title: A microscopically derived formula for alpha-decay half-lives

abstract:
  Although Geiger-Nuttall (GN) law gives a single straight line, if we consider
the experimental data of alpha particle emitters including heavy and super
heavy nuclei with proton numbers as large as 118, instead of getting a single
linear path we observe several linear segments with different slopes and
intercepts. This problem is overcome when the experimental results in logarithm
form are plotted as a function of Viola-Seaborg (VS) parameters with values of
parameters set by hand. By using the fundamental principle of decay, we derive
a formula of logarithm of half-lives in terms of well-defined parameters or
coefficients and this replaces the empirical VS rule.


title: Acceleration of saddle-point methods in smooth cases

abstract:
  In the present paper we propose a novel convergence analysis of the
Alternating Direction Methods of Multipliers (ADMM), based on its equivalence
with the overrelaxed Primal-Dual Hybrid Gradient (oPDHG) algorithm. We consider
the smooth case, which correspond to the cas where the objective function can
be decomposed into one differentiable with Lipschitz continuous gradient part
and one strongly convex part. An accelerated variant of the ADMM is also
proposed, which is shown to converge linearly with same rate as the oPDHG.


title: Spectral multiplier theorems via $H^\infty$ calculus and $R$-bounds

abstract:
  We prove spectral multiplier theorems for H\"ormander classes
$\mathcal{H}^\alpha\_p$ for 0-sectorial operators A on Banach spaces assuming a
bounded $H^\infty(\Sigma\_\sigma)$ calculus for some $\sigma \in (0,\pi)$ and
norm and certain R-bounds on one of the following families of operators: the
semigroup $e^{--zA}$ on $\mathbb{C}\_+$, the wave operators $e^{isA}$ for $s
\in \mathbb{R}$, the resolvent $(\lambda -- A)^{-1}$ on $\mathbb{C} \backslash
\mathbb{R}$, the imaginary powers $A^{it}$ for $t \in \mathbb{R}$ or the
Bochner-Riesz means $(1-A/u)^\alpha\_+$ for $u > 0.$ In contrast to the
existing literature we neither assume that A operates on an Lp scale nor that A
is self-adjoint on a Hilbert space. Furthermore, we replace (generalized)
Gaussian or Poisson bounds and maximal estimates by the weaker notion of
R-bounds, which allow for a unified approach to spectral multiplier theorems in
a more general setting. In this setting our results are close to being optimal.
Moreover, we can give a characterization of the (R-bounded)
$\mathcal{H}^\alpha\_1$ calculus in terms of R-boundedness of Bochner-Riesz
means.


title: Developing a Launch Package for the PEGASUS Launcher

abstract:
  Railguns are capable to far exceed the muzzle energies of current naval deck
guns. Therefore one of the most promising scenario for the future application
of railguns in naval warfare is the long range artillery. Hypervelocity
projectiles being propelled to velocities above 2 km/s reach targets at
distances of 200 km or more. At the French-German Research Institute the
PEGASUS launcher is used for investigations with respect to this scenario. The
6 m long barrel has a square caliber of 40 mm. The power supply unit is able to
deliver 10 MJ to the gun. Within this investigation, a complete launch package
is being developed and experiments are performed that aim at showing that this
package can be accelerated to velocities ranging from 2000 m/s to 2500 m/s. A
launch package consists out of an armature, a sabot and the projectile. The
armature ensures the electrical contact during launch and pushes the sabot with
its payload through the barrel. The sabot guides and protects the payload
during the acceleration. At the same time the accelerating forces generated at
the armature needs to be transferred to the projectile. After the launch
package has left the barrel, the sabot should open and release its payload, the
projectile into free-flight. Here the current status of the launch package
development and results from experiments with the PEGASUS railgun are
presented.


title: Effect of density step on stirring properties of a strain flow

abstract:
  The influence of steep density gradient upon stirring properties of a strain
flow is addressed by considering the problem in which an interface separating
two regions with different constant densities is stabilised within a
stagnation-point flow. The existence of an analytic solution for the
two-dimensional incompressible flow field allows the exact derivation of the
velocity gradient tensor and of parameters describing the local flow topology.
Stirring properties are affected not only through vorticity production and jump
of strain intensity at the interface, but also through rotation of strain
principal axes resulting from anisotropy of pressure Hessian. The strain
persistence parameter, which measures the respective effects of strain and
effective rotation (vorticity plus rotation rate of strain basis), reveals a
complex structure. In particular, for large values of the density ratio it
indicates dominating effective rotation in a restricted area past the
interface. Information on flow structure derived from the Okubo-Weiss
parameter, by contrast, is less detailed. The influence of the density step on
stirring properties is assessed through the Lagrangian evolution of the
gradient of a passive scalar. Even for a moderate density ratio, alignment of
the scalar gradient and growth rate of its norm are deeply altered. Past the
interface effective rotation indeed drives the scalar gradient to align with a
direction determined by the local strain persistence parameter, away from the
compressional strain direction. The jump of strain intensity at the interface,
however, opposes the lessening effect of the latter mechanism on the growth
rate of the scalar gradient norm and promotes the rise of the gradient.


