title:
Cell dynamics simulation of droplet and bridge formation within striped
  nano-capillaries

abstract:
  The kinetics of droplet and bridge formation within striped nano-capillaries
is studied when the wetting film grows via interface-limited growth. The
phenomenological time-dependent Ginzburg-Landau (TDGL)-type model with thermal
noise is used and numerically solved using the cell dynamics method. The model
is two-dimensional and consists of undersaturated vapor confined within a
nano-capillary made of two infinitely wide flat substrates. The surface of the
substrate is chemically heterogeneous with a single stripe of lyophilic domain
that exerts long-range attractive potential to the vapor molecule. The dynamics
of nucleation and subsequent growth of droplet and bridge can be simulated and
visualized. In particular, the evolution of the morphology from droplet or bump
to bridge is clearly identified. Crucial role played by the substrate potential
on the morphology of bridge of nanoscopic size is clarified. Nearly
temperature-independent evolution of capillary condensation is predicted when
the interface-limited growth dominates. In addition, it is shown that the
dynamics of capillary condensation follows the scenario of capillary
condensation proposed by Everett and Haynes three decades ago.


title: Self Excitation of Nano-Mechanical Pillars

abstract:
  Self excitation is a mechanism which is ubiquitous for electromechanical
power devices such as electrical generators. This is conventionally achieved by
making use of the magnetic field component in electrical generators [1], where
a good example are the overall visible wind farm turbines [2]. In other words,
a static force, like wind acting on the rotor blades, can generate a resonant
excitation at a certain mechanical frequency. For nanomechanical systems
[3,4,5] such a self excitation (SE) mechanism is highly desirable as well,
since it can generate mechanical oscillations at radio frequencies by simply
applying a DC bias voltage. This is of great importance for low-power signal
communication devices and detectors, as well as for mechanical computing
elements. For a particular nanomechanical system - the single electron shuttle
- this effect was predicted some time ago by Gorelik et al. [6]. Here, we use a
nano-electromechanical single electron transistor (NEMSET) to demonstrate self
excitation for both the soft and hard regime, respectively. The ability to use
self excitation in nanomechanical systems may enable the detection of quantum
mechanical backaction effects [7] in direct tunneling, macroscopic quantum
tunneling [8], and rectification [9]. All these effects have so far been over
shadowed by the large driving voltages, which had to be applied.


title:
Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature
  Programmed Desorption Experiments

abstract:
  The study of the formation of molecular hydrogen on low temperature surfaces
is of interest both because it allows to explore elementary steps in the
heterogeneous catalysis of a simple molecule and because of the applications in
astrochemistry. Here we report results of experiments of molecular hydrogen
formation on amorphous silicate surfaces using temperature-programmed
desorption (TPD). In these experiments beams of H and D atoms are irradiated on
the surface of an amorphous silicate sample. The desorption rate of HD
molecules is monitored using a mass spectrometer during a subsequent TPD run.
The results are analyzed using rate equations and the activation energies of
the processes leading to molecular hydrogen formation are obtained from the TPD
data. We show that a model based on a single isotope provides the correct
results for the activation energies for diffusion and desorption of H atoms.
These results can thus be used to evaluate the formation rate of H_2 on dust
grains under the actual conditions present in interstellar clouds.


title:
The direct oxygen abundances of metal-rich galaxies derived from
  electron temperature

abstract:
  We aim to derive the electron temperature Te in the gas of metal-rich
star-forming galaxies, which can be obtained from their ratios of auroral lines
[O II]7320,7330 to nebular lines [O II]3727, in order to establish a more
robust mass-metallicity relationship, and compare the Te-based (O/H) abundances
with those from empirical strong-line calibrations, such as R23. We obtained 27
spectra by stacking the spectra of several hundred (even several thousand)
star-forming galaxies selected from the SDSS-DR4 in each of the 27 stellar mass
bins from log(M*) ~8.0 to 10.6 (logMsun). This "stack" method sufficiently
improves the signal-to-noise ratio of the auroral lines [O II]7320,7330, which
allow us to reliably obtain the electron temperature t2 in the low ionization
region from the ratio of [O II]7320,7330 to [O II]3727, then t3 in the high
ionization region from t2 by using a relation, and then the direct (O/H)
abundances from Te. The results show that the empirical R23 method will
overestimate the log(O/H) by 0.2 to 0.6 dex for these moderate metal-rich
galaxies. The new metal-mass relationship of the galaxies with moderate
metallicities is fitted by a linear fit (12+log(O/H) =6.223+0.231*logM*)
confirming that empirical methods significantly overestimate (O/H). We also
derived their (N/O) abundance ratios on the basis of the Te method, which are
consistent with the combination of the primary and secondary components of
nitrogen. For actual use, we re-derive the relations of 12+log(O/H)(Bay) vs.
logM* and 12+log(O/H)(Bay) vs. logR23 from the SDSS-DR4 data, which are a bit
different from those derived from DR2.


title:
Scattered Emission from A Relativistic Outflow and Its Application to
  Gamma-Ray Bursts

abstract:
  We investigate a scenario of photons scattering by electrons within a
relativistic outflow. The outflow is composed of discrete shells with different
speeds. One shell emits radiation for a short duration. Some of this radiation
is scattered by the shell(s) behind. We calculate in a simple two-shell model
the observed scattered flux density as a function of the observed primary flux
density, the normalized arrival time delay between the two emission components,
the Lorentz factor ratio of the two shells and the scattering shell's optical
depth. Thomson scattering in a cold shell and inverse Compton scattering in a
hot shell are both considered. The results of our calculations are applied to
the Gamma-Ray Bursts and the afterglows. We find that the scattered flux from a
cold slower shell is small and likely to be detected only for those bursts with
very weak afterglows. A hot scattering shell could give rise to a scattered
emission as bright as the X-ray shallow decay component detected in many
bursts, on a condition that the isotropically equivalent total energy carried
by the hot electrons is large, $\sim 10^{52-56}$ erg. The scattered emission
from a faster shell could appear as a late short $\gamma$-ray/MeV flash or
become part of the prompt emission depending on the delay of the ejection of
the shell.


title:
Checking the reliability of equivalent width R23 for estimating
  metallicities of galaxies

abstract:
  We verify whether the O/H abundances of galaxies can be derived from the
equivalent width (EW) R23 instead of the extinction-corrected flux R23, and
eventually propose a method of improving the reliability of this empirical
method, which is often used for the non-flux calibrated spectra of galaxies. We
select 37,173 star-forming galaxies from the SDSS-DR2, which offers a wide
range of properties to test the EW method. The EW-R23 method brings with it a
significant bias: for the bulk of SDSS galaxies, it may affect the
determination of log(O/H) by factors ranging from -0.2 to 0.1 dex and for some
galaxies by factors ranging from -0.5 to 0.2 dex. We characterize this
discrepancy (or bias) by alpha = (I_[OII]/I_Hbeta)/(EW_[OII]/EW_Hbeta), which
is virtually independent of dust extinction, while tightly correlating with
Dn(4000), although at a lower significance, with (g-r) colors. The EW-R23
method cannot be used as a proxy for the extinction-corrected flux R23 method.
  From analytical third-order polynomial fits of alpha versus (g-r) colors, we
have been able to correct the EW-R23 method. With this additional and easy
correction, the EW-R23 method provides O/H abundance values similar to those
derived from the extinction-corrected flux R23 method with an accuracy of ~0.1
dex for >92% of the SDSS galaxies.


title:
The Hall Number, Optical Sum Rule and Carrier Density for the
  $t$-$t'$-$J$ model

abstract:
  We revisit the relationship between three classical measures of particle
number, namely the chemical doping $x$, the Hall number $x_{hall}$ and the
particle number inferred from the optical sum rule $x_{opt}$. We study the
$t$-$t'$-$J$ model of correlations on a square lattice, as a minimal model for
High $T_c$ systems, using numerical methods to evaluate the low temperature
Kubo conductivites. These measures disagree significantly in this type of
system, owing to Mott Hubbard correlations. The Hall constant has a complex
behavior with several changes of sign as a function of filling $x$, depending
upon the model parameters. Thus $x_{hall}$ depends sensitively on $t'$ and $J$,
due to a kind of quantum interference.


title:
Evidence for $b \to d \gamma$ Transitions From a Sum of Exclusive Final
  States in the Hadronic Final State Mass Range $1.0 {GeV}/c^2< M(X_d)<1.8
  {GeV}/c^2$

abstract:
  We present preliminary results of a search for $B\to X_d\gamma$ decays with a
hadronic mass 1.0 GeV/$c^2<M(X_d)<$1.8 GeV/$c^2$. We consider seven final
states with up to four charged pions and one neutral pion or $\eta$, which
correspond to about 50% of the total $X_d$ fragmentation in this mass range.
Based on a sample of 383 million $B\bar{B}$ events collected by the BaBar
experiment at PEP-II, we measure a partial branching fraction
$\sum\nolimits^{7}_{X_d=1}{{\ensuremath{\cal B}\xspace}}(B\to
X_d\gamma)|_{(1.0{GeV}/c^2 <M(X_d)<1.8 {GeV}/c^2)}= (3.1\pm0.9 ^{+0.6}_{-0.5}
\pm0.5)\cdot 10^{-6},$ where the uncertainties are statistical, systematic and
model-dependent respectively.


title:
Transverse momentum spectra and elliptic flow: Hydrodynamics with
  QCD-based equations of state

abstract:
  We present a family of equations of state within a quasiparticle model
adjusted to lattice QCD and study the impact on azimuthal flow anisotropies and
transverse momentum spectra within hydrodynamic simulations for heavy-ion
collisions at energies relevant for LHC.


title: Erratum to: Deformation Quantization in Algebraic Geometry

abstract:
  This note contains a correction of the proofs of the main results of the
paper [A. Yekutieli, Deformation quantization in algebraic geometry, Adv. Math.
198 (2005), 383-432]. The results are correct as originally stated.


title: Localized Waves: A scientific and historical introduction

abstract:
  In the first part of this paper (mainly a review) we present general and
formal (simple) introductions to the ordinary gaussian waves and to the Bessel
waves, by explicitly separating the cases of the beams from the cases of the
pulses; and, finally, an analogous introduction is presented for the Localized
Waves (LW), pulses or beams. Always we stress the very different
characteristics of the gaussian with respect to the Bessel waves and to the
LWs, showing the numerous and important properties of the latter w.r.t. the
former ones: Properties that may find application in all fields in which an
essential role is played by a wave-equation (like electromagnetism, optics,
acoustics, seismology, geophysics, gravitation, elementary particle physics,
etc.). In the second part of this paper (namely, in its Appendix), we recall at
first how, in the seventies and eighties, the geometrical methods of Special
Relativity (SR) had predicted --in the sense below specified-- the existence of
the most interesting LWs, i.e., of the X-shaped pulses. At last, in connection
with the circumstance that the X-shaped waves are endowed with Superluminal
group-velocities (as carefully discussed in the first part of this article), we
briefly mention the various experimental sectors of physics in which
Superluminal motions seem to appear: In particular, a bird's-eye view is
presented of the experiments till now performed with evanescent waves (and/or
tunneling photons), and with the "localized Superluminal solutions" to the wave
equations.


