title:
Microscopic thickness determination of thin graphite films formed on SiC
  from quantized oscillation in reflectivity of low-energy electrons

abstract:
  Low-energy electron microscopy (LEEM) was used to measure the reflectivity of
low-energy electrons from graphitized SiC(0001). The reflectivity shows
distinct quantized oscillations as a function of the electron energy and
graphite thickness. Conduction bands in thin graphite films form discrete
energy levels whose wave vectors are normal to the surface. Resonance of the
incident electrons with these quantized conduction band states enhances
electrons to transmit through the film into the SiC substrate, resulting in
dips in the reflectivity. The dip positions are well explained using
tight-binding and first-principles calculations. The graphite thickness
distribution can be determined microscopically from LEEM reflectivity
measurements.


title: A minimal set of generators for the ring of multisymmetric functions

abstract:
  The purpose of this article is to give, for any commutative ring A, an
explicit minimal set of generators for the ring of multisymmetric functions
TS^d_A(A[x_1,...,x_r]) as an A-algebra. In characteristic zero, i.e. when A is
an algebra over the rational numbers, a minimal set of generators has been
known since the 19th century. A rather small generating set in the general case
has also recently been given by Vaccarino but it is not minimal in general. We
also give a sharp degree bound on the generators, improving the degree bound
previously obtained by Fleischmann.


title: Non-perturbative improvement of nHYP smeared Wilson fermions

abstract:
  Using Schroedinger functional techniques, we determine the coefficient of the
clover term necessary for non-perturbative O(a) improvement of hypercubic
smeared Wilson fermions on a quenched plaquette action background. Unlike for
unsmeared Wilson fermions, the resulting clover coefficients are close to the
tree-level value even at coarse lattice spacings, indicating the absence of
large cutoff effects. A number of exploratory tests are also performed with the
improved action.


title:
Ernst equation and spheroidal coordinates with a cosmological constant
  term

abstract:
  We discuss solution generating techniques treating stationary and axially
symmetric metrics in the presence of a cosmological constant. Using the
recently found extended form of Ernst's complex equation, which takes into
account the cosmological constant term, we propose an extension of spheroidal
coordinates adapted to asymptotically de-Sitter and anti de-Sitter static
spacetimes. In the absence of a cosmological constant we show in addition that
any higher dimensional metric parametrised by a single angular momentum can be
given by a 4 dimensional solution and Weyl potentials parametrising the extra
Killing directions. We explicitly show how a stationary, and a static axially
symmetric spacetime solution in 4 dimensions, can be {\it added} together to
give a 5 dimensional stationary and axisymmetric solution.


title:
Reply to 'Difficulty in the Fermi-Liquid-Based Theory for the In-Plane
  Magnetic Anisotropy in Untwinned High-$T_c$ Superconductors'

abstract: A Reply to the Comment by Hou-Jun Zhao and Jun Li


title:
Fractional dynamical systems defined on fractional jet bundle and
  applications in economics

abstract:
  Using Caputo fractional derivative of order $\alpha $ we build the fractional
jet bundle of order $\alpha $ and its main geometrical structures. Defined on
that bundle, some fractional dynamical systems with applications to economics
are studied.


title: DFT-based calculation of Coulomb blockade in molecular junction

abstract:
  Quantum transport through single molecules is very sensitive to the strength
of the molecule-electrode contact. When a molecular junction weakly coupled to
external electrodes, charging effects do play an important role (Coulomb
blockade regime). In this regime, the non-equilibrium Green function is usually
substituted with master equation approaches, which prevents the density
functional theory from describing Coulomb blockade in non-equilibrium case.
Last year, we proposed an Ansatz to combine the non-equilibrium Green function
technique with the equation of motion method. With help of it, Coulomb blockade
was obtained by non-equilibrium Green function, and completely agrees with the
master equation results [Phys. Rev. B \textbf{76}, 045408 (2007)]. Here, by the
Ansatz, we show a new way to introduce Coulomb blockade correction to DFT
calculation in non-equilibrium case. And the characteristics of Coulomb
blockade are obtained in the calculation of a $toy$ molecule correctly.


title: Vortex topology and the continuum limit of lattice gauge theories

abstract:
  We study the stability of Z_2 topological vortex excitations in d+1
dimensional SU(2) Yang-Mills theory on the lattice at T=0. This is found to
depend on d and on the coupling considered. We discuss the connection with
lattice artifacts causing bulk transitions in the beta_A-beta_F plane and draw
some conclusions regarding the continuum limit of the theory.


title: Gravitational time delay of light for various models of modified gravity

abstract:
  We reexamined the gravitational time delay of light, allowing for various
models of modified gravity. We clarify the dependence of the time delay (and
induced frequency shift) on modified gravity models and investigate how to
distinguish those models, when light propagates in static spherically symmetric
spacetimes. Thus experiments by radio signal from spacecrafts at very different
distances from Sun and future space-borne laser interferometric detectors could
be a probe of modified gravity in the solar system.


title: Nonperturbative approach to the quantum Hall bilayer

abstract:
  We develop a nonperturbative approach to the quantum Hall bilayer (QHB) at
\nu=1 using trial wave functions. We predict phases of the QHB for arbitrary
distance d and, our approach, in a dual picture, naturally introduces a new
kind of quasiparticles - neutral fermions. Neutral fermion is a composite of
two merons of the same vorticity and opposite charge. For small d (i.e. in the
superfluid phase), neutral fermions appear as dipoles. At larger d dipoles
dissociate into the phase of the two decoupled Fermi-liquid-like states. This
scenario is relevant for the experimental situation where impurities lock
charged merons. In a translation invariant (clean) system, continuous creation
and annihilation of meron-antimeron pairs evolves the QHB toward a paired
phase. The quantum fluctuations fix the form of the pairing function to
g(z)=1/z^*. A part of the description of the paired phase is the 2D
superconductor i.e. BF Chern-Simons theory. The paired phase is not very
distinct from the superfluid phase.


title:
Determination of the micromagnetic parameters in (Ga,Mn)As using domain
  theory

abstract:
  The magnetic domain structure and magnetic properties of a ferromagnetic
(Ga,Mn)As epilayer with perpendicular magnetic easy-axis are investigated. We
show that, despite strong hysteresis, domain theory at thermodynamical
equilibrium can be used to determine the micromagnetic parameters. Combining
magneto-optical Kerr microscopy, magnetometry and ferromagnetic resonance
measurements, we obtain the characteristic parameter for magnetic domains
$\lambda_c$, the domain wall width and specific energy, and the spin stiffness
constant as a function of temperature. The nucleation barrier for magnetization
reversal and the Walker breakdown velocity for field-driven domain wall
propagation are also estimated.


title:
Smearing and filtering methods in lattice QCD - a quantitative
  comparison

abstract:
  We systematically compare three filtering methods used to extract topological
excitations from lattice gauge configurations, namely smearing, Laplace
filtering and the filtered fermionic topological charge (with chirally improved
fermions). Each of these techniques introduces ambiguities, like its parameter
dependence. We show, however, that all these methods can be tuned to each other
over a broad range of filtering levels and that they reveal very similar
topological structures. For these common structures we find an interesting
power-law relating the number and packing fraction of clusters of filtered
topological charge.


title: Confinement: $G_2$ group case

abstract:
  The gauge group being centreless, $G_2$ gauge theory is a good laboratory for
studying the role of the centre of the group for colour confinement in
Yang-Mills gauge theories. In this paper, we investigate $G_2$ pure gauge
theory at finite temperature on the lattice. By studying the finite size
scaling of the plaquette, the Polyakov loop and their susceptibilities, we show
that a deconfinement phase transition takes place. The analysis of the
pseudocritical exponents give strong evidence of the deconfinement transition
being first order. Implications of our findings for scenarios of colour
confinement are discussed.


title:
Conserving GW scheme for nonequilibrium quantum transport in molecular
  contacts

abstract:
  We give a detailed presentation of our recent scheme to include correlation
effects in molecular transport calculations using the GW approximation within
the non-equilibrium Keldysh formalism. We restrict the GW self-energy to the
central region, and describe the leads by density functional theory (DFT). A
minimal basis of maximally localized Wannier functions is applied both in the
central GW region and the leads. The importance of using a conserving, i.e.
fully self-consistent, GW self-energy is demonstrated both analytically and by
numerical examples. We introduce an effective spin-dependent interaction which
automatically reduces self-interaction errors to all orders in the interaction.
The scheme is applied to the Anderson model in- and out of equilibrium. In
equilibrium at zero temperature we find that GW describes the Kondo resonance
fairly well for intermediate interaction strengths. Out of equilibrium we
demonstrate that the one-shot G0W0 approximation can produce severe errors, in
particular at high bias. Finally, we consider a benzene molecule between
featureless leads. It is found that the molecule's HOMO-LUMO gap as calculated
in GW is significantly reduced as the coupling to the leads is increased,
reflecting the more efficient screening in the strongly coupled junction. For
the IV characteristics of the junction we find that HF and G0W0[G_HF] yield
results closer to GW than does DFT and G0W0[G_DFT]. This is explained in terms
of self-interaction effects and life-time reduction due to electron-electron
interactions.


title: Reduction for constrained variational problems on 3D null curves

abstract:
  We consider the optimal control problem for null curves in de Sitter 3-space
defined by a functional which is linear in the curvature of the trajectory. We
show how techniques based on the method of moving frames and exterior
differential systems, coupled with the reduction procedure for systems with a
Lie group of symmetries lead to the integration by quadratures of the
extremals. Explicit solutions are found in terms of elliptic functions and
integrals.


title: AGN feedback from Jet-ISM/IGM interactions

abstract:
  We study the propagation of relativistic jets originating from AGNs within
the Interstellar/Intergalactic Medium of their host galaxies, and use it to
build a model for the suppression of stellar formation within the expanding
cocoon.


title: Prediction with expert advice for the Brier game

abstract:
  We show that the Brier game of prediction is mixable and find the optimal
learning rate and substitution function for it. The resulting prediction
algorithm is applied to predict results of football and tennis matches. The
theoretical performance guarantee turns out to be rather tight on these data
sets, especially in the case of the more extensive tennis data.


title: Phase-Space Coalescence for heavy and light quarks at RHIC

abstract:
  We review the application and successes of a phase-space coalescence plus
fragmentation model that has been applied for hadronization at RHIC. The
physical concept is discussed together with the practical implementation. The
robustness of main predictions is reviewed together with several open issues
like relevance of three dimensional calculation, finite width of the wave
functions, effects of quark masses, energy-entropy conservation, space-momentum
correlation. Eventually the relevance of coalescence also for the study of the
microscopic interaction of heavy quarks is highlighted.


