title: I(FIB)F: Iterated Bloom Filters for Routing in Named Data Networks

abstract:
  Named Data Networks provide a clean-slate redesign of the Future Internet for
efficient content distribution. Because Internet of Things are expected to
compose a significant part of Future Internet, most content will be managed by
constrained devices. Such devices are often equipped with limited CPU, memory,
bandwidth, and energy supply. However, the current Named Data Networks design
neglects the specific requirements of Internet of Things scenarios and many
data structures need to be further optimised. The purpose of this research is
to provide an efficient strategy to route in Named Data Networks by
constructing a Forwarding Information Base using Iterated Bloom Filters defined
as I(FIB)F. We propose the use of content names based on iterative hashes. This
strategy leads to reduce the overhead of packets. Moreover, the memory and the
complexity required in the forwarding strategy are lower than in current
solutions. We compare our proposal with solutions based on hierarchical names
and Standard Bloom Filters. We show how to further optimise I(FIB)F by
exploiting the structure information contained in hierarchical content names.
Finally, two strategies may be followed to reduce: (i) the overall memory for
routing or (ii) the probability of false positives.


title:
Proximity-induced minimum radius of superconducting thin rings closed by
  the Josephson 0 or pi junction

abstract:
  Superconductivity is shown to be completely destroyed in thin mesoscopic or
nanoscopic rings closed by the junction with a noticeable interfacial pair
breaking and/or a Josephson coupling, if a ring's radius r is less than the
minimum radius r_min. The quantity r_min depends on the phase difference across
the junction, or on the magnetic flux that controls the phase difference in the
flux-biased ring. It also depends on the Josephson and interfacial effective
coupling constants, and in particular, on whether the ring is closed by 0 or pi
junction. The current-phase relation is substantially modified when the ring's
radius exceeds r_min for some of the phase difference values, or slightly goes
beyond its maximum. The modified critical temperature Tc, as well as the
temperature dependent supercurrent near Tc are identified here as functions of
the ring's radius and the magnetic flux.


title:
Joint functional calculus in algebra of polynomial tempered
  distributions

abstract:
  In this paper we develop a functional calculus for a countable system of
generators of contraction strongly continuous semigroups. As a symbol class of
such calculus we use the algebra of polynomial tempered distributions. We prove
a differential property of constructed calculus and describe its image with the
help of the commutant of polynomial shift semigroup. As an application, we
consider a function of countable set of second derivative operators.


title:
Modeling the differentiation of A- and C-type baroreceptor firing
  patterns

abstract:
  The baroreceptor neurons serve as the primary transducers of blood pressure
for the autonomic nervous system and are thus critical in enabling the body to
respond effectively to changes in blood pressure. These neurons can be
separated into two types (A and C) based on the myelination of their axons and
their distinct firing patterns elicited in response to specific pressure
stimuli. This study has developed a comprehensive model of the afferent
baroreceptor discharge built on physiological knowledge of arterial wall
mechanics, firing rate responses to controlled pressure stimuli, and ion
channel dynamics within the baroreceptor neurons. With this model, we were able
to predict firing rates observed in previously published experiments in both A-
and C-type neurons. These results were obtained by adjusting model parameters
determining the maximal ion-channel conductances. The observed variation in the
model parameters are hypothesized to correspond to physiological differences
between A- and C-type neurons. In agreement with published experimental
observations, our simulations suggest that a twofold lower potassium
conductance in C-type neurons is responsible for the observed sustained basal
firing, whereas a tenfold higher mechanosensitive conductance is responsible
for the greater firing rate observed in A-type neurons. A better understanding
of the difference between the two neuron types can potentially be used to gain
more insight into the underlying pathophysiology facilitating development of
targeted interventions improving baroreflex function in diseased individuals,
e.g. in patients with autonomic failure, a syndrome that is difficult to
diagnose in terms of its pathophysiology.


title:
W production at LHC: lepton angular distributions and reference frames
  for probing hard QCD

abstract:
  Precision tests of the Standard Model in the Strong and Electroweak sectors
play an important role, among the physics goals of LHC experiments. Because of
the nature of proton-proton processes, observables based on the measurement of
the direction and energy of leptons provide the most precise signatures.
  In the present paper, we concentrate on the angular distribution of leptons
from W to l nu decays in the lepton-pair rest-frame. The vector nature of the
intermediate state imposes that distributions are to a good precision described
by spherical polynomials of at most second order. We argue, that contrary to
general belief often expressed in the literature, the full set of angular
coefficients can be measured experimentally, despite the presence in the final
state of neutrino escaping detection. There is thus no principle difference
with respect to the phenomenology of the Z/gamma to l^+ l^- Drell-Yan process.
  We show also, that with the proper choice of the coordinate frames, only one
coefficient in this polynomial decomposition remains sizable, even in the
presence of one or more high p_T jets. The necessary stochastic choice of the
frames relies on probabilities independent from any coupling constants. In this
way, electroweak effects (dominated by the V-A nature of W couplings to
fermions) can be better separated from the ones of strong interactions. The
separation is convenient for the measurements interpretation.


title: Zero-Annihilator Graphs of Commutative Rings

abstract:
  Assume that $R$ is a commutative ring with nonzero identity. In this paper,
we introduce and investigate zero-annihilator graph of $R$ denoted by
$\mathtt{ZA}(R)$. It is the graph whose vertex set is the set of all nonzero
nonunit elements of $R$ and two distinct vertices $x$ and $y$ are adjacent
whenever ${\rm Ann}_R(x)\cap {\rm Ann}_R(y)=\{0\}$.


title: Pathways to Naturally Small Dirac Neutrino Masses

abstract:
  If neutrinos are truly Dirac fermions, the smallness of their masses may
still be natural if certain symmetries exist beyond those of the standard model
of quarks and leptons. We perform a systematic study of how this may occur at
tree level and in one loop. We also propose a scotogenic version of the
left-right gauge model with naturally small Dirac neutrino masses in one loop.


title: A quadratic divisor problem and moments of the Riemann zeta-function

abstract:
  We estimate asymptotically the fourth moment of the Riemann zeta-function
twisted by a Dirichlet polynomial of length $T^{\frac14 - \varepsilon}$. Our
work relies crucially on Watt's theorem on averages of Kloosterman fractions.
In the context of the twisted fourth moment, Watt's result is an optimal
replacement for Selberg's eigenvalue conjecture.
  Our work extends the previous result of Hughes and Young, where Dirichlet
polynomials of length $T^{\frac{1}{11}-\varepsilon}$ were considered. Our
result has several applications, among others to the proportion of critical
zeros of the Riemann zeta-function, zero spacing and lower bounds for moments.
  Along the way we obtain an asymptotic formula for a quadratic divisor
problem, where the condition $a m_1 m_2 - b n_1 n_2 = h$ is summed with smooth
averaging on the variables $m_1, m_2, n_1, n_2, h$ and arbitrary weights in the
average on $a,b$. Using Watt's work allows us to exploit all averages
simultaneously. It turns out that averaging over $m_1, m_2, n_1, n_2, h$ right
away in the quadratic divisor problem simplifies considerably the combinatorics
of the main terms in the twisted fourth moment.


title: Non-commutative formality implies commutative and Lie formality

abstract:
  Over a field of characteristic zero we prove two formality conditions. We
prove that a dg Lie algebra is formal if and only if its universal enveloping
algebra is formal. We also prove that a commutative dg algebra is formal as a
dg associative algebra if and only if it is formal as a commutative dg algebra.
We present some consequences of these theorems in rational homotopy theory.


title: Importance sampling type estimators based on approximate marginal MCMC

abstract:
  We consider importance sampling (IS) type weighted estimators based on Markov
chain Monte Carlo (MCMC) targeting an approximate marginal of the target
distribution. In the context of Bayesian latent variable models, the MCMC
typically operates on the hyperparameters, and the subsequent weighting may be
based on IS or sequential Monte Carlo (SMC), but allows for multilevel
techniques as well. The IS approach provides a natural alternative to delayed
acceptance (DA) pseudo-marginal/particle MCMC, and has many advantages over DA,
including a straightforward parallelisation and additional flexibility in MCMC
implementation. We detail minimal conditions which ensure strong consistency of
the suggested estimators, and provide central limit theorems with expressions
for asymptotic variances. We demonstrate how our method can make use of SMC in
the state space models context, using Laplace approximations and
time-discretised diffusions. Our experimental results are promising and show
that the IS type approach can provide substantial gains relative to an
analogous DA scheme, and is often competitive even without parallelisation.


title:
Quantum-Assisted Learning of Hardware-Embedded Probabilistic Graphical
  Models

abstract:
  Mainstream machine-learning techniques such as deep learning and
probabilistic programming rely heavily on sampling from generally intractable
probability distributions. There is increasing interest in the potential
advantages of using quantum computing technologies as sampling engines to speed
up these tasks or to make them more effective. However, some pressing
challenges in state-of-the-art quantum annealers have to be overcome before we
can assess their actual performance. The sparse connectivity, resulting from
the local interaction between quantum bits in physical hardware
implementations, is considered the most severe limitation to the quality of
constructing powerful generative unsupervised machine-learning models. Here we
use embedding techniques to add redundancy to data sets, allowing us to
increase the modeling capacity of quantum annealers. We illustrate our findings
by training hardware-embedded graphical models on a binarized data set of
handwritten digits and two synthetic data sets in experiments with up to 940
quantum bits. Our model can be trained in quantum hardware without full
knowledge of the effective parameters specifying the corresponding quantum
Gibbs-like distribution; therefore, this approach avoids the need to infer the
effective temperature at each iteration, speeding up learning; it also
mitigates the effect of noise in the control parameters, making it robust to
deviations from the reference Gibbs distribution. Our approach demonstrates the
feasibility of using quantum annealers for implementing generative models, and
it provides a suitable framework for benchmarking these quantum technologies on
machine-learning-related tasks.


title: Stochastic lattice dynamical systems with fractional noise

abstract:
  This article is devoted to study stochastic lattice dynamical systems driven
by a fractional Brownian motion with Hurst parameter $H\in(1/2,1)$. First of
all, we investigate the existence and uniqueness of pathwise mild solutions to
such systems by the Young integration setting and prove that the solution
generates a random dynamical system. Further, we analyze the exponential
stability of the trivial solution.


