title: Spectral Convergence of the connection Laplacian from random samples

abstract:
  Spectral methods that are based on eigenvectors and eigenvalues of discrete
graph Laplacians, such as Diffusion Maps and Laplacian Eigenmaps are often used
for manifold learning and non-linear dimensionality reduction. It was
previously shown by Belkin and Niyogi \cite{belkin_niyogi:2007} that the
eigenvectors and eigenvalues of the graph Laplacian converge to the
eigenfunctions and eigenvalues of the Laplace-Beltrami operator of the manifold
in the limit of infinitely many data points sampled independently from the
uniform distribution over the manifold. Recently, we introduced Vector
Diffusion Maps and showed that the connection Laplacian of the tangent bundle
of the manifold can be approximated from random samples. In this paper, we
present a unified framework for approximating other connection Laplacians over
the manifold by considering its principle bundle structure. We prove that the
eigenvectors and eigenvalues of these Laplacians converge in the limit of
infinitely many independent random samples. We generalize the spectral
convergence results to the case where the data points are sampled from a
non-uniform distribution, and for manifolds with and without boundary.


title:
Negative Magnetoresistance and Spin Filtering of Spin-Coupled Diiron-Oxo
  Clusters

abstract:
  Spin dependent transport has been investigated for an {\it open shell
singlet} diiron-oxo cluster. Currents and magnetoresistances have been studied,
as a function of spin state, within the non-equilibrium Green's function
approach. The applied bias can be used for tuning the sign of the observed
magnetoresistance. A colossal magnetoresistance ratio has been determined, on
the order of to 6000$%$, for hydrogen anchoring. Applied biases lower than 0.3
V, in conjunction with sulfur anchoring, induce a negative magnetoresistance
due to lowering of the anchor-scatterer tunneling barrier. In addition, the
diiron-oxo cluster displays nearly perfect spin filtering for parallel
alignment of the iron magnetic moments due to energetic proximity, relative to
the Fermi level, of its highest occupied molecular orbitals.


title:
Pruning-Based Pareto Front Generation for Mixed-Discrete Bi-Objective
  Optimization

abstract:
  This note proposes an effective pruning-based Pareto front generation method
in mixed-discrete bi-objective optimization. The mixed-discrete problem is
decomposed into multiple continuous subproblems; two-phase pruning steps
identify and prune out non-contributory subproblems to the Pareto front
construction. The efficacy of the proposed method is demonstrated on two
benchmark examples.


title:
Explicit Examples of rational and Calabi-Yau threefolds with primitive
  automorphisms of positive entropy

abstract:
  We present the first explicit examples of a rational threefold and a
Calabi-Yau threefold, admitting biregular automorphisms of positive entropy not
preserving any dominant rational maps to lower positive dimensional varieties.
The most crucial part is the rationality of the quotient threefold of a
3-dimensional torus of product type.


title: Autonomous search for a diffusive source in an unknown environment

abstract:
  The paper presents an approach to olfactory search for a diffusive emitting
source of tracer (e.g. aerosol, gas) in an environment with unknown map of
randomly placed and shaped obstacles.
  The measurements of tracer concentration are sporadic, noisy and without
directional information. The search domain is discretised and modelled by a
finite two-dimensional lattice. The links is the lattice represent the
traversable paths for emitted particles and for the searcher. A missing link in
the lattice indicates a blocked paths, due to the walls or obstacles. The
searcher must simultaneously estimate the source parameters, the map of the
search domain and its own location within the map. The solution is formulated
in the sequential Bayesian framework and implemented as a Rao-Blackwellised
particle filter with information-driven motion control. The numerical results
demonstrate the concept and its performance.


title: Variational Data Assimilation via Sparse Regularization

abstract:
  This paper studies the role of sparse regularization in a properly chosen
basis for variational data assimilation (VDA) problems. Specifically, it
focuses on data assimilation of noisy and down-sampled observations while the
state variable of interest exhibits sparsity in the real or transformed domain.
We show that in the presence of sparsity, the $\ell_{1}$-norm regularization
produces more accurate and stable solutions than the classic data assimilation
methods. To motivate further developments of the proposed methodology,
assimilation experiments are conducted in the wavelet and spectral domain using
the linear advection-diffusion equation.


title: The root posets and their rich antichains

abstract:
  Let $\Delta$ be a (connected) Dynkin diagram of rank $n\ge 2$ and $\Phi_+ =
\Phi_+(\Delta)$ the corresponding root poset (it consists of all positive roots
with respect to a fixed root basis). The width of $\Phi_+$ is $n$. We will show
that $\Phi_+$ is "conical": it is the disjoint union of $n$ solid chains.
  The rich antichains in $\Phi_+$ are the antichains of cardinality $n-1$. It
is well known that the number of rich antichains is equal to the cardinality of
$\Phi_+$. The set $\mathcal R(\Delta)$ of rich antichains in $\Phi_+$ can
itself be considered as a poset which is quite similar, but not always
isomorphic, to $\Phi_+$.
  We will show that there always exists a unique rich antichain $A$ such that
any rich antichain is contained in the ideal generated by $A$. For $\Delta\neq
\Bbb E_6$ all roots in $A$ have the same length, namely $e_2$, where $e_1 \le
e_2 \le \dots \le e_n$ are the exponents of $\Delta.$ For $\Delta = \Bbb E_6$,
the antichain $A$ consists of four roots of length $e_2 = 4$ and one root of
length $5$.


title:
Creating high density ensembles of nitrogen-vacancy centers in
  nitrogen-rich type Ib nanodiamonds

abstract:
  This work explores the possibility of increasing the density of negatively
charged nitrogen-vacancy centers [NV-] in nanodiamonds using nitrogen-rich type
Ib diamond powders as the starting materials. The nanodiamonds (10 - 100 nm in
diameters) were prepared by ball-milling of microdiamonds, in which the density
of neutral and automatically dispersed nitrogen atoms [N0] was measured by
diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). A
systematic measurement for the fluorescence intensities and lifetimes of the
crushed monocrystalline diamonds as a function of [N0] indicated that the [NV-]
increases nearly linearly with [N0] at 100 - 200 ppm. The trend, however,
failed to continue for nanodiamonds with higher [N0] (up to 390 ppm) but poorer
crystallinity. We attribute the result to a combined effect of fluorescence
quenching as well as the lower conversion efficiency of vacancies to NV- due to
the presence of more impurities and defects in these as-grown diamond
crystallites. The principles and practice of fabricating brighter and smaller
fluorescent nanodiamonds (FNDs) are discussed.


title: Layered Separators in Minor-Closed Graph Classes with Applications

abstract:
  Graph separators are a ubiquitous tool in graph theory and computer science.
However, in some applications, their usefulness is limited by the fact that the
separator can be as large as $\Omega(\sqrt{n})$ in graphs with $n$ vertices.
This is the case for planar graphs, and more generally, for proper minor-closed
classes. We study a special type of graph separator, called a "layered
separator", which may have linear size in $n$, but has bounded size with
respect to a different measure, called the "width". We prove, for example, that
planar graphs and graphs of bounded Euler genus admit layered separators of
bounded width. More generally, we characterise the minor-closed classes that
admit layered separators of bounded width as those that exclude a fixed apex
graph as a minor.
  We use layered separators to prove $\mathcal{O}(\log n)$ bounds for a number
of problems where $\mathcal{O}(\sqrt{n})$ was a long-standing previous best
bound. This includes the nonrepetitive chromatic number and queue-number of
graphs with bounded Euler genus. We extend these results with a
$\mathcal{O}(\log n)$ bound on the nonrepetitive chromatic number of graphs
excluding a fixed topological minor, and a $\log^{ \mathcal{O}(1)}n$ bound on
the queue-number of graphs excluding a fixed minor. Only for planar graphs were
$\log^{ \mathcal{O}(1)}n$ bounds previously known. Our results imply that every
$n$-vertex graph excluding a fixed minor has a 3-dimensional grid drawing with
$n\log^{ \mathcal{O}(1)}n$ volume, whereas the previous best bound was
$\mathcal{O}(n^{3/2})$.


title: Neron-Severi group preserving lifting of K3 surfaces and applications

abstract:
  For a K3 surface of finite height over a field of odd characteristic, there
exists a smooth lifting to the ring of Witt vectors such that the reduction map
from the Picard group of the generic fiber to the Picard group of the special
fiber is isomorphic. In this paper, using this result, we give a criterion for
a K3 surface of finite height over a field of odd characteristic to be an
Enriques K3 surface or to be a K3 surface in terms of the Neron-Severi lattice.
Then we show every Kummer surface has an Enriques involution. We also give a
classification of K3 surfaces of Picard rank of 20 over odd characteristic.


title: Nucleon GPDs in a light-front quark model derived from soft-wall AdS/QCD

abstract:
  We study the helicity-independent generalized parton distributions of
nucleons in the zero skewness case, based on a particular light-front quark
model derived in a soft-wall AdS/QCD approach.


title: Bayesian factorizations of big sparse tensors

abstract:
  It has become routine to collect data that are structured as multiway arrays
(tensors). There is an enormous literature on low rank and sparse matrix
factorizations, but limited consideration of extensions to the tensor case in
statistics. The most common low rank tensor factorization relies on parallel
factor analysis (PARAFAC), which expresses a rank $k$ tensor as a sum of rank
one tensors. When observations are only available for a tiny subset of the
cells of a big tensor, the low rank assumption is not sufficient and PARAFAC
has poor performance. We induce an additional layer of dimension reduction by
allowing the effective rank to vary across dimensions of the table. For
concreteness, we focus on a contingency table application. Taking a Bayesian
approach, we place priors on terms in the factorization and develop an
efficient Gibbs sampler for posterior computation. Theory is provided showing
posterior concentration rates in high-dimensional settings, and the methods are
shown to have excellent performance in simulations and several real data
applications.


title: New Views of Crystal Symmetry

abstract:
  Already Hermann Grassmann's father Justus (1829, 1830) published two works on
the geometrical description of crystals, influenced by the earlier works of
C.S. Weiss (1780-1856) on three main crystal forces governing crystal
formation. In his 1840 essay on the derivation of crystal shapes from the
general law of crystal formation Hermann established the notion of a
three-dimensional vectorial system of forces with rational coefficients, that
represent the interior crystal structure, regulate its formation, its shape and
physical behavior. In the Ausdehnungslehre 1844 (Paragraph 171) he finally
writes: I shall conclude this presentation by one of the most beautiful
applications which can be made of the science treated, i.e. the application to
crystal figures (Scholz, 1996). The geometry of crystals thus certainly
influenced the Ausdehnungslehre. In this paper we see how Grassmann's work
influenced Clifford's creation of geometric algebras, which in turn leads to a
new geometric description of crystal symmetry suitable for modern computer
algebra graphics.

