Healthy theories beyond Horndeski
Wed, Jul. 02nd 2014, 14:15
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
In search for a candidate that could explain the current acceleration of the Universe, a lot of attention has been given recently to Galileon theories, or in their generalized form, Horndeski theories. They are interesting as they represent the most general scalar tensor theories that do not lead to equations of motion containing more than two derivatives. This restriction is generally thought to be of great importance, as generically, higher order derivatives lead to ghost instabilities. I will present a new class of scalar tensor theories that are broader than Horndeski and, as such, do bring higher order derivatives. However, when studying carefully the theories, it was shown that they do not propagate any additional ghostly degree of freedom. I will give details on how and why this is possible, and I'll further talk about the uncommon phenomenology associated. Indeed, these theories exhibit a new type of coupling to matter, even when the latter is minimally coupled.
Contact : ccaprini