We present the most general covariant ghost-free gravitational action in a Minkowski vacuum. Apart from the much studied f(R) models, this includes a large class of nonlocal actions with improved UV behavior, which nevertheless recover Einstein's general relativity in the IR.
No takes yet. Share an insight, caveat, or question.
Biswas et al. (2012) studied this question.
Synapse has enriched 2 closely related papers on similar clinical questions. Consider them for comparative context: