title:
Embedding AC Power Flow in the Complex Plane Part II: A Reliable
  Framework for Voltage Collapse Analysis

abstract:
  Part II of this paper elaborates on the unique capability of the proposed
power flow analysis framework to obtain the true solution corresponding to the
stable operating point of a network. It explains the significance of obtaining
the true solution for an accurate assessment of the voltage collapse margin.
This feature distinguishes the framework from all iterative and non-iterative
heuristic approaches as demonstrated in the context of a 7-bus network with
Newton-Raphson, its variants and semidefinite and moment-based relaxations of
power flow. Another important feature of this framework is that it obtains the
true solution when it exists and declares its non-existence otherwise. This is
demonstrated in the context of small networks and in comparison with heuristic
approaches. This paper also explores how the proposed framework detects a
limit-induced bifurcation where a network controller reaching its limit can
initiate voltage collapse.


title: Involutions, Trace Maps, and Pseudorandom Numbers

abstract:
  Interesting properties of the partitions of a finite field $\mathbb F_q$
induced by the combination of involutions and trace maps are studied. The
special features of involutions of the form $\frac{u}{z}$, $u$ being a fixed
element of $\mathbb F_q$, are exploited to generate pseudorandom numbers, the
randomness resting on the uniform distribution of the images of zero-trace
elements among the sets of non-zero trace elements of $\mathbb F_q$.


title: Waring's Problem for Polynomial Rings and the Digit Sum of Exponents

abstract:
  Let $F$ be an algebraically closed field of characteristic $p>0$. In this
paper we develop methods to represent arbitrary elements of $F[t]$ as sums of
perfect $k$-th powers for any $k\in\mathbb{N}$ relatively prime to $p$. Using
these methods we establish bounds on the necessary number of $k$-th powers in
terms of the sum of the digits of $k$ in its base-$p$ expansion. As one
particular application we prove that for any fixed prime $p>2$ and any
$\epsilon>0$ the number of $(p^r-1)$-th powers required is
$\mathcal{O}\left(r^{(2+\epsilon)\ln(p)}\right)$ as a function of $r$.


title:
Spectral entropies as information-theoretic tools for complex network
  comparison

abstract:
  Any physical system can be viewed from the perspective that information is
implicitly represented in its state. However, the quantification of this
information when it comes to complex networks has remained largely elusive. In
this work, we use techniques inspired by quantum statistical mechanics to
define an entropy measure for complex networks and to develop a set of
information-theoretic tools, based on network spectral properties, such as
Renyi q-entropy, generalized Kullback-Leibler and Jensen-Shannon divergences,
the latter allowing us to define a natural distance measure between complex
networks. First we show that by minimizing the Kullback-Leibler divergence
between an observed network and a parametric network model, inference of model
parameter(s) by means of maximum-likelihood estimation can be achieved and
model selection can be performed appropriate information criteria. Second, we
show that the information-theoretic metric quantifies the distance between
pairs of networks and we can use it, for instance, to cluster the layers of a
multilayer system. By applying this framework to networks corresponding to
sites of the human microbiome, we perform hierarchical cluster analysis and
recover with high accuracy existing community-based associations. Our results
imply that spectral based statistical inference in complex networks results in
demonstrably superior performance as well as a conceptual backbone, filling a
gap towards a network information theory.


title:
Poly(1-vinyl-1,2,4-triazolium) poly(ionic liquid)s: synthesis and the
  unique behavior in loading metal ions

abstract:
  Herein we report the synthesis of a series of
poly(4-alkyl-1-vinyl-1,2,4-triazolium) poly(ionic liquid)s either via
straightforward free radical polymerization of their corresponding ionic liquid
monomers, or via anion metathesis of the polymer precursors bearing halide as
counter anion. The ionic liquid monomers were first prepared via N-alkylation
reaction of commercially available 1-vinyl-1,2,4-triazole with alkyl iodides,
followed by anion metathesis with targeted fluorinated anions. The thermal
properties and solubilities of these poly(ionic liquid)s have been
systematically investigated. Interestingly, it was found that the
poly(4-ethyl-1-vinyl-1,2,4-triazolium) poly(ionic liquid) exhibited an improved
loading capacity of transition metal ions in comparison with its imidazolium
counterpart.


title: Factorization, resummation and sum rules for heavy-to-light form factors

abstract:
  Precision calculations of heavy-to-light form factors are essential to
sharpen our understanding towards the strong interaction dynamics of the
heavy-quark system and to shed light on a coherent solution of flavor
anomalies. We briefly review factorization properties of heavy-to-light form
factors in the framework of QCD factorization in the heavy quark limit and
discuss the recent progress on the QCD calculation of $B \to \pi$ form factors
from the light-cone sum rules with the $B$-meson distribution amplitudes.
Demonstration of QCD factorization for the vacuum-to-$B$-meson correlation
function used in the sum-rule construction and resummation of large logarithms
in the short-distance functions entering the factorization theorem are
presented in detail. Phenomenological implications of the newly derived sum
rules for $B \to \pi$ form factors are further addressed with a particular
attention to the extraction of the CKM matrix element $|V_{ub}|$.


title: Relating urban scaling, fundamental allometry, and density scaling

abstract:
  We study the connection between urban scaling, fundamental allometry (between
city population and city area), and per capita vs.\ population density scaling.
From simple analytical derivations we obtain the relation between the 3
involved exponents. We discuss particular cases and ranges of the exponents
which we illustrate in a "phase diagram". As we show, the results are
consistent with previous work.


title:
Inequalities of M.G. Krein, Yu.V. Linnik and E.A. Gorin for positive
  definite functions

abstract:
  We investigate inequalities of M.G. Krein, Yu.V. Linnik and E.A. Gorin for
positive definite functions. Modifications and generalizations of these
inequalities are proved. We also prove that multipoint E.A. Gorin's inequality
follows from two--point M.G. Krein's inequality.


title:
The degenerate Fermi gas of $\pi$ electrons in fullerenes and the
  $\sigma$ surface instabilities

abstract:
  The departure from perfect spherical symmetry in the case of fullerenes, C60
being the sole exception, induces instabilities due to the stresses generated
by the pentagonal protrusions in the sigma-bonded surfaces. By assuming sigma
and pi separability and treating pi electrons as a degenerate Fermi gas in the
two shells around the central sigma structure, the resulting degeneracy
pressures can further enhance the sigma-surface initiated instabilities for
non-icosahedral structures especially for those smaller than C60 as well as the
icosahedral fullerenes that are larger than C60, with large protrusions. Under
certain circumstances the net degeneracy pressure across the sigma surface
might have structure-stabilizing effect. The role of the pi electron degeneracy
in a broad range of fullerenes from C20 to C1500 and its effects on fullerene
stability is investigated.


title: An implementation of Deflate in Coq

abstract:
  The widely-used compression format "Deflate" is defined in RFC 1951 and is
based on prefix-free codings and backreferences. There are unclear points about
the way these codings are specified, and several sources for confusion in the
standard. We tried to fix this problem by giving a rigorous mathematical
specification, which we formalized in Coq. We produced a verified
implementation in Coq which achieves competitive performance on inputs of
several megabytes. In this paper we present the several parts of our
implementation: a fully verified implementation of canonical prefix-free
codings, which can be used in other compression formats as well, and an elegant
formalism for specifying sophisticated formats, which we used to implement both
a compression and decompression algorithm in Coq which we formally prove
inverse to each other -- the first time this has been achieved to our
knowledge. The compatibility to other Deflate implementations can be shown
empirically. We furthermore discuss some of the difficulties, specifically
regarding memory and runtime requirements, and our approaches to overcome them.


title: Excluding a large theta graph

abstract:
  A theta graph, denoted $\theta_{a,b,c}$, is a graph of order $a+b+c-1$
consisting of a pair of vertices and three independent paths between them of
lengths $a$, $b$, and $c$. We provide a complete characterization of graphs
that do not contain a large $\theta_{a,b,c}$ as a topological minor. More
specifically, we describe the structure of $\theta_{1,2,t}$-,
$\theta_{2,2,t}$-, $\theta_{1,t,t}$-, $\theta_{2,t,t}$-, and
$\theta_{t,t,t}$-free graphs where $t$ is large. The main result is a
characterization of $\theta_{t,t,t}$-free graphs for large $t$. The
$3$-connected $\theta_{t,t,t}$-free graphs are formed by $3$-summing graphs
without a long path to certain planar graphs. The $2$-connected
$\theta_{t,t,t}$-free graphs are then built up in a similar fashion by 2- and
3-sums. This result implies a well-known theorem of Robertson and Chakravarti
on graphs that do not have a bond containing three specified edges.


title: Stability of the rotation set of area-preserving toral homeomorphisms

abstract:
  We show that if the rotation set of a homeomorphism of the torus is stable
under small perturbations of the dynamics, then it is a convex polygon with
rational vertices. We also show that such homeomorphisms are $C^0$-generic and
have bounded rotational deviations (even for pseudo-orbits). The results hold
both in the area-preserving setting and in the general setting. When the
rotation set is stable, we give explicit estimates on the type of rationals
that may appear as vertices of rotation sets in terms of the stability
constants.


title: Optical Writing of Magnetic Properties by Remanent Photostriction

abstract:
  We present an optically induced remanent photostriction in BiFeO3, resulting
from the photovoltaic effect, which is used to modify the ferromagnetism of Ni
film in a hybrid BiFeO3/Ni structure. The 75% change in coercivity in the Ni
film is achieved via optical and nonvolatile control. This photoferromagnetic
effect can be reversed by static or ac electric depolarization of BiFeO3.
Hence, the strain dependent changes in magnetic properties are written
optically, and erased electrically. Light-mediated straintronics is therefore a
possible approach for low-power multistate control of magnetic elements
relevant for memory and spintronic applications.


title: $r$-Tuple Error Functions and Indefinite Theta Series of Higher-Depth

abstract:
  Theta functions for definite signature lattices constitute a rich source of
modular forms. A natural question is then their generalization to indefinite
signature lattices. One way to ensure a convergent theta series while keeping
the holomorphicity property of definite signature theta series is to restrict
the sum over lattice points to a proper subset. Although such series do not
have the modular properties that a definite signature theta function has, as
shown by Zwegers for signature $(1,n-1)$ lattices, they can be completed to a
function that has these modular properties by compromising on the
holomorphicity property in a certain way. This construction has recently been
generalized to signature $(2,n-2)$ lattices by Alexandrov, Banerjee, Manschot,
and Pioline. A crucial ingredient in this work is the notion of double error
functions which naturally lends itself to generalizations to higher dimensions.
In this work we study the properties of such higher dimensional error functions
which we will call $r$-tuple error functions. We then construct an indefinite
theta series for signature $(r,n-r)$ lattices and show they can be completed to
modular forms by using these $r$-tuple error functions.