title:
Micro-reflectance and transmittance spectroscopy: a versatile and
  powerful tool to characterize 2D materials

abstract:
  Optical spectroscopy techniques such as differential reflectance and
transmittance have proven to be very powerful techniques to study 2D materials.
However, a thorough description of the experimental setups needed to carry out
these measurements is lacking in the literature. We describe a versatile
optical microscope setup to carry out differential reflectance and
transmittance spectroscopy in 2D materials with a lateral resolution of ~1
micron in the visible and near-infrared part of the spectrum. We demonstrate
the potential of the presented setup to determine the number of layers of 2D
materials and to characterize their fundamental optical properties such as
excitonic resonances. We illustrate its performance by studying mechanically
exfoliated and chemical vapor-deposited transition metal dichalcogenide
samples.


title:
Convergence rates of moment-sum-of-squares hierarchies for volume
  approximation of semialgebraic sets

abstract:
  Moment-sum-of-squares hierarchies of semidefinite programs can be used to
approximate the volume of a given compact basic semialgebraic set K. The idea
consists of approximating from above the indicator function of K with a
sequence of polynomials of increasing degree d, so that the integrals of these
polynomials generate a convergence sequence of upper bounds on the volume of K.
We show that the asymptotic rate of this convergence is at least O(1/ log log
d).


title: Theory of magnons in spin systems with Dzyaloshinskii-Moriya interaction

abstract:
  We study in this paper magnetic properties of a system of quantum Heisenberg
spins interacting with each other via a ferromagnetic exchange interaction J
and an in-plane Dzyaloshinskii-Moriya interaction D. The non-collinear ground
state due to the competition between J and D is determined. We employ a
self-consistent Green'function theory to calculate the spin-wave spectrum and
the layer magnetizations at finite T in two and three dimensions as well as in
a thin film with surface effects. Analytical details and the validity of the
method are shown and discussed.


title: Holomorphic extension of the de Gennes function

abstract:
  This note is devoted to prove that the de Gennes function has a holomorphic
extension on a strip containing the real axis.


title:
WKB analysis of generalized derivative nonlinear Schrodinger equations
  without hyperbolicity

abstract:
  We consider the semi-classical limit of nonlinear Schrodinger equations in
the presence of both a polynomial nonlinearity and thederivative in space of a
polynomial nonlinearity. By working in a class of analytic initial data, we do
not have to assume any hyperbolicstructure on the (limiting) phase/amplitude
system. The solution, its approximation, and the error estimates are considered
in time dependent analyticregularity.


title: Coherent Neutrino-Nucleus Scattering and new Neutrino Interactions

abstract:
  We investigate the potential to probe new neutrino physics with future
experiments measuring coherent neutrino-nucleus scattering. Experiments with
high statistics should become feasible soon and allow to constrain parameters
with unprecedented precision. Using a benchmark setup for a future experiment
probing reactor neutrinos, we study the sensitivity on neutrino non-standard
interactions and new exotic neutral currents (scalar, tensor, etc). Compared to
Fermi interaction, percent and permille level strengths of the new interactions
can be probed, superseding for some observables the limits from future neutrino
oscillation experiments by up to two orders of magnitude.


title:
On the topology preservation of Gneiting's functions in image
  registration

abstract:
  The purpose of image registration is to determine a transformation such that
the transformed version of the source image is similar to the target one. In
this paper we focus on landmark-based image registration using radial basis
functions (RBFs) transformations, in particular on the topology preservation of
compactly supported radial basis functions (CSRBFs) transformations. In [1] the
performances of Gneiting's and Wu's functions are compared with the ones of
other well known schemes in image registration, as thin plate spline and
Wendland's functions. Several numerical experiments and real-life cases with
medical images show differences in accuracy and smoothness of the considered
interpolation methods, which can be explained taking into account their
topology preservation properties. Here we analyze analytically and
experimentally the topology preservation performances of Gneiting's functions,
comparing results with the ones obtained in [2], where Wendland's and Wu's
functions are considered.


title:
Modeling of Periodic Array of Cut-through Slits with Periodic Surface
  Conductivity at the Interfaces of an Anisotropic Medium

abstract:
  A periodic arrangement of one-dimensional slits carved in perfect electric
conductor is investigated and an equivalent model based on the effective medium
theory is derived. The proposed model is no longer fully homogeneous and
features periodic surface conductivity on its upper and lower interfaces.
Therefore, and in sheer contrast to all the previous attempts that were
successful in mimicking only the zeroth-order diffracted waves, it is capable
of emulating both specular and non-specular diffraction orders. The parameters
of the equivalent model are found by comparing the scattered waves of the
proposed model against those of the original structure obtained by invoking the
rigorous mode matching technique based on the single mode approximation inside
the slits. The proposed model is characterized by diagonal anisotropic
permittivity and permeability tensors together with a periodic surface
conductivity at the interfaces of the metallic grating and the ambient
environment. The accuracy of the model is verified by the full-wave
simulations. The proposed approach might be useful for devising applications
which work based on the characteristics of higher Floquet orders.


title: Transition from local to global of dFHE and dWCHP

abstract:
  In a previous paper [22] the author studied the directed weak covering
homotopy property (dWCHP)and directed weak fibrations in the category dTop of
directed spaces in the sense of M. Grandis [12], [13], [14]. This type of maps
extend to the category dTop the well known Dold's (or weak)fibrations [6]. In
this paper the transition from local to global of the dFHE (directed fiber
homotopy equivalence) and the dWCHP are studied by proving two Dold type
theorems and respectively a tom Dieck-Kamps-Puppe type theorem [3]. Some new
notions of directed topology are defined: d-halo, d-SEP, d-numerable covering,
d-shrinkable. Some examples and counterexamples are given.


