title: A Morphological and Statistical Analysis of Ansae in Barred Galaxies

abstract:
  Many barred galaxies show a set of symmetric enhancements at the ends of the
stellar bar, called {\it ansae}, or the ``handles'' of the bar. The ansa bars
have been in the literature for some decades, but their origin has still not
been specifically addressed, although, they could be related to the growth
process of bars. But even though ansae have been known for a long time, no
statistical analysis of their relative frequency of occurrence has been
performed yet. Similarly, there has been no study of the varieties in
morphology of ansae even though significant morphological variations are known
to characterise the features. In this paper, we make a quantitative analysis of
the occurrence of ansae in barred galaxies, making use of {\it The de
Vaucouleurs Atlas of Galaxies} by Buta and coworkers. We find that $\sim 40%$
of SB0's show ansae in their bars, thus confirming that ansae are common
features in barred lenticulars. The ansa frequency decreases dramatically with
later types, and hardly any ansae are found in galaxies of type Sb or later.
The bars in galaxies with ansae are stronger in the median than those in
galaxies without ansae, but the presence of inner and outer rings is not
related to the presence of ansae. Implications of these results and theories
for the possible origin of ansae are discussed briefly.


title: Nonequilibrium Electron Interactions in Metal Films

abstract:
  Ultrafast relaxation dynamics of an athermal electron distribution is
investigated in silver films using a femtosecond pump-probe technique with 18
fs pulses in off-resonant conditions. The results yield evidence for an
increase with time of the electron-gas energy loss rate to the lattice and of
the free electron damping during the early stages of the electron-gas
thermalization. These effects are attributed to transient alterations of the
electron average scattering processes due to the athermal nature of the
electron gas, in agreement with numerical simulations.


title: Noncommutative Quantum Mechanics Viewed from Feynman Formalism

abstract:
  Dyson published in 1990 a proof due to Feynman of the Maxwell equations. This
proof is based on the assumption of simple commutation relations between
position and velocity. We first study a nonrelativistic particle using Feynman
formalism. We show that Poincar\'{e}'s magnetic angular momentum and Dirac
magnetic monopole are the direct consequences of the structure of the sO(3) Lie
algebra in Feynman formalism. Then we show how to extend this formalism to the
dual momentum space with the aim of introducing Noncommutative Quantum
Mechanics which was recently the subject of a wide range of works from particle
physics to condensed matter physics.


title:
Competition between final-state and pairing-gap effects in the
  radio-frequency spectra of ultracold Fermi atoms

abstract:
  The radio-frequency spectra of ultracold Fermi atoms are calculated by
including final-state interactions affecting the excited level of the
transition, and compared with the experimental data. A competition is revealed
between pairing-gap effects which tend to push the oscillator strength toward
high frequencies away from threshold, and final-state effects which tend
instead to pull the oscillator strength toward threshold. As a result of this
competition, the position of the peak of the spectra cannot be simply related
to the value of the pairing gap, whose extraction thus requires support from
theoretical calculations.


title: SPH simulations of the chemical evolution of bulges

abstract:
  We have implemented a chemical evolution model on the parallel AP3M+SPH DEVA
code which we use to perform high resolution simulations of spiral galaxy
formation. It includes feedback by SNII and SNIa using the Qij matrix
formalism. We also include a diffusion mechanism that spreads newly introduced
metals. The gas cooling rate depends on its specific composition. We study the
stellar populations of the resulting bulges finding a potential scenario where
they seem to be composed of two populations: an old, metal poor,
$\alpha$-enriched population, formed in a multiclump scenario at the beginning
of the simulation and a younger one, formed by slow accretion of satellites or
gas, possibly from the disk due to instabilities.


title: Spin-gravity coupling and gravity-induced quantum phases

abstract:
  External gravitational fields induce phase factors in the wave functions of
particles. The phases are exact to first order in the background gravitational
field, are manifestly covariant and gauge invariant and provide a useful tool
for the study of spin-gravity coupling and of the optics of particles in
gravitational or inertial fields. We discuss the role that spin-gravity
coupling plays in particular problems.


title:
Astrometry of Galactic Star Forming Region Sharpless 269 with VERA :
  Parallax Measurements and Constraint on Outer Rotation Curve

abstract:
  We have performed high-precision astrometry of H2O maser sources in Galactic
star forming region Sharpless 269 (S269) with VERA. We have successfully
detected a trigonometric parallax of 189+/-8 micro-arcsec, corresponding to the
source distance of 5.28 +0.24/-0.22 kpc. This is the smallest parallax ever
measured, and the first one detected beyond 5 kpc. The source distance as well
as proper motions are used to constrain the outer rotation curve of the Galaxy,
demonstrating that the difference of rotation velocities at the Sun and at S269
(which is 13.1 kpc away from the Galaxy's center) is less than 3%. This gives
the strongest constraint on the flatness of the outer rotation curve and
provides a direct confirmation on the existence of large amount of dark matter
in the Galaxy's outer disk.


title: Random colourings of aperiodic graphs: Ergodic and spectral properties

abstract:
  We study randomly coloured graphs embedded into Euclidean space, whose vertex
sets are infinite, uniformly discrete subsets of finite local complexity. We
construct the appropriate ergodic dynamical systems, explicitly characterise
ergodic measures, and prove an ergodic theorem. For covariant operators of
finite range defined on those graphs, we show the existence and self-averaging
of the integrated density of states, as well as the non-randomness of the
spectrum. Our main result establishes Lifshits tails at the lower spectral edge
of the graph Laplacian on bond percolation subgraphs, for sufficiently small
probabilities. Among other assumptions, its proof requires exponential decay of
the cluster-size distribution for percolation on rather general graphs.


title: Supersymmetric lattice models in one and two dimensions

abstract:
  We study and simulate N=2 supersymmetric Wess-Zumino models in one and two
dimensions. For any choice of the lattice derivative, the theories can be made
manifestly supersymmetric by adding appropriate improvement terms corresponding
to discretizations of surface integrals. In particular, we check that fermionic
and bosonic masses coincide and the unbroken Ward identities are fulfilled to
high accuracy. Equally good results for the effective masses can be obtained in
a model with the SLAC derivative (even without improvement terms). In two
dimensions we introduce a non-standard Wilson term in such a way that the
discretization errors of the kinetic terms are only of order a squared. Masses
extracted from the corresponding manifestly supersymmetric model prove to
approach their continuum values much quicker than those from a model containing
the standard Wilson term. Again, a comparable enhancement can be achieved in a
theory using the SLAC derivative.


title: Reply to ''Comment on 'Regularizing Capacity of Metabolic Networks' ''

abstract:
  In a recent paper [C. Marr, M. Mueller-Linow, and M.-T. Huett, Phys. Rev. E
75, 041917 (2007)] we discuss the pronounced potential of real metabolic
network topologies, compared to randomized counterparts, to regularize complex
binary dynamics. In their comment [P. Holme and M. Huss, arXiv:0705.4084v1],
Holme and Huss criticize our approach and repeat our study with more realistic
dynamics, where stylized reaction kinetics are implemented on sets of pairwise
reactions. The authors find no dynamic difference between the reaction sets
recreated from the metabolic networks and randomized counterparts. We reproduce
the author's observation and find that their algorithm leads to a dynamical
fragmentation and thus eliminates the topological information contained in the
graphs. Hence, their approach cannot rule out a connection between the topology
of metabolic networks and the ubiquity of steady states.


title: On Random Unitary Channels

abstract:
  In this article we provide necessary and sufficient conditions for a
completely positive trace-preserving (CPT) map to be decomposable into a convex
combination of unitary maps. Additionally, we set out to define a proper
distance measure between a given CPT map and the set of random unitary maps,
and methods for calculating it. In this way one could determine whether
non-classical error mechanisms such as spontaneous decay or photon loss
dominate over classical uncertainties, for example in a phase parameter. The
present paper is a step towards achieving this goal.


title: Shaping Planetary Nebulae by Jets

abstract:
  We conduct 2D axisymmetrical hydrodynamical simulations to investigate the
interaction of a collimated fast wind (CFW; wide jets) with a spherical AGB
wind. The code includes radiative cooling. We find that the shape of the
planetary nebula (PN) is sensitive to the exact mass loss history of the AGB
wind, and the opening angle of the CFW. Some typical PN morphologies are
obtained, but many other observed morphologies seem to require more ingredients
than what we assume in our present simulations, e.g., equatorial AGB wind, and
ionization and fast wind during the PN phase. The hot bipolar bubble formed by
the jets is an X-ray source.


title:
Diffuse Galactic light at high Galactic latitude: nature and
  interpretation

abstract:
  The hypothesis of an extended red emission (ERE) in diffuse Galactic light
(DGL) has been put forward in 1998 by Gordon, Witt and Friedmann who found that
scattered starlight was not enough to explain the amount of DGL in the R band,
in some high Galactic latitude directions. This paper re-investigates, for high
Galactic latitudes, the brightnesses and colours of DGL, integrated star and
galaxy light (ISGL), and of the total extrasolar light (ISGL+DGL) measured by
Pioneer. Under the traditional assumption that DGL is forward scattering of
background starlight by interstellar dust on the line of sight, ISGL and
Pioneer have very close colours, as it is found by Gordon, Witt and Friedmann.
Pioneer observations at high |b| thus accept an alternative and simple
interpretation, with no involvement of ERE in DGL.


title: Sympathetic cooling in a mixture of diamagnetic and paramagnetic atoms

abstract:
  We have experimentally realized a hybrid trap for ultracold paramagnetic
rubidium and diamagnetic ytterbium atoms by combining a bichromatic optical
dipole trap for ytterbium with a Ioffe-Pritchard-type magnetic trap for
rubidium. In this hybrid trap, sympathetic cooling of five different ytterbium
isotopes through elastic collisions with rubidium was achieved. A strong
dependence of the interspecies collisional cross section on the mass of the
ytterbium isotope was observed.


title: Study of the core-excited Fano Resonances in the neutron-rich C-isotopes

abstract:
  Fano Resonances are a new continuum excitation mode in light exotic nuclei.
By the QPC model we explain these sharp and asymmetric structures as due to the
coupling of a single particle elastic channel to the closed core-excited
channels. Theoretical model calculations are compared for 15C, 17C and 19C. The
theoretical results for 15C are in qualitative agreement with the experimental
spectrum.


title: Long GRBs from binary stars: runaway, Wolf-Rayet progenitors

abstract:
  The collapsar model for long gamma-ray bursts requires a rapidly rotating
Wolf-Rayet star as progenitor. We test the idea of producing rapidly rotating
Wolf-Rayet stars in massive close binaries through mass accretion and
consecutive quasi-chemically homogeneous evolution; the latter had previously
been shown to provide collapsars below a certain metallicity threshold for
single stars. The binary channel presented here may provide a means for massive
stars to obtain the high rotation rates required to evolve quasi-chemically
homogeneous and fulfill the collapsar scenario. Moreover, it suggests that a
possibly large fraction of long gamma-ray bursts occurs in runaway stars.


title:
Small Angle Scattering and Zeta Potential of Liposomes Loaded with
  Octa(carboranyl)porphyrazine

abstract:
  In this work the physicochemical characterization of liposomes loaded with a
newly synthesised carboranyl porphyrazine (H2HECASPz) is described. This
molecule represents a potential drug for different anticancer therapies, such
as Boron Neutron Capture Therapy, Photodynamic Therapy and Photothermal
Therapy. Different loading methods and different lipid mixtures were tested.
The corresponding loaded vectors were studied by Small Angle Scattering (SANS
and SAXS), light scattering and zeta potential. The combined analysis of
structural data at various length scales and the measurement of the surface
charge allowed to obtain a detailed characterization of the investigated
systems. The mechanisms underlying the onset of differences in relevant
physicochemical parameters (size, polydispersity and charge) were also
critically discussed.


title:
Eigenvalue pinching and application to the stability and the almost
  umbilicity of hypersurfaces

abstract:
  In this paper we give pinching theorems for the first nonzero eigenvalue of
the Laplacian on the compact hypersurfaces of ambient spaces with bounded
sectional curvature. As application we deduce rigidity results for stable
constant mean curvature hypersurfaces $M$ of these spaces $N$. Indeed, we prove
that if $M$ is included in a ball of radius small enough then the
Hausdorff-distance between $M$ and a geodesic sphere $S$ of $N$ is small.
Moreover $M$ is diffeomorphic and quasi-isometric to $S$. As other application,
we give rigidity results for almost umbilic hypersurfaces.


title:
SPLASH: An interactive visualisation tool for Smoothed Particle
  Hydrodynamics simulations

abstract:
  This paper presents SPLASH, a publicly available interactive visualisation
tool for Smoothed Particle Hydrodynamics (SPH) simulations. Visualisation of
SPH data is more complicated than for grid-based codes because the data is
defined on a set of irregular points and therefore requires a mapping procedure
to a two dimensional pixel array. This means that, in practise, many authors
simply produce particle plots which offer a rather crude representation of the
simulation output. Here we describe the techniques and algorithms which are
utilised in SPLASH in order to provide the user with a fast, interactive and
meaningful visualisation of one, two and three dimensional SPH results.


title: An Introduction to Galactic Chemical Evolution

abstract:
  The formalism of the simple model of galactic chemical evolution (GCE) and
its main ingredients (stellar properties, initial mass function, star formation
rate and gas flows) are presented in this tutorial. It is stressed that GCE is
not (yet) an astrophysical theory, but it merely provides a framework in which
the large body of data concerning the chemical composition of stars and gas in
galaxies may be intrepreted. A few examples illustrating those concepts are
provided, through studies of the Solar neighborhood and of the Milky Way's
halo.


title:
AC/DC Susceptibility of the Heavy-Fermion Superconductor CePt3Si under
  Pressure

abstract:
  We have investigated the pressure dependence of ac and dc susceptibilities of
the heavy-fermion superconductor CePt3Si (Tc= 0.75 K) that coexists with
antiferromagnetism (TN = 2.2 K). As hydrostatic pressure is increased, Tc first
decreases rapidly, then rather slowly near the critical pressure Pc = 0.6 GPa
and shows a stronger decrease again at higher pressures, where Pc is the
pressure at which TN becomes zero. A transition width and a difference in the
two transition temperatures defined in the form of structures in the
out-of-phase component of ac susceptibilities also become small near Pc,
indicating that a double transition observed in CePt3Si is caused by some
inhomogeneous property in the sample that leads to a spatial variation of local
pressure. A sudden increase in the Meissner fraction above Pc suggests the
influence of antiferromagnetism on superconductivity.


title: Electromagnetic form factors of the Delta(1232) in Dual-Large N_c QCD

abstract:
  The three electromagnetic form factors of the $\Delta(1232)$ resonance,
$G^*_M(q^2)$, $G^*_E(q^2)$, and $G^*_C(q^2)$ are obtained in the space-like
region using a Dual Resonance Model realization of QCD in the large $N_c$ limit
(Dual-${QCD}_{\infty}$). Each form factor involves a single free parameter
which is fixed by fitting data on $G^*_M(q^2)$, and on the ratios $R_{EM}(q^2)$
and $R_{SM}(q^2)$. Good agreement with experiment is obtained for all three
quantities. Results are then used to predict the $q^2$-dependence of the chiral
effective-field theory form factors $g_M(q^2)$, $g_E(q^2)$, and $g_C(q^2)$.


title:
Light-Cone Sum Rules for the Form Factors of the $N\gamma\Delta$
  transition at Q^2=0

abstract:
  The radiative $\Delta \to \gamma N$ transition is examined at the real photon
point $Q^2=0$ using the framework of light-cone QCD sum rules. In particular,
we determine the sum rules for the transition form factors $G_M(0)$ and
$R_{EM}$ up to twist 4.


title: Categories of categories

abstract:
  A certain amount of category theory is developed in an arbitrary finitely
complete category with a factorization system on it, playing the role of the
comprehensive factorization system on Cat. Those aspects related to the
concepts of finality (in particular terminal objects), discreteness and
components, representability, colimits and universal arrows, seem to be best
expressed in this very general setting. Furthermore, at this level we are in
fact doing not only (E,M)-category theory but, in a sense, also (E,M)-topology.
Other axioms, regarding power objects, duality, exponentials and the arrow
object, are considered.


title:
Modeling long-range cross-correlations in two-component ARFIMA and
  FIARCH processes

abstract:
  We investigate how simultaneously recorded long-range power-law correlated
multi-variate signals cross-correlate. To this end we introduce a two-component
ARFIMA stochastic process and a two-component FIARCH process to generate
coupled fractal signals with long-range power-law correlations which are at the
same time long-range cross-correlated. We study how the degree of
cross-correlations between these signals depends on the scaling exponents
characterizing the fractal correlations in each signal and on the coupling
between the signals. Our findings have relevance when studying parallel outputs
of multiple-component of physical, physiological and social systems.


title: Modelling colossal magnetoresistance manganites

abstract:
  I briefly survey here attempts to model the rich and strange behaviour of
colossal magnetoresistance manganites, after outlining some of the phenomena
observed in them, and describing the three relevant strong local interactions
of the e_g electrons (in two different orbital states at each site), namely
with Jahn-Teller phonon modes (strength g), with resident t_2g spins
(ferromagnetic Hund's rule coupling J_H) and amongst each other (the Mott
Hubbard correlation U) . A new two fluid model of nearly localized l polarons
and band (b) electrons for low energy behaviour emerges for large g; some of
its applications are mentioned here. I describe some results of strong coupling
U, J_H calculations in single site DMFT (Dynamical Mean Field Theory), and show
that in the wide orbital liquid regime many characteristic manganite phenomena
such as an insulating ferromagnetic ground state, thermal insulator metal
transition, colossal magnetoresistance (cmr), materials systematics and the
observed low effective carrier density can all be understood qualitatively and
quantitatively. We also discuss the two 'phase' coexistence frequently found in
these systems, and show that electrostatic coulomb interactions mute lb phase
separation into nanoscale electronic inhomogeneity with l regions and b
puddles. Finally, some problems of current interest as well as general ones
arising, eg polarons and the physics of large electron phonon coupling g in the
adiabatic regime, are mentioned.


title:
Anomalous magnetic hysteresis in the microwave surface resistance of
  MgB2 superconductor

abstract:
  We report experimental results of the field-induced variations of the
microwave surface resistance in samples of MgB2, produced by different methods.
By sweeping the DC magnetic field at increasing and decreasing values, we have
detected a magnetic hysteresis that can be ascribed to the different magnetic
induction, due to the critical state of the fluxon lattice. The hysteresis
observed in the bulk samples has an unusual shape, which cannot be justified in
the framework of the critical-state models.


title: Lattice cohomology of normal surface singularities

abstract:
  For any negative definite plumbed 3-manifold M we construct from its plumbed
graph a graded Z[U]-module. This, for rational homology spheres, conjecturally
equals the Heegaard-Floer homology of Ozsvath and Szabo, but it has even more
structure. If M is a complex singularity link then the normalized
Euler-characteristic can be compared with the analytic invariants. The
Seiberg--Witten Invariant Conjecture is discussed in the light of this new
object.


title: New approach to description of Majorana properties of neutral particles

abstract:
  Two mathematical models based on Pauli transformations including U(1) chiral
group and Pauli SU(2) group, that mixes particle and antiparticle states, are
developed for description of Majorana properties of neutral particles. The
first one describes a system, incorporating left- and right-handed fermions of
the same flavor, and it is a generalization of the Majorana model of his
pioneer article of 1937 year. The second describes a two-flavor neutrino system
with quantum numbers of Zel'dovich-Konopinsky-Mahmoud (ZKM) type. For massless
fermions the Pauli symmetry is exact and leads to the coserved generalized
lepton charge. It is a Pauli isospace vector, whose different directions are
coordinated with Dirac or generalized Majorana properties. In nonzero-mass case
the models describe the combined Dirac-Majorana properties of neutral
particles, which are characterized either by the generalized lepton charges of
ZKM-type or by the eigenvalues of the operator that is the product of the
charge operator and chirality. The latter is connected with operator of the
structure of Lagrangian mass term or with the generalized flavor number of the
second model. The choice of the basic operator depends on the inversion classes
(A-B or C-C - types) of the particles with respect to the space inversion. The
modified second model can be used for description of neutrino oscillation in
the simplest two-flavor case.


title:
Induced Fractional Zero-Point Canonical Angular Momentum on Charged
  Particles of Aharonov - Bohm Vector Potential and "Spectator" Magnetic Field

abstract:
  The induced fractional zero-point canonical angular momentum on charged
particles by the Aharonov - Bohm (AB) vector potential is realized via modified
combined traps. It explores new features for this type of quantum effects: In a
limit of vanishing mechanical kinetic energy the AB vector potential alone
cannot induce a fractional zero-point canonical angular momentum on charged
particles at the quantum mechanical level in the AB magnetic field-free region;
But for the case of the AB vector potential with another one of a "spectator"
magnetic field the AB vector potential induces a fractional zero-point
canonical angular momentum in the same limit. The "spectator" one does not
contribute to such a fractional zero-point quantity, but plays essential role
in guaranteeing non-trivial dynamics survived in this limit at the quantum
mechanical level. These results are significance in investigations of the AB
effects and related fields for both theories and experiments.


title:
On non-asymptotic bounds for estimation in generalized linear models
  with highly correlated design

abstract:
  We study a high-dimensional generalized linear model and penalized empirical
risk minimization with $\ell_1$ penalty. Our aim is to provide a non-trivial
illustration that non-asymptotic bounds for the estimator can be obtained
without relying on the chaining technique and/or the peeling device.


title:
An approach to chemical freeze-out scenario of identified particle
  spectra at 200AGeV Au-Au collisions at RHIC

abstract:
  Thermal model fit indicates early chemical freeze-out of multi-strange
hadrons with small collective velocities at 200AGeV Au-Au collisions at RHIC.
In this work, we present our recent results by SPheRIO hydrodynamical
calculations inspired by this picture. In our model, multi-strange hadrons go
through chemical freeze-out when the system reaches some temperature close to
the phase transition, stopping to make inelastic collisions, and their
abundances are therefore determined only by partonic EOS. At a lower
temperature thermal freeze-out takes place where elastic collisions are brought
to a halt. We calculate the spectra for various hadrons at different centrality
windows, with chemical and thermal freeze-out temperature being fit as a
function of centrality. As it is shown, the result provides a reasonable
panoramic description of the spectra of identified particles. Chemical
freeze-out gives good correction of the multiplicity of certain species of
particles, especially for multi-strange hadrons.


title:
Amplification of compressional MHD waves in systems with forced entropy
  oscillations

abstract:
  The propagation of compressional MHD waves is studied for an externally
driven system. It is assumed that the combined action of the external sources
and sinks of the entropy results in the harmonic oscillation of the entropy
(and temperature) in the system. It is found that with the appropriate resonant
conditions fast and slow waves get amplified due to the phenomenon of
parametric resonance. Besides, it is shown that the considered waves are
mutually coupled as a consequence of the nonequilibrium state of the background
medium. The coupling is strongest when the plasma $\beta \approx 1$. The
proposed formalism is sufficiently general and can be applied for many
dynamical systems, both under terrestrial and astrophysical conditions.


title: Experimental position-time entanglement with degenerate single photons

abstract:
  We report an experiment in which two-photon interference occurs between
degenerate single photons that never meet. The two photons travel in opposite
directions through our fibre-optic interferometer and interference occurs when
the photons reach two different, spatially separated, 2-by-2 couplers at the
same time. We show that this experiment is analogous to the conventional
Franson-type entanglement experiment where the photons are entangled in
position and time. We measure wavefunction overlaps for the two photons as high
as 94 $\pm$ 3%.


title: Infrared phonon dynamics of multiferroic BiFeO3 single crystal

abstract:
  We discuss the first infrared reflectivity measurement on a BiFeO3 single
crystal between 5 K and room temperature. The 9 predicted ab-plane E phonon
modes are fully and unambiguously determined. The frequencies of the 4 A1
c-axis phonons are found. These results settle issues between theory and data
on ceramics. Our findings show that the softening of the lowest frequency E
mode is responsible for the temperature dependence of the dielectric constant,
indicating that the ferroelectric transition in BiFeO3 is soft-mode driven.


title: Enveloping algebras of Hom-Lie algebras

abstract: Enveloping algebras of Hom-Lie and Hom-Leibniz algebras are constructed.


title: On the Galois coverings of a cluster-tilted algebra

abstract:
  We study the module category of a certain Galois covering of a cluster-tilted
algebra which we call the cluster repetitive algebra. Our main result compares
the module categories of the cluster repetitive algebra of a tilted algebra C
and the repetitive algebra of C, in the sense of Hughes and Waschbuesch.


title: On the blocks of the walled Brauer algebra

abstract:
  We determine the blocks of the walled Brauer algebra in characteristic zero.
These can be described in terms of orbits of the action of a Weyl group of type
$A$ on a certain set of weights. In positive characteristic we give a linkage
principle in terms of orbits of the corresponding affine Weyl group. We also
classify the semisimple walled Brauer algebras in all characteristics.


title:
Transformation of auto-B\"{a}cklund type for hyperbolic generalization
  of Burgers equation

abstract:
  We consider the hyperbolic generalization of Burgers equation with polynomial
source term. The transformation of auto-B\"{a}cklund type was found.
Application of the results is shown in the examples, where the pair of two
stationary solutions produces kink and bi-kink solutions.


title:
Quantum Phase Transitions and the Hidden Order in a Two-Chain Extended
  Boson Hubbard Model at Half-Odd-Integer Fillings

abstract:
  We study the phase diagram of two weakly coupled one-dimensional dipolar
boson chains at half-odd-integer fillings. We find that the system contains a
rich phase diagram. Four different phases are found. They are the Mott
insulators, the single-particle resonant superfluid, the paired superfluid, and
the bond- or inter-chain density waves. Moreover, the Mott insulating phase can
be further classified according to a hidden string order parameter, which is
analogous to the one investigated recently in the one-dimensional boson Mott
insulator at integer fillings.


title: Diophantine exponents for mildly restricted approximation

abstract:
  We are studying the Diophantine exponent \mu_{n,l}$ defined for integers 1
\leq l < n and a vector \alpha \in \mathbb{R}^n by letting \mu_{n,l} = \sup{\mu
\geq 0: 0 < ||x \cdot \alpha|| < H(x)^{-\mu} for infinitely many x \in C_{n,l}
\cap \mathbb{Z}^n}, where \cdot is the scalar product and || . || denotes the
distance to the nearest integer and C_{n,l} is the generalised cone consisting
of all vectors with the height attained among the first l coordinates. We show
that the exponent takes all values in the interval [l+1, \infty), with the
value n attained for almost all \alpha. We calculate the Hausdorff dimension of
the set of vectors \alpha with \mu_{n,l} (\alpha) = \mu for \mu \geq n.
Finally, letting w_n denote the exponent obtained by removing the restrictions
on x, we show that there are vectors \alpha for which the gaps in the
increasing sequence \mu_{n,1} (\alpha) \leq ... \leq \mu_{n,n-1} (\alpha) \leq
w_n (\alpha) can be chosen to be arbitrary.


title:
Notes on multiplicativity of maximal output purity for completely
  positive qubit maps

abstract:
  A problem in quantum information theory that has received considerable
attention in recent years is the question of multiplicativity of the so-called
maximal output purity (MOP) of a quantum channel. This quantity is defined as
the maximum value of the purity one can get at the output of a channel by
varying over all physical input states, when purity is measured by the Schatten
$q$-norm, and is denoted by $\nu_q$. The multiplicativity problem is the
question whether two channels used in parallel have a combined $\nu_q$ that is
the product of the $\nu_q$ of the two channels. A positive answer would imply a
number of other additivity results in QIT.
  Very recently, P. Hayden has found counterexamples for every value of $q>1$.
Nevertheless, these counterexamples require that the dimension of these
channels increases with $1-q$ and therefore do not rule out multiplicativity
for $q$ in intervals $[1,q_0)$ with $q_0$ depending on the channel dimension. I
argue that this would be enough to prove additivity of entanglement of
formation and of the classical capacity of quantum channels.
  More importantly, no counterexamples have as yet been found in the important
special case where one of the channels is a qubit-channel, i.e. its input
states are 2-dimensional. In this paper I focus attention to this qubit case
and I rephrase the multiplicativity conjecture in the language of block
matrices and prove the conjecture in a number of special cases.


title: Noncommutative generalization of SU(n)-principal fiber bundles: a review

abstract:
  This is an extended version of a communication made at the international
conference ``Noncommutative Geometry and Physics'' held at Orsay in april 2007.
In this proceeding, we make a review of some noncommutative constructions
connected to the ordinary fiber bundle theory. The noncommutative algebra is
the endomorphism algebra of a SU(n)-vector bundle, and its differential
calculus is based on its Lie algebra of derivations. It is shown that this
noncommutative geometry contains some of the most important constructions
introduced and used in the theory of connections on vector bundles, in
particular, what is needed to introduce gauge models in physics, and it also
contains naturally the essential aspects of the Higgs fields and its associated
mechanics of mass generation. It permits one also to extend some previous
constructions, as for instance symmetric reduction of (here noncommutative)
connections. From a mathematical point of view, these geometrico-algebraic
considerations highlight some new point on view, in particular we introduce a
new construction of the Chern characteristic classes.


title:
Central exclusive production of scalar \chi_c meson at the Tevatron,
  RHIC and LHC energies

abstract:
  We calculate several differential distributions for exclusive double
diffractive $\chi_c(0^{++})$ production in proton-antiproton collisions at the
Tevatron and in proton-proton collisions at RHIC and LHC in terms of
unintegrated gluon distributions (UGDFs) within the $k_t$-factorisation
approach. The uncertainties of the Khoze-Martin-Ryskin approach are discussed
in detail. The $g^* g^* \to \chi_c(0^{++})$ transition vertex is calculated as
a function of gluon virtualities applying the standard pNRQCD technique. The
off-shell effects are discussed and quantified. They lead to a reduction of the
cross section by a factor 2--5, depending on the position in the phase space
and UGDFs. Different models of UGDFs are used and the results are shown and
discussed. The cross section for diffractive component depends strongly on
UGDFs. We calculate also the differential distributions for the $\gamma^*
\gamma^* \to \chi_c(0^{++})$ fusion mechanism. The integrated cross section for
photon-photon fusion is much smaller than that of diffractive origin. The two
components have very different dependence on momentum transfers $t_1, t_2$ in
the nucleon lines as well as azimuthal-angle correlations between both outgoing
nucleons.


title:
Prospects for the direct detection of neutralino dark matter in orbifold
  scenarios

abstract:
  We analyse the phenomenology of orbifold scenarios from the heterotic
superstring, and the resulting theoretical predictions for the direct detection
of neutralino dark matter. In particular, we study the parameter space of these
constructions, computing the low-energy spectrum and taking into account the
most recent experimental and astrophysical constraints, as well as imposing the
absence of dangerous charge and colour breaking minima. In the remaining
allowed regions the spin-independent part of the neutralino-proton cross
section is calculated and compared with the sensitivity of dark matter
detectors. In addition to the usual non universalities of the soft terms in
orbifold scenarios due to the modular weight dependence, we also consider
D-term contributions to scalar masses. These are generated by the presence of
an anomalous U(1), providing more flexibility in the resulting soft terms, and
are crucial in order to avoid charge and colour breaking minima. Thanks to the
D-term contribution, large neutralino detection cross sections can be found,
within the reach of projected dark matter detectors.


title: SNLS Spectroscopy: Testing for Evolution in Type Ia Supernovae

abstract:
  Aims: We present a quantitative study of a new data set of high redshift Type
Ia supernovae spectra, observed at the Gemini telescopes during the first 34
months of the Supernova Legacy Survey. During this time 123 supernovae
candidates were observed, of which 87 have been identified as SNe Ia at a
median redshift of z=0.720. Spectra from the entire second year of the survey
and part of the third year (59 total SNe candidates with 46 confirmed SNe Ia)
are published here for the first time. The spectroscopic measurements made on
this data set are used determine if these distant SNe comprise a population
similar to those observed locally. Methods: Rest-frame equivalent width and
ejection velocity measurements are made on four spectroscopic features.
Corresponding measurements are presented for a set of 167 spectra from 24 low-z
SNe Ia from the literature. Results: We show that there exists a sample at high
redshift with properties similar to nearby SNe. No significant difference was
found between the distributions of measurements at low and high redsift for
three of the features. The fourth feature displays a possible difference that
should be investigated further. Correlations between Type Ia SNe properties and
host galaxy morphology were also found to be similar at low and high z, and
within each host galaxy class we see no evidence for redshift-evolution in SN
properties. A new correlation between SNe Ia peak magnitude and the equivalent
width of SiII absorption is presented. We demonstrate that this correlation
reduces the scatter in SNe Ia luminosity distances in a manner consistent with
the lightcurve shape-luminosity corrections that are used for Type Ia SNe
cosmology. Conclusions: We show that this new sample of SNLS SNe Ia has
spectroscopic properties similar to nearby objects. (Abridged)


title: Techniques for simulating radiative transfer through porous media

abstract:
  In this contribution, I discuss some basic techniques that can be used to
simulate radiative transfer through porous media. As specific examples, I
consider scattering transfer through a clumped slab, and X-ray emission line
formation in a clumped wind.


title: The population of GRB hosts

abstract:
  The properties of their hosts provide important clues to the progenitors of
different classes of gamma-ray bursts (GRBs). The hosts themselves also
constitute a sample of high-redshift star-forming galaxies which, unlike most
other methods, is not selected on the luminosities of the galaxies themselves.
We discuss what we have learnt from and about GRB host galaxies to date.


title: Ring geometries, Two-Weight Codes and Strongly Regular Graphs

abstract:
  It is known that a linear two-weight code $C$ over a finite field $\F_q$
corresponds both to a multiset in a projective space over $\F_q$ that meets
every hyperplane in either $a$ or $b$ points for some integers $a<b$, and to a
strongly regular graph whose vertices may be identified with the codewords of
$C$. Here we extend this classical result to the case of a ring-linear code
with exactly two nonzero homogeneous weights and multisets of points in an
associated projective ring geometry. We will show that a two-weight code over a
finite Frobenius ring gives rise to a strongly regular graph, and we will give
some constructions of two-weight codes using ring geometries. These examples
all yield infinite families of strongly regular graphs with non-trivial
parameters.


title: Asymptotic oracle properties of SCAD-penalized least squares estimators

abstract:
  We study the asymptotic properties of the SCAD-penalized least squares
estimator in sparse, high-dimensional, linear regression models when the number
of covariates may increase with the sample size. We are particularly interested
in the use of this estimator for simultaneous variable selection and
estimation. We show that under appropriate conditions, the SCAD-penalized least
squares estimator is consistent for variable selection and that the estimators
of nonzero coefficients have the same asymptotic distribution as they would
have if the zero coefficients were known in advance. Simulation studies
indicate that this estimator performs well in terms of variable selection and
estimation.


title: On binomial set-theoretic complete intersections in characteristic p

abstract:
  Using aritmethic conditions on affine semigroups we prove that for a
simplicial toric variety of codimension 2 the property of being a set-theoretic
complete intersection on binomials in characteristic $p$ holds either for all
primes $p$, or for no prime $p$, or for exactly one prime $p$.


title:
A scene model of exosolar systems for use in planetary detection and
  characterisation simulations

abstract:
  Instrumental projects that will improve the direct optical finding and
characterisation of exoplanets have advanced sufficiently to trigger organized
investigation and development of corresponding signal processing algorithms.
The first step is the availability of field-of-view (FOV) models. These can
then be submitted to various instrumental models, which in turn produce
simulated data, enabling the testing of processing algorithms. We aim to set
the specifications of a physical model for typical FOVs of these instruments.
  The dynamic in resolution and flux between the various sources present in
such a FOV imposes a multiscale, independent layer approach. From review of
current literature and through extrapolations from currently available data and
models, we derive the features of each source-type in the field of view likely
to pass the instrumental filter at exo-Earth level.
  Stellar limb darkening is shown to cause bias in leakage calibration if
unaccounted for. Occurrence of perturbing background stars or galaxies in the
typical FOV is unlikely. We extract galactic interstellar medium background
emissions for current target lists. Galactic background can be considered
uniform over the FOV, and it should show no significant drift with parallax.
Our model specifications have been embedded into a Java simulator, soon to be
made open-source. We have also designed an associated FITS input/output format
standard that we present here.


title:
Upper limits on the mass of supermassive black holes from STIS archival
  data

abstract:
  The growth of supermassive black holes (SMBHs) appears to be closely linked
with the formation of spheroids. There is a pressing need to acquire better
statistics on SMBH masses, since the existing samples are preferentially
weighted toward early-type galaxies with very massive SMBHs. With this
motivation we started a project aimed at measuring upper limits on the mass of
the SMBHs that can be present in the center of all the nearby galaxies (D<100
Mpc) for which STIS/G750M spectra are available in the HST archive. These upper
limits will be derived by modeling the central emission-line widths ([NII],
Halpha and [SII]) observed over an aperture of ~0.1" (R<50 pc). Here we present
our preliminary results for a subsample of 76 bulges.


title: On critical normal sections for two-dimensional immersions in R^{n+2}

abstract:
  We study orthonormal normal sections of two-dimensional immersions in
$\mathbb R^{n+2},$ $n\ge 2$, at which these sections are critical for a
functional of total torsion. In particular, we establish upper bounds for the
torsion coefficients in the case of non-flat normal bundles. With these notes
we continue a foregoing paper on surfaces in $\mathbb R^4.$


title: A computer simulation of language families

abstract:
  This paper presents Monte Carlo simulations of language populations and the
development of language families, showing how a simple model can lead to
distributions similar to the ones observed empirically. The model used combines
features of two models used in earlier work by phycisists for the simulation of
competition among languages: the "Viviane" model for the migration of people
and propagation of languages and the "Schulze" model, which uses bitstrings as
a way of characterising structural features of languages.


title: Scaling Cosmologies from Duality Twisted Compactifications

abstract:
  Oscillating moduli fields can support a cosmological scaling solution in the
presence of a perfect fluid when the scalar field potential satisfies
appropriate conditions. We examine when such conditions arise in
higher-dimensional, non-linear sigma-models that are reduced to four dimensions
under a generalized Scherk-Schwarz compactification. We show explicitly that
scaling behaviour is possible when the higher-dimensional action exhibits a
global SL(n,R) or O(2,2) symmetry. These underlying symmetries can be exploited
to generate non-trivial scaling solutions when the moduli fields have
non-canonical kinetic energy. We also consider the compactification of
eleven-dimensional vacuum Einstein gravity on an elliptic twisted torus.


title: Universal estimate of the gradient for parabolic equations

abstract:
  We suggest a modification of the estimate for weighted Sobolev norms of
solutions of parabolic equations such that the matrix of the higher order
coefficients is included into the weight for the gradient. More precisely, we
found the upper limit estimate that can be achieved by variations of the zero
order coefficient. As an example of applications, an asymptotic estimate was
obtained for the gradient at initial time. The constant in the estimates is the
same for all possible choices of the dimension, domain, time horizon, and the
coefficients of the parabolic equation. As an another example of application,
existence and regularity results are obtained for parabolic equations with time
delay for the gradient.


title:
New multivariate central limit theorems in linear structural and
  functional error-in-variables models

abstract:
  This paper deals simultaneously with linear structural and functional
error-in-variables models (SEIVM and FEIVM), revisiting in this context
generalized and modified least squares estimators of the slope and intercept,
and some methods of moments estimators of unknown variances of the measurement
errors. New joint central limit theorems (CLT's) are established for these
estimators in the SEIVM and FEIVM under some first time, so far the most
general, respective conditions on the explanatory variables, and under the
existence of four moments of the measurement errors. Moreover, due to them
being in Studentized forms to begin with, the obtained CLT's are a priori
nearly, or completely, data-based, and free of unknown parameters of the
distribution of the errors and any parameters associated with the explanatory
variables. In contrast, in related CLT's in the literature so far, the
covariance matrices of the limiting normal distributions are, in general,
complicated and depend on various, typically unknown parameters that are hard
to estimate. In addition, the very forms of the CLT's in the present paper are
universal for the SEIVM and FEIVM. This extends a previously known interplay
between a SEIVM and a FEIVM. Moreover, though the particular methods and
details of the proofs of the CLT's in the SEIVM and FEIVM that are established
in this paper are quite different, a unified general scheme of these proofs is
constructed for the two models herewith.


title: Cosmological vector modes and quantum gravity effects

abstract:
  In contrast to scalar and tensor modes, vector modes of linear perturbations
around an expanding Friedmann--Robertson--Walker universe decay. This makes
them largely irrelevant for late time cosmology, assuming that all modes
started out at a similar magnitude at some early stage. By now, however,
bouncing models are frequently considered which exhibit a collapsing phase.
Before this phase reaches a minimum size and re-expands, vector modes grow.
Such modes are thus relevant for the bounce and may even signal the breakdown
of perturbation theory if the growth is too strong. Here, a gauge invariant
formulation of vector mode perturbations in Hamiltonian cosmology is presented.
This lays out a framework for studying possible canonical quantum gravity
effects, such as those of loop quantum gravity, at an effective level. As an
explicit example, typical quantum corrections, namely those coming from inverse
densitized triad components and holonomies, are shown to increase the growth
rate of vector perturbations in the contracting phase, but only slightly.
Effects at the bounce of the background geometry can, however, be much
stronger.


title: Pseudo-3-Branes in a Curved 6D Bulk

abstract:
  We consider a model involving a 4-brane in a 6D bulk which carries sigma
model fields. An axion field on the 4-brane cancels the pressure along one
direction leading to an effective codimension-2 3-brane. For a range of
parameters of the theory, we get a transverse space which is non-compact,
providing a possible solution to the cosmological constant problem. A setup
with two branes in a compact space is also treated. In this case, a mild
fine-tuning between the radii of the two 4-branes is necessary. Finally, we
explore the 4-brane problem in the Gauss-Codazzi formulation and we discuss
general aspects of gravity in the presence of additional brane sources.


