Generalized Kerr-Schild gauge
arXiv:2512.17369
Abstract
The Kerr-Schild gauge is generalized to the case that the vector generating the deformation is not null. Contrary to naive expectations, this vector generates a finite expansion for the curvature tensor. We prove a theorem on the conditions for the deformed metric being Ricci flat, namely that the deformation vector must be irrotational (then geodesic) in the background spacetime.
10 pages, LaTeX, errata fixed and reference added, Extra paragraph added