Simultaneous representations in categories of algebras |
| |
Authors: | M Petrich J Sichler V TrnkovÁ |
| |
Institution: | (1) Department of Mathematics, University of Manitoba, R3T 2N2 Winnipeg, Manitoba, Canada;(2) MÚUK, Sokolovskà 83, 186 00 Praha 8, Czechoslovakia |
| |
Abstract: | Hedrlin and Pultr proved that every small category is isomorphic to a full subcategory of the category Alg (Δ) of all algebras of type Δ whenever the sum ∑Δ of their arities satisfies ∑Δ>2. This article deals with simultaneous representation in categories of algebras, a generalization of the related question: given a subcategory k′ of a small category k, when does there exist an extension Δ′ of a type Δ with ∑Δ?2 such that k′ is a full subcategory of Alg(Δ′) while the Alg (Δ)-redacts of algebras representing k′ determine a category isomorphic to k? We characterize simultaneous representability by algebras and their reducts completely, and show that it is closely related to Isbell's dominion. A consequence of the main result states that algebraically representable pairs (k′, k) of one-object categories k′ k are exactly those for which k′ coincides with its dominion in k, and provides an alternative characterization of the dominion. Simultaneous representability by partial algebras is not subject to any such restriction. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|