title:
Classification of Interacting Topological Floquet Phases in One
  Dimension

abstract:
  Periodic driving of a quantum system can enable new topological phases with
no analog in static systems. In this paper we systematically classify
one-dimensional topological and symmetry-protected topological (SPT) phases in
interacting fermionic and bosonic quantum systems subject to periodic driving,
which we dub Floquet SPTs (FSPTs). For physical realizations of interacting
FSPTs, many-body localization by disorder is a crucial ingredient, required to
obtain a stable phase that does not catastrophically heat to infinite
temperature. We demonstrate that bosonic and fermionic FSPTs phases are
classified by the same criteria as equilibrium phases, but with an enlarged
symmetry group $\tilde G$, that now includes discrete time translation symmetry
associated with the Floquet evolution. In particular, 1D bosonic FSPTs are
classified by projective representations of the enlarged symmetry group
$H^2({\tilde G},U(1))$. We construct explicit lattice models for a variety of
systems, and then formalize the classification to demonstrate the completeness
of this construction. We also derive general constraints on localization and
symmetry based on the representation theory of the symmetry group, and show
that symmetry-preserving localized phases are possible only for Abelian
symmetry groups. In particular, this rules out the possibility of many-body
localized SPTs with continuous spin symmetry.


title: Optimal Redshift Weighting For Redshift Space Distortions

abstract:
  The low statistical errors on cosmological parameters promised by future
galaxy surveys will only be realised with the development of new, fast,
analysis methods that reduce potential systematic problems to low levels. We
present an efficient method for measuring the evolution of the growth of
structure using Redshift Space Distortions (RSD), that removes the need to make
measurements in redshift shells. We provide sets of galaxy-weights that cover a
wide range in redshift, but are optimised to provide differential information
about cosmological evolution. These are derived to optimally measure the
coefficients of a parameterisation of the redshift-dependent matter density,
which provides a framework to measure deviations from the concordance
$\Lambda$CDM cosmology, allowing for deviations in both geometric and/or
growth. We test the robustness of the weights by comparing with alternative
schemes and investigate the impact of galaxy bias. We extend the results to
measure the combined anisotropic Baryon Acoustic Oscillation (BAO) and RSD
signals.


title: Weinberg Soft Theorems from Weinberg Adiabatic Modes

abstract:
  Soft theorems for the scattering of low energy photons and gravitons and
cosmological consistency conditions on the squeezed-limit correlation functions
are both understood to be consequences of invariance under large gauge
transformations. We apply the same method used in cosmology -- based on the
identification of an infinite set of "adiabatic modes" and the corresponding
conserved currents -- to derive flat space soft theorems for electrodynamics
and gravity. We discuss how the recent derivations based on the asymptotic
symmetry groups (BMS) can be continued to a finite size sphere surrounding the
scattering event, when the soft photon or graviton has a finite momentum. We
give a finite distance derivation of the antipodal matching condition
previously imposed between future and past null infinities, and explain why all
but one radiative degrees of freedom decouple in the soft limit. In contrast to
earlier works on BMS, we work with adiabatic modes which correspond to large
gauge transformations that are $r$-dependent.


title: Classical static final state of collapse with supertranslation memory

abstract:
  The Kerr metric models the final classical black hole state after
gravitational collapse of matter and radiation. Any stationary metric which is
close to the Kerr metric has been proven to be diffeomorphic to it. Now, finite
supertranslation diffeomorphisms are symmetries which map solutions to
inequivalent solutions as such diffeomorphisms generate conserved superrotation
charges. The final state of gravitational collapse is therefore parameterized
by its mass, angular momentum and supertranslation field, signaled by its
conserved superrotation charges.
  In this paper, we first derive the angle-dependent energy conservation law
relating the asymptotic value of the supertranslation field of the final state
to the details of the collapse and subsequent evolution of the system. We then
generate the static solution with an asymptotic supertranslation field and we
study some of its properties. Up to a caveat, the deviation from the
Schwarzschild metric could therefore be predicted on a case-by-case basis from
accurate modeling of the angular dependence of the ingoing and outgoing energy
fluxes leading to the final state.


title:
Pinning of Fermionic Occupation Numbers: General Concepts and One
  Dimension

abstract:
  Analytical evidence for the physical relevance of generalized Pauli
constraints (GPCs) has recently been provided in [PRL 110, 040404]: Natural
occupation numbers $\vec{\lambda}\equiv (\lambda_i)$ of the ground state of a
model system in the regime of weak couplings $\kappa$ of three spinless
fermions in one spatial dimension were found extremely close, in a distance
$D_{min}\sim \kappa^8$ to the boundary of the allowed region. We provide a
self-contained and complete study of this quasipinning phenomenon. In
particular, we develop tools for its systematic exploration and quantification.
We confirm that quasipinning in one dimension occurs also for larger particle
numbers and extends to intermediate coupling strengths, but vanishes for very
strong couplings. We further explore the non-triviality of our findings by
comparing quasipinning by GPCs to potential quasipinning by the less
restrictive Pauli exclusion principle constraints. This allows us to eventually
confirm the significance of GPCs beyond Pauli's exclusion principle.


title:
The z = 9-10 galaxy population in the Hubble Frontier Fields and CLASH
  surveys: The z=9 LF and further evidence for a smooth decline in UV
  luminosity at z >= 8

abstract:
  We present the results of a search for z=9-10 galaxies within the first 8
pointings of the Hubble Frontier Fields (HFF) (4 clusters plus 4 parallel
fields) and 20 cluster fields from the CLASH survey. Combined with our previous
analysis of the Hubble Ultra-Deep field (HUDF), we have now completed a search
for z=9-10 galaxies over ~130 sq. arcmin, across 29 HST WFC3/IR pointings. As
in our recent study of the first two HFF fields, we confine our primary search
for high-redshift candidates in the HFF imaging to the uniformly deep (i.e.
sigma_160>30 AB mag in 0.5-arcsec diameter apertures), relatively low
magnification regions. In the CLASH fields our search was confined to uniformly
deep regions where sigma_160>28.8 AB mag. Our SED fitting analysis unveils a
sample of 33 galaxy candidates at z_phot>=8.4, five of which have primary
photometric redshift solutions in the range 9.6<z_phot<11.2. By calculating a
de-lensed effective volume for each candidate, the improved statistics and
reduced cosmic variance provided by our new sample allows a more accurate
determination of the UV-selected galaxy luminosity function (LF) at z~9. Our
new results strengthen our previous conclusion that the LF appears to evolve
smoothly from z=8 to z=9, an evolution which can be equally well modelled by a
factor of ~2 drop in density, or a dimming of ~0.5 mag in M*. Moreover, based
on our new sample, we are able to place initial constraints on the z=10 LF,
finding that the number density at M_1500 ~ -19.7 is log(phi) = -4.1
(+0.2,-0.3), a factor of ~2 lower than at z=9. Finally, we use our new results
to re-visit the issue of the decline in UV luminosity density at z>=8. We
conclude that the data continue to support a smooth decline in rho_UV over the
redshift interval 6<z<10, in agreement with simple models of early galaxy
evolution driven by the growth in the underlying dark matter halo mass
function.


title: A 12-Year Activity Cycle for HD 219134

abstract:
  The nearby (6.5 pc) star HD 219134 was recently shown by Motalebi et al.
(2015) and Vogt et al. (2015) to host several planets, the innermost of which
is transiting. We present twenty-seven years of radial velocity observations of
this star from the McDonald Observatory Planet Search program, and nineteen
years of stellar activity data. We detect a long-period activity cycle measured
in the Ca II $S_{HK}$ index, with a period of $4230 \pm 100$ days (11.7 years),
very similar to the 11-year Solar activity cycle. Although the period of the
Saturn-mass planet HD 219134 h is close to half that of the activity cycle, we
argue that it is not an artifact due to stellar activity. We also find a
significant periodicity in the $S_{HK}$ data due to stellar rotation with a
period of 22.8 days. This is identical to the period of planet f identified by
Vogt et al. (2015), suggesting that this radial velocity signal might be caused
by rotational modulation of stellar activity rather than a planet. Analysis of
our radial velocities allows us to detect the long-period planet HD 219134 h
and the transiting super-Earth HD 219134 b. Finally, we use our long time
baseline to constrain the presence of longer-period planets in the system,
excluding to $1\sigma$ objects with $M\sin i>0.36 M_J$ at 12 years
(corresponding to the orbital period of Jupiter) and $M\sin i>0.72 M_J$ at a
period of 16.4 years (assuming a circular orbit for an outer companion).


title:
Fast control of semiconductor qubits beyond the rotating-wave
  approximation

abstract:
  We present a theoretical study of single-qubit operations by oscillatory
fields on various semiconductor platforms. We explicitly show how to perform
faster gate operations by going beyond the universally-used rotating wave
approximation (RWA) regime, while using only two sinusoidal pulses. No
complicated pulse shaping or optimal control sequences are required. We first
show for specific published experiments how much error is currently incurred by
implementing pulses designed using standard RWA. We then show that an even
modest increase in gate speed would cause problems in using RWA for gate design
in the singlet-triplet (ST) and resonant-exchange (RX) qubits. We discuss the
extent to which analytically keeping higher orders in the perturbation theory
would address the problem. More strikingly, we give a new prescription for
gating with strong coupling far beyond the RWA regime. We perform numerical
calculations for the phases and the durations of two consecutive pulses to
realize the key Hadamard and $\frac{\pi}{8}$ gates with coupling strengths up
to several times the qubit splitting. Working in this manifestly non-RWA
regime, the gate operation speeds up by two to three orders of magnitude.


title: Pushing Higgs Effective Theory over the Edge

abstract:
  Based on a vector triplet model we study a possible failure of dimension-6
operators in describing LHC Higgs kinematics. First, we illustrate that
including dimension-6 contributions squared can significantly improve the
agreement between the full model and the dimension-6 approximation, both in
associated Higgs production and in weak-boson-fusion Higgs production. Second,
we test how a simplified model with an additional heavy scalar could improve
the agreement in critical LHC observables. In weak boson fusion we find an
improvement for virtuality-related observables at large energies, but at the
cost of sizeable deviations in interference patterns and angular correlations.


