title: An n-ary Constraint for the Stable Marriage Problem

abstract:
  We present an n-ary constraint for the stable marriage problem. This
constraint acts between two sets of integer variables where the domains of
those variables represent preferences. Our constraint enforces stability and
disallows bigamy. For a stable marriage instance with $n$ men and $n$ women we
require only one of these constraints, and the complexity of enforcing
arc-consistency is $O(n^2)$ which is optimal in the size of input. Our
computational studies show that our n-ary constraint is significantly faster
and more space efficient than the encodings presented in \cite{cp01}. We also
introduce a new problem to the constraint community, the sex-equal stable
marriage problem.


title: Spectroscopic metallicity determinations for W~UMa-type binary stars

abstract:
  This study is an attempt to determine the metallicities of WUMa-type binary
stars using spectroscopy. ~4,500 spectra collected at the David Dunlap
Observatory were subject to the same Broadening Function processing to
determine the combined line strength in the spectral window centered on the MgI
triplet (5080-5285A). Individual integrated BF's were phase averaged to derive
a single line-strength indicator. The sample was limited to 90 EW binaries with
the strict phase-constancy of colors and without spectral contamination by
companions. The best defined results were obtained for a F-type sub-sample
(0.32<(B-V)0<0.62) of 52 stars for which the BF strengths could be interpolated
in the model predictions. The metallicities, [M/H], for the F-type sub-sample
indicate abundances roughly similar to the solar [M/H], but with a large
scatter which is partly due to combined random and systematic errors. Because
of a color trend resulting from limitations in our approach, we set the scale
of metallicities to correspond to that derived from the m_1 index of the
Stromgren photometry for F-type binaries. The trend-adjusted [M/H]1 are
distributed within -0.65<[M/H]1<+0.50, with the spread reflecting genuine
metallicity differences between stars. One half of the F-sub-sample binaries
have [M/H]1 within -0.37<[M/H]1 +0.10, a median of -0.04 and a mean of -0.10,
with a tail towards low metallicities, and a possible bias against very high
metallicities. A parallel study of kinematic data, utilizing the most reliable
and recently obtained proper motion and radial velocity data for 78 stars of
the full sample, shows that the F-type sub-sample binaries have similar
kinematic properties to solar neighborhood, thin-disk dwarfs with ages about 3
- 5.5 Gyr. The F-type binaries which appear to be older than the rest tend to
have systematically smaller mass-ratios than most of the EW binaries of the
same period.


title:
Electronic superlattice revealed by resonant scattering from random
  impurities in Sr3Ru2O7

abstract:
  Resonant elastic x-ray scattering (REXS) is an exquisite element-sensitive
tool for the study of subtle charge, orbital, and spin superlattice orders
driven by the valence electrons, which therefore escape detection in
conventional x-ray diffraction (XRD). Although the power of REXS has been
demonstrated by numerous studies of complex oxides performed in the soft x-ray
regime, the cross section and photon wavelength of the material-specific
elemental absorption edges ultimately set the limit to the smallest
superlattice amplitude and periodicity one can probe. Here we show -- with
simulations and REXS on Mn-substituted Sr$_3$Ru$_2$O$_7$ -- that these
limitations can be overcome by performing resonant scattering experiments at
the absorption edge of a suitably-chosen, dilute impurity. This establishes
that -- in analogy with impurity-based methods used in electron-spin-resonance,
nuclear-magnetic resonance, and M\"ossbauer spectroscopy -- randomly
distributed impurities can serve as a non-invasive, but now momentum-dependent
probe, greatly extending the applicability of resonant x-ray scattering
techniques.


title: Calabi-Yau Geometries: Algorithms, Databases, and Physics

abstract:
  With a bird's-eye view, we survey the landscape of Calabi-Yau threefolds,
compact and non-compact, smooth and singular. Emphasis will be placed on the
algorithms and databases which have been established over the years, and how
they have been useful in the interaction between the physics and the
mathematics, especially in string and gauge theories. A skein which runs
through this review will be algorithmic and computational algebraic geometry
and how, implementing its principles on powerful computers and experimenting
with the vast mathematical data, new physics can be learnt. It is hoped that
this inter-disciplinary glimpse will be of some use to the beginning student.


title: A Time and Space Efficient Junction Tree Architecture

abstract:
  The junction tree algorithm is a way of computing marginals of boolean
multivariate probability distributions that factorise over sets of random
variables. The junction tree algorithm first constructs a tree called a
junction tree who's vertices are sets of random variables. The algorithm then
performs a generalised version of belief propagation on the junction tree. The
Shafer-Shenoy and Hugin architectures are two ways to perform this belief
propagation that tradeoff time and space complexities in different ways: Hugin
propagation is at least as fast as Shafer-Shenoy propagation and in the cases
that we have large vertices of high degree is significantly faster. However,
this speed increase comes at the cost of an increased space complexity. This
paper first introduces a simple novel architecture, ARCH-1, which has the best
of both worlds: the speed of Hugin propagation and the low space requirements
of Shafer-Shenoy propagation. A more complicated novel architecture, ARCH-2, is
then introduced which has, up to a factor only linear in the maximum
cardinality of any vertex, time and space complexities at least as good as
ARCH-1 and in the cases that we have large vertices of high degree is
significantly faster than ARCH-1.


title: Dark Energy Constraints after Planck

abstract:
  The Planck collaboration has recently published maps of the Cosmic Microwave
Background radiation with the highest precision. In the standard flat
$\Lambda$CDM framework, Planck data show that the Hubble constant $H_0$ is in
tension with that measured by the several direct probes on $H_0$. In this
paper, we perform a global analysis from the current observational data in the
general dark energy models and find that resolving this tension on $H_0$
requires the dark energy model with its equation of state (EoS) $w\neq-1$.
Firstly, assuming the $w$ to be a constant, the Planck data favor $w < -1$ at
about $2\,\sigma$ confidence level when combining with the supernovae "SNLS"
compilation. And consequently the value derived on $H_0$, $H_0=71.3\pm2.0$
${\rm km\,s^{-1}\,Mpc^{-1}}$ (68% C.L.), is consistent with that from direct
$H_0$ probes. We then investigate the dark energy model with a time-evolving
$w$, and obtain the 68% C.L. constraints $w_0=-0.81\pm0.19$ and
$w_a=-1.9\pm1.1$ from the Planck data and the "SNLS" compilation. Current data
still slightly favor the Quintom dark energy scenario with EoS across the
cosmological constant boundary $w\equiv-1$.


title: Asymptotically near-optimal RRT for fast, high-quality, motion planning

abstract:
  We present Lower Bound Tree-RRT (LBT-RRT), a single-query sampling-based
algorithm that is asymptotically near-optimal. Namely, the solution extracted
from LBT-RRT converges to a solution that is within an approximation factor of
1+epsilon of the optimal solution. Our algorithm allows for a continuous
interpolation between the fast RRT algorithm and the asymptotically optimal
RRT* and RRG algorithms. When the approximation factor is 1 (i.e., no
approximation is allowed), LBT-RRT behaves like RRG. When the approximation
factor is unbounded, LBT-RRT behaves like RRT. In between, LBT-RRT is shown to
produce paths that have higher quality than RRT would produce and run faster
than RRT* would run. This is done by maintaining a tree which is a sub-graph of
the RRG roadmap and a second, auxiliary graph, which we call the lower-bound
graph. The combination of the two roadmaps, which is faster to maintain than
the roadmap maintained by RRT*, efficiently guarantees asymptotic
near-optimality. We suggest to use LBT-RRT for high-quality, anytime motion
planning. We demonstrate the performance of the algorithm for scenarios ranging
from 3 to 12 degrees of freedom and show that even for small approximation
factors, the algorithm produces high-quality solutions (comparable to RRG and
RRT*) with little running-time overhead when compared to RRT.


title: Escape of the martian protoatmosphere and initial water inventory

abstract:
  Latest research in planet formation indicate that Mars formed within a few
million years (Myr) and remained a planetary embryo that never grew to a more
massive planet. It can also be expected from dynamical models, that most of
Mars' building blocks consisted of material that formed in orbital locations
just beyond the ice line which could have contained ~0.1-0.2 wt. % of H2O. By
using these constraints, we estimate the nebula-captured and catastrophically
outgassed volatile contents during the solidification of Mars' magma ocean and
apply a hydrodynamic upper atmosphere model for the study of the soft X-ray and
extreme ultraviolet (XUV) driven thermal escape of the martian protoatmosphere
during the early active epoch of the young Sun. The amount of gas that has been
captured from the protoplanetary disk into the planetary atmosphere is
calculated by solving the hydrostatic structure equations in the protoplanetary
nebula. Depending on nebular properties such as the dust grain depletion
factor, planetesimal accretion rates and luminosities, hydrogen envelopes with
masses >=3x10^{19} g to <=6.5x10^{22} g could have been captured from the
nebula around early Mars. Depending of the before mentioned parameters, due to
the planets low gravity and a solar XUV flux that was ~100 times stronger
compared to the present value, our results indicate that early Mars would have
lost its nebular captured hydrogen envelope after the nebula gas evaporated,
during a fast period of ~0.1-7.5 Myr. After the solidification of early Mars'
magma ocean, catastrophically outgassed volatiles with the amount of ~50-250
bar H2O and ~10-55 bar CO2 could have been lost during ~0.4-12 Myr, if the
impact related energy flux of large planetesimals and small embryos to the
planet's surface lasted long enough, that the steam atmosphere could have been
prevented from condensing. If this was not the case... (continued)


title: Control of VTOL Vehicles with Thrust-direction Tilting

abstract:
  An approach to the control of a VTOL vehicle equipped with complementary
thrust-direction tilting capabilities that nominally yield full actuation of
the vehicle's position and attitude is developed. The particularity and
difficulty of the control problem are epitomized by the existence of a maximal
thrust-tilting angle which forbids complete and decoupled control of the
vehicle's position and attitude in all situations. This problem is here
addressed via the formalism of primary and secondary objectives and by
extending a solution previously derived in the fixed thrust-direction case. The
proposed control design is also illustrated by simulation results involving a
quadrotor UAV with all propellers axes pointing in the same monitored tilted
direction.


title: Inverse Spin Hall Effect in nanometer-thick YIG/Pt system

abstract:
  High quality nanometer-thick (20 nm, 7 nm and 4 nm) epitaxial YIG films have
been grown on GGG substrates using pulsed laser deposition. The Gilbert damping
coefficient for the 20 nm thick films is 2.3 x 10-4 which is the lowest value
reported for sub-micrometric thick films. We demonstrate Inverse spin Hall
effect (ISHE) detection of propagating spin waves using Pt. The amplitude and
the lineshape of the ISHE voltage correlate well to the increase of the Gilbert
damping when decreasing thickness of YIG. Spin Hall effect based
loss-compensation experiments have been conducted but no change in the
magnetization dynamics could be detected.


