title: Powerful explosions at Z=0 ?

abstract:
  Metal-free stars are assumed to evolve at constant mass because of the very
low stellar winds. This leads to large CO-core mass at the end of the
evolution, so primordial stars with an initial mass between 25 and 85 Msol are
expected to end as direct black holes, the explosion energy being too weak to
remove the full envelope.
  We show that when rotation enters into play, some mass is lost because the
stars are prone to reach the critical velocity during the main sequence
evolution. Contrarily to what happens in the case of very low- but non
zero-metallicity stars, the enrichment of the envelope by rotational mixing is
very small and the total mass lost remains modest. The compactness of the
primordial stars lead to a very inefficient transport of the angular momentum
inside the star, so the profile of Omega(r) is close to Omega r^2 = const. As
the core contracts, the rotation rate increases, and the star ends its life
with a fast spinning core. Such a configuration has been shown to modify
substantially the dynamics of the explosion. Where one expected a weak
explosion or none at all, rotation might boost the explosion energy and drive a
robust supernova. This will have important consequences in the way primordial
stars enriched the early Universe.


title: Drell-Yan production at the LHC in a four site Higgsless model

abstract:
  We consider a four site Higgsless model based on the $SU(2)_L\times
SU(2)_1\times SU(2)_2\times U(1)_Y$ gauge symmetry, which predicts two neutral
and four charged extra gauge bosons, $Z_{1,2}$ and $W^\pm_{1,2}$. We compute
the properties of the new particles, and derive indirect and direct limits on
their masses and couplings from LEP and Tevatron data. In contrast to other
Higgsless models, characterized by fermiophobic extra gauge bosons, here
sizeable fermion-boson couplings are allowed by the electroweak precision data.
The prospects of detecting the new predicted particles in the favoured
Drell-Yan channel at the LHC are thus investigated. The outcome is that all six
extra gauge bosons could be discovered in the early stage of the LHC
low-luminosity run.


title:
A representative particle approach to coagulation and fragmentation of
  dust aggregates and fluid droplets

abstract:
  Context: There is increasing need for good algorithms for modeling the
aggregation and fragmentation of solid particles (dust grains, dust aggregates,
boulders) in various astrophysical settings, including protoplanetary disks,
planetary- and sub-stellar atmospheres and dense molecular cloud cores. Here we
describe a new algorithm that combines advantages of various standard methods
into one.
  Aims: The aim is to develop a method that 1) can solve for aggregation and
fragmentation, 2) can easily include the effect and evolution of grain
properties such as compactness, composition, etc., and 3) can be built as a
coagulation/fragmentation module into a hydrodynamics simulations.
  Methods: We develop a Monte-Carlo method in which we follow the 'life' of a
limited number of representative particles. Each of these particles is
associated with a certain fraction of the total dust mass and thereby
represents a large number of true particles which all are assumed to have the
same properties as their representative particle. Under the assumption that the
total number of true particles vastly exceeds the number of representative
particles, the chance of a representative particle colliding with another
representative particle is negligibly small, and we therefore ignore this
possibility. This now makes it possible to employ a statistical approach to the
evolution of the representative particles.
  Results: The method reproduces the known analytic solutions of simplified
coagulation kernels, and compares well to numerical results for Brownian motion
using other methods. For reasonably well-behaved kernels it produces good
results even for moderate number of swarms.


title:
An Improved Model for Relativistic Solar Proton Acceleration applied to
  the 2005 January 20 and Earlier Events

abstract:
  This paper presents results on modelling the ground level response of the
higher energy protons for the 2005 January 20 ground level enhancement (GLE).
This event, known as GLE 69, produced the highest intensity of relativistic
solar particles since the famous event on 1956 February 23. The location of
recent X-ray and gamma-ray emission (N14 W61) was near to Sun-Earth connecting
magnetic field lines, thus providing the opportunity to directly observe the
acceleration source from Earth. We restrict our analysis to protons of energy
greater than 450 MeV to avoid complications arising from transport processes
that can affect the propagation of low energy protons. In light of this revised
approach we have reinvestigated two previous GLEs: those of 2000 July 14 (GLE
59) and 2001 April 15 (GLE 60). Within the limitations of the spectral forms
employed, we find that from the peak (06:55 UT) to the decline (07:30 UT)
phases of GLE 69, neutron monitor observations from 450 MeV to 10 GeV are best
fitted by the Gallegos-Cruz & Perez-Peraza stochastic acceleration model. In
contrast, the Ellison & Ramaty spectra did not fit the neutron monitor
observations as well. This result suggests that for GLE 69, a stochastic
process cannot be discounted as a mechanism for relativistic particle
acceleration, particularly during the initial stages of this solar event. For
GLE 59 we find evidence that more than one acceleration mechanism was present,
consistent with both shock and stochastic acceleration processes dominating at
different times of the event. For GLE 60 we find that Ellison & Ramaty spectra
better represent the neutron monitor observations compared to stochastic
acceleration spectra. The results for GLEs 59 and 60 are in agreement with our
previous work.


title: On the Depletion Effect in Colloids: Correlated Brownian Motions

abstract:
  Our object is to formulate and analyze a physically plausible and
mathematically sound model to better understand the phenomenon of clumping in
colloid dispersions. Our model is stochastic but rigorously derived from a
deterministic setup in a Newtonian setting. A rigorous transition from
deterministic mean-field dynamics of several large particles and infinitely
many small particles to the stochastic motion of the large particles is
invoked. Then the stochastic motion of the large particles is described by a
system of correlated Brownian motions. The scaling in the transition preserves
a characteristic correlation length. From the limiting stochastic equations we
compute the probability fluxes for the separation between two large particles.
We show that, for short times, two particles sufficiently close together tend
to be attracted to each other. This agrees with the observed depletion
phenomena in colloids. To do this computation, we extend the notion of Van
Kampen's one-dimensional flux rate in an appropriate way to account for higher
dimensional effect.


title: Study of the derivative expansions for the nuclear structure functions

abstract:
  We study the convergence of the series expansions sometimes used in the
analysis of the nuclear effects in Deep Inelastic Scattering (DIS) proccesses
induced by leptons. The recent advances in statistics and quality of the data,
in particular for neutrinos calls for a good control of the theoretical
uncertainties of the models used in the analysis. Using realistic nuclear
spectral functions which include nucleon correlations, we find that the
convergence of the derivative expansions to the full results is poor except at
very low values of $x$.


title:
Origin of the Broad Lifetime Distribution of Localized Excitons in
  InGaN/GaN Quantum Dots

abstract:
  We derive an energy-dependent decay-time distribution function from the
multi-exponential decay of the ensemble photoluminescence (PL) of InGaN/GaN
quantum dots (QDs), which agrees well with recently published single-QD
time-resolved PL measurements. Using eight-band k.p modelling, we show that the
built-in piezo- and pyroelectric fields within the QDs cause a sensitive
dependence of the radiative lifetimes on the exact QD geometry and composition.
Moreover, the radiative lifetimes also depend heavily on the composition of the
direct surrounding of the QDs. A broad lifetime distribution occurs even for
moderate variations of the QD structure. Thus, for unscreened fields a
multi-exponential decay of the ensemble PL is generally expected in this
material system.


title: Two-level Physics in a Model Metallic Break Junction

abstract:
  We consider a model inspired by a metal break-junction hypothetically caught
at its breaking point, where the non-adiabatic center-of-mass motion of the
bridging atom can be treated as a two-level system. By means of Numerical
Renormalization Group (NRG) we calculate the influence of the two level system
on the ballistic conductance across the bridge atom. The results are shown to
be fully consistent with a conformal field theory treatment. We find that the
conductance, calculated by coupling Fermi liquid theory to our NRG is always
finite and fractional at zero temperature, but drops quite fast as the
temperature increases.


title: Adaptive Bayesian and frequentist data processing for quantum tomography

abstract:
  The outcome statistics of an informationally complete quantum measurement for
a system in a given state can be used to evaluate the ensemble expectation of
any linear operator in the same state, by averaging a function of the outcomes
that depends on the specific operator. Here we introduce two novel
data-processing strategies, non-linear in the frequencies, which lead to faster
convergence to theoretical expectations.


title: Adaptive density estimation for directional data using needlets

abstract:
  This paper is concerned with density estimation of directional data on the
sphere. We introduce a procedure based on thresholding on a new type of
spherical wavelets called {\it needlets}. We establish a minimax result and
prove its optimality. We are motivated by astrophysical applications, in
particular in connection with the analysis of ultra high energy cosmic rays.


title: Geometric characterization of flat groups of automorphisms

abstract:
  If H is a flat group of automorphisms of finite rank n of a totally
disconnected, locally compact group G, then each orbit of H in the metric space
B(G) of compact, open subgroups of G is quasi-isometric to n-dimensional
euclidean space. In this note we prove the following partial converse: Assume
that G is a totally disconnected, locally compact group such that B(G) is a
proper metric space and let H be a group of automorphisms of G such that some
(equivalently every) orbit of H in B(G) is quasi-isometric to n-dimensional
euclidean space, then H has a finite index subgroup which is flat of rank n. We
can draw this conclusion under weaker assumptions. We also single out a
naturally defined flat subgroup of such groups of automorphisms.


title: Wind anisotropy and stellar evolution

abstract:
  Mass loss is a determinant factor which strongly affects the evolution and
the fate of massive stars. At low metallicity, stars are supposed to rotate
faster than at the solar one. This favors the existence of stars near the
critical velocity. In this rotation regime, the deformation of the stellar
surface becomes important, and wind anisotropy develops. Polar winds are
expected to be dominant for fast rotating hot stars.
  These polar winds allow the star to lose large quantities of mass and still
retain a high angular momentum, and they modifie the evolution of the surface
velocity and the final angular momentum kept in the star's core. We show here
how these winds affect the final stages of massive stars, according to our
knowledge about Gamma Ray Bursts. Computation of theoretical Gamma Ray Bursts
rate indicates that our models have too fast rotating cores, and that we need
to include an additional effect to spin them down. Magnetic fields in stars act
in this direction, and we show how they modify the evolution of massive star up
to the final stages.


title: Atom-atom correlations in colliding Bose-Einstein condensates

abstract:
  We analyze atom-atom correlations in the s-wave scattering halo of two
colliding condensates. By developing a simple perturbative approach, we obtain
explicit analytic results for the collinear (CL) and back-to-back (BB)
correlations corresponding to realistic density profiles of the colliding
condensates with interactions. The results in the short time limit are in
agreement with the first-principles simulations using the positive-$P$
representation and provide analytic insights into the experimental observations
of Perrin et al. [Phys. Rev. Lett. 99, 150405 (2007)]. For long collision
durations, we predict that the BB correlation becomes broader than the CL
correlation.


