title: Yang-Mills equation for stable Higgs sheaves

abstract:
  We establish a Kobayashi-Hitchin correspondence for the stable Higgs sheaves
on a compact Kaehler manifold. Using it, we also obtain a Kobayashi-Hitchin
correspondence for the stable Higgs G-sheaves, where G is any complex reductive
linear algebraic group.


title: Twin "Fano-Snowflakes" Over the Smallest Ring of Ternions

abstract:
  Given a finite associative ring with unity, $R$, any free (left) cyclic
submodule (FCS) generated by a $uni$modular ($n+1$)-tuple of elements of $R$
represents a point of the $n$-dimensional projective space over $R$. Suppose
that $R$ also features FCSs generated by ($n+1$)-tuples that are $not$
unimodular: what kind of geometry can be ascribed to such FCSs? Here, we
(partially) answer this question for $n=2$ when $R$ is the (unique)
non-commutative ring of order eight. The corresponding geometry is dubbed a
"Fano-Snowflake" due to its diagrammatic appearance and the fact that it
contains the Fano plane in its center. There exist, in fact, two such
configurations -- each being tied to either of the two maximal ideals of the
ring -- which have the Fano plane in common and can, therefore, be viewed as
twins. Potential relevance of these noteworthy configurations to quantum
information theory and stringy black holes is also outlined.


title:
Extension of the SAEM algorithm for nonlinear mixed models with two
  levels of random effects

abstract:
  This article focuses on parameter estimation of multi-levels nonlinear mixed
effects models (MNLMEMs). These models are used to analyze data presenting
multiple hierarchical levels of grouping (cluster data, clinical trials with
several observation periods,...). The variability of the individual parameters
of the regression function is thus decomposed as a between-sub ject variability
and higher levels of variability (for example within-sub ject variability). We
propose maximum likelihood estimates of parameters of those MNLMEMs with two
levels of random effects, using an extension of the SAEM-MCMC algorithm. The
extended SAEM algorithm is split into an explicit direct EM algorithm and a
stochastic EM part. Compared to the original algorithm, additional sufficient
statistics have to be approximated by relying on the conditional distribution
of the second level of random effects. This estimation method is evaluated on
pharmacokinetic cross-over simulated trials, mimicking theophyllin
concentration data. Results obtained on those datasets with either the SAEM
algorithm or the FOCE algorithm (implemented in the nlme function of R
software) are compared: biases and RMSEs of almost all the SAEM estimates are
smaller than the FOCE ones. Finally, we apply the extended SAEM algorithm to
analyze the pharmacokinetic interaction of tenofovir on atazanavir, a novel
protease inhibitor, from the ANRS 107-Puzzle 2 study. A significant decrease of
the area under the curve of atazanavir is found in patients receiving both
treatments.


title:
Stabilising a nulling interferometer using optical path difference
  dithering

abstract:
  Context. Nulling interferometry has been suggested as the underlying
principle for the Darwin and TPF-I exoplanet research missions. Aims. There are
constraints both on the mean value of the nulling ratio, and on its stability.
Instrument instability noise is most detrimental to the stability of the
nulling performance. Methods. We applied a modified version of the classical
dithering technique to the optical path difference in the scientific beam.
Results. Using only this method, we repeatedly stabilised the dark fringe for
several hours. This method alone sufficed to remove the 1/ f component of the
noise in our setup for periods of 10 minutes, typically. These results indicate
that performance stability may be maintained throughout the long-duration data
acquisitions typical of exoplanet spectroscopy. Conclusions. We suggest that
further study of possible stabilisation strategies should be an integral part
of Darwin/TPF-I research and development


title: Periodic unique beta-expansions: the Sharkovskii ordering

abstract:
  Let $\beta\in(1,2)$. Each $x\in[0,\frac{1}{\beta-1}]$ can be represented in
the form \[ x=\sum_{k=1}^\infty \epsilon_k\beta^{-k}, \] where
$\epsilon_k\in\{0,1\}$ for all $k$ (a $\beta$-expansion of $x$). If
$\beta>\frac{1+\sqrt5}{2}$, then, as is well known, there always exist
$x\in(0,\frac1{\beta-1})$ which have a unique $\be$-expansion.
  In the present paper we study (purely) periodic unique $\beta$-expansions and
show that for each $n\ge2$ there exists $\beta_n\in[\frac{1+\sqrt5}{2},2)$ such
that there are no unique periodic $\beta$-expansions of smallest period $n$ for
$\beta\le\beta_n$ and at least one such expansion for $\beta>\beta_n$.
  Furthermore, we prove that $\beta_k<\beta_m$ if and only if $k$ is less than
$m$ in the sense of the Sharkovski\u{\i} ordering. We give two proofs of this
result, one of which is independent, and the other one links it to the dynamics
of a family of trapezoidal maps.


title:
Solar forced Dansgaard-Oeschger events and their phase relation with
  solar proxies

abstract:
  North Atlantic climate during glacial times was characterized by
large-amplitude switchings, the Dansgaard-Oeschger (DO) events, with an
apparent tendency to recur preferably in multiples of about 1470 years. Recent
work interpreted these intervals as resulting from a subharmonic response of a
highly nonlinear system to quasi-periodic solar forcing plus noise. This
hypothesis was challenged as inconsistent with the observed variability in the
phase relation between proxies of solar activity and Greenland climate. Here we
reject the claim of inconsistency by showing that this phase variability is a
robust, generic feature of the nonlinear dynamics of DO events, as described by
a model. This variability is expected from the fact that the events are
threshold crossing events, resulting from a cooperative process between the
periodic forcing and the noise. This process produces a fluctuating phase
relation with the periodic forcing, consistent with proxies of solar activity
and Greenland climate.


title:
Interpreting the Kustaanheimo-Stiefel transform in gravitational
  dynamics

abstract:
  The Kustaanheimo-Stiefel transform turns a gravitational two-body problem
into a harmonic oscillator, by going to four dimensions. In addition to the
mathematical-physics interest, the KS transform has proved very useful in
N-body simulations, where it helps handle close encounters. Yet the formalism
remains somewhat arcane, with the role of the extra dimension being especially
mysterious. This paper shows how the basic transformation can be interpreted as
a rotation in three dimensions. For example, if we slew a telescope from zenith
to a chosen star in one rotation, we can think of the rotation axis and angle
as the KS transform of the star. The non-uniqueness of the rotation axis
encodes the extra dimension. This geometrical interpretation becomes evident on
writing KS transforms in quaternion form, which also helps derive concise
expressions for regularized equations of motion.


title: Covering functors without groups

abstract:
  Coverings in the representation theory of algebras were introduced for the
Auslander-Reiten quiver of a representation finite algebra by Riedtmann and
later for finite dimensional algebras by Bongartz and Gabriel, R.
Martinez-Villa and de la Pe\~na. The best understood class covering functors is
that of Galois covering functors F: A -> B determined by the action of a group
of automorphisms of A. In this work we introduce the balanced covering functors
which include the Galois class and for which classical Galois covering-type
results still hold. For instance, if F:A -> B is a balanced covering functor,
where A and B are linear categories over an algebraically closed field, and B
is tame, then A is tame.


title: Molecular gas in nearby elliptical radio galaxies

abstract:
  Powerful radio-AGN are hosted by massive elliptical galaxies which are
usually very poor in molecular gas. Nevertheless the central Black Hole (BH)
needs molecular gas for the nuclear activity. Thus it is important to study the
origin, the distribution and the kinematics of the molecular gas in such
objects. We have performed at the IRAM-30m telescope a survey of the CO(1-0)
and CO(2-1) emission in the most powerful radio galaxies of the Local Universe,
selected only on the basis of their radio continuum fluxes. The main result of
that survey is the low content in molecular gas of such galaxies compared to
Seyfert galaxies. The median value of the molecular gas mass is 4x10^8 Msun.
Moreover, the CO spectra indicate the presence of a central molecular gas disk
in some of these radio galaxies. We complemented this survey with photometric
data of SPITZER and IRAS fluxes with the purpose to study the dust and its
relation with the molecular gas and AGN.


title: Conjugate gradient heatbath for ill-conditioned actions

abstract:
  We present a method for performing sampling from a Boltzmann distribution of
an ill-conditioned quadratic action. This method is based on heatbath
thermalization along a set of conjugate directions, generated via a
conjugate-gradient procedure. The resulting scheme outperforms local updates
for matrices with very high condition number, since it avoids the slowing down
of modes with lower eigenvalue, and has some advantages over the global
heatbath approach, compared to which it is more stable and allows for more
freedom in devising case-specific optimizations.


title:
Luscher's mu-term and finite volume bootstrap principle for scattering
  states and form factors

abstract:
  We study the leading order finite size correction (Luscher's mu-term)
associated to moving one-particle states, arbitrary scattering states and
finite volume form factors in 1+1 dimensional integrable models. Our method is
based on the idea that the mu-term is intimately connected to the inner
structure of the particles, ie. their composition under the bootstrap program.
We use an appropriate analytic continuation of the Bethe-Yang equations to
quantize bound states in finite volume and obtain the leading mu-term
(associated to symmetric particle fusions) by calculating the deviations from
the predictions of the ordinary Bethe-Yang quantization. Our results are
compared to numerical data of the E8 scattering theory obtained by truncated
fermionic space approach. As a by-product it is shown that the bound state
quantization does not only yield the correct mu-term, but also provides the sum
over a subset of higher order corrections as well.


title: Anti-deSitter universe dynamics in LQC

abstract:
  A model for a flat isotropic universe with a negative cosmological constant
$\Lambda$ and a massless scalar field as sole matter content is studied within
the framework of Loop Quantum Cosmology. By application of the methods
introduced for the model with $\Lambda=0$, the physical Hilbert space and the
set of Dirac observables are constructed. As in that case, the scalar field
plays here the role of an emergent time. The properties of the system are found
to be similar to those of the $k=1$ FRW model: for small energy densities, the
quantum dynamics reproduces the classical one, whereas, due to modifications at
near-Planckian densities, the big bang and big crunch singularities are
replaced by a quantum bounce connecting deterministically the large
semiclassical epochs. Thus in Loop Quantum Cosmology the evolution is
qualitatively cyclic.


title: Viscosity and boost invariance at RHIC and LHC

abstract:
  We consider the longitudinal hydrodynamic evolution of the fireball created
in a relativistic heavy-ion collision. Nonzero shear viscosity reduces the
colling rate of the system and hinders the acceleration of the longitudinal
flow. As a consequence, the initial energy density needed to reproduce the
experimental data at RHIC energies is significantly reduced. At LHC energies,
we expect that shear viscosity helps to conserve a Bjorken plateau in the
rapidity distributions during the expansion.


