# A note on the codimension of the linear section of the Lagrangian-Grassmannian L(6,12)

## TL;DR

This paper investigates the codimension of the linear section of the Lagrangian-Grassmannian in a 12-dimensional symplectic space, revealing how the surjectivity of a contraction map depends on the field's characteristic.

## Contribution

It proves the characteristic-dependent surjectivity of a contraction map for n=6 and calculates the codimension of the associated linear section in all characteristics.

## Key findings

- Surjectivity of the contraction map depends on the characteristic of the base field.
- Calculated the codimension of the linear section for any characteristic.
- Identified the relationship between the contraction map and the geometry of the Lagrangian-Grassmannian.

## Abstract

Consider a $2n$-dimensional symplectic vector space $E$ over an arbitrary field $\mathbb{F}$. Given a contraction map $f: \wedge^n E \rightarrow \wedge^{n-2} E$ such that the Lagrangian--Grassmannian $L(n,2n)=G(n,2n)\cap{\mathbb P}(\ker f)$, where $\wedge^r E$ denotes the $r$-th exterior power of $E$ and ${\mathbb P}(\ker f)$ is the projectivization of $\ker f$. In this paper, for a symplectic vector space $E$ of dimension $n=6$, we prove that the surjectivity of the contraction map $f:\wedge^{6} E \rightarrow \wedge^{4} E$ depends on the characteristic of the base field and we calculate the codimension of the linear section ${\mathbb P}(\ker f)\subseteq {\mathbb P}(\wedge^{6}E)$ for any characteristic.