Surgery on Nullhomologous Tori
  By studying the example of smooth structures on CP^2#3(-CP^2) we illustrate how surgery on a single embedded nullhomologous torus can be utilized to change the symplectic structure, the Seiberg-Witten invariant, and hence the smooth structure on a 4-manifold. 
Ronald Fintushel and Ronald J. Stern
math.GT math.AG math.SG