Four-ball genus bounds and a refinement of the Ozsvath-Szabo   tau-invariant
  Based on work of Rasmussen, we construct a concordance invariant associated to the knot Floer complex, and exhibit examples in which this invariant gives arbitrarily better bounds on the 4-ball genus than the Ozsvath-Szabo tau invariant. 
Jennifer Hom and Zhongtao Wu
math.GT