title: Escape rates for special flows and their higher order asymptotics

abstract:
  In this paper escape rates and local escape rates for special flows are
sudied. In a general context the first result is that the escape rate depends
monotonically on the ceiling function and fulfills certain scaling, invariance,
and continuity properties. For the metric setting local escape rates are
considered. If the base transformation is ergodic and exhibits an exponential
convergence in probability of ergodic sums, then the local escape rate with
respect to the flow is just the local escape rate with respect to the base
transformation, divided by the integral of the ceiling function. Also a
reformulation with respect to induced pressure is presented. Finally, under
additional regularity conditions higher order asymptotics for the local escape
rate are established.


title:
Discovery of concentric broken rings at sub-arcsec separations in the HD
  141569A gas-rich, debris disk with VLT/SPHERE

abstract:
  Transition disks correspond to a short stage between the young protoplanetary
phase and older debris phase. Along this evolutionary sequence, the gas
component disappears leaving room for a dust-dominated environment where
already-formed planets signpost their gravitational perturbations. We endeavor
to study the very inner region of the well-known and complex debris, but still
gas-rich disk, around HD 141569A using the exquisite high-contrast capability
of SPHERE at the VLT. Recent near-infrared (IR) images suggest a relatively
depleted cavity within ~200 au, while former mid-IR data indicate the presence
of dust at separations shorter than ~100 au. We obtained multi-wavelength
images in the near-IR in J, H2, H3 and Ks bands with the IRDIS camera and a
0.95-1.35 micrometers spectral data cube with the IFS. Data were acquired in
pupil-tracking mode, thus allowing for angular differential imaging. We
discovered several new structures inside 1", of which the most prominent is a
bright ring with sharp edges (semi-major axis: 0.4") featuring a strong
north-south brightness asymmetry. Other faint structures are also detected from
0.4" to 1" in the form of concentric ringlets and at least one spiral arm.
Finally, the VISIR data at 8.6 micrometers suggests the presence of an
additional dust population closer in. Besides, we do not detect companions more
massive than 1-3 mass of Jupiter. The performance of SPHERE allows us to
resolve the extended dust component, which was previously detected at thermal
and visible wavelengths, into very complex patterns with strong asymmetries ;
the nature of these asymmetries remains to be understood. Scenarios involving
shepherding by planets or dust-gas interactions will have to be tested against
these observations.


title:
Spectra and probability distributions of thermal flux in turbulent
  Rayleigh-B\'{e}nard convection

abstract:
  The spectra of turbulent heat flux $\mathrm{H}(k)$ in Rayleigh-B\'{e}nard
convection with and without uniform rotation are presented. The spectrum
$\mathrm{H}(k)$ scales with wave number $k$ as $\sim k^{-2}$. The scaling
exponent is almost independent of the Taylor number $\mathrm{Ta}$ and Prandtl
number $\mathrm{Pr}$ for higher values of the reduced Rayleigh number $r$ ($ >
10^3$). The exponent, however, depends on $\mathrm{Ta}$ and $\mathrm{Pr}$ for
smaller values of $r$ ($<10^3$). The probability distribution functions of the
local heat fluxes are non-Gaussian and have exponential tails.


title:
Two-band superfluidity and intrinsic Josephson effect in alkaline-earth
  Fermi gases across an orbital Feshbach resonance

abstract:
  We first show that the many-body Hamiltonian governing the physical
properties of an alkaline-earth Yb-173 Fermi gas across the recently-realized
orbital Feshbach resonance is exactly analogous to that of two-band s-wave
superconductors with contact interactions: i.e., even though the free-particle
bands have a tunable energy offset in between and are coupled by a
Josephson-type attractive inter-band pair scattering, the intra-band
interactions have exactly the same strength. We then introduce two intra-band
order parameters within the BCS mean-field approximation, and investigate the
competition between their in-phase and out-of-phase (i.e., the so-called
\pi-phase) solutions in the entire BCS-BEC evolution at zero temperature.


title: The arithmetical rank of the edge ideals of cactus graphs

abstract:
  We prove that, for the edge ideal of a cactus graph, the arithmetical rank is
bounded above by the sum of the number of cycles and the maximum height of its
associated primes. The bound is sharp, but in many cases it can be improved.
Moreover, we show that the edge ideal of a Cohen-Macaulay graph that contains
exactly one cycle or is chordal or has no cycles of length 4 and 5 is a
set-theoretic complete intersection.


title:
Non-equilibrium variational cluster perturbation theory: quench dynamics
  of the quantum Ising model

abstract:
  We introduce a variational implementation of cluster perturbation theory
(CPT) to address the dynamics of spin systems driven out of equilibrium. We
benchmark the method with the quantum Ising model subject to a sudden quench of
the transverse magnetic field across the transition or within a phase. We treat
both the one-dimensional case, for which an exact solution is available, as
well the two-dimensional one, for which has to resort to numerical results.
Comparison with exact results shows that the approach provides a quite accurate
description of the real-time dynamics up to a characteristic time scale $\tau$
that increses with the size of the cluster used for CPT. In addition, and not
surprisingly $\tau$ is small for quenches across the equilibrium phase
transition, but can be quite larger for quenches within the ordered or
disordered phases.


title: Automorphism groups of randomized structures

abstract:
  We study automorphism groups of randomizations of separable structures, with
focus on the $\aleph_0$-categorical case. We give a description of the
automorphism group of the Borel randomization in terms of the group of the
original structure. In the $\aleph_0$-categorical context, this provides a new
source of Roelcke precompact Polish groups, and we describe the associated
Roelcke compactifications. This allows us also to recover and generalize
preservation results of stable and NIP formulas previously established in the
literature, via a Banach-theoretic translation. Finally, we study and classify
the separable models of the theory of beautiful pairs of randomizations,
showing in particular that this theory is never $\aleph_0$-categorical (except
in basic cases).


title: On Reductions from Multi-Domain Noninterference to the Two-Level Case

abstract:
  The literature on information flow security with respect to transitive
policies has been concentrated largely on the case of policies with two
security domains, High and Low, because of a presumption that more general
policies can be reduced to this two-domain case. The details of the reduction
have not been the subject of careful study, however. Many works in the
literature use a reduction based on a quantification over "Low-down"
partitionings of domains into those below and those not below a given domain in
the information flow order. A few use "High-up" partitionings of domains into
those above and those not above a given domain. Our paper argues that more
general "cut" partitionings are also appropriate, and studies the relationships
between the resulting multi-domain notions of security when the basic notion
for the two-domain case to which we reduce is either Nondeducibility on Inputs
or Generalized Noninterference. The Low-down reduction is shown to be weaker
than the others, and while the High-up reduction is sometimes equivalent to the
cut reduction, both it and the Low-down reduction may have an undesirable
property of non-monotonicity with respect to a natural ordering on policies.
These results suggest that the cut-based partitioning yields a more robust
general approach for reduction to the two-domain case.


title: Rolling Shutter Camera Relative Pose: Generalized Epipolar Geometry

abstract:
  The vast majority of modern consumer-grade cameras employ a rolling shutter
mechanism. In dynamic geometric computer vision applications such as visual
SLAM, the so-called rolling shutter effect therefore needs to be properly taken
into account. A dedicated relative pose solver appears to be the first problem
to solve, as it is of eminent importance to bootstrap any derivation of
multi-view geometry. However, despite its significance, it has received
inadequate attention to date.
  This paper presents a detailed investigation of the geometry of the rolling
shutter relative pose problem. We introduce the rolling shutter essential
matrix, and establish its link to existing models such as the push-broom
cameras, summarized in a clean hierarchy of multi-perspective cameras. The
generalization of well-established concepts from epipolar geometry is completed
by a definition of the Sampson distance in the rolling shutter case. The work
is concluded with a careful investigation of the introduced epipolar geometry
for rolling shutter cameras on several dedicated benchmarks.


title:
Boundedness of Bi-parameter Littlewood-Paley operators on product Hardy
  space

abstract:
  Let $n_1,n_2\ge 1, \lambda_1>1$ and $\lambda_2>1$. For any $x=(x_1,x_2) \in
\mathbb {R}^n\times\mathbb{R}^m$, let $g$ and $g_{\vec{\lambda}}^*$ be the
bi-parameter Littlewood-Paley square functions defined by \begin{align*}
g(f)(x)= \Big(\int_0^{\infty}\int_0^{\infty}|\theta_{t_1,t_2} f(x_1,x_2)|^2
\frac{dt_1}{t_1} \frac{dt_2}{t_2} \Big)^{1/2}, \hbox{and} \end{align*} $$
g_{\vec{\lambda}}^*(f)(x) = \Big(\iint_{\mathbb{R}^{m+1}_{+}}
\iint_{\mathbb{R}^{n+1}_{+}} \prod_{i=1}^2\Big(\frac{t_1}{t_i + |x_i -
y_i|}\Big)^{n_i \lambda_i} |\theta_{t_1,t_2} f(y_1,y_2)|^2 \frac{dy_1
dt_1}{t_1^{n+1}} \frac{dy_2 dt_2}{t_2^{m+1}} \Big)^{1/2}, $$ \noindent where
$\theta_{t_1,t_2} f(x_1, x_2) = \iint_{\mathbb{R}^n\times\mathbb{R}^m}
s_{t_1,t_2}(x_1,x_2,y_1,y_2)f(y_1,y_2) dy_1dy_2$. It is known that the $L^2$
boundedness of bi-parameter $g$ and $g_{\vec{\lambda}}^*$ have been established
recently by Martikainen, and Cao, Xue, respectively. In this paper, under
certain structure conditions assumed on the kernel $s_{t_1,t_2},$ we show that
both $g$ and $g_{\vec{\lambda}}^*$ are bounded from product Hardy space
$H^1(\mathbb{R}^n\times\mathbb{R}^m)$ to $L^1(\mathbb{R}^n\times\mathbb{R}^m)$.
As consequences, the $L^p$ boundedness of $g$ and $g_{\vec{\lambda}}^*$ will be
obtained for $1<p<2$.


title:
Surface-enhanced gallium arsenide photonic resonator with a quality
  factor of six million

abstract:
  Gallium Arsenide and related compound semiconductors lie at the heart of
optoelectronics and integrated laser technologies. Shaped at the micro and
nano-scale, they allow strong interaction with quantum dots and quantum wells,
and promise to result in stunning devices. However gallium arsenide optical
structures presently exhibit lower performances than their silicon-based
counterparts, notably in nanophotonics where the surface plays a chief role.
Here we report on advanced surface control of miniature gallium arsenide
optical resonators, using two distinct techniques that produce permanent
results. One leads to extend the lifetime of free-carriers and enhance
luminescence, while the other strongly reduces surface absorption originating
from mid-gap states and enables ultra-low optical dissipation devices. With
such surface control, the quality factor of wavelength-sized optical disk
resonators is observed to rise up to six million at telecom wavelength, greatly
surpassing previous realizations and opening new prospects for Gallium Arsenide
nanophotonics.


