Abstract
In this article we study the special fiber of the Rapoport–Zink space attached to a quaternionic unitary group. The special fiber is described using the so called Bruhat–Tits stratification and is intimately related to the Bruhat–Tits building of a split symplectic group. As an application we describe the supersingular locus of the related Shimura variety.
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Berthelot, P., Breen, L., Messing, W.: Messing, Théorie de Dieudonné Cristalline. II: Lecture Notes in Mathematics, vol. 930. Springer, Berlin (1982)
Bhatt, B., Scholze, P.: Projectivity of the Witt vector affine Grassmannian. Invent. Math. 209(2), 329–423 (2017)
Cho, S.: The basic locus of the unitary Shimura variety with parahoric level structure and special cycles. arXiv:1807.09997 (Preprint) (2018)
Chen, M.-F., Viehmann, E.: Affine Deligne–Lusztig varieties and the action of \(J\). J. Algebraic Geom. 27(2), 273–304 (2018)
Deligne, P., Lusztig, G.: Representations of reductive groups over finite fields. Ann. Math. (2) 103(1), 103–161 (1976)
Görtz, U., He, X.-H.: Basic loci of Coxeter type in Shimura varieties. Camb. J. Math. 3(3), 323–353 (2015)
Görtz, U., He, X.-H.: Erratum to: Basic loci in Shimura varieties of Coxeter type. Camb. J. Math. 3(3), 323–353 (2018)
Görtz, U., He, X.-H., Nie, S.-A.: Fully Hodge-Newton decomposable Shimura varieties. arXiv:1610.05381 (Preprint) (2016)
Görtz, U.: Stratifications of affine Deligne–Lusztig varieties. arXiv:1802.02225 (Preprint) (2018)
Helm, D.: Towards a geometric Jacquet–Langlands correspondence for unitary Shimura varieties. Duke Math. J. 155(3), 483–518 (2010)
Howard, B., Pappas, G.: On the supersingular locus of the \({\rm GU}(2,2)\) Shimura variety. Algebra Number Theory 8(7), 1659–1699 (2014)
Howard, B., Pappas, G.: Rapoport–Zink spaces for spinor groups. Compos. Math. 153(5), 1050–1118 (2017)
Helm, D., Tian, Y.-C., Xiao, L.: Tate cycles on some unitary Shimura varieties mod \(p\). Algebra Number Theory 11(10), 2213–2288 (2017)
Katsura, T., Oort, F.: Families of supersingular abelian surfaces. Compos. Math. 63(2), 107–167 (1987)
Kottwitz, R.: Points on some Shimura varieties over finite fields. J. Am. Math. Soc. 2, 373–444 (1985)
Kottwitz, R.: Isocrystals with additional structure. II. Compos. Math. 109(3), 225–339 (1997)
Kudla, S., Rapoport, M.: Cycles on Siegel threefolds and derivatives of Eisenstein series. Ann. Sci. École Norm. Sup. (4) 33(5), 695–756 (2000)
Kottwitz, R.: Isocrystals with additional structure. Compos. Math. 56(2), 201–220 (1985)
Madapusi Pera, K.: Integral canonical models for spin Shimura varieties. Compos. Math. 152(4), 769–824 (2016)
Norman, P., Oort, F.: Moduli of abelian varieties. Ann. Math. (2) 112(3), 413–439 (1980)
Oki, Y.: On the supersingular loci of Shimura varieties for quaternion unitary groups of degree 2. Master Thesis, The University of Tokyo. arXiv:1907.07026
Rapoport, M.: A guide to the reduction modulo \(p\) of Shimura varieties. Automorphic forms. I. Astérisque 298, 271–318 (2005)
Rapoport, M., Zink, T.: Period Spaces for \(p\)-Divisible Droups, Annals of Mathematics Studies, vol. 141, p. xxii+324. Princeton University Press, Princeton (1996)
Rapoport, M., Terstiege, U., Wilson, S.: The supersingular locus of the Shimura variety for \({\rm GU}(1, n-1)\) over a ramified prime. Math. Z. 276(3–4), 1165–1188 (2014)
Tits, J.: Reductive Groups Over Local Fields, Automorphic Forms, Representations and L-functions (Proc. Sympos. Pure Math., Oregon State Univ., Corvallis, Ore., 1977). American Mathematical Society, Providence (1979)
Van Hoften, P.: A geometric Jacquet–Langlands correspondence for paramodular Siegel threefolds. arXiv:1906.04008 (preprint) (2019)
Vollaard, I.: The supersingular locus of the Shimura variety for \({\rm GU}(1, s)\). Can. J. Math. 62(3), 668–720 (2010)
Vollaard, I., Wedhorn, T.: The supersingular locus of the Shimura variety of \({\rm GU}(1, n-1)\) II. Invent. Math. 184(3), 591–627 (2011)
Wang, H.-N.: On the Bruhat–Tits stratification for GU(2,2) type Rapoport–Zink space: unramified case. arXiv:1909.10902 (preprint) (2019)
Wang, H-.N.: On a quaternionic unitary Rapoport–Zink space with parahoric level structure. arXiv:1909.12263 (preprint) (2019)
Wang, H.-N.: Level lowering for GSp(4) and vanishing cycles on Siegel threefold. arXiv:1910.07569 (preprint) (2019)
Wu, H-F.: The supersingular locus of unitary Shimura varieties with exotic good reduction. PhD thesis, University of Duisburg-Essen. arXiv:1609.08775 (2016)
Yu, C.-F.: The supersingular loci and mass formulas on Siegel modular varieties. Doc. Math. 11, 449–468 (2006)
Yu, C.-F.: Geometry of the Siegel modular threefold with paramodular level structure. Proc. Am. Math. Soc. 139, 3181–3190 (2011)
Zink, T.: Windows for Displays of \(p\)-Divisible Groups, Moduli of Abelian Varieties (Texel Island, 1999) Progr. Math, vol. 196, pp. 491–518. Birkhäuser, Basel (2001)
Zhu, X.-W.: Affine Grassmannians and the geometric Satake in mixed characteristic. Ann. Math. (2) 185(2), 403–492 (2017)
Acknowledgements
The author would like to thank Henri Darmon for supporting his postdoctoral studies. He would like to thank Liang Xiao for many helpful conversations regarding to Shimura varieties and beyond. He is grateful to Ulrich Görtz for all the help and his comments on this article. He is inspired by reading many works of Chia-Fu Yu on Siegel modular varieties. He also would like to thank Ben Howard, Eyal Goren, Yichao Tian, Xu Shen and Benedict Gross for valuable discussions related to this article. He would like to thank the referees for carefully reading the article and pointing out all the corrections. While this article is being reviewed, Yasuhiro Oki obtained similar results about the supersingular locus of the quaternionic unitary Shimura variety independently. His method is completely different. He exploited the exceptional isomorphisms between the group \(\mathrm {GU}_{B}(2)\) and the non-split \(\mathrm {GSpin}(3,2)\). Then he embedded the non-split \(\mathrm {GSpin}(3,2)\) in the split \(\mathrm {GSpin}(4,2)\). This allows him to use the results of Howard-Pappas [11] mentioned before. We would like to thank Yoichi Mieda for sending Oki’s work to us.
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Communicated by Wei Zhang.
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Wang, H. On the Bruhat–Tits stratification of a quaternionic unitary Rapoport–Zink space. Math. Ann. 376, 1107–1144 (2020). https://doi.org/10.1007/s00208-019-01938-w
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DOI: https://doi.org/10.1007/s00208-019-01938-w