title: Modelling Void Abundance in Modified Gravity

abstract:
  We use a spherical model and an extended excursion set formalism with
drifting diffusive barriers to predict the abundance of cosmic voids in the
context of general relativity as well as f(R) and symmetron models of modified
gravity. We detect spherical voids from a suite of N-body simulations of these
gravity theories and compare the measured void abundance to theory predictions.
We find that our model correctly describes the abundance of both dark matter
and galaxy voids, providing a better fit than previous proposals in the
literature based on static barriers. We use the simulation abundance results to
fit for the abundance model free parameters as a function of modified gravity
parameters, and show that counts of dark matter voids can provide interesting
constraints on modified gravity. For galaxy voids, more closely related to
optical observations, we find that constraining modified gravity from void
abundance alone may be significantly more challenging. In the context of
current and upcoming galaxy surveys, the combination of void and halo
statistics including their abundances, profiles and correlations should be
effective in distinguishing modified gravity models that display different
screening mechanisms.


title: Supervised Learning in Spiking Neural Networks with FORCE Training

abstract:
  Populations of neurons display an extraordinary diversity in the behaviors
they affect and display. Machine learning techniques have recently emerged that
allow us to create networks of model neurons that display behaviours of similar
complexity. Here, we demonstrate the direct applicability of one such
technique, the FORCE method, to spiking neural networks. We train these
networks to mimic dynamical systems, classify inputs, and store discrete
sequences that correspond to the notes of a song. Finally, we use FORCE
training to create two biologically motivated model circuits. One is inspired
by the zebra-finch and successfully reproduces songbird singing. The second
network is motivated by the hippocampus and is trained to store and replay a
movie scene. FORCE trained networks reproduce behaviors comparable in
complexity to their inspired circuits and yield information not easily
obtainable with other techniques such as behavioral responses to
pharmacological manipulations and spike timing statistics.


title:
Congestion-Aware Randomized Routing in Autonomous Mobility-on-Demand
  Systems

abstract:
  In this paper we study the routing and rebalancing problem for a fleet of
autonomous vehicles providing on-demand transportation within a congested urban
road network (that is, a road network where traffic speed depends on vehicle
density). We show that the congestion-free routing and rebalancing problem is
NP-hard and provide a randomized algorithm which finds a low-congestion
solution to the routing and rebalancing problem that approximately minimizes
the number of vehicles on the road in polynomial time. We provide theoretical
bounds on the probability of violating the congestion constraints; we also
characterize the expected number of vehicles required by the solution with a
commonly-used empirical congestion model and provide a bound on the
approximation factor of the algorithm. Numerical experiments on a realistic
road network with real-world customer demands show that our algorithm
introduces very small amounts of congestion. The performance of our algorithm
in terms of travel times and required number of vehicles is very close to (and
sometimes better than) the optimal congestion-free solution.


title:
Steady-state skewness and kurtosis from renormalized cumulants in
  $(2+1)$-dimensional stochastic surface growth

abstract:
  The phenomenon of stochastic growth of a surface on a two-dimensional
substrate occurs in Nature in a variety of circumstances and its statistical
characterization requires the study of higher order cumulants. Here, we
consider the statistical cumulants of height fluctuations governed by the
$(2+1)$-dimensional KPZ equation for flat geometry. We follow a diagrammatic
scheme to derive the expressions for renormalized cumulants up to fourth order
in the stationary state. Assuming a value for the roughness exponent from
reliable numerical predictions, we calculate the second, third and fourth
cumulants, yielding skewness $S=0.2879$ and kurtosis $Q=0.1995$. These values
agree well with the available numerical estimations.


title: On the complexity of finite subgraphs of the curve graph

abstract:
  We say a graph has property $\mathcal{P}_{g,p}$ when it is an induced
subgraph of the curve graph of a surface of genus $g$ with $p$ punctures. Two
well-known graph invariants, the chromatic and clique numbers, can provide
obstructions to $\mathcal{P}_{g,p}$. We introduce a new invariant of a graph,
the 'nested complexity length', which provides a novel obstruction to
$\mathcal{P}_{g,p}$. For the curve graph this invariant captures the
topological complexity of the surface in graph-theoretic terms; indeed we show
that its value is $6g-6+2p$, i.e. twice the size of a maximal multicurve on the
surface. As a consequence we show that large half-graphs do not have
$\mathcal{P}_{g,p}$, and we deduce quantitatively that almost all finite graphs
which pass the chromatic and clique tests do not have $\mathcal{P}_{g,p}$. We
also reinterpret our obstruction in terms of the first-order theory of the
curve graph, and in terms of RAAG subgroups of the mapping class group
(following Kim and Koberda). Finally, we show that large multipartite subgraphs
cannot have $\mathcal{P}_{g,p}$. This allows us to compute the upper density of
the curve graph, and to conclude that clique size, chromatic number, and nested
complexity length are not sufficient to determine $\mathcal{P}_{g,p}$.


title: Learning Lexical Entries for Robotic Commands using Crowdsourcing

abstract:
  Robotic commands in natural language usually contain various spatial
descriptions that are semantically similar but syntactically different. Mapping
such syntactic variants into semantic concepts that can be understood by robots
is challenging due to the high flexibility of natural language expressions. To
tackle this problem, we collect robotic commands for navigation and
manipulation tasks using crowdsourcing. We further define a robot language and
use a generative machine translation model to translate robotic commands from
natural language to robot language. The main purpose of this paper is to
simulate the interaction process between human and robots using crowdsourcing
platforms, and investigate the possibility of translating natural language to
robot language with paraphrases.


title:
Homogeneous Yang-Baxter deformations as non-abelian duals of the AdS_5
  sigma-model

abstract:
  We propose that the Yang-Baxter deformation of the symmetric space
sigma-model parameterized by an r-matrix solving the homogeneous (classical)
Yang-Baxter equation is equivalent to the non-abelian dual of the undeformed
model with respect to a subgroup determined by the structure of the r-matrix.
We explicitly demonstrate this on numerous examples in the case of the AdS_5
sigma-model. The same should also be true for the full AdS_5 x S^5 supercoset
model, providing an explanation for and generalizing several recent
observations relating homogeneous Yang-Baxter deformations based on non-abelian
r-matrices to the undeformed AdS_5 x S^5 model by a combination of T-dualities
and non-linear coordinate redefinitions. This also includes the special case of
deformations based on abelian r-matrices, which correspond to TsT
transformations: they are equivalent to non-abelian duals of the original model
with respect to a central extension of abelian subalgebras.


title: Strong field ionization and gauge dependence of nonlocal potentials

abstract:
  Nonlocal potential models have been used in place of the Coulomb potential in
the Schrodinger equation as an efficient means of exploring high field
laser-atom interaction in previous works. Al- though these models have found
use in modeling phenomena including photo-ionization and ejected electron
momentum spectra, they are known to break electromagnetic gauge invariance.
This paper examines if there is a preferred gauge for the linear field response
and photoionization characteristics of nonlocal atomic binding potentials in
the length and velocity gauges. It is found that the length gauge is preferable
for a wide range of parameters.


title: Machine Learning Phases of Strongly Correlated Fermions

abstract:
  Machine learning offers an unprecedented perspective for the problem of
classifying phases in condensed matter physics. We employ neural-network
machine learning techniques to distinguish finite-temperature phases of the
strongly correlated fermions on cubic lattices. We show that a three
dimensional convolutional network trained on auxiliary field configurations
produced by quantum Monte Carlo simulations of the Hubbard model can correctly
predict the magnetic phase diagram of the model at the average density of one
(half filling). We then use the network, trained at half filling, to explore
the trend in the transition temperature as the system is doped away from half
filling. This transfer learning approach predicts that the instability to the
magnetic phase extends to at least 5% doping in this region. Our results pave
the way for other machine learning applications in correlated quantum many-body
systems.


title:
The Chandra COSMOS Legacy Survey: Clustering of X-ray selected AGN at
  2.9<z<5.5 using photometric redshift Probability Distribution Functions

abstract:
  We present the measurement of the projected and redshift space 2-point
correlation function (2pcf) of the new catalog of Chandra COSMOS-Legacy AGN at
2.9$\leq$z$\leq$5.5 ($\langle L_{bol} \rangle \sim$10$^{46}$ erg/s) using the
generalized clustering estimator based on phot-z probability distribution
functions (Pdfs) in addition to any available spec-z. We model the projected
2pcf estimated using $\pi_{max}$ = 200 h$^{-1}$ Mpc with the 2-halo term and we
derive a bias at z$\sim$3.4 equal to b = 6.6$^{+0.60}_{-0.55}$, which
corresponds to a typical mass of the hosting halos of log M$_h$ =
12.83$^{+0.12}_{-0.11}$ h$^{-1}$ M$_{\odot}$. A similar bias is derived using
the redshift-space 2pcf, modelled including the typical phot-z error $\sigma_z$
= 0.052 of our sample at z$\geq$2.9. Once we integrate the projected 2pcf up to
$\pi_{max}$ = 200 h$^{-1}$ Mpc, the bias of XMM and \textit{Chandra} COSMOS at
z=2.8 used in Allevato et al. (2014) is consistent with our results at higher
redshift. The results suggest only a slight increase of the bias factor of
COSMOS AGN at z$\gtrsim$3 with the typical hosting halo mass of moderate
luminosity AGN almost constant with redshift and equal to logM$_h$ =
12.92$^{+0.13}_{-0.18}$ at z=2.8 and log M$_h$ = 12.83$^{+0.12}_{-0.11}$ at
z$\sim$3.4, respectively. The observed redshift evolution of the bias of COSMOS
AGN implies that moderate luminosity AGN still inhabit group-sized halos at
z$\gtrsim$3, but slightly less massive than observed in different independent
studies using X-ray AGN at z$\leq2$.


title:
A light-stimulated neuromorphic device based on graphene hybrid
  phototransistor

abstract:
  Neuromorphic chip refers to an unconventional computing architecture that is
modelled on biological brains. It is ideally suited for processing sensory data
for intelligence computing, decision-making or context cognition. Despite rapid
development, conventional artificial synapses exhibit poor connection
flexibility and require separate data acquisition circuitry, resulting in
limited functionalities and significant hardware redundancy. Here we report a
novel light-stimulated artificial synapse based on a graphene-nanotube hybrid
phototransistor that can directly convert optical stimuli into a "neural image"
for further neuronal analysis. Our optically-driven synapses involve multiple
steps of plasticity mechanisms and importantly exhibit flexible tuning of both
short- and long-term plasticity. Furthermore, our neuromorphic phototransistor
can take multiple pre-synaptic light stimuli via wavelength-division
multiplexing and allows advanced optical processing through
charge-trap-mediated optical coupling. The capability of complex neuromorphic
functionalities in a simple silicon-compatible device paves the way for novel
neuromorphic computing architectures involving photonics.