title: KMS quantum symmetric states

abstract:
  Let $A$ be a unital C$^*$-algebra and let $\sigma$ be a one-parameter
automorphism group of $A$. We consider $\operatorname{QSS}_\sigma(A)$, the set
of all quantum symmetric states on $*_1^\infty A$ that are also KMS states (for
a fixed inverse temperature, for specificity taken to be $-1$) for the free
product automorphism group $*_1^\infty\sigma$. We characterize the elements of
$\operatorname{QSS}_\sigma(A)$, we show that $\operatorname{QSS}_\sigma(A)$ is
a Choquet simplex whenever it is nonempty and we characterize its extreme
points.


title: The Robustness of Estimator Composition

abstract:
  We formalize notions of robustness for composite estimators via the notion of
a breakdown point. A composite estimator successively applies two (or more)
estimators: on data decomposed into disjoint parts, it applies the first
estimator on each part, then the second estimator on the outputs of the first
estimator. And so on, if the composition is of more than two estimators.
Informally, the breakdown point is the minimum fraction of data points which if
significantly modified will also significantly modify the output of the
estimator, so it is typically desirable to have a large breakdown point. Our
main result shows that, under mild conditions on the individual estimators, the
breakdown point of the composite estimator is the product of the breakdown
points of the individual estimators. We also demonstrate several scenarios,
ranging from regression to statistical testing, where this analysis is easy to
apply, useful in understanding worst case robustness, and sheds powerful
insights onto the associated data analysis.


title:
Completion of metric reconstruction for a particle orbiting a Kerr black
  hole

abstract:
  Vacuum perturbations of the Kerr metric can be reconstructed from the
corresponding perturbation in either of the two Weyl scalars $\psi_0$ or
$\psi_4$, using a procedure described by Chrzanowski and others in the 1970s.
More recent work, motivated within the context of self-force physics, extends
the procedure to metric perturbations sourced by a particle in a bound geodesic
orbit. However, the existing procedure leaves undetermined a certain
stationary, axially-symmetric piece of the metric perturbation. In the vacuum
region away from the particle, this "completion" piece corresponds simply to
mass and angular-momentum perturbations of the Kerr background, with amplitudes
that are, however, a priori unknown. Here we present and implement a rigorous
method for finding the completion piece. The key idea is to impose continuity,
off the particle, of certain gauge-invariant fields constructed from the full
(completed) perturbation, in order to determine the unknown amplitude
parameters of the completion piece. We implement this method in full for bound
(eccentric) geodesic orbits in the equatorial plane of the Kerr black hole. Our
results provide a rigorous underpinning of recent results by Friedman {\it et
al.}\ for circular orbits, and extend them to non-circular orbits.


title:
Towards Automated Melanoma Screening: Exploring Transfer Learning
  Schemes

abstract:
  Deep learning is the current bet for image classification. Its greed for huge
amounts of annotated data limits its usage in medical imaging context. In this
scenario transfer learning appears as a prominent solution. In this report we
aim to clarify how transfer learning schemes may influence classification
results. We are particularly focused in the automated melanoma screening
problem, a case of medical imaging in which transfer learning is still not
widely used. We explored transfer with and without fine-tuning, sequential
transfers and usage of pre-trained models in general and specific datasets.
Although some issues remain open, our findings may drive future researches.


title: Conductivity exponents at the percolation threshold

abstract:
  Connections are found between the two-component percolation problem and the
conductor/insulator percolation problem. These produce relations between
critical exponents, and suggest formulae connecting the conductivity exponents
in different dimensions. Values for the critical exponents are obtained from
calculations on the incipient infinite cluster in two and three dimensions.


title:
Topology in the SU(Nf) chiral symmetry restored phase of unquenched QCD
  and axion cosmology

abstract:
  We investigate the topological properties of unquenched $QCD$ on the basis of
numerical results of simulations at fixed topological charge, recently reported
by Borsanyi et al.. We demonstrate that their results for the mean value of the
chiral condensate at fixed topological charge are inconsistent with the
analytical prediction of the large volume expansion around the saddle point,
and argue that the most plausible explanation for the failure of the saddle
point expansion is a vacuum energy density $\theta$-independent at high
temperatures, but surprisingly not too high $(T\sim 2T_c)$, a result which
would imply a vanishing topological susceptibility, and the absence of all
physical effects of the $U(1)$ axial anomaly at these temperatures. We also
show that under a general assumption concerning the high temperature phase of
$QCD$, where the $SU(N_f)_A$ symmetry is restored, the analytical prediction
for the chiral condensate at fixed topological charge is in very good agreement
with the numerical results of Borsanyi et al., all effects of the axial anomaly
should disappear, the topological susceptibility and all the
$\theta$-derivatives of the vacuum energy density vanish and the theory becomes
$\theta$-independent at any $T>T_c$ in the infinite volume limit.


title: Regularity of the optimal sets for some spectral functionals

abstract:
  In this paper we study the regularity of the optimal sets for the shape
optimization problem \[ \min\Big\{\lambda_1(\Omega)+\dots+\lambda_k(\Omega)\ :\
\Omega\subset\mathbb{R}^d,\ \text{open}\ ,\ |\Omega|=1\Big\}, \] where
$\lambda_1(\cdot),\dots,\lambda_k(\cdot)$ denote the eigenvalues of the
Dirichlet Laplacian and $|\cdot|$ the $d$-dimensional Lebesgue measure. We
prove that the topological boundary of a minimizer $\Omega_k^*$ is composed of
a relatively open regular part which is locally a graph of a $C^{1,\alpha}$
function and a closed singular part, which is empty if $d<d^*$, contains at
most a finite number of isolated points if $d=d^*$ and has Hausdorff dimension
smaller than $(d-d^*)$ if $d>d^*$, where the natural number $d^*\in[5,7]$ is
the smallest dimension at which minimizing one-phase free boundaries admit
singularities.
  To achieve our goal, as an auxiliary result, we shall extend for the first
time the known regularity theory for the one-phase free boundary problem to the
vector-valued case.


title: Residual Cauchy-type formula on Riemann surfaces

abstract: We construct a Cauchy type formula on open subdomains of Riemann surfaces


title: Multivariate Dependence Beyond Shannon Information

abstract:
  Accurately determining dependency structure is critical to discovering a
system's causal organization. We recently showed that the transfer entropy
fails in a key aspect of this---measuring information flow---due to its
conflation of dyadic and polyadic relationships. We extend this observation to
demonstrate that this is true of all such Shannon information measures when
used to analyze multivariate dependencies. This has broad implications,
particularly when employing information to express the organization and
mechanisms embedded in complex systems, including the burgeoning efforts to
combine complex network theory with information theory. Here, we do not suggest
that any aspect of information theory is wrong. Rather, the vast majority of
its informational measures are simply inadequate for determining the meaningful
dependency structure within joint probability distributions. Therefore, such
information measures are inadequate for discovering intrinsic causal relations.
We close by demonstrating that such distributions exist across an arbitrary set
of variables.

categories: cs.IT cond-mat.stat-mech math.IT math.ST stat.ML stat.TH


title: Cooper pair splitting in diffusive magnetic SQUIDs

abstract:
  We study Josephson junctions with weak links consisting of two parallel
disordered arms with magnetic properties -- ferromagnetic, half-metallic or
normal with magnetic impurities. In the case of long links, the Josephson
effect is dominated by mesoscopic fluctuations. In this regime, the system
realises a $\varphi_0$ junction with sample-dependent $\varphi_0$ and critical
current. Cooper pair splitting between the two arms plays a major role and
leads to $2\Phi_0$ periodicity of the current as a function of flux between the
arms. We calculate the current and its flux and polarization dependence for the
three types of magnetic links.


title: PMI Matrix Approximations with Applications to Neural Language Modeling

abstract:
  The negative sampling (NEG) objective function, used in word2vec, is a
simplification of the Noise Contrastive Estimation (NCE) method. NEG was found
to be highly effective in learning continuous word representations. However,
unlike NCE, it was considered inapplicable for the purpose of learning the
parameters of a language model. In this study, we refute this assertion by
providing a principled derivation for NEG-based language modeling, founded on a
novel analysis of a low-dimensional approximation of the matrix of pointwise
mutual information between the contexts and the predicted words. The obtained
language modeling is closely related to NCE language models but is based on a
simplified objective function. We thus provide a unified formulation for two
main language processing tasks, namely word embedding and language modeling,
based on the NEG objective function. Experimental results on two popular
language modeling benchmarks show comparable perplexity results, with a small
advantage to NEG over NCE.


title: Gini means and its applications in polymer chemistry

abstract:
  We consider Gini means with short biographical information and propose a new
proof of the main inequality for these means. Also some applications of Gini
and other means are considered to polymer chemistry.


title:
Blade-shaped (PKN) Hydraulic Fracture Driven By A Turbulent Fluid In An
  Impermeable Rock

abstract:
  High flow rate, water-driven hydraulic fractures are more common now than
ever in the oil and gas industry. Although the fractures are small, the high
injection rate and low viscosity of the water, lead to high Reynolds numbers
and potentially turbulence in the fracture. Here we present a semi-analytical
solution for a blade-shaped (PKN) geometry hydraulic fracture driven by a
turbulent fluid in the limit of zero fluid leak-off to the formation. We model
the turbulence in the PKN fracture using the Gaukler-Manning-Strickler
parametrization, which relates the the flow rate of the water to the pressure
gradient along the fracture. The key parameter in this relation is the
Darcy-Weisbach friction factor for the roughness of the crack wall. Coupling
this turbulence parametrization with conservation of mass allows us to write a
nonlinear pde for the crack width as a function of space and time. By way of a
similarity ansatz, we obtain a semi-analytical solution using an orthogonal
polynomial series. Embedding the asymptotic behavior near the fracture tip into
the polynomial series, we find very rapid convergence: a suitably accurate
solution is obtained with two terms of the series. This closed-form solution
facilitates clear comparisons between the results and parameters for laminar
and turbulent hydraulic fractures. In particular, it resolves one of the well
known problems whereby calibration of models to data has difficulty
simultaneously matching the hydraulic fracture length and wellbore pressure.


title:
Super-character theory and comparison arguments for a random walk on the
  upper triangular matrices

abstract:
  Consider the random walk on the $n \times n$ upper triangular matrices with
ones on the diagonal and elements over $\mathbb{F}_p$ where we pick a row at
random and either add it or subtract it from the row directly above it. The
main result of this paper is to prove that the dependency of the mixing time on
$p$ is $p^2$. This is proven by combining super-character theory and comparison
theory arguments.