title: Stable schemes for dissipative particle dynamics with conserved energy

abstract:
  This article presents a new numerical scheme for the discretization of
dissipative particle dynamics with conserved energy. The key idea is to reduce
elementary pairwise stochastic dynamics (either fluctuation/dissipation or
thermal conduction) to effective single-variable dynamics, and to approximate
the solution of these dynamics with one step of a Metropolis-Hastings
algorithm. This ensures by construction that no negative internal energies are
encountered during the simulation, and hence allows to increase the admissible
timesteps to integrate the dynamics, even for systems with small heat
capacities. Stability is only limited by the Hamiltonian part of the dynamics,
which suggests resorting to multiple timestep strategies where the stochastic
part is integrated less frequently than the Hamiltonian one.


title:
A targeted search for point sources of EeV photons with the Pierre Auger
  Observatory

abstract:
  Simultaneous measurements of air showers with the fluorescence and surface
detectors of the Pierre Auger Observatory allow a sensitive search for EeV
photon point sources. Several Galactic and extragalactic candidate objects are
grouped in classes to reduce the statistical penalty of many trials from that
of a blind search and are analyzed for a significant excess above the
background expectation. The presented search does not find any evidence for
photon emission at candidate sources, and combined $p$-values for every class
are reported. Particle and energy flux upper limits are given for selected
candidate sources. These limits significantly constrain predictions of EeV
proton emission models from non-transient Galactic and nearby extragalactic
sources, as illustrated for the particular case of the Galactic center region.


title:
Mesh density functions based on local bandwidth applied to moving mesh
  methods

abstract:
  Moving mesh methods provide an efficient way of solving partial differential
equations for which large, localised variations in the solution necessitate
locally dense spatial meshes. In one-dimension, meshes are typically specified
using the arclength mesh density function. This choice is well-justified for
piecewise polynomial interpolants, but it is only justified for spectral
methods when model solutions include localised steep gradients. In this paper,
one-dimensional mesh density functions are presented which are based on a
spatially localised measure of the bandwidth of the approximated model
solution. In considering bandwidth, these mesh density functions are
well-justified for spectral methods, but are not strictly tied to the error
properties of any particular spatial interpolant, and are hence widely
applicable. The bandwidth mesh density functions are demonstrated by applying
periodic spectral and finite-difference moving mesh methods to a number of
model problems in acoustics. These problems include a heterogeneous advection
equation, the viscous Burgers' equation, and the Korteweg-de Vries equation.
Simulation results demonstrate solution convergence rates that are up to an
order of magnitude faster using the bandwidth mesh density functions than
uniform meshes, and around three times faster than those using the arclength
mesh density function.


title: Cosmic Topology

abstract:
  This review aims to cover the central aspects of current research in cosmic
topology from a topological and observational perspective. Beginning with an
overview of the basic concepts of cosmology, it is observed that though a
determinant of local curvature, Einstein's equations of relativity do not
constrain the global properties of space-time. The topological requirements of
a universal space time manifold are discussed, including requirements of
space-time orientability and causality. The basic topological concepts used in
classification of spaces, i.e. the concept of the Fundamental Domain and
Universal covering spaces are discussed briefly. The manifold properties and
symmetry groups for three dimensional manifolds of constant curvature for
negative, positive and zero curvature manifolds are laid out.
Multi-connectedness is explored as a possible explanation for the detected
anomalies in the quadrupole and octopole regions of the power spectrum,
pointing at a possible compactness along one or more directions in space. The
statistical significance of the evidence, however, is also scrutinized and I
discuss briefly the bayesian and frequentist interpretation of the posterior
probabilities of observing the anomalies in a Lambda CDM universe. Some of the
major topologies that have been proposed and investigated as possible
candidates of a universal manifold are the Poincare Dodecahedron and Bianchi
Universes, which are studied in detail. Lastly, the methods that have been
proposed for detecting a multi connected signature are discussed. These include
ingenious observational methods like the circles in the sky method, cosmic
crystallography and Bayesian Analysis which provides the additional advantage
of being free from measurement errors and uses the posterior likelihoods of
models. As of the recent Planck mission, no pressing evidence of a multi
connected topology has been detected.


title:
Automated Inference on Sociopsychological Impressions of Attractive
  Female Faces

abstract:
  This article is a sequel to our earlier work [25]. The main objective of our
research is to explore the potential of supervised machine learning in
face-induced social computing and cognition, riding on the momentum of much
heralded successes of face processing, analysis and recognition on the tasks of
biometric-based identification. We present a case study of automated
statistical inference on sociopsychological perceptions of female faces
controlled for race, attractiveness, age and nationality. Our empirical
evidences point to the possibility of training machine learning algorithms,
using example face images characterized by internet users, to predict
perceptions of personality traits and demeanors.


title:
On the periodic approximation of Lyapunov exponents for semi-invertible
  cocycles

abstract:
  We prove that, for semi-invertible linear cocycles, Lyapunov exponents of
ergodic measures may be approximated by Lyapunov exponents on periodic points.


title: Efficient protocol for qubit initialization with a tunable environment

abstract:
  We propose an efficient qubit initialization protocol based on a dissipative
environment that can be dynamically adjusted. Here the qubit is coupled to a
thermal bath through a tunable harmonic oscillator. On-demand initialization is
achieved by sweeping the oscillator rapidly into resonance with the qubit. This
resonant coupling with the engineered environment induces fast relaxation to
the ground state of the system, and a consecutive rapid sweep back to off
resonance guarantees weak excess dissipation during quantum computations. We
solve the corresponding quantum dynamics using a Markovian master equation for
the reduced density operator of the qubit-bath system. This allows us to
optimize the parameters and the initialization protocol for the qubit. Our
analytical calculations show that the ground-state occupation of our system is
well protected during the fast sweeps of the environmental coupling and,
consequently, we obtain an estimate for the duration of our protocol by solving
the transition rates between the low-energy eigenstates with the Jacobian
diagonalization method. Our results suggest that the current experimental state
of the art for the initialization speed of superconducting qubits at a given
fidelity can be considerably improved.


