title: Nonnegative Factorization and The Maximum Edge Biclique Problem

abstract:
  Nonnegative Matrix Factorization (NMF) is a data analysis technique which
allows compression and interpretation of nonnegative data. NMF became widely
studied after the publication of the seminal paper by Lee and Seung (Learning
the Parts of Objects by Nonnegative Matrix Factorization, Nature, 1999, vol.
401, pp. 788--791), which introduced an algorithm based on Multiplicative
Updates (MU). More recently, another class of methods called Hierarchical
Alternating Least Squares (HALS) was introduced that seems to be much more
efficient in practice.
  In this paper, we consider the problem of approximating a not necessarily
nonnegative matrix with the product of two nonnegative matrices, which we refer
to as Nonnegative Factorization (NF); this is the subproblem that HALS methods
implicitly try to solve at each iteration. We prove that NF is NP-hard for any
fixed factorization rank, using a reduction to the maximum edge biclique
problem.
  We also generalize the multiplicative updates to NF, which allows us to shed
some light on the differences between the MU and HALS algorithms for NMF and
give an explanation for the better performance of HALS. Finally, we link
stationary points of NF with feasible solutions of the biclique problem to
obtain a new type of biclique finding algorithm (based on MU) whose iterations
have an algorithmic complexity proportional to the number of edges in the
graph, and show that it performs better than comparable existing methods.


title: Homotopy, monopoles and 't Hooft tensor in QCD with generic gauge group

abstract:
  We study monopoles and corresponding 't Hooft tensor in QCD with a generic
compact gauge group. This issue is relevant to the understanding of color
confinement in terms of dual symmetry.


title: Global shallow water magnetohydrodynamic waves in the solar tachocline

abstract:
  We derive analytical solutions and dispersion relations of global magnetic
Poincar\'e (magneto-gravity) and magnetic Rossby waves in the approximation of
shallow water magnetohydrodynamics. The solutions are obtained in a rotating
spherical coordinate system for strongly and weakly stable stratification
separately in the presence of toroidal magnetic field. In both cases magnetic
Rossby waves split into fast and slow magnetic Rossby modes. In the case of
strongly stable stratification (valid in the radiative part of the tachocline)
all waves are slightly affected by the layer thickness and the toroidal
magnetic field, while in the case of weakly stable stratification (valid in the
upper overshoot layer of the tachocline) magnetic Poincar\'e and fast magnetic
Rossby waves are found to be concentrated near the solar equator, leading to
equatorially trapped waves. However, slow magnetic Rossby waves tend to
concentrate near the poles, leading to polar trapped waves. The frequencies of
all waves are smaller in the upper weakly stable stratification region than in
the lower strongly stable stratification one.


title:
Comparing iterative methods to compute the overlap Dirac operator at
  nonzero chemical potential

abstract:
  The overlap Dirac operator at nonzero quark chemical potential involves the
computation of the sign function of a non-Hermitian matrix. In this talk we
present iterative Krylov subspace approximations, with deflation of critical
eigenvalues, which we developed to compute the operator on large lattices. We
compare the accuracy and efficiency of two alternative approximations based on
the Arnoldi and on the two-sided Lanczos method. The short recurrences used in
the latter method make it faster and more effective for realistic lattice
simulations.


title:
Experimental joint weak measurement on a photon pair as a probe of
  Hardy's Paradox

abstract:
  It has been proposed that the ability to perform joint weak measurements on
post-selected systems would allow us to study quantum paradoxes. These
measurements can investigate the history of those particles that contribute to
the paradoxical outcome. Here, we experimentally perform weak measurements of
joint (i.e. nonlocal) observables. In an implementation of Hardy's Paradox, we
weakly measure the locations of two photons, the subject of the conflicting
statements behind the Paradox. Remarkably, the resulting weak probabilities
verify all these statements but, at the same time, resolve the Paradox.


title:
A relaxation scheme for computation of the joint spectral radius of
  matrix sets

abstract:
  The problem of computation of the joint (generalized) spectral radius of
matrix sets has been discussed in a number of publications. In the paper an
iteration procedure is considered that allows to build numerically Barabanov
norms for the irreducible matrix sets and simultaneously to compute the joint
spectral radius of these sets.


title: Finding SDSS BALQSOs Using Non-Negative Matrix Factorisation

abstract:
  Modern spectroscopic databases provide a wealth of information about the
physical processes and environments associated with astrophysical populations.
Techniques such as blind source separation (BSS), in which sets of spectra are
decomposed into a number of components, offer the prospect of identifying the
signatures of the underlying physical emission processes. Principle Component
Analysis (PCA) has been applied with some success but is severely limited by
the inherent orthogonality restriction that the components must satisfy.
  Non-negative matrix factorisation (NMF) is a relatively new BSS technique
that incorporates a non-negativity constraint on its components. In this
respect, the resulting components may more closely reflect the physical
emission signatures than is the case using PCA. We discuss some of the
considerations that must be made when applying NMF and, through its application
to the quasar spectra in the Sloan Digital Sky Survey (SDSS) DR6, we show that
NMF is a fast method for generating compact and accurate reconstructions of the
spectra.
  The ability to reconstruct spectra accurately has numerous astrophysical
applications. Combined with improved SDSS redshifts, we apply NMF to the
problem of defining robust continua for quasars that exhibit strong broad
absorption line (BAL) systems. The resulting catalogue of SDSS DR6 BAL quasars
will be the largest available. Importantly, the NMF approach allows
quantitative error estimates to be derived for the Balnicity Indices as a
function of key astrophysical and observational parameters, such as the quasar
redshifts and the signal-to-noise ratio of the spectra.


title: Light pollution in Spain. An european perspective

abstract:
  Spain appears in light pollution maps as a country less polluted than their
neighbours in the European Union. This seems to be an illusion due to its low
population density. The data indicate that Spain is one of the most
contaminated countries. To reach these conclusions we compare the Spanish case
to those of other European countries.


title:
A Window on the CP-violating Phases of MSSM from Lepton Flavor Violating
  Processes

abstract:
  It has recently been shown that by measuring the transverse polarization of
the final particles in the LFV processes $\mu \to e\gamma$, $\mu \to eee$ and
$\mu N\to e N$, one can derive information on the CP-violating phases of the
underlying theory. We derive formulas for the transverse polarization of the
final particles in terms of the couplings of the effective potential leading to
these processes. We then study the dependence of the polarizations of $e$ and
$\gamma$ in the $\mu \to e \gamma$ and $\mu N \to e N$ on the parameters of the
Minimal Supersymmetric Standard Model (MSSM). We show that combining the
information on various observables in the $\mu \to e\gamma$ and $\mu N\to e N$
search experiments with the information on the electric dipole moment of the
electron can help us to solve the degeneracies in parameter space and to
determine the values of certain phases.


title:
Spontaneous violation of chiral symmetry in QCD vacuum is the origin of
  baryon masses and determines baryon magnetic moments and their other static
  properties

abstract:
  A short review is presented of the spontaneous violation of chiral symmetry
in QCD vacuum. It is demonstrated, that this phenomenon is the origin of baryon
masses in QCD. The value of nucleon mass is calculated as well as the masses of
hyperons and some baryonic resonances and expressed mainly through the values
of quark condensates -- $<0\mid \bar{q} q \mid 0>, ~q=u,d,s$ -- the vacuum
expectation values (v.e.v.) of quark field. The concept of vacuum expectation
values induced by external fields is introduced. It is demonstrated that such
v.e.v. induced by static electromagnetic field results in quark condensate
magnetic susceptibility, which plays the main role in determination of baryon
magnetic moments. The magnetic moments of proton, neutron and hyperons are
calculated. The results of calculation of baryon octet $\beta$-decay constants
are also presented.


title: Chern subrings

abstract:
  Let p be an odd prime. We show that for a simply-connected semisimple complex
linear algebraic group, if its integral homology has p-torsion, the Chern
classes do not generate the Chow ring of its classifying space.


title: Orbifold quantum D-modules associated to weighted projective spaces

abstract:
  We construct in an abstract fashion the orbifold quantum cohomology (quantum
orbifold cohomology) of weighted projective space, starting from the orbifold
quantum differential operator. We obtain the product, grading, and intersection
form by making use of the associated self-adjoint D-module and the Birkhoff
factorization procedure. The method extends to the more difficult case of Fano
hypersurfaces in weighted projective space. However, in contrast to the case of
weighted projective space itself or a Fano hypersurface in projective space, a
"small Birkhoff cell" can appear in the construction; we give an example of
this phenomenon.


title: Facilitated oriented spin models:some non equilibrium results

abstract:
  We analyze the relaxation to equilibrium for kinetically constrained spin
models (KCSM) when the initial distribution $\nu$ is different from the
reversible one, $\mu$. This setting has been intensively studied in the physics
literature to analyze the slow dynamics which follows a sudden quench from the
liquid to the glass phase. We concentrate on two basic oriented KCSM: the East
model on $\bbZ$, for which the constraint requires that the East neighbor of
the to-be-update vertex is vacant and the model on the binary tree introduced
in \cite{Aldous:2002p1074}, for which the constraint requires the two children
to be vacant. While the former model is ergodic at any $p\neq 1$, the latter
displays an ergodicity breaking transition at $p_c=1/2$. For the East we prove
exponential convergence to equilibrium with rate depending on the spectral gap
if $\nu$ is concentrated on any configuration which does not contain a forever
blocked site or if $\nu$ is a Bernoulli($p'$) product measure for any $p'\neq
1$. For the model on the binary tree we prove similar results in the regime
$p,p'<p_c$ and under the (plausible) assumption that the spectral gap is
positive for $p<p_c$. By constructing a proper test function we also prove that
if $p'>p_c$ and $p\leq p_c$ convergence to equilibrium cannot occur for all
local functions. Finally we present a very simple argument (different from the
one in \cite{Aldous:2002p1074}) based on a combination of combinatorial results
and ``energy barrier'' considerations, which yields the sharp upper bound for
the spectral gap of East when $p\uparrow 1$.