title: Urban Energy Flux: Human Mobility as a Predictor for Spatial Changes

abstract:
  As a key energy challenge, we urgently require a better understanding of how
growing urban populations interact with municipal energy systems and the
resulting impact on energy demand across city neighborhoods, which are dense
hubs of both consumer population and CO2 emissions. Currently, the physical
characteristics of urban infrastructure are the main determinants in predictive
modeling of the demand side of energy in our rapidly growing urban areas;
overlooking influence related to fluctuating human activities. Here, we show
how applying intra-urban human mobility as an indicator for interactions of the
population with local energy systems can be translated into spatial imprints to
predict the spatial distribution of energy use in urban settings. Our findings
establish human mobility as an important element in explaining the spatial
structure underlying urban energy flux and demonstrate the utility of a human
mobility driven approach for predicting future urban energy demand with
implications for CO2 emission strategies.


title: Combinatorial Repairability for Threshold Schemes

abstract:
  In this paper, we consider methods whereby a subset of players in a
$(k,n)$-threshold scheme can "repair" another player's share in the event that
their share has been lost or corrupted. This will take place without the
participation of the dealer who set up the scheme. The repairing protocol
should not compromise the (unconditional) security of the threshold scheme, and
it should be efficient, where efficiency is measured in terms of the amount of
information exchanged during the repairing process. We study two approaches to
repairing. The first method is based on the "enrollment protocol" from
\cite{NSG} which was originally developed to add a new player to a threshold
scheme (without the participation of the dealer) after the scheme was set up.
The second method distributes "multiple shares" to each player, as defined by a
suitable combinatorial design. This method results in larger shares, but lower
communication complexity, as compared to the first method.


title:
Quantum Circuit Design of Integer Division Optimizing Ancillary Qubits
  and T-Count

abstract:
  In this paper, we present Clifford+T gates based quantum circuit design of
integer division having $n$ ancillary qubits. The proposed quantum circuit is
based on restoring division algorithm. The proposed quantum circuit of integer
division consists of (i) quantum circuitry of conditional addition operation,
(ii) quantum circuitry of integer subtraction. To design ancillary and T-count
optimized design of quantum integer division, the optimized quantum circuit
design of integer conditional addition operation and integer subtraction are
presented. The proposed quantum integer division circuitry has 50\% improvement
in terms of ancillary qubits, and 90\% improvement in terms of T-count compared
to the existing design of integer quantum division based on quantum fourier
transform.


title:
An explicit Ricci potential for the Universal Moduli Space of Vector
  Bundles

abstract:
  In this paper we modify the coordinate construction in our previous paper on
the universal moduli space of pair consisting of a Riemann Surfaces and a
stable holomorphic bundles on the Riemann Surface, so as to produce a new set
of coordinates, which are in fact K\" ahler coordinates on this universal
moduli space. Further, we give a functional determinant formula for the Ricci
potential of the universal moduli space.


title: The Curvature of the Hitchin Connection

abstract:
  In this paper we calculate the curvature of the Hitchin connection. We
further show that a slight (possibly trivial) modification of the Hitchin
connection has curvature equal to an explict given multiple of the
Weil-Petersen symplectic form on Teichm\"{u}ller space.


title:
Entangling one polariton with a photon: effect of interactions on a
  single-polariton quantum state

abstract:
  Polaritons are quasi-particles originating from the coupling of light with
matter that demonstrated quantum phenomena at the many-particle mesoscopic
level, such as BEC and superfluidity. A highly sought and long-time missing
feature of polaritons is a genuine quantum manifestation of their dynamics at
the single-particle level. Although they are conceptually perceived as
entangled states and theoretical proposals abound for an explicit manifestation
of their single-particle properties, so far their behaviour has remained fully
accountable for by classical and mean-field theories. In this Article, we
report the first experimental demonstration of a genuinely-quantum
manifestation of microcavity polaritons, by swapping, in a two-photon entangled
state generated by parametric down-conversion, a photon for a polariton.
Furthermore, we show how single polaritons are affected by polariton-polariton
interactions in a propaedeutic demonstration of their qualities for quantum
information applications.


title: Positively ratioed representations

abstract:
  Let S be a closed orientable surface of genus at least 2 and let G be a
semisimple real algebraic group of non-compact type. We consider a class of
representations from the fundamental group of S to G called positively ratioed
representations. These are Anosov representations with the additional condition
that certain associated cross ratios satisfy a positivity property. Examples of
such representations include Hitchin representations and maximal
representations. Using geodesic currents, we show that the corresponding length
functions for these positively ratioed representations are well-behaved. In
particular, we prove a systolic inequality that holds for all such positively
ratioed representations.


title:
Measuring out-of-time-order correlators on a nuclear magnetic resonance
  quantum simulator

abstract:
  The idea of the out-of-time-order correlator (OTOC) has recently emerged in
the study of both condensed matter systems and gravitational systems. It not
only plays a key role in investigating the holographic duality between a
strongly interacting quantum system and a gravitational system, but also
diagnoses the chaotic behavior of many-body quantum systems and characterizes
the information scrambling. Based on the OTOCs, three different concepts --
quantum chaos, holographic duality, and information scrambling -- are found to
be intimately related to each other. Despite of its theoretical importance, the
experimental measurement of the OTOC is quite challenging and so far there is
no experimental measurement of the OTOC for local operators. Here we report the
measurement of OTOCs of local operators for an Ising spin chain on a nuclear
magnetic resonance quantum simulator. We observe that the OTOC behaves
differently in the integrable and non-integrable cases. Based on the recent
discovered relationship between OTOCs and the growth of entanglement entropy in
the many-body system, we extract the entanglement entropy from the measured
OTOCs, which clearly shows that the information entropy oscillates in time for
integrable models and scrambles for non-intgrable models. With the measured
OTOCs, we also obtain the experimental result of the butterfly velocity, which
measures the speed of correlation propagation. Our experiment paves a way for
experimentally studying quantum chaos, holographic duality, and information
scrambling in many-body quantum systems with quantum simulators.


title: Linear polychromatic colorings of hypercube faces

abstract:
  A coloring of the $\ell$-dimensional faces of $Q_n$ is called
$d$-polychromatic if every embedded $Q_d$ has every color on at least one face.
Denote by $p^\ell(d)$ the maximum number of colors such that any $Q_n$ can be
colored in this way. We provide a new lower bound on $p^\ell(d)$ for $\ell >
1$.


title:
Adaptive broadening to improve spectral resolution in the numerical
  renormalization group

abstract:
  We propose an adaptive scheme of broadening the discrete spectral data from
numerical renormalization group (NRG) calculations to improve the resolution of
dynamical properties at finite energies. While the conventional scheme
overbroadens narrow features at large frequency by broadening discrete weights
with constant width in log-frequency, our scheme broadens each discrete
contribution individually based on its sensitivity to a z-shift in the
logarithmic discretization intervals. We demonstrate that the adaptive
broadening better resolves various features in non-interacting and interacting
models at comparable computational cost. The resolution enhancement is more
significant for coarser discretization as typically required in multi-band
calculations. At low frequency below the energy scale of temperature, the
discrete NRG data necessarily needs to be broadened on a linear scale. Here we
provide a method that minimizes transition artefacts in between these
broadening kernels.


title: Gasparyan's Inequality

abstract:
  We consider a new and simpler proof of an inequality of A.S. Gasparyan, which
was originally derived in terms of complex algebraical objects ---
multidimensional hyperdeterminants. Our proof is much simpler and use only
standard technics such as mean inequalities. The main theorem on Gini means is
essentially used. Some corollaries and problems are considered.


title: Contextuality of Identical Particles

abstract:
  A generalisation of quantum contextuality to the case of many indentical
particles is presented. The model consists of a finite collection of modes that
can be occupied by N particles, either bosons or fermions. Measurement
scenarios allow one to measure occupation of each mode in at least two
different measurement contexts. The system is said to be non-contextual if the
occupation numbers can be assigned to modes in each measurement scenario. The
assignment is done under the non-contextuality assumption, i.e., an occupation
number assigned to a mode does not depend on a scenario in which this mode is
measured. In addition, the total number of particles has to be conserved,
therefore the sum of occupation numbers in each measurement context is equal to
N. For N=1 the model does not differ from the standard contextuality scenario.
However, for N>1 the problem reveals new complex features. In particular, it is
shown that a type of contextuality exhibited by the system (state-dependent,
state-independent, or non-contextual) depends on the type and the number of
particles. Further properties of this model and open problems are also
discussed.


title:
Microscopic model of quantum butterfly effect: out-of-time-order
  correlators and traveling combustion waves

abstract:
  We extend the Keldysh technique to enable the computation of out-of-time
order correlators. We show that the behavior of these correlators is described
by equations that display initially an exponential instability which is
followed by a linear propagation of the decoherence between two initially
identically copies of the quantum many body systems with interactions. At large
times the decoherence propagation (quantum butterfly effect) is described by a
diffusion equation with non-linear dissipation known in the theory of
combustion waves. The solution of this equation is a propagating non-linear
wave moving with constant velocity despite the diffusive character of the
underlying dynamics. Our general conclusions are illustrated by the detailed
computations for the specific models describing the electrons interacting with
bosonic degrees of freedom (phonons, two-level-systems etc.) or with each
other.


title:
Analysis of the distribution of precipitable water vapor in the
  Chajnantor area

abstract:
  In this work, we present results from a long-term precipitable water vapor
(PWV) study in the Chajnantor area, in northern Chile. Data from several
instruments located at relevant sites for sub-millimeter and mid-infrared
astronomy were processed to obtain relations between the atmospheric conditions
among the sites. The data used for this study can be considered the richest
dataset to date, because of the geographical sampling of the region, including
sites at different altitudes, a time span from 2005 to 2014, and the different
techniques and instruments used for the measurements. We validate a method to
convert atmospheric opacity from 350 $\mu$m tipper radiometers to PWV. An
average of 0.68 PWV ratio between Cerro Chajnantor and Llano of Chajnantor was
found.


title: Fully stable cosmological solutions with a non-singular classical bounce

abstract:
  We recently showed how it is possible to use a cubic Galileon action to
construct classical cosmological solutions that enter a contracting null energy
condition (NEC) violating phase, bounce at finite values of the scale factor
and exit into an expanding NEC-satisfying phase without encountering any
singularities or pathologies. A drawback of these examples is that singular
behavior is encountered at some time either just before or just after the
NEC-violating phase. In this Letter, we show that it is possible to circumvent
this problem by extending our method to actions that include the next order
${\cal L}_4$ Galileon interaction. Using this approach, we construct
non-singular classical bouncing cosmological solutions that are
non-pathological for all times.


