Fraenkel \(\cal N5\): The Mathias/Pincus Model II (an extension of \(\cal N4\)) | Back to this models page

Description: \(A\) iscountably infinite; \(\precsim\) and \(\le\) are universal homogeneous partialand linear orderings, respectively, on \(A\), (See Jech [1973b]p101 for definitions.); \(\cal G\) is the group of all order automorphismson \((A,\precsim,\le)\); 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
6

\(UT(\aleph_0,\aleph_0,\aleph_0,\Bbb R)\): The union of a denumerable  family  of denumerable subsets of \({\Bbb R}\) is denumerable.

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.

30

Ordering Principle: Every set can be linearly ordered.

37

Lebesgue measure is countably additive.

60

\(C(\infty,WO)\): Every set of non-empty, well orderable sets has a choice function.
Moore, G. [1982], p 125.

91

\(PW\):  The power set of a well ordered set can be well ordered.

130

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

165

\(C(WO,WO)\):  Every well ordered family of non-empty, well orderable sets has a choice function.

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.

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
14

BPI: Every Boolean algebra has a prime ideal.

40

\(C(WO,\infty)\):  Every well orderable set of non-empty sets has a choice function. Moore, G. [1982], p 325.

49

Order Extension Principle: Every partial ordering can be extended to a linear ordering.  Tarski [1924], p 78.

84

\(E(II,III)\) (Howard/Yorke [1989]): \((\forall x)(x\) is \(T\)-finite  if and only if \(\cal P(x)\) is Dedekind finite).

99

Rado's Selection Lemma: Let \(\{K(\lambda): \lambda \in\Lambda\}\) be a family  of finite subsets (of \(X\)) and suppose for each finite \(S\subseteq\Lambda\) there is a function \(\gamma(S): S \rightarrow X\) such that \((\forall\lambda\in S)(\gamma(S)(\lambda)\in K(\lambda))\).  Then there is an \(f: \Lambda\rightarrow X\) such that for every finite \(S\subseteq\Lambda\) there is a finite \(T\) such that \(S\subseteq T\subseteq\Lambda\) and such that \(f\) and \(\gamma (T)\) agree on S.

118

Every linearly orderable topological space is normal.  Birkhoff [1967], p 241.

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 \(x\).

144

Every set is almost well orderable.

Historical background: In\(\cal N5\), \(\precsim\) cannot be extended to a linear ordering on \(A\) (49is false), but every set can be linearly ordered (30 is true). Also, theBoolean Prime Ideal Theorem (14) is false. Since 30 is true, a set is \(T\)finite iff it is finite (Levy [1958]), so \(A\) is not \(T\) finite,but \(\cal P(A)\) is Dedekind finite (84 is false). (\(T\) finite isequivalent to II-finite from Note 94.) Using the fact that theKinna-Wagner Selection Principle (15) is false and that the OrderingPrinciple (30) is true, Krom proves that there is an ordered topologicalspace that is not normal (118 is false). SinceForm 14 is false and form30 impliesForm 62 (\(C(\infty,<\aleph_0)\)), Blass has shown that Rado'sSelection Principle (99) is false. (See Note 33 for the proof that 62 + 99implies 14.) Howard [1973] has shown that in every FM model, 62implies 60 (\(C(\infty, WO)\)), so 60 is true. Moreover, in every FM model,60 + 40 (\(C(WO,\infty)\)) implies AC, so 40 is false. (SeeHoward/Rubin [1995b].) SinceForm 165 (\(C(WO,WO)\)) is true, (60implies 165) it follows from Note 2(8 and 9) that 16 and 24 are also true.

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