title: Technology Beats Algorithms (in Exact String Matching)

abstract:
  More than 120 algorithms have been developed for exact string matching within
the last 40 years. We show by experiments that the \naive{} algorithm
exploiting SIMD instructions of modern CPUs (with symbols compared in a special
order) is the fastest one for patterns of length up to about 50 symbols and
extremely good for longer patterns and small alphabets. The algorithm compares
16 or 32 characters in parallel by applying SSE2 or AVX2 instructions,
respectively. Moreover, it uses loop peeling to further speed up the searching
phase. We tried several orders for comparisons of pattern symbols and the
increasing order of their probabilities in the text was the best.


title:
Eldan's Stochastic Localization and the KLS Conjecture: Isoperimetry,
  Concentration and Mixing

abstract:
  We show that the Cheeger constant for $n$-dimensional isotropic logconcave
measures is $O(n^{1/4})$, improving on the previous best bound of
$O(n^{1/3}\sqrt{\log n}).$ As corollaries we obtain the same improved bound on
the thin-shell estimate, Poincar\'{e} constant and Lipschitz concentration
constant and an alternative proof of this bound for the isotropic (slicing)
constant; it also follows that the ball walk for sampling from an isotropic
logconcave density in ${\bf R}^{n}$ converges in $O^{*}(n^{2.5})$ steps from a
warm start. The proof is based on gradually transforming any logconcave density
to one that has a significant Gaussian factor via a Martingale process.
  Extending this proof technique, we prove that the log-Sobolev constant of any
isotropic logconcave density in ${\bf R}^{n}$ with support of diameter $D$ is
$\Omega(1/D)$, resolving a question posed by Frieze and Kannan in 1997. This is
asymptotically the best possible estimate and improves on the previous bound of
$\Omega(1/D^{2})$ by Kannan-Lov\'{a}sz-Montenegro. It follows that for any
isotropic logconcave density, the ball walk with step size
$\delta=\Theta(1/\sqrt{n})$ mixes in $O\left(n^{2}D\right)$ proper steps from
\emph{any }starting point. This improves on the previous best bound of
$O(n^{2}D^{2})$ and is also asymptotically tight.
  The new bound leads to the following large deviation inequality for an
$L$-Lipschitz function $g$ over an isotropic logconcave density $p$: for any
$t>0$, \[ Pr_{x\sim p}\left(\left|g(x)-\bar{g}\right|\geq L\cdot
t\right)\leq\exp(-\frac{c\cdot t^{2}}{t+\sqrt{n}}) \] where $\bar{g}$ is the
median or mean of $g$ for $x\sim p$; this generalizes and improves on previous
bounds by Paouris and by Guedon-Milman. The technique also bounds the ``small
ball'' probability in terms of the Cheeger constant, and recovers the current
best bound.


title: Estimating Linear and Quadratic forms via Indirect Observations

abstract:
  In this paper, we further develop the approach, originating in [14
(arXiv:1311.6765),20 (arXiv:1604.02576)], to "computation-friendly" hypothesis
testing and statistical estimation via Convex Programming. Specifically, we
focus on estimating a linear or quadratic form of an unknown "signal," known to
belong to a given convex compact set, via noisy indirect observations of the
signal. Most of the existing theoretical results on the subject deal with
precisely stated statistical models and aim at designing statistical inferences
and quantifying their performance in a closed analytic form. In contrast to
this descriptive (and highly instructive) traditional framework, the approach
we promote here can be qualified as operational -- the estimation routines and
their risks are yielded by an efficient computation. All we know in advance is
that under favorable circumstances to be specified below, the risk of the
resulting estimate, whether high or low, is provably near-optimal under the
circumstances. As a compensation for the lack of "explanatory power," this
approach is applicable to a much wider family of observation schemes than those
where "closed form descriptive analysis" is possible.
  The paper is a follow-up to our paper [20 (arXiv:1604.02576)] dealing with
hypothesis testing, in what follows, we apply the machinery developed in this
reference to estimating linear and quadratic forms.


title: Regularity and chaos in cavity QED

abstract:
  The interaction of a quantized electromagnetic field in a cavity with a set
of two-level atoms inside can be described with algebraic Hamiltonians of
increasing complexity, from the Rabi to the Dicke models. Their algebraic
character allows, through the use of coherente states, a semiclassical
description in phase space, where the non-integrable Dicke model has regions
associated with regular and chaotic motion. The appearance of classical chaos
can be quantified calculating the largest Lyapunov exponent in the whole
available phase space for a given energy. In the quantum regime, employing
efficient diagonalization techniques, we are able to perform a detailed
quantitative study of the regular and chaotic regions, where the quantum
Participation Ratio (PR) of coherent states on the eigenenergy basis plays a
role equivalent to the Lyapunov exponent. It is noted that, in the
thermodynamic limit, dividing the Participation Ratio by the number of atoms
leads to a positive value in chaotic regions, while it tends to zero in the
regular ones.


title:
The Effects of Data Quality on the Analysis of Corporate Board Interlock
  Networks

abstract:
  Nowadays, social networks of ever increasing size are studied by researchers
from a range of disciplines. The data underlying these networks is often
automatically gathered from API's, websites or existing databases. As a result,
the quality of this data is typically not manually validated, and the resulting
networks may be based on false, biased or incomplete data. In this paper, we
investigate the effect of data quality issues on the analysis of large
networks. We focus on the global board interlock network, in which nodes
represent firms across the globe, and edges model social ties between firms --
shared board members holding a position at both firms. First, we demonstrate
how we can automatically assess the completeness of a large dataset of 160
million firms, in which data is missing not at random. Second, we present a
novel method to increase the accuracy of the entries in our data. By comparing
the expected and empirical characteristics of the resulting network topology,
we develop a technique that automatically prunes and merges duplicate nodes and
edges. Third, we use a case study of the board interlock network of Sweden to
show how poor quality data results in incorrect network topologies, biased
centrality values and abnormal influence spread under a well-known diffusion
model. Finally, we demonstrate how our data quality assessment methods help
restore the correct network structure, ultimately allowing us to derive
meaningful and correct results from analyzing the network.


title:
HellRank: A Hellinger-based Centrality Measure for Bipartite Social
  Networks

abstract:
  Measuring centrality in a social network, especially in bipartite mode, poses
several challenges such as requirement of full knowledge of the network
topology and lack of properly detection of top-k behavioral representative
users. In this paper, to overcome the aforementioned challenging issues, we
propose an accurate centrality measure, called HellRank, to identify central
nodes in bipartite social networks. HellRank is based on the Hellinger distance
between two nodes on the same side of a bipartite network. We theoretically
analyze the impact of the Hellinger distance on a bipartite network and find an
upper and lower bounds for this distance. The computation of HellRank
centrality measure can be distributed by letting each node uses only local
information on its immediate neighbors and therefore do not need a central
entity to have full knowledge of the network topological structure. We
experimentally evaluate performance of the HellRank measure in correlation with
other centrality measures on real-world networks. The results show partial
ranking similarity between the HellRank and the other conventional metrics
according to the Kendall and Spearman rank correlation coefficient.


title:
Collective nonaffine displacements in amorphous materials during
  large-amplitude oscillatory shear

abstract:
  Using molecular dynamics simulations, we study the transient response of a
binary Lennard-Jones glass subjected to periodic shear deformation. The
amorphous solid is modelled as the three-dimensional Kob-Andersen binary
mixture at a low temperature. The cyclic loading is applied to slowly annealed,
quiescent samples, which induces irreversible particle rearrangements at large
strain amplitudes, leading to stress-strain hysteresis and a drift of the
potential energy towards higher values. We find that the initial response to
cyclic shear near the critical strain amplitude involves disconnected clusters
of atoms with large nonaffine displacements. In contrast, the amplitude of
shear stress oscillations decreases after a certain number of cycles, which is
accompanied by the initiation and subsequent growth of a shear band.

categories: cond-mat.soft cond-mat.dis-nn cond-mat.mes-hall cond-mat.mtrl-sci


title: Essential obstacles to Helly circular-arc graphs

abstract:
  A Helly circular-arc graph is the intersection graph of a set of arcs on a
circle having the Helly property. We introduce essential obstacles, which are a
refinement of the notion of obstacles, and prove that essential obstacles are
precisely the minimal forbidden induced circular-arc subgraphs for the class of
Helly circular-arc graphs. We show that it is possible to find in linear time,
in any given obstacle, some minimal forbidden induced subgraph for the class of
Helly circular-arc graphs contained as an induced subgraph. Moreover, relying
on an existing linear-time algorithm for finding induced obstacles in
circular-arc graphs, we conclude that it is possible to find in linear time an
induced essential obstacle in any circular-arc graph that is not a Helly
circular-arc graph. The problem of finding a forbidden induced subgraph
characterization, not restricted only to circular-arc graphs, for the class of
Helly circular-arc graphs remains unresolved. As a partial answer to this
problem, we find the minimal forbidden induced subgraph characterization for
the class of Helly circular-arc graphs restricted to graphs containing no
induced claw and no induced 5-wheel. Furthermore, we show that there is a
linear-time algorithm for finding, in any given graph that is not a Helly
circular-arc graph, an induced subgraph isomorphic to claw, 5-wheel, or some
minimal forbidden induced subgraph for the class of Helly circular-arc graphs.


title: A Randomized Concurrent Algorithm for Disjoint Set Union

abstract:
  The disjoint set union problem is a basic problem in data structures with a
wide variety of applications. We extend a known efficient sequential algorithm
for this problem to obtain a simple and efficient concurrent wait-free
algorithm running on an asynchronous parallel random access machine (APRAM).
Crucial to our result is the use of randomization. Under a certain independence
assumption, for a problem instance in which there are n elements, m operations,
and p processes, our algorithm does Theta(m (alpha(n, m/(np)) + log(np/m + 1)))
expected work, where the expectation is over the random choices made by the
algorithm and alpha is a functional inverse of Ackermann's function. In
addition, each operation takes O(log n) steps with high probability. Our
algorithm is significantly simpler and more efficient than previous algorithms
proposed by Anderson and Woll. Under our independence assumption, our algorithm
achieves almost-linear speed-up for applications in which all or most of the
processes can be kept busy.


title: Kimura-finiteness of quadric fibrations over smooth curves

abstract:
  In this short note, making use of the recent theory of noncommutative mixed
motives, we prove that the Voevodsky's mixed motive of a quadric fibration over
a smooth curve is Kimura-finite.


title:
Scaling properties of soft matter in equilibrium and under stationary
  flow

abstract:
  A brief review is presented of the scaling of complex fluids, polymers and
polyelectrolytes in solution and in confined geometry, in thermodynamical,
structural and rheology properties using equilibrium and nonequilibrium
dissipative particle dynamics simulations. All simulations were carried out on
high performance computational facilities using parallelized algorithms, solved
on computers using both central and graphical processing units. The scaling
approach is shown to be a unifying axis around which general trends and basic
knowledge can be gained, illustrated through a series of case studies.


