PreprintCC BY 4.0arXiv
Special Loci in the Moduli of Curves
Abstract
We introduce new techniques to study mixed-characteristic special loci in moduli spaces and give several applications, focusing in particular on the moduli space Mg of curves. These applications include Zariski density results for split Jacobians, non-density results for supersingular loci, and lifting results for algebraic cycles, all under appropriate numerical conditions. Our methods generalize to more-or-less arbitrary moduli spaces mapping to Hodge-type Shimura varieties (and even some settings beyond the Shimura case), and relate to questions raised by Oort and de Jong.
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BibTeX
@misc{urbanik2026special,
title = {{Special Loci in the Moduli of Curves}},
author = {David Urbanik and Ziquan Yang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.08382},
eprint = {2610.08382},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.08382},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Special Loci in the Moduli of Curves
AU - David Urbanik
AU - Ziquan Yang
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.08382
UR - https://arxiv.org/abs/2610.08382
AB - We introduce new techniques to study mixed-characteristic special loci in moduli spaces and give several applications, focusing in particular on the moduli space M_g of curves. These applications include Zariski density results for split Jacobians, non-density results for supersingular loci, and lifting results for algebraic cycles, all under appropriate numerical conditions. Our methods generalize to more-or-less arbitrary moduli spaces mapping to Hodge-type Shimura varieties (and even some settings beyond the Shimura case), and relate to questions raised by Oort and de Jong.
ER -