing channel. We find that robustness against
depolarization is increased by adding photons to the coherent states of the
superposition. We obtain the dependence of the critical depolarization
$p_{\text{crit}}$ for null entanglement as a function of $m,n, \alpha$ and
$\beta $.


title: Online Action Detection

abstract:
  In online action detection, the goal is to detect the start of an action in a
video stream as soon as it happens. For instance, if a child is chasing a ball,
an autonomous car should recognize what is going on and respond immediately.
This is a very challenging problem for four reasons. First, only partial
actions are observed. Second, there is a large variability in negative data.
Third, the start of the action is unknown, so it is unclear over what time
window the information should be integrated. Finally, in real world data, large
within-class variability exists. This problem has been addressed before, but
only to some extent. Our contributions to online action detection are
threefold. First, we introduce a realistic dataset composed of 27 episodes from
6 popular TV series. The dataset spans over 16 hours of footage annotated with
30 action classes, totaling 6,231 action instances. Second, we analyze and
compare various baseline methods, showing this is a challenging problem for
which none of the methods provides a good solution. Third, we analyze the
change in performance when there is a variation in viewpoint, occlusion,
truncation, etc. We introduce an evaluation protocol for fair comparison. The
dataset, the baselines and the models will all be made publicly available to
encourage (much needed) further research on online action detection on
realistic data.


title:
A little bit of extra functoriality for Ext and the computation of the
  Gerstenhaber bracket

abstract:
  We show that the action of the Lie algebra HH^1(A) of outer derivations of an
associative algebra A on the Hochschild cohomology HH^*(A) of A given by the
Gerstenhaber bracket can be computed in terms of an arbitrary projective
resolution of A as an A-bimodule, without having recourse to comparison maps
between the resolution and the bar resolution.


title:
HIRL: Hierarchical Inverse Reinforcement Learning for Long-Horizon Tasks
  with Delayed Rewards

abstract:
  Reinforcement Learning (RL) struggles in problems with delayed rewards, and
one approach is to segment the task into sub-tasks with incremental rewards. We
propose a framework called Hierarchical Inverse Reinforcement Learning (HIRL),
which is a model for learning sub-task structure from demonstrations. HIRL
decomposes the task into sub-tasks based on transitions that are consistent
across demonstrations. These transitions are defined as changes in local
linearity w.r.t to a kernel function. Then, HIRL uses the inferred structure to
learn reward functions local to the sub-tasks but also handle any global
dependencies such as sequentiality.
  We have evaluated HIRL on several standard RL benchmarks: Parallel Parking
with noisy dynamics, Two-Link Pendulum, 2D Noisy Motion Planning, and a Pinball
environment. In the parallel parking task, we find that rewards constructed
with HIRL converge to a policy with an 80% success rate in 32% fewer time-steps
than those constructed with Maximum Entropy Inverse RL (MaxEnt IRL), and with
partial state observation, the policies learned with IRL fail to achieve this
accuracy while HIRL still converges. We further find that that the rewards
learned with HIRL are robust to environment noise where they can tolerate 1
stdev. of random perturbation in the poses in the environment obstacles while
maintaining roughly the same convergence rate. We find that HIRL rewards can
converge up-to 6x faster than rewards constructed with IRL.


title: Lynch-Morawska Systems on Strings

abstract:
  We investigate properties of convergent and forward-closed string rewriting
systems in the context of the syntactic criteria introduced in
\cite{LynchMorawska} by Christopher Lynch and Barbara Morawska (we call these
$LM$-Systems). Since a string rewriting system can be viewed as a
term-rewriting system over a signature of purely monadic function symbols, we
adapt their definition to the string rewriting case. We prove that the
subterm-collapse problem for convergent and forward-closed string rewriting
systems is effectively solvable. Therefore, there exists a decision procedure
that verifies if such a system is an $LM$-System. We use the same construction
to prove that the \emph{cap problem} from the field of cryptographic protocol
analysis, which is undecidable for general $LM$-systems, is decidable when
restricted to the string rewriting case.


title:
Time and band limiting for matrix valued functions: an integral and a
  commuting differential operator

abstract:
  The problem of recovering a signal of finite duration from a piece of its
Fourier transform was solved at Bell Labs in the $1960$'s, by exploiting a
"miracle": a certain naturally appearing integral operator commutes with an
explicit differential one. Here we show that this same miracle holds in a
matrix valued version of the same problem.


title:
Parameter Estimation of Gaussian Stationary Processes using the
  Generalized Method of Moments

abstract:
  We consider the class of all stationary Gaussian process with explicit
parametric spectral density. Under some conditions on the autocovariance
function, we defined a GMM estimator that satisfies consistency and asymptotic
normality, using the Breuer-Major theorem and previous results on ergodicity.
This result is applied to the joint estimation of the three parameters of a
stationary Ornstein-Uhlenbeck (fOU) process driven by a fractional Brownian
motion. The asymptotic normality of its GMM estimator applies for any H in
(0,1) and under some restrictions on the remaining parameters. A numerical
study is performed in the fOU case, to illustrate the estimator's practical
performance when the number of datapoints is moderate.


title:
Ground States and Zero-Temperature Measures at the Boundary of Rotation
  Sets

abstract:
  We consider a continuous dynamical system $f:X\to X$ on a compact metric
space $X$ equipped with an $m$-dimensional continuous potential
$\Phi=(\phi_1,\cdots,\phi_m):X\to \bR^m$. We study the set of ground states $
GS(\alpha)$ of the potential $\alpha\cdot \Phi$ as a function of the direction
vector $\alpha\in S^{m-1}$. %We also study the corresponding rotation vectors
$\rv(GS(\alpha))$. We show that the structure of the ground state sets is
naturally related to the geometry of the generalized rotation set of $\Phi$. In
particular, for each $\alpha$ the set of rotation vectors of $ GS(\alpha)$
forms a non-empty, compact and connected subset of a face $F_\alpha(\Phi)$ of
the rotation set associated with $\alpha$. Moreover, every ground state
maximizes entropy among all invariant measures with rotation vectors in
$F_\alpha(\Phi)$. We further establish the occurrence of several quite
unexpected phenomena. Namely, we construct for any $m\in\bN$ examples with an
exposed boundary point (i.e. $F_\alpha(\Phi)$ being a singleton) without a
unique ground state. Further, we establish the possibility of a line segment
face $F_\alpha(\Phi)$ with a unique but non-ergodic ground state. Finally, we
establish the possibility that the set of rotation vectors of $GS(\alpha)$ is a
non-trivial line segment.


title: On the Ramsey Numbers of Trees with Small Diameter

abstract:
  We estimate the Ramsey number r(T) = r(T,T) for various trees T, obtaining a
precise value for r(T) for a large number of trees of diameter 3. Furthermore
we prove that all trees of diameter 3 are Ramsey unsaturated as defined by
Balister, Lehel, and Schelp in their article "Ramsey unsaturated and saturated
graphs."


title: A coaxial line architecture for integrating and scaling 3D cQED systems

abstract:
  Numerous loss mechanisms can limit coherence and scalability of planar and
3D-based circuit quantum electrodynamics (cQED) devices, particularly due to
their packaging. The low loss and natural isolation of 3D enclosures make them
good candidates for coherent scaling. We introduce a coaxial transmission line
device architecture with coherence similar to traditional 3D cQED systems.
Measurements demonstrate well-controlled external and on-chip couplings, a
spectrum absent of cross-talk or spurious modes, and excellent resonator and
qubit lifetimes. We integrate a resonator-qubit system in this architecture
with a seamless 3D cavity, and separately pattern a qubit, readout resonator,
Purcell filter and high-Q stripline resonator on a single chip. Device
coherence and its ease of integration make this a promising tool for complex
experiments.


title: A weighted edge-count two-sample test for multivariate and object data

abstract:
  Two-sample tests for multivariate data and non-Euclidean data are widely used
in many fields. Parametric tests are mostly restrained to certain types of data
that meets the assumptions of the parametric models. In this paper, we study a
nonparametric testing procedure that utilizes graphs representing the
similarity among observations. It can be applied to any data types as long as
an informative similarity measure on the sample space can be defined. The
classic test based on a similarity graph has a problem when the two sample
sizes are different. We solve the problem by applying appropriate weights to
different components of the classic test statistic. The new test exhibits
substantial power gains in simulation studies. Its asymptotic permutation null
distribution is derived and shown to work well under finite samples,
facilitating its application to large datasets. The new test is illustrated
through an analysis on a real dataset of network data.


title: The centralizer of Komuro-expansive flows and expansive R^d-actions

abstract:
  In this paper we study the centralizer of flows and $\mathbb R^d$-actions on
compact Riemannian manifolds. We prove that the centralizer of every $C^\infty$
Komuro-expansive flow with non-ressonant singularities is trivial, meaning it
is the smallest possible, and deduce there exists an open and dense subset of
geometric Lorenz attractors with trivial centralizer. We show that $\mathbb
R^d$-actions obtained as suspension of $\mathbb Z^d$-actions are expansive if
and only if the same holds for the $\mathbb Z^d$-actions. We also show that
homogeneous expansive $\mathbb R^d$-actions have quasi-trivial centralizers,
meaning that it consists of orbit invariant, continuous linear
reparametrizations of the $\mathbb R^d$-action. In particular, homogeneous
Anosov $\mathbb R^d$-actions have quasi-trivial centralizer.


