title:
Empirical Study of DSRC Performance Based on Safety Pilot Model
  Deployment Data

abstract:
  Dedicated Short Range Communication (DSRC) was designed to provide reliable
wireless communication for intelligent transportation system applications.
Sharing information among cars and between cars and the infrastructure,
pedestrians, or "the cloud" has great potential to improve safety, mobility and
fuel economy. DSRC is being considered by the US Department of Transportation
to be required for ground vehicles. In the past, their performance has been
assessed thoroughly in the labs and limited field testing, but not on a large
fleet. In this paper, we present the analysis of DSRC performance using data
from the world's largest connected vehicle test program - Safety Pilot Model
Deployment lead by the University of Michigan. We first investigate their
maximum and effective range, and then study the effect of environmental
factors, such as trees/foliage, weather, buildings, vehicle travel direction,
and road elevation. The results can be used to guide future DSRC equipment
placement and installation, and can be used to develop DSRC communication
models for numerical simulations.


title:
Exploiting the Short-term to Long-term Plasticity Transition in
  Memristive Nanodevice Learning Architectures

abstract:
  Memristive nanodevices offer new frontiers for computing systems that unite
arithmetic and memory operations on-chip. Here, we explore the integration of
electrochemical metallization cell (ECM) nanodevices with tunable filamentary
switching in nanoscale learning systems. Such devices offer a natural
transition between short-term plasticity (STP) and long-term plasticity (LTP).
In this work, we show that this property can be exploited to efficiently solve
noisy classification tasks. A single crossbar learning scheme is first
introduced and evaluated. Perfect classification is possible only for simple
input patterns, within critical timing parameters, and when device variability
is weak. To overcome these limitations, a dual-crossbar learning system partly
inspired by the extreme learning machine (ELM) approach is then introduced.
This approach outperforms a conventional ELM-inspired system when the first
layer is imprinted before training and testing, and especially so when
variability in device timing evolution is considered: variability is therefore
transformed from an issue to a feature. In attempting to classify the MNIST
database under the same conditions, conventional ELM obtains 84%
classification, the imprinted, uniform device system obtains 88%
classification, and the imprinted, variable device system reaches 92%
classification. We discuss benefits and drawbacks of both systems in terms of
energy, complexity, area imprint, and speed. All these results highlight that
tuning and exploiting intrinsic device timing parameters may be of central
interest to future bio-inspired approximate computing systems.


title:
Beamforming Design for Full-Duplex Two-Way Amplify-and-Forward MIMO
  Relay

abstract:
  We consider the full-duplex (FD) two-way amplify-and-forward relay system
with imperfect cancelation of loopback self-interference (SI) and investigate
joint design of relay and receive beamforming for minimizing the mean square
error under a relay transmit power constraint. Due to loopback channel
estimation error and limitation of analog-to-digital converter, the loopback SI
cannot be completely canceled. Multiple antennas at the relay can help loopback
SI suppression but beamforming is required to balance between the residual SI
suppression and the desired signal transmission. Moreover, the relay
beamforming matrix should be updated every time slot because the residual SI in
the previous time slot is amplified by the current beamforming matrix and added
to the received signals from the two sources in the current time slot. We
derive the optimally balanced relay beamforming and receive beamforming
matrices in closed form based on minimum mean square error, taking into account
the propagation of the residual loopback SI from the first to the current time
slot. We also propose beamforming design using only the channels of the m
latest time slots, not from the first time slot. Based on our numerical
results, we also identify when FD is beneficial and propose selection between
FD and half-duplex according to signal-to-noise ratio and interference-to-noise
ratio.


title:
No-go theorem for the characterisation of work fluctuations in coherent
  quantum systems

abstract:
  An open question of fundamental importance in thermodynamics is how to
describe the fluctuations of work for quantum coherent processes. In the
standard approach, based on a projective energy measurement both at the
beginning and at the end of the process, the first measurement destroys any
initial coherence in the energy basis. Here we seek for extensions of this
approach which can possibly account for initially coherent states. We consider
all measurement schemes to estimate work and require that (i) the difference of
average energy corresponds to average work for closed quantum systems, and that
(ii) the work statistics agree with the standard two-measurement scheme for
states with no coherence in the energy basis. We first show that such a scheme
cannot exist. Next, we consider the possibility of performing collective
measurements on several copies of the state and prove that it is still
impossible to satisfy simultaneously requirements (i) and (ii). Nevertheless,
improvements do appear, and in particular we develop a measurement scheme which
acts simultaneously on two copies of the state and allows to describe a whole
class of coherent transformations.


title: On $p$--extended Mathieu series

abstract:
  Motivated by several generalizations of the well--known Mathieu series, the
main object of this paper is to introduce new extension of generalized Mathieu
series and to derive various integral representations of such series. Finally
master bounding inequality is established using the newly derived integral
expression.


title: The right time to learn: mechanisms and optimization of spaced learning

abstract:
  For many types of learning, spaced training that involves repeated long
inter-trial intervals (ITIs) leads to more robust memory formation than does
massed training that involves short or no intervals. Several cognitive theories
have been proposed to explain this superiority, but only recently has data
begun to delineate the underlying cellular and molecular mechanisms of spaced
training. We review these theories and data here. Computational models of the
implicated signaling cascades have predicted that spaced training with
irregular ITIs can enhance learning. This strategy of using models to predict
optimal spaced training protocols, combined with pharmacotherapy, suggests
novel ways to rescue impaired synaptic plasticity and learning.


title:
Many-body eigenstate thermalization from one-body quantum chaos:
  emergent arrow of time

abstract:
  A profound quest of statistical mechanics is the origin of irreversibility -
the arrow of time. New stimulants have been provided, thanks to unprecedented
degree of control reached in experiments with isolated quantum systems and
rapid theoretical developments of manybody localization in disordered
interacting systems. The proposal of (many-body) eigenstate thermalization (ET)
for these systems reinforces the common belief that either interaction or
extrinsic randomness is required for thermalization. Here, we unveil a quantum
thermalization mechanism challenging this belief. We find that, provided
one-body quantum chaos is present, as a pure many-body state evolves the arrow
of time can emerge, even without interaction or randomness. In times much
larger than the Ehrenfest time that signals the breakdown of quantum-classical
correspondence, quantum chaotic motion leads to thermal [Fermi-Dirac (FD) or
Bose-Einstein (BE)] distributions and thermodynamics in individual eigenstates.
Our findings lay dynamical foundation of statistical mechanics and
thermodynamics of isolated quantum systems.


title:
Relativistic persistent currents in ideal Aharonov-Bohm rings and
  cylinders

abstract:
  The exact solutions of the complete (1+3)-dimensional Dirac equation of
fermions moving in ideal Aharonov-Bohm (AB) rings and cylinders are used for
deriving the exact expressions of the relativistic partial currents. It is
shown that these currents can be related to the derivative of the fermion
energy with respect to the flux parameter, just as in the non-relativistic
case. However, a new and remarkable relativistic effect is the saturation of
the partial currents for high values of the total angular momentum. Based on
this property, the total relativistic persistent currents at $T=0$ is evaluated
for rings and cylinders obtaining approximative simple closed formulas.


title: Which ergodic averages have finite asymptotic variance?

abstract:
  We show that the class of $L^2$ functions for which ergodic averages of a
reversible Markov chain have finite asymptotic variance is determined by the
class of $L^2$ functions for which ergodic averages of its associated jump
chain have finite asymptotic variance. This allows us to characterize
completely which ergodic averages have finite asymptotic variance when the
Markov chain is an independence sampler. In addition, we obtain a simple
sufficient condition for all ergodic averages of $L^2$ functions of the primary
variable in a pseudo-marginal Markov chain to have finite asymptotic variance.


title:
Limiting Equivalence Principle Violation and Long-Range Baryonic Force
  from Neutron-Antineutron Oscillation

abstract:
  We point out that if the baryon number violating neutron-antineutron
oscillation is discovered, it would impose strong limits on the departure from
Einstein's equivalence principle at a level of one part in $10^{19}$. If this
departure owes its origin to the existence of long-range forces coupled to
baryon number $B$ (or $B-L$), it would imply very stringent constraints on the
strength of gauge bosons coupling to baryon number current. For instance, if
the force mediating baryon number has strength $\alpha_B$ and its range is
larger than a megaparsec, we find the limit to be $\alpha_B \leq 2\times
10^{-57}$, which is much stronger than all other existing bounds. For smaller
range for the force, we get slightly weaker, but still stringent bounds by
considering the potential of the Earth and the Sun.


title:
Two-dimensional distributed-phase-reference protocol for quantum key
  distribution

abstract:
  Quantum key distribution (QKD) and quantum communication enable the secure
exchange of information between remote parties. Currently, the
distributed-phase-reference (DPR) protocols, which are based on weak coherent
pulses, are among the most practical solutions for long-range QKD. During the
last 10 years, long-distance fiber-based DPR systems have been successfully
demonstrated, although fundamental obstacles such as intrinsic channel losses
limit their performance. Here, we introduce the first two-dimensional DPR-QKD
protocol in which information is encoded in the time and phase of weak coherent
pulses. The ability of extracting two bits of information per detection event,
enables a higher secret key rate in specific realistic network scenarios.
Moreover, despite the use of more dimensions, the proposed protocol remains
simple, practical, and fully integrable.


title:
Determining parameters of Moon's orbital and rotational motion from LLR
  observations using GRAIL and IERS-recommended models

abstract:
  The aim of this work is to combine the model of orbital and rotational motion
of the Moon developed for DE430 with up-to-date astronomical, geodynamical, and
geo- and selenophysical models. The parameters of the orbit and physical
libration are determined in this work from LLR observations made at different
observatories in 1970-2013. Parameters of other models are taken from solutions
that were obtained independently from LLR.
  A new implementation of the DE430 lunar model, including the liquid core
equations, was done within the EPM ephemeris. The postfit residuals of LLR
observations make evident that the terrestrial models and solutions recommended
by the IERS Conventions are compatible with the lunar theory. That includes:
EGM2008 with conventional corrections and variations from solid and ocean
tides; displacement of stations due to solid and ocean loading tides; and
precession-nutation model. Usage of these models in the solution for LLR
observations has allowed us to reduce the number of parameters to be fit. The
fixed model of tidal variations of the geopotential has resulted in a lesser
value of Moon's extra eccentricity rate, as compared to the original DE430
model with two fit parameters.
  A mixed model of lunar gravitational potential was used, with some
coefficients determined from LLR observations, and other taken from the GL660b
solution.
  Solutions obtain accurate positions for the ranging stations and the 5
retroreflectors. Station motion is derived for sites with long data spans.
Dissipation is detected at the lunar fluid core-solid mantle boundary
demonstrating that a fluid core is present. Tidal dissipation is strong at both
Earth and Moon. Consequently, the lunar semimajor axis is expanding by 38.20
mm/yr, the tidal acceleration in mean longitude is -25.90 "/cy2, and the
eccentricity is increasing by 1.48e-11 each year.


