Abstract
We initiate the study of reducts of relational structures up to primitive positive interdefinability: After providing the tools for such a study, we apply these tools in order to obtain a classification of the reducts of the logic of equality. It turns out that there exists a continuum of such reducts. Equivalently, expressed in the language of universal algebra, we classify those locally closed clones over a countable domain which contain all permutations of the domain.
Citation
Manuel Bodirsky. Hubie Chen. Michael Pinsker. "The reducts of equality up to primitive positive interdefinability." J. Symbolic Logic 75 (4) 1249 - 1292, December 2010. https://doi.org/10.2178/jsl/1286198146
Information