Small Cosmological Constant from Running Gravitational Coupling

In this paper, we explore an idea of having Newton’s constant change its value depending on the curvature scale involved. Such modification leads to a particular scalar-tensor gravity theory, with the Lagrangian derived from renormalization group (RG) flow arguments. Assuming running of the (classical) gravitational coupling is described by the same beta function as the (quantum) one in quantum chromodynamics (QCD), one is led to a simple f(R)-type model with several striking features. The model has unique de Sitter attractor, with effective cosmological constant exponentially suppressed relative to Planck scale. Not only cosmological constant appears dynamically in this model, its value is small precisely because the gravity we observe is almost Einstein-like. With the