From Langevin to Fokker-Planck

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SUMMARY

The discussion focuses on the equivalence between the classical Langevin equation and the Fokker-Planck equation in the context of quantum Brownian motion. The specific Langevin equation discussed is of the form m \ddot x(t) + \gamma \dot x(t) + V(x(t)) = F(t). The user seeks a derivation that includes potential energy, contrasting with typical derivations that omit this factor. The recommended resource for further understanding is "Handbook of Stochastic Methods" by C. Gardiner, which provides a clear and physical approach to stochastic processes.

PREREQUISITES
  • Understanding of classical mechanics, particularly the Langevin equation.
  • Familiarity with stochastic processes and their mathematical formulations.
  • Knowledge of quantum Brownian motion concepts.
  • Experience with LaTeX for mathematical expressions.
NEXT STEPS
  • Study the derivation of the Fokker-Planck equation from the Langevin equation, particularly including potential energy terms.
  • Read "Handbook of Stochastic Methods" by C. Gardiner for insights into stochastic processes.
  • Explore the relationship between classical and quantum stochastic processes.
  • Investigate advanced topics in quantum Brownian motion and its applications in statistical mechanics.
USEFUL FOR

Researchers and students in physics, particularly those focusing on quantum mechanics, stochastic processes, and classical mechanics. This discussion is beneficial for anyone looking to deepen their understanding of the Langevin and Fokker-Planck equations.

Jezuz
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Hi.
I'm studying quantum Brownian motion right now and I need to see that the (classical) Langevin equation for a Brownian particle is equivalent to the Fokker-Planck equation for the phase-space distribution function of the same particle.
Does anyone know where I can find such a derivation? I've been looking all over the internet for it but usually they start with a Langevin equation containging only first derivatives (that is the have excluded the possible outer potential felt by the particle).
I need the derivation for the case where i have a Langevin equation of the type:
m \ddot x(t) + \gamma \dot x(t) + V(x(t)) = F(t)
(written in LaTeX syntax).
I would be very grateful for help!
Alternatively, since I have the derivation for the Langevin equation starting with a Lagrangian for a particle interacting linearly with a bath of harmonic oscillators (initially in thermal equilibrium), I could also accept a derviation of the Fokker-Planck equation starting with the same assumptions.
 
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For such stochastic methods, a very good book is "Handbook of Stochastic Methods" by C. Gardiner. Written by an expert in the field, this book is very physical and to the point unlike many other excessively mathematical treatments of stochastic processes.

If you're interested, I can step you through the derivation here, but you should get that book for sure.
 
Okej!
Thank you very much. I'll have a look at that book. Found it at the university library. If there is something I get stuck with I might ask you again :)
 

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