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Fibrations represented by double divisors on the base space

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Speaker: 
Klaus Altmann
Affiliation: 
Berlin
Date: 
Mon, 13/09/2010 - 12:00 - 12:50
Location: 
MPIM Lecture Hall

In two different situations we describe fibrations via divisors on the base space with rather unusual coefficients: First, branched coverings X -> P1 that are the quotient of the action of a finite group A can be encoded by a degree zero divisor on P1 with coefficients in A.
Second, degenerate toric fibrations X -> Y with generic fiber F = TV(sigma) (the toric variety associated to a cone sigma) correspond to a divisor on Y with coefficients being polyhedra in the space N of one-parameter subgroups of the torus.
In the latter case, the polyhedral coefficients can alternatively understood as divisors on modifications of the toric variety TV(sigma-dual). This is refered to by the name "double divisors" in the title.

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