Quantization of Robertson-Walker geometry coupled to a spin-3/2 field

A Robertson-Walker geometry coupled to a spin-(3/2 field is quantized applying Dirac's theory for constrained Hamiltonian systems. An ansatz for the matter field is made, dictated both by the iso- tropy and homogeneity of the geometry and the need to have no negative-norm states at the quantum level. This ansatz also avoids the difficulties of the derivative coupling naturally brought by the spin-(3/2 field. After the factor-ordering problem has been resolved the resulting Wheeler-DeWitt equation is solved. It is thus found that the probability density of finding the system with a scale factor R vanishes, as R approaches the classically singular value R = 0