title:
Optical Spectroscopy and Velocity Dispersions of Galaxy Clusters from
  the SPT-SZ Survey

abstract:
  We present optical spectroscopy of galaxies in clusters detected through the
Sunyaev-Zel'dovich (SZ) effect with the South Pole Telescope (SPT). We report
our own measurements of $61$ spectroscopic cluster redshifts, and $48$ velocity
dispersions each calculated with more than $15$ member galaxies. This catalog
also includes $19$ dispersions of SPT-observed clusters previously reported in
the literature. The majority of the clusters in this paper are SPT-discovered;
of these, most have been previously reported in other SPT cluster catalogs, and
five are reported here as SPT discoveries for the first time. By performing a
resampling analysis of galaxy velocities, we find that unbiased velocity
dispersions can be obtained from a relatively small number of member galaxies
($\lesssim 30$), but with increased systematic scatter. We use this analysis to
determine statistical confidence intervals that include the effect of
membership selection. We fit scaling relations between the observed cluster
velocity dispersions and mass estimates from SZ and X-ray observables. In both
cases, the results are consistent with the scaling relation between velocity
dispersion and mass expected from dark-matter simulations. We measure a
$\sim$30% log-normal scatter in dispersion at fixed mass, and a $\sim$10%
offset in the normalization of the dispersion-mass relation when compared to
the expectation from simulations, which is within the expected level of
systematic uncertainty.


title: Remarks on the conjectured log-Brunn-Minkowski inequality

abstract:
  \footnotesize B\"{o}r\"{o}czky, Lutwak, Yang and Zhang recently conjectured a
certain strengthening of the Brunn-Minkowski inequality for symmetric convex
bodies, the so-called log-Brunn-Minkowski inequality. We establish this
inequality together with its equality cases for pairs of unconditional convex
bodies with respect to some orthonormal basis. Applications of this fact are
discussed. Moreover, we prove that the log-Brunn-Minkowski inequality is
equivalent to the (B)-Theorem for the uniform measure of the cube (this has
been proven by Cordero-Erasquin, Fradelizi and Maurey for the gaussian measure
instead).


title: On the equivalence between two problems of asymmetry on convex bodies

abstract:
  The simplex was conjectured to be the extremal convex body for the two
following "problems of asymmetry":\\ P1) What is the minimal possible value of
the quantity $\max_{K'} |K'|/|K|$? Here, $K'$ ranges over all symmetric convex
bodies contained in $K$.\\ P2) What is the maximal possible volume of the
Blaschke-body of a convex body of volume 1?\\ Our main result states that (P1)
and (P2) admit precisely the same solutions. This complements a result from
[{\rm K. B\"or\"oczky, I. B\'ar\'any, E. Makai Jr. and J. Pach}, Maximal volume
enclosed by plates and proof of the chessboard conjecture], Discrete Math. {\bf
69} (1986), 101--120], stating that if the simplex solves (P1) then the simplex
solves (P2) as well.


title:
The impossibility of exactly flat non-trivial Chern bands in strictly
  local periodic tight binding models

abstract:
  We investigate the possibility of exactly flat non-trivial Chern bands in
tight binding models with local (strictly short-ranged) hopping parameters. We
demonstrate that while any two of three criteria can be simultaneously realized
(exactly flat band, non-zero Chern number, local hopping), it is not possible
to simultaneously satisfy all three. Our theorem covers both the case of a
single flat band, for which we give a rather elementary proof, as well as the
case of multiple degenerate flat bands. In the latter case, our result is
obtained as an application of $K$-theory. We also introduce a class of models
on the Lieb lattice with nearest and next-nearest neighbor hopping parameters,
which have an isolated exactly flat band of zero Chern number but, in general,
non-zero Berry curvature.

categories: cond-mat.str-el math-ph math.MP quant-ph


title: Single photon production by rephased amplified spontaneous emission

abstract:
  The production of single photons using rephased amplified spontaneous
emission is examined. This process produces single photons on demand with high
efficiency by detecting the spontaneous emission from an atomic ensemble, then
applying a population-inverting pulse to rephase the ensemble and produce a
photon echo of the spontaneous emission events. The theoretical limits on the
efficiency of the production are determined for several variants of the scheme.
For an ensemble of uniform optical density, generating the initial spontaneous
emission and its echo using transitions of different strengths is shown to
produce single photons at 70% efficiency, limited by reabsorption. Tailoring
the spatial and spectral density of the atomic ensemble is then shown to
prevent reabsorption of the rephased photon, resulting in emission efficiency
near unity.


title: Adiabatic regularization and particle creation for spin one-half fields

abstract:
  The extension of the adiabatic regularization method to spin-$1/2$ fields
requires a self-consistent adiabatic expansion of the field modes. We provide
here the details of such expansion, which differs from the WKB ansatz that
works well for scalars, to firmly establish the generalization of the adiabatic
renormalization scheme to spin-$1/2$ fields. We focus on the computation of
particle production in de Sitter spacetime and obtain an analytic expression of
the renormalized stress-energy tensor for Dirac fermions.

categories: gr-qc astro-ph.CO hep-th math-ph math.MP


title: UV Suppression by Smearing and Screening Correlators

abstract:
  We investigate the mechanism of smearing in the APE, Stout, HYP and HEX
schemes through their effect on glue and quark Fourier modes. Using this, we
non-perturbatively tune the smearing parameters to their optimum values.
Smearing causes a super-linear improvement in taste symmetry breaking in the
high temperature phase of QCD. We use optimal smearing in the high temperature
phase and find close agreement of meson screening masses with weak coupling
predictions.


title: Bertini irreducibility theorems over finite fields

abstract:
  Given a geometrically irreducible subscheme X in P^n over F_q of dimension at
least 2, we prove that the fraction of degree d hypersurfaces H such that the
intersection of H and X is geometrically irreducible tends to 1 as d tends to
infinity. We also prove variants in which X is over an extension of F_q, and in
which the immersion of X in P^n is replaced by a more general morphism.


title:
Spin bath maser in a cryogenically cooled sapphire whispering gallery
  mode resonator

abstract:
  We report the observation of a mechanism of maser generation in an ensemble
of inter-coupled, inhomogeneously broadened two-level systems, enhanced by high
quality factor electromagnetic cavity modes. In this previously unobserved form
of population inversion, an inseparable quantum system leads to cavity-enhanced
stimulated emission arising from interactions within an ensemble of two-level
systems, as opposed to a traditional ensemble of noninteracting identical three
level systems. The effect is observed in a cryogenically cooled whispering
gallery mode sapphire resonator containing dilute Fe$^{3+}$ impurity ions.
These ions exhibit strong spin-lattice interaction, leading to both electron
spin resonance broadening and phonon mediated spin-spin coupling. The maser
effect is due to a $\left|1/2\right\rangle \rightarrow \left|3/2\right\rangle$
energy transition in electron spin angular momentum observed at zero external
magnetic field. Both continuous and oscillating regimes are observed with
corresponding thresholds both in detuning frequency and incident power.


title: Cyclic Leibniz rule: a formulation of supersymmetry on lattice

abstract:
  For the purpose of constructing supersymmetric(SUSY) theories on lattice, we
propose a new type relation on lattice -cyclic Leibniz rule(CLR)- which is
slightly different from an ordinary Leibniz rule. Actually, we find that CLR
can enlarge the number of SUSYs and construct more Nicolai mappings in a
quantum-mechanical model. In this model, the exact mass degeneracy between
fermion and boson is shown.


title: Comparative Study Of Image Edge Detection Algorithms

abstract:
  Since edge detection is in the forefront of image processing for object
detection, it is crucial to have a good understanding of edge detection
algorithms. The reason for this is that edges form the outline of an object. An
edge is the boundary between an object and the background, and indicates the
boundary between overlapping objects. This means that if the edges in an image
can be identified accurately, all of the objects can be located and basic
properties such as area, perimeter, and shape can be measured. Since computer
vision involves the identification and classification of objects in an image,
edge detection is an essential tool. We tested two edge detectors that use
different methods for detecting edges and compared their results under a
variety of situations to determine which detector was preferable under
different sets of conditions.


title:
TDCS-based Cognitive Radio Networks with Multiuser Interference
  Avoidance

abstract:
  For overlay cognitive radio networks (CRNs), transform domain communication
system (TDCS) has been proposed to support multiuser communications through
spectrum bin nulling and frequency domain spreading. In TDCS-based CRNs, each
user is assigned a specific pseudorandom spreading sequence. However, the
existence of multiuser interference (MUI) is one of main concerns, due to the
non-zero cross-correlations between any pair of TDCS signals. In this paper, a
novel framework of TDCS-based CRNs with the joint design of sequences and
modulation schemes is presented to realize MUI avoidance. With the uncertainty
of spectrum sensing results in CRNs, we first introduce a unique sequence
design through two-dimensional time-frequency synthesis and obtain a class of
almost perfect sequences. That is, periodic auto-correlation and
cross-correlations are identically zero for most circular shifts. These
correlation properties are further exploited in conjunction with a
specially-designed cyclic code shift keying in order to achieve the advantage
of MUI avoidance. Numerical results demonstrate that the proposed TDCS-based
CRNs are considered as preferable candidates for decentralized networks against
the near-far problem.


title:
Study of $\bar{B}_s^0 \to (D_s^+,D_s^{*+}) l^-\bar{\nu}_l$ decays in the
  pQCD factorization approach

abstract:
  The $\bar{B}_s^0 \to D_s^{(*)+} l^- \bar{\nu}_l$ semileptonic decays were
calculated in the framework of the standard model (SM) by employing the
perturbative QCD (pQCD) factorization approach. We defined four ratios of the
branching ratios of the considered decays $R(D_s^{(*)})$ and
$R_{D_s}^{l,\tau}$. From the numerical results and phenomenological analysis we
found that: (a) The pQCD predictions for the branching ratios $Br(\bar{B}_s^0
\to D_s^{(*)+} l^-\bar{\nu}_l)$ generally agree well with the previous
theoretical predictions; (b) For the four ratios, the pQCD predictions are
$R(D_s)= 0.392 \pm 0.022$, $R(D_s^{*})= 0.302\pm 0.011$,
$R_{D_{s}}^l=0.448^{+0.058}_{-0.041}$ and
$R_{D_{s}}^\tau=0.582^{+0.071}_{-0.045}$, which show a very good $SU(3)_F$
flavor symmetry with the corresponding ratios for $B\to D^{(*)} l^-
\bar{\nu}_l$ decays; and (c) we strongly suggest the measurements of the new
ratios $R(D_s^{(*)})$ and $R_{D_{s}}^{l,\tau}$ in the forthcoming Super-B
experiments.