title:
Search for photons with energies above 10$^{18}$ eV using the hybrid
  detector of the Pierre Auger Observatory

abstract:
  A search for ultra-high energy photons with energies above 1 EeV is performed
using nine years of data collected by the Pierre Auger Observatory in hybrid
operation mode. An unprecedented separation power between photon and hadron
primaries is achieved by combining measurements of the longitudinal air-shower
development with the particle content at ground measured by the fluorescence
and surface detectors, respectively. Only three photon candidates at energies 1
- 2 EeV are found, which is compatible with the expected hadron-induced
background. Upper limits on the integral flux of ultra-high energy photons of
0.038, 0.010, 0.009, 0.008 and 0.007 km$^{-2}$ sr$^{-1}$ yr$^{-1}$ are derived
at 95% C.L. for energy thresholds of 1, 2, 3, 5 and 10 EeV. These limits bound
the fractions of photons in the all-particle integral flux below 0.14%, 0.17%,
0.42%, 0.86% and 2.9%. For the first time the photon fraction at EeV energies
is constrained at the sub-percent level. The improved limits are below the flux
of diffuse photons predicted by some astrophysical scenarios for cosmogenic
photon production. The new results rule-out the early top-down models $-$ in
which ultra-high energy cosmic rays are produced by, e.g., the decay of
super-massive particles $-$ and challenge the most recent super-heavy dark
matter models.


title: Probe knots and Hopf insulators with ultracold atoms

abstract:
  Knots and links are fascinating and intricate topological objects. Their
influence spans from DNA and molecular chemistry to vortices in superfluid
helium, defects in liquid crystals and cosmic strings in the early universe.
Here, we find that knotted structures also exist in a peculiar class of
three-dimensional topological insulators---the Hopf insulators. In particular,
we demonstrate that the momentum-space spin textures of Hopf insulators are
twisted in a nontrivial way, which implies the presence of various knot and
link structures. We further illustrate that the knots and nontrivial spin
textures can be probed via standard time-of-flight images in cold atoms as
preimage contours of spin orientations in stereographic coordinates. The
extracted Hopf invariants, knots, and links are validated to be robust to
typical experimental imperfections. Our work establishes the existence of
knotted structures in Hopf insulators, which may have potential applications in
spintronics and quantum information processing.

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


title: Certain geometric structure of $\Lambda$-sequence spaces

abstract:
  The $\Lambda$-sequence spaces $\Lambda_p$ for $1< p\leq\infty$ and its
generalization $\Lambda_{\hat{p}}$ for $1<\hat{p}<\infty$, $\hat{p}=(p_n)$ is
introduced. The James constants and strong $n$-th James constants of
$\Lambda_p$ for $1<p\leq\infty$ is determined. It is proved that generalized
$\Lambda$-sequence space $\Lambda_{\hat{p}}$ is embedded isometrically in the
Nakano sequence space $l_{\hat{p}}(\mathbb{R}^{n+1})$ of finite dimensional
Euclidean space $\mathbb{R}^{n+1}$. Hence it follows that sequence spaces
$\Lambda_p$ and $\Lambda_{\hat{p}}$ possesses the uniform Opial property,
property $(\beta)$ of Rolewicz and weak uniform normal structure. Moreover, it
is established that $\Lambda_{\hat{p}}$ possesses the coordinate wise uniform
Kadec-Klee property. Further necessary and sufficient conditions for element
$x\in S(\Lambda_{\hat{p}})$ to be an extreme point of $B(\Lambda_{\hat{p}})$
are derived. Finally, estimation of von Neumann-Jordan and James constants of
two dimensional $\Lambda$-sequence space $\Lambda_2^{(2)}$ is being carried
out.


title:
Change point detection in autoregressive models with no moment
  assumptions

abstract:
  In this paper we consider the problem of detecting a change in the parameters
of an autoregressive process, where the moments of the innovation process do
not necessarily exist. An empirical likelihood ratio test for the existence of
a change point is proposed and its asymptotic properties are studied. In
contrast to other work on change point tests using empirical likelihood, we do
not assume knowledge of the location of the change point. In particular, we
prove that the maximizer of the empirical likelihood is a consistent estimator
for the parameters of the autoregressive model in the case of no change point
and derive the limiting distribution of the corresponding test statistic under
the null hypothesis. We also establish consistency of the new test. A nice
feature of the method consists in the fact that the resulting test is
asymptotically distribution free and does not require an estimate of the long
run variance. The asymptotic properties of the test are investigated by means
of a small simulation study, which demonstrates good finite sample properties
of the proposed method.


title: The Hong Kong/AAO/Strasbourg Halpha (HASH) Planetary Nebula Database

abstract:
  The Hong Kong/AAO/Strasbourg Halpha (HASH) planetary nebula database is an
online research platform providing free and easy access to the largest and most
comprehensive catalogue of known Galactic planetary nebulae (PNe) and a
repository of observational data (imaging and spectroscopy) for these and
related astronomical objects. The main motivation for creating this system is
resolving some of long standing problems in the field e.g. problems with mimics
and dubious and/or misidentifications, errors in observational data and
consolidation of the widely scattered data-sets. This facility allows
researchers quick and easy access to the archived and new observational data
and creating and sharing of non-redundant PN samples and catalogues.


title:
Increasing blackhole feedback induced quenching with anisotropic thermal
  conduction

abstract:
  Feedback from central supermassive blackholes is often invoked to explain the
low star formation rates in massive galaxies at the centers of galaxy clusters.
However, the detailed physics of the coupling of the injected feedback energy
with the intracluster medium is still unclear. Using high-resolution
magnetohydrodynamic cosmological simulations of galaxy cluster formation, we
investigate the role of anisotropic thermal conduction in shaping the
thermodynamic structure of clusters, and, in particular, in modifying the
impact of black hole feedback. Stratified anisotropically conducting plasmas
are formally always unstable, and thus more prone to mixing, an expectation
borne out by our results. The increased mixing efficiently isotropizes the
injected feedback energy which in turn significantly improves the coupling
between the feedback energy and the intracluster medium. This facilitates an
earlier disruption of the cool core, reduces the star formation rate by more
than an order of magnitude, and results in earlier quenching despite an overall
lower amount of feedback energy injected into the cluster core. With
conduction, the metallicity gradients and dispersions are lowered, aligning
them better with observational constraints. These results highlight the
important role of thermal conduction in establishing and maintaining quiescence
of massive galaxies.


title:
SDSS-IV MaNGA: environmental dependence of stellar age and metallicity
  gradients in nearby galaxies

abstract:
  We present a study on the stellar age and metallicity distributions for 1105
galaxies using the STARLIGHT software on MaNGA integral field spectra. We
derive age and metallicity gradients by fitting straight lines to the radial
profiles, and explore their correlations with total stellar mass M*, NUV-r
colour and environments, as identified by both the large scale structure (LSS)
type and the local density. We find that the mean age and metallicity gradients
are close to zero but slightly negative, which is consistent with the
inside-out formation scenario. Within our sample, we find that both the age and
metallicity gradients show weak or no correlation with either the LSS type or
local density environment. In addition, we also study the environmental
dependence of age and metallicity values at the effective radii. The age and
metallicity values are highly correlated with M* and NUV-r and are also
dependent on LSS type as well as local density. Low-mass galaxies tend to be
younger and have lower metallicity in low-density environments while high-mass
galaxies are less affected by environment.


title:
On the likelihood of detecting gravitational waves from Population III
  compact object binaries

abstract:
  We study the contribution of binary black hole (BH-BH) mergers from the
first, metal-free stars in the Universe (Pop III) to gravitational wave
detection rates. Our study combines initial conditions for the formation of Pop
III stars based on N-body simulations of binary formation (including rates,
binary fraction, initial mass function, orbital separation and eccentricity
distributions) with an updated model of stellar evolution specific for Pop III
stars. We find that the merger rate of these Pop III BH-BH systems is
relatively small (< 0.1 Gpc^-3 yr^-1) at low redshifts (z<2), where it can be
compared with the LIGO empirical estimate of 9-240 Gpc^-3 yr^-1 (Abbott et al.
2016). The predicted rates are even smaller for Pop III double neutron star and
black hole neutron star mergers. Our rates are compatible with those of Hartwig
et al. (2016), but significantly smaller than those found in previous work
(Bond & Carr 1984; Belczynski et al. 2004; Kinugawa et al. 2014, 2016). We
explain the reasons for this discrepancy by means of detailed model comparisons
and point out that (i) identification of Pop III BH-BH mergers may not be
possible by advanced LIGO, and (ii) the level of stochastic gravitational wave
background from Pop III mergers may be lower than recently estimated (Kowalska
et al. 2012; Inayoshi et al. 2016; Dvorkin et al. 2016). We further estimate
gravitational wave detection rates for third-generation interferometric
detectors. Our calculations are relevant for low to moderately rotating Pop III
stars. We can now exclude significant (> 1 per cent) contribution of these
stars to low-redshift BH-BH mergers. However, it remains to be tested whether
(and at what level) rapidly spinning Pop III stars (homogeneous evolution) can
contribute to BH-BH mergers in the local Universe.


title: Light Axial Vectors, Nuclear Transitions, and the $^8$Be Anomaly

abstract:
  New hidden particles could potentially be emitted and discovered in rare
nuclear transitions. In this work we investigate the production of hidden
vector bosons with primarily axial couplings to light quarks in nuclear
transitions, and we apply our results to the recent anomaly seen in $^8$Be
decays. The relevant matrix elements for $^8{\rm Be}^*(1^+) \rightarrow ^8{\rm
Be} (0^+)$ transitions are calculated using ${\it ab \, initio}$ methods with
inter-nucleon forces derived from chiral effective field theory and the
in-medium similarity renormalization group. We find that the emission of a
light axial vector with mass $m_X \simeq 17\, {\rm MeV}$ can account for the
anomaly seen in the $1^+\to 0^+$ isoscalar transition together with the absence
of a significant anomaly in the corresponding isovector transition. We also
show that such an axial vector can be derived from an anomaly-free
ultraviolet-complete theory that is consistent with current experimental data.


