Conference

We review the status of asymptotically safe gravity-matter systems. The existence of a UV fixed point in such systems is guaranteed if the matter-self couplings are weak and if higher-derivative gravity terms are neglected. We show how this can manifest itself in a functional renormalisation group computation. Such gravity-matter systems contain various avatars of the dynamical Newton's coupling, e.g. gravitational self-couplings or matter-graviton couplings. We uncover an effective universality for the dynamical Newton's coupling on the quantum level: its momentum-dependent avatars are in remarkable quantitative agreement in the scaling regime of the UV fixed point. This emergence of effective universality is a strong indication for the physical nature of the UV fixed point and it provides a guiding principle for setting up future truncations.

A field theory is fundamental if it features a UV fixed point (either trivial or interacting). Gravity may not change drastically the UV behavior if the Einstein gravitational interactions are softened above a critical sub-Planckian energy scale. A concrete implementation of this softened gravity can be obtained by adding terms quadratic in the curvature to the Einstein-Hilbert action. One way to implement this scenario consists in requiring that all matter couplings flow to zero at infinite energy (total asymptotic freedom). More generally, some of the couplings flow to zero, while others approach interacting fixed points. The requirement of having a fundamental field theory can have important implications for particle physics phenomenology.

I outline a configuration in which the Standard Model can be embedded into an asymptotically safe gauge-Yukawa theory. The model can be though of as a minimal UV completion of the SM without gravity. I also discuss the remaining issues that need to be addressed for the scheme to be phenomenologically viable, and outline the different energy scales and possible signatures.

Ultralight bosons can induce superradiant instabilities in spinning black holes, tapping their rotational energy to trigger the growth of a bosonic condensate. In this talk I will give an overview on superradiance and its applications focusing on the observational imprints of this process around spinning black holes which include: (i) the emission of monochromatic gravitational waves emitted by bosonic condensate formed through superradiant instabilities, potentially observable by current and future gravitational-wave detectors, and (ii) the formation of “gaps” in the spin versus mass plane of astrophysical black holes.