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


title:
Smoothed weighted empirical likelihood ratio confidence intervals for
  quantiles

abstract:
  Thus far, likelihood-based interval estimates for quantiles have not been
studied in the literature on interval censored case 2 data and partly interval
censored data, and, in this context, the use of smoothing has not been
considered for any type of censored data. This article constructs smoothed
weighted empirical likelihood ratio confidence intervals (WELRCI) for quantiles
in a unified framework for various types of censored data, including right
censored data, doubly censored data, interval censored data and partly interval
censored data. The fourth order expansion of the weighted empirical
log-likelihood ratio is derived and the theoretical coverage accuracy equation
for the proposed WELRCI is established, which generally guarantees at least
`first order' accuracy. In particular, for right censored data, we show that
the coverage accuracy is at least $O(n^{-1/2})$ and our simulation studies show
that in comparison with empirical likelihood-based methods, the smoothing used
in WELRCI generally provides a shorter confidence interval with comparable
coverage accuracy. For interval censored data, it is interesting to find that
with an adjusted rate $n^{-1/3}$, the weighted empirical log-likelihood ratio
has an asymptotic distribution completely different from that obtained by the
empirical likelihood approach and the resulting WELRCI perform favorably in the
available comparison simulation studies.


title:
Gelation as arrested phase separation in short-ranged attractive
  colloid-polymer mixtures

abstract:
  We present further evidence that gelation is an arrested phase separation in
attractive colloid-polymer mixtures, based on a method combining confocal
microscopy experiments with numerical simulations recently established in {\bf
Nature 453, 499 (2008)}. Our results are independent of the form of the
interparticle attractive potential, and therefore should apply broadly to any
attractive particle system with short-ranged, isotropic attractions. We also
give additional characterization of the gel states in terms of their structure,
inhomogeneous character and local density.


title:
Estimates for covering numbers in Schauder's theorem about adjoints of
  compact operators

abstract:
  Let T:X --> Y be a bounded linear map between Banach spaces X and Y. Let S:Y'
--> X' be its adjoint. Let B(X) and B(Y') be the closed unit balls of X and Y'
respectively. We obtain apparently new estimates for the covering numbers of
the set S(B(Y')). These are expressed in terms of the covering numbers of
T(B(X)), or, more generally, in terms of the covering numbers of a
"significant" subset of T(B(X)). The latter more general estimates are best
possible. These estimates follow from our new quantitative version of an
abstract compactness result which generalizes classical theorems of
Arzela-Ascoli and of Schauder. Analogous estimates also hold for the covering
numbers of T(B(X)), in terms of the covering numbers of S(B(Y')) or in terms of
a suitable "significant" subset of S(B(Y')).


title: Masures affines

abstract:
  We give an abstract definition of affine hovels which generalizes the
definition of affine buildings (eventually non simplicial) given by Jacques
Tits and includes the hovels built by Stephane Gaussent and the author for some
Kac-Moody groups over ultrametric fields. We prove that, in such an affine
hovel I, there exist retractions with center a sector germ and that we can add
at the infinity of I a pair of twin buildings or two microaffine buildings. For
some affine hovels I, we prove that the residue at a point of I has a natural
structure of pair of twin buildings and that there exists on I a preorder which
induces on each apartment the preorder associated to the Tits cone.


title: Cluster-induced crater formation

abstract:
  Using molecular-dynamics simulation, we study the crater volumes induced by
energetic impacts ($v= 1- 250$ km/s) of projectiles containing up to N=1000
atoms. We find that for Lennard-Jones bonded material the crater volume depends
solely on the total impact energy $E$. Above a threshold $\Eth$, the volume
rises linearly with $E$. Similar results are obtained for metallic materials.
By scaling the impact energy $E$ to the target cohesive energy $U$, the crater
volumes become independent of the target material. To a first approximation,
the crater volume increases in proportion with the available scaled energy,
$V=aE/U$. The proportionality factor $a$ is termed the cratering efficiency and
assumes values of around 0.5.


title: Supercurrents in color-superconducting quark matter

abstract:
  We review the basic properties of the currCFL-K^0 phase in dense quark
matter. At asymptotically large densities, three-flavor quark matter is in the
color-flavor locked (CFL) state. The currCFL-K^0 state is a way to respond to
``stress'' on the quark Cooper pairing, imposed at more moderate densities by
the strange quark mass and the conditions of electric and color neutrality. We
show how a kaon supercurrent is incorporated in a purely fermionic formalism,
and show that the net current vanishes due to cancellation of fermion and
charge-conjugate fermion contributions.


title: The nimbus of away-side jets

abstract:
  The conical structure around the away-side jets is discussed. The equations
of in-medium gluodynamics are proposed. Their classical lowest order solution
is explicitly shown for a color charge moving with constant speed. For nuclear
permittivity larger than 1 it describes the shock wave induced by emission of
Cherenkov gluons. The values of real and imaginary parts of nuclear
permittivity are estimated from fits of RHIC data. Specific effects at LHC
energies are described.


title:
New possibility for further measurements of nucleon form factors at
  large momentum transfer in time-like region: $\bar{p}+{p}\to \ell^+ +\ell^-$,
  $\ell=e$ or $\mu$

abstract:
  We briefly summarize the status with electromagnetic nucleon form factors,
and give in this framework, arguments to study the angular dependence of the
differential cross section and single-spin polarization phenomena (polarized
target or polarized beam) in $\bar{p}+{p}\to \ell^++\ell^-$, in view of the
availability of future antiproton beams.


title:
A simple derivation of the electromagnetic field of an arbitrarily
  moving charge

abstract:
  The expression for the electromagnetic field of a charge moving along an
arbitrary trajectory is obtained in a direct, elegant, and Lorentz invariant
manner without resorting to more complicated procedures such as differentiation
of the Lienard-Wiechert potentials. The derivation uses arguments based on
Lorentz invariance and a physically transparent expression originally due to
J.J.Thomson for the field of a charge that experiences an impulsive
acceleration.


title:
Dynamical Simulations of Magnetically Channeled Line-Driven Stellar
  Winds: III. Angular Momentum Loss and Rotational Spindown

abstract:
  We examine the angular momentum loss and associated rotational spindown for
magnetic hot stars with a line-driven stellar wind and a rotation-aligned
dipole magnetic field. Our analysis here is based on our previous 2-D numerical
MHD simulation study that examines the interplay among wind, field, and
rotation as a function of two dimensionless parameters, one characterizing the
wind magnetic confinement ($\eta_{\ast} \equiv B_{eq}^{2} R_{\ast}^{2}/{\dot M}
v_{\infty}$), and the other the ratio ($W \equiv V_{rot}/V_{orb}$) of stellar
rotation to critical (orbital) speed. We compare and contrast the 2-D, time
variable angular momentum loss of this dipole model of a hot-star wind with the
classical 1-D steady-state analysis by Weber and Davis (WD), who used an
idealized monopole field to model the angular momentum loss in the solar wind.
Despite the differences, we find that the total angular momentum loss ${\dot
J}$ averaged over both solid angle and time follows closely the general WD
scaling ${\dot J} = (2/3) {\dot M} \Omega R_{A}^{2}$, where ${\dot M}$ is the
mass loss rate, $\Omega$ is the stellar angular velocity, and $R_{A}$ is a
characteristic Alfv\'{e}n radius. However, a key distinction here is that for a
dipole field, this Alfv\'{e}n radius has a strong-field scaling $R_{A}/R_{\ast}
\approx \eta_{\ast}^{1/4}$, instead of the scaling $R_{A}/R_{\ast} \sim
\sqrt{\eta_{\ast}}$ for a monopole field. This leads to a slower stellar
spindown time that in the dipole case scales as $\tau_{spin} = \tau_{mass}
1.5k/\sqrt{\eta_{\ast}}$, where $\tau_{mass} \equiv M/{\dot M}$ is the
characteristic mass loss time, and $k$ is the dimensionless factor for stellar
moment of inertia. The full numerical scaling relation we cite gives typical
spindown times of order 1 Myr for several known magnetic massive stars.


title:
Precision Physics with B^0_s -> J/psi phi at the LHC: The Quest for New
  Physics

abstract:
  CP-violating effects in the time-dependent angular distribution of the B^0_s
-> J/psi[-> ell^+ ell^-] phi[-> K^+K^-] decay products play a key role for the
search of new physics. The hadronic Standard-Model uncertainties are related to
doubly Cabibbo-suppressed penguin contributions and are usually assumed to be
negligibly small. In view of recent results from the Tevatron and the quickly
approaching start of the data taking at the LHC, we have a critical look at the
impact of these terms, which could be enhanced through long-distance QCD
phenomena, and explore the associated uncertainty for the measurement of the
CP-violating B^0_s-\bar B^0_s mixing phase. We point out that these effects can
actually be controlled by means of an analysis of the time-dependent angular
distribution of the B^0_s -> J/psi[-> ell^+ ell^-] \bar K^{*0}[-> pi^+ K^-]
decay products, and illustrate this through numerical studies. Moreover, we
discuss SU(3)-breaking effects, which limit the theoretical accuracy of our
method, and suggest internal consistency checks of SU(3).


title: Ogden's Lemma for Regular Tree Languages

abstract:
  We motivate and prove a strong pumping lemma for regular tree languages. The
new lemma can be seen as the natural correspondent of Ogden's lemma for
context-free string languages.


title:
Estimation of charm particles elementary cross sections relevant to
  GSI-CBM project

abstract:
  This note collects formulas relative to the energy dependence of the cross
sections for open charm and $J/\psi$ production for $NN$-collisions at
threshold. It is a basis for the best input to MonteCarlo calculations, for
associative charm particle production in nucleon-nucleon, nucleon-nucleus,
ion-ion and proton-antiproton collisions.


title: Volume modulus inflection point inflation and the gravitino mass problem

abstract:
  Several models of inflection point inflation with the volume modulus as the
inflaton are investigated. Non-perturbative superpotentials containing two
gaugino condensation terms or one such term with threshold corrections are
considered. It is shown that the gravitino mass may be much smaller than the
Hubble scale during inflation if at least one of the non-perturbative terms has
a positive exponent. Higher order corrections to the Kahler potential have to
be taken into account in such models. Those corrections are used to stabilize
the potential in the axion direction in the vicinity of the inflection point.
Models with only negative exponents require uplifting and in consequence have
the supersymmetry breaking scale higher than the inflation scale. Fine-tuning
of parameters and initial conditions is analyzed in some detail for both types
of models. It is found that fine-tuning of parameters in models with heavy
gravitino is much stronger than in models with light gravitino. It is shown
that recently proposed time dependent potentials can provide a solution to the
problem of the initial conditions only in models with heavy gravitino. Such
potentials can not be used to relax fine tuning of parameters in any model
because this would lead to values of the spectral index well outside the
experimental bounds.


title:
The two photon exchange amplitude in $ep$ and $e\mu $ elastic
  scattering: a comparison

abstract:
  In this note we give arguments in favor of the statement that the
contribution of the box diagram calculated for electron muon elastic scattering
can be considered an upper limit to electron proton scattering. As an exact QED
calculation can be performed, this statement is useful for constraining model
calculations involving the proton structure.


