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  1. Increasing the groupwise density number by c.c.c. forcing.Heike Mildenberger & Saharon Shelah - 2007 - Annals of Pure and Applied Logic 149 (1-3):7-13.
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  • Groupwise density and the cofinality of the infinite symmetric group.Simon Thomas - 1998 - Archive for Mathematical Logic 37 (7):483-493.
    We study the relationship between the cofinality $c(Sym(\omega))$ of the infinite symmetric group and the cardinal invariants $\frak{u}$ and $\frak{g}$ . In particular, we prove the following two results. Theorem 0.1 It is consistent with ZFC that there exists a simple $P_{\omega_{1}}$ -point and that $c(Sym(\omega)) = \omega_{2} = 2^{\omega}$ . Theorem 0.2 If there exist both a simple $P_{\omega_{1}}$ -point and a $P_{\omega_{2}}$ -point, then $c(Sym(\omega)) = \omega_{1}$.
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  • The relative consistency of {$\germ g<{\rm cf})$}.Heike Mildenbergert & Saharon Shelah - 2002 - Journal of Symbolic Logic 67 (1):297-314.
    We prove the consistency result from the title. By forcing we construct a model of g = ℵ l , b = cf(Sym(ω)) = ℵ 2.
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  • Consistency results about filters and the number of inequivalent growth types.Andreas Blass & Claude Laflamme - 1989 - Journal of Symbolic Logic 54 (1):50-56.
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  • The cofinality of the infinite symmetric group and groupwise density.Jörg Brendle & Maria Losada - 2003 - Journal of Symbolic Logic 68 (4):1354-1361.
    We show that g ≤ c(Sym(ω)) where g is the groupwise density number and c(Sym(ω)) is the cofinality of the infinite symmetric group. This solves (the second half of) a problem addressed by Thomas.
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