title: Realtime properties of QCD
creator: Horak, Jan
subject: ddc-530
subject: 530 Physics
description: We present a novel technique for the calculation of fundamental realtime correlation functions in functional approaches to quantum field theory, the spectral functional approach, and demonstrate its potential for the calculation of observables in quantum chromodynamics (QCD). The approach builds on spectral representations for correlation functions, such as the K\"all\'en-Lehmann representation of the propagator, and facilitates dimensional regularisation as well as on-shell renormalisation. We apply the spectral functional approach to the two most prominent functional frameworks for the calculation of non-perturbative fundamental correlation functions in QCD, which are Dyson-Schwinger equations and the functional renormalisation group. Building on this conceptual development, we calculate the spectral functions of all fundamental QCD fields, i.e., quark, gluon and ghost. We complement these results with data from spectral reconstruction with Gaussian process regression, inferring gluon and ghost spectral functions from Euclidean lattice QCD data in a Bayesian, non-parametric manner. Finally, as use cases for the spectral functional approach, we present direct computations of several QCD observables, facilitated by realtime correlator data. These include the shear viscosity of the quark-gluon plasma, the non-perturbative, timelike strong coupling constant, a crucial ingredient for scattering amplitudes, and the hadronic vacuum polarisation in the complex momentum plane, the leading QCD contribution to g-2.
date: 2023
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/33267/1/dissertation-electronic.pdf
identifier: DOI:10.11588/heidok.00033267
identifier: urn:nbn:de:bsz:16-heidok-332679
identifier:   Horak, Jan  (2023) Realtime properties of QCD.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/33267/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng