Title of article
Closed maps on spaces with point-countable bases
Author/Authors
Tsugunori and Shibakov، نويسنده , , Alexander، نويسنده ,
Issue Information
دوماهنامه با شماره پیاپی سال 1999
Pages
14
From page
1
To page
14
Abstract
We prove a version of Lašnevʹs theorem for spaces with point-countable bases.
m. Let X have a point-countable base, f:X→Y be a closed map. Then there is an ω1-relatively-discrete subspace Z of Y such that |Z|≤d(Y) and f−1(y) is compact for every y∈Y\Z.
e study the subspaces of closed images of regular spaces with point-countable bases and show that every such subspace has countable π-character and a point-countable π-base. The latter result is extended to a wider class of spaces which is invariant under closed maps and products with metrizable compacta. The proofs use a structure which controls the convergence properties of the space and those of its closed image.
Keywords
?-character , Point-countable base , Sequential order , ?-base , Closed map , Sequential space , La?nevיs theorem
Journal title
Topology and its Applications
Serial Year
1999
Journal title
Topology and its Applications
Record number
1579440
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