Colliding Axion-Dilaton Plane Waves from Black Holes

TL;DR

This paper extends the Ferrari and Ibañez colliding plane wave metric to axion-dilaton black holes, revealing how black hole horizons relate to colliding wave focal planes and exploring the resulting spacetime singularities and wormhole structures.

Contribution

It introduces a generalization of colliding plane wave spacetimes to include axion-dilaton black holes, connecting black hole horizons with wave focal planes and analyzing their global structure.

Findings

Spacetime singularities occur where the inner horizon is singular.

The extremal limit yields the Bertotti-Robinson metric with constant axion and dilaton fields.

Colliding waves can produce a chain of Reissner-Nordstrom-like wormholes.

Abstract

The colliding plane wave metric discovered by Ferrari and Iba\~{n}ez to be locally isometric to the interior of a Schwarzschild black hole is extended to the case of general axion-dilaton black holes. Because the transformation maps either black hole horizon to the focal plane of the colliding waves, this entire class of colliding plane wave spacetimes only suffers from the formation of spacetime singularities in the limits where the inner horizon itself is singular, which occur in the Schwarzschild and dilaton black hole limits. The supersymmetric limit corresponding to the extreme axion-dilaton black hole yields the Bertotti-Robinson metric with the axion and dilaton fields flowing to fixed constant values. The maximal analytic extension of this metric across the Cauchy horizon yields a spacetime in which two sandwich waves in a cylindrical universe collide to produce a semi-infinite chain of Reissner-Nordstrom-like wormholes. The focussing of particle and string geodesics in this spacetime is explored.