The good, the bad and the ugly • of Hořava gravity

Abstract

I review the good, the bad and the ugly of the non-projectable versions of Hoava gravity. I explain how this non-relativistic theory was constructed and why it was touted with such excitement as a quantum theory of gravity. I then review some of the issues facing the theory, explaining how strong coupling occurs and why this is such a problem for both phenomenology and the question of renormalisability. Finally I comment on possible violations of Equivalence Principle, and explain why these could be an issue for Blas et al's "healthy extension". © 2010 IOP Publishing Ltd.