title:
Nebular Continuum and Line Emission in Stellar Population Synthesis
  Models

abstract:
  Accounting for nebular emission when modeling galaxy spectral energy
distributions (SEDs) is important, as both line and continuum emission can
contribute significantly to the total observed flux. In this work, we present a
new nebular emission model integrated within the Flexible Stellar Population
Synthesis code that computes the total line and continuum emission for complex
stellar populations using the photoionization code Cloudy. The self-consistent
coupling of the nebular emission to the matched ionizing spectrum produces
emission line intensities that correctly scale with the stellar population as a
function of age and metallicity. This more complete model of galaxy SEDs will
improve estimates of global gas properties derived with diagnostic diagrams,
star formation rates based on H$\alpha$, and stellar masses derived from NIR
broadband photometry. Our models agree well with results from other
photoionization models and are able to reproduce observed emission from H II
regions and star-forming galaxies. Our models show improved agreement with the
observed H II regions in the Ne III/O II plane and show satisfactory agreement
with He II emission from $z=2$ galaxies when including rotating stellar models.
Models including post-asymptotic giant branch stars are able to reproduce line
ratios consistent with low-ionization emission regions (LIERs).


title: Pruning to Increase Taylor Dispersion in Physarum polycephalum Networks

abstract:
  How do the topology and geometry of a tubular network affect the spread of
particles within fluid flows? We investigate patterns of effective dispersion
in the hierarchical, biological transport network formed by Physarum
polycephalum. We demonstrate that a change in topology - pruning in the
foraging state - causes a large increase in effective dispersion throughout the
network. By comparison, changes in the hierarchy of tube radii result in
smaller and more localized differences. Pruned networks capitalize on Taylor
dispersion to increase the dispersion capability.


title: Learning Python Code Suggestion with a Sparse Pointer Network

abstract:
  To enhance developer productivity, all modern integrated development
environments (IDEs) include code suggestion functionality that proposes likely
next tokens at the cursor. While current IDEs work well for statically-typed
languages, their reliance on type annotations means that they do not provide
the same level of support for dynamic programming languages as for
statically-typed languages. Moreover, suggestion engines in modern IDEs do not
propose expressions or multi-statement idiomatic code. Recent work has shown
that language models can improve code suggestion systems by learning from
software repositories. This paper introduces a neural language model with a
sparse pointer network aimed at capturing very long-range dependencies. We
release a large-scale code suggestion corpus of 41M lines of Python code
crawled from GitHub. On this corpus, we found standard neural language models
to perform well at suggesting local phenomena, but struggle to refer to
identifiers that are introduced many tokens in the past. By augmenting a neural
language model with a pointer network specialized in referring to predefined
classes of identifiers, we obtain a much lower perplexity and a 5 percentage
points increase in accuracy for code suggestion compared to an LSTM baseline.
In fact, this increase in code suggestion accuracy is due to a 13 times more
accurate prediction of identifiers. Furthermore, a qualitative analysis shows
this model indeed captures interesting long-range dependencies, like referring
to a class member defined over 60 tokens in the past.


title: Proxy Voting for Better Outcomes

abstract:
  We consider a social choice problem where only a small number of people out
of a large population are sufficiently available or motivated to vote. A common
solution to increase participation is to allow voters use a proxy, that is,
transfer their voting rights to another voter. Considering social choice
problems on metric spaces, we compare voting with and without the use of
proxies to see which mechanism better approximates the optimal outcome, and
characterize the regimes in which proxy voting is beneficial. When voters'
opinions are located on an interval, both the median mechanism and the mean
mechanism are substantially improved by proxy voting. When voters vote on many
binary issues, proxy voting is better when the sample of active voters is too
small to provide a good outcome. Our theoretical results extend to situations
where available voters choose strategically whether to participate. We support
our theoretical findings with empirical results showing substantial benefits of
proxy voting on simulated and real preference data.


title:
On Human Intellect and Machine Failures: Troubleshooting Integrative
  Machine Learning Systems

abstract:
  We study the problem of troubleshooting machine learning systems that rely on
analytical pipelines of distinct components. Understanding and fixing errors
that arise in such integrative systems is difficult as failures can occur at
multiple points in the execution workflow. Moreover, errors can propagate,
become amplified or be suppressed, making blame assignment difficult. We
propose a human-in-the-loop methodology which leverages human intellect for
troubleshooting system failures. The approach simulates potential component
fixes through human computation tasks and measures the expected improvements in
the holistic behavior of the system. The method provides guidance to designers
about how they can best improve the system. We demonstrate the effectiveness of
the approach on an automated image captioning system that has been pressed into
real-world use.


title:
White matter deficits underlie the loss of consciousness level and
  predict recovery outcome in disorders of consciousness

abstract:
  This study aimed to identify white matter (WM) deficits underlying the loss
of consciousness in disorder of consciousness (DOC) patients using Diffusion
Tensor Imaging (DTI) and to demonstrate the potential value of DTI parameters
in predicting recovery outcomes of DOC patients. With 30 DOC patients (8
comatose, 8 unresponsive wakefulness syndrome/vegetative state, and 14 minimal
conscious state) and 25 patient controls, we performed group comparison of DTI
parameters across 48 core WM regions of interest (ROIs) using Analysis of
Covariance. Compared with controls, DOC patients had decreased Fractional
anisotropy (FA) and increased diffusivities in widespread WM area.The
corresponding DTI parameters of those WM deficits in DOC patients significantly
correlated with the consciousness level evaluated by Coma Recovery Scale
Revised (CRS-R) and Glasgow Coma Scale (GCS). As for predicting the recovery
outcomes (i.e., regaining consciousness or not, grouped by their Glasgow
Outcome Scale more than 2 or not) at 3 months post scan, radial diffusivity of
left superior cerebellar peduncle and FA of right sagittal stratum reached an
accuracy of 87.5% and 75% respectively. Our findings showed multiple WM
deficits underlying the loss of consciousness level, and demonstrated the
potential value of these WM areas in predicting the recovery outcomes of DOC
patients who have lost awareness of the environment and themselves.


title: Tracing star formation with non-thermal radio emission

abstract:
  A key for understanding the evolution of galaxies and in particular their
star formation history will be future ultra-deep radio surveys. While star
formation rates (SFRs) are regularly estimated with phenomenological formulas
based on the local FIR-radio correlation, we present here a physically
motivated model to relate star formation with radio fluxes. Such a relation
holds only in frequency ranges where the flux is dominated by synchrotron
emission, as this radiation originates from cosmic rays produced in supernova
remnants, therefore reflecting recent star formation. At low frequencies
synchrotron emission can be absorbed by the free-free mechanism. This
suppression becomes stronger with increasing number density of the gas, more
precisely of the free electrons. We estimate the critical observing frequency
below which radio emission is not tracing the SFR, and use the three
well-studied local galaxies M 51, M 82, and Arp 220 as test cases for our
model. If the observed galaxy is at high redshift, this critical frequency
moves along with other spectral features to lower values in the observing
frame. In the absence of systematic evolutionary effects, one would therefore
expect that the method can be applied at lower observing frequencies for high
redshift observations. However, in case of a strong increase of the typical gas
column densities towards high redshift, the increasing free-free absorption may
erase the star formation signatures at low frequencies. At high radio
frequencies both, free-free emission and the thermal bump, can dominate the
spectrum, also limiting the applicability of this method.


title: Major arcs and moments of arithmetical sequences

abstract:
  We give estimates for the first two moments of arithmetical sequences in
progressions. Instead of using the standard approximation, we work with a
generalization of Vaughan's major arcs approximation which is similar to that
appearing in earlier work of Browning and Heath-Brown on norm forms. We apply
our results to the sequence $\tau_k(n)$, and obtain unconditional results in a
wide range of moduli.


title:
A hybridizable discontinuous Galerkin method for solving nonlocal
  optical response models

abstract:
  We propose Hybridizable Discontinuous Galerkin (HDG) methods for solving the
frequency-domain Maxwell's equations coupled to the Nonlocal Hydrodynamic Drude
(NHD) and Generalized Nonlocal Optical Response (GNOR) models, which are
employed to describe the optical properties of nano-plasmonic scatterers and
waveguides. Brief derivations for both the NHD model and the GNOR model are
presented. The formulations of the HDG method are given, in which we introduce
two hybrid variables living only on the skeleton of the mesh. The local field
solutions are expressed in terms of the hybrid variables in each element. Two
conservativity conditions are globally enforced to make the problem solvable
and to guarantee the continuity of the tangential component of the electric
field and the normal component of the current density. Numerical results show
that the proposed HDG methods converge at optimal rate. We benchmark our
implementation and demonstrate that the HDG method has the potential to solve
complex nanophotonic problems.


title:
New long-term braking index measurements for glitching pulsars using a
  glitch-template method

abstract:
  Braking index measurements offer the opportunity to explore the processes
affecting the long-term spin evolution of pulsars and possible evolutionary
connections between the various pulsar populations. For young pulsars the
long-term trends are generally obscured by short term phenomena such as timing
noise and the recoveries form large glitches. Here we present a new method to
overcome the latter and report on braking index measurements for the Vela-like
pulsars PSR B1800-21 and PSR B1823-13, an updated measurement for Vela and new
estimates for four more glitching pulsars observed at Jodrell Bank Observatory.
The values of braking indices describe the long-term evolution of the pulsars
across the P-P' diagram. Despite some measurements being affected by
considerable uncertainties, there is evidence for a common trend involving low
braking indices (n<=2) among young glitching pulsars. Such values introduce a
new variant in the evolution of young pulsars and their relationship with other
populations in the P-P' diagram. Low braking indices also imply that these
pulsars could be a few times older than their characteristic ages. We consider
PSR B1757-24 and conclude that the pulsar could be old enough to be related to
the supernova remnant G5.4-1.2. Between glitches, the short-term evolution of
Vela-like pulsars is characterised by large inter-glitch braking indices n_ig >
10. We interpret both short and long term trends as signatures of the large
glitch activity, and speculate that they are driven by short-term post-glitch
re-coupling and a cumulative long-term decoupling of superfluid to the rotation
of the star.


title: Universal Guard Problems

abstract:
  We provide a spectrum of results for the Universal Guard Problem, in which
one is to obtain a small set of points ("guards") that are "universal" in their
ability to guard any of a set of possible polygonal domains in the plane. We
give upper and lower bounds on the number of universal guards that are always
sufficient to guard all polygons having a given set of n vertices, or to guard
all polygons in a given set of k polygons on an n-point vertex set. Our upper
bound proofs include algorithms to construct universal guard sets of the
respective cardinalities.


