title: Nonlinear lepton-photon interactions in external background fields

abstract:
  Nonlinear phenomena of lepton-photon interactions in external backgrounds
with a generalised periodic plane-wave geometry are studied. We discuss
nonlinear Compton scattering in head-on lepton-photon collisions extended
properly to beyond the soft-photon regime. In addition, our results are applied
to stimulated lepton-antilepton pair production in photon collisions with
unrestricted energies. Derivations are considered semi-classically based on
unperturbed fermionic Volkov representations encoding the full interaction with
the background field. Closed expressions for total probabilities considering
S-matrix elements have been derived. The general formula is applied to Compton
scattering by an electron propagating in an external laser-like background. We
obtain additive contributions in the extended unconstrained result which turns
out to be stringently required in the highly nonlinear regime. A detailed
comparison of contributing harmonics is discussed for various field parameters.


title:
Reduction to a single closed equation for 2 by 2 reaction-diffusion
  systems of Lotka-Volterra type

abstract:
  We consider general models of coupled reaction-diffusion systems for
interacting variants of the same species. When the total population becomes
large with intensive competition, we prove that the frequencies (i.e.
proportions) of the variants can be approached by the solution of a simpler
reaction-diffusion system, through a singular limit method and a relative
compactness argument. As an example of application, we retrieve the classical
bistable equation for Wolbachia's spread into an arthropod population from a
system modeling interaction between infected and uninfected individuals.


title:
A Comparative Study of Ranking-based Semantics for Abstract
  Argumentation

abstract:
  Argumentation is a process of evaluating and comparing a set of arguments. A
way to compare them consists in using a ranking-based semantics which
rank-order arguments from the most to the least acceptable ones. Recently, a
number of such semantics have been proposed independently, often associated
with some desirable properties. However, there is no comparative study which
takes a broader perspective. This is what we propose in this work. We provide a
general comparison of all these semantics with respect to the proposed
properties. That allows to underline the differences of behavior between the
existing semantics.


title: Inverse Problem for a Curved Quantum Guide

abstract:
  In this paper, we consider the Dirichlet Laplacian operator -{\Delta} on a
curved quantum guide in R n (n = 2, 3) with an asymptotically straight
reference curve. We give uniqueness results for the inverse problem associated
to the reconstruction of the curvature by using either observations of spectral
data or a boot-strapping method. keywords: Inverse Problem, Quantum Guide,
Curvature


title: Waveform Optimization for SWIPT with Nonlinear Energy Harvester Modeling

abstract:
  Simultaneous Wireless Information and Power Transfer (SWIPT) has attracted
significant attention in the communication community. The problem of waveform
design for SWIPT has however never been addressed so far. In this paper, a
novel SWIPT transceiver architecture is introduced relying on the superposition
of multisine and OFDM waveforms at the transmitter and a power-splitter
receiver equipped with an energy harvester and an information decoder capable
of cancelling the multisine waveforms. The SWIPT multisine/OFDM waveforms are
optimized so as to maximize the rate-energy region of the whole system. They
are adaptive to the channel state information and result from a posynomial
maximization problem that originates from the non-linearity of the energy
harvester. Numerical results illustrate the performance of the derived
waveforms and SWIPT architecture.


title: Geometry and non-adiabatic response in quantum and classical systems

abstract:
  In these lecture notes, partly based on a course taught at the Karpacz Winter
School in March 2014, we explore the close connections between non-adiabatic
response of a system with respect to macroscopic parameters and the geometry of
quantum and classical states. We center our discussion around adiabatic gauge
potentials, which are the generators of unitary basis transformations in
quantum systems and generators of special canonical transformations in
classical systems. In quantum systems, eigenstate expectation values of these
potentials are the Berry connections and the covariance matrix of these gauge
potentials is the geometric tensor, whose antisymmetric part defines the Berry
curvature and whose symmetric part is the Fubini-Study metric tensor. In
classical systems one simply replaces the eigenstate expectation value by an
average over the micro-canonical shell. For complicated interacting systems, we
show that a variational principle may be used to derive approximate gauge
potentials. We then express the non-adiabatic response of the physical
observables of the system through these gauge potentials, specifically
demonstrating the close connection of the geometric tensor to the notions of
Lorentz force and renormalized mass. We highlight applications of this
formalism to deriving counter-diabatic (dissipationless) driving protocols in
various systems, as well as to finding equations of motion for slow macroscopic
parameters coupled to fast microscopic degrees of freedom that go beyond
macroscopic Hamiltonian dynamics. Finally, we illustrate these ideas with a
number of simple examples and highlight a few more complicated ones drawn from
recent literature.


title: Comparative Study of Differentially Private Data Synthesis Methods

abstract:
  When sharing data among researchers or releasing data for public use, there
is a risk of exposing sensitive information of individuals in the data set.
Data synthesis (DS) is a statistical disclosure limitation technique for
releasing synthetic data sets with pseudo individual records. Traditional DS
techniques often rely on strong assumptions of a data intruder's behaviors and
background knowledge to assess disclosure risk. Differential privacy (DP)
formulates a theoretical approach for a strong and robust privacy guarantee in
data release without having to model intruders' behaviors. Efforts have been
made aiming to incorporate the DP concept in the DS process. In this paper, we
examine current DIfferentially Private Data Synthesis (DIPS) techniques for
releasing individual-level surrogate data for the original data, compare the
techniques conceptually, and evaluate the statistical utility and inferential
properties of the synthetic data via each DIPS technique through extensive
simulation studies. Our work sheds light on the practical feasibility and
utility of the various DIPS approaches, and suggests future research directions
for DIPS.


title: Minimum Regret Search for Single- and Multi-Task Optimization

abstract:
  We propose minimum regret search (MRS), a novel acquisition function for
Bayesian optimization. MRS bears similarities with information-theoretic
approaches such as entropy search (ES). However, while ES aims in each query at
maximizing the information gain with respect to the global maximum, MRS aims at
minimizing the expected simple regret of its ultimate recommendation for the
optimum. While empirically ES and MRS perform similar in most of the cases, MRS
produces fewer outliers with high simple regret than ES. We provide empirical
results both for a synthetic single-task optimization problem as well as for a
simulated multi-task robotic control problem.


title: Distributed Online Data Aggregation in Dynamic Graphs

abstract:
  We consider the problem of aggregating data in a dynamic graph, that is,
aggregating the data that originates from all nodes in the graph to a specific
node, the sink. We are interested in giving lower bounds for this problem,
under different kinds of adversaries. In our model, nodes are endowed with
unlimited memory and unlimited computational power. Yet, we assume that
communications between nodes are carried out with pairwise interactions, where
nodes can exchange control information before deciding whether they transmit
their data or not, given that each node is allowed to transmit its data at most
once. When a node receives a data from a neighbor, the node may aggregate it
with its own data. We consider three possible adversaries: the online adaptive
adversary, the oblivious adversary , and the randomized adversary that chooses
the pairwise interactions uniformly at random. For the online adaptive and the
oblivious adversary, we give impossibility results when nodes have no knowledge
about the graph and are not aware of the future. Also, we give several tight
bounds depending on the knowledge (be it topology related or time related) of
the nodes. For the randomized adversary, we show that the Gathering algorithm,
which always commands a node to transmit, is optimal if nodes have no knowledge
at all. Also, we propose an algorithm called Waiting Greedy, where a node
either waits or transmits depending on some parameter, that is optimal when
each node knows its future pairwise interactions with the sink.


title:
Robust Beamforming for SWIPT Systems with Non-linear Energy Harvesting
  Model

abstract:
  This paper investigates resource allocation for simultaneous wireless
information and power transfer (SWIPT) downlink systems based on a non-linear
energy harvesting model. The resource allocation algorithm design is formulated
as a non-convex optimization problem for the maximization of the total
harvested power. The proposed problem formulation not only takes into account
imperfect channel state information (CSI) but also guarantees the
quality-of-service (QoS) of information transfer. A novel iterative algorithm
is proposed to obtain the globally optimal solution of the considered
non-convex optimization problem. In each iteration, a rank-constrained
semidefinite program (SDP) is solved optimally by SDP relaxation. Simulation
results demonstrate the significant gains in harvested power and the robustness
against CSI imperfection for the proposed optimal resource allocation, compared
to a baseline scheme designed for perfect CSI and the conventional linear
energy harvesting model.


title:
Effective holographic theories of momentum relaxation and violation of
  conductivity bound

abstract:
  We generalize current holographic models with homogeneous breaking of
translation symmetry by incorporating higher derivative couplings, in the
spirit of effective field theories. Focusing on charge transport, we specialize
to two simple couplings between the charge and translation symmetry breaking
sectors. We obtain analytical charged black brane solutions and compute their
DC conductivity in terms of horizon data. We constrain the allowed values of
the couplings and note that the DC conductivity can vanish at zero temperature
for strong translation symmetry breaking, thus showing that in general there is
no lower bound on the conductivity.


title:
Metrizable universal minimal flows of Polish groups have a comeagre
  orbit

abstract:
  We prove that, whenever $G$ is a Polish group with metrizable universal
minimal flow $M(G)$, there exists a comeagre orbit in $M(G)$. It then follows
that there exists an extremely amenable, closed, coprecompact $G^*$ of $G$ such
that $M(G) = \hat{G/G^*}$.


title:
Unusual ferromagnetism in Ising and Potts model on semi-directed
  Barab\'asi-Albert networks

abstract:
  We check the existence of a spontaneous magnetisation of Ising and Potts
spins on semi-directed Barabasi-Albert networks by Monte Carlo simulations. We
verified that the magnetisation for different temperatures $T$ decays after a
characteristic time $\tau(T)$, which we extrapolate to diverge at positive
temperatures $T_c(N)$ by a Vogel-Fulcher law, with $T_c(N)$ increasing
logarithmically with network size $N$.


title:
A note on utility maximization with transaction costs and random
  endoment: num\'eraire-based model and convex duality

abstract:
  In this note, we study the utility maximization problem on the terminal
wealth under proportional transaction costs and bounded random endowment. In
particular, we restrict ourselves to the num\'eraire-based model and work with
utility functions only supporting R+. Under the assumption of existence of
consistent price systems and natural regularity conditions, standard convex
duality results are established. Precisely, we first enlarge the dual domain
from the collection of martingale densities associated with consistent price
systems to a set of finitely additive measures; then the dual formulation of
the utility maximization problem can be regarded as an extension of the paper
of Cvitani\'c-Schachermayer-Wang (2001) to the context under proportional
transaction costs.


