title:
The Influence of Trust and subjective Norms on Citizens Intentions to
  Engage in E-participation on E-government Websites

abstract:
  Advancements in web technology have revolutionised the way citizens interact
with governments. Unlike traditional methods of communication between citizens
and governments, E-Participation via e-government websites enhances
communication and enables citizens to become actively involved in the
policy-making process. Despite the growing importance of e-participation, the
potential factors influencing citizens engagement in e-participation have not
been the subject of investigation. Using responses obtained from Saudi
citizens, this study examines a number of factors that may influence the
intentions of citizens to engage in e-participation activities on e-government
websites. The results suggest that the factors of trust and subjective norms
have a significant impact on the intentions of citizens to engage in
e-participation activities.


title:
Investigating the Impact of Learners Learning Styles on the Acceptance
  of Open Learner Models for Information Sharing

abstract:
  Individual differences in learners learning styles can have a significant
effect on their acceptance of collaboration technologies to facilitate the
sharing of learning information in technology-based collaborative learning.
There is, however, a lack of research in exploring the impact of learning
styles on the acceptance of open learner models for information sharing in this
area. This study investigates the impact of learners learning styles on their
acceptance of open learner models for information sharing. A total of 240
undergraduate students in a university in Malaysia have participated in the
online survey. A chi-square test is performed to explore the relationship
between learning styles and the acceptance of open learner models for
information sharing in a higher education setting. The result reveals that
learning styles have no significant impact on learners acceptance of open
learner models for information sharing. The implications of this study can
assist education instructors to apply appropriate instructional strategies in
adopting open learner models for improving the performance of
technology-mediated learning.


title:
Barriers to the Integration of Information Technology within Early
  Childhood Education and Care Organisations: A Review of the Literature

abstract:
  Employees of early childhood education and care (ECEC) organisations may
experience a wide range of barriers as they attempt to integrate information
technology (IT) into their work practices. However, studies within the ECEC
organisational literature which attempt to identify and understand these
barriers are scant. This literature review is the first to present consolidated
findings from the body of knowledge on barriers to the integration of IT within
ECEC organisations. In addition to highlighting limitations and gaps in the
literature, it proposes a tri-perspective framework to provide for future
research to develop a deeper understanding of not only what barriers exist but
also how they interrelate and shape the IT integration process and the work
practices of ECEC organisational employees.


title:
Fears and Triggers: A Conceptual Study of Vendor-Supplied Maintenance
  and Maintenance Deferral of Standard Package Software

abstract:
  Enterprises rely more on Information Systems (IS) and software than ever
before. However the issue of maintaining a vendor-supplied IS, in particular
standard packaged software, has been poorly represented within academic
literature. This paper presents a conceptual study that synthesises the current
state of research concerning the deferral or execution of vendor-supplied
maintenance by the purchasing organisation. Based on a systematic review
process that adopts the purchasers viewpoint, a series of fears and triggers
emerge and are captured from the literature. Fears are articulated as reasons
for the purchasing organisation deferring the installation of vendor-supplied
maintenance, whereas triggers are events that upset the equilibrium of the
purchasing organisations IS or software and require the installation of the
vendor-supplied maintenance to proceed. Although prevalent in literature, fears
and triggers have not previously been recognised as an area of focus for
academic research.


title:
Multi-synchronous collaboration between desktop and mobile users: A case
  study of report writing for emergency management

abstract:
  The development of multi-synchronous decision support systems to facilitate
collaboration between diverse users is an emerging field in emergency
management. Traditionally, information management for emergency response has
been a centralised effort. However, modern devices such as smartphones provide
new methods for gaining real-time information about a disaster from users in
the field. In this paper, we present a framework for multi-synchronous
collaborative report writing in the scope of emergency management. This
framework supports desktop-based users as information providers and consumers,
alongside mobile users as information providers to facilitate multi-synchronous
collaboration. We consider the benefits of our framework for writing
collaborative Situation Reports and discuss future directions for research.


title:
A Crowd Monitoring Framework using Emotion Analysis of Social Media for
  Emergency Management in Mass Gatherings

abstract:
  In emergency management for mass gathering, the knowledge about crowd types
can highly assist with providing timely response and effective resource
allocation. Crowd monitoring can be achieved using computer vision based
approaches and sensory data analysis. The emergence of social media platforms
presents an opportunity to capture valuable information about how people feel
and think. However, reviewing current works shows that there are a limited
number of studies that use social media in crowd monitoring and/or incorporate
a unified crowd model for consistency and interoperability. This presents a
novel framework for crowd monitoring using social media. It includes a standard
crowd model to represent different types of crowds. The proposed framework
considers the effect of emotion on crowd behaviour and uses the emotion
analysis of social media to identify the crowd types in an event. An experiment
using historical data of a past event to validate our framework and model is
described.


title: How Fluffy is the Cloud ?: Cloud Intelligence for a Not-For-Profit

abstract:
  Business Intelligence (BI) is becoming more accessible and less expensive
with fewer risks through various deployment options available in the Cloud.
Cloud computing facilitates the acquisition of custom solutions for
not-for-profit (NFP) organisations at affordable and scalable costs on a
flexible pay-as-you-go basis. In this paper, we explore the key technical and
organisational aspects of BI in the Cloud (Cloud Intelligence) deployment in an
Australian NFP whose BI maturity is rising although still low. This
organisation aspires to Cloud Intelligence for improved managerial decision
making yet the issues surrounding the adoption of Cloud Intelligence are
complex, especially where corporate and Cloud governance is concerned. From the
findings of the case study, a conceptual framework has been developed and
presented which offers a view of how governance could be deployed so that NFPs
gain maximum leverage through their adoption of the Cloud.


title:
Social learning strategies modify the effect of network structure on
  group performance

abstract:
  The structure of communication networks is an important determinant of the
capacity of teams, organizations and societies to solve policy, business and
science problems. Yet, previous studies reached contradictory results about the
relationship between network structure and performance, finding support for the
superiority of both well-connected efficient and poorly connected inefficient
network structures. Here we argue that understanding how communication networks
affect group performance requires taking into consideration the social learning
strategies of individual team members. We show that efficient networks
outperform inefficient networks when individuals rely on conformity by copying
the most frequent solution among their contacts. However, inefficient networks
are superior when individuals follow the best member by copying the group
member with the highest payoff. In addition, groups relying on conformity based
on a small sample of others excel at complex tasks, while groups following the
best member achieve greatest performance for simple tasks. Our findings
reconcile contradictory results in the literature and have broad implications
for the study of social learning across disciplines.


title: Search for sharp neutrino features from dark matter decay

abstract:
  The discovery of a neutrino line or, more broadly, a sharp feature in
neutrino data could provide a striking hint for the existence of the dark
matter particle. We review here a search for sharp spectral features using
neutrino data from IceCube. No significant hint for a signal from decaying dark
matter was found in the analysed dataset. Yet, we show a strong improvement of
the limits, which makes it worth discussing how they compare to the limits
obtained from gamma-ray data.


title:
Performance Prediction of Nonbinary Forward Error Correction in Optical
  Transmission Experiments

abstract:
  In this paper, we compare different metrics to predict the error rate of
optical systems based on nonbinary forward error correction (FEC). It is shown
that the correct metric to predict the performance of coded modulation based on
nonbinary FEC is the mutual information. The accuracy of the prediction is
verified in a detailed example with multiple constellation formats, FEC
overheads in both simulations and optical transmission experiments over a
recirculating loop. It is shown that the employed FEC codes must be universal
if performance prediction based on thresholds is used. A tutorial introduction
into the computation of the threshold from optical transmission measurements is
also given.


title: Local Lorentz transformations and Thomas effect in general relativity

abstract:
  The tetrad method is used for an introduction of local Lorentz frames and a
detailed analysis of local Lorentz transformations. A formulation of equations
of motion in local Lorentz frames is based on the Pomeransky-Khriplovich
gravitoelectromagnetic fields. These fields are calculated in the most
important special cases and their local Lorentz transformations are determined.
The local Lorentz transformations and the Pomeransky-Khriplovich
gravitoelectromagnetic fields are applied for a rigorous derivation of a
general equation for the Thomas effect in Riemannian spacetimes and for a
consideration of Einstein's equivalence principle and the Mathisson force.


title: A note on reductions between compressed sensing guarantees

abstract:
  In compressed sensing, one wishes to acquire an approximately sparse
high-dimensional signal $x\in\mathbb{R}^n$ via $m\ll n$ noisy linear
measurements, then later approximately recover $x$ given only those measurement
outcomes. Various guarantees have been studied in terms of the notion of
approximation in recovery, and some isolated folklore results are known stating
that some forms of recovery are stronger than others, via black-box reductions.
In this note we provide a general theorem concerning the hierarchy of strengths
of various recovery guarantees. As a corollary of this theorem, by reducing
from well-known results in the compressed sensing literature, we obtain an
efficient $\ell_p/\ell_p$ scheme for any $0<p<1$ with the fewest number of
measurements currently known amongst efficient schemes, improving recent bounds
of [SomaY16].


title:
Dynamics of Axial Symmetric System in Self-Interacting Brans-Dicke
  Gravity

abstract:
  This paper investigates dynamics of axial reflection symmetric model in
self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate
hydrodynamical equations and discuss oscillations using time-dependent
perturbation for both spin as well as spin-independent cases. The expressions
of frequency, total energy density and equation of motion of oscillating model
are obtained. We study instability of oscillating models in weak
approximations. It is found that the oscillations and stability of the model
depend upon the dark energy source along with anisotropy and reflection
effects. We conclude that the axial reflection system remains stable for
stiffness parameter $\Gamma=1$, collapses for $\Gamma>1$ and becomes unstable
for $0<\Gamma<1$.


title:
Planetary Ring Dynamics -- The Streamline Formalism -- 1. From Boltzmann
  Equation to Celestial Mechanics

abstract:
  These 1992 lectures notes present a powerful formalism mostly developed in
the 1980s by Borderies, Goldreich and Tremaine to address planetary ring
dynamical issues. These notes make a special emphasis on ring microphysics,
quantified with the help of the moments of the Boltzmann equation. They also
focus on the standard self-gravity model of narrow ring rigid precession, and
on the physics of linear and nonlinear density waves. These notes have been
corrected but only very marginally extended and not updated.
  They are provided both as an introduction to the streamline formalism and as
a complement on some technical issues for my upcoming review ("Theory of Narrow
rings and Sharp Edges") that will cover the physics not addressed here along
with more recent developments. This review will appear in the "Planetary Ring
System" book (C. Murray and M. Tiscareno, eds.), to be published later on this
year at Cambridge University Press.


