Complexity of term representations of finitary functions

The clone of term operations of an algebraic structure consists of all operations that can be expressed by a term in the language of the structure. We consider bounds for the length and the height of the terms expressing these functions, and we show that these bounds are often robust against the change of the basic operations of the structure

Commutators in Completely Simple Semigroups

We obtain a characterization of the binary commutator on completely simple semigroups, using their Rees matrix representation. Consequently, we prove that a regular semigroup is nilpotent (solvable) if and only if it is simple, and all its $\mathcal{H}$-classes are nilpotent (solvable) groups

O polinomima u algebrama Maljceva

We establish several properties of higher commutators, which were introduced by A. Bulatov, in congruence permutable varieties. We use these commutators to prove that the clone of polynomial functions of a finite Mal’cev algebra whose congruence lattice is of height at most 2, can be described by a finite set of relations. For a finite nilpotent algebra of finite type that is a product of algebras of prime power order and generates congruence modular variety, we are able to show that the property of affine completeness is decidable. Moreover, polynomial equivalence problem has polynomial complexity in the length of the input polynomials.Ustanovljavamo osobine viˇsih komutatora, koje je uveo A. Bulatov, u kongruencijki permutabilnim varijetetima. Te komutatore koristimo da bi dokazali da se klon polinomijalnih funkcija konaˇcne Maljcevljeve algebre ˇcija je mreˇza kongruencija visine najviˇse dva moˇze opisati konaˇcnim skupom relacija. Za konaˇcne nilpotentne algebre konaˇcnog tipa koje su proizvod algebri koje imaju red stepena prostog broja i koje generiˇsu kongruencijki modularan varijetet pokazu-jemo da je osobina afine kompletnosti odluˇciva. Takod¯e, pokazujemo za istu klasu da problem polinomijalne ekvivalencije ima polinomnu sloˇzenost u zavisnosti od duˇzine unetih polinomijalnih terma

O polinomima u algebrama Maljceva

We establish several properties of higher commutators, which were introduced by A. Bulatov, in congruence permutable varieties. We use these commutators to prove that the clone of polynomial functions of a finite Mal’cev algebra whose congruence lattice is of height at most 2, can be described by a finite set of relations. For a finite nilpotent algebra of finite type that is a product of algebras of prime power order and generates congruence modular variety, we are able to show that the property of affine completeness is decidable. Moreover, polynomial equivalence problem has polynomial complexity in the length of the input polynomials.Ustanovljavamo osobine viˇsih komutatora, koje je uveo A. Bulatov, u kongruencijki permutabilnim varijetetima. Te komutatore koristimo da bi dokazali da se klon polinomijalnih funkcija konaˇcne Maljcevljeve algebre ˇcija je mreˇza kongruencija visine najviˇse dva moˇze opisati konaˇcnim skupom relacija. Za konaˇcne nilpotentne algebre konaˇcnog tipa koje su proizvod algebri koje imaju red stepena prostog broja i koje generiˇsu kongruencijki modularan varijetet pokazu-jemo da je osobina afine kompletnosti odluˇciva. Takod¯e, pokazujemo za istu klasu da problem polinomijalne ekvivalencije ima polinomnu sloˇzenost u zavisnosti od duˇzine unetih polinomijalnih terma