Simple Toroidal Vertex Algebras and Their Irreducible Modules

In this paper, we continue the study on toroidal vertex algebras initiated in cite{LTW}, to study concrete toroidal vertex algebras associated to toroidal Lie algebra $L_{r}(hat{frak{g}})=hat{frak{g}}otimes L_r$, where $hat{frak{g}}$ is an untwisted affine Lie algebra and $L_r=$mathbb{C}[t_{1}^{pm 1},ldots,t_{r}^{pm 1}]$. We first construct an $(r+1)$-toroidal vertex algebra $V(T,0)$ and show that the category of restricted $L_{r}(hat{frak{g}})$-modules is canonically isomorphic to that of $V(T,0)$-modules.Let $c$ denote the standard central element of $hat{frak{g}}$ and set $S_c=U(L_r(mathbb{C}c))$. We furthermore study a distinguished subalgebra of $V(T,0)$, denoted by $V(S_c,0)$. We show that (graded) simple quotient toroidal vertex algebras of $V(S_c,0)$ are parametrized by a $mathbb{Z}^r$-graded ring homomorphism $psi:S_crightarrow L_r$ such that Im$psi$ is a $mathbb{Z}^r$-graded simple $S_c$-module. Denote by $L(psi,0}$ the simple $(r+1)$-toroidal vertex algebra of $V(S_c,0)$ associated to $psi$. We determine for which $psi$, $L(psi,0)$ is an integrable $L_{r}(hat{frak{g}})$-module and we then classify irreducible $L(psi,0)$-modules for such a $psi$. For our need, we also obtain various general results.