title: Asymmetric critical $p$-Laplacian problems

abstract:
  We obtain nontrivial solutions for two types of critical $p$-Laplacian
problems with asymmetric nonlinearities in a smooth bounded domain in ${\mathbb
R}^N,\, N \ge 2$. For $p < N$, we consider an asymmetric problem involving the
critical Sobolev exponent $p^\ast = Np/(N - p)$. In the borderline case $p =
N$, we consider an asymmetric critical exponential nonlinearity of the
Trudinger-Moser type. In the absence of a suitable direct sum decomposition, we
use a linking theorem based on the ${\mathbb Z}_2$-cohomological index to
obtain our solutions.


title: Dark matter as a condensate: Deduction of microscopic properties

abstract:
  In the present work we model dark matter as a Bose-Einstein condensate and
the main goal is the deduction of the microscopic properties, namely, mass,
number of particles, and scattering length, related to the particles comprised
in the corresponding condensate. This task is done introducing in the
corresponding model the effects of the thermal cloud of the system. Three
physical conditions are imposed, i.e., mechanical equilibrium of the
condensate, explanation of the rotation curves of stars belonging to dwarf
galaxies, and, finally, the deflection of light due to the presence of dark
matter. These three aforementioned expressions allow us to cast the features of
the particles in terms of detectable astrophysical variables. Finally, the
model is contrasted against observational data and in this manner we obtain
values for the involved microscopic parameters of the condensate. The
statistical errors are seven and eighteen percent for the scattering length and
mass of the dark matter particle, respectively.


title:
Shubnikov-de Haas oscillations of high mobility holes in monolayer and
  bilayer WSe$_2$: Landau level degeneracy, effective mass, and negative
  compressibility

abstract:
  We study the magnetotransport properties of high mobility holes in monolayer
and bilayer WSe$_2$, which display well defined Shubnikov-de Haas (SdH)
oscillations, and quantum Hall states (QHSs) in high magnetic fields. In both
mono and bilayer WSe$_2$, the SdH oscillations and the QHSs occur predominantly
at even filling factors, evincing a two-fold Landau level degeneracy. The
Fourier transform analysis of the SdH oscillations in bilayer WSe$_2$ reveal
the presence of two subbands localized in the top or the bottom layer, as well
as negative compressibility. From the temperature dependence of the SdH
oscillations we determine a hole effective mass of $0.45m_{0}$ for both mono
and bilayer WSe$_2$.


title:
Photocurrents in Bi2Se3: bulk versus surface, and injection versus shift
  currents

abstract:
  Optical injection and detection of charge currents can complement
conventional transport and photoemission measurements without the necessity of
invasive contact that may disturb the system being examined. This is a
particular concern for the surface states of a topological insulator. In this
work one- and two-color sources of photocurrents are examined in epitaxial,
thin films of Bi2Se3. We demonstrate that optical excitation and terahertz
detection simultaneously captures one- and two- color photocurrent
contributions, as previously not required in other material systems. A method
is devised to isolate the two components, and in doing so each can be related
to surface or bulk excitations through symmetry. This strategy allows surface
states to be examined in a model system, where they have independently been
verified with angle-resolved photoemission spectroscopy.


title: Toward Rapid Transformation of Ideas into Software

abstract:
  A key mission of computer science is to enable people realize their creative
ideas as naturally and painlessly as possible. Software engineering is at the
center of this mission -- software technologies enable reification of ideas
into working systems. As computers become ubiquitous, both in availability and
the aspects of human lives they touch, the quantity and diversity of ideas also
rapidly grow. Our programming systems and technologies need to evolve to make
this reification process -- transforming ideas to software -- as quick and
accessible as possible.
  The goal of this paper is twofold. First, it advocates and highlights the
"transforming ideas to software" mission as a moonshot for software engineering
research. This is a long-term direction for the community, and there is no
silver bullet that can get us there. To make this mission a reality, as a
community, we need to improve the status quo across many dimensions. Thus, the
second goal is to outline a number of directions to modernize our contemporary
programming technologies for decades to come, describe work that has been
undertaken along those vectors, and pinpoint critical challenges.


title: On $C_{J}$ and $C_{T}$ in Conformal QED

abstract:
  QED with a large number $N$ of massless fermionic degrees of freedom has a
conformal phase in a range of space-time dimensions. We use a large $N$
diagrammatic approach to calculate the leading corrections to $C_T$, the
coefficient of the two-point function of the stress-energy tensor, and $C_J$,
the coefficient of the two-point function of the global symmetry current. We
present explicit formulae as a function of $d$ and check them versus the
expectations in 2 and $4-\epsilon$ dimensions. Using our results in higher even
dimensions we find a concise formula for $C_T$ of the conformal Maxwell theory
with higher derivative action $F_{\mu \nu} (-\nabla^2)^{\frac{d}{2}-2} F^{\mu
\nu}$. In $d=3$, QED has a topological symmetry current, and we calculate the
correction to its two-point function coefficient, $C^{\textrm{top}}_{J}$. We
also show that some RG flows involving QED in $d=3$ obey $C_T^{\rm UV} >
C_T^{\rm IR}$ and discuss possible implications of this inequality for the
symmetry breaking at small values of $N$.


title: Turaev Torsion Invariants of 3-orbifolds

abstract:
  We construct a combinatorial invariant of 3-orbifolds with singular set a
link that generalizes the Turaev torsion invariant of 3-manifolds. We give
several gluing formulas from which we derive two consequences. The first is an
understanding of how the components of the invariant change when we remove a
curve from the singular set. The second is a formula relating the invariant of
the 3-orbifold to the Turaev torsion invariant of the underlying 3-manifold in
the case when the singular set is a nullhomologous knot.


title: Conformal symmetry and nonlinear extensions of nonlocal gravity

abstract:
  We study two nonlinear extensions of the nonlocal $R\,\Box^{-2}R$ gravity
theory. We extend this theory in two different ways suggested by conformal
symmetry, either replacing $\Box^{-2}$ with $(-\Box + R/6)^{-2}$, which is the
operator that enters the action for a conformally-coupled scalar field, or
replacing $\Box^{-2}$ with the inverse of the Paneitz operator, which is a
four-derivative operator that enters in the effective action induced by the
conformal anomaly. We show that the former modification gives an interesting
and viable cosmological model, with a dark energy equation of state today
$w_{\rm DE}\simeq -1.01$, which very closely mimics $\Lambda$CDM and evolves
asymptotically into a de Sitter solution. The model based on the Paneitz
operator seems instead excluded by the comparison with observations. We also
review some issues about the causality of nonlocal theories, and we point out
that these nonlocal models can be modified so to nicely interpolate between
Starobinski inflation in the primordial universe and accelerated expansion in
the recent epoch.


title:
Design of defect spins in piezoelectric aluminum nitride for solid-state
  hybrid quantum technologies

abstract:
  Spin defects in wide-band gap semiconductors are promising systems for the
realization of quantum bits, or qubits, in solid-state environments. To date,
defect qubits have only been realized in materials with strong covalent bonds.
Here, we introduce a strain-driven scheme to rationally design defect spins in
functional ionic crystals, which may operate as potential qubits. In
particular, using a combination of state-of-the-art ab-initio calculations
based on hybrid density functional and many-body perturbation theory, we
predicted that the negatively charged nitrogen vacancy center in piezoelectric
aluminum nitride exhibits spin-triplet ground states under realistic uni- and
bi-axial strain conditions; such states may be harnessed for the realization of
qubits. The strain-driven strategy adopted here can be readily extended to a
wide range of point defects in other wide-band gap semiconductors, paving the
way to controlling the spin properties of defects in ionic systems for
potential spintronic technologies.


title:
An unfitted discontinuous Galerkin scheme for conservation laws on
  evolving surfaces

abstract:
  Motivated by considering partial differential equations arising from
conservation laws posed on evolving surfaces, a new numerical method for an
advection problem is developed and simple numerical tests are performed. The
method is based on an unfitted discontinuous Galerkin approach where the
surface is not explicitly tracked by the mesh which means the method is
extremely flexible with respect to geometry. Furthermore, the discontinuous
Galerkin approach is well-suited to capture the advection driven by the
evolution of the surface without the need for a space-time formulation,
back-tracking trajectories or streamline diffusion. The method is illustrated
by a one-dimensional example and numerical results are presented that show good
convergence properties for a simple test problem.


title: Measuring the neutron star equation of state using X-ray timing

abstract:
  One of the primary science goals of the next generation of hard X-ray timing
instruments is to determine the equation of state of the matter at supranuclear
densities inside neutron stars, by measuring the radius of neutron stars with
different masses to accuracies of a few percent. Three main techniques can be
used to achieve this goal. The first involves waveform modelling. The flux we
observe from a hotspot on the neutron star surface offset from the rotational
pole will be modulated by the star's rotation, giving rise to a pulsation.
Information about mass and radius is encoded into the pulse profile via
relativistic effects, and tight constraints on mass and radius can be obtained.
The second technique involves characterising the spin distribution of accreting
neutron stars. The most rapidly rotating stars provide a very clean constraint,
since the mass-shedding limit is a function of mass and radius. However the
overall spin distribution also provides a guide to the torque mechanisms in
operation and the moment of inertia, both of which can depend sensitively on
dense matter physics. The third technique is to search for quasi-periodic
oscillations in X-ray flux associated with global seismic vibrations of
magnetars (the most highly magnetized neutron stars), triggered by magnetic
explosions. The vibrational frequencies depend on stellar parameters including
the dense matter equation of state. We illustrate how these complementary X-ray
timing techniques can be used to constrain the dense matter equation of state,
and discuss the results that might be expected from a 10m$^2$ instrument. We
also discuss how the results from such a facility would compare to other
astronomical investigations of neutron star properties. [Modified for arXiv]


title: Nonextensive statistics in spin precession

abstract:
  Many experiments utilize the precession of trapped particles in magnetic
fields to perform high precision measurements. It had been presumed that after
free precession, initially polarized particles will form a Gaussian phase
distribution in the plane of precession. We show that trapped particles in the
presence of magnetic field gradients and electric fields will often form a
non-Gaussian distribution with power-law tails which are consistent with
nonextensive statistics. As the exact shape of the distribution depends upon
many experimental parameters, it provides a potential new technique to directly
measure them.


