title: The Eigenmode Analysis of Human Motion

abstract:
  Rapid advances in modern communication technology are enabling the
accumulation of large-scale, high-resolution observational data of
spatiotemporal movements of humans. Classification and prediction of human
mobility based on the analysis of such data carry great potential in
applications such as urban planning as well as being of theoretical interest. A
robust theoretical framework is therefore required to study and properly
understand human motion. Here we perform the eigenmode analysis of human motion
data gathered from mobile communication records, which allows us to explore the
scaling properties and characteristics of human motion.


title: A canonical lift of Frobenius in Morava E-theory

abstract:
  We prove that the $p$th Hecke operator on the Morava $E$-cohomology of a
space is congruent to the Frobenius mod $p$. This is a generalization of the
fact that the $p$th Adams operation on the complex $K$-theory of a space is
congruent to the Frobenius mod $p$. The proof implies that the $p$th Hecke
operator may be used to test Rezk's congruence criterion.


title:
Modulation-Specific Multiuser Transmit Precoding and User Selection for
  BPSK Signalling

abstract:
  Motivated by challenges to existing multiuser transmission methods in a low
signal to noise ratio (SNR) regime, and emergence of massive numbers of low
data rate ehealth and internet of things (IoT) devices, in this paper we show
that it is beneficial to incorporate knowledge of modulation type into
multiuser transmit precoder design. Particularly, we propose a transmit
precoding (beamforming) specific to BPSK modulation, which has maximum power
efficiency and capacity in poor channel conditions. To be more specific, in a
multiuser scenario, an objective function is formulated based on the weighted
sum of error probabilities of BPSK modulated users. Convex optimization is used
to transform and solve this ill-behaved non-convex minimum probability of error
(MPE) precoding problem. Numerical results confirm significant performance
improvement. We then develop a low-complexity user selection algorithm for MPE
precoding. Based on line packing principles in Grassmannian manifolds, the
number of supported users is able to exceed the number of transmit antennas,
and hence the proposed approach is able to support more simultaneous users
compared with existing multiuser transmit precoding methods.


title: Algorithm for computing $\mu$-bases of univariate polynomials

abstract:
  We present a new algorithm for computing a $\mu$-basis of the syzygy module
of $n$ polynomials in one variable over an arbitrary field $\mathbb{K}$. The
algorithm is conceptually different from the previously-developed algorithms by
Cox, Sederberg, Chen, Zheng, and Wang for $n=3$, and by Song and Goldman for an
arbitrary $n$. It involves computing a "partial" reduced row-echelon form of a
$ (2d+1)\times n(d+1)$ matrix over $\mathbb{K}$, where $d$ is the maximum
degree of the input polynomials. The proof of the algorithm is based on
standard linear algebra and is completely self-contained. It includes a proof
of the existence of the $\mu$-basis and as a consequence provides an
alternative proof of the freeness of the syzygy module. The theoretical (worst
case asymptotic) computational complexity of the algorithm is
$O(d^2n+d^3+n^2)$. We have implemented this algorithm (HHK) and the one
developed by Song and Goldman (SG). Experiments on random inputs indicate that
SG gets faster than HHK when $d$ gets sufficiently large for a fixed $n$, and
that HHK gets faster than SG when $n$ gets sufficiently large for a fixed $d$.


title:
Quantifying discrepancies in opinion spectra from online and offline
  networks

abstract:
  Online social media such as Twitter are widely used for mining public
opinions and sentiments on various issues and topics. The sheer volume of the
data generated and the eager adoption by the online-savvy public are helping to
raise the profile of online media as a convenient source of news and public
opinions on social and political issues as well. Due to the uncontrollable
biases in the population who heavily use the media, however, it is often
difficult to measure how accurately the online sphere reflects the offline
world at large, undermining the usefulness of online media. One way of
identifying and overcoming the online-offline discrepancies is to apply a
common analytical and modeling framework to comparable data sets from online
and offline sources and cross-analyzing the patterns found therein. In this
paper we study the political spectra constructed from Twitter and from
legislators' voting records as an example to demonstrate the potential limits
of online media as the source for accurate public opinion mining.


title: Infrared dielectric properties of low-stress silicon oxide

abstract:
  Silicon oxide thin films play an important role in the realization of optical
coatings and high-performance electrical circuits. Estimates of the dielectric
function in the far- and mid-infrared regime are derived from the observed
transmittance spectrum for a commonly employed low-stress silicon oxide
formulation. The experimental, modeling, and numerical methods used to extract
the dielectric function are presented.


title: Origin of static and dynamic steps in exact Kohn-Sham potentials

abstract:
  Knowledge of exact properties of the exchange-correlation (xc) functional is
important for improving the approximations made within density functional
theory. Features such as steps in the exact xc potential are known to be
necessary for yielding accurate densities, yet little is understood regarding
their shape, magnitude and location. We use systems of a few electrons, where
the exact electron density is known, to demonstrate general properties of
steps. We find that steps occur at points in the electron density where there
is a change in the `local effective ionization energy' of the electrons. We
provide practical arguments, based on the electron density, for determining the
position, shape and height of steps for ground-state systems, and extend the
concepts to time-dependent systems. These arguments are intended to inform the
development of approximate functionals, such as the mixed localization
potential (MLP), which already demonstrate their capability to produce steps in
the Kohn-Sham potential.


title: Beam Induced Electron Cloud Resonances in Dipole Magnetic Fields

abstract:
  The buildup of low energy electrons in an accelerator, known as electron
cloud, can be severely detrimental to machine performance. Under certain beam
conditions, the beam can become resonant with the cloud dynamics, accelerating
the buildup of electrons. This paper will examine two such effects:
multipacting resonances, in which the cloud development time is resonant with
the bunch spacing, and cyclotron resonances, in which the cyclotron period of
electrons in a magnetic field is a multiple of bunch spacing. Both resonances
have been studied directly in dipole fields using retarding field analyzers
installed in the Cornell Electron Storage Ring (CESR). These measurements are
supported by both analytical models and computer simulations.


title: Porosity, Differentiability and Pansu's Theorem

abstract:
  We use porosity to study differentiability of Lipschitz maps on Carnot
groups. Our first result states that directional derivatives of a Lipschitz
function act linearly outside a $\sigma$-porous set. The second result states
that irregular points of a Lipschitz function form a $\sigma$-porous set. We
use these observations to give a new proof of Pansu's theorem for Lipschitz
maps from a general Carnot group to a Euclidean space.


title: Modulating heat conduction by stretching or compressing

abstract:
  Recent studies have revealed that the symmetry of interparticle potential
plays an important role in one-dimensional heat conduction problem. Here we
demonstrate that by stretching or compressing the Fermi-Pasta-Ulam-\b{eta}
lattice, one can control the symmetry of the potential, and thus manipulate the
decaying behavior of the heat current autocorrelation function (HCAF). In fact,
stretching or compressing induces a fast decaying stage (FDS) during which the
HCAF decays faster than power-law manners or in a power law manner but faster
than ~t -1. The time range as well as the decay amplitude of the HCAF over the
FDS increase as the stretching or compressing ratio increase, or as the
temperature decreases. As a consequence, the thermal conductivity calculated
following the Green-Kubo formula shows a truncation-time independent window,
implying a system-size independent conductivity. Stretching or compressing also
changes the exponent of the power-law tail of the HCAF. The complicated heat
conduction behavior induced by stretching or compressing can be connected to
the change of the symmetry of the interparticle potential.


title:
The Resistive-Plate WELL with Argon mixtures - a robust gaseous
  radiation detector

abstract:
  A thin single-element THGEM-based, Resistive-Plate WELL (RPWELL) detector was
operated with 150 GeV/c muon and pion beams in Ne/(5%CH$_4$), Ar/(5%CH$_4$) and
Ar/(7%CO$_2$); signals were recorded with 1 cm$^2$ square pads and SRS/APV25
electronics. Detection efficiency values greater than 98% were reached in all
the gas mixtures, at average pad multiplicity of 1.2. The use of the
10$^9${\Omega}cm resistive plate resulted in a completely discharge-free
operation also in intense pion beams. The efficiency remained essentially
constant at 98-99% up to fluxes of $\sim$10$^4$Hz/cm$^2$, dropping by a few %
when approaching 10$^5$ Hz/cm$^2$. These results pave the way towards
cost-effective, robust, efficient, large-scale detectors for a variety of
applications in future particle, astro-particle and applied fields. A potential
target application is digital hadron calorimetry.


title:
Procedure for systematically tuning up crosstalk in the cross resonance
  gate

abstract:
  We present improvements in both theoretical understanding and experimental
implementation of the cross resonance (CR) gate that have led to shorter
two-qubit gate times and interleaved randomized benchmarking fidelities
exceeding 99%. The CR gate is an all-microwave two-qubit gate offers that does
not require tunability and is therefore well suited to quantum computing
architectures based on 2D superconducting qubits. The performance of the gate
has previously been hindered by long gate times and fidelities averaging
94-96%. We have developed a calibration procedure that accurately measures the
full CR Hamiltonian. The resulting measurements agree with theoretical analysis
of the gate and also elucidate the error terms that have previously limited the
gate fidelity. The increase in fidelity that we have achieved was accomplished
by introducing a second microwave drive tone on the target qubit to cancel
unwanted components of the CR Hamiltonian.


title:
Centralized Repair of Multiple Node Failures with Applications to
  Communication Efficient Secret Sharing

abstract:
  This paper considers a distributed storage system, where multiple storage
nodes can be reconstructed simultaneously at a centralized location. This
centralized multi-node repair (CMR) model is a generalization of regenerating
codes that allow for bandwidth-efficient repair of a single failed node. This
work focuses on the trade-off between the amount of data stored and repair
bandwidth in this CMR model. In particular, repair bandwidth bounds are derived
for the minimum storage multi-node repair (MSMR) and the minimum bandwidth
multi-node repair (MBMR) operating points. The tightness of these bounds are
analyzed via code constructions. The MSMR point is characterized through codes
achieving this point under functional repair for general set of CMR parameters,
as well as with codes enabling exact repair for certain CMR parameters. The
MBMR point, on the other hand, is characterized with exact repair codes for all
CMR parameters for systems that satisfy a certain entropy accumulation
property. Finally, the model proposed here is utilized for the secret sharing
problem, where the codes for the multi-node repair problem is used to construct
communication efficient secret sharing schemes with the property of bandwidth
efficient share repair.


