title:
Color ice states, weathervane modes, and order by disorder in the
  bilinear-biquadratic pyrochlore Heisenberg antiferromagnet

abstract:
  We study the pyrochlore Heisenberg antiferromagnet with additional positive
biquadratic interaction in the semiclassical limit. The classical ground state
manifold of the model contains an extensively large family of non-coplanar spin
states known as "color ice states". Starting from a color ice state, a subset
of spins may rotate collectively at no energy cost. Such excitation may be
viewed in this three-dimensional system as a "membrane-like" analog of the
well-known weathervane modes in the classical kagome Heisenberg
antiferromagnet. We investigate the weathervane modes in detail and elucidate
their physical properties. Furthermore, we study the order by disorder
phenomenon in this model, focusing on the role of harmonic fluctuations. Our
computationally-limited phase space search suggests that quantum fluctuations
select three different states as the magnitude of the biquadratic interaction
increases relative to the bilinear interaction, implying a sequence of phase
transitions solely driven by fluctuations.


title: Structure of Stable Binary Neutron Star Merger Remnants: a Case Study

abstract:
  In this work, we study the merger of two neutron stars with a gravitational
mass of 1.4 M_sol each, employing the Shen-Horowitz-Teige equation of state.
This equation of state is a corner case, allowing the formation of a stable
neutron star with the given total baryonic mass of 3.03 M_sol. We investigate
in unprecedented detail the structure of the remnant, in particular the mass
distribution, the thermal structure, and the rotation profile. We also compute
fluid trajectories both inside the remnant and those relevant for the formation
of the disk. We find a peanut-shaped fluid flow inside the remnant following a
strong m=2 perturbation. Moreover, the flow is locally compressive, causing the
appearance of dynamic hot spots. Further, we introduce new diagnostic measures
that are easy to implement in numeric simulations and that allow to quantify
mass and compactness of merger remnants in a well-defined way. As in previous
studies of supra- and hypermassive stars, we find a remnant with a slowly
rotating core and an outer envelope rotating at nearly Keplerian velocity. We
compute a Tolman-Oppenheimer-Volkoff star model which agrees well with that of
the remnant in the core, while the latter possesses extensive outer layers
rotating close to Kepler velocity. Finally, we extract the gravitational wave
signal and discuss the detectability with modern observatories. This study has
implications for the interpretation of gravitational wave detections from the
post-merger phase, and is relevant for short gamma-ray burst models.


title:
Cosmological constraints on dark matter annihilation and decay:
  Cross-correlation analysis of the extragalactic $\gamma$-ray background and
  cosmic shear

abstract:
  We derive constraints on dark matter (DM) annihilation cross section and
decay lifetime from cross-correlation analyses of the data from Fermi-LAT and
weak lensing surveys that cover a wide area of $\sim660$ squared degrees in
total. We improve upon our previous analyses by using an updated extragalactic
$\gamma$-ray background data reprocessed with the Fermi Pass 8 pipeline, and by
using well-calibrated shape measurements of about twelve million galaxies in
the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence
Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs
from cosmological $N$-body simulations and use them to estimate statistical
errors accurately. The measured cross correlation is consistent with null
detection, which is then used to place strong cosmological constraints on
annihilating and decaying DM. For leptophilic DM, the constraints are improved
by a factor of $\sim100$ in the mass range of O(1) TeV when including
contributions from secondary $\gamma$ rays due to the inverse-Compton
upscattering of background photons. Annihilation cross-sections of $\langle
\sigma v \rangle \sim 10^{-23}\, {\rm cm}^3/{\rm s}$ are excluded for TeV-scale
DM depending on channel. Lifetimes of $\sim 10^{25}$ sec are also excluded for
the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and
exclude the wino mass around 200 GeV. These constraints will be further
tightened, and all the interesting wino DM parameter region can be tested, by
using data from future wide-field cosmology surveys.


title:
Whole-brain substitute CT generation using Markov random field mixture
  models

abstract:
  Computed tomography (CT) equivalent information is needed for attenuation
correction in PET imaging and for dose planning in radiotherapy. Prior work has
shown that Gaussian mixture models can be used to generate a substitute CT
(s-CT) image from a specific set of MRI modalities. This work introduces a more
flexible class of mixture models for s-CT generation, that incorporates spatial
dependency in the data through a Markov random field prior on the latent field
of class memberships associated with a mixture model. Furthermore, the mixture
distributions are extended from Gaussian to normal inverse Gaussian (NIG),
allowing heavier tails and skewness. The amount of data needed to train a model
for s-CT generation is of the order of 100 million voxels. The computational
efficiency of the parameter estimation and prediction methods are hence
paramount, especially when spatial dependency is included in the models. A
stochastic Expectation Maximization (EM) gradient algorithm is proposed in
order to tackle this challenge. The advantages of the spatial model and NIG
distributions are evaluated with a cross-validation study based on data from 14
patients. The study show that the proposed model enhances the predictive
quality of the s-CT images by reducing the mean absolute error with 17.9%.
Also, the distribution of CT values conditioned on the MR images are better
explained by the proposed model as evaluated using continuous ranked
probability scores.


title: Models of the Chisholm set

abstract:
  We give a counter-example showing that Carmo and Jones' condition 5(e) may
conflict with other conditions on the models in their paper \emph{A new
approach to contrary-to-duty obligations}.


title: The elusive stellar halo of the Triangulum Galaxy

abstract:
  The stellar halos of large galaxies represent a vital probe of the processes
of galaxy evolution. They are the remnants of the initial bouts of star
formation during the collapse of the proto-galactic cloud, coupled with imprint
of ancient and on-going accretion events. Previously, we have reported the
tentative detection of a possible, faint, extended stellar halo in the Local
Group spiral, the Triangulum Galaxy (M33). However, the presence of
substructure surrounding M33 made interpretation of this feature difficult.
Here, we employ the final data set from the Pan-Andromeda Archaeological Survey
(PAndAS), combined with an improved calibration and a newly derived
contamination model for the region to revisit this claim. With an array of new
fitting algorithms, fully accounting for contamination and the substantial
substructure beyond the prominent stellar disk in M33, we reanalyse the
surrounds to separate the signal of the stellar halo and the outer halo
substructure. Using more robust search algorithms, we do not detect a large
scale smooth stellar halo and place a limit on the maximum surface brightness
of such a feature of ${\mu}_V$ = 35.5 mags per square arcsec, or a total halo
luminosity of $L < 10^6L_{\odot}$.


title:
Bringing Information Credibility Back Into Transparency: The Case for a
  Global Monitoring System Of Green House Gas Emissions

abstract:
  The goal of climate change governance is to stabilize greenhouse gas
concentrations. This requires the reduction of anthropogenic global net
emissions. In the pursuit of such a reduction, knowledge of greenhouse gas
sources and sinks is critical to define baselines, and assess the effectiveness
of climate governance over time. Such information and the means to
independently verify its credibility continue to remain out of reach including
in the recent Paris agreement. This essay argues that to make real progress in
mitigating future climate change, this status quo must be challenged both
intellectually and practically. First, it proposes to acknowledge and address
the inconsistency between the objectives of a climate regime and the role of
transparency as a mean to achieve these objectives. It does so by redefining
transparency as the addition of publicity and measurability, which turns it
into a credible information generating mechanism for governance. Second, it
shows how in practice, a global monitoring system of greenhouse gas net
emissions, based on this new definition of transparency and designed as a
global public good, could provide the necessary knowledge to help frame
governance solutions by providing both credibility and completeness in
understanding the scope of the problem to solve.


title: Distributed Authorization in Vanadium

abstract:
  In this tutorial, we present an authorization model for distributed systems
that operate with limited internet connectivity. Reliable internet access
remains a luxury for a majority of the world's population. Even for those who
can afford it, a dependence on internet connectivity may lead to sub-optimal
user experiences. With a focus on decentralized deployment, we present an
authorization model that is suitable for scenarios where devices right next to
each other (such as a sensor or a friend's phone) should be able to communicate
securely in a peer-to-peer manner. The model has been deployed as part of an
open-source distributed application framework called Vanadium. As part of this
tutorial, we survey some of the key ideas and techniques used in distributed
authorization, and explain how they are combined in the design of our model.


title:
Rayleigh-Benard stability and the validity of quasi-Boussinesq or
  quasi-anelastic liquid approximations

abstract:
  The linear stability threshold of the Rayleigh-Benard configuration is
analyzed with compressible effects taken into account. It is assumed that the
fluid obeys a Newtonian rheology and Fourier's law of thermal transport with
constant, uniform (dynamic) viscosity and thermal conductivity in a uniform
gravity field. Top and bottom boundaries are maintained at different constant
temperatures and we consider here boundary conditions of zero tangential stress
and impermeable walls. Under these conditions, and with the Boussinesq
approximation, Rayleigh (1916) first obtained analytically the critical value
27pi^4/4 for a dimensionless parameter, now known as the Rayleigh number, at
the onset of convection. This manuscript describes the changes of the critical
Rayleigh number due to the compressibility of the fluid, measured by the
dimensionless dissipation parameter D and due to a finite temperature
difference between the hot and cold boundaries, measured by a dimensionless
temperature gradient a. Different equations of state are examined: ideal gas
equation, Murnaghan's model and a generic equation of state, which can
represent any possible equation of state. We also consider two variations of
this stability analysis. In a so-called quasi-Boussinesq model, we consider
that density perturbations are solely due to temperature perturbations. In a
so-called quasi-anelastic liquid approximation, we consider that entropy
perturbations are solely due to temperature perturbations. In addition to the
numerical Chebyshev-based stability analysis, an analytical approximation is
obtained when temperature fluctuations are written as a combination of only two
modes. This analytical expression allows us to show that the superadiabatic
critical Rayleigh number quadratic departure in a and D from 27pi^4/4 involves
the expansion of density up to the degree three in terms of pressure and
temperature.


