Carmen Nuñez, IAFE, Buenos Aires
The second edition of the Quantum Gravity in the Southern Cone workshop was held at the Centro Atómico Bariloche, Argentina on January 7-10, 1998. It brought together 50 researchers from South America as well as experts from the northern hemisphere, working on different aspects of quantum gravity and related topics. The plenary lectures enabled the participants to obtain a global picture of the status of the field in the various approaches. The meeting was further enriched by poster sessions. The following list summarizes the topics covered by the lecturers.
Canonical Quantum Gravity
J.Pullin overviewed of the attempts to apply the rules of canonical quantization to GR. He stressed the important role played by spin networks and by Thiemann's Hamiltonian. The problems presented by this Hamiltonian (it commutes on non diffeomorfism invariant states) were addressed by R. Gambini, who reported on progress made to solve them. Midi-superspace models of canonical quantum gravity were considered by C. Torre who indicated that one can satisfactorily quantize quantum parameterized field theories on a two-dimensional spacetime, but that the quantization of such theories in higher dimensions is still an open problem. A framework for modelling quantum gravitational collapse was discussed by K. Kuchar who considered the canonical dynamics of matter shells. Both the dynamics of the shell and of the surrounding spacetime were shown to follow from a single variational principle. By formulating GR as a theory of surfaces, C. Kozameh showed how to construct a quantum spacetime using only Scri equipped with free functions as the kinematical structure
String theory and higher dimensional objects
J. Maldacena discussed the large N limit of certain field theories and its relation to gravity. In a similar context, A. Schwimmer referred to N=1 (Seiberg) duality in field theory and its realization through branes. Phenomenological aspects of string theory were covered by G. Aldazabal who discussed non-perturbative orbifold vacua. Branes in supergravities, string theory and M theory were discussed by M. Cederwall. M. Henneaux referred to dyons, charge quantization and electric-magnetic duality for p-form theories in spacetime dimensions with arbitrary gauge invariant self-interactions. B. Carter discussed the geometry of non null p surfaces embedded in n dimensions. Electric 2 branes were presented by R. Aros. J. Zanelli reviewed Chern-Simons supergravity in dimensions, showing that they contain non trivial dynamics leading to interesting classical solutions such as black holes, solitons, membranes, etc.
Black hole physics, semiclassical theories and cosmology
In the context of a two dimensional exactly solvable model, J. Russo outlined the construction of an S-matrix and showed that black holes will radiate out an energy of Planck order, stabilizing after a transitory period. A similar picture appears in 3+1 Einstein gravity with spherical symmetry. R. Bousso discussed the evaporation of Schwarzschild-De Sitter black holes including the one-loop effective action. B.Hu addressed the problem of fluctuations and backreaction in semiclassical cosmology and black holes by presenting a complete history of the subject and conjectured that a stochastic description in terms of Einstein-Langevin equation becomes relevant at the Planck scale. Semiclassical theories were also considered by C. Molina-Paris and S. Ramsey. H. Rubinstein reviewed the status of the big bang standard model and the latest data available from observations.