title:
Massive-Star Mergers and the Recent Transient in NGC4490: A More Massive
  Cousin of V838 Mon and V1309 Sco

abstract:
  The Galactic transient V1309 Sco was the result of a merger in a low-mass
star system, while V838 Mon was thought to be a similar merger event from a
more massive B-type progenitor. In this paper we study an optical/IR transient
discovered in the nearby galaxy NGC4490, which appeared similar to these merger
events (unobscured progenitor, irregular multi-peaked light curve, increasingly
red color, similar optical spectrum, IR excess at late times), but which had a
higher peak luminosity and longer duration in outburst. NGC4490-OT has less in
common with the class of SN~2008S-like transients. A progenitor detected in
pre-eruption HST images, combined with upper limits in the IR, requires a
luminous and blue progenitor that has faded in late-time HST images. The same
source was detected by Spitzer and ground-based data as a luminous IR
transient, indicating a transition to a self-obscured state qualitatively
similar to the evolution seen in other stellar mergers and in LBVs. The
post-outburst dust-obscured source is too luminous and too warm at late times
to be explained with an IR echo, suggesting that the object survived the event.
The luminosity of the enshrouded IR source is similar to that of the
progenitor. Compared to proposed merger events, the more massive progenitor of
NGC4490-OT seems to extend a correlation between stellar mass and peak
luminosity, and may suggest that both of these correlate with duration. We show
that spectra of NGC4490-OT and V838 Mon also resemble light-echo spectra of eta
Car, prompting us to speculate that eta Car may be an extreme extension of this
phenomenon.


title: Some remarks on infinitesimals in MV-algebras

abstract:
  Replacing $\{0\}$ by the whole ideal of infinitesimals yields a weaker notion
of \emph{archimedean element} that we call \emph{quasiarchimedean}. It is known
that semisimple MV-algebras with compact maximal spectrum (in the co-Zarisky
topology) are exactly the hyperarchimedean algebras. We characterise all the
algebras with compact maximal spectrum as being \emph{quasihyperarchimedean}
\mbox{MV-algebras,} which in a sense are non semisimple hyperarchimedean
algebras. We develop some basic facts in the theory of MV-algebras along the
lines of algebraic geometry, where infinitesimals play the role of nilpotent
elements, and prove a MV-algebra version of Hilbert's Nullstellensatz. Finally
we consider the relations (some inedited) between several elementary classes of
MV-algebras in terms of the ideals that characterise them, and present
elementary (first order with denumerable disjunctions) proofs in place of the
\mbox{set-theoretical} usually found in the literature.


title: Primal-Dual Rates and Certificates

abstract:
  We propose an algorithm-independent framework to equip existing optimization
methods with primal-dual certificates. Such certificates and corresponding rate
of convergence guarantees are important for practitioners to diagnose progress,
in particular in machine learning applications. We obtain new primal-dual
convergence rates, e.g., for the Lasso as well as many L1, Elastic Net, group
Lasso and TV-regularized problems. The theory applies to any norm-regularized
generalized linear model. Our approach provides efficiently computable duality
gaps which are globally defined, without modifying the original problems in the
region of interest.


title:
Accretion and Orbital Inspiral in Gas-Assisted Supermassive Black Hole
  Binary Mergers

abstract:
  Many galaxies are expected to harbor binary supermassive black holes (SMBHs)
in their centers. Their interaction with the surrounding gas results in
accretion and exchange of angular momentum via tidal torques, facilitating
binary inspiral. Here we explore the non-trivial coupling between these two
processes and analyze how the global properties of externally supplied
circumbinary disks depend on the binary accretion rate. By formulating our
results in terms of the angular momentum flux driven by internal stresses, we
come up with a very simple classification of the possible global disk
structures, which differ from the standard constant $\dot M$ accretion disk
solution. Suppression of accretion by the binary tides, leading to a
significant mass accumulation in the inner disk, accelerates binary inspiral.
We show that once the disk region strongly perturbed by the viscously
transmitted tidal torque exceeds the binary semi-major axis, the binary can
merge in less than its mass-doubling time due to accretion. Thus, unlike the
inspirals driven by stellar scattering, the gas-assisted merger can occur even
if the binary is embedded in a relatively low mass disk (lower than its own
mass). This is important for resolving the "last parsec" problem for SMBH
binaries and understanding powerful gravitational wave sources in the Universe.
We argue that the enhancement of accretion by the binary found in some recent
simulations cannot persist for a long time and should not affect the long-term
orbital inspiral. We also review the existing simulations of the SMBH
binary-disk coupling and propose a numerical setup, which is particularly well
suited for verifying our theoretical predictions.


title:
Fractional smoothness of distributions of polynomials and a fractional
  analog of the Hardy--Landau--Littlewood inequality

abstract:
  We prove that the distribution density of any non-constant polynomial
$f(\xi_1,\xi_2,\ldots)$ of degree $d$ in independent standard Gaussian random
variables $\xi$ (possibly, in infinitely many variables) always belongs to the
Nikol'skii--Besov space $B^{1/d}(\mathbb{R}^1)$ of fractional order $1/d$ (and
this order is best possible), and an analogous result holds for polynomial
mappings with values in $\mathbb{R}^k$.
  Our second main result is an upper bound on the total variation distance
between two probability measures on $\mathbb{R}^k$ via the Kantorovich distance
between them and a suitable Nikol'skii--Besov norm of their difference.
  As an application we consider the total variation distance between the
distributions of two random $k$-dimensional vectors composed of polynomials of
degree $d$ in Gaussian random variables and show that this distance is
estimated by a fractional power of the Kantorovich distance with an exponent
depending only on $d$ and $k$, but not on the number of variables of the
considered polynomials.


title:
Smoothing spline ANOVA for super-large samples: Scalable computation via
  rounding parameters

abstract:
  In the current era of big data, researchers routinely collect and analyze
data of super-large sample sizes. Data-oriented statistical methods have been
developed to extract information from super-large data. Smoothing spline ANOVA
(SSANOVA) is a promising approach for extracting information from noisy data;
however, the heavy computational cost of SSANOVA hinders its wide application.
In this paper, we propose a new algorithm for fitting SSANOVA models to
super-large sample data. In this algorithm, we introduce rounding parameters to
make the computation scalable. To demonstrate the benefits of the rounding
parameters, we present a simulation study and a real data example using
electroencephalography data. Our results reveal that (using the rounding
parameters) a researcher can fit nonparametric regression models to very large
samples within a few seconds using a standard laptop or tablet computer.


title: Perceptual Vector Quantization For Video Coding

abstract:
  This paper applies energy conservation principles to the Daala video codec
using gain-shape vector quantization to encode a vector of AC coefficients as a
length (gain) and direction (shape). The technique originates from the CELT
mode of the Opus audio codec, where it is used to conserve the spectral
envelope of an audio signal. Conserving energy in video has the potential to
preserve textures rather than low-passing them. Explicitly quantizing a gain
allows a simple contrast masking model with no signaling cost. Vector
quantizing the shape keeps the number of degrees of freedom the same as scalar
quantization, avoiding redundancy in the representation. We demonstrate how to
predict the vector by transforming the space it is encoded in, rather than
subtracting off the predictor, which would make energy conservation impossible.
We also derive an encoding of the vector-quantized codewords that takes
advantage of their non-uniform distribution. We show that the resulting
technique outperforms scalar quantization by an average of 0.90 dB on still
images, equivalent to a 24.8% reduction in bitrate at equal quality, while for
videos, the improvement averages 0.83 dB, equivalent to a 13.7% reduction in
bitrate.


title:
Differentiability of Solutions to the Neumann Problem with
  Low-Regularity Data via Dynamical Systems

abstract:
  We obtain conditions for the differentiability of weak solutions for a
second-order uniformly elliptic equation in divergence form with a homogeneous
co-normal boundary condition. The modulus of continuity for the coefficients is
assumed to satisfy the square-Dini condition and the boundary is assumed to be
differentiable with derivatives also having this modulus of continuity.
Additional conditions for the solution to be Lipschitz continuous or
differentiable at a point on the boundary depend upon the stability of a
dynamical system that is derived from the coefficients of the elliptic
equation.


title: On Solving Ill-Conditioned Linear Systems

abstract:
  This paper presents the first results to combine two theoretically sound
methods (spectral projection and multigrid methods) together to attack
ill-conditioned linear systems. Our preliminary results show that the proposed
algorithm applied to a Krylov subspace method takes much fewer iterations for
solving an ill-conditioned problem downloaded from a popular online sparse
matrix collection.


title:
Coleman-Weinberg symmetry breaking in $SU(8)$ induced by a third rank
  antisymmetric tensor scalar field

abstract:
  We study $SU(8)$ symmetry breaking induced by minimizing the Coleman-Weinberg
effective potential for a third rank antisymmetric tensor scalar field in the
56 representation. Instead of breaking $SU(8) \supset SU(3) \times SU(5)$, we
find that the stable minimum of the potential breaks the original symmetry
according to $SU(8) \supset SU(3) \times Sp(4)$. Using both numerical and
analytical methods, we present results for the potential minimum, the
corresponding Goldstone boson structure and BEH mechanism, and the
group-theoretic classification of the residual states after symmetry breaking.


title: Homogenization of Hamilton-Jacobi equations with rough time dependence

abstract:
  We consider viscosity solutions of Hamilton-Jacobi equations with oscillatory
spatial dependence and rough time dependence. The time dependence is in the
form of the derivative of a continuous path that converges to a possibly
nowhere-differentiable path, for example a Brownian motion. In the case where
the path is one-dimensional, we prove that the solutions converge locally
uniformly to the solution of a spatially homogenous, stochastic Hamilton-Jacobi
equation in the sense of Lions and Souganidis. We also provide examples of
equations in which the path is multi-dimensional, and show that many different
behaviors are possible, including diverging to infinity or converging in law to
a Brownian motion.


title:
Design of the SABAT system for underwater detection of dangerous
  substances

abstract:
  We present status of simulations used to design a novel device for the
detection of hazardous substances in the aquatic environment using neutron
activation. Unlike the other considered methods based on this technique we
propose to use guides for neutron and gamma quanta which speeds up and
simplifies identification. First preliminary results show that both the neutron
guide and the $\gamma$ ray guide increase the performance of underwater threats
detection.


title:
Exploring quantum interference in heteroatom-substituted graphene-like
  molecules

abstract:
  If design principles for controlling quantum interference in single molecules
could be elucidated and verified, then this will lay the foundations for
exploiting such effects in nanoscale devices and thin-film materials.When the
core of a graphene-like polyaromatic hydrocarbon (PAH) is weakly coupled to
external electrodes by atoms i and j, the single-molecule electrical
conductance sigma-ij depends on the choice of connecting atoms i,j.
Furthermore, conductance ratios sigma-ij/sigma-lm corresponding to different
connectivities i,j and l,m are determined by quantum interference within the
PAH core. In this paper, we examine how such conductance ratios change when one
of the carbon atoms within the "parent" PAH core is replaced by a heteroatom to
yield a "daughter" molecule. For bipartite parental cores, in which
odd-numbered sites are connected to even-numbered sites only, the effect of
heteroatom substitution onto an odd-numbered site is summarized by the
following qualitative rules:
  (a) When i and j are odd, both parent and daughter have low conductances (b)
When i is odd and j is even, or vice versa both parent and daughter have high
conductances (c) When i,j are both even, the parent has a low conductance and
the daughter a high conductance. These rules are verified by comparison with
density-functional calculations on naphthalene, anthracene, pyrene and
anthanthrene cores connected via two different anchor groups to gold
electrodes.


