English

Higher direct images of the structure sheaf via the Hilbert-Chow morphism

Algebraic Geometry 2024-12-24 v2

Abstract

Let XX be a projective smooth surface over C\mathbb{C} with H2(OX)=0H^2(\mathcal{O}_X)=0. Let M=M(L,χ)M=M(L,\chi) be the moduli space of 1-dimensional semistable sheaves with determinant OX(L)\mathcal{O}_X(L) and Euler characteristic χ\chi. We have the Hilbert-Chow morphism π:ML\pi:M\rightarrow |L|. We give explicit forms of the higher direct images RiπOMR^i\pi_*\mathcal{O}_M under some mild conditions on MM and L|L|. Our result shows that RiπOMR^i\pi_*\mathcal{O}_M are direct sums of line bundles. In particular, using our result one gets explicit formulas for the Euler characteristic of πOL(m)\pi^*\mathcal{O}_{|L|}(m), which in X=P2X=\mathbb{P}^2 case was once conjectured by Chung-Moon.

Keywords

Cite

@article{arxiv.2412.10013,
  title  = {Higher direct images of the structure sheaf via the Hilbert-Chow morphism},
  author = {Yao Yuan},
  journal= {arXiv preprint arXiv:2412.10013},
  year   = {2024}
}

Comments

This version has generalized previous result and shortened the proof