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

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

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.

*Science > Physics > Astrophysics

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