title:
Numerical posterior distribution error control and expected Bayes
  Factors in the bayesian Uncertainty Quantification of Inverse Problems

abstract:
  In the bayesian analysis of Inverse Problems most relevant cases the forward
maps (FM, or regressor function) are defined in terms of a system of (O, P)DE's
with intractable solutions. These necessarily involve a numerical method to
find approximate versions of such solutions and lead to a numerical/approximate
posterior distribution. Recently several results have been published on the
regularity conditions required on such numerical methods to ensure converge of
the numerical to the theoretical posterior. However, more practical guidelines
are needed to ensure a suitable working numerical posterior. ]Capistran2016]
prove for ODE's that the Bayes Factor of the approximate vs the theoretical
model tends to 1 in the same order as the numerical method order. In this work
we generalize the latter paper in that we consider 1) also PDE's, 2) correlated
observations, 3) practical guidelines in a multidimensional setting and 4)
explore the use of expected Bayes Factors. This permits us to obtain bounds on
the absolute global errors to be tolerated by the FM numerical solver, which we
illustrate with some examples. Since the Bayes Factor is kept above 0.95 we
expect that the resulting numerical posterior is basically indistinguishable
from the theoretical posterior, even though we are using an approximate
numerical FM. The method is illustrated with some examples using synthetic
data.


title: Extracting OPE coefficient of Konishi at four loops

abstract:
  We compute in this short note the OPE coefficient of two 20' operators and
the Konishi. We use the OPE decomposition of a four point function of four 20'
operators and the method of asymptotic expansions to compute the integrals at
the order that it is needed.


title:
Persistent Homology on Grassmann Manifolds for Analysis of Hyperspectral
  Movies

abstract:
  The existence of characteristic structure, or shape, in complex data sets has
been recognized as increasingly important for mathematical data analysis. This
realization has motivated the development of new tools such as persistent
homology for exploring topological invariants, or features, in large data sets.
In this paper we apply persistent homology to the characterization of gas
plumes in time dependent sequences of hyperspectral cubes, i.e. the analysis of
4-way arrays. We investigate hyperspectral movies of Long-Wavelength Infrared
data monitoring an experimental release of chemical simulant into the air. Our
approach models regions of interest within the hyperspectral data cubes as
points on the real Grassmann manifold $G(k, n)$ (whose points parameterize the
$k$-dimensional subspaces of $\mathbb{R}^n$), contrasting our approach with the
more standard framework in Euclidean space. An advantage of this approach is
that it allows a sequence of time slices in a hyperspectral movie to be
collapsed to a sequence of points in such a way that some of the key structure
within and between the slices is encoded by the points on the Grassmann
manifold. This motivates the search for topological features, associated with
the evolution of the frames of a hyperspectral movie, within the corresponding
points on the Grassmann manifold. The proposed mathematical model affords the
processing of large data sets while retaining valuable discriminatory
information. In this paper, we discuss how embedding our data in the Grassmann
manifold, together with topological data analysis, captures dynamical events
that occur as the chemical plume is released and evolves.


title:
A Complex Network Approach for Nanoparticle Agglomeration Analysis in
  Nanoscale Images

abstract:
  Complex networks have been widely used in science and technology because of
their ability to represent several systems. One of these systems is found in
Biochemistry, in which the synthesis of new nanoparticles is a hot topic.
However, the interpretation of experimental results in the search of new
nanoparticles poses several challenges. This is due to the characteristics of
nanoparticles images and due to their multiple intricate properties; one
property of recurrent interest is the agglomeration of particles. Addressing
this issue, this paper introduces an approach that uses complex networks to
detect and describe nanoparticle agglomerates so to foster easier and more
insightful analyses. In this approach, each detected particle in an image
corresponds to a vertice and the distances between the particles define a
criterion for creating edges. Edges are created if the distance is smaller than
a radius of interest. Once this network is set, we calculate several discrete
measures able to reveal the most outstanding agglomerates in a nanoparticle
image. Experimental results using images of Scanning Tunneling Microscopy (STM)
of gold nanoparticles demonstrated the effectiveness of the proposed approach
over several samples, as reflected by the separability between particles in
three usual settings. The results also demonstrated efficacy for both convex
and non-convex agglomerates.


title:
Are There Nuclear Structure Effects on the Isoscalar Giant Monopole
  Resonance and Nuclear Incompressibility near A~90?

abstract:
  "Background-free" spectra of inelastic $\alpha$-particle scattering have been
measured at a beam energy of 385 MeV in $^{90, 92}$Zr and $^{92}$Mo at
extremely forward angles, including 0$^{\circ}$. The ISGMR strength
distributions for the three nuclei coincide with each other, establishing
clearly that nuclear incompressibility is not influenced by nuclear shell
structure near $A\sim$90 as was claimed in recent measurements.


title:
Dissipative Dynamics Of Fermion-Fermion Scattering In A Three-Site
  Optical Lattice

abstract:
  In this article, we investigate the dissipative dynamics of a Fermi gas
trapped in a three-site optical lattice exposed to a fermionic environment. The
lattice sites admit at most one spin-up and one spin-down particle at a time
and its interaction with the fermionic environment cause particles to either be
trapped by or expelled from it. It is then shown that apart from each lattice
site being populated by at least one particle, spin exchange is observed, which
allows the possibility for the system to be used to encrypt information via
quantum cryptography. Furthermore, we also observe entanglement among the
lattice sites, denoting that transport of quantum information among particles
is possible in this ultracold atomic system.


title:
Sapo: Reachability Computation and Parameter Synthesis of Polynomial
  Dynamical Systems

abstract:
  Sapo is a C++ tool for the formal analysis of polynomial dynamical systems.
Its main features are: 1) Reachability computation, i.e., the calculation of
the set of states reachable from a set of initial conditions, and 2) Parameter
synthesis, i.e., the refinement of a set of parameters so that the system
satisfies a given specification. Sapo can represent reachable sets as unions of
boxes, parallelotopes, or parallelotope bundles (symbolic representation of
polytopes). Sets of parameters are represented with polytopes while
specifications are formalized as Signal Temporal Logic (STL) formulas.


title:
Eigenvalue distributions of variance components estimators in
  high-dimensional random effects models

abstract:
  We study the spectra of MANOVA estimators for variance component covariance
matrices in multivariate random effects models. When the dimensionality of the
observations is large and comparable to the number of realizations of each
random effect, we show that the empirical spectra of such estimators are
well-approximated by deterministic laws. The Stieltjes transforms of these laws
are characterized by systems of fixed-point equations, which are numerically
solvable by a simple iterative procedure. Our proof uses operator-valued free
probability theory, and we establish a general asymptotic freeness result for
families of rectangular orthogonally-invariant random matrices, which is of
independent interest. Our work is motivated by the estimation of components of
covariance between multiple phenotypic traits in quantitative genetics, and we
specialize our results to common experimental designs that arise in this
application.


title: Electric Field Screening with Back-Flow at Pulsar Polar Cap

abstract:
  Recent $\gamma$-ray observations suggest that the particle acceleration
occurs at the outer region of the pulsar magnetosphere. The magnetic field
lines in the outer acceleration region (OAR) are connected to the neutron star
surface (NSS). If copious electron--positron pairs are produced near the NSS,
such pairs flow into the OAR and screen the electric field there. To activate
the OAR, the electromagnetic cascade due to the electric field near the NSS
should be suppressed. However, since a return current is expected along the
field lines through the OAR, the outflow extracted from the NSS alone cannot
screen the electric field just above the NSS. In this paper, we analytically
and numerically study the electric-field screening at the NSS taking into
account the effects of the back-flowing particles from the OAR. In certain
limited cases, the electric field is screened without significant pair cascade
if only ultrarelativistic particles ($\gamma\gg1$) flow back to the NSS. On the
other hand, if electron--positron pairs with a significant number density and
mildly relativistic temperature, expected to distribute in a wide region of the
magnetosphere, flow back to the NSS, these particles adjust the current and
charge densities, so that the electric field can be screened without pair
cascade. We obtain the condition for the number density of particles to screen
the electric field at the NSS. We also find that in ion-extracted case from the
NSS, bunches of particles are ejected to the outer region quasi-periodically,
which is a possible mechanism of observed radio emission.


title:
Resonance-enhanced collective effect in a triangle arrangement of
  Rydberg atoms with anisotropic interactions

abstract:
  We investigate the collective excitation effect in a scheme where three
identical Rydberg atoms are arranged in an equilateral triangular lattice. By
using a static electric field polarizing the atomic dipoles, the dipole-dipole
interactions between two Rydberg atoms are essentially anisotropic and can even
disappear in the several special resonance cases. For that fact, we observe
collectively enhanced excitation probability of single Rydberg atom in resonant
areas in the case of strong blockade, and that of double or triple Rydberg
atoms in the case of partial blockade. To give more evidences for this
collective excitation enhancement, we study the two-body quantum correlation
between three Rydberg atoms, as well as the dependence of the blockade radius
on the length of triangle sides, which present a good agreement with the
excitation properties.


title:
Multi Channel-Kernel Canonical Correlation Analysis for Cross-View
  Person Re-Identification

abstract:
  In this paper we introduce a method to overcome one of the main challenges of
person re-identification in multi-camera networks, namely cross-view appearance
changes. The proposed solution addresses the extreme variability of person
appearance in different camera views by exploiting multiple feature
representations. For each feature, Kernel Canonical Correlation Analysis (KCCA)
with different kernels is exploited to learn several projection spaces in which
the appearance correlation between samples of the same person observed from
different cameras is maximized. An iterative logistic regression is finally
used to select and weigh the contributions of each feature projections and
perform the matching between the two views. Experimental evaluation shows that
the proposed solution obtains comparable performance on VIPeR and PRID 450s
datasets and improves on PRID and CUHK01 datasets with respect to the state of
the art.


title:
On the Existence of and Relationship between Canards and Torus Canards
  in Forced Slow/Fast Systems

abstract:
  Canards are special solutions of slow/fast systems which are ubiquitous in
neuroscience and electrical engineering. Two distinct classes of canard
solutions have been identified and carefully studied: folded singularity
canards and torus canards. Recently, an explicit and analytic relationship
between these seemingly unrelated families of solutions was established in the
classical forced van der Pol equation (Burke et al., J. Nonlinear Sci.
26:405--451, 2015). In this article, we generalize the results of Burke et al.
(2015) to the broader class of time-periodically forced planar slow/fast
systems, which includes the forced van der Pol and the forced FitzHugh-Nagumo
equations. We analytically determine the parameter values in this class of
systems for which the two types of canard solutions exist, and show that the
branches of primary canards of folded singularities continue into those of the
torus canards as the forcing frequency is increased. We illustrate our results
in the paradigm problem of the forced FitzHugh-Nagumo system.


title: Faddeev-Jackiw quantization of four dimensional BF theory

abstract:
  The symplectic analysis of a four dimensional $BF$ theory in the context of
the Faddeev-Jackiw symplectic approach is performed. It is shown that this
method is more economical than Dirac's formalism. In particular, the complete
set of Faddeev-Jackiw constraints and the generalized Faddeev-Jackiw brackets
are reported. In addition, we show that the generalized Faddeev-Jackiw brackets
and the Dirac ones coincide to each other. Finally, the similarities and
advantages between Faddeev-Jackiw method and Dirac's formalism are briefly
discussed.


