On the slope of fibred surfaces

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dc.contributor	Universitat Politècnica de Catalunya. Departament de Matemàtica Aplicada I
dc.contributor	Universitat Politècnica de Catalunya. EGSA - Equacions Diferencials, Geometria, Sistemes Dinàmics i de Control, i Aplicacions
dc.contributor.author	Barja Yáñez, Miguel Ángel
dc.contributor.author	Zucconi, Franco
dc.date	2000
dc.identifier.uri	http://hdl.handle.net/2117/815
dc.language.iso	eng
dc.rights	Attribution-NonCommercial-NoDerivs 2.5 Spain
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	http://creativecommons.org/licenses/by-nc-nd/2.5/es/
dc.subject	Geometry, Algebraic
dc.subject	Surfaces
dc.subject	fibred surfaces
dc.subject	Fibrats (Matemàtica)
dc.subject	Superfícies
dc.subject	Varietats (Matemàtica)
dc.subject	Classificació AMS::14 Algebraic geometry::14D Families, fibrations
dc.subject	Classificació AMS::14 Algebraic geometry::14J Surfaces and higher-dimensional varieties
dc.title	On the slope of fibred surfaces
dc.type	info:eu-repo/semantics/article
dc.description.abstract	We give an asymptotically sharp lower bound for the slope $\lambda (f)$ of a fibration $f:S\longrightarrow B$, where $S$ is a surface and $B$ is a curve, if there exists an involution on the general fibre $F$ of $f$. We also construct a new lower bound of $\lambda (f)$ depending increasingly on the irregularity of $S$; as an application of this new bound we have a criteria to control the existence of other fibrations on $S$.