Lorentz Gauge Quantization in a Cosmological Space-time

It has recently been shown that it is not possible to impose the Lorentz gauge condition in a cosmological space-time using the Gutpa-Bleuler method of quantization. It was also shown that it is possible to add $\nabla_{\mu}A^{\mu}$ as a new degree of freedom to the electromagnetic field and that this new degree of freedom might be the dark energy which is producing the accelerated expansion of the Universe. In this paper I show that the Lorentz gauge condition can be imposed using Dirac's method of quantizing constrained dynamical systems. I also compute the vacuum expectation value of the energy-momentum tensor and show that it vanishes. Thus, in Dirac's approach, the electromagnetic field does not make a contribution to the dark energy.