Periodicity and Immortality in Reversible Computing

Jarkko Kari (1) , Nicolas Ollinger (2)

1 FUNDIM - Departement of Mathematics, University of Turku
2 LIF - Laboratoire d'informatique Fondamentale de Marseille - UMR 6166

We investigate the decidability of the periodicity and the immortality problems in three models of reversible computation: reversible counter machines, reversible Turing machines and reversible one-dimensional cellular automata. Immortality and periodicity are properties that describe the behavior of the model starting from arbitrary initial configurations: immortality is the property of having at least one non-halting orbit, while periodicity is the property of always eventually returning back to the starting configuration. It turns out that periodicity and immortality problems are both undecidable in all three models. We also show that it is undecidable whether a (not-necessarily reversible) Turing machine with moving tape has a periodic orbit.

Mots clés: undecidability; counter machines; turing machines; cellular automata; immortality

Domaines: Autre [cs.OH]

Jarkko Kari, Nicolas Ollinger. Periodicity and Immortality in Reversible Computing. 2008. ⟨hal-00270815⟩