Belavin-Polyakov-Schwartz-Tyupkin 1975 ASD instanton: F = -*F minimizes Yang-Mills action; Atiyah-Singer index theorem links instantons to topological charge n=Tr(F wedge F).
Belavin-Polyakov-Schwartz-Tyupkin 1975 ASD instanton: F = -*F minimizes Yang-Mills action; Atiyah-Singer index theorem links instantons to topological charge n=Tr(F wedge F).