title:
Characterization of Methicillin-resistant Staphylococcus aureus Isolates
  from Fitness Centers in Memphis Metropolitan Area, USA

abstract:
  Indoor skin-contact surfaces of public fitness centers may serve as
reservoirs of potential human transmission of methicillin-resistant
Staphylococcus aureus (MRSA). We found a high prevalence of multi-drug
resistant (MDR)-MRSA of CC59 lineage harboring a variety of extracellular toxin
genes from surface swab samples collected from inanimate surfaces of fitness
centers in Memphis metropolitan area, USA. Our findings underscore the role of
inanimate surfaces as potential sources of transmission of MDR-MRSA strains
with considerable genetic diversity.


title: Mitigating Data Exfiltration in Storage-as-a-Service Clouds

abstract:
  Existing processes and methods for incident handling are geared towards
infrastructures and operational models that will be increasingly outdated by
cloud computing. Research has shown that to adapt incident handling to cloud
computing environments, cloud customers must establish clarity about their
requirements on Cloud Service Providers (CSPs) for successful handling of
incidents and contract CSPs accordingly. Secondly, CSPs must strive to support
these requirements and mirror them in their Service Level Agreements. Intrusion
Detection Systems (IDS) have been used widely to detect malicious behaviors in
network communication and hosts. Facing new application scenarios in Cloud
Computing, the IDS approaches yield several problems since the operator of the
IDS should be the user, not the administrator of the Cloud infrastructure.
Cloud providers need to enable possibilities to deploy and configure IDS for
the user - which poses its own challenges. Current research and commercial
solutions primarily focus on protecting against Denial of Service attacks and
attacks against the Cloud's virtual infrastructure. To counter these
challenges, we propose a capability that aims to both detect and prevent the
potential of data exfiltration by using a novel deception-based methodology. We
also introduce a method of increasing the data protection level based on
various threat conditions.


title: Differential bundles and fibrations for tangent categories

abstract:
  Tangent categories are categories equipped with a tangent functor: an
endofunctor with certain natural transformations which make it behave like the
tangent bundle functor on the category of smooth manifolds. They provide an
abstract setting for differential geometry by axiomatizing key aspects of the
subject which allow the basic theory of these geometric settings to be
captured. Importantly, they have models not only in classical differential
geometry and its extensions, but also in algebraic geometry, combinatorics,
computer science, and physics.
  This paper develops the theory of "differential bundles" for such categories,
considers their relation to "differential objects", and develops the theory of
fibrations of tangent categories. Differential bundles generalize the notion of
smooth vector bundles in classical differential geometry. However, the
definition departs from the standard one in several significant ways: in
general, there is no scalar multiplication in the fibres of these bundles, and
in general these bundles need not be locally trivial.
  To understand how these differential bundles relate to differential objects,
which are the generalization of vector spaces in smooth manifolds, requires
some careful handling of the behaviour of pullbacks with respect to the tangent
functor. This is captured by "transverse" and "display" systems for tangent
categories, which leads one into the fibrational theory of tangent categories.
A key example of a tangent fibration is provided by the "display" differential
bundles of a tangent category with a display system. Strikingly, in such
examples the fibres are Cartesian differential categories demonstrating a --
not unexpected -- tight connection between the theory of these categories and
that of tangent categories.


title: Cosmological and astrophysical constraints on tachyon dark energy models

abstract:
  Rolling tachyon field models are among the candidates suggested as
explanations for the recent acceleration of the Universe. In these models the
field is expected to interact with gauge fields and lead to variations of the
fine-structure constant $\alpha$. Here we take advantage of recent
observational progress and use a combination of background cosmological
observations of Type Ia supernovas and astrophysical and local measurements of
$\alpha$ to improve constraints on this class of models. We show that the
constraints on $\alpha$ imply that the field dynamics must be extremely slow,
leading to a constraint of the present-day dark energy equation of state
$(1+w_0)<2.4\times10^{-7}$ at the $99.7\%$ confidence level. Therefore current
and forthcoming standard background cosmology observational probes can't
distinguish this class of models from a cosmological constant, while detections
of $\alpha$ variations could possibly do so since they would have a
characteristic redshift dependence.


title:
Pricing European and American Options under Heston Model using
  Discontinuous Galerkin Finite Elements

abstract:
  This paper deals with pricing of European and American options, when the
underlying asset price follows Heston model, via the interior penalty
discontinuous Galerkin finite element method (dGFEM). The advantages of dGFEM
space discretization with Rannacher smoothing as time integrator with nonsmooth
initial and boundary conditions are illustrated for European vanilla options,
digital call and American put options. The convection dominated Heston model
for vanishing volatility is efficiently solved utilizing the adaptive dGFEM.
For fast solution of the linear complementary problem of the American options,
a projected successive over relaxation (PSOR) method is developed with the norm
preconditioned dGFEM. We show the efficiency and accuracy of dGFEM for option
pricing by conducting comparison analysis with other methods and numerical
experiments.


title:
Tunable inductive coupling of superconducting qubits in the strongly
  nonlinear regime

abstract:
  For a variety of superconducting qubits, tunable interactions are achieved
through mutual inductive coupling to a coupler circuit containing a nonlinear
Josephson element. In this paper we derive the general interaction mediated by
such a circuit under the Born-Oppenheimer Approximation. This interaction
naturally decomposes into a classical part, with origin in the classical
circuit equations, and a quantum part, associated with the coupler's zero-point
energy. Our result is non-perturbative in the qubit-coupler coupling strengths
and in the coupler nonlinearity. This can lead to significant departures from
previous, linear theories for the inter-qubit coupling, including
non-stoquastic and many-body interactions. Our analysis provides explicit and
efficiently computable series for any term in the interaction Hamiltonian and
can be applied to any superconducting qubit type. We conclude with a numerical
investigation of our theory using a case study of two coupled flux qubits, and
in particular study the regime of validity of the Born-Oppenheimer
Approximation.


title: The twist for positroid varieties

abstract:
  The purpose of this note is to connect two maps related to certain graphs
embedded in the disc. The first is Postnikov's boundary measurement map, which
combines partition functions of matchings in the graph into a map from an
algebraic torus to an open positroid variety in a Grassmannian. The second is a
rational map from the open positroid variety to an algebraic torus, given by
certain Pl\"ucker coordinates which are expected to be a cluster in a cluster
structure.
  This paper clarifies the relationship between these two maps, which has been
ambiguous since they were introduced by Postnikov in 2001. The missing
ingredient supplied by this paper is a twist automorphism of the open positroid
variety, which takes the target of the boundary measurement map to the domain
of the (conjectural) cluster. Among other applications, this provides an
inverse to the boundary measurement map, as well as Laurent formulas for twists
of Pl\"ucker coordinates.


title: One-loop renormalization of a gravity-scalar system

abstract:
  Extending the renormalizability proposal of the physical sector of 4D
Einstein gravity, we have recently proposed renormalizability of the 3D
physical sector of gravity-matter systems. The main goal of the present work is
to conduct systematic one-loop renormalization of a gravity-matter system by
applying our foliation-based quantization scheme. In this work we explicitly
carry out renormalization of a gravity-scalar system with a Higgs-type
potential. With the fluctuation part of the scalar field gauged away, the
system becomes renormalizable through a metric field redefinition. We use
dimensional regularization throughout. One of the salient aspects of our
analysis is how the graviton propagator acquires the"mass" term. One-loop
calculations lead to renormalization of the cosmological and Newton's
constants. We discuss other implications of our results as well: time-varying
vacuum energy density and masses of the elementary particles as well as the
potential relevance of Neumann boundary condition for black hole information.


title: Plasmon enhanced optical tweezers with gold-coated black silicon

abstract:
  Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation
of nanoparticles and biomolecules at low photon flux, while femtosecond-laser
optical tweezers can probe the nonlinear optical properties of the trapped
species with applications in biological diagnostics. In order to adopt
plasmonic optical tweezers in real-world applications, it is essential to
develop large-scale fabrication processes without compromising the trapping
efficiency. Here, we develop a novel platform for continuous wave (CW) and
femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In
contrast with traditional lithographic methods, the fabrication method relies
on simple, single-step, maskless tabletop laser processing of silicon in water
that facilitates scalability. Gold-coated black silicon supports repeatable
trapping efficiencies comparable to the highest ones reported to date. From a
more fundamental aspect, a plasmon-mediated efficiency enhancement is a
resonant effect, and therefore, dependent on the wavelength of the trapping
beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping
efficiencies has evaded the literature. Here, we exploit the repeatability of
the recorded trapping efficiency, offered by the gold-coated black silicon
platform, and perform a wavelength-dependent characterization of the trapping
process, revealing the resonant character of the trapping efficiency maxima.
Gold-coated black silicon is a promising platform for large-scale parallel
trapping applications that will broaden the range of optical manipulation in
nanoengineering, biology, and the study of collective biophotonic effects.


title: Non-destructive monitoring of Bloch oscillations in an optical cavity

abstract:
  Bloch oscillations are a hallmark of coherent wave dynamics in periodic
potentials. They occur as the response of quantum mechanical particles in a
lattice if a weak force is applied. In optical lattices with their perfect
periodic structure they can be readily observed and employed as a quantum
mechanical force sensor, for example, for precise measurements of the
gravitational acceleration. However, the destructive character of the
measurement process in previous experimental implementations poses serious
limitations for the precision of such measurements. In this article we show
that the use of an optical cavity operating in the regime of strong cooperative
coupling allows one to directly monitor Bloch oscillations of a cloud of cold
atoms in the light leaking out of the cavity. Hence, with a single atomic
sample the Bloch oscillation dynamics can be mapped out, while in previous
experiments, each data point required the preparation of a new atom cloud. The
use of a cavity-based monitor should greatly improve the precision of Bloch
oscillation measurements for metrological purposes.


