title: The Magnetic Furnace: Intense Core Dynamos in B-stars

abstract:
  The dynamo action achieved in the convective cores of main-sequence massive
stars is explored here through 3D global simulations of convective core dynamos
operating within a young $\Msun{10}$ B-type star, using the anelastic spherical
harmonic (ASH) code. These simulations capture the inner 65\% of this star by
radius, encompassing the convective nuclear-burning core (about 23\% by radius)
and a portion of the overlying radiative envelope. Eight rotation rates are
considered, ranging from 0.05\% to 16\% of the surface breakup velocity,
thereby capturing both convection that barely senses the effects of rotation
and other situations in which the Coriolis forces are prominent. The vigorous
dynamo action realized within all of these turbulent convective cores builds
magnetic fields with peak strengths exceeding a megagauss, with the overall
magnetic energy (ME) in the faster rotators reaching super-equipartition levels
compared to the convective kinetic energy (KE). The core convection typically
involves turbulent columnar velocity structures roughly aligned with the
rotation axis, with magnetic fields threading through these rolls and
possessing complex linkages throughout the core. The very strong fields are
able to coexist with the flows without quenching them through Lorentz forces.
The velocity and magnetic fields achieve such a state by being nearly
co-aligned, and with peak magnetic islands being somewhat displaced from the
fastest flows as the intricate evolution proceeds. As the rotation rate is
increased, the primary force balance shifts from nonlinear advection balancing
Lorentz forces to a magnetostrophic balance between Coriolis and Lorentz
forces.


title: Low energy behaviour of standard model extensions

abstract:
  The integration of heavy scalar fields is discussed in a class of BSM models,
containing more that one representation for scalars and with mixing. The
interplay between integrating out heavy scalars and the Standard Model
decoupling limit is examined. In general, the latter cannot be obtained in
terms of only one large scale and can only be achieved by imposing further
assumptions on the couplings. Systematic low-energy expansions are derived in
the more general, non-decoupling scenario, including mixed tree-loop and mixed
heavy-light generated operators. The number of local operators is larger than
the one usually reported in the literature.


title: On the class of continuous images of non-commutative Valdivia compacta

abstract:
  We investigate the class of continuous images of non-commutative Valdivia
compact spaces, in particular its subclass of weakly non-commutative Cor- son
countably compact spaces. A key tool is the study of non-commutative Corson
countably compact spaces and their stability. The results are the non-
commutative version of results by O. Kalenda (2003). Moreover, we present a
study of retractional skeletons on Aleksandrov duplicates of ordinal spaces.


title: Linear stability of the Skyrmion

abstract:
  We give a rigorous proof for the linear stability of the Skyrmion. In
addition, we provide new proofs for the existence of the Skyrmion and the GGMT
bound.


title: Entanglement entropy in a periodically driven Ising chain

abstract:
  In this work we study the entanglement entropy of a uniform quantum Ising
chain in transverse field undergoing a periodic driving of period $\tau$ . By
means of Floquet theory we show that, for any subchain, the entanglement
entropy tends asymptotically to a value $\tau$ - periodic in time. We provide a
semi-analytical formula for the leading term of this asymptotic regime: It is
constant in time and obeys a volume law. The entropy in the asymptotic regime
is always smaller than the thermal one: because of integrability the system
locally relaxes to a Generalized Gibbs Ensemble (GGE) density matrix. The
leading term of the asymptotic entanglement entropy is completely determined by
this GGE density matrix. Remarkably, the asymptotic entropy shows marked
features in correspondence to some non-equilibrium quantum phase transitions
undergone by a Floquet state analog of the ground state.


title:
Thin film flow and heat transfer over an unsteady stretching sheet with
  thermal radiation, internal heating in presence of external magnetic field

abstract:
  In this paper we present a mathematical analysis of thin film flow and heat
transfer to a laminar liquid film from a horizontal stretching sheet. The flow
of thin liquid film and subsequent heat transfer from the stretching surface is
investigated with the aid of similarity transformations. Similarity
transformations are used to convert unsteady boundary layer equations to a
system of non-linear ordinary differential equations. The resulting non-linear
differential equations are solved numerically using Runge-kutta-Fehlberg and
Newton-Raphson schemes. A relationship between film thickness $\beta$ and the
unsteadiness parameter $S$ is found, the effect of unsteadiness parameter $S$,
and the Prandtl number $Pr$, Magnetic field parameter $Mn$, Radiation parameter
$Nr$ and viscous dissipation parameter $Ec$ and heat source parameter $\gamma$
on the temperature distributions are presented and discussed in detail. Present
analysis shows that the combined effect of magnetic field, thermal radiation,
heat source and viscous dissipation. The results which form special case of the
present study are in excellent agreement with the results reported in the
literature.


title: Wigner transformation, momentum space topology, and anomalous transport

abstract:
  Using derivative expansion applied to the Wigner transform of the two - point
Green function we analyse the anomalous quantum Hall effect (AQHE), and the
chiral magnetic effect (CME). The corresponding currents are proportional to
the momentum space topological invariants. We reproduce the conventional
expression for the Hall conductivity in $2+1$ D. In $3+1$ D our analysis allows
to explain systematically the AQHE in topological insulators and Weyl
semimetals. At the same time using this method it may be proved, that the
equilibrium CME is absent in the wide class of solids, as well as in the
properly regularized relativistic quantum field theory.


title:
On the asymptotic limit of the three dimensional Vlasov-Poisson system
  for large magnetic field : formal derivation

abstract:
  This paper establishes the long time asymptotic limit of the three
dimensional Vlasov-Poisson equation with strong external magnetic field. The
guiding center approximation is investigated in the three dimensional case with
a non-constant magnetic field. In the long time asymptotic limit, the motion
can be split in two parts : one stationary flow along the lines of the magnetic
field and the guiding center motion in the orthogonal plane of the magnetic
field where classical drift velocities are recovered. We discuss in particular
the effect of nonconstant external magnetic fields.


title: Riemann's zeta function and the broadband structure of pure harmonics

abstract:
  Let $a\in (0,1)$ and let $F_s(a)$ be the periodized zeta function that is
defined as $F_s(a) = \sum n^{-s} \exp (2\pi i na)$ for $\Re s >1$, and extended
to the complex plane via analytic continuation. Let $s_n = \sigma_n + it_n, \,
t_n >0 $, denote the sequence of nontrivial zeros of the Riemann zeta function
in the upper halfplane ordered according to nondecreasing ordinates. We
demonstrate that, assuming the Riemann Hypothesis, the Ces\`{a}ro means of the
sequence $F_{s_n} (a)$ converge to the first harmonic $\exp (2\pi i a)$ in the
sense of periodic distributions. This reveals a natural broadband structure of
the pure tone. The proof involves Fujii's refinement of the classical Landau
theorem related to the uniform distribution modulo one of the nontrivial zeros
of $\zeta$.


title:
Critical behavior of su(1|1) supersymmetric spin chains with long-range
  interactions

abstract:
  We introduce a general class of su$(1|1)$ supersymmetric spin chains with
long-range interactions which includes as particular cases the su$(1|1)$
Inozemtsev (elliptic) and Haldane-Shastry chains, as well as the XX model. We
show that this class of models can be fermionized with the help of the
algebraic properties of the su$(1|1)$ permutation operator, and take advantage
of this fact to analyze their quantum criticality when a chemical potential
term is present in the Hamiltonian. We first study the low energy excitations
and the low temperature behavior of the free energy, which coincides with that
of a $(1+1)$-dimensional conformal field theory (CFT) with central charge $c=1$
when the chemical potential lies in the critical interval $(0,\mathcal
E(\pi))$, $\mathcal E(p)$ being the dispersion relation. We also analyze the
von Neumann and R\'enyi ground state entanglement entropies, showing that they
exhibit the logarithmic scaling with the size of the block of spins
characteristic of a one-boson $(1+1)$-dimensional CFT. Our results thus show
that the models under study are quantum critical when the chemical potential
belongs to the critical interval, with central charge $c=1$. From the analysis
of the fermion density at zero temperature, we also conclude that there is a
quantum phase transition at both ends of the critical interval. This is further
confirmed by the behavior of the fermion density at finite temperature, which
is studied analytically (at low temperature), as well as numerically for the
su$(1|1)$ elliptic chain.

categories: quant-ph cond-mat.stat-mech math-ph math.MP nlin.SI


title:
Learning Gaze Transitions from Depth to Improve Video Saliency
  Estimation

abstract:
  In this paper we introduce a novel Depth-Aware Video Saliency approach to
predict human focus of attention when viewing RGBD videos on regular 2D
screens. We train a generative convolutional neural network which predicts a
saliency map for a frame, given the fixation map of the previous frame.
Saliency estimation in this scenario is highly important since in the near
future 3D video content will be easily acquired and yet hard to display. This
can be explained, on the one hand, by the dramatic improvement of 3D-capable
acquisition equipment. On the other hand, despite the considerable progress in
3D display technologies, most of the 3D displays are still expensive and
require wearing special glasses. To evaluate the performance of our approach,
we present a new comprehensive database of eye-fixation ground-truth for RGBD
videos. Our experiments indicate that integrating depth into video saliency
calculation is beneficial. We demonstrate that our approach outperforms
state-of-the-art methods for video saliency, achieving 15% relative
improvement.


title:
Covering factors of the dusty obscurers in radio-loud and radio-quiet
  quasars

abstract:
  We compare covering factors of circumnuclear dusty obscurers in radio-loud
and radio-quiet quasars. The radio-loud quasars are represented by a sample of
FR II quasars obtained by cross-matching a catalog of the FR II radio sources
selected by van Velzen et al. with the SDSS DR7 catalog of quasars. Covering
factors of FR II quasars are compared with covering factors of the radio-quiet
quasars matched with them in redshift, black hole mass, and Eddington-ratio. We
found that covering factors, proxied by the infrared-to-bolometric luminosity
ratio, are on average slightly smaller in FR II quasars than in radio-quiet
quasars, however, this difference is statistically significant only for the
highest Eddington ratios. For both samples, no statistically significant
dependence of a median covering factor on Eddington ratio, black hole mass, nor
redshift can be claimed.


title: Homogeneous Actions on the Random Graph

abstract:
  We show that any free product of two countable groups, one of them being
infinite, admits a faithful and homogeneous action on the Random Graph. We also
show that a large class of HNN extensions or free products, amalgamated over a
finite group, admit such an action and we extend our results to groups acting
on trees. Finally, we show the ubiquity of finitely generated free dense
subgroups of the automorphism group of the Random Graph whose action on it have
all orbits infinite.


