Comment on "Measurability of nonequilibrium thermodynamics in terms of the Hamiltonian of mean force"

TL;DR

This paper critically examines the limitations of using the Hamiltonian of mean force for nonequilibrium thermodynamics, highlighting restrictions and unresolved ambiguities in the approach.

Contribution

It clarifies the severe restrictions of the Hamiltonian of mean force approach and emphasizes unresolved ambiguities in fluctuating thermodynamic potentials.

Findings

Identifies restrictions of the Hamiltonian of mean force approach.

Highlights ambiguities in fluctuating thermodynamic potentials.

Argues limitations in formulating nonequilibrium thermodynamics.

Abstract

In a recent paper [P. Strasberg and M. Esposito, Phys. Rev. E {\bf 101}, 050101(R) (2020)] an attempt is presented to formulate the nonequilibrium thermodynamics of an open system in terms of the Hamiltonian of mean force. The purpose of the present comment is to clarify severe restrictions of this approach and also to stress that recently noted ambiguities [P. Talkner and P. H\"anggi, Phys. Rev. E {\bf 94}, 022143 (2016)] of fluctuating thermodynamic potentials cannot be removed in the suggested way.