title:
Gradient flow and entropy inequalities for quantum Markov semigroups
  with detailed balance

abstract:
  We study a class of ergodic quantum Markov semigroups on finite-dimensional
unital $C^*$-algebras. These semigroups have a unique stationary state
$\sigma$, and we are concerned with those that satisfy a quantum detailed
balance condition with respect to $\sigma$. We show that the evolution on the
set of states that is given by such a quantum Markov semigroup is gradient flow
for the relative entropy with respect to $\sigma$ in a particular Riemannian
metric on the set of states. This metric is a non-commutative analog of the
$2$-Wasserstein metric, and in several interesting cases we are able to show,
in analogy with work of Otto on gradient flows with respect to the classical
$2$-Wasserstein metric, that the relative entropy is strictly and uniformly
convex with respect to the Riemannian metric introduced here. As a consequence,
we obtain a number of new inequalities for the decay of relative entropy for
ergodic quantum Markov semigroups with detailed balance.


title:
Dimension reduction in MHD power generation models: dimensional analysis
  and active subspaces

abstract:
  Magnetohydrodynamics (MHD)---the study of electrically conducting
fluids---can be harnessed to produce efficient, low-emissions power generation.
Today, computational modeling assists engineers in studying candidate designs
for such generators. However, these models are computationally expensive, so
studying the effects of the model's many input parameters on output predictions
is typically infeasible. We study two approaches for reducing the input
dimension of the models: (i) classical dimensional analysis based on the
inputs' units and (ii) active subspaces, which reveal low-dimensional subspaces
in the space of inputs that affect the outputs the most. We also review the
mathematical connection between the two approaches that leads to consistent
application. The dimension reduction yields insights into the driving factors
in the MHD power generation models. We study both the simplified Hartmann
problem, which admits closed form expressions for the quantities of interest,
and a large-scale computational model with adjoint capabilities that enable the
derivative computations needed to estimate the active subspaces.


title:
Derivation of Capture Probabilities for the Corotation Eccentric Mean
  Motion Resonances

abstract:
  We study in this paper the capture of a massless particle into an isolated,
first order Corotation Eccentric Resonance (CER), in the framework of the
Planar, Eccentric and Restricted Three-Body problem near a m+1:m mean motion
commensurability (m integer). While capture into Lindblad Eccentric Resonances
(where the perturber's orbit is circular) has been investigated years ago,
capture into CER (where the perturber's orbit is elliptic) has not yet been
investigated in detail. Here, we derive the generic equations of motion near a
CER in the general case where both the perturber and the test particle migrate.
We derive the probability of capture in that context, and we examine more
closely two particular cases: (i) if only the perturber is migrating, capture
is possible only if the migration is outward from the primary. Notably, the
probability of capture is independent of the way the perturber migrates
outward; (ii) if only the test particle is migrating, then capture is possible
only if the algebraic value of its migration rate is a decreasing function of
orbital radius. In this case, the probability of capture is proportional to the
radial gradient of migration. These results differ from the capture into
Lindblad Eccentric Resonance (LER), where it is necessary that the orbits of
the perturber and the test particle converge for capture to be possible.
Possible applications for planetary satellites are discussed.


title: cf4ocl: a C framework for OpenCL

abstract:
  OpenCL is an open standard for parallel programming of heterogeneous compute
devices, such as GPUs, CPUs, DSPs or FPGAs. However, the verbosity of its C
host API can hinder application development. In this paper we present cf4ocl, a
software library for rapid development of OpenCL programs in pure C. It aims to
reduce the verbosity of the OpenCL API, offering straightforward memory
management, integrated profiling of events (e.g., kernel execution and data
transfers), simple but extensible device selection mechanism and user-friendly
error management. We compare two versions of a conceptual application example,
one based on cf4ocl, the other developed directly with the OpenCL host API.
Results show that the former is simpler to implement and offers more features,
at the cost of an effectively negligible computational overhead. Additionally,
the tools provided with cf4ocl allowed for a quick analysis on how to optimize
the application.


title: Conditional entropy of glueball states

abstract:
  The conditional entropy of glueball states is calculated using a holographic
description. Glueball states are represented by a supergravity dual picture,
consisting of a 5-dimensional graviton-dilaton action of a dynamical
holographic AdS/QCD model. The conditional entropy is studied as a function of
the glueball spin and of the mass, providing information about the stability of
the glueball states.


title: Charge Exchange Losses and Stochastic Acceleration in the Solar Wind

abstract:
  Stochastic acceleration of particles under a pressure balance condition can
accommodate the universal $p^{-5}$ spectra observed under many different
conditions in the inner heliosphere. In this model, in order to avoid an
infinite build up of particle pressure, a relationship between the momentum
diffusion of particles and the adiabatic deceleration in the solar wind must
exist. This constrains both the spatial and momentum diffusion coefficients and
results in the $p^{-5}$ spectrum in the presence of adiabatic losses in the
solar wind. However, this theory cannot explain the presence of such spectra
beyond the termination shock, where adiabatic deceleration is negligible. To
explain this apparent discrepancy, we include the effect of charge exchange
losses, resulting in new forms of both the spatial and momentum diffusion
coefficients that have not previously been considered. Assuming that the
turbulence is of a large-scale compressible nature, we find that a balance
between momentum diffusion and losses can still readily lead to the creation of
$p^{-5}$ suprathermal tails, including those found in the outer heliosphere.


title: Numerical analytic continuation: Answers to well-posed questions

abstract:
  We formulate the problem of numerical analytic continuation in a way that
lets us draw meaningful conclusions about properties of the spectral function
based solely on the input data. Apart from ensuring consistency with the input
data (within their error bars) and the {\it a priori} and {\it a posteriori}
(conditional) constraints, it is crucial to reliably characterize the
accuracy---or even ambiguity---of the output. We explain how these challenges
can be met with two approaches: stochastic optimization with consistent
constraints and the modified maximum entropy method. We perform illustrative
tests for spectra with a double-peak structure, where we critically examine
which spectral properties are accessible and which ones are lost. For an
important practical example, we apply our protocol to the Fermi polaron
problem.


title: Repeated compositions of Moebius transformations

abstract:
  This paper considers a class of dynamical systems generated by finite sets of
Moebius transformations acting on the unit disc. Compositions of such Moebius
transformations give rise to sequences of transformations that are used in the
theory of continued fractions. In that theory, the distinction between
sequences of limit-point type and sequences of limit-disc type is of central
importance. We prove that sequences of limit-disc type only arise in particular
circumstances, and we give necessary and sufficient conditions for a sequence
to be of limit-disc type. We also calculate the Hausdorff dimension of the set
of sequences of limit-disc type in some significant cases. Finally, we obtain
strong and complete results on the convergence of these dynamical systems.


title:
The fourth moment of quadratic Dirichlet $L$--functions over function
  fields

abstract:
  We obtain an asymptotic formula for the fourth moment of quadratic Dirichlet
$L$--functions over $\mathbb{F}_q[x]$, as the base field $\mathbb{F}_q$ is
fixed and the genus of the family goes to infinity. According to conjectures of
Andrade and Keating, we expect the fourth moment to be asymptotic to $q^{2g+1}
P(2g+1)$ up to an error of size $o(q^{2g+1})$, where $P$ is a polynomial of
degree $10$ with explicit coefficients. We prove an asymptotic formula with the
leading three terms, which agrees with the conjectured result.


title:
Series-Expansion Thermal Tensor Network Approach for Quantum Lattice
  Models

abstract:
  In this work we propose a series-expansion thermal tensor network (SETTN)
approach for efficient simulations of quantum lattice models. This
continuous-time SETTN method is based on the numerically exact Taylor series
expansion of equilibrium density operator $e^{-\beta H}$ (with $H$ the total
Hamiltonian and $\beta$ the imaginary time), and is thus Trotter-error free. We
discover, through simulating XXZ spin chain and square-lattice quantum Ising
models, that not only the Hamiltonian $H$, but also its powers $H^n$, can be
efficiently expressed as matrix product operators, which enables us to
calculate with high precision the equilibrium and dynamical properties of
quantum lattice models at finite temperatures. Our SETTN method provides an
alternative to conventional Trotter-Suzuki renormalization group (RG)
approaches, and achieves an unprecedented standard of thermal RG simulations in
terms of accuracy and flexibility.


title: $L_h^2$-functions in unbounded balanced domains

abstract:
  We investigate problems related with the existence of square integrable
holomorphic functions on (unbounded) balanced domains. In particular, we solve
the problem of Wiegerinck for balanced domains in dimension two. We also give a
description of $L_h^2$-domains of holomorphy in the class of balanced domains
and present a purely algebraic criterion for homogeneous polynomials to be
square integrable in a pseudoconvex balanced domain in $\mathbb C^2$. This
allows easily to decide which pseudoconvex balanced domain in $\mathbb C^2$ has
a positive Bergman kernel and which admits the Bergman metric.


title:
Reactive magnetron sputter deposition of superconducting niobium
  titanium nitride thin films with different target sizes

abstract:
  The superconducting critical temperature (Tc > 15K) of niobium titanium
nitride (NbTiN) thin films allows for low-loss circuits up to 1.1 THz, enabling
on-chip spectroscopy and multi-pixel imaging with advanced detectors. The drive
for large scale detector microchips is demanding NbTiN films with uniform
properties over an increasingly larger area. This article provides an
experimental comparison between two reactive d.c. sputter systems with
different target sizes: a small target (100mm diameter) and a large target (127
mm x 444.5 mm). This article focuses on maximizing the Tc of the films and the
accompanying I-V characteristics of the sputter plasma, and we find that both
systems are capable of depositing films with Tc > 15 K. The resulting film
uniformity is presented in a second manuscript in this volume. We find that
these films are deposited within the transition from metallic to compound
sputtering, at the point where target nitridation most strongly depends on
nitrogen flow. Key in the deposition optimization is to increase the system's
pumping speed and gas flows to counteract the hysteretic effects induced by the
target size. Using the I-V characteristics as a guide proves to be an effective
way to optimize a reactive sputter system, for it can show whether the optimal
deposition regime is hysteresis-free and accessible.