title:
A Mechanical Study of a Glass Fabric-Thermoplastic Resin Composite:
  3D-DIC and X-ray tomographic observations explained by numerical simulations
  based on a spectral solver

abstract:
  In the study presented in this paper, we analyzed the mechanical response of
a glass fiber plain weave/polymer composite at the fabric millimetric
mesoscale. The detail of the stress and strain fields in a fabric repeating
unit cell was numerically calculated using CraFT (Composite response and
Fourier Transforms), a code specifically conceived for simulating the
mechanical behaviour of materials with complex microstructure. The local strain
fields obtained by simulation were found to be in very good agreement with
measurements carried out using 3D Digital Image Correlation (3D DIC). From
numerical stress fields calculated with the CraFT solver, we also highlighted
the subregions inside the periodic mesostructure where there is maximum stress.
Furthermore, with X-ray tomography post mortem measurements, we were able to
confirm that certain damage modes were well initiated in these microstructure
subregions of stress concentration.


title:
A Nonconvex Nonsmooth Regularization Method for Compressed Sensing and
  Low-Rank Matrix Completion

abstract:
  In this paper, nonconvex and nonsmooth models for compressed sensing (CS) and
low rank matrix completion (MC) is studied. The problem is formulated as a
nonconvex regularized leat square optimization problems, in which the l0-norm
and the rank function are replaced by l1-norm and nuclear norm, and adding a
nonconvex penalty function respectively. An alternating minimization scheme is
developed, and the existence of a subsequence, which generate by the
alternating algorithm that converges to a critical point, is proved. The NSP,
RIP, and RIP condition for stable recovery guarantees also be analysed for the
nonconvex regularized CS and MC problems respectively. Finally, the performance
of the proposed method is demonstrated through experimental results.


title: Scalable Device-to-Device Communications For Frequency Reuse >> 1

abstract:
  Proximity based applications are becoming fast growing markets suggesting
that Device-to-Device (D2D) communications is becoming an essential part of
future mobile data networks. We propose scalable admission and power control
methods for D2D communications underlay cellular networks to increase the reuse
of frequency resources and thus network capacity while maintaining QoS to all
users. The aim of the proposed methods is to maximize the number of D2D links
under QoS constraints, therefore maximizing network frequency reuse, while
considering different levels of complexity and available channel state
information (CSI) in a multi-cell environment. Numerical results show that by
using D2D and the proposed multi-cell interference coordination and low power
transmission method, the network spectral efficiency can be increased by as
much as ten times, while low outage probability can be assured to provided QoS
for all users.


title: Sharp integral bounds for Wigner distributions

abstract:
  The cross-Wigner distribution $W(f,g)$ of two functions or temperate
distributions $f,g$ is a fundamental tool in quantum mechanics and in signal
analysis. Usually, in applications in time-frequency analysis $f$ and $g$
belong to some modulation space and it is important to know which modulation
spaces $W(f,g)$ belongs to. Although several particular sufficient conditions
have been appeared in this connection, the general problem remains open. In the
present paper we solve completely this issue by providing the full range of
modulation spaces in which the continuity of the cross-Wigner distribution
$W(f,g)$ holds, as a function of $f,g$. The case of weighted modulation spaces
is also considered. The consequences of our results are manifold: new bounds
for the short-time Fourier transform and the ambiguity function, boundedness
results for pseudodifferential (in particular, localization) operators and
properties of the Cohen class.


title:
Compositional Sentence Representation from Character within Large
  Context Text

abstract:
  This paper describes a Hierarchical Composition Recurrent Network (HCRN)
consisting of a 3-level hierarchy of compositional models: character, word and
sentence. This model is designed to overcome two problems of representing a
sentence on the basis of a constituent word sequence. The first is a
data-sparsity problem in word embedding, and the other is a no usage of
inter-sentence dependency. In the HCRN, word representations are built from
characters, thus resolving the data-sparsity problem, and inter-sentence
dependency is embedded into sentence representation at the level of sentence
composition. We adopt a hierarchy-wise learning scheme in order to alleviate
the optimization difficulties of learning deep hierarchical recurrent network
in end-to-end fashion. The HCRN was quantitatively and qualitatively evaluated
on a dialogue act classification task. Especially, sentence representations
with an inter-sentence dependency are able to capture both implicit and
explicit semantics of sentence, significantly improving performance. In the
end, the HCRN achieved state-of-the-art performance with a test error rate of
22.7% for dialogue act classification on the SWBD-DAMSL database.


title: A young SNR illuminating nearby Molecular Clouds with cosmic rays

abstract:
  The Supernova Remnant (SNR) HESS J1731-347 displays strong non-thermal TeV
gamma-ray and X-ray emission, thus the object is at present time accelerating
particles to very high energies. A distinctive feature of this young SNR is the
nearby (~30 pc in projection) extended source HESS J1729-345, which is
currently unidentified but is in spatial projection coinciding with known
molecular clouds (MC). We model the SNR evolution to explore if the TeV
emission from HESS J1729-345 can be explained as emission from runaway hadronic
cosmic rays (CRs) that are illuminating these MCs. The observational data of
HESS J1729-345 and HESS J1731-347 can be reproduced using core-collapse SN
models for HESS J1731-347. Starting with different progenitor stars and their
pre-supernova environment, we model potential SNR evolution histories along
with the CR acceleration in the SNR and the diffusion of the CRs. A simplified
3-dimensional structure of the MCs is introduced based on 12CO data, adopting a
distance of 3.2 kpc to the source. A Monte Carlo-based diffusion model for the
escaping CRs is developed to deal with the inhomogeneous environment. The fast
SNR forward shock speed as implied from the X-ray data can easily be explained
when employing scenarios with progenitor star masses between 20 and 25 solar
masses, where the SNR shock is still expanding inside the main sequence
(MS)-bubble at present time. The TeV spectrum of HESS J1729-345 is
satisfactorily fitted by the emission from the highest-energy CRs that have
escaped the SNR, using a standard galactic CR diffusion coefficient in the
inter-clump medium. The TeV image of HESS J1729-345 can be explained with a
reasonable 3-dimensional structure of MCs. The TeV emission from the SNR itself
is dominated by leptonic emission in this model. We also explore scenarios
where the shock is starting to encounter the dense MS progenitor wind bubble
shell.


title:
Theoretical study of the $\alpha+d$ $\rightarrow$ $^6$Li + $\gamma $
  astrophysical capture process in a three-body model

abstract:
  The astrophysical capture process $\alpha+d$ $\rightarrow$ $^6$Li + $\gamma$
is studied in a three-body model.
  The initial state is factorized into the deuteron bound state and the
$\alpha+d$ scattering state. The final nucleus $^6$Li(1+) is described as a
three-body bound state $\alpha+n+p$ in the hyperspherical Lagrange-mesh method.
  The contribution of the E1 transition operator from the initial isosinglet
states to the isotriplet components of the final state is estimated to be
negligible. An estimation of the forbidden E1 transition to the isosinglet
components of the final state is comparable with the corresponding results of
the two-body model.
  However, the contribution of the E2 transition operator is found to be much
smaller than the corresponding estimations of the two-body model.
  The three-body model perfectly matches the new experimental data of the LUNA
collaboration with the spectroscopic factor 2.586 estimated from the
bound-state wave functions of $^6$Li and deuteron.


title: From Reaction-Diffusion Systems to Confined Brownian Motion

abstract:
  In this note, we demonstrated for the first time that one can derive an
expression for the effective diffusion coefficient, equal to the Lifson-Jackson
formula, using a subsequent homogenization of the 1D
reaction-diffusion-advection equation. The latter has been derived by applying
asymptotic perturbation analysis to the underlying 3D reaction-diffusion
equation with spatially dependent no-flux boundary conditions and incorporates
the effects of boundary interactions on the reactants via a boundary-induced
advection term [S. Martens et al, Phys. Rev. E 91, 022902 (2015)].


title:
Calibrating Effective Ia Supernova Magnitudes using the Distance Duality
  Relation

abstract:
  Using only Ia supernova (SN) observations, it is not possible to distinguish
the evolution of the SN absolute magnitude $M_B$ from an arbitrary evolution of
the Hubble parameter H(z). However, using Etherington's distance-duality
relation, which relates the angular and luminosity distances, together with the
observed angular baryon acoustic oscillation (BAO) scale at any redshift z, one
may calibrate an effective M(z). This calibration involves a scale which
depends on the cosmological model, however the evolution of the effective M(z)
between two redshifts with BAO observations is independent of this scale. The
line of sight BAO scale can be used to extend this calibration to redshifts
near z. As an application, using BOSS BAO at z=0.32 and 2.34, JLA supernova at
low $z$ and Hubble Space Telescope SN at z>1.7, we find a statistically
insignificant downward shift M(2.34)-M(0.32)=-0.08$\pm$0.15. Replacing BOSS
data with the best fit Planck LCDM BAO expectations, we find a shift of
-0.24$\pm$0.13. With the SN that will be observed by the James Webb Space
Telescope, such a calibration at z=2.34 will be more precise, and it will serve
as an anchor for cosmological analyses with the SN that it will observe at yet
higher z.


title: Curtis homomorphisms and the integral Bernstein center for GL_n

abstract:
  We describe two conjectures, one strictly stronger than the other, that give
descriptions of the integral Bernstein center for GL_n(F) (that is, the center
of the category of smooth W(k)[GL_n(F)]-modules, for F a p-adic field and k an
algebraically closed field of characteristic l different from p) in terms of
Galois theory. Moreover, we show that the weak version of the conjecture (for m
at most n) implies the strong version of the conjecture. In a companion paper
[HM] we show that the strong conjecture for n-1 implies the weak conjecture for
n; thus the two papers together give an inductive proof of both conjectures.
The upshot is a description of the integral Bernstein center for GL_n in purely
Galois-theoretic terms; previous work of the author shows that such a
description implies the conjectural "local Langlands correspondence in
families" of Emerton and the author.


title: On the Roots of Characteristic Equations of Delay Differential Systems

abstract:
  We prove that characteristic equations of certain types of delay differential
systems, under some mild conditions on their coefficients, can possess
infinitely many complex roots.