title: Ehrenfest Theorem in Precanonical Quantization of Fields and Gravity

abstract:
  We discuss a generalization of the Ehrenfest theorem to the recently proposed
precanonical quantization of vielbein gravity which proceeds from a space-time
symmetric generalization of the Hamiltonian formalism to field theory.
Classical Einstein-Palatini equations are derived as equations of expectation
values of precanonical quantum operators. The preceding consideration of an
interacting scalar field theory on curved space-time shows how the classical
field equations emerge from the results of precanonical quantization as the
equations of expectation values of the corresponding quantum operators. It also
allows us to identify the connection term in the covariant generalization of
the precanonical Schr\"odinger equation with the spin connection.


title: Simple fluidic digital half-adder

abstract:
  A fluidic one-bit half-adder is made of five channels which intersect at a
junction. Two channels are inputs, two channels are outputs and one channel is
the drain. The channels direct fluid from input fragments to output fragments
and the streams of fluid interact at the junctions. Binary signals are
represented by water droplets introduced in the input channels: presence of a
droplet in an input or output segments symbolises logical {\sc True}, absence
--- {\sc False}. The droplets travel along channels by following a path of
least resistance unless deflected at the junction. We demonstrate the function
of the half-adder in both computer modelling and laboratory experiments, and
propose a design of a one-bit full adder based on simulation.


title: Lambert series and q-functions near q=1

abstract:
  We study the Lambert series $\mathscr{L}_q(s,x) = \sum_{k=1}^\infty k^s q^{k
x}/(1-q^k)$, for all $s \in \mathbb{C}$. We obtain the complete asymptotic
expansion of $\mathscr{L}_q(s,x)$ near $q=1$. Our analysis of the Lambert
series yields the asymptotic forms for several related q-functions: the q-gamma
and q-polygamma functions, the q-Pochhammer symbol, and, in closed form, the
Jacobi theta functions. Some typical results include $\Gamma_2(\frac{1}{4})
\Gamma_2(\frac{3}{4}) \simeq \frac{2^{13/32} \pi}{\log 2}$ and $\vartheta_4
(0,e^{-1/\pi}) \simeq 2 \pi e^{-\pi^3\!/4}$, with relative errors of order
$10^{-25}$ and $10^{-27}$ respectively.


title: Broadband and Resonant Approaches to Axion Dark Matter Detection

abstract:
  When ultralight axion dark matter encounters a static magnetic field, it
sources an effective electric current that follows the magnetic field lines and
oscillates at the axion Compton frequency. We propose a new experiment to
detect this axion effective current. In the presence of axion dark matter, a
large toroidal magnet will act like an oscillating current ring, whose induced
magnetic flux can be measured by an external pickup loop inductively coupled to
a SQUID magnetometer. We consider both resonant and broadband readout circuits
and show that a broadband approach has advantages at small axion masses. We
estimate the reach of this design, taking into account the irreducible sources
of noise, and demonstrate potential sensitivity to axion-like dark matter with
masses in the range of 10^{-14}-10^{-6} eV. In particular, both the broadband
and resonant strategies can probe the QCD axion with a GUT-scale decay
constant.

categories: hep-ph astro-ph.CO hep-ex physics.ins-det


title:
A Recalibration of Strong Line Oxygen Abundance Diagnostics via the
  Direct Method and Implications for the High Redshift Universe

abstract:
  We use direct method oxygen abundances in combination with strong optical
emission lines, stellar masses ($M_{\star}$), and star formation rates (SFRs)
to recalibrate the N2, O3N2, and N2O2 oxygen abundance diagnostics. We stack
spectra of $\sim$200,000 star-forming galaxies from the Sloan Digital Sky
Survey in bins of $M_{\star}$ and SFR offset from the star forming main
sequence to measure the weak emission lines needed to apply the direct method.
All three new calibrations are reliable to within $\pm 0.10$ dex from
$\log(M_{\star}/M_{\odot}) \sim 7.5 - 10.5$ and up to at least $200~M_{\odot}$
yr$^{-1}$ in SFR. The N2O2 diagnostic is the least subject to systematic
biases. We apply the diagnostics to galaxies in the local universe and
investigate the $M_{\star}$-$Z$-${\rm SFR}$ relation. The N2 and O3N2
diagnostics suggest the SFR dependence of the $M_{\star}$-$Z$-${\rm SFR}$
relation varies with both $M_{\star}$ and $\Delta \log(SSFR)$, whereas the N2O2
diagnostic suggests a nearly constant dependence on SFR. We apply our
calibrations to a sample of high redshift galaxies from the literature, and
find them to be metal poor relative to local galaxies with similar $M_{\star}$
and SFR. The calibrations do reproduce direct method abundances of the local
analogs. We conclude that the $M_{\star}$-$Z$-${\rm SFR}$ relation evolves with
redshift.


title:
ASASSN-15oi: A Rapidly Evolving, Luminous Tidal Disruption Event at 216
  Mpc

abstract:
  We present ground-based and Swift photometric and spectroscopic observations
of the tidal disruption event (TDE) ASASSN-15oi, discovered at the center of
2MASX J20390918-3045201 ($d\simeq216$ Mpc) by the All-Sky Automated Survey for
SuperNovae (ASAS-SN). The source peaked at a bolometric luminosity of
$L\simeq1.3\times10^{44}$ ergs s$^{-1}$ and radiated a total energy of
$E\simeq6.6\times10^{50}$ ergs over the first $\sim3.5$ months of observations.
The early optical/UV emission of the source can be fit by a blackbody with
temperature increasing from $T\sim2\times10^4$ K to $T\sim4\times10^4$ K while
the luminosity declines from $L\simeq1.3\times10^{44}$ ergs s$^{-1}$ to
$L\simeq2.3\times10^{43}$ ergs s$^{-1}$, requiring the photosphere to be
shrinking rapidly. The optical/UV luminosity decline during this period is most
consistent with an exponential decline, $L\propto e^{-(t-t_0)/\tau}$, with
$\tau \simeq46.5$ days for $t_0\simeq57241.6$ (MJD), while a power-law decline
of $L\propto (t-t_0)^{-\alpha}$ with $t_0\simeq57212.3$ and $\alpha=1.62$
provides a moderately worse fit. ASASSN-15oi also exhibits roughly constant
soft X-ray emission that is significantly weaker than the optical/UV emission.
Spectra of the source show broad helium emission lines and strong blue
continuum emission in early epochs, although these features fade rapidly and
are not present $\sim3$ months after discovery. The early spectroscopic
features and color evolution of ASASSN-15oi are consistent with a TDE, but the
rapid spectral evolution is unique among optically-selected TDEs.


title:
The Metal Abundances across Cosmic Time ($\mathcal{MACT}$) Survey. I.
  Optical Spectroscopy in the Subaru Deep Field

abstract:
  Deep rest-frame optical spectroscopy is critical for characterizing and
understanding the physical conditions and properties of the ionized gas in
galaxies. Here, we present a new spectroscopic survey called "Metal Abundances
across Cosmic Time" or $\mathcal{MACT}$, which will obtain rest-frame optical
spectra for $\sim$3000 emission-line galaxies. This paper describes the optical
spectroscopy that has been conducted with MMT/Hectospec and Keck/DEIMOS for
$\approx$1900 $z=0.1-1$ emission-line galaxies selected from our narrowband and
intermediate-band imaging in the Subaru Deep Field. In addition, we present a
sample of 164 galaxies for which we have measured the weak [OIII]$\lambda$4363
line (66 with at least 3$\sigma$ detections and 98 with significant upper
limits). This nebular emission line determines the gas-phase metallicity by
measuring the electron temperature of the ionized gas. This paper presents the
optical spectra, emission-line measurements, interstellar properties (e.g.,
metallicity, gas density), and stellar properties (e.g., star formation rates,
stellar mass). Paper II of the $\mathcal{MACT}$ survey (Ly et al.) presents the
first results on the stellar mass--gas metallicity relation at $z\lesssim1$
using the sample with [OIII]$\lambda$4363 measurements.


title: The tight relation between X-ray and ultraviolet luminosity of quasars

abstract:
  The observed relation between the soft X-ray and the optical-ultraviolet
emission in active galactic nuclei (AGN) is non-linear and it is usually
parametrized as a dependence between the logarithm of the monochromatic
luminosity at 2500 {\AA} and at 2 keV. Previous investigations have found that
the dispersion of this relation is rather high (~0.35-0.4 in log units), which
may be caused by measurement uncertainties, variability, and intrinsic
dispersion due to differences in the AGN physical properties (e.g. different
accretion modes). We show that, once optically-selected quasars with
homogeneous SED and X-ray detection are selected, and dust reddened and/or gas
obscured objects are not included, the measured dispersion drops to
significantly lower values (i.e. ~0.21-0.24 dex). We show that the residual
dispersion is due to some extent to variability, and to remaining measurement
uncertainties. Therefore, the real physical intrinsic dispersion should be
<0.21 dex. Such a tight relation, valid over 4 decades in luminosity, must be
the manifestation of an intrinsic (and universal) physical relation between the
disk, emitting the primary radiation, and the hot electron corona emitting
X-rays.


title:
Enhanced X-ray emission from Lyman Break Analogues and a Possible
  $L_{\rm X}$--SFR--Metallicity Plane

abstract:
  The source of energetic photons that heated and reionized the early Universe
remains uncertain. Early galaxies had low metallicity and recent population
synthesis calculations suggest that the number and luminosity of high-mass
X-ray binaries are enhanced in star-forming galaxies with low metallicity,
offering a potentially important and previously overlooked source of heating
and reionization. Lyman break analogue (LBA) galaxies are local galaxies that
strongly resemble the high-redshift, star-forming Lyman Break Galaxies and have
been suggested as local analogues to these metal-deficient galaxies found in
the early Universe. We studied a sample of ten LBAs in order to measure the
relation between star formation rate and X-ray luminosity. We found that for
LBAs with metallicities in the range $12+\log_{10}({\rm O/H}) = 8.15-8.80$, the
$L_X-$SFR relation was $\log_{10} (L_X/{\rm SFR}\, {[\rm erg\ s^{-1}\
M_{\odot}^{-1}\ yr]}) = 39.85(\pm 0.10)$ in the $0.5-8$~keV band with a
dispersion of $\sigma = 0.25$~dex. This is an enhancement of nearly a factor of
$2$ in the $L_{0.5-8\text{keV}}$--SFR relation relative to results for nearby,
near-solar metallicity galaxies. The enhancement is significant at the 98.2\%
level ($2.4\sigma$). Our enhanced $L_X/{\rm SFR}$ relation is consistent with
the metallicity-dependent predicted value from population synthesis models. We
discuss the possibility of a $L_X$--SFR--Metallicity plane for star-forming
galaxies. These results are important to our understanding of reionization and
the formation of early galaxies.


