A sharp Strichartz estimate for the wave equation with data in the   energy space
  We prove a sharp bilinear estimate for the wave equation from which we obtain the sharp constant in the Strichartz estimate which controls the $L^4_{t,x}(\R^{5+1})$ norm of the solution in terms of the energy. We also characterise the maximisers. 
Neal Bez, Keith M. Rogers
math.AP math.CA