Resumen de Oscillations of Anharmonic Fourier Series and The Wave Equation.
In this paper we have collected some partial results on the sign of u(t,x) where u is a (sufficiently regular) solution of ì utt + (-1)m ?mu = 0 (t,x) Î R x O í î u|G = ... = ?m-1 u|G = 0 t Î R.
These results rely on the study of a sign of almost periodic functions of a special form restricted to a bounded interval J.
