Emergent cosmology, inflation and dark energy

• Published in: General relativity and gravitation 2015-02, Vol.47 (2), Article 10
• Main Authors: Guendelman, Eduardo, Herrera, Ramón, Labrana, Pedro, Nissimov, Emil, Pacheva, Svetlana
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics and Cosmology; Classical and Quantum Gravitation; Differential Geometry; Mathematical and Computational Physics; Physics; Physics and Astronomy; Quantum Physics; Relativity Theory; Research Article; Theoretical
• ISSN: 0001-7701; 1572-9532
• DOI: 10.1007/s10714-015-1852-1

A new class of gravity–matter models defined in terms of two independent non-Riemannian volume forms (alternative generally covariant integration measure densities) on the space–time manifold are studied in some detail. These models involve an additional R 2 (square of the scalar curvature) term as well as scalar matter field potentials of appropriate form so that the pertinent action is invariant under global Weyl-scale symmetry. Scale invariance is spontaneously broken upon integration of the equations of motion for the auxiliary volume-form degrees of freedom. After performing transition to the physical Einstein frame we obtain: (1) an effective potential for the scalar field with two flat regions which allows for a unified description of both early universe inflation as well as of present dark energy epoch; (2) for a definite parameter range the model possesses a non-singular “emergent universe” solution which describes an initial phase of evolution that precedes the inflationary phase; (3) for a reasonable choice of the parameters the present model conforms to the Planck Collaboration data.