title:
High pressure operation of the Photon-Assisted Cascaded Electron
  Multiplier

abstract:
  We present the operation of the recently introduced Photon Assisted Cascaded
Electron Multiplier (PACEM) in xenon at high pressure. The PACEM is a multi
step electron multiplier where the VUV scintillation produced in the electron
avalanches is used for signal propagation: the VUV scintillation produced in
the first element of the cascade induces the emission of photoelectrons from a
CsI photocathode placed on the top-surface of the second element. These
photoelectrons are further multiplied, via charge avalanche. A metallic mesh
electrode placed between the first and the second elements of the cascade
completely blocks the charge transfer between them. Optical gains of 103 were
achieved in xenon at atmospheric pressure, dropping to 25 at 3.3 bar, for
applied voltages of 700 and 1100 V, respectively. Taking into account the
subsequent charge multiplication, total gains are higher than those obtained
with a triple GEM and double THGEM.


title: A millisecond quantum memory for scalable quantum networks

abstract:
  Scalable quantum information processing critically depends on the capability
of storage of a quantum state. In particular, a long-lived storable and
retrievable quantum memory for single excitations is of crucial importance to
the atomic-ensemble-based long-distance quantum communication. Although atomic
memories for classical lights and continuous variables have been demonstrated
with milliseconds storage time, there is no equal advance in the development of
quantum memory for single excitations, where only around 10 $\mu$s storage time
was achieved. Here we report our experimental investigations on extending the
storage time of quantum memory for single excitations. We isolate and identify
distinct mechanisms for the decoherence of spin wave (SW) in atomic ensemble
quantum memories. By exploiting the magnetic field insensitive state, ``clock
state", and generating a long-wavelength SW to suppress the dephasing, we
succeed in extending the storage time of the quantum memory to 1 ms. Our result
represents a substantial progress towards long-distance quantum communication
and enables a realistic avenue for large-scale quantum information processing.


title:
Detection of periodic gravitational wave sources by Hough transform in
  the frequency and spin down plane

abstract:
  In the hierarchical search for periodic sources of gravitational waves, the
candidate selection, in the incoherent step, can be performed with Hough
transform procedures. In this paper we analyze the problem of sensitivity loss
due to discretization of the parameters space vs computing cost, comparing the
properties of the sky Hough procedure with those of a new frequency Hough,
which is based on a transformation from the time - observed frequency plane to
the source frequency - spin down plane. Results on simulated peak maps suggest
various advantages in favor of the use of the frequency Hough. The ones which
show up to really make the difference are 1) the possibility to enhance the
frequency resolution without relevantly affecting the computing cost. This
reduces the digitization effects; 2) the excess of candidates due to local
disturbances in some places of the sky map. They do not affect the new analysis
because each map is constructed for only one position in the sky. Pacs.
numbers: 04.80Nn,07.05Kf,97.60Jd 1.


title:
Chemical potential landscape in band filling and bandwidth-control of
  manganites: Photoemission spectroscopy measurements

abstract:
  We have studied the effects of band filling and bandwidth control on the
chemical potential in perovskite manganites $R_{1-x}A_x$MnO$_3$ ($R$ : rare
earth, $A$ : alkaline earth) by measurements of core-level photoemission
spectra. A suppression of the doping-dependent chemical potential shift was
observed in and around the CE-type charge-ordered composition range, indicating
that there is charge self-organization such as stripe formation or its
fluctuations. As a function of bandwidth, we observed a downward chemical
potential shift with increasing bandwidth due to the reduction of the
orthorhombic distortion. After subtracting the latter contribution, we found an
upward chemical potential shift in the ferromagnetic metallic region
$0.3<x<0.5$, which we attribute to the enhancement of double-exchange
interaction involving the Jahn-Teller-split $e_g$ band.


title: Alignment procedure of the LHCb Vertex Detector

abstract:
  LHCb is one of the four main experiments of the Large Hadron Collider (LHC)
project, which will start at CERN in 2008. The experiment is primarily
dedicated to B-Physics and hence requires precise vertex reconstruction. The
silicon vertex locator (VELO) has a single hit precision of better than 10
micron and is used both off-line and in the trigger. These requirements place
strict constraints on its alignment. Additional challenges for the alignment
arise from the detector being retracted between each fill of the LHC and from
its unique circular disc r/phi strip geometry. This paper describes the track
based software alignment procedure developed for the VELO. The procedure is
primarily based on a non-iterative method using a matrix inversion technique.
The procedure is demonstrated with simulated events to be fast, robust and to
achieve a suitable alignment precision.


title: Darwin et la socialit\'e : entre anthropomorphisme et gradualisme

abstract:
  We propose, in this article, an analysis of the Darwin's approach to
sociality. Sociality is perfectly integrated into the selective model, and is
caused by the same process as struggle for existence. Thus, the selective
process does not prohibit demonstrating cooperation, but on the contrary,
explains it. We will see that the unification of sociality, in a more adequate
representation to mammals, is not an expression of a naive anthropomorphism,
but of a methodological anthropomorphism; normal consequence of his gradualist
approach of phylogeny.


title:
Performance of the LHCb Vertex Detector Alignment Algorithm determined
  with Beam Test Data

abstract:
  LHCb is the dedicated heavy flavour experiment at the Large Hadron Collider
at CERN. The partially assembled silicon vertex locator (VELO) of the LHCb
experiment has been tested in a beam test. The data from this beam test have
been used to determine the performance of the VELO alignment algorithm. The
relative alignment of the two silicon sensors in a module and the relative
alignment of the modules has been extracted. This alignment is shown to be
accurate at a level of approximately 2 micron and 0.1 mrad for translations and
rotations, respectively in the plane of the sensors. A single hit precision at
normal track incidence of about 10 micron is obtained for the sensors. The
alignment of the system is shown to be stable at better than the 10 micron
level under air to vacuum pressure changes and mechanical movements of the
assembled system.


title: Pomeranchuk instability in doped graphene

abstract:
  The density of states of graphene has Van Hove singularities that can be
reached by chemical doping and have already been explored in photoemission
experiments. We show that in the presence of Coulomb interactions the system at
the Van Hove filling is likely to undergo a Pomeranchuk instability breaking
the lattice point group symmetry. In the presence of an on--site Hubbard
interaction the system is also unstable towards ferromagnetism. We explore the
competition of the two instabilities and build the phase diagram. We also
suggest that, for doping levels where the trigonal warping is noticeable, the
Fermi liquid state in graphene can be stable up to zero temperature avoiding
the Kohn--Luttinger mechanism and providing an example of two dimensional Fermi
liquid at zero temperature.


title:
Coherence loss and recovery of an electron spin coupled inhomogeneously
  to a one-dimensional interacting spin bath: an adaptive t-DMRG study

abstract:
  Coherence evolution and echo effect of an electron spin, which is coupled
inhomogeneously to an interacting one-dimensional finite spin bath via
hyperfine-type interaction, is studied using the adaptive time dependent
density matrix renormalization group (t-DMRG) method. It is found that the
interplay of the coupling inhomogeneity and the transverse intra-bath
interactions results in two qualitatively different coherence evolutions,
namely, a coherence preserving evolution characterized by periodic oscillation
and a complete decoherence evolution. Correspondingly, the echo effects induced
by an electron spin flip at time $\tau$ exhibit stable recoherence pulse
sequence for the periodic evolution and a single peak at $\sqrt 2 \tau$ for the
decoherence evolution, respectively. With the diagonal intra-bath interaction
included, the specific feature of the periodic regime is kept, while the $\sqrt
2\tau$-type echo effect in the decoherence regime is significantly affected. To
render the experimental verifications possible, the Hahn echo envelope as a
function of $\tau$ is calculated, which eliminates the inhomogeneous broadening
effect and serves for the identification of the different status of the dynamic
coherence evolution, periodic versus decoherence.


title:
Not to normal order - Notes on the kinetic limit for weakly interacting
  quantum fluids

abstract:
  The derivation of the Nordheim-Boltzmann transport equation for weakly
interacting quantum fluids is a longstanding problem in mathematical physics.
Inspired by the method developed to handle classical dilute gases, a
conventional approach is the use of the BBGKY hierarchy for the time-dependent
reduced density matrices. In contrast, our contribution is motivated by the
kinetic theory of the weakly nonlinear Schrodinger equation. The main
observation is that the results obtained in the latter context carry over
directly to weakly interacting quantum fluids provided one does not insist on
normal order in the Duhamel expansion. We discuss the term by term convergence
of the expansion and the equilibrium time correlation <a(t)* a(0)>.


title:
Hyperbolicity and the effective dimension of spatially-extended
  dissipative systems

abstract:
  We show, using covariant Lyapunov vectors, that the chaotic solutions of
spatially extended dissipative systems evolve within a manifold spanned by a
finite number of physical modes hyperbolically isolated from a set of residual
degrees of freedom, themselves individually isolated from each other. In the
context of dissipative partial differential equations, our results imply that a
faithful numerical integration needs to incorporate at least all physical modes
and that increasing the resolution merely increases the number of isolated
modes.


title: Limit theorems for quantum walks driven by many coins

abstract:
  We obtain some rigorous results on limit theorems for quantum walks driven by
many coins introduced by Brun et al. in the long time limit. The results imply
that whether the behavior of a particle is quantum or classical depends on the
three factors: the initial qubit, the number of coins M, d= [t/M], where t is
time step. Our main theorem shows that we can see a transition from classical
behavior to quantum one for a class of three factors.


title: Physical state for non-relativistic quantum electrodynamics

abstract:
  A physical subspace and physical Hilbert space associated with asymptotic
fields of nonrelativistic quantum electrodynamics are constructed through the
Gupta-Bleuler procedure. Asymptotic completeness is shown and a physical
Hamiltonian is defined on the physical Hilbert space.


title: Energy transfers in shell models for MHD turbulence

abstract:
  A systematic procedure to derive shell models for MHD turbulence is proposed.
It takes into account the conservation of ideal quadratic invariants such as
the total energy, the cross-helicity and the magnetic helicity as well as the
conservation of the magnetic energy by the advection term in the induction
equation. This approach also leads to simple expressions for the energy
exchanges as well as to unambiguous definitions for the energy fluxes. When
applied to the existing shell models with nonlinear interactions limited to the
nearest neighbour shells, this procedure reproduces well known models but
suggests a reinterpretation of the energy fluxes.


title:
Affine parameterization of the dark sector: costraints from WMAP5 and
  SDSS

abstract:
  We study a set of universe models where the dark sector is described by a
perfect fluid with an affine equation of state $P=P_0+\alpha \rho$, focusing
specifically on cosmological perturbations in a flat universe. We perform a
Monte Carlo Markov Chain analysis spanning the full parameter space of the
model using the WMAP 5 years data and the SDSS LRG4 survey. The affine fluid
can either play the role of a unified dark matter (UDM), accounting for both
dark matter and a cosmological constant, or work alongside cold dark matter
(CDM), as a form of dark energy. A key ingredient is the sound speed, that
depends on the nature of the fluid and that, for any given background model,
adds a degree of freedom to the perturbations: in the barotropic case the
square of the sound speed is simply equal to the affine parameter $\alpha$; if
entropic perturbations are present the effective sound speed has to be
specified as an additional parameter. In addition to the barotropic case, we
consider the two limiting cases of effective sound speed equal to 0 or 1. For
$\alpha=c_s^2=0$ our UDM model is equivalent to the standard $\Lambda$CDM with
adiabatic perturbations. Apart of a trivial subcase, all models considered
satisfy the data constraints, with quite standard values for the usual
cosmological parameters. In general our analysis confirms that cosmological
datasets require both a collisionless massive and cold component to form the
potential wells that lead to structure formation, and an effective cosmological
constant that drives the late accelerated expansion.


title:
Finite-dimensional attractors for the quasi-linear strongly-damped wave
  equation

abstract:
  We present a new method of investigating the so-called quasi-linear strongly
damped wave equations $$ \partial_t^2u-\gamma\partial_t\Delta_x u-\Delta_x
u+f(u)= \nabla_x\cdot \phi'(\nabla_x u)+g $$ in bounded 3D domains. This method
allows us to establish the existence and uniqueness of energy solutions in the
case where the growth exponent of the non-linearity $\phi$ is less than 6 and
$f$ may have arbitrary polynomial growth rate. Moreover, the existence of a
finite-dimensional global and exponential attractors for the solution semigroup
associated with that equation and their additional regularity are also
established. In a particular case $\phi\equiv0$ which corresponds to the
so-called semi-linear strongly damped wave equation, our result allows to
remove the long-standing growth restriction $|f(u)|\leq C(1+ |u|^5)$.


title:
Illustration of quantum complementarity using single photons interfering
  on a grating

abstract:
  A recent experiment performed by S. S. Afshar et al. has been interpreted as
a violation of Bohr's complementarity principle between interference visibility
and which-path information in a two-path interferometer. We have reproduced
this experiment, using true single-photon pulses propagating in a two-path
wavefront- splitting interferometer realized with a Fresnel's biprism, and
followed by a grating with adjustable transmitting slits. The measured values
of interference visibility V and which-path information, characterized by the
distinguishability parameter D, are found to obey the complementarity relation
V^2+D^2=<1. This result demonstrates that the experiment can be perfectly
explained by the Copenhagen interpretation of quantum mechanics.


title:
Coexistence of ordered and disordered phases in Potts models in the
  continuum

abstract:
  This is the second of two papers on a continuum version of the Potts model,
where particles are points in $\mathbb R^d$, $d\ge 2$, with a spin which may
take $S\ge 3$ possible values. Particles with different spins repel each other
via a Kac pair potential of range $\ga^{-1}$, $\ga>0$. In this paper we prove
phase transition, namely we prove that if the scaling parameter of the Kac
potential is suitably small, given any temperature there is a value of the
chemical potential such that at the given temperature and chemical potential
there exist $S+1$ mutually distinct DLR measures.


title: Boosting Nearest-Neighbour to Long-Range Integrable Spin Chains

abstract:
  We present an integrability-preserving recursion relation for the explicit
construction of long-range spin chain Hamiltonians. These chains are
generalizations of the Haldane-Shastry and Inozemtsev models and they play an
important role in recent advances in string/gauge duality. The method is based
on arbitrary nearest-neighbour integrable spin chains and it sheds light on the
moduli space of deformation parameters. We also derive the closed chain
asymptotic Bethe equations.

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


title: A Monte Carlo Approach to Joe DiMaggio and Streaks in Baseball

abstract:
  We examine Joe DiMaggio's 56-game hitting streak and look at its likelihood,
using a number of simple models. And it turns out that, contrary to many
people's expectations, an extreme streak, while unlikely in any given year, is
not unlikely to have occurred about once within the history of baseball.
Surprisingly, however, such a record should have occurred far earlier in
baseball history: back in the late 1800's or early 1900's. But not in 1941,
when it actually happened.


title: Phase-field crystal study of grain-boundary premelting

abstract:
  We study the phenomenon of grain-boundary premelting for temperatures below
the melting point in the phase-field crystal model of a pure material with
hexagonal ordering in two dimensions. We investigate the structures of
symmetric tilt boundaries as a function of misorientation for two different
inclinations and compute in the grand canonical ensemble the disjoining
potential V(w) that governs the fundamental interaction between crystal-melt
interfaces as a function of the premelted layer width w. The results reveal
qualitatively different behaviors for high-angle grain boundaries that are
uniformly wetted, with w diverging logarithmically as the melting point is
approached from below, and low-angle boundaries that are punctuated by liquid
pools surrounding dislocations, separated by solid bridges. This qualitative
difference between high and low angle boundaries is reflected in the
w-dependence of the disjoining potential that is purely repulsive (V'(w)<0 for
all w) above a critical misorientation, but switches from repulsive at small w
to attractive at large w for low angles. In the latter case, V(w) has a minimum
that corresponds to a premelted boundary of finite width at the melting point.
Furthermore, we find that the standard wetting condition (the grain boundary
energy is equal to twice the solid-liquid free energy) gives a much too low
estimate of the critical misorientation when a low-temperature value of the
grain boundary energy is used. In contrast, a reasonable estimate is obtained
if the grain boundary energy is extrapolated to the melting point, taking into
account both the elastic softening of the material at high temperature and
local melting around dislocations.


title: D-term assisted Anomaly Mediation in E6 motivated models

abstract:
  We investigate effects of D-term contributions to the anomaly mediated
supersymmetry breaking scenario. If we introduce an E6 GUT motivated D-term, it
is possible that slepton mass squared is positive at weak scale even if there
are no other D-term contributions. Moreover, as a consequence of additional
D-term contributions to scalar masses, we obtain various soft supersymmetry
breaking mass spectra, which are different from those obtained in the
conventional anomaly mediation scenario. Then there would be a distinct
signature of this scenario at the LHC. For example, in several cases, there
exist mass splittings between the right-handed sfermion and the left-handed
sfermion. We also discuss some characteristic features of the neutralino dark
matter in this model.


title:
On the Very-High-Energy Gamma Ray Spectra from Typical Supernovae
  Remnants

abstract:
  Recently measured VHE gamma ray spectra from supernovae remnants (SNRs) are
best fit by power laws with an exponential cutoff. But this feature does not
occur at the `knee-equivalent' energy at which VHE gamma ray spectra are
expected to reflect the `knee' in the otherwise featureless cosmic ray
spectrum. In this article, the VHE gamma ray feature is explained as a
consequence of a recently deduced quantum effect. The effect distinguishes
`trajectory energy' from `particle state energy' and requires that the particle
state energy depends strongly on gravitational potential at very high energies.
Based on this effect and the observed CR spectrum, a tight two-parameter fit is
obtained to the combined VHE gamma ray spectra of SNRs RX J1713.7-3946 and RX
J0852.0-4622 and the Galactic Center ridge.


title:
The memory kernel of the self-intermediate scattering function on a
  MD-simulated glass-forming Ni$_{20}$Zr$_{80}$-system

abstract:
  The memory kernel of the self-part of the intermediate scattering function is
studied. We found that the short-time behavior of the memory kernel for our
MD-simulated glass-forming Ni$_{20}$Zr$_{80}$-system shows a deviation from the
polynomial form predicted by MCT. By using the gaussian approximation we give a
more detailed description of the short-time dynamics of the system.


title: Disentangling between Z' and Z* with first LHC data

abstract:
  The resonance production of new chiral spin-1 excited bosons, Z*, and their
detection through the Drell-Yan process in the first physical runs at the CERN
LHC are considered. The new neutral chiral bosons can be observed as a
Breit-Wigner resonance peaks in the invariant dilepton mass distribution in the
same way as the well-known hypothetical gauge bosons, Z'. However, unique new
signatures of the chiral bosons exist. These signatures could be very important
for the interpretation of the first LHC data. First, there is no Jacobian peak
in the lepton transverse momentum distribution at the kinematical endpoint of
the new resonance. Second, the lepton angular distribution in the Collins-Soper
frame for the high on-peak invariant masses of the lepton pairs has a peculiar
"swallowtail" shape.


title: Eddington-Born-Infeld action and the dark side of general relativity

abstract:
  We review a recent proposal to describe dark matter and dark energy based on
an Eddington-Born-Infeld action. The theory is successful in describing the
evolution of the expansion factor as well as galactic flat rotation curves.
Fluctuations and the CMB spectra are currently under study. This paper in
written in honor of Claudio Bunster on the occasion of his sixtieth birthday.


title:
An unbiased measurement of the UV background and its evolution via the
  proximity effect in quasar spectra

abstract:
  We used 40 high resolution, high S/N QSO spectra at 2.1<z<4.7 to search for
the signature of the proximity effect in the HI Lyalpha forest. Comparing the
effective optical depth near each QSO with the expected one, we clearly detect
the proximity effect on the combined QSO sample and towards each individual
QSO. The observed proximity effect strength distribution (PESD) is asymmetric
towards a weak effect. We demonstrate that this is not simply an effect of
gravitational clustering around QSOs. Comparing simulated PESDs with
observations, we argue that the averaging method to determine the UVB intensity
J is heavily biased towards high values because of the PESD asymmetry. Using
instead the mode of the PESD provides an unbiased estimate of J. For our sample
its modal value is log(J)=-21.51+/-0.15 (in units of ergcm^-2s^-1Hz^-1sr^-1) at
z=2.73. We estimated the excess HI absorption attributed to gravitational
clustering. On scales of ~3 Mpc, only a minority of QSOs shows overdensities of
up to a factor of a few in tau_eff; these are exactly the objects with the
weakest proximity effects. After removing them, we redetermined the UVB
intensity arriving at log(J)=-21.46+0.14-0.21. This is the most accurate
measurement of J to date. We present a new diagnostic based on the shape of the
PESD which strongly supports our conclusion that there is no systematic
overdensity bias for the proximity effect. This additional diagnostic breaks
the otherwise unavoidable degeneracy of the proximity effect between UVB and
overdensity. We estimated the redshift evolution of J and found tentative
evidence for a mild decrease with increasing redshift. Our results are in
excellent agreement with predictions for the evolving UVB intensity, supporting
the notion of a substantial contribution of star-forming galaxies.


