We show that quantum gravity does exist as a genuine perturbative quantum field theory (i.e. is renormalizable), with all the correct properties one would expect of such a theory: unitarity, locality, microcausality etc. However it has many novel features not seen in other quantum field theories.
Although it is perturbative in couplings it is non-perturbative in Planck's constant, and the...
The laws of physics should not depend on how we choose to describe them, and we should not be able to change the physical predictions of our theory just by changing notation. However, this is exactly what happens in the standard formulation of quantum field theories. The effective action receives different quantum corrections depending on how we parametrise our fields. Even Feynman diagrams,...
Understanding the laws of inflation can shed light on the processes that govern physics at very high energy scales, beyond current experimental limits. In particular, the characterisation and detection of primordial gravitational waves produced during inflation can be an excellent test for the particle content of the very early universe. We consider an Effective Field Theory of inflation...
In this talk, I will discuss the geometry of attractor theories in a cosmological context, showing that theories which feature poles act as unions of multiple canonical models. This means that poles demarcate different field-space domains which may drastically differ in their phenomenology. Usually, studies of attractor theories are confined within the poles; however, moving beyond the poles...
The path integral gives a very useful framework for understanding quantum mechanics, but actually evaluating it can be tricky. We shall review some recent progress on a method to perform the integration of the real-time path path integral using Picard-Lefschetz techniques.
It is often conjectured that integrable 2d sigma models should be renormalizable (with only finitely many running couplings). After introducing integrability and sigma models, I will explain the intuition behind this conjecture. Although there is no general proof, it has been checked in various non-trivial examples at the leading 1-loop order. I will present recent work where we ask the...
We present the first example of the Bardeen-Moshe-Bander phenomenon in a purely fermionic relativistic quantum field theory. In this talk I will give an overview of the phenomenon, in which a scale invariant theory may nonetheless have massive excitations due to strong coupling effects, before explaining how this situation arises in a purely fermionic field theory: a less symmetric version of...
Quantum sensors that are used to measure gravitational fields and detect dark energy typically use single particle interferometric techniques that are limited by the time of flight in the interferometer arm. In this talk I will present a new detection method that uses quantum resonances and the sensitivity of collective excitations (phonons) to gravitational fields. When phonons in a...
We consider (2+1)d-QFT at finite temperature on a product of time with a static spatial geometry. Generically, free energy of QFTs on curved spacetime can be very difficult to calculate even for free field theories. For perturbations of flat space we show that free energy difference goes quadratically with perturbation amplitude and may be computed from the linear response of the stress...
The production rate of monopoles from strong magnetic fields at high temperatures is determined by an unstable `sphaleron' field configuration. In this talk I will present the results of a study of this sphaleron in the $SU(2)$ Georgi-Glashow model using lattice techniques. I will show how the sphaleron solution changes as the magnetic field strength is increased, and discuss the...