title:
Two-dimensional Black Holes in a Higher Derivative Gravity and Matrix
  Model

abstract:
  We construct perturbatively a class of charged black hole solutions in type
0A string theory with higher derivative terms. They have extremal limit, where
the solution interpolates smoothly between near horizon AdS_2 geometry and the
asymptotic linear dilaton geometry. We compute the free energy and the entropy
of those solution using various methods. In particular, we show that there is
no correction in the leading term of the free energy in the large charge limit.
This supports the duality of the type 0A strings on the extremal black hole and
the 0A matrix model in which the tree level free energy is exact without any
alpha' corrections.


title:
Some inequalities for $(\alpha, \beta)$-normal operators in Hilbert
  spaces

abstract:
  An operator $T$ acting on a Hilbert space is called $(\alpha ,\beta)$-normal
($0\leq \alpha \leq 1\leq \beta $) if \begin{equation*} \alpha ^{2}T^{\ast
}T\leq TT^{\ast}\leq \beta ^{2}T^{\ast}T. \end{equation*} In this paper we
establish various inequalities between the operator norm and its numerical
radius of $(\alpha ,\beta)$-normal operators in Hilbert spaces. For this
purpose, we employ some classical inequalities for vectors in inner product
spaces.


title: Counterexample to a geodesic length conjecture on the 2-sphere

abstract: Paper withdrawn by the author.


title: Improved dispersion relations for \gamma\gamma\to \pi^0\pi^0

abstract:
  We perform a dispersive theoretical study of the reaction \gamma\gamma\to
pi^0\pi^0 emphasizing the low energy region. The large source of theoretical
uncertainty to calculate the \gamma\gamma\to\pi^0\pi^0 total cross section for
\sqrt{s}\gtrsim 0.5 GeV within the dispersive approach is removed. This is
accomplished by taking one more subtraction in the dispersion relations, where
the extra subtraction constant is fixed by considering new low energy
constraints, one of them further refined by taking into consideration the
f_0(980) region. This allows us to make sharper predictions for the cross
section for \sqrt{s}\lesssim 0.8 GeV, below the onset of D-wave contributions.
In this way, were new more precise data on \gamma\gamma\to\pi^0\pi^0 available
one might then distinguish between different parameterizations of the \pi\pi
isoscalar S-wave. We also elaborate on the width of the \sigma resonance to
\gamma\gamma and provide new values.


title:
The Egorov theorem for transverse Dirac type operators on foliated
  manifolds

abstract:
  Egorov's theorem for transversally elliptic operators, acting on sections of
a vector bundle over a compact foliated manifold, is proved. This theorem
relates the quantum evolution of transverse pseudodifferential operators
determined by a first order transversally elliptic operator with the
(classical) evolution of its symbols determined by the parallel transport along
the orbits of the associated transverse bicharacteristic flow. For a particular
case of a transverse Dirac operator, the transverse bicharacteristic flow is
shown to be given by the transverse geodesic flow and the parallel transport by
the parallel transport determined by the transverse Levi-Civita connection.
These results allow us to describe the noncommutative geodesic flow in
noncommutative geometry of Riemannian foliations.


title: Complex algebraic curves. Annuli

abstract:
  We provide the full classification of algebraic embeddings of $\mathbb{C}^*$
into $\mathbb{C}^2$ satisfying certain regularity condition, which
conjecturally holds for all algebraic maps from $\mathbb{C}^*$ into
$\mathbb{C}^2$. The resulting list comprises 1 smooth family, 18 discrete
families and 4 special cases. Any embedding known to us can be reduced to one
of this list by a de Jonqui\`ere transform and a suitable change of variables.
  The classification uses in general tools from previous work "Complex
algebraic curves via Poincare--Hopf formula. I. Parametric lines." (Pacific. J.
Math. 229 (2007) No. 2, 307--338): we carefully estimate Milnor numbers of
singularities that may appear in the embedding of $\mathbb{C}^*$. We use the
regularity condition to bound the sum of so--called codimensions of singular
points. The detailed discussion of this condition can be found in
http://www.mimuw.edu.pl/~mcboro/pliki/artykuly/curv4.pdf


title:
Transition frequency shifts with fine structure constant variation for
  Fe II: Breit and core-valence correlation correction

abstract:
  Transition frequencies of Fe II ion are known to be very sensitive to
variation of the fine structure constant \alpha. The resonance absorption lines
of Fe II from objects at cosmological distances are used in a search for the
possible variation of \alpha in cause of cosmic time. In this paper we
calculated the dependence of the transition frequencies on \alpha^2 (q-factors)
for Fe II ion. We found corrections to these coefficients from valence-valence
and core-valence correlations and from the Breit interaction. Both the
core-valence correlation and Breit corrections to the q-factors appeared to be
larger than had been anticipated previously. Nevertheless our calculation
confirms that the Fe II absorption lines seen in quasar spectra have large
q-factors of both signs and thus the ion Fe II alone can be used in the search
for the \alpha-variation at different cosmological epochs.


title:
Universal Nonlinear Filtering Using Feynman Path Integrals II: The
  Continuous-Continuous Model with Additive Noise

abstract:
  In this paper, the Feynman path integral formulation of the
continuous-continuous filtering problem, a fundamental problem of applied
science, is investigated for the case when the noise in the signal and
measurement model is additive. It is shown that it leads to an independent and
self-contained analysis and solution of the problem. A consequence of this
analysis is Feynman path integral formula for the conditional probability
density that manifests the underlying physics of the problem. A corollary of
the path integral formula is the Yau algorithm that has been shown to be
superior to all other known algorithms. The Feynman path integral formulation
is shown to lead to practical and implementable algorithms. In particular, the
solution of the Yau PDE is reduced to one of function computation and
integration.


title: Interpretations of Octonion Wave Equations

abstract:
  The interpretations of octonion wave equations in eight dimensional
space-time have been discussed. We have made an attempt to discuss the octonion
field equation as the equation of motion for particles carrying simultaneously
electric and magnetic charges (i.e. dyons) in external and internal spaces
respectively. It has been concluded that the component of octonion potential
wave equations behaves neither the generalized electromagnetic fields of
monopoles nor the dyons. Rather, they have the mixed behaviour of
electromagnetic fields associated with the electric and magnetic charges in
external and internal spaces. We have also made an attempt to investigate the
split octonion wave equation and its interpretation in classical
electrodynamics and accordingly the consistent and compact forms of
eight-dimensional potential and current equation of dyons are obtained in terms
of Zorn's vector matrix realization of split octonions.Visualizing the external
four space as the localization space for tachyons, it is shown that the split
octonion wave equation reduces to the Maxwell's equation (field equation) for
bradyons in R^{4}- space as well as that for tachyons in T^{4}- space in the
absence of other.


title:
Entangling a nanomechanical resonator and a superconducting microwave
  cavity

abstract:
  We propose a scheme able to entangle at the steady state a nanomechanical
resonator with a microwave cavity mode of a driven superconducting coplanar
waveguide. The nanomechanical resonator is capacitively coupled with the
central conductor of the waveguide and stationary entanglement is achievable up
to temperatures of tens of milliKelvin.


title:
Angle dependent magnetoresistance measurements in
  Tl$_2$Ba$_2$CuO$_{6+\delta}$ and the need for anisotropic scattering

abstract:
  The angle-dependent interlayer magnetoresistance of overdoped
Tl$_2$Ba$_2$CuO$_{6+\delta}$ has been measured in high magnetic fields up to 45
Tesla. A conventional Boltzmann transport analysis with no basal-plane
anisotropy in the cyclotron frequency $\omega_c$ or transport lifetime $\tau$
is shown to be inadequate for explaining the data. We describe in detail how
the analysis can be modified to incorporate in-plane anisotropy in these two
key quantities and extract the degree of anisotropy for each by assuming a
simple four-fold symmetry. While anisotropy in $\omega_c$ and other Fermi
surface parameters may improve the fit, we demonstrate that the most important
anisotropy is that in the transport lifetime, thus confirming its role in the
physics of overdoped superconducting cuprates.


title: Universal near-horizon conformal structure and black hole entropy

abstract:
  It is shown that a massless scalar probe reveals a universal near-horizon
conformal structure for a wide class of black holes, including the BTZ. The
central charge of the corresponding Virasoro algebra contains information about
the black hole. With a suitable quantization condition on the central charge,
the CFT associated with the black hole in our approach is consistent with the
recent observation of Witten, where the dual theory for the BTZ in the AdS/CFT
framework has been identified with the construction of Frenkel, Lepowsky and
Meurman. This CFT admits the Fischer-Griess monster group as its symmetry. The
logarithm of the dimension of a specific representation of the monster group
has been identified by Witten as the entropy of the BTZ black hole. Our
algebraic approach shows that a wide class of black holes share the same
near-horizon conformal structure as that for the BTZ. With a suitable
quantization condition, the CFT's for all these black holes in our formalism
can be identified with the FLM model, although not through the AdS/CFT
correspondence. The corresponding entropy for the BTZ provides a lower bound
for the entropy of this entire class of black holes.


title:
Measurement of B+ -> D+ D0bar branching fraction and charge asymmetry
  and search for B0 -> D0 D0bar

abstract:
  We report an improved measurement of the B+ -> D+ D0bar and B0 -> D0 D0bar
decays based on 656.7 10^6 BBar events collected with the Belle detector at
KEKB. We measure the branching fraction and charge asymmetry for the B+ -> D+
D0bar decay: Br(B+ -> D+ D0bar)= (3.85 +- 0.31 +- 0.38) 10^-4 and A_{CP}(B+ ->
D+ D0bar)=0.00 +- 0.08 +- 0.02, where the first error is statistical and the
second is systematical. We also set the upper limit for the B0 -> D0 D0bar
decay: Br(B0 -> D0 D0bar) < 0.42 10^-4 at 90% CL.


title:
GaAs delta-doped quantum wire superlattice characterization by quantum
  Hall effect and Shubnikov de Haas oscillations

abstract:
  Quantum wire superlattices (1D) realized by controlled dislocation slipping
in quantum well superlattices (2D) (atomic saw method) have already shown
magnetophonon oscillations. This effect has been used to investigate the
electronic properties of such systems and prove the quantum character of the
physical properties of the wires. By cooling the temperature and using pulsed
magnetic field up to 35 T, we have observed both quantum Hall effect (QHE) and
Shubnikov de Haas (SdH) oscillations for various configurations of the magnetic
field. The effective masses deduced from the values of the fundamental fields
are coherent with those obtained with magnetophonon effect. The field rotation
induces a change in the resonance frequencies due to the modification of the
mass tensor as in a (3D) electron gas. In view the QHE, the plateaus observed
in rho_yz are dephased relatively to rho_zz minima which seems to be linked to
the dephasing of the minima of the density of states of the broadened Landau
levels.