title: Randomized gap and amplitude estimation

abstract:
  We provide a method for estimating spectral gaps in low-dimensional systems.
Unlike traditional phase estimation, our approach does not require ancillary
qubits nor does it require well characterised gates. Instead, it only requires
the ability to perform approximate Haar-random unitary operations, applying the
unitary whose eigenspectrum is sought out and performing measurements in the
computational basis. We discuss application of these ideas to in-place
amplitude estimation and quantum device calibration.


title:
Properties of single cluster structure of $d^*(2380)$ in chiral SU(3)
  quark model

abstract:
  The structure of $d^*(2380)$ is re-studied with the single cluster structure
in the chiral SU(3) quark model which has successfully been employed to explain
the scattering and binding behaviors of baryonic systems. The mass and width
are explicitly calculated with two types of trial wave functions. The result
shows that the $(0s)^6 [6]_{orb}$ configuration is easy to convert to the
configuration with the same $[6]_{orb}$ symmetry but $2\hbar \omega$ excitation
back and forth, however, it is seldom to turn into a two-cluster configuration
with a (1s) relative motion in between. The resultant mass and width are about
$2394$MeV and $25$MeV, respectively, and the stable size is about $0.75fm$,
which are consistent with both the results in the two-cluster configuration
calculation and the data measured by the COSY collaboration. It seems that the
observed $d^*$ is a six-quark dominated exotic state with a spherical shape and
breath mode in the coordinate space. Moreover, if $d^*$ does have $2\hbar
\omega$ excitation, the $d^* \to np\pi\pi\pi$ decay mode might be a good place
to distinguish the real structure of the observed phenomenon by COSY. The
masses of various isospin-spin states of six-light-quark systems are also
computed. It is shown that by considering the coupling with the configurations
with $2\hbar \omega$ excitations, only the mirror state with $IS$=$30$ will be
lower down to the place where whose mass is slightly higher than the value of
the $\Delta\Delta$ threshold.


title: Triggering and Delivery Algorithms for AGN Feedback

abstract:
  We compare several common sub-grid implementations of AGN feedback, focusing
on the effects of different triggering mechanisms and the differences between
thermal and kinetic feedback. Our main result is that pure thermal feedback
that is centrally injected behaves differently from feedback with even a small
kinetic component. Specifically, pure thermal feedback results in excessive
condensation and smothering of the AGN by cold gas because the feedback energy
does not propagate to large enough radii. We do not see large differences
between implementations of different triggering mechanisms, as long as the
spatial resolution is sufficiently high, probably because all of the
implementations tested here trigger strong AGN feedback under similar
conditions. In order to assess the role of resolution, we vary the size of the
"accretion zone" in which properties are measured to determine the AGN
accretion rate and resulting feedback power. We find that a larger accretion
zone results in steadier jets but can also allow too much cold-gas condensation
in simulations with a Bondi-like triggering algorithm. We also vary the opening
angle of jet precession and find that a larger precession angle causes more of
the jet energy to thermalize closer to the AGN, thereby producing results
similar to pure thermal feedback. Our simulations confirm that AGN can regulate
the thermal state of cool-core galaxy clusters and maintain the core in a state
that is marginally susceptable to thermal instability and precipitation.


title: Optimal Data Collection for Randomized Control Trials

abstract:
  In a randomized control trial, the precision of an average treatment effect
estimator can be improved either by collecting data on additional individuals,
or by collecting additional covariates that predict the outcome variable. We
propose the use of pre-experimental data such as a census, or a household
survey, to inform the choice of both the sample size and the covariates to be
collected. Our procedure seeks to minimize the resulting average treatment
effect estimator's mean squared error, subject to the researcher's budget
constraint. We rely on a modification of an orthogonal greedy algorithm that is
conceptually simple and easy to implement in the presence of a large number of
potential covariates, and does not require any tuning parameters. In two
empirical applications, we show that our procedure can lead to substantial
gains of up to 58%, measured either in terms of reductions in data collection
costs or in terms of improvements in the precision of the treatment effect
estimator.


title: Surface roughness scattering in multisubband accumulation layers

abstract:
  Accumulation layers with very large concentrations of electrons where many
subbands are filled became recently available due to ionic liquid and other new
methods of gating. The low temperature mobility in such layers is limited by
the surface roughness scattering. However theories of roughness scattering so
far dealt only with the small-density single subband two-dimensional electron
gas (2DEG). Here we develop a theory of roughness-scattering limited mobility
for the multisubband large concentration case. We show that with growing 2D
electron concentration $n$ the surface dimensionless conductivity
$\sigma/(2e^2/h)$ first decreases as $\propto n^{-6/5}$ and then saturates as
$\sim(da_B/\Delta^2)\gg 1$, where $d$ and $\Delta$ are the characteristic
length and height of the surface roughness, $a_B$ is the effective Bohr radius.
This means that in spite of the shrinkage of the 2DEG width and the related
increase of the scattering rate, the 2DEG remains a good metal. Thus, there is
no re-entrant metal-insulator transition at high concentrations conjectured by
Das Sarma and Hwang [PRB 89, 121413 (2014)].


title:
Self-triggered Model Predictive Control for Nonlinear Input-Affine
  Dynamical Systems via Adaptive Control Samples Selection

abstract:
  In this paper, we propose a self-triggered formulation of Model Predictive
Control for continuous-time nonlinear input-affine networked control systems.
Our control method specifies not only when to execute control tasks but also
provides a way to discretize the optimal control trajectory into several
control samples, so that the reduction of communication load will be obtained.
Stability analysis under the sample-and-hold implementation is also given,
which guarantees that the state converges to a terminal region where the system
can be stabilized by a local state feedback controller. Some simulation
examples validate our proposed framework.


title: Nonstationary Distance Metric Learning

abstract:
  Recent work in distance metric learning has focused on learning
transformations of data that best align with provided sets of pairwise
similarity and dissimilarity constraints. The learned transformations lead to
improved retrieval, classification, and clustering algorithms due to the better
adapted distance or similarity measures. Here, we introduce the problem of
learning these transformations when the underlying constraint generation
process is nonstationary. This nonstationarity can be due to changes in either
the ground-truth clustering used to generate constraints or changes to the
feature subspaces in which the class structure is apparent. We propose and
evaluate COMID-SADL, an adaptive, online approach for learning and tracking
optimal metrics as they change over time that is highly robust to a variety of
nonstationary behaviors in the changing metric. We demonstrate COMID-SADL on
both real and synthetic data sets and show significant performance improvements
relative to previously proposed batch and online distance metric learning
algorithms.


title:
Simultaneous chiral symmetry restoration and deconfinement -
  Consequences for the QCD phase diagram

abstract:
  For studies of quark matter in astrophysical scenarios the thermodynamic bag
model (tdBag) is commonly employed. Although successful, it does not account
for dynamical chiral symmetry breaking (D$\chi$SB) and repulsions due to the
vector interaction which is crucial to explain recent observations of massive,
two solar mass neutron stars. In Kl\"ahn & Fischer (2015) we developed the
novel vBag quark matter model which takes these effects into account. This
article extends vBag to finite temperatures and isospin asymmetry. Another
particular feature of vBag is the determination of the deconfinement bag
constant $B_{\rm dc}$ from a given hadronic equation of state (EoS) in order to
ensure that chiral and deconfinement transitions coincide. We discuss
consequences of this novel approach for the phase transition construction, the
phase diagram, and implications for protoneutron stars.


title: Classifying Gamma-Ray Bursts with Gaussian Mixture Model

abstract:
  Using Gaussian Mixture Model (GMM) and Expectation Maximization Algorithm, we
perform an analysis of time duration ($T_{90}$) for \textit{CGRO}/BATSE,
\textit{Swift}/BAT and \textit{Fermi}/GBM Gamma-Ray Bursts. The $T_{90}$
distributions of 298 redshift-known \textit{Swift}/BAT GRBs have also been
studied in both observer and rest frames. Bayesian Information Criterion has
been used to compare between different GMM models. We find that two Gaussian
components are better to describe the \textit{CGRO}/BATSE and
\textit{Fermi}/GBM GRBs in the observer frame. Also, we caution that two groups
are expected for the \textit{Swift}/BAT bursts in the rest frame, which is
consistent with some previous results. However, \textit{Swift} GRBs in the
observer frame seem to show a trimodal distribution, of which the superficial
intermediate class may result from the selection effect of \textit{Swift}/BAT.


title:
Effects of anisotropy on interacting ghost dark energy in Brans-Dicke
  theories

abstract:
  By interacting ghost dark energy (ghost DE) in the framework of Brans-Dicke
theory, a spatially homogeneous and anisotropic Bianchi type I Universe has
been studied. For this purpose, we use the squared sound speed $c_s^2$ whose
sign determines the stability of the model. As well as we probe observational
constraints on the ghost dark energy models as the unification of dark matter
and dark energy by using the latest observational data. In order to do so, we
focus on observational determinations of the Hubble expansion rate (namely, the
expansion history) $H(z)$. After that we evaluate the evolution of the growth
of perturbations in the linear regime for both ghost DE and Brans-Dicke theory
and compare the results with standard FRW and $\Lambda$CDM models. We display
the effects of the anisotropy on the evolutionary behavior the ghost DE models
where the growth rate is higher in this models. Eventually the growth factor
for the $\Lambda$CDM Universe will always fall behind the ghost DE models in an
anisotropic Universe


title: Ultra Dense Small Cell Networks: Turning Density into Energy Efficiency

abstract:
  In this paper, a novel approach for joint power control and user scheduling
is proposed for optimizing energy efficiency (EE), in terms of bits per unit
energy, in ultra dense small cell networks (UDNs). Due to severe coupling in
interference, this problem is formulated as a dynamic stochastic game (DSG)
between small cell base stations (SBSs). This game enables to capture the
dynamics of both the queues and channel states of the system. To solve this
game, assuming a large homogeneous UDN deployment, the problem is cast as a
mean-field game (MFG) in which the MFG equilibrium is analyzed with the aid of
low-complexity tractable partial differential equations. Exploiting the
stochastic nature of the problem, user scheduling is formulated as a stochastic
optimization problem and solved using the drift plus penalty (DPP) approach in
the framework of Lyapunov optimization. Remarkably, it is shown that by weaving
notions from Lyapunov optimization and mean-field theory, the proposed solution
yields an equilibrium control policy per SBS which maximizes the network
utility while ensuring users' quality-of-service. Simulation results show that
the proposed approach achieves up to 70.7% gains in EE and 99.5% reductions in
the network's outage probabilities compared to a baseline model which focuses
on improving EE while attempting to satisfy the users' instantaneous
quality-of-service requirements.


