title:
Astrophysical supplements to the ASCC-2.5. Ia. Radial velocities of
  about 55000 stars and mean radial velocities of 516 Galactic open clusters
  and associations

abstract:
  We present the 2nd version of the Catalogue of Radial Velocities with
Astrometric Data (CRVAD-2). This is the result of the cross-identification of
stars from the All-Sky Compiled Catalogue of 2.5 Million Stars (ASCC-2.5) with
the General Catalogue of Radial Velocities and with other recently published
radial velocity lists and catalogues. The CRVAD-2 includes accurate J2000
equatorial coordinates, proper motions and trigonometric parallaxes in the
Hipparcos system, $B, V$ photometry in the Johnson system, spectral types,
radial velocities (RVs), multiplicity and variability flags for 54907 ASCC-2.5
stars. We have used the CRVAD-2 for a new determination of mean RVs of 363 open
clusters and stellar associations considering their established members from
proper motions and photometry in the ASCC-2.5. For 330 clusters and
associations we compiled previously published mean RVs from the literature,
critically reviewed and partly revised them. The resulting Catalogue of Radial
Velocities of Open Clusters and Associations (CRVOCA) contains about 460 open
clusters and about 60 stellar associations in the Solar neighbourhood. These
numbers still represent less than 30% of the total number of about 1820 objects
currently known in the Galaxy. The mean RVs of young clusters are generally
better known than those of older ones.


title: Spin transport in magnetic multilayers

abstract:
  We study by extensive Monte Carlo simulations the transport of itinerant
spins travelling inside a multilayer composed of three ferromagnetic films
antiferromagnetically coupled to each other in a sandwich structure. The two
exterior films interact with the middle one through non magnetic spacers. The
spin model is the Ising one and the in-plane transport is considered. Various
interactions are taken into account. We show that the current of the itinerant
spins going through this system depends strongly on the magnetic ordering of
the multilayer: at temperatures $T$ below (above) the transition temperature
$T_c$, a strong (weak) current is observed. This results in a strong jump of
the resistance across $T_c$. Moreover, we observe an anomalous variation,
namely a peak, of the spin current in the critical region just above $T_c$. We
show that this peak is due to the formation of domains in the temperature
region between the low-$T$ ordered phase and the true paramagnetic disordered
phase. The existence of such domains is known in the theory of critical
phenomena. The behavior of the resistance obtained here is compared to a recent
experiment. An excellent agreement with our physical interpretation is
observed. We also show and discuss effects of various physical parameters
entering our model such as interaction range, strength of electric and magnetic
fields and magnetic film and non magnetic spacer thicknesses.


title: Realisation de Hodge du polylogarithme d'un schema abelien

abstract:
  The main result of this article is the fact that the currents defined by
Levin give a description of the polylogarithm of an abelian scheme at the
topological level. This result was a conjecture of Levin. This provides a
method to explicit the Eisenstein classes of an abelian scheme at the
topological level. These classes are of special interest since they have a
motivic origin by a theorem of Kings. In a forthcoming article, we use the main
result of this paper to prove that the Eisenstein classes of the universal
abelian scheme over an Hilbert-Blumenthal variety degenerate at the boundary of
the Baily-Borel compactification of the base in a special value of an
$L$-function associated to the underlying totally real number field. As a
corollary, we get a non vanishing result for some of these Eisenstein classes
in this geometric situation.


abstract:
  A family of generalized composite intersecting S-brane solutions with
orthogonal intersection rules is described.


title: Synchrotron Radiation in the Standard Model Extension

abstract:
  We obtain a system of exact solutions of the Dirac equation for an electron
moving in a constant homogeneous external magnetic field with account of its
vacuum magnetic moment and assumed Lorentz invariance violation in the minimal
CPT-odd form in the framework of the Standard Model Extension. Using these
solutions, characteristics of the particle synchrotron radiation are
calculated, and possible observable effects caused by the Lorentz non-invariant
interaction are described. We demonstrate that the angular distribution of the
radiation has specific asymmetry, which can be explained as a consequence of
non-conservation of transversal electron polarization in the presence of a
background Lorentz non-invariant condensate field.


title: Comment on "Helical MRI in magnetized Taylor-Couette flow"

abstract:
  Liu et al. [Phys. Rev. E 74, 056302 (2006)] have presented a WKB analysis of
the helical magnetorotational instability (HMRI), and claim that it does not
exist for Keplerian rotation profiles. We show that if radial boundary
conditions are included, the HMRI can exist even for rotation profiles as flat
as Keplerian, provided only that at least one of the boundaries is sufficiently
conducting.


title:
Possible influence of the two string events on the hadron formation in a
  nuclear environment

abstract:
  One of the basic assumptions of the string model is that as a result of a DIS
in nucleus a single string arises, which then breaks into hadrons. However the
pomeron exchange considered in this work, leads to the production of two
strings in the one event. The hadrons produced in these events have smaller
formation lengths, than those with the same energy produced in the single
string events. As a consequence, they undergo more substantial absorption in
the nuclear matter.


title: A Review of Maser Polarization and Magnetic Fields

abstract:
  Through polarization observations masers are unique probes of the magnetic
field in a variety of different astronomical objects, with the different maser
species tracing different physical conditions. In recent years maser
polarization observations have provided insights in the magnetic field strength
and morphology in, among others, the envelopes around evolved stars, Planetary
Nebulae (PNe), massive star forming regions and supernova remnants. More
recently, maser observations have even been used to determine the magnetic
field in megamaser galaxies. This review will present an overview of maser
polarization observations and magnetic field determinations of the last several
years and discuss the implications of the magnetic field measurements for
several important fields of study, such as aspherical PNe creation and massive
star formation.


title: Demonstration of one-parameter scaling at the Dirac point in graphene

abstract:
  We numerically calculate the conductivity $\sigma$ of an undoped graphene
sheet (size $L$) in the limit of vanishingly small lattice constant. We
demonstrate one-parameter scaling for random impurity scattering and determine
the scaling function $\beta(\sigma)=d\ln\sigma/d\ln L$. Contrary to a recent
prediction, the scaling flow has no fixed point ($\beta>0$) for conductivities
up to and beyond the symplectic metal-insulator transition. Instead, the data
supports an alternative scaling flow for which the conductivity at the Dirac
point increases logarithmically with sample size in the absence of intervalley
scattering -- without reaching a scale-invariant limit.


title: 37 GHz observations of a large sample of BL Lacertae objects

abstract:
  We present 37 GHz data obtained at Metsahovi Radio Observatory in 2001
December - 2005 April for a large sample of BL Lacertae objects. We also report
the mean variability indices and radio spectral indices in frequency intervals
5 - 37 GHz and 37 - 90 GHz. Approximately 34 % of the sample was detected at 37
GHz, 136 BL Lacertae objects in all. A large majority of the detected sources
were low-energy BL Lacs (LBLs). The variability index values of the sample were
diverse, the mean fractional variability of the sample being \Delta S_2 = 0.31.
The spectral indices also varied widely, but the average radio spectrum of the
sample sources is flat. Our observations show that many of the high-energy BL
Lacs (HBL), which are usually considered radio-quiet, can at times be detected
at 37 GHz.


title: Quasi-additivity of Tsallis entropies and correlated subsystems

abstract:
  We use Beck's quasi-additivity of Tsallis entropies for $n$ independent
subsystems to show that like the case of $n=2$, the entropic index $q$
approaches 1 by increasing system size. Then, we will generalize that concept
to correlated subsystems to find that in the case of correlated subsystems,
when system size increases, $q$ also approaches a value corresponding to the
additive case.


title:
Consistency of $f(R)=\sqrt{R^{2}-R_{0}^2}$ Gravity with the Cosmological
  Observations in Palatini Formalism

abstract:
  In this work we study the dynamics of universe in $f(R)=\sqrt{R^2-R_{0}^2}$
modified gravity with Palatini formalism. We use data from recent observations
as Supernova Type Ia (SNIa) Gold sample and Supernova Legacy Survey (SNLS)
data, size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), the
position of the acoustic peak from the CMB observations and large scale
structure formation (LSS) from the 2dFGRS survey to put constraint on the
parameters of the model. To check the consistency of this action, we compare
the age of old cosmological objects with the age of universe. In the combined
analysis with the all the observations, we find the parameters of model as
$R_0=6.192_{-0.177}^{+0.167}\times H_0^2$ and
$\Omega_m=0.278_{-0.278}^{+0.273}$.


title:
The Strong Coupling Limit of the Scaling Function from the Quantum
  String Bethe Ansatz

abstract:
  Using the quantum string Bethe ansatz we derive the one-loop energy of a
folded string rotating with angular momenta (S,J) in AdS_3 x S^1 inside AdS_5 x
S^5 in the limit 1 << J << S, z=\lambda^(1/2) log(S/J) /(\pi J) fixed. The
one-loop energy is a sum of two contributions, one originating from the
Hernandez-Lopez phase and another one being due to spin chain finite size
effects. We find a result which at the functional level exactly matches the
result of a string theory computation. Expanding the result for large z we
obtain the strong coupling limit of the scaling function for low twist, high
spin operators of the SL(2) sector of N=4 SYM. In particular we recover the
famous -3 log(2)/\pi. Its appearance is a result of non-trivial cancellations
between the finite size effects and the Hernandez-Lopez correction.


title: Opinion Dynamics and Sociophysics

abstract:
  No abstract given. Contents:
  I. Definition and Introduction
  II. Schelling Model
  III. Opinion Dynamics
  IV. Languages, Hierarchies and Football
  V. Future Directions


title: Ds0*(2317) and Ds1(2460) mesons in two-body B-meson decays

abstract:
  We analyze the branching ratios of B to D(*) + Ds0*(Ds1) decays using the
factorization hypothesis. The B to D(*) transition form factors are taken from
a model-independent analysis done by Caprini, Lellouch and Neubert based on
heavy quark spin symmetry and dispersive constraints, including short-distance
and power corrections. The leptonic decay constants fDs0* and fDs1 are
calculated assuming a molecular structure for the Ds0* and Ds1 mesons. The
calculated branching ratios of B-meson two-body decays are compared with
experimental data and other theoretical results.


title: Electrostatic Interactions of Asymmetrically Charged Membranes

abstract:
  We predict the nature (attractive or repulsive) and range (exponentially
screened or long-range power law) of the electrostatic interactions of
oppositely charged and planar plates as a function of the salt concentration
and surface charge densities (whose absolute magnitudes are not necessarily
equal). An analytical expression for the crossover between attractive and
repulsive pressure is obtained as a function of the salt concentration. This
condition reduces to the high-salt limit of Parsegian and Gingell where the
interaction is exponentially screened and to the zero salt limit of Lau and
Pincus in which the important length scales are the inter-plate separation and
the Gouy-Chapman length. In the regime of low salt and high surface charges we
predict - for any ratio of the charges on the surfaces - that the attractive
pressure is long-ranged as a function of the spacing. The attractive pressure
is related to the decrease in counter-ion concentration as the inter-plate
distance is decreased. Our theory predicts several scaling regimes with
different scaling expressions for the pressure as function of salinity and
surface charge densities. The pressure predictions can be related to surface
force experiments of oppositely charged surfaces that are prepared by coating
one of the mica surfaces with an oppositely charged polyelectrolyte.


title:
Origin of the early-type R stars: a binary-merger solution to a
  century-old problem?

abstract:
  The early-R stars are carbon-rich K-type giants. They are enhanced in C12,
C13 and N14, have approximately solar oxygen, magnesium isotopes, s-process and
iron abundances, have the luminosity of core-helium burning stars, are not
rapid rotators, are members of the Galactic thick disk and, most peculiarly of
all, are all single stars. Conventional single-star stellar evolutionary models
cannot explain such stars, but mergers in binary systems have been proposed to
explain their origin.
  We have synthesized binary star populations to calculate the number of merged
stars with helium cores which could be early-R stars. We find many possible
evolutionary channels. The most common of which is the merger of a helium white
dwarf with a hydrogen-burning red giant branch star during a common envelope
phase followed by a helium flash in a rotating core which mixes carbon to the
surface. All the channels together give ten times more early-R stars than we
require to match recent Hipparcos observations - we discuss which channels are
likely to be the true early-R stars and which are not. For the first time we
have constructed a viable model of the early-R stars with which we can test
some of our ideas regarding common envelope evolution in giants, stellar
mergers, rotation, the helium flash and the origin of the early-R stars.


title: Epsilon-Distortion Complexity for Cantor Sets

abstract:
  We define the epsilon-distortion complexity of a set as the shortest program,
running on a universal Turing machine, which produces this set at the precision
epsilon in the sense of Hausdorff distance. Then, we estimate the
epsilon-distortion complexity of various central Cantor sets on the line
generated by iterated function systems (IFS's). In particular, the
epsilon-distortion complexity of a C^k Cantor set depends, in general, on k and
on its box counting dimension, contrarily to Cantor sets generated by
polynomial IFS or random affine Cantor sets.


title:
Variational speed selection for the interface propagation in
  superconductors

abstract:
  We study the interface propagation in superconductors by means of a
variational method. We compute the lower and upper bounds for which the planar
front speed propagation is valid. To take into account delay or memory effects
in the front propagation, an hyperbolic differential equation is introduced as
an extension of the model.


title: Stability of C20 fullerene chains

abstract:
  The stability of (C20)N chains with N = 3 - 7 is analyzed by numerical
simulation using a tight-binding potential and molecular dynamics. Various
channels of losing the cluster-chain structure of the (C20)N complexes are
observed, including the decay of C20 clusters, their coalescence, and the
separation of one C20 fullerene from the chain.


title: Testing anthropic predictions for Lambda and the CMB temperature

abstract:
  It has been claimed that the observed magnitude of the vacuum energy density
is consistent with the distribution predicted in anthropic models, in which an
ensemble of universes is assumed. This calculation is revisited, without making
the assumption that the CMB temperature is known, and considering in detail the
possibility of a recollapsing universe. New accurate approximations for the
growth of perturbations and the mass function of dark haloes are presented.
Structure forms readily in the recollapsing phase of a model with negative
Lambda, so collapse fraction alone cannot forbid Lambda from being large and
negative. A negative Lambda is disfavoured only if we assume that formation of
observers can be neglected once the recollapsing universe has heated to T > 8
K. For the case of positive Lambda, however, the current universe does occupy a
extremely typical position compared to the predicted distribution on the
Lambda-T plane. Contrasting conclusions can be reached if anthropic arguments
are applied to the curvature of the universe, and we discuss the falsifiability
of this mode of anthropic reasoning.


title: C-symmetric quantization of fields leading to a natural normal ordering

abstract:
  At the quantization of fields, due to the non-linear character of the time
reversal, the creation-annihilation operators for the negative frequency modes
should be replaced to the operators of antiparticles not directly in the field
operators, but in the operator products. For the standard minimal Lagrangians
(asymmetrical under the complex conjugated fields) it is shown that the charge
conjugation (C-) symmetry conditions for the Hamiltonian and the charge
operator lead to the identities for the operator products allowing one to
replace the negative frequency operator products to the positive frequency
ones. At the same time the operators in observables become normal ordered and
the zero-point energy does not appear. Only the symmetrized under the field
operators Lagrangians lead to the zero-point energy. The confrontation by the
experiments of the such C-symmetric quantization of fields and the solution
some of the vacuum energy problems are discussed.


abstract:
  In this talk I review the connections between Feynman integrals and multiple
polylogarithms. After an introductory section on loop integrals I discuss the
Mellin-Barnes transformation and shuffle algebras. In a subsequent section
multiple polylogarithms are introduced. Finally, I discuss how certain Feynman
integrals evaluate to multiple polylogarithms.


title: How to release Frege's system from Russell's antinomy

abstract:
  The conditions for proper definitions in mathematics are given, in terms of
the theory of definition, on the basis of the criterions of eliminability and
non-creativity. As a definition, Russell's antinomy is a violation of the
criterion of eliminability (Behmann, 1931; Bochvar, 1943). Following the path
of the criterion of non-creativity, this paper develops a new analysis of
Comprehension schema and, as a consequence, proof that Russell's antinomy
argumentation, despite the words of Frege himself, does not hold in
Grundgesetze der Arithmetik. According to Basic Law (III), the class of classes
not belonging to themselves is a class defined by a function which can not take
as argument its own course of value. In other words, the class of classes not
belonging to themselves is a class whose classes are not identical to the class
itself.


title: The role of elastic stresses on leaf venation morphogenesis

abstract:
  We explore the possible role of elastic mismatch between epidermis and
mesophyll as a driving force for the development of leaf venation. The current
prevalent 'canalization' hypothesis for the formation of veins claims that the
transport of the hormone auxin out of the leaves triggers cell differentiation
to form veins. Although there is evidence that auxin plays a fundamental role
in vein formation, the simple canalization mechanism may not be enough to
explain some features observed in the vascular system of leaves, in particular,
the abundance of vein loops. We present a model based on the existence of
mechanical instabilities that leads very naturally to hierarchical patterns
with a large number of closed loops. When applied to the structure of high
order veins, the numerical results show the same qualitative features as actual
venation patterns and, furthermore, have the same statistical properties. We
argue that the agreement between actual and simulated patterns provides strong
evidence for the role of mechanical effects on venation development.


title: Soliton-fermion systems and stabilised vortex loops

abstract:
  In several self-coupled quantum field theories when treated in semi-classical
limit one obtains solitonic solutions determined by topology of the boundary
conditions. Such solutions, e.g. magnetic monopole in unified theories
\cite{Hooft1974} \cite{Polyakov1974} or the skyrme model of hadrons have been
proposed as possible non-perturbative bound states which remain stable due to
topological quantum numbers. Furthermore when fermions are introduced, under
certain conditions one obtains zero-energy solutions
\cite{Vega1978}\cite{Jackiw1981} for the Dirac equations localised on the
soliton. An implication of such zero-modes is induced fermion number
\cite{Jackiw1977} carried by the soliton.


title:
String Cosmological Model in Cylindrically Symmetric Inhomogeneous
  Universe with Electromagnetic Field

abstract:
  Cylindrically symmetric inhomogeneous string cosmological models in presence
of electromagnetic field is investigated. We have assumed that $F_{12}$ is the
only non-vanishing component of $F_{ij}$. The Maxwell's equations require that
$F_{12}$ is the function of $x$ and $t$ both and the magnetic permeability is
the function of $x$ and $t$ both. To get the deterministic solution, it has
been assumed that the expansion ($\theta$) in the model is proportional to the
eigen value $\sigma^{1}_{1}$ of the shear tensor $\sigma^{i}_{j}$. The derived
model represents the inflationary scenario as the proper volume increases
exponentially with cosmic time. It is observed that the model has a point type
singularity. The physical and geometric aspects of the model are also
discussed.


title:
The unusual hydrocarbon emission from the early carbon star HD 100764:
  The connection between aromatics and aliphatics

abstract:
  We have used the Infrared Spectrograph (IRS) on the Spitzer Space Telescope
to obtain spectra of HD 100764, an apparently single carbon star with a
circumstellar disk. The spectrum shows emission features from polycyclic
aromatic hydrocarbons (PAHs) that are shifted to longer wavelengths than
normally seen, as characteristic of ``class C'' systems in the classification
scheme of Peeters et al. All seven of the known class C PAH sources are
illuminated by radiation fields that are cooler than those which typically
excite PAH emission features. The observed wavelength shifts are consistent
with hydrocarbon mixtures containing both aromatic and aliphatic bonds. We
propose that the class C PAH spectra are distinctive because the carbonaceous
material has not been subjected to a strong ultraviolet radiation field,
allowing relatively fragile aliphatic materials to survive.


title: Remarks on families of singular curves with hyperelliptic normalizations

abstract:
  We give restrictions on the existence of families of curves on smooth
projective surfaces $S$ of nonnegative Kodaira dimension all having constant
geometric genus $g \geq 2$ and hyperelliptic normalizations. In particular, we
prove a Reider-like result whose proof is ``vector bundle-free'' and relies on
deformation theory and bending-and-breaking of rational curves in $\Sym^2(S)$.
We also give examples of families of such curves.


title: Structure of the stationary state of the asymmetric target process

abstract:
  We introduce a novel migration process, the target process. This process is
dual to the zero-range process (ZRP) in the sense that, while for the ZRP the
rate of transfer of a particle only depends on the occupation of the departure
site, it only depends on the occupation of the arrival site for the target
process. More precisely, duality associates to a given ZRP a unique target
process, and vice-versa. If the dynamics is symmetric, i.e., in the absence of
a bias, both processes have the same stationary-state product measure. In this
work we focus our interest on the situation where the latter measure exhibits a
continuous condensation transition at some finite critical density $\rho_c$,
irrespective of the dimensionality. The novelty comes from the case of
asymmetric dynamics, where the target process has a nontrivial fluctuating
stationary state, whose characteristics depend on the dimensionality. In one
dimension, the system remains homogeneous at any finite density. An alternating
scenario however prevails in the high-density regime: typical configurations
consist of long alternating sequences of highly occupied and less occupied
sites. The local density of the latter is equal to $\rho_c$ and their
occupation distribution is critical. In dimension two and above, the asymmetric
target process exhibits a phase transition at a threshold density $\rho_0$ much
larger than $\rho_c$. The system is homogeneous at any density below $\rho_0$,
whereas for higher densities it exhibits an extended condensate elongated along
the direction of the mean current, on top of a critical background with density
$\rho_c$.


title: A note on equicontinuity of families of operators and automorphisms

abstract:
  This note concerns uniform equicontinuity of families of operators on a
separable Hilbert space H, and of families of maps on B(H). It is shown that a
one parameter group of automorphisms is uniformly equicontinuous if and only if
the group of unitaries which implements it is so. A "geometrical" necessary and
sufficient condition is given for a family of operators to be uniformly
equicontinuous.


title: Game-Theoretic Power Control in Impulse Radio UWB Wireless Networks

abstract:
  In this paper, a game-theoretic model for studying power control for wireless
data networks in frequency-selective multipath environments is analyzed. The
uplink of an impulse-radio ultrawideband system is considered. The effects of
self-interference and multiple-access interference on the performance of Rake
receivers are investigated for synchronous systems. Focusing on energy
efficiency, a noncooperative game is proposed in which users in the network are
allowed to choose their transmit powers to maximize their own utilities, and
the Nash equilibrium for the proposed game is derived. It is shown that, due to
the frequency selective multipath, the noncooperative solution is achieved at
different signal-to-interference-plus-noise ratios, respectively of the channel
realization. A large-system analysis is performed to derive explicit
expressions for the achieved utilities. The Pareto-optimal (cooperative)
solution is also discussed and compared with the noncooperative approach.


title: Extrasolar planet taxonomy: a new statistical approach

abstract:
  In this paper we present the guidelines for an extrasolar planet taxonomy.
The discovery of an increasing number of extrasolar planets showing a vast
variety of planetary parameters, like Keplerian orbital elements and
environmental parameters, like stellar masses, spectral types, metallicity
etc., prompts the development of a planetary taxonomy. In this work via
principal component analysis followed by hierarchical clustering analysis, we
report the definition of five robust groups of planets. We also discuss the
physical relevance of such analysis, which may provide a valid basis for
disentangling the role of the several physical parameters involved in the
processes of planet formation and subsequent evolution. For instance, we were
able to divide the hot Jupiters into two main groups on the basis of their
stellar masses and metallicities. Moreover, for some groups, we find strong
correlations between metallicity, semi-major axis and eccentricity. The
implications of these findings are discussed.


title: Composite lacunary polynomials and the proof of a conjecture of Schinzel

abstract:
  Let $g(x)$ be a fixed non-constant complex polynomial. It was conjectured by
Schinzel that if $g(h(x))$ has boundedly many terms, then $h(x)\in \C[x]$ must
also have boundedly many terms. Solving an older conjecture raised by R\'enyi
and by Erd\"os, Schinzel had proved this in the special cases $g(x)=x^d$;
however that method does not extend to the general case. Here we prove the full
Schinzel's conjecture (actually in sharper form) by a completely different
method. Simultaneously we establish an "algorithmic" parametric description of
the general decomposition $f(x)=g(h(x))$, where $f$ is a polynomial with a
given number of terms and $g,h$ are arbitrary polynomials. As a corollary, this
implies for instance that a polynomial with $l$ terms and given coefficients is
non-trivially decomposable if and only if the degree-vector lies in the union
of certain finitely many subgroups of $\Z^l$.


title: Network Structure of Protein Folding Pathways

abstract:
  The classical approach to protein folding inspired by statistical mechanics
avoids the high dimensional structure of the conformation space by using
effective coordinates. Here we introduce a network approach to capture the
statistical properties of the structure of conformation spaces. Conformations
are represented as nodes of the network, while links are transitions via
elementary rotations around a chemical bond. Self-avoidance of a polypeptide
chain introduces degree correlations in the conformation network, which in turn
lead to energy landscape correlations. Folding can be interpreted as a biased
random walk on the conformation network. We show that the folding pathways
along energy gradients organize themselves into scale free networks, thus
explaining previous observations made via molecular dynamics simulations. We
also show that these energy landscape correlations are essential for recovering
the observed connectivity exponent, which belongs to a different universality
class than that of random energy models. In addition, we predict that the
exponent and therefore the structure of the folding network fundamentally
changes at high temperatures, as verified by our simulations on the AK peptide.


title: Photon Dominated Region Modeling of Barnard 68

abstract:
  We use the Barnard 68 dark globule as a test case for a spherically symmetric
PDR model exposed to low-UV radiation fields. With a roughly spherical
morphology and an accurately determined density profile, Barnard 68 is ideal
for this purpose. The processes governing the energy balance in the cloud
surface are studied in detail. We compare the spherically symmetric PDR model
by Stoerzer, Stutzki & Sternberg (1996) to observations of the three lowest
rotational transitions of 12CO, 13CO J = 2-1 and J = 3-2 as well as the [CI]
3P_1-3P_0 fine structure transition. We study the role of Polycyclic Aromatic
Hydrocarbons (PAHs) in the chemical network of the PDR model and consider the
impact of depletion as well as of a variation of the external FUV field. We
find it difficult to simultaneously model the observed 12CO and 13CO emission.
The 12CO and [CI] emission can be explained by a PDR model with a external FUV
field of 1-0.75 chi_0, but this model fails to reproduce the observed 13CO by a
factor of ~2. Adding PAHs to the chemical network increases the [CI] emission
by 50% in our model but makes [CII] very faint. CO depletion only slightly
reduces the 12CO and 13CO line intensity (by <10% and <20%, respectively).
Predictions for the [CII] 2P_3/2-2P_1/2, [CI] 3P_2-3P_1 and 12CO J= 5-4 and 4-3
transitions are presented. This allows a test of our model with future
observations (APEX, NANTEN2, HERSCHEL, SOFIA).


title: A near-infrared/optical/X-ray survey in the centre of sigma Orionis

abstract:
  Because of the intense brightness of the OB-type multiple star system sigma
Ori, the low-mass stellar and substellar populations close to the centre of the
very young sigma Orionis cluster is poorly know. I present an IJHKs survey in
the cluster centre, able to detect from the massive early-type stars down to
cluster members below the deuterium burning mass limit. The near-infrared and
optical data have been complemented with X-ray imaging. Ten objects have been
found for the first time to display high-energy emission. Previously known
stars with clear spectroscopic youth indicators and/or X-ray emission define a
clear sequence in the I vs. I-Ks diagram. I have found six new candidate
cluster members that follow this sequence. One of them, in the magnitude
interval of the brown dwarfs in the cluster, displays X-ray emission and a very
red J-Ks colour, indicative of a disc. Other three low-mass stars have excesses
in the Ks band as well. The frequency of X-ray emitters in the area is 80+/-20
%. The spatial density of stars is very high, of up to 1.6+/-0.1 arcmin-2.
There is no indication of lower abundance of substellar objects in the cluster
centre. Finally, I also report two cluster stars with X-ray emission located at
only 8000-11000 AU to sigma Ori AB, two sources with peculiar colours and an
object with X-ray emission and near-infrared magnitudes similar to those of
previously-known substellar objects in the cluster.


title:
Satisfiability Parsimoniously Reduces to the Tantrix(TM) Rotation Puzzle
  Problem

abstract:
  Holzer and Holzer (Discrete Applied Mathematics 144(3):345--358, 2004) proved
that the Tantrix(TM) rotation puzzle problem is NP-complete. They also showed
that for infinite rotation puzzles, this problem becomes undecidable. We study
the counting version and the unique version of this problem. We prove that the
satisfiability problem parsimoniously reduces to the Tantrix(TM) rotation
puzzle problem. In particular, this reduction preserves the uniqueness of the
solution, which implies that the unique Tantrix(TM) rotation puzzle problem is
as hard as the unique satisfiability problem, and so is DP-complete under
polynomial-time randomized reductions, where DP is the second level of the
boolean hierarchy over NP.


title: Meson and glueball spectra with the relativistic flux tube model

abstract:
  The mass spectra of heavy and light mesons is computed within the framework
of the relativistic flux tube model. A good agreement with the experimental
data is obtained provided that the flux tube contributions, including
retardation and spin-orbit effects, are supplemented by a one-gluon-exchange
potential, a quark self-energy term and instanton-induced interactions. No
arbitrary constant is needed to fit the absolute scale of the mass spectra, and
the different parameters are fitted on lattice QCD in order to strongly
restrict the arbitrariness of our model. The relevance of the present approach
is discussed in the case of glueballs, and the glueball spectrum we compute is
compared to the lattice QCD one. Finally, we make connections between the
results of our model and the nature of some newly discovered experimental
states such as the f_0(1810), X(3940), Y(3940), etc.


title: Particle physics with a laser-driven positronium atom

abstract:
  A detailed quantum-electrodynamic calculation of muon pair creation in
laser-driven electron-positron collisions is presented. The colliding particles
stem from a positronium atom exposed to a superintense laser wave of linear
polarization, which allows for high luminosity. The threshold laser intensity
of this high-energy reaction amounts to a few 10^22 W/cm^2 in the near-infrared
frequency range. The muons produced form an ultrarelativistic, strongly
collimated beam, which is explicable in terms of a classical simple-man's
model. Our results indicate that the process can be observed at high
positronium densities with the help of present-day laser technology.


title: The continuum radio emission from the Sy 1.5 galaxy NGC 5033

abstract:
  We present new continuum VLA observations of the nearby Sy 1.5 galaxy NGC
5033, made at 4.9 and 8.4 GHz on 8 April 2003. Combined with VLA archival
observations at 1.4 and 4.9 GHz made on 7 August 1993, 29 August 1999, and 31
October 1999, we sample the galaxy radio emission at scales ranging from the
nuclear regions (<~ 100 pc) to the outer regions of the disk (~ 40 kpc). The
high-resolution VLA images show a core-jet structure for the Sy 1.5 nucleus.
While the core has a moderately steep non-thermal radio spectrum (S_\nu ~
\nu^\alpha; \alpha_{1.5}^{4.9} \approx -0.4), the inner kpc region shows a
steeper spectrum (\alpha_{1.5}^{8.4} \approx -0.9). This latter spectrum is
typical of galaxies where energy losses are high, indicating that the escape
rate of cosmic ray electrons in NGC 5033 is low. The nucleus contributes little
to the total 1.4 GHz radio power of NGC 5033 and, based on the radio to
far-infrared (FIR) relation, it appears that the radio and far-infrared
emission from NGC 5033 are dominated by a starburst that during the last 10 Myr
produced stars at a rate of ~2.8 M_sun/yr, yielding a supernova (type Ib/c and
II) rate of 0.045 #/yr. This supernova rate corresponds to about 1 SN event
every 22 yr. Finally, from our deep 8.4 GHz VLA-D image, we suggest the
existence of a radio spur in NGC 5033, which could have been due to a hot
superbubble formed as a consequence of sequential supernova explosions
occurring during the lifetime of a giant molecular cloud.


title: Photospheric and chromospheric activity on EY Dra

abstract:
  Magnetic activity in the photosphere and chromosphere of the M dwarf EY Dra
is studied and possible correlations between the two are investigated using
photometric observations in the V and R bands and optical and near infrared
spectroscopy. The longitudinal spot configuration in the photosphere is
obtained from the V band photometry, and the chromospheric structures are
investigated using variations in the H alpha line profile and observations of
the Paschen beta line. The shape of the V band light-curve indicates two active
regions on the stellar surface, about 0.4 in phase apart. The spectroscopic
observations show enhanced H alpha emission observed close to the phases of the
photometrically detected starspots. This could indicate chromospheric plages
associated with the photospheric starspots. Some indications of prominence
structures are also seen. The chromospheric pressure is limited to logTR < -4
based on the non-detection of emission in the Paschen beta wavelength region.


title:
Metaplectic representation on Wiener amalgam spaces and applications to
  the Schr\"odinger equation

abstract:
  We study the action of metaplectic operators on Wiener amalgam spaces, giving
upper bounds for their norms. As an application, we obtain new fixed-time
estimates in these spaces for Schr\"odinger equations with general quadratic
Hamiltonians and Strichartz estimates for the Schr\"odinger equation with
potentials $V(x)=\pm|x|^2$.


title:
Non-zero trilinear parameter in the mSUGRA model - dark matter and
  collider signals at Tevatron and LHC

abstract:
  Phenomenologically viable and interesting regions of parameter space in the
minimal super-gravity (mSUGRA) model with small $m_0$ and small $m_{1/2}$
consistent with the WMAP data on dark matter relic density and the bound on the
mass of the lightest Higgs scalar $ m_h>$ 114 GeV from LEP2 open up if the
rather adhoc assumption $A_0$=0, where $A_0$ is the common trilinear soft
breaking parameter, employed in most of the existing analyses is relaxed. Since
this region corresponds to relatively light squarks and gluinos which are
likely to be probed extensively in the very early stages of the LHC
experiments, the consequences of moderate or large negative values of $A_0$ are
examined in detail. We find that in this region several processes including
lightest supersymmetric particle (LSP) pair annihilation, LSP - lighter tau
slepton (${\tilde \tau}_1$) coannihilation and LSP - lighter top squark
(${\tilde t}_1$) coannihilation contribute to the observed dark matter relic
density. %\sout{The possibility that a relic density producing ${\tilde t}_1$
can be %observed at the current experiments at the Tevatron is wide open.} The
possibility that a ${\tilde t}_1$ that can participate in coannihilation with
the lightest neutralino to satisfy the WMAP bound on relic density and at the
same time be observed at the current experiments at the Tevatron is wide open.
At the LHC a large number of squark - gluino events lead to a very distinctive
semi-inclusive signature $\tau^\pm$+X$_\tau$ (anything without a tau lepton)
with a characteristic size much larger than $e^\pm$+X$_e$ or $\mu^\pm$+X$_\mu$
events.


title:
The substellar mass function in sigma Orionis. II. Optical,
  near-infrared and IRAC/Spitzer photometry of young cluster brown dwarfs and
  planetary-mass objects

abstract:
  We investigate the mass function in the substellar domain down to a few
Jupiter masses in the young sigma Orionis open cluster (3+/-2 Ma, d =
360^+70_-60 pc). We have performed a deep IJ-band search, covering an area of
790 arcmin^2 close to the cluster centre. This survey was complemented with an
infrared follow-up in the HKs- and Spitzer 3.6-8.0 mum-bands. Using
colour-magnitude diagrams, we have selected 49 candidate cluster members in the
magnitude interval 16.1 mag < I < 23.0 mag. Accounting for flux excesses at 8.0
mum and previously known spectral features of youth, 30 objects are bona fide
cluster members. Four are first identified from our optical-near infrared data.
Eleven have most probable masses below the deuterium burning limit and are
classified as planetary-mass object candidates. The slope of the substellar
mass spectrum (Delta N / Delta M = a M^-alpha) in the mass interval 0.11 Msol M
< 0.006 Msol is alpha = +0.6+/-0.2. Any opacity mass-limit, if these objects
form via fragmentation, may lie below 0.006 Msol. The frequency of sigma
Orionis brown dwarfs with circumsubstellar discs is 47+/-15 %. The continuity
in the mass function and in the frequency of discs suggests that very low-mass
stars and substellar objects, even below the deuterium-burning mass limit, may
share the same formation mechanism.


title:
Precise manipulation of a Bose-Einstein condensate using Bragg
  interactions

abstract:
  The use of off-resonant standing light waves to manipulate ultracold atoms is
investigated. Previous work has illustrated that optical pulses can provide
efficient beam-splitting and reflection operations for atomic wave packets. The
performance of these operations is characterized experimentally using
Bose-Einstein condensates confined in a weak magnetic trap. Under optimum
conditions, fidelities of up to 0.99 for beam splitting and 0.98 for reflection
are observed, and splitting operations of up to third order are achieved. The
dependence of the operations on light intensity and atomic velocity is measured
and found to agree well with theoretical estimates.


title: Cosmological implications of Karolyhazy uncertainty relation

abstract:
  Karolyhazy uncertainty relation, which can be viewed also as a relation
between UV and IR scales in the framework of an effective quantum field theory
satisfying a black hole entropy bound, strongly favors the existence of dark
energy with its observed value. Here we estimate the dynamics of dark energy
predicted by the Karolyhazy relation during the cosmological evolution of the
universe.


title: Water Vapour Effects in Mass Measurement

abstract:
  Water vapour inside the mass comparator enclosure is a critical parameter. In
fact, fluctuations of this parameter during mass weighing can lead to errors in
the determination of an unknown mass. To control that, a proposal method is
given and tested. Preliminary results of our observation of water vapour
sorption and desorption processes from walls and mass standard are reported.


title: Two examples of surfaces with normal crossing singularities

abstract:
  This note gives two examples of surfaces with normal crossing singularities.
In the first example the canonical ring is not finitely generated. In the
second, the canonical line bundle is not ample but its pull back to the
normalization is ample. The latter answers in the negative a problem left
unresolved in [EGA,III.2.6.2] and raised again by Viehweg.


title:
Instanton representation of Plebanski gravity. Application to gravitons
  about DeSitter spacetime

abstract:
  Using the instanton representation method, we re-construct graviton solutions
about DeSitter spacetime. We have used this example as a testing arena to
expose the internal structure of the method and to establish that it works for
known solutions. This paper is a precursor for its application to the
construction of new General Relativity solutions in future work.


title:
Anomalous thermopower and Nernst effect in $\rm CeCoIn_5$:
  entropy-current loss in precursor state

abstract:
  The heavy-electron superconductor CeCoIn$_5$ exhibits a puzzling precursor
state above its superconducting critical temperature at $T_c$ = 2.3 K. The
thermopower and Nernst signal are anomalous. Below 15 K, the entropy current of
the electrons undergoes a steep decrease reaching $\sim$0 at $T_c$.
Concurrently, the off-diagonal thermoelectric current $\alpha_{xy}$ is
enhanced. The delicate sensitivity of the zero-entropy state to field implies
phase coherence over large distances. The prominent anomalies in the
thermoelectric current contrast with the relatively weak effects in the
resistivity and magnetization.


title: Charging of a quantum dot coupled to Luttinger liquid leads

abstract:
  Luttinger liquid behavior of one-dimensional correlated electron systems is
characterized by power-law scaling of a variety of physical observables with
exponents determined by a single interaction dependent parameter K. We suggest
a setup to study Luttinger liquid behavior in quantum wires which allows to
determine K from two independent measurements: resonant transport through a
quantum dot embedded in the wire and the charge on the dot. Consistency of the
two measured values of K for a single probe would provide strong experimental
evidence for the Luttinger liquid paradigm.


title:
The "fundamental theorem" for the algebraic K-theory of spaces. III. the
  nil-term

abstract:
  In this paper we identify the ``nil-terms'' for Waldhausen's algebraic
K-theory of spaces functor as the reduced K-theory of a category of equivariant
spaces equipped with a homotopically nilpotent endomorphism.


title: Analysis of a convenient information bound for general quantum channels

abstract:
  Open questions from Sarovar and Milburn (2006 J.Phys. A: Math. Gen. 39 8487)
are answered. Sarovar and Milburn derived a convenient upper bound for the
Fisher information of a one-parameter quantum channel. They showed that for
quasi-classical models their bound is achievable and they gave a necessary and
sufficient condition for positive operator-valued measures (POVMs) attaining
this bound. They asked (i) whether their bound is attainable more generally,
(ii) whether explicit expressions for optimal POVMs can be derived from the
attainability condition. We show that the symmetric logarithmic derivative
(SLD) quantum information is less than or equal to the SM bound, i.e.\
$H(\theta) \leq C_{\Upsilon}(\theta)$ and we find conditions for equality. As
the Fisher information is less than or equal to the SLD quantum information,
i.e. $F_M(\theta) \leq H(\theta)$, we can deduce when equality holds in
$F_M(\theta) \leq C_{\Upsilon}(\theta)$. Equality does not hold for all
channels. As a consequence, the attainability condition cannot be used to test
for optimal POVMs for all channels. These results are extended to
multi-parameter channels.


title:
Variable-Rate Distributed Source Coding in the Presence of Byzantine
  Sensors

abstract:
  The distributed source coding problem is considered when the sensors, or
encoders, are under Byzantine attack; that is, an unknown number of sensors
have been reprogrammed by a malicious intruder to undermine the reconstruction
at the fusion center. Three different forms of the problem are considered. The
first is a variable-rate setup, in which the decoder adaptively chooses the
rates at which the sensors transmit. An explicit characterization of the
variable-rate minimum achievable sum rate is stated, given by the maximum
entropy over the set of distributions indistinguishable from the true source
distribution by the decoder. In addition, two forms of the fixed-rate problem
are considered, one with deterministic coding and one with randomized coding.
The achievable rate regions are given for both these problems, with a larger
region achievable using randomized coding, though both are suboptimal compared
to variable-rate coding.


title: Computing Minimal Polynomials of Matrices

abstract:
  We present and analyse a Monte-Carlo algorithm to compute the minimal
polynomial of an $n\times n$ matrix over a finite field that requires $O(n^3)$
field operations and O(n) random vectors, and is well suited for successful
practical implementation. The algorithm, and its complexity analysis, use
standard algorithms for polynomial and matrix operations. We compare features
of the algorithm with several other algorithms in the literature. In addition
we present a deterministic verification procedure which is similarly efficient
in most cases but has a worst-case complexity of $O(n^4)$. Finally, we report
the results of practical experiments with an implementation of our algorithms
in comparison with the current algorithms in the {\sf GAP} library.


title:
Relic abundance of dark matter in universal extra dimension models with
  right-handed neutrinos

abstract:
  Relic abundance of dark matter is investigated in the framework of universal
extra dimension models with right-handed neutrinos. These models are free from
the serious Kaluza-Klein (KK) graviton problem that the original universal
extra dimension model has. The first KK particle of the right-handed neutrino
is a candidate for dark matter in this framework, and its relic abundance is
determined by three processes, (1) the decay of the KK photon into the first KK
right-handed neutrino in the late universe, (2) production of the first KK
right-handed neutrino from the thermal bath in the early universe, and (3) the
decay of higher KK right-handed neutrinos into the first KK right-handed
neutrino in the late universe. When ordinary neutrino masses are large enough
such as the degenerate mass spectrum case, the last process contribute to the
abundance significantly, even if the reheating temperature is low. The scale of
the extra dimension consistent with cosmological observations can be 500 GeV in
the minimal setup of universal extra dimension models with right-handed
neutrinos.


title: A Planetary Mass Companion to the K0 Giant HD 17092

abstract:
  We report the discovery of a substellar-mass companion to the K0-giant HD
17092 with the Hobby-Eberly Telescope. In the absence of any correlation of the
observed 360-day periodicity with the standard indicators of stellar activity,
the observed radial velocity variations are most plausibly explained in terms
of a Keplerian motion of a planetary-mass body around the star. With the
estimated stellar mass of 2.3Msun, the minimum mass of the planet is 4.6MJ. The
planet's orbit is characterized by a mild eccentricity of e=0.17 and a
semi-major axis of 1.3 AU. This is the tenth published detection of a planetary
companion around a red giant star. Such discoveries add to our understanding of
planet formation around intermediate-mass stars and they provide dynamical
information on the evolution of planetary systems around post-main sequence
stars.


title:
Performance Comparison of Energy-Efficient Power Control for CDMA and
  Multiuser UWB Networks

abstract:
  This paper studies the performance of a wireless data network using
energy-efficient power control techniques when different multiple access
schemes, namely direct-sequence code division multiple access (DS-CDMA) and
impulse-radio ultrawideband (IR-UWB), are considered. Due to the large
bandwidth of the system, the multipath channel is assumed to be
frequency-selective. By making use of noncooperative game-theoretic models and
large-system analysis tools, explicit expressions for the achieved utilities at
the Nash equilibrium are derived in terms of the network parameters. A measure
of the loss of DS-CDMA with respect to IR-UWB is proposed, which proves
substantial equivalence between the two schemes. Simulation results are
provided to validate the analysis.


title: Stability of spinor Fermi gases in tight waveguides

abstract:
  The two and three-body correlation functions of the ground state of an
optically trapped ultracold spin-1/2 Fermi gas (SFG) in a tight waveguide (1D
regime) are calculated in the plane of even and odd-wave coupling constants,
assuming a 1D attractive zero-range odd-wave interaction induced by a 3D p-wave
Feshbach resonance, as well as the usual repulsive zero-range even-wave
interaction stemming from 3D s-wave scattering. The calculations are based on
the exact mapping from the SFG to a ``Lieb-Liniger-Heisenberg'' model with
delta-function repulsions depending on isotropic Heisenberg spin-spin
interactions, and indicate that the SFG should be stable against three-body
recombination in a large region of the coupling constant plane encompassing
parts of both the ferromagnetic and antiferromagnetic phases. However, the
limiting case of the fermionic Tonks-Girardeau gas (FTG), a spin-aligned 1D
Fermi gas with infinitely attractive p-wave interactions, is unstable in this
sense. Effects due to the dipolar interaction and a Zeeman term due to a
resonance-generating magnetic field do not lead to shrinkage of the region of
stability of the SFG.


title: Extremal Graph Theory for Metric Dimension and Diameter

abstract:
  A set of vertices $S$ \emph{resolves} a connected graph $G$ if every vertex
is uniquely determined by its vector of distances to the vertices in $S$. The
\emph{metric dimension} of $G$ is the minimum cardinality of a resolving set of
$G$. Let $\mathcal{G}_{\beta,D}$ be the set of graphs with metric dimension
$\beta$ and diameter $D$. It is well-known that the minimum order of a graph in
$\mathcal{G}_{\beta,D}$ is exactly $\beta+D$. The first contribution of this
paper is to characterise the graphs in $\mathcal{G}_{\beta,D}$ with order
$\beta+D$ for all values of $\beta$ and $D$. Such a characterisation was
previously only known for $D\leq2$ or $\beta\leq1$. The second contribution is
to determine the maximum order of a graph in $\mathcal{G}_{\beta,D}$ for all
values of $D$ and $\beta$. Only a weak upper bound was previously known.


title:
Dominance of many-body effects over one-electron mechanism for band
  structure doping dependence in Nd$_{2-x}$Ce$_x$CuO$_4$: LDA+GTB approach

abstract:
  In the present work we report the band structure calculations for the high
temperature superconductor Nd$_{2-x}$Ce$_x$CuO$_4$ in the regime of strong
electronic correlations within an LDA+GTB method, which combines the local
density approximation (LDA) and the generalized tight-binding method (GTB). The
two mechanisms of band structure doping dependence were taken into account.
Namely, the one-electron mechanism provided by the doping dependence of the
crystal structure, and the many-body mechanism provided by the strong
renormalization of the fermionic quasiparticles due to the large on-site
Coulomb repulsion. We have shown that in the antiferromagnetic and in the
strongly correlated paramagnetic phases of the underdoped cuprates the main
contribution to the doping evolution of band structure and Fermi surface comes
from the many-body mechanism.


title:
The Intrinsically X-ray Weak Quasar PHL 1811. II. Optical and UV Spectra
  and Analysis

abstract:
  This is the second of two papers reporting observations and analysis of the
unusually bright (m_b=14.4), luminous (M_B=-25.5), nearby (z=0.192) narrow-line
quasar PHL 1811. The first paper reported that PHL 1811 is intrinsically X-ray
weak, and presented a spectral energy distribution (SED). Here we present HST
STIS optical and UV spectra, and ground-based optical spectra. The optical and
UV line emission is very unusual. There is no evidence for forbidden or
semiforbidden lines. The near-UV spectrum is dominated by very strong FeII and
FeIII, and unusual low-ionization lines such as NaID and CaII H&K are observed.
High-ionization lines are very weak; CIV has an equivalent width of 6.6A, a
factor of ~5 smaller than measured from quasar composite spectra. An unusual
feature near 1200A can be deblended in terms of Ly\alpha, NV, SiII, and CIII*
using the blueshifted CIV profile as a template. Photoionization modeling shows
that the unusual line emission can be explained qualitatively by the unusually
soft SED. Principally, a low gas temperature results in inefficient emission of
collisionally excited lines, including the semiforbidden lines generally used
as density diagnostics. The emission resembles that of high-density gas; in
both cases this is a consequence of inefficient cooling. PHL 1811 is very
unusual, but we note that quasar surveys are generally biased against finding
similar objects.


title: On spacetime coordinates in special relativity

abstract:
  Starting with two light clocks to derive time dilation expression, as many
textbooks do, and then adding a third one, we work on relativistic spacetime
coordinates relations for some simple events as emission, reflection and return
of light pulses. Besides time dilation, we get, in the following order, Doppler
k-factor, addition of velocities, length contraction, Lorentz Transformations
and spacetime interval invariance. We also use Minkowski spacetime diagram to
show how to interpret some few events in terms of spacetime coordinates in
three different inertial frames.


title: Domestic canonical algebras and simple Lie algebras

abstract:
  For each simply-laced Dynkin graph $\Delta$ we realize the simple complex Lie
algebra of type $\Delta$ as a quotient algebra of the complex degenerate
composition Lie algebra $L(A)_{1}^{\mathbb{C}}$ of a domestic canonical algebra
$A$ of type $\Delta$ by some ideal $I$ of $L(A)_{1}^{\mathbb{C}}$ that is
defined via the Hall algebra of $A$, and give an explicit form of $I$.
Moreover, we show that each root space of $L(A)_{1}^{\mathbb{C}}/I$ has a basis
given by the coset of an indecomposable $A$-module $M$ with root easily
computed by the dimension vector of $M$.


title: Localization by entanglement

abstract:
  We study the localization of bosonic atoms in an optical lattice, which
interact in a spatially confined region. The classical theory predicts that
there is no localization below a threshold value for the strength of
interaction that is inversely proportional to the number of participating
atoms. In a full quantum treatment, however, we find that localized states
exist for arbitrarily weak attractive or repulsive interactions for any number
($>1$) of atoms. We further show, using an explicit solution of the
two-particle bound state and an appropriate measure of entanglement, that the
entanglement tends to a finite value in the limit of weak interactions. Coupled
with the non-existence of localization in an optimized quantum product state,
we conclude that the localization exists by virtue of entanglement.


title: Spin 1/2 Fermions in the Unitary Limit.I

abstract:
  This report concerns the energy of a zero-temperature many-body system of
spin 1/2 fermions interacting via a two-body potential with a free space
infinite scattering length and zero effective range; the Unitary limit. Given
the corresponding phase-shift $\delta(k)=\pi/2$ a one-term separable potential
is obtained by inverse scattering assuming a momentum cut-off $\Lambda$ such
that $\delta(k)=0$ for $k>\Lambda$. The \it effective \rm interaction in the
many-body system is calculated in a pp-ladder approximation with Pauli-blocking
but neglecting mean-field (dispersion) corrections; effective mass $m^{*}=1$.
Using only the zero relative momentum component of this interaction the total
energy is $\xi=4/9$ (in units of the fermigas), a result reported by several
previous authors. Integrating the momentum dependent interaction over the Fermi
sea this energy is revised to $\xi=0.24.$ This result is independent of density
and of the cut-off $\Lambda$ if $\Lambda > \sim 3k_{f}$.
  With $m^{*}\neq 1$ there is however a strong dependence on this cut-off.
  Including hh-ladders estimates give $\xi=0.4\leftrightarrow 0.6$, but a
reliable result would in this case require a Green's function calculation.


title: Phenomenological constraints on low-scale gravity

abstract:
  We study the constraints on gravity scale $M_P$ in extra-dimension
gravitational theory, obtained from gravity-induced processes. The obtained
constraints are subdivided into strong (though not robust) and reliable (though
less strong). The strong constraints can be in principle relaxed due to some
broken gauge symmetries, e.g. family symmetry. The strongest constraint is
given by neutrino oscillations. For different assumptions the lower bound on
$M_P$ is $10^{15} - 10^{18}$ GeV. However, it can be, in principle, reduced by
broken family symmetry. More reliable bounds are due to flavor-conserved
operators or those which change the flavors within one family. These bounds,
obtained using the electron mass and width of $\pi \to e\nu$ decay, are
$1\times 10^5$ GeV and $5\times 10^5$ GeV, for these two cases, respectively.


title: Universal derived equivalences of posets

abstract:
  By using only combinatorial data on two posets X and Y, we construct a set of
so-called formulas. A formula produces simultaneously, for any abelian category
A, a functor between the categories of complexes of diagrams over X and Y with
values in A. This functor induces a triangulated functor between the
corresponding derived categories.
  This allows us to prove, for pairs X, Y of posets sharing certain common
underlying combinatorial structure, that for any abelian category A, regardless
of its nature, the categories of diagrams over X and Y with values in A are
derived equivalent.


title:
String Junction and Diffusion of Baryon Charge in Multiparticle
  Production Processes

abstract:
  We consider the phenomenological consequences of the assumption that the
baryons are the systems of three quarks and string junction. The process of
baryon number transfer due to string junction propagation in rapidity space is
considered in detail. At high energies it leads to a significant effect in the
net baryon production in $hN$ and $hA$ collisions at mid-rapidities and in the
incident meson fragmentation region. The results of numerical calculations in
the framework of the Quark--Gluon String Model are in reasonable agreement with
the data.


title: Generic Oval Billiards

abstract:
  In this paper we show that, under certain generic conditions, billiards on
ovals have only a finite number of periodic orbits, for each period, all
non-degenerate and at least one of them is hyperbolic. Moreover, the invariant
curves of two hyperbolic points are transversal. We explore these properties to
give some dynamical consequences specially about the dynamics in the
instability regions.


title: The moduli space of cubic fourfolds via the period map

abstract:
  We characterize the image of the period map for cubic fourfolds with at worst
simple singularities as the complement of an arrangement of hyperplanes in the
period space. It follows then that the GIT compactification of the moduli space
of cubic fourfolds is isomorphic to the Looijenga's compactification associated
to this arrangement. This work builds on and is a natural continuation of our
previous paper on the GIT compactification of the moduli space of cubic
fourfolds.


title: Contraction semigroups of elliptic quadratic differential operators

abstract:
  We study the contraction semigroups of elliptic quadratic differential
operators. Elliptic quadratic differential operators are the non-selfadjoint
operators defined in the Weyl quantization by complex-valued elliptic quadratic
symbols. We establish in this paper that under the assumption of ellipticity,
as soon as the real part of their Weyl symbols is a non-zero non-positive
quadratic form, the norm of contraction semigroups generated by these operators
decays exponentially in time.


title: The period map for cubic fourfolds

abstract:
  The period map for cubic fourfolds takes values in a locally symmetric
variety of orthogonal type of dimension 20. We determine the image of this
period map (thus confirming a conjecture of Hassett) and give at the same time
a new proof of the theorem of Voisin that asserts that this period map is an
open embedding. An algebraic version of our main result is an identification of
the algebra of SL(6)-invariant polynomials on the space of cubic forms in 6
complex variables with a certain algebra of meromorphic automorphic forms on a
symmetric domain of orthogonal type of dimension 20. We also describe the
stratification of the moduli space of semistable cubic fourfolds in terms of a
Dynkin-Vinberg diagram.


title: An Independent Evaluation of Subspace Face Recognition Algorithms

abstract:
  This paper explores a comparative study of both the linear and kernel
implementations of three of the most popular Appearance-based Face Recognition
projection classes, these being the methodologies of Principal Component
Analysis, Linear Discriminant Analysis and Independent Component Analysis. The
experimental procedure provides a platform of equal working conditions and
examines the ten algorithms in the categories of expression, illumination,
occlusion and temporal delay. The results are then evaluated based on a
sequential combination of assessment tools that facilitate both intuitive and
statistical decisiveness among the intra and interclass comparisons. The best
categorical algorithms are then incorporated into a hybrid methodology, where
the advantageous effects of fusion strategies are considered.


title: Search for color charge dependence of energy loss at RHIC

abstract:
  The non-Abelian feature of quantum chromodynamics (QCD) results in the gluons
losing more energy than quarks in the medium formed in high energy heavy-ion
collisions. Experimental results in p+p collisions when compared to NLO pQCD
calculations show that at high transverse momentum (pT) the produced
protons+anti-protons are dominantly from gluon jets and charged pions have
substantial contribution from quark jets. If such a scenario is applied to
heavy-ion collisions at RHIC, one would expect the difference in quark and
gluon energy loss to have an effect on measured observables, such as high pT
pbar(p)/pi ratios and the nuclear modification factor for various particles
species. We discuss the experimental results and some possible future
measurements.


title: eta, eta-prime --> pi+ pi- l+ l- in a chiral unitary approach

abstract:
  The decays eta, eta-prime --> pi+ pi- l+ l- (with l = e, mu) are investigated
within a chiral unitary approach which combines the chiral effective Lagrangian
with a coupled-channels Bethe-Salpeter equation. Predictions for the decay
widths and spectra are given.


title: Microscopic origin of Magnetic Ferroelectrics in Nonlinear Multiferroics

abstract:
  A simple but general microscopic mechanism to understand the interplay
between the electric and magnetic degrees of freedom is developed. Within this
mechanism, the magnetic structure generates an electric current which induce an
counterbalance electric current from the spin orbital coupling. When the
magnetic structure is described by a single order parameter, the electric
polarization is determined by the single spin orbital coupling parameter, and
the material is predicted to be a half insulator. This mechanism provides a
simple estimation of the value of ferroelectricity and sets a physical
limitation as well.


title:
On Isotropic Sets of Points in the Plane. Application to the Design of
  Robot Archirectures

abstract:
  Various performance indices are used for the design of serial manipulators.
One method of optimization relies on the condition number of the Jacobian
matrix. The minimization of the condition number leads, under certain
conditions, to isotropic configurations, for which the roundoff-error
amplification is lowest. In this paper, the isotropy conditions, introduced
elsewhere, are the motivation behind the introduction of isotropic sets of
points. By connecting together these points, we define families of isotropic
manipulators. This paper is devoted to planar manipulators, the concepts being
currently extended to their spatial counterparts. Furthermore, only
manipulators with revolute joints are considered here.


title: Entanglement and Criticality in Quantum Impurity Systems

abstract:
  We investigate the entanglement between a spin and its environment in
impurity systems which exhibit a second-order quantum phase transition. As an
application, we employ the spin-boson model, describing a two-level system
(spin) coupled to a subohmic bosonic bath with power-law spectral density,
${\cal J}(\omega)\propto \omega^s$ and $0<s<1$. Combining Wilson's Numerical
Renormalization Group method and hyperscaling relations, we demonstrate that
the entanglement between the spin and its environment is always enhanced at the
quantum phase transition resulting in a visible cusp (maximum) in the entropy
of entanglement. We formulate a correspondence between criticality and impurity
entanglement entropy, and the relevance of these ideas to Nano-systems is
outlined.


title:
Topological expansion of mixed correlations in the hermitian 2 Matrix
  Model and x-y symmetry of the F_g invariants

abstract:
  We compute expectation values of mixed traces containing both matrices in a
two matrix model, i.e. generating function for counting bicolored discrete
surfaces with non uniform boundary conditions. As an application, we prove the
$x-y$ symmetry of the algebraic curve invariants introduced in math-ph/0702045.


title:
The Kinematic Analysis of a Symmetrical Three-Degree-of-Freedom Planar
  Parallel Manipulator

abstract:
  Presented in this paper is the kinematic analysis of a symmetrical
three-degree-of-freedom planar parallel manipulator. In opposite to serial
manipulators, parallel manipulators can admit not only multiple inverse
kinematic solutions, but also multiple direct kinematic solutions. This
property produces more complicated kinematic models but allows more flexibility
in trajectory planning. To take into account this property, the notion of
aspects, i.e. the maximal singularity-free domains, was introduced, based on
the notion of working modes, which makes it possible to separate the inverse
kinematic solutions. The aim of this paper is to show that a non-singular
assembly-mode changing trajectory exist for a symmetrical planar parallel
manipulator, with equilateral base and platform triangle.


title: Uniqueness Domains in the Workspace of Parallel Manipulators

abstract:
  This work investigates new kinematic features of parallel manipulators. It is
well known that parallel manipulators admit generally several direct kinematic
solutions for a given set of input joint values. The aim of this paper is to
characterize the uniqueness domains in the workspace of parallel manipulators,
as well as their image in the joint space. The study focuses on the most usual
case of parallel manipulators with only one inverse kinematic solution. The
notion of aspect introduced for serial manipulators in [Borrel 86] is redefined
for such parallel manipulators. Then, it is shown that it is possible to link
several solutions to the forward kinematic problem without meeting a
singularity, thus meaning that the aspects are not uniqueness domains. An
additional set of surfaces, namely the characteristic surfaces, are
characterized which divide the workspace into basic regions and yield new
uniqueness domains. This study is illustrated all along the paper with a 3-RPR
planar parallel manipulator. An octree model of spaces is used to compute the
joint space, the workspace and all other newly defined sets.


title: The Kinematic design of a 3-dof Hybrid Manipulator

abstract:
  This paper focuses on the kinematic properties of a new
three-degree-of-freedom hybrid manipulator. This manipulator is obtained by
adding in series to a five-bar planar mechanism (similar to the one studied by
Bajpai and Roth) a third revolute passing through the line of centers of the
two actuated revolute joints of the above linkage. The resulting architecture
is hybrid in that it has both serial and parallel links. Fully-parallel
manipulators are known for the existence of particularly undesirable
singularities (referred to as parallel singularities) where control is lost [4]
and [6]. On the other hand, due to their cantilever type of kinematic
arrangement, fully serial manipulators suffer from a lack of stiffness and from
relatively large positioning errors. The hybrid manipulator studied is
intrinsically stiffer and more accurate. Furthermore, since all actuators are
located on the first axis, the inertial effects are considerably reduced. In
addition, it is shown that the special kinematic structure of our manipulator
has the potential of avoiding parallel singularities by a suitable choice of
the "working mode", thus leading to larger workspaces. The influence of the
different structural dimensions (e.g. the link lengths) on the kinematic and
mechanical properties are analysed in view of the optimal design of such hybrid
manipulators.


title: Definition sets for the Direct Kinematics of Parallel Manipulators

abstract:
  The aim of this paper is to characterize the uniqueness domains in the
workspace of parallel manipulators, as well as their image in the joint space.
The notion of aspect introduced for serial manipulators in [Borrel 86] is
redefined for such parallel manipulators. Then, it is shown that it is possible
to link several solutions to the direct kinematic problem without meeting a
singularity, thus meaning that the aspects are not uniqueness domains.
Additional surfaces are characterized in the workspace which yield new
uniqueness domains. An octree model of spaces is used to compute the joint
space, the workspace and all other newly defined sets. This study is
illustrated all along the paper with a 3-RPR planar parallel manipulator.


title:
Optical Variability of Infrared Power Law-Selected Galaxies & X-ray
  Sources in the GOODS-South Field

abstract:
  We investigate the use of optical variability to identify and study Active
Galactic Nuclei (AGN) in the GOODS-South field. A sample of 22 mid-infrared
power law sources and 102 X-ray sources with optical counterparts in the HST
ACS images were selected. Each object is classified with a variability
significance value related to the standard deviation of its magnitude in five
epochs separated by 45-day intervals. The variability significance is compared
to the optical, mid-IR, and X-ray properties of the sources. We find that 26%
of all AGN candidates (either X-ray- or mid-IR-selected) are optical variables.
The fraction of optical variables increases to 51% when considering sources
with soft X-ray band ratios. For the mid-IR AGN candidates which have
multiwavelength SEDs, we find optical variability for 64% of those classified
with SEDs like Broad Line AGNs. While mostly unobscured AGN appear to have the
most significant optical variability, some of the more obscured AGNs are also
observed as variables. In particular, we find two mid-IR power law-selected AGN
candidates without X-ray emission that display optical variability, confirming
their AGN nature.


title: Infrared Gluon and Ghost Propagator Exponents From Lattice QCD

abstract:
  The compatibility of the pure power law infrared solution of QCD and lattice
data for the gluon and ghost propagators in Landau gauge is discussed. For the
gluon propagator, the lattice data is well described by a pure power law with
an infrared exponent $\kappa \sim 0.53$, in the Dyson-Schwinger notation.
$\kappa$ is measured using a technique that suppresses finite volume effects.
This value implies a vanishing zero momentum gluon propagator, in agreement
with the Gribov-Zwanziger confinement scenario. For the ghost propagator, the
lattice data seem not to follow a pure power law, at least for the range of
momenta accessed in our simulation.


title: Improved Analysis of Kannan's Shortest Lattice Vector Algorithm

abstract:
  The security of lattice-based cryptosystems such as NTRU, GGH and Ajtai-Dwork
essentially relies upon the intractability of computing a shortest non-zero
lattice vector and a closest lattice vector to a given target vector in high
dimensions. The best algorithms for these tasks are due to Kannan, and, though
remarkably simple, their complexity estimates have not been improved since more
than twenty years. Kannan's algorithm for solving the shortest vector problem
is in particular crucial in Schnorr's celebrated block reduction algorithm, on
which are based the best known attacks against the lattice-based encryption
schemes mentioned above. Understanding precisely Kannan's algorithm is of prime
importance for providing meaningful key-sizes. In this paper we improve the
complexity analyses of Kannan's algorithms and discuss the possibility of
improving the underlying enumeration strategy.


title: On the remote Galactic globular cluster NGC 2419

abstract:
  We present a new, deep (V ~ 26) study of the Galactic globular cluster NGC
2419 based on B,V,I time-series CCD photometry over about 10 years and
extending beyond the cluster published tidal radius. We have identified 101
variable stars of which 60 are new discoveries, doubling the known RR Lyrae
stars and including 12 SX Phoenicis stars. The average period of the RR Lyrae
stars (<Pab>=0.662 d, and <Pc>=0.366 d, for fundamental-mode -RRab- and
first-overtone pulsators, respectively), and the position in the
period-amplitude diagram both confirm that NGC 2419 is an Oosterhoff II
cluster. The average apparent magnitude of the RR Lyrae stars is <V>=20.31 +/-
0.01 (sigma=0.06, 67 stars) and leads to the distance modulus (m-M)o=19.60 +/-
0.05. The Color-Magnitude Diagram, reaching about 2.6 mag below the cluster
turn-off, does not show clear evidence of multiple stellar populations. Cluster
stars are found until r~ 10.5', and possibly as far as r~15', suggesting that
the literature tidal radius might be underestimated. No extra-tidal structures
are clearly detected in the data. NGC 2419 has many blue stragglers and a well
populated horizontal branch extending from the RR Lyrae stars down to an
extremely blue tail ending with the "blue-hook", for the first time recognized
in this cluster. The red giant branch is narrow ruling out significant
metallicity spreads. Our results seem to disfavor the interpretation of NGC
2419 as either having an extragalactic origin or being the relict of a dwarf
galaxy tidally disrupted by the Milky Way.


title: Ultrametric and tree potential

abstract:
  We study infinite tree and ultrametric matrices, and their action on the
boundary of the tree. For each tree matrix we show the existence of a symmetric
random walk associated to it and we study its Green potential. We provide a
representation theorem for harmonic functions that includes simple expressions
for any increasing harmonic function and the Martin kernel. In the boundary, we
construct the Markov kernel whose Green function is the extension of the matrix
and we simulate it by using a cascade of killing independent exponential random
variables and conditionally independent uniform variables. For ultrametric
matrices we supply probabilistic conditions to study its potential properties
when immersed in its minimal tree matrix extension.


title:
Reply to the comment on ``Incomplete equilibrium in long-range
  interacting systems'' by Tsallis et al

abstract:
  After the rejection of their comment [arXiv:cond-mat/0609399v1] to our Phys.
Rev. Lett. {\bf 97}, 100601 (2006), the Authors informed us that an extended
version of their comment is going to be published in a different journal under
the direct editorial responsibility of one of them. We then decided to make
publicly available our formal reply, originally prepared for publication in
Phys. Rev. Lett.


title:
Artificial Neural Networks and Support Vector Machines for Water Demand
  Time Series Forecasting

abstract:
  Water plays a pivotal role in many physical processes, and most importantly
in sustaining human life, animal life and plant life. Water supply entities
therefore have the responsibility to supply clean and safe water at the rate
required by the consumer. It is therefore necessary to implement mechanisms and
systems that can be employed to predict both short-term and long-term water
demands. The increasingly growing field of computational intelligence
techniques has been proposed as an efficient tool in the modelling of dynamic
phenomena. The primary objective of this paper is to compare the efficiency of
two computational intelligence techniques in water demand forecasting. The
techniques under comparison are the Artificial Neural Networks (ANNs) and the
Support Vector Machines (SVMs). In this study it was observed that the ANNs
perform better than the SVMs. This performance is measured against the
generalisation ability of the two.


title:
On a Class of Ideals of the Toeplitz Algebra on the Bergman Space of the
  Unit Ball

abstract:
  Let $\mathfrak{T}$ denote the full Toeplitz algebra on the Bergman space of
the unit ball $\mathbb{B}_n.$ For each subset $G$ of $L^{\infty},$ let
$\mathfrak{CI}(G)$ denote the closed two-sided ideal of $\mathfrak{T}$
generated by all $T_fT_g-T_gT_f$ with $f,g\in G.$ It is known that
$\mathfrak{CI}(C(\bar{\mathbb{B}}_n))=\mathcal{K}$ - the ideal of compact
operators and $\mathfrak{CI}(C(\mathbb{B}_n))=\mathfrak{T}.$ Despite these
``extremal cases'', $\mathfrak{T}$ does contain other non-trivial ideals. This
paper gives a construction of a class of subsets $G$ of $L^{\infty}$ so that
$\mathcal{K}\subsetneq\mathfrak{CI}(G)\subsetneq\mathfrak{T}.$


title: Radio observations of the massive stellar cluster Westerlund 1

abstract:
  High-dynamic range radio observations of Westerlund 1 are presented that
detect a total of 21 stars in the young massive stellar cluster, the richest
population of radio emitting stars known for any young massive galactic cluster
in the Galaxy. We will discuss some of the more remarkable objects, including
the highly radio luminous supergiant B[e] star W9, with an estimated mass-loss
rate ~10^{-3} solarmass/yr, comparable to that of eta Carina, along with the
somewhat unusual detection of thermal emission from almost all the cool red
supergiants and yellow hypergiants. There is strong supporting evidence from
X-ray observations that each of the WR stars with radio emission are likely to
be colliding-wind binaries


title:
Fermionic stabilization and density-wave ground state of a polar
  condensate

abstract:
  We examine the stability of a trapped dipolar condensate mixed with a
single-component fermion gas at T=0. Whereas pure dipolar condensates with
small s-wave interaction are unstable even for small dipole-dipole interaction
strength, we find that the admixture of fermions can significantly stabilize
them, depending on the strength of the boson-fermion interaction. Within the
stable regime we find a region where a ground state is characterized by a
density wave along the soft trap direction.


title: A Connection Between Bulge Properties and the Bimodality of Galaxies

abstract:
  The global colors of galaxies have recently been shown to follow bimodal
distributions. Galaxies separate into a ``red sequence'', populated
prototypically by early-type galaxies, and a ``blue cloud'', whose typical
objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies
populate both regions. It has been suggested that this bimodality reflects the
two-component nature of disk-bulge galaxies. However, it has now been
established that there are two types of bulges: ``classical bulges'' that are
dynamically hot systems resembling (little) ellipticals, and ``pseudobulges'',
dynamically cold, flattened, disk-like structures that could not have formed
via violent relaxation. Therefore thee question is whether at types Sa-Sbc,
where both bulge types are found, the red-blue dichotomy separates galaxies at
some value of disk-to-bulge ratio, $B/T$, or, whether it separates galaxies of
different bulge type, irrespective of their $B/T$. We identify classical bulges
and pseudobulges morphologically with HST images in a sample of nearby
galaxies. Detailed surface photometry reveals that: (1) The red -- blue
dichotomy is a function of bulge type: at the same $B/T$, pseudobulges are in
globally blue galaxies and classical bulges are in globally red galaxies. (2)
Bulge type also predicts where the galaxy lies in other (bimodal) global
structural parameters. (3) Hence, the red -- blue dichotomy is not due to
decreasing bulge prominence alone, and the bulge type of a galaxy carries
significance for the galaxy's evolutionary history ... (Abridged)


title: An Inequality for Mixed Monge-Amp\`ere measures

abstract:
  We generalize an inequality for mixed Monge-Amp\`ere measures. We also give
an example that shows that our assumptions are sharp. The corresponding result
in the setting of compact K\"ahler manifold is also discussed.


title:
Quantum Interference and Superposition in Cognition: Development of a
  Theory for the Disjunction of Concepts

abstract:
  We elaborate a theory for the modeling of concepts using the mathematical
structure of quantum mechanics. Concepts are represented by vectors in the
complex Hilbert space of quantum mechanics and membership weights of items are
modeled by quantum weights calculated following the quantum rules. We apply
this theory to model the disjunction of concepts and show that experimental
data of membership weights of items with respect to the disjunction of concepts
can be modeled accurately. It is the quantum effects of interference and
superposition, combined with an effect of context, that are at the origin of
the effects of overextension and underextension observed as deviations from a
classical use of the disjunction. We put forward a graphical explanation of the
effects of overextension and underextension by interpreting the quantum model
applied to the modeling of the disjunction of concepts.


title:
Some remarks on sinc integrals and their connection with combinatorics,
  geometry and probability

abstract:
  We give an alternative, combinatorial/geometrical evaluation of a class of
improper sinc integrals studied by the Borweins. A probabilistic interpretation
is also noted and used to shed light on a related combinatorial identity.


title:
Stellar Evolution in NGC 6791: Mass Loss on the Red Giant Branch and the
  Formation of Low Mass White Dwarfs

abstract:
  We present the first detailed study of the properties (temperatures,
gravities, and masses) of the NGC 6791 white dwarf population. This unique
stellar system is both one of the oldest (8 Gyr) and most metal-rich ([Fe/H] ~
0.4) open clusters in our Galaxy, and has a color-magnitude diagram (CMD) that
exhibits both a red giant clump and a much hotter extreme horizontal branch.
Fitting the Balmer lines of the white dwarfs in the cluster, using Keck/LRIS
spectra, suggests that most of these stars are undermassive, <M> = 0.43 +/-
0.06 Msun, and therefore could not have formed from canonical stellar evolution
involving the helium flash at the tip of the red giant branch. We show that at
least 40% of NGC 6791's evolved stars must have lost enough mass on the red
giant branch to avoid the flash, and therefore did not convert helium into
carbon-oxygen in their core. Such increased mass loss in the evolution of the
progenitors of these stars is consistent with the presence of the extreme
horizontal branch in the CMD. This unique stellar evolutionary channel also
naturally explains the recent finding of a very young age (2.4 Gyr) for NGC
6791 from white dwarf cooling theory; helium core white dwarfs in this cluster
will cool ~3 times slower than carbon-oxygen core stars and therefore the
corrected white dwarf cooling age is in fact ~7 Gyr, consistent with the well
measured main-sequence turnoff age. These results provide direct empirical
evidence that mass loss is much more efficient in high metallicity environments
and therefore may be critical in interpreting the ultraviolet upturn in
elliptical galaxies.


title:
X-ray Timing of PSR J1852+0040 in Kesteven 79: Evidence of Neutron Stars
  Weakly Magnetized at Birth

abstract:
  The 105-ms X-ray pulsar J1852+0040 is the central compact object (CCO) in SNR
Kes 79. We report a sensitive upper limit on its radio flux density of 12 uJy
at 2 GHz using the NRAO GBT. Timing using XMM and Chandra over a 2.4 yr span
reveals no significant change in its spin period. The 2 sigma upper limit on
the period derivative leads, in the dipole spin-down formalism, to an energy
loss rate E-dot < 7e33 ergs/s, surface magnetic field strength B_p < 1.5e11 G,
and characteristic age tau_c = P/2P-dot > 8 Myr. This tau_c exceeds the age of
the SNR by 3 orders of magnitude, implying that the pulsar was born spinning at
its current period. However, the X-ray luminosity of PSR J1852+0040, L(bol) ~
3e33(d/7.1 kpc)^2 ergs/s is a large fraction of E-dot, which challenges the
rotation-powered assumption. Instead, its high blackbody temperature,
0.46+/-0.04 keV, small blackbody radius ~ 0.8 km, and large pulsed fraction, ~
80%, may be evidence of accretion onto a polar cap, possibly from a fallback
disk made of supernova debris. If B_p < 1e10 G, an accretion disk can penetrate
the light cylinder and interact with the magnetosphere while resulting torques
on the neutron star remain within the observed limits. A weak B-field is also
inferred in another CCO, the 424-ms pulsar 1E 1207.4-5209, from its steady spin
and soft X-ray absorption lines. We propose this origin of radio-quiet CCOs:
the B-field, derived from a turbulent dynamo, is weaker if the NS is formed
spinning slowly, which enables it to accrete SN debris. Accretion excludes
neutron stars born with both B_p < 1e11 G and P > 0.1 s from radio pulsar
surveys, where B_p < 1e11 G is not encountered except among very old (tau_c >
40 Myr) or recycled pulsars. Finally, such a CCO, if born in SN 1987A, could
explain the non-detection of a pulsar there.


title:
Precision measurements of large scale structure with future type Ia
  supernova surveys

abstract:
  Type Ia supernovae are currently the best known standard candles at
cosmological distances. In addition to providing a powerful probe of dark
energy they are an ideal source of information about the peculiar velocity
field of the local universe. Even with the very small number of supernovae
presently available it has been possible to measure the dipole and quadrupole
of the local velocity field out to z~0.025. With future continuous all-sky
surveys like the LSST project the luminosity distances of tens of thousands of
nearby supernovae will be measured accurately. This will allow for a
determination of the local velocity structure of the universe as a function of
redshift with unprecedented accuracy, provided the redshifts of the host
galaxies are known. Using catalogues of mock surveys we estimate that future
low redshift supernova surveys will be able to probe sigma-8 to a precision of
roughly 5% at 95% C.L. This is comparable to the precision in future galaxy and
weak lensing surveys and with a relatively modest observational effort it will
provide a crucial cross-check on future measurements of the matter power
spectrum.


title: Charting the landscape of supercritical string theory

abstract:
  Special solutions of string theory in supercritical dimensions can
interpolate in time between theories with different numbers of spacetime
dimensions (via dimension quenching) and different amounts of worldsheet
supersymmetry (via c-duality). These solutions connect supercritical string
theories to the more familiar string duality web in ten dimensions, and provide
a precise link between supersymmetric and purely bosonic string theories.
Dimension quenching and c-duality appear to be natural concepts in string
theory, giving rise to large networks of interconnected theories. We describe
some of these networks in detail and discuss general consistency constraints on
the types of transitions that arise in this framework.


title:
Can We Detect the Anisotropic Shapes of Quasar HII Regions During
  Reionization Through The Small-Scale Redshifted 21cm Power Spectrum?

abstract:
  Light travel time delays distort the apparent shapes of HII regions
surrounding bright quasars during early stages of cosmic reionization.
Individual HII regions may remain undetectable in forthcoming redshifted 21 cm
experiments. However, the systematic deformation along the line of sight may be
detectable statistically, either by stacking tomographic 21cm images of quasars
identified, for example, by JWST, or as small-scale anisotropy in the
three-dimensional 21cm power spectrum. Here we consider the detectability of
this effect. The anisotropy is largest when HII regions are large and expand
rapidly, and we find that if bright quasars contributed to the early stages of
reionization, then they can produce significant anisotropy, on scales
comparable to the typical sizes of HII regions of the bright quasars (approx.
30 Mpc and below). The effect therefore cannot be ignored when analyzing future
21cm power spectra on small scales. If 10 percent of the volume of the IGM at
redshift z=10 is ionized by quasars with typical ionizing luminosity of S= 5 x
10^{56} photons/second, the distortions can enhance by more than 10 percent the
21cm power spectrum in the radial (redshift) direction, relative to the
transverse directions. The level of this anisotropy exceeds that due to
redshift-space distortion, and has the opposite sign. We show that on-going
experiments such as MWA should be able to detect this effect. A detection would
reveal the presence of bright quasars, and shed light on the ionizing yield and
age of the ionizing sources, and the distribution and small-scale clumping of
neutral intergalactic gas in their vicinity.


title: A New Three-DOF Parallel Mechanism: Milling Machine Applications

abstract:
  This paper describes a new parallel kinematic architecture for machining
applications, namely, the orthoglide. This machine features three fixed
parallel linear joints which are mounted orthogonally and a mobile platform
which moves in the Cartesian x-y-z space with fixed orientation. The main
interest of the orthoglide is that it takes benefit from the advantages of the
popular PPP serial machines (regular Cartesian workspace shape and uniform
performances) as well as from the parallel kinematic arrangement of the links
(less inertia and better dynamic performances), which makes the orthoglide well
suited to high-speed machining applications. Possible extension of the
orthoglide to 5-axis machining is also investigated.


title:
Nonsupersymmetric Brane/Antibrane Configurations in Type IIA and M
  Theory

abstract:
  We study metastable nonsupersymmetric configurations in type IIA string
theory, obtained by suspending D4-branes and anti-D4-branes between
holomorphically curved NS5's, which are related to those of hep-th/0610249 by
T-duality. When the numbers of branes and antibranes are the same, we are able
to obtain an exact M theory lift which can be used to reliably describe the
vacuum configuration as a curved NS5 with dissolved RR flux for g_s<<1 and as a
curved M5 for g_s>>1. When our weakly coupled description is reliable, it is
related by T-duality to the deformed IIB geometry with flux of hep-th/0610249
with moduli exactly minimizing the potential derived therein using special
geometry. Moreover, we can use a direct analysis of the action to argue that
this agreement must also hold for the more general brane/antibrane
configurations of hep-th/0610249. On the other hand, when our strongly coupled
description is reliable, the M5 wraps a nonholomorphic minimal area curve that
can exhibit quite different properties, suggesting that the residual structure
remaining after spontaneous breaking of supersymmetry at tree level can be
further broken by the effects of string interactions. Finally, we discuss the
boundary condition issues raised in hep-th/0608157 for nonsupersymmetric IIA
configurations, their implications for our setup, and their realization on the
type IIB side.


title: Vicious walkers and random contraction matrices

abstract:
  The ensemble $\CUE^{(q)}$ of truncated random unitary matrices is a
deformation of the usual Circular Unitary Ensemble depending on a discrete
non-negative parameter $q.$ $\CUE^{(q)}$ is an exactly solved model of random
contraction matrices originally introduced in the context of scattering theory.
In this article, we exhibit a connection between $\CUE^{(q)}$ and Fisher's
random-turns vicious walker model from statistical mechanics. In particular, we
show that the moment generating function of the trace of a random matrix from
$\CUE^{(q)}$ is a generating series for the partition function of Fisher's
model, when the walkers are assumed to represent mutually attracting particles.


title: A remark on left invariant metrics on compact Lie groups

abstract:
  We show that a left invariant metric on a compact Lie group $G$ which is
obtained by stretching a biinvariant metric in the direction of a subalgebra
$\h$ of $\g$ always has some negative sectional curvature, unless the
semi-simple part of $\h$ is an ideal of $\g$.


title:
What Can the Cosmic Microwave Background Tell Us About the Outer Solar
  System?

abstract:
  We discuss two new observational techniques that use observations of the
Cosmic Microwave Background (CMB) to place constraints upon the mass, distance,
and size distribution of small objects in the Kuiper Belt and inner Oort Cloud,
collectively known as Trans-Neptunian Objects (TNOs). The first new technique
considers the spectral distortion of the isotropic, or monopole, CMB by TNOs
that have been heated by solar radiation to temperatures above that of the CMB.
We apply this technique to the spectral measurements of the CMB by the Far
Infrared Absolute Spectrophotometer (FIRAS) on the Cosmic Background Explorer
(COBE). The second technique utilizes the change in amplitude of the TNO signal
due to the orbital motion of the observer to separate the TNO signal from the
invariant extra-galactic CMB and construct a map of the mass distribution in
the outer Solar System. We estimate the ability of future CMB experiments to
create such a map.