Abstract. We completely determine all lower-modular elements of the lattice of all semigroup varieties. As a corollary, we show that a lower-modular element of this lattice is modular.
AMS Subject Classification
(1991): 20M07, 08B15
lattice of varieties,
Received February 24, 2010, and in final form May 6, 2010. (Registered under 15/2010.)