Multi-hump Collapsing Solutions in the Nonlinear Schr{\"o}dinger Problem: Existence, Stability and Dynamics

In the present work we examine multi-hump solutions of the nonlinear Schr{\"o}dinger equation in the blowup regime of the one-dimensional model with power law nonlinearity, bearing a suitable exponent of $\sigma>2$. We find that families of such solutions exist for arbitrary pulse numbers, with all of them bifurcating from the critical case of $\sigma=2$. Remarkably, all of them involve ``bifurcations from infinity'', i.e., the pulses come inward from an infinite distance as the exponent $\sigma$ increases past the critical point. The position of the pulses is quantified and the stability of the waveforms is also systematically examined in the so-called ``co-exploding frame''. Both the equilibrium distance between the pulse peaks and the point spectrum eigenvalues associated with the multi-hump configurations are obtained as a function of the blowup rate $G$ theoretically, and these findings are supported by detailed numerical computations. Finally, some prototypical dynamical scenarios are explored, and an outlook towards such multi-hump solutions in higher dimensions is provided.