Gauss-Bonnet cosmologies: Crossing the phantom divide and the transition from matter dominance to dark energy
Feb, 200741 pages
Published in:
- JCAP 05 (2007) 019
e-Print:
- hep-th/0702002 [hep-th]
Report number:
- CERN-PH-TH-2006-273
Citations per year
Abstract:
Dark energy cosmologies with an equation of state parameter 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 nonsingular 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.- cosmological model
- Gauss-Bonnet term
- dark energy
- inflation
- field theory: scalar
- field equations: solution
- phantom
- null-energy condition: violation
- potential
- ghost
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