The post-Minkowskian limit of f(R)-gravity

TL;DR

This paper analyzes the post-Minkowskian limit of f(R)-gravity in the Jordan frame, revealing the existence of massive scalar modes alongside massless gravitons, which could impact gravitational wave detection.

Contribution

It develops the post-Minkowskian analysis of f(R)-gravity without conformal transformations, highlighting the emergence of massive scalar modes and their relation to the theory's parameters.

Findings

Presence of massive scalar modes in f(R)-gravity

Massless gravitons are only in General Relativity

Curvature stress-energy tensor generalizes Landau-Lifshitz tensor

Abstract

We formally discuss the post-Minkowskian limit of $f(R)$-gravity without adopting conformal transformations but developing all the calculations in the original Jordan frame. It is shown that such an approach gives rise, in general, together with the standard massless graviton, to massive scalar modes whose masses are directly related to the analytic parameters of the theory. In this sense, the presence of massless gravitons only is a peculiar feature of General Relativity. This fact is never stressed enough and could have dramatic consequences in detection of gravitational waves. Finally the role of curvature stress-energy tensor of $f(R)$-gravity is discussed showing that it generalizes the so called Landau-Lifshitz tensor of General Relativity. The further degrees of freedom, giving rise to the massive modes, are directly related to the structure of such a tensor.