title: Fission waves can oscillate

abstract:
  Under the right conditions, self sustaining fission waves can form in fertile
nuclear materials. These waves result from the transport and absorption of
neutrons and the resulting production of fissile isotopes. When these fission,
additional neutrons are produced and the chain reaction propagates until it is
poisoned by the buildup of fission products. It is typically assumed that
fission waves are soliton-like and self stabilizing. However, we show that in
uranium, coupling of the neutron field to the 239U->239Np->239Pu decay chain
can lead to a Hopf bifurcation. The fission reaction then ramps up and down,
along with the wave velocity. The critical driver for the instability is a
delay, caused by the half-life of 239U, between the time evolution of the
neutron field and the production of 239Pu. This allows the 239Pu to accumulate
and burn out in a self limiting oscillation that is characteristic of a Hopf
bifurcation. Time dependent results are obtained using a numerical
implementation of a reduced order reaction-diffusion model for a fast neutron
field. Monte Carlo simulations in combination with a linear stability analysis
are used to confirm the results for the full system and to establish the
parameter space where the Hopf occurs.


title:
Projections for measuring the size of the solar core with
  neutrino-electron scattering

abstract:
  We quantify the amount of data needed in order to measure the size and
position of the $^8$B neutrino production region within the solar core, for
experiments looking at elastic scattering between electrons and solar
neutrinos. The directions of the electrons immediately after scattering are
strongly correlated with the incident directions of the neutrinos, however this
is degraded significantly by the subsequent scattering of these electrons in
the detector medium. We generate distributions of such electrons for different
neutrino production profiles, and use a maximum likelihood analysis to make
projections for future experimental sensitivity. We find that with
approximately 20 years worth of data the Super Kamiokande experiment could
constrain the central radius of the shell in which $^8$B neutrinos are produced
to be less than 0.22 of the total solar radius at 95% confidence.


title: Andreev reflection near the Dirac point at Graphene - NbSe2 junction

abstract:
  Despite extensive search for about a decade, specular Andreev reflection is
only recently realized in bilayer graphene-superconductor interface. However,
the evolution from the typical retro type Andreev reflection to the unique
specular Andreev reflection in single layer graphene has not yet been observed.
We investigate this transition by measuring the differential conductance at the
van der Walls interface of single layer graphene and NbSe2 superconductor. We
find that the normalized conductance becomes suppressed as we pass through the
Dirac cone via tuning the Fermi level and bias energy, which manifests the
transition from retro to non-retro type Andreev reflection. The suppression
indicates the blockage of Andreev reflection beyond a critical angle of the
incident electron with respect to the normal between the single layer graphene
and the superconductor junction. The results are compared with a theoretical
model of the corresponding setup.


title:
Towards End-to-End Learning for Dialog State Tracking and Management
  using Deep Reinforcement Learning

abstract:
  This paper presents an end-to-end framework for task-oriented dialog systems
using a variant of Deep Recurrent Q-Networks (DRQN). The model is able to
interface with a relational database and jointly learn policies for both
language understanding and dialog strategy. Moreover, we propose a hybrid
algorithm that combines the strength of reinforcement learning and supervised
learning to achieve faster learning speed. We evaluated the proposed model on a
20 Question Game conversational game simulator. Results show that the proposed
method outperforms the modular-based baseline and learns a distributed
representation of the latent dialog state.


title: Coupling of Magnetic Orders in La2CuO4+x

abstract:
  High transverse magnetic field and zero field muon spin rotation and
relaxation measurements have been carried out in a lightly oxygen-doped high-Tc
parent compound La2CuO4 in a temperature range from 2 K to 300 K. As in the
stoichiometric compound, muon spin rotation spectra reveal, along with the
antiferromagnetic local field, the presence of an additional source of magnetic
field at the muon. The results indicate that this second magnetic order is
driven by the antiferromagnetism at low temperature but the two magnetic orders
decouple at higher temperature. The ability of muSR to detect this additional
magnetism deteriorates with doping, thus rendering the technique impotent to
reveal time-reversal symmetry breaking in superconductors.


title:
DialPort: Connecting the Spoken Dialog Research Community to Real User
  Data

abstract:
  This paper describes a new spoken dialog portal that connects systems
produced by the spoken dialog academic research community and gives them access
to real users. We introduce a distributed, multi-modal, multi-agent prototype
dialog framework that affords easy integration with various remote resources,
ranging from end-to-end dialog systems to external knowledge APIs. To date, the
DialPort portal has successfully connected to the multi-domain spoken dialog
system at Cambridge University, the NOAA (National Oceanic and Atmospheric
Administration) weather API and the Yelp API.


title: A Remark on the Kelvin Transform for a Quasilinear Equation

abstract:
  The p-harmonic functions are preserved under reflections in spheres only if
the exponent p > 1 is equal to the dimension of the underlying Euclidean space.
In the linear case p = 2 the Kelvin transform corrects this lack of invariance.
We shall show that the Kelvin transform has no reasonable counterpart for
general values of the exponent p.


title:
Fringe field control of one-dimensional room temperature quantum
  transport in site controlled AlGaN/GaN lateral nanowires

abstract:
  We have demonstrated effective fringe field control of one-dimensional
electron gas (1-DEG) in AlGaN/GaN lateral nanowires. The nanowires are site
controlled and formed by a combination of dry and anisotropic wet etching. The
nanowire dimensions are well controlled and can have a very high length/width
aspect ratio of 10 um/5 nm or larger. The transport is controlled by a fringe
gate and shows room temperature quantum transport where gradual filling of 1-D
subbands gets manifested as oscillations in the transconductance. The fringe
gate threshold voltage for depletion of one-dimensional electron gas is found
to increase with increasing drain voltage indicating efficient control of
1-DEG. The transport characteristics and fringe field operation are explained
by taking into account quantum capacitance in addition to the conventional
geometric capacitance. The effect of nanowire width and fringe gate position is
also discussed.


title: Self-accelerating Universe in modified gravity with dynamical torsion

abstract:
  We consider a model belonging to the class of gravities with dynamical
torsion. The model is free of ghosts and gradient instabilities about Minkowski
and torsionless Einstein backgrounds. We find that at zero cosmological
constant, the model admits a self-accelerating solution with non-Riemannian
connection. Small value of the effective cosmological constant is obtained at
the expense of the hierarchy between the dimensionless couplings.


title: A moment-matching Ferguson and Klass algorithm

abstract:
  Completely random measures (CRM) represent the key building block of a wide
variety of popular stochastic models and play a pivotal role in modern Bayesian
Nonparametrics. A popular representation of CRMs as a random series with
decreasing jumps is due to Ferguson and Klass (1972). This can immediately be
turned into an algorithm for sampling realizations of CRMs or more elaborate
models involving transformed CRMs. However, concrete implementation requires to
truncate the random series at some threshold resulting in an approximation
error. The goal of this paper is to quantify the quality of the approximation
by a moment-matching criterion, which consists in evaluating a measure of
discrepancy between actual moments and moments based on the simulation output.
Seen as a function of the truncation level, the methodology can be used to
determine the truncation level needed to reach a certain level of precision.
The resulting moment-matching \FK algorithm is then implemented and illustrated
on several popular Bayesian nonparametric models.


title: Homogeneous models of C3 Monge geometries

abstract:
  Distributions of Monge type are a class of strongly regular
bracket-generating distributions introduced by I. Anderson, Zh. Nie and P.
Nurowski. Their symbol algebras prolong to simple graded Lie algebras, thus
allowing one to associate a parabolic geometry to any given Monge distribution.
This article is devoted to the classification problem for homogeneous models of
Monge distributions of type C3 in dimension eight, and is complementary to a
paper by I. Anderson and P. Nurowski. The general classification algorithm, as
well as most of its application to the particular problem, are joint work with
Ian Anderson.


title:
Action of $\mathrm{M}(0,2n)$ on some kernel spaces coming from
  $\mathrm{SU}(2)$-TQFT

abstract:
  For $n$ an even number, we study representations of the mapping class group
of the $n$-punctured sphere arising from $\mathrm{SU}(2)$-TQFT when all
punctures are colored by the same integer $N \geq 1$. We prove that the
conjecture of Andersen, Masbaum and Ueno holds for the $4$-punctured sphere for
all $N \geq 2$. In the case $n \geq 6$ of punctures, we prove it for the
pseudo-Anosovs satisfying a homological condition, namely they should act with
a non trivial stretching factor on certain eigenspaces of homology of a
$\frac{n}{2}$-fold branched cover considered by McMullen. The main idea is to
consider the kernel space which is the kernel of the natural map from the skein
module to the $\mathrm{SU}(2)$-TQFT. Our main theorem identifies, as
representations of mapping class groups, certain of these kernel spaces with
homology eigenspaces considered by McMullen. Our results concerning the AMU
conjecture are obtained by taking appropriate limits of the quantum
representations in which such a kernel space may appear as a subspace of the
limit representation.


title: Ensemble Distribution for Immiscible Two-Phase Flow in Porous Media

abstract:
  We construct an ensemble distribution to describe steady immiscible two-phase
flow of two incompressible fluids in a porous medium. The system is found to be
ergodic. The distribution is used to compute macroscopic flow parameters. In
particular, we find an expression for the overall mobility of the system from
the ensemble distribution. The entropy production at the scale of the porous
medium is shown to give the expected product of the average flow and its
driving force, obtained from a black-box description. We test numerically some
of the central theoretical results.


title: Using Game Theory to Study the Evolution of Cultural Norms

abstract:
  We discuss how to use evolutionary game theory (EGT) as a framework for
studying how cultural dynamics and structural properties can influence the
evolution of norms and behaviors within a society. We provide a brief tutorial
on how EGT works, and discuss what kinds of insights it can provide. We then
describe three published studies in which we have developed EGT models that
help explain how structural and external conditions in a society affect the
emergence of social norms.

categories: cs.CY cs.GT cs.MA physics.soc-ph q-bio.PE


title: Scheme Dependence and Multiple Couplings

abstract:
  For theories with multiple couplings the perturbative $\beta$-functions for
scalar, Yukawa couplings are expressible in terms of contributions
corresponding to one particle irreducible graphs and also contributions which
are one particle reducible depending on the anomalous dimension. Here we
discuss redefinitions, or changes of scheme, which preserve this structure. The
redefinitions allow for IPR contributions of a specific form, as is necessary
to encompass the relation between MS and momentum subtraction renormalisation
schemes. Many multiply 1PR terms in the transformed $\beta$-function are
generated but these can all be absorbed into antisymmetric contributions to the
anomalous dimensions which are essentially arbitrary and can be discarded. As
an illustration the results are applied to the scheme dependence of the
anomalous dimension, which determines the $\beta$-function, for ${\cal N}=1$
supersymmetric scalar fermion theories in four dimensions up to four loops.