title: How Efficient is Rotational Mixing in Massive Stars ?

abstract:
  The VLT-Flames Survey for Massive Stars (Evans05,Evans06) provides recise
measurements of rotational velocities and nitrogen surface abundances of
massive stars in the Magellanic Clouds. Specifically, for the first time, such
abundances have been estimated for stars with significant rotational
velocities. This extraordinary data set gives us the unique possibility to
calibrate rotationally and magnetically induced mixing processes. Therefore, we
have computed a grid of stellar evolution models varying in mass, initial
rotational velocity and chemical composition. In our models we find that
although magnetic fields generated by the Spruit-Taylor dynamo are essential to
understand the internal angular momentum transport (and hence the rotational
behavior), the corresponding chemical mixing must be neglected to reproduce the
observations. Further we show that for low metallicities detailed initial
abundances are of prime importance, as solar-scaled abundances may result in
significant calibration errors.


title:
Determining the metric of the Cosmos: stability, accuracy, and
  consistency

abstract:
  The ultimate application of Einstein's field equations is to empirically
determine the geometry of the Universe from its matter content, rather than
simply assuming the Universe can be represented by a homogeneous model on all
scales. Choosing an LTB model as the most convenient inhomogeneous model for
the early stages of development, a data reduction procedure was recently
validated using perfect test data. Here we simulate observational uncertainties
and improve the previous numerical scheme to ensure that it will be usable with
real data as soon as observational surveys are sufficiently deep and complete.
Two regions require special treatment--the origin and the maximum in the areal
radius. To minimize numerical errors near the origin, we use an LTB series
expansion to provide the initial values for integrating the differential
equations. We also use an improved method to match the numerical integration to
the series expansion that bridges the region near the maximum in the areal
radius. Because the mass enclosed within the maximum obeys a specific
relationship, we show that it is possible to correct for a fixed systematic
error in either the distance scale or the redshift-space mass density, such
that the integrated values are consistent with the data at the maximum.


title:
Vibrational absorption sidebands in the Coulomb blockade regime of
  single-molecule transistors

abstract:
  Current-driven vibrational non-equilibrium induces vibrational sidebands in
single-molecule transistors which arise from tunneling processes accompanied by
absorption of vibrational quanta. Unlike conventional sidebands, these
absorption sidebands occur in a regime where the current is nominally Coulomb
blockaded. Here, we develop a detailed and analytical theory of absorption
sidebands, including current-voltage characteristics as well as shot noise. We
discuss the relation of our predictions to recent experiments.


title: The Dust Trail of Comet 67P/Churyumov-Gerasimenko

abstract:
  We report the detection of comet 67P/Churyumov-Gerasimenko's dust trail and
nucleus in 24 micron Spitzer Space Telescope images taken February 2004. The
dust trail is not found in optical Palomar images taken June 2003. Both the
optical and infrared images show a distinct neck-line tail structure, offset
from the projected orbit of the comet. We compare our observations to simulated
images using a Monte Carlo approach and a dynamical model for comet dust. We
estimate the trail to be at least one orbit old (6.6 years) and consist of
particles of size >~100 micron. The neck-line is composed of similar sized
particles, particles of size but younger in age. Together, our observations and
simulations suggest grains 100 micron and larger in size dominate the total
mass ejected from the comet. The radiometric effective radius of the nucleus is
1.87 +/- 0.08 km, derived from the Spitzer observation. The Rosetta spacecraft
is expected to arrive at and orbit this comet in 2014. Assuming the trail is
comprised solely of 1 mm radius grains, we compute a low probability (~10^-3)
of a trail grain impacting with Rosetta during approach and orbit insertion.


title: Pattern Avoiding Ballot Paths and Finite Operator Calculus

abstract:
  Counting pattern avoiding ballot paths begins with a careful analysis of the
pattern. Not the length, but the characteristics of the pattern are responsible
for the difficulties in finding explicit solutions. Certain features, like
overlap and difference in number of right and up steps determine the solution
of the recursion formula. If the recursion can be solved by a polynomial
sequence, we apply the Finite Operator Calculus to find an explicit form of the
solution in terms of binomial coefficients. Keywords: Pattern avoidance, ballot
path, Dyck path, Finite Operator Calculus, Umbral Calculus


title:
Raman and Infra-red properties and layer dependence of the phonon
  dispersions in multi-layered graphene

abstract:
  The symmetry group analysis is applied to classify the phonon modes of
$N$-stacked graphene layers (NSGL's) with AB- and AA-stacking, particularly
their infra-red and Raman properties. The dispersions of various phonon modes
are calculated in a multi-layer vibrational model, which is generalized from
the lattice vibrational potentials of graphene to including the inter-layer
interactions in NSGL's. The experimentally reported red shift phenomena in the
layer number dependence of the intra-layer optical C-C stretching mode
frequencies are interpreted. An interesting low frequency inter-layer optical
mode is revealed to be Raman or Infra-red active in even or odd NSGL's
respectively. Its frequency shift is sensitive to the layer number and
saturated at about 10 layers.


title: Shaping single walled nanotubes

abstract:
  We show that electron irradiation in a dedicated scanning transmission
microscope can be used as a nano-electron-lithography technique allowing the
controlled reshaping of single walled carbon and boron nitride nanotubes. The
required irradiation conditions have been optimised on the basis of total
knock-on cross sections calculated within density functional based methods. It
is then possible to induce morphological modifications, such as a change of the
tube chirality, by removing severals tens of atoms with a nanometrical spatial
resolution. These irradiation techniques could open new opportunities for
nano-engeneering a large variety of nanostructured materials.


title: The X-ray soft excess in classical T Tauri stars

abstract:
  We study an anomaly in the X-ray flux (or luminosity) ratio between the OVII
21.6-22.1A triplet and the OVIII Lya line seen in classical T Tauri stars
(CTTS). This ratio is unusually high when compared with ratios for
main-sequence and non-accreting T Tauri stars (Telleschi et al. 2007). We
compare these samples to identify the source of the excess. A sample of
recently discovered X-ray stars with a soft component attributed to jet
emission is also considered. We discuss data obtained from the XMM-Newton
Extended Survey of the Taurus Molecular Cloud (XEST) project, complemented by
data from the published literature. We also present data from the CTTS RU Lup.
All CTTS in the sample show an anomalous OVII/OVIII flux ratio when compared
with WTTS or MS stars. The anomaly is due to an excess of cool, OVII emitting
material rather than a deficiency of hotter plasma. The excess plasma must
therefore have temperatures of <~2 MK. This soft excess does not correlate with
UV excesses of CTTS, but seems to be related with the stellar X-ray luminosity.
The spectra of the jet-driving TTS do not fit into this picture. The soft
excess depends both on the presence of accretion streams in CTTS and on
magnetic activity. The gas may be shock-heated near the surface, although it
may also be heated in the magnetospheric accretion funnels. The soft component
of the jet-driving sources is unlikely to be due to the same process.


title: On the combinatorics of rigid objects in 2-Calabi-Yau categories

abstract:
  Given a triangulated 2-Calabi-Yau category C and a cluster-tilting
subcategory T, the index of an object X of C is a certain element of the
Grothendieck group of the additive category T. In this note, we show that a
rigid object of C is determined by its index, that the indices of the
indecomposables of a cluster-tilting subcategory T' form a basis of the
Grothendieck group of T and that, if T and T' are related by a mutation, then
the indices with respect to T and T' are related by a certain piecewise linear
transformation introduced by Fomin and Zelevinsky in their study of cluster
algebras with coefficients. This allows us to give a combinatorial construction
of the indices of all rigid objects reachable from the given cluster-tilting
subcategory T. Conjecturally, these indices coincide with Fomin-Zelevinsky's
g-vectors.


title:
Liquid State Machines in Adbiatic Quantum Computers for General
  Computation

abstract: Major mistakes do not read


title:
General structure of the solutions of the Hamiltonian constraints of
  gravity

abstract:
  A general framework for the solutions of the constraints of pure gravity is
constructed. It provides with well defined mathematical criteria to classify
their solutions in four classes. Complete families of solutions are obtained in
some cases. A starting point for the systematic study of the solutions of
Einstein gravity is suggested.


title:
Two algorithms for evaluation of the Newman digit sum, and a new proof
  of Coquet's theorem

abstract:
  We give two simple algorithms for the evaluation of difference between the
numbers of multiples of 3 with even and odd binary digit sums in interval
[0,x), and give an elementary proof of Coquet's sharp estimates for it.


title:
On Axial and Plane--Mirror Inhomogeneities in the WMAP3 Cosmic Microwave
  Background Maps

abstract:
  We study inhomogeneities in the distribution of the excursion sets in the
Cosmic Microwave Background (CMB) temperature maps obtained by the three years
survey of the Wilkinson Microwave Anisotropy Probe (WMAP). At temperature
thresholds |T|<90 \mu K, the distributions of the excursion sets with over 200
pixels are concentrated in two regions, nearly at the antipodes, with galactic
coordinates l= 94^\circ.7, b= 34^\circ.4 and l= 279^\circ.8, b= -29^\circ.2.
The centers of these two regions drift towards the equator when the temperature
threshold is increased. The centers are located close to one of the vectors of
\ell =3 multipole. The two patterns of the substructures in the distribution of
the excursion sets are mirrored, with \chi^2=0.7-1.5. There is no obvious
origin of this effect in the noise structure of WMAP, and there is no evidence
for a dependence on the galactic cut. Would this effect be cosmological, it
could be an indication of an anomalously large component of horizon-size
density perturbations, independent of one of the spatial coordinates, and/or of
a non-trivial slab-like spatial topology of the Universe.


title: Almost Euclidean subspaces of \ell_1^N via expander codes

abstract:
  We give an explicit (in particular, deterministic polynomial time)
construction of subspaces X of R^N of dimension (1-o(1))N such that for every
element x in X, |x|_1 and N^{1/2} |x|_2 are equivalent up to a factor of (log
N)^{log log log N}. If we are allowed to use N^{o(1)} random bits, this factor
can be improved to poly(log N).
  Our construction makes use of unbalanced bipartite graphs to impose local
linear constraints on vectors in the subspace, and our analysis relies on
expansion properties of the graph. This is inspired by similar constructions of
error-correcting codes.


title: Additive isotone regression

abstract:
  This paper is about optimal estimation of the additive components of a
nonparametric, additive isotone regression model. It is shown that
asymptotically up to first order, each additive component can be estimated as
well as it could be by a least squares estimator if the other components were
known. The algorithm for the calculation of the estimator uses backfitting.
Convergence of the algorithm is shown. Finite sample properties are also
compared through simulation experiments.


title: A polydisperse lattice-gas model

abstract:
  We describe a lattice-gas model suitable for studying the generic effects of
polydispersity on liquid-vapor phase equilibria. Using Monte Carlo simulation
methods tailored for the accurate determination of phase behaviour under
conditions of fixed polydispersity, we trace the cloud and shadow curves for a
particular Schulz distribution of the polydisperse attribute. Although
polydispersity enters the model solely in terms of the strengths of the
interparticle interactions, this is sufficient to induce the broad separation
of cloud and shadow curves seen both in more realistic models and experiments.


title: White noise flashing Brownian pump

abstract:
  A Brownian pump of particles powered by a stochastic flashing ratchet
mechanism is studied. The pumping device is embedded in a finite region and
bounded by particle reservoirs. In the steady state, we exactly calculate the
spatial density profile, the concentration ratio between both reservoirs and
the particle flux. A simple numerical scheme is presented allowing for the
consistent evaluation of all such observable quantities.


title: Spherical symmetry in $f(R)$-gravity

abstract:
  Spherical symmetry in $f(R)$ gravity is discussed in details considering also
the relations with the weak field limit. Exact solutions are obtained for
constant Ricci curvature scalar and for Ricci scalar depending on the radial
coordinate. In particular, we discuss how to obtain results which can be
consistently compared with General Relativity giving the well known
post-Newtonian and post-Minkowskian limits. Furthermore, we implement a
perturbation approach to obtain solutions up to the first order starting from
spherically symmetric backgrounds. Exact solutions are given for several
classes of $f(R)$ theories in both $R =$ constant and $R = R(r)$.


title: Zitterbewegung of a Model Universe

abstract:
  We investigate the quantum evolution of the metric operators for Bianchi-Type
I model universes in the Heisenberg picture in order to remove the need to
consider the wave function of the universe and interpret its "spin" variables.
The calculation is analogous to that of the Zitterbewegung of the Dirac
electron. We consider the behavior of the metric near the classical
singularity, and consider the curvature there. Although factor ordering
questions preclude the presentation of an unambiguous result for the curvature
invariants, it does seem that the classical $t^{-4}$ divergence of the
Kretschmann scalar is not removed by quantization.


title: Dynamic Multiscaling in Turbulence

abstract:
  We give an overview of the progress that has been made in recent years in
understanding the dynamic multiscaling of homogeneous, isotropic turbulence and
related problems. We emphasise the similarity of this problem with the dynamic
scaling of time-dependent correlation functions in the vicinity of a critical
point in, e.g., a spin system. The universality of dynamic-multiscaling
exponents in fluid turbulence is explored by detailed simulations of the GOY
shell model for fluid turbulence.


title: Comment on "Ultrametricity in the Edwards-Anderson Model"

abstract:
  In a recent interesting Letter Contucci {\it et al.} have investigated
several properties of the three-dimensional (3d) Edwards-Anderson (EA) Ising
spin glass. They claim to have found strong numerical evidence for the presence
of a complex ultrametric structure similar to the one described by the replica
symmetry breaking solution of the mean field model. We illustrate by numerical
simulations that the relations used by Contucci {\it et al.} as evidence for an
ultrametric structure in the 3d EA model are fulfilled to similar accuracy in
the two-dimensional EA model, which is well-described by the droplet picture
and has no spin glass phase at finite temperature. We conclude that the data
presented in the Contucci {\it et al.} Letter is not sufficient to dismiss the
possibility that, e.g., the droplet model might describe the behavior of the 3d
EA model.


title:
Vortex nucleation in Bose-Einstein Condensates subject to light induced
  effective magnetic fields

abstract:
  We numerically simulate vortex nucleation in a Bose-Einstein Condensate (BEC)
subject to an effective magnetic field. The effective magnetic field is
generated from the interplay between light with a non-trivial phase structure
and the BEC, and can be shaped and controlled by appropriate modifications to
the phase and intensity of the light. We demonstrate that the nucleation of
vortices is seeded by instabilities in surface excitations which are coupled to
by an asymmetric trapping potential (similar to the case of condensates subject
to mechanical rotation) and show that this picture also holds when the applied
effective magnetic field is not homogeneous. The eventual configuration of
vortices in the cloud depends on the geometry of the applied field.


title:
Open Access does not increase citations for research articles from The
  Astrophysical Journal

abstract:
  We demonstrate conclusively that there is no "Open Access Advantage" for
papers from the Astrophysical Journal. The two to one citation advantage
enjoyed by papers deposited in the arXiv e-print server is due entirely to the
nature and timing of the deposited papers. This may have implications for other
disciplines.


title: Symmetric Group Character Degrees and Hook Numbers

abstract:
  In this article we prove the following result: that for any two natural
numbers k and j, and for all sufficiently large symmetric groups Sym(n), there
are k disjoint sets of j irreducible characters of Sym(n), such that each set
consists of characters with the same degree, and distinct sets have different
degrees. In particular, this resolves a conjecture most recently made by
Moret\'o. The methods employed here are based upon the duality between
irreducible characters of the symmetric groups and the partitions to which they
correspond. Consequently, the paper is combinatorial in nature.


title: Space-time uncertainty relation and operational definition of dimension

abstract:
  Operational definition of space-time in light of quantum mechanics and
general relativity inevitably indicates an intrinsic imprecision in space-time
structure which has to do with space-time dimension as well. The operational
dimension of space-time turns out to be a scale dependent quantity slightly
smaller than four at distances $\gg l_P$. Close to the Planck length the
deviation of space-time dimension from four becomes appreciable. The
experimental bounds on the deviation of space-time dimension from four coming
from the electron ${\tt g} - 2$ factor, Lamb shift in hydrogen atom and the
perihelion shift in the planetary motion are still far from the theoretical
predictions.


title: Physics at International Linear Collider (ILC)

abstract:
  International Linear Collider (ILC) is an electron-positron collider with the
initial center-of-mass energy of 500 GeV which is upgradable to about 1 TeV
later on. Its goal is to study the physics at TeV scale with unprecedented high
sensitivities. The main topics include precision measurements of the Higgs
particle properties, studies of supersymmtric particles and the underlying
theoretical structure if supersymmetry turns out to be realized in nature,
probing alternative possibilities for the origin of mass, and the cosmological
connections thereof. In many channels, Higgs and leptonic sector in particular,
ILC is substantially more sensitive than LHC, and is complementary to LHC
overall. In this short article, we will have a quick look at the capabilities
of ILC.


title:
Isospin-dependent properties of asymmetric nuclear matter in
  relativistic mean-field models

abstract:
  Using various relativistic mean-field models, including the nonlinear ones
with meson field self-interactions, those with density-dependent meson-nucleon
couplings, and the point-coupling models without meson fields, we have studied
the isospin-dependent bulk and single-particle properties of asymmetric nuclear
matter. In particular, we have determined the density dependence of nuclear
symmetry energy from these different relativistic mean-field models and compare
the results with the constraints recently extracted from analyses of
experimental data on isospin diffusion and isotopic scaling in
intermediate-energy heavy ion collisions as well as from measured isotopic
dependence of the giant monopole resonances in even-A Sn isotopes. Among the 23
parameter sets in the relativistic mean-filed model that are commonly used for
nuclear structure studies, only a few are found to give symmetry energies that
are consistent with the empirical constraints. We have also studied the nuclear
symmetry potential and the isospin-splitting of the nucleon effective mass in
isospin asymmetric nuclear matter. We find that both the momentum dependence of
the nuclear symmetry potential at fixed baryon density and the
isospin-splitting of the nucleon effective mass in neutron-rich nuclear matter
depend not only on the nuclear interactions but also on the definition of the
nucleon optical potential.


title:
Transverse target spin asymmetry in inclusive DIS with two-photon
  exchange

abstract:
  We study the transverse target spin dependence of the cross section for
inclusive electron-nucleon scattering with unpolarized beam. Such dependence is
absent in the one-photon exchange approximation (Christ-Lee theorem) and arises
only in higher orders of the QED expansion, from the interference of one-photon
and absorptive two-photon exchange amplitudes as well as from real photon
emission (bremsstrahlung). We demonstrate that the transverse spin-dependent
two-photon exchange cross section is free of QED infrared and collinear
divergences. We argue that in DIS kinematics the transverse spin dependence
should be governed by a "parton-like" mechanism in which the two-photon
exchange couples mainly to a single quark. We calculate the normal spin
asymmetry in an approximation where the dominant contribution arises from quark
helicity flip due to interactions with non-perturbative vacuum fields
(constituent quark picture) and is proportional to the quark transversity
distribution in the nucleon. Such helicity-flip processes are not significantly
Sudakov-suppressed if the infrared scale for gluon emission in the photon-quark
subprocess is of the order of the chiral symmetry breaking scale, mu_chiral^2
>> Lambda_QCD^2. We estimate the asymmetry in the kinematics of the planned
Jefferson Lab Hall A experiment to be of the order 10^{-4}, with different sign
for proton and neutron. We also comment on the spin dependence in the limit of
soft high-energy scattering.


title: 3/2-Fermi liquid: the secret of high-Tc cuprates

abstract:
  Electrical and magnetic properties of underdoped cuprates in the spin gap
phase, a precursor to high Tc superconducting state, is riddled with puzzles.
We propose a novel reference state to study this phase, where each hole dopant
adds one real holon and one real spinon, with Haldane exclusion statistics
$g_{\rm h} =1$ and $g_{\rm s} = {1/2}$, to a fairly inert (pseudo gaped) spin
liquid vacuum, resulting in a low density spin-charge liquid. Spins and charges
interact and form a novel collective state, a \textit{3/2-Fermi liquid}. A
holon pairs with a spinon; this hole like fermion composite carries charge +e
and a spin-\hlf moment and novel exclusion statistics $g_{\rm hole} = {3/2}$.
We explain an anomalous expansion of Fermi sea area by 3/2, seen in recent
quantum oscillation experiments at two different dopings.


title:
The TQ equation of the 8 vertex model for complex elliptic roots of
  unity

abstract:
  We extend our studies of the TQ equation introduced by Baxter in his 1972
solution of the 8 vertex model with parameter $\eta$ given by
$2L\eta=2m_1K+im_2K'$ from $m_2=0$ to the more general case of complex $\eta.$
We find that there are several different cases depending on the parity of $m_1$
and $m_2$.