title:
Paving the way for the JWST: witnessing globular cluster formation at
  z>3

abstract:
  We report on five compact, extremely young (<10Myr) and blue (\beta_UV<-2.5,
F_\lambda =\lambda^\beta) objects observed with VLT/MUSE at redshift 3.1169,
3.235, in addition to three objects at z=6.145. These sources are magnified by
the Hubble Frontier Field galaxy clusters MACS~J0416 and AS1063. Their
de-lensed half light radii (Re) are between 16 to 140pc, the stellar masses are
~1-20 X 10^6 Msun, the magnitudes are m_uv=28.8 - 31.4 (-17<Muv<-15) and
specific star formation rates can be as large as ~800Gyr^-1. Multiple images of
these systems are widely separated in the sky (up to 50'') and individually
magnified by factors 3-40. Remarkably, the inferred physical properties of two
objects are similar to those expected in some globular cluster formation
scenarios, representing the best candidate proto-globular clusters (proto-GC)
discovered so far. Rest-frame optical high dispersion spectroscopy of one of
them at z=3.1169 yields a velocity dispersion \sigma_v~20km/s, implying a
dynamical mass dominated by the stellar mass. Another object at z=6.145, with
de-lensed Muv ~ -15.3 (m_uv ~ 31.4), shows a stellar mass and a star-formation
rate surface density consistent with the values expected from popular GC
formation scenarios. An additional star-forming region at z=6.145, with
de-lensed m_uv ~ 32, a stellar mass of 0.5 X 10^6 Msun and a star formation
rate of 0.06 Msun/yr is also identified. These objects currently represent the
faintest spectroscopically confirmed star-forming systems at z>3, elusive even
in the deepest blank fields. We discuss how proto-GCs might contribute to the
ionization budget of the universe and augment Lya visibility during
reionization. This work underlines the crucial role of JWST in characterizing
the rest-frame optical and near-infrared properties of such low-luminosity
high-z objects.


title: Matrix multiplication algorithms from group orbits

abstract:
  We show how to construct highly symmetric algorithms for matrix
multiplication. In particular, we consider algorithms which decompose the
matrix multiplication tensor into a sum of rank-1 tensors, where the
decomposition itself consists of orbits under some finite group action. We show
how to use the representation theory of the corresponding group to derive
simple constraints on the decomposition, which we solve by hand for n=2,3,4,5,
recovering Strassen's algorithm (in a particularly symmetric form) and new
algorithms for larger n. While these new algorithms do not improve the known
upper bounds on tensor rank or the matrix multiplication exponent, they are
beautiful in their own right, and we point out modifications of this idea that
could plausibly lead to further improvements. Our constructions also suggest
further patterns that could be mined for new algorithms, including a
tantalizing connection with lattices. In particular, using lattices we give the
most transparent proof to date of Strassen's algorithm; the same proof works
for all n, to yield a decomposition with $n^3 - n + 1$ terms.


title: Gaia's view of the $\lambda$ Boo star puzzle

abstract:
  The evolutionary status of the chemically peculiar class of $\lambda$ Boo
stars has been intensely debated. It is now agreed that the $\lambda$ Boo
phenomenon affects A stars of all ages, from star formation to the terminal age
main sequence, but the cause of the chemical peculiarity is still a puzzle. We
revisit the debate of their ages and temperatures in order to shed light on the
phenomenon, using the new parallaxes in Gaia Data Release 1 with existing
Hipparcos parallaxes and multicolour photometry. We find that no single
formation mechanism is able to explain all the observations, and suggest that
there are multiple channels producing $\lambda$ Boo spectra. The relative
importance of these channels varies with age, temperature and environment.


title: The tangential velocity excess of the Milky Way satellites

abstract:
  We estimate the systemic orbital kinematics of the Milky Way classical
satellites and compare them with predictions from the \Lambda{} cold dark
matter (\Lambda{}CDM) model derived from a semi-analytical galaxy formation
model applied to high resolution cosmological N-body simulations. We find that
the Galactic satellite system is atypical of \Lambda{}CDM systems. The subset
of 10 Galactic satellites with proper motion measurements has a velocity
anisotropy, \beta=-2.2$\pm$0.4, that lies in the 2.9% tail of the \Lambda{}CDM
distribution. Individually, the Milky Way satellites have radial velocities
that are lower than expected for their proper motions, with 9 out of the 10
having at most 20% of their orbital kinetic energy invested in radial motion.
Such extreme values are expected in only 1.5% of \Lambda{}CDM satellites
systems. This tangential motion excess is unrelated to the existence of a
Galactic "disc of satellites". We present theoretical predictions for larger
satellite samples that may become available as more proper motion measurements
are obtained.


title:
Temperature Dependence of the Energy Levels of Methylammonium Lead
  Iodide Perovskite from First Principles

abstract:
  Environmental effects and intrinsic energy-loss processes lead to
fluctuations in the operational temperature of solar cells, which can
profoundly influence their power conversion efficiency. Here we determine from
first principles the effects of temperature on the band gap and band edges of
the hybrid pervoskite CH$_3$NH$_3$PbI$_3$ by accounting for electron-phonon
coupling and thermal expansion. From $290$ to $380$ K, the computed band gap
change of $40$ meV coincides with the experimental change of $30$-$40$ meV. The
calculation of electron-phonon coupling in CH$_3$NH$_3$PbI$_3$ is particularly
intricate, as the commonly used Allen-Heine-Cardona theory overestimates the
band gap change with temperature, and excellent agreement with experiment is
only obtained when including high-order terms in the electron-phonon
interaction. We also find that spin-orbit coupling enhances the electron-phonon
coupling strength, but that the inclusion of nonlocal correlations using hybrid
functionals has little effect. We reach similar conclusions in the metal-halide
perovskite CsPbI$_3$. Our results unambiguously confirm for the first time the
importance of high-order terms in the electron-phonon coupling by direct
comparison with experiment.


title: Splashback Shells of Cold Dark Matter Halos

abstract:
  The density field in the outskirts of dark matter halos is discontinuous due
to a caustic formed by matter at its first apocenter after infall. In this
paper, we present an algorithm to identify the "splashback shell" formed by
these apocenters in individual simulated halos using only a single snapshot of
the density field. We implement this algorithm in the code SHELLFISH (SHELL
Finding In Spheroidal Halos) and demonstrate that the code identifies
splashback shells correctly and measures their properties with an accuracy of
$<5\%$ for halos with more than 50,000 particles and mass accretion rates of
$\Gamma_\textrm{DK14}>0.5$. Using SHELLFISH, we present the first estimates for
several basic properties of individual splashback shells, such as radius,
$R_\textrm{sp}$, mass, and overdensity, and provide fits to the distribution of
these quantities as functions of $\Gamma_\textrm{DK14}$, $\nu_\textrm{200m}$,
and $z.$ We confirm previous findings that $R_\textrm{sp}$ decreases with
increasing $\Gamma_\textrm{DK14}$, but we show that independent of accretion
rate, it also decreases with increasing $\nu_\textrm{200m}$. We also study the
3D structures of these shells and find that they generally have non-ellipsoidal
oval shapes. We find that splashback radii estimated by SHELLFISH are
$20\%-30\%$ larger than those estimated in previous studies from stacked
density profiles at high accretion rates. We demonstrate that the latter are
biased low due to the contribution of high-mass subhalos to these profiles and
show that using the median instead of mean density in each radial bin mitigates
the effect of substructure on density profiles and removes the bias.


title: EXor outbursts from disk amplification of stellar magnetic cycles

abstract:
  EXor outbursts - moderate-amplitude disk accretion events observed in Class I
and Class II protostellar sources - have time scales and amplitudes that are
consistent with the viscous accumulation and release of gas in the inner disk
near the dead zone boundary. We suggest that outbursts are indirectly triggered
by stellar dynamo cycles, via poloidal magnetic flux that diffuses radially
outward through the disk. Interior to the dead zone the strength of the net
field modulates the efficiency of angular momentum transport by the
magnetorotational instability. In the dead zone changes in the polarity of the
net field may lead to stronger outbursts because of the dominant role of the
Hall effect in this region of the disk. At the level of simple estimates we
show that changes to kG-strength stellar fields could stimulate disk outbursts
on 0.1 AU scales, though this optimistic conclusion depends upon the uncertain
efficiency of net flux transport through the inner disk. The model predicts a
close association between observational tracers of stellar magnetic activity
and EXor events.


title:
Estimating the weak-lensing rotation signal in radio cosmic shear
  surveys

abstract:
  Weak lensing has become an increasingly important tool in cosmology and the
use of galaxy shapes to measure cosmic shear has become routine. The
weak-lensing distortion tensor contains two other effects in addition to the
two components of shear: the convergence and rotation. The rotation mode is not
measurable using the standard cosmic shear estimators based on galaxy shapes,
as there is no information on the original shapes of the images before they
were lensed. Due to this, no estimator has been proposed for the rotation mode
in cosmological weak-lensing surveys, and the rotation mode has never been
constrained. Here, we derive an estimator for this quantity, which is based on
the use of radio polarisation measurements of the intrinsic position angles of
galaxies. The rotation mode can be sourced by physics beyond $\Lambda$CDM, and
also offers the chance to perform consistency checks of $\Lambda$CDM and of
weak-lensing surveys themselves. We present simulations of this estimator and
show that, for the pedagogical example of cosmic string spectra, this estimator
could detect a signal that is consistent with the constraints from Planck. We
examine the connection between the rotation mode and the shear $B$-modes and
thus how this estimator could help control systematics in future radio
weak-lensing surveys.


title:
ZFIRE: Similar Stellar Growth in H$\alpha$-emitting Cluster and Field
  Galaxies at z~2

abstract:
  We compare galaxy scaling relations as a function of environment at $z\sim2$
with our ZFIRE survey where we have measured H$\alpha$ fluxes for 90
star-forming galaxies selected from a mass-limited
[$\log(M_{\star}/M_{\odot})>9$] sample based on ZFOURGE. The cluster galaxies
(37) are part of a confirmed system at z=2.095 and the field galaxies (53) are
at $1.9<z<2.4$; all are in the COSMOS legacy field. There is no statistical
difference between H$\alpha$-emitting cluster and field populations when
comparing their star formation rate (SFR), stellar mass ($M_{\star}$), galaxy
size ($r_{eff}$), SFR surface density [$\Sigma$(H$\alpha_{star}$)], and stellar
age distributions. The only difference is that at fixed stellar mass, the
H$\alpha$-emitting cluster galaxies are $\log(r_{eff})\sim0.1$ larger than in
the field. Approximately 19% of the H$\alpha$-emitters in the cluster and 26%
in the field are IR-luminous ($L_{IR}>2\times10^{11} L_{\odot}$). Because the
LIRGs in our combined sample are $\sim5$ times more massive than the low-IR
galaxies, their radii are $\sim70$% larger. To track stellar growth, we
separate galaxies into those that lie above, on, and below the H$\alpha$
star-forming main sequence (SFMS) using $\Delta$SFR$(M_{\star})=\pm0.2$ dex.
Galaxies above the SFMS (starbursts) tend to have higher H$\alpha$ SFR surface
densities and younger light-weighted stellar ages compared to galaxies below
the SFMS. Our results indicate that starbursts (+SFMS) in the cluster and field
at $z\sim2$ are growing their stellar cores. Lastly, we compare to the
(SFR-$M_{\star}$) relation from RHAPSODY cluster simulations and find the
predicted slope is nominally consistent with the observations. However, the
predicted cluster SFRs tend to be too low by a factor of $\sim2$ which seems to
be a common problem for simulations across environment.


