Suppose that G is a locally compact abelian group, and write M(G) for the algebra of bounded, regular, complex-valued measures under convolution. A measure μ ∈ M(G) is said to be idempotent if μ ∗ μ = μ, or alternatively if μ̂ takes only the values 0 and 1. The Cohen-Helson-Rudin idempotent theorem states that a measure μ is idempotent if and only if the set {γ ∈ Ĝ : μ̂(γ) = 1} belongs to the cos...

In this article, we discuss the family of cellular automata generated by so-called idempotent cellular automata (CA G such that G 2 = G) on the full shift. We prove a characterization of products of idempotent CA, and show examples of CA which are not easy to directly decompose into a product of idempotents, but which are trivially seen to satisfy the conditions of the characterization. Our pro...

The order of hypersubstitutions, all idempotent elements on the monoid of all hypersubstitutions of type τ 2 were studied by K. Denecke and Sh. L. Wismath and all idempotent elements on the monoid of all hypersubstitutions of type τ 2, 2 were studied by Th. Changpas and K. Denecke. We want to study similar problems for the monoid of all generalized hypersubstitutions of type τ 2 . In this paper...

We consider a common generalization of the embedding and intersection problems for latin squares. Specifically, we extend the definition of embedding to squares whose sides do not meet the necessary condition for embedding and extend the intersection problem to squares of different orders. Results are given for arbitrary latin squares, and those which are idempotent and idempotent symmetric. Th...

A language L ⊆ A∗ is literally idempotent in case that uav ∈ L if and only if uav ∈ L, for each u, v ∈ A∗, a ∈ A. We already studied classes of such languages closely related to the (positive) varieties of the famous StraubingThérien hierarchy. In the present paper we start a systematic study of literal varieties of literally idempotent languages, namely we deal with the case of two letter alph...

We show that every (finite or not) typing derivation of system M, using non-idempotent intersection, which is the infinitary version of de Carvalho’s system M0, can be represented in a rigid, non-idempotent intersection type system S. Namely, whereas non-idempotent intersection is represented by multisets in system M, system S resort to families of types indexed by integers, called tracks. The ...