title:
Production of charged heavy quarkonium-like states at the LHC and the
  Tevatron

abstract:
  We study prompt hadroproduction of the charged bottomonium-like states
$Z_b^\pm (10610)$ and $Z_b^\pm (10650)$, and the charged charmonium-like states
$Z_c^\pm (3900)$ and $Z_c^\pm (4020)$, at the Tevatron and the LHC, provided
that these states are $S$-wave hadronic molecules. Using two Monte Carlo event
generators, Herwig and Pythia, to simulate the production of heavy meson pairs,
we derive an order-of-magnitude estimate of the production rates for these four
particles. Our estimates yield a cross section at the nb level for the
$Z_b(10610)$ and $Z_b(10650)$. The results for the $Z_c(3900)$ and $Z_c(4020)$
are larger by a factor of 20-30. These cross sections are large enough to be
observed, and measurements at hadron colliders in the future will supplement
the study using electron-positron collisions, and therefore allow to explore
the mysterious nature of these exotic states.


title: Tau neutrino search with Cherenkov telescopes

abstract:
  Cherenkov telescopes could have the capability of detecting high energy tau
neutrinos by searching for very inclined showers. If a tau lepton, produced by
a tau neutrino, escapes from the Earth crust, it will decay and initiate an air
shower which can be detected by a fluorescence/Cherenkov telescope. Here we
present a detailed Monte Carlo simulation of event rates induced by tau
neutrinos in the energy range from 1 PeV to 1 EeV. Topographic conditions are
taken into account for a set of example locations. As expected, we find a
neutrino sensitivity which depends on the shape of the energy spectrum from
astrophysical sources. We compare our findings with the sensitivity of the
dedicated IceCube neutrino telescope under different conditions. We also find
that a difference of several factors can be observed depending on the
topographic conditions of the sites sampled.


title:
Modeling the Shell of Cassiopeia A to find the TeV Gamma-ray Emission
  Region

abstract:
  We will present the multi-wavelength modeling of the supernova remnant
Cassiopeia A's shell based on radio, X-rays, and GeV-TeV gamma rays. Our aim is
to estimate the location of TeV gamma rays with the help of spectral analysis
of X-rays from different regions of the shell, because Chandra X-ray
observations have a far better angular resolution than the gamma-ray
measurements. Our analysis shows X-ray flux levels from various regions of the
remnant to be different. We find that leptonic model is unable to explain the
GeV and TeV data, simultaneously. So, we invoke a hadronic model as an
additional component to explain the GeV and TeV data.


title: Mechanical Stability of Cylindrical Thin-Shell Wormholes

abstract:
  In this paper, we apply the cut and paste procedure to charged black string
for the construction of thin-shell wormhole. We consider the Darmois-Israel
formalism to determine the surface stresses of the shell. We take Chaplygin gas
to deal with the matter distribution on shell. The radial perturbation approach
(preserving the symmetry) is used to investigate the stability of static
solutions. We conclude that stable static solutions exist both for uncharged
and charged black string thin-shell wormholes for particular values of the
parameters.


title:
Some Plane Symmetric Inhomogeneous Cosmological Models in the
  Scalar-Tensor Theory of Gravitation

abstract:
  The present study deals with the inhomogeneous plane symmetric models in
scalar - tensor theory of gravitation. We used symmetry group analysis method
to solve the field equations analytically. A new class of similarity solutions
have been obtained by considering the inhomogeneous nature of metric potential.
The physical behavior and geometrical aspects of the derived models are also
discussed.


title: Anomalous biased diffusion in networks

abstract:
  We study diffusion with a bias towards a target node in networks. This
problem is relevant to efficient routing strategies in emerging communication
networks like optical networks. Bias is represented by a probability $p$ of the
packet/particle to travel at every hop towards a site which is along the
shortest path to the target node. We investigate the scaling of the mean first
passage time (MFPT) with the size of the network. We find by using theoretical
analysis and computer simulations that for Random Regular (RR) and
Erd\H{o}s-R\'{e}nyi (ER) networks, there exists a threshold probability,
$p_{th}$, such that for $p<p_{th}$ the MFPT scales anomalously as $N^\alpha$,
where $N$ is the number of nodes, and $\alpha$ depends on $p$. For $p>p_{th}$
the MFPT scales logarithmically with $N$. The threshold value $p_{th}$ of the
bias parameter for which the regime transition occurs is found to depend only
on the mean degree of the nodes. An exact solution for every value of $p$ is
given for the scaling of the MFPT in RR networks. The regime transition is also
observed for the second moment of the probability distribution function, the
standard deviation.


title:
Magnetostatic wave analog of integer quantum Hall state in patterned
  magnetic films

abstract:
  A magnetostatic spin wave analog of integer quantum Hall (IQH) state is
proposed in realistic patterned ferromagnetic thin films. Due to magnetic shape
anisotropy, magnetic moments in a thin film lie within the plane, while all
spin-wave excitations are fully gapped. Under an out-of-plane magnetic field,
the film acquires a finite magnetization, where some of the gapped magnons
become significantly softened near a saturation field. It is shown that, owing
to a spin-orbit locking nature of the magnetic dipolar interaction, these soft
spin-wave volume-mode bands become chiral volume-mode bands with finite
topological Chern integers. A bulk-edge correspondence in IQH physics suggests
that such volume-mode bands are accompanied by a chiral magnetostatic spin-wave
edge mode. The existence of the edge mode is justified both by micromagnetic
simulations and by band calculations based on a linearized Landau-Lifshitz
equation. Employing intuitive physical arguments, we introduce proper
tight-binding models for these soft volume-mode bands. Based on the
tight-binding models, we further discuss possible applications to other systems
such as magnetic ultrathin films with perpendicular magnetic anisotropy (PMA).


title: A family of linearisable recurrences with the Laurent property

abstract:
  We consider a family of nonlinear recurrences with the Laurent property.
Although these recurrences are not generated by mutations in a cluster algebra,
they fit within the broader framework of Laurent phenomenon algebras, as
introduced recently by Lam and Pylyavskyy. Furthermore, each member of this
family is shown to be linearisable in two different ways, in the sense that its
iterates satisfy both a linear relation with constant coefficients and a linear
relation with periodic coefficients. Associated monodromy matrices and first
integrals are constructed, and the connection with the dressing chain for
Schrodinger operators is also explained.


title:
The Spitzer-South Pole Telescope Deep Field: Survey Design and IRAC
  Catalogs

abstract:
  The Spitzer-South Pole Telescope Deep Field (SSDF) is a wide-area survey
using Spitzer's Infrared Array Camera (IRAC) to cover 94 square degrees of
extragalactic sky, making it the largest IRAC survey completed to date outside
the Milky Way midplane. The SSDF is centered at 23:30,-55:00, in a region that
combines observations spanning a broad wavelength range from numerous
facilities. These include millimeter imaging from the South Pole Telescope,
far-infrared observations from Herschel/SPIRE, X-ray observations from the XMM
XXL survey, near-infrared observations from the VISTA Hemisphere Survey, and
radio-wavelength imaging from the Australia Telescope Compact Array, in a
panchromatic project designed to address major outstanding questions
surrounding galaxy clusters and the baryon budget. Here we describe the
Spitzer/IRAC observations of the SSDF, including the survey design,
observations, processing, source extraction, and publicly available data
products. In particular, we present two band-merged catalogs, one for each of
the two warm IRAC selection bands. They contain roughly 5.5 and 3.7 million
distinct sources, the vast majority of which are galaxies, down to the SSDF
5-sigma sensitivity limits of 19.0 and 18.2 Vega mag (7.0 and 9.4 microJy) at
3.6 and 4.5 microns, respectively.


title:
In-medium decay widths of hidden and open charm vector mesons in a field
  theoretic model for composite hadrons

abstract:
  We calculate the decay widths of the charmonium states, $J/\psi$, $\psi
(3686)$ and $\psi(3770)$, to $D\bar D$ pairs, as well as the decay width of
$D^* \rightarrow D\pi$, in isospin asymmetric strange hadronic matter, using a
field theoretical model for composite hadrons with quark constituents. For this
purpose we use the quark antiquark pair creation term of the free Dirac
Hamiltonian written in terms of the constituent quark field operators, and use
explicit charmonium, $D$, $\bar {D}$, $D^*$ and $\pi$ states to evaluate the
matrix elements for the charmonium as well as $D^*$ decay amplitudes. The
medium modifications of the partial decay widths of charmonium to $D\bar D$
pair, arising from the mass modifications of the $D(\bar D)$ and the charmonium
states calculated in a chiral effective model, are also included. The effects
of the isospin asymmetry, the strangeness fraction of the hadronic matter on
the masses of the charmonium states and $D(\bar D)$ mesons and hence on the
decay widths, have also been studied. The decay width of $D^* \rightarrow D
\pi$ in the hadronic matter has also been calculated within the composite quark
model in the present work, accounting for the medium modifications of the $D$
and $D^*$ masses. The density modifications of the charmonium states and
$D(D^*)$ mesons, which are observed to be appreciable at high densities, will
be of relevance in the compressed baryonic matter (CBM) experiments at the
future facility of FAIR, GSI, where charmed hadrons will be produced by
annihilation of antiprotons on nuclei. The interactions of the charmonium
states and $D(D^*)$ with the nuclear medium could lead to the possiblility of
the formation of exotic bound states of the nuclei with the (excited)
charmonium states as well as with $D(D^*)$ mesons.


title:
Exchange relaxation as the mechanism of ultrafast spin reorientation in
  two-sublattice ferrimagnets

abstract:
  In the exchange approximation, an exact solution is obtained for the
sublattice magnetizations evolution in a two-sublattice ferrimagnet. Nonlinear
regimes of spin dynamics are found that include both the longitudinal and
precessional evolution of the sublattice magnetizations, with the account taken
of the exchange relaxation. In particular, those regimes describe the spin
switching observed in the GdFeCo alloy under the influence of a femtosecond
laser pulse.


