LUMINOSITY VARIATIONS OF 3C 345 - IS THERE ANY EVIDENCE OF LOW-DIMENSIONAL CHAOS

We analyze the light curve of the optically violent variable quasar 3C 345, with the goal of determining the possible presence of low-dimens ional chaos in the system dynamics. The results of the phase-space rec onstruction and of the correlation integral analysis provide a converg ent, noninteger estimate of the correlation dimension, naively suggest ing the presence of deterministic chaos. However, we show that this re sult is generated by the long memory and by the power-law shape of the power spectrum of the signal, with no relationship to any underlying chaotic behavior. In fact, the light curve of 3C 345 is consistent wit h the output of a nonlinear stochastic process, and it is characterize d by a well-defined intermittent nature.