Remarks on the Scalar Graviton Decoupling and Consistency of Horava Gravity

TL;DR

This paper analyzes the scalar graviton mode in Horava gravity, demonstrating that it can be consistently decoupled from tensor modes in Minkowski space by applying specific constraints, addressing previous concerns about the model's consistency.

Contribution

It clarifies the conditions under which the scalar graviton decouples in Horava gravity, enhancing understanding of its consistency in Minkowski backgrounds.

Findings

Scalar graviton can be decoupled with constraints

Decoupling occurs in Minkowski vacuum

Addresses previous confusion about model consistency

Abstract

Recently Horava proposed a renormalizable gravity theory with higher derivatives by abandoning the Lorenz invariance in UV. But there have been confusions regarding the extra scalar graviton mode and the consistency of the Horava model. I reconsider these problems and show that, in the Minkowski vacuum background, the scalar graviton mode can be consistency decoupled from the usual tensor graviton modes by imposing the (local) Hamiltonian as well as the momentum constraints.