Generalized LKF Transformations for $$\boldsymbol{N}$$ -Point Fermion Correlators in QED

Within the worldline approach to quantum electrodynamics (QED), a change of the photon’s covariant gauge parameter $$\xi$$ is investigated to analyse the non-perturbative gauge dependence of the configuration space fermion correlation functions, deriving a generalization of the Landau–Khatnikov–Fradkin transformations (LKFt). These transformations reveal how the non-perturbative gauge dependence of position space amplitudes can be extracted into a multiplicative exponential factor.