title:
Massive MIMO Pilot Retransmission Strategies for Robustification against
  Jamming

abstract:
  This letter proposes anti-jamming strategies based on pilot retransmission
for a single user uplink massive MIMO under jamming attack. A jammer is assumed
to attack the system both in the training and data transmission phases. We
first derive an achievable rate which enables us to analyze the effect of
jamming attacks on the system performance. Counter-attack strategies are then
proposed to mitigate this effect under two different scenarios: random and
deterministic jamming attacks. Numerical results illustrate our analysis and
benefit of the proposed schemes.


title: Axisymmetric pulse train solutions in narrow-gap spherical Couette flow

abstract:
  We numerically compute the flow induced in a spherical shell by fixing the
outer sphere and rotating the inner one. The aspect ratio
$\epsilon=(r_o-r_i)/r_i$ is set at 0.04 and 0.02, and in each case the Reynolds
number measuring the inner sphere's rotation rate is increased to $\sim10\%$
beyond the first bifurcation from the basic state flow. For $\epsilon =0.04$
the initial bifurcations are the same as in previous numerical work at
$\epsilon=0.154$, and result in steady one- and two-vortex states. Further
bifurcations yield travelling wave solutions similar to previous analytic
results valid in the $\epsilon\to0$ limit. For $\epsilon=0.02$ the steady
one-vortex state no longer exists, and the first bifurcation is directly to
these travelling wave solutions, consisting of pulse trains of Taylor vortices
travelling toward the equator from both hemispheres, and annihilating there in
distinct phase-slip events. We explore these time-dependent solutions in
detail, and find that they can be both equatorially symmetric and asymmetric,
as well as periodic or quasi-periodic in time.


title: Mild and viscosity solutions to semilinear parabolic path-dependent PDEs

abstract:
  We study and compare two concepts for weak solutions to semilinear parabolic
path-dependent partial differential equations (PPDEs). The first is that of
mild solutions as it appears, e.g., in the log-Laplace functionals of
historical superprocesses. The aim of this paper is to show that mild solutions
are also solutions in a viscosity sense. This result is motivated by the fact
that mild solutions can provide value functions and optimal strategies for
problems of stochastic optimal control. Since unique mild solutions exist under
weak conditions, we obtain as a corollary a general existence result for
viscosity solutions to semiilinear parabolic PPDEs.


title:
The Impact of Vehicular Traffic Demand on 5G Caching Architectures: a
  Data-Driven Study

abstract:
  The emergence of in-vehicle entertainment systems and self-driving vehicles,
and the latter's need for high-resolution, up-to-date maps, will bring a
further increase in the amount of data vehicles consume. Considering how
difficult WiFi offloading in vehicular environments is, the bulk of this
additional load will be served by cellular networks. Cellular networks, in
turn, will resort to caching at the network edge in order to reduce the strain
on their core network, an approach also known as mobile edge computing, or fog
computing. In this work, we exploit a real-world, large-scale trace coming from
the users of the We-Fi app in order to (i) understand how significant the
contribution of vehicular users is to the global traffic demand; (ii) compare
the performance of different caching architectures; and (iii) studying how such
a performance is influenced by recommendation systems and content locality. We
express the price of fog computing through a metric called price-of-fog,
accounting for the extra caches to deploy compared to a traditional,
centralized approach. We find that fog computing allows a very significant
reduction of the load on the core network, and the price thereof is low in all
cases and becomes negligible if content demand is location specific. We can
therefore conclude that vehicular networks make an excellent case for the
transition to mobile-edge caching: thanks to the peculiar features of vehicular
demand, we can obtain all the benefits of fog computing, including a reduction
of the load on the core network, reducing the disadvantages to a minimum.


title: Scattering for the 3D Gross-Pitaevskii equation

abstract:
  We study the Cauchy problem for the 3D Gross-Pitaevskii equation. The global
well-posedness in the natural energy space was proved by G\'erard
\cite{Gerard}. In this paper we prove scattering for small data in the same
space with some additional angular regularity, and in particular in the radial
case we obtain small energy scattering.


title:
Training and Evaluating Multimodal Word Embeddings with Large-scale Web
  Annotated Images

abstract:
  In this paper, we focus on training and evaluating effective word embeddings
with both text and visual information. More specifically, we introduce a
large-scale dataset with 300 million sentences describing over 40 million
images crawled and downloaded from publicly available Pins (i.e. an image with
sentence descriptions uploaded by users) on Pinterest. This dataset is more
than 200 times larger than MS COCO, the standard large-scale image dataset with
sentence descriptions. In addition, we construct an evaluation dataset to
directly assess the effectiveness of word embeddings in terms of finding
semantically similar or related words and phrases. The word/phrase pairs in
this evaluation dataset are collected from the click data with millions of
users in an image search system, thus contain rich semantic relationships.
Based on these datasets, we propose and compare several Recurrent Neural
Networks (RNNs) based multimodal (text and image) models. Experiments show that
our model benefits from incorporating the visual information into the word
embeddings, and a weight sharing strategy is crucial for learning such
multimodal embeddings. The project page is:
http://www.stat.ucla.edu/~junhua.mao/multimodal_embedding.html


title:
Incremental analysis of nonlinear systems with efficient methods for
  piecewise-affine systems

abstract:
  This paper is concerned with incremental stability properties of nonlinear
systems. We propose conditions to compute an upper bound on the incremental
L2-gain and to assess incremental asymptotic stability of piecewise-affine
(PWA) systems. The conditions are derived from dissipativity analysis, and are
based on the construction of piecewise-quadratic functions via linear matrix
inequalities (LMI) that can be efficiently solved numerically. The developments
are shown to be less conservative than previous results, and are illustrated
with numerical examples. In the last part of this paper, we study the
connection between incremental L2-gain stability and incremental asymptotic
stability. It is shown that, with appropriate observability and reachability
assumptions on the input-output operator, incremental L2-gain implies
incremental asymptotic stability. Finally, it is shown that the converse
implication follows provided some regularity conditions on the state space
representation are met.


title:
Full-Resolution Residual Networks for Semantic Segmentation in Street
  Scenes

abstract:
  Semantic image segmentation is an essential component of modern autonomous
driving systems, as an accurate understanding of the surrounding scene is
crucial to navigation and action planning. Current state-of-the-art approaches
in semantic image segmentation rely on pre-trained networks that were initially
developed for classifying images as a whole. While these networks exhibit
outstanding recognition performance (i.e., what is visible?), they lack
localization accuracy (i.e., where precisely is something located?). Therefore,
additional processing steps have to be performed in order to obtain
pixel-accurate segmentation masks at the full image resolution. To alleviate
this problem we propose a novel ResNet-like architecture that exhibits strong
localization and recognition performance. We combine multi-scale context with
pixel-level accuracy by using two processing streams within our network: One
stream carries information at the full image resolution, enabling precise
adherence to segment boundaries. The other stream undergoes a sequence of
pooling operations to obtain robust features for recognition. The two streams
are coupled at the full image resolution using residuals. Without additional
processing steps and without pre-training, our approach achieves an
intersection-over-union score of 71.8% on the Cityscapes dataset.


title: Multilevel higher order Quasi-Monte Carlo Bayesian Estimation

abstract:
  We propose and analyze deterministic multilevel approximations for Bayesian
inversion of operator equations with uncertain distributed parameters, subject
to additive Gaussian measurement data. The algorithms use a multilevel (ML)
approach based on deterministic, higher order quasi-Monte Carlo (HoQMC)
quadrature for approximating the high-dimensional expectations, which arise in
the Bayesian estimators, and a Petrov-Galerkin (PG) method for approximating
the solution to the underlying partial differential equation (PDE). This
extends the previous single-level approach from [J. Dick, R. N. Gantner, Q. T.
Le Gia and Ch. Schwab, Higher order Quasi-Monte Carlo integration for Bayesian
Estimation. Report 2016-13, Seminar for Applied Mathematics, ETH Z\"urich (in
review)].
  We obtain sufficient conditions which allow us to achieve arbitrarily high,
algebraic convergence rates in terms of work, which are independent of the
dimension of the parameter space. The convergence rates are limited only by the
spatial regularity of the forward problem,the discretization order achieved by
the Petrov Galerkin discretization, and by the sparsity of the uncertainty
parametrization. We provide detailed numerical experiments for linear elliptic
problems in two space dimensions, with $s=1024$ parameters characterizing the
uncertain input, confirming the theory and showing that the ML HoQMC algorithms
outperform, in terms of error vs.~computational work, both multilevel Monte
Carlo (MLMC) methods and single-level (SL) HoQMC methods.


title: Multi-Loop Positivity of the Planar ${\cal N}=4$ SYM Six-Point Amplitude

abstract:
  We study the six-point NMHV ratio function in planar ${\cal N}=4$ SYM theory
in the context of positive geometry. The Amplituhedron construction of the
integrand for the amplitudes provides a kinematical region in which the
integrand was observed to be positive. It is natural to conjecture that this
property survives integration, i.e. that the final result for the ratio
function is also positive in this region. Establishing such a result would
imply that preserving positivity is a surprising property of the Minkowski
contour of integration and it might indicate some deeper underlying structure.
We find that the ratio function is positive everywhere we have tested it,
including analytic results for special kinematical regions at one and two
loops, as well as robust numerical evidence through five loops. There is also
evidence for not just positivity, but monotonicity in a "radial" direction. We
also investigate positivity of the MHV six-gluon amplitude. While the remainder
function ceases to be positive at four loops, the BDS-like normalized MHV
amplitude appears to be positive through five loops.


title: Detecting communities is hard, and counting them is even harder

abstract:
  We consider the algorithmic problem of community detection in networks. Given
an undirected friendship graph $G=\left(V,E\right)$, a subset $S\subseteq V$ is
an $\left(\alpha,\beta\right)$-community if:
  * Every member of the community is friends with an $\alpha$-fraction of the
community;
  * Every non-member is friends with at most a $\beta$-fraction of the
community.
  Arora et al [AGSS12] gave a quasi-polynomial time algorithm for enumerating
all the $\left(\alpha,\beta\right)$-communities for any constants
$\alpha>\beta$.
  Here, we prove that, assuming the Exponential Time Hypothesis (ETH),
quasi-polynomial time is in fact necessary - and even for a much weaker
approximation desideratum. Namely, distinguishing between:
  * $G$ contains an $\left(1,o\left(1\right)\right)$-community; and
  * $G$ does not contain an
$\left(\beta+o\left(1\right),\beta\right)$-community for any
$\beta\in\left[0,1\right]$.
  We also prove that counting the number of
$\left(1,o\left(1\right)\right)$-communities requires quasi-polynomial time
assuming the weaker #ETH.


