On the vacuum theta angle in Yang-Mills field theories
  Recently, MIT group found a numerical solution to non-abelian gauge fields which is shown to contain non-integer topological number. Using this fact, V.V.Khoze has argued that the vacuum theta angle is zero. Here, we study this in a complimentary way--its physical respect. The key point is MIT solution has an infinite action. Using this, we prove the vacuum theta angle is zero at semiclassical level. 
Liang-Xin Li and Bing-Lin Young