… M a finite set of relations R yielding an undecidable word … EM, yielding an undecidable
identity problem using the … e which cause undecidability by non-implication from E, finite …

… Both these problems are known to be undecidable [11,4,3]. About the Emptiness problem,
we provide a new simple undecidability proof and prove that it is undecidable for automata …

It is shown that the universe problem L (A γ)= A* is undecidable for 4-state finite automata A
with integer weight function γ on its transitions. This holds even in the case, where A is …

… finite automata systems which have been introduced in [16]. Due to the close relation of PCFAs
to one-way multi-head finite automata… for one-way multi-head finite automata. To this end, …

Our model in this paper is a 1.5. way quantum finite automaton which can move its head 0 or+
1 position but not-1 position. It is shown that the most fundamental decision question, the …

… the nilpotency problem for cellular automata is unsolvable. … undecidable for NW-deterministic
Wang tile set. It follows that the finiteness problem for automaton semigroups is undecidable…

… when undecidable is no longer the simplest undecidable property. Lemma 4.1: There exist
undecidable propertie~ … L in Q..., if and only if the minimum state finite automaton accepting …

… theory and of automata theory. When languages of finite words are considered it is well
known that most problems about regular languages accepted by finite automata are decidable. …

… We shall also study the borderline between decidable and undecidable cases. Our second
technical result shows that the schedulability checking problem will be undecidable if the …

… A cellular automaton is a set of copies of the same finite automaton, in contrast with the
situation with neurons. They are also connected in a uniform way, each cell having the same kind …