title:
Incremental stability of Lur'e systems through piecewise-affine
  approximations

abstract:
  Lur'e-type nonlinear systems are virtually ubiquitous in applied control
theory, which explains the great interest they have attracted throughout the
years. The purpose of this paper is to propose conditions to assess incremental
asymptotic stability of Lur'e systems that are less conservative than those
obtained with the incremental circle criterion. The method is based on the
approximation of the nonlinearity by a piecewise-affine function. The Lur'e
system can then be rewritten as a so-called piecewise-affine Lur'e system, for
which sufficient conditions for asymptotic incremental stability are provided.
These conditions are expressed as linear matrix inequalities (LMIs) allowing
the construction of a continuous piecewise-quadratic incremental Lyapunov
function, which can be efficiently solved numerically. The results are
illustrated with numerical examples.


title: Edge-preserving maps of curve graphs

abstract:
  Suppose $S_{1}$ and $S_{2}$ are orientable surfaces of finite topological
type such that $S_{1}$ has genus at least $3$ and the complexity of $S_{1}$ is
an upper bound of the complexity of $S_{2}$. Let $\varphi : \mathcal{C}(S_{1})
\rightarrow \mathcal{C}(S_{2})$ be an edge-preserving map; then $S_{1}$ is
homeomorphic to $S_{2}$, and in fact $\varphi$ is induced by a homeomorphism.
To prove this, we use several simplicial properties of rigid expansions, which
we prove here.


title: Tracing dense and diffuse neutral hydrogen in the halo of the Milky Way

abstract:
  We have combined observations of Galactic high-velocity HI from two surveys:
a very sensitive survey from the Green Bank 140ft Telescope with limited sky
coverage, and the less sensitive but complete Galactic All Sky Survey from the
64m Parkes Radio Telescope. The two surveys preferentially detect different
forms of neutral gas due to their sensitivity. We adopt a machine learning
approach to divide our data into two populations that separate across a range
in column density: 1) a narrow line-width population typical of the majority of
bright high velocity cloud components, and 2) a fainter, broad line-width
population that aligns well with that of the population found in the Green Bank
survey. We refer to these populations as dense and diffuse gas respectively,
and find that diffuse gas is typically located at the edges and in the tails of
high velocity clouds, surrounding dense components in the core. A fit to the
average spectrum of each type of gas in the Galactic All Sky Survey data
reveals the dense population to have a typical line width of ~20 km/s and
brightness temperature of ~0.3 K, while the diffuse population has a typical
line width of ~30 km/s and a brightness temperature of ~0.2 K. Our results
confirm that most surveys of high velocity gas in the Milky Way halo are
missing the majority of the ubiquitous diffuse gas, and that this gas is likely
to contribute at least as much mass as the dense gas.


title:
The 2015-2017 policy changes to the means-tests of Australian Age
  Pension: implication to decisions in retirement

abstract:
  The Australian Government uses the means-test as a way of managing the
pension budget. Changes in Age Pension policy impose difficulties in retirement
modelling due to policy risk, but any major changes tend to be `grandfathered'
meaning that current retirees are exempt from the new changes. In 2015, two
important changes were made in regards to allocated pension accounts -- the
income means-test is now based on deemed income rather than account
withdrawals, and the income-test deduction no longer applies. We examine the
implications of the new changes in regards to optimal decisions for
consumption, investment, and housing. We account for regulatory minimum
withdrawal rules that are imposed by regulations on allocated pension accounts,
as well as the 2017 asset-test rebalancing. The new policy changes are modelled
in a utility maximizing lifecycle model and solved as an optimal stochastic
control problem. We find that the new rules decrease the benefits from planning
the consumption in relation to the means-test, while the housing allocation
increases slightly in order to receive additional Age Pension. The difference
in optimal drawdown between the old and new policy are only noticeable early in
retirement until regulatory minimum withdrawal rates are enforced. However, the
amount of extra Age Pension received for many households is now significantly
different due to the new deeming income rules, which benefit slightly wealthier
households who previously would receive no Age Pension due to the income-test
and minimum withdrawals.


title:
An Overview on Data Representation Learning: From Traditional Feature
  Learning to Recent Deep Learning

abstract:
  Since about 100 years ago, to learn the intrinsic structure of data, many
representation learning approaches have been proposed, including both linear
ones and nonlinear ones, supervised ones and unsupervised ones. Particularly,
deep architectures are widely applied for representation learning in recent
years, and have delivered top results in many tasks, such as image
classification, object detection and speech recognition. In this paper, we
review the development of data representation learning methods. Specifically,
we investigate both traditional feature learning algorithms and
state-of-the-art deep learning models. The history of data representation
learning is introduced, while available resources (e.g. online course, tutorial
and book information) and toolboxes are provided. Finally, we conclude this
paper with remarks and some interesting research directions on data
representation learning.


title: Deriving phosphorus atomic chain from few-layer black phosphorus

abstract:
  Phosphorus atomic chains, the utmost-narrow nanostructures of black
phosphorus (BP), are highly relevant to the in-depth development of BP into
one-dimensional (1D) regime. In this contribution, we report a top-down route
to prepare atomic chains of BP via electron beam sculpting inside a
transmission electron microscope (TEM). The growth and dynamics (i.e. rupture
and edge migration) of 1D phosphorus chains are experimentally captured for the
first time. Furthermore, the dynamic behaviors and associated energetics of the
as-formed phosphorus chains are further corroborated by density functional
theory (DFT) calculations. The 1D counterpart of BP will serve as a novel
platform and inspire further exploration of the versatile properties of BP.


title:
The fractal dimensions of Laplacian growth: an analytical approach based
  on a universal dimensionality function

abstract:
  Laplacian growth, associated to the diffusion-limited aggregation (DLA) model
or the more general dielectric-breakdown model (DBM), is a fundamental
out-of-equilibrium process that generates structures with characteristic
fractal/non-fractal morphologies. However, despite of diverse numerical and
theoretical attempts, a data-consistent description of the fractal dimensions
of the mass-distributions of these structures has been missing. Here, an
analytical description to the fractal dimensions of the DBM and DLA is provided
by means of a recently introduced general dimensionality equation for the
scaling of clusters undergoing a continuous morphological transition.
Particularly, this equation relies on an effective information-function
dependent on the Euclidean dimension of the embedding-space and the control
parameter of the system. Numerical and theoretical approaches are used in order
to determine this information-function for both DLA and DBM. In the latter, a
connection to the R\'enyi entropies and generalized dimensions of the cluster
is made, showing that DLA could be considered as the point of maximum
information-entropy production along the DBM transition. These findings are in
good agreement with previous theoretical and numerical results (two- and
three-dimensional DBM, and high-dimensional DLA). Notably, the DBM dimensions
can be conformed to a universal description independently of the initial
cluster-configuration and the embedding-space.


title:
Exploring the helium core of the delta Scuti star CoRoT 102749568 with
  asteroseismology

abstract:
  Based on regularities in rotational splittings, we seek possible multiplets
for the observed frequencies of CoRoT 102749568. Twenty-one sets of multiplets
are identified, including four sets of multiplets with $l=1$, nine sets of
multiplets with $l=2$, and eight sets of multiplets with $l=3$. In particular,
there are three complete triplets ($f_{10}$, $f_{12}$, $f_{14}$), ($f_{31}$,
$f_{34}$, $f_{35}$), and ($f_{41}$, $f_{43}$, $f_{44}$). The rotational period
of CoRoT 102749568 is estimated to be $1.34^{+0.04}_{-0.05}$ days. When doing
model fittings, three $l=1$ modes ($f_{12}$, $f_{34}$, and $f_{43}$) and the
radial first overtone $f_{13}$ are used. Our results shows that the three
nonradial modes ($f_{12}$, $f_{34}$, and $f_{43}$) are mixed modes, which
mainly provide constraints on the helium core. The radial first overtone
$f_{13}$ mainly provides constraint on the stellar envelope. Hence the size of
the helium core of CoRoT 102749568 is determined to be $M_{\rm He}$ = 0.148
$\pm$ 0.003 $M_{\odot}$ and $R_{\rm He}$ = 0.0581 $\pm$ 0.0007 $R_{\odot}$. The
fundamental parameters of CoRoT 102749568 are determined to be $M$ = 1.54 $\pm$
0.03 $M_{\odot}$, $Z=$ 0.006, $f_{\rm ov}$ = 0.004 $\pm$ 0.002, $\log g$ =
3.696 $\pm$ 0.003, $T_{\rm eff}$ = 6886 $\pm$ 70 K, $R$ = 2.916 $\pm$ 0.039
$R_{\odot}$, and $L$ = 17.12 $\pm$ 1.13 $L_{\odot}$.


title: Non-stationary Navier-Stokes Equations with Mixed Boundary Conditions

abstract:
  In this paper we are concerned with the initial boundary value problem of the
2, 3-D Navier-Stokes equations with mixed boundary conditions including
conditions for velocity, static pressure, stress, rotation and Navier slip
condition together. Under a compatibility condition at the initial instance it
is proved that for the small data there exists a unique solution on the given
interval of time. Also, it is proved that if a solution is given, then there
exists a unique solution for small perturbed data satisfying the compatibility
condition. Our smoothness condition for initial functions in the compatibility
condition is weaker than one in such a previous result.


title:
The steady Navier-Stokes and Stokes systems with mixed boundary
  conditions including one-sided leaks and pressure

abstract:
  In this paper we are concerned with the steady Navier-Stokes and Stokes
problems with mixed boundary conditions involving Tresca slip, leak condition,
one-sided leak conditions, velocity, pressure, rotation, stress and normal
derivative of velocity together. Relying on the relations among strain,
rotation, normal derivative of velocity and shape of boundary surface, we have
variational formulations for the problems, which consist of five formulae with
five unknowns. We get the variational inequalities equivalent to the formulated
variational problems, which have one unknown. Then, we study the corresponding
variational inequalities and relying the results for variational inequalities,
we get existence, uniqueness and estimates of solutions to the Navier-Stokes
and Stokes problems with the boundary conditions. Our estimates for solutions
do not depend on the thresholds for slip and leaks.


