On IR solutions in Horava gravity theories

TL;DR

This paper investigates large-distance solutions in Horava gravity, showing how adding IR terms can recover general relativity solutions but reintroduces the cosmological constant problem, with insights from pp wave solutions.

Contribution

It demonstrates that IR dominant terms in Horava gravity can produce GR-like solutions at observable scales, highlighting the need for fine-tuning and analyzing wave solutions.

Findings

IR solutions asymptote to IR only above horizon scale

Adding IR terms recovers GR solutions with fine-tuning

PP wave solutions provide insights into relativistic properties

Abstract

In this note we search for large distance solutions of Horava gravity. In the case of the "detailed balance" action, gravity solutions asymptote to IR only above the cosmological constant ($\sim$horizon) scale. However, if one adds IR dominant terms $\alpha R^{(3)}+\beta \Lambda_W$, one can recover general relativity solutions on usual scales in the real Universe, provided one fine-tunes the cosmological constant, reobtaining the usual cosmological constant problem. We comment on pp wave solutions, in order to gain insight into the relativistic properties of the theory.