title: Sublinear Random Access Generators for Preferential Attachment Graphs

abstract:
  We consider the problem of sampling from a distribution on graphs,
specifically when the distribution is defined by an evolving graph model, and
consider the time, space and randomness complexities of such samplers.
  In the standard approach, the whole graph is chosen randomly according to the
randomized evolving process, stored in full, and then queries on the sampled
graph are answered by simply accessing the stored graph. This may require
prohibitive amounts of time, space and random bits, especially when only a
small number of queries are actually issued. Instead, we propose to generate
the graph on-the-fly, in response to queries, and therefore to require amounts
of time, space, and random bits which are a function of the actual number of
queries.
  We focus on two random graph models: the Barab{\'{a}}si-Albert Preferential
Attachment model (BA-graphs) and the random recursive tree model. We give
on-the-fly generation algorithms for both models. With probability
$1-1/\mbox{poly}(n)$, each and every query is answered in $\mbox{polylog}(n)$
time, and the increase in space and the number of random bits consumed by any
single query are both $\mbox{polylog}(n)$, where $n$ denotes the number of
vertices in the graph.
  Our results show that, although the BA random graph model is defined by a
sequential process, efficient random access to the graph's nodes is possible.
In addition to the conceptual contribution, efficient on-the-fly generation of
random graphs can serve as a tool for the efficient simulation of sublinear
algorithms over large BA-graphs, and the efficient estimation of their
performance on such graphs.


title: A Weighted Divisor Problem

abstract:
  We study a weighted divisor function $\mathop{{\sum}'}\limits_{mn\leq
x}\cos(2\pi m\theta_1)\sin(2\pi n\theta_2)$, where $\theta_i (0<\theta_i<1)$ is
a rational number. By connecting it with the divisor problem with congruence
conditions, we establish the upper bound, mean-value, mean-square and some
power-moments.


title:
Abaqus/Standard-based quantification of human cardiac mechanical
  properties

abstract:
  Computational modeling can provide critical insight into existing and
potential new surgical procedures, medical or minimally-invasive treatments for
heart failure, one of the leading causes of deaths in the world that has
reached epidemic proportions. In this paper, we present our
Abaqus/Standard-based pipeline to create subject-specific left ventricular
models. We first review our generic left ventricular model, and then the
personalization process based on magnetic resonance images. Identification of
subject-specific cardiac material properties is done by coupling
Abaqus/Standard to the python optimization library NL-Opt. Compared to previous
studies from our group, the emphasis is here on the fully implicit solving of
the model, and the two-parameter optimization of the passive cardiac material
properties.


title:
Interactive tutorial to improve student understanding of single photon
  experiments involving a Mach-Zehnder Interferometer

abstract:
  We have developed and evaluated a Quantum Interactive Learning Tutorial
(QuILT) on a Mach-Zehnder Interferometer with single photons to expose
upper-level students in quantum mechanics courses to contemporary quantum
optics applications. The QuILT strives to help students develop the ability to
apply fundamental quantum principles to physical situations in quantum optics
and explore the differences between classical and quantum ideas. The QuILT
adapts visualization tools to help students build physical intuition about
counter-intuitive quantum optics phenomena with single photons including a
quantum eraser setup and focuses on helping them integrate qualitative and
quantitative understanding. We discuss findings from in-class evaluations.


title: Dispersive shock waves and modulation theory

abstract:
  There is growing physical and mathematical interest in the hydrodynamics of
dissipationless/dispersive media. Since G.~B.~Whitham's seminal publication
fifty years ago that ushered in the mathematical study of dispersive
hydrodynamics, there has been a significant body of work in this area. However,
there has been no comprehensive survey of the field of dispersive
hydrodynamics. Utilizing Whitham's averaging theory as the primary mathematical
tool, we review the rich mathematical developments over the past fifty years
with an emphasis on physical applications. The fundamental, large scale,
coherent excitation in dispersive hydrodynamic systems is an expanding,
oscillatory dispersive shock wave or DSW. Both the macroscopic and microscopic
properties of DSWs are analyzed in detail within the context of the universal,
integrable, and foundational models for uni-directional (Korteweg-de Vries
equation) and bi-directional (Nonlinear Schr\"{o}dinger equation) dispersive
hydrodynamics. A DSW fitting procedure that does not rely upon integrable
structure yet reveals important macroscopic DSW properties is described. DSW
theory is then applied to a number of physical applications: superfluids,
nonlinear optics, geophysics, and fluid dynamics. Finally, we survey some of
the more recent developments including non-classical DSWs, DSW interactions,
DSWs in perturbed and inhomogeneous environments, and two-dimensional, oblique
DSWs.


title:
Irreversibility in a unitary finite-rate protocol: The concept of
  internal friction

abstract:
  The concept of internal friction, a fully quantum mechanical phenomena, is
investigated in a simple, experimentally accessible quantum system in which a
spin-1/2 is driven by a transverse magnetic field in a quantum adiabatic
process. The irreversible production of the waste energy due to the quantum
friction is quantitatively analyzed in a forward-backward unitary transform of
the system Hamiltonian by using the quantum relative entropy between the actual
density matrix obtained in a parametric transformation and the one in a
reversible adiabatic process. Analyzing the role of total transformation time
and the different pulse control schemes on the internal friction reveal the
non-monotone character of the internal friction as a function of the total
protocol time and the possibility for almost frictionless solutions in
finite-time transformations.


title:
Improving student understanding of addition of angular momentum in
  quantum mechanics

abstract:
  We describe the difficulties advanced undergraduate and graduate students
have with concepts related to addition of angular momentum in quantum
mechanics. We also describe the development and implementation of a
research-based learning tool, a Quantum Interactive Learning Tutorial (QuILT),
to reduce these difficulties. The preliminary evaluation shows that the QuILT
related to the basics of the addition of angular momentum is helpful in
improving students' understanding of these concepts.


title:
Effect of quantified irreducibility on the computability of subshift
  entropy

abstract:
  We study the difficulty of computing topological entropy of subshifts
subjected to mixing restrictions. This problem is well-studied for
multidimensional subshifts of finite type : there exists a threshold in the
irreducibility rate where the difficulty jumps from computable to uncomputable,
but its location is an open problem. In this paper, we establish the location
of this threshold for a more general class, subshifts with decidable languages,
in any dimension.


title:
Deployment of 5G Networking Infrastructure with Machine Type
  Communication Considerations

abstract:
  Designing optimal strategies to deploy small cell stations is crucial to meet
the quality-of-service requirements in next-generation cellular networks with
constrained deployment costs. In this paper, a general deployment framework is
proposed to jointly optimize the locations of backhaul aggregate nodes, small
base stations, machine aggregators, and multi-hop wireless backhaul links to
accommodate both human-type and machine-type communications. The goal is to
provide deployment solutions with best coverage performance under cost
constraints. The formulated problem is shown to be a multi-objective integer
programming for which it is challenging to obtain the optimal solutions. To
solve the problem, a heuristic algorithm is proposed by combining Lagrangian
relaxation, the weighted sum method, the $\epsilon$-constraint method and tabu
search to obtain both the solutions and bounds, for the objective function.
Simulation results show that the proposed framework can provide solutions with
better performance compared with conventional deployment models in scenarios
where available fiber connections are scarce. Furthermore, the gap between
obtained solutions and the lower bounds is quite tight.


title: A study of double- and multi-mode RR Lyrae variables

abstract:
  We present the results of our new study of known RR Lyrae variable stars. All
observations available for these stars in the Catalina Surveys were analyzed,
and double-mode variations were identified. We studied the Petersen diagram and
period distribution for the double-mode RR Lyrae variables in the Galactic
field, pulsating in the first-overtone and fundamental modes. The double-peaked
character of the period distribution was detected for Galactic RR(B) stars,
corresponding to Oosterhoff's classes of globular clusters, which indicates
that the age and evolution stage of RR(B) stars in the field and RR Lyrae
variables in globular clusters are probably the same. Besides, we discovered
five RRC stars with two simultaneously excited non-radial pulsations
(equidistant triplets).


title: Competitive Path Computation and Function Placement in SDNs

abstract:
  We consider a task of serving requests that arrive in an online fashion in
Software-Defined Networks (SDNs) with network function virtualization (NFV).
Each request specifies an abstract routing and processing "plan" for a flow.
Each processing function can be performed by a specified subset of servers in
the system. The algorithm needs to either reject the request or admit it and
return detailed routing (a.k.a. "path computation") and processing assignment
("function placement"). Each request also specifies the communication bandwidth
and the processing load it requires. Components in the system (links and
processors) have bounded capacity; a feasible solution may not violate the
capacity constraints. Requests have benefits and the goal is to maximize the
total benefit of accepted requests.
  In this paper we first formalize the problem, and propose a new service model
that allows us to cope with requests with unknown duration. The new service
model augments the traditional accept/reject schemes with a new possible
response of "stand by." Our main result is an online algorithm for path
computation and function placement that guarantees, in each time step,
throughput of at least $\Omega\left(\frac{\text{OPT}^*}{\log n}\right)$, where
$n$ is the system size and $\text{OPT}^*$ is an upper bound on the maximal
possible throughput. The guarantee holds assuming that requests ask for at most
an $O\left(1/{\log n}\right)$-fraction of the capacity of any component in the
system. Furthermore, the guarantee holds even though our algorithm serves
requests in an all-or-nothing fashion using a single path and never preempts
accepted flows, while $\text{OPT}^*$ may serve fractional requests, may split
the allocation over multiple paths, and may arbitrarily preempt and resume
service of requests.


title:
A segmented conical electric lens for optimization of the beam spot of
  the low-energy muon facility at PSI: a Geant4 simulation analysis

abstract:
  The low-energy muon facility at PSI provides nearly fully polarized positive
muons with tunable energies in the keV range to carry out muon spin rotation
(LE-muSR) experiments with nanometer depth resolution on thin films,
heterostructures, and near-surface regions. The low-energy muon beam is focused
and transported to the sample by electrostatic lenses. In order to achieve a
minimum beam spot size at the sample position and to enable the steering of the
beam in the horizontal and vertical direction, a special electrostatic device
has been implemented close to the sample position. It consists of a cylinder at
ground potential followed by four conically shaped electrodes, which can be
operated at different electric potential. In LE-muSR experiments, an electric
field at the sample along the beam direction can be applied to
accelerate/decelerate muons to different energies (0.5-30 keV). Additionally, a
horizontal or vertical magnetic field can be superimposed for transverse or
longitudinal field muSR experiments. The focusing properties of the conical
lens in the presence of these additional electric and magnetic fields have been
investigated and optimized by Geant4 simulations. Some experimental tests were
also performed and show that the simulation well describes the experimental
setup.


