The Kodaira dimension and minimal models of π6
Abstract
We prove that the moduli space π6 of principally polarized abelian sixfolds has Kodaira dimension zero, determining the remaining case in the Kodaira classification of the spaces πg. More precisely, every nonzero scalar Siegel modular form of genus six, weight k and positive boundary order b satisfies kβ₯ 7b, with equality precisely for powers of the weight-fourteen harmonic theta series of Dittmann, Salvati Manni and Scheithauer. The canonical ring is therefore a polynomial ring on one generator of degree two. We also prove numerical dimension zero and construct the unique projective β-factorial terminal minimal model. Its Picard number is one and its canonical divisor has order two. The perfect cone compactification is a Mori dream space, and the birational automorphism group of π6 is trivial. The proof combines normal vanishing on the Prym locus, polar intersections on abelian boundary fibers, and an exact theta calculation. A discrepancy estimate recovers the modular open subset from the minimal model.
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BibTeX
@misc{wang2026kodaira,
title = {{The Kodaira dimension and minimal models of $\mathcalA_6$}},
author = {Haowu Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.40136},
eprint = {2610.40136},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.40136},
}
RIS
TY - UNPB
TI - The Kodaira dimension and minimal models of π_6
AU - Haowu Wang
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.40136
UR - https://arxiv.org/abs/2610.40136
AB - We prove that the moduli space π_6 of principally polarized abelian sixfolds has Kodaira dimension zero, determining the remaining case in the Kodaira classification of the spaces π_g. More precisely, every nonzero scalar Siegel modular form of genus six, weight k and positive boundary order b satisfies kβ₯ 7b, with equality precisely for powers of the weight-fourteen harmonic theta series of Dittmann, Salvati Manni and Scheithauer. The canonical ring is therefore a polynomial ring on one generator of degree two. We also prove numerical dimension zero and construct the unique projective β-factorial terminal minimal model. Its Picard number is one and its canonical divisor has order two. The perfect cone compactification is a Mori dream space, and the birational automorphism group of π_6 is trivial. The proof combines normal vanishing on the Prym locus, polar intersections on abelian boundary fibers, and an exact theta calculation. A discrepancy estimate recovers the modular open subset from the minimal model.
ER -