title: "WM"-Shaped Growth of GaN on Patterned Sapphire Substrates

abstract:
  In metal organic vapor phase epitaxy of GaN, the growth mode is sensitive to
reactor temperature. In this study, V-pit-shaped GaN has been grown on normal
c-plane cone-patterned sapphire substrate by decreasing the growth temperature
of high-temperature-GaN to around 950 oC, which leads to the 3-dimensional
growth of GaN. The so-called "WM" well describes the shape that the bottom of
GaN V-pit is just right over the top of sapphire cone, and the regular
arrangement of V-pits follows the patterns of sapphire substrate strictly. Two
types of semipolar facets (1101) and (1122) expose on sidewalls of V-pits.
Furthermore, by raising the growth temperature to 1000 oC, the growth mode of
GaN can be transferred to 2-demonsional growth. Accordingly, the size of V-pits
becomes smaller and the area of c-plane GaN becomes larger, while the total
thickness of GaN keeps almost unchanged during this process. As long as the
2-demonsional growth lasts, the V-pits will disappear and only flat c-plane GaN
remains. This means the area ratio of c-plane and semipolar plane GaN can be
controlled by the duration time of 2-demonsional growth.


title:
A gradient discretisation method to analyse numerical schemes for
  non-linear variational inequalities, application to the seepage problem

abstract:
  Using the gradient discretisation method (GDM), we provide a complete and
unified numerical analysis for non-linear variational inequalities (VIs) based
on Leray--Lions operators and subject to non-homogeneous Dirichlet and
Signorini boundary conditions. This analysis is proved to be easily extended to
the obstacle and Bulkley models, which can be formulated as non-linear VIs. It
also enables us to establish convergence results for many conforming and
nonconforming numerical schemes included in the GDM, and not previously studied
for these models. Our theoretical results are applied to the hybrid mimetic
mixed method (HMM), a family of schemes that fit into the GDM. Numerical
results are provided for HMM on the seepage model, and demonstrate that, even
on distorted meshes, this method provides accurate results.


title: Sperner's colorings and optimal partitioning of the simplex

abstract:
  We discuss coloring and partitioning questions related to Sperner's Lemma,
originally motivated by an application in hardness of approximation.
Informally, we call a partitioning of the $(k-1)$-dimensional simplex into $k$
parts, or a labeling of a lattice inside the simplex by $k$ colors,
"Sperner-admissible" if color $i$ avoids the face opposite to vertex $i$. The
questions we study are of the following flavor: What is the Sperner-admissible
labeling/partitioning that makes the total area of the boundary between
different colors/parts as small as possible?
  First, for a natural arrangement of "cells" in the simplex, we prove an
optimal lower bound on the number of cells that must be non-monochromatic in
any Sperner-admissible labeling. This lower bound is matched by a simple
labeling where each vertex receives the minimum admissible color.
  Second, we show for this arrangement that in contrast to Sperner's Lemma,
there is a Sperner-admissible labeling such that every cell contains at most
$4$ colors.
  Finally, we prove a geometric variant of the first result: For any
Sperner-admissible partition of the regular simplex, the total surface area of
the boundary shared by at least two different parts is minimized by the Voronoi
partition $(A^*_1,\ldots,A^*_k)$ where $A^*_i$ contains all the points whose
closest vertex is $i$. We also discuss possible extensions of this result to
general polytopes and some open questions.


title:
Resolutions with conical slices and descent for the Brauer group classes
  of certain central reductions of differential operators in characteristic $p$

abstract:
  For a smooth variety $X$ over an algebraically closed field of characteristic
$p$, to a differential 1-form $\alpha$ on the Frobenius twist $X^{(1)}$ one can
associate an Azumaya algebra $\mathcal D_{X,\alpha}$, defined as a certain
central reduction of the algebra $\mathcal D_X$ of "crystalline differential
operators" on $X$. For a resolution of singularities $\pi:X\to Y$ of an affine
variety $Y$, we study for which $\alpha$ does the class $[\mathcal
D_{X,\alpha}]$ in the Brauer group $\mathrm{Br}(X^{(1)})$ descend to $Y^{(1)}$.
In the case when $X$ is symplectic, this question is related to Fedosov
quantizations in characteristic $p$ and the construction of non-commutative
resolutions of $Y$. We prove that the classes $[\mathcal D_{X,\alpha}]$ descend
\'etale locally for all $\alpha$ if $\mathcal O_Y\simeq \pi_* \mathcal O_X$ and
$R^{1,2}\pi_*\mathcal O_X =0$. We also define a certain class of resolutions
which we call resolutions with conical slices, and prove that for a general
reduction of a resolution with conical slices in characteristic $0$ to an
algebraically closed field of characteristic $p$ classes $[\mathcal
D_{X,\alpha}]$ descend to $Y^{(1)}$ globally for all $\alpha$. Finally we give
some examples, in particular we show that Slodowy slices, Nakajima quiver
varieties and hypertoric varieties are resolutions with conical slices.


title: Sparticle spectroscopy of the minimal SO(10) model

abstract:
  The supersymmetric (SUSY) minimal SO(10) model is a well-motivated grand
unified theory, where the Standard Model (SM) fermions have Yukawa couplings
with only one ${\bf 10}$-plet and one $\overline{\bf 126}$-plet Higgs fields
and it is highly non-trivial if the realistic quark and lepton mass matrices
can be reproduced in this context. It has been known that the best fit for all
the SM fermion mass matrices is achieved by a vacuum expectation value of the
$\overline{\bf 126}$-plet Higgs field being at the intermediate scale of around
${\cal O}(10^{13})$ GeV. Under the presence of the SO(10) symmetry breaking at
the intermediate scale, the successful SM gauge coupling unification is at risk
and likely to be spoiled. Recently, it has been shown that the low-energy
fermion mass matrices, except for the down-quark mass predicted to be too low,
are very well-fitted without the intermediate scale. In order to resolve the
too-low down quark mass while keeping the other fittings intact, we consider
SUSY threshold corrections to reproduce the right down quark mass. It turns out
that this requires flavor-dependent soft parameters. Motivated by this fact, we
calculate particle mass spectra at low energies with flavor-dependent sfermion
masses at the grand unification scale. We present a benchmark particle mass
spectrum which satisfies a variety of phenomenological constraints, in
particular, the observed SM-like Higgs boson mass of around 125 GeV and the
relic abundance of the neutralino dark matter as well as the experimental
result of the muon anomalous magnetic moment. In the resultant mass spectrum,
sleptons in the first and second generations, bino and winos are all light, and
this scenario can be tested at the LHC Run-2 in the near future.


title:
Wide-range-tunable Dirac-cone band structure in a chiral-time-symmetric
  non-Hermitian system

abstract:
  We establish a connection between an arbitrary Hermitian tight-binding model
with chiral (C) symmetry and its non-Hermitian counterpart with chiral-time (CT
) symmetry.We show that such a non-Hermitian Hamiltonian is pseudo-Hermitian.
The eigenvalues and eigenvectors of the non-Hermitian Hamiltonian can be easily
obtained from those of its parent Hermitian Hamiltonian. It provides a way to
generate a class of non-Hermitian models with a tunable full real band
structure by means of additional imaginary potentials.We also present an
illustrative example that could achieve a cone structure from the energy band
of a two-layer Hermitian square lattice model.


title:
Global optimization framework for real-time route guidance via variable
  message sign

abstract:
  Variable message sign (VMS) is an effective traffic management tool for
congestion mitigation. The VMS is primarily used as a means of providing
factual travel information or genuine route guidance to travelers. However,
this may be rendered sub-optimal on a network level by potential network
paradoxes and lack of consideration for its cascading effect on the rest of the
network. This paper focuses on the design of optimal display strategy of VMS in
response to real-time traffic information and its coordination with other
intelligent transportation systems such as signal control, in order to explore
the full potential of real-time route guidance in combating congestion. We
invoke the linear decision rule framework to design the optimal on-line VMS
strategy, and test its effectiveness in conjunction with on-line signal
control. A simulation case study is conducted on a real-world test network in
China, which shows the advantage of the proposed adaptive VMS display strategy
over genuine route guidance, as well as its synergies with on-line signal
control for congestion mitigation.


title:
Study of lattice QCD at finite baryon density using the canonical
  approach

abstract:
  At finite baryon density lattice QCD first-principle calculations can not be
performed due to the sign problem. In order to circumvent this problem, we use
the canonical approach, which provides reliable analytical continuation from
the imaginary chemical potential region to the real chemical potential region.
We briefly present the canonical partition function method, describe our
formulation, and show the results, obtained for two temperatures: $T/T_c =
0.93$ and $T/T_c = 0.99$ in lattice QCD with two flavors of improved Wilson
fermions.


title: Renormalized Volumes with Boundary

abstract:
  We develop a general regulated volume expansion for the volume of a manifold
with boundary whose measure is suitably singular along a separating
hypersurface. The expansion is shown to have a regulator independent anomaly
term and a renormalized volume term given by the primitive of an associated
anomaly operator. These results apply to a wide range of structures. We detail
applications in the setting of measures derived from a conformally singular
metric. In particular, we show that the anomaly generates invariant
(Q-curvature, transgression)-type pairs for hypersurfaces with boundary. For
the special case of anomalies coming from the volume enclosed by a minimal
hypersurface ending on the boundary of a Poincare--Einstein structure, this
result recovers Branson's Q-curvature and corresponding transgression. When the
singular metric solves a boundary version of the constant scalar curvature
Yamabe problem, the anomaly gives generalized Willmore energy functionals for
hypersurfaces with boundary. Our approach yields computational algorithms for
all the above quantities, and we give explicit results for surfaces embedded in
3-manifolds.


title:
Unified picture of non-geometric fluxes and T-duality in double field
  theory via graded symplectic manifolds

abstract:
  We give a systematic derivation of the local expressions of the NS H-flux,
geometric F- as well as non-geometric Q- and R-fluxes in terms of bivector
beta- and two-form B-potentials including vielbeins. They are obtained using a
supergeometric method on QP-manifolds by twist of the standard Courant
algebroid on the generalized tangent space without flux. Bianchi identities of
the fluxes are easily deduced. We extend the discussion to the case of the
double space and present a formulation of T-duality in terms of canonical
transformations between graded symplectic manifolds. Finally, the construction
is compared to the formerly introduced Poisson Courant algebroid, a Courant
algebroid on a Poisson manifold, as a model for R-flux.


title: Homological dimension and dimensional full-valuedness

abstract:
  There are different definitions of homological dimension of metric compacta
involving either \v{C}ech homology or exact (Steenrod) homology. In this paper
we investigate the relation between these homological dimensions with respect
to different groups. It is shown that all homological dimensions of a metric
compactum X with respect to any field coincide provided X is homologically
locally connected with respect to the singular homology up to dimension n=dim
X. We also prove that any two-dimensional lc^2 metric compactum X satisfies the
equality dim(X times Y)=dim X+dim Y for any metric compactum Y. This improves
the well known result of Kodama that every two-dimensional ANR is dimensionally
full-valued. Actually, the condition X to be lc^2 can be weaken to the
existence at every point x a neighborhood V of x such that the inclusion
homomorphism H_k(V;S^1)\to H_k(X;S^1)$ is trivial for all k=1,2.