title:
Alkali-metal-induced Fermi level and two dimensional electrons at
  cleaved InAs(110) surfaces

abstract:
  Low-temperature Hall measurements have been performed on two-dimensional
electron gases (2DEGs) induced by deposition of Cs or Na on in situ cleaved
surfaces of p-type InAs. The surface donor level, at which the Fermi energy of
the 2DEG is pinned, is calculated from the observed saturation surface electron
density using a surface potential determined self-consistently. The results are
compared to those of previous photoelectron spectroscopy measurements.


title: General relativistic plasma in higher dimensional space time

abstract:
  The well known (3+1) decomposition of Thorne and Macdonald is invoked to
write down the Einstein-Maxwell equations generalised to (d+1) dimensions and
also to formulate the plasma equations in a flat FRW like spacetime in higher
dimensions (HD). Assuming an equation of state for the background metric we
find solutions as also dispersion relations in different regimes of the
universe in a unified manner both for magnetised(un) cold plasma. We find that
for a free photon in expanding background we get maximum redshift in 4D
spacetime, while for a particular dimension it is so in pre recombination era.
Further wave propagation in magnetised plasma is possible for a restricted
frequency range only, depending on the number of dimensions. Relevant to point
out that unlike the special relativistic result this allowed range evolves with
time. Interestingly the dielectric constant of the plasma media remains
constant, not sharing the expansion of the background, which generalises a
similar 4D result of Holcomb-Tajima in radiation background to the case of
higher dimensions with cosmic matter obeying an equation of state . Further,
analogous to the flat space static case we observe the phenomenon of Faraday
rotation in higher dimensional case also.


title: Avalanche dynamics on a rough inclined plane

abstract:
  Avalanche behavior of gravitationally-forced granular layers on a rough
inclined plane are investigated experimentally for different materials and for
a variety of grain shapes ranging from spherical beads to highly anisotropic
particles with dendritic shape. We measure the front velocity, area and the
height of many avalanches and correlate the motion with the area and height. We
also measure the avalanche profiles for several example cases. As the shape
irregularity of the grains is increased, there is a dramatic qualitative change
in avalanche properties. For rough non-spherical grains, avalanches are faster,
bigger and overturning in the sense that individual particles have down-slope
speeds $u_p$ that exceed the front speed $u_f$ as compared with avalanches of
spherical glass beads that are quantitatively slower, smaller and where
particles always travel slower than the front speed. There is a linear increase
of three quantities i) dimensionless avalanche height ii) ratio of particle to
front speed and iii) the growth rate of avalanche speed with increasing
avalanche size with increasing $\tan\theta_r$ where $\theta_r$ is the bulk
angle of repose, or with increasing $\beta_P$, the slope of the depth averaged
flow rule, where both $\theta_r$ and $\beta_P$ reflect the grain shape
irregularity. These relations provide a tool for predicting important dynamical
properties of avalanches as a function of grain shape irregularity. A
relatively simple depth-averaged theoretical description captures some
important elements of the avalanche motion, notably the existence of two
regimes of this motion.


title:
Evidence for Direct CP Violation from Dalitz-plot analysis of B+/- ->
  K+/- pi+/- pi-/+

abstract:
  We report a Dalitz-plot analysis of the charmless hadronic decays of charged
B mesons to the final state K+/- pi+/- pi-/+. Using a sample of 383.2 +/- 4.2
million BBbar pairs collected by the BaBar detector, we measure CP-averaged
branching fractions and direct CP asymmetries for intermediate resonant and
nonresonant contributions. We find evidence for direct CP violation in the
decay B+ -> rho0(770) K+, with a CP violation parameter A_CP = (+44 +/- 10 +/-
4 +5,-13)%.


title:
Comptage de courbes sur le plan projectif \'eclat\'e en trois points
  align\'es

abstract:
  We prove a version of Manin's conjecture for the projective plane blown up in
three collinear points, the base field being a global field of positive
characteristic.


title: Symmetry-noise interplay in quantum walk on an n-cycle

abstract:
  Augmenting the unitary transformation which generates a quantum walk by a
generalized phase gate G is a symmetry for both noisy and noiseless quantum
walk on a line, in the sense that it leaves the position probability
distribution invariant. However, this symmetry breaks down in the case of a
quantum walk on an n-cycle, and hence can be regarded as a probe of the walk
topology. Noise, modelled here as phase flip and generalized amplitude damping
channels, tends to restore the symmetry because it classicalizes the walk.
However, symmetry restoration happens even in the regime where the walker is
not entirely classical, because noise also has the effect of desensitizing the
operation G to the walk topology. We discuss methods for physical
implementation, and talk about the wider implications to condensed matter
systems.


title: On finite simple and nonsolvable groups acting on closed 4-manifolds

abstract:
  We show that the only finite nonabelian simple groups which admit a locally
linear, homologically trivial action on a closed simply connected 4-manifold
$M$ (or on a 4-manifold with trivial first homology) are the alternating groups
$A_5$, $A_6$ and the linear fractional group PSL(2,7) (we note that for
homologically nontrivial actions all finite groups occur). The situation
depends strongly on the second Betti number $b_2(M)$ of $M$ and has been known
before if $b_2(M)$ is different from two, so the main new result of the paper
concerns the case $b_2(M)=2$. We prove that the only simple group that occurs
in this case is $A_5$, and then give a short list of finite nonsolvable groups
which contains all candidates for actions of such groups.


title:
Transient optical response of ultrafast nonequilibrium excited metals:
  Effects of electron-electron contribution to collisional absorption

abstract:
  Approaching energy coupling in laser-irradiated metals, we point out the role
of electron-electron collision as an efficient control factor for ultrafast
optical absorption. The high degree of laser-induced electron-ion
nonequilibrium drives a complex absorption pattern with consequences on the
transient optical properties. Consequently, high electronic temperatures
determine largely the collision frequency and establish a transition between
absorptive regimes in solid and plasma phases. In particular, taking into
account umklapp electron-electron collisions, we performed hydrodynamic
simulations of the laser-matter interaction to calculate laser energy
deposition during the electron-ion nonequilibrium stage and subsequent matter
transformation phases. We observe strong correlations between optical and
thermodynamic properties according to the experimental situations. A suitable
connection between solid and plasma regimes is chosen in accordance with models
that describe the behavior in extreme, asymptotic regimes. The proposed
approach describes as well situations encountered in pump-probe types of
experiments, where the state of matter is probed after initial excitation.
Comparison with experimental measurements shows simulation results which are
sufficiently accurate to interpret the observed material behavior. A numerical
probe is proposed to analyze the transient optical properties of matter exposed
to ultrashort pulsed laser irradiation at moderate and high intensities.
Various thermodynamic states are assigned to the observed optical variation.
Qualitative indications of the amount of energy coupled in the irradiated
targets are obtained.
  Keywords: ultrafast absorption ; umklapp electron-electron collision ;
collisional absorption ; laser-matter interaction


title:
N-MODY: a code for collisionless N-body simulations in modified
  Newtonian dynamics

abstract:
  We describe the numerical code N-MODY, a parallel particle-mesh code for
collisionless N-body simulations in modified Newtonian dynamics (MOND). N-MODY
is based on a numerical potential solver in spherical coordinates that solves
the non-linear MOND field equation, and is ideally suited to simulate isolated
stellar systems. N-MODY can be used also to compute the MOND potential of
arbitrary static density distributions. A few applications of N-MODY indicate
that some astrophysically relevant dynamical processes are profoundly different
in MOND and in Newtonian gravity with dark matter.


title: Stochastic solution of a nonlinear fractional differential equation

abstract:
  A stochastic solution is constructed for a fractional generalization of the
KPP (Kolmogorov, Petrovskii, Piskunov) equation. The solution uses a fractional
generalization of the branching exponential process and propagation processes
which are spectral integrals of Levy processes


title: Rayleigh-B\'enard Convection as a Nambu-metriplectic problem

abstract:
  The traditional Hamiltonian structure of the equations governing conservative
Rayleigh-B\'enard convection (RBC) is singular, i.e. it's Poisson bracket
possesses nontrivial Casimir functionals. We show that a special form of one of
these Casimirs can be used to extend the bilinear Poisson bracket to a
trilinear generalised Nambu bracket. It is further shown that the equations
governing dissipative RBC can be written as the superposition of the
conservative Nambu bracket with a dissipative symmetric bracket. This leads to
a Nambu-metriplectic system, which completes the geometrical picture of RBC.


title: Report on GRG18, Session A3, Mathematical Studies of the Field Equations

abstract:
  In this report I will give a summary of some of the main topics covered in
Session A3, mathematical studies of the field equations, at GRG18, Sydney.
Unfortunately, due to length constraints, some of the topics covered at the
session will be very briefly mentioned or left out altogether. The summary is
mainly based on extended abstracts submitted by the speakers and some of those
who presented posters at the session. I would like to thank all participants
for their contributions and help with this summary.


title: On the role of meson loops in the $f_0(1710)$ decay into $V\gamma$

abstract:
  We investigate the relevance of the meson loops in the $f_0(1710)$ scalar
meson decay into one photon and one vector meson, ($\rho$, $\omega$ and
$\phi$). In particular we estimate the size of the loops coming from the decay
of the $f_0(1710)$ into two pseudoscalar mesons, containing three pseudoscalar
mesons in the loop or two pseudoscalar and one vector meson. The results,
despite having large uncertainties, manifest that the contribution of the meson
loops to these radiative decays is quite relevant and should be taken into
account by the theoretical calculations which use this observables as a test of
the possible glueball nature of this resonance.


title:
Localization of Inner-Shell Photoelectron Emission and Interatomic
  Coulombic Decay in Ne$_2$

abstract:
  We used Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) to
investigate the decay of Ne$_2$ after K-shell photoionization. The breakup into
Ne$^{1+}$ / Ne$^{2+}$ shows interatomic Coulombic decay (ICD) occurring after a
preceding atomic Auger decay. The molecular frame angular distributions of the
photoelectron and the ICD electron show distinct, asymmetric features, which
imply localization of the K-vacancy created at one of the two atomic sites of
the Ne$_2$ and an emission of the ICD electron from a localized site. The
experimental results are supported by calculations in frozen core Hartree-Fock
approach.