title: Nonzero-sum Risk-sensitive Stochastic Games on a Countable State Space

abstract:
  The infinite horizon risk-sensitive discounted-cost and ergodic-cost
nonzero-sum stochastic games for controlled Markov chains with countably many
states are analyzed. For the discounted-cost game, we prove the existence of
Nash equilibrium strategies in the class of Markov strategies under fairly
general conditions. Under an additional geometric ergodicity condition and a
small cost criterion, the existence of Nash equilibrium strategies in the class
of stationary Markov strategies is proved for the ergodic-cost game.


title:
Investigating the role of model-based reasoning while troubleshooting an
  electric circuit

abstract:
  We explore the overlap of two nationally-recognized learning outcomes for
physics lab courses, namely, the ability to model experimental systems and the
ability to troubleshoot a malfunctioning apparatus. Modeling and
troubleshooting are both nonlinear, recursive processes that involve using
models to inform revisions to an apparatus. To probe the overlap of modeling
and troubleshooting, we collected audiovisual data from think-aloud activities
in which eight pairs of students from two institutions attempted to diagnose
and repair a malfunctioning electrical circuit. We characterize the cognitive
tasks and model-based reasoning that students employed during this activity. In
doing so, we demonstrate that troubleshooting engages students in the core
scientific practice of modeling.


title:
Determination of the edge of criticality in echo state networks through
  Fisher information maximization

abstract:
  It is a widely accepted fact that the computational capability of recurrent
neural networks is maximized on the so-called "edge of criticality". Once the
network operates in this configuration, it performs efficiently on a specific
application both in terms of (i) low prediction error and (ii) high short-term
memory capacity. Since the behavior of recurrent networks is strongly
influenced by the particular input signal driving the dynamics, a universal,
application-independent method for determining the edge of criticality is still
missing. In this paper, we aim at addressing this issue by proposing a
theoretically motivated, unsupervised method based on Fisher information for
determining the edge of criticality in recurrent neural networks. It is proven
that Fisher information is maximized for (finite-size) systems operating in
such critical regions. However, Fisher information is notoriously difficult to
compute and either requires the probability density function or the conditional
dependence of the system states with respect to the model parameters. The paper
takes advantage of a recently-developed non-parametric estimator of the Fisher
information matrix and provides a method to determine the critical region of
echo state networks, a particular class of recurrent networks. The considered
control parameters, which indirectly affect the echo state network performance,
are explored to identify those configurations lying on the edge of criticality
and, as such, maximizing Fisher information and computational performance.
Experimental results on benchmarks and real-world data demonstrate the
effectiveness of the proposed method.


title: Using Peer Feedback to Promote Reflection on Open-Ended Problems

abstract:
  This paper describes a new approach for learning from homework, called
Peer-Assisted Reflection (PAR). PAR involves students using peer feedback to
improve their work on open-ended homework problems. Collaborating with peers
and revising one's work based on the feedback of others are important aspects
of doing and learning physics. While notable exceptions exist, homework and
exams are generally individual activities that do not support collaboration and
refinement, which misses important opportunities to use assessment for
learning. In contrast, PAR provides students with a structure to iteratively
engage with challenging, open-ended problems and solicit the input of their
peers to improve their work.


title:
A Mechanism of Long-Range Order Induced by Random Local Fields:
  Effective Anisotropy Created by Defects

abstract:
  We propose a microscopic mechanism of the long-range order in two-dimensional
space induced by random local fields of crystal defects. The anisotropic
distribution of defect-induced random local field directions in the
n-dimensional space of vector order parameter with the O(n) symmetry is shown
to give rise to the defect-induced effective anisotropy in the system. The
expression for the effective anisotropy constant is found. A weak anisotropy of
the "easy axis" type transforms the X-Y model and the Heisenberg model to the
class of Ising models, and brings into existence the long-range order in the
system.


title: Skyrmions in square-lattice antiferromagnets

abstract:
  The ground states of square lattice two-dimensional antiferromagnets with
anisotropy in an external magnetic field are determined using Monte Carlo
simulations and compared to theoretical analysis. We find a new phase in
between the spin-flop and spiral phase that shows strong similarity to
skyrmions in ferromagnetic thin films. We show that this phase arises as a
result of the competition between Zeeman and Dzyaloshinskii-Moriya interaction
energies of the magnetic system. Moreover, we find that isolated
(anti-)skyrmions are stabilized in finite-sized systems, even at higher
temperatures. The existence of thermodynamically stable skyrmions in
square-lattice antiferromagnets provides an appealing alternative over
skyrmions in ferromagnets as data carriers.


title: Path integral for multi-field inflation

abstract:
  We develop the path integral formalism for studying cosmological
perturbations in multi-field inflation, which is particularly well suited to
study quantum theories with gauge symmetries such as diffeomorphism invariance.
We formulate the gauge fixing conditions based on the Poisson brackets of the
constraints, from which we derive two convenient gauges that are appropriate
for multi-field inflation. We then adopt the in-in formalism to derive the most
general expression for the power spectrum of the curvature perturbation
including the corrections from the interactions of the curvature mode with
other light degrees of freedom. We also discuss the contributions of the
interactions to the bispectrum.


title:
Modeling SNR Cassiopeia A from the Supernova Explosion to its Current
  Age: The role of post-explosion anisotropies of ejecta

abstract:
  The remnants of core-collapse supernovae (SNe) have complex morphologies that
may reflect asymmetries and structures developed during the progenitor SN
explosion. Here we investigate how the morphology of the SNR Cassiopeia A (Cas
A) reflects the characteristics of the progenitor SN with the aim to derive the
energies and masses of the post-explosion anisotropies responsible for the
observed spatial distribution of Fe and Si/S. We model the evolution of Cas A
from the immediate aftermath of the progenitor SN to the three-dimensional
interaction of the remnant with the surrounding medium. The post-explosion
structure of the ejecta is described by small-scale clumping of material and
larger-scale anisotropies. The hydrodynamic multi-species simulations consider
an appropriate post-explosion isotopic composition of the ejecta. The observed
average expansion rate and shock velocities can be well reproduced by models
with ejecta mass $M_{\rm ej}\approx 4M_{\odot}$ and explosion energy $E_{\rm
SN}\approx 2.3\times 10^{51}$ erg. The post-explosion anisotropies (pistons)
reproduce the observed distributions of Fe and Si/S if they had a total mass of
$\approx 0.25\,M_{\odot}$ and a total kinetic energy of $\approx 1.5\times
10^{50}$ erg. The pistons produce a spatial inversion of ejecta layers at the
epoch of Cas A, leading to the Si/S-rich ejecta physically interior to the
Fe-rich ejecta. The pistons are also responsible for the development of bright
rings of Si/S-rich material which form at the intersection between the reverse
shock and the material accumulated around the pistons during their propagation.
Our result supports the idea that the bulk of asymmetries observed in Cas A are
intrinsic to the explosion.


title: Topologizing Lie algebra cohomology

abstract:
  We show that the theory of Lie algebra cohomology can be recast in a
topological setting and that classical results, such as the Shapiro lemma and
the van Est isomorphism, carry over to this augmented context.


title: On Black Hole Structures in Scalar-Tensor Theories of Gravity

abstract:
  We review some properties of black hole structures appearing in gravity with
a massless scalar field, with both minimal and nonminimal coupling. The main
properties of the resulting cold black holes are described. The study of black
holes in scalar-gravity systems is extended to $k$-essence theories, and some
examples are explicitly worked out. In these cases, even while the existence of
horizons is possible, the metric regularity requirement on the horizon implies
either a cold black type structure or a singular behavior of the scalar field.


title:
Absolutely continuous copulas obtained by regularization of the
  Frech\'{e}t--Hoeffding bounds

abstract:
  We show that the lower and upper Frech\'{e}t-Hoeffding copulas, which are
singular, can be regularized to absolutely continuous copulas. The method,
which is constructive and explicit, states sufficient conditions for when an
absolutely continuous copula can be achieved by averaging. A higher degree of
regularisation cannot be achieved with the proposed method.


title: Inference of internal stress in a cell monolayer

abstract:
  We combine traction force data with Bayesian inversion to obtain an absolute
estimate of the internal stress field of a cell monolayer. The method, Bayesian
inversion stress microscopy (BISM), is validated using numerical simulations
performed in a wide range of conditions. It is robust to changes in each
ingredient of the underlying statistical model. Importantly, its accuracy does
not depend on the rheology of the tissue. We apply BISM to experimental
traction force data measured in a narrow ring of cohesive epithelial cells, and
check that the inferred stress field coincides with that obtained by direct
spatial integration of the traction force data in this quasi-one-dimensional
geometry.


title:
Energy Harvesting Communication System with SOC-Dependent Energy Storage
  Losses

abstract:
  The popularity of Energy Harvesting Devices (EHDs) has grown in the past few
years, thanks to their capability of prolonging the network lifetime. In
reality, EHDs are affected by several inefficiencies, e.g., energy leakage,
battery degradation or storage losses. In this work we consider an energy
harvesting transmitter with storage inefficiencies. In particular, we assume
that when new energy has to be stored in the battery, part of this is wasted
and the losses depend upon the current state of charge of the device. This is a
practical realistic assumption, e.g., for a capacitor, that changes the
structure of the optimal transmission policy. We analyze the throughput
maximization problem with a dynamic programming approach and prove that, given
the battery status and the channel gain, the optimal transmission policy is
deterministic. We derive numerical results for the energy losses in a capacitor
and show the presence of a \emph{loop effect} that degrades the system
performance if the optimal policy is not considered.


title: Dark matter decays from non-minimal coupling to gravity

abstract:
  We consider the Standard Model extended with a dark matter particle in curved
spacetime, motivated by the fact that the only current evidence for dark matter
is through its gravitational interactions, and we investigate the impact on the
dark matter stability of terms in the Lagrangian linear in the dark matter
field and proportional to the Ricci scalar. We show that this "gravity portal"
induces decay even if the dark matter particle only has gravitational
interactions, and that the decay branching ratios into Standard Model particles
only depend on one free parameter: the dark matter mass. We study in detail the
case of a singlet scalar as dark matter candidate, which is assumed to be
absolutely stable in flat spacetime due to a discrete $Z_2$ symmetry, but which
may decay in curved spacetimes due to a $Z_2$-breaking non-minimal coupling to
gravity. We calculate the dark matter decay widths and we set conservative
limits on the non-minimal coupling parameter from experiments. The limits are
very stringent and suggest that there must exist an additional mechanism
protecting the singlet scalar from decaying via this gravity portal.


