title:
Dust diffusion and settling in the presence of collisions: Trapping
  (sub)micron grains in the midplane

abstract:
  In protoplanetary disks, the distribution and abundance of small (sub)micron
grains are important for a range of physical and chemical processes. For
example, they dominate the optical depth at short wavelengths and their
surfaces are the sites of many important chemical reactions such as the
formation of water. Based on their aerodynamical properties (i.e., their strong
dynamical coupling with the surrounding gas) it is often assumed that these
small grains are well-mixed with the gas. Our goal is to study the vertical
(re)distribution of grains taking into account settling, turbulent diffusion,
as well as collisions with other dust grains. Assuming a fragmentation-limited
background dust population, we developed a Monte Carlo approach that follows
single monomers as they move through a vertical column of gas and become
incorporated in different aggregates as they undergo sticking and fragmenting
collisions. We find that (sub)micron grains are not necessarily well-mixed
vertically, but can become trapped in a thin layer with a scale-height that is
significantly smaller than that of the gas. This collisional trapping occurs
when the timescale for diffusion is comparable to or longer than the collision
timescale in the midplane and its effect is strongest when the most massive
particles in the size-distribution show significant settling. Based on
simulations and analytical considerations we conclude that for typical
dust-to-gas ratios and turbulence levels, the collisional trapping of small
grains should be a relatively common phenomenon. The absence of trapping could
then indicate a low dust-to-gas ratio, possibly because a large portion of the
dust mass has been removed through radial drift or is locked up in
planetesimals.


title: How to avoid mass matrix for linear hyperbolic problems

abstract:
  We are interested in the numerical solution of linear hyperbolic problems
using continuous finite elements of arbitrary order. It is well known that this
kind of methods, once the weak formulation has been written, leads to a system
of ordinary differential equations in $\R^N$, where $N$ is the number of
degrees of freedom. The solution of the resulting ODE system involves the
inversion of a sparse mass matrix that is not block diagonal. Here we show how
to avoid this step, and what are the consequences of the choice of the finite
element space. Numerical examples show the correctness of our approach.


title:
98% directional guiding of spin currents with 90 micrometer relaxation
  length in bilayer graphene using carrier drift

abstract:
  Electrical control of spin signals and long distance spin transport are major
requirements in the field of spin electronics. Here we report the efficient
guiding of spin currents at room temperature in high mobility hexagonal boron
nitride encapsulated bilayer graphene using carrier drift. Our experiments,
together with modelling, show that the spin relaxation length can be tuned from
2 to 88 micrometers when applying a DC current of $\mp$40 uA respectively. Our
model predicts that, extending the range up to $\mathrm{I_{dc}}=\mp$150 uA, the
spin relaxation length can be tuned from 0.6 to 320 um respectively, indicating
that spin relaxation lengths in the millimeter range are within scope in near
future with moderate current densities. Our results also show that we are able
to direct spin currents on either side of a spin injection contact. 98% of the
injected spins flow to the left when $\mathrm{I_{dc}}$= -40 uA and 65% flow to
the right when the drift current is reversed. Our model shows that, for
$\mathrm{I_{dc}}=\mp$150 uA the numbers reach 99.8% and 95% respectively
showing the potential of carrier drift for spin-based logic operations and
devices.


title:
Temperatures and metallicities of M giants in the galactic Bulge from
  low-resolution K-band spectra

abstract:
  With the existing and upcoming large multi-fibre low-resolution
spectrographs, the question arises how precise stellar parameters such as Teff
and [Fe/H] can be obtained from low-resolution K-band spectra with respect to
traditional photometric temperature measurements. Until now, most of the
effective temperatures in galactic Bulge studies come directly from photometric
techniques. Uncertainties in interstellar reddening and in the assumed
extinction law could lead to large systematic errors. We aim to obtain and
calibrate the relation between Teff and the $\rm ^{12}CO$ first overtone bands
for M giants in the galactic Bulge covering a wide range in metallicity. We use
low-resolution spectra for 20 M giants with well-studied parameters from
photometric measurements covering the temperature range 3200 < Teff < 4500 K
and a metallicity range from 0.5 dex down to -1.2 dex and study the behaviour
of Teff and [Fe/H] on the spectral indices. We find a tight relation between
Teff and the $\rm ^{12}CO(2-0)$ band with a dispersion of 95 K as well as
between Teff and the $\rm ^{12}CO(3-1)$ with a dispersion of 120 K. We do not
find any dependence of these relations on the metallicity of the star, making
them relation attractive for galactic Bulge studies. This relation is also not
sensitive to the spectral resolution allowing to apply this relation in a more
general way.
  We also found a correlation between the combination of the NaI, CaI and the
$\rm ^{12}CO$ band with the metallicity of the star. However this relation is
only valid for sub-solar metallicities. We show that low-resolution spectra
provide a powerful tool to obtain effective temperatures of M giants. We show
that this relation does not depend on the metallicity of the star within the
investigated range and is also applicable to different spectral resolution.


title:
Influence of the stiffness of the equation of state and in-medium
  effects on the cooling of compact stars

abstract:
  Measurements demonstrate the existence of compact stars with masses in a
broad range from 1.2 to 2 $M_\odot$. The most massive of these objects might be
hybrid stars. To fulfill the constraint $M_{\rm max}>2~M_{\odot}$ with a
reserve we exploit the stiff DD2 hadronic equation of state (EoS) without and
with excluded volume (DD2vex) correction, which produce maximum neutron star
masses of $M_{\rm max} = 2.43~M_{\odot}$ and $2.70~M_{\odot}$, respectively. We
show that the stiffness of the EoS does not preclude an explanation of the
whole set of cooling data within "nuclear medium cooling" scenario for compact
stars by a variation of the star masses. We select appropriate proton gap
profiles from those exploited in the literature and allow for a variation of
the effective pion gap controlling the efficiency of the medium modified Urca
process. However, we suppress the possibility of pion condensation. In general,
the stiffer the EoS the steeper a decrease with density of the effective pion
gap is required. Results are compared with previously obtained ones for the HDD
EoS for which $M_{\rm max} =2.06~M_{\odot}$. The cooling of the compact star in
the supernova remnant Cassiopeia A (Cas A) is explained mainly by an efficient
medium modified Urca process. With the DD2vex EoS and using an effective pion
gap steeper decreasing with the density and/or a proton gap shifted to smaller
densities we are also able to reproduce both a strong decline compatible with
ACIS-S data and HRC-S instrument data. The mass of Cas A is estimated as $1.6 -
1.9~M_{\odot}$, above the value $1.5~M_{\odot}$, which we have evaluated with
the softer HDD equation of state. Different mass choices for the hottest object
XMMU J173203.3-344518 are discussed. We make general remarks also on hybrid
star cooling and on its dependence on the stiffness of the hadronic EoS.


title:
Constraints on cosmological viscosity and self interacting dark matter
  from gravitational wave observations

abstract:
  It has been shown that gravitational waves propagate through ideal fluids
without experiencing any dispersion or dissipation. However, if the medium has
a non-zero shear viscosity $\eta$ , gravitational waves will be dissipated at a
rate proportional to $G \,\eta$. We constrain dark matter and dark energy
models with non-zero shear viscosity by calculating the dissipation of
gravitational waves from GW150914 which propagate over a distance of $410\, $
Mpc through the dissipative fluid and comparing the data with the theoretical
prediction. This provides a proof-of-principle demonstration of the fact that
future observations gravitational waves at LIGO have the potential of better
constraining the viscosity of dark matter and dark energy.


title:
DROW: Real-Time Deep Learning based Wheelchair Detection in 2D Range
  Data

abstract:
  We introduce the DROW detector, a deep learning based detector for 2D range
data. Laser scanners are lighting invariant, provide accurate range data, and
typically cover a large field of view, making them interesting sensors for
robotics applications. So far, research on detection in laser range data has
been dominated by hand-crafted features and boosted classifiers, potentially
losing performance due to suboptimal design choices. We propose a Convolutional
Neural Network (CNN) based detector for this task. We show how to effectively
apply CNNs for detection in 2D range data, and propose a depth preprocessing
step and voting scheme that significantly improve CNN performance. We
demonstrate our approach on wheelchairs and walkers, obtaining state of the art
detection results. Apart from the training data, none of our design choices
limits the detector to these two classes, though. We provide a ROS node for our
detector and release our dataset containing 464k laser scans, out of which 24k
were annotated.


title: LHC Benchmarks from Flavored Gauge Mediation

abstract:
  We present benchmark points for LHC searches from flavored gauge mediation
models, in which messenger-matter couplings give flavor-dependent squark
masses. Our examples include spectra in which a single squark - stop, scharm,
or sup - is much lighter than all other colored superpartners, motivating
improved quark flavor tagging at the LHC. Many examples feature flavor mixing;
in particular, large stop-scharm mixing is possible. The correct Higgs mass is
obtained in some examples by virtue of the large stop A-term. We also revisit
the general flavor and CP structure of the models. Even though the A-terms can
be substantial, their contributions to EDM's are very suppressed, because of
the particular dependence of the A-terms on the messenger coupling. This holds
regardless of the messenger-coupling texture. More generally, the special
structure of the soft terms often leads to stronger suppression of flavor- and
CP-violating processes, compared to naive estimates.


title: Small ensembles of kriging models for optimization

abstract:
  The Efficient Global Optimization (EGO) algorithm uses a conditional
Gaus-sian Process (GP) to approximate an objective function known at a finite
number of observation points and sequentially adds new points which maximize
the Expected Improvement criterion according to the GP. The important factor
that controls the efficiency of EGO is the GP covariance function (or kernel)
which should be chosen according to the objective function. Traditionally, a
pa-rameterized family of covariance functions is considered whose parameters
are learned through statistical procedures such as maximum likelihood or
cross-validation. However, it may be questioned whether statistical procedures
for learning covariance functions are the most efficient for optimization as
they target a global agreement between the GP and the observations which is not
the ultimate goal of optimization. Furthermore, statistical learning procedures
are computationally expensive. The main alternative to the statistical learning
of the GP is self-adaptation, where the algorithm tunes the kernel parameters
based on their contribution to objective function improvement. After
questioning the possibility of self-adaptation for kriging based optimizers,
this paper proposes a novel approach for tuning the length-scale of the GP in
EGO: At each iteration, a small ensemble of kriging models structured by their
length-scales is created. All of the models contribute to an iterate in an
EGO-like fashion. Then, the set of models is densified around the model whose
length-scale yielded the best iterate and further points are produced.
Numerical experiments are provided which motivate the use of many
length-scales. The tested implementation does not perform better than the
classical EGO algorithm in a sequential context but show the potential of the
approach for parallel implementations.