title: Hyperelliptic curves, L-polynomials, and random matrices

abstract:
  We analyze the distribution of unitarized L-polynomials Lp(T) (as p varies)
obtained from a hyperelliptic curve of genus g <= 3 defined over Q. In the
generic case, we find experimental agreement with a predicted correspondence
(based on the Katz-Sarnak random matrix model) between the distributions of
Lp(T) and of characteristic polynomials of random matrices in the compact Lie
group USp(2g). We then formulate an analogue of the Sato-Tate conjecture for
curves of genus 2, in which the generic distribution is augmented by 22
exceptional distributions, each corresponding to a compact subgroup of USp(4).
In every case, we exhibit a curve closely matching the proposed distribution,
and can find no curves unaccounted for by our classification.


title: Star Formation in Massive LSB Galaxies

abstract:
  Massive low surface brightness galaxies have disk central surface
brightnesses at least one magnitude fainter than the night sky, but total
magnitudes and masses that show they are among the largest galaxies known. Like
all low surface brightness (LSB) galaxies, massive LSB galaxies are often in
the midst of star formation yet their stellar light has remained diffuse,
raising the question of how star formation is proceeding within these systems.
HI observations have played a crucial role in studying LSB galaxies as they are
typically extremely gas rich. In the past few years we have more than
quadrupled the total number of massive LSB galaxies,primarily through HI
surveys. To clarify their structural parameters and stellar and gas content, we
have undertaken a multi-wavelength study of these enigmatic systems. The
results of this study, which includes HI, CO, optical, near UV, and far UV
images of the galaxies, will provide the most in depth study done to date of
how, when, and where star formation proceeds within this unique subset of the
galaxy population.


title:
Tip-enhanced Raman imaging and spectroscopy: sensitivity, symmetry and
  selection rules

abstract:
  This article reviews the new developments in Tip-enhanced Raman scattering
(TERS). The fundamental mechanisms underlying the Raman enhancement are
discussed, including the role of the plasmonic character of the metallic tips,
the nature of the optical tip-sample coupling and the resulting local-field
confinement responsible for ultrahigh spatial resolution down to just several
nanometers. Criteria for the distinction of near-field signature from far-field
imaging artifacts are addressed and TERS results of molecules and
nanostructures are presented. With enhancement factors as high as 10$^9$,
single molecule spectroscopy is demonstrated. Spatially resolved vibrational
mapping of crystalline nanostructures and determination of crystallographic
orientation and domains is shown making use of the unique symmetry properties
of the tip in conjunction with the intrinsic Raman selection rules.


title: Concepts of inertial, gravitational and elementary particle masses

abstract:
  In this article the concept of mass is analyzed based on the special and
general relativity theories and particle (quantum) physics. The mass of a
particle (m=E(0)/c^2) is determined by the minimum (rest) energy to create that
particle which is invariant under Lorentz transformations. The mass of a bound
particle in the any field is described by m<E80)/c^2 and for free particles in
the non-relativistic case the relation m=E/c^2 is valid. This relation is not
correct in general, and it is wrong to apply it to the radiation and fields. In
atoms or nuclei (i.e. if the energies are quantized) the mass of the particles
changes discretely. In non-relativistic cases, mass can be considered as a
measure of gravitation and inertia.


title: On the strength of dependent products in the type theory of Martin-L\"of

abstract:
  One may formulate the dependent product types of Martin-L\"of type theory
either in terms of abstraction and application operators like those for the
lambda-calculus; or in terms of introduction and elimination rules like those
for the other constructors of type theory. It is known that the latter rules
are at least as strong as the former: we show that they are in fact strictly
stronger. We also show, in the presence of the identity types, that the
elimination rule for dependent products--which is a "higher-order" inference
rule in the sense of Schroeder-Heister--can be reformulated in a first-order
manner. Finally, we consider the principle of function extensionality in type
theory, which asserts that two elements of a dependent product type which are
pointwise propositionally equal, are themselves propositionally equal. We
demonstrate that the usual formulation of this principle fails to verify a
number of very natural propositional equalities; and suggest an alternative
formulation which rectifies this deficiency.


title:
Switchable collective pinning of flux quanta using magnetic vortex
  arrays

abstract:
  We constructed a superconducting/ferromagnetic hybrid system in which the
ordering of the pinning potential landscape for flux quanta can be manipulated.
Flux pinning is induced by an array of magnetic nanodots in the magnetic vortex
state, and controlled by the magnetic history. This allows switching on and off
the collective pinning of the flux-lattice. In addition, we observed
field-induced superconductivity that originates from the annihilation of flux
quanta induced by the stray fields from the magnetic vortices.


title: Breakdown of the Luttinger sum rule within the Mott-Hubbard insulator

abstract:
  The validity of the Luttinger sum rule is investigated within the prototype
tight-binding model of interacting fermions in one dimension, i.e., the t-V
model including the next-nearest neighbor hopping t' in order to break the
particle-hole symmetry. Scaling analysis of finite-system results at
half-filling reveals evident breakdown of the sum rule in the regime of large
gap at V >> t, while the sum rule appears to recover together with vanishing of
the Mott-Hubbard gap.


title:
Two-step model versus one-step model of the inter-polarization
  conversion and statistics of CdSe/ZnSe quantum dot elongations

abstract:
  The magneto-optical inter-polarization conversions by a layer of quantum dots
have been investigated. Various types of polarization response of the sample
were observed as a function of external magnetic field and of the orientation
of the sample. The full set of experimental dependences is analyzed in terms of
a one-step and a two-step model of spin evolution. The angular distribution of
the quantum dots over the directions of elongation in the plane of the sample
is taken into account in terms of the two models, and the model predictions are
compared with experimental observations.


title:
New Hubble Space Telescope imaging of the counterparts to six
  ultraluminous X-ray sources

abstract:
  We report the results of new Hubble Space Telescope imaging of the positions
of six ultraluminous X-ray sources (ULXs). Using images in three ACS filters we
detect good candidate counterparts to four out of six ULXs, with one more
possible detection, and observed magnitudes in the range m ~ 22 - 26 in the
F606W filter. The extinction-corrected colours and absolute magnitudes vary
from source to source, even after correcting for additional extinction in the
host galaxy, and only one counterpart is readily explained as an OB star.
Nevertheless, these counterparts are decent candidates for future follow-up in
pursuit of dynamical mass constraints on the likely black holes powering these
sources.


title: Westerlund 1: bound or unbound?

abstract:
  The Galactic open cluster Westerlund 1 (Wd 1) represents the ideal local
template for extragalactic young massive star clusters, because it is currently
the only nearby young cluster which reaches a mass of around 10^5 Msun. The
proximity makes spatially resolved studies of its stellar population feasible,
and additionally permits direct comparison of its properties with measurements
of velocity dispersion and dynamical mass for spatially unresolved
extragalactic clusters.
  Recently, we published the dynamical mass estimate based on spectra of four
red supergiants. We have now identified six additional stars which allow a
determination of radial velocity from the wavelength covered in our VLT/ISAAC
near-infrared spectra (CO bandhead region near 2.29micron), improving
statistics significantly. Using a combination of stepping and scanning the slit
across the cluster centre, we covered an area which included the following
suitable spectral types: four red supergiants, five yellow hypergiants, and one
B-type emission line star.
  Our measured velocity dispersion is 9.2 km/s. Together with the cluster size
of 0.86 pc, derived from archival near-infrared SOFI-NTT images, this yields a
dynamical mass of 1.5x10^5 Msun. Comparing this to the mass derived via
photometry, there is no indication that the cluster is currently undergoing
dissolution.


title: Spin-Statistics Violations from Heterotic String Worldsheet Instantons

abstract:
  In this paper we consider the role that worldsheet instantons in the
heterotic string could play in spin-statistics violations. Such violations are
nonperturbative in the string tension and so would not appear in the spacetime
effective action, producing a unique signature of string theory and the details
of compactification. By performing a Bogomol'nyi transformation it is shown
that there are no instanton solutions in the simplest model proposed by Harvey
and Liu, but it is conjectured that more sophisticated models may yield
solutions. If such instantons do exist, their effect might be measured by
upcoming experiments.


title: Ernest Michael and theory of continuous selections

abstract:
  This is the introductory paper to the special issue of Topology and Its
Applications entirely dedicated to the theory of continuous selections of
multivalued mappings. Since the pioneering work of Ernest Michael from 1956 can
rightfully be considered as the year of birth of this theory, this issue of the
journal is in fact dedicated to the 50th anniversary of the theory of
continuous selections. At the same time the papers of this issue are all
dedicated to the 80th anniversary of the founder of this theory - Ernest
Michael.


title: Brane Tilings and Their Applications

abstract:
  We review recent developments in the theory of brane tilings and
four-dimensional N=1 supersymmetric quiver gauge theories. This review consists
of two parts. In part I, we describe foundations of brane tilings, emphasizing
the physical interpretation of brane tilings as fivebrane systems. In part II,
we discuss application of brane tilings to AdS/CFT correspondence and
homological mirror symmetry. More topics, such as orientifold of brane tilings,
phenomenological model building, similarities with BPS solitons in
supersymmetric gauge theories, are also briefly discussed.
  This paper is a revised version of the author's master's thesis submitted to
Department of Physics, Faculty of Science, the University of Tokyo on January
2008, and is based on his several papers: math.AG/0605780, math.AG/0606548,
hep-th/0702049, math.AG/0703267, arXiv:0801.3528 and some works in progress.


title:
New results from the NA48/2 experiment at CERN SPS: radiative
  nonleptonic kaon decays

abstract:
  The NA48/2 experiment at the CERN SPS carried out data taking in 2003 and
2004. Analysis of the selected data samples of 7,146 $K^\pm\to\pi^\pm e^+e^-$
decay candidates with 0.6% background, 1,164 $K^\pm\to\pi^\pm\gamma\gamma$
candidates with 3.3% background, and 120 $K^\pm\to\pi^\pm\gamma e^+e^-$
candidates with 6.1% background allowed precise measurements of branching
fractions and other characteristics of these rare kaon decays.


title: Quotients of bounded homogeneous domains by cyclic groups

abstract:
  Let $D$ be a bounded homogeneous domain in $\mbb{C}^n$ and let $\Gamma$ be a
cyclic discrete subgroup of the automorphism group of $D$. It is shown that the
complex space $D/\Gamma$ is Stein.


title:
Model-Independent Determination of the WIMP Mass from Direct Dark Matter
  Detection Data

abstract:
  Weakly Interacting Massive Particles (WIMPs) are one of the leading
candidates for Dark Matter. We develop a model-independent method for
determining the mass $m_\chi$ of the WIMP by using data (i.e., measured recoil
energies) of direct detection experiments. Our method is independent of the as
yet unknown WIMP density near the Earth, of the form of the WIMP velocity
distribution, as well as of the WIMP-nucleus cross section. However, it
requires positive signals from at least two detectors with different target
nuclei. In a background-free environment, $m_\chi \sim 50$ GeV could in
principle be determined with an error of $\sim 35%$ with only $2 \times 50$
events; in practice upper and lower limits on the recoil energy of signal
events, imposed to reduce backgrounds, can increase the error. The method also
loses precision if $m_\chi$ significantly exceeds the mass of the heaviest
target nucleus used.


