2024-04-08 - 2024-04-12
Benjamin Knorr
Nordic Institute for Theoretical Physics, Stockholm
Gravity is the only fundamental interaction that we do not agree on how to quantise - all other forces and particles fit neatly into the Standard Model of Particle Physics, a hugely successful and well-tested quantum field theory. One of many issues with quantum gravity treated in the same way as the Standard Model is that scattering amplitudes are ill-behaved: their associated probabilities are not bounded by one, and unitarity is lost.
A popular solution to this is string theory: via the introduction of massive higher spin particles, amplitudes are turned into well-behaved objects. The price to pay for this is leaving the realm of quantum field theory, and introducing extra dimensions, a gigantic tower of so far unobserved particles, and a large number of possible universes which may or may not contain ours.
If this price is too high for you, then this lecture makes a different offer: I can sell you a theory of quantum gravity that can be formulated as a quantum field theory with all the nice properties that we want from it! My price, you ask? The use of non-perturbative tools. Are you willing to pay? If so, you will learn about Asymptotic Safety, non-perturbative renormalisation group techniques and the computation of non-perturbative gravitational scattering amplitudes within this approach
