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 . 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 part of the physical conserved stress–energy.