title:
Observing magnetic anisotropy in electronic transport through individual
  single-molecule magnets

abstract:
  We review different electron transport methods to probe the magnetic
properties, such as the magnetic anisotropy, of an individual Fe4 SMM. The
different approaches comprise first and higher order transport through the
molecule. Gate spectroscopy, focusing on the charge degeneracy-point, is
presented as a robust technique to quantify the longitudinal magnetic
anisotropy of the SMM in different redox states. We provide statistics showing
the robustness and reproducibility of the different methods. In addition,
conductance measurements typically show high-energy excited states well beyond
the ground spin multiplet of SMM. Some of these excitations have their origin
in excited spin multiplets, others in vibrational modes of the molecule. The
interplay between vibrations, charge and spin may yield a new approach for spin
control.


title: Self-service Ad-hoc Querying Using Controlled Natural Language

abstract:
  The ad-hoc querying process is slow and error prone due to inability of
business experts of accessing data directly without involving IT experts. The
problem lies in complexity of means used to query data. We propose a new
natural language- and semistar ontology-based ad-hoc querying approach which
lowers the steep learning curve required to be able to query data. The proposed
approach would significantly shorten the time needed to master the ad-hoc
querying and to gain the direct access to data by business experts, thus
facilitating the decision making process in enterprises, government
institutions and other organizations.


title:
An explicit description of the irreducible components of the set of
  matrix pencils with bounded normal rank

abstract:
  The set of mxn singular matrix pencils with normal rank at most r is an
algebraic set with r+1 irreducible components. These components are the closure
of the orbits (under strict equivalence) of r+1 matrix pencils which are in
Kronecker canonical form. In this paper, we provide a new explicit description
of each of these irreducible components which is a parametrization of each
component. Therefore one can explicitly construct any pencil in each of these
components. The new description of each of these irreducible components
consists of the sum of r rank-1 matrix pencils, namely, a column polynomial
vector of degree at most 1 times a row polynomial vector of degree at most 1,
where we impose one of these two vectors to have degree zero. The number of row
vectors with zero degree determines each irreducible component.


title:
Landau theory of nuclear level density and its application in
  description of nuclear level density in the region of discrete and s-wave
  neutron resonance energies

abstract:
  In this work, the reliability of the Landau expression for the nuclear level
density calculations is tested, for the first-time, to describe nuclear level
densities of some light, intermediate mass and heavy nuclei at excitations
corresponding to discrete and s-wave neutron resonance energies. The chi-2
minimizing method is used in treatment of the experimental data for the two
suggested energy range of discrete energies given by Nuclear Data Sheet [1] and
by the systematic for nuclear level density parametrization in [2]. Our
comparison with the related data in the discrete energy range has shown that
the results obtained by the Landau expression are better than those of
back-shifted Fermi-gas model and constant temperature approximation. This
result is also valid for some nuclei of interest when the s-wave neutron
resonance level density is included to check theoretical prescriptions in the
energy range from initial bound states to unbound states near the neutron
binding energy.


title:
Time evolution during and after finite-time quantum quenches in
  Luttinger liquids

abstract:
  We consider finite-time quantum quenches in the interacting
Tomonaga--Luttinger model, for example time-dependent changes of the
nearest-neighbour interactions for spinless fermions. We use the exact
solutions for specific protocols including the linear and cosine ramps (or,
more generally, periodic pumping). We study the dynamics of the total and
kinetic energy as well as the Green functions during as well as after the
quench. For the latter we find that the light-cone picture remains applicable,
however, the propagating front is delayed as compared to the sudden quench. We
extract the universal behaviour of the Green functions and in particular
provide analytic, non-perturbative results for the delay applicable to quenches
of short to moderate duration but arbitrary time dependency.


title: The power of Sherali-Adams relaxations for general-valued CSPs

abstract:
  We give a precise algebraic characterisation of the power of Sherali-Adams
relaxations for solvability of valued constraint satisfaction problems to
optimality. The condition is that of bounded width which has already been shown
to capture the power of local consistency methods for decision CSPs and the
power of semidefinite programming for robust approximation of CSPs.
  Our characterisation has several algorithmic and complexity consequences. On
the algorithmic side, we show that several novel and many known valued
constraint languages are tractable via the third level of the Sherali-Adams
relaxation. For the known languages, this is a significantly simpler algorithm
than the previously obtained ones. On the complexity side, we obtain a
dichotomy theorem for valued constraint languages that can express an injective
unary function. This implies a simple proof of the dichotomy theorem for
conservative valued constraint languages established by Kolmogorov and Zivny
[JACM'13], and also a dichotomy theorem for the exact solvability of
Minimum-Solution problems. These are generalisations of Minimum-Ones problems
to arbitrary finite domains. Our result improves on several previous
classifications by Khanna et al. [SICOMP'00], Jonsson et al. [SICOMP'08], and
Uppman [ICALP'13].


title:
Self and partial gluing theorems for Alexandrov spaces with a lower
  curvature bound

abstract:
  This paper is devoted to prove that if an Alexandrov space of curvature not
less than $\kappa$ with a codimension one extremal subset which admits an
isometric involution with respect to the induced length metric, then the metric
space obtained by gluing the extremal subset along the isometry is an
Alexandrov space of curvature not less than $\kappa$. This is a generalization
of Perelman's doubling and Petrunin's gluing theorems.


title:
From Liquid Structure to Configurational Entropy: Introducing Structural
  Covariance

abstract:
  We connect the configurational entropy of a liquid to the geometrical
properties of its local energy landscape, using a high-temperature expansion.
It is proposed that correlations between local structures arises from their
overlap and, being geometrical in nature, can be usefully determined using the
inherent structures of high temperature liquids. We show quantitatively how the
high-temperature covariance of these local structural fluctuations arising from
their geometrical overlap, combined with their energetic stability, control the
decrease of entropy with decreasing energy. We apply this formalism to a family
of Favoured Local Structure (FLS) lattice models with two low symmetry FLS's
which are found to either crystallize or form a glass on cooling. The
covariance, crystal energy and estimated freezing temperature are tested as
possible predictors of glass-forming ability in the model system.


title: Convolution by Evolution: Differentiable Pattern Producing Networks

abstract:
  In this work we introduce a differentiable version of the Compositional
Pattern Producing Network, called the DPPN. Unlike a standard CPPN, the
topology of a DPPN is evolved but the weights are learned. A Lamarckian
algorithm, that combines evolution and learning, produces DPPNs to reconstruct
an image. Our main result is that DPPNs can be evolved/trained to compress the
weights of a denoising autoencoder from 157684 to roughly 200 parameters, while
achieving a reconstruction accuracy comparable to a fully connected network
with more than two orders of magnitude more parameters. The regularization
ability of the DPPN allows it to rediscover (approximate) convolutional network
architectures embedded within a fully connected architecture. Such
convolutional architectures are the current state of the art for many computer
vision applications, so it is satisfying that DPPNs are capable of discovering
this structure rather than having to build it in by design. DPPNs exhibit
better generalization when tested on the Omniglot dataset after being trained
on MNIST, than directly encoded fully connected autoencoders. DPPNs are
therefore a new framework for integrating learning and evolution.


title: Length of epsilon-neighborhoods of orbits of Dulac maps

abstract:
  By Dulac maps we mean first return maps of hyperbolic polycycles of analytic
planar vector fields. We study the fractal properties of the orbits of a
parabolic Dulac map. To this end, we prove that it admits a Fatou coordinate
with an asympotic expansion in terms of power-iterated logarithm transseries.
This allows to introduce a new notion, the \emph{continuous time length of
$\varepsilon$-neighborhoods of orbits}, and to prove that this function of
$\varepsilon$ admits an asymptotic expansion in the same scale. We show that,
under some hypotheses, this expansion determines the class of formal conjugacy
of the Dulac map.


title:
Relativistic quasi-solitons and embedded solitons with circular
  polarization in cold plasmas

abstract:
  The existence of localized electromagnetic structures is discussed in the
framework of the 1-dimensional relativistic Maxwell-fluid model for a cold
plasma with immobile ions. New partially localized solutions are found with a
finite-difference algorithm designed to locate numerically exact solutions of
the Maxwell-fluid system. These solutions are called quasi-solitons and consist
of a localized electromagnetic wave trapped in a spatially extended electron
plasma wave. They are organized in families characterized by the number of
nodes $p$ of the vector potential and exist in a continuous range of parameters
in the $\omega-V$ plane, where $V$ is the velocity of propagation and $\omega$
is the vector potential angular frequency. A parametric study shows that the
familiar fully localized relativistic solitons are special members of the
families of partially localized quasi-solitons. Soliton solution branches with
$p>1$ are therefore parametrically embedded in the continuum of quasi-solitons.
On the other hand, geometric arguments and numerical simulations indicate that
$p=0$ solitons exist only in the limit of either small amplitude or vanishing
velocity. Direct numerical simulations of the Maxwell-fluid model indicate that
the $p>0$ quasi-solitons (and embedded solitons) are unstable and lead to wake
excitation, while $p=0$ quasi-solitons appear stable. This helps explain the
ubiquitous observation of structures that resemble $p=0$ solitons in numerical
simulations of laser-plasma interaction.


title: The Dark Side of Ethical Robots

abstract:
  Concerns over the risks associated with advances in Artificial Intelligence
have prompted calls for greater efforts toward robust and beneficial AI,
including machine ethics. Recently, roboticists have responded by initiating
the development of so-called ethical robots. These robots would, ideally,
evaluate the consequences of their actions and morally justify their choices.
This emerging field promises to develop extensively over the next years.
However, in this paper, we point out an inherent limitation of the emerging
field of ethical robots. We show that building ethical robots also necessarily
facilitates the construction of unethical robots. In three experiments, we show
that it is remarkably easy to modify an ethical robot so that it behaves
competitively, or even aggressively. The reason for this is that the specific
AI, required to make an ethical robot, can always be exploited to make
unethical robots. Hence, the development of ethical robots will not guarantee
the responsible deployment of AI. While advocating for ethical robots, we
conclude that preventing the misuse of robots is beyond the scope of
engineering, and requires instead governance frameworks underpinned by
legislation. Without this, the development of ethical robots will serve to
increase the risks of robotic malpractice instead of diminishing it.