title: Lattice Gauge Field Theory and Prismatic Sets

abstract:
  We study prismatics sets analogously to simplical sets except that
realization involves prisms, i.e., products of simplices rather than just
simplices. Particular examples are the prismatic subdivision of a simplicial
set S and the prismatic star of S. Both have the same homotopy type as S and in
particular the latter we use to study lattice gauge theory in the sense of
Phillips and Stone. Thus for a Lie group G and a set of parallel transport
functions defining the transition over faces of the simplices, we define a
classifying map from the prismatic star to a prismatic version of the
classifying space of G. In turn this defines a G-bundle over the prismatic
star.


title: Message-passing for Maximum Weight Independent Set

abstract:
  We investigate the use of message-passing algorithms for the problem of
finding the max-weight independent set (MWIS) in a graph. First, we study the
performance of the classical loopy max-product belief propagation. We show that
each fixed point estimate of max-product can be mapped in a natural way to an
extreme point of the LP polytope associated with the MWIS problem. However,
this extreme point may not be the one that maximizes the value of node weights;
the particular extreme point at final convergence depends on the initialization
of max-product. We then show that if max-product is started from the natural
initialization of uninformative messages, it always solves the correct LP -- if
it converges. This result is obtained via a direct analysis of the iterative
algorithm, and cannot be obtained by looking only at fixed points.
  The tightness of the LP relaxation is thus necessary for max-product
optimality, but it is not sufficient. Motivated by this observation, we show
that a simple modification of max-product becomes gradient descent on (a
convexified version of) the dual of the LP, and converges to the dual optimum.
We also develop a message-passing algorithm that recovers the primal MWIS
solution from the output of the descent algorithm. We show that the MWIS
estimate obtained using these two algorithms in conjunction is correct when the
graph is bipartite and the MWIS is unique.
  Finally, we show that any problem of MAP estimation for probability
distributions over finite domains can be reduced to an MWIS problem. We believe
this reduction will yield new insights and algorithms for MAP estimation.


title:
Lipid Flip-Flop Driven Mechanical and Morphological Changes in Model
  Membranes

abstract:
  We study, using dissipative particle dynamics simulations, the effect of
active lipid flip-flop on model fluid bilayer membranes. We consider both cases
of symmetric as well as asymmetric flip-flops. Symmetric flip-flop leads to a
steady state of the membrane with an effective temperature higher than that of
the equilibrium membrane and an effective surface tension lower than that of
the equilibrium membrane. Asymmetric flip-flop leads to transient
conformational changes of the membrane in the form of bud or blister formation,
depending on the flip rate.


title:
Theoretical Formulation of the Origin of Cataclysmic Late Heavy
  Bombardment Era based on the New Perspective of Birth & Evolution of Solar
  Systems

abstract:
  Based on the planet-satellite dynamics, a new perspective on the birth and
evolution of the Solar System was proposed in 2004. This new perspective has
1:2 Mean Motion Resonance (1:2 MMR, that is Ps/Pj = 2) implicit in itself .
This paper has shown that if we assume the sequential birth of the planets with
the heaviest, i.e. Jupiter, being born the earliest and this axiom is central
to the new perspective then there is an unique initial condition for which 1:2
MMR crossing occurs exactly 300My after the birth of Jupiter. It is shown that
25 My time gap between the birth of Jupiter and Saturn results in the 300 My
time delay in the occurrence of 1:2 MMR. Because the process by which Late
Heavy Bombardment is triggered involves the movement of Neptune over enormous
distances hence almost 200 My time delay occurs between 1:2MMR crossing and the
actual spike in the Meteoritic Shower on all the terrestrial planets as
evidenced by the petrology record on the Moon. The analytical derivation of the
time delay in the spike is a vindication of this new perspective of the
application of planet-satellite dynamics to the birth and evolution of Solar
Systems.


title:
The structure of strong linear preservers of gw-majorization on $
  \mathbf{M}_{{n,m}

abstract:
  Let M_{n,m} be the set of all n by m matrices with entries in F, where F is
the field of real or complex numbers. A matrix R in M_{n} with the property
Re=e, is said to be a g-row stochastic (generalized row stochastic) matrix. Let
A,B in M_{n,m}, so B is said to be gw-majorized by A if there exists an n by n
g-row stochastic matrix R such that B=RA. In this paper we characterize all
linear operators that strongly preserve gw-majorization on M_{n,m} and all
linear operators that strongly preserve matrix majorization on M_{n} .


title: Non-invasive detection of molecular bonds in quantum dots

abstract:
  We performed charge detection on a lateral triple quantum dot with star-like
geometry. The setup allows us to interpret the results in terms of two double
dots with one common dot. One double dot features weak tunnel coupling and can
be understood with atom-like electronic states, the other one is strongly
coupled forming molecule-like states. In nonlinear measurements we identified
patterns that can be analyzed in terms of the symmetry of tunneling rates.
Those patterns strongly depend on the strength of interdot tunnel coupling and
are completely different for atomic- or molecule-like coupled quantum dots
allowing the non-invasive detection of molecular bonds.


title: Moment bounds for non-linear functionals of the periodogram

abstract:
  In this paper, we prove the validity of the Edgeworth expansion of the
Discrete Fourier transforms of some linear time series. This result is applied
to approach moments of non linear functionals of the periodogram. As an
illustration, we give an expression of the mean square error of the Geweke and
Porter-Hudak estimator of the long memory parameter. We prove that this
estimator is rate optimal, extending the result of Giraitis, Robinson, Samarov
(1997) from Gaussian to linear processes.


title: WISP hunting - some new experimental ideas

abstract:
  We present several new ideas on how to search for weakly interacting sub-eV
particles in laboratory experiments. The first experiment is sensitive to
minicharged particles. It exploits that in strong electric fields particle -
antiparticle pairs are produced by the Schwinger mechanism. The charged
particles move along the lines of the electric field and generate a current
that can be measured. The other two experiments are designed to search for
hidden-sector photons. They are based on photon - hidden photon oscillations
and resemble classic light shining through a wall experiments. One uses
(nearly) constant magnetic fields instead of the laser light. Photon - hidden
photon mixing would allow these magnetic fields to leak through superconducting
shielding which would ordinarily eliminate all magnetic fields. The other one
replaces the laser light with microwaves inside cavities. The latter can
achieve much higher quality factors than optical cavities increasing the
sensitivity.


title:
Efficient upconversion of sub-THz radiation in a high-Q whispering
  gallery resonator

abstract:
  We demonstrate efficient upconversion of sub-THz radiation into the optical
domain in a high-Q whispering gallery mode resonator with quadratic optical
nonlinearity. The 5x10^{-3} power conversion efficiency of continuous wave
100GHz signal is achieved with only 16 mW of optical pump.


title:
Spatially resolved near-infrared spectroscopy of the massive
  star-forming region IRAS 19410+2336

abstract:
  IRAS19410+2336 is a young massive star forming region with an intense outflow
activity. We present here spatially resolved NIR spectroscopy which allows us
to verify whether the H2 emission detected in this object originates from
thermal emission in shock fronts or from fluorescence excitation by
non-ionizing UV photons. Moreover, NIR spectroscopy also offers the possibility
of studying the characteristics of the putative driving source(s) of the H2
emission by the detection of photospheric and circumstellar spectral features,
and of the environmental conditions (e.g. extinction). We obtained long-slit,
intermediate-resolution, NIR spectra of IRAS19410+2336 using LIRIS. As a
complement, we also obtained J, H and K_s images with the Las Campanas 2.5m Du
Pont Telescope, and archival mid-infrared (MIR) Spitzer images at 3.6, 4.5, 5.8
and 8.0 um. We confirm the shocked nature of the H2 emission, with an
excitation temperature of about 2000 K. We have also identified objects with
very different properties and evolutionary stages in IRAS19410+2336. The most
massive source at millimeter wavelengths, mm1, with a mass of a few tens of
solar masses, has a bright NIR (and MIR) counterpart. This suggests that
emission is leaking at these wavelengths. The second most massive millimeter
source, mm2, is only detected at lambda > 6 um, suggesting that it could be a
high-mass protostar still in its main accretion phase. The NIR spectra of some
neighboring sources show CO first-overtone bandhead emission which is
associated with neutral material located in the inner regions of the
circumstellar environment of YSOs.


title: On a theorem of Shkredov

abstract:
  We show that if A is a finite subset of an abelian group with additive energy
at least c|A|^3 then there is a subset L of A with |L|=O(c^{-1}\log |A|) such
that |A \cap Span(L)| >> c^{1/3}|A|.


title: Roth's theorem in Z_4^n

abstract:
  We show that if A is a subset of Z_4^n containing no three-term arithmetic
progression in which all the elements are distinct then |A|=o(4^n/n).


title: Limiting Temperatures in Multifragmentation

abstract:
  The systematic data set on isotopic effects in spectator fragmentation
collected recently at the GSI laboratory permits the investigation of the N/Z
dependence of the nuclear caloric curve which is of interest in several
respects. In particular, new light is shed on the proposed interpretation of
chemical breakup temperatures as a manifestation of the limiting temperatures
predicted by the Hartree-Fock model. The obtained results are discussed within
the general context of temperature measurements in multifragmentation
reactions.


title: Long Tail of Quantum Decay from Scattering Data

abstract:
  Whereas the short time behaviour of an unstable quantum mechanical system is
well understood from its theoretical as well as experimental side, the long
time tail of the very same systems has neither been measured experimentally nor
is there a theoretical agreement on how to handle it. We suggest a possible way
out of this unsatisfactory state of art. Theoretically we suggest that the
correct spectral function entering the Fock-Krylov method to calculate the
survival amplitude is proportional to the density of states of a resonance. The
latter is essentially the energy derivative of a phase shift. As a bonus, we
can connect the survival probability to scattering data via the phase shift.
The method then not only establishes the spectral function, but is per se a
semi-empirical method to extract the large time behaviour from scattering data.


title: Chowla's cosine problem

abstract:
  Suppose that G is a discrete abelian group and A is a finite symmetric subset
of G. We show two main results. i) Either there is a set H of O(log^c|A|)
subgroups of G with |A \triangle \bigcup H| = o(|A|), or there is a character X
on G such that -wh{1_A}(X) >> log^c|A|. ii) If G is finite and |A|>> |G| then
either there is a subgroup H of G such that |A \triangle H| = o(|A|), or there
is a character X on G such that -wh{1_A}(X)>> |A|^c.


title: HD 98800: A most unusual debris disc

abstract:
  The dynamics of planetesimals in the circumbinary debris disc of the
quadruple star system HD 98800 are investigated. Evolving a spherical shell of
test particles from a million years ago to the present day indicates that both
coplanar and retrograde warped discs could exist, as well as a high inclination
halo of material. Significant gaps are seen in the discs, as well as unexpected
regions of stability due to the retrograde nature of the stellar orbits.
Despite a viewing angle almost perpendicular to the direction of the warp of
the planetesimal disc it is still intersected by the line of sight for
eccentricities of the outer orbit of 0.5 or less.


