Galois Descent for Real Spectra

Abstract

We prove analogs of faithfully flat descent and Galois descent for categories of modules over $E_{\infty}$-ring spectra using the $\infty$-categorical Barr-Beck theorem proved by Lurie. In particular, faithful $G$-Galois extensions are shown to be of effective descent for modules. Using this we study the category of $ER(n)$-modules, where $ER(n)$ is the $\mathbb{Z}/2$-fixed points under complex conjugation of a generalized Johnson-Wilson spectrum $E(n)$. In particular, we show that $ER(n)$-modules is equivalent to $\mathbb{Z}$/2-equivariant $E(n)$-modules as stable $\infty$-categories.