Quadratic Level Quasigroup Equations With Four Variables II: the Lattice of Varieties
Quasiequational theories of flat algebras
We prove that finite flat digraph algebras and, more generally, finite compatible flat algebras satisfying a certain condition are finitely -based (possess a finite basis for their quasiequations). We also exhibit an example of a twelve-element compatible flat algebra that is not finitely -based.
Quasigroups, isotopic to a group
Quasivarieties of pseudocomplemented semilattices
Two properties of the lattice of quasivarieties of pseudocomplemented semilattices are established, namely, in the quasivariety generated by the 3-element chain, there is a sublattice freely generated by ω elements and there are quasivarieties.
Quelques applications des catégories à involution aux algèbres universelles