title: Thermal Dark Matter From A Highly Decoupled Sector

abstract:
  It has recently been shown that if the dark matter is in thermal equilibrium
with a sector that is highly decoupled from the Standard Model, it can
freeze-out with an acceptable relic abundance, even if the dark matter is as
heavy as ~1-100 PeV. In such scenarios, both the dark and visible sectors are
populated after inflation, but with independent temperatures. The lightest
particle in the dark sector will be generically long-lived, and can come to
dominate the energy density of the universe. Upon decaying, these particles can
significantly reheat the visible sector, diluting the abundance of dark matter
and thus allowing for dark matter particles that are much heavier than
conventional WIMPs. In this paper, we present a systematic and pedagogical
treatment of the cosmological history in this class of models, emphasizing the
simplest scenarios in which a dark matter candidate annihilates into hidden
sector particles which then decay into visible matter through the vector,
Higgs, or lepton portals. In each case, we find ample parameter space in which
very heavy dark matter particles can provide an acceptable thermal relic
abundance. We also discuss possible extensions of models featuring these
dynamics.


title: Black hole formation in a contracting universe

abstract:
  We study the evolution of cosmological perturbations in a contracting
universe. We aim to determine under which conditions density perturbations grow
to form large inhomogeneities and collapse into black holes. Our method
consists in solving the cosmological perturbation equations in complete
generality for a hydrodynamical fluid. We then describe the evolution of the
fluctuations over the different length scales of interest and as a function of
the equation of state for the fluid, and we explore two different types of
initial conditions: quantum vacuum and thermal fluctuations. We also derive a
general requirement for black hole collapse on sub-Hubble scales, and we use
the Press-Schechter formalism to describe the black hole formation probability.
For a fluid with a small sound speed (e.g., dust), we find that both quantum
and thermal initial fluctuations grow in a contracting universe, and the
largest inhomogeneities that first collapse into black holes are of Hubble size
and the collapse occurs well before reaching the Planck scale. For a
radiation-dominated fluid, we find that no black hole can form before reaching
the Planck scale. In the context of matter bounce cosmology, it thus appears
that only models in which a radiation-dominated era begins early in the
cosmological evolution are robust against the formation of black holes. Yet,
the formation of black holes might be an interesting feature for other models.
We comment on a number of possible alternative early universe scenarios that
could take advantage of this feature.


title:
Staying away from the bar: the local dynamical signature of slow and
  fast bars in the Milky Way

abstract:
  Both the three-dimensional density of red clump giants and the gas kinematics
in the inner Galaxy indicate that the pattern speed of the Galactic bar could
be much lower than previously estimated. Here, we show that such slow bar
models are unable to reproduce the bimodality observed in local stellar
velocity space. We do so by computing the response of stars in the Solar
neighbourhood to the gravitational potential of slow and fast bars, in terms of
their perturbed distribution function in action-angle space up to second order,
as well as by identifying resonantly trapped orbits. We also check that the
bimodality is unlikely to be produced through perturbations from spiral arms,
and conclude that, contrary to gas kinematics, local stellar kinematics still
favour a fast bar in the Milky Way, with a pattern speed of the order of almost
twice (and no less than 1.8 times) the circular frequency at the Sun's
position. This leaves open the question of the nature of the long flat
extension of the bar in the Milky Way.


title:
One-loop supergravity on $\mathrm{AdS}_4\times S^7/\mathbb{Z}_k$ and
  comparison with ABJM theory

abstract:
  The large-$N$ limit of ABJM theory is holographically dual to M-theory on
AdS$_4\times S^7/\mathbb{Z}_k$. The 3-sphere partition function has been
obtained via localization, and its leading behavior $F_{\text{ABJM}}^{(0)}\sim
k^{1/2}N^{3/2}$ is exactly reproduced in the dual theory by tree-level
supergravity. We extend this comparison to the sub-leading $\mathcal O(N^0)$
order by computing the one-loop supergravity free energy as a function of $k$
and comparing it with the ABJM result. Curiously, we find that the expressions
do not match, with $F_{\text{SUGRA}}^{(1)}\sim k^6$, while
$F_{\text{ABJM}}^{(1)}\sim k^2$. This suggests that the low-energy
approximation $Z_{\text{M-theory}}=Z_{\text{SUGRA}}$ breaks down at one-loop
order.


title:
Imaging protoplanets: observing transition disks with non-redundant
  masking

abstract:
  Transition disks, protoplanetary disks with inner clearings, are promising
objects in which to directly image forming planets. The high contrast imaging
technique of non-redundant masking is well posed to detect planetary mass
companions at several to tens of AU in nearby transition disks. We present
non-redundant masking observations of the T Cha and LkCa 15 transition disks,
both of which host posited sub-stellar mass companions. However, due to a loss
of information intrinsic to the technique, observations of extended sources
(e.g. scattered light from disks) can be misinterpreted as moving companions.
We discuss tests to distinguish between these two scenarios, with applications
to the T Cha and LkCa 15 observations. We argue that a static,
forward-scattering disk can explain the T Cha data, while LkCa 15 is best
explained by multiple orbiting companions.


title: A series of (2+1)d Stable Self-Dual Interacting Conformal Field Theories

abstract:
  Using the duality between seemingly different (2+1)d conformal field theories
(CFT) proposed recently, we study a series of (2+1)d stable self-dual
interacting CFTs. These CFTs can be realized (for instance) on the boundary of
the (3+1)d bosonic topological insulator protected by U(1) and time-reversal
symmetry, and they remain stable as long as these symmetries are preserved.
When realized as a boundary system, these CFTs can be driven into anomalous
fractional quantum Hall states once time-reversal is broken. We demonstrate
that the newly proposed dualities allow us to study these CFTs quantitatively
through a controlled calculation, without relying on a large flavor number of
matter fields.


title: On the Formation of Molecular Clumps in QSO Outflows

abstract:
  We study the origin of the cold molecular clumps in quasar outflows, recently
detected in CO and HCN emission. We first describe the physical properties of
such radiation-driven outflows and show that a transition from a momentum- to
an energy-driven flow must occur at a radial distance of R ~ 0.25 kpc. During
this transition, the shell of swept up material fragments due to
Rayleigh-Taylor instabilities, but these clumps contain little mass and are
likely to be rapidly ablated by the hot gas in which they are immersed. We then
explore an alternative scenario in which clumps form from thermal instabilities
at R >~ 1 kpc, possibly containing enough dust to catalyze molecule formation.
We investigate this processes with 3D two-fluid (gas+dust) numerical
simulations of a kpc^3 patch of the outflow, including atomic and dust cooling,
thermal conduction, dust sputtering, and photoionization from the QSO radiation
field. In all cases, dust grains are rapidly destroyed in ~10,000 years; and
while some cold clumps form at later times, they are present only as transient
features, which disappear as cooling becomes more widespread. In fact, we only
find a stable two-phase medium with dense clumps if we artificially enhance the
QSO radiation field by a factor 100. This result, together with the complete
destruction of dust grains, renders the interpretation of molecular outflows a
very challenging problem.


title: Complexity Classes and Completeness in Algebraic Geometry

abstract:
  We study the computational complexity of sequences of projective varieties.
We define analogues of the complexity classes P and NP for these and prove the
NP-completeness of a sequence called the universal circuit resultant. This is
the first family of compact spaces shown to be NP-complete in a geometric
setting.


title:
Mass and eccentricity constraints on the planetary debris orbiting the
  white dwarf WD 1145+017

abstract:
  Being the first of its kind, the white dwarf WD 1145+017 exhibits a complex
system of disintegrating debris which offers a unique opportunity to study its
disruption process in real time. Even with plenty of transit observations there
are no clear constraints on the masses or eccentricities of such debris. Using
$N$-body simulations we show that masses greater than approximately $10^{20}$
kg (a tenth of the mass of Ceres) or orbits that are not nearly circular
($\mathrm{eccentricity}>10^{-3}$) dramatically increase the chances of the
system becoming unstable within two years, which would contrast with the
observational data over this timespan. We also provide a direct comparison
between transit phase shifts detected in the observations and by our numerical
simulations.


title: Superfluid Black Holes

abstract:
  We present what we believe is the first example of a "$\lambda$-line" phase
transition in black hole thermodynamics. This is a line of (continuous) second
order phase transitions which in the case of liquid $^4$He marks the onset of
superfluidity. The phase transition occurs for a class of asymptotically AdS
hairy black holes in Lovelock gravity where a real scalar field is conformally
coupled to gravity. We discuss the origin of this phase transition and outline
the circumstances under which it (or generalizations of it) could occur.


title: Competing Adiabatic Thouless Pumps in Enlarged Parameter Spaces

abstract:
  The transfer of conserved charges through insulating matter via smooth
deformations of the Hamiltonian is known as quantum adiabatic, or Thouless,
pumping. Central to this phenomenon are Hamiltonians whose insulating gap is
controlled by a multi-dimensional (usually two-dimensional) parameter space in
which paths can be defined for adiabatic changes in the Hamiltonian, i.e.,
without closing the gap. Here, we extend the concept of Thouless pumps of band
insulators by considering a larger, three-dimensional parameter space. We show
that the connectivity of this parameter space is crucial for defining quantum
pumps, demonstrating that, as opposed to the conventional two-dimensional case,
pumped quantities depend not only on the initial and final points of
Hamiltonian evolution but also on the class of the chosen path and preserved
symmetries. As such, we distinguish the scenarios of closed/open paths of
Hamiltonian evolution, finding that different closed cycles can lead to the
pumping of different quantum numbers, and that different open paths may point
to distinct scenarios for surface physics. As explicit examples, we consider
models similar to simple models used to describe topological insulators, but
with doubled degrees of freedom compared to a minimal topological insulator
model. The extra fermionic flavors from doubling allow for extra gapping
terms/adiabatic parameters - besides the usual topological mass which preserves
the topology-protecting discrete symmetries - generating an enlarged adiabatic
parameter-space. We consider cases in one and three \emph{spatial} dimensions,
and our results in three dimensions may be realized in the context of
crystalline topological insulators, as we briefly discuss.


