Extended Horava gravity and Einstein-aether theory

TL;DR

This paper explores the relationship between Einstein-aether theory and an extended version of Horava gravity, showing that hypersurface orthogonal solutions are shared, thus connecting results across these theories.

Contribution

It demonstrates the equivalence of hypersurface orthogonal solutions in Einstein-aether theory with the IR limit of an extended Horava gravity, linking their solution spaces.

Findings

Hypersurface orthogonal solutions are common to both theories.

Results from Einstein-aether theory apply to the IR limit of extended Horava gravity.

The connection simplifies analysis of solutions in these theories.

Abstract

Einstein-aether theory is general relativity coupled to a dynamical, unit timelike vector. If this vector is restricted in the action to be hypersurface orthogonal, the theory is identical to the IR limit of the extension of Horava gravity proposed by Blas, Pujol\`{a}s and Sibiryakov. Hypersurface orthogonal solutions of Einstein-aether theory are solutions to the IR limit of this theory, hence numerous results already obtained for Einstein-aether theory carry over.