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Universal expansion of semigroup varieties by regular involution.

V. Koubek (1993)

Semigroup forum

Universal groups on semilattices of reversible cancellative semigroups .

K.E. Osondu (1991)

Semigroup forum

Universal semigroups.

Jakobsen, Per K., Lychagin, V.V. (2005)

Lobachevskii Journal of Mathematics

[unknown]

Klaus Denecke, Jörg Koppitz, Nittiya Pabhapote (2008)

Discussiones Mathematicae - General Algebra and Applications

A regular hypersubstitution is a mapping which takes every $n_{i}$ -ary operation symbol to an $n_{i}$ -ary term. A variety is called regular-solid if it contains all algebras derived by regular hypersubstitutions. We determine the greatest regular-solid variety of semigroups. This result will be used to give a new proof for the equational description of the greatest solid variety of semigroups. We show that every variety of semigroups which is finitely based by hyperidentities is also finitely based by identities....

Upper semicomplements and a definable element in the lattice of groupoid varieties

Jaroslav Ježek (1971)

Commentationes Mathematicae Universitatis Carolinae

Utilisation d'APL pour calculer des monoïdes finis

Jean-François Perrot (1977)

Mémoires de la Société Mathématique de France

Valuations of lines

Josef Mlček (1992)

Commentationes Mathematicae Universitatis Carolinae

We enlarge the problem of valuations of triads on so called lines. A line in an $e$ -structure $𝔸 = 〈 A, F, E 〉$ (it means that $〈 A, F 〉$ is a semigroup and $E$ is an automorphism or an antiautomorphism on $〈 A, F 〉$ such that $E \circ E = 𝐈𝐝 ↾ A$ ) is, generally, a sequence $𝔸 ↾ B$ , $𝔸 ↾ U_{c}$ , $c \in 𝐅𝐙$ (where $𝐅𝐙$ is the class of finite integers) of substructures of $𝔸$ such that $B \subseteq U_{c} \subseteq U_{d}$ holds for each $c \leq d$ . We denote this line as $𝔸 {(U_{c}, B)}_{c \in 𝐅𝐙}$ and we say that a mapping $H$ is a valuation of the line $𝔸 {(U_{c}, B)}_{c \in 𝐅𝐙}$ in a line $\hat{𝔸} {({\hat{U}}_{c}, \hat{B})}_{c \in 𝐅𝐙}$ if it is, for each $c \in 𝐅𝐙$ , a valuation of the triad $𝔸 (U_{c}, B)$ in $\hat{𝔸} ({\hat{U}}_{c}, \hat{B})$ . Some theorems on an existence of...