title: Spin-transfer torque induced reversal in magnetic domains

abstract:
  Using the complex stereographic variable representation for the macrospin,
from a study of the nonlinear dynamics underlying the generalized
Landau-Lifshitz(LL) equation with Gilbert damping, we show that the
spin-transfer torque is effectively equivalent to an applied magnetic field. We
study the macrospin switching on a Stoner particle due to spin-transfer torque
on application of a spin polarized current. We find that the switching due to
spin-transfer torque is a more effective alternative to switching by an applied
external field in the presence of damping. We demonstrate numerically that a
spin-polarized current in the form of a short pulse can be effectively employed
to achieve the desired macro-spin switching.


title: Nonlinear Gravitational Waves: Their Form and Effects

abstract:
  A gravitational wave must be nonlinear to be able to transport its own
source, that is, energy and momentum. A physical gravitational wave, therefore,
cannot be represented by a solution to a linear wave equation. Relying on this
property, the second-order solution describing such physical waves is obtained.
The effects they produce on free particles are found to consist of nonlinear
oscillations along the direction of propagation.


title:
Holographic Geometric Entropy at Finite Temperature from Black Holes in
  Global Anti de Sitter Spaces

abstract:
  Using a holographic proposal for the geometric entropy we study its behavior
in the geometry of Schwarzschild black holes in global $AdS_p$ for $p=3,4,5$.
Holographically, the entropy is determined by a minimal surface. On the gravity
side, due to the presence of a horizon on the background, generically there are
two solutions to the surfaces determining the entanglement entropy. In the case
of $AdS_3$, the calculation reproduces precisely the geometric entropy of an
interval of length $l$ in a two dimensional conformal field theory with
periodic boundary conditions. We demonstrate that in the cases of $AdS_{4}$ and
$AdS_{5}$ the sign of the difference of the geometric entropies changes,
signaling a transition. Euclideanization implies that various embedding of the
holographic surface are possible. We study some of them and find that the
transitions are ubiquitous. In particular, our analysis renders a very
intricate phase space, showing, for some ranges of the temperature, up to three
branches. We observe a remarkable universality in the type of results we obtain
from $AdS_4$ and $AdS_5$.


title:
Uniqueness of the stationary distribution and stabilizability in Zhang's
  sandpile model

abstract:
  We show that Zhang's sandpile model (N,[a,b]) on N sites and with uniform
additions on [a,b] has a unique stationary measure for all 0 <= a < b <= 1.
This generalizes earlier results where this was shown in some special cases.
  We define the infinite volume Zhang's sandpile model in dimension d >= 1, in
which topplings occur according to a Markov toppling process, and we study the
stabilizability of initial configurations chosen according to some measure \mu.
We show that for a stationary ergodic measure \mu with density \rho, for all
\rho < 1/2, \mu is stabilizable; for all \rho >= 1, \mu is not stabilizable;
for 1/2 <= \rho < 1, when \rho is near to 1/2 or 1, both possibilities can
occur.


title: Foreground removal from CMB temperature maps using an MLP neural network

abstract:
  One of the main obstacles in extracting the Cosmic Microwave Background (CMB)
signal from observations in the mm-submm range is the foreground contamination
by emission from galactic components: mainly synchrotron, free-free and thermal
dust emission. Due to the statistical nature of the intrinsic CMB signal it is
essential to minimize the systematic errors in the CMB temperature
determinations. Following the available knowledge of the spectral behavior of
the galactic foregrounds simple, power law-like spectra have been assumed. The
feasibility of using a simple neural network for extracting the CMB temperature
signal from the combined CMB and foreground signals has been investigated. As a
specific example, we have analysed simulated data, like that expected from the
ESA Planck Surveyor mission. A simple multilayer perceptron neural network with
2 hidden layers can provide temperature estimates, over more than 80 percent of
the sky, that are to a high degree uncorrelated with the foreground signals. A
single network will be able to cover the dynamic range of the Planck noise
level over the entire sky.


title: Searches for Contact Interactions at HERA

abstract:
  The H1 and ZEUS collaborations at HERA have searched for signatures of
physics beyond the Standard Model with high Q^2 neutral current deep inelastic
electron-proton and positron-proton scattering events. No significant
deviations from Standard Model predictions were observed. Various eeqq contact
nteraction models have been considered. Limits on the compositeness scale in
general eeqq contact interaction models, mass to the Yukawa coupling ratio for
heavy leptoquarks, the effective Planck mass scale in models with large extra
dimensions and the effective quark charge radius are presented.


title: Quaternion-Loop Quantum Gravity

abstract:
  It is shown that the Riemannian curvature of the 3-dimensional hypersurfaces
in space-time, described by the Wilson loop integral, can be represented by a
quaternion quantum operator induced by the SU(2) gauge potential, thus
providing a justification for quaternion quantum gravity at the Tev energy
scale.


title: Leptoquarks and Contact Interactions at LeHC

abstract:
  The sensitivity of LeHC to different models of "new physics" has been
studied, both for the resonance production and in the contact interaction
approximation. Expected limits are compared for different running scenarios.
Direct leptoquark production can be studied for masses up to about 2 TeV. For
contact interaction models scales up to about 70 TeV can be explored.
Significant improvement of existing limits is also expected for models with
large extra dimensions. Effective Plank mass scales up to about 5.4 TeV can be
probed. LeHC will be sensitive to the quark substructure of the order of 1E-19
m.


title:
The representation type of Ariki-Koike algebras and cyclotomic q-Schur
  algebras

abstract:
  We give a necessary and sufficient condition on parameters for Ariki-Koike
algebras (resp. cyclotomic q-Schur algebras) to be of finite representation
type.


title:
Effect of dopant atoms on local superexchange in cuprate
  superconductors: a perturbative treatment

abstract:
  Recent scanning tunneling spectroscopy experiments have provided evidence
that dopant impurities in high- Tc superconductors can strongly modify the
electronic structure of the CuO2 planes nearby, and possibly influence the
pairing. To investigate this connection, we calculate the local magnetic
superexchange J between Cu ions in the presence of dopants within the framework
of the three-band Hubbard model, up to fifth-order in perturbation theory. We
demonstrate that the sign of the change in J depends on the relative
dopant-induced spatial variation of the atomic levels in the CuO2 plane,
contrary to results obtained within the one-band Hubbard model. We discuss some
realistic cases and their relevance for theories of the pairing mechanism in
the cuprates


title: Transfer and Chern classes for extraspecial p-groups

abstract:
  In the cohomology ring of an extraspecial p-group, the subring generated by
Chern classes and transfers is studied. This subring is strictly larger than
the Chern subring, but still not the whole cohomology ring, even modulo
nilradical. A formula is obtained relating Chern classes to transfers.


title:
Enhanced spin Hall effect by resonant skew scattering in
  orbital-selective Kondo effect

abstract:
  The enhanced spin Hall effect in Au metal due to the resonant skew scattering
is studied with first-principles band structure calculations. Especially the
gigantic spin Hall angle $\gamma_S \cong 0.1$ observed recently (T.Seki et al.,
Nature Materials {\bf 7}, 125 (2008)) is attributed to the orbital-dependent
Kondo effect of Fe in the Au host metal, where the $t_{2g}$-orbitals are in the
mixed-valence region while $e_g$-orbitals are in the Kondo limit. The enhanced
spin-orbit interaction by the electron correlation in the $t_{2g}$-orbitals
leads to the gigantic spin Hall effect. Impurities with 5d orbitals are also
discussed.


title:
Supplementary Information: Quantum phase transition in a single-molecule
  quantum dot

abstract:
  Quantum criticality is the intriguing possibility offered by the laws of
quantum mechanics when the wave function of a many-particle physical system is
forced to evolve continuously between two distinct, competing ground states.
This phenomenon, often related to a zero-temperature magnetic phase transition,
can be observed in several strongly correlated materials such as heavy fermion
compounds or possibly high-temperature superconductors, and is believed to
govern many of their fascinating, yet still unexplained properties. In contrast
to these bulk materials with very complex electronic structure, artificial
nanoscale devices could offer a new and simpler vista to the comprehension of
quantum phase transitions. This long-sought possibility is demonstrated by our
work in a fullerene molecular junction, where gate voltage induces a crossing
of singlet and triplet spin states at zero magnetic field. Electronic tunneling
from metallic contacts into the $\rm{C_{60}}$ quantum dot provides here the
necessary many-body correlations to observe a true quantum critical behavior.


title: Codimension Two Branes and Distributional Curvature

abstract:
  In general relativity, there is a well-developed formalism for working with
the approximation that a gravitational source is concentrated on a shell, or
codimension one surface. By contrast, there are obstacles to concentrating
sources on surfaces that have a higher codimension, for example, a string in a
spacetime with dimension greater than or equal to four. Here it is shown that,
by giving up some of the generality of the codimension one case, curvature can
be concentrated on submanifolds that have codimension two. A class of metrics
is identified such that (1) the scalar curvature and Ricci densities exist as
distributions with support on a co-dimension two submanifold, and (2) using the
Einstein equation, the distributional curvature corresponds to a concentrated
stress-energy with equation of state p equals minus the energy density, where p
is the isotropic pressure tangent to the submanifold. This is the appropriate
stress-energy to describe a self-gravitating brane that is governed by an area
action, or a brane world deSitter cosmology. The possibility of having a
different equation of state arise from a wider class of metrics is discussed.


title: Topological Twisting of Multiple M2-brane Theory

abstract:
  Bagger-Lambert-Gustavsson theory with infinite dimensional gauge group has
been suggested to describe M5-brane as a condensation of multiple M2-branes.
Here we perform a topological twisting of the Bagger-Lambert-Gustavsson theory.
The original SO(8) R-symmetry is broken to SO(3)XSO(5), where the former may be
interpreted as a diagonal subgroup of the Euclidean M5-brane world-volume
symmetry SO(6), while the latter is the isometry of the transverse five
directions. Accordingly the resulting action contains an one-form and five
scalars as for the bosonic dynamical fields. We further lift the action to a
generic curved three manifold. In order to make sure the genuine topological
invariance, we construct an off-shell formalism such that the scalar
supersymmetry transformations are nilpotent strictly off-shell and independent
of the metric of the three manifold. The one loop partition function around a
trivial background yields the Ray-Singer torsion. The BPS equation involves an
M2-brane charge density given by a Nambu-Goto action defined in an internal
three-manifold.


title: Thom series of contact singularities

abstract:
  Thom polynomials measure how global topology forces singularities. The power
of Thom polynomials predestine them to be a useful tool not only in
differential topology, but also in algebraic geometry (enumerative geometry,
moduli spaces) and algebraic combinatorics. The main obstacle of their
widespread application is that only a few, sporadic Thom polynomials have been
known explicitly. In this paper we develop a general method for calculating
Thom polynomials of contact singularities. Along the way, relations with the
equivariant geometry of (punctual, local) Hilbert schemes, and with iterated
residue identities are revealed.