title: Enumerating submodules invariant under an endomorphism

abstract:
  We study zeta functions enumerating submodules invariant under a given
endomorphism of a finitely generated module over the ring of ($S$-)integers of
a number field. In particular, we compute explicit formulae involving Dedekind
zeta functions and establish meromorphic continuation of these zeta functions
to the complex plane. As an application, we show that ideal zeta functions
associated with nilpotent Lie algebras of maximal class have abscissa of
convergence $2$.


title:
Exploring QCD dynamics in medium energy $\gamma A$ semiexclusive
  collisions

abstract:
  We demonstrate that studies of the semiexclusive large angle photon - nucleus
reactions: $\gamma + A\to h_1+h_2 +(A-1)^*$ with tagged photon beams of
energies $6 \div 10$ GeV which can be performed in Hall D at Thomas Jefferson
National Acceleration Facility (TJNAF) would allow to probe several aspects of
the QCD dynamics: establish the $t$-range in which transition from soft to hard
dynamics occurs, compare the strength of the interaction of various mesons and
baryons with nucleons at the energies of few GeV, as well as look for the color
transparency effects.


title: Multicolour Ramsey numbers of paths and even cycles

abstract:
  We prove new upper bounds on the multicolour Ramsey numbers of paths and even
cycles. It is well known that $(k-1)n+o(n)\leq R_k(P_n)\leq R_k(C_n)\leq
kn+o(n)$. The upper bound was recently improved by S\'ark\"ozy who showed that
$R_k(C_n)\leq\left(k-\frac{k}{16k^3+1}\right)n+o(n)$. Here we show $R_k(C_n)
\leq (k-\frac14)n +o(n)$, obtaining the first improvement to the coefficient of
the linear term by an absolute constant.


title:
Band structure and spin texture of Bi$_2$Se$_3$/3d ferromagnetic metal
  interface

abstract:
  The spin-helical surface states in three-dimensional topological insulator
(TI), such as Bi2Se3, are predicted to have superior efficiency in converting
charge current into spin polarization. This property is said to be responsible
for the giant spin-orbit torques observed in ferromagnetic metal/TI structures.
In this work, using first-principles and model tight-binding calculations, we
investigate the interface between the topological insulator Bi2Se3 and
3d-transition ferromagnetic metals Ni and Co. We find that the difference in
the work functions of the topological insulator and the ferromagnetic metals
shift the topological surface states down about 0.5 eV below the Fermi energy
where the hybridization of these surface states with the metal bands destroys
their helical spin structure. The band alignment of Bi2Se3 and Ni (Co) places
the Fermi energy far in the conduction band of bulk Bi2Se3, where the spin of
the carriers is aligned with the magnetization in the metal. Our results
indicate that the topological surface states are unlikely to be responsible for
the huge spin-orbit torque effect observed experimentally in these systems.


title: Torus link homology and the nabla operator

abstract:
  In recent work, Elias and Hogancamp develop a recurrence for the Poincar\'e
series of the triply graded Hochschild homology of certain links, one of which
is the $(n,n)$ torus link. In this case, Elias and Hogancamp give a
combinatorial formula for this homology that is reminiscent of the
combinatorics of the modified Macdonald polynomial eigenoperator $\nabla$. We
give a combinatorial formula for the homologies of all links considered by
Elias and Hogancamp. Our first formula is not easily computable, so we show how
to transform it into a computable version. Finally, we conjecture a direct
relationship between the $(n,n)$ torus link case of our formula and the
symmetric function $\nabla p_{1^n}$.


title: Perspectives for Muon Colliders and Neutrino Factories

abstract:
  High brilliance muon beams are needed for future facilities such as a
Neutrino Factory, an Higgs-factory or a multi-TeV Muon Collider. The R&D path
involves many aspects, of which cooling of the incoming muon beams is
essential.


title:
Energy localization and shape transformations in semiflexible polymer
  rings

abstract:
  Shape transformations in driven and damped molecular chains are considered.
Closed chains of weakly coupled molecular subunits under the action of
spatially homogeneous time-periodic external field are studied. The coupling
between the internal excitations and the bending degrees of freedom of the
chain modifies the local bending rigidity of the chain. In the absence of
driving the array takes a circular shape. When the energy pumped into the
system exceeds some critical value the chain undergoes a non-equilibrium phase
transition: the circular shape of the aggregate becomes unstable and the chain
takes the shape of an ellipse or, in general, of a polygon. The excitation
energy distribution becomes spatially nonuniform: it localizes in such places
where the chain is more flat. The weak interaction of the chain with a flat
surface restricts the dynamics to a flat manifold


title:
The small-scale turbulent dynamo in smoothed particle
  magnetohydrodynamics

abstract:
  Supersonic turbulence is believed to be at the heart of star formation. We
have performed smoothed particle magnetohydrodynamics (SPMHD) simulations of
the small-scale dynamo amplification of magnetic fields in supersonic
turbulence. The calculations use isothermal gas driven at rms velocity of Mach
10 so that conditions are representative of star-forming molecular clouds in
the Milky Way. The growth of magnetic energy is followed for 10 orders in
magnitude until it reaches saturation, a few percent of the kinetic energy. The
results of our dynamo calculations are compared with results from grid-based
methods, finding excellent agreement on their statistics and their qualitative
behaviour. The simulations utilise the latest algorithmic developments we have
developed, in particular, a new divergence cleaning approach to maintain the
solenoidal constraint on the magnetic field and a method to reduce the
numerical dissipation of the magnetic shock capturing scheme. We demonstrate
that our divergence cleaning method may be used to achieve $\nabla \cdot {\bf
B}=0$ to machine precision, albeit at significant computational expense.


title:
Effect of a skin-deep surface zone on formation of two-dimensional
  electron gas at a semiconductor surface

abstract:
  Two dimensional electron gases (2DEGs) at surfaces and interfaces of
semiconductors are described straightforwardly with a 1D self-consistent
Poisson-Schr\"{o}dinger scheme. However, their band energies have not been
modeled correctly in this way. Using angle-resolved photoelectron spectroscopy
we study the band structures of 2DEGs formed at sulfur-passivated surfaces of
InAs(001) as a model system. Electronic properties of these surfaces are tuned
by changing the S coverage, while keeping a high-quality interface, free of
defects and with a constant doping density. In contrast to earlier studies we
show that the Poisson-Schr\"{o}dinger scheme predicts the 2DEG bands energies
correctly but it is indispensable to take into account the existence of the
physical surface. The surface substantially influences the band energies beyond
simple electrostatics, by setting nontrivial boundary conditions for 2DEG
wavefunctions.


title: Emergent gravity on covariant quantum spaces in the IKKT model

abstract:
  We study perturbations of 4-dimensional fuzzy spheres as backgrounds in the
IKKT or IIB matrix model. Gauge fields and metric fluctuations are identified
among the excitation modes with lowest spin, supplemented by a tower of
higher-spin fields. They arise from an internal structure which can be viewed
as a twisted bundle over $S^4$, leading to a covariant noncommutative geometry.
The linearized 4-dimensional Einstein equations are obtained from the classical
matrix model action under certain conditions, modified by an IR cutoff. Some
one-loop contributions to the effective action are computed using the formalism
of string states.


title:
Different numerical estimators for main effect global sensitivity
  indices

abstract:
  The variance-based method of global sensitivity indices based on Sobol
sensitivity indices became very popular among practitioners due to its easiness
of interpretation. For complex practical problems computation of Sobol indices
generally requires a large number of function evaluations to achieve reasonable
convergence. Four different direct formulas for computing Sobol main effect
sensitivity indices are compared on a set of test problems for which there are
analytical results. These formulas are based on high-dimensional integrals
which are evaluated using MC and QMC techniques. Direct formulas are also
compared with a different approach based on the so-called double loop
reordering formula. It is found that the double loop reordering (DLR) approach
shows a superior performance among all methods both for models with independent
and dependent variables.


title:
Phenomenological Consequences of Enhanced Bulk Viscosity Near the QCD
  Critical Point

abstract:
  In the proximity of the QCD critical point the bulk viscosity of quark-gluon
matter is expected to be proportional to nearly the third power of the critical
correlation length, and become significantly enhanced. This work is the first
attempt to study the phenomenological consequences of enhanced bulk viscosity
near the QCD critical point. For this purpose, we implement the expected
critical behavior of the bulk viscosity within a non-boost-invariant,
longitudinally expanding $1+1$ dimensional causal relativistic hydrodynamical
evolution at non-zero baryon density. We demonstrate that the
critically-enhanced bulk viscosity induces a substantial non-equilibrium
pressure, effectively softening the equation of state, and leads to sizable
effects in the flow velocity and single particle distributions at the
freeze-out. The observable effects that may arise due to the enhanced bulk
viscosity in the vicinity of the QCD critical point can be used as
complimentary information to facilitate searches for the QCD critical point.


title:
A constructive proof that the Hanoi towers group has non-trivial rigid
  kernel

abstract:
  In 2012, Bartholdi, Siegenthaler, and Zalesskii computed the rigid kernel of
the Hanoi towers group. We present a simpler proof that the rigid kernel is the
Klein 4 group. In the course of the proof, we also compute the rigid
stabilizers and present proofs that this group is a self-similar, recurrent,
regular branch group.


title: Engineering spin exchange in non-bipartite graphene zigzag edges

abstract:
  The rules that govern spin exchange interaction in pristine graphene
nanostructures are constrained by the bipartite character of the lattice, so
that the sign of the exchange is determined by whether magnetic moments are on
the same sublattice or else. The synthesis of graphene ribbons with perfect
zigzag edges and a fluoranthene group with a pentagon ring, a defect that
breaks the bipartite nature of the honeycomb lattice, has been recently
demonstrated. Here we address how the electronic and spin properties of these
structures are modified by such defects, both for indirect exchange
interactions as well as the emergent edge magnetism, studied both with DFT and
mean field Hubbard model calculations. In all instances we find that the local
breakdown of the bipartite nature at the defect reverts the sign of the
otherwise ferromagnetic correlations along the edge, introducing a locally
antiferromagnetic intra-edge coupling and, for narrow ribbons, also revert the
antiferromagnetic inter-edge interactions that are normally found in pristine
ribbons. Our findings show that these pentagon defects are a resource that
permits to engineer the spin exchange interactions in graphene based
nano-structures.


