Abstract
We introduce a preorder on an inverse semigroup S associated to any normal inverse subsemigroup N, that lies between the natural partial order and Green’s \({\mathcal {J}}\)–relation. The corresponding equivalence relation \(\simeq _N\) is not necessarily a congruence on S, but the quotient set does inherit a natural ordered groupoid structure. We show that this construction permits the factorisation of any inverse semigroup homomorphism into a composition of a quotient map and a star-injective functor, and that this decomposition implies a classification of congruences on S. We give an application to the congruence and certain normal inverse subsemigroups associate to an inverse monoid presentation.
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Communicated by Norman R. Reilly.
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Alyamani, N., Gilbert, N.D. Ordered groupoid quotients and congruences on inverse semigroups. Semigroup Forum 96, 506–522 (2018). https://doi.org/10.1007/s00233-017-9891-4
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DOI: https://doi.org/10.1007/s00233-017-9891-4