title: $2$-nilpotent co-Higgs structures

abstract:
  A co-Higgs sheaf is a pair of a torsion-free coherent sheaf $\mathcal{E}$ and
a global section of $\mathcal{E}nd(\mathcal{E})\otimes T_X$ with $T_X$ the
tangent bundle. We construct $2$-nilpotent co-Higgs sheaves of rank two for
some rational surfaces and of rank three for $\mathbb{P}^3$, using the
Hartshorne-Serre correspondence. Then we investigate the non-existence,
specially over projective spaces.


title:
Fully Convolutional Networks for Dense Semantic Labelling of
  High-Resolution Aerial Imagery

abstract:
  The trend towards higher resolution remote sensing imagery facilitates a
transition from land-use classification to object-level scene understanding.
Rather than relying purely on spectral content, appearance-based image features
come into play. In this work, deep convolutional neural networks (CNNs) are
applied to semantic labelling of high-resolution remote sensing data. Recent
advances in fully convolutional networks (FCNs) are adapted to overhead data
and shown to be as effective as in other domains. A full-resolution labelling
is inferred using a deep FCN with no downsampling, obviating the need for
deconvolution or interpolation. To make better use of image features, a
pre-trained CNN is fine-tuned on remote sensing data in a hybrid network
context, resulting in superior results compared to a network trained from
scratch. The proposed approach is applied to the problem of labelling
high-resolution aerial imagery, where fine boundary detail is important. The
dense labelling yields state-of-the-art accuracy for the ISPRS Vaihingen and
Potsdam benchmark data sets.


title:
Commissioning experience and beam physics measurements at the SwissFEL
  Injector Test Facility

abstract:
  The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute
between 2010 and 2014, serving as a pilot plant and testbed for the development
and realization of SwissFEL, the X-ray Free-Electron Laser facility under
construction at the same institute. The test facility consisted of a
laser-driven rf electron gun followed by an S-band booster linac, a magnetic
bunch compression chicane and a diagnostic section including a transverse
deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and
up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements
performed at the test facility not only demonstrated the beam parameters
required to drive the first stage of an FEL facility, but also led to
significant advances in instrumentation technologies, beam characterization
methods and the generation, transport and compression of ultra-low-emittance
beams. We give a comprehensive overview of the commissioning experience of the
principal subsystems and the beam physics measurements performed during the
operation of the test facility, including the results of the test of an
in-vacuum undulator prototype generating radiation in the vacuum ultraviolet
and optical range.


title:
Locating Temporal Functional Dynamics of Visual Short-Term Memory
  Binding using Graph Modular Dirichlet Energy

abstract:
  Visual short-term memory binding tasks are a promising early marker for
Alzheimer's disease (AD). To uncover functional deficits of AD in these tasks
it is meaningful to first study unimpaired brain function. Electroencephalogram
recordings were obtained from encoding and maintenance periods of tasks
performed by healthy young volunteers. We probe the task's transient
physiological underpinnings by contrasting shape only (Shape) and shape-colour
binding (Bind) conditions, displayed in the left and right sides of the screen,
separately. Particularly, we introduce and implement a novel technique named
Modular Dirichlet Energy (MDE) which allows robust and flexible analysis of the
functional network with unprecedented temporal precision. We find that
connectivity in the Bind condition is less integrated with the global network
than in the Shape condition in occipital and frontal modules during the
encoding period of the right screen condition. Using MDE we are able to discern
driving effects in the occipital module between 100-140ms, coinciding with the
P100 visually evoked potential, followed by a driving effect in the frontal
module between 140-180ms, suggesting that the differences found constitute an
information processing difference between these modules. This provides
temporally precise information over a heterogeneous population in promising
tasks for the detection of AD.


title: 1-Loop Matching of gauge invariant dim-6 operators for B decays

abstract:
  Physics beyond the Standard Model, realized above the electroweak scale, can
be incorporated in a model independent way in the Wilson coefficients of higher
dimensional gauge invariant operators. In these proceedings we review the
matching of the $SU(3)_C\times SU(2)_L\times U(1)_Y$ gauge invariant
dimension-six operators on the effective Hamiltonian governing $b\to s$ and
$b\to c$ transitions, including the leading 1-loop effects.


title: The Gaps of Consecutive Eigenvalues of Laplacian on Riemannian Manifolds

abstract:
  In this paper, we investigate the Dirichlet problem of Laplacian on complete
Riemannian manifolds. By constructing new trial functions, we obtain a sharp
upper bound of the gap of the consecutive eigenvalues in the sense of the
order, which affirmatively answers to a conjecture proposed by Chen-Zheng-Yang.
In addition, we also exploit the closed eigenvalue problem of Laplacian and
obtain a similar optimal upper bound. As some important examples, we
investigate the eigenvalues of the eigenvalue problem of the Laplacian on the
unit sphere and cylinder, compact homogeneous Riemannian manifolds without
boundary, connected bounded domain and compact complex hypersurface without
boundary in the standard complex projective space $\mathbb{C}P^{n}(4)$ with
holomorphic sectional curvature $4$, and some intrinsic estimates for the
eigenvalue gap is obtained. As the author know, for the Dirichlet problem, the
gap $\lambda_{k+1}-\lambda_{k}$ is bounded by the first $k$-th eigenvalues in
the previous literatures. However, by a large number of numerical calculations,
the author surprisingly find that the gap of the consecutive eigenvalues of the
Dirichlet problem on the $n$-dimensional Euclidean space $R^{n}$ can be bounded
only by the first two eigenvalues. Therefore, we venture to conjecture that all
of the eigenvalues satisfy: $\lambda_{k+1}-\lambda_{k}\leq
\mathfrak{S}_{i}(\Omega)(\lambda_{2}-\lambda_{1})k^{1/n}$, where
$\mathfrak{S}_{i}(\Omega),i=1,2$ denote the first shape coefficient and the
second shape coefficient. In particular, if we consider the second shape
coefficient, then there is a close connection between this universal inequality
and the famous Panye-P\'olya-Weinberger conjecture in general form. By
calculating some important examples, we adduce some good evidence on the
correctness of this conjecture.


title: A note on the predictability of flat galactic rotation curves

abstract:
  Based on an exact solution of the Einstein field equations, it is proposed in
this note that the dark-matter hypothesis could have led to the prediction of
flat galactic rotation curves long before the discovery thereof by assuming
that on large scales the matter in the Universe, including dark matter, is a
perfect fluid.


title:
Piecewise Weierstrass preparation and division for o-minimal holomorphic
  functions

abstract:
  Given an o-minimal structure expanding the field of reals, we show a
piecewise Weierstrass preparation theorem and a piecewise Weierstrass division
theorem for definable holomorphic functions. In the semialgebraic setting and
for the structure of globally subanalytic sets and functions we obtain the
corresponding results for definable real analytic functions. As an application
we show a definable global Nullstellensatz for principal ideals.


title: Stability of quasi-simple heteroclinic cycles

abstract:
  The stability of heteroclinic cycles may be obtained from the value of the
local stability index along each connection of the cycle. We establish a way of
calculating the local stability index for quasi-simple cycles: cycles whose
connections are 1-dimensional and contained in flow-invariant spaces of equal
dimension. These heteroclinic cycles exist both in symmetric and non-symmetric
contexts. We make one assumption on the dynamics along the connections to
ensure that the transition matrices have a convenient form. Our method applies
to all simple heteroclinic cycles of type Z and to various heteroclinic cycles
arising in population dynamics, namely non-simple heteroclinic cycles, as well
as to cycles that are part of a heteroclinic network. We illustrate our results
with a non-simple cycle present in a heteroclinic network of the
Rock-Scissors-Paper game.


title:
Structure Preserving Equivalent Martingale Measures for
  $\mathscr{H}$-SII Models

abstract:
  In this article we relate the set of structure preserving equivalent
martingale measures $(\mathcal{M})$ for financial models driven by
semimartingales with conditionally independent increments to a set of
measurable and integrable functions $(\mathscr{Y})$. More precisely, we prove
that $(\mathcal{M}\not = \emptyset)$ if, and only if, $(\mathscr{Y}\not =
\emptyset)$, and connect the sets $(\mathcal{M})$ and $(\mathscr{Y})$ to the
semimartingale characteristics of the driving process. As examples we consider
integrated L\'evy models with independent stochastic factors and time-changed
L\'evy models and derive mild conditions for $(\mathcal{M} \not = \emptyset)$.


title: Ensemble-free configurational temperature for spin systems

abstract:
  An estimator for the dynamical temperature in an arbitrary ensemble is
derived in the framework of Bayesian statistical mechanics and the maximum
entropy principle. We test this estimator numerically by a simulation of the
two-dimensional XY-model in the canonical ensemble. As this model is critical
in the whole region of temperatures below the Berezinski-Kosterlitz-Thouless
critical temperature $T_{BKT}$, we use a generalization of Wolff's uni-cluster
algorithm. The numerical results allow us to confirm the robustness of the
analytical expression for the microscopic estimator of the temperature. This
microscopic estimator has also the advantage that it gives a direct measure of
the thermalization process and can be used to compute absolute errors
associated to statistical fluctuations. In consequence, this estimator allows
for a direct, absolute and astringent test of the ergodicity of the underlying
Markov process, which encodes the algorithm used in a numerical simulation.


title:
A kinematic spiral arm shock signature: "Ringing" in the vertical motion
  of stars

abstract:
  We analyze the motion of stars in the direction perpendicular to the galactic
plane following a spiral arm passage. We show that the fast change in the
vertical galactic potential causes a thermalized distribution to develop a
distinctive "ringing"-like non-thermal signature. We use A and F-stars from the
extended Hipparocos catalogue to show that a spiral arm passage (or passages),
with an amplitude (or randomly combined amplitudes) of at least {\delta}{\rho}
/ {\rho} > ~0.15 must have taken place in the past (with {\rho} being the total
background density). Presently, the local stellar distribution within ~100 pc
of the plane, appears (at the 2.5{\sigma} level) to be contracting towards it.


