MG11 
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Gravitational instanton, Inflation and Cosmological Constant

Quantum fluctuation about gravitational instantons causes the instability of flat space at finite temperature, leading to the spontaneous process of nucleating quantum black holes. The energy-density of quantum black holes gives the cosmological term in the Einstein equation. This naturally results in the inflationary phase of Early Universe. The reheating phase is attributed to the radiation of these quantum black holes. In the Standard cosmology era, this cosmological term, depending on the reheating temperature, asymptotically approaches to the cosmological constant observed.

Adiabatic versus fully radiative regimes in gamma ray bursts

We examine the acceleration and deceleration stages of GRBs and the crucial role of adiabatic and fully-radiative regimes. The consequences of the approach followed by our group based on fully-radiative condition during entire afterglow phase [1] are compared and contrasted to the model of shocks, magnetic field and synchrotron radiation in the literature, assumed adiabatic condition [2]. References: 1. R. Ruffini, C.L. Bianco, P. Chardonnet, F. Fraschetti, L. Vitagliano, S.-S. Xue, AIP Conf.Proc. 668 (2003) 16 2. T. Piran, Phys. Rep. 314 (1999) 575