Auxiliary results on group representations

This chapter contains several results on the linear representations of a group G ; we shall apply them in Chapter 6 to G = Gal(Q/Q).

Let us first recall some definitions and notation (cf. [A VIII, §§11,20,21]).

5.1.1.1. G-modules. In what follows, G is a group, and K is a field of characteristic 0 (except in 5.1.1.4 below).