632 research outputs found
Combinatorial and topological phase structure of non-perturbative n-dimensional quantum gravity
We provide a non-perturbative geometrical characterization of the partition
function of -dimensional quantum gravity based on a coarse classification of
riemannian geometries. We show that, under natural geometrical constraints, the
theory admits a continuum limit with a non-trivial phase structure parametrized
by the homotopy types of the class of manifolds considered. The results
obtained qualitatively coincide, when specialized to dimension two, with those
of two-dimensional quantum gravity models based on random triangulations of
surfaces.Comment: 13 page
On the Black-Hole Conformal Field Theory Coupled to the Polyakov's String Theory. A Non Perturbative Analysis
We couple the 2D black-hole conformal field theory discovered by Witten to a
dimensional Euclidean bosonic string. We demonstrate that the resulting
planar (=zero genus) string susceptibility is real for any .Comment: 5 page
On the Stability of a Stringy Black Hole
We study the stability under perturbations of a charged four dimensional
stringy black hole arising from gauging a previously studied WZW model. We find
that the black hole is stable only in the extremal case .Comment: 14 pages + 1 figure (not included but available on request
Insights and Puzzles from Branes: 4d SUSY Yang-Mills from 6d Models
5-branes of nontrivial topology are associated in the
Diaconescu-Hanany-Witten-Witten (DHWW) approach with the Seiberg-Witten (SW)
theory of low-energy effective actions. There are two different "pictures",
related to the IIA and IIB phases of M-theory. They differ by the choice of
theory on the 5-brane world volume. In the IIB picture it is just the 6d
SUSY Yang-Mills, while in the IIA picture it is a theory of SUSY self-dual
2-form. These two pictures appear capable to describe the (non-abelian) Lax
operator and (abelian) low-energy effective action respectively. Thus IIB-IIA
duality is related to the duality between Hitchin and Whitham integrable
structures.Comment: LaTeX, 12pp, 4 figs in ps-format requiring psfig.te
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