On the long time behavior of solutions to the Intermediate Long Wave equation

Abstract: We show that the limit infimum, as time $\,t\,$ goes to infinity, of any uniformly bounded in time $H^{3/2+}\cap L^1$ solution to the Intermediate Long Wave equation converge to zero locally in an increasing-in-time region of space of order $\,t/\log(t)$. Also, for solutions with a mild $L^1$-norm growth in time is established that its limit infimum converge to zero, as time goes to infinity. This confirms the non existence of breathers and other solutions for the ILW model moving with a speed "slower" than a soliton. We also prove that in the far field linearly dominated region, the $L^2$ norm of the solution also converges to zero as time approaches infinity. In addition, we deduced several scenarios for which the initial value problem associated to the generalized Benjamin-Ono and the generalized Intermediate Long Wave equations cannot possess time periodic solutions (breathers). Finally, as it was previously demonstrated in solutions of the KdV and BO equations, we establish the following propagation of regularity result : if the datum $u_0\in H^{3/2+}(\mathbb R)\cap H^m((x_0,\infty))$, for some $\;x_0\in\mathbb R,\,m\in Z^+,\,m\geq 2$, then the corresponding solution $u(t,\cdot)$ of the Intermediate Long Wave equation belongs to $H^m(\beta,\infty)$, for any $t>0$ and $\beta\in\mathbb R$.