title:
Two-term, asymptotically sharp estimates for eigenvalue means of the
  Laplacian

abstract:
  We present asymptotically sharp inequalities for the eigenvalues $\mu_k$ of
the Laplacian on a domain with Neumann boundary conditions, using the averaged
variational principle introduced in \cite{HaSt14}. For the Riesz mean $R_1(z)$
of the eigenvalues we improve the known sharp semiclassical bound in terms of
the volume of the domain with a second term with the best possible expected
power of $z$.
  In addition, we obtain two-sided bounds for individual $\mu_k$, which are
semiclassically sharp. In a final section, we remark upon the Dirichlet case
with the same methods.


title:
The regular semisimple locus of the affine quotient of the cotangent
  bundle of the Grothendieck-Springer resolution

abstract:
  Let $G= GL_n(\mathbb{C})$, the general linear group over the complex numbers,
and let $B$ be the set of invertible upper triangular matrices in $G$. Let
$\mathfrak{b}=\text{Lie}(B)$. For $\mu:T^*(\mathfrak{b}\times
\mathbb{C}^n)\rightarrow \mathfrak{b}^*$, where $\mathfrak{b}^*\cong
\mathfrak{g}/\mathfrak{u}$ and $\mathfrak{u}$ being strictly upper triangular
matrices in $\mathfrak{g}=\text{Lie}(G)$, we prove that the Hamiltonian
reduction $\mu^{-1}(0)^{rss}/\!\!/B$ of the extended regular semisimple locus
$\mathfrak{b}^{rss}$ of the Borel subalgebra is smooth, affine, reduced, and
scheme-theoretically isomorphic to a dense open locus of $\mathbb{C}^{2n}$. We
also show that the $B$-invariant functions on the regular semisimple locus of
the Hamiltonian reduction of $\mathfrak{b}\times \mathbb{C}^n$ arise as the
trace of a certain product of matrices.


title:
On semi-invariants of filtered representations of quivers and the
  cotangent bundle of the enhanced Grothendieck-Springer resolution

abstract:
  We introduce the notion of filtered representations of quivers, which is
related to usual quiver representations, but is a systematic generalization of
conjugacy classes of $n\times n$ matrices to (block) upper triangular matrices
up to conjugation by invertible (block) upper triangular matrices. With this
notion in mind, we describe the ring of invariant polynomials for interesting
families of quivers, namely, finite $ADE$-Dynkin quivers and affine type
$\widetilde{A}$-Dynkin quivers. We then study their relation to an important
and fundamental object in representation theory called the
Grothendieck-Springer resolution, and we conclude by stating several
conjectures, suggesting further research.


title: Subspace Arrangements as Generalized Star Configurations

abstract:
  In these notes we show that any projective subspace arrangement can be
realized as a generalized star configuration variety. This type of
interpolation result may be useful in designing linear codes with prescribed
codewords of minimum weight, as well as in answering a couple of questions
asked by the author in previous work, about the number of equations needed to
define a generalized star configuration.


title: Constraints on cosmic ray loading and PeV neutrino production in blazars

abstract:
  IceCube has detected a cumulative flux of PeV neutrinos, which origin is
unknown. Blazars, active galactic nuclei with relativistic jets pointing to us,
are long and widely expected to be one of the strong candidates of high energy
neutrino sources. The neutrino production depends strongly on the cosmic ray
power of blazar jets, which is largely unknown. The recent null results in
stacking searches of neutrinos for several blazar samples by IceCube put upper
limits on the neutrino fluxes from these blazars. Here we compute the cosmic
ray power and PeV neutrino flux of Fermi-LAT blazars, and find that the upper
limits for known blazar sources give stringent constraint on the cosmic ray
loading factor of blazar jets (i.e., the ratio of the cosmic ray to bolometric
radiation luminosity of blazar jets), $\xi_{\rm cr}\la(2-10)\zeta^{-1}$ (with
$\zeta\la1$ the remained fraction of cosmic ray energy when propagate into the
blazar broad line region) for flat cosmic ray spectrum, and that the cumulative
PeV neutrino flux contributed by all-sky blazars is a fraction $\la(10-50)\%$
of the IceCube detected flux.


title: A Global Model For Circumgalactic and Cluster-Core Precipitation

abstract:
  We provide an analytic framework for interpreting observations of multiphase
circumgalactic gas that is heavily informed by recent numerical simulations of
thermal instability and precipitation in cool-core galaxy clusters. We start by
considering the local conditions required for the formation of multiphase gas
via two different modes: (1) uplift of ambient gas by galactic outflows, and
(2) condensation in a stratified stationary medium in which thermal balance is
explicitly maintained. Analytic exploration of these two modes provides
insights into the relationships between the local ratio of the cooling and
freefall time scales (i.e., t_cool / t_ff), the large-scale gradient of
specific entropy, and development of precipitation and multiphase media in
circumgalactic gas. We then use these analytic findings to interpret recent
simulations of circumgalactic gas in which global thermal balance is
maintained. We show that long-lasting configurations of gas with 5 < t_cool /
t_ff < 20 and radial entropy profiles similar to observations of local
cool-core galaxy cluster cores are a natural outcome of precipitation-regulated
feedback. We conclude with some observational predictions that follow from
these models. This work focuses primarily on precipitation and AGN feedback in
galaxy cluster cores, because that is where the observations of multiphase gas
around galaxies are most complete. However, many of the physical principles
that govern condensation in those environments apply to circumgalactic gas
around galaxies of all masses.


title: Downward catastrophe of solar magnetic flux ropes

abstract:
  2.5D time-dependent ideal magnetohydrodynamic (MHD) models in Cartesian
coordinates were used in previous studies to seek MHD equilibria involving a
magnetic flux rope embedded in a bipolar, partially open background field. As
demonstrated by these studies, the equilibrium solutions of the system are
separated into two branches: the flux rope sticks to the photosphere for
solutions at the lower branch but is suspended in the corona for those at the
upper branch. Moreover, a solution originally at the lower branch jumps to the
upper, as the related control parameter increases and reaches a critical value,
and the associated jump is here referred to as upward catastrophe. The present
paper advances these studies in three aspects. First, the magnetic field is
changed to be force-free. The system still experiences an upward catastrophe
with an increase in each control parameter. Secondly, under the force-free
approximation, there also exists a downward catastrophe, characterized by a
jump of a solution from the upper branch to the lower. Both catastrophes are
irreversible processes connecting the two branches of equilibrium solutions so
as to form a cycle. Finally, the magnetic energy in the numerical domain is
calculated. It is found that there exists a magnetic energy release for both
catastrophes. The Amp\`{e}re's force, which vanishes everywhere for force-free
fields, appears only during the catastrophes and does a positive work, which
serves as a major mechanism for the energy release. The implications of the
downward catastrophe and its relevance to solar activities are briefly
discussed.


title:
Large Scale GPU Accelerated PPMLR-MHD Simulations for Space Weather
  Forecast

abstract:
  PPMLR-MHD is a new magnetohydrodynamics (MHD) model used to simulate the
interactions of the solar wind with the magnetosphere, which has been proved to
be the key element of the space weather cause-and-effect chain process from the
Sun to Earth. Compared to existing MHD methods, PPMLR-MHD achieves the
advantage of high order spatial accuracy and low numerical dissipation.
However, the accuracy comes at a cost. On one hand, this method requires more
intensive computation. On the other hand, more boundary data is subject to be
transferred during the process of simulation.s In this work, we present a
parallel hybrid solution of the PPMLR-MHD model implemented using the computing
capabilities of both CPUs and GPUs. We demonstrate that our optimized
implementation alleviates the data transfer overhead by using GPU Direct
technology and can scale up to 151 processes and achieve significant
performance gains by distributing the workload among the CPUs and GPUs on Titan
at Oak Ridge National Laboratory. The performance results show that our
implementation is fast enough to carry out highly accurate MHD simulations in
real time.


title: Dawes Review 5: Australian Aboriginal Astronomy and Navigation

abstract:
  The traditional cultures of Aboriginal Australians include a significant
astronomical component, perpetuated through oral tradition, ceremony, and art.
This astronomical knowledge includes a deep understanding of the motion of
objects in the sky, which was used for practical purposes such as constructing
calendars and for navigation. There is also evidence that traditional
Aboriginal Australians made careful records and measurements of cyclical
phenomena, recorded unexpected phenomena such as eclipses and meteorite
impacts, and could determine the cardinal points to an accuracy of a few
degrees. Putative explanations of celestial phenomena appear throughout the
oral record, suggesting traditional Aborig- inal Australians sought to
understand the natural world around them, in the same way as modern scientists,
but within their own cultural context. There is also a growing body of evidence
for sophisticated navigational skills, including the use of astronomically
based songlines. Songlines are effectively oral maps of the landscape, and are
an efficient way of transmitting oral navigational skills in cultures that do
not have a written language. The study of Aboriginal astronomy has had an
impact extending beyond mere academic curiosity, facilitating cross-cultural
understanding, demonstrating the intimate links between science and culture,
and helping students to engage with science.


title:
Search for continuous gravitational waves from neutron stars in globular
  cluster NGC 6544

abstract:
  We describe a directed search for continuous gravitational waves in data from
the sixth LIGO science run. The target was the nearby globular cluster NGC 6544
at a distance of 2.7 kpc. The search covered a broad band of frequencies along
with first and second frequency derivatives for a fixed sky position. The
search coherently integrated data from the two LIGO interferometers over a time
span of 9.2 days using the matched-filtering F-statistic. We found no
gravitational-wave signals and set 95% confidence upper limits as stringent as
6.0 X 10^{-25} on intrinsic strain and 8.5 X 10^{-6} on fiducial ellipticity.
These values beat the indirect limits from energy conservation for stars with
characteristic spindown ages older than 300 years and are within the range of
theoretical predictions for possible neutron-star ellipticities. An important
feature of this search was use of a barycentric resampling algorithm which
substantially reduced computational cost; this method will be used extensively
in searches of Advanced LIGO and Virgo detector data.