title: Formation of a black hole from an AdS spacetime

abstract:
  We shall first discuss motivation for higher dimension even for classical
description of gravitational dynamics and then construct a black hole out of an
anti-deSitter (AdS) spacetime by prescribing a coupling between Gauss-Bonnet
parameter, constant curvature of extra dimensional space and $\Lambda$. This is
a creation of pure curvature which establishes the fundamental reciprocity
between matter and gravity/curvature.


title:
Harnack inequality and applications for stochastic generalized porous
  media equations

abstract:
  By using coupling and Girsanov transformations, the dimension-free Harnack
inequality and the strong Feller property are proved for transition semigroups
of solutions to a class of stochastic generalized porous media equations. As
applications, explicit upper bounds of the $L^p$-norm of the density as well as
hypercontractivity, ultracontractivity and compactness of the corresponding
semigroup are derived.


title: Studying Transition Region Phenomena with Solar-B/EIS

abstract:
  Transition region lines in active regions can become strongly enhanced in
coronal footpoints and active region blinkers. The weak transition region lines
found in the Solar-B/EIS wavebands will thus become useful for diagnostic
studies of these events. EIS count rates predicted from SOHO/CDS spectra are
presented, and a Mg VII density diagnostic is highlighted.


title:
Optimized minigaps for negative differential resistance creation in
  strongly delta-doped (1D) superlattices

abstract:
  The "atomic saw method" uses the passage of dislocations in two-dimensional
(2D) quantum-well superlattices to create periodic slipping layers and
one-dimensional (1D) quantum wire superlattices. The effects of this space
structuring of the samples on the allowed energies are analysed in the case of
GaAs d-doped superlattices. If they are sufficiently large, the various
minigaps appearing in the 1D band structure could be responsible for the
presence of negative differential resistance (NDR) with high critical current
in these systems. The purpose is to determine the evolution of the minigaps in
terms of the sample parameters and to obtain the means to determine both the 2D
and 1D structural characteristics where NDR could appear.


title: Broadening processes in GaAs delta-doped quantum wire superlattices

abstract:
  We use both Quantum Hall and Shubnikov de Haas experiments at high magnetic
field and low temperature to analyse broadening processes of Landau levels in a
delta-doped 2D quantum well superlattice and a 1D quantum wire superlattice
generated from the first one by controlled dislocation slips. We deduce first
the origin of the broadening from the damping factor in the Shubnikov de Haas
curves in various configurations of the magnetic field and the measured current
for both kinds of superlattice. Then, we write a general formula for the
resistivity in the Quantum Hall effect introducing a dephasing factor we link
to the process of localization.


title: Major Indices and Perfect Bases for Complex Reflection Groups

abstract:
  It is shown that, under mild conditions, a complex reflection group
$G(r,p,n)$ may be decomposed into a set-wise direct product of cyclic
subgroups. This property is then used to extend the notion of major index and a
corresponding Hilbert series identity to these and other closely related
groups.


title: Curve crossing for random walks reflected at their maximum

abstract:
  Let $R_n=\max_{0\leq j\leq n}S_j-S_n$ be a random walk $S_n$ reflected in its
maximum. Except in the trivial case when $P(X\ge0)=1$, $R_n$ will pass over a
horizontal boundary of any height in a finite time, with probability 1. We
extend this by giving necessary and sufficient conditions for finiteness of
passage times of $R_n$ above certain curved (power law) boundaries, as well.
The intuition that a degree of heaviness of the negative tail of the
distribution of the increments of $S_n$ is necessary for passage of $R_n$ above
a high level is correct in most, but not all, cases, as we show. Conditions are
also given for the finiteness of the expected passage time of $R_n$ above
linear and square root boundaries.


title:
Possible connections between whiskered categories and groupoids, many
  object Leibniz algebras, automorphism structures and local-to-global
  questions

abstract:
  We define the notion of whiskered categories and groupoids, showing that
whiskered groupoids have a commutator theory. So also do whiskered
$R$-categories, thus answering questions of what might be `commutative
versions' of these theories. We relate these ideas to the theory of Leibniz
algebras, but the commutator theory here does not satisfy the Leibniz identity.
We also discuss potential applications and extensions, for example to
resolutions of monoids.


title: Theory about Atlas morphology (Saturn moon)

abstract:
  On June 12, 2007 the Cassini probe sent the images of a small moon of Saturn
called Atlas which is located between the ring A and the small ring R/2004 S 1.
These images have shown that the Atlas morphology is very different from other
moons of similar dimensions. In the present article we propose a reasonable
theory, to that we denominated "flying dune", that explains its morphologic
characteristics from its magnitudes like mass, diameters and orbital radius, as
well as its orbital position and the interpretation of the images caught by the
Cassini probe.


title: Assisted Inflation from Geometric Tachyon

abstract:
  We study the effect of rolling of N D3-branes in the vicinity of NS5-branes.
We find out that this system coupled with the four dimensional gravity gives
the slow roll assisted inflation of the scalar field theory. Once again this
expectation is exactly similar to that of N-tachyon assisted inflation on
unstable D-branes.


title:
An exactly solvable model of reversible adsorption on a disordered
  substrate

abstract:
  We consider the reversible adsorption of dimers on a regular lattice, where
adsorption occurs on a finite fraction of sites selected randomly. By comparing
this system to the pure system where all sites are available for adsorption, we
show that when the activity goes to infinity, there exists a mapping between
this model and the pure system at the same density. By examining the
susceptibilities, we demonstrate that there is no mapping at finite activity.
However, when the site density is small or moderate, this mapping exists up to
second order in site density. We also propose and evaluate approximate
approaches that may be applied to systems where no analytic result is known.


title:
Spin valve effect by ballistic transport in ferromagnetic metal (MnAs) /
  semiconductor (GaAs) hybrid heterostructures

abstract:
  We demonstrate the spin valve effect by ballistic transport in fully
epitaxial MnAs ferromagnetic metal / GaAs semiconductor / GaAs:MnAs granular
hybrid heterostructures. The GaAs:MnAs material contains ferromagnetic MnAs
nanoparticles in a GaAs matrix, and acts as a spin injector and a spin
detector. Although the barrier height of the GaAs/MnAs interface was found to
be very small, relatively large magnetoresistance was observed. This result
shows that by using ballistic transport, we can realize a large spin valve
effect without inserting a high tunnel barrier at the ferromagnetic metal /
semiconductor interface.


title:
Growth dynamics of vertically aligned single-walled carbon nanotubes
  from in situ measurements

abstract:
  An in situ optical absorbance measurement was used to study the growth
dynamics of vertically aligned single-walled carbon nanotubes (VA-SWCNTs)
synthesized by chemical vapor deposition of ethanol. The growth rate of the
VA-SWCNT film was found to decay exponentially from an initial maximum,
resulting in an effective growth time of approximately 15 minutes.
Investigation of various growth conditions revealed an optimum pressure at
which growth is maximized, and this pressure depends on the growth temperature.
Below this optimum pressure the synthesis reaction is first-order, and the
rate-limiting step is the arrival of ethanol at the catalyst. We also present a
novel method for determining the burning temperature of low-mass materials,
which combines the in situ absorbance measurement with controlled oxidation.


title:
Prospects for GMRT to Observe Radio Waves from UHE Particles Interacting
  with the Moon

abstract:
  Ultra high energy (UHE) particles of cosmic origin impact the lunar regolith
and produce radio signals through Askaryan effect, signals that can be detected
by Earth based radio telescopes. We calculate the expected sensitivity for
observation of such events at the Giant Metrewave Radio Telescope (GMRT), both
for UHE cosmic rays (CR) and UHE neutrino interactions. We find that for 30
days of observation time a significant number of detectable events is expected
above $10^{20}$ eV for UHECR or neutrino fluxes close to the current limits.
Null detection over a period of 30 days will lower the experimental bounds on
UHE particle fluxes by magnitudes competitive to both present and future
experiments at the very highest energies.


title:
Current-induced non-adiabatic spin torques and domain wall motion with
  spin relaxation in a ferromagnetic metallic wire

abstract:
  Within the s-d model description, we derive the current-driven spin torque in
a ferromagnet, taking explicitly into account a spin-relaxing Caldeira-Leggett
bath coupling to the s-electrons. We derive Bloch-Redfield equations of motion
for the s-electron spin dynamics, and formulate a systematic gradient expansion
to obtain non-adiabatic (higher-order) corrections to the well-known adiabatic
(first-order) spin torque. We provide simple analytical expressions for the
second-order spin torque. The theory is applied to current-driven domain wall
motion. Second-order contributions imply a deformation of a transverse
tail-to-tail domain wall. The wall center still moves with a constant velocity
that now depends on the spin-polarized current in a non-trivial manner.


title:
Vector bundles on degenerations of elliptic curves and Yang-Baxter
  equations

abstract:
  In this paper we introduce the notion of a geometric associative r-matrix
attached to a genus one fibration with a section and irreducible fibres. It
allows us to study degenerations of solutions of the classical Yang-Baxter
equation using the approach of Polishchuk. We also calculate certain solutions
of the classical, quantum and associative Yang-Baxter equations obtained from
moduli spaces of (semi-)stable vector bundles on Weierstrass cubic curves.


title: On the exotic eikosiheptaplet

abstract:
  We use the chiral quark soliton model to estimate masses and widths of the
two eikosiheptaplets (27-plets of SU(3) flavor) of spin 3/2 and 1/2 that emerge
in the rigid rotator quantization. We use as input: hyperon decays, Theta+ mass
and width. While 27_{3/2} has small widths (although much larger than the
values allowed by the partial wave analysis), 27_{1/2} has large decay widths
to antidecuplet. However exactly for this decay channels the widths are
suppressed in the large N_{c} limit.


title: Confining Effective Theories Based on Instantons and Merons

abstract:
  An effective theory based on ensembles of either regular gauge instantons or
merons is shown to produce confinement in SU(2) Yang-Mills theory. When the
scale is set by the string tension, the action density, topological
susceptibility and low-lying glueball spectrum are similar to those arising in
lattice QCD. The physical mechanism producing confinement is explained, and a
number of analytical insights into the effective theory are presented.


title: Perturbations on steady spherical accretion in Schwarzschild geometry

abstract:
  The stationary background flow in the spherically symmetric infall of a
compressible fluid, coupled to the space-time defined by the static
Schwarzschild metric, has been subjected to linearized perturbations. The
perturbative procedure is based on the continuity condition and it shows that
the coupling of the flow with the geometry of space-time brings about greater
stability for the flow, to the extent that the amplitude of the perturbation,
treated as a standing wave, decays in time, as opposed to the amplitude
remaining constant in the Newtonian limit. In qualitative terms this situation
simulates the effect of a dissipative mechanism in the classical Bondi
accretion flow, defined in the Newtonian construct of space and time. As a
result of this approach it becomes impossible to define an acoustic metric for
a conserved spherically symmetric flow, described within the framework of
Schwarzschild geometry. In keeping with this view, the perturbation, considered
separately as a high-frequency travelling wave, also has its amplitude reduced.


