A Stringy Composite Graviton and the Cosmological Constant Problem

A heuristic model of a composite graviton is presented motivated by open string field theory. The model simply assumes a composite closed string sector, world sheet conformal invariance and the observed open string states, i.e., standard model particles, as an input. A UV to IR map from the open string to the closed string sectors naturally emerges. The IR cutoff of the lightest observed fermion loops gets mapped to a UV cutoff for the scalar mode of the graviton/dilaton. This provides a UV cutoff for gravity via the dilaton coupling to G. Based on recent estimates of the lightest fermion (neutrino) mass this gives an energy cutoff for the graviton near the current estimates of the dark energy density of 10 eV.