Is Gibbs free energy ever relevant for particle physics?

[Simfish]

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?

[Bill_K]

It's used in discussions about neutron stars.

[fzero]

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.

[element4]

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.