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Title

Gauss-Bonnet cosmologies: crossing the phantom divide and the transition from matter dominance to dark energy
Authors

Ben M. Leith
Organization: University of Canterbury
Department: Department of Physics and Astronomy
Ishwaree P. Neupane
Organization: CERN
Department: Theory Division
Journal / Anthology

Journal of Cosmology and Astroparticle Physics
Year: 2007
Description

Dark energy cosmologies with an equation of state parameter w less than -1 are often found to violate the null energy condition and show unstable behaviour. A solution to this problem may require the existence of a consistent effective theory that violates the null energy condition only momentarily and does not develop any instabilities or other pathological features for a late time cosmology. A model which incorporates a dynamical scalar field coupled to the quadratic Riemann invariant of the Gauss-Bonnet form is a viable proposal. Such an effective theory is shown to admit non-singular cosmological evolutions for a wide range of scalar-Gauss-Bonnet coupling. We discuss the conditions for which our model yields observationally supported spectra of scalar and tensor fluctuations, under cosmological perturbations. The model can provide a reasonable explanation for the transition from matter dominance to dark energy regime and the late time cosmic acceleration, offering an interesting testing ground for investigations of the cosmological modified gravity.
Subject

*Science > Physics > Astrophysics
Keywords

dark energy theory, cosmological perturbation theory, string theory and cosmology, inflation