title:
Singular effective slip length for longitudinal flow over a dense bubble
  mattress

abstract:
  We consider the effective hydrophobicity of a periodically grooved surface
immersed in liquid, with trapped shear-free bubbles protruding between the
no-slip ridges at a $\pi/2$ contact angle. Specifically, we carry out a
singular-perturbation analysis in the limit $\epsilon\ll1$ where the bubbles
are closely spaced, finding the effective slip length (normalised by the bubble
radius) for longitudinal flow along the the ridges as
${\pi}/{\sqrt{2\epsilon}}-(12/\pi)\ln 2 + (13\pi/24)\sqrt{2\epsilon}+
o(\sqrt{\epsilon})$, the small parameter $\epsilon$ being the planform solid
fraction. The square-root divergence highlights the strong hydrophobic
character of this configuration; this leading singular term (along with the
third term) follows from a local lubrication-like analysis of the gap regions
between the bubbles, together with general matching considerations and a global
conservation relation. The $O(1)$ constant term is found by matching with a
leading-order solution in the "outer'" region, where the bubbles appear to be
touching. We find excellent agreement between our slip-length formula and a
numerical scheme recently derived using a "unified-transform" method (D.
Crowdy, IMA J. Appl. Math., 80 1902, 2015). The comparison demonstrates that
our asymptotic formula, together with the diametric "dilute-limit"
approximation (D. Crowdy, J. Fluid Mech., 791 R7, 2016), provides an elementary
analytical description for essentially arbitrary no-slip fractions.


title: Spin-flavor structure of chiral-odd GPDs in the large-N_c limit

abstract:
  We study the spin-flavor structure of the nucleon's chiral-odd generalized
parton distributions (transversity GPDs) in the large-N_c limit of QCD. In
contrast to the chiral-even case, only three combinations of the four
chiral-odd GPDs are non-zero in the leading order of the 1/N_c expansion:
E_T-bar = E_T + 2 H_T-tilde, H_T and E_T-tilde. The degeneracy is explained by
the absence of spin-orbit interactions correlating the transverse momentum
transfer with the transverse quark spin. It can also be deduced from the
natural N_c-scaling of the quark-nucleon helicity amplitudes associated with
the GPDs. In the GPD E_T-bar the flavor-singlet component u + d is leading in
the 1/N_c expansion, while in H_T and E_T-tilde it is the flavor-nonsinglet
components u - d. The large-N_c relations are consistent with the spin-flavor
structure extracted from hard exclusive pi0 and eta electroproduction data, if
it is assumed that the processes are mediated by twist-3 amplitudes involving
the chiral-odd GPDs and the chiral-odd pseudoscalar meson distribution
amplitudes.


title: Minimax theorems for convex functions

abstract:
  In this paper provide sufficient and necessary conditions for the minimax
equality for extended-valued $\Phi$-convex functions. As an application we
establish sufficient and necessary conditions for the minimax equality for
convex-concave functions.


title: Revisiting Visual Question Answering Baselines

abstract:
  Visual question answering (VQA) is an interesting learning setting for
evaluating the abilities and shortcomings of current systems for image
understanding. Many of the recently proposed VQA systems include attention or
memory mechanisms designed to support "reasoning". For multiple-choice VQA,
nearly all of these systems train a multi-class classifier on image and
question features to predict an answer. This paper questions the value of these
common practices and develops a simple alternative model based on binary
classification. Instead of treating answers as competing choices, our model
receives the answer as input and predicts whether or not an
image-question-answer triplet is correct. We evaluate our model on the Visual7W
Telling and the VQA Real Multiple Choice tasks, and find that even simple
versions of our model perform competitively. Our best model achieves
state-of-the-art performance on the Visual7W Telling task and compares
surprisingly well with the most complex systems proposed for the VQA Real
Multiple Choice task. We explore variants of the model and study its
transferability between both datasets. We also present an error analysis of our
model that suggests a key problem of current VQA systems lies in the lack of
visual grounding of concepts that occur in the questions and answers. Overall,
our results suggest that the performance of current VQA systems is not
significantly better than that of systems designed to exploit dataset biases.


title:
Search for the Higgs boson produced in association with a $W$ boson and
  decaying to four $b$-quarks via two spin-zero particles in $pp$ collisions at
  13 TeV with the ATLAS detector

abstract:
  This paper presents a dedicated search for exotic decays of the Higgs boson
to a pair of new spin-zero particles, $H \rightarrow aa$, where the particle
$a$ decays to $b$-quarks and has a mass in the range of 20-60 GeV. The search
is performed in events where the Higgs boson is produced in association with a
$W$ boson, giving rise to a signature of a lepton (electron or muon), missing
transverse momentum, and multiple jets from $b$-quark decays. The analysis is
based on the full dataset of $pp$ collisions at $\sqrt{s} = 13$ TeV recorded in
2015 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to
an integrated luminosity of 3.2 fb$^{-1}$. No significant excess of events
above the Standard Model prediction is observed, and a $95\%$ confidence-level
upper limit is derived for the product of the production cross section for $pp
\rightarrow WH$ times the branching ratio for the decay $H \rightarrow aa
\rightarrow 4b$. The upper limit ranges from 6.2 pb for an $a$-boson mass $m_a
= 20$ GeV to 1.5 pb for $m_a = 60$ GeV.


title: Driven open quantum systems and Floquet stroboscopic dynamics

abstract:
  We provide an analytic solution to the problem of system-bath dynamics under
the effect of high-frequency driving that has applications in a large class of
settings, such as driven-dissipative many-body systems. Our method relies on
discrete symmetries of the system-bath Hamiltonian and provides the time
evolution operator of the full system, including bath degrees of freedom,
without weak-coupling or Markovian assumptions. An interpretation of the
solution in terms of the strobo- scopic evolution of a family of observables
under the influence of an effective static Hamiltonian is proposed, which
constitutes a flexible simulation procedure of non-trivial Hamiltonians. We
instan- tiate the result with the study of the spin-boson model with
time-dependent tunneling amplitude. We analyze the class of Hamiltonians that
may be stroboscopically accessed for this example and illustrate the dynamics
of system and bath degrees of freedom.


title: Location of the Adsorption Transition for Lattice Polymers

abstract:
  We consider various lattice models of polymers: lattice trees, lattice
animals, and self-avoiding walks. The polymer interacts with a surface
(hyperplane), receiving a unit energy reward for each site in the surface.
There is an adsorption transition of the polymer at a critical value of
$\beta$, the inverse temperature. We present a new proof of the result of
Hammersley, Torrie, and Whittington (1982) that the transition occurs at a
strictly positive value of $\beta$ when the surface is impenetrable, i.e. when
the polymer is restricted to a half-space. In contrast, for a penetrable
surface, it is an open problem to prove that the transition occurs at $\beta=0$
(i.e., infinite temperature). We reduce this problem to showing that the
fraction of N-site polymers whose span is less than $N/\log^2 N$ is not too
small.


title:
Finite-key analysis for time-energy high-dimensional quantum key
  distribution

abstract:
  Time-energy high-dimensional quantum key distribution (HD-QKD) leverages the
high-dimensional nature of time-energy entangled biphotons and the loss
tolerance of single-photon detection to achieve long-distance key distribution
with high photon information efficiency. To date, the general-attack security
of HD-QKD has only been proven in the asymptotic regime, while HD-QKD's
finite-key security has only been established for a limited set of attacks.
Here we fill this gap by providing a rigorous HD-QKD security proof for general
attacks in the finite-key regime. Our proof relies on a novel entropic
uncertainty relation that we derive for time and conjugate-time measurements
using dispersive optics, and our analysis includes an efficient decoy-state
protocol in its parameter estimation. We present numerically-evaluated
secret-key rates illustrating the feasibility of secure and composable HD-QKD
over metropolitan-area distances when the system is subjected to the most
powerful eavesdropping attack.


title: Polynomial Form of the Matrix Exponential

abstract:
  An algorithm for numerically computing the exponential of a matrix is
presented. We have derived a polynomial expansion of $e^x$ by computing it as
an initial value problem using a symbolic programming language. This algorithm
is shown to be comparable in operation count and convergence with the
state--of--the--art method which is based on a Pade approximation of the
exponential matrix function. The present polynomial form, however, is more
reliable because the evaluation requires only linear combinations of the input
matrix. We also show that the technique used to solve the differential
equation, when implemented symbolically, leads to a rational as well as a
polynomial form of the solution function. The rational form is the well-known
diagonal Pade approximation of $e^x$. The polynomial form, after some
rearranging to minimize operation count, will be used to evaluate the
exponential of a matrix so as to illustrate its advantages as compared with the
Pade form.


title:
Revisiting the Lie-group symmetry method for turbulent channel flow with
  wall transpiration

abstract:
  The Lie-group-based symmetry analysis, as first proposed in Avsarkisov et al.
(2014) and then later modified in Oberlack et al. (2015), to generate invariant
solutions in order to predict the scaling behavior of a channel flow with
uniform wall transpiration, is revisited. By focusing first on the results
obtained in Avsarkisov et al. (2014), we failed to reproduce two key results:
(i) For different transpiration rates at a constant Reynolds number, the mean
velocity profiles (in deficit form) do not universally collapse onto a single
curve as claimed. (ii) The universally proposed logarithmic scaling law in the
center of the channel does not match the direct numerical simulation (DNS) data
for the presented parameter values. In fact, no universal scaling behavior in
the center of the channel can be detected from their DNS data, as it is
misleadingly claimed in Avsarkisov et al. (2014). Moreover, we will demonstrate
that the assumption of a Reynolds-number independent symmetry analysis is not
justified for the flow conditions considered therein. Only when including also
the viscous terms, an overall consistent symmetry analysis can be provided.
This has been attempted in their subsequent study Oberlack et al. (2015). But,
also the (viscous) Lie-group-based scaling theory proposed therein is
inconsistent, apart from the additional fact that this study of Oberlack et al.
(2015) is also technically flawed. The reason for this permanent inconsistency
is that their symmetry analysis constantly involves several unphysical
statistical symmetries that are incompatible to the underlying deterministic
description of Navier-Stokes turbulence.


title: Long range scattering for the cubic Dirac equation on $\mathbf{R}^{1+1}$

abstract:
  We show that the cubic Dirac equation, also known as the Thirring model,
scatters at infinity to a linear solution modulo a phase correction.


