منابع مشابه
Unramified Abelian Extensions of Galois Covers
We consider a ramified Galois cover φ : X̂ → Px of the Riemann sphere Px, with monodromy group G. The monodromy group over Px of the maximal unramified abelian exponent n cover of X̂ is an extension nG̃ of G by the group (Z/nZ), where g is the genus of X̂. Denote the set of linear equivalence classes of divisors of degree k on X̂ by Pic(X̂) = Pic. This is equipped with a natural G action. We show tha...
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Galois connections play a very important role in the theory of continuous lattices and their various generalizations. (See, for example, [1], [2], [a], [4], [5], [7] and [9].) Morphisms of continuous lattices, as defined in [2], are precisely those upper adjoints of Galois connections which preserve directed sups. In [1] Bandelf and Ernd suggested that the right choice of morphisms for Z-contin...
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This paper studies the structure of U(g)-Galois extensions. In particular, we use a result of Bell to construct a “PBW-like” free basis for faithfully flat U(g)-Galois extensions. We then move to non-faithfully flat extensions and propose a possible equivalent condition for a U(g)-extension to be Galois. We get a partial result for this.
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Let X → Y be a Galois covering of curves, where the genus of X is ≥ 2 and the genus of Y is ≤ 2. We prove that under certain hypotheses, X has an unramified cover that dominates a hyperelliptic curve; our results apply, for instance, to all tamely superelliptic curves. Combining this with a theorem of Bogomolov and Tschinkel shows that X has an unramified cover that dominates y = x − 1, if char...
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ژورنال
عنوان ژورنال: Journal of Algebra
سال: 1984
ISSN: 0021-8693
DOI: 10.1016/0021-8693(84)90103-0