Theory HEP Seminar

ew nonlinear massive gravity and its cosmological application

Emmanuel Saridakis

National Technical University of Athens

The idea of adding mass to the graviton is quite old, but the straightforward linear approach leads to the vDVZ discontinuity, that is the zero-mass limit of the obtained results does not provide the General Relativity results. This discontinuity can be removed if one incorporates nonlinear terms, however it was soon realized that these necessary nonlinear terms introduce the Boulware-Deser (BD) ghost degree-of-freedom making the theory unstable. However, very recently, a specific nonlinear extension of massive gravity was formulated, requiring the BD ghost to be systematically removed. Unfortunately, although consistent and promising, this new theory does not exhibit cosmological behavior in agreement with observations. Thus, suitably extensions are necessary, such as varying mass massive gravity, f(R) massive gravity, partially massive gravity, or bi-gravity theories.