Early-time cosmological solutions in Einstein-scalar-Gauss-Bonnet theory

Panagiota Kanti, Radouane Gannouji, Naresh Dadhich

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


In this work, we consider a generalized gravitational theory that contains the Einstein term, a scalar field, and the quadratic Gauss-Bonnet (GB) term. We focus on the early-universe dynamics, and demonstrate that a simple choice of the coupling function between the scalar field and the Gauss-Bonnet term and a simplifying assumption regarding the role of the Ricci scalar can lead to new, analytical, elegant solutions with interesting characteristics. We first argue, and demonstrate in the context of two different models, that the presence of the Ricci scalar in the theory at early times (when the curvature is strong) does not affect the actual cosmological solutions. By considering therefore a pure scalar-GB theory with a quadratic coupling function we derive a plethora of interesting, analytic solutions: for a negative coupling parameter, we obtain inflationary, de Sitter-type solutions or expanding solutions with a de Sitter phase in their past and a natural exit mechanism at later times; for a positive coupling function, we find instead singularity-free solutions with no big bang singularity. We show that the aforementioned solutions arise only for this particular choice of coupling function, a result that may hint at some fundamental role that this coupling function may hold in the context of an ultimate theory.

Original languageEnglish
Article number083524
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number8
StatePublished - 21 Oct 2015


Dive into the research topics of 'Early-time cosmological solutions in Einstein-scalar-Gauss-Bonnet theory'. Together they form a unique fingerprint.

Cite this