  We re-consider the graviton self-energy induced by a loop of massless,
minimally coupled scalars on de Sitter background. On flat space background it
can be represented as a sum of two tensor differential operators acting on
scalar structure functions. On a general background these tensor differential
operators can be constructed from the linearized Ricci scalar and the
linearized Weyl tensor. However, in cosmology one requires a third contribution
which we derive here.
