Critical slowing down of the kinetic Gaussian model on hierarchical lattices

The critical slowing down of the kinetic Gaussian model on hierarchical lattices is studied by means of a real-space time-dependent renormalization-group transformation. The dynamic critical exponent z and the exponent Delta are calculated. For hierarchical lattices with reducible generators, both the dynamic critical exponent z and the exponent Delta are independent of the fractal dimension Df of the lattice, the number of branches m, and the number of bonds per branch b of the generator--i.e., z = 2 and Delta = 1. For hierarchical lattices with irreducible generators, the exponent Delta is the same--i.e., Delta = 1; however, the dynamic critical exponent z is dependent on the concrete geometrical structure of these lattices. In addition, it was found that the lattice dependence of the correlation-length critical exponent nu is the same as that of the dynamic critical exponent z. Finally we give a brief discussion about universality for critical dynamics.