4,696 research outputs found
The meteorology of Mars and Venus Final report
Meteorology of Mars and Venu
Exact solutions with AdS asymptotics of Einstein and Einstein-Maxwell gravity minimally coupled to a scalar field
We propose a general method for solving exactly the static field equations of
Einstein and Einstein-Maxwell gravity minimally coupled to a scalar field. Our
method starts from an ansatz for the scalar field profile, and determines,
together with the metric functions, the corresponding form of the scalar
self-interaction potential. Using this method we prove a new no-hair theorem
about the existence of hairy black-hole and black-brane solutions and derive
broad classes of static solutions with radial symmetry of the theory, which may
play an important role in applications of the AdS/CFT correspondence to
condensed matter and strongly coupled QFTs. These solutions include: 1) four-
or generic -dimensional solutions with planar, spherical or hyperbolic
horizon topology; 2) solutions with AdS, domain wall and Lifshitz asymptotics;
3) solutions interpolating between an AdS spacetime in the asymptotic region
and a domain wall or conformal Lifshitz spacetime in the near-horizon region.Comment: Some references adde
Displacement Data Assimilation
We show that modifying a Bayesian data assimilation scheme by incorporating
kinematically-consistent displacement corrections produces a scheme that is
demonstrably better at estimating partially observed state vectors in a setting
where feature information important. While the displacement transformation is
not tied to any particular assimilation scheme, here we implement it within an
ensemble Kalman Filter and demonstrate its effectiveness in tracking
stochastically perturbed vortices.Comment: 26 Pages, 9 figures, 5 table
Effect of nonadiabatic switching of dynamic perturbations in 1d Fermi systems
We study a two-dimensional fermionic QFT used to model 1D strongly correlated
electrons in the presence of a time-dependent impurity that drives the system
out of equilibrium. In contrast to previous investigations, we consider a
dynamic barrier switched on at a finite time. We compute the total energy
density (TED) of the system and establish two well defined regimes in terms of
the relationship between the frequency of the time-dependent perturbation
and the electron energy . Finally, we derive a relaxation time
such that for times shorter than the finite-time switching
process is relevant.Comment: 9 pages, 4 figures. Changed title. Added comments on backscattering.
Added result for electrical current. Version accepted in PR
Evolution of Galaxy morphologies in Clusters
We have studied the evolution of galaxian morphologies from ground-based,
good-seeing images of 9 clusters at z=0.09-0.25. The comparison of our data
with those relative to higher redshift clusters (Dressler et al. 1997) allowed
us to trace for the first time the evolution of the morphological mix at a
look-back time of 2-4 Gyr, finding a dependence of the observed evolutionary
trends on the cluster properties.Comment: 4 pages with 2 figures in Latex-Kluwer style. To be published in the
proceedings of the Granada Euroconference "The Evolution of
Galaxies.I-Observational Clues
Galaxy Morphological Segregation in Clusters: Local vs. Global Conditions
We study the relative fraction of galaxy morphological types in clusters, as
a function of the projected local galaxy density and different global
parameters: cluster projected gas density, cluster projected total mass density
, and reduced clustercentric distance. Since local and global densities are
correlated, we have considered different tests to search for the parameters to
which segregation show the strongest dependence. Also, we have explored the
results of our analysis applied to the central regions of the clusters and
their outskirts. We consider a sample of clusters of galaxies with temperature
estimates to derive the projected mass density profile and the 500 density
contrast radius () using the NFW model and the scaling relation
respectively. The X-ray surface brightness profiles are used to obtain the
projected gas density assuming the hydrostatic equilibrium model. Our results
suggest that the morphological segregation in clusters is controlled by the
local galaxy density in the outskirts. On the other hand, the global projected
mass density, shows the strongest correlation with the fraction of
morphological types in the central high density region, with a marginal
dependence on the local galaxy density.Comment: 10 pages, 8 figures, Accepted AJ (February 2001 issue
Reply Comment on "Entropy of 2D black holes from counting microstates"
We show that the arguments proposed by Park and Yee against our recent
derivation of the statistical entropy of 2D black holes do not apply to the
case under considerationComment: 3 pages, LaTex file, reply to comment hep-th/991021
Berry phase in homogeneous K\"ahler manifolds with linear Hamiltonians
We study the total (dynamical plus geometrical (Berry)) phase of cyclic
quantum motion for coherent states over homogeneous K\"ahler manifolds X=G/H,
which can be considered as the phase spaces of classical systems and which are,
in particular cases, coadjoint orbits of some Lie groups G. When the
Hamiltonian is linear in the generators of a Lie group, both phases can be
calculated exactly in terms of {\em classical} objects. In particular, the
geometric phase is given by the symplectic area enclosed by the (purely
classical) motion in the space of coherent states.Comment: LaTeX fil
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