A weak version of ◊ which follows from 2ℵ0<2ℵ1
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We prove that if CH holds (or even if 2ℵ0 < 2ℵ1), then a weak version of ◊ holds. This weak version of ◊ is a ◊-like principle, and is strong enough to yield some of the known consequences of ◊.
[1] D. Passman. What is a Group Ring , 1976 .
[2] Saharon Shelah,et al. Whitehead groups may be not free, even assuming CH, I , 1977 .
[3] Saharon Shelah,et al. Infinite abelian groups, whitehead problem and some constructions , 1974 .
[4] Saharon Shelah,et al. A compactness theorem for singular cardinals, free algebras, Whitehead problem and tranversals , 1975 .
[5] Paul C. Eklof,et al. Whitehead's Problem is Undecidable , 1976 .