title: Minimal and minimum unit circular-arc models

abstract:
  A proper circular-arc (PCA) model is a pair ${\cal M} = (C, \cal A)$ where
$C$ is a circle and $\cal A$ is a family of inclusion-free arcs on $C$ in which
no two arcs of $\cal A$ cover $C$. A PCA model $\cal U = (C,\cal A)$ is a $(c,
\ell)$-CA model when $C$ has circumference $c$, all the arcs in $\cal A$ have
length $\ell$, and all the extremes of the arcs in $\cal A$ are at a distance
at least $1$. If $c \leq c'$ and $\ell \leq \ell'$ for every $(c', \ell')$-CA
model equivalent (resp. isomorphic) to $\cal U$, then $\cal U$ is minimal
(resp. minimum). In this article we prove that every PCA model is isomorphic to
a minimum model. Our main tool is a new characterization of those PCA models
that are equivalent to $(c,\ell)$-CA models, that allows us to conclude that
$c$ and $\ell$ are integer when $\cal U$ is minimal. As a consequence, we
obtain an $O(n^3)$ time and $O(n^2)$ space algorithm to solve the minimal
representation problem, while we prove that the minimum representation problem
is NP-complete.


title:
Newton flows for elliptic functions I Structural stability:
  Characterization & Genericity

abstract:
  Newton flows are dynamical systems generated by a continuous, desingularized
Newton method for mappings from a Euclidean space to itself. We focus on the
special case of meromorphic functions on the complex plane. Inspired by the
analogy between the rational (complex) and the elliptic (i.e., doubly periodic
meromorphic) functions, a theory on the class of so-called Elliptic Newton
flows is developed.
  With respect to an appropriate topology on the set of all elliptic functions
$f$ of fixed order $ r (\geqslant 2)$ we prove: For almost all functions $f$,
the corresponding Newton flows are structurally stable i.e., topologically
invariant under small perturbations of the zeros and poles for $f$ [
genericity]. They can be described in terms of nondegeneracy-properties of $f$
similar to the rational case [characterization].


title:
Engineering and probing topological properties of Dirac semimetal films
  by asymmetric charge transfer

abstract:
  Dirac semimetals (DSMs) have topologically robust three-dimensional Dirac
(doubled Weyl) nodes with Fermi-arc states. In heterostructures involving DSMs,
charge transfer occurs at the interfaces, which can be used to probe and
control their bulk and surface topological properties through surface-bulk
connectivity. Here we demonstrate that despite a band gap in DSM films,
asymmetric charge transfer at the surface enables one to accurately identify
locations of the Dirac-node projections from gapless band crossings and to
examine and engineer properties of the topological Fermi-arc surface states
connecting the projections, by simulating adatom-adsorbed DSM films using a
first-principles method with an effective model. The positions of the
Dirac-node projections are insensitive to charge transfer amount or slab
thickness except for extremely thin films. By varying the amount of charge
transfer, unique spin textures near the projections and a separation between
the Fermi-arc states change, which can be observed by gating without adatoms.


title: On finite Morse index solutions to the quadharmonic Lane-Emden equation

abstract:
  In this paper, we compute the Joseph-Lundgren exponent for the quadharmonic
Lane-Emden equation, derive a monotonicity formula and classify the finite
Morse index solution to the following quadharmonic Lane-Emden equation:
\noindent \begin{equation}\nonumber \Delta^4
u=|u|^{p-1}u\;\;\;\;\hbox{in}\;\;\;\;\; \R^n. \end{equation} As a byproduct, we
also get a monotonicity formula for the quadharmonic maps $ \Delta^4 u=0$.


title: A collective phase in resource competition in a highly diverse ecosystem

abstract:
  Organisms shape their own environment, which in turn affects their survival.
This feedback becomes especially important for communities containing a large
number of species; however, few existing approaches allow studying this regime,
except in simulations. Here, we use methods of statistical physics to
analytically solve a classic ecological model of resource competition
introduced by MacArthur in 1969. We show that the non-intuitive phenomenology
of highly diverse ecosystems includes a phase where the environment constructed
by the community becomes fully decoupled from the outside world.


title: Emergence of a Turbulent Cascade in a Quantum Gas

abstract:
  In the modern understanding of turbulence, a central concept is the existence
of cascades of excitations from large to small lengthscales, or vice-versa.
This concept was introduced in 1941 by Kolmogorov and Obukhov, and the
phenomenon has since been observed in a variety of systems, including
interplanetary plasmas, supernovae, ocean waves, and financial markets. Despite
a lot of progress, quantitative understanding of turbulence remains a challenge
due to the interplay of many lengthscales that usually thwarts theoretical
simulations of realistic experimental conditions. Here we observe the emergence
of a turbulent cascade in a weakly interacting homogeneous Bose gas, a quantum
fluid that is amenable to a theoretical description on all relevant
lengthscales. We prepare a Bose-Einstein condensate (BEC) in an optical box,
drive it out of equilibrium with an oscillating force that pumps energy into
the system at the largest lengthscale, study the BEC's nonlinear response to
the periodic drive, and observe a gradual development of a cascade
characterised by an isotropic power-law distribution in momentum space. We
numerically model our experiments using the Gross-Pitaevskii equation (GPE) and
find excellent agreement with the measurements. Our experiments establish the
uniform Bose gas as a promising new platform for investigating many aspects of
turbulence, including the interplay of vortex and wave turbulence and the
relative importance of quantum and classical effects.

categories: cond-mat.quant-gas physics.atom-ph physics.flu-dyn quant-ph


title: Weakening Gravity on Redshift-Survey Scales with Kinetic Matter Mixing

abstract:
  We explore general scalar-tensor models in the presence of a kinetic mixing
between matter and the scalar field, which we call Kinetic Matter Mixing. In
the frame where gravity is de-mixed from the scalar this is due to disformal
couplings of matter species to the gravitational sector, with disformal
coefficients that depend on the gradient of the scalar field. In the frame
where matter is minimally coupled, it originates from the so-called beyond
Horndeski quadratic Lagrangian. We extend the Effective Theory of Interacting
Dark Energy by allowing disformal coupling coefficients to depend on the
gradient of the scalar field as well. In this very general approach, we derive
the conditions to avoid ghost and gradient instabilities and we define Kinetic
Matter Mixing independently of the frame metric used to described the action.
We study its phenomenological consequences for a $\Lambda$CDM background
evolution, first analytically on small scales. Then, we compute the matter
power spectrum and the angular spectra of the CMB anisotropies and the CMB
lensing potential, on all scales. We employ the public version of COOP, a
numerical Einstein-Boltzmann solver that implements very general scalar-tensor
modifications of gravity. Rather uniquely, Kinetic Matter Mixing weakens
gravity on short scales, predicting a lower $\sigma_8$ with respect to the
$\Lambda$CDM case. We propose this as a possible solution to the tension
between the CMB best-fit model and low-redshift observables.


title: Lipschitz Embeddings of Random Fields

abstract:
  We consider the problem of embedding one i.i.d.\ collection of Bernoulli
random variables indexed by $\mathbb{Z}^d$ into an independent copy in an
injective $M$-Lipschitz manner. For the case $d=1$, it was shown by Basu and
Sly (PTRF, 2014) to be possible almost surely for sufficiently large $M$. In
this paper we provide a multi-scale argument extending this result to higher
dimensions.


title:
Options as Silver Bullets: Valuation of Term Loans, Inventory
  Management, Emissions Trading and Insurance Risk Mitigation using Option
  Theory

abstract:
  Models to price long term loans in the securities lending business are
developed. These longer horizon deals can be viewed as contracts with
optionality embedded in them. This insight leads to the usage of established
methods from derivatives theory to price such contracts. Numerical simulations
are used to demonstrate the practical applicability of these models. The
techniques advanced here can lead to greater synergies between the management
of derivative and delta-one trading desks, perhaps even being able to combine
certain aspects of the day to day operations of these seemingly disparate
entities. These models are part of one of the least explored, yet profit laden,
areas of modern investment management.
  A heuristic is developed to mitigate any loss of information, which might set
in when parameters are estimated first and then the valuations are performed,
by directly calculating valuations using the historical time series. This
approach to valuations can lead to reduced models errors, robust estimation
systems, greater financial stability and economic strength. An illustration is
provided regarding how the methodologies developed here could be useful for
inventory management, emissions trading and insurance risk mitigation. All
these techniques could have applications for dealing with other financial
instruments, non-financial commodities and many forms of uncertainty.


title: The mechanical modes of a $2$-periodic triangulated surface

abstract:
  A recent "hidden symmetry" conjecture of B. Gin-ge Chen et al is resolved,
concerning the dimension of the mechanical modes of a generic $2$-periodic
triangulated surface $O$ in $R^3$ whose structure graph corresponds to a
triangular tiling of $R^2$. We introduce an indexing of the terms in an
associated sparse determinant $p_O(z_1, z_2)$ by means of oriented
$3$-colourings of the underlying sparse graph, and use this and vertex
splitting arguments to show that $p_O(z_1,z_2)$ is palindromic or
antipalindromic, up to a shift index. This implies the conjectured dimension
$1$ phenomenon for these surfaces. As a corollary we obtain the topological
stability of the generic modes of a $1$-periodic triangulated nanotube.


title: Small Representations of Finite Classical Groups

abstract:
  Finite group theorists have established many formulas that express
interesting properties of a finite group in terms of sums of characters of the
group. An obstacle to applying these formulas is lack of control over the
dimensions of representations of the group. In particular, the representations
of small dimensions tend to contribute the largest terms to these sums, so a
systematic knowledge of these small representations could lead to proofs of
important conjectures which are currently out of reach. Despite the
classification by Lusztig of the irreducible representations of finite groups
of Lie type, it seems that this aspect remains obscure. In this note we develop
a language which seems to be adequate for the description of the "small"
representations of finite classical groups and puts in the forefront the notion
of rank of a representation. We describe a method, the "eta correspondence", to
construct small representations, and we conjecture that our construction is
exhaustive. We also give a strong estimate on the dimension of small
representations in terms of their rank. For the sake of clarity, in this note
we describe in detail only the case of the finite symplectic groups.


title:
OpenSBLI: A framework for the automated derivation and parallel
  execution of finite difference solvers on a range of computer architectures

abstract:
  Exascale computing will feature novel and potentially disruptive hardware
architectures. Exploiting these to their full potential is non-trivial.
Numerical modelling frameworks involving finite difference methods are
currently limited by the 'static' nature of the hand-coded discretisation
schemes and repeatedly may have to be re-written to run efficiently on new
hardware. In contrast, OpenSBLI uses code generation to derive the model's code
from a high-level specification. Users focus on the equations to solve, whilst
not concerning themselves with the detailed implementation. Source-to-source
translation is used to tailor the code and enable its execution on a variety of
hardware.


