Kommutative Teilhabgruppen der Kompositionshalbgruppe von Polynomen und formalen Potenzreihen.
Komplementäre Halbgruppen Kongruenzen und Quotienten
Kongruenzen in Rechtsverbandshalbgruppen.
Krohn-Rhodes complexity pseudovarieties are not finitely based
We prove that the pseudovariety of monoids of Krohn-Rhodes complexity at most is not finitely based for all . More specifically, for each pair of positive integers , we construct a monoid of complexity , all of whose -generated submonoids have complexity at most .
Krohn-Rhodes complexity pseudovarieties are not finitely based
We prove that the pseudovariety of monoids of Krohn-Rhodes complexity at most n is not finitely based for all n>0. More specifically, for each pair of positive integers n,k, we construct a monoid of complexity n+1, all of whose k-generated submonoids have complexity at most n.
Kurepa's functional equation on semigroups.
The functional equation to which the title refers is:F(x,y) + F(xy,z) = F(x,yz) + F(y,z),where x, y and z are in a commutative semigroup S and F: S x S --> X with (X,+) a divisible abelian group (Divisibility means that for any y belonging to X and natural number n there exists a (unique) solution x belonging to X to nx = y).