title: Subsampling for Graph Power Spectrum Estimation

abstract:
  In this paper we focus on subsampling stationary random processes that reside
on the vertices of undirected graphs. Second-order stationary graph signals are
obtained by filtering white noise and they admit a well-defined power spectrum.
Estimating the graph power spectrum forms a central component of stationary
graph signal processing and related inference tasks. We show that by sampling a
significantly smaller subset of vertices and using simple least squares, we can
reconstruct the power spectrum of the graph signal from the subsampled
observations, without any spectral priors. In addition, a near-optimal greedy
algorithm is developed to design the subsampling scheme.


title:
The Seiberg-Witten equations on end-periodic manifolds and an
  obstruction to positive scalar curvature metrics

abstract:
  By studying the Seiberg-Witten equations on end-periodic manifolds, we give
an obstruction on the existence of positive scalar curvature metric on compact
$4$-manifolds with the same homology as $S^{1}\times S^{3}$. This obstruction
is given in terms of the relation between the Fr{\o}yshov invariant of the
generator of $H_{3}(X;Z)$ with the $4$-dimensional Casson invariant
$\lambda_{SW}(X)$ defined by Mrowka-Ruberman-Saveliev. Along the way, we
develop a framework that can be useful in further study of the Seiberg-Witten
theory on general end-periodic manifolds.


title: On the physical realizability of quantum stochastic walks

abstract:
  Quantum walks are a promising framework that can be used to both understand
and implement quantum information processing tasks. The quantum stochastic walk
is a recently developed framework that combines the concept of a quantum walk
with that of a classical random walk, through open system evolution of a
quantum system. Quantum stochastic walks have been shown to have applications
in as far reaching fields as artificial intelligence. However, there are
significant constraints on the kind of open system evolutions that can be
realized in a physical experiment. In this work, we discuss the restrictions on
the allowed open system evolution, and the physical assumptions underpinning
them. We show that general implementations would require the complete solution
of the underlying unitary dynamics, and sophisticated reservoir engineering,
thus weakening the benefits of experimental investigations.


title: An integral approach to the Gardner-Fisher and untwisted Dowker sums

abstract:
  We present a new and elegant integral approach to computing the
Gardner-Fisher trigonometric power sum, which is given by $$
S_{m,v}=\left(\frac
\pi{2m}\right)^{2v}\sum_{k=1}^{m-1}\cos^{-2v}\left(\frac{k\pi}{2m}\right)\, ,
$$ We present a new and elegant integral approach to computing the
Gardner-Fisher trigonometric power sum, which is given by $$
S_{m,v}=\left(\frac
\pi{2m}\right)^{2v}\sum_{k=1}^{m-1}\cos^{-2v}\left(\frac{k\pi}{2m}\right)\, ,
$$ where $m$ and $v$ are positive integers. This method not only confirms the
results obtained earlier by an empirical method, but it is also much more
expedient from a computational point of view. By comparing the formulas from
both methods, we derive several new interesting number theoretic results
involving symmetric polynomials over the set of quadratic powers up to
$(v-1)^2$ and the generalized cosecant numbers. The method is then extended to
other related trigonometric power sums including the untwisted Dowker sum. By
comparing both forms for this important sum, we derive new formulas for
specific values of the N\"{o}rlund polynomials. Finally, by using the results
appearing in the tables, we consider more advanced sums involving the product
of powers of cotangent and tangent with powers of cosecant and secant
respectively.


title:
Hysteresis of noninteracting and spin-orbit coupled atomic Fermi gases
  with relaxation

abstract:
  Hysteresis can be found in driven many-body systems such as magnets and
superfluids. Rate-dependent hysteresis arises when a system is driven
periodically while relaxing towards equilibrium. A two-state paramagnet driven
by an oscillating magnetic field in the relaxation approximation clearly
demonstrates rate-dependent hysteresis. A noninteracting atomic Fermi gas in an
optical ring potential, when driven by a periodic artificial gauge field and
subjected to dissipation, is shown to exhibit hysteresis loops of atomic
current due to a competition of the driving time and the relaxation time. This
is in contrast to electronic systems exhibiting equilibrium persistent current
driven by magnetic flux due to rapid relaxation. Universal behavior of the
dissipated energy in one hysteresis loop is observed in both the magnetic and
atomic systems, showing linear and inverse-linear dependence on the relaxation
time in the strong and weak dissipation regimes. While interactions in general
invalidate the framework for rate-dependent hysteresis, an atomic Fermi gas
with artificial spin-orbit coupling exhibits hysteresis loops of atomic
currents. Cold-atoms in ring-shape potentials are thus promising in
demonstrating rate-dependent hysteresis and its associated phenomena.


title: Weak Cayley table groups of some crystallographic groups

abstract:
  For a group $G$, a weak Cayley isomorphism is a bijection $f:G \to G$ such
that $f(g_1g_2)$ is conjugate to $ f(g_1)f(g_2)$ for all $g_1,g_2 \in G$. They
form a group $\mathcal W(G)$ that is the group of symmetries of the weak Cayley
table of $G$. We determine $\mathcal W(G)$ for each of the seventeen wallpaper
groups $G$, and for some other crystallographic groups.


title: Searching for Topological Symmetry in Data Haystack

abstract:
  Finding interesting symmetrical topological structures in high-dimensional
systems is an important problem in statistical machine learning. Limited amount
of available high-dimensional data and its sensitivity to noise pose
computational challenges to find symmetry. Our paper presents a new method to
find local symmetries in a low-dimensional 2-D grid structure which is embedded
in high-dimensional structure. To compute the symmetry in a grid structure, we
introduce three legal grid moves (i) Commutation (ii) Cyclic Permutation (iii)
Stabilization on sets of local grid squares, grid blocks. The three grid moves
are legal transformations as they preserve the statistical distribution of
hamming distances in each grid block. We propose and coin the term of grid
symmetry of data on the 2-D data grid as the invariance of statistical
distributions of hamming distance are preserved after a sequence of grid moves.
We have computed and analyzed the grid symmetry of data on multivariate
Gaussian distributions and Gamma distributions with noise.


title:
Magnetic structures of rare earth intermetallic compounds RCuAs$_2$ (R =
  Pr, Nd, Tb, Dy, Ho, and Yb)

abstract:
  Neutron scattering studies have been carried out on polycrystalline samples
of a series of rare earth intermetallic compounds RCuAs$_2$ (R = Pr, Nd, Dy,
Tb, Ho and Yb) as a function of temperature to determine the magnetic
structures and the order parameters. These compounds crystallize in the
ZrCuSi$_2$ type structure, which is similar to that of the RFeAsO (space group
P4/nmm) class of iron-based superconductors. PrCuAs$_2$ develops commensurate
magnetic order with K = (0, 0, 0.5) below T$_N$ = 6.4 (2) K, with the ordered
moments pointing along the c-axis. The irreducible representation analysis
shows either a ${\Gamma}$$^1_2$ or ${\Gamma}$$^1_3$ representation. NdCuAs$_2$
and DyCuAs$_2$ order below T$_N$ = 3.54(5) K and T$_N$ = 10.1(2) K,
respectively, with the same ordering wave vector but the moments lying in the
a-b plane (with a ${\Gamma}$$^2_9$ or ${\Gamma}$$^2_{10}$ representation).
TbCuAs$_2$ and HoCuAs$_2$ exhibit incommensurate magnetic structures below
T$_N$ = 9.44(7) and 4.41(2) K, respectively. For TbCuAs$_2$, two separate
magnetic ordering wave vectors are established as K$_{1(Tb)}$ =
(0.240,0.155,0.48) and K$_{2(Tb)}$ = (0.205, 0.115, 0.28), whereas HoCuAs$_2$
forms a single K$_{(Ho)}$ = (0.121, 0.041, 0.376) magnetic structure with
3$^{rd}$ order harmonic magnetic peaks. YbCuAs$_2$ does not exhibit any
magnetic Bragg peaks at 1.5 K, while susceptibility measurements indicate an
antiferromagnetic-like transition at 4 K, suggesting that either the ordering
is not long range in nature or the ordered moment is below the sensitivity
limit of $\approx$ 0.2 $\mu_B$.


title: Probabilistic Models for the (sub)Tree(s) of Life

abstract:
  The goal of these lectures is to review some mathematical aspects of random
tree models used in evolutionary biology to model gene trees or species trees.
We start with stochastic models of tree shapes (finite trees without edge
lengths), culminating in the $\beta$-family of Aldous' branching models. We
next introduce real trees (trees as metric spaces) and show how to study them
through their contour, provided they are properly measured and ordered. We then
focus on the reduced tree, or coalescent tree, which is the tree spanned by
individuals/species alive at the same fixed time. We show how reduced trees,
like any compact ultrametric space, can be represented in a simple way via the
so-called comb metric. Beautiful examples of random combs include the Kingman
coalescent and coalescent point processes. We end up displaying some recent
biological applications of coalescent point processes to the inference of
species diversification, to conservation biology and to epidemiology.


title: Quantifying the global atmospheric power budget

abstract:
  The power of atmospheric circulation is a key measure of the Earth's climate
system. The mismatch between predictions and observations under a warming
climate calls for a reassessment of how atmospheric power $W$ is defined,
estimated and constrained. Here we review published formulations for $W$ and
show how they differ when applied to a moist atmosphere. Three factors, a
non-zero source/sink in the continuity equation, the difference between
velocities of gaseous air and condensate, and interaction between the gas and
condensate modifying the equations of motion, affect the formulation of $W$.
Starting from the thermodynamic definition of mechanical work, we derive an
expression for $W$ from an explicit consideration of the equations of motion
and continuity. Our analyses clarify how some past formulations are incomplete
or invalid. Three caveats are identified. First, $W$ critically depends on the
boundary condition for gaseous air velocity at the Earth's surface. Second,
confusion between gaseous air velocity and mean velocity of air and condensate
in the expression for $W$ results in gross errors despite the observed
magnitudes of these velocities are very close. Third, $W$ expressed in terms of
measurable atmospheric parameters, air pressure and velocity, is
scale-specific; this must be taken into account when adding contributions to
$W$ from different processes. We present a formulation of the atmospheric power
budget, which distinguishes three components of $W$: the kinetic power
associated with horizontal pressure gradients ($W_K$), the gravitational power
of precipitation ($W_P$) and the condensate loading ($W_c$). We use MERRA and
NCAR/NCEP re-analyses to evaluate the atmospheric power budget at different
scales: $W_K$ increases with temporal resolution approaching our theoretical
estimate for condensation-induced circulation when all convective motion is
resolved.


