title:
Numerical Color-Magnitude Diagram Analysis of SDSS Data and Application
  to the New Milky Way satellites

abstract:
  We have tested the application to Sloan Digital Sky Survey data of the
software package MATCH, which fits color-magnitude diagrams (CMDs) to estimate
stellar population parameters and distances. These tests on a set of six
globular clusters show that these techniques recover their known properties.
New ways of using the CMD-fitting software enable us to deal with an extended
distribution of stars along the line-of-sight, to constrain the overall
properties of sparsely populated objects, and to detect the presence of stellar
overdensities in wide-area surveys. We then also apply MATCH to CMDs for twelve
recently discovered Milky Way satellites to derive in a uniform fashion their
distances, ages and metallicities. While the majority of them appear consistent
with a single stellar population, CVn I, UMa II, and Leo T exhibit (from SDSS
data alone) a more complex history with multiple epochs of star formation.


title: Roper resonances in chiral quark models

abstract:
  We derive a method to calculate the multi-channel K matrix applicable to a
broad class of models in which mesons linearly couple to the quark core. The
method is used to calculate pion scattering amplitudes in the energy region of
low-lying P11 and P33 resonances. A good agreement with experimental data is
achieved if in addition to the elastic channel we include the $\pi\Delta$ and
$\sigma N$ ($\sigma\Delta$) channels where the $\sigma$-meson models the
correlated two-pion decay. We solve the integral equation for the K matrix in
the approximation of separable kernels; it yields a sizable increase of the
widths of the $\Delta(1232)$ and the N(1440) resonances compared to the bare
quark values.


title: Interaction between ionic lattices and superconducting condensates

abstract:
  The interaction of the ionic lattice with the superconducting condensate is
treated in terms of the electrostatic force in superconductors. It is shown
that this force is similar but not identical to the force suggested by the
volume difference of the normal and superconducting states. The BCS theory
shows larger deviations than the two-fluid model.


title:
Multi-agent systems, Equiprobability, Gamma distributions and other
  Geometrical questions

abstract:
  A set of many identical interacting agents obeying a global additive
constraint is considered. Under the hypothesis of equiprobability in the
high-dimensional volume delimited in phase space by the constraint, the
statistical behavior of a generic agent over the ensemble is worked out. The
asymptotic distribution of that statistical behavior is derived from
geometrical arguments. This distribution is related with the Gamma
distributions found in several multi-agent economy models. The parallelism with
all these systems is established. Also, as a collateral result, a formula for
the volume of high-dimensional symmetrical bodies is proposed.

categories: nlin.CD cond-mat.stat-mech cs.MA physics.soc-ph


title: Where is the pseudoscalar glueball ?

abstract:
  The pseudoscalar mesons with the masses higher than 1 GeV are assumed to
belong to the meson decuplet including the glueball as the basis state
supplementing the standard $SU(3)_F$ nonet of light $q\bar{q}$ states
$(u,d,s)$. The decuplet is investigated by means of an algebraic approach based
on hypothesis of vanishing the exotic $SU(3)_F$ commutators of "charges" and
their time derivatives. These commutators result in a system of equations
determining contents of the isoscalar octet state in the physical isoscalar
mesons as well as the mass formula including all masses of the decuplet:
$\pi(1300)$, K(1460), $\eta(1295)$, $\eta(1405)$ and $\eta(1475)$. The physical
isoscalar mesons $\eta_i$, are expressed as superpositions of the "ideal"
$q\bar{q}$ states ($N$ and $S$) and the glueball $G$ with the mixing
coefficient matrix following from the exotic commutator restrictions. Among
four one-parameter families of the calculated mixing matrix (numerous solutions
result from bad quality of data on the $\pi(1300)$ and K(1460) masses) there is
one family attributing the glueball-dominant composition to the $\eta(1405)$
meson. Similarity between the pseudoscalar and scalar decuplets, analogy
between the whole spectra of the $0^{-+}$ and $0^{++}$ mesons and affinity of
the glueball with excited $q\bar{q}$ states are also noticed.


title: Rate of Escape on Free Products

abstract:
  Suppose we are given the free product $V$ of a finite family of finite or
countable sets $(V_i)_{i\in\mathcal{I}}$ and probability measures on each
$V_i$, which govern random walks on it. We consider a transient random walk on
the free product arising naturally from the random walks on the $V_i$. We prove
the existence of the rate of escape with respect to the block length, that is,
the speed, at which the random walk escapes to infinity, and furthermore we
compute formulas for it. For this purpose, we present three different
techniques providing three different, equivalent formulas.


title:
A Radio Resource Management strategy for downlink cooperation in
  distributed networks

abstract: This paper has been withdrawn by the author


title:
The effects of lepton KK modes on the lepton electric dipole moments in
  the Randall Sundrum scenario

abstract:
  We study the charged lepton electric dipole moments in the Randall Sundrum
model where the leptons and the gauge fields are accessible to the extra
dimension. We observe that the electron (muon; tau) electric dipole moment
reaches to the value of the order of 10^{-26} e-cm (10^{-20} e-cm; 10^{-20}
e-cm) with the inclusion of the lepton KK modes.


title: Rate of Escape on the Lamplighter Tree

abstract:
  Suppose we are given a homogeneous tree $\mathcal{T}_q$ of degree $q\geq 3$,
where at each vertex sits a lamp, which can be switched on or off. This
structure can be described by the wreath product $(\mathbb{Z}/2)\wr \Gamma$,
where $\Gamma=\ast_{i=1}^q \mathbb{Z}/2$ is the free product group of $q$
factors $\mathbb{Z}/2$. We consider a transient random walk on a Cayley graph
of $(\mathbb{Z}/2)\wr \Gamma$, for which we want to compute lower and upper
bounds for the rate of escape, that is, the speed at which the random walk
flees to infinity.


title: Acceleration of Lamplighter Random Walks

abstract:
  Suppose we are given an infinite, finitely generated group $G$ and a
transient random walk on the wreath product $(\mathbb{Z}/ 2\mathbb{Z})\wr G$,
such that its projection on $G$ is transient and has finite first moment. This
random walk can be interpreted as a lamplighter random walk on $G$. Our aim is
to show that the random walk on the wreath product escapes to infinity with
respect to a suitable (pseudo-)metric faster than its projection onto $G$. We
also address the case where the pseudo-metric is the length of a shortest
``travelling salesman tour''. In this context, and excluding some degenerate
cases if $G=\mathbb{Z}$, the linear rate of escape is strictly bigger than the
rate of escape of the lamplighter random walk's projection on $G$.


title:
Scenario of inflationary cosmology from the phenomenological $\Lambda$
  models

abstract:
  Choosing the three phenomenological models of the dynamical cosmological term
$\Lambda$, viz., $\Lambda \sim (\dot a/a)^2$, $\Lambda \sim {\ddot a/a}$ and
$\Lambda \sim \rho$ where $a$ is the cosmic scale factor, it has been shown by
the method of numerical analysis that the three models are equivalent for the
flat Universe $k=0$. The evolution plots for dynamical cosmological term
$\Lambda$ vs. time $t$ and also the cosmic scale factor $a$ vs. $t$ are drawn
here for $k=0, +1$. A qualitative analysis has been made from the plots which
supports the idea of inflation and hence expanding Universe.


title: Ultraviolet light emission from Si in a scanning tunneling microscope

abstract:
  Ultraviolet and visible radiation is observed from the contacts of a scanning
tunneling microscope with Si(100) and (111) wafers. This luminescence relies on
the presence of hot electrons in silicon, which are supplied, at positive bias
on n- and p-type samples, through the injection from the tip, or, at negative
bias on p-samples, by Zener tunneling. Measured spectra reveal a contribution
of direct optical transitions in Si bulk. The necessary holes well below the
valence band edge are injected from the tip or generated by Auger processes.


title:
Squark and gaugino hadroproduction and decays in non-minimal flavour
  violating supersymmetry

abstract:
  We implement non-minimal flavour violation (NMFV) in the MSSM at low scale.
In this framework, we propose benchmark points for the mSUGRA scenario
including non-minimal flavour violation by evaluating a number of experimental
low-energy, electroweak precision and cosmological constraints. We finally
discuss phenomenological aspects of our NMFV scenario and present a numerical
analysis of squark and gaugino production cross sections at the LHC.


title: Atomic structure analysis of nanocrystalline Boehmite AlO(OH)

abstract:
  Nanocrystalline n-AlO(OH) (Disperal P2(R) of Sasol) was investigated by means
of the atomic pair distribution function (PDF). The PDF is derived from powder
diffraction data, an ideally resolved PDF is obtained from a synchrotron source
which provides a large maximal scattering vector length Qmax > 300 nm-1. Here,
however, we were able to reveal atomic structure details of the about 4 nm
particles from in-house diffraction data (Qmax = 130 nm-1): PDF least squares
model refinements show that n-AlO(OH) is of the layered Boehmite structure type
(oC16, Cmcm). But the structure is uniformly distorted in domains of ca. 2 nm
size within the nano particles. The hydrogen bonds between the layers are
widened up significantly by +13 pm, accounting for the higher reactivity when
compared to microcrystalline Boehmite. Our results from only one
"nanocrystallographic" experiment are consistent with a trend which was found
via the Rietveld technique on a series of AlO(OH) of different crystallite size
(Bokhimi et al., 2001). In addition, the PDF contains information on structural
distortion as a function of (coherence) domain size within the nano particles.


title: Discretely Holomorphic Parafermions in Lattice Z(N) Models

abstract:
  We construct lattice parafermions - local products of order and disorder
operators - in nearest-neighbor Z(N) models on regular isotropic planar
lattices, and show that they are discretely holomorphic, that is they satisfy
discrete Cauchy-Riemann equations, precisely at the critical
Fateev-Zamolodchikov (FZ) integrable points. We generalize our analysis to
models with anisotropic interactions, showing that, as long as the lattice is
correctly embedded in the plane, such discretely holomorphic parafermions exist
for particular values of the couplings which we identify as the anisotropic FZ
points. These results extend to more general inhomogeneous lattice models as
long as the covering lattice admits a rhombic embedding in the plane.

categories: math-ph cond-mat.stat-mech hep-th math.MP


title:
Exact density matrix of the Gutzwiller wave function: II. Minority spin
  component

abstract:
  The density matrix, i.e. the Fourier transform of the momentum distribution,
is obtained analytically for all magnetization of the Gutzwiller wave function
in one dimension with exclusion of double occupancy per site. The present
result complements the previous analytic derivation of the density matrix for
the majority spin. The derivation makes use of a determinantal form of the
squared wave function, and multiple integrals over particle coordinates are
performed with the help of a diagrammatic representation. In the thermodynamic
limit, the density matrix at distance x is completely characterized by
quantities v_c x and v_s x, where v_s and v_c are spin and charge velocities in
the supersymmetric t-J model for which the Gutzwiller wave function gives the
exact ground state. The present result then gives the exact density matrix of
the t-J model for all densities and all magnetization at zero temperature.
Discontinuity, slope, and curvature singularities in the momentum distribution
are identified. The momentum distribution obtained by numerical Fourier
transform is in excellent agreement with existing result.