title:
Existence analysis of a single-phase flow mixture model with van der
  Waals pressure

abstract:
  The transport of single-phase fluid mixtures in porous media is described by
cross-diffusion equations for the mass densities. The equations are obtained in
a thermodynamic consistent way from mass balance, Darcy's law, and the van der
Waals equation of state for mixtures. The model consists of parabolic equations
with cross diffusion with a hypocoercive diffusion operator. The global-in-time
existence of weak solutions in a bounded domain with equilibrium boundary
conditions is proved, extending the boundedness-by-entropy method. Based on the
free energy inequality, the large-time convergence of the solution to the
constant equilibrium mass density is shown. For the two-species model and
specific diffusion matrices, an integral inequality is proved, which reveals a
minimum principle for the mass fractions. Without mass diffusion, the
two-dimensional pressure is shown to converge exponentially fast to a constant.
Numerical examples in one space dimension illustrate this convergence.


title: Violations of L\"owensteins rule in zeolites

abstract:
  Zeolites, microporous aluminosilicates, are amongst the most widely used
catalysts in the petrochemical industry. Zeolite catalytic functionality is
coupled to the distribution of tetrahedral alumina (AlO4-) and associated
counter-cations throughout the aluminosilicate framework, yet little is
definitively known about the factors that govern framework aluminium
arrangement. It is generally accepted that all zeolites obey Lowensteins rule
of aluminium avoidance and that Al-O-Al linkages are forbidden. Here, we
describe the unprecedented screening of aluminium distribution in catalytically
active zeolite SSZ-13 in both its protonated and sodium containing forms,
H-SSZ-13 and Na-SSZ-13, using density functional theory. We predict violations
of Lowensteins rule in high and low silica H-SSZ-13 and other protonated
frameworks considered in this investigation, H-LTA, H-RHO and H-ABW. The
synthetic realisation of these zeolites could spur the development of new
catalytic routes and materials, and the optimisation of existing zeolite
catalysts.


title: Noninteger-spin magnonic excitations in untextured magnets

abstract:
  Interactions are responsible for intriguing physics, e.g. emergence of exotic
ground states and excitations, in a wide range of systems. Here we
theoretically demonstrate that dipole-dipole interaction leads to bosonic
eigen-excitations with average spin ranging from zero to above $\hbar$ in
magnets with uniformly magnetized ground states. These exotic excitations can
be interpreted as quantum coherent conglomerates of spin $\hbar$ magnons, the
eigen-excitations when the dipolar interactions are disregarded. We further
find that the eigenmodes in an easy-axis antiferromagnet are spin-zero
quasiparticles instead of the widely believed spin $\pm \hbar$ magnons. The
latter re-emerge when the symmetry is broken by a sufficiently large applied
magnetic field. The average spin greater than $\hbar$ is accompanied by vacuum
fluctuations and may be considered to be a weak form of frustration.


title: Keeping Continuous Deliveries Safe

abstract:
  Allowing swift release cycles, Continuous Delivery has become popular in
application software development and is starting to be applied in
safety-critical domains such as the automotive industry. These domains require
thorough analysis regarding safety constraints, which can be achieved by formal
verification and the execution of safety tests resulting from a safety analysis
on the product. With continuous delivery in place, such tests need to be
executed with every build to ensure the latest software still fulfills all
safety requirements. Even more though, the safety analysis has to be updated
with every change to ensure the safety test suite is still up-to-date. We thus
propose that a safety analysis should be treated no differently from other
deliverables such as source-code and dependencies, formulate guidelines on how
to achieve this and advert areas where future research is needed.


title:
Information and Power Transfer by Energy Harvesting Transmitters over a
  Fading Multiple Access Channel with Minimum Rate Constraints

abstract:
  We consider the problem of Simultaneous Wireless Information and Power
Transfer (SWIPT) over a fading multiple access channel with additive Gaussian
noise. The transmitters as well as the receiver harvest energy from ambient
sources. We assume that the transmitters have two classes of data to send, viz.
delay sensitive and delay tolerant data. Each transmitter sends the delay
sensitive data at a certain minimum rate irrespective of the channel conditions
(fading states). In addition, if the channel conditions are good, the delay
tolerant data is sent. {Along with data, the transmitters also transfer power
to aid the receiver in meeting its energy requirements.} In this setting, we
characterize the \textit{minimum-rate capacity region} which provides the
fundamental limit of transferring information and power simultaneously with
minimum rate guarantees. Owing to the limitations of current technology, these
limits might not be achievable in practice. Among the practical receiver
structures proposed for SWIPT in literature, two popular architectures are the
\textit{time switching} and \textit{power splitting} receivers. For each of
these architectures, we derive the minimum-rate capacity regions. We show that
power splitting receivers although more complex, provide a larger capacity
region.


