Hall 123

Extendability of Spacetime and Causal Structure of Dynamical Charged Black Holes

Suman Ganguli

IMSc

It has long been speculated that gravitational collapse of charged dust into a Reissner-Nordstrom black hole leads to two different causal structure: either the singularity forms within the dust cloud or the dust cloud re-expands into another universe without singularity occurring inside the dust. However, the final state of the collapse is still an open issue. The shell crossing along with density singularity leads to breakdown of dust model for collapse of timelike particles. In this talk we will analyse the collapse of charged null particles, where shell crossing can be prevented. We will show that if the mass and charge functions of collapsing shell are of the form M ~ v^m and Q ~ v^n, where v is ingoing null coordinate, then if m > n the singularity forms within the dust. For m = n the shell bounces within (for not too big of a shell) the horizon. In this case we will show that the solution at least have a C^{1-} extension into flat spacetime deep inside the black hole. The case m < n is more subtle and will be discussed if time permits. We will discuss various implication of this result in the context of black hole information paradox and instability at Cauchy horizon.