title: Collective thermoelectrophoresis of charged colloids

abstract:
  Thermally driven colloidal transport is, to a large extent, due to the
thermoelectric or Seebeck effect of the charged solution.We show that, contrary
to the generally adopted single-particle picture, the transport coefficient
depends on the colloidal concentration. For solutions that are dilute in the
hydrodynamic sense, collective effects may significantly affect the
thermophoretic mobility. Our results provide an explanation for recent
experimental observations on polyelectrolytes and charged particles and suggest
that for charged colloids collective behavior is the rule rather than the
exception.


title:
Turbulence Mitigation Scheme for Optical Communications using Orbital
  Angular Momentum Multiplexing Based on Channel Coding and Wavefront
  Correction

abstract:
  The free-space optical (FSO) communication links with orbital angular
momentum (OAM) multiplexing have been demonstrated that they can largely
enhance the systems' capacity without a corresponding increase in spectral
bandwidth, but the performance of the system is unavoidably disturbed by
atmospheric turbulence (AT). Different from the existed AT disturbance, the
OAM-multiplexed systems will cause both the burst and random errors for a
single OAM state carrier and the `crosstalk' interference between the different
OAM states carriers. In this paper, we propose a turbulence mitigation method
to improve AT tolerance of OAM-multiplexed FSO communication links. In the
proposed scheme, we use channel codes to correct the burst and random errors
caused by AT for a single OAM state carrier; And we use wavefront correction
method to correct the `crosstalk' interference between the different OAM states
carriers. The improvements of AT tolerance are discussed by comparing the
performance of OAM-multiplexed FSO communication links with or without channel
coding or Shark-Hartmann wavefront correction method. The numerical simulation
results show that the OAM-multiplexed FSO communication links have enhanced
their AT tolerance. The usage of channel codes and wavefront correction methods
together has improved greatly the performance of OAM-multiplexed FSO
communication links over atmospheric turbulence.


title: Giant planet and brown dwarf formation

abstract:
  Understanding the dominant brown dwarf and giant planet formation processes,
and finding out whether these processes rely on completely different mechanisms
or share common channels represents one of the major challenges of astronomy
and remains the subject of heated debates. It is the aim of this review to
summarize the latest developments in this field and to address the issue of
origin by confronting different brown dwarf and giant planet formation
scenarios to presently available observational constraints. As examined in the
review, if objects are classified as "Brown Dwarfs" or "Giant Planets" on the
basis of their formation mechanism, it has now become clear that their mass
domains overlap and that there is no mass limit between these two distinct
populations.
  Furthermore, while there is increasing observational evidence for the
existence of non-deuterium burning brown dwarfs, some giant planets,
characterized by a significantly metal enriched composition, might be massive
enough to ignite deuterium burning in their core. Deuterium burning (or lack
of) thus plays no role in either brown dwarf or giant planet formation.
Consequently, we argue that the IAU definition to distinguish these two
populations has no physical justification and brings scientific confusion. In
contrast, brown dwarfs and giant planets might bear some imprints of their
formation mechanism, notably in their mean density and in the physical
properties of their atmosphere. Future direct imaging surveys will undoubtedly
provide crucial information and perhaps provide some clear observational
diagnostics to unambiguously distinguish these different astrophysical objects.


title: Preferred attachment model of affiliation network

abstract:
  In an affiliation network vertices are linked to attributes and two vertices
are declared adjacent whenever they share a common attribute. For example, two
customers of an internet shop are called adjacent if they have purchased the
same or similar items. Assuming that each newly arrived customer is linked
preferentially to already popular items we obtain a preferred attachment model
of an evolving affiliation network. We show that the network has a scale-free
property and establish the asymptotic degree distribution.


title: On some developments in the Nonsymmetric Kaluza-Klein Theory

abstract:
  We consider a condition for a charge confinement and gravito-electromagnetic
wave solutions in the Nonsymmetric Kaluza-Klein Theory.We consider also an
influence of a cosmological constant on a static,spherically symmetric
solution.We remind to the reader some fudamentals of the Nonsymmetric
Kaluza-Klein Theory and a geometrcal background behind the
theory.Simultaneously we give some remarks concerning misunderstanding
connected to several notions of the Nonsymmetric Kaluza-Klein Theory,Einstein
Unified Field Theory,geometrization and unification of physical interactions
.We reconsider Dirac field in the Nonsymmetric Kaluza-Klein Theory.


title:
Detailed and simplified non-equilibrium helium ionization in the solar
  atmosphere

abstract:
  Helium ionization plays an important role in the energy balance of the upper
chromosphere and transition region. Helium spectral lines are also often used
as diagnostics of these regions. We carry out 1D radiation-hydrodynamics
simulations of the solar atmosphere and find that the helium ionization is
mostly set by photoionization and direct collisional ionization, counteracted
by radiative recombination cascades. By introducing an additional recombination
rate mimicking the recombination cascades, we construct a simplified 3 level
helium model atom consisting of only the ground states. This model atom is
suitable for modeling non-equilibrium helium ionization in 3D numerical models.
We perform a brief investigation of the formation of the He I 10830 and He II
304 spectral lines. Both lines show non-equilibrium features that are not
recovered with statistical equilibrium models, and caution should therefore be
exercised when such models are used as a basis in the interpretation of
observations.


title:
Optimal space of linear classical observables for Maxwell $k$-forms via
  spacelike and timelike compact de Rham cohomologies

abstract:
  Being motivated by open questions in gauge field theories, we consider
non-standard de Rham cohomology groups for timelike compact and spacelike
compact support systems. These cohomology groups are shown to be isomorphic
respectively to the usual de Rham cohomology of a spacelike Cauchy surface and
its counterpart with compact support. Furthermore, an analog of the usual
Poincar\'e duality for de Rham cohomology is shown to hold for the case with
non-standard supports as well. We apply these results to find optimal spaces of
linear observables for analogs of arbitrary degree $k$ of both the vector
potential and the Faraday tensor. The term optimal has to be intended in the
following sense: The spaces of linear observables we consider distinguish
between different configurations; in addition to that, there are no redundant
observables. This last point in particular heavily relies on the analog of
Poincar\'e duality for the new cohomology groups.


title: Fast quantum gate via Feshbach-Pauli blocking in a nanoplasmonic trap

abstract:
  We propose a simple idea for realizing a quantum gate with two identical
fermions in a double well trap via external optical pulses without addressing
the atoms individually. The key components of the scheme are Feshbach resonance
and Pauli blocking, which decouple unwanted states from the dynamics. As a
physical example we study atoms in the presence of a magnetic Feshbach
resonance in a nanoplasmonic trap and discuss the constraints on the operation
times for realistic parameters, reaching a fidelity above $99.9\%$ within
$42\mu$s.


title: Orbifold Biquotients of SU(3)

abstract:
  One of the main methods of constructing new spaces with positive or almost
positive curvature is the study of biquotients first studied in detail by
Eschenburg. We classify orbifold biquotients of the Lie Group $SU(3)$, and
construct a new example of a 5-dimensional orbifold with almost positive
curvature. Furthermore, we extend the work of Florit and Ziller on the
geometric properties of the orbifolds $SU(3)//T^2$.


title:
A Demonstration of Wavefront Sensing and Mirror Phasing from the Image
  Domain

abstract:
  In astronomy and microscopy, distortions in the wavefront affect the dynamic
range of a high contrast imaging system. These aberrations are either imposed
by a turbulent medium such as the atmosphere, by static or thermal aberrations
in the optical path, or by imperfectly phased subapertures in a segmented
mirror. Active and adaptive optics (AO), consisting of a wavefront sensor and a
deformable mirror, are employed to address this problem. Nevertheless, the
non-common-path between the wavefront sensor and the science camera leads to
persistent quasi-static speckles that are difficult to calibrate and which
impose a floor on the image contrast. In this paper we present the first
experimental demonstration of a novel wavefront sensor requiring only a minor
asymmetric obscuration of the pupil, using the science camera itself to detect
high order wavefront errors from the speckle pattern produced. We apply this to
correct errors imposed on a deformable microelectromechanical (MEMS) segmented
mirror in a closed loop, restoring a high quality point spread function (PSF)
and residual wavefront errors of order $\sim 10$ nm using 1600 nm light, from a
starting point of $\sim 300$ nm in piston and $\sim 0.3$ mrad in tip-tilt. We
recommend this as a method for measuring the non-common-path error in
AO-equipped ground based telescopes, as well as as an approach to phasing
difficult segmented mirrors such as on the \emph{James Webb Space Telescope}
primary and as a future direction for extreme adaptive optics.


title: How do digits emerge? - Mathematical Models of Limb Development

abstract:
  The mechanism that controls digit formation has long intrigued developmental
and theoretical biologists, and many different models and mechanisms have been
proposed. Here we review models of limb development with a specific focus on
digit and long bone formation. Decades of experiments have revealed the basic
signalling circuits that control limb development, and recent advances in
imaging and molecular technologies provide us with unprecedented spatial detail
and a broader view on the regulatory networks. Computational approaches are
important to integrate the available information into a consistent framework
that will allow us to achieve a deeper level of understanding and that will
help with the future planning and interpretation of complex experiments, paving
the way to in silico genetics. Previous models of development had to be focused
on very few, simple regulatory interactions. Algorithmic developments and
increasing computing power now enable the generation and validation of
increasingly realistic models that can be used to test old theories and uncover
new mechanisms.


title:
Normal approximation on Poisson spaces: Mehler's formula, second order
  Poincar\'e inequalities and stabilization

abstract:
  We prove a new class of inequalities, yielding bounds for the normal
approximation in the Wasserstein and the Kolmogorov distance of functionals of
a general Poisson process (Poisson random measure). Our approach is based on an
iteration of the classical Poincar\'e inequality, as well as on the use of
Malliavin operators, of Stein's method, and of an (integrated) Mehler's
formula, providing a representation of the Ornstein-Uhlenbeck semigroup in
terms of thinned Poisson processes. Our estimates only involve first and second
order differential operators, and have consequently a clear geometric
interpretation. In particular we will show that our results are perfectly
tailored to deal with the normal approximation of geometric functionals
displaying a weak form of stabilization, and with non-linear functionals of
Poisson shot-noise processes. We discuss two examples of stabilizing
functionals in great detail: (i) the edge length of the $k$-nearest neighbour
graph, (ii) intrinsic volumes of $k$-faces of Voronoi tessellations. In all
these examples we obtain rates of convergence (in the Kolmogorov and the
Wasserstein distance) that one can reasonably conjecture to be optimal, thus
significantly improving previous findings in the literature. As a necessary
step in our analysis, we also derive new lower bounds for variances of Poisson
functionals.


