* Astronomy

Title: e^-e^+ pair creation by vacuum polarisation around electromagnetic black holes
Authors: C. Cherubini, A. Geralico, J. Rueda, R. Ruffini

The concept of "dyadotorus" was recently introduced to identify in the Kerr-Newman geometry the region where vacuum polarisation processes may occur, leading to the creation of e^--e^+ pairs. This concept generalises the original concept of "dyadosphere" initially introduced for Reissner-Nordstrom geometries. The topology of the axially symmetric dyadotorus is studied for selected values of the electric field and its electromagnetic energy is estimated by using three different methods all giving the same result. It is shown by a specific example the difference between a dyadotorus and a dyadosphere. The comparison is made for a Kerr-Newman black hole with the same total mass energy and the same charge to mass ratio of a Reissner-Nordstrom black hole. It turns out that the Kerr-Newman black hole leads to larger values of the electromagnetic field and energy when compared to the electric field and energy of the Reissner-Nordstrom one. The significance of these theoretical results for the realistic description of the process of gravitational collapse leading to black hole formation as well as the energy source of gamma ray bursts are also discussed.

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