title:
Explosive percolation on scale-free multifractal weighted planar
  stochastic lattice

abstract:
  In this article, we investigate explosive bond percolation (EBP) with product
rule, formally known as Achlioptas process, on a scale-free multifractal
weighted planar stochastic lattice (WPSL). One of the key features of the EBP
transition is the delay, compared to corresponding random bond percolation
(RBP), in the onset of spanning cluster. However, when it happens, it happens
so dramatically that initially it was believed, albeit ultimately proved wrong,
that explosive percolation (EP) exhibits first order transition. In the case of
EP, much efforts were devoted to resolving the issue of its order of transition
and almost no effort being devoted to find critical point, critical exponents
etc., to classify it into universality classes. This is in sharp contrast to
the classical random percolation. We do not even know all the exponents of EP
for regular planar lattice or for Erd\"{o}s-Renyi network. We first find
numerically the critical point $p_c$ and then obtain all the critical exponents
$\beta, \gamma, \nu$ as well as the Fisher exponent $\tau$ and the fractal
dimension $d_f$ of the spanning cluster. We also compare our results for EBP
with those of the RBP and find that all the exponents of EBP obeys the same
scaling relations as do the RBP. Our findings suggests that EBP is no special
except the fact that the exponent $\beta$ is unusually small compared to that
of RBP.


title:
The 26 December 2001 Solar Eruptive Event Responsible for GLE63. II.
  Multi-Loop Structure of Microwave Sources in a Major Long-Duration flare

abstract:
  Analysis of the observations of the SOL2001-12-26 event related to
ground-level-event GLE63, including microwave spectra and images from NoRH at
17 and 34 GHz, SSRT at 5.7 GHz, and TRACE in 1600 \AA\ has led to the following
results. A flare ribbon overlapped with the sunspot umbra, which is typical of
large particle events. Atypical were: i) long duration of the flare of more
than one hour; ii) moderate intensity of a microwave burst, about $10^4$ sfu;
iii) low peak frequency of the gyrosynchrotron spectrum, around 6 GHz; and its
insensitivity to the flux increase by more than one order of magnitude. This
was accompanied by a nearly constant ratio of the flux emitted by the volume in
the high-frequency part of the spectrum to its elevated low-frequency part
determined by the area of the source. With the self-similarity of the spectrum,
a similarity was observed between the moving microwave sources and the
brightest parts of the flare ribbons in 1600 \AA. Comparison of the 17 GHz and
1600 \AA\ images has confirmed that the microwave sources were associated with
multiple flare loops, whose footpoints appeared in ultraviolet as intermittent
bright kernels. To understand the properties of the event, we simulated its
microwave emission using a system of several homogeneous gyrosynchrotron
sources above the ribbons. The scatter between the spectra and sizes of the
individual sources is determined by the inhomogeneity of the magnetic field
within the ribbons. The microwave flux is mainly governed by the magnetic flux
passing through the ribbons and the sources. An apparent simplicity of
microwave structures is caused by a poorer spatial resolution and dynamic range
of the microwave imaging. The results indicate that microwave manifestations of
accelerated electrons correspond to the structures observed in thermal
emissions, as well-known models predict.


title: Learning an Invariant Hilbert Space for Domain Adaptation

abstract:
  This paper introduces a learning scheme to construct a Hilbert space (i.e., a
vector space along its inner product) to address both unsupervised and
semi-supervised domain adaptation problems. This is achieved by learning
projections from each domain to a latent space along the Mahalanobis metric of
the latent space to simultaneously minimizing a notion of domain variance while
maximizing a measure of discriminatory power. In particular, we make use of the
Riemannian optimization techniques to match statistical properties (e.g., first
and second order statistics) between samples projected into the latent space
from different domains. Upon availability of class labels, we further deem
samples sharing the same label to form more compact clusters while pulling away
samples coming from different classes.We extensively evaluate and contrast our
proposal against state-of-the-art methods for the task of visual domain
adaptation using both handcrafted and deep-net features. Our experiments show
that even with a simple nearest neighbor classifier, the proposed method can
outperform several state-of-the-art methods benefitting from more involved
classification schemes.


title:
Fine-grained Mining of Illicit Drug Use Patterns Using Social Multimedia
  Data from Instagram

abstract:
  According to NSDUH (National Survey on Drug Use and Health), 20 million
Americans consumed drugs in the past few 30 days. Combating illicit drug use is
of great interest to public health and law enforcement agencies. Despite of the
importance, most of the existing studies on drug uses rely on surveys. Surveys
on sensitive topics such as drug use may not be answered truthfully by the
people taking them. Selecting a representative sample to survey is another
major challenge. In this paper, we explore the possibility of using big
multimedia data, including both images and text, from social media in order to
discover drug use patterns at fine granularity with respect to demographics.
Instagram posts are searched and collected by drug related terms by analyzing
the hashtags supplied with each post. A large and dynamic dictionary of
frequent drug related slangs is used to find these posts. User demographics are
extracted using robust face image analysis algorithms. These posts are then
mined to find common trends with regard to the time and location they are
posted, and further in terms of age and gender of the drug users. Furthermore,
by studying the accounts followed by the users of drug related posts, we
extract common interests shared by drug users.


title: Equivalence Notions for Discrete-Time Stochastic Linear Control Systems

abstract:
  In this paper we propose definitions of equivalence via stochastic
bisimulation and of equivalence of stochastic external behavior for the class
of discrete-time stochastic linear control systems with possibly degenerate
normally distributed disturbances. The first notion is inspired by the notion
of probabilistic bisimulation for probabilistic chains while the second one by
the notion of equivalence of external behavior for (nonstochastic) behavioral
systems. Geometric necessary and sufficient conditions for checking these
notions are derived. Model reduction via Kalman-like decomposition is also
proposed. Connections with stochastic linear realization theory and stochastic
reachability are established.


title: An In Vitro Nematic Model for Proliferating Cell Cultures

abstract:
  Confluent populations of elongated cells give rise to ordered patterns seen
in nematic phase liquid crystals. We correlate cell elongation and
intercellular distance with intercellular alignment using an amorphous spin
glass model. We compare in vitro time-lapse imaging with Monte Carlo simulation
results by framing a novel hard ellipses model in terms of Boltzmann
statistics. Furthermore, we find a statistically distinct alignment energy at
quasi-steady state among fibroblasts, smooth muscle cells, and pluripotent cell
populations when cultured in vitro. These findings have important implications
in both non-invasive clinical screening of the stem cell differentiation
process and in relating shape parameters to coupling in active crystal systems
such as nematic cell monolayers.


title: A search for long-timescale, low-frequency radio transients

abstract:
  We present a search for transient and highly variable sources at low radio
frequencies (150-200 MHz) that explores long timescales of 1-3 years. We
conducted this search by comparing the TIFR GMRT Sky Survey Alternative Data
Release 1 (TGSS ADR1) and the GaLactic and Extragalactic All-sky Murchison
Widefield Array (GLEAM) survey catalogues. To account for the different
completeness thresholds in the individual surveys, we searched for compact
GLEAM sources above a flux density limit of 100 mJy that were not present in
the TGSS ADR1; and also for compact TGSS ADR1 sources above a flux density
limit of 200 mJy that had no counterpart in GLEAM. From a total sample of 234
333 GLEAM sources and 275 612 TGSS ADR1 sources in the overlap region between
the two surveys, there were 99658 GLEAM sources and 38 978 TGSS ADR sources
that passed our flux density cutoff and compactness criteria. Analysis of these
sources resulted in three candidate transient sources. Further analysis ruled
out two candidates as imaging artefacts. We analyse the third candidate and
show it is likely to be real, with a flux density of 182 +/- 26 mJy at 147.5
MHz. This gives a transient surface density of rho = (6.2 +/- 6) x 10-5 deg-2 .
We present initial follow-up observations and discuss possible causes for this
candidate. The small number of spurious sources from this search demonstrates
the high reliability of these two new low-frequency radio catalogues.


title:
Global smooth solutions of 3-D null-form wave equations in exterior
  domains with Neumann boundary conditions

abstract:
  The paper is devoted to investigating long time behavior of smooth small data
solutions to 3-D quasilinear wave equations outside of compact convex obstacles
with Neumann boundary conditions.


title: On boundary points at which the squeezing function tends to one

abstract:
  J. E. Fornaess has posed the question whether the boundary point of smoothly
bounded pseudoconvex domain is strictly pseudoconvex, if the asymptotic limit
of the squeezing function is 1. The purpose of this paper is to give an
affirmative answer when the domain is in C^2 with smooth boundary of finite
type in the sense of D'Angelo.


title:
A study of raining influence on the environmental radiation background
  spectra with HXMT/HE

abstract:
  Full functional and performance tests were performed many times before the
Hard X-ray Modulation Telescope (HXMT) launch. During one of the tests, the
count rate curves of the 18 High Energy Detectors (HED) have been found
increased consistently within an interval of time. A further study on the
correlation between the count rate and rainfall was carried out,and the
increased net spectrum was also analyzed. The analysis results indicate that
the short-lived 222Rn decay products (214Pb and 214Bi) in rainwater were
responsible for the transient changes of the background radiation spectra in
HEDs. The results show that the HXMT/HEDs have a good detection sensitivity on
X/gamma rays, and the detector calibration results are effective.


title: Kannada Spell Checker with Sandhi Splitter

abstract:
  Spelling errors are introduced in text either during typing, or when the user
does not know the correct phoneme or grapheme. If a language contains complex
words like sandhi where two or more morphemes join based on some rules, spell
checking becomes very tedious. In such situations, having a spell checker with
sandhi splitter which alerts the user by flagging the errors and providing
suggestions is very useful. A novel algorithm of sandhi splitting is proposed
in this paper. The sandhi splitter can split about 7000 most common sandhi
words in Kannada language used as test samples. The sandhi splitter was
integrated with a Kannada spell checker and a mechanism for generating
suggestions was added. A comprehensive, platform independent, standalone spell
checker with sandhi splitter application software was thus developed and tested
extensively for its efficiency and correctness. A comparative analysis of this
spell checker with sandhi splitter was made and results concluded that the
Kannada spell checker with sandhi splitter has an improved performance. It is
twice as fast, 200 times more space efficient, and it is 90% accurate in case
of complex nouns and 50% accurate for complex verbs. Such a spell checker with
sandhi splitter will be of foremost significance in machine translation
systems, voice processing, etc. This is the first sandhi splitter in Kannada
and the advantage of the novel algorithm is that, it can be extended to all
Indian languages.