title: On the notion of geometry over $\F_1$

abstract:
  We refine the notion of variety over the "field with one element" developed
by C. Soul\'e by introducing a grading in the associated functor to the
category of sets, and show that this notion becomes compatible with the
geometric viewpoint developed by J. Tits. We then solve an open question of C.
Soul\'e by proving, using results of J. Tits and C. Chevalley, that Chevalley
group schemes are examples of varieties over a quadratic extension of the above
"field".


title: Star cluster survival and compressive tides in Antennae-like mergers

abstract:
  Gravitational tides are widely understood to strip and destroy galactic
substructures. In the course of a galaxy merger, however, transient totally
compressive tides may develop and prevent star forming regions from dissolving,
after they condensed to form clusters of stars. We study the statistics of such
compressive modes in an N-body model of the galaxy merger NGC 4038/39 (the
Antennae) and show that ~15% of the disc material undergoes compressive tides
at pericentre. The spatial distribution of observed young clusters in the
overlap and nuclear regions of the Antennae matches surprisingly well the
location of compressive tides obtained from simulation data. Furthermore, the
statistics of time intervals spent by individual particles embedded in a
compressive tide yields a log-normal distribution of characteristic time ~10
Myr, comparable to star cluster formation timescales. We argue that this
generic process is operative in galaxy mergers at all redshifts and possibly
enhances the formation of star clusters. We show with a model calculation that
this process will prevent the dissolution of a star cluster during the
formation phase, even for a star formation efficiency as low as ~10%. The
transient nature of compressive tides implies that clusters may dissolve
rapidly once the tidal field switches to the usual disruptive mode.


title: Polarimetry with a soft x-ray spectrometer

abstract:
  An approach for measuring linear X-ray polarization over a broad-band using
conventional spectroscopic optics is described. A set of multilayer-coated
flats reflect the dispersed X-rays to the instrument detectors. The intensity
variation as a function of energy and position angle is measured to determine
three Stokes parameters: I, Q, and U. By laterally grading the multilayer
optics and matching the dispersion of the gratings, one may take advantage of
high multilayer reflectivities and achieve modulation factors over 80% over the
entire 0.2 to 0.8 keV band. A sample design is shown that could be used with a
small orbiting mission.


title: Hadronic B Decays to Charm and Charmonium With the BaBar Experiment

abstract:
  The {\it BaBar} experiment has recorded the decays of more than 465$\times
10^6 B\bar{B}$ pairs since 1999, and is reaching an unprecedented precision in
the measurement of hadronic B decays. The following results are presented:
tests of QCD factorization with the decays $B\to \chi_{c0}K^{*} $, $B\to
\chi_{c1,2}K^{(*)} $, and $\bar{B}^{0}\to D^{(*)0}h^{0}$, $h^0=\pi^0, \eta,\
\omega, \eta'$, study of the decays to charmonium $B\to \eta_c K^{(*)},\
\eta_c(2S) K^{(*)}$ and $h_cK^{(*)}$, measurement of the mass difference
between neutral and charged $B$'s, measurement of the "r" parameters for the
extraction of the CKM angles $\sin(2\beta+\gamma)$ with the decays $B\to
D_s^{(*)}h, h=\pi^-, \rho^-, K^{(*)+}$, study of the three-body rare decays
$B\to J/\psi\phi K$, study of the baryonic decays
$\bar{B}^0\to\Lambda_c^+\bar{p}$, $B^-\to\Lambda_c^+\pi^-\bar{p}$, and
$B^-\to\Lambda_c^+\pi^0\bar{p}$. Except for the published results, all the
given numbers are preliminary.


title:
Vortex trapping and expulsion in thin-film type-II superconducting
  strips

abstract:
  Vortex trapping is investigated in thin-film strips of superconducting
material. We present a model for the critical field above which vortex trapping
occurs in these strips. This model includes the pairing energy of
vortex-antivortex pairs in addition to the energy of single vortices.
Experimental verification of the model with a scanning SQUID microscope shows
very good agreement between the model and experiments on YBa2Cu3O7-delta and Nb
strips. Statistical analysis of the vortex distribution in the strips above the
critical field has been performed and a comparison has been made between Nb and
YBa2Cu3O7-delta for the distributions in the lateral and longitudinal
directions.


title:
An Efficient Algorithm for Cooperative Spectrum Sensing in Cognitive
  Radio Networks

abstract:
  We consider the problem of Spectrum Sensing in Cognitive Radio Systems. We
have developed a distributed algorithm that the Secondary users can run to
sense the channel cooperatively. It is based on sequential detection algorithms
which optimally use the past observations. We use the algorithm on secondary
users with energy detectors although it can be used with matched filter and
other spectrum sensing algorithms also. The algorithm provides very low
detection delays and also consumes little energy. Furthermore it causes low
interference to the primary users. We compare this algorithm to several
recently proposed algorithms and show that it detects changes in spectrum
faster than these algorithms and uses significantly less energy.


title: Stability Selection

abstract:
  Estimation of structure, such as in variable selection, graphical modelling
or cluster analysis is notoriously difficult, especially for high-dimensional
data. We introduce stability selection. It is based on subsampling in
combination with (high-dimensional) selection algorithms. As such, the method
is extremely general and has a very wide range of applicability. Stability
selection provides finite sample control for some error rates of false
discoveries and hence a transparent principle to choose a proper amount of
regularisation for structure estimation. Variable selection and structure
estimation improve markedly for a range of selection methods if stability
selection is applied. We prove for randomised Lasso that stability selection
will be variable selection consistent even if the necessary conditions needed
for consistency of the original Lasso method are violated. We demonstrate
stability selection for variable selection and Gaussian graphical modelling,
using real and simulated data.


title: J/Psi production in heavy ion collisions and gluon saturation

abstract:
  We calculate the inclusive J/Psi production in heavy ion collisions including
the effects of gluon saturation in the wave functions of the colliding nuclei.
We argue that the dominant production mechanism in proton--nucleus and
nucleus--nucleus collisions for heavy nuclei is different from the one in
hadron-hadron interactions. We find that the rapidity distribution of primary
J/Psi production is more peaked around midrapidity than the analogous
distribution in elementary pp collisions. We discuss the consequences of this
fact on the experimentally observed J/Psi suppression in Au-Au collisions at
RHIC energies.


title: A new modified-rate approach for gas-grain chemical simulations

abstract:
  Understanding grain-surface processes is crucial to interpreting the
chemistry of the ISM. However, accurate surface chemistry models are
computationally expensive and are difficult to integrate with gas-phase
simulations. A new modified-rate method for solving grain-surface chemical
systems is presented. Its purpose is accurately to model highly complex systems
that can otherwise only be treated using the sometimes inadequate rate-equation
approach. In contrast to previous rate-modification techniques, the functional
form of the surface production rates was modified, and not simply the rate
coefficient. This form is appropriate to the extreme "small-grain" limit, and
can be verified using an analytical master-equation approach. Various further
modifications were made to this basic form, to account for competition between
processes, to improve estimates of surface occupation probabilities, and to
allow a switch-over to the normal rate equations where these are applicable.
The new method was tested against systems solved previously using exact
techniques. Even the simplest method is quite accurate, and a great improvement
over rate equations. Further modifications allow the master-equation results to
be reproduced exactly for the methanol-producing system, within computational
accuracy. Small discrepancies arise when non-zero activation energies are
assumed for the methanol system, which result from complex reaction-competition
processes that cannot be resolved easily without using exact methods.
Inaccuracies in computed abundances are never greater than a few tens of
percent, and typically of the order of one percent, in the most complex systems
tested. Implementation of the method in simple networks, including
hydrogen-only systems, is trivial, whilst the results are highly accurate.


title: Manipulating the torsion of molecules by strong laser pulses

abstract:
  A proof-of-principle experiment is reported, where torsional motion of a
molecule, consisting of a pair of phenyl rings, is induced by strong laser
pulses. A nanosecond laser pulse spatially aligns the carbon-carbon bond axis,
connecting the two phenyl rings, allowing a perpendicularly polarized, intense
femtosecond pulse to initiate torsional motion accompanied by an overall
rotation about the fixed axis. The induced motion is monitored by femtosecond
time-resolved Coulomb explosion imaging. Our theoretical analysis accounts for
and generalizes the experimental findings.


title: What we (would like to) know about the neutrino mass

abstract:
  We present updated values for the mass-mixing parameters relevant to neutrino
oscillations, with particular attention to emerging hints in favor of
theta_13>0. We also discuss the status of absolute neutrino mass observables,
and a possible approach to constrain theoretical uncertainties in neutrinoless
double beta decay. Desiderata for all these issues are also briefly mentioned.


title:
Ordering of localized electronic states in multiferroic TbMnO3: a soft
  X-ray resonant scattering study

abstract:
  Soft X-ray resonant scattering (XRS) has been used to observe directly, for
the first time, the ordering of localized electronic states on both the Mn and
Tb sites in multiferroic TbMnO$_3$. Large resonant enhancement of the X-ray
scattering cross-section were observed when the incident photon energy was
tuned to either the Mn $L$ or Tb $M$ edges which provide information on the Mn
3d and Tb $4f$ electronic states, respectively. The temperature dependence of
the XRS signal establishes, in a model independent way, that in the
high-temperature phase (28 K $\leq$ T $\leq$ 42 K) the Mn 3d sublattices
displays long-range order. The Tb $4f$ sublattices are found to order only on
entering the combined ferroelectric/magnetic state below 28 K. Our results are
discussed with respect to recent hard XRS experiments (sensitive to spatially
extended orbitals) and neutron scattering.


title: Entropy and Poincar\'e recurrence from a geometrical viewpoint

abstract:
  We study Poincar\'e recurrence from a purely geometrical viewpoint. We prove
that the metric entropy is given by the exponential growth rate of return times
to dynamical balls. This is the geometrical counterpart of Ornstein-Weiss
theorem. Moreover, we show that minimal return times to dynamical balls grow
linearly with respect to its length. Finally, some interesting relations
between recurrence, dimension, entropy and Lyapunov exponents of ergodic
measures are given.


title:
Radiation-hydrodynamics simulations of surface convection in low-mass
  stars: connections to stellar structure and asteroseismology

abstract:
  Radiation-hydrodynamical simulations of surface convection in low-mass stars
can be exploited to derive estimates of i) the efficiency of the convective
energy transport in the stellar surface layers; ii) the convection-related
photometric micro-variability. We comment on the universality of the
mixing-length parameter, and point out potential pitfalls in the process of its
calibration which may be in part responsible for the contradictory findings
about its variability across the Hertzsprung-Russell digramme. We further
comment on the modelling of the photometric micro-variability in HD49933 - one
of the first main COROT targets.