title:
Modelling Mechanical Heating in Star-Forming Galaxies: CO and 13CO Line
  Ratios as Sensitive Probes

abstract:
  We apply photo-dissociation region (PDR) molecular line emission models, that
have varying degrees of enhanced mechanical heating rates, to the gaseous
component of simulations of star-forming galaxies taken from the literature.
Snapshots of these simulations are used to produce line emission maps for the
rotational transitions of the CO molecule and its 13CO isotope up to J = 4-3.
  We consider two galaxy models: a small disk galaxy of solar metallicity and a
lighter dwarf galaxy with 0.2 \zsun metallicity. Elevated excitation
temperatures for CO(1 - 0) correlate positively with mechanical feedback, that
is enhanced towards the central region of both model galaxies. The emission
maps of these model galaxies are used to compute line ratios of CO and 13CO
transitions. These line ratios are used as diagnostics where we attempt to
match them These line ratios are used as diagnostics where we attempt to match
them to mechanically heated single component (i.e. uniform density, Far-UV
flux, visual extinction and velocity gradient) equilibrium PDR models.
  We find that PDRs ignoring mechanical feedback in the heating budget
over-estimate the gas density by a factor of 100 and the far-UV flux by factors
of ~10 - 1000. In contrast, PDRs that take mechanical feedback into account are
able to fit all the line ratios for the central < 2 kpc of the fiducial disk
galaxy quite well. The mean mechanical heating rate per H atom that we recover
from the line ratio fits of this region varies between $10^{-27}$ --
$10^{-26}$~erg s$^{-1}$.


title: Constraining cloud parameters using high density gas tracers in galaxies

abstract:
  Far-infrared molecular emission is an important tool used to understand the
excitation mechanisms of the gas in the inter-stellar medium of star-forming
galaxies. In the present work, we model the emission from rotational
transitions with critical densities n >~ 10^4 cm-3. We include 4-3 < J <= 15-14
transitions of CO and 13CO, in addition to J <= 7-6 transitions of HCN, HNC,
and HCO+ on galactic scales. We do this by re-sampling high density gas in a
hydrodynamic model of a gas-rich disk galaxy, assuming that the density field
of the interstellar medium of the model galaxy follows the probability density
function (PDF) inferred from the resolved low density scales. We find that in a
narrow gas density PDF, with a mean density of ~10 cm-3 and a dispersion \sigma
= 2.1 in the log of the density, most of the emission of molecular lines,
emanates from the 10-1000 cm-3 part of the PDF. We construct synthetic emission
maps for the central 2 kpc of the galaxy and fit the line ratios of CO and 13CO
up to J = 15-14, as well as HCN, HNC, and HCO+ up to J = 7-6, using one
photo-dissociation region (PDR) model. We attribute the goodness of the one
component fits for our model galaxy to the fact that the distribution of the
luminosity, as a function of density, is peaked at gas densities between 10 and
1000 cm-3.
  We explore the impact of different log-normal density PDFs on the
distribution of the line-luminosity as a function of density, and we show that
it is necessary to have a broad dispersion, corresponding to Mach numbers >~ 30
in order to obtain significant emission from n > 10^4 cm-3 gas. Such Mach
numbers are expected in star-forming galaxies, LIRGS, and ULIRGS. By fitting
line ratios of HCN(1-0), HNC(1-0), and HCO+(1-0) for a sample of LIRGS and
ULIRGS using mechanically heated PDRs, we constrain the Mach number of these
galaxies to 29 < M < 77.


title: Natural constraints on the gluon-quark vertex

abstract:
  In principle, the strong-interaction sector of the Standard Model is
characterised by a unique renormalisation-group-invariant (RGI) running
interaction and a unique form for the dressed--gluon-quark vertex,
$\Gamma_\mu$; but, whilst much has been learnt about the former, the latter is
still obscure. In order to improve this situation, we use a RGI
running-interaction that reconciles both top-down and bottom-up analyses of the
gauge sector in quantum chromodynamics (QCD) to compute dressed-quark gap
equation solutions with 1,660,000 distinct Ansaetze for $\Gamma_\mu$. Each one
of the solutions is then tested for compatibility with three physical criteria
and, remarkably, we find that merely 0.55% of the solutions survive the test.
Plainly, therefore, even a small selection of observables places extremely
tight bounds on the domain of realistic vertex Ansaetze. This analysis and its
results should prove useful in constraining insightful contemporary studies of
QCD and hadronic phenomena.


title:
Evidence from SOFIA Imaging of Polycyclic Aromatic Hydrocarbon Formation
  along a Recent Outflow in NGC 7027

abstract:
  We report spatially resolved (FWHM$\sim3.8-4.6"$) mid-IR imaging observations
of the planetary nebula (PN) NGC 7027 taken with the 2.5-m telescope aboard the
Stratospheric Observatory for Infrared Astronomy (SOFIA). Images of NGC 7027
were acquired at 6.3, 6.6, 11.1, 19.7, 24.2, 33.6, and 37.1 $\mu\mathrm{m}$
using the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST).The
observations reveal emission from Polycyclic Aromatic Hydrocarbon (PAH) and
warm dust ($T_D\sim90$ K) from the illuminated inner edge of the molecular
envelope surrounding the ionized gas and central star. The DustEM code was used
to fit the spectral energy distribution of fluxes obtained by FORCAST and the
archival infrared spectrum of NGC 7027 acquired by the Short Wavelength
Spectrometer (SWS) on the Infrared Space Observatory (ISO). Best-fit dust
models provide a total dust mass of $5.8^{+2.3}_{-2.6}\times10^{-3}$
$\mathrm{M}_\odot$, where carbonaceous large ($a=1.5$ $\mu$m) and very small
($a \sim12\AA$) grains, and PAHs ($3.1\AA<a<12\AA$) compose 96.5, 2.2, and 1.3
$\%$ of the dust by mass, respectively. The 37 $\mu$m optical depth map shows
minima in the dust column density at regions in the envelope that are
coincident with a previously identified collimated outflow from the central
star. The optical depth minima are also spatially coincident with enhancements
in the 6.2 $\mu$m PAH feature, which is derived from the 6.3 and 6.6 $\mu$m
maps. We interpret the spatial anti-correlation of the dust optical depth and
PAH 6.2 $\mu$m feature strength and their alignment with the outflow from the
central star as evidence of dust processing and rapid PAH formation via
grain-grain collisions in the post-shock environment of the dense
($n_H\sim10^5\,\mathrm{cm}^{-3}$) photo-dissociation region (PDR) and molecular
envelope.


title:
Non-Detection of HC$_{11}$N toward TMC-1: Constraining the Chemistry of
  Large Carbon-Chain Molecules

abstract:
  Bell et al. (1997) reported the first detection of the cyanopolyyne
HC$_{11}$N toward the cold dark cloud TMC-1; no subsequent detections have been
reported toward any source. Additional observations of cyanopolyynes and other
carbon-chain molecules toward TMC-1 have shown a log-linear trend between
molecule size and column density, and in an effort to further explore the
underlying chemical processes driving this trend, we have analyzed GBT
observations of HC$_9$N and HC$_{11}$N toward TMC-1. Although we find an
HC$_9$N column density consistent with previous values, HC$_{11}$N is not
detected and we derive an upper limit column density significantly below that
reported in Bell et al. Using a state-of-the-art chemical model, we have
investigated possible explanations of non-linearity in the column density
trend. Despite updating the chemical model to better account for ion-dipole
interactions, we are not able to explain the non-detection of HC$_{11}$N, and
we interpret this as evidence of previously unknown carbon-chain chemistry. We
propose that cyclization reactions may be responsible for the depleted
HC$_{11}$N abundance, and that products of these cyclization reactions should
be investigated as candidate interstellar molecules.


title: Tracing Primordial Black Holes in Nonsingular Bouncing Cosmology

abstract:
  We in this paper investigate the formation and evolution of primordial black
holes (PBHs) in nonsingular bouncing cosmologies. We discuss the formation of
PBH in the contracting phase and calculate the PBH abundance as a function of
the sound speed and Hubble parameter. Afterwards, by taking into account the
subsequent PBH evolution during the bouncing phase, we derive the density of
PBHs and their Hawking radiation. Our analysis shows that nonsingular bounce
models can be constrained from the backreaction of PBHs.


title: Baryons and Chiral Symmetry

abstract:
  The relevance of chiral symmetry in baryons is highlighted in three examples
in the nucleon spectroscopy and structure. The first one is the importance of
chiral dynamics in understanding the Roper resonance. The second one is the
role of chiral symmetry in the lattice calculation of $\pi N \sigma$ term and
strangeness. The third one is the role of chiral $U(1)$ anomaly in the
anomalous Ward identity in evaluating the quark spin and the quark orbital
angular momentum. Finally, the chiral effective theory for baryons is
discussed.


title:
Demonstration of sub-luminal propagation of single-cycle terahertz
  pulses for particle acceleration

abstract:
  The sub-luminal phase velocity of electromagnetic waves in free space is
generally unobtainable, being closely linked to forbidden faster than light
group velocities. The requirement of effective sub-luminal phase-velocity in
laser-driven particle acceleration schemes imposes a fundamental limit on the
total acceleration achievable in free-space, and necessitates the use of
dielectric structures and waveguides for extending the field-particle
interaction. Here we demonstrate a new travelling-source and free space
propagation approach to overcoming the sub-luminal propagation limits. The
approach exploits the relative ease of generating ultrafast optical sources
with slow group velocity propagation, and a group-to-phase front conversion
through non-linear optical interaction near a material-vacuum boundary. The
concept is demonstrated with two terahertz generation processes, non-linear
optical rectification and current-surge rectification. The phase velocity is
tunable, both above and below vacuum speed of light $c$, and we report
measurements of longitudinally polarized electric fields propagating between
$0.77c$ and $1.75c$. The ability to scale to multi-MV/m field strengths is
demonstrated. Our approach paves the way towards the realization of cheap and
compact particle accelerators with unprecedented femtosecond scale control of
particles.


title: Fermionic topological quantum states as tensor networks

abstract:
  Tensor network states, and in particular projected entangled pair states,
play an important role in the description of strongly correlated quantum
lattice systems. They do not only serve as variational states in numerical
simulation methods, but also provide a framework for classifying phases of
quantum matter and capture notions of topological order in a stringent and
rigorous language. The rapid development in this field for spin models and
bosonic systems has not yet been mirrored by an analogous development for
fermionic models. In this work, we introduce a framework of tensor networks
having a fermionic component capable of capturing notions of topological order.
At the heart of the formalism are axioms of fermionic matrix product operator
injectivity, stable under concatenation. Building upon that, we formulate a
Grassmann number tensor network ansatz for the ground state of fermionic
twisted quantum double models. A specific focus is put on the paradigmatic
example of the fermionic toric code. This work shows that the program of
describing topologically ordered systems using tensor networks carries over to
fermionic models.

