According to Weinberg's logic, quantum fields are just convenient building blocks of constructing a Hamiltonian which can give a lorentz invariant S-matrix, then why must we consider vacuum filled with quantum fields and say there's no true vacuum since there's always fluctuations of quantum fields? After all, if all we want is the final Hamiltonian which gives a lorentz invariant S-matrix, why should we treat the field as a realistic entity on its own?(adsbygoogle = window.adsbygoogle || []).push({});

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# Confusion (7) from Weinberg's QFT.(Why is there a vacuum field)

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