title: Supernova neutrinos: Strong coupling effects of weak interactions

abstract:
  In core-collapse supernovae, neutrinos and antineutrinos are initially
subject to significant self-interactions induced by weak neutral currents,
which may induce strong-coupling effects on the flavor evolution (collective
transitions). The interpretation of the effects is simplified when self-induced
collective transitions are decoupled from ordinary matter oscillations, as for
the matter density profile that we discuss. In this case, approximate
analytical tools can be used (pendulum analogy, swap of energy spectra). For
inverted neutrino mass hierarchy, the sequence of effects involves:
synchronization, bipolar oscillations, and spectral split. Our simulations
shows that the main features of these regimes are not altered when passing from
simplified (angle-averaged) treatments to full, multi-angle numerical
experiments.


title:
First Measurement of the Neutron $\beta$-Asymmetry with Ultracold
  Neutrons

abstract:
  We report the first measurement of angular correlation parameters in neutron
$\beta$-decay using polarized ultracold neutrons (UCN). We utilize UCN with
energies below about 200 neV, which we guide and store for $\sim 30$ s in a Cu
decay volume. The $\vec{\mu}_n \cdot \vec{B}$ potential of a static 7 T field
external to the decay volume provides a 420 neV potential energy barrier to the
spin state parallel to the field, polarizing the UCN before they pass through
an adiabatic fast passage (AFP) spin-flipper and enter a decay volume, situated
within a 1 T, $2 \times 2\pi$ superconducting solenoidal spectrometer. We
determine a value for the $\beta$-asymmetry parameter $A_0$, proportional to
the angular correlation between the neutron polarization and the electron
momentum, of $A_0 = -0.1138 \pm 0.0051$.


title: Effects of mirror dark matter on neutron stars

abstract:
  If dark matter is made of mirror baryons, they are present in all
gravitationally bound structures. Here we investigate some effects of mirror
dark matter on neutron stars and discuss possible observational consequences.
The general-relativistic hydrostatic equations are generalized to spherical
objects with multiple fluids that interact by gravity. We use the minimal
parity-symmetric extension of the standard model, which implies that the
microphysics is the same in the two sectors. We find that the mass-radius
relation is significantly modified in the presence of a few percent mirror
baryons. This effect mimics that of other exotica, e.g., quark matter. In
contrast to the common view that the neutron-star equilibrium sequence is
unique, we show that it depends on the relative number of mirror baryons to
ordinary baryons. It is therefore history dependent. The critical mass for core
collapse, i.e., the process by which neutron stars are created, is modified in
the presence of mirror baryons. We calculate the modified Chandrasekhar mass
and fit it with a polynomial. A few percent mirror baryons is sufficient to
lower the critical mass for core collapse by ~0.1 M_sun. This could allow for
the formation of extraordinary compact neutron stars with low mass.


title:
Large-amplitude intraday variability in QSO 1156+295 observed during a
  VLBI experiment

abstract:
  We present here the discovery of rapid, large amplitude intraday variability
in the compact flat-spectrum radio quasar 1156+295. The detection of 40% flux
density variations at 15 GHz on a timescale of only 2.7 hours was
serendipitously made when the source was observed with the Very Long Baseline
Array as a part of the MOJAVE survey programme on February 5, 2007. Intraday
variability on timescales of a few hours or less is rare, and there exist very
few sources that show large-amplitude variations on a timescale as short as
what is now observed for 1156+295. The shape of the visibility function of the
source changes very little during the observation, although the correlated flux
density changes by 40%. This suggests that the variability occurs in a single
dominant compact component. The observed variability characteristics are
consistent with interstellar scintillation in nearby, highly turbulent medium.
The rms amplitude of modulation at 15 GHz is unusually large and it implies a
rather high scattering measure along the line-of-sight towards 1156+295.


title: Distributional solutions to the Maxwell-Vlasov equations

abstract:
  The distributional form of the Maxwell-Vlasov equations are formulated.
Submanifold distributions are analysed and the general submanifold
distributional solutions to the Vlasov equations are given. The properties
required so that these solutions can be a distributional source to Maxwell's
equations are analysed and it is shown that a sufficient condition is that
spacetime be globally hyperbolic. The cold fluid, multicurrent and water bag
models of charge are shown to be particular cases of the distributional
Maxwell-Vlasov system.


title: The fate of a gravitational wave in de Sitter spacetime

abstract:
  If we want to explain the recently discovered accelerated stage of the
universe, one of the option we have is to modify the Einstein tensor. The
simplest such modification, in agreement with all observations, is the positive
cosmological constant $\Lambda$. Such a modification will also have its impact
on local observables and on the propagation of weak gravitational waves. We
show here that the inclusion of a cosmological constant impedes the detection
of a gravitational wave if the latter is produced at a distance larger than
${\cal L}_{\rm crit}=(6\sqrt{2}\pi f \hat{h}/\sqrt{5})r_{\Lambda}^2$ where
$r_{\Lambda}=1/\sqrt{\Lambda}$ and $f$ and $\hat{h}$ are the frequency and the
strain of the wave, respectively. ${\cal L}_{\rm crit}$ is of astrophysical
order of magnitude. We interpret the result in the sense that the gravitational
wave interpretation is only possible if the characteristic wave properties are
smaller than the non-oscillatory solution due to $\Lambda$.


title:
CdSe quantum dots in ZnSe nanowires as efficient source for single
  photons up to 220 K

abstract:
  ZnSe nanowire heterostructures were grown by molecular beam epitaxy in the
vapour-liquid-solid growth mode assisted by gold catalysts. Size, shape and
crystal structure are found to strongly depend on the growth conditions. Both,
zinc-blende and wurtzite crystal structures are observed using transmission
electron microscopy. At low growth temperature, cone-shaped nano-needles are
formed. For higher growth temperature, the nanowires are uniform and have a
high aspect ratio with sizes of 1-2 $\mu$m in length and 20-50 nm in width as
observed by scanning electron microscopy. Growing a nanowire on top of a
nano-needle allows us to obtain very narrow nanorods with a diameter less than
10 nm and a low density of stacking fault defects. These results allow us the
insertion of CdSe quantum dots in a ZnSe nanowire. An effcient photon
anti-bunching was observed up to 220 K, demonstrating a high-temperature
single-photon source.


title: On $v$--domains and star operations

abstract:
  Let $\ast$ be a star operation on an integral domain $D$. Let $\f(D)$ be the
set of all nonzero finitely generated fractional ideals of $D$. Call $D$ a
$\ast$--Pr\"ufer (respectively, $(\ast, v)$--Pr\"ufer) domain if
$(FF^{-1})^{\ast}=D$ (respectively, $(F^vF^{-1})^{\ast}=D$) for all $F\in
\f(D)$. We establish that $\ast$--Pr\"ufer domains (and $(\ast, v)$--Pr\"ufer
domains) for various star operations $\ast $ span a major portion of the known
generalizations of Pr\"{u}fer domains inside the class of $v$--domains. We also
use Theorem 6.6 of the Larsen and McCarthy book [Multiplicative Theory of
Ideals, Academic Press, New York--London, 1971], which gives several equivalent
conditions for an integral domain to be a Pr\"ufer domain, as a model, and we
show which statements of that theorem on Pr\"ufer domains can be generalized in
a natural way and proved for $\ast$--Pr\"ufer domains, and which cannot be. We
also show that in a $\ast $--Pr\"ufer domain, each pair of $\ast $-invertible
$\ast $-ideals admits a GCD in the set of $\ast $-invertible $\ast $-ideals,
obtaining a remarkable generalization of a property holding for the "classical"
class of Pr\"ufer $v$--multiplication domains. We also link $D$ being $\ast
$--Pr\"ufer (or $(\ast, v)$--Pr\"ufer) with the group Inv$^{\ast}(D)$ of $\ast
$-invertible $\ast $-ideals (under $\ast$-multiplication) being
lattice-ordered.


title: Extremely metal-poor stars from the SDSS

abstract:
  We give a progress report about the activities within the CIFIST Team related
to the search for extremely metal-poor stars in the Sloan Digital Sky Survey's
spectroscopic catalog. So far the search has provided 25 candidates with
metallicities around or smaller -3. For 15 candidates high resolution
spectroscopy with UVES at the VLT has confirmed their extremely metal-poor
status. Work is under way to extend the search to the SDSS's photometric
catalog by augmenting the SDSS photometry, and by gauging the capabilities of
X-shooter when going to significantly fainter targets.


title: Collective phenomena in non-central nuclear collisions

abstract:
  Recent developments in the field of anisotropic flow in nuclear collision are
reviewed. The results from the top AGS energy to the top RHIC energy are
discussed with emphasis on techniques, interpretation, and uncertainties in the
measurements.


title: Population extinction in a fluctuating environment

abstract:
  Environmental noise can cause an exponential reduction in the mean time to
extinction (MTE) of an isolated population. We study this effect on an example
of a stochastic birth-death process with rates modulated by a colored Gaussian
noise. A path integral formulation yields a transparent way of evaluating the
MTE and finding the optimal realization of the environmental noise that
determines the most probable path to extinction. The population-size dependence
of the MTE changes from exponential in the absence of the environmental noise
to a power law for a short-correlated noise and to no dependence for
long-correlated noise. We also establish the validity domains of the limits of
white noise and adiabatic noise.


title:
Polarization Rotation, Switching and E-T phase diagrams of BaTiO$_3$: A
  Molecular Dynamics Study

abstract:
  We use molecular dynamics simulations to understand the mechanisms of
polarization switching in ferroelectric BaTiO$_3$ achieved with external
electric field. For tetragonal and orthorhombic ferroelectric phases, we
determine the switching paths, and show that polarization rotation through
intermediate monoclinic phases (a) facilitates switching at low fields (b) is
responsible for a sharp anisotropy in polarization switching. We develop
understanding of this through determination of detailed electric
field-temperature phase diagrams, that are fundamental to technological
applications based on electromechanical and switching response of
ferroelectrics.


title: Neutral Solar Wind Generated by Lunar Exospheric Dust at the Terminator

abstract:
  We calculate the flux of neutral solar wind observed on the lunar surface at
the terminator due to solar wind protons penetrating exospheric dust grains
with (1) radii greater than 0.1 microns and (2) radii greater than 0.01
microns. For grains with radii larger than 0.1 microns, the ratio of the
neutral solar wind flux produced by exospheric dust to the incident ionized
solar wind flux is estimated to be about 10^-4-10^-3 for solar wind speeds in
excess of 800 km/s, but much lower (less than 10^-5) at average to slow solar
wind speeds. However, when the smaller grain sizes are considered, this ratio
is estimated to be greater than 10^-5 at all speeds, and at speeds in excess of
700 km/s reaches about 10^-3. These neutral solar wind fluxes are easily
measurable with current low energy neutral atom instrumentation. Observations
of neutral solar wind from the surface of the Moon would provide independent
information on the distribution of very small dust grains in the lunar
exosphere that would complement and constrain optical measurements at
ultraviolet and visible wavelengths.