title:
Active hydrodynamics of synchronization and ordering in moving
  oscillators

abstract:
  The nature of emergent collective behaviors of moving physical agents
interacting with their neighborhood is a long-standing open issue in physical
and biological systems alike. This calls for studies on the control of
synchronization and the degree of order in a collection of diffusively moving
noisy oscillators. We address this by constructing a generic hydrodynamic
theory for active phase fluctuations in a collection of large number of nearly
phase-coherent moving oscillators in two dimensions. Our theory describes the
general situation where phase fluctuations and oscillator mobility mutually
affect each other. We show that the interplay between the active effects and
the mobility of the oscillators leads to a variety of phenomena, ranging from
synchronization with long range, nearly long range and quasi long range orders
to instabilities and desynchronization with short range order of the oscillator
phases. We highlight the complex dependences of synchronization on the active
effects. These should be testable in wide ranging systems, e.g., oscillating
chemical reactions in the presence of different reaction
inhibitors/facilitators, live oriented cytoskeletal extracts, or vertebrate
segmentation clocks.


title: A tour about existence and uniqueness of dg enhancements and lifts

abstract:
  This paper surveys the recent advances concerning the relations between
triangulated (or derived) categories and their dg enhancements. We explain when
some interesting triangulated categories arising in algebraic geometry have a
unique dg enhancement. This is the case, for example, for the unbounded derived
category of quasi-coherent sheaves on an algebraic stack or for its full
triangulated subcategory of perfect complexes. Moreover we give an account of
the recent results about the possibility to lift exact functors between the
bounded derived categories of coherent sheaves on smooth schemes to dg
(quasi-)functors.


title:
Response of simple quantum systems to different polarizations of
  gravitational waves in noncommutative phase-space

abstract:
  Owing to the extreme smallness of any noncommutative scale that may exist in
nature, both in the spatial and momentum sector of the quantum phase-space, a
credible possibility of their detection lies in the present day gravitational
wave detector set-ups, which effectively detects the relative length-scale
variations ${\cal{O}}\left[10^{-23} \right]$. With this motivation, we have
considered how a free particle and harmonic oscillator in a quantum domain will
respond to linearly and circularly polarized gravitational waves if the given
phase-space has a noncommutative structure. The results show resonance
behaviour in the responses of both free particle and HO systems to GW with both
kind of polarizations. We critically analyze all the responses, and their
implications in possible detection of noncommutativity. We use the currently
available upper-bound estimates on various noncommutative parameters to
anticipate the relative size of various response terms. We also argue how the
quantum harmonic oscillator system we considered here can be very relevant in
context of the resonant bar detectors of GW which are already operational
currently.


title:
High level implementation of geometric multigrid solvers for finite
  element problems: applications in atmospheric modelling

abstract:
  The implementation of efficient multigrid preconditioners for elliptic
partial differential equations (PDEs) is a challenge due to the complexity of
the resulting algorithms and corresponding computer code. For sophisticated
finite element discretisations on unstructured grids an efficient
implementation can be very time consuming and requires the programmer to have
in-depth knowledge of the mathematical theory, parallel computing and
optimisation techniques on manycore CPUs. In this paper we show how the
development of bespoke multigrid preconditioners can be simplified
significantly by using a framework which allows the expression of the each
component of the algorithm at the correct abstraction level. Our approach (1)
allows the expression of the finite element problem in a language which is
close to the mathematical formulation of the problem, (2) guarantees the
automatic generation and efficient execution of parallel optimised low-level
computer code and (3) is flexible enough to support different abstraction
levels and give the programmer control over details of the preconditioner. We
use the composable abstractions of the Firedrake/PyOP2 package to demonstrate
the efficiency of this approach for the solution of strongly anisotropic PDEs
in atmospheric modelling. The weak formulation of the PDE is expressed in
Unified Form Language (UFL) and the lower PyOP2 abstraction layer allows the
manual design of computational kernels for a bespoke geometric multigrid
preconditioner. We compare the performance of this preconditioner to a
single-level method and hypre's BoomerAMG algorithm. The Firedrake/PyOP2 code
is inherently parallel and we present a detailed performance analysis for a
single node (24 cores) on the ARCHER supercomputer. Our implementation utilises
a significant fraction of the available memory bandwidth and shows very good
weak scaling on up to 6,144 compute cores.


title: Measuring the speed of light with electric and magnetic pendulum

abstract:
  This problem was given at the Fourth Open and International Experimental
Physics Olympiad (EPO4) Day of Light on 23 April 2016 in Sofia organized by the
Sofia Branch of the Union of Physicists in Bulgaria and the Society of
Physicists of the Republic of Macedonia, Strumica.


title: Localized travelling waves in the asymptotic suction boundary layer

abstract:
  We present two spanwise-localized travelling wave solutions in the asymptotic
suction boundary layer, obtained by continuation of solutions of plane Couette
flow. One of the solutions has the vortical structures located close to the
wall, similar to spanwise-localized edge states previously found for this
system. The vortical structures of the second solution are located in the free
stream far above the laminar boundary layer and are supported by a secondary
shear gradient that is created by a large-scale low-speed streak. The
dynamically relevant eigenmodes of this solution are concentrated in the free
stream, and the departure into turbulence from this solution evolves in the
free stream towards the walls. For invariant solutions in free-stream
turbulence, this solution thus shows that that the source of energy of the
vortical structures can be a dynamical structure of the solution itself,
instead of the laminar boundary layer.


title:
Coalition Formability Semantics with Conflict-Eliminable Sets of
  Arguments

abstract:
  We consider abstract-argumentation-theoretic coalition formability in this
work. Taking a model from political alliance among political parties, we will
contemplate profitability, and then formability, of a coalition. As is commonly
understood, a group forms a coalition with another group for a greater good,
the goodness measured against some criteria. As is also commonly understood,
however, a coalition may deliver benefits to a group X at the sacrifice of
something that X was able to do before coalition formation, which X may be no
longer able to do under the coalition. Use of the typical conflict-free sets of
arguments is not very fitting for accommodating this aspect of coalition, which
prompts us to turn to a weaker notion, conflict-eliminability, as a property
that a set of arguments should primarily satisfy. We require numerical
quantification of attack strengths as well as of argument strengths for its
characterisation. We will first analyse semantics of profitability of a given
conflict-eliminable set forming a coalition with another conflict-eliminable
set, and will then provide four coalition formability semantics, each of which
formalises certain utility postulate(s) taking the coalition profitability into
account.


title: IceCube and GRB neutrinos propagating in quantum spacetime

abstract:
  Two recent publications have reported intriguing analyses, tentatively
suggesting that some aspects of IceCube data might be manifestations of
quantum-gravity-modified laws of propagation for neutrinos. We here propose a
strategy of data analysis which has the advantage of being applicable to
several alternative possibilities for the laws of propagation of neutrinos in a
quantum spacetime. In all scenarios here of interest one should find a
correlation between the energy of an observed neutrino and the difference
between the time of observation of that neutrino and the trigger time of a GRB.
We select accordingly some GRB-neutrino candidates among IceCube events, and
our data analysis finds a rather strong such correlation. This sort of studies
naturally lends itself to the introduction of a "false alarm probability",
which for our analysis we estimate conservatively to be of 1%. We therefore
argue that our findings should motivate a vigorous program of investigation
following the strategy here advocated.


title: Spacetime-noncommutativity regime of Loop Quantum Gravity

abstract:
  A recent study by Bojowald and Paily provided a path toward the
identification of an effective quantum-spacetime picture of Loop Quantum
Gravity, applicable in the "Minkowski regime", the regime where the large-scale
(coarse-grained) spacetime metric is flat. A pivotal role in the analysis is
played by Loop-Quantum-Gravity-based modifications to the hypersurface
deformation algebra, which leave a trace in the Minkowski regime. We here show
that the symmetry-algebra results reported by Bojowald and Paily are consistent
with a description of spacetime in the Minkowski regime given in terms of the
$\kappa$-Minkowski noncommutative spacetime, whose relevance for the study of
the quantum-gravity problem had already been proposed for independent reasons.


title: Inspector: A Data Provenance Library for Multithreaded Programs

abstract:
  Data provenance strives for explaining how the computation was performed by
recording a trace of the execution. The provenance trace is useful across a
wide-range of workflows to improve the dependability, security, and efficiency
of software systems. In this paper, we present Inspector, a POSIX-compliant
data provenance library for shared-memory multithreaded programs. The Inspector
library is completely transparent and easy to use: it can be used as a
replacement for the pthreads library by a simple exchange of libraries linked,
without even recompiling the application code. To achieve this result, we
present a parallel provenance algorithm that records control, data, and
schedule dependencies using a Concurrent Provenance Graph (CPG). We implemented
our algorithm to operate at the compiled binary code level by leveraging a
combination of OS-specific mechanisms, and recently released Intel PT ISA
extensions as part of the Broadwell micro-architecture. Our evaluation on a
multicore platform using applications from multithreaded benchmarks suites
(PARSEC and Phoenix) shows reasonable provenance overheads for a majority of
applications. Lastly, we briefly describe three case-studies where the generic
interface exported by Inspector is being used to improve the dependability,
security, and efficiency of systems. The Inspector library is publicly
available for further use in a wide range of other provenance workflows.


title: Monte Carlo Confidence Sets for Identified Sets

abstract:
  In complicated/nonlinear parametric models, it is generally hard to know
whether the model parameters are point identified. We provide computationally
attractive procedures to construct confidence sets (CSs) for identified sets of
full parameters and of subvectors in models defined through a likelihood or a
vector of moment equalities or inequalities. These CSs are based on level sets
of optimal sample criterion functions (such as likelihood or optimally-weighted
or continuously-updated GMM criterions). The level sets are constructed using
cutoffs that are computed via Monte Carlo (MC) simulations directly from the
quasi-posterior distributions of the criterions. We establish new Bernstein-von
Mises (or Bayesian Wilks) type theorems for the quasi-posterior distributions
of the quasi-likelihood ratio (QLR) and profile QLR in partially-identified
regular models and some non-regular models. These results imply that our MC CSs
have exact asymptotic frequentist coverage for identified sets of full
parameters and of subvectors in partially-identified regular models, and have
valid but potentially conservative coverage in models with reduced-form
parameters on the boundary. Our MC CSs for identified sets of subvectors are
shown to have exact asymptotic coverage in models with singularities. We also
provide results on uniform validity of our CSs over classes of DGPs that
include point and partially identified models. We demonstrate good
finite-sample coverage properties of our procedures in two simulation
experiments. Finally, our procedures are applied to two non-trivial empirical
examples: an airline entry game and a model of trade flows.


