Local structure of the Hilbert scheme of conics in quintic del Pezzo varieties

Abstract

Let $X$ be the quintic del Pezzo $4$-fold. It is very well-known that $X$ is realized by a smooth linear section of Grassmannian $\mathrm{Gr}(2,5)$. In this paper, we prove that the Hilbert scheme of conics in $X$ is a smooth variety of dimension $7$ by using a torus action on $X$, which provides a more direct proof about the first named author's previous result.

v2: 17 pages, 3 tables, typos fixed, minor changes in preliminaries