title:
Improved Razumikhin and Krasovskii Stability Criteria for Time-Varying
  Stochastic Time-Delay Systems

abstract:
  The problem of p-th moment stability for time-varying stochastic time-delay
systems with Markovian switching is investigated in this paper. Some novel
stability criteria are obtained by applying the generalized Razumikhin and
Krasovskii stability theorems. Both p-th moment asymptotic stability and
(integral) input-to-state stability are considered based on the notion and
properties of uniformly stable functions and the improved comparison
principles. The established results show that time-derivatives of the
constructed Razumikhin functions and Krasovskii functionals are allowed to be
indefinite, which improve the existing results on this topic. By applying the
obtained results for stochastic systems, we also analyze briefly the stability
of time-varying deterministic time-delay systems. Finally, examples are
provided to illustrate the effectiveness of the proposed results.


title:
A polynomial time algorithm to compute quantum invariants of 3-manifolds
  with bounded first Betti number

abstract:
  In this article, we introduce a fixed parameter tractable algorithm for
computing the Turaev-Viro invariants TV(4,q), using the dimension of the first
homology group of the manifold as parameter.
  This is, to our knowledge, the first parameterised algorithm in computational
3-manifold topology using a topological parameter. The computation of TV(4,q)
is known to be #P-hard in general; using a topological parameter provides an
algorithm polynomial in the size of the input triangulation for the extremely
large family of 3-manifolds with first homology group of bounded rank.
  Our algorithm is easy to implement and running times are comparable with
running times to compute integral homology groups for standard libraries of
triangulated 3-manifolds. The invariants we can compute this way are powerful:
in combination with integral homology and using standard data sets we are able
to roughly double the pairs of 3-manifolds we can distinguish.
  We hope this qualifies TV(4,q) to be added to the short list of standard
properties (such as orientability, connectedness, Betti numbers, etc.) that can
be computed ad-hoc when first investigating an unknown triangulation.


title: Concentration of Geodesics in Directed Bernoulli Percolation

abstract:
  For directed Bernoulli last passage percolation with i.i.d.~weights on
vertices over a $n\times n$ grid and for $n$ large enough, the geodesics are
shown to be concentrated in a cylinder, centered on the main diagonal and of
width of order $n^{(2\kappa+2)/(2\kappa+3)}\sqrt{\ln n}$, where
$1\le\kappa<\infty$ is the curvature power of the shape function at $(1,1)$.
The methodology of proof is robust enough to also apply to directed Bernoulli
first passage site percolation, and further to longest common subsequences in
random words.


title:
Electrosynthetic control of CNT conductivity & morphology: Scale-up of
  the transformation of the greenhouse gas CO2 into carbon nanotubes by molten
  carbonate electrolysis

abstract:
  Transformation of carbon dioxide into carbon nanotubes, CNTs, by electrolysis
in molten carbonates provides a low cost route to extract and store this
greenhouse gas. CNTs are more stable, compact and valuable than fuels or other
CO2 conversion products, providing an incentive to remove CO2 for climate
mitigation. Previously, solid core carbon nanofibers, CNFs were formed with
C-13 isotope CO2, whereas hollow core fibers - carbon nanotubes, CNTs, were
formed with natural isotope CO2 splitting in molten lithium carbonate. Here we
demonstrate the extraordinary range of specific morphologies and conductivities
of CNTs that can be achieved through control of the electrolysis conditions in
a one pot-synthesis, and scale-up of this process by which the greenhouse gas
CO2 is transformed into carbon nanotubes by molten carbonate electrolysis.
Addition of Li2BO3, boron dopes and greatly enhances CNT conductivity formed at
the galvanized steel cathode. Addition of CaCO3 to the Li2CO3 electrolyte,
decreases oxide solubility in the region of CNT growth, producing straight
thin-walled CNTs.


title: Can we remove the systematic error due to isotropic inhomogeneities?

abstract:
  Usually, we assume that there is no inhomogeneity isotropic in terms of our
location in our uni- verse. This assumption has not been observationally
confirmed yet in sufficient accuracy, and we need to consider the possibility
that there are non-negligible large-scale isotropic inhomogeneities in our
universe. The existence of large-scale isotropic inhomogeneities affects the
determination of the cosmological parameters. In particular, from only the
distance-redshift relation, we can not dis- tinguish the inhomogeneous
isotropic universe model from the homogeneous isotropic one, because of the
ambiguity in the cosmological parameters. In this paper, in order to avoid such
ambiguity, we consider three observables, the distance-redshift relation, the
fluctuation spectrum of the cosmic microwave background radiation(CMBR) and the
scale of the baryon acoustic oscillation(BAO), and compare these observables in
two universe models; One is the inhomogeneous isotropic uni- verse model with
the cosmological constant and the other is the homogeneous isotropic universe
model with the dark energy other than the cosmological constant. We show that
these two universe models can not predict the same observational data of all
three observables but the same ones of only two of three, as long as the
perturbations are adiabatic. In principle, we can distinguish the inhomogeneous
isotropic universe from the homogeneous isotropic one through appropriate three
observables, if the perturbations are adiabatic.


title: Rokhlin dimension for flows

abstract:
  We introduce a notion of Rokhlin dimension for one parameter automorphism
groups of C*-algebras. This generalizes Kishimoto's Rokhlin property for flows,
and is analogous to the notion of Rokhlin dimension for actions of the integers
and other discrete groups introduced by the authors and Zacharias in previous
papers. We show that finite nuclear dimension and absorption of a strongly
self-absorbing C*-algebra are preserved under forming crossed products by flows
with finite Rokhlin dimension, and that these crossed products are stable.
Furthermore, we show that a flow on a commutative C*-algebra arising from a
free topological flow has finite Rokhlin dimension, whenever the spectrum is a
locally compact metrizable space with finite covering dimension. For flows that
are both free and minimal, this has strong consequences for the associated
crossed product C*-algebras: Those containing a non-zero projection are
classified by the Elliott invariant (for compact manifolds this consists of
topological K-theory together with the space of invariant probability measures
and a natural pairing given by the Ruelle-Sullivan map).


title: Periodic points on T - fiber bundles over the circle

abstract:
  The main purppose this work is to study periodic points of fiber-preserving
maps on fiber bundles with base circle and fiber torus.


title:
A perturbation problem involving singular perturbations of domains for
  Hamilton-Jacobi equations

abstract:
  We investigate a singular perturbation for Hamilton-Jacobi equations in an
open subset of two dimensional Euclidean space, where the set is determined
through a Hamiltonian function and the Hamilton-Jacobi equations are the
dynamic programming equations for optimal control of the Hamiltonian flow of
the Hamiltonian. We establish the convergence of solutions of the
Hamilton-Jacobi equations and identify the limit of the solutions as solutions
of systems of ordinary differential equations on a graph. The perturbation is
singular in the sense that the domain degenerates to the graph in the limit
process. Our result can be seen as a perturbation analysis, in the viewpoint of
optimal control, of the Hamiltonian flow.


title: Hybrid Information Flow Analysis for Programs with Arrays

abstract:
  Information flow analysis checks whether certain pieces of (confidential)
data may affect the results of computations in unwanted ways and thus leak
information. Dynamic information flow analysis adds instrumentation code to the
target software to track flows at run time and raise alarms if a flow policy is
violated; hybrid analyses combine this with preliminary static analysis.
  Using a subset of C as the target language, we extend previous work on hybrid
information flow analysis that handled pointers to scalars. Our extended
formulation handles arrays, pointers to array elements, and pointer arithmetic.
Information flow through arrays of pointers is tracked precisely while arrays
of non-pointer types are summarized efficiently.
  A prototype of our approach is implemented using the Frama-C program analysis
and transformation framework. Work on a full machine-checked proof of the
correctness of our approach using Isabelle/HOL is well underway; we present the
existing parts and sketch the rest of the correctness argument.


title: Renaming Global Variables in C Mechanically Proved Correct

abstract:
  Most integrated development environments are shipped with refactoring tools.
However, their refactoring operations are often known to be unreliable. As a
consequence, developers have to test their code after applying an automatic
refactoring. In this article, we consider a refactoring operation (renaming of
global variables in C), and we prove that its core implementation preserves the
set of possible behaviors of transformed programs. That proof of correctness
relies on the operational semantics of C provided by CompCert C in Coq.


title: Generating Counterexamples for Model Checking by Transformation

abstract:
  Counterexamples explain why a desired temporal logic property fails to hold.
The generation of counterexamples is considered to be one of the primary
advantages of model checking as a verification technique. Furthermore, when
model checking does succeed in verifying a property, there is typically no
independently checkable witness that can be used as evidence for the verified
property. Previously, we have shown how program transformation techniques can
be used for the verification of both safety and liveness properties of reactive
systems. However, no counterexamples or witnesses were generated using the
described techniques. In this paper, we address this issue. In particular, we
show how the program transformation technique distillation can be used to
facilitate the construction of counterexamples and witnesses for temporal
properties of reactive systems. Example systems which are intended to model
mutual exclusion are analysed using these techniques with respect to both
safety (mutual exclusion) and liveness (non-starvation), with counterexamples
being generated for those properties which do not hold.


title: Towards Trustworthy Refactoring in Erlang

abstract:
  Tool-assisted refactoring transformations must be trustworthy if programmers
are to be confident in applying them on arbitrarily extensive and complex code
in order to improve style or efficiency. We propose a simple, high-level but
rigorous, notation for defining refactoring transformations in Erlang, and show
that this notation provides an extensible, verifiable and executable
specification language for refactoring. To demonstrate the applicability of our
approach, we show how to define and verify a number of example refactorings in
the system.


title: Program Transformation to Identify List-Based Parallel Skeletons

abstract:
  Algorithmic skeletons are used as building-blocks to ease the task of
parallel programming by abstracting the details of parallel implementation from
the developer. Most existing libraries provide implementations of skeletons
that are defined over flat data types such as lists or arrays. However,
skeleton-based parallel programming is still very challenging as it requires
intricate analysis of the underlying algorithm and often uses inefficient
intermediate data structures. Further, the algorithmic structure of a given
program may not match those of list-based skeletons. In this paper, we present
a method to automatically transform any given program to one that is defined
over a list and is more likely to contain instances of list-based skeletons.
This facilitates the parallel execution of a transformed program using existing
implementations of list-based parallel skeletons. Further, by using an existing
transformation called distillation in conjunction with our method, we produce
transformed programs that contain fewer inefficient intermediate data
structures.