title:
Axial anomaly and energy dependence of hyperon polarization in Heavy-Ion
  Collisions

abstract:
  We address the issue of energy and charge dependence of global polarization
of $\Lambda$ hyperons in peripheral $Au-Au$ collisions recently observed by the
STAR collaboration at RHIC. We compare different contributions to the anomalous
mechanism relating polarization to vorticity and hydrodynamic helicity in QCD
matter. We stress that the suppression of the gravitational anomaly
contribution in strongly correlated matter observed in lattice simulations
confirms our earlier prediction of rapid decrease of polarization with
increasing collision energy. Our mechanism leads to polarization of $\bar
\Lambda$ of the same sign and larger magnitude than the polarization of
$\Lambda$. The energy and charge dependence of polarization is suggested as a
sensitive probe of fine details of QCD matter structure.


title:
High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends
  of element ratios with stellar age

abstract:
  A previous study of correlations between element abundance ratios, [X/Fe],
and ages of solar twin stars is extended to include Sc, Mn, Cu, and Ba. HARPS
spectra with S/N > 600 are used to derive very precise (+/- 0.01 dex)
differential abundances, and stellar ages with internal errors less than 1 Gyr
are obtained by interpolation in the logg - Teff diagram between isochrones
calculated with the Aarhus Stellar Evolution Code. For stars younger than 6
Gyr, [X/Fe] is tightly correlated with stellar age for all elements. For ages
between 6 and 9 Gyr, the [X/Fe] - age correlations break down and the stars
split up into two groups having respectively high and low [X/Fe] for the odd-Z
elements. It is concluded that while stars in the solar neighborhood younger
than about 6 Gyr were formed from interstellar gas with a smooth chemical
evolution, older stars have originated from regions enriched by supernovae with
different neutron excesses. Furthermore, the correlations between abundance
ratios and stellar age suggest that: i) Sc is made in Type II supernovae along
with the alpha-capture elements, ii) the Type II to Ia SNe yield ratio is about
the same for Mn and Fe, iii) Cu is mainly made by the weak s-process in massive
stars, iv) the Ba/Y yield ratio for AGB stars increases with decreasing stellar
mass, v) [Y/Mg] and [Y/Al] can be used as "chemical clocks" when determining
ages of solar metallicity stars.


title:
Robust and rate-optimal Gibbs posterior inference on the boundary of a
  noisy image

abstract:
  Detection of an image boundary when the pixel intensities are measured with
noise is an important problem in image segmentation, with numerous applications
in medical imaging and engineering. From a statistical point of view, the
challenge is that likelihood-based methods require modeling the pixel
intensities inside and outside the image boundary, even though these are
typically of no practical interest. Since misspecification of the pixel
intensity models can negatively affect inference on the image boundary, it
would be desirable to avoid this modeling step altogether. Towards this, we
develop a robust Gibbs approach that constructs a posterior distribution for
the image boundary directly, without modeling the pixel intensities. We prove
that, for a suitable prior on the image boundary, the Gibbs posterior
concentrates asymptotically at the minimax optimal rate, adaptive to the
boundary smoothness. Monte Carlo computation of the Gibbs posterior is
straightforward, and simulation experiments show that the corresponding
inference is more accurate than that based on existing Bayesian methodology.


title: User Assignment in C-RAN Systems: Algorithms and Bounds

abstract:
  In this work, we investigate the problem of mitigating interference between
so called antenna domains of a cloud radio access network (C-RAN). In contrast
to previous work, we turn to an approach utilizing primarily the optimal
assignment of users to central processors in a C-RAN deployment. We formulate
this user assignment problem as an integer optimization problem, and propose an
iterative algorithm for obtaining a solution. Motivated by the lack of
optimality guarantees on such solutions, we opt to find lower bounds on the
problem, and the resulting interference leakage in the network. We thus derive
the corresponding Dantzig-Wolfe decomposition, formulate the dual problem, and
show that the former offers a tighter bound than the latter. We highlight the
fact that the bounds in question consist of linear problems with an exponential
number of variables, and adapt the column generation method for solving them.
In addition to shedding light on the tightness of the bounds in question, our
numerical results show significant sum-rate gains over several comparison
schemes. Moreover, the proposed scheme delivers similar performance as W-MMSE
with a significantly lower complexity (around 10 times less).


title: The role of leptonic cascades in $B_c \to B_s$ at the LHC

abstract:
  We study the feasibility and advantages of investigating the $c\to s$ decay
channel of the $B_c$ meson through the cascade decay $B_c\to B_s\pi$, $B_s\to
D_s\ell\nu$. We take into account possible contaminations coming from the
vector excitations (like $B_s^*$, $D_s^*$ or $\rho$ in the intermediate stages
of the cascade) too, as well as the opposite cascade $B_c\to B_s\ell\nu$,
$B_s\to D_s\pi$. We show how the $p_T$ distribution of the pion and the lepton
can possibly help to differentiate between various form factor models, for
which we either need more integrated luminosity at the LHC, or a
high-luminosity $e^+e^-$ B factory producing $B_c$ mesons too.


title:
Non-signaling deterministic models for non-local correlations have to be
  uncomputable

abstract:
  Quantum mechanics postulates random outcomes. However, a model making the
same output predictions but in a deterministic manner would be, in principle,
experimentally indistinguishable from quantum theory. In this work we consider
such models in the context of non-locality on a device independent scenario.
That is, we study pairs of non-local boxes that produce their outputs
deterministically. It is known that, for these boxes to be non-local, at least
one of the boxes' output has to depend on the other party's input via some kind
of hidden signaling. We prove that, if the deterministic mechanism is also
algorithmic, there is a protocol which, with the sole knowledge of any upper
bound on the time complexity of such algorithm, extracts that hidden signaling
and uses it for the communication of information.


title:
Review on Physically Flexible Nonvolatile Memory for Internet of
  Everything Electronics

abstract:
  Solid-state memory is an essential component of the digital age. With
advancements in healthcare technology and the Internet of Things (IoT), the
demand for ultra-dense, ultra-low-power memory is increasing. In this review,
we present a comprehensive perspective on the most notable approaches to the
fabrication of physically flexible memory devices. With the future goal of
replacing traditional mechanical hard disks with solid-state storage devices, a
fully flexible electronic system will need two basic devices: transistors and
nonvolatile memory. Transistors are used for logic operations and gating memory
arrays, while nonvolatile memory (NVM) devices are required for storing
information in the main memory and cache storage. Since the highest density of
transistors and storage structures is manifested in memories, the focus of this
review is flexible NVM. Flexible NVM components are discussed in terms of their
functionality, performance metrics, and reliability aspects, all of which are
critical components for NVM technology to be part of mainstream consumer
electronics, IoT, and advanced healthcare devices. Finally, flexible NVMs are
benchmarked and future prospects are provided.


title: Dynamic Subarrays for Hybrid Precoding in Wideband mmWave MIMO Systems

abstract:
  Hybrid analog/digital precoding architectures can address the trade-off
between achievable spectral efficiency and power consumption in large-scale
MIMO systems. This makes it a promising candidate for millimeter wave systems,
which require deploying large antenna arrays at both the transmitter and
receiver to guarantee sufficient received signal power. Most prior work on
hybrid precoding focused on narrowband channels and assumed fully-connected
hybrid architectures. MmWave systems, though, are expected to be wideband with
frequency selectivity. In this paper, a closed-form solution for
fully-connected OFDM-based hybrid analog/digital precoding is developed for
frequency selective mmWave systems. This solution is then extended to
partially-connected but fixed architectures in which each RF chain is connected
to a specific subset of the antennas. The derived solutions give insights into
how the hybrid subarray structures should be designed. Based on them, a novel
technique that dynamically constructs the hybrid subarrays based on the
long-term channel characteristics is developed. Simulation results show that
the proposed hybrid precoding solutions achieve spectral efficiencies close to
that obtained with fully-digital architectures in wideband mmWave channels.
Further, the results indicate that the developed dynamic subarray solution
outperforms the fixed hybrid subarray structures in various system and channel
conditions.


title: The Apps You Use Bring The Blogs to Follow

abstract:
  We tackle the blog recommendation problem in Tumblr for mobile users in this
paper. Blog recommendation is challenging since most mobile users would suffer
from the cold start when there are only a limited number of blogs followed by
the user. Specifically to address this problem in the mobile domain, we take
into account mobile apps, which typically provide rich information from the
users. Based on the assumption that the user interests can be reflected from
their app usage patterns, we propose to exploit the app usage data for
improving blog recommendation. Building on the state-of-the-art recommendation
framework, Factorization Machines (FM), we implement app-based FM that
integrates app usage data with the user-blog follow relations. In this approach
the blog recommendation is generated not only based on the blogs that the user
followed before, but also the apps that the user has often used. We demonstrate
in a series of experiments that app-based FM can outperform other alternative
approaches to a significant extent. Our experimental results also show that
exploiting app usage information is particularly effective for improving blog
recommendation quality for cold start users.


title: Wireless Sensors Networks for Internet of Things

abstract:
  The Internet is smoothly migrating from an Internet of people towards an
Internet of Things (IoT). By 2020, it is expected to have 50 billion things
connected to the Internet. However, such a migration induces a strong level of
complexity when handling interoperability between the heterogeneous Inter- net
things, e.g., RFIDs (Radio Frequency Identification), mobile handheld devices,
and wireless sensors. In this context, a couple of standards have been already
set, e.g., IPv6, 6LoWPAN (IPv6 over Low power Wireless Personal Area Networks),
and M2M (Machine to Machine communications). In this paper, we focus on the
integration of wireless sensor networks into IoT, and shed further light on the
subtleties of such integration. We present a real-world test bed deployment
where wireless sensors are used to control electrical appliances in a smart
building. Encountered problems are highlighted and suitable solutions are
presented.


title: Roadmap to Majorana surface codes

abstract:
  Surface codes offer a very promising avenue towards fault-tolerant quantum
computation. We argue that two-dimensional interacting networks of Majorana
bound states in topological superconductor/semiconductor heterostructures hold
several distinct advantages in that direction, both concerning the hardware
realization and the actual operation of the code. We here discuss how
topologically protected logical qubits in this Majorana surface code
architecture can be defined, initialized, manipulated, and read out. All
physical ingredients needed to implement these operations are routinely used in
topologically trivial quantum devices. In particular, we show that by means of
quantum interference terms in linear conductance measurements, composite
single-electron pumping protocols, and gate-tunable tunnel barriers, the full
set of quantum gates required for universal quantum computation can be
implemented.