title:
Diphoton decay for a 750 GeV scalar boson in a $SU(6)\otimes U(1)_{X}$
  model

abstract:
  We propose a new $SU(6)\otimes U(1)_{X}$ GUT model free from anomalies, with
a 750 GeV scalar candidate which can decay into two photons, compatible with
the recent diphoton signal reported by ATLAS and CMS collaborations. This model
gives masses to all fermions and may explain the 750GeV signal through one loop
decays to $\gamma\gamma$ with charged vector and charged Higgs bosons, as well
as up- and electron-like exotic particles that arise naturally from the
condition of cancellation of anomalies of the $SU(6)\otimes U(1)_{X}$ group. We
obtain, for different width approximations, allowed mass regions from 900 GeV
to 3 TeV for the exotic up-like quark, in agreement with ATLAS and CMS
collaborations data.


title: Low rank tensor recovery via iterative hard thresholding

abstract:
  We study extensions of compressive sensing and low rank matrix recovery
(matrix completion) to the recovery of low rank tensors of higher order from a
small number of linear measurements. While the theoretical understanding of low
rank matrix recovery is already well-developed, only few contributions on the
low rank tensor recovery problem are available so far. In this paper, we
introduce versions of the iterative hard thresholding algorithm for several
tensor decompositions, namely the higher order singular value decomposition
(HOSVD), the tensor train format (TT), and the general hierarchical Tucker
decomposition (HT). We provide a partial convergence result for these
algorithms which is based on a variant of the restricted isometry property of
the measurement operator adapted to the tensor decomposition at hand that
induces a corresponding notion of tensor rank. We show that subgaussian
measurement ensembles satisfy the tensor restricted isometry property with high
probability under a certain almost optimal bound on the number of measurements
which depends on the corresponding tensor format. These bounds are extended to
partial Fourier maps combined with random sign flips of the tensor entries.
Finally, we illustrate the performance of iterative hard thresholding methods
for tensor recovery via numerical experiments where we consider recovery from
Gaussian random measurements, tensor completion (recovery of missing entries),
and Fourier measurements for third order tensors.


title:
Reflection and transmission of elastic waves at interfaces embedded in
  non-local band-gap metamaterials: a comprehensive study via the relaxed
  micromorphic model

abstract:
  In this paper we derive, by means of a suitable least action principle, the
duality jump conditions to be imposed at surfaces of discontinuity of the
material properties in non-dissipative, linear-elastic, isotropic, Mindlin's
and relaxed micromorphic media, respectively. The introduced theoretical
framework allows the transparent set-up of different types of micro-macro
connections which are intrinsically compatible with the governing bulk
equations. To illustrate the interest of the many introduced jump conditions,
we focus on the case of an interface between a classical Cauchy continuum on
one side and a relaxed micromorphic one on the other side. As expected, we find
a complete reflection in the frequency intervals for which band-gaps are known
to occur in the relaxed micromorphic continuum and precise
microstructure-related reflective patterns are identified. We repeat a similar
study for analogous connections between a classical Cauchy continuum and a
Mindlin's micromorphic one and we show that the reflective properties of the
considered interfaces are drastically modified due to the fact that band-gaps
are not allowed in standard Mindlin's micromorphic media. The present work
opens the way towards the possibility of conceiving complex metastructures in
which band-gap metamaterials and classical materials are coupled together to
produce structures with completely new and unorthodox properties with respect
to wave propagation, transmission and reflection. Last, but not least, indirect
measurements of the material coefficients of the relaxed micromorphic model
based upon real experiments of reflection and transmission in band-gap
metamaterials are uncovered by the present work which makes them finally
realizable in the short term.


title: Discrete Density of States

abstract:
  By considering the quantum-mechanically minimum allowable energy interval, we
exactly count number of states (NOS) and introduce discrete density of states
(DOS) concept for a particle in a box for various dimensions. Expressions for
bounded and unbounded continua are analytically recovered from discrete ones.
Even though substantial fluctuations prevail in discrete DOS, they're almost
completely flatten out after summation or integration operation. It's seen that
relative errors of analytical expressions of bounded/unbounded continua rapidly
decrease for high NOS values (weak confinement or high energy conditions),
while the proposed analytical expressions based on Weyl's conjecture always
preserve their lower error characteristic.


title: BioSpaun: A large-scale behaving brain model with complex neurons

abstract:
  We describe a large-scale functional brain model that includes detailed,
conductance-based, compartmental models of individual neurons. We call the
model BioSpaun, to indicate the increased biological plausibility of these
neurons, and because it is a direct extension of the Spaun model
\cite{Eliasmith2012b}. We demonstrate that including these detailed
compartmental models does not adversely affect performance across a variety of
tasks, including digit recognition, serial working memory, and counting. We
then explore the effects of applying TTX, a sodium channel blocking drug, to
the model. We characterize the behavioral changes that result from this
molecular level intervention. We believe this is the first demonstration of a
large-scale brain model that clearly links low-level molecular interventions
and high-level behavior.


title: Patterns of Scalable Bayesian Inference

abstract:
  Datasets are growing not just in size but in complexity, creating a demand
for rich models and quantification of uncertainty. Bayesian methods are an
excellent fit for this demand, but scaling Bayesian inference is a challenge.
In response to this challenge, there has been considerable recent work based on
varying assumptions about model structure, underlying computational resources,
and the importance of asymptotic correctness. As a result, there is a zoo of
ideas with few clear overarching principles.
  In this paper, we seek to identify unifying principles, patterns, and
intuitions for scaling Bayesian inference. We review existing work on utilizing
modern computing resources with both MCMC and variational approximation
techniques. From this taxonomy of ideas, we characterize the general principles
that have proven successful for designing scalable inference procedures and
comment on the path forward.


title:
Marder's Two-Fluid Dark Energy Cosmological Models In Saez-Ballester
  Theory of Gravitation

abstract:
  The present paper deals with cylindrically symmetric metric in the form of
Marder (1958) with Saez-Ballester theory of gravitation in the presence of
perfect fluid and dark energy. In order to obtain the deterministic solution of
the field equations we have assumed that the expansion scalar in the model is
proportional to the Eigen value of the shear tensor. We have also assumed that
the two sources, here the perfect fluid and dark energy interact minimally with
separate conservative parts of their energy momentum tensors together with the
constant EoS parameter of the perfect fluid. The role of the dark energy in the
present model with variable equation of state parameter is studied more in
detail. Some physical properties of model are also discussed.


title: Tilted and Non Tilted C-Field Cosmological Models

abstract:
  Tilted and non tilted homogeneous plane symmetric C-field cosmological models
are investigated. Using the method of Narlikar and Padmanabhan [4], the
solutions have been presented when the creation field C is function of time t
only. To get the deterministic model, we have assumed the supplementary
condition between pressure and density . The behaviour of different stages of
the universe has been studied in non tilted models. We have also investigated
the behaviours of some physical parameters.


title:
A simple and general proof for the convergence of Markov processes to
  their mean-field limits

abstract:
  Mean-field models approximate large stochastic systems by simpler
differential equations that are supposed to approximate the mean of the larger
system. It is generally assumed that as the stochastic systems get larger
(i.e., more people or particles), they converge to the mean-field models.
Mean-field models are common in many fields, but their convergence is rarely
proved. The existing approaches rely on operator semigroups, martingales, PDEs,
or infinite systems of ODEs. We give a general proof for their convergence
using only Taylor's theorem and basic ODE results. We hope this allows applied
researchers to routinely show convergence of their mean-field models, putting
their work on a stronger foundation.


title: Moving Mesh Discontinuous Galerkin Methods for PDEs with Traveling Waves

abstract:
  In this paper, a moving mesh discontinuous Galerkin (dG) method is developed
for nonlinear partial differential equations (PDEs) with traveling wave
solutions. The moving mesh strategy for one dimensional PDEs is based on the
rezoning approach which decouples the solution of the PDE from the moving mesh
equation. We show that the dG moving mesh method is able to resolve sharp wave
fronts and wave speeds accurately for the optimal, arc-length and curvature
monitor functions. Numerical results reveal the efficiency of the proposed
moving mesh dG method for solving Burgers', Burgers'-Fisher and
Schl\"ogl(Nagumo) equations.


title:
Potential of the J-PET detector for studies of discrete symmetries in
  decays of positronium atom - a purely leptonic system

abstract:
  The Jagiellonian Positron Emission Tomograph (J-PET) was constructed as a
prototype of the cost-effective scanner for the simultaneous metabolic imaging
of the whole human body. Being optimized for the detection of photons from the
electron-positron annihilation with high time- and high angular-resolution, it
constitutes a multi-purpose detector providing new opportunities for studying
the decays of positronium atoms. Positronium is the lightest purely leptonic
object decaying into photons. As an atom bound by a central potential it is a
parity eigenstate, and as an atom built out of an electron and an anti-electron
it is an eigenstate of the charge conjugation operator. Therefore, the
positronium is a unique laboratory to study discrete symmetries whose precision
is limited in principle by the effects due to the weak interactions expected at
the level of (~10$^{-14}$) and photon-photon interactions expected at the level
of (~10$^{-9}$). The J-PET detector enables to perform tests of discrete
symmetries in the leptonic sector via the determination of the expectation
values of the discrete-symmetries-odd operators, which may be constructed from
the spin of ortho-positronium atom and the momenta and polarization vectors of
photons originating from its annihilation. In this article we present the
potential of the J-PET detector to test the C, CP, T and CPT symmetries in the
decays of positronium atoms.


title:
Compact pairwise models for epidemics with multiple infectious stages on
  degree heterogeneous and clustered networks

abstract:
  This paper presents a compact pairwise model that describes the spread of
multi-stage epidemics on networks. The multi-stage model corresponds to a
gamma-distributed infectious period which interpolates between the classical
Markovian models with exponentially distributed infectious period and epidemics
with a constant infectious period. We show how the compact approach leads to a
system of equations whose size is independent of the range of node degrees,
thus significantly reducing the complexity of the model. Network clustering is
incorporated into the model to provide a more accurate representation of
realistic contact networks, and the accuracy of proposed closures is analysed
for different levels of clustering and number of infection stages. Our results
support recent findings that standard closure techniques are likely to perform
better when the infectious period is constant.


