On the Chern–Gauss–Bonnet theorem for the noncommutative 4-sphere

We construct a differential calculus over the noncommutative 4-sphere in the framework of pseudo-Riemannian calculi, and show that for every metric in a conformal class of perturbations of the round metric, there exists a unique metric and torsion-free connection. Furthermore, we find a localization of the projective module corresponding to the space of vector fields, which allows us to formulate a Chern–Gauss–Bonnet type theorem for the noncommutative 4-sphere.