title:
Production of exotic charmonium in $\gamma \gamma$ interactions at
  hadronic colliders

abstract:
  In this paper we investigate the Exotic Charmonium (EC) production in $\gamma
\gamma$ interactions present in proton-proton, proton-nucleus and
nucleus-nucleus collisions at the CERN Large Hadron Collider (LHC) energies as
well as for the proposed energies of the Future Circular Collider (FCC). Our
results demonstrate that the experimental study of these processes is feasible
and can be used to constrain the theoretical decay widths and shed some light
on the configuration of the considered multiquark states.


title:
Mathematical analysis of inertial waves in rectangular basins with one
  sloping boundary

abstract:
  Here we consider the problem of small oscillations of a rotating inviscid
incompressible fluid.
  From a mathematical point of view, new exact solutions to the two-dimensional
Poincar\'e-Sobolev equation in a class of domains including trapezoid are found
in an explicit form and their main properties are described. These solutions
correspond to the absolutely continuous spectrum of a linear operator that is
associated with this system of equations.
  For specialists in Astrophysics and Geophysics the existence of these
solutions signifies the existence of some previously unknown type of inertial
waves corresponding to the continuous spectrum of inertial oscillations. A
fundamental distinction between monochromatic inertial waves and waves of the
new type is shown: usual characteristics (frequency, amplitude, wave vector,
dispersion relation, direction of energy propagation, and so on) are not
applicable to the last. Main properties of these waves are described. In
particular it is proved that they are progressive. Main features of their
energy transfer are described. The existence of such inertial waves enables us
to explain in a new way a lot of experimental data that were obtained in
Geophysics in the past two decades and to predict the occurrence of such
oscillations in natural waters.


title:
Morphological and Biochemical Adaptive Changes Associated With A
  Short-period Starvation of Adult Male Japanese Quail (Coturnix japonica)

abstract:
  Background The morphological and biochemical impact of a short-period of
starvation on Japanese quail was investigated. Materials and methods Ten adult
male Japanese quail were divided into two groups; control fed and starved. The
control-fed group was offered food and water ad libitum and the starved group
was subjected to a short-period of food deprivation. After 2.5 days, the serum
was obtained and different parameters including the total protein, AST, ALT,
triglyceride, HDL, LDL, creatinine and urea were assessed. Gastrointestinal
tract, stomach and liver were excised and their masses were estimated. Paraffin
and resin embedded sections from the proventriculus, gizzard, liver, duodenum,
kidney and pancreas were examined with a light microscopy. Results Significant
decreases in the masses of body, gastrointestinal tract, stomach and liver of
the starved group were recorded. The liver and duodenum were the most affected
organs. The liver showed depletion of glycogen, vacuolation, hyperemia and
cellular infiltrations. Duodenal villi showed degenerative changes in lamina
epithelialis and cellular infiltrations in the lamina propria. Biochemical
analysis revealed a decreased level of total protein, AST and ALT, increased
cholesterol, triglycerides and LDL, and unchanged HDL, urea and creatinine by
starvation. Conclusion The current study described in details the effect of
short time starvation on quail organs. Time-point adaptive responses of male
quail to starvation and refeeding on quail organs will be investigated in
future studies.


title: Optimal Bitter Coil Solenoid

abstract:
  Bitter coil is an electromagnet used for the generation of exceptionally
strong magnetic fields. The upper bound of magnet flux density is restricted by
several factors. One principal restriction is the high stresses due to Lorentz
forces in the coil. The Lorentz forces generate the distributed body force,
which acts as the pressure of magnetic field. The common radial thickness
profile of the Bitter coil is constant. In this paper the possibility of
optimization by means of non-constant radial thickness profile of the Bitter
coil is studied. The close form expression for optimal thickness profile is
obtained. Both designs are compared and the considerable improvement of
magnetic flux density is demonstrated. Moreover, the optimal design improves
the shape of cooling channels. Namely, the highest cross-section of cooling
channel is at the most thermally loaded inner surface of the coil.


title:
Lumbar degenerative spondylolisthesis epidemiology: a systemic review
  with a focus on gender-specific and age-specific prevalence

abstract:
  The epidemiology of lumbar degenerative spondylolisthesis (DS) remains
controversial. We performed a systemic review with the aim to have a better
understanding of DS's prevalence in general population. The results showed the
prevalence of DS is very gender specific and age specific. Both women and men
have few DS before 50 years old, after 50 years old both women and men start to
develop DS, with women having a faster developing rate than men. For elderly
Chinese (>=65 yrs, mean age: 72.5 yrs), large population based studies
(MsOS(Hong Kong) and MrOS (Hong Kong), females n=2000 and males n=2000) showed
DS prevalence was for 25.0% for women and 19.1% for men, and the prevalence F:M
(women:men) ratio was 1.3:1. The published data (MsOS(USA) and MrOS(USA)
studies) seem to show elderly Caucasian American has a higher DS prevalence,
being approximately 60-70% higher than elderly Chinese; however the prevalence
F:M ratio was similar to elderly Chinese population. Patient data showed female
patients more often received treatment than men; and preliminary data show the
ratio of numbers of female patients received treatment compared with men did
not differ between Northeast Asians (Chinese, Japanese, and Korean) and
European and American Caucasians, being around 2:1 in elderly population. The
existing data also suggest that menopause may be a contributing factor for the
accelerated DS development in post-menopausal


title: BP Piscium: its flaring disk imaged with SPHERE/ZIMPOL

abstract:
  Whether BP Piscium (BP Psc) is either a pre-main sequence T Tauri star at d ~
80 pc, or a post-main sequence G giant at d ~ 300 pc is still not clear. As a
first-ascent giant, it is the first to be observed with a molecular and dust
disk. Alternatively, BP Psc would be among the nearest T Tauri stars with a
protoplanetary disk (PPD). We investigate whether the disk geometry resembles
typical PPDs, by comparing polarimetric images with radiative transfer models.
Our VLT/SPHERE/ZIMPOL observations allow us to perform Polarimetric
Differential Imaging; Reference Star Differential Imaging; and Richardson-Lucy
deconvolution. We present the first visible light polarization and intensity
images of the disk of BP Psc. Our deconvolution confirms the disk shape as
detected before, mainly showing the southern side of the disk. In polarized
intensity the disk is imaged at larger detail and also shows the northern side,
giving it the typical shape of high inclination flared disks. We explain the
observed disk features by retrieving the large-scale geometry with MCMax
radiative transfer modeling, which yields a strongly flared model, atypical for
disks of T Tauri stars.


title: Degrees of regular sequences with a symmetric group action

abstract:
  We consider ideals in a polynomial ring that are generated by regular
sequences of homogeneous polynomials and are stable under the action of the
symmetric group permuting the variables. In previous work, we determined the
possible isomorphism types for these ideals. Following up on that work, we now
analyze the possible degrees of the elements in such regular sequences. For
each case of our classification, we provide some criteria guaranteeing the
existence of regular sequences in certain degrees.


title: The Broadband Spectral Variability of Holmberg IX X-1

abstract:
  We present results from four new broadband X-ray observations of the extreme
ultraluminous X-ray source Holmberg IX X-1 ($L_{\rm{X}} > 10^{40}$ erg/s),
performed by $Suzaku$ and $NuSTAR$ in coordination. Combined with the archival
data, we now have broadband observations of this remarkable source from six
separate epochs. Two of these new observations probe lower fluxes than seen
previously, allowing us to extend our knowledge of the broadband spectral
variability exhibited. The spectra are well fit by two thermal blackbody
components, which dominate the emission below 10 keV, as well as a steep
($\Gamma \sim 3.5$) powerlaw tail which dominates above $\sim$15 keV.
Remarkably, while the 0.3-10.0 keV flux varies by a factor of $\sim$3 between
all these epochs, the 15-40 keV flux varies by only $\sim$20%. Although the
spectral variability is strongest in the $\sim$1-10 keV band, both of the
thermal components are required to vary when all epochs are considered. We also
re-visit the search for iron absorption features, leveraging the high-energy
$NuSTAR$ data to improve our sensitivity to extreme velocity outflows in light
of the ultra-fast outflow recently detected in NGC 1313 X-1. Iron absorption
from a similar outflow along our line of sight can be ruled out in this case.
We discuss these results in the context of super-Eddington accretion models
that invoke a funnel-like geometry for the inner flow, and propose a scenario
in which we have an almost face-on view of a funnel that expands to larger
radii with increasing flux, resulting in an increasing degree of geometrical
collimation for the emission from intermediate temperature regions.


title: Toric surfaces over an arbitrary field

abstract:
  We study toric varieties over an arbitrary field with an emphasis on toric
surfaces in the Merkurjev-Panin motivic category of "K-motives". We explore the
decomposition of certain toric varieties as K-motives into products of central
simple algebras, the geometric and topological information encoded in these
central simple algebras, and the relationship between the decomposition of the
K-motives and the semiorthogonal decomposition of the derived categories. We
obtain the information mentioned above for toric surfaces by explicitly
classifying all minimal smooth projective toric surfaces using toric geometry.


title: The fixation probability and time for a doubly beneficial mutant

abstract:
  For a highly beneficial mutant $A$ entering a randomly reproducing population
of constant size, we study the situation when a second beneficial mutant $B$
arises before $A$ has fixed. If the selection coefficient of $B$ is greater
than the selection coefficient of $A$, and if $A$ and $B$ can recombine at some
rate $\rho$, there is a chance that the double beneficial mutant $AB$ forms and
eventually fixes. We give a convergence result for the fixation probability of
$AB$ and its fixation time for large selection coefficients.


title:
Solving Multi-Objective Optimization via Adaptive Stochastic Search with
  Domination Measure

abstract:
  For general multi-objective optimization problems, we propose a novel
performance metric called domination measure to measure the quality of a
solution, which can be intuitively interpreted as the size of the portion of
the solution space that dominates that solution. As a result, we reformulate
the original multi-objective problem into a stochastic single-objective one and
propose a model-based approach to solve it. We show that an ideal version
algorithm of the proposed approach converges to a set representation of the
global optima of the reformulated problem. We also investigate the numerical
performance of an implementable version algorithm by comparing it with numerous
existing multi-objective optimization methods on popular benchmark test
functions. The numerical results show that the proposed approach is effective
in generating a finite and uniformly spread approximation of the Pareto optimal
set of the original multi-objective problem, and is competitive to the tested
existing methods.