title:
Threshold corrections to rapidity distributions of Z and W^\pm bosons
  beyond N^2 LO at hadron colliders

abstract:
  Threshold enhanced perturbative QCD corrections to rapidity distributions of
$Z$ and $W^\pm$ bosons at hadron colliders are presented using the Sudakov
resummed cross sections at N${}^3$LO level. We have used renormalisation group
invariance and the mass factorisation theorem that these hard scattering cross
sections satisfy to construct the QCD amplitudes. We show that these higher
order threshold QCD corrections stabilise the theoretical predictions for
vector boson production at the LHC under variations of both renormalisation and
factorisation scales.


title:
On fractional Euler-Lagrange and Hamilton equations and the fractional
  generalization of total time derivative

abstract:
  Fractional mechanics describes both conservative and non-conservative
systems. The fractional variational principles gained importance in studying
the fractional mechanics and several versions are proposed. In classical
mechanics the equivalent Lagrangians play an important role because they admit
the same Euler-Lagrange equations. By adding a total time derivative of a
suitable function to a given classical Lagrangian or by multiplying with a
constant the Lagrangian we obtain the same equations of motion.
  In this study, the fractional discrete Lagrangians which differs by a
fractional derivative are analyzed within Riemann-Liouville fractional
derivatives.
  As a consequence of applying this procedure the classical results are
reobtained as a special case. The fractional generalization of $Fa\grave{a}$ di
Bruno formula is used in order to obtain the concrete expression of the
fractional Lagrangians which differs from a given fractional Lagrangian by
adding a fractional derivative. The fractional Euler-Lagrange and Hamilton
equations corresponding to the obtained fractional Lagrangians are investigated
and two examples are analyzed in details.


title:
PET monitoring of cancer therapy with He-3 and C-12 beams: a study with
  the GEANT4 toolkit

abstract:
  We study the spatial distributions of $\beta^+$-activity produced by
therapeutic beams of $^3$He and $^{12}$C ions in various tissue-like materials.
The calculations were performed within a Monte Carlo model for Heavy-Ion
Therapy (MCHIT) based on the GEANT4 toolkit. The contributions from
$^{10,11}$C, $^{13}$N, $^{14,15}$O, $^{17,18}$F and $^{30}$P positron-emitting
nuclei were calculated and compared with experimental data obtained during and
after irradiation. Positron emitting nuclei are created by $^{12}$C beam in
fragmentation reactions of projectile and target nuclei. This leads to a
$\beta^+$-activity profile characterised by a noticeable peak located close to
the Bragg peak in the corresponding depth-dose distribution. On the contrary,
as the most of positron-emitting nuclei are produced by $^3$He beam in target
fragmentation reactions, the calculated total $\beta^+$-activity during or soon
after the irradiation period is evenly distributed within the projectile range.
However, we predict also the presence of $^{13}$N, $^{14}$O, $^{17,18}$F
created in charge-transfer reactions by low-energy $^3$He ions close to the end
of their range in several tissue-like media. The time evolution of
$\beta^+$-activity profiles was investigated for both kinds of beams. Due to
the production of $^{18}$F nuclide the $\beta^+$-activity profile measured 2 or
3 hours after irradiation with $^{3}$He ions will have a distinct peak
correlated with the maximum of depth-dose distribution. We found certain
advantages of low-energy $^{3}$He beams over low-energy proton beams for
reliable PET monitoring during particle therapy of shallow located tumours. In
this case the distal edge of $\beta^+$-activity distribution from $^{17}$F
nuclei clearly marks the range of $^{3}$He in tissues.


title:
High fidelity all-optical control of quantum dot spins: detailed study
  of the adiabatic approach

abstract:
  Confined electron spins are preferred candidates for embodying quantum
information in the solid state. A popular idea is the use of optical excitation
to achieve the ``best of both worlds'', i.e. marrying the long spin decoherence
times with rapid gating. Here we study an all-optical adiabatic approach to
generating single qubit phase gates. We find that such a gate can be extremely
robust against the combined effect of all principal sources of decoherence,
with an achievable fidelity of 0.999 even at finite temperature. Crucially this
performance can be obtained with only a small time cost: the adiabatic gate
duration is within about an order of magnitude of a simple dynamic
implementation. An experimental verification of these predictions is
immediately feasible with only modest resources.


title:
Orbital Ordering Structures in (Nd,Pr)0.5Sr0.5MnO3 Manganite Thin Films
  on Perovskite (011) Substrates

abstract:
  Structural study of orbital-ordered manganite thin films has been conducted
using synchrotron radiation, and a ground state electronic phase diagram is
made. The lattice parameters of four manganite thin films, Nd0.5Sr0.5MnO3
(NSMO) or Pr0.5Sr0.5MnO3 (PSMO) on (011) surfaces of SrTiO3 (STO) or
[(LaAlO3){0.3}(SrAl0.5Ta0.5O3){0.7}] (LSAT), were measured as a function of
temperature. The result shows, as expected based on previous knowledge of bulk
materials, that the films' resistivity is closely related to their structures.
Observed superlattice reflections indicate that NSMO thin films have an
antiferro-orbital-ordered phase as their low-temperature phase while PSMO film
on LSAT has a ferro-orbital-ordered phase, and that on STO has no
orbital-ordered phase. A metallic ground state was observed only in films
having a narrow region of A-site ion radius, while larger ions favor
ferro-orbital-ordered structure and smaller ions stabilize
antiferro-orbital-ordered structure. The key to the orbital-ordering transition
in (011) film is found to be the in-plane displacement along [0-1 1] direction.


title:
Stability of equilibrium under constraints: Role of second-order
  constrained derivatives

abstract:
  In the stability analysis of an equilibrium, given by a stationary point of a
functional F[n] (free energy functional, e.g.), the second derivative of F[n]
plays the essential role. If the system in equilibrium is subject to the
conservation constraint of some extensive property (e.g. volume, material, or
energy conservation), the Euler equation determining the stationary point
corresponding to the equilibrium alters according to the method of Lagrange
multipliers. Here, the question as to how the effects of constraints can be
taken into account in a stability analysis based on second functional
derivatives is examined. It is shown that the concept of constrained second
derivatives incorporates all the effects due to constraints; therefore
constrained second derivatives provide the proper tool for the stability
analysis of equilibria under constraints. For a physically important type of
constraints, it is demonstrated how the presented theory works. Further, the
rigorous derivation of a recently obtained stability condition for a special
case of equilibrium of ultrathin-film binary mixtures is given, presenting a
guide for similar analyses. [For details on constrained derivatives, see also
math-ph/0603027, physics/0603129, physics/0701145.]

categories: physics.flu-dyn cond-mat.stat-mech math-ph math.FA math.MP


title: Derived Semidistributive Lattices

abstract:
  For L a finite lattice, let C(L) denote the set of pairs g = (g_0,g_1) such
that g_0 is a lower cover of g_1 and order it as follows: g <= d iff g_0 <=
d_0, g_1 <= d_1, but not g_1 <= d_0. Let C(L,g) denote the connected component
of g in this poset. Our main result states that C(L,g) is a semidistributive
lattice if L is semidistributive, and that C(L,g) is a bounded lattice if L is
bounded. Let S_n be the permutohedron on n letters and T_n be the associahedron
on n+1 letters. Explicit computations show that C(S_n,a) = S_{n-1} and C(T_n,a)
= T_{n-1}, up to isomorphism, whenever a is an atom. These results are
consequences of new characterizations of finite join semidistributive and
finite lower bounded lattices: (i) a finite lattice is join semidistributive if
and only if the projection sending g in C(L) to g_0 in L creates pullbacks,
(ii) a finite join semidistributive lattice is lower bounded if and only if it
has a strict facet labelling. Strict facet labellings, as defined here, are
generalization of the tools used by Barbut et al. to prove that lattices of
Coxeter groups are bounded.


title: Charge Ordering in alpha-(BEDT-TTF)2I3 by synchrotron x-ray diffraction

abstract:
  The spatial charge arrangement of a typical quasi-two-dimensional organic
conductor alpha-(BEDT-TTF)2I3 is revealed by single crystal structure analysis
using synchrotron radiation. The results show that the horizontal stripe type
structure, which was suggested by mean field theory, is established. We also
find the charge disproportion above the metal-insulator transition temperature
and a significant change in transfer integrals caused by the phase transition.
Our result elucidates the insulating phase of this material as a 2k_F charge
density localization.


title: NLO QED contributions to top-pair production at hadron collider

abstract:
  Electroweak one-loop calculations for production of top-quark pairs at
colliders are completed by providing the missing QED type contributions from
real and virtual photons, where also effects from interference between QED and
QCD contributions have to be taken into account. Moreover, photon-induced $t
\bar{t}$ production is included as another partonic channel.


title:
Vanishing theorem for transverse Dirac operators on Riemannian
  foliations

abstract:
  We obtain a vanishing theorem for the half-kernel of a transverse ${\rm
Spin}\sp c$ Dirac operator on a compact manifold endowed with a transversely
almost complex Riemannian foliation twisted by a sufficiently large power of a
line bundle, whose curvature vanishes along the leaves and is transversely
non-degenerate at any point of the ambient manifold.


title:
Magnetic reconnection during collisionless, stressed, X-point collapse
  using Particle-in-Cell simulation

abstract:
  Two cases of weakly and strongly stressed X-point collapse were considered.
Here descriptors weakly and strongly refer to 20 % and 124 % unidirectional
spatial compression of the X-point, respectively. In the weakly stressed case,
the reconnection rate, defined as the out-of-plane electric field in the
X-point (the magnetic null) normalised by the product of external magnetic
field and Alfv\'en speeds, peaks at 0.11, with its average over 1.25 Alfv\'en
times being 0.04. Electron energy distribution in the current sheet, at the
high energy end of the spectrum, shows a power law distribution with the index
varying in time, attaining a maximal value of -4.1 at the final simulation time
step (1.25 Alfv\'en times). In the strongly stressed case, magnetic
reconnection peak occurs 3.4 times faster and is more efficient. The peak
reconnection rate now attains value 2.5, with the average reconnection rate
over 1.25 Alfv\'en times being 0.5. The power law energy spectrum for the
electrons in the current sheet attains now a steeper index of -5.5, a value
close to the ones observed in the vicinity of X-type region in the Earth's
magneto-tail. Within about one Alfv\'en time, 2% and 20% of the initial
magnteic energy is converted into heat and accelerated particle energy in the
case of weak and strong stress, respectively. In the both cases, during the
peak of the reconnection, the quadruple out-of-plane magnetic field is
generated, hinting possibly to the Hall regime of the reconnection. These
results strongly suggest the importance of the collionless, stressed X-point
collapse as a possible contributing factor to the solution of the solar coronal
heating problem or more generally, as an efficient mechanism of converting
magnetic energy into heat and super-thermal particle energy.