title: Duality of cones of positive maps

abstract:
  We study the so-called K-positive linear maps from B(L) into B(H) for finite
dimensional Hilbert spaces L and H and give characterizations of the dual cone
of the cone of K-positive maps. Applications are given to decomposable maps and
PPT-states.


title:
Dependence of cosmic shear covariances on cosmology - Impact on
  parameter estimation

abstract:
  In cosmic shear likelihood analyses the covariance is most commonly assumed
to be constant in parameter space. Therefore, when calculating the covariance
matrix (analytically or from simulations), its underlying cosmology should not
influence the likelihood contours. We examine whether the aforementioned
assumption holds and quantify how strong cosmic shear covariances vary within a
reasonable parameter range. Furthermore, we examine the impact on likelihood
contours when assuming different cosmologies in the covariance. We find that
covariances vary significantly within the considered parameter range
(Omega_m=[0.2;0.4], sigma_8=[0.6;1.0]) and that this has a non-negligible
impact on the size of likelihood contours. This impact increases with
increasing survey size, increasing number density of source galaxies,
decreasing ellipticity noise, and when using non-Gaussian covariances. To
improve on the assumption of a constant covariance we present two methods. The
adaptive covariance is the most accurate method, but it is computationally
expensive. To reduce the computational costs we give a scaling relation for
covariances. As a second method we outline the concept of an iterative
likelihood analysis. Here, we additionally account for non-Gaussianity using a
ray-tracing covariance derived from the Millennium simulation.


title: The hadronization of partons

abstract:
  We review the description of inclusive single unpolarized light hadron
production using fragmentation functions in the framework of the factorization
theorem. We summarize the factorization of quantities into perturbatively
calculable quantities and these universal fragmentation functions, and then
discuss some improvements beyond the standard fixed order approach. We discuss
the extraction of fragmentation functions for light charged and neutral hadrons
using these theoretical tools through global fits to experimental data from
reactions at various colliders, in particular from accurate e+e- reactions at
LEP, and the subsequent successful predictions of other experimental data, such
as data gathered at HERA, the Tevatron and RHIC from these fitted fragmentation
functions as allowed by factorization universality. These global fits also
impose competitive constraints on alpha_s(M_Z). Emphasis is placed on the need
for accurate data from ep and pp(pbar) reactions in which the hadron species is
identified in order to constrain the separate fragmentation functions of each
quark flavour and hadron species.


title:
Convergent null data expansions at space-like infinity of stationary
  vacuum solutions

abstract:
  We present a characterization of the asymptotics of all asymptotically flat
stationary vacuum solutions of Einstein's field equations. This
characterization is given in terms of two sequences of symmetric trace free
tensors (we call them the `null data'), which determine a formal expansion of
the solution, and which are in a one to one correspondence to Hansen's
multipoles. We obtain necessary and sufficient growth estimates on the null
data to define an absolutely convergent series in a neighbourhood of spatial
infinity. This provides a complete characterization of all asymptotically flat
stationary vacuum solutions to the field equations.


title: Charmed hadron signals of partonic medium

abstract:
  We present a short review of our results on the collectivity and the
suppression pattern of charmed mesons in heavy-ion collisions based on the
microscopic Hadron-String Dynamics (HSD) transport approach for different
scenarios of charm interactions with the surrounding matter - the 'comover'
dissociation by mesons with further recreation by D+Dbar channels and
'pre-hadronic' interaction scenarios. While at SPS energies the hadronic
'comover' absorption scenario is found to be compatible with the experimental
data, the dynamics of c and cbar quarks at RHIC are dominated by partonic or
'pre-hadronic' interactions in the strongly coupled quark-gluon plasma stage
and cannot be modeled by pure hadronic interactions. We find that the
collective flow of charm in the purely hadronic scenario appears compatible
with the data at SPS energies but underestimates the data at top RHIC energies.
Thus, the large elliptic flow v2 of D mesons and the low R_AA(pT) of J/Psi seen
experimentally at RHIC have to be attributed to early interactions of
non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic
interactions are mandatory in order to describe the narrowing of the J/Psi
rapidity distribution from p+p to central Au+Au collisions at the top RHIC
energy. We demonstrate additionally that the strong quenching of high-pT
J/Psi's in central Au+Au collisions indicates that a fraction of final J/Psi
mesons is created by a coalescence mechanism close to the phase boundary.


title: Molecules as Sources for Indistinguishable Single Photons

abstract:
  We report on the triggered generation of indistinguishable photons by
solid-state single-photon sources in two separate cryogenic laser scanning
microscopes. Organic fluorescent molecules were used as emitters and
investigated by means of high resolution laser spectroscopy. Continuous-wave
photon correlation measurements on individual molecules proved the isolation of
single quantum systems. By using frequency selective pulsed excitation of the
molecule and efficient spectral filtering of its emission, we produced
triggered Fourier-limited single photons. In a further step, local electric
fields were applied to match the emission wavelengths of two different
molecules via Stark effect. Identical single photons are indispensible for the
realization of various quantum information processing schemes proposed. The
solid-state approach presented here prepares the way towards the integration of
multiple bright sources of single photons on a single chip.


title:
On the spectrum of the twisted Dolbeault Laplacian on line bundles over
  K\"ahler manifolds

abstract:
  We use Dirac operator techniques to establish a sharp lower bound for the
first eigenvalue of the twisted Dolbeault Laplacian on holomorphic line bundles
over compact K\"ahler manifolds.


title: Quasi-energy function for diffeomorphisms with wild separatrices

abstract:
  According to Pixton, there are Morse-Smale diffeomorphisms of the 3-sphere
which have no energy function, that is a Lyapunov function whose critical
points are all periodic points of the diffeomorphism. We introduce the concept
of quasi-energy function for a Morse-Smale diffeomorphism as a Lyapunov
function with the least number of critical points and construct a quasi-energy
function for any diffeomorphism from some class of Morse-Smale diffeomorphisms
on the 3-sphere.


title: Results of WEBT, VLBA and RXTE monitoring of 3C 279 during 2006-2007

abstract:
  We present radio-to-optical data taken by the WEBT, supplemented by VLBA and
RXTE observations, of 3C 279. Our goal is to use this extensive database to
draw inferences regarding the physics of the relativistic jet. We assemble
multifrequency light curves with data from 30 ground-based observatories and
the space-based instruments, along with linear polarization vs. time in the
optical R band. In addition, we present a sequence of 22 images (with
polarization vectors) at 43 GHz at resolution 0.15 milliarcsec, obtained with
the VLBA. We analyse the light curves and polarization, as well as the spectral
energy distributions at different epochs, corresponding to different brightness
states. The IR-optical-UV continuum spectrum of the variable component
corresponds to a power law with a constant slope of -1.6, while in the 2.4-10
keV X-ray band it varies in slope from -1.1 to -1.6. The steepest X-ray
spectrum occurs at a flux minimum. During a decline in flux from maximum in
late 2006, the optical and 43 GHz core polarization vectors rotate by ~300
degrees. The continuum spectrum agrees with steady injection of relativistic
electrons with a power-law energy distribution of slope -3.2 that is steepened
to -4.2 at high energies by radiative losses. The X-ray emission at flux
minimum comes most likely from a new component that starts in an upstream
section of the jet where inverse Compton scattering of seed photons from
outside the jet is important. The rotation of the polarization vector implies
that the jet contains a helical magnetic field that extends ~20 pc past the 43
GHz core.


title: Renormalisation of out-of-equilibrium quantum fields

abstract:
  We consider the initial value problem and its renormalisation in the
framework of the two-particle-irreducible (2PI) effective action. We argue that
in the case of appropriately chosen self-consistent initial conditions, the
counterterms needed to renormalise the system in equilibrium are also
sufficient to renormalise its time evolution. In this way we improve on
Gaussian initial conditions which have the disadvantage of generically not
showing a continuum limit. For a more detailed discussion see arXiv:0809.0496.


title:
Adaptive estimation of the conditional intensity of marker-dependent
  counting processes

abstract:
  We propose in this work an original estimator of the conditional intensity of
a marker-dependent counting process, that is, a counting process with
covariates. We use model selection methods and provide a non asymptotic bound
for the risk of our estimator on a compact set. We show that our estimator
reaches automatically a convergence rate over a functional class with a given
(unknown) anisotropic regularity. Then, we prove a lower bound which
establishes that this rate is optimal. Lastly, we provide a short illustration
of the way the estimator works in the context of conditional hazard estimation.


title: Vacancy defect positron lifetimes in strontium titanate

abstract:
  The results of positron annihilation lifetime spectroscopy measurements on
undoped, electron irradiated, and Nb doped SrTiO3 single crystals are reported.
Perfect lattice and vacancy defect positron lifetimes were calculated using two
different first-principles schemes. The Sr vacancy defect related positron
lifetime was obtained from measurements on Nb doped, electron irradiated, and
vacuum annealed samples. Undoped crystals showed a defect lifetime component
dominated by trapping to Ti vacancy related defects.


title:
Perfectly elastic collisions as origin of quantum states of
  superconductivity and magnetic order

abstract:
  One of the most interesting properties of solid materials is the ability to
form different collective quantum states, such as superconductivity and
magnetic order. This paper presents a model of perfectly elastic collisions
(p.e.c.) as the universal origin of these collective quantum states. The superb
agreement between calculated values and experimental data for critical
temperatures, moreover, the explanation of the isotope effect in
superconductivity and magnetic order confirms that this model successfully
describes these two quantum states.


title: Tunable thermal emission at infrared frequencies via tungsten gratings

abstract:
  The author investigates the manipulation of thermal emission by using
one-dimensional tungsten gratings with different groove depths. It is found
that, by systematically increasing the depth of the groove, the linearly
polarized emission at particular frequencies can be substantially enhanced to
achieve that of the blackbody radiation limit, whereas the emission in other
frequency ranges shows no noticeable changes. The results can provide useful
insights into the design of thermovoltaic applications.


title: Gamma rays from the annihilation of singlet scalar dark matter

abstract:
  We consider an extension of the Standard Model by a singlet scalar that
accounts for the dark matter of the Universe. Within this model we compute the
expected gamma ray flux from the annihilation of dark matter particles in a
consistent way. To do so, an updated analysis of the parameter space of the
model is first presented. By enforcing the relic density constraint from the
very beginning, the viable parameter space gets reduced to just two variables:
the singlet mass and the higgs mass. Current direct detection constraints are
then found to require a singlet mass larger than 50 GeV. Finally, we compute
the gamma ray flux and annihilation cross section and show that a large
fraction of the viable parameter space lies within the sensitivity of
Fermi-GLAST.