title: Data-driven parameterization of the generalized Langevin equation

abstract:
  We present a data-driven approach to determine the memory kernel and random
noise in generalized Langevin equations. To facilitate practical
implementations, we parameterize the kernel function in the Laplace domain by a
rational function, with coefficients directly linked to the equilibrium
statistics of the coarse-grain variables. We show that such an approximation
can be constructed to arbitrarily high order and the resulting generalized
Langevin dynamics can be embedded in an extended stochastic model without
explicit memory. We demonstrate how to introduce the stochastic noise so that
the second fluctuation-dissipation theorem is exactly satisfied. Results from
several numerical tests are presented to demonstrate the effectiveness of the
proposed method.


title: Excess reciprocity distorts reputation in online social networks

abstract:
  The peer-to-peer (P2P) economy relies on establishing trust in distributed
networked systems, where the reliability of a user is assessed through digital
peer-review processes that aggregate ratings into reputation scores. Here we
present evidence of a network effect which biases digital reputation, revealing
that P2P networks display exceedingly high levels of reciprocity. In fact,
these are much higher than those compatible with a null assumption that
preserves the empirically observed level of agreement between all pairs of
nodes, and rather close to the highest levels structurally compatible with the
networks' reputation landscape. This indicates that the crowdsourcing process
underpinning digital reputation can be significantly distorted by the attempt
of users to mutually boost reputation, or to retaliate, through the exchange of
ratings. We uncover that the least active users are predominantly responsible
for such reciprocity-induced bias, and that this fact can be exploited to
obtain more reliable reputation estimates. Our findings are robust across
different P2P platforms, including both cases where ratings are used to vote on
the content produced by users and to vote on user profiles.


title:
Topologically stable magnetization states on a spherical shell:
  curvature stabilized skyrmions

abstract:
  Topologically stable structures include vortices in a wide variety of matter,
such as skyrmions in ferro- and antiferromagnets, and hedgehog point defects in
liquid crystals and ferromagnets. These are characterized by integer-valued
topological quantum numbers. In this context, closed surfaces are a prominent
subject of study as they form a link between fundamental mathematical theorems
and real physical systems. Here we perform an analysis on the topology and
stability of equilibrium magnetization states for a thin spherical shell with
easy-axis anisotropy in normal directions. Skyrmion solutions are found for a
range of parameters. These magnetic skyrmions on a spherical shell have two
distinct differences compared to their planar counterpart: (i) they are
topologically trivial, and (ii) can be stabilized by curvature effects, even
when Dzyaloshinskii-Moriya interactions are absent. Due to its specific
topological nature a skyrmion on a spherical shell can be simply induced by a
uniform external magnetic field.


title:
SDNFV: Flexible and Dynamic Software Defined Control of an Application-
  and Flow-Aware Data Plane

abstract:
  Software Defined Networking (SDN) promises greater flexibility for directing
packet flows, and Network Function Virtualization promises to enable dynamic
management of software-based network functions. However, the current divide
between an intelligent control plane and an overly simple, stateless data plane
results in the inability to exploit the flexibility of a software based
network. In this paper we propose SDNFV, a framework that expands the
capabilities of network processing-and-forwarding elements to flexibly manage
packet flows, while retaining both a high performance data plane and an easily
managed control plane.
  SDNFV proposes a hierarchical control framework where decisions are made
across the SDN controller, a host-level manager, and individual VMs to best
exploit state available at each level. This increases the network's flexibility
compared to existing SDNs where controllers often make decisions solely based
on the first packet header of a flow. SDNFV intelligently places network
services across hosts and connects them in sequential and parallel chains,
giving both the SDN controller and individual network functions the ability to
enhance and update flow rules to adapt to changing conditions. Our prototype
demonstrates how to efficiently and flexibly reroute flows based on data plane
state such as packet payloads and traffic characteristics.


title: Beam Charge Measurement for the g2p/GEp experiments

abstract:
  The g2p/GEp experiments used a solid NH3 polarized target, where the
polarization of the target is sensitive to temperature and radiation. The beam
current was limited to 5-100 nA during the experiment to avoid too much
depolarization of target (The typical Hall A running condition for beam current
is 1 uA to 100 uA). The measured charge was further used to get the accurate
physics cross sections. New BCM (Beam Current Monitor) receivers and a DAQ
system were used to measure the beam current at such a low current range. A
tungsten calorimeter was used to calibrate the BCMs. This technical note
summarizes the calibration procedure and the performance of the BCMs.


title: A Joint Model for Word Embedding and Word Morphology

abstract:
  This paper presents a joint model for performing unsupervised morphological
analysis on words, and learning a character-level composition function from
morphemes to word embeddings. Our model splits individual words into segments,
and weights each segment according to its ability to predict context words. Our
morphological analysis is comparable to dedicated morphological analyzers at
the task of morpheme boundary recovery, and also performs better than
word-based embedding models at the task of syntactic analogy answering.
Finally, we show that incorporating morphology explicitly into character-level
models help them produce embeddings for unseen words which correlate better
with human judgments.


title: Current large deviations for driven periodic diffusions

abstract:
  We study the large deviations of the time-integrated current for a driven
diffusion on the circle, often used as a model of nonequilibrium systems. We
obtain the large deviation functions describing the current fluctuations using
a Fourier-Bloch decomposition of the so-called tilted generator and also
construct from this decomposition the effective (biased, auxiliary or driven)
Markov process describing the diffusion as current fluctuations are observed in
time. This effective process provides a clear physical explanation of the
various fluctuation regimes observed. It is used here to obtain an upper bound
on the current large deviation function, which we compare to a recently-derived
entropic bound, and to study the low-noise limit of large deviations.


title: Robot-stated limitations but not intentions promote user assistance

abstract:
  Human-Robot-Interaction (HRI) research is typically built around the premise
that the robot serves to assist a human in achieving a human-led goal or shared
task. However, there are many circumstances during HRI in which a robot may
need the assistance of a human in shared tasks or to achieve goals. We use the
ROBO-GUIDE model as a case study, and insights from social psychology, to
examine how a robot's personality can impact on user cooperation. A study of
364 participants indicates that individuals may prefer to use likable social
robots ahead of those designed to appear more capable; this outcome reflects
known social decisions in human interpersonal relationships. This work further
demonstrates the value of social psychology in developing social robots and
exploring HRI.


title: On a geometric framework for Lagrangian supermechanics

abstract:
  We re-examine classical mechanics with both commuting and anticommuting
degrees of freedom. We do this by defining the phase dynamics of a general
Lagrangian system as an implicit differential equation in the spirit of
Tulczyjew. Rather than parametrising our basic degrees of freedom by a
specified Grassmann algebra, we use arbitrary supermanifolds by following the
categorical approach to supermanifolds.


title: Non-commutative integrable systems on $b$-symplectic manifolds

abstract:
  In this paper we study non-commutative integrable systems on $b$-Poisson
manifolds. One important source of examples (and motivation) of such systems
comes from considering non-commutative systems on manifolds with boundary
having the right asymptotics on the boundary. In this paper we describe this
and other examples and we prove an action-angle theorem for non-commutative
integrable systems on a $b$-symplectic manifold in a neighbourhood of a
Liouville torus inside the critical set of the Poisson structure associated to
the $b$-symplectic structure.


title: Quantization of the Horava theory at the kinetic-conformal point

abstract:
  The Horava theory depends on several coupling constants. The kinetic term of
its Lagrangian depends on one dimensionless coupling constant lambda. For the
particular value lambda = 1/3 the kinetic term becomes conformal invariant,
although the full Lagrangian does not have this symmetry. For any value of
lambda the nonprojectable version of the theory has second-class constraints
which play a central role in the process of quantization. Here we study the
complete nonprojectable theory, including the Blas-Pujolas-Sibiryakov
interacting terms, at the kinetic-conformal point lambda = 1/3. The generic
counting of degrees of freedom indicates that this theory propagates the same
physical degrees of freedom of General Relativity. We analyze this point
rigorously taking into account all the z=1,2,3 terms that contribute to the
action describing quadratic perturbations around the Minkowski spacetime. We
show that the constraints of the theory and equations determining the Lagrange
multipliers are strongly elliptic partial differential equations, an essential
condition for a constrained phase-space structure in field theory. We show how
their solutions lead to the two independent tensorial physical modes propagated
by the theory. We also obtain the reduced Hamiltonian. These arguments
strengthen the consistency of the theory. We find the restrictions on the space
of coupling constants to ensure the positiveness of the reduced Hamiltonian. We
obtain the propagator of the physical modes, showing that there are not ghosts
and that the propagator effectively acquires the z=3 scaling for all physical
degrees of freedom at the high energy regime. By evaluating the superficial
degree of divergence, taking into account the second-class constraints, we show
that the theory is power-counting renormalizable. ...


title:
Modulated phases in external fields: when is reentrant behavior to be
  expected?

abstract:
  We introduce a new coarse grain model capable of describing the phase
behavior of two dimensional ferromagnetic systems with competing exchange and
dipolar interactions, as well as an external magnetic field. An improved
expression for the mean field entropic contribution allows to compute the phase
diagram in the whole temperature versus external field plane. We find that the
topology of the phase diagram may be qualitatively different depending on the
ratio between the strength of the competing interactions. In the regime
relevant for ultrathin ferromagnetic films with perpendicular anisotropy we
confirm the presence of inverse symmetry breaking from a modulated phase to a
homogenous one as the temperature is lowered at constant magnetic field, as
reported in experiments. For other values of the competing interactions we show
that reentrance may be absent. Comparing thermodynamic quantities in both
cases, as well as the evolution of magnetization profiles in the modulated
phases, we conclude that the reentrant behavior is a consequence of the
suppression of domain wall degrees of freedom at low temperatures at constant
fields.


title: Fast and Extensible Online Multivariate Kernel Density Estimation

abstract:
  We present xokde++, a state-of-the-art online kernel density estimation
approach that maintains Gaussian mixture models input data streams. The
approach follows state-of-the-art work on online density estimation, but was
redesigned with computational efficiency, numerical robustness, and
extensibility in mind. Our approach produces comparable or better results than
the current state-of-the-art, while achieving significant computational
performance gains and improved numerical stability. The use of diagonal
covariance Gaussian kernels, which further improve performance and stability,
at a small loss of modelling quality, is also explored. Our approach is up to
40 times faster, while requiring 90\% less memory than the closest
state-of-the-art counterpart.