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


title: Self-interaction effects on charge-transfer collisions

abstract:
  In this article, we investigate the role of the self-interaction error in the
simulation of collisions using time-dependent density functional theory (TDDFT)
and Ehrenfest dynamics. We compare many different approximations of the
exchange and correlation potential, using as a test system the collision of
$\mathrm{H^+ + CH_4}$ at $30~\mathrm{eV}$. We find that semi-local
approximations, like PBE, and even hybrid functionals, like B3LYP, produce
qualitatively incorrect predictions for the scattering of the proton. This
discrepancy appears because the self-interaction error allows the electrons to
jump too easily to the proton, leading to radically different forces with
respect to the non-self-interacting case. From our results, we conclude that
using a functional that is self-interaction free is essential to properly
describe charge-transfer collisions between ions and molecules in TDDFT.


title:
MagAO Imaging of Long-period Objects (MILO). II. A Puzzling White Dwarf
  around the Sun-like Star HD 11112

abstract:
  HD 11112 is an old, Sun-like star that has a long-term radial velocity (RV)
trend indicative of a massive companion on a wide orbit. Here we present direct
images of the source responsible for the trend using the Magellan Adaptive
Optics system. We detect the object (HD 11112B) at a separation of 2\fasec 2
(100 AU) at multiple wavelengths spanning 0.6-4 \microns ~and show that it is
most likely a gravitationally-bound cool white dwarf. Modeling its spectral
energy distribution (SED) suggests that its mass is 0.9-1.1 \msun, which
corresponds to very high-eccentricity, near edge-on orbits from Markov chain
Monte Carlo analysis of the RV and imaging data together. The total age of the
white dwarf is $>2\sigma$ discrepant with that of the primary star under most
assumptions. The problem can be resolved if the white dwarf progenitor was
initially a double white dwarf binary that then merged into the observed
high-mass white dwarf. HD 11112B is a unique and intriguing benchmark object
that can be used to calibrate atmospheric and evolutionary models of cool white
dwarfs and should thus continue to be monitored by RV and direct imaging over
the coming years.


title: Random Walks and Boundaries of CAT(0) Cubical complexes

abstract:
  We show under weak hypotheses that the pushforward $\{Z_no\}$ of a
random-walk to a CAT(0) cube complex converges to a point on the boundary. We
introduce the notion of squeezing points, which allows us to consider the
convergence in either the Roller boundary or the visual boundary, with the
appropriate hypotheses. This study allows us to show that any nonelementary
action necessarily contains regular elements, that is, elements that act as
rank-1 hyperbolic isometries in each irreducible factor of the essential core.


title: Fast and Efficient Stochastic Optimization for Analytic Continuation

abstract:
  The analytic continuation of imaginary-time quantum Monte Carlo data to
extract real-frequency spectra remains a key problem in connecting theory with
experiment. Here we present a fast and efficient stochastic optimization method
(FESOM) as a more accessible variant of the stochastic optimization method
introduced by Mishchenko et al. and benchmark the resulting spectra with those
obtained by the standard Maximum Entropy method for three representative test
cases, in- cluding data taken from studies of the two-dimensional Hubbard
model. We generally find that our FESOM approach gives spectra similar to the
Maximum Entropy results. In particular, while the Maximum Entropy method gives
superior results when the quality of the data is strong, we find that FESOM is
able to resolve fine structure with more detail when the quality of the data is
poor. In addition, because of its stochastic nature, the method provides
detailed information on the frequency dependent uncertainty of the resulting
spectra, while the Maximum Entropy method does so only for the spectral weight
integrated over a finite frequency region. We therefore believe that this
variant of the stochastic optimization approach provides a viable alternative
to the routinely used Maximum Entropy method especially for data with poor
quality.


title:
Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the
  Gaia Era

abstract:
  We present fits to the broadband photometric spectral energy distributions
(SEDs) of 158 eclipsing binaries (EBs) in the Tycho-2 catalog. These EBs were
selected because they have highly precise stellar radii, effective
temperatures, and in many cases metallicities previously determined in the
literature, and thus have bolometric luminosities that are typically good to
$\lesssim$ 10%. In most cases the available broadband photometry spans a
wavelength range 0.4-10 $\mu$m, and in many cases spans 0.15-22 $\mu$m. The
resulting SED fits, which have only extinction as a free parameter, provide a
virtually model-independent measure of the bolometric flux at Earth. The SED
fits are satisfactory for 156 of the EBs, for which we achieve typical
precisions in the bolometric flux of $\approx$ 3%. Combined with the accurately
known bolometric luminosity, the result for each EB is a predicted parallax
that is typically precise to $\lesssim$ 5%. These predicted parallaxes---with
typical uncertainties of 200 $\mu$as---are 4-5 times more precise than those
determined by Hipparcos for 99 of the EBs in our sample, with which we find
excellent agreement. There is no evidence among this sample for significant
systematics in the Hipparcos parallaxes of the sort that notoriously afflicted
the Pleiades measurement. The EBs are distributed over the entire sky, span
more than 10 mag in brightness, reach distances of more than 5 kpc, and in many
cases our predicted parallaxes should also be more precise than those expected
from the Gaia first data release. The EBs studied here can thus serve as
empirical, independent benchmarks for these upcoming fundamental parallax
measurements.


title:
The thermalization of soft modes in non-expanding isotropic quark gluon
  plasmas

abstract:
  We discuss the role of elastic and inelastic collisions and their interplay
in the thermalization of the quark-gluon plasma. We consider a simplified
situation of a static plasma, spatially uniform and isotropic in momentum
space. We focus on the small momentum region, which equilibrates first, and on
a short time scale. We obtain a simple kinetic equation that allows for an
analytic description of the most important regimes. The present analysis
suggests that the formation of a Bose condensate, expected when only elastic
collisions are present, is strongly hindered by the inelastic, radiative,
processes.


title: The Pseudo-hyperresolution and Applications

abstract:
  Homological algebra techniques can be found in almost all modern areas of
mathematics. Many interesting problems in mathematics can be formulated,
computed, or can find their equivalence in terms of Ext-groups. For instance,
important (co)homology theories, such as the Mac Lane cohomology for rings or
the Hochschild and cyclic homology of commutative algebras can be defined as
Ext-groups in suitable functor categories; homotopical invariants can also gain
information from homological data with the help of the unstable Adams spectral
sequence, whose input takes the form of Ext-groups in the category of unstable
modules over the Steenrod algebra. Therefore, the constructions of explicit
injective (projective) resolutions in an abelian category is of great
importance. In this article, we introduce a new method, called
Pseudo-hyperresolution, to study such constructions. This method originates in
the category of unstable modules, and aims at building explicit resolutions for
the reduced singular cohomology of spheres. In particular, for all integers
$n\geq 0$, we can describe a large range of the minimal injective resolution of
the sphere $S^{n}$ based on the Bockstein operation of the Steenrod algebra.
Moreover, many classical constructions in algebraic topology, such as the
algebraic EHP sequence or the Lambda algebra can be recovered using the
Pseudo-hyperresolution method. A particular connection between spheres and the
infinite complex projective space is also established. Despite its origin,
Pseudo-hyperresolution generalizes to all abelian categories. In particular,
many explicit resolutions of classical strict polynomial functors can be
reunified in view of Pseudo-hyperresolution. As a consequence, we recover the
global dimension of the category of homogeneous strict polynomial functors of
finite degree as well as the Mac Lane cohomology of finite fields.


title:
Influence of non-magnetic impurity scattering on the spin dynamics in
  diluted magnetic semiconductors

abstract:
  The doping of semiconductors with magnetic impurities gives rise not only to
a spin-spin interaction between quasi-free carriers and magnetic impurities,
but also to a local spin-independent disorder potential for the carriers. Based
on a quantum kinetic theory for the carrier and impurity density matrices as
well as the magnetic and non-magnetic carrier-impurity correlations, the
influence of the non-magnetic scattering potential on the spin dynamics in DMS
after optical excitation with circularly polarized light is investigated using
the example of Mn-doped CdTe. It is shown that non-Markovian effects, which are
predicted in calculations where only the magnetic carrier-impurity interaction
is accounted for, can be strongly suppressed in the presence of non-magnetic
impurity scattering. This effect can be traced back to a significant
redistribution of carriers in $\mathbf{k}$-space which is enabled by the
build-up of large carrier-impurity correlation energies. A comparison with the
Markov limit of the quantum kinetic theory shows that, in the presence of an
external magnetic field parallel to the initial carrier polarization, the
asymptotic value of the spin polarization at long times is significantly
different in the quantum kinetic and the Markovian calculations. This effect
can also be attributed to the formation of strong correlations which
invalidates the semiclassical Markovian picture and it is stronger when the
non-magnetic carrier-impurity interaction is accounted for. In an external
magnetic field perpendicular to the initial carrier spin, the correlations are
also responsible for a renormalization of the carrier spin precession
frequency.


title: Bottom-up Instance Segmentation using Deep Higher-Order CRFs

abstract:
  Traditional Scene Understanding problems such as Object Detection and
Semantic Segmentation have made breakthroughs in recent years due to the
adoption of deep learning. However, the former task is not able to localise
objects at a pixel level, and the latter task has no notion of different
instances of objects of the same class. We focus on the task of Instance
Segmentation which recognises and localises objects down to a pixel level. Our
model is based on a deep neural network trained for semantic segmentation. This
network incorporates a Conditional Random Field with end-to-end trainable
higher order potentials based on object detector outputs. This allows us to
reason about instances from an initial, category-level semantic segmentation.
Our simple method effectively leverages the great progress recently made in
semantic segmentation and object detection. The accurate instance-level
segmentations that our network produces is reflected by the considerable
improvements obtained over previous work.


