Please consider the following theorem
![](https://www.physicsoverflow.org/?qa=blob&qa_blobid=16462086954717108891)
According with such theorem, w2(X) is a topological obstruction or topological accident or topological wound which does not permit the existence of spinors on X. In order to heal the topological wound of X a magnetic monopole is introduced via the cohomological flux c. With such therapy, now X admits the existence of spinors.·