Home Mathematics Smooth Hilbert schemes: Their classification and geometry
Article
Licensed
Unlicensed Requires Authentication

Smooth Hilbert schemes: Their classification and geometry

  • and EMAIL logo
Published/Copyright: November 29, 2022

Abstract

Closed subschemes in projective space with a fixed Hilbert polynomial are parametrized by a Hilbert scheme. We classify the smooth ones. We identify numerical conditions on a polynomial that completely determine when the Hilbert scheme is smooth. We also reinterpret these smooth Hilbert schemes as generalized partial flag varieties and describe the subschemes being parametrized.

Funding statement: Gregory G. Smith was partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Knut and Alice Wallenberg Foundation.

Acknowledgements

We thank Dave Anderson, Sam Payne, Mike Roth, Mike Stillman, and an anonymous referee for their suggestions. Computational experiments done in Macaulay2 [10] were indispensable.

References

[1] A. Beauville, Variétés Kähleriennes dont la première classe de Chern est nulle, J. Differential Geom. 18 (1983), no. 4, 755–782. 10.4310/jdg/1214438181Search in Google Scholar

[2] W. Bruns and J. Herzog, Cohen–Macaulay rings, Cambridge Stud. Adv. Math. 39, Cambridge University, Cambridge 1993. Search in Google Scholar

[3] J. Cheah, Cellular decompositions for nested Hilbert schemes of points, Pacific J. Math. 183 (1998), no. 1, 39–90. 10.2140/pjm.1998.183.39Search in Google Scholar

[4] D. Chen, I. Coskun and S. Nollet, Hilbert scheme of a pair of codimension two linear subspaces, Comm. Algebra 39 (2011), no. 8, 3021–3043. 10.1080/00927872.2010.498396Search in Google Scholar

[5] P. Ellia, A. Hirschowitz and E. Mezzetti, On the number of irreducible components of the Hilbert scheme of smooth space curves, Internat. J. Math. 3 (1992), no. 6, 799–807. 10.1142/S0129167X92000369Search in Google Scholar

[6] J. Fogarty, Algebraic families on an algebraic surface, Amer. J. Math. 90 (1968), 511–521. 10.2307/2373541Search in Google Scholar

[7] W. Fulton, Intersection theory, 2nd ed., Ergeb. Math. Grenzgeb. (3) 2, Springer, Berlin 1998. 10.1007/978-1-4612-1700-8Search in Google Scholar

[8] G. Gotzmann, Eine Bedingung für die Flachheit und das Hilbertpolynom eines graduierten Ringes, Math. Z. 158 (1978), no. 1, 61–70. 10.1007/BF01214566Search in Google Scholar

[9] R. L. Graham, D. E. Knuth and O. Patashnik, Concrete mathematics, 2nd ed., Addison-Wesley, Reading 1994. Search in Google Scholar

[10] D. R. Grayson and M. E. Stillman, Macaulay2, a software system for research in algebraic geometry, available at http://www.math.uiuc.edu/Macaulay2/. Search in Google Scholar

[11] I. Grojnowski, Instantons and affine algebras. I. The Hilbert scheme and vertex operators, Math. Res. Lett. 3 (1996), no. 2, 275–291. 10.4310/MRL.1996.v3.n2.a12Search in Google Scholar

[12] A. Grothendieck and J. A. Dieudonné, Éléments de géométrie algébrique. I, Grundlehren Math. Wiss. 166, Springer, Berlin 1971. Search in Google Scholar

[13] M. Haiman, Hilbert schemes, polygraphs and the Macdonald positivity conjecture, J. Amer. Math. Soc. 14 (2001), no. 4, 941–1006. 10.1090/S0894-0347-01-00373-3Search in Google Scholar

[14] R. Hartshorne, Connectedness of the Hilbert scheme, Publ. Math. Inst. Hautes Études Sci. 29 (1966), 5–48. 10.1007/BF02684803Search in Google Scholar

[15] N. M. Katz and B. Mazur, Arithmetic moduli of elliptic curves, Ann. of Math. Stud. 108, Princeton University, Princeton 1985. 10.1515/9781400881710Search in Google Scholar

[16] J. Kollár, Rational curves on algebraic varieties, Ergeb. Math. Grenzgeb. (3) 32, Springer, Berlin 1996. 10.1007/978-3-662-03276-3Search in Google Scholar

[17] K. H. Lin, When are Hilbert schemes smooth?, MathOverflow, Question 244, https://mathoverflow.net/q/244, 2009. Search in Google Scholar

[18] F. S. Macaulay, Some properties of enumeration in the theory of modular systems, Proc. Lond. Math. Soc. (2) 26 (1927), 531–555. 10.1112/plms/s2-26.1.531Search in Google Scholar

[19] I. G. Macdonald, Symmetric functions and Hall polynomials, 2nd ed., Oxford Class. Texts Phys. Sci., The Clarendon, New York 2015. Search in Google Scholar

[20] D. Mumford, Further pathologies in algebraic geometry, Amer. J. Math. 84 (1962), 642–648. 10.1007/978-1-4757-4265-7_26Search in Google Scholar

[21] H. Nakajima, Heisenberg algebra and Hilbert schemes of points on projective surfaces, Ann. of Math. (2) 145 (1997), no. 2, 379–388. 10.2307/2951818Search in Google Scholar

[22] I. Peeva and M. Stillman, The minimal free resolution of a Borel ideal, Expo. Math. 26 (2008), no. 3, 237–247. 10.1016/j.exmath.2007.10.003Search in Google Scholar

[23] R. Piene and M. Schlessinger, On the Hilbert scheme compactification of the space of twisted cubics, Amer. J. Math. 107 (1985), no. 4, 761–774. 10.2307/2374355Search in Google Scholar

[24] R. Ramkumar, Hilbert schemes with few borel-fixed points, preprint (2019), https://arxiv.org/abs/1907.13335; to appear in J. Algebra. Search in Google Scholar

[25] A. Reeves and M. Stillman, Smoothness of the lexicographic point, J. Algebraic Geom. 6 (1997), no. 2, 235–246. Search in Google Scholar

[26] A. A. Reeves, The radius of the Hilbert scheme, J. Algebraic Geom. 4 (1995), no. 4, 639–657. Search in Google Scholar

[27] A. P. Staal, The ubiquity of smooth Hilbert schemes, Math. Z. 296 (2020), no. 3–4, 1593–1611. 10.1007/s00209-020-02479-8Search in Google Scholar

[28] A. P. Staal, Hilbert schemes with two borel-fixed points in arbitrary characteristic, preprint (2021), https://arxiv.org/abs/2107.02204. Search in Google Scholar

[29] R. Vakil, Murphy’s law in algebraic geometry: Badly-behaved deformation spaces, Invent. Math. 164 (2006), no. 3, 569–590. 10.1007/s00222-005-0481-9Search in Google Scholar

Received: 2022-02-16
Revised: 2022-05-01
Published Online: 2022-11-29
Published in Print: 2023-01-01

© 2022 Walter de Gruyter GmbH, Berlin/Boston

Downloaded on 22.3.2026 from https://www.degruyterbrill.com/document/doi/10.1515/crelle-2022-0083/html
Scroll to top button