title:
VLT-SINFONI sub-kpc study of the star formation in local LIRGs and
  ULIRGs: Analysis of the global $\Sigma_{\rm SFR}$ structure and
  characterisation of individual star-forming clumps

abstract:
  We present a 2D study of star formation at kpc and sub-kpc scales of a sample
of local (z<0.1) U/LIRGs, based on near-IR VLT-SINFONI observations. We
obtained integrated measurements of the star formation rate (SFR) and star
formation rate surface density, together with their 2D distributions, based on
Br_gamma and Pa_alpha emission. We observe a tight linear correlation between
the SFR derived from our extinction-corrected measurements and that derived
from 24 micron data, and a reasonable agreement with SFR derived from total IR
luminosity. Our near-IR measurements are on average a factor 3 larger than
optical SFR, even when extinction corrections are applied. We found that LIRGs
have a median-observed star formation rate surface density of 1.72
Msun/yr/kpc^2 for the extinction-corrected distribution, whilst ULIRGs have
0.23 Msun/yr/kpc^2, respectively. These median values for ULIRGs increase up to
2.90 Msun/yr/kpc^2, when only their inner regions, covering the same size as
the average FoV of LIRGs, are considered. We identified a total of 95
individual SF clumps in our sample, with sizes within 60-1500pc, and
extinction-corrected Pa_alpha luminosities of 10^5-10^8 Lsun. Star-forming
clumps in LIRGs are about ten times larger and thousands of times more luminous
than typical clumps in spiral galaxies. Clumps in ULIRGs have sizes similar
(x0.5-1) to those of high-z clumps, having Pa_alpha luminosities similar to
some high-z clumps, and about 10 times less luminous than the most luminous
high-z clumps identified so far. We also observed a change in the slope of the
L-r relation. A likely explanation is that most luminous galaxies are
interacting and merging, and therefore their size represents a combination of
the distribution of the star-forming clumps within each galaxy in the system
plus the effect of the projected distance.


title: A containment result in $\mathbb{P}^n$ and the Chudnovsky conjecture

abstract:
  In the paper we prove the containment $I^{(nm)}\subset M^{(n-1)m}I^m$, for a
radical ideal $I$ of $s$ general points in $\mathbb{P}^n$, where $s\geq 2^n$.
As a corollary we get that the Chudnovsky Conjecture holds for a very general
set of at least $2^n$ points in $\mathbb{P}^n$.


title: AKARI far-infrared maps of the zodiacal dust bands

abstract:
  Zodiacal emission is thermal emission from interplanetary dust. Its
contribution to the sky brightness is non-negligible in the region near the
ecliptic plane, even in the far-infrared (far-IR) wavelength regime. We analyse
zodiacal emission observed by the AKARI far-IR all-sky survey, which covers 97%
of the entire sky at arcminute-scale resolution in four photometric bands, with
central wavelengths of 65, 90, 140, and 160 $\mu$m. AKARI detected small-scale
structures in the zodiacal dust cloud, including the asteroidal dust bands and
the circumsolar ring, at far-IR wavelengths. Although the smooth component of
the zodiacal emission structure in the far-IR sky can be reproduced well by
models based on existing far-IR observations, previous zodiacal emission models
have discrepancies in the small-scale structures compared with observations. We
investigate the geometry of the small-scale dust-band structures in the AKARI
far-IR all-sky maps and construct template maps of the asteroidal dust bands
and the circumsolar ring components based on the AKARI far-IR maps. In the
maps, $\pm 1.4\deg$, $\pm 2.1\deg$ and $\pm 10\deg$ asteroidal dust-band
structures are detected in the 65 $\mu$m and 90 $\mu$m bands. A possible $\pm
17\deg$ band may also have been detected. No evident dust-band structures are
identified in either the 140 $\mu$m or the 160 $\mu$m bands. By subtracting the
dust-band templates constructed in this paper, we can achieve a similar level
of flux calibration of the AKARI far-IR all-sky maps in the $|\beta| < 40\deg$
region to that in the region for $|\beta| > 40\deg$.


title:
Why 2 times 2 ain't necessarily 4 - at least not in IT security risk
  assessment

abstract:
  Recently, a novel approach towards semi-quantitative IT security risk
assessment has been proposed in the draft IEC 62443-3-2. This approach is
analyzed from several different angles, e.g. embedding into the overall
standard series, semantic and methodological aspects. As a result, several
systematic flaws in the approach are exposed. As a way forward, an alternative
approach is proposed which blends together semi-quantitative risk assessment as
well as threat and risk analysis.


title:
The effect of multiple particle sizes on cooling rates of chondrules
  produced in large-scale shocks in the solar nebula

abstract:
  Chondrules represent one of the best probes of the physical conditions and
processes acting in the early solar nebula. Proposed chondrule formation models
are assessed based on their ability to match the meteoritic evidence,
especially experimental constraints on their thermal histories. The model most
consistent with chondrule thermal histories is passage through shock waves in
the solar nebula. Existing models of heating by shocks generally yield a good
first-order approximation to inferred chondrule cooling rates. However, they
predict prolonged heating in the pre-shock region, which would cause volatile
loss and isotopic fractionation, which are not observed. These models have
typically included particles of a single (large) size, i.e., chondrule
precursors, or at most, large particles accompanied by micron-sized grains. The
size distribution of solids present during chondrule formation controls the
opacity of the affected region, and significantly affects the thermal histories
of chondrules. Micron-sized grains evaporate too quickly to prevent excessive
heating of chondrule precursors. However, isolated grains in chondrule-forming
regions would rapidly coagulate into fractal aggregates. Pre-shock heating by
infrared radiation from the shock front would cause these aggregates to melt
and collapse into intermediate-sized (tens of microns) particles. We show that
inclusion of such particles yields chondrule cooling rates consistent with
petrologic and isotopic constraints.


title:
On the accuracy of the Pade-resummed master equation approach to
  dissipative quantum dynamics

abstract:
  Well--defined criteria are proposed for assessing the accuracy of quantum
master equations whose memory functions are approximated by Pad\'e resummation
of the first two moments in the electronic coupling. These criteria partition
the parameter space into distinct levels of expected accuracy, ranging from
quantitatively accurate regimes to regions of parameter space where the
approach is not expected to be applicable. Extensive comparison of
Pad\'e--resummed master equations with numerically exact results in the context
of the spin--boson model demonstrate that the proposed criteria correctly
demarcate the regions of parameter space where the Pad\'e approximation is
reliable. The applicability analysis we present is not confined to the
specifics of the Hamiltonian under consideration and should provide guidelines
for other classes of resummation techniques.


title:
Cost-sensitive Learning for Utility Optimization in Online Advertising
  Auctions

abstract:
  One of the most challenging problems in computational advertising is the
prediction of click-through and conversion rates for bidding in online
advertising auctions. An unaddressed problem in previous approaches is the
existence of highly non-uniform misprediction costs. While for model evaluation
these costs have been taken into account through recently proposed
business-aware offline metrics -- such as the Utility metric which measures the
impact on advertiser profit -- this is not the case when training the models
themselves. In this paper, to bridge the gap, we formally analyze the
relationship between optimizing the Utility metric and the log loss, which is
considered as one of the state-of-the-art approaches in conversion modeling.
Our analysis motivates the idea of weighting the log loss with the business
value of the predicted outcome. We present and analyze a new cost weighting
scheme and show that significant gains in offline and online performance can be
achieved.


title: Distribution Free Learning with Local Queries

abstract:
  The model of learning with \emph{local membership queries} interpolates
between the PAC model and the membership queries model by allowing the learner
to query the label of any example that is similar to an example in the training
set. This model, recently proposed and studied by Awasthi, Feldman and Kanade,
aims to facilitate practical use of membership queries.
  We continue this line of work, proving both positive and negative results in
the {\em distribution free} setting. We restrict to the boolean cube $\{-1,
1\}^n$, and say that a query is $q$-local if it is of a hamming distance $\le
q$ from some training example. On the positive side, we show that $1$-local
queries already give an additional strength, and allow to learn a certain type
of DNF formulas. On the negative side, we show that even
$\left(n^{0.99}\right)$-local queries cannot help to learn various classes
including Automata, DNFs and more. Likewise, $q$-local queries for any constant
$q$ cannot help to learn Juntas, Decision Trees, Sparse Polynomials and more.
Moreover, for these classes, an algorithm that uses
$\left(\log^{0.99}(n)\right)$-local queries would lead to a breakthrough in the
best known running times.


title: Generalized bipyramids and hyperbolic volumes of tiling links

abstract:
  We present explicit geometric decompositions of the complement of tiling
links, which are alternating links whose projection graphs are uniform tilings
of the 2-sphere, the Euclidean plane or the hyperbolic plane. This requires
generalizing the angle structures program of Casson and Rivin for
triangulations with a mixture of finite, ideal, and truncated (i.e.
ultra-ideal) vertices. A consequence of this decomposition is that the volumes
of spherical tiling links are precisely twice the maximal volumes of the ideal
Archimedean solids of the same combinatorial description. In the case of
hyperbolic tiling links, we are led to consider links embedded in thickened
surfaces S_g x I with genus g at least 2. We generalize the bipyramid
construction of Adams to truncated bipyramids and use them to prove that the
set of possible volume densities for links in S_g x I, ranging over all g at
least 2, is a dense subset of the interval [0, 2v_{oct}], where v_{oct},
approximately 3.66386, is the volume of the regular ideal octahedron.


title: Phase Transformation in Self-Organized Carbon Tribolayers

abstract:
  The simplest way to obtain thin carbon layers is to draw or rub with a
graphite rod. During rubbing, forces of friction acting in graphite/substrate
tribological system cause drastic changes in the structure of the interface
stratum developing thereby stable self-organized and ordered thin structure. We
present a pioneering experimental investigation of structural and morphological
transformations in carbon tribolayers (CTL). By optical microscopy observation
it is found that CTL is a multilayer structure, the essential building block of
which is a transparent phase shaped as a lamina in-between the surface and
bottom disordered layers of CTL. The surface of the lamina exhibits non-linear
electrical conductivity near zero bias on I-V characteristics. The optical
properties of the whole CTL are mostly controlled by physical processes
occurring in the transparent lamina. The Raman spectrum of CTL contains narrow
bands at 1,589 cm-1 and 1,346 cm-1 corresponding to G and D bands of carbon
crystal lattice. The observed features are interpreted using the relationship
between the bond length and corresponding band frequency, r2{\omega}= const.
Optical absorption of CTL has a feature at 4.6 eV originating from strong
electron-hole interaction. From comparative analysis of experimental data,
structural-spectral correspondence is found. It is concluded that because of
phase transformation during rubbing, a carbon structure consisting of sp3
lamina with a nano-scaled thick sp2 layer on the top is shaped.


