Mirror World, Supersymmetric Axion and Gamma Ray Bursts
  A modification of the relation between axion mass and the PQ constant permits a relaxation of the astrophysical constraints, considerably enlarging the allowed axion parameter space. We develop this idea in this paper, discussing a model for an {\it ultramassive} axion, which essentially represents a supersymmetric Weinberg-Wilczek axion of the mirror world. The experimental and astrophysical limits allow a PQ scale f_a ~ 10^4-10^6 GeV and a mass m_a ~ 1MeV, which can be accessible for future experiments.   On a phenomenological ground, such an {\it ultramassive} axion turns out to be quite interesting. It can be produced during the gravitational collapse or during the merging of two compact objects, and its subsequent decay into e+e- provides an efficient mechanism for the transfer of the gravitational energy of the collapsing system to the electron-positron plasma. This could resolve the energy budget problem in the Gamma Ray Bursts and also help in understanding the SN type II explosion phenomena. 
L. Gianfagna, M. Giannotti, F. Nesti