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In a recent paper (2018), D. Hofmann, R. Neves and P. Nora proved that the dual of the category of compact ordered spaces and monotone continuous maps is a quasi-variety -not finitary, but bounded by $\aleph_1$. An open question was: is it also a variety? We show that the answer is affirmative. We describe the variety by means of a set of finitary operations, together with an operation of countably infinite arity, and equational axioms. The dual equivalence is induced by the dualizing object [0,1].
@article{TAC_2019_34_a43, author = {Marco Abbadini}, title = {The dual of compact ordered spaces is a variety}, journal = {Theory and applications of categories}, pages = {1401--1439}, publisher = {mathdoc}, volume = {34}, year = {2019}, language = {en}, url = {http://geodesic.mathdoc.fr/item/TAC_2019_34_a43/} }
Marco Abbadini. The dual of compact ordered spaces is a variety. Theory and applications of categories, Tome 34 (2019), pp. 1401-1439. http://geodesic.mathdoc.fr/item/TAC_2019_34_a43/