title:
Peculiar architectures for the WASP-53 and WASP-81 planet-hosting
  systems

abstract:
  We report the detection of two new systems containing transiting planets.
Both were identified by WASP as worthy transiting planet candidates.
Radial-velocity observations quickly verified that the photometric signals were
indeed produced by two transiting hot Jupiters. Our observations also show the
presence of additional Doppler signals. In addition to short-period hot
Jupiters, we find that the WASP-53 and WASP-81 systems also host brown dwarfs,
on fairly eccentric orbits with semi-major axes of a few astronomical units.
WASP-53c is over 16 $M_{\rm Jup} \sin i_{\rm c}$ and WASP-81c is 57 $M_{\rm
Jup} \sin i_{\rm c}$. The presence of these tight, massive companions restricts
theories of how the inner planets were assembled. We propose two alternative
interpretations: a formation of the hot Jupiters within the snow line, or the
late dynamical arrival of the brown dwarfs after disc-dispersal.
  We also attempted to measure the Rossiter--McLaughlin effect for both hot
Jupiters. In the case of WASP-81b we fail to detect a signal. For WASP-53b we
find that the planet is aligned with respect to the stellar spin axis. In
addition we explore the prospect of transit timing variations, and of using
Gaia's astrometry to measure the true masses of both brown dwarfs and also
their relative inclination with respect to the inner transiting hot Jupiters.


title: Feedback-charging a metallic island

abstract:
  We consider electronic transport through a single-electron quantum dot that
is tunnel-coupled to an electronic lead and a metallic island. A background
reservoir keeps the metallic island at a thermal state with the ambient
temperature, while the charge accumulated on the island is reflected in a
time-dependent chemical potential. Without feedback, a current would flow
through the system until the chemical potentials of island and lead are
equilibrated. A feedback loop can be implemented by a quantum point contact
detecting the dot state, classical processing of the result and appropriate
feedback actions on the electronic tunneling rates taken, with the objective to
direct the current in a preferred direction. Since we directly take the
detector counting statistics into account, this automatically includes
measurement errors in the description. When mainly the rates are modified but
hardly any energy is exchanged with the system, this feedback loop effectively
implements a Maxwell demon, capable of transporting electrons against an
electric bias and thereby charging the metallic island. Once the feedback
protocol is stopped, the metallic island simply discharges. We find that a
quantitative detector model may be useful for a realistic statistical
description of feedback loops.


title:
Modular quantum key distribution setup for research and development
  applications

abstract:
  Quantum key distribution (QKD), ensuring the unconditional security of
information, attracts a significant deal of interest. An important task is to
design QKD systems as a platform for education as well as for research and
development applications and fast prototyping new QKD protocols. Here we
present a modular QKD setup driven by National Instruments (NI) cards with open
source LabView code, open source Python code for post-processing procedures,
and open source protocol for external applications. An important feature of the
developed apparatus is its flexibility offering possibilities to modify optical
schemes and verify novel QKD protocols. Another distinctive feature of the
developed setup is the implementation of the decoy-state protocol, which is a
standard tool for secure long-distance quantum communications. By testing the
plug-and-play scheme realizing BB84 and decoy-state BB84 QKD protocols, we
demonstrate that developed QKD setup shows a high degree of robustness beyond
laboratory conditions. We demonstrate the results of the use of the developed
modular setup for urban QKD experiments.


title: Self avoiding walk on the seven regular triangulation

abstract:
  It is shown that self avoiding walk on the seven regular infinite planar
triangulation has linear expected displacement.


title: Filter-Laver Measurability

abstract:
  We study sigma-ideals and regularity properties related to the "filter-Laver"
and "dual-filter-Laver" forcing partial orders. An important innovation which
enables this study is a dichotomy theorem proved recently by Miller [1].
  [1] Arnold Miller, "Hechler and Laver Trees", Preprint 2012 (arXiv:1204.5198
[math.LO]).


title:
Spontaneous aggregation and global polar ordering in squirmer
  suspensions

abstract:
  We have developed numerical simulations of three dimensional suspensions of
active particles to characterize the capabilities of the hydrodynamic stresses
induced by active swimmers to promote global order and emergent structures in
active suspensions. We have considered squirmer suspensions embedded in a fluid
modeled under a Lattice Boltzmann scheme. We have found that active stresses
play a central role to decorrelate the collective motion of squirmers and that
contractile squirmers develop significant aggregates.


title: A connection between matchings and removal in abelian groups

abstract:
  In a finite abelian group $G$, define an additive matching to be a collection
of triples $(x_i, y_i, z_i)$ such that $x_i + y_j + z_k = 0$ if and only if $i
= j = k$. In the case that $G = \mathbb{F}_2^n$, Kleinberg, building on work of
Croot-Lev-Pach and Ellenberg-Gijswijt, proved a polynomial upper bound on the
size of an additive matching. Fox and Lov\'{a}sz used this to deduce polynomial
bounds on Green's arithmetic removal lemma in $\mathbb{F}_2^n$.
  If $G$ is taken to be an arbitrary finite abelian group, the questions of
bounding the size of an additive matching and giving bounds for Green's
arithmetic removal lemma are much less well understood. In this note, we adapt
the methods of Fox and Lov\'{a}sz to prove that, provided we can assume a
sufficiently strong bound on the size of an additive matching in cyclic groups,
a similar bound should hold in the case of removal.


