Baily--Borel compactifications of period images and the b-semiampleness conjecture

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Main Authors: Bakker, Benjamin, Filipazzi, Stefano, Mauri, Mirko, Tsimerman, Jacob
Format: Preprint
Published: 2025
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author Bakker, Benjamin
Filipazzi, Stefano
Mauri, Mirko
Tsimerman, Jacob
author_facet Bakker, Benjamin
Filipazzi, Stefano
Mauri, Mirko
Tsimerman, Jacob
contents We address two questions related to the semiampleness of line bundles arising from Hodge theory. First, we prove there is a functorial compactification of the image of a period map of a polarizable integral pure variation of Hodge structures for which the Griffiths bundle extends amply. In particular the Griffiths bundle is semiample. We prove more generally that the Hodge bundle of a Calabi--Yau variation of Hodge structures is semiample subject to some extra conditions, and as our second result deduce the b-semiampleness conjecture and the existence of a functorial Hodge-theoretic compactification of moduli spaces of polarized Calabi--Yau varieties. The semiampleness results (and the construction of the Baily--Borel compactifications) crucially use o-minimal GAGA, and the deduction of the b-semiampleness conjecture uses work of Ambro and results of Kollár on the geometry of minimal lc centers to verify the extra conditions.
format Preprint
id arxiv_https___arxiv_org_abs_2508_19215
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Baily--Borel compactifications of period images and the b-semiampleness conjecture
Bakker, Benjamin
Filipazzi, Stefano
Mauri, Mirko
Tsimerman, Jacob
Algebraic Geometry
Complex Variables
Number Theory
Primary: 14D07. Secondary: 14E30, 14C30, 14J10, 03C64
We address two questions related to the semiampleness of line bundles arising from Hodge theory. First, we prove there is a functorial compactification of the image of a period map of a polarizable integral pure variation of Hodge structures for which the Griffiths bundle extends amply. In particular the Griffiths bundle is semiample. We prove more generally that the Hodge bundle of a Calabi--Yau variation of Hodge structures is semiample subject to some extra conditions, and as our second result deduce the b-semiampleness conjecture and the existence of a functorial Hodge-theoretic compactification of moduli spaces of polarized Calabi--Yau varieties. The semiampleness results (and the construction of the Baily--Borel compactifications) crucially use o-minimal GAGA, and the deduction of the b-semiampleness conjecture uses work of Ambro and results of Kollár on the geometry of minimal lc centers to verify the extra conditions.
title Baily--Borel compactifications of period images and the b-semiampleness conjecture
topic Algebraic Geometry
Complex Variables
Number Theory
Primary: 14D07. Secondary: 14E30, 14C30, 14J10, 03C64
url https://arxiv.org/abs/2508.19215