title: Incidences between points on a variety and planes in R^3

abstract:
  In this paper we establish an improved bound for the number of incidences
between a set $P$ of $m$ points and a set $H$ of $n$ planes in $\mathbb R^3$,
provided that the points lie on a two-dimensional nonlinear irreducible
algebraic variety $V$ of constant degree. Specifically, the bound is $$ O\left(
m^{2/3}n^{2/3} + m^{6/11}n^{9/11}\log^\beta(m^3/n) + m + n + \sum_\ell
|P_\ell|\cdot |H_\ell| \right) , $$ where the constant of proportionality and
the constant exponent $\beta$ depend on the degree of $V$, and where the sum
ranges over all lines $\ell$ that are fully contained in $V$ and contain at
least one point of $P$, so that, for each such $\ell$, $P_\ell = P\cap\ell$ and
$H_\ell$ is the set of the planes of H that contain $\ell$. In addition,
$\sum_\ell |P_\ell| = O(m)$ and $\sum_\ell |H_\ell| = O(n)$.
  This improves, for this special case, the earlier more general bound of
Apfelbaum and Sharir (see also Brass and Knauer as well as Elekes and T\'oth).
  This is a generalization of the incidence bound for points and circles in the
plane (cf. Aronov et al., Aronov and Sharir, Marcus and Tardos), and is based
on a recent result of Sharir and Zahl on the number of cuts that turn a
collection of algebraic curves into pseudo-segments.
  The case where $V$ is a quadric is simpler to analyze, does not require the
result of Sharir and Zahl, and yields the same bound as above, with
$\beta=2/11$.
  We present an interesting application of our results to a problem, studied by
Rudnev, on obtaining a lower bound on the number of distinct cross-ratios
determined by $n$ real points, where our bound leads to a slight improvement in
Rudnev's bound.


title: Soft Heisenberg hair on black holes in three dimensions

abstract:
  Three-dimensional Einstein gravity with negative cosmological constant admits
stationary black holes that are not necessarily spherically symmetric. We
propose boundary conditions for the near horizon region of these black holes
that lead to a surprisingly simple near horizon symmetry algebra consisting of
two affine u(1) current algebras. The symmetry algebra is essentially
equivalent to the Heisenberg algebra. The associated charges give a specific
example of "soft hair" on the horizon, as defined by Hawking, Perry and
Strominger. We show that soft hair does not contribute to the
Bekenstein-Hawking entropy of Banados-Teitelboim-Zanelli black holes and "black
flower" generalizations. From the near horizon perspective the conformal
generators at asymptotic infinity appear as composite operators, which we
interpret in the spirit of black hole complementarity. Another remarkable
feature of our boundary conditions is that they are singled out by requiring
that the whole spectrum is compatible with regularity at the horizon,
regardless the value of the global charges like mass or angular momentum.
Finally, we address black hole microstates and generalizations to cosmological
horizons.


title: Radio transient following FRB 150418: afterglow or coincident AGN flare?

abstract:
  Recently, Keane et al. reported the discovery of a fading radio transient
following FRB 150418, and interpreted it as the afterglow of the FRB. Williams
\& Berger, on the other hand, suggested that the radio transient is analogous
to a group of variable radio sources, so that it could be a coincident AGN
flare in the observational beam of the FRB. A new observation with VLA showed a
re-brightening, which is consistent with the AGN picture. Here, using the radio
survey data of Ofek et al., we statistically examine the chance coincidence
probability to produce an event like the FRB 150418 transient. We find that the
probabilities to produce a variable radio transient with at least the same
variability amplitude and signal-to-noise ratio as the FRB 150415 transient,
without and with the VLA point, are $P_1 \sim 6 \times 10^{-4}$ and $P_1 \sim 2
\times 10^{-3}$, respectively. In addition, the chance probability to have a
fading transient detected following a random time (FRB time) is less than $P_2
\sim 10^{-2.9\pm 1.3}$. Putting these together and assuming that the number of
radio sources within one Parkes beam is 16, the final chance coincidence of
having an FRB 150418-like radio transient to be unrelated to the FRB is $<
10^{-4.9\pm1.3}$ and $< 10^{-4.4\pm1.3}$, respectively, without and with the
VLA point. We conclude that the radio transient following FRB 150418 has a low
probability being an unrelated AGN flare, and the possibility of being the
afterglow of FRB 150418 is not ruled out.


title:
FAST-PT: a novel algorithm to calculate convolution integrals in
  cosmological perturbation theory

abstract:
  We present a novel algorithm, FAST-PT, for performing convolution or
mode-coupling integrals that appear in nonlinear cosmological perturbation
theory. The algorithm uses several properties of gravitational structure
formation -- the locality of the dark matter equations and the scale invariance
of the problem -- as well as Fast Fourier Transforms to describe the input
power spectrum as a superposition of power laws. This yields extremely fast
performance, enabling mode-coupling integral computations fast enough to embed
in Monte Carlo Markov Chain parameter estimation. We describe the algorithm and
demonstrate its application to calculating nonlinear corrections to the matter
power spectrum, including one-loop standard perturbation theory and the
renormalization group approach. We also describe our public code (in Python) to
implement this algorithm, including the applications described here.


title:
A Realization of the Haldane-Kane-Mele Model in a System of Localized
  Spins

abstract:
  We theoretically study a spin Hamiltonian for spin-orbit-coupled ferromagnets
on the honeycomb lattice. We find that the effective Hamiltonian for magnons, a
quanta of spin-wave excitations from ordered states, is equivalent to the
Haldane model for electrons in the honeycomb lattice, which indicates the
nontrivial topology of the magnon bands and the existence of the associated
edge state. We also take the Schwinger boson (or bosonic spinon)
representations of spins that are applicable both to ordered and disordered
phases. We show that the spinon bands within the mean-field treatment are
topologically nontrivial, which causes a spin Nernst effect, by adopting the
properties of the Kane-Mele model. A feasible experimental realization of the
spin Hamiltonian is proposed.


title: Criticality in vibrated frictional flows at finite strain rate

abstract:
  We evidence critical fluctuations in the strain-rate of granular flows that
are weakly vibrated. Strikingly, the critical point arises at {\em finite}
values of the mean strain rate and vibration strength, far away from the
yielding critical point at zero flow rate. We show that the global rheology, as
well as the amplitude and correlation time of the fluctuations, are consistent
with a mean-field, Landau like description, where strain rate and stress act as
conjugated variables. We introduce a general model which captures the observed
phenomenology, and argue that this type of critical behavior generically arises
when self fluidization competes with friction.


title:
Entangling distant resonant exchange qubits via circuit quantum
  electrodynamics

abstract:
  We investigate a hybrid quantum system consisting of spatially separated
resonant exchange qubits, defined in three-electron semiconductor triple
quantum dots, that are coupled via a superconducting transmission line
resonator. Drawing on methods from circuit quantum electrodynamics and
Hartmann-Hahn double resonance techniques, we analyze three specific approaches
for implementing resonator-mediated two-qubit entangling gates in both
dispersive and resonant regimes of interaction. We calculate entangling gate
fidelities as well as the rate of relaxation via phonons for resonant exchange
qubits in silicon triple dots and show that such an implementation is
particularly well-suited to achieving the strong coupling regime. Our approach
combines the favorable coherence properties of encoded spin qubits in silicon
with the rapid and robust long-range entanglement provided by circuit QED
systems.


title:
Boosting Room-Temperature Li$^+$ Conductivity via strain in solid
  electrolytes for Lithium-ion Batteries

abstract:
  Room-temperature (RT) conductivity of most candidates for solid electrolytes
of miniaturized lithium-ion batteries is still 1-2 orders of magnitude below
commercial requirements, therefore several approaches are being pursued aiming
the enhancement of such values. In this letter, we report for the first time
direct theoretical evidence that epitaxial strain can be an efficient tool to
reach this goal.


title: Admissible morphisms for Shimura varieties with parahoric levels

abstract:
  In \textit{Shimuravariet\"{a}ten und Gerben} \cite{LR87}, Langlands and
Rapoport developed the theory of pseudo-motivic Galois gerb and admissible
morphisms between Galois gerbs, with a view to formulating a conjectural
description of the $\bar{\mathbb{F}}_p$-point set of the good reduction of a
Shimura variety with hyperspecial level, as well as to providing potential
tools for its resolution. Here, we generalize, and also improve to some extent,
their works to parahoric levels when the group is quasi-split at $p$. In
particular, we show that every admissible morphism is conjugate to a special
admissible morphism, and, when the level is special maximal parahoric, that any
Kottwitz triple with trivial Kottwitz invariant, if it satisfies some obvious
necessary conditions implied by the conjecture, comes from an admissible pair.
As applications, we give natural effectivity criteria for admissible pairs and
Kottwitz triples, and establish non-emptiness of Newton strata in the relevant
cases. Along the way, we fill some gaps in the original work.


title: On Euler's example of a completely multiplicative function with sum 0

abstract:
  Euler wrote a formula expressing that l(n)/n is a completely multiplicative
function with sum 0 (a CMO function) , where l(n) is the completely
multiplicative function equal to -1 on the prime numbers (the Liouville
function). We extend this formula to Beurling generalized numbers, using a
result of Diamond. As an application we show how to construct a CMO function
carried by a set of integers whose counting function is of the form D x^a
(1+o(1) ) for any a between 0 and 1.


title:
Ensemble of Deep Convolutional Neural Networks for Learning to Detect
  Retinal Vessels in Fundus Images

abstract:
  Vision impairment due to pathological damage of the retina can largely be
prevented through periodic screening using fundus color imaging. However the
challenge with large scale screening is the inability to exhaustively detect
fine blood vessels crucial to disease diagnosis. In this work we present a
computational imaging framework using deep and ensemble learning for reliable
detection of blood vessels in fundus color images. An ensemble of deep
convolutional neural networks is trained to segment vessel and non-vessel areas
of a color fundus image. During inference, the responses of the individual
ConvNets of the ensemble are averaged to form the final segmentation. In
experimental evaluation with the DRIVE database, we achieve the objective of
vessel detection with maximum average accuracy of 94.7\% and area under ROC
curve of 0.9283.


title: Mobile Beamforming & Spatially Controlled Relay Communications

abstract:
  We consider stochastic motion planning in single-source single-destination
robotic relay networks, under a cooperative beamforming framework. Assuming
that the communication medium constitutes a spatiotemporal stochastic field, we
propose a 2-stage stochastic programming formulation of the problem of
specifying the positions of the relays, such that the expected reciprocal of
their total beamforming power is maximized. Stochastic decision making is made
on the basis of random causal CSI. Recognizing the intractability of the
original problem, we propose a lower bound relaxation, resulting to a
nontrivial optimization problem with respect to the relay locations, which is
equivalent to a small set of simple, tractable subproblems. Our formulation
results in spatial controllers with a predictive character; at each time slot,
the new relay positions should be such that the expected power reciprocal at
the next time slot is maximized. Quite interestingly, the optimal control
policy to the relaxed problem is purely selective; under a certain sense, only
the best relay should move.