title: Effective Field Theory for Lattice Nuclei

abstract:
  We show how nuclear effective field theory (EFT) and ab initio
nuclear-structure methods can turn input from lattice quantum chromodynamics
(LQCD) into predictions for the properties of nuclei. We argue that pionless
EFT is the appropriate theory to describe the light nuclei obtained in recent
LQCD simulations carried out at pion masses much heavier than the physical pion
mass. We solve the EFT using the effective-interaction hyperspherical harmonics
and auxiliary-field diffusion Monte Carlo methods. Fitting the three
leading-order EFT parameters to the deuteron, dineutron and triton LQCD
energies at $m_{\pi}\approx 800$ MeV, we reproduce the corresponding
alpha-particle binding and predict the binding energies of mass-5 and 6 ground
states.


title:
On the Generating Functionals of a Class of Random Packing Point
  Processes

abstract:
  Consider a symmetrical conflict relationship between the points of a point
process. The Mat\'ern type constructions provide a generic way of selecting a
subset of this point process which is conflict-free. The simplest one consists
in keeping only conflict-free points. There is however a wide class of Mat\'ern
type processes based on more elaborate selection rules and providing larger
sets of selected points. The general idea being that if a point is discarded
because of a given conflict, there is no need to discard other points with
which it is also in conflict. The ultimate selection rule within this class is
the so called Random Sequential Adsorption, where the cardinality of the
sequence of conflicts allowing one to decide whether a given point is selected
is not bounded. The present paper provides a sufficient condition on the span
of the conflict relationship under which all the above point processes are well
defined when the initial point process is Poisson. It then establishes, still
in the Poisson case, a set of differential equations satisfied by the
probability generating functionals of these Mat\'ern type point processes.
Integral equations are also given for the Palm distributions.


title:
Unstable Angina is a syndrome correlated to mixed Th17 and Th1 immune
  disorder

abstract:
  Unstable angina is common clinical manifestation of atherosclerosis. However,
the detailed pathogenesis of unstable angina is still not known. Here, I
propose that unstable angina is a mixed TH17 and TH1 immune disorder. By using
microarray analysis, I find out that TH1 and TH17 related cytokine, cytokine
receptor, chemokines, complement, immune-related transcription factors,
anti-bacterial genes, Toll-like receptors, and heat shock proteins are all
up-regulated in peripheral leukocytes of unstable angina. In addition,
H-ATPase, glycolytic genes, platelet and RBC related genes are also
up-regulated in peripheral leukocytes of during unstable angina. It also
implies that atherosclerosis is a mixed TH17 and TH1 autoimmune disease. If we
know the etiology of unstable angina as well as atherosclerosis better, we can
have better methods to control and prevent this detrimental illness.


title: Recursive formula for arithmetic Asian option prices

abstract:
  We derive a recursive formula for arithmetic Asian option prices with finite
observation times in semimartingale models. The method is based on the
relationship between the risk-neutral expectation of the quadratic variation of
the return process and European option prices. The computation of arithmetic
Asian option prices is straightforward whenever European option prices are
available. Applications with numerical results under the Black-Scholes
framework and the exponential L\'evy model are proposed.


title: Weak null singularities in general relativity

abstract:
  We construct a class of spacetimes (without symmetry assumptions) satisfying
the vacuum Einstein equations with singular boundaries on two null
hypersurfaces intersecting in the future on a 2-sphere. The metric of these
spacetimes extends continuously beyond the singularities while the Christoffel
symbols fail to be square integrable in a neighborhood of any point on the
singular boundaries. The construction shows moreover that the singularities are
stable in a suitable sense. These singularities are stronger than the impulsive
gravitational spacetimes considered by Luk-Rodnianski and conjecturally they
are present in the interior of generic black holes arising from gravitational
collapse.


title: Geodesic distances and intrinsic distances on some fractal sets

abstract:
  Given strong local Dirichlet forms and $\mathbb{R}^N$-valued functions on a
metrizable space, we introduce the concepts of geodesic distance and intrinsic
distance on the basis of these objects. They are defined in a geometric and an
analytic way, respectively, and they are closely related with each other in
some classical situations. In this paper, we study the relations of these
distances when the underlying space has a fractal structure. In particular, we
prove their coincidence for a class of self-similar fractals.


title: Fermi acceleration in chaotic shape-preserving billiards

abstract:
  We study theoretically and numerically the velocity dynamics of fully chaotic
time-dependent shape-preserving billiards. The average velocity of an ensemble
of initial conditions generally asymptotically follows the power law $v =
n^{\beta}$ with respect to the number of collisions n. If the shape of the
chaotic time-dependent billiard is not preserved it is well known that the
acceleration exponent is $\beta = 1/2$. We show, on the other hand, that if the
shape of the billiard is preserved then the only possible values of $\beta$ are
$1/4$, $1/6$ and in a special case $0$. We show that the value of $\beta$ is
determined solely by whether the angular momentum of the billiard is preserved
or not. Our theory is centered around the detailed study of the energy
fluctuations in the adiabatic limit. We show that three quantities, two scalars
and one tensor, completely determine the energy fluctuations of the billiard
for arbitrary time-dependent shape-preserving transformations. Finally we
provide several interesting numerical examples all in a perfect agreement with
the theory.


title: High moment variations and their application

abstract:
  We propose a new method of measuring the third and fourth moments of return
distribution based on quadratic variation method when the return process is
assumed to have zero drift. The realized third and fourth moments variations
computed from high frequency return series are good approximations to
corresponding actual moments of the return distribution. An investor holding an
asset with skewed or fat-tailed distribution is able to hedge the tail risk by
contracting the third or fourth moment swap under which the float leg of
realized variation and the predetermined fixed leg are exchanged. Thus
constructed portfolio follows more Gaussian-like distribution and hence the
investor effectively hedge the tail risk.


title:
H I Free-Bound Emission of Planetary Nebulae with Large Abundance
  Discrepancies: Two-Component Models versus Kappa-distributed electrons

abstract:
  The "abundance discrepancy" problem in the study of planetary nebulae (PNe),
viz., the problem concerning systematically higher heavy-element abundances
derived from optical recombination lines relative to those from collisionally
excited lines, has been under discussion for decades, but no consensus on its
solution has yet been reached. In this paper we investigate the hydrogen
free-bound emission near the Balmer jump region of four PNe that are among
those with the largest abundance discrepancies, aiming to examine two recently
proposed solutions to this problem: two-component models and Kappa electron
energy distributions. We find that the Balmer jump intensities and the spectrum
slopes cannot be simultaneously matched by the theoretical calculations based
upon single Maxwell-Boltzmann electron-energy distributions, whereas the
fitting can be equally improved by introducing Kappa electron energy
distributions or an additional Maxwell-Boltzmann component. We show that
although H I free-bound emission alone cannot distinguish the two scenarios, it
can provide important constraints on the electron energy distributions,
especially for cold and low-Kappa plasmas.


title:
Enhancement of image resolution beyond the diffraction-limit by
  interacting dark resonances

abstract:
  We show how quantum coherence effects can be used to improve the resolution
and the contrast of diffraction-limited images imprinted onto a probe field.
The narrow and sharp spectral features generated by double-dark resonances
(DDR) are exploited to control absorption, dispersion and diffraction
properties of the medium. The spatial modulated control field can produce
inhomoge- neous susceptibility of the medium that encodes the spatial feature
of the control image to probe field in the presence of DDR. The transmission of
cloned image can be enhanced by use of incoher- ent pump field. We find that
the feature size of cloned image is four times smaller than the initial
characteristic size of the control image even though the control image is
completely distorted after propagation through 3 cm long Rb vapour cell. We
further discuss how spatial optical switching is possible by using of induced
transparency and absorption of the medium.


title:
Asymptotic equivalence of quantum state tomography and noisy matrix
  completion

abstract:
  Matrix completion and quantum tomography are two unrelated research areas
with great current interest in many modern scientific studies. This paper
investigates the statistical relationship between trace regression in matrix
completion and quantum state tomography in quantum physics and quantum
information science. As quantum state tomography and trace regression share the
common goal of recovering an unknown matrix, it is nature to put them in the Le
Cam paradigm for statistical comparison. Regarding the two types of matrix
inference problems as two statistical experiments, we establish their
asymptotic equivalence in terms of deficiency distance. The equivalence study
motivates us to introduce a new trace regression model. The asymptotic
equivalence provides a sound statistical foundation for applying matrix
completion methods to quantum state tomography. We investigate the asymptotic
equivalence for sparse density matrices and low rank density matrices and
demonstrate that sparsity and low rank are not necessarily helpful for
achieving the asymptotic equivalence of quantum state tomography and trace
regression. In particular, we show that popular Pauli measurements are bad for
establishing the asymptotic equivalence for sparse density matrices and low
rank density matrices.


title: Conditional correlation in asset return and GARCH intensity model

abstract:
  In an asset return series there is a conditional asymmetric dependence
between current return and past volatility depending on the current return's
sign. To take into account the conditional asymmetry, we introduce new models
for asset return dynamics in which frequencies of the up and down movements of
asset price have conditionally independent Poisson distributions with
stochastic intensities. The intensities are assumed to be stochastic recurrence
equations of the GARCH type in order to capture the volatility clustering and
the leverage effect. We provide an important linkage between our model and
existing GARCH, explain how to apply maximum likelihood estimation to determine
the parameters in the intensity model and show empirical results with the S&P
500 index return series.


title:
Pioneer 10 and 11 orbit determination analysis shows no discrepancy with
  Newton-Einstein's laws of gravity

abstract:
  The present work describes the investigation of the navigation anomaly of
Pioneer 10 and 11 probes which became known as the Pioneer Anomaly. It appeared
as a linear drift in the Doppler data received by the spacecraft, which has
been ascribed to an approximately constant sunward acceleration of about $8.5
\times 10^{-13} km/s^2$. Since then, the existence of the anomaly has been
confirmed independently by several groups and a large effort was devoted to
find its origin. The present study consists of two main parts: thermal modeling
of the spacecraft throughout its trajectory, and orbit determination analysis.
Based on existing documentation and published telemetry data we built a thermal
finite element model of the spacecraft, whose complexity has been constrained
to a degree allowing for sensitivity analysis, leading to the computation of
its formal uncertainty. The trajectory analysis and orbit determination was
carried out using NASA/JPL's ODP (Orbit Determination Program) and our results
show that orbital solutions may be achieved that do not require the addition of
any "unknown" acceleration other than the one of thermal origin.


