The general scalar-tensor Hamiltonian with deformed covariance

Abstract

We derive the scalar-tensor Hamiltonian constraint to all orders of momenta when the canonical constraint algebra is deformed by a phase space function as predicted by some studies into loop quantum cosmology. We find that the momenta and spatial derivatives from gravity and matter fields must combine in a very specific form to maintain a deformed general covariance. This suggests that the deformation should be equally caused by matter field derivatives as it is by gravitational curvature. We demonstrate the cosmological consequences of a variety of deformation functions. Some cause a big bounce at high energy densities and others cause a sudden singularity.