Derivation of a Langevin equation in a system with multiple scales: The case of negative temperatures.We consider the problem of building a continuous stochastic model, i.e., a Langevin or Fokker-Planck equation, through a well-controlled coarse-graining procedure. 
Langevin
Derivation of a Langevin equation in a system with multiple scales: The case of negative temperatures.We consider the problem of building a continuous stochastic model, i.e., a Langevin or Fokker-Planck equation, through a well-controlled coarse-graining procedure.  A Chapman-Enskog-like expansion allows us to rigorously derive the Fokker-Planck equation from the microscopic dynamics. 
Fokker-Planck
A Chapman-Enskog-like expansion allows us to rigorously derive the Fokker-Planck equation from the microscopic dynamics. 
Chapman-Enskog