title: Cosmology: theory

abstract:
  The discovery of 126 GeV Higgs boson and observations of no signs of new
physics at the LHC implies that the Standard Model of elementary particles is a
self-consistent weakly-coupled effective field theory all the way up to the
Planck scale without the addition of any new particles. I will discuss possible
consequences of these findings for cosmology.


title: Detection of entanglement between collective spins

abstract:
  Entanglement between individual spins can be detected by using thermodynamics
quantities as entanglement witnesses. This applies to collective spins also,
provided that their internal degrees of freedom are frozen, as in the limit of
weakly-coupled nanomagnets. Here, we extend such approach to the detection of
entanglement between subsystems of a spin cluster, beyond such weak-coupling
limit. The resulting inequalities are violated in spin clusters with different
geometries, thus allowing the detection of zero- and finite-temperature
entanglement. Under relevant and experimentally verifiable conditions, all the
required expectation values can be traced back to correlation functions of
individual spins, that are now made selectively available by four-dimensional
inelastic neutron scattering.


title: Calibrating nonconvex penalized regression in ultra-high dimension

abstract:
  We investigate high-dimensional nonconvex penalized regression, where the
number of covariates may grow at an exponential rate. Although recent
asymptotic theory established that there exists a local minimum possessing the
oracle property under general conditions, it is still largely an open problem
how to identify the oracle estimator among potentially multiple local minima.
There are two main obstacles: (1) due to the presence of multiple minima, the
solution path is nonunique and is not guaranteed to contain the oracle
estimator; (2) even if a solution path is known to contain the oracle
estimator, the optimal tuning parameter depends on many unknown factors and is
hard to estimate. To address these two challenging issues, we first prove that
an easy-to-calculate calibrated CCCP algorithm produces a consistent solution
path which contains the oracle estimator with probability approaching one.
Furthermore, we propose a high-dimensional BIC criterion and show that it can
be applied to the solution path to select the optimal tuning parameter which
asymptotically identifies the oracle estimator. The theory for a general class
of nonconvex penalties in the ultra-high dimensional setup is established when
the random errors follow the sub-Gaussian distribution. Monte Carlo studies
confirm that the calibrated CCCP algorithm combined with the proposed
high-dimensional BIC has desirable performance in identifying the underlying
sparsity pattern for high-dimensional data analysis.


title: Annihilation of low energy antiprotons in silicon

abstract:
  The goal of the AE$\mathrm{\bar{g}}$IS experiment at the Antiproton
Decelerator (AD) at CERN, is to measure directly the Earth's gravitational
acceleration on antimatter. To achieve this goal, the AE$\mathrm{\bar{g}}$IS
collaboration will produce a pulsed, cold (100 mK) antihydrogen beam with a
velocity of a few 100 m/s and measure the magnitude of the vertical deflection
of the beam from a straight path. The final position of the falling
antihydrogen will be detected by a position sensitive detector. This detector
will consist of an active silicon part, where the annihilations take place,
followed by an emulsion part. Together, they allow to achieve 1$%$ precision on
the measurement of $\bar{g}$ with about 600 reconstructed and time tagged
annihilations.
  We present here, to the best of our knowledge, the first direct measurement
of antiproton annihilation in a segmented silicon sensor, the first step
towards designing a position sensitive silicon detector for the
AE$\mathrm{\bar{g}}$IS experiment. We also present a first comparison with
Monte Carlo simulations (GEANT4) for antiproton energies below 5 MeV


title:
Van der Waals density functional study of the structural and electronic
  properties of La-doped phenanthrene

abstract:
  By the first principles calculations based on the van der Waals density
functional theory, we study the crystal structures and electronic properties of
La-doped phenanthrene. Two stable atomic geometries of La$_1$phenanthrene are
obtained by relaxation of atomic positions from various initial structures. The
structure-\uppercase\expandafter{\romannumeral1} is a metal with two energy
bands crossing the Fermi level, while the
structure-\uppercase\expandafter{\romannumeral2} displays a semiconducting
state with an energy gap of 0.15 eV, which has an energy gain of 0.42 eV per
unit cell compared to the structure-\uppercase\expandafter{\romannumeral1}. The
most striking feature of La$_1$phenanthrene is that La $5d$ electrons make a
significant contribution to the total density of state (DOS) around the Fermi
level, which is distinct from potassium doped phenanthrene and picene. Our
findings provide an important foundation for the understanding of
superconductivity in La-doped phenanthrene.


title: Review of Summation-by-parts schemes for initial-boundary-value problems

abstract:
  High-order finite difference methods are efficient, easy to program, scales
well in multiple dimensions and can be modified locally for various reasons
(such as shock treatment for example). The main drawback have been the
complicated and sometimes even mysterious stability treatment at boundaries and
interfaces required for a stable scheme. The research on summation-by-parts
operators and weak boundary conditions during the last 20 years have removed
this drawback and now reached a mature state. It is now possible to construct
stable and high order accurate multi-block finite difference schemes in a
systematic building-block-like manner. In this paper we will review this
development, point out the main contributions and speculate about the next
lines of research in this area.


title: Translationally invariant conservation laws of local Lindblad equations

abstract:
  We study the conditions under which one can conserve local translationally
invariant operators by local translationally invariant Lindblad equations in
one-dimensional rings of spin-1/2 particles. We prove that for any 1-local
operator (e.g., particle density) there exist Lindblad dissipators that
conserve that operator, while on the other hand we prove that among 2-local
operators (e.g., energy density) only trivial ones of the Ising type can be
conserved, while all the other cannot be conserved, neither locally nor
globally, by any 2- or 3-local translationally invariant Lindblad equation. Our
statements hold for rings of any finite length larger than some minimal length
determined by the locality of Lindblad equation. These results show in
particular that conservation of energy density in interacting systems is
fundamentally more difficult than conservation of 1-local quantities.


title:
Preparations for detecting and characterizing gravitational-wave signals
  from binary black hole coalescences

abstract:
  We evaluate how well EOBNR waveforms, obtained from the effective one-body
formalism, perform in detecting gravitational wave (GW) signals from binary
black hole (BBH) coalescences modelled by numerical relativity (NR) groups
participating in the second edition of the numerical injection analysis
(NINJA-2). In this study, NINJA-2 NR-based signals that are available in the
public domain were injected in simulated Gaussian, stationary data prepared for
three LIGO-Virgo detectors with early Advanced LIGO sensitivities. Here we
studied only non-spinning BBH signals. A total of 2000 such signals from 20
NR-based signal families were injected in a two-month long data set. The
all-sky, all-time compact binary coalescence (CBC) search pipeline was run
along with an added coherent stage to search for those signals. We find that
the EOBNR templates are only slightly less efficient (by a few percent) in
detecting non-spinning NR-based signals than in detecting EOBNR injections. On
the other hand, the coherent stage improves the signal detectability by a few
percent over a coincident search.


title: Analyzing Evolutionary Optimization in Noisy Environments

abstract:
  Many optimization tasks have to be handled in noisy environments, where we
cannot obtain the exact evaluation of a solution but only a noisy one. For
noisy optimization tasks, evolutionary algorithms (EAs), a kind of stochastic
metaheuristic search algorithm, have been widely and successfully applied.
Previous work mainly focuses on empirical studying and designing EAs for noisy
optimization, while, the theoretical counterpart has been little investigated.
In this paper, we investigate a largely ignored question, i.e., whether an
optimization problem will always become harder for EAs in a noisy environment.
We prove that the answer is negative, with respect to the measurement of the
expected running time. The result implies that, for optimization tasks that
have already been quite hard to solve, the noise may not have a negative
effect, and the easier a task the more negatively affected by the noise. On a
representative problem where the noise has a strong negative effect, we examine
two commonly employed mechanisms in EAs dealing with noise, the re-evaluation
and the threshold selection strategies. The analysis discloses that the two
strategies, however, both are not effective, i.e., they do not make the EA more
noise tolerant. We then find that a small modification of the threshold
selection allows it to be proven as an effective strategy for dealing with the
noise in the problem.


title: TERZAN 5: the remnant of a pristine fragment of the Galactic Bulge?

abstract:
  Terzan 5 is a stellar system in the Galactic bulge commonly catalogued as a
globular cluster. Through dedicated NIR photometry and spectroscopy we have
discovered that it harbors two main stellar populations defining two distinct
red clumps (RCs) in the colour-magnitude diagram, and displaying different iron
content: [Fe/H] = -0.2 and [Fe/H]=+0.3 for the faint and the bright red clumps,
respectively. In addition, a third minor population with significantly lower
metallicity ([Fe/H]=-0.79) has been recently detected, thus enlarging the
metallicity range covered by Terzan 5 to Delta[Fe/H] ~ 1 dex. This evidence
demonstrates that, similarly to omega Centauri in the Galactic halo, Terzan 5
is not a genuine globular cluster, but a stellar system that experienced a much
more complex star formation and chemical enrichment history. Moreover the
striking chemical similarity with the bulge stars suggests that Terzan 5 could
be the relic of one of the massive clumps that contributed through strong
dynamical interactions with other similar sub-structures) to the formation of
the Galactic bulge.


title:
Classical and strong convexity of sublevel sets and application to
  attainable sets of nonlinear systems

abstract:
  Necessary and sufficient conditions for convexity and strong convexity,
respectively, of sublevel sets that are defined by finitely many real-valued
$C^{1,1}$-maps are presented. A novel characterization of strongly convex sets
in terms of the so-called local quadratic support is proved. The results
concerning strong convexity are used to derive sufficient conditions for
attainable sets of continuous-time nonlinear systems to be strongly convex. An
application of these conditions is a novel method to over-approximate
attainable sets when strong convexity is present.


title:
Polarization-Dependent Three-Dimensional Angle-Resolved Photoemission
  Spectroscopy of BaFe$_{1.8}$Co$_{0.2}$As$_{2}$

abstract:
  We performed polarization- and photon-energy-dependent angle-resolved
photoemission spectroscopy of a slightly overdoped iron pnictide
superconductor, BaFe$_{1.8}$Co$_{0.2}$As$_{2}$, to clarify the
three-dimensional electronic structure including its orbital characters at the
Brillouin zone center. Two hole Fermi surfaces (FSs) with $d_{xz/yz}$ and
$d_{xy/x^2-y^2}$ orbitals were observed but $d_{z^2}$ hole FS, which has nodes
according to a theory of the spin-fluctuation superconductivity mechanism, did
not appear. These results suggest that no node will appear at hole FSs at the
zone center.


