Cosmological solutions to Hořava-Lifshitz gravity

Abstract

The well-documented inconsistency between general relativity and quantum mechanics has led to several alternative theories of gravity, including Hořava-Lifshitz gravity. Analyzing the cosmological implications of these theories is one important way to test their viability. We study Friedmann-Lemaître-Robertson-Walker (FLRW) cosmological solutions in (3+1)-dimensional Hořava-Lifshitz gravity truncated to the two Lagrangian terms that are most relevant at low energies. We obtain several analytic and numerical cosmological solution classes: an eternally expanding, expanding and then collapsing, purely collapsing, bouncing, linear, constant flat, and an oscillatory solution. The eternally expanding solutions are reminiscent of cosmic inflation, but do not require an inflaton field, the expanding and collapsing solutions are reminiscent of a Big Bang and Big Crunch, and the bouncing solutions only allow for non-singular bounces.