Simplification of higher-twist evolution in the large N-c limit: why and why not

Working in the light-cone gauge, we find a simple procedure to calculate th e autonomous one-loop Q(2) evolution of the twist-three part of the nucleon gr(x, Q(2)) structure function in the large-N-c, limit. Our approach allow s us to investigate the possibility of a similar large-N-c simplification f or other higher-twist evolutions. In particular, we show that it does not o ccur for the twist-four part of the f(4)(x, Q(2)), g(3)(x, Q(2)) and h(3)(x , Q(2)) distributions. We also argue that the simplification of the twist-t hree evolution does not persist beyond one loop.