title:
A note on the geometry and topology of almost even-Clifford Hermitian
  manifolds

abstract:
  We compute the structure groups of almost even-Clifford Hermitian manifolds
and determine when such groups lead to Spin structures.


title: Zooming in on $B\to K^\ast \ell\ell$ decays at low recoil

abstract:
  We analyse $B\to K^\ast \ell\ell$ decays in the region of low hadronic
recoil, where an operator product expansion (OPE) in $1/m_b$ applies. Using a
local model for charm contributions based on $e^+ e^- \to hadrons$ against the
OPE provides a data-driven method to access the limitations to the OPE's
accuracy related to binnings in the dilepton mass. Model-independent fits to
$B\to K^\ast \mu \mu $ low recoil angular observables exhibit presently only
small sensitivity to different charm models. They give similar results as the
fits based on the OPE, and are in agreement with the standard model, but leave
also room for new physics. Measurements with resolution small enough to probe
charm resonances would be desirable.


title:
Multiresolution Recurrent Neural Networks: An Application to Dialogue
  Response Generation

abstract:
  We introduce the multiresolution recurrent neural network, which extends the
sequence-to-sequence framework to model natural language generation as two
parallel discrete stochastic processes: a sequence of high-level coarse tokens,
and a sequence of natural language tokens. There are many ways to estimate or
learn the high-level coarse tokens, but we argue that a simple extraction
procedure is sufficient to capture a wealth of high-level discourse semantics.
Such procedure allows training the multiresolution recurrent neural network by
maximizing the exact joint log-likelihood over both sequences. In contrast to
the standard log- likelihood objective w.r.t. natural language tokens (word
perplexity), optimizing the joint log-likelihood biases the model towards
modeling high-level abstractions. We apply the proposed model to the task of
dialogue response generation in two challenging domains: the Ubuntu technical
support domain, and Twitter conversations. On Ubuntu, the model outperforms
competing approaches by a substantial margin, achieving state-of-the-art
results according to both automatic evaluation metrics and a human evaluation
study. On Twitter, the model appears to generate more relevant and on-topic
responses according to automatic evaluation metrics. Finally, our experiments
demonstrate that the proposed model is more adept at overcoming the sparsity of
natural language and is better able to capture long-term structure.


title:
Dipole factorization for DIS at NLO I: Loop correction to the photon to
  quark-antiquark light-front wave-functions

abstract:
  The one-loop QCD corrections to the light-front wave-function for the
quark-antiquark Fock state inside a transverse or longitudinal off-shell photon
are explicitly calculated, both in full momentum space and in mixed space
(a.k.a. dipole space). These results provide one of the main contributions to
virtual NLO corrections to many DIS observables (inclusive or not) in the
dipole factorization formalism at low Bjorken x.
  In a follow-up article, these one-loop corrections are combined with earlier
results on the wave-function for the quark-antiquark-gluon Fock state, in order
to get the full set of NLO corrections to the DIS structure functions $F_2$ and
$F_L$ in the dipole factorization formalism, valid at low Bjorken x.


title:
Four-dimensional cohomogeneity one Ricci flow and nonnegative sectional
  curvature

abstract:
  We exhibit the first examples of closed 4-manifolds with nonnegative
sectional curvature that lose this property when evolved via Ricci flow.


title: Classification of Thurston-relation subfactor planar algebras

abstract:
  Bisch and Jones suggested the skein theoretic classification of planar
algebras and investigated the ones generated by 2-boxes with the second author.
In this paper, we consider 3-box generators and classify subfactor planar
algebras generated by a non-trivial 3-box satisfying a relation proposed by
Thurston. The subfactor planar algebras in the classification are either $E^6$
or the ones from representations of quantum $SU(N)$. We introduce a new method
to determine positivity of planar algebras and new techniques to reduce the
complexity of computations.


title:
Long-term eclipse timing of white dwarf binaries: an observational hint
  of a magnetic mechanism at work

abstract:
  We present a long-term programme for timing the eclipses of white dwarfs in
close binaries to measure apparent and/or real variations in their orbital
periods. Our programme includes 67 close binaries, both detached and
semi-detached and with M-dwarfs, K-dwarfs, brown dwarfs or white dwarfs
secondaries. In total, we have observed more than 650 white dwarf eclipses. We
use this sample to search for orbital period variations and aim to identify the
underlying cause of these variations. We find that the probability of observing
orbital period variations increases significantly with the observational
baseline. In particular, all binaries with baselines exceeding 10 yrs, with
secondaries of spectral type K2 -- M5.5, show variations in the eclipse arrival
times that in most cases amount to several minutes. In addition, among those
with baselines shorter than 10 yrs, binaries with late spectral type (>M6),
brown dwarf or white dwarf secondaries appear to show no orbital period
variations. This is in agreement with the so-called Applegate mechanism, which
proposes that magnetic cycles in the secondary stars can drive variability in
the binary orbits. We also present new eclipse times of NN Ser, which are still
compatible with the previously published circumbinary planetary system model,
although only with the addition of a quadratic term to the ephemeris. Finally,
we conclude that we are limited by the relatively short observational baseline
for many of the binaries in the eclipse timing programme, and therefore cannot
yet draw robust conclusions about the cause of orbital period variations in
evolved, white dwarf binaries.


title:
Topological recursion, topological quantum field theory and
  Gromov-Witten invariants of BG

abstract:
  The purpose of this paper is to give a twisted version of the Eynard-Orantin
topological recursion by a 2D Topological Quantum Field Theory. We define a
kernel for a 2D TQFT and use an algebraic definition for a topological
recursion to define how to twist a standard topological recursion by a 2D TQFT.
The A-model side enumerative problem consists of counting cell graphs where in
addition vertices are decorated by elements in a Frobenius algebra, and which
are a twisted version of the generalized Catalan numbers of
Dumitrescu-Mulase-Safnuk-Sorkin. We show that the function which counts these
decorated graphs satisfies a twisted version of the same type of recursion of
Catalan numbers with respect to the edge-contraction axioms of
Dumitrescu-Mulase. The path we follow to pass from the A-model side to the
remodelled B-model side is to use a discrete Laplace transform based on the
ideas of the group of Mulase. We show that a twisted version by a 2D TQFT of
the Eynard-Orantin differentials satisfies a twisted generalization of the
topological recursion formula. We shall illustrate these results with a toy
model for the theory arising from the orbifold cohomology of the classifying
space of a finite group. In this example, the graphs are drawn on an orbifold
punctured Riemann surface and defined out of the moduli space of stable
morphisms from twisted curves to the classifying space of a finite group. In
particular we show that the cotangent class intersection numbers on this moduli
space satisfy a twisted Eynard-Orantin topological recursion and we derive an
orbifold DVV equation as a consequence of it. This proves from a different
perspective a result of Jarvis-Kimura, which states that the cotangent class
intersection numbers on that moduli space satisfy the Virasoro constraint
condition.


title: Digital Shy Maps

abstract: We study properties of shy maps in digital topology.


title: VHEeP: A very high energy electron-proton collider

abstract:
  Based on current CERN infrastructure, an electron--proton collider is
proposed at a centre-of-mass energy of about 9 TeV. A 7 TeV LHC bunch is used
as the proton driver to create a plasma wakefield which then accelerates
electrons to 3\,TeV, these then colliding with the other 7 TeV LHC proton beam.
Although of very high energy, the collider has a modest projected integrated
luminosity of $10-100$ pb$^{-1}$. For such a collider, with a centre-of-mass
energy 30 times greater than HERA, parton momentum fractions, $x$, down to
about $10^{-8}$ are accessible for photon virtualities, $Q^2$, of 1 GeV$^2$.
The energy dependence of hadronic cross sections at high energies, such as the
the total photon--proton cross section, which has synergy with cosmic-ray
physics, can be measured and QCD and the structure of matter better understood
in a region where the effects are completely unknown. Searches at high $Q^2$
for physics beyond the Standard Model will be possible, in particular the
significantly increased sensitivity to the production of leptoquarks. These and
other physics highlights of a very high energy electron--proton collider are
outlined.


title:
Test of the no-signaling principle in the Hensen "loophole-free CHSH
  experiment"

abstract:
  We analyze the data from the loophole-free CHSH experiment performed by
Hensen et al., and show that it is actually not exempt of an important
loophole. By increasing the size of the sample of event-ready detections, one
can exhibit in the experimental data a violation of the no-signaling principle
with a statistical significance at least similar to that of the reported
violation of the CHSH inequality, if not stronger.


title:
Piano Transcription in the Studio Using an Extensible Alternating
  Directions Framework

abstract:
  Given a musical audio recording, the goal of automatic music transcription is
to determine a score-like representation of the piece underlying the recording.
Despite significant interest within the research community, several studies
have reported on a 'glass ceiling' effect, an apparent limit on the
transcription accuracy that current methods seem incapable of overcoming. In
this paper, we explore how much this effect can be mitigated by focusing on a
specific instrument class and making use of additional information on the
recording conditions available in studio or home recording scenarios. In
particular, exploiting the availability of single note recordings for the
instrument in use we develop a novel signal model employing variable-length
spectro-temporal patterns as its central building blocks - tailored for pitched
percussive instruments such as the piano. Temporal dependencies between
spectral templates are modeled, resembling characteristics of factorial scaled
hidden Markov models (FS-HMM) and other methods combining Non-Negative Matrix
Factorization with Markov processes. In contrast to FS-HMMs, our parameter
estimation is developed in a global, relaxed form within the extensible
alternating direction method of multipliers (ADMM) framework, which enables the
systematic combination of basic regularizers propagating sparsity and local
stationarity in note activity with more complex regularizers imposing temporal
semantics. The proposed method achieves an f-measure of 93-95% for note onsets
on pieces recorded on a Yamaha Disklavier (MAPS DB).


