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Congruence intersection properties for varieties of algebras

Published online by Cambridge University Press:  09 April 2009

Paolo Agliano
Affiliation:
Dipartimento di Matematica Via del Capitano 15 53100 Siena Italy e-mail: agliano@unisi.it
Kirby A. Baker
Affiliation:
Department of Mathematics UCLA Los Angeles CA 90095-1555 USA e-mail: baker@math.ucla.edu
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Abstract

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It is shown that a variety ν has distributive congruence lattices if and only if the intersection of two principal congruence relations is definable by equations involving terms with parameters. The nature of the terms involved then provides a useful classification of congruence distributive varieties. In particular, the classification puts into proper perspective two stronger properties. A variety is said to have the Principal Intersection Property if the intersection of any two principal congruence relations is principal, or the Compact Intersection Property if the intersection of two compact congruence relations is compact. For non-congruence-distributive varieties, it is shown that some useful constuctions are nevertheless possible.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 1999

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