title: Pliability, or the whitney extension theorem for curves in carnot groups

abstract:
  The Whitney extension theorem is a classical result in analysis giving a
necessary and sufficient condition for a function defined on a closed set to be
extendable to the whole space with a given class of regularity. It has been
adapted to several settings, among which the one of Carnot groups. However, the
target space has generally been assumed to be equal to R^d for some d $\ge$ 1.
We focus here on the extendability problem for general ordered pairs
(G\_1,G\_2) (with G\_2 non-Abelian). We analyze in particular the case G\_1 = R
and characterize the groups G\_2 for which the Whitney extension property
holds, in terms of a newly introduced notion that we call pliability.
Pliability happens to be related to rigidity as defined by Bryant an Hsu. We
exploit this relation in order to provide examples of non-pliable Carnot
groups, that is, Carnot groups so that the Whitney extension property does not
hold. We use geometric control theory results on the accessibility of control
affine systems in order to test the pliability of a Carnot group. In
particular, we recover some recent results by Le Donne, Speight and Zimmermann
about Lusin approximation in Carnot groups of step 2 and Whitney extension in
Heisenberg groups. We extend such results to all pliable Carnot groups, and we
show that the latter may be of arbitrarily large step.


title: Mining Hierarchical Temporal Roles with Multiple Metrics

abstract:
  Temporal role-based access control (TRBAC) extends role-based access control
to limit the times at which roles are enabled. This paper presents a new
algorithm for mining high-quality TRBAC policies from timed ACLs (i.e., ACLs
with time limits in the entries) and optionally user attribute information.
Such algorithms have potential to significantly reduce the cost of migration
from timed ACLs to TRBAC. The algorithm is parameterized by the policy quality
metric. We consider multiple quality metrics, including number of roles,
weighted structural complexity (a generalization of policy size), and (when
user attribute information is available) interpretability, i.e., how well role
membership can be characterized in terms of user attributes. Ours is the first
TRBAC policy mining algorithm that produces hierarchical policies, and the
first that optimizes weighted structural complexity or interpretability. In
experiments with datasets based on real-world ACL policies, our algorithm is
more effective than previous algorithms at optimizing policy quality.


title: A Hybrid Linear Logic for Constrained Transition Systems

abstract:
  Linear implication can represent state transitions, but real transition
systems operate under temporal, stochastic or probabilistic constraints that
are not directly representable in ordinary linear logic. We propose a general
modal extension of intuitionistic linear logic where logical truth is indexed
by constraints and hybrid connectives combine constraint reasoning with logical
reasoning. The logic has a focused cut-free sequent calculus that can be used
to internalize the rules of particular constrained transition systems; we
illustrate this with an adequate encoding of the synchronous stochastic
pi-calculus.


title: A Tangible Volume for Portable 3D Interaction

abstract:
  We present a new approach to achieve tangible object manipulation with a
single, fully portable and self-contained device. Our solution is based on the
concept of a "tangible volume". We turn a tangible object into a handheld
fish-tank display. The tangible volume represents a volume of space that can be
freely manipulated within a virtual scene. This volume can be positioned onto
virtual objects to directly grasp them, and to manipulate them in 3D space. We
investigate this concept through two user studies. The first study evaluates
the intuitiveness of using a tangible volume for grasping and manipulating
virtual objects. The second study evaluates the effects of the limited field of
view on spatial awareness. Finally, we present a generalization of this concept
to other forms of interaction through the surface of the volume.


title:
Semidirect products of C*-quantum groups: multiplicative unitaries
  approach

abstract:
  C*-quantum groups with projection are the noncommutative analogues of
semidirect products of groups. Radford's Theorem about Hopf algebras with
projection suggests that any C*quantum group with projection decomposes
uniquely into an ordinary C*-quantum group and a "braided" C*-quantum group. We
establish this on the level of manageable multiplicative unitaries.


title:
Online but Accurate Inference for Latent Variable Models with Local
  Gibbs Sampling

abstract:
  We study parameter inference in large-scale latent variable models. We first
propose an unified treatment of online inference for latent variable models
from a non-canonical exponential family, and draw explicit links between
several previously proposed frequentist or Bayesian methods. We then propose a
novel inference method for the frequentist estimation of parameters, that
adapts MCMC methods to online inference of latent variable models with the
proper use of local Gibbs sampling. Then, for latent Dirich-let allocation,we
provide an extensive set of experiments and comparisons with existing work,
where our new approach outperforms all previously proposed methods. In
particular, using Gibbs sampling for latent variable inference is superior to
variational inference in terms of test log-likelihoods. Moreover, Bayesian
inference through variational methods perform poorly, sometimes leading to
worse fits with latent variables of higher dimensionality.


title:
Radio Galaxy Zoo: host galaxies and radio morphologies for large surveys
  from visual inspection

abstract:
  We present early results from Radio Galaxy Zoo, a web-based citizen science
project for visual inspection and classification of images from all-sky radio
surveys. The goals of the project are to classify individual radio sources
(particularly galaxies with multiple lobes and/or complex morphologies) as well
as matching the continuum radio emission to the host galaxy. Radio images come
from the FIRST and ATLAS surveys, while matches to potential hosts are
performed with infrared imaging from WISE and SWIRE. The first twelve months of
classification yielded more than 1 million classifications of more than 60,000
sources. For images with at least 75% consensus by the volunteer classifiers,
the accuracy is comparable to visual inspection by the expert science team.
Based on mid-infrared colors, the hosts associated with radio emission are
primarily a mixture of elliptical galaxies, QSOs, and LIRGs, which are in good
agreement with previous studies. The full catalog of radio lobes and their host
galaxies will measure the relative populations of host types as a function of
radio morphology and power. Radio Galaxy Zoo has also been an effective method
for detecting extremely rare objects, such as HyMORs and giant radio galaxies.
Results from the project are being used to train automatic algorithms for host
matching for use in future large continuum surveys such as EMU, as well as
establishing roles for citizen science in projects such as the SKA.


title:
Family of intersecting totally real manifolds of $(C^n ,0)$ and germs of
  holomorphic diffeomorphisms

abstract:
  We prove the existence (and give a characterization) of a germ of complex
analytic set left invariant by an abelian group of germs of holomorphic
diffeomorphisms at a common fixed point.We also give condition that ensure that
such a group can be linearized holomorphically near the fixed point. It rests
on a "small divisors condition" of the family of linear parts. The second part
of this article is devoted to the study families of totally real intersecting
n-submanifolds of (C n , 0). We give some conditions which allow to straighten
holomorphically the family. If this is not possible to do it formally, we
construct a germ of complex analytic set at the origin which interesection with
the family can be holomorphically straightened. The second part is an
application of the first.


title: Finite Temperature Phase Transitions in the SU$(N)$ Hubbard model

abstract:
  We investigate the SU($N$) Hubbard model for the multi-component fermionic
optical lattice system, combining dynamical mean-field theory with the
continuous-time quantum Monte Carlo method. We obtain the finite temperature
phase diagrams with $N\le 6$ and find that low temperature properties depends
on the parity of the components. The magnetically ordered state competes with
the correlated metallic state in the system with the even number of components
$(N\ge 4)$, yielding the first-order phase transition. It is also clarified
that, in the odd-component system, the ordered state is realized at relatively
lower temperatures and the critical temperature is constant in the strong
coupling limit.


title: The Maslov and Morse indices for Schrodinger operators on [0,1]

abstract:
  Assuming a symmetric potential and separated self-adjoint boundary
conditions, we relate the Maslov and Morse indices for Schr\"odinger operators
on $[0, 1]$. We find that the Morse index can be computed in terms of the
Maslov index and two associated matrix eigenvalue problems. This provides an
efficient way to compute the Morse index for such operators.


title: A regularization-based approach for unsupervised image segmentation

abstract:
  We propose a novel unsupervised image segmentation algorithm, which aims to
segment an image into several coherent parts. It requires no user input, no
supervised learning phase and assumes an unknown number of segments. It
achieves this by first over-segmenting the image into several hundred
superpixels. These are iteratively joined on the basis of a discriminative
classifier trained on color and texture information obtained from each
superpixel. The output of the classifier is regularized by a Markov random
field that lends more influence to neighbouring superpixels that are more
similar. In each iteration, similar superpixels fall under the same label,
until only a few coherent regions remain in the image. The algorithm was tested
on a standard evaluation data set, where it performs on par with
state-of-the-art algorithms in term of precision and greatly outperforms the
state of the art by reducing the oversegmentation of the object of interest.


title:
An MILP Approach for Real-time Optimal Controller Synthesis with Metric
  Temporal Logic Specifications

abstract:
  The fundamental idea of this work is to synthesize reactive controllers such
that closed-loop execution trajectories of the system satisfy desired
specifications that ensure correct system behaviors, while optimizing a desired
performance criteria. In our approach, the correctness of a system's behavior
can be defined according to the system's relation to the environment, for
example, the output trajectories of the system terminate in a goal set without
entering an unsafe set. Using Metric Temporal Logic (MTL) specifications we can
further capture complex system behaviors and timing requirements, such as the
output trajectories must pass through a number of way-points within a certain
time frame before terminating in the goal set. Given a Mixed Logical Dynamical
(MLD) system and system specifications in terms of MTL formula or simpler
reach-avoid specifications, our goal is to find a closed-loop trajectory that
satisfies the specifications, in non-deterministic environments. Using an MILP
framework we search over the space of input signals to obtain such valid
trajectories of the system, by adding constraints to satisfy the MTL formula
only when necessary, to avoid the exponential complexity of solving MILP
problems. We also present experimental results for planning a path for a mobile
robot through a dynamically changing environment with a desired task
specification.


title: Resource Sharing in 5G mmWave Cellular Networks

abstract:
  In this paper, we discuss resource sharing, a key dimension in mmWave network
design in which spectrum, access and/or network infrastructure resources can be
shared by multiple operators. It is argued that this sharing paradigm will be
essential to fully exploit the tremendous amounts of bandwidth and the large
number of antenna degrees of freedom available in these bands, and to provide
statistical multiplexing to accommodate the highly variable nature of the
traffic. In this paper, we investigate and compare various sharing
configurations in order to capture the enhanced potential of mmWave
communications. Our results reflect both the technical and the economical
aspects of the various sharing paradigms. We deliver a number of key insights,
corroborated by detailed simulations, which include an analysis of the effects
of the distinctive propagation characteristics of the mmWave channel, along
with a rigorous multi-antenna characterization. Key findings of this study
include (i) the strong dependence of the comparative results on channel
propagation and antenna characteristics, and therefore the need to accurately
model them, and (ii) the desirability of a full spectrum and infrastructure
sharing configuration, which may result in increased user rate as well as in
economical advantages for both service provider.


