44,664 research outputs found
B\"acklund transformations in 2D dilaton gravity
We give a B\"acklund transformation connecting a generic 2D dilaton gravity
theory to a generally covariant free field theory. This transformation provides
an explicit canonical transformation relating both theories.Comment: LaTeX file, 7 page
Virasoro Orbits, AdS_3 Quantum Gravity and Entropy
We analyse the canonical structure of AdS_3 gravity in terms of the coadjoint
orbits of the Virasoro group. There is one subset of orbits, associated to BTZ
black hole solutions, that can be described by a pair of chiral free fields
with a background charge. There is also a second subset of orbits, associated
to point-particle solutions, that are described by two pairs of chiral free
fields obeying a constraint. All these orbits admit K\"ahler quantization and
generate a Hilbert space which, despite of having ,
does not provide the right degeneracy to account for the Bekenstein-Hawking
entropy due to the breakdown of modular invariance. Therefore, additional
degrees of freedom, reestablishing modular invariance, are necessarily required
to properly account for the black hole entropy.Comment: LaTex file, 12 pages. New references adde
Minimal mass-size of a stable 3He cluster
The minimal number of 3He atoms required to form a bound cluster has been
estimated by means of a Diffusion Monte Carlo procedure within the fixed-node
approximation. Several importance sampling wave functions have been employed in
order to consider different shell-model configurations. The resulting upper
bound for the minimal number is 32 atoms.Comment: 2 pages, no figure
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