title:
Phonon limit to simultaneous near-unity efficiency and
  indistinguishability in semiconductor single photon sources

abstract:
  Semiconductor quantum dots have recently emerged as a leading platform to
efficiently generate highly indistinguishable photons, and this work addresses
the timely question of how good these solid-state sources can ultimately be. We
establish the crucial role of lattice relaxation in these systems in giving
rise to trade-offs between indistinguishability and efficiency. We analyse the
two source architectures most commonly employed: a quantum dot embedded in a
waveguide and a quantum dot coupled to an optical cavity. For waveguides, we
demonstrate that the broadband Purcell effect results in a simple inverse
relationship, where indistinguishability and efficiency cannot be
simultaneously increased. For cavities, the frequency selectivity of the
Purcell enhancement results in a more subtle trade-off, where
indistinguishability and efficiency can be simultaneously increased, though by
the same mechanism not arbitrarily, limiting a source with near-unity
indistinguishability ($>99$\%) to an efficiency of approximately 96\% for
realistic parameters.


title:
Models of retrieval in sentence comprehension: A computational
  evaluation using Bayesian hierarchical modeling

abstract:
  Research on interference has provided evidence that the formation of
dependencies between non-adjacent words relies on a cue-based retrieval
mechanism. Two different models can account for one of the main predictions of
interference, i.e., a slowdown at a retrieval site, when several items share a
feature associated with a retrieval cue: Lewis and Vasishth's (2005)
activation-based model and McElree's (2000) direct access model. Even though
these two models have been used almost interchangeably, they are based on
different assumptions and predict differences in the relationship between
reading times and response accuracy. The activation-based model follows the
assumptions of ACT-R, and its retrieval process behaves as a lognormal race
between accumulators of evidence with a single variance. Under this model,
accuracy of the retrieval is determined by the winner of the race and retrieval
time by its rate of accumulation. In contrast, the direct access model assumes
a model of memory where only the probability of retrieval varies between items;
in this model, differences in latencies are a by-product of the possibility and
repairing incorrect retrievals. We implemented both models in a Bayesian
hierarchical framework in order to evaluate them and compare them. We show that
some aspects of the data are better fit under the direct access model than
under the activation-based model. We suggest that this finding does not rule
out the possibility that retrieval may be behaving as a race model with
assumptions that follow less closely the ones from the ACT-R framework. We show
that by introducing a modification of the activation model, i.e, by assuming
that the accumulation of evidence for retrieval of incorrect items is not only
slower but noisier (i.e., different variances for the correct and incorrect
items), the model can provide a fit as good as the one of the direct access
model.


title:
Minimizing movements for mean curvature flow of droplets with prescribed
  contact angle

abstract:
  We study the mean curvature motion of a droplet flowing by mean curvature on
a horizontal hyperplane with a possibly nonconstant prescribed contact angle.
Using the minimizing movements method we show the existence of a weak
evolution, and its compatibility with a distributional solution. We also prove
various comparison results.


title: Jointly Broadcasting Data and Power with Quality of Service Guarantees

abstract:
  In this work, we consider a scenario wherein an energy harvesting wireless
radio equipment sends information to multiple receivers alongside powering
them. In addition to harvesting the incoming radio frequency (RF) energy, the
receivers also harvest energy from {its environment (e.g., solar energy)}. This
communication framework is captured by a fading Gaussian Broadcast Channel
(GBC) with energy harvesting transmitter and receivers. In order to ensure
{some quality of service (QoS)} in data reception among the receivers, we
impose a \textit{minimum-rate} requirement on data transmission. For the
setting in place, we characterize the fundamental limits in jointly
transmitting information and power subject to a QoS guarantee, for three
cardinal receiver structures namely, \textit{ideal}, \textit{time-switching}
and \textit{power-splitting}. We show that a time-switching receiver can
{switch} between {information reception mode} and {energy harvesting mode},
\textit{without} the transmitter's knowledge of the same and \textit{without}
any extra \textit{rate loss}. We also prove that, for the same amount of power
transferred, on average, a power-splitting receiver supports higher data rates
compared to a time-switching receiver.


title: Cosmology in nonlinear multidimensional gravity and the Casimir effect

abstract:
  We study the possible cosmological models in Kaluza-Klein-type
multidimensional gravity with a curvature-nonlinear Lagrangian and a spherical
extra space, taking into account the Casimir energy. First, we find a minimum
of the effective potential of extra dimensions, leading to a physically
reasonable value of the effective cosmological constant in our 4D space-time.
In this model, the huge Casimir energy density is compensated by a fine-tuned
contribution of the curvature-nonlinear terms in the original action. Second,
we present a viable model with slowly evolving extra dimensions and power-law
inflation in our space-time. In both models, the results formulated in Einstein
and Jordan frames are compared.


title: Optically Polarized $^3$He

abstract:
  This article reviews the physics and technology of producing large quantities
of highly spin-polarized, or hyperpolarized, $^3$He nuclei using spin-exchange
(SEOP) and metastability-exchange (MEOP) optical pumping, and surveys
applications of polarized $^3$He. Several recent developments are emphasized
for each method. For SEOP, the use of spectrally narrowed lasers and Rb/K
mixtures has substantially increased the achievable polarization and polarizing
rate. MEOP in high magnetic fields has likewise significantly increased the
pressure at which this method can be performed, and has led to the observation
of a light-induced relaxation mechanism. In both methods the increased
capabilities have led to more extensive study and modeling of the basic
underlying physics. New unexplained dependences of relaxation on temperature
and magnetic field have been discovered in SEOP cells. Applications of both
methods are also reviewed, including targets for charged particle and photon
beams, neutron spin filters, magnetic resonance imaging, and precision
measurements.

