P. Amodio, C. Budd, O. Koch, V. Rottschäfer, G. Settanni, E. Weinmüller:

"Near critical, self-similar, blow-up solutions of the generalised Korteweg-de Vries equation: asymptotics and computations";

in: "ASC Report 02/2019", issued by: Institute for Analysis and Scientific Computing; Vienna University of Technology, Wien, 2019, ISBN: 978-3-902627-12-4, 1 - 37.

In this article we give a detailed asymptotic analysis of the near critical self-similar blowup solutions to the Generalized Korteweg-de Vries equation (GKdV).We compare this analysis to some careful numerical calculations. It has been known that for a nonlinearity that has a power larger than the critical value p = 5, solitary waves of

the GKdV can become unstable and become infinite in finite time, in other words they blow up. Numerical simulations presented in [1] indicate that if p > 5 the solitary waves travel to the right with an increasing speed, and simultaneously, form a similarity structure as they approach the blow-up time. This structure breaks down at p = 5.

Based on these observations, we rescale the GKdV equation to give an equation that will be analysed by using asymptotic methods as p ! 5+. By doing this we resolve the complete structure of these self-similar blow-up solutions and study the singular nature of the solutions in the critical limit. In both the numerics and the asymptotics,

we find that the solution has sech-like behaviour near the peak. Moreover, it becomes asymmetric with slow algebraic decay to the left of the peak and much more rapid algebraic decay to the right. The asymptotic expressions agree to high accuracy with the numerical results, performed by adaptive high-order solvers based on collocation

or finite difference methods. Based on these expressions we make some conjectures about the approximately self-similar form of the solutions when p = 5.

Generalised Korteweg-de Vries equation, Blow-up solutions, Asymptotic analysis, Numerical methods

http://www.asc.tuwien.ac.at/preprint/2019/asc02x2019.pdf

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