The singularity category and duality for complete intersection groups

Abstract: If G is a finite group, some aspects of the modular representation theory depend on the cochains C^*(BG; k), viewed as a commutative ring spectrum. We consider here its singularity category (in the sense of the author and Stevenson arxiv 1702.07957) and show that if C^*(BG; k) is a homotopical complete intersection in a strong sense, then the singularity category is the bounded derived category of the k-nullification of the connective ring spectrum C_(\Omega BG_p). In the course of this we establish a form of Gorenstein duality for C_(\Omega BG_p) for these groups. [v2 has expanded sections on localization, better account of squeezed resolutions, and added examples.]