2-PARAMETER REGULARIZATION OF CROSSOVER FROM DIRECTED TO ISOTROPIC PERCOLATION

A continuous Hamiltonian describing, as special cases, ordinary and di rected percolations is investigated on the basis of a renormalization scheme with two small parameters (the deviation from the corresponding critical dimension and the crossover index). A new physical realizati on of such a model is proposed - percolation phase transitions in syst ems without an inversion center, for example, percolation-type transit ions into a ferroelectric phase in some disordered crystals and cerami cs. (C) 1995 American Institute of Physics.