title:
A Posterior Probability Approach for Gene Regulatory Network Inference
  in Genetic Perturbation Data

abstract:
  Inferring gene regulatory networks is an important problem in systems
biology. However, these networks can be hard to infer from experimental data
because of the inherent variability in biological data as well as the large
number of genes involved. We propose a fast, simple method for inferring
regulatory relationships between genes from knockdown experiments in the NIH
LINCS dataset by calculating posterior probabilities, incorporating prior
information. We show that the method is able to find previously identified
edges from TRANSFAC and JASPAR and discuss the merits and limitations of this
approach.


title: The chromatic number of dense random graphs

abstract:
  The chromatic number $\chi(G)$ of a graph $G$ is defined as the minimum
number of colours required for a vertex colouring where no two adjacent
vertices are coloured the same. The chromatic number of the dense random graph
$G \sim G(n,p)$ where $p \in (0,1)$ is constant has been intensively studied
since the 1970s, and a landmark result by Bollob\'as in 1987 first established
the asymptotic value of $\chi(G)$. Despite several improvements of this result,
the exact value of $\chi(G)$ remains open. In this paper, new upper and lower
bounds for $\chi(G)$ are established. These bounds are the first ones that
match each other up to a term of size $o(1)$ in the denominator: they narrow
down the colouring rate $n/\chi(G)$ of $G \sim G(n,p)$ to an explicit interval
of length $o(1)$, answering a question of Kang and McDiarmid.


title:
Theoretical Insight into the Internal Quantum Efficiencies of
  Polymer/C$_{60}$ and Polymer/SWNT Photovoltaic Devices

abstract:
  The internal quantum efficiency (IQE) of an organic photovoltaic device (OPV)
is proportional to the number of free charge carriers generated and their
conductivity, per absorbed photon. However, both the IQE and the quantities
that determine it, for example, electron-hole binding, charge separation,
electron-hole recombination, and conductivity, can only be inferred indirectly
from experiments. Using density functional theory, we calculate the
excited-state formation energy, charge transfer, and zero-bias conductance in
the singlet ground state and triplet excited state across polymer/fullerene and
polymer/single walled carbon nanotube (SWNT) OPV donor/acceptor bulk
heterojunctions. Specifically, we compare polythiophene (PT) and
poly(3-methylthiophene-2,5-diyl) (P3MT) as donors and C$_{60}$ chains with
(6,4), (6,5), and (10,5) SWNTs as acceptors. We find the conductivity increases
substantially for both the excited triplet relative to the singlet ground state
and for PT compared with P3MT due to the increased charge transfer and the
resulting improvement in donor/acceptor level alignment. Similarly, the (6,4)
SWNT, with a larger SWNT band gap and greater conductivity than fullerenes,
provides the highest conductivities of 5 and 9\% of the theoretical maximum for
electron and hole carriers, respectively. This work has important implications
for both the optimization of polymer/SWNT bulk heterojunctions and the design
of new OPV bulk heterojunctions in silico.


title:
Hierarchical image simplification and segmentation based on
  Mumford-Shah-salient level line selection

abstract:
  Hierarchies, such as the tree of shapes, are popular representations for
image simplification and segmentation thanks to their multiscale structures.
Selecting meaningful level lines (boundaries of shapes) yields to simplify
image while preserving intact salient structures. Many image simplification and
segmentation methods are driven by the optimization of an energy functional,
for instance the celebrated Mumford-Shah functional. In this paper, we propose
an efficient approach to hierarchical image simplification and segmentation
based on the minimization of the piecewise-constant Mumford-Shah functional.
This method conforms to the current trend that consists in producing
hierarchical results rather than a unique partition. Contrary to classical
approaches which compute optimal hierarchical segmentations from an input
hierarchy of segmentations, we rely on the tree of shapes, a unique and
well-defined representation equivalent to the image. Simply put, we compute for
each level line of the image an attribute function that characterizes its
persistence under the energy minimization. Then we stack the level lines from
meaningless ones to salient ones through a saliency map based on extinction
values defined on the tree-based shape space. Qualitative illustrations and
quantitative evaluation on Weizmann segmentation evaluation database
demonstrate the state-of-the-art performance of our method.


title:
Line Spread Functions of Blazed Off-Plane Gratings Operated in the
  Littrow Mounting

abstract:
  Future soft X-ray (10 - 50 Angstrom) spectroscopy missions require higher
effective areas and resolutions to perform critical science that cannot be done
by instruments on current missions. An X-ray grating spectrometer employing
off-plane reflection gratings would be capable of meeting these performance
criteria. Off-plane gratings with blazed groove facets operated in the Littrow
mounting can be used to achieve excellent throughput into orders achieving high
resolutions. We have fabricated two off-plane gratings with blazed groove
profiles via a technique which uses commonly available microfabrication
processes, is easily scaled for mass production, and yields gratings customized
for a given mission architecture. Both fabricated gratings were tested in the
Littrow mounting at the Max-Planck-Institute for extraterrestrial Physics
PANTER X-ray test facility to assess their performance. The line spread
functions of diffracted orders were measured, and a maximum resolution of 800
$\pm$ 20 is reported. In addition, we also observe evidence of a `blaze' effect
from measurements of relative efficiencies of the diffracted orders.


title:
On the contribution of fluorescence to Ly$\alpha$ halos (LAHs) around
  star forming galaxies

abstract:
  We quantify the contribution of Ly$\alpha$ fluorescence to observed spatially
extended Ly$\alpha$ halos around Ly$\alpha$ emitters (LAE) at redshift ${\rm
z=3.1}$. The key physical quantities that describe the fluorescent signal
include (${\it i}$) the distribution of cold gas in the circum-galactic medium
(CGM); we explore simple analytical models and fitting functions to recent
hydrodynamical simulations; (${\it ii}$) local variations in the ionizing
background due to ionizing sources that cluster around the central galaxy. We
account for clustering by boosting the observationally inferred volumetric
production rate of ionizing photons, $\epsilon_{\rm LyC}$, by a factor of
$1+\xi_{\rm LyC}(r)$, in which $\xi_{\rm LyC}(r)$ quantifies the clustering of
ionizing sources around the central galaxy. We compute $\xi_{\rm LyC}(r)$ by
assigning an 'effective' bias parameter to the ionizing sources. This novel
approach allows us to quantify our ignorance of the population of ionizing
sources in a simple parametrized form. We find a maximum enhancement in the
local ionizing background in the range $50-200$ at $r \sim 10$ physical kpc.
For spatially uncorrelated ionizing sources and fluorescing clouds we find that
fluorescence can contribute up to $\sim 50-60\%$ of the observed spatially
extended Ly$\alpha$ emission. We briefly discuss how future observations can
shed light on the nature of Ly$\alpha$ halos around star forming galaxies.


title:
On a multidimensional spherically invariant extension of the
  Rademacher--Gaussian comparison

abstract:
  It is shown that \begin{equation*}
  \mathsf{P}(\|a_1U_1+\dots+a_nU_n\|>u)\le c\,\mathsf{P}(a\|Z_d\|>u)
\end{equation*} for all real $u$, where $U_1,\dots,U_n$ are independent random
vectors uniformly distributed on the unit sphere in $\mathbb{R}^d$,
$a_1,\dots,a_n$ are any real numbers, $a:=\sqrt{(a_1^2+\dots+a_n^2)/d}$, $Z_d$
is a standard normal random vector in $\mathbb{R}^d$, and $c=2e^3/9=4.46\dots$.
This constant factor is about $89$ times as small as the one in a recent result
by Nayar and Tkocz, who proved, by a different method, a corresponding
conjecture by Oleszkiewicz. As an immediate application, a corresponding upper
bound on the tail probabilities for the norm of the sum of arbitrary
independent spherically invariant random vectors is given.


title:
Matrix geometric approach for random walks: stability condition and
  equilibrium distribution

abstract:
  In this paper, we analyse a sub-class of two-dimensional homogeneous nearest
neighbour (simple) random walk restricted on the lattice using the matrix
geometric approach. In particular, we first present an alternative approach for
the calculation of the stability condition, extending the result of Neuts drift
conditions [30] and connecting it with the result of Fayolle et al. which is
based on Lyapunov functions [13]. Furthermore, we consider the sub-class of
random walks with equilibrium distributions given as series of product-forms
and, for this class of random walks, we calculate the eigenvalues and the
corresponding eigenvectors of the infinite matrix $\mathbf{R}$ appearing in the
matrix geometric approach. This result is obtained by connecting and extending
three existing approaches available for such an analysis: the matrix geometric
approach, the compensation approach and the boundary value problem method. In
this paper, we also present the spectral properties of the infinite matrix
$\mathbf{R}$.


title:
Approximating faces of marginal polytopes in discrete hierarchical
  models

abstract:
  The existence of the maximum likelihood estimate in hierarchical loglinear
models is crucial to the reliability of inference for this model. Determining
whether the estimate exists is equivalent to finding whether the sufficient
statistics vector $t$ belongs to the boundary of the marginal polytope of the
model. The dimension of the smallest face $F_t$ containing $t$ determines the
dimension of the reduced model which should be considered for correct
inference. For higher-dimensional problems, it is not possible to compute
$F_{t}$ exactly. Massam and Wang (2015) found an outer approximation to $F_t$
using a collection of sub-models of the original model. This paper refines the
methodology to find an outer approximation and devises a new methodology to
find an inner approximation. The inner approximation is given not in terms of a
face of the marginal polytope, but in terms of a subset of the vertices of
$F_t$.
  Knowing $F_t$ exactly indicates which cell probabilities have maximum
likelihood estimates equal to $0$. When $F_t$ cannot be obtained exactly, we
can use, first, the outer approximation $F_2$ to reduce the dimension of the
problem and, then, the inner approximation $F_1$ to obtain correct estimates of
cell probabilities corresponding to elements of $F_1$ and improve the estimates
of the remaining probabilities corresponding to elements in $F_2\setminus F_1$.
Using both real-world and simulated data, we illustrate our results, and show
that our methodology scales to high dimensions.


title:
Experimental measurements of the permeability of fibrous carbon at high
  temperature

abstract:
  A series of experiments was performed to obtain permeability data on
FiberForm(R), a commercial carbon preform used for manufacturing thermal
protection systems. A porous sample was placed in a quartz flow-tube heated by
an isothermal furnace. The setup was instrumented to measure mass flow through
and pressure drop across the sample. The intrinsic permeability and the
Klinkenberg correction, which accounts for rarefied effects, were computed from
the experimental data. The role of the gas temperature and pressure on the
effective permeability is shown, and it is demonstrated that with proper data
reduction, the intrinsic permeability is strictly a function of the
micro-structure of the material. A function for the effective permeability of
FiberForm, dependent on temperature, pressure, pore geometry, and type of gas
is proposed. The intrinsic permeability was evaluated at $K_0 = 5.57 \times
10^{-11}$ m$^2$, with a Klinkenberg parameter of $8c/d_p = 2.51 \times 10^5$
m$^{-1}$ and a reference porosity of $\phi^\dagger = 0.87$.


