History of cosmic evolution with modified Gauss–Bonnet-dilatonic coupled term

• Main Authors: Subhra Debnath, Soumendra Nath Ruz, Ranajit Mandal, Abhik Kumar Sanyal
• Format: Article
• Language: English
• Published: SpringerOpen 2017-05-01
• Series: European Physical Journal C: Particles and Fields
• Online Access: http://link.springer.com/article/10.1140/epjc/s10052-017-4877-7

Abstract Gauss–Bonnet-dilatonic coupling in four dimensions plays an important role to explain late-time cosmic evolution. However, this term is an outcome of the low energy string effective action and thus ought to be important in the early universe too. Unfortunately, a phase-space formulation of such a theory does not exist in the literature due to branching. We therefore consider a modified theory of gravity, which contains a nonminimally coupled scalar–tensor sector in addition to a higher-order scalar curvature invariant term with Gauss–Bonnet-dilatonic coupling. Such an action unifies early inflation with late-time cosmic acceleration. The quantum version of the theory is also well behaved.