categories: cond-mat.mtrl-sci cs.GR math.RA physics.hist-ph


title:
The Effects of Spectrograph Slit Modes on the Accuracy of Stellar Radial
  Velocity Measurement and Atmospheric Parameter Estimation

abstract:
  Spectrograph slit is conventionally used to enhance the spectral resolution
and manage how much light can be allowed to enter spectrograph. A narrower slit
provides a higher resolution but sacrifices efficiency of spectrograph and
results in a low signal to noise ratio (S/N) spectra product. We take
GuoShouJing telescope as an example and carry out a series of experiments to
study how its 2/3 slit mode affects the precision of stellar radial velocity
measurement and atmosphere parameters estimate. By transforming the resolution
and adding a Gaussian White Noise to the extremely high quality spectra from
the Sloan Digital Sky Survey, we generate synthetic stellar spectra of various
brightness with different S/Ns. Comparing the measurements on these noise added
spectra with the original high quality ones, we summarize the influences of the
2/3 slit mode on the measurement accuracy of stellar radial velocity and
atmospheric parameters.


title: Distilling single-photon entanglement from photon loss and decoherence

abstract:
  Single-photon entanglement may be the simplest type of entanglement but it is
of vice importance in quantum communication. Here we present a practical
protocol for distilling the single-photon entanglement from both photon loss
and decoherence. With the help of some local single photons, the probability of
single photon loss can be decreased and the less-entangled state can also be
recovered to maximally entangled state simultaneously.
  It only requires some linear optical elements which makes it feasible in
current experiment condition. This protocol might find applications in current
quantum communications based on the quantum repeaters.


title:
An efficient spectral method for computing dynamics of rotating
  two-component Bose--Einstein condensates via coordinate transformation

abstract:
  In this paper, we propose an efficient and accurate numerical method for
computing the dynamics of rotating two-component Bose--Einstein condensates
(BECs) which is described by coupled Gross--Pitaevskii equations (CGPEs) with
an angular momentum rotation term and an external driving field. By introducing
rotating Lagrangian coordinates, we eliminate the angular momentum rotation
term from the CGPEs, which allows us to develop an efficient numerical method.
Our method has spectral accuracy in all spatial dimensions and moreover it can
be easily implemented in practice. To examine its performance, we compare our
method with those reported in literature. Numerical results show that to
achieve the same accuracy, our method needs much shorter computing time. We
also applied our method to study the dynamic properties of rotating
two-component BECs. Furthermore, we generalize our method to solve the vector
Gross--Pitaevskii equations (VGPEs) which is used to study rotating
multi-component BECs.


title: Infrared face recognition: a literature review

abstract:
  Automatic face recognition (AFR) is an area with immense practical potential
which includes a wide range of commercial and law enforcement applications, and
it continues to be one of the most active research areas of computer vision.
Even after over three decades of intense research, the state-of-the-art in AFR
continues to improve, benefiting from advances in a range of different fields
including image processing, pattern recognition, computer graphics and
physiology. However, systems based on visible spectrum images continue to face
challenges in the presence of illumination, pose and expression changes, as
well as facial disguises, all of which can significantly decrease their
accuracy. Amongst various approaches which have been proposed in an attempt to
overcome these limitations, the use of infrared (IR) imaging has emerged as a
particularly promising research direction. This paper presents a comprehensive
and timely review of the literature on this subject.


title: Design Based Teaching for Science and Engineering Students

abstract:
  In this paper, we will explain a successfully proven lecturing method based
entirely on system design. Wireless communications will be used as an example
to explain this new teaching philosophy.


title: Complex one-frequency cocycles

abstract:
  We show that on a dense open set of analytic one-frequency complex valued
cocycles in arbitrary dimension Oseledets filtration is either dominated or
trivial. The underlying mechanism is different from that of the Bochi-Viana
Theorem for continuous cocycles, which links non-domination with discontinuity
of the Lyapunov exponent. Indeed, in our setting the Lyapunov exponents are
shown to depend continuously on the cocycle, even if the initial irrational
frequency is allowed to vary. On the other hand, this last property provides a
good control of the periodic approximations of a cocycle, allowing us to show
that domination can be characterized, in the presence of a gap in the Lyapunov
spectrum, by additional regularity of the dependence of sums of Lyapunov
exponents.


title: Photonic polarization gears for ultra-sensitive angular measurements

abstract:
  Quantum metrology bears a great promise in enhancing measurement precision,
but is unlikely to become practical in the near future. Its concepts can
nevertheless inspire classical or hybrid methods of immediate value. Here, we
demonstrate NOON-like photonic states of m quanta of angular momentum up to
m=100, in a setup that acts as a "photonic gear", converting, for each photon,
a mechanical rotation of an angle {\theta} into an amplified rotation of the
optical polarization by m{\theta}, corresponding to a "super-resolving" Malus'
law. We show that this effect leads to single-photon angular measurements with
the same precision of polarization-only quantum strategies with m photons, but
robust to photon losses. Moreover, we combine the gear effect with the quantum
enhancement due to entanglement, thus exploiting the advantages of both
approaches. The high "gear ratio" m boosts the current state-of-the-art of
optical non-contact angular measurements by almost two orders of magnitude.


title: On two higher Chow groups of schemes over a finite field

abstract:
  Given a separated scheme $X$ of finite type over a finite field, its higher
Chow groups $CH_{-1}(X, 1)$ and $CH_{-2}(X, 3)$ are computed explicitly.


title: Formation of Stable Magnetars from Binary Neutron Star Mergers

abstract:
  By performing fully general relativistic magnetohydrodynamic simulations of
binary neutron star mergers, we investigate the possibility that the end result
of the merger is a stable magnetar. In particular, we show that, for a binary
composed of two equal-mass neutron stars (NSs) of gravitational mass M~1.2 Msun
and equation of state similar to Shen et al. at high densities, the merger
product is a stable NS. Such NS is found to be differentially rotating and
ultraspinning with spin parameter J/M^2~0.86, where J is its total angular
momentum, and it is surrounded by a disk of ~0.1 Msun. While in our global
simulations the magnetic field is amplified by about two orders of magnitude,
local simulations have shown that hydrodynamic instabilities and the onset of
the magnetorotational instability could further increase the magnetic field
strength up to magnetar levels. This leads to the interesting possibility that,
for some NS mergers, a stable and magnetized NS surrounded by an accretion disk
could be formed. We discuss the impact of these new results for the emission of
electromagnetic counterparts of gravitational wave signals and for the central
engine of short gamma-ray bursts.


title:
Vesselness features and the inverse compositional AAM for robust face
  recognition using thermal IR

abstract:
  Over the course of the last decade, infrared (IR) and particularly thermal IR
imaging based face recognition has emerged as a promising complement to
conventional, visible spectrum based approaches which continue to struggle when
applied in the real world. While inherently insensitive to visible spectrum
illumination changes, IR images introduce specific challenges of their own,
most notably sensitivity to factors which affect facial heat emission patterns,
e.g. emotional state, ambient temperature, and alcohol intake. In addition,
facial expression and pose changes are more difficult to correct in IR images
because they are less rich in high frequency detail which is an important cue
for fitting any deformable model. We describe a novel method which addresses
these challenges. To normalize for pose and facial expression changes we
generate a synthetic frontal image of a face in a canonical, neutral facial
expression from an image of the face in an arbitrary pose and facial
expression. This is achieved by piecewise affine warping which follows active
appearance model (AAM) fitting. This is the first publication which explores
the use of an AAM on thermal IR images; we propose a pre-processing step which
enhances detail in thermal images, making AAM convergence faster and more
accurate. To overcome the problem of thermal IR image sensitivity to the
pattern of facial temperature emissions we describe a representation based on
reliable anatomical features. In contrast to previous approaches, our
representation is not binary; rather, our method accounts for the reliability
of the extracted features. This makes the proposed representation much more
robust both to pose and scale changes. The effectiveness of the proposed
approach is demonstrated on the largest public database of thermal IR images of
faces on which it achieved 100% identification, significantly outperforming
previous methods.


title:
Entanglement dynamics of a two-qubit system coupled individually to
  Ohmic baths

abstract:
  Developed originally for the Holstein polaron, the Davydov D1 ansatz is an
efficient, yet extremely accurate trial state for time-dependent variation of
the spin-boson model [J. Chem. Phys. 138, 084111 (2013)]. In this work, the
Dirac-Frenkel time-dependent variational procedure utilizing the Davydov D1
ansatz is implemented to study entanglement dynamics of two qubits under the
influence of two independent baths. The Ohmic spectral density is used without
the Born-Markov approximation or the rotating-wave approximation. In the strong
coupling regime finite-time disentanglement is always found to exist, while at
the intermediate coupling regime, the entanglement dynamics calculated by
Davydov D1 ansatz displays oscillatory behavior in addition to entanglement
disappearance and revival.


title:
Strong anisotropy in quasi-static magnetohydrodynamic turbulence for
  high interaction parameters

abstract:
  We simulate forced quasi-static magnetohydrodynamic turbulence and
investigate the anisotropy, energy spectrum, and energy flux of the flow,
specially for large interaction parameters ($N$). We show that the angular
dependence of the energy spectrum is well quantified using Legendre
polynomials. For large $N$, the energy spectrum is exponential. Our direct
computation of energy flux reveals an inverse cascade of energy at low
wavenumbers, similar to that in two-dimensional turbulence. We observe the flow
be two-dimensional (2D) for moderate $N$ ($N \sim 20$), and two-dimensional
three-component (2D-3C) type for $N \ge 27$. In our forced simulation, the
transition from 2D to 2D-3C occurs at higher value of $N$ than Favier et al.,
["On the two-dimensionalization of quasistatic magnetohydrodynamic turbulence,"
Phys. Fluids 22, 075104 (2010)] who employ decaying simulations.


