title: A cautionary note about composite Galactic star formation relations

abstract:
  We explore the pitfalls which affect the comparison of the star-formation
(SF) relation for nearby molecular clouds with that for distant compact
molecular clumps. We show that both relations behave differently in the
($\Sigma_{gas}$, $\Sigma_{SFR}$) space, where $\Sigma_{gas}$ and $\Sigma_{SFR}$
are, respectively, the gas and SF rate surface densities, even when the physics
of star formation is the same. This is because the SF relation of nearby clouds
relates gas and star surface densities measured locally, that is, within a
given interval of gas surface density, or at a given protostar location. We
refer to such measurements as local measurements, and the corresponding SF
relation as the local relation. In contrast, the stellar content of a distant
molecular clump remains unresolved. Only the mean SF rate can be obtained from
e.g. the clump infrared luminosity. One clump therefore provides one single
point to the ($\Sigma_{gas}$, $\Sigma_{SFR}$) space, that is, its mean gas
surface density and SF rate surface density. We refer to this SF relation as a
global relation since it builds on the global properties of molecular clumps.
Its definition therefore requires an ensemble of cluster-forming clumps. We
show that, although the local and global relations have different slopes, this
per se cannot be taken as evidence for a change in the physics of SF with gas
surface density. It therefore appears that great caution should be taken when
physically interpreting a composite SF relation, that is, a relation combining
together local and global measurements.


title: The LPM effect in sequential bremsstrahlung 2: factorization

abstract:
  The splitting processes of bremsstrahlung and pair production in a medium are
coherent over large distances in the very high energy limit, which leads to a
suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper,
we continue analysis of the case when the coherence lengths of two consecutive
splitting processes overlap (which is important for understanding corrections
to standard treatments of the LPM effect in QCD), avoiding soft-gluon
approximations. In particular, this paper analyzes the subtle problem of how to
precisely separate overlapping double splitting (e.g.\ overlapping double
bremsstrahlung) from the case of consecutive, independent bremsstrahlung (which
is the case that would be implemented in a Monte Carlo simulation based solely
on single splitting rates). As an example of the method, we consider the rate
of real double gluon bremsstrahlung from an initial gluon with various
simplifying assumptions (thick media; $\hat q$ approximation; large $N_c$; and
neglect for the moment of processes involving 4-gluon vertices) and explicitly
compute the correction $\Delta\,d\Gamma/dx\,dy$ due to overlapping formation
times.


title: Hairy black holes in the general Skyrme model

abstract:
  We study the existence of hairy black holes in the generalized
Einstein-Skyrme model. It is proven that in the BPS model limit there are no
hairy black hole solutions, although the model admits gravitating (and flat
space) solitons. Furthermore, we find strong evidence that a necessary
condition for the existence of black holes with Skyrmionic hair is the
inclusion of the Skyrme term $\mathcal{L}_4$. As an example, we show that there
are no hairy black holes in the $\mathcal{L}_2+\mathcal{L}_6+\mathcal{L}_0$
model and present a new kind of black hole solutions with compact Skyrmion hair
in the $\mathcal{L}_4+\mathcal{L}_6+\mathcal{L}_0$ model.


title:
Suppressing star formation in quiescent galaxies with supermassive black
  hole winds

abstract:
  Quiescent galaxies with little or no ongoing star formation dominate the
galaxy population above $M_{*}\sim 2 \times 10^{10}~M_{\odot}$, where their
numbers have increased by a factor of $\sim25$ since $z\sim2$. Once star
formation is initially shut down, perhaps during the quasar phase of rapid
accretion onto a supermassive black hole, an unknown mechanism must remove or
heat subsequently accreted gas from stellar mass loss or mergers that would
otherwise cool to form stars. Energy output from a black hole accreting at a
low rate has been proposed, but observational evidence for this in the form of
expanding hot gas shells is indirect and limited to radio galaxies at the
centers of clusters, which are too rare to explain the vast majority of the
quiescent population. Here we report bisymmetric emission features co-aligned
with strong ionized gas velocity gradients from which we infer the presence of
centrally-driven winds in typical quiescent galaxies that host low-luminosity
active nuclei. These galaxies are surprisingly common, accounting for as much
as $10\%$ of the population at $M_* \sim 2 \times 10^{10}~ M_{\odot}$. In a
prototypical example, we calculate that the energy input from the galaxy's
low-level active nucleus is capable of driving the observed wind, which
contains sufficient mechanical energy to heat ambient, cooler gas (also
detected) and thereby suppress star formation.


title:
Adiabatic continuity, wavefunction overlap and topological phase
  transitions

abstract:
  In this article, we study the relation between wavefunction overlap and
adiabatic continuity in gapped quantum systems. We show that for two band
insulators, a scalar function can be defined in the momentum space, which
characterizes the wavefunction overlap between Bloch states in the two
insulators. If this overlap is nonzero for all momentum points in the Brillouin
zone, these two insulators are adiabatically connected, i.e. we can deform one
insulator into the other smoothly without closing the band gap. In addition, we
further prove that this adiabatic path preserves all the symmetries of the
insulators. The existence of such an adiabatic path implies that two insulators
with nonzero wavefunction overlap belong to the same topological phase. This
relation, between adiabatic continuity and wavefunction overlap, can be further
generalized to correlated systems. The generalized relation cannot be applied
to study generic many-body systems in the thermodynamic limit, because of the
orthogonality catastrophe. However, for certain interacting systems (e.g.
quantum Hall systems), the quantum wavefunction overlap can be utilized to
distinguish different quantum states. Experimental implications are also
discussed.


title: Quantum metrology with a single spin-$3/2$ defect in silicon carbide

abstract:
  We show that implementations for quantum sensing with exceptional sensitivity
and spatial resolution can be made using spin-3/2 semiconductor defect states.
We illustrate this using the silicon monovacancy deep center in hexagonal SiC
based on our rigorous derivation of this defect's ground state and of its
electronic and optical properties. For a single $\textrm{V}_{\textrm{Si}}^-$
defect, we obtain magnetic field sensitivities capable of detecting individual
nuclear magnetic moments. We also show that its zero-field splitting has an
exceptional strain and temperature sensitivity within the technologically
desirable near-infrared window of biological systems. The concepts and sensing
schemes developed here are applicable to other point defects with half spin
multiplet ($S\geq 3/2$) configuration.


title:
Correct implementation of polarization constants in wurtzite materials
  and impact on III-nitrides

abstract:
  Accurate values for polarization discontinuities between pyroelectric
materials are critical for understanding and designing the electronic
properties of heterostructures. For wurtzite materials, the zincblende
structure has been used in the literature as a reference to determine the
effective spontaneous polarization constants. We show that, because the
zincblende structure has a nonzero formal polarization, this method results in
a spurious contribution to the spontaneous polarization differences between
materials. In addition, we address the correct choice of "improper" versus
"proper" piezoelectric constants. For the technologically important III-nitride
materials GaN, AlN, and InN, we determine polarization discontinuities using a
consistent reference based on the layered hexagonal structure and the correct
choice of piezoelectric constants, and discuss the results in light of
available experimental data.


title: Leading Gravitational Corrections and a Unified Universe

abstract:
  Leading order gravitational corrections to the Einstein-Hilbert action can
lead to a consistent picture of the universe by unifying the epochs of
inflation and dark energy in a single framework. While the leading local
correction induces an inflationary phase in the early universe, the leading
non-local term leads to an accelerated expansion of the universe at the present
epoch. We argue that both the leading UV and IR terms can be obtained within
the framework of a covariant effective field theory of gravity. The
perturbative gravitational corrections therefore provide a fundamental basis
for understanding a possible connection between the two epochs.


title:
Scanning of the Supersymmetry Breaking Scale and the Gravitino Mass in
  Supergravity

abstract:
  We consider the minimal three-form ${\cal N}=1$ supergravity coupled to
nilpotent three-form chiral superfields. The supersymmetry breaking is sourced
by the three-forms of the chiral multiplets, while the value of the gravitino
mass is controlled by the three-form of the supergravity multiplet. The
three-forms can nucleate membranes which scan both the supersymmetry breaking
scale and the gravitino mass. The peculiar supergravity feature that the
cosmological constant is the sum of a positive contribution from the
supersymmetry breaking scale and a negative contribution from the gravitino
mass makes the cosmological constant jump. This can lead to a
phenomenologically allowed small value of the cosmological constant even though
the supersymmetry breaking scale and the gravitino mass are dynamically large.


The space density distribution of galaxies in the absolute magnitude -
  rotation velocity plane: a volume-complete Tully-Fisher relation from CALIFA
  stellar kinematics


title: On the Standard Model predictions for $R_K$ and $R_{K^*}$

abstract:
  We evaluate the impact of radiative corrections in the ratios $\Gamma[B\to M
\mu^+\mu^-]/\Gamma[B\to M e^+e^-]$ when the meson $M$ is a $K$ or a $K^*$.
Employing the cuts on $m^2_{\ell\ell}$ and the reconstructed $B$-meson mass
presently applied by the LHCb Collaboration, such corrections do not exceed a
few $\%$. Moreover, their effect is well described (and corrected for) by
existing Montecarlo codes. Our analysis reinforces the interest of these
observables as clean probe of physics beyond the Standard Model.


title:
Generalized multiscale finite element methods for space-time
  heterogeneous parabolic equations

abstract:
  In this paper, we consider local multiscale model reduction for problems with
multiple scales in space and time. We developed our approaches within the
framework of the Generalized Multiscale Finite Element Method (GMsFEM) using
space-time coarse cells. The main idea of GMsFEM is to construct a local
snapshot space and a local spectral decomposition in the snapshot space.
Previous research in developing multiscale spaces within GMsFEM focused on
constructing multiscale spaces and relevant ingredients in space only. In this
paper, our main objective is to develop a multiscale model reduction framework
within GMsFEM that uses space-time coarse cells. We construct space-time
snapshot and offline spaces. We compute these snapshot solutions by solving
local problems. A complete snapshot space will use all possible boundary
conditions; however, this can be very expensive. We propose using randomized
boundary conditions and oversampling. We construct the local spectral
decomposition based on our analysis, as presented in the paper. We present
numerical results to confirm our theoretical findings and to show that using
our proposed approaches, we can obtain an accurate solution with low
dimensional coarse spaces. We remark that the proposed method is a significant
extension compared to existing methods, which use coarse cells in space only
because of (1) the parabolic nature of cell solutions, (2) extra degrees of
freedom associated with space-time cells, and (3) local boundary conditions in
space-time cells.