title:
Robust Model Reduction Of Hyperbolic Problems by $L^1$-norm Minimization
  and Dictionary Approximation

abstract:
  We propose a novel model reduction approach for the approximation of non
linear hyperbolic equations in the scalar and the system cases. The approach
relies on an offline computation of a dictionary of solutions together with an
online $L^1$-norm minimization of the residual. It is shown why this is a
natural framework for hyperbolic problems and tested on nonlinear problems such
as Burgers' equation and the one-dimensional Euler equations involving shocks
and discontinuities. Efficient algorithms are presented for the computation of
the $L^1$-norm minimizer, both in the cases of linear and nonlinear residuals.
Results indicate that the method has the potential of being accurate when
involving only very few modes, generating physically acceptable,
oscillation-free, solutions.


title: Linear Versus Non-linear Supersymmetry, in General

abstract:
  We study superconformal and supergravity models with constrained superfields.
The underlying version of such models with all unconstrained superfields and
linearly realized supersymmetry is presented here, in addition to the physical
multiplets there are Lagrange multiplier (LM) superfields. Once the equations
of motion for the LM superfields are solved, some of the physical superfields
become constrained. The linear supersymmetry of the original models becomes
non-linearly realized, its exact form can be deduced from the original linear
supersymmetry. Known examples of constrained superfields are shown to require
the following LM's: chiral superfields, linear superfields, general complex
superfields, some of them are multiplets with a spin.


title:
Experimental study of three-wave interactions among capillary-gravity
  surface waves

abstract:
  In propagating wave systems, three or four-wave resonant interactions
constitute a classical non-linear mechanism exchanging energy between the
different scales. Here we investigate three-wave interactions for
gravity-capillary surface waves in a closed laboratory tank. We generate two
crossing wave-trains and we study their interaction. Using two optical methods,
a local one (Laser Doppler Vibrometry) and a spatio-temporal one (Diffusive
Light Photography), a third wave of smaller amplitude is detected, verifying
the three-wave resonance conditions in frequency and in wavenumber.
Furthermore, by focusing on the stationary regime and by taking into account
viscous dissipation, we directly estimate the growth rate of the resonant mode.
The latter is then compared to the predictions of the weakly non-linear triadic
resonance interaction theory. The obtained results confirm qualitatively and
extend previous experimental results obtained only for collinear wave-trains.
Finally, we discuss the relevance of three-wave interaction mechanisms in
recent experiments studying gravity-capillary turbulence.


title:
Study and evaluation of an Irregular Graph Algorithm on Multicore and
  GPU Processor Architectures

abstract:
  One area of Computing applications which poses significant challenge of
performance scalability on Chip Multiprocessors(CMP's) are Irregular
applications. Such applications have very little computation and unpredictable
memory access patterns making them memory-bound in contrast to compute-bound
applications. Since the gap between processor and memory performance continues
to exist, difficulty to hide and decrease this gap is one of the important
factors which results in poor performance of these applications on CMP's.
  The goal of this thesis is to overcome many such challenges posed during
performance acceleration of an irregular graph algorithm called Triad Census.
We accelerated the Triad Census algorithm on two significantly different Chip
Multiprocessors: Dual-socket Intel Xeon Multicore (8 hardware threads per
socket) and 240-processor core NVIDIA Tesla C1060 GPGPU(128 hardware threads
per core).
  The experimental results obtained on Intel Multicore Xeon system shows
performance speedups (w.r.t baseline sequential) of maximum 56x , average 33x
and minimum 8.3x for real world graph data sets. On NVIDIA Tesla C1060 GPGPU,
we were able to match almost equally the Multicore results - 58.4x maximum,
32.8x average and 4.2x minimum speedups w.r.t baseline sequential. In terms of
raw performance, for the graph data set called Patents network, our results on
Intel Xeon Multicore(16 hw threads) were 1.27x times faster than previous
results on Cray XMT(16 hw threads) while results achieved on GPGPU were
comparatively slower(0.72x). To the best of our knowledge, this algorithm has
only been accelerated on supercomputer class computer named Cray XMT and no
work exists that demonstrates performance evaluation and comparison of this
algorithm on relatively lower-cost Multicore and GPGPU based platforms.


title:
Structural and Electrical Properties of MoTe$_2$ and MoSe$_2$ Grown by
  Molecular Beam Epitaxy

abstract:
  We demonstrate the growth of thin films of molybdenum ditelluride and
molybdenum diselenide on sapphire substrates by molecular beam epitaxy. In-situ
structural and chemical analyses reveal stoichiometric layered film growth with
atomically smooth surface morphologies. Film growth along the (001) direction
is confirmed by X-ray diffraction, and the crystalline nature of growth in the
2H phase is evident from Raman spectroscopy. Transmission electron microscopy
is used to confirm the layered film structure and hexagonal arrangement of
surface atoms. Temperature dependent electrical measurements show an insulating
behavior which agrees well with a two-dimensional variable-range hopping model,
suggesting that transport in these films is dominated by localized
charge-carrier states.


title: Data-driven probability concentration and sampling on manifold

abstract:
  A new methodology is proposed for generating realizations of a random vector
with values in a finite-dimensional Euclidean space that are statistically
consistent with a data set of observations of this vector. The probability
distribution of this random vector, while a-priori not known, is presumed to be
concentrated on an unknown subset of the Euclidean space. A random matrix is
introduced whose columns are independent copies of the random vector and for
which the number of columns is the number of data points in the data set. The
approach is based on the use of (i) the multidimensional kernel-density
estimation method for estimating the probability distribution of the random
matrix, (ii) a MCMC method for generating realizations for the random matrix,
(iii) the diffusion-maps approach for discovering and characterizing the
geometry and the structure of the data set, and (iv) a reduced-order
representation of the random matrix, which is constructed using the
diffusion-maps vectors associated with the first eigenvalues of the transition
matrix relative to the given data set. The convergence aspects of the proposed
methodology are analyzed and a numerical validation is explored through three
applications of increasing complexity. The proposed method is found to be
robust to noise levels and data complexity as well as to the intrinsic
dimension of data and the size of experimental data sets. Both the methodology
and the underlying mathematical framework presented in this paper contribute
new capabilities and perspectives at the interface of uncertainty
quantification, statistical data analysis, stochastic modeling and associated
statistical inverse problems.


title:
Convergence of a Normalized Gradient Algorithm for Computing Ground
  States

abstract:
  We consider the approximation of the ground state of the one-dimensional
cubic nonlinear Schr{\"o}dinger equation by a normalized gradient algorithm
combined with linearly implicit time integrator, and finite difference space
approximation. We show that this method, also called imaginary time evolution
method in the physics literature, is con-vergent, and we provide error
estimates: the algorithm converges exponentially towards a modified solitons
that is a space discretization of the exact soliton, with error estimates
depending on the discretization parameters.


title: Searching for Cosmological Preferred Axis using cosmographic approach

abstract:
  Recent released Planck data and other astronomical observations show that the
universe may be anisotropic on large scales. This hints a cosmological
privileged axis in our anisotropic expanding universe. This paper proceeds a
modified redshift in anisotropic cosmological model as $
1+\tilde{z}(t,\hat{\textbf{p}})=\frac{a(t_{0)}}{a(t)}(1-A(\hat{\textbf{n}}.\hat{\textbf{p}}))$
(where $A$ is the magnitude of anisotropy ,$\hat{\textbf{n}}$ is the direction
of privileged axis, and $\hat{\textbf{p}}$ is the direction of each SNe Ia
sample to galactic coordinates) along with anisotropic parameter
$\delta=\frac{A(\hat{\textbf{n}}.\hat{\textbf{p}})}{1+A(\hat{\textbf{n}}.\hat{\textbf{p}})}$.
The luminosity distance is expanded with model-independent cosmographic
parameters as a function of modified redshift $\tilde{z}$. As the
transformation matrix $M(n\times n)$ is obtained to convert the Taylor series
coefficients of isotropic luminosity distance to corresponding anisotropic
parameters. These results culminate the magnitude of anisotropy about $\mid
A\mid \simeq 10^{-3}$ and the direction of preferred axis as
$(l,b)=(297^{-34}_{+34},3^{-28}_{+28})$, which are consistent with other
studies in $1-\sigma$ confidence level.


title: LG/CY Correspondence for Elliptic Orbifold Curves via Modularity

abstract:
  We prove the Landau-Ginzburg/Calabi-Yau correspondence between the
Gromov-Witten theory of each elliptic orbifold curve and its
Fan-Jarvis-Ruan-Witten theory counterpart via modularity. We show that the
correlation functions in these two enumerative theories are different
representations of the same set of quasi-modular forms, expanded around
different points on the upper-half plane. We relate these two representations
by the Cayley transform.


title: Orthogonal Nilpotent Superfields from Linear Models

abstract:
  We derive supersymmetry/supergravity models with constrained orthogonal
nilpotent superfields from the linear models in the formal limit where the
masses of the sgoldstino, inflatino and sinflaton tend to infinity. The case
where the sinflaton mass remains finite leads to a model with a `relaxed'
constraint, where the sinflaton remains an independent field. Our procedure is
equivalent to a requirement that some of the components of the curvature of the
moduli space tend to infinity.


title:
CONAN -- the cruncher of local exchange coefficients for strongly
  interacting confined systems in one dimension

abstract:
  We consider a one-dimensional system of particles with strong zero-range
interactions. This system can be mapped onto a spin chain of the Heisenberg
type with exchange coefficients that depend on the external trap. In this
paper, we present an algorithm that can be used to compute these exchange
coefficients. We introduce an open source code CONAN (Coefficients of
One-dimensional N-Atom Networks) which is based on this algorithm. CONAN works
with arbitrary external potentials and we have tested its reliability for
system sizes up to around 35 particles. As illustrative examples, we consider a
harmonic trap and a box trap with a superimposed asymmetric tilted potential.
For these examples, the computation time typically scales with the number of
particles as $O(N^{3.5 \pm 0.4})$. Computation times are around 10 seconds for
$N=10$ particles and less than 10 minutes for $N=20$ particles.

