Ultrahigh energy particle collisions in curved spacetimes

Terrestrial particle accelerators can collide particles at center of mass energies 10TeV. Physics beyond this scale upto Planck scale remains unexplored. Therefore it is worth exploring whether strong gravity regions around compact astrophysical objects could be exploited for this purpose. Since General relativity describes the gravitational field around the compact objects, as a first step towards this goal, I will try to explore various spacetime geometries from the perspective of ultrahigh energy collisions. I will talk about spacetimes containing blackholes, naked singularities as well as perfectly regular geometries without horizons and singularities. I will describe the ultrahigh energy particle collision process in the background of Reissner-Nordstrom blackhole and naked singularity and point out the subtle differences in two cases. I will then check the validity of the test particle approximation of the particles by investigating  the effect of self-gravity of the particles on the center of mass energy collision. The motion and collision of the thin shells of the particles will be studied for this purpose in an exact calculation taking into account the self-gravity. It will be shown that, in the blackhole case, the the upper bound on the center of mass energy is less than the Planck scale. It can exceed Planck scale in naked singularity case, thereby proving an extremely simple and elegant situation which can be exploited as a theoretical laboratory for quantum gravity gedanken experiments.
I will describe the process of high energy collisions  in a general spherically symmetric static spacetime and as an example I will discuss Bardeen metric. I will end my talk with possible astrophysical implications of the process of high energy collisions.