title:
Electron spin blockade and singlet-triplet transition in a silicon
  single electron transistor

abstract:
  We investigate a silicon single-electron transistor (SET) in a
metal-oxide-semiconductor (MOS) structure by applying a magnetic field
perpendicular to the sample surface. The quantum dot is defined
electrostatically in a point contact channel and by the potential barriers from
negatively charged interface traps. The magnetic field dependence of the
excitation spectrum is primarily driven by the Zeeman effect. In the
two-electron singlet-triplet (ST) transition, electron-electron Coulomb
interaction plays a significant role. The evolution of Coulomb blockade peaks
with magnetic field B is also owing to the Zeeman splitting with no obvious
orbital effect up to 9 T. The filling pattern shows an alternate
spin-up-spin-down sequence. The amplitude spectroscopy allows for the
observation of the spin blockade effect, where the two-electron system forms a
singlet state at low fields, and the spin polarized injection from the lead
reduces the tunneling conductance by a factor of 8. At a higher magnetic field,
due to the ST transition, the spin blockade effect is lifted and the
conductance is fully recovered.


title: Reverse rotations in the circularly-driven motion of a rigid body

abstract:
  We study the dynamical response of a circularly-driven rigid body, focusing
on the description of intrinsic rotational behavior (reverse rotations). The
model system we address is integrable but nontrivial, allowing for qualitative
and quantitative analysis. A scale free expression defining the separation
between possible spinning regimes is obtained.


title: Membrane fluctuations near a plane rigid surface

abstract:
  We use analytical calculations and Monte Carlo simulations to determine the
thermal fluctuation spectrum of a membrane patch of a few tens of nanometer in
size, whose corners are located at a fixed distance $d$ above a plane rigid
surface. Our analysis shows that the surface influence on the bilayer
fluctuations can be effectively described in terms of a uniform confining
potential that grows quadratically with the height of the membrane $h$ relative
to the surface: $V=(1/2)\gamma h^2$. The strength $\gamma$ of the harmonic
confining potential vanishes when the corners of the membrane patch are placed
directly on the surface ($d=0$), and achieves its maximum value when $d$ is of
the order of a few nanometers. However, even at maximum strength the
confinement effect is quite small and has noticeable impact only on the
amplitude of the largest bending mode.


title: Symmetry and Time Changed Brownian Motions

abstract:
  In this paper we examine which Brownian Subordination with drift exhibits the
symmetry property introduced by Fajardo and Mordecki (2006). We obtain that
when the subordination results in a L\'evy process, a necessary and sufficient
condition for the symmetry to hold is that drift must be equal to -1/2.


title:
Polarization dependent interface properties of ferroelectric Schottky
  barriers studied by soft X-ray absorption spectroscopy

abstract:
  We applied soft X-ray absorption spectroscopy to study the Ti L-edge in
ferroelectric capacitors using a modified total electron yield method. The
inner photo currents and the X-ray absorption spectra were polarization state
dependent. The results are explained on the basis of photo electric effects and
the inner potential in the ferroelectric capacitors as a result of back-to-back
Schottky barriers superimposed by the potential due to the depolarization
field. In general, the presented method offers the opportunity to investigate
the electronic structure of buried metal-insulator and metal-semiconductor
interfaces in thin film devices. Corresponding author:
h.h.kohlstedt@fz-juelich.de


title:
A holomorphic and background independent partition function for matrix
  models and topological strings

abstract:
  We study various properties of a nonperturbative partition function which can
be associated to any spectral curve. When the spectral curve arises from a
matrix model, this nonperturbative partition function is given by a sum of
matrix integrals over all possible filling fractions, and includes all the
multi-instanton corrections to the perturbative 1/N expansion. We show that the
nonperturbative partition function, which is manifestly holomorphic, is also
modular and background independent: it transforms as the partition function of
a twisted fermion on the spectral curve. Therefore, modularity is restored by
nonperturbative corrections. We also show that this nonperturbative partition
function obeys the Hirota equation and provides a natural nonperturbative
completion for topological string theory on local Calabi-Yau threefolds.


title: Dynamical NNLO parton distributions

abstract:
  Utilizing recent DIS measurements (\sigma_r, F_{2,3,L}) and data on hadronic
dilepton production we determine at NNLO (3-loop) of QCD the dynamical parton
distributions of the nucleon generated radiatively from valencelike positive
input distributions at an optimally chosen low resolution scale (Q_0^2 < 1
GeV^2). These are compared with `standard' NNLO distributions generated from
positive input distributions at some fixed and higher resolution scale (Q_0^2 >
1 GeV^2). Although the NNLO corrections imply in both approaches an improved
value of \chi^2, typically \chi^2_{NNLO} \simeq 0.9 \chi^2_{NLO}, present DIS
data are still not sufficiently accurate to distinguish between NLO results and
the minute NNLO effects of a few percent, despite of the fact that the
dynamical NNLO uncertainties are somewhat smaller than the NLO ones and both
are, as expected, smaller than those of their `standard' counterparts. The
dynamical predictions for F_L(x,Q^2) become perturbatively stable already at
Q^2 = 2-3 GeV^2 where precision measurements could even delineate NNLO effects
in the very small-x region. This is in contrast to the common `standard'
approach but NNLO/NLO differences are here less distinguishable due to the much
larger 1\sigma uncertainty bands. Within the dynamical approach we obtain
\alpha_s(M_Z^2)=0.1124 \pm 0.0020, whereas the somewhat less constrained
`standard' fit gives \alpha_s(M_Z^2)=0.1158 \pm 0.0035.


title: Pressure Correction in Density Functional Theory Calculations

abstract:
  First-principles calculations based on density functional theory have been
widely used in studies of the structural, thermoelastic, rheological, and
electronic properties of earth-forming materials. The exchange-correlation
term, however, is implemented based on various approximations, and this is
believed to be the main reason for discrepancies between experiments and
theoretical predictions. In this work, by using periclase MgO as a prototype
system we examine the discrepancies in pressure and Kohn-Sham energy that are
due to the choice of the exchange-correlation functional. For instance, we
choose local density approximation and generalized gradient approximation. We
perform extensive first-principles calculations at various temperatures and
volumes and find that the exchange-correlation-based discrepancies in Kohn-Sham
energy and pressure should be independent of temperature. This implies that the
physical quantities, such as the equation of states, heat capacity, and the
Gr\"{u}neisen parameter, estimated by a particular choice of
exchange-correlation functional can easily be transformed into those estimated
by another exchange-correlation functional. Our findings may be helpful in
providing useful constraints on mineral properties %at thermodynamic conditions
compatible to deep Earth. at deep Earth thermodynamic conditions.


title: Theory Summary of the Hadron Structure and QCD Workshop 2008

abstract:
  This paper is the write-up version of the theory summary talk given at the
HSQCD 2008 Workshop in Gatchina, Russia. Recent theoretical developments and
results are summarized focusing on works that point out new perspectives,
ranging from perturbative QCD, DGLAP and ERBL evolution, polarized and
unpolarized parton distribution functions, small-x physics to nonperturbative
QCD, lattice simulations, quark-gluon matter, hadron spectroscopy, and
predictions for the LHC.


title:
Phase separation of electrons strongly coupled with phonons in cuprates
  and manganites

abstract:
  Recent advanced Monte Carlo simulations have not found superconductivity and
phase separation in the Hubbard model with on-site repulsive electron-electron
correlations. We argue that microscopic phase separations in cuprate
superconductors and colossal magnetoresistance (CMR) manganites originate from
a strong electron-phonon interaction (EPI) combined with unavoidable disorder.
Attractive electron correlations, caused by an almost unretarded EPI, are
sufficient to overcome the direct inter-site Coulomb repulsion in these
charge-transfer Mott-Hubbard insulators, so that low energy physics is that of
small polarons and small bipolarons (real-space electron (hole) pairs dressed
by phonons). They form clusters localised by disorder below the mobility edge,
but propagate as the Bloch states above the mobility edge. I identify the
Froehlich finite-range EPI with optical phonons as the most essential for
pairing and phase separation in superconducting layered cuprates. The pairing
of oxygen holes into heavy bipolarons in the paramagnetic phase
(current-carrier density collapse (CCDC)) explains also CMR of doped manganites
due to magnetic break-up of bipolarons in the ferromagnetic phase. Here I
briefly present an explanation of high and low-resistance phase coexistence
near the ferromagnetic transition as a mixture of polaronic ferromagnetic and
bipolaronic paramagnetic domains due to unavoidable disorder in doped
manganites.


title: Magnetic properties of LaO$_{1-x}$F$_x$FeAs

abstract:
  Using state-of-the-art first-principles calculations we have elucidated the
complex magnetic and structural dependence of LaOFeAs upon doping. Our key
findings are that (i) doping results in an orthorhombic ground state and (ii)
there is a commensurate to incommensurate transition in the magnetic structure
between $x=0.025$ and $x=0.04$. Our calculations further imply that in this
system magnetic order persists up to the onset of superconductivity at the
critical doping of $x=0.05$. Finally, our investigations of the undoped parent
compound reveal an unusually pronounced dependence of the magnetic moment on
details of the exchange-correlation (xc) functional used in the calculation.
However, for all choices of xc functional an orthorhombic structure is found.


title:
Smooth projective toric varieties whose nontrivial nef line bundles are
  big

abstract:
  For any $n\geq 3$, we explicitly construct smooth projective toric $n$-folds
of Picard number $\geq 5$, where any nontrivial nef line bundles are big.


title:
Thermopower across the pseudogap critical point of
  La(1.6-x)Nd(0.4)Sr(x)CuO(4): Evidence for a quantum critical point in a
  hole-doped high-Tc superconductor

abstract:
  The thermopower S of the high-Tc superconductor La(1.6-x)Nd(0.4)Sr(x)CuO(4)
was measured as a function of temperature T near its pseudogap critical point,
the critical hole doping p* where the pseudogap temperature T* goes to zero.
Just above p*, S/T varies as ln(1/T) over a decade of temperature. Below p*,
S/T undergoes a large increase below T*. As with the temperature dependence of
the resistivity, which is linear just above p* and undergoes a large upturn
below T*, these are typical signatures of a quantum phase transition. This
suggests that p* is a quantum critical point below which some order sets in,
causing a reconstruction of the Fermi surface, whose fluctuations are
presumably responsible for the linear-T resistivity and logarithmic
thermopower. We discuss the possibility that this order is the "stripe" order
known to exist in this material.