title:
The Illusory Appeal of Decoherence in the Everettian Picture: Affirming
  the Consequent

abstract:
  The idea that decoherence in a unitary-only quantum theory suffices to
explain emergence of classical phenomena has been shown in the peer-reviewed
literature to be seriously flawed due to circularity. However, claims continue
to be made that this approach, also known as "Quantum Darwinism," is the
correct way to understand classical emergence. This Letter reviews the basic
problem and points out an additional logical flaw in the argument. It is
concluded that the "Quantum Darwinism" program fails.


title:
Characterisation of silicon microstrip detectors for the ATLAS Phase-II
  Upgrade with a micro-focused X-ray beam

abstract:
  The planned HL-LHC (High Luminosity LHC) in 2025 is being designed to
maximise the physics potential through a sizable increase in the luminosity up
to 6*10^34 cm^-2 s^-1. A consequence of this increased luminosity is the
expected radiation damage at 3000 fb^-1 after ten years of operation, requiring
the tracking detectors to withstand fluences to over 1*10^16 1 MeV n_eq/cm^2 .
In order to cope with the consequent increased readout rates, a complete
re-design of the current ATLAS Inner Detector (ID) is being developed as the
Inner Tracker (ITk). Two proposed detectors for the ATLAS strip tracker region
of the ITk were characterized at the Diamond Light Source with a 3 um FWHM 15
keV micro focused X-ray beam. The devices under test were a 320 Um thick
silicon stereo (Barrel) ATLAS12 strip mini sensor wire bonded to a 130 nm CMOS
binary readout chip (ABC130) and a 320 Um thick full size radial (end-cap)
strip sensor - utilizing bi-metal readout layers - wire bonded to 250 nm CMOS
binary readout chips (ABCN-25). A resolution better than the inter strip pitch
of the 74.5 um strips was achieved for both detectors. The effect of the p-stop
diffusion layers between strips was investigated in detail for the wire bond
pad regions. Inter strip charge collection measurements indicate that the
effective width of the strip on the silicon sensors is determined by p-stop
regions between the strips rather than the strip pitch.


title: Averages of short correlations: a note

abstract:
  We give a completely elementary study for averages of short correlations of
so-called sieve functions (a pretty general class of arithmetic functions).


title: Piezoelectric Tunable Microwave Superconducting Cavity

abstract:
  In the context of engineered quantum systems, there is a demand for
superconducting tunable devices able to operate with high Q-factors at power
levels equivalent to only a few photons. In this work, we developed a 3D
microwave reentrant cavity with such characteristics ready to provide a very
fine-tuning of a high-Q resonant mode over a large dynamic range. This system
has an electronic tuning mechanism based on a mechanically amplified
piezoelectric actuator, which controls the resonator dominant mode frequency by
changing the cavity narrow gap by very small displacements. Experiments were
conducted at room and dilution refrigerator temperatures showing a large
dynamic range up to 4 GHz and 1 GHz, respectively, and were compared to a FEM
model simulated data. At elevated microwave power input, nonlinear thermal
effects were observed to destroy the superconductivity of the cavity due to the
large electric fields generated in the small gap of the reentrant cavity.


title:
The 2QDES Pilot : The luminosity and redshift dependence of quasar
  clustering

abstract:
  We present a new redshift survey, the 2dF Quasar Dark Energy Survey pilot
(2QDESp), which consists of ${\approx}10000$ quasars from ${\approx}150$
deg$^2$ of the southern sky, based on VST-ATLAS imaging and 2dF/AAOmega
spectroscopy. Combining our optical photometry with the WISE (W1,W2) bands we
can select essentially contamination free quasar samples with $0.8{<}z{<}2.5$
and $g{<}20.5$. At fainter magnitudes, optical UVX selection is still required
to reach our $g{\approx}22.5$ limit. Using both these techniques we observed
quasar redshifts at sky densities up to $90$ deg$^{-2}$. By comparing 2QDESp
with other surveys (SDSS, 2QZ and 2SLAQ) we find that quasar clustering is
approximately luminosity independent, with results for all four surveys
consistent with a correlation scale of $r_{0}{=}6.1{\pm}0.1 \: h^{-1}$Mpc,
despite their decade range in luminosity. We find a significant redshift
dependence of clustering, particularly when BOSS data with $r_{0}{=}7.3{\pm}0.1
\: h^{-1}$Mpc are included at $z{\approx}2.4$. All quasars remain consistent
with having a single host halo mass of ${\approx}2{\pm}1{\times}10^{12} \:
h^{-1}M_\odot$. This result implies that either quasars do not radiate at a
fixed fraction of the Eddington luminosity or AGN black hole and dark matter
halo masses are weakly correlated. No significant evidence is found to support
fainter, X-ray selected quasars at low redshift having larger halo masses as
predicted by the `hot halo' mode AGN model of Fanidakis et al. 2013. Finally,
although the combined quasar sample reaches an effective volume as large as
that of the original SDSS LRG sample, we do not detect the BAO feature in these
data.


title:
Kinetic simulations of the lowest-order unstable mode of relativistic
  magnetostatic equilibria

abstract:
  We present the results of particle-in-cell numerical pair plasma simulations
of relativistic 2D magnetostatic equilibria known as the 'ABC' fields. In
particular, we focus on the lowest-order unstable configuration consisting of
two minima and two maxima of the magnetic vector potential. Breaking of the
initial symmetry leads to exponential growth of the electric energy and to the
formation of two current layers, which is consistent with the picture of
'X-point collapse' first described by Syrovatskii. Magnetic reconnection within
the layers heats a fraction of particles to very high energies. After the
saturation of the linear instability, the current layers are disrupted and the
system evolves chaotically, diffusing the particle energies in a stochastic
second-order Fermi process leading to the formation of power-law energy
distributions. The power-law slopes harden with the increasing mean
magnetization, but they are significantly softer than those produced in
simulations initiated from Harris-type layers. The maximum particle energy is
proportional to the mean magnetization, which is attributed partly to the
increase of the effective electric field and partly to the increase of the
acceleration time scale. We describe in detail the evolving structure of the
dynamical current layers, and report on the conservation of magnetic helicity.
These results can be applied to highly magnetized astrophysical environments,
where ideal plasma instabilities trigger rapid magnetic dissipation with
efficient particle acceleration and flares of high-energy radiation.


title: Cosmological tests of an axiverse-inspired quintessence field

abstract:
  Inspired by the string axiverse idea, it has been suggested that the recent
transition from decelerated to accelerated cosmic expansion is driven by an
axion-like quintessence field with a sub-Planckian decay constant. The scenario
requires that the axion field be rather near the maximum of its potential, but
is less finely tuned than other explanations of cosmic acceleration. The model
is parametrized by an axion decay constant $f$, the axion mass $m$, and an
initial misalignment angle $|\theta_i|$ which is close to $\pi$. In order to
determine the $m$ and $\theta_{i}$ values consistent with observations, these
parameters are mapped onto observables: the Hubble parameter $H(z)$ at and
angular diameter distance $d_{A}(z)$ to redshift $z= 0.57$, as well as the
angular sound horizon of the cosmic microwave background (CMB). Measurements of
the baryon acoustic oscillation (BAO) scale at $z\simeq 0.57$ by the BOSS
survey and Planck measurements of CMB temperature anisotropies are then used to
probe the $\left\{m,f,\theta_i\right\}$ parameter space. With current data, CMB
constraints are the most powerful, allowing a fraction of only $\sim 0.2$ of
the parameter-space volume. Measurements of the BAO scale made using the
SPHEREx or SKA experiments could go further, observationally distinguishing all
but $\sim 10^{-2}$ or $\sim 10^{-5}$ of the parameter-space volume (allowed by
simple priors) from the $\Lambda$CDM model.


title: Compton-thick Accretion in the local Universe

abstract:
  Heavily obscured accretion is believed to represent an important stage in the
growth of supermassive black holes, and to play an important role in shaping
the observed spectrum of the Cosmic X-ray Background (CXB). Hard X-ray (E$>$10
keV) selected samples are less affected by absorption than samples selected at
lower energies, and are therefore one of the best ways to detect and identify
Compton-thick (CT, $\log N_{\rm\,H}\geq 24$) Active Galactic Nuclei (AGN). In
this letter we present the first results of the largest broad-band (0.3-150
keV) X-ray spectral study of hard X-ray selected AGN to date, focusing on the
properties of heavily obscured sources. Our sample includes the 834 AGN (728
non-blazar, average redshift $z\simeq 0.055$) reported in the 70-months catalog
of the all-sky hard X-ray Swift/BAT survey. We find 55 CT AGN, which represent
$7.6^{+1.1}_{-2.1}\%$ of our non-blazar sample. Of these, 26 are reported as
candidate CT AGN for the first time. We correct for selection bias and derive
the intrinsic column density distribution of AGN in the local Universe in two
different luminosity ranges. We find a significant decrease in the fraction of
obscured Compton-thin AGN for increasing luminosity, from $46\pm3\%$ (for $\log
L_{\rm\,14-195} = 40-43.7$) to $39\pm3\%$ (for $\log L_{\rm\,14-195} =
43.7-46$). A similar trend is also found for CT AGN. The intrinsic fraction of
CT AGN with $\log N_{\rm\,H}=24-25$ normalised to unity in the $\log N_{\rm H}
= 20-25$ range is $27\pm4\%$, and is consistent with the observed value
obtained for AGN located within 20 Mpc.


title: Resolving the Planetesimal Belt of HR 8799 with ALMA

abstract:
  The star HR 8799 hosts one of the largest known debris discs and at least
four giant planets. Previous observations have found evidence for a warm belt
within the orbits of the planets, a cold planetesimal belt beyond their orbits
and a halo of small grains. With the infrared data, it is hard to distinguish
the planetesimal belt emission from that of the grains in the halo. With this
in mind, the system has been observed with ALMA in band 6 (1.34 mm) using a
compact array format. These observations allow the inner edge of the
planetesimal belt to be resolved for the first time. A radial distribution of
dust grains is fitted to the data using an MCMC method. The disc is best fit by
a broad ring between $145^{+12}_{-12}$ AU and $429^{+37}_{-32}$ AU at an
inclination of $40^{+5}_{-6}${\deg} and a position angle of
$51^{+8}_{-8}${\deg}. A disc edge at ~145 AU is too far out to be explained
simply by interactions with planet b, requiring either a more complicated
dynamical history or an extra planet beyond the orbit of planet b.