title: Quantum interference in bilayer graphene

abstract:
  We report the first experimental study of the quantum interference correction
to the conductivity of bilayer graphene. Low-field, positive
magnetoconductivity due to the weak localisation effect is investigated at
different carrier densities, including those around the electroneutrality
region. Unlike conventional 2D systems, weak localisation in bilayer graphene
is affected by elastic scattering processes such as intervalley scattering.
Analysis of the dephasing determined from the magnetoconductivity is
complemented by a study of the field- and density-dependent fluctuations of the
conductance. Good agreement in the value of the coherence length is found
between these two studies.


title:
Effective Field Theory of Gravity: Leading Quantum Gravitational
  Corrections to Newtons and Coulombs Law

abstract:
  In this paper we consider general relativity and its combination with scalar
quantum electrodynamics (QED) as an effective quantum field theory at energies
well below the Planck scale. This enables us to compute the one-loop quantum
corrections to the Newton and Coulomb potential induced by the combination of
graviton and photon fluctuations. We derive the relevant Feynman rules and
compute the nonanalytical contributions to the one-loop scattering matrix for
charged scalars in the nonrelativistic limit. In particular, we derive the
post-Newtonian corrections of order $Gm/\text c^2 r$ from general relativity
and the genuine quantum corrections of order $G\hbar/\text c^3 r^2$.


title:
Optical response of ferromagnetic YTiO_3 studied by spectral
  ellipsometry

abstract:
  We have studied the temperature dependence of spectroscopic ellipsometry
spectra of an electrically insulating, nearly stoichiometric YTiO_3 single
crystal with ferromagnetic Curie temperature T_C = 30 K. The optical response
exhibits a weak but noticeable anisotropy. Using a classical dispersion
analysis, we identify three low-energy optical bands at 2.0, 2.9, and 3.7 eV.
Although the optical conductivity spectra are only weakly temperature dependent
below 300 K, we are able to distinguish high- and low-temperature regimes with
a distinct crossover point around 100 K. The low-temperature regime in the
optical response coincides with the temperature range in which significant
deviations from Curie-Weiss mean field behavior are observed in the
magnetization. Using an analysis based on a simple superexchange model, the
spectral weight rearrangement can be attributed to intersite d_i^1d_j^1
\longrightarrow d_i^2d_j^0 optical transitions. In particular, Kramers-Kronig
consistent changes in optical spectra around 2.9 eV can be associated with the
high-spin-state (^3T_1) optical transition. This indicates that other
mechanisms, such as weakly dipole-allowed p-d transitions and/or
exciton-polaron excitations, can contribute significantly to the optical band
at 2 eV. The recorded optical spectral weight gain of 2.9 eV optical band is
significantly suppressed and anisotropic, which we associate with complex
spin-orbit-lattice phenomena near ferromagnetic ordering temperature in YTiO_3.


title: Point-form quantum field theory

abstract:
  We examine canonical quantization of relativistic field theories on the
forward hyperboloid, a Lorentz-invariant surface of the form $x_\mu x^\mu =
\tau^2$. This choice of quantization surface implies that all components of the
4-momentum operator are affected by interactions (if present), whereas rotation
and boost generators remain interaction free -- a feature characteristic of
Dirac's `` point-form\rq\rq of relativistic dynamics. Unlike previous attempts
to quantize fields on space-time hyperboloids, we keep the usual plane-wave
expansion of the field operators and consider evolution of the system generated
by the 4-momentum operator. We verify that the Fock-space representations of
the Poincar\'e generators for free scalar and spin-1/2 fields look the same as
for equal-time quantization. Scattering is formulated for interacting fields in
a covariant interaction picture and it is shown that the familiar perturbative
expansion of the S-operator is recovered by our approach. An appendix analyzes
special distributions, integrals over the forward hyperboloid, that are used
repeatedly in the paper.


title: Proper Motions in the Andromeda Subgroup

abstract:
  This article presents results of VLBI observations of regions of H2O maser
activity in the Local Group galaxies M33 and IC10. Since all position
measurements were made relative to extragalactic background sources, the proper
motions of the two galaxies could be measured. For M33, this provides this
galaxy's three dimensional velocity, showing that this galaxy is moving with a
velocity of 190 +/- 59 km\s relative to the Milky Way. For IC10, we obtain a
motion of 215 +/- 42 km/s relative to the Milky Way. These measurements promise
a new handle on dynamical models for the Local Group and the mass and dark
matter halo of Andromeda and the Milky Way.


title:
Quantum gravity: unification of principles and interactions, and
  promises of spectral geometry

abstract:
  Quantum gravity was born as that branch of modern theoretical physics that
tries to unify its guiding principles, i.e., quantum mechanics and general
relativity. Nowadays it is providing new insight into the unification of all
fundamental interactions, while giving rise to new developments in modern
mathematics. It is however unclear whether it will ever become a falsifiable
physical theory, since it deals with Planck-scale physics. Reviewing a wide
range of spectral geometry from index theory to spectral triples, we hope to
dismiss the general opinion that the mere mathematical complexity of the
unification programme will obstruct that programme.


title:
Weak Solutions of Stochastic Differential Equations over the Field of
  p-Adic Numbers

abstract:
  Study of stochastic differential equations on the field of p-adic numbers was
initiated by the second author and has been developed by the first author, who
proved several results for the p-adic case, similar to the theory of ordinary
stochastic integral with respect to Levy processes on the Euclidean spaces. In
this article, we present an improved definition of a stochastic integral on the
field and prove the joint (time and space) continuity of the local time for
p-adic stable processes. Then we use the method of random time change to obtain
sufficient conditions for the existence of a weak solution of a stochastic
differential equation on the field, driven by the p-adic stable process, with a
Borel measurable coefficient.


title: The Minimum Rank Problem: a counterexample

abstract:
  We provide a counterexample to a recent conjecture that the minimum rank of
every sign pattern matrix can be realized by a rational matrix. We use one of
the equivalences of the conjecture and some results from projective geometry.
As a consequence of the counterexample, we show that there is a graph for which
the minimum rank over the reals is strictly smaller than the minimum rank over
the rationals. We also make some comments on the minimum rank of sign pattern
matrices over different subfields of $\mathbb R$.


title:
On the absence of a spiral magnetic order in Li2CuO2 with
  one-dimensional CuO2 ribbon chains

abstract:
  On the basis of first principles density functional theory electronic
structure calculations as well as classical spin analysis, we explored why the
magnetic oxide Li2CuO2, consisting of CuO2 ribbon chains made up of
edge-sharing CuO4 squares, does not exhibit a spiral-magnetic order. Our work
shows that, due to the next-nearest-neighbor interchain interactions, the
observed collinear magnetic structure becomes only slightly less stable than
the spin-spiral ground state, and many states become nearly degenerate in
energy with the observed collinear structure. This suggests that the collinear
magnetic structure of Li2CuO2 is a consequence of order-by-disorder induced by
next-nearest-neighbor interchain interactions.


title:
Radio detection of high-energy cosmic rays at the Pierre Auger
  Observatory

abstract:
  The southern Auger Observatory provides an excellent test bed to study the
radio detection of extensive air showers as an alternative, cost-effective, and
accurate tool for cosmic-ray physics. The data from the radio setup can be
correlated with those from the well-calibrated baseline detectors of the Pierre
Auger Observatory. Furthermore, human-induced radio noise levels at the
southern Auger site are relatively low. We have started an R&D program to test
various radio-detection concepts. Our studies will reveal Radio Frequency
Interferences (RFI) caused by natural effects such as day-night variations,
thunderstorms, and by human-made disturbances. These RFI studies are conducted
to optimise detection parameters such as antenna design, frequency interval,
antenna spacing and signal processing. The data from our initial setups, which
presently consist of typically 3 - 4 antennas, will be used to characterise the
shower from radio signals and to optimise the initial concepts. Furthermore,
the operation of a large detection array requires autonomous detector stations.
The current design is aiming at stations with antennas for two polarisations,
solar power, wireless communication, and local trigger logic. The results of
this initial phase will provide an important stepping stone for the design of a
few tens kilometers square engineering array


title:
Formaldehyde as a Tracer of Extragalactic Molecular Gas I. Para-H_2CO
  Emission From M 82

abstract:
  Using the IRAM 30-m telescope and the 15-m JCMT, we explore the value of
para-formaldehyde (p-H_2CO) as a tracer of density and temperature of the
molecular gas in external galaxies. The target of our observations are the
lobes of the molecular ring around the center of the nearby prototypical
starburst galaxy M 82. It is shown that p-H_2CO provides one of the rare direct
molecular thermometers. Reproducing the measured line intensities with a large
velocity gradient (LVG) model, we find densities of n_H2 ~ 7 10^3 cm^-3 and
kinetic temperatures of T_kin ~ 200 K. The derived kinetic temperature is
significantly higher than the dust temperature or the temperature deduced from
ammonia (NH_3) lines, but our results agree well with the properties of the
high-excitation component seen in CO. We also present the serendipitous
discovery of the 4_2 - 3_1 line of methanol (CH_3OH) in the northeastern lobe,
which shows -- unlike CO and H_2CO -- significantly different line intensities
in the two lobes.


title: Generators of simple Lie algebras in arbitrary characteristics

abstract:
  In this paper we study the minimal number of generators for simple Lie
algebras in characteristic 0 or p > 3. We show that any such algebra can be
generated by 2 elements. We also examine the 'one and a half generation'
property, i.e. when every non-zero element can be completed to a generating
pair. We show that classical simple algebras have this property, and that the
only simple Cartan type algebras of type W which have this property are the
Zassenhaus algebras.


title:
Collective Excitations Spectrum in Density Modulated One-Dimensional
  Electron Gas in a Magnetic Field

abstract:
  We determine the collective excitations spectrum and discuss the numerical
results for a parabolically confined density modulated quasi-one dimensional
electron gas (1DEG) in the presence of an external magnetic field. We derive
the inter-and intra-band magnetoplasmon spectrum within the Self Consistent
Field (SCF) approach. In this work we focus on magnetoplasmon oscillations in
this system and as such results are presented for the intra-Landau-band
magnetoplasmon spectrum that exhibits oscillatory behavior, these oscillations
are not with constant period in 1/B and are significantly effected at low B and
corresponding high 1/B.


title: Modeling the Fermi arc in underdoped cuprates

abstract:
  Angle resolved photoemission data in the pseudogap phase of underdoped
cuprates have revealed the presence of a truncated Fermi surface consisting of
Fermi arcs. We compare a number of proposed models for the arcs, and find that
the one that best models the data is a d-wave energy gap with a lifetime
broadening whose temperature dependence is suggestive of fluctuating pairs.