title: Thermal non-equilibrium effects in quantum reflection

abstract:
  We show that the quantum reflection coefficient of ultracold heavy atoms
scattering off a dielectric surface can be tuned in a wide range by suitable
choice of surface and environment temperatures. This effect results from a
temperature dependent long-range repulsive part of the van der
Waals-Casimir-Polder-Lifshitz atom-surface interaction potential.


title:
A Microscopic Derivation of the Time-Dependent Hartree-Fock Equation
  with Coulomb Two-Body Interaction

abstract:
  We study the dynamics of a Fermi gas with a Coulomb interaction potential,
and show that, in a mean-field limiting regime, the dynamics is described by
the Hartree-Fock equation. This extends previous work of Bardos et al. to the
case of unbounded interaction potentials. We also express the mean-field limit
as a "superhamiltonian" system, and state our main result in terms of a
Heisenberg-picture dynamics of observables. This is a Egorov-type theorem.


title:
Correlation energy of two-dimensional systems: Toward non-empirical and
  universal modeling

abstract:
  The capability of density-functional theory to deal with the ground-state of
strongly correlated low-dimensional systems, such as semiconductor quantum
dots, depends on the accuracy of functionals developed for the exchange and
correlation energies. Here we extend a successful approximation for the
correlation energy of the three dimensional inhomogeneous electron gas,
originally introduced by Becke [J. Chem. Phys. {\bf 88}, 1053 (1988)], to the
two-dimensional case. The approach aims to non-empirical modeling of the
correlation-hole functions satisfying a set of exact properties. Furthermore,
the electron current and spin are explicitly taken into account. As a result,
good performance is obtained in comparison with numerically exact data for
quantum dots with varying external magnetic field, and for the homogeneous
two-dimensional electron gas, respectively.


title:
Bc Meson Formfactors and Bc-->PV Decays Involving Flavor Dependence of
  Transverse Quark Momentum

abstract:
  We present a detailed analysis of the Bc form factors in the BSW framework,
by investigating the effects of the flavor dependence on the average transverse
quark momentum inside a meson. Branching ratios of two body decays of Bc meson
to pseudoscalar and vector mesons are predicted.


title: Exponential algebraicity in exponential fields

abstract:
  I give an algebraic proof that the exponential algebraic closure operator in
an exponential field is always a pregeometry, and show that its dimension
function satisfies a weak Schanuel property. A corollary is that there are at
most countably many essential counterexamples to Schanuel's conjecture.


title: Magnetic moment manipulation by a Josephson current

abstract:
  We consider a Josephson junction where the weak-link is formed by a
non-centrosymmetric ferromagnet. In such a junction, the superconducting
current acts as a direct driving force on the magnetic moment. We show that the
a.c. Josephson effect generates a magnetic precession providing then a feedback
to the current. Magnetic dynamics result in several anomalies of current-phase
relations (second harmonic, dissipative current) which are strongly enhanced
near the ferromagnetic resonance frequency.


title: Polarization from the Structured Envelopes of Cool Evolved Stars

abstract:
  We present preliminary calculations of electron scattering polarizations from
models of structured cool star envelopes. We note that net polarizations from
unresolved sources can result from non-spherical scattering envelopes and/or
anisotropic illumination from a photosphere that has brightness variations. The
resultant polarizations are quite small (hundreths of a percent); however,
Rayleigh scattering from molecular opacity and/or dust scattering from the more
extended envelope under similar considerations may produce higher
polarizations.


title: A low-frequency radio halo associated with a cluster of galaxies

abstract:
  Clusters of galaxies are the largest gravitationally bound objects in the
Universe, containing about 10^15 solar masses of hot (10^8 K) gas, galaxies and
dark matter in a typical volume of about 10 Mpc^3. Magnetic fields and
relativistic particles are mixed with the gas as revealed by giant radio
haloes, which arise from diffuse, megaparsec-scale synchrotron radiation at
cluster center. Radio haloes require that the emitting electrons are
accelerated in situ (by turbulence), or are injected (as secondary particles)
by proton collisions into the intergalactic medium. They are found only in a
fraction of massive clusters that have complex dynamics, which suggests a
connection between these mechanisms and cluster mergers. Here we report a radio
halo at low frequencies associated with the merging cluster Abell 521. This
halo has an extremely steep radio spectrum, which implies a high frequency
cut-off; this makes the halo difficult to detect with observations at 1.4 GHz
(the frequency at which all other known radio haloes have been best studied).
The spectrum of the halo is inconsistent with a secondary origin of the
relativistic electrons, but instead supports turbulent acceleration, which
suggests that many radio haloes in the Universe should emit mainly at low
frequencies.


title:
A solution to a problem of Cassels and Diophantine properties of cubic
  numbers

abstract:
  We prove that almost any pair of real numbers a,b, satisfies the following
inhomogeneous uniform version of Littlewood's conjecture:
  (*) forall x,y in R, liminf_{|n|\to\infty} |n|<na - x> <nb - y> = 0, where
<-> denotes the distance from the nearest integer. The existence of even a
single pair that satisfies (*), solves a problem of Cassels from the 50's. We
then prove that if 1,a,b span a totally real number field, then a,b, satisfy
(*). It is further shown that if 1,a,b, are linearly dependent over Q, a,b
cannot satisfy (*). The results are then applied to give examples of irregular
orbit closures of the diagonal groups of a new type.


title:
Overview of the lithium problem in metal-poor stars and new results on
  6Li

abstract:
  Two problems are discussed here. The first one is the 0.4 dex discrepancy
between the 7Li abundance derived from the spectra of metal-poor halo stars on
the one hand, and from Big Bang nucleosynthesis, based on the cosmological
parameters constrained by the WMAP measurements, on the other hand. Lithium,
indeed, can be depleted in the convection zone of unevolved stars. The
understanding of the hydrodynamics of the crucial zone near the bottom of the
convective envelope in dwarfs or turn-off stars of solar metallicity has
recently made enormous progress with the inclusion of internal gravity waves.
However, similar work for metal-poor stars is still lacking. Therefore it is
not yet clear whether the depletion occurring in the metal-poor stars
themselves is adequate to produce a 7Li plateau. The second problem pertains to
the large amount of 6Li recently found in metal-poor halo stars. The
convection-related asymmetry of the 7Li line could mimic the signal attributed
so far to the weak blend of 6Li in the red wing of the 7Li line. Theoretical
computations show that the signal generated by the asymmetry of 7Li is 2.0,
2.1, and 3.7 per cent for [Fe/H]= -3.0, -2.0, -1.0, respectively (Teff =6250 K
and log g=4.0 [cgs]). In addition we re-investigate the statistical properties
of the 6Li plateau and show that previous analyses were biased. Our conclusion
is that the 6Li plateau can be reinterpreted in terms of intrinsic line
asymmetry, without the need to invoke a contribution of 6Li. (abridged)


title:
Classifying A-field and B-field configurations in the presence of
  D-branes

abstract:
  We "solve" the Freed-Witten anomaly equation, i.e., we find a geometrical
classification of the B-field and A-field configurations in the presence of
D-branes that are anomaly-free. The mathematical setting being provided by the
geometry of gerbes, we find that the allowed configurations are jointly
described by a coset of a certain hypercohomology group. We then describe in
detail various cases that arise according to such classification. As is
well-known, only under suitable hypotheses the A-field turns out to be a
connection on a canonical gauge bundle. However, even in these cases, there is
a residual freedom in the choice of the bundle, naturally arising from the
hypercohomological description. For a B-field which is flat on a D-brane,
fractional or irrational charges of subbranes naturally appear; for a suitable
gauge choice, they can be seen as arising from "gauge bundles with not integral
Chern class": we give a precise geometric interpretation of these objects.


title:
The effects of aging of scientists on their publication and citation
  patterns

abstract:
  The average age at which U.S. researchers get their first grant from NIH has
increased from 34.3 in 1970, to 41.7 in 2004. These data raise the crucial
question of the effects of aging on the scientific creativity and productivity
of researchers. Those who worry about the aging of scientists usually believe
that the younger they are the more creative and productive they will be. Using
a large population of 13,680 university professors in Quebec, we show that,
while scientific productivity rises sharply between 28 and 40, it increases at
a slower pace between 41 and 50 and stabilizes afterward until retirement for
the most active researchers. The average scientific impact per paper decreases
linearly until 50-55 years old, but the average number of papers in highly
cited journals and among highly cited papers rises continuously until
retirement. Our results clearly show for the first time the natural history of
the scientific productivity of scientists over their entire career and bring to
light the fact that researchers over 55 still contribute significantly to the
scientific community by producing high impact papers.


title:
On the Structure of QFT in the Particle Picture of the Path Integral
  Formulation

abstract:
  In quantum field theory the path integral is usually formulated in the wave
picture, i.e., as a sum over field evolutions. This path integral is difficult
to define rigorously because of analytic problems whose resolution may
ultimately require knowledge of non-perturbative or even Planck scale physics.
Alternatively, QFT can be formulated directly in the particle picture, namely
as a sum over all multi-particle paths, i.e., over Feynman graphs. This path
integral is well-defined, as a map between rings of formal power series. This
suggests a program for determining which structures of QFT are provable for
this path integral and thus are combinatorial in nature, and which structures
are actually sensitive to analytic issues. For a start, we show that the fact
that the Legendre transform of the sum of connected graphs yields the effective
action is indeed combinatorial in nature and is thus independent of analytic
assumptions. Our proof also leads to new methods for the efficient
decomposition of Feynman graphs into $n$-particle irreducible (nPI) subgraphs.


title: Holomorphic shadows in the eyes of model theory

abstract:
  We define a subset of an almost complex manifold (M,J) to be a holomorphic
shadow if it is the image of a J-holomorphic map from a compact complex
manifold. Notice that a J-holomorphic curve is a holomorphic shadow, and so is
a complex subvariety of a compact complex manifold.
  We show that under some conditions on an almost complex structure J on a
manifold M, the holomorphic shadows in the Cartesian products of (M,J) form a
Zariski-type structure. Checking this leads to non-trivial geometric questions
and results. We then apply the work of Hrushovski and Zilber on Zariski-type
structures.
  We also restate results of Gromov and McDuff on J-holomorphic curves in
symplectic geometry in the language of shadows structures.


title:
The thermal evolution of nuclear matter at zero temperature and definite
  baryon number density in chiral perturbation theory

abstract:
  The thermal properties of cold dense nuclear matter are investigated with
chiral perturbation theory.
  The evolution curves for the baryon number density, baryon number
susceptibility, pressure and the equation of state are obtained.
  The chiral condensate is calculated and our result shows that when the baryon
chemical potential goes beyond $1150 \mathrm{MeV}$, the absolute value of the
quark condensate decreases rapidly, which indicates a tendency of chiral
restoration.