title:
Magnetic anisotropy of large floating-zone-grown single-crystals of
  SrRuO3

abstract:
  SrRuO3 is a highly interesting material due to its anomalous-metal properties
related with ferromagnetism and its relevance as conductive perovskite layer or
substrate in heterostructure devices. We have used optical floating zone
technique in an infrared image furnace to grow large single crystals of SrRuO3
with volumes attaining several hundred mm3. Crystals obtained for optimized
growth parameters exhibit a high ferromagnetic Curie temperature of 165 K and a
low-temperature magnetization of 1.6 muB at a magnetic field of 6 T. The high
quality of the crystals is further documented by large residual resistance
ratios of 75 and by crystal structure and chemical analyzes. With these
crystals the magnetic anisotropy could be determined.


title: Surveying Students' Understanding of Quantum Mechanics

abstract:
  Development of conceptual multiple-choice tests related to a particular
physics topic is important for designing research-based learning tools to
reduce the difficulties. We explore the difficulties that the advanced
undergraduate and graduate students have with non-relativistic quantum
mechanics of one particle in one spatial dimension. We developed a
research-based conceptual multiple-choice survey that targets these issues to
obtain information about the common difficulties and administered it to more
than a hundred students from seven different institutions. The issues targeted
in the survey include the set of possible wavefunctions, bound and scattering
states, quantum measurement, expectation values, the role of the Hamiltonian,
time-dependence of wavefunction and time-dependence of expectation value. We
find that the advanced undergraduate and graduate students have many common
difficulties with these concepts and that research-based tutorials and
peer-instruction tools can significantly reduce these difficulties. The survey
can be administered to assess the effectiveness of various intructional
strategies.


title: On small univoque bases of real numbers

abstract:
  Given a positive real number $x$, we consider the smallest base
$q_s(x)\in(1,2)$ for which there exists a unique sequence $(d_i)$ of zeros and
ones such that \[ x=\sum_{i=1}^\infty\frac{d_i}{(q_s(x))^i}. \] In this paper
we give complete characterizations of those $x$'s for which $q_s(x)\le q_{KL}$,
where $q_{KL}$ is the Komornik-Loreti constant. Furthermore, we show that
$q_s(x)=q_{KL}$ if and only if \[ x\in\left\{1, ~\frac{q_{KL}}{q_{KL}^2-1},~
\frac{1}{q_{KL}^2-1}, ~\frac{1}{q_{KL}(q_{KL}^2-1)}\right\}. \]
  Finally, we determine the explicit value of $q_s(x)$ if $q_s(x)<q_{KL}$.


title:
A Constant Approximation Algorithm for Scheduling Packets on Line
  Networks

abstract:
  In this paper we improve the approximation ratio for the problem of
scheduling packets on line networks with bounded buffers, where the aim is that
of maximizing the throughput. Each node in the network has a local buffer of
bounded size $B$, and each edge (or link) can transmit a limited number, $c$,
of packets in every time unit. The input to the problem consists of a set of
packet requests, each defined by a source node, a destination node, and a
release time. We denote by $n$ the size of the network. A solution for this
problem is a schedule that delivers (some of the) packets to their destinations
without violating the capacity constraints of the network (buffers or edges).
Our goal is to design an efficient algorithm that computes a schedule that
maximizes the number of packets that arrive to their respective destinations.
  We give a randomized approximation algorithm with constant approximation
ratio for the case where $B=\Theta(c)$. This improves over the previously best
result of $O(\log^* n)$ (R\"acke and Ros\'en, Theory Comput. Syst., 49(4),
2011). Our improvement is based on a new combinatorial lemma that we prove,
stating, roughly speaking, that if packets are allowed to stay put in buffers
only a limited number of time steps, $2d$, where $d$ is the longest
source-destination distance of any input packet, then the cardinality of the
optimal solution is decreased by only a constant factor. This claim was not
previously known in the directed integral (i.e., unsplittable, zero-one) case,
and may find additional applications for routing and scheduling algorithms.


title:
ELATE: An open-source online application for analysis and visualization
  of elastic tensors

abstract:
  We report on the implementation of a tool for the analysis of second-order
elastic stiffness tensors, provided with both an open-source Python module and
a standalone online application providing visualization tools of anisotropic
mechanical properties. After describing the software features, how we compute
the conventional elastic constants and how we represent them graphically, we
explain our technical choices for the implementation. In particular, we focus
on why a Python module is used to generate the HTML web page with embedded
Javascript for dynamical plots.


title: Magnetic field-induced squeezing effect at RHIC and at the LHC

abstract:
  In off-central heavy-ion collisions, the quark-gluon plasma (QGP) is exposed
to the strongest magnetic fields ever created in the universe. Due to the
paramagnetic nature of the QGP at high temperatures, the spatially
inhomogeneous magnetic field configuration exerts an anisotropic force density
that competes with the pressure gradients resulting from purely geometric
effects. In this paper, we simulate (3+1)-dimensional ideal hydrodynamics with
external magnetic fields to estimate the effect of this force density on the
anisotropic expansion of the QGP in collisions at RHIC and at the LHC. While
negligible for quickly decaying magnetic fields, we find that long-lived fields
generate a substantial force density that suppresses the momentum anisotropy of
the plasma by up to $20\%$ at the LHC energy, and also leaves its imprint on
the elliptic flow $v_2$ of charged pions.


title: Duality formulas for robust pricing and hedging in discrete time

abstract:
  In this paper we derive robust super- and subhedging dualities for contingent
claims that can depend on several underlying assets. In addition to strict
super- and subhedging, we also consider relaxed versions which, instead of
eliminating the shortfall risk completely, aim to reduce it to an acceptable
level. This yields robust price bounds with tighter spreads. As examples we
study strict super- and subhedging with general convex transaction costs and
trading constraints as well as risk-based hedging with respect to robust
versions of the average value at risk and entropic risk measure. Our approach
is based on representation results for increasing convex functionals and allows
for general financial market structures. As a side result it yields a robust
version of the fundamental theorem of asset pricing.


title: Generalized Kahler Taub-NUTs and Two Exceptional Instantons

abstract:
  We study the one-parameter family of twisted Kahler Taub-NUT metrics
(discovered by Donaldson), along with two exceptional Taub-NUT-like instantons,
and understand them to the extend that should be sufficient for blow-up and
gluing arguments. In particular we parametrize their geodesics from the origin,
determine curvature fall-off rates, volume growth rates for metric balls, and
find blow-down limits.


title: Weyl formulae for the Robin Laplacian in the semiclassical limit

abstract:
  This paper is devoted to establish semiclassical Weyl formulae for the Robin
Laplacian on smooth domains in any dimension. Theirs proofs are reminiscent of
the Born-Oppenheimer method.


title:
An Approach to Constrained Polynomial Optimization via Nonnegative
  Circuit Polynomials and Geometric Programming

abstract:
  In this article we combine two developments in polynomial optimization. On
the one hand, we consider nonnegativity certificates based on sums of
nonnegative circuit polynomials, which were recently introduced by the second
and the third author. On the other hand, we investigate geometric programming
methods for constrained polynomial optimization problems, which were recently
developed by Ghasemi and Marshall. We show that the combination of both results
yields a new method to solve certain classes of constrained polynomial
optimization problems. We test the new method experimentally and compare it to
semidefinite programming in various examples.


title: Spatial instabilities in a cloud of cold atoms

abstract:
  Dense cold atomic clouds have been shown to be similar to plasmas. Previous
studies showed that such clouds exhibit instabilities induced by long-range
interactions. However they did not describe the spatial properties of the
dynamics. In this Letter, we study experimentally the spatial nature of
stochastic instabilities and find out that the dynamics is localized. Data are
analyzed both in the spectral domain and in the spatial domain (principal
component analysis). Both methods fail to describe the dynamics in terms of
eigenmodes, showing that space and time are not separable.


title:
Macrostate equivalence of two general ensembles and specific relative
  entropies

abstract:
  The two criteria of ensemble equivalence, i.e. the macrostate equivalence and
the measure equivalence, are investigated for a general pair of states. The
macrostate equivalence implies the two ensembles are indistinguishable by the
measurement of macroscopic quantities obeying the large-deviation principle,
and the measure equivalence means that the specific relative entropy of these
two states vanishes in the thermodynamic limit. It is shown that the measure
equivalence implies the macrostate equivalence for a general pair of states by
deriving an inequality connecting the large-deviation rate functions to the
specific relative Renyi entropies. The result is applicable to both quantum and
classical systems. As applications, a sufficient condition for thermalization,
the timescale of quantum dynamics of macrovariables, and the second law with
strict irreversibility in a quantum quench are discussed.


title: Node-By-Node Greedy Deep Learning for Interpretable Features

abstract:
  Multilayer networks have seen a resurgence under the umbrella of deep
learning. Current deep learning algorithms train the layers of the network
sequentially, improving algorithmic performance as well as providing some
regularization. We present a new training algorithm for deep networks which
trains \emph{each node in the network} sequentially. Our algorithm is orders of
magnitude faster, creates more interpretable internal representations at the
node level, while not sacrificing on the ultimate out-of-sample performance.


title:
Magnetic excitations in the S = 1/2 antiferromagnetic-ferromagnetic
  chain compound BaCu2V2O8 at zero and finite temperature

abstract:
  Unlike most quantum systems which rapidly become incoherent as temperature is
raised, strong correlations persist at elevated temperatures in $S=1/2$ dimer
magnets, as revealed by the unusual asymmetric lineshape of their excitations
at finite temperatures. Here we quantitatively explore and parameterize the
strongly correlated magnetic excitations at finite temperatures using the high
resolution inelastic neutron scattering on the model compound
BaCu$_2$V$_2$O$_8$ which we show to be an alternating
antiferromagnetic-ferromagnetic spin$-1/2$ chain. Comparison to state of the
art computational techniques shows excellent agreement over a wide temperature
range. Our findings hence demonstrate the possibility to quantitatively predict
coherent behavior at elevated temperatures in quantum magnets.


