Axiom Of Choice

We have the following indirect implication of form equivalence classes:

202 $\Rightarrow$ 211 given by the following sequence of implications, with a reference to its direct proof:

Implication	Reference
202 $\Rightarrow$ 40	clear
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 $\Rightarrow$ 211	clear

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

Howard-Rubin Number	Statement
202:	$C(LO,\infty)$: Every linearly ordered family of non-empty sets has a choice function.
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.
211:	$DCR$: Dependent choice for relations on $\Bbb R$: If $R\subseteq\Bbb R\times\Bbb R$ satisfies $(\forall x\in \Bbb R)(\exists y\in\Bbb R)(x\mathrel R y)$ then there is a sequence $\langle x(n): n\in\omega\rangle$ of real numbers such that $(\forall n\in\omega)(x(n)\mathrel R x(n+1))$.

Comment:

Back

Implication	Reference
202 \(\Rightarrow\) 40	clear
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 \(\Rightarrow\) 211	clear

Howard-Rubin Number	Statement
202:	\(C(LO,\infty)\): Every linearly ordered family of non-empty sets has a choice function.
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.
211:	\(DCR\): Dependent choice for relations on \(\Bbb R\): If \(R\subseteq\Bbb R\times\Bbb R\) satisfies \((\forall x\in \Bbb R)(\exists y\in\Bbb R)(x\mathrel R y)\) then there is a sequence \(\langle x(n): n\in\omega\rangle\) of real numbers such that \((\forall n\in\omega)(x(n)\mathrel R x(n+1))\).