title: Supernova explosions in magnetized, primordial dark matter halos

abstract:
  The first supernova explosions are potentially relevant sources for the
production of the first large-scale magnetic fields. For this reason we present
a set of high resolution simulations studying the effect of supernova
explosions on magnetized, primordial halos. We focus on the evolution of an
initially small-scale magnetic field formed during the collapse of the halo. We
vary the degree of magnetization, the halo mass, and the amount of explosion
energy in order to account for expected variations as well as to infer
systematical dependencies of the results on initial conditions. Our simulations
suggest that core collapse supernovae with an explosion energy of 10^51 erg and
more violent pair instability supernovae with 10^53 erg are able to disrupt
halos with masses up to a about 10^6 and 10^7 M_sun, respectively. The peak of
the magnetic field spectra shows a continuous shift towards smaller k-values,
i.e. larger length scales, over time reaching values as low as k = 4. On small
scales the magnetic energy decreases at the cost of the energy on large scales
resulting in a well-ordered magnetic field with a strength up to ~ 10^-8 G
depending on the initial conditions. The coherence length of the magnetic field
inferred from the spectra reaches values up to 250 pc in agreement with those
obtained from autocorrelation functions. We find the coherence length to be as
large as $50\%$ of the radius of the supernova bubble. Extrapolating this
relation to later stages we suggest that significantly strong magnetic fields
with coherence lengths as large as 1.5 kpc could be created. We discuss
possible implications of our results on processes like recollapse of the halo,
first galaxy formation, and the magnetization of the intergalactic medium.


title: Chiral Structure of Vector and Axial-Vector Tetraquark Currents

abstract:
  We investigate the chiral structure of local vector and axial-vector
tetraquark currents, and study their chiral transformation properties. We
consider the charge-conjugation parity and classify all the isovector vector
and axial-vector local tetraquark currents of quantum numbers
I(G)J(PC)=1(-)1(-+), I(G)J(PC)=1(+)1(--), I(G)J(PC)=1(-)1(++) and
I(G)J(PC)=1(+)1(+-). We find that there is a one to one correspondence among
them. Using these currents, we perform QCD sum rule analyses. Our results
suggest that there is a missing b1 state having I(G)J(PC)=1(+)1(+-) and a mass
around 1.47-1.66 GeV.


title: About the x-y symmetry of the F_g algebraic invariants

abstract:
  We complete the proof of the x-y symmetry of symplectic invariants of [EO].
We recall the main steps of the proof of [EO2], and we include the integration
constants absent in [EO2].


title: On the solutions to the multi-parametric Yang-Baxter equations

abstract:
  A unified approach is applied in the consideration of the multi-parametric
(colored) Yang-Baxter equations (YBE) and the usual YBE with two-parametric
R-matrices, relying on the existence of the arbitrary functions in the general
solutions. The colored YBE are considered with the R-matrices defined on two
and three dimensional states. We present an exhaustive study and the overall
solutions for the YBE with $4 \times 4$ colored R-matrices. The established
classification includes new multi-parametric free fermionic solutions. In the
context of the given approach there are obtained the colored solutions to the
YBE with $9 \times 9$ R-matrices having 15 non-zero elements.


title: Toward a new foundation of statistical thermodynamics

abstract:
  We propose a new approach concerning the introduction of time-irreversibility
in statistical mechanics. It is based on a transition function defined in terms
of path integral and verifying a time-irreversible equation. We show first how
dynamic processes may enter in the description of equilibrium states. In order
to do that a characteristic time is associated with closed paths. For large
isolated systems at equilibrium or for systems in contact with a thermostat our
results are identical with those obtained with the Gibbs ensemble methods. For
a model used in the microscopic approaches of the brownian motion no new basic
assumption is required to predict a transition from a quantum state to a
classical one exhibiting a time-irreversible behavior. This demonstration is
sufficient to show that very well accepted approximations can lead to
time-irreversible behaviors for a large class of systems. The difference
between our work and the system+reservoir approaches is underlined. Here
equilibrium states and irreversible processes are described on the same footing
representing a progress in the question of time-irreversibility in statistical
physics. The transition function is also used for describing a small system for
which there is no thermodynamics. By adding to the transition function a second
one characterizing the reverse motion we may describe time-reversible systems.
In a simple case we replace two real valued transition functions by a complex
function verifying a Schrodinger like equation. From this we see how to break
the time-reversibility of this equation and how to investigate the connection
quantum mechanics-thermodynamics from a very fundamental point of view.


title: Upper functions for $L_p$-norm of gaussian random fields

abstract:
  In this paper we are interested in finding upper functions for a collection
of random variables $\big\{\big\|\xi_{\vec{h}}\big\|_p,
\vec{h}\in\mathrm{H}\big\}, 1\leq p<\infty$. Here $\xi_{\vec{h}}(x),
x\in(-b,b)^d, d\geq 1$ is a kernel-type gaussian random field and $\|\cdot\|_p$
stands for $L_p$-norm on $(-b,b)^d$. The set $\mathrm{H}$ consists of
$d$-variate vector-functions defined on $(-b,b)^d$ and taking values in some
countable net in $R^d_+$. We seek a non-random family
$\left\{\Psi_\alpha\big(\vec{h}\big),\;\;\vec{h}\in\mathrm{H}\right\}$ such
that $
E\big\{\sup_{\vec{h}\in\mathrm{H}}\big[\big\|\xi_{\vec{h}}\big\|_p-\Psi_\alpha\big(\vec{h}\big)\big]_+\big\}^q\leq
\alpha^q,\; q\geq 1, $ where $\alpha>0$ is prescribed level.


title: No universal group in a cardinal

abstract:
  For many classes of models there are universal members in any cardinal
$\lambda$ which "essentially satisfied GCH", i.e. $\lambda = 2^{< \lambda}$.
But if the class is "complicated enough", e.g. the class of linear orders, we
know that if $\lambda$ is "regular and not so close to satisfying GCH" then
there is no universal member. Here we find new sufficient conditions (which we
call the olive property), not covered by earlier cases (i.e. fail the so-called
SOP$_4$). The advantage of those conditions is witnessed by proving that the
class of groups satisfies one of those conditions.


title: Quantum Simulation of Non-Abelian Lattice Gauge Theories

abstract:
  We use quantum link models to construct a quantum simulator for U(N) and
SU(N) lattice gauge theories. These models replace Wilson's classical link
variables by quantum link operators, reducing the link Hilbert space to a
finite number of dimensions. We show how to embody these quantum link models
with fermionic matter with ultracold alkaline-earth atoms using optical
lattices. Unlike classical simulations, a quantum simulator does not suffer
from sign problems and can thus address the corresponding dynamics in real
time. Using exact diagonalization results we show that these systems share
qualitative features with QCD, including chiral symmetry breaking and we study
the expansion of a chirally restored region in space in real time.


title: Probabilistic approach to Appell polynomials

abstract:
  In this paper we study Appell polynomials by connecting them to random
variables. This probabilistic approach yields, e.g., the mean value property
which is fundamental in the sense that many other properties can be derived
from it. We also discuss moment representations of Appell polynomials. In the
latter part of the paper the presented general theory is applied to study some
classical explicitly given polynomials.


title:
Convergence rates of eigenvector empirical spectral distribution of
  large dimensional sample covariance matrix

abstract:
  The eigenvector Empirical Spectral Distribution (VESD) is adopted to
investigate the limiting behavior of eigenvectors and eigenvalues of covariance
matrices. In this paper, we shall show that the Kolmogorov distance between the
expected VESD of sample covariance matrix and the Mar\v{c}enko-Pastur
distribution function is of order $O(N^{-1/2})$. Given that data dimension $n$
to sample size $N$ ratio is bounded between 0 and 1, this convergence rate is
established under finite 10th moment condition of the underlying distribution.
It is also shown that, for any fixed $\eta>0$, the convergence rates of VESD
are $O(N^{-1/4})$ in probability and $O(N^{-1/4+\eta})$ almost surely,
requiring finite 8th moment of the underlying distribution.


title:
Two-loop low-energy effective action in Abelian supersymmetric
  Chern-Simons matter models

abstract:
  We compute two-loop low-energy effective actions in Abelian Chern-Simons
matter models with N=2 and N=3 supersymmetry up to four-derivative order.
Calculations are performed with a slowly-varying gauge superfield background.
Though the gauge superfield propagator depends on the gauge fixing parameter,
it is shown that the obtained results are independent of this parameter. In the
massless case the considered models are superconformal. We demonstrate that the
superconformal symmetry strongly restricts the form of two-loop quantum
corrections to the effective actions such that the obtained terms have simpler
structure than the analogous ones in the effective action of three-dimensional
supersymmetric electrodynamics (SQED) with vanishing topological mass.


title:
Lorentz Invariant Berry Phase for a Perturbed Relativistic Four
  Dimensional Harmonic Oscillator

abstract:
  We show the existence of Lorentz invariant Berry phases generated, in the
Stueckleberg-Horwitz-Piron manifestly covariant quantum theory (SHP), by a
perturbed four dimensional harmonic oscillator. These phases are associated
with a fractional perturbation of the azimuthal symmetry of the oscillator.
They are computed numerically by using time independent perturbation theory and
the definition of the Berry phase generalized to the framework of SHP
relativistic quantum theory.


title:
Fault-tolerant thresholds for quantum error correction with the surface
  code

abstract:
  The surface code is a promising candidate for fault-tolerant quantum
computation, achieving a high threshold error rate with nearest-neighbor gates
in two spatial dimensions. Here, through a series of numerical simulations, we
investigate how the precise value of the threshold depends on the noise model,
measurement circuits, and decoding algorithm. We observe thresholds between
0.502(1)% and 1.140(1)% per gate, values which are generally lower than
previous estimates.


title: Constructions of minimal periodic surfaces and minimal annuli in Sol3

abstract:
  We construct two one-parameter families of minimal properly embedded surfaces
in the Lie group Sol3 using a Weierstrass-type representation. These surfaces
are not invariant by a one-parameter group of ambient isometries. The first one
can be viewed as a family of helicoids, and the second one is a family of
minimal annuli called catenoids. Finally we study limits of these catenoids,
and in particular we show that one of these limits is a new minimal entire
graph.


title:
Measurement of the ratio of the leptonic widths
  $\Gamma_{ee}/\Gamma_{\mu\mu}$ for the $J/\psi$ meson

abstract:
  The ratio of the electron and muon widths of the $J/\psi$ meson has been
measured using direct $J/\psi$ decays in the KEDR experiment at the VEPP-4M
electron-positron collider. The result
$\Gamma_{ee}(J/\psi)/\Gamma_{\mu\mu}(J/\psi)=1.0022\pm0.0044\pm0.0048\
(0.65\%)$ is in good agreement with the lepton universality. The experience
collected during this analysis will be used for a $J/\psi$ lepton width
determination with up to 1% accuracy.