title: Generalised quasi-linear approximation of the HMRI

abstract:
  Motivated by recent advances in Direct Statistical Simulation (DSS) of
astrophysical phenomena such as out of equilibrium jets, we perform a Direct
Numerical Simulation (DNS) of the helical magnetorotational instability (HMRI)
under the generalised quasilinear approximation (GQL). This approximation
generalises the quasilinear approximation (QL) to include the self-consistent
interaction of large-scale modes, interpolating between fully nonlinear DNS and
QL DNS whilst still remaining formally linear in the small scales. In this
paper we address whether GQL can more accurately describe low-order statistics
of axisymmetric HMRI when compared with QL by performing DNS under various
degrees of GQL approximation. We utilise various diagnostics, such as energy
spectra in addition to first and second cumulants, for calculations performed
for a range of Reynolds and Hartmann numbers (describing rotation and imposed
magnetic field strength respectively). We find that GQL performs significantly
better than QL in describing the statistics of the HMRI even when relatively
few large-scale modes are kept in the formalism. We conclude that DSS based on
GQL (GCE2) will be significantly more accurate than that based on QL (CE2).


title: Noise Fit, Estimation Error and a Sharpe Information Criterion

abstract:
  When the in-sample Sharpe ratio is obtained by optimizing over a
k-dimensional parameter space, it is a biased estimator for what can be
expected on unseen data (out-of-sample). We derive (1) an unbiased estimator
adjusting for both sources of bias: noise fit and estimation error. We then
show (2) how to use the adjusted Sharpe ratio as model selection criterion
analogously to the Akaike Information Criterion (AIC). Selecting a model with
the highest adjusted Sharpe ratio selects the model with the highest estimated
out-of-sample Sharpe ratio in the same way as selection by AIC does for the
log-likelihood as measure of fit.


title:
Existence results for variational-hemivariational problems with lack
  ofconvexity

abstract:
  We establish existence results of Hartmann-Stampacchia type for a class of
variational-hemivariationalinequalities on closed and convex sets (either
bounded or unbounded) in a Hilbert space.


title: Blunt Honesty, Incentives, and Knowledge Exchange

abstract:
  We propose a simple mechanism to facilitate the buying and selling of useful,
bluntly honest information. The for-profit, arm's length knowledge exchange
this mechanism enables may dramatically increase the pace of scientific
progress.


title: Accrual valuation and mark to market adjustment

abstract:
  This paper provides intuition on the relationship of accrual and
mark-to-market valuation for cash and forward interest rate trades. Discounted
cashflow valuation is compared to spread-based valuation for forward trades,
which explains the trader's view on valuation. This is followed by Taylor
series approximation for cash trades, uncovering simple intuition behind
accrual valuation and mark-to-market adjustment. It is followed by the PNL
example modelled in R. Within the Taylor approximation framework, theta and
delta are explained. The concept of deferral is explained taking Forward Rate
Agreement (FRA) as an example.


title:
Optical Transients Powered by Magnetars: Dynamics, Light Curves, and
  Transition to the Nebular Phase

abstract:
  Millisecond magnetars can be formed via several channels: core-collapse of
massive stars, accretion-induced collapse of white dwarfs (WDs), double WD
mergers, double neutron star (NS) mergers, and WD-NS mergers. Because the mass
of ejecta from these channels could be quite different, their light curves are
also expected to be diverse. We evaluate the dynamic evolution of optical
transients powered by millisecond magnetars. We find that the magnetar with
short spin-down timescale converts its rotational energy mostly into the
kinetic energy of the transient, while the energy of a magnetar with long
spin-down timescale goes into radiation of the transient. This leads us to
speculate that hypernovae could be powered by magnetars with short spin-down
timescales. At late times the optical transients will gradually evolve into a
nebular phase because of the photospheric recession. We treat the photosphere
and nebula separately because their radiation mechanisms are different. In some
cases the ejecta could be light enough that the magnetar can accelerate it to a
relativistic speed. It is well known that the peak luminosity of a supernova
(SN) occurs when the luminosity is equal to the instantaneous energy input
rate, as shown by Arnett (1979). We show that photospheric recession and
relativistic motion can modify this law. The photospheric recession always
leads to a delay of the peak time $t_{\mathrm{pk}}$ relative to the time
$t_{\times }$ at which the SN luminosity equals the instantaneous energy input
rate. Relativistic motion, however, may change this result significantly.


title: Alexander invariants of ribbon tangles and planar algebras

abstract:
  Ribbon tangles are proper embeddings of tori and cylinders in the
$4$-ball~$B^4$, "bounding" $3$-manifolds with only ribbon disks as
singularities. We construct an Alexander invariant $\mathsf{A}$ of ribbon
tangles equipped with a representation of the fundamental group of their
exterior in a free abelian group $G$. This invariant induces a functor in a
certain category $\mathsf{R}ib_G$ of tangles, which restricts to the exterior
powers of Burau-Gassner representation for ribbon braids, that are analogous to
usual braids in this context. We define a circuit algebra $\mathsf{C}ob_G$ over
the operad of smooth cobordisms, inspired by diagrammatic planar algebras
introduced by Jones, and prove that the invariant $\mathsf{A}$ commutes with
the compositions in this algebra. On the other hand, ribbon tangles admit
diagrammatic representations, throught welded diagrams. We give a simple
combinatorial description of $\mathsf{A}$ and of the algebra $\mathsf{C}ob_G$,
and observe that our construction is a topological incarnation of the Alexander
invariant of Archibald. When restricted to diagrams without virtual crossings,
$\mathsf{A}$ provides a purely local description of the usual Alexander
poynomial of links, and extends the construction by Bigelow, Cattabriga and the
second author.


title: Computer simulation of electronic excitations in beryllium

abstract:
  An effective method for the quantitative description of the electronic
excited states of polyatomic systems is developed by using computer technology.
The proposed method allows calculating various properties of matter at the
atomic level within the uniform scheme. A special attention is paid to the
description of beryllium atoms interactions with the external fields,
comparable by power to the fields in atoms, molecules and clusters.


title: Helical currents in metallic Rashba strips

abstract:
  We study the texture of helical currents in metallic planar strips in the
presence of Rashba spin-orbit coupling (RSOC) on the lattice at zero
temperature. In the noninteracting case, and in the absence of external
electromagnetic sources, we determine by exact numerical diagonalization of the
single-particle Hamiltonian, the distribution across the strip section of these
Rashba helical currents (RHC) as well as their sign oscillation, as a function
of the RSOC strength, strip width, electron filling, and strip boundary
conditions. Then, we study the effects of charge currents introduced into the
system by an Aharonov-Bohm flux for the case of rings or by a voltage bias in
the case of open strips. The former setup is studied by variational Monte
Carlo, and the later, by the time-dependent density-matrix-renormalization
group technique. Particularly for strips formed by two, three and four coupled
chains, we show how these RHC vary in the presence of such induced charge
current, and how their differences between spin-up and spin-down electron
currents on each chain, help to explain the distribution across the strip of
charge currents, both of the spin conserving and the spin flipping types. We
also predict the appearance of polarized charge currents on each chain.
Finally, we show that these Rashba helical currents and their derived features
remain in the presence of an on-site Hubbard repulsion as long as the system
remains metallic, at quarter filling, and even at half-filling where a
Mott-Hubbard metal-insulator transition occurs for large Hubbard repulsion.


title:
Search for new phenomena in final states with large jet multiplicities
  and missing transverse momentum with ATLAS using $\sqrt{s} =13$ TeV
  proton--proton collisions

abstract:
  Results are reported of a search for new phenomena, such as supersymmetric
particle production, that could be observed in high-energy proton--proton
collisions. Events with large numbers of jets, together with missing transverse
momentum from unobserved particles, are selected. The data analysed were
recorded by the ATLAS experiment during 2015 using the 13 TeV centre-of-mass
proton--proton collisions at the Large Hadron Collider, and correspond to an
integrated luminosity of 3.2 fb$^{-1}$. The search selected events with various
jet multiplicities from $\ge 7$ to $\ge 10$ jets, and with various $b$-jet
multiplicity requirements to enhance sensitivity. No excess above Standard
Model expectations is observed. The results are interpreted within two
supersymmetry models, where gluino masses up to 1400 GeV are excluded at 95%
confidence level, significantly extending previous limits.


title: Self-Organized Hydrodynamics with nonconstant velocity

abstract:
  Motivated by recent experimental and computational results that show a
motility-induced clustering transition in self-propelled particle systems, we
study an individual model and its corresponding Self-Organized Hydrodynamic
model for collective behaviour that incorporates a density-dependent velocity,
as well as inter-particle alignment. The modal analysis of the hydrodynamic
model elucidates the relationship between the stability of the equilibria and
the changing velocity, and the formation of clusters. We find, in agreement
with earlier results for non-aligning particles, that the key criterion for
stability is $(\rho v(\rho))'> 0$, i.e. a non-rapid decrease of velocity with
density. Numerical simulation for both the individual and hydrodynamic models
with a velocity function inspired by experiment demonstrates the validity of
the theoretical results.


title:
Submillimeter Array Observations of NGC 2264-C: Molecular Outflows and
  Driving Sources

abstract:
  We present 1.3mm Submillimeter Array (SMA) observations at
$\sim$3$^{\prime\prime}$ resolution towards the brightest section of the
intermediate/massive star forming cluster NGC 2264-C. The millimetre continuum
emission reveals ten 1.3mm continuum peaks, of which four are new detections.
The observed frequency range includes the known molecular jet/outflow tracer
SiO (5-4), thus providing the first high resolution observations of SiO towards
NGC 2264-C. We also detect molecular lines of twelve additional species towards
this region, including CH$_3$CN, CH$_3$OH, SO, H$_2$CO, DCN, HC$_3$N, and
$^{12}$CO. The SiO (5-4) emission reveals the presence of two collimated, high
velocity (up to 30kms$^{-1}$ with respect to the systemic velocity) bi-polar
outflows in NGC 2264-C. In addition, the outflows are traced by emission from
$^{12}$CO, SO, H$_2$CO, and CH$_3$OH. We find an evolutionary spread between
cores residing in the same parent cloud. The two unambiguous outflows are
driven by the brightest mm continuum cores, which are IR-dark, molecular line
weak, and likely the youngest cores in the region. Furthermore, towards the RMS
source AFGL 989-IRS1, the IR-bright and most evolved source in NGC 2264-C, we
observe no molecular outflow emission. A molecular line rich ridge feature,
with no obvious directly associated continuum source, lies on the edge of a low
density cavity and may be formed from a wind driven by AFGL 989-IRS1. In
addition, 229GHz class I maser emission is detected towards this feature.


title: The rigid Horowitz-Myers conjecture

abstract:
  The "new positive energy conjecture" Horowitz and Myers (1999) probes a
possible nonsupersymmetric AdS/CFT correspondence. We consider a version
formulated for complete, asymptotically Poincar\'e-Einstein Riemannian metrics
$(M,g)$ with bounded scalar curvature $R\ge -n(n-1)$. This version then asserts
that any such $(M,g)$ must have mass not less than the mass $m_0$ of a metric
$g_0$ induced on a time-symmetric slice of a certain AdS soliton spacetime. The
conjecture remains unproved, having so far resisted standard techniques. Little
is known other than that the conjecture is true for metrics which are
sufficiently small perturbations of $g_0$. We pose another test for the
conjecture. We assume its validity and attempt to prove as a corollary the
corresponding scalar curvature rigidity statement, that $g_0$ is the unique
asymptotically Poincar\'e-Einstein metric with mass $m=m_0$ obeying $R\ge
-n(n-1)$. Were a second such metric $g_1$ not isometric to $g_0$ to exist, it
then may well admit perturbations of lower mass, contradicting the assumed
validity of the conjecture. We find that the minimum mass metric must be static
Einstein, so the problem is reduced to that of static uniqueness. When $n=3$
the manifold is isometric to a time-symmetric slice of an AdS soliton
spacetime, unless it has a non-compact horizon. En route we study the mass
aspect, obtaining and generalizing known results. The mass aspect is (i)
related to the holographic energy density, (ii) a weighted invariant under
boundary conformal transformations when the bulk dimension is odd, and (iii)
zero for negative Einstein manifolds with Einstein conformal boundary.


title: Enhancing the Higgs associated production with a top quark pair

abstract:
  It is pointed out that in a wide class of models reminiscent of type-II
Two-Higgs-Doublet Models (2HDM) the signal of the Higgs produced in association
with a top-antitop quark pair ($tth$) and decaying into gauge bosons can be
significantly larger than the Standard Model (SM) prediction without violating
any experimental constraints. The crucial feature of these models is enhanced
(suppressed) Higgs coupling to top (bottom) quarks and existence of light
colored particles that give negative contribution to the effective Higgs
coupling to gluons resulting in the gluon fusion rates in the gauge boson decay
channels close to SM predictions. We demonstrate this mechanism in NMSSM with
light stops and show that $tth$ signal in the $WW$ decay channel can be two
times larger than the SM prediction, as suggested by the excesses observed by
ATLAS and CMS, provided that the Higgs-singlet superpotential coupling
$\lambda\gtrsim0.8$ and the MSSM-like Higgs boson masses are in the range of
160 to 300 GeV.


title: Asymptotic Analysis and Spatial Coupling of Counter Braids

abstract:
  A counter braid (CB) is a novel counter architecture introduced by Lu et al.
in 2007 for per-flow measurements on high-speed links which can be decoded with
low complexity using message passing (MP). CBs achieve an asymptotic
compression rate (under optimal decoding) that matches the entropy lower bound
of the flow size distribution. In this paper, we apply the concept of spatial
coupling to CBs to improve the performance of the original CBs and analyze the
performance of the resulting spatially-coupled CBs (SC-CBs). We introduce an
equivalent bipartite graph representation of CBs with identical
iteration-by-iteration finite-length and asymptotic performance. Based on this
equivalent representation, we then analyze the asymptotic performance of
single-layer CBs and SC-CBs under the MP decoding algorithm proposed by Lu et
al.. In particular, we derive the potential threshold of the uncoupled system
and show that it is equal to the area threshold. We also derive the Maxwell
decoder for CBs and prove that the potential threshold is an upper bound on the
Maxwell decoding threshold. We show that the area under the extended MP
extrinsic information transfer curve is equal to zero precisely at the area
threshold. This, combined with the analysis of the Maxwell decoder and
simulation results, leads us to the conjecture that the potential threshold is
equal to the Maxwell decoding threshold and hence a lower bound on the maximum
a posteriori decoding threshold. Interestingly, SC-CBs do not show the
well-known phenomenon of threshold saturation of the MP decoding threshold to
the potential threshold characteristic of spatially-coupled low-density
parity-check codes and other coupled systems. However, SC-CBs yield better MP
decoding thresholds than their uncoupled counterparts. Finally, we also
consider SC-CBs as a compressed sensing scheme and show that low undersampling
factors can be achieved.


title: The Register Function and Reductions of Binary Trees and Lattice Paths

abstract:
  The register function (or Horton-Strahler number) of a binary tree is a
well-known combinatorial parameter. We study a reduction procedure for binary
trees which offers a new interpretation for the register function as the
maximal number of reductions that can be applied to a given tree. In
particular, the precise asymptotic behavior of the number of certain
substructures ("branches") that occur when reducing a tree repeatedly is
determined. In the same manner we introduce a reduction for simple
two-dimensional lattice paths from which a complexity measure similar to the
register function can be derived. We analyze this quantity, as well as the
(cumulative) size of an (iteratively) reduced lattice path asymptotically.


title:
A systematic study of magnetodynamic properties at finite temperatures
  in doped permalloy from first principles calculations

abstract:
  By means of first principles calculations, we have systematically
investigated how the magnetodynamic properties Gilbert damping, magnetization
and exchange stiffness are affected when permalloy (Py)
(Fe$_{0.19}$Ni$_{0.81}$) is doped with 4d or 5d transition metal impurities. We
find that the trends in the Gilbert damping can be understood from relatively
few basic parameters such as the density of states at the Fermi level, the
spin-orbit coupling and the impurity concentration. % The temperature
dependence of the Gilbert damping is found to be very weak which we relate to
the lack of intraband transitions in alloys. % Doping with $4d$ elements has no
major impact on the studied Gilbert damping, apart from diluting the host.
However, the $5d$ elements have a profound effect on the damping and allows it
to be tuned over a large interval while maintaining the magnetization and
exchange stiffness. % As regards spin stiffness, doping with early transition
metals results in considerable softening, whereas late transition metals have a
minor impact. % Our result agree well with earlier calculations where
available. In comparison to experiments, the computed Gilbert damping appears
slightly underestimated while the spin stiffness show good general agreement.


title: Nonparametric Functional Calibration of Computer Models

abstract:
  Standard methods in computer model calibration treat the calibration
parameters as constant throughout the domain of control inputs. In many
applications, systematic variation may cause the best values for the
calibration parameters to change between different settings. When not accounted
for in the code, this variation can make the computer model inadequate. In this
article, we propose a framework for modeling the calibration parameters as
functions of the control inputs to account for a computer model's incomplete
system representation in this regard while simultaneously allowing for possible
constraints imposed by prior expert opinion. We demonstrate how inappropriate
modeling assumptions can mislead a researcher into thinking a calibrated model
is in need of an empirical discrepancy term when it is only needed to allow for
a functional dependence of the calibration parameters on the inputs. We apply
our approach to plastic deformation of a visco-plastic self-consistent material
in which the critical resolved shear stress is known to vary with temperature.


title: Mean and variance of balanced P\'olya urns

abstract:
  It is well known that in a small P\'olya urn, i.e., an urn where second
largest real part of an eigenvalue is at most half the largest eigenvalue, the
distribution of the numbers of balls of different colours in the urn is
asymptotically normal under weak additional conditions. We consider the
balanced case, and then give asymptotics of the mean and the covariance matrix,
showing that after appropriate normalization, the mean and covariance matrix
converge to the mean and variance of the limiting normal distribution.


title:
Molecular beam epitaxy of single crystalline GaN nanowires on a flexible
  Ti foil

abstract:
  We demonstrate the self-assembled growth of vertically aligned GaN nanowire
ensembles on a flexible Ti foil by plasma-assisted molecular beam epitaxy. The
analysis of single nanowires by transmission electron microscopy reveals that
they are single crystalline. Low-temperature photoluminescence spectroscopy
demonstrates that, in comparison to standard GaN nanowires grown on Si, the
nanowires prepared on the Ti foil exhibit a equivalent crystalline perfection,
a higher density of basal-plane stacking faults, but a reduced density of
inversion domain boundaries. The room-temperature photoluminescence spectrum of
the nanowire ensemble is not influenced or degraded by the bending of the
substrate. The present results pave the way for the fabrication of flexible
optoelectronic devices based on GaN nanowires on metal foils.


title: On the infinitesimal space of uqr mappings

abstract:
  Generalized derivatives and infinitesimal spaces generalize the idea of
derivatives to mappings which need not be differentiable. It is particularly
powerful in the context of quasiregular mappings, where normal family arguments
imply generalized derivatives always exist. The main result of this paper is to
show that if $f$ is any uniformly quasiregular mapping with $x_0$ a
topologically attracting or repelling fixed point, at which $f$ is locally
injective, then $f$ may be conjugated to a uniformly quasiregular mapping $g$
with fixed point $0$ and so that the infinitesimal space of $g$ at $0$ contains
uncountably many elements. This should be contrasted with the fact that $f$
(and also $g$) is conjugate to $x\mapsto x/2$ or $x\mapsto 2x$ in the
attracting or repelling cases respectively.


title: Discrete Symmetries CP, T, CPT

abstract:
  The role of Symmetry Breaking mechanisms to search for New Physics is of
highest importance. We discuss the status and prospects of the Discrete
Symmetries CP, T, CPT looking for their separate Violation in LHC experiments
and meson factories.


title: LHC optics and elastic scattering measured by the TOTEM experiment

abstract:
  The TOTEM experiment at the LHC has measured proton-proton elastic scattering
in dedicated runs at $\sqrt{s}=7$ and 8 TeV centre-of-mass LHC energies. The
proton-proton total cross-section $\sigma_{\rm tot}$ has been derived for both
energies using a luminosity independent method. TOTEM has excluded a purely
exponential differential cross-section for elastic proton-proton scattering
with significance greater than 7$\sigma$ in the $|t|$ range from 0.027 to 0.2
GeV$^{2}$ at $\sqrt{s}=8$ TeV.


title: Every positive integer is a sum of three palindromes

abstract:
  For integer $g\ge 5$, we prove that any positive integer can be written as a
sum of three palindromes in base $g$.


