Hi folks, originally I read Peskin & Schroeder but then I realised it was too concise for me.(adsbygoogle = window.adsbygoogle || []).push({});

So I switched to Srednicki and am reading up to Chapter 5.

(referring to the textbook online edition on Srednicki's website)

Two questions:

1. In the free real scalar field theory, the creation operator given by eq. 5.2 is time-independent.

But in eq. 4.5, when [itex]\phi^{+}[/itex] evolves with time, the time evolution acts on [itex]a^{\dagger}(k)[/itex], which is time-independent, and it gets an extra phase.

I know it follows directly from the commutation relation with H0,

but it looks to me that [itex]a^{\dagger}(k)[/itex] becomes time-dependent.

Can anyone explain it?

2. Srednicki argues that [itex]\left \langle 0|\phi (0)|0 \right \rangle = 0[/itex], which makes sense to me if I consider eq. 5.15.

But for [itex]\left \langle p|\phi (x)|0 \right \rangle=e^{-ipx}\left \langle p|\phi (0)|0 \right \rangle[/itex]

I have trouble with justifying that [itex]\left \langle p|\phi (0)|0 \right \rangle=1[/itex] ensures the 1-particle state normalisation,

if I consider eq. 5.15 again, (looks like) [itex]-\partial ^2+m^2 (e^{-ipx}\left \langle p|\phi (0)|0 \right \rangle)[/itex] gives me zero.

What's wrong with this logic and what should be the correct one?

Reading a QFT book alone is never easy... #sigh#

hope I can finish this book before the next June.

Thanks for your generous help

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# Srednicki Ch5 creation operator time dependence

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