title:
G\'en\'eralisation de l'homologie d'Heegaard-Floer aux entrelacs
  singuliers & Raffinement de l'homologie de Khovanov aux entrelacs restreints

abstract:
  A categorification of a polynomial link invariant is an homological invariant
which contains the polynomial one as its graded Euler characteristic. This
field has been initiated by Khovanov categorification of the Jones polynomial.
Later, P. Ozsvath and Z. Szabo gave a categorification of Alexander polynomial.
Besides their increased abilities for distinguishing knots, this new invariants
seem to carry many geometrical informations. On the other hand, Vassiliev works
gives another way to study link invariant, by generalizing them to singular
links i.e. links with a finite number of rigid transverse double points. The
first part of this thesis deals with a possible relation between these two
approaches in the case of the Alexander polynomial. To this purpose, we extend
grid presentation for links to singular links. Then we use it to generalize
Ozsvath and Szabo invariant to singular links. Besides the consistency of its
definition, we prove that this invariant is acyclic under some conditions which
naturally make its Euler characteristic vanish. This work can be considered as
a first step toward a categorification of Vassiliev theory. In a second part,
we give a refinement of Khovanov homology to restricted links. Restricted links
are link diagrams up to a restricted set of Reidemeister moves. In particular,
closed braids can be seen as a subset of them. Such a refinement give then a
new tool for studying knots and their deformations.


title:
Unconditionally secure computers, algorithms and hardware, such as
  memories, processors, keyboards, flash and hard drives

abstract:
  In the case of the need of extraordinary security,
Kirchhoff-loop-Johnson-(like)-noise ciphers can easily be integrated on
existing types of digital chips in order to provide secure data communication
between hardware processors, memory chips, hard disks and other units within a
computer or other data processor system. The secure key exchange can take place
at the very first run and the system can renew the key later at random times
with an authenticated fashion to prohibit man-in-the-middle attack. The key can
be stored in flash memories within the communicating chip units at hidden
random addresses among other random bits that are continuously generated by the
secure line but are never actually used. Thus, even if the system is
disassembled, and the eavesdropper can have direct access to the communication
lines between the units, or even if she is trying to use a man-in-the-middle
attack, no information can be extracted. The only way to break the code is to
learn the chip structure, to understand the machine code program and to read
out the information during running by accessing the proper internal ports of
the working chips. However such an attack needs extraordinary resources and
even that can be prohibited by a password lockout. The unconditional security
of commercial algorithms against piracy can be provided in a similar way.


title:
ARCH and GARCH Models vs. Martingale Volatility of Finance Market
  Returns

abstract:
  ARCH and GARCH models assume either i.i.d. or (what economists lable as)
white noise as is usual in regression analysis while assuming memory in a
conditional mean square fluctuation with stationary increments. We will show
that ARCH/GARCH is inconsistent with uncorrelated increments, violating the
i.i.d. and white assumptions and finance data and the efficient market
hypothesis as well.


title:
Kinetic Monte Carlo modelling of dipole blockade in Rydberg excitation
  experiment

abstract:
  We present a method to model the interaction and the dynamics of atoms
excited to Rydberg states. We show a way to solve the optical Bloch equations
for laser excitation of the frozen gas in good agreement with the experiment. A
second method, the Kinetic Monte Carlo method gives an exact solution of rate
equations. Using a simple N-body integrator (Verlet), we are able to describe
dynamical processes in space and time. Unlike more sophisticated methods, the
Kinetic Monte Carlo simulation offers the possibility of numerically following
the evolution of tens of thousands of atoms within a reasonable computation
time. The Kinetic Monte Carlo simulation gives good agreement with
dipole-blockade type of experiment. The role of ions and the individual
particle effects are investigated.


title:
The transition from adiabatic inspiral to geodesic plunge for a compact
  object around a massive Kerr black hole: Generic orbits

abstract:
  The inspiral of a stellar mass compact object falling into a massive Kerr
black hole can be broken into three different regimes: An adiabatic inspiral
phase, where the inspiral timescale is much larger than the orbital period; a
late-time radial infall, which can be approximated as a plunging geodesic; and
a regime where the body transitions from the inspiral to plunge. In earlier
work, Ori and Thorne have outlined a method to compute the trajectory during
this transition for a compact object in a circular, equatorial orbit. We
generalize this technique to include inclination and eccentricity.


title:
Numerical techniques for solving the quantum constraint equation of
  generic lattice-refined models in loop quantum cosmology

abstract:
  To avoid instabilities in the continuum semi-classical limit of loop quantum
cosmology models, refinement of the underlying lattice is necessary. The
lattice refinement leads to new dynamical difference equations which, in
general, do not have a uniform step-size, implying complications in their
analysis and solutions. We propose a numerical method based on Taylor
expansions, which can give us the necessary information to calculate the
wave-function at any given lattice point. The method we propose can be applied
in any lattice-refined model, while in addition the accuracy of the method can
be estimated. Moreover, we confirm numerically the stability criterion which
was earlier found following a von Neumann analysis. Finally, the `motion' of
the wave-function due to the underlying discreteness of the space-time is
investigated, for both a constant lattice, as well as lattice refinement
models.


title: Recollapsing quantum cosmologies and the question of entropy

abstract:
  Recollapsing homogeneous and isotropic models present one of the key
ingredients for cyclic scenarios. This is considered here within a quantum
cosmological framework in presence of a free scalar field with, in turn, a
negative cosmological constant and spatial curvature. Effective equations shed
light on the quantum dynamics around a recollapsing phase and the evolution of
state parameters such as fluctuations and correlations through such a turn
around. In the models considered here, the squeezing of an initial state is
found to be strictly monotonic in time during the expansion, turn around and
contraction phases. The presence of such monotonicity is of potential
importance in relation to a long standing intensive debate concerning the
(a)symmetry between the expanding and contracting phases in a recollapsing
universe. Furthermore, together with recent analogous results concerning a
bounce one can extend this monotonicity throughout an entire cycle. This
provides a strong motivation for employing the degree of squeezing as an
alternative measure of (quantum) entropy. It may also serve as a new concept of
emergent time described by a variable without classical analog. The evolution
of the squeezing in emergent oscillating scenarios can in principle provide
constraints on the viability of such models.


title: The High Energy Limit of QCD: BFKL Cross Sections

abstract:
  In this contribution we describe in some detail different aspects of the
construction of BFKL cross sections. We focus on several effects which are
relevant at next-to-leading order. In particular, we describe QCD coherence in
DIS final states, improvements of the collinear region in multi-Regge
kinematics, inclusive jet production at next-to-leading order, and azimuthal
angle decorrelations of Mueller-Navelet jets at hadron colliders.


title: On the maximum size of a $(k,l)$-sum-free subset of an abelian group

abstract:
  A subset $A$ of a given finite abelian group $G$ is called $(k,l)$-sum-free
if the sum of $k$ (not necessarily distinct) elements of $A$ does not equal the
sum of $l$ (not necessarily distinct) elements of $A$. We are interested in
finding the maximum size $\lambda_{k,l}(G)$ of a $(k,l)$-sum-free subset in
$G$.
  A $(2,1)$-sum-free set is simply called a sum-free set. The maximum size of a
sum-free set in the cyclic group $\mathbb{Z}_n$ was found almost forty years
ago by Diamanda and Yap; the general case for arbitrary finite abelian groups
was recently settled by Green and Ruzsa. Here we find the value of
$\lambda_{3,1}(\mathbb{Z}_n)$. More generally, a recent paper of Hamidoune and
Plagne examines $(k,l)$-sum-free sets in $G$ when $k-l$ and the order of $G$
are relatively prime; we extend their results to see what happens without this
assumption.


title: Enhanced Orbital Degeneracy in Momentum Space for LaOFeAs

abstract:
  The Fermi surfaces (FS) of LaOFeAs (in $k_z$=0 plane) consist of two
hole-type circles around $\Gamma$ point, which do not touch each other, and two
electron-type co-centered ellipses around M point, which are degenerate along
the M-X line. By first-principles calculations, here we show that additional
degeneracy exists for the two electron-type FS, and the crucial role of
F-doping and pressure is to enhance this orbital degeneracy. It is suggested
that the inter-orbital fluctuation is the key point to understand the
unconventional superconductivity in these materials.


title:
Schrodinger-Newton equation as a possible generator of quantum state
  reduction

abstract:
  It has been suggested by Diosi and Penrose that the occurrence of quantum
state reduction in macroscopic objects is related to a manifestation of
gravitational effects in quantum mechanics. Although within Penrose's framework
the dynamics of the quantum state reduction is not prescribed, it was suggested
that the so called Schrodinger-Newton equation can be used to at least identify
the resulting classical end states. Here we analyze the extent to which the
Schrodinger-Newton equation can be used as a model to generate a full, time
dependent description of the quantum state reduction process. We find that when
supplied with an imaginary gravitational potential, the Schrodinger-Newton
equation offers a rationalisation for some of the hitherto unexplained
characteristics of quantum state reduction. The description remains incomplete
however, because it is unclear how to fully recover Born's rule.


title: Can the fluctuations of a black hole be treated thermodynamically?

abstract:
  Since the temperature of a typical Schwarzschild black hole is very low, some
doubts are raised about whether the fluctuations of the black hole can be
treated thermodynamically. It is shown that this is not the case: the
thermodynamic fluctuations of a black hole are considerably larger than the
corresponding quantum fluctuations. Moreover the ratio of the mean square
thermodynamic fluctuation to the corresponding quantum fluctuation can be
interpreted as a number of the effective constituents of a black hole.


title: Controlling the spontaneous emission of a superconducting transmon qubit

abstract:
  We present a detailed characterization of coherence in seven transmon qubits
in a circuit QED architecture. We find that spontaneous emission rates are
strongly influenced by far off-resonant modes of the cavity and can be
understood within a semiclassical circuit model. A careful analysis of the
spontaneous qubit decay into a microwave transmission-line cavity can
accurately predict the qubit lifetimes over two orders of magnitude in time and
more than an octave in frequency. Coherence times $T_1$ and $T_2^*$ of more
than a microsecond are reproducibly demonstrated.