title: Weighted projective spaces and minimal nilpotent orbits

abstract:
  We investigate (twisted) rings of differential operators on the resolution of
singularities of a particular irreducible component of the (Zarisky) closure of
the minimal orbit $\bar O_{\mathrm{min}}$ of $\mathfrak{sp}_{2n}$, intersected
with the Borel subalgebra $\mathfrak n_+$ of $\mathfrak{sp}_{2n}$, using toric
geometry and show that they are homomorphic images of a subalgebra of the
Universal Enveloping Algebra (UEA) of $\mathfrak{sp}_{2n}$, which contains the
maximal parabolic subalgebra $\mathfrak p$ determining the minimal nilpotent
orbit. Further, using Fourier transforms on Weyl algebras, we show that
(twisted) rings of well-suited weighted projective spaces are obtained from the
same subalgebra. Finally, investigating this subalgebra from the
representation-theoretical point of view, we find new primitive ideals and
rediscover old ones for the UEA of $\mathfrak{sp}_{2n}$ coming from the
aforementioned resolution of singularities.


title: On the Structure of General Mean-Variance Hedging Strategies

abstract:
  We provide a new characterization of mean-variance hedging strategies in a
general semimartingale market. The key point is the introduction of a new
probability measure $P^{\star}$ which turns the dynamic asset allocation
problem into a myopic one. The minimal martingale measure relative to
$P^{\star}$ coincides with the variance-optimal martingale measure relative to
the original probability measure $P$.


title: Age, metallicity and alpha-elements abundance in stellar population

abstract:
  We built modelled spectra of stellar population at high resolution and with
variable alpha-elements enhancements. Analysing spectra of Galactic globular
clusters we show that it is possible to derive reliably and efficiently [Mg/Fe]
using spectra integrated along the line-of-sight. These detailed measurements
open perspectives for investigating the enrichment process on galaxies and star
clusters.


title: Energy conservation and scaling violations in particle production

abstract:
  We use a simple Colour Glass Condensate/String Percolation Model argument to
show the existence, due to energy conservation, of bounds to the violation of
Feynman scaling and limiting fragmentation.


title: Dynamics of Jackson networks: perturbation theory

abstract:
  We introduce a new formalism for dealing with networks of queues. The
formalism is based on the Doi-Peliti second quantization method for reaction
diffusion systems. As a demonstration of the method's utility we compute
perturbatively the different time busy-busy correlations between two servers in
a Jackson network.


title:
Characters of the Unitarizable Highest Weight Modules over the N=2
  Superconformal Algebras

abstract:
  The characters of the unitarizable highest weight modules over the N=2
superconformal algebras are presented. This is a slightly extended version of
an Encyclopedia entry.


title: On asymptotics of eigenvectors of large sample covariance matrix

abstract:
  Let \{$X_{ij}$\}, $i,j=...,$ be a double array of i.i.d. complex random
variables with $EX_{11}=0,E|X_{11}|^2=1$ and $E|X_{11}|^4<\infty$, and let
$A_n=\frac{1}{N}T_n^{{1}/{2}}X_nX_n^*T_n^{{1}/{2}}$, where $T_n^{{1}/{2}}$ is
the square root of a nonnegative definite matrix $T_n$ and $X_n$ is the
$n\times N$ matrix of the upper-left corner of the double array. The matrix
$A_n$ can be considered as a sample covariance matrix of an i.i.d. sample from
a population with mean zero and covariance matrix $T_n$, or as a multivariate
$F$ matrix if $T_n$ is the inverse of another sample covariance matrix. To
investigate the limiting behavior of the eigenvectors of $A_n$, a new form of
empirical spectral distribution is defined with weights defined by eigenvectors
and it is then shown that this has the same limiting spectral distribution as
the empirical spectral distribution defined by equal weights. Moreover, if
\{$X_{ij}$\} and $T_n$ are either real or complex and some additional moment
assumptions are made then linear spectral statistics defined by the
eigenvectors of $A_n$ are proved to have Gaussian limits, which suggests that
the eigenvector matrix of $A_n$ is nearly Haar distributed when $T_n$ is a
multiple of the identity matrix, an easy consequence for a Wishart matrix.


title:
Are the spectra of geometrical operators in Loop Quantum Gravity really
  discrete?

abstract:
  One of the celebrated results of Loop Quantum Gravity (LQG) is the
discreteness of the spectrum of geometrical operators such as length, area and
volume operators. This is an indication that Planck scale geometry in LQG is
discontinuous rather than smooth. However, there is no rigorous proof thereof
at present, because the afore mentioned operators are not gauge invariant, they
do not commute with the quantum constraints. The relational formalism in the
incarnation of Rovelli's partial and complete observables provides a possible
mechanism for turning a non gauge invariant operator into a gauge invariant
one. In this paper we investigate whether the spectrum of such a physical, that
is gauge invariant, observable can be predicted from the spectrum of the
corresponding gauge variant observables. We will not do this in full LQG but
rather consider much simpler examples where field theoretical complications are
absent. We find, even in those simpler cases, that kinematical discreteness of
the spectrum does not necessarily survive at the gauge invariant level. Whether
or not this happens depends crucially on how the gauge invariant completion is
performed. This indicates that ``fundamental discreteness at Planck scale in
LQG'' is far from established. To prove it, one must provide the detailed
construction of gauge invariant versions of geometrical operators.


title:
Saffman-Taylor streamers: mutual finger interaction in an electric
  breakdown

abstract:
  Bunches of streamers form the early stages of sparks and lightning but theory
presently concentrates on single streamers or on coarse approximations of whole
breakdown trees. Here a periodic array of interacting streamer discharges in a
strong homogeneous electric field is studied in PDE approximation in two
dimensions. If the period of the streamer array is small enough, the streamers
do not branch, but approach uniform translation. When the streamers are close
to the branching regime, the enhanced field at the tip of the streamer is close
to $2 E_{\infty}$, where $E_{\infty}$ is the homogeneous field applied between
the electrodes. We discuss a moving boundary approximation to the set of PDEs.
This moving boundary model turns out to be essentially the same as the one for
two-fluid Hele-Shaw flows. In two dimensions, this model possesses a known
analytical solution. The shape of the 2D interacting streamers in uniform
motion obtained from the PDE simulations is actually well fitted by the
analytically known ``selected Saffman-Taylor finger''. This finding helps to
understand streamer interactions and raises new questions on the general theory
of finger selection in moving boundary problems.


title: Hybrid Branching-Time Logics

abstract:
  Hybrid branching-time logics are introduced as extensions of CTL-like logics
with state variables and the downarrow-binder. Following recent work in the
linear framework, only logics with a single variable are considered. The
expressive power and the complexity of satisfiability of the resulting logics
is investigated.
  As main result, the satisfiability problem for the hybrid versions of several
branching-time logics is proved to be 2EXPTIME-complete. These branching-time
logics range from strict fragments of CTL to extensions of CTL that can talk
about the past and express fairness-properties. The complexity gap relative to
CTL is explained by a corresponding succinctness result.
  To prove the upper bound, the automata-theoretic approach to branching-time
logics is extended to hybrid logics, showing that non-emptiness of alternating
one-pebble Buchi tree automata is 2EXPTIME-complete.


title:
The ALFA Zone of Avoidance Survey: Results from the Precursor
  Observations

abstract:
  The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA) will map
1350-1800 square degrees at low Galactic latitude, providing HI spectra for
galaxies in regions of the sky where our knowledge of local large scale
structure remains incomplete, owing to obscuration from dust and high stellar
confusion near the Galactic plane. Because of these effects, a substantial
fraction of the galaxies detected in the survey will have no optical or
infrared counterparts. However, near infrared follow up observations of ALFA
ZOA sources found in regions of lowest obscuration could reveal whether some of
these sources could be objects in which little or no star formation has taken
place ("dark galaxies"). We present here the results of ALFA ZOA precursor
observations on two patches of sky totaling 140 square degrees (near l=40
degrees, and l=192 degrees). We have measured HI parameters for detections from
these observations, and cross-correlated with the NASA/IPAC Extragalactic
Database (NED). A significant fraction of the objects have never been detected
at any wavelength. For those galaxies that have been previously detected, a
significant fraction have no previously known redshift, and no previous HI
detection.


title: Design: One, but in different forms

abstract:
  This overview paper defends an augmented cognitively oriented generic-design
hypothesis: there are both significant similarities between the design
activities implemented in different situations and crucial differences between
these and other cognitive activities; yet, characteristics of a design
situation (related to the design process, the designers, and the artefact)
introduce specificities in the corresponding cognitive activities and
structures that are used, and in the resulting designs. We thus augment the
classical generic-design hypothesis with that of different forms of designing.
We review the data available in the cognitive design research literature and
propose a series of candidates underlying such forms of design, outlining a
number of directions requiring further elaboration.


title:
Differential inequalities of continuous functions and removing
  singularities of Rado type for J-holomorphic maps

abstract:
  We consider a continuous function $f$ on a domain in $\mathbf C^n$ satisfying
the inequality that $|\bar \partial f|\leq |f|$ off its zero set. The main
conclusion is that the zero set of $f$ is a complex variety.
  We also obtain removable singularity theorem of Rado type for J-holomorphic
maps. Let $\Omega$ be an open subset in $\mathbf C$ and let $E$ be a closed
polar subset of $\Omega$. Let $u$ be a continuous map from $\Omega$ into an
almost complex manifold $(M,J)$ with $J$ of class $C^1$. We show that if $u$ is
J-holomorphic on $\Omega\setminus E$ then it is J-holomorphic on $\Omega$.


title: Tropical bases by regular projections

abstract:
  We consider the tropical variety $\mathcal{T}(I)$ of a prime ideal $I$
generated by the polynomials $f_1, ..., f_r$ and revisit the regular projection
technique introduced by Bieri and Groves from a computational point of view. In
particular, we show that $I$ has a short tropical basis of cardinality at most
$r + \codim I + 1$ at the price of increased degrees, and we provide a
computational description of these bases.


title: Search for Extra Dimensions at CDF

abstract:
  This poster, presented at the 2006 Duke Hadron Collider Symposium, presents
the results from searches for large extra dimensions, as proposed by
Arkani-Hamed, Dimopoulos and Dvali (ADD), and Randall-Sundrum (RS) model warped
extra dimensions, at CDF.


title: Light quark mass effects in the on-shell renormalization constants

abstract:
  We compute the three-loop relation between the pole and the minimally
subtracted quark mass allowing for virtual effects from a second massive quark.
We also consider the analogue effects for the on-shell wave function
renormalization constant.


title: Conical limit sets and continued fractions

abstract:
  Inspired by questions of convergence in continued fraction theory, Erd\H{o}s,
Piranian and Thron studied the possible sets of divergence for arbitrary
sequences of M\"obius maps acting on the Riemann sphere, $S^2$. By identifying
$S^2$ with the boundary of three-dimensional hyperbolic space, $H^3$, we show
that these sets of divergence are precisely the sets that arise as conical
limit sets of subsets of $H^3$. Using hyperbolic geometry, we give simple
geometric proofs of the theorems of Erd\H{o}s, Piranian and Thron that
generalise to arbitrary dimensions. New results are also obtained about the
class of conical limit sets, for example, that it is closed under locally
quasisymmetric homeomorphisms. Applications are given to continued fractions.


