Computability and Beltrami fields in Euclidean space
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Inclou dades d'ús des de 2022
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hdl:2117/365660
Tipus de documentReport de recerca
Data publicació2022-11-15
Condicions d'accésAccés obert
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Abstract
In this article, we pursue our investigation of the connections between the theory of computation and hydrodynamics. We prove the existence of stationary solutions of the Euler equations in Euclidean space, of Beltrami type, that can simulate a universal Turing machine. In particular, these solutions possess undecidable trajectories. Heretofore, the known Turing complete constructions of steady Euler flows in dimension 3 or higher were not associated to a prescribed metric. Our solutions do not have finite energy, and their construction makes crucial use of the non-compactness of R3, however they can be employed to show that an arbitrary tape-bounded Turing machine can be robustly simulated by a Beltrami flow on T3 (with the standard flat metric). This shows that there exist steady solutions to the Euler equations on the flat torus exhibiting dynamical phenomena of (robust) arbitrarily high computational complexity. We also quantify the energetic cost for a Beltrami field on T3 to simulate a tape-bounded Turing machine, thus providing additional support for the space-bounded Church-Turing thesis. Another implication of our construction is that a Gaussian random Beltrami field on Euclidean space exhibits arbitrarily high computational complexity with probability 1. Finally, our proof also yields Turing complete flows and maps on S2 with zero topological entropy, thus disclosing a certain degree of independence within different hierarchies of complexity.
CitacióMiranda, E.; Peralta, D.; Cardona, R. Computability and Beltrami fields in Euclidean space. 2022.
Altres identificadorshttps://arxiv.org/abs/2111.03559
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