Quantum Gravity at Astrophysical Distances?

TL;DR

This paper explores how Quantum Einstein Gravity could explain galaxy rotation curves and the small cosmological constant without dark matter or fine-tuning, by analyzing the renormalization group flow of Newton's constant.

Contribution

It identifies a specific RG trajectory in Quantum Einstein Gravity that accounts for astrophysical phenomena and addresses the cosmological constant problem.

Findings

Growth of Newton's constant at galactic scales explains flat rotation curves.

RG trajectories naturally lead to a small cosmological constant.

Quantum gravity effects could resolve dark matter and cosmological constant issues.

Abstract

Assuming that Quantum Einstein Gravity (QEG) is the correct theory of gravity on all length scales we use analytical results from nonperturbative renormalization group (RG) equations as well as experimental input in order to characterize the special RG trajectory of QEG which is realized in Nature and to determine its parameters. On this trajectory, we identify a regime of scales where gravitational physics is well described by classical General Relativity. Strong renormalization effects occur at both larger and smaller momentum scales. The latter lead to a growth of Newton's constant at large distances. We argue that this effect becomes visible at the scale of galaxies and could provide a solution to the astrophysical missing mass problem which does not require any dark matter. We show that an extremely weak power law running of Newton's constant leads to flat galaxy rotation curves similar to those observed in Nature. Furthermore, a possible resolution of the cosmological constant problem is proposed by noting that all RG trajectories admitting a long classical regime automatically give rise to a small cosmological constant.