Cp. Constantinidis et al., Regular bouncing cosmological solutions in effective actions in four dimensions - art. no. 043503, PHYS REV D, 6104(4), 2000, pp. 3503
We study cosmological scenarios resulting from effective actions in four di
mensions which are, under some assumptions, connected with multidimensional
, supergravity and string theories. These effective actions are labeled by
the parameters omega, the dilaton coupling constant, and n which establishe
s the coupling between the dilaton and a scalar field originating from the
gauge field existing in the original theories. There is a large class of bo
uncing as well as Friedmann-like solutions. We investigate under which cond
itions bouncing regular solutions can be obtained. In the case of the strin
g effective action, regularity is obtained through the inclusion of contrib
utions from the Ramond-Ramond sector of superstring.