title:
An Examination of the Multi-Peaked Analytically Extended Function for
  Approximation of Lightning Channel-Base Currents

abstract:
  A multi-peaked version of the analytically extended function (AEF) intended
for approximation of multi-peaked lightning current wave-forms will be
presented along with some of its basic properties. A general framework for
estimating the parameters of the AEF using the Marquardt least-squares method
(MLSM) for a waveform with an arbitrary (finite) number of peaks as well as a
given charge trans-fer and specific energy will also be described. This
framework is used to find parameters for some common single-peak wave-forms and
some advantages and disadvantages of the approach will be discussed.


title: Approximation Vector Machines for Large-scale Online Learning

abstract:
  One of the most challenging problems in kernel online learning is to bound
the model size and to promote the model sparsity. Sparse models not only
improve computation and memory usage, but also enhance the generalization
capacity, a principle that concurs with the law of parsimony. However,
inappropriate sparsity modeling may also significantly degrade the performance.
In this paper, we propose Approximation Vector Machine (AVM), a model that can
simultaneously encourage the sparsity and safeguard its risk in compromising
the performance. When an incoming instance arrives, we approximate this
instance by one of its neighbors whose distance to it is less than a predefined
threshold. Our key intuition is that since the newly seen instance is expressed
by its nearby neighbor the optimal performance can be analytically formulated
and maintained. We develop theoretical foundations to support this intuition
and further establish an analysis to characterize the gap between the
approximation and optimal solutions. This gap crucially depends on the
frequency of approximation and the predefined threshold. We perform the
convergence analysis for a wide spectrum of loss functions including Hinge,
smooth Hinge, and Logistic for classification task, and $l_1$, $l_2$, and
$\epsilon$-insensitive for regression task. We conducted extensive experiments
for classification task in batch and online modes, and regression task in
online mode over several benchmark datasets. The results show that our proposed
AVM achieved a comparable predictive performance with current state-of-the-art
methods while simultaneously achieving significant computational speed-up due
to the ability of the proposed AVM in maintaining the model size.


title:
Enhanced superconductivity by strain and carrier-doping in borophene: A
  first principles prediction

abstract:
  We predict by first principles calculations that the recently prepared
borophene is a pristine two-dimensional (2D) monolayer superconductor, in which
the superconductivity can be significantly enhanced by strain and charge
carrier doping. The intrinsic metallic ground state with high density of states
at Fermi energy and strong Fermi surface nesting lead to sizeable
electron-phonon coupling, making the freestanding borophene superconduct with
$T_c$ close to 19.0 K. The tensile strain can increase $T_c$ to 27.4 K, while
the hole doping can notably increase $T_c$ to 34.8 K. The results indicate that
the borophene grown on substrates with large lattice parameters or under
photoexcitation can show enhanced superconductivity with $T_c$ far more above
liquid hydrogen temperature of 20.3 K, which will largely broaden the
applications of such novel material.


title:
Gravitational Leptogenesis in the Axion Inflation with an SU(2) gauge
  field

abstract:
  We present an intrinsic leptogenesis mechanism in models of axion inflation
with a classical SU(2) gauge field. The gauge field is coupled to the axion
with a Chern-Simons interaction and comprises a tiny fraction of the total
energy, $\frac{\rho_{_{\rm YM}}}{\rho_{_{\rm tot}}}\lesssim\epsilon^2$.
However, it has spin-2 fluctuations which breaks the parity and leads to the
generation of chiral gravitational waves during inflation. By the gravitational
anomaly in SM, it naturally creates a net lepton number density, sufficient to
explain the matter asymmetry. We show that this mechanism can generate the
observed value of baryon to photon number density in a natural range of
parameters and yet has a small chiral tensor power spectrum on large scales.


title:
High-resolution three-dimensional spin- and angle-resolved photoelectron
  spectrometer using vacuum ultraviolet laser light

abstract:
  We describe a spin- and angle-resolved photoelectron spectroscopy (SARPES)
apparatus with a vacuum-ultraviolet (VUV) laser ($h\nu$= 6.994 eV) developed at
the Laser and Synchrotron Research Center at the Institute for Solid State
Physics, The University of Tokyo. The spectrometer consists of a hemispherical
photoelectron analyzer equipped with an electron deflector function and twin
very-low-energy-electron-diffraction-type spin detectors, which allows us to
analyze the spin vector of a photoelectron three-dimensionally with both high
energy and angular resolutions. The combination of the high-performance
spectrometer and the high-photon-flux VUV laser can achieve an energy
resolution of 1.7 meV for SARPES. We demonstrate that the present laser-SARPES
machine realizes a quick SARPES on the spin-split band structure of a Bi(111)
film even with 7 meV energy and 0.7$^\circ$ angular resolutions along the
entrance-slit direction. This laser-SARPES machine is applicable to the
investigation of spin-dependent electronic states on an energy scale of a few
meV.


title: Gamma-weibull kernel estimation of the heavy tailed densities

abstract:
  We consider the nonparametric estimation of the univariate heavy tailed
probability density function (pdf) with a support on $[0,\infty)$ by
independent data. To this end we construct the new kernel estimator as a
combination of the asymmetric gamma and weibull kernels, ss. gamma-weibull
kernel. The gamma kernel is nonnegative, changes the shape depending on the
position on the semi-axis and possess good boundary properties for a wide class
of densities. Thus, we use it to estimate the pdf near the zero boundary. The
weibull kernel is based on the weibull distribution which can be heavy tailed
and hence we use it to estimate the tail of the unknown pdf. The theoretical
asymptotic properties of the proposed density estimator like bias and variance
are derived. We obtain the optimal bandwidth selection for the estimate as a
minimum of the mean integrated squared error (MISE). Optimal rate of
convergence of the MISE for the density is found.


title:
Single-Order Transmission Diffraction Gratings based on Dispersion
  Engineered All-dielectric Metasurfaces

abstract:
  A single-order transmission diffraction grating based on dispersion
engineered all-dielectric metasurfaces is proposed and its wavelength
discriminating properties have been theoretically described and confirmed using
numerical simulations. The metasurface is designed using a 2D array of
all-dielectric resonators, which emulates a Huygens source configuration to
achieve a perfect match to free-space in broad bandwidth. Using a holey
dielectric nanodisk structure as the unit cell, the resonant wavelength is
tapered across the metasurface to engineer the wavelength dependent spatial
phase gradient, to emulate a dispersive prism. Consequently, different
wavelengths are steered towards different directions and thus are discriminated
on the output image plane. Due to subwavelength periodicities involved, the
wavelength discrimination is achieved directly in the zeroth diffraction order
of the device, unlike conventional diffraction gratings, thereby providing a
high efficiency wavelength discriminating device.


title: A note on cohering power and de-cohering power

abstract:
  Cohering power and de-cohering power have recently been proposed to quantify
the ability of a quantum operation to produce and erase coherence respectively.
In this paper, we investigate the properties of cohering power and de-cohering
power. First, we prove the equivalence between two different kinds of cohering
power for any quantum operation on single qubit systems, which implies that l1
norm of coherence is monotone under Maximally incoherent operation (MIO) and
Dephasing-covariant operation (DIO) in 2-dimensional space. In higher
dimensions, however, we show that the monotonicity under MIO or DIO does not
hold. Besides, we compare the set of quantum operations with zero cohering
power with Maximally incoherent operation (MIO) and Incoherent operation (IO).
Moreover, two different types of de-cohering power are defined and we find that
they are not equal in single qubit systems. Finally, we make a comparison
between cohering power and de-cohering power for single qubit unitary
operations and show that cohering power is always larger than decohering power.


title:
Opt: A Domain Specific Language for Non-linear Least Squares
  Optimization in Graphics and Imaging

abstract:
  Many graphics and vision problems can be expressed as non-linear least
squares optimizations of objective functions over visual data, such as images
and meshes. The mathematical descriptions of these functions are extremely
concise, but their implementation in real code is tedious, especially when
optimized for real-time performance on modern GPUs in interactive applications.
In this work, we propose a new language, Opt (available under
http://optlang.org), for writing these objective functions over image- or
graph-structured unknowns concisely and at a high level. Our compiler
automatically transforms these specifications into state-of-the-art GPU solvers
based on Gauss-Newton or Levenberg-Marquardt methods. Opt can generate
different variations of the solver, so users can easily explore tradeoffs in
numerical precision, matrix-free methods, and solver approaches. In our
results, we implement a variety of real-world graphics and vision applications.
Their energy functions are expressible in tens of lines of code, and produce
highly-optimized GPU solver implementations. These solver have performance
competitive with the best published hand-tuned, application-specific GPU
solvers, and orders of magnitude beyond a general-purpose auto-generated
solver.


title:
Temperature-induced band selective localization and coherent-incoherent
  crossover in single-layer FeSe/Nb:BaTiO3 /KTaO3

abstract:
  Iron chalcogenide superconductors are multi-band systems with strong electron
correlations. Here we use angle-resolved photoemission spectroscopy to study
band dependent correlation effects in single-layer FeSe/Nb:BaTiO3/KTaO3, a new
iron chalcogenide superconductor with non-degenerate electron pockets and
interface-enhanced superconductivity. The non-degeneracy of the electron bands
helps to resolve the temperature dependent evolution of different bands. With
increasing temperature, the single layer FeSe undergoes a band-selective
localization, in which the coherent spectral weight of one electron band is
completely depleted while that of the other one remains finite. In addition,
the spectral weight of the incoherent background is enhanced with increasing
temperature, indicating a coherent-incoherent crossover. Signatures of
polaronic behavior are observed, suggesting electron-boson interactions. These
phenomena help to construct a more complete picture of electron correlations in
the FeSe family.


