I'm not sure why you have a problem with their work. All they are saying is that the energy-momentum tensor need not be divergence free and they explore the consequences of that possibility. It gives rise to slightly different field equations and thus to different solutions, and these solutions...
Did anybody else hear the news?
A recent paper examines the derivation of Einstein's field equations and proposes that the original assumption of a divergence-free energy-momentum tensor may not be valid anymore due to the discovery of dark matter and dark energy. The authors derive new field...