title: A Composite Model for the 750 GeV Diphoton Excess

abstract:
  We study a simple model in which the recently reported 750 GeV diphoton
excess arises from a composite pseudo Nambu-Goldstone boson---hidden
pion---produced by gluon fusion and decaying into two photons. The model only
introduces an extra hidden gauge group at the TeV scale with a vectorlike quark
in the bifundamental representation of the hidden and standard model gauge
groups. We calculate the masses of all the hidden pions and analyze their
experimental signatures and constraints. We find that two colored hidden pions
must be near the current experimental limits, and hence are probed in the near
future. We study physics of would-be stable particles---the composite states
that do not decay purely by the hidden and standard model gauge dynamics---in
detail, including constraints from cosmology. We discuss possible theoretical
structures above the TeV scale, e.g. conformal dynamics and supersymmetry, and
their phenomenological implications. We also discuss an extension of the
minimal model in which there is an extra hidden quark that is singlet under the
standard model and has a mass smaller than the hidden dynamical scale. This
provides two standard model singlet hidden pions that can both be viewed as
diphoton/diboson resonances produced by gluon fusion. We discuss several
scenarios in which these (and other) resonances can be used to explain various
excesses seen in the LHC data.


title:
Modular transformations through sequences of topological charge
  projections

abstract:
  The ground state subspace of a topological phase of matter forms a
representation of the mapping class group of the space on which the state is
defined. We show that elements of the mapping class group of a surface of genus
$g$ can be obtained through a sequence of topological charge projections along
at least three mutually intersecting non-contractible cycles. We demonstrate
this both through the algebraic theory of anyons and also through an analysis
of the topology of the space-time manifold. We combine this result with two
observations: (i) that surfaces of genus $g$ can be effectively simulated in
planar geometries by using bilayer, or doubled, versions of the topological
phase of interest, and inducing the appropriate types of gapped boundaries; and
(ii) that the required topological charge projections can be implemented as
adiabatic unitary transformations by locally tuning microscopic parameters of
the system, such as the energy gap. These observations suggest a possible path
towards effectively implementing modular transformations in physical systems.
In particular, they also show how the $\text{Ising} \otimes
\overline{\text{Ising}}$ state, in the presence of disconnected gapped
boundaries, can support universal topological quantum computation.


title: Shocking Features in the Merging Galaxy Cluster RXJ0334.2-0111

abstract:
  We present a 66 ksec $\textit{Chandra}$ X-ray observation of the galaxy
cluster RXJ0334.2-0111. This deep observation revealed a unique bow shock
system associated with a wide angle tail (WAT) radio galaxy and several
intriguing substructures. The temperature across the bow shock jumps by a
factor of $\sim$ 1.5 (from 4.1 keV to 6.2 keV), and is consistent with the Mach
number $M = 1.6_{-0.3}^{+0.5}$. A second inner surface brightness edge is a
cold front that marks the border between infalling subcluster cool core and the
ICM of the main cluster. The temperature across the cold front increases from
$1.3_{-0.8}^{+0.3}$ keV to $6.2_{-0.6}^{+0.6}$ keV. We find an overpressurized
region $\sim$ 250 kpc east of the cold front that is named "the eastern
extension (EE)". The EE may be a part of the third subcluster in the ongoing
merger. We also find a tail shaped feature that originates near the bow shock
and may extend up to a distance of $\sim$ 1 Mpc. This feature is also likely
overpressurized. The luminous FR-I radio galaxy, 3C89, appears to be the cD
galaxy of the infalling subcluster. We estimated 3C89's jet power from jet
bending and the possible interaction between the X-ray gas and the radio lobes.
A comparison between the shock stand-off distance and the Mach number for all
known shock front/cold front combinations suggests that the core is
continuously shrinking in size by stripping.


title: How Dense is Your Gas? On the recoverability of LVG model parameters

abstract:
  We explore the recoverability of gas physical conditions with the Large
Velocity Gradient (LVG) model, using the public code RADEX and the molecules
HCN and CO. Examining a wide parameter range with a series of models of
increasing complexity we use both grid and Monte Carlo Markov Chain (MCMC)
methods to recover the input conditions, and quantify the inherent and noise
induced uncertainties in the model results. We find that even with the benefit
of generous assumptions the LVG models struggle to recover any parameter better
than to within half a dex, although we find no evidence of systemic offsets.
Examining isotopologue lines we demonstrate that it is always preferable to
model the isotopologue abundance ratio as a free parameter, due to large biases
introduced in all other parameters when an incorrect ratio is assumed. Finally,
we explore the effects of the background radiation temperature on CO and HCN
line ratios, with an emphasis on the effect of the CMB at $z>4$, and show that
while the effect on the line ratios is minor, the effect on the SLED peak is
significant and that the CO$(1-0)$ line luminosity to H$_2$ mass conversion
factor ($\alpha_{\rm CO}$) needs to be altered to account for the loss of
contrast against the hotter CMB as redshift increases.


title:
UV to IR Luminosities and Dust Attenuation Determined from ~4000
  K-Selected Galaxies at 1<z<3 in the ZFOURGE Survey

abstract:
  We build a set of composite galaxy SEDs by de-redshifting and scaling
multi-wavelength photometry from galaxies in the ZFOURGE survey, covering the
CDFS, COSMOS, and UDS fields. From a sample of ~4000 K_s-band selected
galaxies, we define 38 composite galaxy SEDs that yield continuous
low-resolution spectra (R~45) over the rest-frame range 0.1-4 um. Additionally,
we include far infrared photometry from the Spitzer Space Telescope and the
Herschel Space Observatory to characterize the infrared properties of our
diverse set of composite SEDs. From these composite SEDs we analyze the
rest-frame UVJ colors, as well as the ratio of IR to UV light (IRX) and the UV
slope ($\beta$) in the IRX$-\beta$ dust relation at 1<z<3. Blue star-forming
composite SEDs show IRX and $\beta$ values consistent with local relations;
dusty star-forming galaxies have considerable scatter, as found for local IR
bright sources, but on average appear bluer than expected for their IR fluxes.
We measure a tight linear relation between rest-frame UVJ colors and dust
attenuation for star-forming composites, providing a direct method for
estimating dust content from either (U-V) or (V-J) rest-frame colors for
star-forming galaxies at intermediate redshifts.


title:
Reconstructing Merger Timelines Using Star Cluster Age Distributions:
  the Case of MCG+08-11-002

abstract:
  We present near infrared imaging and integral field spectroscopy of the
centre of the dusty luminous infrared galaxy merger MCG+08-11-002, taken using
the Near InfraRed Camera 2 (NIRC2) and the OH-Suppressing InfraRed Imaging
Spectrograph (OSIRIS) on Keck II. We achieve a spatial resolution of ~25 pc in
the K band, allowing us to resolve 41 star clusters in the NIRC2 images. We
calculate the ages of 22/25 star clusters within the OSIRIS field using the
equivalent widths of the CO 2.3$\mu$m absorption feature and the Br$\gamma$
nebular emission line. The star cluster age distribution has a clear peak at
ages < 20 Myr, indicative of current starburst activity associated with the
final coalescence of the progenitor galaxies. There is a possible second peak
at ~65 Myr which may be a product of the previous close passage of the galaxy
nuclei. We fit single and double starburst models to the star cluster age
distribution and use Monte Carlo sampling combined with two-sided K-S tests to
calculate the probability that the observed data are drawn from each of the
best fit distributions. There is a >90 per cent chance that the data are drawn
from either a single or double starburst star formation history, but stochastic
sampling prevents us from distinguishing between the two scenarios. Our
analysis of MCG+08-11-002 indicates that star cluster age distributions provide
valuable insights into the timelines of galaxy interactions and may therefore
play an important role in the future development of precise merger stage
classification systems.


title:
The Metal Abundances across Cosmic Time ($\mathcal{MACT}$) Survey. II.
  Evolution of the Mass-Metallicity Relation over 8 Billion Years, using
  [OIII]$\lambda$4363\AA-based Metallicities

abstract:
  We present the first results from MMT and Keck spectroscopy for a large
sample of $0.1\leq z\leq1$ emission-line galaxies selected from our narrow-band
imaging in the Subaru Deep Field. We measured the weak [OIII]$\lambda$4363
emission line for 164 galaxies (66 with at least 3$\sigma$ detections, and 98
with significant upper limits). The strength of this line is set by the
electron temperature for the ionized gas. Because the gas temperature is
regulated by the metal content, the gas-phase oxygen abundance is inversely
correlated with [OIII]$\lambda$4363 line strength. Our temperature-based
metallicity study is the first to span $\approx$8 Gyr of cosmic time and
$\approx$3 dex in stellar mass for low-mass galaxies, $\log{\left(M_{\rm
star}/M_{\rm sun}\right)}\approx6.0-9.0$. Using extensive multi-wavelength
photometry, we measure the evolution of the stellar mass--gas metallicity
relation and its dependence on dust-corrected star formation rate (SFR). The
latter is obtained from high signal-to-noise Balmer emission-line measurements.
Our mass-metallicity relation is consistent with Andrews & Martini at
$z\leq0.3$, and evolves toward lower abundances at a given stellar mass,
$\log{({\rm O/H})}\propto(1+z)^{-2.32^{+0.52}_{-0.26}}$. We find that galaxies
with lower metallicities have higher SFRs at a given stellar mass and redshift,
although the scatter is large ($\approx$0.3 dex), and the trend is weaker than
seen in local studies. We also compare our mass--metallicity relation against
predictions from high-resolution galaxy formation simulations, and find good
agreement with models that adopt energy- and momentum-driven stellar feedback.
We have identified 16 extremely metal-poor galaxies with abundances less than a
tenth of solar; our most metal-poor galaxy at $z\approx0.84$ is similar to I Zw
18.


title:
Hierarchical Galaxy Growth and Scatter in the Stellar Mass - Halo Mass
  Relation

abstract:
  The relation between galaxies and dark matter halos reflects the combined
effects of many distinct physical processes. Observations indicate that the
$z=0$ stellar mass-halo mass (SMHM) relation has remarkably small scatter in
stellar mass at fixed halo mass ($\lesssim$ 0.2 dex) with little dependence on
halo mass. We investigate the origins of this scatter by combining N-body
simulations with observational constraints on the SMHM relation. We find that
at the group and cluster scale ($M_{\rm vir}>10^{14}{M_\odot}$) the scatter due
purely to hierarchical assembly is $\approx0.16$ dex, which is comparable to
recent direct observational estimates. At lower masses, mass buildup since
$z\approx2$ is driven largely by in-situ growth. We include a model for the
in-situ buildup of stellar mass and find that an intrinsic scatter in this
growth channel of $0.2$ dex produces a relation between scatter and halo mass
that is consistent with observations from $10^{12}{M_\odot}<M_{\rm
vir}<10^{14.75}{M_\odot}$. The approximately constant scatter across a wide
range of halo masses at $z=0$ thus appears to be a coincidence as it is
determined largely by in-situ growth at low masses and by hierarchical assembly
at high masses. These results indicate that the scatter in the SMHM relation
can provide unique insight into the regularity of the galaxy formation process.


