Fraenkel \(\cal N26\): Brunner/Pincus Model, a variation of \(\cal N2\) | Back to this models page

Description: The set ofatoms \(A=\bigcup_{n\in\omega} P_n\), where the \(P_n\)'s are pairwisedisjoint denumerable sets; \(\cal G\) is the set of all permutations\(\sigma\) on \(A\) such that \(\sigma(P_n)=P_n\), for all \(n\in\omega\); and \(S\)is the set of all finite subsets of \(A\)

When the book was first being written, only the following form classes were known to be true in this model:

Form Howard-Rubin Number Statement
16

\(C(\aleph_{0},\le 2^{\aleph_{0}})\):  Every denumerable collection of non-empty sets  each with power \(\le  2^{\aleph_{0}}\) has a choice function.

23

\((\forall \alpha)(UT(\aleph_{\alpha},\aleph_{\alpha}, \aleph_{\alpha}))\): For every ordinal \(\alpha\), if \(A\) and every member of \(A\) has cardinality \(\aleph_{\alpha}\), then \(|\bigcup A| = \aleph _{\alpha }\).

24

\(C(\aleph_0,2^{(2^{\aleph_0})})\): Every denumerable collection of non-empty sets each with power \(2^{(2^{\aleph_{0}})}\) has a choice function.

37

Lebesgue measure is countably additive.

130

\({\cal P}(\Bbb R)\) is well orderable.

133  

Every set is either well orderable or has an infinite amorphous subset.

191

\(SVC\): There is a set \(S\) such that for every set \(a\), there is an ordinal \(\alpha\) and a function from \(S\times\alpha\) onto \(a\).

273

There is a subset of \({\Bbb R}\) which is not Borel.

305

There are \(2^{\aleph_0}\) Vitali equivalence classes. (Vitali equivalence classes are equivalence classes of the real numbers under the relation \(x\equiv y\leftrightarrow(\exists q\in{\Bbb Q})(x-y=q)\).). \ac{Kanovei} \cite{1991}.

309

The Banach-Tarski Paradox: There are three finite partitions \(\{P_1,\ldots\), \(P_n\}\), \(\{Q_1,\ldots,Q_r\}\) and \(\{S_1,\ldots,S_n, T_1,\ldots,T_r\}\) of \(B^3 = \{x\in {\Bbb R}^3 : |x| \le 1\}\) such that \(P_i\) is congruent to \(S_i\) for \(1\le i\le n\) and \(Q_i\) is congruent to \(T_i\) for \(1\le i\le r\).

313

\(\Bbb Z\) (the set of integers under addition) is amenable.  (\(G\) is {\it amenable} if there is a finitely additive measure \(\mu\) on \(\cal P(G)\) such that \(\mu(G) = 1\) and \(\forall A\subseteq G, \forall g\in G\), \(\mu(gA)=\mu(A)\).)

340

Every Lindelöf metric space is separable.

361

In \(\Bbb R\), the union of a denumerable number of analytic sets is analytic. G. Moore [1982], pp 181 and 325.

363

There are exactly \(2^{\aleph_0}\) Borel sets in \(\Bbb R\). G. Moore [1982], p 325.

380

\(PC(\infty,WO,\infty)\):  For every infinite family of non-empty well orderable sets, there is an infinite subfamily \(Y\) of \(X\) which has a choice function.

When the book was first being written, only the following form classes were known to be false in this model:

Form Howard-Rubin Number Statement
64

\(E(I,Ia)\) There are no amorphous sets. (Equivalently, every infinite set is the union of two disjoint infinite sets.)

131

\(MC_\omega(\aleph_0,\infty)\): For every denumerable family \(X\) of pairwise disjoint non-empty sets, there is a function \(f\) such that for each \(x\in X\), f(x) is a non-empty countable subset of \(x\).

167

\(PKW(\aleph_{0},\ge 2,\infty)\), Partial Kinna-Wagner Principle:  For every denumerable family \(F\) such that for all \(x\in F\), \(|x|\ge 2\), there is an infinite subset \(H\subseteq F\) and a function \(f\) such that for all \(x\in H\), \(\emptyset\neq f(x) \subsetneq x\).

344

If \((E_i)_{i\in I}\) is a family of non-empty sets, then there is a family \((U_i)_{i\in I}\) such that \(\forall i\in I\), \(U_i\) is an ultrafilter on \(E_i\).

355

\(KW(\aleph_0,\infty)\), The Kinna-Wagner Selection Principle for a denumerable family of sets: For every denumerable set \(M\) there is a function \(f\) such that for all \(A\in M\), if \(|A| > 1\) then \(\emptyset\neq f(A)\subsetneq A\).

Historical background: Each \(P_n\) for \(n\in\omega\) isamorphous (64 is false) and each set that cannot be well ordered has aninfinite subset in 1--1 correspondence with \(A\). Thus, Brunner proves thatevery set is either well orderable or has an infinite amorphous subset(133 is true). It is clear that the partial Kinna-Wagner Principle,\(PKW(\aleph_0,\infty,\infty)\) (167), the Kinna-Wagner Principle,\(KW(\aleph_0,\infty)\) (355), and the multiple- choice axiom,\(MC_\omega(\aleph_0,\infty)\) (131), are all false for the set \(\{P_n :n\in\omega\}\). It is shown in Note 123 that 133 implies 231(\(UT(WO,WO,WO)\)). In every FM model 231 implies 23((\(\forall\alpha)UT(\aleph_\alpha, \aleph_\alpha,\aleph_\alpha)\)). Itfollows that 23 is also true. De la Cruz and Di Prisco have shown thatevery infinite collection of non-empty well orderable sets has an infinitesubfamily with a choice function (380 is true). SinceForm 165(\(C(WO,WO)\)) is true, (133 implies 165) it follows from Note 2(8 and 9)that 16 and 24 are also true. It was shown in De la Cruz, Hall,Howard, Keremedis, Rubin [2002a] thatForm 340: Every Lindel\"ofmetric space is separable. is true in this model.

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