Normal Distribution, Maxwell Boltzmann, Brownian Motion, Diffusion Equation, Entropy.
introduced the number density ρ(x, t + τ) , i.e. the number of particles per unit volume around x at time (t + τ), to describe its temporal evolution. Expanding ρ(x, t + τ) in Taylor series gives Because of the conservation of the number of particles, the number of particles per unit volume around