title:
The dust scattering component of X-ray extinction: Effects on continuum
  fitting and high-resolution absorption edge structure

abstract:
  Small angle scattering by dust grains causes a significant contribution to
the total interstellar extinction for any X-ray instrument with sub-arcminute
resolution (Chandra, Swift, XMM-Newton). However, the dust scattering component
is not included in the current absorption models: phabs, tbabs, and tbnew. We
simulate a large number of Chandra spectra to explore the bias in the spectral
fit and NH measurements obtained without including extinction from dust
scattering. We find that without incorporating dust scattering, the measured NH
will be too large by a baseline level of 25%. This effect is modulated by the
imaging resolution of the telescope, because some amount of unresolved
scattered light will be captured within the aperture used to extract point
source information. In high resolution spectroscopy, dust scattering
significantly enhances the total extinction optical depth and the shape of the
photoelectric absorption edges. We focus in particular on the Fe-L edge at 0.7
keV, showing that the total extinction template fits well to the high
resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9,
XTE J1817-330, and Cyg X-1. In cases where dust is intrinsic to the source, a
covering factor based on the angular extent of the dusty material must be
applied to the extinction curve, regardless of angular imaging resolution. This
approach will be particularly relevant for dust in quasar absorption line
systems and might constrain clump sizes in active galactic nuclei.


title: Three-point Functions in Duality-Invariant Higher-Derivative Gravity

abstract:
  Doubled $\alpha'$-geometry is the simplest higher-derivative gravitational
theory with exact global duality symmetry. We use the double metric formulation
of this theory to compute on-shell three-point functions to all orders in
$\alpha'$. A simple pattern emerges when comparing with the analogous bosonic
and heterotic three-point functions. As in these theories, the amplitudes
factorize. The theory has no Gauss-Bonnet term, but contains a Riemann-cubed
interaction to second order in $\alpha'$.


title: A direct approach to quantum tunneling

abstract:
  The decay rates of quasistable states in quantum field theories are usually
calculated using instanton methods. Standard derivations of these methods rely
in a crucial way upon deformations and analytic continuations of the physical
potential, and on the saddle point approximation. While the resulting procedure
can be checked against other semi-classical approaches in some one-dimensional
cases, it is challenging to trace the role of the relevant physical scales, and
any intuitive handle on the precision of the approximations involved are at
best obscure. In this paper, we use a physical definition of the tunneling
probability to derive a formula for the decay rate in both quantum mechanics
and quantum field theory directly from the Minkowski path integral, without
reference to unphysical deformations of the potential. There are numerous
benefits to this approach, from non-perturbative applications to precision
calculations and aesthetic simplicity.


title:
Winning Arguments: Interaction Dynamics and Persuasion Strategies in
  Good-faith Online Discussions

abstract:
  Changing someone's opinion is arguably one of the most important challenges
of social interaction. The underlying process proves difficult to study: it is
hard to know how someone's opinions are formed and whether and how someone's
views shift. Fortunately, ChangeMyView, an active community on Reddit, provides
a platform where users present their own opinions and reasoning, invite others
to contest them, and acknowledge when the ensuing discussions change their
original views. In this work, we study these interactions to understand the
mechanisms behind persuasion.
  We find that persuasive arguments are characterized by interesting patterns
of interaction dynamics, such as participant entry-order and degree of
back-and-forth exchange. Furthermore, by comparing similar counterarguments to
the same opinion, we show that language factors play an essential role. In
particular, the interplay between the language of the opinion holder and that
of the counterargument provides highly predictive cues of persuasiveness.
Finally, since even in this favorable setting people may not be persuaded, we
investigate the problem of determining whether someone's opinion is susceptible
to being changed at all. For this more difficult task, we show that stylistic
choices in how the opinion is expressed carry predictive power.


title: RR Lyrae stars in the Gaia era

abstract:
  Gaia, the European Space Agency spacecraft successfully launched on 19
December 2013, entered into nominal science operations on 18 July 2014 after a
few months of commissioning, and has been scanning the sky to a faint limit of
G = 20.7 mag since then. Gaia is expected to observe more than a hundred
thousand RR Lyrae stars in the Galactic halo and bulge (most of which will be
new discoveries), and to provide parallax measurements with about 10 {\mu}as
uncertainty for those brighter than <V>$\sim$ 12-13 mag. Status and activities
of the spacecraft since launch are briefly reviewed with emphasis on
preliminary results obtained for RR Lyrae stars observed in the Large
Magellanic Cloud during the first 28 days of science operations spent in
Ecliptic Pole scanning mode and in light of the first Gaia data release which
is scheduled for summer 2016.


title:
The SLUGGS Survey: globular clusters and the dark matter content of
  early-type galaxies

abstract:
  A strong correlation exists between the total mass of a globular cluster (GC)
system and the virial halo mass of the host galaxy. However, the total halo
mass in this correlation is a statistical measure conducted on spatial scales
that are some ten times that of a typical GC system. Here we investigate the
connection between GC systems and galaxy's dark matter on comparable spatial
scales, using dynamical masses measured on a galaxy-by-galaxy basis. Our sample
consists of 17 well-studied massive (stellar mass $\sim$10$^{11}$ M$_{\odot}$)
early-type galaxies from the SLUGGS survey. We find the strongest correlation
to be that of the blue (metal-poor) GC subpopulation and the dark matter
content. This correlation implies that the dark matter mass of a galaxy can be
estimated to within a factor of two from careful imaging of its GC system. The
ratio of the GC system mass to that of the enclosed dark matter is nearly
constant. We also find a strong correlation between the fraction of blue GCs
and the fraction of enclosed dark matter, so that a typical galaxy with a blue
GC fraction of 60 per cent has a dark matter fraction of 86 per cent over
similar spatial scales. Both halo growth and removal (via tidal stripping) may
play some role in shaping this trend. In the context of the two-phase model for
galaxy formation, we find galaxies with the highest fractions of accreted stars
to have higher dark matter fractions for a given fraction of blue GCs.


title: Dynamic stratification in drying films of colloidal mixtures

abstract:
  In simulations and experiments, we study the drying of films containing
mixtures of large and small colloidal particles in water. During drying, the
mixture stratifies into a layer of the larger particles at the bottom with a
layer of the smaller particles on top. We developed a model to show that a
gradient in osmotic pressure, which develops dynamically during drying, is
responsible for the segregation mechanism behind stratification.


title: Do Cascades Recur?

abstract:
  Cascades of information-sharing are a primary mechanism by which content
reaches its audience on social media, and an active line of research has
studied how such cascades, which form as content is reshared from person to
person, develop and subside. In this paper, we perform a large-scale analysis
of cascades on Facebook over significantly longer time scales, and find that a
more complex picture emerges, in which many large cascades recur, exhibiting
multiple bursts of popularity with periods of quiescence in between. We
characterize recurrence by measuring the time elapsed between bursts, their
overlap and proximity in the social network, and the diversity in the
demographics of individuals participating in each peak. We discover that
content virality, as revealed by its initial popularity, is a main driver of
recurrence, with the availability of multiple copies of that content helping to
spark new bursts. Still, beyond a certain popularity of content, the rate of
recurrence drops as cascades start exhausting the population of interested
individuals. We reproduce these observed patterns in a simple model of content
recurrence simulated on a real social network. Using only characteristics of a
cascade's initial burst, we demonstrate strong performance in predicting
whether it will recur in the future.


title:
Emergence of spontaneous symmetry breaking in dissipative lattice
  systems

abstract:
  A cornerstone of the theory of phase transitions is the observation that
many-body systems exhibiting a spontaneous symmetry breaking in the
thermodynamic limit generally show extensive fluctuations of an order parameter
in large but finite systems. In this work, we introduce the dynamical analogue
of such a theory. Specifically, we consider local dissipative dynamics
preparing a steady-state of quantum spins on a lattice exhibiting a discrete or
continuous symmetry but with extensive fluctuations in a local order parameter.
We show that for all such processes satisfying detailed balance, there exist
metastable symmetry-breaking states, i.e., states that become stationary in the
thermodynamic limit and give a finite value to the order parameter. We give
results both for discrete and continuous symmetries and explicitly show how to
construct the symmetry-breaking states. Our results show in a simple way that,
in large systems, local dissipative dynamics satisfying detailed balance cannot
uniquely and efficiently prepare states with extensive fluctuations with
respect to local operators. We discuss the implications of our results for
quantum simulators and dissipative state preparation.

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


title:
On the existence of shadow prices for optimal investment with random
  endowment

abstract:
  In this paper, we consider a num\'eraire-based utility maximization problem
under constant proportional transaction costs and random endowment. Assuming
that the agent cannot short sell assets and is endowed with a strictly positive
contingent claim, a primal optimizer of this utility maximization problem
exists. Moreover, we observe that the original market with transaction costs
can be replaced by a frictionless shadow market that yields the same
optimality. On the other hand, we present an example to show that in some case
when these constraints are relaxed, the existence of shadow prices is still
warranted.


title: Inclusive jet spectrum for small-radius jets

abstract:
  Following on our earlier work on leading-logarithmic (LLR) resummations for
the properties of jets with a small radius, R, we here examine the
phenomenological considerations for the inclusive jet spectrum. We discuss how
to match the NLO predictions with small-R resummation. As part of the study we
propose a new, physically-inspired prescription for fixed-order predictions and
their uncertainties. We investigate the R-dependent part of the
next-to-next-to-leading order (NNLO) corrections, which is found to be
substantial, and comment on the implications for scale choices in inclusive jet
calculations. We also examine hadronisation corrections, identifying potential
limitations of earlier analytical work with regards to their $p_t$-dependence.
Finally we assemble these different elements in order to compare matched
(N)NLO+LLR predictions to data from ALICE and ATLAS, finding improved
consistency for the R-dependence of the results relative to NLO predictions.