categories: physics.atom-ph nucl-ex physics.ins-det physics.med-ph


title: De Sitter and power-law solutions in some models of modified gravity

abstract:
  Inspired by some recent works of Lovelock Brans-Dicke gravity and mimetic
gravity, cosmology solutions in extensions of these two modified gravities are
investigated. A non-local term is added to the Lovelock Brans-Dicke action and
Gauss-Bonnet terms to the mimetic action,correspondingly. De Sitter and power
scale factor solutions are then obtained in both theories. They can provide
natural new approaches to a more accurate description of the unverse evolution.


title:
Continuum Dynamics on Manifolds: Application to Elasticity of
  Residually-Stressed Bodies

abstract:
  This paper is concerned with the dynamics of continua on differentiable
manifolds. We present a covariant derivation of equations of motion, viewing
motion as a curve in an infinite-dimensional Banach space of embeddings of a
body manifold in a space manifold. Our main application is the motion of
residually-stressed elastic bodies; residual stress results from a geometric
incompatibility between body and space manifolds. We then study a particular
example of elastic vibrations of a two- dimensional curved annulus embedded in
a sphere.


title: Pattern of confined chemical garden controlled by injection speed

abstract:
  Pattern of confined chemical garden was controlled by the speed of injected
fluid, and their mechanism is discussed. A confined chemical garden system was
constructed where an aqueous solution of cobalt chloride was injected into a
cell filled with sodium silicate solution. The reaction of these two solutions
resulted in the formation of precipitation. The viscosities of the prepared
aqueous solutions were set to be similar in order to rule out the possibility
of Saffman-Taylor instability. The injection front showed three distinctive
patterns: algaes, shells, and filaments, which were dependent on injection
speed. The injection pressure and the spatio-temporal pattern of the injected
fluid were measured, and a significant increase in the injection pressure was
observed when the filament pattern appeared, which indicated the existence of
thin lubrication layer between the precipitation and the substrate. The
filament pattern was further analyzed quantitatively, and the number of active
filaments was determined to be proportional to the injection speed. A
mathematical model was constructed that considered both the viscous effect from
the thin luburiation layer and the Laplace pressure. This model successfully
reproduced the characteristic filament dynamics.


title:
Global existence and Hadamard differentiability of
  hysteresis-reaction-diffusion systems

abstract:
  We consider a class of semilinear parabolic evolution equations subject to a
hysteresis operator and a Bochner-Lebesgue integrable source term. The
underlying spatial domain is allowed to have a very general boundary. In the
first part of the paper, we apply semigroup theory to prove well-posedness and
boundedness of the solution operator. Rate independence in reaction-diffusion
systems complicates the analysis, since the reaction term acts no longer local
in time. This demands careful estimates when working with semigroup methods. In
the second part, we show Lipschitz continuity and Hadamard differentiability of
the solution operator. We use fixed point arguments to derive a representation
for the derivative in terms of the evolution system. Finally, we apply our
results to an optimal control problem in which the source term acts as a
control function and show existence of an optimal solution.


title:
Interactive (statistical) visualisation and exploration of a billion
  objects with Vaex

abstract:
  With new catalogues arriving such as the Gaia DR1, containing more than a
billion objects, new methods of handling and visualizing these data volumes are
needed. In visualization, one problem is that the number of datapoints can
become so large, that a scatter plot becomes cluttered. Another problem is that
with over a billion objects, only a few cpu cycles are available per object if
one wants to process them within a second, making traditional methods by
rendering glyphs not viable. Instead, we show that by calculating statistics on
a regular (N-dimensional) grid, visualizations of a billion objects can be done
within a second on a modern desktop computer. This is achieved using memory
mapping of hdf5 files together with a simple binning algorithm, which are part
of a Python library called vaex. This enables efficient exploration or large
datasets interactively, making science exploration of large catalogues
feasible. Vaex is a Python library, which also integrates well in the
Jupyter/Numpy/Astropy/matplotlib stack. Build on top of this is the vaex
application, which allows for interactive exploration and visualization. The
motivation for developing vaex is the catalogue of the Gaia satellite, however,
vaex can also be used on SPH or N-body simulations, any other (future)
catalogues such as SDSS, Pan-STARRS, LSST, WISE, 2MASS, etc. or other tabular
data. The homepage for vaex is http://vaex.astro.rug.nl.


title:
Matters of Gravity, The Newsletter of the Division of Gravitational
  Physics of the American Physical Society, Volume 48, December 2016

abstract:
  DGRAV News: we hear that ...
  DGRAV program at the APS meeting in Washington D.C.
  Obituary:
  Remembering John Stewart
  Conference Reports:
  CPT and Lorentz Symmetry


title:
Sleep Apnea Detection Based on Thoracic and Abdominal Movement Signals
  of Wearable Piezo-Electric Bands

abstract:
  Physiologically, the thoracic (THO) and abdominal (ABD) movement signals,
captured using wearable piezo-electric bands, provide information about various
types of apnea, including central sleep apnea (CSA) and obstructive sleep apnea
(OSA). However, the use of piezo-electric wearables in detecting sleep apnea
events has been seldom explored in the literature. This study explored the
possibility of identifying sleep apnea events, including OSA and CSA, by solely
analyzing {one or both the THO and ABD signals. An adaptive non-harmonic model
was introduced to model the THO and ABD signals, which allows us to design
features for sleep apnea events. To confirm the suitability of the extracted
features, a support vector machine was applied to classify three categories --
normal and hypopnea, OSA, and CSA. According to a database of} 34 subjects, the
overall classification accuracies were on average $75.9\%\pm 11.7\%$ and
$73.8\%\pm 4.4\%$, respectively, based on the cross validation. When the
features determined from the THO and ABD signals were combined, the overall
classification accuracy became $81.8\%\pm 9.4\%$. These features were applied
for designing a state machine for online apnea event detection. Two
event-by-event accuracy indices, S and I, were proposed for evaluating the
performance {of the state machine. For the same database, the} S index was
$84.01\%\pm 9.06\%$, and the I index was $77.21\%\pm 19.01\%$. The results
indicate the considerable potential of applying the proposed algorithm to
clinical examinations for both screening and homecare purposes.


