R^n gravity and the chameleon

TL;DR

This paper demonstrates that R^n gravity theories are highly constrained by Solar System tests, as the chameleon mechanism only works when n is very close to 1, limiting their viability.

Contribution

It provides a detailed analysis showing the limitations of the chameleon mechanism in R^n gravity theories, constraining the exponent n to values near unity.

Findings

R^n gravity is severely constrained by Solar System bounds.

The chameleon mechanism requires n to be very close to 1.

Theories with n far from 1 are incompatible with Solar System tests.

Abstract

The Solar System bounds on R^n gravity are often ignored in the literature by invoking the chameleon mechanism. We show that in order for the latter to work, the exponent n must be ridicolously close to unity and, therefore, these theories are severely constrained.