The wavefunctions are functions not only of the bosonic variables, x ∈ ∈ X , but also of the Grassmann numbers or fermions, χ χ ∈ ∈ T X , from the tangent space of X . The wavefunctions can be viewed as differential forms on X with the fermions playing the role of the differentials χ χ ≡ ≡ d x ∧ ∧ . The concept of infinitesimal SEO generalizes the Fokker–Planck operator, which is essentially the SEO acting on top differential forms that have the meaning of the total probability distributions. Differential forms of lesser degree can be interpreted, at least locally on X , as conditional probability distributions. Viewing the spaces of differential forms of all degrees as wavefunctions of the model is a mathematical necessity. Without it, the Witten index representing the most fundamental object of the model—the partition function of the noise—would not exist and the dynamical partition function would not represent the number of fixed points of the SDE (see below). The most general understanding of the wavefunctions is the coordinate-free objects that contain information not only on trajectories but also on the evolution of the differentials and/or Lyapunov exponents.