Resumen de Upper-modular elements of the lattice of semigroup varieties

B. M. Vernikov

• We completely determine all commutative semigroup varieties that are upper-modular elements of the lattice of all semigroup varieties. It is verified that if a semigroup variety is an upper-modular element of this lattice and different from the variety of all semigroups then it is a periodic variety and every nilsemigroup in the variety is commutative and satisfies the identity x2y = xy2.