title: Indagini in Deep Inference

abstract:
  Italian master's thesis in Computer Science. It is an overview of the
standard tecniques developed in the field of Proof Theory, ending with some
results in the new field of Deep Inference, plus an original contribution
trying to relate Deep Inference and Process Algebras.


title: Non-emptiness of Brill-Noether loci in M(2,K)

abstract:
  Let C be a smooth projective complex curve of genus $g\geq2$. We investigate
the Brill-Noether locus consisting of stable bundles of rank 2 and canonical
determinant having at least $k$ independent sections. Using the Hecke
correpondence we construct a fundamental class, which determines the
non-emptiness of this locus at least when $C$ is a Petri curve. We prove that
in many expected cases the Brill-Noether locus is non-empty. For some values of
$k$ the result is best possible.


title: Type Ia Supernovae from Merging White Dwarfs I. Prompt Detonations

abstract:
  Merging white dwarfs are a possible progenitor of Type Ia supernovae (SNe
Ia). While it is not entirely clear if and when an explosion is triggered in
such systems, numerical models suggest that a detonation might be initiated
before the stars have coalesced to form a single compact object. Here we study
such "peri-merger" detonations by means of numerical simulations, modeling the
disruption and nucleosynthesis of the stars until the ejecta reach the coasting
phase. Synthetic light curves and spectra are generated for comparison with
observations. Three models are considered with primary masses 0.96 Msun, 1.06
Msun, and 1.20 Msun. Of these, the 0.96 Msun dwarf merging with an 0.81 Msun
companion, with a Ni56 yield of 0.58 Msun, is the most promising candidate for
reproducing common SNe Ia. The more massive mergers produce unusually luminous
SNe Ia with peak luminosities approaching those attributed to
"super-Chandrasekhar" mass SNe Ia. While the synthetic light curves and spectra
of some of the models resemble observed SNe Ia, the significant asymmetry of
the ejecta leads to large orientation effects. The peak bolometric luminosity
varies by more than a factor of 2 with the viewing angle, and the velocities of
the spectral absorption features are lower when observed from angles where the
light curve is brightest. The largest orientation effects are seen in the
ultraviolet, where the flux varies by more than an order of magnitude. Despite
the large variation with viewing angle, the set of three models roughly obeys a
width-luminosity relation, with the brighter light curves declining more slowly
in the B-band. Spectral features due to unburned carbon from the secondary star
are also seen in some cases.


title: Dual-tip-enhanced ultrafast CARS nanoscopy

abstract:
  Coherent anti-Stokes Raman scattering (CARS) and, in particular, femtosecond
adaptive spectroscopic techniques (FAST CARS) have been successfully used for
molecular spectroscopy and microscopic imaging. Recent progress in ultrafast
nanooptics provides flexibility in generation and control of optical near
fields, and holds promise to extend CARS techniques to the nanoscale. In this
theoretical study, we demonstrate ultrafast subwavelentgh control of coherent
Raman spectra of molecules in the vicinity of a plasmonic nanostructure excited
by ultrashort laser pulses. The simulated nanostructure design provides
localized excitation sources for CARS by focusing incident laser pulses into
subwavelength hot spots via two self-similar nanolens antennas connected by a
waveguide. Hot-spot-selective dual-tip-enhanced CARS (2TECARS) nanospectra of
DNA nucleobases are obtained by simulating optimized pump, Stokes and probe
near fields using tips, laser polarization- and pulse-shaping. This technique
may be used to explore ultrafast energy and electron transfer dynamics in real
space with nanometre resolution and to develop novel approaches to DNA
sequencing.


title: SU(3) flavour symmetry breaking and charmed states

abstract:
  By extending the SU(3) flavour symmetry breaking expansion from up, down and
strange sea quark masses to partially quenched valence quark masses we propose
a method to determine charmed quark hadron masses including possible QCD
isospin breaking effects. Initial results for some open charmed pseudoscalar
meson states and singly and doubly charmed baryon states are encouraging and
demonstrate the potential of the procedure. Essential for the method is the
determination of the scale using singlet quantities, and to this end we also
give here a preliminary estimation of the recently introduced Wilson flow
scales.


title:
Scattering systems with several evolutions and formal reproducing kernel
  Hilbert spaces

abstract:
  A Schur-class function in $d$ variables is defined to be an analytic
contractive-operator valued function on the unit polydisk. Such a function is
said to be in the Schur--Agler class if it is contractive when evaluated on any
commutative $d$-tuple of strict contractions on a Hilbert space. It is known
that the Schur--Agler class is a strictly proper subclass of the Schur class if
the number of variables $d$ is more than two. The Schur--Agler class is also
characterized as those functions arising as the transfer function of a certain
type (Givone--Roesser) of conservative multidimensional linear system. Previous
work of the authors identified the Schur--Agler class as those Schur-class
functions which arise as the scattering matrix for a certain type of (not
necessarily minimal) Lax--Phillips multievolution scattering system having some
additional geometric structure. The present paper links this additional
geometric scattering structure directly with a known reproducing-kernel
characterization of the Schur--Agler class. We use extensively the technique of
formal reproducing kernel Hilbert spaces that was previously introduced by the
authors and that allows us to manipulate formal power series in several
commuting variables and their inverses (e.g., Fourier series of elements of
$L^2$ on a torus) in the same way as one manipulates analytic functions in the
usual setting of reproducing kernel Hilbert spaces.


title:
Derivation of capture and reaction cross sections from experimental
  quasi-elastic and elastic backscattering probabilities

abstract:
  The direct measurement of the reaction or capture (fusion) cross section is a
difficult task since it would require the measurement of individual cross
sections of many reaction channels, and most of them could be reached only by
specific experiments. This would require different experimental set-ups not
always available at the same laboratory and, consequently, such direct
measurements would demand a large amount of beam time and would take probably
some years to be reached. Because of that, the measurements of elastic
scattering angular distributions that cover full angular ranges and optical
model analysis have been used for the determination of reaction cross sections.
This traditional method consists in deriving the parameters of the complex
optical potentials which fit the experimental elastic scattering angular
distributions and then of deriving the reaction cross sections predicted by
these potentials. Even so, both the experimental part and the analysis of this
latter method are not so simple. In the present work we present a much simpler
methods to determine reaction and capture (fusion) cross sections. They consist
of measuring only elastic or quasi-elastic scattering at one backward angle,
and from that, the extraction of the reaction or capture cross sections can
easily be performed.


title:
Data Mining Model for the Data Retrieval from Central Server
  Configuration

abstract:
  A server, which is to keep track of heavy document traffic, is unable to
filter the documents that are most relevant and updated for continuous text
search queries. This paper focuses on handling continuous text extraction
sustaining high document traffic. The main objective is to retrieve recent
updated documents that are most relevant to the query by applying sliding
window technique. Our solution indexes the streamed documents in the main
memory with structure based on the principles of inverted file, and processes
document arrival and expiration events with incremental threshold-based method.
It also ensures elimination of duplicate document retrieval using unsupervised
duplicate detection. The documents are ranked based on user feedback and given
higher priority for retrieval.


title: Policing 802.11 MAC Misbehaviours

abstract:
  With the increasing availability of flexible wireless 802.11 devices, the
potential exists for users to selfishly manipulate their channel access
parameters and gain a performance advantage. Such practices can have a severe
negative impact on compliant stations. To enable access points to counteract
these selfish behaviours and preserve fairness in wireless networks, in this
paper we propose a policing mechanism that drives misbehaving users into
compliant operation without requiring any cooperation from clients. This
approach is demonstrably effective against a broad class of misbehaviours,
soundly-based, i.e. provably hard to circumvent and amenable to practical
implementation on existing commodity hardware.


title: Linear-drifting sub-pulse sources in radio pulsars

abstract:
  Analysis of plasma acceleration in pulsars with positive corotational charge
density has shown that any element of area on the polar cap is bi-stable: it
can be in phases either of pure proton emission or of mixed ions and protons
(the ion phase). Ion-phase zones are concentrated near the edge of the polar
cap, and are a physical basis for the coherent radio emission observed as
components within the mean pulse profile. The state of the polar cap is
generally chaotic, but organized linear motion of ion zones in a peripheral
band is possible and is the likely source of sub-pulse drift. It is shown that
several patterns of limited movement are possible and can account for the
varied phenomena observed including mirror and bi-directional drifting.


title: A Short History of Spin

abstract:
  The paper outlines the historical development of spin in physics from about
1920 to the present day. It aims to provide the student with an accurate
chronology of important developments, both scientific and technical.


title:
Rapid mixing for the Lorenz attractor and statistical limit laws for
  their time-1 maps

abstract:
  We prove that every geometric Lorenz attractor has superpolynomial decay of
correlations with respect to the unique SRB measure. Moreover, we prove the
Central Limit Theorem and Almost Sure Invariance Principle for the time-1 map
of the flow of geometric Lorenz attractors. In particular, our results apply to
the classical Lorenz attractor.


title:
On the impact of explicit or semi-implicit integration methods over the
  stability of real-time numerical simulations

abstract:
  Physics-based animation of soft or rigid bodies for real-time applications
often suffers from numerical instabilities. We analyse one of the most common
sources of unwanted behaviour: the numerical integration strategy. To assess
the impact of popular integration methods, we consider a scenario where soft
and hard constraints are added to a custom designed deformable linear object.
Since the goal for this class of simulation methods is to attain interactive
frame-rates, we present the drawbacks of using explicit integration methods
over inherently stable, implicit integrators. To help numerical solver
designers better understand the impact of an integrator on a certain simulated
world, we have conceived a method of benchmarking the efficiency of an
integrator with respect to its speed, stability and symplecticity.


title: Levy-Lieb Principle meets Quantum Monte Carlo

abstract:
  We review an approach where the energy functional of Density-Functional
Theory (DFT) can be determined without empiricism via a Quantum Monte Carlo
(QMC) procedure. The idea consists of a nested iterative loop where the
configurational space of the electrons in the QMC procedure is determined by a
trial oneparticle electron density; this allows then for the determination of a
first guess for the energy functional, which is then in turn used for a DFT
minimization process. This latter delivers a new electron density and the loop
is repeated iteratively until convergence is reached and thus the electronic
structure of the system determined. In essence, from the applied point of view,
such an approach is a compromise between the large computational cost but high
accuracy of QMC and the reasonable computational cost but lower accuracy of
DFT. The proposed approach goes beyond the standard Kohn-Sham method, which is
the standard in DFT, and requires neither orbitals nor the a priori
specification of the exchange and correlation functional. From the conceptual
point of view, the relevant aspect is that the 3N-dimensional wavefunction is
derived as a function(al) of the three-dimensional electron density, which is
the key principle of DFT.