title: Strong gravitational lensing in $f\left(\chi\right)=\chi^{3/2}$ gravity

abstract:
  We discuss the phenomenology of gravitational lensing in the purely metric
$f\left(\chi\right)$ gravity, an $f(R)$ gravity where the action of the
gravitational field depends on the source mass. We focus on the strong lensing
regime in galaxy-galaxy lens systems and in clusters of galaxies. Using an
approximate metric solution accurate to second order of the velocity field
$v/c$, we show how, in the $f\left(\chi\right)=\chi^{3/2}$ gravity, the same
light deflection can be produced by point-like lenses with masses smaller than
in General Relativity; this mass difference increases with increasing impact
parameter and decreasing lens mass. However, for sufficiently massive
point-like lenses and small impact parameters, $f\left(\chi\right)=\chi^{3/2}$
and GR yield indistinguishable light deflection angles: this regime occurs both
in observed galaxy-galaxy lens systems and in the central regions of galaxy
clusters. In the former systems, the GR and $f\left(\chi\right)$ masses are
compatible with the mass of standard stellar populations and little or no dark
matter, whereas, on the scales of the core of galaxy clusters, the presence of
substantial dark matter is required both in General Relativity, and in our
approximate $f\left(\chi\right)=\chi^{3/2}$ point-like lens solution. We thus
conclude that our approximate metric solution of
$f\left(\chi\right)=\chi^{3/2}$ is unable to describe the observed
phenomenology of the strong lensing regime without the aid of dark matter.


title: Bootstrapping $\mathcal{N}=3$ superconformal theories

abstract:
  We initiate the bootstrap program for $\mathcal{N}=3$ superconformal field
theories (SCFTs) in four dimensions. The problem is considered from two fronts:
the protected subsector described by a $2d$ chiral algebra, and crossing
symmetry for half-BPS operators whose superconformal primaries parametrize the
Coulomb branch of $\mathcal{N}=3$ theories. With the goal of describing a
protected subsector of a family of $\mathcal{N}=3$ SCFTs, we propose a new $2d$
chiral algebra with super Virasoro symmetry that depends on an arbitrary
parameter, identified with the central charge of the theory. Turning to the
crossing equations, we work out the superconformal block expansion and apply
standard numerical bootstrap techniques in order to constrain the CFT data. We
obtain bounds valid for any theory but also, thanks to input from the chiral
algebra results, we are able to exclude solutions with $\mathcal{N}=4$
supersymmetry, allowing us to zoom in on a specific $\mathcal{N}=3$ SCFT.


title:
B field in OB stars (BOB): The outstandingly strong magnetic field in
  the evolved He-strong star CPD-62 2124

abstract:
  The origin and evolution of magnetism in OB stars is far from being well
understood. With approximately 70 magnetic OB stars known, any new object with
unusual characteristics may turn out to be a key piece of the puzzle. We report
the detection of an exceptionally strong magnetic field in the He-strong B2IV
star CPD-62 2124. Spectropolarimetric FORS2 and HARPSpol observations were
analysed by two independent teams and procedures, concluding on a strong
longitudinal magnetic field of approximately 5.2 kG. The quantitative
characterisation of the stellar atmosphere yields an effective temperature of
23650$\pm$250 K, a surface gravity of 3.95$\pm$0.10 dex and a surface helium
fraction of 0.35$\pm$0.02 by number. The metal composition is in agreement with
the cosmic abundance standard, except for Mg, Si and S, which are slightly
non-solar. The strong and broad ($\sim$300 km/s) disc-like emission displayed
by the H$\alpha$ line suggests a centrifugal magnetosphere supported by the
strong magnetic field. Our results imply that CPD-62 2124 is an early B-type
star hosting one of the strongest magnetic fields discovered to date, and one
of the most evolved He-strong stars known, with a fractional main-sequence
lifetime of approximately 0.6.


title:
Lupus disks with faint CO isotopologues: low gas/dust or large carbon
  depletion?

abstract:
  An era has started in which gas and dust can be observed independently in
protoplanetary disks, thanks to the recent surveys with ALMA. The first
near-complete high-resolution disk survey in both dust and gas in a single
star-forming region has been carried out in Lupus, finding surprisingly low
gas/dust ratios. The goal of this work is to fully exploit CO isotopologues
observations in Lupus, comparing them with physical-chemical model results, in
order to obtain gas masses for a large number of disks. We have employed
physical-chemical models to analyze continuum and CO isotopologues observations
of Lupus disks, including isotope-selective processes and freeze-out. Employing
also the ALMA 13CO-only detections, disk gas masses have been calculated for a
total of 34 sources, expanding the sample of 10 disks studied by Ansdell et al.
(2016), where also C18O was detected. We confirm that overall gas-masses are
very low, often smaller than 1 $M_{\rm J}$, if volatile carbon is not depleted.
Accordingly, global gas/dust ratios predominantly between 1 and 10. Low
CO-based gas masses and gas/dust ratios may indicate rapid loss of gas, or
alternatively chemical evolution, e.g. via sequestering of carbon from CO to
more complex molecules, or carbon locked up in larger bodies. Current ALMA
observations cannot distinguish between these two hypotheses. We have simulated
both scenarios, but chemical model results do not allow us to rule out one of
the two. Assuming that all Lupus disks have evolved mainly due to viscous
processes over the past few Myr, the observed correlation between the current
mass accretion rate and dust mass found by Manara et al. (2016) implies a
constant gas-to-dust ratio, which is close to 100 based on the observed $M_{\rm
disk}/\dot{M}_{\rm acc}$ ratio. This in turn points to a scenario in which
carbon depletion is responsible for the low CO isotopologue line luminosities.


title:
Dark matter substructure cannot explain properties of the Fermi Galactic
  Centre excess

abstract:
  An excess of gamma rays has been identified at the centre of the Milky Way,
and annihilation of dark matter has been posited as a potential source. This
hypothesis faces significant challenges: difficulty characterizing
astrophysical backgrounds, the need for a non-trivial adiabatic contraction of
the inner part of the Milky Way's dark matter halo, and recent observations of
photon clustering, which suggest that the majority of the excess is due to
unresolved point sources. Here we point out that the apparent point-like nature
of the emission rules out the dark matter interpretation of the excess
entirely. Attempting to model the emission with dark matter point sources
either worsens the problem with the inner slope, requires an unrealistically
large minihalo fraction toward the Galactic Centre, or overproduces the
observed emission at higher latitudes.


title: Courant Algebroid Connections and String Effective Actions

abstract:
  Courant algebroids are a natural generalization of quadratic Lie algebras,
appearing in various contexts in mathematical physics. A connection on a
Courant algebroid gives an analogue of a covariant derivative compatible with a
given fiber-wise metric. Imposing further conditions resembling standard
Levi-Civita connections, one obtains a class of connections whose curvature
tensor in certain cases gives a new geometrical description of equations of
motion of low energy effective action of string theory. Two examples are given.
One is the so called symplectic gravity, the second one is an application to
the the so called heterotic reduction. All necessary definitions, propositions
and theorems are given in a detailed and self-contained way.


title: Emergent Weyl nodes and Fermi arcs in a Floquet Weyl semimetal

abstract:
  When a Dirac semimetal is subject to a circularly polarized laser, it is
predicted that the Dirac cone splits into two Weyl nodes and a nonequilibrium
transient state called the Floquet Weyl semimetal is realized. We focus on the
previously unexplored low-frequency regime, where the upper and lower Dirac
bands resonantly couple with each other through multi-photon processes, which
is a realistic situation in solid state ultrafast pump-probe experiments. We
find a series of new Weyl nodes emerging in pairs when the Floquet replica
bands hybridize with each other. The nature of the Floquet Weyl semimetal with
regard to the number, locations, and monopole charges of these Weyl nodes is
highly tunable with the amplitude and frequency of the light. We derive an
effective low energy theory using Brillouin-Wigner expansion and further
regularize the theory on a cubic lattice. The monopole charges obtained from
the low-energy Hamiltonian can be reconciled with the number of Fermi arcs on
the lattice which we find numerically.


title:
Superconductivity and non-Fermi liquid behavior near a nematic quantum
  critical point

abstract:
  Using determinantal quantum Monte Carlo, we compute the properties of a
lattice model with spin $\frac 1 2$ itinerant electrons tuned through a quantum
phase transition to an Ising nematic phase. The nematic fluctuations induce
superconductivity with a broad dome in the superconducting $T_c$ enclosing the
nematic quantum critical point. For temperatures above $T_c$, we see strikingly
non-Fermi liquid behavior, including a "nodal - anti nodal dichotomy"
reminiscent of that seen in several transition metal oxides. In addition, the
critical fluctuations have a strong effect on the low frequency optical
conductivity, resulting in behavior consistent with "bad metal" phenomenology.


title: Towards the Limit of Network Quantization

abstract:
  Network quantization is one of network compression techniques to reduce the
redundancy of deep neural networks. It reduces the number of distinct network
parameter values by quantization in order to save the storage for them. In this
paper, we design network quantization schemes that minimize the performance
loss due to quantization given a compression ratio constraint. We analyze the
quantitative relation of quantization errors to the neural network loss
function and identify that the Hessian-weighted distortion measure is locally
the right objective function for the optimization of network quantization. As a
result, Hessian-weighted k-means clustering is proposed for clustering network
parameters to quantize. When optimal variable-length binary codes, e.g.,
Huffman codes, are employed for further compression, we derive that the network
quantization problem can be related to the entropy-constrained scalar
quantization (ECSQ) problem in information theory and consequently propose two
solutions of ECSQ for network quantization, i.e., uniform quantization and an
iterative solution similar to Lloyd's algorithm. Finally, using the simple
uniform quantization followed by Huffman coding, we show from our experiments
that the compression ratios of 51.25, 22.17 and 40.65 are achievable for LeNet,
32-layer ResNet and AlexNet, respectively.


title: Quasar UV luminosity function evolution up to z=8

abstract:
  We study the redshift evolution of the quasar UV Luminosity Function (LF) for
0.5 < z < 6.5, by collecting the most up to date observational data and, in
particular, the recently discovered population of faint AGNs. We fit the QSO LF
using either a double power-law or a Schechter function, finding that both
forms provide good fits to the data. We derive empirical relations for the LF
parameters as a function of redshift and, based on these results, predict the
quasar UV LF at z=8. From the inferred LF evolution, we compute the redshift
evolution of the QSO/AGN comoving ionizing emissivity and hydrogen
photoionization rate. If faint AGNs are included, the contribution of quasars
to reionization increases substantially. However, their level of contribution
critically depends on the detailed shape of the QSO LF, which can be
constrained by efficient searches of high-z quasars. To this aim, we predict
the expected (i) number of z>6 quasars detectable by ongoing and future NIR
surveys (as EUCLID and WFIRST), and (ii) number counts for a single
radio-recombination line observation with SKA-MID (FoV = 0.49 deg^2) as a
function of the Hnalpha flux density, at 0<z<8. These surveys (even at z<6)
will be fundamental to better constrain the role of quasars as reionization
sources.


