The Graviton Propagator in de Donder Gauge on de Sitter Background

Understand

We construct the graviton propagator on de Sitter background in exact de Donder gauge.

• We prove that it must break de Sitter invariance, just like the propagator of the massless, minimally coupled scalar.
• Our explicit solutions for its two scalar structure functions preserve spatial homogeneity and isotropy so that the propagator can be used within the larger context of inflationary cosmology, however, it is simple to alter the residual symmetry.
• Because our gauge condition is de Sitter invariant (although no solution for the propagator can be) renormalization should be simpler using this propagator than one based on a noncovariant gauge.