centra

Abstract: I will speak about Horava-Lifshitz gravity, which has been proposed as an ultraviolet completion to general relativity. Adding to the gravitational action higher order spatial derivatives without adding higher-order time derivatives leads to a modification of the graviton propagator, which renders the theory power counting renormalizable at the expense of violating Lorentz symmetry. Perhaps surprisingly, the theory appears to be phenomenologically viable in its more general form. However, it has the unappealing feature of having a very large number of higher order terms in the action. I will consider the possibility of limiting the proliferation of independent couplings by imposing various restrictions to the theory and I will critically discuss the shortcomings of the various restrictions one can use.