Einstein and Rastall Theories of Gravitation in Comparison

Abstract

We profit by a recent paper of Visser claiming that Rastall gravity is equivalent to Einstein gravity to compare the two gravitational theories in a general way. Our conclusions are different from Visser's ones. We indeed argue that these two theories are not equivalent. In fact, Rastall theory of gravity is an "open" theory when compared to Einstein general theory of relativity. Thus, it is ready to accept the challenges of observational cosmology and quantum gravity.

8 pages, comment on the paper arXiv:1711.11500, "Rastall gravity is equivalent to Einstein gravity", by Matt Visser. Final version matching the paper published in the European Physical Journal C