Displaying similar documents to “Normal cryptogroups with an associate subgroup”

Generalized F -semigroups

E. Giraldes, P. Marques-Smith, Heinz Mitsch (2005)

Mathematica Bohemica

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A semigroup S is called a generalized F -semigroup if there exists a group congruence on S such that the identity class contains a greatest element with respect to the natural partial order ≤ S of S . Using the concept of an anticone, all partially ordered groups which are epimorphic images of a semigroup ( S , · , ≤ S ) are determined. It is shown that a semigroup S is a generalized F -semigroup if and only if S contains an anticone, which is a principal order ideal of ( S , ≤ S ) . Also a characterization by means...

On left C - 𝒰 -liberal semigroups

Yong He, Fang Shao, Shi-qun Li, Wei Gao (2006)

Czechoslovak Mathematical Journal

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In this paper the equivalence 𝒬 ˜ U on a semigroup S in terms of a set U of idempotents in S is defined. A semigroup S is called a 𝒰 -liberal semigroup with U as the set of projections and denoted by S ( U ) if every 𝒬 ˜ U -class in it contains an element in U . A class of 𝒰 -liberal semigroups is characterized and some special cases are considered.

Good and very good magnifiers

Marin Gutan (2000)

Bollettino dell'Unione Matematica Italiana

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Un elemento a di un semigruppo S è un elemento accrescitivo sinistro se la traslazione λ a di S , associata all'elemento a , è surgettiva e non è iniettiva (E. S. Ljapin, [13], § 5). Così, per ogni elemento accrescitivo sinistro a , esiste un sottoinsieme proprio M di S tale che la restrizione a M di λ a è biunivoca. Se M è un sottosemigruppo (risp. un ideale destro) di S , l'elemento accrescitivo sinistro a viene detto buono (risp. molto buono) (F. Migliorini [15], [16], [17]). Utilizzando...

On finiteness conditions for Rees matrix semigroups

Hayrullah Ayik (2005)

Czechoslovak Mathematical Journal

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Let T = ℳ [ S ; I , J ; P ] be a Rees matrix semigroup where S is a semigroup, I and J are index sets, and P is a J × I matrix with entries from S , and let U be the ideal generated by all the entries of P . If U has finite index in S , then we prove that T is periodic (locally finite) if and only if S is periodic (locally finite). Moreover, residual finiteness and having solvable word problem are investigated.

On the theory of remediability

Hassan Emamirad (2003)

Banach Center Publications

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Suppose G ₁ ( t ) t ≥ 0 and G ₂ ( t ) t ≥ 0 are two families of semigroups on a Banach space X (not necessarily of class C₀) such that for some initial datum u₀, G₁(t)u₀ tends towards an undesirable state u*. After remedying by means of an operator ρ we continue the evolution of the state by applying G₂(t) and after time 2t we retrieve a prosperous state u given by u = G₂(t)ρG₁(t)u₀. Here we are concerned with various properties of the semigroup (t): ρ → G₂(t)ρG₁(t). We define (X) to be the space of remedial operators...

Is A - 1 an infinitesimal generator?

Hans Zwart (2007)

Banach Center Publications

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In this paper we study the question whether A - 1 is the infinitesimal generator of a bounded C₀-semigroup if A generates a bounded C₀-semigroup. If the semigroup generated by A is analytic and sectorially bounded, then the same holds for the semigroup generated by A - 1 . However, we construct a contraction semigroup with growth bound minus infinity for which A - 1 does not generate a bounded semigroup. Using this example we construct an infinitesimal generator of a bounded semigroup for which its...