title: Fusion at near-barrier energies within quantum diffusion approach

abstract:
  The nuclear deformation and neutron-transfer process have been identified as
playing a major role in the magnitude of the sub-barrier fusion (capture) cross
sections. There are a several experimental evidences which confirm the
importance of nuclear deformation on the fusion. The influence of nuclear
deformation is straightforward. If the target nucleus is prolate in the ground
state, the Coulomb field on its tips is lower than on its sides, that then
increases the capture or fusion probability at energies below the barrier
corresponding to the spherical nuclei. The role of neutron transfer reactions
is less clear. The importance of neutron transfer with positive Q-values on
nuclear fusion (capture) originates from the fact that neutrons are insensitive
to the Coulomb barrier and therefore they can start being transferred at larger
separations before the projectile is captured by target-nucleus. Therefore, it
is generally thought that the sub-barrier fusion cross section will increase
because of the neutron transfer. The fusion (capture) dynamics induced by
loosely bound radioactive ion beams is currently being extensively studied.
However, the long-standing question whether fusion (capture) is enhanced or
suppressed with these beams has not yet been answered unambiguously. The study
of the fusion reactions involving nuclei at the drip-lines has led to
contradictory results.


title: Nonlinear response of a linear chain to weak driving

abstract:
  We study the escape of a chain of coupled units over the barrier of a
metastable potential. It is demonstrated that a very weak external driving
field with suitably chosen frequency suffices to accomplish speedy escape. The
latter requires the passage through a transition state the formation of which
is triggered by permanent feeding of energy from a phonon background into humps
of localised energy and elastic interaction of the arising breather solutions.
In fact, cooperativity between the units of the chain entailing coordinated
energy transfer is shown to be crucial for enhancing the rate of escape in an
extremely effective and low-energy cost way where the effect of entropic
localisation and breather coalescence conspire.


title: Extended Formulations for Online Linear Bandit Optimization

abstract:
  On-line linear optimization on combinatorial action sets (d-dimensional
actions) with bandit feedback, is known to have complexity in the order of the
dimension of the problem. The exponential weighted strategy achieves the best
known regret bound that is of the order of $d^{2}\sqrt{n}$ (where $d$ is the
dimension of the problem, $n$ is the time horizon). However, such strategies
are provably suboptimal or computationally inefficient. The complexity is
attributed to the combinatorial structure of the action set and the dearth of
efficient exploration strategies of the set. Mirror descent with entropic
regularization function comes close to solving this problem by enforcing a
meticulous projection of weights with an inherent boundary condition. Entropic
regularization in mirror descent is the only known way of achieving a
logarithmic dependence on the dimension. Here, we argue otherwise and recover
the original intuition of exponential weighting by borrowing a technique from
discrete optimization and approximation algorithms called `extended
formulation'. Such formulations appeal to the underlying geometry of the set
with a guaranteed logarithmic dependence on the dimension underpinned by an
information theoretic entropic analysis.


title:
Brownian motion in strongly coupled, anisotropic Yang-Mills plasma: A
  holographic approach

abstract:
  We employ methods of gauge/string duality to analyze the Brownian motion and
the concomitant Langevin equation of a heavy quark in a strongly coupled,
thermal, anisotropic Yang-Mills plasma. We consider fluctuations both along and
perpendicular to the direction of anisotropy and study the effects of
anisotropy on the drag coefficient, the diffusion constant and the Langevin
coefficient for both the directions. We also verify the fluctuation-dissipation
theorem for Brownian motion in an anisotropic medium.


title: Minimax rate of convergence and the performance of ERM in phase recovery

abstract:
  We study the performance of Empirical Risk Minimization in noisy phase
retrieval problems, indexed by subsets of $\R^n$ and relative to subgaussian
sampling; that is, when the given data is $y_i=\inr{a_i,x_0}^2+w_i$ for a
subgaussian random vector $a$, independent noise $w$ and a fixed but unknown
$x_0$ that belongs to a given subset of $\R^n$.
  We show that ERM produces $\hat{x}$ whose Euclidean distance to either $x_0$
or $-x_0$ depends on the gaussian mean-width of the indexing set and on the
signal-to-noise ratio of the problem. The bound coincides with the one for
linear regression when $\|x_0\|_2$ is of the order of a constant. In addition,
we obtain a minimax lower bound for the problem and identify sets for which ERM
is a minimax procedure. As examples, we study the class of $d$-sparse vectors
in $\R^n$ and the unit ball in $\ell_1^n$.


title:
Effects of the next-to-leading order terms in the chiral SU(3)
  Lagrangian on the strangeness -1 s-wave meson-baryon interactions

abstract:
  The meson-baryon interactions in s-wave in the strangeness S=-1 sector are
studied using a chiral unitarity approach based on the next-to-leading order
chiral SU(3) Lagrangian. The model is fitted to the large set of experimental
data in different two-body channels. Particular attention is paid to the $\Xi$
hyperon production reaction, $\bar{K} N \rightarrow K \Xi$, where the effect of
the next-to-leading order terms in the Lagrangian play a crucial role, since
the cross section of this reaction at tree level is zero.


title: Electromagnetic Form Factors for the $\Lambda$(1405)

abstract:
  Building on our successful technique to isolate the otherwise-elusive
$\Lambda$(1405) using correlation matrix techniques and multiple source and
sink smearings, we present calculations of the quark sector contributions to
the electric form factors of the $\Lambda$(1405). Using the PACS-CS
$(2+1)$-flavour full-QCD ensembles available through the ILDG, our calculations
reveal behaviour consistent with the development of a non-trivial molecular
$\overline{K}N$ bound-state component as one approaches the physical values of
the $u$ and $d$ quark masses.


title: Erd\H{o}s-Pyber theorem for hypergraphs and secret sharing

abstract:
  A new, constructive proof with a small explicit constant is given to the
Erd\H{o}s-Pyber theorem which says that the edges of a graph on $n$ vertices
can be partitioned into complete bipartite subgraphs so that every vertex is
covered at most $O(n/\log n)$ times. The theorem is generalized to uniform
hypergraphs. Similar bounds with smaller constant value is provided for
fractional partitioning both for graphs and for uniform hypergraphs. We show
that these latter constants cannot be improved by more than a factor of 1.89
even for fractional covering by arbitrary complete multipartite subgraphs or
subhypergraphs. In the case every vertex of the graph is connected to at least
$n-m$ other vertices, we prove the existence of a fractional covering of the
edges by complete bipartite graphs such that every vertex is covered at most
$O(m/\log m)$ times, with only a slightly worse explicit constant. This result
also generalizes to uniform hypergraphs. Our results give new improved bounds
on the complexity of graph and uniform hypergraph based secret sharing schemes,
and show the limits of the method at the same time.


title:
Existence of $\mathcal{H}$-matrix approximants to the inverses of BEM
  matrices: the simple-layer operator

abstract:
  We consider the question of approximating the inverse $\mathbf W = \mathbf
V^{-1}$ of the Galerkin stiffness matrix $\mathbf V$ obtained by discretizing
the simple-layer operator $V$ with piecewise constant functions. The block
partitioning of $\mathbf W$ is assumed to satisfy any of the standard
admissibility criteria that are employed in connection with clustering
algorithms to approximate the discrete BEM operator $\mathbf V$. We show that
$\mathbf W$ can be approximated by blockwise low-rank matrices such that the
error decays exponentially in the block rank employed. Similar exponential
approximability results are shown for the Cholesky factorization of $\mathbf
V$.


title: Optimization of the Oktay-Kronfeld Action Conjugate Gradient Inverter

abstract:
  Improving the Fermilab action to third order in heavy quark effective theory
yields the Oktay-Kronfeld action, a promising candidate for precise
calculations of the spectra of heavy quark systems and weak matrix elements
relevant to searches for new physics. We have optimized the bi-stabilized
conjugate gradient inverter in the SciDAC QOPQDP library and are developing a
GPU code. The action is rewritten and the needed gauge-link combinations are
precalculated. In tests with a MILC coarse lattice, this procedure accelerates
the inverter by a factor of four. The remaining floating-point operations are
mostly simple matrix multiplications between gauge links and fermion vectors,
which we accelerate by more than an order of magnitude by using CUDA. Further
gains could be achieved by using QUDA.


title:
Super-Eddington Accretion in the Ultraluminous X-ray Source NGC1313 X-2:
  An Ephemeral Feast

abstract:
  We investigate the X-ray spectrum, variability and the surrounding ionized
bubble of NGC1313 X-2 to explore the physics of super-Eddington accretion.
Beyond the Eddington luminosity, the accretion disk of NGC1313 X-2 is truncated
at a large radius ($\sim$ 50 times of innermost stable circular orbit), and
displays the similar evolution track with both luminous Galactic black-hole and
neutron star X-ray binaries. In super-critical accretion, the speed of
radiatively driven outflows from the inner disk is mildly relativistic. Such
ultra-fast outflows would be over ionized and might produce weak Fe K
absorption lines, which may be detected by the coming X-ray mission {\it
Astro-H}. If the NGC1313 X-2 is a massive stellar X-ray binary, the high
luminosity indicates that an ephemeral feast is held in the source. That is,
the source must be accreting at a hyper-Eddington mass rate to give the
super-Eddington emission over $\sim 10^{4}-10^{5}$ yr. The expansion of the
surrounding bubble nebula with a velocity of $\sim$ 100 km~s$^{-1}$ might
indicate that it has existed over $\sim 10^{6}$ yr and is inflated by the
radiatively driven outflows from the transient with a duty cycle of activity of
$\sim$ a few percent. Alternatively, if the surrounding bubble nebula is
produced by line-driven winds, less energy is required than the radiatively
driven outflow scenario, and the radius of the Str\"{o}mgren radius agrees with
the nebula size. Our results are in favor of the line-driven winds scenario,
which can avoid the conflict between the short accretion age and the apparently
much longer bubble age inferred from the expansion velocity in the nebula.


title: Boolean Witt vectors and an integral Edrei-Thoma theorem

abstract:
  A subtraction-free definition of the big Witt vector construction was
recently given by the first author. This allows one to define the big Witt
vectors of any semiring. Here we give an explicit combinatorial description of
the big Witt vectors of the Boolean semiring. We do the same for two variants
of the big Witt vector construction: the Schur Witt vectors and the $p$-typical
Witt vectors. We use this to give an explicit description of the Schur Witt
vectors of the natural numbers, which can be viewed as the classification of
totally positive power series with integral coefficients, first obtained by
Davydov. We also determine the cardinalities of some Witt vector algebras with
entries in various concrete arithmetic semirings.