title: High-fidelity trapped-ion quantum logic using near-field microwaves

abstract:
  We demonstrate a two-qubit logic gate driven by near-field microwaves in a
room-temperature microfabricated ion trap. We measure a gate fidelity of
99.7(1)\%, which is above the minimum threshold required for fault-tolerant
quantum computing. The gate is applied directly to $^{43}$Ca$^+$ "atomic clock"
qubits (coherence time $T_2^*\approx 50\,\mathrm{s}$) using the microwave
magnetic field gradient produced by a trap electrode. We introduce a
dynamically-decoupled gate method, which stabilizes the qubits against
fluctuating a.c.\ Zeeman shifts and avoids the need to null the microwave
field.


title:
Building Airflow Monitoring and Control using Wireless Sensor Networks
  for Smart Grid Application

abstract:
  The electricity grid is crucial to our lives. House- holds and institutions
count on it. In recent years, the sources of energy have become less and less
available and they are driving the price of electricity higher and higher. It
has been estimated that 40% of power is spent in residential and institutional
buildings. Most of this power is absorbed by space cooling and heating. In
modern buildings, the HVAC (heating, ventilation, and air conditioning) system
is centralised and operated by a department usually called the central plant.
The central plant produces chilled water and steam that is then consumed by the
building AHUs (Air Handling Units) to maintain the buildings at a comfortable
temperature. However, the heating and cooling model does not take into account
human occupancy. The AHU within the building distributes air according to the
design parameters of the building ignoring the occupancy. As a matter of fact,
there is a potential for optimization lowering consumption to utilize energy
efficiently and also to be able to adapt to the changing cost of energy in a
micro-grid environment. This system makes it possible to reduce the consumption
when needed minimizing impact on the consumer. In this study, we will show,
through a set of studies conducted at the University of Houston, that there is
a potential for energy conservation and efficiency in both the buildings and
the central plant. We also present a strategy that can be undertaken to meet
this goal. This strategy, airflow monitoring and control, is tested in a
software simulation and the results are presented. This system enables the user
to control and monitor the temperature in the individual rooms according the
locals needs.


title:
Towards single-valued polylogarithms in two variables for the
  seven-point remainder function in multi-Regge-kinematics

abstract:
  We investigate single-valued polylogarithms in two complex variables, which
are relevant for the seven-point remainder function in N=4 super-Yang-Mills
theory in the multi-Regge regime. After constructing these two-dimensional
polylogarithms, we determine the leading logarithmic approximation of the
seven-point remainder function up to and including five loops.


title: The kernel method for lattice paths below a line of rational slope

abstract:
  We analyse some enumerative and asymptotic properties of lattice paths below
a line of rational slope. We illustrate our approach with Dyck paths under a
line of slope $2/5$. This answers Knuth's problem #4 from his "Flajolet
lecture" during the conference "Analysis of Algorithms" (AofA'2014) in Paris in
June 2014. Our approach extends the work of Banderier and Flajolet for
asymptotics and enumeration of directed lattice paths to the case of generating
functions involving several dominant singularities, and has applications to a
full class of problems involving some "periodicities". A key ingredient in the
proof is the generalization of an old trick by Knuth himself (for enumerating
permutations sortable by a stack), promoted by Flajolet and others as the
"kernel method". All the corresponding generating functions are algebraic, and
they offer some new combinatorial identities, which can also be tackled in the
A=B spirit of Wilf-Zeilberger-Petkovsek. We show how to obtain similar results
for any rational slope. An interesting case is e.g. Dyck paths below the slope
$2/3$ (this corresponds to the so-called Duchon's club model), for which we
solve a conjecture related to the asymptotics of the area below such lattice
paths. Our work also gives access to lattice paths below an irrational slope
(e.g. Dyck paths below $y=x/\sqrt{2}$), a problem that we study in a companion
article.


title: The telescope conjecture for algebraic stacks

abstract:
  Using Balmer--Favi's generalized idempotents, we establish the telescope
conjecture for many algebraic stacks. Along the way, we classify the thick
tensor ideals of perfect complexes of stacks.


title:
Functorial factorization of birational maps for qe schemes in
  characteristic 0

abstract:
  We prove functorial weak factorization of projective birational morphisms of
regular quasi-excellent schemes in characteristic 0 broadly based on the
existing line of proof for varieties. From this general functorial statement we
deduce factorization results for algebraic stacks, formal schemes, complex
analytic germs, Berkovich analytic and rigid analytic spaces.


title: Gaussian Error Linear Units (GELUs)

abstract:
  We propose the Gaussian Error Linear Unit (GELU), a high-performing neural
network activation function. The GELU activation function is $x\Phi(x)$, where
$\Phi(x)$ the standard Gaussian cumulative distribution function. The GELU
nonlinearity weights inputs by their value, rather than gates inputs by their
sign as in ReLUs ($x\mathbf{1}_{x>0}$). We perform an empirical evaluation of
the GELU nonlinearity against the ReLU and ELU activations and find performance
improvements across all considered computer vision, natural language
processing, and speech tasks.


title:
Computation of ancestry scores with mixed families and unrelated
  individuals

abstract:
  The issue of robustness to family relationships in computing genotype
ancestry scores such as eigenvector projections has received increased
attention in genetic association, as the scores are widely used to control
spurious association. We use a motivational example from the North American
Cystic Fibrosis (CF) Consortium genetic association study with 3444 individuals
and 898 family members to illustrate the challenge of computing ancestry scores
when sets of both unrelated individuals and closely-related family members are
included. We propose novel methods to obtain ancestry scores and demonstrate
that the proposed methods outperform existing methods. The current standard is
to compute loadings (left singular vectors) using unrelated individuals and to
compute projected scores for remaining family members. However, projected
ancestry scores from this approach suffer from shrinkage toward zero. We
consider in turn alternate strategies: (i) within-family data
orthogonalization, (ii) matrix substitution based on decomposition of a target
family-orthogonalized covariance matrix, (iii) covariance-preserving whitening,
retaining covariances between unrelated pairs while orthogonalizing family
members, and (iv) using family-averaged data to obtain loadings. Except for
within-family orthogonalization, our proposed approaches offer similar
performance and are superior to the standard approaches. We illustrate the
performance via simulation and analysis of the CF dataset.


title: Min-max formulas for nonlocal elliptic operators

abstract:
  In this work, we give a characterization of Lipschitz operators on spaces of
$C^2(M)$ functions (also $C^{1,1}$, $C^{1,\gamma}$, $C^1$, $C^\gamma$) that
obey the global comparison property-- i.e. those that preserve the global
ordering of input functions at any points where their graphs may touch, often
called "elliptic" operators. Here $M$ is a complete Riemannian manifold. In
particular, we show that all such operators can be written as a min-max over
linear operators that are a combination of drift-diffusion and
integro-differential parts. In the \emph{linear} (and nonlocal) case,
Courr\`ege had characterized these operators in the 1960's, and in the
\emph{local, but nonlinear} case-- e.g. local Hamilton-Jacobi-Bellman
operators-- this characterization has also been known for quite some time. Our
result gives both a nonlinear extension of Courr\`ege's and a nonlocal
extension of well known results for local Hamilton-Jacobi-Bellman equations. It
also shows any nonlinear scalar elliptic equation can be represented as an
Isaacs equation for an appropriate differential game. Our approach is to
"project" the operator to a finite dimensional space, where a min-max formula
is easier, and then the min-max can be appropriately lifted to the original
operator on the infinite dimensional space. As one application, we mention some
preliminary results about the structure of Dirichlet-to-Neumann mappings for
second order elliptic equations, including fully nonlinear equations. This is
the Director's cut, and it contains extra details for our own sanity.


title: Outermost apparent horizons diffeomorphic to unit normal bundles

abstract:
  Given a submanifold $S \subset \mathbb R^n$ of codimension at least three, we
construct an asymptotically Euclidean Riemannian metric on $\mathbb R^n$ with
nonnegative scalar curvature for which the outermost apparent horizon is
diffeomorphic to the unit normal bundle of $S$.


title:
Anomalous Thouless energy and critical statistics on the metallic side
  of the many-body localization transition

abstract:
  We study a one-dimensional (1d) XXZ spin-chain in a random field on the
metallic side of the many-body localization transition by level statistics. For
a fixed interaction, and intermediate disorder below the many-body localization
transition, we find that, asymptotically, the number variance grows faster than
linear with a disorder dependent exponent. This is consistent with the
existence of an anomlaous Thouless energy in the spectrum. In non-interacting
disordered metals this is an energy scale related to the typical time for a
particle to diffuse across the sample. In the interacting case it seems related
to a more intricate anomalous diffusion process. This interpretation is not
fully consistent with recent claims that, for intermediate disorder, level
statistics are described by a plasma model with power-law decaying interactions
whose number variance grows slower than linear. As disorder is further
increased, still on the metallic side, the Thouless energy is gradually washed
out. In the range of sizes we can explore, level statistics are scale invariant
and approach Poisson statistics at the many-body localization transition.
Slightly below the many-body localization transition, spectral correlations,
well described by critical statistics, are quantitatively similar to those of a
high dimensional, non-interacting, disordered conductor at the Anderson
transition.


title: An averaged Chowla and Elliott conjecture along independent polynomials

abstract:
  We generalize a result of Matom\"aki, Radziwi{\l}{\l}, and Tao, by proving an
averaged version of a conjecture of Chowla and a conjecture of Elliott
regarding correlations of the Liouville function, or more general bounded
multiplicative functions, with shifts given by independent polynomials in
several variables. A new feature is that we recast the problem in ergodic terms
and use a multiple ergodic theorem to prove it; its hypothesis is verified
using recent results by Matom\"aki and Radziwi{\l}{\l} on mean values of
multiplicative functions on typical short intervals. We deduce several
consequences about patterns that can be found on the range of various
arithmetic sequences along shifts of independent polynomials.


