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I came across this in the lecture notes of quantum field theory by David Tong. Inside time ordering interactions aren’t taken to be normal ordered. Interaction hamiltonian should be normal ordered otherwise it is not well defined (due to ordering ambiguity and related singularities). Most standard QFT textbooks don’t address this issue. Am i missing something here or normal ordering was assumed?

Roy
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Here there should be normal ordering for individual interaction terms inside time ordering.

Roy
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Most standard QFT textbooks don’t address this issue. Am i missing something here or normal ordering was assumed?

What? No. What could you possibly mean by "most standard QFT textbooks..."?

Check out the section titled "Wick's Theorem" in Peskin and Schroeder's textbook titled: "An Introduction to Quantum Field Theory" (first edition, copyright 1995).

In the first edition of the above-mentioned textbook, Wick's Theorem is discussed in section 4.3 on page 88.

hft
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