Parameter mapping and physical reconstruction of Akhmediev breathers at the interface of two fluid half-spaces

Abstract

A methodology combining parameter mapping and physical reconstruction of Akhmediev breathers at the interface between two fluid half-spaces is developed on the basis of the Nayfeh model. Parameter maps are constructed to characterize the breather modulation period, the modulational instability growth rate, and the relative contribution of the bound second harmonic to the reconstructed interfacial profile. Their combined analysis provides a physically meaningful classification of breather regimes beyond the conventional focusing condition of the nonlinear Schrödinger equation. Reconstruction of the physical interfacial profile establishes a quantitative relation between nonlinear wave deformation and the contribution of the bound second harmonic, making it possible to identify the range of applicability of the weakly nonlinear approximation. Representative regimes from different modulational instability regions are analyzed to demonstrate the influence of resonance and focusing boundaries on breather characteristics and interfacial wave profiles. The proposed approach provides a direct link between the mathematical description of Akhmediev breathers and their physical interpretation and can be extended to other localized solutions of the nonlinear Schrödinger equation and to a broad class of stratified hydrodynamic systems.