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JOURNALS // Sibirskii Matematicheskii Zhurnal // Archive

Sibirsk. Mat. Zh., 2004 Volume 45, Number 5, Pages 1160–1177 (Mi smj1126)

On homeomorphisms of effective topological spaces

A. S. Morozov

Sobolev Institute of Mathematics, Siberian Branch of the Russian Academy of Sciences

Abstract: We study effective presentations and homeomorphisms of effective topological spaces. By constructing a functor from the category of computable models into the category of effective topological spaces, we show in particular that there exist homeomorphic effective topological spaces admitting no hyperarithmetical homeomorphism between them and there exist effective topological spaces whose autohomeomorphism group has the cardinality of the continuum but whose only hyperarithmetical autohomeomorphism is trivial. It is also shown that if the group of autohomeomorphisms of a hyperarithmetical topological space has cardinality less than $2^\omega$ then this group is hyperarithmetical. We introduce the notion of strong computable homeomorphism and solve the problem of the number of effective presentations of $T_0$-spaces with effective bases of clopen sets with respect to strong homeomorphisms.

Keywords: effective topological space, effective topology, homeomorphism, autohomeomorphism, computable model, constructive model.

UDC: 510.53, 515.1

Received: 25.04.2003


 English version:
Siberian Mathematical Journal, 2004, 45:5, 956–968

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© Steklov Math. Inst. of RAS, 2025