title: A note on the Gaussian maximal functions

abstract:
  This note presents a proof that the non-tangential maximal function of the
Ornstein-Uhlenbeck semigroup is bounded almost surely by the Gaussian
Hardy-Littlewood maximal function. In particular this entails improvement on a
result by Pineda and Urbina who proved a similar result for a `trunctated'
version of the non-tangential maximal function. We actually obtain boundedness
of the maximal function on non-tangential cones of arbitrary aperture.


title:
Possible polarized neutron-nucleus scattering search for a new
  spin-dependent nucleon-nucleon coupling in a Fm range

abstract:
  An experimental opportunity is presented for the future to measure possible
P- and T-non-invariant axion-like interaction between nucleons in a Fm range.
This interaction may be searched for in the measurement spin-dependent
asymmetry of scattering of polarized neutrons in a keV-MeV energy range by
heavy nuclei.


title:
Experimental detection of polarization-frequency quantum correlations in
  a photonic quantum channel by local operations

abstract:
  The measurement of correlations between different degrees of freedom is an
important, but in general extremely difficult task in many applications of
quantum mechanics. Here, we report an all-optical experimental detection and
quantification of quantum correlations between the polarization and the
frequency degrees of freedom of single photons by means of local operations
acting only on the polarization degree of freedom. These operations only
require experimental control over an easily accessible two-dimensional
subsystem, despite handling strongly mixed quantum states comprised of a
continuum of orthogonal frequency states. Our experiment thus represents a
photonic realization of a scheme for the local detection of quantum
correlations in a truly infinite-dimensional continuous-variable system, which
excludes an efficient finite-dimensional truncation.


title:
An independent determination of Fomalhaut b's orbit and the dynamical
  effects on the outer dust belt

abstract:
  The nearby star Fomalhaut harbours a cold, moderately eccentric dust belt
with a sharp inner edge near 133 au. A low-mass, common proper motion companion
(Fom b), was discovered near the inner edge and was identified as a planet
candidate that could account for the belt morphology. However, the most recent
orbit determination based on four epochs of astrometry over eight years reveals
a highly eccentric orbit that appears to cross the belt in the sky plane
projection. We perform here a full orbital determination based on the available
astrometric data to independently validate the orbit estimates previously
presented. Adopting our values for the orbital elements and their associated
uncertainties, we then study the dynamical interaction between the planet and
the dust ring, to check whether the proposed disk sculpting scenario by Fom b
is plausible. We used a dedicated MCMC code to derive the statistical
distributions of the orbital elements of Fom b. Then we used symplectic N-body
integration to investigate the dynamics of the dust belt, as perturbed by a
single planet. Different attempts were made assuming different masses for Fom
b. We also performed a semi-analytical study to explain our results. Our
results are in good agreement with others regarding the orbit of Fom b. We find
that the orbit is highly eccentric, is close to apsidally aligned with the
belt, and has a moderate mutual inclination relative to the belt plane of. If
coplanar, this orbit crosses the disk. Our dynamical study then reveals that
the observed planet could sculpt a transient belt configuration with a similar
eccentricity to what is observed, but it would not be simultaneously apsidally
aligned with the planet. This transient configuration only occurs a short time
after the planet is placed on such an orbit (assuming an initially circular
disk), a time that is inversely proportional to the planet's mass, and that is
in any case much less than the 440 Myr age of the star. We constrain how long
the observed dust belt could have survived with Fom b on its current orbit, as
a function of its possible mass. This analysis leads us to conclude that Fom b
is likely to have low mass, that it is unlikely to be responsible for the
sculpting of the belt, and that it supports the hypothesis of a more massive,
less eccentric planet companion Fom c.


title:
Probabilistic and statistical properties of moment variations and their
  use in inference and estimation based on high frequency return data

abstract:
  We discuss the probabilistic properties of the variation based third and
fourth moments of financial returns as estimators of the actual moments of the
return distributions. The moment variations are defined under non-parametric
assumptions with quadratic variation method but for the computational
tractability, we use a square root stochastic volatility model for the
derivations of moment conditions for estimations. Using the S\&P 500 index high
frequency data, the realized versions of the moment variations is used for the
estimation of a stochastic volatility model. We propose a simple estimation
method of a stochastic volatility model using the sample averages of the
variations and ARMA estimation. In addition, we compare the results with a
generalized method of moments estimation based on the successive relation
between realized moments and their lagged values.


title: Time-reversed two-photon interferometry for phase super-resolution

abstract:
  We observed two-photon phase super-resolution in an unbalanced Michelson
interferometer with classical Gaussian laser pulses. Our work is a
time-reversed version of a two-photon interference experiment using an
unbalanced Michelson interferometer. A measured interferogram exhibits
two-photon phase super-resolution with a high visibility of 97.9% \pm 0.4%. Its
coherence length is about 22 times longer than that of the input laser pulses.
It is a classical analogue to the large difference between the one- and
two-photon coherence lengths of entangled photon pairs.


title:
Vanishing spin gap in a competing spin-liquid phase in the kagome
  Heisenberg antiferromagnet

abstract:
  We provide strong numerical evidence, using improved variational wave
functions, for a ground state with vanishing spin gap in the spin-$1/2$ quantum
Heisenberg model on the kagome lattice. Starting from the algebraic $U(1)$
Dirac spin liquid state proposed by Y. Ran $et al.$ [Phys. Rev. Lett. $98$,
$117205$ ($2007$)] and iteratively applying a few Lanczos steps, we compute the
lowest $S=2$ excitation constructed by exciting spinons close to the Dirac
nodes. Our results are compatible with a vanishing spin gap in the
thermodynamic limit and in consonance with a power-law decay of long distance
spin-spin correlations in real space. The competition with a gapped
(topological) spin liquid is discussed.


title: Face numbers of down-sets

abstract:
  We compare various viewpoints on down-sets (simplicial complexes),
illustrating how the combinatorial inclusion-exclusion principle may serve as
an alternative to more advanced methods of studying their face numbers.


title: Sodium in the Atmospheres of Thick-Disk Red Giants

abstract:
  The parameters and elemental abundances of atmospheres for ten thick-disk red
giants was determined from high-resolution spectra by the method of model
stellar atmospheres. The results of a comparative analysis of the [Na/Fe]
abundances in the atmospheres of the investigated stars and thin disk red
giants are presented. Sodium in the atmospheres of thick-disk red giants is
shown to have no overabundances typical of thin-disk red giants.


title:
Upgrading electron temperature and electron density diagnostic diagrams
  of forbidden line emission

abstract:
  Diagnostic diagrams of forbidden lines have been a useful tool for observers
in astrophysics for many decades now. They are used to obtain information on
the basic physical properties of thin gaseous nebulae. Some diagnostic diagrams
are in wavelength domains which were difficult to take either due to missing
wavelength coverage or low resolution of older spectrographs. Furthermore, most
of the diagrams were calculated using just the species involved as a single
atom gas, although several are affected by well-known fluorescence mechanisms
as well. Additionally the atomic data have improved up to the present time. Aim
of this work was a recalculation of well-known, but also of sparsely used,
unnoted diagnostics diagrams. The new diagrams provide observers with modern,
easy-to-use recipes to determine electron temperature and densities. The new
diagnostic diagrams are calculated using large grids of parameter space in the
photoionization code CLOUDY. For a given basic parameter (e.g. electron density
or temperature) the solutions with cooling-heating-equilibrium are chosen to
derive the diagnostic diagrams. Empirical numerical functions are fitted to
provide formulas usable in e.g. data reduction pipelines. The resulting
diagrams differ significantly from those used up to now and will improve the
thermodynamic calculations. To our knowledge, for the first time detailed
directly applicable fit formulas are given, leading to electron temperature or
density from the line ratios.


title: Exploring Hot Gas at Junctions of Galaxy Filaments with Suzaku

abstract:
  We performed five pointing observations with Suzaku to search for hot gases
associated with the junctions of galaxy filaments where no significant diffuse
X-ray sources were detected so far. We discovered X-ray sources successfully in
all five regions and analyzed two bright sources in each field. Spectral
analysis indicates that three sources originate from X-ray diffuse halos
associated with optically bright galaxies or groups of galaxies with kT~0.6-0.8
keV. Other three sources are possibly group- and cluster-scale X-ray halos with
temperatures of ~1 keV and ~4 keV, respectively while the others are compact
object origins such as AGNs. All the three observed intracluster media within
the junctions of the galaxy filaments previously found are involved in ongoing
mergers. Thus, we demonstrate that deep X-ray observations at the filament
junctions identified by galaxy surveys are a powerful mean to explore growing
halos in a hierarchical structure undetected so far.


title: Attracting Lagrangian Coherent Structures on Riemannian manifolds

abstract:
  It is a wide-spread convention to identify repelling Lagrangian Coherent
Structures (LCSs) with ridges of the forward finite-time Lyapunov exponent
(FTLE) field, and attracting LCSs with ridges of the backward FTLE. We show
that in two-dimensional incompressible flows attracting LCSs appear as ridges
of the forward FTLE field, too. This raises the issue of characterization of
attracting LCSs from a forward finite-time Lyapunov analysis. To this end, we
extend recent results by Haller & Sapsis (2011) [1], regarding the relation
between forward and backward maximal and minimal FTLEs, to both the whole
finite-time Lyapunov spectrum and to stretch directions. This is accomplished
by considering the singular value decomposition (SVD) of the linearized flow
map. By virtue of geometrical insights from the SVD, we give a short and direct
proof of the main result of Farazmand & Haller (2013) [2], and prove a new
characterization of attracting LCSs in forward time for Haller's variational
approach to hyperbolic LCSs [3]. We apply these results to the attracting FTLE
ridge of the incompressible saddle flow.

categories: math.DS nlin.CD physics.ao-ph physics.flu-dyn


title: On consistent truncations in ${\cal N}=2^*$ holography

abstract:
  Although Pilch-Warner (PW) gravitational renormalization group flow
[arXiv:hep-th/0004063] passes a number of important consistency checks to be
identified as a holographic dual to a large-$N$ $SU(N)$ ${\cal N}=2^*$
supersymmetric gauge theory, it fails to reproduce the free energy of the
theory on $S^4$, computed with the localization techniques. This disagreement
points to the existence of a larger dual gravitational consistent truncation,
which in the gauge theory flat-space limit reduces to a PW flow. Such
truncation was recently identified by Bobev-Elvang-Freedman-Pufu (BEFP)
[arXiv:1311.1508]. Additional bulk scalars of the BEFP gravitation truncation
might lead to destabilization of the finite-temperature deformed PW flows, and
thus modify the low-temperature thermodynamics and hydrodynamics of ${\cal N}
=2^*$ plasma. We compute the quasinormal spectrum of these bulk scalar fields
in the thermal PW flows and demonstrate that these modes do not condense, as
long as the masses of the ${\cal N}=2^*$ hypermultiplet components are real.


title: Microscopic Description of Coherent Transport by Thermal Phonons

abstract:
  We demonstrate the coherent transport of thermal energy in superlattices by
introducing a microscopic definition of the phonon coherence length. We
demonstrate how to distinguish a coherent transport regime from diffuse
interface scattering and discuss how these can be specifically controlled by
several physical parameters. Our approach provides a convenient framework for
the interpretation of previous experiments and thermal conductivity
calculations and paves the way for the design of a new class of thermal
interface materials.