title: Popular difference sets

abstract:
  We provide further explanation of the significance of a construction in a
recent paper of Wolf [Israel J. Math. 179 (2010), 253-278] in the context of
the problem of finding large subspaces in sumsets.


title:
Stability properties for some non-autonomous dissipative phenomena
  proved by families of Liapunov functionals

abstract:
  We prove some new results regarding the boundedness, stability and
attractivity of the solutions of a class of initial-boundary-value problems
characterized by a quasi-linear third order equation which may contain
time-dependent coefficients. The class includes equations arising in
Superconductor Theory, and in the Theory of Viscoelastic Materials. In the
proof we use a family of Liapunov functionals W depending on two parameters,
which we adapt to the `error', i.e. to the size of the chosen neighbourhood of
the null solution.


title:
A decade of radio imaging the relativistic outflow in the peculiar X-ray
  binary Circinus X-1

abstract:
  We present observations of the neutron star X-ray binary and relativistic jet
source Circinus X-1 made at 4.8 and 8.6 GHz with the Australia Telescope
Compact Array during a time interval of almost 10 years. The system shows
significant variations in the morphology and brightness of the radio features
on all timescales from days to years. Using the time delay between the
successive brightening of the different components of the radio emission we
were able to provide further evidence for the relativistic nature of the arcsec
scale outflow, with an apparent velocity beta_app >= 12. No compelling evidence
for an evolution of the orientation of the jet axis was found. We also place an
upper limit on the proper motion of the system which is consistent with
previous optical studies. Besides the previously reported radio flares close to
the orbital phase 0.0 (interpreted as enhanced accretion at periastron
passage), we also identified outbursts with similar properties near the orbital
phase 0.5. The global spectral index revealed a preferentially steep spectrum
over the entire period of monitoring with a mean value and standard deviation
alpha=-0.9 +/- 0.6 (F_nu ~ nu^{alpha}), which became significantly flatter
during the outbursts. Polarization was detected in one third of the epochs and
in one case Faraday rotation close to the core of the system was measured.


title: On the dependence of the avalanche angle on the granular layer thickness

abstract:
  A layer of sand of thickness h flows down a rough surface if the inclination
is larger than some threshold value theta which decreases with h. A tentative
microscopic model for the dependence of theta with h is proposed for rigid
frictional grains, based on the following hypothesis: (i) a horizontal layer of
sand has some coordination z larger than a critical value z_c where mechanical
stability is lost (ii) as the tilt angle is increased, the configurations
visited present a growing proportion $_s of sliding contacts. Instability with
respect to flow occurs when z-z_s=z_c. This criterion leads to a prediction for
theta(h) in good agreement with empirical observations.


title:
Thomas-Fermi versus one- and two-dimensional regimes of a trapped
  dipolar Bose-Einstein condensate

abstract:
  We derive the criteria for the Thomas-Fermi regime of a dipolar Bose-Einstein
condensate in cigar, pancake and spherical geometries. This also naturally
gives the criteria for the mean-field one- and two-dimensional regimes. Our
predictions, including the Thomas-Fermi density profiles, are shown to be in
excellent agreement with numerical solutions. Importantly, the anisotropy of
the interactions has a profound effect on the Thomas-Fermi/low-dimensional
criteria.


title: Finding Dense Subgraphs in G(n,1/2)

abstract:
  Finding the largest clique is a notoriously hard problem, even on random
graphs. It is known that the clique number of a random graph G(n,1/2) is almost
surely either k or k+1, where k = 2log n - 2log(log n) - 1. However, a simple
greedy algorithm finds a clique of size only (1+o(1))log n, with high
probability, and finding larger cliques -- that of size even (1+ epsilon)log n
-- in randomized polynomial time has been a long-standing open problem. In this
paper, we study the following generalization: given a random graph G(n,1/2),
find the largest subgraph with edge density at least (1-delta). We show that a
simple modification of the greedy algorithm finds a subset of 2log n vertices
whose induced subgraph has edge density at least 0.951, with high probability.
To complement this, we show that almost surely there is no subset of 2.784log n
vertices whose induced subgraph has edge density 0.951 or more.


title:
A Realistic Radiative Fermion Mass Hierarchy in Non-supersymmetric
  SO(10)

abstract:
  A non-supersymmetric grand unified theory can exhibit a "radiative fermion
mass hierarchy", in which the heavier quarks and leptons get mass at tree level
and the lighter ones get mass from loop diagrams. Recently the first predictive
model of this type was proposed. Here it is analyzed numerically and it is
shown to give an excellent fit to the quark and lepton masses and mixings,
including the CP phase violating phase $\delta_{CKM}$. A relation between the
neutrino angle $\theta_{13}$ and the atmospheric neutrino angle is obtained


title: Topological branes, p-algebras and generalized Nahm equations

abstract:
  Inspired by the recent advances in multiple M2-brane theory, we consider the
generalizations of Nahm equations for arbitrary p-algebras. We construct the
topological p-algebra quantum mechanics associated to them and we show that
this can be obtained as a truncation of the topological p-brane theory
previously studied by the authors. The resulting topological p-algebra quantum
mechanics is discussed in detail and the relation with the M2-M5 system is
pointed out in the p=3 case, providing a geometrical argument for the emergence
of the 3-algebra structure in the Bagger-Lambert-Gustavsson theory


title:
On the longitudinal response function of interferometers for massive
  gravitational waves from a bimetric theory of gravity

abstract:
  Recently, some papers in the literature have shown that, from a bimetric
theory of gravity, it is possible to produce massive gravitational waves which
generate a longitudinal component in a particular polarization of the wave.
After a review of previous works, in this paper the longitudinal response
function of interferometers for this particular polarization of the wave is
computed in two different gauges, showing the gauge invariance, and in its full
frequency dependence, with specific application to the Virgo and LIGO
interferometers.


title: Delocalized Betti numbers and Morse type inequalities

abstract:
  In this paper we state and prove Morse type inequalities for Morse functions
as well as for closed differential 1-forms. These inequalities involve
delocalized Betti numbers. As an immediate consequence, we prove the vanishing
of delocalized Betti numbers of manifolds fibering over the circle.


title:
The reduced effect of a single scattering with a low-mass particle via a
  point interaction

abstract:
  In this article, we study a second-order expansion for the effect induced on
a large quantum particle which undergoes a single scattering with a low-mass
particle via a repulsive point interaction. We give an approximation with
third-order error in $\lambda$ to the map $G\to \Tr_{2}[(I\otimes
\rho)S_{\lambda}^{*}(G\otimes I)S_{\lambda}]$, where $G\in \Bi(L^{2}(\R^{n}))$
is a heavy-particle observable, $\rho\in \Bi_{1}(\R^{n})$ is the density matrix
corresponding to the state of the light particle, $\lambda=\frac{m}{M}$ is the
mass ratio of the light particle to the heavy particle, $S_{\lambda}\in
\Bi(L^{2}(\R^{n})\otimes L^{2}(\R^{n}))$ is the scattering matrix between the
two particles due to a repulsive point interaction, and the trace is over the
light-particle Hilbert space. The third-order error is bounded in operator norm
for dimensions one and three using a weighted operator norm on $G$.


title: Formality of the homotopy calculus algebra of Hochschild (co)chains

abstract:
  The Kontsevich-Soibelman solution of the cyclic version of Deligne's
conjecture and the formality of the operad of little discs on a cylinder
provide us with a natural homotopy calculus structure on the pair (C^*(A),
C_*(A)) ``Hochschild cochains + Hochschild chains'' of an associative algebra
A. We show that for an arbitrary smooth algebraic variety X with the structure
sheaf O_X the sheaf (C^*(O_X), C_*(O_X)) of homotopy calculi is formal. This
result was announced in paper [29] by the second and the third author.


title: Some Basic Concepts of Perturbative QCD

abstract:
  This is a brief review of some of the basic concepts of perturbative QCD,
including infrared safety and factorization, relating them to more familiar
ideas from quantum mechanics and relativity. It is intended to offer
perspective on methods and terms whose use is commonplace, but whose physical
origins are sometimes obscure.


title:
Formation of Pt islets on facets of Ru nanoparticles: a first-principles
  study

abstract:
  We have carried out density functional theory based calculations of the size
dependent formation energy and geometry of Pt islands on Ru(0001), to model
Pt-Ru nanocatalysts which have been recently proposed as fuel cell anode. The
Pt islands are found to prefer two-dimensional structures. Furthermore, a
monotonic decrease in the formation energy per Pt atom suggests a propensity of
Pt atoms to wet the Ru(0001) surface. Calculated energy barriers for the
diffusion of Pt monomers and dimers on the facets and through the edges of a
superstructure modeling a Ru nanoparticle indicate that these edges help reduce
considerably the diffusion rates across them such that the Pt atoms prefer to
remain in the facet on which they were adsorbed originally and form 2D islands.


title: Accelerated Option Pricing in Multiple Scenarios

abstract:
  This paper covers a massive acceleration of Monte-Carlo based pricing method
for financial products and financial derivatives. The method is applicable in
risk management settings, where a financial product has to be priced under a
number of potential future scenarios. Instead of starting a separate nested
Monte Carlo simulation for each scenario under consideration, the new method
covers the utilization of very few representative nested simulations and
estimating the product prices at each scenario by a smoothing method based on
the state-space. This smoothing technique can be e.g. non-parametric regression
or kernel smoothing.


title:
The supremum of autoconvolutions, with applications to additive number
  theory

abstract:
  We adapt a number-theoretic technique of Yu to prove a purely analytic
theorem: if f(x) is in L^1 and L^2, is nonnegative, and is supported on an
interval of length I, then the supremum of the convolution f*f is at least
0.631 \| f \|_1^2 / I. This improves the previous bound of 0.591389 \| f \|_1^2
/ I. Consequently, we improve the known bounds on several related
number-theoretic problems. For a subset A of {1,2, ..., n}, let g be the
maximum multiplicity of any element of the multiset {a+b: a,b in A}. Our main
corollary is the inequality gn>0.631|A|^2, which holds uniformly for all g, n,
and A.


title: Morse inequalities for manifolds with boundary

abstract:
  The aim of this paper is to provide a proof for a version of Morse inequality
for manifolds with boundary. Our main results are certainly known to the
experts on Morse theory, nevertheless it seems necessary to write down a
complete proof for it. Our proof is analytic and is based on J. Roe's account
of Witten's approach to Morse Theory.


title: The role of Lambda in the cosmological lens equation

abstract:
  The cosmological constant Lambda affects cosmological gravitational lensing.
Effects due to Lambda can be studied in the framework of the Schwarzschild-de
Sitter spacetime. Two novel contributions, which can not be accounted for by a
proper use of angular diameter distances, are derived. First, a term 2m b
Lambda/3 has to be added to the bending angle, where "m" is the lens mass and
"b" the impact parameter. Second, Lambda brings about a difference in the
redshifts of multiple images. Both effects are quite small for real
astrophysical systems (contribution to the bending < 0.1 microarcsec and
difference in redshift < 10^{-7}).


title: Quantum Functor $Mor$

abstract:
  Let $Top_c$ be the category of compact spaces and continuous maps and
$Top_f\subset Top_c$ be the full subcategory of finite spaces. Consider the
covariant functor $Mor:Top_f^{op}\times Top_c\to Top_c$ that associates any
pair $(X,Y)$ with the space of all morphisms from $X$ to $Y$. In this paper, we
describe a non commutative version of $Mor$. More pricelessly, we define a
functor $\mathfrak{M}\mathfrak{o}\mathfrak{r}$, that takes any pair $(B,C)$ of
a finitely generated unital C*-algebra $B$ and a finite dimensional C*-algebra
$C$ to the quantum family of all morphism from $B$ to $C$.


title:
Steady base states for Navier-Stokes granular hydrodynamics with
  boundary heating and shear

abstract:
  We study the Navier-Stokes steady states for a low density monodisperse hard
sphere granular gas (i.e, a hard sphere ideal monatomic gas with inelastic
interparticle collisions). We present a classification of the uniform steady
states that can arise from shear and temperature (or energy input) applied at
the boundaries (parallel walls). We consider both symmetric and asymmetric
boundary conditions and find steady states not previously reported, including
sheared states with linear temperature profiles. We provide explicit
expressions for the hydrodynamic profiles for all these steady states. Our
results are validated by the numerical solution of the Boltzmann kinetic
equation for the granular gas obtained by the direct simulation Monte Carlo
method, and by molecular dynamics simulations. We discuss the physical origin
of the new steady states and derive conditions for the validity of
Navier-Stokes hydrodynamics.


title: Phase-Covariant Quantum Benchmarks

abstract:
  We give a quantum benchmark for teleportation and quantum storage experiments
suited for pure and mixed test states. The benchmark is based on the average
fidelity over a family of phase-covariant states and certifies that an
experiment can not be emulated by a classical setup, i.e., by a
measure-and-prepare scheme. We give an analytical solution for qubits, which
shows important differences with standard state estimation approach, and
compute the value of the benchmark for coherent and squeezed states, both pure
and mixed.


title: On quark masses in holographic QCD

abstract:
  Recently certain nonlocal operators were proposed to provide quark masses for
the holographic model of QCD developed by Sakai and Sugimoto. The properties of
these operators at strong coupling are examined in detail using holographic
techniques. We find the renormalization procedure for these operators is
modified by the running of the five-dimensional gauge coupling. We explicitly
evaluate the chiral condensate characterized by these operators.


title: pi pi Phase shifts from K to 2 pi

abstract:
  We update the numerical results for the s-wave pi pi scattering phase-shift
difference delta_0^0 - delta_0^2 at s = m_K^2 from a previous study of isospin
breaking in K to 2 pi amplitudes in chiral perturbation theory. We include
recent data for the K_S to pi pi and K^+ to pi^+ pi^0 decay widths and include
experimental correlations.


title:
Geometrical barriers and the growth of flux domes in thin ideal
  superconducting disks

abstract:
  When an ideal (no bulk pinning) flat type-II superconducting disk is
subjected to a perpendicular magnetic field H_a, the first vortex nucleates at
the rim when H_a = H_0, the threshold field, and moves quickly to the center of
the disk. As H_a increases above H_0, additional vortices join the others, and
together they produce a domelike field distribution of radius b. In this paper
I present analytic solutions for the resulting magnetic-field and
sheet-current-density distributions. I show how these distributions vary as b
increases with H_a, and I calculate the corresponding field-increasing
magnetization.


title:
Can the energy density of gravitational field be interpreted as dark
  energy?

abstract:
  After a brief review of the Maxwell-like approach to gravity we consider the
issue of the negative energy of gravitational field which is a consequence of
the field approach to the phenomenon of gravitation. Due to the existence of
the negative field energy {\it within} a mass body its total energy content is
smaller than the positive energy assigned to its mass energy. We study the
total energy content of a spherically symmetrical mass body having constant
matter density, and show that its total energy content depends on its radius.
We show that under certain circumstances, the total energy content of a mass
body achieves negative values so that the force at its surface becomes
repulsive. We apply this idea to the evolution of universe filled by matter and
the negative energy density of its gravitational field. Since the negative
energy density causes the negative pressure it might be considered as an agent
which causes the acceleration of the universe.


title: BMOA estimates and radial growth of $B_{\phi}$ functions

abstract:
  BMO estimates and the radial growth of Bloch functions have been studied by
B. Korenblum [3]. The present paper contains some natural generalizations of
these results.


title:
Engineering Superposition States and Tailored Probes for Nano-resonators
  Via Open-Loop Control

abstract:
  We show that a nano-resonator can be prepared in mesoscopic-superposition
states merely by monitoring a qubit coupled to the square of the resonators
position. This works for thermal initial states, and does not require a
third-order nonlinearity. The required coupling can be generated using a simple
open-loop control protocol, obtained with optimal control theory. We simulate
the complete preparation process, including environmental noise. Our results
indicate the power of open-loop control for state-engineering and measurement
in quantum nano-systems.


title: The Local Environment of the FUor-like Objects AR 6A and 6B

abstract:
  We present new 12CO J=3-2 and HCN J=3-2 molecular line maps of the region
surrounding the young star AR 6 using the 15 metre James Clerk Maxwell
Telescope. AR 6 was previously found to be a double source with both components
exhibiting several characteristics of FU Orionis (FUor) eruptive variable
stars. Our data indicates that AR 6, like FU Orionis itself, does not possess a
CO outflow and likewise, does not show evidence for large amounts of molecular
g as in its circumstellar environment. We conclude that from the near-IR to the
sub-mm, AR 6 is similar to FU Orionis in several respects. We interpret the
lack of significant dust and molecular gas in the circumstellar environment of
AR 6, together with the large near-IR thermal excess, as evidence that the
sources have exhausted their natal envelopes, that they have at least small hot
circumstellar disks, and that they are more evolved than Class I protostars.
This, in itself, suggests that, since FUor eruptions have also been observed in
stars with large dust mass envelopes (e.g. V346 Nor) and with CO outflows (e.g.
L1551 IRS5), FUor events probably occur at many different stages in the early,
formative phase of a star's life, and lends support to the idea that FUor
outbursts are repetitive like their shorter-lived relatives occurring in EXor
eruptive variables. Finally, we show that, being part of the 'Spokes' young
stellar cluster, AR 6 is unlike many FUors which typically are located in more
sparsely populated regions.


title: Superconformal M2-branes and generalized Jordan triple systems

abstract:
  Three-dimensional conformal theories with six supersymmetries and SU(4)
R-symmetry describing stacks of M2-branes are here proposed to be related to
generalized Jordan triple systems. Writing the four-index structure constants
in an appropriate form, the Chern-Simons part of the action immediately
suggests a connection to such triple systems. In contrast to the previously
considered three-algebras, the additional structure of a generalized Jordan
triple system is associated to a graded Lie algebra, which corresponds to an
extension of the gauge group. In this note we show that the whole theory with
six manifest supersymmetries can be naturally expressed in terms of such a
graded Lie algebra. Also the BLG theory with eight supersymmetries is included
as a special case.


title:
On some generalizations of Newton non degeneracy for hypersurface
  singularities

abstract:
  We introduce two generalizations of Newton-non-degenerate (Nnd) singularities
of hypersurfaces. Roughly speaking, an isolated hypersurface singularity is
called topologically Newton-non-degenerate (tNnd) if the local embedded
topological singularity type can be restored from a collection of Newton
diagrams (for some coordinate choices).
  A singularity that is not tNnd is called essentially Newton-degenerate. For
plane curves we give an explicit characterization of tNnd singularities; for
hypersurfaces we provide several examples.
  Next, we treat the question: whether Nnd or tNnd is a property of singularity
types or of particular representatives. Namely, is the non-degeneracy preserved
in an equi-singular family? This fact is proved for curves. For hypersurfaces
we give an example of a Nnd hypersurface whose equi-singular deformation
consists of essentially Newton-degenerate hypersurfaces.
  Finally, we define the directionally Newton-non-degenerate germs, a subclass
of tNnd germs. For such singularities the classical formulas for the Milnor
number and the zeta function of the Nnd hypersurface are generalized.


title:
Superfast convergence effect in large orders of the perturbative and
  $\epsilon$ expansions for the O(N) symmetric $\phi^4$ model

abstract:
  Usually the asymptotic behavior for large orders of the perturbation theory
is reached rather slowly. However, in the case of the N-component $\phi^4$
model in D=4 dimensions one can find a special quantity that exhibits an
extremely fast convergence to the asymptotic form. A comparison of the
available 5-loop result for this quantity with the asymptotic value shows
agreement at the 0.1% level. An analogous superfast convergence to the
asymptotic form happens in the case of the O(N)-symmetric anharmonic oscillator
where this convergence has inverse factorial type. The large orders of the
$\epsilon$ expansion for critical exponents manifest a similar effect.


title:
The temporal changes of the pulsational periods of the pre-white dwarf
  PG 1159-035

abstract:
  PG 1159-035, a pre-white dwarf with T=140000 K, is the prototype of the
PG1159 spectroscopic class and the DOV pulsating class. Changes in the star
cause variations in its oscillation periods. The measurement of temporal change
in the oscillation periods, dP/dt, allows us to estimate directly rates of
stellar evolutionary changes, such as the cooling rate and the envelope
contraction rate, providing a way to test and refine evolutionary models for
pre-white dwarf pulsating stars.
  We measured 27 pulsation modes period changes. The periods varied at rates of
between 1 and 100 ms/yr, and several can be directly measured with a relative
standard uncertainty below 10%. For the 516.0 s mode (the highest in amplitude)
in particular, not only the value of dP/dt can be measured directly with a
relative standard uncertainty of 2%, but the second order period change,
d(dP/dt)/dt, can also be calculated reliably. By using the (O-C) method we
refined the dP/dt and estimated the d(dP/dt)/dt for six other pulsation
periods. As a first application, we calculated the change in the PG 1559-035
rotation period, dP_rot/dt = -2.13*10^{-6} s/s, the envelope contraction rate
dR/dt = -2.2*10^{-13} solar radius/s, and the cooling rante dT/dt =
-1.42*10^{-3} K/s.


