  Let (G, \mu) be a pair of a reductive group G over the p-adic integers and a
minuscule cocharacter {\mu} of G defined over an unramified extension. We
introduce and study "(G, \mu)-displays" which generalize Zink's Witt vector
displays. We use these to define certain Rapoport-Zink formal schemes purely
group theoretically, i.e. without p-divisible groups.