title:
Towards Better Response Times and Higher-Quality Queries in Interactive
  Knowledge Base Debugging

abstract:
  Many AI applications rely on knowledge encoded in a locigal knowledge base
(KB). The most essential benefit of such logical KBs is the opportunity to
perform automatic reasoning which however requires a KB to meet some minimal
quality criteria such as consistency. Without adequate tool assistance, the
task of resolving such violated quality criteria in a KB can be extremely hard,
especially when the problematic KB is large and complex. To this end,
interactive KB debuggers have been introduced which ask a user queries whether
certain statements must or must not hold in the intended domain. The given
answers help to gradually restrict the search space for KB repairs.
  Existing interactive debuggers often rely on a pool-based strategy for query
computation. A pool of query candidates is precomputed, from which the best
candidate according to some query quality criterion is selected to be shown to
the user. This often leads to the generation of many unnecessary query
candidates and thus to a high number of expensive calls to logical reasoning
services. We tackle this issue by an in-depth mathematical analysis of diverse
real-valued active learning query selection measures in order to determine
qualitative criteria that make a query favorable. These criteria are the key to
devising efficient heuristic query search methods. The proposed methods enable
for the first time a completely reasoner-free query generation for interactive
KB debugging while at the same time guaranteeing optimality conditions, e.g.
minimal cardinality or best understandability for the user, of the generated
query that existing methods cannot realize.
  Further, we study different relations between active learning measures. The
obtained picture gives a hint about which measures are more favorable in which
situation or which measures always lead to the same outcomes, based on given
types of queries.


title:
Evidence of Ballistic Thermal Transport in Lithium Niobate at Room
  Temperature

abstract:
  In ballistic transport, heat carriers such as phonons travel through the
solid without any scattering or interaction. Therefore, there is no temperature
gradient in the solid, which seems to transport the heat without getting heated
itself. Ballistic transport is typically seen in high purity crystals at either
temperatures below ~10 K, or physical size below ~100 nm, where the mean free
path of the carrier is larger than the solid itself. In this letter, we show
evidence of ballistic transport at room temperature in lithium niobate wafers
in the in-plane and cross-plane directions under both steady state and high
frequency heating that are monitored using both infrared and resistance
thermometry. We report phonon mean free path in lithium niobate around 425
microns, which is about 50 times higher than the largest phonon mean free path
in the literature at room temperature. Above this length-scale, temperature
gradient gradually emerges and the material shows completely diffusive, bulk
transport at about 4 mm length. Our observations will impact phonon-based
electronics such as thermal transistor, thermal logic gate and memory currently
impossible at room temperature. If 1 micron electron mean free path in graphene
gives the highest-mobility, the 425 microns mean free path of phonons in this
research may realize phononics without any need for nanoscale size or
ultra-cold temperatures.


title: Three Aspects of Typicality in Multiverse Cosmology

abstract:
  Extracting predictions from cosmological theories that describe a multiverse,
for what we are likely to observe in our domain, is crucial to establishing the
validity of these theories. One way to extract such predictions is from
theory-generated probability distributions that allow for selection
effects---generally expressed in terms of assumptions about anthropic
conditionalization and how typical we are. In this paper, I urge three lessons
about typicality in multiverse settings. (i) Because it is difficult to
characterize our observational situation in the multiverse, we cannot assume
that we are typical (as in the 'principle of mediocrity'): nor can we ignore
the issue of typicality, for it has a measurable impact on predictions for our
observations. (ii) There are spectra of assumptions about both
conditionalization and typicality, which lead to coincident predictions for our
observations, leading to problems of confirmation in multiverse cosmology. And
moreover, (iii) when one has the freedom to consider competing theories of the
multiverse, the assumption of typicality may not lead to the highest
likelihoods for our observations. These three entwined aspects of typicality
imply that positive assertions about our typicality, such as the 'principle of
mediocrity', are more questionable than has been recently claimed.


title: How many bits specify a quantum state?

abstract:
  Quantum mechanics suggests that nature is discrete, with one state per phase
space volume $\hbar^{3N}$. This appears to contradict the idea that the state
of an N-particle system can have infinite precision and is described by a set
of exponentially many complex numbers. Using a finite-temperature gas confined
in a box as an example, this short paper argues that there are indeed limits to
the precision of wave functions, and that this may help at understanding the
quantum-to-classical transition.


title: Josef Meixner: his life and his orthogonal polynomials

abstract:
  This paper starts with a biographical sketch of the life of Josef Meixner.
Then his motivations to work on orthogonal polynomials and special functions
are reviewed. Meixner's 1934 paper introducing the Meixner and
Meixner-Pollaczek polynomials is discussed in detail. Truksa's forgotten 1931
paper, which already contains the Meixner polynomials, is mentioned. The paper
ends with a survey of the reception of Meixner's 1934 paper.


title: Barycenters in uniformly convex geodesic spaces

abstract:
  This note proves a result on the existence of barycenters in a class of
uniformly convex geodesic spaces.


title: Collectivity and electromagnetic radiation in small systems

abstract:
  Collective behaviour has been observed in hadronic measurements of high
multiplicity proton+lead collisions at the Large Hadron Collider (LHC), as well
as in (proton, deuteron, helium-3)+gold collisions at the Relativistic
Heavy-Ion Collider (RHIC). To better understand the evolution dynamics and the
properties of the matter created in these small systems, a systematic study of
the soft hadronic observables together with electromagnetic radiation from
these collisions is performed, using a hydrodynamic framework. Quantitative
agreement is found between theoretical calculations and existing experimental
hadronic observables. The validity of the fluid dynamical description is
estimated by calculating Knudsen and inverse Reynolds numbers. Sizeable thermal
yields are predicted for low $p_T$ photons. Further predictions of higher order
charged hadron anisotropic flow coefficients and of thermal photon enhancement
are proposed.


title:
Collective Dynamics and Strong Pinning near the Onset of Charge Order in
  La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$

abstract:
  The dynamics of charge-ordered states is one of the key issues in underdoped
cuprate high-temperature superconductors, but static short-range charge-order
(CO) domains have been detected in almost all cuprates. We probe the dynamics
across the CO (and structural) transition in
La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$ by measuring nonequilibrium charge
transport, or resistance $R$ as the system responds to a change in temperature
and to an applied magnetic field. We find evidence for metastable states,
collective behavior, and criticality. The collective dynamics in the critical
regime indicates strong pinning by disorder. Surprisingly, nonequilibrium
effects, such as avalanches in $R$, are revealed only when the critical region
is approached from the charge-ordered phase. Our results on
La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$ provide the long-sought evidence for
the fluctuating order across the CO transition, and also set important
constraints on theories of dynamic stripes.


title: Shaping ideal cities: the graph representation of the urban utopia

abstract:
  The ideal Renaissance city is designed as a star-shaped fortress, where the
streets and squares are organized to speed the movement of people and soldiers.
Symmetry and accessibility represent the key features for the organization of
the urban space. The resulting city is hierarchized and does not always
guarantee an optimal degree of connectivity. Taking the baton from the work
done by space syntax in the definition of properties of spatial graph
representation, we introduce a method to compute urban graphs from the
Euclidean representation, the corresponding line graph and the contraction of
nodes with the same urban function. We analyze the urban graphs of five
historic cities: Vitry le Fran\c{c}ois, Avola, Neuf Brisach, Grammichele and
Palmanova and compare the analysis restults with the corresponding results from
space syntax. Analysis of the spectral gap and the relative asymmetry
distribution show a similar structure for these cities. The irregular or
reticular housing structure seems to ensure connectivity and accessibility more
than the regular grids. However connectivity is ensured by the most peripheral
streets, which in the space syntax representation play a marginal role.


title: Multiple predator based capture process on complex networks

abstract:
  The predator/prey (capture) problem is a prototype of many network-related
applications. We study the capture process on complex networks by considering
multiple predators from multiple sources. In our model, some lions start from
multiple sources simultaneously to capture the lamb by biased random walks,
which are controlled with a free parameter $\alpha$. We derive the distribution
of the lamb's lifetime and the expected lifetime $\left\langle T\right\rangle
$. Through simulation, we find that the expected lifetime drops substantially
with the increasing number of lions. We also study how the underlying
topological structure affects the capture process, and obtain that locating on
small-degree nodes is better than large-degree nodes to prolong the lifetime of
the lamb. Moreover, dense or homogeneous network structures are against the
survival of the lamb.


title:
Ground State Properties of the One-Dimensional Unconstrained
  Pseudo-Anyon Hubbard Model

abstract:
  We study the (pseudo-) anyon Hubbard model on a one-dimensional lattice
without the presence of a three-body hardcore constraint. In particular, for
the pseudo-fermion limit of a large statistical angle $\theta\approx\pi$, we
observe a wealth of exotic properties including {a first order transition}
between different superfluid phases and a {two-component} partially paired
phase for large fillings without need of an additional three-body hardcore
constraint.In this limit, we analyze the effect of an induced hardcore
constraint, which leads to the stabilization of superfluid {ground states} for
vanishing or even small attractive on-site interactions. For finite statistical
angles, we study the unconventional broken-symmetry superfluid peaked at a
finite momentum, resulting in an interesting beat phenomenon of single particle
correlation functions.We show how some features of various ground state phases,
including an analog of the partially paired phase in the pseudo-fermion limit,
may be reproduced in a naive mean field frame.


title: Magnetic catalysis of a finite size pion condensate

abstract:
  We study the Bose-Einstein condensation of a finite size pion gas subject to
the influence of a magnetic field. We find the expressions for the critical
chemical potential and temperature for the onset of condensation. We show that
for values of the external magnetic flux larger than the elemental flux, the
critical temperature is larger than the one obtained by considering only finite
size effects. We use experimentally reported values of pion source sizes and
multiplicities at LHC energies to show that if the magnetic flux, produced
initially in peripheral heavy-ion collision, is at least partially preserved up
to the hadronic phase, the combined finite size and magnetic field effects give
rise to a critical temperature above the kinetic freeze-out temperature. We
discuss the implications for the evolution of the pion system created in
relativistic heavy-ion collisions.


title:
A Stackelberg Game for Incentive Proactive Caching Mechanisms in
  Wireless Networks

abstract:
  In this paper, an incentive proactive cache mechanism in cache-enabled small
cell networks (SCNs) is proposed, in order to motivate the content providers
(CPs) to participate in the caching procedure. A network composed of a single
mobile network operator (MNO) and multiple CPs is considered. The MNO aims to
define the price it charges the CPs to maximize its revenue while the CPs
compete to determine the number of files they cache at the MNO's small base
stations (SBSs) to improve the quality of service (QoS) of their users. This
problem is formulated as a Stackelberg game where a single MNO is considered as
the leader and the multiple CPs willing to cache files are the followers. The
followers game is modeled as a non-cooperative game and both the existence and
uniqueness of a Nash equilibrium (NE) are proved. The closed-form expression of
the NE which corresponds to the amount of storage each CP requests from the MNO
is derived. An optimization problem is formulated at the MNO side to determine
the optimal price that the MNO should charge the CPs. Simulation results show
that at the equilibrium, the MNO and CPs can all achieve a utility that is up
to 50% higher than the cases in which the prices and storage quantities are
requested arbitrarily.