title: A single electron transistor with quantum rings

abstract:
  We Have developed the concept of a new kind of single-electron transistor in
which the transport of the electron through a quantum wire is controlled by
charged quantum rings. Using a 2D harmonic potential as the transverse
constraint, we numerically investigated the transport of the electron through
the wire. We have shown that in the low energy limit, for a suitable
configuration of the rings, called the quadrupole configuration, we are able to
adjust the conductance of the wire and therefore control the switching process.


title:
Measurement of the cross section and longitudinal double-spin asymmetry
  for di-jet production in polarized $pp$ collisions at $\sqrt{s}$ = 200 GeV

abstract:
  We report the first measurement of the longitudinal double-spin asymmetry
$A_{LL}$ for mid-rapidity di-jet production in polarized $pp$ collisions at a
center-of-mass energy of $\sqrt{s} = 200$ GeV. The di-jet cross section was
measured and is shown to be consistent with next-to-leading order (NLO)
perturbative QCD predictions. $A_{LL}$ results are presented for two distinct
topologies, defined by the jet pseudorapidities, and are compared to
predictions from several recent NLO global analyses. The measured asymmetries,
the first such correlation measurements, support those analyses that find
positive gluon polarization at the level of roughly 0.2 over the region of
Bjorken-$x > 0.05$.


title: Generating invariant rings of quivers in arbitrary characteristic

abstract:
  It is well known that the ring of polynomial invariants of a reductive group
is finitely generated. However, it is difficult to give strong upper bounds on
the degrees of the generators, especially over fields of positive
characteristic. In this paper, we make use of the theory of good filtrations
along with recent results on the null cone to provide polynomial bounds for
matrix semi-invariants in arbitrary characteristic, and consequently for matrix
invariants. Our results generalize to invariants and semi-invariants of
quivers.


title: An Efficient Optimal Algorithm for the Successive Minima Problem

abstract:
  In many applications including integer-forcing linear multiple-input and
multiple-output (MIMO) receiver design, one needs to solve a successive minima
problem (SMP) on an $n$-dimensional lattice to get an optimal integer
coefficient matrix $\A^\star\in \mathbb{Z}^{n\times n}$. In this paper, we
first propose an efficient optimal SMP algorithm with an $\bigO(n^2)$ memory
complexity. The main idea behind the new algorithm is it first initializes with
a suitable suboptimal solution, which is then updated, via a novel algorithm
with only $\bigO(n^2)$ flops in each updating, until $\A^{\star}$ is obtained.
Different from existing algorithms which find $\A^\star$ column by column
through using a sphere decoding search strategy $n$ times, the new algorithm
uses a search strategy once only. We then rigorously prove the optimality of
the proposed algorithm. Furthermore, we theoretically analyze its complexity.
In particular, we not only show that the new algorithm is $\Omega(n)$ times
faster than the most efficient existing algorithm with polynomial memory
complexity, but also assert that it is even more efficient than the most
efficient existing algorithm with exponential memory complexity. Finally,
numerical simulations are presented to illustrate the optimality and efficiency
of our novel SMP algorithm.


title: Functional Asynchronous Networks: Factorization of Dynamics and Function

abstract:
  In this note we describe the theory of functional asynchronous networks and
one of the main results, the Modularization of Dynamics Theorem, which for a
large class of functional asynchronous networks gives a factorization of
dynamics in terms of constituent subnetworks. For these networks we can give a
complete description of the network function in terms of the function of the
events comprising the network and thereby answer a question originally raised
by Alon in the context of biological networks.


title: Proposing Plausible Answers for Open-ended Visual Question Answering

abstract:
  Answering open-ended questions is an essential capability for any intelligent
agent. One of the most interesting recent open-ended question answering
challenges is Visual Question Answering (VQA) which attempts to evaluate a
system's visual understanding through its answers to natural language questions
about images. There exist many approaches to VQA, the majority of which do not
exhibit deeper semantic understanding of the candidate answers they produce. We
study the importance of generating plausible answers to a given question by
introducing the novel task of `Answer Proposal': for a given open-ended
question, a system should generate a ranked list of candidate answers informed
by the semantics of the question. We experiment with various models including a
neural generative model as well as a semantic graph matching one. We provide
both intrinsic and extrinsic evaluations for the task of Answer Proposal,
showing that our best model learns to propose plausible answers with a high
recall and performs competitively with some other solutions to VQA.


title:
Non-reciprocal quantum interactions and devices via autonomous
  feed-forward

abstract:
  In a recent work [A. Metelmann and A. A. Clerk, Phys. Rev. X 5, 021025
(2015)], a general reservoir-engineering approach for generating non-reciprocal
quantum interactions and devices was described. We show here how in many cases
this general recipe can be viewed as an example of autonomous feed-forward: the
full dissipative evolution is identical to the unconditional evolution in a
setup where an observer performs an ideal quantum measurement of one system,
and then uses the results to drive a second system. We also extend the
application of this approach to non-reciprocal quantum amplifiers, showing the
added functionality possible when using two engineered reservoirs. In
particular, we demonstrate how to construct an ideal phase-preserving
cavity-based amplifier which is full non-reciprocal, quantum-limited and free
of any fundamental gain-bandwidth constraint.


title:
Double stage nematic bond-ordering above double stripe magnetism:
  application to BaTi$_2$Sb$_2$O

abstract:
  Spin-driven nematicity, or the breaking of the point-group symmetry of the
lattice without long-range magnetic order, is clearly quite important in
iron-based superconductors. From a symmetry point of view, nematic order can be
described as a coherent locking of spin fluctuations in two interpenetrating
N\'eel sublattices with ensuing nearest-neighbor bond order and an absence of
static magnetism. Here, we argue that the low-temperature state of the recently
discovered superconductor BaTi$_2$Sb$_2$O is a strong candidate for a more
exotic form of spin-driven nematic order, in which fluctuations occurring in
four N\'eel sublattices promote both nearest- and next-nearest neighbor bond
order. We develop a low-energy field theory of this state and show that it can
have, as a function of temperature, up to two separate bond-order phase
transitions -- namely, one that breaks rotation symmetry and one that breaks
reflection and translation symmetries of the lattice. The resulting state has
an orthorhombic lattice distortion, an intra-unit-cell charge density wave, and
no long-range magnetic order, all consistent with reported measurements of the
low-temperature phase of BaTi$_2$Sb$_2$O. We then use density functional theory
calculations to extract exchange parameters to confirm that the model is
applicable to BaTi$_2$Sb$_2$O.


title: Fractional Schrodinger-Poisson Equations With General Nonlinearities

abstract:
  In this paper we investigate the existence of positive solutions and ground
state solution for a class of fractional Schr\"odinger-Poisson equations in
$\mathbb R^3$ with general nonlinearities.


title: Degree of W-operator and Noncrossing Partition

abstract:
  Goulden and Jackson first introduced the cut-and-join operator. The
cut-and-join is widely used in studying the Hurwitz number and many other
topological recursion problems. Mironov, Morosov and Natanzon give a more
general construction and call it W-operator W([n]). As a special case, the
cut-and-join operator is W([2]). In this paper, we study the structure of
W([n]). We prove that W([n]) can be written as the sum of n! terms and each
term corresponds uniquely to a permutation in Sn. We also define the degree of
each term. We prove that there is a correspondence between the terms of W([n])
with highest degree and the noncrossing partitions.


title: M@TE - Monitoring at TeV Energies

abstract:
  Blazars are extremely variable objects emitting radiation across the
electromagnetic spectrum and showing variability on time scales from minutes to
years. For the understanding of the emission mechanisms, simultaneous
multi-wavelength observations are crucial. Various models for flares predict
simultaneous flux increases in the X-ray and gamma-ray band or more complex
variability patterns, depending on the dominant process responsible for the
gamma-ray emission. Monitoring at TeV energies is providing important
information to distinguish between different models. To study duty cycle and
variability time scales of an object, an unbiased data sample is essential, and
good sensitivity and continuous monitoring are needed to resolve smaller time
scales. A dedicated long-term monitoring program at TeV energies has been
started by the FACT project. Its success clearly illustrated that the usage of
silicon based photo sensors (SIPMs) is ideal for long-term monitoring. They
provide not only an excellent and stable detector performance, but also allow
for observations during bright ambient light minimizing observational gaps and
increasing the instrument's duty cycle. The observation time in a single
longitude is limited to 6 hours. To study typical variability time scales of
few hours to one day, the ultimate goal is 24/7 monitoring with a network of
small telescopes around the globe (DWARF project). The installation of an
Imaging Air Cherenkov Telescope is planned in San Pedro Martir, Mexico. For the
M@TE (Monitoring at TeV energies) telescope, a mount from a previous experiment
is being refurbished to be equipped with a camera using the new generation of
SiPMs. In the presentation, the status of the M@TE project will be reported
outlining the scientific potential, including the possibility to extend
monitoring campaigns to 12 hours by coordinated observations together with
FACT.


title:
Chimera states in a network-organized public goods game with destructive
  agents

abstract:
  We found that a network-organized metapopulation of cooperators, defectors
and destructive agents playing the public goods game with mutations, can
collectively reach global synchronization or chimera states. Global
synchronization is accompanied by a collective periodic burst of cooperation,
whereas chimera states reflect the tendency of the networked metapopulation to
be fragmented in clusters of synchronous and incoherent bursts of cooperation.
Numerical simulations have shown that the system's dynamics alternates between
these two steady states through a first order transition. Depending on the
parameters determining the dynamical and topological properties, chimera states
with different numbers of coherent and incoherent clusters are observed. Our
results present the first systematic study of chimera states and their
characterization in the context of evolutionary game theory. This provides a
valuable insight into the details of their occurrence, extending the relevance
of such states to natural and social systems.


title: First Study of Combined Blazar Light Curves with FACT and HAWC

abstract:
  For studying variable sources like blazars, it is crucial to achieve unbiased
monitoring, either with dedicated telescopes in pointing mode or survey
instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC)
observatory monitors approximately two thirds of the sky every day. It uses the
water Cherenkov technique, which provides an excellent duty cycle independent
of weather and season. The First G-APD Cherenkov Telescope (FACT) monitors a
small sample of sources with better sensitivity, using the imaging air
Cherenkov technique. Thanks to its camera with silicon-based photosensors, FACT
features an excellent detector performance and stability and extends its
observations to times with strong moonlight, increasing the duty cycle compared
to other imaging air Cherenkov telescopes. As FACT and HAWC have overlapping
energy ranges, a joint study can exploit the longer daily coverage given that
the observatories' locations are offset by 5.3 hours. Furthermore, the better
sensitivity of FACT adds a finer resolution of features on hour-long time
scales, while the continuous duty cycle of HAWC ensures evenly sampled
long-term coverage. Thus, the two instruments complement each other to provide
a more complete picture of blazar variability. In this presentation, the first
joint study of light curves from the two instruments will be shown, correlating
long-term measurements with daily sampling between air and water Cherenkov
telescopes. The presented results focus on the study of the variability of the
bright blazars Mrk 421 and Mrk 501 during the last two years featuring various
flaring activities.


