We define a conformal subalgebra of a Kac-Moody algebra as a subalgebra which has the same Sugawara conformal generator as the algebra in which it is embedded. This guarantees the preservation of conformal invariance, for instance, in the recently proposed construction of bosonic strings with nonsimply laced gauge groups. We present a complete list of all such conformal subalgebras.

• Received 14 May 1986

DOI:https://doi.org/10.1103/PhysRevD.34.3092