Graviton Loop Corrections to Vacuum Polarization in de Sitter in a General Covariant Gauge

Understand

We evaluate the one-graviton loop contribution to the vacuum polarization on de Sitter background in a 1-parameter family of exact, de Sitter invariant gauges.

• Our result is computed using dimensional regularization and fully renormalized with BPHZ counterterms, which must include a noninvariant owing to the time-ordered interactions.
• Because the graviton propagator engenders a physical breaking of de Sitter invariance two structure functions are needed to express the result.
• In addition to its relevance for the gauge issue this is the first time a covariant gauge graviton propagator has been used to compute a noncoincident loop.