The structure of surfaces and threefolds mapping to the moduli stack of canonically polarized varieties

Generalizing the well-known Shafarevich hyperbolicity conjecture, it has been conjectured by Viehweg that a quasi-projective manifold that admits a generically finite morphism to the moduli stack of canonically polarized varieties is necessarily of log general type. Given a quasi-projective threefol...

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Bibliographic Details
Published in:Duke mathematical journal 2010-10, Vol.155 (1), p.1-33
Main Authors: Kebekus, Stefan, Kovács, Sándor J.
Format: Article
Language:English
Subjects:
14D22
14J10
classification: algebraic theory
Families
Fine and coarse moduli spaces
moduli
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Summary:Generalizing the well-known Shafarevich hyperbolicity conjecture, it has been conjectured by Viehweg that a quasi-projective manifold that admits a generically finite morphism to the moduli stack of canonically polarized varieties is necessarily of log general type. Given a quasi-projective threefold Y ° that admits a nonconstant map to the moduli stack, we employ extension properties of logarithmic pluriforms to establish a strong relationship between the moduli map and the minimal model program of Y ° : in all relevant cases the minimal model program leads to a fiber space whose fibration factors the moduli map. A much-refined affirmative answer to Viehweg's conjecture for families over threefolds follows as a corollary. For families over surfaces, the moduli map can often be described quite explicitly. Slightly weaker results are obtained for families of varieties with trivial or more generally semiample canonical bundle.
ISSN:0012-7094
1547-7398
DOI:10.1215/00127094-2010-049