title:
Dynamics of stainless steel turning: Analysis by flicker-noise
  spectroscopy

abstract:
  We use flicker-noise spectroscopy (FNS), a phenomenological method for the
analysis of time and spatial series operating on structure functions and power
spectrum estimates, to identify and study harmful chatter vibrations in a
regenerative turning process. The 3D cutting force components experimentally
measured during stainless steel turning are analyzed, and the parameters of
their stochastic dynamics are estimated. Our analysis shows that the system
initially exhibiting regular vibrations associated with spindle rotation
becomes unstable to high-frequency noisy oscillations (chatter) at larger
cutting depths. We suggest that the chatter may be attributed to frictional
stick-and-slip interactions between the contact surfaces of cutting tool and
workpiece. We compare our findings with previously reported results obtained by
statistical, recurrence, multifractal, and wavelet methods. We discuss the
potential of FNS in monitoring the turning process in manufacturing practice.


title: Rydberg tomography of an ultra-cold atomic cloud

abstract:
  One of the most striking features of the strong interactions between Rydberg
atoms is the dipole blockade effect, which allows only a single excitation to
the Rydberg state within the volume of the blockade sphere. Here we present a
method that spatially visualizes this phenomenon in an inhomogeneous gas of
ultra-cold rubidium atoms. In our experiment we scan the position of one of the
excitation lasers across the cold cloud and determine the number of Rydberg
excitations detected as a function of position. Comparing this distribution to
the one obtained for the number of ions created by a two-photon ionization
process via the intermediate 5P level, we demonstrate that the blockade effect
modifies the width of the Rydberg excitation profile. Furthermore, we study the
dynamics of the Rydberg excitation and find that the timescale for the
excitation depends on the atomic density at the beam position.


title: A 64-dimensional two-distance counterexample to Borsuk's conjecture

abstract:
  In 1933 Karol Borsuk asked whether each bounded set in the n-dimensional
Euclidean space can be divided into n+1 parts of smaller diameter. The diameter
of a set is defined as the supremum (least upper bound) of the distances of
contained points. Implicitly, the whole set is assumed to contain at least two
points.
  The hypothesis that the answer to that question is positive became famous
under the name Borsuk's conjecture. Beginning with Jeff Kahn and Gil Kalai,
from 1993 to 2003 several authors have proved that in certain (almost all) high
dimensions such a division is not generally possible.
  In a paper published in 2013, Andriy V. Bondarenko constructed a
65-dimensional two-distance set of 416 vectors that cannot be divided into less
than 84 parts of smaller diameter. That was not just the first known
two-distance counterexample to Borsuk's conjecture but also a considerable
reduction of the lowest known dimension the conjecture fails in in general.
  This article presents a 64-dimensional subset of the vector set mentioned
above that cannot be divided into less than 71 (by A. Bondarenko 72) parts of
smaller diameter, that way delivering a two-distance counterexample to Borsuk's
conjecture in dimension 64.
  The contained proof relies on the results of some (combinatorial)
calculations. The additionally (in the source package) provided small computer
program G24CHK needs about one second for that task on a 1 GHz Intel PIII.
  Meanwhile a short paper by this author and Andries E. Brouwer that follows
the principal idea of this article but avoids the extensive computational part
has been submitted to The Electronic Journal of Combinatorics.


title: Understanding Nuclei in the upper sd - shell

abstract:
  Nuclei in the upper-$sd$ shell usually exhibit characteristics of spherical
single particle excitations. In the recent years, employment of sophisticated
techniques of gamma spectroscopy has led to observation of high spin states of
several nuclei near A$\simeq$ 40. In a few of them multiparticle, multihole
rotational states coexist with states of single particle nature. We have
studied a few nuclei in this mass region experimentally, using various
campaigns of the Indian National Gamma Array setup. We have compared and
combined our empirical observations with the large-scale shell model results to
interpret the structure of these nuclei. Indication of population of states of
large deformation has been found in our data. This gives us an opportunity to
investigate the interplay of single particle and collective degrees of freedom
in this mass region.


title: Diophantine approximation and coloring

abstract:
  We demonstrate how connections between graph theory and Diophantine
approximation can be used in conjunction to give simple and accessible proofs
of seemingly difficult results in both subjects.


title: On the Verification of a WiMax Design Using Symbolic Simulation

abstract:
  In top-down multi-level design methodologies, design descriptions at higher
levels of abstraction are incrementally refined to the final realizations.
Simulation based techniques have traditionally been used to verify that such
model refinements do not change the design functionality. Unfortunately, with
computer simulations it is not possible to completely check that a design
transformation is correct in a reasonable amount of time, as the number of test
patterns required to do so increase exponentially with the number of system
state variables. In this paper, we propose a methodology for the verification
of conformance of models generated at higher levels of abstraction in the
design process to the design specifications. We model the system behavior using
sequence of recurrence equations. We then use symbolic simulation together with
equivalence checking and property checking techniques for design verification.
Using our proposed method, we have verified the equivalence of three WiMax
system models at different levels of design abstraction, and the correctness of
various system properties on those models. Our symbolic modeling and
verification experiments show that the proposed verification methodology
provides performance advantage over its numerical counterpart.


title: Gold, Oil, and Stocks

abstract:
  We employ a wavelet approach and conduct a time-frequency analysis of dynamic
correlations between pairs of key traded assets (gold, oil, and stocks)
covering the period from 1987 to 2012. The analysis is performed on both
intra-day and daily data. We show that heterogeneity in correlations across a
number of investment horizons between pairs of assets is a dominant feature
during times of economic downturn and financial turbulence for all three pairs
of the assets under research. Heterogeneity prevails in correlations between
gold and stocks. After the 2008 crisis, correlations among all three assets
increase and become homogenous: the timing differs for the three pairs but
coincides with the structural breaks that are identified in specific
correlation dynamics. A strong implication emerges: during the period under
research, and from a different-investment-horizons perspective, all three
assets could be used in a well-diversified portfolio only during relatively
short periods.


title: On Kolmogorov Complexity of Random Very Long Braided Words

abstract:
  Any positive word comprised of random sequence of tokens form a finite
alphabet can be reduced (without change of length) using an appropriate size
Braid group relationships. Surprisingly the Braid relations dramatically reduce
the Kolmogorov Complexity of the original random word and do so in distinct
bands of (rate of change) values with gaps in between. Distribution of these
bands are estimated and empirical statistics collected by actually coding
approximations to the Kolmogorov Complexity (in Mathematica 9.0).
Lempel-Ziv-Welch lossless compression algorithm techniques used to estimate the
distribution for gaped bands. Evidence provided that such distributions of
reduction in Kolmogorov Complexity based upon Braid groups are universal i.e.
they can model more general algebraic structures other than Braid groups.


title:
Photonic Design: From Fundamental Solar Cell Physics to Computational
  Inverse Design

abstract:
  Photonic innovation is becoming ever more important in the modern world.
Optical systems are dominating shorter and shorter communications distances,
LED's are rapidly emerging for a variety of applications, and solar cells show
potential to be a mainstream technology in the energy space. The need for
novel, energy-efficient photonic and optoelectronic devices will only increase.
This work unites fundamental physics and a novel computational inverse design
approach towards such innovation.
  The first half of the dissertation is devoted to the physics of
high-efficiency solar cells. As solar cells approach fundamental efficiency
limits, their internal physics transforms. Photonic considerations, instead of
electronic ones, are the key to reaching the highest voltages and efficiencies.
Proper photon management led to Alta Device's recent dramatic increase of the
solar cell efficiency record to 28.3%. Moreover, approaching the
Shockley-Queisser limit for any solar cell technology will require light
extraction to become a part of all future designs.
  The second half of the dissertation introduces inverse design as a new
computational paradigm in photonics. An assortment of techniques (FDTD, FEM,
etc.) have enabled quick and accurate simulation of the "forward problem" of
finding fields for a given geometry. However, scientists and engineers are
typically more interested in the inverse problem: for a desired functionality,
what geometry is needed? Answering this question breaks from the emphasis on
the forward problem and forges a new path in computational photonics. The
framework of shape calculus enables one to quickly find superior, non-intuitive
designs. Novel designs for optical cloaking and sub-wavelength solar cell
applications are presented.


title: On the strength of the nonlinearity in isotropic turbulence

abstract:
  Turbulence governed by the Navier-Stokes equations shows a tendency to evolve
towards a state in which the nonlinearity is diminished. In fully developed
turbulence this tendency can be measured by comparing the variance of the
nonlinear term to the variance of the same quantity measured in a Gaussian
field with the same energy distribution. In order to study this phenomenon at
high Reynolds numbers, a version of the Direct Interaction Approximation is
used to obtain a closed expression for the statistical average of the
mean-square nonlinearity. The wavenumber spectrum of the mean-square nonlinear
term is evaluated and its scaling in the inertial range is investigated as a
function of the Reynolds number. Its scaling is dominated by the sweeping by
the energetic scales, but this sweeping is weaker than predicted by a random
sweeping estimate. At inertial range scales, the depletion of nonlinearity as a
function of the wavenumber is observed to be constant. At large it is observed
that the mean-square nonlinearity is larger than its Gaussian estimate, which
is shown to be related to the non-Gaussianity of the Reynolds-stress
fluctuations at these scales.


title:
A saddle-point approach to the Monge-Kantorovich optimal transport
  problem

abstract:
  The Monge-Kantorovich problem is revisited by means of a variant of the
saddle-point method without appealing to $c$-conjugates. A new abstract
characterization of the optimal plans is obtained in the case where the cost
function takes infinite values. It leads us to new explicit sufficient and
necessary optimality conditions. As by-products, we obtain a new proof of the
well-known Kantorovich dual equality and an improvement of the convergence of
the minimizing sequences.


title:
A survey of the Schr\"odinger problem and some of its connections with
  optimal transport

abstract:
  This article is aimed at presenting the Schr\"odinger problem and some of its
connections with optimal transport. We hope that it can be used as a basic
user's guide to Schr\"odinger problem. We also give a survey of the related
literature. In addition, some new results are proved.


title: Asteroids in retrograde resonance with Jupiter and Saturn

abstract:
  We identify a set of asteroids among Centaurs and Damocloids, that orbit
contrary to the common direction of motion in the Solar System and that enter
into resonance with Jupiter and Saturn. Their orbits have inclinations I >= 140
deg and semi-major axes a < 15 AU. Two objects are currently in retrograde
resonance with Jupiter: 2006 BZ8 in the 2/-5 resonance and 2008 SO218 in the
1/-2 resonance. One object, 2009 QY6, is currently in the 2/-3 retrograde
resonance with Saturn. These are the first examples of Solar System objects in
retrograde resonance. The present resonant configurations last for several
thousand years. Brief captures in retrograde resonance with Saturn are also
possible during the 20,000 years integration timespan, particularly in the 1/-1
resonance (2006 BZ8) and the 9/-7 resonance (1999 LE31).