title:
Zombie Vortex Instability. II. Thresholds to Trigger Instability and the
  Properties of Zombie Turbulence in the Dead Zones of Protoplanetary Disks

abstract:
  In Zombie Vortex Instability (ZVI), perturbations excite critical layers in
stratified, rotating shear flow (as in protoplanetary disks), causing them to
generate vortex layers, which roll-up into anticyclonic zombie vortices and
cyclonic vortex sheets. The process is self-sustaining as zombie vortices
perturb new critical layers, spawning a next generation of zombie vortices.
Here, we focus on two issues: the minimum threshold of perturbations that
trigger self-sustaining vortex generation, and the properties of the late-time
zombie turbulence on large and small scales. The critical parameter that
determines whether ZVI is triggered is the magnitude of the vorticity on the
small scales (and not velocity), the minimum Rossby number needed for
instability is $Ro_{crit}\sim0.2$ for $\beta\equiv N/\Omega = 2$, where $N$ is
the Brunt-V\"ais\"al\"a frequency. While the threshold is set by vorticity, it
is useful to infer a criterion on the Mach number, for Kolmogorov noise, the
critical Mach number scales with Reynolds number: $Ma_{crit}\sim
Ro_{crit}Re^{-1/2}$. In protoplanetary disks, this is $Ma_{crit}\sim10^{-6}$.
On large scales, zombie turbulence is characterized by anticyclones and
cyclonic sheets with typical Rossby number $\sim$0.3. The spacing of the
cyclonic sheets and anticyclones appears to have a "memory" of the spacing of
the critical layers. On the small scales, zombie turbulence has no memory of
the initial conditions and has a Kolmogorov-like energy spectrum. While our
earlier work was in the limit of uniform stratification, we have demonstrated
that ZVI works for non-uniform Brunt-V\"ais\"al\"a frequency profiles that may
be found in protoplanetary disks.


title: Fixed point structure of the conformal factor field in quantum gravity

abstract:
  The $\mathcal{O}(\partial^2)$ background independent flow equations for
conformally reduced gravity are shown to be equivalent to flow equations
naturally adapted to scalar field theory with a wrong sign kinetic term. This
sign change is shown to have a profound effect on the renormalization group
properties, broadly resulting in a continuum of fixed points supporting both a
discrete and a continuous eigenoperator spectrum, the latter always including
relevant directions. The properties at the Gaussian fixed point are understood
in particular depth, but also detailed studies of the local potential
approximation, and the full $\mathcal{O}(\partial^2)$ approximation are given.
These results are related to evidence for asymptotic safety found by other
authors.


title:
Many-Body Quantum Optics with Decaying Atomic Spin States: ($\gamma$,
  $\kappa$) Dicke model

abstract:
  We provide a theory for quantum-optical realizations of the open Dicke model
with internal, atomic spin states subject to spontaneous emission with rate
$\gamma$. This introduces a second decay channel for excitations to
irreversibly dissipate into the environment, in addition to the photon loss
with rate $\kappa$, which is composed of individual atomic decay processes and
a collective atomic decay mechanism. The strength of the latter is determined
by the cavity geometry. We compute the mean-field non-equilibrium steady states
for spin and photon observables in the long-time limit, $t\rightarrow \infty$.
Although $\gamma$ does not conserve the total angular momentum of the spin
array, we argue that our solution is exact in the thermodynamic limit, for the
number of atoms $N\rightarrow \infty$. In light of recent and upcoming
experiments realizing superradiant phase transitions using internal atomic
states with pinned atoms in optical lattices, our work lays the foundation for
the pursuit of a new class of open quantum magnets coupled to quantum light.


title: Coherent magneto-elastic oscillations in superfluid magnetars

abstract:
  We study the effect of superfluidity on torsional oscillations of highly
magnetised neutron stars (magnetars) with a microphysical equation of state by
means of two-dimensional, magnetohydrodynamical- elastic simulations. The
superfluid properties of the neutrons in the neutron star core are treated in a
parametric way in which we effectively decouple part of the core matter from
the oscillations. Our simulations confirm the existence of two groups of
oscillations, namely continuum oscillations that are confined to the neutron
star core and are of Alfv\'enic character, and global oscillations with
constant phase and that are of mixed magneto-elastic type. The latter might
explain the quasi-periodic oscillations observed in magnetar giant flares,
since they do not suffer from the additional damping mechanism due to phase
mixing, contrary to what happens for continuum oscillations. However, we cannot
prove rigorously that the coherent oscillations with constant phase are normal
modes. Moreover, we find no crustal shear modes for the magnetic field
strengths typical for magnetars.We provide fits to our numerical simulations
that give the oscillation frequencies as functions of magnetic field strength
and proton fraction in the core.


title:
Tensor networks, $p$-adic fields, and algebraic curves: arithmetic and
  the AdS$_3$/CFT$_2$ correspondence

abstract:
  One of the many remarkable properties of conformal field theory in two
dimensions is its connection to algebraic geometry. Since every compact Riemann
surface is a projective algebraic curve, many constructions of interest in
physics (which a priori depend on the analytic structure of the spacetime) can
be formulated in purely algebraic language. This opens the door to interesting
generalizations, obtained by taking another choice of field: for instance, the
$p$-adics. We generalize the AdS/CFT correspondence according to this
principle; the result is a formulation of holography in which the bulk geometry
is discrete---the Bruhat--Tits tree for $\mathrm{PGL}(2,\mathbb{Q}_p)$---but
the group of bulk isometries nonetheless agrees with that of boundary conformal
transformations and is not broken by discretization. We suggest that this forms
the natural geometric setting for tensor networks that have been proposed as
models of bulk reconstruction via quantum error correcting codes; in certain
cases, geodesics in the Bruhat--Tits tree reproduce those constructed using
quantum error correction. Other aspects of holography also hold: Standard
holographic results for massive free scalar fields in a fixed background carry
over to the tree, whose vertical direction can be interpreted as a
renormalization-group scale for modes in the boundary CFT. Higher-genus bulk
geometries (the BTZ black hole and its generalizations) can be understood
straightforwardly in our setting, and the Ryu-Takayanagi formula for the
entanglement entropy appears naturally.


title:
Deep wideband single pointings and mosaics in radio interferometry - How
  accurately do we reconstruct intensities and spectral indices of faint
  sources?

abstract:
  Many deep wide-band wide-field radio interferometric surveys are being
designed to accurately measure intensities, spectral indices and polarization
properties of faint source populations. In this paper we compare various
wideband imaging methods to evaluate the accuracy to which intensities and
spectral indices of sources close to the confusion limit can be reconstructed.
We simulated a wideband single-pointing (C-array, L-Band (1-2GHz)) and
46-pointing mosaic(D-array, C-Band (4-8GHz)) JVLA observation using realistic
brightness distribution ranging from $1\mu$Jy to $100m$Jy and time-,frequency-,
polarization- and direction-dependent instrumental effects. The main results
from these comparisons are (a) errors in the reconstructed intensities and
spectral indices are larger for weaker sources even in the absence of simulated
noise, (b) errors are systematically lower for joint reconstruction methods
(such as MT-MFS) along with A-Projection for accurate primary beam correction,
and (c) use of MT-MFS for image reconstruction eliminates Clean-bias (which is
present otherwise). Auxiliary tests include solutions for deficiencies of data
partitioning methods (e.g. the use of masks to remove clean bias and hybrid
methods to remove sidelobes from sources left undeconvolved), the effect of
sources not at pixel centers and the consequences of various other numerical
approximations within software implementations. This paper also demonstrates
the level of detail at which such simulations must be done in order to reflect
reality, enable one to systematically identify specific reasons for every trend
that is observed and to estimate scientifically defensible imaging performance
metrics and the associated computational complexity of the algorithms/analysis
procedures.


title:
Generalized Dyson model: nature of zero mode and its implication in
  dynamics

abstract:
  We study the role of the anomalous $E=0$ state in dynamical properties of
non-interacting fermionic chains with chiral symmetry and correlated bond
disorder in one dimension. These models posses a diverging density of states at
zero energy leading to a divergent localization length at the band center. By
analytically calculating the localization length for a finite system, we show
that correlations in the disorder modify the spatial decay of the $E = 0$ state
from being quasilocalized to extended. We numerically simulate charge and
entanglement propagation and provide evidence that states close to $E=0$
dominate the dynamical properties. Remarkably, we find that correlations lead
to subdiffusive charge propagation, whereas the growth of entanglement is
logarithmically slow. A logarithmic scaling of entanglement saturation with
system size is also observed, which indicates a behavior akin to quantum
critical glasses.


title:
Casimir forces and quantum friction from Ginzburg radiation in atomic
  BECs

abstract:
  We theoretically propose an experimentally viable scheme to use an impurity
atom in an atomic Bose-Einstein condensate, in order to realize
condensed-matter analogs of quantum vacuum effects. In a suitable atomic level
configuration, the collisional interaction between the impurity atom and the
density fluctuations in the condensate can be tailored to closely reproduce the
electric-dipole coupling of quantum electrodynamics. By virtue of this analogy,
we recover and extend the paradigm of electromagnetic vacuum forces to the
domain of cold atoms, showing in particular the emergence, at supersonic atomic
speeds, of a novel power-law scaling of the Casimir force felt by the atomic
impurity, as well as the occurrence of a quantum frictional force, accompanied
by the Ginzburg emis- sion of Bogoliubov quanta. Observable consequences of
these quantum vacuum effects in realistic spectroscopic experiments are
discussed.


title: Electron electric dipole moment in Inverse Seesaw models

abstract:
  We consider the contribution of sterile neutrinos to the electric dipole
moment of charged leptons in the most minimal realisation of the Inverse Seesaw
mechanism, in which the Standard Model is extended by two right-handed
neutrinos and two sterile fermion states. Our study shows that the two pairs of
(heavy) pseudo-Dirac mass eigenstates can give significant contributions to the
electron electric dipole moment, lying close to future experimental sensitivity
if their masses are above the electroweak scale. The major contribution comes
from two-loop diagrams with pseudo-Dirac neutrino states running in the loops.
In our analysis we further discuss the possibility of having a successful
leptogenesis in this framework, compatible with a large electron electric
dipole moment.