title:
Determination of pion and kaon fragmentation functions including spin
  asymmetries data in a global analysis

abstract:
  We present new functional form of pion and kaon fragmentation functions up to
next-to-leading order obtained through a global fit to single-inclusive
electron-positron annihilation data and also employ, the semi-inclusive deep
inelastic scattering asymmetry data from HERMES and COMPASS to determine
fragmentation functions. Also we apply very recently electron-positron
annihilation data from BaBar and Belle at $\sqrt{s}=10.54$ GeV and
$\sqrt{s}=10.52$ GeV, respectively. In this analysis we consider the impression
of semi-inclusive deep inelastic scattering asymmetry data on the fragmentation
functions, where the produced hadrons of different electric charge are
identified. We break symmetry assumption between quark and anti-quark
fragmentation functions for favored partons by using the asymmetry data. The
results of our analysis are in good agreement with electron-positron
annihilation data and also with all the semi-inclusive deep inelastic
scattering asymmetry data. Also we apply the obtained fragmentation functions
to predict the scaled-energy distribution of $\pi^+/K^+$ inclusively produced
in top-quark decays at next-to-leading order using the zero-mass
variable-flavor-number scheme exploiting the universality and scaling
violations of fragmentation functions.


title:
Scheme for proton-driven plasma-wakefield acceleration of positively
  charged particles in a hollow plasma channel

abstract:
  A new scheme for accelerating positively charged particles in a plasma
wakefield accelerator is proposed. If the proton drive beam propagates in a
hollow plasma channel, and the beam radius is of order of the channel width,
the space charge force of the driver causes charge separation at the channel
wall, which helps to focus the positively charged witness bunch propagating
along the beam axis. In the channel, the acceleration buckets for positively
charged particles are much larger than in the blowout regime of the uniform
plasma, and stable acceleration over long distances is possible. In addition,
phasing of the witness with respect to the wave can be tuned by changing the
radius of the channel to ensure the acceleration is optimal. Two dimensional
simulations suggest that, for proton drivers likely available in future,
positively charged particles can be stably accelerated over 1 km with the
average acceleration gradient of 1.3 GeV/m.


title:
Temporal Variation of the Fundamental Physical Quantities in a Static
  Universe

abstract:
  The standard interpretation of the observed redshifted spectra and
luminosities towards distant astrophysical objects is that the universe is
expanding, an inference which is found to be consistent with other cosmological
probes as well. Clearly, only the interpretation of {\it dimensionless}
quantities does not depend on the physical unit system as opposed to {\it
dimensional} quantities whose dynamics does depend on the arbitrarily chosen
system of units. All that redshift or luminosity measurements really indicate
is that cosmological scales expand {\it relative} to local scales. An
alternative choice of a ruler could be the distance between two remote
galaxies, in which case local distances have to decrease with time (with
respect to the ruler) for consistency with redshift measurements. In the latter
choice, microscopic scales such as the Compton wavelength, or the Planck
length, decrease with time, and consequently fundamental `constants' such as
the Planck constant, speed of light, Newton gravitational constant, and
particle masses, are spacetime-dependent. To illustrate this fundamental
indeterminacy we construct an alternative interpretation to the expanding model
that is characterized by a static metric with time-dependent fundamental
physical quantities. The two alternative descriptions, are referred to as the
`expanding' and `static' space perspectives, respectively. Cosmological
inflation, recombination, and all other early universe processes are unaltered;
the `expanding' and `static' perspectives are associated with exactly the same
cosmological model.


title: Real Clifford Algebra Cl(n,0), n=2,3(mod 4) Wavelet Transform

abstract:
  We show how for $n=2,3 (\mod 4)$ continuous Clifford (geometric) algebra (GA)
$Cl_n$-valued admissible wavelets can be constructed using the similitude group
$SIM(n)$. We strictly aim for real geometric interpretation, and replace the
imaginary unit $i \in \C$ therefore with a GA blade squaring to $-1$.
Consequences due to non-commutativity arise. We express the admissibility
condition in terms of a $Cl_{n}$ Clifford Fourier Transform and then derive a
set of important properties such as dilation, translation and rotation
covariance, a reproducing kernel, and show how to invert the Clifford wavelet
transform. As an example, we introduce Clifford Gabor wavelets. We further
invent a generalized Clifford wavelet uncertainty principle.


title:
Scale Invariant Gravitation and Unambiguous Interpretation of Physical
  Theories

abstract:
  Our conventional system of physical units is based on local or microscopic
{\it dimensional} quantities which are {\it defined}, for convenience or
otherwise aesthetic reasons, to be spacetime-independent. A more general choice
of units may entail variation of fundamental physical quantities (`constants')
in spacetime. The theory of gravitation generally does not satisfy conformal
symmetry, i.e. it is not invariant to local changes of the unit of length.
Consequently, the {\it dimensionless} action associated with the
Einstein-Hilbert action ($S_{EH}$) of gravitation, $\phi_{EH}=S_{EH}/\hbar$, is
not invariant to local changes of the length unit; clearly an unsatisfactory
feature for a dimensionless quantity. Here we amend the phase by adding extra
terms that account for spacetime variation of the physical `constants' in
arbitrary unit systems. In such a unit system, all dimensional quantities are
implicitly spacetime-dependent; this is achieved by a conformal transformation
of the metric augmented by appropriate metric-dependent rescalings of the
dimensional quantities. The resulting modified dimensionless action is
scale-invariant, i.e. independent of the unit system, as desired. The deep
connection between gravitation, dimensionless physical quantities, and quantum
mechanics, is elucidated and the implicit ambiguity in interpretations of
dimensional quantities is underlined.


title: On Isosystolic Inequalities for T^n, RP^n, and M^3

abstract:
  If a closed smooth n-manifold M admits a finite cover whose Z/2Z-cohomology
has the maximal cup-length, then for any riemannian metric g on M, we show that
the systole Sys(M,g) and the volume Vol(M,g) of the riemannian manifold (M,g)
are related by the following isosystolic inequality: Sys(M,g)^n \leq n!
Vol(M,g). The inequality can be regarded as a generalization of Burago and
Hebda's inequality for closed essential surfaces and as a refinement of Guth's
inequality for closed n-manifolds whose Z/2Z-cohomology has the maximal
cup-length. We also establish the same inequality in the context of possibly
non-compact manifolds under a similar cohomological condition. The inequality
applies to (i) T^n and all other compact euclidean space forms, (ii) RP^n and
many other spherical space forms including the Poincar\'e dodecahedral space,
and (iii) most closed essential 3-manifolds including all closed aspherical
3-manifolds.


title:
A BOINC based, citizen-science project for pixel Spectral Energy
  Distribution fitting of resolved galaxies in multi-wavelength surveys

abstract:
  In this work we present our experience from the first year of theSkyNet
Pan-STARRS1 Optical Galaxy Survey (POGS) project. This citizen-scientist driven
research project uses the Berkeley Open Infrastructure for Network Computing
(BOINC) middleware and thousands of Internet-connected computers to measure the
resolved galactic structural properties of ~100,000 low redshift galaxies. We
are combining the spectral coverage of GALEX, Pan-STARRS1, SDSS, and WISE to
generate a value-added, multi-wavelength UV-optical-NIR galaxy atlas for the
nearby Universe. Specifically, we are measuring physical parameters (such as
local stellar mass, star formation rate, and first-order star formation
history) on a resolved pixel-by-pixel basis using spectral energy distribution
(SED) fitting techniques in a distributed computing mode.


title:
Statistical Denoising for single molecule fluorescence microscopic
  images

abstract:
  Single molecule fluorescence microscopy is a powerful technique for
uncovering detailed information about biological systems, both in vitro and in
vivo. In such experiments, the inherently low signal to noise ratios mean that
accurate algorithms to separate true signal and background noise are essential
to generate meaningful results. To this end, we have developed a new and robust
method to reduce noise in single molecule fluorescence images by using a
Gaussian Markov Random Field (GMRF) prior in a Bayesian framework. Two
different strategies are proposed to build the prior - an intrinsic GMRF, with
a stationary relationship between pixels and a heterogeneous intrinsic GMRF,
with a differently weighted relationship between pixels classified as molecules
and background. Testing with synthetic and real experimental fluorescence
images demonstrates that the heterogeneous intrinsic GMRF is superior to other
conventional de-noising approaches.


title: Clifford (Geometric) Algebra Wavelet Transform

abstract:
  While the Clifford (geometric) algebra Fourier Transform (CFT) is global, we
introduce here the local Clifford (geometric) algebra (GA) wavelet concept.
  We show how for $n=2,3 (\mod 4)$ continuous $Cl_n$-valued admissible wavelets
can be constructed using the similitude group $SIM(n)$. We strictly aim for
real geometric interpretation, and replace the imaginary unit $i \in \C$
therefore with a GA blade squaring to $-1$. Consequences due to
non-commutativity arise. We express the admissibility condition in terms of a
$Cl_{n}$ CFT and then derive a set of important properties such as dilation,
translation and rotation covariance, a reproducing kernel, and show how to
invert the Clifford wavelet transform. As an explicit example, we introduce
Clifford Gabor wavelets. We further invent a generalized Clifford wavelet
uncertainty principle. Extensions of CFTs and Clifford wavelets to $Cl_{0,n'},
n' = 1,2 (\mod 4)$ appear straight forward.
  Keywords: Clifford geometric algebra, Clifford wavelet transform,
multidimensional wavelets, continuous wavelets, similitude group.


title:
Preprocess the Photospheric Vector Magnetograms for NLFFF Extrapolation
  using a Potential Field Model and an Optimization Method

abstract:
  Numerical reconstruction/extrapolation of coronal nonlinear force-free
magnetic field (NLFFF) usually takes the photospheric vector magnetogram as
input at the bottom boundary. Magnetic field observed at the photosphere,
however, contains force which is in conflict with the fundamental assumption of
the force-free model and measurement noise which is unfavorable for practical
computation. Preprocessing of the raw magnetogram has been proposed by
Wiegelmann, Inhester, and Sakurai (2006) to remove the force and noise for
providing better input for NLFFF modeling. In this paper we develop a new code
of magnetogram preprocessing which is consistent with our extrapolation method
CESE-MHD-NLFFF (Jiang, Feng, and Xiang, 2012; Jiang and Feng, 2012). Basing on
a magnetic-splitting rule that a magnetic field can be split into a potential
field part and a non-potential part, we split the magnetogram and deal with the
two parts separately. Preprocessing of the magnetogram's potential part is
based on a numerical potential field model, and the non-potential part is
preprocessed using the similar optimization method of Wiegelmann et al (2006).
The code is applied to the SDO/HMI data and results show that the method can
remove efficiently the force and noise and improve the quality of
extrapolation.


