So. Alexeyev et al., Non-singular cosmological models in string gravity with constant dilaton and second-order curvature corrections, CLASS QUANT, 17(11), 2000, pp. 2243-2254
We investigate FRW cosmological solutions in the theory of a modulus field
coupled to gravity through a Gauss-Bonnet term. The explicit analytical for
ms of non-singular asymptotics are presented for power-law and exponentiall
y steep modulus coupling functions. We study the influence of a modulus fie
ld potential on these asymptotic regimes and find some forms of the potenti
al which do not destroy the non-singular behaviour. In particular, we obtai
n that exponentially steep coupling functions arising from the string theor
y do not allow non-singular past asymptotic unless the modulus field potent
ial tends to zero for a modulus field psi --> +/-infinity. Finally, the mod
ification of the chaotic dynamics in the closed FRW universe due to presenc
e of the Gauss-Bonnet term is discussed.