title: Crossing of the phantom divide in modified gravity

abstract:
  We reconstruct an explicit model of modified gravity in which a crossing of
the phantom divide can be realized. It is shown that the (finite-time) Big Rip
singularity appears in the model of modified gravity (i.e., in the so-called
Jordan frame), whereas that in the corresponding scalar field theory obtained
through the conformal transformation (i.e., in the so-called Einstein frame)
the singularity becomes the infinite-time one. Furthermore, we investigate the
relations between the scalar field theories with realizing a crossing of the
phantom divide and the corresponding modified gravitational theories by using
the inverse conformal transformation. It is demonstrated that the scalar field
theories describing the non-phantom phase (phantom one with the Big Rip) can be
represented as the theories of real (complex) $F(R)$ gravity through the
inverse (complex) conformal transformation. We also study a viable model of
modified gravity in which the transition from the de Sitter universe to the
phantom phase can occur. In addition, we explore the stability for the obtained
solutions of the crossing of the phantom divide under a quantum correction
coming from conformal anomaly.


title:
Probing the Galactic cosmic ray flux with submillimeter and gamma ray
  data

abstract:
  The study of Galactic diffuse $\gamma$ radiation combined with the knowledge
of the distribution of the molecular hydrogen in the Galaxy offers a unique
tool to probe the cosmic ray flux in the Galaxy. A methodology to study the
level of the cosmic ray "sea" and to unveil target-accelerator systems in the
Galaxy, which makes use of the data from the high resolution survey of the
Galactic molecular clouds performed with the NANTEN telescope and of the data
from gamma-ray instruments, has been developed. Some predictions concerning the
level of the cosmic ray "sea" and the $\gamma$-ray emission close to cosmic ray
sources for instruments such as Fermi and Cherenkov Telescope Array are
presented.


title: On a generalization of Littlewood's conjecture

abstract:
  We present a class of lattices in R^d (d >= 2) which we call GL-lattices and
conjecture that any lattice is such. This conjecture is referred to as GLC.
Littlewood's conjecture amounts to saying that Z^2 is GL. We then prove
existence of GL lattices by first establishing a dimension bound for the set of
possible exceptions. Existence of vectors (GL-vectors) in R^d with special
Diophantine properties is proved by similar methods. For dimension d >= 3 we
give explicit constructions of GL lattices (and in fact a much stronger
property). We also show that GLC is implied by a conjecture of G. A. Margulis
concerning bounded orbits of the diagonal group. The unifying theme of the
methods is to exploit rigidity results in dynamics and derive results in
Diophantine approximations or the geometry of numbers.


title: A Phase Transition between Small and Large Field Models of Inflation

abstract:
  We show that models of inflection point inflation exhibit a phase transition
from a region in parameter space where they are of large field type to a region
where they are of small field type. The phase transition is between a universal
behavior, with respect to the initial condition, at the large field region and
non-universal behavior at the small field region. The order parameter is the
number of e-foldings. We find integer critical exponents at the transition
between the two phases.


title: Measure theoretical entropy of covers

abstract:
  In this paper we introduce three notions of measure theoretical entropy of a
measurable cover U in a measure theoretical dynamical system. Two of them were
already introduced in [R] and the new one is defined only in the ergodic case.
We then prove that these three notions coincide, thus answering a question
posed in [R] and recover a variational inequality (proved in [GW]) and a proof
of the classical variational principle based on a comparison between the
entropies of covers and partitions.


title: The elliptic genus from split flows and Donaldson-Thomas invariants

abstract:
  We analyze a mixed ensemble of low charge D4-D2-D0 brane states on the
quintic and show that these can be successfully enumerated using attractor flow
tree techniques and Donaldson-Thomas invariants. In this low charge regime one
needs to take into account worldsheet instanton corrections to the central
charges, which is accomplished by making use of mirror symmetry. All the
charges considered can be realized as fluxed D6-D2-D0 and anti-D6-D2-D0 pairs
which we enumerate using DT invariants. Our procedure uses the low charge
counterpart of the picture developed Denef and Moore. By establishing the
existence of flow trees numerically and refining the index factorization
scheme, we reproduce and improve some results obtained by Gaiotto, Strominger
and Yin. Our results provide appealing evidence that the strong split flow tree
conjecture holds and allows to compute exact results for an important sector of
the theory. Our refined scheme for computing indices might shed some light on
how to improve index computations for systems with larger charges.


title: Comparative study of semiclassical approaches to quantum dynamics

abstract:
  Quantum states can be described equivalently by density matrices, Wigner
functions or quantum tomograms. We analyze the accuracy and performance of
three related semiclassical approaches to quantum dynamics, in particular with
respect to their numerical implementation. As test cases, we consider the time
evolution of Gaussian wave packets in different one-dimensional geometries,
whereby tunneling, resonance and anharmonicity effects are taken into account.
The results and methods are benchmarked against an exact quantum mechanical
treatment of the system, which is based on a highly efficient Chebyshev
expansion technique of the time evolution operator.


title: Charged Higgs production at photon colliders in 2HDM-III

abstract:
  We study charged Higgs production in the process $\gamma\gamma\to A^0\to W^-
H^+$. The processes $\gamma\gamma\to A^0$ are loop mediated in a 2HDM. This is
due to the fact that photons only couple directly to charged particles and the
Higgs only couples to particles with mass acquired via Higgs mechanism.
Although in MSSM the contribution from the process $\gamma\gamma\to A^0$ is too
small, it has been found that in a more general 2HDM it could be enhanced. On
the other hand, the boson $A^0$ can decay in $W^- H^+$ at tree level and the
charged Higgs can decay in fermions. So, the whole process under study is
$\gamma\gamma\to A^0\to (W^-\to l\nu) (H^+\to f_if_j)$ in 2HDM-III. Evidence
about charged Higgs existence could demonstrate that structure of the Higgs
sector has several multiplets.


title: Gravitational waves in vector inflation

abstract:
  We discuss the gravitational waves (GW) in the context of vector inflation.
We derive the action for tensor perturbations and find that tachyonic
instabilities are present in most (but not all) of the inflationary models with
large fields. In contrast, the stability of the small field inflation
($A_{\mu}A^{\mu}\ll\frac{1}{N}$) is ensured by the usual slow-roll conditions,
where $N$ is the total number of fields. For example, the Coleman-Weinberg
potential and the power-law inflation are always stable in the small fields
limit with an approximately flat spectrum of GW. We also provide some examples
which lead to a rapid decay of GW and predict the absence of tensor modes in
the CMB.


title:
On the renormalization of contact interactions for the
  configuration-interaction method in two dimensions

abstract:
  The configuration interaction (CI) method for calculating the exact
eigenstates of a quantum-mechanical few-body system is problematic when applied
to particles interacting through contact forces. In dimensions higher than one
the approach fails due to the pathology of the Dirac delta-potential, making it
impossible to reach convergence by gradually increasing the size of the Hilbert
space. However, this problem may be cured in a rather simple manner by
renormalizing the strength of the contact potential when diagonalizing in a
truncated Hilbert space. One hereby relies on the comparison of the CI results
to the two-body ground-state energy obtained by the exact solution of the
Schroedinger equation for a regularized contact interaction. We here discuss a
scheme that provides cutoff-independent few-body physical observables. The
method is applied to a few-body system of ultracold atoms confined by a
two-dimensional harmonic oscillator.


title: Collective Phenomena in the Non-Equilibrium Quark-Gluon Plasma

abstract:
  In this work we study the non-equilibrium dynamics of a quark-gluon plasma,
as created in heavy-ion collisions. We investigate how big of a role plasma
instabilities can play in the isotropization and equilibration of a quark-gluon
plasma. In particular, we determine, among other things, how much collisions
between the particles can reduce the growth rate of unstable modes. This is
done both in a model calculation using the hard-loop approximation, as well as
in a real-time lattice simulation combining both classical Yang-Mills-fields as
well as inter-particle collisions. The new extended version of the simulation
is also used to investigate jet transport in isotropic media, leading to a
cutoff-independent result for the transport coefficient q-hat. The precise
determination of such transport coefficients is essential, since they can
provide important information about the medium created in heavy-ion collisions.
In anisotropic media, the effect of instabilities on jet transport is studied,
leading to a possible explanation for the experimental observation that
high-energy jets traversing the plasma perpendicular to the beam axis
experience much stronger broadening in rapidity than in azimuth. The
investigation of collective modes in the hard-loop limit is extended to
fermionic modes, which are shown to be all stable. Finally, we study the
possibility of using high energy photon production as a tool to experimentally
determine the anisotropy of the created system. Knowledge of the degree of
local momentum-space anisotropy reached in a heavy-ion collision is essential
for the study of instabilities and their role for isotropization and
thermalization, because their growth rate depends strongly on the anisotropy


title: On the central core in MHD winds and jets

abstract:
  We demonstrate that the 1D cylindrical version of the Grad-Shafranov equation
is more rich than classical self-similar ones, and more suitable for the
astrophysical jets we observe. In particular, it allows us to describe the
central (and, hence, the most energetic) part of the flow. Both relativistic
and non-relativistic versions are discussed. It is shown that taking into
account the finite pressure of the external media one can determine the
magnetic flux within the central core. We found as well that for
non-relativistic flows which are magnetically dominated near the origin the
solution can be constructed only in the presense of the oblique shock near the
base of a jet where the additional heating is to take place.


title:
Matter Power Spectrum for the Generalized Chaplygin Gas Model: The
  Newtonian Approach

abstract:
  We model the cosmic medium as the mixture of a generalized Chaplygin gas and
a pressureless matter component. Within a neo-Newtonian approach (in which,
different from standard Newtonian cosmology, the pressure enters the
homogeneous and isotropic background dynamics) we compute the matter power
spectrum. The 2dFGRS data are used to discriminate between unified models of
the dark sector (a purely baryonic matter component of roughly 5 percent of the
total energy content and roughly 95 percent generalized Chaplygin gas) and
different models, for which there is separate dark matter, in addition to that
accounted for by the generalized Chaplygin gas. Leaving the corresponding
density parameters free, we find that the unified models are strongly
disfavored. On the other hand, using unified model priors, the observational
data are also well described, in particular for small and large values of the
generalized Chaplygin gas parameter $\alpha$. The latter result is in agreement
with a recent, more qualitative but fully relativistic, perturbation analysis
in Gorini et al.


