# Normal Products and Zimmermann Identities in Configuration Space BPHZ Renormalization

August 14, 2017

The notion of normal products, a generalization of Wick products, is derived
with respect to BPHZ renormalization formulated entirely in configuration
space. If inserted into time-ordered products, they admit the limit of
coinciding field operators, which constitute the normal product. The derivation
requires the introduction of Zimmermann identities, which relate field
monomials or renormalization parts with differing subtraction degree.
Furthermore, we calculate the action of wave operators on elementary fields
inserted into time-ordered products using the properties of normal products.

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