Homomorphisms and Higher Extensions for Schur Algebras and Symmetric Groups

Abstract

Abstract. This paper surveys, and in some cases generalises, many of the recent results on homomorphisms and the higher Ext groups for q-Schur algebras and for the Hecke algebra of type A. We review various results giving isomorphisms between Ext groups in the two categories, and discuss those cases where explicit results have been determined.

Integral Ext groups between hook Weyl modules

“…As the modular extension groups are intimately related to the integral ones, we mention the result on neighboring Weyl modules [19] Part II Section 7, and the SL 2 result in [27] for all i generalizing [17] and [10]. More can be found in [12]. In [15] the case where λ is arbitrary and µ is a single row is settled for i 1.…”