Weil representations of $U(n,n)({\mathbb{F}}_{q^2}/{\mathbb{F}}_q)$, $q>3$ odd via presentation and compatibility of methods

Abstract

In this article we construct Weil representations of quasi-split unitary groups $U(n,n)({\mathbb{F}}_{q^2}/{\mathbb{F}}_q)$ associated to quadratic extensions of finite fields. We define these representations by using an adequate presentation Bruhat like of those groups. More precisely, we define Weil representations of $U(n,n)({\mathbb{F}}_{q^2}/{\mathbb{F}}_q)$ associating to each generator a linear map of a suitable $\mathbb{C}$-vector space satisfying the relations of the aforementioned presentation. In addition, we also address the natural question on the compatibility of our representation of $U(n,n)({\mathbb{F}}_{q^2}/{\mathbb{F}}_q)$ with the classical one constructed by Gérardin.