Spectral functions from the real-time functional renormalization group

Abstract

We employ the functional renormalization group approach formulated on the Schwinger-Keldysh contour to calculate real-time correlation functions in scalar field theories. We provide a detailed description of the formalism, discuss suitable truncation schemes for real-time calculations as well as the numerical procedure to self-consistently solve the flow equations for the spectral function. Subsequently, we discuss the relations to other perturbative and non-perturbative approaches to calculate spectral functions, and present a detailed comparison and benchmark in $d=0+1$ dimensions.

arXiv comment40 pages + 16 pages appendix, 8 figures

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• Real-time methods for spectral functions
• An algebraic QFT approach to the Wetterich equation on Lorentzian manifolds
• On the quark spectral function in QCD
• The QCD moat regime and its real-time properties
• Self-consistent $O(4)$ model spectral functions from analytically continued FRG flows
• Dissipation dynamics of a scalar field
• Real-time correlators in 3+1D thermal lattice gauge theory
• Universality of pseudo-Goldstone damping near critical points