title: Fisher Lecture: Dimension Reduction in Regression

abstract:
  Beginning with a discussion of R. A. Fisher's early written remarks that
relate to dimension reduction, this article revisits principal components as a
reductive method in regression, develops several model-based extensions and
ends with descriptions of general approaches to model-based and model-free
dimension reduction in regression. It is argued that the role for principal
components and related methodology may be broader than previously seen and that
the common practice of conditioning on observed values of the predictors may
unnecessarily limit the choice of regression methodology.


title: Decoherence of encoded quantum registers

abstract:
  In order to eliminate disturbing effects of decoherence, encoding of quantum
information in decoherence-free subspaces has been suggested. We analyze the
benefits of this concept for a quantum register that is realized in a spin
chain in contact with a common bosonic bath. Within a dissipation-less model we
provide explicit analytical results for the average fidelity of plain and
encoded quantum registers. For the investigation of dissipative spin-boson
couplings we employ a master equation of Bloch-Redfield type.


abstract: Comment: Fisher Lecture: Dimension Reduction in Regression [arXiv:0708.3774]


title: Comment: Fisher Lecture: Dimension Reduction in Regression


title: Symplectic geometries on supermanifolds

abstract:
  Extension of symplectic geometry on manifolds to the supersymmetric case is
considered. In the even case it leads to the even symplectic geometry (or,
equivalently, to the geometry on supermanifolds endowed with a non-degenerate
Poisson bracket) or to the geometry on an even Fedosov supermanifolds. It is
proven that in the odd case there are two different scalar symplectic
structures (namely, an odd closed differential 2-form and the antibracket)
which can be used for construction of symplectic geometries on supermanifolds.


title: The optical emission line spectrum of Mark 110

abstract:
  We analyse in detail the rich emission line spectrum of Mark 110 to determine
the physical conditions in the nucleus of this object, a peculiar NLS1 without
any detectable Fe II emission associated with the broad line region and with a
$\lambda5007/H\beta$ line ratio unusually large for a NLS1. We use 24 spectra
obtained with the Marcario Low Resolution Spectrograph attached at the prime
focus of the 9.2 m Hobby-Eberly telescope at the McDonald observatory. We
fitted the spectrum by identifying all the emission lines (about 220) detected
in the wavelength range 4200-6900 \AA (at rest). The narrow emission lines are
probably produced in a region with a density gradient in the range
10$^{3}-10^{6}$ cm$^{-3}$ with a rather high column density (5$\times10^{21}$
cm$^{-2}$). In addition to a narrow line system, three major broad line systems
with different line velocity and width are required. We confirm the absence of
broad Fe II emission lines. We speculate that Mark 110 is in fact a BLS1 with
relatively "narrow" broad lines but with a BH mass large enough compared to its
luminosity to have a lower than Eddington luminosity.


abstract:
  Rejoinder: Fisher Lecture: Dimension Reduction in Regression
[arXiv:0708.3774]


title:
QCD-resummation and non-minimal flavour-violation for supersymmetric
  particle production at hadron colliders

abstract:
  Cross sections for supersymmetric particles production at hadron colliders
have been extensively studied in the past at leading order and also at
next-to-leading order of perturbative QCD. The radiative corrections include
large logarithms which have to be resummed to all orders in the strong coupling
constant in order to get reliable perturbative results. In this work, we
perform a first and extensive study of the resummation effects for
supersymmetric particle pair production at hadron colliders. We focus on
Drell-Yan like slepton-pair and slepton-sneutrino associated production in
minimal supergravity and gauge-mediated supersymmetry-breaking scenarios, and
present accurate transverse-momentum and invariant-mass distributions, as well
as total cross sections.
  In non-minimal supersymmetric models, novel effects of flavour violation may
occur. In this case, the flavour structure in the squark sector cannot be
directly deduced from the trilinear Yukawa couplings of the fermion and Higgs
supermultiplets. We perform a precise numerical analysis of the experimentally
allowed parameter space in the case of minimal supergravity scenarios with
non-minimal flavour violation, looking for regions allowed by low-energy,
electroweak precision, and cosmological data. Leading order cross sections for
the production of squarks and gauginos at hadron colliders are implemented in a
flexible computer program, allowing us to study in detail the dependence of
these cross sections on flavour violation.


title:
Resonantly damped surface and body MHD waves in a solar coronal slab
  with oblique propagation

abstract:
  The theory of magnetohydrodynamic (MHD) waves in solar coronal slabs in a
zero-$\beta$ configuration and for parallel propagation of waves does not allow
the existence of surface waves. When oblique propagation of perturbations is
considered both surface and body waves are able to propagate. When the
perpendicular wave number is larger than a certain value, the body kink mode
becomes a surface wave. In addition, a sausage surface mode is found below the
internal cut-off frequency. When non-uniformity in the equilibrium is included,
surface and body modes are damped due to resonant absorption. In this paper,
first, a normal-mode analysis is performed and the period, the damping rate,
and the spatial structure of eigenfunctions are obtained. Then, the
time-dependent problem is solved, and the conditions under which one or the
other type of mode is excited are investigated.


title: Localization of quantum wave packets

abstract:
  We study the semiclassical propagation of squeezed Gau{\ss}ian states. We do
so by considering the propagation theorem introduced by Combescure and Robert
\cite{CR97} approximating the evolution generated by the Weyl-quantization of
symbols $H$. We examine the particular case when the Hessian
$H^{\prime\prime}(X_{t})$ evaluated at the corresponding solution $X_{t}$ of
Hamilton's equations of motion is periodic in time. Under this assumption, we
show that the width of the wave packet can remain small up to the Ehrenfest
time. We also determine conditions for ``classical revivals'' in that case.
More generally, we may define recurrences of the initial width. Some of these
results include the case of unbounded classical motion. In the classically
unstable case we recover an exponential spreading of the wave packet as in
\cite{CR97}.


title:
Perfect Teleportation, Quantum state sharing and Superdense Coding
  through a Genuinely Entangled Five-qubit State

abstract:
  We investigate the usefulness of a recently introduced five qubit state by
Brown $\it et al. \normalfont$ \cite{Brown} for quantum teleportation, quantum
state sharing and superdense coding. It is shown that this five-qubit state can
be utilized for perfect teleportation of arbitrary single and two qubit
systems. We devise various schemes for quantum state sharing of an arbitrary
single and two particle state via cooperative teleportation. We later show that
this state can be used for superdense coding as well. It is found that five
classical bits can be sent by sending only three quantum bits.


title:
Temperature and Polarization CMB Maps from Primordial non-Gaussianities
  of the Local Type

abstract:
  The forthcoming Planck experiment will provide high sensitivity polarization
measurements that will allow us to further tighten the f_NL bounds from the
temperature data. Monte Carlo simulations of non-Gaussian CMB maps have been
used as a fundamental tool to characterize non-Gaussian signatures in the data,
as they allow us to calibrate any statistical estimators and understand the
effect of systematics, foregrounds and other contaminants. We describe an
algorithm to generate high-angular resolution simulations of non-Gaussian CMB
maps in temperature and polarization. We consider non-Gaussianities of the
local type, for which the level of non-Gaussianity is defined by the
dimensionless parameter, f_NL. We then apply the temperature and polarization
fast cubic statistics recently developed by Yadav et al. to a set of
non-Gaussian temperature and polarization simulations. We compare our results
to theoretical expectations based on a Fisher matrix analysis, test the
unbiasedness of the estimator, and study the dependence of the error bars on
f_NL. All our results are in very good agreement with theoretical predictions,
thus confirming the reliability of both the simulation algorithm and the fast
cubic temperature and polarization estimator.


title: Black-Hole Mass and Growth Rate at High Redshift

abstract:
  We present new H and K bands spectroscopy of 15 high luminosity active
galactic nuclei (AGNs) at redshifts 2.3-3.4 obtained on Gemini South. We
combined the data with spectra of additional 29 high-luminosity sources to
obtain a sample with 10^{45.2}<\lambda L_{\lambda}(5100A)<10^{47.3} ergs/sec
and black hole (BH) mass range, using reverberation mapping relationships based
on the H_beta method, of 10^{8.8}-10^{10.7} M_sun. We do not find a correlation
of L/L_Edd with M_BH but find a correlation with \lambda L_{\lambda}(5100A)
which might be due to selection effects. The L/L_Edd distribution is broad and
covers the range ~0.07-1.6, similar to what is observed in lower redshift,
lower luminosity AGNs. We suggest that this consistently measured and
calibrated sample gives the best representation of L/L_Edd at those redshifts
and note potential discrepancies with recent theoretical and observational
studies. The lower accretion rates are not in accord with growth scenarios for
BHs at such redshifts and the growth times of many of the sources are longer
than the age of the universe at the corresponding epochs. This suggests earlier
episodes of faster growth at z>~3 for those sources. The use of the C IV method
gives considerably different results and a larger scatter; this method seems to
be a poor M_BH and L/L_Edd estimator at very high luminosity.


title: Dimensional Reduction of Conformal Tensors and Einstein-Weyl Spaces

abstract:
  Conformal Weyl and Cotton tensors are dimensionally reduced by a Kaluza-Klein
procedure. Explicit formulas are given for reducing from four and three
dimensions to three and two dimensions, respectively. When the higher
dimensional conformal tensor vanishes because the space is conformallly flat,
the lower-dimensional Kaluza-Klein functions satisfy equations that coincide
with the Einstein-Weyl equations in three dimensions and kink equations in two
dimensions.


title:
Efficient qubit detection using alkali earth metal ions and a double
  STIRAP process

abstract:
  We present a scheme for robust and efficient projection measurement of a
qubit consisting of the two magnetic sublevels in the electronic ground state
of alkali earth metal ions. The scheme is based on two stimulated Raman
adiabatic passages (STIRAP) involving four partially coherent laser fields. We
show how the efficiency depends on experimentally relevant parameters: Rabi
frequencies, pulse widths, laser linewidths, one- and two-photon detunings,
residual laser power, laser polarization and ion motion.


title:
Singlet fermion dark matter and electroweak baryogenesis with radiative
  neutrino mass

abstract:
  The model of radiative neutrino mass with dark matter proposed by one of us
is extended to include a real singlet scalar field. There are then two
important new consequences. One is the realistic possibility of having the
lightest neutral singlet fermion (instead of the lightest neutral component of
the dark scalar doublet) as the dark matter of the Universe. The other is a
modification of the effective Higgs potential of the Standard Model, consistent
with electroweak baryogenesis.


title:
Critical phenomena in a highly constrained classical spin system: Neel
  ordering from the Coulomb phase

abstract:
  Many classical, geometrically frustrated antiferromagnets have
macroscopically degenerate ground states. In a class of three-dimensional
systems, the set of degenerate ground states has power-law correlations and is
an example of a Coulomb phase. We investigate Neel ordering from such a Coulomb
phase, induced by weak additional interactions that lift the degeneracy. We
show that the critical point belongs to a universality class that is different
from the one for the equivalent transition out of the paramagnetic phase, and
that it is characterised by effective long-range interactions; alternatively,
ordering may be discontinuous. We suggest that a transition of this type may be
realised by applying uniaxial stress to a pyrochlore antiferromagnet.


title: Gelfand-Dickey Algebra and Higher Spin Symmetries On $T^2=S^1\times S^1$

abstract:
  We focus in this work to renew the interest in higher conformal spins
symmetries and their relations to quantum field theories and integrable models.
We consider the extension of the conformal Frappat et al. symmetries containing
the Virasoro and the Antoniadis et al. algebras as particular cases describing
geometrically special diffeomorphisms of the two dimensional torus $T^2$. We
show in a consistent way, and explicitly, how one can extract these generalized
symmetries from the Gelfand-Dickey algebra. The link with Liouville and Toda
conformal field theories is established and various important properties are
discussed.


title: Low upper bounds of ideals

abstract:
  We show that there is a low T-upper bound for the class of K-trivial sets,
namely those which are weak from the point of view of algorithmic randomness.
This result is a special case of a more general characterization of ideals in
the T-degrees below 0' for which there is a low T-upper bound.


title: Time-optimal control of a two-level dissipative quantum system

abstract:
  We propose an analysis of the time-optimal control of a dissipative two-level
quantum system whose dynamics is governed by the Lindblad equation. This simple
system allows one to use tools of geometric control theory and to construct its
optimal synthesis, i.e. to determine the set of all the optimal trajectories
starting from a given initial point. We study different processes such as
conversion of a pure state into a mixed state and purification of a mixed
state. In particular cases, we show that dissipation is not undesirable and can
help accelerating the control.


title:
White dwarf atmosphere models with Ly-$\alpha$ opacity in the analysis
  of the white dwarf cooling sequence of NGC 6397

abstract:
  We discuss the importance of pure hydrogen white dwarf atmosphere models with
Ly-$\rm \alpha$ far red wing opacity in the analysis of the white dwarf cooling
sequence of the globular cluster NGC 6397. Our recently improved atmosphere
models account for the previously missing opacity from the Ly-$\rm \alpha$
hydrogen line broadened by collisions of the absorbing hydrogen atoms with
molecular and atomic hydrogen. These models are the first that well reproduce
the UV colors and spectral energy distributions of cool white dwarfs with
$T_{\rm eff}<6000 \rm K$ observed in the Galactic Disk. Fitting the observed
$F814W$ magnitude and $F606W-F814W$ color we obtained a value for the true
distance modulus, $\mu=12.00 \pm 0.02$, that is in agreement with recent
analyses. We show that the stars at the end of the cooling sequence appear to
be $\rm \sim 160 K$ cooler when models that account for Ly-$\rm \alpha$ opacity
are used. This indicates that the age of NGC 6397 derived from the white dwarf
cooling sequence using atmosphere models that do not include the correct
Ly-$\alpha$ opacity is underestimated by $\sim 0.5$ Gyr. Our analysis shows
that it is essential to use white dwarf atmosphere models with Ly-$\rm \alpha$
opacity for precise dating of old stellar populations from white dwarf cooling
sequences.


title: Embedding Population Dynamics Models in Inference

abstract:
  Increasing pressures on the environment are generating an ever-increasing
need to manage animal and plant populations sustainably, and to protect and
rebuild endangered populations. Effective management requires reliable
mathematical models, so that the effects of management action can be predicted,
and the uncertainty in these predictions quantified. These models must be able
to predict the response of populations to anthropogenic change, while handling
the major sources of uncertainty. We describe a simple ``building block''
approach to formulating discrete-time models. We show how to estimate the
parameters of such models from time series of data, and how to quantify
uncertainty in those estimates and in numbers of individuals of different types
in populations, using computer-intensive Bayesian methods. We also discuss
advantages and pitfalls of the approach, and give an example using the British
grey seal population.


title: A General Framework for the Parametrization of Hierarchical Models

abstract:
  In this paper, we describe centering and noncentering methodology as
complementary techniques for use in parametrization of broad classes of
hierarchical models, with a view to the construction of effective MCMC
algorithms for exploring posterior distributions from these models. We give a
clear qualitative understanding as to when centering and noncentering work
well, and introduce theory concerning the convergence time complexity of Gibbs
samplers using centered and noncentered parametrizations. We give general
recipes for the construction of noncentered parametrizations, including an
auxiliary variable technique called the state-space expansion technique. We
also describe partially noncentered methods, and demonstrate their use in
constructing robust Gibbs sampler algorithms whose convergence properties are
not overly sensitive to the data.


title: Impedance-matched Hyperlens

abstract:
  We propose an approach to optical imaging beyond the diffraction limit, based
on transformation optics in concentric circular cylinder domains. The resulting
systems allow image magnification and minimize reflection losses due to the
impedance matching at the input or output boundaries. While perfect impedance
matching at both surfaces can only be obtained in a system with
radius-dependent magnetic permeability, we demonstrate that comparable
performance can be achieved in an optimized non-magnetic design.


title:
Spatially nonuniform phases in the one-dimensional SU(n) Hubbard model
  for commensurate fillings

abstract:
  The one-dimensional repulsive SU$(n)$ Hubbard model is investigated
analytically by bosonization approach and numerically using the density-matrix
renormalization-group (DMRG) method for $n=3,4$, and 5 for commensurate
fillings $f=p/q$ where $p$ and $q$ are relatively prime. It is shown that the
behavior of the system is drastically different depending on whether $q>n$,
$q=n$, or $q<n$. When $q>n$, the umklapp processes are irrelevant, the model is
equivalent to an $n$-component Luttinger liquid with central charge $c=n$. When
$q=n$, the charge and spin modes are decoupled, the umklapp processes open a
charge gap for finite $U>0$, whereas the spin modes remain gapless and the
central charge $c=n-1$. The translational symmetry is not broken in the ground
state for any $n$. On the other hand, when $q<n$, the charge and spin modes are
coupled, the umklapp processes open gaps in all excitation branches, and a
spatially nonuniform ground state develops. Bond-ordered dimerized, trimerized
or tetramerized phases are found depending on the filling.


title: Coupled quintessence and vacuum decay

abstract:
  We discuss observational consequences of a class of cosmological models
characterized by the dilution of pressureless matter attenuated with respect to
the usual $a^{-3}$ scaling due to the decay of vacuum energy. We carry out a
joint statistical analysis of observational data from the new \emph{gold}
sample of 182 SNe Ia, recent estimates of the CMB shift parameter, and BAO
measurements from the SDSS to show that such models favor the decay of vacuum
only into the dark matter sector, and that the separately conserved baryons
cannot be neglected. In order to explore ways to more fundamentally motivated
models, we also derive a coupled scalar field version for this general class of
vacuum decay scenarios.


title: Heavy-quark production from Glauber-Gribov theory at LHC

abstract:
  We present predictions for heavy-quark production for proton-lead collisions
at LHC energy 5.5 TeV from Glauber-Gribov theory of nuclear shadowing. We have
also made predictions for baseline cold-matter (in other words inital-state)
nuclear effects in lead-lead collisions at the same energy that has to be taken
into account to understand properly final-state effects.


title: Unparticle physics in top pair signals at the LHC and ILC

abstract:
  We study the effects of unparticle physics in the pair productions of top
quarks at the LHC and ILC. By considering vector, tensor and scalar unparticle
operators, as appropriate, we compute the total cross sections for pair
production processes depending on scale dimension $d_{\U}$. We find that the
existence of unparticles would lead to measurable enhancements on the SM
predictions at the LHC. In the case of ILC this may become two orders of
magnitude larger than that of SM, for smaller values of $d_\U$, a very striking
signal for unparticles.


title:
Multiplicity and cold-nuclear matter effects from Glauber-Gribov theory
  at LHC

abstract:
  We present predictions for nuclear modification factor in proton-lead
collisions at LHC energy 5.5 TeV from Glauber-Gribov theory of nuclear
shadowing. We have also made predictions for baseline cold-matter nuclear
effects in lead-lead collisions at the same energy.


title: Free Quarks and Antiquarks versus Hadronic Matter

abstract:
  Meson-meson reactions A(q_1 \bar{q}_1) + B(q_2 \bar{q}_2) to q_1 + \bar{q}_1
+ q_2 + \bar{q}_2 in high-temperature hadronic matter are found to produce an
appreciable amount of quarks and antiquarks freely moving in hadronic matter
and to establish a new mechanism for deconfinement of quarks and antiquarks in
hadronic matter.


title: Moduli stabilization in heterotic M-theory

abstract:
  We reconsider the ingredients of moduli stabilization in heterotic M-theory.
On this line we close a gap in the literature deriving the Kaehler potential
dependence on vector bundle moduli and charged matter. Crucial in this
derivation is our superspace formulation of 5d heterotic M-theory taking into
account the Bianchi identities modified by brane terms. Likewise, we obtain the
Fayet-Iliopolous terms due to brane localised anomalous U(1)'s. After
assembling perturbative and non-perturbative contributions to the
superpotential, we study supersymmetric (adS) vacua. It is found that the susy
condition decouples the bundle moduli from the geometric moduli. We show that
M-theory supersymmetric vacua without five-branes can be found, albeit not at
phenomenologically interesting values of the geometric moduli. This result is
fairly independent of the choice of vector bundle at the observable brane.


title: Instantons in N=2 magnetized D-brane worlds

abstract:
  In a toroidal orbifold of type IIB string theory we study instanton effects
in N=2 super Yang-Mills theories engineered with systems of wrapped magnetized
D9 branes and Euclidean D5 branes. We analyze the various open string sectors
in this brane system and study the 1-loop amplitudes described by annulus
diagrams with mixed boundary conditions, explaining their role in the stringy
instanton calculus. We show in particular that the non-holomorphic terms in
these annulus amplitudes precisely reconstruct the appropriate Kahler metric
factors that are needed to write the instanton correlators in terms of purely
holomorphic variables. We also explicitly derive the correct holomorphic
structure of the instanton induced low energy effective action in the Coulomb
branch.


