Quantum Stress Tensor Fluctuations of a Conformal Field and Inflationary Cosmology

Understand

We discuss the additional perturbation introduced during inflation by quantum stress tensor fluctuations of a conformally invariant field such as the photon.

• We consider both a kinematical model, which deals only with the expansion fluctuations of geodesics, and a dynamical model which treats the coupling of the stress tensor fluctuations to a scalar inflaton.
• In neither model do we find any growth at late times, in accordance with a theorem due to Weinberg.
• What we find instead is a correction which becomes larger the earlier one starts inflation.