title: Reflection positivity and invertible topological phases

abstract:
  We implement an extended version of reflection positivity (Wick-rotated
unitarity) for invertible topological quantum field theories and compute the
abelian group of deformation classes using stable homotopy theory. We apply
these field theory considerations to lattice systems, assuming the existence
and validity of low energy effective field theory approximations, and thereby
produce a general formula for the group of Symmetry Protected Topological (SPT)
phases in terms of Thom's bordism spectra; the only input is the dimension and
symmetry group. We provide computations for fermionic systems in physically
relevant dimensions. Other topics include symmetry in quantum field theories, a
relativistic 10-fold way, the homotopy theory of relativistic free fermions,
and a topological spin-statistics theorem.

categories: hep-th cond-mat.str-el math-ph math.AT math.MP


title:
Luneburg-lens-like universal structural Pauli attraction in
  nucleus-nucleus interactions: origin of emergence of cluster structures and
  nuclear rainbows

abstract:
  The Pauli exclusion principle plays an important role in many-body fermion
systems preventing them from collapsing by repulsion. For example, the Pauli
principle causes a repulsive potential at short distances between two $\alpha$
particles. On the other hand, the existence of nuclear rainbows demonstrates
that the inter-nuclear potential is sufficiently attractive in the internal
region to cause refraction. The two concepts of repulsion and attraction are
seemingly irreconcilable. Contrary to traditional understanding, it is shown
that the Pauli principle causes a {\it universal structural Pauli attraction}
between nuclei rather than a {\it structural repulsive core}. Through
systematic studies of $\alpha$+$\alpha$, $\alpha$+$^{16}$O, $\alpha$+$^{40}$Ca
and $^{16}$O+$^{16}$O systems, it is shown that the emergence of cluster
structures near the threshold energy at low energies and nuclear rainbows at
high energies is a direct consequence of the Pauli principle.


title: Dependency Parsing with LSTMs: An Empirical Evaluation

abstract:
  We propose a transition-based dependency parser using Recurrent Neural
Networks with Long Short-Term Memory (LSTM) units. This extends the feedforward
neural network parser of Chen and Manning (2014) and enables modelling of
entire sequences of shift/reduce transition decisions. On the Google Web
Treebank, our LSTM parser is competitive with the best feedforward parser on
overall accuracy and notably achieves more than 3% improvement for long-range
dependencies, which has proved difficult for previous transition-based parsers
due to error propagation and limited context information. Our findings
additionally suggest that dropout regularisation on the embedding layer is
crucial to improve the LSTM's generalisation.


title: Relations for Grothendieck groups of Gorenstein rings

abstract:
  We consider the converse of the Butler, Auslander-Reiten's Theorem which is
on the relations for Grothendieck groups. We show that a Gorenstein ring is of
finite representation type if the Auslander-Reiten sequences generate the
relations for Grothendieck groups. This gives an affirmative answer of the
conjecture due to Auslander.


title: The Synergistic Gains of Coded Caching and Delayed Feedback

abstract:
  In this paper, we consider the $K$-user cache-aided wireless MISO broadcast
channel (BC) with random fading and delayed CSIT, and identify the optimal
cache-aided degrees-of-freedom (DoF) performance within a factor of 4. The
achieved performance is due to a scheme that combines basic coded-caching with
MAT-type schemes, and which efficiently exploits the prospective-hindsight
similarities between these two methods. This delivers a powerful synergy
between coded caching and delayed feedback, in the sense that the total
synergistic DoF-gain can be much larger than the sum of the individual gains
from delayed CSIT and from coded caching.
  The derived performance interestingly reveals --- for the first time ---
substantial DoF gains from coded caching, even when the (normalized) cache size
$\gamma$ (fraction of the library stored at each receiving device) is very
small. Specifically, a microscopic $\gamma \approx e^{-G}$ can come within a
factor of $G$ from the interference-free optimal. For example, storing at each
device only a \emph{thousandth} of what is deemed as `popular' content
($\gamma\approx 10^{-3}$), we approach the interference-free optimal within a
factor of $ln(10^3) \approx 7$ (per user DoF of $1/7$), for any number of
users. This result carries an additional practical ramification as it reveals
how to use coded caching to essentially buffer CSI, thus partially ameliorating
the burden of having to acquire real-time CSIT.


title:
Application of Bayesian Neural Networks to Energy Reconstruction in EAS
  Experiments for ground-based TeV Astrophysics

abstract:
  A toy detector array is designed to detect a shower generated by the
interaction between a TeV cosmic ray and the atmosphere. In the present paper,
the primary energies of showers detected by the detector array are
reconstructed with the algorithm of Bayesian neural networks (BNNs) and a
standard method like the LHAASO experiment \cite{lhaaso-ma}, respectively.
Compared to the standard method, the energy resolutions are significantly
improved using the BNNs. And the improvement is more obvious for the high
energy showers than the low energy ones.


title:
A New Non-Planetary Interpretation of the Microlensing Event
  OGLE-2013-BLG-0723

abstract:
  Recently, the discovery of a Venus-mass planet orbiting a brown-dwarf host in
a binary system was reported from the analysis of the microlensing event
OGLE-2013-BLG-0723. We reanalyze the event considering the possibility of other
interpretations. From this, we find a new solution where the lens is composed
of 2 bodies in contrast to the 3-body solution of the previous analysis. The
new solution better explains the observed light curve than the previous
solution with $\Delta\chi^2\sim 202$, suggesting that the new solution is a
correct model for the event. From the estimation of the physical parameters
based on the new interpretation, we find that the lens system is composed of
two low-mass stars with $\sim 0.2\ M_\odot$ and $\sim 0.1\ M_\odot$ and located
at a distance $\sim 3$ kpc. The fact that the physical parameters correspond to
those of the most common lens population located at a distance with a large
lensing probability further supports the likelihood of the new interpretation.
Considering that two dramatically different solutions can approximately explain
the observed light curve, the event suggests the need of carefully testing all
possible lens-system geometries.


title:
General properties of overlap operators in disordered quantum spin
  systems

abstract:
  We study short-range quantum spin systems with Gaussian disorder. We obtain
quantum mechanical extensions of the Ghirlanda-Guerra identities. We discuss
properties of overlap spin operators with these identities.


title:
Generation of interfaces for multi-dimensional stochastic Allen-Cahn
  equation with a noise smooth in space

abstract:
  In this paper, we study the generation of interfaces for a stochastic
Allen-Cahn equation with general initial value in the multi-dimensional case
that external noise is given by Q-Brownian motion. We prove that interfaces,
for d-dimensional stochastic Allen-Cahn equation with scaling parameter are
generated at the time of logarithmic order. Especially, in one-dimensional
case, we give more detailed estimate and shape of the generated interface.
Assuming that the Q-Brownian motion is smooth in space variable, we extend a
comparison theorem for PDE to SPDE's in order to prove the generation.
Moreover, we connect the generated interface to the motion of interface in
one-dimension which is result of Funaki.


title:
Parameter-free prediction of DNA dynamics in planar extensional flow of
  semidilute solutions

abstract:
  The dynamics of individual DNA molecules in semidilute solutions undergoing
planar extensional flow is simulated using a multi-particle Brownian dynamics
algorithm, which incorporates hydrodynamic and excluded volume interactions in
the context of a coarse-grained bead-spring chain model for DNA. The successive
fine-graining protocol [1, 2], in which simulation data acquired for
bead-spring chains with increasing values of the number of beads $N_b$, is
extrapolated to the number of Kuhn steps $N_\text{K}$ in DNA (while keeping key
physical parameters invariant), is used to obtain parameter-free predictions
for a range of Weissenberg numbers and Hencky strain units. A systematic
comparison of simulation predictions is carried out with the experimental
observations of [3], who have recently used single molecule techniques to
investigate the dynamics of dilute and semidilute solutions of $\lambda$-phage
DNA in planar extensional flow. In particular, they examine the response of
individual chains to step-strain deformation followed by cessation of flow,
thereby capturing both chain stretch and relaxation in a single experiment. The
successive fine-graining technique is shown to lead to quantitatively accurate
predictions of the experimental observations in the stretching and relaxation
phases. Additionally, the transient chain stretch following a step strain
deformation is shown to be much smaller in semidilute solutions than in dilute
solutions, in agreement with experimental observations.


title: Relativistic collapse dynamics and black hole information loss

abstract:
  We study a proposal for the resolution of the black hole information puzzle
within the context of modified versions of quantum theory involving spontaneous
reduction of the quantum state. The theories of this kind, which were developed
in order to address the so called "measurement problem" in quantum theory have,
in the past, been framed in a non-relativistic setting and in that form they
were previously applied to the black hole information problem. Here, and for
the first time, we show in a simple toy model, a treatment of the problem
within a fully relativistic setting. We also discuss the issues that the
present analysis leaves as open problems to be dealt with in future refinements
of the present approach.


