AN ELEMENTARY PROOF OF GLOBAL OR ALMOST GLOBAL EXISTENCE FOR QUASI-LINEAR WAVE EQUATIONS

Abstract

We give a new, elementary proof of the global or almost global existence theorem of S. Klainerman. Our result also covers the almost global existence theorem of M. Keel, F. Smith, and C. D. Sogge. The proof is carried out in line with S. Klainerman and T. C. Sideris.