On varieties of completely regular semigroups III.
Libor Polák (1988)
Semigroup forum
Alfonz Haviar, Roman Nedela (1998)
Discussiones Mathematicae Graph Theory
In this paper, we introduce the notion of a variety of graphs closed under isomorphic images, subgraph identifications and induced subgraphs (induced connected subgraphs) firstly and next closed under isomorphic images, subgraph identifications, circuits and cliques. The structure of the corresponding lattices is investigated.
David Stanovský (2004)
Discussiones Mathematicae - General Algebra and Applications
We describe a part of the lattice of subvarieties of left distributive left idempotent groupoids (i.e. those satisfying the identities x(yz) ≈ (xy)(xz) and (xx)y ≈ xy) modulo the lattice of subvarieties of left distributive idempotent groupoids. A free groupoid in a subvariety of LDLI groupoids satisfying an identity xⁿ ≈ x decomposes as the direct product of its largest idempotent factor and a cycle. Some properties of subdirectly ireducible LDLI groupoids are found.
Alfonz Haviar, Gabriela Monoszová (2001)
Discussiones Mathematicae Graph Theory
In this paper we investigate varieties of orgraphs (that is, oriented graphs) as classes of orgraphs closed under isomorphic images, suborgraph identifications and induced suborgraphs, and we study the lattice of varieties of tournament-free orgraphs.
Ján Jakubík (2003)
Czechoslovak Mathematical Journal
In this paper we investigate the relation between the lattice of varieties of pseudo -algebras and the lattice of varieties of lattice ordered groups.
N.R. Reilly, S. Zhang (1996)
Semigroup forum
Avapa Chantasartrassmee, Jörg Koppitz (2005)
Discussiones Mathematicae - General Algebra and Applications
he class of all M-solid varieties of a given type t forms a complete sublattice of the lattice ℒ(τ) of all varieties of algebrasof type t. This gives a tool for a better description of the lattice ℒ(τ) by characterization of complete sublattices. In particular, this was done for varieties of semigroups by L. Polák ([10]) as well as by Denecke and Koppitz ([4], [5]). Denecke and Hounnon characterized M-solid varieties of semirings ([3]) and M-solid varieties of groups were characterized by Koppitz...
K. Denecke, Jörg Koppitz (1995)
Archivum Mathematicum
Pre-hyperidentities generalize the concept of a hyperidentity. A variety is said to be pre-solid if every identity in is a pre-hyperidentity. Every solid variety is pre-solid. We consider pre-solid varieties of semigroups which are not solid, determine the smallest and the largest of them, and some elements in this interval.
Sarawut Phuapong, Sorasak Leeratanavalee (2011)
Discussiones Mathematicae - General Algebra and Applications
Generalized hypersubstitutions are mappings from the set of all fundamental operations into the set of all terms of the same language do not necessarily preserve the arities. Strong hyperidentities are identities which are closed under the generalized hypersubstitutions and a strongly solid variety is a variety which every its identity is a strong hyperidentity. In this paper we give an example of pre-strongly solid varieties of commutative semigroups and determine the least and the greatest pre-strongly...
F. Pastijn (1991)
Semigroup forum
Aleksandar Krapež (2013)
Publications de l'Institut Mathématique
M. Adams, Wiesław Dziobiak, Matthew Gould, Jürg Schmid (1995)
Fundamenta Mathematicae
Two properties of the lattice of quasivarieties of pseudocomplemented semilattices are established, namely, in the quasivariety generated by the 3-element chain, there is a sublattice freely generated by ω elements and there are quasivarieties.
Sarawut Phuapong, Sorasak Leeratanavalee (2011)
Matematički Vesnik
Petrich, Mario, Silva, Pedro V. (2000)
Beiträge zur Algebra und Geometrie
Jaroslav Ježek, Norbert Newrly, Jiří Tůma (1990)
Commentationes Mathematicae Universitatis Carolinae
Ján Jakubík (1990)
Czechoslovak Mathematical Journal
Danica Jakubíková-Studenovská (1997)
Czechoslovak Mathematical Journal
Jaroslav Ježek, Tomáš Kepka (2006)
Acta Universitatis Carolinae. Mathematica et Physica
David Stanovský (2011)
Acta Universitatis Carolinae. Mathematica et Physica
J. Almeida (1990)
Semigroup forum