|Speaker:||Enrico Trincherini (SISSA, Trieste)|
|Date (JST):||Thu, Nov 18, 2010, 13:00 - 14:00|
|Place:||Seminar Room A|
I will first review the recently proposed theory of a scalar field invariant under an internal "galilean" symmetry, under which the field's gradient shifts by a constant.
Then I will show how this class of theories may be relevant to describe our Universe. It has "self-accelerating" de Sitter solutions with no ghost-like instabilities and a natural implementation of the Vainshtein screening mechanism at short scales. For these reasons it can be seen as a possible explanation of the present acceleration of the Universe. Alternatively, it can give rise to a novel cosmological scenario, the galilean genesis, in which standard inflation ---the primordial acceleration--- is replaced by an expanding phase with a drastic violation of the Null Energy Condition. This scenario describes a Universe that is asymptotically Minkowski in the past, expands with increasing energy density until it exits the regime of validity of the effective field theory and reheats, starting the standard radiation-dominated era.