title: The determinism and boundedness of self-assembling structures

abstract:
  Self-assembly processes are widespread in nature, and lie at the heart of
many biological and physical phenomena. The characteristics of self-assembly
building blocks determine the structures that they form. Two crucial properties
are the determinism and boundedness of the self-assembly. The former tells us
whether the same set of building blocks always generates the same structure,
and the latter whether it grows indefinitely. These properties are highly
relevant in the context of protein structures, as the difference between
deterministic protein self-assembly and nondeterministic protein aggregation is
central to a number of diseases. Here we introduce a graph theoretical approach
that can determine the determinism and boundedness for several geometries and
dimensionalities of self-assembly more accurately and quickly than conventional
methods. We apply this methodology to a previously studied lattice
self-assembly model and discuss generalizations to a wide range of other
self-assembling systems


title: Solvable normal subgroups of 2-knot groups

abstract:
  If $X$ is an orientable, strongly minimal $PD_4$-complex and $\pi_1(X)$ has
one end then it has no nontrivial locally-finite normal subgroup. Hence if
$\pi$ is a 2-knot group then (a) if $\pi$ is virtually solvable then either
$\pi$ has two ends or $\pi\cong\Phi$, with presentation
$\langle{a,t}|ta=a^2t\rangle$, or $\pi$ is torsion-free and polycyclic of
Hirsch length 4; (b) either $\pi$ has two ends, or $\pi$ has one end and the
centre $\zeta\pi$ is torsion-free, or $\pi$ has infinitely many ends and
$\zeta\pi$ is finite; and (c) the Hirsch-Plotkin radical $\sqrt\pi$ is
nilpotent.


title:
Selective addressing of solid-state spins at the nanoscale via magnetic
  resonance frequency encoding

abstract:
  The nitrogen-vacancy (NV) centre in diamond is a leading platform for
nanoscale sensing and imaging, as well as quantum information processing in the
solid state. To date, individual control of two NV electronic spins at the
nanoscale has been demonstrated. However, a key challenge is to scale up such
control to arrays of NV spins. Here we apply nanoscale magnetic resonance
frequency encoding to realize site-selective addressing and coherent control of
a four-site array of NV spins. Sites in the array are separated by 100 nm, with
each site containing multiple NVs separated by ~15 nm. Microcoils fabricated on
the diamond chip provide electrically tuneable magnetic-field gradients ~0.1
G/nm. Tailored application of gradient fields and resonant microwaves allow
site-selective NV spin manipulation and sensing applications, including Rabi
oscillations, imaging, and nuclear magnetic resonance (NMR) spectroscopy with
nanoscale resolution. Microcoil-based magnetic resonance of solid-state spins
provides a practical platform for quantum-assisted sensing, quantum information
processing, and the study of nanoscale spin networks.


title: Inverse Power Flow Problem

abstract:
  This paper formulates the inverse power flow problem which is to infer the
nodal admittance matrix (hence the network structure of the power system) from
voltage and current phasors measured at a number of buses. We show that the
admittance matrix can be uniquely identified from a sequence of measurements
corresponding to different steady states when every node in the system is
equipped with a measurement device, and a Kron-reduced admittance matrix can be
determined even if some nodes in the system are not monitored (hidden nodes).
Furthermore, we propose effective algorithms based on graph theory to uncover
the actual admittance matrix of radial systems with hidden nodes. We provide
theoretical guarantees for the recovered admittance matrix and demonstrate that
the actual admittance matrix can be fully recovered even from the Kron-reduced
admittance matrix under some mild assumptions. Simulations on standard test
systems confirm that these algorithms are capable of providing accurate
estimates of the admittance matrix from noisy sensor data.


title:
Sampling hyperparameters in hierarchical models: improving on Gibbs for
  high-dimensional latent fields and large data sets

abstract:
  We consider posterior sampling in the very common Bayesian hierarchical model
in which observed data depends on high-dimensional latent variables that, in
turn, depend on relatively few hyperparameters. When the full conditional over
the latent variables has a known form, the marginal posterior distribution over
hyperparameters is accessible and can be sampled using a Markov chain Monte
Carlo (MCMC) method on a low-dimensional parameter space. This may improve
computational efficiency over standard Gibbs sampling since computation is not
over the high-dimensional space of latent variables and correlations between
hyperparameters and latent variables become irrelevant. When the marginal
posterior over hyperparameters depends on a fixed-dimensional sufficient
statistic, precomputation of the sufficient statistic renders the cost of the
low-dimensional MCMC independent of data size. Then, when the hyperparameters
are the primary variables of interest, inference may be performed in big-data
settings at modest cost. Moreover, since the form of the full conditional for
the latent variables does not depend on the form of the hyperprior
distribution, the method imposes no restriction on the hyperprior, unlike Gibbs
sampling that typically requires conjugate distributions. We demonstrate these
efficiency gains in four computed examples.


title: Novelty Learning via Collaborative Proximity Filtering

abstract:
  The vast majority of recommender systems model preferences as static or
slowly changing due to observable user experience. However, spontaneous changes
in user preferences are ubiquitous in many domains like media consumption and
key factors that drive changes in preferences are not directly observable.
These latent sources of preference change pose new challenges. When systems do
not track and adapt to users' tastes, users lose confidence and trust,
increasing the risk of user churn. We meet these challenges by developing a
model of novelty preferences that learns and tracks latent user tastes. We
combine three innovations: a new measure of item similarity based on patterns
of consumption co-occurrence; model for {\em spontaneous} changes in
preferences; and a learning agent that tracks each user's dynamic preferences
and learns individualized policies for variety. The resulting framework
adaptively provides users with novelty tailored to their preferences for change
per se.


title:
Characteristic Polynomials of Symmetric Matrices over the Univariate
  Polynomial Ring

abstract:
  Viewing a bivariate polynomial f in R[x,t] as a family of univariate
polynomials in t parametrized by real numbers x, we call f real rooted if this
family consists of monic polynomials with only real roots. If f is the
characteristic polynomial of a symmetric matrix with entries in R[x], it is
obviously real rooted. In this article the converse is established, namely that
every real rooted bivariate polynomial is the characteristic polynomial of a
symmetric matrix over the univariate real polynomial ring. As a byproduct we
present a purely algebraic proof of the Helton-Vinnikov Theorem which solved
the 60 year old Lax conjecture on the existence of definite determinantal
representation of ternary hyperbolic forms.


title:
Observation of vortex-antivortex pairing in decaying 2D turbulence of a
  superfluid gas

abstract:
  In a two-dimensional (2D) classical fluid, a large-scale flow structure
emerges out of turbulence, which is known as the inverse energy cascade where
energy flows from small to large length scales. An interesting question is
whether this phenomenon can occur in a superfluid, which is inviscid and
irrotational by nature. Atomic Bose-Einstein condensates (BECs) of highly
oblate geometry provide an experimental venue for studying 2D superfluid
turbulence, but their full investigation has been hindered due to a lack of the
circulation sign information of individual quantum vortices in a turbulent
sample. Here, we demonstrate a vortex sign detection method by using Bragg
scattering, and we investigate decaying turbulence in a highly oblate BEC at
low temperatures, with our lowest being $\sim 0.5 T_c$, where $T_c$ is the
superfluid critical temperature. We observe that weak spatial pairing between
vortices and antivortices develops in the turbulent BEC, which corresponds to
the vortex-dipole gas regime predicted for high dissipation. Our results
provide a direct quantitative marker for the survey of various 2D turbulence
regimes in the BEC system.


title:
Three phase classification of an uninterrupted traffic flow: a $k$-means
  clustering study

abstract:
  We investigate the speed time series of the vehicles recorded by a camera at
a section of a highway in the city of Isfahan, Iran. Using $k$-means clustering
algorithm, we find that the natural number of clustering for this set of data
is $3$. This is in agreement with the three-phase theory of uninterrupted
traffic flows. According to this theory, the three traffic phases are
categorized as {\em free flow} (F), {\em synchronized} (S) and {\em wide moving
jam} (J). We obtain the transition speeds and densities at F-S and also S-J
transitions. We also apply the Shannon entropy analysis on the speed time
series over finite windows, which equips us to monitor in areal time the
instant state of a traffic flow.


title: Decoherence Can Relax Cosmic Acceleration: an Example

abstract:
  We investigate back reaction in de Sitter space in an approach where only
states that are observationally accessible are included in the density matrix.
Using the Bunch-Davies vacuum as the initial condition we find for a conformal
scalar field and a cosmological constant that tracing over the unobservable
states beyond the cosmological horizon leads to a thermal spectrum of particles
and that such a configuration is unstable under semi-classical back reaction.
It is concluded that this prescription results in an instability of de Sitter
space with a gradually increasing horizon size.


title: Additive unit structure of endomorphism rings and invariance of modules

abstract:
  We use the type theory for rings of operators due to Kaplansky to describe
the structure of modules that are invariant under automorphisms of their
injective envelopes. Also, we highlight the importance of Boolean rings in the
study of such modules. As a consequence of this approach, we are able to
further the study initiated by Dickson and Fuller regarding when a module
invariant under automorphisms of its injective envelope is invariant under any
endomorphism of it. In particular, we find conditions for several classes of
noetherian rings which ensure that modules invariant under automorphisms of
their injective envelopes are quasi-injective. In the case of a commutative
noetherian ring, we show that any automorphism-invariant module is
quasi-injective. We also provide multiple examples that show that our
conditions are the best possible, in the sense that if we relax them further
then there exist automorphism-invariant modules which are not quasi-injective.
We finish this paper by dualizing our results to the automorphism-coinvariant
case.


title: Localized $L^p$-estimates for eigenfunctions: II

abstract:
  If $(M,g)$ is a compact Riemannian manifold of dimension $n\ge 2$ we give
necessary and sufficient conditions for improved $L^p(M)$-norms of
eigenfunctions for all $2<p\ne p_c=\tfrac{2(n+1)}{n-1}$, the critical exponent.
Since improved $L^{p_c}(M)$ bounds imply improvement all other exponents, these
conditions are necessary for improved bounds for the critical space. We also
show that improved $L^{p_c}(M)$ bounds are valid if these conditions are met
and if the half-wave operators, $U(t)$, have no caustics when $t\ne 0$. The
problem of finding a necessary and sufficient condition for $L^{p_c}(M)$
improvement remains an interesting open problem.


