Chaos in cosmological models [a.2,p.1,p.2]

We obtain the first evidence of chaotic behaviour in cosmology. The model under consideration corresponds to the spatially homogeneous Bianchi-type IX cosmological model within the Jordan-Brans-Dicke theory of gravitation. The model is cast by a large set of coupled stiff ordinary differential equations. For parameter values in agreement with current cosmological observations we obtain evidence that the considered model behaves in a chaotic manner. The evidence is given in terms of the existence of at least one positive Lyapunov exponent. When varying some of the model parameters we again obtain strong evidence of chaotic behaviour. This suggests that our findings may still be qualitatively valid even though the current observed parameters might not be completely accurate. This work was entitled with the award ``Premio a la investigación Cientiífica'' (scientific research award) given by Universidad Autónoma Metropolitana, November 1995. Award announcement (in Spanish): http://www.uam.mx/organo-uam/documentos/V-II/ii19-02.html.