title: Cell lineage tracing using nuclease barcoding

abstract:
  Lineage tracing, the determination and mapping of progeny arising from single
cells, is an important approach enabling the elucidation of mechanisms
underlying diverse biological processes ranging from development to disease. We
developed a dynamic sequence-based barcode for lineage tracing and have
demonstrated its performance in C. elegans, a model organism whose lineage tree
is well established. The strategy we use creates lineage trees based upon the
introduction of specific mutations into cells and the propagation of these
mutations to daughter cells at each cell division. We present an experimental
proof of concept along with a corresponding simulation and analytical model for
deeper understanding of the coding capacity of the system. By introducing
mutations in a predictable manner using CRISPR/Cas9, our technology will enable
more complete investigations of cellular processes.


title: Post-Inference Prior Swapping

abstract:
  While Bayesian methods are praised for their ability to incorporate useful
prior knowledge, in practice, convenient priors that allow for computationally
cheap or tractable inference are commonly used. In this paper, we investigate
the following question: for a given model, is it possible to compute an
inference result with any convenient false prior, and afterwards, given any
target prior of interest, quickly transform this result into the target
posterior? A potential solution is to use importance sampling (IS). However, we
demonstrate that IS will fail for many choices of the target prior, depending
on its parametric form and similarity to the false prior. Instead, we propose
prior swapping, a method that leverages the pre-inferred false posterior to
efficiently generate accurate posterior samples under arbitrary target priors.
Prior swapping lets us apply less-costly inference algorithms to certain
models, and incorporate new or updated prior information "post-inference". We
give theoretical guarantees about our method, and demonstrate it empirically on
a number of models and priors.


title:
Existence and asymptotic behavior of standing waves of the nonlinear
  Helmholtz equation in the plane

abstract:
  In this paper we study the semilinear elliptic problem $$ -\Delta u
-k^2u=Q|u|^{p-2}u\quad\text{ in }\mathbb{R}^2, $$ where $k>0$, $p\geq 6$ and
$Q$ is a bounded function. We prove the existence of real-valued
$W^{2,p}$-solutions, both for decaying and for periodic coefficient $Q$. In
addition, a nonlinear far-field relation is derived for these solutions.


title: Matrix representations by means of interpolation

abstract:
  We examine implicit representations of parametric or point cloud models,
based on interpolation matrices, which are not sensitive to base points. We
show how interpolation matrices can be used for ray shooting of a parametric
ray with a surface patch, including the case of high-multiplicity
intersections. Most matrix operations are executed during pre-processing since
they solely depend on the surface. For a given ray, the bottleneck is equation
solving. Our Maple code handles bicubic patches in $\le 1$~sec, though
numerical issues might arise. Our second contribution is to extend the method
to parametric space curves and, generally, to codimension $> 1$, by computing
the equations of (hyper)surfaces intersecting precisely at the given object. By
means of Chow forms, we propose a new, practical, randomized algorithm that
always produces correct output but possibly with a non-minimal number of
surfaces. For space curves, we obtain 3 surfaces whose polynomials are of
near-optimal degree; in this case, computation reduces to a Sylvester
resultant. We illustrate our algorithm through a series of examples and compare
our Maple prototype with other methods implemented in Maple i.e., Groebner
basis and implicit matrix representations. Our Maple prototype is not faster
but yields fewer equations and seems more robust than Maple's {\tt
implicitize}; it is also comparable with the other methods for degrees up to 6.


title:
A classification of polynomial functions satisfying the Jacobi identity
  over integral domains

abstract:
  The Jacobi identity is one of the properties that are used to define the
concept of Lie algebra and in this context is closely related to associativity.
In this paper we provide a complete description of all bivariate polynomials
that satisfy the Jacobi identity over infinite integral domains. Although this
description depends on the characteristic of the domain, it turns out that all
these polynomials are of degree at most one in each indeterminate.


title: Conformal embeddings and higher-spin bulk duals

abstract:
  It is well-known that conformal embeddings can be used to construct
non-diagonal modular invariants for affine lie algebras. This idea can be
extended to construct infinite series of non-diagonal modular invariants for
coset CFTs. In this paper, we systematically approach the problem of
identifying higher-spin bulk duals for these kind of non-diagonal invariants.
In particular, for a special value of the 't Hooft coupling, there exist a
class of partition functions that have enhanced supersymmetry, which should be
reflected in a bulk dual. As a illustration of this, we show that a partition
function of a orthogonal group coset CFT has a $\mathcal N=1$ supersymmetric
higher-spin bulk dual, in the 't Hooft limit. We also propose that two of the
series of CFT partition functions, obtained from conformal embeddings, are
equal, generalising the well-known dual interpretation of the 3-state Potts
model as a $\frac{SU(2)_3 \otimes SU(2)_1}{SU(2)_4}$ and also as a
$\frac{SU(3)_1 \otimes SU(3)_1}{SU(3)_2}$ coset model.


title: Liouville Theory on Horizons: Towards a Quantum Theory of Black Holes

abstract:
  We show that any nonextremal black hole can be described by a Liouville
theory that lives on its very near horizon region. In classical Liouville
theory, the black hole corresponds to a field configuration that reproduces the
Rindler metric. In quantum Liouville theory, the black hole state in the CFT is
created by the puncture operator that gives rise to a conical singularity with
a deficit angle of $2 \pi$. This state is "heavy" with a nonnormalizable wave
function in the minisuperspace approximation. Black hole entropy counts the
number of ways the "heavy" black hole state can be obtained by acting with a
product of "light, quantum" operators in the CFT. Black hole hair is described
by the "background charge" in the CFT but its physical nature is unclear.


title: Exact solution of the $D_3$ non-Abelian anyon chain

abstract:
  Commuting transfer matrices for linear chains of interacting non-Abelian
anyons from the two-dimensional irreducible representation of the dihedral
group $D_3$ (or, equivalently, the integer sector of the $su(2)_4$ spin-$1$
chain) are constructed using the spin-anyon correspondence to a $D_3$-symmetric
formulation of the XXZ Heisenberg spin chain. The spectral problem is solved
using discrete inversion identities satisfied by these transfer matrices and
functional Bethe ansatz methods. The resulting spectrum can be related to that
of the XXZ spin-$1/2$ Heisenberg chain with boundary conditions depending on
the topological sector of the anyon chain. The properties of this model in the
critical regime are studied by finite size analysis of the spectrum. In
particular, points in the phase diagram where the anyon chain realizes some of
the rational $\mathbb{Z}_2$ orbifold theories are identified.


title: $\Psi$DM and the Bullet Cluster: Couple Inflaton to Higgs Field

abstract:
  Electroweak theory is extended to $SU_L(2)\times U_Y(1)\times U_{\phi}(1)$,
where $U_{\phi}(1)$ comes from the coupling of inflaton field to Higgs field.
There arises an extremely light boson, $Y_{\mu}$. We resemble it as the
wavelike dark matter, $\Psi$DM, through the dynamical analysis. The
interactions of $Y_{\mu}$ may provide an explanation for the Bullet Cluster
observations. Besides, a possible mechanism to produce $Y_{\mu}$ is discussed.


title: Hemoglobin Strain Field Waves and Allometric Functionality

abstract:
  Hemoglobin (Hgb) forms tetramers (dimerized dimers), which enhance its
globular stability and may also facilitate small gas molecule transport, as
shown by recent all-atom Newtonian solvated simulations. Hydropathic
bioinformatic scaling reveals many wave-like features of strained Hgb
structures at the coarse-grained amino acid level, while distinguishing between
these features thermodynamically. Strain fields localized near hemes interfere
with extended strain fields associated with dimer interfacial misfit, resulting
in wave-length dependent dimer correlation function antiresonances.


title:
The Formation of a Milky Way-sized Disk Galaxy 1. A Comparison of
  Numerical Methods

abstract:
  The long-standing challenge of creating a Milky Way-like disk galaxy from
cosmological simulations has motivated significant developments in both
numerical methods and physical models in recent years. We investigate these two
fundamental aspects in a new comparison project using a set of cosmological
hydrodynamic simulations of the formation and evolution of a Milky Way-size
galaxy. In this study, we focus on the comparison of two particle-based
hydrodynamics methods: the improved smoothed particle hydrodynamics (SPH) code
Gadget, and the Lagrangian Meshless Finite-Mass (MFM) code GIZMO. All the
simulations in this paper use the same initial conditions and physical models,
which include physics of both dark matter and baryons, star formation,
"energy-driven" outflow, metal-dependent cooling, stellar evolution and metal
enrichment from supernovae. We find that both numerical schemes produce a
late-type galaxy with extended gaseous and stellar disks. However, notable
differences are present in a wide range of galaxy properties and their
evolution, including star formation history, gas content, disk structure and
kinematics. In particular, there is significant difference in gas properties
and their evolution between the two simulations. Compared to GIZMO, Gadget
simulation produces a larger fraction of cold, dense gas at high redshift which
fuels rapid star formation and results in a higher stellar mass by $20\%$ and a
lower gas fraction by $10\%$ at $z = 0$, and the resulting gas disk is smoother
and more coherent in rotation due to damping of turbulent motion by the
numerical viscosity in SPH, in contrast to the GIZMO simulation which shows
more prominent spiral structure. Given its better convergence properties and
lower computational cost, we argue that MFM method is a promising alternative
to the widely used SPH in cosmological hydrodynamic simulations.


title: Electronic and optical properties of bilayer blue phosphorus

abstract:
  We investigate the electronic and optical properties of monolayer and
stacking dependent bilayer blue phosphorus in the framework of density
functional theory (DFT) and tight-binding approximations. We extract the
hopping parameters of TB Hamiltonian for monolayer and bilayer blue phosphorus
by using the DFT results. The variation of energy band gap with applied
external electric field for two different stacks of bilayer blue phosphorus are
also shown. We examine the linear response of the systems due to the external
electromagnetic radiation in terms of the dielectric functions in the DFT
theory. The relatively large electronic band gap and possibility of exfoliation
form bulk structure due to weak interlayer coupling, make blue phosphorus an
appropriate candidate for future electronic devices.