title: Axion and Neutrino physics in a $U(1)$-enhanced supersymmetric model

abstract:
  Motivated by the flavored Peccei-Quinn symmetry for unifying the flavor
physics and string theory, we construct an explicit model by introducing a
$U(1)$ symmetry such that the $U(1)_X$-$[gravity]^2$ anomaly-free condition
together with the standard model flavor structure demands additional sterile
neutrinos as well as no axionic domain-wall problem. Such additional sterile
neutrinos play the role of a realization of baryogenesis via a new Affleck-Dine
leptogenesis. We provide grounds for that the $U(1)_X$ symmetry could be
interpreted as a fundamental symmetry of nature. The model will resolve rather
recent, but fast-growing issues in astro-particle physics, including leptonic
mixings and CP violation in neutrino oscillation, high-energy neutrinos, QCD
axion, and axion cooling of stars. The QCD axion decay constant, through its
connection to the astrophysical constraints of stellar evolution and the SM
fermion masses, is shown to be fixed at $F_A=1.30^{+0.66}_{-0.54}\times10^{9}$
GeV (consequently, its mass is $m_a=4.34^{+3.37}_{-1.49}$ meV and axion-photon
coupling is $|g_{a\gamma\gamma}|=1.30^{+1.01}_{-0.45}\times10^{-12}\,{\rm
GeV}^{-1}$). Interestingly enough, we show that neutrino oscillations at low
energies could be connected to astronomical-scale baseline neutrino
oscillations. The model predicts non-observational neutrinoless double beta
($0\nu\beta\beta$) decay rate as well as a remarkable pattern between leptonic
Dirac CP phase ($\delta_{CP}$) and atmospheric mixing angle ($\theta_{23}$);
{\it e.g.} $\delta_{CP}\simeq220^{\circ}-240^{\circ}$,
$120^{\circ}-140^{\circ}$ for $\theta_{23}=42.3^{\circ}$ for normal mass
ordering, and $\delta_{CP}\simeq283^{\circ},250^{\circ},100^{\circ},70^{\circ}$
for $\theta_{23}=49.5^{\circ}$ for inverted one.


title:
Casimir torque between two inhomogeneous semi-transparent concentric
  cylinders

abstract:
  Motivated by the problem of Casimir energy, we investigate the idea of using
inhomogeneity of surfaces instead of their corrugation, which leads to Casimir
interaction between two inhomogeneous semi-transparent concentric cylinders.
Using the multiple scattering method, we study the Casimir energy and torque
between the cylinders with different potentials subjected to Dirichlet boundary
conditions, both in weak and strong coupling regimes. We also extend our
formalism to the case of two inhomogeneous dielectrics in a weak coupling
regime.


title:
Bogoliubov Theory for a Superfluid Bose Gas Flowing in a Random
  Potential: Stability and Critical Velocity

abstract:
  We investigate the stability and critical velocity of a weakly interacting
Bose gas flowing in a random potential. By applying the Bogoliubov theory to a
disordered Bose system with a steady flow, the condensate density and the
superfluid density are determined as functions of the disorder strength, flow
velocity, and temperature. The critical velocity, at which the steady flow
becomes unstable, is calculated from the spectrum of hydrodynamic excitation.
We also show that in two dimensions the critical velocity strongly depends on
the system size.


title:
Accurate Prediction of Potential Energy Surface via Thermodynamically
  Equilibrium Structure

abstract:
  In order to predict the potential energy surface (PES) from measured
structure in equilibrium state, one should typically perform trial-and-error
statistical thermodynamic simulation with assumed multibody interactions. Very
recently, we derive map from a set of equilibrium structure in crystalline
solids to that of corresponding PES in explicit matrix form, where the PES can
be inversely determined from the measured structure. The practical problem to
construct the map appears when system size of measured structure is not
sufficiently large, which results in non-trivial treatment of asymmetry problem
in the map. The present study proposes alternative approach to avoiding
treatment of the asymmetry problem, demonstrating more accurate prediction of
the PES than the map constructed by explicitly treating the asymmetry.


title: Optical properties of anatase and rutile TiO2 studied by GGA+U

abstract:
  The optical properties of thermally annealed TiO2 samples depend on their
preparation process, and the TiO2 thin films usually exist in the form of
anatase or rutile or the mixture of the two phases. The electronic structures
and optical properties of anatase and rutile TiO2 are calculated by means of
First-principles generalized gradient approximation (GGA) +U approach. By
Introducing the Coulomb interactions on 3d orbitals of Ti atom (Ud) and 2p
orbitals of O atom (Up), we can reproduce the experimental values of the band
gap. The optical properties of anatase and rutile TiO2 are obtained by means of
GGA+U method, well agreeing with experimental results and other theoretical
data. Further we present the comparison of the electronic structure,
birefringence and anisotropy between the two phases of TiO2.


title:
Robust Sequential Path Planning Under Disturbances and Adversarial
  Intruder

abstract:
  Provably safe and scalable multi-vehicle path planning is an important and
urgent problem due to the expected increase of automation in civilian airspace
in the near future. Although this problem has been studied in the past, there
has not been a method that guarantees both goal satisfaction and safety for
vehicles with general nonlinear dynamics while taking into account disturbances
and potential adversarial agents, to the best of our knowledge. Hamilton-Jacobi
(HJ) reachability is the ideal tool for guaranteeing goal satisfaction and
safety under such scenarios, and has been successfully applied to many
small-scale problems. However, a direct application of HJ reachability in most
cases becomes intractable when there are more than two vehicles due to the
exponentially scaling computational complexity with respect to system
dimension. In this paper, we take advantage of the guarantees HJ reachability
provides, and eliminate the computation burden by assigning a strict priority
ordering to the vehicles under consideration. Under this sequential path
planning (SPP) scheme, vehicles reserve "space-time" portions in the airspace,
and the space-time portions guarantee dynamic feasibility, collision avoidance,
and optimality of the paths given the priority ordering. With a computation
complexity that scales quadratically when accounting for both disturbances and
an intruder, and linearly when accounting for only disturbances, SPP can
tractably solve the multi-vehicle path planning problem for vehicles with
general nonlinear dynamics in a practical setting. We demonstrate our theory in
representative simulations.


title:
Escape Routes, Weak Links, and Desynchronization in Fluctuation-driven
  Networks

abstract:
  Shifting our electricity generation from fossil fuel to renewable energy
sources introduces large fluctuations to the power system. Here, we demonstrate
how increased fluctuations, reduced damping and reduced intertia may undermine
the dynamical robustness of power grid networks. Focusing on fundamental noise
models, we derive analytic insights into which factors limit the dynamic
robustness and how fluctuations may induce a system escape from an operating
state. Moreover, we identify weak links in the grid that make it particularly
vulnerable to fluctuations. These results thereby not only contribute to a
theoretical understanding of how fluctuations act on distributed network
dynamics, they may also help designing future renewable energy systems to be
more robust.


title: Local Discriminant Hyperalignment for multi-subject fMRI data alignment

abstract:
  Multivariate Pattern (MVP) classification can map different cognitive states
to the brain tasks. One of the main challenges in MVP analysis is validating
the generated results across subjects. However, analyzing multi-subject fMRI
data requires accurate functional alignments between neuronal activities of
different subjects, which can rapidly increase the performance and robustness
of the final results. Hyperalignment (HA) is one of the most effective
functional alignment methods, which can be mathematically formulated by the
Canonical Correlation Analysis (CCA) methods. Since HA mostly uses the
unsupervised CCA techniques, its solution may not be optimized for MVP
analysis. By incorporating the idea of Local Discriminant Analysis (LDA) into
CCA, this paper proposes Local Discriminant Hyperalignment (LDHA) as a novel
supervised HA method, which can provide better functional alignment for MVP
analysis. Indeed, the locality is defined based on the stimuli categories in
the train-set, where the correlation between all stimuli in the same category
will be maximized and the correlation between distinct categories of stimuli
approaches to near zero. Experimental studies on multi-subject MVP analysis
confirm that the LDHA method achieves superior performance to other
state-of-the-art HA algorithms.


title: Determining Optimal Rates for Communication for Omniscience

abstract:
  This paper considers the communication for omniscience (CO) problem: A set of
users observe a discrete memoryless multiple source and want to recover the
entire multiple source via noise-free broadcast communications. We study the
problem of how to determine an optimal rate vector that attains omniscience
with the minimum sum-rate, the total number of communications. The results
cover both asymptotic and non-asymptotic models where the transmission rates
are real and integral, respectively. We propose a modified decomposition
algorithm (MDA) and a sum-rate increment algorithm (SIA) for the asymptotic and
non-asymptotic models, respectively, both of which determine the value of the
minimum sum-rate and a corresponding optimal rate vector in polynomial time.
For the coordinate saturation capacity (CoordSatCap) algorithm, a nesting
algorithm in MDA and SIA, we propose to implement it by a fusion method and
show by experimental results that this fusion method contributes to a reduction
in computation complexity. Finally, we show that the separable convex
minimization problem over the optimal rate vector set in the asymptotic model
can be decomposed by the fundamental partition, the optimal partition of the
user set that determines the minimum sum-rate, so that the problem can be
solved more efficiently.


title:
A physically inspired model of Dip d792 and d1519 of the Kepler light
  curve seen at KIC8462852

abstract:
  The star KIC 8462852 shows a very unusual and hard to comprehend light curve.
The dip d7922 absorbs 16% of the starlight. The light curve is unusually smooth
but the very steep edges make it hard to find a simple natural explanation by
covering due to comets or other well-known planetary objects. We describe a
mathematical approximation to the light curve, which is motivated by a
physically meaningful event of a large stellar beam which generates an orbiting
cloud. The data might fit to the science fiction idea of star lifting, a mining
technology that could extract star matter. We extend the model to d1519 and
d1568 using multiple beams and get an encouraging result that fits essential
parts of the dips but misses other parts of the measured flux. We recommend
further exploration of this concept with refined models.


title:
The second cohomology groups of nilpotent orbits in classical Lie
  algebras

abstract:
  The second de Rham cohomology groups of nilpotent orbits in non-compact real
forms of classical complex simple Lie algebras are explicitly computed.
Furthermore, the first de Rham cohomology groups of nilpotent orbits in
non-compact classical simple Lie algebras are computed; they are proven to be
zero for nilpotent orbits in all the complex simple Lie algebras. A key
component in these computations is a description of the second and first
cohomology groups of homogeneous spaces of general connected Lie groups which
is obtained here. This description, which generalizes a previous theorem of the
first two authors, may be of independent interest.


