Equivariant vertex coalgebras, $C_2$-coalgebras and duality for diagonalisable group schemes
Antoine Caradot, Zongzhu Lin
TL;DR
The paper develops a framework for vertex (co)algebras and their representation theory within the category of rational $G_\Gamma$-modules, introducing $(G_\Gamma,\beta,\gamma_0)$-vertex (co)algebras and their (co)modules and analyzing how a group-equivariant loop algebra and continuous distributions govern their structure. It extends Zhu-style $C_2$-constructions to the $G_\Gamma$-equivariant setting, defining $C_2$-algebras and $C_2$-coalgebras and proving that $R(V)$ carries a $\beta$-commutative Poisson algebra while $\mathcal{R}(V)$ carries a $\beta$-cocommutative co-Poisson coalgebra. A central result is a duality between vertex algebras and vertex coalgebras in this non-rigid ambient category, together with corresponding dualities for their $C_2$-objects and modules/comodules, yielding a rich interplay between algebraic and coalgebraic perspectives. The work provides a categorical blueprint for studying equivariant vertex structures over derived stacks and suggests avenues for derived vertex algebras and geometric invariant theory in this context. Overall, it unifies operator-distribution viewpoints with categorical and Poisson-theoretic structures in a diagonalisable-group setting, laying foundations for further representation-theoretic and geometric applications.
Abstract
In this paper, we define vertex algebras and vertex coalgebras in the category of rational $G_Γ$-modules, where $G_Γ$ is the group scheme defined by the group algebra $\mathsf k Γ$ for an abelian group $Γ$. In this context, we introduce the notion of $C_2$-coalgebra for a vertex coalgebra. We prove that there exists a duality between vertex algebras and vertex coalgebras in the category of $G_Γ$-modules, and this duality establishes a connection between $C_2$-algebras and $C_2$-coalgebras. Moreover, we also investigate the relationship between their respective modules/comodules.
