Abstract
We study the asymptotic safety conjecture for quantum gravity in the presence of matter fields. A general line of reasoning is put forward explaining why gravitons dominate the high-energy behaviour, largely independently of the matter fields as long as these remain sufficiently weakly coupled. Our considerations are put to work for gravity coupled to Yang-Mills theories with the help of the functional renormalisation group. In an expansion about flat backgrounds, explicit results for beta functions, fixed points, universal exponents, and scaling solutions are given in systematic approximations exploiting running propagators, vertices, and background couplings. Invariably, we find that the gauge coupling becomes asymptotically free while the gravitational sector becomes asymptotically safe. The dependence on matter field multiplicities is weak. We also explain how the scheme dependence, which is more pronounced, can be handled without changing the physics. Our findings offer a new interpretation of many earlier results, which is explained in detail. The results generalise to theories with minimally coupled scalar and fermionic matter. Some implications for the ultraviolet closure of the Standard Model or its extensions are given.
Highlights
The Standard Model of particle physics combines three of the four fundamentally known forces of nature
We investigate the scheme dependence, which is found to be more pronounced, and explain how it can be handled without changing the physics
The present analysis is important for the evaluation of general matter-gravity systems: we have argued that asymptotic freedom of the Yang-Mills theory allows us to successively integrate out the degrees of freedom, starting first with the Yang-Mills sector
Summary
The Standard Model of particle physics combines three of the four fundamentally known forces of nature. In expansions about flat backgrounds, it was noticed that the graviton dominates over free matter field fluctuations, either via an enhancement of the graviton propagator or the growth of the graviton coupling [79] This pattern should play a role for asymptotic safety of the fully coupled theory and for weak gravity bounds [82,85,86]. A main new addition is a formal line of reasoning, which explains why and how gravitons dominate the highenergy behavior, largely independently of the matter fields as long as these remain sufficiently weakly coupled Using functional renormalization, this is put to work for SUðNcÞ Yang-Mills theory coupled to gravity.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