title:
Electronic structure of the high and low pressure polymorphs of
  MgSiN$_{2}$

abstract:
  We have performed density functional calculations on the group II-IV nitride
MgSiN$_{2}$. At a pressure of about 20~GPa the ground state wurtzite derived
MgSiN$_{2}$ structure (LP-MgSiN$_{2}$) transforms into a rock-salt derived
structure (HP-MgSiN$_{2}$) in agreement with previous theoretical and
experimental studies. Both phases are wide band gap semiconductors with
indirect band gaps at equilibrium of 5.58 eV (LP-MgSiN$_{2}$) and 5.87 eV
(HP-MgSiN$_{2}$), respectively. As the pressure increases, the band gaps become
larger for both phases, however, the band gap in LP-MgSiN$_{2}$ increases
faster than the gap in HP-MgSiN$_{2}$ and with a high enough pressure the band
gap in LP-MgSiN$_{2}$ becomes larger than the band gap in HP-MgSiN$_{2}$.


title: Fermat's Last Theorem: Algebra and Number Theory

abstract:
  In our work we give the examples using Fermat's Last Theorem for solving some
problems from algebra and number theory.


title: Diffractive Propagation on Conic Manifolds

abstract:
  In this survey, we review some applications and extensions of the author's
results with Richard Melrose on propagation of singularities for solutions to
the wave equation on manifolds with conical singularities. These results mainly
concern: the local decay of energy on noncompact manifolds with diffractive
trapped orbits (joint work with Dean Baskin); singularities of the wave trace
created by diffractive closed geodesics (joint work with G. Austin Ford); and
the distribution of scattering resonances associated to such closed geodesics
(joint work with Luc Hillairet).


title:
Comparing SSN Index to X-ray Flare and Coronal Mass Ejection Rates from
  Solar Cycles 22-24

abstract:
  The newly revised sunspot number series allows for placing historical
geoeffective storms in the context of several hundred years of solar activity.
Using statistical analyses of the Geostationary Operational Environmental
Satellites (GOES) X-ray observations from the past ~30 years and the Solar and
Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph
(LASCO) Coronal Mass Ejection (CME) catalog (1996-present), we present
sunspot-number-dependent flare and CME rates. In particular, we present X-ray
flare rates as a function of sunspot number for the past three cycles. We also
show that the 1-8 AA X-ray background flux is strongly correlated with sunspot
number across solar cycles. Similarly, we show that the CME properties (e.g.,
proxies related to the CME linear speed and width) are also correlated with
sunspot number for SC 23 and 24. These updated rates will enable future
predictions for geoeffective events and place historical storms in the context
of present solar activity.


title:
A HIFI view on circumstellar H2O in M-type AGB stars: radiative
  transfer, velocity profiles, and H2O line cooling

abstract:
  We aim to constrain the temperature and velocity structures, and H2O
abundances in the winds of a sample of M-type AGB stars. We further aim to
determine the effect of H2O line cooling on the energy balance in the inner
circumstellar envelope. We use two radiative-transfer codes to model molecular
emission lines of CO and H2O towards four M-type AGB stars. We focus on
spectrally resolved observations of CO and H2O from HIFI. The observations are
complemented by ground-based CO observations, and spectrally unresolved CO and
H2O observations with PAC. The observed line profiles constrain the velocity
structure throughout the circumstellar envelopes (CSEs), while the CO
intensities constrain the temperature structure in the CSEs. The H2O
observations constrain the o-H2O and p-H2O abundances relative to H2. Finally,
the radiative-transfer modelling allows to solve the energy balance in the CSE,
in principle including also H2O line cooling. The fits to the line profiles
only set moderate constraints on the velocity profile, indicating shallower
acceleration profiles in the winds of M-type AGB stars than predicted by
dynamical models, while the CO observations effectively constrain the
temperature structure. Including H2O line cooling in the energy balance was
only possible for the low-mass-loss-rate objects in the sample, and required an
ad hoc adjustment of the dust velocity profile in order to counteract extreme
cooling in the inner CSE. H2O line cooling was therefore excluded from the
models. The constraints set on the temperature profile by the CO lines
nevertheless allowed us to derive H2O abundances. The derived H2O abundances
confirm previous estimates and are consistent with chemical models. However,
the uncertainties in the derived abundances are relatively large, in particular
for p-H2O, and consequently the derived o/p-H2O ratios are not well
constrained.


title: Dynamics of Transformation from Segregation to Mixed Wealth Cities

abstract:
  We model the dynamics of the Schelling model for agents described simply by a
continuously distributed variable - wealth. Agents move to neighborhoods where
their wealth is not lesser than that of some proportion of their neighbors, the
threshold level. As in the case of the classic Schelling model where
segregation obtains between two races, we find here that wealth-based
segregation occurs and persists. However, introducing uncertainty into the
decision to move - that is, with some probability, if agents are allowed to
move even though the threshold level condition is contravened - we find that
even for small proportions of such disallowed moves, the dynamics no longer
yield segregation but instead sharply transition into a persistent mixed wealth
distribution. We investigate the nature of this sharp transformation between
segregated and mixed states, and find that it is because of a non-linear
relationship between allowed moves and disallowed moves. For small increases in
disallowed moves, there is a rapid corresponding increase in allowed moves, but
this tapers off as the fraction of disallowed moves increase further and
finally settles at a stable value, remaining invariant to any further increase
in disallowed moves. It is the overall effect of the dynamics in the initial
region (with small numbers of disallowed moves) that shifts the system away
from a state of segregation rapidly to a mixed wealth state.
  The contravention of the tolerance condition could be interpreted as public
policy interventions like minimal levels of social housing or housing benefit
transfers to poorer households. Our finding therefore suggests that it might
require only very limited levels of such public intervention - just sufficient
to enable a small fraction of disallowed moves, because the dynamics generated
by such moves could spur the transformation from a segregated to mixed
equilibrium.


title: On rational functions without Froissart doublets

abstract:
  In this paper we consider the problem of working with rational functions in a
numeric environment. A particular problem when modeling with such functions is
the existence of Froissart doublets, where a zero is close to a pole. We
discuss three different parameters which allow one to monitor the absence of
Froissart doublets for a given general rational function. These include the
euclidean condition number of an underlying Sylvester-type matrix, a parameter
for determing coprimeness of two numerical polynomials and bounds on the
spherical derivative. We show that our parameters sharpen those found in a
previous paper by two of the autours.


title: Methods for Sparse and Low-Rank Recovery under Simplex Constraints

abstract:
  The de-facto standard approach of promoting sparsity by means of
$\ell_1$-regularization becomes ineffective in the presence of simplex
constraints, i.e.,~the target is known to have non-negative entries summing up
to a given constant. The situation is analogous for the use of nuclear norm
regularization for low-rank recovery of Hermitian positive semidefinite
matrices with given trace. In the present paper, we discuss several strategies
to deal with this situation, from simple to more complex. As a starting point,
we consider empirical risk minimization (ERM). It follows from existing theory
that ERM enjoys better theoretical properties w.r.t.~prediction and
$\ell_2$-estimation error than $\ell_1$-regularization. In light of this, we
argue that ERM combined with a subsequent sparsification step like thresholding
is superior to the heuristic of using $\ell_1$-regularization after dropping
the sum constraint and subsequent normalization.
  At the next level, we show that any sparsity-promoting regularizer under
simplex constraints cannot be convex. A novel sparsity-promoting regularization
scheme based on the inverse or negative of the squared $\ell_2$-norm is
proposed, which avoids shortcomings of various alternative methods from the
literature. Our approach naturally extends to Hermitian positive semidefinite
matrices with given trace. Numerical studies concerning compressed sensing,
sparse mixture density estimation, portfolio optimization and quantum state
tomography are used to illustrate the key points of the paper.


title:
Towards an Appropriate Beamforming Scheme for Initial Cell Discovery in
  mmW 5G Cellular Networks

abstract:
  Beamforming is an essential requirement to combat high pathloss and to
improve signal-to-noise ratio during initial cell discovery in future
millimeter wave cellular networks. The choice of an appropriate beamforming is
directly coupled with its energy consumption. The energy consumption is even of
more concern at a battery limited mobile station (MS). In this work, we provide
an energy consumption based comparison of different beamforming schemes while
considering both a low power and a high power analog-to-digital converter (ADC)
for a millimeter wave based receiver at the MS. We analyze both context
information (CI) (GPS positioning based) and non context information based
schemes, and show that analog beamforming with CI (where mobile station's
positioning information is already available) can result in a lower energy
consumption, while in all other scenarios digital beamforming has a lower
energy consumption than analog and hybrid beamforming. We also show that under
certain scenarios recently proposed phase shifters network architecture can
result in a lower energy consumption than other beamforming schemes. Moreover,
we show that the energy consumption trend among different beamforming schemes
is valid irrespective of the number of ADC bits. Finally, we propose a new
signaling structure which utilizes a relatively higher frequency sub-carrier
for primary synchronization signals compared to other signaling, which allows a
further reduction in initial cell search delay and energy consumption of the
MS.


title: Quantifying the changing role of past publications

abstract:
  Our current societies increasingly rely on electronic repositories of
collective knowledge. An archetype of these databases is the Web of Science
(WoS) that stores scientific publications. In contrast to several other forms
of knowledge -- e.g., Wikipedia articles -- a scientific paper does not change
after its "birth". Nonetheless, from the moment a paper is published it exists
within the evolving web of other papers, thus, its actual meaning to the reader
changes. To track how scientific ideas (represented by groups of scientific
papers) appear and evolve, we apply a novel combination of algorithms
explicitly allowing for papers to change their groups. We (i) identify the
overlapping clusters of the undirected yearly co-citation networks of the WoS
(1975-2008) and (ii) match these yearly clusters (groups) to form group
timelines. After visualizing the longest lived groups of the entire data set we
assign topic labels to the groups. We find that in the entire Web of Science
multidisciplinarity is clearly over-represented among cutting edge ideas. In
addition, we provide detailed examples for papers that (i) change their topic
labels and (ii) move between groups.