title:
Detecting super-Nyquist-frequency gravitational waves using a pulsar
  timing array

abstract:
  The maximum frequency of gravitational waves (GWs) detectable with
traditional pulsar timing methods is set by the Nyquist frequency
($f_{\rm{Ny}}$) of the observation. Beyond this frequency, GWs leave no
temporal-correlated signals; instead, they appear as white noise in the timing
residuals. The variance of the GW-induced white noise is a function of the
position of the pulsars relative to the GW source. By observing this unique
functional form in the timing data, we propose that we can detect GWs of
frequency $>$ $f_{\rm{Ny}}$ (super-Nyquist frequency GWs; SNFGWs). We
demonstrate the feasibility of the proposed method with simulated timing data.
Using a selected dataset from the Parkes Pulsar Timing Array data release 1 and
the North American Nanohertz Observatory for Gravitational Waves publicly
available datasets, we try to detect the signals from single SNFGW sources. The
result is consistent with no GW detection with 65.5\% probability. An all-sky
map of the sensitivity of the selected pulsar timing array to single SNFGW
sources is generated, and the position of the GW source where the selected
pulsar timing array is most sensitive to is $\lambda_{\rm{s}}=-0.82$,
$\beta_{\rm{s}}=-1.03$ (rad); the corresponding minimum GW strain is
$h=6.31\times10^{-11}$ at $f=1\times10^{-5}$ Hz.


title: Probing molecular spin clusters by local measurements

abstract:
  We address the characterization of molecular nanomagnets at the quantum level
and analyze the performance of local measurements in estimating the physical
parameters in their spin Hamiltonians. To this aim, we compute key quantities
in quantum estimation theory, such as the classical and the quantum Fisher
information, in the prototypical case of an heterometallic antiferromagnetic
ring. We show that local measurements, performed only on a portion of the
molecule, allow a precise estimate of the parameters related to both magnetic
defects and avoided level crossings.


title:
Analytical results for the multi-objective design of model-predictive
  control

abstract:
  In model-predictive control (MPC), achieving the best closed-loop performance
under a given computational resource is the underlying design consideration.
This paper analyzes the MPC design problem with control performance and
required computational resource as competing design objectives. The proposed
multi-objective design of MPC (MOD-MPC) approach extends current methods that
treat control performance and the computational resource separately -- often
with the latter as a fixed constraint -- which requires the implementation
hardware to be known a priori. The proposed approach focuses on the tuning of
structural MPC parameters, namely sampling time and prediction horizon length,
to produce a set of optimal choices available to the practitioner. The posed
design problem is then analyzed to reveal key properties, including smoothness
of the design objectives and parameter bounds, and establish certain validated
guarantees. Founded on these properties, necessary and sufficient conditions
for an effective and efficient solver are presented, leading to a specialized
multi-objective optimizer for the MOD-MPC being proposed. Finally, two
real-world control problems are used to illustrate the results of the design
approach and importance of the developed conditions for an effective solver of
the MOD-MPC problem.


title:
Thermoelectric Properties of Antiperovskite Calcium Oxides Ca3PbO and
  Ca3SnO

abstract:
  We report the thermoelectric properties of polycrystalline samples of
Ca3Pb1-xBixO (x = 0, 0.1, 0.2) and Ca3SnO, both crystallizing in a cubic
antiperovskite-type structure. The Ca3SnO sample shows metallic resistivity and
its thermoelectric power approaches 100 uV K-1 at room temperature, resulting
in the thermoelectric power factor of Ca3SnO being larger than that of
Ca3Pb1-xBixO. On the basis of Hall and Sommerfeld coefficients, the Ca3SnO
sample is found to be a p-type metal with a carrier density of ~1019 cm-3, a
mobility of ~80 cm2 V-1 s-1, both comparable to those in degenerated
semiconductors, and a moderately large hole carrier effective mass. The
coexistence of moderately high mobility and large effective mass observed in
Ca3SnO, as well as possible emergence of a mutivalley electronic structure with
a small band gap at low-symmetry points in k-space, suggests that the
antiperovskite Ca oxides have strong potential as a thermoelectric material.


title:
Direct experimental evidence of pi magnetism of a single atomic vacancy
  in graphene

abstract:
  The pristine graphene is strongly diamagnetic. However, graphene with single
carbon atom defects could exhibit paramagnetism with local magnetic moments ~
1.5 per vacancy1-6. Theoretically, both the electrons and electrons of graphene
contribute to the magnetic moment of the defects, and the pi magnetism is
characterizing of two spin-split DOS (density-of-states) peaks close to the
Dirac point1,6. Since its prediction, many experiments attempt to study this pi
magnetism in graphene, whereas, only a notable resonance peak has been observed
around the atomic defects6-9, leaving the pi magnetism experimentally so
elusive. Here, we report direct experimental evidence of the pi magnetism by
using scanning tunnelling microscope. We demonstrate that the localized state
of the atomic defects is split into two DOS peaks with energy separations of
several tens meV and the two spin-polarized states degenerate into a profound
peak at positions with distance of ~ 1 nm away from the monovacancy. Strong
magnetic fields further increase the energy separations of the two
spin-polarized peaks and lead to a Zeeman-like splitting. The effective
g-factors geff around the atomic defect is measured to be about 40. Such a
giant enhancement of the g-factor is attributed to the strong spin polarization
of electron density and large electron-electron interactions near the atomic
vacancy.


title: An optimal first order method based on optimal quadratic averaging

abstract:
  In a recent paper, Bubeck, Lee, and Singh introduced a new first order method
for minimizing smooth strongly convex functions. Their geometric descent
algorithm, largely inspired by the ellipsoid method, enjoys the optimal linear
rate of convergence. We show that the same iterate sequence is generated by a
scheme that in each iteration computes an optimal average of quadratic
lower-models of the function. Indeed, the minimum of the averaged quadratic
approaches the true minimum at an optimal rate. This intuitive viewpoint
reveals clear connections to the original fast-gradient methods and cutting
plane ideas, and leads to limited-memory extensions with improved performance.


title: On the equivalence among stress tensors in a gauge-fluid system

abstract:
  In this paper we bring out the subtleties involved in the study of a first
order relativistic field theory with auxiliary field variables playing an
essential role. In particular we discuss the nonisentropic Eulerian (or
Hamiltonian) fluid model. Interactions are introduced by coupling the fluid to
a {\it dynamical} Maxwell ($U(1)$) gauge field. This dynamical nature of the
gauge field is crucial in showing the equivalence, on the physical subspace, of
the stress tensor derived from two definitions, {\it{ie.}} the canonical
(Noether) one and the symmetric one. In the conventional equal-time formalism,
we have shown that the generators of the spacetime transformations obtained
from these two definitions agree, modulo the Gauss constraint. This equivalence
in the physical sector has been achieved only because of the dynamical nature
of the gauge fields. Subsequently we have explicitly demonstrated the validity
of the Schwinger condition. A detailed analysis of the model in lightcone
formalism has also been done where several interesting features are revealed.


title:
The Influence of Thin Film Confinement on Surface Plasticity in
  Polystyrene and Poly(2-vinylpyridine) Homopolymer and Block Copolymer Films

abstract:
  Thin block copolymer films have attracted considerable academic attention
because of their ability to self-assemble into various microstructures, many of
which have potential technological applications. Despite the ongoing interest,
little effort has focused on the onset of plasticity and failure which are
important factors for the eventual adoption of these materials. Here we use
delamination to impart a quantifiable local stain on thin films of homopolymer
polystyrene and poly(2-vinylpyridine), as well as block copolymers made of
styrene and 2-vinylpyridine. Direct observation of the damage caused by bending
with atomic force microscopy and laser scanning confocal microscopy, leads to
the identification of a critical strain for the onset of plasticity. Moving
beyond our initial scaling analysis, the more quantitative analysis presented
here shows strain levels for thick films to be comparable to bulk measurements.
Monitoring the critical strain leads to several observations: 1.) as-cast
PS-P2VP has low critical strain, 2.) annealing slowly increases critical strain
as microstructural ordering takes place, and 3.) similar to the homopolymer,
both as cast and ordered films both show increasing critical strain under
confinement.


title:
Theoretical methods for understanding advanced magnetic materials: the
  case of frustrated thin films

abstract:
  Materials science has been intensively developed during the last 30 years.
This is due, on the one hand, to an increasing demand of new materials for new
applications and, on the other hand, to technological progress which allows for
the synthesis of materials of desired characteristics and to investigate their
properties with sophisticated experimental apparatus. Among these advanced
materials, magnetic materials at nanometric scale such as ultra thin films or
ultra fine aggregates are no doubt among the most important for electronic
devices.In this review, we show advanced theoretical methods and solved
examples that help understand microscopic mechanisms leading to experimental
observations in magnetic thin films. Attention is paid to the case of
magnetically frustrated systems in which two or more magnetic interactions are
present and competing. The interplay between spin frustration and surface
effects is the origin of spectacular phenomena which often occur at boundaries
of phases with different symmetries: reentrance, disorder lines, coexistence of
order and disorder at equilibrium. These phenomena are shown and explained
using of some exact methods, the Green's function and Monte Carlo simulation.
We show in particular how to calculate surface spin-wave modes, surface
magnetization, surface reorientation transition and spin transport.


