Quantum gravity at astrophysical distances?

Abstract

Assuming that quantum Einstein gravity (QEG) is the correct theory of gravity on alllength scales, we use analytical results from nonperturbative renormalization group (RG)equations as well as experimental input in order to characterize the special RGtrajectory of QEG which is realized in Nature and to determine its parameters. Onthis trajectory, we identify a regime of scales where gravitational physics is welldescribed by classical general relativity. Strong renormalization effects occur at bothlarger and smaller momentum scales. The latter lead to a growth of Newton’sconstant at large distances. We argue that this effect becomes visible at the scale ofgalaxies and could provide a solution to the astrophysical missing mass problemwhich does not require any dark matter. We show that an extremely weak powerlaw running of Newton’s constant leads to flat galaxy rotation curves similar tothose observed in Nature. Furthermore, a possible resolution of the cosmologicalconstant problem is proposed by noting that all RG trajectories admitting along classical regime automatically give rise to a small cosmological constant.