BRST invariant branching functions of G/H coset models

Abstract

We compute branching functions of $G/H$ coset models using a BRST invariant branching function formulae, i.e. a branching function that respects a BRST invariance of the model. This ensures that only the coset degrees of freedom will propagate. We consider $G/H$ for rank$(G/H)=0$ models which includes the Kazama-Suzuki construction, and $G_{k_1}\times G_{k_2}/G_{k_1+k_2}$ models. Our calculations here confirm in part previous results for those models which have been obtained under an assumption in a free field approach. We also consider $G_{k_1}\times H_{k_2}/H_{k_1+k_2}$, where $H$ is a subgroup of $G$, and $\prod_{a=1}^mG_{k_a}/G_{\sum_{a=1}^nk_a}$, whose branching functions, to our knowledge, has not been calculated before.