Limitations on the Fraenkel-Mostowski method of independence proofs

1973 ◽  
Vol 38 (3) ◽  
pp. 416-422 ◽  
Author(s):  
Paul E. Howard
Keyword(s):  
Prime Ideal ◽  
Axiom Of Choice ◽  
Finite Sets ◽  
Independence Results ◽  
The Axiom Of Choice ◽  
Weakened Form ◽  
Prime Ideal Theorem

AbstractThe Fraenkel-Mostowski method has been widely used to prove independence results among weak versions of the axiom of choice. In this paper it is shown that certain statements cannot be proved by this method. More specifically it is shown that in all Fraenkel-Mostowski models the following hold:1. The axiom of choice for sets of finite sets implies the axiom of choice for sets of well-orderable sets.2. The Boolean prime ideal theorem implies a weakened form of Sikorski's theorem.

Independence results concerning Dedekindfinite sets

1975 ◽  
Vol 19 (1) ◽  
pp. 35-46 ◽  
Author(s):  
G. P. Monro
Keyword(s):  
Axiom Of Choice ◽  
Finite Sets ◽  
Finite Set ◽  
Independence Results ◽  
The Axiom Of Choice

A Dedekind-finite set is one not equinumerous with any of its proper subsets; it is well known that the axiom of choice implies that all such sets are finite. In this paper we show that in the absence of the axiom of choice it is possible to construct Dedekind-finite sets which are large, in the sense that they can be mapped onto large ordinals; we extend the result to proper classes. It is also shown that the axiom of choice for countable sets is not implied by the assumption that all Dedekind-finite sets are finite.

The dense linear ordering principle

1997 ◽  
Vol 62 (2) ◽  
pp. 438-456 ◽  
Author(s):  
David Pincus
Keyword(s):  
Prime Ideal ◽  
Set Theory ◽  
Ordered Set ◽  
Axiom Of Choice ◽  
Linear Ordering ◽  
Independence Result ◽  
The Axiom Of Choice ◽  
Infinite Set ◽  
Prime Ideal Theorem ◽  
The Way

AbstractLet DO denote the principle: Every infinite set has a dense linear ordering. DO is compared to other ordering principles such as O, the Linear Ordering principle, KW, the Kinna-Wagner Principle, and PI, the Prime Ideal Theorem, in ZF, Zermelo-Fraenkel set theory without AC, the Axiom of Choice.The main result is:Theorem. AC ⇒ KW ⇒ DO ⇒ O, and none of the implications is reversible in ZF + PI.The first and third implications and their irreversibilities were known. The middle one is new. Along the way other results of interest are established. O, while not quite implying DO, does imply that every set differs finitely from a densely ordered set. The independence result for ZF is reduced to one for Fraenkel-Mostowski models by showing that DO falls into two of the known classes of statements automatically transferable from Fraenkel-Mostowski to ZF models. Finally, the proof of PI in the Fraenkel-Mostowski model leads naturally to versions of the Ramsey and Ehrenfeucht-Mostowski theorems involving sets that are both ordered and colored.

scholarly journals On a cardinal equation in set theory

1972 ◽  
Vol 6 (3) ◽  
pp. 447-457 ◽  
Author(s):  
J.L. Hickman
Keyword(s):  
Set Theory ◽  
Axiom Of Choice ◽  
Linear Ordering ◽  
Finite Sets ◽  
Intrinsic Interest ◽  
The Axiom Of Choice ◽  
Infinite Set ◽  
Finiteness Criterion

We work in a Zermelo-Fraenkel set theory without the Axiom of Choice. In the appendix to his paper “Sur les ensembles finis”, Tarski proposed a finiteness criterion that we have called “C-finiteness”: a nonempty set is called “C-finite” if it cannot be partitioned into two blocks, each block being equivalent to the whole set. Despite the fact that this criterion can be shown to possess several features that are undesirable in a finiteness criterion, it has a fair amount of intrinsic interest. In Section 1 of this paper we look at a certain class of C-finite sets; in Section 2 we derive a few consequences from the negation of C-finiteness; and in Section 3 we show that not every C-infinite set necessarily possesses a linear ordering. Any unexplained notation is given in my paper, “Some definitions of finiteness”, Bull. Austral. Math. Soc. 5 (1971).

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