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«THE BULLETIN OF IRKUTSK STATE UNIVERSITY». SERIES «MATHEMATICS»
«IZVESTIYA IRKUTSKOGO GOSUDARSTVENNOGO UNIVERSITETA». SERIYA «MATEMATIKA»
ISSN 1997-7670 (Print)
ISSN 2541-8785 (Online)

List of issues > Series «Mathematics». 2026. Vol 55

Composite-type Differential Equations with Degeneration

Author(s)

Alexander I. Kozhanov1, Bato V. Zhigzhitzhapov2

1 Novosibirsk State University, Novosibirsk, Russian Federation 

2 Buryat State University, Ulan-Ude, Russian Federation

Abstract
The paper is devoted to the study of the solvability of boundary value problems for fourth-order linear composite-type differential equations. A distinctive feature of the considered equations is that the operator coefficient at the highest derivative with respect to the time (distinguished) variable may be non-invertible. For the problems under study, theorems on the existence and uniqueness of regular solutions are proved—solutions that possess all generalized derivatives in the sense of S.L. Sobolev entering the corresponding equation.
About the Authors

Alexander I. Kozhanov, Dr. Sci. (Phys.–Math.), Prof., Novosibirsk State University, Novosibirsk, 630090, Russian Federation, kozhanov@math.nsc.ru

Bato V. Zhigzhitzhapov, Buryat State University, Ulan-Ude, 670000, Russian Federation, zhbat120401@gmail.com

For citation
Kozhanov A. I., Zhigzhitzhapov B. V. Composite-type Differential Equations with Degeneration. The Bulletin of Irkutsk State University. Series Mathematics, 2026, vol. 55, pp. 31–45. (in Russian) https://doi.org/10.26516/1997-7670.2026.55.31
Keywords
composite type differential equations, degeneracy, boundary value problems, regular solutions, existence, uniqueness
UDC
517.955
MSC
35A23, 35615, 35699
DOI
https://doi.org/10.26516/1997-7670.2026.55.31
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