Bosonic Loop Diagrams as Perturbative Solutions of the Classical Field Equations in ϕ⁴ Theory

Felix Finster and Jürgen Tolksdorf

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Submission date: 24. Feb. 2012 (revised version: October 2013)
Pages: 39
published in: Journal of mathematical physics, 53 (2012) 5, art-no. 052305 
DOI number (of the published article): 10.1063/1.4718333
Bibtex
MSC-Numbers: 70Sxx, 81T10, 81Uxx
PACS-Numbers: 11.10Ef, 11.10Lm, 11.15Kc
Keywords and phrases: Classical Nonlinear Scattering Problem, Feynman Diagrams, Stochastic Initial Values
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Abstract:
Solutions of the classical ϕ⁴-theory in Minkowski space-time are analyzed in a perturbation expansion in the nonlinearity. Using the language of Feynman diagrams, the solution of the Cauchy problem is expressed in terms of tree diagrams which involve the retarded Green’s function and have one outgoing leg. In order to obtain general tree diagrams, we set up a “classical measurement process” in which a virtual observer of a scattering experiment modifies the field and detects suitable energy differences. By adding a classical stochastic background field, we even obtain all loop diagrams. The expansions are compared with the standard Feynman diagrams of the corresponding quantum field theory.