title: Transversality and alternating projections for nonconvex sets

abstract:
  We consider the method of alternating projections for finding a point in the
intersection of two closed sets, possibly nonconvex. Assuming only the standard
transversality condition (or a weaker version thereof), we prove local linear
convergence. When the two sets are semi-algebraic and bounded, but not
necessarily transversal, we nonetheless prove subsequence convergence.


title:
The EUV spectrum of the Sun: SOHO CDS NIS radiances during solar cycle
  23

abstract:
  For the first time, we present and discuss EUV radiances of the solar
transition region (TR) and corona obtained during a solar cycle. The
measurements were obtained with the SOHO/coronal diagnostic spectrometer (CDS)
during the period from 1996 to 2010. We find that limb-brightening
significantly affects any characterisation of the solar radiances. We present
the limb-brightening function for the main lines and find that it does not
change measurably during the cycle. We confirm earlier findings that the
radiance histogram of the cooler lines have a well defined, log-normal
quiet-Sun component, although our results differ from previous ones. The width
of the lowest-radiance log-normal distribution is constant along the cycle.
Both the analysis of the centre-to-limb variation and of the radiance
statistical distribution point to a constant QS emission along solar cycle 23.
Lines formed above 1 MK are dramatically affected by the presence of active
regions, and indeed, no "quiet Sun" region can be defined during periods of
maximum activity. Much of the irradiance variability in lines formed below 1.5
MK is due to a change in the emitting area. For hotter lines, the emitting area
saturates to almost 100% of full solar disk at the maximum of activity, while
simultaneously the emission due to active regions increases by more than an
order of magnitude. We show that structures around active regions, sometimes
referred to as dark halos or dark canopies, are common and discuss their
similarities and differences with coronal holes. In particular, we show how
they are well visible in TR lines, contrary to coronal holes.


title:
Analytical Models of Exoplanetary Atmospheres. I. Atmospheric Dynamics
  via the Shallow Water System

abstract:
  Within the context of exoplanetary atmospheres, we present a comprehensive
linear analysis of forced, damped, magnetized shallow water systems, exploring
the effects of dimensionality, geometry (Cartesian, pseudo-spherical and
spherical), rotation, magnetic tension and hydrodynamic and magnetic sources of
friction. Across a broad range of conditions, we find that the key governing
equation for atmospheres and quantum harmonic oscillators are identical, even
when forcing (stellar irradiation), sources of friction (molecular viscosity,
Rayleigh drag and magnetic drag) and magnetic tension are included. The global
atmospheric structure is largely controlled by a single, key parameter that
involves the Rossby and Prandtl numbers. This near-universality breaks down
when either molecular viscosity or magnetic drag acts non-uniformly across
latitude or a poloidal magnetic field is present, suggesting that these effects
will introduce qualitative changes to the familiar chevron-shaped feature
witnessed in simulations of atmospheric circulation. We also find that
hydrodynamic and magnetic sources of friction have dissimilar phase signatures
and affect the flow in fundamentally different ways, implying that using
Rayleigh drag to mimic magnetic drag is inaccurate. We exhaustively lay down
the theoretical formalism (dispersion relations, governing equations and
time-dependent wave solutions) for a broad suite of models. In all situations,
we derive the steady state of an atmosphere, which is relevant to interpreting
infrared phase and eclipse maps of exoplanetary atmospheres. We elucidate a
pinching effect that confines the atmospheric structure to be near the equator.
Our suite of analytical models may be used to decisively develop physical
intuition and as a reference point for three-dimensional, magnetohydrodynamic
(MHD) simulations of atmospheric circulation.


title:
Initial correlation in a system of a spin coupled to a spin bath through
  an intermediate spin

abstract:
  The strong system-bath correlation is a typical initial condition in many
condensed matter and some quantum optical systems. Here, the dynamics of a spin
interacting with a spin bath through an intermediate spin are studied. Initial
correlations between the spin and the intermediate spin are taken into account.
The exact analytical expression for the evolution operator of the spin is
found. Furthermore, correlated projection superoperator techniques are applied
to the model and a time-convolutionless master equation to second order is
derived. It is shown that the time-convolutionless master equation to second
order reproduces the exact dynamics for time-scales of the order 1/{\gamma},
where {\gamma} is the coupling of the central spin to the intermediate spin. It
is found that there is a strong dependence on the initial system-bath
correlations in the dynamics of the reduced system, which cannot be neglected.


title: Trapping energy of a spherical particle on a curved liquid interface

abstract:
  We derive the trapping energy of a colloidal particle at a liquid interface
with contact angle h and principal curvatures c1 and c2. The boundary
conditions at the particle surface are significantly simplified by introducing
the shift e of its vertical position. We discuss the undulating contact line
and the curvatureinduced lateral forces for a single particle and a pair of
nearby particles. The single-particle trapping energy is found to decrease with
the square of both the total curvature c1 + c2 and the anisotropy c1 ? c2. In
the case of non-uniform curvatures, the resulting lateral force pushes
particles toward more strongly curved regions.


title: Causal Network Inference by Optimal Causation Entropy

abstract:
  The broad abundance of time series data, which is in sharp contrast to
limited knowledge of the underlying network dynamic processes that produce such
observations, calls for a rigorous and efficient method of causal network
inference. Here we develop mathematical theory of causation entropy, an
information-theoretic statistic designed for model-free causality inference.
For stationary Markov processes, we prove that for a given node in the network,
its causal parents forms the minimal set of nodes that maximizes causation
entropy, a result we refer to as the optimal causation entropy principle.
Furthermore, this principle guides us to develop computational and data
efficient algorithms for causal network inference based on a two-step discovery
and removal algorithm for time series data for a network-couple dynamical
system. Validation in terms of analytical and numerical results for Gaussian
processes on large random networks highlight that inference by our algorithm
outperforms previous leading methods including conditioned Granger causality
and transfer entropy. Interestingly, our numerical results suggest that the
number of samples required for accurate inference depends strongly on network
characteristics such as the density of links and information diffusion rate and
not necessarily on the number of nodes.


title:
Arbitrary spin in a spin bath: Exact dynamics and approximation
  techniques

abstract:
  A model of an arbitrary spin coupled to a bath of spins 1/2 in a star
configuration is considered. The exact reduced dynamics of the central spin is
found for the case of non-correlated initial conditions of the system and the
bath. The exact solution is used to test two approximation techniques, namely,
the Nakajima-Zwanzig projection operator technique and the time-convolutionless
projection operator technique corresponding to the second order of the coupling
constant. Two types of projection operators are used for deriving the master
equations and the results are compared with the exact solution for a central
spin equal to one. It is shown that the approximate master equations reproduce
the exact dynamics on time-scales $1/(A\sqrt{N})$, where A is the coupling
constant and N is the number of spins in the bath.


title:
The poisoning effect of Mn in LaFe(1-x)Mn(x)AsO(0.89)F(0.11): unveiling
  a quantum critical point in the phase diagram of iron-based superconductors

abstract:
  A superconducting-to-magnetic transition is reported for
LaFe$_{1-x}$Mn$_x$AsO$_{0.89}$F$_{0.11}$ where a per thousand amount of Mn
impurities is dispersed. By employing local spectroscopic techniques like muon
spin rotation (muSR) and nuclear quadrupole resonance (NQR) on compounds with
Mn contents ranging from x=0.025% to x=0.75%, we find that the electronic
properties are extremely sensitive to the Mn impurities. In fact, a small
amount of Mn as low as 0.2% suppresses superconductivity completely. Static
magnetism, involving the FeAs planes, is observed to arise for x > 0.1% and
becomes further enhanced upon increasing Mn substitution. Also a progressive
increase of low energy spin fluctuations, leading to an enhancement of the NQR
spin-lattice relaxation rate 1/T1, is observed upon Mn substitution. The
analysis of 1/T1 for the sample closest to the the crossover between
superconductivity and magnetism (x = 0.2%) points towards the presence of an
antiferromagnetic quantum critical point around that doping level.


title: Localization in random geometric graphs with too many edges

abstract:
  We consider a random geometric graph $G(\chi_n, r_n)$, given by connecting
two vertices of a Poisson point process $\chi_n$ of intensity $n$ on the unit
torus whenever their distance is smaller than the parameter $r_n$. The model is
conditioned on the rare event that the number of edges observed, $|E|$, is
greater than $(1 + \delta)\mathbb{E}(|E|)$, for some fixed $\delta >0$. This
article proves that upon conditioning, with high probability there exists a
ball of diameter $r_n$ which contains a clique of at least $\sqrt{2 \delta
\mathbb{E}(|E|)}(1 - \varepsilon)$ vertices, for any given $\varepsilon >0$.
Intuitively, this region contains all the "excess" edges the graph is forced to
contain by the conditioning event, up to lower order corrections. As a
consequence of this result, we prove a large deviations principle for the upper
tail of the edge count of the random geometric graph. The rate function of this
large deviation principle turns out to be non-convex.


title:
Single crystal fiber growth of cerium doped strontium yttrate,
  SrY2O4:Ce3+

abstract:
  First single crystal fibers of cerium doped strontium yttrate are fabricated
using the laser-heated pedestal growth technique. Through thermodynamic
equilibrium calculations and by high-temperature mass spectrometry suitable
growth conditions can be determined. The atmosphere plays an important role
during crystallization. It affects the composition shift, on the one hand, and
the valence state of cerium, on the other hand. These properties can be
explained by combining X-ray diffraction, elemental analysis, and optical
spectroscopy. Crystallization in slightly reducing nitrogen atmosphere proves
to be a reasonable choice, because evaporation is suppressed and trivalent
cerium is stabilized. Strong green emission that depends on the oxygen fugacity
during crystallization can be excited using UV light. Optical transmission of
SrY2O4:Ce3+ is measured for the first time.


title: Transformation elastodynamics and cloaking for flexural waves

abstract:
  The paper addresses an important issue of cloaking transformations for
fourth-order partial differential equations representing flexural waves in thin
elastic plates. It is shown that, in contrast with the Helmholtz equation, the
general form of the partial differential equation is not invariant with respect
to the cloaking transformation. The significant result of this paper is the
analysis of the transformed equation and its interpretation in the framework of
the linear theory of pre-stressed plates. The paper provides a formal framework
for transformation elastodynamics as applied to elastic plates. Furthermore, an
algorithm is proposed for designing a square cloak for flexural waves, which
employs a regularised push-out transformation. Illustrative numerical examples
show high accuracy and efficiency of the proposed cloaking algorithm. In
particular, a physical configuration involving a perturbation of an
interference pattern generated by two coherent sources is presented. It is
demonstrated that the perturbation produced by a cloaked defect is negligibly
small even for such a delicate interference pattern.