title: Lattice supersymmetry in 1D with two supercharges

abstract:
  A consistent formulation of a fully supersymmetric theory on the lattice has
been a long standing challenge. In recent years there has been a renewed
interest on this problem with different approaches. At the basis of the
formulation we present in the following there is the Dirac-Kahler twisting
procedure, which was proposed in the continuum for a number of theories,
including N=4 SUSY in four dimensions. Following the formalism developed in
recent papers, an exact supersymmetric theory with two supercharges on a one
dimensional lattice is realized using a matrix-based model. The matrix
structure is obtained from the shift and clock matrices used in two dimensional
non-commutative field theories. The matrix structure reproduces on a one
dimensional lattice the expected modified Leibniz rule. Recent claims of
inconsistency of the formalism are discussed and shown not to be relevant.


title: On the ratio of string tensions in the 3D Z_4 lattice gauge theory

abstract:
  It was recently pointed out that simple scaling properties of Polyakov
correlation functions of gauge systems in the confining phase suggest that the
ratios of k-string tensions in the low temperature region is constant up to
terms of order T^3. Here we argue that, at least in a three-dimensional Z_4
gauge model, the above ratios are constant in the whole confining phase. This
result is obtained by combining numerical experiments with known exact results
on the mass spectrum of an integrable two-dimensional spin model describing the
infrared behaviour of the gauge system near the deconfining transition.


title: P- and D-wave spin-orbit splittings in heavy-light mesons

abstract:
  This is a summary of a detailed study of heavy-light meson excited state
energies. Our lattice measurements include both radial and orbital excitations.
Particular attention is paid to the spin-orbit splittings, to see which one of
the states (for a given angular momentum L) has the lower energy. In nature the
closest equivalent of this heavy-light system is the B_s meson, which allows us
to compare our lattice calculations to experimental results (where available)
or give a prediction where the excited states, particularly P-wave states,
should lie.


title: Dynamics of galactic nuclei: Mass segregation and collisions

abstract:
  Massive black holes (MBHs) with a mass below ~ 1e7 Msun are likely to reside
at the centre of dense stellar nuclei shaped by 2-body relaxation, close
interactions with the MBH and direct collisions. In this contribution, we
stress the role of mass segregation of stellar-mass black holes into the
innermost tenths of a parsec and point to the importance of hydrodynamical
collisions between stars. At the Galactic centre, collisions must affect giant
stars and some of the S-stars.


title:
Analysis of Linear Difference Schemes in the Sparse Grid Combination
  Technique

abstract:
  Sparse grids are tailored to the approximation of smooth high-dimensional
functions. On a $d$-dimensional tensor product space, the number of grid points
is $N = \mathcal O(h^{-1} |\log h|^{d-1})$, where $h$ is a mesh parameter. The
so-called combination technique, based on hierarchical decomposition and
extrapolation, requires specific multivariate error expansions of the
discretisation error on Cartesian grids to hold. We derive such error
expansions for linear difference schemes through an error correction technique
of semi-discretisations. We obtain overall error formulae of the type $\epsilon
= \mathcal{O} (h^p |\log h|^{d-1})$ and analyse the convergence, with its
dependence on dimension and smoothness, by examples of linear elliptic and
parabolic problems, with numerical illustrations in up to eight dimensions.


title: On the second Paneitz-Branson invariant

abstract:
  We define the second Paneitz-Branson operator on a compact Einsteinian
manifold of dimension $n\geq 5$ and we give sufficient conditions that make it
attained.


title:
Planar trees, free nonassociative algebras, invariants, and elliptic
  integrals

abstract:
  We consider absolutely free nonassociative algebras and, more generally,
absolutely free algebras with (maybe infinitely) many multilinear operations.
Such algebras are described in terms of labeled reduced planar rooted trees.
This allows to apply combinatorial techniques to study their Hilbert series and
the asymptotics of their coefficients. These algebras satisfy the
Nielsen-Schreier property and their subalgebras are also free. Then, over a
field of characteristic 0, we investigate the subalgebras of invariants under
the action of a linear group, their sets of free generators and their Hilbert
series. It has turned out that, except in the trivial cases, the algebra of
invariants is never finitely generated. In important partial cases the Hilbert
series of the algebras of invariants and the generating functions of their sets
of free generators are expressed in terms of elliptic integrals.


title: The z=0.8 precursors of today's bulges

abstract:
  We study the color structure of disk galaxies in the Groth strip at redshifts
0.1<z<1.2. Our aim is to test formation models in which bulges form
before/after the disk. We find smooth color distributions with gentle outward
blueing across the galaxy image: bulges are not distinctly redder than their
disks; and bulge colors strongly correlate with global colors. The results
suggest a roughly coeval evolution of bulges and disks. About 50% of the nuclei
of galaxies with central light excesses above the outer exponential profile
hold passively evolving red populations. The remainder 50% are galaxies with
central blue colors similar to their disks. They may be bulges in formation, or
the central parts of disks with non-exponential surface brightness profiles.


title:
Lineshape distortion in a nonlinear auto-oscillator near generation
  threshold: Application to spin-torque nano-oscillators

abstract:
  The lineshape in an auto-oscillator with a large nonlinear frequency shift in
the presence of thermal noise is calculated. Near the generation threshold,
this lineshape becomes strongly non-Lorentzian, broadened, and asymmetric. A
Lorentzian lineshape is recovered far below and far above threshold, which
suggests that lineshape distortions provide a signature of the generation
threshold. The theory developed adequately describes the observed behavior of a
strongly nonlinear spin-torque nano-oscillator.


title:
Microscopic mechanisms of spin-dependent electric polarization in 3d
  oxides

abstract:
  We address a systematic microscopic theory of spin-dependent electric
polarization in 3d oxides starting with a generic three-site two-hole cluster.
A perturbation scheme realistic for 3d oxides is applied which implies the
quenching of orbital moments by low-symmetry crystal field, strong intra-atomic
correlations, the dp-transfer effects, and rather small spin-orbital coupling.
An effective spin operator of the electric dipole moment is deduced
incorporating both nonrelativistic and relativistic terms. The nonrelativistic
electronic polarization mechanism related with the effects of the
redistribution of the local on-site charge density due to $pd$ covalency and
exchange coupling is believed to govern the multiferroic behaviour in 3d
oxides. The relativistic exchange-dipole moment is mainly stems from the
nonrelativistic one due to the perturbation effect of Dzyaloshinsky-Moriya
coupling and is estimated to be a weak contributor to the electric polarization
observed in the most of 3d multiferroics.


title: A Joint Search for Gravitational Wave Bursts with AURIGA and LIGO

abstract:
  The first simultaneous operation of the AURIGA detector and the LIGO
observatory was an opportunity to explore real data, joint analysis methods
between two very different types of gravitational wave detectors: resonant bars
and interferometers. This paper describes a coincident gravitational wave burst
search, where data from the LIGO interferometers are cross-correlated at the
time of AURIGA candidate events to identify coherent transients. The analysis
pipeline is tuned with two thresholds, on the signal-to-noise ratio of AURIGA
candidate events and on the significance of the cross-correlation test in LIGO.
The false alarm rate is estimated by introducing time shifts between data sets
and the network detection efficiency is measured with simulated signals with
power in the narrower AURIGA band. In the absence of a detection, we discuss
how to set an upper limit on the rate of gravitational waves and to interpret
it according to different source models. Due to the short amount of analyzed
data and to the high rate of non-Gaussian transients in the detectors noise at
the time, the relevance of this study is methodological: this was the first
joint search for gravitational wave bursts among detectors with such different
spectral sensitivity and the first opportunity for the resonant and
interferometric communities to unify languages and techniques in the pursuit of
their common goal.


title: Screening at finite temperature and density

abstract:
  We present lattice QCD results on heavy quark free energies, extract from its
temperature dependence entropy and internal energy contributions, and discuss
the onset of medium effects that lead to screening of static quark-antiquark
sources in a thermal medium. Most results are obtained in (2+1)-flavour QCD on
a line of constant physics with almost realistic quark masses and compared to
previous results from 2-flavor QCD as well as pure gauge theory. Furthermore,
we discuss results on the density dependence of screening masses that have been
obtained using a leading order Taylor expansion in the baryon chemical
potential.


title: A silicate disk in the heart of the Ant

abstract:
  We aim at getting high spatial resolution information on the dusty core of
bipolar planetary nebulae to directly constrain the shaping process. Methods:
We present observations of the dusty core of the extreme bipolar planetary
nebula Menzel 3 (Mz 3, Hen 2-154, the Ant) taken with the mid-infrared
interferometer MIDI/VLTI and the adaptive optics NACO/VLT. The core of Mz 3 is
clearly resolved with MIDI in the interferometric mode, whereas it is
unresolved from the Ks to the N bands with single dish 8.2 m observations on a
scale ranging from 60 to 250 mas. A striking dependence of the dust core size
with the PA angle of the baselines is observed, that is highly suggestive of an
edge-on disk whose major axis is perpendicular to the axis of the bipolar
lobes. The MIDI spectrum and the visibilities of Mz 3 exhibit a clear signature
of amorphous silicate, in contrast to the signatures of crystalline silicates
detected in binary post-AGB systems, suggesting that the disk might be
relatively young. We used radiative-transfer Monte Carlo simulations of a
passive disk to constrain its geometrical and physical parameters. Its
inclination (74 degrees $\pm$ 3 degrees) and position angle (5 degrees $\pm$ 5
degrees) are in accordance with the values derived from the study of the lobes.
The inner radius is 9$\pm$ 1 AU and the disk is relatively flat. The dust mass
stored in the disk, estimated as 1 x 10-5Msun, represents only a small fraction
of the dust mass found in the lobes and might be a kind of relic of an
essentially polar ejection process.


title: Infrared problem and spatially local observables in electrodynamics

abstract:
  An algebra previously proposed as an asymptotic field structure in
electrodynamics is considered in respect of localization properties of fields.
Fields are 'spatially local' -- localized in regions resulting as unions of two
intersecting (solid) lightcones: a future- and a past-lightcone. This
localization remains in concord with the usual idealizations connected with the
scattering theory. Fields thus localized naturally include infrared
characteristics normally placed at spacelike infinity and form a structure
respecting Gauss law. When applied to the description of the radiation of an
external classical current the model is free of 'infrared catastrophe'.


title: Form factors of boundary fields for A(2)-affine Toda field theory

abstract:
  In this paper we carry out the boundary form factor program for the
A(2)-affine Toda field theory at the self-dual point. The latter is an
integrable model consisting of a pair of particles which are conjugated to each
other and possessing two bound states resulting from the scattering processes 1
+1 -> 2 and 2+2-> 1. We obtain solutions up to four particle form factors for
two families of fields which can be identified with spinless and spin-1 fields
of the bulk theory. Previously known as well as new bulk form factor solutions
are obtained as a particular limit of ours. Minimal solutions of the boundary
form factor equations for all A(n)-affine Toda field theories are given, which
will serve as starting point for a generalisation of our results to higher rank
algebras.


