Global periodic solutions of the nonlinear wave equation (Q1067100)

The authors investigate the problem of the existence of doubly T-periodic continuous solutions u of the nonlinear wave equation \(u_{tt}- u_{ss}=F(t,s)+g(u)\), \((t,s)\in R^ 2\), where F is doubly T-periodic scalar function on \(R^ 2\) and g is a scalar function on R. The solution u is considered in the sense of distributions. They illustrate their results by a concrete example. The connections with previous results on this subject are pointed out.