title: Gluino Coannihilation and Observability of Gluinos at LHC RUN II

abstract:
  The observability of a gluino at LHC RUN II is analyzed for the case where
the gluino lies in the gluino-neutralino coannihilation region and the mass gap
between the gluino and the neutralino is small. The analysis is carried out
under the Higgs boson mass constraint and the constraint of dark matter relic
density consistent with the WMAP and Planck experiment. It is shown that in
this case a gluino with mass much smaller than the current lower limit of $\sim
1500$ GeV as given by LHC RUN II at 3.2 fb$^{-1}$ of integrated luminosity
would have escaped detection. The analysis is done using the signal regions
used by the ATLAS Collaboration where an optimization of signal regions was
carried out to determine the best regions for gluino discovery in the
gluino-neutralino coannihilation region. It is shown that under the Higgs boson
mass constraint and the relic density constraint, a gluino mass of $\sim 700$
GeV would require 14 fb$^{-1}$ of integrated luminosity for discovery and a
gluino of mass $\sim 1250$ GeV would require 3400 fb$^{-1}$ of integrated
luminosity for discovery at LHC RUN II. An analysis of dark matter for this
case is also given. It is found that for the range of gluino masses considered,
the neutralino mass lies within less than 100 GeV of the gluino mass. Thus a
measurement of the gluino mass in the gluino-neutralino coannihilation region
will provide a determination of the neutralino mass. In this region the
neutralino is dominantly a gaugino and the spin-independent proton-neutralino
cross section is small but much larger than the neutrino floor lying in the
range $\sim (1-10)\times 10^{-47}$ cm$^{2}$. Thus a significant part of the
parameter space of the model will lie within the reach of the next generation
LUX-ZEPLIN dark matter experiment.


title:
Organized Chaos: Scatter in the relation between stellar mass and halo
  mass in small galaxies

abstract:
  We use Local Group galaxy counts together with the ELVIS N-body simulations
to explore the relationship between the scatter and slope in the stellar mass
vs. halo mass relation at low masses, $M_\star \simeq 10^5 - 10^8 M_\odot$.
Assuming models with log-normal scatter about a median relation of the form
$M_\star \propto M_\mathrm{halo}^\alpha$, the preferred log-slope steepens from
$\alpha \simeq 1.8$ in the limit of zero scatter to $\alpha \simeq 2.6$ in the
case of $2$ dex of scatter in $M_\star$ at fixed halo mass. We provide fitting
functions for the best-fit relations as a function of scatter, including cases
where the relation becomes increasingly stochastic with decreasing mass. We
show that if the scatter at fixed halo mass is large enough ($\gtrsim 1$ dex)
and if the median relation is steep enough ($\alpha \gtrsim 2$), then the
"too-big-to-fail" problem seen in the Local Group can be self-consistently
eliminated in about $\sim 5-10\%$ of realizations. This scenario requires that
the most massive subhalos host unobservable ultra-faint dwarfs fairly often; we
discuss potentially observable signatures of these systems. Finally, we compare
our derived constraints to recent high-resolution simulations of dwarf galaxy
formation in the literature. Though simulation-to-simulation scatter in
$M_\star$ at fixed $M_\mathrm{halo}$ is large among separate authors ($\sim 2$
dex), individual codes produce relations with much less scatter and usually
give relations that would over-produce local galaxy counts.


title: Black Hole Collapse in the 1/c Expansion

abstract:
  We present a first-principles CFT calculation corresponding to the spherical
collapse of a shell of matter in three dimensional quantum gravity. In field
theory terms, we describe the equilibration process, from early times to
thermalization, of a CFT following a sudden injection of energy at time t=0. By
formulating a continuum version of Zamolodchikov's monodromy method to
calculate conformal blocks at large central charge c, we give a framework to
compute a general class of probe observables in the collapse state,
incorporating the full backreaction of matter fields on the dual geometry. This
is illustrated by calculating a scalar field two-point function at time-like
separation and the time-dependent entanglement entropy of an interval, both
showing thermalization at late times. The results are in perfect agreement with
previous gravity calculations in the AdS$_3$-Vaidya geometry. Information loss
appears in the CFT as an explicit violation of unitarity in the 1/c expansion,
restored by nonperturbative corrections.

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


title:
Insights into planet formation from debris disks: II. Giant impacts in
  extrasolar planetary systems

abstract:
  Giant impacts refer to collisions between two objects each of which is
massive enough to be considered at least a planetary embryo. The putative
collision suffered by the proto-Earth that created the Moon is a prime example,
though most Solar System bodies bear signatures of such collisions. Current
planet formation models predict that an epoch of giant impacts may be
inevitable, and observations of debris around other stars are providing
mounting evidence that giant impacts feature in the evolution of many planetary
systems. This chapter reviews giant impacts, focussing on what we can learn
about planet formation by studying debris around other stars. Giant impact
debris evolves through mutual collisions and dynamical interactions with
planets. General aspects of this evolution are outlined, noting the importance
of the collision-point geometry. The detectability of the debris is discussed
using the example of the Moon-forming impact. Such debris could be detectable
around another star up to 10Myr post-impact, but model uncertainties could
reduce detectability to a few 100yr window. Nevertheless the 3% of young stars
with debris at levels expected during terrestrial planet formation provide
valuable constraints on formation models; implications for super-Earth
formation are also discussed. Variability recently observed in some bright
disks promises to illuminate the evolution during the earliest phases when
vapour condensates may be optically thick and acutely affected by the
collision-point geometry. The outer reaches of planetary systems may also
exhibit signatures of giant impacts, such as the clumpy debris structures seen
around some stars.


title:
Iron in galaxy groups and clusters: Confronting galaxy evolution models
  with a newly homogenised dataset

abstract:
  We present an analysis of the iron abundance in the hot gas surrounding
galaxy groups and clusters. To do this, we first compile and homogenise a large
dataset of 79 low-redshift (|z| = 0.03) systems (159 individual measurements)
from the literature. Our analysis accounts for differences in aperture size,
solar abundance, and cosmology, and scales all measurements using customised
radial profiles for the temperature (T), gas density, and iron abundance (Z).
We then compare this dataset to groups and clusters in the L-Galaxies galaxy
evolution model.
  Our homogenised dataset reveals a tight T-Z relation for clusters, with a
scatter in Z of only 0.10 dex and a slight negative gradient. After examining
potential measurement biases, we conclude that at least some of this negative
gradient has a physical origin. Our model suggests greater accretion of
hydrogen in the hottest systems, via stripping of gas from infalling
satellites, as a cause. At lower temperatures, L-Galaxies over-estimates Z in
groups, indicating that metal-rich gas removal (via e.g. AGN feedback) is
required.
  L-Galaxies provides a reasonable match to the observed Z in the intracluster
medium (ICM) of the hottest clusters from at least z ~ 1.3 to 0.3. This is
achieved without needing to modify any of the galactic chemical evolution (GCE)
model parameters. However, the Z in intermediate-temperature clusters appears
to be under-estimated in our model at z = 0. The merits and problems with
modifying the GCE modelling to correct this are discussed.


title:
Dark Matter Inelastic Up-Scattering with the Interstellar Plasma: An
  Exciting New Source of X-Ray Lines, including at 3.5 keV

abstract:
  We explore the phenomenology of a class of models where the dark matter
particle can inelastically up-scatter to a heavier excited state via
off-diagonal dipolar interactions with the interstellar plasma (gas or free
electrons). The heavier particle then rapidly decays back to the dark matter
particle plus a quasi-monochromatic photon. For the process to occur at
appreciable rates, the mass splitting between the heavier state and the dark
matter must be comparable to, or smaller than, the kinetic energy of particles
in the plasma. As a result, the predicted photon line falls in the soft X-ray
range, or, potentially, at arbitrarily lower energies. We explore experimental
constraints from cosmology and particle physics, and present accurate
calculations of the dark matter thermal relic density and of the flux of
monochromatic X-rays from thermal plasma excitation. We find that the model
provides a natural explanation for the observed 3.5 keV line from clusters of
galaxies and from the Galactic center, and is consistent with null detections
of the line from dwarf galaxies. The unique line shape, which will be resolved
by future observations with the Hitomi (formerly Astro-H) satellite, and the
predicted unique morphology and target-temperature dependence will enable easy
discrimination of this class of models versus other scenarios for the
generation of the 3.5 keV line or of any other unidentified line across the
electromagnetic spectrum.


title:
An Empirical Determination of the Dust Mass Absorption Coefficient,
  $\kappa_{d}$, Using the Herschel Reference Survey

abstract:
  We use the published photometry and spectroscopy of 22 galaxies in the
Herschel Reference Survey to determine that the value of the dust mass
absorption coefficient $\kappa_{d}$ at a wavelength of 500 $\mu m$ is
$\kappa_{500} = 0.051^{+0.070}_{-0.026}\,{\rm m^{2}\,kg^{-1}}$. We do so by
taking advantage of the fact that the dust-to-metals ratio in the interstellar
medium of galaxies appears to be constant. We argue that our value for
$\kappa_{d}$ supersedes that of James et al. (2002) -- who pioneered this
approach for determining $\kappa_{d}$ -- because we take advantage of superior
data, and account for a number of significant systematic effects that they did
not consider. We comprehensively incorporate all methodological and
observational contributions to establish the uncertainty on our value, which
represents a marked improvement on the oft-quoted 'order-of-magnitude'
uncertainty on $\kappa_{d}$. We find no evidence that the value of $\kappa_{d}$
differs significantly between galaxies, or that it correlates with any other
measured or derived galaxy properties. We note, however, that the availability
of data limits our sample to relatively massive
($10^{9.7}<{M_{\star}}<10^{11.0}\ {\rm M_{\odot}}$), high metallicity
($8.61<[12+{\rm log}_{10}\frac{O}{H}]<8.86$) galaxies; future work will allow
us to investigate a wider range of systems.


title:
Footprints of hyperfine, spin-orbit, and decoherence effects in Pauli
  spin blockade

abstract:
  We detect in real time inter-dot tunneling events in a weakly coupled two
electron double quantum dot in GaAs. At finite magnetic fields, we observe two
characteristic tunneling times, T_d and T_b, belonging to, respectively, a
direct and a blocked (spin-flip-assisted) tunneling. The latter corresponds to
lifting of a Pauli spin blockade and the tunneling times ratio eta=T_b/T_d
characterizes the blockade efficiency. We find pronounced changes in the
behavior of eta upon increasing the magnetic field, with eta increasing,
saturating and increasing again. We explain this behavior as due to the
crossover of the dominant blockade lifting mechanism from the hyperfine to
spin-orbit interactions and due to a change in the contribution of the charge
decoherence.


title: Are Infrared Dark Clouds Really Quiescent?

