A new look at the Ashtekar-Magnon energy condition

In 1975, Ashtekar and Magnon showed that an energy condition selects a uniq ue quantization procedure for hypersurface orthogonal observers in general, curved spacetimes. We generalize this result in two important ways, by eli minating the need to assume a particular form for the (quantum) Hamiltonian , and by considering the surprisingly nontrivial extension to non-minimal c oupling, for which the classical Hamiltonian differs from the classical ene rgy calculated from the stress-energy tensor.