categories: cs.DL cs.SI physics.data-an physics.soc-ph


title:
ElEvoHI: a novel CME prediction tool for heliospheric imaging combining
  an elliptical front with drag-based model fitting

abstract:
  In this study, we present a new method for forecasting arrival times and
speeds of coronal mass ejections (CMEs) at any location in the inner
heliosphere. This new approach enables the adoption of a highly flexible
geometrical shape for the CME front with an adjustable CME angular width and an
adjustable radius of curvature of its leading edge, i.e. the assumed geometry
is elliptical. Using, as input, STEREO heliospheric imager (HI) observations, a
new elliptic conversion (ElCon) method is introduced and combined with the use
of drag-based model (DBM) fitting to quantify the deceleration or acceleration
experienced by CMEs during propagation. The result is then used as input for
the Ellipse Evolution Model (ElEvo). Together, ElCon, DBM fitting, and ElEvo
form the novel ElEvoHI forecasting utility. To demonstrate the applicability of
ElEvoHI, we forecast the arrival times and speeds of 21 CMEs remotely observed
from STEREO/HI and compare them to in situ arrival times and speeds at 1 AU.
Compared to the commonly used STEREO/HI fitting techniques (Fixed-$\Phi$,
Harmonic Mean, and Self-similar Expansion fitting), ElEvoHI improves the
arrival time forecast by about 2 hours to $\pm 6.5$ hours and the arrival speed
forecast by $\approx 250$ km s$^{-1}$ to $\pm 53$ km s$^{-1}$, depending on the
ellipse aspect ratio assumed. In particular, the remarkable improvement of the
arrival speed prediction is potentially beneficial for predicting geomagnetic
storm strength at Earth.


title: Geometric approach to the explicit local Langlands correspondence

abstract:
  We propose a geometric strategy of giving explicit description of the
Langlands parameter of an irreducible supercuspidal representation of GL(n)
over a non-archimedean local field. The key is to compare the cohomology of an
affinoid in the Lubin-Tate space at infinite level and that of the reduction of
its formal model. As examples, we treat the cases of depth 0 supercuspidal
representations and simple supercuspidal representations.


title:
Spacetime Variation of Lorentz-Violation Coefficients at Nonrelativistic
  Scale

abstract:
  The notion of uniform and/or constant tensor fields of rank $>0$ is
incompatible with general curved spacetimes. This work considers the
consequences of certain tensor-valued coefficients for Lorentz violation in the
Standard-Model Extension varying with spacetime position. We focus on two of
the coefficients, $a_\mu$ and $b_\mu$, that characterize Lorentz violation in
massive fermions, particularly in those fermions that constitute ordinary
matter. We calculate the nonrelativistic hamiltonian describing these effects,
and use it to extract the sensitivity of several precision experiments to
coefficient variation.


title:
Fuzzy clustering of distribution-valued data using adaptive L2
  Wasserstein distances

abstract:
  Distributional (or distribution-valued) data are a new type of data arising
from several sources and are considered as realizations of distributional
variables. A new set of fuzzy c-means algorithms for data described by
distributional variables is proposed.
  The algorithms use the $L2$ Wasserstein distance between distributions as
dissimilarity measures. Beside the extension of the fuzzy c-means algorithm for
distributional data, and considering a decomposition of the squared $L2$
Wasserstein distance, we propose a set of algorithms using different automatic
way to compute the weights associated with the variables as well as with their
components, globally or cluster-wise. The relevance weights are computed in the
clustering process introducing product-to-one constraints.
  The relevance weights induce adaptive distances expressing the importance of
each variable or of each component in the clustering process, acting also as a
variable selection method in clustering. We have tested the proposed algorithms
on artificial and real-world data. Results confirm that the proposed methods
are able to better take into account the cluster structure of the data with
respect to the standard fuzzy c-means, with non-adaptive distances.


title: Catalytic Decoupling of Quantum Information

abstract:
  The decoupling technique is a fundamental tool in quantum information theory
with applications ranging from quantum thermodynamics to quantum many body
physics to the study of black hole radiation. In this work we introduce the
notion of catalytic decoupling, that is, decoupling in the presence of an
uncorrelated ancilla system. This removes a restriction on the standard notion
of decoupling, which becomes important for structureless resources, and yields
a tight characterization in terms of the max-mutual information. Catalytic
decoupling naturally unifies various tasks like the erasure of correlations and
quantum state merging, and leads to a resource theory of decoupling.


title: The Gaia-ESO Survey: the selection function of the Milky Way field stars

abstract:
  The Gaia-ESO Survey was designed to target all major Galactic components
(i.e., bulge, thin and thick discs, halo and clusters), with the goal of
constraining the chemical and dynamical evolution of the Milky Way. This paper
presents the methodology and considerations that drive the selection of the
targeted, allocated and successfully observed Milky Way field stars. The
detailed understanding of the survey construction, specifically the influence
of target selection criteria on observed Milky Way field stars is required in
order to analyse and interpret the survey data correctly. We present the target
selection process for the Milky Way field stars observed with VLT/FLAMES and
provide the weights that characterise the survey target selection. The weights
can be used to account for the selection effects in the Gaia-ESO Survey data
for scientific studies. We provide a couple of simple examples to highlight the
necessity of including such information in studies of the stellar populations
in the Milky Way.


title:
First Principles Prediction of Amorphous Phases Using Evolutionary
  Algorithms

abstract:
  We discuss the efficacy of evolutionary method for the purpose of structural
analysis of amorphous solids. At present ab initio molecular dynamics (MD)
based melt-quench technique is used and this deterministic approach has proven
to be successful to study amorphous materials. We show that a stochastic
approach motivated by Darwinian evolution can also be used to simulate
amorphous structures. Applying this method, in conjunction with density
functional theory (DFT) based electronic, ionic and cell relaxation, we
re-investigate two well known amorphous semiconductors, namely silicon and
indium gallium zinc oxide (IGZO). We find that characteristic structural
parameters like average bond length and bond angle are within $\sim$ 2% to
those reported by ab initio MD calculations and experimental studies.


title:
Uncovering dispersion properties in semiconductor waveguides to study
  photon-pair generation

abstract:
  We investigate the dispersion properties of ridge Bragg-reflection waveguides
to deduce their phasematching characteristics. These are crucial for exploiting
them as sources of parametric down-conversion (PDC). In order to estimate the
phasematching bandwidth we first determine the group refractive indices of the
interacting modes via Fabry-Perot experiments in two distant wavelength
regions. Second, by measuring the spectra of the emitted PDC photons we gain
access to their group index dispersion. Our results offer a simple approach for
determining the PDC process parameters in the spectral domain and provide an
important feedback for designing such sources, especially in the broadband
case.


title: On the spectrum of AdS3 x S3 x T4 strings with Ramond-Ramond flux

abstract:
  We analyze the spectrum of perturbative closed strings on AdS3 x S3 x T4 with
Ramond-Ramond flux using integrable methods. By solving the crossing equations
we determine the massless and mixed-mass dressing factors of the worldsheet S
matrix and derive the Bethe equations. Using these, we construct the underlying
integrable spin chain and show that it reproduces the reducible spin chain
conjectured at weak coupling in arXiv:1211.1952. We find that the string-theory
massless modes are described by gapless excitations of the spin chain. The
resulting degeneracy of vacua matches precisely the protected supergravity
spectrum found by de Boer.


title: Linear-time Outlier Detection via Sensitivity

abstract:
  Outliers are ubiquitous in modern data sets. Distance-based techniques are a
popular non-parametric approach to outlier detection as they require no prior
assumptions on the data generating distribution and are simple to implement.
Scaling these techniques to massive data sets without sacrificing accuracy is a
challenging task. We propose a novel algorithm based on the intuition that
outliers have a significant influence on the quality of divergence-based
clustering solutions. We propose sensitivity - the worst-case impact of a data
point on the clustering objective - as a measure of outlierness. We then prove
that influence, a (non-trivial) upper-bound on the sensitivity, can be computed
by a simple linear time algorithm. To scale beyond a single machine, we propose
a communication efficient distributed algorithm. In an extensive experimental
evaluation, we demonstrate the effectiveness and establish the statistical
significance of the proposed approach. In particular, it outperforms the most
popular distance-based approaches while being several orders of magnitude
faster.


title: Turbulent Plasmoid Reconnection

abstract:
  The plasmoid instability may lead to fast magnetic reconnection through long
current sheets(CS). It is well known that large-Reynolds-number plasmas easily
become turbulent. We address the question whether turbulence enhances the
energy conversion rate of plasmoid-unstable current sheets. We carry out
appropriate numerical MHD simulations, but resolving simultaneously the
relevant large-scale (mean-) fields and the corresponding small-scale,
turbulent, quantities by means of direct numerical simulations (DNS) is not
possible. Hence we investigate the influence of small scale turbulence on large
scale MHD processes by utilizing a subgrid-scale (SGS) turbulence model. We
verify the applicability of our SGS model and then use it to investigate the
influence of turbulence on the plasmoid instability. We start the simulations
with Harris-type and force-free CS equilibria in the presence of a finite guide
field in the direction perpendicular to the reconnection plane. We use the DNS
results to investigate the growth of the plasmoid instability. The energy and
cross-helicity due to turbulence are obtained in terms of the mean fields by a
Gaussian filtering formulation from a Reynolds averaging turbulence model. The
influence of turbulence on the reconnection rate of the plasmoid instability is
investigated. To verify the predictions of the SGS-model, the electromotive
force (${\bf\cal{E}}$) is calculated for the coarse data obtained by filtering
and compared to the SGS-model. The symmetry breakage with respect to the guide
field direction causes a turbulent helicity which reduces the influence of the
apparent turbulent resistivity. The reduced reconnection rate of guide field
plasmoid reconnection is attributed to a balancing between the different
physical effects related to turbulence.


title:
Quasisolitons in self-diffusive excitable systems, or Why asymmetric
  diffusivity does not violate the Second Law

abstract:
  Solitons, defined as nonlinear waves which can reflect from boundaries or
transmit through each other, are found in conservative, fully integrable
systems. Similar phenomena, dubbed quasi-solitons, have been observed also in
dissipative, "excitable" systems, either at finely tuned parameters (near a
bifurcation) or in systems with cross-diffusion. Here we demonstrate that
quasi-solitons can be robustly observed in excitable systems with excitable
kinetics and with self-diffusion only. This includes quasi-solitons of fixed
shape (like KdV solitons) or envelope quasi-solitons (like NLS solitons). This
can happen in systems with more than two components, and can be explained by
effective cross-diffusion, which emerges via adiabatic elimination of a fast
but diffusing component. We describe here a reduction procedure can be used for
the search of complicated wave regimes in multi-component, stiff systems by
studying simplified, soft systems.


title:
On the possible wind nebula of magnetar Swift J1834.9-0846: a
  magnetism-powered synchrotron nebula

abstract:
  Recently, the magnetar Swift J1834.9$-$0846 is reported to have a possible
wind nebula. It is shown that both the magnetar and its wind nebula are
understandable in the wind braking scenario. The magnetar's rotational energy
loss rate is not enough to power the particle luminosity. The required particle
luminosity should be about $10^{36} \,\rm erg \,s^{-1}$ to $10^{38} \,\rm erg
\,s^{-1}$. It is obtained in three different approaches: considering wind
braking of Swift J1834.9$-$0846; the spectral and spatial observations of the
wind nebula; and an empirical upper bound on wind nebula X-ray luminosity. The
nebula magnetic field is about $10^{-4} \,\rm G$. The possible wind nebula of
Swift J1834.9$-$0846 should be a magnetar wind nebula. It is powered by the
magnetic energy release of the magnetar.