title:
Cooperative Channel Estimation for Coordinated Transmission with Limited
  Backhaul

abstract:
  Obtaining accurate global channel state information (CSI) at multiple
transmitter devices is critical to the performance of many coordinated
transmission schemes. Practical CSI local feedback often leads to noisy and
partial CSI estimates at each transmitter. With rate-limited bi-directional
backhaul, transmitters have the opportunity to exchange few CSI-related bits to
establish global channel state information at transmitter (CSIT). This work
investigates possible strategies towards this goal. We propose a novel
decentralized algorithm that produces minimum mean square error (MMSE)-optimal
global channel estimates at each device from combining local feedback and
information exchanged through backhauls. The method adapts to arbitrary initial
information topologies and feedback noise statistics and can do that with a
combination of closed-form and convex approaches. Simulations for coordinated
multi-point (CoMP) transmission systems with two or three transmitters exhibit
the advantage of the proposed algorithm over conventional CSI exchange
mechanisms when the coordination backhauls are limited.


title:
Birth and growth of nonlinear massive gravity and its transition to
  nonlinear electrodynamics in a system of Mp-branes

abstract:
  Recently, an interesting mechanism [Phys.Rev.Lett.106:231101,2011] has been
proposed which produces all nonlinear terms in massive gravity to all orders .
In this work, we reproduce these results in M-theory and consider the process
of birth and growth of nonlinear gravity during the construction of Mp-branes.
It has been shown that Mp brane are built up of p- M1-branes which each of them
are connected to M1-branes of other Mp-brane through a wormhole. In this model,
by increasing the number of dimensions, the number of nonlinear terms in
relevant action of branes enhances and some theories like lovelock and
nonlinear gravity are raised. By compacting M-branes, graviton fields in
nonlinear gravity converts to photon fields and thus nonlinear electrodynamics
are produced.


title: Observational constraints on cosmological future singularities

abstract:
  In this work we consider a family of cosmological models featuring future
singularities. This type of cosmological evolution is typical of dark energy
models with an equation of state violating some of the standard energy
conditions (e.g. the null energy condition). Such kind of behavior, widely
studied in the literature, may arise in cosmologies with phantom fields,
theories of modified gravity or models with interacting dark matter/dark
energy. We briefly review the physical consequences of these cosmological
evolution regarding geodesic completeness and the divergence of tidal forces in
order to emphasize under which circumstances the singularities in some
cosmological quantities correspond to actual singular spacetimes. We then
introduce several phenomenological parameterizations of the Hubble expansion
rate to model different singularities existing in the literature and use SN Ia,
BAO and H(z) data to constrain how far in the future the singularity needs to
be (under some reasonable assumptions on the behaviour of the Hubble factor).
We show that, for our family of parameterizations, the lower bound for the
singularity time can not be smaller than about 1.2 times the age of the
universe, what roughly speaking means about 2.8 Gyrs from the present time.


title:
Star formation in W3 - AFGL333: Young stellar content, properties and
  roles of external feedback

abstract:
  One of the key questions in the field of star formation is the role of
stellar feedback on subsequent star formation process. The W3 giant molecular
cloud complex at the western border of the W4 super bubble is thought to be
influenced by the stellar winds of the massive stars in W4. AFGL333 is a ~10^4
Msun cloud within W3. This paper presents a study of the star formation
activity within AFGL333 using deep JHKs photometry obtained from the NOAO
Extremely Wide-Field Infrared Imager combined with Spitzer-IRAC-MIPS
photometry. Based on the infrared excess, we identify 812 candidate young
stellar objects in the complex, of which 99 are classified as Class I and 713
are classified as Class II sources. The stellar density analysis of young
stellar objects reveals three major stellar aggregates within AFGL333, named
here AFGL333-main, AFGL333-NW1 and AFGL333-NW2. The disk fraction within
AFGL333 is estimated to be ~50-60%. We use the extinction map made from the
H-Ks colors of the background stars to understand the cloud structure and to
estimate the cloud mass. The CO-derived extinction map corroborates the cloud
structure and mass estimates from NIR color method. From the stellar mass and
cloud mass associated with AFGL333, we infer that the region is currently
forming stars with an efficiency of ~4.5% and at a rate of ~2 - 3 Msun
Myr-1pc-2. In general, the star formation activity within AFGL333 is comparable
to that of nearby low mass star-forming regions. We do not find any strong
evidence to suggest that the stellar feedback from the massive stars of nearby
W4 super bubble has affected the global star formation properties of the
AFGL333 region.


title: Modeling Stock Price Dynamics with Fuzzy Opinion Networks

abstract:
  We propose a mathematical model for the word-of-mouth communications among
stock investors through social networks and explore how the changes of the
investors' social networks influence the stock price dynamics and vice versa.
An investor is modeled as a Gaussian fuzzy set (a fuzzy opinion) with the
center and standard deviation as inputs and the fuzzy set itself as output.
Investors are connected in the following fashion: the center input of an
investor is taken as the average of the neighbors' outputs, where two investors
are neighbors if their fuzzy opinions are close enough to each other, and the
standard deviation (uncertainty) input is taken with local, global or external
reference schemes to model different scenarios of how investors define
uncertainties. The centers and standard deviations of the fuzzy opinions are
the expected prices and their uncertainties, respectively, that are used as
inputs to the price dynamic equation. We prove that with the local reference
scheme the investors converge to different groups in finite time, while with
the global or external reference schemes all investors converge to a consensus
within finite time and the consensus may change with time in the external
reference case. We show how to model trend followers, contrarians and
manipulators within this mathematical framework and prove that the biggest
enemy of a manipulator is the other manipulators. We perform Monte Carlo
simulations to show how the model parameters influence the price dynamics, and
we apply a modified version of the model to the daily closing prices of fifteen
top banking and real estate stocks in Hong Kong for the recent two years from
Dec. 5, 2013 to Dec. 4, 2015 and discover that a sharp increase of the combined
uncertainty is a reliable signal to predict the reversal of the current price
trend.


title: Magnetic effects in sulfur-decorated graphene

abstract:
  The interaction between two different materials can present novel phenomena
that are quite different from the physical properties observed when each
material stands alone. Strong electronic correlations, such as magnetism and
superconductivity, can be produced as the result of enhanced Coulomb
interactions between electrons. Two-dimensional materials are powerful
candidates to search for the novel phenomena because of the easiness of
arranging them and modifying their properties accordingly. In this work, we
report magnetic effects of graphene, a prototypical non-magnetic
two-dimensional semi-metal, in the proximity with sulfur, a diamagnetic
insulator. In contrast to the well-defined metallic behaviour of clean
graphene, an energy gap develops at the Fermi energy for the graphene/sulfur
compound with decreasing temperature. This is accompanied by a steep increase
of the resistance, a sign change of the slope in the magneto-resistance between
high and low fields, and magnetic hysteresis. A possible origin of the observed
electronic and magnetic responses is discussed in terms of the onset of
low-temperature magnetic ordering. These results provide intriguing insights on
the search for novel quantum phases in graphene-based compounds.


title: Big Data Meets Telcos: A Proactive Caching Perspective

abstract:
  Mobile cellular networks are becoming increasingly complex to manage while
classical deployment/optimization techniques and current solutions (i.e., cell
densification, acquiring more spectrum, etc.) are cost-ineffective and thus
seen as stopgaps. This calls for development of novel approaches that leverage
recent advances in storage/memory, context-awareness, edge/cloud computing, and
falls into framework of big data. However, the big data by itself is yet
another complex phenomena to handle and comes with its notorious 4V: velocity,
voracity, volume and variety. In this work, we address these issues in
optimization of 5G wireless networks via the notion of proactive caching at the
base stations. In particular, we investigate the gains of proactive caching in
terms of backhaul offloadings and request satisfactions, while tackling the
large-amount of available data for content popularity estimation. In order to
estimate the content popularity, we first collect users' mobile traffic data
from a Turkish telecom operator from several base stations in hours of time
interval. Then, an analysis is carried out locally on a big data platform and
the gains of proactive caching at the base stations are investigated via
numerical simulations. It turns out that several gains are possible depending
on the level of available information and storage size. For instance, with 10%
of content ratings and 15.4 Gbyte of storage size (87% of total catalog size),
proactive caching achieves 100% of request satisfaction and offloads 98% of the
backhaul when considering 16 base stations.


title:
Probing the pairing symmetry in the over-doped Fe-based superconductor
  Ba_0.35Rb_0.65Fe_2As_2 as a function of hydrostatic pressure

abstract:
  We report muon spin rotation experiments on the magnetic penetration depth
lambda and the temperature dependence of lambda^{-2} in the over-doped Fe-based
high-temperature superconductor (Fe-HTS) Ba_{1-x}Rb_ xFe_2As_2 (x = 0.65)
studied at ambient and under hydrostatic pressures up to p = 2.3 GPa. We find
that in this system lambda^{-2}(T) is best described by d-wave scenario. This
is in contrast to the case of the optimally doped x = 0.35 system which is
known to be a nodeless s^{+-}-wave superconductor. This suggests that the
doping induces the change of the pairing symmetry from s^{+-} to d-wave in
Ba_{1-x}Rb_{x}Fe_{2}As_{2}. In addition, we find that the d-wave order
parameter is robust against pressure, suggesting that d is the common and
dominant pairing symmetry in over-doped Ba_{1-x}Rb_{x}Fe_{2}As_{2}. Application
of pressure of p = 2.3 GPa causes a decrease of lambda(0) by less than 5 %,
while at optimal doping x = 0.35 a significant decrease of lambda(0) was
reported. The superconducting transition temperature T_c as well as the gap to
T_c ratio 2Delta/k_BT_c show only a modest decrease with pressure. By combining
the present data with those previously obtained for optimally doped system x =
0.35 and for the end member x = 1 we conclude that the SC gap symmetry as well
as the pressure effects on the SC quantities strongly depend on the Rb doping
level. These results are discussed in the light of the putative Lifshitz
transition, i.e., a disappearance of the electron pockets in the Fermi surface
of Ba_{1-x}Rb_{x}Fe_{2}As_{2} upon hole doping.


title:
Synchronization and functional central limit theorems for interacting
  reinforced random walks

abstract:
  We obtain Central Limit Theorems in Functional form for a class of
time-inhomogeneous interacting random walks on the simplex of probability
measures over a finite set. Due to a reinforcement mechanism, the increments of
the walks are correlated, forcing their convergence to the same, possibly
random, limit. Random walks of this form have been introduced in the context of
urn models and in stochastic approximation. We also propose an application to
opinion dynamics in a random network evolving via preferential attachment. We
study, in particular, random walks interacting through a mean-field rule and
compare the rate they converge to their limit with the rate of synchronization,
i.e. the rate at which their mutual distances converge to zero. Under certain
conditions, synchronization is faster than convergence.


