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Modeling of the general circulation with the LMD-AOPP-IAA GCM: Update on model design and comparison with observations
The LMD-AOPP GCM is developed conjointly by LMD in Paris and AOPP in Oxford, with the collaboration of
IAA in Granada for the physical processes specific to the upper atmosphere. The collaboration between the
two teams is based on the use of two different dynamical core (gridpoint at LMD, spectral at AOPP), which
allow us to estimate the likely uncertainty arising from certain types of modeling errors. Similarly, we use
different schemes to compute tracer transport, etc. The work has benefited from support from ESA (since 1995)
and CNES (since 2000). Within that context, the GCMs are used to produce a Martian climate 'database' which
is used by more than 30 teams around the world for mission design and scientific studies (see Bingham et al.,
this issue and Lewis et al., 1999). The baseline version of the GCM is described in detail in Forget et al. (1999). Here we describe the recent improvement and design changes since this publication. Compared to this previous version, the new GCM covers a wider range of altitude, from 0 to 120km in the vertical, it uses improved topography and thermal inertia surface
maps from Mars Global Surveyor (MGS), and includes a new 'dust scenario' to describe the distribution of airborne dust in the atmosphere
Gravitational cooling of self-gravitating Bose-Condensates
Equilibrium configurations for a self-gravitating scalar field with
self-interaction are constructed. The corresponding Schr\"odinger-Poisson (SP)
system is solved using finite differences assuming spherical symmetry. It is
shown that equilibrium configurations of the SP system are late-time attractor
solutions for initially quite arbitrary density profiles, which relax and
virialize through the emission of scalar field bursts; a process dubbed
gravitational cooling. Among other potential applications, these results
indicate that scalar field dark matter models (in its different flavors)
tolerate the introduction of a self-interaction term in the SP equations. This
study can be useful in exploring models in which dark matter in galaxies is not
point-like.Comment: 10 aastex pages, 12 eps figures. Accepted for publication in Ap
Dynamics of Holes and Universality Class of the Antiferromagnetic Transition in the Two Dimensional Hubbard Model
The dynamics of a single hole (or electron) in the two dimensional Hubbard
model is investigated. The antiferromagnetic background is described by a
N\`eel state, and the hopping of the carrier is analyzed within a configuration
interaction approach. Results are in agreement with other methods and with
experimental data when available. All data are compatible with the opening of a
mean field gap in a Fermi liquid of spin polarons, the so called Slater type of
transition. In particular, this hypothesis explains the unusual dispersion
relation of the quasiparticle bands near the transition. Recent photoemission
data for CaCuOCl are analyzed within this context.Comment: New results and comparison with recent data adde
Transverse transport in graphite
Graphite is a layered material showing a strong anisotropy. Among the
unconventional properties reported by experiments, the electronic transport
along the c-axis, which has direct implications in order to build graphitic
devices, remains a controversial topic. We study the influence of inelastic
scattering on the electron tunnelling between layers. In the presence of
electron electron interactions, tunnelling processes are modified by inelastic
scattering events.Comment: 9 pages, no figures Proceedings of the Graphene Conference, MPI PKS
Dresden, September 200
Simulated evaluation of faceted browsing based on feature selection
In this paper we explore the limitations of facet based browsing which uses sub-needs of an information need for querying and organising the search process in video retrieval. The underlying assumption of this approach is that the search effectiveness will be enhanced if such an approach is employed for interactive video retrieval using textual and visual features. We explore the performance bounds of a faceted system by carrying out a simulated user evaluation on TRECVid data sets, and also on the logs of a prior user experiment with the system. We first present a methodology to reduce the dimensionality of features by selecting the most important ones. Then, we discuss the simulated evaluation strategies employed in our evaluation and the effect on the use of both textual and visual features. Facets created by users are simulated by clustering video shots using textual and visual features. The experimental results of our study demonstrate that the faceted browser can potentially improve the search effectiveness
Detection of the old stellar component of the major Galactic bar
We present near-IR colour--magnitude diagrams and star counts for a number of
regions along the Galactic plane. It is shown that along the l=27 b=0 line of
sight there is a feature at 5.7 +-0.7kpc with a density of stars at least a
factor two and probably more than a factor five times that of the disc at the
same position. This feature forms a distinct clump on an H vs. J-H diagram and
is seen at all longitudes from the bulge to about l=28, but at no longitude
greater than this. The distance to the feature at l=20 is about 0.5kpc further
than at l=27 and by l=10 it has merged with, or has become, the bulge. Given
that at l=27 and l=21 there is also a clustering of very young stars, the only
component that can reasonably explain what is seen is a bar with half length of
around 4kpc and a position angle of about 43+-7.Comment: 5 pages, 5 figures accepted as a letter in MNRA
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