title: Stellar Photon and Blazar Archaeology with Gamma-rays

abstract:
  Ongoing deep surveys of galaxy luminosity functions, spectral energy
distributions and backwards evolution models of star formation rates can be
used to calculate the past history of intergalactic photon densities and, from
them, the present and past optical depth of the universe. This procedure can be
reversed by looking for sharp cutoffs in the spectra of extragalactic gamma-ray
sources at high redshifts in the multi-GeV energy range with GLAST. Determining
the cutoff energies of sources with known redshifts and little intrinsic
absorption can enable a more precise determination of the past intergalactic
photon density and thus allow a better determination of the past history of the
total star formation rate, including that from galaxies too faint to be
observed. Conversely, observations of sharp high energy cutoffs in the
gamma-ray spectra of blazars at unknown redshifts can be used instead of
spectral lines to give a measure of their redshifts. Also, given a knowledge
photon densities, one can derive the intrinsic gamma-ray spectra and
luminosities of blazars over a range of redshifts and look for possible trends
in blazar evolution. I present some evidence hinting that TeV blazars with
flatter spectra have higher intrinsic TeV gamma-ray luminosities and that there
may be a correlation of flatness and luminosity with redshift. (abridged)


title:
The hydrodynamical relevance of the Camassa-Holm and Degasperis-Procesi
  equations

abstract:
  In recent years two nonlinear dispersive partial differential equations have
attracted a lot of attention due to their integrable structure. We prove that
both equations arise in the modeling of the propagation of shallow water waves
over a flat bed. The equations capture stronger nonlinear effects than the
classical nonlinear dispersive Benjamin-Bona-Mahoney and Korteweg-de Vries
equations. In particular, they accomodate wave breaking phenomena.


title:
A Greedy Randomized Adaptive Search Procedure for Technicians and
  Interventions Scheduling for Telecommunications

abstract:
  The subject of the 5th challenge proposed by the French Society of Operations
Research and Decision Analysis (ROADEF) consists in scheduling technicians and
interventions for telecommunications
(http://www.g-scop.inpg.fr/ChallengeROADEF2007/ or http://www.roadef.org/). We
detail the algorithm we proposed for this challenge which is a Greedy
Randomized Adaptative Search Procedure (GRASP). Computational results led us to
the 1st position in the Junior category and to the 4th position in All category
of the Challenge ROADEF 2007.


title:
Computability of probability measures and Martin-Lof randomness over
  metric spaces

abstract:
  In this paper we investigate algorithmic randomness on more general spaces
than the Cantor space, namely computable metric spaces. To do this, we first
develop a unified framework allowing computations with probability measures. We
show that any computable metric space with a computable probability measure is
isomorphic to the Cantor space in a computable and measure-theoretic sense. We
show that any computable metric space admits a universal uniform randomness
test (without further assumption).


title: Water in Comet 2/2003 K4 (LINEAR) with Spitzer

abstract:
  We present sensitive 5.5 to 7.6 micron spectra of comet C/2003 K4 (LINEAR)
obtained on 16 July 2004 (r_{h} = 1.760 AU, Delta_{Spitzer} = 1.409 AU, phase
angle 35.4 degrees) with the Spitzer Space Telescope. The nu_{2} vibrational
band of water is detected with a high signal-to-noise ratio (> 50). Model
fitting to the best spectrum yields a water ortho-to-para ratio of 2.47 +/-
0.27, which corresponds to a spin temperature of 28.5^{+6.5}_{-3.5} K. Spectra
acquired at different offset positions show that the rotational temperature
decreases with increasing distance from the nucleus, which is consistent with
evolution from thermal to fluorescence equilibrium. The inferred water
production rate is (2.43 +/- 0.25) \times 10^{29} molec. s^{-1}. The spectra do
not show any evidence for emission from PAHs and carbonate minerals, in
contrast to results reported for comets 9P/Tempel 1 and C/1995 O1 (Hale-Bopp).
However, residual emission is observed near 7.3 micron the origin of which
remains unidentified.


title: Spontaneous breaking of discrete symmetries in QCD on a small volume

abstract:
  In a compact space with non-trivial cycles, for sufficiently small values of
the compact dimensions, charge conjugation (C), spatial reflection (P) and time
reversal (T) are spontaneously broken in QCD. The order parameter for the
symmetry breaking is the trace of the Wilson line wrapping around the compact
dimension, which acquires an imaginary part in the broken phase. We show that a
physical signature for the symmetry breaking is a persistent baryonic current
wrapping in the compact directions. The existence of such a current is derived
analytically at first order in perturbation theory and confirmed in the
non-perturbative regime by lattice simulations.


title: On a class of metrics related to graph layout problems

abstract:
  We examine the metrics that arise when a finite set of points is embedded in
the real line, in such a way that the distance between each pair of points is
at least 1. These metrics are closely related to some other known metrics in
the literature, and also to a class of combinatorial optimization problems
known as graph layout problems. We prove several results about the structure of
these metrics. In particular, it is shown that their convex hull is not closed
in general. We then show that certain linear inequalities define facets of the
closure of the convex hull. Finally, we characterise the unbounded edges of the
convex hull and of its closure.


title: An Explicit Construction of Quantum Expanders

abstract:
  Quantum expanders are a natural generalization of classical expanders. These
objects were introduced and studied by Ben-Aroya and Ta-Shma and by Hastings.
In this note we show how to construct explicit, constant-degree quantum
expanders. The construction is essentially the classical Zig-Zag expander
construction, applied to quantum expanders.


title:
Spitzer observations of the Orion OB1 association: disk census in the
  low mass stars

abstract:
  We present new Spitzer Space Telescope observations of two fields in the
Orion OB1 association. We report here IRAC/MIPS observations for 115 confirmed
members and 41 photometric candidates of the ~10 Myr 25 Orionis aggregate in
the OB1a subassociation, and 106 confirmed members and 65 photometric
candidates of the 5 Myr region located in the OB1b subassociation. The 25
Orionis aggregate shows a disk frequency of 6% while the field in the OB1b
subassociation shows a disk frequency of 13%. Combining IRAC, MIPS and 2MASS
photometry we place stars bearing disks in several classes: stars with
optically thick disks (class II systems), stars with an inner transitional
disks (transitional disk candidates) and stars with "evolved disks"; the last
exhibit smaller IRAC/MIPS excesses than class II systems. In all, we identify 1
transitional disk candidate in the 25 Orionis aggregate and 3 in the OB1b
field; this represents ~10% of the disk bearing stars, indicating that the
transitional disk phase can be relatively fast. We find that the frequency of
disks is a function of the stellar mass, suggesting a maximum around stars with
spectral type M0. Comparing the infrared excess in the IRAC bands among several
stellar groups we find that inner disk emission decays with stellar age,
showing a correlation with the respective disk frequencies. The disk emission
at the IRAC and MIPS bands in several stellar groups indicates that disk
dissipation takes place faster in the inner region of the disks. Comparison
with models of irradiated accretion disks, computed with several degrees of
settling, suggests that the decrease in the overall accretion rate observed in
young stellar groups is not sufficient to explain the weak disk emission
observed in the IRAC bands for disk bearing stars with ages 5 Myr or older.


title: Kondo behavior in the asymmetric Anderson model: Analytic approach

abstract:
  The low-temperature behavior of the asymmetric single-impurity
  Anderson model is studied by diagrammatic methods resulting in analytically
controllable approximations. We first discuss the ways one can simplify parquet
equations in critical regions of singularities in the two-particle vertex. The
scale vanishing at the critical point defines the Kondo temperature at which
the electron-hole correlation function saturates. We show that the Kondo
temperature exists at any filling of the impurity level. A quasiparticle
resonance peak in the spectral function, however, forms only in almost
electron-hole symmetric situations. We relate the Kondo temperature with the
width of the resonance peak. Finally we discuss the existence of satellite
Hubbard bands in the spectral function.


title:
Microscopic Theory for the Markovian Decay of Magnetization Fluctuations
  in Nanomagnets

abstract:
  We present a microscopic theory for the phonon-driven decay of the
magnetization fluctuations in a wide class of nanomagnets where the dominant
energy is set by isotropic exchange and/or uniaxial anisotropy. Based on the
Zwanzig-Mori projection formalism, the theory reveals that the magnetization
fluctuations are governed by a single decay rate $\omega_c$, which we further
identify with the zero-frequency portion of the associated self-energy. This
dynamical decoupling from the remaining slow degrees of freedom is attributed
to a conservation law and the discreteness of the energy spectrum, and explains
the omnipresent mono-exponential decay of the magnetization over several
decades in time, as observed experimentally. A physically transparent
analytical expression for $\omega_c$ is derived which highlights the three
specific mechanisms of the slowing down effect which are known so far in
nanomagnets.


title: Product Systems; a Survey with Commutants in View

abstract:
  The theory of product systems both of Hilbert spaces (Arveson systems) and
product systems of Hilbert modules has reached a status where it seems
appropriate to rest a moment and to have a look at what is known so far and
what are open problems. However, the attempt to give an approximately complete
account in view pages is destined to fail already for Arveson systems since
Tsirelson, Powers and Liebscher have discovered their powerful methods to
construct large classes of examples. In this survey we concentrate on that part
of the theory that works also for Hilbert modules. This does not only help to
make a selection among the possible topics, but it also helps to shed some new
light on the case of Arveson systems. Often, proofs that work for Hilbert
modules also lead to simpler proofs in the case of Hilbert spaces. We put
emphasis on those aspects that arise from recent results about commutants of
von Neumann correspondences, which, in the case of Hilbert spaces, explain the
relation between the Arveson system and the Bhat system associated with an
E_0--semigroup on B(H).


title:
A comparison of duality and energy aposteriori estimates for
  L?(0,T;L2({\Omega})) in parabolic problems

abstract:
  We use the elliptic reconstruction technique in combination with a duality
approach to prove aposteriori error estimates for fully discrete back- ward
Euler scheme for linear parabolic equations. As an application, we com- bine
our result with the residual based estimators from the aposteriori esti- mation
for elliptic problems to derive space-error indicators and thus a fully
practical version of the estimators bounding the error in the L \infty (0, T ;
L2({\Omega})) norm. These estimators, which are of optimal order, extend those
introduced by Eriksson and Johnson (1991) by taking into account the error
induced by the mesh changes and allowing for a more flexible use of the
elliptic estima- tors. For comparison with previous results we derive also an
energy-based aposteriori estimate for the L \infty (0, T ; L2({\Omega}))-error
which simplifies a previous one given in Lakkis and Makridakis (2006). We then
compare both estimators (duality vs. energy) in practical situations and draw
conclusions.


