Born-Infeld gravity with a Brans-Dicke scalar

Soumya Jana; Sayan Kar

doi:10.1103/PhysRevD.96.024050

paper

Born-Infeld gravity with a Brans-Dicke scalar

arXiv:1706.03209 · doi:10.1103/PhysRevD.96.024050

Abstract

Recently proposed Born-Infeld (BI) theories of gravity assume a constant BI parameter ( $κ$ ). However, no clear consensus exists on the sign and value of $κ$ . Recalling the Brans-Dicke (BD) approach, where a scalar field was used to generate the gravitational constant $G$ , we suggest an extension of Born-Infeld gravity with a similar Brans-Dicke flavor. Thus, a new action, with $κ$ elevated to a spacetime dependent real scalar field, is proposed. We illustrate this new theory in a cosmological setting with pressureless dust and radiation as matter. Assuming a functional form of $κ (t)$ , we numerically obtain the scale factor evolution and other details of the background cosmology. It is known that BI gravity differs from general relativity (GR) in the strong-field regime but reduces to GR for intermediate and weak fields. Our studies in cosmology demonstrate how, with this new, scalar-tensor BI gravity, deviations from GR as well as usual BI gravity, may arise in the weak-field regime too. For example, we note a late-time acceleration without any dark energy contribution. Apart from such qualitative differences, we note that fixing the sign and value of $κ$ is no longer a necessity in this theory, though the origin of the BD scalar does remain an open question.

arXiv comment25 pages, 7 figures. Published version

Born-Infeld gravity with a Brans-Dicke scalar

Abstract

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