title: The Asymptotics of Quantum Max-Flow Min-Cut

abstract:
  The quantum max-flow min-cut conjecture relates the rank of a tensor network
to the minimum cut in the case that all tensors in the network are
identical\cite{mfmc1}. This conjecture was shown to be false in Ref.
\onlinecite{mfmc2} by an explicit counter-example. Here, we show that the
conjecture is almost true, in that the ratio of the quantum max-flow to the
quantum min-cut converges to $1$ as the dimension $N$ of the degrees of freedom
on the edges of the network tends to infinity. The proof is based on estimating
moments of the singular values of the network. We introduce a generalization of
"rainbow diagrams"\cite{rainbow} to tensor networks to estimate the dominant
diagrams. A direct comparison of second and fourth moments lower bounds the
ratio of the quantum max-flow to the quantum min-cut by a constant. To show the
tighter bound that the ratio tends to $1$, we consider higher moments. In
addition, we show that the limiting moments as $N \rightarrow \infty$ agree
with that in a different ensemble where tensors in the network are chosen
independently, this is used to show that the distributions of singular values
in the two different ensembles weakly converge to the same limiting
distribution. We present also a numerical study of one particular tensor
network, which shows a surprising dependence of the rank deficit on $N \mod 4$
and suggests further conjecture on the limiting behavior of the rank.


title:
Optimal control of a charge qubit in a double quantum dot with a Coulomb
  impurity

abstract:
  We study the efficiency of modulated laser pulses to produce efficient and
fast charge localization transitions in a two-electron double quantum dot. We
use a configuration interaction method to calculate the electronic structure of
a quantum dot model within the effective mass approximation. The interaction
with the electric field of the laser is considered within the dipole
approximation and optimal control theory is applied to design high-fidelity
ultrafast pulses in pristine samples. We assessed the influence of the presence
of Coulomb charged impurities on the efficiency and speed of the pulses. A
protocol based on a two-step optimization is proposed for preserving both
advantages of the original pulse. The processes affecting the charge
localization is explained from the dipole transitions of the lowest lying
two-electron states, as described by a discrete model with an effective
electron-electron interaction.


title:
Model Selection for Graphical Log-linear Models: A Forward Model
  Selection Algorithm based on Mutual Conditional Independence

abstract:
  Model selection and learning the structure of graphical models from the data
sample constitutes an important field of probabilistic graphical model
research, as in most of the situations the structure is unknown and has to be
learnt from the given dataset. In this paper, we present a new forward model
selection algorithm for graphical log-linear models. We use mutual conditional
independence check to reduce the search space which also takes care of the
evaluation of the joint effects and chances of missing important interactions
are eliminated. We illustrate our algorithm with a real dataset example.


title: Unexpected biases in the distribution of consecutive primes

abstract:
  While the sequence of primes is very well distributed in the reduced residue
classes (mod $q$), the distribution of pairs of consecutive primes among the
permissible $\phi(q)^2$ pairs of reduced residue classes (mod $q$) is
surprisingly erratic. This paper proposes a conjectural explanation for this
phenomenon, based on the Hardy-Littlewood conjectures. The conjectures are then
compared to numerical data, and the observed fit is very good.


title: Stability of contact lines in fluids: 2D Stokes Flow

abstract:
  In an effort to study the stability of contact lines in fluids, we consider
the dynamics of an incompressible viscous Stokes fluid evolving in a
two-dimensional open-top vessel under the influence of gravity. This is a free
boundary problem: the interface between the fluid in the vessel and the air
above (modeled by a trivial fluid) is free to move and experiences capillary
forces. The three-phase interface where the fluid, air, and solid vessel wall
meet is known as a contact point, and the angle formed between the free
interface and the vessel is called the contact angle. We consider a model of
this problem that allows for fully dynamic contact points and angles. We
develop a scheme of a priori estimates for the model, which then allow us to
show that for initial data sufficiently close to equilibrium, the model admits
global solutions that decay to equilibrium exponentially fast.


title:
Optical Conductivity of Weyl Semimetals and Signatures of the Gapped
  Semimetal Phase Transition

abstract:
  The interband optical response of a three-dimensional Dirac cone is linear in
photon energy ($\Omega$). Here, we study the evolution of the interband
response within a model Hamiltonian which contains Dirac, Weyl and gapped
semimetal phases. In the pure Dirac case, a single linear dependence is
observed, while in the Weyl phase, we find two quasilinear regions with
different slopes. These regions are also distinct from the large-$\Omega$
dependence. As the boundary between the Weyl (WSM) and gapped phases is
approached, the slope of the low-$\Omega$ response increases, while the
photon-energy range over which it applies decreases. At the phase boundary, a
square root behaviour is obtained which is followed by a gapped response in the
gapped semimetal phase. The density of states parallels these behaviours with
the linear law replaced by quadratic behaviour in the WSM phase and the square
root dependence at the phase boundary changed to $|\omega|^{3/2}$. The optical
spectral weight under the intraband (Drude) response at low temperature ($T$)
and/or small chemical potential ($\mu$) is found to change from $T^2$ ($\mu^2$)
in the WSM phase to $T^{3/2}$ ($|\mu|^{3/2}$) at the phase boundary.


title: Quantum clock: A critical discussion on spacetime

abstract:
  We critically discuss the measure of very short time intervals. By means of a
Gedankenexperiment, we describe an ideal clock based on the occurrence of
completely random events. Many previous thought experiments have suggested
fundamental Planck-scale limits on measurements of distance and time. Here we
present a new type of thought experiment, based on a different type of clock,
that provide further support for the existence of such limits. We show that the
minimum time interval $\Delta t$ that this clock can measure scales as the
inverse of its size $\Delta r$. This implies an uncertainty relation between
space and time: $\Delta r$ $\Delta t$ $> G \hbar / c^4$; where G, $\hbar$ and c
are the gravitational constant, the reduced Planck constant, and the speed of
light, respectively. We outline and briefly discuss the implications of this
uncertainty conjecture.


title:
Efficient Clustering of Correlated Variables and Variable Selection in
  High-Dimensional Linear Models

abstract:
  In this paper, we introduce Adaptive Cluster Lasso(ACL) method for variable
selection in high dimensional sparse regression models with strongly correlated
variables. To handle correlated variables, the concept of clustering or
grouping variables and then pursuing model fitting is widely accepted. When the
dimension is very high, finding an appropriate group structure is as difficult
as the original problem. The ACL is a three-stage procedure where, at the first
stage, we use the Lasso(or its adaptive or thresholded version) to do initial
selection, then we also include those variables which are not selected by the
Lasso but are strongly correlated with the variables selected by the Lasso. At
the second stage we cluster the variables based on the reduced set of
predictors and in the third stage we perform sparse estimation such as Lasso on
cluster representatives or the group Lasso based on the structures generated by
clustering procedure. We show that our procedure is consistent and efficient in
finding true underlying population group structure(under assumption of
irrepresentable and beta-min conditions). We also study the group selection
consistency of our method and we support the theory using simulated and
pseudo-real dataset examples.


title:
A Multi-Channel Spectrum Sensing Fusion Mechanism for Cognitive Radio
  Networks: Design and Application to IEEE 802.22 WRANs

abstract:
  The IEEE 802.22 is a new cognitive radio standard that is aimed at extending
wireless outreach to rural areas. Known as wireless regional area networks, and
designed based on the not-to-interfere spectrum sharing model, WRANs are
channelized and centrally-controlled networks working on the under-utilized
UHF/VHF TV bands to establish communication with remote users, so-called
customer premises equipment (CPEs). Despite the importance of reliable and
interference-free operation in these frequencies, spectrum sensing fusion
mechanisms suggested in IEEE 802.22 are rudimentary and fail to satisfy the
stringent mandated sensing requirements. Other deep-rooted shortcomings are
performance non-uniformity over different signal-to-noise-ratio regimes,
unbalanced performance, instability and lack of flexibility. Inspired by these
observations, in this paper we propose a distributed spectrum sensing technique
for WRANs, named multi-channel learning-based distributed sensing fusion
mechanism (MC-LDS). MC-LDS is demonstrated to be self-trained, stable and to
compensate for fault reports through its inherent reward-penalty approach.
Moreover, MC-LDS exhibits a better uniform performance in all traffic regimes,
is fair (reduces the false-alarm/misdetection gap), adjustable (works with
several degrees of freedom) and bandwidth efficient (opens transmission
opportunities for more CPEs). Simulation results and comparisons unanimously
corroborate that MC-LDS outperforms IEEE 802.22 recommended algorithms, i.e.,
the AND, OR and VOTING rules.


title: Parametric down-conversion photon pair source on a nanophotonic chip

abstract:
  Quantum photonic chips, which integrate quantum light sources alongside
active and passive optical elements, as well as single photon detectors, show
great potential for photonic quantum information processing and quantum
technology. Mature semiconductor nanofabrication processes allow for scaling
such photonic integrated circuits to on-chip networks of increasing complexity.
Second order nonlinear materials are the method of choice for generating
photonic quantum states in the overwhelming part of linear optic experiments
using bulk components but integration with waveguide circuitry on a
nanophotonic chip proved to be challenging. Here we demonstrate such an on-chip
parametric down-conversion source of photon pairs based on second order
nonlinearity in an Aluminum nitride microring resonator. We show the potential
of our source for quantum information processing by measuring high-visibility
antibunching of heralded single photons with nearly ideal state purity. Our
down conversion source operates with high brightness and low noise, yielding
pairs of correlated photons at MHz-rates with high coincidence-to-accidental
ratio. The generated photon pairs are spectrally far separated from the pump
field, providing good potential for realizing sufficient on-chip filtering and
monolithic integration of quantum light sources, waveguide circuits and single
photon detectors.


title: Session Types in a Linearly Typed Multi-Threaded Lambda-Calculus

abstract:
  We present a formalization of session types in a multi-threaded
lambda-calculus (MTLC) equipped with a linear type system, establishing for the
MTLC both type preservation and global progress. The latter (global progress)
implies that the evaluation of a well-typed program in the MTLC can never reach
a deadlock. As this formulated MTLC can be readily embedded into ATS, a
full-fledged language with a functional programming core that supports both
dependent types (of DML-style) and linear types, we obtain a direct
implementation of session types in ATS. In addition, we gain immediate support
for a form of dependent session types based on this embedding into ATS.
Compared to various existing formalizations of session types, we see the one
given in this paper is unique in its closeness to concrete implementation. In
particular, we report such an implementation ready for practical use that
generates Erlang code from well-typed ATS source (making use of session types),
thus taking great advantage of the infrastructural support for distributed
computing in Erlang.