title: Primary invariants of Hurwitz Frobenius manifolds

abstract:
  Hurwitz spaces parameterizing covers of the Riemann sphere can be equipped
with a Frobenius structure. In this review, we recall the construction of such
Hurwitz Frobenius manifolds as well as the correspondence between semisimple
Frobenius manifolds and the topological recursion formalism. We then apply this
correspondence to Hurwitz Frobenius manifolds by explaining that the
corresponding primary invariants can be obtained as periods of
multidifferentials globally defined on a compact Riemann surface by topological
recursion. Finally, we use this construction to reply to the following question
in a large class of cases: given a compact Riemann surface, what does the
topological recursion compute?


title:
Online Adaptive Local Multiscale Model Reduction for Heterogeneous
  Problems in Perforated Domains

abstract:
  In this paper, we develop and analyze an adaptive multiscale approach for
heterogeneous problems in perforated domains. In many applications, these
problems have a multiscale nature arising because of the perforations, their
geometries, the sizes of the perforations, and configurations. In this paper,
we present a general offline/online procedure, which can adequately and
adaptively represent the local degrees of freedom and derive appropriate
coarse-grid equations. The main contributions of this paper are (1) the
rigorous analysis of the offline approach (2) the development of the online
procedures and their analysis (3) the development of adaptive strategies. We
present an online procedure, which allows adaptively incorporating global
information and is important for a fast convergence when combined with the
adaptivity. Our methodology allows adding and guides constructing new online
multiscale basis functions adaptively in appropriate regions. We present the
convergence analysis of the online adaptive enrichment algorithm for the Stokes
system. In particular, we show that the online procedure has a rapid
convergence with a rate related to the number of offline basis functions, and
one can obtain fast convergence by a sufficient number of offline basis
functions, which are computed in the offline stage. To illustrate the
performance of our method, we present numerical results with both small and
large perforations. We see that only a few (1 or 2) online iterations can
significantly improve the offline solution.


title: AIMS:Average Information Matrix Splitting

abstract:
  For linear mixed models with co-variance matrices which are not linearly
dependent on variance component parameters, we prove that the average of the
observed information and the Fisher information can be split into two parts.
The essential part enjoys a simple and computational friendly formula, while
the other part which involves a lot of computations is a random zero matrix and
thus is negligible.


title: The Dynamics of Vector-Borne Relapsing Diseases

abstract:
  In this paper we describe the dynamics of a vector-borne relapsing disease,
such as tick-borne relapsing fever, using the methods of compartmental models.
After some motivation, model description, and a brief overview of the theory of
compartmental models, we compute a general form of the reproductive ratio
$R_0$, which is the average number of new infections produced by a single
infected individual. A disease free equilibrium undergoes a bifurcation at $R_0
=1$ and we show that for an arbitrary number of relapses it is a transcritical
bifurcation with a single branch of endemic equilibria that is locally
asymptotically stable for $R_0$ sufficiently close to 1. We close with some
discussion and directions for future research.


title: FractalNet: Ultra-Deep Neural Networks without Residuals

abstract:
  We introduce a design strategy for neural network macro-architecture based on
self-similarity. Repeated application of a simple expansion rule generates deep
networks whose structural layouts are precisely truncated fractals. These
networks contain interacting subpaths of different lengths, but do not include
any pass-through or residual connections; every internal signal is transformed
by a filter and nonlinearity before being seen by subsequent layers. In
experiments, fractal networks match the excellent performance of standard
residual networks on both CIFAR and ImageNet classification tasks, thereby
demonstrating that residual representations may not be fundamental to the
success of extremely deep convolutional neural networks. Rather, the key may be
the ability to transition, during training, from effectively shallow to deep.
We note similarities with student-teacher behavior and develop drop-path, a
natural extension of dropout, to regularize co-adaptation of subpaths in
fractal architectures. Such regularization allows extraction of
high-performance fixed-depth subnetworks. Additionally, fractal networks
exhibit an anytime property: shallow subnetworks provide a quick answer, while
deeper subnetworks, with higher latency, provide a more accurate answer.


title:
Numerical evidence for a phase transition in 4d spin foam quantum
  gravity

abstract:
  Building on recent advances in defining Wilsonian RG flows, and in particular
the notion of scales, for background-independent theories, we present a first
investigation of the renormalization of the 4d spin foam path integral for
quantum gravity, both analytically and numerically. Focussing on a specific
truncation of the model using a hypercubic lattice, we compute the RG flow and
find strong indications for a phase transition, as well as an interesting
interplay between the different observed phases and the (broken) diffeomorphism
symmetry of the model. Most notably, it appears that the critical point between
the phases, which is a fixed point of the RG flow, is precisely where broken
diffeomorphism symmetry is restored, which suggests that it might allow for the
definition a continuum limit of the quantum gravity theory.


title: Blind Analysis of CT Image Noise Using Residual Denoised Images

abstract:
  CT protocol design and quality control would benefit from automated tools to
estimate the quality of generated CT images. These tools could be used to
identify erroneous CT acquisitions or refine protocols to achieve certain
signal to noise characteristics. This paper investigates blind estimation
methods to determine global signal strength and noise levels in chest CT
images. Methods: We propose novel performance metrics corresponding to the
accuracy of noise and signal estimation. We implement and evaluate the noise
estimation performance of six spatial- and frequency- based methods, derived
from conventional image filtering algorithms. Algorithms were tested on patient
data sets from whole-body repeat CT acquisitions performed with a higher and
lower dose technique over the same scan region. Results: The proposed
performance metrics can evaluate the relative tradeoff of filter parameters and
noise estimation performance. The proposed automated methods tend to
underestimate CT image noise at low-flux levels. Initial application of
methodology suggests that anisotropic diffusion and Wavelet-transform based
filters provide optimal estimates of noise. Furthermore, methodology does not
provide accurate estimates of absolute noise levels, but can provide estimates
of relative change and/or trends in noise levels.


title: Self Paced Deep Learning for Weakly Supervised Object Detection

abstract:
  In a weakly-supervised scenario object detectors need to be trained using
image-level annotation alone. Since bounding-box-level ground truth is not
available, most of the solutions proposed so far are based on an iterative,
Multiple Instance Learning framework in which the current classifier is used to
select the highest-confidence boxes in each image, which are treated as
pseudo-ground truth in the next training iteration. However, the errors of an
immature classifier can make the process drift, usually introducing many of
false positives in the training dataset. To alleviate this problem, we propose
in this paper a training protocol based on the self-paced learning paradigm.
The main idea is to iteratively select a subset of images and boxes that are
the most reliable, and use them for training. While in the past few years
similar strategies have been adopted for SVMs and other classifiers, we are the
first showing that a self-paced approach can be used with deep-network-based
classifiers in an end-to-end training pipeline. The method we propose is built
on the fully-supervised Fast-RCNN architecture and can be applied to similar
architectures which represent the input image as a bag of boxes. We show
state-of-the-art results on Pascal VOC 2007, Pascal VOC 2010 and ILSVRC 2013.
On ILSVRC 2013 our results based on a low-capacity AlexNet network outperform
even those weakly-supervised approaches which are based on much higher-capacity
networks.


title:
Survival, decay, and topological protection in non-Hermitian quantum
  transport

abstract:
  Non-Hermitian quantum systems can exhibit unique observables characterizing
topologically protected transport in the presence of decay. The topological
protection arises from winding numbers associated with non-decaying dark
states, which are decoupled from the environment and thus immune to
dissipation. Here we develop a classification of topological dynamical phases
for one-dimensional quantum systems with periodically-arranged absorbing sites.
This is done using the framework of Bloch theory to describe the dark states
and associated topological invariants. The observables, such as the average
particle displacement over its life span, feature quantized contributions that
are governed by the winding numbers of cycles around dark-state submanifolds in
the Hamiltonian parameter space. Changes in the winding numbers at topological
transitions are manifested in non-analytic behavior of the observables. We
discuss the conditions under which nontrivial topological phases may be found,
and provide examples that demonstrate how additional constraints or symmetries
can lead to rich topological phase diagrams.


title: Photonic nanowire-based single-photon source with polarization control

abstract:
  This document describes a modal method for optical simulations of structures
with elliptical cross sections and its application to the design of the
photonic nanowire (NW)-based single-photon source (SPS). The work was carried
out in the framework of the EMRP SIQUTE project ending May 31st 2016. The
document summarizes the new method used to treat the elliptical cross section
in an efficient manner and additionally presents design parameters for the
photonic NW SPS with elliptical cross section for polarization control. The
document does not introduce the new method and the elliptical photonic NW SPS
design in the context of existing literature but instead dives directly into
the equations. Additionally, the document assumes that the reader possess
expert knowledge of general modal expansion techniques. The presented formalism
does not implement Li's factorization rules nor the recently proposed open
boundary geometry formalism with fast convergence towards the open geometry
limit but instead relies on (older) formalism based on coordinate
transformations for emulating open systems. However, the document does contain
all the information needed for the expert reader to implement the method and
reproduce the simulations.


title: The Cuntz semigroup and domain theory

abstract:
  Domain theory has its origins in Mathematics and Theoretical Computer
Science. Mathematically it combines order and topology. Its central concepts
have their origin in the idea of approximating ideal objects by their
relatively finite or, more generally, relatively compact parts.
  The development of domain theory in recent years was mainly motivated by
question in denotational semantics and the theory of computation. But since
2008, domain theoretical notions and methods are used in the theory of
C*-algebras in connection with the Cuntz semigroup.
  This paper is largely expository. It presents those notions of domain theory
that seem to be relevant for the theory of Cuntz semigroups and have sometimes
been developed independently in both communities. It also contains a new aspect
in presenting results of Elliott, Ivanescu and Santiago on the cone of traces
of a C*-algebra as a particular case of the dual of a Cuntz semigroup.


title: Poincar\'e-type Inequalities and Finding Good Parameterizations

abstract:
  A very important question in geometric measure theory is how geometric
features of a set translate into analytic information about it. In 1960, E. R.
Reifenberg proved that if a set is well approximated by planes at every point
and at every scale, then the set is a bi-H\"older image of a plane. It is known
today that Carleson-type conditions on these approximating planes guarantee a
bi-Lipschitz parameterization of the set. In this paper, we consider an
$n$-Ahlfors regular rectifiable set $M \subset \mathbb{R}^{n+d}$ that satisfies
a Poincar\'{e}-type inequality involving the tangential derivative. Then, we
show that a Carleson-type condition on the oscillations of the tangent planes
of $M$ guarantees that $M$ is contained in a bi-Lipschitz image of an
$n$-plane. We also explore the Poincar\'e-type inequality considered here and
show that it is in fact equivalent to other Poincar\'e-type inequalities
considered on general metric measure spaces.