title:
A Liapunov function approach to the stabilization of second order
  coupled systems

abstract:
  In 2002, Fatiha Alabau, Piermarco Cannarsa and Vilmos Komornik investigated
the extent of asymptotic stability of the null solution for weakly coupled
partially damped equations of the second order in time. The main point is that
the damping operator acts only on the first component and, whenever it is
bounded, the coupling is not strong enough to produce an exponential decay in
the energy space associated to the conservative part of the system. As a
consequence, for initial data in the energy space, the rate of decay is not
exponential. Due to the nature of the result it seems at first sight impossible
to obtain the asymptotic stability result by the classical Liapunov method.
Surprisingly enough, this turns out to be possible and we exhibit, under some
compatibility conditions on the operators, an explicit class of Liapunov
functions which allows to do 3 different things: 1) When the problem is reduced
to a stable finite dimensional space, we recover the exponential decay by a
single differential inequality and we estimate the logarithmic decrement of the
solutions with worst (slowest) decay. The estimate is optimal at least for some
values of the parameters.


title:
Quantum Systems Engineering: A structured approach to accelerating the
  development of a quantum technology industry

abstract:
  The exciting possibilities in the field of new quantum technologies extend
far beyond the well-reported application of quantum computing. Precision
timing, gravity sensors and imagers, cryptography, navigation, metrology,
energy harvesting and recovery, biomedical sensors and imagers, and real-time
optimisers all indicate the potential for quantum technologies to provide the
basis of a technological revolution. From the field of Systems Engineering
emerges a focused strategy for the development cycle, enabling the existence of
hugely complex products. It is through the adoption of systems thinking that
the semiconductor industry has achieved massive industrial and economic impact.
Quantum technologies rely on delicate, non-local and/or entangled degrees of
freedom - leading to great potential, but also posing new challenges to the
development of products and industries. We discuss some of the challenges and
opportunities regarding the implementation of Systems Engineering and systems
thinking into the quantum technologies space.


title:
Dielectric matrix formulation of correlation energies in the Random
  Phase Approximation (RPA): inclusion of exchange effects

abstract:
  Starting from the general expression for the ground state correlation energy
in the adiabatic connection fluctuation dissipation theorem (ACFDT) framework,
it is shown that the dielectric matrix formulation, which is usually applied to
calculate the direct random phase approximation (dRPA) correlation energy, can
be used for alternative RPA expressions including exchange effects. Within this
famework, the ACFDT analog of the second order screened exchange (SOSEX)
approximation leads to a logarithmic formula for the correlation energy similar
to the direct RPA expression. Alternatively, the contribution of the exchange
can be included in the kernel used to evaluate the response functions. In this
case the use of an approximate kernel is crucial to simplify the formalism and
to obtain a correlation energy in logarithmic form. Technical details of the
implementation of these methods are discussed and it is shown that one can take
advantage of density fitting or Cholesky decomposition techniques to improve
the computational efficiency; a discussion on the numerical quadrature made on
the frequency variable is also provided. A series of test calculations on
atomic correlation energies and molecular reaction energies shows that exchange
effects are instrumental to improve over direct RPA results.


title:
On the Bargmann-Michel-Telegdi equations, and spin-orbit coupling: a
  tribute to Raymond Stora

abstract:
  The Bargmann-Michel-Telegdi equations describing the motions of a spinning,
charged, relativistic particle endowed with an anomalous magnetic moment in an
electromagnetic field, are reconsidered. They are shown to duly stem from the
linearization of the characteristic distribution of a pre-symplectic structure
refining the original one of Souriau. In this model, once specialized to the
case of a static electric-like field, the angular momentum and energy given by
the associated moment map now correctly restore the spin-orbit coupling term.
This is the state-of-the-art of unfinished joint work with Raymond Stora.


title:
Crossed modules as maps between connected components of topological
  groups

abstract:
  The purpose of this note is to observe that a homomorphism of discrete groups
$f:\Gamma\to G$ arises as the induced map $\pi_0(\mathfrak{M})\to
\pi_0(\mathfrak{X})$ on path components of some closed normal inclusion of
topological groups $\mathfrak{M}\subseteq \mathfrak{X},$ if and only if the map
$f$ can be equipped with a crossed module structure. In that case an
essentially unique realization $\mathfrak{M}\subseteq \mathfrak{X}$ exists by
homotopically discrete topological groups.


title:
Interacting Large-Scale Magnetic Fields and Ionised Gas in the W50/SS433
  System

abstract:
  The W50/SS433 system is an unusual Galactic outflow-driven object of
debatable origin. We have used the Australia Telescope Compact Array (ATCA) to
observe a new 198 pointing mosaic, covering $3^\circ \times 2^\circ$, and
present the highest-sensitivity full-Stokes data of W50 to date using
wide-field, wide-band imaging over a 2 GHz bandwidth centred at 2.1 GHz. We
also present a complementary H$\alpha$ mosaic created using the Isaac Newton
Telescope Photometric H$\alpha$ Survey of the Northern Galactic Plane (IPHAS).
The magnetic structure of W50 is found to be consistent with the prevailing
hypothesis that the nebula is a reanimated shell-like supernova remnant (SNR),
that has been re-energised by the jets from SS433. We observe strong
depolarization effects that correlate with diffuse H$\alpha$ emission, likely
due to spatially-varying Faraday rotation measure (RM) fluctuations of $\ge48$
to 61 rad m$^{-2}$ on scales $\le4.5$ to 6 pc. We also report the discovery of
numerous, faint, H$\alpha$ filaments that are unambiguously associated with the
central region of W50. These thin filaments are suggestive of a SNR's shock
emission, and almost all have a radio counterpart. Furthermore, an RM-gradient
is detected across the central region of W50, which we interpret as a loop
magnetic field with a symmetry axis offset by $\approx90^{\circ}$ to the
east-west jet-alignment axis, and implying that the evolutionary processes of
both the jets and the SNR must be coupled. A separate RM-gradient is associated
with the termination shock in the Eastern ear, which we interpret as a
ring-like field located where the shock of the jet interacts with the
circumstellar medium. Future optical observations will be able to use the new
H$\alpha$ filaments to probe the kinematics of the shell of W50, potentially
allowing for a definitive experiment on W50's formation history.


title:
Density Evolution for Deterministic Generalized Product Codes with
  Higher-Order Modulation

abstract:
  Generalized product codes (GPCs) are extensions of product codes (PCs) where
coded bits are protected by two component codes but not necessarily arranged in
a rectangular array. It has recently been shown that there exists a large class
of deterministic GPCs (including, e.g., irregular PCs, half-product codes,
staircase codes, and certain braided codes) for which the asymptotic
performance under iterative bounded-distance decoding over the binary erasure
channel (BEC) can be rigorously characterized in terms of a density evolution
analysis. In this paper, the analysis is extended to the case where
transmission takes place over parallel BECs with different erasure
probabilities. We use this model to predict the code performance in a coded
modulation setup with higher-order signal constellations. We also discuss the
design of the bit mapper that determines the allocation of the coded bits to
the modulation bits of the signal constellation.


title: Deformations of the braid arrangement and Trees

abstract:
  We establish counting formulas and bijections for deformations of the braid
arrangement. Precisely, we consider real hyperplane arrangements such that all
the hyperplanes are of the form $x\_i-x\_j=s$ for some integer $s$. Classical
examples include the braid, Catalan, Shi, semiorder and Linial arrangements, as
well as graphical arrangements. We express the number of regions of any such
arrangement as a signed count of decorated plane trees. The characteristic and
coboundary polynomials of these arrangements also have simple expressions in
terms of these trees. We then focus on certain "well-behaved" deformations of
the braid arrangement that we call transitive. This includes the Catalan, Shi,
semiorder and Linial arrangements, as well as many other arrangements appearing
in the literature. For any transitive deformation of the braid arrangement we
establish a simple bijection between regions of the arrangement and a set of
plane trees defined by local conditions. This answers a question of Gessel.


title:
Error estimates for phaseless inverse scattering in the Born
  approximation at high energies

abstract:
  We study explicit formulas for phaseless inverse scattering in the Born
approximation at high energies for the Schr\"odinger equation with compactly
supported potential in dimension d $\ge$ 2. We obtain error estimates for these
formulas in the configuration space.


title:
Repeating Pulsed Magnet System for Axion-like Particle Searches and
  Vacuum Birefringence Experiments

abstract:
  We have developed a repeating pulsed magnet system which generates magnetic
fields of about 10 T in a direction transverse to an incident beam over a
length of 0.8 m with a repetition rate of 0.2 Hz. Its repetition rate is by two
orders of magnitude higher than usual pulsed magnets. It is composed of four
low resistance racetrack coils and a 30 kJ transportable capacitor bank as a
power supply. The system aims at axion-like particle searches with a pulsed
light source and vacuum birefringence measurements. We report on the details of
the system and its performances.


title: Upper critical field of the noncentrosymmetric superconductor BiPd

abstract:
  The superconducting parameters and upper critical field of the
noncentrosymmetric superconductor BiPd have proven contentious. This material
is of particular interest because it is a singular example of a
$4f$-electron-free noncentrosymmetric superconductor of which crystals may be
grown and cleaved, enabling surface-sensitive spectroscopies. Here, using bulk
probes augmented by tunnelling data on defects, we establish that the lower of
the previously reported upper critical fields corresponds to the bulk
transition. The material behaves as a nearly-weak-coupled BCS s-wave
superconductor, and we report its superconducting parameters as drawn from the
bulk upper critical field. Possible reasons behind the order-of-magnitude
discrepancy in the reported upper critical fields are discussed.


