Fraenkel \(\cal N12(\aleph_2)\): Another variation of \(\cal N1\) | Back to this models page

Description: Change "\(\aleph_1\)" to "\(\aleph_2\)" in \(\cal N12(\aleph_1)\) above

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
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 \(|\bigcup A| = \aleph _{\alpha }\).

40

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

44

\(DC(\aleph _{1})\):  Given a relation \(R\) such that for every  subset \(Y\) of a set \(X\) with \(|Y| < \aleph_{1}\) there is an \(x \in  X\)  with \(Y \mathrel R x\), then there is a function \(f: \aleph_{1} \rightarrow  X\) such that \((\forall\beta < \aleph_{1}) (\{f(\gamma ): \gamma < b \} \mathrel R f(\beta))\).

63

\(SPI\): Weak ultrafilter principle: Every infinite set has a non-trivial ultrafilter.
Jech [1973b], p 172 prob 8.5.

91

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

130

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

135

If \(X\) is a \(T_2\) space with at least two points and \(X^{Y}\) is hereditarily metacompact then \(Y\) is  countable. (A space is metacompact if every open cover has an open point finite refinement. If \(B\) and \(B'\) are covers of a space \(X\), then \(B'\) is a refinement of \(B\) if \((\forall x\in B')(\exists y\in B)(x\subseteq y)\). \(B\) is point finite if \((\forall t\in X)\) there are only finitely many \(x\in B\) such that \(t\in x\).) van Douwen [1980]

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 \(a\).

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 \(\forall A\subseteq G, \forall g\in G\), \(\mu(gA)=\mu(A)\).)

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
60

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

62

\(C(\infty,< \aleph_{0})\):  Every set of non-empty finite  sets  has  a choice function.

67

\(MC(\infty,\infty)\) \((MC)\), The Axiom of Multiple Choice: For every set \(M\) of non-empty sets there is a function \(f\) such that \((\forall x\in M)(\emptyset\neq f(x)\subseteq x\) and \(f(x)\) is finite).

133  

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

152

\(D_{\aleph_{0}}\): Every non-well-orderable set is the union of a pairwise disjoint, well orderable family of denumerable sets.  (See note 27 for \(D_{\kappa}\), \(\kappa\) a well ordered cardinal.)

161

Definability of cardinal addition in terms of \(\le\): There is a first order formula whose only non-logical symbol is \( \le \) (for cardinals) that defines cardinal addition.

163

Every non-well-orderable set has an infinite, Dedekind finite subset.

192

\(EP\) sets: For every set \(A\) there is a projective set \(X\) and a function from \(X\) onto \(A\).

193

\(EFP\ Ab\): Every Abelian group is a homomorphic image of a free projective Abelian group.

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 \(E_i\).

347

Idemmultiple Partition Principle: If \(y\) is idemmultiple (\(2\times y\approx y\)) and \(x\precsim ^* y\), then \(x\precsim y\).

Historical background: Thus, \(A\)has cardinality \(\aleph_2\), \(\cal G\) is the group of all permutations of\(A\), and \(S\) is the set of all subsets of \(A\) of cardinality at most\(\aleph_1\). It follows from Jech [1973b] (p 127, Theorem 8.9),that the Axiom of Choice for a well ordered family of sets (40) is true,the Principle of Dependent Choices for \(\omega_1\) sets (44) is true, butthe \(2m=m\) principle (3) is false. Since 40 implies \(UT(WO,WO,WO)\) (231)and in every FM model 231 implies \((\forall \alpha)UT(\aleph_{\alpha},\aleph_{\alpha},\aleph_{\alpha})\),Form 23 is true.H\"aussler [1983] has shown that cardinal addition is notdefinable in terms of \(\le\) in this model. Thus, 161 is false. Since 40implies 8 (\(C(\aleph_0,\infty)\)), it follows from Brunner [1982a] that in this model there is a set that cannot be well orderedand does not have an infinite Dedekind finite subset, (163 is false).(Form 8 plusForm 163 iff AC.) Since 40 implies 9 (Every Dedekind finiteset is finite.) and 70 (There is a non-trivial ultrafilter on \(\omega\).)is true in every FM model, it follows that 63 (Every infinite set has anon-trivial ultrafilter.) is also true. Form 44 implies forms 39(\(C(\aleph_1,\infty)\)) and 41 (For each cardinal \(m\), \(m\le\aleph_1\) or\(\aleph_1\le m\).). van Douwen [1980] has shown that 39 + 41implies 135 (If \(X\) is a \(T_2\) space with at least two points and \(X^Y\)is hereditarily metacompact, then \(Y\) is countable.), soForm 135 is alsotrue. Blass [1979] has shown that 191 (There is a set \(X\) suchthat for each set \(a\) there is an ordinal \(\alpha\) and a function \(f\)mapping \(X\times\alpha\) onto \(a\).) is true in every permutation model witha set of atoms. He has also shown that 8 (\(C(\aleph_0,\infty)\)) + 191 +193 (Every Abelian group is a homomorphic image of a free projectiveAbelian group.) iff AC. Since 40 implies 8,Form 193 must be false. (SeeNote 60 for definitions.) It is shown in Howard/Rubin [1995b]that in every FM model 40 + 60 (\(C(\infty, WO)\)) implies AC, so 60 isfalse. Howard [1973] proves that in every FM model 62(\(C(\infty,<\aleph_0)\)) implies 60, so 62 is also false. Since\(C(WO,<\aleph_0)\) (122) is true (40 implies 122) it follows that MC (67)is false because 67 + 122 implies AC. (See [67 B].) It is shown inHigasikawa [1995] that the Idemmultiple Partition Principle,form 347, is false.

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