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Gergő Gyenizse (University of Szeged): Digraph powers and congruence permutability 



Wednesday, 15. September 2021, 10:00  12:00


Abstract. I sketch a semantical proof that congruence permutability is prime in the lattice of interpretability types of varieties. This proof settles a 1984 conjecture of Garcia and Taylor. The main ingredient of the proof is an entirely combinatorial statement: given two digraphs G and H so that each contains a universal vertex, there is a nonempty graph X so that G^X and H^X are isomorphic. 
Location : Riesz Lecture Hall, 1st Floor, Bolyai Institute, Aradi Vértanúk tere 1., Szeged 
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