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Ambiguity in free field operators

I am interested in the ambiguities which exist in defining the composite free field operators--i.e., operators corresponding to monomials of the fundamental field operator (and their derivatives). In ...
1
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2answers
100 views

A problem related to Wick's theorem from RG analysis of KT transition

Recently, I was reading a review paper by John B. Kogut An introduction to lattice gauge theory and spin systems, when he was doing the RG analysis for the X-Y model, on page 702, to go from (7.61a) ...
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votes
1answer
214 views

Meaning of approximation $\cos(\phi)=\frac{\phi^2}{2}\mathrm{e}^{-\frac{1}{2}\langle{\phi^2}\rangle}$ in a field theory?

In Appendix E.1 (linking to a pdf) of Giamarchi's book "Quantum physics in one dimension", when deriving renormalization group equations (irrelevant to this question at all), formula (E.18) is used to ...
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1answer
198 views

Wick renormalization

I'm trying to understand the Wick renormalization in the framework of the Ito integral. I saw the Wick theorem as presented on Wikipedia in a QFT course and I would like to understand how that is ...