title: Towards extracting the best possible results from NOvA

abstract:
  The NuMI Off-Axis $\nu_{e}$ Appearance (NO$\nu$A) is the currently running
leading long-baseline neutrino oscillation experiment, whose main physics goal
is to explore the current issues in the neutrino sector, such as determination
of the neutrino mass ordering, resolution of the octant of atmospheric mixing
angle and to constrain the Dirac-type CP violating phase $\delta_{CP}$. In this
paper, we would like to investigate whether it is possible to extract the best
possible results from NO$\nu$A with a shorter time-span than its scheduled run
period by analyzing its capability to discriminate the degeneracy among various
neutrino oscillation parameters within four years of run time, with two years
in each neutrino and antineutrino modes. Further, we study the same by adding
the data from T2K experiment for a total of five years run with 3.5 years in
neutrino mode and 1.5 years in antineutrino mode. We find that NO$\nu$A (2+2)
has a better oscillation parameter degeneracy discrimination capability
compared to its scheduled run period for four years, i.e, NO$\nu$A (3+1).


title:
Phase diagrams of vortex matter with multi-scale inter-vortex
  interactions in layered superconductors

abstract:
  It was recently proposed to use the stray magnetic fields of superconducting
vortex lattices to trap ultracold atoms for building quantum emulators. This
calls for new methods for engineering and manipulating of the vortex states.
One of the possible routes utilizes type-1.5 superconducting layered systems
with multi-scale inter-vortex interactions. In order to explore the possible
vortex states that can be engineered, we present two phase diagrams of
phenomenological vortex matter models with multi-scale inter-vortex
interactions featuring several attractive and repulsive length scales. The
phase diagrams exhibit a plethora of phases, including conventional 2D lattice
phases, five stripe phases, dimer, trimer, and tetramer phases, void phases,
and stable low-temperature disordered phases. The transitions between these
states can be controlled by the value of an applied external field.


title: Intermediary LEO propagation including higher order zonal harmonics

abstract:
  Two new intermediary orbits of the artificial satellite problem are proposed.
The analytical solutions include higher order effects of the Geopotential, and
are obtained by means of a torsion transformation applied to the
quasi-Keplerian system resulting after the elimination of the parallax
simplification, for the first intermediary, and after the elimination of the
parallax and perigee simplifications, for the second one. The new
intermediaries perform notably well for low earth orbits propagation, are free
from special functions, and result advantageous, both in accuracy and
efficiency, when compared to the standard Cowell integration of the J2 problem,
thus providing appealing alternatives for onboard, short-term, orbit
propagation under limited computational resources.


title:
A modified sequence domain impedance definition and its equivalence to
  the dq-domain impedance definition for the stability analysis of AC power
  electronic systems

abstract:
  Representations of AC power systems by frequency dependent impedance
equivalents is an emerging technique in the dynamic analysis of power systems
including power electronic converters. The technique has been applied for
decades in DC-power systems, and it was recently adopted to map the impedances
in AC systems. Most of the work on AC systems can be categorized in two
approaches. One is the analysis of the system in the \textit{dq}-domain,
whereas the other applies harmonic linearization in the phase domain through
symmetric components. Impedance models based on analytical calculations,
numerical simulation and experimental studies have been previously developed
and verified in both domains independently. The authors of previous studies
discuss the advantages and disadvantages of each domain separately, but neither
a rigorous comparison nor an attempt to bridge them has been conducted. The
present paper attempts to close this gap by deriving the mathematical
formulation that shows the equivalence between the \textit{dq}-domain and the
sequence domain impedances. A modified form of the sequence domain impedance
matrix is proposed, and with this definition the stability estimates obtained
with the Generalized Nyquist Criterion (GNC) become equivalent in both domains.
The second contribution of the paper is the definition of a \textit{Mirror
Frequency Decoupled} (MFD) system. The analysis of MFD systems is less complex
than that of non-MFD systems because the positive and negative sequences are
decoupled. This paper shows that if a system is incorrectly assumed to be MFD,
this will lead to an erroneous or ambiguous estimation of the equivalent
impedance.


title:
Role of syndrome information on a one-way quantum repeater using
  teleportation-based error correction

abstract:
  We investigate a quantum repeater scheme for quantum key distribution based
on the work by Muralidharan et al., Phys. Rev. Lett. 112, 250501 (2014). Our
scheme extends that work by making use of error syndrome measurement outcomes
available at the repeater stations. We show how to calculate the secret key
rates for the case of optimizing the syndrome information, while the known key
rate is based on a scenario of coarse-graining the syndrome information. We
show that these key rates can surpass the Pirandola-Laurenza-Ottaviani-Banchi
bound on secret key rates of direct transmission over lossy bosonic channels.


title: Minimising the number of triangular edges

abstract:
  We consider the problem of minimising the number of edges that are contained
in triangles, among $n$-vertex graphs with a given number of edges. We prove a
conjecture of F\"uredi and Maleki that gives an exact formula for this minimum,
for sufficiently large $n$.


title: Tradeoffs for Space, Time, Data and Risk in Unsupervised Learning

abstract:
  Faced with massive data, is it possible to trade off (statistical) risk, and
(computational) space and time? This challenge lies at the heart of large-scale
machine learning. Using k-means clustering as a prototypical unsupervised
learning problem, we show how we can strategically summarize the data (control
space) in order to trade off risk and time when data is generated by a
probabilistic model. Our summarization is based on coreset constructions from
computational geometry. We also develop an algorithm, TRAM, to navigate the
space/time/data/risk tradeoff in practice. In particular, we show that for a
fixed risk (or data size), as the data size increases (resp. risk increases)
the running time of TRAM decreases. Our extensive experiments on real data sets
demonstrate the existence and practical utility of such tradeoffs, not only for
k-means but also for Gaussian Mixture Models.


title: Brans-Dicke inflation in light of the Planck 2015 data

abstract:
  We study inflation in the Brans-Dicke gravity as a special model of the
scalar-tensor gravity. We obtain the inflationary observables containing the
scalar spectral index, the tensor-to-scalar ratio, the running of the scalar
spectral index and the equilateral non-Gaussianity parameter in terms of the
general form of the potential in the Jordan frame. Then, we compare the results
for various inflationary potentials in light of the Planck 2015 data. Our study
shows that in the Brans-Dicke gravity, the power-law, inverse power-law and
exponential potentials are ruled out by the Planck 2015 data. But, the hilltop,
Higgs, Coleman-Weinberg and natural potentials can be compatible with Planck
2015 TT,TE,EE+lowP data at 95\% CL. Moreover, the D-brane, SB SUSY and
displaced quadratic potentials can be in well agreement with the observational
data since their results can lie inside the 68\% CL region of Planck 2015
TT,TE,EE+lowP data.


title: Random Antagonistic Matrices

abstract:
  The ensemble of antagonistic matrices is introduced and studied. In
antagonistic matrices the entries $\mathcal A_{i,j}$ and $\mathcal A_{j,i}$ are
real and have opposite signs, or are both zero, and the diagonal is zero. This
generalization of antisymmetric matrices is suggested by the linearized
dynamics of competitive species in ecology.

categories: math-ph cond-mat.stat-mech math.MP q-bio.PE


title:
Parameterized complexity of the MINCCA problem on graphs of bounded
  decomposability

abstract:
  In an edge-colored graph, the cost incurred at a vertex on a path when two
incident edges with different colors are traversed is called reload or
changeover cost. The "Minimum Changeover Cost Arborescence" (MINCCA) problem
consists in finding an arborescence with a given root vertex such that the
total changeover cost of the internal vertices is minimized. It has been
recently proved by G\"oz\"upek et al. [TCS 2016] that the problem is FPT when
parameterized by the treewidth and the maximum degree of the input graph. In
this article we present the following results for the MINCCA problem:
  - the problem is W[1]-hard parameterized by the treedepth of the input graph,
even on graphs of average degree at most 8. In particular, it is W[1]-hard
parameterized by the treewidth of the input graph, which answers the main open
problem of G\"oz\"upek et al. [TCS 2016];
  - it is W[1]-hard on multigraphs parameterized by the tree-cutwidth of the
input multigraph;
  - it is FPT parameterized by the star tree-cutwidth of the input graph, which
is a slightly restricted version of tree-cutwidth. This result strictly
generalizes the FPT result given in G\"oz\"upek et al. [TCS 2016];
  - it remains NP-hard on planar graphs even when restricted to instances with
at most 6 colors and 0/1 symmetric costs, or when restricted to instances with
at most 8 colors, maximum degree bounded by 4, and 0/1 symmetric costs.


title: Real time change-point detection in a nonlinear quantile model

abstract:
  Most studies in real time change-point detection either focus on the linear
model or use the CUSUM method under classical assumptions on model errors. This
paper considers the sequential change-point detection in a nonlinear quantile
model. A test statistic based on the CUSUM of the quantile process subgradient
is proposed and studied. Under null hypothesis that the model does not change,
the asymptotic distribution of the test statistic is determined. Under
alternative hypothesis that at some unknown observation there is a change in
model, the proposed test statistic converges in probability to $\infty$. These
results allow to build the critical regions on open-end and on closed-end
procedures. Simulation results, using Monte Carlo technique, investigate the
performance of the test statistic, specially for heavy-tailed error
distributions. We also compare it with the classical CUSUM test statistic.


title: Ramsey-type phase control of free electron beams

abstract:
  Interference between multiple distinct paths is a defining property of
quantum physics, where "paths" may involve actual physical trajectories, as in
interferometry, or transitions between different internal (e.g. spin) states,
or both. A hallmark of quantum coherent evolution is the possibility to
interact with a system multiple times in a phase-preserving manner. This
principle underpins powerful multi-dimensional optical and nuclear magnetic
resonance spectroscopies and related techniques, including Ramsey's method of
separated oscillatory fields used in atomic clocks. Previously established for
atomic, molecular and quantum dot systems, recent developments in the optical
quantum state preparation of free electron beams suggest a transfer of such
concepts to the realm of ultrafast electron imaging and spectroscopy. Here, we
demonstrate the sequential coherent interaction of free electron states with
two spatially separated, phase-controlled optical near-fields. Ultrashort
electron pulses are acted upon in a tailored nanostructure featuring two
near-field regions with anisotropic polarization response. The amplitude and
relative phase of these two near-fields are independently controlled by the
incident polarization state, allowing for constructive and destructive quantum
interference of the subsequent interactions. Future implementations of such
electron-light interferometers may yield unprecedented access to optically
phase-resolved electronic dynamics and dephasing mechanisms with attosecond
precision.