title: Some properties of path measures

abstract:
  We call any measure on a path space, a path measure. Some notions about path
measures which appear naturally when solving the Schr\"odinger problem are
presented and worked out in detail.


title:
Flat bundles, von Neumann algebras and $K$-theory with
  $\R/\Z$-coefficients

abstract:
  Let $M$ be a closed manifold and $\alpha : \pi_1(M)\to U_n$ a representation.
We give a purely $K$-theoretic description of the associated element $[\alpha]$
in the $K$-theory of $M$ with $\R/\Z$-coefficients. To that end, it is
convenient to describe the $\R/\Z$-$K$-theory as a relative $K$-theory with
respect to the inclusion of $\C$ in a finite von Neumann algebra $B$. We use
the following fact: there is, associated with $\alpha$, a finite von Neumann
algebra $B$ together with a flat bundle $\cE\to M$ with fibers $B$, such that
$E_\a\otimes \cE$ is canonically isomorphic with $\C^n\otimes \cE$, where
$E_\alpha$ denotes the flat bundle with fiber $\C^n$ associated with $\alpha$.
We also discuss the spectral flow and rho type description of the pairing of
the class $[\alpha]$ with the $K$-homology class of an elliptic selfadjoint
(pseudo)-differential operator $D$ of order 1.


title: Instruction sequence expressions for the secure hash algorithm SHA-256

abstract:
  The secure hash function SHA-256 is a function on bit strings. This means
that its restriction to the bit strings of any given length can be computed by
a finite instruction sequence that contains only instructions to set and get
the content of Boolean registers, forward jump instructions, and a termination
instruction. We describe such instruction sequences for the restrictions to bit
strings of the different possible lengths by means of uniform terms from an
algebraic theory.


title: Partitions of single exterior type

abstract:
  We characterize the irreducible representations of the general linear group
GL(V) that have multiplicity 1 in the direct sum of all Schur modules of a
given exterior power of V. These have come up in connection with the relations
of the lower order minors of a generic matrix. We show that the minimal
relations conjectured by Bruns, Conca and Varbaro are exactly those coming from
partitions of single exterior type.


title: A model with two quantum particles similar to the hydrogen atom

abstract:
  The hydrogen atom with the Coulomb interaction is one of the exactly solvable
non-relativistic quantum models. Unlike many other exactly solvable models it
describes a real physical object providing the formulas for energy levels and
stationary state wave functions of a real hydrogen atom. In this paper we
modify the model replacing the Coulomb interaction by the interaction of the
proton and the electron with the classical electromagnetic field serving as an
intermediary transmitting the electromagnetic interaction of these two charged
quantum particles.


title: Transition from resonances to surface waves in pi^+-p elastic scattering

abstract:
  In this article we study resonances and surface waves in $\pi^+$--p
scattering. We focus on the sequence whose spin-parity values are given by $J^p
= {3/2}^+,{7/2}^+, {11/2}^+, {15/2}^+,{19/2}^+$. A widely-held belief takes for
granted that this sequence can be connected by a moving pole in the complex
angular momentum (CAM) plane, which gives rise to a linear trajectory of the
form $J = \alpha_0+\alpha' m^2$, $\alpha'\sim 1/(\mathrm{GeV})^2$, which is the
standard expression of the Regge pole trajectory. But the phenomenology shows
that only the first few resonances lie on a trajectory of this type. For higher
$J^p$ this rule is violated and is substituted by the relation $J\sim kR$,
where $k$ is the pion--nucleon c.m.s.-momentum, and $R\sim 1$ fm. In this
article we prove: (a) Starting from a non-relativistic model of the proton,
regarded as composed by three quarks confined by harmonic potentials, we prove
that the first three members of this $\pi^+$-p resonance sequence can be
associated with a vibrational spectrum of the proton generated by an algebra
$Sp(3,R)$. Accordingly, these first three members of the sequence can be
described by Regge poles and lie on a standard linear trajectory. (b) At higher
energies the amplitudes are dominated by diffractive scattering, and the
creeping waves play a dominant role. They can be described by a second class of
poles, which can be called Sommerfeld's poles, and lie on a line nearly
parallel to the imaginary axis of the CAM-plane. (c) The Sommerfeld pole which
is closest to the real axis of the CAM-plane is dominant at large angles, and
describes in a proper way the backward diffractive peak in both the following
cases: at fixed $k$, as a function of the scattering angle, and at fixed
scattering angle $\theta=\pi$, as a function of $k$. (d) The evolution of this
pole, as a function of $k$, is given in first approximation by $J\simeq kR$.


title:
Performance Analysis of VoIP Traffic in WiMAX using various Service
  Classes

abstract:
  Worldwide Interoperability for Microwave Access (WiMAX) is currently one of
the hottest technologies in wireless, it is a standard-based on the IEEE 802.16
wireless technology that provides high throughput broadband connections over
long distance, which supports Point to MultiPoint (PMP) broadband wireless
access. In parallel, Voice over Internet Protocol is a promising new technology
which provides access to voice communication over internet protocol based
network, it becomes an alternative to public switched telephone networks due to
its capability of transmission of voice as packets over IP networks. Therefore
VoIP is largely intolerant of delay and hence it needs a high priority
transmission. In this paper we investigate the performances of the most common
VoIP codecs, which are G711, G7231 and G729 over a WiMAX network using various
service classes and NOAH as a transport protocol. To analyze the QoS
parameters, the popular network simulator ns2 was used. Various parameters that
determine QoS of real life usage scenarios and traffic flows of applications is
analyzed. The objective is to compare different types of service classes with
respect to the QoS parameters, such as, throughput, average jitter and average
delay.


title: Piecewise rigid curve deformation via a Finsler steepest descent

abstract:
  This paper introduces a novel steepest descent flow in Banach spaces. This
extends previous works on generalized gradient descent, notably the work of
Charpiat et al., to the setting of Finsler metrics. Such a generalized gradient
allows one to take into account a prior on deformations (e.g., piecewise rigid)
in order to favor some specific evolutions. We define a Finsler gradient
descent method to minimize a functional defined on a Banach space and we prove
a convergence theorem for such a method. In particular, we show that the use of
non-Hilbertian norms on Banach spaces is useful to study non-convex
optimization problems where the geometry of the space might play a crucial role
to avoid poor local minima. We show some applications to the curve matching
problem. In particular, we characterize piecewise rigid deformations on the
space of curves and we study several models to perform piecewise rigid
evolution of curves.


title:
Engineering three-body interaction and Pfaffian states in circuit QED
  systems

abstract:
  We demonstrate a scheme to engineer the three-body interaction in circuit-QED
systems by tuning a fluxonium qubit. Connecting such qubits in a square lattice
and controlling the tunneling dynamics, in the form of a synthesized magnetic
field, for the photon-like excitations of the system, allows the implementation
of a parent Hamiltonian whose ground state is the Pfaffian wave function.
Furthermore, we show that the addition of the next-nearest neighbor tunneling
stabilizes the ground state, recovering the expected topological degeneracy
even for small lattices. Finally, we discuss the implementation of these ideas
with the current technology.


title: Lazy random walks and optimal transport on graphs

abstract:
  This paper is about the construction of displacement interpolations on a
discrete metric graph. Our approach is based on the approximation of any
optimal transport problem whose cost function is a distance on a discrete graph
by a sequence of Schr\"odinger problems associated with random walks whose jump
frequencies tend down to zero. Displacement interpolations are defined as the
limit of the time-marginal flows of the solutions to the Schr\"odinger
problems. This allows to work with these interpolations by doing stochastic
calculus on the approximating random walks which are regular objects, and then
to pass to the limit in a slowing down procedure. The main convergence results
are based on Gamma-convergence of entropy minimization problems. As a
by-product, we obtain new results about optimal transport on graphs.


title: An Enhanced Features Extractor for a Portfolio of Constraint Solvers

abstract:
  Recent research has shown that a single arbitrarily efficient solver can be
significantly outperformed by a portfolio of possibly slower on-average
solvers. The solver selection is usually done by means of (un)supervised
learning techniques which exploit features extracted from the problem
specification. In this paper we present an useful and flexible framework that
is able to extract an extensive set of features from a Constraint
(Satisfaction/Optimization) Problem defined in possibly different modeling
languages: MiniZinc, FlatZinc or XCSP. We also report some empirical results
showing that the performances that can be obtained using these features are
effective and competitive with state of the art CSP portfolio techniques.


title:
An inverse problem for a class of canonical systems and its applications
  to self-reciprocal polynomials

abstract:
  A canonical system is a kind of first-order system of ordinary differential
equations on an interval of the real line parametrized by complex numbers. It
is known that any solution of a canonical system generates an entire function
of the Hermite-Biehler class. In this paper, we deal with the inverse problem
to recover a canonical system from a given entire function of the
Hermite-Biehler class satisfying appropriate conditions. This type inverse
problem was solved by de Branges in 1960s. However his results are often not
enough to investigate a Hamiltonian of recovered canonical system. In this
paper, we present an explicit way to recover a Hamiltonian from a given
exponential polynomial belonging to the Hermite-Biehler class. After that, we
apply it to study distributions of roots of self-reciprocal polynomials.


title: Cosmological Sigma Model with Non-Minimal Coupling to the Target Space

abstract:
  A homogeneous and isotropic Universe in the framework of nonlinear sigma
model with non-minimal coupling to the target space is considered. A
two-component model of such a sort is preliminary investigated. Some solutions
for this model are given. Perspectives and directions of development of such a
sort of models are designated.


title:
Dependence of the leptonic decays of H^- on the neutrino mixing angles
  theta_{13} and theta_{23} in models with neutrinophilic charged scalars

abstract:
  In the Higgs Triplet Model and the neutrinophilic Two-Higgs-Doublet Model the
observed neutrinos obtain mass from a vacuum expectation value which is much
smaller than the vacuum expectation value of the Higgs boson in the Standard
Model. Both models contain a singly charged Higgs boson (H^-) whose Yukawa
coupling is directly related to the neutrino mass (i.e. a "neutrinophilic
charged Higgs"). The partial decay widths of H^- into a charged lepton and a
neutrino (H^- to l^- nu) depend identically on the neutrino masses and mixings
in the two models. We quantify the impact of the recent measurement of
sin^2(2theta_{13}), which plays a crucial role in determining the magnitude of
the branching ratio of H^- to e^- nu for the case of a normal neutrino mass
ordering if the lightest neutrino mass m_0 < 10^{-3} eV. We also discuss the
sizeable dependence of H^- to mu^- nu and H^- to tau^- nu on sin^2(theta_{23}),
which would enable information to be obtained on sin^2(theta_{23}) and the sign
of \Delta m^2_{31} if these decays are measured. Such information would help
neutrino oscillation experiments to determine the CP-violating phase \delta.


