On the Elementary Equivalence of Automorphism Groups of Boolean Algebras; Downward Skolem Lowenheim Theorems and Compactness of Related Quantifiers
Rubin, Matatyahu ; Shelah, Saharon
J. Symbolic Logic, Tome 45 (1980) no. 1, p. 265-283 / Harvested from Project Euclid
THEOREM 1. $(\Diamond_{\aleph_1})$ If B is an infinite Boolean algebra (BA), then there is $B_1$ such that $|\operatorname{Aut} (B_1)| \leq B_1| = \aleph_1$ and $\langle B_1, \operatorname{Aut} (B_1)\rangle \equiv \langle B, \operatorname{Aut}(B)\rangle$. THEOREM 2. $(\Diamond_{\aleph_1})$ There is a countably compact logic stronger than first-order logic even on finite models. This partially answers a question of H. Friedman. These theorems appear in $\S\S 1$ and 2. THEOREM 3. (a) $(\Diamond_{\aleph_1})$ If B is an atomic $\aleph_1$-saturated infinite $BA, \psi \epsilon L_{\omega 1\omega}$ and $\langle B, \operatorname{Aut} (B)\rangle \models\psi$ then there is $B_1$ such that $|\operatorname{Aut}(B_1)| \leq |B_1| = \aleph_1$ and $\langle B_1, \operatorname{Aut}(B_1)\rangle\models\psi$. In particular if $B$ is 1-homogeneous so is $B_1$. (b) (a) holds for $B = P(\omega)$ even if we assume only CH.
Publié le : 1980-06-14
Classification: 
@article{1183740558,
     author = {Rubin, Matatyahu and Shelah, Saharon},
     title = {On the Elementary Equivalence of Automorphism Groups of Boolean Algebras; Downward Skolem Lowenheim Theorems and Compactness of Related Quantifiers},
     journal = {J. Symbolic Logic},
     volume = {45},
     number = {1},
     year = {1980},
     pages = { 265-283},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1183740558}
}
Rubin, Matatyahu; Shelah, Saharon. On the Elementary Equivalence of Automorphism Groups of Boolean Algebras; Downward Skolem Lowenheim Theorems and Compactness of Related Quantifiers. J. Symbolic Logic, Tome 45 (1980) no. 1, pp.  265-283. http://gdmltest.u-ga.fr/item/1183740558/