Key points are not available for this paper at this time.
We prove the equivalence, near the critical point, of a D-dimensional spin system in a random external magnetic field with a (D-2) -dimensional spin system in the absence of a magnetic field. This is due to the hidden supersymmetry of the associated stochastic differential equation. We identify a space with one anticommuting coordinate with a space having negative dimensions -2.
Parisi et al. (Mon,) studied this question.