title: Spin effects in strong-field laser-electron interactions

abstract:
  The electron spin degree of freedom can play a significant role in
relativistic scattering processes involving intense laser fields. In this
contribution we discuss the influence of the electron spin on (i) Kapitza-Dirac
scattering in an x-ray laser field of high intensity, (ii) photo-induced
electron-positron pair production in a strong laser wave and (iii) multiphoton
electron-positron pair production on an atomic nucleus. We show that in all
cases under consideration the electron spin can have a characteristic impact on
the process properties and their total probabilities. To this end,
spin-resolved calculations based on the Dirac equation in the presence of an
intense laser field are performed. The predictions from Dirac theory are also
compared with the corresponding results from the Klein-Gordon equation.


title: Euclidean wormholes with minimally coupled scalar fields

abstract:
  A detailed study of quantum and semiclassical Euclidean wormholes for
Einstein's theory with a minimally coupled scalar field has been performed for
a class of potentials. Massless, constant, massive (quadratic in the scalar
field) and inverse (linear) potentials admit Hawking and Page wormhole boundary
condition both in the classically forbidden and allowed regions. Inverse
quartic potential has been found to exhibit semiclassical wormhole
configuration. Classical wormholes under suitable back-reaction leading to a
finite radius of the throat, where strong energy condition is satisfied, have
been found for the zero, constant, quadratic and exponential potentials.
Treating such classical Euclidean wormholes as initial condition, late stage of
cosmological evolution has been found to remain unaltered from standard
Friedmann cosmology, except for the constant potential which under
back-reaction produces a term like negative cosmological constant.


title:
Metropolis Monte Carlo on the Lefschetz thimble: application to a
  one-plaquette model

abstract:
  We propose a new algorithm based on the Metropolis sampling method to perform
Monte Carlo integration for path integrals in the recently proposed formulation
of quantum field theories on the Lefschetz thimble. The algorithm is based on a
mapping between the curved manifold defined by the Lefschetz thimble of the
full action and the flat manifold associated with the corresponding quadratic
action. We discuss an explicit method to calculate the residual phase due to
the curvature of the Lefschetz thimble. Finally, we apply this new algorithm to
a simple one-plaquette model where our results are in perfect agreement with
the analytic integration. We also show that for this system the residual phase
does not represent a sign problem.

categories: physics.comp-ph cond-mat.str-el hep-lat nucl-th


title:
Explicit recurrence criteria for symmetric gradient type Dirichlet forms
  satisfying a Hamza type condition

abstract:
  In this note, we present explicit conditions for symmetric gradient type
Dirichlet forms to be recurrent. This type of Dirichlet form is typically
strongly local and hence associated to a diffusion. We consider the one
dimensional case and the multidimensional case, as well as the case with
reflecting boundary conditions. Our main achievement is that the explicit
results are obtained under quite weak assumptions on the closability, hence
regularity of the underlying coefficients. Especially in dimension one, where a
Hamza type condition is assumed, the construction of the sequence of functions
$(u_n)_{n\in \N}$ in the Dirichlet space that determine recurrence works for
quite general Dirichlet forms but is still explicit.


title:
The Detector System for the Stratospheric Kinetic Inductance Polarimeter
  (SKIP)

abstract:
  The Stratospheric Kinetic Inductance Polarimeter (SKIP) is a proposed
balloon-borne experiment designed to study the cosmic microwave background, the
cosmic infrared background and Galactic dust emission by observing 1133 square
degrees of sky in the Northern Hemisphere with launches from Kiruna, Sweden.
The instrument contains 2317 single-polarization, horn-coupled, aluminum
lumped-element kinetic inductance detectors (LEKID). The LEKIDs will be
maintained at 100 mK with an adiabatic demagnetization refrigerator. The
polarimeter operates in two configurations, one sensitive to a spectral band
centered on 150 GHz and the other sensitive to 260 and 350 GHz bands. The
detector readout system is based on the ROACH-1 board, and the detectors will
be biased below 300 MHz. The detector array is fed by an F/2.4 crossed-Dragone
telescope with a 500 mm aperture yielding a 15 arcmin FWHM beam at 150 GHz. To
minimize detector loading and maximize sensitivity, the entire optical system
will be cooled to 1 K. Linearly polarized sky signals will be modulated with a
metal-mesh half-wave plate that is mounted at the telescope aperture and
rotated by a superconducting magnetic bearing. The observation program consists
of at least two, five-day flights beginning with the 150 GHz observations.


title: The index of geometric operators on Lie groupoids

abstract:
  We revisit the cohomological index theorem for elliptic elements in the
universal enveloping algebra of a Lie groupoid previously proved by the
authors. We prove a Thom isomorphism for Lie algebroids which enables us to
rewrite the "topological side" of the index theorem. This results in index
formulae for Lie groupoid analogues of the familiar geometric operators on
manifolds such as the signature and Dirac operator expressed in terms of the
usual characteristic classes in Lie algebroid cohomology.


title:
Leadership without Leaders? Starters and Followers in Online Collective
  Action

abstract:
  The Internet has been ascribed a prominent role in collective action,
particularly with widespread use of social media. But most mobilisations fail.
We investigate the characteristics of those few mobilisations that succeed and
hypothesise that the presence of 'starters' with low thresholds for joining
will determine whether a mobilisation achieves success, as suggested by
threshold models. We use experimental data from public good games to identify
personality types associated with willingness to start in collective action. We
find a significant association between both extraversion and internal locus of
control, and willingness to start, while agreeableness is associated with a
tendency to follow. Rounds without at least a minimum level of extraversion
among the participants are unlikely to be funded, providing some support for
the hypothesis.


title: A quantum memory for orbital angular momentum photonic qubits

abstract:
  Among the optical degrees of freedom, the orbital angular momentum of light
provides unique properties, including mechanical torque action with
applications for light manipulation, enhanced sensitivity in imaging techniques
and potential high-density information coding for optical communication
systems. Recent years have also seen a tremendous interest in exploiting
orbital angular momentum at the single-photon level in quantum information
technologies. In this endeavor, here we demonstrate the implementation of a
quantum memory for quantum bits encoded in this optical degree of freedom. We
generate various qubits with computer-controlled holograms, store and retrieve
them on demand. We further analyse the retrieved states by quantum tomography
and thereby demonstrate fidelities exceeding the classical benchmark,
confirming the quantum functioning of our storage process. Our results provide
an essential capability for future networks exploring the promises of orbital
angular momentum of photons for quantum information applications.


title: Modeling the Rise in Internet-based Petitions

abstract:
  Contemporary collective action, much of which involves social media and other
Internet-based platforms, leaves a digital imprint which may be harvested to
better understand the dynamics of mobilization. Petition signing is an example
of collective action which has gained in popularity with rising use of social
media and provides such data for the whole population of petition signatories
for a given platform. This paper tracks the growth curves of all 20,000
petitions to the UK government over 18 months, analyzing the rate of growth and
outreach mechanism. Previous research has suggested the importance of the first
day to the ultimate success of a petition, but has not examined early growth
within that day, made possible here through hourly resolution in the data. The
analysis shows that the vast majority of petitions do not achieve any measure
of success; over 99 percent fail to get the 10,000 signatures required for an
official response and only 0.1 percent attain the 100,000 required for a
parliamentary debate. We analyze the data through a multiplicative process
model framework to explain the heterogeneous growth of signatures at the
population level. We define and measure an average outreach factor for
petitions and show that it decays very fast (reducing to 0.1% after 10 hours).
After 24 hours, a petition's fate is virtually set. The findings seem to
challenge conventional analyses of collective action from economics and
political science, where the production function has been assumed to follow an
S-shaped curve.

categories: physics.soc-ph cs.CY cs.HC cs.SI physics.data-an


title:
Vortex precession frequency and its amplitude-dependent shift in
  cylindrical nanomagnets

abstract:
  Frequency of free magnetic vortex precession in circular soft ferromagnetic
nano-cylinders (magnetic dots) of various sizes is an important parameter, used
in design of spintronic devices (such as spin-torque microwave
nano-oscillators) and characterization of magnetic nanostructures. Here, using
a recently developed collective-variable approach to non-linear dynamics of
magnetic textures in planar nano-magnets, this frequency and its
amplitude-dependent shift are computed analytically and plotted for the full
range of cylinder geometries. The frequency shift is positive in large planar
dots, but becomes negative in smaller and more elongated ones. At certain dot
dimensions a zero frequency shift is realized, which can be important for
enhancing frequency stability of magnetic nano-oscillators.


title:
Electron-Impact Excitation Collision Strengths and Theoretical Line
  Intensities for Fine-Structure Transitions in S III

abstract:
  We present Maxwellian-averaged effective collision strengths for the
electron-impact excitation of S III over a wide range of electron temperatures
of astrophysical importance, log T(K) = 3.0-6.0. The calculation incorporates
53 fine-structure levels arising from the six lowest configurations, giving
rise to 1378 individual lines, and is undertaken using the recently developed
RMATRX II plus FINE95 suite of codes. A detailed comparison is made with a
previous R-matrix calculation and significant differences are found for some
transitions. The atomic data are subsequently incorporated into the modeling
code CLOUDY to generate line intensities for a range of plasma parameters, with
emphasis on allowed UV and EUV emission lines detected from the Io plasma
torus. Electron density-sensitive line ratios are calculated with the present
atomic data and compared with those from CHIANTI v7.1, as well as with Io
plasma torus spectra obtained by FUSE and EUVE. The present line intensities
are found to agree well with the observational results and provide a noticeable
improvement upon the values predicted by CHIANTI.


title:
Dynamics and decoherence in the central spin model in the low-field
  limit

abstract:
  We present a combination of analytic calculations and a powerful numerical
method for large spin baths in the low-field limit. The hyperfine interaction
between the central spin and the bath is fully captured by the density matrix
renormalization group. The adoption of the density matrix renormalization group
for the central spin model is presented and a proper method for calculating the
real-time evolution at infinite temperature is identified. In addition, we
study to which extent a semiclassical model, where a quantum spin-1/2 interacts
with a bath of classical Gaussian fluctuations, can capture the physics of the
central spin model. The model is treated by average Hamiltonian theory and by
numerical simulation.


