Creation of particles by shell-focusing singularities

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Abstract
The creation of massless scalar particles in asymptotically flat spacetimes containing shell-focusing naked singularities which evolve from nonsingular initial data is studied. In the case where the singularity is marginally naked, i.e., its Cauchy horizon coincides with the event horizon, we are able to compute the spectrum of created particles by Hawking's method. The spectrum of particles is no longer thermal, but can be expressed as a quasithermal spectrum with a frequency-dependent temperature. In the high-frequency limit the effective temperature approaches a constant value greater than the Hawking temperature. In the more general case where the Cauchy horizon and event horizon do not coincide, we calculate the expectation value of the stress-energy tensor of the scalar field in the two-dimensional spacetimes obtained by suppressing the spherical coordinates. In all cases the energy flux along the Cauchy horizon diverges in a positive sense. This strongly suggests that the metric's back-reaction to the flux of created particles will prevent the formation of naked shell-focusing singularities.