title: Folding Assembly by Means of Dual-Arm Robotic Manipulation

abstract:
  In this paper, we consider folding assembly as an assembly primitive suitable
for dual-arm robotic assembly, that can be integrated in a higher level
assembly strategy. The system composed by two pieces in contact is modelled as
an articulated object, connected by a prismatic-revolute joint. Different
grasping scenarios were considered in order to model the system, and a simple
controller based on feedback linearisation is proposed, using force torque
measurements to compute the contact point kinematics. The folding assembly
controller has been experimentally tested with two sample parts, in order to
showcase folding assembly as a viable assembly primitive.


title: Conformal Differential Invariants

abstract:
  We compute the Hilbert polynomial and the Poincare function counting the
number of fixed jet-order differential invariants of conformal metric
structures modulo local diffeomorphisms, and we describe the field of rational
differential invariants separating generic orbits of the diffeomorphism
pseudogroup action. This resolves the local recognition problem for conformal
structures.


title: A feasible interpolation for random resolution

abstract:
  Random resolution, defined by Buss, Kolodziejczyk and Thapen (JSL, 2014), is
a sound propositional proof system that extends the resolution proof system by
the possibility to augment any set of initial clauses by a set of randomly
chosen clauses (modulo a technical condition). We show how to apply the general
feasible interpolation theorem for semantic derivations of Krajicek (JSL, 1997)
to random resolution. As a consequence we get a lower bound for random
resolution refutations of the clique-coloring formulas.


title: A general framework for the Quantum Zeno and anti-Zeno effects

abstract:
  A general treatment of the quantum Zeno and anti-Zeno effects is presented
which is valid for an arbitrary system-environment model in the weak
system-environment coupling regime. It is shown that the effective lifetime of
a quantum state that is subjected to repeated projective measurements depends
on the overlap of the spectral density of the environment and a generalized
`filter function' which in turn depends on the system state that is repeatedly
being prepared, the measurement interval, the system parameters, the
system-environment coupling, and the environment correlation function. This
general framework is then used to study explicitly the Zeno to anti-Zeno
crossover behavior for the spin-boson model where a single two-level system is
coupled to a bosonic environment. It is shown that our framework reproduces
results for the usual population decay case as well as for the pure dephasing
model, while at the same time allowing us to study the Zeno to anti-Zeno
transition when both decay and dephasing take place. These results are then
extended to many two-level systems coupled collectively to the bosonic
environment to show that the distinction between the Zeno and anti-Zeno effects
becomes more pronounced as the number of two-level systems increases.


title:
Self-assembly of tetracyanonaphtho-quinodimethane (TNAP) based
  metal-organic networks on Pb(111): Structural, electronic, and magnetic
  properties

abstract:
  We use scanning tunneling microscopy and spectroscopy to investigate
structural and electronic properties of tetracyanonaphtho-quinodimethane (TNAP)
based metal-organic networks on a superconducting Pb(111) surface. At low
temperatures, the TNAP molecules form densely packed islands. When deposited at
room temperature, Pb adatoms are incorporated into fourfold bonding nodes with
the TNAP molecules leading to long-range ordered porous structures.
Co-deposition of NaCl with TNAP yields a Na source for an ionically bonded
Na-TNAP structure. Fourfold bonding motifs are also created by Fe atoms with
the cyano terminations of TNAP. However, the structures are irregular and do
not sustain the formation of long-range ordered networks. Some Fe centers with
molecules surrounded in a local C2 symmetry exhibit Shiba states as a
fingerprint of a magnetic interaction with the superconducting surface.


title: Bursting Money Bins, the ice and water structure

abstract:
  That water expands when freezing is a well-known fact, and it is at the basis
of an experiment that is often involuntary performed with beer bottles in
freezers. But why does the water behave this way? And, more difficult, how can
one illustrate this phenomenon in simple terms?


title: Delicious ice Creams in Plain Awful. Why does salt thaw ice?

abstract:
  Plain Awful is an imaginary valley on the Andes populated by a
highly-imitative, cubical people for which the most criminal offence is to
exhibit round objects. The duck family (Scrooge, Donald and nephews) are
teaming against Scrooge's worst enemy, Flintheart Glomgold, trying to buy the
famous Plain Awful square eggs. Inadvertently, Scrooge violates the taboo,
showing his Number One Dime, and is imprisoned in the stone quarries. He can be
released only after the presentation of an ice cream soda to the President of
Plain Awful. Donald and his nephews fly with Flintheart to deliver it, but
Scrooge's enemy, of course, betrays the previous agreement after getting the
ice cream, forcing the ducks into making an emergence replacement on the spot.
Using dried milk, sugar and chocolate from their ration packs, plus some snow
and salt for cooling they are able make the ice cream, and after dressing it
with the carbonated water from a fire extinguisher they finally manage to
produce the desired dessert. This comic may serve as an introduction to the
"mysterious" phenomenon that added salt melts the ice and, even more
surprising, does it by lowering the temperature of the mixture.


title: Liquid money or hard cash? Drowning into granular material

abstract:
  In British English, the term "hard cash" refers to the form of payment using
coins or bill, rather than cheques or credit or money transfer. In American
English, it is often prefixed by the adjective "cold". On the contrary, in
Italian the equivalent expression "denaro liquido" can be literary translated
as "liquid money". In French the expression is equivalent with the additional
factor, with respect to the rest of this discussion, that money becomes
"argent". We have therefore two very different points of view: Is money hard
and cold, or rather liquid and "jingling" ("moneta sonante")? As usual, we
shall investigate this topic starting from some comics about the duck family.


title:
Galactic Gamma Ray Excess and Dark Matter Phenomenology in a
  $U(1)_{B-L}$ Model

abstract:
  In this work, we have considered a gauged $U(1)_{\rm B-L}$ extension of the
Standard Model (SM) with three right handed neutrinos for anomaly cancellation
and two additional SM singlet complex scalars with non-trivial B-L charges. One
of these is used to spontaneously break the $U(1)_{\rm B-L}$ gauge symmetry,
leading to Majorana masses for the neutrinos through the standard Type I seesaw
mechanism, while the other becomes the dark matter (DM) candidate in the model.
We test the viability of the model to simultaneously explain the DM relic
density observed in the CMB data as well as the Galactic Centre (GC)
$\gamma$-ray excess seen by Fermi-LAT. We show that for DM masses in the range
40-55 GeV and for a wide range of $U(1)_{\rm B-L}$ gauge boson masses, one can
satisfy both these constraints if the additional neutral Higgs scalar has a
mass around the resonance region. In studying the dark matter phenomenology and
GC excess, we have taken into account theoretical as well as experimental
constraints coming from vacuum stability condition, PLANCK bound on DM relic
density, LHC and LUX and present allowed areas in the model parameter space
consistent with all relevant data, calculate the predicted gamma ray flux from
the GC and discuss the related phenomenology.


title:
Concurrent Regenerating Codes and Scalable Application in Network
  Storage

abstract:
  To recover simultaneous multiple failures in erasure coded storage systems,
Patrick Lee et al introduce concurrent repair based minimal storage
regenerating codes to reduce repair traffic. The architecture of this approach
is simpler and more practical than that of the cooperative mechanism in
non-fully distributed environment, hence this paper unifies such class of
regenerating codes as concurrent regenerating codes and further studies its
characteristics by analyzing cut-based information flow graph in the
multiple-node recovery model. We present a general storage-bandwidth tradeoff
and give closed-form expressions for the points on the curve, including
concurrent repair mechanism based on minimal bandwidth regenerating codes. We
show that the general concurrent regenerating codes can be constructed by
reforming the existing single-node regenerating codes or multiplenode
cooperative regenerating codes. Moreover, a connection to strong-MDS is also
analyzed. On the other respect, the application of RGC is hardly limited to
"repairing". It is of great significance for "scaling", a scenario where we
need to increase(decrease) nodes to upgrade(degrade) redundancy and
reliability. Thus, by clarifying the similarities and differences, we integrate
them into a unified model to adjust to the dynamic storage network.


title:
Graph-based Composite Local Bregman Divergences on Discrete Sample
  Spaces

abstract:
  One of the most common methods for statistical inference is the maximum
likelihood estimator (MLE). The MLE needs to compute the normalization constant
in statistical models, and it is often intractable. Using unnormalized
statistical models and replacing the likelihood with the other scoring rule are
a good way to circumvent such high computation cost, where the scoring rule
measures the goodness of fit of the model to observed samples. The scoring rule
is closely related to the Bregman divergence, which is a discrepancy measure
between two probability distributions. In this paper, the purpose is to provide
a general framework of statistical inference using unnormalized statistical
models on discrete sample spaces. A localized version of scoring rules is
important to obtain computationally efficient estimators. We show that the
local scoring rules are related to the localized version of Bregman
divergences. Through the localized Bregman divergence, we investigate the
statistical consistency of local scoring rules. We show that the consistency is
determined by the structure of neighborhood system defined on discrete sample
spaces. In addition, we show a way of applying local scoring rules to
classification problems. In numerical experiments, we investigated the relation
between the neighborhood system and the estimation accuracy.


title: Frustrated Ising chains on the triangular lattice in Sr$_3$NiIrO$_6$

abstract:
  Inelastic neutron scattering study on the spin-chain compound Sr$_3$NiIrO$_6$
reveals gapped quasi-1D magnetic excitations. The observed one-magnon band
between 29.5 and 39 meV consists of magnon modes of the Ni$^{2+}$ ions. The
fitting of the spin wave spectrum reveals strongly coupled Ising-like chains
along the $c$-axis that are weakly coupled into a frustrated triangular lattice
in the $ab$-plane. The magnetic excitations survive up to 200 K well above the
magnetic ordering temperature of $T_N \sim 75$ K, also indicating a quasi-1D
nature of the magnetic interactions in Sr$_3$NiIrO$_6$. Our microscopic model
is in good agreement with ab initio electronic structure calculations and
explains the giant spin flip field observed in bulk magnetization measurements.


title: A Classifier-guided Approach for Top-down Salient Object Detection

abstract:
  We propose a framework for top-down salient object detection that
incorporates a tightly coupled image classification module. The classifier is
trained on novel category-aware sparse codes computed on object dictionaries
used for saliency modeling. A misclassification indicates that the
corresponding saliency model is inaccurate. Hence, the classifier selects
images for which the saliency models need to be updated. The category-aware
sparse coding produces better image classification accuracy as compared to
conventional sparse coding with a reduced computational complexity. A
saliency-weighted max-pooling is proposed to improve image classification,
which is further used to refine the saliency maps. Experimental results on
Graz-02 and PASCAL VOC-07 datasets demonstrate the effectiveness of salient
object detection. Although the role of the classifier is to support salient
object detection, we evaluate its performance in image classification and also
illustrate the utility of thresholded saliency maps for image segmentation.


title:
Sum-Rate Analysis and Optimization of Self-Backhauling Based Full-Duplex
  Radio Access System

abstract:
  In this article, a radio access system with a self-backhauling full-duplex
access node serving legacy half-duplex mobile devices is studied and analyzed.
In particular, it is assumed that the access node is using the same center
frequency for all the transmissions, meaning that also the backhauling is done
using the same frequency resources as the uplink and downlink transmissions. It
is further assumed that the access node has a massive array to facilitate
efficient beamforming and self-interference nulling in its own receiver. As a
starting point, the signal model for the considered access node is first
derived, including all the transmitted and received signals within the cell.
This is then used as a basis for obtaining the sum-rate expressions, which
depict the overall rates experienced by the mobile users that are served by the
access node. In addition, the data rate for the bi-directional backhaul link is
also derived, since the access node must be able to backhaul itself wirelessly.
The maximum achievable sum-rate is then determined by numerically solving an
optimization problem constructed from the data rate expressions. The
full-duplex scheme is also compared to two alternative transmission schemes,
which perform all or some of the transmissions in half-duplex mode. The results
show that the full-duplex capability of the access node is beneficial for
maximizing the sum-rate, meaning that a simple half-duplex transmission scheme
is typically not optimal. In particular, the highest sum-rate is usually
provided by a relay type solution, where the access node acts as a full-duplex
relay between the mobiles and the backhaul node.


title: Nanoscale control of heat and spin conductance in artificial spin chains

abstract:
  We describe a mechanism to control energy and magnetisation currents in an
artificial spin-chain, consisting of an array of Permalloy nano-disks coupled
through the magneto-dipolar interaction. The chain is kept out of equilibrium
by two thermal baths with different temperatures connected to its ends, which
control the current propagation. Transport is enhanced by applying a uniform
radio frequency pump field resonating with some of the spin-wave modes of the
chain. Moreover, the two currents can be controlled independently by tuning the
static field applied on the chain. Thus we describe two effective means for the
independent control of coupled currents and the enhancement of thermal and
spin-wave conductivity in a realistic magnonics device, suggesting that similar
effects could be observed in a large class of nonlinear oscillating systems.


title: Convolutional Two-Stream Network Fusion for Video Action Recognition

abstract:
  Recent applications of Convolutional Neural Networks (ConvNets) for human
action recognition in videos have proposed different solutions for
incorporating the appearance and motion information. We study a number of ways
of fusing ConvNet towers both spatially and temporally in order to best take
advantage of this spatio-temporal information. We make the following findings:
(i) that rather than fusing at the softmax layer, a spatial and temporal
network can be fused at a convolution layer without loss of performance, but
with a substantial saving in parameters; (ii) that it is better to fuse such
networks spatially at the last convolutional layer than earlier, and that
additionally fusing at the class prediction layer can boost accuracy; finally
(iii) that pooling of abstract convolutional features over spatiotemporal
neighbourhoods further boosts performance. Based on these studies we propose a
new ConvNet architecture for spatiotemporal fusion of video snippets, and
evaluate its performance on standard benchmarks where this architecture
achieves state-of-the-art results.


title: Feed-Forward Staircase Codes

abstract:
  We propose two variants of staircase codes that resolve the issue of
parity-propagation in their encoding process. The proposed codes provide a
systematic way of terminating a staircase code after an arbitrary number of
blocks. The class of feed-forward staircase codes are introduced, which uses a
self-protection technique to avoid parity-propagation. We also introduce the
class of partial feed-forward staircase codes, which allows parity-propagation
to occur over a given number of blocks. By amortizing the complexity of
self-protection over several standard staircase blocks, the encoding complexity
of these codes is made comparable to staircase codes. Partial feed-forward
staircase codes have the same error-floor as staircase codes. Simulations
confirm that the performance of the proposed codes in both the waterfall and
error-floor regions is similar to the original staircase codes. The proposed
codes help extend the domain of application of staircase codes to systems in
which parity-propagation is undesirable or termination is necessary.


title: Swift thermal steering of domain walls in ferromagnetic MnBi stripes

abstract:
  We predict a fast domain wall (DW) motion induced by a thermal gradient
across a nanoscopic ferromagnetic stripe of MnBi. The driving mechanism is an
exchange torque fueled by magnon accumulation at the DWs. Depending on the
thickness of the sample, both hot-to-cold and cold-to-hot DW motion directions
are possible. The finding unveils an energy efficient way to manipulate DWs as
an essential element in magnetic information processing such as racetrack
memory.


title:
Veiled singularities for the spherically symmetric massless
  Einstein-Vlasov system

abstract:
  This paper continues the investigation of the formation of naked
singularities in the collapse of collisionless matter initiated in [RV]. There
the existence of certain classes of non-smooth solutions of the Einstein-Vlasov
system was proved. Those solutions are self-similar and hence not
asymptotically flat. To obtain solutions which are more physically relevant it
makes sense to attempt to cut off these solutions in a suitable way so as to
make them asymptotically flat. This task, which turns out to be technically
challenging, will be carried out in this paper.
  [RV] A. D. Rendall and J. J. L. Vel\'{a}zquez, A class of dust-like
self-similar solutions of the massless Einstein-Vlasov system. Annales Henri
Poincare 12, 919-964, (2011).


title:
CT-Mapper: Mapping Sparse Multimodal Cellular Trajectories using a
  Multilayer Transportation Network

abstract:
  Mobile phone data have recently become an attractive source of information
about mobility behavior. Since cell phone data can be captured in a passive way
for a large user population, they can be harnessed to collect well-sampled
mobility information. In this paper, we propose CT-Mapper, an unsupervised
algorithm that enables the mapping of mobile phone traces over a multimodal
transport network. One of the main strengths of CT-Mapper is its capability to
map noisy sparse cellular multimodal trajectories over a multilayer
transportation network where the layers have different physical properties and
not only to map trajectories associated with a single layer. Such a network is
modeled by a large multilayer graph in which the nodes correspond to
metro/train stations or road intersections and edges correspond to connections
between them. The mapping problem is modeled by an unsupervised HMM where the
observations correspond to sparse user mobile trajectories and the hidden
states to the multilayer graph nodes. The HMM is unsupervised as the transition
and emission probabilities are inferred using respectively the physical
transportation properties and the information on the spatial coverage of
antenna base stations. To evaluate CT-Mapper we collected cellular traces with
their corresponding GPS trajectories for a group of volunteer users in Paris
and vicinity (France). We show that CT-Mapper is able to accurately retrieve
the real cell phone user paths despite the sparsity of the observed trace
trajectories. Furthermore our transition probability model is up to 20% more
accurate than other naive models.


title: Joint Source-Channel Coding with One-Bit ADC Front End

abstract:
  Motivated by the practical constraints arising in emerging sensor network and
Internet-of-Things (IoT) applications, the zero-delay transmission of a
Gaussian measurement over a real single-input multiple-output (SIMO) additive
white Gaussian noise (AWGN) channel is studied with a low-resolution
analog-to-digital converter (ADC) front end. Joint optimization of the encoder
and the decoder mapping is tackled under both the mean squared error (MSE)
distortion and the distortion outage probability (DOP) criteria, with an
average power constraint on the channel input. Optimal encoder and decoder
mappings are identified for a one-bit ADC front end under both criteria. For
the MSE distortion, the optimal encoder mapping is shown to be non-linear in
general, while it tends to a linear encoder in the low signal-to-noise ratio
(SNR) regime, and to an antipodal digital encoder in the high SNR regime. This
is in contrast to the optimality of linear encoding at all SNR values in the
presence of a full-precision front end. For the DOP criterion, it is shown that
the optimal encoder mapping is piecewise constant and can take only two
opposite values when it is non-zero. For both the MSE distortion and the DOP
criteria, necessary optimality conditions are then derived for $K$-level ADC
front ends as well as front ends with multiple one-bit ADCs. These conditions
are used to obtain numerically optimized solutions. Extensive numerical results
are also provided in order to gain insights into the structure of the optimal
encoding and decoding mappings.


