Green's functions and Hadamard parametrices for vector and tensor fields in general linear covariant gauges

Markus B. Fröb, Mojtaba Taslimi Tehrani
August 01, 2017
We determine the Green's functions and Hadamard parametrices in curved spacetimes for linearized massive and massless gauge bosons and linearized Einstein gravity with a cosmological constant in general linear covariant gauges. These vector and tensor parametrices are more singular than their Feynman/de Donder-gauge counterpart, with the most singular part proportional to $\sigma^{-2}$ and $\sigma^{-3}$, respectively. We also give explicit recursion relations for the Hadamard coefficients, and indicate their generalization to $n$ dimensions. Furthermore, we express the divergence and trace of the vector and tensor Green's functions in terms of derivatives of scalar and vector Green's functions, and show how these relations appear as Ward identities in the free quantum theory.