Constraints on Gauss-Bonnet Gravity in Dark Energy Cosmologies
Abstract
Accelerating four dimensional cosmologies, whose dark energy component includes the general contribution from second order gravity terms, are investigated. In particular the Gauss-Bonnet invariant, which couples via the dark energy scalar field to the cosmological equations, is included. Such models are shown to appear naturally from Kaluza-Klein compactifications of pure, higher-dimensional gravity. Various limiting cases are considered in which the majority of the dark energy originates from a conventional quintessence scalar field. It is shown that such models, due to the change in geometry, have time-varying gravitational coupling constants, and so are subject to constraints from solar system gravity experiments. This is similar to scalar-matter coupling constraints in Brans-Dicke theory. The constraints obtained imply that the size of the present cosmic density fraction associated with the Gauss-Bonnet term must be at most of order 0.01. Such an effect could be detectable with cosmic microwave background observations.Keywords
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