Modularity and distributivity of tolerance lattices of commutative separative semigroups
We develop problems of monotonic valuations of triads. A theorem on monotonic valuations of triads of the type is presented. We study, using the notion of the monotonic valuation, representations of ideals by monotone and subadditive mappings. We prove, for example, that there exists, for each ideal of the type on a set , a monotone and subadditive set-mapping on with values in non-negative rational numbers such that . Some analogical results are proved for ideals of the types and...
∗ The research of the author was supported by the Alexander v. Humboldt-Stiftung.The basic concepts are M -hyperidentities, where M is a monoid of hypersubstitutions. The set of all M -solid varieties of semigroups forms a complete sublattice of the lattice of all varieties of semigroups. We fix some specific varieties V of commutative semigroups and study the set of all M -solid subvarieties of V , in particular, if V is nilpotent.