categories: cond-mat.quant-gas cond-mat.mes-hall physics.comp-ph quant-ph


title: Predictions for diphoton production at the LHC through NNLO in QCD

abstract:
  In this paper we present a next-to-next-to-leading order (NNLO) calculation
of the process $pp\rightarrow \gamma\gamma$ that we have implemented into the
parton level Monte Carlo code MCFM. We do not find agreement with the previous
calculation of this process in the literature. In addition to the
$\mathcal{O}(\alpha_s^2)$ corrections present at NNLO, we include some effects
arising at $\mathcal{O}(\alpha_s^3)$, namely those associated with
gluon-initiated closed fermion loops. We investigate the role of this process
in the context of studies of QCD at colliders and as a background for searches
for new physics, paying particular attention to the diphoton invariant mass
spectrum. We demonstrate that the NNLO QCD prediction for the shape of this
spectrum agrees well with functional forms used in recent data-driven fits.


title:
Interpreting the CMB aberration and Doppler measurements: boost or
  intrinsic dipole?

abstract:
  The aberration and Doppler coupling effects of the Cosmic Microwave
Background (CMB) were recently measured by the Planck satellite. The most
straightforward interpretation leads to a direct detection of our peculiar
velocity $\beta$, consistent with the measurement of the well-known dipole. In
this paper we discuss the assumptions behind such interpretation. We show that
Doppler-like couplings appear from two effects: our peculiar velocity and a
second order large-scale effect due to the dipolar part of the gravitational
potential. We find that the two effects are exactly degenerate but only if we
assume second-order initial conditions from single-field Inflation. Thus,
detecting a discrepancy in the value of $\beta$ from the dipole and the Doppler
couplings implies the presence of a primordial non-Gaussianity. We also show
that aberration-like signals likewise arise from two independent effects: our
peculiar velocity and lensing due to a first order large-scale dipolar
gravitational potential, independently on Gaussianity of the initial
conditions. In general such effects are not degenerate and so a discrepancy
between the measured $\beta$ from the dipole and aberration could be accounted
for by a dipolar gravitational potential. Only through a fine-tuning of the
radial profile of the potential it is possible to have a complete degeneracy
with a boost effect. Finally we discuss that we also expect other signatures
due to integrated second order terms, which may be further used to disentangle
this scenario from a simple boost.


title:
A Note on Bootstrapping M-estimates from Unstable AR(2) Process with
  Infinite Variance Innovations

abstract:
  The limiting distribution for M-estimates in a non-stationary autoregressive
model with heavy-tailed error is computationally intractable. To make
inferences based on the M-estimates, the bootstrap procedure can be used to
approximate the sampling distribution. In this paper, we show that the
bootstrap scheme with $m=o(n)$ resampling sample size when $m/n \to 0$ is
approximately valid in a multiple unit roots time series with innovations in
the domain of attraction of a stable law with index $0<\alpha\leq2$.


title: The Moduli Space in the Gauged Linear Sigma Model

abstract:
  This is a survey article for the mathematical theory of Witten's Gauged
Linear Sigma Model, as developed recently by the authors. Instead of developing
the theory in the most general setting, in this paper we focus on the
description of the moduli.


title:
Continuum mechanics of the interaction of phase boundaries and
  dislocations in solids

abstract:
  The continuum mechanics of line defects representing singularities due to
terminating discontinuities of the elastic displacement and its gradient field
is developed. The development is intended for application to coupled phase
transformation, grain boundary, and plasticity-related phenomena at the level
of individual line defects and domain walls. The continuously distributed
defect approach is developed as a generalization of the discrete, isolated
defect case. Constitutive guidance for equilibrium response and dissipative
driving forces respecting frame-indifference and non-negative mechanical
dissipation is derived. A differential geometric interpretation of the defect
kinematics is developed, and the relative simplicity of the actual adopted
kinematics is pointed out. The kinematic structure of the theory strongly
points to the incompatibility of dissipation with strict deformation
compatibility.


title: Hyperbolic geodesics, Krzyz's conjecture and beyond

abstract:
  In 1968, Krzyz conjectured that for non-vanishing holomorphic functions $f(z)
= c_0 + c_1 z + \dots$ in the unit disk with $|f(z)| \leq 1$, we have the sharp
bound $|c_n| \leq 2/e$ for all $n \geq 1$, with equality only for the function
$f(z) = exp [(z^n - 1)/(z^n + 1)]$ and its rotations. This conjecture was
considered by many researchers, but only partial results have been established.
The desired estimate has been proved only for $n \leq 5$.
  We provide here two different proofs of this conjecture and its
generalizations based on completely different ideas.


title: Photonic Simulation of Entanglement Growth After a Spin Chain Quench

abstract:
  The time evolution of quantum many-body systems is one of the least
understood frontiers of physics. The most curious feature of such dynamics is,
generically, the growth of quantum entanglement with time to an amount
proportional to the system size (volume law) even when the interactions are
local. This phenomenon, unobserved to date, has great ramifications for
fundamental issues such as thermalisation and black-hole formation, while its
optimisation clearly has an impact on technology (e.g., for on-chip quantum
networking). Here we use an integrated photonic chip to simulate the dynamics
of a spin chain, a canonical many-body system. A digital approach is used to
engineer the evolution so as to maximise the generation of entanglement. The
resulting volume law growth of entanglement is certified by constructing a
second chip, which simultaneously measures the entanglement between multiple
distant pairs of simulated spins. This is the first experimental verification
of the volume law and opens up the use of photonic circuits as a unique tool
for the optimisation of quantum devices.

categories: quant-ph cond-mat.other cond-mat.stat-mech cond-mat.str-el


title: Instability of black strings in third-order Lovelock theory

abstract:
  We show that homogeneous black strings of third-order Lovelock theory are
unstable under s-wave perturbations. This analysis is done in dimension $D=9$,
which is the lowest dimension that allows the existence of homogeneous black
strings in a theory that contains only the third-order Lovelock term in the
Lagrangian. As is the case in general relativity, the instability is produced
by long wavelength perturbations and it stands for the perturbative counterpart
of a thermal instability. We also provide a comparative analysis of the
instabilities of black strings at a fixed radius in general relativity,
Gauss-Bonnet and third-order Lovelock theory. We show that the minimum critical
wavelength that triggers the instability grows with the power of the curvature
defined in the Lagrangian. The maximum exponential growth during the time of
the perturbation is the largest in general relativity and it decreases with the
number of curvatures involved in the Lagrangian.


title: Multi-prover Proof-of-Retrievability

abstract:
  There has been considerable recent interest in "cloud storage" wherein a user
asks a server to store a large file. One issue is whether the user can verify
that the server is actually storing the file, and typically a
challenge-response protocol is employed to convince the user that the file is
indeed being stored correctly. The security of these schemes is phrased in
terms of an extractor which will recover the file given any "proving algorithm"
that has a sufficiently high success probability. This forms the basis of
\emph{proof-of-retrievability} ($\mathsf{PoR}$) systems.
  In this paper, we study multiple server $\mathsf{PoR}$ systems. We formalize
security definitions for two possible scenarios: (i) when a threshold of
servers succeed with high enough probability (worst-case) and (ii) when the
average of the success probability of all the servers is above a threshold
(average-case). We also motivate the study of confidentiality of the outsourced
message. We give $\mathsf{M}\mbox{-}\mathsf{PoR}$ schemes which are secure
under both these security definitions and provide reasonable confidentiality
guarantees even when there is no restriction on the computational power of the
servers. We also show how classical statistical techniques used by Paterson,
Stinson and Upadhyay (Journal of Mathematical Cryptology: 7(3)) can be extended
to evaluate whether the responses of the provers are accurate enough to permit
successful extraction. We also look at one specific instantiation of our
construction when instantiated with the unconditionally secure version of the
Shacham-Waters scheme (Asiacrypt, 2008). This scheme gives reasonable security
and privacy guarantee. We show that, in the multi-server setting with
computationally unbounded provers, one can overcome the limitation that the
verifier needs to store as much secret information as the provers.


title:
FORS2/VLT survey of Milky Way globular clusters II. Fe and Mg abundances
  of 51 Milky Way globular clusters on a homogeneous scale

abstract:
  (ABRIDGED) Globular clusters trace the formation and evolution of the Milky
Way and surrounding galaxies, and outline their chemical enrichment history. To
accomplish these tasks it is important to have large samples of clusters with
homogeneous data and analysis to derive kinematics, chemical abundances, ages
and locations. We obtain homogeneous metallicities and alpha-element
enhancement for over 800 red giant stars in 51 Galactic bulge, disc, and halo
globular clusters that are among the most distant and/or highly reddened in the
Galaxy's globular cluster system. We observed R ~ 2000 spectra in the
wavelength interval 456-586 nm and applied full spectrum fitting technique. We
compared the mean abundances of all clusters with previous work and with field
stars. We used the relation between mean metallicity and horizontal branch
morphology defined by all clusters to select outliers for discussion. We find
our metallicities are comparable to those derived from high-resolution data to
within sigma = 0.08 dex over the interval -2.5 < [Fe/H] < 0.0. We also find
that the distribution of [Mg/Fe] and [alpha/Fe] with [Fe/H] for the 51 clusters
follows the general trend exhibited by field stars. It is the first time that
the following clusters have been included in a large sample of homogeneous
stellar spectroscopic observations and metallicity derivation: BH 176, Djorg 2,
Pal 10, NGC 6426, Lynga 7, and Terzan 8. In particular, only photometric
metallicities were available previously for the first three clusters, and the
available metallicity for NGC 6426 was based on integrated spectroscopy and
photometry. Two other clusters, HP 1 and NGC 6558, are confirmed as candidates
for the oldest globular clusters in the Milky Way. The technique used here can
also be applied to globular cluster systems in nearby galaxies with current
instruments and to distant galaxies with the advent of ELTs.


title: Filtering the Heegaard Floer contact invariant

abstract:
  We define an invariant of contact structures in dimension three from Heegaard
Floer homology. This invariant takes values in the set
$\mathbb{Z}_{\geq0}\cup\{\infty\}$. It is zero for overtwisted contact
structures, $\infty$ for Stein fillable contact structures, non-decreasing
under Legendrian surgery, and computable from any supporting open book
decomposition. As an application, we obstruct Stein fillability on contact
3-manifolds with non-vanishing Ozsv\'ath-Szab\'o contact class.