title: The Strength of Regolith and Rubble Pile Asteroids

abstract:
  We explore the hypothesis that, due to small van der Waals forces between
constituent grains, small rubble pile asteroids have a small but non-zero
cohesive strength. The nature of this model predicts that the cohesive strength
should be constant independent of asteroid size, which creates a scale
dependence with relative strength increasing as size decreases. This model
counters classical theory that rubble pile asteroids should behave as
scale-independent cohesionless collections of rocks. We explore a simple model
for asteroid strength that is based on these weak forces, validate it through
granular mechanics simulations and comparisons with properties of lunar
regolith, and then explore its implications and ability to explain and predict
observed properties of small asteroids in the NEA and Main Belt populations,
and in particular of asteroid 2008 TC3. One conclusion is that the population
of rapidly rotating asteroids could consist of both distributions of smaller
grains (i.e., rubble piles) and of monolithic boulders.


title:
Generalized second law at linear order for actions that are functions of
  Lovelock densities

abstract:
  In this article we consider the second law of black holes (and other causal
horizons) in theories where the gravitational action is an arbitrary function
of the Lovelock densities. We show that there exists an entropy which increases
locally, for linearized perturbations to regular Killing horizons. In addition
to a classical increase theorem, we also prove a generalized second law for
semiclassical, minimally-coupled matter fields.


title: Metric Description of Defects in Amorphous Materials

abstract:
  Classical elasticity is concerned with bodies that can be modeled as smooth
manifolds endowed with a reference metric that represents local equilibrium
distances between neighboring material elements. The elastic energy associated
with a configuration of a body in classical elasticity is the sum of local
contributions that arise from a discrepancy between the actual metric and the
reference metric. In contrast, the modeling of defects in solids has
traditionally involved extra structure on the material manifold, notably
torsion to quantify the density of dislocations and non-metricity to represent
the density of point defects. We show that all the classical defects can be
described within the framework of classical elasticity using tensor fields that
only assume a metric structure. Specifically, bodies with singular defects can
be viewed as affine manifolds; both disclinations and dislocations are captured
by the monodromy that maps curves that surround the loci of the defects into
affine transformations. Finally, we show that two dimensional defects with
trivial monodromy are purely local in the sense that if we remove from the
manifold a compact set that contains the locus of the defect, the punctured
manifold can be isometrically embedded in Euclidean space.


title:
Strong constraints on magnetized white dwarfs surpassing the
  Chandrasekhar mass limit

abstract:
  We show that recently proposed white dwarf models with masses well in excess
of the Chandrasekhar limit, based on modifying the equation of state by a
super-strong magnetic field in the centre, are very far from equilibrium
because of the neglect of Lorentz forces. An upper bound on the central
magnetic fields, from a spherically averaged hydrostatic equation, is much
smaller than the values assumed. Robust estimates of the Lorentz forces are
also made without assuming spherical averaging. These again bear out the
results obtained from a spherically averaged model. In our assessment, these
estimates rule out the possibility that magnetic tension could change the
situation in favor of larger magnetic fields. We conclude that such
super-Chandrasekhar models are unphysical and exploration of their
astrophysical consequences is premature.
  Erratum : We correct certain numerical estimates made in our paper. This
correction however does not alter the conclusion that when Lorentz forces are
taken into account the super-massive white dwarf models, obtained simply by
modifying the equation of state in presence of a super-strong magnetic field in
the centre, fail to be in equilibrium.


title:
Ground Penetrating Radar: Analysis of point diffractors for modeling and
  inversion

abstract:
  The three electromagnetic properties appearing in Maxwell's equations are
dielectric permittivity, electrical conductivity and magnetic permeability. The
study of point diffractors in a homogeneous, isotropic, linear medium suggests
the use of logarithms to describe the variations of electromagnetic properties
in the earth. A small anomaly in electrical properties (permittivity and
conductivity) responds to an incident electromagnetic field as an electric
dipole, whereas a small anomaly in the magnetic property responds as a magnetic
dipole. Neither property variation can be neglected without justification.
Considering radiation patterns of the different diffracting points, diagnostic
interpretation of electric and magnetic variations is theoretically feasible
but is not an easy task using Ground Penetrating Radar. However, using an
effective electromagnetic impedance and an effective electromagnetic velocity
to describe a medium, the radiation patterns of a small anomaly behave
completely differently with source-receiver offset. Zero-offset reflection data
give a direct image of impedance variations while large-offset reflection data
contain information on velocity variations.


title:
Saturated hydraulic conductivity determined by on ground mono-offset
  Ground-Penetrating Radar inside a single ring infiltrometer

abstract:
  In this study we show how to use GPR data acquired along the infiltration of
water inside a single ring infiltrometer to inverse the saturated hydraulic
conductivity. We used Hydrus-1D to simulate the water infiltration. We
generated water content profiles at each time step of infiltration, based on a
particular value of the saturated hydraulic conductivity, knowing the other van
Genuchten parameters. Water content profiles were converted to dielectric
permittivity profiles using the Complex Refractive Index Method relation. We
then used the GprMax suite of programs to generate radargrams and to follow the
wetting front using arrival time of electromagnetic waves recorded by a
Ground-Penetrating Radar (GPR). Theoretically, the 1D time convolution between
reflectivity and GPR signal at any infiltration time step is related to the
peak of the reflected amplitude recorded in the corresponding trace in the
radargram. We used this relation ship to invert the saturated hydraulic
conductivity for constant and falling head infiltrations. We present our method
on synthetic examples and on two experiments carried out on sand soil. We
further discuss on the uncertainties on the retrieved saturated hydraulic
conductivity computed by our algorithm from the van Genuchten parameters.


title:
The complex time behaviour of the microquasar GRS 1915+105 in the
  \rho-class observed with BeppoSAX. III: The hard X-ray delay and limit cycle
  mapping

abstract:
  The microquasar GRS1915+105 was observed by BeppoSAX in October 2000 for
about ten days while the source was in \rho-mode, which is characterized by a
quasi-regular type I bursting activity. This paper presents a systematic
analysis of the delay of the hard and soft X-ray emission at the burst peaks.
The lag, also apparent from the comparison of the [1.7-3.4] keV light curves
with those in the [6.8-10.2] keV range, is evaluated and studied as a function
of time, spectral parameters, and flux. We apply the limit cycle mapping
technique, using as independent variables the count rate and the mean photon
rate. The results using this technique were also cross-checked using a more
standard approach with the cross-correlation methods. Data are organized in
runs, each relative to a continuous observation interval. The detected
hard-soft delay changes in the course of the pointing from about 3 s to about
10 s and presents a clear correlation with the baseline count rate.


title: Angles between subspaces

abstract:
  We first review the definition of the angle between subspaces and how it is
computed using matrix algebra. Then we introduce the Grassmann and Clifford
algebra description of subspaces. The geometric product of two subspaces yields
the full relative angular information in an explicit manner. We explain and
interpret the result of the geometric product of subspaces gaining thus full
access to the relative orientation information.


title:
Enhancing Tourism Destination Accessibility in Developing Countries
  through Virtual Worlds

abstract:
  The problem of destination accessibility is a vital concern in the
sustainable tourism development in the emerging regions due to the increasing
numbers of tourism business growth in the recent times. Tourism is one of the
potential foreign exchange earning sectors, which place sustainability as one
of the main success metrics for benchmarking the overall development of the
industry. On the other hand, there are several destinations, which are
inaccessible to tourists due to several reasons. Underutilization of potential
destinations in both pre purchase and consumption stages is a strategic
disadvantage for emerging countries on leading their tourism industry towards
sustainability. This research embarks on a content analysis of second life
based tourism groups and places. Requirement of a virtual world model to
increase the destination accessibility of tourism products has been outlined.
The model has to be designed with visual and auditory experience to tourists.
The model is expected to enhance the accessibility of destinations for users of
different categories.


title:
Upsilon suppression at energies available at the BNL Relativistic Heavy
  Ion Collider and at the CERN Large Hadron Collider in a modified color
  screening scenario

abstract:
  The suppression of heavy quarkonia e.g. $J/\psi$, $\Upsilon$ etc. is
considered as a suitable probe to identify the nature of the matter created in
heavy ion collisions. Recently we have presented a modified colour screening
model for $J/\psi$ suppression in the quark gluon plasma (QGP) using
quasiparticle model as the equation of state. In this paper, we extend our
model to calculate the anomalous suppression of various states of $\Upsilon$
arising due to QGP medium alone. We obtain the suppression patterns of
different bottomonia states with respect to centrality at various available
collision energies and compare them with the available experimental data.


title: A Generalized Channel Coding Theory for Distributed Communication

abstract:
  This paper presents generalized channel coding theorems for a time-slotted
distributed communication system where a transmitter-receiver pair is
communicating in parallel with other transmitters. Assume that the channel code
of each transmitter is chosen arbitrarily in each time slot. The coding choice
of a transmitter is denoted by a code index parameter, which is known neither
to other transmitters nor to the receiver. Fundamental performance limitation
of the system is characterized using an achievable region defined in the space
of the code index vectors. As the codeword length is taken to infinity, for all
code index vectors inside the region, the receiver will decode the message
reliably, while for all code index vectors outside the region, the receiver
will report a collision reliably. A generalized system error performance
measure is defined as the weighted sum of probabilities of different types of
communication error events. Assume that the receiver chooses an "operation
region" and intends to decode the message if the code index vector is inside
the operation region. Achievable bounds on the tradeoff between the operation
region and the generalize error performance measure are obtained under the
assumption of a finite codeword length.


title: Free energy generalization of the Peierls potential in iron

abstract:
  In body-centered cubic (bcc) crystals, ${1}{2}111$ screw dislocations exhibit
high intrinsic lattice friction as a consequence of their non-planar core
structure, which results in a periodic energy landscape known as the Peierls
potential, $U_P$. The main features determining plastic flow, including its
stress and temperature dependences, can be derived directly from this
potential, hence its importance. In this Letter, we use thermodynamic
integration to provide a full thermodynamic extension of $U_P$ for bcc Fe. We
compute the Peierls free energy path as a function of stress and temperature
and show that the critical stress vanishes at 700K, supplying the qualitative
elements that explain plastic behavior in the athermal limit.


