The class of 2-dimensional neat reducts is not elementary

Volume 172 / 2002

Tarek Sayed Ahmed Fundamenta Mathematicae 172 (2002), 61-81 MSC: Primary 03G15; Secondary 06E25, 08B99. DOI: 10.4064/fm172-1-5


$SC$, $CA$, $QA$ and $QEA$ stand for the classes of Pinter's substitution algebras, Tarski's cylindric algebras, Halmos' quasipolyadic algebras and Halmos' quasipolyadic algebras with equality, respectively. Generalizing a result of Andréka and Németi on cylindric algebras, we show that for $K\in \{SC,QA,CA,QEA\}$ and any $\beta >2$ the class of $2$-dimensional neat reducts of $\beta $-dimensional algebras in $K$ is not closed under forming elementary subalgebras, hence is not elementary. Whether this result extends to higher dimensions is open.


  • Tarek Sayed AhmedDepartment of Mathematics
    Faculty of Science
    Cairo University
    Giza, Egypt

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