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Published online by Cambridge University Press: 14 November 2011
The relations v1 and v2 defined on the lattice ℒ of varieties of inverse semigroups by v1
if and only if
and
v2
if and only if
, where
denotes tie variety of groups, are both congruences on ℒ the class
v1, is simply the lattice of varieties of grcups and is therefore known to have cardinality
.
The class v2 is precisely the sublattice of ℒ consisting of those varieties containing
. Each v1-class contains preciselyone element of
v2. The main result of this paper establishes that the sublattice
v2 of ℒ has breadth
. From this it follows that the lattice ℒ/v1 also has breadth
. Some consequences concerning varieties generated by fundamental inverse semigroups are also considered.