Galois theory and Lubin-Tate cochains on classifying spaces

Abstract

We consider brave new cochain extensions F(BG +,R) → F(EG +,R), where R is either a Lubin-Tate spectrum E n or the related 2-periodic Morava K-theory K n , and G is a finite group. When R is an Eilenberg-Mac Lane spectrum, in some good cases such an extension is a G-Galois extension in the sense of John Rognes, but not always faithful. We prove that for E n and K n these extensions are always faithful in the K n local category. However, for a cyclic p-group \(C_{p^r } \), the cochain extension \(F(BC_{p^r + } ,E_n ) \to F(EC_{p^r + } ,E_n )\) is not a Galois extension because it ramifies. As a consequence, it follows that the E n -theory Eilenberg-Moore spectral sequence for G and BGdoes not always converge to its expected target.