The Picard group of equivariant stable homotopy theory

Let G be a compact Lie group. We describe the Picard group Pic(HoGS) of inv ertible objects in the stable homotopy category of G-spectra in terms of a suitable class of homotopy representations of G. Combining this with result s of tom. Dieck and Petrie, which we reprove, we deduce an exact sequence t hat gives an essentially algebraic description of Pic(HoGS) in terms of the Picard group of the Burnside ring of G. The deduction is based on an embed ding of the Picard group of the endomorphism ring of the unit object of any stable homotopy category C in the Picard group of C. (C) 2001 Academic Pre ss.