title: Critical groups of group representations

abstract:
  This paper investigates the critical group of a faithful representation of a
finite group. It computes the order of the critical group in terms of the
character values, and gives some restrictions on its subgroup structure. It
also computes the precise structure of the critical group both for the regular
representation of any finite group, and for the reflection representation of
the symmetric group.


title:
Multi-Agent Modeling of Dynamical Systems: A Self-organized, Emergent,
  Homeostatic and Autopoietic Approach

abstract:
  This thesis presents the theoretical, conceptual and methodological aspects
that support the modeling of dynamical systems (DS) by using several agents.
The modeling approach permits the assessment of properties representing order,
change, equilibrium, adaptability, and autonomy, in DS. The modeling processes
were supported by a conceptual corpus regarding systems dynamics, multi-agent
systems, graph theory, and, particularly, the information theory. Besides to
the specification of the dynamical systems as a computational network of
agents, metrics that allow characterizing and assessing the inherent complexity
of such systems were defined. As a result, properties associated with
emergence, self-organization, complexity, homeostasis and autopoiesis were
defined, formalized and measured. The validation of the underlying DS model was
carried out on discrete systems (boolean networks and cellular automata) and
ecological systems. The central contribution of this thesis was the development
of a methodological approach for DS modeling. This approach includes a larger
set of properties than in traditional studies, what allows us to deepen in
questioning essential issues associated with the DS field. All this was
achieved from a simple base of calculation and interpretation, which does not
require advanced mathematical knowledge, and facilitates their application in
different fields of science.


title: Multi-View Treelet Transform

abstract:
  Current multi-view factorization methods make assumptions that are not
acceptable for many kinds of data, and in particular, for graphical data with
hierarchical structure. At the same time, current hierarchical methods work
only in the single-view setting. We generalize the Treelet Transform to the
Multi-View Treelet Transform (MVTT) to allow for the capture of hierarchical
structure when multiple views are available. Further, we show how this
generalization is consistent with the existing theory and how it might be used
in denoising empirical networks and in computing the shared response of
functional brain data.


title: Problems with classic homeomorphisms and three-point boundary conditions

abstract:
  Using Leray-Schauder degree theory we study the existence of at least one
solution for the boundary value problem of the type (\varphi(u' ))' =
f(t,u,u'), u'(0)=u(0), u'(T)= bu'(0), where \varphi is a homeomorphism such
that \varphi(0)=0, f is a continuous function, and T a positive real number and
b some non zero real number.


title:
A Spiking Network that Learns to Extract Spike Signatures from Speech
  Signals

abstract:
  Spiking neural networks (SNNs) with adaptive synapses reflect core properties
of biological neural networks. Speech recognition, as an application involving
audio coding and dynamic learning, provides a good test problem to study SNN
functionality. We present a simple, novel, and efficient nonrecurrent SNN that
learns to convert a speech signal into a spike train signature. The signature
is distinguishable from signatures for other speech signals representing
different words, thereby enabling digit recognition and discrimination in
devices that use only spiking neurons. The method uses a small, nonrecurrent
SNN consisting of Izhikevich neurons equipped with spike timing dependent
plasticity (STDP) and biologically realistic synapses. This approach introduces
an efficient and fast network without error-feedback training, although it does
require supervised training. The new simulation results produce discriminative
spike train patterns for spoken digits in which highly correlated spike trains
belong to the same category and low correlated patterns belong to different
categories. The proposed SNN is evaluated using a spoken digit recognition task
where a subset of the Aurora speech dataset is used. The experimental results
show that the network performs well in terms of accuracy rate and complexity.


title: Locality-Aware Laplacian Mesh Smoothing

abstract:
  In this paper, we propose a novel reordering scheme to improve the
performance of a Laplacian Mesh Smoothing (LMS). While the Laplacian smoothing
algorithm is well optimized and studied, we show how a simple reordering of the
vertices of the mesh can greatly improve the execution time of the smoothing
algorithm. The idea of our reordering is based on (i) the postulate that cache
misses are a very time consuming part of the execution of LMS, and (ii) the
study of the reuse distance patterns of various executions of the LMS
algorithm.
  Our reordering algorithm is very simple but allows for huge performance
improvement. We ran it on a Westmere-EX platform and obtained a speedup of 75
on 32 cores compared to the single core execution without reordering, and a
gain in execution of 32% on 32 cores compared to state of the art reordering.
Finally, we show that we leave little room for a better ordering by reducing
the L2 and L3 cache misses to a bare minimum.


title: Some Results on Reversible Gate Classes Over Non-Binary Alphabets

abstract:
  We present a collection of results concerning the structure of reversible
gate classes over non-binary alphabets, including (1) a reversible gate class
over non-binary alphabets that is not finitely generated (2) an explicit set of
generators for the class of all gates, the class of all conservative gates, and
a class of generalizations of the two (3) an embedding of the poset of
reversible gate classes over an alphabet of size $k$ into that of an alphabet
of size $k+1$ (4) a classification of gate classes containing the class of
$(k-1,1)$-conservative gates, meaning gates that preserve the number of
occurrences of a certain element in the alphabet.


title: Extended propagation of powerful laser pulses in focusing Kerr media

abstract:
  Powerful incoherent laser pulses can propagate in focusing Kerr media much
longer distances than can coherent pulses, due to the fast phase mixing that
prevents transverse filamentation. This distance is limited by 4-wave
scattering, which accumulates waves at small transverse wavenumbers, where
phase mixing is too slow to retain the incoherence and thus prevent the
filamentation. However, we identify how this theoretical limit can be overcome
by countering this accumulation through transverse heating of the pulse by
random fluctuations of the refractive index. In these new regimes, the laser
pulse propagation distances are significantly extended, making feasible a new
class of random lasers, in particular, ultra-powerful random lasers in plasmas.


title:
On complete hypersurfaces with constant mean and scalar curvatures in
  Euclidean spaces

abstract:
  Generalizing a theorem of Huang, Cheng and Wan classified the complete
hypersurfaces of $\mathbb R^4$ with non-zero constant mean curvature and
constant scalar curvature. In our work, we obtain results of this nature in
higher dimensions. In particular, we prove that if a complete hypersurface of
$\mathbb R^5$ has constant mean curvature $H\neq 0$ and constant scalar
curvature $R\geq\frac{2}{3}H^2$, then $R=H^2$, $R=\frac{8}{9}H^2$ or
$R=\frac{2}{3}H^2$. Moreover, we characterize the hypersurface in the cases
$R=H^2$ and $R=\frac{8}{9}H^2$, and provide an example in the case
$R=\frac{2}{3}H^2$. The proofs are based on the principal curvature theorem of
Smyth-Xavier and a well known formula for the Laplacian of the squared norm of
the second fundamental form of a hypersurface in a space form.


title:
A Parallel Implementation of the Ensemble Kalman Filter Based on
  Modified Cholesky Decomposition

abstract:
  This paper discusses an efficient parallel implementation of the ensemble
Kalman filter based on the modified Cholesky decomposition. The proposed
implementation starts with decomposing the domain into sub-domains. In each
sub-domain a sparse estimation of the inverse background error covariance
matrix is computed via a modified Cholesky decomposition; the estimates are
computed concurrently on separate processors. The sparsity of this estimator is
dictated by the conditional independence of model components for some radius of
influence. Then, the assimilation step is carried out in parallel without the
need of inter-processor communication. Once the local analysis states are
computed, the analysis sub-domains are mapped back onto the global domain to
obtain the analysis ensemble. Computational experiments are performed using the
Atmospheric General Circulation Model (SPEEDY) with the T-63 resolution on the
Blueridge cluster at Virginia Tech. The number of processors used in the
experiments ranges from 96 to 2,048. The proposed implementation outperforms in
terms of accuracy the well-known local ensemble transform Kalman filter (LETKF)
for all the model variables. The computational time of the proposed
implementation is similar to that of the parallel LETKF method (where no
covariance estimation is performed). Finally, for the largest number of
processors, the proposed parallel implementation is 400 times faster than the
serial version of the proposed method.


title: Amenable absorption in amalgamated free product von Neumann algebras

abstract:
  We investigate the position of amenable subalgebras in arbitrary amalgamated
free product von Neumann algebras $M = M_1 \ast_B M_2$. Our main result states
that under natural analytic assumptions, any amenable subalgebra of $M$ that
has a large intersection with $M_1$ is actually contained in $M_1$. The proof
does not rely on Popa's asymptotic orthogonality property but on the study of
non normal conditional expectations.


title:
On Jump-Diffusive Driving Noise Sources: Some Explicit Results and
  Applications

abstract:
  We study some linear and nonlinear shot noise models where the jumps are
drawn from a compound Poisson process with jump sizes following an Erlang-$m$
distribution. We show that the associated Master equation can be written as a
spatial $m^{{\rm th}}$ order partial differential equation without integral
term. This differential form is valid for state-dependent Poisson rates and we
use it to characterize, via a mean-field approach, the collective dynamics of a
large population of pure jump processes interacting via their Poisson rates. We
explicitly show that for an appropriate class of interactions, the speed of a
tight collective traveling wave behavior can be triggered by the jump size
parameter $m$. As a second application we consider an exceptional class of
stochastic differential equations with nonlinear drift, Poisson shot noise and
an additional White Gaussian Noise term, for which explicit solutions to the
associated Master equation are derived.


title: Aspects of Superconformal Multiplets in D>4

abstract:
  We explicitly construct and list all unitary superconformal multiplets, along
with their index contributions, in five and six dimensions. From this data, we
uncover various unifying themes in the representation theory of five- and
six-dimensional superconformal field theories. At the same time, we provide a
detailed argument for the complete classification of unitary irreducible
representations in five dimensions using a combination of physical and
mathematical techniques.


