Displaying similar documents to “Canonical divisors and the additivity of the Kodaira dimension for morphisms or relative dimension one”

Limit Weierstrass schemes on stable curves with 2 irreducible components

Marc Coppens, Letterio Gatto (2001)

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

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We are concerned with limits of Weierstrass points under degeneration of smooth curves to stable curves of non compact type, union of two irreducible smooth components meeting transversely at m ≥ 1 points. The case m = 1 having already been treated by Eisenbud and Harris in [8], we analyze the situation for m > 1 .

Curves with only triple ramification

Stefan Schröer (2003)

Annales de l'Institut Fourier

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We show that the set of smooth curves of genus g ≥ 0 admitting a branched covering X → ℙ 1 with only triple ramification points is of dimension at least max ( 2 g - 3 , g ) . In characteristic two, such curves have tame rational functions and an analog of Belyi’s Theorem applies to them.

Families of curves and alterations

A. Johan De Jong (1997)

Annales de l'institut Fourier

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In this article it is shown that any family of curves can be altered into a semi-stable family. This implies that if S is an excellent scheme of dimension at most 2 and X is a separated integral scheme of finite type over S , then X can be altered into a regular scheme. This result is stronger then the results of [ Smoothness, semi-stability and alterations to appear in Publ. Math. IHES]. In addition we deal with situations where a finite group acts.