Chern, Pontrjagin, and Euler Classes of Vector Bundles
摘要
LetDe Rham cohomology M be a smooth manifold and let \(\Omega ^p(M,{\mathbb K})\) be the space of differential p-forms on M with values in \({\mathbb K}\) ; if \(p > \dim M\) , then \(\Omega ^p(M,{\mathbb K}) = 0\) . The exterior derivative d takes p-forms into \((p+1)\) -forms. One of the main properties of the exterior derivative is that \( d^2 = 0. \) Recall that the forms \(\varphi \) for which \(d \varphi = 0\) are called closed and those of the form \(\psi = d \varphi \) - exact.