title: Turchin's Relation for Call-by-Name Computations: A Formal Approach

abstract:
  Supercompilation is a program transformation technique that was first
described by V. F. Turchin in the 1970s. In supercompilation, Turchin's
relation as a similarity relation on call-stack configurations is used both for
call-by-value and call-by-name semantics to terminate unfolding of the program
being transformed. In this paper, we give a formal grammar model of
call-by-name stack behaviour. We classify the model in terms of the Chomsky
hierarchy and then formally prove that Turchin's relation can terminate all
computations generated by the model.


title: Resiliency with Aggregate Computing: State of the Art and Roadmap

abstract:
  One of the difficulties in developing collective adaptive systems is the
challenge of simultaneously engineering both the desired resilient behaviour of
the collective and the details of its implementation on individual devices.
Aggregate computing simplifies this problem by separating these aspects into
different layers of abstraction by means of a unifying notion of computational
field and a functional computational model. We review the state of the art in
aggregate computing, discuss the various resiliency properties it supports, and
develop a roadmap of foundational problems still needing to be addressed in the
continued development of this emerging discipline.


title:
A Formal Framework for Modeling Trust and Reputation in Collective
  Adaptive Systems

abstract:
  Trust and reputation models for distributed, collaborative systems have been
studied and applied in several domains, in order to stimulate cooperation while
preventing selfish and malicious behaviors. Nonetheless, such models have
received less attention in the process of specifying and analyzing formally the
functionalities of the systems mentioned above. The objective of this paper is
to define a process algebraic framework for the modeling of systems that use
(i) trust and reputation to govern the interactions among nodes, and (ii)
communication models characterized by a high level of adaptiveness and
flexibility. Hence, we propose a formalism for verifying, through model
checking techniques, the robustness of these systems with respect to the
typical attacks conducted against webs of trust.


title:
On Formal Methods for Collective Adaptive System Engineering. {Scalable
  Approximated, Spatial} Analysis Techniques. Extended Abstract

abstract:
  In this extended abstract a view on the role of Formal Methods in System
Engineering is briefly presented. Then two examples of useful analysis
techniques based on solid mathematical theories are discussed as well as the
software tools which have been built for supporting such techniques. The first
technique is Scalable Approximated Population DTMC Model-checking. The second
one is Spatial Model-checking for Closure Spaces. Both techniques have been
developed in the context of the EU funded project QUANTICOL.


title: Stochastic and Spatial Equivalences for PALOMA

abstract:
  We concentrate our study on a recent process algebra - PALOMA - intended to
capture interactions between spatially distributed agents, for example in
collective adaptive systems. New agent-based semantic rules for deriving the
underlying continuous time Markov chain are given in terms of State to Function
Labelled Transition Systems. Furthermore we define a bisimulation with respect
to an isometric transformation of space allowing us to compare PALOMA models
with respect to their relative rather than absolute locations.


title:
From Collective Adaptive Systems to Human Centric Computation and Back:
  Spatial Model Checking for Medical Imaging

abstract:
  Recent research on formal verification for Collective Adaptive Systems (CAS)
pushed advancements in spatial and spatio-temporal model checking, and as a
side result provided novel image analysis methodologies, rooted in logical
methods for topological spaces. Medical Imaging (MI) is a field where such
technologies show potential for ground-breaking innovation. In this position
paper, we present a preliminary investigation centred on applications of
spatial model checking to MI. The focus is shifted from pure logics to a
mixture of logical, statistical and algorithmic approaches, driven by the
logical nature intrinsic to the specification of the properties of interest in
the field. As a result, novel operators are introduced, that could as well be
brought back to the setting of CAS.


title: Sets of Lengths of Powers of a Variable

abstract:
  A positive integer k is a length of a polynomial if that polynomial factors
into a product of k irreducible polynomials. We find the set of lengths of
polynomials of the form x^n in R[x], where (R, m) is an Artinian local ring
with m^2 = 0.


title: Solid hulls of weighted Banach spaces of entire functions

abstract:
  Given a continuous, radial, rapidly decreasing weight $v$ on the complex
plane $\mathbf{C}$, we study the solid hull of its associated weighted space
$H_v^\infty(\mathbf{C})$ of all the entire functions $f$ such that $v|f|$ is
bounded. The solid hull is found for a large class of weights satisfying the
condition (B) of Lusky. Precise formulations are obtained for weights of the
form $v(r)=\exp(-ar^p), a>0, p>0$. Applications to spaces of multipliers are
included.


title: Incremental Quantitative Analysis on Dynamic Costs

abstract:
  In quantitative program analysis, values are assigned to execution traces to
represent a quality measure. Such analyses cover important applications, e.g.
resource usage. Examining all traces is well known to be intractable and
therefore traditional algorithms reason over an over-approximated set.
Typically, inaccuracy arises due to inclusion of infeasible paths in this set.
Thus path-sensitivity is one cure. However, there is another reason for the
inaccuracy: that the cost model, i.e., the way in which the analysis of each
trace is quantified, is dynamic. That is, the cost of a trace is dependent on
the context in which the trace is executed. Thus the goal of accurate analysis,
already challenged by path-sensitivity, is now further challenged by
context-sensitivity.
  In this paper, we address the problem of quantitative analysis defined over a
dynamic cost model. Our algorithm is an "anytime" algorithm: it generates an
answer quickly, but if the analysis resource budget allows, it progressively
produces better solutions via refinement iterations. The result of each
iteration remains sound, but importantly, must converge to an exact analysis
when given an unlimited resource budget. In order to be scalable, our algorithm
is designed to be incremental. We finally give evidence that a new level of
practicality is achieved by an evaluation on a realistic collection of
benchmarks.


title:
Magnetic structure of divalent europium compound EuGa$_4$ studied by
  single crystal time-of-flight neutron diffraction

abstract:
  The magnetic structure of the intermetallic compound EuGa$_4$ was
investigated using single-crystal neutron diffraction with the time-of-flight
(TOF) Laue technique on the new diffractometer SENJU at MLF of J-PARC. In spite
of high neutron absorption of Eu, a vast number of diffraction spots were
observed without isotope enrichment. The magnetic reflections were appeared at
the positions with the diffraction indices of $h+k+l{\neq}2n$ below 16 K,
indicating that the ordering vector is ${\bf q}=(0~0~0)$. Continuous evolution
of magnetic reflection intensity below $T_{\rm N}$ follows a squared Brillouin
function for $S$=7/2. By adopting a wavelength-dependent absorption collection,
the magnetic structure of EuGa$_4$ was revealed that a nearly full magnetic
moment of 6.4$~{\mu}_{\rm B}$ of Eu lies within the basal plane of the lattice.
The present study reveals a well-localized divalent Eu magnetism in EuGa$_4$
and demonstrates a high ability of SENJU to investigate materials with high
neutron absorption.


title: Ghost Imaging with Atoms

abstract:
  Ghost imaging is a technique -- first realized in quantum optics -- in which
the image emerges from cross-correlation between particles in two separate
beams. One beam passes through the object to a bucket (single-pixel) detector,
while the second beam's spatial profile is measured by a high resolution
(multi-pixel) detector but never interacts with the object. Neither detector
can reconstruct the image independently. However, until now ghost imaging has
only been demonstrated with photons.
  Here we report the first realisation of ghost imaging of an object using
massive particles. In our experiment, the two beams are formed by correlated
pairs of ultracold metastable helium atoms, originating from two colliding
Bose-Einstein condensates (BECs) via $s$-wave scattering. We use the
higher-order Kapitza-Dirac effect to generate the large number of correlated
atom pairs required, enabling the creation of a ghost image with good
visibility and sub-millimetre resolution.
  Future extensions could include ghost interference as well as tests of EPR
entantlement and Bell's inequalities.

categories: cond-mat.quant-gas physics.atom-ph physics.optics quant-ph


title:
Overcoming Challenges in Fixed Point Training of Deep Convolutional
  Networks

abstract:
  It is known that training deep neural networks, in particular, deep
convolutional networks, with aggressively reduced numerical precision is
challenging. The stochastic gradient descent algorithm becomes unstable in the
presence of noisy gradient updates resulting from arithmetic with limited
numeric precision. One of the well-accepted solutions facilitating the training
of low precision fixed point networks is stochastic rounding. However, to the
best of our knowledge, the source of the instability in training neural
networks with noisy gradient updates has not been well investigated. This work
is an attempt to draw a theoretical connection between low numerical precision
and training algorithm stability. In doing so, we will also propose and verify
through experiments methods that are able to improve the training performance
of deep convolutional networks in fixed point.


title: Global topology of Weyl semimetals and Fermi arcs

abstract:
  We provide a manifestly topological classification scheme for generalised
Weyl semimetals, in any spatial dimension and with arbitrary Weyl surfaces
which may be non-trivially linked. The classification naturally incorporates
that of Chern insulators. Our analysis refines, in a mathematically precise
sense, some well-known 3D constructions to account for subtle but important
global aspects of the topology of semimetals. Using a fundamental locality
principle, we derive a generalized charge cancellation condition for the Weyl
surface components. We analyse the bulk-boundary correspondence under a duality
transformation, which reveals explicitly the topological nature of the
resulting surface Fermi arcs. We also analyse the effect of moving Weyl points
on the bulk and boundary topological semimetal invariants.

categories: cond-mat.mes-hall hep-th math-ph math.MP


title:
Diffuse Gas in Retired Galaxies: Nebular Emission Templates and
  Constraints on the Sources of Ionization

abstract:
  We present emission line templates for passively evolving ("retired")
galaxies, useful for investigation of the evolution of the ISM in these
galaxies, and characterization of their high-temperature source populations.
The templates are based on high signal-to-noise ($>800$) co-added spectra
($3700-6800$\AA) of $\sim11500$ gas-rich Sloan Digital Sky Survey galaxies
devoid of star-formation and active galactic nuclei. Stacked spectra are
provided for the entire sample and sub-samples binned by mean stellar age. In
Johansson~et al (2014), these spectra provided the first measurements of the He
II 4686\AA\ line in passively-evolving galaxies, and the observed He
II/H$\beta$ ratio constrained the contribution of accreting white dwarfs (the
"single-degenerate" scenario) to the type Ia supernova rate. In this paper, the
full range of unambiguously detected emission lines are presented. Comparison
of the observed [O I] 6300\AA/H$\alpha$ ratio with photoionization models
further constrains any high-temperature single-degenerate scenario for type Ia
supernovae (with 1.5 $\lesssim$ T/$10^{5}K$ $\lesssim$ 10) to $\lesssim$3-6\%
of the observed rate in the youngest age bin (i.e. highest SN Ia rate). Hence,
for the same temperatures, in the presence of an ambient population of post-AGB
stars, we exclude additional high-temperature sources with a combined ionizing
luminosity of $\approx 1.35\times 10^{30} L_{\odot}/M_{\odot,*}$ for stellar
populations with mean ages of 1 - 4 Gyrs. Furthermore, we investigate the
extinction affecting both the stellar and nebular continuum. The latter shows
about five times higher values. This contradicts isotropically distributed dust
and gas that renders similar extinction values for both cases.


