Generic Polynomials with Few Parameters |
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Authors: | Gregor Kemper |
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Affiliation: | a IWR, Universität Heidelberg, Im Neuenheimer Feld 368, 69 120, Heidelberg, Germany;b Fachbereich 06 Mathematik und Informatik, Universität Gesamthochschule Essen, Universitätsstr. 2, 45 117, Essen 1, Germany |
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Abstract: | We call a polynomial g(t1, . . . , tm,X ) over a field K generic for a group G if it has Galois group G as a polynomial inX , and if every Galois field extension N / L withK L and Gal(N / L) ≤ G arises as the splitting field of a suitable specializationg (λ1, . . . , λm, X) withλi L. We discuss how the rationality of the invariant field of a faithful linear representation leads to a generic polynomial which is often particularly simple and therefore useful. Then we consider various examples and applications in characteristic 0 and in positive characteristic. These include results on so-called vectorial polynomials and a generalization of an embedding criterion given by Abhyankar. We give recursive formulas for generic polynomials over a field of defining characteristic for the groups of upper unipotent and upper triangular matrices, and explicit formulae for generic polynomials for the groups GU2(q2) andGO3 (q). |
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