title:
On the $C^1$ regularity of solutions to divergence form elliptic systems
  with Dini-continuous coefficients

abstract:
  We prove $C^1$ regularity of solutions to divergence form elliptic systems
with Dini-continuous coefficients


title:
Fast Mapping of Terahertz Bursting Thresholds and Characteristics at
  Synchrotron Light Sources

abstract:
  Dedicated optics with extremely short electron bunches enable synchrotron
light sources to generate intense coherent THz radiation. The high degree of
spatial compression in this so-called low-alpha optics entails a complex
longitudinal dynamics of the electron bunches, which can be probed studying the
fluctuations in the emitted terahertz radiation caused by the micro-bunching
instability ("bursting"). This article presents a "quasi-instantaneous" method
for measuring the bursting characteristics by simultaneously collecting and
evaluating the information from all bunches in a multi-bunch fill, reducing the
measurement time from hours to seconds. This speed-up allows systematic studies
of the bursting characteristics for various accelerator settings within a
single fill of the machine, enabling a comprehensive comparison of the measured
bursting thresholds with theoretical predictions by the bunched-beam theory.
This paper introduces the method and presents first results obtained at the
ANKA synchrotron radiation facility.


title: The interaction of $He^{-}$ with fullerenes

abstract:
  The effects of interactions between He- and clusters of fullerenes in helium
nanodroplets are described. Electron transfer from $He^{-}$ to $(C_{60})_n$ and
$(C_{70})_n$ clusters results in the formation of the corresponding fullerene
cluster dianions. This unusual double electron transfer appears to be concerted
and is most likely guided by electron correlation between the two very weakly
bound outer electrons in $He^{-}$. We suggest a mechanism which involves long
range electron transfer followed by the conversion of $He^{+}$ into
$He_{2}^{+}$, where formation of the $He-He$ bond in $He_{2}^{+}$ releases
sufficient kinetic energy for the cation and the dianion to escape their
Coulombic attraction. By analogy with the corresponding dications, the
observation of a threshold size of n \geq 5 for formation of both
$(C_{60})_n^{2-}$ and $(C_{70})_n^{2-}$ is attributed to Coulomb explosion
rather than an energetic constraint. We also find that smaller dianions can be
observed if water is added as a co-dopant. Other aspects of $He^{-}$ chemistry
that are explored include its role in the formation of multiply charged
fullerene cluster cations and the sensitivity of cluster dianion formation on
the incident electron energy.


title: Counterexamples to the quadrisecant approximation conjecture

abstract:
  A quadrisecant of a knot is a straight line intersecting the knot at four
points. If a knot has finitely many quadrisecants, one can replace each subarc
between two adjacent secant points by the line segment between them to get the
quadrisecant approximation of the original knot. It was conjectured that the
quadrisecant approximation is always a knot with the same knot type as the
original knot. We show that every knot type contains two knots, the
quadrisecant approximation of one knot has self intersections while the
quadrisecant approximation of the other knot is a knot with different knot
type.


title:
Introduction to Quantum-limited Parametric Amplification of Quantum
  Signals with Josephson Circuits

abstract:
  This short and opinionated review starts with a concept of quantum signals at
microwave frequencies and focuses on the principle of linear parametric
amplification. The amplification process arises from the dispersive
nonlinearity of Josephson junctions driven with appropriate tones. We discuss
two defining characteristics of these amplifiers: the number of modes receiving
the signal, idler and pump waves and the number of independent ports through
which these waves enter into the circuit.


title:
Active role of the nonmagnetic cations in magnetic interactions for the
  double-perovskite Sr2BOsO6 (B=Y, In, Sc)

abstract:
  Using first-principles density functional theory, we have investigated the
electronic and magnetic properties of recently synthesized and characterized 5d
double-perovskites Sr2BOsO6 (B=Y, In, Sc). The electronic structure
calculations show that in all compounds, the Os5+ (5d3) site is the only
magnetically active one, while Y3+, In3+ and Sc3+ remain in nonmagnetic states,
with Sc/Y and In featuring d0 and d10 electronic configurations, respectively.
Our studies reveal the important role of closed-shell (d10) versus open-shell
(d0) electronic configurations of the nonmagnetic sites in determining the
overall magnetic exchange interactions. Although the magnetic Os5+ (5d3) site
is the same in all compounds, the magnetic super-exchange interactions mediated
by non-magnetic Y/In/Sc species are strongest for Sr2ScOsO6, weakest for
Sr2InOsO6, and intermediate in case of the Y (d0), due to different energy
overlaps between Os-5d and Y/In/Sc-d states. This explains the experimentally
observed substantial differences in the magnetic transition temperatures of
these materials, despite of an identical magnetic site and underlying magnetic
ground state. Furthermore, short range Os-Os exchange-interactions are more
prominent than long range Os-Os interactions in these compounds, which
contrasts with the behavior of other 3d-5d double-perovskites.


title:
Higher-order approximations of the residual-mean eddy streamfunction and
  the quasi-Stokes streamfunction

abstract:
  The series expansion of the residual-mean eddy streamfunction and the
quasi-Stokes streamfunction are compared up to third order in buoyancy
perturbation, both formally and by using several idealised eddy-permitting
zonal channel model experiments. In model configurations with flat bottom, both
streamfunctions may be well approximated by the first one or two leading order
terms in the ocean interior, although terms up to third order still
significantly impact the implied interior circulations. Further, differences in
both series expansions up to third order remain small here. Near surface and
bottom boundaries, on the other hand, the leading order terms differ and are
initially of alternating sign and of increasing magnitude such that the low
order approximate expressions break down there. In more realistic model
configurations with significant topographic features, physically inconsistent
recirculation cells also appear in the ocean interior and are not effectively
reduced by the next higher order terms. A measure indicating an initially
increasing or decreasing series expansion is proposed.


title:
Interference Effects in the Decays of Spin-Zero Resonances into $\gamma
  \gamma$ and $t\bar{t}$

abstract:
  We consider interference effects in the production via gluon fusion in LHC
collisions at 13 TeV and decays into $\gamma \gamma$ and $t {\bar t}$ final
states of one or two putative new resonant states $\Phi$, assumed here to be
scalar and/or pseudo scalar particles. Although our approach is general, we use
for our numerical analysis the example of the putative $750$ GeV state for
which a slight excess was observed in the initial LHC $13$ TeV data. We revisit
previous calculations of the interferences between the heavy-fermion
loop-induced $gg \to \Phi \to \gamma \gamma$ signal and the continuum $gg\to
\gamma\gamma$ QCD background, which can alter the production rate as well as
modify the line-shape and apparent mass. We find a modest enhancement by $\sim
20$% under favorable circumstances, for a large $\Phi$ width. The effect of
interference on the apparent scalar-pseudoscalar mass difference in a
two-Higgs-doublet model is found to be also modest. An exploratory study
indicates that similar effects are to be expected in the $gg \to \Phi \to Z
\gamma$ channel. In this and other models with a large $\Phi$ total width, the
dominant $\Phi$ decays are expected to be into $t \bar t$ final states. We
therefore also study the effects of interference of the $gg\to \Phi \to t\bar
t$ signal with the $gg\to t \bar t$ continuum QCD background and show that in
the presence of standard fermions only in the $gg\to \Phi$ loops, it is
destructive causing a dip in the $t \bar t$ mass distribution. Including
additional vector-like quarks leads to a different picture as peaks followed by
dips can then occur. We use the absence of such effects in ATLAS and CMS data
to constrain models of the production and decays of the $\Phi$ state(s).


title:
Skyrmion Black Hole Hair: Conservation of Baryon Number by Black Holes
  and Observable Manifestations

abstract:
  We show that the existence of black holes with classical skyrmion hair
invalidates standard proofs that global charges, such as the baryon number,
cannot be conserved by a black hole. By carefully analyzing the standard
arguments based on a Gedankenexperiment in which a black hole is
seemingly-unable to return the baryon number that it swallowed, we identify
inconsistencies in this reasoning, which does not take into the account neither
the existence of skyrmion black holes nor the baryon/skyrmion correspondence.
We then perform a refined Gedankenexperiment by incorporating the new knowledge
and show that no contradiction with conservation of baryon number takes place
at any stage of black hole evolution. Our analysis also indicates no conflict
between semi-classical black holes and the existence of baryonic gauge
interaction arbitrarily-weaker than gravity. Next, we study classical cross
sections of a minimally-coupled massless probe scalar field scattered by a
skyrmion black hole. We investigate how the skyrmion hair manifests itself by
comparing this cross section with the analogous cross section caused by a
Schwarzschild black hole which has the same ADM mass as the skyrmion black
hole. Here we find an order-one difference in the positions of the
characteristic peaks in the cross sections. The peaks are shifted to smaller
scattering angles when the skyrmion hair is present. This comes from the fact
that the skyrmion hair changes the near horizon geometry of the black hole when
compared to a Schwarzschild black hole with same ADM mass. We keep the study of
this second aspect general so that the qualitative results which we obtain can
also be applied to black holes with classical hair of different kind.


title: Free boundary regularity in the parabolic fractional obstacle problem

abstract:
  The parabolic obstacle problem for the fractional Laplacian naturally arises
in American option models when the assets prices are driven by pure jump L\'evy
processes. In this paper we study the regularity of the free boundary. Our main
result establishes that, when $s>\frac12$, the free boundary is a
$C^{1,\alpha}$ graph in $x$ and $t$ near any regular free boundary point
$(x_0,t_0)\in \partial\{u>\varphi\}$. Furthermore, we also prove that solutions
$u$ are $C^{1+s}$ in $x$ and $t$ near such points, with a precise expansion of
the form \[u(x,t)-\varphi(x)=c_0\bigl((x-x_0)\cdot
e+a(t-t_0)\bigr)_+^{1+s}+o\bigl(|x-x_0|^{1+s+\alpha}+
|t-t_0|^{1+s+\alpha}\bigr),\] with $c_0>0$, $e\in \mathbb{S}^{n-1}$, and $a>0$.