title: On some a priori majorant of eigenvalues of Sturm--Liouville problems

abstract:
  Let $M_\gamma$ be precise a priori majorant of first eigenvalues of
Sturm--Liouville problems $-y"+qy=\lambda y,\quad y(0)=y(1)=0$, where
$q\leqslant 0$ and $\int_0^1 |q|^\gamma\,dx=1$, $\gamma\in (0,1/2)$. It is
shown that the inequality $M_\gamma<\pi^2$ is true.


title: Gravitational Frames and Scalar Field Dynamics

abstract:
  Scalar fields describe interesting phenomena such as Higgs bosons, dark
matter and dark energy, and are found to be quite common in physical theories.
These fields are susceptible to gravitational forces so that being massless is
not enough to remain conformal invariant. They should also be connected
directly to the scalar curvature. Because of this characteristics, we
investigated the structure and interactions of scalar fields under the
conformal transformations. We show how to reduce the quadratic quantum
contributions in the single scalar field theory. In the multi-scalar field
theories, we analyzed interactions in certain limits. We suggest a new method
for stabilizing Higgs bosons.


title:
Porosity Results for Sets of Strict Contractions on Geodesic Metric
  Spaces

abstract:
  We consider a large class of geodesic metric spaces, including Banach spaces,
hyperbolic spaces and geodesic $\mathrm{CAT}(\kappa)$-spaces, and investigate
the space of nonexpansive mappings on either a convex or a star-shaped subset
in these settings. We prove that the strict contractions form a negligible
subset of this space in the sense that they form a $\sigma$-porous subset. For
separable metric spaces we show that a generic nonexpansive mapping has
Lipschitz constant one at typical points of its domain. These results contain
the case of nonexpansive self-mappings and the case of nonexpansive set-valued
mappings as particular cases.


title:
Development and Experimentation of a Software Tool for Identifying High
  Risk Spreadsheets for Auditing

abstract:
  Heavy use of spreadsheets by organisations bears many potential risks such as
errors, ambiguity, data loss, duplication, and fraud. In this paper these risks
are briefly outlined along with their available mitigation methods such as:
documentation, centralisation, auditing and user training. However, because of
the large quantities of spreadsheets used in organisations, applying these
methods on all spreadsheets is impossible. This fact is considered as a
deficiency in these methods, a gap which is addressed in this paper.
  In this paper a new software tool for managing spreadsheets and identifying
the risk levels they include is proposed, developed and tested. As an add-in
for Microsoft Excel application, "Risk Calculator" can automatically collect
and record spreadsheet properties in an inventory database and assign risk
scores based on their importance, use and complexity. Consequently, auditing
processes can be targeted to high risk spreadsheets. Such a method saves time,
effort, and money.


title: Work-Efficient Parallel and Incremental Graph Connectivity

abstract:
  On an evolving graph that is continuously updated by a high-velocity stream
of edges, how can one efficiently maintain if two vertices are connected? This
is the connectivity problem, a fundamental and widely studied problem on
graphs. We present the first shared-memory parallel algorithm for incremental
graph connectivity that is both provably work-efficient and has polylogarithmic
parallel depth. We also present a simpler algorithm with slightly worse
theoretical properties, but which is easier to implement and has good practical
performance. Our experiments show a throughput of hundreds of millions of edges
per second on a $20$-core machine.


title: Quasicoherent sheaves on projective schemes over F_1

abstract:
  Given a graded monoid A with 1, one can construct a projective monoid scheme
MProj(A) analogous to Proj(R) of a graded ring R. This paper is concerned with
the study of quasicoherent sheaves (of pointed sets) on MProj(A), and we prove
several basic results regarding these. We show that:
  1.) Every quasicoherent sheaf F on MProj(A) can be constructed from a graded
A--set in analogy with the construction of quasicoherent sheaves on Proj(R)
from graded R--modules.
  2.) High enough twists of coherent sheaves are generated by finitely many
global sections, hence that every coherent sheaf is a quotient of a locally
free sheaf.
  3.) Coherent sheaves have finite spaces of global sections.
  The last part of the paper is devoted to classifying coherent sheaves on P^1
in terms of certain directed graphs and gluing data. The classification of
these over F_1 is shown to be much richer and combinatorially interesting than
in the case of ordinary P^1, and several new phenomena emerge.


title: Di-neutrons in neutron matter within Brueckner-Hartree-Fock approach

abstract:
  We investigate the appearance of di-neutron bound states in pure neutron
matter within the Brueckner-Hartree-Fock approach at zero temperature. We
consider Argonne $v_{18}$ and Paris bare interactions as well as chiral two-
and three-nucleon forces. Self-consistent single-particle potentials are
calculated controlling explicitly singularities in the $g$ matrix associated
with bound states. Di-neutrons are loosely bound, with binding energies below
$1$ MeV, but are unambiguously present for Fermi momenta below $1$ fm$^{-1}$
for all interactions. Within the same framework we are able to calculate and
characterize di-neutron bound states, obtaining mean radii as high as $\sim
110$ fm. The resulting equations of state and mass-radius relations for pure
neutron stars are analyzed including di-neutron contributions.


title:
Effective bias and potentials in steady-state quantum transport: A NEGF
  reverse-engineering study

abstract:
  Using non-equilibrium Green's functions combined with many-body perturbation
theory, we have calculated steady-state densities and currents through short
interacting chains subject to a finite electric bias. By using a steady-state
reverse-engineering procedure, the effective potential and bias which reproduce
such densities and currents in a non-interacting system have been determined.
The role of the effective bias is characterised with the aid of the so-called
exchange-correlation bias, recently introduced in a steady-state
density-functional-theory formulation for partitioned systems. We find that the
effective bias (or, equivalently, the exchange-correlation bias) depends
strongly on the interaction strength and the length of the central (chain)
region. Moreover, it is rather sensitive to the level of many-body
approximation used. Our study shows the importance of the
effective/exchange-correlation bias out of equilibrium, thereby offering hints
on how to improve the description of density-functional-theory based approaches
to quantum transport.


title: A Sparse PCA Approach to Clustering

abstract:
  We discuss a clustering method for Gaussian mixture model based on the sparse
principal component analysis (SPCA) method and compare it with the IF-PCA
method. We also discuss the dependent case where the covariance matrix $\Sigma$
is not necessarily diagonal.


title:
FPTAS for Mixed-Strategy Nash Equilibria in Tree Graphical Games and
  Their Generalizations

abstract:
  We provide the first fully polynomial time approximation scheme (FPTAS) for
computing an approximate mixed-strategy Nash equilibrium in tree-structured
graphical multi-hypermatrix games (GMhGs). GMhGs are generalizations of
normal-form games, graphical games, graphical polymatrix games, and
hypergraphical games. Computing an exact mixed-strategy Nash equilibria in
graphical polymatrix games is PPAD-complete and thus generally believed to be
intractable. In contrast, to the best of our knowledge, we are the first to
establish an FPTAS for tree polymatrix games as well as tree graphical games
when the number of actions is bounded by a constant. As a corollary, we give a
quasi-polynomial time approximation scheme (quasi-PTAS) when the number of
actions is bounded by the logarithm of the number of players.


title:
A Unified Monte-Carlo Jackknife for Small Area Estimation after Model
  Selection

abstract:
  We consider estimation of measure of uncertainty in small area estimation
(SAE) when a procedure of model selection is involved prior to the estimation.
A unified Monte-Carlo jackknife method, called McJack, is proposed for
estimating the logarithm of the mean squared prediction error. We prove the
second-order unbiasedness of McJack, and demonstrate the performance of McJack
in assessing uncertainty in SAE after model selection through empirical
investigations that include simulation studies and real-data analyses.


title:
MAGIC observations of the February 2014 flare of 1ES 1011+496 and
  ensuing constraint of the EBL density

abstract:
  In February-March 2014, the MAGIC telescopes observed the high-frequency
peaked BL Lac 1ES 1011+496 (z=0.212) in flaring state at very-high energy (VHE,
E>100GeV). The flux reached a level more than 10 times higher than any
previously recorded flaring state of the source. We present the description of
the characteristics of the flare presenting the light curve and the spectral
parameters of the night-wise spectra and the average spectrum of the whole
period. From these data we aim at detecting the imprint of the Extragalactic
Background Light (EBL) in the VHE spectrum of the source, in order to constrain
its intensity in the optical band. For this we implement the method developed
by the H.E.S.S. collaboration in which the intrinsic energy spectrum of the
source is modeled with a simple function, and the EBL-induced optical depth is
calculated using a template EBL model. The likelihood of the observed spectrum
is then maximized, including a normalization factor for the EBL opacity among
the free parameters. From the data collected differential energy spectra was
produced for all nights of the observed period. Evaluating the changes in the
fit parameters we conclude that the spectral shape for most of the nights were
compatible, regardless of the flux level, which enabled us to produce an
average spectrum from which the EBL imprint could be constrained. The
likelihood ratio test shows that the model with an EBL density
1.07(-0.20,+0.24)_{stat+sys}, relative to the one in the tested EBL template
(Dominguez et al.2011), is preferred at the 4.6 sigma level to the no-EBL
hypothesis, with the assumption that the intrinsic source spectrum can be
modeled as a log-parabola. This would translate into a constraint of the EBL
density in the wavelength range [0.24 um,4.25 um], with a peak value at 1.4 um
of F=12.27_{-2.29}^{+2.75} nW m^{-2} sr^{-1}, including systematics.


title: Robust Influence Maximization

abstract:
  Uncertainty about models and data is ubiquitous in the computational social
sciences, and it creates a need for robust social network algorithms, which can
simultaneously provide guarantees across a spectrum of models and parameter
settings. We begin an investigation into this broad domain by studying robust
algorithms for the Influence Maximization problem, in which the goal is to
identify a set of k nodes in a social network whose joint influence on the
network is maximized.
  We define a Robust Influence Maximization framework wherein an algorithm is
presented with a set of influence functions, typically derived from different
influence models or different parameter settings for the same model. The
different parameter settings could be derived from observed cascades on
different topics, under different conditions, or at different times. The
algorithm's goal is to identify a set of k nodes who are simultaneously
influential for all influence functions, compared to the (function-specific)
optimum solutions.
  We show strong approximation hardness results for this problem unless the
algorithm gets to select at least a logarithmic factor more seeds than the
optimum solution. However, when enough extra seeds may be selected, we show
that techniques of Krause et al. can be used to approximate the optimum robust
influence to within a factor of 1 - 1/e. We evaluate this bicriteria
approximation algorithm against natural heuristics on several real-world data
sets. Our experiments indicate that the worst-case hardness does not
necessarily translate into bad performance on real-world data sets; all
algorithms perform fairly well.