title: Sequential bottomonium production at high temperatures

abstract:
  Bottomonium production in heavy ion collisions is modified compared with any
simple extrapolation from elementary collisions. This modification is most
likely caused by the presence of a deconfined system of quarks and gluons for
times of several fm/c. In such a medium, bottomonium can be destroyed, but the
constituent bottom quarks will likely stay spatially correlated due to small
mean free paths in this system. With these facts in mind, we describe
bottomonium formation with a coupled set of equations. A rate equation
describes the destruction of $\Upsilon(1S)$ particles, while a Langevin
equation describes how the bottom quarks stay correlated for a sufficiently
long time so that recombination into bottomonia is possible. We show that
within this approach it is possible to understand the magnitude of
$\Upsilon(1S)$ suppression in heavy ion collisions and the larger suppression
of the $\Upsilon(2S)$ state, implying that the reduction in the ratio of
$\Upsilon(1S)/\Upsilon(2S)$ yield in heavy ion collision does not necessarily
correspond to sequential melting picture.


title: Prior knowledge and Markov parameters of linear time-invariant models

abstract:
  In many practical cases, the engineer has access to prior knowledge like
rough values of the DC-gain or the main time constant of the system. In order
to improve the accuracy of subspace-based identification techniques using the
model Markov parameters, we derive in this short paper the direct links between
these impulse response coefficients and this prior information. The next step
will consist in introducing this prior knowledge explicitly in Kung's algorithm
thank to dedicated equality and equality constraints.


title: XMM-Newton Large Program on SN1006 - II: Thermal Emission

abstract:
  Based on the XMM-Newton large program on SN1006 and our newly developed
spatially resolved spectroscopy tools (Paper~I), we study the thermal emission
from ISM and ejecta of SN1006 by analyzing the spectra extracted from 583
tessellated regions dominated by thermal emission. With some key improvements
in spectral analysis as compared to Paper~I, we obtain much better spectral
fitting results with less residuals. The spatial distributions of the thermal
and ionization states of the ISM and ejecta show different features, which are
consistent with a scenario that the ISM (ejecta) is heated and ionized by the
forward (reverse) shock propagating outward (inward). Different elements have
different spatial distributions and origins, with Ne mostly from the ISM, Si
and S from the ejecta, and O and Mg from both ISM and ejecta. Fe L-shell lines
are only detected in a small shell-like region SE to the center of SN1006,
indicating that most of the Fe-rich ejecta has not yet or just recently been
reached by the reverse shock. The overall ejecta abundance patterns for most of
the heavy elements, except for Fe and sometimes S, are consistent with typical
Type~Ia SN products. The NW half of the SNR interior probably represents a
region with turbulently mixed ISM and ejecta, so has enhanced emission from O,
Mg, Si, S, lower ejecta temperature, and a large diversity of ionization age.
In addition to the asymmetric ISM distribution, an asymmetric explosion of the
progenitor star is also needed to explain the asymmetric ejecta distribution.


title:
Exact factorization-based density functional theory of electrons and
  nuclei

abstract:
  The ground state energy of a system of electrons and nuclei is proven to be a
variational functional of the conditional electronic density $n_R(\mathbf{r})$,
the nuclear wavefunction $\chi(R)$ and an induced vector potential $A_{\mu}(R)$
and quantum geometric tensor $\mathcal{T}_{\mu\nu}(R)$ derived from the
conditional electronic wavefunction $\Phi_R(r)$ over nuclear configuration
space, where $r=\mathbf{r}_1,\mathbf{r}_2,\ldots$ are electronic coordinates
and $R=\mathbf{R}_1,\mathbf{R}_2,\ldots$ are nuclear coordinates. The ground
state $(n_R,\chi,A_{\mu},\mathcal{T}_{\mu\nu})$ can be calculated by solving
self-consistently (i) conditional Kohn-Sham equations containing an effective
potential $v_{\rm s}(\mathbf{r})$ that depends parametrically on $R$, (ii) the
Schr\"odinger equation for $\chi(R)$ and (iii) Euler-Lagrange equations that
determine $\mathcal{T}_{\mu\nu}$. The theory is applied to the $E\otimes e$
Jahn-Teller model.


title:
Predicting the Relative Difficulty of Single Sentences With and Without
  Surrounding Context

abstract:
  The problem of accurately predicting relative reading difficulty across a set
of sentences arises in a number of important natural language applications,
such as finding and curating effective usage examples for intelligent language
tutoring systems. Yet while significant research has explored document- and
passage-level reading difficulty, the special challenges involved in assessing
aspects of readability for single sentences have received much less attention,
particularly when considering the role of surrounding passages. We introduce
and evaluate a novel approach for estimating the relative reading difficulty of
a set of sentences, with and without surrounding context. Using different sets
of lexical and grammatical features, we explore models for predicting pairwise
relative difficulty using logistic regression, and examine rankings generated
by aggregating pairwise difficulty labels using a Bayesian rating system to
form a final ranking. We also compare rankings derived for sentences assessed
with and without context, and find that contextual features can help predict
differences in relative difficulty judgments across these two conditions.


title: On modules arising from quantum groups at $p^r$-th roots of unity

abstract:
  This paper studies the "reduction mod $p$" method, which constructs large
classes of representations for a semisimple algebraic group $G$ from
representations for the corresponding Lusztig quantum group $U_\zeta$ at a
$p^r$-th root of unity. The $G$-modules arising in this way include the Weyl
modules, the induced modules, and various reduced versions of these modules. We
present a relation between $\operatorname{Ext}^n_G(V,W)$ and
$\operatorname{Ext}^n_{U_\zeta}(V',W')$, when $V,W$ are obtained from $V',W'$
by reduction mod $p$. Since the dimensions of $\operatorname{Ext}^n$-spaces for
$U_\zeta$-modules are known in many cases, our result guarantees the existence
of many new extension classes and homomorphisms between certain rational
$G$-modules. One application is a new proof of James Franklin's result on
certain homomorphisms between two Weyl modules. We also provide some examples
which show that the $p$-th root of unity case and a general $p^r$-th root of
unity case are essentially different.


title:
Linearized self-consistent quasiparticle GW method: Application to
  semiconductors and simple metals

abstract:
  We present a code implementing the linearized self-consistent quasiparticle
GW method (scQPGW) in the LAPW basis. Our approach is based on the
linearization of the self-energy around zero frequency which differs it from
the existing implementations of the scQPGW method. The linearization allows us
to use Matsubara frequencies instead of real ones. As a result it gives us an
advantage in terms of efficiency, allowing us easily switch to the imaginary
time representation the same way as in the space time method. The all electron
LAPW basis set eliminates the need for pseudopotentials. We discuss the
advantages of our approach, such as its N^3 scaling with the system size, as
well as its shortcomings.
  We apply our approach to study electronic properties of selected
semiconductors, insulators, and simple metals and show that our code produces
results very close to the previously published scQPGW data. Our implementation
is a good platform for further many body diagrammatic resummations such as
GW+DMFT.


title: Rigidity of down-up algebras with respect to finite group coactions

abstract:
  If a nontrivial finite group coacts on a graded noetherian down-up algebra
$A$ inner faithfully and homogeneously, then the fixed subring is not
isomorphic to $A$. Therefore graded noetherian down-up algebras are rigid with
respect to finite group coactions, in the sense of Alev-Polo. An example is
given to show that this rigidity under group coactions does not have all the
same consequences as the rigidity under group actions.


title: Infrared Computations of Defect Schur Indices

abstract:
  We conjecture a formula for the Schur index of N=2 four-dimensional theories
in the presence of boundary conditions and/or line defects, in terms of the
low-energy effective Seiberg-Witten description of the system together with
massive BPS excitations. We test our proposal in a variety of examples for
SU(2) gauge theories, either conformal or asymptotically free. We use the
conjecture to compute these defect-enriched Schur indices for theories which
lack a Lagrangian description, such as Argyres-Douglas theories. We demonstrate
in various examples that line defect indices can be expressed as sums of
characters of the associated two-dimensional chiral algebra and that for
Argyres-Douglas theories the line defect OPE reduces in the index to the
Verlinde algebra.


title:
Landau-Zener extension of the Tavis-Cummings model: structure of the
  solution

abstract:
  We explore the recently discovered solution of the driven Tavis-Cummings
model (DTCM). It describes interaction of arbitrary number of two-level systems
with a bosonic mode that has linearly time-dependent frequency. We derive
compact and tractable expressions for transition probabilities in terms of the
well known special functions. In the new form, our formulas are suitable for
fast numerical calculations and analytical approximations. As an application,
we obtain the semiclassical limit of the exact solution and compare it to prior
approximations. We also reveal connection between DTCM and $q$-deformed
binomial statistics.

categories: quant-ph cond-mat.mes-hall math-ph math.MP


title: Energy stable model order reduction for the Allen-Cahn equation

abstract:
  The Allen-Cahn equation is a gradient system, where the free-energy
functional decreases monotonically in time. We develop an energy stable reduced
order model (ROM) for a gradient system, which inherits the energy decreasing
property of the full order model (FOM). For the space discretization we apply a
discontinuous Galerkin (dG) method and for time discretization the energy
stable average vector field (AVF) method. We construct ROMs with proper
orthogonal decomposition (POD)-greedy adaptive sampling of the snapshots in
time and evaluating the nonlinear function with greedy discrete empirical
interpolation method (DEIM). The computational efficiency and accuracy of the
reduced solutions are demonstrated numerically for the parametrized Allen-Cahn
equation with Neumann and periodic boundary conditions.


title: On two conjectural supercongruences of Apagodu and Zeilberger

abstract:
  Let the numbers $\alpha_n,\beta_n$ and $\gamma_n$ denote \begin{align*}
\alpha_n=\sum_{k=0}^{n-1}{2k\choose k},\quad \beta_n=\sum_{k=0}^{n-1}{2k\choose
k}\frac{1}{k+1}\quad\text{and}\quad \gamma_n=\sum_{k=0}^{n-1}{2k\choose
k}\frac{3k+2}{k+1}, \end{align*} respectively. We prove that for any prime
$p\ge 5$ and positive integer $n$ \begin{align*} \alpha_{np}&\equiv
\left(\frac{p}{3}\right) \alpha_n \pmod{p^2},\\ \beta_{np}&\equiv \begin{cases}
\displaystyle \beta_n \pmod{p^2},\quad &\text{if $p\equiv 1\pmod{3}$},\\
-\gamma_n \pmod{p^2},\quad &\text{if $p\equiv 2\pmod{3}$}, \end{cases}
\end{align*} where $\left(\frac{\cdot}{p}\right)$ denotes the Legendre symbol.
These two supercongruences were recently conjectured by Apagodu and Zeilberger.