title: Doniach diagram for ordered, disordered and underscreened Kondo lattices

abstract:
  The Doniach's diagram has been originally proposed to describe the
competition between the local Kondo effect and the intersite RKKY interactions
in cerium compounds. Here we discuss the extension of this diagram to different
variations of Kondo lattice model. We consider a) ordered cerium compounds
where the competition between magnetic order and Kondo effect plays an
important role, as $CeRh_2Si_2$, b) disordered cerium systems with competing
spin glass phase, magnetic ordered phases and a Kondo phase, as the heavy
fermion cerium alloy $CeCu_xNi_{1-x}$ and, c) uranium compounds where a
coexistence between Kondo effect and ferromagnetic order has been observed, as
UTe. We show that all these cases can be described by a generalized Doniach
phase diagram.


title: PAHs in the Halo of NGC 5529

abstract:
  We present sensitive ISO $\lambda 6.7 \mu$m observations of the edge-on
galaxy, NGC 5529, finding an extensive MIR halo around NGC 5529. The emission
is dominated by PAHs in this band. The PAH halo has an exponential scale height
of 3.7 kpc but can still be detected as far as $\approx 10$ kpc from the plane
to the limits of the high dynamic range (1770/1) data. This is the most
extensive PAH halo yet detected in a normal galaxy. This halo shows
substructure and the PAHs likely originate from some type of disk outflow. PAHs
are long-lived in a halo environment and therefore continuous replenishment
from the disk is not required (unless halo PAHs are also being destroyed or
removed), consistent with the current low SFR of the galaxy. The PAHs correlate
spatially with halo H$\alpha$ emission, previously observed by Miller &
Veilleux (2003); both components are likely excited/ionized by in-disk photons
that are leaking into the halo. The presence of halo gas may be related to the
environment of NGC 5529 which contains at least 17 galaxies in a small group of
which NGC 5529 is the dominant member. Of these, we have identified two new
companions from the SDSS.


title:
Design Strategies for the Geometric Synthesis of Orthoglide-type
  Mechanisms

abstract:
  The paper addresses the geometric synthesis of Orthoglide-type mechanism, a
family of 3-DOF parallel manipulators for rapid machining applications, which
combine advantages of both serial mechanisms and parallel kinematic
architectures. These manipulators possess quasi-isotropic kinematic
performances and are made up of three actuated fixed prismatic joints, which
are mutually orthogonal and connected to a mobile platform via three
parallelogram chains. The platform moves in the Cartesian space with fixed
orientation, similar to conventional XYZ-machine. Three strategies have been
proposed to define the Orthoglide geometric parameters (manipulator link
lengths and actuated joint limits) as functions of a cubic workspace size and
dextrous properties expressed by bounds on the velocity transmission factors,
manipulability or the Jacobian condition number. Low inertia and intrinsic
stiffness have been set as additional design goals expressed by the minimal
link length requirement. For each design strategy, analytical expressions for
computing the Orthoglide parameters are proposed. It is showed that the
proposed strategies yield Pareto-optimal solutions, which differ by the
kinematic performances outside the prescribed Cartesian cube (but within the
workspace bounded by the actuated joint limits). The proposed technique is
illustrated with numerical examples for the Orthoglide prototype design.


title: From the Planck to the Photon Scale

abstract:
  Using considerations from the Quantum Zero Point Field and Thermodynamics, we
show that the Planck Scale is the minimum (maximum mass) and the Photon Scale
is the maximum (minimum mass) Scale in the universe. The arguments also deduce
the residual cosmic energy of $10^{-33}eV$ observed lately.


title:
An Exhaustive Study of the Workspaces Tolopogies of all 3R Orthogonal
  Manipulators with Geometric Simplifications

abstract:
  This paper proposes a classification of three-revolute orthogonal
manipulators that have at least one of their DH parameters equal to zero. This
classification is based on the topology of their workspace. The workspace is
characterized in a half-cross section by the singular curves. The workspace
topology is defined by the number of cusps and nodes that appear on these
singular curves. The manipulators are classified into different types with
similar kinematic properties. Each type is evaluated according to interesting
kinematic properties such as, whether the workspace is fully reachable with
four inverse kinematic solutions or not, the existence of voids, and the
feasibility of continuous trajectories in the workspace. It is found that
several orthogonal manipulators have a "well-connected" workspace, that is,
their workspace is fully accessible with four inverse kinematic solutions and
any continuous trajectory is feasible. This result is of interest for the
design of alternative manipulator geometries.


title:
Search for new charmonium states in the processes e+ e- --> J/psi D(*)
  D(*) at sqrt{s} ~ 10.6 GeV

abstract:
  We present a study of the X(3940) state in the process e+e- -> J/psi D* Dbar.
The X(3940) mass and width are measured to be (3942 +7 -6 +- 6)MeV/c^2 and
Gamma=(37 + 26 - 15 +- 8 MeV. In the process e+e- -> J/psi D* D*bar we have
observed another charmonium-like state, which we denote as X(4160), in the
spectrum of invariant masses of D*+ D*- combinations. The X(4160) parameters
are M= 4156 + 25 - 20 +- 15 MeV/c^2 and Gamma = 139 + 111 -61 +- 21 MeV. The
analysis is based on a data sample with an integrated luminosity of 693 /fb
recorded near the Upsilon(4S) resonance with the Belle detector at the KEKB e+
e- asymmetric-energy collider.


title:
Non-Commutativity of Effective Space-Time Coordinates and the Minimal
  Length

abstract:
  Considering that a position measurement can effectively involve a
momentum-dependent shift and rescaling of the "true" space-time coordinates, we
construct a set of effective space-time coordinates which are naturally
non-commutative. They lead to a minimum length and are shown to be related to
Snyder's coordinates and the five-dimensional formulation of Deformed Special
Relativity. This effective approach then provides a natural physical
interpretation for both the extra fifth dimension and the deformed momenta
appearing in this context.


title:
Extending BCCNR flavored geometry to the negative coupling constant
  region

abstract:
  We extend BCCNR's flavored KW and KS geometries into the negative coupling
constant region and try giving physical explanations from the dual gauge theory
side. We show that, in the extended region, except the coupling constant being
negative, all other fields of the super-gravity theory having good properties
which can be described by the dual gauge theory.


title: Flavor Hierarchy Quadratic Rule and Dual Quark-Neutrino Mixing Patterns

abstract:
  Flavor physics is about particle mass-degeneracy-deviations (DMD) and mixing
and especially about hierarchies of those deviations. On the one hand there is
no established theory of particle flavor at present; on the other hand there
are growing data indications on interesting empirical flavor regularities that
are described here by two semi-empirical rules: quadratic DMD-hierarchy and
Dirac-Majorana DMD-duality rules. First rule unites neutrino solar-atmospheric
hierarchy parameter with charged lepton (CL) and quark mass-ratio hierarchies
and simultaneously unites the hierarchies in the mixing matrices of quarks and
neutrinos; the second rule predicts quasi-degenerate neutrinos from the fact of
CL and quark large mass hierarchy and explains quark-neutrino complementarity
mixing relations. The neutrino and quark mixing data seem very different, but
it results that small deviations from maximal neutrino mixing are nearly equal
to the small deviations from minimal mixing of quarks. Those deviations are
quantitatively described by only one new small flavor parameter ~0.0067.


title:
Constraining the equation of state of supra-nuclear dense matter from
  XMM-Newton observations of neutron stars in globular clusters

abstract:
  We report on the detailed modelling of the X-ray spectra of three likely
neutron stars. The neutron stars, observed with XMM-Newton are found in three
quiescent X-ray binaries in the globular clusters: omega Cen, M 13 and NGC
2808. Whether they are accreting at very low rates or radiating energy from an
accretion heated core, their X-ray spectra are expected to be those of a
hydrogen atmosphere. We use and compare publicly available hydrogen atmosphere
models, with constant and varying surface gravities to constrain the masses and
radii of the neutron stars. Thanks to the high XMM-Newton throughput, and the
accurate distances available for these clusters, using the latest science
analysis software release and calibration of the XMM-Newton EPIC cameras, we
derive the most stringent constraints on the masses and radii of the neutron
stars obtained to date from these systems. A comparison of the models indicate
that previously used hydrogen atmosphere models (assuming constant surface
gravity) tend to underestimate the mass and overestimate the radius of neutron
stars. Our data constrain the allowed equations of state to those which concern
normal nucleonic matter and one possible strange quark matter model, thus
constraining radii to be from 8 km and masses up to 2.4 M$_\odot$.


title:
Fractionally Quantized Hall Effect: Liquid-Crystal Ground-State and it
  Excitations

abstract:
  It is shown that the ground-state and the lowest excited-states of
two-dimensional electron system (2DES), with ion jellium background, correspond
to partial crystal-like (with the period $L_{x}^{\square}=\sqrt{2 m \pi}
\ell_{0}$) correlation order among $N$ electrons of the main region (MR; $L_{x}
\times L_{y}$). Many-body variational ground-state wave function of 2DES is
presented at the fractional and the integral filling factors $\nu=1/m$;
$m=2\ell+1$ and $\ell=0, 1, 2,...$. The ground-state manifests the broken
symmetry liquid-crystal state with 2DES density that is periodic along the $y-$
direction, with the period $L_{x}^{\square}/m$, and independent of $x$. At
$m=3, 5$, the ground-state has essentially lower energy per electron than the
Laughlin, uniform liquid, ground-state; the same holds at $m=1$. At $m \geq 3$,
the compound form of the many-body ground-state wave function leads to the
compound structure of each electron within the main strip (MS; $L_{x}^{\square}
\times L_{y}$). Obtained compound exciton and compound spin-exciton states show
finite excitation gaps. The excited compound electron (hole) is composed,
within MS, from $m$ strongly correlated quasielectrons (quasiholes) of the
total charge $e/m$ ($-e/m$) each. The activation gap is obtained: it is given
by the excitation gap of relevant compound exciton, at $m \geq 3$, and by the
gap of pertinent compound spin-exciton, at $m=1$. Quantized Hall conductance
$\sigma_{H}=e^{2}/(2 m \pi \hbar)$ is obtained. The theory is in good agreement
with experiments.


title: All-sky search for periodic gravitational waves in LIGO S4 data

abstract:
  We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50-1000 Hz and with the frequency's
time derivative in the range -1.0E-8 Hz/s to zero. Data from the fourth LIGO
science run (S4) have been used in this search. Three different semi-coherent
methods of transforming and summing strain power from Short Fourier Transforms
(SFTs) of the calibrated data have been used. The first, known as "StackSlide",
averages normalized power from each SFT. A "weighted Hough" scheme is also
developed and used, and which also allows for a multi-interferometer search.
The third method, known as "PowerFlux", is a variant of the StackSlide method
in which the power is weighted before summing. In both the weighted Hough and
PowerFlux methods, the weights are chosen according to the noise and detector
antenna-pattern to maximize the signal-to-noise ratio. The respective
advantages and disadvantages of these methods are discussed. Observing no
evidence of periodic gravitational radiation, we report upper limits; we
interpret these as limits on this radiation from isolated rotating neutron
stars. The best population-based upper limit with 95% confidence on the
gravitational-wave strain amplitude, found for simulated sources distributed
isotropically across the sky and with isotropically distributed spin-axes, is
4.28E-24 (near 140 Hz). Strict upper limits are also obtained for small patches
on the sky for best-case and worst-case inclinations of the spin axes.


title: Line shift, line asymmetry, and the 6Li/7Li isotopic ratio determination

abstract:
  Context: Line asymmetries are generated by convective Doppler shifts in
stellar atmospheres, especially in metal-poor stars, where convective motions
penetrate to higher atmospheric levels. Such asymmetries are usually neglected
in abundance analyses. The determination of the 6Li/7Li isotopic ratio is prone
to suffering from such asymmetries, as the contribution of 6Li is a slight
blending reinforcement of the red wing of each component of the corresponding
7Li line, with respect to its blue wing. Aims: The present paper studies the
halo star HD 74000 and estimates the impact of convection-related asymmetries
on the Li isotopic ratio determination. Method: Two methods are used to meet
this aim. The first, which is purely empirical, consists in deriving a template
profile from another element that can be assumed to originate in the same
stellar atmospheric layers as Li I, producing absorption lines of approximately
the same equivalent width as individual components of the 7Li I resonance line.
The second method consists in conducting the abundance analysis based on NLTE
line formation in a 3D hydrodynamical model atmosphere, taking into account the
effects of photospheric convection. Results: The results of the first method
show that the convective asymmetry generates an excess absorption in the red
wing of the 7Li absorption feature that mimics the presence of 6Li at a level
comparable to the hitherto published values. This opens the possibility that
only an upper limit on 6Li/7Li has thus far been derived. The second method
confirms these findings. Conclusions: From this work, it appears that a
systematic reappraisal of former determinations of 6Li abundances in halo stars
is warranted.


title: Vacuum polarization for lukewarm black holes

abstract:
  We compute the renormalized expectation value of the square of a quantum
scalar field on a Reissner-Nordstrom-de Sitter black hole in which the
temperatures of the event and cosmological horizons are equal (`lukewarm' black
hole). Our numerical calculations for a thermal state at the same temperature
as the two horizons indicate that this renormalized expectation value is
regular on both the event and cosmological horizons. We are able to show
analytically, using an approximation for the field modes near the horizons,
that this is indeed the case.


title: Fundamental and composite scalars from extra dimensions

abstract:
  We discuss a scenario consisting of an effective 4D theory containing
fundamental and composite fields. The strong dynamics sector responsible for
the compositeness is assumed to be of extra dimensional origin. In the 4D
effective theory the SM fermion and gauge fields are taken as fundamental
fields. The scalar sector of the theory resembles a bosonic topcolor in the
sense there are two scalar Higgs fields, a composite scalar field and a
fundamental gauge-Higgs unification scalar. A detailed analysis of the scalar
spectrum is presented in order to explore the parameter space consistent with
experiment. It is found that, under the model assumptions, the acceptable
parameter space is quite constrained. As a part of our phenomenological study
of the model, we evaluate the branching ratio of the lightest Higgs boson and
find that our model predicts a large FCNC mode h -> tc, which can be as large
as O(10^{-3}). Similarly, a large BR for the top FCNC decay is obtained, namely
B.R.(t -> c + H) \simeq 10^{-4}


title: Critical Topology for Optimization on the Symplectic Group

abstract:
  Optimization problems over compact Lie groups have been extensively studied
due to their broad applications in linear programming and optimal control. This
paper analyzes least square problems over a noncompact Lie group, the
symplectic group $\Sp(2N,\R)$, which can be used to assess the optimality of
control over dynamical transformations in classical mechanics and quantum
optics. The critical topology for minimizing the Frobenius distance from a
target symplectic transformation is solved. It is shown that the critical
points include a unique local minimum and a number of saddle points. The
topology is more complicated than those of previously studied problems on
compact Lie groups such as the orthogonal and unitary groups because the
incompatibility of the Frobenius norm with the pseudo-Riemannian structure on
the symplectic group brings significant nonlinearity to the problem.
Nonetheless, the lack of traps guarantees the global convergence of local
optimization algorithms.


title:
Reduction without reduction: Adding KK-monopoles to five dimensional
  stationary axisymmetric solutions

abstract:
  We present a general method to add KK-monopole charge to any asymptotically
flat stationary axisymmetric solution of five dimensional General Relativity.
The technique exploits the underlying SL(3,R) invariance of the system by
identifying a particular element of the symmetry group which changes the
asymptotic boundary condition and adds KK-monopole charge. Furthermore, we
develop a set of technical tools which allow us to apply the SL(3,R)
transformations to solutions produced by the Inverse Scattering method. As an
example of our methods, we construct the exact solution describing a static
black ring carrying KK-monopole charge.


title: Radio Detection of Neutrinos from Behind a Mountain

abstract:
  We explore the sensitivity of a neutrino detector employing strongly
directional high gain radio antennae to detect the conversion of neutrinos
above $10^{16}$ eV in a mountain or the earth crust. The directionality of the
antennae will allow both, the low threshold and the suppression of background.
This technology would have the advantage that it does not require a suitable
atmosphere as optical detectors do and could therefore be deployed at any
promising place on the planet. In particular one could choose suitable
topographies at latitudes that are matched to promising source candidates.


title: Stochastic Fluctuations in Epidemics on Networks

abstract:
  The effects of demographic stochasticity in the long term behaviour of
endemic infectious diseases have been considered for long as a necessary
addition to an underlying deterministic theory. The latter would explain the
regular behaviour of recurrent epidemics, and the former the superimposed noise
of observed incidence patterns. Recently, a stochastic theory based on a
mechanism of resonance with internal noise has shifted the role of
stochasticity closer to the center stage, by showing that the major dynamic
patterns found in the incidence data can be explained as resonant fluctuations,
whose behaviour is largely independent of the amplitude of seasonal forcing,
and by contrast very sensitive to the basic epidemiological parameters. Here we
elaborate on that approach, by adding an ingredient which is missing in
standard epidemic models, the 'mixing network' through which infection may
propagate. We find that spatial correlations have a major effect in the
enhancement of the amplitude and the coherence of the resonant stochastic
fluctuations, providing the ordered patterns of recurrent epidemics, whose
period may differ significantly from that of the small oscillations around the
deterministic equilibrium. We also show that the inclusion of a more realistic,
time correlated, recovery profile instead of exponentially distributed
infectious periods may, even in the random-mixing limit, contribute to the same
effect.


title:
Trapping radioactive ^{82}Rb in an optical dipole trap and evidence of
  spontaneous spin polarization

abstract:
  Optical trapping of selected species of radioactive atoms has great potential
in precision measurements for testing fundamental physics such as EDM, PNC and
parity violating beta-decay asymmetry correlation coefficients. We report
trapping of 10^4 radioactive ^{82}Rb atoms (t_{1/2}=75 s) with a trap lifetime
of ~55 seconds in an optical dipole trap. Transfer efficiency from the
magneto-optical trap was ~14%. We further report the evidence of spontaneous
spin polarization of the atoms in optical dipole trap loading. This advancement
is an important step towards a new generation of precision J-beta correlations
measurements with polarized ^{82}Rb atoms.


title: Linear frictional forces cause orbits to neither circularize nor precess

abstract:
  For the undamped Kepler potential the lack of precession has historically
been understood in terms of the Runge-Lenz symmetry. For the damped Kepler
problem this result may be understood in terms of the generalization of Poisson
structure to damped systems suggested recently by Tarasov[1]. In this
generalized algebraic structure the orbit-averaged Runge-Lenz vector remains a
constant in the linearly damped Kepler problem to leading order in the damping
coe


title: Leptogenesis from Pseudo-Scalar Driven Inflation

abstract:
  We examine recent claims for a considerable amount of leptogenesis, in some
inflationary scenarios, through the gravitational anomaly in the lepton number
current. We find that when the short distances contributions are properly
included the amount of lepton number generated is actually much smaller.


title: A Non Parametric Model for the Forecasting of the Venezuelan Oil Prices

abstract:
  A neural net model for forecasting the prices of Venezuelan crude oil is
proposed. The inputs of the neural net are selected by reference to a dynamic
system model of oil prices by Mashayekhi (1995, 2001) and its performance is
evaluated using two criteria: the Excess Profitability test by Anatoliev and
Gerko (2005) and the characteristics of the equity curve generated by a trading
strategy based on the neural net predictions.
  -----
  Se introduce aqui un modelo no parametrico para pronosticar los precios del
petroleo Venezolano cuyos insumos son seleccionados en base a un sistema
dinamico que explica los precios en terminos de dichos insumos. Se describe el
proceso de recoleccion y pre-procesamiento de datos y la corrida de la red y se
evaluan sus pronosticos a traves de un test estadistico de predictibilidad y de
las caracteristicas del Equity Curve inducido por la estrategia de compraventa
bursatil generada por dichos pronosticos.


title:
Entanglement and the nonlinear elastic behavior of forests of coiled
  carbon nanotubes

abstract:
  Helical or coiled nanostructures have been object of intense experimental and
theoretical studies due to their special electronic and mechanical properties.
Recently, it was experimentally reported that the dynamical response of
foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a
nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The
physical origin of this unusual behavior is not yet fully understood. In this
work, based on analytical models, we show that the entanglement among
neighboring coils in the superior part of the forest surface must be taken into
account for a full description of the strongly nonlinear behavior of the impact
response of a drop-ball onto a forest of coiled carbon nanotubes.


title: Twisted Alexander Polynomials and Representation Shifts

abstract:
  For any knot, the following are equivalent. (1) The infinite cyclic cover has
uncountably many finite covers; (2) there exists a finite-image representation
of the knot group for which the twisted Alexander polynomial vanishes; (3) the
knot group admits a finite-image representation such that the image of the
fundamental group of an incompressible Seifert surface is a proper subgroup of
the image of the commutator subgroup of the knot group.


title:
An H2CO 6cm Maser Pinpointing a Possible Circumstellar Torus in
  IRAS18566+0408

abstract:
  We report observations of 6cm, 3.6cm, 1.3cm, and 7mm radio continuum,
conducted with the Very Large Array towards IRAS18566+0408, one of the few
sources known to harbor H2CO 6cm maser emission. Our observations reveal that
the emission is dominated by an ionized jet at cm wavelengths. Spitzer/IRAC
images from GLIMPSE support this interpretation, given the presence of 4.5um
excess emission at approximately the same orientation as the cm continuum. The
7mm emission is dominated by thermal dust from a flattened structure almost
perpendicular to the ionized jet, thus, the 7mm emission appears to trace a
torus associated with a young massive stellar object. The H2CO 6cm maser is
coincident with the center of the torus-like structure. Our observations rule
out radiative pumping via radio continuum as the excitation mechanism for the
H2CO 6cm maser in IRAS18566+0408.


title: The Symbiotic System SS73 17 Seen with Suzaku

abstract:
  We observed with Suzaku the symbiotic star SS73 17, motivated by the
discovery by the INTEGRAL satellite and the Swift BAT survey that it emits hard
X-rays. Our observations showed a highly-absorbed X-ray spectrum with NH >
10^23 cm-2, equivalent to A_V > 26, although the source has B magnitude 11.3
and is also bright in UV. The source also shows strong, narrow iron lines
including fluorescent Fe K as well as Fe xxv and Fe xxvi. The X-ray spectrum
can be fit with a thermal model including an absorption component that
partially covers the source. Most of the equivalent width of the iron
fluorescent line in this model can be explained as a combination of
reprocessing in a dense absorber plus reflection off a white dwarf surface, but
it is likely that the continuum is partially seen in reflection as well. Unlike
other symbiotic systems that show hard X-ray emission (CH Cyg, RT Cru, T CrB,
GX1+4), SS73 17 is not known to have shown nova-like optical variability, X-ray
flashes, or pulsations, and has always shown faint soft X-ray emission. As a
result, although it is likely a white dwarf, the nature of the compact object
in SS73 17 is still uncertain. SS73 17 is probably an extreme example of the
recently discovered and relatively small class of hard X-ray emitting symbiotic
systems.


title: A simple evolutionary game with feedback between perception and reality

abstract:
  We study an evolutionary game of chance in which the probabilities for
different outcomes (e.g., heads or tails) depend on the amount wagered on those
outcomes. The game is perhaps the simplest possible probabilistic game in which
perception affects reality. By varying the `reality map', which relates the
amount wagered to the probability of the outcome, it is possible to move
continuously from a purely objective game in which probabilities have no
dependence on wagers, to a purely subjective game in which probabilities equal
the amount wagered. The reality map can reflect self-reinforcing strategies or
self-defeating strategies. In self-reinforcing games, rational players can
achieve increasing returns and manipulate the outcome probabilities to their
advantage; consequently, an early lead in the game, whether acquired by chance
or by strategy, typically gives a persistent advantage. We investigate the game
both in and out of equilibrium and with and without rational players. We
introduce a method of measuring the inefficiency of the game and show that in
the large time limit the inefficiency decreases slowly in its approach to
equilibrium as a power law with an exponent between zero and one, depending on
the subjectivity of the game.


title: A 5D non compact and non Ricci flat Kaluza-Klein Cosmology

abstract:
  A model universe is proposed in the framework of 5-dimensional noncompact
Kaluza-Klein cosmology which is not Ricci flat. The 4D part as the
Robertson-Walker metric is coupled to conventional perfect fluid, and its
extra-dimensional part is coupled to a dark pressure through a scalar field. It
is shown that neither early inflation nor current acceleration of the 4D
universe would happen if the non-vacuum states of the scalar field would
contribute to 4D cosmology.


title: Inelastic scattering rates in d-wave superconductors

abstract:
  The inelastic scattering rates of quasiparticles in a two-dimensional d-wave
superconductor, which arise from interactions with either acoustic phonons or
other quasiparticles, are calculated within second order perturbation theory.
We discover a strong enhancement of scattering with collinear momenta, brouth
about by the special kinematics of the two-dimensional fermions with Dirac-like
spectrum near the nodes of the d-wave order parameter. In the case of a local
instantaneous interparticle potential we find that either an RPA-type
resummation of the perturbation series or an inclusion of non-linear
corrections to the Dirac spectrum is called for in order to obtain a finite
scattering rate in the limit $\omega/T\to 0$. In either way, we find drastic
changes in the scattering rate, as compared to the naively expected cubic
temperature dependence.


title: Possible Magnetic Activity in the Low Mass X-ray Binary EXO 0748-676

abstract:
  We report evidence of magnetic activity associated with the secondary star in
the EXO 0748-676 low mass X-ray binary system. An analysis of a sequence of
five consecutive X-ray eclipses observed during December 2003 with the RXTE
satellite brings out a feature occurring during ingress we interpret as the
X-ray photoelectric absorption shadow, as seen by an observer at Earth, of a
plasma structure suspended above the surface of the secondary star. The light
curve feature consists of an initial drop in count rate to near zero (the
absorption shadow) with a very short rebound to a significant fraction of the
pre-ingress count rate and then a final plunge to totality over a total time
scale of ~25 s. The ingress feature persists for at least 5 consecutive orbital
periods (a total of ~19 hr), and possibly up to 5 days in our data. Our data
also show significant post-egress dipping during this eclipse sequence, unusual
for this source, indicating possible secondary star mass ejection during this
episode.


title: Spectroscopic follow-up of a cluster candidate at z = 1.45

abstract:
  We have obtained deep optical spectroscopic data of the highest-redshift
cluster candidate (z ~ 1.4, CVB13) selected by Van Breukelen et al. (2006) in a
photometric optical/infrared catalogue of the Subaru XMM-Newton Deep Field. The
data, which comprise 104 targeted galaxies, were taken with the DEep Imaging
Multi-Object Spectrograph (DEIMOS) on the Keck 2 telescope and yielded 31
secure redshifts in the range 1.25 < z < 1.54 within a 7' x 4' field centred on
CVB13. Instead of one massive cluster at z = 1.4, we find evidence for three
projected structures at z = 1.40, z = 1.45, and z = 1.48. The most
statistically robust of these structures, at z = 1.454, has six
spectroscopically confirmed galaxies. Its total mass is estimated at > 10^14
M_sun and it may therefore be termed a cluster. There is an X-ray source at the
cluster position which is marginally spatially resolved but whose X-ray
spectrum is too hard to be thermal cluster emission. Its origin could be the
summed X-ray emission from active galaxies in, and projected onto, the cluster.
Serendipitously we have discovered a cluster at z = 1.28 with a mass of > 10^14
M_sun at the same position on the sky, comprising six spectroscopically
confirmed cluster galaxies and at least one additional radio source. The
selection of CVB13 for the cluster catalogue was evidently aided by the
superposition of other, presumably lower-mass, structures, whereas the single
cluster at z = 1.28 contained too few galaxies to be isolated by the same
algorithm. Given the complicated nature of such structures, caution must be
employed when measuring the mass function of putative high-redshift clusters
with photometric techniques alone.


title: Derived classification of gentle algebras with two cycles

abstract:
  We classify gentle algebras defined by quivers with two cycles under derived
equivalence in a non degenerate case, by using some combinatorial invariants
constructed from the quiver with relations defining these algebras. We also
present a list of normal forms; any such algebra is derived equivalent to one
of the algebras in the list.


title: Formal analytical solutions for the Gross-Pitaevskii equation

abstract:
  Considering the Gross-Pitaevskii integral equation we are able to formally
obtain an analytical solution for the order parameter $\Phi (x)$ and for the
chemical potential $\mu $ as a function of a unique dimensionless non-linear
parameter $\Lambda $. We report solutions for different range of values for the
repulsive and the attractive non-linear interactions in the condensate. Also,
we study a bright soliton-like variational solution for the order parameter for
positive and negative values of $\Lambda $. Introducing an accumulated error
function we have performed a quantitative analysis with other well-established
methods as: the perturbation theory, the Thomas-Fermi approximation, and the
numerical solution. This study gives a very useful result establishing the
universal range of the $\Lambda $-values where each solution can be easily
implemented. In particular we showed that for $\Lambda <-9$, the bright soliton
function reproduces the exact solution of GPE wave function.


title: Mesoscopic gap fluctuations in an unconventional superconductor

abstract:
  We study mesoscopic disorder fluctuations in an anisotropic gap
superconductor, which lead to the spatial variations of the local pairing
temperature and formation of superconducting islands above the mean-field
transition. We derive the probability distribution function of the pairing
temperatures and superconducting gaps. It is shown that above the mean-field
transition, a disordered BCS superconductor with an unusual pairing symmetry is
described by a network of superconducting islands and metallic regions with a
strongly suppressed density of states due to superconducting fluctuations. We
argue that the phenomena associated with mesoscopic disorder fluctuations may
also be relevant to the high-temperature superconductors, in particular, to
recent STM experiments, where gap inhomogeneities have been explicitly
observed. It is suggested that the gap fluctuations in the pseudogap phase
should be directly related to the corresponding fluctuations of the pairing
temperature.


title: Triple charged-particle decays of resonances illustrated by 12C-states

abstract:
  The hyperspherical adiabatic expansion is combined with complex scaling and
used to calculate the energy distributions of the particles arising from
three-body decaying low-lying $^{12}$C resonances. The large distance continuum
properties of the wavefunctions are crucial and must be accurately calculated.
The substantial changes from small to large distances determine the decay
mechanisms. We illustrate by computing the energy distributions from decays of
the $1^{-}$, $2^-$ and $4^{-}$-resonances in $^{12}$C. These states are
dominated by sequential ($1^-$), through the $^{8}$Be ground state, and direct
($2^-$, $4^-$) decays.


title:
Real-time electron dynamics with exact-exchange time-dependent
  density-functional theory

abstract:
  The exact exchange potential in time-dependent density-functional theory is
defined as an orbital functional through the time-dependent optimized effective
potential (TDOEP) method. We numerically solve the TDOEP integral equation for
the real-time nonlinear intersubband electron dynamics in a semiconductor
quantum well with two occupied subbands. By comparison with adiabatic
approximations, it is found that memory effects in the exact exchange potential
become significant when the electron dynamics takes place in the vicinity of
intersubband resonances.


title: Bubbling the False Vacuum Away

abstract:
  We investigate the role of nonperturbative, bubble-like inhomogeneities on
the decay rate of false-vacuum states in two and three-dimensional scalar field
theories. The inhomogeneities are induced by setting up large-amplitude
oscillations of the field about the false vacuum as, for example, after a rapid
quench or in certain models of cosmological inflation. We show that, for a wide
range of parameters, the presence of large-amplitude bubble-like
inhomogeneities greatly accelerates the decay rate, changing it from the
well-known exponential suppression of homogeneous nucleation to a power-law
suppression. It is argued that this fast, power-law vacuum decay -- known as
resonant nucleation -- is promoted by the presence of long-lived oscillons
among the nonperturbative fluctuations about the false vacuum. A phase diagram
is obtained distinguishing three possible mechanisms for vacuum decay:
homogeneous nucleation, resonant nucleation, and cross-over. Possible
applications are briefly discussed.

