arXiv subjects

J. Barbieri

Publications and source records attributed to J. Barbieri.

3 recordsLinked to original sources

arXiv2018

MACHO Messages from the Big Bang

The present day mass spectrum for dark matter compact objects is calculated based on the assumption that a uniform population of PBHs was created at a definite red-shift, and that the mass spectrum evolved as a result of gravitational radiation. The predicted present day spectrum extends over many decades of mass and allows one to connect the abundance of MACHOs in the halo of our galaxy with the abundance of galactic seeds. Present day astrophysical constraints on the abundance of dark matter PBHs appear to be consistent with our predicted mass spectrum if it is assumed that the seeds for the present day dark matter MACHOs were created at a time ~ 10-4 second after the big bang. Remarkably the total cosmological energy density at this time obtained by extrapolating the sum of the present day dark matter and CMB energies backward in time is very close to the mass-energy density of an Einstein-de Sitter universe at the same time. This suggests that the radiation precursor to the CMB was created at about the same time as the seeds for the present day dark matter.

gr-qc↗

arXiv2008

A signature for the absence of event horizons

A sharp dip in the spectrum of gamma rays coming from compact objects below 70 MeV would be an unambiguous signal that compact astrophysical objects have a physical surface, and there is no event horizon. Observation of this effect would open a window for the empirical study of Planck scale physics

astro-ph↗

arXiv2008

High Energy Gamma Rays from Protons Hitting Compact Objects

In a previous paper the spectrum of positrons produced by matter initially at rest falling onto a massive compact object was calculated. In this paper this calculation is generalized to obtain both the spectrum of in-flight positron annihilation and pi0 decay gamma rays produced when protons with a cosmic ray-like spectrum hit the surface. The resulting pi0 decay gamma ray spectrum reflects the high energy proton energy spectrum, and is largely independent of the mass of the compact object. One notable prediction for all compact objects is a dip in the spectrum below 70 MeV. As applied to the 10^6 solar mass massive compact object near to the center of our galaxy, our theory shows promise for explaining the gamma rays coming from the galactic center as observed by both the Compton satellite and HESS ground based array.

astro-ph↗