Exact Solutions and Stress Tensor of the Maxwell Field with Gauge Fixing Term in the Radiation-Dominant and Matter-Dominant Stages of the Expanding Universe
The Maxwell field with a general gauge fixing term is studied in the radiation-dominant and matter-dominant stages of the expanding universe. Exact solutions are derived, covariant canonical quantization is performed, and the stress tensor is obtained in the Gupta-Bleuler physical states. The regularized vacuum stress tensor is found to be zero, independent of the gauge fixing constant, and there is no trace anomaly.