title:
A Generalized Correlation Index for Quantifying Signal Morphological
  Similarity

abstract:
  In biomedical applications, the similarity between a signal measured from an
injured subject and a reference signal measured from a normal subject can be
used to quantify the injury severity. This paper proposes a generalization of
the adaptive signed correlation index (ASCI) to account for specific signal
features of interest and extend the trichotomization of conventional ASCI to an
arbitrary number of levels. In the context of spinal cord injury assessment, a
computational example is presented to illustrate the enhanced resolution of the
proposed measure and its ability to offer a more refined measure of the level
of injury.


title:
Non-uniform sampling schemes of the Brillouin zone for many-electron
  perturbation-theory calculations in reduced dimensionality

abstract:
  First principles calculations based on many-electron perturbation theory
methods, such as the \textit{ab initio} GW and GW plus Bethe-Salpeter equation
(GW-BSE) approach, are reliable ways to predict quasiparticle and optical
properties of materials, respectively. However, these methods involve more care
in treating the electron-electron interaction and are considerably more
computationally demanding when applied to systems with reduced dimensionality,
since the electronic confinement leads a slower convergence of sums over the
Brillouin zone due to a much more complicated screening environment that
manifests in the "head" and "neck" elements of the dielectric matrix. Here, we
present two new schemes to sample the Brillouin zone for GW and GW-BSE
calculations: the non-uniform neck subsampling method and the clustered
sampling interpolation method, which can respectively be used for a family of
single-particle problems, such as GW calculations, and for problems involving
the scattering of two-particle states, such as when solving the BSE. We tested
these methods on several few-layer semiconductors and graphene and show that
they perform a much more efficient sampling of the Brillouin zone and yield two
to three orders of magnitude reduction in the computer time. These two methods
can be readily incorporated into several \textit{ab initio} packages that
compute electronic and optical properties through the GW and GW-BSE approaches.


title:
Gas and stellar spiral arms and their offsets in the grand-design spiral
  galaxy M51

abstract:
  Theoretical studies on the response of interstellar gas to a gravitational
potential disc with a quasi-stationary spiral arm pattern suggest that the gas
experiences a sudden compression due to standing shock waves at spiral arms.
This mechanism, called a galactic shock wave, predicts that gas spiral arms
move from downstream to upstream of stellar arms with increasing radius inside
a corotation radius. In order to investigate if this mechanism is at work in
the grand-design spiral galaxy M51, we have measured azimuthal offsets between
the peaks of stellar mass and gas mass distributions in its two spiral arms.
The stellar mass distribution is created by the spatially resolved spectral
energy distribution fitting to optical and near infrared images, while the gas
mass distribution is obtained by high-resolution CO and HI data. For the inner
region (r < 150"), we find that one arm is consistent with the galactic shock
while the other is not. For the outer region, results are less certain due to
the narrower range of offset values, the weakness of stellar arms, and the
smaller number of successful offset measurements. The results suggest that the
nature of two inner spiral arms are different, which is likely due to an
interaction with the companion galaxy.


title:
Theoretical Study Of The Effects Of Magnetic Field Geometry On The
  High-Energy Emission Of Blazars

abstract:
  The knowledge of the structure of the magnetic field inside a blazar jet, as
deduced from polarization observations at radio to optical wavelengths, is
closely related to the formation and propagation of relativistic jets that
result from accretion onto supermassive black holes. However, a largely
unexplored aspect of the theoretical understanding of radiation transfer
physics in blazar jets has been the magnetic field geometry as revealed by the
polarized emission and the connection between the variability in polarization
and flux across the spectrum. Here, we explore the effects of various magnetic
geometries that can exist inside a blazar jet: parallel, oblique, toroidal, and
tangled. We investigate the effects of changing the orientation of the magnetic
field, according to the above-mentioned geometries, on the resulting
high-energy spectral energy distributions (SEDs) and spectral variability
patterns (SVPs) of a typical blazar. We use the MUlti-ZOne Radiation Feedback
(MUZORF) model of Joshi et al. (2014) to carry out this study and to relate the
geometry of the field to the observed SEDs at X-ray and gamma-ray energies.
  One of the goals of the study is to understand the relationship between
synchrotron and inverse Compton peaks in blazar SEDs and the reason for the
appearance of gamma-ray "orphan flares" observed in some blazars. This can be
associated with the directionality of the magnetic field, which creates a
difference in the radiation field as seen by an observer versus that seen by
the electrons in the emission region.


title: Minimal Skew energy of oriented bicyclic graphs with a given diameter

abstract:
  Let $S(G^{\sigma})$ be the skew-adjacency matrix of the oriented graph
$G^{\sigma}$, which is obtained from a simple undirected graph $G$ by assigning
an orientation $\sigma$ to each of its edges. The skew energy of an oriented
graph $G^{\sigma}$ is defined as the sum of absolute values of all eigenvalues
of $S(G^{\sigma})$. For any positive integer $d$ with $3\leq d\leq n-3$, we
determine the graph with minimal skew energy among all oriented bicyclic graphs
that contain no vertex disjoint odd cycle of lengths $s$ and $l$ with
$s+l\equiv 2(mod 4)$ on $n$ vertices with a given diameter $d$.


title: The role of phases in detecting three-qubit entanglement

abstract:
  We propose separability criteria for three-qubit states in terms of diagonal
and anti-diagonal entries to detect entanglement with positive partial
transposes. We report that the phases, that is, the angular parts of
anti-diagonal entries, play a crucial role in determining whether a given
three-qubit state is separable or entangled, and they must obey even an
identity for separability in some cases. These criteria are strong enough to
detect PPT (positive partial transpose) entanglement with nonzero volume. In
several cases when all the entries are zero except for diagonal and
anti-diagonal entries, we characterize separability using phases. These include
the cases when anti-diagonal entries of such states share a common magnitude,
and when ranks are less than or equal to six. We also compute the lengths of
rank six cases, and find three-qubit separable states with lengths $8$ whose
maximum ranks of partial transposes are $7$.


title: The Computational Complexity of Ball Permutations

abstract:
  Inspired by connections to two dimensional quantum theory, we define several
models of computation based on permuting distinguishable particles (which we
call balls), and characterize their computational complexity. In the quantum
setting, we find that the computational power of this model depends on the
initial input states. More precisely, with a standard basis input state, we
show how to approximate the amplitudes of this model within additive error
using the model DQC1 (the class of problems solvable with one clean qubit),
providing evidence that the model in this case is weaker than universal quantum
computing. However, for specific choices of input states, the model is shown to
be universal for BQP in an encoded sense. We use representation theory of the
symmetric group to partially classify the computational complexity of this
model for arbitrary input states. Interestingly, we find some input states
which yield a model intermediate between DQC1 and BQP. Furthermore, we consider
a restricted version of this model based on an integrable scattering problem in
1+1 dimensions. We show it is universal under postselection, if we allow
intermediate destructive measurements and specific input states. Therefore, the
existence of any classical procedure to sample from the output distribution of
this model within multiplicative error implies collapse of polynomial hierarchy
to its third level. Finally, we define a classical version of this model in
which one can probabilistically permute balls. We find this yields a complexity
class which is intermediate between L and BPP. Moreover, we find a
nondeterministic version of this model is NP-complete.


title:
Photoproduction of Upsilon states in ultraperipheral collisions at the
  CERN Large Hadron Collider within the color dipole approach

abstract:
  The exclusive photoproduction of upsilon states $\Upsilon(1S)$ and its
radially excited states $\Upsilon(2S,3S)$ is investigated in the context of
ultra-peripheral collisions at the LHC energies. Predictions are presented for
their production in proton-proton, proton-nucleus and nucleus-nucleus collision
at the energies available at the LHC run 2. The rapidity and transverse
momentum distributions are shown, and the robustness of the model is tested
against the experimental results considering $\psi(1S,2S)$ and $\Upsilon(1S)$
states. The theoretical framework considered in the analysis is the light-cone
color dipole formalism, which includes consistently parton saturation effects
and nuclear shadowing corrections.


title: KMS states on the operator algebras of reducible higher-rank graphs

abstract:
  We study the equilibrium or KMS states of the Toeplitz C*-algebra of a finite
higher-rank graph which is reducible. The Toeplitz algebra carries a gauge
action of a higher-dimensional torus, and a dynamics arises by choosing an
embedding of the real numbers in the torus. Here we use an embedding which
leads to a dynamics which has previously been identified as "preferred", and we
scale the dynamics so that 1 is a critical inverse temperature. As with
1-graphs, we study the strongly connected components of the vertices of the
graph. The behaviour of the KMS states depends on both the graphical
relationships between the components and the relative size of the spectral
radii of the vertex matrices of the components.
  We test our theorems on graphs with two connected components. We find that
our techniques give a complete analysis of the KMS states with inverse
temperatures down to a second critical temperature beta_c<1.


title:
Electric dipole moments of charged leptons at one loop in the presence
  of massive neutrinos

abstract:
  Violation of $CP$ invariance is a quite relevant phenomenon that is found in
the Standard Model (SM), though in small amounts. This has been an incentive to
look for high-energy descriptions in which $CP$ violation is increased, thus
enhancing effects that are suppressed in the SM, such as the electric dipole
moments (EDMs) of elementary particles. In the present investigation, we point
out that charged currents in which axial couplings are different from vector
couplings are able to produce one-loop contributions to EDMs of charged leptons
if neutrinos are massive and if these currents violate $CP$. We develop our
discussion around charged currents involving heavy neutrinos and a $W'$ gauge
boson coupling to SM charged leptons. Using the most stringent bound on the
electron EDM, provided by the ACME Collaboration, we determine that the upper
bound on the difference between axial and vector currents lies within
$\sim10^{-10}$ and $\sim10^{-7}$ for heavy-neutrino masses between $0.5\,{\rm
TeV}$ and $6\,{\rm TeV}$ and if the $W'$ mass is within $0.45\,{\rm
TeV}-7\,{\rm TeV}$. This possibility is analyzed altogether with the anomalous
magnetic moments of charged leptons, among which we estimate, for the $\tau$
lepton, an anomalous magnetic moment contribution between $\sim10^{-8}$ and
$\sim10^{-10}$ for neutrino masses ranging from $0.5\,{\rm TeV}$ to $6\,{\rm
TeV}$ and a $W'$ mass between $0.45\,{\rm TeV}$ and $7\,{\rm TeV}$. The general
charged currents are also used to calculate the branching ratio for $\mu\to
e\gamma$, which gets suppressed if the set of masses of heavy neutrinos is
quasidegenerate. In a scenario of nondegenerate neutrino masses, we find that
regions of neutrino and $W'$ masses in which the contributions to this flavor
changing branching ratio are lower than the current upper bound exist. We show
that such regions can be widened if the $W'$ gauge boson mass is larger.