title: Elastic Gauge Fields in Weyl Semimetals

abstract:
  We show that, as it happens in graphene, elastic deformations couple to the
electronic degrees of freedom as pseudo gauge fields in Weyl semimetals. We
derive the form of the elastic gauge fields in a tight-binding model hosting
Weyl nodes and see that this vector electron-phonon coupling is chiral,
providing an example of axial gauge fields in three dimensions. As an example
of the new response functions that arise associated to these elastic gauge
fields, we derive a non-zero phonon Hall viscosity for the neutral system at
zero temperature. The axial nature of the fields provides a test of the chiral
anomaly in high energy with three axial vector couplings.


title:
Growth of half-metallic CrO2 nanostructures for superconducting
  spintronic applications

abstract:
  Superconductor-ferromagnet (S-F) hybrids based on half-metallic ferromagnets,
such as CrO2, are excellent candidates for superconducting spintronic
applications. This is primarily due to their fully spin polarized nature, which
produces significantly enhanced long-range triplet proximity effects.. However,
reliable production of CrO2-based Josephson junctions (JJs) is challenging,
mainly because of the difficulty to control the transparency of the S/F
interface. We have grown CrO2 nanowires by chemical vapor deposition on TiO2
substrates combined with selective area growth in trenches defined with
amorphous SiOx. This allows us to create lateral JJs, with the nanowire as the
weak link. We show that the nature of the growth is highly anisotropic, and
that the morphology of the CrO2 nanostructructures changes systematically
during the growth process, depending on the width of the trench. The detailed
growth study enables us to synthesise multifaceted and highly homogeneous CrO2
wires. These are utilized to fabricate JJs with high S/F interface
transparency, leading to large supercurrents. The well-defined geometry of the
device allows us to reliably estimate an exceptionally high critical current
density Jc = 10^9~Am^{-2} over a distance of 600~nm.


title:
Magnetic black holes and monopoles in a nonminimal Einstein-Yang-Mills
  theory with a cosmological constant: Exact solutions

abstract:
  Alternative theories of gravity and their solutions are of considerable
importance since at some fundamental level the world can reveal new features.
Indeed, it is suspected that the gravitational field might be nonminimally
coupled to the other fields at scales not yet probed, bringing into the
forefront nonminimally coupled theories. In this mode, we consider a nonminimal
Einstein-Yang-Mills theory with a cosmological constant. Imposing spherical
symmetry and staticity for the spacetime and a magnetic Wu-Yang ansatz for the
Yang-Mills field, we find expressions for the solutions of the theory. Further
imposing constraints on the nonminimal parameters, we find a family of exact
solutions of the theory depending on five parameters, namely, two nonminimal
parameters, the cosmological constant, the magnetic charge, and the mass. These
solutions represent magnetic monopoles and black holes in magnetic monopoles
with de Sitter, Minkowskian, and anti-de Sitter asymptotics, depending on the
sign and value of the cosmological constant $\Lambda$. We classify completely
the family of solutions with respect to the number and the type of horizons and
show that the spacetime solutions can have, at most, four horizons. For
particular sets of the parameters, these horizons can become double, triple,
and quadruple. For instance, for a positive cosmological constant $\Lambda$,
there is a critical $\Lambda_c$ for which the solution admits a quadruple
horizon, evocative of the $\Lambda_c$ that appears for a given energy density
in both the Einstein static and Eddington-Lema\^{\i}tre dynamical universes. As
an example of our classification, we analyze solutions in the Drummond-Hathrell
nonminimal theory that describe nonminimal black holes. Another application is
with a set of regular black holes previously treated.


title:
On the Hamiltonian Analysis of Spin-3 Chern-Simons-Like Theories of
  Gravity

abstract:
  In this paper, we consider spin-3 Chern-Simons-like theories of gravity as
extended theories of spin-3 gravity in (2+1)- dimension. In order to determine
the number of local degrees of freedom we present the Hamiltonian formulation
of these theories. We extract the Hamiltonian density, then we find primary and
secondary constraints of these theories. Then we obtain the Poisson brackets of
the primary and the secondary constraints. After that we count the number of
local degrees of freedom of spin-3 Chern-Simons-like theories of gravity. We
apply this method on spin-3 Einstein-Cartan gravity and spin-3 topologically
massive gravity. According to the our results the spin-3 Einstein-Cartan
gravity and the spin-3 topologically massive gravity have respectively zero and
one bulk local degree of freedom.


title:
Holographic Superconductors with Logarithmic Nonlinear Electrodynamics
  in an External Magnetic Field

abstract:
  Based on the matching method, we explore the effects of adding an external
magnetic field on the $s$-wave holographic superconductor when the gauge field
is in the form of the logarithmic nonlinear source. First, we obtain the
critical temperature as well as the condensation operator in the presence of
logarithmic nonlinear electrodynamics and understand that they depend on the
nonlinear parameter $b$. We show that the critical temperature decreases with
increasing $b$, which implies that the nonlinear gauge field makes the
condensation harder. Then, we turn on the magnetic field in the bulk and find
the critical magnetic field, $B_c$, in terms of the temperature, which also
depends on the nonlinear parameter $b$. We observe that for temperature smaller
than the critical temperature, $T<T_c$, the critical magnetic field increases
with increasing $b$ and goes to zero as $T\rightarrow T_c$, independent of the
nonlinear parameter $b$. In the limiting case where $ b\rightarrow0 $, all
results restore those of the holographic superconductor with magnetic field in
Maxwell theory.


title: The Local Group: The Ultimate Deep Field

abstract:
  Near-field cosmology -- using detailed observations of the Local Group and
its environs to study wide-ranging questions in galaxy formation and dark
matter physics -- has become a mature and rich field over the past decade.
There are lingering concerns, however, that the relatively small size of the
present-day Local Group ($\sim 2$ Mpc diameter) imposes insurmountable
sample-variance uncertainties, limiting its broader utility. We consider the
region spanned by the Local Group's progenitors at earlier times and show that
it reaches $3' \approx 7$ co-moving Mpc in linear size (a volume of $\approx
350\,{\rm Mpc}^3$) at $z=7$. This size at early cosmic epochs is large enough
to be representative in terms of the matter density and counts of dark matter
halos with $M_{\rm vir}(z=7) \lesssim 2\times 10^{9}\,M_{\odot}$. The Local
Group's stellar fossil record traces the cosmic evolution of galaxies with
$10^{3} \lesssim M_{\star}(z=0) / M_{\odot} \lesssim 10^{9}$ (reaching
$M_{1500} > -9$ at $z\sim7$) over a region that is comparable to or larger than
the Hubble Ultra-Deep Field (HUDF) for the entire history of the Universe. It
is highly complementary to the HUDF, as it probes much fainter galaxies but
does not contain the intrinsically rarer, brighter sources that are detectable
in the HUDF. Archaeological studies in the Local Group also provide the ability
to trace the evolution of individual galaxies across time as opposed to
evaluating statistical connections between temporally distinct populations. In
the JWST era, resolved stellar populations will probe regions larger than the
HUDF and any deep JWST fields, further enhancing the value of near-field
cosmology.


title: Vacuum Stability of a General Scalar Potential of a Few Fields

abstract:
  We find analytical vacuum stability or bounded below conditions for general
scalar potentials of a few fields. After a brief review of copositivity we go
beyond it. We discuss the vacuum stability conditions of the general potential
of two real scalars, without and with the Higgs boson included in the
potential. As further examples, we give explicit vacuum stability conditions
for the two Higgs doublet model with no explicit CP breaking, and for the
$\mathbb{Z}_{3}$ scalar dark matter with an inert doublet and a complex
singlet. We give a short overview of positivity conditions for tensors of
quartic couplings via tensor eigenvalues. A Mathematica notebook with the
conditions is included with the source files.


title: Three-dimensional Hubbard model in the thermodynamic limit

abstract:
  We employ the numerical linked-cluster expansion to study finite-temperature
properties of the uniform cubic lattice Hubbard model in the thermodynamic
limit for a wide range of interaction strengths and densities. We carry out the
expansion to the 9th order and find that the convergence of the series extends
to lower temperatures as the strength of the interaction increases, giving us
access to regions of the parameter space that are difficult to reach by most
other numerical methods. We study the precise trends in the specific heat, the
double occupancy, and magnetic correlations at temperatures as low as 0.2 of
the hopping amplitude in the strong-coupling regime. We show that in this
regime, accurate estimates for transition temperatures to the N\'{e}el ordered
phase, in agreement with the predicted asymptotic behavior, can be deduced from
the low-temperature magnetic structure factor. We also find evidence for
possible instability to the magnetically ordered phase away from, but close to,
half filling. Our results have important implications for parametrizing
fermionic systems in optical lattice experiments and for benchmarking other
numerical methods.


title:
Formation of the Andromeda Giant Stream: Asymmetric Structure and Disc
  Progenitor

abstract:
  We focus on the evidence of a past minor merger discovered in the halo of the
Andromeda galaxy (M31). Previous N-body studies have enjoyed moderate success
in producing the observed giant stellar stream (GSS) and stellar shells in
M31's halo. The observed distribution of stars in the halo of M31 shows an
asymmetric surface brightness profile across the GSS; however, the effect of
the morphology of the progenitor galaxy on the internal structure of the GSS
requires further investigation in theoretical studies. To investigate the
physical connection between the characteristic surface brightness in the GSS
and the morphology of the progenitor dwarf galaxy, we systematically vary the
thickness, rotation velocity and initial inclination of the disc dwarf galaxy
in N-body simulations. The formation of the observed structures appears to be
dominated by the progenitor's rotation. Besides reproducing the observed GSS
and two shells in detail, we predict additional structures for further
observations. We predict the detectability of the progenitor's stellar core in
the phase-space density distribution, azimuthal metallicity gradient of the
western shell-like structure and an additional extended shell in the
north-western direction that may constrain the properties of the progenitor
galaxy.


title: Spin slush in an extended spin ice model

abstract:
  We introduce a new classical spin liquid on the pyrochlore lattice by
extending spin ice with further neighbour interactions. We find that this
disorder free spin model exhibits a form of dynamical heterogeneity with
extremely slow relaxation for some spins while others fluctuate quickly down to
zero temperature. We thus call this state "spin slush", in analogy to the
heterogeneous mixture of solid and liquid water. This behaviour is driven by
the structure of the ground state manifold which extends the celebrated the
two-in/two-out ice states to include branching structures built from
three-in/one-out, three-out/one-in and all-in/all-out tetrahedra defects.
Distinctive liquid-like patterns in the spin correlations serve as a signature
of this intermediate range order. Possible applications to materials as well
the effects of quantum tunneling are discussed.