title: Rigidity of quasisymmetric mappings on self-affine carpets

abstract:
  We show that the class of quasisymmetric maps between horizontal self-affine
carpets is rigid. Such maps can only exist when the dimensions of the carpets
coincide, and in this case, the quasisymmetric maps are quasi-Lipschitz. We
also show that horizontal self-affine carpets are minimal for the conformal
Assouad dimension.


title: Moments convergence of powered normal extremes

abstract:
  In this paper, convergence for moments of powered normal extremes is
considered under an optimal choice of normalizing constants. It is shown that
the rates of convergence for normalized powered normal extremes depend on the
power index. However, the dependence disappears for higher-order expansions of
moments.


title:
Does the gamma-ray signal from the central Milky Way indicate Sommerfeld
  enhancement of dark matter annihilation?

abstract:
  Recently, Daylan et al. (2014) show that the GeV gamma-ray excess signal from
the central Milky Way can be explained by the annihilation of $\sim 40$ GeV
dark matter through $b\bar{b}$ channel. Based on the morphology of the
gamma-ray flux, the best-fit inner slope of the dark matter density profile is
$\gamma=1.26$. However, recent analyses of Milky Way dark matter profile favor
$\gamma=0.6-0.8$. In this article, we show that the GeV gamma-ray excess can
also be explained by the Sommerfeld-enhanced dark matter annihilation through
$b\bar{b}$ channel with $\gamma=0.85-1.05$. We constrain the parameters of the
Sommerfeld-enhanced annihilation by using the data from Fermi-LAT. We also show
that the predicted gamma-ray fluxes emitted from dwarf galaxies generally
satisfy the recent upper limits of gamma-ray fluxes detected by Fermi-LAT.


title: Note on Caranti's Method of Construction of Miller groups

abstract:
  The non-abelian groups with abelian group of automorphisms are widely
studied. Following Earnley, such groups are called Miller groups, since the
first example of such a group was given by Miller in 1913. Many other examples
of Miller $p$-groups have been constructed by several authors. Recently, A.
Caranti [{\it Israel J. Mathematics {\bf 205} (2015), 235-246}] provided module
theoretic methods for constructing non-special Miller $p$-groups from special
Miller $p$-groups. By constructing examples, we show that these methods do not
always work. We also provide a sufficient condition on special Miller $p$-group
for which the methods of Caranti work.


title:
On the Log-Likelihood Ratio Evaluation of CWCU Linear and Widely Linear
  MMSE Data Estimators

abstract:
  In soft decoding of data bits, the log-likelihood ratios are evaluated from
the estimated data symbols. For proper constellation diagrams such as QPSK or
16-QAM, these data symbols are often estimated using the linear minimum mean
square error (LMMSE) estimator. The LMMSE estimator only fulfills the weak
Bayesian unbiasedness constraint. Recently, estimators fulfilling the more
stringent component-wise conditionally unbiased (CWCU) constraints have been
investigated, such as the CWCU LMMSE estimator. In this paper, we prove that
the CWCU LMMSE estimates result in the very same log-likelihood ratios as the
LMMSE estimates. For improper constellation diagrams such as 8-QAM, widely
linear estimators are used. For this case, we show that the widely linear
versions of the LMMSE estimator and the CWCU LMMSE estimator also yield
identical log-likelihood ratios. Finally, we give a simulation example which
illustrates a number of interesting properties of the discussed widely linear
estimators.


title:
Low-Complexity Sub-band Digital Predistortion for Spurious Emission
  Suppression in Noncontiguous Spectrum Access

abstract:
  Noncontiguous transmission schemes combined with high power-efficiency
requirements pose big challenges for radio transmitter and power amplifier (PA)
design and implementation. Due to the nonlinear nature of the PA, severe
unwanted emissions can occur, which can potentially interfere with neighboring
channel signals or even desensitize the own receiver in frequency division
duplexing (FDD) transceivers. In this article, to suppress such unwanted
emissions, a low-complexity sub-band DPD solution, specifically tailored for
spectrally noncontiguous transmission schemes in low-cost devices, is proposed.
The proposed technique aims at mitigating only the selected spurious
intermodulation distortion components at the PA output, hence allowing for
substantially reduced processing complexity compared to classical linearization
solutions. Furthermore, novel decorrelation based parameter learning solutions
are also proposed and formulated, which offer reduced computing complexity in
parameter estimation as well as the ability to track time-varying features
adaptively. Comprehensive simulation and RF measurement results are provided,
using a commercial LTE-Advanced mobile PA, to evaluate and validate the
effectiveness of the proposed solution in real world scenarios. The obtained
results demonstrate that highly efficient spurious component suppression can be
obtained using the proposed solutions.


title:
Consensus Attention-based Neural Networks for Chinese Reading
  Comprehension

abstract:
  Reading comprehension has embraced a booming in recent NLP research. Several
institutes have released the Cloze-style reading comprehension data, and these
have greatly accelerated the research of machine comprehension. In this work,
we firstly present Chinese reading comprehension datasets, which consist of
People Daily news dataset and Children's Fairy Tale (CFT) dataset. Also, we
propose a consensus attention-based neural network architecture to tackle the
Cloze-style reading comprehension problem, which aims to induce a consensus
attention over every words in the query. Experimental results show that the
proposed neural network significantly outperforms the state-of-the-art
baselines in several public datasets. Furthermore, we setup a baseline for
Chinese reading comprehension task, and hopefully this would speed up the
process for future research.


title:
A High-Resolution, Wave and Current Resource Assessment of Japan: The
  Web GIS Dataset

abstract:
  The University of Tokyo and JAMSTEC have conducted state-of-the-art wave and
current resource assessments to assist with generator site identification and
construction in Japan. These assessments are publicly-available and accessible
via a web GIS service designed by WebBrain that utilizes TDS and GeoServer
software with Leaflet libraries. The web GIS dataset contains statistical
analyses of wave power, ocean and tidal current power, ocean temperature power,
and other basic physical variables. The data (2D maps, time charts, depth
profiles, etc.) is accessed through interactive browser sessions and
downloadable files.


title: Exponential ergodicity for a class of non-Markovian stochastic processes

abstract:
  We prove the convergence at an exponential rate towards the invariant
probability measure for a class of solutions of stochastic differential
equations with finite delay. This is done, in this non-Markovian setting, using
the cluster expansion method, inspired from [4] or [14]. As a consequence, the
results hold for small perturbations of ergodic diffusions.


title: Stochastic extensions of symbols in Wiener spaces and heat operator

abstract:
  The construction, in [AJN], of a pseudodifferential calculus analogous to the
Weyl calculus, in an infinite dimensional setting, required the introduction of
convenient classes of symbols.
  In this article, we proceed with the study of these classes in order to
establish, later on, the properties that a pseudodifferential calculus is
expected to satisfy. The introduction and the study of a new class are rendered
necessary in view of applications in QED.
  We prove here that the symbols of both classes and the terms of their
Taylorexpansions admit stochastic extensions. We define, in this infinite
dimensional setting, a semigroup $H_t$ analogous to the heat semigroup, acting
on the symbols belonging to both classes of symbols. The heat operator commutes
with a second order operator similar to the Laplacian, which is its
infinitesimal generator. For the class defined there, we give an expansion in
powers of $t$ of $H_tf$,according to the classes of symbols.


title:
Solution-generating methods of Einstein's equations by Hamiltonian
  reduction

abstract:
  The purpose of this paper is to demonstrate a new method of generating exact
solutions to the Einstein's equations obtained by the Hamiltonian reduction.
The key element to the successful Hamiltonian reduction is finding the
privileged spacetime coordinates in which physical degrees of freedom
manifestly reside in the conformal two-metric, and all the other metric
components are determined by the conformal two-metric. In the privileged
coordinates the Einstein's constraint equations become trivial; the Hamiltonian
and momentum constraints are simply the defining equations of a non-vanishing
gravitational Hamiltonian and momentum densities in terms of conformal
two-metric and its conjugate momentum, respectively. Thus, given any conformal
two-metric, which is a constraint-free data, one can construct the whole
4-dimensional spacetime by integrating the first-order superpotential
equations. As the first examples of using Hamiltonian reduction in solving the
Einstein's equations, we found two exact solutions to the Einstein's equations
in the privileged coordinates. Suitable coordinate transformations from the
privileged to the standard coordinates show that they are just the
Einstein-Rosen wave and the Schwarzschild solution. The local gravitational
Hamiltonian and momentum densities of these spacetimes are also presented in
the privileged coordinates.


title: The black hole binary V404 Cygni: an obscured AGN analogue

abstract:
  Typical black hole binaries in outburst show spectral states and transitions,
characterized by a clear connection between the inflow onto the black hole and
outflow from its vicinity. The transient stellar mass black hole binary V404
Cyg apparently does not fit in this picture. Its outbursts are characterized by
intense flares and intermittent low-flux states, with a dynamical range of
several orders of magnitude on timescales of hours. During the 2015 June-July
X-ray outburst a joint Swift and INTEGRAL observing campaign captured V404 Cyg
in one of these low-flux states. The simultaneous Swift/XRT and
INTEGRAL/JEM-X/ISGRI spectrum is reminiscent of that of obscured/absorbed AGN.
It can be modeled as a Comptonization spectrum, heavily absorbed by a partial
covering, high-column density material ($N_\textrm{H} \approx
1.4\times10^{24}\,\textrm{cm}^{-2}$), and a dominant reflection component,
including a narrow Iron-K$\alpha$ line. Such spectral distribution can be
produced by a geometrically thick accretion flow able to launch a clumpy mass
outflow, likely responsible for both the high intrinsic absorption and the
intense reflection emission observed. Similarly to what happens in certain
obscured AGN, the low-flux states might not be solely related to a decrease in
the intrinsic luminosity, but could instead be caused by an almost complete
obscuration of the inner accretion flow.


title:
Detecting non-Markovianity of quantum evolution via spectra of dynamical
  maps

abstract:
  We provide an analysis on non-Markovian quantum evolution based on the
spectral properties of dynamical maps. We introduce the dynamical analog of
entanglement witness to detect non-Markovianity and we illustrate its behaviour
with several instructive examples. It is shown that for a certain class of
dynamical maps the shape of the body of accessible states provides a simple
non-Markovianity witness.


