2011/03/31 by E. I. Guendelman, E. I. GUENDELMAN
Engineering · Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmological constant #Cosmology and Gravitation Theories #Dark energy #De Sitter universe #Dilaton #False vacuum #Material Science and Thermodynamics #Metric expansion of space #Particle horizon #Scalar field #Universe #Vacuum energy #gr-qc #hep-th
paper · pdf · doi:10.1142/s0217751x11053614
published as Int.J.Mod.Phys.A26:2951-2972,2011 · 28 pages, short version of this paper awarded an honorable mention by the Gravity Research Foundation, 2011, accepted for publication in International Journal of Modern Physics A
arxiv created 2011/05/15 · openalex publication_date 2011/05/31 · arxiv updated 2015/05/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We consider a nonsingular origin for the universe starting from an Einstein static universe, the so-called "emergent universe" scenario, in the framework of a theory which uses two volume elements [Formula: see text] and Φd 4 x, where Φ is a metric independent density, used as an additional measure of integration. Also curvature, curvature square terms and for scale invariance a dilaton field ϕ are considered in the action. The first-order formalism is applied. The integration of the equations of motion associated with the new measure gives rise to the spontaneous symmetry breaking of scale invariance. After spontaneous symmetry breaking of scale invariance it is found that a nontrivial potential for the dilaton is generated. In the Einstein frame we also add a cosmological term that parametrizes the zero point fluctuations. The resulting effective potential for the dilaton contains two flat regions, for ϕ → ∞ relevant for the nonsingular origin of the universe, followed by an inflationary phase and ϕ → - ∞, describing our present universe. The dynamics of the scalar field becomes nonlinear and these nonlinearities are instrumental in the stability of some of the emergent universe solutions, which exists for a parameter range of values of the vacuum energy in ϕ → - ∞, which must be positive but not very big, avoiding the extreme fine tuning required to keep the vacuum energy density of the present universe small. Zero vacuum energy density for the present universe defines the threshold for the creation of the universe.