As for gravity, the first studies concerning this new concept were performed in d = 2 + ϵ ϵ spacetime dimensions in the late seventies. In exactly two dimensions there is a theory of pure gravity that is renormalizable according to the old point of view. (In order to render the Einstein–Hilbert action 1 16 π π G ∫ ∫ d 2 x g R dimensionless, Newton's constant G must have mass dimension zero.) For small but finite ϵ ϵ perturbation theory is still applicable, and one can expand the beta-function ( β β -function) describing the renormalization group running of Newton's constant as a power series in ϵ ϵ . Indeed, in this spirit it was possible to prove that it displays a nontrivial fixed point.