On June 9, 2017 (Friday), at 1 p.m., in Room 578 of the Institute of Mathematics and Informatics, the new member of the Algebra and Logic Department, Assoc. Prof. Joerg Koppitz will deliver his inaugural public lecture on

FROM TOURNAMENTS TO LJAPIN'S IDENTITIES

Everybody is invited.

Abstract. We would like to draw an arc from the Graph Theory over transformation semigroups and completely regular semigroups until Birkhoff Theory. In this presentation, we will uncover a relationship between endomorphisms on tournaments and semigroups of order-preserving transformations. One can extend the idea of order-preserving transformations from chains to fences (zig-zag posets). Recently, coregular semigroups of fence-preserving transformations were studied. The concept of coregularity was introduced byTodorov and Bijev in the 80’s. Coregular semigroups are particular completely regular semigroups. But we will show how completely regular semigroups can be described by classes "next" to Birkhoff`s varieties (introduced by Ljapin) due to an idea by J. P. Aroujo (2015).