Root Systems for Levi Factors and Borel-de Siebenthal Theory

Bertram Kostant

Let $\mathfrak{m}$ be a Levi factor of a proper parabolic subalgebra $\mathfrak{q}$ of a complex semisimple Lie algebra $\mathfrak{g}$. Let $\mathfrak{t}=cent\mathfrak{m}$. A nonzero element $ν\in…