title:
A phase transition in excursions from infinity of the "fast"
  fragmentation-coalescence process

abstract:
  An important property of Kingman's coalescent is that, starting from a state
with an infinite number of blocks, over any positive time horizon, it
transitions into an almost surely finite number of blocks. This is known as
`coming down from infinity'. Moreover, of the many different (exchangeable)
stochastic coalescent models, Kingman's coalescent is the `fastest' to come
down from infinity. In this article we study what happens when we counteract
this `fastest' coalescent with the action of an extreme form of fragmentation.
We augment Kingman's coalescent, where any two blocks merge at rate $c>0$, with
a fragmentation mechanism where each block fragments at constant rate,
$\lambda>0$, into it's constituent elements. We prove that there exists a phase
transition at $\lambda=c/2$, between regimes where the resulting `fast'
fragmentation-coalescence process is able to come down from infinity or not. In
the case that $\lambda<c/2$ we develop an excursion theory for the fast
fragmentation-coalescence process out of which a number of interesting
quantities can be computed explicitly.


title:
Monte Carlo Markov Chain Algorithms for Sampling Strongly Rayleigh
  Distributions and Determinantal Point Processes

abstract:
  Strongly Rayleigh distributions are natural generalizations of product and
determinantal probability distributions and satisfy strongest form of negative
dependence properties. We show that the "natural" Monte Carlo Markov Chain
(MCMC) is rapidly mixing in the support of a {\em homogeneous} strongly
Rayleigh distribution. As a byproduct, our proof implies Markov chains can be
used to efficiently generate approximate samples of a $k$-determinantal point
process. This answers an open question raised by Deshpande and Rademacher.


title:
Beam profile investigation of the new collimator system for the J-PET
  detector

abstract:
  Jagiellonian Positron Emission Tomograph (J-PET) is a multi-purpose detector
which will be used for search for discrete symmetries violations in the decays
of positronium atoms and for investigations with positronium atoms in
life-sciences and medical diagnostics. In this article we present three methods
for determination of the beam profile of collimated annihilation gamma quanta.
Precise monitoring of this profile is essential for time and energy calibration
of the J-PET detector and for the determination of the library of model signals
used in the hit-time and hit-position reconstruction. We have we have shown
that usage of two lead bricks with dimensions of 5x10x20 cm^3 enables to form a
beam of annihilation quanta with Gaussian profile characterized by 1 mm FWHM.
Determination of this characteristic is essential for designing and
construction the collimator system for the 24-module J-PET prototype.
Simulations of the beam profile for different collimator dimensions were
performed. This allowed us to choose optimal collimation system in terms of the
beam profile parameters, dimensions and weight of the collimator taking into
account the design of the 24 module J-PET detector.


title: Z/m-graded Lie algebras and perverse sheaves, I

abstract:
  We give a block decomposition of the equivariant derived category arising
from a cyclically graded Lie algebra. This generalizes certain aspects of the
generalized Springer correspondence to the graded setting.


title: Mixing of discontinuously deforming media

abstract:
  Mixing of materials is fundamental to many natural phenomena and engineering
applications. The presence of discontinuous deformations - such as shear
banding or wall slip - creates new mechanisms for mixing and transport beyond
those predicted by classical dynamical systems theory. Here we show how a novel
mixing mechanism combining stretching with cutting and shuffling yields
exponential mixing rates, quantified by a positive Lyapunov exponent, an
impossibility for systems with cutting and shuffling alone or bounded systems
with stretching alone, and demonstrate it in a fluid flow. While dynamical
systems theory provides a framework for understanding mixing in smoothly
deforming media, a theory of discontinuous mixing is yet to be fully developed.
New methods are needed to systematize, explain and extrapolate measurements on
systems with discontinuous deformations. Here we investigate 'webs' of
Lagrangian discontinuities and show that they provide a template for the
overall transport dynamics. Considering slip deformations as the asymptotic
limit of increasingly localised smooth shear we also demonstrate exactly how
some of the new structures introduced by discontinuous deformations are
analogous to structures in smoothly deforming systems.


title:
Maximizing the hyperpolarizability of 1D potentials with multiple
  electrons

abstract:
  We optimize the first and second intrinsic hyperpolarizabilities for a 1D
piecewise linear potential dressed with Dirac delta functions for $N$
non-interacting electrons. The optimized values fall rapidly for $N>1$, but
approach constant values of $\beta_{int}=0.40$, $\gamma_{int}^{+}=0.16$ and
$\gamma_{int}^{-}=-0.061$ above $N\gtrsim8$. These apparent bounds are achieved
with only 2 parameters with more general potentials achieving no better value.
In contrast to previous studies, analysis of the hessian matrices of
$\beta_{int}$ and $\gamma_{int}$ taken with respect to these parameters shows
that the eigenvectors are well aligned with the basis vectors of the parameter
space, indicating that the parametrization was well-chosen. The physical
significance of the important parameters is also discussed.


title: The Computation of Key Properties of Markov Chains via Perturbations

abstract:
  Computational procedures for the stationary probability distribution, the
group inverse of the Markovian kernel and the mean first passage times of an
irreducible Markov chain, are developed using perturbations. The derivation of
these expressions involves the solution of systems of linear equations and,
structurally, inevitably the inverses of matrices. By using a perturbation
technique, starting from a simple base where no such derivations are formally
required, we update a sequence of matrices, formed by linking the solution
procedures via generalized matrix inverses and utilising matrix and vector
multiplications. Six different algorithms are given, some modifications are
discussed, and numerical comparisons made using a test example. The derivations
are based upon the ideas outlined in Hunter, J.J., The computation of
stationary distributions of Markov chains through perturbations, Journal of
Applied Mathematics and Stochastic Analysis, 4, 29-46, (1991).


title:
Proportional Approval Method using Squared loads, Approval removal and
  Coin-flip approval transformation (PAMSAC) - a new system of proportional
  representation using approval voting

abstract:
  Several multi-winner systems that use approval voting have been developed but
they each suffer from various problems. Six of these methods are discussed in
this paper. They are Satisfaction Approval Voting, Minimax Approval Voting,
Proportional Approval Voting, Monroe's Fully Proportional Representation,
Chamberlin-Courant's Rule, and Ebert's method. They all fail at least one of
Proportional Representation (PR), strong PR, monotonicity or positive support.
However, the new method described in this paper - Proportional Approval Method
using Squared loads, Approval removal and Coin-flip approval transformation
(PAMSAC) - passes them all. PAMSAC uses the squared loads of Ebert's method,
but removes non-beneficial approvals to restore monotonicity. It also uses the
Coin-Flip Approval Transformation (CFAT), where voters are "split" into two for
each candidate they approve, and where one half of this split voter approves
and the other half does not approve each candidate approved on the ballot. This
restores positive support, and also makes the method equivalent to the D'Hondt
party-list method for party voting. PAMSAC reduces to simple approval voting in
the single-winner case. A score voting version is described that also reduces
to simple score voting in the single-winner case.


title:
Beamforming Errors in Murchison Widefield Array Phased Array Antennas
  and their effects on Epoch of Reionization Science

abstract:
  Accurate antenna beam models are critical for radio observations aiming to
isolate the redshifted 21cm spectral line emission from the Dark Ages and the
Epoch of Reionization and unlock the scientific potential of 21cm cosmology.
Past work has focused on characterizing mean antenna beam models using either
satellite signals or astronomical sources as calibrators, but
antenna-to-antenna variation due to imperfect instrumentation has remained
unexplored. We characterize this variation for the Murchison Widefield Array
(MWA) through laboratory measurements and simulations, finding typical
deviations of order +/- 10-20% near the edges of the main lobe and in the
sidelobes. We consider the ramifications of these results for image- and power
spectrum-based science. In particular, we simulate visibilities measured by a
100m baseline and find that using an otherwise perfect foreground model,
unmodeled beamforming errors severely limit foreground subtraction accuracy
within the region of Fourier space contaminated by foreground emission (the
"wedge"). This region likely contains much of the cosmological signal, and
accessing it will require measurement of per-antenna beam patterns. However,
unmodeled beamforming errors do not contaminate the Fourier space region
expected to be free of foreground contamination (the "EOR window"), showing
that foreground avoidance remains a viable strategy.


title:
Critical Temperature of Chiral Symmetry Restoration for Quark Matter
  with a Chiral Chemical Potential

abstract:
  In this article we study restoration of chiral symmetry at finite temperature
for quark matter with a chiral chemical potential, $\mu_5$, by means of a
nonlocal Nambu-Jona-Lasinio model. This model allows to introduce in the
simplest way possible a Euclidean momentum, $p_E$, dependent quark mass
function which decays (neglecting logarithms) as $1/p_E^2$ for large $p_E$, in
agreement with asymptotic behaviour expected in QCD in presence of a
nonperturbative quark condensate. We focus on the critical temperature for
chiral symmetry restoration in the chiral limit, $T_c$, versus $\mu_5$, as well
as on the order of the phase transition. We find that $T_c$ increases with
$\mu_5$, and that the transition remains of the second order for the whole
range of $\mu_5$ considered.


title: Sampling FEE and Trigger-less DAQ for the J-PET Scanner

abstract:
  In this paper, we present a complete Data Acquisition System (DAQ) together
with the readout mechanisms for the J-PET tomography scanner. In general
detector readout chain is constructed out of Front-End Electronics (FEE),
measurement devices like Time-to-Digital or Analog-to-Digital Converters (TDCs
or ADCs), data collectors and storage. We have developed a system capable for
maintaining continuous readout of digitized data without preliminary selection.
Such operation mode results in up to 8 Gbps data stream, therefore it is
required to introduce a dedicated module for online event building and feature
extraction. The Central Controller Module, equipped with Xilinx Zynq SoC and 16
optical transceivers serves as such true real time computing facility. Our
solution for the continuous data recording (trigger-less) is a novel approach
in such detector systems and assures that most of the information is preserved
on the storage for further, high-level processing. Signal discrimination
applies an unique method of using LVDS buffers located in the FPGA fabric.


title:
Stellar Origins of Extremely $^{\text{13}}C$- and $^{15}N$-enriched
  Presolar SiC Grains: Novae or Supernovae?

