The Epstein-Glaser approach to pQFT: Graphs and Hopf algebras
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Submission date: 22. Mar. 2004 (revised version: May 2004)
published in: Journal of mathematical physics, 46 (2005) 6, art-no. 062304
DOI number (of the published article): 10.1063/1.1893215
with the following different title: The Epstein-Glaser approach to perturbative quantum field theory: graphs and Hopf algebras
MSC-Numbers: 81U20, 81T08, 81T15, 81T18, 16W30
PACS-Numbers: 03.70.+k, 11.10.Gh, 11.15.Bt, 11.55.-m
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The paper aims at investigating perturbative quantum field theory (pQFT) in the approach of Epstein and Glaser (EG) and, in particular, its formulation in the language of graphs and Hopf algebras (HAs). Various HAs are encountered, each one associated with a special combination of physical concepts such as normalization, localization, pseudo-unitarity, causal(ity and an associated) regularization, and renormalization. The algebraic structures, representing the perturbative expansion of the S-matrix, are imposed on the operator-valued distributions which are equipped with appropriate graph indices. Translation invariance ensures the algebras to be analytically well-defined and graded total symmetry allows to formulate bialgebras. The algebraic results are given embedded in the physical framework, which covers the two recent EG versions by Fredenhagen and Scharf that differ with respect to the concrete recursive implementation of causality. Besides, the ultraviolet divergences occuring in Feynman's representation are mathematically reasoned. As a final result, the change of the renormalization scheme in the EG framework is modeled via a HA which can be seen as the EG-analog of Kreimer's HA.