Fraenkel \(\cal N55\): Keremedis/Tachtsis Model: The set of atoms \(A=\bigcup \{A_n: n\in \omega\}\), where \(A_n=\{a_{n,x}: x\in B(0,\frac1n)\}\) and \(B(0,\frac1n)= \{x: \rho(x,0)=\frac1n\}\), where \(\rho\) is the Euclidean metric | Back to this models page

Description: The group of permutations \(\cal G\), is the group of all rotations of the \(A_n\) through an angle \(\theta\in [0,2\pi)\), and supports are finite

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.

9

Finite \(\Leftrightarrow\) Dedekind finite: \(W_{\aleph_{0}}\) Jech [1973b]: \(E(I,IV)\) Howard/Yorke [1989]): Every Dedekind finite set is finite.

37

Lebesgue measure is countably additive.

91

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

92

\(C(WO,{\Bbb R})\):  Every well ordered family of non-empty subsets of \({\Bbb R}\) has a choice function.

130

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

182

There is an aleph whose cofinality is greater than \(\aleph_{0}\).

189

\(EI\ Ab\): For every Abelian group \(A\) there is an injective Abelian group \(G\) and a one to one homomorphism from \(A\) into \(G\).

190

There is a non-trivial injective Abelian group.

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(\(n\)).  

116

Every compact \(T_2\) space is weakly  Loeb. Weakly Loeb means the set of non-empty closed subsets has a multiple choice function.

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 \(x\).

154

Tychonoff's Compactness Theorem for Countably Many \(T_2\) Spaces: The product of countably many \(T_2\) compact spaces is compact.

165

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

343

A product of non-empty, compact \(T_2\) topological spaces is non-empty.

421   \(UT(\aleph_0,WO,WO)\): The union of a denumerable set of well orderable sets can be well ordered.

Historical background: It is shown inKeremedis/Tachtsis [1999a] thatForm 9 (Finite \(\Leftrightarrow\)Dedekind finite) is true in this model, but forms 131(\(MC_\omega(\aleph_0,\infty)\), 154 (Tychonoff's Compactness Theorem forCountably Many \(T_2\) Spaces), 165 (\(C(WO,WO)\), and 343 ( A product ofnon-empty, compact \(T_2\) topological spaces is non-empty.) are false. It isshown in Keremedis/Tachtsis [2000] that 116 (Compact T\(_2\) spacesare weakly Loeb.) is also false. The set \(\{A_n : n\in \omega\}\) is acountable collection of well orderable sets whose union is not wellorderable, so 421 is false.

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