English

$\mathbb{A}^1$--connectedness of moduli stack of semi-stable and parabolic semi-stable vector bundles over a curve

Algebraic Geometry 2026-04-22 v3

Abstract

Let CC be an irreducible smooth projective curve of genus g2g\geq 2 over an algebraically closed field. We prove that the moduli stack of semi-stable vector bundles on CC of fixed rank and determinant is A1\mathbb{A}^1--connected. We also show that the moduli stack of quasi-parabolic vector bundles with a fixed determinant and a given quasi-parabolic data along a set of points in CC is A1\mathbb{A}^1-connected. Moreover, for small and generic weights α\boldsymbol{\alpha} with gcd(n,degL)=1\gcd(n, \deg L) = 1, the open substack of α\boldsymbol{\alpha}-semistable parabolic vector bundles is also A1\mathbb{A}^1-connected.

Keywords

Cite

@article{arxiv.2512.14464,
  title  = {$\mathbb{A}^1$--connectedness of moduli stack of semi-stable and parabolic semi-stable vector bundles over a curve},
  author = {Sujoy Chakraborty and Saurav Holme Choudhury},
  journal= {arXiv preprint arXiv:2512.14464},
  year   = {2026}
}

Comments

Substantial changes have been made in Section 2 to address a gap in the earlier version. The main result in Section 2 remains unchanged. In Section 3, some additional assumptions on weights have been added for the final theorem. Comments are welcome