title:
SDSS-IV MaNGA: stellar population gradients as a function of galaxy
  environment

abstract:
  We study the internal radial gradients of stellar population properties
within $1.5\;R_{\rm e}$ and analyse the impact of galaxy environment. We use a
representative sample of 721 galaxies with masses ranging between
$10^{9}\;M_{\odot}$ to $10^{11.5}\;M_{\odot}$ from the SDSS-IV survey MaNGA. We
split this sample by morphology into early-type and late-type galaxies. Using
the full spectral fitting code FIREFLY, we derive the light and mass-weighted
stellar population properties age and metallicity, and calculate the gradients
of these properties. We use three independent methods to quantify galaxy
environment, namely the $N^{th}$ nearest neighbour, the tidal strength
parameter $Q$ and distinguish between central and satellite galaxies. In our
analysis, we find that early-type galaxies generally exhibit shallow
light-weighted age gradients in agreement with the literature and mass-weighted
median age gradients tend to be slightly positive. Late-type galaxies, instead,
have negative light-weighted age gradients. We detect negative metallicity
gradients in both early and late-type galaxies that correlate with galaxy mass,
with the gradients being steeper and the correlation with mass being stronger
in late-types. We find, however, that stellar population gradients, for both
morphological classifications, have no significant correlation with galaxy
environment for all three characterisations of environment. Our results suggest
that galaxy mass is the main driver of stellar population gradients in both
early and late-type galaxies, and any environmental dependence, if present at
all, must be very subtle.


title:
SDSS-IV MaNGA: Spatially resolved star formation histories in galaxies
  as a function of galaxy mass and type

abstract:
  We study the internal gradients of stellar population properties within
$1.5\;R_{\rm e}$ for a representative sample of 721 galaxies with stellar
masses ranging between $10^{9}\;M_{\odot}$ to $10^{11.5}\;M_{\odot}$ from the
SDSS-IV MaNGA IFU survey. Through the use of our full spectral fitting code
FIREFLY, we derive light and mass-weighted stellar population properties and
their radial gradients, as well as full star formation and metal enrichment
histories. We also quanfify the impact that different stellar population models
and full spectral fitting routines have on the derived stellar population
properties, and the radial gradient measurements. In our analysis, we find that
age gradients tend to be shallow for both early-type and late-type galaxies.
{\em Mass-weighted} age gradients of early-types are positive ($\sim 0.09\;
{\rm dex}/R_{\rm e}$) pointing to "outside-in" progression of star formation,
while late-type galaxies have negative {\em light-weighted} age gradients
($\sim -0.11\; {\rm dex}/R_{\rm e}$), suggesting an "inside-out" formation of
discs. We detect negative metallicity gradients in both early and late-type
galaxies, but these are significantly steeper in late-types, suggesting that
radial dependence of chemical enrichment processes and the effect of gas inflow
and metal transport are far more pronounced in discs. Metallicity gradients of
both morphological classes correlate with galaxy mass, with negative
metallicity gradients becoming steeper with increasing galaxy mass. The
correlation with mass is stronger for late-type galaxies, with a slope of
$d(\nabla [Z/H])/d(\log M)\sim -0.2\pm 0.05\;$, compared to $d(\nabla
[Z/H])/d(\log M)\sim -0.05\pm 0.05\;$ for early-types. This result suggests
that the merger history plays a relatively small role in shaping metallicity
gradients of galaxies.


title: Transport in Superfluid Mixtures

abstract:
  We present a general method for constructing effective field theories for
non-relativistic superfluids, generalizing the previous approaches of Greiter,
Witten, and Wilczek, and Son and Wingate to the case of several superfluids in
solution. We investigate transport in mixtures with broken parity and find a
parity odd "Hall drag" in the presence of independent motion as well as a
pinning of mass, charge, and energy to sites of nonzero relative velocity. Both
effects have a simple geometric interpretation in terms of the signed volumes
and directed areas of various sub-complexes of a "velocity polyhedron": the
convex hull formed by the endpoints of the velocity vectors of a superfluid
mixture. We also provide a simple quasi-one-dimensional model that exhibits
non-zero Hall drag.


title:
$\mathbb{Z}_3$ parafermionic zero modes without Andreev backscattering
  from the $2/3$ fractional quantum Hall state

abstract:
  Parafermionic zero modes are a novel set of excitations displaying
non-Abelian statistics somewhat richer than that of Majorana modes. These modes
are predicted to occur when nearby fractional quantum Hall edge states are
gapped by an interposed superconductor. Despite substantial experimental
progress, we argue that the necessary crossed Andreev reflection in this
arrangement is a challenging milestone to reach. We propose a superconducting
quantum dot array structure on a fractional quantum Hall edge that can lead to
parafermionic zero modes from coherent superconducting forward scattering on a
quantum Hall edge. Such coherent forward scattering has already been
demonstrated in recent experiments. We show that for a spin-singlet
superconductor interacting with loops of spin unpolarized $2/3$ fractional
quantum edge, even an array size of order ten should allow one to
systematically tune into a parafermionic degeneracy.


title:
Young stellar populations in type II quasars: timing the onset of star
  formation and nuclear activity

abstract:
  Despite the emerging morphological evidence that luminous quasar-like AGN are
triggered in galaxy mergers, the natures of the triggering mergers and the
order of events in the triggering sequence remain uncertain. In this work, we
present a detailed study of the stellar populations of the host galaxies of 21
type II quasars, with the aim of understanding the sequence of events between
the onset of the merger, the triggering of the associated starburst and the
initiation of the quasar activity. To this end, we model high quality, wide
spectral coverage, intermediate resolution optical spectra of the type II
quasars. We find that of the 21 objects, the higher-order Balmer absorption
lines, characteristic of young stellar populations (YSP) , are directly
detected in ~62% of the sample. We also fit these spectra using a number of
combinations of stellar and/or power-law components, representative of viable
formation histories, as well as including the possibility of scattered AGN
light. We find that 90 % of the type II quasar host galaxies require the
inclusion of a YSP to adequately model their spectra, whilst 71 % of the sample
require the inclusion of a YSP with age < 100 Myr. Since the ages of the YSP in
most type II quasar host galaxies are comparable with the expected lifetimes of
the AGN activity, these results provide strong evidence that the quasars are
triggered close to the peaks of the merger-induced starbursts.


title: First Order Galilean Superfluid Dynamics

abstract:
  We study dynamics of (anomalous) Galilean superfluid up to first order in
derivative expansion, both in parity-even and parity-odd sectors. We construct
a relativistic system -- null superfluid, which is a null fluid (introduced in
[arXiv:1509.04718]) with a spontaneously broken global $U(1)$ symmetry. A null
superfluid is in one to one correspondence with Galilean superfluid in one
lower dimension, i.e. they have same symmetries, thermodynamics, constitutive
relations and are related to each other by a mere choice of basis. The
correspondence is based on null reduction, which is known to reduce the
Poincar\'{e} symmetry of a theory to Galilean symmetry in one lower dimension.
To perform this analysis, we use offshell formalism of (super)fluid dynamics,
adopting it appropriately to null (super)fluids.


title: Deep learning in color: towards automated quark/gluon jet discrimination

abstract:
  Artificial intelligence offers the potential to automate challenging
data-processing tasks in collider physics. To establish its prospects, we
explore to what extent deep learning with convolutional neural networks can
discriminate quark and gluon jets better than observables designed by
physicists. Our approach builds upon the paradigm that a jet can be treated as
an image, with intensity given by the local calorimeter deposits. We supplement
this construction by adding color to the images, with red, green and blue
intensities given by the transverse momentum in charged particles, transverse
momentum in neutral particles, and pixel-level charged particle counts.
Overall, the deep networks match or outperform traditional jet variables. We
also find that, while various simulations produce different quark and gluon
jets, the neural networks are surprisingly insensitive to these differences,
similar to traditional observables. This suggests that the networks can extract
robust physical information from imperfect simulations.


title:
Generalized relativistic harmonic oscillator in minimal length quantum
  mechanics

abstract:
  We solve the generalized relativistic harmonic oscillator in 1+1 dimensions
in the presence of a minimal length. Using the momentum space representation,
we explore all the possible signs of the potentials and discuss their
bound-state solutions for fermion and antifermions. Furthermore, we also find
an isolated solution from the Sturm-Liouville scheme. All cases already
analyzed in the literature, are obtained as particular cases.


title: Privacy Patterns

abstract:
  Inspired by the design patterns of object-oriented software architecture, we
offer an initial set of "privacy patterns". Our intent is to describe the most
important ways in which software systems can offer privacy to their
stakeholders. We express our privacy patterns as class diagrams in the UML
(Universal Modelling Language), because this is a commonly-used language for
expressing the high-level architecture of an object-oriented system. In this
initial set of privacy patterns, we sketch how each of Westin's four states of
privacy can be implemented in a software system. In addition to Westin's states
of Solitude, Intimacy, Anonymity, and Reserve, we develop a privacy pattern for
an institutionalised form of Intimacy which we call Confidence.


title: Robustness of Control Barrier Functions for Safety Critical Control

abstract:
  Barrier functions (also called certificates) have been an important tool for
the verification of hybrid systems, and have also played important roles in
optimization and multi-objective control. The extension of a barrier function
to a controlled system results in a control barrier function. This can be
thought of as being analogous to how Sontag extended Lyapunov functions to
control Lyapunov functions in order to enable controller synthesis for
stabilization tasks. A control barrier function enables controller synthesis
for safety requirements specified by forward invariance of a set using a
Lyapunov-like condition. This paper develops several important extensions to
the notion of a control barrier function. The first involves robustness under
perturbations to the vector field defining the system. Input-to-State stability
conditions are given that provide for forward invariance, when disturbances are
present, of a "relaxation" of set rendered invariant without disturbances. A
control barrier function can be combined with a control Lyapunov function in a
quadratic program to achieve a control objective subject to safety guarantees.
The second result of the paper gives conditions for the control law obtained by
solving the quadratic program to be Lipschitz continuous and therefore to gives
rise to well-defined solutions of the resulting closed-loop system.