title: Exploring the phase diagram of sextet QCD

abstract:
  As a follow up to the previous talk about the beta function of SU(3) gauge
theory with Nf=2 symmetric representation (clover) fermions [arXiv:0809.2885
[hep-lat]], we describe our explorations of the beta-kappa plane, away from the
massless limit. Our simulations are mostly done on lattices of length L=8 and
12. We observe a phase transition from a strong coupling confined phase to a
deconfined, chirally restored phase. The line of transitions avoids (so far)
the location of the infrared fixed point discussed in the last talk.


title: Diagnosing space telescope misalignment and jitter using stellar images

abstract:
  Accurate knowledge of the telescope's point spread function (PSF) is
essential for the weak gravitational lensing measurements that hold great
promise for cosmological constraints. For space telescopes, the PSF may vary
with time due to thermal drifts in the telescope structure, and/or due to
jitter in the spacecraft pointing (ground-based telescopes have additional
sources of variation). We describe and simulate a procedure for using the
images of the stars in each exposure to determine the misalignment and jitter
parameters, and reconstruct the PSF at any point in that exposure's field of
view. The simulation uses the design of the SNAP (http://snap.lbl.gov)
telescope. Stellar-image data in a typical exposure determines secondary-mirror
positions as precisely as $20 {\rm nm}$. The PSF ellipticities and size, which
are the quantities of interest for weak lensing are determined to $4.0 \times
10^{-4}$ and $2.2 \times 10^{-4}$ accuracies respectively in each exposure,
sufficient to meet weak-lensing requirements. We show that, for the case of a
space telescope, the PSF estimation errors scale inversely with the square root
of the total number of photons collected from all the usable stars in the
exposure.


title: Diboson Production at the Tevatron

abstract:
  We present the latest results on the production of WW, WZ, Wgamma, Zgamma and
ZZ events at the Fermilab Tevatron Collider. The results are based on the
analyses of 0.2 -- 2 /fb of data collected in p pbar collisions at sqrt(s) =
1.96 TeV by CDF and DO experiments during the Tevatron Run II. Analyses of the
diboson production processes provide crucial test of the Standard Model,
directly probing its predictions on the Trilinear Gauge Couplings.


title:
Communication-Efficient Construction of the Plane Localized Delaunay
  Graph

abstract:
  Let $V$ be a finite set of points in the plane. We present a 2-local
algorithm that constructs a plane $\frac{4 \pi \sqrt{3}}{9}$-spanner of the
unit-disk graph $\UDG(V)$. This algorithm makes only one round of communication
and each point of $V$ broadcasts at most 5 messages. This improves the
previously best message-bound of 11 by Ara\'{u}jo and Rodrigues (Fast localized
Delaunay triangulation, Lecture Notes in Computer Science, volume 3544, 2004).


title: Sorting by Placement and Shift

abstract:
  In sorting situations where the final destination of each item is known, it
is natural to repeatedly choose items and place them where they belong,
allowing the intervening items to shift by one to make room. (In fact, a
special case of this algorithm is commonly used to hand-sort files.) However,
it is not obvious that this algorithm necessarily terminates.
  We show that in fact the algorithm terminates after at most $2^{n-1}-1$ steps
in the worst case (confirming a conjecture of L. Larson), and that there are
super-exponentially many permutations for which this exact bound can be
achieved. The proof involves a curious symmetrical binary representation.


title: Strong Law of Large Numbers for Fragmentation Processes

abstract:
  In the spirit of a classical results for Crump-Mode-Jagers processes, we
prove a strong law of large numbers for homogenous fragmentation processes.
Specifically, for self-similar fragmentation processes, including homogenous
processes, we prove the almost sure convergence of an empirical measure
associated with the stopping line corresponding to first fragments of size
strictly smaller than $\eta$ for $1\geq \eta >0$.


title: Fermi condensates for dynamic imaging of electro-magnetic fields

abstract:
  Ultracold gases provide micrometer size atomic samples whose sensitivity to
external fields may be exploited in sensor applications. Bose-Einstein
condensates of atomic gases have been demonstrated to perform excellently as
magnetic field sensors \cite{Wildermuth2005a} in atom chip
\cite{Folman2002a,Fortagh2007a} experiments. As such, they offer a combination
of resolution and sensitivity presently unattainable by other methods
\cite{Wildermuth2006a}. Here we propose that condensates of Fermionic atoms can
be used for non-invasive sensing of time-dependent and static magnetic and
electric fields, by utilizing the tunable energy gap in the excitation spectrum
as a frequency filter. Perturbations of the gas by the field create both
collective excitations and quasiparticles. Excitation of quasiparticles
requires the frequency of the perturbation to exceed the energy gap. Thus, by
tuning the gap, the frequencies of the field may be selectively monitored from
the amount of quasiparticles which is measurable for instance by
RF-spectroscopy. We analyse the proposed method by calculating the
density-density susceptibility, i.e. the dynamic structure factor, of the gas.
We discuss the sensitivity and spatial resolution of the method which may, with
advanced techniques for quasiparticle observation \cite{Schirotzek2008a}, be in
the half a micron scale.


title: Topological Phase Transitions and Holonomies in the Dimer Model

abstract:
  We demonstrate that the classical dimer model defined on a toroidal hexagonal
lattice acquires holonomy phases in the thermodynamic limit. When all
activities are equal the lattice sizes must be considered mod 6 in which case
the finite size corrections to the bulk partition function correspond to a
massless Dirac Fermion in the presence of a flat connection with nontrivial
holonomy. For general bond activities we find that the phase transition in this
model is a topological one, where the torus degenerates and its modular
parameter becomes real at the critical temperature. We argue that these
features are generic to bipartite dimer models and we present a more general
lattice whose continuum partition function is that of a massive Dirac Fermion.

categories: hep-th cond-mat.str-el hep-lat math-ph math.AG math.CO math.MP


title: Novel binding mechanism for ultra-long range molecules

abstract:
  Molecular bonds can be divided into four primary types: ionic, covalent, van
der Waals and hydrogen bonds. At ultralow temperatures a novel binding type
emerges paving the way for novel molecules and ultracold chemistry [1,2]. The
underlying mechanism for this new type of chemical bond is low-energy electron
scattering of Rydberg electrons from polarisable ground state atoms [3]. This
quantum scattering process can generate an attractive potential that is able to
bind the ground state atom to the Rydberg atom at a well localized position
within the Rydberg electron wave function. The resulting giant molecules can
have an internuclear separation of several thousand Bohr radii, which places
them among the largest known molecules to date. Their binding energies are much
smaller than the Kepler frequencies of the Rydberg electrons i.e. the atomic
Rydberg electron state is essentially unchanged by the bound ground state atom.
Ultracold and dense samples of atoms enable the creation of these molecules via
Rydberg excitation. In this paper we present spectroscopic evidence for the
vibrational ground and first excited state of a Rubidium dimer Rb(5S)-Rb(nS).
We apply a Born-Oppenheimer model to explain the measured binding energies for
principal quantum numbers n between 34 and 40 and extract the s-wave scattering
length for electron-Rb(5S) scattering in the relevant low energy regime Ekin <
100 meV. We also determine the lifetimes and the polarisabilities of these
molecules. P-wave bound states [2], Trimer states [4] as well as bound states
for large angular momentum of the Rydberg electron - socalled trilobite
molecules [1] - are within reach in the near future and will further refine our
conceptual understanding of the chemical bond.


title:
Generalized gauge-invariant formulations of the strong-field
  approximation

abstract:
  The gauge problem in the so-called strong-field approximation (SFA)
describing atomic or molecular systems exposed to intense laser fields is
investigated. Introducing a generalized gauge and partitioning of the
Hamiltonian it is demonstrated that the S-matrix expansion obtained in the SFA
depends on both gauge and partitioning in such a way that two gauges always
yield the same S-matrix expansion, if the partitioning is properly chosen.


title:
New Discretization of Complex Analysis: The Euclidean and Hyperbolic
  Planes

abstract:
  Few years ago we developed jointly with I.Dynnikov new discretization of
complex analysis (DCA) based on the two-dimensional manifolds with colored
black/white triangulation. Especially deep results were obtained for the
Euclidean plane with equilateral triangle lattice. In the present work we
develop a DCA theory for the analogs of equilateral triangle lattice in
Hyperbolic plane. Some specific very interesting "dynamical phenomena" appear
in this case solving most fundamental boundary problems. Mike Boyle from the
University of Maryland helped to use here the methods of symbolic dynamics


title: First echoes of relativity in Argentine astronomy

abstract:
  We consider the attitude of astronomers in Argentina in connection with the
new problems posed by relativity theory, before and after GR was presented. We
begin considering the sequence of "technical" publications that appeared and
use it to attempt to identify who were the relativity leaders and authors in
the Argentina scientific community of the 1910-1920s. Among them there are
natives of Argentina, permanent resident scientists, and occasional foreign
visitors. They are either academic scientists, or high school teachers; we
leave aside the {\it philosophers} and the {\it aficionados}. We discuss the
scientific facts and publications they handled, the modernity of their
information and the "language" they use to transmit their ideas. Finally, we
consider astronomers proper; first Charles Perrine, an astronomer interested in
astrophysics, contracted by the government of Argentina in the USA as director
of its main observatory. He became interested in testing the possible
deflection of light rays by the Sun towards 1912; his Argentine expedition was
the first to attempt that test. Perhaps Perrine was not so much interested in
relativity as in testing the particular astronomical effects it predicted. In
any case, he attempted the test with the acquiescence and financial support of
the Argentine state, and as a leading member of its official scientific elite.
We contrast his very specific and strictly scientific efforts with those of our
second astronomer, Jos\'e Ubach, SJ, a secondary school teacher of science at a
leading Buenos Aires Catholic school who reported in response to Eddington's
expedition. Finally, our third astronomer is F\'elix Aguilar, who made an
effort to contribute to the public understanding of Einstein's theories in
1924, when Einstein's visit to Argentina had become a certainty. [abridged]


title: On Time-Bounded Incompressibility of Compressible Strings and Sequences

abstract:
  For every total recursive time bound $t$, a constant fraction of all
compressible (low Kolmogorov complexity) strings is $t$-bounded incompressible
(high time-bounded Kolmogorov complexity); there are uncountably many infinite
sequences of which every initial segment of length $n$ is compressible to $\log
n$ yet $t$-bounded incompressible below ${1/4}n - \log n$; and there are
countable infinitely many recursive infinite sequence of which every initial
segment is similarly $t$-bounded incompressible. These results are related to,
but different from, Barzdins's lemma.