title: Strict contractions and exotic SO_0(d,1) quotients

abstract:
  For d < 5, we describe an elementary construction of nonzero degree, strict
contractions between closed, oriented hyperbolic d-oribifolds. Appealing to
work of Gueritaud-Kassel and Tholozan, these examples determine exotic
quotients of SO_0(d,1).


title: The complex social network from The Lord of The Rings

abstract:
  Studies of social structures has been grown on the last years, because its
sharing form and content creation attracted the public in general. Such
structures are observed, as an example, in literary pieces. A featured author
is J.R.R. Tolkien, with his books that describe a fictional world and its
inhabitants. These books bring a narrative of the creation of the Middle-Earth
and all of its mythology. His main pieces are: The Silmarillion, The Hobbit and
The Lord of the rings, The objective of this article is the analysis of the
social structures emerging of the conjunction of these works, where the social
relations are described by the reference criteria, shared events and direct
bonds, with the major centrality measures together with the structural entropy
of first order. Enabling the doing of an analogy with the canonic ensemble of
the mechanics statistics and enabling analyzing the degree of homogeneity of
the bonds between the formed communities.


title: Nilpotent orbits in real symmetric pairs and stationary black holes

abstract:
  In the classification of stationary solutions in extended supergravities with
symmetric scalar manifolds, the nilpotent orbits of a real symmetric pair play
an important role. In this paper we discuss two approaches to determining the
nilpotent orbits of a real symmetric pair. We apply our methods to an explicit
example, and thereby classify the nilpotent orbits of SL_2(R)^4 acting on the
fourth tensor power of the natural 2-dimensional SL_2(R)-module. This makes it
possible to classify all stationary solutions of the so-called STU-supergravity
model.


title:
Minimum Restraint Functions for unbounded dynamics: general and
  control-polynomial systems

abstract:
  We consider an exit-time minimum problem with a running cost, $l\geq 0$ and
unbounded controls. The occurrence of points where $l=0$ can be regarded as a
transversality loss. Furthermore, since controls range over unbounded sets, the
family of admissible trajectories may lack important compactness properties. In
the first part of the paper we show that the existence of a $p_0$-minimum
restraint function provides not only global asymptotic controllability (despite
non-transversality) but also a state-dependent upper bound for the value
function (provided $p_0>0$). This extends to unbounded dynamics a former result
which heavily relied on the compactness of the control set.
  In the second part of the paper we apply the general result to the case when
the system is polynomial in the control variable. Some elementary, algebraic,
properties of the convex hull of vector-valued polynomials' ranges allow some
simplifications of the main result, in terms of either near-affine-control
systems or reduction to weak subsystems for the original dynamics.


title: Shortest Trajectories and Reversibility in Boolean Automata Networks

abstract:
  The question this research report explores is the following: when does a
shortest trajectory between two configurations, or between one configuration
and an attractor need to change several times the state of one automaton?


title:
Measurements of the Separated Longitudinal Structure Function F_L from
  Hydrogen and Deuterium Targets at Low Q^2

abstract:
  Structure functions, as measured in lepton-nucleon scattering, have proven to
be very useful in studying the quark dynamics within the nucleon. However, it
is experimentally difficult to separately determine the longitudinal and
transverse structure functions, and consequently there are substantially less
data available for the longitudinal structure function in particular. Here we
present separated structure functions for hydrogen and deuterium at low
four--momentum transfer squared, Q^2< 1 GeV^2, and compare these with parton
distribution parameterizations and a k_T factorization approach. While
differences are found, the parameterizations generally agree with the data even
at the very low Q^2 scale of the data. The deuterium data show a smaller
longitudinal structure function, and smaller ratio of longitudinal to
transverse cross section R, than the proton. This suggests either an unexpected
difference in R for the proton and neutron or a suppression of the gluonic
distribution in nuclei.


title:
Specific Differential Entropy Rate Estimation for Continuous-Valued Time
  Series

abstract:
  We introduce a method for quantifying the inherent unpredictability of a
continuous-valued time series via an extension of the differential Shannon
entropy rate. Our extension, the specific entropy rate, quantifies the amount
of predictive uncertainty associated with a specific state, rather than
averaged over all states. We relate the specific entropy rate to popular
`complexity' measures such as Approximate and Sample Entropies. We provide a
data-driven approach for estimating the specific entropy rate of an observed
time series. Finally, we consider three case studies of estimating specific
entropy rate from synthetic and physiological data relevant to the analysis of
heart rate variability.


title:
Generalized Pauli channels and a class of non-Markovian quantum
  evolution

abstract:
  We analyze the quantum evolution represented by a time-dependent family of
generalized Pauli channels. This evolution is provided by the random
decoherence channels with respect to the maximal number of mutually unbiased
bases. We derive the necessary and sufficient conditions for the vanishing
back-flow of information.


title: Efficient Estimation of k for the Nearest Neighbors Class of Methods

abstract:
  The k Nearest Neighbors (kNN) method has received much attention in the past
decades, where some theoretical bounds on its performance were identified and
where practical optimizations were proposed for making it work fairly well in
high dimensional spaces and on large datasets. From countless experiments of
the past it became widely accepted that the value of k has a significant impact
on the performance of this method. However, the efficient optimization of this
parameter has not received so much attention in literature. Today, the most
common approach is to cross-validate or bootstrap this value for all values in
question. This approach forces distances to be recomputed many times, even if
efficient methods are used. Hence, estimating the optimal k can become
expensive even on modern systems. Frequently, this circumstance leads to a
sparse manual search of k. In this paper we want to point out that a systematic
and thorough estimation of the parameter k can be performed efficiently. The
discussed approach relies on large matrices, but we want to argue, that in
practice a higher space complexity is often much less of a problem than
repetitive distance computations.


abstract:
  The problem of time in quantum mechanics concerns the fact that in the
Schr\"odinger equation time is a parameter, not an operator. Pauli's objection
to a time-energy uncertainty relation analogue to the position-momentum one,
conjectured by Heisenberg early on, seemed to exclude the existence of such an
operator. However Dirac's formulation of electron's relativistic quantum
mechanics (RQM) does allow the introduction of a dynamical time operator that
is self-adjoint. Consequently, it can be considered as the generator of a
unitary transformation of the system,as well as an additional system observable
subject to uncertainty. In the present paper these aspects are examined within
the standard framework of RQM.


title: Analysis of rippling in incommensurate one-dimensional coupled chains

abstract:
  Graphene and other recently developed 2D materials exhibit exceptionally
strong in-plane stiffness. Relaxation of few-layer structures, either
free-standing or on slightly mismatched substrates occurs mostly through
out-of-plane bending and the creation of large-scale ripples. In this work, we
present a novel double chain model, where we allow relaxation to occur by
bending of the incommensurate coupled system of chains. As we will see, this
model can be seen as a new application of the well-known Frenkel-Kontorova
model for a one-dimensional atomic chain lying in a periodic potential. We
focus in particular on modeling and analyzing ripples occurring in ground state
configurations, as well as their numerical simulation.


title: False periodicities in quasar time-domain surveys

abstract:
  There have recently been several reports of apparently periodic variations in
the light curves of quasars, e.g. PG 1302-102 by Graham et al. (2015a). Any
quasar showing periodic oscillations in brightness would be a strong candidate
to be a close binary supermassive black hole and, in turn, a candidate for
gravitational wave studies. However, normal quasars -- powered by accretion
onto a single, supermassive black hole -- usually show stochastic variability
over a wide range of timescales. It is therefore important to carefully assess
the methods for identifying periodic candidates from among a population
dominated by stochastic variability. Using a Bayesian analysis of the light
curve of PG 1302-102, we find that a simple stochastic process is preferred
over a sinusoidal variations. We then discuss some of the problems one
encounters when searching for rare, strictly periodic signals among a large
number of irregularly sampled, stochastic time series, and use simulations of
quasar light curves to illustrate these points. From a few thousand simulations
of steep spectrum (`red noise') stochastic processes, we find many simulations
that display few-cycle periodicity like that seen in PG 1302-102. We emphasise
the importance of calibrating the false positive rate when the number of
targets in a search is very large.


title: Structure of irreducible homomorphisms to/from free modules

abstract:
  The primary goal of this paper is to investigate the structure of irreducible
monomorphisms to and irreducible epimorphisms from finitely generated free
modules over a noetherian local ring. Then we show that over such a ring,
self-vanishing of Ext and Tor for a finitely generated module admitting such an
irreducible homomorphism forces the ring to be regular.


title:
Influence of the Coulomb interaction on the exchange coupling in
  granular magnets

abstract:
  We develop a theory of the exchange interaction between ferromagnetic (FM)
metallic grains embedded into insulating matrix by taking into account the
Coulomb blockade effects. For bulk ferromagnets separated by the insulating
layer the exchange interaction strongly depends on the height and thickness of
the tunneling barrier created by the insulator. We show that for FM grains
embedded into insulating matrix the exchange coupling additionally depends on
the dielectric properties of this matrix due to the Coulomb blockade effects.
In particular, the FM coupling decreases with decreasing the dielectric
permittivity of insulating matrix. We find that the change in the exchange
interaction due to the Coulomb blockade effects can be a few tens of percent.
Also, we study dependence of the intergrain exchange interaction on the grain
size and other parameters of the system.


title:
On extremizers for Strichartz estimates for higher order Schr\"odinger
  equations

abstract:
  For an appropriate class of convex functions $\phi$, we study the Fourier
extension operator on the surface $\{(y, |y|^2+\phi(y)):y\in\mathbb{R}^2\}$
equipped with projection measure. For the corresponding extension inequality,
we compute optimal constants and prove that extremizers do not exist. The main
tool is a new comparison principle for convolutions of certain singular
measures that holds in all dimensions. Using tools of concentration-compactness
flavor, we further investigate the behavior of general extremizing sequences.
Our work is directly related to the study of extremizers and optimal constants
for Strichartz estimates of certain higher order Schr\"odinger equations. In
particular, we resolve a dichotomy from the recent literature concerning the
existence of extremizers for a family of fourth order Schr\"odinger equations,
and compute the corresponding operator norms exactly where only lower bounds
were previously known.


