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Results tagged with perturbation-theory
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user 21270
Perturbation theory refers to methods for understanding physical systems by treating them as small modifications to exactly solvable systems.
3
votes
1
answer
654
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Lagrangian density of an interacting real scalar field theory
Srednicki writes the Lagrangian density of an interacting scalar field theory as
$$ \mathcal{L} = -\frac{1}{2} Z_\phi \partial^\mu \phi \partial_\mu \phi -\frac{1}{2} Z_m m^2 \phi^2 + \frac{1}{6} Z_g …
- 3,053
1
vote
1
answer
145
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Sinusoidal drive of two level system: why can we ignore one of the two terms?
I am studying the time-dependent perturbation theory from Griffith's Introduction to Quantum Mechanics. The context is a two-level system under a sinusoidal perturbation: $H'(\textbf{r}, t) = V(\textb …
- 3,053
3
votes
0
answers
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Vacuum to vacuum transition amplitude [duplicate]
I have two questions about Vacuum to vacuum transition amplitude.
Can any particle stay in $|0\rangle$?
I was studying this topic from Srednicki's QFT book. He writes in eq.$(6.22)$
$$\langle0|0 \r …
- 3,053