title:
Nuclear matter and neutron matter for improved quark mass density-
  dependent model with $\rho$ mesons

abstract:
  A new improved quark mass density-dependent model including u, d quarks,
$\sigma$ mesons, $\omega$ mesons and $\rho$ mesons is presented. Employing this
model, the properties of nuclear matter, neutron matter and neutron star are
studied. We find that it can describe above properties successfully. The
results given by the new improved quark mass density- dependent model and by
the quark meson coupling model are compared.


title: Prime numbers in logarithmic intervals

abstract:
  Let $X$ be a large parameter. We will first give a new estimate for the
integral moments of primes in short intervals of the type $(p,p+h]$, where
$p\leq X$ is a prime number and $h=\odi{X}$. Then we will apply this to prove
that for every $\lambda>1/2$ there exists a positive proportion of primes
$p\leq X$ such that the interval $(p,p+ \lambda\log X]$ contains at least a
prime number. As a consequence we improve Cheer and Goldston's result on the
size of real numbers $\lambda>1$ with the property that there is a positive
proportion of integers $m\leq X$ such that the interval $(m,m+ \lambda\log X]$
contains no primes. We also prove other results concerning the moments of the
gaps between consecutive primes and about the positive proportion of integers
$m\leq X$ such that the interval $(m,m+ \lambda\log X]$ contains at least a
prime number. The last application of these techniques are two theorems (the
first one unconditional and the second one in which we assume the validity of
the Riemann Hypothesis and of a form of the Montgomery pair correlation
conjecture) on the positive proportion of primes $p\leq X$ such that the
interval $(p,p+ \lambda\log X]$ contains no primes.


title: Bounds on Covering Codes with the Rank Metric

abstract:
  In this paper, we investigate geometrical properties of the rank metric space
and covering properties of rank metric codes. We first establish an analytical
expression for the intersection of two balls with rank radii, and then derive
an upper bound on the volume of the union of multiple balls with rank radii.
Using these geometrical properties, we derive both upper and lower bounds on
the minimum cardinality of a code with a given rank covering radius. The
geometrical properties and bounds proposed in this paper are significant to the
design, decoding, and performance analysis of rank metric codes.


title:
Efficient Monte Carlo algorithm in quasi-one-dimensional Ising spin
  systems

abstract:
  We have developed an efficient Monte Carlo algorithm, which accelerates slow
Monte Carlo dynamics in quasi-one-dimensional Ising spin systems. The loop
algorithm of the quantum Monte Carlo method is applied to the classical spin
models with highly anisotropic exchange interactions. Both correlation time and
real CPU time are reduced drastically. The algorithm is demonstrated in the
layered triangular-lattice antiferromagnetic Ising model. We have obtained the
relation between the transition temperature and the exchange interaction
parameters, which modifies the result of the chain-mean-field theory.


title: Single source shortest paths in $H$-minor free graphs

abstract:
  We present an algorithm for the Single Source Shortest Paths (SSSP) problem
in \emph{$H$-minor free} graphs. For every fixed $H$, if $G$ is a graph with
$n$ vertices having integer edge lengths and $s$ is a designated source vertex
of $G$, the algorithm runs in $\tilde{O}(n^{\sqrt{11.5}-2} \log L) \le
O(n^{1.392} \log L)$ time, where $L$ is the absolute value of the smallest edge
length. The algorithm computes shortest paths and the distances from $s$ to all
vertices of the graph, or else provides a certificate that $G$ is not $H$-minor
free. Our result improves an earlier $O(n^{1.5} \log L)$ time algorithm for
this problem, which follows from a general SSSP algorithm of Goldberg.


title: Poisson Limit for Associated Random Fields

abstract:
  We prove that under an easily verifiable set of conditions a sequence of
associated random fields converges under rescaling to the Poisson Point Process
and give a couple of examples.


title:
QCD with two flavors of Wilson fermions: The QCD vacuum, the Aoki vacuum
  and other vacua

abstract:
  We discuss the vacuum structure of QCD with two flavors of Wilson fermions.
We derive two possible scenarios: (i) If the spectral density
$\rho_U(\lambda,\kappa)$ of the overlap hamiltonian in a fixed background gauge
field is not symmetric in $\lambda$, Hermiticity is violated and Hermiticity
violation effects could influence numerical determinations of the $\eta$ meson
mass if we are not near enough to the continuum limit, where Hermiticity should
be recovered; (ii) otherwise we argue that, under certain assumptions, new
phases appear beside the Aoki phase, which can be characterized by a
nonvanishing vacuum expectation value of
$i\bar\psi_u\gamma_5\psi_u+i\bar\psi_d\gamma_5\psi_d$, and with vacuum states
that cannot be connected with the Aoki vacua by parity-flavor symmetry
transformations. Quenched numerical simulations suggest that the second
scenario is more likely realized.


title: Colored extrinsic fluctuations and stochastic gene expression

abstract:
  Stochasticity is both exploited and controlled by cells. Although the
intrinsic stochasticity inherent in biochemistry is relatively well understood,
cellular variation, or 'noise', is predominantly generated by interactions of
the system of interest with other stochastic systems in the cell or its
environment. Such extrinsic fluctuations are nonspecific, affecting many system
components, and have a substantial lifetime, comparable to the cell cycle (they
are 'colored'). Here, we extend the standard stochastic simulation algorithm to
include extrinsic fluctuations. We show that these fluctuations affect mean
protein numbers and intrinsic noise, can speed up typical network response
times, and can explain trends in high-throughput measurements of variation. If
extrinsic fluctuations in two components of the network are correlated, they
may combine constructively (amplifying each other) or destructively
(attenuating each other). Consequently, we predict that incoherent feedforward
loops attenuate stochasticity, while coherent feedforwards amplify it. Our
results demonstrate that both the timescales of extrinsic fluctuations and
their nonspecificity substantially affect the function and performance of
biochemical networks.


title: Thermodynamic Limit for Large Random Trees

abstract:
  We consider Gibbs distributions on finite random plane trees with bounded
branching. We show that as the order of the tree grows to infinity, the
distribution of any finite neighborhood of the root of the tree converges to a
limit. We compute the limiting distribution explicitly and study its
properties. We introduce an infinite random tree consistent with these limiting
distributions and show that it satisfies a certain form of the Markov property.
We also study the growth of this tree and prove several limit theorems
including a diffusion approximation.


title:
Log-Poisson Hierarchical Clustering of Cosmic Neutral Hydrogen and
  Ly-alpha Transmitted Flux of QSO Absorption Spectrum

abstract:
  we study, in this paper, the non-Gaussian features of the mass density field
of neutral hydrogen fluid and the Ly-alpha transmitted flux of QSO absorption
spectrum from the point-of-view of self-similar log-Poisson hierarchy. It has
been shown recently that, in the scale range from the onset of nonlinear
evolution to dissipation, the velocity and mass density fields of cosmic baryon
fluid are extremely well described by the She-Leveque's scaling formula, which
is due to the log-Poisson hierarchical cascade. Since the mass density ratio
between ionized hydrogen to total hydrogen is not uniform in space, the mass
density field of neutral hydrogen component is not given by a similar mapping
of total baryon fluid. Nevertheless, we show, with hydrodynamic simulation
samples of the concordance $\Lambda$CDM universe, that the mass density field
of neutral hydrogen, is also well described by the log-Poisson hierarchy. We
then investigate the field of Ly$\alpha$ transmitted flux of QSO absorption
spectrum. Due to redshift distortion, Ly$\alpha$ transmitted flux fluctuations
are no longer to show all features of the log-Poisson hierarchy. However, some
non-Gaussian features predicted by the log-Poisson hierarchy are not affected
by the redshift distortion. We test these predictions with the high resolution
and high S/N data of quasars Ly$\alpha$ absorption spectra. All results given
by real data, including $\beta$-hierarchy, high order moments and scale-scale
correlation, are found to be well consistent with the log-Poisson hierarchy. We
compare the log-Poisson hierarchy with the popular log-normal model of the
Ly$\alpha$ transmitted flux. The later is found to yield too strong
non-Gaussianity at high orders, while the log-Poisson hierarchy is in agreement
with observed data.


title: A Bose-Einstein Condensate in a Uniform Light-induced Vector Potential

abstract:
  We use a two-photon dressing field to create an effective vector gauge
potential for Bose-condensed Rb atoms in the F=1 hyperfine ground state. The
dressed states in this Raman field are spin and momentum superpositions, and we
adiabatically load the atoms into the lowest energy dressed state. The
effective Hamiltonian of these neutral atoms is like that of charged particles
in a uniform magnetic vector potential, whose magnitude is set by the strength
and detuning of Raman coupling. The spin and momentum decomposition of the
dressed states reveals the strength of the effective vector potential, and our
measurements agree quantitatively with a simple single-particle model. While
the uniform effective vector potential described here corresponds to zero
magnetic field, our technique can be extended to non-uniform vector potentials,
giving non-zero effective magnetic fields.


title: Physics potential of future supernova neutrino observations

abstract:
  We point out possible features of neutrino spectra from a future galactic
core collapse supernova that will enhance our understanding of neutrino mixing
as well as supernova astrophysics. We describe the neutrino flavor conversions
inside the star, emphasizing the role of "collective effects" that has been
appreciated and understood only very recently. These collective effects change
the traditional predictions of flavor conversion substantially, and enable the
identification of neutrino mixing scenarios through signatures like Earth
matter effects.


title: A local construction of the Smith normal form of a matrix polynomial

abstract:
  We present an algorithm for computing a Smith form with multipliers of a
regular matrix polynomial over a field. This algorithm differs from previous
ones in that it computes a local Smith form for each irreducible factor in the
determinant separately and then combines them into a global Smith form, whereas
other algorithms apply a sequence of unimodular row and column operations to
the original matrix. The performance of the algorithm in exact arithmetic is
reported for several test cases.


title: Coloring Simple Hypergraphs

abstract:
  Fix an integer $k \ge 3$. A $k$-uniform hypergraph is simple if every two
edges share at most one vertex. We prove that there is a constant $c$ depending
only on $k$ such that every simple $k$-uniform hypergraph $H$ with maximum
degree $\D$ has chromatic number satisfying $$\chi(H) <c (\frac{\D}{\log
\D})^{\frac{1}{k-1}}.$$ This implies a classical result of
Ajtai-Koml\'os-Pintz-Spencer-Szemer\'edi and its strengthening due to
Duke-Lefmann-R\"odl. The result is sharp apart from the constant $c$.


