Small Mathieu group coverings in characteristic two
نویسندگان
چکیده
منابع مشابه
Alternating group coverings of the affine line for characteristic two
Unramified coverings of the affine line in characteristic two are constructed having alternating groups as Galois groups. The proof uses Jacobson’s criterion for the Galois group of an equation to be contained in the alternating group. Alternative proofs use the Berlekamp discriminant or the Revoy discriminant. These are related to the Arf invariant.
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Let Aθ be the rotation C*-algebra for angle θ. For θ = p/q with p and q relatively prime, Aθ is the sub-C*-algebra of Mq(C(T )) generated by a pair of unitaries u and v satisfying uv = e2πiθvu. Let hθ,λ = u+u +λ/2(v+ v) be the almost Mathieu operator. By proving an identity of rational functions we show that for q even, the constant term in the characteristic polynomial of hθ,λ is (−1) q/2(1 + ...
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ژورنال
عنوان ژورنال: Proceedings of the American Mathematical Society
سال: 1995
ISSN: 0002-9939
DOI: 10.1090/s0002-9939-1995-1246511-9