title:
Status Report: A Detector for Measuring the Ground State Hyperfine
  Splitting of Antihydrogen

abstract:
  The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons)
collaboration at the Antiproton Decelerator at CERN aims to measure the ground
state hyperfine structure of antihydrogen. A Rabi-like spectrometer line has
been built for this purpose. A detector for counting antihydrogen is located at
the end of the beam line. This contribution will focus on the tracking
detector, whose challenging task it is to discriminate between background
events and antiproton annihilations originating from antihydrogen atoms which
are produced only in small amounts.


title:
Violating the no-signaling principle with classical inseparable beams in
  an optical parity-time symmetric system

abstract:
  We show that the no-signaling principle can be violated with classical
inseparable beams in the presence of a parity-time (PT) symmetric subsystem.
Thus, the problems associated to PT-symmetric quantum theories recently
discovered by Lee et al. [Phys. Rev. Lett. 112, 130404 (2014)] are not
exclusive to quantum mechanics, but already exist in the classical case. The
possibility to implement local optical PT-symmetric subsystems via light-matter
interactions enables the experimental exploration of local PT symmetry and
subtle quantum concepts via classical analogues.


title: Molecular gas in the star-forming region IRAS 08589-4714

abstract:
  We present an analysis of the region IRAS 08589-4714 with the aim of
characterizing the molecular environment. We observed the CO(3-2),
^{13}CO(3-2), C^{18}O(3-2), HCO+(3-2), and HCN(3-2) molecular lines in a region
of 150" x 150", centered on the IRAS source, to analyze the distribution and
characteristics of the molecular gas linked to the IRAS source. The molecular
gas distribution reveals a molecular clump that is coincident with IRAS
08589-4714 and with a dust clump detected at 1.2 mm. The molecular clump is
0.45 pc in radius and its mass and H_2 volume density are 310 Mo and 1.2 x 10^4
cm^{-3}, respectively. Two overdensities were identified within the clump in
HCN and HCO lines. A comparison of the LTE and virial masses suggests that the
clump is collapsing in regions that harbor young stellar objects. An analysis
of the molecular lines suggests that they are driving molecular outflows.


title: Punctures for Theories of Class $\mathcal{S}_\Gamma$

abstract:
  With the aim of understanding compactifications of 6D superconformal field
theories to four dimensions, we study punctures for theories of class
$\mathcal{S}_{\Gamma}$. The class $\mathcal{S}_{\Gamma}$ theories arise from
M5-branes probing $\mathbb{C}^2 / \Gamma$, an ADE singularity. The resulting 4D
theories descend from compactification on Riemann surfaces decorated with
punctures. We show that for class $\mathcal{S}_{\Gamma}$ theories, a puncture
is specified by singular boundary conditions for fields in the 5D quiver gauge
theory obtained from compactification of the 6D theory on a cylinder geometry.
We determine general boundary conditions and study in detail solutions with
first order poles. This yields a generalization of the Nahm pole data present
for $1/2$ BPS punctures for theories of class $\mathcal{S}$. Focusing on
specific algebraic structures, we show how the standard discussion of nilpotent
orbits and its connection to representations of $\mathfrak{su}(2)$ generalizes
in this broader context.


title:
A sharper view of Pal 5's tails: Discovery of stream perturbations with
  a novel non-parametric technique

abstract:
  Only in the Milky Way is it possible to conduct an experiment which uses
stellar streams to detect low-mass dark matter subhaloes. In smooth and static
host potentials, tidal tails of disrupting satellites appear highly symmetric.
However, perturbations from dark subhaloes, as well as from GMCs and the Milky
Way bar, can induce density fluctuations that destroy this symmetry. Motivated
by the recent release of unprecedentedly deep and wide imaging data around the
Pal~5 stellar stream, we develop a new probabilistic, adaptive and
non-parametric technique which allows us to bring the cluster's tidal tails
into clear focus. Strikingly, we uncover a stream whose density exhibits
visible changes on a variety of angular scales. We detect significant bumps and
dips, both narrow and broad: two peaks on either side of the progenitor, each
only a fraction of a degree across, and two gaps, $\sim2^{\circ}$ and
$\sim9^{\circ}$ wide, the latter accompanied by a gargantuan lump of debris.
This largest density feature results in a pronounced inter-tail asymmetry which
cannot be made consistent with an unperturbed stream according to a suite of
simulations we have produced. We conjecture that the sharp peaks around Pal 5
are epicyclic overdensities, while the two dips are consistent with impacts by
subhaloes. Assuming an age of 3.4 Gyr for Pal 5, these two gaps would
correspond to the characteristic size of gaps created by subhaloes in the mass
range of $10^6-10^7 M_\odot$ and $10^7-10^8 M_\odot$ respectively. In addition
to dark substructure, we find that the bar of the Milky Way can plausibly
produce the asymmetric density seen in Pal 5 and that GMCs could cause the
smaller gap.


title:
The search for failed supernovae with the Large Binocular Telescope:
  confirmation of a disappearing star

abstract:
  We present Hubble Space Telescope imaging confirming the optical
disappearance of the failed supernova (SN) candidate identified by Gerke et al.
(2015). This $\sim 25~M_{\odot}$ red supergiant experienced a weak $\sim
10^{6}~L_{\odot}$ optical outburst in 2009 and is now at least 5 magnitudes
fainter than the progenitor in the optical. The mid-IR flux has slowly
decreased to the lowest levels since the first measurements in 2004. There is
faint ($2000-3000~L_{\odot}$) near-IR emission likely associated with the
source. We find the late-time evolution of the source to be inconsistent with
obscuration from an ejected, dusty shell. Models of the spectral energy
distribution indicate that the remaining bolometric luminosity is $>6$ times
fainter than that of the progenitor and is decreasing as $\sim t^{-4/3}$. We
conclude that the transient is unlikely to be a SN impostor or stellar merger.
The event is consistent with the ejection of the envelope of a red supergiant
in a failed SN and the late-time emission could be powered by fallback
accretion onto a newly-formed black hole. Future IR and X-ray observations are
needed to confirm this interpretation of the fate for the star.


title:
Testing the imprint of non-standard cosmologies on void profiles using
  Monte Carlo random walks

abstract:
  Using a Monte Carlo random walks of a log-normal distribution, we show how to
qualitatively study void properties for non-standard cosmologies. We apply this
method to an f(R) modified gravity model and recover the N-body simulation
results of (Achitouv et al. 2016) for the void profiles and their deviation
from GR. This method can potentially be extended to study other properties of
the large scale structures such as the abundance of voids or overdense
environments. We also introduce a new way to identify voids in the cosmic web,
using only a few measurements of the density fluctuations around random
positions. This algorithm allows to select voids with specific profiles and
radii. As a consequence, we can target classes of voids with higher differences
between f(R) and standard gravity void profiles. Finally we apply our void
criteria to galaxy mock catalogues and discuss how the flexibility of our void
finder can be used to reduce systematics errors when probing the growth rate in
the galaxy-void correlation function.


title: Subwavelength-width optical tunnel junctions for ultracold atoms

abstract:
  We propose a new method for creating far-field optical barrier potentials for
ultracold atoms with widths that are narrower than the diffraction limit and
can approach tens of nanometers. The reduced widths stem from the nonlinear
atomic response to control fields that create spatially varying dark
resonances. The subwavelenth barrier is the result of the geometric scalar
potential experienced by an atom prepared in such a spatially varying dark
state. The performance of this technique, as well as its applications to the
study of many-body physics and to the implementation of quantum information
protocols with ultracold atoms, are discussed, with a focus on the
implementation of tunnel junctions.


title:
Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity:
  Stability, ringdown, and gravitational-wave emission

abstract:
  Gravitational waves emitted by distorted black holes---such as those arising
from the coalescence of two neutron stars or black holes---carry not only
information about the corresponding spacetime but also about the underlying
theory of gravity. Although general relativity remains the simplest, most
elegant and viable theory of gravitation, there are generic and robust
arguments indicating that it is not the ultimate description of the
gravitational universe. Here we focus on a particularly appealing extension of
general relativity, which corrects Einstein's theory through the addition of
terms which are second order in curvature: the topological Gauss-Bonnet
invariant coupled to a dilaton. We study gravitational-wave emission from black
holes in this theory, and {\bf(i)} find strong evidence that black holes are
linearly (mode) stable against both axial and polar perturbations; {\bf(ii)}
discuss how the quasinormal modes of black holes can be excited during
collisions involving black holes, and finally {\bf(iii)} show that future
ringdown detections with large signal-to-noise ratio would improve current
constraints on the coupling parameter of the theory.


title: Holographic Entanglement Entropy

abstract:
  We review the developments in the past decade on holographic entanglement
entropy, a subject that has garnered much attention owing to its potential to
teach us about the emergence of spacetime in holography. We provide an
introduction to the concept of entanglement entropy in quantum field theories,
review the holographic proposals for computing the same, providing some
justification for where these proposals arise from in the first two parts. The
final part addresses recent developments linking entanglement and geometry. We
provide an overview of the various arguments and technical developments that
teach us how to use field theory entanglement to detect geometry. Our
discussion is by design eclectic; we have chosen to focus on developments that
appear to us most promising for further insights into the holographic map.
  This is a draft of a few chapters of a book which will appear sometime in the
near future, to be published by Springer. The book in addition contains a
discussion of application of holographic ideas to computation of entanglement
entropy in strongly coupled field theories, and discussion of tensor networks
and holography, which we have chosen to exclude from the current manuscript.


title: Statistical Bubble Localization with Random Interactions

abstract:
  We study one-dimensional spinless fermions with random interactions, but
without any on-site disorder. We find that random interactions generically
stabilize a many-body localized phase, in spite of the completely extended
single-particle degrees of freedom. In the large randomness limit, we construct
"bubble-neck" eigenstates having a universal area-law entanglement entropy on
average, with the number of volume-law states being exponentially suppressed.
We argue that this statistical localization is beyond the phenomenological
local-integrals-of-motion description of many-body localization. With exact
diagonalization, we confirm the robustness of the many-body localized phase at
finite randomness by investigating eigenstate properties such as level
statistics, entanglement/participation entropies, and nonergodic quantum
dynamics. At weak random interactions, the system develops a thermalization
transition when the single-particle hopping becomes dominant.

