diagonality laplacian Maruyama multiscale SPDE advective interfacial inkjet microfluidic spinodal orthonormality solvability Wasserstein Galerkin Ornstein Uhlenbeck Desai Zwanzig McKean Vlasov Kolmogorov NumPy discretizing Kutta SciPy arclength stochastic tensorization Markovianity SDE SDEs coercivity invertibility hypocoercive underdamped Langevin overdamped