title: Levitation of a drop over a moving surface

abstract:
  We investigate the levitation of a drop gently deposited onto the inner wall
of a rotating hollow cylinder. For a sufficient velocity of the wall, the drop
steadily levitates over a thin air film and reaches a stable angular position
in the cylinder, where the drag and lift balance the weight of the drop.
Interferometric measurement yields the three-dimensional (3D) air film
thickness under the drop and reveals the asymmetry of the profile along the
direction of the wall motion. A two-dimensional (2D) model is presented which
explains the levitation mechanism, captures the main characteristics of the air
film shape and predicts two asymptotic regimes for the film thickness $h_0$:
For large drops $h_0\sim\ca^{2/3}\kappa_b^{-1}$, as in the Bretherton problem,
where $\ca$ is the capillary number based on the air viscosity and $\kappa_b$
is the curvature at the bottom of the drop. For small drops
$h_0\sim\ca^{4/5}(a\kappa_b)^{4/5}\kappa_b^{-1}$, where $a$ is the capillary
length.


title:
Electron-doped organics: Charge-disproportionate insulators and
  Hubbard-Fr\"ohlich metals

abstract:
  Several examples of metallic electron doped polycyclic aromatic hydrocarbons
(PAHs) molecular crystals have recently been experimentally proposed. Some of
them have superconducting components, but most other details are still unknown
beginning with structure and the nature of metallicity. We carried out
ab-initio density functional calculations for La-Phenanthrene (La-PA), here
meant to represent a generic case of three-electron doping, to investigate
structure and properties of a conceptually simple case. To our surprise we
found first of all that the lowest energy state is not metallic but band
insulating, with a disproportionation of two inequivalent PA molecular ions and
a low P1 symmetry, questioning the common assumption that three electrons will
automatically metallize a PAH crystal. Our best metallic structure is
metastable and slightly higher in energy, and retains equivalent PA ions and a
higher P21 symmetry -- the same generally claimed for metallic PAHs. We show
that a "dimerizing" periodic distortion opens very effectively a gap in place
of a symmetry related degeneracy of all P21 structures near the Fermi level,
foreshadowing a possible role of that special intermolecular phonon in
superconductivity of metallic PAHs. A Hubbard-Frohlich model describing that
situation is formulated for future studies.


title:
The Effective field theory of 2+1 dimensional topological insulator in
  the presence of Rashba spin-orbit interaction

abstract:
  2+1 dimensional topological insulator described by the Kane-Mele model in the
presence of Rashba spin-orbit interaction is considered. The effective action
of the external fields coupled to electromagnetic and spin degrees of freedom
is accomplished within this model. The Hamiltonian methods are adopted to
provide the coefficients appearing in the action. It is demonstrated
straightforwardly that the coefficients of the Chern-Simons terms are given by
the first Chern number attained through the related non-Abelian Berry gauge
field. The effective theory which we obtain is in accord with the existence of
the spin Hall phase where the value of the spin Hall conductivity is very close
to the quantized one.

categories: cond-mat.mes-hall hep-th math-ph math.MP


title:
Reconstruction of f(T) and f(R) gravity according to (m,n)-type
  holographic dark energy

abstract:
  Motivated by earlier works on reconstruction of modified gravity models with
dark energy components, we extend them by considering a newly proposed model of
(m, n)- type of holographic dark energy for two models of modified gravity,
f(R) and f(T) theories, where R and T represent Ricci scalar and torsion scalar
respectively. Specifically we reconstruct the two later gravity models and
discuss their viability and cosmography. The obtained gravity models are ghost
free, compatible with local solar system tests and describe effective positive
gravitational constant.


title: Three solutions to discrete anisotropic problems with two parameters

abstract:
  In this note we derive a type of a three critical point theorem which we
further apply to investigate the multiplicity of solutions to discrete
anisotropic problems with two parameters.


title: Delivering IT as A Utility- A Systematic Review

abstract:
  Utility Computing has facilitated the creation of new markets that has made
it possible to realize the long held dream of delivering IT as a Utility. Even
though utility computing is in its nascent stage today, the proponents of
utility computing envisage that it will become a commodity business in the
upcoming time and utility service providers will meet all the IT requests of
the companies. This paper takes a cross-sectional view at the emergence of
utility computing along with different requirements needed to realize utility
model. It also surveys the current trends in utility computing highlighting
diverse architecture models aligned towards delivering IT as a utility.
Different resource management systems for proficient allocation of resources
have been listed together with various resource scheduling and pricing
strategies used by them. Further, a review of generic key perspectives closely
related to the concept of delivering IT as a Utility has been taken citing the
contenders for the future enhancements in this technology in the form of Grid
and Cloud Computing.


title:
Synchrotron and inverse-Compton emission from radio galaxies with
  non-uniform magnetic field and electron distributions

abstract:
  I investigate the effect of non-uniform magnetic fields in the extended
structures of radio galaxies on the observed synchrotron and inverse-Compton
emission. On the assumption of an isotropic field, with a given power spectrum
and a Gaussian distribution of the Cartesian components of the magnetic field
strength, I derive a simple integral that can be used numerically to calculate
the synchrotron emissivity from any electron population. In the case of
power-law spectra, I show that it is possible to estimate the difference
between the synchrotron emissivity from a region with such a field and that
from the commonly assumed arrangement where $B$ is constant everywhere, though
fully tangled, and that this difference is small, though it increases if the
electron energy density scales with the field. An aged electron spectrum in
such a field produces a characteristic curved synchrotron spectrum which
differs significantly from the classical Jaffe-Perola spectrum, and I discuss
some effects that this might have on standard spectral age fitting. Finally, I
show that inverse-Compton scattering of the cosmic microwave background is only
moderately affected by such a field structure, with the effects becoming more
important if the electrons follow the field. Magnetic-field estimates in the
literature from combined synchrotron and inverse-Compton modelling will give
reasonable estimates of the mean magnetic field energy density if the field is
non-uniform but isotropic.


title:
The equivariant $K$-theory and cobordism rings of divisive weighted
  projective spaces

abstract:
  We apply results of Harada, Holm and Henriques to prove that the Atiyah-Segal
equivariant complex $K$-theory ring of a divisive weighted projective space
(which is singular for nontrivial weights) is isomorphic to the ring of
integral piecewise Laurent polynomials on the associated fan. Analogues of this
description hold for other complex-oriented equivariant cohomology theories, as
we confirm in the case of homotopical complex cobordism, which is the universal
example. We also prove that the Borel versions of the equivariant $K$-theory
and complex cobordism rings of more general singular toric varieties, namely
those whose integral cohomology is concentrated in even dimensions, are
isomorphic to rings of appropriate piecewise formal power series. Finally, we
confirm the corresponding descriptions for any smooth, compact, projective
toric variety, and rewrite them in a face ring context. In many cases our
results agree with those of Vezzosi and Vistoli for algebraic $K$-theory,
Anderson and Payne for operational $K$-theory, Krishna and Uma for algebraic
cobordism, and Gonzalez and Karu for operational cobordism; as we proceed, we
summarize the details of these coincidences.


title: Dark Sector Coupling Bends the Superclusters

abstract:
  The galaxy clusters exhibit noticeably anisotropic pattern in their
clustering, which is vividly manifested by the presence of rich filament-like
superclusters. The more anisotropic the clustering of galaxy clusters is, the
more straight the rich filament-like superclusters become. Given that the
degree of the anisotropy in the largest-scale clustering depends sensitively on
the nature of dark energy, the supercluster straightness may play a
complimentary role in testing dynamic dark energy models. Here we focus on the
coupled dark energy (cDE) models which assume the existence of dark sector
coupling between scalar field dark energy and nonbaryonic dark matter.
Determining the spines of the superclusters identified in the publicly
available group catalogs from the CODECS (COupled Dark Energy Cosmological
Simulations) for four different cDE models as well as for the LCDM model, we
quantify the straightness of each supercluster as the spatial extent of its
spine per member cluster where a supercluster spine represents the main stem of
the minimal spanning tree constructed out of the member clusters. It is shown
that the dark sector coupling plays a role in making the supercluster less
straight relative to the LCDM case and that in a cDE model with supergravity
potential the superclusters are least straight. We also find that the
difference in the degree of the supercluster straightness between the cDE and
the LCDM cases increases with redshifts. A physical interpretation of our
result as well as its cosmological implication are discussed.


title: NGC 1252: a high altitude, metal poor open cluster remnant

abstract:
  If stars form in clusters but most stars belong to the field, understanding
the details of the transition from the former to the latter is imperative to
explain the observational properties of the field. Aging open clusters are one
of the sources of field stars. The disruption rate of open clusters slows down
with age but, as an object gets older, the distinction between the remaining
cluster or open cluster remnant (OCR) and the surrounding field becomes less
and less obvious. As a result, finding good OCR candidates or confirming the
OCR nature of some of the best candidates still remains elusive. One of these
objects is NGC 1252, a scattered group of about 20 stars in Horologium. Here we
use new wide-field photometry in the UBVI pass-bands, proper motions from the
Yale/San Juan SPM 4.0 catalogue and high resolution spectroscopy concurrently
with results from N-body simulations to decipher NGC 1252's enigmatic
character. Spectroscopy shows that most of the brightest stars in the studied
area are chemically, kinematically and spatially unrelated to each other.
However, after analysing proper motions, we find one relevant kinematic group.
This sparse object is relatively close (about 1 kpc), metal poor and is
probably not only one of the oldest clusters (3 Gyr) within 1.5 kpc from the
Sun but also one of the clusters located farthest from the disc, at an altitude
of nearly -900 pc. That makes NGC 1252 the first open cluster that can be truly
considered a high Galactic altitude OCR: an unusual object that may hint at a
star formation event induced on a high Galactic altitude gas cloud. TW Hor and
HD 20286 are unlikely to be part of NGC 1252. NGC 1252 17 is identified as an
unrelated, Population II cannonball star moving at about 400 km/s.


title: Magnetic Fields of Neutron Stars : The AMXP Connection

abstract:
  This article briefly reviews our current understanding (or lack thereof) of
the evolution of magnetic fields in neutron stars, with an emphasis on the
binary systems. In particular, the significance of the newly emerging
population of accreting millisecond pulsars (AMXP) is discussed.


title:
A geometric realization of the periodic discrete Toda lattice and its
  tropicalization

abstract:
  An explicit formula concerning curve intersections equivalent to the time
evolution of the periodic discrete Toda lattice is presented. First, the time
evolution is realized as a point addition on a hyperelliptic curve, which is
the spectral curve of the periodic discrete Toda lattice, then the point
addition is translated into curve intersections. Next, it is shown that the
curves which appear in the curve intersections are explicitly given by using
the conserved quantities of the periodic discrete Toda lattice. Finally, the
formulation is lifted to the framework of tropical geometry, and a tropical
geometric realization of the periodic box-ball system is constructed via
tropical curve intersections.


