Quintessence with two energy scales - art. no. 083505

We study quintessence models using low energy supergravity inspired from st ring theory. We consider effective supergravity with two scales m(S), the s tring scale, and m(Pl), the Planck scale, and show that quintessence natura lly arises from a supersymmetry breaking hidden sector. As long as supersym metry is broken by the F-term of a Polonyi-like field coupled to the quinte ssence field in the Kahler potential we find that the Ratra-Peebles potenti al and its supergravity version are generic predictions. This requires that the string scale decouples from the Planck scale, m(s)<<m(Pl). In the cont ext of supergravity, the potential possesses a minimum induced by the super gravity corrections to the Ratra-Peebles potential at low redshifts. We stu dy the physical consequences of the presence of this minimum.