Regular subalgebras of affine Kac–Moody algebras
Regular subalgebras of affine Kac–Moody algebras
We classify regular subalgebras of Kac–Moody algebras in terms of their root systems. In the process, we establish that a root system of a subalgebra is always an intersection of the root system of the algebra with a sublattice of its root lattice. We also discuss applications to investigations of …