Cylindrical gravitational waves in expanding universes: Models for waves from compact sources

TL;DR

This paper introduces a new class of cylindrical gravitational wave solutions in expanding universes, providing models that exhibit more regular behavior at infinity and differ from classical Einstein-Rosen waves.

Contribution

It presents novel boundary conditions leading to a new family of solutions describing cylindrical waves in an expanding Kasner universe, improving regularity at null infinity.

Findings

Wave amplitudes decay faster than in Einstein-Rosen solutions

Space sections are flat and nonconical where waves haven't reached

Solutions allow more regular null infinity

Abstract

New boundary conditions are imposed on the familiar cylindrical gravitational wave vacuum spacetimes. The new spacetime family represents cylindrical waves in a flat expanding (Kasner) universe. Space sections are flat and nonconical where the waves have not reached and wave amplitudes fall off more rapidly than they do in Einstein-Rosen solutions, permitting a more regular null inifinity.