title: Eco-evolutionary dynamics of social dilemmas

abstract:
  Social dilemmas are an integral part of social interactions. Cooperative
actions, ranging from secreting extra-cellular products in microbial
populations to donating blood in humans, are costly to the actor and hence
create an incentive to shirk and avoid the costs. Nevertheless, cooperation is
ubiquitous in nature. Both costs and benefits often depend non-linearly on the
number and types of individuals involved -- as captured by idioms such as `too
many cooks spoil the broth' where additional contributions are discounted, or
`two heads are better than one' where cooperators synergistically enhance the
group benefit. Interaction group sizes may depend on the size of the population
and hence on ecological processes. This results in feedback mechanisms between
ecological and evolutionary processes, which jointly affect and determine the
evolutionary trajectory. Only recently combined eco-evolutionary processes
became experimentally tractable in microbial social dilemmas. Here we analyse
the evolutionary dynamics of non-linear social dilemmas in settings where the
population fluctuates in size and the environment changes over time. In
particular, cooperation is often supported and maintained at high densities
through ecological fluctuations. Moreover, we find that the combination of the
two processes routinely reveals highly complex dynamics, which suggests common
occurrence in nature.


title: Parametric-Rate Inference for One-Sided Differentiable Parameters

abstract:
  Suppose one has a collection of parameters indexed by a (possibly infinite
dimensional) set. Given data generated from some distribution, the objective is
to estimate the maximal parameter in this collection evaluated at this
distribution. This estimation problem is typically non-regular when the
maximizing parameter is non-unique, and as a result standard asymptotic
techniques generally fail in this case. We present a technique for developing
parametric-rate confidence intervals for the quantity of interest in these
non-regular settings. We show that our estimator is asymptotically efficient
when the maximizing parameter is unique so that regular estimation is possible.
We apply our technique to a recent example from the literature in which one
wishes to report the maximal absolute correlation between a prespecified
outcome and one of p predictors. The simplicity of our technique enables an
analysis of the previously open case where p grows with sample size.
Specifically, we only require that log(p) grows slower than the square root of
n, where n is the sample size. We show that, unlike earlier approaches, our
method scales to massive data sets: the point estimate and confidence intervals
can be constructed in O(np) time.


title:
Modeling flow in porous media with double porosity/permeability:
  Mathematical model, properties, and analytical solutions

abstract:
  Geo-materials such as vuggy carbonates are known to exhibit multiple spatial
scales. A common manifestation of spatial scales is the presence of (at least)
two different scales of pores, which is commonly referred to as double
porosity. To complicate things, the pore-network at each scale exhibits
different permeability, and these networks are connected through fissure and
conduits. Although some models are available in the literature, they lack a
strong theoretical basis. This paper aims to fill this lacuna by providing the
much needed theoretical foundations of the flow in porous media which exhibit
double porosity/permeability. We first obtain a mathematical model for double
porosity/permeability using the maximization of rate of dissipation hypothesis,
and thereby providing a firm thermodynamic underpinning. We then present, along
with mathematical proofs, several important mathematical properties that the
solutions to the double porosity/permeability model satisfy. These properties
are important in their own right as well as serve as good (mechanics-based) a
posteriori measures to assess the accuracy of numerical solutions. We also
present several canonical problems and obtain the corresponding analytical
solutions, which are used to gain insights into the velocity and pressure
profiles, and the mass transfer across the two pore-networks. In particular, we
highlight how the solutions under the double porosity/permeability differ from
the corresponding solutions under Darcy equations.


title:
Adaptive Newton Method for Empirical Risk Minimization to Statistical
  Accuracy

abstract:
  We consider empirical risk minimization for large-scale datasets. We
introduce Ada Newton as an adaptive algorithm that uses Newton's method with
adaptive sample sizes. The main idea of Ada Newton is to increase the size of
the training set by a factor larger than one in a way that the minimization
variable for the current training set is in the local neighborhood of the
optimal argument of the next training set. This allows to exploit the quadratic
convergence property of Newton's method and reach the statistical accuracy of
each training set with only one iteration of Newton's method. We show
theoretically and empirically that Ada Newton can double the size of the
training set in each iteration to achieve the statistical accuracy of the full
training set with about two passes over the dataset.


title:
Three Dimensional Measurements by Deflectometry and Double Hilbert
  Transform

abstract:
  An improved phase retrieval method based Hilbert transform is introduced to
quantitatively calculate the phase distribution from distorted fringe pattern.
Also phase measurement deflectomety are widely used in specular type samples.
The background noise or bias should be suppressed prior to apply Hilbert
transform. A method for suppression background noise double Hilbert transform
is presented, which requires only one image. The method is easy to implement,
and it is able to conducting automated fast measurements. We have demonstrated
the double Hilbert transform method to retrieve the phase and background
suppression by computer simulation and experiment in phase measuring
deflectometry method.


title:
Impact of General Channel Aging Conditions on the Downlink Performance
  of Massive MIMO

abstract:
  Recent works have identified massive multiple-input-multiple-output (MIMO) as
a key technology for achieving substantial gains in spectral and energy
efficiency. Additionally, the turn to low-cost transceivers, being prone to
hardware impairments is the most effective and attractive way for
cost-efficient applications concerning massive MIMO systems. In this context,
the impact of channel aging, which severely affects the performance, is
investigated herein by considering a generalized model. Specifically, we show
that both Doppler shift because of the users' relative movement as well as
phase noise due to noisy local oscillators (LOs) contribute to channel aging.
To this end, we first propose a joint model, encompassing both effects, in
order to investigate the performance of a massive MIMO system based on the
inevitable time-varying nature of realistic mobile communications. Then, we
derive the deterministic equivalents (DEs) for the
signal-to-noise-and-interference ratios (SINRs) with maximum ratio transmission
(MRT) and regularized zero-forcing precoding (RZF). Our analysis not only
demonstrates a performance comparison between MRT and RZF under these
conditions, but most importantly, it reveals interesting properties regarding
the effects of user mobility and phase noise. In particular, the large antenna
limit behavior depends profoundly on both effects, but the burden due to user
mobility is much more detrimental than phase noise even for moderate user
velocities ($\approx30$ km/h), while the negative impact of phase noise is
noteworthy at lower mobility conditions.


title: In-situ 3D Imaging of Catalysis Induced Strain in Gold Nanoparticles

abstract:
  Multi-electron transfer processes, such as hydrogen and oxygen evolution
reactions, are crucially important in energy and biological science but require
favorable catalysts to achieve fast kinetics. Nanostructuring catalysts can
dramatically improve their properties, which can be difficult to understand due
to strain and size dependent thermodynamics, the influence of defects, and
substrate dependent activities. Here, we report 3D imaging of single gold
nanoparticles during catalysis of ascorbic acid decomposition using Bragg
coherent diffractive imaging (BCDI) as a route to eliminate ensemble effects
while elucidating the strain-activity connection. Local strains were measured
in single nanoparticles and modeled using reactive molecular dynamics (RMD)
simulations and finite element analysis (FEA) simulations. RMD reveals a new
chemical pathway for local strain generation in the gold lattice: chemisorption
of hydroxyl ions. FEA reveals that the RMD results are transferable to the
larger nanocrystal sizes studied in the experiment. Our study reveals the
strain-activity connection and opens a powerful new avenue for joint
theoretical and experimental studies of multi-electron transfer processes
catalyzed by nanocrystals.


title:
Estimating the Malaria Attributable Fever Fraction Accounting for
  Parasites Being Killed by Fever and Measurement Error

abstract:
  Malaria is a parasitic disease that is a major health problem in many
tropical regions. The most characteristic symptom of malaria is fever. The
fraction of fevers that are attributable to malaria, the malaria attributable
fever fraction (MAFF), is an important public health measure for assessing the
effect of malaria control programs and other purposes. Estimating the MAFF is
not straightforward because there is no gold standard diagnosis of a malaria
attributable fever; an individual can have malaria parasites in her blood and a
fever, but the individual may have developed partial immunity that allows her
to tolerate the parasites and the fever is being caused by another infection.
We define the MAFF using the potential outcome framework for causal inference
and show what assumptions underlie current estimation methods. Current
estimation methods rely on an assumption that the parasite density is correctly
measured. However, this assumption does not generally hold because (i) fever
kills some parasites and (ii) the measurement of parasite density has
measurement error. In the presence of these problems, we show current
estimation methods do not perform well. We propose a novel maximum likelihood
estimation method based on exponential family g-modeling. Under the assumption
that the measurement error mechanism and the magnitude of the fever killing
effect are known, we show that our proposed method provides approximately
unbiased estimates of the MAFF in simulation studies. A sensitivity analysis
can be used to assess the impact of different magnitudes of fever killing and
different measurement error mechanisms. We apply our proposed method to
estimate the MAFF in Kilombero, Tanzania.


title:
Correspondence between Einstein-Yang-Mills-Lorentz systems and dynamical
  torsion models

abstract:
  In the framework of Einstein-Yang-Mills theories, we study the gauge Lorentz
group and establish a particular correspondence between this case and a certain
class of theories with torsion within Riemann-Cartan space-times. This relation
is specially useful in order to simplify the problem of finding exact solutions
to the Einstein-Yang-Mills equations. The applicability of the method is
divided into two approaches: one associated with the Lorentz group SO(1,n-1) of
the space-time rotations and another one with its subgroup SO(n-2). Solutions
for both cases are presented by the explicit use of this correspondence and,
interestingly, for the last one by imposing on our ansatz the same kind of
rotation and reflection symmetry properties as for a nonvanishing space-time
torsion. Although these solutions were found in previous literature by a
different approach, our method provides an alternative way to obtain them and
it may be used in future research to find other exact solutions within this
theory.


title:
Diffractive $\rho$ and $\phi$ production at HERA using an AdS/QCD
  holographic light-front meson wavefunction

abstract:
  We use an anti-de Sitter/Quantum Chromodynamics (AdS/QCD) holographic
light-front wavefunction for the $\rho$ and $\phi$ mesons, in conjunction with
the Color Glass Condensate (CGC) dipole cross-section whose parameters are
fitted to the most recent 2015 high precision HERA data on inclusive Deep
Inelastic Scattering (DIS), in order to predict the cross-sections for
diffractive $\rho$ and $\phi$ electroproduction. Our results suggest that the
holographic meson light-front wavefunction is able to give a simultaneous
description of the $\rho$ and $\phi$ production data provided we use a set of
light quark masses with $m_{u,d}$ < $m_{s}$ ~ 0.14 GeV.


