Bounce Cosmology in a Locally Scale Invariant Physics with a U(1) Symmetry

Abstract

An asymmetric non-singular bouncing cosmological model is proposed in the framework of a locally scale-invariant scalar-tensor version of the standard model of particle physics and gravitation. The scalar field ϕ is complex. In addition to local scale invariance, the theory is U(1)-symmetric and has a conserved global charge associated with time variations of the phase of ϕ. An interplay between the positive energy density contributions of relativistic and non-relativistic matter and that of the negative kinetic energy associated with the phase of ϕ results in a classical non-singular stable bouncing dynamics deep in the radiation-dominated era. This encompasses the observed redshifting era, which is preceded by a blueshifting era. The proposed model potentially avoids the flatness and horizon problems, as well as allowing for the generation of a scale-invariant spectrum of metric perturbations of the scalar type during a matter-dominated-like pre-bounce phase, with no recourse to an inflationary era.

Keywords

• cosmology
• nonsingular bounce
• scalar-tensor gravity