The Non-Classical Boltzmann Equation, and Diffusion-Based Approximations   to the Boltzmann Equation
  We show that several diffusion-based approximations (classical diffusion or SP1, SP2, SP3) to the linear Boltzmann equation can (for an infinite, homogeneous medium) be represented exactly by a non-classical transport equation. As a consequence, we indicate a method to solve diffusion-based approximations to the Boltzmann equation via Monte Carlo, with only statistical errors - no truncation errors. 
Martin Frank, Kai Krycki, Edward W. Larsen, Richard Vasques
math-ph math.MP nucl-th