title:
Quantum and classical aspects of scalar and vector fields around black
  holes

abstract:
  This thesis presents recent studies on test scalar and vector fields around
black holes. It is separated in two parts according to the asymptotic
properties of the spacetime under study. In the first part, we investigate
scalar and Proca fields on an asymptotically flat background. For the Proca
field, we obtain a complete set of equations of motion in higher dimensional
spherically symmetric backgrounds. These equations are solved numerically, both
to compute Hawking radiation spectra and quasi-bound states. In the former
case, we carry out a precise study of the longitudinal degrees of freedom
induced by the field mass. This can be used to improve the model in the black
hole event generators currently used at the Large Hadron Collider. Regarding
quasi-bound states, we find arbitrarily long lived modes for a charged Proca
field, as well as for a charged scalar field, in a Reissner-Nordstr\"om black
hole. The second part of this thesis presents research on superradiant
instabilities of scalar and Maxwell fields on an asymptotically anti-de Sitter
background. For the scalar case, we introduce a charge coupling between the
field and the background, and show that superradiant instabilities do exist for
all $\ell$ modes, in higher dimensions. For the Maxwell case, we first propose
a general prescription to impose boundary conditions on the Kerr-anti-de Sitter
spacetime, and obtain two Robin boundary conditions. Then these two conditions
are implemented to study superradiant unstable modes and vector clouds. In
particular, we find that the new branch of quasinormal modes may be unstable in
a larger parameter space. Furthermore, the existence of vector clouds indicates
that one may find a vector hairy black hole solution for the
Einstein-Maxwell-anti-de Sitter system at the nonlinear level, which implies
that, in such system, the Kerr-Newman-anti-de Sitter black hole is not a unique
solution.


title:
The regularized tau estimator: A robust and efficient solution to
  ill-posed linear inverse problems

abstract:
  Linear inverse problems are ubiquitous. Often the measurements do not follow
a Gaussian distribution. Additionally, a model matrix with a large condition
number can complicate the problem further by making it ill-posed. In this case,
the performance of popular estimators may deteriorate significantly. We have
developed a new estimator that is both nearly optimal in the presence of
Gaussian errors while being also robust against outliers. Furthermore, it
obtains meaningful estimates when the problem is ill-posed through the
inclusion of $\ell_1$ and $\ell_2$ regularizations. The computation of our
estimate involves minimizing a non-convex objective function. Hence, we are not
guaranteed to find the global minimum in a reasonable amount of time. Thus, we
propose two algorithms that converge to a good local minimum in a reasonable
(and adjustable) amount of time, as an approximation of the global minimum. We
also analyze how the introduction of the regularization term affects the
statistical properties of our estimator. We confirm high robustness against
outliers and asymptotic efficiency for Gaussian distributions by deriving
measures of robustness such as the influence function, sensitivity curve, bias,
asymptotic variance, and mean square error. We verify the theoretical results
using numerical experiments and show that the proposed estimator outperforms
recently proposed methods, especially for increasing amounts of outlier
contamination. Python code for all of the algorithms are available online in
the spirit of reproducible research.


title:
Generalized Root Models: Beyond Pairwise Graphical Models for Univariate
  Exponential Families

abstract:
  We present a novel k-way high-dimensional graphical model called the
Generalized Root Model (GRM) that explicitly models dependencies between
variable sets of size k > 2---where k = 2 is the standard pairwise graphical
model. This model is based on taking the k-th root of the original sufficient
statistics of any univariate exponential family with positive sufficient
statistics, including the Poisson and exponential distributions. As in the
recent work with square root graphical (SQR) models [Inouye et al.
2016]---which was restricted to pairwise dependencies---we give the conditions
of the parameters that are needed for normalization using the radial
conditionals similar to the pairwise case [Inouye et al. 2016]. In particular,
we show that the Poisson GRM has no restrictions on the parameters and the
exponential GRM only has a restriction akin to negative definiteness. We
develop a simple but general learning algorithm based on L1-regularized
node-wise regressions. We also present a general way of numerically
approximating the log partition function and associated derivatives of the GRM
univariate node conditionals---in contrast to [Inouye et al. 2016], which only
provided algorithm for estimating the exponential SQR. To illustrate GRM, we
model word counts with a Poisson GRM and show the associated k-sized variable
sets. We finish by discussing methods for reducing the parameter space in
various situations.


title: A note on the non-Artinianness of top local cohomology modules

abstract:
  Let $R$ be a Noetherian ring, $I$ an ideal of $R$ and $M$ an $R$-module. In
this article, we examine the question of whether an arbitrary top local
cohomology module, $\operatorname{H}^{\operatorname{cd}(I,M)}_I(M)$, is
Artinian, or not. Several results related to this question are obtained; in
particular, we prove that over a Noetherian local unique factorization domain
$R$ of dimension three, for a finitely generated faithful module $M$, a top
local cohomology module is Artinian if and only if $\operatorname{cd}(I,M)= 3$.


title: On self-dual double negacirculant codes

abstract:
  Double negacirculant (DN) codes are the analogues in odd characteristic of
double circulant codes. Self-dual DN codes of odd dimension are shown to be
consta-dihedral. Exact counting formulae are derived for DN codes. The special
class of length a power of two is studied by means of Dickson polynomials, and
is shown to contain families of codes with relative distances satisfying a
modified Gilbert-Varshamov bound.


title: Quantum integrable multi-well tunneling models

abstract:
  In this work we present a general construction of integrable models for boson
tunneling in multi-well systems. We show how the models may be derived through
the Quantum Inverse Scattering Method and solved by algebraic Bethe ansatz
means. From the transfer matrix we find only two conserved operators. However,
we construct additional conserved operators through a different method. As a
consequence the models admit multiple pseudovacua, each associated to a set of
Bethe ansatz equations. We show that all sets of Bethe ansatz equations are
needed to obtain a complete set of eigenstates.

categories: math-ph cond-mat.quant-gas math.MP nlin.SI quant-ph


title: Implementing and characterizing precise multi-qubit measurements

abstract:
  There are two general requirements to harness the computational power of
quantum mechanics: the ability to manipulate the evolution of an isolated
system and the ability to faithfully extract information from it. Quantum error
correction and simulation often make a more exacting demand: the ability to
perform non-destructive measurements of specific correlations within that
system. We realize such measurements by employing a protocol adapted from [S.
Nigg and S. M. Girvin, Phys. Rev. Lett. 110, 243604 (2013)], enabling real-time
selection of arbitrary register-wide Pauli operators. Our implementation
consists of a simple circuit quantum electrodynamics (cQED) module of four
highly-coherent 3D transmon qubits, collectively coupled to a high-Q
superconducting microwave cavity. As a demonstration, we enact all seven
nontrivial subset-parity measurements on our three-qubit register. For each we
fully characterize the realized measurement by analyzing the detector
(observable operators) via quantum detector tomography and by analyzing the
quantum back-action via conditioned process tomography. No single quantity
completely encapsulates the performance of a measurement, and standard figures
of merit have not yet emerged. Accordingly, we consider several new fidelity
measures for both the detector and the complete measurement process. We measure
all of these quantities and report high fidelities, indicating that we are
measuring the desired quantities precisely and that the measurements are highly
non-demolition. We further show that both results are improved significantly by
an additional error-heralding measurement. The analyses presented here form a
useful basis for the future characterization and validation of quantum
measurements, anticipating the demands of emerging quantum technologies.


title:
Evidence for ion migration in hybrid perovskite solar cells with minimal
  hysteresis

abstract:
  Ionic migration has been proposed as a possible cause of photovoltaic
current-voltage hysteresis in hybrid perovskite solar cells. However, a major
objection to this hypothesis is that hysteresis can be reduced by changing the
interfacial contact materials, which are unlikely to significantly influence
the behaviour of ionic defects within the perovskite phase. Here we use
transient optoelectronic measurements, combined with device simulations, to
show that the primary effects of ionic migration can in fact be observed both
in devices with hysteresis, and with hysteresis free type contact materials.
The data indicate that electric-field screening, consistent with ionic
migration, is similar or identical in both high and low hysteresis CH3NH3PbI3
cells. Simulation of the transients shows that hysteresis requires the
combination of both mobile ionic charge and recombination near the contacts.
Passivating contact recombination results in higher photogenerated charge
concentrations at forward bias which screen the ionic charge, reducing
hysteresis.


title:
Matrix Factorization using Window Sampling and Negative Sampling for
  Improved Word Representations

abstract:
  In this paper, we propose LexVec, a new method for generating distributed
word representations that uses low-rank, weighted factorization of the Positive
Point-wise Mutual Information matrix via stochastic gradient descent, employing
a weighting scheme that assigns heavier penalties for errors on frequent
co-occurrences while still accounting for negative co-occurrence. Evaluation on
word similarity and analogy tasks shows that LexVec matches and often
outperforms state-of-the-art methods on many of these tasks.


title:
Hybrid Multi-Walled Carbon Nanotube TiO2 Electrode Material for Next
  Generation Energy Storage Devices

abstract:
  Current supercapacitors present several distinct limitations that severely
inhibit the efficiency, power, and electrical capacitance of energy storage
devices. Supercapacitors present an exciting prospect that has countless
applications in renewable energy storage and modern day electronic devices. In
recent years the exciting development of carbon nanotubes (CNTs) has presented
an advantage in electrode development. CNTs, however beneficial for their
increased electrode surface area, have severe limitations regarding
conductivity and electrode density. Creating a nanocomposite hybrid out of a
transition metal-oxide and carbon nanotube array would help the current
limitations of the modern supercapacitor. TiO2 was chosen for its common
occurrence in everyday materials and promising capacitance levels. A
multi-walled carbon nanotube array was grown on a SiO2 precursor via CCVD. The
transition metal oxide was then deposited via RF Sputtering methods to a MWCNT
array. Recharge tests and characterization were conducted using scanning
capacitance microscopy (SCM). While these tests are preliminary, this novel
hybrid electrode represents an exciting prospect for the future of the
efficiency of electrochemical energy storage as well as an advance towards a
future of providing inexpensive energy storage solutions around the world.


title:
Towards a statistical mechanics of consciousness: maximization of number
  of connections is associated with conscious awareness

abstract:
  It has been said that complexity lies between order and disorder. In the case
of brain activity, and physiology in general, complexity issues are being
considered with increased emphasis. We sought to identify features of brain
organization that are optimal for sensory processing, and that may guide the
emergence of cognition and consciousness, by analysing neurophysiological
recordings in conscious and unconscious states. We find a surprisingly simple
result: normal wakeful states are characterised by the greatest number of
possible configurations of interactions between brain networks, representing
highest entropy values. Therefore, the information content is larger in the
network associated to conscious states, suggesting that consciousness could be
the result of an optimization of information processing. These findings
encapsulate three main current theories of cognition, as discussed in the text,
and more specifically the conceptualization of consciousness in terms of brain
complexity. We hope our study represents the preliminary attempt at finding
organising principles of brain function that will help to guide in a more
formal sense inquiry into how consciousness arises from the organization of
matter.


