TY - JOUR

T1 - Discrete hungry integrable systems — 40 years from the Physica D paper by W.W. Symes

AU - Shinjo, Masato

AU - Fukuda, Akiko

AU - Kondo, Koichi

AU - Yamamoto, Yusaku

AU - Ishiwata, Emiko

AU - Iwasaki, Masashi

AU - Nakamura, Yoshimasa

N1 - Funding Information:
The authors thank the reviewers for their careful reading and constructive suggestions. This work was supported by the Grant-in-Aid for Early-Career Scientists No. 21K13844 from the Japan Society for the Promotion of Science . All authors have read and agreed to the modified version of the manuscript.
Publisher Copyright:
© 2022 The Author(s)

PY - 2022/11

Y1 - 2022/11

N2 - The Toda equation is a famous integrable system studied in multiple fields, including mathematical physics and numerical computing. Forty years ago, Symes showed that the time-1 evolution in the Toda equation corresponds to the 1-step of the well-known QR algorithm whose target matrices are tridiagonal exponentials. The discrete Toda (dToda) equation proposed by Hirota is, in fact, just the recursion formula of the quotient-difference (qd) algorithm for computing tridiagonal eigenvalues. The discrete Lotka–Volterra (dLV) system describing predator–prey interactions is closely related to the dToda equation and can be used to compute tridiagonal matrices. In this paper, by focusing on relationships to Hessenberg eigenvalues, we summarize results for discrete hungry integrable systems that are extensions of the dToda equation and the dLV system. Our main approach is to utilize polynomial sequences with two types of discrete time. We simultaneously clarify the solutions to the discrete hungry integrable systems and their Bäcklund transformations. We then describe continuous analogues of the discrete hungry integrable systems. Moreover, we present desirable properties of practical algorithms based on the discrete hungry integrable systems.

AB - The Toda equation is a famous integrable system studied in multiple fields, including mathematical physics and numerical computing. Forty years ago, Symes showed that the time-1 evolution in the Toda equation corresponds to the 1-step of the well-known QR algorithm whose target matrices are tridiagonal exponentials. The discrete Toda (dToda) equation proposed by Hirota is, in fact, just the recursion formula of the quotient-difference (qd) algorithm for computing tridiagonal eigenvalues. The discrete Lotka–Volterra (dLV) system describing predator–prey interactions is closely related to the dToda equation and can be used to compute tridiagonal matrices. In this paper, by focusing on relationships to Hessenberg eigenvalues, we summarize results for discrete hungry integrable systems that are extensions of the dToda equation and the dLV system. Our main approach is to utilize polynomial sequences with two types of discrete time. We simultaneously clarify the solutions to the discrete hungry integrable systems and their Bäcklund transformations. We then describe continuous analogues of the discrete hungry integrable systems. Moreover, we present desirable properties of practical algorithms based on the discrete hungry integrable systems.

KW - Determinantal solution

KW - Discrete hungry integrable system

KW - Eigenvalue problems

KW - Kostant–Toda equation

KW - Lax representation

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U2 - 10.1016/j.physd.2022.133422

DO - 10.1016/j.physd.2022.133422

M3 - Review article

AN - SCOPUS:85132886589

SN - 0167-2789

VL - 439

JO - Physica D: Nonlinear Phenomena

JF - Physica D: Nonlinear Phenomena

M1 - 133422

ER -