Higher d Eisenstein series and a duality-invariant distance measure

Abstract

Abstract The Petersson inner product is a natural inner product on the space of modular invariant functions. We derive a formula, written as a convergent sum over elementary functions, for the inner product Es(G, B) of the real analytic Eisenstein series $${E}_{s}\left(\tau ,\overline{\tau }\right)$$ and a general point in Narain moduli space. We also discuss the utility of the Petersson inner product as a distance measure on the space of 2d CFTs, and apply our procedure to evaluate this distance in various examples.