  A theoretical and numerically study of dynamical properties in the sol-gel
transition is presented. In particular, the complex phenomenology observed
experimentally and numerically in gelling systems is reproduced in the
framework of percolation theory, under simple assumptions on the relaxation of
single clusters. By neglecting the correlation between particles belonging to
different clusters, the quantities of interest (such as the self intermediate
scattering function, the dynamical susceptibility, the Van-Hove function, and
the non-Gaussian parameter) are written as superposition of those due to single
clusters. Connection between these behaviors and the critical exponents of
percolation are given. The theoretical predictions are checked in a model for
permanent gels, where bonds between monomers are described by a finitely
extendable nonlinear elastic potential. The data obtained in the numerical
simulations are in good agreement with the analytical predictions.
