A coherent approach to Spacetime Foam

A coherent superposition of N Schwarzschild wormholes is proposed as a model for spacetime foam. Following the subtraction procedure for manifolds with boundaries, we calculate by variational methods the Casimir energy. A proposal for an alternative foamy model formed by N Schwarzschild-Anti-de Sitter wormholes is here considered. Finally, a conjecture about the foam evolution is proposed.Comment: 3 pages. To be submitted to the proceedings of the 3rd Workshop of `Mysteries, Puzzles And Paradoxes In Quantum Mechanics' Gargnano (Italy), 17-23 September 200

Black Hole Formation and Gamma Ray Bursts

Recent work on the dyadosphere of a black hole is reviewed with special emphasis on the explanation of gamma ray bursts. A change of paradigm in the observations of black holes is presented.Comment: 10 pages, 4 figures, to appear in the proceedings of the ESO workshop on "Black Holes in Binaries and Galactic Nuclei", in honour of Prof. R. Giacconi, edited by L. Kaper, E.P.J. van den Heuvel, and P.A. Woudt, and printed in the series ESO Astrophysics Symposia by Springer (2000