title: Continuous time limits of the Utterance Selection Model

abstract:
  In this paper, we derive new continuous time limits of the Utterance
Selection Model (USM) for language change (Baxter et al., Phys. Rev. E {\bf
73}, 046118, 2006). This is motivated by the fact that the Fokker-Planck
continuous time limit derived in the original version of the USM is only valid
for a small range of parameters. We investigate the consequences of relaxing
these constraints on parameters. Using the normal approximation of the
multinomial approximation, we derive a new continuous time limit of the USM in
the form of a weak-noise stochastic differential equation. We argue that this
weak noise, not captured by the Kramers-Moyal expansion, can not be neglected.
We then propose a coarse-graining procedure, which takes the form of a
stochastic version of the \emph{heterogeneous mean field} approximation. This
approximation groups the behaviour of nodes of same degree, reducing the
complexity of the problem. With the help of this approximation, we study in
detail two simple families of networks: the regular networks and the
star-shaped networks. The analysis reveals and quantifies a finite size effect
of the dynamics. If we increase the size of the network by keeping all the
other parameters constant, we transition from a state where conventions emerge
to a state when no convention emerges. Furthermore, we show that the degree of
a node acts as a time scale. For heterogeneous networks such as star-shaped
networks, the time scale difference can become very large leading to a noisier
behaviour of highly connected nodes.


title: Summation formulas involving generalized harmonic numbers

abstract:
  In terms of the derivative operator and three hypergeometric series
identities, several interesting summation formulas involving generalized
harmonic numbers are established.


title:
Insights from Synthetic Star-forming Regions: II. Verifying Dust Surface
  Density, Dust Temperature & Gas Mass Measurements with Modified Blackbody
  Fitting

abstract:
  We use a large data-set of realistic synthetic observations (PaperI) to
assess how observational techniques affect the measurement of physical
properties of star-forming regions. In this paper (PaperII), we explore the
reliability of the measured total gas mass, dust surface density and dust
temperature maps derived from modified blackbody fitting of synthetic Herschel
observations. We found from our pixel-by-pixel analysis of the measured dust
surface density and dust temperature a worrisome error spread especially close
to star-formation sites and low-density regions, where for those "contaminated"
pixels the surface densities can be under/overestimated by up to three orders
of magnitude. In light of this, we recommend to treat the pixel-based results
from this technique with caution in regions with active star formation. In
regions of high background typical in the inner Galactic plane, we are not able
to recover reliable surface density maps of individual synthetic regions, since
low-mass regions are lost in the FIR background. When measuring the total gas
mass of regions in moderate background, we find that modified blackbody fitting
works well (absolute error:+9%;-13%) up to 10kpc distance (errors increase with
distance). Commonly, the initial images are convolved to the largest common
beam-size, which smears contaminated pixels over large areas. The resulting
information loss makes this commonly-used technique less verifiable as now
chi^2-values cannot be used as a quality indicator of a fitted pixel. Our
control measurements of the total gas mass (without the step of convolution to
the largest common beam size) produce similar results (absolute error:+20%;-7%)
while having much lower median errors especially for the high-mass stellar
feedback phase. In upcoming papers (III&IV) we test the reliability of measured
star-formation rate with direct and indirect techniques.


title:
Non-local Supercurrent of Quartets in a Three-Terminal Josephson
  Junction

abstract:
  We report an observation of a new, non dissipative and non local
supercurrent, carried by quartets; each consisting of four entangled electrons.
The supercurrent is a result of a novel Andreev bound state (ABS), formed among
three superconducting terminals. While in a two-terminal Josephson junction the
usual ABS, and thus the DC Josephson current, exist only in equilibrium, in the
present realization the ABS exists also in the strongly nonlinear regime
(biased terminals). The presence of supercurrent carried by quartets was
established by performing non-local conductance and cross-correlation of
current fluctuations measurements, in different devices made of aluminum-InAs
nanowire junctions. An extensive and detailed theoretical study is intertwined
with the experimental results.


title: Evidence for a Lattice Weak Gravity Conjecture

abstract:
  The Weak Gravity Conjecture postulates the existence of superextremal charged
particles, i.e. those with mass smaller than or equal to their charge in Planck
units. We present further evidence for our recent observation that in known
examples a much stronger statement is true: an infinite tower of superextremal
particles of different charges exists. We show that effective Kaluza-Klein
field theories and perturbative string vacua respect the Sublattice Weak
Gravity Conjecture, namely that a finite index sublattice of the full charge
lattice exists with a superextremal particle at each site. In perturbative
string theory we show that this follows from modular invariance. However, we
present counterexamples to the stronger possibility that a superextremal
particle exists at every lattice site, including an example in which the
lightest charged particle is subextremal. The Sublattice Weak Gravity
Conjecture has many implications both for abstract theories of quantum gravity
and for real-world physics. For instance, it implies that if a gauge group with
very small coupling $e$ exists, then the fundamental gravitational cutoff
energy of the theory is no higher than $\sim e^{1/3} M_{\rm Pl}$.


title: The Weak Gravity Conjecture in three dimensions

abstract:
  We study weakly coupled $U(1)$ theories in $AdS_3$, their associated charged
BTZ solutions, and their charged spectra. We find that modular invariance of
the holographic dual two-dimensional CFT and compactness of the gauge group
together imply the existence of charged operators with conformal dimension
significantly below the black hole threshold. We regard this as a form of the
Weak Gravity Conjecture (WGC) in three dimensions. We also explore the
constraints posed by modular invariance on a particular discrete $\mathbb{Z}_N$
symmetry which arises in our discussion. In this case, modular invariance does
not guarantee the existence of light $\mathbb{Z}_N$-charged states. We also
highlight the differences between our discussion and the usual heuristic
arguments for the WGC based on black hole remnants.


title:
Superfluidity in the absence of kinetics in spin-orbit-coupled optical
  lattices

abstract:
  At low temperatures bosons typically condense to minimize their
single-particle kinetic energy while interactions stabilize superfluidity.
Optical lattices with artificial spin-orbit coupling challenge this paradigm
because here kinetic energy can be quenched in an extreme regime where the
single-particle band flattens. To probe the fate of superfluidity in the
absence of kinetics we construct and numerically solve interaction-only
tight-binding models in flat bands. We find that novel superfluid states arise
entirely from interactions operating in quenched kinetic energy bands, thus
revealing a distinct and unexpected condensation mechanism. Our results have
important implications for the identification of quantum condensed phases of
ultracold bosons beyond conventional paradigms.


title:
A consistent model for both the HI and stellar mass functions of
  galaxies

abstract:
  Using the L-Galaxies semi-analytic model we simultaneously fit the HI mass
function, stellar mass function and galaxy colours. We find good fits to all
three observations at z = 0 and to the stellar mass function and galaxy colours
at z = 2. Using Markov Chain Monte Carlo (MCMC) techniques we adjust the
L-Galaxies parameters to best fit the constraining data. In order to fit the HI
mass function we must greatly reduce the gas surface density threshold for star
formation, thus lowering the number of low HI mass galaxies. A simultaneous
reduction in the star formation efficiency prevents the over production of
stellar content. A simplified model in which the surface density threshold is
eliminated altogether also provides a good fit to the data. Unfortunately,
these changes weaken the fit to the Kennicutt-Schmidt relation and raise the
star-formation rate density at recent times, suggesting that a change to the
model is required to prevent accumulation of gas onto dwarf galaxies in the
local universe.


title: Five Planets Transiting a Ninth Magnitude Star

abstract:
  The Kepler mission has revealed a great diversity of planetary systems and
architectures, but most of the planets discovered by Kepler orbit faint stars.
Using new data from the K2 mission, we present the discovery of a five planet
system transiting a bright (V = 8.9, K = 7.7) star called HIP 41378. HIP 41378
is a slightly metal-poor late F-type star with moderate rotation (v sin(i) = 7
km/s) and lies at a distance of 116 +/- 18 from Earth. We find that HIP 41378
hosts two sub-Neptune sized planets orbiting 3.5% outside a 2:1 period
commensurability in 15.6 and 31.7 day orbits. In addition, we detect three
planets which each transit once during the 75 days spanned by K2 observations.
One planet is Neptune sized in a likely ~160 day orbit, one is sub-Saturn sized
likely in a ~130 day orbit, and one is a Jupiter sized planet in a likely ~1
year orbit. We show that these estimates for the orbital periods can be made
more precise by taking into account dynamical stability considerations. We also
calculate the distribution of stellar reflex velocities expected for this
system, and show that it provides a good target for future radial velocity
observations. If a precise orbital period can be determined for the outer
Jovian planet through future observations, it will be an excellent candidate
for follow-up transit observations to study its atmosphere and measure its
oblateness.


title:
Evidence of suppression of star formation by quasar-driven winds in
  gas-rich host galaxies at z<1?

abstract:
  Feedback from active galactic nuclei (AGN) is widely considered to be the
main driver in regulating the growth of massive galaxies through heating or
driving gas out of the galaxy, preventing further increase in stellar mass.
Observational proof for this scenario has, however, been scarce. We have
assembled a sample of 132 radio-quiet type-2 and red AGN at 0.1<z<1. We measure
the kinematics of the AGN-ionized gas, the host galaxies' stellar masses and
star formation rates and investigate the relationships between AGN
luminosities, specific star formation rates (sSFR) and outflow strengths W90 --
the 90\% velocity width of the [OIII]5007 line power and a proxy for the
AGN-driven outflow speed. Outflow strength is independent of sSFR for AGN
selected on their mid-IR luminosity, in agreement with previous work
demonstrating that star formation is not sufficient to produce the observed
ionized gas outflows which have to be powered by AGN activity. More
importantly, we find a negative correlation between W90 and sSFR in the AGN
hosts with the highest SFRs, i.e., with the highest gas content, where
presumably the coupling of the AGN-driven wind to the gas is strongest. This
implies that AGN with strong outflow signatures are hosted in galaxies that are
more `quenched' than galaxies with weaker outflow signatures. Despite the
galaxies' high SFRs, we demonstrate that the outflows are not star-formation
driven but indeed due to AGN-powering. This observation is consistent with the
AGN having a net suppression, `negative' impact, through feedback on the
galaxies' star formation history.


