Simple toroidal vertex algebras and their irreducible modules

In this paper, we continue the study on toroidal vertex algebras initiated in [15], to study concrete toroidal vertex algebras associated to toroidal Lie algebra Lr(ĝ)=ĝ⊗Lr, where ĝ is an untwisted affine Lie algebra and Lr=C[t1±1,. .,tr±1]. We first construct an (r+. 1)-toroidal vertex algebra V(T, 0) and show that the category of restricted Lr(ĝ)-modules is canonically isomorphic to that of V(T, 0)-modules. Let c denote the standard central element of ĝ and set Sc=U(Lr(Cc)). We furthermore study a distinguished subalgebra of V(T, 0), denoted by V(Sc,0). We show that (graded) simple quotient toroidal vertex algebras of V(Sc,0) are parametrized by a Zr-graded ring homomorphism ψ:Sc→Lr such that Im. ψ is a Zr-graded simple Sc-module. Denote by L(ψ, 0) the simple quotient (r+ 1)-toroidal vertex algebra of V(Sc,0) associated to ψ. We determine for which ψ, L(ψ, 0) is an integrable Lr(ĝ)-module and we then classify irreducible L(ψ, 0)-modules for such a ψ. For our need, we also obtain various general results.