title:
Local Energy Conservation Law for Spatially-Discretized Hamiltonian
  Vlasov-Maxwell System

abstract:
  Structure-preserving geometric algorithm for the Vlasov-Maxwell (VM)
equations is currently an active research topic. We show that
spatially-discretized Hamiltonian systems for the VM equations admit a local
energy conservation law in space-time. This is accomplished by proving that for
a general spatially-discretized system, a global conservation law always
implies a discrete local conservation law in space-time when the algorithm is
local. This general result demonstrates that Hamiltonian discretizations can
preserve local conservation laws, in addition to the symplectic structure, both
of which are the intrinsic physical properties of infinite dimensional
Hamiltonian systems in physics.


title: How to find finite topological spaces with given quotient-spaces

abstract:
  Our main problem is to find finite topological spaces to within
homeomorphism, given (also to within homeomorphism) the quotient-spaces
obtained by identifying one point of the space with each one of the other
points. In a previous version of this paper, our aim was to reconstruct a
topological space from its quotient-spaces; but a reconstruction is not always
possible either in the sense that several non-homeomorphic topological spaces
yield the same quotient-spaces, or in the sense that no topological space
yields an arbitrarily given family of quotient-spaces. In this version of the
paper we present an algorithm that detects, and deals with, all these
situations.


title: Faint progenitors of luminous $z \sim 6$ quasars: why don't we see them?

abstract:
  Observational searches for faint active nuclei at $z > 6$ have been extremely
elusive, with a few candidates whose high-$z$ nature is still to be confirmed.
Interpreting this lack of detections is crucial to improve our understanding of
high-$z$ supermassive black holes (SMBHs) formation and growth. In this work,
we present a model for the emission of accreting BHs in the X-ray band, taking
into account super-Eddington accretion, which can be very common in gas-rich
systems at high-$z$. We compute the spectral energy distribution for a sample
of active galaxies simulated in a cosmological context, which represent the
progenitors of a $z \sim 6$ SMBH with $M_{\rm BH} \sim 10^9 \, M_\odot$. We
find an average Compton thick fraction of $\sim 45\%$ and large typical column
densities ($N_H \gtrsim 10^{23} \rm \, cm^2$). However, faint progenitors are
still luminous enough to be detected in the X-ray band of current surveys. Even
accounting for a maximum obscuration effect, the number of detectable BHs is
reduced at most by a factor 2. In our simulated sample, observations of faint
quasars are mainly limited by their very low active fraction ($f_{\rm act} \sim
1 \%$), which is the result of short, super-critical growth episodes. We
suggest that to detect high-$z$ SMBHs progenitors, large area surveys with
shallower sensitivities, such as Cosmos Legacy and XMM-LSS+XXL, are to be
preferred with respect to deep surveys probing smaller fields, such as CDF-S.


title: Relative projectivity and transferability for partial lattices

abstract:
  A partial lattice P is ideal-projective, with respect to a class C of
lattices, if for every K $\in$ C and every homomorphism $\phi$ of partial
lattices from P to the ideal lattice of K, there are arbitrarily large choice
functions f : P $\rightarrow$ K for $\phi$ that are also homomorphisms of
partial lattices. This extends the traditional concept of (sharp)
transferability of a lattice with respect to C. We prove the following: (1) A
finite lattice P, belonging to a variety V, is sharply transferable with
respect to V iff it is projective with respect to V and weakly distributive
lattice homomorphisms, iff it is ideal-projective with respect to V. (2) Every
finite distributive lattice is sharply transferable with respect to the class R
mod of all relatively complemented modular lattices. (3) The gluing D 4 of two
squares, the top of one being identified with the bottom of the other one, is
sharply transferable with respect to a variety V iff V is contained in the
variety M$\omega$ generated by all lattices of length 2. (4) D 4 is projective,
but not ideal-projective, with respect to R mod. (5) D 4 is transferable, but
not sharply transferable, with respect to the variety M of all modular
lattices. This solves a 1978 problem of G. Gr\"atzer. (6) We construct a
modular lattice whose canonical embedding into its ideal lattice is not pure.
This solves a 1974 problem of E. Nelson.


title:
Maximizing switching current of superconductor nanowires via improved
  impedance matching

abstract:
  The temporary resistance triggered by phase slip will result in the switching
of superconductor nanowire to a permanent normal state, decreasing the
switching current. In this letter, we propose an improved impedance matching
circuit that releases the transition triggered by phase slips to the load
resistor through the RF port of a bias tee. The transportation properties with
different load resistors indicate that the switching current decreases due to
the reflection caused by impedance mismatching, and is maximized by optimized
impedance matching. Compared to the same setup without impedance matching
circuit, the switching current was increased from 8.0 micro A to 12.2 micro A
in a niobium nitride nanowire after releasing the temporary transition
triggered by phase slips. The leakage process with impedance matching outputs a
voltage pulse which enables the user to directly register the transition
triggered by phase slips. The technique for maximizing the switching current
has potential practical application in superconductor devices, and the
technique for counting phase slips may be applied to explore the quantum
behavior of phase slips.