title:
Improving visibility in photoacoustic imaging using dynamic speckle
  illumination

abstract:
  In high-frequency photoacoustic imaging with uniform illumination,
homogeneous photo-absorbing structures may be invisible because of their large
size or limited-view issues. Here we show that, by exploiting dynamic speckle
illumination, it is possible to reveal features which are normally invisible
with a photoacoustic system comprised of a 20MHz linear ultrasound array. We
demonstrate imaging of a 5 mm diameter absorbing cylinder and a 30 micrometer
black thread arranged in a complex shape. The hidden structures are directly
retrieved from photoacoustic images recorded for different random speckle
illuminations of the phantoms by assessing the variation in the value of each
pixel over the illumination patterns.


title: Effects of disorder on Coulomb-assisted braiding of Majorana zero modes

abstract:
  Majorana zero modes in one-dimensional topological superconductors obey
non-Abelian braiding statistics. Braiding manipulations can be realized by
controlling Coulomb couplings in hybrid Majorana-transmon devices. However,
strong disorder may induce accidental Majorana modes, which are expected to
have detrimental effects on braiding statistics. Nevertheless, we show that the
Coulomb-assisted braiding protocol is efficiently realized also in the presence
of accidental modes. The errors occurring during the braiding cycle are small
if the couplings of the computational Majorana modes to the accidental ones are
much weaker than the maximum Coulomb coupling.


title:
Implementing an analytical formula for calculating M(3000)F2 in the
  ionosonde operated in Havana

abstract:
  Determining the factor M(3000)F2 is very important for ionograms analysis
obtained of Ionosonde. M(3000)F2 is the result of the maximum usable frequency
(MUF), for to 3000 km distance, divided by the critical frequency of the F2
layer (FoF2). Nowadays, the graphic method to determine the M(3000)F2 is used
in Havana station in the ionograms analysis. The purpose of this work is to
implement an analytic method that allows us the direct obtaining of M(3000)F2,
so it could be programmed and incorporated as part of ionograms elaboration
process in Havana station. When is used a PC, some points in the ionogram can
be determined. This dataset (f; h') are used to calculate analytically the
factor M(3000)F2 . Comparison between the analytic method implemented and the
old graphic method are shown. The new method is more accurate and the errors
are diminished in the factor M(3000)F2.


title:
Observation of TeV-PeV cosmic ray anisotropy with IceCube, IceTop and
  AMANDA

abstract:
  The study of cosmic ray anisotropy in the TeV-PeV energy range could provide
clues about the origin and propagation of cosmic rays in our galactic
neighborhood. Because the observed anisotropy is very small, below the
per-mille level, large event volumes are needed in order to characterize it in
sufficient detail. Over the last six years, the IceCube Observatory has
collected 150 billion cosmic ray induced muon events. This large data sample
made it possible to detect anisotropies in the southern hemisphere, down to the
10$^{-5}$ level, at primary energies in excess of 10 TeV. The observed
anisotropy is not a simple dipole, but it can be described as composed of
multipole components of the spherical harmonic expansion, to about
10$^{\circ}$. A change in topological structure of the cosmic ray arrival
distribution is observed above 100 TeV. Data collected with the air shower
array IceTop above 300 TeV confirm the observations up to the PeV energy scale.
Moreover, the addition of data collected with the AMANDA neutrino telescope,
which operated between 2000 and 2007, has enabled us to search for time
variability in the observed TeV anisotropy.


title:
Predicative Lexicographic Path Orders: An Application of Term Rewriting
  to the Region of Primitive Recursive Functions

abstract:
  In this paper we present a novel termination order the {\em predicative
lexicographic path order} (PLPO for short), a syntactic restriction of the
lexicographic path order. As well as lexicographic path orders, several
non-trivial primitive recursive equations, e.g., primitive recursion with
parameter substitution, unnested multiple recursion, or simple nested
recursion, can be oriented with PLPOs. It can be shown that the PLPO however
only induces primitive recursive upper bounds on derivation lengths of
compatible rewrite systems. This yields an alternative proof of a classical
fact that the class of primitive recursive functions is closed under those
non-trivial primitive recursive equations.


title: Nearly Gaussian random variables and application to meteorology

abstract:
  We consider a nearly Gaussian random variable $X$ (see \cite{Lefebvre}) that,
after a power transformation, the variable $X^c$ where $c=\{(2k+1)/(2j+1)\}$,
$k,j=\{0,1,\dots\}$, is approximately Gaussian. This transformation is useful
to model errors in temperature forecasts.


title: The Dark Mass Problem

abstract:
  I discuss some of the basic properties of a potential theory derived from a
modified Newton's law of action at a distance that includes a $1/r$ attractive
force.


title: Extension of H\"older's Theorem in Diff_{+}^{1+\epsilon}(I)

abstract:
  We prove that if \Gamma is subgroup of Diff_{+}^{1+\epsilon}(I) and N is a
natural number such that every non-identity element of \Gamma has at most N
fixed points then \Gamma is solvable. If in addition \Gamma is a subgroup of
Diff_{+}^{2}(I) then we can claim that \Gamma is metaabelian.


title: Azumaya monads and comonads

abstract:
  The definition of Azumaya algebras over commutative rings $R$ require the
tensor product of modules over $R$ and the twist map for the tensor product of
any two $R$-modules. Similar constructions are available in braided monoidal
categories and Azumaya algebras were defined in these settings. Here we
introduce Azumaya monads on any category $\A$ by considering a monad $\bF$ on
$\A$ endowed with a distributive law $\lambda: FF\to FF$ satisfying the
Yang-Baxter equation (BD-law). This allows to introduce an {\em opposite monad}
$\bF^\la$ and a monad structure on $FF^\la$. For an {\em Azumaya monad} we
impose the condition that the canonical comparison functor induces an
equivalence between the category $\A$ and the category of $\bF\bF^\la$-modules.
Properties and characterisations of these monads are studied, in particular for
the case when $F$ allows for a right adjoint functor. Dual to Azumaya monads we
define {\em Azumaya comonads} and investigate the interplay between these
notions.
  In braided categories $(\V,\ot,I,\tau)$, for any $\V$-algebra $A$, the
braiding induces a BD-law $\tau_{A,A}:A\ot A\to A\ot A$ and $A$ is called left
(right) Azumaya, provided the monad $A\ot-$ (resp. $-\ot A$) is Azumaya. If
$\tau$ is a symmetry, or if the category $\V$ admits equalisers and
coequalisers, the notions of left and right Azumaya algebras coincide. The
general theory provides the definition of coalgebras in $\V$. Given a
cocommutative $\V$-coalgebra $\bD$, coalgebras $\bC$ over $\bD$ are defined as
coalgebras in the monoidal category of $\bD$-comodules and we describe when
these have the Azumaya property. In particular, over commutative rings $R$, a
coalgebra $C$ is Azumaya if and only if the dual $R$-algebra $C^*=\Hom_R(C,R)$
is an Azumaya algebra.


title: Synthetic spectra for O and B type subdwarf stars

abstract:
  We present a grid of optical (3200--7200 \AA) synthetic spectra calculated
with Tlusty/Synspec. The new NLTE model atmospheres include the most recent
hydrogen Stark broadening profiles; were calculated in opacity sampling and
limited to pure H/He composition. The grid covers the observed parameter space
of (He-)sdB and (He-)sdO stars, therefore it is suitable for the homogeneous
spectral analyses of such evolved stars.


title:
Half-Semiconductor antiferromagnets and Spin-Gapless-Semiconductor
  antiferromagnets

abstract:
  We propose a concept of half-semiconductor antiferromagnets in which both
spin-polarized valence and conduction bands belong to the same spin channel
with completely compensated spontaneous magnetization. Using density functional
theory plus Hubbard U (DFT+U) methods, we find a viable approach to achieve the
half-semiconductor antiferromagnets through the transition metal (TM) Fe and Cr
codoped boron nitride(BN) sheet. Moreover, spin gapless semiconductor
antiferromagnets with zero magnetic moment are also achieved in such systems.


title: Recent developments in nonleptonic kaon decays

abstract:
  I review the current status of nonleptonic kaon decays, placing special
emphasis on the recent theoretical progress. In particular, I concentrate on 3
points: (i) the improved determination of \epsilon_K, including both
perturbative and nonperturbative contributions; (ii) the efforts to tame (K ->
2\pi) transitions in lattice QCD; and (iii) the use of holographic methods to
solve the vector meson dominance puzzle in (K -> 3\pi).


title:
Network topology: detecting topological phase transitions in the Kitaev
  chain and the rotor plane

abstract:
  We propose a novel network measure of topological invariants, called
small-worldness, for identifying topological phase transitions of quantum and
classical spin models. Small-worldness is usually defined in the study of
social networks based on the best known discovery that one can find a short
chain of acquaintances connecting almost any two people on the planet. Here we
demonstrate that the small-world effect provides a useful description to
distinguish topologically trivial and non-trivial phases in the Kitaev chain
and accurately capture the Kosterlitz-Thouless transition in the rotor plane.
Our results further suggest that the small-worldness containing both locality
and non-locality of the network topology can be a practical approach to extract
characteristic quantities of topological states of matter.


title: Applications of continuous functions in topological CAD data

abstract:
  Most CAD or other spatial data models, in particular boundary representation
models, are called "topological" and represent spatial data by a structured
collection of "topological primitives" like edges, vertices, faces, and
volumes. These then represent spatial objects in geo-information- (GIS) or CAD
systems or in building information models (BIM). Volume objects may then either
be represented by their 2D boundary or by a dedicated 3D-element, the "solid".
The latter may share common boundary elements with other solids, just as
2D-polygon topologies in GIS share common boundary edges. Despite the frequent
reference to "topology" in publications on spatial modelling the formal link
between mathematical topology and these "topological" models is hardly
described in the literature. Such link, for example, cannot be established by
the often cited nine-intersections model which is too elementary for that
purpose. Mathematically, the link between spatial data and the modelled "real
world" entities is established by a chain of "continuous functions" - a very
important topological notion, yet often overlooked by spatial data modellers.
This article investigates how spatial data can actually be considered
topological spaces, how continuous functions between them are defined, and how
CAD systems can make use of them. Having found examples of applications of
continuity in CAD data models it turns out that of continuity has much
practical relevance for CAD systems.


title: Colombeau Algebra: A pedagogical introduction

abstract:
  A simple pedagogical introduction to the Colombeau algebra of generalised
functions is presented, leading the standard definition.