categories: physics.class-ph cond-mat.mtrl-sci math-ph math.MP


title:
Strong decays of the bottom mesons $B_1(5721)$, $B_2(5747)$,
  $B_{s1}(5830)$, $B_{s2}(5840)$ and $B(5970)$

abstract:
  In this article, we study the two-body strong decays of the bottom mesons
with the heavy meson effective theory in the leading order approximation, and
obtain all the analytical expressions of the decay widths of the light
pseudoscalar mesons transitions among the S-wave, P-wave and D-wave bottom
mesons. As an application, we tentatively assign the bottom meson $B(5970)$ as
the $2{\rm S}\,1^-$, $1{\rm D}\,1^-$ and $1{\rm D}\,3^-$ states, respectively,
and calculate the decay widths of the $B_1(5721)$, $B_2(5747)$, $B_{s1}(5830)$,
$B_{s2}(5840)$ and $B(5970)$, which can be confronted with the experimental
data in the future.


title:
One-dimensional Schroedinger operators with delta-prime-interactions on
  Cantor-type sets

abstract:
  We introduce a novel approach for defining a $\delta'$-interaction on a
subset of the real line of Lebesgue measure zero which is based on
Sturm-Liouville differential expression with measure coefficients. This enables
us to establish basic spectral properties (e.g., self-adjointness, lower
semiboundedness and spectral asymptotics) of Hamiltonians with
$\delta'$-interactions concentrated on sets of complicated structures.


title:
Representations of Cuntz algebras associated to quasi-invariant Markov
  measures

abstract:
  In this paper, we answer the question of equivalence, or singularity, of two
given quasi-stationary Markov measures on one-sided infinite words, and the
corresponding question of equivalence of associated Cuntz algebra $\O_N$
representations. We do this by associating certain monic representations of
$\O_N$ to quasi-stationary Markov measures, and then proving that equivalence
for pairs of measures is decided by unitary equivalence of the corresponding
pair of representations.


title: Practical Challenges with Spreadsheet Auditing Tools

abstract:
  Just like other software, spreadsheets can contain significant faults. Static
analysis is an accepted and well-established technique in software engineering
known for its capability to discover faults. In recent years, a growing number
of tool vendors started offering tools that allow casual end-users to run
various static analyses on spreadsheets as well. We supervised a study where
three undergraduate software engineering students examined a selection of 14
spreadsheet auditing tools, trying to give a concrete recommendation for an
industry partner. Reflecting on the study's results, we found that most of
these tools do provide useful aids in finding problems in spreadsheets, but we
have also spotted several areas where tools had significant issues. Some of
these issues could be remedied if spreadsheet auditing tool vendors would pick
up some ideas of static analysis tools for traditional software development and
adopt some of their solution approaches.


title: XLSearch: A Search Engine for Spreadsheets

abstract:
  Spreadsheets are end-user programs and domain models that are heavily
employed in administration, financial forecasting, education, and science
because of their intuitive, flexible, and direct approach to computation. As a
result, institutions are swamped by millions of spreadsheets that are becoming
increasingly difficult to manage, access, and control.
  This note presents the XLSearch system, a novel search engine for
spreadsheets. It indexes spreadsheet formulae and efficiently answers formula
queries via unification (a complex query language that allows metavariables in
both the query as well as the index). But a web-based search engine is only one
application of the underlying technology: Spreadsheet formula export to web
standards like MathML combined with formula indexing can be used to find
similar spreadsheets or common formula errors.


title:
Mie scattering of Laguerre-Gaussian beams: photonic nanojets and
  near-field optical vortices

abstract:
  We study Mie scattering of Laguerre-Gaussian (LG) light beams remodelled
using the method of far-field matching. The theoretical results are used to
analyze the optical field in the near-field region for purely azimuthal LG
beams characterized by a nonzero azimuthal mode number $m_{LG}$. The mode
number $m_{LG}$ is found to have a profound effect on the morphology of
photonic nanojets and the near-field structure of optical vortices associated
with the components of the electric field.


title: Excel 2013 Spreadsheet Inquire

abstract:
  Excel 2013 (version 15) includes an add-in "Inquire" for auditing
spreadsheets. We describe the evolution of such tools in the third-party
marketplace and assess the usefulness of Microsoft's own add-in in this
context. We compare in detail the features of Inquire with similar products and
make suggestions for how it could be enhanced. We offer a free helper add-in
that in our opinion corrects one major shortcoming of Inquire.


title:
Spin correlations in the Drell-Yan process, parton entanglement, and
  other unconventional QCD effects

abstract:
  We review ideas on the structure of the QCD vacuum which had served as
motivation for the discussion of various non-standard QCD effects in
high-energy reactions in articles from 1984 to 1995. These effects include, in
particular, transverse-momentum and spin correlations in the Drell-Yan process
and soft photon production in hadron-hadron collisions. We discuss the relation
of the approach introduced in the above-mentioned articles to the approach,
developed later, using transverse-momentum-dependent parton distributions
(TDMs). The latter approach is a special case of our more general one which
allows for parton entanglement in high-energy reactions. We discuss signatures
of parton entanglement in the Drell-Yan reaction. Also for Higgs-boson
production in pp collisions via gluon-gluon annihilation effects of
entanglement of the two gluons are discussed and are found to be potentially
important. These effects can be looked for in the current LHC experiments. In
our opinion studying parton-entanglement effects in high-energy reactions is,
on the one hand, very worthwhile by itself and, on the other hand, it allows to
perform quantitative tests of standard factorisation assumptions. Clearly, the
experimental observation of parton-entanglement effects in the Drell-Yan
reaction and/or in Higgs-boson production would have a great impact on our
understanding how QCD works in high-energy collisions.


title: On the rate of accumulation of $\alpha\zeta^{n}$ mod 1 to 0

abstract:
  In this paper we study the distribution of the sequence $(\alpha
\zeta^{n})_{n\geq 1}$ mod $1$, where $\alpha,\zeta$ are fixed positive real
numbers, with special focus on the accumulation point $0$. For this purpose we
introduce approximation constants
$\underline{\sigma}(\alpha,\zeta),\overline{\sigma}(\alpha, \zeta)$ and study
their properties in dependence of $\alpha,\zeta$, distinguishing in particular
the cases of Pisot numbers, algebraic non Pisot numbers and transcendental
values of $\alpha$ as well as $\zeta$.


title: Footprints of ancient balanced polymorphisms in genetic variation data

abstract:
  When long-lived, balancing selection can lead to trans-species polymorphisms
that are shared by two or more species identical by descent. In this case, the
gene genealogies at the selected sites cluster by allele instead of by species
and, because of linkage, nearby neutral sites also have unusual genealogies.
Although it is clear that this scenario should lead to discernible footprints
in genetic variation data, notably the presence of additional neutral
polymorphisms shared between species and the absence of fixed differences, the
effects remain poorly characterized. We focus on the case of a single site
under long-lived balancing selection and derive approximations for summaries of
the data that are sensitive to a trans-species polymorphism: the length of the
segment that carries most of the signals, the expected number of shared neutral
SNPs within the segment and the patterns of allelic associations among them.
Coalescent simulations of ancient balancing selection confirm the accuracy of
our approximations. We further show that for humans and chimpanzees, and more
generally for pairs of species with low genetic diversity levels, the patterns
of genetic variation on which we focus are highly unlikely to be generated by
neutral recurrent mutations, so these statistics are specific as well as
sensitive. We discuss the implications of our results for the design and
interpretation of genome scans for ancient balancing selection in apes and
other taxa.


title: A new gauge slice for the relative Bauer-Furuta invariants

abstract:
  In this paper, we study Manolescu's construction of the relative Bauer-Furuta
invariants arising from the Seiberg-Witten equations on 4-manifolds with
boundary. The main goal is to introduce a new gauge fixing condition in order
to apply the finite dimensional approximation technique. We also hope to
provide a framework to extend Manolescu's construction to general 4-manifolds.


title: Experimental Evaluation of Algorithms for the Food-Selection Problem

abstract:
  In this paper, we describe the result of our experiments on Algorithms for
the Food-Selection Problem, which is the fundamental problem first stated and
addressed in the seminal paper \cite{pigout}. Because the key aspect of any
experimental evaluation is the \textbf{reproducibility}, we detail deeply the
setup of all our experiments, thus leaving to the interested eater the
opportunity to reproduce all the results described in this paper. More
specifically, we describe all the answers we provided to the questions proposed
in \cite{pigout}: Where can I have dinner tonight? What is the typical Roman
cuisine that I should (not) miss? Where can I find the best coffee or gelato in
town?


title: Valence-Bond Quantum Monte Carlo Algorithms Defined on Trees

abstract:
  We present a new class of algorithms for performing valence-bond quantum
Monte Carlo of quantum spin models. Valence-bond quantum Monte Carlo is a T=0
Monte Carlo method based on sampling of a set of operator-strings that can be
viewed as forming a tree-like structure. The algorithms presented here utilize
the notion of a worm that moves up and down this tree and changes the
associated operator-string. In quite general terms we derive a set of equations
whose solutions correspond to a new class of algorithms. As specific examples
of this class of algorithms we focus on two cases. The bouncing worm algorithm,
for which updates are always accepted by allowing the worm to bounce up and
down the tree and the driven worm algorithm, where a single parameter controls
how far up the tree the worm reaches before turning around. The latter
algorithm involves only a single bounce where the worm turns from going up the
tree to going down. The presence of the control parameter necessitates the
introduction of an acceptance probability for the update.


title:
Two-point G$^2$ Hermite interpolation with spirals by inversion of
  conics: summary

abstract:
  The article completes the research of two-point G$^2$ Hermite interpolation
problem with spirals by inversion of conics. A simple algorithm is proposed to
construct a family of 4th degree rational spirals, matching given G$^2$ Hermite
data. A possibility to reduce the degree to cubic is discussed.