title:
Charge self-consistency in density functional theory + dynamical mean
  field theory: k-space reoccupation and orbital order

abstract:
  We study effects of charge self-consistency within the combination of density
functional theory (DFT; Wien2k) with dynamical mean field theory (DMFT;
w2dynamics) in a basis of maximally localized Wannier orbitals. Using the
example of two cuprates, we demonstrate that even if there is only a single
Wannier orbital with fixed filling, a noteworthy charge redistribution can
occur. This effect stems from a reoccupation of the Wannier orbital in k-space
when going from the single, metallic DFT band to the split, insulating Hubbard
bands of DMFT. We analyze another charge self-consistency effect beyond moving
charge from one site to another: the correlation-enhanced orbital polarization
in a freestanding layer of SrVO3.


title:
Kepler K2 Observations of Sco X-1: Orbital Modulations and Correlations
  with Fermi GBM and MAXI

abstract:
  We present a multi-wavelength study of the low-mass X-ray binary Sco X-1
using Kepler K2 optical data and Fermi GBM and MAXI X-ray data. We recover a
clear sinusoidal orbital modulation from the Kepler data. Optical fluxes are
distributed bimodally around the mean orbital light curve, with both high and
low states showing the same modulation. The high state is broadly consistent
with the flaring branch of the Z diagram and the low state with the normal
branch. We see both rapid optical flares and slower dips in the high state, and
slow brightenings in the low state. High state flares exhibit a narrow range of
amplitudes with a striking cut-off at a maximum amplitude. Optical fluxes
correlate with X-ray fluxes in the high state, but in the low state they are
anti-correlated. These patterns can be seen clearly in both flux-flux diagrams
and cross-correlation functions and are consistent between MAXI and GBM. The
high state correlation arises promptly with at most a few minutes lag. We
attribute this to thermal reprocessing of X-ray flares. The low state
anti-correlation is broader, consistent with optical lags of between zero and 3
~min, and strongest with respect to high energy X-rays. We suggest that the
decreases in optical flux in the low state may reflect decreasing efficiency of
disc irradiation, caused by changes in the illumination geometry. These changes
could reflect the vertical extent or covering factor of obscuration or the
optical depth of scattering material.


title: Features of Quantum Mechanics on a Ring

abstract:
  Aspects of quantum mechanics on a ring are studied. Either one or two
impenetrable barriers are inserted at nodal and non-nodal points to turn the
ring into either one or two infinite square wells. In the process, the wave
function of a particle can change its energy, as it gets entangled with the
barriers and the insertion points become nodes. Two seemingly innocuous
assumptions representing locality and linearity are investigated. Namely, a
barrier insertion at a fixed node needs no energy, and barrier insertions can
be described by linear maps. It will be shown that the two assumptions are
incompatible.


title:
Superconducting Topological Surface States in Non-centrosymmetric Bulk
  Superconductor PbTaSe2

abstract:
  The search for topological superconductors (TSCs) is one of the most urgent
contemporary problems in condensed matter systems. TSCs are characterized by a
full superconducting gap in the bulk and topologically protected gapless
surface (or edge) states. Within each vortex core of TSCs, there exist the zero
energy Majorana bound states, which are predicted to exhibit non-Abelian
statistics and to form the basis of the fault-tolerant quantum computation. So
far, no stoichiometric bulk material exhibits the required topological surface
states (TSSs) at Fermi level combined with fully gapped bulk superconductivity.
Here, we report atomic scale visualization of the TSSs of the
non-centrosymmetric fully-gapped superconductor, PbTaSe2. Using quasiparticle
scattering interference (QPI) imaging, we find two TSSs with a Dirac point at
E~1.0eV, of which the inner TSS and partial outer TSS cross Fermi level, on the
Pb-terminated surface of this fully gapped superconductor. This discovery
reveals PbTaSe2 as a promising candidate as a TSC.


title:
Coexistence of quantized and non-quantized geometric phases in
  quasi-one-dimensional systems without inversion symmetry

abstract:
  It is well known that inversion symmetry in one-dimensional (1D) systems
leads to the quantization of the geometric Zak phase to values of either 0 or
{\pi}. When the system has particle-hole symmetry, this topological property
ensures the existence of zero-energy interface states at the interface of two
bulk systems carrying different Zak phases. In the absence of inversion
symmetry, the Zak phase can take any value and the existence of interface
states is not ensured. We show here that the situation is different when the
unit cell contains multiple degrees of freedom and a hidden inversion symmetry
exists in a subspace of the system. As an example, we consider a system of two
Su-Schrieffer-Heeger (SSH) chains coupled by a coupler chain. Although the
introduction of coupler chain breaks the inversion symmetry of the system, a
certain hidden inversion symmetry ensures the existence of a decoupled
$2\times2$ SSH Hamiltonian in the subspace of the entire system and the two
bands associated with this subspace have quantized Zak phases. These
"quantized" bands in turn can provide topological boundary or interface states
in such systems. Since the entire system has no inversion symmetry, the
bulk-boundary correspondence may not hold exactly. The above is also true when
next-nearest-neighbor hoppings are included. Our systems can be realized
straightforwardly in systems such as coupled single-mode optical waveguides or
coupled acoustic cavities.


title:
Partial oxidation of Step-Bound Water Leads to Anomalous pH Effects on
  Metal Electrode Step-Edges

abstract:
  The design of better heterogeneous catalysts for applications such as fuel
cells and electrolyzers requires a mechanistic understanding of
electrocatalytic reactions and the dependence of their activity on operating
conditions such as pH. A satisfactory explanation for the unexpected pH
dependence of electrochemical properties of platinum surfaces has so far
remained elusive, with previous explanations resorting to complex co-adsorption
of multiple species and resulting in limited predictive power. This knowledge
gap suggests that the fundamental properties of these catalysts are not yet
understood, limiting systematic improvement. Here, we analyze the change in
charge and free energies upon adsorption using density-functional theory (DFT)
to establish that water adsorbs on platinum step edges across a wide voltage
range, including the double-layer region, with a loss of approximately 0.2
electrons upon adsorption. We show how this as-yet unreported change in net
surface charge due to this water explains the anomalous pH variations of the
hydrogen underpotential deposition (Hupd) and the potentials of zero total
charge (PZTC) observed in published experimental data. This partial oxidation
of water is not limited to platinum metal step edges, and we report the charge
of the water on metal step edges of commonly used catalytic metals, including
copper, silver, iridium, and palladium, illustrating that this partial
oxidation of water broadly influences the reactivity of metal electrodes.


title: Compatible finite element spaces for geophysical fluid dynamics

abstract:
  Compatible finite elements provide a framework for preserving important
structures in equations of geophysical fluid dynamics, and are becoming
important in their use for building atmosphere and ocean models. We survey the
application of compatible finite element spaces to geophysical fluid dynamics,
including the application to the nonlinear rotating shallow water equations,
and the three-dimensional compressible Euler equations. We summarise analytic
results about dispersion relations and conservation properties, and present new
results on approximation properties in three dimensions on the sphere, and on
hydrostatic balance properties.


title: Emergent Cosmos in Einstein-Cartan Theory

abstract:
  Based on the Padmanabhan's proposal, the accelerated expansion of the
universe can be driven by the difference between the surface and bulk degrees
of freedom in a region of space, described by the relation
$dV/dt=N_{sur}-N_{bulk}$ where $N_{sur}$ and $N_{bulk}=-N_{em}+N_{de}$ are the
degrees of freedom assigned to the surface area and the matter-energy content
inside the bulk such that the indexes $"em"$ and $"de"$ represent
energy-momentum and dark energy, respectively. In the present work, the
dynamical effect of the Weyssenhoff perfect fluid with intrinsic spin and its
corresponding spin degrees of freedom in the framework of Einstein-Cartan (EC)
theory are investigated. Based on the modification of Friedmann equations due
to the spin-spin interactions, a correction term for the Padmanabhan's original
relation $dV/dt=N_{sur}+N_{em}-N_{de}$ including the number of degrees of
freedom related to this spin interactions is obtained through the modification
in $N_{bulk}$ term as $N_{bulk}=-N_{em}+N_{spin}+N_{de}$ leading to $dV /d
t=N_{sur}+N_{em}-N_{spin} -N_{de}$ in which $N_{spin}$ is the corresponding
degrees of freedom related to the intrinsic spin of the matter content of the
universe. Moreover, the validity of the unified first law and the generalized
second law of thermodynamics for the Einstein-Cartan cosmos are investigated.
Finally, by considering the covariant entropy conjecture and the bound
resulting from the emergent scenario, a total entropy bound is obtained. Using
this bound, it is shown that the for the universe as an expanding
thermodynamical system, the total effective Komar energy never exceeds the
square of the expansion rate with a factor of $\frac{3}{4\pi}$.


title:
Glass transitions in monodisperse cluster-forming ensembles: vortex
  matter in type-1.5 superconductors

abstract:
  At low enough temperatures and high densities, the equilibrium configuration
of an ensemble of ultrasoft particles is a self-assembled, ordered,
cluster-crystal. In the present work we explore the out-of-equilibrium dynamics
for a two-dimensional realization, which is relevant to superconducting
materials with multi-scale intervortex forces. We find that for small
temperatures following a quench, the suppression of the thermally-activated
particle hopping hinders the ordering. This results in a glass transition for a
monodispersed ensemble, for which we derive a microscopic explanation in terms
of an "effective polydispersity" induced by multi-scale interactions. This
demonstrates that a vortex glass can form in clean systems of thin films of
"type-1.5" superconductors. An additional setup to study this physics can be
layered superconducting systems, where the shape of the effective vortex-vortex
interactions can be engineered.


title: NLO QCD and electroweak corrections to $WWW$ production at the LHC

abstract:
  In this paper we calculate the next-to-leading order (NLO) QCD $[{\cal
O}(\alpha_s \alpha^3)]$ and electroweak (EW) $[{\cal O}(\alpha^4)]$ corrections
to the $WWW$ production at the LHC and deal with the subsequent leptonic decays
from $W$ bosons by adopting an improved narrow-width approximation which takes
into account the spin correlation and finite-width effects. The NLO QCD
correction from the real jet radiation is discussed, which significantly
enhances the production rate, particularly in the high-energy region. We also
provide the integrated cross section for the $WWW$ production and various
kinematic distributions of final products at the QCD+EW NLO. We find that the
convergence of the perturbative QCD description can be improved by applying a
hard jet veto in the event selection, but this jet veto would introduce a new
source of theoretical uncertainty. The pure NLO QCD relative correction to the
integrated cross section for the $W^+W^-W^+$ production at the $14~{\rm TeV}$
LHC is on the order of $30\%$ in the jet-veto event selection scheme with
$p^{\, {\rm cut}}_{T,\, {\rm jet}} = 50~{\rm GeV}$, while the genuine NLO EW
relative correction can reach about $15\%$ in the inclusive event selection
scheme. Our numerical results show that both the NLO QCD and NLO EW corrections
should be taken into consideration in precision predictions.