We write and for the cardinalities of the set of finite sequences and the set of finite subsets, respectively, of a set which is of cardinality. With the axiom of choice (), for every infinite cardinal but, without, any relationship between and for an arbitrary infinite cardinal cannot be proved. In this paper, we give conditions that make and comparable for an infinite cardinal. Among our results, we show that, if we assume the axiom of choice for sets of finite (...) sets, then for every Dedekind‐infinite cardinal and the condition that is Dedekind‐infinite cannot be weakened to weakly Dedekind‐infinite. (shrink)

A set x is Dedekind infinite if there is an injection from ω into x; otherwise x is Dedekind finite. A set x is power Dedekind infinite if math formula, the power set of x, is Dedekind infinite; otherwise x is power Dedekind finite. For a set x, let pdfin be the set of all power Dedekind finite subsets of x. In this paper, we prove in math formula two generalizations of Cantor's theorem : The first one is that for (...) all power Dedekind infinite sets x, there are no Dedekind finite to one maps from math formula into pdfin. The second one is that for all sets math formula, if x is infinite and there is a power Dedekind finite to one map from y into x, then there are no surjections from y onto math formula. We also obtain some related results. (shrink)

It is proved in (without the axiom of choice) that for all infinite cardinals and all natural numbers, where is the cardinality of the set of permutations with exactly non‐fixed points of a set which is of cardinality.