Displaying similar documents to “Polynomial bounds for abelian groups of automorphisms”

On the automorphisms of surfaces of general type in positive characteristic, II

Edoardo Ballico (1994)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

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Here we give an upper polynomial bound (as function of K X 2 but independent on p ) for the order of a p -subgroup of A ⁢ u ⁢ t ⁢ X r ⁢ e ⁢ d with X minimal surface of general type defined over the field K with c ⁢ h ⁢ a ⁢ r ⁢ K = p > 0 . Then we discuss the non existence of similar bounds for the dimension as K -vector space of the structural sheaf of the scheme A ⁢ u ⁢ t ⁢ X .

Extension of maps defined on many fibres.

Miguel A. Barja, Juan Carlos Naranjo (1998)

Collectanea Mathematica

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Let S be a fibred surface. We prove that the existence of morphisms from non countably many fibres to curves implies, up to base change, the existence of a rational map from S to another surface fibred over the same base reflecting the properties of the original morphisms. Under some conditions of unicity base change is not needed and one recovers exactly the initial maps.