title: Effects of heavy bosonic excitations on QED vacuum

abstract:
  We discuss the contribution of axion-like excitations (ALE) to the vacuum
birrefringence in the limit $m_A \gtrsim \omega$, where $m_A$ is the mass of
the excitation and $\omega$ the energy of test photons interacting with an
external (intense) magnetic field. The relevance of this term with respect to
the QED contribution depends on the ratio $g_A/m_A$ and, from present bounds on
the mass and the coupling constant $g_A$, we find that in the present low
energy regime, it ranges from $10^{-14}$ to $10^2$ suggesting an interesting
alternative to explore.


title: Charm of small $x$ neutrino DIS

abstract:
  Due to the weak current non-conservation the diffractive excitation of charm
and strangeness dominates the longitudinal structure function $F_L(x,Q^2)$ of
neutrino DIS at small Bjorken $x$. Based on the color dipole BFKL approach we
report quantitative predictions for this effect in the kinematical range of the
CCFR/NuTeV experiment. We comment on the relevance of our findings to
experimental tests of PCAC.


title: On mass corrections to the decays P \to l^+l^-

abstract:
  We use the Mellin-Barnes representation in order to improve the theoretical
estimate of mass corrections to the width of light pseudoscalar meson decay
into a lepton pair, $P\to l^+l^-$ . The full resummation of the terms
$\ln(m_l^2/\Lambda^2)(m_l^2/\Lambda^2)^n$ and $(m_l^2/\Lambda^2)^n$ to the
decay amplitude is performed, where $m_l$ is the lepton mass and
$\Lambda\approx m_\rho$ is the characteristic scale of the
$P\to\gamma^*\gamma^*$ form factor. The total effect of mass corrections for
the $e^+e^-$ channel is negligible and for the $\mu^+\mu^-$ channel its order
is of a few per cent.


title: A class of Lorentzian manifolds with indecomposable holonomy groups

abstract:
  We consider a class of $S^{1}$-bundles whose total space admits a nowhere
vanishing recurrent lightlike vector field with respect to a Lorentzian metric.
This metric can be modified such that its restricted holonomy group is
indecomposable and reducible. We apply Hodge theory to construct examples with
Hermitian screen holonomy. Finally, we construct complete pp-waves.


title: Heat capacity of Schottky type in low-dimensional spin system

abstract:
  The heat capacity of low-dimensional spin systems is studied using
theoretical and numerical techniques. Keeping only two energy states, the
system is mapped onto the two -level-system (TLS) model. Using the low
temperature Lanczos method, it is confirmed that the behavior of $T_{M}$ and
the energy gap as functions of the control parameter is the same in the two
models studied; a conclusion that can probably be extrapolated to the general
case of any system that possesses an energy gap.


title:
Poisson Cluster Measures: Quasi-invariance, Integration by Parts and
  Equilibrium Stochastic Dynamics

abstract:
  The distribution $\mu_{cl}$ of a Poisson cluster process in
$X=\mathbb{R}^{d}$ (with i.i.d. clusters) is studied via an auxiliary Poisson
measure on the space of configurations in $\mathfrak{X}=\sqcup_{n} X^n$, with
intensity measure defined as a convolution of the background intensity of
cluster centres and the probability distribution of a generic cluster. We show
that the measure $\mu_{cl}$ is quasi-invariant with respect to the group of
compactly supported diffeomorphisms of $X$ and prove an integration-by-parts
formula for $\mu_{cl}$. The corresponding equilibrium stochastic dynamics is
then constructed using the method of Dirichlet forms.


title: Transverse Symmetry and Spin-3/2 Fields

abstract:
  We study the possible covariant Lagrangians that describe the propagation of
pure spin-3/2 particles. We show that, apart from the well-known
Rarita-Schwinger Lagrangian, there is another possibility where the field is
described by a gamma-traceless combination and that both Lagrangians yield the
same physical predictions for the interaction of conserved sources. We also
prove that for the case when the spin-2 field is described by a traceless
field, there is no possible spin-3/2 action that makes the system
supersymmetric. Nevertheless, the interaction between this field andthe
spin-3/2 field may be possible.


title: Statistical mechanics of multipartite entanglement

abstract:
  We characterize the multipartite entanglement of a system of n qubits in
terms of the distribution function of the bipartite purity over all balanced
bipartitions. We search for those (maximally multipartite entangled) states
whose purity is minimum for all bipartitions and recast this optimization
problem into a problem of statistical mechanics.


title: Spectral Modeling of Magnetohydrodynamic Turbulent Flows

abstract:
  We present a dynamical spectral model for Large Eddy Simulation of the
incompressible magnetohydrodynamic (MHD) equations based on the Eddy Damped
Quasi Normal Markovian approximation. This model extends classical spectral
Large Eddy Simulations for the Navier-Stokes equations to incorporate general
(non Kolmogorovian) spectra as well as eddy noise. We derive the model for MHD
and show that introducing a new eddy-damping time for the dynamics of spectral
tensors in the absence of equipartition between the velocity and magnetic
fields leads to better agreement with direct numerical simulations, an
important point for dynamo computations.


title:
PT Symmetry of the non-Hermitian XX Spin-Chain: Non-local Bulk
  Interaction from Complex Boundary Fields

abstract:
  The XX spin-chain with non-Hermitian diagonal boundary conditions is shown to
be quasi-Hermitian for special values of the boundary parameters. This is
proved by explicit construction of a new inner product employing a
"quasi-fermion" algebra in momentum space where creation and annihilation
operators are not related via Hermitian conjugation. For a special example,
when the boundary fields lie on the imaginary axis, we show the spectral
equivalence of the quasi-Hermitian XX spin-chain with a non-local fermion
model, where long range hopping of the particles occurs as the non-Hermitian
boundary fields increase in strength. The corresponding Hamiltonian
interpolates between the open XX and the quantum group invariant XXZ model at
the free fermion point. For an even number of sites the former is known to be
related to a CFT with central charge c=1, while the latter has been connected
to a logarithmic CFT with central charge c=-2. We discuss the underlying
algebraic structures and show that for an odd number of sites the superalgebra
symmetry U(gl(1|1)) can be extended from the unit circle along the imaginary
axis. We relate the vanishing of one of its central elements to the appearance
of Jordan blocks in the Hamiltonian.


title:
Small Extra Dimensions from the Interplay of Gauge and Supersymmetry
  Breaking

abstract:
  Higher-dimensional theories provide a promising framework for unified
extensions of the supersymmetric standard model. Compactifications to four
dimensions often lead to U(1) symmetries beyond the standard model gauge group,
whose breaking scale is classically undetermined. Without supersymmetry
breaking, this is also the case for the size of the compact dimensions.
Fayet-Iliopoulos terms generically fix the scale M of gauge symmetry breaking.
The interplay with supersymmetry breaking can then stabilize the compact
dimensions at a size 1/M, much smaller than the inverse supersymmetry breaking
scale 1/mu. We illustrate this mechanism with an SO(10) model in six
dimensions, compactified on an orbifold.


title: Study of the HII regions in the spiral galaxy NGC6384

abstract:
  The galaxy NGC6384 has been observed with an IPCS through H alpha and [NII]
narrow-band interference filters for direct imagery with the 2.6 m Byurakan
telescope. We studied main physical parameters of identified 98 HII regions,
their diameter and luminosity functions, as well [NII]/H alpha ratio
distribution. The integrated distribution function of the HII region diameters
can be well fitted by the exponential function. The characteristic diameter has
the value (Do = 217 pc) predicted for a galaxy of its measured absolute
luminosity. The luminosity function of HII regions has double power laws
profile with relatively shallow slope at low luminosities (a = - 0.4), an
abrupt turnover at log L(H alpha) = 38.75, and sharper slope at higher
luminosities (a = - 2.3). Correlation between luminosity and diameter of HII
regions confirms that in general they are constant density, radiation-bound
systems. [NII]/H alpha ratio data for HII regions show that there is a negative
radial gradient of [NII]/H alpha. In the central region of the galaxy, nitrogen
abundance is higher than in the periphery. The properties of the HII regions
population of this AGN galaxy does not differs significantly from the
properties of the HII regions population of the "normal" galaxies. Reexamining
the location of the type Ia SN 1971L in the galaxy, we confirm that it lies on
the spiral arm at about 8.6" far from the closest HII region #53 (F81). Such a
location can be taken as prove that the progenitor of this SN do not belong to
an old, evolved stellar population.


title:
Frequency evaluation of the doubly forbidden $^1S_0\to ^3P_0$ transition
  in bosonic $^{174}$Yb

abstract:
  We report an uncertainty evaluation of an optical lattice clock based on the
$^1S_0\leftrightarrow^3P_0$ transition in the bosonic isotope $^{174}$Yb by use
of magnetically induced spectroscopy. The absolute frequency of the
$^1S_0\leftrightarrow^3P_0$ transition has been determined through comparisons
with optical and microwave standards at NIST. The weighted mean of the
evaluations is $\nu$($^{174}$Yb)=518 294 025 309 217.8(0.9) Hz. The uncertainty
due to systematic effects has been reduced to less than 0.8 Hz, which
represents $1.5\times10^{-15}$ in fractional frequency.


title: A New Approach to Testing Dark Energy Models by Observations

abstract:
  We propose a new approach to the consistency test of dark energy models with
observations. To test a category of dark energy models, we suggest introducing
a characteristic Q(z) that in general varies with the redshift z but in those
models plays the role of a (constant) distinct parameter. Then, by
reconstructing dQ(z)/dz from observational data and comparing it with zero we
can assess the consistency between data and the models under consideration. For
a category of models that passes the test, we can further constrain the
distinct parameter of those models by reconstructing Q(z) from data. For
demonstration, in this paper we concentrate on quintessence. In particular we
examine the exponential potential and the power-law potential via a widely used
parametrization of the dark energy equation of state, w(z) = w_0 + w_a z/(1+z),
for data analysis. This method of the consistency test is particularly
efficient because for all models we invoke the constraint of only a single
parameter space that by choice can be easily accessed. The general principle of
our approach is not limited to dark energy. It may also be applied to the
testing of various cosmological models and even the models in other fields
beyond the scope of cosmology.


title:
Fragmentation branching ratios of highly excited hydrocarbon molecules
  CnH and their cations CnH+ (n<4)

abstract:
  We have measured fragmentation branching ratios of neutral CnH and CnH+
cations produced in high velocity (4.5 a.u) collisions between incident CnH+
cations and helium atoms. Electron capture gives rise to excited neutral
species CnH and electronic excitation to excited cations CnH+. Thanks to a
dedicated set-up, based on coincident detection of all fragments, the
dissociation of the neutral and cationic parents were recorded separately and
in a complete way. For the fragmentation of CnH, the H-loss channel is found to
be dominant, as already observed by other authors. By contrast, the H-loss and
C-loss channels equally dominate the two-fragment break up of CnH+ species. For
these cations, we provide the first fragmentation data (n > 2). Results are
also discussed in the context of astrochemistry.