title:
Unifying Geometric Features and Facial Action Units for Improved
  Performance of Facial Expression Analysis

abstract:
  Previous approaches to model and analyze facial expression analysis use three
different techniques: facial action units, geometric features and graph based
modelling. However, previous approaches have treated these technique
separately. There is an interrelationship between these techniques. The facial
expression analysis is significantly improved by utilizing these mappings
between major geometric features involved in facial expressions and the subset
of facial action units whose presence or absence are unique to a facial
expression. This paper combines dimension reduction techniques and image
classification with search space pruning achieved by this unique subset of
facial action units to significantly prune the search space. The performance
results on the publicly facial expression database shows an improvement in
performance by 70% over time while maintaining the emotion recognition
correctness.


title:
Magnetic properties of the $\alpha$-$T_3$ model: magneto-optical
  conductivity and the Hofstadter butterfly

abstract:
  The $\alpha$-$T_3$ model extrapolates between the pseudospin $S=1/2$
honeycomb lattice of graphene and the pseudospin $S=1$ dice lattice via
parameter $\alpha$. We present calculations of the magnetic properties of this
hybrid pseudospin model, namely the absorptive magneto-optical conductivity and
the Hofstadter butterfly spectra. In the magneto-optics curves, signatures of
the hybrid system corollary a doublet structure present in the peaks, resulting
from differing Landau level energies in the $K$ and $K^{\prime}$ valleys. In
the Hofstadter spectra, we detail the evolution of the Hofstadter butterfly as
it changes its periodicity by a factor of three as we vary between the two
limiting cases of the $\alpha$-$T_3$ model.


title: Self-bound dipolar droplet: a localized matter-wave in free space

abstract:
  We demonstrate that a dipolar condensate can be prepared into a
three-dimensional wavepacket that remains localized when released in
free-space. Such self-bound states arise from the interplay of the two-body
interactions and quantum fluctuations. We develop a phase diagram for the
parameter regimes where these self-bound states are stable, examine their
properties, and demonstrate how they can be produced in current experiments.


title: Training a Hidden Markov Model with a Bayesian Spiking Neural Network

abstract:
  It is of some interest to understand how statistically based mechanisms for
signal processing might be integrated with biologically motivated mechanisms
such as neural networks. This paper explores a novel hybrid approach for
classifying segments of sequential data, such as individual spoken works. The
approach combines a hidden Markov model (HMM) with a spiking neural network
(SNN). The HMM, consisting of states and transitions, forms a fixed backbone
with nonadaptive transition probabilities. The SNN, however, implements a
biologically based Bayesian computation that derives from the spike
timing-dependent plasticity (STDP) learning rule. The emission (observation)
probabilities of the HMM are represented in the SNN and trained with the STDP
rule. A separate SNN, each with the same architecture, is associated with each
of the states of the HMM. Because of the STDP training, each SNN implements an
expectation maximization algorithm to learn the emission probabilities for one
HMM state. The model was studied on synthesized spike-train data and also on
spoken word data. Preliminary results suggest its performance compares
favorably with other biologically motivated approaches. Because of the model's
uniqueness and initial promise, it warrants further study. It provides some new
ideas on how the brain might implement the equivalent of an HMM in a neural
circuit.


title:
On a spectral property of one-dimensional representations of compact
  quantum groups

abstract:
  In the $C^*$-algebraic setting the spectrum of any group-like element of a
compact quantum group is shown to be a closed subgroup of the one-dimensional
torus. A number of consequences of this fact are then illustrated, along with a
loose connection with the so-called Kadison-Kaplansky conjecture.


title: Microtron for Smog Particles Photo Ionization

abstract:
  The article discusses a possibility of removing smog particles from a boiler
smoke. To do this, the boiler smoke is passed through a flow of gamma
radiation, formed by interaction of the microtron beam with a heavy target. The
energy of the microtron electrons twenty five megaelectronvolts, the beam
current one hundred microamperes. Smog particles are ionized with gamma
radiation and then sat down on the plates of the electrostatic filter. The
height of the filter plates is one m, the electric field between the plates one
kilovolt per centimeter. The smog particles on the plates should be removed
regularly to a specialized dust collector.


title: Finitely generated and not finitely generated rings

abstract:
  Let $R_1$ be a commutative ring, let $R_2$ be a finitely generated extension
ring of $R_1$, and let $S$ be a ring that is intermediate between $R_1$ and
$R_2$. For $R_1 = R[x]$ and $R_2 = R[x,y]$, this paper gives simple
combinatorial constructions of intermediate rings $S$ that are not finitely
generated over $R[x]$.


title: Asymptotics of self-similar growth-fragmentation processes

abstract:
  Markovian growth-fragmentation processes introduced by Bertoin extend the
pure fragmentation model by allowing the fragments to grow larger or smaller
between dislocation events. What becomes of the known asymptotic behaviors of
self-similar pure fragmentations when growth is added to the fragments is a
natural question that we investigate in this paper. Our results involve the
terminal value of some additive martingales whose uniform integrability is an
essential requirement. Dwelling first on the homogeneous case, we exploit the
connection with branching random walks and in particular the martingale
convergence of Biggins to derive precise asymptotic estimates. The self-similar
case is treated in a second part; under the so called Malthusian hypotheses and
with the help of several martingale-flavored features recently developed by
Bertoin et al., we obtain limit theorems for empirical measures of the
fragments.


title: Stability of Charged Global AdS$_4$ Spacetimes

abstract:
  We study linear and nonlinear stability of asymptotically AdS$_4$ solutions
in Einstein-Maxwell-scalar theory. After summarizing the set of static
solutions we first examine thermodynamical stability in the grand canonical
ensemble and the phase transitions that occur among them. In the second part of
the paper we focus on nonlinear stability in the microcanonical ensemble by
evolving radial perturbations numerically. We find hints of an instability
corner for vanishingly small perturbations of the same kind as the ones present
in the uncharged case. Collapses are avoided, instead, if the charge and mass
of the perturbations come to close the line of solitons. Finally we examine the
soliton solutions. The linear spectrum of normal modes is not resonant and
instability turns on at extrema of the mass curve. Linear stability extends to
nonlinear stability up to some threshold for the amplitude of the perturbation.
Beyond that, the soliton is destroyed and collapses to a hairy black hole. The
relative width of this stability band scales down with the charge Q, and does
not survive the blow up limit to a planar geometry.


title:
Kepler Eclipsing Binaries with $\delta$ Scuti/$\gamma$ Doradus Pulsating
  Components 1: KIC 9851944

abstract:
  KIC 9851944 is a short period ($P=2.16$ days) eclipsing binary in the {\it
Kepler} field of view. By combining the analysis of {\it Kepler} photometry and
phase resolved spectra from Kitt Peak National Observatory and Lowell
Observatory, we determine the atmospheric and physical parameters of both
stars. The two components have very different radii ($2.27R_{\odot}$,
$3.19R_{\odot}$) but close masses ($1.76 M_{\odot}$, $1.79M_{\odot}$) and
effective temperatures ($7026$K, $6902$K), indicating different evolutionary
stages. The hotter primary is still on the main sequence (MS), while the cooler
and larger secondary star has evolved to post-MS, burning hydrogen in a shell.
A comparison with coeval evolutionary models shows that it requires solar
metallicity and a higher mass ratio to fit the radii and temperatures of both
stars simultaneously. Both components show $\delta$ Scuti type pulsations which
we interpret as p-modes and p and g mixed modes. After a close examination of
the evolution of $\delta$ Scuti pulsational frequencies, we make a comparison
of the observed frequencies with those calculated from MESA/GYRE.


title:
High Dimensional Multivariate Regression and Precision Matrix Estimation
  via Nonconvex Optimization

abstract:
  We propose a nonconvex estimator for joint multivariate regression and
precision matrix estimation in the high dimensional regime, under sparsity
constraints. A gradient descent algorithm with hard thresholding is developed
to solve the nonconvex estimator, and it attains a linear rate of convergence
to the true regression coefficients and precision matrix simultaneously, up to
the statistical error. Compared with existing methods along this line of
research, which have little theoretical guarantee, the proposed algorithm not
only is computationally much more efficient with provable convergence
guarantee, but also attains the optimal finite sample statistical rate up to a
logarithmic factor. Thorough experiments on both synthetic and real datasets
back up our theory.


title:
A new algorithm for optimizing the wavelength coverage for spectroscopic
  studies: Spectral Wavelength Optimization Code (SWOC)

abstract:
  The past decade and a half has seen the design and execution of several
ground-based spectroscopic surveys, both Galactic and Extra-galactic.
Additionally, new surveys are being designed that extend the boundaries of
current surveys. In this context, many important considerations must be done
when designing a spectrograph for the future. Among these is the determination
of the optimum wavelength coverage. In this work, we present a new code for
determining the wavelength ranges that provide the optimal amount of
information to achieve the required science goals for a given survey. In its
first mode, it utilizes a user-defined list of spectral features to compute a
figure-of-merit for different spectral configurations. The second mode utilizes
a set of flux-calibrated spectra, determining the spectral regions that show
the largest differences among the spectra. Our algorithm is easily adaptable
for any set of science requirements and any spectrograph design. We apply the
algorithm to several examples, including 4MOST, showing the method yields
important design constraints to the wavelength regions.


title: The dependence of convective core overshooting on stellar mass

abstract:
  Convective core overshooting extends the main-sequence lifetime of a star.
Evolutionary tracks computed with overshooting are quite different from those
that use the classical Schwarzschild criterion, which leads to rather different
predictions for the stellar properties. Attempts over the last two decades to
calibrate the degree of overshooting with stellar mass using detached
double-lined eclipsing binaries have been largely inconclusive, mainly due to a
lack of suitable observational data. Here we revisit the question of a possible
mass dependence of overshooting with a more complete sample of binaries, and
examine any additional relation there might be with evolutionary state or metal
abundance Z. We use a carefully selected sample of 33 double-lined eclipsing
binaries strategically positioned in the H-R diagram, with accurate absolute
dimensions and component masses ranging from 1.2 to 4.4 solar masses. We
compare their measured properties with stellar evolution calculations to infer
semi-empirical values of the overshooting parameter alpha(ov) for each star.
Our models use the common prescription for the overshoot distance d(ov) =
alpha(ov) Hp, where Hp is the pressure scale height at the edge of the
convective core as given by the Schwarzschild criterion, and alpha(ov) is a
free parameter. We find a relation between alpha(ov) and mass that is defined
much more clearly than in previous work, and indicates a significant rise up to
about 2 solar masses followed by little or no change beyond this mass. No
appreciable dependence is seen with evolutionary state at a given mass, or with
metallicity at a given mass despite the fact that the stars in our sample span
a range of a factor of ten in [Fe/H], from -1.01 to +0.01.


