Zero curvature conditions and conformal covariance

Akemann G, Grimm R. Zero curvature conditions and conformal covariance. J.Math.Phys. 1993;34(2):818-835.Two‐dimensional zero curvature conditions with special emphasis on conformal properties are investigated in detail and the appearance of covariant higher order differential operators constructed in terms of a projective connection is elucidated. The analysis is based on the Kostant decomposition of simple Lie algebras in terms of representations with respect to their ‘‘principal’’ SL(2) subalgebra