title:
Linear-Time Algorithms for the Paired-Domination Problem in Interval
  Graphs and Circular-Arc Graphs

abstract:
  In a graph $G$, a vertex subset $S\subseteq V(G)$ is said to be a dominating
set of $G$ if every vertex not in $S$ is adjacent to a vertex in $S$. A
dominating set $S$ of a graph $G$ is called a paired-dominating set if the
induced subgraph $G[S]$ contains a perfect matching. The paired-domination
problem involves finding a smallest paired-dominating set of $G$. Given an
intersection model of an interval graph $G$ with sorted endpoints, Cheng et al.
designed an $O(m+n)$-time algorithm for interval graphs and an $O(m(m+n))$-time
algorithm for circular-arc graphs. In this paper, to solve the
paired-domination problem in interval graphs, we propose an $O(n)$-time
algorithm that searches for a minimum paired-dominating set of $G$
incrementally in a greedy manner. Then, we extend the results to design an
algorithm for circular-arc graphs that also runs in $O(n)$ time.


title: SPARC Collaboration: New Strategy for Storage Ring Physics at FAIR

abstract:
  SPARC collaboration at FAIR pursues the worldwide unique research program by
utilizing storage ring and trapping facilities for highly-charged heavy ions.
The main focus is laid on the exploration of the physics at strong, ultra-short
electromagnetic fields including the fundamental interactions between electrons
and heavy nuclei as well as on the experiments at the border between nuclear
and atomic physics. Very recently SPARC worked out a realization scheme for
experiments with highly-charged heavy-ions at relativistic energies in the
High-Energy Storage Ring HESR and at very low-energies at the CRYRING coupled
to the present ESR. Both facilities provide unprecedented physics opportunities
already at the very early stage of FAIR operation. The installation of CRYRING,
dedicated Low-energy Storage Ring (LSR) for FLAIR, may even enable a much
earlier realisation of the physics program of FLAIR with slow anti-protons.


title: Jordan groups and elliptic ruled surfaces

abstract:
  We prove that an analogue of Jordan's theorem on finite subgroups of general
linear groups holds for the groups of biregular automorphisms of elliptic ruled
surfaces. This gives a positive answer to a question of Vladimir L. Popov.


title:
Constraining Dark Matter-Neutrino Interactions using the CMB and
  Large-Scale Structure

abstract:
  We present a new study on the elastic scattering cross section of dark matter
(DM) and neutrinos using the latest cosmological data from Planck and
large-scale structure experiments. We find that the strongest constraints are
set by the Lyman-alpha forest, giving sigma_{DM-neutrino} < 10^{-33} (m_DM/GeV)
cm^2 if the cross section is constant and a present-day value of
sigma_{DM-neutrino} < 10^{-45} (m_DM/GeV) cm^2 if it scales as the temperature
squared. These are the most robust limits on DM-neutrino interactions to date,
demonstrating that one can use the distribution of matter in the Universe to
probe dark ("invisible") interactions. Additionally, we show that scenarios
involving thermal MeV DM and a constant elastic scattering cross section
naturally predict (i) a cut-off in the matter power spectrum at the Lyman-alpha
scale, (ii) N_eff ~ 3.5 +/- 0.4, (iii) H_0 ~ 71 +/- 3 km/s/Mpc and (iv) the
possible generation of neutrino masses.


title: Paul Erd\H os and additive bases

abstract:
  This is a survey of some of Erd\H os's work on bases in additive number
theory.


title:
Parabolic Boundary Harnack Principles in Domains with Thin Lipschitz
  Complement

abstract:
  We prove forward and backward parabolic boundary Harnack principles for
nonnegative solutions of the heat equation in the complements of thin parabolic
Lipschitz sets given as subgraphs $E=\{(x,t): x_{n-1}\leq
f(x'',t),x_n=0\}\subset \mathbb{R}^{n-1}\times\mathbb{R} $ for parabolically
Lipschitz functions $f$ on $\mathbb{R}^{n-2}\times\mathbb{R}$. We are motivated
by applications to parabolic free boundary problems with thin (i.e co-dimension
two) free boundaries. In particular, at the end of the paper we show how to
prove the spatial $C^{1,\alpha}$ regularity of the free boundary in the
parabolic Signorini problem.


title:
Classification of spherical algebraic subalgebras of real simple Lie
  algebras of rank 1

abstract:
  We determine all spherical algebraic subalgebras in any simple Lie algebra of
real rank 1.


title:
On the Detection of Molecules in the Atmosphere of HD189733b using HST
  NICMOS Transmission Spectroscopy

abstract:
  The HST/NICMOS transmission spectrum measurements of HD 189733b that suggest
the detection of methane (CH$_{4}$) in an exoplanet atmosphere have been a
source of significant controversy. With what is probably the best analyzed
exoplanet spectroscopy data set to date, different teams, using different
methods, have claimed evidence both contradicting and supporting the original
findings. Here, we report results from a uniform spectral retrieval analysis of
the three, independent, published spectra together with null hypothesis
testing. Based on Bayesian model comparison, we find that two of the three
spectra show strong evidence ($\geq$ 3.6$\sigma$) for the detection of
molecular features mainly due to water and methane while the third is
consistent with a weak molecular detection at the 2.2$\sigma$ level. We
interpret the agreement in the spectral modulation established by previous
authors and the atmospheric retrieval results presented here, as a confirmation
of the original detection of molecular absorbers in the atmosphere of HD
189733b.


title:
Probabilistic model for constraining the Galactic potential using tidal
  streams

abstract:
  We present a generative probabilistic model for a tidal stream and
demonstrate how this model is used to constrain the Galactic potential. The
model takes advantage of the simple structure of a stream in angle and
frequency space for the correct potential. We investigate how the method
performs on full 6D mock stream data, and mock data with outliers included. As
currently formulated the technique is computationally costly when applied to
data with large observational errors, but we describe several modifications
that promise to make the technique computationally tractable.


title: Full Waveform Inversion for Time-Distance Helioseismology

abstract:
  Inferring interior properties of the Sun from photospheric measurements of
the seismic wavefield constitutes the helioseismic inverse problem. Deviations
in seismic measurements (such as wave travel times) from their fiducial values
estimated for a given model of the solar interior imply that the model is
inaccurate. Contemporary inversions in local helioseismology assume that
properties of the solar interior are linearly related to measured travel-time
deviations. It is widely known, however, that this assumption is invalid for
sunspots and active regions, and likely for supergranular flows as well. Here,
we introduce nonlinear optimization, executed iteratively, as a means of
inverting for the sub-surface structure of large-amplitude perturbations.
Defining the penalty functional as the $L_2$ norm of wave travel-time
deviations, we compute the the total misfit gradient of this functional with
respect to the relevant model parameters %(only sound speed in this case) at
each iteration around the corresponding model. The model is successively
improved using either steepest descent, conjugate gradient, or quasi-Newton
limited-memory BFGS. Performing nonlinear iterations requires privileging
pixels (such as those in the near-field of the scatterer), a practice not
compliant with the standard assumption of translational invariance.
Measurements for these inversions, although similar in principle to those used
in time-distance helioseismology, require some retooling. For the sake of
simplicity in illustrating the method, we consider a 2-D inverse problem with
only a sound-speed perturbation.


title:
Distributed Load Balancing with Nonconvex Constraints: A Randomized
  Algorithm with Application to Electric Vehicle Charging Scheduling

abstract:
  To schedule a large number of EVs with the presence of practical nonconvex
charging constraints, a distributed and randomized algorithm is proposed in
this paper. The algorithm assumes the availability of a coordinator which can
communicate with all EVs. In each iteration of the algorithm, the coordinator
receives tentative charging profiles from the EVs and computes a broadcast
control signal. After receiving this broadcast control signal, each EV
generates a probability distribution over its admissible charging profiles, and
samples from the distribution to update its tentative charging profile.
  We prove that the algorithm converges almost surely to a charging profile in
finite iterations. The final charging profile (that the algorithm converges to)
is random, i.e., it depends on the realization. We characterize the final
charging profile---a charging profile can be a realization of the final
charging profile if and only if it is a Nash equilibrium of the game in which
each EV seeks to minimize the inner product of its own charging profile and the
aggregate electricity demand. Furthermore, we provide a uniform suboptimality
upper bound, that scales O(1/n) in the number n of EVs, for all realizations of
the final charging profile.


title:
Fractional Quantum Hall Effect at $\nu=1/2$ in Hole Systems Confined to
  GaAs Quantum Wells

abstract:
  We observe fractional quantum Hall effect (FQHE) at the even-denominator
Landau level filling factor $\nu=1/2$ in two-dimensional hole systems confined
to GaAs quantum wells of width 30 to 50 nm and having bilayer-like charge
distributions. The $\nu=1/2$ FQHE is stable when the charge distribution is
symmetric and only in a range of intermediate densities, qualitatively similar
to what is seen in two-dimensional electron systems confined to approximately
twice wider GaAs quantum wells. Despite the complexity of the hole Landau level
structure, originating from the coexistence and mixing of the heavy- and
light-hole states, we find the hole $\nu=1/2$ FQHE to be consistent with a
two-component, Halperin-Laughlin ($\Psi_{331}$) state.


title:
An exact solution of the Currie-Hill equations in 1 + 1 dimensional
  Minkowski space

abstract:
  We present an exact two-particle solution of the Currie-Hill equations of
Predictive Relativistic Mechanics in $1 + 1$ dimensional Minkowski space. The
instantaneous accelerations are given in terms of elementary functions
depending on the relative particle position and velocities. The general
solution of the equations of motion is given and by studying the global phase
space of this system it is shown that this is a subspace of the full kinematic
phase space.


title:
Advective transport of interstellar plasma into the heliosphere across
  the reconnecting heliopause

abstract:
  We discuss results of magnetohydrodynamical model simulations of plasma
dynamics in the proximity of the heliopause (HP). The model is shown to fit
details of the magnetic field variations observed by Voyager 1 spacecraft
during the transition from the heliosphere to the local interstellar medium
(LISM). We propose an interpretation of magnetic field structures observed by
Voyager 1 in terms of fine-scale physical processes. Our simulations reveal an
effective transport mechanism of relatively dense LISM plasma across the
reconnecting HP into the heliosphere. The mechanism is associated with
annihilation of magnetic sectors in the heliospheric plasma near the HP.


title:
Quantum magnetism of ultracold atoms with a dynamical pseudospin degree
  of freedom

abstract:
  We consider bosons in a Hubbard lattice with an SU($\cal N$) pseudospin
degree of freedom which is made dynamical via a coherent transfer term. It is
shown that, in the basis which diagonalizes the pseudospin coupling, a generic
hopping process affects the spin state, similar to a spin-orbit coupling. This
results, for the system in the Mott phase, in a ferromagnetic phase with
variable quantization axis. In extreme cases, it can even give rise to
antiferromagnetic order.