title:
Multi-Species Measurements of the Firehose and Mirror Instability
  Thresholds in the Solar Wind

abstract:
  The firehose and mirror instabilities are thought to arise in a variety of
space and astrophysical plasmas, constraining the pressure anisotropies and
drifts between particle species. The plasma stability depends on all species
simultaneously, meaning that a combined analysis is required. Here, we present
the first such analysis in the solar wind, using the long-wavelength stability
parameters to combine the anisotropies and drifts of all major species (core
and beam protons, alphas, and electrons). At the threshold, the firehose
parameter was found to be dominated by protons (67%), but also to have
significant contributions from electrons (18%) and alphas (15%). Drifts were
also found to be important, contributing 57% in the presence of a proton beam.
A similar situation was found for the mirror, with contributions of 61%, 28%,
and 11% for protons, electrons, and alphas, respectively. The parallel electric
field contribution, however, was found to be small at 9%. Overall, the
long-wavelength thresholds constrain the data well (<1% unstable), and the
implications of this are discussed.

categories: physics.space-ph astro-ph.EP astro-ph.SR physics.plasm-ph


title:
Measurement of the Inelastic Proton-Proton Cross Section at $\sqrt{s} =
  13$ TeV with the ATLAS Detector at the LHC

abstract:
  This Letter presents a measurement of the inelastic proton-proton cross
section using 60 $\mu$b$^{-1}$ of $pp$ collisions at a center-of-mass energy
$\sqrt{s}$ of $13$ TeV with the ATLAS detector at the LHC. Inelastic
interactions are selected using rings of plastic scintillators in the forward
region ($2.07<|\eta|<3.86$) of the detector. A cross section of $68.1\pm 1.4$
mb is measured in the fiducial region $\xi=M_X^2/s>10^{-6}$, where $M_X$ is the
larger invariant mass of the two hadronic systems separated by the largest
rapidity gap in the event. In this $\xi$ range the scintillators are highly
efficient. For diffractive events this corresponds to cases where at least one
proton dissociates to a system with $M_X>13$ GeV. The measured cross section is
compared with a range of theoretical predictions. When extrapolated to the full
phase space, a cross-section of $78.1 \pm 2.9$ mb is measured, consistent with
the inelastic cross section increasing with center-of-mass energy.


title:
Wideband Excitation of Microbubbles with Chirps to Maximize the
  Sonoporation Efficiency and Contrast in Ultrasound Imaging

abstract:
  The importance of the excitation bandwidth is well known in diagnostic
ultrasound imaging. However, the effect of excitation bandwidth in therapeutic
applications of microbubbles has been mostly overlooked. A majority of contrast
agent production techniques generate polydisperse microbubble populations, so a
wide range of resonance frequencies exist. Therefore, wideband excitation is
necessary to fully utilize microbubble resonance behavior and maximize the
reradiated energy from a microbubble population, both for imaging and therapy.
  Oscillations of sixty SonoVue microbubbles in proximity of a rigid boundary
were captured on a high speed camera at 3 Mfps, excited with a peak negative
pressure of 50 kPa at 1 MHz. Measurements were analyzed according to their peak
radiated pressure, radial oscillations, root mean squared pressure, and shear
stress generated by microbubbles. Results showed that long duration and
wideband excitation at low intensity levels was preferable for sonoporation,
where microbubbles can be driven in a stable oscillation state without
experiencing inertial cavitation or destruction.


title: Brains on Beats

abstract:
  We developed task-optimized deep neural networks (DNNs) that achieved
state-of-the-art performance in different evaluation scenarios for automatic
music tagging. These DNNs were subsequently used to probe the neural
representations of music. Representational similarity analysis revealed the
existence of a representational gradient across the superior temporal gyrus
(STG). Anterior STG was shown to be more sensitive to low-level stimulus
features encoded in shallow DNN layers whereas posterior STG was shown to be
more sensitive to high-level stimulus features encoded in deep DNN layers.


title: Local field enhancement: comparing self-similar and dimer nanoantennas

abstract:
  We study the local field enhancement properties of self-similar nanolenses
and compare the obtained results with the performance of standard dimer
nanoantennas. We report that, despite the additional structural complexity,
self-similar nanolenses are unable to provide significant improvements over the
field enhancement performance of standard plasmonic dimers.


title:
Research-based assessment of students' beliefs about experimental
  physics: When is gender a factor?

abstract:
  The existence of gender differences in student performance on conceptual
assessments and their responses to attitudinal assessments has been repeatedly
demonstrated. This difference is often present in students' preinstruction
responses and persists in their postinstruction responses. However, one area in
which the presence of gender differences has not been extensively explored is
undergraduate laboratory courses. For example, one of the few laboratory
focused research-based assessments, the Colorado Learning Attitudes about
Science Survey for Experimental Physics (E-CLASS), has not been tested for the
existence of gender differences in students' responses. Here, we utilize a
national data set of responses to the E-CLASS to determine if they demonstrate
significant gender differences. We also investigate how these differences vary
along multiple student and course demographic slices, including course level
(first-year vs.\ beyond-first-year) and major (physics vs.\ non-physics). We
observe a gender gap in pre- and postinstruction E-CLASS scores in the
aggregate data both for the overall score and for most items individually.
However, for some subpopulations (e.g., beyond-first-year students) the size or
even existence of the gender gap depends on another dimension (e.g., student
major). We also find that for all groups the gap in postinstruction scores
vanishes or is greatly reduced when controlling for preinstruction scores,
course level, and student major.


title: Routh reduction and Cartan mechanics

abstract:
  In the present work a Cartan mechanics version for Routh reduction is
considered, as an intermediate step toward Routh reduction in field theory.
Motivation for this generalization comes from an scheme for integrable systems
[12], used for understanding the occurrence of Toda field theories in so called
Hamiltonian reduction of WZNW field theories [11]. As a way to accomplish with
this intermediate aim, this article also contains a formulation of the
Lagrangian Adler-Kostant-Symes systems discussed in [12] in terms of Routh
reduction.


title:
Basic sets for the double covering groups of the symmetric and
  alternating groups in odd characteristic

abstract:
  In this paper, following the methods of http://arxiv.org/abs/1305.7449v2, we
show that the double covering groups of the symmetric and alternating groups
have p-basic sets for any odd prime p.


title:
Towards learning through robotic interaction alone: the joint guided
  search task

abstract:
  This work proposes a biologically inspired approach that focuses on attention
systems that are able to inhibit or constrain what is relevant at any one
moment. We propose a radically new approach to making progress in human-robot
joint attention called "the joint guided search task". Visual guided search is
the activity of the eye as it saccades from position to position recognizing
objects in each fixation location until the target object is found. Our
research focuses on the exchange of nonverbal behavior toward changing the
fixation location while also performing object recognition. Our main goal is a
very ambitious goal of sharing attention through probing synthetic foreground
maps (i.e. what is being considered by the robotic agent) and the biological
attention system of the human.


title:
Lowest degree invariant 2nd order PDEs over rational homogeneous contact
  manifolds

abstract:
  For each simple Lie algebra $\mathfrak{g}$ (excluding, for trivial reasons,
type ${\sf C}$) we find the lowest possible degree of an invariant second-order
PDE over the adjoint variety in $\mathbb{P}\mathfrak{g}$, a homogeneous contact
manifold. Here a PDE $F(x^i,u,u_i,u_{ij})=0$ has degree $\le d$ if $F$ is a
polynomial of degree $\le d$ in the minors of $(u_{ij})$, with coefficients
functions of the contact coordinates $x^i$, $u$, $u_i$ (e.g., Monge-Amp\`ere
equations have degree 1). For $\mathfrak{g}$ of type ${\sf A}$ or ${\sf G}$ we
show that this gives all invariant second-order PDEs. For $\mathfrak{g}$ of
type ${\sf B}$ and ${\sf D}$ we provide an explicit formula for the
lowest-degree invariant second-order PDEs. For $\mathfrak{g}$ of type ${\sf E}$
and ${\sf F}$ we prove uniqueness of the lowest-degree invariant second-order
PDE; we also conjecture that uniqueness holds in type ${\sf D}$.


title:
Optimal multilinear restriction estimates for a class of surfaces with
  curvature

abstract:
  Bennett, Carbery and Tao considered the $k$-linear restriction estimate in
$\mathbb{R}^{n+1}$ and established the near optimal $L^\frac2{k-1}$ estimate
under transversality assumptions only. We have shown that the trilinear
restriction estimate improves its range of exponents under some curvature
assumptions. In this paper we establish almost sharp multilinear estimates for
a class of hypersurfaces with curvature for $4 \leq k \leq n$. Together with
previous results in the literature, this shows that curvature improves the
range of exponents in the multilinear restriction estimate at all levels of
lower multilinearity, that is when $k \leq n$.


title:
Feedback Scheduling for Energy-Efficient Real-Time Homogeneous
  Multiprocessor Systems

abstract:
  Real-time scheduling algorithms proposed in the literature are often based on
worst-case estimates of task parameters. The performance of an open-loop scheme
can be degraded significantly if there are uncertainties in task parameters,
such as the execution times of the tasks. Therefore, to cope with such a
situation, a closed-loop scheme, where feedback is exploited to adjust the
system parameters, can be applied. We propose an optimal control framework that
takes advantage of feeding back information of finished tasks to solve a
real-time multiprocessor scheduling problem with uncertainty in task execution
times, with the objective of minimizing the total energy consumption.
Specifically, we propose a linear programming based algorithm to solve a
workload partitioning problem and adopt McNaughton's wrap around algorithm to
find the task execution order. The simulation results illustrate that our
feedback scheduling algorithm can save energy by as much as 40% compared to an
open-loop method for two processor models, i.e. a PowerPC 405LP and an XScale
processor.


title:
Electronic structures of free-standing nanowires made from indirect
  bandgap semiconductor gallium phosphide

abstract:
  We present a theoretical study of the electronic structures of freestanding
nanowires made from gallium phosphide (GaP)--a III-V semiconductor with an
indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and
rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal
cross sections. Based on tight binding models, both the band structures and
wave functions of the nanowires are calculated. For the [001]-oriented GaP
nanowires, the bands show anti-crossing structures, while the bands of the
[111]-oriented nanowires display crossing structures. Two minima are observed
in the conduction bands, while the maximum of the valence bands is always at
the $\Gamma$-point. Using double group theory, we analyze the symmetry
properties of the lowest conduction band states and highest valence band states
of GaP nanowires with different sizes and directions. The band state wave
functions of the lowest conduction bands and the highest valence bands of the
nanowires are evaluated by spatial probability distributions. For practical
use, we fit the confinement energies of the electrons and holes in the
nanowires to obtain an empirical formula.


