# Parameterized post-Newtonian limit of general teleparallel gravity theories

## TL;DR

This paper derives the post-Newtonian limit of a broad class of teleparallel gravity theories, showing that $f(T)$ theories share the same post-Newtonian parameters as general relativity, thus cannot be distinguished by such measurements.

## Contribution

It provides a general derivation of the post-Newtonian limit for teleparallel gravity theories, including $f(T)$ and new general relativity, revealing their parameter equivalence to GR.

## Key findings

- The class of theories is fully conservative with only $eta$ and $ extgamma$ deviations.
- $f(T)$ theories have the same post-Newtonian limit as GR.
- Post-Newtonian parameters cannot distinguish $f(T)$ theories from GR.

## Abstract

We derive the post-Newtonian limit of a general class of teleparallel gravity theories, whose action is given by a free function of three scalar quantities obtained from the torsion of the teleparallel connection. This class of theories is chosen to be sufficiently generic in order to include the $f(T)$ class of theories as well as new general relativity as subclasses. To derive its post-Newtonian limit, we first impose the Weitzenb\"ock gauge, and then introduce a post-Newtonian approximation of the tetrad field around a Minkowski background solution. Our results show that the class of theories we consider is fully conservative, with only the parameters $\beta$ and $\gamma$ potentially deviating from their general relativity values. In particular, we find that the post-Newtonian limit of any $f(T)$ theory is identical to that of general relativity, so that these theories cannot be distinguished by measurements of the post-Newtonian parameters alone.