Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In mathematics, the Chern Weil homomorphism is a basic construction in the Chern Weil theory, relating for a smooth manifold M the curvature of M to the de Rham cohomology groups of M, i.e., geometry to topology. This theory of Shiing-Shen Chern and André Weil from the 1940s was an important step in the theory of characteristic classes. It is a generalization of the Chern Gauss Bonnet theorem.