title:
Parameters of the lowest order chiral Lagrangian from fermion
  eigenvalues

abstract:
  Recent advances in Random Matrix Theory enable one to determine the
pseudoscalar decay constant from the response of eigenmodes of quenched
fermions to an imaginary isospin chemical potential. We perform a pilot test of
this idea, from simulations with two flavors of dynamical overlap fermions.


title: Perturbative Vacua from IIB Matrix Model

abstract:
  It has not been clarified whether a matrix model can describe various vacua
of string theory. In this paper, we show that the IIB matrix model includes
type IIA string theory. In the naive large N limit of the IIB matrix model,
configurations consisting of simultaneously diagonalizable matrices form a
moduli space, although the unique vacuum would be determined by complicated
dynamics. This moduli space should correspond to a part of perturbatively
stable vacua of string theory. Actually, one point on the moduli space
represents type IIA string theory. Instead of integrating over the moduli space
in the path-integral, we can consider each of the simultaneously diagonalizable
configurations as a background and set the fluctuations of the diagonal
elements to zero. Such procedure is known as quenching in the context of the
large N reduced models. By quenching the diagonal elements of the matrices to
an appropriate configuration, we show that the quenched IIB matrix model is
equivalent to the two-dimensional large N N=8 super Yang-Mills theory on a
cylinder. This theory is nothing but matrix string theory and is known to be
equivalent to type IIA string theory. As a result, we find the manner to take
the large N limit in the IIB matrix model.


title: A distance based test on random trees

abstract:
  In this paper, we address the question of comparison between populations of
trees. We study an statistical test based on the distance between empirical
mean trees, as an analog of the two sample z statistic for comparing two means.
Despite its simplicity, we can report that the test is quite powerful to
separate distributions with different means but it does not distinguish between
different populations with the same mean, a more complicated test should be
applied in that setting. The performance of the test is studied via simulations
on Galton-Watson branching processes. We also show an application to a real
data problem in genomics.


title: Event-by-event Simulation of Quantum Cryptography Protocols

abstract:
  We present a new approach to simulate quantum cryptography protocols using
event-based processes. The method is validated by simulating the BB84 protocol
and the Ekert protocol, both without and with the presence of an eavesdropper.


title: Graphite and graphene as perfect spin filters

abstract:
  Based upon the observations (i) that their in-plane lattice constants match
almost perfectly and (ii) that their electronic structures overlap in
reciprocal space for one spin direction only, we predict perfect spin filtering
for interfaces between graphite and (111) fcc or (0001) hcp Ni or Co. The spin
filtering is quite insensitive to roughness and disorder. The formation of a
chemical bond between graphite and the open $d$-shell transition metals that
might complicate or even prevent spin injection into a single graphene sheet
can be simply prevented by dusting Ni or Co with one or a few monolayers of Cu
while still preserving the ideal spin injection property.


title:
The Peculiar Horizontal Branch Morphology of the Galactic Globular
  Clusters NGC 6388 and NGC 6441: new insights from UV observations

abstract:
  In this paper we present multiband optical and UV Hubble Space Telescope
photometry of the two Galactic globular clusters NGC 6388 and NGC 6441. We have
obtained the first UV color-magnitude diagrams for NGC 6388 and NGC 6441. These
diagrams confirm previous results, obtained in optical bands, about the
presence of a sizeable stellar population of extremely hot horizontal branch
stars. At least in NGC 6388, we find a clear indication that at the hot end of
the horizontal branch the distribution of stars forms a hook-like feature,
closely resembling those observed in NGC 2808 and Omega Centauri. We briefly
review the theoretical scenarios that have been suggested for interpreting this
observational feature. We also investigate the tilted horizontal branch
morphology and provide further evidence that supports early suggestions that
this feature cannot be interpreted as an effect of differential reddening. We
show that a possible solution of the puzzle is to assume that a small fraction
- ranging between 10-20% - of the stellar population in the two clusters is
strongly helium enriched (Y=0.40 in NGC 6388 and Y=0.35 in NGC 6441). The
occurrence of a spread in the He abundance between the canonical value (Y=0.26)
and the quoted upper limits can significantly help in explaining the whole
morphology of the horizontal branch and the pulsational properties of the
variable stars in the target clusters.


title: Lorentz Violation for Photons and Ultra-High Energy Cosmic Rays

abstract:
  Lorentz symmetry breaking at very high energies may lead to photon dispersion
relations of the form omega^2=k^2+xi_n k^2(k/M_Pl)^n with new terms suppressed
by a power n of the Planck mass M_Pl. We show that first and second order terms
of size xi_1 > 10^(-14) and xi_2 < -10^(-6), respectively, would lead to a
photon component in cosmic rays above 10^(19) eV that should already have been
detected, if corresponding terms for electrons and positrons are significantly
smaller. This suggests that Lorentz invariance breakings suppressed up to
second order in the Planck scale are unlikely to be phenomenologically viable
for photons.


title:
Measurement of the Branching Fractions of Exclusive anti-B -> D/D*/D(*)
  pi l- anti-nu_l Decays in Events Tagged by a Fully Reconstructed B Meson

abstract:
  We present a measurement of the branching fractions for anti-B -> D/D*/D(*)
pi l^- anti-nu_l decays based on 341.1 fb-1 of data collected at the
Upsilon(4S) resonance with the BaBar detector at the pep-II e^+e^- storage
rings. Events are tagged by fully reconstructing one of the B mesons in a
hadronic decay mode. We obtain BF (B^- -> D^0 l^- anti-nu_l) = (2.33 +/-
0.09(stat.) +/- 0.09(syst.))%, BF (B^- -> D^*0 l^- anti-nu_l) = (5.83 +/-
0.15(stat.) +/- 0.30(syst.))%, BF (B0bar -> D^+ l^- anti-nu_l) = (2.21 +/-
0.11(stat.) +/- 0.12(syst.))%,
  BF (B0bar -> D^*+ l^- anti-nu_l) =
  (5.49 +/- 0.16(stat.) +/- 0.25(syst.))%, BF
  (B^- -> D^+ pi^- l^- anti-nu_l) = (0.42 +/- 0.06(stat.)
  +/- 0.03(syst.))%, BF (B^- -> D^*+ pi^- l^- anti-nu_l) = (0.59 +/-
0.05(stat.) +/- 0.04(syst.))%, BF (B0bar -> D^0 pi^+ l^- anti-nu_l) = (0.43 +/-
0.08(stat.) +/- 0.03(syst.))% and BF (B0bar -> D^*0 pi^+ l^- anti-nu_l) = (0.48
+/- 0.08(stat.) +/- 0.04(syst.))%.


title: The infinite valley for a recurrent random walk in random environment

abstract:
  We consider a one-dimensional recurrent random walk in random environment
(RWRE). We show that the - suitably centered - empirical distributions of the
RWRE converge weakly to a certain limit law which describes the stationary
distribution of a random walk in an infinite valley. The construction of the
infinite valley goes back to Golosov. As a consequence, we show weak
convergence for both the maximal local time and the self-intersection local
time of the RWRE and also determine the exact constant in the almost sure upper
limit of the maximal local time.


title: Classical behavior of deformed sine-Gordon models

abstract:
  In this work we deform the phi^4 model with distinct deformation functions,
to propose a diversity of sine-Gordon-like models. We investigate the proposed
models and we obtain all the topological solutions they engender. In
particular, we introduce non-polynomial potentials which support some exotic
two-kink solutions.


title: The inner automorphism 3-group of a strict 2-group

abstract:
  Any group $G$ gives rise to a 2-group of inner automorphisms,
$\mathrm{INN}(G)$. It is an old result by Segal that the nerve of this is the
universal $G$-bundle. We discuss that, similarly, for every 2-group $G_{(2)}$
there is a 3-group $\mathrm{INN}(G_{(2)})$ and a slightly smaller 3-group
$\mathrm{INN}_0(G_{(2)})$ of inner automorphisms. We describe these for
$G_{(2)}$ any strict 2-group, discuss how $\mathrm{INN}_0(G_{(2)})$ can be
understood as arising from the mapping cone of the identity on $G_{(2)}$ and
show that its underlying 2-groupoid structure fits into a short exact sequence
$G_{(2)} \to \mathrm{INN}_0(G_{(2)}) \to \Sigma G_{(2)}$.
  As a consequence, $\mathrm{INN}_0(G_{(2)})$ encodes the properties of the
universal $G_{(2)}$ 2-bundle.


title: Green functions and Euclidean fields near the bifurcate Killing horizon

abstract:
  We approximate a Euclidean version of a D+1 dimensional manifold with a
bifurcate Killing horizon by a product of a two-dimensional Rindler space and a
D-1 dimensional manifold M. We obtain approximate formulas for the Green
functions. We study the behaviour of Green functions near the horizon and their
dimensional reduction. We show that if M is compact then the massless minimally
coupled quantum field contains a zero mode which is a conformal invariant free
field on R^2. Then, the Green function near the horizon can be approximated by
the Green function of the two-dimensional quantum field theory. The correction
term is exponentially small away from the horizon. If the volume of a geodesic
ball is growing to infinity with its radius then the Green function cannot be
approximated by a two-dimensional one.


title: Production of long-lived atomic vapor inside high-density buffer gas

abstract:
  Atomic vapor of four different paramagnetic species: gold, silver, lithium,
and rubidium, is produced and studied inside several buffer gases: helium,
nitrogen, neon, and argon. The paramagnetic atoms are injected into the buffer
gas using laser ablation. Wires with diameters 25 $\mu$m, 50 $\mu$m, and 100
$\mu$m are used as ablation targets for gold and silver, bulk targets are used
for lithium and rubidium. The buffer gas cools and confines the ablated atoms,
slowing down their transport to the cell walls. Buffer gas temperatures between
20 K and 295 K, and densities between $10^{16}$ cm$^{-3}$ and $2\times10^{19}$
cm$^{-3}$ are explored. Peak paramagnetic atom densities of $10^{11}$ cm$^{-3}$
are routinely achieved. The longest observed paramagnetic vapor density decay
times are 110 ms for silver at 20 K and 4 ms for lithium at 32 K. The
candidates for the principal paramagnetic-atom loss mechanism are impurities in
the buffer gas, dimer formation and atom loss on sputtered clusters.


title: Fermi surface nesting and the origin of Charge Density Waves in metals

abstract:
  The concept of a CDW induced by Fermi-surface nesting originated from the
Peierls idea of electronic instabilities in purely 1D metals and is now often
applied to charge ordering in real low-dimensional materials. The idea is that
if Fermi surface contours coincide when shifted along the observed CDW wave
vector, then the CDW is considered to be nesting-derived. We show that in most
cases this procedure has no predictive power, since Fermi surfaces either do
not nest at the right wave vector, or nest more strongly at the wrong vector.
We argue that only a tiny fraction, if any, of the observed charge ordering
phase transitions are true analogues of the Peierls instability because
electronic instabilities are easily destroyed by even small deviations from
perfect nesting conditions. Using prototypical CDW materials NbSe$_2$,
TaSe$_2$, and CeTe$_3$, we show that such conditions are hardly ever fulfilled,
and that the CDW phases are actually structural phase transitions, driven by
the concerted action of electronic and ionic subsystems, \textit{i.e.,}
\textbf{q}-dependent electron-phonon coupling plays an indispensable part. We
also show mathematically that the original Peierls construction is so fragile
as to be unlikely to apply to real materials. We argue that no meaningful
distinction between a CDW and an incommensurate lattice transition exists.