title: Optical Leaky-Wave Antenna Integrated in Ring Resonator

abstract:
  A leaky-wave antenna at optical frequencies is designed and integrated with a
ring resonator at 1550 nm wavelength. The leaky wave is generated by using
periodic perturbations in the integrated dielectric waveguide that excite the
-1 spatial harmonic. The antenna consists of a dielectric waveguides with
semiconductor corrugations, and it is compatible with CMOS fabrication
technology. We show that integrating the leaky wave antenna in an optical ring
resonator that is fed by directional couplers, we can improve the electronic
control of the radiation through carrier injection into the semiconductor
corrugations.


title:
Measurement of the electroweak production of dijets in association with
  a Z-boson and distributions sensitive to vector boson fusion in proton-proton
  collisions at sqrt(s) = 8 TeV using the ATLAS detector

abstract:
  Measurements of fiducial cross sections for the electroweak production of two
jets in association with a Z-boson are presented. The measurements are
performed using 20.3 inverse femtobarns of proton-proton collision data
collected at a centre-of-mass energy of sqrt(s)=8 TeV by the ATLAS experiment
at the Large Hadron Collider. The electroweak component is extracted by a fit
to the dijet invariant mass distribution in a fiducial region chosen to enhance
the electroweak contribution over the dominant background in which the jets are
produced via the strong interaction. The electroweak cross sections measured in
two fiducial regions are in good agreement with the Standard Model expectations
and the background-only hypothesis is rejected with significance above the 5
sigma level. The electroweak process includes the vector boson fusion
production of a Z-boson and the data are used to place limits on anomalous
triple gauge boson couplings. In addition, measurements of cross sections and
differential distributions for inclusive Z-boson-plus-dijet production are
performed in five fiducial regions, each with different sensitivity to the
electroweak contribution. The results are corrected for detector effects and
compared to predictions from the SHERPA and POWHEG event generators.


title:
Accessing the Transverse Dynamics and Polarization of Gluons inside the
  Proton at the LHC

abstract:
  We argue that the study of heavy quarkonia, in particular that of $\Upsilon$,
produced back-to-back with an isolated photon in $pp$ collisions at the LHC is
the best --and currently unique-- way to access the distribution of both the
transverse momentum and the polarization of the gluon in an unpolarized proton.
These encode fundamental information on the dynamics of QCD. We have derived
analytical expressions for various transverse-momentum distributions which can
be measured at the LHC and which allow for a direct extraction of the
aforementioned quantities. To assess the feasibility of such measurements, we
have evaluated the expected yields and the relevant transverse-momentum
distributions for different models of the gluon dynamics inside a proton.


title: Mathematical Modelling of Turning Delays in Swarm Robotics

abstract:
  We investigate the effect of turning delays on the behaviour of groups of
differential wheeled robots and show that the group-level behaviour can be
described by a transport equation with a suitably incorporated delay. The
results of our mathematical analysis are supported by numerical simulations and
experiments with e-puck robots. The experimental quantity we compare to our
revised model is the mean time for robots to find the target area in an unknown
environment. The transport equation with delay better predicts the mean time to
find the target than the standard transport equation without delay.


title: Energy density fluctuations in Early Universe

abstract:
  The primordial nucleosinthesys of the element can be influenced by the
transitions of phase that take place after the Big Bang, such as the QCD
transition. In order to study the effect of this phase transition, in this work
we compute the time evolution of thermodynamical quantities of the early
universe, focusing on temperature and energy density fluctuations, by solving
the relevant equations of motion using as input the lattice QCD equation of
state to describe the strongly interacting matter in the early universe plasma.
We also study the effect of a primordial strong magnetic field by means of a
phenomenological equation of state. Our results show that small inhomogeneities
of strongly interacting matter in the early Universe are moderately damped
during the crossover.


title: New identities for sessile drops

abstract:
  A new set of mathematical identities is presented for axi-symmetric sessile
drops on flat and curved substrates. The geometrical parameters, including the
apex curvature and height, and the contact radius, are related by the
identities. The validity of the identities are checked by various numerical
solutions both for flat and curved substrates.


title:
Testing for rational speculative bubbles in the Brazilian residential
  real-estate market

abstract:
  Speculative bubbles have been occurring periodically in local or global real
estate markets and are considered a potential cause of economic crises. In this
context, the detection of explosive behaviors in the financial market and the
implementation of early warning diagnosis tests are of critical importance. The
recent increase in Brazilian housing prices has risen concerns that the
Brazilian economy may have a speculative housing bubble. In the present paper,
we employ a recently proposed recursive unit root test in order to identify
possible speculative bubbles in data from the Brazilian residential real-estate
market. The empirical results show evidence for speculative price bubbles both
in Rio de Janeiro and Sao Paulo, the two main Brazilian cities.


title: A New Approach to Analyzing Robin Hood Hashing

abstract:
  Robin Hood hashing is a variation on open addressing hashing designed to
reduce the maximum search time as well as the variance in the search time for
elements in the hash table. While the case of insertions only using Robin Hood
hashing is well understood, the behavior with deletions has remained open. Here
we show that Robin Hood hashing can be analyzed under the framework of
finite-level finite-dimensional jump Markov chains. This framework allows us to
re-derive some past results for the insertion-only case with some new insight,
as well as provide a new analysis for a standard deletion model, where we
alternate between deleting a random old key and inserting a new one. In
particular, we show that a simple but apparently unstudied approach for
handling deletions with Robin Hood hashing offers good performance even under
high loads.


title:
An incompressible 2D didactic model with singularity and explicit
  solutions of the 2D Boussinesq equations

abstract:
  We give an example of a well posed, finite energy, 2D incompressible active
scalar equation with the same scaling as the surface quasi-geostrophic equation
and prove that it can produce finite time singularities. In spite of its
simplicity, this seems to be the first such example. Further, we construct
explicit solutions of the 2D Boussinesq equations whose gradients grow
exponentially in time for all time. In addition, we introduce a variant of the
2D Boussinesq equations which is perhaps a more faithful companion of the 3D
axisymmetric Euler equations than the usual 2D Boussinesq equations.


title: Semiclassical strings and Non-Abelian T-duality

abstract:
  We study semiclassical strings in the Klebanov-Witten and in the Non-abelian
T-dual Klebanov-Witten backgrounds. We show that both backgrounds share a
subsector of equivalent states up to conditions on the T-dual coordinates which
also impose a breaking of the R-symmetry by a discrete group. We also analyze
string configurations where the strings are stretched along the T-dual
coordinates. This semiclassical analysis predicts the existence of chiral
primary operators for the dual (strongly coupled) superconformal field theory
whose anomalous dimension depends on the T-dual coordinates. We briefly discuss
the Penrose limit of the dualised background.


title:
M\'etodo de elementos finitos aplicado a las ecuaciones de Stokes y de
  Advecci\'on-Difusi\'on

abstract:
  This work consists in two parts. The first part is a review of the finite
element method (FEM) for one and two-dimensional problems. The second part,
concerns the application of the FEM to find numerical solutions of the Stokes
equation and the Convection-Diffusion equation. Finally, it couples the stokes
velocity to be the convection of the Convection-Diffusion equation.


title: Bayesian nonparametric comorbidity analysis of psychiatric disorders

abstract:
  The analysis of comorbidity is an open and complex research field in the
branch of psychiatry, where clinical experience and several studies suggest
that the relation among the psychiatric disorders may have etiological and
treatment implications. In this paper, we are interested in applying latent
feature modeling to find the latent structure behind the psychiatric disorders
that can help to examine and explain the relationships among them. To this end,
we use the large amount of information collected in the National Epidemiologic
Survey on Alcohol and Related Conditions (NESARC) database and propose to model
these data using a nonparametric latent model based on the Indian Buffet
Process (IBP). Due to the discrete nature of the data, we first need to adapt
the observation model for discrete random variables. We propose a generative
model in which the observations are drawn from a multinomial-logit distribution
given the IBP matrix. The implementation of an efficient Gibbs sampler is
accomplished using the Laplace approximation, which allows integrating out the
weighting factors of the multinomial-logit likelihood model. We also provide a
variational inference algorithm for this model, which provides a complementary
(and less expensive in terms of computational complexity) alternative to the
Gibbs sampler allowing us to deal with a larger number of data. Finally, we use
the model to analyze comorbidity among the psychiatric disorders diagnosed by
experts from the NESARC database.


title:
Deeply Virtual Compton Scattering to the twist-four accuracy: Impact of
  finite-$t$ and target mass corrections

abstract:
  We carry out the first complete calculation of kinematic power corrections
$\sim t/Q^2$ and $\sim m^2/Q^2$ to several key observables in Deeply Virtual
Compton Scattering. The issue of convention dependence of the leading twist
approximation is discussed in detail. In addition we work out representations
for the higher twist corrections in terms of double distributions,
Mellin-Barnes integrals and also within a dissipative framework. This study
removes an important source of uncertainties in the QCD predictions for
intermediate photon virtualities $Q^2\sim 1$-$5\,{\rm GeV}^2$ that are
accessible in the existing and planned experiments. In particular the
finite-$t$ corrections are significant and must be taken into account in the
data analysis.


title:
Relativistic formulation of coordinate light time, Doppler and
  astrometric observables up to the second post-Minkowskian order

abstract:
  Given the extreme accuracy of modern space science, a precise relativistic
modeling of observations is required. In particular, it is important to
describe properly light propagation through the Solar System. For two decades,
several modeling efforts based on the solution of the null geodesic equations
have been proposed but they are mainly valid only for the first order
Post-Newtonian approximation. However, with the increasing precision of ongoing
space missions as Gaia, GAME, BepiColombo, JUNO or JUICE, we know that some
corrections up to the second order have to be taken into account for future
experiments. We present a procedure to compute the relativistic coordinate time
delay, Doppler and astrometric observables avoiding the integration of the null
geodesic equation. This is possible using the Time Transfer Function formalism,
a powerful tool providing key quantities such as the time of flight of a light
signal between two point-events and the tangent vector to its null-geodesic.
Indeed we show how to compute the Time Transfer Functions and their derivatives
(and thus range, Doppler and astrometric observables) up to the second
post-Minkowskian order. We express these quantities as quadratures of some
functions that depend only on the metric and its derivatives evaluated along a
Minkowskian straight line. This method is particularly well adapted for
numerical estimations. As an illustration, we provide explicit expressions in
static and spherically symmetric space-time up to second post-Minkowskian
order. Then we give the order of magnitude of these corrections for the
range/Doppler on the BepiColombo mission and for astrometry in a GAME-like
observation.


