Infinite-dimensional symmetries in plane wave spacetimes

TL;DR

This paper investigates the asymptotic symmetries of a four-dimensional plane wave spacetime, revealing an infinite-dimensional algebra with potential implications for black hole physics.

Contribution

It uncovers a new infinite-dimensional symmetry algebra in Nappi-Witten spacetime with boundary conditions, extending to general four-dimensional pp-waves including Kerr limits.

Findings

Discovered a new infinite-dimensional symmetry algebra with central extensions.

The phase space includes the most general four-dimensional pp-wave metrics.

The analysis is based on boundary conditions at large transverse distances.

Abstract

We study the asymptotic symmetries of the Nappi-Witten spacetime in four dimensions, a plane wave arising as the Penrose limit of AdS$_2\times S^2$. Imposing suitable boundary conditions at large transverse distance, we uncover a new infinite-dimensional symmetry algebra allowing for non-trivial central extensions. The corresponding phase space encompasses the most general four-dimensional pp-wave metric, including in particular the Penrose limit of Kerr black holes.