Gradient flows and instantons at a Lifshitz point

Abstract

I provide a broad framework to embed gradient flow equations in non–relativistic field theory models that exhibit anisotropic scaling. The prime example is the heat equation arising from a Lifshitz scalar field theory; other examples include the Allen–Cahn equation that models the evolution of phase boundaries. Then, I review recent results reported in arXiv:1002.0062 describing instantons of Hořava-Lifshitz gravity as eternal solutions of certain geometric flow equations on 3–manifolds. These instanton solutions are in general chiral when the anisotropic scaling exponent is z = 3. Some general connections with the Onsager–Machlup theory of non-equilibrium processes are also briefly discussed in this context. Thus, theories of Lifshitz type in d + 1 dimensions can be used as off-shell toy models for dynamical vacuum selection of relativistic field theories in d dimensions.