Abstract
Again we note first of all that if F is a non-principal ultrafilter in a BA A, then tF ≥ ω. To see this, note that for each x ∈ F there is a y ∉ F such that 0 < y < x; hence there is an ultrafilter G x such that x ∈ G x but G x ≠ F. Let Y = {G x : x ∈ F}.
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© 1996 Springer Basel AG
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Monk, J.D. (1996). Tightness. In: Cardinal Invariants on Boolean Algebras. Progress in Mathematics. Birkhäuser, Basel. https://doi.org/10.1007/978-3-0346-0334-8_13
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DOI: https://doi.org/10.1007/978-3-0346-0334-8_13
Publisher Name: Birkhäuser, Basel
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