Elastic critical behaviour in a 3d model for polymer gels

The elastic response in polymeric gels is studied by means of a percolation dynamic model. By numerical simulations the fluctuations in the gyration radius and in the center of mass motion of the percolating cluster are determined. Their scaling behaviour at the gelation threshold gives a critical exponent for the elastic modulus $f \sim 2.5 \pm 0.1$ in agreement with the prediction $f = d \nu$.