Sphalerons and Conformally Compactified Minkowski Spacetime
  Solutions to the Yang-Mills field equations which describe exploding or imploding shells of gauge field and which may serve as approximations to the exploding sphaleron are discussed. The solutions are conformally related to $SO(2)\times SO(4)$ invariant Yang-Mills solutions. The behavior of fermions in the gauge field background and higher gauge groups are also considered. 
G.W. Gibbons and Alan R. Steif