abstract:
  Extreme excesses of $^{13}C$ ($^{12}C$/$^{13}C$<10) and $^{15}N$
($^{14}N$/$^{15}N$<20) in rare presolar SiC grains have been considered
diagnostic of an origin in classical novae, though an origin in core collapse
supernovae (CCSNe) has also been proposed. We report C, N, and Si isotope data
for 14 submicron- to micron-sized $^{13}C$- and $^{15}N$-enriched presolar SiC
grains ($^{12}C$/$^{13}C$<16 and $^{14}N$/$^{15}N$<~100) from Murchison, and
their correlated Mg-Al, S, and Ca-Ti isotope data when available. These grains
are enriched in $^{13}C$ and $^{15}N$, but with quite diverse Si isotopic
signatures. Four grains with $^{29,30}Si$ excesses similar to those of type C
SiC grains likely came from CCSNe, which experienced explosive H burning
occurred during explosions. The independent coexistence of proton- and
neutron-capture isotopic signatures in these grains strongly supports
heterogeneous H ingestion into the He shell in pre-supernovae. Two of the seven
putative nova grains with $^{30}Si$ excesses and $^{29}Si$ depletions show
lower-than-solar $^{34}S$/$^{32}S$ ratios that cannot be explained by classical
nova nucleosynthetic models. We discuss these signatures within the CCSN
scenario. For the remaining five putative nova grains, both nova and supernova
origins are viable because explosive H burning in the two stellar sites could
result in quite similar proton-capture isotopic signatures. Three of the grains
are sub-type AB grains that are also $^{13}C$ enriched, but have a range of
higher $^{14}N$/$^{15}N$. We found that $^{15}N$-enriched AB grains
(~50<$^{14}N$/$^{15}N$<~100) have distinctive isotopic signatures compared to
putative nova grains, such as higher $^{14}N$/$^{15}N$, lower
$^{26}Al$/$^{27}Al$, and lack of $^{30}Si$ excess, indicating weaker
proton-capture nucleosynthetic environments.


title:
Fractional Spin Fluctuation as a Precursor of Quantum Spin Liquids:
  Majorana Dynamical Mean-Field Study for the Kitaev Model

abstract:
  Experimental identification of quantum spin liquids remains a challenge, as
the pristine nature is to be seen in asymptotically low temperatures. We here
theoretically show that the precursor of quantum spin liquids appears in the
spin dynamics in the paramagnetic state over a wide temperature range. Using
the cluster dynamical mean-field theory and the continuous-time quantum Monte
Carlo method, which are newly developed in the Majorana fermion representation,
we calculate the dynamical spin structure factor, relaxation rate in nuclear
magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model
whose ground state is a canonical example of the quantum spin liquid. We find
that dynamical spin correlations show peculiar temperature and frequency
dependence even below the temperature where static correlations saturate. The
results provide the experimentally-accessible symptoms of the fluctuating
fractionalized spins evincing the quantum spin liquids.


title: Higher genus doubly periodic minimal surfaces

abstract:
  We construct Weierstrass data for higher genus embedded doubly periodic
minimal surfaces and present numerical evidence that the associated period
problem can be solved. In the orthogonal ends case, there previously was only
one known surface for each genus. We illustrate multiple new examples for each
genus g>2. In the parallel ends case, the known examples limit as a foliation
of parallel planes with nodes. We construct a new example for each genus g>2
that limit as g-1 singly periodic Scherk surfaces glued between two doubly
periodic Scherk surfaces and also as a singly periodic surface with four
vertical and 2g horizontal Scherk ends.


title: Symmetry breaking in non conservative systems

abstract:
  We apply Noether's theorem to show how the invariances of conservative
systems are broken for nonconservative systems, in the variational formulation
of Galley. This formulation considers a conservative action, extended by the
inclusion of a time reversed sector and a nonconservative generalized
potential. We assume that this potential is invariant under the symmetries of
the initial conservative system. The breaking occurs because the time reversed
sector requires inverse symmetry transformations, under which the
nonconservative potential is not invariant. The resulting violation of the
conservation laws is consistent with the equations of motion. We generalize
this formulation for fermionic and sypersymmetric systems. In the case of a
supersymmetric oscillator, the effect of damping is that the bosonic and
fermionic components become different frequencies. Considering that initially
the nonconservative action is invariant under supersymmetry, and that the
breaking is associated to an instability, this result is reminiscent of
spontaneous symmetry breaking.


title: 2D SEM images turn into 3D object models

abstract:
  The scanning electron microscopy (SEM) is probably one the most fascinating
examination approach that has been used since more than two decades to detailed
inspection of micro scale objects. Most of the scanning electron microscopes
could only produce 2D images that could not assist operational analysis of
microscopic surface properties. Computer vision algorithms combined with very
advanced geometry and mathematical approaches turn any SEM into a full 3D
measurement device. This work focuses on a methodical literature review for
automatic 3D surface reconstruction of scanning electron microscope images.


title:
Peak Criterion for Choosing Gaussian Kernel Bandwidth in Support Vector
  Data Description

abstract:
  Support Vector Data Description (SVDD) is a machine-learning technique used
for single class classification and outlier detection. SVDD formulation with
kernel function provides a flexible boundary around data. The value of kernel
function parameters affects the nature of the data boundary. For example, it is
observed that with a Gaussian kernel, as the value of kernel bandwidth is
lowered, the data boundary changes from spherical to wiggly. The spherical data
boundary leads to underfitting, and an extremely wiggly data boundary leads to
overfitting. In this paper, we propose empirical criterion to obtain good
values of the Gaussian kernel bandwidth parameter. This criterion provides a
smooth boundary that captures the essential geometric features of the data.


title: Oxygen abundance determination of B-type stars with the OI 7771-5A lines

abstract:
  Oxygen abundances of 34 B-type stars in the effective temperature range of
Teff~10000-28000K with diversified rotational velocities (vesini~ 0-250km/s)
were determined from the OI triplet lines at 7771-5A, with an aim to examine
whether this OI feature can be a reliable abundance indicator for such
high-temperature stars including rapid rotators. It revealed that the required
non-LTE abundance correction is distinctly large (ranging from ~-0.6dex to
~-1.7dex) and its consideration is indispensable. On the condition that the
non-LTE effect is taken into account, this triplet is a useful O abundance
indicator (with a precision of <~0.2dex) up to Teff <~25000K, since its total
equivalent width is sufficiently large (>~200mA). In contrast, it is not
adequate for abundance derivation for stars at Teff >~25000K, where its
strength rapidly drops down toward a hardly detectable level (except for
sharp-lined stars) and its sensitivity to Teff or log g becomes considerably
large. The resulting non-LTE oxygen abundances turned out to be almost normal
(i.e., near-solar around ~8.7-8.8 within +/-~0.2dex) for most stars without any
dependence upon projected rotational velocity as well as luminosity (or mass),
which is consistent with the prediction of recent stellar evolution
calculations.


title:
On the operator homology of the Fourier algebra and its $cb$-multiplier
  completion

abstract:
  We study various operator homological properties of the Fourier algebra
$A(G)$ of a locally compact group $G$. Establishing the converse of two results
of Ruan and Xu, we show that $A(G)$ is relatively operator 1-projective if and
only if $G$ is IN, and that $A(G)$ is relatively operator 1-flat if and only if
$G$ is inner amenable. We also exhibit the first known class of groups for
which $A(G)$ is not relatively operator $C$-flat for any $C\geq1$. As
applications of our techniques, we establish a hereditary property of inner
amenability, answer an open question of Lau and Paterson, and answer an open
question of Anantharaman--Delaroche on the equivalence of inner amenability and
Property (W). In the bimodule setting, we show that relative operator
1-biflatness of $A(G)$ is equivalent to the existence of a contractive
approximate indicator for the diagonal $G_\Delta$ in the Fourier--Stieltjes
algebra $B(G\times G)$, thereby establishing the converse to a result of
Aristov, Runde, and Spronk. We conjecture that relative $1$-biflatness of
$A(G)$ is equivalent to the existence of a quasi-central bounded approximate
identity in $L^1(G)$, that is, $G$ is QSIN, and verify the conjecture in many
special cases. We finish with an application to the operator homology of
$A_{cb}(G)$, giving examples of weakly amenable groups for which $A_{cb}(G)$ is
not operator amenable.


title: Instability of a witness bunch in a plasma bubble

abstract:
  The stability of a trailing witness bunch, accelerated by a plasma wake
accelerator (PWA) in a blow-out regime, is discussed. The instability growth
rate as well as the energy spread, required for BNS damping, are obtained. A
relationship between the PWA power efficiency and the BNS energy spread is
derived.


title:
Simulating Surfactant Spreading: Impact of a Physically Motivated
  Equation of State

abstract:
  For more than two decades, a single model for the spreading of a
surfactant-driven thin liquid film has dominated the applied mathematics
literature on the subject. Recently, through the use of fluorescently-tagged
lipids, it has become possible to make direct, quantitative comparisons between
experiments and models. These comparisons have revealed two important
discrepancies between simulations and experiments: the spatial distribution of
the surfactant layer, and the timescale over which spreading occurs. In this
paper, we present numerical simulations that demonstrate the impact of the
particular choice of the equation of state (EoS) relating the surfactant
concentration to the surface tension. Previous choices of the model EoS have
been an ad-hoc decreasing function. Here, we instead propose an
empirically-motivated equation of state; this provides a route to resolving
some discrepancies and raises new issues to be pursued in future experiments.
In addition, we test the influence of the choice of initial conditions and
values for the non-dimensional groups. We demonstrate that the choice of EoS
improves the agreement in surfactant distribution morphology between
simulations and experiments, and impacts the dynamics of the simulations. The
relevant feature of the EoS, the gradient, has distinct regions for empirically
motivated choices, which suggests that future work will need to consider more
than one timescale. We observe that the non-dimensional number controlling the
relative importance of gravitational vs. capillary forces has a larger impact
on the dynamics than the other non-dimensional groups. Finally, we observe that
the experimental approach of using a ring to contain the surfactant could
affect the surfactant and fluid dynamics if it disrupts the intended initial
surfactant distribution. However, the meniscus itself does not significantly
affect the dynamics.


