Algebra in superextensions of groups, I: zeros and commutativity

• Published in: Algebra and Discrete Mathematics
• Date: 2008
• Main Authors: Banakh, T.T., Gavrylkiv, V., Nykyforchyn, O.
• Format: Article
• Language: English
• Published: Інститут прикладної математики і механіки НАН України 2008
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/153373
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Algebra in superextensions of groups, I: zeros and commutativity / T.T. Banakh, V. Gavrylkiv, O. Nykyforchyn // Algebra and Discrete Mathematics. — 2008. — Vol. 7, № 3. — С. 1–29. — Бібліогр.: 13 назв. — англ.

Given a group X we study the algebraic structure of its superextension λ(X). This is a right-topological semigroup consisting of all maximal linked systems on X endowed with the operation A∘B={C⊂X:{x∈X:x−1C∈B}∈A} that extends the group operation of X. We characterize right zeros of λ(X) as invariant maximal linked systems on X and prove that λ(X) has a right zero if and only if each element of X has odd order. On the other hand, the semigroup λ(X) contains a left zero if and only if it contains a zero if and only if X has odd order |X|≤5. The semigroup λ(X) is commutative if and only if |X|≤4. We finish the paper with a complete description of the algebraic structure of the semigroups λ(X) for all groups X of cardinality |X|≤5.