Comment on "Energy conditions in \(f(Q)\) gravity"

Abstract

In Phys. Rev. D 102, 024057 (2020), the authors studied energy conditions in \(f(Q)\) theory following the same path as researchers handled the energy conditions in the curvature-based modified gravity theories, like \(f(R)\) or \(f(R,G)\) theories. However, the field equations in the \(f(Q)\) theory was not expressed as an effective theory in the literature earlier and in the above mentioned paper [1], the authors claimed that the pressure and energy density follow a set of energy condition criteria without showing how they came to this conclusion. In this comment, we express \(f(Q)\) theory as an effective theory in Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe. And from there, the correct energy conditions are obtained in the traditional (general relativistic) way. Unfortunately, some missing terms in the published work [1] are noticed.