Classically and quantum stable emergent universe from conservation laws - Eduardo Guendelman

It has been recently pointed out by Mithani-Vilenkin that certain non singular models of the early universe belonging to the "emergent universe scenarios" which can be classically stable, are nevertheless unstable semiclassically to collapse. Here, we show that there is a class of emergent universes derived from scale invariant two measures theories with spontaneous symmetry breaking (s.s.b) of the scale invariance, which can have both classical stability and do not suffer the instability pointed out by Mithani-Vilenkin towards collapse. We find that this stability is due to the presence of a symmetry in the "emergent phase", which together with the non linearities of the theory, does not allow that the FLRW scale factor to be smaller that a certain minimum value in a certain protected region.