Phenomenology of asymptotic safety

Abstract

In this work we explore the collider prospects for the asymptotic safety scenario being realized as a quantum theory of gravity. Testing gravity at colliders becomes a real possibility in the case of extra dimensional models, or with additional physics leading to a fundamental scale of gravity significantly lower than the Planck mass. We present several approximations for the full non-perturbative renormalization group running, and show how these can be implemented at the level of the graviton wave-function renormalization. The issue of scale identi fication of the physical process with the renormalization group scale k is clarified and several different choices are compared. The various approximations are resolved and shown in most cases to generate scheme independent results. On the phenomenological side, we investigate two separate observables. First, at tree-level we present results on LHC di-muon production due to asymptotically safe gravitons. By including fixed point scaling Kaluza- Klein modes, the predicted signal is enhanced and simultaneously problems associated with the breakdown of perturbative unitarity are reduced. At the one-loop level, we outline our calculation for the contribution to electro-weak precision observables originating from asymptotically safe gravity. New bounds are derived which show different behaviour as a function of the number of extra dimensions compared with previous effective field theory results. Finally, we comment on possible further directions for exploring the frontier of collider physics and quantum gravity.