## Chris Ripken: De Sitter scattering amplitudes in the Born approximation

A basic calculation in QFT is the construction of the Yukawa potential from a tree-level scattering amplitude. In the massless limit, this reproduces the 1/r...

A basic calculation in QFT is the construction of the Yukawa potential from a tree-level scattering amplitude. In the massless limit, this reproduces the 1/r...

One of the greatest issues for a quantum theory of gravitation is how to generalise the notion of local observable quantities. A viable approach is to constr...

U(1)ā extensions of the SM with generation-dependent couplings to quarks and leptons are a popular explanation of anomalies in rare B-decays, such as the R_K...

We compute non-perturbative flow equations for the couplings of quantum gravity in fourth order of a derivative expansion. The gauge invariant functional flo...

We present the first direct and non-perturbative computation of the graviton spectral function in quantum gravity. This is achieved with the help of a novel ...

The propagator stores important information about the causality and unitarity of a theory, and is related to the spectral function, if it exists. Studying th...