Global homotopy theory via partially lax limits

Abstract

We provide new $\infty$-categorical models for unstable and stable global homotopy theory. We use the notion of partially lax limits to formalize the idea that a global object is a collection of $G$-objects, one for each compact Lie group $G$, which are compatible with the restriction-inflation functors. More precisely, we show that the $\infty$-category of global spaces is equivalent to a partially lax limit of the functor sending a compact Lie group $G$ to the $\infty$-category of $G$-spaces. We also prove the stable version of this result, showing that the $\infty$-category of global spectra is equivalent to the partially lax limit of a diagram of $G$-spectra. Finally, the techniques employed in the previous cases allow us to describe the $\infty$-category of proper $G$-spectra for a Lie group $G$, as a limit of a diagram of $H$-spectra for $H$ running over all compact subgroups of $G$.

70 pages. Improved introduction plus small reorganization of some results. Comments welcome!