Exact gyratons in higher and infinite derivative gravity

TL;DR

This paper derives exact solutions for spinning null sources, called gyratons, in higher and infinite derivative gravity theories, demonstrating their solvability and providing explicit solutions in specific models.

Contribution

It introduces a method to find exact gyraton solutions in complex gravity theories with higher derivatives, including non-local gravity, by exploiting simplifications from algebraic type III pp-waves.

Findings

Exact gyraton solutions are obtained in Stelle's fourth derivative gravity.

Explicit solutions are found in non-local gravity with infinite derivatives.

The field equations simplify to exactly solvable linear differential equations.

Abstract

We study solutions describing spinning null sources called gyratons in generic theories of gravity with terms that are quadratic in curvature and contain an arbitrary number of covariant derivatives. In particular, we show that the properties of pp-waves of the algebraic type III allow for extreme simplification of the field equations. It turns out that the resulting differential equations are exactly solvable due to partial decoupling and linearity of the equations. This is demonstrated explicitly by finding axially symmetric gyraton solutions in Stelle's fourth derivative gravity and the non-local gravity with an infinite number of derivatives.