title:
A universal deformation formula for Connes-Moscovici's Hopf algebra
  without any projective structure

abstract:
  We construct a universal deformation formula for Connes-Moscovici's Hopf
algebra without any projective structure using Fedosov's quantization of
symplectic diffeomorphisms.


title:
Social diversity and promotion of cooperation in the spatial prisoner's
  dilemma game

abstract:
  The diversity in wealth and social status is present not only among humans,
but throughout the animal world. We account for this observation by generating
random variables that determ ine the social diversity of players engaging in
the prisoner's dilemma game. Here the term social diversity is used to address
extrinsic factors that determine the mapping of game pay offs to individual
fitness. These factors may increase or decrease the fitness of a player
depending on its location on the spatial grid. We consider different
distributions of extrin sic factors that determine the social diversity of
players, and find that the power-law distribution enables the best promotion of
cooperation. The facilitation of the cooperative str ategy relies mostly on the
inhomogeneous social state of players, resulting in the formation of
cooperative clusters which are ruled by socially high-ranking players that are
able to prevail against the defectors even when there is a large temptation to
defect. To confirm this, we also study the impact of spatially correlated
social diversity and find that coopera tion deteriorates as the spatial
correlation length increases. Our results suggest that the distribution of
wealth and social status might have played a crucial role by the evolution of
cooperation amongst egoistic individuals.


title: Orbits in the Field of a Gravitating Magnetic Monopole

abstract:
  Orbits of test particles and light rays are an important tool to study the
properties of space-time metrics. Here we systematically study the properties
of the gravitational field of a globally regular magnetic monopole in terms of
the geodesics of test particles and light. The gravitational field depends on
two dimensionless parameters, defined as ratios of the characteristic mass
scales present. For critical values of these parameters the resulting metric
coefficients develop a singular behavior, which has profound influence on the
properties of the resulting space-time and which is clearly reflected in the
orbits of the test particles and light rays.


title: r-Process Nucleosynthesis in Shocked Surface Layers of O-Ne-Mg Cores

abstract:
  We demonstrate that rapid expansion of the shocked surface layers of an
O-Ne-Mg core following its collapse can result in r-process nucleosynthesis. As
the supernova shock accelerates through these layers, it makes them expand so
rapidly that free nucleons remain in disequilibrium with alpha-particles
throughout most of the expansion. This allows heavy r-process isotopes
including the actinides to form in spite of the very low initial neutron excess
of the matter. We estimate that yields of heavy r-process nuclei from this site
may be sufficient to explain the Galactic inventory of these isotopes.


title:
Efficiency of quantum Monte Carlo impurity solvers for dynamical
  mean-field theory

abstract:
  Since the inception of the dynamical mean-field theory, numerous numerical
studies have relied on the Hirsch-Fye quantum Monte Carlo (HF-QMC) method for
solving the associated impurity problem. Recently developed continuous-time
algorithms (CT-QMC) avoid the Trotter discretization error and allow for faster
configuration updates, which makes them candidates for replacing HF-QMC. We
demonstrate, however, that a state-of-the-art implementation of HF-QMC (with
extrapolation of discretization delta_tau -> 0) is competitive with CT-QMC. A
quantitative analysis of Trotter errors in HF-QMC estimates and of appropriate
delta_tau values is included.


title: Dark-State Polaritons in Single- and Double-$\Lambda$ Media

abstract:
  We derive the properties of polaritons in single-$\Lambda$ and
double-$\Lambda$ media using a microscopic equation-of-motion technique. In
each case, the polaritonic dispersion relation and composition arise from a
matrix eigenvalue problem for arbitrary control field strengths. We show that
the double-$\Lambda$ medium can be used to up- or down-convert single photons
while preserving quantum coherence. The existence of a dark-state polariton
protects this single-photon four-wave mixing effect against incoherent decay of
the excited atomic states. The efficiency of this conversion is limited mainly
by the sample size and the lifetime of the metastable state.


title:
Superconducting islands, phase fluctuations and the
  superconductor-insulator transition

abstract:
  Properties of disordered thin films are discussed based on the viewpoint that
superconducting islands are formed in the system. These lead to superconducting
correlations confined in space, which are known to form spontaneously in thin
films. Application of a perpendicular magnetic field can drive the system from
the superconducting state (characterized by phase-rigidity between the sample
edges) to an insulating state in which there are no phase-correlations between
the edges of the system. On the insulating side the existence of
superconducting islands leads to a non-monotonic magnetoresistance. Several
other features seen in experiment are explained.


title: Validation of the new Hipparcos reduction

abstract:
  Context.A new reduction of the astrometric data as produced by the Hipparcos
mission has been published, claiming accuracies for nearly all stars brighter
than magnitude Hp = 8 to be better, by up to a factor 4, than in the original
catalogue. Aims.The new Hipparcos astrometric catalogue is checked for the
quality of the data and the consistency of the formal errors as well as the
possible presence of error correlations. The differences with the earlier
publication are explained. Methods. The internal errors are followed through
the reduction process, and the external errors are investigated on the basis of
a comparison with radio observations of a small selection of stars, and the
distribution of negative parallaxes. Error correlation levels are investigated
and the reduction by more than a factor 10 as obtained in the new catalogue is
explained. Results.The formal errors on the parallaxes for the new catalogue
are confirmed. The presence of a small amount of additional noise, though
unlikely, cannot be ruled out. Conclusions. The new reduction of the Hipparcos
astrometric data provides an improvement by a factor 2.2 in the total weight
compared to the catalogue published in 1997, and provides much improved data
for a wide range of studies on stellar luminosities and local galactic
kinematics.


title:
Measurement of the $B^0\to X_{u}^- \ell^+ {\nu_\ell} $ decays near the
  kinematic endpoint of the lepton spectrum and search for violation of isospin
  symmetry

abstract:
  We present the first measurement of the $B^0\to X_{u}^- \ell^+ {\nu_\ell} $
partial branching fraction in the end-point region of the lepton momentum
spectrum, above the threshold for $B\to X_c\ell {\nu_\ell}$ decays. The
analysis is based on a sample of 383 million $\Upsilon(4S)$ decays into $B{\bar
B}$ pairs collected with the {\sc BaBar} detector at the PEP-II $e^+e^-$
storage rings. We select $B^0{\bar B}^0$ events by partially reconstructing one
$\B$ meson via the ${\bar B}^0\to D^{*+} \ell^- \bar{\nu}_\ell$ decays then
select $B^0\to X_{u}^- \ell^+ {\nu_\ell} $ decays identifying a second high
momentum lepton. In the momentum interval ranging from 2.3 to 2.6 GeV/c we
measure the partial branching fraction $\Delta{\cal B}(B^0\to
X_u\ell\nu)=(1.30\pm0.21_{stat}\pm0.07_{syst})\times 10^{-4}$ where the first
error is statistical and the second is systematic. By comparing this
measurement with the one obtained from untagged B decays we obtain
$R^{+/0}=\Delta{\cal B}(B^0\to X_u\ell\nu)/\Delta{\cal B}(B^+\to X_u\ell\nu)=
1.18 \pm 0.35_{stat} \pm 0.17_{syst}$. Using this measurement we extract a
limit on the contributions from processes breaking isospin symmetry in
charmless semileptonic B decays.


title:
Treatment of Linear and Nonlinear Dielectric Property of Molecular
  Monolayer and Submonolayer with Microscopic Dipole Lattice Model: I. Second
  Harmonic Generation and Sum-Frequency Generation

abstract:
  In the currently accepted models of the nonlinear optics, the nonlinear
radiation was treated as the result of an infinitesimally thin polarization
sheet layer, and a three layer model was generally employed. The direct
consequence of this approach is that an apriori dielectric constant, which
still does not have a clear definition, has to be assigned to this polarization
layer. Because the Second Harmonic Generation (SHG) and the Sum-Frequency
Generation vibrational Spectroscopy (SFG-VS) have been proven as the sensitive
probes for interfaces with the submonolayer coverage, the treatment based on
the more realistic discrete induced dipole model needs to be developed. Here we
show that following the molecular optics theory approach the SHG, as well as
the SFG-VS, radiation from the monolayer or submonolayer at an interface can be
rigorously treated as the radiation from an induced dipole lattice at the
interface. In this approach, the introduction of the polarization sheet is no
longer necessary. Therefore, the ambiguity of the unaccounted dielectric
constant of the polarization layer is no longer an issue. Moreover, the
anisotropic two dimensional microscopic local field factors can be explicitly
expressed with the linear polarizability tensors of the interfacial molecules.
Based on the planewise dipole sum rule in the molecular monolayer, crucial
experimental tests of this microscopic treatment with SHG and SFG-VS are
discussed. Many puzzles in the literature of surface SHG and SFG spectroscopy
studies can also be understood or resolved in this framework. This new
treatment may provide a solid basis for the quantitative analysis in the
surface SHG and SFG studies.


title: Biperiodic superlattices and the transparent state

abstract:
  Coquelin et al. studied biperiodic semiconductor superlattices, which consist
of alternating cell types, one with wide wells and the other narrow wells,
separated by equal strength barriers. If the wells were identical, it would be
a simply periodic system of $N = 2n$ half-cells. When asymmetry is introduced,
an allowed band splits at the Bragg point into two disjoint allowed bands. The
Bragg resonance turns into a transparent state located close to the band edge
of the lower(upper) band when the first(second) well is the wider. Analysis of
this system gives insight into how band splitting occurs. Further we consider
semi-periodic systems having $N= 2n+1$ half-cells. Surprisingly these have very
different transmission properties, with an envelope of maximum transmission
probability that crosses the envelope of minima at the transparent point.


title:
Optimal execution strategies in limit order books with general shape
  functions

abstract:
  We consider optimal execution strategies for block market orders placed in a
limit order book (LOB). We build on the resilience model proposed by Obizhaeva
and Wang (2005) but allow for a general shape of the LOB defined via a given
density function. Thus, we can allow for empirically observed LOB shapes and
obtain a nonlinear price impact of market orders. We distinguish two
possibilities for modeling the resilience of the LOB after a large market
order: the exponential recovery of the number of limit orders, i.e., of the
volume of the LOB, or the exponential recovery of the bid-ask spread. We
consider both of these resilience modes and, in each case, derive explicit
optimal execution strategies in discrete time. Applying our results to a
block-shaped LOB, we obtain a new closed-form representation for the optimal
strategy, which explicitly solves the recursive scheme given in Obizhaeva and
Wang (2005). We also provide some evidence for the robustness of optimal
strategies with respect to the choice of the shape function and the
resilience-type.