title: Braid zeta function and some formulae for the torus type

abstract:
  There is a well-known zeta function of the $\mathbb{Z}$-dynamical system
generated by an element of the symmetric group. By considering this zeta
function as a model, we can construct a new zeta function of an element of the
braid group.In this paper,we show that the Alexander polynomial which is the
most classical polynomial invariant of knots can be expressed in terms of this
braid zeta function.Furthermore we define the function $Z_q$ associated with
some braids. We show that this function can be expressed by some braid zeta
function for the case of special braids whose closures are isotopic to certain
torus knots.


title: Pre-flare coronal dimmings

abstract:
  In this paper, we focus on the pre-flare coronal dimmings. We report our
multiwavelength observations of the GOES X1.6 solar flare and the accompanying
halo CME produced by the eruption of a sigmoidal magnetic flux rope (MFR) in
NOAA active region (AR) 12158 on 2014 September 10. The eruption was observed
by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamic Observatory
(SDO). The photospheric line-of-sight magnetograms were observed by the
Helioseismic and Magnetic Imager (HMI) aboard SDO. The soft X-ray (SXR) fluxes
were recorded by the GOES spacecraft. The halo CME was observed by the white
light coronagraphs of the Large Angle Spectroscopic Coronagraph (LASCO) aboard
SOHO.} {About 96 minutes before the onset of flare/CME, narrow pre-flare
coronal dimmings appeared at the two ends of the twisted MFR. They extended
very slowly with their intensities decreasing with time, while their apparent
widths (8$-$9 Mm) nearly kept constant. During the impulsive and decay phases
of flare, typical fanlike twin dimmings appeared and expanded with much larger
extent and lower intensities than the pre-flare dimmings. The percentage of 171
{\AA} intensity decrease reaches 40\%. The pre-flare dimmings are most striking
in 171, 193, and 211 {\AA} with formation temperatures of 0.6$-$2.5 MK. The
northern part of the pre-flare dimmings could also be recognized in 131 and 335
{\AA}.} To our knowledge, this is the first detailed study of pre-flare coronal
dimmings, which can be explained by the density depletion as a result of the
gradual expansion of the coronal loop system surrounding the MFR during the
slow rise of the MFR.


title: A Unified Convex Surrogate for the Schatten-$p$ Norm

abstract:
  The Schatten-$p$ norm ($0<p<1$) has been widely used to replace the nuclear
norm for better approximating the rank function. However, existing methods are
either 1) not scalable for large scale problems due to relying on singular
value decomposition (SVD) in every iteration, or 2) specific to some $p$
values, e.g., $1/2$, and $2/3$. In this paper, we show that for any $p$, $p_1$,
and $p_2 >0$ satisfying $1/p=1/p_1+1/p_2$, there is an equivalence between the
Schatten-$p$ norm of one matrix and the Schatten-$p_1$ and the Schatten-$p_2$
norms of its two factor matrices. We further extend the equivalence to multiple
factor matrices and show that all the factor norms can be convex and smooth for
any $p>0$. In contrast, the original Schatten-$p$ norm for $0<p<1$ is
non-convex and non-smooth. As an example we conduct experiments on matrix
completion. To utilize the convexity of the factor matrix norms, we adopt the
accelerated proximal alternating linearized minimization algorithm and
establish its sequence convergence. Experiments on both synthetic and real
datasets exhibit its superior performance over the state-of-the-art methods.
Its speed is also highly competitive.


title: Bidirectional LSTM-CRF for Clinical Concept Extraction

abstract:
  Automated extraction of concepts from patient clinical records is an
essential facilitator of clinical research. For this reason, the 2010 i2b2/VA
Natural Language Processing Challenges for Clinical Records introduced a
concept extraction task aimed at identifying and classifying concepts into
predefined categories (i.e., treatments, tests and problems). State-of-the-art
concept extraction approaches heavily rely on handcrafted features and
domain-specific resources which are hard to collect and define. For this
reason, this paper proposes an alternative, streamlined approach: a recurrent
neural network (the bidirectional LSTM with CRF decoding) initialized with
general-purpose, off-the-shelf word embeddings. The experimental results
achieved on the 2010 i2b2/VA reference corpora using the proposed framework
outperform all recent methods and ranks closely to the best submission from the
original 2010 i2b2/VA challenge.


title:
Decision Support Systems in Fisheries and Aquaculture: A systematic
  review

abstract:
  Decision support systems help decision makers make better decisions in the
face of complex decision problems (e.g. investment or policy decisions).
Fisheries and Aquaculture is a domain where decision makers face such decisions
since they involve factors from many different scientific fields. No systematic
overview of literature describing decision support systems and their
application in fisheries and aquaculture has been conducted. This paper
summarizes scientific literature that describes decision support systems
applied to the domain of Fisheries and Aquaculture. We use an established
systematic mapping survey method to conduct our literature mapping. Our
research questions are: What decision support systems for fisheries and
aquaculture exists? What are the most investigated fishery and aquaculture
decision support systems topics and how have these changed over time? Do any
current DSS for fisheries provide real- time analytics? Do DSSes in Fisheries
and Aquaculture build their models using machine learning done on captured and
grounded data? The paper then detail how we employ the systematic mapping
method in answering these questions. This results in 27 papers being identified
as relevant and gives an exposition on the primary methods concluded in the
study for designing a decision support system. We provide an analysis of the
research done in the studies collected. We discovered that most literature does
not consider multiple aspects for multiple stakeholders in their work. In
addition we observed that little or no work has been done with real-time
analysis in these decision support systems.


title:
The effect of the thermal reduction on the kinetics of low temperature
  4He sorption and the structural characteristics of graphene oxide

abstract:
  The kinetics of the sorption and the subsequent desorption of 4He by the
starting graphite oxide (GtO) and the thermally reduced graphene oxide samples
(TRGO, Treduction = 200, 300, 500, 700 and 900 C) have been investigated in the
temperature interval 1.5 - 20 K. The effect of the annealing temperature on the
structural characteristics of the samples was examined by the X-ray diffraction
(XRD) technique. On lowering the temperature from 20 K to 11-12 K, the time of
4He sorption increased for all the samples, which is typically observed under
the condition of thermally activated diffusion. Below 5 K the characteristic
times of 4He sorption by the GtO and TRGO-200 samples were only weakly
dependent on temperature, suggesting the dominance of the tunnel mechanism. In
the same region (T<5 K) the characteristic times of the TRGOs reduced at higher
temperatures (300, 500, 700 and 900 C) were growing with lowering temperature,
presumably due to the defects generated in the carbon planes on removing the
oxygen functional groups (oFGs). The estimates of the activation energy (Ea) of
4He diffusion show that in the TRGO-200 sample the Ea value is 2.9 times lower
as compared to the parent GtO, which is accounted for by GtO exfoliation due to
evaporation of the water intercalated in the interlayer space of carbon. The
nonmonotonic dependences Ea vs T for the GtO samples treated above 200 C are
determined by a competition between two processes - the recovery of the
graphite carbon structure, which increases the activation energy, and the
generation of defects, which decreases the activation energy by opening
additional surface areas and ways for sorption. The dependence of the
activation energy on treatment temperature correlates well with the contents of
the crystalline phase in GtO varying with a rise of the annealing temperature.


title:
Spectral variability of the 3C 390.3 nucleus for more than twenty years.
  I. Variability of the broad and narrow emission-line fluxes

abstract:
  We summarize results of the analysis of the optical variability of the
continuum and emission-line fluxes in the 3C390.3 nucleus during 1992-2014. The
[OIII]5007 flux increases monotonically by $\approx$30 per cent in 2003-2014.
The narrow Balmer lines show similar monotonic increase, while the variability
patterns of the [OI]6300 narrow line are completely different from that of
[OIII]. The reverberation lags are found to be 88.6$\pm$8.4, 161$\pm$15, and
113$\pm$14d for the H$\beta$, H$\alpha$, and H$\gamma$ broad emission-lines,
respectively. The reverberation mass of the central black hole equals to
(1.87$\pm$0.26)$\times10^9\,M_\odot$ and (2.81$\pm$0.38)$\times10^9\,M_\odot$,
for the H$\beta$ and H$\alpha$ lines and assuming a scaling factor that
converts the virial product to a mass to be f=5.5. A difference between both
masses can point to a difference between kinematics of the H$\alpha$ and
H$\beta$ emission regions. We show that the reverberation mapping can only be
applied to the entire period of observations of the 3C390.3 nucleus after
removing a long-term trend. This trend has been expressed by a slowly varying
scalefactor c(t) in the power-law relationship between the line and continuum
fluxes: $F_{line}\propto c(t)\,F_{cont}^a$. We find the power-law index $a$
equals to 0.77 and 0.54 for the H$\beta$ and H$\alpha$ lines, respectively. The
observed relationship between the Balmer decrement and the optical continuum
flux is as follows: $F(H\alpha)/F(H\beta) \propto F_{cont}^{-0.20}$ and
$F(H\beta)/F(H\gamma) \propto F_{cont}^{-0.18}$. The 3C390.3 nucleus is an
"outsider" in the relationship between optical luminosity and black hole mass.
Its Eddington ratio is $E_{bol}/E_{Edd}$ = 0.0037.


title: English-Medium Instruction Calculus: Is flipping helpful?

abstract:
  This paper addresses some of the experiences encountered and some of the
strategies utilized while using flipped classroom pedagogy in an undergraduate
Single Variable Calculus (SVC) course in a Confucian Heritage Culture (CHC)
environment. Due to issues related to instructor-student communication and
students' learning styles, a theoretical framework is built upon three
components for learning environments: inverted Bloom's taxonomy for educational
learning objectives, English-medium instruction (EMI) and integrating
technology in the classroom. In this study, four different types of instruction
were designed; three classes were flipped while the fourth acts as a control.
Type A means entirely flipped with instructor-created videos and integrating
CAS {\sl Maxima}. Type B means entirely flipped with third-party videos. Type C
is similar to Type A, but instead of the entire course being flipped, a single
topic is flipped. Type D uses the traditional lecture style. By considering
exam scores and students' feedback, both quantitative and qualitative aspects
of the flipped pedagogy were investigated. Quantitative analysis indicates a
statistically significant difference in the exam scores between instruction
Type A and Type C as determined by one-way ANOVA ($F(3,306) = 2.67$, $p =
0.0477$) with small practical significance of the effect size ($\eta^2 =
0.0255$). Qualitative findings suggest that although students' engagement and
communication with instructors have been enhanced, some challenges related to
language and culture, along with minimizing competition and learning about a
new technological tool remain to persist.


