A perturbative approach to the Wetterich equation for Bosonic and Fermionic interacting fields

TL;DR

This paper develops a perturbative approach to the Lorentzian Wetterich RG equation for interacting quantum fields on curved spacetimes, deriving flow equations, computing beta functions, and proving local well-posedness.

Contribution

It introduces a perturbative method for Lorentzian Wetterich RG equations in curved backgrounds, including scalar and Dirac fields, with new connections to stochastic models and rigorous well-posedness results.

Findings

Derived RG flow equations for scalar and Dirac fields.

Computed beta functions for relevant couplings.

Proved local existence and uniqueness of solutions.

Abstract

We study the Lorentzian Wetterich Renormalization Group (RG) flow equation for interacting quantum fields on curved backgrounds within the framework of perturbative Algebraic Quantum Field Theory (pAQFT). Specifically, we consider two classes of models: two mutually interacting scalar fields on globally hyperbolic spacetimes without boundary and, under the further assumption that the underlying background is spin, self-interacting Dirac fields. In both cases, we derive the corresponding RG flow equations within a Local Potential Approximation and compute the beta functions for the relevant couplings. For the scalar model, we also discuss an asymmetric interaction potential which is formally reminiscent of the Martin-Siggia-Rose description of a stochastic dynamics, thereby indicating a possible connection between Lorentzian algebraic RG methods [DDP+24] and stochastic field-theoretic models, [Duc25]. In addition, we address the local well-posedness of the resulting flow equations. Adapting the strategy detailed in [DP23] and based on the the Nash-Moser theorem, we prove local existence and uniqueness of solutions for both the scalar and the Dirac models.