Scattering amplitudes in Quantum Gravity
In the asymptotic safety scenario, the high-energy behaviour of quantum gravity is governed by an interacting ultraviolet fixed point, which renders the theory finite and renormalisable. Over the past decades, significant evidence in favour of the existence of such a fixed point was gathered. By now, asymptotically safe gravity is a strong contender for the fundamental theory of quantum gravity. In this project, you will venture beyond the existence of a fixed point and compute crucial observables of the theory. You will deal with graviton-mediated scattering amplitudes, which test the unitarity and causality of the theory and help us to understand the physical implications of an interacting high-energy fixed point.
Quantum Gravity implications for the Standard Model and beyond
A theory of quantum gravity must be able to encompass the matter degrees of freedom in our Universe, such as the Standard Model. In asymptotically safe gravity, this is an intriguing two-way street: on the one hand, matter degrees of freedom influence the existence of the high-energy fixed point, and on the other hand, the high-energy fixed point dictates many properties of the low-energy theory. In other words, the theory of quantum gravity imposes constraints on the low-energy matter theory, in straight analogy to swampland conjectures in string theory. In your project, you will dissect this important interplay between matter and gravity, and determine which models are compatible with quantum gravity. This includes the Standard Model itself and beyond SM theories for dark matter and inflation.