title: An Improved Lower Bound for $n$-Brinkhuis $k$-Triples

abstract:
  Let $s_n$ be the number of words consisting of the ternary alphabet
consisting of the digits 0, 1, and 2 such that no subword (or factor) is a
square (a word concatenated with itself, e.g., $11$, $1212$, or $102102$). From
computational evidence, $s_n$ grows exponentially at a rate of about
$1.317277^n$. While known upper bounds are already relatively close to the
conjectured rate, effective lower bounds are much more difficult to obtain. In
this paper, we construct a $54$-Brinkhuis $952$-triple, which leads to an
improved lower bound on the number of $n$-letter ternary squarefree words:
$952^{n/53} \approx 1.1381531^n$.


title:
Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic
  globular clusters. IV. Kinematic profiles and average masses of blue
  straggler stars

abstract:
  We make use of the Hubble Space Telescope proper-motion catalogs derived by
Bellini et al. (2014) to produce the first radial velocity-dispersion profiles
sigma(R) for blue straggler stars (BSSs) in Galactic globular clusters (GCs),
as well as the first dynamical estimates for the average mass of the entire BSS
population. We show that BSSs typically have lower velocity dispersions than
stars with mass equal to the main-sequence turnoff mass, as one would expect
for a more massive population of stars. Since GCs are expected to experience
some degree of energy equipartition, we use the relation sigma~M^-eta, where
eta is related to the degree of energy equipartition, along with our
velocity-dispersion profiles to estimate BSS masses. We estimate eta as a
function of cluster relaxation from recent Monte Carlo cluster simulations by
Bianchini et al. (2016b) and then derive an average mass ratio M_BSS
/M_MSTO=1.50+/-0.14 and an average mass M_BSS=1.22+/-0.12 M_Sun from 598 BSSs
across 19 GCs. The final error bars include any systematic errors that are
random between different clusters, but not any potential biases inherent to our
methodology. Our results are in good agreement with the average mass of
M_BSS=1.22+/-0.06 M_Sun for the 35 BSSs in Galactic GCs in the literature with
properties that have allowed individual mass determination.


title:
Pseudo-scalar Higgs boson production at
  N$^3$LO$_{\text{A}}$+N$^3$LL$^\prime$

abstract:
  We consider the production of a pseudo-scalar particle $A$ at the LHC, and
present accurate theoretical predictions for its inclusive cross section in
gluon fusion. The prediction is based on combining fixed-order perturbation
theory and all-order threshold resummation. At fixed order we include the exact
next-to-next-to-leading order (NNLO) plus an approximate
next-to-next-to-next-to-leading order (N$^3$LO$_{\rm A}$) which is based on the
recent computation at this order for the scalar case. We then add threshold
resummation at next-to-next-to-next-to leading logarithmic accuracy
(N$^3$LL$^\prime$). Various forms of threshold resummation are considered,
differing by the treatment of subleading terms, allowing a robust estimate of
the theoretical uncertainties due to missing higher orders. With particular
attention to pseudo-scalar masses of $200$ GeV and $750$ GeV, we also observe
that perturbative convergence is much improved when resummation is included.
Additionally, results obtained with threshold resummation in direct QCD are
compared with analogous results as computed in soft-collinear effective theory,
which turn out to be in good agreement. We provide precise predictions for
pseudo-scalar inclusive cross section at $13$ TeV LHC for a wide range of
masses. The results are available through updated versions of the public codes
ggHiggs and TROLL.


title: Towards Fluid Instabilities of Stationary Non-Killing Horizons

abstract:
  Flowing black holes are asymptotically locally AdS spacetimes that are
stationary but have non-Killing horizons. Holographically, they are dual to a
steady-state heat flow in the boundary field theory. We investigate the
stability of these black holes in the limit in which they are well-described by
the relativistic conformal Navier-Stokes equations. More precisely, we study
the quasi-normal modes of the linearized ideal fluid equations. Though we find
no unstable modes, there are an infinite number at finite transverse momentum
which are arbitrarily long-lived. This suggests the possibility that either
non-modal effects or nonlinear interactions between these modes can give rise
to new types of gravitational instabilities.


title:
Cross-correlation between thermal Sunyaev-Zeldovich effect and the
  integrated Sachs-Wolfe effect

abstract:
  Large-angle fluctuations in the cosmic microwave background temperature
induced by the integrated Sachs-Wolfe effect and Compton-y distortions from the
thermal Sunyaev-Zeldovich (tSZ) effect are both due to line-of-sight density
perturbations. Here we calculate the cross-correlation between these two
signals. Measurement of this cross-correlation can be used to test the redshift
distribution of the tSZ distortion, which has implications for the redshift at
which astrophysical processes in clusters begin to operate. We also evaluate
the detectability of a yT cross-correlation from exotic early-Universe sources
in the presence of this late-time effect.


title: Vector-boson fusion Higgs production at N$^3$LO in QCD

abstract:
  We calculate the next-to-next-to-next-to-leading-order (N$^3$LO) QCD
corrections to inclusive vector-boson fusion (VBF) Higgs production at proton
colliders, in the limit in which there is no colour exchange between the
hadronic systems associated with the two colliding protons. We also provide
differential cross sections for the Higgs transverse momentum and rapidity
distributions. We find that the corrections are at the 1-2 permille level, well
within the scale-uncertainty of the next-to-next-to-leading-order (NNLO)
calculation. The associated scale-uncertainty of the N$^3$LO calculation is
typically found to be below the 2 permille level. We also consider theoretical
uncertainties due to missing higher order parton distribution functions, and
provide an estimate of their importance.


title:
The Hubble Legacy Fields (HLF-GOODS-S) v1.5 Data Products: Combining
  2442 Orbits of GOODS-S/CDF-S Region ACS and WFC3/IR Images

abstract:
  We have submitted to MAST the 1.5 version data release of the Hubble Legacy
Fields (HLF) project covering a 25 x 25 arcmin area over the GOODS-S (ECDF-S)
region from the HST archival program AR-13252. The release combines exposures
from Hubble's two main cameras, the Advanced Camera for Surveys (ACS/WFC) and
the Wide Field Camera 3 (WFC3/IR), taken over more than a decade between
mid-2002 to the end of 2016. The HLF includes essentially all optical (ACS/WFC
F435W, F606W, F775W, F814W and F850LP filters) and infrared (WFC3/ IR F098M,
F105W, F125W, F140W and F160W filters) data taken by Hubble over the original
CDF-S region including the GOODS-S, ERS, CANDELS and many other programs (31 in
total). The data has been released at https://archive.stsci.edu/prepds/hlf/ as
images with a common astrometric reference frame, with corresponding inverse
variance weight maps. We provide one image per filter of WFC3/IR images at 60
mas per pixel resolution and two ACS/WFC images per filter, at both 30 and 60
mas per pixel. Since this comprehensive dataset combines data from 31 programs
on the GOODS-S/CDF-S, the AR proposal identified the MAST products by the
global name "Hubble Legacy Field", with this region being identified by
"HLF-GOODS-S". This dataset complements that of the Frontier Fields program.
The total incorporated in the HLF-GOODS-S is 5.8 Msec in 7211 exposures from
2442 orbits. This is ~70% of a HST full cycle!


title:
Primordial power spectrum features in phenomenological descriptions of
  inflation

abstract:
  We extend an alternative, phenomenological approach to inflation by means of
an equation of state and a sound speed, both of them functions of the number of
$e$-folds and four phenomenological parameters. This approach captures a number
of possible inflationary models, including those with non-canonical kinetic
terms or scale-dependent non-gaussianities. We perform Markov Chain Monte Carlo
analyses using the latest cosmological publicly available measurements, which
include Cosmic Microwave Background (CMB) data from the Planck satellite.
Within this parametrization, we discard scale invariance with a significance of
about $10\sigma$, and the running of the spectral index is constrained as
$\alpha_s=-0.60\,^{+0.08}_{-0.10}\times 10^{-3}$ ($68\%$~CL errors). The limit
on the tensor-to-scalar ratio is $r<0.005$ at $95\%$~CL from CMB data alone. We
find no significant evidence for this alternative parameterization with present
cosmological observations. The maximum amplitude of the equilateral
non-gaussianity that we obtain, $|f^{\text{equil}}_{\text{NL}}|< 1$, is much
smaller than the current Planck mission errors, strengthening the case for
future high-redshift, all-sky surveys, which could reach the required accuracy
on equilateral non-gaussianities.


title: Massive Double White Dwarfs and the AM CVn Birthrate

abstract:
  We present Chandra and Swift X-ray observations of four extremely low-mass
(ELM) white dwarfs with massive companions. We place stringent limits on X-ray
emission from all four systems, indicating that neutron star companions are
extremely unlikely and that the companions are almost certainly white dwarfs.
Given the observed orbital periods and radial velocity amplitudes, the total
masses of these binaries are greater than 1.02 to 1.39 Msun. The extreme mass
ratios between the two components make it unlikely that these binary white
dwarfs will merge and explode as Type Ia or underluminous supernovae. Instead,
they will likely go through stable mass transfer through an accretion disk and
turn into interacting AM CVn. Along with three previously known systems, we
identify two of our targets, J0811 and J2132, as systems that will definitely
undergo stable mass transfer. In addition, we use the binary white dwarf sample
from the ELM Survey to constrain the inspiral rate of systems with extreme mass
ratios. This rate, 0.00017/year, is consistent with the AM CVn space density
estimated from the Sloan Digital Sky Survey. Hence, stable mass transfer double
white dwarf progenitors can account for the entire AM CVn population in the
Galaxy.