Alladi Ramakrishnan Hall

Collapse of Charged Null Fluid and Energy Conditions

Suman Ganguli

IMSc

In this talk a detailed study of gravitational collapse of
charged null fluid in asymptotically flat and AdS spacetimes of arbitrary
dimensions will be presented. The solutions, which are generalization of
Vaidya solution, always have critical hypersurfaces, "beyond" which the
energy momentum tensor of charged null fluid violates energy conditions.
Both the locations and causal properties of these hypersurfaces depend on
distribution profile of charge and energy in the collapsing shells. It was
shown by Ori* that, when the effects of repulsive Lorentz force are
considered, the four momenta of constituent particles vanish on these
critical hypersurfaces and the fluid "bounces off" it by reversing its
direction of momentum and therefore does not get into the region where
energy conditions are violated. In this talk it will be shown that if the
distribution profile of charge and energy in the collapsing shell obey
certain conditions, then the fluid indeed bounces back and the energy
conditions are satisfied in both asymptotically flat and AdS spacetime of
arbitrary dimensions. Further, it will be shown that for the simplest
distribution of charge and energy critical, the hypersurface is spacelike
and lies inside the trapped spacetime region. The apparent violation in
this type of configurations due to inevitability of collapse "beyond" the
critical hypersurface will be addressed. The causal structure of the spacetime
will be discussed.