A Characterisation of a Class of Semigroups with Locally Commuting Idempotents

McAlister proved that a necessary and sufficient condition for a regular semigroup S to be locally inverse is that it can be embedded as a quasi-ideal in a semigroup T which satisfies the following two conditions: (1) T = TeT, for some idempotent e; and (2) eTe is inverse. We generalise this result to the class of semigroups with local units in which all local submonoids have commuting idempotents.     

On Weierstrass semigroups and sets: a review with new results

In this work we present a survey of the main results in the theory of Weierstrass semigroups at several points, with special attention to the determination of bounds for the cardinality of its set of gaps. We also review results on applications to the theory of error correcting codes. We then recall a generalization of the concept of Weierstrass semigroup, which is the Weierstrass set associated to a linear system and several points. We finish by presenting new results on this Weierstrass set, including some on the cardinality of its set of gaps.      

The nisio semigroup for controlled diffusions with partial observations

A one parameter semigroup of nonlinear operators on an appropriate Banach space is constructed in the spirit of Nisio for controlled diffusions with partial observations. The method is based upon considering an equivalent problem of controlling a measure-valued process representing the conditional law of the state given past observations. The latter evolves according to the usual equations of nonlinear filtering. By considering an appropriate augmentation of the class of controls, it is shown that the “minimum cost” operators associated with this control problem indeed form a semigroup of nonlinear contractions on the space of bounded continuous real-valued functions on the state space of the above measure-valued process.     

0-Minimal Quasi-ideals of Generalized Linear Transformation Semigroups

Abstract

For vector spaces V and W over a field F, L _F (V, W) denotes the set of all linear transformations α : V → W, and for a cardinal number k > 0, let L _F (V, W, k) be the set of all α ∈ L _F (V, W) of rank less than k. For θ ∈ L _F (W, V), let (L _F (V, W, k), θ) denote the semigroup L _F (V, W, k) under the operation ? defined by α ? β = αθβ for all α, β ∈ L _F (V, W, k). In this paper, all 0-minimal quasi-ideals of the semigroup (L _F (V, W, k), θ) are completely characterized. It is also shown from this characterization that every nonzero semigroup (L _F (V, W, k), θ) always has a 0-minimal quasi-ideal.     

α-次积分半群的Trotter-kato定理

§１．　ＩｎｔｒｏｄｕｃｔｉｏｎＷｈｅｎｗｅｉｎｔｅｇｒａｔｅｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａｔｉｏｎｓ,ｗｅｃａｎｆｏｒｍｕｌａｔｅｍａｎｙｏｆｔｈｅｍａｓａｎａｂｓｔｒａｃｔＣａｕｃｈｙｐｒｏｂｌｅｍ．ＡｎａｔｕｒａｌｑｕｅｓｔｉｏｎｉｎｔｈｅｔｈｅｏｒｙｉｓｔｏｆｉｎｄｓｕｉｔａｂｌｅｃｏｎｄｉｔｉｏｎｓｕｎｄｅｒｗｈｉｃｈａｓｅｑｕｅｎｃｅｏｆａａｂｓｔｒａｃｔＣａｕｃｈｙｐｒｏｂｌｅｍ．ｕ′ｎ＝Ａｎｕｎ（ｔ）,ｕｎ（０）＝ｘｎ,ｆｏｒｔ≥０,ｎ＝１,２,…ｉｎａｎａｒｂｔｉｒａｒｙＢａ…     

Approximation of local convoluted semigroups

We extend the Trotter-Kato theorem on C₀-semigroups to local convoluted semigroups on dual spaces and apply these results to the general Banach space setting. Compared to known results we obtain weaker convergence assumptions on the resolvent.     

Stability of Jensen functional equation on semigroups

In this paper we introduce a Jensen type functional equation on semigroups and study the Hyers-Ulam stability of this equation. It is proved that every semigroup can be embedded into a semigroup in which the Jensen equation is stable.     

Resolvents of operators and partial functional differential equations with nonautonomous past

To a backward evolution family on a Banach space X we associate an abstract differential operator G through the integral equation on a Banach space of X-valued functions on . We compute the resolvent of the restriction of this operator to a smaller domain to obtain a generator. We then apply the results to prove existence, exponential stability and exponential dichotomy of solutions to partial functional equations with nonautonomous past as discussed in [S. Brendle, R. Nagel, Dist. Contin. Dynam. Systems 8 (2002) 953-966]. Our main tools are spectral mapping theorems for evolution semigroups and hyperbolicity criteria.