Abstract:

The cosmological constant problem, dark matter, and the anomalous pioneer acceleration all suggest that gravity itself may be modified at cosmological distances. This talk will discuss theoretically consistent modifications of general relativity at long distances: massive gravity, and a model of "brane localized" gravity with extra dimensions. It has recently been shown that these models also require modification of gravity at much shorter distances, and are therefore ruled out experimentally. This subject is in its early stages, and this talk will give an introduction to this emerging subject.