title: The Sigma Invariants of Thompson's Group F

abstract:
  Thompson's group F is the group of all increasing dyadic piecewise linear
homeomorphisms of the closed unit interval. We compute Sigma^m(F) and
Sigma^m(F;Z), the homotopical and homological Bieri-Neumann-Strebel-Renz
invariants of F, and we show that Sigma^m(F) = Sigma^m(F;Z). As an application,
we show that, for every m, F has subgroups of type F_{m-1} which are not of
type F_{m}.


title: A note on strong Jordan separation

abstract:
  We provide a strengthening of Jordan separation, to the setting of maps from
a compact topological space X into a sphere, where the source space X is not
necessarily a codimension one sphere, and the map is not necessarily injective.


title:
Galactic Globular and Open Clusters in the Sloan Digital Sky Survey. I.
  Crowded Field Photometry and Cluster Fiducial Sequences in ugriz

abstract:
  We present photometry for globular and open cluster stars observed with the
Sloan Digital Sky Survey (SDSS). In order to exploit over 100 million stellar
objects with r < 22.5 mag observed by SDSS, we need to understand the
characteristics of stars in the SDSS ugriz filters. While star clusters provide
important calibration samples for stellar colors, the regions close to globular
clusters, where the fraction of field stars is smallest, are too crowded for
the standard SDSS photometric pipeline to process. To complement the SDSS
imaging survey, we reduce the SDSS imaging data for crowded cluster fields
using the DAOPHOT/ALLFRAME suite of programs and present photometry for 17
globular clusters and 3 open clusters in a SDSS value-added catalog. Our
photometry and cluster fiducial sequences are on the native SDSS 2.5-meter
ugriz photometric system, and the fiducial sequences can be directly applied to
the SDSS photometry without relying upon any transformations. Model photometry
for red giant branch and main-sequence stars obtained by Girardi et al. cannot
be matched simultaneously to fiducial sequences; their colors differ by
~0.02-0.05 mag. Good agreement (< ~0.02 mag in colors) is found with Clem et
al. empirical fiducial sequences in u'g'r'i'z' when using the transformation
equations in Tucker et al.


title:
Particle Physics in the Sky and Astrophysics Underground: Connecting the
  Universe's Largest and Smallest Scales

abstract:
  Particles have tremendous potential as astronomical messengers, and
conversely, studying the universe as a whole also teaches us about particle
physics. This thesis encompasses both of these research directions.
  Many models predict a diffuse flux of high energy neutrinos from active
galactic nuclei and other astrophysical sources. The "Astrophysics Underground"
portion of this thesis describes a search for this neutrino flux performed by
looking for very high energy upward-going muons using the Super-K detector.
  In addition to using particles to do astronomy, we can also use the universe
itself as a particle physics lab. The "Particle Physics in the Sky" portion of
this thesis focuses on extracting cosmological information from galaxy surveys.
  To overcome technical challenges faced by the latest galaxy surveys, we
produced a comprehensive upgrade to mangle, a software package that processes
the angular masks defining the survey area on the sky. We added dramatically
faster algorithms and new useful features that are necessary for managing
complex masks of current and next-generation galaxy surveys.
  With this software in hand, we utilized SDSS data to investigate the relation
between galaxies and dark matter by studying relative bias, i.e., the relation
between different types of galaxies. Separating galaxies by their luminosities
and colors reveals a complicated picture: red galaxies are clustered more
strongly than blue galaxies, with both the brightest and the faintest red
galaxies showing the strongest clustering. Furthermore, red and blue galaxies
tend to occupy different regions of space. In order to make precise
measurements from the next generation of galaxy surveys, it will be essential
to account for this complexity.


title:
Testing cosmological structure formation using redshift-space
  distortions

abstract:
  Observations of redshift-space distortions in spectroscopic galaxy surveys
offer an attractive method for observing the build-up of cosmological
structure. In this paper we develop and test a new statistic based on
anisotropies in the measured galaxy power spectrum, which is independent of
galaxy bias and matches the matter power spectrum shape on large scales. The
amplitude provides a constraint on the derivative of the linear growth rate
through f.sigma_8. This demonstrates that spectroscopic galaxy surveys offer
many of the same advantages as weak lensing surveys, in that they both use
galaxies as test particles to probe all matter in the Universe. They are
complementary as redshift-space distortions probe non-relativistic velocities
and therefore the temporal metric perturbations, while weak lensing tests the
sum of the temporal and spatial metric perturbations. The degree to which our
estimator can be pushed into the non-linear regime is considered and we show
that a simple Gaussian damping model, similar to that previously used to model
the behaviour of the power spectrum on very small scales, can also model the
quasi-linear behaviour of our estimator. This enhances the information that can
be extracted from surveys for LCDM models.


title:
Inferring statistics of planet populations by means of automated
  microlensing searches

abstract:
  (abridged) The study of other worlds is key to understanding our own, and not
only provides clues to the origin of our civilization, but also looks into its
future. Rather than in identifying nearby systems and learning about their
individual properties, the main value of the technique of gravitational
microlensing is in obtaining the statistics of planetary populations within the
Milky Way and beyond. Only the complementarity of different techniques
currently employed promises to yield a complete picture of planet formation
that has sufficient predictive power to let us understand how habitable worlds
like ours evolve, and how abundant such systems are in the Universe. A
cooperative three-step strategy of survey, follow-up, and anomaly monitoring of
microlensing targets, realized by means of an automated expert system and a
network of ground-based telescopes is ready right now to be used to obtain a
first census of cool planets with masses reaching even below that of Earth
orbiting K and M dwarfs in two distinct stellar populations, namely the
Galactic bulge and disk. The hunt for extra-solar planets acts as a principal
science driver for time-domain astronomy with robotic-telescope networks
adopting fully-automated strategies. Several initiatives, both into facilities
as well as into advanced software and strategies, are supposed to see the
capabilities of gravitational microlensing programmes step-wise increasing over
the next 10 years. New opportunities will show up with high-precision
astrometry becoming available and studying the abundance of planets around
stars in neighbouring galaxies becoming possible. Finally, we should not miss
out on sharing the vision with the general public, and make its realization to
profit not only the scientists but all the wider society.


title:
Towards A Census of Earth-mass Exo-planets with Gravitational
  Microlensing

abstract:
  Thirteen exo-planets have been discovered using the gravitational
microlensing technique (out of which 7 have been published). These planets
already demonstrate that super-Earths (with mass up to ~10 Earth masses) beyond
the snow line are common and multiple planet systems are not rare. In this
White Paper we introduce the basic concepts of the gravitational microlensing
technique, summarise the current mode of discovery and outline future steps
towards a complete census of planets including Earth-mass planets. In the
near-term (over the next 5 years) we advocate a strategy of automated follow-up
with existing and upgraded telescopes which will significantly increase the
current planet detection efficiency. In the medium 5-10 year term, we envision
an international network of wide-field 2m class telescopes to discover
Earth-mass and free-floating exo-planets. In the long (10-15 year) term, we
strongly advocate a space microlensing telescope which, when combined with
Kepler, will provide a complete census of planets down to Earth mass at almost
all separations. Such a survey could be undertaken as a science programme on
Euclid, a dark energy probe with a wide-field imager which has been proposed to
ESA's Cosmic Vision Programme.


title:
Observation of the $\phi(1680)$ and the Y(2175) in $e^+ e^- \to
  \phi\pi^+\pi^-$

abstract:
  The cross sections for $e^+ e^- \to \phi\pi^+\pi^-$ and $e^+ e^- \to \phi
\fzero$ are measured from threshold to $\sqrt{s}=3.0$ $\hbox{GeV}$ using
initial state radiation. The analysis is based on a data sample of 673
fb$^{-1}$ collected on and below the $\Upsilon(4S)$ resonance with the Belle
detector at the KEKB asymmetric-energy $e^+e^-$ collider. First measurements
are reported for the resonance parameters of the $\phi(1680)$ in the
$\phi\pi^+\pi^-$ mode: $m=(1689\pm 7\pm 10)$ MeV/$c^2$ and $\Gamma=(211\pm
14\pm 19)$ MeV/$c^2$. A structure at $\sqrt{s}=2.1 \hbox{GeV}/c^2$,
corresponding to the so called Y(2175), is observed; its mass and width are
determined to be $2079\pm13^{+79}_{-28}$ MeV/$c^2$ and $192\pm23^{+25}_{-61}
\hbox{MeV}/c^2$, respectively.


title: The Impact of ICM Substructure on Ram Pressure Stripping

abstract:
  Cluster galaxies moving through the intracluster medium (ICM) are expected to
lose some of their interstellar medium (ISM) through ram pressure stripping and
related ISM-ICM interactions. Using high-resolution cosmological simulations of
a large galaxy cluster including star formation, we show that the ram pressure
a galaxy experiences at a fixed distance from the cluster center can vary by
well over an order of magnitude We find that this variation in ram pressure is
due in almost equal parts to variation in the ICM density and in the relative
velocity between the galaxy and the ICM. We also find that the ICM and galaxy
velocities are weakly correlated for in-falling galaxies.


title: Wigner crystal vs. Friedel oscillations in the 1D Hubbard model

abstract:
  We analyze the fermion density of the one-dimensional Hubbard model using
bosonization and numerical DMRG calculations. For finite systems we find a
relatively sharp crossover even for moderate short range interactions into a
region with $4k_F$ density waves as a function of density. The results show
that the unstable fixed point of a spin-incoherent state can dominate the
physical behavior in a large region of parameter space in finite systems. The
crossover may be observable in ultra cold fermionic gases in optical lattices
and in finite quantum wires.


title: Non-Gaussianity from isocurvature perturbations

abstract:
  We develop a formalism to study non-Gaussianity in both curvature and
isocurvature perturbations. It is shown that non-Gaussianity in the
isocurvature perturbation between dark matter and photons leaves distinct
signatures in the CMB temperature fluctuations, which may be confirmed in
future experiments, or possibly, even in the currently available observational
data. As an explicit example, we consider the QCD axion and show that it can
actually induce sizable non-Gaussianity for the inflationary scale, H_{inf} =
O(10^9 - 10^{11})GeV.


title: Evolution of the UV Excess in Early-Type Galaxies

abstract:
  We examine the UV emission from luminous early-type galaxies as a function of
redshift. We perform a stacking analysis using Galaxy Evolution Explorer
(GALEX) images of galaxies in the NOAO Deep Wide Field Survey (NDWFS) Bo\"otes
field and examine the evolution in the UV colors of the average galaxy. Our
sample, selected to have minimal ongoing star formation based on the optical to
mid-IR SEDs of the galaxies, includes 1843 galaxies spanning the redshift range
$0.05\leq z\leq0.65$. We find evidence that the strength of the UV excess
decreases, on average, with redshift, and our measurements also show moderate
disagreement with previous models of the UV excess. Our results show little
evolution in the shape of the UV continuum with redshift, consistent either
with the binary model for the formation of Extreme Horizontal Branch (EHB)
stars or with no evolution in EHB morphology with look-back time. However, the
binary formation model predicts that the strength of the UV excess should also
be relatively constant, in contradiction with our measured results. Finally, we
see no significant influence of a galaxy's environment on the strength of its
UV excess.