title:
Dynamical resonances and SSF singularities for a magnetic Schroedinger
  operator

abstract:
  We consider the Hamiltonian $H$ of a 3D spinless non-relativistic quantum
particle subject to parallel constant magnetic and non-constant electric field.
The operator $H$ has infinitely many eigenvalues of infinite multiplicity
embedded in its continuous spectrum. We perturb $H$ by appropriate scalar
potentials $V$ and investigate the transformation of these embedded eigenvalues
into resonances. First, we assume that the electric potentials are
dilation-analytic with respect to the variable along the magnetic field, and
obtain an asymptotic expansion of the resonances as the coupling constant
$\varkappa$ of the perturbation tends to zero. Further, under the assumption
that the Fermi Golden Rule holds true, we deduce estimates for the time
evolution of the resonance states with and without analyticity assumptions; in
the second case we obtain these results as a corollary of suitable Mourre
estimates and a recent article of Cattaneo, Graf and Hunziker \cite{cgh}. Next,
we describe sets of perturbations $V$ for which the Fermi Golden Rule is valid
at each embedded eigenvalue of $H$; these sets turn out to be dense in various
suitable topologies. Finally, we assume that $V$ decays fast enough at infinity
and is of definite sign, introduce the Krein spectral shift function for the
operator pair $(H+V, H)$, and study its singularities at the energies which
coincide with eigenvalues of infinite multiplicity of the unperturbed operator
$H$.


title:
Unified Approach to the Large-Signal and High-Frequency Theory of
  $p-n$-Junctions

abstract:
  Spectral approach to the charge carrier transport in $p-n$-junctions has
allowed us to revise the theoretical results relating to large signal operation
of the junction to make them valid for both the low and high frequencies
ranges. The spectral composition of the external circuit current includes both
the DC and AC components. The former produces the static current--voltage
characteristic with the modified Bessel function of zeroth order, $I_0(\beta
V_\sim)$, while the latter yields the dynamic admittance with the modified
Bessel function of first order, $I_1(\beta V_\sim)$, either of them depend on
the signal amplitude. Our experimental results are consistent with the
theoretical ones if a fitting parameter allowing for recombination processes in
the depletion layer is taken into account.


title:
Wilson Loop in Classical Lattice Gauge Theory and the Thermal Width of
  Heavy Quarkonium

abstract:
  We present an estimate for the imaginary part of the recently introduced
finite temperature real-time static potential. It can be extracted from the
time evolution of the Wilson loop in classical lattice gauge theory. The
real-time static potential determines, through a Schroedinger-type equation and
a subsequent Fourier-transform of its solution, the spectral function of heavy
quarkonium in finite-temperature QCD. We also compare the results of the
classical simulations with those of Hard Thermal Loop improved simulations, as
well as with analytic expectations based on resummed perturbation theory.


title:
1/N Expansion of the 2D CP^{N-1} Model on Non(anti)commutative
  Superspace

abstract:
  We study UV properties of the two-dimensional supersymmetric CP^{N-1} model
on non(anti)commutative superspace. We show that the deformed model has the
same UV property as the ordinary model in the leading order of 1/N and the
deformation give rise to UV divergence which cannot be dealt with in the
next-to-leading order.


title: Spitzer View of Lyman Break Galaxies

abstract:
  Using a combination of deep MID-IR observations obtained by IRAC, MIPS and
IRS on board Spitzer we investigate the MID-IR properties of Lyman Break
Galaxies (LBGs) at z~3, establish a better understanding of their nature and
attempt a complete characterisation of the population. With deep mid-infrared
and optical observations of ~1000 LBGs covered by IRAC/MIPS and from the ground
respectively, we extend the spectral energy distributions (SEDs) of the LBGs to
mid-infrared. Spitzer data reveal for the first time that the mid-infrared
properties of the population are inhomogeneous ranging from those with marginal
IRAC detections to those with bright rest-frame near-infrared colors and those
detected at 24mu MIPS band revealing the newly discovered population of the
Infrared Luminous Lyman Break Galaxies (ILLBGs). To investigate this diversity,
we examine the photometric properties of the population and we use stellar
population synthesis models to probe the stellar content of these galaxies. We
find that a fraction of LBGs have very red colors and large estimated stellar
masses M* > 5x10^10Mo. We discuss the link between these LBGs and
submm-luminous galaxies and we report the detection of rest frame 6.2 and 7.7mu
emission features arising from Polycyclic Aromatic Hydrocarbons (PAH) in the
Spitzer/IRS spectrum of an infrared-luminous Lyman break galaxy at z=3.01.


title:
Results related to generalizations of Hilbert's non-immersibility
  theorem for the hyperbolic plane

abstract:
  We discuss generalizations of the well-known theorem of Hilbert that there is
no complete isometric immersion of the hyperbolic plane into Euclidean 3-space.
We show that this problem is expressed very naturally as the question of the
existence of certain homotheties of reflective submanifolds of a symmetric
space. As such, we conclude that the only other (non-compact) cases to which
this theorem could generalize are the problem of isometric immersions with flat
normal bundle of the hyperbolic space $H^n$ into a Euclidean space $E^{n+k}$,
$n \geq 2$, and the problem of Lagrangian isometric immersions of $H^n$ into
$\cc^n$, $n \geq 2$. Moreover, there are natural compact counterparts to these
problems, and for the compact cases we prove that the theorem does in fact
generalize: local embeddings exist, but complete immersions do not.


title: Structured variable selection in support vector machines

abstract:
  When applying the support vector machine (SVM) to high-dimensional
classification problems, we often impose a sparse structure in the SVM to
eliminate the influences of the irrelevant predictors. The lasso and other
variable selection techniques have been successfully used in the SVM to perform
automatic variable selection. In some problems, there is a natural hierarchical
structure among the variables. Thus, in order to have an interpretable SVM
classifier, it is important to respect the heredity principle when enforcing
the sparsity in the SVM. Many variable selection methods, however, do not
respect the heredity principle. In this paper we enforce both sparsity and the
heredity principle in the SVM by using the so-called structured variable
selection (SVS) framework originally proposed in Yuan, Joseph and Zou (2007).
We minimize the empirical hinge loss under a set of linear inequality
constraints and a lasso-type penalty. The solution always obeys the desired
heredity principle and enjoys sparsity. The new SVM classifier can be
efficiently fitted, because the optimization problem is a linear program.
Another contribution of this work is to present a nonparametric extension of
the SVS framework, and we propose nonparametric heredity SVMs. Simulated and
real data are used to illustrate the merits of the proposed method.


title: Techniques on mesh generation for the brain shift simulation

abstract:
  Neurosurgery interventions involve complex tracking systems because a tissue
deformation takesplace. The neuronavigation system relies only on preoperative
images. In order to overcome the soft tissue deformations and guarantee the
accuracy of the navigation a biomechanical model can be used during surgery to
simulate the deformation of the brain. Therefore, a mesh generation for an
optimal real-time Finite Element Model (FEM) becomes crucial. In this work we
present different alternatives from a meshgeneration point of view that were
evaluated to optimize the process in terms of elements quantity and quality as
well as constraints of a intraoperative application and patient specific data.


title: Q-adic Transform revisited

abstract:
  We present an algorithm to perform a simultaneous modular reduction of
several residues. This algorithm is applied fast modular polynomial
multiplication. The idea is to convert the $X$-adic representation of modular
polynomials, with $X$ an indeterminate, to a $q$-adic representation where $q$
is an integer larger than the field characteristic. With some control on the
different involved sizes it is then possible to perform some of the $q$-adic
arithmetic directly with machine integers or floating points. Depending also on
the number of performed numerical operations one can then convert back to the
$q$-adic or $X$-adic representation and eventually mod out high residues. In
this note we present a new version of both conversions: more tabulations and a
way to reduce the number of divisions involved in the process are presented.
The polynomial multiplication is then applied to arithmetic in small finite
field extensions.


title:
Constraints on exact Lagrangians in cotangent bundles of manifolds
  fibred over the circle

abstract:
  We give topological obstructions to the existence of a closed exact
Lagrangian submanifold in the cotangent bundle of a closed manifold M which is
the total space of a fibration over the circle. For instance we show that the
fundamental group of such a Lagrangian submanifold cannot be the free product
of two non-trivial groups and that in any finite presentation of this group the
difference between the number of generators and the number of relations is less
than two.


title: Strong coupling expansion for Yang-Mills theory at finite temperature

abstract:
  Euclidean strong coupling expansion of the partition function is applied to
lattice Yang-Mills theory at finite temperature, i.e. for lattices with a
compactified temporal direction. The expansions have a finite radius of
convergence and thus are valid only for $\beta<\beta_c$, where $\beta_c$
denotes the nearest singularity of the free energy on the real axis. The
accessible temperature range is thus the confined regime up to the
deconfinement transition. We have calculated the first few orders of these
expansions of the free energy density as well as the screening masses for the
gauge groups SU(2) and SU(3). The resulting free energy series can be summed up
and corresponds to a glueball gas of the lowest mass glueballs up to the
calculated order. Our result can be used to fix the lower integration constant
for Monte Carlo calculations of the thermodynamic pressure via the integral
method, and shows from first principles that in the confined phase this
constant is indeed exponentially small. Similarly, our results also explain the
weak temperature dependence of glueball screening masses below $T_c$, as
observed in Monte Carlo simulations. Possibilities and difficulties in
extracting $\beta_c$ from the series are discussed.


title:
Heisenberg model of the high-energy hadron collision in terms of chiral
  fields

abstract:
  Properties of chiral Born-Infeld Theory proposed as the model for shock-wave
fireball production in the hadron-hadron collisions was studied. The role of
the shock-waves in the multi-particle production was discussed.


title:
Miller's instability, microchaos and the short-term evolution of
  initially nearby orbits

abstract:
  We study the phase-space behaviour of nearby trajectories in integrable
potentials. We show that the separation of nearby orbits initially diverges
very fast, mimicking a nearly exponential behaviour, while at late times it
grows linearly. This initial exponential phase, known as Miller's instability,
is commonly found in N-body simulations, and has been attributed to short-term
(microscopic) N-body chaos. However we show here analytically that the initial
divergence is simply due to the shape of an orbit in phase-space. This result
confirms previous suspicions that this transient phenomenon is not related to
an instability in the sense of non-integrable behaviour in the dynamics of
N-body systems.