title:
Negative energy ground states for the $L^2$-critical NLSE on metric
  graphs

abstract:
  We investigate the existence of ground states with prescribed mass for the
focusing nonlinear Schr\"odinger equation with $L^2$-critical power
nonlinearity on noncompact quantum graphs. We prove that, unlike the case of
the real line, for certain classes of graphs there exist ground states with
negative energy for a whole interval of masses. A key role is played by a
thorough analysis of Gagliardo-Nirenberg inequalities and on estimates of the
optimal constants. Most of the techniques are new and suited to the
investigation of variational problems on metric graphs.


title:
Exploring the mass assembly of the early-type disc galaxy NGC3115 with
  MUSE

abstract:
  We present MUSE integral field spectroscopic data of the S0 galaxy NGC 3115
obtained during the instrument commissioning at the ESO Very Large Telescope
(VLT). We analyse the galaxy stellar kinematics and stellar populations and
present two dimensional maps of their associated quantities. We thus illustrate
the capacity of MUSE to map extra-galactic sources to large radii in an
efficient manner, i.e., ~4 Re, and provide relevant constraints on its mass
assembly. We probe the well known set of substructures of NGC 3115 (its nuclear
disc, stellar rings, outer kpc-scale stellar disc and spheroid) and show their
individual associated signatures in the MUSE stellar kinematics and stellar
populations maps. In particular, we confirm that NGC 3115 has a thin fast
rotating stellar disc embedded in a fast rotating spheroid, and that these two
structures show clear differences in their stellar age and metallicity
properties. We emphasise an observed correlation between the radial stellar
velocity, V, and the Gauss-Hermite moment, h3, creating a "butterfly" shape in
the central 15" of the h3 map. We further detect the previously reported weak
spiral and ring-like structures, and find evidence that these features can be
associated with regions of younger mean stellar ages. We provide tentative
evidence for the presence of a bar, despite the fact that the V-h3 correlation
can be reproduced by a simple axisymmetric dynamical model. Finally, we present
a reconstruction of the two dimensional star formation history of NGC 3115 and
find that most of its current stellar mass was formed at early epochs (>12Gyr
ago), while star formation continued in the outer (kpc-scale) stellar disc
until recently. Since z~2, and within ~4 Re, we suggest that NGC 3115 has been
mainly shaped by secular processes.


title: First axion bounds from a pulsating helium-rich white dwarf star

abstract:
  The Peccei-Quinn mechanism proposed to solve the CP problem of Quantum
Chromodynamics has as consequence the existence of axions, hypothetical weakly
interacting particles whose mass is constrained to be on the sub-eV range. If
these particles exist and interact with electrons, they would be emitted from
the dense interior of white dwarfs, becoming an important energy sink for the
star. Due to their well known physics, white dwarfs are good laboratories to
study the properties of fundamental particles such as the axions. We study the
general effect of axion emission on the evolution of helium-rich white dwarfs
and on their pulsational properties. To this aim, we calculate evolutionary
helium-rich white dwarf models with axion emission, and asses the pulsational
properties of this models. Our results indicate that the rates of change of
pulsation periods are significantly affected by the existence of axions. We are
able for the first time to independently constrain the mass of the axion from
the study of pulsating helium-rich white dwarfs. To do this, we use an
estimation of the rate of change of period of the pulsating white dwarf PG
1351+489 corresponding to the dominant pulsation period. From an
asteroseismological model of PG 1351+489 we obtain $g_{ae}<3.3\times10^{-13}$
for the axion-electron coupling constant, or $m_a\cos^2{\beta}\lesssim$ 11.5
meV for the axion mass. This constraint is relaxed to
$g_{ae}<5.5\times10^{-13}$ ($m_a\cos^2{\beta}\lesssim$ 19.5 meV), when no
detailed asteroseismological model is adopted for the comparison with
observations.


title:
On-line Active Reward Learning for Policy Optimisation in Spoken
  Dialogue Systems

abstract:
  The ability to compute an accurate reward function is essential for
optimising a dialogue policy via reinforcement learning. In real-world
applications, using explicit user feedback as the reward signal is often
unreliable and costly to collect. This problem can be mitigated if the user's
intent is known in advance or data is available to pre-train a task success
predictor off-line. In practice neither of these apply for most real world
applications. Here we propose an on-line learning framework whereby the
dialogue policy is jointly trained alongside the reward model via active
learning with a Gaussian process model. This Gaussian process operates on a
continuous space dialogue representation generated in an unsupervised fashion
using a recurrent neural network encoder-decoder. The experimental results
demonstrate that the proposed framework is able to significantly reduce data
annotation costs and mitigate noisy user feedback in dialogue policy learning.


title: On the conditions for existence and continuity of fractional velocity

abstract:
  H\"older functions represent mathematical models of nonlinear physical
phenomena. This work investigates the general conditions of existence of
fractional velocity as a localized generalization of ordinary derivative with
regard to the exponent order. Fractional velocity is defined as the limit of
the difference quotient of the function's increment and the difference of its
argument raised to a fractional power. A relationship to the point-wise
H\"older exponent of a function, its point-wise oscillation and the existence
of fractional velocity is established. It is demonstrated that wherever the
fractional velocity of non-integral order is continuous then it vanishes. The
work further demonstrates the use of fractional velocity as a tool for
characterization of the discontinuity set of the derivatives of functions thus
providing a natural characterization of strongly non-linear local behavior.
Finally the equivalence with the Kolwankar-Gangal local fractional derivative
is investigated.


title: Orderings and flexibility of some subgroups of $Homeo_+(\mathbb{R})$

abstract:
  In this work we exhibit flexibility phenomena for some (countable) groups
acting by order preserving homeomorphisms of the line. More precisely, we show
that if a left orderable group admits an amalgam decomposition of the form
$G=\mathbb{F}_n*_{\mathbb Z} \mathbb{F}_m$ where $n+m\geq 3$, then every
faithful action of $G$ on the line by order preserving homeomorphisms can be
approximated by another action (without global fixed points) that is not
semi-conjugated to the initial action. We deduce that $\mathcal{LO}(G)$, the
space of left orders of $G$, is a Cantor set.
  In the special case where $G=\pi_1(\Sigma)$ is the fundamental group of a
closed hyperbolic surface, we found finer techniques of perturbation. For
instance, we exhibit a single representation whose conjugacy class in dense in
the space of representations. This entails that the space of representations
without global fixed points of $\pi_1(\Sigma)$ into $Homeo_+(\mathbb R)$ is
connected, and also that the natural conjugation action of $\pi_1(\Sigma)$ on
$\mathcal{LO}(\pi_1(\Sigma))$ has a dense orbit.


title: A review of metasurfaces: physics and applications

abstract:
  Metamaterials are composed of periodic subwavelength metal/dielectric
structures that resonantly couple to the electric and/or magnetic components of
the incident electromagnetic fields, exhibiting properties that are not found
in nature. Planar metamaterials with subwavelength thickness, or metasurfaces,
consisting of single-layer or few-layer stacks of planar structures, can be
readily fabricated using lithography and nanoprinting methods, and the
ultrathin thickness in the wave propagation direction can greatly suppress the
undesirable losses. Metasurfaces enable a spatially varying optical response,
mold optical wavefronts into shapes that can be designed at will, and
facilitate the integration of functional materials to accomplish active control
and greatly enhanced nonlinear response. This paper reviews recent progress in
the physics of metasurfaces operating at wavelengths ranging from microwave to
visible. We provide an overview of key metasurface concepts such as anomalous
reflection and refraction, and introduce metasurfaces based on the
Pancharatnam-Berry phase and Huygens' metasurfaces, as well as their use in
wavefront shaping and beam forming applications, followed by a discussion of
polarization conversion in few-layer metasurfaces and their related properties.
An overview of dielectric metasurfaces reveals their ability to realize unique
functionalities coupled with Mie resonances and their low ohmic losses. We also
describe metasurfaces for wave guidance and radiation control, as well as
active and nonlinear metasurfaces. Finally, we conclude by providing our
opinions of opportunities and challenges in this rapidly developing research
field.


title: Requirements for storing electrophysiology data

abstract:
  The purpose of this document is to specify the basic data types required for
storing electrophysiology and optical imaging data to facilitate computer-based
neuroscience studies and data sharing. These requirements are being developed
within a working group of the Electrophysiology Task Force in the International
Neuroinformatics Coordinating Facility (INCF) Program on Standards for Data
Sharing. While this document describes the requirements of the standard
independent of the actual storage technology, the Task Force has recommended
basing a standard on HDF5. This is in line with a number of groups who are
already using HDF5 to store electrophysiology data, although currently without
being based on a standard.


title:
Demonstration of qubit operations below a rigorous fault tolerance
  threshold with gate set tomography

abstract:
  Quantum information processors promise fast algorithms for problems
inaccessible to classical computers. But since qubits are noisy and
error-prone, they will depend on fault-tolerant quantum error correction
(FTQEC) to compute reliably. Quantum error correction can protect against
general noise if -- and only if -- the error in each physical qubit operation
is smaller than a certain threshold. The threshold for general errors is
quantified by their diamond norm. Until now, qubits have been assessed
primarily by randomized benchmarking, which reports a different "error rate"
that is not sensitive to all errors, and cannot be compared directly to diamond
norm thresholds. Here we use gate set tomography (GST) to completely
characterize operations on a trapped-Yb$^+$-ion qubit and demonstrate with very
high ($>95\%$) confidence that they satisfy a rigorous threshold for FTQEC
(diamond norm $\leq6.7\times10^{-4}$).


title: Hybrid Markov-mass action law for cell activation by rare binding events

abstract:
  The binding of molecules, ions or proteins to specific target sites is a
generic step for cell activation. However, this step relies on rare events
where stochastic particles located in a large bulk are searching for small and
often hidden targets and thus remains difficult to study. We present here a
hybrid discrete-continuum model where the large ensemble of particles is
described by mass-action laws. The rare discrete binding events are modeled by
a Markov chain for the encounter of a finite number of small targets by few
Brownian particles, for which the arrival time is Poissonian. This model is
applied for predicting the time distribution of vesicular release at neuronal
synapses that remains elusive. This release is triggered by the binding of few
calcium ions that can originate either from the synaptic bulk or from the
transient entry through calcium channels. We report that the distribution of
release time is bimodal although triggered by a single fast action potential:
while the first peak follows a stimulation, the second corresponds to the
random arrival over much longer time of ions located in the bulk to small
binding targets. To conclude, the present multiscale stochastic chemical
reaction modeling allows studying cellular events based on integrating discrete
molecular events over various time scales.


