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JOURNALS // Sibirskii Matematicheskii Zhurnal // Archive

Sibirsk. Mat. Zh., 2024 Volume 65, Number 5, Pages 863–875 (Mi smj7897)

On formal solutions to $q$-difference equations containing logarithms

N. V. Gaianova, A. V. Parusnikovab

a National Research University Higher School of Economics, Moscow
b Moscow Institute of Electronics and Mathematics — Higher School of Economics

Abstract: We derive a special form of the $q$-difference equations whose solutions exist in the form of a Dulac series. We find the coefficients of the Dulac series from some algebraic difference equations having a polynomial solution under appropriate conditions. An example is given of a $q$-difference equation which demonstrates the lack of upper bounds for the degrees of these polynomial solutions. We provide an upper bound for the degrees of the polynomial coefficients in terms of the coefficient degrees of the initial segment of the Dulac series. We also give some examples of calculating the expansions of solutions to $q$-difference equations in the form of Dulac series.

Keywords: asymptotic expansion, $q$-difference equation, Dulac series.

UDC: 517.529.8+527.928.1

MSC: 35R30

Received: 17.12.2023
Revised: 13.08.2024
Accepted: 20.08.2024

DOI: 10.33048/smzh.2024.65.508


 English version:
Siberian Mathematical Journal, 2024, 65:5, 1062–1073


© Steklov Math. Inst. of RAS, 2026