title: Graph matching: relax or not?

abstract:
  We consider the problem of exact and inexact matching of weighted undirected
graphs, in which a bijective correspondence is sought to minimize a quadratic
weight disagreement. This computationally challenging problem is often relaxed
as a convex quadratic program, in which the space of permutations is replaced
by the space of doubly-stochastic matrices. However, the applicability of such
a relaxation is poorly understood. We define a broad class of friendly graphs
characterized by an easily verifiable spectral property. We prove that for
friendly graphs, the convex relaxation is guaranteed to find the exact
isomorphism or certify its inexistence. This result is further extended to
approximately isomorphic graphs, for which we develop an explicit bound on the
amount of weight disagreement under which the relaxation is guaranteed to find
the globally optimal approximate isomorphism. We also show that in many cases,
the graph matching problem can be further harmlessly relaxed to a convex
quadratic program with only n separable linear equality constraints, which is
substantially more efficient than the standard relaxation involving 2n equality
and n^2 inequality constraints. Finally, we show that our results are still
valid for unfriendly graphs if additional information in the form of seeds or
attributes is allowed, with the latter satisfying an easy to verify spectral
characteristic.


title:
Correlation Functions of XX0 Heisenberg Chain, q-Binomial Determinants,
  and Random Walks

abstract:
  The XX0 Heisenberg model on a cyclic chain is considered. The representation
of the Bethe wave functions via the Schur functions allows to apply the
well-developed theory of the symmetric functions to the calculation of the
thermal correlation functions. The determinantal expressions of the
form-factors and of the thermal correlation functions are obtained. The
q-binomial determinants enable the connection of the form-factors with the
generating functions both of boxed plane partitions and of self-avoiding
lattice paths. The asymptotical behavior of the thermal correlation functions
is studied in the limit of low temperature provided that the characteristic
parameters of the system are large enough.

categories: math-ph cond-mat.stat-mech hep-th math.CO math.MP


title: RES: Regularized Stochastic BFGS Algorithm

abstract:
  RES, a regularized stochastic version of the Broyden-Fletcher-Goldfarb-Shanno
(BFGS) quasi-Newton method is proposed to solve convex optimization problems
with stochastic objectives. The use of stochastic gradient descent algorithms
is widespread, but the number of iterations required to approximate optimal
arguments can be prohibitive in high dimensional problems. Application of
second order methods, on the other hand, is impracticable because computation
of objective function Hessian inverses incurs excessive computational cost.
BFGS modifies gradient descent by introducing a Hessian approximation matrix
computed from finite gradient differences. RES utilizes stochastic gradients in
lieu of deterministic gradients for both, the determination of descent
directions and the approximation of the objective function's curvature. Since
stochastic gradients can be computed at manageable computational cost RES is
realizable and retains the convergence rate advantages of its deterministic
counterparts. Convergence results show that lower and upper bounds on the
Hessian egeinvalues of the sample functions are sufficient to guarantee
convergence to optimal arguments. Numerical experiments showcase reductions in
convergence time relative to stochastic gradient descent algorithms and
non-regularized stochastic versions of BFGS. An application of RES to the
implementation of support vector machines is developed.


title: Asymptotic dynamics of reflecting spiral waves

abstract:
  Resonantly forced spiral waves in excitable media drift in straight-line
paths, their rotation centers behaving as point-like objects moving along
trajectories with a constant velocity. Interaction with medium boundaries
alters this velocity and may often result in a reflection of the drift
trajectory. Such reflections have diverse characteristics and are known to be
highly nonspecular in general. In this context we apply the theory of response
functions, which via numerically computable integrals, reduces the
reaction-diffusion equations governing the whole excitable medium to the
dynamics of just the rotation center and rotation phase of a spiral wave.
Spiral reflection trajectories are computed by this method for both small- and
large-core spiral waves in the Barkley model. Such calculations provide insight
into the process of reflection as well as explanations for differences in
trajectories across parameters, including the effects of incidence angle and
forcing amplitude. Qualitative aspects of these results are preserved far
beyond the asymptotic limit of weak boundary effects and slow resonant drift.


title: Distribution theory for Schr\"odinger's integral equation

abstract:
  Much of the literature on point interactions in quantum mechanics has focused
on the differential form of Schr\"odinger's equation. This paper, in contrast,
investigates the integral form of Schr\"odinger's equation. While both forms
are known to be equivalent for smooth potentials, this is not true for
distributional potentials. Here, we assume that the potential is given by a
distribution defined on the space of discontinuous test functions.
  First, by using Schr\"odinger's integral equation, we confirm a seminal
result by Kurasov, which was originally obtained in the context of
Schr\"odinger's differential equation. This hints at a possible deeper
connection between both forms of the equation. We also sketch a generalisation
of Kurasov's result to hypersurfaces.
  Second, we derive a new closed-form solution to Schr\"odinger's integral
equation with a delta prime potential. This potential has attracted
considerable attention, including some controversy. Interestingly, the derived
propagator satisfies boundary conditions that were previously derived using
Schr\"odinger's differential equation.
  Third, we derive boundary conditions for `super-singular' potentials given by
higher-order derivatives of the delta potential. These boundary conditions
cannot be incorporated into the normal framework of self-adjoint extensions. We
show that the boundary conditions depend on the energy of the solution, and
that probability is conserved.
  This paper thereby confirms several seminal results and derives some new
ones. In sum, it shows that Schr\"odinger's integral equation is viable tool
for studying singular interactions in quantum mechanics.


title:
Chiral Gravity Waves and Leptogenesis in Inflationary Models with
  non-Abelian Gauge Fields

abstract:
  We present a leptogenesis scenario associated with inflationary models
involving non-Abelian gauge fields within the standard model of particle
physics (SM). We show that this class of inflationary models generates
intrinsic birefringent gravitational waves that through the gravitational
chiral anomaly in SM, can naturally create a net lepton number density. The CP
violating interaction is produced by tensor fluctuations of the gauge field,
while the efficiency of this process is determined by the effective background
value of the gauge field. We demonstrate that this mechanism can create the
observed value of baryon to photon number density in a natural range of
parameters of these models.


title: Quantization and dynamisation of Trace-Poisson brackets

abstract:
  The quantization problem for the trace-bracket algebra, derived from double
Poisson brackets, is discussed. We obtain a generalization of the boundary YBE
(or so-called ABCD-algebra) for the quantization of quadratic trace-brackets. A
dynamical deformation is proposed on the lines of Gervais-Neveu-Felder
dynamical quantum algebras.


title: Nuclear dynamics in the EMC effect at Next-to-Next-to-Leading order

abstract:
  We study in details the parameterizations of the nuclear parton distributions
at the next-to-next-to-leading order (NNLO) of $\alpha_s$. In low $x$ and
$Q_0^2$, we observe negative gluon distribution at this order which signals the
saturation condition or the quark-gluon plasma condition. Our study also shows
the gluon distribution at (NNLO) is less than next-to-leading order (NLO) of
$\alpha_s$, and the sea quark distribution at (NNLO) is larger than (NLO).


title:
Slope Instability of the Earthen Levee in Boston, UK: Numerical
  Simulation and Sensor Data Analysis

abstract:
  The paper presents a slope stability analysis for a heterogeneous earthen
levee in Boston, UK, which is prone to occasional slope failures under tidal
loads. Dynamic behavior of the levee under tidal fluctuations was simulated
using a finite element model of variably saturated linear elastic perfectly
plastic soil. Hydraulic conductivities of the soil strata have been calibrated
according to piezometers readings, in order to obtain correct range of
hydraulic loads in tidal mode. Finite element simulation was complemented with
series of limit equilibrium analyses. Stability analyses have shown that slope
failure occurs with the development of a circular slip surface located in the
soft clay layer. Both models (FEM and LEM) confirm that the least stable
hydraulic condition is the combination of the minimum river levels at low tide
with the maximal saturation of soil layers. FEM results indicate that in winter
time the levee is almost at its limit state, at the margin of safety (strength
reduction factor values are 1.03 and 1.04 for the low-tide and high-tide
phases, respectively); these results agree with real-life observations. The
stability analyses have been implemented as real-time components integrated
into the UrbanFlood early warning system for flood protection.


title:
Majorations explicites de fonctions de Hilbert-Samuel g\'eom\'etrique et
  arithm\'etique

abstract:
  By using the $\mathbb R$-filtration approach of Arakelov geometry, one
establishes explicit upper bounds for geometric and arithmetic Hilbert-Samuel
function for line bundles on projective varieties and hermitian line bundles on
arithmetic projective varieties.


title:
Constrained optimization in classes of analytic functions with
  prescribed pointwise values

abstract:
  We consider an overdetermined problem for Laplace equation on a disk with
partial boundary data where additional pointwise data inside the disk have to
be taken into account. After reformulation, this ill-posed problem reduces to a
bounded extremal problem of best norm-constrained approximation of partial L2
boundary data by traces of holomorphic functions which satisfy given pointwise
interpolation conditions. The problem of best norm-constrained approximation of
a given L2 function on a subset of the circle by the trace of a H2 function has
been considered in [Baratchart \& Leblond, 1998]. In the present work, we
extend such a formulation to the case where the additional interpolation
conditions are imposed. We also obtain some new results that can be applied to
the original problem: we carry out stability analysis and propose a novel
method of evaluation of the approximation and blow-up rates of the solution in
terms of a Lagrange parameter leading to a highly-efficient computational
algorithm for solving the problem.


title: Convexity of parabolic subgroups in Artin groups

abstract:
  We prove that any standard parabolic subgroup of any Artin group is convex
with respect to the standard generating set.