title:
Bimodal gas accretion in the Horizon-MareNostrum galaxy formation
  simulation

abstract:
  (abridged) The physics of diffuse gas accretion and the properties of the
cold and hot modes of accretion onto proto-galaxies between z=2 and z=5.4 is
investigated using the large cosmological simulation performed with the RAMSES
code on the MareNostrum supercomputing facility. Galactic winds, chemical
enrichment, UV background heating and radiative cooling are taken into account
in this very high resolution simulation. Using accretion--weighted temperature
histograms, we have perfomed two different measurements of the thermal state of
the gas accreted towards the central galaxy. The first measurement, performed
using accretion--weighted histograms on a spherical surface of radius 0.2 Rvir
centred on the densest gas structure near the halo centre of mass, is a good
indicator of the presence of an accretion shock in the vicinity of the galactic
disc. We define the hot shock mass, Mshock, as the typical halo mass separating
cold dominated from hot dominated accretion in the vicinity of the galaxy. The
second measurement is performed by radially averaging histograms between 0.2
Rvir and Rvir, in order to detect radially extended structures such as gas
filaments: this is a good proxy for detecting cold streams feeding the central
galaxy. We define Mstream as the transition mass separating cold dominated from
hot dominated accretion in the outer halo, marking the disappearance of these
cold streams. We find a hot shock transition mass of Mshock=10^{11.6} Msun
(dark matter), with no significant evolution with redshift. Conversely, we find
that Mstream increases sharply with z. Our measurements are in agreement with
the analytical predictions of Birnboim & Dekel (2003) and Dekel & Birnboim
(2006), if we correct their model by assuming low metallicity (< 10^{-3} Zsun)
for the filaments, correspondingly to our measurements.


title:
Recombination Lines and Free-Free Continua formed in Asymptotic Ionized
  Winds: Analytic solution for the radiative transfer

abstract:
  In dense hot star winds, the infrared and radio continua are dominated by
free-free opacity and recombination emission line spectra. In the case of a
spherically symmetric outflow that is isothermal and expanding at constant
radial speed, the radiative transfer for the continuum emission from a dense
wind is analytic. Even the emission profile shape for a recombination line can
be derived. Key to these derivations is that the opacity scales with only the
square of the density. These results are well-known. Here an extension of the
derivation is developed that also allows for line blends and the inclusion of
an additional power-law dependence beyond just the density dependence. The
additional power-law is promoted as a representation of a radius dependent
clumping factor. It is shown that differences in the line widths and equivalent
widths of the emission lines depend on the steepness of the clumping power-law.
Assuming relative level populations in LTE in the upper levels of He {\sc ii},
an illustrative application of the model to {\em Spitzer}/IRS spectral data of
the carbon-rich star WR 90 is given.


title:
Approaching the Ground State of a Quantum Spin Glass using a
  Zero-Temperature Quantum Monte Carlo

abstract:
  Here we discuss the annealing behavior of an infinite-range $\pm J$ Ising
spin glass in presence of a transverse field using a zero-temperature quantum
Monte Carlo. Within the simulation scheme, we demonstrate that quantum
annealing not only helps finding the ground state of a classical spin glass,
but can also help simulating the ground state of a quantum spin glass, in
particularly, when the transverse field is low, much more efficiently.


abstract:
  Cavity-enhanced direct frequency comb spectroscopy combines broad spectral
bandwidth, high spectral resolution, precise frequency calibration, and
ultrahigh detection sensitivity, all in one experimental platform based on an
optical frequency comb interacting with a high-finesse optical cavity. Precise
control of the optical frequency comb allows highly efficient, coherent
coupling of individual comb components with corresponding resonant modes of the
high-finesse cavity. The long cavity lifetime dramatically enhances the
effective interaction between the light field and intracavity matter,
increasing the sensitivity for measurement of optical losses by a factor that
is on the order of the cavity finesse. The use of low-dispersion mirrors
permits almost the entire spectral bandwidth of the frequency comb to be
employed for detection, covering a range of ~10% of the actual optical
frequency. The light transmitted from the cavity is spectrally resolved to
provide a multitude of detection channels with spectral resolutions ranging
from a several gigahertz to hundreds of kilohertz. In this review we will
discuss the principle of cavity-enhanced direct frequency comb spectroscopy and
the various implementations of such systems. In particular, we discuss several
types of UV, optical, and IR frequency comb sources and optical cavity designs
that can be used for specific spectroscopic applications. We present several
cavity-comb coupling methods to take advantage of the broad spectral bandwidth
and narrow spectral components of a frequency comb. Finally, we present a
series of experimental measurements on trace gas detections, human breath
analysis, and characterization of cold molecular beams.


title: A Spitzer view of star formation in early-type galaxies

abstract:
  Many early-type galaxies are detected at 24 to 160 micron but the emission is
usually dominated by an AGN or heating from the evolved stellar population.
Here we present MIPS observations of a sample of elliptical and lenticular
galaxies which are rich in cold molecular gas, and we investigate how much of
the MIR to FIR emission could be due to star formation activity. The 24 micron
images show a rich variety of structures, including nuclear point sources,
rings, disks, and smooth extended emission, and comparisons to
matched-resolution CO and radio continuum images suggest that the bulk of the
24 micron emission can be traced to star formation. The star formation
efficiencies are comparable to those found in normal spirals. Some future
directions for progress are also mentioned.


title: The aDORe Federation Architecture

abstract:
  The need to federate repositories emerges in two distinctive scenarios. In
one scenario, scalability-related problems in the operation of a repository
reach a point beyond which continued service requires parallelization and hence
federation of the repository infrastructure. In the other scenario, multiple
distributed repositories manage collections of interest to certain communities
or applications, and federation is an approach to present a unified perspective
across these repositories. The high-level, 3-Tier aDORe federation architecture
can be used as a guideline to federate repositories in both cases. This paper
describes the architecture, consisting of core interfaces for federated
repositories in Tier-1, two shared infrastructure components in Tier-2, and a
single-point of access to the federation in Tier-3. The paper also illustrates
two large-scale deployments of the aDORe federation architecture: the aDORe
Archive repository (over 100,000,000 digital objects) at the Los Alamos
National Laboratory and the Ghent University Image Repository federation
(multiple terabytes of image files).


title:
Geometry and intersection theory on Hilbert schemes of families of nodal
  curves

abstract:
  We study the relative Hilbert scheme of a family of nodal (or smooth) curves,
over a base of arbitrary dimension, via its (birational) cycle map, going to
the relative symmetric product. We show the cycle map is the blowing up of the
discriminant locus, which consists of cycles with multiple points. We work out
the action of the blowup or 'discriminant' polarization on some natural cycles
in the Hilbert scheme, including generalized diagonals and cycles, called 'node
scrolls', parametrizing schemes supported on singular points. We derive an
intersection calculus for Chern classes of tautological vector bundles, which
are closely related to enumerative geometry.


title:
Muon spin rotation study of the magnetic penetration depth in the
  intercalated graphite superconductor CaC6

abstract:
  We report temperature- and magnetic field-dependent bulk muon spin rotation
measurements in a c-axis oriented superconductor CaC6 in the mixed state. Using
both a simple second moment analysis and the more precise analytical
Ginzburg-Landau model, we obtained a field independent in-plane magnetic
penetration depth {\lambda}ab (0) = 72(3) nm. The temperature dependencies of
the normalized muon spin relaxation rate and of the normalized superfluid
density result to be identical, and both are well represented by the clean
limit BCS model with 2\Delta/kB Tc = 3.6(1), suggesting that CaC6 is a fully
gapped BCS superconductor in the clean limit regime.


title:
Impurity resonance states in noncentrosymmetric superconductor
  $CePt_{3}Si$: a probe for Cooper-pairing symmetry

abstract:
  Motivated by the recent discovery of noncentrosymmetric superconductors, such
as $CePt_{3}Si$, $CeRhSi_{3}$ and $CeIrSi_{3}$, we investigate theoretically
the impurity resonance states with coexisting $s$- and p-wave pairing
symmetries. Due to the nodal structure of the gap function, we find single
nonmagnetic impurity-induced resonances appearing in the local density of state
(LDOS). In particular, we analyze the evolution of the local density of states
for coexisting isotropic s-wave and p-wave superconducting states and compare
with that of anisotropic s-wave and p-wave symmetries of the superconducting
gap. Our results show that the scanning tunneling microscopy can shed light on
the particular structure of the superconducting gap in non-centrosymmetric
superconductors.


title:
Influence of the losses on the super-resolution performances of an
  impedance matched negative index material

abstract:
  We discuss by a Poynting vector analysis how the losses of a negative index
material (NIM) affect the resolution performances of a Veselago-Pendry lens and
we analyze those performances in the framework of the Abbe criterion. Both the
limit of high losses and low losses are explored. We find that the impedance
matched NIM is able to resolve 30% better than the limit imposed by the Abbe
criterion even when the imaginary part of the refractive index (the material
losses) exceeds the absolute value of the real part of the refractive index.
The NIM is described by a lossy Drude model with equal permittivity and
permeability. By increasing the damping parameter of the Drude model we also
explore the regime where both permittivity and permeability are positive and
point out the conditions under which the metamaterial is still able to
super-resolve.


title: A Dual Polynomial for OR

abstract:
  We reprove that the approximate degree of the OR function on n bits is
Omega(sqrt(n)). We consider a linear program which is feasible if and only if
there is an approximate polynomial for a given function, and apply the duality
theory. The duality theory says that the primal program has no solution if and
only if its dual has a solution. Therefore one can prove the nonexistence of an
approximate polynomial by exhibiting a dual solution, coined the dual
polynomial. We construct such a polynomial.


title: Q-spaces and the foundations of quantum mechanics

abstract:
  Our aim in this paper is to take quite seriously Heinz Post's claim that the
non-individuality and the indiscernibility of quantum objects should be
introduced right at the start, and not made a posteriori by introducing
symmetry conditions. Using a different mathematical framework, namely,
quasi-set theory, we avoid working within a
label-tensor-product-vector-space-formalism, to use Redhead and Teller's words,
and get a more intuitive way of dealing with the formalism of quantum
mechanics, although the underlying logic should be modified. Thus, this paper
can be regarded as a tentative to follow and enlarge Heinsenberg's suggestion
that new phenomena require the formation of a new "closed" (that is, axiomatic)
theory, coping also with the physical theory's underlying logic and
mathematics.