title:
Generalized entropy theory of glass-formation in fully flexible polymer
  melts

abstract:
  The generalized entropy theory (GET) offers many insights into how molecular
parameters influence polymer glass-formation. Given the fact that chain
rigidity often plays a critical role in understanding the glass-formation of
polymer materials, the GET was originally developed based on models of
semiflexible chains. Consequently, all previous calculations within the GET
considered polymers with some degree of chain rigidity. Motivated by unexpected
results from computer simulations of fully flexible polymer melts concerning
the dependence of thermodynamic and dynamic properties on the cohesive
interaction strength ($\epsilon$), the present paper employs the GET to explore
the influence of $\epsilon$ on glass-formation in models of polymer melts with
a vanishing bending rigidity, i.e., fully flexible polymer melts. In accord
with simulations, the GET for fully flexible polymer melts predicts that basic
dimensionless thermodynamic properties (such as the thermal expansion
coefficient and isothermal compressibility) are universal functions of the
temperature scaled by $\epsilon$ in the regime of low pressures. Similar
scaling behavior is also found for the configurational entropy density in the
GET for fully flexible polymer melts. Moreover, we find that the characteristic
temperatures of glass-formation increase linearly with $\epsilon$ and that the
fragility is independent of $\epsilon$ in fully flexible polymer melts,
predictions that are again consistent with simulations of glass-forming polymer
melts composed of fully flexible chains. Beyond an explanation of these general
trends observed in simulations, the GET for fully flexible polymer melts
predicts the presence of a positive residual configurational entropy at low
temperatures, indicating a return to Arrhenius relaxation in the low
temperature glassy state.


title:
The Evolution of Sentiment Analysis - A Review of Research Topics,
  Venues, and Top Cited Papers

abstract:
  Sentiment analysis is one of the fastest growing research areas in computer
science, making it challenging to keep track of all the activities in the area.
We present a computer-assisted literature review, where we utilize both text
mining and qualitative coding, and analyze 6,996 papers from Scopus. We find
that the roots of sentiment analysis are in the studies on public opinion
analysis at the beginning of 20th century and in the text subjectivity analysis
performed by the computational linguistics community in 1990's. However, the
outbreak of computer-based sentiment analysis only occurred with the
availability of subjective texts on the Web. Consequently, 99% of the papers
have been published after 2004. Sentiment analysis papers are scattered to
multiple publication venues, and the combined number of papers in the top-15
venues only represent ca. 30% of the papers in total. We present the top-20
cited papers from Google Scholar and Scopus and a taxonomy of research topics.
In recent years, sentiment analysis has shifted from analyzing online product
reviews to social media texts from Twitter and Facebook. Many topics beyond
product reviews like stock markets, elections, disasters, medicine, software
engineering and cyberbullying extend the utilization of sentiment analysis


title: Spatial Anisotropy in Nonrelativistic Holography

abstract:
  We examine holographic theories where Lifshitz symmetry is broken with
spatial anisotropy. In particular, we focus on the conditions imposed by the
null energy condition, and demonstrate that it is possible to have unusual
anisotropic fixed points where a subset of the spatial dimensions have negative
scaling exponents. We also construct interpolating solutions between UV and IR
fixed points and show that there is essentially no restriction placed on the
endpoints of the flow once anisotropic scaling is allowed. As an example, we
demonstrate a flow from AdS to AdS with $c_{IR}>c_{UV}$ that is allowed by the
null energy condition since it proceeds through an intermediate
Lorentz-violating region. Finally, we examine the holographic Green's function
in anisotropic Lifshitz spacetimes.


title: Koszul Algebras Defined by Three Relations

abstract:
  This work concerns commutative algebras of the form $R=Q/I$, where $Q$ is a
standard graded polynomial ring and $I$ is a homogenous ideal in $Q$. It has
been proposed that when $R$ is Koszul the $i$th Betti number of $R$ over $Q$ is
at most $\binom gi$, where $g$ is the number of generators of $I$; in
particular, the projective dimension of $R$ over $Q$ is at most $g$. The main
result of this work settles this question, in the affirmative, when $g\le 3$.


title: Missing solution in a relativistic Killingbeck potential

abstract:
  Missing bound-state solutions for fermions in the background of a Killingbeck
radial potential including an external magnetic and Aharonov-Bohm (AB) flux
fields are examined. The correct quadratic form of the Dirac equation with
vector and scalar couplings under the spin and pseudo-spin symmetries is showed
and also we point out a misleading treatment in the literature regarding to
bound-state solutions for this problem.


title:
Prolate rotation and metallicity gradient in the transforming dwarf
  galaxy Phoenix

abstract:
  Transition type dwarf galaxies are thought to be systems undergoing the
process of transformation from a star-forming into a passively evolving dwarf,
which makes them particularly suitable to study evolutionary processes driving
the existence of different dwarf morphological types. Here we present results
from a spectroscopic survey of ~200 individual red giant branch stars in the
Phoenix dwarf, the closest transition type with a comparable luminosity to
"classical" dwarf galaxies. We measure a systemic heliocentric velocity V =
-21.2 km/s. Our survey reveals the clear presence of prolate rotation, which is
aligned with the peculiar spatial distribution of the youngest stars in
Phoenix. We speculate that both features might have arisen from the same event,
possibly an accretion of a smaller system. The evolved stellar population of
Phoenix is relatively metal-poor (<[Fe/H]> = -1.49+/-0.04 dex) and shows a
large metallicity spread ($\sigma_{\rm [Fe/H]} = 0.51\pm0.04$\,dex), with a
pronounced metallicity gradient of -0.13+/-0.01 dex per arcmin similar to
luminous, passive dwarf galaxies. We also report a discovery of an extremely
metal-poor star candidate in Phoenix and discuss the importance of correcting
for spatial sampling when interpreting the chemical properties of galaxies with
metallicity gradients. This study presents a major leap forward in our
knowledge of the internal kinematics of the Phoenix transition type dwarf
galaxy, and the first wide area spectroscopic survey of its metallicity
properties.


title:
Mathematical model of plant-virus interactions mediated by RNA
  interference

abstract:
  Cross-protection, which refers to a process whereby artificially inoculating
a plant with a mild strain provides protection against a more aggressive
isolate of the virus, is known to be an effective tool of disease control in
plants. In this paper we derive and analyse a new mathematical model of the
interactions between two competing viruses with particular account for RNA
interference. Our results show that co-infection of the host can either
increase or decrease the potency of individual infections depending on the
levels of cross-protection or cross-enhancement between different viruses.
Analytical and numerical bifurcation analyses are employed to investigate the
stability of all steady states of the model in order to identify parameter
regions where the system exhibits synergistic or antagonistic behaviour between
viral strains, as well as different types of host recovery. We show that not
only viral attributes but also the propagating component of RNA-interference in
plants can play an important role in determining the dynamics.


title:
Asymptotic blow-up for a class of semilinear wave equations on extremal
  Reissner-Nordstr\"om spacetimes

abstract:
  We prove small data global existence for a class of semilinear wave equations
satisfying the null condition on extremal Reissner-Nordstrom black hole
backgrounds with nonlinear terms that degenerate at the event horizon. We
impose no symmetry assumptions. The study of such equations is motivated by
their covariance properties under the Couch-Torrence conformal isometry. We
show decay, non-decay and asymptotic blow-up results analogous to those in the
linear case.


title: Light-hole Exciton in Nanowire Quantum Dot

abstract:
  Quantum dots inserted inside semiconductor nanowires are extremely promising
candidates as building blocks for solid-state based quantum computation and
communication. They provide very high crystalline and optical properties and
offer a convenient geometry for electrical contacting. Having a complete
determination and full control of their emission properties is one of the key
goals of nanoscience researchers. Here we use strain as a tool to create in a
single magnetic nanowire quantum dot a light-hole exciton, an optically active
quasiparticle formed from a single electron bound to a single light hole. In
this frame, we provide a general description of the mixing within the hole
quadruplet induced by strain or confinement. A multi-instrumental combination
of cathodoluminescence, polarisation-resolved Fourier imaging and
magneto-optical spectroscopy, allow us to fully characterize the hole ground
state, including its valence band mixing with heavy hole states.


title: MIMO Secret Communications Against an Active Eavesdropper

abstract:
  This paper considers a scenario in which an Alice-Bob pair wishes to
communicate in secret in the presence of an active Eve, who is capable of
jamming as well as eavesdropping in Full-Duplex (FD) mode. As countermeasure,
Bob also operates in FD mode, using a subset of its antennas to act as
receiver, and the remaining antennas to act as jammer and transmit noise. With
a goal to maximize the achievable secrecy degrees of freedom (S.D.o.F.) of the
system, we provide the optimal transmit/receive antennas allocation at Bob,
based on which we determine in closed form the maximum achievable S.D.o.F.. We
further investigate the adverse scenario in which Eve knows Bob's transmission
strategy and optimizes its transmit/receive antennas allocation in order to
minimize the achievable S.D.o.F.. For that case we find the worst-case
achievable S.D.o.F.. We also provide a method for constructing the precoding
matrices of Alice and Bob, based on which the maximum S.D.o.F. can be achieved.
Numerical results validate the theoretical findings and demonstrate the
performance of the proposed method in realistic settings.


title:
A vector field approach to almost-sharp decay for the wave equation on
  spherically symmetric, stationary spacetimes

abstract:
  We present a new vector field approach to almost-sharp decay for the wave
equation on spherically symmetric, stationary and asymptotically flat
spacetimes. Specifically, we derive a new hierarchy of higher-order weighted
energy estimates by employing appropriate commutator vector fields. In cases
where an integrated local energy decay estimate holds, like in the case of
sub-extremal Reissner-Nordstrom black holes, this hierarchy leads to
almost-sharp global energy and pointwise time-decay estimates with decay rates
that go beyond those obtained by the traditional vector field method. Our
estimates play a fundamental role in our companion paper where precise
late-time asymptotics are obtained for linear scalar fields on such
backgrounds.


title:
Late-time asymptotics for the wave equation on spherically symmetric,
  stationary spacetimes

abstract:
  We derive precise late-time asymptotics for solutions to the wave equation on
spherically symmetric, stationary and asymptotically flat spacetimes including
as special cases the Schwarzschild and Reissner-Nordstrom families of black
holes. We also obtain late-time asymptotics for the time derivatives of all
orders and for the radiation field along null infinity. We show that the
leading-order term in the asymptotic expansion is related to the existence of
the conserved Newman-Penrose quantities on null infinity. As a corollary we
obtain a characterization of all solutions which satisfy Price's polynomial law
as a lower bound. Our analysis relies on physical space techniques and uses the
vector field approach for almost-sharp decay estimates introduced in our
companion paper. In the black hole case, our estimates hold in the domain of
outer communications up to and including the event horizon. Our work is
motivated by the stability problem for black hole exteriors and strong cosmic
censorship for black hole interiors.