title:
Tailored Source Code Transformations to Synthesize Computationally
  Diverse Program Variants

abstract:
  The predictability of program execution provides attackers a rich source of
knowledge who can exploit it to spy or remotely control the program. Moving
target defense addresses this issue by constantly switching between many
diverse variants of a program, which reduces the certainty that an attacker can
have about the program execution. The effectiveness of this approach relies on
the availability of a large number of software variants that exhibit different
executions. However, current approaches rely on the natural diversity provided
by off-the-shelf components, which is very limited. In this paper, we explore
the automatic synthesis of large sets of program variants, called sosies.
Sosies provide the same expected functionality as the original program, while
exhibiting different executions. They are said to be computationally diverse.
This work addresses two objectives: comparing different transformations for
increasing the likelihood of sosie synthesis (densifying the search space for
sosies); demonstrating computation diversity in synthesized sosies. We
synthesized 30184 sosies in total, for 9 large, real-world, open source
applications. For all these programs we identified one type of program analysis
that systematically increases the density of sosies; we measured computation
diversity for sosies of 3 programs and found diversity in method calls or data
in more than 40% of sosies. This is a step towards controlled massive
unpredictability of software.


title:
On the Fattorini Criterion for Approximate Controllability and
  Stabilizability of Parabolic Systems

abstract:
  In this paper, we consider the well-known Fattorini's criterion for
approximate controllability of infinite dimensional linear systems of type
$y'=A y+Bu$. We precise the result proved by H. O. Fattorini in
\cite{Fattorini1966} for bounded input $B$, in the case where $B$ can be
unbounded or in the case of finite-dimensional controls. More precisely, we
prove that if Fattorini's criterion is satisfied and if the set of geometric
multiplicities of $A$ is bounded then approximate controllability can be
achieved with finite dimensional controls. An important consequence of this
result consists in using the Fattorini's criterion to obtain the feedback
stabilizability of linear and nonlinear parabolic systems with feedback
controls in a finite dimensional space. In particular, for systems described by
partial differential equations, such a criterion reduces to a unique
continuation theorem for a stationary system. We illustrate such a method by
tackling some coupled Navier-Stokes type equations (MHD system and micropolar
fluid system) and we sketch a systematic procedure relying on Fattorini's
criterion for checking stabilizability of such nonlinear systems. In that case,
the unique continuation theorems rely on local Carleman inequalities for
stationary Stokes type systems.


title: Guaman Poma's Yupana and Inca Astronomy

abstract:
  An explanation is provided for the Inca counting board described by Guaman
Poma in 1615. Although the board could have been used in more than one way, we
show that based on certain reasonable assumptions regarding non-uniform
representation of numbers its most likely use was counting in multiples of 6,
24, and 72. The independent numbers represented on its five rows are 92, 31,
29, 79, and 56 that appear to be astronomically connected to sub-periods within
the year and planet periods in a manner similar to Mayan astronomy. Based on
these and other considerations we propose that the board fulfilled an
astronomical counting function.


title: Einstein Static Universe in Braneworld Scenario

abstract:
  The stability of Einstein static universe against homogeneous scalar
perturbations in the context of braneworld scenario is investigated. The
stability regions are obtained in terms of the constant geometric linear
equation of state parameter $\omega_{extr}=p_{extr}/\rho_{extr}$ and are
studied for each evolutionary era of the universe. The results are discussed
for the case of closed, open or flat universe in each era under the obtained
restricting conditions. We also briefly investigate the stability against
vector and tensor perturbations. Contrary to the classical general relativity,
it is found that a stable Einstein static universe may exist in a braneworld
theory of gravity against scalar, vector and tensor perturbations for some
suitable values and ranges of the cosmological parameters.


title: Stability of the Einstein static universe in Einstein-Cartan theory

abstract:
  The existence and stability of the Einstein static solution have been built
in the Einstein-Cartan gravity. We show that this solution in the presence of
perfect fluid with spin density satisfying the Weyssenhoff restriction is
cyclically stable around a center equilibrium point. Thus, study of this
solution is interesting because it supports non-singular emergent cosmological
models in which the early universe oscillates indeterminately about an initial
Einstein static solution and is thus past eternal.


title: Modulus of families of walks on graphs

abstract:
  We introduce the notion of modulus of families of walks on graphs. We show
how Beurling's famous criterion for extremality, that was formulated in the
continuous case, can be interpreted on graphs as an instance of the
Karush-Kuhn-Tucker conditions. We then develop an algorithm to numerically
compute modulus using Beurling's criterion as our guide.


title:
Frenkel electron on an arbitrary electromagnetic background and magnetic
  Zitterbewegung

abstract:
  We present Lagrangian which implies both necessary constraints and dynamical
equations for position and spin of relativistic spin one-half particle. The
model is consistent for any value of magnetic moment $\mu$ and for arbitrary
electromagnetic background. Our equations coincide with those of Frenkel in the
approximation in which the latter have been obtained by Frenkel. Transition
from approximate to exact equations yields two structural modifications of the
theory. First, Frenkel condition on spin-tensor turns into the Pirani
condition. Second, canonical momentum is no more proportional to velocity. Due
to this, even when $\mu=1$ (Frenkel case), the complete and approximate
equations predict different behavior of particle. The difference between
momentum and velocity means extra contribution into spin-orbit interaction. To
estimate the contribution, we found exact solution to complete equations for
the case of uniform magnetic field. While Frenkel electron moves around the
circle, our particle experiences magnetic {\it Zitterbewegung}, that is
oscillates in the direction of magnetic field with amplitude of order of
Compton wavelength for the fast particle. Besides, the particle has dipole
electric moment.


title:
Scattered Light Correction of HAYABUSA/AMICA Data and Quantitative
  Spectral Comparisons of Itokawa

abstract:
  The Hayabusa spacecraft rendezvoused with its target asteroid 25143 Itokawa
in 2005 and brought an asteroidal sample back to the Earth in 2010. The onboard
camera, AMICA, took more than 1400 images of Itokawa during the rendezvous
phase. It was reported that the AMICA images were severely contaminated by
light scatter inside the optics. The effect made it difficult to produce the
color maps at longer wavelengths (>800 nm). In this paper, we demonstrate a
method to subtract the scattered light by investigating the dim halos of
Itokawa and the Moon taken by AMICA during the inflight operation. As the
result, we found that the overall data reduction scheme including the scattered
light correction enables to recognize ~3% regional differences in the relative
reflectance spectra of Itokawa. We confirmed that the color variation in
Itokawa was largely attributed to space weathering.


title: Bimodal island size distribution in heteroepitaxial growth

abstract:
  A bimodal size distribution of two dimensional islands is inferred during
interface formation in heteroepitaxial growth of Bismuth Ferrite on (001)
oriented SrTiO3 by sputter deposition. Features observed by in-situ x-ray
scattering are explained by a model where coalescence of islands determines the
growth kinetics with negligible surface diffusion on SrTiO3. Small clusters
maintain a compact shape as they coalesce, while clusters beyond a critical
size impinge to form large irregular connected islands and a population of
smaller clusters forms in the spaces between the larger ones.


title: Spin-polarons in an exchange model

abstract:
  Spin-polarons are obtained using an Ising-like exchange model consisting of
double and super-exchange interactions in low dimensional systems. At zero
temperature, a new phase separation between small magnetic polarons, one
conduction electron self-trapped in a magnetic domain of two or three sites,
and the anti-ferromagnetic phase was previously reported. On the other hand the
important effect of temperature was missed. Temperature diminishes Boltzmann
probability allowing excited states in the system. Static magnetic
susceptibility and short-range spin-spin correlations at zero magnetic field
were calculated to explore the spin-polaron formation. At high temperature
Curie-Weiss behavior is obtained and compared with the Curie-like behavior
observed in a nickelate one-dimensional compound.


title:
Comment on "Detecting Novel Associations In Large Data Sets" by Reshef
  Et Al, Science Dec 16, 2011

abstract:
  The proposal of Reshef et al. (2011) is an interesting new approach for
discovering non-linear dependencies among pairs of measurements in exploratory
data mining. However, it has a potentially serious drawback. The authors laud
the fact that MIC has no preference for some alternatives over others, but as
the authors know, there is no free lunch in Statistics: tests which strive to
have high power against all alternatives can have low power in many important
situations. To investigate this, we ran simulations to compare the power of MIC
to that of standard Pearson correlation and distance correlation (dcor). We
simulated pairs of variables with different relationships (most of which were
considered by the Reshef et. al.), but with varying levels of noise added. To
determine proper cutoffs for testing the independence hypothesis, we simulated
independent data with the appropriate marginals. As one can see from the
Figure, MIC has lower power than dcor, in every case except the somewhat
pathological high-frequency sine wave. MIC is sometimes less powerful than
Pearson correlation as well, the linear case being particularly worrisome.


title: Characterizing intermediate tense logics in terms of Galois connections

abstract:
  We propose a uniform way of defining for every logic ${\sf L}$ intermediate
between intuitionistic and classical logics, the corresponding intermediate
minimal tense logic ${\sf LK_t}$. This is done by building the fusion of two
copies of intermediate logic with a Galois connection ${\sf LGC}$, and then
interlinking their operators by two Fischer Servi axioms. The resulting system
is called here ${\sf L2GC{+}FS}$. In the cases of intuitionistic logic ${\sf
Int}$ and classical logic ${\sf Cl}$, it is noted that ${\sf Int2GC{+}FS}$ is
syntactically equivalent to intuitionistic minimal tense logic ${\sf IK_t}$ by
W. B. Ewald and ${\sf Cl2GC{+}FS}$ equals classical minimal tense logic ${\sf
K_t}$. This justifies to consider ${\sf L2GC{+}FS}$ as minimal ${\sf L}$-tense
logic ${\sf LK_t}$ for any intermediate logic ${\sf L}$. We define
H2GC+FS-algebras as expansions of HK1-algebras, introduced by E. Orlowska and
I. Rewitzky. For each intermediate logic ${\sf L}$, we show algebraic
completeness of ${\sf L2GC{+}FS}$ and its conservativeness over ${\sf L}$. We
prove relational completeness of ${\sf Int2GC{+}FS}$ with respect to the models
defined on ${\sf IK}$-frames introduced by G. Fischer Servi. We also prove a
representation theorem stating that every H2GC+FS-algebra can be embedded into
the complex algebra of its canonical ${\sf IK}$-frame.


title: Epipelagic representations and rigid local systems

abstract:
  We construct automorphic representations for quasi-split groups $G$ over the
function field $F=k(t)$ one of whose local components is an epipelagic
representation in the sense of Reeder and Yu. We also construct the attached
Galois representations under the Langlands correspondence. These Galois
representations give new classes of conjecturally rigid, wildly ramified
$^{L}G$-local systems over $\mathbb{P}^{1}-\{0,\infty\}$ that generalize the
Kloosterman sheaves constructed earlier by Heinloth, Ng\^o and the author. We
study the monodromy of these local systems and compute all examples when $G$ is
a classical group.


