Variational principles and nonequilibrium thermodynamics

P. Ván, R. Kovács

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Variational principles play a fundamental role in deriving the evolution equations of physics. They work well in the case of non-dissipative evolution, but for dissipative systems, the variational principles are not unique and not constructive. With the methods of modern nonequilibrium thermodynamics, one can derive evolution equations for dissipative phenomena and, surprisingly, in several cases, one can also reproduce the Euler-Lagrange form and symplectic structure of the evolution equations for non-dissipative processes. In this work, we examine some demonstrative examples and compare thermodynamic and variational techniques. Then, we argue that, instead of searching for variational principles for dissipative systems, there is another viable programme: The second law alone can be an effective tool to construct evolution equations for both dissipative and non-dissipative processes. This article is part of the theme issue 'Fundamental aspects of nonequilibrium thermodynamics'.

Original languageEnglish
Article number20190178
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume378
Issue number2170
DOIs
Publication statusPublished - May 1 2020

Keywords

  • Korteweg
  • Metriplectic
  • Newtonian gravity
  • Phase fields
  • Symplectic

ASJC Scopus subject areas

  • Mathematics(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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