categories: cond-mat.stat-mech cond-mat.dis-nn cond-mat.quant-gas quant-ph


title:
keV Sterile Neutrino Dark Matter from Singlet Scalar Decays: The Most
  General Case

abstract:
  We investigate the early Universe production of sterile neutrino Dark Matter
by the decays of singlet scalars. All previous studies applied simplifying
assumptions and/or studied the process only on the level of number densities,
which makes it impossible to give statements about cosmic structure formation.
We overcome these issues by dropping all simplifying assumptions (except for
one we showed earlier to work perfectly) and by computing the full course of
Dark Matter production on the level of non-thermal momentum distribution
functions. We are thus in the position to study all aspects of the resulting
settings and apply all relevant bounds in a reliable manner. We have a
particular focus on how to incorporate bounds from structure formation on the
level of the linear power spectrum, since the simplistic estimate using the
free-streaming horizon clearly fails for highly non-thermal distributions. Our
work comprises the most detailed and comprehensive study of sterile neutrino
Dark Matter production by scalar decays presented so far.


title:
Next-to-leading order unitarity fits in Two-Higgs-Doublet models with
  soft $\mathbb{Z}_2$ breaking

abstract:
  We fit the next-to-leading order unitarity conditions to the
Two-Higgs-Doublet model with a softly broken $\mathbb{Z}_2$ symmetry. In doing
so, we alleviate the existing uncertainty on how to treat higher order
corrections to quartic couplings of its Higgs potential. A simplified approach
to implementing the next-to-leading order unitarity conditions is presented.
These new bounds are then combined with all other relevant constraints,
including the complete set of LHC Run I data. The upper $95\%$ bounds we find
are $4.2$ on the absolute values of the quartic couplings, and $235$ GeV ($100$
GeV) for the mass degeneracies between the heavy Higgs particles in the type I
(type II) scenario. In type II, we exclude an unbroken $\mathbb{Z}_2$ symmetry
with a probability of $95\%$. All fits are performed using the open-source code
HEPfit.


title:
ALMA HCN and HCO+ J=3-2 observations of optical Seyfert and luminous
  infrared galaxies -- Confirmation of elevated HCN-to-HCO+ flux ratios in AGNs
  --

abstract:
  We present the results of our ALMA observations of three AGN-dominated nuclei
in optical Seyfert 1 galaxies (NGC 7469, I Zw 1, and IC 4329 A) and eleven
luminous infrared galaxies (LIRGs) with various levels of infrared estimated
energetic contributions by AGNs at the HCN and HCO+ J=3-2 emission lines. The
HCN and HCO+ J=3-2 emission lines are clearly detected at the main nuclei of
all sources, except for IC 4329 A. The vibrationally excited (v2=1f) HCN J=3-2
and HCO+ J=3-2 emission lines are simultaneously covered, and HCN v2=1f J=3-2
emission line signatures are seen in the main nuclei of two LIRGs, IRAS
12112+0305 and IRAS 22491-1808, neither of which show clear buried AGN
signatures in the infrared. If the vibrational excitation is dominated by
infrared radiative pumping, through the absorption of infrared 14 um photons,
primarily originating from AGN-heated hot dust emission, then these two LIRGs
may contain infrared-elusive, but (sub)millimeter-detectable, extremely deeply
buried AGNs. These vibrationally excited emission lines are not detected in the
three AGN-dominated optical Seyfert 1 nuclei. However, the observed HCN v2=1f
to v=0 flux ratios in these optical Seyferts are still consistent with the
intrinsic flux ratios in LIRGs with detectable HCN v2=1f emission lines. The
observed HCN-to-HCO+ J=3-2 flux ratios tend to be higher in galactic nuclei
with luminous AGN signatures compared with starburst-dominated regions, as
previously seen at J=1-0 and J=4-3.


title:
Gravitational wave extraction in higher dimensional numerical relativity
  using the Weyl tensor

abstract:
  Gravitational waves are one of the most important diagnostic tools in the
analysis of strong-gravity dynamics and have been turned into an observational
channel with LIGO's detection of GW150914. Aside from their importance in
astrophysics, black holes and compact matter distributions have also assumed a
central role in many other branches of physics. These applications often
involve spacetimes with $D>4$ dimensions where the calculation of gravitational
waves is more involved than in the four dimensional case, but has now become
possible thanks to substantial progress in the theoretical study of general
relativity in $D>4$. Here, we develop a numerical implementation of the
formalism by Godazgar and Reall (Ref.[1]) -- based on projections of the Weyl
tensor analogous to the Newman-Penrose scalars -- that allows for the
calculation of gravitational waves in higher dimensional spacetimes with
rotational symmetry. We apply and test this method in black-hole head-on
collisions from rest in $D=6$ spacetime dimensions and find that a fraction
$(8.19\pm 0.05)\times 10^{-4}$ of the Arnowitt-Deser-Misner mass is radiated
away from the system, in excellent agreement with literature results based on
the Kodama-Ishibashi perturbation technique. The method presented here
complements the perturbative approach by automatically including contributions
from all multipoles rather than computing the energy content of individual
multipoles.


title:
Living on a Flare: Relativistic Reflection in V404 Cyg Observed by
  NuSTAR During its Summer 2015 Outburst

abstract:
  We present first results from a series of $NuSTAR$ observations of the black
hole X-ray binary V404 Cyg obtained during its summer 2015 outburst, primarily
focusing on observations during the height of this outburst activity. The
$NuSTAR$ data show extreme variability in both the flux and spectral properties
of the source. This is partly driven by strong and variable line-of-sight
absorption, similar to previous outbursts. The latter stages of this
observation are dominated by strong flares, reaching luminosities close to
Eddington. During these flares, the central source appears to be relatively
unobscured and the data show clear evidence for a strong contribution from
relativistic reflection, providing a means to probe the geometry of the
innermost accretion flow. Based on the flare properties, analogy with other
Galactic black hole binaries, and also the simultaneous onset of radio
activity, we argue that this intense X-ray flaring is related to transient jet
activity during which the ejected plasma is the primary source of illumination
for the accretion disk. If this is the case, then our reflection modelling
implies that these jets are launched in close proximity to the black hole (as
close as a few gravitational radii), consistent with expectations for jet
launching models that tap either the spin of the central black hole, or the
very innermost accretion disk. Our analysis also allows us to place the first
constraints on the black hole spin for this source, which we find to be $a^* >
0.92$ (99% statistical uncertainty, based on an idealized lamppost geometry).


title: New insight on the origin of the double red clump in the Milky Way bulge

abstract:
  The double red clump (RC) observed in the Milky Way bulge is widely
interpreted as evidence for an X-shaped structure. We have recently suggested,
however, an alternative interpretation based on the multiple population
phenomenon, where the bright RC is from helium enhanced second-generation stars
(G2), while the faint RC is representing first-generation stars (G1) with
normal helium abundance. Here our RC models are constructed in a large
parameter space to see the effects of metallicity, age, and helium abundance on
the double RC feature. Our models show that the luminosity of RC stars is
mainly affected by helium abundance, while the RC color is primarily affected
by metallicity. The effect of age is relatively small, unless it is older than
12 Gyr or much younger than 6 Gyr. The observed double RC feature can therefore
be reproduced in a relatively large parameter space, once {\Delta}Y between G2
and G1 is assumed to be greater than $\sim$0.10. We further show that the
longitude dependence of the double RC feature at $b \approx -8.5 \deg$, which
was pointed out by Gonzalez et al. (2015) as a potential problem of our model,
is well explained in our scenario by a classical bulge embedded in a tilted
bar.


title:
SpaceTime from Hilbert Space: Decompositions of Hilbert Space as
  Instances of Time

abstract:
  There has been recent interest in identifying entanglement as the fundamental
concept from which space may emerge. We note that the particular way that a
Hilbert space is decomposed into tensor factors is important in what the
resulting geometry looks like. We then propose that time may be regarded as a
variable that parameterizes a family of such decompositions, thus giving rise
to a family of spatial geometries. As a proof of concept, this idea is
demonstrated in two toy models based on Kitaev's toric code, which feature a
dynamical change of dimension and topology.


title:
Snap, Crackle, Pop: sub-grid supernova feedback in AMR simulations of
  disk galaxies

abstract:
  We compare 5 sub-grid models for supernova (SN) feedback in adaptive mesh
refinement (AMR) simulations of isolated dwarf and L-star disk galaxies with
20-40 pc resolution. The models are thermal dump, stochastic thermal,
'mechanical' (injecting energy or momentum depending on the resolution),
kinetic, and delayed cooling feedback. We focus on the ability of each model to
suppress star formation and generate outflows. Our highest-resolution runs
marginally resolve the adiabatic phase of the feedback events, which correspond
to 40 SN explosions, and the first three models yield nearly identical results,
possibly indicating that kinetic and delayed cooling feedback converge to wrong
results. At lower resolution all models differ, with thermal dump feedback
becoming inefficient. Thermal dump, stochastic, and mechanical feedback
generate multiphase outflows with mass loading factors $\beta \ll 1$, which is
much lower than observed. For the case of stochastic feedback we compare to
published SPH simulations, and find much lower outflow rates. Kinetic feedback
yields fast, hot outflows with $\beta\sim 1$, but only if the wind is in effect
hydrodynamically decoupled from the disk by using a large bubble radius.
Delayed cooling generates cold, dense and slow winds with $\beta> 1$, but large
amounts of gas occupy regions of temperature-density space with short cooling
times. We conclude that either our resolution is too low to warrant physically
motivated models for SN feedback, that feedback mechanisms other than SNe are
important, or that other aspects of galaxy evolution, such as star formation,
require better treatment.


title:
Slowly decaying resonances of charged massive scalar fields in the
  Reissner-Nordstr\"om black-hole spacetime

abstract:
  We determine the characteristic timescales associated with the linearized
relaxation dynamics of the composed
Reissner-Nordstr\"om-black-hole-charged-massive-scalar-field system. To that
end, the quasinormal resonant frequencies
$\{\omega_n(\mu,q,M,Q)\}_{n=0}^{n=\infty}$ which characterize the dynamics of a
charged scalar field of mass $\mu$ and charge coupling constant $q$ in the
charged Reissner-Nordstr\"om black-hole spacetime of mass $M$ and electric
charge $Q$ are determined {\it analytically} in the eikonal regime $1\ll
M\mu<qQ$. Interestingly, we find that, for a given value of the dimensionless
black-hole electric charge $Q/M$, the imaginary part of the resonant
oscillation frequency is a monotonically {\it decreasing} function of the
dimensionless ratio $\mu/q$. In particular, it is shown that the quasinormal
resonance spectrum is characterized by the asymptotic behavior $\Im\omega\to0$
in the limiting case $M\mu\to qQ$. This intriguing finding implies that the
composed Reissner-Nordstr\"om-black-hole-charged-massive-scalar-field system is
characterized by extremely long relaxation times $\tau_{\text{relax}}\equiv
1/\Im\omega\to\infty$ in the $M\mu/qQ\to 1^-$ limit.