title:
A sharp look at the gravitationally lensed quasar SDSS J0806+2006 with
  Laser Guide Star Adaptive Optics

abstract:
  We present the first VLT near-IR observations of a gravitationally lensed
quasar, using adaptive optics and laser guide star. These observations can be
considered as a test bench for future systematic observations of lensed quasars
with adaptive optics, even when bright natural guide stars are not available in
the nearby field. With only 14 minutes of observing time, we derived very
accurate astrometry of the quasar images and of the lensing galaxy, with 0.05
\arcsec spatial resolution, comparable to the Hubble Space Telescope (HST). In
combination with deep VLT optical spectra of the quasar images, we use our
adaptive optics images to constrain simple models for the mass distribution of
the lensing galaxy. The latter is almost circular and does not need any strong
external shear to fit the data. The time delay predicted for SDSS0806+2006,
assuming a singular isothermal ellipsoid model and the concordance cosmology,
is Delta t \simeq 50 days. Our optical spectra indicate a flux ratio between
the quasar images of A/B=1.3 in the continuum and A/B=2.2 in both the MgII and
in the CIII] broad emission lines. This suggests that microlensing affects the
continuum emission. However, the constant ratio between the two emission lines
indicates that the broad emission line region is not microlensed. Finally, we
see no evidence of reddening by dust in the lensing galaxy.


title: Presenting the cohomology of a Schubert variety

abstract:
  We extend the short presentation due to [Borel '53] of the cohomology ring of
a generalized flag manifold to a relatively short presentation of the
cohomology of any of its Schubert varieties. Our result is stated in a
root-system uniform manner by introducing the essential set of a Coxeter group
element, generalizing and giving a new characterization of [Fulton '92]'s
definition for permutations. Further refinements are obtained in type A.


title: Curvature Spectra and Nongaussianities in the Roulette Inflation Model

abstract:
  Using the gradient expansion method of Rigopoulos, Shellard and van Tent
which treats cosmological perturbations as gradients on top of a homogeneous
and isotropic FRW background, we study the production of nongaussianities in
the roulette model of inflation. Investigating a number of trajectories within
this two-field model of inflation, we find that while the superhorizon
influence of the isocurvature modes on the curvature bispectrum produces
nonzero contribution to f_NL, the effect is negligible next to the standard
inflationary prediction |f_NL| ~ n_s - 1. This is the case in both the squeezed
and equilateral configurations of the bispectrum, although the former is
slightly larger in the trajectories under consideration.


title:
Microlensing to probe the quasar structure: spectrophotometry of
  Q2237+0305 and of J1131-1231

abstract:
  We present the main results of the first long-term spectrophotometric
monitoring of the ``Einstein cross'' Q2237+0305 and of the single-epoch spectra
of the lensed quasar J1131-1231.
  From October 2004 to December 2006, we find that two prominent microlensing
events affect images A & B in Q2237+0305 while images C & D remain grossly
unaffected by microlensing on a time scale of a few months. Microlensing in A &
B goes with chromatic variations of the quasar continuum. We observe stronger
micro-amplification in the blue than in the red part of the spectrum, as
expected for continuum emission arising from a standard accretion disk.
Microlensing induced variations of the CIII] emission are observed both in the
integrated line intensity and profile. Finally, we also find that images C & D
are about 0.1-0.3 mag redder than images A & B. The spectra of images A-B-C in
J1131-1231 reveal that, in April 2003, microlensing was at work in images A and
C. We find that microlensing de-amplifies the continuum emission and the Broad
Line Region (BLR) in these images. Contrary to the case of Q2237+0305, we do
not find evidence for chromatic microlensing of the continuum emission. On the
other hand, we observe that the Balmer and MgII broad line profiles are
deformed by microlensing. These deformations imply an anti-correlation between
the width of the emission line and the size of the corresponding emitting
region. Finally, the differential microlensing of the FeII emission suggests
that the bulk of FeII is emitted in the outer parts of the BLR while another
fraction of FeII is produced in a compact region.


title:
The effect of Coulomb interaction at ferromagnetic-paramagnetic metallic
  perovskite junctions

abstract:
  We study the effect of Coulomb interactions in transition metal oxides
junctions. In this paper we analyze charge transfer at the interface of a three
layer ferromagnetic-paramagnetic-ferromagnetic metallic oxide system. We choose
a charge model considering a few atomic planes within each layer and obtain
results for the magnetic coupling between the ferromagnetic layers. For large
number of planes in the paramagnetic spacer we find that the coupling
oscillates with the same period as in RKKY but the amplitude is sensitive to
the Coulomb energy. At small spacer thickness however, large differences may
appear as function of : the number of electrons per atom in the ferromagnetics
and paramagnetics materials, the dielectric constant at each component, and the
charge defects at the interface plane emphasizing the effects of charge
transfer.


title: Spectroscopy of atomic hydrogen. How is the Rydberg constant determined?

abstract:
  This article presents a review of the most recent theoretical and
experimental results in hydrogen. We particularly emphasize the methods used to
deduce the Rydberg constant $R_\infty$ and we consider the prospects for future
improvements in the precision of $R_\infty$.


title:
Subdiffusion and lateral diffusion coefficient of lipid atoms and
  molecules in phospholipid bilayers

abstract:
  We use a long, all-atom molecular dynamics (MD) simulation combined with
theoretical modeling to investigate the dynamics of selected lipid atoms and
lipid molecules in a hydrated diyristoyl-phosphatidylcholine (DMPC) lipid
bilayer. From the analysis of a 0.1 $\mu$s MD trajectory we find that the time
evolution of the mean square displacement, [\delta{r}(t)]^2, of lipid atoms and
molecules exhibits three well separated dynamical regions: (i) ballistic, with
[\delta{r}(t)]^2 ~ t^2 for t < 10 fs; (ii) subdiffusive, with [\delta{r}(t)]^2
~ t^{\beta} with \beta<1, for 10 ps < t < 10 ns; and (iii) Fickian diffusion,
with [\delta{r}(t)]^2 ~ t for t > 30 ns. We propose a memory function approach
for calculating [\delta{r}(t)]^2 over the entire time range extending from the
ballistic to the Fickian diffusion regimes. The results are in very good
agreement with the ones from the MD simulations. We also examine the
implications of the presence of the subdiffusive dynamics of lipids on the
self-intermediate scattering function and the incoherent dynamics structure
factor measured in neutron scattering experiments.


title:
Weak localization of electromagnetic waves and radar polarimetry of
  Saturn's rings

abstract:
  We use a state-of-the-art physics-based model of electromagnetic scattering
to analyze average circular polarization ratios measured for the A and B rings
of Saturn at a wavelength of 12.6 cm. This model is directly based on the
Maxwell equations and accounts for the effects of polarization, multiple
scattering, weak localization of electromagnetic waves, and ring particle
nonsphericity. Our analysis is based on the assumption that the observed
polarization ratios are accurate, mutually consistent, and show a quasi-linear
dependence on the opening angle. Also, we assume that the ring system is not
strongly stratified in the vertical direction. Our numerical simulations rule
out the model of spherical ring particles, favor the model of ring bodies in
the form of nearly spherical particles with small-scale surface roughness, and
rule out nonspherical particles with aspect ratios significantly exceeding 1.2.
They also favor particles with effective radii in the range 4-10 cm and
definitely rule out effective radii significantly smaller than 4 cm.
Furthermore, they seem to rule out effective radii significantly greater than
10 cm. The retrieved ring optical thickness values are in the range 2-3 or even
larger. If the rings do have a wake-like horizontal structure, as has been
recently suggested, then these optical thickness values should be attributed to
an average wake rather than to the optical thickness averaged over the entire
horizontal extent of the rings.


title: The Lawson-Yau Formula and its generalization

abstract:
  The Euler characteristic of Chow varieties of algebraic cycles of a given
degree in complex projective spaces was computed by Blaine Lawson and Stephen
Yau by using holomorphic symmetries of cycles spaces. In this paper we compute
this in a direct and elementary way and generalize this formula to the l-adic
Euler-Poincare characteristic for Chow varieties over any algebraically closed
field. Moreover, the Euler characteristic for Chow varieties with certain group
action is calculated. In particular, we calculate the Euler characteristic of
the space of right quaternionic cycles of a given dimension and degree in
complex projective spaces.


title: Uniform estimates for order statistics and Orlicz functions

abstract:
  We establish uniform estimates for order statistics of sequences of
independent identically distributed random variables with log-concave
distribution in terms of Orlicz norms associated with the distribution function
of the random variables.


title:
Radio constraints on dark matter annihilation in the galactic halo and
  its substructures

abstract:
  Annihilation of Dark Matter usually produces together with gamma rays
comparable amounts of electrons and positrons. The e+e- gyrating in the
galactic magnetic field then produce secondary synchrotron radiation which thus
provides an indirect mean to constrain the DM signal itself. To this purpose,
we calculate the radio emission from the galactic halo as well as from its
expected substructures and we then compare it with the measured diffuse radio
background. We employ a multi-frequency approach using data in the relevant
frequency range 100 MHz-100 GHz, as well as the WMAP Haze data at 23 GHz. The
derived constraints are of the order <sigma_A*v>=10^{-24} cm3 s^{-1} for a DM
mass m_chi=100 GeV sensibly depending however on the astrophysical
uncertainties, in particular on the assumption on the galactic magnetic field
model. The signal from single bright clumps is instead largely attenuated by
diffusion effects and offers only poor detection perspectives.


title:
Are the red halos of galaxies made of low-mass stars? Constraints from
  subdwarf star counts in the Milky Way halo

abstract:
  Surface photometry detections of red and exceedingly faint halos around
galaxies have resurrected the old question of whether some non-negligible
fraction of the missing baryons of the Universe could be hiding in the form of
faint, hydrogen-burning stars. The optical/near-infrared colours of these red
halos have proved very difficult to reconcile with any normal type of stellar
population, but can in principle be explained by advocating a bottom-heavy
stellar initial mass function. This implies a high stellar mass-to-light ratio
and hence a substantial baryonic mass locked up in such halos. Here, we explore
the constraints imposed by current observations of ordinary stellar halo
subdwarfs on a putative red halo of low-mass stars around the Milky Way.
Assuming structural parameters similar to those of the red halo recently
detected in stacked images of external disk galaxies, we find that a smooth
halo component with a bottom-heavy initial mass function is completely ruled
out by current star count data for the Milky Way. All viable smooth red halo
models with a density slope even remotely similar to that of the stacked halo
moreover contain far too little mass to have any bearing on the missing-baryon
problem. However, we note that these constraints can be sidestepped if the red
halo stars are locked up in star clusters, and discuss potential observations
of other nearby galaxies that may be able to put such scenarios to the test.


title: Counting invariant of perverse coherent sheaves and its wall-crossing

abstract:
  We introduce moduli spaces of stable perverse coherent systems on small
crepant resolutions of Calabi-Yau 3-folds and consider their Donaldson-Thomas
type counting invariants. The stability depends on the choice of a component (=
a chamber) in the complement of finitely many lines (= walls) in the plane. We
determine all walls and compute generating functions of invariants for all
choices of chambers when the Calabi-Yau is the resolved conifold. For suitable
choices of chambers, our invariants are specialized to Donaldson-Thomas,
Pandharipande-Thomas and Szendroi invariants.


