Commentationes Mathematicae Universitatis Carolinae
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چکیده
For Tychonoff X and α an infinite cardinal, let αdef X := the minimum number of α cozero-sets of the Čech-Stone compactification which intersect to X (generalizing R-defect), and let rtX := minα max(α, α def X). Give C(X) the compact-open topology. It is shown that τC(X) ≤ nχC(X) ≤ rtX = max(L(X), L(X) def X), where: τ is tightness; nχ is the network character; L(X) is the Lindelöf number. For example, it follows that, for X Čech-complete, τC(X) = L(X). The (apparently new) cardinal functions nχC and rt are compared with several others.
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Commentationes Mathematicae Universitatis Carolinae
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