### Abstract

We study Noether's problem for various subgroups H of the normalizer of a group Cs generated by an 8-cycle in 5s, the symmetric group of degree 8, in three aspects according to the way they act on rational function fields, i.e., ℚ(X_{0},. . ., X_{7}), ℚ(x_{1},. . .,x _{4}), and ℚ(x, y). We prove that it has affirmative answers for those H containing C_{8} properly and derive a ℚ-generic polynomial with four parameters for each H. On the other hand, it is known in connection to the negative answer to the same problem for C_{8}/ℚ that there does not exist a ℚ-generic polynomial for C_{8}. This leads us to the question whether and how one can describe, for a given field K of characteristic zero, the set of C_{8}-extensions L/K. One of the main results of this paper gives an answer to this question.

Original language | English |
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Pages (from-to) | 1153-1183 |

Number of pages | 31 |

Journal | Mathematics of Computation |

Volume | 77 |

Issue number | 262 |

DOIs | |

Publication status | Published - 2008 Apr 1 |

### ASJC Scopus subject areas

- Algebra and Number Theory
- Computational Mathematics
- Applied Mathematics

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## Cite this

_{8}and its subgroups.

*Mathematics of Computation*,

*77*(262), 1153-1183. https://doi.org/10.1090/S0025-5718-07-02094-7