A Kirchoff-Sobolev parametrix for the wave equation and applications
  We propose a geometric construction of a first order physical space parametrix for solutions to covariant, tensorial wave equations on a curved background. We describe its applications to a large data breakdown criterion in General Relativity and also give a new gauge independent proof of the Eardley-Moncrief result on large data global existence result for the 3+1-dimensional Yang-MIlls equations. 
S. Klainerman and I. Rodnianski