# Achilles and the tortoise climbing up the hyper-arithmetical hiearchy

1 PROTHEO - Constraints, automatic deduction and software properties proofs
INRIA Lorraine, LORIA - Laboratoire Lorrain de Recherche en Informatique et ses Applications
Abstract : In this paper, we characterize the computational power of dynamical systems with piecewise constant derivatives (PCD) considered as computational machines working on a continuous real space with a continuous real time: we prove that piecewise constant derivative systems recognize precisely the languages of the ${\omega ^{k}} ^{th}$ (respectively: ${\omega ^{k}+1} ^{th}$) level of the hyper-arithmetical hierarchy in dimension $d=2k+3$ (respectively: $d=2k+4$), $k \ge 0$. Hence we prove that the reachability problem for PCD systems of dimension $d=2k+3$ (resp. $d=2k+4$), $k \ge 1$, is hyper-arithmetical and is $\Sigma_{\omega ^{k}}$-complete (resp. $\Sigma_{\omega ^{k}+1}$-complete).
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Journal articles
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https://hal.inria.fr/inria-00100818
Contributor : Publications Loria <>
Submitted on : Tuesday, September 26, 2006 - 2:51:33 PM
Last modification on : Friday, February 26, 2021 - 3:28:05 PM

### Identifiers

• HAL Id : inria-00100818, version 1

### Citation

Olivier Bournez. Achilles and the tortoise climbing up the hyper-arithmetical hiearchy. Theoretical Computer Science, Elsevier, 1999, 210 (1), pp.21-71. ⟨inria-00100818⟩

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