Is Gibbs free energy ever relevant for particle physics?

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Discussion Overview

The discussion revolves around the relevance of Gibbs free energy in the context of particle physics, particularly questioning its application and the reversibility of reactions in this field. It touches on theoretical concepts, applications in cosmology, and the relationship between thermodynamics and particle interactions.

Discussion Character

  • Debate/contested, Conceptual clarification, Technical explanation

Main Points Raised

  • Some participants question whether reactions in particle physics are reversible and why Gibbs free energy is not commonly used in particle physics equations.
  • One participant notes that Gibbs free energy is relevant in discussions about neutron stars.
  • Another participant asserts that all known processes in quantum field theory (QFT) are reversible at the microscopic level, suggesting that Gibbs free energy is a statistical concept applicable to large systems rather than small particle interactions.
  • A participant mentions that thermodynamic principles can be relevant in cosmology, particularly in nucleosynthesis and recombination, where large numbers of particles undergo reversible reactions.
  • Another participant introduces the idea that there are quantum field theoretical analogs of Helmholtz and Gibbs free energy, referred to as generating functionals and effective actions, but clarifies that these are not statistical objects.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of Gibbs free energy in particle physics, with some asserting its irrelevance at the microscopic level while others suggest specific contexts where it may be applicable, such as in cosmology.

Contextual Notes

The discussion highlights the limitations of applying thermodynamic concepts to particle physics, particularly the dependence on the scale of the system and the nature of the processes involved.

Simfish
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And are reactions in particle physics reversible at all?

If so, why don't we ever see Gibbs free energy used in particle physics equations?
 
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It's used in discussions about neutron stars.
 
Simfish said:
And are reactions in particle physics reversible at all?

All known processes in QFT are completely reversible at the microscopic level.

If so, why don't we ever see Gibbs free energy used in particle physics equations?

Because it is a statistical concept that applies to systems of large numbers of particles. Those concepts, including entropy, don't apply to microscopic processes involving a handful of particles.

If you wish to see thermodynamic principles applied to particle physics, one place to look would be in the context of cosmology where particle physics reaction rates are applied to things like nucleosynthesis and recombination. The proper explanation of these involves large numbers of particles undergoing reversible reactions many times in both directions. It makes sense to define a temperature for these systems and thermodynamic considerations drive the equilibrium configuration.
 
fzero has given a good answer, but let me add there actually exist quantum field theoretical analogs of Helmholtz and Gibbs free energy going under the names of generating functionals and effective actions. But they are of course not statistical objects and only analog to free energies.
 

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