A sharp bound for the slope of double cover fibrations

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dc.creatorCornalba, M.
dc.creatorStoppino, L.
dc.date2005-10-07
dc.date2008-01-17
dc.date.accessioned2026-07-07T12:29:16Z
dc.date.available2026-07-07T12:29:16Z
dc.descriptionLet f: X->B be a fibred surface of genus g whose general fibre is a double cover of a smooth curve of genus gamma. We show that, for g > 4gamma+1, the number 4(g-1)/(g-gamma) is a sharp lower bound for the slope of f, proving a conjecture of Barja. Moreover, we give a characterisation of the fibred surfaces that reach the bound. In the case g = 4gamma+1 we obtain the same sharp bound under the assumption that the involutions on the general fibres glue to a global involution on X.
dc.description13 pages, revised version
dc.identifierhttps://arxiv.org/abs/math/0510144
dc.identifierhttp://arxiv.org/abs/math/0510144
dc.identifierMichigan Math. J. 56 (2008), 551-561
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/215816
dc.subjectAlgebraic Geometry
dc.titleA sharp bound for the slope of double cover fibrations
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