“…We need only minimize S YM on this class of invariant connections, which is quite easy to do numerically. There is a fairly extensive literature on minimizing S Y M over connections with specific prescribed symmetries [13,14,[18][19][20][21][22][23][24][25][26][27], but seemingly not the U (2) × Z 2 2 symmetry of interest here. The closest seems to be [25], which studies U (2) invariant connections on non-round S 4 and finds a solution of the Yang-Mills equation which degenerates, in the round limit, to a zero-size instanton/anti-instanton pair.…”