title:
Some numerical computations on Reidemeister torsion for homology
  3-spheres obtained by Dehn surgeries along the figure-eight knot

abstract:
  We show some computations on representations of the fundamental group in
SL(2;C) and Reidemeister torsion for a homology 3-sphere obtained by Dehn
surgery along the figure-eight knot. This is the second version. We recorrected
several errors in the first version.


title: Penta and Hexa Valued Representation of Neutrosophic Information

abstract:
  Starting from the primary representation of neutrosophic information, namely
the degree of truth, degree of indeterminacy and degree of falsity, we define a
nuanced representation in a penta valued fuzzy space, described by the index of
truth, index of falsity, index of ignorance, index of contradiction and index
of hesitation. Also, it was constructed an associated penta valued logic and
then using this logic, it was defined for the proposed penta valued structure
the following operators: union, intersection, negation, complement and dual.
Then, the penta valued representation is extended to a hexa valued one, adding
the sixth component, namely the index of ambiguity.


title: Frame-Covariant Formulation of Inflation in Scalar-Curvature Theories

abstract:
  We develop a frame-covariant formulation of inflation in the slow-roll
approximation by generalizing the inflationary attractor solution for
scalar-curvature theories. Our formulation gives rise to new generalized forms
for the potential slow-roll parameters, which enable us to examine the effect
of conformal transformations and inflaton reparameterizations in
scalar-curvature theories. We find that cosmological observables, such as the
power spectrum, the spectral indices and their runnings, can be expressed in a
concise manner in terms of the generalized potential slow-roll parameters which
depend on the scalar-curvature coupling function, the inflaton wavefunction,
and the inflaton potential. We show how the cosmological observables of
inflation are frame-invariant in this generalized potential slow-roll
formalism, as long as the end-of-inflation condition is appropriately extended
to become frame-invariant as well. We then apply our formalism to specific
scenarios, such as the induced gravity inflation, Higgs inflation and $F(R)$
models of inflation, and obtain more accurate results, without making
additional approximations to the potential. Our results are shown to be
consistent to lowest order with those presented in the literature. Finally, we
outline how our frame-covariant formalism can be naturally extended beyond the
tree-level approximation, within the framework of the Vilkovisky--DeWitt
effective action.


title:
The VLA view of the HL Tau Disk - Disk Mass, Grain Evolution, and Early
  Planet Formation

abstract:
  The first long-baseline ALMA campaign resolved the disk around the young star
HL Tau into a number of axisymmetric bright and dark rings. Despite the very
young age of HL Tau these structures have been interpreted as signatures for
the presence of (proto)planets. The ALMA images triggered numerous theoretical
studies based on disk-planet interactions, magnetically driven disk structures,
and grain evolution. Of special interest are the inner parts of disks, where
terrestrial planets are expected to form. However, the emission from these
regions in HL Tau turned out to be optically thick at all ALMA wavelengths,
preventing the derivation of surface density profiles and grain size
distributions. Here, we present the most sensitive images of HL Tau obtained to
date with the Karl G. Jansky Very Large Array at 7.0 mm wavelength with a
spatial resolution comparable to the ALMA images. At this long wavelength the
dust emission from HL Tau is optically thin, allowing a comprehensive study of
the inner disk. We obtain a total disk dust mass of 0.001 - 0.003 Msun,
depending on the assumed opacity and disk temperature. Our optically thin data
also indicate fast grain growth, fragmentation, and formation of dense clumps
in the inner densest parts of the disk. Our results suggest that the HL Tau
disk may be actually in a very early stage of planetary formation, with planets
not already formed in the gaps but in the process of future formation in the
bright rings.


title:
Smart Context-aware Rejuvenation of Engagement on Urban Ambient
  Augmented Things

abstract:
  The concern over global urbanization trend imposes smart-city as enabling
information and communication technology (ICT) to improve urban governance.
However, the light trance on better living space is stimulated by socioeconomic
impact of escalated senior generation. Hence, ambient assisted living (AAL)
emerges for the autonomous provisioning of pervasive things or objects from
relevant perturbation for advanced scientific instrumentation. Meanwhile,
citizens are observed in being transfixed by lively stimuli of monotonous urban
events with the advent of virtual reality or augmented things. Thus, due to the
involvement of situation-awareness or contextualization,
engagement/participation information as a utility promises to improve urban
experience. However, it is complex to grapple meaningful concepts due to
personalization obstacles, such as citizen psychology, information gap,
service-visualization. Moreover, recommended practices deficit adaptation to
monochromatic choice, disparate impairments, mobility and annotation-richness
in urban space. Hence, rejuvenation of engagement relates to monitoring and
quantification of 'service consumption and graceful degradation' of experience.
However, paramount challenges are imposed on this stipulation, such as,
unobservability, independence and composite relationship of contexts.
Therefore, a parametric Bayesian based model is envisioned to address
observability and scalability of contexts and its conjugal relationship with
engagement. Last but not the least, systematic framework is demonstrated, which
pinpoints key goals of context-aware engagement from participants' opinions,
usages and feed-backs.


title:
Mutual Conditional Independence and its Applications to Inference in
  Markov Networks

abstract:
  The fundamental concepts underlying in Markov networks are the conditional
independence and the set of rules called Markov properties that translates
conditional independence constraints into graphs. In this article we introduce
the concept of mutual conditional independence relationship among elements of
an independent set of a Markov network. We first prove that the mutual
conditional independence property holds within the elements of a maximal
independent set afterwards we prove equivalence between the set of mutual
conditional independence relations encoded by all the maximal independent sets
and the three Markov properties(pair-wise, local and the global) under certain
regularity conditions. The proof employs diverse methods involving graphoid
axioms, factorization of the joint probability density functions and the graph
theory. We present inference methods for decomposable and non-decomposable
graphical models exploiting newly revealed mutual conditional independence
property.


title: Internal Model Based Active Disturbance Rejection Control

abstract:
  The basic active disturbance rejection control (BADRC) algorithm with only
one order higher extended state observer (ESO) proves to be robust to both
internal and external disturbances. An advantage of BADRC is that in many
applications it can achieve high disturbance attenuation level without
requiring a detailed model of the plant or disturbance. However, this can be
regarded as a disadvantage when the disturbance characteristic is known since
the BADRC algorithm cannot exploit such information. This paper proposes an
internal model based ADRC (IADRC) method, which can take advantage of knowing
disturbance characteristic to achieve perfect estimation of the disturbance
under some mild assumptions. The effectiveness of the proposed method is
validated by comprehensive simulations and comparisons with the BADRC
algorithm.


title: Faraday cage angled-etching of nanostructures in bulk dielectrics

abstract:
  For many emerging optoelectronic materials, heteroepitaxial growth techniques
do not offer the same high material quality afforded by bulk, single-crystal
growth. However, the need for optical, electrical, or mechanical isolation at
the nanoscale level often necessitates the use of a dissimilar substrate, upon
which the active device layer stands. Faraday cage angled-etching (FCAE)
obviates the need for these planar, thin-film technologies by enabling in-situ
device release and isolation through an angled-etching process. By placing a
Faraday cage around the sample during inductively-coupled plasma reactive ion
etching (ICP-RIE), the etching plasma develops an equipotential at the cage
surface, directing ions normal to its face. In this Article, the effects
Faraday cage angle, mesh size, and sample placement have on etch angle,
uniformity, and mask selectivity are investigated within a silicon etching
platform. Simulation results qualitatively confirm experiments and help to
clarify the physical mechanisms at work. These results will help guide FCAE
process design across a wide range of material platforms.


title: Magnon-drag thermopower and Nernst coefficient in Fe, Co, and Ni

abstract:
  Magnon-drag is shown to dominate the thermopower of elemental Fe from 2 to 80
K and of elemental Co from 150 to 600 K; it is also shown to contribute to the
thermopower of elemental Ni from 50 to 500 K. Two theoretical models are
presented for magnon-drag thermopower. One is a hydrodynamic theory based
purely on non-relativistic, Galilean, spin-preserving electron-magnon
scattering. The second is based on spin-motive forces, where the thermopower
results from the electric current pumped by the dynamic magnetization
associated with a magnon heat flux. In spite of their very different
microscopic origins, the two give similar predictions for pure metals at low
temperature, allowing us to semi-quantitatively explain the observed
thermopower of elemental Fe and Co without adjustable parameters. We also find
that magnon-drag may contribute to the thermopower of Ni. A spin-mixing model
is presented that describes the magnon-drag contribution to the Anomalous
Nernst Effect in Fe, again enabling a semi-quantitative match to the
experimental data without fitting parameters. Our work suggests that particle
non-conserving processes may play an important role in other types of drag
phenomena, and also gives a predicative theory for improving metals as
thermoelectric materials.


title: A Hukuhara approach to the study of hybrid fuzzy systems on time scales

abstract:
  We introduce a new approach to study the practical stability of hybrid fuzzy
systems on time scales in the Lyapunov sense. Our method is based on the
delta-Hukuhara derivative for fuzzy valued functions and allow us to obtain new
interesting stability criteria. We also show the validity of the results of [M.
Sambandham: Hybrid fuzzy systems on time scales, Dynam. Systems Appl. 12
(2003), no. 1-2, 217-227], by embedding the space of all fuzzy subsets into a
suitable Banach space.


title:
Four new planets around giant stars and the mass-metallicity correlation
  of planet-hosting stars

abstract:
  CONTEXT. Exoplanet searches have demonstrated that giant planets are
preferentially found around metal-rich stars and that their fraction increases
with the stellar mass. AIMS. During the past six years, we have conducted a
radial velocity follow-up program of 166 giant stars, to detect substellar
companions, and characterizing their orbital properties. Using this
information, we aim to study the role of the stellar evolution in the orbital
parameters of the companions, and to unveil possible correlations between the
stellar properties and the occurrence rate of giant planets. METHODS. Using
FEROS and CHIRON spectra, we have computed precision radial velocities and we
have derived atmospheric and physical parameters for all of our targets.
Additionally, velocities computed from UCLES spectra are presented here. By
studying the periodic radial velocity signals, we have detected the presence of
several substellar companions. RESULTS. We present four new planetary systems
around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally,
we find that giant planets are more frequent around metal-rich stars, reaching
a peak in the detection of $f$ = 16.7$^{+15.5}_{-5.9}$% around stars with
[Fe/H] $\sim$ 0.35 dex. Similarly, we observe a positive correlation of the
planet occurrence rate with the stellar mass, between M$_\star$ $\sim$ 1.0 -2.1
M$_\odot$, with a maximum of $f$ = 13.0$^{+10.1}_{-4.2}$%, at M$_\star$ = 2.1
M$_\odot$. CONCLUSIONS. We conclude that giant planets are preferentially
formed around metal-rich stars. Also, we conclude that they are more
efficiently formed around more massive stars, in the mass range of M$_\star$
$\sim$ 1.0 - 2.1 M$_\odot$. These observational results confirm previous
findings for solar-type and post-MS hosting stars, and provide further support
to the core-accretion formation model.


