PHYSICAL REVIEW D
We explore the dependence of fermion propagators on the covariant gauge fixing parameter in quantum electrodynamics (QED) with the number of spacetime dimensions kept explicit. Gauge covariance is controlled by the Landau-Khalatnikov-Fradkin transformation (LKFT). Utilizing its group nature, the LKFT for a fermion propagator in Minkowski space is solved exactly. The special scenario of 3D is used to test claims made for general cases. When renormalized correctly, a simplification of the LKFT in 4D has been achieved with the help of fractional calculus.
Jia, Shaoyang and Pennington, M. R., Landau-Khalatnikov-Fradkin transformation for the fermion propagator in QED in arbitrary dimensions (2017). PHYSICAL REVIEW D, 95(7).