title:
Poynting's theorem and energy conservation in the propagation of light
  in bounded media

abstract:
  Starting from the Maxwell-Lorentz equations, Poynting's theorem is
reconsidered. The energy flux vector is introduced as S_e=(E x B)/mu_0 instead
of E x H, because only by this choice the energy dissipation can be related to
the balance of the kinetic energy of the matter subsystem. Conservation of the
total energy as the sum of kinetic and electromagnetic energy follows. In our
discussion, media and their microscopic nature are represented exactly by their
susceptibility functions, which do not necessarily have to be known. On this
footing, it can be shown that energy conservation in the propagation of light
through bounded media is ensured by Maxwell's boundary conditions alone, even
for some frequently used approximations. This is demonstrated for approaches
using additional boundary conditions and the dielectric approximation in
detail, the latter of which suspected to violate energy conservation for
decades.


title: Essential curves in handlebodies and topological contractions

abstract:
  If $X$ is a compact set, a {\it topological contraction} is a self-embedding
$f$ such that the intersection of the successive images $f^k(X)$, $k>0$,
consists of one point. In dimension 3, we prove that there are smooth
topological contractions of the handlebodies of genus $\geq 2$ whose image is
essential. Our proof is based on an easy criterion for a simple curve to be
essential in a handlebody.


title: The notion of persistence applied to breathers in thermal equilibrium

abstract:
  We study the thermal equilibrium of nonlinear Klein-Gordon chains at the
limit of small coupling (anticontinuum limit). We show that the persistence
distribution associated to the local energy density is a useful tool to study
the statistical distribution of so-called thermal breathers, mainly when the
equilibrium is characterized by long-lived static excitations; in that case,
the distribution of persistence intervals turns out to be a powerlaw. We
demonstrate also that this generic behaviour has a counterpart in the power
spectra, where the high frequencies domains nicely collapse if properly
rescaled. These results are also compared to non linear Klein-Gordon chains
with a soft nonlinearity, for which the thermal breathers are rather mobile
entities. Finally, we discuss the possibility of a breather-induced anomalous
diffusion law, and show that despite a strong slowing-down of the energy
diffusion, there are numerical evidences for a normal asymptotic diffusion
mechanism, but with exceptionnally small diffusion coefficients.


title:
Self-directed growth of AlGaAs core-shell nanowires for visible light
  applications

abstract:
  Al(0.37)Ga(0.63)As nanowires (NWs) were grown in a molecular beam epitaxy
system on GaAs(111)B substrates. Micro-photoluminescence measurements and
energy dispersive X-ray spectroscopy indicated a core-shell structure and Al
composition gradient along the NW axis, producing a potential minimum for
carrier confinement. The core-shell structure formed during the growth as a
consequence of the different Al and Ga adatom diffusion lengths.


title: Differential Invariants of Conformal and Projective Surfaces

abstract:
  We show that, for both the conformal and projective groups, all the
differential invariants of a generic surface in three-dimensional space can be
written as combinations of the invariant derivatives of a single differential
invariant. The proof is based on the equivariant method of moving frames.


title: Mining the Local Volume

abstract:
  After recent systematic optical, IR, and HI surveys, the total number of
known galaxies within 10 Mpc has increased from 179 to 550. About half this
Local Volume (LV) sample is now been imaged with HST, yielding the galaxy
distances with an accuracy of about 8%. For the majority of the LV galaxies we
currently have H-alpha fluxes that allow us to reconstruct the star formation
history of our neighbourhood.
  For the late-type LV galaxies their HI masses and angular momentum follow the
linear relation in the range of 4 orders, which is expected for rotating
gaseous disks being near the gravitational instability threshold.
  The data obtained on the LV galaxies imply important cosmological parameters,
in particular, the mean local matter density and HI mass density, as well as
SFR density.
  Surprisingly, the local Hubble flow around the LV groups is very quiet, with
1D rms deviations of 25 km/s,which is a signature of the Universe
vacuum-dominated on small scales. The cold infall pattern around nearby groups
provides us with a new method to determine the total mass of the groups
independent from virial mass estimates.


title: Kinetic Equationins in the Theory of Normal Fermi Liquid

abstract:
  On the bases of the improved approximation for the spectral function of
one-particle states the Landau-Silin kinetic equations for the normal Fermi
liquids of neutral and electrically charged particles are shown to be valid at
finite temperature above the temperature of superfluid transition.


title:
Localization and delocalization of ultracold bosonic atoms in finite
  optical lattices

abstract:
  We study bosonic atoms in small optical lattices by exact diagonalization and
observe a striking similarity to the superfluid to Mott insulator transition in
macroscopic systems. The momentum distribution, the formation of an energy gap,
and the pair correlation function show only a weak size dependence. For
noncommensurate filling we reveal in deep lattices a mixture of localized and
delocalized particles, which is sensitive to lattice imperfections. Breaking
the lattice symmetry causes a Bose-glass-like behavior. We discuss the nature
of excited states and orbital effects by using an exact diagonalization
technique that includes higher bands.


title: Fluctuation theorem applied to Dictyostelium discoideum system

abstract:
  In this paper, we analyze the electrotactic movement of Dictyostelium
discoideum from the viewpoint of non-equilibrium statistical mechanics. Because
we can observe fluctuating behavior of cellular trajectories, we analyze the
probability distribution of the trajectories with the aid of the fluctuation
theorem. Recently, the validity of the fluctuation theorem was verified in a
colloidal system, and it has also been applied to granular systems, turbulent
systems and chemical oscillatory waves to investigate some of their statistical
properties that are not yet completely understood. Noting that the fluctuation
theorem is potentially applicable to cellular electrotaxis, here we employ it
to help us obtain a phenomenological model of this biological system.


title: Raman spectra of unfilled and filled carbon nanotubes: Theory

abstract:
  The Raman spectra of two G-bands and a radial breathing mode (RBM) of
unfilled and filled single-wall semiconducting and metallic carbon nanotubes
have been investigated theoretically, in the presence of electron-phonon and
phonon-phonon interactions. Excitation of low frequency optical plasmons in the
metallic nanotube is responsible for the peak known as the Breit-Wigner-Fano
(BWF) line shape in the G-band Raman spectra. In a filled nanotube there is an
additional peak due to excitation of the phonon of the filling atom or
molecule. Positions, shapes and relative strengths of these Raman peaks depend
on the phonon frequencies of the nanotube and that of the filling atoms, and
strengths and forms of the plasmon-phonon and phonon-phonon interactions. For
example, filling atoms with phonon frequency close to the RBM frequency of the
nanotube may broaden and lower the RBM Raman peak to such an extent that it may
become barely visible. Hybridization between the G-bands and the filling atom
phonon is also strong when these two frequencies are close to each other and it
has important effects on the G-band and the BWF line shapes. When the phonon
frequency of the filling atom is far from the RBM and G-band frequencies, it
gives rise to a separate peak with modest effects on the RBM and G-band
spectra. Raman spectra of semiconducting unfilled and filled nanotubes have
similar behavior as those of metallic nanotubes except that normally they have
Lorentzian line shapes and do not show a BWF line shape. However, if a
semiconducting nanotube is filled with donor atoms, it is predicted that the
BWF type line shape may be observed near the RBM, or the G-band or the filling
atom Raman peak.


title: Hunting long-lived gluinos at the Pierre Auger Observatory

abstract:
  Eventual signals of split sypersymmetry in cosmic ray physics are analyzed in
detail. The study focusses particularly on quasi-stable colorless R-hadrons
originating through confinement of long-lived gluinos (with quarks,
anti-quarks, and gluons) produced in pp collisions at astrophysical sources.
Because of parton density requirements, the gluino has a momentum which is
considerable smaller than the energy of the primary proton, and so production
of heavy (mass ~ 500 GeV) R-hadrons requires powerful cosmic ray engines able
to accelerate particles up to extreme energies, somewhat above 10^{13.6} GeV.
Using a realistic Monte Carlo simulation with the AIRES engine, we study the
main characteristics of the air showers triggered when one of these exotic
hadrons impinges on a stationary nucleon of the Earth atmosphere. We show that
R-hadron air showers present clear differences with respect to those initiated
by standard particles. We use this shower characteristics to construct
observables which may be used to distinguish long-lived gluinos at the Pierre
Auger Observatory.


title: H^\pm W^\mp production in the MSSM at the LHC

abstract:
  We investigate the viability of observing charged Higgs bosons (H^\pm)
produced in association with W bosons at the CERN Large Hadron Collider, using
the leptonic decay H^+ -> tau^+ nu_tau and hadronic W decay, within the Minimal
Supersymmetric Standard Model. Performing a parton level study we show how the
irreducible Standard Model background from W + 2 jets can be controlled by
applying appropriate cuts. In the standard m_h^max scenario we find a viable
signal for large tan beta and intermediate H^\pm masses (~ m_t).


title:
The ANTARES detector: background sources and effects on detector
  performance

abstract:
  The ANTARES Collaboration is deploying a large neutrino detector at a depth
of 2475 m in the Mediterranean Sea, 40 km off shore from La Seyne-sur-Mer in
South France. The construction of this 12-line detector with 75 phototubes per
line will be completed early 2008. Data taking has begun since April 2005 with
an instrumentation line also equipped with optical modules. The first 5
detector lines are operational since January 2007. The telescope is aimed to
observe high energy cosmic neutrinos through the detection of the Cerenkov
light produced by up-going induced muons. Background sources are due to
atmospheric neutrinos as well as misreconstructed atmospheric muons. Additional
backgrounds inherent to the sea water environment come from 40K decay and
marine organisms' luminescence. While the contribution of the former is
expected to be constant at a level of about 45 kHz, the bioluminescence has
shown large time variations, with periods of very high activity, up to several
hundred kHz. Description of these background sources will be reported, and
effects on detector performance will be described. Methods recently developed
to improve the detection efficiency in high background periods will be
described, together with some of the results obtained.


title: On the interaction between sharing and linearity

abstract:
  In the analysis of logic programs, abstract domains for detecting sharing and
linearity information are widely used. Devising abstract unification algorithms
for such domains has proved to be rather hard. At the moment, the available
algorithms are correct but not optimal, i.e., they cannot fully exploit the
information conveyed by the abstract domains. In this paper, we define a new
(infinite) domain ShLin-w which can be thought of as a general framework from
which other domains can be easily derived by abstraction. ShLin-w makes the
interaction between sharing and linearity explicit. We provide a constructive
characterization of the optimal abstract unification operator on ShLin-w and we
lift it to two well-known abstractions of ShLin-w. Namely, to the classical
Sharing X Lin abstract domain and to the more precise ShLin-2 abstract domain
by Andy King. In the case of single binding substitutions, we obtain optimal
abstract unification algorithms for such domains.
  To appear in Theory and Practice of Logic Programming (TPLP).


