Motivic renormalization and singularities

TL;DR

This paper introduces a new regularization method for parametric Feynman integrals using Leray coboundaries, connecting it to mixed Hodge structures, motivic sheaves, and the Connes--Kreimer renormalization framework.

Contribution

It develops a novel regularization approach based on Leray coboundaries, extending the Hopf algebra of Feynman graphs and relating dimensional regularization to motivic and Hodge-theoretic concepts.

Findings

New regularization method for Feynman integrals using Leray coboundaries

Connection between dimensional regularization and Gelfand--Leray forms

Proposal of a geometric model involving logarithmic motives

Abstract

We consider parametric Feynman integrals and their dimensional regularization from the point of view of differential forms on hypersurface complements and the approach to mixed Hodge structures via oscillatory integrals. We consider restrictions to linear subspaces that slice the singular locus, to handle the presence of non-isolated singularities. In order to account for all possible choices of slicing, we encode this extra datum as an enrichment of the Hopf algebra of Feynman graphs. We introduce a new regularization method for parametric Feynman integrals, which is based on Leray coboundaries and, like dimensional regularization, replaces a divergent integral with a Laurent series in a complex parameter. The Connes--Kreimer formulation of renormalization can be applied to this regularization method. We relate the dimensional regularization of the Feynman integral to the Mellin transforms of certain Gelfand--Leray forms and we show that, upon varying the external momenta, the Feynman integrals for a given graph span a family of subspaces in the cohomological Milnor fibration. We show how to pass from regular singular Picard--Fuchs equations to irregular singular flat equisingular connections. In the last section, which is more speculative in nature, we propose a geometric model for dimensional regularization in terms of logarithmic motives and motivic sheaves.