The Wu-Yang potential of Magnetic Skyrmion from SU(2) Flat Connection.

The theoretical research of the origin of magnetic skyrmion is very interesting. By using decomposition theory of gauge potential and the gauge parallel condition of local bases of $su(2)$ Lie algebra, its $SU(2)$ gauge potential is expressed as flat connection. As an example of application, we obtain the inner topological structure of second Chern number by $SU(2)$ flat connection method. It's well known that if magnetic monopole exists in electrodynamics, its Wu-Yang potential is indispensable in $U(1)$ invariant electromagnetic field. In $2$-dim magnetic materials, we prove that if magnetic skyrmion exists, its integral kernel must be $U(1)$ Wu-Yang curvature, where its $U(1)$ Wu-Yang potential is the projection of $SU(2)$ flat connection on $su(2)$ local Cartan subalgebra. The magnetic skyrmion can be created by performing concrete $SU(2)$ local gauge transformation to $su(2)$ Cartan subalgebra $\sigma_3$. The components of the $U(1)$ Wu-Yang curvature correspond to the emergent electromagnetic field of magnetic skyrmion