- #1
cedricyu803
- 20
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Hi folks, originally I read Peskin & Schroeder but then I realized it was too concise for me.
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
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