title: Crystal planes and reciprocal space in Clifford geometric algebra

abstract:
  This paper discusses the geometry of $k$D crystal cells given by $(k+1)$
points in a projective space $\R^{n+1}$. We show how the concepts of
barycentric and fractional (crystallographic) coordinates, reciprocal vectors
and dual representation are related (and geometrically interpreted) in the
projective geometric algebra $Cl(\R^{n+1})$ (see Grassmann H., edited by Engel
F., Die Ausdehnungslehre von 1844 und die Geom. Anal., vol. 1, part 1, Teubner:
Leipzig, 1894.) and in the conformal algebra $Cl(\R^{n+1,1})$. The
crystallographic notions of $d$-spacing, phase angle, structure factors,
conditions for Bragg reflections, and the interfacial angles of crystal planes
are obtained in the same context.
  Keywords: Clifford geometric algebra, crystallography, reciprocal space,
$d$-spacing, phase angle, structure factors, Bragg reflections, interfacial
angles


title:
Explicit Semi-invariants and Integrals of the Full Symmetric sl(n) Toda
  Lattice

abstract:
  We show how to construct semi-invariants and integrals of the full symmetric
sl(n) Toda lattice for all n. Using the Toda equations for the Lax eigenvector
matrix we prove the existence of semi-invariants which are homogeneous
coordinates in the corresponding projective spaces. Then we use these
semi-invariants to construct the integrals. The existence of additional
integrals which constitute a full set of independent non-involutive integrals
was known but the chopping and Kostant procedures have crucial computational
complexities already for low-rank Lax matrices and are practically not
applicable for higher ranks. Our new approach solves this problem and results
in simple explicit formulae for the full set of independent semi-invariants and
integrals expressed in terms of the Lax matrix and its eigenvectors, and of
eigenvalue matrices for the full symmetric sl(n) Toda lattice.


title:
Mixtures of anisotropic and spherical colloids: Phase behavior,
  confinement, percolation phenomena and kinetics

abstract:
  Purely entropic systems such as suspensions of hard rods, platelets and
spheres show rich phase behavior. Rods and platelets have successfully been
used as models to predict the equilibrium properties of liquid crystals for
several decades. Over the past years hard particle models have also been
studied in the context of non-equilibrium statistical mechanics, in particular
regarding the glass transition, jamming, sedimentation and crystallization.
Recently suspensions of hard anisotropic particles also moved into the focus of
materials scientists who work on conducting soft matter composites. An
insulating polymer resin that is mixed with conductive filler particles becomes
conductive when the filler percolates. In this context the mathematical topic
of connectivity percolation finds an application in modern nano-technology. In
this article, we briefly review recent work on the phase behavior, confinement
effects, percolation transition and phase transition kinetics in hard particle
models. In the first part, we discuss the effects that particle anisotropy and
depletion have on the percolation transition. In the second part, we present
results on the kinetics of the liquid-to-crystal transition in suspensions of
spheres and of ellipsoids.


title: An Extended Discrete Hardy-Littlewood-Sobolev Inequality

abstract:
  Hardy-Littlewood-Sobolev (HLS) Inequality fails in the "critical" case:
\mu=n. However, for discrete HLS, we can derive a finite form of HLS inequality
with logarithm correction for a critical case: \mu=n and p=q, by limiting the
inequality on a finite domain. The best constant in the inequality and its
corresponding solution, the optimizer, are studied. First, we obtain a sharp
estimate for the best constant. Then for the optimizer, we prove the uniqueness
and a symmetry property. This is achieved by proving that the corresponding
Euler-Lagrange equation has a unique nontrivial nonnegative critical point.
Also, by using a discrete version of maximum principle, we prove certain
monotonicity of this optimizer.


title:
OPS-QFTs: A new type of quaternion Fourier transforms based on the
  orthogonal planes split with one or two general pure quaternions

abstract:
  We explain the orthogonal planes split (OPS) of quaternions based on the
arbitrary choice of one or two linearly independent pure unit quaternions
$f,g$. Next we systematically generalize the quaternionic Fourier transform
(QFT) applied to quaternion fields to conform with the OPS determined by $f,g$,
or by only one pure unit quaternion $f$, comment on their geometric meaning,
and establish inverse transformations.
  Keywords: Clifford geometric algebra, quaternion geometry, quaternion Fourier
transform, inverse Fourier transform, orthogonal planes split


title:
Accurate Indoor Localization Using Acoustic Direction Finding via Smart
  Phones

abstract:
  We propose and implement a novel indoor localization scheme, Swadloon, built
upon an accurate acoustic direction finding. Swadloon leverages sensors of the
smartphone without the requirement of any specialized devices. The scheme
Swadloon does not rely on any fingerprints and is very easy to use: a user only
needs to shake the phone for a short duration before walking and localization.
Our Swadloon design exploits a key observation: the relative shift and velocity
of the phone-shaking movement corresponds to the subtle phase and frequency
shift of the Doppler effects experienced in the received acoustic signal by the
phone. A novel method is designed to derive the direction from the phone to the
acoustic source by combining the velocity calculated from the subtle Doppler
shift with the one from the inertial sensors of the phone. Then a real-time
precise localization and tracking is enabled by using a few anchor speakers
with known locations. Major challenges in implementing Swadloon are to measure
the frequency shift precisely and to estimate the shaking velocity accurately
when the speed of phone-shaking is low and changes arbitrarily. We propose
rigorous methods to address these challenges, then design and deploy Swadloon
in several floors of an indoor building each with area about 2000m^2. Our
extensive experiments show that the mean error of direction finding is around
2.1 degree when the acoustic source is within the range of 32m. For indoor
localization, the 90-percentile errors are under 0.92m, while the maximum error
is 1.73m and the mean is about 0.5m. For real-time tracking, the errors are
within 0.4m for walks of 51m.


title: On the accumulation of deleterious mutations during range expansions

abstract:
  We investigate the effect of spatial range expansions on the evolution of
fitness when beneficial and deleterious mutations co-segregate. We perform
individual-based simulations of a uniform linear habitat and complement them
with analytical approximations for the evolution of mean fitness at the edge of
the expansion. We find that deleterious mutations accumulate steadily on the
wave front during range expansions, thus creating an expansion load. Reduced
fitness due to the expansion load is not restricted to the wave front but
occurs over a large proportion of newly colonized habitats. The expansion load
can persist and represent a major fraction of the total mutation load thousands
of generations after the expansion. Our results extend qualitatively and
quantitatively to two-dimensional expansions. The phenomenon of expansion load
may explain growing evidence that populations that have recently expanded,
including humans, show an excess of deleterious mutations. To test the
predictions of our model, we analyze patterns of neutral and non-neutral
genetic diversity in humans and find an excellent fit between theory and data.


title:
Non-constant bounded holomorphic functions of hyperbolic numbers -
  Candidates for hyperbolic activation functions

abstract:
  The Liouville theorem states that bounded holomorphic complex functions are
necessarily constant. Holomorphic functions fulfill the socalled Cauchy-Riemann
(CR) conditions. The CR conditions mean that a complex $z$-derivative is
independent of the direction. Holomorphic functions are ideal for activation
functions of complex neural networks, but the Liouville theorem makes them
useless. Yet recently the use of hyperbolic numbers, lead to the construction
of hyperbolic number neural networks. We will describe the Cauchy-Riemann
conditions for hyperbolic numbers and show that there exists a new interesting
type of bounded holomorphic functions of hyperbolic numbers, which are not
constant. We give examples of such functions. They therefore substantially
expand the available candidates for holomorphic activation functions for
hyperbolic number neural networks.
  Keywords: Hyperbolic numbers, Liouville theorem, Cauchy-Riemann conditions,
bounded holomorphic functions


title:
The origin of the 6.4 keV line emission and H$_2$ ionization in the
  diffuse molecular gas of the Galactic center region

abstract:
  We investigate the origin of the diffuse 6.4 keV line emission recently
detected by Suzaku and the source of H_2ionization in the diffuse molecular gas
of the Galactic Center (GC) region. We show that Fe atoms and H_2 molecules in
the diffuse interstellar medium of the GC are not ionized by the same
particles. The Fe atoms are most likely ionized by X-ray photons emitted by Sgr
A* during a previous period of flaring activity of the supermassive black hole.
The measured longitudinal intensity distribution of the diffuse 6.4 keV line
emission is best explained if the past activity of Sgr A$* lasted at least
several hundred years and released a mean 2-100 keV luminosity > 10^38} erg
s^{-1}. The H_2 molecules of the diffuse gas can not be ionized by photons from
Sgr A*, because soft photons are strongly absorbed in the interstellar gas
around the central black hole. The molecular hydrogen in the GC region is most
likely ionized by low-energy cosmic rays, probably protons rather than
electrons, whose contribution into the diffuse 6.4 keV line emission is
negligible.


title:
Some relationships between intrinsic and extrinsic invariants of
  submanifolds in generalized S-space-forms

abstract:
  We establish some inequalities of Chen's type between certain intrinsic
invariants (involving sectional, Ricci and scalar curvatures) and the squared
mean curvature of submanifolds tangent to the structure vector fields of a
generalized S-space-form and we discuss the equality cases of them. We apply
the obtained results to slant submanifolds.


title:
Results on independent sets in categorical products of graphs, the
  ultimate categorical independence ratio and the ultimate categorical
  independent domination ratio

abstract:
  We show that there are polynomial-time algorithms to compute maximum
independent sets in the categorical products of two cographs and two
splitgraphs. The ultimate categorical independence ratio of a graph G is
defined as lim_{k --> infty} \alpha(G^k)/n^k. The ultimate categorical
independence ratio is polynomial for cographs, permutation graphs, interval
graphs, graphs of bounded treewidth and splitgraphs. When G is a planar graph
of maximal degree three then alpha(G \times K_4) is NP-complete. We present a
PTAS for the ultimate categorical independence ratio of planar graphs. We
present an O^*(n^{n/3}) exact, exponential algorithm for general graphs. We
prove that the ultimate categorical independent domination ratio for complete
multipartite graphs is zero, except when the graph is complete bipartite with
color classes of equal size (in which case it is 1/2).