title:
Green's functions on finite lattices and their connection to the
  infinite lattice limit

abstract:
  It is shown that the Green's function on a finite lattice in arbitrary space
dimension can be obtained from that of an infinite lattice by means of
translation operator. Explicit examples are given for one- and two-dimensional
lattices.


title:
Near-Infrared photometry of carbon stars in the Sagittarius dwarf
  irregular galaxy and DDO 210

abstract:
  We investigate the intermediate-age asymptotic giant branch stellar
population of two Local Group dwarf irregular galaxies to characterize their
carbon star population in near-infrared (IR). Our work is based on J and K-band
SOFI near-IR photometry complemented with optical ground based and HST
photometry. We show that near-IR photometry is a very powerful tool for carbon
star detection. We recovered two out of three previously-known carbon stars in
DDO 210 and discovered six additional objects in this galaxy which have optical
and near-IR colors consistent with carbon giants. This brings the total number
of bona-fide C-star candidates in DDO 210 to nine. We detected a large
population of C-star candidates in SagDIG, 18 of which were previously
identified in Demers & Battinelli (2002) and Cook (1987), and six new bona-fide
carbon stars. We present their optical and near-IR colors and use their
luminosity function to put constraints on the star formation history (SFH) in
this dwarf irregular galaxy.


title: Note on pre-Courant algebroid structures for parabolic geometries

abstract:
  This note aims to demonstrate that every parabolic geometry has a naturally
defined per-Courant algebro\"id structure. This structure is a Courant
algebro\"id if and only if the the curvature $\kappa$ of the Cartan connection
vanishes. In all other cases, if the parabolic geometry is regular, there does
not exist a natural universal expression for a Courant bracket.


title: Dynamic Nuclear Polarization with Single Electron Spins

abstract:
  We polarize nuclear spins in a GaAs double quantum dot by controlling
two-electron spin states near the anti-crossing of the singlet (S) and m_S=+1
triplet (T+) using pulsed gates. An initialized S state is cyclically brought
into resonance with the T+ state, where hyperfine fields drive rapid rotations
between S and T+, 'flipping' an electron spin and 'flopping' a nuclear spin.
The resulting Overhauser field approaches 80 mT, in agreement with a simple
rate-equation model. A self-limiting pulse sequence is developed that allows
the steady-state nuclear polarization to be set using a gate voltage.


title: Universal tunneling time for all fields

abstract:
  Tunneling is an important physical process. The observation that particles
surmount a high mountain in spite of the fact that they don't have the
necessary energy cannot be explained by classical physics. However, this so
called tunneling became allowed by quantum mechanics. Experimental tunneling
studies with different photonic barriers from microwave frequencies up to
ultraviolet frequencies pointed towards a universal tunneling time
(Haibel,Esposito). Experiments and calculations have shown that the tunneling
time of opaque photonic barriers (optical mirrors, e.g.) equals approximately
the reciprocal frequency of the corresponding electromagnetic wave. The
tunneling process is described by virtual photons. Virtual particles like
photons or electrons are not observable. However, from the theoretical point of
view, they represent necessary intermediate states between observable real
states. In the case of tunneling there is a virtual particle between the
incident and the transmitted particle. Tunneling modes have a purely imaginary
wave number. They represent solutions of the Schroedinger equation and of the
classical Helmholtz equation. Recent experimental and theoretical data of
electron and sound tunneling confirmed the conjecture that the tunneling
process is characterized by a universal tunneling time independent of the kind
of field. Tunneling proceeds at a time of the order of the reciprocal frequency
of the wave.


title: Estimating the size of the solution space of metabolic networks

abstract:
  In this work we propose a novel algorithmic strategy that allows for an
efficient characterization of the whole set of stable fluxes compatible with
the metabolic constraints. The algorithm, based on the well-known Bethe
approximation, allows the computation in polynomial time of the volume of a non
full-dimensional convex polytope in high dimensions. The result of our
algorithm match closely the prediction of Monte Carlo based estimations of the
flux distributions of the Red Blood Cell metabolic network but in incomparably
shorter time. We also analyze the statistical properties of the average fluxes
of the reactions in the E-Coli metabolic network and finally to test the effect
of gene knock-outs on the size of the solution space of the E-Coli central
metabolism.

categories: cond-mat.dis-nn cond-mat.stat-mech q-bio.MN q-bio.QM


title: Communities in networks - a continuous approach

abstract:
  A system of differential equations is proposed designed as to identify
communities in weighted networks. The input is a symmetric connectivity matrix
$A_{ij}$. A priori information on the number of communities is not needed. To
verify the dynamics, we prepared sets of separate, fully connected clusters. In
this case, the matrix $A$ has a block structure of zeros and units. A noise is
introduced as positive random numbers added to zeros and subtracted from units.
The task of the dynamics is to reproduce the initial block structure. In this
test, the system outperforms the modularity algorithm, if the number of
clusters is larger than four.


title: Cosmological effects of neutrino mixing

abstract:
  We report on the recent result that a contribution to the dark energy can be
achieved by the vacuum condensate induced by neutrino mixing phenomenon.


title:
Toward a New Distance to the Active Galaxy NGC 4258: II. Centripetal
  Accelerations and Investigation of Spiral Structure

abstract:
  We report measurements of centripetal accelerations of maser spectral
components of NGC 4258 for 51 epochs spanning 1994 to 2004. This is the second
paper of a series, in which the goal is determination of a new geometric maser
distance to NGC 4258 accurate to possibly ~3%. We measure accelerations using a
formal analysis method that involves simultaneous decomposition of maser
spectra for all epochs into multiple, Gaussian components. Components are
coupled between epochs by linear drifts (accelerations) from their centroid
velocities at a reference epoch. For high-velocity emission, accelerations lie
in the range -0.7 to +0.7 km/s/yr indicating an origin within 13 degrees of the
disk midline (the perpendicular to the line-of-sight to the black hole).
Comparison of high-velocity emission projected positions in VLBI images, with
those derived from acceleration data, provides evidence that masers trace real
gas dynamics. High-velocity emission accelerations do not support a model of
trailing shocks associated with spiral arms in the disk. However, we find
strengthened evidence for spatial periodicity in high-velocity emission, of
wavelength 0.75 mas. This supports suggestions of spiral structure due to
density waves in the nuclear accretion disk of an active galaxy. Accelerations
of low-velocity (systemic) emission lie in the range 7.7 to 8.9 km/s/yr,
consistent with emission originating from a concavity where the thin, warped
disk is tangent to the line-of-sight. A trend in accelerations of low-velocity
emission as a function of Doppler velocity may be associated with disk geometry
and orientation, or with the presence of spiral structure.


title: Deeply Virtual Neutrino Scattering

abstract:
  We investigate the extension of the deeply virtual Compton scattering process
into the weak interaction sector.


title:
An experimental program for demonstrating precision jet energy
  measurement at the ILC

abstract:
  We outline a physics program at Fermilab that would significantly improve our
ability to understand the behavior of hadronic showers in calorimeters. This
would involve a two-pronged approach designed to measure particle production
cross sections of hadronic beams on several nuclei to improve shower simulation
programs and the validation of the improved shower simulation predictions using
test beams (including tagged neutral beams) in which calorimeter modules built
using various technologies are deployed in the test beam. Such a program would
be of immediate benefit to the efforts to design and build optimal calorimeters
for the International Linear Collider.


title: Robust mixtures in the presence of measurement errors

abstract:
  We develop a mixture-based approach to robust density modeling and outlier
detection for experimental multivariate data that includes measurement error
information. Our model is designed to infer atypical measurements that are not
due to errors, aiming to retrieve potentially interesting peculiar objects.
Since exact inference is not possible in this model, we develop a
tree-structured variational EM solution. This compares favorably against a
fully factorial approximation scheme, approaching the accuracy of a
Markov-Chain-EM, while maintaining computational simplicity. We demonstrate the
benefits of including measurement errors in the model, in terms of improved
outlier detection rates in varying measurement uncertainty conditions. We then
use this approach in detecting peculiar quasars from an astrophysical survey,
given photometric measurements with errors.


title: Analysis of network by generalized mutual entropies

abstract:
  Generalized mutual entropy is defined for networks and applied for analysis
of complex network structures. The method is tested for the case of computer
simulated scale free networks, random networks, and their mixtures. The
possible applications for real network analysis are discussed.


title:
Unification of the phonon mode behaviour in semiconductor alloys: Theory
  and ab initio calculations

abstract:
  We demonstrate how to overcome serious problems in understanding and
classification of vibration spectra in semiconductor alloys, following from
traditional use of the virtual crystal approximation (VCA). We show that such
different systems as InGaAs (1-bond->1-mode behavior), InGaP (modified 2-mode)
and ZnTeSe (2-bond->1-mode) obey in fact the same phonon mode behavior - hence
probably a universal one - of a percolation-type (1-bond->2-mode). The change
of paradigm from the `VCA insight' (an averaged microscopic one) to the
`percolation insight' (a mesoscopic one) offers a promising link towards the
understanding of alloy disorder. The discussion is supported by ab initio
simulation of the phonon density of states at the zone-center of representative
supercells at intermediary composition (ZnTeSe) and at the impurity-dilute
limits (all systems). In particular, we propose a simple ab initio `protocol'
to estimate the basic input parameters of our semi-empirical `percolation'
model for the calculation of the 1-bond->2-mode vibration spectra of zincblende
alloys. With this, the model turns self-sufficient.


title: Quantum brachistochrone problem for spin-1 in a magnetic field

abstract:
  We study quantum brachistochrone problem for the spin-1 system in a magnetic
field of a constant absolute value. Such system gives us a possibility to
examine in detail the statement of papers [A. Carlini {\it et al.}, Phys. Rev.
Lett. {\bf 96}, 060503 (2006), D. C. Brody, D. W. Hook, J. Phys. A {\bf 39},
L167, (2006)] that {\it the state vectors realizing the evolution with the
minimal time of passage evolve along the subspace spanned by the initial and
final state vectors.} Using explicit example we show the existence of quantum
brachistochrone with minimal possible time, but the state vector of which,
during the evolution {\em leaves} the subspace spanned by the initial and final
state vectors. This is the result of the choice of more constrained Hamiltonian
then assumed in the general quantum brachistochrone problem, but what is worth
noting, despite that such evolution is more complicated it is still time
optimal. This might be important for experiment, where general Hamiltonian with
the all allowed parameters is difficult to implement, but constrained one
depending on magnetic field can be realized. However for pre-constrained
Hamiltonian not all final states are accessible. Present result does not
contradict general statement of the quantum brachistochrone problem, but gives
new insight how time optimal passage can be realized.