title: Evidence for B semileptonic decays into the charmed baryon Lambda_c+

abstract:
  We present the first evidence for B semileptonic decays into the charmed
baryon Lambda_c+ based on 420 fb-1 of data collected at the Upsilon(4S)
resonance with the BABAR detector at the PEP-II e+e- storage rings. Events are
tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We
measure the relative branching fraction BF(Bbar -> Lambda_c+ X l-
nubar_l)/BF(Bbar -> Lambda_c+/Lambda_c- X) = (3.2 +/- 0.9_stat +/- 0.9_syst)%.
The significance of the signal including the systematic uncertainty is 4.9
standard deviations.


title: Lectures on Probability, Entropy, and Statistical Physics

abstract:
  These lectures deal with the problem of inductive inference, that is, the
problem of reasoning under conditions of incomplete information. Is there a
general method for handling uncertainty? Or, at least, are there rules that
could in principle be followed by an ideally rational mind when discussing
scientific matters? What makes one statement more plausible than another? How
much more plausible? And then, when new information is acquired how do we
change our minds? Or, to put it differently, are there rules for learning? Are
there rules for processing information that are objective and consistent? Are
they unique? And, come to think of it, what, after all, is information? It is
clear that data contains or conveys information, but what does this precisely
mean? Can information be conveyed in other ways? Is information physical? Can
we measure amounts of information? Do we need to? Our goal is to develop the
main tools for inductive inference--probability and entropy--from a thoroughly
Bayesian point of view and to illustrate their use in physics with examples
borrowed from the foundations of classical statistical physics.

categories: physics.data-an cond-mat.stat-mech cs.IT math.IT math.ST physics.gen-ph stat.TH


title: Sigma Invariants of Direct Products of Groups

abstract:
  The Product Conjecture for the homological Bieri-Neumann-Strebel-Renz
invariants is proved over a field. Under certain hypotheses the Product
Conjecture is shown to also hold over Z, even though D. Schuetz has recently
shown that the Conjecture is false in general over Z. Our version over Z is
applied in a joint paper with D. Kochloukova to derive new information about
subgroups of Thompson's group F, namely that F has subgroups F_m which are not
of type F_{m+1}.


title: Local chiral fermions

abstract:
  Borici's construction of minimally doubled chiral fermions builds on a linear
combination of two unitarily related naive fermion actions. Being strictly
local, extremely efficient numerical implementation should be possible. The
resulting system is symmetric under the subgroup of the hypercubic group that
preserves a major hypercube diagonal. The symmetry includes both parity even
and odd transformations, but allows for an anisotropy to appear at finite
lattice spacing.


title: Directed flow in non-adiabatic stochastic pumps

abstract:
  We analyze the operation of a molecular machine driven by the non-adiabatic
variation of external parameters. We derive a formula for the integrated flow
from one configuration to another, obtain a "no-pumping theorem" for cyclic
processes with thermally activated transitions, and show that in the adiabatic
limit the pumped current is given by a geometric expression.


title: Disc instabilities and semi-analytic modelling of galaxy formation

abstract:
  The Efstathiou, Lake and Negroponte (1982) criterion can not distinguish bar
stable from bar unstable discs and thus should not be used in semi-analytic
galaxy formation simulations. I discuss the reasons for this, illustrate it
with examples and point out shortcomings in the recipes used for spheroid
formation. I propose an alternative, although much less straightforward,
possibility.


title:
Search for Invisible Decays of a Light Scalar in Radiative Transitions
  Upsilon(3S) -> gamma A0

abstract:
  We search for a light scalar particle produced in single-photon decays of the
Upsilon(3S) resonance through the process Upsilon(3S) -> gamma A0, A0 ->
invisible. Such an object appears in Next-to-Minimal Supersymmetric extensions
of the Standard Model, where a light CP-odd Higgs boson naturally couples
strongly to b-quarks. If, in addition, there exists a light, stable neutralino,
decays of A0 could be preferentially to an invisible final state. We search for
events with a single high-energy photon and a large missing mass, consistent
with a 2-body decay of Upsilon(3S). We find no evidence for such processes in a
sample of 122*10^6 Upsilon(3S) decays collected by the BABAR collaboration at
the PEP-II B-factory, and set 90% C.L. upper limits on the branching fraction
B(Upsilon(3S) -> gamma A0)*B(A0 -> invisible) at (0.7-31)*10^{-6} in the mass
range m(A0)<=7.8 GeV. The results are preliminary.


title:
Ca II Triplet Spectroscopy of Small Magellanic Cloud Red Giants. I.
  Abundances and Velocities for a Sample of Clusters

abstract:
  We have obtained near-infrared spectra covering the Ca II triplet lines for a
number of stars associated with 16 SMC clusters using the VLT + FORS2. These
data compose the largest available sample of SMC clusters with
spectroscopically derived abundances and velocities. Our clusters span a wide
range of ages and provide good areal coverage of the galaxy. Cluster members
are selected using a combination of their positions relative to the cluster
center as well as their abundances and radial velocities. We determine mean
cluster velocities to typically 2.7 km/s and metallicities to 0.05 dex (random
errors), from an average of 6.4 members per cluster. (continued in paper)


title: Geometries enumeratives complexe, reelle et tropicale

abstract:
  This text is an introduction to algebraic enumerative geometry and to
applications of tropical geometry to classical geometry, based on a course
given during the X-UPS mathematical days, 2008 May 14th and 15th. The aim of
this text is to be understandable by a first year master student.


title: Finite Size Corrections to Entanglement in Quantum Critical Systems

abstract:
  We analyze the finite size corrections to entanglement in quantum critical
systems. By using conformal symmetry and density functional theory, we discuss
the structure of the finite size contributions to a general measure of ground
state entanglement, which are ruled by the central charge of the underlying
conformal field theory. More generally, we show that all conformal towers
formed by an infinite number of excited states (as the size of the system $L
\to \infty$) exhibit a unique pattern of entanglement, which differ only at
leading order $(1/L)^2$. In this case, entanglement is also shown to obey a
universal structure, given by the anomalous dimensions of the primary operators
of the theory. As an illustration, we discuss the behavior of pairwise
entanglement for the eigenspectrum of the spin-1/2 XXZ chain with an arbitrary
length $L$ for both periodic and twisted boundary conditions.


title:
Short-range Charge and Spin Superstructures in Doped Layered Co
  Perovskites

abstract:
  We have investigated cobaltite relatives of the layered perovskite cuprates
and nickelates, Pr$_{2-x}$Ca$_x$CoO$_4$ ($0.39 \leq x \leq 0.73$) and
La$_{2-x}$Sr$_x$CoO$_4$ ($x = 0.61$), using elastic neutron scattering. We have
discovered doping-dependent incommensurate short-range ordering of charges and
magnetic moments, which in cobaltites occur in the range of heavy doping, $ 0.5
\lesssim x \lesssim 0.75$. The charge order exists already at room temperature
and shows no change on cooling. The incommensurability of its propagation
vector, ${\bf Q}_c = (\epsilon_c,0,l)$, roughly scales with the concentration
of Co$^{2+}$ ions, $\epsilon_c \sim (1-x)$. Magnetic order is only established
at low T$\lesssim 40$ K and has twice larger periodicity, indicating a dominant
antiferromagnetic correlation between the nearest Co$^{2+}$ spins.


title:
Parton transport and hadronization from the dynamical quasiparticle
  point of view

abstract:
  The hadronization of an expanding partonic fireball is studied within the
Parton-Hadron-Strings Dynamics (PHSD) approach which is based on a dynamical
quasiparticle model (DQPM) matched to reproduce lattice QCD results in
thermodynamic equilibrium. Apart from strong parton interactions the expansion
and development of collective flow is driven by strong gradients in the parton
mean-fields. An analysis of the elliptic flow $v_2$ demonstrates a linear
correlation with the spatial eccentricity $\epsilon$ as in case of ideal
hydrodynamics. The hadronization occurs by quark-antiquark fusion or 3 quark/3
antiquark recombination which is described by covariant transition rates. Since
the dynamical quarks become very massive, the formed resonant 'pre-hadronic'
color-dipole states ($q\bar{q}$ or $qqq$) are of high invariant mass, too, and
sequentially decay to the groundstate meson and baryon octets increasing the
total entropy. This solves the entropy problem in hadronization in a natural
way. The resulting particle ratios turn out to be in line with those from a
grandcanonical partition function at temperature $T \approx 170$ MeV rather
independent from the initial temperature and indicate an approximate
strangeness equilibration.


title: Branching proofs of infeasibility in low density subset sum problems

abstract:
  We prove that the subset sum problem has a polynomial time computable
certificate of infeasibility for all $a$ weight vectors with density at most
$1/(2n)$ and for almost all integer right hand sides. The certificate is
branching on a hyperplane, i.e. by a methodology dual to the one explored by
Lagarias and Odlyzko; Frieze; Furst and Kannan; and Coster et. al.
  The proof has two ingredients. We first prove that a vector that is near
parallel to $a$ is a suitable branching direction, regardless of the density.
Then we show that for a low density $a$ such a near parallel vector can be
computed using diophantine approximation, via a methodology introduced by Frank
and Tardos.
  We also show that there is a small number of long intervals whose disjoint
union covers the integer right hand sides, for which the infeasibility is
proven by branching on the above hyperplane.


title: Homotopy classification of maps into homogeneous spaces

abstract:
  We give an alternative to Postnikov's homotopy classification of maps from
3-dimensional CW-complexes to homogeneous spaces G/H of Lie groups. It
describes homotopy classes in terms of lifts to the group G and is suitable for
extending the notion of homotopy to Sobolev maps. This is required for
applications to variational problems of mathematical physics.


title: A Note on B-observables in Ponzano-Regge 3d Quantum Gravity

abstract:
  We study the insertion and value of metric observables in the (discrete) path
integral formulation of the Ponzano-Regge spinfoam model for 3d quantum
gravity. In particular, we discuss the length spectrum and the relation between
insertion of such B-observables and gauge fixing in the path integral.


title:
Determination of the Superfluid Gap in Atomic Fermi Gases by
  Quasiparticle Spectroscopy

abstract:
  We present majority and minority radiofrequency (RF) spectra of strongly
interacting imbalanced Fermi gases of Li-6. We observed a smooth evolution in
the nature of pairing correlations from pairing in the superfluid region to
polaron binding in the highly polarized normal region. The imbalance induces
quasiparticles in the superfluid region even at very low temperature. This
leads to a local bimodal spectral response, which allows us to determine the
superfluid gap \Delta and the Hartree energy U.