title: Parametric Auto-Excitation of Magnetic Droplet Soliton Perimeter Modes

abstract:
  Recent experiments performed in current-driven nano-contacts with strong
perpendicular anisotropy have shown that spin-transfer torque can drive
self-localized spin waves [1, 2] that above a certain threshold intensity can
condense into a highly nonlinear magnetodynamic and nano-sized state known as a
magnetic droplet soliton [3]. Here we demonstrate analytically, numerically,
and experimentally that at sufficiently large driving currents, and for a spin
polarization that is tilted away from the film normal, the circular droplet
soliton can become unstable to periodic excitations of its perimeter. We
furthermore show that these perimeter excitation modes (PEMs) are
parametrically excited when the fundamental droplet soliton precession
frequency is close to twice the frequency of one or more of the PEMs. As a
consequence, for increasing applied fields, progressively higher PEMs can be
excited. Quantitative agreement with experiment confirms this picture.


title:
Chromospheric polarimetry through multi-line observations of the 850 nm
  spectral region

abstract:
  Future solar missions and ground-based telescopes aim to understand the
magnetism of the solar chromosphere. We performed a supporting study in
Quintero Noda et al. (2016) focused on the infrared Ca II 8542 A line and we
concluded that is one of the best candidates because it is sensitive to a large
range of atmospheric heights, from the photosphere to the middle chromosphere.
However, we believe that it is worth to try improving the results produced by
this line observing additional spectral lines. In that regard, we examined the
neighbour solar spectrum looking for spectral lines that could increase the
sensitivity to the atmospheric parameters. Interestingly, we discovered several
photospheric lines that greatly improve the photospheric sensitivity to the
magnetic field vector. Moreover, they are located close to a second
chromospheric line that also belongs to the Ca II infrared triplet, i.e. the Ca
II 8498 A line, and enhances the sensitivity to the atmospheric parameters at
chromospheric layers. We conclude that the lines in the vicinity of the Ca II
8542 A line not only increase its sensitivity to the atmospheric parameters at
all layers, but also they constitute an excellent spectral window for
chromospheric polarimetry.


title:
Enhancing quantum correlations and entanglement in an optomechanical
  system via cross-Kerr nonlinearity

abstract:
  In this work, we theoretically study the quantum correlations present in an
optomechanical system by invoking an additional cross-Kerr coupling between the
optical and mechanical mode. Under experimentally achievable conditions, we
first show that a significant enhancement of the steady-state entanglement
could be achieved at a considerably lower driving power, which is also
extremely robust with respect to system parameters and environmental
temperature. Then, we employ Gaussian quantum discord as a witness of the
genuine quantumness of the correlation present in the system and discuss its
dependence on the cross-Kerr nonlinearity.


title:
Achiral symmetry breaking and positive Gaussian modulus lead to
  scalloped colloidal membranes

abstract:
  In the presence of a non-adsorbing polymer, monodisperse rod-like particles
assemble into colloidal membranes, which are one rod-length thick liquid-like
monolayers of aligned rods. Unlike 3D edgeless bilayer vesicles, colloidal
monolayer membranes form open structures with an exposed edge, thus presenting
an opportunity to study physics of thin elastic sheets. Membranes assembled
from single-component chiral rods form flat disks with uniform edge twist. In
comparison, membranes comprised of mixture of rods with opposite chiralities
can have the edge twist of either handedness. In this limit disk-shaped
membranes become unstable, instead forming structures with scalloped edges,
where two adjacent lobes with opposite handedness are separated by a
cusp-shaped point defect. Such membranes adopt a 3D configuration, with cusp
defects alternatively located above and below the membrane plane. In the
achiral regime the cusp defects have repulsive interactions, but away from this
limit we measure effective long-ranged attractive binding. A phenomenological
model shows that the increase in the edge energy of scalloped membranes is
compensated by concomitant decrease in the deformation energy due to Gaussian
curvature associated with scalloped edges, demonstrating that colloidal
membranes have positive Gaussian modulus. A simple excluded volume argument
predicts the sign and magnitude of the Gaussian curvature modulus that is in
agreement with experimental measurements. Our results provide insight into how
the interplay between membrane elasticity, geometrical frustration and achiral
symmetry breaking can be used to fold colloidal membranes into 3D shapes.


title: Partitions of Equiangular Tight Frames

abstract:
  We present a new efficient algorithm to construct partitions of a special
class of equiangular tight frames (ETFs) that satisfy the operator norm bound
established by a theorem of Marcus, Spielman, and Srivastava (MSS), which they
proved as a corollary yields a positive solution to the Kadison-Singer problem.
In particular, we prove that certain diagonal partitions of complex ETFs
generated by recursive skew-symmetric conference matrices yield a refinement of
the MSS bound. Moreover, we prove that all partitions of ETFs whose largest
subset has cardinality three or less also satisfy the MSS bound.


title:
Immune Therapeutic Strategies Using Optimal Controls with $L^1$ and
  $L^2$ Type Objectives

abstract:
  Therapeutic strategies to correct an excessive immune response to pathogenic
infection is investigated as an optimal control problem. The control problem is
formulated around a four dimensional mathematical model describing the
inflammatory response to a pathogenic insult with two therapeutic control
inputs which have either a direct pro- or anti-inflammatory effect in the given
system. We use Pontryagin's maximum principle and discuss necessary optimality
conditions. We consider both an $L^1$ type objective functional as well as an
$L^2$ type objective. For the former, the presence of singular control will be
addressed. For each case, numerical simulations using a nonlinear programming
optimization solver to acquire different drug treatment strategies are
presented and discussed. The results provide insight for possible treatment
strategies and the methods could be a relevant tool for future practice to
assist in better prediction of clinical outcomes and subsequently better
treatment for patients.


title: Single Pass PCA of Matrix Products

abstract:
  In this paper we present a new algorithm for computing a low rank
approximation of the product $A^TB$ by taking only a single pass of the two
matrices $A$ and $B$. The straightforward way to do this is to (a) first sketch
$A$ and $B$ individually, and then (b) find the top components using PCA on the
sketch. Our algorithm in contrast retains additional summary information about
$A,B$ (e.g. row and column norms etc.) and uses this additional information to
obtain an improved approximation from the sketches. Our main analytical result
establishes a comparable spectral norm guarantee to existing two-pass methods;
in addition we also provide results from an Apache Spark implementation that
shows better computational and statistical performance on real-world and
synthetic evaluation datasets.


title: Multispectral Kerr frequency comb initiated by Faraday ripples

abstract:
  In a uniform microresonator, the generation of a broadband Kerr frequency
comb is triggered by Turing patterns. Here, we study a distinctly different
route to initiate the Kerr frequency comb by Faraday ripples. Momentum
conservation is ensured by azimuthal modulation of the cavity dispersion. With
a good agreement with the theoretical analysis, we demonstrate a multispectral
Kerr frequency comb covering telecommunication O, C, L, and 2 {\mu}m bands.
Comb coherence and absence of a subcomb offset are confirmed by cw heterodyne
beat note and amplitude noise spectra measurements. The device can be used for
achieving broadband optical frequency synthesizer and high-capacity coherent
telecommunication.


title: Public Computation & Boundary Play

abstract:
  In this paper, we introduce 'public computation' as a genre of learning
environments that can be used to radically broaden public participation in
authentic, computation-enabled STEM disciplinary practices. Our paradigmatic
approach utilizes open source software designed for professional scientists,
engineers and digital artists, and situates them in an undiluted form,
alongside live and archived expert support, in a public space. We present a
case study of DigiPlay, a prototypical public computation space we designed at
the University of Calgary, where users can interact directly with scientific
simulations as well as the underlying open source code using an array of
massive multi- touch screens. We argue that in such a space, public
interactions with the code can be thought of as boundary work and play, through
which public participation becomes legitimate scientific act, as the public
engages in scientific creation through truly open-ended explorations with the
code.


title:
Analysis of One-Bit Quantized Precoding for the Multiuser Massive MIMO
  Downlink

abstract:
  We present a mathematical analysis of linear precoders for downlink massive
MIMO multiuser systems that employ one-bit digital-to-analog converters at the
basestation in order to reduce complexity and mitigate power usage. The
analysis is based on the Bussgang theorem, and applies generally to any linear
precoding scheme. We examine in detail the special case of the quantized
zero-forcing (ZF) precoder, and derive a simple asymptotic expression for the
resulting symbol error rate at each terminal. Our analysis illustrates that the
performance of the quantized ZF precoder depends primarily on the ratio of the
number of antennas to the number of users, and our simulations show that it can
outperform the much more complicated maximum likelihood encoder for
low-to-moderate signal to noise ratios, where massive MIMO systems are presumed
to operate. We also use the Bussgang theorem to derive a new linear precoder
optimized for the case of one-bit quantization, and illustrate its improved
performance.


title:
Semistochastic Heat-bath Configuration Interaction method: selected
  configuration interaction with semistochastic perturbation theory

abstract:
  We extend the recently proposed heat-bath configuration interaction (HCI)
method [Holmes, Tubman, Umrigar, J. Chem. Theory Comput. 12, 3674 (2016)], by
introducing a semistochastic algorithm for performing multireference
Epstein-Nesbet perturbation theory, in order to completely eliminate the severe
memory bottleneck of the original method. The proposed algorithm has several
attractive features. First, there is no sign problem that plagues several
quantum Monte Carlo methods. Second, instead of using Metropolis-Hastings
sampling, we use the Alias method to directly sample determinants from the
reference wavefunction, thus avoiding correlations between consecutive samples.
Third, in addition to removing the memory bottleneck, semistochastic HCI (SHCI)
is faster than the deterministic variant for many systems if a stochastic error
of 0.1 mHa is acceptable. Fourth, within the SHCI algorithm one can trade
memory for a modest increase in computer time. Fifth, the perturbative
calculation is embarrassingly parallel. The SHCI algorithm extends the range of
applicability of the original algorithm, allowing us to calculate the
correlation energy of very large active spaces. We demonstrate this by
performing calculations on several first row dimers including F2 with an active
space of (14e, 108o), Mn-Salen cluster with an active space of (28e, 22o), and
Cr2 dimer with up to a quadruple-zeta basis set with an active space of (12e,
190o). For these systems we were able to obtain better than 1 mHa accuracy with
a wall time of merely 55 seconds, 37 seconds, and 56 minutes on 1, 1, and 4
nodes, respectively.