title: Cornering gapless quantum states via their torus entanglement

abstract:
  The entanglement entropy (EE) has emerged as an important window into the
structure of complex quantum states of matter. We analyze the universal part of
the EE for gapless systems put on tori in 2d/3d, denoted by $\chi$. Focusing on
scale invariant systems, we derive general non-perturbative properties for the
shape dependence of $\chi$, and reveal surprising relations to the EE
associated with corners in the entangling surface. We obtain closed-form
expressions for $\chi$ in 2d/3d within a model that arises in the study of
conformal field theories (CFTs), and use them to obtain ansatzes without
fitting parameters for the 2d/3d free boson CFTs. Our numerical lattice
calculations show that the ansatzes are highly accurate. Finally, we discuss
how the torus EE can act as a fingerprint of exotic states such as gapless
quantum spin liquids, e.g. Kitaev's honeycomb model.


title: Declining rotation curves of galaxies as a test of gravitational theory

abstract:
  Unlike Newtonian dynamics which is linear and obeys the strong equivalence
principle, in any nonlinear gravitation such as Milgromian dynamics (MOND), the
strong version of the equivalence principle is violated and the gravitational
dynamics of a system is influenced by the external gravitational field in which
it is embedded. This so called External Field Effect (EFE) is one of the
important implications of MOND and provides a special context to test
Milgromian dynamics. Here, we study the rotation curves (RCs) of 18 spiral
galaxies and find that their shapes constrain the EFE. We show that the EFE can
successfully remedy the overestimation of rotation velocities in 80\% of the
sample galaxies in Milgromian dynamics fits by decreasing the velocity in the
outer part of the RCs. We compare the implied external field with the
gravitational field for non-negligible nearby sources of each individual galaxy
and find that in many cases it is compatible with the EFE within the
uncertainties. We therefore argue that in the framework of Milgromian dynamics,
one can constrain the gravitational field induced from the environment of
galaxies using their RCs. We finally show that taking into account the EFE
yields more realistic values for the stellar mass-to-light ratio in terms of
stellar population synthesis than the ones implied without the EFE.


title:
A deterministic alternative to the full configuration interaction
  quantum Monte Carlo method

abstract:
  Development of exponentially scaling methods has seen great progress in
tackling larger systems than previously thought possible. One such technique,
full configuration interaction quantum Monte Carlo, is a useful algorithm that
allows exact diagonalization through stochastically sampling determinants. The
method derives its utility from the information in the matrix elements of the
Hamiltonian, along with a stochastic projected wave function, to find the
important parts of Hilbert space. However, the stochastic representation of the
wave function is not required to search Hilbert space efficiently, and here we
describe a highly efficient deterministic method to achieve chemical accuracy
for a wide range of systems, including the difficult Cr$_{2}$ dimer. In
addition our method also allows efficient calculation of excited state
energies, for which we illustrate with benchmark results for the excited states
of C$_{2}$.


title: Kerr black holes with Proca hair

abstract:
  Bekenstein proved that in Einstein's gravity minimally coupled to one (or
many) real, Abelian, Proca field, stationary black holes (BHs) cannot have
Proca hair. Dropping Bekenstein's assumption that matter inherits spacetime
symmetries, we show this model admits asymptotically flat, stationary,
axi-symmetric, regular on and outside an event horizon BHs with Proca hair, for
an even number of real (or an arbitrary number of complex) Proca fields. To
establish it, we start by showing that a test, complex Proca field can form
bound states, with real frequency, around Kerr BHs: stationary Proca clouds.
These states exist at the threshold of superradiance. It was conjectured in
arXiv:1403.2757, that the existence of such clouds at the linear level implies
the existence of a new family of BH solutions at the non-linear level. We
confirm this expectation and explicitly construct examples of such Kerr black
holes with Proca hair (KBHsPH). For a single complex Proca field, these BHs
form a countable number of families with three continuous parameters (ADM mass,
ADM angular momentum and Noether charge). They branch off from the Kerr
solutions that can support stationary Proca clouds and reduce to Proca stars
when the horizon size vanishes. We present the domain of existence of one
family of KBHsPH, as well as its phase space in terms of ADM quantities. Some
physical properties of the solutions are discussed; in particular, and in
contrast with Kerr BHs with scalar hair, some spacetime regions can be
counter-rotating with respect to the horizon. We further establish a
no-Proca-hair theorem for static, spherically symmetric BHs but allowing the
complex Proca field to have a harmonic time dependence, which shows BHs with
Proca hair in this model require rotation and have no static limit. KBHsPH are
also disconnected from Kerr-Newman BHs with a real, massless vector field.


title: Constraining the efficiency of cosmic ray acceleration by cluster shocks

abstract:
  We study the acceleration of cosmic rays by collisionless structure formation
shocks with ENZO grid simulations. Data from the FERMI satellite enable the use
of galaxy clusters as a testbed for particle acceleration models. Based on
advanced cosmological simulations that include different prescriptions for gas
and cosmic rays physics, we use the predicted {\gamma}-ray emission to
constrain the shock acceleration efficiency. We infer that the efficiency must
be on average <0.1% for cosmic shocks, particularly for the 2<M<5 merger shocks
that are mostly responsible for the thermalisation of the intracluster medium.
These results emerge, both, from non-radiative and radiative runs including
feedback from active galactic nuclei, as well as from zoomed resimulations of a
cluster resembling MACSJ1752.0+0440. The limit on the acceleration efficiency
we report is lower than what has been assumed in the literature so far.
Combined with the information from radio emission in clusters, it appears that
a revision of the present understanding of shock acceleration in the ICM is
unavoidable.


title:
Ages of massive galaxies at $0.5 < z < 2.0$ from 3D-HST rest-frame
  optical spectroscopy

abstract:
  We present low-resolution near-infrared stacked spectra from the 3D-HST
survey up to $z=2.0$ and fit them with commonly used stellar population
synthesis models: BC03 (Bruzual & Charlot, 2003), FSPS10 (Flexible Stellar
Population Synthesis, Conroy & Gunn 2010), and FSPS-C3K (Conroy, Kurucz,
Cargile, Castelli, in prep). The accuracy of the grism redshifts allows the
unambiguous detection of many emission and absorption features, and thus a
first systematic exploration of the rest-frame optical spectra of galaxies up
to $z=2$. We select massive galaxies ($\rm log(M_{*} / M_{\odot}) > 10.8$), we
divide them into quiescent and star-forming via a rest-frame color-color
technique, and we median-stack the samples in 3 redshift bins between $z=0.5$
and $z=2.0$. We find that stellar population models fit the observations well
at wavelengths below $\rm 6500 \AA$ rest-frame, but show systematic residuals
at redder wavelengths. The FSPS-C3K model generally provides the best fits
(evaluated with a $\chi^2_{red}$ statistics) for quiescent galaxies, while BC03
performs the best for star-forming galaxies. The stellar ages of quiescent
galaxies implied by the models, assuming solar metallicity, vary from 4 Gyr at
$z \sim 0.75$ to 1.5 Gyr at $z \sim 1.75$, with an uncertainty of a factor of 2
caused by the unknown metallicity. On average the stellar ages are half the age
of the Universe at these redshifts. We show that the inferred evolution of ages
of quiescent galaxies is in agreement with fundamental plane measurements,
assuming an 8 Gyr age for local galaxies. For star-forming galaxies the
inferred ages depend strongly on the stellar population model and the shape of
the assumed star-formation history.


title:
On the Role of the $\Omega\Gamma$ Limit in the Formation of Population
  III Massive Stars

abstract:
  We explore the role of the modified Eddington limit due to rapid rotation
(the so-called $\Omega\Gamma-$limit) in the formation of Population III stars.
We performed one-dimensional stellar evolution simulations of mass-accreting
zero-metallicity protostars at a very high rate ($\dot{M} \sim
10^{-3}~\mathrm{M_\odot~yr^{-1}}$) and dealt with stellar rotation as a
separate post-process. The protostar would reach the Keplerian rotation very
soon after the onset of mass accretion, but mass accretion would continue as
stellar angular momentum is transferred outward to the accretion disk by
viscous stress. The protostar envelope expands rapidly when the stellar mass
reaches $5\sim7~\mathrm{M_\odot}$ and the Eddington factor sharply increases.
This makes the protostar rotate critically at a rate that is significantly
below the Keplerian value (i.e., the $\Omega\Gamma-$limit). The resultant
positive gradient of the angluar velocity in the boundary layer between the
protostar and the Keplerian disk prohibits angular momentum transport from the
star to the disk, and consequently further rapid mass accretion. This would
prevent the protostar from growing significantly beyond $20 -
40~\mathrm{M_\odot}$. Another important consequence of the $\Omega\Gamma-$limit
is that the protostar can remain fairly compact ($R \lesssim
50~\mathrm{R_\odot}$) and avoid a fluffy structure ($R \gtrsim
500~\mathrm{R_\odot}$) that is usually found with a very high mass accretion
rate. This effect would make the protostar less prone to binary interactions
during the protostar phase. Although our analysis is based on Pop III protostar
models, this role of the $\Omega\Gamma-$limit would be universal in the
formation process of massive stars, regardless of metallicity.


title: Magnetic fields in early protostellar disk formation

abstract:
  We consider formation of accretion disks from a realistically turbulent
molecular gas using 3D MHD simulations. In particular, we analyze the effect of
the fast turbulent reconnection described by the Lazarian & Vishniac (1999)
model for the removal of magnetic flux from a disk. With our numerical
simulations we demonstrate how the fast reconnection enables protostellar disk
formation resolving the so-called "magnetic braking catastrophe". In
particular, we provide a detailed study of the dynamics of a 0.5 M$_\odot$
protostar and the formation of its disk for up to several thousands years. We
measure the evolution of the mass, angular momentum, magnetic field, and
turbulence around the star. We consider effects of two processes that strongly
affect the magnetic transfer of angular momentum, both of which are based on
turbulent reconnection: the first, "reconnection diffusion", removes the
magnetic flux from the disk, the other involves the change of the magnetic
field's topology, but does not change the absolute value of the magnetic flux
through the disk. We demonstrate that for the first mechanism, turbulence
causes a magnetic flux transport outward from the inner disk to the ambient
medium, thus decreasing the coupling of the disk to the ambient material. A
similar effect is achieved through the change of the magnetic field's topology
from a split monopole configuration to a dipole configuration. We explore how
both mechanisms prevent the catastrophic loss of disk angular momentum and
compare both above turbulent reconnection mechanisms with alternative
mechanisms from the literature.