abstract:
  The dense, cold regions where high-mass stars form are poorly characterised,
yet they represent an ideal opportunity to learn more about the initial
conditions of high-mass star formation (HMSF), since high-mass starless cores
(HMSCs) lack the violent feedback seen at later evolutionary stages.
  We present continuum maps obtained from the Submillimeter Array (SMA)
interferometry at 1.1 mm for four infrared dark clouds (IRDCs, G28.34S, IRDC
18530, IRDC 18306, and IRDC 18308). We also present 1 mm/3 mm line surveys
using IRAM 30 m single-dish observations.
  Our results are: (1) At a spatial resolution of 10^4 AU, the 1.1 mm SMA
observations resolve each source into several fragments. The mass of each
fragment is on average >10 Msun, which exceeds the predicted thermal Jeans mass
of the whole clump by a factor of up to 30, indicating that thermal pressure
does not dominate the fragmentation process. Our measured velocity dispersions
in the 30 m lines imply that non-thermal motions provides the extra support
against gravity in the fragments. (2) Both non-detection of high-J transitions
and the hyperfine multiplet fit of N2H+(1-0), C2H(1-0), HCN(1-0), and
H13CN(1-0) indicate that our sources are cold and young. However, obvious
detection of SiO and the asymmetric line profile of HCO+(1-0) in G28.34S
indicate a potential protostellar object and probable infall motion. (3) With a
large number of N-bearing species, the existence of carbon rings and molecular
ions, and the anti-correlated spatial distributions between N2H+/NH2D and CO,
our large-scale high-mass clumps exhibit similar chemical features as
small-scale low-mass prestellar objects. This study of a small sample of IRDCs
illustrates that thermal Jeans instability alone cannot explain the
fragmentation of the clump into cold (~15 K), dense (>10^5 cm-3) cores and that
these IRDCs are not completely quiescent.


title:
Stellar Mass--Gas-phase Metallicity Relation at $0.5\leq z\leq0.7$: A
  Power Law with Increasing Scatter toward the Low-mass Regime

abstract:
  We present the stellar mass ($M_{*}$)--gas-phase metallicity relation (MZR)
and its scatter at intermediate redshifts ($0.5\leq z\leq0.7$) for 1381 field
galaxies collected from deep spectroscopic surveys. The star formation rate
(SFR) and color at a given $M_{*}$ of this magnitude-limited ($R\lesssim24$ AB)
sample are representative of normal star-forming galaxies. For masses below
$10^9 M_\odot$, our sample of 237 galaxies is $\sim$10 times larger than those
in previous studies beyond the local universe. This huge gain in sample size
enables superior constraints on the MZR and its scatter in the low-mass regime.
We find a power-law MZR at $10^{8} M_\odot < M_{*} < 10^{11} M_\odot$:
${12+log(O/H) = (5.83\pm0.19) + (0.30\pm0.02)log(M_{*}/M_\odot)}$. Our MZR
shows good agreement with others measured at similar redshifts in the
literature in the intermediate and massive regimes, but is shallower than the
extrapolation of the MZRs of others to masses below $10^{9} M_\odot$. The SFR
dependence of the MZR in our sample is weaker than that found for local
galaxies (known as the Fundamental Metallicity Relation). Compared to a variety
of theoretical models, the slope of our MZR for low-mass galaxies agrees well
with predictions incorporating supernova energy-driven winds. Being robust
against currently uncertain metallicity calibrations, the scatter of the MZR
serves as a powerful diagnostic of the stochastic history of gas accretion, gas
recycling, and star formation of low-mass galaxies. Our major result is that
the scatter of our MZR increases as $M_{*}$ decreases. Our result implies that
either the scatter of the baryonic accretion rate or the scatter of the
$M_{*}$--$M_{halo}$ relation increases as $M_{*}$ decreases. Moreover, our
measures of scatter at $z=0.7$ appears consistent with that found for local
galaxies.


title:
Dark-soliton-like excitations in the Yang-Gaudin gas of attractively
  interacting fermions

abstract:
  Yrast states are the lowest energy states at given non-zero momentum and
provide a natural extension of the concept of dark solitons to
strongly-interacting one-dimensional quantum gases. Here we study the yrast
states of the balanced spin-$\frac{1}{2}$ Fermi gas with attractive
delta-function interactions in one dimension with the exactly solvable
Yang-Gaudin model. The corresponding Bethe-ansatz equations are solved for
finite particle number and in the thermodynamic limit. Properties corresponding
to the soliton-like nature of the yrast excitations are calculated including
the missing particle number, phase step, and inertial and physical masses. The
inertial to physical mass ratio, which is related to the frequency of
oscillations in a trapped gas, is found to be unity in the limits of strong and
weak attraction and falls to $\approx 0.78$ in the crossover regime. This
result is contrasted by one-dimensional mean field theory, which predicts a
divergent mass ratio in the weakly attractive limit. By means of an exact
mapping our results also predict the existence and properties of
dark-soliton-like excitations in the super Tonks-Girardeau gas. The prospects
for experimental observations are briefly discussed.


title: Robust Machine Learning for Encrypted Traffic Classification

abstract:
  Desktops and laptops can be maliciously exploited to violate privacy. In this
paper, we consider the daily battle between the passive attacker who is
targeting a specific user against a user that may be adversarial opponent. In
this scenario, while the attacker tries to choose the best vector attack by
surreptitiously monitoring the victims encrypted network traffic in order to
identify users parameters such as the Operating System (OS), browser and apps.
The user may use tools such as a Virtual Private Network (VPN) or even change
protocols parameters to protect his/her privacy. We provide a large dataset of
more than 20,000 examples for this task. We run a comprehensive set of
experiments, that achieves high (above 85) classification accuracy, robustness
and resilience to changes of features as a function of different network
conditions at test time. We also show the effect of a small training set on the
accuracy.


title: SN 2015U: A Rapidly Evolving and Luminous Type Ibn Supernova

abstract:
  Supernova (SN) 2015U (also known as PSN J07285387+3349106) was discovered in
NGC 2388 on 2015 Feb. 11. A rapidly evolving and luminous event, it showed
effectively hydrogen-free spectra dominated by relatively narrow helium P-Cygni
spectral features and it was classified as a SN Ibn. In this paper we present
photometric, spectroscopic, and spectropolarimetric observations of SN 2015U,
including a Keck/DEIMOS spectrum (resolution $\approx$ 5000) which fully
resolves the optical emission and absorption features. We find that SN 2015U is
best understood via models of shock breakout from extended and dense
circumstellar material (CSM), likely created by a history of mass loss from the
progenitor with an extreme outburst within $\sim$1-2 yr of core collapse (but
we do not detect any outburst in our archival imaging of NGC 2388). We argue
that the high luminosity of SN 2015U was powered not through $^{56}$Ni decay
but via the deposition of kinetic energy into the ejecta/CSM shock interface.
Though our analysis is hampered by strong host-galaxy dust obscuration (which
likely exhibits multiple components), our dataset makes SN 2015U one of the
best-studied Type Ibn supernovae and provides a bridge of understanding to
other rapidly fading transients, both luminous and relatively faint.


title: Characterizing the SHARDS of Disrupted Milky Way Satellites with LAMOST

abstract:
  We derive the fraction of substructure in the Galactic halo using a sample of
over 10,000 spectroscopically-confirmed halo giant stars from the LAMOST
spectroscopic survey. By observing 100 synthetic models along each line of
sight with the LAMOST selection function in that sky area, we statistically
characterize the expected halo populations. We define as SHARDS (Stellar Halo
Accretion Related Debris Structures) any stars in >3-sigma excesses above the
model predictions. We find that at least 10% of the Milky Way halo stars from
LAMOST are part of SHARDS. By running our algorithm on smooth halos observed
with the LAMOST selection function, we show that the LAMOST data contain excess
substructure over all Galactocentric radii R_GC < 40 kpc, beyond what is
expected due to statistical fluctuations and incomplete sampling of a smooth
halo. The level of substructure is consistent with the fraction of stars in
SHARDS in model halos created entirely from accreted satellites. This work
illustrates the potential of vast spectroscopic surveys with high filling
factors over large sky areas to recreate the merging history of the Milky Way.


title:
Efficient Global Point Cloud Alignment using Bayesian Nonparametric
  Mixtures

abstract:
  Point cloud alignment is a common problem in computer vision and robotics,
with applications ranging from 3D object recognition to reconstruction. We
propose a novel approach to the alignment problem that utilizes Bayesian
nonparametrics to describe the point cloud and surface normal densities, and
branch and bound (BB) optimization to recover the relative transformation. BB
uses a novel, refinable, near-uniform tessellation of rotation space using 4D
tetrahedra, leading to more efficient optimization compared to the common
axis-angle tessellation. We provide objective function bounds for pruning given
the proposed tessellation, and prove that BB converges to the optimum of the
cost function along with providing its computational complexity. Finally, we
empirically demonstrate the efficiency of the proposed approach as well as its
robustness to real-world conditions such as missing data and partial overlap.


title:
Reaction Time for Trimolecular Reactions in Compartment-based
  Reaction-Diffusion Models

abstract:
  Trimolecular reaction models are investigated in the compartment-based
(lattice-based) framework for stochastic reaction-diffusion modelling. The
formulae for the first collision time and the mean reaction time are derived
for the case where three molecules are present in the solution.


title:
An Adaptive Finite Element Method in Quantitative Reconstruction of
  Small Inclusions from Limited Observations

abstract:
  We consider a coefficient inverse problem for the dielectric permittivity in
Maxwell's equations, with data consisting of boundary measurements of one or
two backscattered or transmitted waves. The problem is treated using a
Lagrangian approach to the minimization of a Tikhonov functional, where an
adaptive finite element method forms the basis of the computations. A new a
posteriori error estimate for the coefficient is derived. The method is tested
successfully in numerical experiments for the reconstruction of two, three, and
four small inclusions with low contrast, as well as the reconstruction of a
superposition of two Gaussian functions.


title:
Combining the Best of Convolutional Layers and Recurrent Layers: A
  Hybrid Network for Semantic Segmentation

abstract:
  State-of-the-art results of semantic segmentation are established by Fully
Convolutional neural Networks (FCNs). FCNs rely on cascaded convolutional and
pooling layers to gradually enlarge the receptive fields of neurons, resulting
in an indirect way of modeling the distant contextual dependence. In this work,
we advocate the use of spatially recurrent layers (i.e. ReNet layers) which
directly capture global contexts and lead to improved feature representations.
We demonstrate the effectiveness of ReNet layers by building a Naive deep ReNet
(N-ReNet), which achieves competitive performance on Stanford Background
dataset. Furthermore, we integrate ReNet layers with FCNs, and develop a novel
Hybrid deep ReNet (H-ReNet). It enjoys a few remarkable properties, including
full-image receptive fields, end-to-end training, and efficient network
execution. On the PASCAL VOC 2012 benchmark, the H-ReNet improves the results
of state-of-the-art approaches Piecewise, CRFasRNN and DeepParsing by 3.6%,
2.3% and 0.2%, respectively, and achieves the highest IoUs for 13 out of the 20
object classes.


