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On the large-order asymtptics of Kuznetsov-Ma breathers

We study the large-order asymptotics for the Kuznetsov-Ma breather of the nonlinear Schrödinger equation in the far-field regime. With the aid of Darboux transformation, we first derive the corresponding Riemann-Hilbert representation for the high-order Kuznetsov-Ma breathers. Under the far-field limit, there are five asymptotical regions in the space-time plane where the breathers behave differently, the genus-two region, the algebraic-decay region, and three distinct genus-zero regions. With the aid of the Deift-Zhou nonlinear steepest decent method, we give the leading order term for each region and verify the consistency between the exact solution and the asymptotic solution numerically. Compared to the previous studies about the large-order asymptotic analysis of rogue waves and solitons, we find a novel genus-two asymptotic region, which further enriches the research of large-order dynamics.