Axiom Of Choice

We have the following indirect implication of form equivalence classes:

40 $\Rightarrow$ 155 given by the following sequence of implications, with a reference to its direct proof:

Implication	Reference
40 $\Rightarrow$ 43	Consistency results for $ZF$, Jensen, R.B. 1967, Notices Amer. Math. Soc. On cardinals and their successors, Jech, T. 1966a, Bull. Acad. Polon. Sci. S'er. Sci. Math. Astronom. Phys.
43 $\Rightarrow$ 78	The Axiom of Choice, Jech, [1973b] The Axiom of Choice, Jech, [1973b]
78 $\Rightarrow$ 155	Geordnete Lauchli Kontinuen, Brunner, N. 1983a, Fund. Math.

Here are the links and statements of the form equivalence classes referenced above:

Howard-Rubin Number	Statement
40:	$C(WO,\infty)$: Every well orderable set of non-empty sets has a choice function. Moore, G. [1982], p 325.
43:	$DC(\omega)$ (DC), Principle of Dependent Choices: If $S$ is a relation on a non-empty set $A$ and $(\forall x\in A) (\exists y\in A)(x S y)$ then there is a sequence $a(0), a(1), a(2), \ldots$ of elements of $A$ such that $(\forall n\in\omega)(a(n)\mathrel S a(n+1))$. See Tarski [1948], p 96, Levy [1964], p. 136.
78:	Urysohn's Lemma: If $A$ and $B$ are disjoint closed sets in a normal space $S$, then there is a continuous $f:S\rightarrow [0,1]$ which is 1 everywhere in $A$ and 0 everywhere in $B$. Urysohn [1925], pp 290-292.
155:	$LC$: There are no non-trivial Läuchli continua. (A Läuchli continuum is a strongly connected continuum. Continuum $\equiv$ compact, connected, Hausdorff space; and strongly connected $\equiv$ every continuous real valued function is constant.)

Comment:

Back

Implication	Reference
40 \(\Rightarrow\) 43	Consistency results for $ZF$, Jensen, R.B. 1967, Notices Amer. Math. Soc. On cardinals and their successors, Jech, T. 1966a, Bull. Acad. Polon. Sci. S'er. Sci. Math. Astronom. Phys.
43 \(\Rightarrow\) 78	The Axiom of Choice, Jech, [1973b] The Axiom of Choice, Jech, [1973b]
78 \(\Rightarrow\) 155	Geordnete Lauchli Kontinuen, Brunner, N. 1983a, Fund. Math.

Howard-Rubin Number	Statement
40:	\(C(WO,\infty)\): Every well orderable set of non-empty sets has a choice function. Moore, G. [1982], p 325.
43:	\(DC(\omega)\) (DC), Principle of Dependent Choices: If \(S\) is a relation on a non-empty set \(A\) and \((\forall x\in A) (\exists y\in A)(x S y)\) then there is a sequence \(a(0), a(1), a(2), \ldots\) of elements of \(A\) such that \((\forall n\in\omega)(a(n)\mathrel S a(n+1))\). See Tarski [1948], p 96, Levy [1964], p. 136.
78:	Urysohn's Lemma: If \(A\) and \(B\) are disjoint closed sets in a normal space \(S\), then there is a continuous \(f:S\rightarrow [0,1]\) which is 1 everywhere in \(A\) and 0 everywhere in \(B\). Urysohn [1925], pp 290-292.
155:	\(LC\): There are no non-trivial Läuchli continua. (A Läuchli continuum is a strongly connected continuum. Continuum \(\equiv\) compact, connected, Hausdorff space; and strongly connected \(\equiv\) every continuous real valued function is constant.)