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Mat. Zametki, 2025 Volume 117, Issue 4, Pages 591–599 (Mi mzm14387)

Continuity theorems for a class of computable operators

M. Kh. Faizrahmanov

Kazan (Volga Region) Federal University

Abstract: Computable operators corresponding to the concept of a left computably enumerable real number, called \textit{$\mathrm{L}$-operators}, are studied. Their continuity properties most commonly used in the constructive mathematical analysis of A. A. Markov's school are examined. It is proved that any $\mathrm{L}$-operator is nondecreasing and almost left continuous. An example of an $\mathrm{L}$-operator which is neither left continuous nor right pseudocontinuous at some point is constructed. An almost continuity criterion for an $\mathrm{L}$-operator is found. This criterion is used to prove that almost continuous $\mathrm{L}$-operators are not necessarily continuous or pseudouniformly continuous on a closed interval.

Keywords: constructive real number, left computably enumerable real number, pseudonumber, continuous operator, almost continuous operator, pseudocontinuous operator.

UDC: 510.57+510.25

MSC: 03D78, 03F60

Received: 28.05.2024
Revised: 08.07.2024

DOI: 10.4213/mzm14387


 English version:
Mathematical Notes, 2025, 117:4, 643–649


© Steklov Math. Inst. of RAS, 2025