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A Stratification of the Semistable Locus

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Part of the Lecture Notes in Mathematics book series (LNM,volume 2122)

Abstract

Consider the following sublocus of \(\mathrm{Ch}^{-1}(\mathrm{Chow}_{d}^{\mathit{ss}}) \subset \mathrm{Hilb}_{d}\):

$$\displaystyle{ \mathrm{Ch}^{-1}(\mathrm{Chow}_{ d}^{\mathit{ss}})^{o}:=\{ [X \subset \mathbb{P}^{r}] \in \mathrm{Ch}^{-1}(\mathrm{Chow}_{ d}^{\mathit{ss}}) \subset \mathrm{Hilb}_{ d}\::\: X\text{ is connected}\}. }$$
(10.1)

If d > 2(2g − 2), the condition of being connected is both closed and open in \(\mathrm{Ch}^{-1}(\mathrm{Chow}_{d}^{\mathit{ss}})\): it is closed because of its natural interpretation as a topological condition; it is open because \([X \subset \mathbb{P}^{r}] \in \mathrm{Ch}^{-1}(\mathrm{Chow}_{d}^{\mathit{ss}})\) is a reduced curve by the Potential pseudo-stability Theorem 5.1 and therefore X is connected if and only if \(h^{0}(X,\mathcal{O}_{X}) = 1\), which is an open condition by upper-semicontinuity.

Keywords

  • Line Bundle
  • Automorphism Group
  • Algebraic Geometry
  • Disjoint Union
  • Order Relation

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Fig. 10.1
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Fig. 10.5
Fig. 10.6

Notes

  1. 1.

    Here there is an abuse of notation: W X, ρ (m) is referred to \([X \subset \mathbb{P}^{r}]\), while \(W_{X,\rho ^{{\ast}}}(m)\) is referred to \([X\stackrel{\vert \phi ^{{\ast}}L\vert }{\hookrightarrow }\mathbb{P}^{r}]\).

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Bini, G., Felici, F., Melo, M., Viviani, F. (2014). A Stratification of the Semistable Locus. In: Geometric Invariant Theory for Polarized Curves. Lecture Notes in Mathematics, vol 2122. Springer, Cham. https://doi.org/10.1007/978-3-319-11337-1_10

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