Comment on ``Reexamination of experimental tests of the fluctuation theorem" by Narayan and Dhar

TL;DR

This paper clarifies that a recent critique of a new heat fluctuation theorem for Brownian particles is based on a misinterpretation and an incorrect assumption, reaffirming the validity of the original theorem.

Contribution

The authors demonstrate that the recent critique is based on a misformulation and an incorrect assumption, defending the validity of their new fluctuation theorem.

Findings

The critique misinterprets the fluctuation theorem formulation.

The critique's limiting case is physically irrelevant.

An incorrect assumption was identified in the critique's derivation.

Abstract

Our result in cond-mat/0305147 that, instead of the conventional heat fluctuation theorem (FT), a new FT holds for heat fluctuations for a Brownian particle in a moving confining potential[Wang et al. 2002], was claimed to be disproved in a very recent preprint by Narayan and Dhar, cond-mat/0307148. This comment is meant to show that their assertion is not correct. The point is that they formulate their FT differently than we do ours. Effectively, their FT speaks about a physically irrelevant limiting case of our new FT. This implies that the two \FT s are not in contradiction with each other. Furthermore, we point out an incorrect assumption in their derivation.