title: Topological Superconductivity in Metal/Quantum-Spin-Ice Heterostructures

abstract:
  The original proposal to achieve superconductivity by starting from a quantum
spin-liquid (QSL) and doping it with charge carriers, as proposed by Anderson
in 1987, has yet to be realized. Here we propose an alternative strategy: use a
QSL as a substrate for heterostructure growth of metallic films to design
exotic superconductors. By spatially separating the two key ingredients of
superconductivity, i.e., charge carriers (metal) and pairing interaction (QSL),
the proposed setup naturally lands on the parameter regime conducive to a
controlled theoretical prediction. Moreover, the proposed setup allows us to
"customize" electron-electron interaction imprinted on the metallic layer. The
QSL material of our choice is quantum spin ice well-known for its emergent
gauge-field description of spin frustration. Assuming the metallic layer forms
an isotropic single Fermi pocket, we predict that the coupling between the
emergent gauge-field and the electrons of the metallic layer will drive
topological odd-parity pairing. We further present guiding principles for
materializing the suitable heterostructure using ab initio calculations and
describe the band structure we predict for the case of
Y$_2$Sn$_{2-x}$Sb$_x$O$_7$ grown on the (111) surface of Pr$_2$Zr$_2$O$_7$.
Using this microscopic information, we predict topological odd-parity
superconductivity at a few Kelvin in this heterostructure, which is comparable
to the $T_c$ of the only other confirmed odd-parity superconductor
Sr$_2$RuO$_4$.


title:
Galactic synchrotron emission and the FIR-radio correlation at high
  redshift

abstract:
  Galactic magnetic fields in the local Universe are strong and omnipresent.
There is mounting evidence that galaxies were magnetized already in the early
Universe. Theoretical scenarios including the turbulent small-scale dynamo
predict magnetic energy densities comparable to the one of turbulence. Based on
the assumption of this energy equipartition, we determine the galactic
synchrotron flux as a function of redshift z. The conditions in the early
Universe are different from the present day, in particular the galaxies have
more intense star formation. To cover a large range of conditions we consider
models based on two different systems: one model galaxy comparable to the Milky
Way and one typical high-z starburst galaxy. We include a model of the steady
state cosmic ray spectrum and find that synchrotron emission can be detected up
to cosmological redshifts with current and future radio telescopes. Turbulent
dynamo theory is in agreement with the origin of the observed correlation
between the far-infrared (FIR) luminosity L_FIR and the radio luminosity
L_radio. Our model reproduces this correlation well at z=0. We extrapolate the
FIR-radio correlation to higher redshift and predict a time evolution with a
significant deviation from its present-day appearance already at z~2 for a gas
density that increases strongly with z. In particular, we predict a decrease of
the radio luminosity with redshift which is caused by the increase of cosmic
ray energy losses at high z. The result is an increase of the ratio between
L_FIR and L_radio. Simultaneously, we predict that the slope of the FIR-radio
correlation becomes shallower with redshift. This behavior of the correlation
could be observed in the near future with ultra-deep radio surveys.


title: Geometry defects in Bosonic symmetry protected topological phases

abstract:
  In this paper we focus on the interplay between geometry defects and
topological properties in bosonic symmetry protected topological(SPT) phases.
We start from eight copies of 3D time-reversal($\mathcal{T}$) invariant
topological superconductors(TSC) on a crystal lattice. We melt the lattice by
condensation of disclinations and therefore restore the rotation symmetry. Such
disclination condensation procedure confines the fermion and afterwards turns
the system into a 3D boson topological liquid crystal(TCL). The low energy
effective theory of this crystalline-liquid transition contains a topological
term inherited from the geometry axion response in TSC. In addition, we
investigate the interplay between dislocation and superfluid vortex on the
surface of TCL. We demonstrate that the $\mathcal{T}$ and translation invariant
surface state is a double $[e\mathcal{T}m\mathcal{T}]$ state with intrinsic
surface topological order. We also look into the exotic behavior of dislocation
in 2D boson SPT state described by an $O(4)$ non-linear
$\sigma$-model(NL$\sigma $M) with topological $\Theta$-term. By dressing the
$O(4)$ vector with spiral order and gauge the symmetry, the dislocation has
mutual semion statistics with the gauge flux. Further reduce the $O(4)$
NL$\sigma M$ to the Ising limit, we arrive at the Levin-Gu model with stripy
modulation whose dislocation has nontrivial braiding statistics.


title: Rank Aggregation for Course Sequence Discovery

abstract:
  In this work, we adapt the rank aggregation framework for the discovery of
optimal course sequences at the university level. Each student provides a
partial ranking of the courses taken throughout his or her undergraduate
career. We compute pairwise rank comparisons between courses based on the order
students typically take them, aggregate the results over the entire student
population, and then obtain a proxy for the rank offset between pairs of
courses. We extract a global ranking of the courses via several state-of-the
art algorithms for ranking with pairwise noisy information, including
SerialRank, Rank Centrality, and the recent SyncRank based on the group
synchronization problem. We test this application of rank aggregation on 15
years of student data from the Department of Mathematics at the University of
California, Los Angeles (UCLA). Furthermore, we experiment with the above
approach on different subsets of the student population conditioned on final
GPA, and highlight several differences in the obtained rankings that uncover
hidden pre-requisites in the Mathematics curriculum.


title:
Composite Particle Theory of Three-dimensional Gapped Fermionic Phases:
  Fractional Topological Insulators and Charge-Loop Excitation Symmetry

abstract:
  Topological phases of matter are usually realized in deconfined phases of
gauge theories. In this context, confined phases with strongly fluctuating
gauge fields seem to be irrelevant to the physics of topological phases. For
example, the low-energy theory of the two-dimensional (2D) toric code model
(i.e. the deconfined phase of $\mathbb{Z}_2$ gauge theory) is a $U(1)\times
U(1)$ Chern-Simons theory in which gauge charges (i.e., $e$ and $m$ particles)
are deconfined and the gauge fields are gapped, while the confined phase is
topologically trivial. In this paper, we point out a new route to constructing
exotic 3D gapped fermionic phases in a confining phase of a gauge theory.
Starting from a parton construction with strongly fluctuating compact
$U(1)\times U(1)$ gauge fields, we construct gapped phases of interacting
fermions by condensing two linearly independent bosonic composite particles
consisting of partons and $U(1)\times U(1)$ magnetic monopoles. This can be
regarded as a 3D generalization of the 2D Bais-Slingerland condensation
mechanism. Charge fractionalization results from a Debye-H\"uckel-like
screening cloud formed by the condensed composite particles. Within our general
framework, we explore two aspects of symmetry-enriched 3D Abelian topological
phases. First, we construct a new fermionic state of matter with time-reversal
symmetry and $\Theta\neq \pi$, the fractional topological insulator. Second, we
generalize the notion of anyonic symmetry of 2D Abelian topological phases to
the charge-loop excitation symmetry ($\mathsf{Charles}$) of 3D Abelian
topological phases. We show that line twist defects, which realize
$\mathsf{Charles}$ transformations, exhibit non-Abelian fusion properties.

categories: cond-mat.str-el cond-mat.mtrl-sci hep-th math-ph math.MP


title:
Generation of a North/South Magnetic Field Component from Variations in
  the Photospheric Magnetic Field

abstract:
  We address the problem of calculating the transverse magnetic field in the
solar wind outside of the hypothetical sphere called the source surface where
the solar wind originates. This calculation must overcome a widely used
fundamental assumption about the source surface -- the field is normally
required to purely radial at the source surface. Our model rests on the fact
that a change in the radial field strength at the source surface is a change in
the field line density. Surrounding field lines must move laterally in order to
accommodate this field line density change. As the outward wind velocity drags
field lines past the source surface this lateral component of motion produces a
tilt implying there is a transverse component to the field.
  An analytic method of calculating the lateral translation speed of the field
lines is developed. We apply the technique to an interval of approximately two
Carrington rotations at the beginning of 2011 using 2-h averages of data from
the Helioseismic Magnetic Imager instrument on the Solar Dynamics Observatory
spacecraft. We find that the value of the transverse magnetic field is
dominated on a global scale by the effects of high latitude concentrations of
field lines being buffetted by supergranular motions.


title: Masses, Radii, and Equation of State of Neutron Stars

abstract:
  We summarize our current knowledge of neutron star masses and radii. Recent
instrumentation and computational advances have resulted in a rapid increase in
the discovery rate and precise timing of radio pulsars in binaries in the last
few years, leading to a large number of mass measurements. These discoveries
show that the neutron star mass distribution is much wider than previously
thought, with 3 known pulsars now firmly in the 1.9-2.0 Msun mass range. For
radii, large, high quality datasets from X-ray satellites as well as
significant progress in theoretical modeling led to considerable progress in
the measurements, placing them in the 9.9-11.2 km range and shrinking their
uncertainties due to a better understanding of the sources of systematic
errors. The combination of the massive neutron star discoveries, the tighter
radius measurements, and improved laboratory constraints of the properties of
dense matter has already made a substantial impact on our understanding of the
composition and bulk properties of cold nuclear matter at densities higher than
that of the atomic nucleus, a major unsolved problem in modern physics.


title:
Weak Factorizations of the Hardy space $H^1(\mathbb{R}^n)$ in terms of
  Multilinear Riesz Transforms

abstract:
  This paper provides a constructive proof of the weak factorizations of the
classical Hardy space $H^1(\mathbb{R}^n)$ in terms of multilinear Riesz
transforms. As a direct application, we obtain a new proof of the
characterization of ${\rm BMO}(\mathbb{R}^n)$ (the dual of $H^1(\mathbb{R}^n)$)
via commutators of the multilinear Riesz transforms.


title:
Insight from elliptic flow of open charm mesons using quark coalescence
  model at RHIC and LHC energies

abstract:
  A study of elliptic flow of open charm mesons, $D^0$ and $D_S ^\pm$ using
quark coalescence as a mechanism of hadronization of heavy quarks implemented
in conjunction with A Multi Phase Transport (AMPT) model has been presented. We
have studied the transverse momentum dependence of the elliptic flow parameter
at mid-rapidity ($|y|$ $<$ 1.0) for Au+Au collisions at $\sqrt{s_{NN}} = 200$
GeV (RHIC) and Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV (LHC) for
different values of partonic interaction cross-section and QCD coupling
constant. We have compared our calculations with the experimentally measured
data at the LHC energy. We have also studied the effect of shear viscosity on
elliptic flow of open charm mesons within the transport model approach. Our
study indicates that the elliptic flow of open charmed mesons is more sensitive
to viscous properties of QGP medium as compared to light charged hadrons.


