Plane Gravitational Waves in String Theory

TL;DR

This paper constructs exact string theory backgrounds representing plane gravitational waves and their duals using coset models, revealing new dualities and families of singular geometries with varying symmetries.

Contribution

It introduces a new class of exact string vacua based on coset models that generalize known plane wave backgrounds and explores their duality relations.

Findings

Constructed a class of exact string vacua describing plane gravitational waves.

Identified duality relations between different wave backgrounds.

Discovered families of singular geometries with specific isometries.

Abstract

We analyze the coset model $(E_2^c \ti E_2^c)/E_2^c$ and construct a class of exact string vacua which describe plane gravitational waves and their duals, generalizing the plane wave background found by Nappi and Witten. In particular, the vector gauging describes a two-parameter family of singular geometries with two isometries, which is dual to plane gravitational waves. In addition, there is a mixed vector-axial gauging which describes a one-parameter family of plane waves with five isometries. These two backgrounds are related by a duality transformation which generalizes the known axial-vector duality for abelian subgroups.