Abstract
We point out a generic inconsistency of the coupling of ordinary gravity as described by general relativity with matter invariant only under unimodular diffeomorphisms, and some previously studied exceptions are pointed out. The most general Lagrangian invariant under unimodular diffeomorphism up to dimension-five operators is determined, and consistency with existing observations is studied in some cases.
- Received 15 August 2007
DOI:https://doi.org/10.1103/PhysRevD.76.124016
©2007 American Physical Society