title: Engineering Giant Nonlinearities in Quantum Nanosystems

abstract:
  We describe a method to engineer giant nonlinearities in, and probes to
measure nonlinear observables of, mesoscopic quantum resonators. This involves
tailoring the Hamiltonian of a simple auxiliary system perturbatively coupled
to the resonator, and has the potential to engineer a wide range of
nonlinearities to high accuracy. We give a number of explicit examples,
including a readily realizable two-qubit auxiliary system that creates an x^4
potential and a Chi^(3) (Kerr) nonlinearity, valid to fifth-order in the
perturbative coupling.


title:
Derived categories of small toric Calabi-Yau 3-folds and counting
  invariants

abstract:
  We first construct a derived equivalence between a small crepant resolution
of an affine toric Calabi-Yau 3-fold and a certain quiver with a
superpotential. Under this derived equivalence we establish a wall-crossing
formula for the generating function of the counting invariants of perverse
coherent systems. As an application we provide certain equations on
Donaldson-Thomas, Pandeharipande-Thomas and Szendroi's invariants. Finally, we
show that moduli spaces associated with a quiver given by successive mutations
are realized as the moduli spaces associated the original quiver by changing
the stability conditions.


title: Navigating ultrasmall worlds in ultrashort time

abstract:
  Random scale-free networks are ultrasmall worlds. The average length of the
shortest paths in networks of size N scales as lnlnN. Here we show that these
ultrasmall worlds can be navigated in ultrashort time. Greedy routing on
scale-free networks embedded in metric spaces finds paths with the average
length scaling also as lnlnN. Greedy routing uses only local information to
navigate a network. Nevertheless, it finds asymptotically the shortest paths, a
direct computation of which requires global topology knowledge. Our findings
imply that the peculiar structure of complex networks ensures that the lack of
global topological awareness has asymptotically no impact on the length of
communication paths. These results have important consequences for
communication systems such as the Internet, where maintaining knowledge of
current topology is a major scalability bottleneck.


title: General Massive Spin-2 on de Sitter Background

abstract:
  We study linearized massive gravity on the de Sitter background. With a
small-enough graviton mass this may have had relevance to inflation, or the
present-day cosmic acceleration. Higuchi has shown that this theory has a ghost
as long as the dS curvature exceeds the graviton mass, 2H^2 > m^2; this would
entail rapid instabilities. In this work we extend the model and observe that
the helicity-0 mode which is a ghost, can be turned into a positive energy
state via kinetic mixing with the conformal mode. The latter gets restricted
here by the requirement that the Bianchi identities be satisfied. This
eliminates the ghost from the linearized theory. However, the spectrum still
contains scalar tachyonic instabilities with the time scale ~1/H. This would
have been problematic for the early univesre, however, may be acceptable for
the present-day accelerated expansion as the tachyon instability would take the
age of the universe to develop.


title:
Microlensing Event MOA-2007-BLG-400: Exhuming the Buried Signature of a
  Cool, Jovian-Mass Planet

abstract:
  We report the detection of the cool, Jovian-mass planet MOA-2007-BLG-400Lb.
The planet was detected in a high-magnification microlensing event (with peak
magnification A_max = 628) in which the primary lens transited the source,
resulting in a dramatic smoothing of the peak of the event. The angular extent
of the region of perturbation due to the planet is significantly smaller than
the angular size of the source, and as a result the planetary signature is also
smoothed out by the finite source size. Thus the deviation from a single-lens
fit is broad and relatively weak (~ few percent). Nevertheless, we demonstrate
that the planetary nature of the deviation can be unambiguously ascertained
from the gross features of the residuals, and detailed analysis yields a fairly
precise planet/star mass ratio of q = 0.0026+/-0.0004, in accord with the large
significance (\Delta\chi^2=1070) of the detection. The planet/star projected
separation is subject to a strong close/wide degeneracy, leading to two
indistinguishable solutions that differ in separation by a factor of ~8.5.
Upper limits on flux from the lens constrain its mass to be M < 0.75 M_Sun
(assuming it is a main-sequence star). A Bayesian analysis that includes all
available observational constraints indicates a primary in the Galactic bulge
with a mass of ~0.2-0.5 M_Sun and thus a planet mass of ~ 0.5-1.3 M_Jupiter.
The separation and equilibrium temperature are ~0.6-1.1AU (~5.3-9.7AU) and
~103K (~34K) for the close (wide) solution. If the primary is a main-sequence
star, follow-up observations would enable the detection of its light and so a
measurement of its mass and distance.


title:
Observation of Pulsed Gamma-rays Above 25 GeV from the Crab Pulsar with
  MAGIC

abstract:
  One fundamental question about pulsars concerns the mechanism of their pulsed
electromagnetic emission. Measuring the high-end region of a pulsar's spectrum
would shed light on this question. By developing a new electronic trigger, we
lowered the threshold of the Major Atmospheric gamma-ray Imaging Cherenkov
(MAGIC) telescope to 25 GeV. In this configuration, we detected pulsed
gamma-rays from the Crab pulsar that were greater than 25 GeV, revealing a
relatively high cutoff energy in the phase-averaged spectrum. This indicates
that the emission occurs far out in the magnetosphere, hence excluding the
polar-cap scenario as a possible explanation of our measurement. The high
cutoff energy also challenges the slot-gap scenario.


title:
The Growth of Central and Satellite Galaxies in Cosmological Smoothed
  Particle Hydrodynamics Simulations

abstract:
  We examine the accretion and merger histories of central and satellite
galaxies in a smoothed particle hydrodynamics (SPH) cosmological simulation
that resolves galaxies down to 7e9 M[Sun]. Most friends-of-friends halos in the
simulation have a distinct central galaxy, typically two to five times more
massive than the most massive satellite. As expected, satellites have
systematically higher assembly redshifts than central galaxies of the same
baryonic mass, and satellites in more massive halos form earlier. However,
contrary to the simplest expectations, satellite galaxies continue to accrete
gas and convert it to stars; the gas accretion declines steadily over a period
of 0.5-1 Gyr after the satellite halo merges with a larger parent halo.
Satellites in a cluster mass halo eventually begin to lose baryonic mass. Since
z=1, 27% of central galaxies (above 3e10 M[Sun]) and 22% of present-day
satellite galaxies have merged with a smaller system above a 1:4 mass ratio;
about half of the satellite mergers occurred after the galaxy became a
satellite and half before. In effect, satellite galaxies can remain "central"
objects of halo substructures, with continuing accretion and mergers, making
the transition in assembly histories and physical properties a gradual one.
Implementing such a gradual transformation in semi-analytic models would
improve their agreement with the observed colour distributions of satellite
galaxies in groups and with the observed colour dependence of galaxy
clustering.


title: Parton energy loss at strong coupling and the universal bound

abstract:
  The apparent universality of jet quenching observed in heavy ion collisions
at RHIC for light and heavy quarks, as well as for quarks and gluons, is very
puzzling and calls for a theoretical explanation. Recently it has been proposed
that the synchrotron--like radiation at strong coupling gives rise to a
universal bound on the energy of a parton escaping from the medium. Since this
bound appears quite low, almost all of the observed particles at high
transverse momentum have to originate from the surface of the hot fireball.
Here I make a first attempt of checking this scenario against the RHIC data and
formulate a "Universal Bound Model" of jet quenching that can be further tested
at RHIC and LHC.


title:
Binary frequency of very young brown dwarfs at separations smaller than
  3 AU

abstract:
  Searches for companions of brown dwarfs by direct imaging mainly probe
orbital separations > 3-10 AU. On the other hand, previous radial velocity
surveys of brown dwarfs are mainly sensitive to separations smaller than 0.6
AU. It has been speculated that the peak of the separation distribution of
brown dwarf binaries lies right in the unprobed range. This work extends
high-precision radial velocity surveys of brown dwarfs for the first time out
to 3 AU. Based on more than six years UVES/VLT spectroscopy the binary
frequency of brown dwarfs and (very) low-mass stars (M4.25-M8) in ChaI was
determined: 18% for the whole sample and 10% for the subsample of ten brown
dwarfs and VLMS (M < 0.1 Msun). Two spectroscopic binaries were confirmed, the
brown dwarf candidate ChaHa8 (previously discovered by Joergens & Mueller) and
the low-mass star CHXR74. Since their orbital separations appear to be 1 AU or
greater, the binary frequency at < 1 AU might be less than 10%. Now for the
first time companion searches of (young) brown dwarfs cover the whole orbital
separation range, and the following observational constraints for models of
brown dwarf formation can be derived: (i) the frequency of brown dwarf and very
low-mass stellar binaries at < 3 AU does not significantly exceed that at > 3
AU; i.e. direct imaging surveys do not miss a significant fraction of brown
dwarf binaries; (ii) the overall binary frequency of brown dwarfs and very
low-mass stars is 10-30 %; (iii) the decline in the separation distribution of
brown dwarfs towards smaller separations seems to occur between 1 and 3 AU;
(iv) the observed continuous decrease in the binary frequency from the stellar
to the substellar regime is confirmed at < 3 AU providing further evidence of a
continuous formation mechanism from low-mass stars to brown dwarfs.


title:
Forecasting the Dark Energy Measurement with Baryon Acoustic
  Oscillations: Prospects for the LAMOST surveys

abstract:
  The Large Area Multi-Object Spectroscopic Telescope (LAMOST) is a dedicated
spectroscopic survey telescope being built in China, with an effective aperture
of 4 meters and equiped with 4000 fibers. Using the LAMOST telescope, one could
make redshift survey of the large scale structure (LSS). The baryon acoustic
oscillation (BAO) features in the LSS power spectrum provide standard rulers
for measuring dark energy and other cosmological parameters. In this paper we
investigate the meaurement precision achievable for a few possible surveys: (1)
a magnitude limited survey of all galaxies, (2) a survey of color selected red
luminous galaxies (LRG), and (3) a magnitude limited, high density survey of
z<2 quasars. For each survey, we use the halo model to estimate the bias of the
sample, and calculate the effective volume. We then use the Fisher matrix
method to forecast the error on the dark energy equation of state and other
cosmological parameters for different survey parameters. In a few cases we also
use the Markov Chain Monte Carlo (MCMC) method to make the same forecast as a
comparison. The fiber time required for each of these surveys is also
estimated. These results would be useful in designing the surveys for LAMOST.


title: Associated Production of a W Boson and One b Jet

abstract:
  We calculate the production of a W boson and a single b jet to
next-to-leading order in QCD at the Fermilab Tevatron and the CERN Large Hadron
Collider. Both exclusive and inclusive cross sections are presented. We
separately consider the cross section for jets containing a single b quark and
jets containing a b-anti b pair. There are a wide variety of processes that
contribute, and it is necessary to include them all in order to have a complete
description at both colliders.


