We prove global equivariant refinements of Miller's stable splittings of the infinite orthogonal, unitary and symplectic groups, and more generally of the spaces O/O(m), U/U (m) and Sp/Sp(m). As such, our results encode compatible equivariant stable splittings, for all compact Lie groups, of specific equivariant refinements of these spaces.In the unitary and symplectic case, we also take the actions of the Galois groups into account. To properly formulate these Galois-global statements, we introduce a generalization of global stable homotopy theory in the presence of an extrinsic action of an additional topological group.
ContentsIntroduction 1 1. Warm-up: the global stable splitting of O 3 2. The unstable filtration 6 3. The stable splitting 11 4. The limit case 16 Appendix A. A glimpse of C-global homotopy theory 19 Appendix B. Some linear algebra 34 References 39 1. Warm-up: the global stable splitting of OIn this short section we sketch the global stable splitting of the orthogonal space O made from the orthogonal groups. This section is logically redundant, as the splitting of Theorem 1.5 is a special case of our main result, Theorem 3.8. I am prepending this section because it already exhibits all the key features of the later arguments in a simpler form, without the two additional layers of complexity arising