  Classical statistical particle mechanics in the configuration space can be
represented by a nonlinear Schrodinger equation. Even without assuming the
existence of deterministic particle trajectories, the resulting quantum-like
statistical interpretation is sufficient to predict all measurable results of
classical mechanics. In the classical case, the wave function that satisfies a
linear equation is positive, which is the main source of the fundamental
difference between classical and quantum mechanics.

Quantum Physics;Classical Physics