We calculate the spectral function of light quark flavours in 2+1 flavour vacuum QCD in the isospin-symmetric approximation. We employ spectral Dyson-Schwinger equations and compute the non-perturbative quark propagator directly in real-time, using recent spectral reconstruction results from Gaussian process regression of gluon propagator data in 2+1 flavour lattice QCD. Our results feature a pole structure at time-like momenta larger than the propagator’s gapping scale as well as a negative scattering continuum. The computation is augmented with a general discussion of the impact of the quark-gluon vertex and the gluon propagator on the analytic structure of the quark propagator. In particular, we investigate under which conditions the quark propagator shows unphysical poles. Our results offer a wide range of applications, encompassing the ab-initio calculation of transport as well as resonance properties in QCD.
J. Horak, J. M. Pawlowski, N. Wink, “On the quark spectral function in QCD”, Oct. 14, 2022, arXiv:2210.07597 (2022).
Related to Project A02, C06