title: Formule de Trace pour le Anneaux de Witt

abstract:
  Our purpose is to give a generalization of Pulita exponential series. After
that, we shall use these series to give an analytic expression to a Gauss sums
and to a trace formula for Witt vector rings.


title:
Analysis of intermittency in submillimeter radio and hard X-Rays during
  the impulsive phase of a solar flare

abstract:
  We present an analysis of intermittent processes occurred during the
impulsive phase of the flare SOL2012-03-13, using hard X-rays and submillimeter
radio data. Intermittency is a key characteristic in turbulent plasmas and have
been a analyzed recently for hard X-rays data only. Since in a typical flare
the same accelerated electron population is believed to produce both hard
X-rays and gyrosynchrotron, we compare both time profiles searching for
intermittency signatures. For that we define a cross-wavelet power spectrum,
that is used to obtain the Local Intermittency Measure or LIM. When greater
than three, the square LIM coefficients indicate a local intermittent process.
The LIM$^2$ coefficient distribution in time and scale helps to identify
avalanche or cascade energy release processes. We find two different and well
separated intermittent behaviors in the submillimeter data: for scales greater
than 20 s, a broad distribution during the rising and maximum phases of the
emission seems to favor a cascade process; for scales below 1 s, short pulses
centered on the peak time, are representative of avalanches. When applying the
same analysis to hard X-rays, we find only the scales above 10 s producing a
distribution related to a cascade energy fragmentation. Our results suggest
that different acceleration mechanisms are responsible for tens of keV and MeV
energy ranges of electrons.


title: An Analysis of Deep Neural Network Models for Practical Applications

abstract:
  Since the emergence of Deep Neural Networks (DNNs) as a prominent technique
in the field of computer vision, the ImageNet classification challenge has
played a major role in advancing the state-of-the-art. While accuracy figures
have steadily increased, the resource utilisation of winning models has not
been properly taken into account. In this work, we present a comprehensive
analysis of important metrics in practical applications: accuracy, memory
footprint, parameters, operations count, inference time and power consumption.
Key findings are: (1) power consumption is independent of batch size and
architecture; (2) accuracy and inference time are in a hyperbolic relationship;
(3) energy constraint is an upper bound on the maximum achievable accuracy and
model complexity; (4) the number of operations is a reliable estimate of the
inference time. We believe our analysis provides a compelling set of
information that helps design and engineer efficient DNNs.


title:
A Fundamental Limitation on Maximum Parameter Dimension for Accurate
  Estimation with Quantized Data

abstract:
  It is revealed that there is a link between the quantization approach
employed and the dimension of the vector parameter which can be accurately
estimated by a quantized estimation system. A critical quantity called
inestimable dimension for quantized data (IDQD) is introduced, which doesn't
depend on the quantization regions and the statistical models of the
observations but instead depends only on the number of sensors and on the
precision of the vector quantizers employed by the system. It is shown that the
IDQD describes a quantization induced fundamental limitation on the estimation
capabilities of the system. To be specific, if the dimension of the desired
vector parameter is larger than the IDQD of the quantized estimation system,
then the Fisher information matrix for estimating the desired vector parameter
is singular, and moreover, there exist infinitely many nonidentifiable vector
parameter points in the vector parameter space. Furthermore, it is shown that
under some common assumptions on the statistical models of the observations and
the quantization system, a smaller IDQD can be obtained, which can specify an
even more limiting quantization induced fundamental limitation on the
estimation capabilities of the system.


title: Generalized Subjective Lexicographic Expected Utility Representation

abstract:
  We provide foundations for decisions in face of unlikely events by extending
the standard framework of Savage to include preferences indexed by a family of
events. We derive a subjective lexicographic expected utility representation
which allows for infinitely many lexicographically ordered levels of events and
for event-dependent attitudes toward risk. Our model thus provides foundations
for models in finance that rely on different attitudes toward risk (e.g.
Skiadas [9]) and for off-equilibrium reasonings in infinite dynamic games, thus
extending and generalizing the analysis in Blume, Brandenburger and Dekel [3].


title: Convolutional Random Walk Networks for Semantic Image Segmentation

abstract:
  Most current semantic segmentation methods rely on fully convolutional
networks (FCNs). However, their use of large receptive fields and many pooling
layers cause low spatial resolution inside the deep layers. This leads to
predictions with poor localization around the boundaries. Prior work has
attempted to address this issue by post-processing predictions with CRFs or
MRFs. But such models often fail to capture semantic relationships between
objects, which causes spatially disjoint predictions. To overcome these
problems, recent methods integrated CRFs or MRFs into an FCN framework. The
downside of these new models is that they have much higher complexity than
traditional FCNs, which renders training and testing more challenging.
  In this work we introduce a simple, yet effective Convolutional Random Walk
Network (RWN) that addresses the issues of poor boundary localization and
spatially fragmented predictions with very little increase in model complexity.
Our proposed RWN jointly optimizes the objectives of pixelwise affinity and
semantic segmentation. It combines these two objectives via a novel random walk
layer that enforces consistent spatial grouping in the deep layers of the
network. Our RWN is implemented using standard convolution and matrix
multiplication. This allows an easy integration into existing FCN frameworks
and it enables end-to-end training of the whole network via standard
back-propagation. Our implementation of RWN requires just $131$ additional
parameters compared to the traditional FCNs, and yet it consistently produces
an improvement over the FCNs on semantic segmentation and scene labeling.


title:
Thermoelectric transport in the layered Ca$_3$Co$_{4-x}$Rh$_x$O$_9$
  single crystals

abstract:
  We have examined an isovalent Rh substitution effect on the transport
properties of the thermoelectric oxide Ca$_3$Co$_{4}$O$_9$ using
single-crystalline form. With increasing Rh content $x$, both the electrical
resistivity and the Seebeck coefficient change systematically up to $x=0.6$ for
Ca$_3$Co$_{4-x}$Rh$_{x}$O$_9$ samples. In the Fermi-liquid regime where the
resistivity behaves as $\rho=\rho_0+AT^2$ around 120 K, the $A$ value decreases
with increasing Rh content, indicating that the correlation effect is weakened
by Rh $4d$ electrons with extended orbitals. We find that, in contrast to such
a weak correlation effect observed in the resistivity of Rh-substituted
samples, the low-temperature Seebeck coefficient is increased with increasing
Rh content, which is explained with a possible enhancement of a pseudogap
associated with the short-range order of spin density wave. In high-temperature
range above room temperature, we show that the resistivity is largely
suppressed by Rh substitution while the Seebeck coefficient becomes almost
temperature-independent, leading to a significant improvement of the power
factor in Rh-substituted samples. This result is also discussed in terms of the
differences in the orbital size and the associated spin state between Co $3d$
and Rh $4d$ electrons.


title: Learning End-to-End Goal-Oriented Dialog

abstract:
  Traditional dialog systems used in goal-oriented applications require a lot
of domain-specific handcrafting, which hinders scaling up to new domains.
End-to-end dialog systems, in which all components are trained from the dialogs
themselves, escape this limitation. But the encouraging success recently
obtained in chit-chat dialog may not carry over to goal-oriented settings. This
paper proposes a testbed to break down the strengths and shortcomings of
end-to-end dialog systems in goal-oriented applications. Set in the context of
restaurant reservation, our tasks require manipulating sentences and symbols,
so as to properly conduct conversations, issue API calls and use the outputs of
such calls. We show that an end-to-end dialog system based on Memory Networks
can reach promising, yet imperfect, performance and learn to perform
non-trivial operations. We confirm those results by comparing our system to a
hand-crafted slot-filling baseline on data from the second Dialog State
Tracking Challenge (Henderson et al., 2014a). We show similar result patterns
on data extracted from an online concierge service.


title: On Non-Orthogonal Multiple Access in Downlink

abstract:
  Non orthogonal multiple access (NOMA) in the downlink is discussed in this
letter. When combined with soft frequency reuse, NOMA is detrimental to user
fairness by increasing the data rate of a near user at the cost of data rate of
a far user.


title: Characterizing and Avoiding Routing Detours Through Surveillance States

abstract:
  An increasing number of countries are passing laws that facilitate the mass
surveillance of Internet traffic. In response, governments and citizens are
increasingly paying attention to the countries that their Internet traffic
traverses. In some cases, countries are taking extreme steps, such as building
new Internet Exchange Points (IXPs), which allow networks to interconnect
directly, and encouraging local interconnection to keep local traffic local. We
find that although many of these efforts are extensive, they are often futile,
due to the inherent lack of hosting and route diversity for many popular sites.
By measuring the country-level paths to popular domains, we characterize
transnational routing detours. We find that traffic is traversing known
surveillance states, even when the traffic originates and ends in a country
that does not conduct mass surveillance. Then, we investigate how clients can
use overlay network relays and the open DNS resolver infrastructure to prevent
their traffic from traversing certain jurisdictions. We find that 84\% of paths
originating in Brazil traverse the United States, but when relays are used for
country avoidance, only 37\% of Brazilian paths traverse the United States.
Using the open DNS resolver infrastructure allows Kenyan clients to avoid the
United States on 17\% more paths. Unfortunately, we find that some of the more
prominent surveillance states (e.g., the U.S.) are also some of the least
avoidable countries.


title: Local Perturb-and-MAP for Structured Prediction

abstract:
  Conditional random fields (CRFs) provide a powerful tool for structured
prediction, but cast significant challenges in both the learning and inference
steps. Approximation techniques are widely used in both steps, which should be
considered jointly to guarantee good performance (a.k.a. "inferning").
Perturb-and-MAP models provide a promising alternative to CRFs, but require
global combinatorial optimization and hence they are usable only on specific
models. In this work, we present a new Local Perturb-and-MAP (locPMAP)
framework that replaces the global optimization with a local optimization by
exploiting our observed connection between locPMAP and the pseudolikelihood of
the original CRF model. We test our approach on three different vision tasks
and show that our method achieves consistently improved performance over other
approximate inference techniques optimized to a pseudolikelihood objective.
Additionally, we demonstrate that we can integrate our method in the fully
convolutional network framework to increase our model's complexity. Finally,
our observed connection between locPMAP and the pseudolikelihood leads to a
novel perspective for understanding and using pseudolikelihood.


