Rastall gravity is equivalent to Einstein gravity

Rastall gravity, originally developed in 1972, is currently undergoing a significant surge in popularity. Rastall gravity purports to be a modified theory of gravity, with a non-conserved stress-energy tensor, and an unusual non-minimal coupling between matter and geometry, the Rastall stress-energy satisfying [T-R](;b)(ab) = lambda/4 g(ab)R(;b). Unfortunately, a deeper look shows that Rastall gravity is completely equivalent to Einstein gravity - usual general relativity. The gravity sector is completely standard, based as usual on the Einstein tensor, while in the matter sector Rastall's stress-energy tensor corresponds to an artificially isolated partof the physical conserved stress-energy. (C) 2018 The Author. Published by Elsevier B.V.