title:
Cu-Au type orderings in the staggered quadrupolar region of the fcc
  Blume Emery Griffiths model

abstract:
  The spin-1 Ising (BEG) model has been simulated using a cellular automaton
(CA) algorithm improved from the Creutz cellular automaton (CCA) for a
face-centered cubic (fcc) lattice. The ground state diagram ($k$, $d$) of the
fcc BEG model has ferromagnetic ($F$), quadrupolar ($Q$) and staggered
quadrupolar ($SQ$) ordering regions. The simulations have been made in the
staggered quadrupolar region for the parameter values in the intervals $
-24\leq d=D/J<0$ and $-3\leq k=K/J\leq 0$ . The phase diagrams on the ($
kT_{C}/J$, $d$) and the ($kT_{C}/J$, $k$) planes have been obtained through $
k=-3$ and $d=-4$ lines, respectively. The staggered quadrupolar ordering region
separates into five ordering regions ($A_{3}B(a)$, $A_{3}B(f)$, $AB$ (type-I),
$AB$(type-II) and $AB_{3}(f)$) which have the different stoichiometric Cu-Au
type structures.


title:
Parametrizing the lepton mixing matrix in terms of deviations from
  tri-bimaximal mixing

abstract:
  We propose a parametrization of the lepton mixing matrix in terms of an
expansion in powers of the deviations of the reactor, solar and atmospheric
mixing angles from their tri-bimaximal values. We show that unitarity triangles
and neutrino oscillation formulae have a very compact form when expressed in
this parametrization, resulting in considerable simplifications when dealing
with neutrino phenomenology. The parametrization, which is completely general,
should help to establish possible relations between the deviations of the
reactor, solar and atmospheric mixing angles from their tri-bimaximal values,
and hence enable models which predict such relations to be more directly
compared to experiment.


title:
The Problem of Localization in Networks of Randomly Deployed Nodes:
  Asymptotic and Finite Analysis, and Thresholds

abstract:
  We derive the probability that a randomly chosen NL-node over $S$ gets
localized as a function of a variety of parameters. Then, we derive the
probability that the whole network of NL-nodes over $S$ gets localized. In
connection with the asymptotic thresholds, we show the presence of asymptotic
thresholds on the network localization probability in two different scenarios.
The first refers to dense networks, which arise when the domain $S$ is bounded
and the densities of the two kinds of nodes tend to grow unboundedly. The
second kind of thresholds manifest themselves when the considered domain
increases but the number of nodes grow in such a way that the L-node density
remains constant throughout the investigated domain. In this scenario, what
matters is the minimum value of the maximum transmission range averaged over
the fading process, denoted as $d_{max}$, above which the network of NL-nodes
almost surely gets asymptotically localized.


title:
Harmonic oscillator model for current- and field-driven magnetic
  vortices

abstract:
  In experiments the distinction between spin-torque and Oersted-field driven
magnetization dynamics is still an open problem. Here, the gyroscopic motion of
current- and field-driven magnetic vortices in small thin-film elements is
investigated by analytical calculations and by numerical simulations. It is
found that for small harmonic excitations the vortex core performs an
elliptical rotation around its equilibrium position. The global phase of the
rotation and the ratio between the semi-axes are determined by the frequency
and the amplitude of the Oersted field and the spin torque.


title:
Preliminary results on the homogenization of thin piezoelectric
  perforated shells

abstract:
  We consider a composite piezoelectric material whose reference configuration
is a thin shell with fixed thickness. In this work, we give a new approach
based on the periodic unfolding method to justify the modelling of a thin
piezoelectric perforated shells and we establish the limit constitutive law by
letting the size of holes is supposed to go to zero. This allows to use the
homogenization technique to derive the limitting equations and the homogenizaed
coefficients are explicity described.


title: On the chemical freeze-out criteria in a hot and dense fireball

abstract:
  Intensive investigations of freeze-out criteria in a hot and dense fireball
provide important information regarding particle emission from the fireball. A
systematic comparison of these proposals is presented here in the framework of
a thermodynamically consistent excluded volume model which has been found to
describe the properties of hadron gas (HG) quite well. We find that the impact
of excluded volume correction is considerably large and the average energy per
hadron is 0.9 GeV, $n_b+n_{\bar b}$ stays nearly constant at 0.12/fm$^3$ and
the normalized entropy density $s/T^3\approx 6$ in this model. Moreover, these
values are independent of the beam or center-of-mass energy and also of the
target and beam nuclei. In ideal HG model these quantities show substantial
energy dependence. Further we have compared the predictions of various excluded
volume models in the precise determination of these criteria and we find that
the thermodynamically consistent excluded volume models give the best results.
In addition, we find another important criterion that entropy per hadron has a
constant value at 6 in our model. We hope that these findings will throw
considerable light on the expansion dynamics and the bulk thermodynamic
properties of the fireball before chemical freeze-out.


title:
Antiferromagnetic order driven by the molecular orbital order of
  C$_{60}$ in $\alpha'$--tetra--$kis$--(dimethylamino)--ethylene--C$_{60}$

abstract:
  We have studied the ground state of a fullerene--based magnet, the
$\alpha'$--phase tetra--$kis$--(dimethylamino)--ethylene--C$_{60}$
($\alpha'$--TDAE--C$_{60}$), by electron spin resonance (ESR) and magnetic
torque measurements. Below T$_N=7$ K, non--paramagnetic field dependent
resonances with a finite excitation gap (1.7 GHz) are observed along the
$a$--axis. Strong enhancement in their intensity as temperature is decreased is
inconsistent with excitation from a singlet state, which had been proposed for
the $\alpha'$--phase ground state. Below T$_N$, non--quadratic field dependence
of magnetic torque signal is also observed in contrast to quadratic field
dependence in the paramagnetic phase. The angle--dependent torque signals below
T$_N$ indicate the existence of an anisotropy of the bulk magnetization. From
both experiments, we propose an antiferromagnetic ground state driven by the
cooperative orientational ordering of C$_{60}$ in the
$\alpha'$--TDAE--C$_{60}$.


title: Chiral Limit and Light Quark Masses in 2+1 Flavor Domain Wall QCD

abstract:
  We present results for meson masses and decay constants measured on 24^3x64
lattices using the domain wall fermion formulation with an extension of the
fifth dimension of L_s=16 for N_f=2+1 dynamical quark flavors. The lightest
dynamical meson mass in our set-up is around 331 MeV, while partially quenched
mesons reach masses as low as 250 MeV. The applicability of SU(3)xSU(3) and
SU(2)xSU(2) (partially quenched) chiral perturbation theory will be compared
and we quote values for the low-energy constants from both approaches. We will
extract the average light quark and strange quark masses and use a
non-perturbative renormalization technique (RI/MOM) to quote their physical
values. The pion and kaon decay constants are determined at those values from
our chiral fits and their ratio is used to obtain the CKM-matrix element
|V_us|. The results presented here include statistical errors only.


title:
Dispersion Law of the Form $\epsilon(p)=\hbar^2p^2/2m +\widetilde
  V(p)-\widetilde V(0)$ for Elementary Excitations of Nonideal Fermi Gas in the
  Pair Interaction Approximation $(i\leftrightarrow j)$, $V(|x_i-x_j|)$

abstract:
  We give a derivation of the dispersion law $\epsilon(p)=\hbar^2p^2/2m
+\widetilde V(p)-\widetilde V(0)$, where $\widetilde V(p)$ is the Fourier
transform of the pair interaction potential $V(r)$. (The interaction between
particles $x_i$ and $x_j$ is $V(|x_i-x_j|)$.)


title: Gap theory of rectification in ballistic three-terminal conductors

abstract:
  We introduce a model for rectification in three-terminal ballistic
conductors, where the central connecting node is modeled as a chaotic cavity.
For bias voltages comparable to the Fermi energy, a strong nonlinearity is
created by the opening of a gap in the transport window. Both noninteracting
cavity electrons at arbitrary temperature as well as the hot electron regime
are considered. Charging effects are treated within the transmission formalism
using a self-consistent analysis. The conductance of the third lead in a
voltage probe configuration is varied to also model inelastic effects. We find
that the basic transport features are insensitive to all of these changes,
indicating that the nonlinearity is robust and well suited to applications such
as current rectification in ballistic systems. Our findings are in broad
agreement with several recent experiments.


title: A Novel Solution to the ATT48 Benchmark Problem

abstract:
  A solution to the benchmark ATT48 Traveling Salesman Problem (from the
TSPLIB95 library) results from isolating the set of vertices into ten
open-ended zones with nine lengthwise boundaries. In each zone, a
minimum-length Hamiltonian Path (HP) is found for each combination of boundary
vertices, leading to an approximation for the minimum-length Hamiltonian Cycle
(HC). Determination of the optimal HPs for subsequent zones has the effect of
automatically filtering out non-optimal HPs from earlier zones. Although the
optimal HC for ATT48 involves only two crossing edges between all zones (with
one exception), adding inter-zone edges can accommodate more complex problems.


title: A disc in the heart of the Ant nebula

abstract:
  We present the discovery of a silicate disc at the centre of the planetary
nebula Mz3 (the Ant). The nebula was observed with MIDI on the Very Large
Telescope Interferometer (VLTI). The visibilities obtained at different
orientations clearly indicate the presence of a dusty, nearly edge-on disc in
the heart of the nebula. An amorphous silicate absorption feature is clearly
seen in our mid-IR spectrum and visibility curves. We used radiative transfer
Monte Carlo simulations to constrain the geometrical and physical parameters of
the disc. We derive an inner radius of 9 AU (~6mas assuming D=1.4kpc). This
disc is perpendicular to, but a factor of 10^{3} smaller than the optical
bipolar outflow.


title: Chiral Analysis of the Generalized Form Factors of the Nucleon

abstract:
  We apply the methods of Chiral Perturbation Theory to the analysis of the
first moments of the Generalized Parton Distributions in a Nucleon, usually
known as generalized form factors. These quantities are currently also under
investigation in Lattice QCD analyses of baryon structure, providing simulation
results at large quark masses to be extrapolated to the "real world" via Chiral
Effective Field Theory. We have performed a leading-one-loop calculation in the
covariant framework of Baryon Chiral Perturbation Theory (BChPT), predicting
both the momentum and the quark-mass dependence for all the vector and axial
(generalized) form factors. In particular we discuss the results for the limit
of vanishing four-momentum transfer where the GPD-moments reduce to the well
known moments of Parton Distribution Functions (PDFs). We fit our results to
available lattice QCD data, extrapolating down to the physical point. We
conclude by presenting outstanding results from a combined fit to different
GPDs-moments.


