Multiplicity-free representations of algebraic groups II

Abstract

We continue our work, started in [9], on the program of classifying triples (X,Y,V), where X,Y are simple algebraic groups over an algebraically closed field of characteristic zero with X<Y, and V is an irreducible module for Y such that the restriction V↓X is multiplicity-free. In this paper we handle the case where X is of type A, and is irreducibly embedded in Y of type B,C or D. It turns out that there are relatively few triples for X of arbitrary rank, but a number of interesting exceptional examples arise for small ranks.