title: Efficient computation of Sobol' indices for stochastic models

abstract:
  Stochastic models are necessary for the realistic description of an
increasing number of applications. The ability to identify influential
parameters and variables is critical to a thorough analysis and understanding
of the underlying phenomena. We present a new global sensitivity analysis
approach for stochastic models, i.e., models with both uncertain parameters and
intrinsic stochasticity. Our method relies on an analysis of variance through a
generalization of Sobol' indices and on the use of surrogate models. We show
how to efficiently compute the statistical properties of the resulting indices
and illustrate the effectiveness of our approach by computing first order
Sobol' indices for two stochastic models.


title: Global Patterns of Human Synchronization

abstract:
  Social media are transforming global communication and coordination and
provide unprecedented opportunities for studying socio-technical domains. Here
we study global dynamical patterns of communication on Twitter across many
scales. Underlying the observed patterns is both the diurnal rotation of the
earth, day and night, and the synchrony required for contingency of actions
between individuals. We find that urban areas show a cyclic contraction and
expansion that resembles heartbeats linked to social rather than natural
cycles. Different urban areas have characteristic signatures of daily
collective activities. We show that the differences detected are consistent
with a new emergent global synchrony that couples behavior in distant regions
across the world. Although local synchrony is the major force that shapes the
collective behavior in cities, a larger-scale synchronization is beginning to
occur.


title: Kleene's Two Kinds of Recursion

abstract:
  This is an elementary expository article regarding the application of
Kleene's Recursion Theorems in making definitions by recursion. Whereas the
Second Recursion Theorem (SRT) is applicable in a first-order setting, the
First Recursion Theorem (FRT) requires a higher-order setting. In some cases
both theorems are applicable, but one is stronger than the other: the FRT
always produces least fixed points, but this is not always the case with the
SRT. Nevertheless, an old result by Rogers allows us to bridge this gap by
subtly redefining the implementation of a higher-order functional in order to
bring it to a `standard form.'


title: Endofunctors modelling higher-order behaviours

abstract:
  In this paper we show how the abstract behaviours of higher-order systems can
be modelled as final coalgebras of suitable behavioural functors. These
functors have the challenging peculiarity to be circularly defined with their
own final coalgebra. Our main contribution is a general construction for
defining these functors, solving this circularity which is the essence of
higher-order behaviours. This characterisation is syntax agnostic. To achieve
this property, we shift from term passing to behaviour passing: in the former
higher-order is expressed by passing around syntactic objects (such as terms or
processes) as representations of behaviours whereas the former ditches the
syntactic encoding altogether and works directly with behaviours i.e. semantic
objects. From this perspective, the former can be seen as syntactic
higher-order whereas the later as semantic higher-order.


title: Smooth functions on algebraic K-theory

abstract:
  For any complex scheme X or any dg category, there is an associated K-theory
presheaf on the category of complex affine schemes. We study real smooth
functions on this presheaf, defined by Kan extension, and show that they are
closely related to real Deligne cohomology. When X is quasi-compact and
semi-separated, and for various non-commutative derived schemes, these smooth
functions on K-theory are dual to the homotopy fibre of the Chern character
from Blanc's semi-topological K-theory to cyclic homology.


title: Rules of Acquisition for Mementos and Their Content

abstract:
  Text extraction from web pages has many applications, including web crawling
optimization and document clustering. Though much has been written about the
acquisition of content from live web pages, content acquisition of archived web
pages, known as mementos, remains a relatively new enterprise. In the course of
conducting a study with almost 700,000 web pages, we encountered issues
acquiring mementos and extracting text from them. The acquisition of memento
content via HTTP is expected to be a relatively painless exercise, but we have
found cases to the contrary. We also find that the parsing of HTML, already
known to be problematic, can be more complex when one attempts to extract the
text of mementos across many web archives, due to issues involving different
memento presentation behaviors, as well as the age of the HTML in their
mementos. For the benefit of others acquiring mementos across many web
archives, we document those experiences here.


title:
In-plane vibrations of a rectangular plate: plane wave expansion
  modelling and experiment

abstract:
  Theoretical and experimental results for in-plane vibrations of a uniform
rectangular plate with free boundary conditions are obtained. The experimental
setup uses electromagnetic-acoustic transducers and a vector network analyzer.
The theoretical calculations were obtained using the plane wave expansion
method applied to the in-plane thin plate vibration theory. The agreement
between theory and experiment is excellent for the lower 95 modes covering a
very wide frequency range from DC to 20 kHz. Some measured normal-mode wave
amplitudes were compared with the theoretical predictions; very good agreement
was observed. The excellent agreement of the classical theory of in-plane
vibrations confirms its reliability up to very high frequencies.


title: GAP Safe Screening Rules for Sparse-Group-Lasso

abstract:
  In high dimensional settings, sparse structures are crucial for efficiency,
either in term of memory, computation or performance. In some contexts, it is
natural to handle more refined structures than pure sparsity, such as for
instance group sparsity. Sparse-Group Lasso has recently been introduced in the
context of linear regression to enforce sparsity both at the feature level and
at the group level. We adapt to the case of Sparse-Group Lasso recent safe
screening rules that discard early in the solver irrelevant features/groups.
Such rules have led to important speed-ups for a wide range of iterative
methods. Thanks to dual gap computations, we provide new safe screening rules
for Sparse-Group Lasso and show significant gains in term of computing time for
a coordinate descent implementation.


title: Decomposable theta divisors and generic vanishing

abstract:
  We study ample divisors X with only rational singularities on abelian
varieties that decompose into a sum of two lower dimensional subvarieties,
X=V+W. For instance, we prove an optimal lower bound on the degree of the
corresponding addition map, and show that the minimum can only be achieved if X
is a theta divisor. Conjecturally, the latter happens only on Jacobians of
curves and intermediate Jacobians of cubic threefolds. As an application, we
prove that nondegenerate generic vanishing subschemes of indecomposable
principally polarized abelian varieties are automatically reduced and
irreducible, have the expected geometric genus, and property (P) with respect
to their theta duals.


title: Comparing Fr\'echet-Urysohn filters with two pre-orders

abstract:
  A filter $\F$ on $\w$ is called Fr\'echet-Urysohn if the space with only one
non-isolated point $\w \cup \{\F\}$ is a Fr\'echet-Urysohn space, where the
neighborhoods of the non-isolated point are determined by the elements of $\F$.
In this paper, we distinguish some Fr\'echet-Urysohn filters by using two
pre-orderings of filters: One is the Rudin-Keisler pre-order and the other one
was introduced by Todor\v{c}evi\'c-Uzc\'ategui in \cite{tu05}. In this paper,
we construct an $RK$-chain of size $\c^+$ which is $RK$-above of avery
$FU$-filter. Also, we show that there is an infinite $RK$-antichain of
$FU$-filters.


title:
Numerical models for stationary superfluid neutron stars in general
  relativity with realistic equations of state

abstract:
  We present a numerical model for uniformly rotating superfluid neutron stars,
for the first time with realistic microphysics including entrainment, in a
fully general relativistic framework. We compute stationary and axisymmetric
configurations of neutron stars composed of two fluids, namely superfluid
neutrons and charged particles (protons and electrons), rotating with different
rates around a common axis. Both fluids are coupled by entrainment, a
non-dissipative interaction which in case of a non-vanishing relative velocity
between the fluids, causes the fluid momenta being not aligned with the
respective fluid velocities. We extend the formalism by Comer and Joynt (2003)
in order to calculate the equation of state (EoS) and entrainment parameters
for an arbitrary relative velocity. The resulting entrainment matrix fulfills
all necessary sum rules and in the limit of small relative velocity our results
agree with Fermi liquid theory ones, derived to lowest order in the velocity.
This formalism is applied to two new nuclear equations of state which are
implemented in the numerical model. We are able to obtain precise equilibrium
configurations. Resulting density profiles and moments of inertia are discussed
employing both EoSs, showing the impact of entrainment and the dependence on
the EoS.


title: On the security of 2-key triple DES

abstract:
  This paper reconsiders the security offered by 2-key triple DES, an
encryption technique that remains widely used despite recently being
de-standardised by NIST. A generalisation of the 1990 van Oorschot-Wiener
attack is described, constituting the first advance in cryptanalysis of 2-key
triple DES since 1990. We give further attack enhancements that together imply
that the widely used estimate that 2-key triple DES provides 80 bits of
security can no longer be regarded as conservative; the widely stated assertion
that the scheme is secure as long as the key is changed regularly is also
challenged. The main conclusion is that, whilst not completely broken, the
margin of safety for 2-key triple DES is slim, and efforts to replace it, at
least with its 3-key variant, should be pursued with some urgency.


title:
Sparse Signal Detection with Compressive Measurements via Partial
  Support Set Estimation

abstract:
  In this paper, we consider the problem of sparse signal detection based on
partial support set estimation with compressive measurements in a distributed
network. Multiple nodes in the network are assumed to observe sparse signals
which share a common but unknown support. While in the traditional compressive
sensing (CS) framework, the goal is to recover the complete sparse signal, in
sparse signal detection, complete signal recovery may not be necessary to make
a reliable detection decision. In particular, detection can be performed based
on partially or inaccurately estimated signals which requires less
computational burden than that is required for complete signal recovery. To
that end, we investigate the problem of sparse signal detection based on
partially estimated support set. First, we discuss how to determine the minimum
fraction of the support set to be known so that a desired detection performance
is achieved in a centralized setting. Second, we develop two distributed
algorithms for sparse signal detection when the raw compressed observations are
not available at the central fusion center. In these algorithms, the final
decision statistic is computed based on locally estimated partial support sets
via orthogonal matching pursuit (OMP) at individual nodes. The proposed
distributed algorithms with less communication overhead are shown to provide
comparable performance (sometimes better) to the centralized approach when the
size of the estimated partial support set is very small.


title: Generic vanishing and minimal cohomology classes on abelian fivefolds

abstract:
  We classify GV-subschemes of five-dimensional ppavs, showing that they exist
only on Jacobians of curves and intermediate Jacobians of cubic threefolds, and
confirming a conjecture of Pareschi--Popa in this case. The result is implied
by a more general statement about subvarieties of minimal cohomology class
whose sum is a theta divisor.


title: Generalized low solution of $\mathsf{RT}_k^1$ problem

abstract:
  We study the "coding power" of an arbitrary $\mathsf{RT}_k^1$-instance. We
prove that every $\mathsf{RT}_k^1$-instance admit non trivial generalized low
solution. This is somewhat related to a problem proposed by Patey. We also
answer a question proposed by Liu, i.e., we prove that there exists a
$\mathbf{0}'$-computable $\mathsf{RT}_3^1$-instance, $I_3^1$, such that every
$\mathsf{RT}_2^1$-instance admit a non trivial solution that does not compute
any non trivial solution of $I_3^1$.


