Forbidding-enforcing systems (fe-systems) define classes of languages (fe-families) based on boundary conditions. We characterize f -families having not necessarily finite forbidders and prove that none of the Chomsky families of languages can be defined with an fe-system, hence, fe-systems provide a completely new way of defining classes of languages. We show that f -families map to f -familie...

In a recent paper with L. Q. Zamboni, the authors introduced the class of θ-episturmian words. An infinite word over A is standard θepisturmian, where θ is an involutory antimorphism of A∗, if its set of factors is closed under θ and its left special factors are prefixes. When θ is the reversal operator, one obtains the usual standard episturmian words. In this paper, we introduce and study θ-c...

A code over a group ring is defined to be a submodule of that group ring. For a code C over a group ring RG, C is said to be checkable if there is v ∈ RG such that C = {x ∈ RG : xv = 0}. In [6], Jitman et al. introduced the notion of code-checkable group ring. We say that a group ring RG is code-checkable if every ideal in RG is a checkable code. In their paper, Jitman et al. gave a necessary a...

Zusammenfassung As mathematical model for the evolutionary equations of species the masterequation is choiced. Two formulations will be demonstrated to include the changes of parameters into the masterequation that is, on the one hand, the formation of a second masterequation for the development of parameters, and, on the other hand, the use of the Wigner-distribution to describe the developmen...