title: Nuclear skin emergence in Skyrme deformed Hartree-Fock calculations

abstract:
  A study of the charge and matter densities and the corresponding rms radii
for even-even isotopes of Ni, Kr, and Sn has been performed in the framework of
deformed self-consistent mean field Skyrme HF+BCS method. The resulting charge
radii and neutron skin thicknesses of these nuclei are compared with available
experimental data, as well as with other theoretical predictions. The formation
of a neutron skin, which manifests itself in an excess of neutrons at distances
greater than the radius of the proton distribution, is analyzed in terms of
various definitions. Formation of a proton skin is shown to be unlikely. The
effects of deformation on the neutron skins in even-even deformed nuclei far
from the stability line are discussed.


title: Bounds on the Light Quark Masses: the scalar channel revisited

abstract:
  We evaluate lower bounds on the sum of the up and down quark masses. The
bounds follow from the constraints provided by the dispersion relation obeyed
by the two--point function of the scalar current density when combined with
properties of the scalar spectral function at long--distances and perturbative
QCD at short--distances. Our results point to values of $m_u+m_d$ somewhat
higher than those reported recently in the literature using lattice QCD
simulations.


title:
Scalar-tensor analysis of an exponential Lagrangian for the
  Gravitational Field

abstract:
  Within the scheme of modified gravity, an exponential Lagrangian density will
be considered, and the corresponding scalar-tensor description will be
addressed for both positive and negative values of the cosmological constant.
For negative values of the cosmological term, the potential of the scalar field
exhibits a minimum, around which scalar-field equations can be linearized. The
study of the deSitter regime shows that a comparison with the modified-gravity
description is possible in an off-shell region, i.e., in a region where the
classical equivalence between the two formulations is not fulfilled.
Furthermore, despite the negative cosmological constant, an accelerating
deSitter phase is predicted in the region where the series expansion of the
exponential term does not hold. For positive values of the cosmological
constant, the quantum regime is analyzed within the framework of Loop Quantum
Cosmology.


title: Synchrotron emission from secondary leptons in microquasar jets

abstract:
  We present a model to estimate the synchrotron radio emission generated in
microquasar (MQ) jets due to secondary pairs created via decay of charged pions
produced in proton-proton collisions between stellar wind ions and jet
relativistic protons. Signatures of electrons/positrons are obtained from
consistent particle energy distributions that take into account energy losses
due to synchrotron and inverse Compton (IC) processes, as well as adiabatic
expansion. The space parameter for the model is explored and the corresponding
spectral energy distributions (SEDs) are presented. We conclude that secondary
leptonic emission represents a significant though hardly dominant contribution
to the total radio emission in MQs, with observational consequences that can be
used to test some still unknown processes occurring in these objects as well as
the nature of the matter outflowing in their jets.


title: Surface Flows From Magnetograms

abstract:
  Estimates of velocities from time series of photospheric and/or chromospheric
vector magnetograms can be used to determine fluxes of magnetic energy (the
Poynting flux) and helicity across the magnetogram layer, and to provide
time-dependent boundary conditions for data-driven simulations of the solar
atmosphere above this layer. Velocity components perpendicular to the magnetic
field are necessary both to compute these transport rates and to derive model
boundary conditions. Here, we discuss some possible approaches to estimating
perpendicular flows from magnetograms. Since Doppler shifts contain
contributions from flows parallel to the magnetic field, perpendicular
velocities are not generally recoverable from Doppler shifts alone. The
induction equation's vertical component relates evolution in $B_z$ to the
perpendicular flow field, but has a finite null space, meaning some ``null''
flows, e.g., motions along contours of normal field, do not affect $B_z$.
Consequently, additional information is required to accurately specify the
perpendicular flow field. Tracking methods, which analyze $\partial_t B_z$ in a
neighborhood, have a long heritage, but other approaches have recently been
developed. In a recent paper, several such techniques were tested using
synthetic magnetograms from MHD simulations. Here, we use the same test data to
characterize: 1) the ability of the induction equation's normal component, by
itself, to estimate flows; and 2) a tracking method's ability to recover flow
components that are perpendicular to $\mathbf{B}$ and parallel to contours of
$B_z$. This work has been supported by NASA Heliophysics Theory grant
NNG05G144G.


title: Anatomy of a Young Massive Star Cluster: NGC 1569-B

abstract:
  We present new H-band echelle spectra, obtained with the NIRSPEC spectrograph
at Keck II, for the massive star cluster "B" in the nearby dwarf irregular
galaxy NGC 1569. From spectral synthesis and equivalent width measurements we
obtain abundances and abundance patterns. We derive an Fe abundance of
[Fe/H]=-0.63+/-0.08, a super-solar [alpha/Fe] abundance ratio of +0.31+/-0.09,
and an O abundance of [O/H]=-0.29+/-0.07. We also measure a low 12C/13C = 5+/-1
isotopic ratio. Using archival imaging from the Advanced Camera for Surveys on
board HST, we construct a colour-magnitude diagram (CMD) for the cluster in
which we identify about 60 red supergiant (RSG) stars, consistent with the
strong RSG features seen in the H-band spectrum. The mean effective temperature
of these RSGs, derived from their observed colours and weighted by their
estimated H-band luminosities, is 3790 K, in excellent agreement with our
spectroscopic estimate of Teff = 3800+/-200 K. From the CMD we derive an age of
15-25 Myr, slightly older than previous estimates based on integrated
broad-band colours. We derive a radial velocity of -78+/-3 km/s and a velocity
dispersion of 9.6+/-0.3 km/s. In combination with an estimate of the half-light
radius of 0.20"+/-0.05" from the HST data, this leads to a dynamical mass of
(4.4+/-1.1)E5 Msun. The dynamical mass agrees very well with the mass predicted
by simple stellar population models for a cluster of this age and luminosity,
assuming a normal stellar IMF. The cluster core radius appears smaller at
longer wavelengths, as has previously been found in other extragalactic young
star clusters.


title:
Analyticity constraints on the strangeness changing vector current and
  applications to $\tau\to K\pi \nu_\tau$, $\tau\to K\pi\pi \nu_\tau$

abstract:
  We discuss matrix elements of the strangeness changing vector current using
their relation, due to analyticity, with $\pi K$ scattering in the $P$-wave. We
take into account experimental phase-shift measurements in the elastic channel
as well as results, obtained by the LASS collaboration, on the details of
inelastic scattering, which show the dominance of two quasi two-body channels
at medium energies.The associated form factors are shown to be completely
determined, up to one flavour symmetry breaking parameter, imposing boundary
conditions at $t=0$ from chiral and flavour symmetries and at $t\to\infty$ from
QCD. We apply the results to the $\tau\to K\pi \nu_\tau$ and $\tau\to K\pi\pi
\nu_\tau$ amplitudes and compare the former to recent high statistics results
from B factories.


title:
Coulomb gauge Green functions and Gribov copies in SU(2) lattice gauge
  theory

abstract:
  We reconsider the lattice measurement of Green functions in Coulomb gauge,
both in 2+1 and 3+1 dimensions, using an improved gauge fixing scheme. The
influence of Gribov copies is examined and we find clear indications that Green
functions are more strongly affected than previously assumed, in particular for
low momenta. Qualitatively, our improved lattice results in the infra-red
compare more favourably with recent continuum calculations in the Hamiltonian
approach.


title: Community Detection in Complex Networks by Dynamical Simplex Evolution

abstract:
  We benchmark the dynamical simplex evolution (DSE) method with several of the
currently available algorithms to detect communities in complex networks by
comparing the fraction of correctly identified nodes for different levels of
``fuzziness'' of random networks composed of well defined communities. The
potential benefits of the DSE method to detect hierarchical sub structures in
complex networks are discussed.


title: 2+1 flavor QCD with the fixed point action in the $\epsilon$-regime

abstract:
  We generated configurations with the approximate fixed-point Dirac operator
$D_\mathrm{FP}$ on a $12^4$ lattice with $a \approx 0.13 $fm where the scale
was set by $r_0$. The distributions of the low lying eigenvalues in different
topological sectors were compared with those of the Random Matrix Theory which
leads to a prediction of the chiral condensate.


title: High loop renormalization constants by NSPT: a status report

abstract:
  We present an update on Numerical Stochastic Perturbation Theory projects for
Lattice QCD, which are by now run on apeNEXT. As a first issue, we discuss a
strategy to tackle finite size effects which can be quite sizeable in the
computation of logarithmically divergent renormalization constants. Our first
high loop determination of quark bilinears for Wilson fermions was limited to
finite constants and finite ratios. A precise determination of Z_P and Z_S (and
hence of Z_m) now becomes possible. We also give an account of computations for
actions different from the standard regularization we have taken into account
so far (Wilson gauge action and Wilson fermions). In particular, we present the
status of computations for the Lattice QCD regularization defined by tree level
Symanzik improved gauge action and Wilson fermions, which became quite popular
in recent times. We also take the chance to discuss the related topic of the
computation of the gluon and ghost propagators (which we undertook in
collaboration with another group). This is relevant in order to better
understand non-perturbative computations of propagators aiming at
qualitative/quantitative understanding of confinement.


title:
Zooming in on light relic neutralinos by direct detection and
  measurements of galactic antimatter

abstract:
  The DAMA Collaboration has recently analyzed its data of the extensive WIMP
direct search (DAMA/NaI) which detected an annual modulation, by taking into
account the channelling effect which occurs when an ion traverses a detector
with a crystalline structure. Among possible implications, this Collaboration
has considered the case of a coherent WIMP-nucleus interaction and then derived
the form of the annual modulation region in the plane of the WIMP-nucleon cross
section versus the WIMP mass, using a specific modelling for the channelling
effect. In the present paper we first show that light neutralinos fit the
annual modulation region also when channelling is taken into account. To
discuss the connection with indirect signals consisting in galactic antimatter,
in our analysis we pick up a specific galactic model, the cored
isothermal-sphere. In this scheme we determine the sets of supersymmetric
models selected by the annual modulation regions and then prove that these sets
are compatible with the available data on galactic antiprotons. We comment on
implications when other galactic distribution functions are employed. Finally,
we show that future measurements on galactic antiprotons and antideuterons will
be able to shed further light on the populations of light neutralinos singled
out by the annual modulation data.