title: Lattice QCD spectroscopy for hadronic CP violation

abstract:
  The interpretation of nuclear electric dipole moment (EDM) experiments is
clouded by large theoretical uncertainties associated with nonperturbative
matrix elements. In various beyond-the-Standard Model scenarios nuclear and
diamagnetic atomic EDMs are expected to be dominated by CP-violating
pion-nucleon interactions that arise from quark chromo-electric dipole moments.
The corresponding CP-violating pion-nucleon coupling strengths are, however,
poorly known. In this work we propose a strategy to calculate these couplings
by using spectroscopic lattice QCD techniques. Instead of directly calculating
the pion-nucleon coupling constants, a challenging task, we use chiral symmetry
relations that link the pion-nucleon couplings to nucleon sigma terms and mass
splittings that are significantly easier to calculate. In this work, we show
that these relations are reliable up to next-to-next-to-leading order in the
chiral expansion in both SU(2) and SU(3) chiral perturbation theory. We
conclude with a brief discussion about practical details regarding the required
lattice QCD calculations and the phenomenological impact of an improved
understanding of CP-violating matrix elements.


title:
Regularity theory for solutions to second order elliptic operators with
  complex coefficients and the $L^p$ Dirichlet problem

abstract:
  We establish a new theory of regularity for elliptic complex valued second
order equations of the form $\mathcal L=$div$A(\nabla\cdot)$, when the
coefficients of the matrix $A$ satisfy a natural algebraic condition, a
strengthened version of a condition known in the literature as
$L^p$-dissipativity. Precisely, the regularity result is a reverse H\"older
condition for $L^p$ averages of solutions on interior balls, and serves as a
replacement for the De Giorgi - Nash - Moser regularity of solutions to
real-valued divergence form elliptic operators. In a series of papers, Cialdea
and Maz'ya studied necessary and sufficient conditions for $L^p$-dissipativity
of second order complex coefficient operators and systems. Recently, Carbonaro
and Dragi\v{c}evi\'c introduced a condition they termed $p$-ellipticity, and
showed that it had implications for boundedness of certain bilinear operators
that arise from complex valued second order differential operators. Their
$p$-ellipticity condition is exactly our strengthened version of
$L^p$-dissipativity. The regularity results of the present paper are applied to
solve $L^p$ Dirichlet problems for $\mathcal
L=$div$A(\nabla\cdot)+B\cdot\nabla$ when $A$ and $B$ satisfy a natural and
familiar Carleson measure condition. We show solvability of the $L^p$ Dirichlet
boundary value problem for $p$ in the range where $A$ is $p$-elliptic.


title: Is String Phenomenology an Oxymoron?

abstract:
  A brief discussion is presented assessing the achievements and challenges of
string phenomenology: the subfield dedicated to study the potential for string
theory to make contact with particle physics and cosmology. Building from the
well understood case of the standard model as a very particular example within
quantum field theory we highlight the very few generic observable implications
of string theory, most of them inaccessible to low-energy experiments, and
indicate the need to extract concrete scenarios and classes of models that
could eventually be contrasted with searches in collider physics and other
particle experiments as well as in cosmological observations. The impact that
this subfield has had in mathematics and in a better understanding of string
theory is emphasised as spin-offs of string phenomenology. Moduli fields,
measuring the size and shape of extra dimensions, are highlighted as generic
low-energy remnants of string theory that can play a key role for supersymmetry
breaking as well as for inflationary and post-inflationary early universe
cosmology. It is argued that the answer to the question in the title should be,
as usual, {\it No}. Future challenges for this field are briefly mentioned.
This essay is a contribution to the conference: "Why Trust a Theory?", Munich,
December 2015.


title:
Dynamical realization of magnetic states in a strongly interacting Bose
  mixture

abstract:
  We describe the dynamical preparation of magnetic states in a strongly
interacting two-component Bose gas in a harmonic trap. By mapping this system
to an effective spin chain model, we obtain the dynamical spin densities and
the fidelities for a few-body system. We show that the spatial profiles transit
between ferromagnetic and antiferromagnetic states as the intraspecies
interaction parameter is slowly increased.


title: Time-delayed model of RNA interference

abstract:
  RNA interference (RNAi) is a fundamental cellular process that inhibits gene
expression through cleavage and destruction of target mRNA. It is responsible
for a number of important intracellular functions, from being the first line of
immune defence against pathogens to regulating development and morphogenesis.
In this paper we consider a mathematical model of RNAi with particular emphasis
on time delays associated with two aspects of primed amplification: binding of
siRNA to aberrant RNA, and binding of siRNA to mRNA, both of which result in
the expanded production of dsRNA responsible for RNA silencing. Analytical and
numerical stability analyses are performed to identify regions of stability of
different steady states and to determine conditions on parameters that lead to
instability. Our results suggest that while the original model without time
delays exhibits a bi-stability due to the presence of a hysteresis loop, under
the influence of time delays, one of the two steady states with the high
(default) or small (silenced) concentration of mRNA can actually lose its
stability via a Hopf bifurcation. This leads to the co-existence of a stable
steady state and a stable periodic orbit, which has a profound effect on the
dynamics of the system.


title: Strongly proper forcing and some problems of Foreman

abstract:
  We provide solutions to several problems of Foreman about ideals, several of
which are closely related to Mitchell's notion of \emph{strongly proper}
forcing. We prove: 1) Presaturation of a normal ideal implies projective
antichain catching, enabling us to provide a solution to a problem from
Foreman~\cite{MR2768692} about ideal projections which is more comprehensive
and simpler than the solution obtained in \cite{MR3343538}. 2) We solve an
older question from Foreman~\cite{MR819932} about the relationship between
generic hugeness and generic almost hugeness. 3) Finally, we provide solutions
to two technical questions from Foreman~\cite{MR3038554} and \cite{MR2768692}
related to his \emph{Duality Theorem}.


title:
Functional limit theorems for Galton-Watson processes with very active
  immigration

abstract:
  We prove weak convergence on the Skorokhod space of Galton-Watson processes
with immigration, properly normalized, under the assumption that the tail of
the immigration distribution has a logarithmic decay. The limits are extremal
shot noise processes. By considering marginal distributions, we recover the
results of Pakes [Adv. Appl. Probab., 11(1979), 31--62].


title:
High-Bandwidth and Large Coupling Tolerance Graded-Index Multimode
  Polymer Waveguides for On-board High-Speed Optical Interconnects

abstract:
  Optical interconnects have attracted significant research interest for use in
short-reach board-level optical communication links in supercomputers and data
centres. Multimode polymer waveguides in particular constitute an attractive
technology for on-board optical interconnects as they provide high bandwidth,
offer relaxed alignment tolerances, and can be cost-effectively integrated onto
standard printed circuit boards (PCBs). However, the continuing improvements in
bandwidth performance of optical sources make it important to investigate
approaches to develop high bandwidth polymer waveguides. In this paper, we
present dispersion studies on a graded-index (GI) waveguide in siloxane
materials designed to deliver high bandwidth over a range of launch conditions.
Bandwidth-length products of >70 GHzxm and ~65 GHzxm are observed using a
50/125 um multimode fibre (MMF) launch for input offsets of +/- 10 um without
and with the use of a mode mixer respectively; and enhanced values of >100
GHzxm are found under a 10x microscope objective launch for input offsets of
~18 x 20 um^2. The large range of offsets is within the -1 dB alignment
tolerances. A theoretical model is developed using the measured refractive
index profile of the waveguide, and general agreement is found with
experimental bandwidth measurements. The reported results clearly demonstrate
the potential of this technology for use in high-speed board-level optical
links, and indicate that data transmission of 100 Gb/s over a multimode polymer
waveguide is feasible with appropriate refractive index engineering.


title:
Correct Small-Truncated Excited State Wave functions Obtained via
  Minimization Principle for Excited States compared / opposed to
  Hylleraas-Undheim and McDonald higher roots

abstract:
  We demonstrate that, if a truncated expansion of a wave function is Large,
then the standard excited states computational method, of optimizing one root
of a secular equation, according to the theorem of Hylleraas, Undheim and
McDonald (HUM), tends to the correct excited wave function, comparable to that
obtained via our proposed minimization principle for excited states [J. Comput.
Meth. Sci. Eng. 8, 277 (2008)] (independent of orthogonality to lower lying
approximants). However, if a truncated expansion of a wave function is Small -
that would be desirable for large systems - then the HUM-based methods may lead
to an incorrect wave function - despite the correct energy (: according to the
HUM theorem) whereas our method leads to correct, reliable, albeit Small
truncated wave functions. The demonstration is done in He excited states, using
truncated series Small expansions both in Hylleraas coordinates, and via
standard configuration-interaction truncated Small expansions, in comparison
with corresponding Large expansions. Beyond that, we give some examples of
linear combinations of Hamiltonian eigenfunctions that have the energy of the
1st excited state, albeit they are orthogonal to it, demonstrating that the
correct energy is not a criterion of correctness of the wave function.


title: Spatial Mixing and Systematic Scan Markov chains

abstract:
  We consider spin systems on the integer lattice graph $\mathbb{Z}^d$ with
nearest-neighbor interactions. We develop a combinatorial framework for
establishing that exponential decay with distance of spin correlations,
specifically the strong spatial mixing condition (SSM), implies rapid mixing of
a large class of Markov chains. As a first application of our method we prove
that SSM implies $O(\log n)$ mixing of systematic scan dynamics (under mild
conditions) on an $n$-vertex $d$-dimensional cube of the integer lattice graph
$\mathbb{Z}^d$. Systematic scan dynamics are widely employed in practice but
have proved hard to analyze. A second application of our technology concerns
the Swendsen-Wang dynamics for the ferromagnetic Ising and Potts models. We
show that SSM implies an $O(1)$ bound for the relaxation time (i.e., the
inverse spectral gap). As a by-product of this implication we observe that the
relaxation time of the Swendsen-Wang dynamics in square boxes of $\mathbb{Z}^2$
is $O(1)$ throughout the subcritical regime of the $q$-state Potts model, for
all $q \ge 2$. We also use our combinatorial framework to give a simple
coupling proof of the classical result that SSM entails optimal mixing time of
the Glauber dynamics. Although our results in the paper focus on
$d$-dimensional cubes in $\mathbb{Z}^d$, they generalize straightforwardly to
arbitrary regions of $\mathbb{Z}^d$ and to graphs with subexponential growth.