title: Thermo Activated Hysteresis on High Quality Graphene/h-BN Devices

abstract:
  We report on gate hysteresis in resistance on high quality graphene/h-BN
devices. We observe a thermal activated hysteretic behavior in resistance as a
function of the applied gate voltage at temperatures above 375K. In order to
investigate the origin of the hysteretic phenomenon, we design heterostructures
involving graphene/h-BN devices with different underlying substrates such as:
SiO2/Si and graphite; where heavily doped silicon and graphite are used as a
back gate electrodes, respectively. The gate hysteretic behavior of the
resistance shows to be present only in devices with an h-BN/SiO2 interface and
is dependent on the orientation of the applied gate electric field and sweep
rate. Finally, we suggest a phenomenological model, which captures all of our
findings based on charges trapped at the h-BN/SiO2. Certainly, such hysteretic
behavior in graphene resistance represents a technological problem for the
application of graphene devices at high temperatures, but conversely, it can
open new routes for applications on digital electronics and graphene memory
devices.


title: Tuning the pn junction at a metal-graphene interface via H2 exposure

abstract:
  Combining experiment and theory, we investigate how the naturally created
heterojunction at a graphene and metallic contact is modulated via interaction
with molecular hydrogen (H2). Due to electrostatic interaction, a Cr/Au
electrode induces a pn junction in graphene, leading to an asymmetrical
resistance between the charge carriers (electron and hole). This asymmetry is
well modeled by considering the preferential charge scattering at the pn
junction, and we show that it can be modulated in a reversible, selective and
asymmetrical manner by exposing H2 to the metal-graphene interface. Our results
are valuable for understanding the nature of the metal-graphene interfaces and
demonstrate a novel route towards hydrogen sensor application. KEYWORDS:
graphene, contact resistance,


title: Implication of CMS data on photon PDFs

abstract:
  As part of a recent analysis of exclusive two-photon production of W+ W-
pairs at the LHC, the CMS experiment used di-lepton data to obtain an
"effective" photon-photon luminosity. We show how the CMS analysis on their 8
TeV data, along with some assumptions about the likelihood for events in which
the proton breaks up to pass the selection criteria, can be used to
significantly constrain the photon parton distribution functions, such as those
from the CTEQ, MRST, and NNPDF collaborations. We compare the data with
predictions using these photon distributions, as well as the new LUXqed photon
distribution. We study the impact of including these data on the NNPDF2.3QED,
NNPDF3.0QED and CT14QEDinc fits. We find that these data place a usefil and
complementary cross-check on the photon distribution, which is consistent with
LUXqed prediction while suggesting that the NNPDF photon error band should be
significantly reduced. Additionally, we propose a simple model for describing
the two-photon production of W+ W- at the LHC. Using this model, we constrain
the amount of inelastic photon that remains after the experimental cuts are
applied.


title: Study of Performance of Bakelite Resistive Plate Chamber (RPC)

abstract:
  Resistive Plate Chamber (RPC) is a type of gaseous detector having excellent
time and position resolutions. VECC is involved in the R\&D of indigenously
developed bakelite RPCs. The largest size of bakelite RPC developed in India is
100 cm $\times$ 100 cm. We present here the test results of a bakelite sample
along with the cosmic ray test results of a bakelite RPC (30 cm $\times$ 30 cm
$\times$ 0.2cm) fabricated at VECC. The steps taken towards the development of
a large size (240 cm $\times$ 120 cm $\times$ 0.2 cm) bakelite RPC have also
been discussed.


title: Neutron stars in Horndeski gravity

abstract:
  Horndeski's theory of gravity is the most general scalar-tensor theory with a
single scalar whose equations of motion contain at most second-order
derivatives. A subsector of Horndeski's theory known as "Fab Four" gravity
allows for dynamical self-tuning of the quantum vacuum energy, and therefore it
has received particular attention in cosmology as a possible alternative to the
$\Lambda$CDM model. Here we study compact stars in Fab Four gravity, which
includes as special cases general relativity ("George"),
Einstein-dilaton-Gauss-Bonnet gravity ("Ringo"), theories with a nonminimal
coupling with the Einstein tensor ("John") and theories involving the
double-dual of the Riemann tensor ("Paul"). We generalize and extend previous
results in theories of the John class and were not able to find realistic
compact stars in theories involving the Paul class.


title:
Polyhedral Embeddings and Immersions of Many Triangulated 2-Manifolds
  with Few Vertices

abstract:
  This article presents an improvement and extension of the heuristic first
presented by Hougardy, Lutz, and Zelke in 2010 for realizing triangulated
orientable surfaces with few vertices by a simplex-wise linear embedding. The
improvement consists in the applicability to non-orientable surfaces
(simplex-wise linear immersions) as well as symmetric realizations. With the
help of our algorithm, numerous - often symmetric - realizations of
non-orientable surfaces with the minimal number or few vertices have been
obtained for the first time. These examples include the the Projective Plane
with one or two handles and the Klein Bottle with one or two handles.


title: A viscous-convective instability in laminar Keplerian thin discs

abstract:
  Using the anelastic approximation of linearized hydrodynamic equations, we
investigate the development of axially symmetric small perturbations in thin
Keplerian discs. Dispersion relation is found as a solution of general
Sturm-Liouville eigenvalue problem for different values of relevant physical
parameters (viscosity, heat conductivity, disc semithickness). The analysis
reveals the appearance of overstable mode for Prandtl parameter higher than
some critical value. These modes have a viscous-convective nature and can serve
as a seed for turbulence in astrophysical discs even in the absence of magnetic
fields.


title: On self-similar finite $p$-groups

abstract:
  In this paper, we address the following question: when is a finite $p$-group
$G$ self-similar, i.e. when can $G$ be faithfully represented as a self-similar
group of automorphisms of the $p$-adic tree? We show that, if $G$ is a
self-similar finite $p$-group of rank $r$, then its order is bounded by a
function of $p$ and $r$. This applies in particular to finite $p$-groups of a
given coclass. In the particular case of groups of maximal class, that is, of
coclass $1$, we can fully answer the question above: a $p$-group of maximal
class $G$ is self-similar if and only if it contains an elementary abelian
maximal subgroup over which $G$ splits. Furthermore, in that case the order of
$G$ is at most $p^p+1$, and this bound is sharp.


title:
Interstellar Scintillation and the Radio Counterpart of the Fast Radio
  Burst FRB150418

abstract:
  Keane et al. (2016) have recently reported the discovery of a new fast radio
burst, FRB150418, with a promising radio counterpart at 5.5 and 7.5 GHz -- a
rapidly decaying source, falling from 200-300 $\mu$Jy to 100 $\mu$Jy on
timescales of $\sim$6 d. This transient source may be associated with an
elliptical galaxy at redshift $z=0.492$, providing the first firm spectroscopic
redshift for a FRB and the ability to estimate the density of baryons in the
intergalactic medium via the combination of known redshift and radio dispersion
of the FRB. An alternative explanation, first suggested by Williams & Berger
(2016b), is that the identified counterpart may instead be a compact AGN. The
putative counterpart's variation may then instead be extrinsic, caused by
refractive scintillation in the ionized interstellar medium of the Milky Way,
which would invalidate the association with FRB150418. We examine this latter
explanation in detail and show that the reported observations are consistent
with scintillating radio emission from the core of a radio-loud active galactic
nucleus (AGN) having a brightness temperature $T_{\rm b} \gtrsim 10^9 {\rm K}$.
Using numerical simulations of the expected scattering for the line of sight to
FRB150418, we provide example images and light curves of such an AGN at 5.5 and
7.5 GHz. These results can be compared with continued radio monitoring to
conclusively determine the importance of scintillation for the observed radio
variability, and they show that scintillation is a critical consideration for
continued searches for FRB counterparts at radio wavelengths.


title:
Extending integrate-and-fire model neurons to account for the effects of
  weak electric fields and input filtering mediated by the dendrite

abstract:
  How extracellular electric fields, as generated endogenously or through
transcranial brain stimulation, affect the dynamics of large neuronal
populations is of great interest but not well understood. To study the
collective dynamics of large populations single-compartment (point) model
neurons have been proven very successful. These models, however, lack the
dendritic morphology to biophysically account for the effects of electric
fields, and for changes in synaptic integration due to morphology alone. Here
we (i) characterize the response of a canonical spatial (ball-and-stick) model
neuron to fluctuating synaptic input as well as an oscillatory, weak electric
field, and (ii) analytically derive an extension for popular integrate-and-fire
point neuron models to accurately reproduce these responses. We obtain distinct
filters mediated by the dendrite for inputs at the soma (high-pass filter) or
at the distal dendritic site (low-pass filter), and find that the electric
field induces spike rate resonance in the beta and gamma frequency bands or
even higher frequencies, depending on the location of synaptic background
input. Due to their computational efficiency the extended point models are well
suited for application in large populations of coupled neurons with different
morphology, exposed to extracellular electric fields.


title:
Bias Correction for Regularized Regression and its Application in
  Learning with Streaming Data

abstract:
  We propose an approach to reduce the bias of ridge regression and
regularization kernel network. When applied to a single data set the new
algorithms have comparable learning performance with the original ones. When
applied to incremental learning with block wise streaming data the new
algorithms are more efficient due to bias reduction. Both theoretical
characterizations and simulation studies are used to verify the effectiveness
of these new algorithms.


title: Ordering in rolled-up single-walled ferromagnetic nanomembranes

abstract:
  Magnetization of soft-ferromagnetic nano- and microtubes of nanometer-thin
walls (a single-widening rolled-up nanomembranes) is theoretically studied
using analytical and numerical approaches including different stress-induced
anisotropies. Within the analytical study, we consider magnetostatic effects
qualitatively, with an effective anisotropy, while they are fully treated in
the micromagnetic simulations (limited to the tubes of submicrometer diameters
however). Basic types of the periodic ordering have been established and their
presence in nanotubes of polycrystalline Permalloy and cobalt has been verified
within the simulations. The domain structure is basically determined by a
material-deposition-induced helical stress or a cooling-induced axial stress
via the volume magnetostriction while it is influenced by the distribution of
magnetic charges as well. Also, it is dependent on the initial state of the
magnetization process.


title:
Suppressing structure formation at dwarf galaxy scales and below: late
  kinetic decoupling as a compelling alternative to warm dark matter

abstract:
  Warm dark matter cosmologies have been widely studied as an alternative to
the cold dark matter paradigm, the characteristic feature being a suppression
of structure formation on small cosmological scales. A very similar situation
occurs if standard cold dark matter particles are kept in local thermal
equilibrium with a, possibly dark, relativistic species until the universe has
cooled down to keV temperatures. We perform a systematic phenomenological study
of this possibility, and classify all minimal models containing dark matter and
an arbitrary radiation component that allow such a late kinetic decoupling. We
recover explicit cases recently discussed in the literature and identify new
classes of examples that are very interesting from a model-building point of
view. In some of these models dark matter is inevitably self-interacting, which
is remarkable in view of recent observational support for this possibility.
Hence, dark matter models featuring late kinetic decoupling have the potential
not only to alleviate the missing satellites problem but also to address other
problems of the cosmological concordance model on small scales, in particular
the cusp-core and too-big-too-fail problems, in some cases without invoking any
additional input.


