Baldi, Pietro20052011-09-0720052011-09-072005Discrete Contin. Dyn. Syst. 15 (2006) 883-903https://openscience.sissa.it/handle/1963/1722We consider 1D completely resonant nonlinear wave equations of the type vtt -vxx = -v 3 +O(v 4) with spatial periodic boundary conditions. We prove the existence of a new type of quasi-periodic small amplitude solutions with two frequencies, for more general nonlinearities. These solutions turn out to be, at the first order, the superposition of a traveling wave and a modulation of long period, depending only on time.237540 bytesapplication/pdfen-USPreprint