title: CP Violation and Neutrino Oscillations

abstract:
  We review the basic mechanisms of neutrino mass generation and the
corresponding structure of the lepton mixing matrix. We summarize the status of
three-neutrino oscillation parameters as determined from current observations,
using state-of-the-art solar and atmospheric neutrino fluxes, as well as latest
experimental data as of September 2007. We also comment on recent attempts to
account for these results and to understand flavour from first principles. We
discuss extensively the prospects for probing the strength of CP violation in
two near term accelerator neutrino oscillation experiments, T2K and NOvA, as
well as possible extensions such as T2KK and a second large off-axis detector
near the NOvA detector. We also briefly discuss the possibility of probing the
effect of Majorana phases in future neutrinoless double beta decay searches and
discuss other implications of leptonic CP violation such as leptogenesis.
Finally we comment on the issue of robustness of the current oscillation
interpretation and possible ways of probing for non-standard neutrino
interactions in precision oscillation studies.


title: Investigation of one boundary-value problem for elliptic type equation

abstract:
  The goal of the paper is to study a spectral problem corresponding to the
mixed problem for a sixth order weak parabolic equation.


title: A Game Theoretic Approach to Quantum Information

abstract:
  This work is an application of game theory to quantum information. In a state
estimate, we are given observations distributed according to an unknown
distribution $P_{\theta}$ (associated with award $Q$), which Nature chooses at
random from the set $\{P_{\theta}: \theta \in \Theta \}$ according to a known
prior distribution $\mu$ on $\Theta$, we produce an estimate $M$ for the
unknown distribution $P_{\theta}$, and in the end, we will suffer a relative
entropy cost $\mathcal{R}(P;M)$, measuring the quality of this estimate,
therefore the whole utility is taken as $P \cdot Q -\mathcal{R}(P; M)$.
  In an introduction to strategic game, a sufficient condition for minimax
theorem is obtained; An estimate is explored in the frame of game theory, and
in the view of convex conjugate, we reach one new approach to quantum relative
entropy, correspondingly quantum mutual entropy, and quantum channel capacity,
which are more general, in the sense, without Radon-Nikodym (RN) derivatives.
Also the monotonicity of quantum relative entropy and the additivity of quantum
channel capacity are investigated.


title:
Trace ideals for pseudo-differential operators and their commutators
  with symbols in $\alpha$-modulation spaces

abstract:
  In this paper, we consider the trace property of pseudo-differential
operators with symbols in $\alpha$-modulation spaces.


title: The Stellar Mass Distribution in the Giant Star Forming Region NGC 346

abstract:
  Deep F555W and F814W Hubble Space Telescope ACS images are the basis for a
study of the present day mass function (PDMF) of NGC346, the largest active
star forming region in the Small Magellanic Cloud (SMC). We find a PDMF slope
of Gamma=-1.43+/-0.18 in the mass range 0.8-60 Mo, in excellent agreement with
the Salpeter Initial Mass Function (IMF) in the solar neighborhood. Caveats on
the conversion of the PDMF to the IMF are discussed. The PDMF slope changes, as
a function of the radial distance from the center of the NGC 346 star cluster,
indicating a segregation of the most massive stars. This segregation is likely
primordial considering the young age (~3 Myr) of NGC346, and its clumpy
structure which suggests that the cluster has likely not had sufficient time to
relax. Comparing our results for NGC346 with those derived for other star
clusters in the SMC and the Milky Way (MW), we conclude that, while the star
formation process might depend on the local cloud conditions, the IMF does not
seem to be affected by general environmental effects such as galaxy type,
metallicity, and dust content.


title:
Panel and Pseudo-Panel Estimation of Cross-Sectional and Time Series
  Elasticities of Food Consumption: The Case of American and Polish Data

abstract:
  The problem addressed in this article is the bias to income and expenditure
elasticities estimated on pseudo-panel data caused by measurement error and
unobserved heterogeneity. We gauge empirically these biases by comparing
cross-sectional, pseudo-panel and true panel data from both Polish and American
expenditure surveys. Our results suggest that unobserved heterogeneity imparts
a downward bias to cross-section estimates of income elasticities of at-home
food expenditures and an upward bias to estimates of income elasticities of
away-from-home food expenditures. "Within" and first-difference estimators
suffer less bias, but only if the effects of measurement error are accounted
for with instrumental variables.


title: The lattice gluon propagator in stochastic perturbation theory

abstract:
  We calculate loop contributions up to four loops to the Landau gauge gluon
propagator in numerical stochastic perturbation theory. For different lattice
volumes we carefully extrapolate the Euler time step to zero for the Langevin
dynamics derived from the Wilson action. The one-loop result for the gluon
propagator is compared to the infinite volume limit of standard lattice
perturbation theory.


title: Extragalactic Surveys: AGN physics and evolution

abstract:
  We review the most important findings on AGN physics and cosmological
evolution as obtained by extragalactic X-ray surveys and associated
multiwavelength observations. We briefly discuss the perspectives for future
enterprises and in particular the scientific case for an extremely deep (2-3
Ms) XMM survey.


title: On the Origin of Strong-Field Polarity Inversion Lines

abstract:
  Several studies have correlated observations of impulsive solar activity --
flares and coronal mass ejections (CMEs) -- with the amount of magnetic flux
near strong-field polarity inversion lines (PILs) in active regions'
photospheric magnetic fields, as measured in line-of-sight (LOS) magnetograms.
Practically, this empirical correlation holds promise as a space weather
forecasting tool. Scientifically, however, the mechanisms that generate strong
gradients in photospheric magnetic fields remain unknown. Hypotheses include:
the (1) emergence of highly twisted or kinked flux ropes, which possess strong,
opposite-polarity fields in close proximity; (2) emergence of new flux in close
proximity to old flux; and (3) flux cancellation driven by photospheric flows
acting fields that have already emerged. If such concentrations of flux near
strong gradients are formed by emergence, then increases in unsigned flux near
strong gradients should be correlated with increases in total unsigned magnetic
flux -- a signature of emergence. Here, we analyze time series of MDI
line-of-sight (LOS) magnetograms from several dozen active regions, and
conclude that increases in unsigned flux near strong gradients tend to occur
during emergence, though strong gradients can arise without flux emergence. We
acknowledge support from NSF-ATM 04-51438.


title: Newly observed charmed states: the case of X(3872)

abstract:
  I briefly review the properties of the hidden charm meson X(3872), discussing
some puzzling aspects concerning its theoretical interpretation.


title: TP Decoding

abstract:
  `Tree pruning' (TP) is an algorithm for probabilistic inference on binary
Markov random fields. It has been recently derived by Dror Weitz and used to
construct the first fully polynomial approximation scheme for counting
independent sets up to the `tree uniqueness threshold.' It can be regarded as a
clever method for pruning the belief propagation computation tree, in such a
way to exactly account for the effect of loops.
  In this paper we generalize the original algorithm to make it suitable for
decoding linear codes, and discuss various schemes for pruning the computation
tree. Further, we present the outcomes of numerical simulations on several
linear codes, showing that tree pruning allows to interpolate continuously
between belief propagation and maximum a posteriori decoding. Finally, we
discuss theoretical implications of the new method.


title:
Quantum key distribution using a triggered quantum dot source emitting
  near 1.3 microns

abstract:
  We report the distribution of a cryptographic key, secure from photon number
splitting attacks, over 35 km of optical fiber using single photons from an
InAs quantum dot emitting ~1.3 microns in a pillar microcavity. Using below
GaAs-bandgap optical excitation, we demonstrate suppression of multiphoton
emission to 10% of the Poissonian level without detector dark count
subtraction. The source is incorporated into a phase encoded interferometric
scheme implementing the BB84 protocol for key distribution over standard
telecommunication optical fiber. We show a transmission distance advantage over
that possible with (length-optimized) uniform intensity weak coherent pulses at
1310 nm in the same system.


title:
Post-Outburst Observations of V1647 Ori: Detection of a Brief Warm,
  Molecular Outflow

abstract:
  We present new observations of the fundamental ro-vibrational CO spectrum of
V1647 Ori, the young star whose recent outburst illuminated McNeil's Nebula.
Previous spectra, acquired during outburst in 2004 February and July, had shown
the CO emission lines to be broad and centrally peaked-similar to the CO
spectrum of a typical classical T Tauri star. In this paper, we present CO
spectra acquired shortly after the luminosity of the source returned to its
pre-outburst level (2006 February) and roughly one year later (2006 December
and 2007 February). The spectrum taken in 2006 February revealed blue-shifted
CO absorption lines superimposed on the previously observed CO emission lines.
The projected velocity, column density, and temperature of this outflowing gas
was 30 km/s, 3^{+2}_{-1}E18 cm^{-2$, and 700^{+300}_{-100} K, respectively. The
absorption lines were not observed in the 2006 December and 2007 February data,
and so their strengths must have decreased in the interim by a factor of 9 or
more. We discuss three mechanisms that could give rise to this unusual outflow.


title:
Dynamical Wave Function Collapse: Could It Have Cosmological
  Consequences?

abstract:
  This talk was in response to the conference injunction to present "one bold
but half-baked idea that you have been thinking about recently.. .". After a
brief introduction to the ideas and formalism of the CSL theory of dynamical
wave function collapse, some possible cosmological effects associated with
applying it to the creation of the universe are discussed.


title: Sparticle masses from hadronic decays

abstract:
  We present our work on reconstructing sparticle masses in purely hadronic
decay chains, using the $k_T$ jet-algorithm on Monte Carlo simulated events at
LHC energies.


title: Twisted mass QCD at finite temperature

abstract:
  We discuss the use of Wilson fermions with twisted mass for simulations of
QCD thermodynamics. As a prerequisite for a future analysis of the
finite-temperature transition making use of automatic O(a) improvement, we
investigate the phase structure in the space spanned by the hopping parameter
kappa, the coupling beta, and the twisted mass parameter mu. We present results
for N_f=2 degenerate quarks on a 16^3x8 lattice, for which we investigate the
possibility of an Aoki phase existing at strong coupling and vanishing mu, as
well as of a thermal phase transition at moderate gauge couplings and
non-vanishing mu.


title: Dirac phase leptogenesis

abstract:
  I present here a concise summary of the preprint arXiv:0707.3024, written in
collaboration with A. Anisimov and P. Di Bari. There we discuss leptogenesis
when {\em CP} violation stems exlusively from the Dirac phase in the PMNS
mixing matrix. Under this assumption it turns out that the situation is very
constrained when a hierarchical heavy right-handed (RH) neutrino spectrum is
considered: the allowed regions are small and the final asymmetry depends on
the initial conditions. On the other hand, for a quasi-degenerate spectrum of
RH neutrinos, the {\em CP} asymmetry can be enhanced and the situation becomes
much more favorable, with no dependence on the initial conditions.
Interestingly, in the extreme case of resonant leptogenesis, in order to match
the observed baryon asymmetry of the Universe, we obtain a lower bound on \sin
\q_{13} which depends on the lightest active neutrino mass m_1.


