CTs are not a change of coordinates but an actual change of the geometry, right? In principle, we can change the Minkowski spacetime into Riemannian one even Riemann-Cartan one by some kind of CT. In the Riemann-Cartan spacetime there is torsion while it is torsion-free for Minkowski spacetime. So how do we understand the problem? Can we consider the torsion coming from the CT and torsion is not an intrinsic geometrical quantity ? Thanks for any reply!