Directional dynamics along arbitrary curves in cellular automata

  • Authors:
  • M. Delacourt;V. Poupet;M. Sablik;G. Theyssier

  • Affiliations:
  • LIF, Aix-Marseille Université, CNRS, 39 rue Joliot-Curie, 13 013 Marseille, France;LIF, Aix-Marseille Université, CNRS, 39 rue Joliot-Curie, 13 013 Marseille, France;LATP, Université de Provence, CNRS, 39, rue Joliot-Curie, 13 453 Marseille Cedex 13, France;LAMA, Université de Savoie, CNRS, 73 376 Le Bourget-du-Lac Cedex, France

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2011

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Abstract

This paper studies directional dynamics on one-dimensional cellular automata, a formalism previously introduced by the third author. The central idea is to study the dynamical behavior of a cellular automaton through the conjoint action of its global rule (temporal action) and the shift map (spacial action): qualitative behaviors inherited from topological dynamics (equicontinuity, sensitivity, expansivity) are thus considered along arbitrary curves in space-time. The main contributions of the paper concern equicontinuous dynamics which can be connected to the notion of consequences of a word. We show that there is a cellular automaton with an equicontinuous dynamics along a parabola, but which is sensitive along any linear direction. We also show that real numbers that occur as the slope of a limit linear direction with equicontinuous dynamics in some cellular automaton are exactly the computably enumerable numbers.