title: On skew tau-functions in higher spin theory

abstract:
  Recent studies of higher spin theory in three dimensions concentrate on
Wilson loops in Chern-Simons theory, which in the classical limit reduce to
peculiar corner matrix elements between the highest and lowest weight states in
a given representation of SL(N). Despite these "skew" tau-functions can seem
very different from conventional ones, which are the matrix elements between
the two highest weight states, they also satisfy the Toda recursion between
different fundamental representations. Moreover, in the most popular examples
they possess simple representations in terms of matrix models and Schur
functions. We provide a brief introduction to this new interesting field,
which, after quantization, can serve as an additional bridge between knot and
integrability theories.


title: Household Income Distribution in the USA

abstract:
  In this article we present an alternative model for the distribution of
household incomes in the United States. We provide arguments from two differing
perspectives which both yield the proposed income distribution curve, and then
fit this curve to empirical data on household income distribution obtained from
the United States Census Bureau.


title:
A Mutual Contamination Analysis of Mixed Membership and Partial Label
  Models

abstract:
  Many machine learning problems can be characterized by mutual contamination
models. In these problems, one observes several random samples from different
convex combinations of a set of unknown base distributions. It is of interest
to decontaminate mutual contamination models, i.e., to recover the base
distributions either exactly or up to a permutation. This paper considers the
general setting where the base distributions are defined on arbitrary
probability spaces. We examine the decontamination problem in two mutual
contamination models that describe popular machine learning tasks: recovering
the base distributions up to a permutation in a mixed membership model, and
recovering the base distributions exactly in a partial label model for
classification. We give necessary and sufficient conditions for identifiability
of both mutual contamination models, algorithms for both problems in the
infinite and finite sample cases, and introduce novel proof techniques based on
affine geometry.


title: Communication Cost in Parallel Query Processing

abstract:
  We study the problem of computing conjunctive queries over large databases on
parallel architectures without shared storage. Using the structure of such a
query $q$ and the skew in the data, we study tradeoffs between the number of
processors, the number of rounds of communication, and the per-processor load
-- the number of bits each processor can send or can receive in a single round
-- that are required to compute $q$.
  When the data is free of skew, we obtain essentially tight upper and lower
bounds for one round algorithms and we show how the bounds degrade when there
is skew in the data. In the case of skewed data, we show how to improve the
algorithms when approximate degrees of the heavy-hitter elements are available,
obtaining essentially optimal algorithms for queries such as simple joins and
triangle join queries.
  For queries that we identify as tree-like, we also prove nearly matching
upper and lower bounds for multi-round algorithms for a natural class of
skew-free databases. One consequence of these latter lower bounds is that for
any $\varepsilon>0$, using $p$ processors to compute the connected components
of a graph, or to output the path, if any, between a specified pair of vertices
of a graph with $m$ edges and per-processor load that is
$O(m/p^{1-\varepsilon})$ requires $\Omega(\log p)$ rounds of communication.
  Our upper bounds are given by simple structured algorithms using MapReduce.
Our one-round lower bounds are proved in a very general model, which we call
the Massively Parallel Communication (MPC) model, that allows processors to
communicate arbitrary bits. Our multi-round lower bounds apply in a restricted
version of the MPC model in which processors in subsequent rounds after the
first communication round are only allowed to send tuples.


title: Abelian varieties isogenous to a power of an elliptic curve

abstract:
  Let $E$ be an elliptic curve over a field $k$. Let $R:= \text{End}\, E$.
There is a functor $\mathscr{H}\!\!\mathit{om}_R(-,E)$ from the category of
finitely presented torsion-free left $R$-modules to the category of abelian
varieties isogenous to a power of $E$, and a functor $\text{Hom}(-,E)$ in the
opposite direction. We prove necessary and sufficient conditions on $E$ for
these functors to be equivalences of categories.


title: Emergence of Robustness in Network of Networks

abstract:
  A model of interdependent networks of networks (NoN) has been introduced
recently in the context of brain activation to identify the neural collective
influencers in the brain NoN. Here we develop a new approach to derive an exact
expression for the random percolation transition in Erd\"{o}s-R\'enyi NoN.
Analytical calculations are in excellent agreement with numerical simulations
and highlight the robustness of the NoN against random node failures.
Interestingly, the phase diagram of the model unveils particular patterns of
interconnectivity for which the NoN is most vulnerable. Our results help to
understand the emergence of robustness in such interdependent architectures.


title:
On a recursive construction of circular paths and the search for $\pi$
  on the integer lattice $\mathbb{Z}^2$

abstract:
  Digital circles not only play an important role in various technological
settings, but also provide a lively playground for more fundamental
number-theoretical questions. In this paper, we present a new recursive
algorithm for the construction of digital circles on the integer lattice
$\mathbb{Z}^2$, which makes sole use of the signum function. By briefly
elaborating on the nature of discretization of circular paths, we then find
that this algorithm recovers, in a space endowed with $\ell^1$-norm, the
defining constant $\pi$ of a circle in $\mathbb{R}^2$.


title:
Proximity induced superconductivity within the insulating
  (Li$_{0.84}$Fe$_{0.16}$)OH layers in (Li$_{0.84}$Fe$_{0.16}$)OHFe$_{0.98}$Se

abstract:
  The role played by the insulating intermediate (Li$_{0.84}$Fe$_{0.16}$)OH
layer on magnetic and superconducting properties of
(Li$_{0.84}$Fe$_{0.16}$)OHFe$_{0.98}$Se was studied by means of muon-spin
rotation. It was found that it is not only enhances the coupling between the
FeSe layers for temperatures below $\simeq 10$ K, but becomes superconducting
by itself due to the proximity to the FeSe ones. Superconductivity in
(Li$_{0.84}$Fe$_{0.16}$)OH layers is most probably filamentary-like and the
energy gap value, depending on the order parameter symmetry, does not exceed
1-1.5 meV.


title: Existence of Surface Smectic States of Liquid Crystals

abstract:
  The Landau-de Gennes model of liquid crystals is a functional acting on wave
functions (order parameters) and vector fields (director fields). In a specific
asymptotic limit of the physical parameters, we construct critical points such
that the wave function (order parameter) is localized near the boundary of the
domain, and we determine a sharp localization of the boundary region where the
wave function concentrates. Furthermore, we compute the asymptotics of the
energy of such critical points along with a boundary energy that may serve in
localizing the director field. In physical terms, our results prove the
existence of a surface smectic state.


title:
A gapless micro-dielectric-barrier-discharge ion source for analytical
  applications

abstract:
  Use of dielectric barrier discharge (DBD) as an ion source for sensitive
chemical analysis is uncommon because barrier discharges generate excess noise
due to spatial and temporal instability. This design uses contacted, crossed
glass-coated micro-wires to focus the field into a gradually vanishing gap,
suppressing spatial and temporal variability, reducing pressure, temperature,
and humidity effects, stabilizing discharge initiation and limiting chemical
fragmentation. Positive-ion-mode proton transfer, chemical fragmentation from a
micro-discharge, and NO+ adducts combine to allow broad chemical sensitivity.
We analyze noise properties of the ion source and report chemical responsivity
for a wide range of volatile organic compounds. Source noise spectral density
is compared for three systems: the contacted coated wires source, a gapped
dielectric barrier discharge source, and a 5 mCi Ni-63 radioactive source. The
crossed-wires source shows noise properties approaching those of the
white-noise Ni-63 source, while gapped discharge exhibits 1/f noise from
area-discharge random path and intensity variations. For chemical sensitivity
testing, dilute samples are delivered by vapor flow injection or by gas
chromatography, and then detected by differential ion mobility spectrometry
(DMS / FAIMS) and, in a few cases by mass spectrometry. The compounds tested in
positive ion mode include ketones and alcohols, simple aromatics (benzene,
toluene, xylenes, ethyl and propyl benzene), chlorinated and nitrated solvents
and aliphatics (hexanes and n-octane), with sensitivities from ppt to ppb
levels. The wires source for trace vapor detection is stable under a range of
environmental conditions from very low (ppb) humidity levels upward, has wider
chemical coverage than the radioactive nickel source with nearly equivalent
noise properties, and is adjustable to higher intensity.


title: Strain-induced topological transition in SrRu$_2$O$_6$ and CaOs$_2$O$_6$

abstract:
  The topological property of SrRu$_2$O$_6$ and isostructural CaOs$_2$O$_6$
under various strain conditions is investigated using density functional
theory. Based on an analysis of parity eigenvalues, we anticipate that a
three-dimensional strong topological insulating state should be realized when
band inversion is induced at the A point in the hexagonal Brillouin zone. For
SrRu$_2$O$_6$, such a transition requires rather unrealistic tuning, where only
the $c$ axis is reduced while other structural parameters are unchanged.
However, given the larger spin-orbit coupling and smaller lattice constants in
CaOs$_2$O$_6$, the desired topological transition does occur under uniform
compressive strain. Our study paves a way to realize a topological insulating
state in a complex oxide, which has not been experimentally demonstrated so
far.


title: P-adic L-functions for GL(2)

abstract:
  Since Rob Pollack and Glenn Stevens used overconvergent modular symbols to
construct p-adic L-functions for non-critical slope rational modular forms, the
theory has been extended to construct p-adic L-functions for non-critical slope
automorphic forms over totally real and imaginary quadratic fields by the first
and second authors respectively. In this paper, we give an analogous
construction over a general number field. In particular, we start by proving a
control theorem stating that the specialisation map from overconvergent to
classical modular symbols is an isomorphism on the small slope subspace. We
then show that if one takes the modular symbol attached to a small slope
cuspidal eigenform, then there is a canonical way of constructing a ray class
distribution from the corresponding overconvergent symbol, that moreover
interpolates critical values of the L-function of the eigenform. We thus define
its p-adic L-function to be this distribution.


title:
Scaffoldings and Spines: Organizing High-Dimensional Data Using Cover
  Trees, Local Principal Component Analysis, and Persistent Homology

abstract:
  We propose a flexible and multi-scale method for organizing, visualizing, and
understanding datasets sampled from or near stratified spaces. The first part
of the algorithm produces a cover tree using adaptive thresholds based on a
combination of multi-scale local principal component analysis and topological
data analysis. The resulting cover tree nodes consist of points within or near
the same stratum of the stratified space. They are then connected to form a
\emph{scaffolding} graph, which is then simplified and collapsed down into a
\emph{spine} graph. From this latter graph the stratified structure becomes
apparent. We demonstrate our technique on several synthetic point cloud
examples and we use it to understand song structure in musical audio data.