title:
Spin transport and dynamics in all-oxide perovskite
  La$_{2/3}$Sr$_{1/3}$MnO$_3$/SrRuO$_3$ bilayers probed by ferromagnetic
  resonance

abstract:
  Thin films of perovskite oxides offer the possibility of combining emerging
concepts of strongly correlated electron phenomena and spin current in magnetic
devices. However, spin transport and magnetization dynamics in these complex
oxide materials are not well understood. Here, we experimentally quantify spin
transport parameters and magnetization damping in epitaxial perovskite
ferromagnet/paramagnet bilayers of La$_{2/3}$Sr$_{1/3}$MnO$_3$/SrRuO$_3$
(LSMO/SRO) by broadband ferromagnetic resonance spectroscopy. From the SRO
thickness dependence of Gilbert damping, we estimate a short spin diffusion
length of $\lesssim$1 nm in SRO and an interfacial spin-mixing conductance
comparable to other ferromagnet/paramagnetic-metal bilayers. Moreover, we find
that anisotropic non-Gilbert damping due to two-magnon scattering also
increases with the addition of SRO. Our results demonstrate LSMO/SRO as a
spin-source/spin-sink system that may be a foundation for examining
spin-current transport in various perovskite heterostructures.


title: Unveiling the Multi-fractal Structure of Complex Networks

abstract:
  The fractal nature of graphs has traditionally been investigated by using the
nodes of networks as the basic units. Here, instead, we propose to concentrate
on the graph edges, and introduce a practical and computationally not demanding
method for revealing changes in the fractal behavior of networks, and
particularly for allowing distinction between mono-fractal, quasi mono-fractal,
and multi-fractal structures. We show that degree homogeneity plays a crucial
role in determining the fractal nature of the underlying network, and report on
six different protein-protein interaction networks along with their
corresponding random networks. Our analysis allows to identify varying levels
of complexity in the species.


title: On torsion-free nilpotent loops

abstract:
  We show that a torsion-free nilpotent loop (that is, a loop nilpotent with
respect to the dimension filtration) has a torsion-free nilpotent left
multiplication group of, at most, the same class. We also prove that a free
loop is residually torsion-free nilpotent and that the same holds for any free
commutative loop. Although this last result is much stronger than the usual
residual nilpotency of the free loop proved by Higman, it is proved,
essentially, by the same method.


title: Stochastic Gradient MCMC with Stale Gradients

abstract:
  Stochastic gradient MCMC (SG-MCMC) has played an important role in
large-scale Bayesian learning, with well-developed theoretical convergence
properties. In such applications of SG-MCMC, it is becoming increasingly
popular to employ distributed systems, where stochastic gradients are computed
based on some outdated parameters, yielding what are termed stale gradients.
While stale gradients could be directly used in SG-MCMC, their impact on
convergence properties has not been well studied. In this paper we develop
theory to show that while the bias and MSE of an SG-MCMC algorithm depend on
the staleness of stochastic gradients, its estimation variance (relative to the
expected estimate, based on a prescribed number of samples) is independent of
it. In a simple Bayesian distributed system with SG-MCMC, where stale gradients
are computed asynchronously by a set of workers, our theory indicates a linear
speedup on the decrease of estimation variance w.r.t. the number of workers.
Experiments on synthetic data and deep neural networks validate our theory,
demonstrating the effectiveness and scalability of SG-MCMC with stale
gradients.


title:
On the Convergence of Stochastic Gradient MCMC Algorithms with
  High-Order Integrators

abstract:
  Recent advances in Bayesian learning with large-scale data have witnessed
emergence of stochastic gradient MCMC algorithms (SG-MCMC), such as stochastic
gradient Langevin dynamics (SGLD), stochastic gradient Hamiltonian MCMC
(SGHMC), and the stochastic gradient thermostat. While finite-time convergence
properties of the SGLD with a 1st-order Euler integrator have recently been
studied, corresponding theory for general SG-MCMCs has not been explored. In
this paper we consider general SG-MCMCs with high-order integrators, and
develop theory to analyze finite-time convergence properties and their
asymptotic invariant measures. Our theoretical results show faster convergence
rates and more accurate invariant measures for SG-MCMCs with higher-order
integrators. For example, with the proposed efficient 2nd-order symmetric
splitting integrator, the {\em mean square error} (MSE) of the posterior
average for the SGHMC achieves an optimal convergence rate of $L^{-4/5}$ at $L$
iterations, compared to $L^{-2/3}$ for the SGHMC and SGLD with 1st-order Euler
integrators. Furthermore, convergence results of decreasing-step-size SG-MCMCs
are also developed, with the same convergence rates as their fixed-step-size
counterparts for a specific decreasing sequence. Experiments on both synthetic
and real datasets verify our theory, and show advantages of the proposed method
in two large-scale real applications.


title:
Short-term prediction of localized cloud motion using ground-based sky
  imagers

abstract:
  Fine-scale short-term cloud motion prediction is needed for several
applications, including solar energy generation and satellite communications.
In tropical regions such as Singapore, clouds are mostly formed by convection;
they are very localized, and evolve quickly. We capture hemispherical images of
the sky at regular intervals of time using ground-based cameras. They provide a
high resolution and localized cloud images. We use two successive frames to
compute optical flow and predict the future location of clouds. We achieve good
prediction accuracy for a lead time of up to 5 minutes.


title: Detecting Rainfall Onset Using Sky Images

abstract:
  Ground-based sky cameras (popularly known as Whole Sky Imagers) are
increasingly used now-a-days for continuous monitoring of the atmosphere. These
imagers have higher temporal and spatial resolutions compared to conventional
satellite images. In this paper, we use ground-based sky cameras to detect the
onset of rainfall. These images contain additional information about cloud
coverage and movement and are therefore useful for accurate rainfall nowcast.
We validate our results using rain gauge measurement recordings and achieve an
accuracy of 89% for correct detection of rainfall onset.


title: Maass Spezialschar of Level N

abstract:
  In this paper the image of the Saito-Kurokawa lift of level $N$ with
Dirichlet character is studied. We give a new characterization of this so
called Maass Spezialschar of level $N$ by symmetries involving Hecke operators
related to $\Gamma_0(N)$. We finally obtain for all prime numbers $p$ local
Maass relations. This generalizes known results for level $N=1$.


title: Scalable Pooled Time Series of Big Video Data from the Deep Web

abstract:
  We contribute a scalable implementation of Ryoo et al's Pooled Time Series
algorithm from CVPR 2015. The updated algorithm has been evaluated on a large
and diverse dataset of approximately 6800 videos collected from a crawl of the
deep web related to human trafficking on DARPA's MEMEX effort. We describe the
properties of Pooled Time Series and the motivation for using it to relate
videos collected from the deep web. We highlight issues that we found while
running Pooled Time Series on larger datasets and discuss solutions for those
issues. Our solution centers are re-imagining Pooled Time Series as a
Hadoop-based algorithm in which we compute portions of the eventual solution in
parallel on large commodity clusters. We demonstrate that our new Hadoop-based
algorithm works well on the 6800 video dataset and shares all of the properties
described in the CVPR 2015 paper. We suggest avenues of future work in the
project.


title:
Stochastic analysis in a tubular neighborhood or Onsager-Machlup
  functions revisited

abstract:
  Yet another proof of Onsager-Machlup formula for diffusion processes on a
Riemannian manifold after Takahashi-Watanabe, Fujita-Kotani. The proof is
purely probabilistic and contains a precise study on an ergodic effect for a
key Wiener functional.


title: Multi-view metric learning for multi-instance image classification

abstract:
  It is critical and meaningful to make image classification since it can help
human in image retrieval and recognition, object detection, etc. In this paper,
three-sides efforts are made to accomplish the task. First, visual features
with bag-of-words representation, not single vector, are extracted to
characterize the image. To improve the performance, the idea of multi-view
learning is implemented and three kinds of features are provided, each one
corresponds to a single view. The information from three views is complementary
to each other, which can be unified together. Then a new distance function is
designed for bags by computing the weighted sum of the distances between
instances. The technique of metric learning is explored to construct a
data-dependent distance metric to measure the relationships between instances,
meanwhile between bags and images, more accurately. Last, a novel approach,
called MVML, is proposed, which optimizes the joint probability that every
image is similar with its nearest image. MVML learns multiple distance metrics,
each one models a single view, to unifies the information from multiple views.
The method can be solved by alternate optimization iteratively. Gradient ascent
and positive semi-definite projection are utilized in the iterations. Distance
comparisons verified that the new bag distance function is prior to previous
functions. In model evaluation, numerical experiments show that MVML with
multiple views performs better than single view condition, which demonstrates
that our model can assemble the complementary information efficiently and
measure the distance between images more precisely. Experiments on influence of
parameters and instance number validate the consistency of the method.


title: The Broadcaster-Repacking Problem

abstract:
  The Federal Communications Commission's (FCC's) ongoing Incentive Auction
will, if successful, transfer billions of dollars of radio spectrum from
television broadcasters to mobile-network operators. Hundreds of broadcasters
may go off the air. Most of those remaining on the air, including hundreds of
Canadian broadcasters not bidding, will have to move to new channels to
continue broadcasting. The auction can only end if all these broadcasters will
fit into the spectrum remaining for television. Whether a given set of
broadcasters fits is the broadcaster-repacking problem. The FCC must calculate
its solutions thousands of times per round of bidding. Speed is essential.
  By reducing the broadcaster-repacking problem to the maximum independent set
problem, we show that the former is $\mathcal{NP}$-complete. This reduction
also allows us to expand on sparsity-exploiting heuristics in the literature,
which have made the FCC's repacking-problem instances tractable. We conclude by
relating the heuristics to satisfiability and integer programming reductions.
These provide a basis for implementing algorithms in off-the-shelf software to
solve the broadcaster-repacking problem.


title: Probabilistic Cosmological Mass Mapping from Weak Lensing Shear

abstract:
  We infer gravitational lensing shear and convergence fields from galaxy
ellipticity catalogs under a spatial process prior for the lensing potential.
We demonstrate the performance of our algorithm with simulated
Gaussian-distributed cosmological lensing shear maps and a reconstruction of
the mass distribution of the merging galaxy cluster Abell 781 using galaxy
ellipticities measured with the Deep Lens Survey. Given interim posterior
samples of lensing shear or convergence fields on the sky, we describe an
algorithm to infer cosmological parameters via lens field marginalization. In
the most general formulation of our algorithm we make no assumptions about weak
shear or Gaussian distributed shape noise or shears. Because we require
solutions and matrix determinants of a linear system of dimension that scales
with the number of galaxies, we expect our algorithm to require parallel
high-performance computing resources for application to ongoing wide field
lensing surveys.


