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JOURNALS // Vestnik Moskovskogo Universiteta. Seriya 1. Matematika. Mekhanika // Archive

Vestnik Moskov. Univ. Ser. 1. Mat. Mekh., 2025 Number 3, Pages 31–38 (Mi vmumm4687)

Mathematics

Complete and almost complete constructive metric spaces

M. Kh. Faizrahmanov

Scientific-Educational Mathematical Center of Volga Federal District

Abstract: The paper establishes the existence of a non-complete constructive metric space, complete with respect to each element of some class of measure 1 in the Cantor space, containing all Martin-Löf random sequences. It is proved that any constructive metric space defined in a standard way on an invariant set of constructive reals and complete with respect to each element of some class of measure 1 is complete. An example of a constructive metric space is constructed in which every fundamental sequence converges, but there is no class of measure 1 such that the space is complete with respect to each of its elements.

Key words: constructive metric space, constructive real, complete metric space, Cantor space.

UDC: 510.57+510.25

Received: 13.05.2024

DOI: 10.55959/MSU0579-9368-1-66-3-5



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© Steklov Math. Inst. of RAS, 2025