categories: hep-th cond-mat.stat-mech hep-lat nlin.PS


title: Non-supersymmetric microstates of the D1-D5-KK system

abstract:
  We construct a discrete family of smooth non-supersymmetric three charge
geometries carrying D1 brane, D5 brane and Kaluza-Klein monopole charges in
Type IIB supergravity compactified on a six-torus, which can be interpreted as
the geometric description of some special states of the brane system. These
solutions are asymptotically flat in four dimensions, and generalise previous
supersymmetric solutions. The solutions have a qualitatively similar structure
to previous non-supersymmetric smooth solutions carrying D1 and D5 brane
charges in five dimensions, and indeed can be viewed as the five-dimensional
system placed at the core of a Kaluza-Klein monopole. The geometries are
smooth, free of horizons and do not have closed timelike curves. One notable
difference from the five-dimensional case is that the four-dimensional geometry
has no ergoregion.


title: Simulating Reionization: Character and Observability

abstract:
  In recent years there has been considerable progress in our understanding of
the nature and properties of the reionization process. In particular, the
numerical simulations of this epoch have made a qualitative leap forward,
reaching sufficiently large scales to derive the characteristic scales of the
reionization process and thus allowing for realistic observational predictions.
Our group has recently performed the first such large-scale radiative transfer
simulations of reionization, run on top of state-of-the-art simulations of
early structure formation. This allowed us to make the first realistic
observational predictions about the Epoch of Reionization based on detailed
radiative transfer and structure formation simulations. We discuss the basic
features of reionization derived from our simulations and some recent results
on the observational implications for the high-redshift Ly-alpha sources.


title: Tropical Lines on Cubic Surfaces

abstract:
  Given a tropical line $L$ and a smooth tropical surface $X$, we look at the
position of $L$ on $X$. We introduce its primal and dual motif which are
respectively a decorated graph and a subcomplex of the dual triangulation of
$X$. They encode the combinatorial position of $L$ on $X$. We classify all
possible motifs of tropical lines on general smooth tropical surfaces. This
classification allows to give an upper bound for the number of tropical lines
on a general smooth tropical surface with a given subdivision. We focus in
particular on surfaces of degree three. As a concrete example, we look at
tropical cubic surfaces dual to a fixed honeycomb triangulation, showing that a
general surface contains exactly $27$ tropical lines.


title: The Second Stars

abstract:
  The ejecta of the first probably very massive stars polluted the Big Bang
primordial element mix with the first heavier elements. The resulting ultra
metal-poor abundance distribution provided the initial conditions for the
second stars of a wide range of initial masses reaching down to intermediate
and low masses. The importance of these second stars for understanding the
origin of the elements in the early universe are manifold. While the massive
first stars have long vanished the second stars are still around and currently
observed. They are the carriers of the information about the first stars, but
they are also capable of nuclear production themselves. For example, in order
to use ultra or extremely metal-poor stars as a probe for the r-process in the
early universe a reliable model of the s-process in the second stars is needed.
Eventually, the second stars may provide us with important clues on questions
ranging from structure formation to how the stars actually make the elements,
not only in the early but also in the present universe. In particular the
C-rich extremely metal-poor stars, most of which show the s-process signature,
are thought to be associated with chemical yields from the evolved giant phase
of intermediate mass stars. Models of such AGB stars at extremely low
metallicity now exist, and comparison with observation show important
discrepancies, for example with regard to the synthesis of nitrogen. This may
hint at burning and mixing aspects of extremely metal-poor evolved stars that
are not yet included in the standard picture of evolution, as for example the
hydrogen-ingestion flash. The second stars of intermediate mass may have also
played an important role in the formation of heavy elements that form through
slow neutron capture reaction chains (s-process). Comparison of models with
observations reveal which aspects of the physics input and assumptions need to
be improved. The s-process is a particularly useful diagnostic tool for probing
the physical processes that are responsible for the creation of elements in
stars, like for example rotation. As new observational techniques and
strategies continue to penetrate the field, for example the multi-object
spectroscopy, or the future spectroscopic surveys, the extremely metal-poor
stars will play an increasingly important role to address some of the most
fundamental and challenging, current questions of astronomy.


title: How much of the inflaton potential do we see?

abstract:
  We discuss the latest constraints on a Taylor-expanded scalar inflaton
potential, obtained focusing on its observable part only. This is in contrast
with other works in which an extrapolation of the potential is applied using
the slow-roll hierarchy. We find significant differences. The results discussed
here apply to a broader range of models, since no assumption about the
invisible e-folds of inflation has to be made, thereby remaining conservative.


title: The nature of GRB-selected submillimeter galaxies: hot and young

abstract:
  We present detailed fits of the spectral energy distributions (SEDs) of four
submillimeter (submm) galaxies selected by the presence of a gamma-ray burst
(GRB) event (GRBs 980703, 000210, 000418 and 010222). These faint ~3 mJy submm
emitters at redshift ~1 are characterized by an unusual combination of long-
and short-wavelength properties, namely enhanced submm and/or radio emission
combined with optical faintness and blue colors. We exclude an active galactic
nucleus as the source of long-wavelength emission. From the SED fits we
conclude that the four galaxies are young (ages <2 Gyr), highly starforming
(star formation rates ~150 MSun/yr), low-mass (stellar masses ~10^10 MSun) and
dusty (dust masses ~3x10^8 MSun). Their high dust temperatures (Td>45 K)
indicate that GRB host galaxies are hotter, younger, and less massive
counterparts to submm-selected galaxies detected so far. Future facilities like
Herschel, JCMT/SCUBA-2 and ALMA will test this hypothesis enabling measurement
of dust temperatures of fainter GRB-selected galaxies.


title: Multiplicity Among Young Brown Dwarfs and Very Low Mass Stars

abstract:
  Characterizing multiplicity in the very low mass (VLM) domain is a topic of
much current interest and fundamental importance. Here we report on a near-IR
AO imaging survey of 31 young brown dwarfs and VLM stars, 28 of which are in
Chamaeleon I, using the ESO VLT. Our survey is sensitive enough to detect equal
mass binaries down to separations of 0.04-0.07" (6-10 AU at 160 pc) and,
typically, companions with mass ratios as low as 0.2 outside of 0.2" (~30 AU).
We resolve the suspected 0.16" (~26 AU) binary Cha_Halpha 2 and present two new
binaries, Hn 13 and CHXR 15, with separations of 0.13" (~20 AU) and 0.30" (~50
AU); the latter is one of the widest VLM systems discovered to date. We do not
find companions around the majority of our targets, giving a binary frequency
of 11% [+9,-6], thus confirming the trend for a lower binary frequency with
decreasing mass. By combining our work with previous surveys, we arrive at the
largest sample of young VLMOs (72) with high angular resolution imaging to
date. Its multiplicity fraction is in statistical agreement with that for VLMOs
in the field. In addition we note that many field stellar binaries with lower
binding energies and/or wider cross sections have survived dynamical evolution
and that statistical models suggest tidal disruption by passing stars is
unlikely to affect the binary properties of our systems. Thus, we argue that
there is no significant evolution of multiplicity with age among brown dwarfs
and VLM stars in OB and T associations between a few Myr to several Gyr.
Instead, the observations to date suggest that VLM objects are either less
likely to be born in fragile multiple systems than solar mass stars or such
systems are disrupted very early.


title: Probing singularities in quantum cosmology with curvature scalars

abstract:
  We provide further evidence that the canonical quantization of cosmological
models eliminates the classical Big Bang singularity, using the {\it
DeBroglie-Bohm} interpretation of quantum mechanics. The usual criterion for
absence of the Big Bang singularity in Friedmann-Robertson-Walker quantum
cosmological models is the non-vanishing of the expectation value of the scale
factor. We compute the `local expectation value' of the Ricci and Kretschmann
scalars, for some quantum FRW models. We show that they are finite for all
time. Since these scalars are elements of general scalar polynomials in the
metric and the Riemann tensor, this result indicates that, for the quantum
models treated here, the `local expectation value' of these general scalar
polynomials should be finite everywhere. Therefore, we have further evidence
that the quantization of the models treated here eliminates the classical Big
Bang singularity. PACS: 04.40.Nr, 04.60.Ds, 98.80.Qc.


title:
WSRT Ultra-Deep Neutral Hydrogen Imaging of Galaxy Clusters at z=0.2, a
  Pilot Survey of Abell 963 and Abell 2192

abstract:
  A pilot study with the powerful new backend of the Westerbork Synthesis Radio
Telescope (WSRT) of two galaxy clusters at z=0.2 has revealed neutral hydrogen
emission from 42 galaxies. The WSRT probes a total combined volume of 3.4x10^4
Mpc^3 at resolutions of 54x86 kpc^2 and 19.7 km/s, surveying both clusters and
the large scale structure in which they are embedded. In Abell 963, a
dynamically relaxed, lensing Butcher-Oemler cluster with a high blue fraction,
most of the gas-rich galaxies are located between 1 and 3 Mpc in projection,
northeast from the cluster core. Their velocities are slightly redshifted with
respect to the cluster, and this is likely a background group. None of the blue
galaxies in the core of Abell 963 are detected in HI, although they have
similar colors and luminosities as the HI detected galaxies in the cluster
outskirts and field. Abell 2192 is less massive and more diffuse. Here, the
gas-rich galaxies are more uniformly distributed. The detected HI masses range
from 5x10^9 to 4x10^10 Msun. Some galaxies are spatially resolved, providing
rudimentary rotation curves useful for detailed kinematic studies of galaxies
in various environments. This is a pilot for ultra-deep integrations down to HI
masses of 8x10^8 Msun, providing a complete survey of the gas content of
galaxies at z=0.2, probing environments ranging from cluster cores to voids.


title: Conformal operators on forms and detour complexes on Einstein manifolds

abstract:
  For even dimensional conformal manifolds several new conformally invariant
objects were found recently: invariant differential complexes related to, but
distinct from, the de Rham complex (these are elliptic in the case of
Riemannian signature); the cohomology spaces of these; conformally stable form
spaces that we may view as spaces of conformal harmonics; operators that
generalise Branson's Q-curvature; global pairings between differential form
bundles that descend to cohomology pairings. Here we show that these operators,
spaces, and the theory underlying them, simplify significantly on conformally
Einstein manifolds. We give explicit formulae for all the operators concerned.
The null spaces for these, the conformal harmonics, and the cohomology spaces
are expressed explicitly in terms of direct sums of subspaces of eigenspaces of
the form Laplacian. For the case of non-Ricci flat spaces this applies in all
signatures and without topological restrictions. In the case of Riemannian
signature and compact manifolds, this leads to new results on the global
invariant pairings, including for the integral of Q-curvature against the null
space of the dimensional order conformal Laplacian of Graham et al..


title: Ising Dynamics with Damping

abstract:
  We show for the Ising model that is possible construct a discrete time
stochastic model analogous to the Langevin equation that incorporates an
arbitrary amount of damping. It is shown to give the correct equilibrium
statistics and is then used to investigate nonequilibrium phenomena, in
particular, magnetic avalanches. The value of damping can greatly alter the
shape of hysteresis loops, and for small damping and high disorder, the
morphology of large avalanches can be drastically effected. Small damping also
alters the size distribution of avalanches at criticality.


