The Riemann zeta function as an equivariant Dirac index

Abstract. In this note an interpretation of Riemann’s zeta function is provided in terms of an R-equivariant L^2 -index of a Dirac-Ramond type operator, akin to the one on (mean zero) loops in flat space constructed by the present author and T. Wurzbacher. We build on the formal similarity between Euler’s partitio numerorum function (the S^1 -equivariant L^2 -index of the loop space Dirac-Ramond operator) and Riemann's zeta function. Also, a Lefschetz-Atiyah-Bott interpretation of the result together with a generalisation to M. Lapidus’ fractal membranes are also discussed. A fermionic Bost-Connes type statistical mechanical model is presented as well, exhibiting a “phase transition at (inverse) temperature β = 1”, which also holds for some “well-behaved” g-prime systems in the sense of Hilberdink-Lapidus.