title:
Limiting distributions of the classical error terms of prime number
  theory

abstract:
  In this article we prove a general theorem which establishes the existence of
limiting distributions for a wide class of error terms from prime number
theory. As a corollary to our main theorem, we deduce previous results of
Wintner (1935), Rubinstein and Sarnak (1994), and of Ng (2004). In addition, we
establish limiting distribution results for the error term in the prime number
theorem for an automorphic $L$-function, weighted sums of the M\"{o}bius
function, weighted sums of the Liouville function, the sum of the M\"{o}bius
function in an arithmetic progression, and the error term in Chebotarev's
density theorem.


title: Theory of carrier-mediated magnonic superlattices

abstract:
  We present a minimal one-dimensional model of collective spin excitations in
itinerant ferromagnetic superlattices within the regime of parabolic
spin-carrier dispersion. We discuss the cases of weakly and strongly modulated
magnetic profiles finding evidences of antiferromagnetic correlations for
long-wave magnons (especially significant in layered systems), with an insight
into the ground state properties. In addition, the presence of local minima in
the magnonic dispersion suggests the possibility of (thermal) excitation of
spin waves with a relatively well controlled wave length. Some of these
features could be experimentally tested in DMS superlattices based on thin
doped magnetic layers, acting as natural interfaces between (spin)electronic
and magnonic degrees of freedom.


title: Spin and the Thermal Equilibrium Distribution of Wave Functions

abstract:
  Consider a quantum system $S$ weakly interacting with a very large but finite
system $B$ called the heat bath, and suppose that the composite $S\cup B$ is in
a pure state $\Psi$ with participating energies between $E$ and $E+\delta$ with
small $\delta$. Then, it is known that for most $\Psi$ the reduced density
matrix of $S$ is (approximately) equal to the canonical density matrix. That
is, the reduced density matrix is universal in the sense that it depends only
on $S$'s Hamiltonian and the temperature but not on $B$'s Hamiltonian, on the
interaction Hamiltonian, or on the details of $\Psi$. It has also been pointed
out that $S$ can also be attributed a random wave function $\psi$ whose
probability distribution is universal in the same sense. This distribution is
known as the "Scrooge measure" or "Gaussian adjusted projected (GAP) measure";
we regard it as the thermal equilibrium distribution of wave functions. The
relevant concept of the wave function of a subsystem is known as the
"conditional wave function". In this paper, we develop analogous considerations
for particles with spin. One can either use some kind of conditional wave
function or, more naturally, the "conditional density matrix", which is in
general different from the reduced density matrix. We ask what the thermal
equilibrium distribution of the conditional density matrix is, and find the
answer that for most $\Psi$ the conditional density matrix is (approximately)
deterministic, in fact (approximately) equal to the canonical density matrix.


title: Introduction to Clifford's Geometric Algebra

abstract:
  Geometric algebra was initiated by W.K. Clifford over 130 years ago. It
unifies all branches of physics, and has found rich applications in robotics,
signal processing, ray tracing, virtual reality, computer vision, vector field
processing, tracking, geographic information systems and neural computing. This
tutorial explains the basics of geometric algebra, with concrete examples of
the plane, of 3D space, of spacetime, and the popular conformal model.
Geometric algebras are ideal to represent geometric transformations in the
general framework of Clifford groups (also called versor or Lipschitz groups).
Geometric (algebra based) calculus allows, e.g., to optimize learning
algorithms of Clifford neurons, etc.
  Keywords: Hypercomplex algebra, hypercomplex analysis, geometry, science,
engineering.


title:
Dr TIM: Ray-tracer TIM, with additional specialist scientific
  capabilities

abstract:
  We describe several extensions to TIM, a raytracing program for ray-optics
research. These include relativistic raytracing; simulation of the external
appearance of Eaton lenses, Luneburg lenses and generalized focusing
gradient-index (GGRIN) lenses, which are types of perfect imaging devices;
raytracing through interfaces between spaces with different optical metrics;
and refraction with generalised confocal lenslet arrays, which are particularly
versatile METATOYs.


title: Receiver Concepts and Resource Allocation for OSC Downlink Transmission

abstract:
  Voice services over Adaptive Multi-user channels on One Slot (VAMOS) has been
standardized as an extension to the Global System for Mobile Communications
(GSM). The aim of VAMOS is to increase the capacity of GSM, while maintaining
backward compatibility with the legacy system. To this end, the Orthogonal
Sub-channels (OSC) concept is employed, where two Gaussian minimum-shift keying
(GMSK) signals are transmitted in the same time slot and with the same carrier
frequency. To fully exploit the possible capacity gain of OSC, new receiver
concepts are necessary. In contrast to the base station, where multiple
antennas can be employed, the mobile station is typically equipped with only
one receive antenna. Therefore, the downlink receiver design is a very
challenging task. Different concepts for channel estimation, user separation,
and equalization at the receiver of an OSC downlink transmission are introduced
in this paper. Furthermore, the system capacity must be improved by suitable
downlink power and resource allocation algorithms. Making realistic assumptions
on the information available at the base station, an algorithm for joint power
and radio resource allocation is proposed. Simulation results show the
excellent performance of the proposed channel estimation algorithms,
equalization schemes, and joint radio resource and power allocation algorithms
in realistic VAMOS environments.


title:
Field-induced reentrant superconductivity in thin films of nodal
  superconductor

abstract:
  Previous works on nodal d-wave superconductors have shown that a
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like modulated superconducting (SC)
state can be realized with no magnetic field when quasiparticles acquire an
additional linear term in the wavevector in their dispersion. In the present
work, stability of such a novel modulated SC state in an artificial film
against an applied magnetic field is studied. As a reflection of the presence
of the two different FFLO states, one close to zero field and the other at the
high field end, in a single field v.s. temperature phase diagram of thin films,
the conventional uniform SC state generally tends to appear as a reentrant
ordered phase bounded by the normal phase in {\it lower} fields.


title:
An algebraic RF sheath model for all excitation waveforms and
  amplitudes, and all levels of collisionality

abstract:
  The boundary sheath of a low temperature plasma comprises typically only a
small fraction of its volume but is responsible for many aspects of the
macroscopic behavior. A thorough understanding of the sheath dynamics is
therefore of theoretical and practical importance. This work focusses on the
so-called "algebraic" approach which strives to describe the electrical
behavior of RF modulated boundary sheaths in closed analytical form, i.e.,
without the need to solve differential equations. A mathematically simple,
analytical expression for the charge-voltage relation of a sheath is presented
which holds for all excitation wave forms and amplitudes and covers all regimes
from the collision-less motion at low gas pressure to the collision dominated
motion at gas high pressure. A comparison with the results of self-consistent
particle-in-cell simulations is also presented.


title:
Single Bit and Reduced Dimension Diffusion Strategies Over Distributed
  Networks

abstract:
  We introduce novel diffusion based adaptive estimation strategies for
distributed networks that have significantly less communication load and
achieve comparable performance to the full information exchange configurations.
After local estimates of the desired data is produced in each node, a single
bit of information (or a reduced dimensional data vector) is generated using
certain random projections of the local estimates. This newly generated data is
diffused and then used in neighboring nodes to recover the original full
information. We provide the complete state-space description and the mean
stability analysis of our algorithms.


title: Plasmons and screening in a monolayer of MoS$_2$

abstract:
  We investigate the dynamical dielectric function of a monolayer of molybdenum
disulfide within the random phase approximation. While in graphene damping of
plasmons is caused by interband transitions, due to the large direct band gap
in monolayer MoS$_2$ collective charge excitations enter the intraband electron
hole continuum similar to the situation in two-dimensional electron and hole
gases. Since there is no electron-hole symmetry in MoS$_2$, the plasmon
energies in p- and n-doped samples clearly differ. The breaking of spin
degeneracy caused by the large intrinsic spin-orbit interaction leads to a
beating of Friedel oscillations for sufficiently large carrier concentrations,
for holes as well as for electrons.


title:
First passage behaviour of multi-dimensional fractional Brownian motion
  and application to reaction phenomena

abstract:
  Fractional Brownian motion is a generalised Gaussian diffusive process that
is found to describe numerous stochastic phenomena in physics and biology. Here
we introduce a multi-dimensional fractional Brownian motion (FBM) defined as a
superposition of conventional FBM for each coordinate in analogy to
multi-dimensional Brownian motion, and study its first passage properties.
Starting from the well-established first passage time statistics of
one-dimensional FBM and the associated approximation schemes, we explore the
first passage time behaviour of multi-dimensional FBM and compare these results
with simulations. The asymptotic kinetic behaviour of diffusion-limited
reactions of reactant particles performing FBM in a one- and multi-dimensional
space is studied based on the corresponding first passage time statistics.


title: Terminating black holes in asymptotically free quantum gravity

abstract:
  We study the homogeneous gravitational collapse of a spherical cloud of
matter in a super-renormalizable and asymptotically free theory of gravity. We
find a picture that differs substantially from the classical scenario. The
central singularity appearing in classical general relativity is replaced by a
bounce, after which the cloud re-expands indefinitely. We argue that a black
hole, strictly speaking, never forms. The collapse only generates a temporary
trapped surface, which can be interpreted as a black hole when the
observational timescale is much shorter than the one of the collapse. However,
it may also be possible that the gravitational collapse produces a black hole
and that after the bounce the original cloud of matter evolves into a new
universe.


title: Quaternionic Fourier-Mellin Transform

abstract:
  In this contribution we generalize the classical Fourier Mellin transform [S.
Dorrode and F. Ghorbel, Robust and efficient Fourier-Mellin transform
approximations for gray-level image reconstruction and complete invariant
description, Computer Vision and Image Understanding, 83(1) (2001), 57-78, DOI
10.1006/cviu.2001.0922.], which transforms functions $f$ representing, e.g., a
gray level image defined over a compact set of $\mathbb{R}^2$. The quaternionic
Fourier Mellin transform (QFMT) applies to functions $f: \mathbb{R}^2
\rightarrow \mathbb{H}$, for which $|f|$ is summable over $\mathbb{R}_+^*
\times \mathbb{S}^1$ under the measure $d\theta \frac{dr}{r}$. $\mathbb{R}_+^*$
is the multiplicative group of positive and non-zero real numbers. We
investigate the properties of the QFMT similar to the investigation of the
quaternionic Fourier Transform (QFT) in [E. Hitzer, Quaternion Fourier
Transform on Quaternion Fields and Generalizations, Advances in Applied
Clifford Algebras, 17(3) (2007), 497-517.; E. Hitzer, Directional Uncertainty
Principle for Quaternion Fourier Transforms, Advances in Applied Clifford
Algebras, 20(2) (2010), 271-284, online since 08 July 2009.].