title: Young star clusters in M31

abstract:
  In our study of M31's globular cluster system with MMT/Hectospec, we have
obtained high-quality spectra of 85 clusters with ages less than 1 Gyr. With
the exception of Hubble V, the young cluster in NGC 205, we find that these
young clusters have kinematics and spatial distribution consistent with
membership in M31's young disk. Preliminary estimates of the cluster masses and
structural parameters, using spectroscopically derived ages and HST imaging,
confirms earlier suggestions that M31 has clusters similar to the LMC's young
populous clusters.


title: The TeV Energy Spectrum of Mrk 421 Measured in A High Flaring State

abstract:
  The BL Lac object (blazar) Mrk 421 was observed during its outburst in April
2004 with the Whipple 10 m telescope for a total of about 24.5 hours. The
measured gamma-ray rate varied substantially over the range from 4 to 10
gamma's/min and eventually exceeded the steady gamma-ray rate of the Crab
Nebula (standard candle) by a factor of 3. The overall significance of the
gamma-ray signal exceeded 70 sigma and the total number of excess events was
more than 10,000. The signal light curve does not show any particular
variability pattern. This unique Mrk 421 outburst enabled the measurement of a
high quality spectrum of very high-energy gamma rays in a high state of
emission. This spectrum is a power-law and it extends beyond 10 TeV.


title:
A Deep Chandra Observation of Kepler's Supernova Remnant: A Type Ia
  Event with Circumstellar Interaction

abstract:
  We present initial results of a 750 ks Chandra observation of the remnant of
Kepler's supernova of AD 1604. The strength and prominence of iron emission,
together with the absence of O-rich ejecta, demonstrate that Kepler resulted
from a thermonuclear supernova, even though evidence for circumstellar
interaction is also strong. We have analyzed spectra of over 100 small regions,
and find that they fall into three classes. (1) The vast majority show Fe L
emission between 0.7 and 1 keV and Si and S K alpha emission; we associate
these with shocked ejecta. A few of these are found at or beyond the mean blast
wave radius. (2) A very few regions show solar O/Fe abundance rations; these we
associate with shocked circumstellar medium (CSM). Otherwise O is scarce. (3) A
few regions are dominated by continuum, probably synchrotron radiation.
Finally, we find no central point source, with a limit about 100 times fainter
than the central object in Cas A. The evidence that the blast wave is
interacting with CSM may indicate a Ia explosion in a more massive progenitor.


title: Limits of zeros of polynomial sequences

abstract:
  In the present paper we consider $F_k(x)=x^{k}-\sum_{t=0}^{k-1}x^t,$ the
characteristic polynomial of the $k$-th order Fibonacci sequence, the latter
denoted $G(k,l).$ We determine the limits of the real roots of certain odd and
even degree polynomials related to the derivatives and integrals of $F_k(x),$
that form infinite sequences of polynomials, of increasing degree. In
particular, as $k \to \infty,$ the limiting values of the zeros are determined,
for both odd and even cases. It is also shown, in both cases, that the
convergence is monotone for sufficiently large degree. We give an upper bound
for the modulus of the complex zeros of the polynomials for each sequence. This
gives a general solution related to problems considered by Dubeau 1989, 1993,
Miles 1960, Flores 1967, Miller 1971 and later by the second author in the
present paper, and Narayan 1997.


title:
Fragile three-dimensionality in the quasi-one-dimensional cuprate
  PrBa_2Cu_4O_8

abstract:
  In this article we report on the experimental realization of dimensional
crossover phenomena in the chain compound PrBa$_2$Cu$_4$O$_8$ using
temperature, high magnetic fields and disorder as independent tuning
parameters. In purer crystals of PrBa$_2$Cu$_4$O$_8$, a highly anisotropic
three-dimensional Fermi-liquid state develops at low temperatures. This
metallic state is extremely susceptible to disorder however and localization
rapidly sets in. We show, through quantitative comparison of the relevant
energy scales, that this metal/insulator crossover occurs precisely when the
scattering rate within the chain exceeds the interchain hopping rate(s), i.e.
once carriers become confined to a single conducting element.


title: Calculating the image of the second Johnson-Morita representation

abstract:
  Johnson has defined a surjective homomorphism from the Torelli subgroup of
the mapping class group of the surface of genus $g$ with one boundary component
to $\wedge^3 H$, the third exterior product of the homology of the surface.
Morita then extended Johnson's homomorphism to a homomorphism from the entire
mapping class group to ${1/2} \wedge^3 H \semi \sp(H)$. This Johnson-Morita
homomorphism is not surjective, but its image is finite index in ${1/2}
\wedge^3 H \semi \sp(H)$. Here we give a description of the exact image of
Morita's homomorphism. Further, we compute the image of the handlebody subgroup
of the mapping class group under the same map.


title:
Scattering of spin 1/2 particles by the 2+1 dimensional noncommutative
  Aharonov-Bohm potential

abstract:
  In this work we study modifications in the Aharonov-Bohm effect for
relativistic spin 1/2 particles due to the noncommutativity of spacetime in $2
+ 1$ dimensions. The noncommutativity gives rise to a correction to the
Aharonov-Bohm potential which is highly singular at the origin, producing
divergences in a perturbative expansion around the usual solution of the free
Dirac equation. This problem is surmounted by using a perturbative expansion
around the exact solution of the \textit{commutative} Aharonov-Bohm problem. We
calculate, in this setting, the scattering amplitude and the corrections to the
differential and total cross sections for a spin 1/2 particle, in the
small-flux limit.


title:
Condensed Surfaces of Magnetic Neutron Stars, Thermal Surface Emission,
  and Particle Acceleration Above Pulsar Polar Caps

abstract:
  For sufficiently strong magnetic fields and/or low temperatures, the neutron
star surface may be in a condensed state with little gas or plasma above it.
Such surface condensation can significantly affect the thermal emission from
isolated neutron stars, and may lead to the formation of a charge-depleted
acceleration zone ("vacuum gap") in the magnetosphere above the stellar polar
cap. Using the latest results on the cohesive property of magnetic condensed
matter, we quantitatively determine the conditions for surface condensation and
vacuum gap formation in magnetic neutron stars. We find that condensation can
occur if the thermal energy kT of the neutron star surface is less than about
8% of its cohesive energy Q_s, and that a vacuum gap can form if the neutron
star's rotation axis and magnetic moment point in opposite directions and kT is
less than about 4% of Q_s. Thus, vacuum gap accelerators may exist for some
neutron stars. Motivated by this result, we also study the physics of pair
cascades in the vacuum gap model for photon emission by accelerating electrons
and positrons due to both curvature radiation and resonant/nonresonant inverse
Compton scattering. Our calculations of the condition of cascade-induced vacuum
breakdown and the related pulsar death line/boundary generalize previous works
to the superstrong field regime. We find that inverse Compton scatterings do
not produce a sufficient number of high energy photons in the gap and thus do
not lead to pair cascades for most neutron star parameters. We discuss the
implications of our results for the recent observations of neutron star thermal
radiation as well as for the detection/non-detection of radio emission from
high-B pulsars and magnetars.


title:
3He-Driven Mixing in Low-Mass Red Giants: Convective Instability in
  Radiative and Adiabatic Limits

abstract:
  We examine the stability and observational consequences of mixing induced by
3He burning in the envelopes of first ascent red giants. We demonstrate that
there are two unstable modes: a rapid, nearly adiabatic mode that we cannot
identify with an underlying physical mechanism, and a slow, nearly radiative
mode that can be identified with thermohaline convection. We present
observational constraints that make the operation of the rapid mode unlikely to
occur in real stars. Thermohaline convection turns out to be fast enough only
if fluid elements have finger-like structures with a length to diameter ratio
l/d > 10. We identify some potentially serious obstacles for thermohaline
convection as the predominant mixing mechanism for giants. We show that
rotation-induced horizontal turbulent diffusion may suppress the 3He-driven
thermohaline convection. Another potentially serious problem for it is to
explain observational evidence of enhanced extra mixing. The 3He exhaustion in
stars approaching the red giant branch (RGB) tip should make the 3He mixing
inefficient on the asymptotic giant branch (AGB). In spite of this, there are
observational data indicating the presence of extra mixing in low-mass AGB
stars similar to that operating on the RGB. Overmixing may also occur in
carbon-enhanced metal-poor stars.


title:
Design Study of a Low Energy IACT Array for Ground-Based Gamma-Ray
  Astronomy

abstract:
  Recently, ground-based very high-energy (VHE) gamma-ray astronomy achieved a
remarkable advancement in the development of the observational technique for
the registration and study of gamma-ray emission above 100 GeV. Construction of
telescopes of substantially larger sizes than the currently used 12 m class
telescopes can drastically improve the sensitivity of ground-based detectors to
gamma rays of energy from 10 GeV to 100 GeV. Based on Monte Carlo simulations
we have studied the response of an array of three large area imaging
atmospheric Cherenkov telescopes (IACT) as a prototype for a future large-scale
low energy ground-based experiment. The sensitivity of a three-telescope array
as a function of optical reflector size was investigated here in detail.


title:
Carrier multiplication yields in CdSe and CdTe nanocrystals by transient
  photoluminescence

abstract:
  Engineering semiconductors to enhance carrier multiplication (CM) could lead
to increased photovoltaic cell performance and a significant widening of the
materials range suitable for future solar technologies. Semiconductor
nanocrystals (NCs) have been proposed as a favourable structure for CM
enhancement, and recent measurements by transient absorption have shown
evidence for highly efficient CM in lead chalcogenide and CdSe NCs. We report
here an assessment of CM yields in CdSe and CdTe NCs by a quantitative analysis
of biexciton and exciton signatures in transient photoluminescence decays.
Although the technique is particularly sensitive due to enhanced biexciton
radiative rates relative to the exciton, kradBX > 2 kradX, we find no evidence
for CM in CdSe and CdTe NCs up to photon energies E > 3 Eg, well above
previously reported relative energy thresholds.


title:
Normal matrix models, dbar-problem, and orthogonal polynomials on the
  complex plane

abstract:
  We introduce a dbar-formulation of the orthogonal polynomials on the complex
plane, and hence of the related normal matrix model, which is expected to play
the same role as the Riemann-Hilbert formalism in the theory of orthogonal
polynomials on the line and for the related Hermitian model. We propose an
analog of Deift-Kriecherbauer-McLaughlin-Venakides-Zhou asymptotic method for
the analysis of the relevant dbar-problem, and indicate how familiar steps for
the Hermitian model, e.g. the g-function ``undressing'', might look like in the
case of the normal model. We use the particular model considered recently by P.
Elbau and G. Felder as a case study.