title:
Two-dimensional topological semimetal state in a nanopatterned
  semiconductor system

abstract:
  We propose the creation of a two-dimensional topological semimetal in a
semiconductor artificial lattice with triangular symmetry. An in-plane magnetic
field drives a quantum phase transition between the topological insulating and
topological semimetal phases. The topological semimetal is characterized by
robust band touching points which carry quantized Berry flux and edge states
which terminate at the band touching points. The topological phase transition
is predicted to occur at magnetic fields $\sim 4\text{T}$ in high mobility GaAs
artificial lattices, and can be detected via the anomalous behaviour of the
edge conductance.


title: Black holes in Einsteinian cubic gravity

abstract:
  Using numerical and perturbative methods, we construct the first examples of
black hole solutions in Einsteinian cubic gravity and study their
thermodynamics. Focusing first on four dimensional solutions, we show that
these black holes have a novel equation of state in which the pressure is a
quadratic function of the temperature. Despite this, they undergo a first order
phase transition with associated van der Waals behaviour. We then construct
perturbative solutions for general $D \ge 5$ and study the properties of these
solutions for $D=5$ and $D=6$ in particular. We note that for $D >4$ the
solutions are described by two independent metric functions. We find novel
examples of super-entropic behaviour over a large portion of the parameter
space. We analyse the specific heat, determining that the black holes are
thermodynamically stable over large regions of parameter space.


title:
Implications of CP-violating Top-Higgs Couplings at LHC and Higgs
  Factories

abstract:
  We utilise the LHC Run-1 and -2 Higgs data to constrain the CP-violating
top-Higgs couplings. In order to satisfy the current full Higgs data sets at
$2\sigma$ level, the CP-odd component $C^p_t$ and the CP-even component $C^s_t$
have to be within the ranges $|C^p_t|< 0.37$ and $0.85 <C^s_t< 1.20$,
respectively, which is stronger than the LHC Run-1 bound $|C^p_t|< 0.54$ and
$0.68 <C^s_t< 1.20$. With the new bound, we explore the impact on the
CP-violating top-Higgs couplings in the Higgs production processes $pp \to
t\bar{t}h, thj, hh$ at 13 TeV LHC, and $e^+e^- \to hZ, h\gamma$ at future 240
GeV Higgs factories. We find that the cross sections of $pp \to t\bar{t}h$, $pp
\to thj$, $pp \to hh$, $e^+e^- \to hZ$ and $e^+e^- \to h\gamma$ can be enhanced
up to 1.41, 1.18, 2.20, 1.001 and 1.09 times as large as the SM predictions,
respectively. The future precision measurement of the process $e^+e^- \to
h\gamma$ with an accuracy of 5\% will be able to constrain $|C^p_t|<0.19$ at
most at a 240 GeV $e^+e^-$ Higgs factory.


title: Performance of the PRAXyS X-ray Polarimeter

abstract:
  The performance of the Time Projection Chamber (TPC) polarimeter for the
Polarimeter for Relativistic Astrophysical X-ray Sources (PRAXyS) Small
Explorer was evaluated using polarized and unpolarized X-ray sources. The
PRAXyS mission will enable exploration of the universe through X-ray
polarimetry in the 2-10 keV energy band. We carried out performance tests of
the polarimeter at the Brookhaven National Laboratory, National Synchrotron
Light Source (BNL-NSLS) and at NASA's Goddard Space Flight Center. The
polarimeter was tested with linearly polarized, monochromatic X-rays at 11
different energies between 2.5 and 8.0 keV. At maximum sensitivity, the
measured modulation factors at 2.7, 4.5 and 8.0 keV are 27%, 43% and 59%,
respectively and the measured angle of polarization is consistent with the
expected value at all energies. Measurements with a broadband, unpolarized
X-ray source placed a limit of less than 1% on false polarization in the PRAXyS
polarimeter.


title:
Nonlinear Helicons ---an analytical solution elucidating multi-scale
  structure

abstract:
  The helicon waves exhibit varying characters depending on plasma parameters,
geometry, and wave numbers. Here we elucidate an intrinsic multi-scale property
embodied by the combination of dispersive effect and nonlinearity. The extended
magnetohydrodynamics model (exMHD) is capable of describing wide range of
parameter space. By using the underlying Hamiltonian structure of exMHD, we
construct an exact nonlinear solution which turns out to be a combination of
two distinct modes, the helicon and Trivelpiece-Gould (TG) waves. In the regime
of relatively low frequency or high density, however, the combination is made
of the TG mode and an ion cyclotron wave (slow wave). The energy partition
between these modes is determined by the helicities carried by the wave fields.


title: Invariants of links of Conway type

abstract:
  The purpose of this paper is to present a certain combinatorial method of
constructing invariants of isotopy classes of oriented tame links. This arises
as a generalization of the known polynomial invariants of Conway and Jones.
These invariants have one striking common feature. If L+, L- and L0 are
diagrams of oriented links which are identical, except near one crossing point
(as in Conway or Jones polynomials), then an invariant w(L) has the property:
w(L+) is uniquely determined by w(L-) and w(L0), and also w(L-) is uniquely
determined by w(L+) and w(L0). To formalize this property we introduce a
concept of a Conway algebra and quasi Conway algebra. The paper is now almost
32 years old and it contains the PT contribution to HOMFLYPT polynomial. We
believe it should be available in arXiv.


title:
A Carleman type estimate of variable order space-fractional diffusion
  equations and applications to some inverse problems

abstract:
  Variable order space-fractional diffusion equation derived as an important
model to describe complex anomalous diffusion phenomenon. In this article,
well-posedness theory has been constructed for equations with the "Dirichlet"
or the "Neumann" type volume-constrained conditions by using the technique of
the nonlocal vector calculus. Then some regularity properties have been
obtained under the variable-order Sobolev space framework. By choosing a
space-independent weight function and using the technique of the nonlocal
vector calculus, a Carleman type estimate has been obtained. At last, the
Carleman type estimate has been used both to a backward diffusion problem and
an inverse source problem to obtain some uniqueness and stability results.


title:
A Convex Programming-based Algorithm for Mean Payoff Stochastic Games
  with Perfect Information

abstract:
  We consider two-person zero-sum stochastic mean payoff games with perfect
information, or BWR-games, given by a digraph $G = (V, E)$, with local rewards
$r: E \to \ZZ$, and three types of positions: black $V_B$, white $V_W$, and
random $V_R$ forming a partition of $V$. It is a long-standing open question
whether a polynomial time algorithm for BWR-games exists, even when $|V_R|=0$.
In fact, a pseudo-polynomial algorithm for BWR-games would already imply their
polynomial solvability. In this short note, we show that BWR-games can be
solved via convex programming in pseudo-polynomial time if the number of random
positions is a constant.


title:
KATANA - a charge-sensitive triggering system for the S$\pi$RIT
  experiment

abstract:
  KATANA - the Krakow Array for Triggering with Amplitude discrimiNAtion - has
been built and used as a trigger and veto detector for the S$\pi$RIT TPC at
RIKEN. Its construction allows operating in magnetic field and providing fast
response for ionizing particles, giving the approximate forward multiplicity
and charge information. Depending on this information, trigger and veto signals
are generated. The article presents performance of the detector and details of
its construction. A simple phenomenological parametrization of the number of
emitted scintillation photons in plastic scintillator is proposed. The effect
of the light output deterioration in the plastic scintillator due to the
in-beam irradiation is discussed.


title:
New Survey Questions and Estimators for Network Clustering with
  Respondent-Driven Sampling Data

abstract:
  Respondent-driven sampling (RDS) is a popular method for sampling
hard-to-survey populations that leverages social network connections through
peer recruitment. While RDS is most frequently applied to estimate the
prevalence of infections and risk behaviors of interest to public health, like
HIV/AIDS or condom use, it is rarely used to draw inferences about the
structural properties of social networks among such populations because it does
not typically collect the necessary data. Drawing on recent advances in
computer science, we introduce a set of data collection instruments and RDS
estimators for network clustering, an important topological property that has
been linked to a network's potential for diffusion of information, disease, and
health behaviors. We use simulations to explore how these estimators,
originally developed for random walk samples of computer networks, perform when
applied to RDS samples with characteristics encountered in realistic field
settings that depart from random walks. In particular, we explore the effects
of multiple seeds, without vs. with replacement, branching chains, imperfect
response rates, preferential recruitment, and misreporting of ties. We find
that clustering coefficient estimators retain desirable properties in RDS
samples. This paper takes an important step towards calculating network
characteristics using non-traditional sampling methods, and it expands RDS's
potential to tell researchers more about hidden populations and the social
factors driving disease prevalence.


title:
Blow-up for a Three Dimensional Keller-Segel Model with Consumption of
  Chemoattractant

abstract:
  We investigate blow-up properties for the initial-boundary value problem of a
Keller-Segel model with consumption of chemoattractant when the spatial
dimension is three. Through a kinetic reformulation of the Keller-Segel model,
we first derive some higher-order estimates and obtain certain blow-up criteria
for the local classical solutions. These blow-up criteria generalize the
results in [4,5] from the whole space $\mathbb{R}^3$ to the case of bounded
smooth domain $\Omega\subset \mathbb{R}^3$. Lower global blow-up estimate on
$\|n\|_{L^\infty(\Omega)}$ is also obtained based on our higher-order
estimates. Moreover, we prove local non-degeneracy for blow-up points.


title:
Error estimates with explicit constants for the Sinc approximation over
  infinite intervals

abstract:
  The Sinc approximation is a function approximation formula that attains
exponential convergence for rapidly decaying functions defined on the whole
real axis. Even for other functions, the Sinc approximation works accurately
when combined with a proper variable transformation. The convergence rate has
been analyzed for typical cases including finite, semi-infinite, and infinite
intervals. Recently, for verified numerical computations, a more explicit,
"computable" error bound has been given in the case of a finite interval. In
this paper, such explicit error bounds are derived for other cases.