title: A Protostellar Jet Emanating from a Hypercompact HII Region

abstract:
  We present radio continuum observations of the high-mass young stellar object
(HMYSO) G345.4938+01.4677 made using the Australia Telescope Compact Array
(ATCA) at 5, 9, 17, and 19 GHz. These observations provide definite evidence
that the outer and inner pairs of radio lobes consist of shock ionized material
being excited by an underlying collimated and fast protostellar jet emanating
from a hypercompact HII region. By comparing with images taken 6 yr earlier at
5 and 9 GHz using the same telescope, we assess the proper motions of the radio
sources. The outer West and East lobes exhibit proper motions of $64\pm12$ and
$48\pm13$ milliarcsec yr$^{-1}$, indicating velocities projected in the plane
of the sky and receding from G345.4938+01.4677 of $520$ and $390$ km s$^{-1}$,
respectively. The internal radio lobes also display proper motion signals
consistently receding from the HMYSO, with magnitudes of $17\pm11$ and
$35\pm10$ milliarcsec yr$^{-1}$ for the inner West and East lobes,
respectively. The morphology of the outer West lobe is that of a detached bow
shock. At 17 and 19 GHz, the outer East lobe displays an arcuate morphology
also suggesting a bow shock. These results show that disk accretion and jet
acceleration --- possibly occurring in a very similar way compared with
low-mass protostars --- is taking place in G345.4938+01.4677 despite the
presence of ionizing radiation and the associated hypercompact HII region.


title:
New invariants for a real valued and angle valued map (an Alternative to
  Morse- Novikov theory)

abstract:
  This paper but section 6 is essentially my lecture at The Eighth Congress of
Romanian Mathematicians, June 26 - July 1, 2015, Iasi, Romania. The paper
summarizes the definitions and the properties of the invariants associated to a
real or an angle valued map in the framework of what we call an Alternative to
Morse-Novikov theory. These invariants are configurations of points in the
complex plane, configurations of vector spaces or modules indexed by complex
numbers and collections of Jordan cells. The first are refinements of Betti
numbers, the second of homology and the third of monodromy. Although not
discussed in this paper but discussed in works this report is based on, these
invariants are computer friendly (i.e. can be calculated by computer
implementable algorithms when the source of the map is a simplicial complex and
the map is simplicial) and are of relevance for the dynamics of flows which
admit Lyapunov real or angle valued map.


title: Communication-Efficient Distributed Statistical Inference

abstract:
  We present a Communication-efficient Surrogate Likelihood (CSL) framework for
solving distributed statistical inference problems. CSL provides a
communication-efficient surrogate to the global likelihood that can be used for
low-dimensional estimation, high-dimensional regularized estimation and
Bayesian inference. For low-dimensional estimation, CSL provably improves upon
naive averaging schemes and facilitates the construction of confidence
intervals. For high-dimensional regularized estimation, CSL leads to a
minimax-optimal estimator with controlled communication cost. For Bayesian
inference, CSL can be used to form a communication-efficient quasi-posterior
distribution that converges to the true posterior. This quasi-posterior
procedure significantly improves the computational efficiency of MCMC
algorithms even in a non-distributed setting. We present both theoretical
analysis and experiments to explore the properties of the CSL approximation.

categories: stat.ML cs.IT cs.LG math.IT math.OC stat.ME


title: Games of multicellularity

abstract:
  Evolutionary game dynamics are often studied in the context of different
population structures. Here we propose a new population structure that is
inspired by simple multicellular life forms. In our model, cells reproduce but
can stay together after reproduction. They reach complexes of a certain size,
n, before producing single cells again. The cells within a complex derive
payoff from an evolutionary game by interacting with each other. The
reproductive rate of cells is proportional to their payoff. We consider all
two-strategy games. We study deterministic evolutionary dynamics with
mutations, and derive exact conditions for selection to favor one strategy over
another. Our main result has the same symmetry as the well-known sigma
condition, which has been proven for stochastic game dynamics and weak
selection. For a maximum complex size of n=2 our result holds for any intensity
of selection. For n > 2 it holds for weak selection. As specific examples we
study the prisoner's dilemma and hawk-dove games. Our model advances
theoretical work on multicellularity by allowing for frequency-dependent
interactions within groups.


title:
The Use of Extraterrestrial Resources to Facilitate Space Science and
  Exploration

abstract:
  To-date, all human economic activity has depended on the resources of a
single planet, and it has long been recognized that developments in space
exploration could in principle open our closed planetary economy to external
resources of energy and raw materials. Recently, there has been renewed
interest in these possibilities, with several private companies established
with the stated aim of exploiting extraterrestrial resources. Space science and
exploration are among the potential beneficiaries of space resources because
their use may permit the construction and operation of scientific facilities in
space that will be unaffordable if all the required material and energy
resources have to be lifted out of Earth's gravity. Examples may include the
next generation of large space telescopes, sample return missions to the outer
Solar System, and human research stations on the Moon and Mars. These potential
scientific benefits of extraterrestrial resource utilisation were the topic of
a Royal Astronomical Society specialist discussion meeting held on 8 April 2016
and summarised here.


title: GROUPS-NET: Group Meetings Aware Routing in Multi-Hop D2D Networks

abstract:
  In the next generation cellular networks, device-to-device (D2D)
communication is already considered a fundamental feature. A problem of
multi-hop D2D networks is on how to define forwarding algorithms that achieve,
at the same time, high delivery ratio and low network overhead. In this paper
we aim to understand group meetings' properties by looking at their structure
and regularity with the final goal of applying such knowledge in the design of
a forwarding algorithm for D2D multi-hop networks. We introduce a forwarding
protocol, namely GROUPS-NET, which is aware of social group meetings and their
evolution over time. Our algorithm is parameter-calibration free and does not
require any knowledge about the social network structure of the system. In
particular, different from the state of the art algorithms, GROUPS-NET does not
need communities detection, which is a complex and expensive task. We validate
our algorithm using different publicly available data-sources. In real large
scale scenarios, our algorithm achieves approximately the same delivery ratio
of the state-of-art solution with up to 40% less network overhead.


title:
Probing Strong Correlations with Light Scattering: the Example of the
  Quantum Ising model

abstract:
  In this paper we calculate the nonlinear susceptibility and the resonant
Raman cross section for the paramagnetic phase of the ferromagnetic Quantum
Ising model in one dimension. In this region the spectrum of the Ising model
has a gap $m$. The Raman cross section has a strong singularity when the energy
of the outgoing photon is at the spectral gap $\omega_{f} \approx m$ and a
square root threshold when the frequency difference between the incident and
outgoing photons $\omega_{i} -\omega_{f} \approx 2m$. The latter feature
reflects the fermionic nature of the Ising model excitations.


title: Rationally $4$-periodic biquotients

abstract:
  An $n$-dimensional manifold $M$ is said to be rationally $4$-periodic if
there is an element $e\in H^4(M;\mathbb{Q})$ with the property that cupping
with $e$, $\cdot \cup e:H^\ast(M;\mathbb{Q})\rightarrow H^{\ast +
4}(M;\mathbb{Q})$ is injective for $0< \ast \leq \dim M-4$ and surjective when
$0\leq \ast < \dim M-4$. We classify all compact simply connected biquotients
which are rationally $4$-periodic. In addition, we show that if a simply
connected rationally elliptic CW-complex $X$ of dimension at least $6$ is
rationally $4$-periodic, then the cohomology ring is either singly generated,
or $X$ is rationally homotopy equivalent to $S^2\times \mathbb{H}P^n$,
$S^3\times \mathbb{H}P^n$, or $S^3\times S^3$.


title:
Production of rubidium Bose-Einstein condensate in an optically-plugged
  magnetic quadrupole trap

abstract:
  We have experimentally produced rubidium Bose-Einstein condensate in an
optically-plugged magnetic quadrupole (OPQ) trap. A far blue-detuned focused
laser beam with a wavelength of 532 nm is plugged in the center of the magnetic
quadrupole trap to increase the number of trapped atoms and suppress the
heating. A radio frequency (RF) evaporative cooling in the magneto-optical
hybrid trap is applied to decrease the atom temperature into degeneracy. The
atom number of the condensate is $1.2(0.4)\times10^5$ and the temperature is
below 100 nK. We have also studied characteristic behaviors of the condensate,
such as phase space density (PSD), condensate fraction and anisotropic
expansion.


title: Exact Exponent in Optimal Rates for Crowdsourcing

abstract:
  In many machine learning applications, crowdsourcing has become the primary
means for label collection. In this paper, we study the optimal error rate for
aggregating labels provided by a set of non-expert workers. Under the classic
Dawid-Skene model, we establish matching upper and lower bounds with an exact
exponent $mI(\pi)$ in which $m$ is the number of workers and $I(\pi)$ the
average Chernoff information that characterizes the workers' collective
ability. Such an exact characterization of the error exponent allows us to
state a precise sample size requirement
$m>\frac{1}{I(\pi)}\log\frac{1}{\epsilon}$ in order to achieve an $\epsilon$
misclassification error. In addition, our results imply the optimality of
various EM algorithms for crowdsourcing initialized by consistent estimators.


title:
A new method of probing mechanical losses of coatings at cryogenic
  temperatures

abstract:
  A new method of probing mechanical losses and comparing the corresponding
deposition processes of metallic and dielectric coatings in 1-100 MHz frequency
range and cryogenic temperatures is presented. The method is based on the use
of extremely high-quality quartz acoustic cavities whose internal losses are
orders of magnitude lower than any available coatings nowadays. The approach is
demonstrated for Chromium, Chromium/Gold and a multilayer tantala/silica
coatings. The ${\rm Ta}_2{\rm O}_5/{\rm Si}{\rm O}_2$ coating has been found to
exhibit a loss angle lower than $1.6\times10^{-5}$ near 30 {\rm MHz} at 4 {\rm
K}. The results are compared to the previous measurements.