On the simultaneous edge coloring of graphs


title:
Supplemental Material to "A first-principles linear response description
  of the spin Nernst effect"

abstract:
  A first-principles description of the spin Nernst effect, denoting the
occurrence of a transverse spin current due to a temperature gradient, is
presented. The approach, based on an extension to the Kubo-Streda equation for
spin transport, supplies in particular the formal basis for investigations of
diluted as well as concentrated alloys. Results for corresponding applications
to the alloy system Au-Cu give the intrinsic and extrinsic contributions to the
relevant transport coefficients. Using scaling laws allows in addition to split
the extrinsic contribution into its skew scattering and side-jump parts.


title: String graphs and separators

abstract:
  String graphs, that is, intersection graphs of curves in the plane, have been
studied since the 1960s. We provide an expository presentation of several
results, including very recent ones: some string graphs require an exponential
number of crossings in every string representation; exponential number is
always sufficient; string graphs have small separators; and the current best
bound on the crossing number of a graph in terms of the pair-crossing number.
For the existence of small separators, unwrapping the complete proof include
generally useful results on approximate flow-cut dualities.


title: Isomorphic and Strongly Connected Components

abstract:
  We study the partial orderings of the form $\langle {\mathbb P} ({\mathbb
X}), \subset \rangle $, where ${\mathbb X}$ is a binary relational structure
with the connectivity components isomorphic to a strongly connected structure
${\mathbb Y}$ and ${\mathbb P} ({\mathbb X})$ is the set of (domains of)
substructures of ${\mathbb X}$ isomorphic to ${\mathbb X}$. We show that, for
example, for a countable ${\mathbb X}$, the poset $\langle {\mathbb P}
({\mathbb X}), \subset \rangle $ is either isomorphic to a finite power of
${\mathbb P} ({\mathbb Y})$ or forcing equivalent to a separative atomless
$\sigma$-closed poset and, consistently, to $P(\omega )/$Fin. In particular,
this holds for each ultrahomogeneous structure ${\mathbb X}$ such that
${\mathbb X}$ or ${\mathbb X} ^c$ is a disconnected structure and in this case
${\mathbb Y}$ can be replaced by an ultrahomogeneous connected digraph.


title:
Negative photoconductance in a biased multiquantum well with filter
  barriers

abstract:
  In this paper the photon-assisted electron motion in a multiquantum well
(MQW) semiconductor heterostructure in the presence of an electric field is
investigated. The time-dependent Schrodinger equation is solved by using the
split-operator technique to determine the photocurrent generated by the
electron movement through the biased MQW system. An analysis of the energy
shifts in the photocurrent spectra reveals interesting features coming from the
contributions of localized and extended states on the MQW system. The
photocurrent signal is found to increase for certain values of electric field,
leading to the analogue of the negative-conductance in resonant tunneling
diodes. The origin of this enhancement is traced to the mixing of localized
states in the QWs with those in the continuum. This mixing appears as
anticrossings between the localized and extended states and the enhanced
photocurrent can be related to the dynamically induced
Landau-Zener-Stuckelberg-Majorana transition between two levels at the
anticrossing.


title: Separating path systems

abstract:
  We study separating systems of the edges of a graph where each member of the
separating system is a path. We conjecture that every $n$-vertex graph admits a
separating path system of size $O(n)$ and prove this in certain interesting
special cases. In particular, we establish this conjecture for random graphs
and graphs with linear minimum degree. We also obtain tight bounds on the size
of a minimal separating path system in the case of trees.


title: Robust estimation of risks from small samples

abstract:
  Data-driven risk analysis involves the inference of probability distributions
from measured or simulated data. In the case of a highly reliable system, such
as the electricity grid, the amount of relevant data is often exceedingly
limited, but the impact of estimation errors may be very large. This paper
presents a robust nonparametric Bayesian method to infer possible underlying
distributions. The method obtains rigorous error bounds even for small samples
taken from ill-behaved distributions. The approach taken has a natural
interpretation in terms of the intervals between ordered observations, where
allocation of probability mass across intervals is well-specified, but the
location of that mass within each interval is unconstrained. This formulation
gives rise to a straightforward computational resampling method: Bayesian
Interval Sampling. In a comparison with common alternative approaches, it is
shown to satisfy strict error bounds even for ill-behaved distributions.


title:
Correlating Fourier phase information with real-space higher order
  statistics

abstract:
  We establish for the first time heuristic correlations between harmonic space
phase information and higher order statistics. Using the spherical full-sky
maps of the cosmic microwave background as an example we demonstrate that known
phase correlations at large spatial scales can gradually be diminished when
subtracting a suitable best-fit (Bianchi-) template map of given strength. The
weaker phase correlations lead in turn to a vanishing signature of anisotropy
when measuring the Minkowski functionals and scaling indices in real-space and
comparing them with surrogate maps being free of phase correlations. Those
investigations can open a new road to a better understanding of signatures of
non-Gaussianities in complex spatial structures by elucidating the meaning of
Fourier phase correlations and their influence on higher order statistics.


title: Sunspot splitting triggering an eruptive flare

abstract:
  We investigate how the splitting of the leading sunspot and associated flux
emergence and cancellation in active region NOAA 11515 caused an eruptive M5.6
flare on 2012 July 2. Our study employs multi-wavelength observations from HMI,
AIA and ChroTel. Emerging flux formed a neutral line ahead of the leading
sunspot and new satellite spots. The sunspot splitting caused a long-lasting
flow toward this neutral line, where a filament formed. Further flux emergence,
partly of mixed-polarity, as well as episodes of flux cancellation occurred
repeatedly at the neutral line. Following a nearby C-class precursor flare with
signs of interaction with the filament, the filament erupted nearly
simultaneously with the onset of the M5.6 flare and evolved into a coronal mass
ejection. The sunspot stretched without forming a light bridge, splitting
unusually fast (within about a day, complete approximately 6 hours after the
eruption) in two nearly equal parts. The front part separated strongly from the
active region to approach the neighbouring active region where all its coronal
magnetic connections were rooted. It also rotated rapidly (by 4.9 degree/hr)
and caused significant shear flows at its edge. The eruption resulted from a
complex sequence of processes in the (sub-)photosphere and corona. The
persistent flows toward the neutral line likely caused the formation of a flux
rope which held the filament. These flows and their associated flux
cancellation, the emerging flux, and the precursor flare all contributed to the
destabilization of the flux rope. We interpret the sunspot splitting as the
separation of two flux bundles differently rooted in the convection zone and
only temporarily joined in the spot. This explains the rotation as continued
rise of the separating flux and implies that at least this part of the sunspot
was still connected to its roots deep in the convection zone.


title: Activating membranes

abstract:
  We present a general dynamical theory of a membrane coupled to an actin
cortex containing polymerizing filaments with active stresses and currents, and
demonstrate that active membrane dynamics [Phys. Rev. Lett \textbf{84}, 3494
(2000)] and spontaneous shape oscillations emerge from this description. We
also consider membrane instabilities and patterns induced by the presence of
filaments with polar orientational correlations in the tangent plane of the
membrane. The dynamical features we predict should be seen in a variety of
cellular contexts involving the dynamics of the membrane-cytoskeleton composite
and cytoskeletal extracts coupled to synthetic vesicles.


title: Homogeneous 2-partite digraphs

abstract:
  We call a 2-partite digraph D homogeneous if every isomorphism between finite
induced subdigraphs that respects the 2-partition of D extends to an
automorphism of D that does the same. In this note, we classify the homogeneous
2-partite digraphs.


title: The chromomagnetic operator on the lattice

abstract:
  We study matrix elements of the "chromomagnetic" operator on the lattice.
This operator is contained in the strangeness-changing effective Hamiltonian
which describes electroweak effects in the Standard Model and beyond.
  Having dimension 5, the chromomagnetic operator is characterized by a rich
pattern of mixing with other operators of equal and lower dimensionality,
including also non gauge invariant quantities; it is thus quite a challenge to
extract from lattice simulations a clear signal for the hadronic matrix
elements of this operator.
  We compute all relevant mixing coefficients to one loop in lattice
perturbation theory; this necessitates calculating both 2-point
(quark-antiquark) and 3-point (gluon-quark-antiquark) Green's functions at
nonzero quark masses. We use the twisted mass lattice formulation, with
Symanzik improved gluon action.
  For a comprehensive presentation of our results, along with detailed
explanations and a more complete list of references, we refer to our
forthcoming publication [1].


title:
Proceedings Second International Workshop on Trends in Tree Automata and
  Tree Transducers

abstract:
  This volume contains the papers that were presented at the second
international workshop on Trends in Tree Automata and Transducers (TTATT 2013)
which took place on October 19th, 2013 in Hanoi/Vietnam. The workshop was
colocated with the verification conference ATVA. The first edition of the
workshop was colocated with RTA and took place in Nagoya/Japan. The interest of
the workshop lies at the intersection of programming languages, verification,
and database theory, which are areas to which tree automata and transducers are
applied recently.


title: On the Topology of the Inflaton Field in Minimal Supergravity Models

abstract:
  We consider global issues in minimal supergravity models where a single field
inflaton potential emerges. In a particular case we reproduce the Starobinsky
model and its description dual to a certain formulation of R+R^2 supergravity.
For definiteness we confine our analysis to spaces at constant curvature,
either vanishing or negative. Five distinct models arise, two flat models with
respectively a quadratic and a quartic potential and three based on the
SU(1,1)/U(1) space where its distinct isometries, elliptic, hyperbolic and
parabolic are gauged. Fayet-Iliopoulos terms are introduced in a geometric way
and they turn out to be a crucial ingredient in order to describe the de Sitter
inflationary phase of the Starobinsky model.