No abstract

Abstract:We define essential idempotents in group algebras and use them to prove that every mininmal abelian non-cyclic code is a repetition code. Also we use them to prove that every minimal abelian code is equivalent to a minimal cyclic code of the same length. Finally, we show that a binary cyclic code is simplex if and only if is of length of the form n = 2 k − 1 and is generated by an essential idempotent.

No abstract

No abstract

We dedicate this work to the memory of Sheila Brenner.Abstract: The purpose of this work is to show that if Λ a strongly simply connected semi-regular iterated tubular algebra and M is an indecomposable Λ-module then Λ[M ] is tame if and only if q Λ[M ] is weakly non negative.