W. Eholzer et Np. Skoruppa, MODULAR INVARIANCE AND UNIQUENESS OF CONFORMAL CHARACTERS, Communications in Mathematical Physics, 174(1), 1995, pp. 117-136
We show that the conformal characters of various rational models of W-
algebras can be already uniquely determined if one merely knows the ce
ntral charge and the conformal dimensions. As a side result we develop
several tools for studying representations of SL(2, Z) on spaces of m
odular functions. These methods, applied here only to certain rational
conformal field theories, may be useful for the analysis of many othe
rs.