title: Faster Arctic sea ice retreat in CMIP5 than in CMIP3 due to volcanoes

abstract:
  The downward trend in Arctic sea ice extent is one of the most dramatic
signals of climate change during recent decades. Comprehensive climate models
have struggled to reproduce this, typically simulating a slower rate of sea ice
retreat than has been observed. However, this bias has been widely noted to
have decreased in models participating in the most recent phase of the Coupled
Model Intercomparison Project (CMIP5) compared with the previous generation of
models (CMIP3). Here we examine simulations from both CMIP3 and CMIP5. We find
that simulated historical sea ice trends are influenced by volcanic forcing,
which was included in all of the CMIP5 models but in only about half of the
CMIP3 models. The volcanic forcing causes temporary simulated cooling in the
1980s and 1990s, which contributes to raising the simulated 1979-2013
global-mean surface temperature trends to values substantially larger than
observed. We show that this warming bias is accompanied by an enhanced rate of
Arctic sea ice retreat and hence a simulated sea ice trend that is closer to
the observed value, which is consistent with previous findings of an
approximately linear relationship between sea ice extent and global-mean
surface temperature. We find that both generations of climate models simulate
Arctic sea ice that is substantially less sensitive to global warming than has
been observed. The results imply that the much of the difference in Arctic sea
ice trends between CMIP3 and CMIP5 occurred due to the inclusion of volcanic
forcing, rather than improved sea ice physics or model resolution.


title: Engineering Deep Representations for Modeling Aesthetic Perception

abstract:
  Many aesthetic models in computer vision suffer from two shortcomings: 1) the
low descriptiveness and interpretability of those hand-crafted aesthetic
criteria (i.e., nonindicative of region-level aesthetics), and 2) the
difficulty of engineering aesthetic features adaptively and automatically
toward different image sets. To remedy these problems, we develop a deep
architecture to learn aesthetically-relevant visual attributes from Flickr1,
which are localized by multiple textual attributes in a weakly-supervised
setting. More specifically, using a bag-ofwords (BoW) representation of the
frequent Flickr image tags, a sparsity-constrained subspace algorithm discovers
a compact set of textual attributes (e.g., landscape and sunset) for each
image. Then, a weakly-supervised learning algorithm projects the textual
attributes at image-level to the highly-responsive image patches at
pixel-level. These patches indicate where humans look at appealing regions with
respect to each textual attribute, which are employed to learn the visual
attributes. Psychological and anatomical studies have shown that humans
perceive visual concepts hierarchically. Hence, we normalize these patches and
feed them into a five-layer convolutional neural network (CNN) to mimick the
hierarchy of human perceiving the visual attributes. We apply the learned deep
features on image retargeting, aesthetics ranking, and retrieval. Both
subjective and objective experimental results thoroughly demonstrate the
competitiveness of our approach.


title: Learning Purposeful Behaviour in the Absence of Rewards

abstract:
  Artificial intelligence is commonly defined as the ability to achieve goals
in the world. In the reinforcement learning framework, goals are encoded as
reward functions that guide agent behaviour, and the sum of observed rewards
provide a notion of progress. However, some domains have no such reward signal,
or have a reward signal so sparse as to appear absent. Without reward feedback,
agent behaviour is typically random, often dithering aimlessly and lacking
intentionality. In this paper we present an algorithm capable of learning
purposeful behaviour in the absence of rewards. The algorithm proceeds by
constructing temporally extended actions (options), through the identification
of purposes that are "just out of reach" of the agent's current behaviour.
These purposes establish intrinsic goals for the agent to learn, ultimately
resulting in a suite of behaviours that encourage the agent to visit different
parts of the state space. Moreover, the approach is particularly suited for
settings where rewards are very sparse, and such behaviours can help in the
exploration of the environment until reward is observed.


title:
Maximal function characterizations for Hardy spaces associated to
  nonnegative self-adjoint operators on spaces of homogeneous type

abstract:
  Let $X$ be a metric measure space with a doubling measure and $L$ be a
nonnegative self-adjoint operator acting on $L^2(X)$. Assume that $L$ generates
an analytic semigroup $e^{-tL}$ whose kernels $p_t(x,y)$ satisfy Gaussian upper
bounds but without any assumptions on the regularity of space variables $x$ and
$y$. In this article we continue a study in \cite{SY} to give an atomic
decomposition for the Hardy spaces $ H^p_{L,max}(X)$ in terms of the
nontangential maximal function associated with the heat semigroup of $L$, and
hence we establish characterizations of Hardy spaces associated to an operator
$L$, via an atomic decomposition or the nontangential maximal function. We also
obtain an equivalence of $ H^p_{L, max}(X)$ in terms of the radial maximal
function.


title:
Automatically generating Fukaya categories and computing quantum
  cohomology

abstract:
  Suppose one has found a non-empty sub-category $\mathcal{A}$ of the Fukaya
category of a compact Calabi-Yau manifold $X$ which is homologically smooth in
the sense of non-commutative geometry, a condition intrinsic to $\mathcal{A}$.
Then, we show $\mathcal{A}$ split-generates the Fukaya category and moreoever,
that our hypothesis implies (and is therefore equivalent to the assertion that)
$\mathcal{A}$ satisfies Abouzaid's geometric generation criterion [Abo]. An
immediate consequence of earlier work [G1, GPS1, GPS2] is that the open-closed
and closed-open maps, relating quantum cohomology to the Hochschild invariants
of the Fukaya category, are also isomorphisms. Our result continues to hold
when $c_1(X) \neq 0$ (for instance, when $X$ is monotone Fano), under a further
hypothesis: the 0th Hochschild cohomology of $\mathcal{A}$
$\mathrm{HH}^0(\mathcal{A})$ should have sufficiently large rank: $\mathrm{rk}\
\mathrm{HH}^0(\mathcal{A}) \geq \mathrm{rk}\ \mathrm{QH}^0(X)$. Our proof
depends only on formal properties of Fukaya categories and open-closed maps,
the most recent and crucial of which, compatibility of the open-closed map with
pairings, was observed independently in ongoing joint work of the author with
Perutz and Sheridan [GPS2] and by Abouzaid-Fukaya-Oh-Ohta-Ono [AFO+]; a proof
in the simplest settings appears here in an Appendix. Because categories Morita
equivalent to categories of coherent sheaves or matrix factorizations are
homologically smooth, our result applies to resolve the split-generation
question in homological mirror symmetry for compact symplectic manifolds
(generalizing a result of Perutz-Sheridan [PS2] proven in the case $c_1(X) =
0$): any embedding of coherent sheaves or matrix factorizations into the
split-closed derived Fukaya category is automatically a Morita equivalence when
it has large enough $\mathrm{HH}^0$ (which it always does if $c_1(X)=0$).


title:
Light Drag Effect of Vacuum Tube Versus Light Propagation in Stationary
  Vacuum Tube with Moving Source and Receiver

abstract:
  We presented a new way to examine the principle of relativity of Special
Relativity. According to the principle of relativity, the light dragging by
moving media and the light propagation in stationary media with moving source
and receiver should be two totally equivalent phenomena. We select a vacuum
tube with two glass rods at two ends as the optical media. The length of the
middle vacuum cell is L and the thicknesses of the glass rods with refractive
index n are D1 and D2. The light drag effect of the moving vacuum tube with
speed v is a first-order effect, delta t = 2(n-1)(D1+D2)v/c^2, which is
independent of L because vacuum does not perform a drag effect. Predicted by
the principle of relativity, the change of the light propagation time interval
with stationary vacuum tube and moving source and receiver must be the same,
i.e., delta tao = delta t = 2(n-1)(D1+D2)v/c^2. However all analyses have shown
that the change of the propagation time interval delta tao is caused by the
motion of the receiver during the light propagation in the vacuum tube. Thus,
the contribution of the glass rods in delta tao is 2n(D1+D2)v/c^2, not
2(n-1)(D1+D2)v/c^2 in delta t. Importantly, the contribution of the vacuum cell
in delta tao is 2Lv/c^2, not zero in delta t. Our analyses are solid in optics.
The genuine tests of the prediction of the principle of relativity can be
conducted by the experiments with two atomic clocks, or the experiments with
fiber Sagnac interferometers.


title: Understanding the Smartrouter-based Peer CDN for Video Streaming

abstract:
  Recent years have witnessed a new video delivery paradigm: smartrouter-based
video delivery network, which is enabled by smartrouters deployed at users'
homes, together with the conventional video servers deployed in the
datacenters. Recently, ChinaCache, a large content delivery network (CDN)
provider, and Youku, a video service provider using smartrouters to assist
video delivery, announced their cooperation to create a new paradigm of content
delivery based on householders' network resources. This new paradigm is
different from the conventional peer-to-peer (P2P) approach, because such
dedicated smartrouters are inherently operated by the centralized video service
providers in a coordinative manner. It is intriguing to study the strategies,
performance and potential impact on the content delivery ecosystem of such peer
CDN systems. In this paper, we study the Youku peer CDN, which has deployed
over 300K smartrouter devices for its video streaming. In our measurement, 78K
videos were investigated and 3TB traffic has been analyzed, over controlled
routers and players. Our contributions are the following measurement insights.
First, a global replication and caching strategy is essential for the peer CDN
systems, and proactively scheduling replication and caching on a daily basis
can guarantee their performance. Second, such peer CDN deployment can itself
form an effective Quality of Service (QoS) monitoring sub-system, which can be
used for fine-grained user request redirection. We also provide our analysis on
the performance issues and potential improvements to the peer CDN systems.


title:
Understanding Content Placement Strategies in Smartrouter-based Peer CDN
  for Video Streaming

abstract:
  Recent years have witnessed a new video delivery paradigm: smartrouter-based
peer video content delivery network, which is enabled by smartrouters deployed
at users' homes. ChinaCache (one of the largest CDN providers in China) and
Youku (a video provider using smartrouters to assist video delivery) announced
their cooperation in 2015, to create a new paradigm of content delivery based
on householders' network resources. This new paradigm is different from the
conventional peer-to-peer (P2P) approach, because millions of dedicated
smartrouters are operated by the centralized video service providers in a
coordinative manner. Thus it is intriguing to study the content placement
strategies used in a smartrouter-based content delivery system, as well as its
potential impact on the content delivery ecosystem. In this paper, we carry out
measurement studies of Youku's peer video CDN, who has deployed over 300K
smartrouter devices for its video delivery. In our measurement studies, 104K
videos were investigated and 4TB traffic has been analyzed, over controlled
smartrouter nodes and players. Our measurement insights are as follows. First,
a global content replication strategy is essential for the peer CDN systems.
Second, such peer CDN deployment itself can form an effective sub-system for
end-to-end QoS monitoring, which can be used for fine-grained request
redirection (e.g., user-level) and content replication. We also show our
analysis on the performance limitations and propose potential improvements to
the peer CDN systems.