denotes the microcanonical equilibrium distribution. "Fast" variables, by definition, are orthogonal to all functions G ( A ( Γ Γ ) ) of A ( Γ Γ ) under this scalar product. This definition states that fluctuations of fast and slow variables are uncorrelated, and according to the ergodic hypothesis this also is true for time averages. If a generic function f ( Γ Γ ) is correlated with some slow variables, then one may subtract functions of slow variables until there remains the uncorrelated fast part of f ( Γ Γ ) . The product of a slow and a fast variable is a fast variable.