title:
Charged Higgs and Neutral Higgs pair production of weak gauge bosons
  fusion process in e+ e- collision

abstract:
  In this paper, we study the pair production and their decays of the Higges in
the neutrinophilic Higgs two doublet model. The pair production occurs through
W and Z gauge bosons fusion process. In the neutrinophilic model, the vacuum
expectation value (VEV) of the second Higgs doublet is small and is
proportional to the neutrino mass. The smallness of VEV is associated with the
approximate global U(1) symmetry which is slightly broken. Therefore, there is
a suppression factor for the U(1) charge breaking process. The second Higgs
doublet has U(1) charge and its single production from the gauge boson fusion
violates the U(1) charge conservation and is suppressed strongly to occur. In
contrast to the single production, the pair production of the Higgses conserves
U(1) charge and the approximate symmetry does not forbid it. To search for the
pair productions in collider experiment,we study the production cross section
of a pair of the charged Higgs and neutral Higgs bosons in e+ e- collision with
center of energy from 600 (GeV) to 2000 (GeV). The total cross section varies
from 10^{-4}(fb) to 10^{-3}(fb) for degenerate (200 GeV) charged and neutral
Higgses mass case. The background process to the signal is gauge bosons pair W
+ Z production and their decays. We show the signal over background ratio is
about 2% ~ 3% by combining the cross section ratio with ratios of branching
fractions.


title: Symmetric and asymmetric excitations of a strong-leg quantum spin ladder

abstract:
  The zero-field excitation spectrum of the strong-leg spin ladder
(C$_7$H$_10$N)$_2$CuBr$_4$ (DIMPY) is studied with a neutron time-of-flight
technique. The spectrum is decomposed into its symmetric and asymmetric parts
with respect to the rung momentum and compared with theoretical results
obtained by the density matrix renormalization group method. Additionally, the
calculated dynamical correlations are shown for a wide range of rung and leg
coupling ratios in order to point out the evolution of arising excitations, as
e.g. of the two-magnon bound state from the strong to the weak coupling limit.


title:
On the Possibility of Detecting Class A Stellar Engines Using Exoplanet
  Transit Curves

abstract:
  The Class A stellar engine (also known as a Shkadov thruster) is a spherical
arc mirror, designed to use the impulse from a star's radiation pressure to
generate a thrust force, perturbing the star's motion. If this mirror obstructs
part of the stellar disc during the transit of an exoplanet, then this may be
detected by studying the shape of the transit light curve, presenting another
potential means by which the action of extraterrestrial intelligence (ETI) can
be discerned. We model the light curves produced by exoplanets transiting a
star which possesses a Shkadov thruster, and show how the parameters of the
planet and the properties of the thruster can be disentangled. provided that
radial velocity follow-up measurements are possible, and that other obscuring
phenomena typical to exoplanet transit curves (such as the presence of
starspots or intrinsic stellar noise) do not dominate. These difficulties
aside, we estimate the a priori probability of detecting a Shkadov thruster
during an exoplanet transit, which even given optimistic assumptions remains
stubbornly low. Despite this, many exoplanet transit surveys designed for
radial velocity follow-up are on the horizon, so we argue that this remains a
useful serendipitous SETI technique. At worst, this technique will place an
upper limit on the number of Class A stellar engines in the Solar
neighbourhood; at best, this could help identify unusual transiting exoplanet
systems as candidates for further investigation with other SETI methods.


title:
Dispersion corrections in graphenic systems: a simple and effective
  model of binding

abstract:
  We combine high-level theoretical and \emph{ab initio} understanding of
graphite to develop a simple, parametrised force-field model of interlayer
binding in graphite, including the difficult non-pairwise-additive
coupled-fluctuation dispersion interactions. The model is given as a simple
additive correction to standard density functional theory (DFT) calculations,
of form $\Delta U(D)=f(D)[U^{vdW}(D)-U^{DFT}(D)]$ where $D$ is the interlayer
distance. The functions are parametrised by matching contact properties, and
long-range dispersion to known values, and the model is found to accurately
match high-level \emph{ab initio} results for graphite across a wide range of
$D$ values. We employ the correction on the difficult bigraphene binding and
graphite exfoliation problems, as well as lithium intercalated graphite
LiC$_6$. We predict the binding energy of bigraphene to be 0.27 J/m^2, and the
exfoliation energy of graphite to be 0.31 J/m^2, respectively slightly less and
slightly more than the bulk layer binding energy 0.295 J/m^2/layer. Material
properties of LiC$_6$ are found to be essentially unchanged compared to the
local density approximation. This is appropriate in view of the relative
unimportance of dispersion interactions for LiC$_6$ layer binding.


title:
Superconducting Circuits for Quantum Simulation of Dynamical Gauge
  Fields

abstract:
  We describe a superconducting-circuit lattice design for the implementation
and simulation of dynamical lattice gauge theories. We illustrate our proposal
by analyzing a one-dimensional U(1) quantum-link model, where superconducting
qubits play the role of matter fields on the lattice sites and the gauge fields
are represented by two coupled microwave resonators on each link between
neighboring sites. A detailed analysis of a minimal experimental protocol for
probing the physics related to string breaking effects shows that despite the
presence of decoherence in these systems, distinctive phenomena from
condensed-matter and high-energy physics can be visualized with
state-of-the-art technology in small superconducting-circuit arrays.


title:
Introduction to Mathematical Physics. Calculus of Variations and
  Boundary-value Problems

abstract:
  This book considers posing and the methods of solving simple linear
boundary-value problems in classical mathematical physics. The questions
encompassed include: the fundamentals of calculus of variations;
one-dimensional boundary-value problems in the oscillation and heat conduction
theories, with a detailed analysis of the Sturm-Liouville boundary-value
problem and substantiation of the Fourier method; sample solutions of the
corresponding problems in two and three dimensions, with essential elements of
the special function theory. The text is designed for Physics, Engineering, and
Mathematics majors.


title: Algebraic foundations of split hypercomplex nonlinear adaptive filtering

abstract:
  A split hypercomplex learning algorithm for the training of nonlinear finite
impulse response adaptive filters for the processing of hypercomplex signals of
any dimension is proposed. The derivation strictly takes into account the laws
of hypercomplex algebra and hypercomplex calculus, some of which have been
neglected in existing learning approaches (e.g. for quaternions). Already in
the case of quaternions we can predict improvements in performance of
hypercomplex processes. The convergence of the proposed algorithms is
rigorously analyzed.
  Keywords: Quaternionic adaptive filtering, Hypercomplex adaptive filtering,
Nonlinear adaptive filtering, Hypercomplex Multilayer Perceptron, Clifford
geometric algebra


title: On the Structure of Equilibria in Basic Network Formation

abstract:
  We study network connection games where the nodes of a network perform edge
swaps in order to improve their communication costs. For the model proposed by
Alon et al. (2010), in which the selfish cost of a node is the sum of all
shortest path distances to the other nodes, we use the probabilistic method to
provide a new, structural characterization of equilibrium graphs. We show how
to use this characterization in order to prove upper bounds on the diameter of
equilibrium graphs in terms of the size of the largest $k$-vicinity (defined as
the the set of vertices within distance $k$ from a vertex), for any $k \geq 1$
and in terms of the number of edges, thus settling positively a conjecture of
Alon et al. in the cases of graphs of large $k$-vicinity size (including graphs
of large maximum degree) and of graphs which are dense enough.
  Next, we present a new swap-based network creation game, in which selfish
costs depend on the immediate neighborhood of each node; in particular, the
profit of a node is defined as the sum of the degrees of its neighbors. We
prove that, in contrast to the previous model, this network creation game
admits an exact potential, and also that any equilibrium graph contains an
induced star. The existence of the potential function is exploited in order to
show that an equilibrium can be reached in expected polynomial time even in the
case where nodes can only acquire limited knowledge concerning non-neighboring
nodes.


title:
A discrete time event-history approach to informative drop-out in
  multivariate latent Markov models with covariates

abstract:
  Latent Markov (LM) models represent an important tool of analysis of
longitudinal data when response variables are affected by time-varying
unobserved heterogeneity, which is accounted for by a hidden Markov chain. In
order to avoid bias when using a model of this type in the presence of
informative drop-out, we propose an event-history (EH) extension of the LM
approach that may be used with multivariate longitudinal data, in which one or
more outcomes of a different nature are observed at each time occasion. The EH
component of the resulting model is referred to the interval-censored drop-out,
and bias in LM modeling is avoided by correlated random effects, included in
the different model components, which follow a common Markov chain. In order to
perform maximum likelihood estimation of the proposed model by the
Expectation-Maximization algorithm, we extend the usual backward-forward
recursions of Baum and Welch. The algorithm has the same complexity of the one
adopted in cases of non-informative drop-out. Standard errors for the parameter
estimates are derived by using the Oakes' identity. We illustrate the proposed
approach through an application based on data coming from a medical study about
primary biliary cirrhosis in which there are two outcomes of interest, the
first of which is continuous and the second is binary.


title:
Clifford Fourier-Mellin transform with two real square roots of -1 in
  Cl(p,q), p+q=2

abstract:
  We describe a non-commutative generalization of the complex Fourier-Mellin
transform to Clifford algebra valued signal functions over the domain
$\R^{p,q}$ taking values in Cl(p,q), p+q=2.
  Keywords: algebra, Fourier transforms; Logic, set theory, and algebra,
Fourier analysis, Integral transforms


title: Chandra Study of the Massive and Distant Galaxy Cluster SDSS J0150-1005

abstract:
  In this work, we present a high spatial resolution study of a fossil cluster,
SDSS J0150-1005 ($z \simeq 0.364$), based on the imaging spectroscopic analysis
of \chandra\ observation. The \chandra\ X-ray image shows a relax and symmetric
morphology, which indicates SDSS J0150-1005 is a well-developed galaxy cluster
with no sign of recent merger. Its global gas temperature is 5.73 $\pm$ 0.80
keV, and the virial mass is 6.23 $\pm$ 1.34 $\times 10^{14} $ M$_{\odot}$
according to the isothermal model. Compared with polytropic temperature model,
the mass calculated based on isothermal model overestimates 49 $\pm$ 11%. The
central gas entropy, $S_{0.1r_{200}} = 143.9 \pm 18.3$ keV cm$^2$, is
significantly lower than average value of the normal galaxy clusters with
similar temperatures. Our results indicate the early formation epoch of SDSS
J0150-1005.