title:
Capacity of Cooperative Vehicular Networks with Infrastructure Support:
  Multi-user Case

abstract:
  Capacity of vehicular networks with infrastructure support is both an
interesting and challenging problem as the capacity is determined by the
inter-play of multiple factors including vehicle-to-infrastructure (V2I)
communications, vehicle-to-vehicle (V2V) communications, density and mobility
of vehicles, and cooperation among vehicles and infrastructure. In this paper,
we consider a typical delay-tolerant application scenario with a subset of
vehicles, termed Vehicles of Interest (VoIs), having download requests. Each
VoI downloads a distinct large-size file from the Internet and other vehicles
without download requests assist the delivery of the files to the VoIs. A
cooperative communication strategy is proposed that explores the combined use
of V2I communications, V2V communications, mobility of vehicles and cooperation
among vehicles and infrastructure to improve the capacity of vehicular
networks. An analytical framework is developed to model the data dissemination
process using this strategy, and a closed form expression of the achievable
capacity is obtained, which reveals the relationship between the capacity and
its major performance-impacting parameters such as inter-infrastructure
distance, radio ranges of infrastructure and vehicles, sensing range of
vehicles, transmission rates of V2I and V2V communications, vehicular density
and proportion of VoIs. Numerical result shows that the proposed cooperative
communication strategy significantly boosts the capacity of vehicular networks,
especially when the proportion of VoIs is low. Our results provide guidance on
the optimum deployment of vehicular network infrastructure and the design of
cooperative communication strategy to maximize the capacity.


title:
Nuclear Outflow of the Milky Way: Studying the Kinematics and Spatial
  Extent of the Northern Fermi Bubble

abstract:
  We report new observations from a systematic, spectroscopic, ultraviolet
absorption-line survey that maps the spatial and kinematic properties of the
high-velocity gas in the Galactic Center region. We examine the hypothesis that
this gas traces the biconical nuclear outflow. We use ultraviolet spectra of 47
background QSOs and halo stars projected inside and outside the northern Fermi
Bubble from the Hubble Space Telescope to study the incidence of high velocity
absorption around it. We use five lines of sight inside the northern Fermi
Bubble to constrain the velocity and column densities of outflowing gas traced
by O I, Al II, C II, C IV, Si II, Si III, Si IV and other species. All five
lines of sight inside the northern Fermi Bubble exhibit blueshifted high
velocity absorption components, whereas only 9 out of the 42 lines of sight
outside the northern Fermi Bubble exhibit blueshifted high velocity absorption
components. The observed outflow velocity profile decreases with Galactic
latitude and radial distance (R) from the Galactic Center. The observed
blueshifted velocities change from $v_{GSR}$=-265 km/s at R~2.3 kpc to
$v_{GSR}$=-91 km/s at R~6.5 kpc. We derive the metallicity of the entrained gas
along the 1H1613-097 sightline, which passes through the center of the northern
Fermi Bubble, finding [O/H] $\gtrsim -0.54 \pm 0.15$. A simple kinematic model
tuned to match the observed absorption component velocities along the five
lines of sight inside the Bubble, constrains the outflow velocities to
~1000$-$1300 km/s, and the age of the outflow to be ~ 6$-$9 Myr. We estimate a
minimum mass outflow rate for the nuclear outflow to be $\gtrsim$ 0.2 $\rm{
M_{\odot}\; yr^{-1}}$. Combining the age and mass outflow rates, we determine a
minimum mass of total UV absorbing cool gas entrained in the Fermi Bubbles to
be $\gtrsim \rm{ 2 \times 10^{6} M_{\odot}}$.


title: Stability of sulphur dimers S2 in cometary ices

abstract:
  S2 has been observed for decades in comets, including comet
67P/Churyumov-Gerasimenko. Despite the fact that this molecule appears
ubiquitous in these bodies, the nature of its source remains unknown. In this
study, we assume that S2 is formed by irradiation (photolysis and/or
radiolysis) of S-bearing molecules embedded in the icy grain precursors of
comets, and that the cosmic ray flux simultaneously creates voids in ices
within which the produced molecules can accumulate. We investigate the
stability of S2 molecules in such cavities, assuming that the surrounding ice
is made of H2S or H2O. We show that the stabilization energy of S2 molecules in
such voids is close to that of the H2O ice binding energy, implying that they
can only leave the icy matrix when this latter sublimates. Because S2 has a
short lifetime in the vapor phase, we derive that its formation in grains via
irradiation must occur only in low density environments such as the ISM or the
upper layers of the protosolar nebula, where the local temperature is extremely
low. In the first case, comets would have agglomerated from icy grains that
remained pristine when entering the nebula. In the second case, comets would
have agglomerated from icy grains condensed in the protosolar nebula and that
would have been efficiently irradiated during their turbulent transport towards
the upper layers of the disk. Both scenarios are found consistent with the
presence of molecular oxygen in comets.


title: QSFit: Automatic analysis of optical AGN spectra

abstract:
  We present QSFit, a new software package to automatically perform the
analysis of Active Galactic Nuclei (AGN) optical spectra. The software provides
luminosity estimates for the AGN continuum, the Balmer continuum, both optical
and UV iron blended complex, host galaxy and emission lines, as well as width,
velocity offset and equivalent width of 20 emission lines. Improving on a
number of previous studies on AGN spectral analysis, QSFit fits all the
components simultaneously, using an AGN continuum model which extends over the
entire available spectrum, and is thus a probe of the actual AGN continuum
whose estimates are scarcely influenced by localized features (e.g. emission
lines) in the spectrum. We used QSFit to analyze 71,251 optical spectra of Type
1 AGN at z < 2 (obtained by the Sloan Digital Sky Survey, SDSS) and to produce
a publicly available catalog of AGN spectral properties. Such catalog allowed
us (for the first time) to estimate the AGN continuum slope and the Balmer
continuum luminosity on a very large sample, and to show that there is no
evident correlation between these quantities the redshift. All data in the
catalog, the plots with best fitting model and residuals, and the IDL code we
used to perform the analysis, are available on a dedicated website. The whole
fitting process is customizable for specific needs, and can be extended to
analyze spectra from other data sources. The ultimate purpose of QSFit is to
allow astronomers to run standardized recipes to analyze the AGN data, in a
simple, replicable and shareable way.


title:
Kinematics of a young low-mass star forming core: Understanding the
  evolutionary state of the First Core Candidate L1451-mm

abstract:
  We use 3mm multi-line and continuum CARMA observations towards the first
hydrostatic core (FHSC) candidate L1451-mm to characterize the envelope
kinematics at 1000 AU scales and investigate its evolutionary state. We detect
evidence of infall and rotation in the N2H+(1-0), NH2D(1(1,1)-1(0,1)) and
HCN(1-0) molecular lines. We compare the position velocity diagram of the NH2D
line with a simple kinematic model and find that it is consistent with an
envelope that is both infalling and rotating while conserving angular momentum
around a central mass of about 0.06 Msun. The N2H+(1-0) LTE mass of the
envelope along with the inferred infall velocity leads to a mass infall rate of
approximately 6e-6 Msun/yr, implying a young age of 10,000 years for this FHSC
candidate. Assuming that the accretion onto the central object is the same as
the infall rate we obtain that the minimum source size is 1.5-5 AU consistent
with the size expected for a first core. We do not see any evidence of outflow
motions or signs of outflow-envelope interaction at scales > 2000 AU. This is
consistent with previous observations that revealed a very compact outflow
(<500 AU). We conclude that L1451-mm is indeed at a very early stage of
evolution, either a first core or an extremely young Class 0 protostar. Our
results provide strong evidence that L1451-mm is the best candidate for being a
bonafide first core.


title: Isomorphisms of Discriminant Algebras

abstract:
  For each natural number $n$, we define a category whose objects are
discriminant algebras in rank $n$, i.e. functorial means of attaching to each
rank-$n$ algebra a quadratic algebra with the same discriminant. We show that
the discriminant algebras defined in [2], [6], and [10] are all isomorphic in
this category, and prove furthermore that in ranks $n \leq 3$ discriminant
algebras are unique up to unique isomorphism.


title: Monodromy of the $SL(n)$ and $GL(n)$ Hitchin fibrations

abstract:
  We compute the monodromy of the Hitchin fibration for the moduli space of
$L$-twisted $SL(n,\mathbb{C})$ and $GL(n,\mathbb{C})$-Higgs bundles for any
$n$, on a compact Riemann surface of genus $g>1$. We require the line bundle
$L$ to either be the canonical bundle or satisfy $deg(L) > 2g-2$. The monodromy
group is generated by Picard-Lefschetz transformations associated to vanishing
cycles of singular spectral curves. We construct such vanishing cycles
explicitly and use this to show that the $SL(n,\mathbb{C})$ monodromy group is
a {\em skew-symmetric vanishing lattice} in the sense of Janssen. Using the
classification of vanishing lattices over $\mathbb{Z}$, we completely determine
the structure of the monodromy groups of the $SL(n,\mathbb{C})$ and
$GL(n,\mathbb{C})$ Hitchin fibrations. As an application we determine the image
of the restriction map from the cohomology of the moduli space of Higgs bundles
to the cohomology of a non-singular fibre of the Hitchin fibration.


title: Quasi parton distributions and the gradient flow

abstract:
  We propose a new approach to determining quasi parton distribution functions
(PDFs) from lattice quantum chromodynamics. By incorporating the gradient flow,
this method guarantees that the lattice quasi PDFs are finite in the continuum
limit and evades the thorny, and as yet unresolved, issue of the
renormalization of quasi PDFs on the lattice. In the limit that the flow time
is much smaller than the length scale set by the nucleon momentum, the moments
of the smeared quasi PDF are proportional to those of the light-front PDF. We
use this relation to derive evolution equations for the matching kernel that
relates the smeared quasi PDF and the light-front PDF. As part of this
discussion, we elucidate the relationship between the quasi and light-front
PDFs.


title: Preprojective algebras of tree-type quivers

abstract:
  Let $Q$ be a tree-type quiver, $\mathbf{k} Q$ its path algebra, and $\lambda$
a nonzero element in the field $\mathbf{k}$. We construct irreducible morphisms
in the Auslander-Reiten quiver of the transjective component of the bounded
derived category of $\mathbf{k} Q$ that satisfy what we call the
$\lambda$-relations. When $\lambda=1$, the relations are known as mesh
relations. When $\lambda=-1$, they are known as commutativity relations. Using
this technique together with the results given by Baer-Geigle-Lenzing,
Crawley-Boevey, Ringel, and others, we show that for any tree-type quiver,
several descriptions of its preprojective algebra are equivalent.


title:
A One-Field Monolithic Fictitious Domain Method for Fluid-Structure
  Interactions

abstract:
  In this article, we present a one-field monolithic fictitious domain (FD)
method for simulation of general fluid-structure interactions (FSI). One-field
means only one velocity field is solved in the whole domain, based upon the use
of an appropriate L2 projection. Monolithic means the fluid and solid equations
are solved synchronously (rather than sequentially). We argue that the proposed
method has the same generality and robustness as FD methods with distributed
Lagrange multiplier (DLM) but is significantly more computationally efficient
(because of one-field) whilst being very straightforward to implement. The
method is described in detail, followed by the presentation of multiple
computational examples in order to validate it across a wide range of fluid and
solid parameters and interactions.