Dynamic observables from spectral functional methods

by Jonas Wessely (Heidelberg University)

Thursday 5 Dec 2024, 14:15 → 15:45 Europe/Berlin

Abbeanum/Ground floor-HS 2 - Hörsaal 2 (TPI, FSU Jena)

Many non-perturbative aspects of equilibrium quantum field theory are typically computed in a Euclidean formulation. On the other hand, in particular dynamic observables, such as bound-state or transport properties, require real-time correlation functions. Since extrapolations of Euclidean data from the lattice or sophisticated functional computations often suffer from large systematic errors, we address this issue with a direct approach based on a combination of functional diagrammatic methods and spectral representations of correlation functions. We start by introducing the spectral functional method at the example of a scalar field theory and discuss the numerical computation of non-perturbative propagator spectral functions with (spectral) Dyson-Schwinger equations or the (spectral) functional Renormalisation Group. We explain how these spectral functions can be used to compute bound-state masses directly on the real frequency axis with the (spectral) Bethe-Salpeter equation. The last part of the talk will focus on the application to QCD, where we discuss recent results for the quark-spectral function and preliminary results for the heavy quark diffusion coefficient.