Galactic Rotation Dynamics in f(T) gravity

Abstract

We investigate galactic rotation curves in $f(T)$ gravity, where $T$ represents a torsional quantity. Our study centers on the particular Lagrangian $f(T)=T+\alpha{T^n}$, where $|n|\neq 1$ and $\alpha$ is a small unknown constant. To do this we treat galactic rotation curves as being composed from two distinct features of galaxies, namely the disk and the bulge. This process is carried out for several values of the index $n$. The resulting curve is then compared with Milky Way profile data to constrain the value of the index $n$ while fitting for the parameter $\alpha$. These values are then further tested on three other galaxies with different morphologies. On the galactic scale we find that $f(T)$ gravity departs from standard Newtonian theory in an important way. For a small range of values of $n$ we find good agreement with data without the need for exotic matter components to be introduced.