The issues of quintessence and cosmic acceleration can be discussed in the framework of higher order theories of gravity. We can define effective pressure and energy density directly connected to the Ricci scalar of curvature of a generic fourth order theory and then ask for the conditions to get an accelerated expansion. Exact accelerated expanding solutions can be achieved for several fourth order theories so that we get an alternative scheme to the standard quintessence scalar field, minimally coupled to gravity, usually adopted. We discuss also conformal transformations in order to see the links of quintessence between the Jordan and Einstein frames.
International Journal of Modern Physics D
- Pub Date:
- Particle-theory and field-theory models of the early Universe;
- Exact solutions;
- General Relativity and Quantum Cosmology
- 10 pages, LATEX files, to appear on IJMPD