title:
On reduced twisted group C*-algebras that are simple and/or have a
  unique trace

abstract:
  We study the problem of determining when the reduced twisted group C*-algebra
associated with a discrete group G is simple and/or has a unique tracial state,
and present new sufficient conditions for this to hold. One of our main tools
is a combinatorial property, that we call the relative Kleppner condition,
which ensures that a quotient group G/H acts by freely acting automorphisms on
the twisted group von Neumann algebra associated to a normal subgroup H. We
apply our results to different types of groups, e.g. wreath products and
Baumslag-Solitar groups.


title: Addressing Limited Data for Textual Entailment Across Domains

abstract:
  We seek to address the lack of labeled data (and high cost of annotation) for
textual entailment in some domains. To that end, we first create (for
experimental purposes) an entailment dataset for the clinical domain, and a
highly competitive supervised entailment system, ENT, that is effective (out of
the box) on two domains. We then explore self-training and active learning
strategies to address the lack of labeled data. With self-training, we
successfully exploit unlabeled data to improve over ENT by 15% F-score on the
newswire domain, and 13% F-score on clinical data. On the other hand, our
active learning experiments demonstrate that we can match (and even beat) ENT
using only 6.6% of the training data in the clinical domain, and only 5.8% of
the training data in the newswire domain.


title: On the monoid generated by a Lucas sequence

abstract:
  A Lucas sequence is a sequence of the general form $v_n = (\phi^n -
\bar{\phi}^n)/(\phi-\bar{\phi})$, where $\phi$ and $\bar{\phi}$ are real
algebraic integers such that $\phi+\bar{\phi}$ and $\phi\bar{\phi}$ are both
rational. Famous examples include the Fibonacci numbers, the Pell numbers, and
the Mersenne numbers. We study the monoid that is generated by such a sequence;
as it turns out, it is almost freely generated. We provide an asymptotic
formula for the number of positive integers $\leq x$ in this monoid, and also
prove Erd\H{o}s-Kac type theorems for the distribution of the number of
factors, with and without multiplicity. While the limiting distribution is
Gaussian if only distinct factors are counted, this is no longer the case when
multiplicities are taken into account.


title:
On a coupled system of a Ginzburg-Landau equation with a quasilinear
  conservation law

abstract:
  We study the Cauchy problem for a coupled system of a complex Ginzburg-Landau
equation with a quasilinear conservation law $$ \left\{\begin{array}{rlll}
e^{-i\theta}u_t&=&u_{xx}-|u|^2u-\alpha g(v)u& v_t+(f(v))_x&=&\alpha
(g'(v)|u|^2)_x& \end{array}\right. \qquad x\in\mathbb{R},\, t \geq 0, $$ which
can describe the interaction between a laser beam and a fluid flow (see
[Aranson, Kramer, Rev. Med. Phys. 74 (2002)]). We prove the existence of a
local in time strong solution for the associated Cauchy problem and, for a
certain class of flux functions, the existence of global weak solutions.
Furthermore we prove the existence of standing waves of the form
$(u(t,x),v(t,x))=(U(x),V(x))$ in several cases.


title: A High Quartets Distance Construction

abstract:
  Given two binary trees on $N$ labeled leaves, the quartet distance between
the trees is the number of disagreeing quartets. By permuting the leaves at
random, the expected quartets distance between the two trees is
$\frac{2}{3}\binom{N}{4}$. However, no strongly explicit construction reaching
this bound asymptotically was known.
  We consider complete, balanced binary trees on $N=2^n$ leaves, labeled by $n$
long bit sequences. Ordering the leaves in one tree by the prefix order, and in
the other tree by the suffix order, we show that the resulting quartet distance
is $\left(\frac{2}{3} + o(1)\right)\binom{N}{4}$, and it always exceeds the
$\frac{2}{3}\binom{N}{4}$ bound.


title: Jacobi series for general parameters and applications

abstract:
  Representation of analytic functions as convergent series in Jacobi
polynomials $P_n^{(a,b)}$ is reformulated using a unified approach for almost
all complex $a, b$. The coefficients of the series are given as usual integrals
in the classical case (when $\Re a, \Re b >-1$), or by the Hadamard principal
part of these integrals when they diverge. As an application it is shown that
inhomogeneous hypergeometric equations do generically have a unique solution
which is analytic at both singular points in the complex plane.


title: Model Checking Flat Freeze LTL on One-Counter Automata

abstract:
  Freeze LTL is a temporal logic with registers that is suitable for specifying
properties of data words. In this paper we study the model checking problem for
Freeze LTL on one-counter automata. This problem is known to be undecidable in
general and PSPACE-complete for the special case of deterministic one-counter
automata. Several years ago, Demri and Sangnier investigated the model checking
problem for the flat fragment of Freeze LTL on several classes of counter
automata and posed the decidability of model checking flat Freeze LTL on
one-counter automata as an open problem. In this paper we resolve this problem
positively, utilising a known reduction to a reachability problem on
one-counter automata with parameterised equality and disequality tests. Our
main technical contribution is to show decidability of the latter problem by
translation to Presburger arithmetic.


title:
The generalized Taylor series approach is not equivalent to the homotopy
  analysis method

abstract:
  In recent work on the area of approximation methods for the solution of
nonlinear differential equations, it has been suggested that the so-called
generalized Taylor series approach is equivalent to the homotopy analysis
method. In the present paper, we demonstrate that such a view is only valid in
very special cases, and in general the homotopy analysis method is far more
robust. In particular, the equivalence is only valid when the solution is
represented as a power series in the independent variable. As has been shown
many times, alternative basis functions can greatly improve the error
properties of homotopy solutions, and when the base functions are not
polynomials or power functions, we no longer have that the generalized Taylor
series approach is equivalent to the homotopy analysis method. We demonstrate
this by consideration of an example where the generalizes Taylor series must
always have a finite radius of convergence (and hence limited applicability),
while the homotopy solution is valid over the entire infinite domain. We then
give a second example for which the exact solution is not analytic, and hence
it will not agree with the generalized Taylor series over the domain. We
conclude that the generalized Taylor series approach is not equivalent to the
homotopy analysis method. In particular, the generalized Taylor series can at
best recover local information about solutions, whereas the homotopy analysis
method can recover the solutions globally if appropriate base functions are
selected. Such results have important implications for how series are
calculated when approximating solutions to nonlinear differential equations.


title: Simplified Boardgames

abstract:
  We formalize Simplified Boardgames language, which describes a subclass of
arbitrary board games. The language structure is based on the regular
expressions, which makes the rules easily machine-processable while keeping the
rules concise and fairly human-readable.


title: Exact solutions to quadratic gravity

abstract:
  Since all Einstein spacetimes are vacuum solutions to quadratic gravity in
four dimensions, in this paper we study various aspects of non-Einstein vacuum
solutions to this theory. Most such known solutions are of traceless Ricci and
Petrov type N with a constant Ricci scalar. Thus we assume the Ricci scalar to
be constant which leads to a substantial simplification of the field equations.
We prove that a vacuum solution to quadratic gravity with traceless Ricci
tensor of type N and aligned Weyl tensor of any Petrov type is necessarily a
Kundt spacetime. This will considerably simplify the search for new
non-Einstein solutions. Similarly, a vacuum solution to quadratic gravity with
traceless Ricci type III and aligned Weyl tensor of Petrov type II or more
special is again necessarily a Kundt spacetime.
  Then we study the general role of conformal transformations in constructing
vacuum solutions to quadratic gravity. We find that such solutions can be
obtained by solving one non-linear partial differential equation for a
conformal factor on any Einstein spacetime or, more generally, on any
background with vanishing Bach tensor. In particular, we show that all
geometries conformal to Kundt are either Kundt or Robinson-Trautman, and we
provide some explicit Kundt and Robinson-Trautman solutions to quadratic
gravity by solving the above mentioned equation on certain Kundt backgrounds.


title: Safe and Efficient Off-Policy Reinforcement Learning

abstract:
  In this work, we take a fresh look at some old and new algorithms for
off-policy, return-based reinforcement learning. Expressing these in a common
form, we derive a novel algorithm, Retrace($\lambda$), with three desired
properties: (1) it has low variance; (2) it safely uses samples collected from
any behaviour policy, whatever its degree of "off-policyness"; and (3) it is
efficient as it makes the best use of samples collected from near on-policy
behaviour policies. We analyze the contractive nature of the related operator
under both off-policy policy evaluation and control settings and derive online
sample-based algorithms. We believe this is the first return-based off-policy
control algorithm converging a.s. to $Q^*$ without the GLIE assumption (Greedy
in the Limit with Infinite Exploration). As a corollary, we prove the
convergence of Watkins' Q($\lambda$), which was an open problem since 1989. We
illustrate the benefits of Retrace($\lambda$) on a standard suite of Atari 2600
games.


title: A priori feedback estimates for multiscale reaction-diffusion systems

abstract:
  We study the approximation of a multiscale reaction-diffusion system posed on
both macroscopic and microscopic space scales. The coupling between the scales
is done via micro-macro flux conditions. Our target system has a typical
structure for reaction-diffusion-flow problems in media with distributed
microstructures (also called, double porosity materials). Besides ensuring
basic estimates for the convergence of two-scale semi-discrete Galerkin
approximations, we provide a set of {\em a priori} feedback estimates and a
local feedback error estimator that help in designing a distributed-high-errors
strategy to allow for a computationally efficient zooming in and out from
microscopic structures. The error control on the feedback estimates relies on
two-scale-energy, regularity, and interpolation estimates as well as on a fine
bookeeping of the sources responsible with the propagation of the (multiscale)
approximation errors. The working technique based on {\em a priori } feedback
estimates is in principle applicable to a large class of systems of PDEs with
dual structure admitting strong solutions.