title:
Fe Line Diagnostics of Cataclysmic Variables and Galactic Ridge X-ray
  Emission

abstract:
  The properties of the Galactic Ridge X-ray Emission (GRXE) observed in the
2-10 keV band place fundamental constraints on various types of X-ray sources
in the Milky Way. Although the primarily discrete origin of the emission is now
well established, the responsible populations of these sources remain
uncertain, especially at relatively low fluxes. To provide insights into this
issue, we systematically characterize the Fe emission line properties of the
candidate types of the sources in the solar neighborhood and compare them with
those measured for the GRXE. Our source sample includes 6 symbiotic stars
(SSs), 16 intermediate polars (IPs), 3 polars, 16 quiescent dwarf novae (DNe)
and 4 active binaries (ABs). We find that the mean equivalent width
($EW_{6.7}$) of the 6.7-keV line and the mean 7.0/6.7-keV line ratio are
$107\pm16.0$ eV and $0.71\pm 0.04$ for intermediate polars and $221\pm 135$ eV
and $0.44\pm 0.14$ for polars, respectively, which are all substantially
different from those ($490\pm15 $~eV and $0.2\pm 0.08$) for the GRXE. Instead,
the GRXE values are better agreed by the $EW_{6.7}$ ($438\pm 84.6$~eV) and the
ratio ($0.27\pm 0.06$) observed for the DNe.
  We further find that the $EW_{6.7}$ is strongly correlated with the 2-10-keV
luminosity of the DNe, which can be characterized by the relation
$EW_{6.7}=(438\pm95 {\rm~eV}) (L/10^{31}~{\rm~ergs~s^{-1} })^{(-0.31\pm0.15)}$.
Accounting for this correlation, the agreement can be improved further,
especially when the contributions from other classes sources to the GRXE are
considered, which all have low $EW_{6.7}$ values. We conclude that the GRXE
mostly consists of typically faint, but numerous DNe, plus ABs, while magnetic
CVs are probably mainly the high-flux representatives of the responsible
populations and dominate the GRXE only in harder energy bands.


title: Scheduling MapReduce Jobs under Multi-Round Precedences

abstract:
  We consider non-preemptive scheduling of MapReduce jobs with multiple tasks
in the practical scenario where each job requires several map-reduce rounds. We
seek to minimize the average weighted completion time and consider scheduling
on identical and unrelated parallel processors. For identical processors, we
present LP-based O(1)-approximation algorithms. For unrelated processors, the
approximation ratio naturally depends on the maximum number of rounds of any
job. Since the number of rounds per job in typical MapReduce algorithms is a
small constant, our scheduling algorithms achieve a small approximation ratio
in practice. For the single-round case, we substantially improve on previously
best known approximation guarantees for both identical and unrelated
processors. Moreover, we conduct an experimental analysis and compare the
performance of our algorithms against a fast heuristic and a lower bound on the
optimal solution, thus demonstrating their promising practical performance.


title: Anomaly Detection in Clutter using Spectrally Enhanced Ladar

abstract:
  Discrete return (DR) Laser Detection and Ranging (Ladar) systems provide a
series of echoes that reflect from objects in a scene. These can be first, last
or multi-echo returns. In contrast, Full-Waveform (FW)-Ladar systems measure
the intensity of light reflected from objects continuously over a period of
time. In a camouflaged scenario, e.g., objects hidden behind dense foliage, a
FW-Ladar penetrates such foliage and returns a sequence of echoes including
buried faint echoes. The aim of this paper is to learn local-patterns of
co-occurring echoes characterised by their measured spectra. A deviation from
such patterns defines an abnormal event in a forest/tree depth profile. As far
as the authors know, neither DR or FW-Ladar, along with several spectral
measurements, has not been applied to anomaly detection. This work presents an
algorithm that allows detection of spectral and temporal anomalies in FW-Multi
Spectral Ladar (FW-MSL) data samples. An anomaly is defined as a full waveform
temporal and spectral signature that does not conform to a prior expectation,
represented using a learnt subspace (dictionary) and set of coefficients that
capture co-occurring local-patterns using an overlapping temporal window. A
modified optimization scheme is proposed for subspace learning based on
stochastic approximations. The objective function is augmented with a
discriminative term that represents the subspace's separability properties and
supports anomaly characterisation. The algorithm detects several man-made
objects and anomalous spectra hidden in a dense clutter of vegetation and also
allows tree species classification.

categories: physics.optics cs.LG physics.ins-det stat.AP stat.ML


title: Harmonic parametrization of surfaces of arbitrary genus

abstract:
  The Weierstrass representation for minimal surfaces in $\mathbb{R}^3$
provides a flexible method for constructing minimal surfaces of arbitrary
genus. The topological limitations of minimal surfaces interfere with this
providing a more general geometric modeling tool. Minimal surfaces lie in the
larger class of harmonic surfaces, which in general don't have the same
topological limitations of minimal surfaces and can have complicated embedded
ends. In this paper we demonstrate the flexibility of using the Weierstrass
representation for harmonic surfaces to combine embedded harmonic ends together
to construct embedded harmonic surfaces of arbitrary genus.


title: A note on special polynomials and minimal surfaces

abstract:
  When using Traizet's regeneration technique to construct minimal surfaces,
the simplest nontrivial configurations are given as the roots of polynomials
that satisfy a hypergeometric differential equation. We exhibit examples of
simple minimal surfaces exhibiting the same behavior.


title:
Geometry of Moduli Stacks of $(k,l)$-stable vector bundles over an
  algebraic curve

abstract:
  We study the geometry of the moduli stack of vector bundles of fixed rank and
degree over an algebraic curve by introducing a filtration made of open
substacks build from $(k, l)$-stable vector bundles. $(k, l)$-stability was
introduced by Narasimhan and Ramanan to study the geometry of the coarse moduli
space of stable bundles. We will exhibit the stacky picture and analyse the
geometric and cohomological properties of the moduli stacks of $(k, l)$-stable
vector bundles. For particular pairs $(k, l) $ of integers we also show that
these moduli stacks admit coarse moduli spaces and we discuss their interplay.


title:
Shape reconstruction of nanoparticles from their associated plasmonic
  resonances

abstract:
  We prove by means of a couple of examples that plasmonic resonances can be
used on one hand to classify shapes of nanoparticles with real algebraic
boundaries and on the other hand to reconstruct the separation distance between
two nanoparticles from measurements of their first collective plasmonic
resonances. To this end, we explicitly compute the spectral decompositions of
the Neumann-Poincar\'{e} operators associated with a class of quadrature
domains and two nearly touching disks. Numerical results are included in
support of our main findings.


title:
Quantum oscillations from `open' Fermi surface in quasi-one-dimensional
  lattices: Application to YBa2Cu3O6 cuprates, organic salts, ladder compounds,
  and related systems

abstract:
  According to the celebrated Onsagar-Lifshitz paradigm, the observation of
Shubnikov de-Haas and de-Haas van Alphen (SdHvA) oscillations is an indication
of the presence of `closed' orbit Fermi surface in the bulk. We present a
real-space based calculation of SdHvA oscillations in generalized
quasi-one-dimensional lattices by relaxing the quasi-classical approximations
embedded in this decades old Onsagar-Lifshitz paradigm. We find that sizable
quantum oscillation can arise from `open' Fermi surfaces as long as cyclotron
orbits can form in real-space with finite, but not necessarily equal, electron
hopping along both x- and y-directions. Our results quantitatively explain the
puzzling emergence of SdHvA oscillation in various quasi-one-dimensional
materials, including the chain state of YBa2Cu3O6 cuprates, organic materials,
various ladder compounds, weakly coupled linear chains, or quantum wires, and
other related systems.


title: Chaotic Mixing in Three Dimensional Porous Media

abstract:
  Under steady flow conditions, the topological complexity inherent to all
random 3D porous media imparts complicated flow and transport dynamics. It has
been established that this complexity generates persistent chaotic advection
via a three-dimensional (3D) fluid mechanical analogue of the baker's map which
rapidly accelerates scalar mixing in the presence of molecular diffusion. Hence
pore-scale fluid mixing is governed by the interplay between chaotic advection,
molecular diffusion and the broad (power-law) distribution of fluid particle
travel times which arise from the non-slip condition at pore walls. To
understand and quantify mixing in 3D porous media, we consider these processes
in a model 3D open porous network and develop a novel stretching continuous
time random walk (CTRW) which provides analytic estimates of pore-scale mixing
which compare well with direct numerical simulations. We find that chaotic
advection inherent to 3D porous media imparts scalar mixing which scales
exponentially with longitudinal advection, whereas the topological constraints
associated with 2D porous media limits mixing to scale algebraically. These
results decipher the role of wide transit time distributions and complex
topologies on porous media mixing dynamics, and provide the building blocks for
macroscopic models of dilution and mixing which resolve these mechanisms.


title: Collective Motion of Self-Propelled Particles with Memory

abstract:
  We show that memory, in the form of underdamped angular dynamics, is a
crucial ingredient for the collective properties of self-propelled particles.
Using Vicsek-style models with an Ornstein-Uhlenbeck process acting on angular
velocity, we uncover a rich variety of collective phases not observed in usual
overdamped systems, including vortex lattices and active foams. In a model with
strictly nematic interactions the smectic arrangement of Vicsek waves giving
rise to global polar order is observed. We also provide a calculation of the
effective interaction between vortices in the case where a telegraphic noise
process is at play, explaining thus the emergence and structure of the vortex
lattices observed here and in motility assay experiments.


title: The likely determines the unlikely

abstract:
  We point out that the functional form describing the frequency of sizes of
events in complex systems (e.g. earthquakes, forest fires, bursts of neuronal
activity) can be obtained from maximal likelihood inference, which, remarkably,
only involve a few available observed measures such as number of events, total
event size and extremes. Most importantly, the method is able to predict with
high accuracy the frequency of the rare extreme events. To be able to predict
the few, often big impact events, from the frequent small events is of course
of great general importance. For a data set of wind speed we are able to
predict the frequency of gales with good precision. We analyse several examples
ranging from the shortest length of a recruit to the number of Chinese
characters which occur only once in a text.


title: The Lagrangian Deformation Structure of Three-Dimensional Steady Flow

abstract:
  Fluid deformation and strain history are central to wide range of fluid
mechanical phenomena ranging from fluid mixing and particle transport to stress
development in complex fluids and the formation of Lagrangian coherent
structures (LCSs). To understand and model these processes it is necessary to
quantify Lagrangian deformation in terms of Eulerian flow properties, currently
an open problem. To elucidate this link we develop a Protean (streamline)
coordinate transform for steady three-dimensional (3D) flows which renders both
the velocity gradient and deformation gradient upper triangular. This frame not
only simplifies computation of fluid deformation metrics such as finite-time
Lyapunov exponents (FTLEs) and elucidates the deformation structure of the
flow, but moreover explicitly recovers kinematic and topological constraints
upon deformation such as those related to helicity density and the
Poincar\'{e}-Bendixson theorem. We apply this transform to several classes of
steady 3D flow, including helical and non-helical, compressible and
incompressible flows, and find random flows exhibit remarkably simple
(Gaussian) deformation structure, and so are fully characterised in terms of a
small number of parameters. As such this technique provides the basis for the
development of stochastic models of fluid deformation in random flows which
adhere to the kinematic constraints inherent to various flow classes.