title:
Time-dependent Photoionization of Gaseous Nebulae: the Pure Hydrogen
  Case

abstract:
  We study the problem of time-dependent photoionization of low density gaseous
nebulae subjected to sudden changes in the intensity of ionizing radiation. To
this end, we write a computer code that solves the full time-dependent energy
balance, ionization balance, and radiation transfer equations in a
self-consistent fashion for a simplified pure hydrogen case. It is shown that
changes in the ionizing radiation yield ionization/thermal fronts that
propagate through the cloud, but the propagation times and response times to
such fronts vary widely and non-linearly from the illuminated face of the cloud
to the ionization front (IF). Ionization/thermal fronts are often supersonic,
and in slabs initially in pressure equilibrium such fronts yield large pressure
imbalances that are likely to produce important dynamical effects in the cloud.
  Further, we studied the case of periodic variations in the ionizing flux. It
is found that the physical conditions of the plasma have complex behaviors that
differ from any steady-state solutions. Moreover, even the time average
ionization and temperature is different from any steady-state case. This time
average is characterized by over-ionization and a broader IF with respect to
the steady-state solution for a mean value of the radiation flux. Around the
time average of physical conditions there is large dispersion in instantaneous
conditions, particularly across the IF, which increases with the period of
radiation flux variations. Moreover, the variations in physical conditions are
asynchronous along the slab due to the combination of non-linear propagation
times for thermal/ionization fronts and equilibration times.


title:
Reservoir engineering of a mechanical resonator: generating a
  macroscopic superposition state and monitoring its decoherence

abstract:
  A deterministic scheme for generating a macroscopic superposition state of a
nanomechanical resonator is proposed. The nonclassical state is generated
through a suitably engineered dissipative dynamics exploiting the
optomechanical quadratic interaction with a bichromatically driven optical
cavity mode. The resulting driven dissipative dynamics can be employed for
monitoring and testing the decoherence processes affecting the nanomechanical
resonator under controlled conditions.


title: SD1000 Collaboration: Hunting down the subdwarf populations

abstract:
  Separating the subdwarf populations may shed light on their formation history
and give unique insights into the atmospheric processes that are thought to be
responsible for their abundance diversity. Such a task requires complex and
time consuming spectral analyses, which we started to tailor to our objectives
a year ago. Here we report the updates that have been made over the past year
and will be the standard method in SD1000.


title: Relationship between molecular cloud structure and density PDFs

abstract:
  Volume and column density PDFs in molecular clouds are important diagnostics
for understanding their general structure. We developed a novel approach to
trace the cloud structure by varying the lower PDF cut-off and exploring a
suggested mass-density relationship with a power-law index $x^\prime$. The
correspondence of x' as a function of spatial scale to the slope of the
high-density PDF tail is studied. To validate the proposed model, we use
results from hydrodynamical simulations of a turbulent self-gravitating cloud
and recent data on dust continuum emission from the Planck mission.


title: Self healing of vacancy defects in single layer graphene and silicene

abstract:
  Self healing mechanisms of vacancy defects in graphene and silicene are
studied using first principles calculations. We investigated host adatom
adsorption, diffusion, vacancy formation and revealed atomistic mechanisms in
the healing of single, double and triple vacancies of single layer graphene and
silicene. Silicon adatom, which is adsorbed to silicene at the top site forms a
dumbbell like structure by pushing one Si atom underneath. The asymmetric
reconstruction of the single vacancy in graphene is induced by the
magnetization through the rebonding of two dangling bonds and acquiring a
significant magnetic moment through remaining unsaturated dangling bond. In
silicene, three two-fold coordinated atoms surrounding the single vacancy
become four-fold coordinated and nonmagnetic through rebonding. The energy
gained through new bond formation becomes the driving force for the
reconstruction. Under the external supply of host atoms, while the vacancy
defects of graphene heal perfectly, Stone-Wales defect can form in the course
of healing of silicene vacancy. The electronic and magnetic properties of
suspended, single layer graphene and silicene are modified by reconstructed
vacancy defects.


title: Color Glass Condensate in Schwinger-Keldysh QCD

abstract:
  Within the Schwinger-Keldysh representation of many-body QCD, it is shown
that the leading quantum corrections to the strong classical color field is
classical in the sense that the fluctuation field still obeys the classical
Jacobi-field equation, while the quantum effects solely resides in the
fluctuations of the initial field configurations. Within this context, a
systematic derivation of the JIMWLK renormalization group equation is
presented. A clear identification of the correct form of gauge transformation
rules and the correct form of the matter-field Lagrangian in the
Schwinger-Keldysh QCD is also presented.


title:
Full counting statistics of laser excited Rydberg aggregates in a
  one-dimensional geometry

abstract:
  We experimentally study the full counting statistics of few-body Rydberg
aggregates excited from a quasi-one-dimensional Rydberg gas. We measure
asymmetric excitation spectra and increased second and third order statistical
moments of the Rydberg number distribution, from which we determine the average
aggregate size. Direct comparisons with numerical simulations reveal the
presence of liquid-like spatial correlations, and indicate sequential growth of
the aggregates around an initial grain. These findings demonstrate the
importance of dissipative effects in strongly correlated Rydberg gases and
introduce a way to study spatio-temporal correlations in strongly-interacting
many-body quantum systems without imaging.


title:
Quantum field theory in curved graphene spacetimes, Lobachevsky
  geometry, Weyl symmetry, Hawking effect, and all that

abstract:
  The solutions of many issues, of the ongoing efforts to make deformed
graphene a tabletop quantum field theory in curved spacetimes, are presented. A
detailed explanation of the special features of curved spacetimes, originating
from embedding portions of the Lobachevsky plane into $\mathbf{R}^3$, is given,
and the special role of coordinates for the physical realizations in graphene,
is explicitly shown, in general, and for various examples. The Rindler
spacetime is reobtained, with new important differences with respect to earlier
results. The de Sitter spacetime naturally emerges, for the first time, paving
the way to future applications in cosmology. The role of the BTZ black hole is
also briefly addressed. The singular boundary of the pseudospheres, "Hilbert
horizon", is seen to be closely related to event horizon of the Rindler, de
Sitter, and BTZ kind. This gives new, and stronger, arguments for the Hawking
phenomenon to take place. An important geometric parameter, $c$, overlooked in
earlier work, takes here its place for physical applications, and it is shown
to be related to graphene's lattice spacing, $\ell$. It is shown that all
surfaces of constant negative curvature, ${\cal K} = -r^{-2}$, are unified, in
the limit $c/r \to 0$, where they are locally applicable to the Beltrami
pseudosphere. This, and $c = \ell$, allow us a) to have a phenomenological
control on the reaching of the horizon; b) to use spacetimes different than
Rindler for the Hawking phenomenon; c) to approach the generic surface of the
family. An improved expression for the thermal LDOS is obtained. A non-thermal
term for the total LDOS is found. It takes into account: a) the peculiarities
of the graphene-based Rindler spacetime; b) the finiteness of a laboratory
surface; c) the optimal use of the Minkowski quantum vacuum, through the choice
of this Minkowski-static boundary.


title:
Local algorithms, regular graphs of large girth, and random regular
  graphs

abstract:
  We introduce a general class of algorithms and supply a number of general
results useful for analysing these algorithms when applied to regular graphs of
large girth. As a result, we can transfer a number of results proved for random
regular graphs into (deterministic) results about all regular graphs with
sufficiently large girth. This is an uncommon direction of transfer of results,
which is usually from the deterministic setting to the random one. In
particular, this approach enables, for the first time, the achievement of
results equivalent to those obtained on random regular graphs by a powerful
class of algorithms which contain prioritised actions. As examples, we obtain
new upper or lower bounds on the size of maximum independent sets, minimum
dominating sets, maximum and minimum bisection, maximum $k$-independent sets,
minimum $k$-dominating sets and minimum connected and weakly-connected
dominating sets in $r$-regular graphs with large girth.


title: Text Compression using Abstract Numeration System on a Regular Language

abstract:
  An abstract numeration system (ANS) is a numeration system that provides a
one-to-one correspondence between the natural numbers and a regular language.
In this paper, we define an ANS-based compression as an extension of this
correspondence. In addition, we show the following results: 1) an average
compression ratio is computable from a language, 2) an ANS-based compression
runs in sublinear time with respect to the length of the input string, and 3)
an ANS-based compression can be extended to block-based compression using a
factorial language.


title:
Proceedings 9th International Workshop on Automated Specification and
  Verification of Web Systems

abstract:
  This volume contains the accepted papers of the 9th International Workshop on
Automated Specification and Verification of Web Systems (WWV'13), which took
place in Florence, Italy, on June 6, as a satellite event of the 8th
International Federated Conferences on Distributed Computing Techniques
(DisCoTec 2013).


title: Semi-degree threshold for anti-directed Hamiltonian cycles

abstract:
  In 1960, Ghouila-Houri extended Dirac's theorem to directed graphs by proving
that if D is a directed graph on n vertices with minimum out-degree and
in-degree at least n/2 (i.e. minimum semi-degree at least n/2), then D contains
a directed Hamiltonian cycle. Of course there are other orientations of a cycle
in a directed graph and it is not clear that the semi-degree threshold for the
directed Hamiltonian cycle is the same as the semi-degree threshold for some
other orientation. In 1980, Grant initiated the problem of determining the
minimum semi-degree threshold for the anti-directed Hamiltonian cycle (an
orientation in which consecutive edges alternate direction). We prove that for
sufficiently large even n, if D is a directed graph on n vertices with minimum
semi-degree at least n/2+1, then D contains an anti-directed Hamiltonian cycle.
This result is sharp.


title:
Unification of Bell, Leggett-Garg and Kochen-Specker inequalities: A
  hybrid spatio-temporal inequality

abstract:
  The Bell-type (spatial), Kochen-Specker (contextuality) or Leggett-Garg
(temporal) inequalities are based on classically plausible but otherwise quite
distinct assumptions. For any of these inequalities, satisfaction is equivalent
to a joint probability distribution for all observables in the experiment. This
implies a joint distribution for all pairs of observables, and is indifferent
to whether or not they commute in the theory. This indifference underpins a
unification of the above inequalities into a general framework of correlation
inequalities. When the physical scenario is such that the correlated pairs are
all compatible, the resulting correlation is non-signaling, which may be local
or multi-particle, corresponding to contextuality or Bell-type inequalities. If
the pairs are incompatible, the resulting correlation corresponds to
Leggett-Garg (LG) inequalities. That quantum mechanics (QM) violates all these
inequalities suggests a close connection between the local, spatial and
temporal properties of the theory. As a concrete manifestation of the
unification, we extend the method due to Roy and Singh (J. Phys. A, 11, L167
(1978)) to derive and study a new class of hybrid spatio-temporal inequalities,
where the correlated pairs in the experiment are both compatible or
incompatible. The implications for cryptography and monogamy inequalities of
the unification are briefly touched upon.