title:
The shape of the inner Milky Way halo from observations of the Pal 5 and
  GD-1 stellar streams

abstract:
  We constrain the shape of the Milky Way's halo by dynamical modeling of the
observed phase-space tracks of the Pal 5 and GD-1 tidal streams. We find that
the only information about the potential gleaned from the tracks of these
streams are precise measurements of the shape of the gravitational
potential---the ratio of vertical to radial acceleration---at the location of
the streams, with weaker constraints on the radial and vertical accelerations
separately. The latter will improve significantly with precise proper-motion
measurements from Gaia. We measure that the overall potential flattening is
0.95 +/- 0.04 at the location of GD-1 ([R,z] ~ [12.5,6.7] kpc) and 0.94 +/-
0.05 at the position of Pal 5 ([R,z] ~ [8.4,16.8] kpc). Combined with
constraints on the force field near the Galactic disk, we determine that the
axis ratio of the dark-matter halo's density distribution is 1.05 +/- 0.14
within the inner 20 kpc, with a hint that the halo becomes more flattened near
the edge of this volume. The halo mass within 20 kpc is 1.1 +/- 0.1 x 10^{11}
M_sun. A dark-matter halo this close to spherical is in tension with the
predictions from numerical simulations of the formation of dark-matter halos.


title:
SDSS-IV MaNGA: Faint quenched galaxies I- Sample selection and evidence
  for environmental quenching

abstract:
  Using kinematic maps from the Sloan Digital Sky Survey (SDSS) Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA) survey, we reveal that the
majority of low-mass quenched galaxies exhibit coherent rotation in their
stellar kinematics. Our sample includes all 39 quenched low-mass galaxies
observed in the first year of MaNGA. The galaxies are selected with $M_{r} >
-19.1$, stellar masses $10^{9}$ M$_{\odot} < M_{\star} < 5\times10^{9}$
M$_{\odot}$, EW$_{H\alpha} <2$ \AA, and all have red colours $(u-r)>1.9$. They
lie on the size-magnitude and $\sigma$-luminosity relations for previously
studied dwarf galaxies. Just six ($15\pm5.7$ per cent) are found to have
rotation speeds $v_{e,rot} < 15$ km s$^{-1}$ at $\sim1$ $R_{e}$, and may be
dominated by pressure support at all radii. Two galaxies in our sample have
kinematically distinct cores in their stellar component, likely the result of
accretion. Six contain ionised gas despite not hosting ongoing star formation,
and this gas is typically kinematically misaligned from their stellar
component. This is the first large-scale Integral Field Unit (IFU) study of low
mass galaxies selected without bias against low-density environments.
Nevertheless, we find the majority of these galaxies are within $\sim1.5$ Mpc
of a bright neighbour ($M_{K} < -23$; or M$_{\star} > 5\times10^{10}$
M$_{\odot}$), supporting the hypothesis that galaxy-galaxy or galaxy-group
interactions quench star formation in low-mass galaxies. The local bright
galaxy density for our sample is $\rho_{proj} = 8.2\pm2.0$ Mpc$^{-2}$, compared
to $\rho_{proj} = 2.1\pm0.4$ Mpc$^{-2}$ for a star forming comparison sample,
confirming that the quenched low mass galaxies are preferentially found in
higher density environments.


title: Secondary Cosmic Positrons in an Inhomogeneous Diffusion Model

abstract:
  One aim of cosmic ray measurements is the search for possible signatures of
annihilating or decaying dark matter. The so-called positron excess has
attracted a lot of attention in this context. On the other hand it has been
proposed that the data might challenge the established diffusion model for
cosmic ray propagation. We investigate an inhomogeneous diffusion model by
solving the corresponding equations analytically. Depending on the propagation
parameters we find that the spectral features of the positron spectrum are
affected significantly. We also discuss the influence of the inhomogeneity on
hadronic spectra.


title: The properties of "dark" {\Lambda}CDM halos in the Local Group

abstract:
  We examine the baryon content of low-mass {\Lambda}CDM halos
$(10^8<M_{200}/{\rm M_\odot}<5\times 10^{9})$ using the APOSTLE cosmological
hydrodynamical simulations. Most of these systems are free of stars and have a
gaseous content set by the combined effects of cosmic reionization, which
imposes a mass-dependent upper limit, and of ram pressure stripping, which
reduces it further in high-density regions. Halos mainly affected by
reionization (RELHICs; REionization-Limited HI Clouds) inhabit preferentially
low-density regions and make up a population where the gas is in hydrostatic
equilibrium with the dark matter potential and in thermal equilibrium with the
ionizing UV background. Their thermodynamic properties are well specified, and
their gas density and temperature profiles may be predicted in detail. Gas in
RELHICs is nearly fully ionized but with neutral cores that span a large range
of HI masses and column densities and have negligible non-thermal broadening.
We present predictions for their characteristic sizes and central column
densities: the massive tail of the distribution should be within reach of
future blind HI surveys. Local Group RELHICs (LGRs) have some properties
consistent with observed Ultra Compact High Velocity Clouds (UCHVCs) but the
sheer number of the latter suggests that most UCHVCs are not RELHICs. Our
results suggest that LGRs (i) should typically be beyond 500 kpc from the Milky
Way or M31; (ii) have positive Galactocentric radial velocities; (iii) HI sizes
not exceeding 1 kpc, and (iv) should be nearly round. The detection and
characterization of RELHICs would offer a unique probe of the small-scale
clustering of cold dark matter.


title:
Evidence for multiple populations in the intermediate age cluster
  Lindsay 1 in the SMC

abstract:
  Lindsay 1 is an intermediate age (approx 8 Gyr) massive cluster in the Small
Magellanic Cloud (SMC). Using VLT FORS2 spectra of 16 probable cluster members
on the lower RGB of the cluster, we measure CN and CH band strengths (at 3883
and 4300 Angstroms respectively), along with carbon and nitrogen abundances and
find that a sub-population of stars has significant nitrogen enrichment. A lack
of spread in carbon abundances excludes evolutionary mixing as the source of
this enrichment, so we conclude that this is evidence of multiple populations.
Therefore, L1 is the youngest cluster to show such variations, implying that
the process triggering the onset of multiple populations must operate until at
least redshift ~1.


title:
Hund's induced Fermi-liquid instabilities and enhanced quasiparticle
  interactions

abstract:
  Hund's coupling is shown to generally favor, in a doped half-filled Mott
insulator, an increase in the compressibility culminating in a Fermi-liquid
instability towards phase separation. The largest effect is found about the
frontier between an ordinary and an orbitally-decoupled ("Hund's") metal. The
increased compressibility implies an enhancement of quasiparticle scattering,
thus favoring other possible symmetry breakings. This physics is shown to
happen in simulations of the 122 Fe-based superconductors, possibly implying
the relevance of this mechanism in the enhancement of the the critical
temperature for superconductivity.


title:
SDSS IV MaNGA: The global and local stellar mass assemby histories of
  galaxies

abstract:
  By means of the fossil record method implemented through Pipe3D, we
reconstruct the global and radial stellar mass growth histories (MGHs) of an
unprecedentedly large sample of galaxies, ranging from dwarf to giant objects,
from the "Mapping Nearby Galaxies at the Apache Point Observatory" survey. We
confirm that the main driver of the global MGHs is mass, with more massive
galaxies assembling their masses earlier (downsizing), though for a given mass,
the global MGHs segregate by color, specific star formation rate (sSFR), and
morphological type. From the inferred radial mean MGHs, we find that at the
late evolutionary stages (or for fractions of assembled mass larger than ~
80%), the innermost regions formed stars on average earlier than the outermost
ones (inside-out). At earlier epochs, when the age resolution of the method
becomes poor, the mass assembly seems to be spatially homogeneous or even in
the outside-in mode, specially for the red/quiescent/early-type galaxies. The
innermost MGHs are in general more regular (less scatter around the mean) than
the outermost ones. For dwarf and low-mass galaxies, we do not find evidence of
an outside-in formation mode; instead their radial MGHs are very diverse most
of the time, with periods of outside- in and inside-out modes (or strong radial
migration), suggesting this an episodic SF history. Blue/star-forming/late-type
galaxies present on average a significantly more pronounced inside-out
formation mode than red/quiescent/early-type galaxies, independently of mass.
We discuss our results in the light of the processes of galaxy formation,
quenching, and radial migration. We discuss also on the uncertainties and
biases of the fossil record method and how they could affect our results.


title: The E-ELT Multi-Object Spectrograph: latest news from MOSAIC

abstract:
  There are 8000 galaxies, including 1600 at z larger than 1.6, which could be
simultaneously observed in an E-ELT field of view of 40 sq. arcmin. A
considerable fraction of astrophysical discoveries require large statistical
samples, which can only be obtained with multi-object spectrographs (MOS).
MOSAIC will provide a vast discovery space, enabled by a multiplex of 200 and
spectral resolving powers of R=5000 and 20000. MOSAIC will also offer the
unique capability of more than 10 "high-definition" (multi-object adaptive
optics, MOAO) integral-field units, optimised to investigate the physics of the
sources of reionization. The combination of these modes will make MOSAIC the
world-leading MOS facility, contributing to all fields of contemporary
astronomy, from extra-solar planets, to the study of the halo of the Milky Way
and its satellites, and from resolved stellar populations in nearby galaxies
out to observations of the earliest "first-light" structures in the Universe.
It will also study the distribution of the dark and ordinary matter at all
scales and epochs of the Universe. Recent studies of critical technical issues
such as sky-background subtraction and MOAO have demonstrated that such a MOS
is feasible with state-of-the-art technology and techniques. Current studies of
the MOSAIC team include further trade-offs on the wavelength coverage, a
solution for compensating for the non-telecentric new design of the telescope,
and tests of the saturation of skylines especially in the near-IR bands. In the
2020s the E-ELT will become the world's largest optical/IR telescope, and we
argue that it has to be equipped as soon as possible with a MOS to provide the
most efficient, and likely the best way to follow-up on James Webb Space
Telescope (JWST) observations.


title: Local Pauli stabilizers of symmetric hypergraph states

abstract:
  Hypergraph states of many quantum bits share the rich interplay between
simple combinatorial description and nontrivial entanglement properties enjoyed
by the graph states that they generalize. In this paper, we consider hypergraph
states that are also permutationally invariant. We characterize the states in
this class that have nontrivial local Pauli stabilizers and give applications
to nonlocality and error correction.