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A Remark on Ascending Chain Conditions, the Countable Axiom of Choice and the Principle of Dependent Choices
Author(s) -
Diener KarlHeinz
Publication year - 1994
Publication title -
mathematical logic quarterly
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.473
H-Index - 28
eISSN - 1521-3870
pISSN - 0942-5616
DOI - 10.1002/malq.19940400310
Subject(s) - mathematics , axiom of choice , countable set , axiom , statement (logic) , transitive relation , choice function , discrete mathematics , chain (unit) , combinatorics , set (abstract data type) , pure mathematics , set theory , physics , geometry , astronomy , computer science , political science , law , programming language
It is easy to prove in ZF − (= Zermelo‐Fraenkel set theory without the axioms of choice and foundation) that a relation R satisfies the maximal condition if and only if its transitive hull R * does; equivalently: R is well‐founded if and only if R * is. We will show in the following that, if the maximal condition is replaced by the (finite ascending) chain condition, as is often the case in Algebra, the resulting statement is not provable in ZF − anymore (if ZF − is consistent). More precisely, we will prove that this statement is equivalent in ZF − to the countable axiom of choice AC ω . Moreover, applying this result we will prove that the axiom of dependent choices, restricted to partial orders as used in Algebra, already implies the general form for arbitrary relations as formulated first by Teichmüller and, independently, some time later by Bernays and Tarski. Mathematics Subject Classification : 06B05, 08A65, 08B20, 03E99.