The Free Action of Nonequilibrium Dynamics

Qianxiao Li, Weinan E

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


In general nonequilibrium steady states, directly replacing the canonical ensemble by the nonequilibrium invariant distribution yields a free energy function that is insufficient in characterizing the dynamical landscape. We address the problem by defining the free action, which is like a free energy on path space. Through a representative example, we demonstrate the conceptual and practical usefulness of the free action for quantifying the dynamics of nonequilibrium steady states, including those exhibiting phase transitions.

Original languageEnglish (US)
Pages (from-to)300-325
Number of pages26
JournalJournal of Statistical Physics
Issue number2
StatePublished - Oct 30 2015

All Science Journal Classification (ASJC) codes

  • Statistical and Nonlinear Physics
  • Mathematical Physics


  • Free energy
  • Nonequilibrium steady state
  • Phase transition
  • Quasipotential


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