title: On the four-loop strong coupling beta-function in the SM

abstract:
  In the talk the leading four-loop contribution to the beta-function of the
strong coupling in the SM is discussed. Some details of calculation techniques
are provided. Special attention is paid to the ambiguity due to utilized
$\gamma_5$ treatment and a particular prescription with anticommuting
$\gamma_5$ is advocated. As a by-product of our computation the four-loop
beta-function in QCD with "gluino" is also obtained.


title: Disintermediation of Inter-Blockchain Transactions

abstract:
  Different versions of peer-to-peer electronic cash exist as data represented
by separate blockchains. Payments between such systems cannot be sent directly
from one party to another without going through a financial institution.
Bitcoin provided part of the solution but its utility is limited to
intra-blockchain transactions. The benefits are lost if a trusted third party
is required to execute inter-blockchain transactions. We propose a solution to
the inter-blockchain transaction problem using the same fundamental principles
of Bitcoin. The protocol is described by the Uberledger framework, a
hierarchical meta-blockchain layer that encapsulates information regarding the
fidelity of peer-to-peer transaction facilitators.


title:
Fate of the one-dimensional Ising quantum critical point coupled to a
  gapless boson

abstract:
  The problem of a quantum Ising degree of freedom coupled to a gapless bosonic
mode appears naturally in many one dimensional systems, yet surprisingly little
is known how such a coupling affects the Ising quantum critical point. We
investigate the fate of the critical point in a regime, where the weak coupling
renormalization group (RG) indicates a flow toward strong coupling. Using a
renormalization group analysis and numerical density matrix renormalization
group (DMRG) calculations we show that, depending on the ratio of velocities of
the gapless bosonic mode and the Ising critical fluctuations, the transition
may remain continuous or become fluctuation-driven first order. The two regimes
are separated by a tri-critical point of a novel type.


title:
The boundaries of golden-mean Siegel disks in the complex quadratic
  H\'enon family are not smooth

abstract:
  As was recently shown by the first author and others, golden-mean Siegel
disks of sufficiently dissipative complex quadratic H\'enon maps are bounded by
topological circles. In this paper we investigate the geometric properties of
such curves, and demonstrate that they cannot be $C^1$-smooth.


title: How long do particles spend in vortical regions in turbulent flows?

abstract:
  We obtain the probability distribution functions (PDFs) of the time that a
Lagrangian tracer or a heavy inertial particle spends in vortical or
strain-dominated regions of a turbulent flow, by carrying out direct numerical
simulation (DNS) of such particles advected by statistically steady,
homogeneous and isotropic turbulence in the forced, three-dimensional,
incompressible Navier-Stokes equation. We use the two invariants, $Q$ and $R$,
of the velocity-gradient tensor to distinguish between vortical and
strain-dominated regions of the flow and partition the $Q-R$ plane into four
different regions depending on the topology of the flow; out of these four
regions two correspond to vorticity-dominated regions of the flow and two
correspond to strain-dominated ones. We obtain $Q$ and $R$ along the
trajectories of tracers and heavy inertial particles and find out the time
$\mathrm{t_{pers}}$ for which they remain in one of the four regions of the
$Q-R$ plane. We find that the PDFs of $\mathrm{t_{pers}}$ display exponentially
decaying tails for all four regions for tracers and heavy inertial particles.
From these PDFs we extract characteristic times scales, which help us to
quantify the time that such particles spend in vortical or strain-dominated
regions of the flow.


title:
The Role of Angular Momentum Transport in Establishing the Accretion
  Rate--Protostellar Mass Correlation

abstract:
  We model the mass accretion rate $\dot{M}$ to stellar mass $M_*$ correlation
that has been inferred from observations of intermediate to upper mass T Tauri
stars---that is $\dot{M} \propto M_*^{1.3 \pm 0.3}$. We explain this
correlation within the framework of quiescent disk evolution, in which
accretion is driven largely by gravitational torques acting in the bulk of the
mass and volume of the disk. Stresses within the disk arise from the action of
gravitationally driven torques parameterized in our 1D model in terms of
Toomre's $Q$ criterion. We do not model the hot inner sub-AU scale region of
the disk that is likely stable according to this criterion, and appeal to other
mechanisms to remove or redistribute angular momentum and allow accretion onto
the star. Our model has the advantage of agreeing with large-scale
angle-averaged values from more complex nonaxisymmetric calculations. The model
disk transitions from an early phase (dominated by initial conditions inherited
from the burst mode of accretion) into a later self-similar mode characterized
by a steeper temporal decline in $\dot{M}$. The models effectively reproduce
the spread in mass accretion rates that have been observed for protostellar
objects of $0.2\,\mbox{M}_\odot \le M_* \le 3.0\,\mbox{M}_\odot$, such as those
found in the $\rho$ Ophiuchus and Taurus star forming regions. We then compare
realistically sampled populations of young stellar objects produced by our
model to their observational counterparts. We find these populations to be
statistically coincident, which we argue is evidence for the role of
gravitational torques in the late time evolution of quiescent protostellar
disks.


title:
Cutting down energy usage in wireless sensor networks using Duty Cycle
  technique and multi-hop routing

abstract:
  A wireless sensor network is composed of many sensor nodes that have been
given out in a specific zone and each of them had an ability of collecting
information from the environment and sending collected data to the sink. The
most significant issues in wireless sensor networks despite the recent progress
is the trouble of the severe limitations of energy resources. Since that in
different applications of sensor nets we could throw a static or mobile sink
then all aspects of such networks should be planned with an awareness of
energy. One of the most significant topics related to these networks is
routing. One of the most widely used and efficient methods of routing is a
hierarchy (based on clustering) method. In The present study with the objective
of cutting down energy consumption and persistence of network coverage we have
offered a novel algorithm based on clustering algorithms and multi hop routing.
To achieve this goal first we layer the network environment based on the size
of the network. We will identify the optimal number of cluster heads and every
cluster head based on the mechanism of topology control will start to accept
members. Likewise we set the first layer as gate layer and subsequently
identifying the gate nodes we would turn away half of the sensors and then stop
using energy and the remaining nodes in this layer will join the gate nodes
because they hold a critical part in bettering the functioning of the system.
Cluster heads off following layers send the information to cluster heads in the
above layer until sent data will be sent to gate nodes and finally will be sent
to sink. We have tested the proposed algorithm in two situations 1) when the
sink is off and 2) when a sink is on and simulation data shows that proposed
algorithm has better performance in terms of the life span of a network than
LEACH and E LEACH protocols.


title: On gravitational waves from classical three body problem

abstract:
  Using an effective one body approach we describe in detail gravitational
waves from classical three body problem on a non-rotating straight line and
derive their basic physical characteristics. Special attention is paid to the
irregular motions of such systems and to the significance of double and triple
collisions. The conclusive role of the collinear solutions is also discussed in
short. It is shown that the residuals may contain information about irregular
motion of the source of gravitational waves.


title: Cube term blockers without finiteness

abstract:
  We show that an idempotent variety has a $d$-dimensional cube term if and
only if its free algebra on two generators has no $d$-ary compatible cross. We
employ Hall's Marriage Theorem to show that a variety of finite signature whose
fundamental operations have arities $n_1, \ldots, n_k$ has a $d$-dimensional
cube term if and only if it has one of dimension $d=1+\sum_{i=1}^k (n_i-1)$.
This lower bound on dimension is shown to be sharp. We show that a pure cyclic
term variety has a cube term if and only if it contains no $2$-element
semilattice. We prove that the Maltsev condition "existence of a cube term" is
join prime in the lattice of idempotent Maltsev conditions.


title:
On Sequential Elimination Algorithms for Best-Arm Identification in
  Multi-Armed Bandits

abstract:
  We consider the best-arm identification problem in multi-armed bandits, which
focuses purely on exploration. A player is given a fixed budget to explore a
finite set of arms, and the rewards of each arm are drawn independently from a
fixed, unknown distribution. The player aims to identify the arm with the
largest expected reward. We propose a general framework to unify sequential
elimination algorithms, where the arms are dismissed iteratively until a unique
arm is left. Our analysis reveals a novel performance measure expressed in
terms of the sampling mechanism and number of eliminated arms at each round.
Based on this result, we develop an algorithm that divides the budget according
to a nonlinear function of remaining arms at each round. We provide theoretical
guarantees for the algorithm, characterizing the suitable nonlinearity for
different problem environments described by the number of competitive arms.
Matching the theoretical results, our experiments show that the nonlinear
algorithm outperforms the state-of-the-art. We finally study the
side-observation model, where pulling an arm reveals the rewards of its related
arms, and we establish improved theoretical guarantees in the pure-exploration
setting.


title: [Fe II] jets from intermediate-mass protostars in Carina

abstract:
  We present new HST/WFC3-IR narrowband [Fe II] images of protostellar jets in
the Carina Nebula. Combined with 5 previously published sources, we have a
sample of 18 jets and 2 HH objects. All of the jets we targeted with WFC3 show
bright infrared [Fe II] emission, and a few H$\alpha$ candidate jets are
confirmed as collimated outflows based on the morphology of their [Fe II]
emission. Continuum-subtracted images clearly separate jet emission from the
adjacent ionization front, providing a better tracer of the collimated jet than
H$\alpha$ and allowing us to connect these jets with their embedded driving
sources. The [Fe II] 1.64 $\mu$m/H$\alpha$ flux ratio measured in the jets is
$\gtrsim 5$ times larger than in the adjacent ionization fronts. The
low-ionization jet core requires high densities to shield Fe$^+$ against
further ionization by the FUV radiation from O-type stars in the H II region.
High jet densities imply high mass-loss rates, consistent with the
intermediate-mass driving sources we identify for 13 jets. The remaining jets
emerge from opaque globules that obscure emission from the protostar. In many
respects, the HH jets in Carina look like a scaled-up version of the jets
driven by low-mass protostars. Altogether, these observations suggest that [Fe
II] emission is a reliable tracer of dense, irradiated jets driven by
intermediate-mass protostars. We argue that highly collimated outflows are
common to more massive protostars, and that they suggest the outflow physics
inferred for low-mass stars formation scales up to at least $\sim8$
M$_{\odot}$.


