Directed complete poset congruences |
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Authors: | Mojgan Mahmoudi Halimeh Moghbeli Konrad Pióro |
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Affiliation: | 1. Department of Mathematics, Shahid Beheshti University, Tehran 19839, Iran;2. Department of Mathematics, Faculty of Science, University of Jiroft, Jiroft, Iran;3. Institute of Mathematics, University of Warsaw, ul. Banacha 2, Warsaw, PL-02-097, Poland |
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Abstract: | The study of algebraic properties of ordered structures has shown that their behavior in many cases is different from algebraic structures. For example, the analogues of the fundamental mapping theorem for sets which characterizes surjective maps as quotient sets modulo their kernel relations, is not true for order-preserving maps between posets (partially ordered sets). The main objective of this paper is to study the quotients of dcpos (directed complete partially ordered sets), and their relations with surjective dcpo maps (directed join preserving maps). The motivation of studying such infinitary ordered structures is their importance in domain theory, a theory on the borderline of mathematics and theoretical computer science.In this paper, introducing the notion of a pre-congruence on dcpos (directed complete partially ordered sets), we give a characterization of dcpo congruences. Also, it is proved that unlike natural dcpo congruences, the dcpo congruences are precisely kernels of surjective dcpo maps. Also, while it is known that the image of a dcpo map is not necessarily a subdcpo of its codomain, we find equivalent conditions on a dcpo map to satisfy this property. Moreover, we prove the Decomposition Theorem and its consequences for dcpo maps. |
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Keywords: | 06A11 06B10 06F99 08A02 08A30 18A32 Pre-congruence Dcpo congruence Directed complete partially ordered set Dcpo map Quotient |
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