A story of webs: the webs by conics on del Pezzo quartic surfaces and Gelfand-MacPherson's web of the spinor tenfold

TL;DR

This paper explores the intricate web structures associated with del Pezzo quartic surfaces and spinor varieties, revealing deep connections and generalizations of classical web properties and functional identities.

Contribution

It demonstrates that the web related to del Pezzo surfaces can be viewed as a quotient of a Gelfand-MacPherson web on spinor varieties, extending known web properties and introducing a new rank 5 web with a unique 2-abelian relation.

Findings

Many properties of Bol's web extend to the Gelfand-MacPherson web.

The Gelfand-MacPherson web acts as a natural generalization of Bol's web.

A new 2-abelian relation generalizes Abel's five-term relation.

Abstract

In a previous paper, we studied the web by conics $\boldsymbol{\mathcal W}_{{\rm dP}_4}$ on a del Pezzo quartic surface ${\rm dP}_4$ and proved that it enjoys suitable versions of most of the remarkable properties satisfied by Bol's web $\boldsymbol{\mathcal B}$. In particular, Bol's web can be seen as the toric quotient of the Gelfand-MacPherson web naturally defined on the $A_4$-grassmannian variety $G_2(\mathbf C^5)$ and we have shown that $\boldsymbol{\mathcal W}_{{\rm dP}_4}$ can be obtained in a similar way from the web $\boldsymbol{\mathcal W}^{GM}_{ \hspace{-0.05cm} \boldsymbol{\mathcal Y}_5}$ which is the quotient by the Cartan torus of ${\rm Spin}_{10}(\mathbf C)$, of the Gelfand-MacPherson 10-web naturally defined on the tenfold spinor variety $\mathbb S_5$, a peculiar projective homogenous variety of type $D_5$. In the present paper, by means of direct and explicit computations, we show that many of the remarkable similarities between $\boldsymbol{\mathcal B}$ and $\boldsymbol{\mathcal W}_{{\rm dP}_4}$ actually can be extended to, or from an opposite perspective, can be seen as coming from some similarities between Bol's web and $\boldsymbol{\mathcal W}^{GM}_{ \hspace{-0.05cm} \boldsymbol{\mathcal Y}_5}$. The latter web can be seen as a natural uniquely defined rank 5 generalization of Bol's web. In particular, it carries a peculiar 2-abelian relation, denoted by ${\bf HLOG}_{ \boldsymbol{\mathcal Y}_5}$, which appears as a natural generalization of Abel's five terms relation of the dilogarithm and from which one can recover the weight 3 hyperlogarithmic functional identity of any quartic del Pezzo surface.