title:
Coupled dynamics of flow, microstructure, and conductivity in sheared
  suspensions

abstract:
  We propose a model for the evolution of the conductivity tensor for a flowing
suspension of electrically conductive particles. We use discrete particle
numerical simulations together with a continuum physical framework to construct
an evolution law for the suspension microsutructure during flow. This model is
then coupled with a relationship between the microstructure and the electrical
conductivity tensor. The parameters of the joint model are fit experimentally
using rheo- electrical conductivity measurements of carbon black suspensions
under flow over a range of shear rates. The model is applied to the case of
steady shearing as well as time-varying conductivity of unsteady flow
experiments. We find that the model prediction agrees closely with the measured
experimental data in all cases.


title:
Chaotic Advection at the Pore Scale: Mechanisms, Upscaling and
  Implications for Macroscopic Transport

abstract:
  The macroscopic spreading and mixing of solute plumes in saturated porous
media is ultimately controlled by processes operating at the pore scale. Whilst
the conventional picture of pore-scale mechanical dispersion and molecular
diffusion leading to persistent hydrodynamic dispersion is well accepted, this
paradigm is inherently two-dimensional (2D) in nature and neglects important
three-dimensional (3D) phenomena. We discuss how the kinematics of steady 3D
flow at the porescale generate chaotic advection, involving exponential
stretching and folding of fluid elements,the mechanisms by which it arises and
implications of microscopic chaos for macroscopic dispersion and mixing.
Prohibited in steady 2D flow due to topological constraints, these phenomena
are ubiquitous due to the topological complexity inherent to all 3D porous
media. Consequently 3D porous media flows generate profoundly different fluid
deformation and mixing processes to those of 2D flow. The interplay of chaotic
advection and broad transit time distributions can be incorporated into a
continuous-time random walk (CTRW) framework to predict macroscopic solute
mixing and spreading. We show how these results may be generalised to real
porous architectures via a CTRW model of fluid deformation, leading to
stochastic models of macroscopic dispersion and mixing which both honour the
pore-scale kinematics and are directly conditioned on the pore-scale
tomography.


title:
A Model for Pseudo-Dirac Neutrinos: Leptogenesis and Ultra-High Energy
  Neutrinos

abstract:
  We propose a model where sterile neutrinos are introduced to make light
neutrinos to be pseudo-Dirac particles. It is shown how tiny mass splitting
necessary for realizing pseudo-Dirac neutrinos can be achieved. Within the
model, we show how leptogenesis can be successfully generated. Motivated by the
recent observation of very high energy neutrino events at IceCube, we study a
possibility to observe the effects of the pseudo-Dirac property of neutrinos by
performing astronomical-scale baseline experiments to uncover the oscillation
effects of very tiny mass splitting. Using the result of global fit to neutrino
data for the input of neutrino mixing angles and CP phase at $1\sigma$ C.L. and
fixing neutrino energy and mass splittings, we study how the oscillation
effects induced by pseudo-Dirac neutrinos may affect the track-to-shower ratio
obtained from IceCube data. We also discuss future prospect to observe the
effects of the pseudo-Dirac property of neutrinos at high energy neutrino
experiments.


title:
Fermionic response from fractionalization in an insulating
  two-dimensional magnet

abstract:
  Conventionally ordered magnets possess bosonic elementary excitations, called
magnons. By contrast, no magnetic insulators in more than one dimension are
known whose excitations are not bosons but fermions. Theoretically, some
quantum spin liquids (QSLs) -- new topological phases which can occur when
quantum fluctuations preclude an ordered state -- are known to exhibit Majorana
fermions as quasiparticles arising from fractionalization of spins. Alas,
despite much searching, their experimental observation remains elusive. Here,
we show that fermionic excitations are remarkably directly evident in
experimental Raman scattering data across a broad energy and temperature range
in the two-dimensional material $\alpha$-RuCl$_3$. This shows the importance of
magnetic materials as hosts of Majorana fermions. In turn, this first
systematic evaluation of the dynamics of a QSL at finite temperature emphasizes
the role of excited states for detecting such exotic properties associated with
otherwise hard-to-identify topological QSLs.


title: Length filtration of the separable states

abstract:
  We investigate the separable states $\r$ of an arbitrary multipartite quantum
system with Hilbert space $\cH$ of dimensionin $d$. The length $L(\r)$ of $\r$
is defined as the smallest number of pure product states having $\r$ as their
mixture. The length filtration of the set of separable states, $\cS$, is the
increasing chain $\emptyset\subset\cS'_1\subseteq\cS'_2\subseteq\cdots$, where
$\cS'_i=\{\r\in\cS:L(\r)\le i\}$. We define the maximum length, $L_{\rm
max}=\max_{\r\in\cS} L(\r)$, critical length, $L_{\rm crit}$, and yet another
special length, $L_c$, which was defined by a simple formula in one of our
previous papers. The critical length indicates the first term in the length
filtrartion whose dimension is equal to $\dim\cS$. We show that in general
$d\le L_c\le L_{\rm crit}\le L_{\rm max}\le d^2$.
  We conjecture that the equality $L_{\rm crit}=L_c$ holds for all
finite-dimensional multipartite quantum systems. Our main result is that
$L_{\rm crit}=L_c$ for the bipartite systems having a single qubit as one of
the parties. This is accomplished by computing the rank of the Jacobian matrix
of a suitable map having $\cS$ as its range.


title: Archimedes' quadrature of the parabola and minimal covers

abstract:
  The generalization of Archimedes strategy to obtain the area of a parabolic
segment leads to combinatorial formulas involving minimal covers of sets.
These, in turn, are conjecturally related to $q$-binomial coefficients.


title:
Multifractality and Laplace spectrum of horizontal visibility graphs
  constructed from fractional Brownian motions

abstract:
  Many studies have shown that additional information can be gained on time
series by investigating their associated complex networks. In this work, we
investigate the multifractal property and Laplace spectrum of the horizontal
visibility graphs (HVGs) constructed from fractional Brownian motions. We aim
to identify via simulation and curve fitting the form of these properties in
terms of the Hurst index $H$. First, we use the sandbox algorithm to study the
multifractality of these HVGs. It is found that multifractality exists in these
HVGs. We find that the average fractal dimension $\langle D(0)\rangle$ of HVGs
approximately satisfies the prominent linear formula $\langle D(0)\rangle = 2 -
H$; while the average information dimension $\langle D(1)\rangle$ and average
correlation dimension $\langle D(2)\rangle$ are all approximately bi-linear
functions of $H$ when $H\ge 0.15$. Then, we calculate the spectrum and energy
for the general Laplacian operator and normalized Laplacian operator of these
HVGs. We find that, for the general Laplacian operator, the average logarithm
of second-smallest eigenvalue $\langle \ln (u_2) \rangle$, the average
logarithm of third-smallest eigenvalue $\langle \ln (u_3) \rangle$, and the
average logarithm of maximum eigenvalue $\langle \ln (u_n) \rangle$ of these
HVGs are approximately linear functions of $H$; while the average Laplacian
energy $\langle E_{nL} \rangle$ is approximately a quadratic polynomial
function of $H$. For the normalized Laplacian operator, $\langle \ln (u_2)
\rangle$ and $\langle \ln (u_3) \rangle$ of these HVGs approximately satisfy
linear functions of $H$; while $\langle \ln (u_n) \rangle$ and $\langle E_{nL}
\rangle$ are approximately a 4th and cubic polynomial function of $H$
respectively.


title:
Generalized Jensen Inequalities with Application to Stability Analysis
  of Systems with Distributed Delays over Infinite Time-Horizons

abstract:
  The Jensen inequality has been recognized as a powerful tool to deal with the
stability of time-delay systems. Recently, a new inequality that encompasses
the Jensen inequality was proposed for the stability analysis of systems with
finite delays. In this paper, we first present a generalized integral
inequality and its double integral extension. It is shown how these
inequalities can be applied to improve the stability result for linear
continuous-time systems with gamma-distributed delays. Then, for the
discrete-time counterpart we provide an extended Jensen summation inequality
with infinite sequences, which leads to less conservative stability conditions
for linear discrete-time systems with poisson-distributed delays. The
improvements obtained thanks to the introduced generalized inequalities are
demonstrated by examples.


title:
Variations of geometric invariant quotients for pairs, a computational
  approach

abstract:
  We study the GIT compactifications of pairs formed by a hypersurface and a
hyperplane. We provide a general setting to characterize all polarizations
which give rise to different GIT quotients. Furthermore, we describe a finite
set of one-parameter subgroups sufficient to determine the stability of any GIT
quotient. We characterize all maximal orbits of non stable and strictly
semistable pairs, as well as minimal closed orbits of strictly semistable
pairs. Our construction gives natural compactifications of the space of log
smooth pairs for Fano and Calabi-Yau hypersurfaces.


title: The Force and Gravity of Events

abstract:
  Local events are characterized by "where", "when" and "what". Just as
(bosonic) spacetime forms the backdrop for location and time, (fermionic)
property space can serve as the backdrop for the attributes of a system. With
such a scenario I shall describe a scheme that is capable of unifying
gravitation and the other forces of nature. The generalized metric contains the
curvature of spacetime and property separately, with the gauge fields linking
the bosonic and fermionic arenas. The super-Ricci scalar can then automatically
yield the spacetime Lagrangian of gravitation and the standard model (plus a
cosmological constant) upon integration over property coordinates.


title:
Deviation from Fermi-liquid behavior in two-dimensional surface states
  of Au-induced nanowires on Ge(001) by correlation and localization

abstract:
  The electronic states of Au-induced atomic nanowires on Ge(001) (Au/Ge(001)
NWs) have been investigated by angle-resolved photoelectron spectroscopy with
linearly polarized light. We have found three electron pockets around
$\bar{J}\bar{K}$, where the Fermi surfaces are closed in a surface Brillouin
zone, indicating that the surface states of Au/Ge(001) NWs are two-dimensional
whereas the atomic structure is one-dimensional. The two-dimensional metallic
states exhibit remarkable suppression of the photoelectron intensity near a
Fermi energy. This suppression can be explained by the correlation and
localization effects in disordered metals, which is a deviation from a
Fermi-liquid model.


title: Choice by Elimination via Deep Neural Networks

abstract:
  We introduce Neural Choice by Elimination, a new framework that integrates
deep neural networks into probabilistic sequential choice models for learning
to rank. Given a set of items to chose from, the elimination strategy starts
with the whole item set and iteratively eliminates the least worthy item in the
remaining subset. We prove that the choice by elimination is equivalent to
marginalizing out the random Gompertz latent utilities. Coupled with the choice
model is the recently introduced Neural Highway Networks for approximating
arbitrarily complex rank functions. We evaluate the proposed framework on a
large-scale public dataset with over 425K items, drawn from the Yahoo! learning
to rank challenge. It is demonstrated that the proposed method is competitive
against state-of-the-art learning to rank methods.