The asymptotic theory for semilinear wave equations in two space dimensions

This paper deals with the asymptotic theory of initial value problems for semilinear wave equations in two space dimensions. The well-posedness and validity of formal approximations on a long time scale including 0 less than or equal to t less than or equal to T = O(\ is an element of \ (-sigma)) (sigma > 0, is an element of --> 0) and 0 less than or equal to t less than or equal to T = infinity are discussed in the classical sense of C-2. These results describe the behavior of long time existence for the validity of formal approximations.