On decay of the solutions for the dispersion generalized-Benjamin-Ono and Benjamin-Ono equations

We show that uniqueness results of the kind those obtained for KdV and Schr\"odinger equations ([7], [28]), are not valid for the dispersion generalized-Benjamin-Ono equation in the weighted Sobolev spaces $$H^s(\R)\cap L^2(x^{2r}dx),$$ for appropriated $s$ and $r$. In particular, we obtain that the uniqueness result proved for the dispersion generalized-Benjamin-Ono equation ([13]), is not true for all pairs of solutions $u_1\neq 0$ and $u_2\neq 0$. To achieve these results we employ the techniques present in our recent work [6]. We also improve some Theorems established for the dispersion generalized-Benjamin-Ono equation and for the Benjamin-Ono equation ([13], [12]).