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On the Jacobson radical of graded rings

Andrei V. Kelarev (1992)

Commentationes Mathematicae Universitatis Carolinae

All commutative semigroups S are described such that the Jacobson radical is homogeneous in each ring graded by S .

On the K-theory of the C * -algebra generated by the left regular representation of an Ore semigroup

Joachim Cuntz, Siegfried Echterhoff, Xin Li (2015)

Journal of the European Mathematical Society

We compute the K -theory of C * -algebras generated by the left regular representation of left Ore semigroups satisfying certain regularity conditions. Our result describes the K -theory of these semigroup C * -algebras in terms of the K -theory for the reduced group C * -algebras of certain groups which are typically easier to handle. Then we apply our result to specific semigroups from algebraic number theory.

On the lattice of congruences on inverse semirings

Anwesha Bhuniya, Anjan Kumar Bhuniya (2008)

Discussiones Mathematicae - General Algebra and Applications

Let S be a semiring whose additive reduct (S,+) is an inverse semigroup. The relations θ and k, induced by tr and ker (resp.), are congruences on the lattice C(S) of all congruences on S. For ρ ∈ C(S), we have introduced four congruences ρ m i n , ρ m a x , ρ m i n and ρ m a x on S and showed that ρ θ = [ ρ m i n , ρ m a x ] and ρ κ = [ ρ m i n , ρ m a x ] . Different properties of ρθ and ρκ have been considered here. A congruence ρ on S is a Clifford congruence if and only if ρ m a x is a distributive lattice congruence and ρ m a x is a skew-ring congruence on S. If η (σ) is the least distributive...

On the maximal subsemigroups of the semigroup of all monotone transformations

Iliya Gyudzhenov, Ilinka Dimitrova (2006)

Discussiones Mathematicae - General Algebra and Applications

In this paper we consider the semigroup Mₙ of all monotone transformations on the chain Xₙ under the operation of composition of transformations. First we give a presentation of the semigroup Mₙ and some propositions connected with its structure. Also, we give a description and some properties of the class J ̃ n - 1 of all monotone transformations with rank n-1. After that we characterize the maximal subsemigroups of the semigroup Mₙ and the subsemigroups of Mₙ which are maximal in J ̃ n - 1 .

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