title:
A Three-Dimensional Magnetohydrodynamic Model of Planetary Nebula Jets,
  Knots, and Filaments

abstract:
  The morphologies of planetary nebulae are believed to be self-organized
configurations. These configurations are modeled by three-dimensional
temporally self-similar magnetohydrodynamic solutions with radial flow, under
the gravitational field of a central star of mass $M$. These solutions
reproduce basic features, such as jets, point-symmetric knots, and filaments,
through plasma pressure, mass density, and magnetic field lines. The time
evolution function of the radial velocity starts as a slow wind and terminates
as a fast wind.


title:
Ages and Metallicities of Early-Type Void Galaxies from Line Strength
  Measurements

abstract:
  We present spectroscopic observations of 26 galaxies of type E and S0, based
on their blue morphologies, located in voids by the study of Grogin & Geller
(1999). Measurements of redshift, velocity dispersion, and four Lick line
indices, Mgb, Fe5270, Fe5335, and Hbeta with their errors are given for all of
these galaxies, along with Hbeta, [OIII], Halpha, and [NII] emission line
strengths for a subset of these objects. These sources are brighter than M star
for low density regions and tend to be bluer than their counterpart early-type
objects in high density regions. Using the models of Thomas et al. (2003) gives
metal abundances and ages with a median alpha enhancement, [alpha/Fe] = +0.13,
and median metals abundance, [Z/H] = +0.22, values comparable to those found
for E and S0 galaxies in clusters, but with a wider spread in [Z/H] towards low
values. If the emission line subsample is interpreted as younger, the
proportion of young objects is higher than for early-types in higher density
regions. There is a significant incidence of sources in the sample with
emission lines in their spectra (46% with Hbeta and [OIII] and 69% with Halpha
or [NII]) as well as shells and rings in their morphologies (19%). The
diagnostic log[NII/Halpha], log[OIII/Hbeta] diagram places 10 of 12 emission
line galaxies in or near the star forming and liner region and two among the
Seyferts. The Halpha fluxes indicate star formation rates of 0.2 to 1.0 Msun
per yr. The percentage of these early-type void galaxies undergoing star
formation appears to be higher compared to their cluster counterparts and the
range of ages wider.


title:
2D skew scattering in the vicinity and away from resonant scattering
  condition

abstract:
  We studied the energy dependence of the 2D skew scattering from strong
potential, for which the Born approximation is not applicable. Since the skew
scattering cross section is zero both at low and at high energies, it exhibits
a maximum as a function of energy of incident electron. We found analytically
the shape of the maximum for an exactly solvable model of circular-barrier
potential. Within a rescaling factor, this shape is universal for strong
potentials. If the repulsive potential has an attractive core, the discrete
levels of the core become quasilocal due to degeneracy with continuum. For
energy of incident electron close to the quasilocal state with zero angular
momentum, the enhancement of the net cross section is accompanied by resonant
enhancement of the skew scattering. By contrast, near the resonance with
quasilocal states having momenta $\pm 1$, the skew scattering cross section is
an odd function of energy deviation from the resonance, and passes through
zero, i.e., it exhibits a sign reversal. In the latter case, in the presence of
the Fermi sea, the Kondo resonance manifests itself in strong temperature
dependence of the skew scattering.


title: Hole superconductivity in Arsenic-Iron compounds

abstract:
  Superconductivity above 25K, and possibly above 40K, has recently been
discovered in $LaO_{1-x}F_xFeAs$ and related compounds. We propose that this is
another example of the mechanism of hole superconductivity at play. This
requires the existence of hole carriers at the Fermi energy, which appears to
contradict current observations. We propose that two-band conduction is taking
place in these materials, that the negative ion $As^{-3}$ plays a key role, and
that superconductivity is non-phononic and driven by pairing and undressing of
heavily dressed hole carriers to lower their kinetic energy. We make several
predictions of future observations based on our theory.


title:
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) 2005:
  Calibration and Targeted Sources

abstract:
  The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated
successfully during a 100-hour flight from northern Sweden in June 2005
(BLAST05). As part of the calibration and pointing procedures, several compact
sources were mapped, including solar system, Galactic, and extragalactic
targets, specifically Pallas, CRL 2688, LDN 1014, IRAS 20126+4104, IRAS
21078+5211, IRAS 21307+5049, IRAS 22134+5834, IRAS 23011+6126, K3-50, W 75N,
and Mrk 231. One additional source, Arp 220, was observed and used as our
primary calibrator. Details of the overall BLAST05 calibration procedure are
discussed here. The BLAST observations of each compact source are described,
flux densities and spectral energy distributions are reported, and these are
compared with previous measurements at other wavelengths. The 250, 350, and 500
um BLAST data can provide useful constraints to the amplitude and slope of the
submillimeter continuum, which in turn may be useful for the improved
calibration of other submillimeter instruments.


title: The clustering of the first galaxy halos

abstract:
  We explore the clustering properties of high redshift dark matter halos,
focusing on halos massive enough to host early generations of stars or galaxies
at redshift 10 and greater. Halos are extracted from an array of dark matter
simulations able to resolve down to the "mini-halo" mass scale at redshifts as
high as 30, thus encompassing the expected full mass range of halos capable of
hosting luminous objects and sources of reionization. Halo clustering on
large-scales agrees with the Sheth, Mo & Tormen halo bias relation within all
our simulations, greatly extending the regime where large-scale clustering is
confirmed to be "universal" at the 10-20% level (which means, for example, that
3sigma halos of cluster mass at z=0 have the same large-scale bias with respect
to the mass distribution as 3sigma halos of galaxy mass at z=10). However, on
small-scales, the clustering of our massive halos (> ~10^9 Msun/h) at these
high redshifts is stronger than expected from comparisons with small-scale halo
clustering extrapolated from lower redshifts. This implies "non-universality"
in the scale-dependence of halo clustering, at least for the commonly used
parameterizations of the scale-dependence of bias that we consider. We provide
a fit for the scale-dependence of bias in our results. This study provides a
basis for using extraordinarily high redshift galaxies (redshift ~10) as a
probe of cosmology and galaxy formation at its earliest stages. We show also
that mass and halo kinematics are strongly affected by finite simulation
volumes. This suggests the potential for adverse affects on gas dynamics in
hydrodynamic simulations of limited volumes, such as is typical in simulations
of the formation of the "first stars", though further study is warranted.


title:
Emerging Massive Star Clusters Revealed: High Resolution Imaging of NGC
  4449 from the Radio to the Ultraviolet

abstract:
  We present a multi-wavelength study of embedded massive clusters in the
nearby (3.9 Mpc) starburst galaxy NGC 4449 in an effort to uncover the earliest
phases of massive cluster evolution. By combining high resolution imaging from
the radio to the ultraviolet, we reveal these clusters in the process of
emerging from their gaseous and dusty birth cocoons. We use Very Large Array
(VLA) observations at centimeter wavelengths to identify young clusters
surrounded by ultra-dense HII regions, detectable via their production of
thermal free-free radio continuum. Ultraviolet, optical and infrared
observations are obtained from the Hubble and Spitzer Space Telescope archives
for comparison. We detect 39 compact radio sources towards NGC 4449 at 3.6 cm
using the highest resolution (1.3") and sensitivity (RMS ~ 12 uJy) VLA image of
the galaxy to date. We reliably identify 13 thermal radio sources and their
physical properties are derived using both nebular emission from the HII
regions and SED fitting to the stellar continuum. These radio detected clusters
have ages < 5 Myr and stellar masses of order 10^4 Msun. The measured
extinctions are quite low: 12 of the 13 thermal radio sources have Av < 1.5,
while the most obscured source has Av ~ 4.3. By combining results from the
nebular and stellar emission, we find an I-band excess that is anti-correlated
with cluster age and an apparent mass-age correlation. Additionally, we find
evidence that local processes such as supernovae and stellar winds are likely
playing an important role in triggering the current bursts of star formation
within NGC 4449.


title: Embedding in a perfect code

abstract:
  A binary 1-error-correcting code can always be embedded in a 1-perfect code
of some larger length


title: Stochastic Mean-Field Theory for the Disordered Bose-Hubbard Model

abstract:
  We investigate the effect of diagonal disorder on bosons in an optical
lattice described by an Anderson-Hubbard model at zero temperature. It is known
that within Gutzwiller mean-field theory spatially resolved calculations suffer
particularly from finite system sizes in the disordered case, while arithmetic
averaging of the order parameter cannot describe the Bose glass phase for
finite hopping $J>0$. Here we present and apply a new \emph{stochastic}
mean-field theory which captures localization due to disorder, includes
non-trivial dimensional effects beyond the mean-field scaling level and is
applicable in the thermodynamic limit. In contrast to fermionic systems, we
find the existence of a critical hopping strength, above which the system
remains superfluid for arbitrarily strong disorder.


title:
Emergent complexity: what uphill analysis or downhill invention can not
  do

abstract:
  In these notes we review emergent phenomena in complex systems, emphasizing
ways to identify potential underlying universal mechanisms that generates
complexity. The discussion is centered around the emergence of collective
behavior in dynamical systems when they are poised near a critical point of a
phase transition, either by tuning or by self-organization. We then argue the
rationale for our proposal that the brain is naturally poised near criticality
reviewing recent results as well as the implications of this view of the
functioning brain.


title:
All timelike supersymmetric solutions of N=2, D=4 gauged supergravity
  coupled to abelian vector multiplets

abstract:
  The timelike supersymmetric solutions of N=2, D=4 gauged supergravity coupled
to an arbitrary number of abelian vector multiplets are classified using
spinorial geometry techniques. We show that the generalized holonomy group for
vacua preserving N supersymmetries is GL((8-N)/2,C) $\ltimes$ N/2 C^((8-N)/2)
$\subseteq$ GL(8,R), where N=0,2,4,6,8. The spacetime turns out to be a
fibration over a three-dimensional base manifold with U(1) holonomy and
nontrivial torsion. Our results can be used to construct new supersymmetric AdS
black holes with nontrivial scalar fields turned on.


title: Triangle Area Numbers and Solid Rectangular Numbers

abstract:
  In this work, we define a triangle area number to be the area number of a
triangle whose sides have integer lengths, and whose area is a rational number.
In Result 3, on page 17, we prove that every triangle area number is in fact an
integer which is a multiple of 6. Certain divisibility and other conditions and
formulas are also derived, which the three integer sidelengths must satisfy. On
pages 20 and 21, we list all the triangle area numbers not exceeding 999.


title: Classical and Quantum Tensor Product Expanders

abstract:
  We introduce the concept of quantum tensor product expanders. These are
expanders that act on several copies of a given system, where the Kraus
operators are tensor products of the Kraus operator on a single system. We
begin with the classical case, and show that a classical two-copy expander can
be used to produce a quantum expander. We then discuss the quantum case and
give applications to the Solovay-Kitaev problem. We give probabilistic
constructions in both classical and quantum cases, giving tight bounds on the
expectation value of the largest nontrivial eigenvalue in the quantum case.