title: Deviations from universality of slepton masses in the MSSM

abstract:
  In this paper we propose an ansatz that applies to the slepton mass matrices.
In our approach these matrices contain a dominant sector that can be
diagonalized exactly. We study the numerical results for the slepton mass
eigenstates, looking for deviations from universality, which is usually assumed
when one evaluates the production of sleptons at future colliders.


title: Unitarity of SL(2)-conformal blocks in genus zero

abstract:
  This submission has been withdrawn by arXiv administrators due to an
unresolved conflict between the authors. This article was submitted without
consent of E. Looijenga.


title: Unified Description of Dark Energy and Dark Matter

abstract:
  Dark energy in the universe is assumed to be vacuum energy. The
energy-momentum of vacuum is described by a scale-dependent cosmological
constant. The equations of motion imply for the density of matter (dust) the
sum of the usual matter density (luminous matter) and an additional matter
density (dark matter) similar to the dark energy. The scale-dependent
cosmological constant is given up to an exponent which is approximated by the
experimentally decided density parameters of dark matter and dark energy. This
yields that dark matter is one third of dark energy for all times implying an
explanation of the coincidence of dark matter and dark energy. In the final
state, the universe becomes dark, consisting of dark matter and dark energy.


title: Jumps in current-voltage characteristics in disordered films

abstract:
  We argue that giant jumps of current at finite voltages observed in
disordered samples of InO, TiN and YSi manifest a bistability caused by the
overheating of electrons. One of the stable states is overheated and thus
low-resistive, while the other, high-resistive state is heated much less by the
same voltage. The bistability occurs provided that cooling of electrons is
inefficient and the temperature dependence of the equilibrium resistance, R(T),
is steep enough. We use experimental R(T) and assume phonon mechanism of the
cooling taking into account its strong suppression by disorder. Our description
of details of the I-V characteristics does not involve adjustable parameters
and turns out to be in a quantitative agreement with the experiments. We
propose experiments for more direct checks of this physical picture.


title: Light Higgs Boson Production in Two Higgs Doublets Models type III

abstract:
  By using the Cheng, Sher and Yuan's anzats, we study the light Higgs Boson
production associated with $b$ quark production at TEVATRON using the 2HDM type
III.
  We compare the simulations with experimental results coming from TEVATRON,
finding valid ranges for the $bb$ coupling. By using these results, we
calculate the cross section for the process $pp \to b\bar bh(b\bar b)$ for the
LHC collider.


title: Discrete Morse theory for totally non-negative flag varieties

abstract:
  In a seminal 1994 paper, Lusztig extended the theory of total positivity by
introducing the totally non-negative part (G/P)_{\geq 0} of an arbitrary
(generalized, partial) flag variety G/P. He referred to this space as a
"remarkable polyhedral subspace", and conjectured a decomposition into cells,
which was subsequently proven by the first author. Subsequently the second
author made the concrete conjecture that this cell decomposed space is the next
best thing to a polyhedron, by conjecturing it to be a regular CW complex that
is homeomorphic to a closed ball. In this article we use discrete Morse theory
to prove this conjecture up to homotopy-equivalence. Explicitly, we prove that
the boundaries of the cells are homotopic to spheres, and the closures of cells
are contractible. The latter part generalizes a result of Lusztig's that
(G/P)_{\geq 0} -- the closure of the top-dimensional cell -- is contractible.
Concerning our result on the boundaries of cells, even the special case that
the boundary of the top-dimensional cell (G/P)_{> 0} is homotopic to a sphere,
is new for all G/P other than projective space.


title: A formal system for Euclid's Elements

abstract:
  We present a formal system, E, which provides a faithful model of the proofs
in Euclid's Elements, including the use of diagrammatic reasoning.


title: Social Aggregation as a Cooperative Game

abstract:
  A new approach for the description of phenomena of social aggregation is
suggested. On the basis of psychological concepts (as for instance social norms
and cultural coordinates), we deduce a general mechanism for the social
aggregation in which different clusters of individuals can merge according to
the cooperation among the agents. In their turn, the agents can cooperate or
defect according to the clusters distribution inside the system. The fitness of
an individual increases with the size of its cluster, but decreases with the
work the individual had to do in order to join it. In order to test the
reliability of such new approach, we introduce a couple of simple toy models
with the features illustrated above. We see, from this preliminary study, how
the cooperation is the most convenient strategy only in presence of very large
clusters, while on the other hand it is not necessary to have one hundred
percent of cooperators for reaching a totally ordered configuration with only
one megacluster filling the whole system.


title: Gaussian wave packets in phase space: The Fermi g_F function

abstract:
  Any pure quantum state can be equivalently represented by means of its wave
function psi(q) or of the Fermi function g_F(q,p), with q and p coordinates and
conjugate momenta of the system under investigation.We show that a Gaussian
wave packet can be conveniently visualized in phase space by means of the curve
g_F(q,p)=0. The evolution in time of the g_F=0 curve is then computed for a
Gaussian packet evolving freely or under a constant or a harmonic force. As a
result, the spreading or shrinking of the packet is easily interpreted in phase
space. Finally, we discuss a gedanken prism microscope experiment for measuring
the position-momentum correlation. This gedanken experiment, together with the
well-known Heisenberg microscope and von Neumann velocimeter, is sufficient to
fully determine the state of a Gaussian packet.


title:
Charged current reactions in the NuSOnG and a test of neutrino-W
  couplings

abstract:
  We explore the physics potential of NuSOnG experiment to probe new physics
contributions to $W\mu\nu_\mu$ couplings in inverse muon decay and charged
current deep inelastic scattering processes. We show that NuSOnG provides two
order of magnitude improvement in $W\mu\nu_\mu$ compared to LEP bound at 95%
C.L.. Combining the results presented here with our earlier results, we obtain
a significant improvement in the limits on neutrino flavor universality
violation in neutrino-W and neutrino-Z couplings.


title: Non-locality of non-Abelian anyons

abstract:
  Topological systems, such as fractional quantum Hall liquids, promise to
successfully combat environmental decoherence while performing quantum
computation. These highly correlated systems can support non-Abelian anyonic
quasiparticles that can encode exotic entangled states. To reveal the non-local
character of these encoded states we demonstrate the violation of suitable Bell
inequalities. We provide an explicit recipe for the preparation, manipulation
and measurement of the desired correlations for a large class of topological
models. This proposal gives an operational measure of non-locality for anyonic
states and it opens up the possibility to violate the Bell inequalities in
quantum Hall liquids or spin lattices.


title: Heegaard genus, cut number, weak p-congruence, and quantum invariants

abstract:
  We use quantum invariants to define a 3-manifold invariant j_p which lies in
the non-negative integers. We relate j_p to the Heegard genus, and the cut
number. We show that j_$ is an invariant of weak p-congruence.


title: Z (+jets) At The Tevatron

abstract:
  We report on recent Z (+jets) measurements from the Fermilab Tevatron proton
anti-proton collider. A new D0 measurement of the transverse momentum of Z
bosons yields the best measurement to date of the non-perturbative form factor,
g2. The production of Z+jets is an major background to many rare signals, and
is a vital testing ground for theoretical predictions. Measurements from CDF
and D0 of differential cross sections in Z+jet production test NLO pQCD, and in
the case of D0, the latest tree-level matrix element with matched parton shower
calculations. Improving modelling of this signal will impact results from the
Fermilab Tevatron and CERN LHC.


title: What is the optimal shape of a pipe?

abstract:
  We consider an incompressible fluid in a three-dimensional pipe, following
the Navier-Stokes system with classical boundary conditions. We are interested
in the following question: is there any optimal shape for the criterion "energy
dissipated by the fluid"? Moreover, is the cylinder the optimal shape? We prove
that there exists an optimal shape in a reasonable class of admissible domains,
but the cylinder is not optimal. For that purpose, we explicit the first order
optimality condition, thanks to adjoint state and we prove that it is
impossible that the adjoint state be a solution of this over-determined system
when the domain is the cylinder. At last, we show some numerical simulations
for that problem.


title:
Compensation strategies for a lip-tube perturbation of French [u]: an
  acoustic and perceptual study of 4-year-old children

abstract:
  The relations between production and perception in 4-year-old children were
examined in a study of compensation strategies for a lip-tube perturbation.
Acoustic and perceptual analyses of the rounded vowel [u] produced by twelve
4-year-old French speakers were conducted under two conditions: normal and with
a 15-mm-diameter tube inserted between the lips. Recordings of isolated vowels
were made in the normal condition before any perturbation (N1), immediately
upon insertion of the tube and for the next 19 trials in this perturbed
condition, with (P2) or without articulatory instructions (P1), and in the
normal condition after the perturbed trials (N2). The results of the acoustic
analyses reveal speaker-dependent alterations of F1, F2, and/or F0 in the
perturbed conditions and after the removal of the tube. For some subjects, the
presence of the tube resulted in very little change; for others, an increase in
F2 was observed in P1, which was generally reduced in some of the 20
repetitions, but not systematically and not continuously. The use of
articulatory instructions provided in the P2 condition was detrimental to the
achievement of a good acoustic target. Perceptual data are used to determine
optimal combinations of F0, F1, and F2 (in Bark) related to these patterns. The
data are compared to a previous study conducted with adults [Savariaux et al.,
J. Acoust. Soc. Am. 106, 381-393 (1999)].


title: The two-dimensional hydrogen atom in The momentum representation

abstract:
  The analytic expression of the momentum representation in terms of the
associated Legendre function is determined by a direct integration of Fourier
transform of the wave function of coordinates using the Levi-Civita
transformation and the generating function method. A new generating function
for the associated Legendre functions are obtained.


title: Universal Flow in the First Stage of Relativistic Heavy Ion Collisions

abstract:
  In the first moments of a relativistic heavy ion collision explosive
collective flow begins to grow before the matter has yet equilibrated. Here it
is found that as long as the stress-energy tensor is traceless, early flow is
independent of whether the matter is composed of fields or particles,
equilibrated or not, or whether the stress-energy tensor is isotropic. This
eliminates much of the uncertainty in modeling early stages of a collision.


title: Topics in Mitigating Radar Bias

abstract:
  In this paper, we investigate two topics related to mitigating the effect of
radar bias in ballistic missile tracking applications. We determine the
absolute bias between two radars in polar coordinates when their relative bias
is given in rectangular coordinates. Using this result, we then obtain the
optimized steady-state filter to handle the random bias.


title: Continuity of the SLE trace in simply connected domains

abstract:
  We prove that the $SLE_\kappa$ trace in any simply connected domain $G$ is
continuous (except possibly near its endpoints) if $\kappa<8$. We also prove an
SLE analog of Makarov's Theorem about the support of harmonic measure.