title: Alignment of galaxies relative to their local environment in SDSS-DR8

abstract:
  We study the alignment of galaxies relative to their local environment in
SDSS-DR8 and, using these data, we discuss evolution scenarios for different
types of galaxies. We defined a vector field of the direction of anisotropy of
the local environment of galaxies. We summed the unit direction vectors of all
close neighbours of a given galaxy in a particular way to estimate this field.
We found the alignment angles between the spin axes of disc galaxies, or the
minor axes of elliptical galaxies, and the direction of anisotropy. The
distributions of cosines of these angles are compared to the random
distributions to analyse the alignment of galaxies. Sab galaxies show
perpendicular alignment relative to the direction of anisotropy in a sparse
environment, for single galaxies and galaxies of low luminosity. Most of the
parallel alignment of Scd galaxies comes from dense regions, from 2...3 member
groups and from galaxies with low luminosity. The perpendicular alignment of S0
galaxies does not depend strongly on environmental density nor luminosity; it
is detected for single and 2...3 member group galaxies, and for main galaxies
of 4...10 member groups. The perpendicular alignment of elliptical galaxies is
clearly detected for single galaxies and for members of < 11 member groups; the
alignment increases with environmental density and luminosity. We confirm the
existence of fossil tidally induced alignment of Sab galaxies at low z. The
alignment of Scd galaxies can be explained via the infall of matter to
filaments. S0 galaxies may have encountered relatively massive mergers along
the direction of anisotropy. Major mergers along this direction can explain the
alignment of elliptical galaxies. Less massive, but repeated mergers are
possibly responsible for the formation of elliptical galaxies in sparser areas
and for less luminous elliptical galaxies.


title:
Bulk viscous corrections to screening and damping in QCD at high
  temperatures

abstract:
  Non-equilibrium corrections to the distribution functions of quarks and
gluons in a hot and dense QCD medium modify the "hard thermal loops" (HTL). The
HTLs determine the retarded, advanced, and symmetric (time-ordered) propagators
for gluons with soft momenta as well as the Debye screening and Landau damping
mass scales. We compute such corrections to a thermal as well as to a
non-thermal fixed point.The screening and damping mass scales are sensitive to
the bulk pressure and hence to (pseudo-) critical dynamical scaling of the bulk
viscosity in the vicinity of a second-order critical point. This could be
reflected in the properties of quarkonium bound states in the deconfined phase
and in the dynamics of soft gluon fields.


title: Mappings preserving approximate orthogonality in Hilbert $C^*$-modules

abstract:
  We introduce a notion of approximate orthogonality preserving mappings
between Hilbert $C^*$-modules. We define the concept of $(\delta,
\varepsilon)$-orthogonality preserving mapping and give some sufficient
conditions for a linear mapping to be $(\delta, \varepsilon)$-orthogonality
preserving. In particular, if $\mathscr{E}$ is a full Hilbert
$\mathscr{A}$-module with $\mathbb{K}(\mathscr{H})\subseteq \mathscr{A}
\subseteq \mathbb{B}(\mathscr{H})$ and $T, S:\mathscr{E}\longrightarrow
\mathscr{E}$ are two linear mappings satisfying $\big|\langle Sx,
Sy\rangle\big| = \|S\|^2\,|\langle x, y\rangle|$ for all $x, y\in \mathscr{E}$
and $\|T - S\| \leq \theta \|S\|$, then we show that $T$ is a $(\delta,
\varepsilon)$-orthogonality preserving mapping. We also prove whenever
$\mathbb{K}(\mathscr{H})\subseteq \mathscr{A} \subseteq
\mathbb{B}(\mathscr{H})$ and $T: \mathscr{E} \longrightarrow \mathscr{F}$ is a
nonzero $\mathscr{A}$-linear $(\delta, \varepsilon)$-orthogonality preserving
mapping between $\mathscr{A}$-modules, then $$\big\|\langle Tx, Ty\rangle -
\|T\|^2\langle x, y\rangle\big\|\leq \frac{4(\varepsilon - \delta)}{(1 -
\delta)(1 + \varepsilon)} \|Tx\|\,\|Ty\|\qquad (x, y\in \mathscr{E}).$$ As a
result, we present some characterizations of the orthogonality preserving
mappings.


title: Rise time of proton cut-off energy in 2D and 3D PIC simulations

abstract:
  The Target Normal Sheath Acceleration (TNSA) regime for proton acceleration
by laser pulses is experimentally consolidated and fairly well understood.
However, uncertainties remain in the analysis of particle-in-cell (PIC)
simulation results.
  The energy spectrum is exponential with a cut-off, but the maximum energy
depends on the simulation time, following different laws in two and three
dimensional (2D, 3D) PIC simulations, so that the determination of an
asymptotic value has some arbitrariness.
  We propose two empirical laws for rise time of the cut-off energy in 2D and
3D PIC simulations, suggested by a model in which the proton acceleration is
due to a surface charge distribution on the target rear side. The kinetic
energy of the protons that we obtain follows two distinct laws, which appear to
be nicely satisfied by PIC simulations. The laws depend on two parameters: the
scaling time, at which the energy starts to rise, and the asymptotic cut-off
energy.
  The values of the cut-off energy, obtained by fitting the 2D and 3D
simulations for the same target and laser pulse, are comparable. This suggests
that parametric scans can be performed with 2D simulations, since 3D ones are
computationally very expensive. In this paper, the simulations are carried out
for $a_0=3$ with the PIC code ALaDyn by changing the target thickness $L$ and
the incidence angle $\alpha$. A monotonic dependence, on $L$ for normal
incidence and on $\alpha$ for fixed $L$, is found, as in the experimental
results for high temporal contrast pulses.


title: Conditionally positive definite kernels in Hilbert $C^*$-modules

abstract:
  We investigate the notion of conditionally positive definite in the context
of Hilbert $C^*$-modules and present a characterization of the conditionally
positive definiteness in terms of the usual positive definiteness. We give a
Kolmogorov type representation of conditionally positive definite kernels in
Hilbert $C^*$-modules. As a consequence, we show that a $C^*$-metric space $(S,
d)$ is $C^*$-isometric to a subset of a Hilbert $C^*$-module if and only if
$K(s,t)=-d(s,t)^2$ is a conditionally positive definite kernel. We also present
a characterization of the order $K'\leq K$ between conditionally positive
definite kernels.


title: A single fractal pinwheel tile

abstract:
  The pinwheel triangle of Conway and Radin is a standard example for tilings
with self-similarity and statistical circular symmetry. Many modifications were
constructed, all based on partitions of triangles or rectangles. The fractal
example of Frank and Whittaker requires 13 different types of tiles. We present
an example of a single tile with fractal boundary and very simple geometric
structure which has the same symmetry and spectral properties as the pinwheel
triangle.


title:
On the PeV knee of cosmic rays spectrum and TeV cutoff of electron
  spectrum

abstract:
  Spectra of Cosmic Rays (CRs), particularly their features, may hold essential
information about astroparticle and fundamental physics. Realizing that both
$4$ PeV CR knee and electron's TeV break have nearly identical Lorentz factor,
i.e. $\gamma \sim 10^6$, we propose that both CR nuclei and electron experience
a threshold interaction with unknown light particle $\rm X$, widespread in the
diffusive halo. The interaction occurs only when the Lorentz factor of CRs is
larger than $10^6$. Via this process, the energy spectrum of each component has
deformation above the threshold Lorentz factor, so both knee and spectral break
of electrons can be naturally reproduced. Given the large uncertainties of the
available measurements and simplified assumption, our model accommodates a wide
mass range of the particle X, which is allowable from ultralight value to $\sim
1$ eV.


title: Analysis of the minimal representation of Sp(r,R)

abstract:
  The minimal representations of Sp(r,R) can be realized on a Hilbert space of
holomorphic functions. This is the analogue of the Brylinski-Kostant model. It
can also be realized on a Hilbert space of L^2 functions on R^r. This is the
Schr\"oodinger model. We will describe the two realizations and a
transformation which maps one model to the other. It involves the classical
Bargmann transform and can be seen as its analogue.


title: Derived equivalence of Ito-Miura-Okawa-Ueda Calabi-Yau 3-folds

abstract:
  We prove derived equivalence of Calabi-Yau threefolds constructed by
Ito-Miura-Okawa-Ueda as an example of non-birational Calabi-Yau varieties whose
difference in the Grothendieck ring of varieties is annihilated by the affine
line.


title: Deep Video Deblurring

abstract:
  Motion blur from camera shake is a major problem in videos captured by
hand-held devices. Unlike single-image deblurring, video-based approaches can
take advantage of the abundant information that exists across neighboring
frames. As a result the best performing methods rely on aligning nearby frames.
However, aligning images is a computationally expensive and fragile procedure,
and methods that aggregate information must therefore be able to identify which
regions have been accurately aligned and which have not, a task which requires
high level scene understanding. In this work, we introduce a deep learning
solution to video deblurring, where a CNN is trained end-to-end to learn how to
accumulate information across frames. To train this network, we collected a
dataset of real videos recorded with a high framerate camera, which we use to
generate synthetic motion blur for supervision. We show that the features
learned from this dataset extend to deblurring motion blur that arises due to
camera shake in a wide range of videos, and compare the quality of results to a
number of other baselines.


title: QCD with Flavored Minimally Doubled Fermions

abstract:
  I discuss minimally doubled fermions fermions as an ultra-local formulation
on the lattice for sea quarks that realize a non-singlet chiral symmetry. I
introduce a non-singlet mass term for Karsten-Wilczek fermions and identify the
appropriate representation of the SU(2) flavor group at finite lattice spacing.
I present an algebraic proof that the symmetry of the quark determinant under
charge conjugation and reflections of the Euclidean axes is preserved for
Karsten-Wilczek fermions as sea quarks. Finally, I discuss how the flavor
components in meson correlation functions with Karsten-Wilczek fermions emerge
naturally and I show how taste-breaking can be avoided without fine tuning.


title: Color Constancy with Derivative Colors

abstract:
  Information about the illuminant color is well contained in both achromatic
regions and the specular components of highlight regions. In this paper, we
propose a novel way to achieve color constancy by exploiting such clues. The
key to our approach lies in the use of suitably extracted derivative colors,
which are able to compute the illuminant color robustly with kernel density
estimation. While extracting derivative colors from achromatic regions to
approximate the illuminant color well is basically straightforward, the success
of our extraction in highlight regions is attributed to the different rates of
variation of the diffuse and specular magnitudes in the dichromatic reflection
model. The proposed approach requires no training phase and is simple to
implement. More significantly, it performs quite satisfactorily under
inter-database parameter settings. Our experiments on three standard databases
demonstrate its effectiveness and fine performance in comparison to
state-of-the-art methods.