# New test on general relativity and $f(T)$ torsional gravity from galaxy-galaxy weak lensing surveys

## TL;DR

This paper uses galaxy-galaxy weak lensing data to test general relativity and $f(T)$ torsional gravity, setting stringent constraints on deviations from GR at low-redshift and weak-field regimes.

## Contribution

It introduces a novel method to constrain $f(T)$ gravity using weak lensing data, providing the first high-precision verification of GR at these scales.

## Key findings

- Upper bound on deviation parameter $oxed{ ext{log}_{10}\Omega_ ext{ extalpha} extless -18.52}$
- First high-precision test of GR at these scales using weak lensing data
- Constraints mainly affected by astrophysical modeling uncertainties

## Abstract

We use galaxy-galaxy weak lensing data to perform a novel test on general relativity (GR) and $f(T)$ torsional gravity. In particular, we impose strong constraints using the torsional (teleparallel) formulation of gravity in which the deviation from GR is quantified by a single parameter $\alpha$, an approximation which is always valid at low-redshift Universe and weak gravitational fields. We calculate the difference in the deflection angle and eventually derive the modified excess surface density profile, which is mainly affected at small scales. Confronting the predictions with weak lensing data from the Sloan Digital Sky Survey Data Release 7, we obtain the upper bound on the deviation parameter, which, expressed via the dimensionless percentage in the Universe energy content, reads as ${\rm{log_{10}}}\Omega_\alpha\le -18.52_{-0.42}^{+0.80}$(stat)$_{-0.37}^{+1.50}$(sys)$ [R_c/0.015R_{200}]$ with systematics mainly arising from the modelling of astrophysics, upon a reasonable choice of cut-off radius for $f(T)$ gravity in form of $T + \alpha T^2$. To our knowledge, this is the first time that GR is verified at such an accuracy at the corresponding scales.