't Hooft tensor for generic gauge group
  We study monopoles in gauge theories with generic gauge group. Magnetic charges are in one-to-one correspondence with the second homotopy classes at spatial infinity (${\Pi}_2$), which are therefore identified by the 't Hooft tensor. We determine the 't Hooft tensor in the general case. These issues are relevant to the understanding of Color Confinement. 
A.Di Giacomo, L. Lepori, F. Pucci