title: Modelling Circumbinary Planets: The case of Kepler-38

abstract:
  Recently, a number of planets orbiting binary stars have been discovered by
the Kepler space telescope. In a few systems the planets reside close to the
dynamical stability limit. Due to the difficulty of forming planets in such
close orbits, it is believed that they have formed further out in the disk and
migrated to their present locations. Our goal is to construct more realistic
models of planet migration in circumbinary disks, and to determine the final
position of these planets. In our work, we focus on the system Kepler-38. The
evolution of the circumbinary disk is studied using two-dimensional
hydrodynamical simulations. We study locally isothermal disks as well as more
realistic models with viscous heating, radiative cooling from the disk
surfaces, and radiative diffusion in the disk mid plane. After the disk has
been brought into equilibrium, a 115 Earth-mass planet is embedded and its
evolution is followed. In all cases the planets stop inward migration near the
inner edge of the disk. In isothermal disks with a typical disk scale height of
H/r = 0.05, the final outcome agrees very well with the observed location of
planet Kepler-38b. For the radiative models, the disk thickness and location of
the inner edge is determined by the mass in the system. For surface densities
in the order of 3000 g/cm^2 at 1 AU, the inner gap lies close to the binary and
planets stop in the region between the 5:1 and 4:1 mean-motion resonances with
the binary. A model with a disk with approximately a quarter of the mass yields
a final position very close to the observed one. For planets migrating in
circumbinary disks, the final position is dictated by the structure of the
disk. Knowing the observed orbits of circumbinary planets, radiative disk
simulations with embedded planets can provide important information on the
physical state of the system during the final stages of its evolution.


title:
Magnetic-Field-Modulated Resonant Tunneling in
  Ferromagnetic-Insulator-Nonmagnetic junctions

abstract:
  We present a theory for resonance-tunneling magnetoresistance (MR) in
Ferromagnetic-Insulator-Nonmagnetic junctions. The theory sheds light on many
of the recent electrical spin injection experiments, suggesting that this MR
effect rather than spin accumulation in the nonmagnetic channel corresponds to
the electrically detected signal. We quantify the dependence of the tunnel
current on the magnetic field by quantum rate equations derived from the
Anderson impurity model, with important addition of impurity spin interactions.
Considering the on-site Coulomb correlation, the MR effect is caused by
competition between the field, spin interactions and coupling to the magnetic
lead. By extending the theory, we present a basis for operation of novel
nm-size memories.


title:
Large global-in-time solutions of the parabolic-parabolic Keller-Segel
  system on the plane

abstract:
  As it is well known, the parabolic-elliptic Keller-Segel system of chemotaxis
on the plane has global-in-time regular nonnegative solutions with total mass
below the critical value $8\pi$. Solutions with mass above $8\pi$ blow up in a
finite time. We show that the case of the parabolic-parabolic Keller-Segel is
different: each mass may lead to a global-in-time-solution, even if the initial
data is a finite signed measure.
  These solutions need not be unique, even if we limit ourselves to nonnegative
solutions.


title: Controlling a Software-Defined Network via Distributed Controllers

abstract:
  In this paper, we propose a distributed OpenFlow controller and an associated
coordination framework that achieves scalability and reliability even under
heavy data center loads. The proposed framework, which is designed to work with
all existing OpenFlow controllers with minimal or no required changes, provides
support for dynamic addition and removal of controllers to the cluster without
any interruption to the network operation. We demonstrate performance results
of the proposed framework implemented over an experimental testbed that uses
controllers running Beacon.


title: A Note on Optimal Design of Multiphase Elastic Structures

abstract:
  The paper describes the first exact results in optimal design of three-phase
elastic structures. Two isotropic materials, the "strong" and the "weak" one,
are laid out with void in a given two-dimensional domain so that the compliance
plus weight of a structure is minimized. As in the classical two-phase problem,
the optimal layout of three phases is also determined on two levels: macro- and
microscopic. On the macrolevel, the design domain is divided into several
subdomains. Some are filled with pure phases, and others with their mixtures
(composites). The main aim of the paper is to discuss the non-uniqueness of the
optimal macroscopic multiphase distribution. This phenomenon does not occur in
the two-phase problem, and in the three-phase design it arises only when the
moduli of material isotropy of "strong" and "weak" phases are in certain
relation.


title:
The Celestial Buffet: multiple populations and globular cluster
  formation in dwarf galaxies

abstract:
  We present a framework that explains the commonly observed variation in light
element abundances in globular clusters. If globular clusters form in the
centres of dwarf galaxies, they will be pumped onto larger orbits as star
formation progresses. The potential well will only retain the moderate velocity
AGB ejecta, the expected source of enrichment, but not supernova ejecta. There
is no need to increase the initial cluster mass, a requirement of
self-enrichment scenarios, as all the stars within the dwarf can contribute. As
the clusters move through the dwarf centre they sweep up a mix of AGB ejecta
and in-falling pristine gas to form a second generation of stars. The specific
mix will vary in time and is thus able to explain the spread in second
generation abundances observed in different clusters. The globular clusters
will survive to the present day or be stripped as part of the hierarchical
merging process of larger galaxies. We illustrate how this process may operate
using a high-resolution simulation of a dwarf galaxy at high redshift.


title: Conformal Data from Finite Entanglement Scaling

abstract:
  In this paper we apply the formalism of translation invariant (continuous)
matrix product states in the thermodynamic limit to $(1+1)$ dimensional
critical models. Finite bond dimension bounds the entanglement entropy and
introduces an effective finite correlation length, so that the state is
perturbed away from criticality. The assumption that the scaling hypothesis
holds for this kind of perturbation is known in the literature as finite
entanglement scaling. We provide further evidence for the validity of finite
entanglement scaling and based on this formulate a scaling algorithm to
estimate the central charge and critical exponents of the conformally invariant
field theories describing the critical models under investigation. The
algorithm is applied to three exemplary models; the cMPS version to the
non-relativistic Lieb-Liniger model and the relativistic massless boson, and
MPS version to the one-dimensional quantum Ising model at the critical point.
Another new aspect to our approach is that we directly use the (c)MPS induced
correlation length rather than the bond dimension as scaling parameter. This
choice is motivated by several theoretical arguments as well as by the
remarkable accuracy of our results.

categories: quant-ph cond-mat.stat-mech cond-mat.str-el hep-th


title: Inversion of the star transform

abstract:
  We define the star transform as a generalization of the broken ray transform
introduced by us in previous work. The advantages of using the star transform
include the possibility to reconstruct the absorption and the scattering
coefficients of the medium separately and simultaneously (from the same data)
and the possibility to utilize scattered radiation which, in the case of the
conventional X-ray tomography, is discarded. In this paper, we derive the star
transform from physical principles, discuss its mathematical properties and
analyze numerical stability of inversion. In particular, it is shown that
stable inversion of the star transform can be obtained only for configurations
involving odd number of rays. Several computationally-efficient inversion
algorithms are derived and tested numerically.


title:
Magnetic polaron structures in the one-dimensional double and
  super-exchange model

abstract:
  An analytical and numerical study of the one-dimensional double and
super-exchange model is presented. A phase separation between ferromagnetic and
anti-ferromagnetic phases occurs at low super-exchange interaction energy. When
the super-exchange interaction energy gets larger, the conduction electrons are
self-trapped within separate small magnetic polarons. These magnetic polarons
contain a single electron inside two or three sites depending on the conduction
electron density and form a Wigner crystallization. A new phase separation is
found between these small polarons and the anti-ferromagnetic phase. Our
results could explain the spin-glass-like behavior observed in the nickelate
one-dimensional compound Y(2-x)CaxBaNiO5.


title: Analytical model for non-thermal pressure in galaxy clusters

abstract:
  Non-thermal pressure in the intracluster gas has been found ubiquitously in
numerical simulations, and observed indirectly. In this paper we develop an
analytical model for intracluster non-thermal pressure in the virial region of
relaxed clusters. We write down and solve a first-order differential equation
describing the evolution of non-thermal velocity dispersion. This equation is
based on insights gained from observations, numerical simulations, and theory
of turbulence. The non-thermal energy is sourced, in a self-similar fashion, by
the mass growth of clusters via mergers and accretion, and dissipates with a
time-scale determined by the turnover time of the largest turbulence eddies.
Our model predicts a radial profile of non-thermal pressure for relaxed
clusters. The non-thermal fraction increases with radius, redshift, and cluster
mass, in agreement with numerical simulations. The radial dependence is due to
a rapid increase of the dissipation time-scale with radii, and the mass and
redshift dependence comes from the mass growth history. Combing our model for
the non-thermal fraction with the Komatsu-Seljak model for the total pressure,
we obtain thermal pressure profiles, and compute the hydrostatic mass bias. We
find typically 10% bias for the hydrostatic mass enclosed within $r_{500}$.


title:
Upper bounds on the error probabilities and asymptotic error exponents
  in quantum multiple state discrimination

abstract:
  We consider the multiple hypothesis testing problem for symmetric quantum
state discrimination between r given states \sigma_1,...,\sigma_r. By splitting
up the overall test into multiple binary tests in various ways we obtain a
number of upper bounds on the optimal error probability in terms of the binary
error probabilities. These upper bounds allow us to deduce various bounds on
the asymptotic error rate, for which it has been hypothesised that it is given
by the multi-hypothesis quantum Chernoff bound (or Chernoff divergence)
C(\sigma_1,...,\sigma_r), as recently introduced by Nussbaum and Szko{\l}a in
analogy with Salikhov's classical multi-hypothesis Chernoff bound. This
quantity is defined as the minimum of the pairwise binary Chernoff divergences
min_{j<k}C(\sigma_j,\sigma_k). It was known already that the optimal asymptotic
rate must lie between C/3 and C, and that for certain classes of sets of states
the bound is actually achieved. It was known to be achieved, in particular,
when the state pair that is closest together in Chernoff divergence is more
than 6 times closer than the next closest pair. Our results improve on this in
two ways. Firstly, we show that the optimal asymptotic rate must lie between
C/2 and C. Secondly, we show that the Chernoff bound is already achieved when
the closest state pair is more than 2 times closer than the next closest pair.
We also show that the Chernoff bound is achieved when at least $r-2$ of the
states are pure, improving on a previous result by Nussbaum and Szko{\l}a.
Finally, we indicate a number of potential pathways along which a proof (or
disproof) may eventually be found that the multi-hypothesis quantum Chernoff
bound is always achieved.