Abstract
We study gravity, in which the curvature appearing in the gravitational Lagrangian is replaced by an arbitrary function of the curvature and the trace of the stress-energy tensor. We focus primarily on situations where is separable, so that . We argue that the term should be included in the matter Lagrangian , and therefore has no physical significance. We demonstrate explicitly how this can be done for the cases of free fields and for perfect fluids. We argue that all uses of for cosmological modeling and all attempts to place limits on parameters describing are misguided.
- Received 19 August 2019
DOI:https://doi.org/10.1103/PhysRevD.100.064059
© 2019 American Physical Society
Physics Subject Headings (PhySH)
Gravitation, Cosmology & Astrophysics