Let k be a global field of characteristic not 2, and let f is an element of k[X] be an irreducible polynomial. We show that a non-degenerate quadratic space has an isometry with minimal polynomial f if and only if such an isometry exists over all the completions of k. This gives a partial answer to a question of Milnor.
机构:
Tianjin Univ Technol, Dept Math, Tianjin 300384, Peoples R China
Nankai Univ, Sch Math Sci, Tianjin 300071, Peoples R ChinaTianjin Univ Technol, Dept Math, Tianjin 300384, Peoples R China