On the Lattice of Subvarieties of the Wreath Product of the Variety of Semilattices and the Variety of Semigroups with Zero Multiplication

详细

It is known that the monoid wreath product of any two semigroup varieties that are atoms in the lattice of all semigroup varieties may have a finite as well as an infinite lattice of subvarieties. If this lattice is finite, then as a rule it has at most eleven elements. This was proved in a paper of the author in 2007. The exclusion is the monoid wreath product Sl w N₂ of the variety of semilattices and the variety of semigroups with zero multiplication. The number of elements of the lattice L(Sl w N₂) of subvarieties of Sl w N₂ is still unknown. In our paper, we show that the lattice L(Sl w N₂) contains no less than 33 elements. In addition, we give some exponential upper bound of the cardinality of this lattice.