Relation algebra reducts of cylindric algebras and complete representations

被引:9
|
作者
Hirsch, Robin [1 ]
机构
[1] UCL, Dept Comp Sci, London WC1E 6BT, England
关键词
relation algebra; cylindric algebra; complete representation;
D O I
10.2178/jsl/1185803629
中图分类号
O1 [数学];
学科分类号
0701 ; 070101 ;
摘要
We show, lot any ordinal gamma >= 3. that the class RaCA gamma is pseudo-elementary and has a recursively enumerable elementary theory. S,K denotes the class of strong subalgebras of members of the class K. We devise games, F-n (3 <= n <= omega) G. H. and show, for an atomic relation algebra A with countably many atoms. that there exists has a winning strategy in F-omega (At(A)) double left right arrow A is an element of S(c)RaCA(omega), there exists has a winning strategy in F-n (At(A)) double left arrow A is an element of S(c)RaCA(n), there exists has a winning strategy in G (At(A)) double left arrow A is an element of RaCA(omega), there exists has a winning strategy in H (At(A)) double right arrow A is an element of RaCA(omega) for 3 <= n < omega. We use these games to show, for gamma >= 5 and any class K of relation algebras satisfying RaRCA(gamma) subset of K subset of S(c)RaCA(5), that K is not closed under subalgebras and is not elementary. For infinite gamma, the inclusion RaCA(gamma) subset of S(c)RaCA(7) is strict. For infinite gamma and for a countable relation algebra X we show that W has a complete representation if and only if X is atomic and 3 has a winning strategy in F(At(A)) if and only if A is atomic and A is an element of S(c)RaCA(gamma).
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页码:673 / 703
页数:31
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