title: Compositional Dictionaries for Domain Adaptive Face Recognition

abstract:
  We present a dictionary learning approach to compensate for the
transformation of faces due to changes in view point, illumination, resolution,
etc. The key idea of our approach is to force domain-invariant sparse coding,
i.e., design a consistent sparse representation of the same face in different
domains. In this way, classifiers trained on the sparse codes in the source
domain consisting of frontal faces for example can be applied to the target
domain (consisting of faces in different poses, illumination conditions, etc)
without much loss in recognition accuracy. The approach is to first learn a
domain base dictionary, and then describe each domain shift (identity, pose,
illumination) using a sparse representation over the base dictionary. The
dictionary adapted to each domain is expressed as sparse linear combinations of
the base dictionary. In the context of face recognition, with the proposed
compositional dictionary approach, a face image can be decomposed into sparse
representations for a given subject, pose and illumination respectively. This
approach has three advantages: first, the extracted sparse representation for a
subject is consistent across domains and enables pose and illumination
insensitive face recognition. Second, sparse representations for pose and
illumination can subsequently be used to estimate the pose and illumination
condition of a face image. Finally, by composing sparse representations for
subject and the different domains, we can also perform pose alignment and
illumination normalization. Extensive experiments using two public face
datasets are presented to demonstrate the effectiveness of our approach for
face recognition.


title:
Global Solutions of Hartree-Fock Theory and their Consequences for
  Strongly Correlated Quantum Systems

abstract:
  We present a density matrix approach for computing global solutions of
Hartree-Fock theory, based on semidefinite programming (SDP), that gives upper
and lower bounds on the Hartree-Fock energy of quantum systems. Equality of the
upper- and lower-bound energies guarantees that the computed solution is the
globally optimal solution of Hartree-Fock theory. For strongly correlated
systems the SDP approach requires us to reassess the accuracy of the
Hartree-Fock energies and densities from standard software packages for
electronic structure theory. Calculations of the H$_{4}$ dimer and N$_{2}$
molecule show that the energies from SDP Hartree-Fock are lower than those from
standard Hartree-Fock methods by 100-200 kcal/mol in the dissociation region.
The present findings have important consequences for the computation and
interpretation of electron correlation, which is typically defined relative to
the Hartree-Fock energy and density.

categories: physics.chem-ph math-ph math.MP physics.comp-ph quant-ph


title: Learning Robust Subspace Clustering

abstract:
  We propose a low-rank transformation-learning framework to robustify subspace
clustering. Many high-dimensional data, such as face images and motion
sequences, lie in a union of low-dimensional subspaces. The subspace clustering
problem has been extensively studied in the literature to partition such
high-dimensional data into clusters corresponding to their underlying
low-dimensional subspaces. However, low-dimensional intrinsic structures are
often violated for real-world observations, as they can be corrupted by errors
or deviate from ideal models. We propose to address this by learning a linear
transformation on subspaces using matrix rank, via its convex surrogate nuclear
norm, as the optimization criteria. The learned linear transformation restores
a low-rank structure for data from the same subspace, and, at the same time,
forces a high-rank structure for data from different subspaces. In this way, we
reduce variations within the subspaces, and increase separations between the
subspaces for more accurate subspace clustering. This proposed learned robust
subspace clustering framework significantly enhances the performance of
existing subspace clustering methods. To exploit the low-rank structures of the
transformed subspaces, we further introduce a subspace clustering technique,
called Robust Sparse Subspace Clustering, which efficiently combines robust PCA
with sparse modeling. We also discuss the online learning of the
transformation, and learning of the transformation while simultaneously
reducing the data dimensionality. Extensive experiments using public datasets
are presented, showing that the proposed approach significantly outperforms
state-of-the-art subspace clustering methods.


title: Proton Decay at $M_{pl}$ and the Scale of SUSY-Breaking

abstract:
  It is sometimes argued that a virtue of pushing the supersymmetry breaking
scale above 1 PeV is that no particular flavor structure is required in the
soft sector in order to evade bounds on flavor-changing neutral currents.
However, without flavor structure, suppressing generic Planck-suppressed
contributions to proton decay requires even higher SUSY scales, of order
$10^{11}$ ($10^9$) GeV for degenerate (mini-split) gauginos and scalars. With
flavor structure, the question of whether proton decay or flavor symmetries are
more constraining is model-dependent, but it straightforward to find simple
models where both constraints are satisfied for much lower SUSY scales.


title: Domain-invariant Face Recognition using Learned Low-rank Transformation

abstract:
  We present a low-rank transformation approach to compensate for face
variations due to changes in visual domains, such as pose and illumination. The
key idea is to learn discriminative linear transformations for face images
using matrix rank as the optimization criteria. The learned linear
transformations restore a shared low-rank structure for faces from the same
subject, and, at the same time, force a high-rank structure for faces from
different subjects. In this way, among the transformed faces, we reduce
variations caused by domain changes within the classes, and increase
separations between the classes for better face recognition across domains.
Extensive experiments using public datasets are presented to demonstrate the
effectiveness of our approach for face recognition across domains. The
potential of the approach for feature extraction in generic object recognition
and coded aperture design are discussed as well.


title:
Electromagnetic two-point functions and the Casimir effect in
  Friedmann-Robertson-Walker cosmologies

abstract:
  We evaluate the two-point functions of the electromagnetic field in (D+1)
-dimensional spatially flat Friedmann-Robertson-Walker universes with a
power-law scale factor, assuming that the field is prepared in the Bunch-Davies
vacuum state. The range of powers are specified in which the two-point
functions are infrared convergent and the Bunch-Davies vacuum for the
electromagnetic field is a physically realizable state. The two-point functions
are applied for the investigation of the vacuum expectation values of the field
squared and the energy-momentum tensor, induced by a single and two parallel
conducting plates. Unlike to the case of conducting plates in the Minkowski
bulk, in the problem under consideration the stresses along the directions
parallel to the plates are not equal to the energy density. We show that, in
addition to the diagonal components, the vacuum energy-momentum tensor has a
nonzero off-diagonal component which describes energy flux along the direction
normal to the plates. For a single plate this flux is directed from the plate.
The Casimir forces are investigated in the geometry of two plates. At
separations between the plates smaller than the curvature radius of the
background spacetime, to the leading order, we recover the corresponding result
in the Minkowski spacetime and in this case the forces are attractive. At
larger separations, the influence of the curvature on the Casimir forces is
essential with different asymptotic behavior for decelerated and accelerated
expansions. In particular, for the latter case there is a range of powers of
the expansion law in which the forces become repulsive at large separations
between the plates.


title:
Dynamical Phase Transitions as Properties of the Stationary State:
  Analytic Results after Quantum Quenches in the Spin-1/2 XXZ Chain

abstract:
  The (Loschmidt) overlap between the state at different times after a quantum
quench is attracting increasing interest, as it was recently shown that in the
thermodynamic limit its logarithm per unit of length has a non-analytic
behavior if a Hamiltonian parameter is quenched across a critical point. This
phenomenon was called a "dynamical phase transition" in analogy with the
behavior of the canonical partition function at an equilibrium phase
transition. We distinguish between local and nonlocal contributions to the
aforementioned quantity and derive an analytic expression for the time
evolution of the local part after quantum quenches in the XXZ spin-1/2 chain.
The state that describes the stationary properties of (local) observables can
be represented by a Gibbs ensemble of a generalized Hamiltonian; we reveal a
deep connection between the appearance of singularities and the excitation
energies of the generalized Hamiltonian.

categories: cond-mat.stat-mech math-ph math.MP quant-ph


title:
Quantifying the role of population subdivision in evolution on rugged
  fitness landscapes

abstract:
  Natural selection drives populations towards higher fitness, but crossing
fitness valleys or plateaus may facilitate progress up a rugged fitness
landscape involving epistasis. We investigate quantitatively the effect of
subdividing an asexual population on the time it takes to cross a fitness
valley or plateau. We focus on a generic and minimal model that includes only
population subdivision into equivalent demes connected by global migration, and
does not require significant size changes of the demes, environmental
heterogeneity or specific geographic structure. We determine the optimal
speedup of valley or plateau crossing that can be gained by subdivision, if the
process is driven by the deme that crosses fastest. We show that isolated demes
have to be in the sequential fixation regime for subdivision to significantly
accelerate crossing. Using Markov chain theory, we obtain analytical
expressions for the conditions under which optimal speedup is achieved: valley
or plateau crossing by the subdivided population is then as fast as that of its
fastest deme. We verify our analytical predictions through stochastic
simulations. We demonstrate that subdivision can substantially accelerate the
crossing of fitness valleys and plateaus in a wide range of parameters
extending beyond the optimal window. We study the effect of varying the degree
of subdivision of a population, and investigate the trade-off between the
magnitude of the optimal speedup and the width of the parameter range over
which it occurs. Our results also hold for weakly beneficial intermediate
mutations. We extend our work to the case of a population connected by
migration to one or several smaller islands. Our results demonstrate that
subdivision with migration alone can significantly accelerate the crossing of
fitness valleys and plateaus, and shed light onto the quantitative conditions
necessary for this to occur.


title:
Fast X-Ray/IR cross-correlations and relativistic jet formation in GRS
  1915+105

abstract:
  We present cross-correlation analyses of simultaneous X-ray and near-infrared
(near-IR) observations of the microquasar GRS 1915+105 during relativistic
jet-producing epochs (X-ray class $\alpha$ and $\beta$). While previous studies
have linked the large-amplitude IR flares and X-ray behaviors to jet formation
in these states, our new analyses are sensitive to much lower-amplitude IR
variability, providing more sensitive probes of the jet formation process. The
X-ray to IR cross-correlation function (CCF) shows significant correlations
which vary in form between the different X-ray states. During low/hard dips in
both classes, we find no significant X-ray/IR correlation. During
high-variability epochs, we find consistently significant correlations in both
$\alpha$ and $\beta$ classes, but with strong differences in the CCF structure.
The high-variability $\alpha$ CCF shows strong anti-correlation between
X-ray/IR, with the X-ray preceding the IR by $\sim$ 13 $\pm$ 2s. The
high-variability $\beta$ state shows time-variable CCF structure, which is
statistically significant but without a clearly consistent lag. Our simulated
IR light curves, designed to match the observed CCFs, show variably-flickering
IR emission during the class $\beta$ high-variability epoch, while the class
$\alpha$ can be fit by IR flickering with frequencies in the range 0.1 to 0.3
Hz, strengthening $\sim$10 s after every X-ray subflare. We interpret these
features in the context of the X-ray-emitting accretion disk and IR emission
from relativistic jet formation in GRS 1915+105, concluding that the CCF
analysis places the origin in a synchrotron-emitting relativistic compact jet
at a distance from the compact object of $\sim$0.02AU.