title:
Light pseudoscalar meson masses and decay constants from mixed action
  lattice QCD

abstract:
  We calculate the light pseudoscalar decay constants, f_pi and f_K, and their
ratio using domain wall valence quarks and 2+1 flavors of dynamical staggered
quarks. Use of the MILC gauge configurations allows us to simulate at several
sea quark masses and spatial volumes, and with two lattice spacings. We study
how well our numerical lattice data for light decay constants and meson masses
is described by next-to-leading order SU(3) mixed action chiral perturbation
theory and explain our strategy for the chiral and continuum extrapolation.
Combining our result for f_K/f_pi with experimental measurements of pion and
kaon leptonic decays allows a model-independent determination of |V_us|/|V_ud|;
we find a preliminary value of |V_us|/|V_ud| = 0.2315(45)(7).


title:
Reducing the gravitational lensing scatter of Type Ia supernovae without
  introducing any extra bias

abstract:
  Magnification and de-magnification due to gravitational lensing will
contribute to the brightness scatter of Type Ia supernovae (SNe Ia). The
purpose of this paper is to investigate the possibility to decrease this
scatter by correcting individual SNe Ia using observations of galaxies in the
foreground, without introducing any extra bias. We simulate a large number of
SN Ia lines of sight populated by galaxies. For each line of sight the true
magnification factor and an estimate thereof are calculated. The estimated
magnification factor corresponds to what an observer would infer from a survey
like SNLS. Using the simulated data we investigate the possibility to estimate
the magnification of individual supernovae with enough precision to be able to
correct their brightness for gravitational lensing with negligible bias. Our
simulations show that the bias arising from gravitational lensing corrections
of individual SNe Ia is negligible for current and next generation surveys and
that the scatter from lensing can be reduced by approximately a factor 2. The
total scatter in the SN Ia magnitudes could be reduced by 4% for an intrinsic
dispersion of 0.13 mag. For an intrinsic dispersion of 0.09 mag, which might
not be to unrealistic for future surveys, the total scatter could be reduced by
6%. This will reduce the errors on cosmological parameters derived from
supernova data by 4-8%. The prospect of correcting for lensing is thus very
good.


title: Loop quantum cosmology and tensor perturbations in the early universe

abstract:
  We study the tensor modes of linear metric perturbations within an effective
framework of loop quantum cosmology. After a review of inverse-volume and
holonomy corrections in the background equations of motion, we solve the
linearized tensor modes equations and extract their spectrum. Ignoring holonomy
corrections, the tensor spectrum is blue tilted in the near-Planckian
superinflationary regime and may be observationally disfavoured. However, in
this case background dynamics is highly nonperturbative, hence the use of
standard perturbative techniques may not be very reliable. On the other hand,
in the quasi-classical regime the tensor index receives a small negative
quantum correction, slightly enhancing the standard red tilt in slow-roll
inflation. We discuss possible interpretations of this correction, which
depends on the choice of semiclassical state.


title:
Most quantum states are too entangled to be useful as computational
  resources

abstract:
  It is often argued that entanglement is at the root of the speedup for
quantum compared to classical computation, and that one needs a sufficient
amount of entanglement for this speedup to be manifest. In measurement-based
quantum computing (MBQC), the need for a highly entangled initial state is
particularly obvious. Defying this intuition, we show that quantum states can
be too entangled to be useful for the purpose of computation. We prove that
this phenomenon occurs for a dramatic majority of all states: the fraction of
useful n-qubit pure states is less than exp(-n^2). Computational universality
is hence a rare property in quantum states. This work highlights a new aspect
of the question concerning the role entanglement plays for quantum
computational speed-ups. The statements remain true if one allows for certain
forms of post-selection and also cover the notion of CQ-universality. We
identify scale-invariant states resulting from a MERA construction as likely
candidates for physically relevant states subject to this effect.


title:
Statistical properties of the Burgers equation with Brownian initial
  velocity

abstract:
  We study the one-dimensional Burgers equation in the inviscid limit for
Brownian initial velocity (i.e. the initial velocity is a two-sided Brownian
motion that starts from the origin x=0). We obtain the one-point distribution
of the velocity field in closed analytical form. In the limit where we are far
from the origin, we also obtain the two-point and higher-order distributions.
We show how they factorize and recover the statistical invariance through
translations for the distributions of velocity increments and Lagrangian
increments. We also derive the velocity structure functions and we recover the
bifractality of the inverse Lagrangian map. Then, for the case where the
initial density is uniform, we obtain the distribution of the density field and
its $n$-point correlations. In the same limit, we derive the $n-$point
distributions of the Lagrangian displacement field and the properties of
shocks. We note that both the stable-clustering ansatz and the Press-Schechter
mass function, that are widely used in the cosmological context, happen to be
exact for this one-dimensional version of the adhesion model.


title:
Simultaneous polarization monitoring of supernovae SN2008D/XT080109 and
  SN2007uy: isolating geometry from dust

abstract:
  The possible existence of a continuum encompassing the diversity of explosive
stellar deaths,ranging from ordinary SNe to relativistic hypernovae associated
with long duration GRBs, is under intense debate. In this context, SN2008D
associated with XT080109 could represent a paradigmatic case, since it might
exemplify a potential borderline event. The main aim is to infer geometric
information of SN2008D through the evolution of its linear optical
polarization. We also report the polarization evolution of SN2007uy, and
discuss the properties of the host ISM towards the XT. The final goal is to
compare the polarization properties, and hence the geometries of both SNe,
which shone contemporaneously in NGC2770. This fortunate coincidence brought us
the opportunity to observe both SNe simultaneously, and most importantly, with
identical instrumental setups. The observations span 74.9 days, starting 3.6
days after the XT and are distributed in 11 visits. In addition we performed
observations in the mm range in order to identify the dominant polarization. We
report positive linear polarization detections at several epochs for SN2008D at
a level of ~1% and at ~1.5% for SN2007uy. SN2007uy shows constant polarization,
which could be described by the host interstellar polarization plus a constant
eccentricity expansion on the sky plane. A statistical analysis of the
distribution of the SN2008D Stokes parametres suggests that it could show an
intrinsic variable polarization component. Assuming the SN2007uy polarization
is constant, we find that the evolution of the intrinsic SN2008D polarization
could be explained by an aspherical axisymmetric expansion with variable
eccentricity. We come to the same result even if we make no assumption on
SN2007uy, although at a lower significance level. We suggest that at least the
projected, if not the intrinsic, geometries of both SNe could differ.


title:
Dissecting the Red Sequence--I. Star Formation Histories of Quiescent
  Galaxies: The Color-Magnitude vs. the Color-Sigma Relation

abstract:
  We use a sample of ~16,000 non-emission line galaxies from the SDSS to
investigate the physical parameters underlying the well-known color-magnitude
and color-sigma relations. Galaxies are sorted in terms of velocity dispersions
(sigma), luminosity (L), and color, and their spectra are stacked to obtain
very high S/N mean spectra for stellar population analysis. This allows us to
map mean luminosity-weighted ages, [Fe/H], [Mg/H], and [Mg/Fe] in sigma-L-color
space. Our first result is that there are many different red sequences, with
age, [Fe/H], [Mg/H], and [Mg/Fe] showing different amounts of slope and scatter
when plotted versus sigma, L, or color. These behaviors are explained if the
star formation histories of the galaxies populate a two-dimensional parameter
space. One parameter is the previously well-known increase in age, [Fe/H],
[Mg/H], and [Mg/Fe] with sigma. In addition to this, we find systematic
variations at fixed sigma, such that more luminous galaxies are younger, more
Fe-rich, but have lower [Mg/Fe] than their fainter counterparts. The main sigma
trends support a paradigm in which more massive galaxies form their stars more
rapidly and at earlier times than less massive galaxies. The trends at fixed
sigma are consistent with scatter in the duration of star formation for
galaxies at a given sigma. The co-variation of stellar population properties
and L residuals at fixed sigma that we present here has a number of
implications: it explains the differing behavior of stellar population
indicators when investigated versus sigma as compared to L, and it reveals that
L is not as efficient as sigma for indicating galaxy "size" in stellar
population studies.


title: Consistency of the Adiabatic Theorem

abstract:
  The adiabatic theorem provides the basis for the adiabatic model of quantum
computation. Recently the conditions required for the adiabatic theorem to hold
have become a subject of some controversy. Here we show that the reported
violations of the adiabatic theorem all arise from resonant transitions between
energy levels. In the absence of fast driven oscillations the traditional
adiabatic theorem holds. Implications for adiabatic quantum computation is
discussed.


title:
The luminosity function of galaxies to $M_{BgVriz} \sim -14$ in $z \sim
  0.3$ clusters

abstract:
  We present deep composite luminosity functions in $B$, $g$, $V$, $r$, $i$ and
$z$ for six clusters at $0.14 < z < 0.40$ observed with the Hubble Space
Telescope Advanced Camera for Surveys. The luminosity functions reach to
absolute magnitude of $\sim -14 + 5\log h$ mag. and are well fitted by a single
Schechter function with $M^*_{BgVriz}=-19.8, -20.9 -21.9, -22.0, -21.7, -22.3$
mag. and $\alpha \sim -1.3$ (in all bands). The observations suggest that the
galaxy luminosity function is dominated by objects on the red sequence to at
least 6 mags. below the $L^*$ point. Comparison with local data shows that the
red sequence is well established at least at $z \sim 0.3$ down to $\sim
1/600^{th}$ of the luminosity of the Milky Way and that galaxies down to the
regime of dwarf spheroidals have been completely assembled in clusters at this
redshift. We do not detect a steepening of the luminosity function at $M > -16$
as is observed locally. If the faint end upturn is real, the steepening of the
luminosity function must be due to a newly infalling population of faint dwarf
galaxies.


title: On the Formation and Evolution of cD Galaxies

abstract:
  The cannibalism mechanism of formation of cD galaxies in clusters of
Bautz-Morgan class I is analyzed. Dependences between absolute magnitude of cD
galaxies, and of the clusters in which they reside (richness, redshifts) are
considered. Evidences are presented in favor of formation of cD galaxies by
cannibalism and their evolution.


title: Algorithms for translational tiling

abstract:
  In this paper we study algorithms for tiling problems. We show that the
conditions $(T1)$ and $(T2)$ of Coven and Meyerowitz, conjectured to be
necessary and sufficient for a finite set $A$ to tile the integers, can be
checked in time polynomial in ${diam}(A)$. We also give heuristic algorithms to
find all non-periodic tilings of a cyclic group $Z_N$. In particular we carry
out a full classification of all non-periodic tilings of $Z_{144}$.