title:
High Tc via spin fluctuations from incipient bands: application to
  monolayers and intercalates of FeSe

abstract:
  We investigate superconductivity in a two-band system with an electron- and
hole-like band, where one of the bands is away from the Fermi level (or
incipient). We argue that the incipient band contributes significantly to
spin-fluctuation pairing in the strong coupling limit where the system is close
to a magnetic instability, and can lead to a large Tc. In this case, Tc is
limited by a competition between the frequency range of the coupling (set by an
isolated paramagnon) and the coupling strength itself, such that a dome-like Tc
dependence on the incipient band position is obtained. The coupling of
electrons to phonons is found to further enhance Tc. The results are discussed
in the context of experiments on monolayers and intercalates of FeSe.


title:
Raman scattering and anomalous Stokes anti-Stokes ratio in MoTe2 atomic
  layers

abstract:
  Stokes and anti-Stokes Raman scattering are performed on atomic layers of
hexagonal molybdenum ditelluride (MoTe2), a prototypical transition metal
dichalcogenide (TMDC) semiconductor. The data reveal all six types of zone
center optical phonons, along with their corresponding Davydov splittings,
which have been challenging to see in other TMDCs. We discover that the
anti-Stokes Raman intensity of the low energy layer-breathing mode becomes more
intense than the Stokes peak under certain experimental conditions, and find
the effect to be tunable by excitation frequency and number of atomic layers.
These observations are interpreted as a result of resonance effects arising
from the C excitons in the vicinity of the Brillouin zone center in the
photon-electron-phonon interaction process.


title: Nontrivial nuciferous graphs exist

abstract:
  A nuciferous graph is a simple graph with a non-singular $0$-$1$ adjacency
matrix $A$ such that all the diagonal entries of $A^{-1}$ are zero and all the
off-diagonal entries of $A^{-1}$ are non-zero. Sciriha et al. conjectured that
except $K_2$, no nuciferous graph exists. We disprove this conjecture.
Moreover, we conjecture that there infinitely many nuciferous Cayley graphs.


title: Robust concurrent remote entanglement between two superconducting qubits

abstract:
  Entangling two remote quantum systems which never interact directly is an
essential primitive in quantum information science and forms the basis for the
modular architecture of quantum computing. When protocols to generate these
remote entangled pairs rely on using traveling single photon states as carriers
of quantum information, they can be made robust to photon losses, unlike
schemes that rely on continuous variable states. However, efficiently detecting
single photons is challenging in the domain of superconducting quantum circuits
because of the low energy of microwave quanta. Here, we report the realization
of a robust form of concurrent remote entanglement based on a novel microwave
photon detector implemented in the superconducting circuit quantum
electrodynamics (cQED) platform of quantum information. Remote entangled pairs
with a fidelity of $0.57\pm0.01$ are generated at $200$ Hz. Our experiment
opens the way for the implementation of the modular architecture of quantum
computation with superconducting qubits.


title:
Time-dependent density functional theory with twist-averaged boundary
  conditions

abstract:
  Time-dependent density functional theory is widely used to describe
excitations of many-fermion systems. In its many applications, 3D
coordinate-space representation is used, and infinite-domain calculations are
limited to a finite volume represented by a box. For finite quantum systems
(atoms, molecules, nuclei), the commonly used periodic or reflecting boundary
conditions introduce spurious quantization of the continuum states and
artificial reflections from boundary; hence, an incorrect treatment of
evaporated particles. These artifacts can be practically cured by introducing
absorbing boundary conditions (ABC) through an absorbing potential in a certain
boundary region sufficiently far from the described system. But also the
calculations of infinite matter (crystal electrons, quantum fluids, neutron
star crust) suffer artifacts from a finite computational box. In this regime,
twist- averaged boundary conditions (TABC) have been used successfully to
diminish the finite-volume effects. In this work, we extend TABC to
time-dependent framework and apply it to resolve the box artifacts for finite
quantum systems using as test case small- and large-amplitude nuclear
vibrations. We demonstrate that by using such a method, one can reduce finite
volume effects drastically without adding any additional parameters. While they
are almost equivalent in the linear regime, TABC and ABC differ in the
nonlinear regime in their treatment of evaporated particles.


title: Transverse Mode Coupling Instability with Space Charge

abstract:
  Transverse mode coupling instability of a bunch with space charge and wake
field is considered in frameworks of the boxcar model. Eigenfunctions of the
bunch without wake are used as the basis for solution of the equations with the
wake field included. Dispersion equation for the bunch eigentunes is obtained
in the form of an infinite continued fraction. It is shown that influence of
space charge on the instability essentially depends on the wake sign. In
particular, threshold of the negative wake increases in absolute value until
the space charge tune shift is rather small, and goes to zero at higher space
charge. The explanation of this behavior is developed by analysis of the bunch
spectrum. A comparison of the results with published articles is represented.


title:
Orbital stability of solitary waves for derivative nonlinear
  Schr\"odinger equation

abstract:
  In this paper, we show the orbital stability of solitons arising in the cubic
derivative nonlinear Schrodinger equations. We consider the zero mass case that
is not covered by earlier works [8, 3]. As this case enjoys L^2 scaling
invariance, we expect the orbital stability in the sense up to scaling
symmetry, in addition to spatial and phase translations. For the proof, we are
based on the variational argument and extend a similar argument in [21].
Moreover, we also show a self-similar type blow up criteria of solutions with
the critical mass 4{\pi}.


title:
Unified Homogenization of Photonic/Phononic Crystals: Controllable
  First-band Negative Refraction

abstract:
  It is shown, for the first time, that negative refraction with positive phase
velocity refraction can be realized (and controlled) over a wide range of
frequency on the first (lowest) pass band of simple photonic and phononic
crystals. First a unified approach is presented to accurately, efficiently, and
uniquely produce the homogenized effective material properties of doubly
periodic phononic crystals for anti-plane shear (SH) and photonic crystals for
transverse electric (TE) and transverse magnetic (TM) electromagnetic
Bloch-form waves in such a manner that they exactly reproduce the band
structure of the composite over any desired frequency band. Then the
correspondence between phononic and photonic field equations is established and
their effective homogenized material parameters are calculated. Finally
illustrative examples are worked out for each case, revealing a rich body of
refractive characteristics of these crystals, and showing by means of these
examples that the homogenized effective parameters do yield the exact results,
and that the resulting homogenized medium does in fact embody exactly the
actual band structure and dispersive properties of the considered
phononic/photonic crystal. As a consequence when the homogenized medium is
placed in contact with a normal homogeneous half-space, it could display, even
on the first pass band, positive, negative, or even no energy refraction
depending on the frequency and wave vector of plane waves incident from the
normal homogeneous solid to the interface.


title:
Discrete-Time Quadratic Hedging of Barrier Options in Exponential
  L\'{e}vy Model

abstract:
  We examine optimal quadratic hedging of barrier options in a discretely
sampled exponential L\'{e}vy model that has been realistically calibrated to
reflect the leptokurtic nature of equity returns. Our main finding is that the
impact of hedging errors on prices is several times higher than the impact of
other pricing biases studied in the literature.


title:
Structural phase transition and material properties of few-layer
  monochalcogenides

abstract:
  GeSe and SnSe monochalcogenide monolayers and bilayers undergo a
two-dimensional phase transition from a rectangular unit cell to a square unit
cell at a temperature $T_c$ well below the melting point. Its consequences on
material properties are studied within the framework of Car-Parrinello
molecular dynamics and density-functional theory. No in-gap states develop as
the structural transition takes place, so that these phase-change materials
remain semiconducting below and above $T_c$. As the in-plane lattice transforms
from a rectangle onto a square at $T_c$, the electronic, spin, optical, and
piezo-electric properties dramatically depart from earlier predictions. Indeed,
the $Y-$ and $X-$points in the Brillouin zone become effectively equivalent at
$T_c$, leading to a symmetric electronic structure. The spin polarization at
the conduction valley edge vanishes, and the hole conductivity must display an
anomalous thermal increase at $T_c$. The linear optical absorption band edge
must change its polarization as well, making this structural and electronic
evolution verifiable by optical means. Much excitement has been drawn by
theoretical predictions of giant piezo-electricity and ferroelectricity in
these materials, and we estimate a pyroelectric response of about $3\times
10^{-12}$ $C/K m$ here. These results uncover the fundamental role of
temperature as a control knob for the physical properties of few-layer group-IV
monochalcogenides


title: Black hole nonmodal linear stability: the Schwarzschild (A)dS cases

abstract:
  The nonmodal linear stability of the Schwarzschild black hole established in
Phys. Rev. Lett. 112 (2014) 191101 is generalized to the case of a nonnegative
cosmological constant $\Lambda$. Two gauge invariant combinations $G_{\pm}$ of
perturbed scalars made out of the Weyl tensor and its first covariant
derivative are found such that the map $[h_{\alpha \beta}] \to \left( G_-
\left([h_{\alpha \beta}] \right), G_+ \left([h_{\alpha \beta}] \right) \right)$
with domain the set of equivalent classes $[h_{\alpha \beta}]$ under gauge
transformations of solutions of the linearized Einstein's equation, is
invertible. The way to reconstruct a representative of $[h_{\alpha \beta}]$ in
terms of $(G_-,G_+)$ is given. It is proved that, for an arbitrary perturbation
consistent with the background asymptote, $G_+$ and $G_-$ are bounded in the
the outer static region. At large times, the perturbation decays leaving a
linearized Kerr black hole around the Schwarzschild or Schwarschild de Sitter
background solution. For negative cosmological constant it is shown that there
is a choice of boundary conditions at the time-like boundary under which the
Schwarzschild anti de Sitter black hole is unstable. The root of
Chandrasekhar's duality relating odd and even modes is exhibited, and some
technicalities related to this duality and omitted in the original proof of the
$\Lambda=0$ case are explained in detail.