title: A Holographic Proof of R\'enyi Entropic Inequalities

abstract:
  We prove R\'enyi entropic inequalities in a holographic setup based on the
recent proposal for the holographic formula of R\'enyi entropies when the bulk
is stable against any perturbation. Regarding the R\'enyi parameter as an
inverse temperature, we reformulate the entropies in analogy with statistical
mechanics, which provides us a concise interpretation of the inequalities as
the positivities of entropy, energy and heat capacity. This analogy also makes
clear a thermodynamic structure in deriving the holographic formula. As a
by-product of the proof we obtain a holographic formula to calculate the
quantum fluctuation of the modular Hamiltonian. A few examples of the capacity
of entanglement are examined in detail.


title: Space from Hilbert Space: Recovering Geometry from Bulk Entanglement

abstract:
  We examine how to construct a spatial manifold and its geometry from the
entanglement structure of an abstract quantum state in Hilbert space. Given a
decomposition of Hilbert space $\mathcal{H}$ into a tensor product of factors,
we consider a class of "redundancy-constrained states" in $\mathcal{H}$ that
generalize the area-law behavior for entanglement entropy usually found in
condensed-matter systems with gapped local Hamiltonians. Using mutual
information to define a distance measure on the graph, we employ classical
multidimensional scaling to extract the best-fit spatial dimensionality of the
emergent geometry. We then show that entanglement perturbations on such
emergent geometries naturally give rise to local modifications of spatial
curvature which obey a (spatial) analog of Einstein's equation. The Hilbert
space corresponding to a region of flat space is finite-dimensional and scales
as the volume, though the entropy (and the maximum change thereof) scales like
the area of the boundary. A version of the ER=EPR conjecture is recovered, in
that perturbations that entangle distant parts of the emergent geometry
generate a configuration that may be considered as a highly quantum wormhole.


title:
The Turbulent Origin of Outflow and Spin Misalignment in Multiple Star
  Systems

abstract:
  The protostellar outflows of wide-separation forming binaries frequently
appear misaligned. We use magneto-hydrodynamic simulations to investigate the
alignment of protostellar spin and molecular outflows for forming binary pairs.
We show that the protostellar pairs, which form from turbulent fragmentation
within a single parent core, have randomly oriented angular momenta. Although
the pairs migrate to closer separations, their spins remain partially
misaligned. We produce $^{12}$CO(2-1) synthetic observations of the simulations
and characterize the outflow orientation in the emission maps. The
CO-identified outflows exhibit a similar random distribution and are also
statistically consistent with the observed distribution of molecular outflows.
We conclude that observed misalignment provides a clear signature of binary
formation via turbulent fragmentation. The persistence of misaligned outflows
and stellar spins following dynamical evolution may provide a signature of
binary origins for more evolved multiple star systems.


title: Z_2 and Chiral Anomalies in Topological Dirac Semimetals

abstract:
  We demonstrate that topological Dirac semimetals, which possess two Dirac
nodes, separated in momentum space along a rotation axis and protected by
rotational symmetry, exhibit an additional quantum anomaly, distinct from the
chiral anomaly. This anomaly, which we call the $ \mathbb Z_2$ anomaly, is a
consequence of the fact that the Dirac nodes in topological Dirac semimetals
carry a $\mathbb Z_2$ topological charge. The $\mathbb Z_2$ anomaly refers to
nonconservation of this charge in the presence of external fields due to
quantum effects and has observable consequences due to its interplay with the
chiral anomaly. We discuss possible implications of this for the interpretation
of magnetotransport experiments on topological Dirac semimetals. We also
provide a possible explanation for the magnetic field dependent angular
narrowing of the negative longitudinal magnetoresistance, observed in a recent
experiment on Na$_3$Bi.


title:
Search for an exosphere in sodium and calcium in the transmission
  spectrum of exoplanet 55 Cancri e

abstract:
  [Abridged] The aim of this work is to search for an absorption signal from
exospheric sodium (Na) and singly ionized calcium (Ca$^+$) in the optical
transmission spectrum of the hot rocky super-Earth 55 Cancri e. Although the
current best-fitting models to the planet mass and radius require a possible
atmospheric component, uncertainties in the radius exist, making it possible
that 55 Cancri e could be a hot rocky planet without an atmosphere. High
resolution (R$\sim$110000) time-series spectra of five transits of 55 Cancri e,
obtained with three different telescopes (UVES/VLT, HARPS/ESO 3.6m &
HARPS-N/TNG) were analysed. Targeting the sodium D lines and the calcium H and
K lines, the potential planet exospheric signal was filtered out from the much
stronger stellar and telluric signals, making use of the change of the radial
component of the orbital velocity of the planet over the transit from -57 to
+57 km/sec. Combining all five transit data sets, we detect a signal
potentially associated with sodium in the planet exosphere at a statistical
significance level of 3$\sigma$. Combining the four HARPS transits that cover
the calcium H and K lines, we also find a potential signal from ionized calcium
(4.1 $\sigma$). Interestingly, this latter signal originates from just one of
the transit measurements - with a 4.9$\sigma$ detection at this epoch.
Unfortunately, due to the low significance of the measured sodium signal and
the potentially variable Ca$^+$ signal, we estimate the p-values of these
signals to be too high (corresponding to <4$\sigma$) to claim unambiguous
exospheric detections. By comparing the observed signals with artificial
signals injected early in the analysis, the absorption by Na and Ca$^+$ are
estimated to be at a level of approximately 2.3$\times 10^{-3}$ and 7.0$\times
10^{-2}$ respectively, relative to the stellar spectrum.


title: Relative Likelihood for Life as a Function of Cosmic Time

abstract:
  Is life most likely to emerge at the present cosmic time near a star like the
Sun? We address this question by calculating the relative formation probability
per unit time of habitable Earth-like planets within a fixed comoving volume of
the Universe, dP(t)/dt, starting from the first stars and continuing to the
distant cosmic future. We conservatively restrict our attention to the context
of "life as we know it" and the standard cosmological model, LCDM. We find that
unless habitability around low mass stars is suppressed, life is most likely to
exist near 0.1 solar-mass stars ten trillion years from now. Spectroscopic
searches for biosignatures in the atmospheres of transiting Earth-mass planets
around low mass stars will determine whether present-day life is indeed
premature or typical from a cosmic perspective.

categories: astro-ph.CO astro-ph.EP astro-ph.SR hep-th


title: Cosmic microwave background and inflation in multi-fractional spacetimes

abstract:
  We use FIRAS and Planck 2015 data to place observational bounds on
inflationary scenarios in multi-fractional spacetimes with $q$-derivatives.
While a power-law expansion in the geometric time coordinate is subject to the
usual constraints from the tensor-to-scalar ratio, model-independent best fits
of the black-body and scalar spectra yield upper limits on the free parameters
of the multi-fractal measure of the theory. When the measure describing the
fractal spacetime geometry is non-oscillating, information on the CMB
black-body spectrum places constraints on the theory independent from but
weaker than those obtained from the Standard Model, astrophysical gravitational
waves and gamma-ray bursts (GRBs). When log oscillations are included and the
measure describes a discrete fractal spacetime at microscopic scales, we obtain
the first observational constraints on the amplitudes of such oscillations and
find, in general, strong constraints on the multi-scale geometry and on the
dimension of space. These results complete the scan and reduction of the
parameter space of the theory. Black-body bounds are obtained also for the
theory with weighted derivatives.


title:
Controlling Majorana states in topologically inhomogeneous
  superconductors

abstract:
  Majorana bound states have been recently observed at the boundaries of
one-dimensional topological superconductors. Yet, controlling the localization
of the Majorana states, which is essential to the realization of any
topological quantum device, is an ongoing challenge. To this end, we introduce
a mechanism which can break a topologically homogeneous state via the formation
of topological domains, and which can be exploited to control the position of
Majorana states. We found in fact that in the presence of amplitude-modulated
fields, contiguous magnetic domains can become topologically inequivalent and,
as a consequence, Majorana states can be pinned to the domain walls of the
magnetic structure. The formation of topological domains and the position of
Majorana states can be externally controlled by tuning an applied field (e.g.,
magnetic or gate).


title:
Mode-sum regularization of $\left\langle \phi^{2} \right\rangle$ in the
  angular-splitting method

abstract:
  The computation of the renormalized stress-energy tensor or
$\left\langle\phi^{2}\right\rangle_{ren}$ in curved spacetime is a challenging
task, at both the conceptual and technical levels. Recently we developed a new
approach to compute such renormalized quantities in asymptotically-flat curved
spacetimes, based on the point-splitting procedure. Our approach requires the
spacetime to admit some symmetry. We already implemented this approach to
compute $\left\langle \phi^{2}\right\rangle _{ren}$ in a stationary spacetime
using t-splitting, namely splitting in the time-translation direction. Here we
present the angular-splitting version of this approach, aimed for computing
renormalized quantities in a general (possibly dynamical) spherically-symmetric
spacetime. To illustrate how the angular-splitting method works, we use it here
to compute $\left\langle \phi^{2}\right\rangle _{ren}$ for a quantum massless
scalar field in Schwarzschild background, in various quantum states (Boulware,
Unruh, and Hartle-Hawking states). We find excellent agreement with the results
obtained from the t-splitting variant, and also with other methods. Our main
goal in pursuing this new mode-sum approach was to enable the computation of
the renormalized stress-energy tensor in a dynamical spherically symmetric
background, e.g. an evaporating black hole. The angular-splitting variant
presented here is most suitable to this purpose.


title: Probing Majorana and Andreev Bound States with Waiting Times

abstract:
  We consider a biased Normal-Superconducting junction with various types of
superconductivity. Depending on the class of superconductivity, a Majorana
bound state may appear at the interface. We show that this has important
consequences on the distribution of waiting times of electrons flowing out of
such an interface. Therefore, the waiting time distribution is shown to be a
clear fingerprint of Majorana bound state physics and may be considered as an
experimental signature of its presence.


title: Unified Treatment of the Luminosity Distance in Cosmology

abstract:
  Comparing the luminosity distance measurements to its theoretical predictions
is one of the cornerstones in establishing the modern cosmology. However, as
shown in Biern & Yoo, its theoretical predictions in literature are often
plagued with infrared divergences and gauge-dependences. This trend calls into
question the sanity of the methods used to derive the luminosity distance. Here
we critically investigate four different methods --- the geometric approach,
the Sachs approach, the Jacobi mapping approach, and the geodesic light cone
(GLC) approach to modeling the luminosity distance, and we present a unified
treatment of such methods, facilitating the comparison among the methods and
checking their sanity. All of these four methods, if exercised properly, can be
used to reproduce the correct description of the luminosity distance.