title: Time resolved photoemission of Sr$_2$IrO$_4$

abstract:
  We investigate the temporal evolution of electronic states in strontium
iridate Sr$_2$IrO$_4$. The time resolved photoemission spectra of intrinsic,
electron doped and the hole doped samples are monitored in identical
experimental conditions. Our data on intrinsic and electron doped samples, show
that primary doublon-holon pairs relax near to the chemical potential on a
timescale shorter than $70$ fs. The subsequent cooling of low energy
excitations takes place in two step: a rapid dynamics of $\cong120$ fs is
followed by a slower decay of $\cong 1$ ps. The reported timescales endorse the
analogies between Sr$_2$IrO$_4$ and copper oxides.


title:
Radio Polarization Observations of the Snail: A Crushed Pulsar Wind
  Nebula in G327.1-1.1 with a Highly Ordered Magnetic Field

abstract:
  Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic
rays in the Galaxy. While the magnetic field plays an important role in the
acceleration process, previous observations of magnetic field configurations of
PWNe are rare, particularly for evolved systems. We present a radio
polarization study of the "Snail" PWN inside the supernova remnant G327.1-1.1
using the Australia Telescope Compact Array. This PWN is believed to have been
recently crushed by the supernova (SN) reverse shock. The radio morphology is
composed of a main circular body with a finger-like protrusion. We detected a
strong linear polarization signal from the emission, which reflects a highly
ordered magnetic field in the PWN and is in contrast to the turbulent
environment with a tangled magnetic field generally expected from
hydrodynamical simulations. This could suggest that the characteristic
turbulence scale is larger than the radio beam size. We built a toy model to
explore this possibility, and found that a simulated PWN with a turbulence
scale of about one-eighth to one-sixth of the nebula radius and a pulsar wind
filling factor of 50--75% provides the best match to observations. This implies
substantial mixing between the SN ejecta and pulsar wind material in this
system.


title:
Symmetrization of Rational Maps: Arithmetic Properties and Families of
  Latt\`es Maps of $\mathbb P^k$

abstract:
  In this paper we study properties of endomorphisms of $\mathbb P^k$ using a
symmetric product construction $(\mathbb P^1)^k/\mathfrak{S}_k \cong \mathbb
P^k$. Symmetric products have been used to produce examples of endomorphisms of
$\mathbb P^k$ with certain characteristics, $k\geq2$. In the present note, we
discuss the use of these maps to enlighten arithmetic phenomena and stability
phenomena in parameter spaces. In particular, we study notions of uniform
boundedness of rational preperiodic points via good reduction information,
$k$-deep postcritically finite maps, and characterize families of Latt\`es
maps.


title:
Constructions of exotic actions on product manifolds with an asymmetric
  factor

abstract:
  We explore transformation groups of manifolds of the form $M\times S^n$,
where $M$ is an asymmetric manifold, i.e. a manifold which does not admit any
non-trivial action of a finite group. In particular, we prove that for $n=2$
there exists an infinite family of distinct non-diagonal effective circle
actions on such products. A similar result holds for actions of cyclic groups
of prime order. We also discuss free circle actions on $M \times S^1$, where
$M$ belongs to the class of "almost asymmetric" manifolds considered previously
by V. Puppe and M. Kreck.


title:
Collective dynamics of multimode bosonic systems induced by weak quantum
  measurement

abstract:
  In contrast to the fully projective limit of strong quantum measurement,
where the evolution is locked to a small subspace (quantum Zeno dynamics), or
even frozen completely (quantum Zeno effect), the weak non-projective
measurement can effectively compete with standard unitary dynamics leading to
nontrivial effects. Here we consider global weak measurement addressing
collective variables, thus preserving quantum superpositions due to the lack of
which path information. While for certainty we focus on ultracold atoms, the
idea can be generalized to other multimode quantum systems, including various
quantum emitters, optomechanical arrays, and purely photonic systems with
multiple-path interferometers (photonic circuits). We show that light
scattering from ultracold bosons in optical lattices can be used for defining
macroscopically occupied spatial modes that exhibit long-range coherent
dynamics. Even if the measurement strength remains constant, the quantum
measurement backaction acts on the atomic ensemble quasi-periodically and
induces collective oscillatory dynamics of all the atoms. We introduce an
effective model for the evolution of the spatial modes and present an analytic
solution showing that the quantum jumps drive the system away from its stable
point. We confirm our finding describing the atomic observables in terms of
stochastic differential equations.

categories: quant-ph cond-mat.quant-gas physics.atom-ph physics.optics


title: Spatial entanglement of nonvacuum Gaussian states

abstract:
  The vacuum state of a relativistic quantum field contains entanglement
between regions separated by spacelike intervals. Such spatial entanglement can
be revealed using an operational method introduced in Ann. Phys. 351, 112
(2014), Phys. Rev. D 91, 016005 (2014). In this approach, a cavity is
instantaneously divided into halves by an introduction of an extra perfect
mirror. Causal separation of the two regions of the cavity reveals nonlocal
spatial correlations present in the field, which can be quantified by measuring
particles generated in the process. We use this method to study spatial
entanglement properties of nonvacuum Gaussian field states. In particular we
show how to enhance the amount of harvested spatial entanglement by an
appropriate choice of the initial state of the field in the cavity. We find a
counterintuitive influence of the initial entanglement between cavity modes on
the spatial entanglement which is revealed by dividing the cavity in half.


title: Distributed Newest Vertex Bisection

abstract:
  Distributed adaptive conforming refinement requires multiple iterations of
the serial refinement algorithm and global communication as the refinement can
be propagated over several processor boundaries. We show bounds on the maximum
number of iterations. The algorithm is implemented within the software package
DUNE-ALUGrid.


title: The landscape of bounds for binary search trees

abstract:
  Binary search trees (BSTs) with rotations can adapt to various kinds of
structure in search sequences, achieving amortized access times substantially
better than the Theta(log n) worst-case guarantee. Classical examples of
structural properties include static optimality, sequential access, working
set, key-independent optimality, and dynamic finger, all of which are now known
to be achieved by the two famous online BST algorithms (Splay and Greedy).
(...)
  In this paper, we introduce novel properties that explain the efficiency of
sequences not captured by any of the previously known properties, and which
provide new barriers to the dynamic optimality conjecture. We also establish
connections between various properties, old and new. For instance, we show the
following.
  (i) A tight bound of O(n log d) on the cost of Greedy for d-decomposable
sequences. The result builds on the recent lazy finger result of Iacono and
Langerman (SODA 2016). On the other hand, we show that lazy finger alone cannot
explain the efficiency of pattern avoiding sequences even in some of the
simplest cases. (ii) A hierarchy of bounds using multiple lazy fingers,
addressing a recent question of Iacono and Langerman. (iii) The optimality of
the Move-to-root heuristic in the key-independent setting introduced by Iacono
(Algorithmica 2005). (iv) A new tool that allows combining any finite number of
sound structural properties. As an application, we show an upper bound on the
cost of a class of sequences that all known properties fail to capture. (v) The
equivalence between two families of BST properties. The observation on which
this connection is based was known before - we make it explicit, and apply it
to classical BST properties. (...)


title:
Performance Bounds for Nash Equilibria in Submodular Utility Systems
  with User Groups

abstract:
  In this paper, we consider variations of the utility system considered by
Vetta, in which users are grouped together. Our aim is to establish how
grouping and cooperation among users affect performance bounds. We consider two
types of grouping. The first type is from \cite{Zhang2014}, where each user
belongs to a group of users having social ties with it. For this type of
utility system, each user's strategy maximizes its social group utility
function, giving rise to the notion of \emph{social-aware Nash equilibrium}. We
prove that this social utility system yields to the bounding results of Vetta
for non-cooperative system, thus establishing provable performance guarantees
for the social-aware Nash equilibrium. For the second type of grouping, the set
of users is partitioned into $l$ disjoint groups, where the users within a
group cooperate to maximize their group utility function, giving rise to the
notion of \emph{group Nash equilibrium}. In this case, each group can be viewed
as a new user with vector-valued actions, and a 1/2 bound for the performance
of group Nash equilibrium follows from the result of Vetta. But as we show
tighter bounds involving curvature can be established. By defining the group
curvature $c_{k_i}$ associated with group $i$ with $k_i$ users, we show that if
the social utility function is nondecreasing and submodular, then any group
Nash equilibrium achieves at least $1/(1+\max_{1\leq i\leq l}c_{k_i})$ of the
optimal social utility, which is tighter than that for the case without
grouping. As a special case, if each user has the same action space, then we
have that any group Nash equilibrium achieves at least $1/(1+c_{k^*})$ of the
optimal social utility, where $k^*$ is the least number of users among the $l$
groups. Finally, we present an example of a utility system for database
assisted spectrum access to illustrate our results.


title: On the boundedness of SLC surfaces of general type

abstract:
  The purpose of this note is to give a new proof of Alexeev's boundedness
result for stable surfaces which is independent of the base field and to
highlight some important consequences of this result.


title: Optical and UV Spectra of the Remnant of SN 1885 (S And) in M31

abstract:
  We present optical and ultraviolet spectra of SN 1885 (S And), visible in
absorption against the bulge of the Andromeda galaxy (M31), using the Hubble
Space Telescope's STIS spectrograph to probe the three dimensional arrangement
of the supernova debris. Spectra covering 2900 to 5700 A taken using six 0.2"
slit positions in two orientations show broad Ca II absorption with blue and
red radial velocities out to at least 11,500 km/s, consistent with HST Ca II
images of S And. Enhanced Ca II absorption is seen between 2000 to 6000 km/s
suggestive of a Ca II-rich shell. The spectra also show strong, asymmetric Ca I
4227 A absorption extending out to +12,400 km/s, along with weak Fe I 3720 A
absorption in a shell with velocities between 2000 and 9000 km/s. Ultraviolet
spectra obtained revealed weak broad absorption shortward of 3000 A consistent
with model predictions. The STIS spectra, together with previous HST images,
show a layered structure with a well defined Ca-rich outer edge indicative of a
delayed detonation phase. The remnant's clumpy inner Ca-rich shell plus only a
handful of Fe-rich plumes is unlike morphologies expected from dynamical or
violent merger scenarios. The small number of Fe-rich plumes suggest their
formation during a deflagration phase by Rayleigh-Taylor instabilities but less
well developed without extended mixing as expected from hydrodynamic
calculations. The suppression of strong Rayleigh-Taylor instabilities is
possibly the result of strong magnetic fields. We propose SN 1885 was an
off-center, delayed detonation and slightly subluminous SN Ia similar to SN
1986g.