Non-Gaussianity excess problem in classical bouncing cosmologies

Xian Gao , Marc Lilley (1) , Patrick Peter (1)

1 IAP - Institut d'Astrophysique de Paris

The simplest possible classical model leading to a cosmological bounce is examined in the light of the non-Gaussianities it can generate. Concentrating solely on the transition between contraction and expansion, and assuming initially purely Gaussian perturbations at the end of the contracting phase, we find that the bounce acts as a source such that the resulting value for the post-bounce f_NL may largely exceed all current limits, to the point of potentially casting doubts on the validity of the perturbative expansion. We conjecture that if one can assume that the non-Gaussianity production depends only on the bouncing behavior of the scale factor and not on the specifics of the model examined, then many realistic models in which a nonsingular classical bounce takes place could exhibit a generic non-Gaussianity excess problem that would need to be addressed for each case.

Keywords: 98.70.Vc; 98.80.Cq; Background radiations; Particle-theory and field-theory models of the early Universe; General Relativity and Quantum Cosmology; Astrophysics - Cosmology and Nongalactic Astrophysics; High Energy Physics - Theory

Domains: Sciences of the Universe [physics]

Xian Gao, Marc Lilley, Patrick Peter. Non-Gaussianity excess problem in classical bouncing cosmologies. Physical Review D, 2015, 91, ⟨10.1103/PhysRevD.91.023516⟩. ⟨insu-03644777⟩