title: Speckle statistics of entangled photons

abstract:
  We consider the propagation of several entangled photons through an
elastically scattering medium and study statistical properties of their speckle
patterns. We find the spatial correlations of multiphoton speckles and their
sensitivity to changes of system parameters. Our analysis covers both the
directed-wave regime, where rays propagate almost ballistically while
experiencing small-angle diffusion, and the real-space diffusive regime. We
demonstrate that long-range correlations of the speckle patterns dominate
experimental signatures for large-aperture photon detectors. We also show that
speckle sensitivity depends strongly on the number of photons $N$ in the
incoming beam, increasing as $\sqrt{N}$ in the directed-wave regime and as $N$
in the diffusive regime.


title:
The formation and evolution of reconnection-driven slow-mode shocks in a
  partially ionised plasma

abstract:
  The role of slow-mode MHD shocks in magnetic reconnection is one of great
importance for energy conversion and transport, but in many astrophysical
plasmas the plasma is not fully ionised. In this paper, we investigate, using
numerical simulations, the role of collisional coupling between a
proton-electron charge-neutral fluid and a neutral hydrogen fluid for the 1D
Riemann problem initiated in a constant pressure and density background state
by a discontinuity in the magnetic field. This system, in the MHD limit, is
characterised by two waves: a fast-mode rarefaction wave that drives a flow
towards a slow-mode MHD shock. The system evolves through four stage:
initiation, weak coupling, intermediate coupling and a quasi steady state. The
initial stages are characterised by an over-pressured neutral region that
expands with characteristics of a blast wave. In the later stages, the system
tends towards a self-similar solution where the main drift velocity is
concentrated in the thin region of the shock front. Due to the nature of the
system, the neutral fluid is overpressured by the shock when compared to a
purely hydrodynamic shock which results in the neutral fluid expanding to form
the shock precursor. The thickness of the shockfront once it has formed
proportional to the ionisation fraction to the power -1.2, which is a smaller
exponent than would be naively expected from simple scaling arguments. One
interesting result is that the shock front is a continuous transition of the
physical variables for sub-sonic velocity upstream of the shock front (a
c-shock) to a sharp jump in the physical variables followed by a relaxation to
the downstream values for supersonic upstream velocity (a j-shock). The
frictional heating that results from the velocity drift across the shock front
can amount to approximately two per cent of the reference magnetic energy.


title: Non-Zhang-Rice singlet character of the first ionization state of T-CuO

abstract:
  We argue that tetragonal CuO (T-CuO) has the potential to finally settle
long-standing modelling issues for cuprate physics. We compare the one-hole
quasiparticle (qp) dispersion of T-CuO to that of cuprates, in the framework of
the strongly-correlated ($U_{dd}\rightarrow \infty$) limit of the three-band
Emery model. Unlike in CuO$_2$, magnetic frustration in T-CuO breaks the $C_4$
rotational symmetry and leads to strong deviations from the Zhang-Rice singlet
picture in parts of the reciprocal space. Our results are consistent with
angle-resolved photoemission spectroscopy data but in sharp contradiction to
those of a one-band model previously suggested for them. These differences
identify T-CuO as an ideal material to test a variety of scenarios proposed for
explaining cuprate phenomenology.


title: Ruling out the light WIMP explanation of the galactic 511 keV line

abstract:
  Over the past few decades, an anomalous 511 keV gamma-ray line has been
observed from the centre of the Milky Way. Dark matter (DM) in the form of
light weakly interacting massive particles (WIMPs) annihilating into
electron-positron pairs has been one of the leading hypotheses of the observed
emission. Given the small required cross section, a further coupling to lighter
particles is required to produce the correct relic density. Here, we derive
constraints from the Planck satellite on light WIMPs that were in equilibrium
with either the neutrino or electron sector in the early universe. For the
neutrino sector, we obtain a lower bound on the WIMP mass of 4 MeV for a real
scalar and 10 MeV for a Dirac fermion DM particle, at 95% CL. For the electron
sector, we find even stronger bounds of 7 and 11 MeV, respectively. Using these
results, we show that, in the absence of additional ingredients such as dark
radiation, the light thermally produced WIMP explanation of the 511 keV excess
is strongly disfavoured by the latest cosmological data. This suggests an
unknown astrophysical or more exotic DM source of the signal.


title: Automated Pipelines for Spectroscopic Analysis

abstract:
  The Gaia mission will have a profound impact on our understanding of the
structure and dynamics of the Milky Way. Gaia is providing an exhaustive census
of stellar parallaxes, proper motions, positions, colors and radial velocities,
but also leaves some flaring holes in an otherwise complete data set. The
radial velocities measured with the on-board high-resolution spectrograph will
only reach some 10% of the full sample of stars with astrometry and photometry
from the mission, and detailed chemical information will be obtained for less
than 1%. Teams all over the world are organizing large-scale projects to
provide complementary radial velocities and chemistry, since this can now be
done very efficiently from the ground thanks to large and mid-size telescopes
with a wide field-of-view and multi-object spectrographs. As a result,
automated data processing is taking an ever increasing relevance, and the
concept is applying to many more areas, from targeting to analysis. In this
paper, I provide a quick overview of recent, ongoing, and upcoming
spectroscopic surveys, and the strategies adopted in their automated analysis
pipelines.


title: Efficient Index for Weighted Sequences

abstract:
  The problem of finding factors of a text string which are identical or
similar to a given pattern string is a central problem in computer science. A
generalised version of this problem consists in implementing an index over the
text to support efficient on-line pattern queries. We study this problem in the
case where the text is weighted: for every position of the text and every
letter of the alphabet a probability of occurrence of this letter at this
position is given. Sequences of this type, also called position weight
matrices, are commonly used to represent imprecise or uncertain data. A
weighted sequence may represent many different strings, each with probability
of occurrence equal to the product of probabilities of its letters at
subsequent positions. Given a probability threshold $1/z$, we say that a
pattern string $P$ matches a weighted text at position $i$ if the product of
probabilities of the letters of $P$ at positions $i,\ldots,i+|P|-1$ in the text
is at least $1/z$. In this article, we present an $O(nz)$-time construction of
an $O(nz)$-sized index that can answer pattern matching queries in a weighted
text in optimal time improving upon the state of the art by a factor of $z \log
z$. Other applications of this data structure include an $O(nz)$-time
construction of the weighted prefix table and an $O(nz)$-time computation of
all covers of a weighted sequence, which improve upon the state of the art by
the same factor.


abstract:
  A complete classification is established of Minkowski valuations on lattice
polytopes that intertwine the special linear group over the integers and are
translation invariant. In the contravariant case, the only such valuations are
multiples of projection bodies. In the equivariant case, the only such
valuations are generalized difference bodies combined with multiples of the
newly defined discrete Steiner point.


title:
Dynamics of condensate formation in stochastic transport with
  pair-factorized steady states: Nucleation and coarsening time scales

abstract:
  Driven diffusive systems such as the zero-range process (ZRP) and the
pair-factorized steady states (PFSS) stochastic transport process are versatile
tools that lend themselves to the study of transport phenomena on a generic
level. While their mathematical structure is simple enough to allow significant
analytical treatment, they offer a variety of interesting phenomena. With
appropriate dynamics, the ZRP and PFSS models feature a condensation transition
where for a supercritical density the translational symmetry breaks
spontaneously and excess particles form a single-site or spatially extended
condensate, respectively. In this paper we numerically study the typical time
scales of the two stages of this condensation process: Nucleation and
coarsening. Nucleation is the first stage of condensation where the bulk system
relaxes to its stationary distribution and droplet nuclei form in the system.
These droplets then gradually grow or evaporate in the coarsening regime to
finally coalesce in a single condensate when the system finally relaxes to the
stationary state.
  We use the ZRP condensation model to discuss the choice of the estimation
method for the nucleation time scale and present scaling exponents for the ZRP
and PFSS condensation models with respect to the choice of the typical droplet
mass. We then proceed to present scaling exponents in the coarsening regime of
the ZRP for partial-asymmetric dynamics and the PFSS model for symmetric and
asymmetric dynamics.


title:
Anisotropic flow of charged particles in Pb-Pb collisions at
  $\sqrt{s_{\rm NN}}=5.02$ TeV

abstract:
  We report the first results of elliptic ($v_2$), triangular ($v_3$) and
quadrangular flow ($v_4$) of charged particles in Pb-Pb collisions at
$\sqrt{s_{\rm NN}}=5.02$ TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurements are performed in the central pseudorapidity region
$|\eta|<0.8$ and for the transverse momentum range $0.2<p_{\rm T}<5$ GeV/$c$.
The anisotropic flow is measured using two-particle correlations with a
pseudorapidity gap greater than one unit and with the multi-particle cumulant
method. Compared to results from Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$
TeV, the anisotropic flow coefficients $v_{2}$, $v_{3}$ and $v_{4}$ are found
to increase by ($3.0\pm0.6$)%, ($4.3\pm1.4$)% and ($10.2\pm3.8$)%,
respectively, in the centrality range 0-50%. This increase can be attributed
mostly to an increase of the average transverse momentum between the two
energies. The measurements are found to be compatible with hydrodynamic model
calculations. This comparison provides a unique opportunity to test the
validity of the hydrodynamic picture and the power to further discriminate
between various possibilities for the temperature dependence of shear viscosity
to entropy density ratio of the produced matter in heavy-ion collisions at the
highest energies.


title:
On the Nystr\"om and Column-Sampling Methods for the Approximate
  Principal Components Analysis of Large Data Sets

abstract:
  In this paper we analyze approximate methods for undertaking a principal
components analysis (PCA) on large data sets. PCA is a classical dimension
reduction method that involves the projection of the data onto the subspace
spanned by the leading eigenvectors of the covariance matrix. This projection
can be used either for exploratory purposes or as an input for further
analysis, e.g. regression. If the data have billions of entries or more, the
computational and storage requirements for saving and manipulating the design
matrix in fast memory is prohibitive. Recently, the Nystr\"om and
column-sampling methods have appeared in the numerical linear algebra community
for the randomized approximation of the singular value decomposition of large
matrices. However, their utility for statistical applications remains unclear.
We compare these approximations theoretically by bounding the distance between
the induced subspaces and the desired, but computationally infeasible, PCA
subspace. Additionally we show empirically, through simulations and a real data
example involving a corpus of emails, the trade-off of approximation accuracy
and computational complexity.


title: Solar and Stellar Photospheric Abundances

abstract:
  The determination of photospheric abundances in late-type stars from
spectroscopic observations is a well-established field, built on solid
theoretical foundations. Improving those foundations to refine the accuracy of
the inferred abundances has proven challenging, but progress has been made. In
parallel, developments on instrumentation, chiefly regarding multi-object
spectroscopy, have been spectacular, and a number of projects are collecting
large numbers of observations for stars across the Milky Way and nearby
galaxies, promising important advances in our understanding of galaxy formation
and evolution. After providing a brief description of the basic physics and
input data involved in the analysis of stellar spectra, a review is made of the
analysis steps, and the available tools to cope with large observational
efforts. The paper closes with a quick overview of relevant ongoing and planned
spectroscopic surveys, and highlights of recent research on photospheric
abundances.


title:
Size-induced depression of first-order transition lines and entropy-jump
  in extremely-layered nanocrystalline vortex matter

abstract:
  We detect the persistence of the solidification and order-disorder
first-order transition lines in the phase diagram of nanocrystalline
Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ vortex matter down to a system size of less
than hundred vortices. The temperature-location of the vortex solidification
transition line is not altered by decreasing the sample size although there is
a depletion of the entropy-jump at the transition with respect to macroscopic
vortex matter. The solid order-disorder phase transition field moves upward on
decreasing the system size due to the increase of the surface-to-volume ratio
of vortices entailing a decrease on the average vortex binding energy.


title:
Simultaneous spectroscopic and photometric analysis of galaxies with
  STARLIGHT: CALIFA $+$ GALEX

abstract:
  We present an extended version of the spectral synthesis code STARLIGHT
designed to incorporate both $\lambda$-by-$\lambda$ spectra and photometric
fluxes in the estimation of stellar population properties of galaxies. The code
is tested with simulations and data for 260 galaxies culled from the CALIFA
survey, spatially matching the 3700--7000 \AA\ optical datacubes to GALEX near
and far UV images. The sample spans E--Sd galaxies with masses from $10^9$ to
$10^{12} M_\odot$ and stellar populations all the way from star-forming to old,
passive systems. Comparing results derived from purely optical fits with those
which also consider the NUV and FUV data we find that: (1) The new code is
capable of matching the input UV data within the errors while keeping the
quality of the optical fit essentially unchanged. (2) Despite being unreliable
predictors of the UV fluxes, purely optical fits yield stellar population
properties which agree well with those obtained in optical+UV fits for nearly
90% of our sample. (3) The addition of UV constraints has little impact on
properties such as stellar mass and dust optical depth. Mean stellar ages and
metallicities also remain nearly the same for most galaxies, the exception
being low-mass, late-type galaxies, which become older and less enriched due to
rearrangements of their youngest populations. (4) The revised ages are better
correlated with observables such as the 4000 \AA\ break index, and the $NUV -
r$ and $u - r$ colours, an empirical indication that the addition of UV
constraints helps mitigating the effects of age-metallicity-extinction
degeneracies.


title:
Non accelerated efficient numerical methods for sparse quadratic
  optimization problems and its generalizations

abstract:
  We investigate primal gradient method with l1-norm and conditional gradient
method (both methods are non accelerated). We show that these methods can
outperform well known accelerated approaches for some classes of sparse
quadratic problems. Moreover we discuss some generalizations.


title:
Fitting a 3D Morphable Model to Edges: A Comparison Between Hard and
  Soft Correspondences

abstract:
  We propose a fully automatic method for fitting a 3D morphable model to
single face images in arbitrary pose and lighting. Our approach relies on
geometric features (edges and landmarks) and, inspired by the iterated closest
point algorithm, is based on computing hard correspondences between model
vertices and edge pixels. We demonstrate that this is superior to previous work
that uses soft correspondences to form an edge-derived cost surface that is
minimised by nonlinear optimisation.


title: A Combinatorial Approach to the Symmetry of $q,t$-Catalan Numbers

abstract:
  The \emph{$q,t$-Catalan numbers} $C_n(q,t)$ are polynomials in $q$ and $t$
that reduce to the ordinary Catalan numbers when $q=t=1$. These polynomials
have important connections to representation theory, algebraic geometry, and
symmetric functions. Haglund and Haiman discovered combinatorial formulas for
$C_n(q,t)$ as weighted sums of Dyck paths (or equivalently, integer partitions
contained in a staircase shape). This paper undertakes a combinatorial
investigation of the joint symmetry property $C_n(q,t)=C_n(t,q)$. We conjecture
some structural decompositions of Dyck objects into "mutually opposite"
subcollections that lead to a bijective explanation of joint symmetry in
certain cases. A key new idea is the construction of infinite chains of
partitions that are independent of $n$ but induce the joint symmetry for all
$n$ simultaneously. Using these methods, we prove combinatorially that for
$0\leq k\leq 9$ and all $n$, the terms in $C_n(q,t)$ of total degree
$\binom{n}{2}-k$ have the required symmetry property.


title: QP-structures of degree 3 and CLWX 2-algebroids

abstract:
  In this paper, we give the notion of a CLWX 2-algebroid and show that a
QP-structure of degree 3 gives rise to a CLWX 2-algebroid. This is the higher
analogue of the result that a QP-structure of degree 2 gives rise to a Courant
algebroid. A CLWX 2-algebroid can also be viewed as a categorified Courant
algebroid. We show that one can obtain a Lie 3-algebra from a CLWX 2-algebroid.
Furthermore, CLWX 2-algebroids are constructed from split Lie 2-algebroids and
split Lie 2-bialgebroids.


title:
Max Consensus in Sensor Networks: Non-linear Bounded Transmission and
  Additive Noise

abstract:
  A distributed consensus algorithm for estimating the maximum value of the
initial measurements in a sensor network with communication noise is proposed.
In the absence of communication noise, max estimation can be done by updating
the state value with the largest received measurements in every iteration at
each sensor. In the presence of communication noise, however, the maximum
estimate will incorrectly drift and the estimate at each sensor will diverge.
As a result, a soft-max approximation together with a non-linear consensus
algorithm is introduced herein. A design parameter controls the trade-off
between the soft-max error and convergence speed. An analysis of this trade-off
gives a guideline towards how to choose the design parameter for the max
estimate. We also show that if some prior knowledge of the initial measurements
is available, the consensus process can converge faster by using an optimal
step size in the iterative algorithm. A shifted non-linear bounded transmit
function is also introduced for faster convergence when sensor nodes have some
prior knowledge of the initial measurements. Simulation results corroborating
the theory are also provided.


title: Twisted cohomology pairings of knots I; diagrammatic computation

abstract:
  We provide a diagrammatic computation for the bilinear form, which is defined
as the pairing between the (relative) cup products with every local
coefficients and every integral homology 2-class of every links in the
3-sphere. As a corollary, we construct bilinear forms on the twisted Alexander
modules of links.


title:
GraphPrints: Towards a Graph Analytic Method for Network Anomaly
  Detection

abstract:
  This paper introduces a novel graph-analytic approach for detecting anomalies
in network flow data called GraphPrints. Building on foundational
network-mining techniques, our method represents time slices of traffic as a
graph, then counts graphlets -- small induced subgraphs that describe local
topology. By performing outlier detection on the sequence of graphlet counts,
anomalous intervals of traffic are identified, and furthermore, individual IPs
experiencing abnormal behavior are singled-out. Initial testing of GraphPrints
is performed on real network data with an implanted anomaly. Evaluation shows
false positive rates bounded by 2.84% at the time-interval level, and 0.05% at
the IP-level with 100% true positive rates at both.


title: Twisted cohomology pairings of knots II; to classical invariants

abstract:
  We show that bilinear cup products with local coefficients of closed
3-manifolds recover some twisted pairings of infinite covers and the
Casson-Gordon local signatures. As a result, we further give diagrammatic
computations of the pairings and signatures.


title: Interactive algorithms: from pool to stream

abstract:
  We consider interactive algorithms in the pool-based setting, and in the
stream-based setting. Interactive algorithms observe suggested elements
(representing actions or queries), and interactively select some of them and
receive responses. Pool-based algorithms can select elements at any order,
while stream-based algorithms observe elements in sequence, and can only select
elements immediately after observing them. We assume that the suggested
elements are generated independently from some source distribution, and ask
what is the stream size required for emulating a pool algorithm with a given
pool size. We provide algorithms and matching lower bounds for general pool
algorithms, and for utility-based pool algorithms. We further show that a
maximal gap between the two settings exists also in the special case of active
learning for binary classification.


title: On sums of triangular numbers

abstract:
  We study decompositions of natural numbers into triangular summands. For
instance, we prove that any natural number can be represented as a sum of four
triangular numbers, two of them having even indices and the other two having
odd indices. This settles a conjecture by Zhi-Wei Sun (arXiv:1503.03743v8).


title:
Magnetic Field Tunable Capacitive Dielectric:Ionic-liquid Sandwich
  Composites

abstract:
  We examined the tunability of the capacitance for GaFeO3-ionic liquid-GaFeO3
composite material by external magnetic and electric field. Up to 1.6 folds of
capacitance tunability could be achieved at 957kHz with voltage 4v and magnetic
field 0.02T applied. We show that the capacitance enhancement is due to the
polarization coupling between dielectric layer and ionic liquid layer.


title: Why Super-Quantum, Non-Signaling Correlations Cannot Exist

abstract:
  The idea that non-local correlations stronger than quantum correlations
between two no-signaling systems could theoretically exist is based on an
incorrect statistical interpretation of the no-signaling condition. This
article shows that any physically realizable no-signaling box involving local
incompatible observables indeed requires to be described in a non-commutative,
quantum-like language of operators -which leads to the derivation of the
Tsirelson bound and then contradicts this idea.


title:
Coexistence of magneto-resistance and -capacitance tunability in
  Sm2Ga2Fe2O9

abstract:
  We propose that charge gradient resulting in the coexisting
magneto-resistance and-capacitance tunability in material systems. We have
experimentally observed coexisting of tunable magneto-resistance and
-capacitance in Sm2Ga2Fe2O9. Our model fits well with the experimental result.


title: A Dual Embedding Space Model for Document Ranking

abstract:
  A fundamental goal of search engines is to identify, given a query, documents
that have relevant text. This is intrinsically difficult because the query and
the document may use different vocabulary, or the document may contain query
words without being relevant. We investigate neural word embeddings as a source
of evidence in document ranking. We train a word2vec embedding model on a large
unlabelled query corpus, but in contrast to how the model is commonly used, we
retain both the input and the output projections, allowing us to leverage both
the embedding spaces to derive richer distributional relationships. During
ranking we map the query words into the input space and the document words into
the output space, and compute a query-document relevance score by aggregating
the cosine similarities across all the query-document word pairs.
  We postulate that the proposed Dual Embedding Space Model (DESM) captures
evidence on whether a document is about a query term in addition to what is
modelled by traditional term-frequency based approaches. Our experiments show
that the DESM can re-rank top documents returned by a commercial Web search
engine, like Bing, better than a term-matching based signal like TF-IDF.
However, when ranking a larger set of candidate documents, we find the
embeddings-based approach is prone to false positives, retrieving documents
that are only loosely related to the query. We demonstrate that this problem
can be solved effectively by ranking based on a linear mixture of the DESM and
the word counting features.