title:
Towards Media Intercloud Standardization Evaluating Impact of Cloud
  Storage Heterogeneity

abstract:
  Digital media has been increasing very rapidly, resulting in cloud
computing's popularity gain. Cloud computing provides ease of management of
large amount of data and resources. With a lot of devices communicating over
the Internet and with the rapidly increasing user demands, solitary clouds have
to communicate to other clouds to fulfill the demands and discover services
elsewhere. This scenario is called intercloud computing or cloud federation.
Intercloud computing still lacks standard architecture. Prior works discuss
some of the architectural blueprints, but none of them highlight the key issues
involved and their impact, so that a valid and reliable architecture could be
envisioned. In this paper, we discuss the importance of intercloud computing
and present in detail its architectural components. Intercloud computing also
involves some issues. We discuss key issues as well and present impact of
storage heterogeneity. We have evaluated some of the most noteworthy cloud
storage services, namely Dropbox, Amazon CloudDrive, GoogleDrive, Microsoft
OneDrive (formerly SkyDrive), Box, and SugarSync in terms of Quality of
Experience (QoE), Quality of Service (QoS), and storage space efficiency.
Discussion on the results shows the acceptability level of these storage
services and the shortcomings in their design.


title:
From quantum to thermal topological-sector fluctuations of strongly
  interacting bosons in a ring lattice

abstract:
  Inspired by recent experiments on Bose-Einstein condensates in ring traps, we
investigate the topological properties of the phase of a one-dimensional Bose
field in the presence of both thermal and quantum fluctuations -- the latter
ones being tuned by the depth of an optical lattice applied along the ring. In
the regime of large filling of the lattice, quantum Monte Carlo simulations
give direct access to the full statistics of fluctuations of the Bose-field
phase, and of its winding number $W$ along the ring. At zero temperature the
winding-number (or topological-sector) fluctuations are driven by quantum phase
slips localized around a Josephson link between two lattice wells, and their {
susceptibility} is found to jump at the superfluid-Mott insulator transition.
At finite (but low) temperature, on the other hand, the winding number
fluctuations are driven by thermal activation of nearly uniform phase twists,
whose activation rate is governed by the superfluid fraction. A
quantum-to-thermal crossover in winding number fluctuations is therefore
exhibited by the system, and it is characterized by a conformational change in
the topologically non-trivial configurations, from localized to uniform phase
twists, which can be experimentally observed in ultracold Bose gases via
matter-wave interference.


title: Digital-Analog Quantum Simulation of Spin Models in Trapped Ions

abstract:
  We propose a method to simulate spin models in trapped ions using a
digital-analog approach, consisting in a suitable gate decomposition in terms
of analog blocks and digital steps. In this way, we show that the quantum
dynamics of an enhanced variety of spin models could be implemented with
substantially less number of gates than a fully digital approach. Typically,
analog blocks are built of multipartite dynamics providing the complexity of
the simulated model, while the digital steps are local operations bringing
versatility to it. Finally, we describe a possible experimental implementation
in trapped-ion technologies.


title: Lower complexity bounds for positive contactomorphisms

abstract:
  Let $S^*Q$ be the spherization of a closed connected manifold of dimension at
least two. Consider a contactomorphism $\varphi$ that can be reached by a
contact isotopy that is everywhere positively transverse to the contact
structure. In other words, $\varphi$ is the time-1-map of a time-dependent Reeb
flow. We show that the volume growth of $\varphi$ is bounded from below by the
topological complexity of the loop space of $Q$. Denote by $\Omega Q_0(q)$ the
component of the based loop space that contains the constant loop. We show that
if the fundamental group or the homology of $\Omega Q_0(q)$ grows
exponentially, then the volume growth of $\varphi$ is exponential, and thus its
topological entropy is positive. A similar statement holds for polynomial
growths. This result generalizes work of Dinaburg, Gromov, Paternain and Petean
on geodesic flows and of Macarini, Frauenfelder, Labrousse and Schlenk on Reeb
flows. Our main tool is a version of Rabinowitz--Floer homology developed by
Albers and Frauenfelder.


title: Quantum Control Landscapes Beyond the Dipole Approximation

abstract:
  We investigate the control landscapes of closed, finite level quantum systems
beyond the dipole approximation by including a polarizability term in the
Hamiltonian. Theoretical analysis is presented for the $n$ level case and
formulas for singular controls, which are candidates for landscape traps, are
compared to their analogues in the dipole approximation. A numerical analysis
of the existence of traps in control landscapes beyond the dipole approximation
is made in the four level case. A numerical exploration of these control
landscapes is achieved by generating many random Hamiltonians which include a
term quadratic in a single control field. The landscapes of such systems are
found numerically to be trap free in general. This extends a great body of
recent work on typical landscapes of quantum systems where the dipole
approximation is made. We further investigate the relationship between the
magnitude of the polarizability and the magnitude of the controls resulting
from optimization. It is shown numerically that including a polarizability term
in an otherwise uncontrollable system removes traps from the landscapes of a
specific family of systems by restoring controllability. We numerically assess
the effect of a random polarizability term on the know example of a three level
system with a second order trap in its control landscape. It is found that the
addition of polarizability removes the trap from the landscape. The
implications for laboratory control are discussed.


title: Planck-scale gravity test at PETRA -- Letter of Intent

abstract:
  Quantum or torsion gravity models predict unusual properties of space-time at
very short distances. In particular, near the Planck length, around
$10^{-35}m$, empty space may behave as a crystal, singly or doubly refractive.
This hypothesis, however, remains uncheckable for any direct measurement since
the smallest distance accessible in experiment is about $10^{-19}m$ at the LHC.
Here we propose a laboratory test to measure space birefringence or
refractivity induced by gravity. A sensitivity $10^{-31}m$ for doubly and
$10^{-28}m$ for singly refractive vacuum could be reached with PETRA 6 GeV beam
exploring UV laser Compton scattering.


title:
First and Second Laws of Thermodynamics in Modified Ho\v{r}ava-Lifshitz
  $F(R)$ Gravity

abstract:
  In this paper we discuss the thermodynamics of the apparent horizon in $F(R)$
Ho\v{r}ava-Lifshitz gravity in equilibrium and non-equilibrium ensembles. We
show that the second law of thermodynamics can be satisfied in this non
relativistic theory.


title: An AP-Structure with Finslerian Flavor: Path Equations

abstract:
  The Bazanski approach for deriving paths is applied to Finsler geometry. The
approach is generalized and applied to a new developed geometry called
"Absolute parallelism with a Finslerian Flavor" (FAP). A sets of path equations
is derived for the FAP. This is the horizontal (h) set. A striking feature
appears in this set, that is: the coefficient of torsion term, in the set,
jumps by a step of one-half from one equation to the other. This is tempting to
believe that the h-set admits some quantum features. Comparisons with the
corresponding sets in other geometries are given. Conditions to reduce the set
of path equations obtained, to well known path equations in some geometries are
summarized in a schematic diagram.


title:
A Metaphysical Reflection on the Notion of Background in Modern
  Spacetime Physics

abstract:
  The paper presents a metaphysical characterization of spatiotemporal
backgrounds from a realist perspective. The conceptual analysis is based on a
heuristic sketch that encompasses the common formal traits of the major
spacetime theories, such as Newtonian mechanics and general relativity. It is
shown how this framework can be interpreted in a fully realist fashion, and
what is the role of background structures in such a picture. In the end it is
argued that, although backgrounds are a source of metaphysical discomfort,
still they make a spacetime theory easy to interpret. It is also suggested that
this conclusion partially explains why the notion of background independence
carries a lot of conceptual difficulties.


title: The UV-bright Quasar Survey (UVQS): DR1

abstract:
  We present the first data release (DR1) from our UV-bright Quasar Survey
(UVQS) for new $z \sim 1$ active galactic nuclei (AGN) across the sky. Using
simple GALEX UV and WISE near-IR color selection criteria, we generated a list
of 1450 primary candidates with $FUV < 18.5$ mag. We obtained discovery
spectra, primarily on 3m-class telescopes, for 1040 of these candidates and
confirmed 86% as AGN with redshifts generally at $z>0.5$. Including a small set
of observed secondary candidates, we report the discovery of 217 AGN with $FUV
< 18$ mag that had no previously reported spectroscopic redshift. These are
excellent potential targets for UV spectroscopy before the end of the {\it
Hubble Space Telescope} mission. The main data products are publicly released
through the Mikulski Archive for Space Telescopes.


title: Growth Rates of Sublinear Functional and Volterra Differential Equations

abstract:
  This paper considers the growth rates of positive solutions of scalar
nonlinear functional and Volterra differential equations. The equations are
assumed to be autonomous (or asymptotically so), and the nonlinear dependence
grows less rapidly than any linear function. We impose extra regularity
properties on a function asymptotic to this nonlinear function, rather than on
the nonlinearity itself. The main result of the paper demonstrates that the
growth rate of the solution can be found by determining the rate of growth of a
trivial functional differential equation (FDE) with the same nonlinearity and
all its associated measure concentrated at zero; the trivial FDE is nothing
other than an autonomous nonlinear ODE. We also supply direct asymptotic
information about the solution of the FDE under additional conditions on the
nonlinearity, and exploit the theory of regular variation to sharpen and extend
the results.


title:
String Consistency, Heavy Exotics, and the 750 GeV Diphoton Excess at
  the LHC: Addendum

abstract:
  We study models with heavy exotics that account for the LHC $750$ GeV
diphoton excess in light of current vector-like quark bounds. Utilizing only
exotics that may appear in three-stack and four-stack D-brane models, we show
that a narrow width diphoton excess can be accounted for while evading existing
bounds if multiple exotics are added, with vector-like leptons of mass
$M_L\lesssim 375$ GeV and vector-like quarks with masses up to $\simeq 3$ TeV.
However, a large width $(\Gamma/M \sim 0.06)$, as suggested by the ATLAS data,
cannot be easily accommodated in this framework. Renormalization group
equations with GUT-scale boundary conditions show that these supersymmetric
models are perturbative and stable. Type IIA compactifications on toroidal
orbifolds allow for $O(10)$ Yukawa couplings in the ultraviolet.