Fraenkel \(\cal N46\): Höft/Howard Model I | Back to this models page
Description: The set \(A\) of atoms is denumerable andordered by \(\le\) so that \((A,\le)\) is order isomorphic to the rationals.\(A\) is written as the union \(A = D_1 \cup D_2 \cup D_3\) of three densedisjoint subsets
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 |
|---|---|
| 6 | \(UT(\aleph_0,\aleph_0,\aleph_0,\Bbb R)\): The union of a denumerable family of denumerable subsets of \({\Bbb R}\) is denumerable. |
| 37 | Lebesgue measure is countably additive. |
| 84 | \(E(II,III)\) (Howard/Yorke [1989]): \((\forall x)(x\) is \(T\)-finite if and only if \(\cal P(x)\) is Dedekind finite). |
| 91 | \(PW\): The power set of a well ordered set can be well ordered. |
| 130 | \({\cal P}(\Bbb R)\) is well orderable. |
| 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 \(\forall A\subseteq G, \forall g\in G\), \(\mu(gA)=\mu(A)\).) |
| 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. |
| 368 | The set of all denumerable subsets of \(\Bbb R\) has power \(2^{\aleph_0}\). |
| 369 | If \(\Bbb R\) is partitioned into two sets, at least one of them has cardinality \(2^{\aleph_0}\). |
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 |
|---|---|
| 15 | \(KW(\infty,\infty)\) (KW), The Kinna-Wagner Selection Principle: For every set \(M\) there is a function \(f\) such that for all \(A\in M\), if \(|A|>1\) then \(\emptyset\neq f(A)\subsetneq A\). (See Form 81(\(n\)). |
| 185 | Every linearly ordered Dedekind finite set is finite. |
Historical background: \(G\) is the group of all order automorphisms \(\phi\) of\(A\) such that \(\phi(D_i) = D_i\) for \(i=1, 2, 3\). \(S\) is the set of allsubsets \(E\) of \(A\) which satisfy the following three conditions: (a)\(E\cap D_1\) is finite, (b) \(E\cap D_2\) is well ordered by \(\le\) and (c) If\(b:\alpha \to E\cap D_2\) is an order preserving bijection from an ordinal\(\alpha\) onto \(E\cap D_2\) and \(\lambda \le \alpha\) is a limit ordinal,then the least upper bound of \(\{b(\gamma):\gamma<\lambda\}\) in \((A,\le)\)exists and is in \(D_3\). In H\"oft/Howard [1994], it is shownthat in \(\cal N46\), \(D_1\) is an infinite linearly orderable set which isDedekind finite (form 185 is false) and that \(\forall X\), if \(\cal P(X)\)is Dedekind finite then every subset of \(\cal P(X)\) which is linearlyordered by \(\subseteq\) has a maximum element (form 84 is true).
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