title: A Rn-220 source for the calibration of low-background experiments

abstract:
  We characterize two 40 kBq sources of electrodeposited Th-228 for use in
low-background experiments. The sources efficiently emanate Rn-220, a noble gas
that can diffuse in a detector volume. Rn-220 and its daughter isotopes produce
alpha, beta, and gamma-radiation, which may used to calibrate a variety of
detector responses and features, before decaying completely in only a few days.
We perform various tests to place limits on the release of other long-lived
isotopes. In particular, we find an emanation of <0.008 atoms/min/kBq (90% CL)
for Th-228 and 1.53 atoms/min/kBq for Ra-224. The sources lend themselves in
particular to the calibration of detectors employing liquid noble elements such
as argon and xenon. With the source mounted in a noble gas system, we
demonstrate that filters are highly efficient in reducing the activity of these
longer-lived isotopes further. We thus confirm the suitability of these sources
even for use in next-generation experiments, such as XENON1T/XENONnT, LZ, and
nEXO.


title: Throughput Analysis of Massive MIMO Uplink with Low-Resolution ADCs

abstract:
  We investigate the uplink throughput achievable by a multiple-user (MU)
massive multiple-input multiple-output (MIMO) system in which the base station
is equipped with a large number of low-resolution analog-to-digital converters
(ADCs). Our focus is on the case where neither the transmitter nor the receiver
have any a priori channel state information. This implies that the fading
realizations have to be learned through pilot transmission followed by channel
estimation at the receiver, based on coarsely quantized observations. We
propose a novel channel estimator, based on Bussgang's decomposition, and a
novel approximation to the rate achievable with finite-resolution ADCs, both
for the case of finite-cardinality constellations and of Gaussian inputs, that
is accurate for a broad range of system parameters. Through numerical results,
we illustrate that, for the 1-bit quantized case, pilot-based channel
estimation together with maximal-ratio combing or zero-forcing detection
enables reliable multi-user communication with high-order constellations in
spite of the severe nonlinearity introduced by the ADCs. Furthermore, we show
that the rate achievable in the infinite-resolution (no quantization) case can
be approached using ADCs with only a few bits of resolution. We finally
investigate the robustness of low-ADC-resolution MU-MIMO uplink against receive
power imbalances between the different users, caused for example by imperfect
power control.


title:
On the Maximum Entropy of a Sum with Constraints and Channel Capacity
  Applications

abstract:
  We study the maximum achievable differential entropy at the output of a
system assigning to each input X the sum X+N, with N a given noise with
probability law absolutely continuous with respect to the Lebesgue measure and
where the input and the noise are allowed to be dependent. We consider fairly
general average cost constraints in the input, as well as amplitude
constraints. It is shown that the corresponding search for the optimum may be
performed over joint distributions for the input and the noise concentrated in
lower dimensional geometrical objects represented by graphs of sufficiently
regular functions in the associated noise-input plane. The results are then
applied to correspondingly characterize the independent input and noise case,
so providing bounds for channel capacity. Analysis of achievable bounds and
associated capacity-achieving input distributions is also provided. General
conditions for the existence of a maximum achievable entropy at the output are
provided for such a system, as well as for the independent input and noise
case, so establishing conditions for capacity to be achievable. The laws of
such capacity-achieving input distributions are also uniquely specified. A
general approximation to capacity scheme is also provided, showing that in the
not achievable case the corresponding noise can be written as the limit of a
sequence of noise random variables with associated channels being capacity
achievable, and whose capacities converge to the capacity of the original
channel. The relationship between our results for this input and noise
dependent setting and the notion of feedback capacity are also explored.


title: Quantum dust collapse in 2+1 dimensions

abstract:
  In this paper we will examine the consequence of a canonical theory of
quantum dust collapse in 2+1 dimensions. The solution of the WDW equation
describing the collapse indicates that collapsing shells outside the apparent
horizon are accompanied by outgoing shells within the apparent horizon during
their collapse phase and stop collapsing once they reach the apparent horizon.
Taking this picture of quantum collapse seriously, we determine a static
solution with energy density corresponding to a dust ball whose collapse has
terminated at the apparent horizon. We show that the boundary radius of the
ball is larger than the BTZ radius confirming that no event horizon is formed.
The ball is sustained by radial pressure which we determine and which we
attribute to the Unruh radiation within it.


title: On expansions of the real field by complex subgroups

abstract:
  We construct a class of finite rank multiplicative subgroups of the complex
numbers such that the expansion of the real field by such a group is
model-theoretically well-behaved. As an application we show that a
classification of expansions of the real field by cyclic multiplicative
subgroups of the complex numbers due to Hieronymi does not even extend to
expansions by subgroups with two generators.


title: Decompositions of the higher order polars of plane branches

abstract:
  \noindent In \cite{Casas} Casas-Alvero found decompositions of higher order
polars of an irreducible plane curve generalizing the results of Merle. We
improve his result giving a finer decomposition where we determine the
topological type and the number of a kind of branches that we call {\em
threshold semi-roots}.


title:
The Effects of Lyman-Limit Systems on the Evolution and Observability of
  the Epoch of Reionization

abstract:
  We present the first large-scale, full radiative transfer simulations of the
reionization of the intergalactic medium in the presence of Lyman-limit systems
(LLSs). To illustrate the impact of LLS opacity, possibly missed by previous
simulations, we add either a uniform or spatially-varying hydrogen bound-free
opacity. This opacity, implemented as the mean free path (mfp) of the ionizing
photons, extrapolates the observed, post-reionization redshift dependence into
the epoch of reionization. In qualitative agreement with previous studies, we
find that at late times the presence of LLSs slows down the ionization fronts,
and alters the size distribution of H II regions. We quantitatively
characterize the size distribution and morphological evolution of H II regions
and examine the effects of the LLSs on the redshifted 21-cm signal from the
patchy reionization. The presence of LLSs extends the ionization history by
$\Delta z \sim 0.8$. The LLS absorbers significantly impede the late-time
growth of the H II regions. The position dependent LLS distribution slows
reionization further and additionally limits the late growth of the ionized
regions. However, there is no "freeze out" of the H II regions and the largest
regions grow to the size of the simulation volume. The 21-cm power spectra show
that at large scales the power drops by a factor of 2 for 50% and 75%
ionization stages (at $k = 0.1$ $\text{h} \, \text{Mpc}^{-1} $) reflecting the
limiting effect of the LLSs on the growth of ionized patches. The statistical
observables such as the RMS of the brightness temperature fluctuations and the
peak amplitudes of the 21-cm power spectra at large-scales ($k = 0.05 - 0.1$
$\text{h} \, \text{Mpc}^{-1} $) are diminished by the presence of LLS.


title: Spin-adapted Matrix Product States and Operators

abstract:
  Matrix product states (MPSs) and matrix product operators (MPOs) allow an
alternative formulation of the density matrix renormalization group algorithm
introduced by White. Here, we describe how non-abelian spin symmetry can be
exploited in MPSs and MPOs by virtue of the Wigner--Eckart theorem at the
example of the spin-adapted quantum chemical Hamiltonian operator.


title: Symplectic meanders

abstract:
  Analogous to the sl(n) case, we address the computation of the index of
seaweed subalgebras of sp(2n) by introducing graphical representations called
symplectic meanders. Formulas for the algebra's index may be computed by
counting the connected components of its associated meander. In certain cases,
formulas for the index can be given in terms of elementary functions.


title: Entanglement negativity, Holography and Black holes

abstract:
  We investigate the application of our recent holographic entanglement
negativity conjecture for higher dimensional conformal field theories to
specific examples which serve as crucial consistency checks. In this context we
compute the holographic entanglement negativity for bipartite pure and finite
temperature mixed state configurations in $d$-dimensional conformal field
theories dual to bulk pure $AdS_{d+1}$ geometry and $AdS_{d+1}$-Schwarzschild
black holes respectively. It is observed that the holographic entanglement
negativity characterizes the distillable entanglement for the finite
temperature mixed states through the elimination of the thermal contributions.
Significantly our examples correctly reproduce universal features of the
entanglement negativity for corresponding two dimensional conformal field
theories, in higher dimensions.


title: Eta Carinae's Thermal X-ray Tail Measured with XMM-Newton and NuSTAR

abstract:
  The evolved, massive highly eccentric binary system, eta Carinae, underwent a
periastron passage in the summer of 2014. We obtained two coordinated X-ray
observations with XMM-Newton and NuSTAR during the elevated X-ray flux state
and just before the X-ray minimum flux state around this passage. These NuSTAR
observations clearly detected X-ray emission associated with eta Car extending
up to ~50 keV for the first time. The NuSTAR spectrum above 10 keV can be fit
with the bremsstrahlung tail from a kT ~6 keV plasma. This temperature is Delta
kT ~2 keV higher than those measured from the iron K emission line complex, if
the shocked gas is in collisional ionization equilibrium. This result may
suggest that the companion star's pre-shock wind velocity is underestimated.
The NuSTAR observation near the X-ray minimum state showed a gradual decline in
the X-ray emission by 40% at energies above 5 keV in a day, the largest rate of
change of the X-ray flux yet observed in individual eta Car observations. The
column density to the hardest emission component, NH ~1e24 cm-2, marked one of
the highest values ever observed for eta Car, strongly suggesting increased
obscuration of the wind-wind colliding X-ray emission by the thick primary
stellar wind prior to superior conjunction. Neither observation detected the
power-law component in the extremely hard band that INTEGRAL and Suzaku
observed prior to 2011. If the non-detection by NuSTAR is caused by absorption,
the power-law source must be small and located very near the WWC apex.
Alternatively, it may be that the power-law source is not related to either eta
Car or the GeV gamma-ray source.


title: Secure Index Coding: Existence and Construction

abstract:
  We investigate the construction of weakly-secure index codes for a sender to
send messages to multiple receivers with side information in the presence of an
eavesdropper. We derive a sufficient and necessary condition for the existence
of index codes that are secure against an eavesdropper with access to any
subset of messages of cardinality $t$, for any fixed $t$. In contrast to the
benefits of using random keys in secure network coding, we prove that random
keys do not promote security in three classes of index-coding instances.