title: Theory of ground state factorization in quantum cooperative systems

abstract:
  We introduce a general analytic approach to the study of factorization points
and factorized ground states in quantum cooperative systems. The method allows
to determine rigorously existence, location, and exact form of separable ground
states in a large variety of, generally non-exactly solvable, spin models
belonging to different universality classes. The theory applies to
translationally invariant systems, irrespective of spatial dimensionality, and
for spin-spin interactions of arbitrary range.

categories: cond-mat.other hep-th math-ph math.MP quant-ph


title: Survival of the Dirac points in rippled graphene

abstract:
  We study the effects of the rippling of the graphene sheet on the
quasiparticle dispersion. This is achieved using a generalization to the
honeycomb lattice of the Momentum Average approximation, which is accurate for
all coupling strengths and at all energies. We show that even though the
position of the Dirac points may move and the Fermi speed can be renormalized
significantly, quasiparticles with very long lifetimes survive near the Dirac
points even for very strong couplings.


title: Gamma-Ray Bursts from tidally spun-up Wolf-Rayet stars?

abstract:
  The collapsar model requires rapidly rotating Wolf-Rayet stars as progenitors
of long gamma-ray bursts. However, Galactic Wolf-Rayet stars rapidly lose
angular momentum due to their intense stellar winds. We investigate whether the
tidal interaction of a Wolf-Rayet star with a compact object in a binary system
can spin up the Wolf-Rayet star enough to produce a collapsar. We compute the
evolution of close Wolf-Rayet binaries, including tidal angular momentum
exchange, differential rotation of the Wolf-Rayet star, internal magnetic
fields, stellar wind mass loss, and mass transfer. The Wolf-Rayet companion is
approximated as a point mass. We then employ a population synthesis code to
infer the occurrence rates of the various relevant binary evolution channels.
We find that the simple scenario -- i.e., the Wolf-Rayet star being tidally
spun up and producing a collapsar -- does not occur at solar metallicity and
may only occur with low probability at low metallicity. It is limited by the
widening of the binary orbit induced by the strong Wolf-Rayet wind or by the
radius evolution of the Wolf-Rayet star that most often leads to a binary
merger. The tidal effects enhance the merger rate of Wolf-Rayet stars with
black holes such that it becomes comparable to the occurrence rate of long
gamma-ray bursts.


title: Neutrino tri-bi-maximal mixing through sequential dominance

abstract:
  We consider an existing framework of models where the neutrino Dirac and
Majorana mass terms are related, and clarify how the mass structures interact
through the type I seesaw mechanism, producing exact tri-bi-maximal mixing for
the effective neutrinos in the limit of strong Majorana mass hierarchy
(sequential dominance). In order to better illustrate this, we draw the seesaw
diagrams expanded to show the relevant details, discuss an underlying symmetry
that must be preserved by the neutrino mass terms, and diagonalise the
effective neutrino mass matrix corresponding to the sequential dominance limit.


title: Relativity Revisited

abstract:
  Was Einstein wrong? This paper provides a detailed technical review of
Einstein's special and general relativity from an astrophysical perspective,
including the historical development of the theories, experimental tests,
modern applications to black holes, cosmology and parallel universes, and last
but not least, novel ways of expressing their seven most important equations.


title: Time Parallel Scalable Multiphysics/Multiscale Framework

abstract:
  We propose a new computational framework that combines the recently developed
time-parallel (TP) and the compound wavelet matrix (CWM) methods. The
framework, termed tpCWM, offers significant computational acceleration by
making multiscale/multiphysics simulations computationally scalable in time and
space domains. We demonstrate the accuracy and the scalability of the method on
a prototype problem with oscillatory trajectory. The method corrects the coarse
solution by iterative use of the CWM, which compounds the fine and the coarse
solutions for the processes. Computational savings, over the fine solution as
well as the TP method, in terms of the real time required to perform the
simulations, can reach several orders of magnitude. We believe that this method
is general enough to be applicable to a wide-class of computational physics
problems. Tendency towards large number of cores and processors in parallel
computers is compatible with the computational scalability of the algorithm.


title: In search of a structural model for a thiolate-protected Au38 cluster

abstract:
  The structure of thiolate-protected gold cluster Au38(SR)24 has not been
determined experimentally and the best available signature is its measured
optical spectrum. Using this signature and energetic stability as criteria and
SCH3 for SR, we compare four candidate structures: two from others and two we
obtained. Our models are distinct from others in that thiolate groups form
monomers and dimers of the staple motif (a nearly linear RS-Au-SR bonding
unit). We examine the energetics and electronic structures of the four
structures with density functional theory (DFT) and compute their optical
spectra with time-dependent DFT. We show that our dimer-dominated model is over
2.6 eV lower in energy than the two models from others and 1.3 eV lower than
our previous monomer-dominated model. The dimer-dominated model also presents
good agreement with experiment for optical absorption.


title: The stellar halo of the Galaxy

abstract:
  Stellar halos may hold some of the best preserved fossils of the formation
history of galaxies. They are a natural product of the merging processes that
probably take place during the assembly of a galaxy, and hence may well be the
most ubiquitous component of galaxies, independently of their Hubble type. This
review focuses on our current understanding of the spatial structure, the
kinematics and chemistry of halo stars in the Milky Way. In recent years, we
have experienced a change in paradigm thanks to the discovery of large amounts
of substructure, especially in the outer halo. I discuss the implications of
the currently available observational constraints and fold them into several
possible formation scenarios. Unraveling the formation of the Galactic halo
will be possible in the near future through a combination of large wide field
photometric and spectroscopic surveys, and especially in the era of Gaia.


title: D0 - D0bar Mixing Analyses at BaBar

abstract:
  We summarise results of analyses of D0 meson mixing parameters performed by
the BaBar collaboration.


title: A Search for Interstellar CH$_2$D$^+$

abstract:
  We report on a search for Interstellar CH2D+. Four transitions occur in
easily accessible portions of the spectrum; we report on emission at the
frequencies of these transitions toward high column density star-forming
regions. While the observations can be interpreted as being consistent with a
detection of the molecule, further observations will be needed to secure that
identification. The CH2D+ rotational spectrum has not been measured to high
accuracy. Lines are weak, as the dipole moment induced by the inclusion of
deuterium in the molecule is small. Astronomical detection is favored by
observations toward strongly deuterium-fractionated sources. However, enhanced
deuteration is expected to be most significant at low temperatures. The
sparseness of the available spectrum and the low excitation in regions of high
fractionation make secure identification of CH2D+ difficult. Nonetheless, owing
to the importance of CH3+ to interstellar chemistry, and the lack of rotational
transitions of that molecule owing to its planar symmetric structure, a measure
of its abundance would provide key data to astrochemical models.


title: Quantum Bit Strings and Prefix-Free Hilbert Spaces

abstract:
  We give a mathematical framework for manipulating indeterminate-length
quantum bit strings. In particular, we define prefixes, fragments, tensor
products and concatenation of such strings of qubits, and study their
properties and relationships.
  The results are then used to define prefix-free Hilbert spaces in a more
general way than in previous work, without assuming the existence of a basis of
length eigenstates. We prove a quantum analogue of the Kraft inequality,
illustrate the results with some examples and discuss the relevance of
prefix-free Hilbert spaces for lossless compression.


title:
Exact Solution for the Stokes Problem of an Infinite Cylinder in a Fluid
  with Harmonic Boundary Conditions at Infinity

abstract:
  We present an exact solution for the time-dependent Stokes problem of an
infinite cylinder of radius r=a in a fluid with harmonic boundary conditions at
infinity. This is a 3-dimensional problem but, because of translational
invariance along the axis of the cylinder it effectively reduces to a
2-dimensional one. The Stokes problem being a linear reduction of the full
Navier-Stokes equations, we show how to satisfy the no-slip boundary condition
at the cylinder surface and the harmonic boundary condition at infinity,
exhibit the full velocity field for radius r>a, and discuss the nature of the
solutions for the specific case of air at sea level.


title: The Mass of Virialized Dark Matter Haloes

abstract:
  Virial mass is used as an estimator for the mass of a dark matter halo.
However, the commonly used constant overdensity criterion does not reflect the
dynamical structure of haloes. Here we analyze dark matter cosmological
simulations in order to obtain properties of haloes of different masses
focusing on the size of the region with zero mean radial velocity. Dark matter
inside this region is stationary, and thus the mass of this region is a much
better approximation for the virial mass.


title: Distortion of Mappings and $L_{q,p}$-Cohomology

abstract:
  We study some relation between some geometrically defined classes of
diffeomorphisms between manifolds and the $L_{q,p}$-cohomology of these
manifolds. Some applications to vanishing and non vanishing results in
$L_{q,p}$-cohomology are given.


title:
Discrete series characters for affine Hecke algebras and their formal
  degrees

abstract:
  We introduce the generic central character of an irreducible discrete series
representation of an affine Hecke algebra. Using this invariant we give a new
classification of the irreducible discrete series characters for all abstract
affine Hecke algebras (except for the types E) with arbitrary positive
parameters and we prove an explicit product formula for their formal degrees
(in all cases).


title: A combinatorial proof of Rayleigh monotonicity for graphs

abstract:
  We give an elementary, self-contained, and purely combinatorial proof of the
Rayleigh monotonicity property of graphs.


title: Nuclearity-related properties for nonselfadjoint algebras

abstract:
  In analogy with the C*-algebra theory, we study variants appropriate to
nonselfadjoint algebras of nuclearity, the local lifting property, exactness,
and the weak expectation property. In addition, we study the relationships
between these notions, and how they are connected with the classical C*-algebra
theory through the use of C*-algebras generated by the algebra.


title: The HI distribution in the outskirts of M33 with the ALFALFA survey

abstract:
  Spiral galaxies appear to be dynamical systems whose disks are still forming
at the current epoch and which continue to accrete mass. The presence of
extraplanar gas in spirals indicates that galactic halos can contain at least
part of the material needed to fuel the star formation activity in their disks.
Here we present the analysis of the ALFALFA survey data in the region of M33
aimed at searching high velocity clouds around this Local Group galaxy. We find
a varied population of HI clouds with masses ranging between 4 x 10^4 and few
times 10^6 M_sun. We also detect an extended HI complex at anomalous
velocities, whose extragalactic nature cannot be firmly established. We
estimate that the total amount of neutral hydrogen mass associated to these
clouds is around 10^7 M_sun.