Recently i am reading A.Zee's Quantum Field Theory in a Nutshell 2nd Edition. there is a equation that i can not derive by myself. I suspect its correctness.(adsbygoogle = window.adsbygoogle || []).push({});

<k1k2|exp(-iHT)|k3k4>=<k1k2|exp(i∫dxL(x))|k3k4>, where the L(x) on the RHS is an operator function of space-time.

This equation appears on page 64, chapter I.8, under the section 'Scattering Amplitude'.

Zee used this equation to calculate the corresponding scattering amplitude in λψ^4 theory and thus justified the Feynman Rules given in previous chapters, so i think this equation is of crucial importance in Zee's book.

Can someone tell me how to derive it?

Thanks!

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# The Lagrangian formalism of Quantum Field Theory

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