title:
Current Redistribution in Resistor Networks: Fat-Tail Statistics in
  Regular and Small-World Networks

abstract:
  The redistribution of electrical currents in resistor networks after
single-bond failures is analyzed in terms of current-redistribution factors
that are shown to depend only on the topology of the network and on the values
of the bond resistances. We investigate the properties of these
current-redistribution factors for regular network topologies (e.g.
$d$-dimensional hypercubic lattices) as well as for small-world networks. In
particular, we find that the statistics of the current redistribution factors
exhibits a fat-tail behavior, which reflects the long-range nature of the
current redistribution as determined by Kirchhoff's circuit laws.


title:
Target decoupling in a coupled optical system resistant to random
  perturbation

abstract:
  To suppress unwanted crosstalks between nearby optical elements, the
decoupling technique for integrated systems has been desired for the target
control of light flows. Although cloaking methods have enabled complete
decoupling of optical elements by manipulating electromagnetic waves
microscopically, it is neither feasible nor necessary to control each unit
element in coupled systems when considering severe restrictions on material
parameters for cloaking. Here we develop the macroscopic approach to design
crosstalk-free regions in coupled optical systems. By inversely designing the
eigenstate which encompasses target elements, the stable decoupling of the
elements from the coupled system is achieved, being completely independent from
the random alteration of the decoupled region, and at the same time, allowing
coherent and scattering-free wave transport with desired spatial profiles. We
also demonstrate the decoupling in disordered systems, overcoming the transport
blockade from Anderson localization. Our results provide an attractive solution
for 'target hiding' of elements inside coupled systems.


title:
Multispectral image denoising with optimized vector non-local mean
  filter

abstract:
  Nowadays, many applications rely on images of high quality to ensure good
performance in conducting their tasks. However, noise goes against this
objective as it is an unavoidable issue in most applications. Therefore, it is
essential to develop techniques to attenuate the impact of noise, while
maintaining the integrity of relevant information in images. We propose in this
work to extend the application of the Non-Local Means filter (NLM) to the
vector case and apply it for denoising multispectral images. The objective is
to benefit from the additional information brought by multispectral imaging
systems. The NLM filter exploits the redundancy of information in an image to
remove noise. A restored pixel is a weighted average of all pixels in the
image. In our contribution, we propose an optimization framework where we
dynamically fine tune the NLM filter parameters and attenuate its computational
complexity by considering only pixels which are most similar to each other in
computing a restored pixel. Filter parameters are optimized using Stein's
Unbiased Risk Estimator (SURE) rather than using ad hoc means. Experiments have
been conducted on multispectral images corrupted with additive white Gaussian
noise and PSNR and similarity comparison with other approaches are provided to
illustrate the efficiency of our approach in terms of both denoising
performance and computation complexity.


title: A geometric second main theorem

abstract:
  We prove a truncated second main theorem in the projective plane for entire
curves which cluster on an algebraic curve.


title: Analog rotating black holes in a magnetohydrodynamic inflow

abstract:
  We present a model of the analog geometry in a magnetohydrodynamic (MHD)
flow. For the MHD flow with magnetic pressure-dominated and gas
pressure-dominated conditions, we obtain the magnetoacoustic metric for the
fast MHD mode. For the slow MHD mode, on the other hand, the wave is governed
by the advective-type equation without an isotropic dispersion term. Thus, the
"distance" perpendicular to the wave propagation is not defined and the
magnetoacoustic metric cannot be introduced. To investigate the properties of
the magnetoacoustic geometry for the fast mode, we prepare a two-dimensional
axisymmetric inflow and examine the behavior of magnetoacoustic rays which is a
counterpart of the MHD waves in the eikonal limit. We find that the
magnetoacoustic geometry is classified into three types depending on two
parameters characterizing the background flow:~analog spacetimes of rotating
black holes, ultra spinning stars with ergoregions, and spinning stars without
ergoregions. We address the effects of the magnetic pressure on the effective
geometries.


title:
Tempered Fractional Multistable Motion and Tempered Multifractional
  Stable Motion

abstract:
  This work defines two classes of processes, that we term {\it tempered
fractional multistable motion} and {\it tempered multifractional stable
motion}. They are extensions of fractional multistable motion and
multifractional stable motion, respectively, obtained by adding an exponential
tempering to the integrands. We investigate certain basic features of these
processes, including scaling property, tail probabilities, absolute moment,
sample path properties, pointwise H\"{o}lder exponent, H\"{o}lder continuity of
quasi norm, (strong) localisability and semi-long-range dependence structure.
These processes may provide useful models for data that exhibit both dependence
and varying local regularity/intensity of jumps.


title: An electric-field representation of the harmonic XY model

abstract:
  The two-dimensional harmonic XY (HXY) model is a spin model in which the
classical spins interact via a piecewise parabolic potential. We argue that the
HXY model should be regarded as the canonical classical lattice spin model of
phase fluctuations in two-dimensional condensates, as it is the simplest model
that guarantees the modular symmetry of the experimental systems. Here we
formulate a lattice electric-field representation of the HXY model and contrast
this with an analogous representation of the Villain model and the
two-dimensional Coulomb gas with a purely rotational auxiliary field. We find
that the HXY model is a spin-model analogue of a lattice electric-field model
of the Coulomb gas with an auxiliary field, but with a temperature-dependent
vacuum (electric) permittivity that encodes the coupling of the spin vortices
to their background spin-wave medium. The spin vortices map to the Coulomb
charges, while the spin-wave fluctuations correspond to auxiliary-field
fluctuations. The coupling explains the striking differences in the
high-temperature asymptotes of the specific heats of the HXY model and the
Coulomb gas with an auxiliary field. Our results elucidate the propagation of
effective long-range interactions throughout the HXY model (whose interactions
are purely local) by the lattice electric fields. They also imply that global
spin-twist excitations (topological-sector fluctuations) generated by local
spin dynamics are ergodically excluded in the low-temperature phase. We discuss
the relevance of these results to condensate physics.


title: Exact $\nabla^4 R^4$ couplings and helicity supertraces

abstract:
  In type II string theory compactified on a $d$-dimensional torus $T^d$ down
to $D=10-d$ dimensions, the $R^4$ and $\nabla^4 R^4$ four-graviton couplings
are known exactly, for all values of the moduli, in terms of certain Eisenstein
series of the U-duality group $E_{d}(\mathbb{Z})$. In the limit where one
circle in the torus becomes large, these couplings are expected to reduce to
their counterpart in dimension $D+1$, plus threshold effects and exponentially
suppressed corrections corresponding to BPS black holes in dimension $D+1$
whose worldline winds around the circle. By combining the weak coupling and
large radius limits, we determine these exponentially suppressed corrections
exactly, and demonstrate that the contributions of 1/4-BPS black holes to the
$\nabla^4 R^4$ coupling are proportional to the appropriate helicity
supertrace. Mathematically, our results provide the complete Fourier expansion
of the next-to-minimal theta series of $E_{d+1}(\mathbb{Z})$ with respect to
the maximal parabolic subgroup with Levi component $E_{d}$ for $d\leq 6$, and
the complete Abelian part of the Fourier expansion of the same for $d=7$.


title:
ODIN: Obfuscation-based privacy preserving consensus algorithm for
  Decentralized Information fusion in smart device Networks

abstract:
  The large spread of sensors and smart devices in urban infrastructures are
motivating research in the area of Internet of Thing (IoT), to develop new
services and improve citizens' quality of life. Sensors and smart devices
generate large amount of measurement data from sensing the environment, which
is used to enable services, such as control power consumption or traffic
density. To deal with such a large amount of information, and provide accurate
measurements, service providers can adopt information fusion, which, given the
decentralized nature of urban deployments, can be performed by means of
consensus algorithms. These algorithms allow distributed agents to
(iteratively) compute linear functions on the exchanged data, and take
decisions based on the outcome, without the need for the support of a central
entity. However, the use of consensus algorithms raises several security
concerns, especially when private or security critical information are involved
in the computation. This paper proposes ODIN, a novel algorithm that allows
information fusion over encrypted data. ODIN is a privacy-preserving extension
of the popular consensus gossip algorithm, that prevents distributed agents
have direct access to the data while they iteratively reach consensus; agents
cannot access even the final consensus value, but can only retrieve partial
information, e.g., a binary decision. ODIN uses efficient additive obfuscation
and proxy re-encryption during the update steps, and Garbled Circuits to take
final decisions on the obfuscated consensus. We discuss the security of our
proposal, and show its practicability and efficiency on real-world resource
constrained devices, developing a prototype implementation for Raspberry Pi
devices.


title:
Electromotive forces generated in 3d-transition ferromagnetic metal
  films themselves under their ferromagnetic resonance

abstract:
  We report the electromotive force (EMF) properties generated in 3d-transition
ferromagnetic metal (FM = Fe, Co, and Ni80Fe20) films themselves under their
ferromagnetic resonance (FMR). For Fe and Co films, the EMF due to the
anomalous-Hall effect is dominantly generated under their FMR. Meanwhile, for a
Ni80Fe20 film, the EMF due to the inverse spin-Hall effect in the Ni80Fe20 film
itself under the FMR is mainly generated. This tendency is qualitatively
explained with differences of the spin polarization, the spin Hall
conductivity, the anomalous Hall conductivity, the magnetization saturation,
and the resistivity of the FM films.


title:
Distal actions on coset spaces in totally disconnected, locally compact
  groups

abstract:
  Let $G$ be a totally disconnected, locally compact group and let $H$ be an
equicontinuously (for example, compactly) generated group of automorphisms of
$G$. We show that every distal action of $H$ on a coset space of $G$ is a SIN
action, with the small invariant neighbourhoods arising from open $H$-invariant
subgroups. We obtain a number of consequences for the structure of the
collection of open subgroups. For example, it follows that for every compactly
generated subgroup $K$ of $G$, there is a compactly generated open subgroup $E$
of $G$ such that $K \le E$ and such that every open subgroup of $G$ containing
a finite index subgroup of $K$ contains a finite index subgroup of $E$. We also
show that for a large class of closed subgroups $L$ of $G$ (including for
instance all closed subgroups $L$ such that $L$ is an intersection of subnormal
subgroups of open subgroups), every compactly generated open subgroup of $L$
can be realized as $L \cap O$ for an open subgroup of $G$.


title: Reproducing pairs and Gabor systems at critical density

abstract:
  We use the concept of reproducing pairs to study Gabor systems at critical
density. First, we present a generalization of the Balian-Low theorem to the
reproducing pairs setting. Then, we prove our main result that there exists a
reproducing partner for the Gabor system of integer time-frequency shifts of
the Gaussian. In other words, the coefficients for this Gabor expansion of a
square integrable function can be calculated using inner products with an
unstructured family of vectors in $ L^2(\R)$. This solves the possibly last
open question for this system.