Simplified functional flow equation

We adapt the precise definition of the flowing effective action in order to obtain a functional flow equation with simple properties close to physical intuition. The simplified flow equation is invariant under local gauge transformations and suitable for both euclidean and Minkowski signature and an...

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Main Author: C. Wetterich
Format: Article
Language:English
Published: Elsevier 2025-05-01
Series:Physics Letters B
Online Access:http://www.sciencedirect.com/science/article/pii/S0370269325001960
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author C. Wetterich
author_facet C. Wetterich
author_sort C. Wetterich
collection DOAJ
description We adapt the precise definition of the flowing effective action in order to obtain a functional flow equation with simple properties close to physical intuition. The simplified flow equation is invariant under local gauge transformations and suitable for both euclidean and Minkowski signature and analytic continuation. The cutoff always removes fluctuations close to zeros of the inverse full propagator. A formulation of the simplified flow equation in terms of renormalized scale invariant fields permits direct access to scaling solutions and associated fixed points. Our setting is based on a particular choice of cutoff function which depends on the macroscopic fields. Corrections to the simplified flow equation involve a field-dependent modification of the cutoff for which we discuss a systematic expansion. Truncated solutions for a scalar field theory in four dimensions suggest a new fixed point with a field-dependent coefficient of the kinetic term.
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spelling doaj-art-4eaf84e3a80d48239b8def0377849aef2025-08-20T03:18:10ZengElsevierPhysics Letters B0370-26932025-05-0186413943510.1016/j.physletb.2025.139435Simplified functional flow equationC. Wetterich0Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D-69120, Heidelberg, GermanyWe adapt the precise definition of the flowing effective action in order to obtain a functional flow equation with simple properties close to physical intuition. The simplified flow equation is invariant under local gauge transformations and suitable for both euclidean and Minkowski signature and analytic continuation. The cutoff always removes fluctuations close to zeros of the inverse full propagator. A formulation of the simplified flow equation in terms of renormalized scale invariant fields permits direct access to scaling solutions and associated fixed points. Our setting is based on a particular choice of cutoff function which depends on the macroscopic fields. Corrections to the simplified flow equation involve a field-dependent modification of the cutoff for which we discuss a systematic expansion. Truncated solutions for a scalar field theory in four dimensions suggest a new fixed point with a field-dependent coefficient of the kinetic term.http://www.sciencedirect.com/science/article/pii/S0370269325001960
spellingShingle C. Wetterich
Simplified functional flow equation
Physics Letters B
title Simplified functional flow equation
title_full Simplified functional flow equation
title_fullStr Simplified functional flow equation
title_full_unstemmed Simplified functional flow equation
title_short Simplified functional flow equation
title_sort simplified functional flow equation
url http://www.sciencedirect.com/science/article/pii/S0370269325001960
work_keys_str_mv AT cwetterich simplifiedfunctionalflowequation