title:
Siamese Regression Networks with Efficient mid-level Feature Extraction
  for 3D Object Pose Estimation

abstract:
  In this paper we tackle the problem of estimating the 3D pose of object
instances, using convolutional neural networks. State of the art methods
usually solve the challenging problem of regression in angle space indirectly,
focusing on learning discriminative features that are later fed into a separate
architecture for 3D pose estimation. In contrast, we propose an end-to-end
learning framework for directly regressing object poses by exploiting Siamese
Networks. For a given image pair, we enforce a similarity measure between the
representation of the sample images in the feature and pose space respectively,
that is shown to boost regression performance. Furthermore, we argue that our
pose-guided feature learning using our Siamese Regression Network generates
more discriminative features that outperform the state of the art. Last, our
feature learning formulation provides the ability of learning features that can
perform under severe occlusions, demonstrating high performance on our novel
hand-object dataset.


title:
Waiter-Client and Client-Waiter colourability games on a $k$-uniform
  hypergraph and the $k$-SAT game

abstract:
  Waiter-Client and Client-Waiter games are two-player, perfect information
games, with no chance moves, played on a finite set (board) with special
subsets known as the winning sets. Each round of the biased $(1:q)$ game begins
with Waiter offering $q+1$ previously unclaimed elements of the board to
Client, who claims one. The $q$ elements remaining are then claimed by Waiter.
If Client fully claims a winning set by the time all board elements have been
offered, he wins in the Client-Waiter game and loses in the Waiter-Client game.
We give an estimate for the threshold bias of the $(1:q)$ Waiter-Client and
Client-Waiter versions of two different games: the non-2-colourability game,
played on the complete $k$-uniform hypergraph, and the $k$-SAT game. In
particular, we show that the unique value of $q$ at which the winner of the
Client-Waiter version of the non-2-colourability game changes is
$\frac{1}{n}\binom{n}{k}2^{-k(1+o_k(1))}$ and, for the Waiter-Client version,
the corresponding value of $q$ is $\frac{1}{n}\binom{n}{k}2^{\Theta_k(k)}$.
Additionally, we show that the threshold bias for the Waiter-Client and
Client-Waiter versions of the $k$-SAT game is $\frac{1}{n}\binom{n}{k}$ up to a
factor that is exponential and polynomial in $k$ respectively. This shows that
these games exhibit the "probabilistic intuition".


title: Maximum Entropy and Sufficiency

abstract:
  The notion of Bregman divergence and sufficiency will be defined on general
convex state spaces. It is demonstrated that only spectral sets can have a
Bregman divergence that satisfies a sufficiency condition. Positive elements
with trace 1 in a Jordan algebra are examples of spectral sets, and the most
important example is the set of density matrices with complex entries. It is
conjectured that information theoretic considerations lead directly to the
notion of Jordan algebra under some regularity conditions.


title: Signals of Two Universal Extra Dimensions at the LHC

abstract:
  Extensions of the standard model with universal extra dimensions are
interesting both as phenomenological templates as well as model-building
fertile ground. For instance, they are one the prototypes for theories
exhibiting compressed spectra, leading to difficult searches at the LHC since
the decay products of new states are soft and immersed in a large standard
model background. Here we study the phenomenology at the LHC of theories with
two universal extra dimensions. We obtain the current bound by using the
production of second level excitations of electroweak gauge bosons decaying to
a pair of leptons and study the reach of the LHC Run~II in this channel. We
also introduce a new channel originating in higher dimensional operators and
resulting in the single production of a second level quark excitation. Its
subsequent decay into a hard jet and lepton pair resonance would allow the
identification of a more model-specific process, unlike the more generic vector
resonance signal. We show that the sensitivity of this channel to the
compactification scale is very similar to the one obtained using the vector
resonance.


title:
Optimization of periodic single-photon sources based on combined
  multiplexing

abstract:
  We consider periodic single-photon sources with combined multiplexing in
which the outputs of several time-multiplexed sources are spatially
multiplexed. We give a full statistical description of such systems in order to
optimize them with respect to maximal single-photon probability. We carry out
the optimization for a particular scenario which can be realized in bulk optics
and its expected performance is potentially the best at the present state of
the art. We find that combined multiplexing outperforms purely spatially or
time multiplexed sources for certain parameters only, and we characterize these
cases. Combined multiplexing can have the advantages of possibly using less
nonlinear sources, achieving higher repetition rates, and the potential
applicability for continuous pumping. We estimate an achievable single-photon
probability between 85% and 89%.


title: Group graded basic Morita equivalences

abstract:
  We introduce group graded basic Morita equivalences between algebras deter-
mined by blocks of normal subgroups, and by using the extended Brauer quotient,
we show that they induce graded basic Morita equivalences at local levels.


title: On the Fukaya-Seidel categories of surface Lefschetz fibrations

abstract:
  We prove that a positive allowable Lefschetz fibration, PALF in short, admits
a structure of exact Lefschetz fibration in the sense of Seidel \cite{Se08}. If
the two-fold first Chern class of the total space is zero, we obtain the
Fukaya-Seidel category. We prove that the derived Fukaya-Seidel category of
PALF is independent of the choice of the symplectic structure. At the end of
this paper, we study examples and show that derived Fukaya-Seidel categories
have more information than the Milnor lattices of PALFs.


title: Squeezing of X waves with orbital angular momentum

abstract:
  Multi-level quantum protocols may potentially supersede standard quantum
optical polarization-encoded protocols in terms of amount of information
transmission and security. However, for free space telecomunications, we do not
have tools for limiting loss due to diffraction and perturbations, as for
example turbulence in air. Here we study propagation invariant quantum X-waves
with angular momentum; this representation expresses the electromagnetic field
as a quantum gas of weakly interacting bosons. The resulting spatio-temporal
quantized light pulses are not subject to diffraction and dispersion, and are
intrinsically resilient to disturbances in propagation. We show that
spontaneous down-conversion generates squeezed X-waves useful for quantum
protocols. Surprisingly the orbital angural momentum affects the squeezing
angle, and we predict the existence of a characteristic axicon aperture for
maximal squeezing. There results may boost the applications in free space of
quantum optical transmission and multi-level quantum protocols, and may also be
relevant for novel kinds of interferometers, as satellite-based gravitational
wave detectors.


title: Interacting Quantum Fields on de Sitter Space

abstract:
  In 1975 Figari, H{\o}egh-Krohn and Nappi constructed the P(phi)_2 model on
the de Sitter space. Here we complement their work with new results, as well as
by connecting this model to various areas of mathematics. In particular, i.) we
discuss the causal structure of de Sitter space and the induces representations
of the Lorentz group. We show that the UIRs of SO_0(1,2) for both the principal
and the complementary series can be formulated on Hilbert spaces whose
functions are supported on a Cauchy surface, ii.) we describe the free
classical dynamical system in both its covariant and canonical form, and
present the associated quantum one-particle KMS structures in the sense of Kay,
iii.) we discuss the localisation properties of one-particle wave functions and
how these properties are inherited by the algebras of local observables. In
addition, we describe the relations between the modular objects (in the sense
of Tomita-Takesaki theory) associated to wedge algebras and the representations
of the Lorentz group, iv.) we connect the representations of SO(1,2) to unitary
representations of SO(3) on the Euclidean sphere, and discuss how the P(phi)_2
interaction can be represented by a rotation invariant vector in the Euclidean
Fock space. We present a novel Osterwalder-Schrader reconstruction theorem,
which shows that physical infrared problems are absent on de Sitter space, v.)
we explain how the generators of the boosts and the rotations for the
interacting quantum field theory arise arise from the stress-energy tensor.
Finally, we show that the interacting quantum fields satisfy the equations of
motion in their covariant form. In summary, we argue that the de Sitter
P(phi)_2 model is the simplest and most explicit relativistic quantum field
theory, which satisfies basic expectations, like covariance, particle creation,
stability and finite speed of light.


title:
SMA observations towards the compact, short-lived bipolar water maser
  outflow in the LkH{\alpha} 234 region

abstract:
  We present Submillimeter Array (SMA) 1.35 mm subarcsecond angular resolution
observations toward the LkH{\alpha} 234 intermediate-mass star-forming region.
The dust emission arises from a filamentary structure of $\sim$5 arcsec
($\sim$4500 au) enclosing VLA 1-3 and MM 1, perpendicular to the different
outflows detected in the region. The most evolved objects are located at the
southeastern edge of the dust filamentary structure and the youngest ones at
the northeastern edge. The circumstellar structures around VLA 1, VLA 3, and MM
1 have radii between $\sim$200 and $\sim$375 au and masses in the
$\sim$0.08-0.3 M$_{\odot}$ range. The 1.35 mm emission of VLA 2 arises from an
unresolved (r$< 135$ au) circumstellar disk with a mass of $\sim$0.02
M$_{\odot}$. This source is powering a compact ($\sim$4000 au), low radial
velocity ($\sim$7 km s$^{-1}$) SiO bipolar outflow, close to the plane of the
sky. We conclude that this outflow is the "large-scale" counterpart of the
short-lived, episodic, bipolar outflow observed through H$_2$O masers at much
smaller scales ($\sim $180 au), and that has been created by the accumulation
of the ejection of several episodic collimated events of material. The
circumstellar gas around VLA 2 and VLA 3 is hot ($\sim$130 K) and exhibits
velocity gradients that could trace rotation. There is a bridge of warm and
dense molecular gas connecting VLA 2 and VLA 3. We discuss the possibility that
this bridge could trace a stream of gas between VLA 3 and VLA 2, increasing the
accretion rate onto VLA 2 to explain why this source has an important outflow
activity.


title: Production of light nuclei in the thermal and coalescence models

abstract:
  The thermal model properly describes the production yields of light nuclei in
relativistic heavy-ion collisions even so the loosely bound sizable nuclei
cannot exist in the dense and hot hadron gas at a chemical freeze-out. Within
the coalescence model, light nuclei are formed at the latest stage of nuclear
collisions - a kinetic freeze-out - due to final state interactions. After
discussing the models, we derive simple analytic formulas and, using model
parameters directly inferred from experimental data, we show that the thermal
and coalescence model predictions are quantitatively close to each other. A
possibility to falsify one of the two models is suggested.