title: B_s mixing phase and lepton flavor violation in supersymmetric SU(5)

abstract:
  The connection between B_s mixing phase and lepton flavor violation is
studied in SU(5) GUT. The O(1) phase, preferring a non-vanishing squark mixing,
generically implies tau -> (e + mu) gamma and mu -> e gamma. In addition to the
facts already well-known, stresses are put on the role of gaugino to scalar
mass ratio at the GUT scale and the possible modifications due to
Planck-suppressed non-renormalizable operators.


title:
Disk Dominated States of 4U 1957+11: Chandra, XMM, and RXTE Observations
  of Ostensibly the Most Rapidly Spinning Galactic Black Hole

abstract:
  We present simultaneous Chandra-HETG and RXTE observations of a moderate flux
`soft state' of the black hole candidate 4U1957+11. These spectra, having a
minimally discernible hard X-ray excess, are an excellent test of modern disk
atmosphere models that include the effects of black hole spin. The HETG data
show that the soft disk spectrum is only very mildly absorbed with N_H =1-2 X
10^{21} cm^-2. These data additionally reveal 13.449 A NeIX absorption
consistent with the warm/hot phase of the interstellar medium. The fitted disk
model implies a highly inclined disk around a low mass black hole rapidly
rotating with normalized spin a*~1. We show, however, that pure Schwarzschild
black hole models describe the data extremely well, albeit with large disk
atmosphere ``color-correction'' factors. Standard color-correction factors can
be attained if one additionally incorporates mild Comptonization. We find that
the Chandra observations do not uniquely determine spin. Similarly, XMM/RXTE
observations, taken only six weeks later, are equally unconstraining. This lack
of constraint is partly driven by the unknown mass and unknown distance of
4U1957+11; however, it is also driven by the limited bandpass of Chandra and
XMM. We therefore present a series of 48 RXTE observations taken over the span
of several years and at different brightness/hardness levels. These data prefer
a spin of a*~1, even when including a mild Comptonization component; however,
they also show evolution of the disk atmosphere color-correction factors. If
the rapid spin models with standard atmosphere color-correction factors of
h_d=1.7 are to be believed, then the RXTE observations predict that 4U1957+11
can range from a 3 M_sun black hole at 10 kpc with a*~0.83 to a 16 M_sun black
hole at 22 kpc with a* ~ 1, with the latter being statistically preferred.


title: Chemical evolution with radial mixing

abstract:
  Models of the chemical evolution of our Galaxy are extended to include radial
migration of stars and flow of gas through the disc. The models track the
production of both iron and alpha elements. A model is chosen that provides an
excellent fit to the metallicity distribution of stars in the Geneva-Copenhagen
survey (GCS) of the solar neighbourhood, and a good fit to the local Hess
diagram. The model provides a good fit to the distribution of GCS stars in the
age-metallicity plane although this plane was not used in the fitting process.
Although this model's star-formation rate is monotonic declining, its disc
naturally splits into an alpha-enhanced thick disc and a normal thin disc. In
particular the model's distribution of stars in the ([O/Fe],[Fe/H]) plane
resembles that of Galactic stars in displaying a ridge line for each disc. The
thin-disc's ridge line is entirely due to stellar migration and there is the
characteristic variation of stellar angular momentum along it that has been
noted by Haywood in survey data. Radial mixing of stellar populations with high
sigma_z from inner regions of the disc to the solar neighbourhood provides a
natural explanation of why measurements yield a steeper increase of sigma_z
with age than predicted by theory. The metallicity gradient in the ISM is
predicted to be steeper than in earlier models, but appears to be in good
agreement with data for both our Galaxy and external galaxies. The models are
inconsistent with a cutoff in the star-formation rate at low gas surface
densities. The absolute magnitude of the disc is given as a function of time in
several photometric bands, and radial colour profiles are plotted for
representative times.


title: W Mass as a Calibration of the Jet Energy Scale at ATLAS

abstract:
  Top-antitop pairs will be copiously produced at the LHC, at a rate of roughly
one per second at a luminosity of10^{33} cm^{-2} s^{-1}. These events have low
background and produce large numbers of jets via the hadronic decay of the W's
which may be used to calibrate the jet energy scale and resolution with
experimental data and simulations.


title:
The Brown Dwarf Kinematics Project (BDKP) I. Proper Motions and
  Tangential Velocities for a Large Sample of Late-type M, L and T Dwarfs

abstract:
  We report proper motion measurements for 427 late-type M, L and T dwarfs, 332
of which have been measured for the first time. Combining these new proper
motions with previously published measurements yields a sample of 841 M7-T8
dwarfs. We combined parallax measurements or calculated spectrophotometric
distances and computed tangential velocities for the entire sample. We find
that kinematics for the full and volume-limited 20 pc samples are consistent
with those expected for the Galactic thin disk, with no significant differences
between late-type M, L, and T dwarfs. Applying an age-velocity relation we
conclude that the average kinematic age of the 20 pc sample of ultracool dwarfs
is older than recent kinematic estimates and more consistent with age results
calculated with population synthesis models. There is a statistically distinct
population of high tangential velocity sources whose kinematics suggest an even
older population of ultracool dwarfs belonging to either the Galactic thick
disk or halo. We isolate subsets of the entire sample, including low
surface-gravity dwarfs, unusually blue L dwarfs, and photometric outliers in
J-Ks color and investigate their kinematics. We find that the spectroscopically
distinct class of unusually blue L dwarfs has kinematics clearly consistent
with old age, implying that high surface-gravity and/or low metallicity may be
relevant to their spectral properties. The low surface-gravity dwarfs are
kinematically younger than the overall population, and the kinematics of the
red and blue ultracool dwarfs suggest ages that are younger and older than the
full sample, respectively. We also present a reduced proper motion diagram at
2MASS Ks for the entire population and find that a limit of H_Ks > 18 excludes
M dwarfs from the L and T dwarf population regardless of near-infrared color.


title: Metrics-Based Spreadsheet Visualization: Support for Focused Maintenance

abstract:
  Legacy spreadsheets are both, an asset, and an enduring problem concerning
spreadsheets in business. To make spreadsheets stay alive and remain correct,
comprehension of a given spreadsheet is highly important. Visualization
techniques should ease the complex and mindblowing challenges of finding
structures in a huge set of spreadsheet cells for building an adequate mental
model of spreadsheet programs. Since spreadsheet programs are as diverse as the
purpose they are serving and as inhomogeneous as their programmers, to find an
appropriate representation or visualization technique for every spreadsheet
program seems futile. We thus propose different visualization and
representation methods that may ease spreadsheet comprehension but should not
be applied with all kind of spreadsheet programs. Therefore, this paper
proposes to use (complexity) measures as indicators for proper visualization.


title:
Improved Upper Bounds for the Information Rates of the Secret Sharing
  Schemes Induced by the Vamos Matroid

abstract:
  An access structure specifying the qualified sets of a secret sharing scheme
must have information rate less than or equal to one. The Vamos matroid induces
two non-isomorphic access structures V1 and V6, which were shown by Marti-Farre
and Padro to have information rates of at least 3/4. Beimel, Livne, and Padro
showed that the information rates of V1 and V6 are bounded above by 10/11 and
9/10 respectively. Here we improve those upper bounds to 19/21 for V1 and 17/19
for V6.


title:
Multidimensional Dilation Operators, Boyd and Shimogaki Indices of
  Bilateral Weight Grand Lebesque Spaces

abstract:
  In this paper we compute the norm of dilation operators, multidimensional
Boyd`s and Shimogaki`s indices in the Bilateral Grand Lebesgue Spaces and
consider some applications.


title: NICI: combining coronagraphy, ADI, and SDI

abstract:
  The Near-Infrared Coronagraphic Imager (NICI) is a high-contrast AO imager at
the Gemini South telescope. The camera includes a coronagraphic mask and dual
channel imaging for Spectral Differential Imaging (SDI). The instrument can
also be used in a fixed Cassegrain Rotator mode for Angular Differential
Imaging (ADI). While coronagraphy, SDI, and ADI have been applied before in
direct imaging searches for exoplanets. NICI represents the first time that
these 3 techniques can be combined. We present preliminary NICI commissioning
data using these techniques and show that combining SDI and ADI results in
significant gains.


title:
Vacuum energies due to delta-like currents: simulating classical objects
  along branes with arbitrary codimensions

abstract:
  In this paper we investigate the vacuum energies of several models of quantum
fields interacting with static external currents (linear couplings)
concentrated along parallel branes with an arbitrary number of codimensions. We
show that we can simulate the presence of static charges distributions as well
as the presence of classical static dipoles in any dimension for massive and
massless fields. We also show that we can produce confining potentials with
massless self interacting scalar fields as well as long range anisotropic
potentials.


title: Partial duality and Bollobas and Riordan's ribbon graph polynomial

abstract:
  Recently S. Chmutov introduced a generalization of the dual of a ribbon (or
embedded) graph and proved a relation between Bollobas and Riordan's ribbon
graph polynomial of a ribbon graph and its generalized duals. Here I show that
the duality relation satisfied by the ribbon graph polynomial can be understood
in terms of knot theory and I give a simple proof of the relation via the
homfly polynomial of a knot.


title: Strominger--Yau--Zaslow geometry, Affine Spheres and Painlev\'e III

abstract:
  We give a gauge invariant characterisation of the elliptic affine sphere
equation and the closely related Tzitz\'eica equation as reductions of real
forms of $SL(3, \C)$ anti--self--dual Yang--Mills equations by two
translations, or equivalently as a special case of the Hitchin equation.
  We use the Loftin--Yau--Zaslow construction to give an explicit expression
for a six--real dimensional semi--flat Calabi--Yau metric in terms of a
solution to the affine-sphere equation and show how a subclass of such metrics
arises from 3rd Painlev\'e transcendents.


title: Automating Spreadsheet Discovery & Risk Assessment

abstract:
  There have been many articles and mishaps published about the risks of
uncontrolled spreadsheets in today's business environment, including
non-compliance, operational risk, errors, and fraud all leading to significant
loss events. Spreadsheets fall into the realm of end user developed
applications and are often absent the proper safeguards and controls an IT
organization would enforce for enterprise applications. There is also an
overall lack of software programming discipline enforced in how spreadsheets
are developed. However, before an organization can apply proper controls and
discipline to critical spreadsheets, an accurate and living inventory of
spreadsheets across the enterprise must be created, and all critical
spreadsheets must be identified. As such, this paper proposes an automated
approach to the initial stages of the spreadsheet management lifecycle -
discovery, inventory and risk assessment. Without the use of technology, these
phases are often treated as a one-off project. By leveraging technology, they
become a sustainable business process.