Bogoyavlensky lattices and generalized Catalan numbers

TL;DR

This paper analyzes the decay of initial step data in Bogoyavlensky lattices, revealing an exactly solvable problem linked to generalized Catalan numbers and hypergeometric functions, with implications for integrable systems.

Contribution

It introduces a novel solvable approach for Bogoyavlensky lattices using hypergeometric functions and combinatorial determinants, extending understanding of initial data decay in integrable lattices.

Findings

Decay problem is exactly solvable for Bogoyavlensky lattices.

Solution involves generalized hypergeometric functions and Catalan numbers.

Finite-dimensional reduction enables analysis of broader initial data.

Abstract

We study the problem of the decay of initial data in the form of a unit step for the Bogoyavlensky lattices. In contrast to the Gurevich--Pitaevskii problem of the decay of initial discontinuity for the KdV equation, it turns out to be exactly solvable, since the dynamics is linearizable due to termination on the half-line. The answer is written in terms of generalized hypergeometric functions, which serve as exponential generating functions for generalized Catalan numbers. This can be proved by the fact that the generalized Hankel determinants for these numbers are equal to 1, which is a well-known result in combinatorics. Another method is based on a non-autonomous symmetry reduction consistent with the dynamics. It reduces the lattice equation to a finite-dimensional system and makes it possible to solve the problem for a more general finite-parameter family of initial data.