title: Inertia-induced accumulation of flotsam in the subtropical gyres

abstract:
  Recent surveys of marine plastic debris density have revealed high levels in
the center of the subtropical gyres. Earlier studies have argued that the
formation of great garbage patches is due to Ekman convergence in such regions.
In this work we report a tendency so far overlooked of drogued and undrogued
drifters to accumulate distinctly over the subtropical gyres, with undrogued
drifters accumulating in the same areas where plastic debris accumulate. We
show that the observed accumulation is too fast for Ekman convergence to
explain it. We demonstrate that the accumulation is controlled by finite-size
and buoyancy (i.e., inertial) effects on undrogued drifter motion subjected to
ocean current and wind drags. We infer that the motion of flotsam in general is
constrained by similar effects. This is done by using a newly proposed
Maxey--Riley equation which models the submerged (surfaced) drifter portion as
a sphere of the fractional volume that is submerged (surfaced).


title:
Birkeland current effects on high-latitude groundmagnetic field
  perturbations

abstract:
  Magnetic perturbations on ground at high latitudes are directly associated
only with the divergence-free component of the height-integrated horizontal
ionospheric current, $\textbf{J}_{\perp,df}$. Here we show how
$\textbf{J}_{\perp,df}$ can be expressed as the total horizontal current
$\textbf{J}_\perp$ minus its curl-free component, the latter being completely
determined by the global Birkeland current pattern. Thus in regions where
$\textbf{J}_\perp = 0$, the global Birkeland current distribution alone
determines the local magnetic perturbation. We show with observations from
ground and space that in the polar cap, the ground magnetic field perturbations
tend to align with the Birkeland current contribution in darkness but not in
sunlight. We also show that in sunlight, the magnetic perturbations are
typically such that the equivalent overhead current is anti-parallel to the
convection, indicating that the Hall current system dominates. Thus the ground
magnetic field in the polar cap relates to different current systems in
sunlight and in darkness.


title:
A new technique for determining Substorm Onsets and Phases from Indices
  of the Electrojet (SOPHIE)

abstract:
  We present a new quantitative technique that determines the times and
durations of substorm expansion and recovery phases and possible growth phases
based on percentiles of the rate of change of auroral electrojet indices. By
being able to prescribe different percentile values, we can determine the onset
and duration of substorm phases for smaller or larger variations of the auroral
index or indeed any auroral zone ground-based magnetometer data. We apply this
technique to the SuperMAG AL (SML) index and compare our expansion phase onset
times with previous lists of substorm onsets. We find that more than 50% of
events in previous lists occur within 20 min of our identified onsets. We also
present a comparison of superposed epoch analyses of SML based on our onsets
identified by our technique and existing onset lists and find that the general
characteristics of the substorm bay are comparable. By prescribing user-defined
thresholds, this automated, quantitative technique represents an improvement
over any visual identification of substorm onsets or indeed any fixed threshold
method.


title:
Severe and localized GNSS scintillation at the poleward edge of the
  nightside auroral oval during intense substorm aurora

abstract:
  In this paper we study how GPS, GLONASS, and Galileo navigation signals are
compromised by strong irregularities causing severe phase scintillation
($\mathit{\sigma }_{\phi }$ > 1) in the nightside high-latitude ionosphere
during a substorm on 3 November 2013. Substorm onset and a later
intensification coincided with polar cap patches entering the auroral oval to
become auroral blobs. Using Global Navigation Satellite Systems (GNSS)
receivers and optical data, we show severe scintillation driven by intense
auroral emissions in the line of sight between the receiver and the satellites.
During substorm expansion, the area of scintillation followed the intense
poleward edge of the auroral oval. The intense auroral emissions were colocated
with polar cap patches (blobs). The patches did not contain strong
irregularities, neither before entering the auroral oval nor after the aurora
had faded. Signals from all three GNSS constellations were similarly affected
by the irregularities. Furthermore, two receivers spaced around 120km apart
reported highly different scintillation impacts, with strong scintillation on
half of the satellites in one receiver and no scintillation in the other. This
shows that areas of severe irregularities in the nightside ionosphere can be
highly localized. Amplitude scintillations were low throughout the entire
interval.


title:
An extensive survey of dayside diffuse aurora based on optical
  observations at Yellow River Station

abstract:
  By using 7 years optical auroral observations obtained at Yellow River
Station (magnetic latitude $76.24\,^{\circ}{\rm C}$N) at Ny-Alesund, Svalbard,
we performed the first extensive survey for the dayside diffuse auroras (DDAs)
and acquired observational results as follows. (1) The DDAs can be classified
into two broad categories, i.e., unstructured and structured DDAs. The
unstructured DDAs are mainly distributed in the morning and afternoon, but the
structured DDAs predominantly occurred around the magnetic local noon (MLN).
(2) The unstructured DDAs observed in morning and afternoon present obviously
different properties. The afternoon ones are much stable and seldom show
pulsating property. (3) The DDAs are more easily observed under geomagnetically
quiet times. (4) The structured DDAsmainly show patchy, stripy, and irregular
forms and are often pulsating and drifting. The drifting directions are mostly
westward (with speed $\sim$5km/s), but there are cases showing eastward or
poleward drifting. (5) The stripy DDAs are exclusively observed near theMLN
and,most importantly, their alignments are confirmed to be consistent with the
direction of ionospheric convection near the MLN. (6) A new auroral form,
called throat aurora, is found to be developed from the stripy DDAs. Based on
the observational results and previous studies, we proposed our explanations to
the DDAs. We suggest that the unstructured DDAs observed in the morning are
extensions of the nightside diffuse aurora to the dayside, but that observed in
the afternoon are predominantly caused by proton precipitations.
$\textit{(Abstract continues in PDF).}$


title:
Scintillation and loss of signal lock from poleward moving auroral forms
  in the cusp ionosphere

abstract:
  We present two examples from the cusp ionosphere over Svalbard,where poleward
moving auroral forms (PMAFs) are causing significant phase scintillation in
signals from navigation satellites. The data were obtained using a combination
of ground-based optical instruments and a newly installed multiconstellation
navigation signal receiver at Longyearbyen. Both events affected signals from
GPS and Global Navigation Satellite System (GLONASS). When one intense PMAF
appeared, the signal from one GPS spacecraft also experienced a temporary loss
of signal lock. Although several polar cap patches were also observed in the
area as enhancements in total electron content, the most severe scintillation
and loss of signal lock appear to be attributed to very intense PMAF activity.
This shows that PMAFs are locations of strong ionospheric irregularities, which
at times may cause more severe disturbances in the cusp ionosphere for
navigation signals than polar cap patches.


title:
Network analysis of geomagnetic substorms using the SuperMAG database of
  ground-based magnetometer stations

abstract:
  The overall morphology and dynamics of magnetospheric substorms is well
established in terms of the observed qualitative auroral features seen in
ground-based magnetometers. This paper focuses on the quantitative
characterization of substorm dynamics captured by ground-based magnetometer
stations. We present the first analysis of substorms using dynamical networks
obtained from the full available set of ground-based magnetometer observations
in the Northern Hemisphere. The stations are connected in the network when the
correlation between the vector magnetometer time series from pairs of stations
within a running time window exceeds a threshold. Dimensionless parameters can
then be obtained that characterize the network and by extension, the
spatiotemporal dynamics of the substorm under observation. We analyze four
isolated substorm test cases as well as a steady magnetic convection (SMC)
event and a day in which no substorms occur. These test case substorms are
found to give a consistent characteristic network response at onset in terms of
their spatial correlation. Such responses are differentiable from responses to
the SMC event and nonsubstorm times. We present a method to optimize network
parametrization with respect to the different individual station responses, the
spatial inhomogeneity of stations in the Northern Hemisphere, and the choice of
correlation window sizes. Our results suggest that dynamical network analysis
has potential to quantitatively categorize substorms.


title:
Spatial structure and temporal evolution of energetic particle
  injections in the inner magnetosphere during the 14 July 2013 substorm event

abstract:
  Recent results by the Van Allen Probes mission showed that the occurrence of
energetic ion injections inside geosynchronous orbit could be very frequent
throughout the main phase of a geomagnetic storm. Understanding, therefore, the
formation and evolution of energetic particle injections is critical in order
to quantify their effect in the inner magnetosphere. We present a case study of
a substorm event that occurred during a weak storm $\textit{ Dst }$ $\sim$
-40nT on 14 July 2013. Van Allen Probe B, inside geosynchronous orbit, observed
two energetic proton injections within 10min, with different dipolarization
signatures and duration. The first one is a dispersionless, short-timescale
injection pulse accompanied by a sharp dipolarization signature, while the
second one is a dispersed, longer-timescale injection pulse accompanied by a
gradual dipolarization signature. We combined ground magnetometer data from
various stations and in situ particle and magnetic field data from multiple
satellites in the inner magnetosphere and near-Earth plasma sheet to determine
the spatial extent of these injections, their temporal evolution, and their
effects in the inner magnetosphere. Our results indicate that there are
different spatial and temporal scales at which injections can occur in the
inner magnetosphere and depict the necessity of multipoint observations of both
particle and magnetic field data in order to determine these scales.


title:
A large-scale view of Space Technology 5 magnetometer response to solar
  wind drivers

abstract:
  In this data report we discuss reprocessing of the Space Technology 5 (ST5)
magnetometer database for inclusion in NASA's Coordinated Data Analysis Web
(CDAWeb) virtual observatory. The mission consisted of three spacecraft flying
in elliptical orbits, from 27 March to 27 June 2006. Reprocessing includes (1)
transforming the data into the Modified Apex Coordinate System for projection
to a common reference altitude of 110km, (2) correcting gain jumps, and (3)
validating the results. We display the averaged magnetic perturbations as a
keogram, which allows direct comparison of the full-mission data with the solar
wind values and geomagnetic indices.With the data referenced to a common
altitude, we find the following: (1) Magnetic perturbations that track the
passage of corotating interaction regions and high-speed solar wind; (2)
unexpectedly strong dayside perturbations during a solstice magnetospheric
sawtooth oscillation interval characterized by a radial interplanetary magnetic
field (IMF) component that may have enhanced the accompanying modest southward
IMF; and (3) intervals of reduced magnetic perturbations or "calms," associated
with periods of slow solar wind, interspersed among variable-length episodic
enhancements. These calms aremost evidentwhen the IMF is northward or
projectswith a northward component onto the geomagnetic dipole. The reprocessed
ST5 data are in very good agreement with magnetic perturbations from the
Defense Meteorological Satellite Program (DMSP) spacecraft, which we also map
to 110km. We briefly discuss the methods used to remap the ST5 data and the
means of validating the results against DMSP. Our methods form the basis for
future intermission comparisons of space-based magnetometer data.