Plane Waves: To infinity and beyond!

TL;DR

This paper investigates the asymptotic boundary structure of homogeneous plane wave spacetimes, comparing causal and conformal boundaries, and explores extensions to time-dependent solutions derived from Dp-branes.

Contribution

It provides a detailed analysis of the boundary at infinity for plane wave spacetimes using causal structure, and extends the construction to time-dependent solutions from Penrose limits.

Findings

Causal and conformal boundaries agree for maximally supersymmetric plane waves.

The structure of light cones allows for going beyond or around infinity.

Extension of boundary construction to time-dependent plane waves from Dp-branes.

Abstract

We describe the asymptotic boundary of the general homogeneous plane wave spacetime, using a construction of the `points at infinity' from the causal structure of the spacetime as introduced by Geroch, Kronheimer and Penrose. We show that this construction agrees with the conformal boundary obtained by Berenstein and Nastase for the maximally supersymmetric ten-dimensional plane wave. We see in detail how the possibility to go beyond (or around) infinity arises from the structure of light cones. We also discuss the extension of the construction to time-dependent plane wave solutions, focusing on the examples obtained from the Penrose limit of Dp-branes.