Remarks on the scalar graviton decoupling and consistency of Horava gravity

Recently Horava proposed a renormalizable gravity theory with higher derivatives by abandoning the Lorenz invariance in UV. But there have been confusions regarding an 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 the consistency decoupled from the usual tensor graviton modes, by imposing the (local) Hamiltonian as well as the momentum constraints.