title:
Testing of coalescence mechanism in high energy heavy ion collisions
  using two-particle correlations with identified particle trigger

abstract:
  In central Au-Au collisions at top RHIC energy, two particle correlation
measurements with identified hadron trigger have shown attenuation of near side
proton triggered jet-like yield at intermediate transverse momentum ($p{_T}$),
2$< p{_T} <$ 6 GeV/$\it{c}$. The attenuation has been attributed to the
anomalous baryon enhancement observed in the single inclusive measurements at
the same $p{_T}$ range. The enhancement has been found to be in agreement with
the models invoking coalescence of quarks as a mechanism of hadronization.
Baryon enhancement has also been observed at LHC in the single inclusive
spectra. We study the consequence of such an enhancement on two particle
correlations at LHC energy within the framework of A Multi Phase Transport
(AMPT) model that implements quark coalescence as a mode of hadronization. In
this paper we have calculated the proton over pion ratio and the near side per
trigger yield associated to pion and proton triggers at intermediate $p{_T}$
from String Melting (SM) version of AMPT. Results obtained are contrasted with
the AMPT Default (Def.) which does not include coalescence. Baryon enhancement
has been observed in AMPT SM at intermediate $p{_T}$. Near side jet-like
correlated yield associated to baryon (proton) trigger in the momentum region
where baryon generation is enhanced is found to be suppressed as compared to
the corresponding yields for the meson (pion) trigger in most central Pb-Pb
events. No such effect has been found in the Default version of AMPT.


title:
An Iterative Method for Nonconvex Quadratically Constrained Quadratic
  Programs

abstract:
  This paper examines the nonconvex quadratically constrained quadratic
programming (QCQP) problems using an iterative method. One of the existing
approaches for solving nonconvex QCQP problems relaxes the rank one constraint
on the unknown matrix into semidefinite constraint to obtain the bound on the
optimal value without finding the exact solution. By reconsidering the rank one
matrix, an iterative rank minimization (IRM) method is proposed to gradually
approach the rank one constraint. Each iteration of IRM is formulated as a
convex problem with semidefinite constraints. An augmented Lagrangian method,
named extended Uzawa algorithm, is developed to solve the subproblem at each
iteration of IRM for improved scalability and computational efficiency.
Simulation examples are presented using the proposed method and comparative
results obtained from the other methods are provided and discussed.


title: An enriched multiscale mortar space for high contrast flow problems

abstract:
  Mortar methods are widely used techniques for discretizations of partial
differential equations and preconditioners for the algebraic systems resulting
from the discretizations. For problems with high contrast and multiple scales,
the standard mortar spaces are not robust, and some enrichments are necessary
in order to obtain an efficient and robust mortar space. In this paper, we
consider a class of flow problems in high contrast heterogeneous media, and
develop a systematic approach to obtain an enriched multiscale mortar space.
Our approach is based on the constructions of local multiscale basis functions.
The multiscale basis functions are constructed from local problems by following
the framework of the Generalized Multiscale Finite Element Method (GMsFEM). In
particular, we first create a local snapshot space. Then we select the
dominated modes within the snapshot space using an appropriate Proper
Orthogonal Decomposition (POD) technique. These multiscale basis functions show
better accuracy than polynomial basis for multiscale problems. Using the
proposed multiscale mortar space, we will construct a multiscale finite element
method to solve the flow problem on a coarse grid and a preconditioning
technique for the fine scale discretization of the flow problem. In particular,
we develop a multiscale mortar mixed finite element method using the mortar
space. In addition, we will design a two-level additive preconditioner and a
two-level hybrid preconditioner based on the proposed mortar space for the
iterative method applied to the fine scale discretization of the flow problem.
We present several numerical examples to demonstrate the efficiency and
robustness of our proposed mortar space with respect to both the coarse
multiscale solver and the preconditioners.


title:
A queueing system with on-demand servers: local stability of fluid
  limits

abstract:
  We study a system, where a random flow of customers is served by servers
(called agents) invited on-demand. Each invited agent arrives into the system
after a random time; after each service completion, an agent returns to the
system or leaves it with some fixed probabilities. Customers and/or agents may
be impatient, that is, while waiting in queue, they leave the system at a
certain rate (which may be zero). We consider the queue-length-based feedback
scheme, which controls the number of pending agent invitations, depending on
the customer and agent queue lengths and their changes. The basic objective is
to minimize both customer and agent waiting times.
  We establish the system process fluid limits in the asymptotic regime where
the customer arrival rate goes to infinity. We use the machinery of switched
linear systems and common quadratic Lyapunov functions to approach the
stability of fluid limits at the desired equilibrium point, and derive a
variety of sufficient local stability conditions. For our model, we conjecture
that local stability is in fact sufficient for global stability of fluid
limits; the validity of this conjecture is supported by numerical and
simulation experiments. When local stability conditions do hold, simulations
show good overall performance of the scheme.


title: Generating Videos with Scene Dynamics

abstract:
  We capitalize on large amounts of unlabeled video in order to learn a model
of scene dynamics for both video recognition tasks (e.g. action classification)
and video generation tasks (e.g. future prediction). We propose a generative
adversarial network for video with a spatio-temporal convolutional architecture
that untangles the scene's foreground from the background. Experiments suggest
this model can generate tiny videos up to a second at full frame rate better
than simple baselines, and we show its utility at predicting plausible futures
of static images. Moreover, experiments and visualizations show the model
internally learns useful features for recognizing actions with minimal
supervision, suggesting scene dynamics are a promising signal for
representation learning. We believe generative video models can impact many
applications in video understanding and simulation.


title:
Why is Differential Evolution Better than Grid Search for Tuning Defect
  Predictors?

abstract:
  Context: One of the black arts of data mining is learning the magic
parameters which control the learners. In software analytics, at least for
defect prediction, several methods, like grid search and differential evolution
(DE), have been proposed to learn these parameters, which has been proved to be
able to improve the performance scores of learners.
  Objective: We want to evaluate which method can find better parameters in
terms of performance score and runtime cost.
  Methods: This paper compares grid search to differential evolution, which is
an evolutionary algorithm that makes extensive use of stochastic jumps around
the search space.
  Results: We find that the seemingly complete approach of grid search does no
better, and sometimes worse, than the stochastic search. When repeated 20 times
to check for conclusion validity, DE was over 210 times faster than grid search
to tune Random Forests on 17 testing data sets with F-Measure
  Conclusions: These results are puzzling: why does a quick partial search be
just as effective as a much slower, and much more, extensive search? To answer
that question, we turned to the theoretical optimization literature. Bergstra
and Bengio conjecture that grid search is not more effective than more
randomized searchers if the underlying search space is inherently low
dimensional. This is significant since recent results show that defect
prediction exhibits very low intrinsic dimensionality-- an observation that
explains why a fast method like DE may work as well as a seemingly more
thorough grid search. This suggests, as a future research direction, that it
might be possible to peek at data sets before doing any optimization in order
to match the optimization algorithm to the problem at hand.


title: Block antiferromagnetism and possible ferroelectricity in KFe$_2$Se$_2$

abstract:
  Superconductors and multiferroics are two of the hottest branches in
condensed matter physics. The connections between those two fields are
fundamentally meaningful to unify the physical rules of correlated electrons.
Recently, BaFe$_2$Se$_3$, was predicted to be multiferroic [Phys. Rev. Lett.
113, 187204 (2014)] due to its unique one-dimensional block-type
antiferromagnetism. Here, another iron-selenide KFe$_2$Se$_2$, a parent state
of iron-based superconductor, is predicted to be multiferroic. Its
two-dimensional block-type antiferromagnetism can generate a moderate electric
dipole for each Fe-Se layer via the Fe-Se-Fe exchange striction. Different
stacking configurations of these magnetic blocks give closely proximate
energies and thus the ground state of KFe$_2$Se$_2$ may be switchable between
antiferroelectric and ferroelectric phases.


title: Lectures on the Strominger system

abstract:
  These notes give an introduction to the Strominger system of partial
differential equations, and are based on lectures given in September 2015 at
the GEOQUANT School, held at the Institute of Mathematical Sciences (ICMAT) in
Madrid. We describe the links with the theory of balanced metrics in hermitian
geometry, the Hermite-Yang-Mills equations, and its origins in physics, that we
illustrate with many examples. We also cover some recent developments in the
moduli problem and the interrelation of the Strominger system with generalized
geometry, via the cohomological notion of string class.


title: Nontrivial homeomorphisms of \v{C}ech-Stone remainders

abstract:
  We study the group of automorphisms of certain corona C*-algebras. As a
corollary of a more general C*-algebraic result, we show that, under the
Continuum Hypothesis, $\beta X\setminus X$ has nontrivial homeomorphisms,
whenever $X$ is a noncompact locally compact metrizable manifold.


title: Measuring Multi-Configurational Character by Orbital Entanglement

abstract:
  One of the most critical tasks at the very beginning of a quantum chemical
investigation is the choice of either a multi- or single-configurational
method. Naturally, many proposals exist to define a suitable diagnostic of the
multi-configurational character for various types of wave functions in order to
assist this crucial decision. Here, we present a new orbital-entanglement based
multi-configurational diagnostic termed $Z_{s(1)}$. The correspondence of
orbital entanglement and static (or nondynamic) electron correlation permits
the definition of such a diagnostic. We chose our diagnostic to meet important
requirements such as well-defined limits for pure single-configurational and
multi-configurational wave functions. The $Z_{s(1)}$ diagnostic can be
evaluated from a partially converged, but qualitatively correct, and therefore
inexpensive density matrix renormalization group wave function as in our
recently presented automated active orbital selection protocol. Its robustness
and the fact that it can be evaluated at low cost make this diagnostic a
practical tool for routine applications.

categories: physics.chem-ph cond-mat.str-el physics.comp-ph quant-ph


title:
Raman lasing and Fano lineshapes in a packaged fiber-coupled
  whispering-gallerymode microresonator

abstract:
  We report Raman lasing and the optical analog of
electromagnetically-induced-transparency (EIT) in a whispering-gallerymode
(WGM) microtoroid resonator embedded in a low refractive index polymer matrix
together with a tapered fiber coupler. The Raman laser supports both single and
multimode operation with low power thresholds. Observations of Fano and
EIT-like pheonomena in a packaged microresonator will enable high resolution
sensors and can be used in networks where slow light process is needed. These
results open the way for portable, robust, and stable WGM microlasers and
laserbased sensors for applications in various environments.