title:
Impacts of biasing schemes in the one-loop integrated perturbation
  theory

abstract:
  The impact of biasing schemes on the clustering of tracers of the large-scale
structure is analytically studied in the weakly nonlinear regime. For this
purpose, we use the one-loop approximation of the integrated perturbation
theory together with the renormalized bias functions of various, physically
motivated Lagrangian bias schemes. These include the halo, peaks and excursion
set peaks model, for which we derive useful formulae for the evaluation of
their renormalized bias functions. The shapes of the power spectra and
correlation functions are affected by the different bias models at the level of
a few percent on weakly nonlinear scales. These effects are studied
quantitatively both in real and redshift space. The amplitude of the
scale-dependent bias in the presence of primordial non-Gaussianity also depends
on the details of the bias models. If left unaccounted for, these theoretical
uncertainties could affect the robustness of the cosmological constraints
extracted from galaxy clustering data.


title: The Menu-Size Complexity of Revenue Approximation

abstract:
  Consider a monopolist selling $n$ items to an additive buyer whose item
values are drawn from independent distributions $F_1,F_2,\ldots,F_n$ possibly
having unbounded support. Unlike in the single-item case, it is well known that
the revenue-optimal selling mechanism (a pricing scheme) may be complex,
sometimes requiring a continuum of menu entries. Also known is that simple
mechanisms with a bounded number of menu entries can extract a constant
fraction of the optimal revenue. Nonetheless, whether an arbitrarily high
fraction of the optimal revenue can be extracted via a bounded menu size
remained open.
  We give an affirmative answer: for every $n$ and $\varepsilon>0$, there
exists $C=C(n,\varepsilon)$ s.t. mechanisms of menu size at most $C$ suffice
for obtaining $(1-\varepsilon)$ of the optimal revenue from any
$F_1,\ldots,F_n$. We prove upper and lower bounds on the revenue-approximation
complexity $C(n,\varepsilon)$ and on the deterministic communication complexity
required to run a mechanism achieving such an approximation.


title:
DISSECT-CF: a simulator to foster energy-aware scheduling in
  infrastructure clouds

abstract:
  Infrastructure as a service (IaaS) systems offer on demand virtual
infrastructures so reliably and flexibly that users expect a high service
level. Therefore, even with regards to internal IaaS behaviour, production
clouds only adopt novel ideas that are proven not to hinder established service
levels. To analyse their expected behaviour, new ideas are often evaluated with
simulators in production IaaS system-like scenarios. For instance, new research
could enable collaboration amongst several layers of schedulers or could
consider new optimisation objectives such as energy consumption. Unfortunately,
current cloud simulators are hard to employ and they often have performance
issues when several layers of schedulers interact in them. To target these
issues, a new IaaS simulation framework (called DISSECT-CF) was designed. The
new simulator's foundation has the following goals: easy extensibility, support
energy evaluation of IaaSs and to enable fast evaluation of many scheduling and
IaaS internal behaviour related scenarios. In response to the requirements of
such scenarios, the new simulator introduces concepts such as: a unified model
for resource sharing and a new energy metering framework with hierarchical and
indirect metering options. Then, the comparison of several simulated situations
to real-life IaaS behaviour is used to validate the simulator's functionality.
Finally, a performance comparison is presented between DISSECT-CF and some
currently available simulators.


title: Kernelized Covariance for Action Recognition

abstract:
  In this paper we aim at increasing the descriptive power of the covariance
matrix, limited in capturing linear mutual dependencies between variables only.
We present a rigorous and principled mathematical pipeline to recover the
kernel trick for computing the covariance matrix, enhancing it to model more
complex, non-linear relationships conveyed by the raw data. To this end, we
propose Kernelized-COV, which generalizes the original covariance
representation without compromising the efficiency of the computation. In the
experiments, we validate the proposed framework against many previous
approaches in the literature, scoring on par or superior with respect to the
state of the art on benchmark datasets for 3D action recognition.


title:
SweLL on the rise: Swedish Learner Language corpus for European
  Reference Level studies

abstract:
  We present a new resource for Swedish, SweLL, a corpus of Swedish Learner
essays linked to learners' performance according to the Common European
Framework of Reference (CEFR). SweLL consists of three subcorpora - SpIn,
SW1203 and Tisus, collected from three different educational establishments.
The common metadata for all subcorpora includes age, gender, native languages,
time of residence in Sweden, type of written task. Depending on the subcorpus,
learner texts may contain additional information, such as text genres, topics,
grades. Five of the six CEFR levels are represented in the corpus: A1, A2, B1,
B2 and C1 comprising in total 339 essays. C2 level is not included since
courses at C2 level are not offered. The work flow consists of collection of
essays and permits, essay digitization and registration, meta-data annotation,
automatic linguistic annotation. Inter-rater agreement is presented on the
basis of SW1203 subcorpus. The work on SweLL is still ongoing with more than
100 essays waiting in the pipeline. This article both describes the resource
and the "how-to" behind the compilation of SweLL.


title:
Spacetime Quanta? : The Discrete Spectrum of a Quantum Spacetime
  Four-Volume Operator in Unimodular Loop Quantum Cosmology

abstract:
  This study considers the operator $\hat{T}$ corresponding to the classical
spacetime four-volume $\tilde{T}$ (on-shell) of a finite patch of spacetime in
the context of Unimodular Loop Quantum Cosmology for the homogeneous and
isotropic model with flat spatial sections and without matter sources. Since
the spacetime four-volume is canonically conjugate to the cosmological
"constant", the operator $\hat{T}$ is constructed by solving its canonical
commutation relation with $\hat{\Lambda}$ - the operator corresponding to the
classical cosmological constant on-shell $\tilde{\Lambda}$. This conjugacy,
along with the action of $\hat{T}$ on definite volume states reducing to
$\tilde{T}$, allows us to interpret that $\hat{T}$ is indeed a quantum
spacetime four-volume operator. The discrete spectrum of $\hat{T}$ is
calculated by considering the set of all $\tau$'s where the eigenvalue equation
has a solution $\Phi_{\tau}$ in the domain of $\hat{T}$. It turns out that,
upon assigning the maximal domain $D(\hat{T})$ to $\hat{T}$, we have
$\Phi_{\tau}\in D(\hat{T})$ for all $\tau\in\mathbb{C}$ so that the spectrum of
$\hat{T}$ is purely discrete and is the entire complex plane. A family of
operators $\hat{T}^{(b_0,\phi_0)}$ was also considered as possible self-adjoint
versions of $\hat{T}$. They represent the restrictions of $\hat{T}$ on their
respective domains $D(\hat{T}^{(b_0,\phi_0)})$ which are just the maximal
domain with additional quasi-periodic conditions. Their possible
self-adjointness is motivated by their discrete spectra only containing real
and discrete numbers $\tau_m$ for $m=0,\pm1,\pm2,...$.


title: Exploring universality of transversity in proton-proton collisions

abstract:
  We consider the azimuthal correlations of charged hadron pairs with large
total transverse momentum and small relative momentum, produced in
proton-proton collisions with one transversely polarized proton. One of these
correlations directly probes the chiral-odd transversity parton distribution in
connection with a chiral-odd interference fragmentation function. We present
predictions for this observable based on previous extractions of transversity
(from charged pion pair production in semi-inclusive deep-inelastic scattering)
and of the interference fragmentation function (from the production of
back-to-back charged pion pairs in electron-positron annihilations). All
analyses are performed in the framework of collinear factorization. We compare
our predictions to the recent data on proton-proton collisions released by the
STAR collaboration at RHIC, and we find them reasonably compatible. This
comparison confirms for the first time the predicted role of transversity in
proton-proton collisions and it allows to test its universality.


title:
On the Representation of Primes by Binary Quadratic Forms, and Elliptic
  Curves

abstract:
  It is shown that, under some mild technical conditions, representations of
prime numbers by binary quadratic forms can be computed in polynomial
complexity by exploiting Schoof's algorithm, which counts the number of
$\mathbb F_q$-points of an elliptic curve over a finite field $\mathbb F_q$.
Further, a method is described which computes representations of primes from
reduced quadratic forms by means of the integral roots of polynomials over
$\mathbb Z$. Lastly, some progress is made on the still-unsettled general
problem of deciding which primes are represented by which classes of quadratic
forms of given discriminant.


title:
From dilute matter to the equilibrium point in the
  energy--density--functional theory

abstract:
  Due to the large value of the scattering length in nuclear systems, standard
density--functional theories based on effective interactions usually fail to
reproduce the nuclear Fermi liquid behavior both at very low densities and
close to equilibrium. Guided on one side by the success of the Skyrme density
functional and, on the other side, by resummation techniques used in Effective
Field Theories for systems with large scattering lengths, a new energy--density
functional is proposed. This functional, adjusted on microscopic calculations,
reproduces the nuclear equations of state of neutron and symmetric matter at
various densities. Furthermore, it provides reasonable saturation properties as
well as an appropriate density dependence for the symmetry energy.


title:
Radio Access Network and Spectrum Sharing in Mobile Networks: A
  Stochastic Geometry Perspective

abstract:
  Next generation mobile networks will rely ever more heavily on resource
sharing. In this article we study the sharing of radio access network and
spectrum among mobile operators. We assess the impact of sharing these two
types of resources on the performance of spatially distributed mobile networks.
We apply stochastic geometry to observe the combined effect of, for example,
the level of spatial clustering among the deployed base stations, the shared
network size, or the coordination in shared spectrum use on network coverage
and expected user data rate. We uncover some complex effects of mobile network
resource sharing, which involve non-linearly scaling gains and performance
trade-offs related to the sharing scenario or the spatial clustering level.