English

Torus quotient of the Grassmannian $G_{n,2n}$

Algebraic Geometry 2024-03-18 v2 Combinatorics Representation Theory

Abstract

Let Gn,2nG_{n,2n} be the Grassmannian parameterizing the nn-dimensional subspaces of C2n.\mathbb{C}^{2n}. The Picard group of Gn,2nG_{n,2n} is generated by a unique ample line bundle O(1).\mathcal{O}(1). Let TT be a maximal torus of SL(2n,C)SL(2n,\mathbb{C}) which acts on Gn,2nG_{n,2n} and O(1).\mathcal{O}(1). By \cite[Theorem 3.10, p.764]{Kum}, 22 is the minimal integer kk such that O(k)\mathcal{O}(k) descends to the GIT quotient. In this article, we prove that the GIT quotient of Gn,2nG_{n,2n} (n3n\ge 3) by TT with respect to O(2)=O(1)2\mathcal{O}(2)=\mathcal{O}(1)^{\otimes 2} is not projectively normal when polarized with the descent of O(2).\mathcal{O}(2).

Keywords

Cite

@article{arxiv.2111.00802,
  title  = {Torus quotient of the Grassmannian $G_{n,2n}$},
  author = {Arpita Nayek and Pinakinath Saha},
  journal= {arXiv preprint arXiv:2111.00802},
  year   = {2024}
}

Comments

11pages. arXiv admin note: text overlap with arXiv:2103.12621, arXiv:1906.09759 Due to the reviewer's feedback, the presentation style and final exposition of the paper were significantly revised