The Small-Dispersion Limit of the Intermediate Long Wave Equation via Semiclassical Soliton Ensembles

We study the small dispersion limit of the intermediate long wave (ILW) equation, specifically on a class of well-behaved initial conditions $u_0$ where the number of solitons in the solution increases without bound. First, we conduct a formal WKB-style analysis on the ILW direct scattering problem, generating approximate eigenvalues and norming constants. We then use this to define a modified set of scattering data and rigorously analyze the associated inverse scattering problem. The main results include demonstrating $L^2$-convergence of the solution at $t=0$ to the original initial condition $u_0$ and for $0<t<t_{\mathrm{c}}$ to the associated solution of invicid Burgers’ equation, where $t_{\mathrm{c}}$ is the time of gradient catastrophe.