title: Analytic Expressions for Geometric Measure of Three Qubit States

abstract:
  A new method is developed to derive an algebraic equations for the geometric
measure of entanglement of three qubit pure states. The equations are derived
explicitly and solved in cases of most interest. These equations allow oneself
to derive the analytic expressions of the geometric entanglement measure in the
wide range of the three qubit systems, including the general class of W-states
and states which are symmetric under permutation of two qubits. The nearest
separable states are not necessarily unique and highly entangled states are
surrounded by the one-parametric set of equally distant separable states. A
possibility for the physical applications of the various three qubit states to
quantum teleportation and superdense coding is suggested from the aspect of the
entanglement.


title: The diagonal of the Stasheff polytope

abstract:
  We construct an A-infinity structure on the tensor product of two A-infinity
algebras by using the simplicial decomposition of the Stasheff polytope. The
key point is the construction of an operad AA-infinity based on the simplicial
Stasheff polytope. The operad AA-infinity admits a coassociative diagonal and
the operad A-infinity is a retract by deformation of it. We compare these
constructions with analogous constructions due to Saneblidze-Umble and
Markl-Shnider based on the Boardman-Vogt cubical decomposition of the Stasheff
polytope.


title: Nonlinear Brownian Motion and Higgs Mechanism

abstract:
  An extension of the stochastic quantization scheme is proposed by adding
nonlinear terms to the field equations. Our modification is motivated by the
recently established theory of active Brownian motion. We discuss a way of
promoting this theory to the case of infinite degrees of freedom. Equilibrium
distributions can be calculated exactly and are interpreted as path integral
densities of quantum field theories. By applying our procedure to scalar QED,
the symmetry breaking potential of the Higgs mechanism arises as the
equilibrium solution.


title:
Combinatorial Aspects of Elliptic Curves II: Relationship between
  Elliptic Curves and Chip-Firing Games on Graphs

abstract:
  Let q be a power of a prime and E be an elliptic curve defined over F_q. In
"Combinatorial aspects of elliptic curves" [17], the present author examined a
sequence of polynomials which express the N_k's, the number of points on E over
the field extensions F_{q^k}, in terms of the parameters q and N_1 = #E(F_q).
These polynomials have integral coefficients which alternate in sign, and a
combinatorial interpretation in terms of spanning trees of wheel graphs. In
this sequel, we explore further ramifications of this connection. In
particular, we highlight a relationship between elliptic curves and chip-firing
games on graphs by comparing the groups structures of both. As a coda, we
construct a cyclic rational language whose zeta function is dual to that of an
elliptic curve.


title: Hadronic photon-photon scattering at LEP

abstract:
  Hadronic interactions of two quasi-real photons have been studied extensively
both during the LEP1 and the LEP2 data taking periods. The higher energies
available at LEP2 in particular opened regions of phase space where hadronic
processes can be predicted reliably by perturbative QCD calculations, usually
available to next-to-leading order in the strong coupling constant for the
process concerned. Over a wide range of observables and phase space good
agreement is observed between measurements and theory, however, there are a few
exceptions. The L3 collaboration has found large discrepancies for high
momentum particle and jet production between theory and experiment, and
measurements of open b-quark production by DELPHI, L3, and OPAL are
consistently in excess of the theoretical values. Three new measurements have
now become available and will be discussed in this paper: on jet and hadron
production by OPAL and open beauty production by ALEPH.


title:
Shrinkage and spectral filtering of correlation matrices: a comparison
  via the Kullback-Leibler distance

abstract:
  The problem of filtering information from large correlation matrices is of
great importance in many applications. We have recently proposed the use of the
Kullback-Leibler distance to measure the performance of filtering algorithms in
recovering the underlying correlation matrix when the variables are described
by a multivariate Gaussian distribution. Here we use the Kullback-Leibler
distance to investigate the performance of filtering methods based on Random
Matrix Theory and on the shrinkage technique. We also present some results on
the application of the Kullback-Leibler distance to multivariate data which are
non Gaussian distributed.


title:
Multi-Orbital Lattice Model for (Ga,Mn)As and Other Lightly Magnetically
  Doped Zinc-Blende-Type Semiconductors

abstract:
  We present a Hamiltonian in real space which is well suited to study
numerically the behavior of holes introduced in III-V semiconductors by Mn
doping when the III$^{3+}$ ion is replaced by Mn$^{2+}$. We consider the actual
lattice with the diamond structure. Since the focus is on light doping by
acceptors, a bonding combination of III and V p-orbitals is considered since
the top of the valence band, located at the $\Gamma$ point, has p character in
these materials. As a result, an effective model in which the holes hop between
the sites of an fcc lattice is obtained. We show that around the $\Gamma$ point
in momentum space the Hamiltonian for the undoped case is identical to the one
for the Luttinger-Kohn model. The spin-orbit interaction is included as well as
the on-site interaction between the spin of the magnetic impurity and the spin
of the doped holes. The effect of Coulomb interactions between Mn$^{2+}$ and
holes, as well as Mn$^{3+}$ doping are discussed. Through large-scale Monte
Carlo simulations on a Cray XT3 supercomputer, we show that this model
reproduces many experimental results for ${\rm Ga_{\it 1-x}Mn_{\it x}As}$ and
${\rm Ga_{\it 1-x}Mn_{\it x}Sb}$, and that the Curie temperature does not
increase monotonically with $x$. The cases of Mn doped GaP and GaN, in which
Mn$^{3+}$ is believed to play a role, are also studied.


title: The B-meson mass splitting from non-perturbative quenched lattice QCD

abstract:
  We perform the non-perturbative (quenched) renormalization of the
chromo-magnetic operator in Heavy Quark Effective Theory and its three-loop
matching to QCD. At order 1/m of the expansion, the operator is responsible for
the mass splitting between the pseudoscalar and vector B-mesons. These new
computed factors are affected by an uncertainty negligible in comparison to the
known bare matrix element of the operator between B-states. Furthermore, they
push the quenched determination of the spin splitting for the Bs-meson much
closer to its experimental value than the previous perturbatively renormalized
computations. The renormalization factor for three commonly used heavy quark
actions and the Wilson gauge action and useful parametrizations of the matching
coefficient are provided.


title:
Late stages of the evolution of A-type stars on the main sequence:
  comparison between observed chemical abundances and diffusion models for 8 Am
  stars of the Praesepe cluster

abstract:
  Aims. We aim to provide observational constraints on diffusion models that
predict peculiar chemical abundances in the atmospheres of Am stars. We also
intend to check if chemical peculiarities and slow rotation can be explained by
the presence of a weak magnetic field.
  Methods. We have obtained high resolution, high signal-to-noise ratio spectra
of eight previously-classified Am stars, two normal A-type stars and one Blue
Straggler, considered to be members of the Praesepe cluster. For all of these
stars we have determined fundamental parameters and photospheric abundances for
a large number of chemical elements, with a higher precision than was ever
obtained before for this cluster. For seven of these stars we also obtained
spectra in circular polarization and applied the LSD technique to constrain the
longitudinal magnetic field.
  Results. No magnetic field was detected in any of the analysed stars. HD
73666, a Blue Straggler previously considered as an Ap (Si) star, turns out to
have the abundances of a normal A-type star. Am classification is not confirmed
for HD 72942. For HD 73709 we have also calculated synthetic Delta-a photometry
that is in good agreement with the observations. There is a generally good
agreement between abundance predictions of diffusion models and values that we
have obtained for the remaining Am stars. However, the observed Na and S
abundances deviate from the predictions by 0.6 dex and >0.25 dex respectively.
Li appears to be overabundant in three stars of our sample.


title: Primordial magnetic fields at preheating

abstract:
  Using lattice techniques we investigate the generation of long range
cosmological magnetic fields during a cold electroweak transition. We will show
how magnetic fields arise, during bubble collisions, in the form of magnetic
strings. We conjecture that these magnetic strings originate from the alignment
of magnetic dipoles associated with EW sphaleron-like configurations. We also
discuss the early thermalisation of photons and the turbulent behaviour of the
scalar fields after tachyonic preheating.


title:
Quark and lepton masses and mixing in SO(10) with a GUT-scale vector
  matter

abstract:
  We explore in detail the effective matter fermion mass sum-rules in a class
of renormalizable SUSY SO(10) grand unified models where the quark and lepton
mass and mixing patterns originate from non-decoupling effects of an extra
vector matter multiplet living around the unification scale. If the
renormalizable type-II contribution governed by the SU(2)_L-triplet in 54_H
dominates the seesaw formula, we obtain an interesting correlation between the
maximality of the atmospheric neutrino mixing and the proximity of y_s/y_b to
V_cb in the quark sector.


title: Quantum Spin Hall Insulator State in HgTe Quantum Wells

abstract:
  Recent theory predicted that the Quantum Spin Hall Effect, a fundamentally
novel quantum state of matter that exists at zero external magnetic field, may
be realized in HgTe/(Hg,Cd)Te quantum wells. We have fabricated such sample
structures with low density and high mobility in which we can tune, through an
external gate voltage, the carrier conduction from n-type to the p-type,
passing through an insulating regime. For thin quantum wells with well width d
< 6.3 nm, the insulating regime shows the conventional behavior of vanishingly
small conductance at low temperature. However, for thicker quantum wells (d >
6.3 nm), the nominally insulating regime shows a plateau of residual
conductance close to 2e^2/h. The residual conductance is independent of the
sample width, indicating that it is caused by edge states. Furthermore, the
residual conductance is destroyed by a small external magnetic field. The
quantum phase transition at the critical thickness, d = 6.3 nm, is also
independently determined from the magnetic field induced insulator to metal
transition. These observations provide experimental evidence of the quantum
spin Hall effect.


title: The SF running coupling with four flavours of staggered quarks

abstract:
  In order to study the running coupling in four-flavour QCD, we review the
set-up of the Schr\"odinger functional (SF) with staggered quarks. Staggered
quarks require lattices which, in the usual counting, have even spatial lattice
extent $L/a$ while the time extent $T/a$ must be odd. Setting $T=L$ is
therefore only possible up to ${\rm O}(a)$, which introduces different cutoff
effects already in the pure gauge theory. We re-define the SF such as to cope
with this situation and determine the corresponding classical background field.
A perturbative calculation yields the coefficient of the pure gauge ${\rm
O}(a)$ boundary counterterm to one-loop order.


title: Exotic physics with ultrahigh energy cosmic rays

abstract:
  Ultrahigh energy cosmic rays provide a unique ground for probing new physics.
In this talk we review the possibility of testing TeV gravity in interactions
of cosmogenic neutrinos and the potential to discover long-lived exotic
particles in nucleon-produced air showers, such as gluinos of split-SUSY models
or staus of supersymmetric models with a gravitino LSP.