title: Non Gaussian Minkowski functionals and extrema counts for 2D sky maps

abstract:
  In the conference presentation we have reviewed the theory of non-Gaussian
geometrical measures for the 3D Cosmic Web of the matter distribution in the
Universe and 2D sky data, such as Cosmic Microwave Background (CMB) maps that
was developed in a series of our papers. The theory leverages symmetry of
isotropic statistics such as Minkowski functionals and extrema counts to
develop post- Gaussian expansion of the statistics in orthogonal polynomials of
invariant descriptors of the field, its first and second derivatives. The
application of the approach to 2D fields defined on a spherical sky was
suggested, but never rigorously developed. In this paper we present such
development treating effects of the curvature and finiteness of the spherical
space $S_2$ exactly, without relying on the flat-sky approximation. We present
Minkowski functionals, including Euler characteristic and extrema counts to the
first non-Gaussian correction, suitable for weakly non-Gaussian fields on a
sphere, of which CMB is the prime example.


title: Topology from enrichment: the curious case of partial metrics

abstract:
  For any small quantaloid $\Q$, there is a new quantaloid $\D(\Q)$ of
diagonals in $\Q$. If $\Q$ is divisible then so is $\D(\Q)$ (and vice versa),
and then it is particularly interesting to compare categories enriched in $\Q$
with categories enriched in $\D(\Q)$. Taking Lawvere's quantale of extended
positive real numbers as base quantale, $\Q$-categories are generalised metric
spaces, and $\D(\Q)$-categories are generalised partial metric spaces, i.e.\
metric spaces in which self-distance need not be zero and with a suitably
modified triangular inequality. We show how every small quantaloid-enriched
category has a canonical closure operator on its set of objects: this makes for
a functor from quantaloid-enriched categories to closure spaces. Under mild
necessary-and-sufficient conditions on the base quantaloid, this functor lands
in the category of topological spaces; and an involutive quantaloid is
Cauchy-bilateral (a property discovered earlier in the context of distributive
laws) if and only if the closure on any enriched category is identical to the
closure on its symmetrisation. As this now applies to metric spaces and partial
metric spaces alike, we demonstrate how these general categorical constructions
produce the "correct" definitions of convergence and Cauchyness of sequences in
generalised partial metric spaces. Finally we describe the Cauchy-completion,
the Hausdorff contruction and exponentiability of a partial metric space, again
by application of general quantaloid-enriched category theory.


title:
Creation of p-wave Feshbach molecules in the selected angular momentum
  states using an optical lattice

abstract:
  We selectively create p-wave Feshbach molecules in the $m_{l}=\pm 1$ orbital
angular momentum projection state of $^{6}$Li. We use an optical lattice
potential to restrict the relative momentum of the atoms such that only the
$m_{l}=\pm 1$ molecular state couples to the atoms at the Feshbach resonance.
We observe the hollow-centered dissociation profile, which is a clear
indication of the selective creation of p-wave molecules in the $m_{l}=\pm1$
states. We also measure the dissociation energy of the p-wave molecules created
in the optical lattice and develop a theoretical formulation to explain the
dissociation energy as a function of the magnetic field ramp rate for
dissociation. The capability of selecting one of the two closely-residing
p-wave Feshbach resonances is useful for the precise characterization of the
p-wave Feshbach resonances.


title:
Rearrangement zone around a crack tip in a double self-assembled
  transient network

abstract:
  We investigate the nucleation and propagation of cracks in self-assembled
viscoelastic fluids, which are made of surfactant micelles reversibly linked by
telechelic polymers. The morphology of the micelles can be continuously tuned,
from spherical to rod-like to wormlike, thus producing transient double
networks when the micelles are sufficiently long and entangled, and transient
single networks otherwise. For a single network, we show that cracks nucleate
when the sample deformation rate involved is comparable to the relaxation time
scale of the network. For a double network, by contrast, significant
rearrangements of the micelles occur as a crack nucleates and propagates. We
show that birefringence develops at the crack tip over a finite length, $\xi$,
which corresponds to the length scale over which micelles alignment occur. We
find that $\xi$ is larger for slower cracks, suggesting an increase of
ductility.


title:
Effective time reversal and echo dynamics in the transverse field Ising
  model

abstract:
  The question of thermalisation in closed quantum many-body systems has
received a lot of attention in the past few years. An intimately related
question is whether a closed quantum system shows irreversible dynamics.
However, irreversibility and what we actually mean by this in a quantum
many-body system with unitary dynamics has been explored very little. In this
work we investigate the dynamics of the Ising model in a transverse magnetic
field involving an imperfect effective time reversal. We propose a definition
of irreversibility based on the echo peak decay of observables. Inducing the
effective time reversal by different protocols we find algebraic decay of the
echo peak heights or an ever persisting echo peak indicating that the dynamics
in this model is well reversible.


title:
Inversion of Strong Field Photoelectron Spectra for Molecular Orbital
  Imaging

abstract:
  Imaging structures at the molecular level is a fast developing
interdisciplinary research field that spans across the boundaries of physics
and chemistry. High spatial resolution images of molecules can be obtained with
photons or ultrafast electrons. In addition, images of valence molecular
orbitals can be extracted via tomographic techniques based on the coherent XUV
radiation emitted by a molecular gas exposed to an intense ultra-short infrared
laser pulse. In this paper, we demonstrate that similar information can be
obtained by inverting energy resolved photoelectron spectra using a simplified
analytical model.


title: Galaxies with conspicuous optical warps

abstract:
  In this paper, we present results of a photometric and kinematic study for a
sample of 13 edge-on spiral galaxies with pronounced integral-shape warps of
their stellar discs. The global structure of the galaxies is analyzed on the
basis of the Sloan Digital Sky Survey (SDSS) imaging, in the g, r and i
passbands. Spectroscopic observations are obtained with the 6-m Special
Astrophysical Observatory telescope. In general, galaxies of the sample are
typical bright spiral galaxies satisfying the Tully-Fisher relation. Most of
the galaxies reside in dense spatial environments and, therefore, tidal
encounters are the most probable mechanism for generating their stellar warps.
We carried out a detailed analysis of the galaxies and their warps and obtained
the following main results: (i) maximum angles of stellar warps in our sample
are about 20{\deg}; (ii) warps start, on average, between 2 and 3 exponential
scale lengths of a disc; (iii) stronger warps start closer to the center, weak
warps start farther; (iv) warps are asymmetric, with the typical degree of
asymmetry of about several degrees (warp angle); (v) massive dark halo is
likely to preclude the formation of strong and asymmetric warps.


title:
Reliability of the two-point measurement of the spatial correlation
  length from Gaussian-shaped fluctuating signals in fusion-grade plasmas

abstract:
  A statistical method for the estimation of spatial correlation lengths of
Gaussian-shaped fluctuating signals with two measurement points is examined to
quantitatively evaluate its reliability (variance) and accuracy (bias error).
The standard deviation of the correlation value is analytically derived for
randomly distributed Gaussian shaped fluctuations satisfying stationarity and
homogeneity, allowing us to evaluate, as a function of fluctuation-to-noise
ratios, sizes of averaging time windows and ratios of the distance between the
two measurement points to the true correlation length, the goodness of the
two-point measurement for estimating the spatial correlation length. Analytic
results are confirmed with numerically generated synthetic data and real
experimental data obtained with the KSTAR beam emission spectroscopy
diagnostic. Our results can be applied to Gaussian-shaped fluctuating signals
where a correlation length must be measured with only two measurement points.


title: Second order time dependent tangent bundles and their applications

abstract:
  The aim of this paper is to geometrize time dependent Lagrangian mechanics in
a way that the framework of second order tangent bundles plays an essential
role. To this end, we first introduce the concepts of time dependent
connections and time dependent semisprays on a manifold $M$ and their induced
vector bundle structures on the second order time dependent tangent bundle
$\R\times T^2M$. Then we turn our attention to regular time Lagrangians and
their interaction with $\R\times T^2M$ in different situations such as
mechanical systems with potential fields, external forces and holonomic
constraints. Finally we propose an examples to support our theory.


title: Observation of the spin Nernst effect

abstract:
  The observation of the spin Hall effect triggered intense research on pure
spin current transport. With the spin Hall effect, the spin Seebeck effect, and
the spin Peltier effect already observed, our picture of pure spin current
transport is almost complete. The only missing piece is the spin Nernst
(-Ettingshausen) effect, that so far has only been discussed on theoretical
grounds. Here, we report the observation of the spin Nernst effect. By applying
a longitudinal temperature gradient, we generate a pure transverse spin current
in a Pt thin film. For readout, we exploit the
magnetization-orientation-dependent spin transfer to an adjacent Yttrium Iron
Garnet layer, converting the spin Nernst current in Pt into a controlled change
of the longitudinal thermopower voltage. Our experiments show that the spin
Nernst and the spin Hall effect in Pt are of comparable magnitude, but differ
in sign, as corroborated by first-principles calculations.


title: Diclique clustering in a directed random graph

abstract:
  We discuss a notion of clustering for directed graphs, which describes how
likely two followers of a node are to follow a common target. The associated
network motifs, called dicliques or bi-fans, have been found to be key
structural components in various real-world networks. We introduce a two-mode
statistical network model consisting of actors and auxiliary attributes, where
an actor i decides to follow an actor j whenever i demands an attribute
supplied by j. We show that the digraph admits nontrivial clustering properties
of the aforementioned type, as well as power-law indegree and outdegree
distributions.


title: Rates of DNA Sequence Profiles for Practical Values of Read Lengths

abstract:
  A recent study by one of the authors has demonstrated the importance of
profile vectors in DNA-based data storage. We provide exact values and lower
bounds on the number of profile vectors for finite values of alphabet size $q$,
read length $\ell$, and word length $n$.Consequently, we demonstrate that for
$q\ge 2$ and $n\le q^{\ell/2-1}$, the number of profile vectors is at least
$q^{\kappa n}$ with $\kappa$ very close to one.In addition to enumeration
results, we provide a set of efficient encoding and decoding algorithms for
each of two particular families of profile vectors.


title: Alternative set of defining constants for redefinition of four SI units

abstract:
  We discuss different sets of defining constants, fixed values of which are
considered in connection with the transition to new definitions of four SI
units (the kilogram, the mole, the ampere, and the kelvin). The notion of
constant's order in a given system of units is suggested. We propose an
alternative set of fixed constants applicable for new definitions of the four
SI units. We analyse and discuss in detail the set, which consists of the
Planck constant, the Avogadro constant, the Boltzmann constant and the magnetic
constant.