Galois groups in rational conformal field theory II. The discriminant

We express the discriminant of the polynomial relations of the fusion ring, in any conformal field theory, as the product of the rows of the modular matrix to the power -2. The discriminant is shown to be an integer, always, which is a product of primes which divide the level. Detailed formulas for the discriminant are given for all WZW conformal field theories.Comment: 19 pages, one table. Minor typos correcte

On New Conformal Field Theories with Affine Fusion Rules

Some time ago, conformal data with affine fusion rules were found. Our purpose here is to realize some of these conformal data, using systems of free bosons and parafermions. The so constructed theories have an extended $W$ algebras which are close analogues of affine algebras. Exact character formulae is given, and the realizations are shown to be full fledged unitary conformal field theories.Comment: Minor correction in an example and some typo

Generalized Fusion Potentials

Recently, DiFrancesco and Zuber have characterized the RCFTs which have a description in terms of a fusion potential in one variable, and proposed a generalized potential to describe other theories. In this note we give a simple criterion to determine when such a generalized description is possible. We also determine which RCFTs can be described by a fusion potential in more than one variable, finding that in fact all RCFTs can be described in such a way, as conjectured by Gepner.Comment: TAUP-2029-93, 16 pages of plain Tex. (Added a reference

On The Characters of Parafermionic Field Theories

We study cosets of the type $H_l/U(1)^r$, where $H$ is any Lie algebra at level $l$ and rank $r$. These theories are parafermionic and their characters are related to the string functions, which are generating functions for the multiplicities of weights in the affine representations. An identity for the characters is described, which apply to all the algebras and all the levels. The expression is of the Rogers Ramanujan type. We verify this conjecture, for many algebras and levels, using Freudenthal Kac formula, which calculates the multiplicities in the affine representations, recursively, up to some grade. Our conjecture encapsulates all the known results about these string functions, along with giving a vast wealth of new ones.Comment: 13 pages. The fortran program ALGEBRA.for is available from the source file

Mirror Symmetry as a Gauge Symmetry

It is shown that in string theory mirror duality is a gauge symmetry (a Weyl transformation) in the moduli space of $N=2$ backgrounds on group manifolds, and we conjecture on the possible generalization to other backgrounds, such as Calabi-Yau manifolds.Comment: 11 page