title: Transport Layer Performance in 5G mmWave Cellular

abstract:
  The millimeter wave (mmWave) bands are likely to play a significant role in
next generation cellular systems due to the possibility of very high throughput
thanks to the availability of massive bandwidth and high-dimensional antennas.
Especially in Non-Line-of-Sight conditions, significant variations in the
received RF power can occur as a result of the scattering from nearby building
and terrain surfaces. Scattering objects come and go as the user moves through
the local environment. At the higher end of the mmWave band, rough surface
scatter generates cluster-based small-scale fading, where signal levels can
vary by more than 20 dB over just a few wavelengths. This high level of channel
variability may present significant challenges for congestion control. Using
our recently developed end-to-end mmWave ns3-based framework, this paper
presents the first performance evaluation of TCP congestion control in
next-generation mmWave networks. Importantly, the framework can incorporate
detailed models of the mmWave channel, beam- forming and tracking algorithms,
and builds on statistical channel models derived from real measurements in New
York City, as well as detailed ray traces.


title:
The BAHAMAS project: Calibrated hydrodynamical simulations for
  large-scale structure cosmology

abstract:
  The evolution of the large-scale distribution of matter is sensitive to a
variety of fundamental parameters that characterise the dark matter, dark
energy, and other aspects of our cosmological framework. Since the majority of
the mass density is in the form of dark matter that cannot be directly
observed, to do cosmology with large-scale structure one must use observable
(baryonic) quantities that trace the underlying matter distribution in a
(hopefully) predictable way. However, recent numerical studies have
demonstrated that the mapping between observable and total mass, as well as the
total mass itself, are sensitive to unresolved feedback processes associated
with galaxy formation, motivating explicit calibration of the feedback
efficiencies. Here we construct a new suite of large-volume cosmological
hydrodynamical simulations (called BAHAMAS, for BAryons and HAloes of MAssive
Systems) where subgrid models of stellar and Active Galactic Nucleus (AGN)
feedback have been calibrated to reproduce the present-day galaxy stellar mass
function and the hot gas mass fractions of groups and clusters in order to
ensure the effects of feedback on the overall matter distribution are broadly
correct. We show that the calibrated simulations reproduce an unprecedentedly
wide range of properties of massive systems, including the various observed
mappings between galaxies, hot gas, total mass, and black holes, and represent
a significant advance in our ability to mitigate the primary systematic
uncertainty in most present large-scale structure tests.


title:
Methylacetylene (CH3CCH) and propene (C3H6) formation in cold dense
  clouds: a case of dust grain chemistry

abstract:
  We present an extensive review of gas phase reactions producing
methylacetylene and propene showing that these relatively abundant unsaturated
hydrocarbons cannot be synthesized through gas-phase reactions. We explain the
formation of propene and methylacetylene through surface hydrogenation of C3
depleted onto interstellar ices, C3 being a very abundant species in the gas
phase.


title: Thresholds for universal concatenated quantum codes

abstract:
  Quantum error correction and fault-tolerance make it possible to perform
quantum computations in the presence of imprecision and imperfections of
realistic devices. An important question is to find the noise rate at which
errors can be arbitrarily suppressed. By concatenating the 7-qubit Steane and
15-qubit Reed-Muller codes, the 105-qubit code enables a universal set of
fault-tolerant gates despite not all of them being transversal. Importantly,
the CNOT gate remains transversal in both codes, and as such has increased
error protection relative to the other single qubit logical gates. We show that
while the level-1 pseudo-threshold for the concatenated scheme is limited by
the logical Hadamard, the error suppression of the logical CNOT gates allows
for the asymptotic threshold to increase by orders of magnitude at higher
levels. We establish a lower bound of $1.28~\times~10^{-3}$ for the asymptotic
threshold of this code which is competitive with known concatenated models and
does not rely on ancillary magic state preparation for universal computation.


title: Quantifying Causal Effects on Query Answering in Databases

abstract:
  The notion of actual causation, as formalized by Halpern and Pearl, has been
recently applied to relational databases, to characterize and compute actual
causes for possibly unexpected answers to monotone queries. Causes take the
form of database tuples, and can be ranked according to their causal
responsibility, a numerical measure of their relevance as a cause to the query
answer. In this work we revisit this notion, introducing and making a case for
an alternative measure of causal contribution, that of causal effect. The
measure generalizes actual causes, and can be applied beyond monotone queries.
We show that causal effect provides intuitive and intended results.


title: On the weak-field limit of Pleba\'nski class electrodynamics

abstract:
  Pleba\'nski's class of nonlinear vacuum electrodynamics is considered which
is for several reasons of interest at the present time. In particular the
question is answered under which circumstances Maxwell's original field
equations are recovered approximately and which post-Maxwellian effects could
arrise. To this end a weak field approximation method is developed allowing to
calculate post-Maxwellian corrections up to Nth order. In some respect this is
analogue of determining "post-newtonian" corrections from relativistic
mechanics by a low velocity approximation. As a result we got a series of
linear field equations which can be solved order by order. In this context the
solutions of the lower orders occur as source terms inside the higher order
field equations and represent a "post-Maxwellian" self-interaction of the
electromagnetic field which increases order by order. One has to decide between
problems with and without external source-terms, because without also high
frequency solutions can be approximately described by Maxwell's original
equations. The higher order approximations which describe "post-Maxwellian"
effects can give rise for experimental tests of Pleba\'nksi's class. Finally
two boundary value problems are discussed to have examples at hand.


title:
Bulk universality for random lozenge tilings near straight boundaries
  and for tensor products

abstract:
  We prove that the asymptotic of the bulk local statistics in models of random
lozenge tilings is universal in the vicinity of straight boundaries of the
tiled domains. The result applies to uniformly random lozenge tilings of large
polygonal domains on triangular lattice and to the probability measures
describing the decomposition in Gelfand-Tsetlin bases of tensor products of
representations of unitary groups. In a weaker form our theorem also applies to
random domino tilings.


title: Exploring $X(5568)$ as a meson molecule

abstract:
  The parameters, i.e. the mass and current coupling of the exotic $X(5568)$
state observed by the D0 Collaboration as well as the decay width of the
process $X \to B_s^{0}\pi^{+}$ are explored using $B\bar{K}$ molecule
assumption on its structure. Employed computational methods include QCD
two-point and light-cone sum rules, latter being considered in the soft-meson
approximation. The obtained results are compared with the data of the D0
Collaboration as well as with the predictions of the diquark-antidiquark model.
This comparison strengthens a diquark-antidiquark picture for the $X(5568)$
state rather than a meson molecule structure.


title:
Merging Binaries in the Galactic Center: The eccentric Kozai-Lidov
  mechanism with stellar evolution

abstract:
  Most, if not all, stars in the field are born in binary configurations or
higher multiplicity systems. In dense stellar environment such as the Galactic
Center (GC), many stars are expected to be in binary configurations as well.
These binaries form hierarchical triple body systems, with the massive black
hole (MBH) as the third, distant object. The stellar binaries are expected to
undergo large amplitude eccentricity and inclination oscillations via the
so-called "eccentric Kozai-Lidov" (EKL) mechanism. These eccentricity
excitations, combined with post main sequence stellar evolution, can drive the
inner stellar binaries to merge. We study the mergers of stellar binaries in
the inner 0.1 pc of the GC caused by gravitational perturbations due to the
MBH. We run a large set of Monte Carlo simulations that include the secular
evolution of the orbits, general relativistic precession, tides, and
post-main-sequence stellar evolution. We find that about 13 % of the initial
binary population will have merged after a few million years and about 29 %
after a few billion years. These expected merged systems represent a new class
of objects at the GC and we speculate that they are connected to G2-like
objects and the young stellar population.


title:
The subarcsecond mid-infrared view of local active galactic nuclei: III.
  Polar dust emission

abstract:
  Recent mid-infrared (MIR) interferometric observations showed in few active
galactic nuclei (AGN) that the bulk of the infrared emission originates from
the polar region above the putative torus, where only little dust should be
present. Here, we investigate whether such strong polar dust emission is common
in AGN. Out of 149 Seyferts in the MIR atlas of local AGN (Asmus et al.), 21
show extended MIR emission on single dish images. In 18 objects, the extended
MIR emission aligns with the system axis position angle, established by [OIII],
radio, polarisation and maser based position angle measurements. The relative
amount of resolved MIR emission is at least 40 per cent and scales with the
[OIV] fluxes implying a strong connection between the extended continuum and
[OIV] emitters. These results together with the radio-quiet nature of the
Seyferts support the scenario that the bulk of MIR emission is emitted by dust
in the polar region and not by the torus, which would demand a new paradigm for
the infrared emission structure in AGN. The current low detection rate of polar
dust in the AGN of the MIR atlas is explained by the lack of sufficient high
quality MIR data and the requirement for the orientation, NLR strength and
distance of the AGN. The James-Webb Space Telescope will enable much deeper
nuclear MIR studies with comparable angular resolution, allowing us to resolve
the polar emission and surroundings in most of the nearby AGN.


title: Spectral radius and fractional matchings in graphs

abstract:
  A {\it fractional matching} of a graph $G$ is a function $f$ giving each edge
a number in $[0,1]$ so that $\sum_{e \in \Gamma(v)} f(e) \le 1$ for each $v\in
V(G)$, where $\Gamma(v)$ is the set of edges incident to $v$. The {\it
fractional matching number} of $G$, written $\alpha'_*(G)$, is the maximum of
$\sum_{e \in E(G)} f(e)$ over all fractional matchings $f$. Let $G$ be an
$n$-vertex connected graph with minimum degree $d$, let $\lambda_1(G)$ be the
largest eigenvalue of $G$, and let $k$ be a positive integer less than $n$. In
this paper, we prove that if $\lambda_1(G) < d\sqrt{1+\frac{2k}{n-k}}$, then
$\alpha'_*(G) > \frac{n-k}{2}$. As a result, we prove $\alpha'_*(G) \ge
\frac{nd^2}{\lambda_1(G)^2 + d^2}$, we characterize when equality holds in the
bound.