Abstract
We introduce a class of normal complex spaces having only mild singularities (close to quotient singularities) for which we generalize the notion of a (analytic) fundamental class for an analytic cycle and also the notion of a relative fundamental class for an analytic family of cycles. We also generalize to these spaces the geometric intersection theory for analytic cycles with rational positive coefficients and show that it behaves well with respect to analytic families of cycles. We prove that this intersection theory has most of the usual properties of the standard geometric intersection theory on complex manifolds, but with the exception that the intersection cycle of two cycles with positive integral coefficients that intersect properly may have rational coefficients.
Similar content being viewed by others
Notes
This means that the space is locally isomorphic to a quotient of a complex manifold by a finite group of automorphisms.
For the notion of a current on a reduced complex space see for example [4].
See theorem IV.3.3.1 in [4]; “very general” means outside a countable union of locally closed analytic subsets with no interior point.
Holomorphic simply means that the family of cycles \((\varphi (y))_{y \in N}\) is analytic; see [4] ch.IV for a definition.
The space \({\tilde{Z}}\) is pure dimensional, and the map \(\pi \) is proper, finite and surjective but not geometrically flat in general.
This open set is constructed by removing finitely many times a nowhere dense analytic subset in the previous open dense subset. A section of the sheaf \(\underline{H}_{Y}^{p}(\omega _{M}^{p})\) is determined by its restriction to an open set of this kind.
This reduces to show that the natural map \((\mathcal {O}_{S,s}\hat{\otimes }_{{{\mathrm{\mathbb {C}}}}}\mathcal {O}_{M,q(x)})\otimes _{\mathcal {O}_{M,q(x)}}\mathcal {O}_{{\tilde{M}},x} \longrightarrow \mathcal {O}_{S,s}\hat{\otimes }_{{{\mathrm{\mathbb {C}}}}}\mathcal {O}_{{\tilde{M}},x}\) is an isomorphism for every (s, x) in \(S\times {\tilde{M}}\), which is straightforward. Here \(\hat{\otimes }_{{{\mathrm{\mathbb {C}}}}}\) denotes the completed tensor product.
They will be found in the book [5].
Note that, as N is normal, this just means that f is equidimensional.
References
Barlet, D.: Espace analytique réduit des cycles analytiques compacts d’un espace analytique complexe de dimension finie, in Sém. F. Norguet II, Lecture Notes, vol. 482, pp. 1–158. Springer, New York (1975)
Barlet, D.: Le faisceau \(\omega_{X}^{\bullet }\) sur un espace complexe réduit de dimension pure, in Sém. F. Norguet III, Lecture Notes, vol. 670, pp. 187–204. Springer, New York (1978)
Barlet, D.: Familles analytiques de cycles et classes fondamentales relatives, in Sém. F. Norguet IV, Lecture Notes, vol. 807, pp. 1–24. Springer, New York (1980)
Barlet, D., Magnússon, J.: Cycles analytiques I: théorèmes de préparation des cycles. Cours spécialisés 22, SMF (2014)
Barlet, D., Magnússon, J.: Cycles analytiques complexes II. Cours spécialiés of the SMF (to appear)
Campana, F., Peternell, T.: Cycle Spaces, Several Complex Variables-Enc. Math, vol. 74. Springer, New York (1994)
Draper, R.: Intersection theory in complex analytic geometry. Math. Ann. 180, 175–204 (1969)
Fulton, W.: Intersection Theory, 2nd edn. Springer, Berlin (1998)
Fulton, W., MacPherson, R.: Defining algebraic intersections. In: Proceeding of Symposium on Algebraic Geometry. University Tromsö, Tromsö, 1977), pp. 1–30, Lecture Notes in Math., vol. 687, Springer, Berlin, (1978)
Greb, D., Kebekus, S., Kovacs, S., Peternell, T.: Differential forms on log canonical spaces. Publ. Math. Inst. Hautes Etudes Sci. No. 114, 87–169 (2011)
Kollár, J.: Lectures on Resolution of Singularities. Priceton University Press, Priceton (2009)
Tworzewski, P.: Intersection theory in complex analytic geometry. Ann. Polon. Math. 62(2), 177–191 (1995)
Acknowledgements
The authors would like to thank the referee for comments that lead to improvements of the paper.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Barlet, D., Magnússon, J. On nearly smooth complex spaces. Math. Z. 292, 317–341 (2019). https://doi.org/10.1007/s00209-018-2202-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00209-018-2202-2
Keywords
- Quotient singularity
- The sheaf \(\omega _{X}^{\bullet }\)
- Fundamental class of cycles
- Analytic family of cycles
- Geometric intersection theory