From pp-Waves to Galilean Spacetimes

TL;DR

This paper classifies all spatially isotropic homogeneous Galilean spacetimes of dimension at least four as null reductions of pp-wave spacetimes, including new torsional cases, and studies their properties and sources.

Contribution

It provides a complete classification of homogeneous Galilean spacetimes via null reductions of pp-waves, introducing novel torsional examples and analyzing their global features.

Findings

All such Galilean spacetimes are null reductions of homogeneous pp-waves.

The pp-waves are sourced by pure radiation fields.

The global properties of these spacetimes are characterized.

Abstract

We exhibit all spatially isotropic homogeneous Galilean spacetimes of dimension $(n+1) \geq 4$, including the novel torsional ones, as null reductions of homogeneous pp-wave spacetimes. We also show that the pp-waves are sourced by pure radiation fields and analyse their global properties.