Tagged Questions
3
votes
1answer
73 views
Gell-Mann Low Theorem and Vacuum Energy
I know that the sum of vacuum bubbles can be related to the Vacuum energy, but I'm trying to understand how this follows from the Gell-Mann Low theorem/equation. My question will use equations from ...
1
vote
0answers
70 views
Range of forces from mass of force carrier?
Why is $\frac{\hbar}{mc}$ a good estimate of the range of the four forces, where $m$ is the mass of the carrier particle of the force? Inputting the pion mass gives $1.4\ \mathrm{fm}$ for the hadronic ...
4
votes
1answer
262 views
Interpretation of derivative interaction term in QFT
I am trying to understand what a term like $$ \mathcal{L}_{int} = (\partial^{\mu}A )^2 B^2 $$ with $A$ and $B$ being scalar fields for instance means. I understand how to draw an interaction term in ...
4
votes
2answers
117 views
Interpretation of an “interaction” term
In QFT a polynomial (of degree >2) in the fields is said to be an interaction term, Ex.: $\lambda\phi^4$.
Question
Is it possible to give an interpretation to terms like $\frac{1}{\phi^n}$? (for ...
1
vote
1answer
178 views
How does the dressed Klein-Gordon propagator look in position space?
The free Klein-Gordon propagator in momentum space $\sim (p^2-m^2+i\epsilon)^{-1}$ has just a single pole at $p^2=m^2$. The passage to Fourier space is difficult but possible. The result is very ...
2
votes
2answers
311 views
Why $\lambda\phi^4$ theory, where $\lambda>0$, is not bounded from below?
Why the following interaction, in QFT, $$\displaystyle{\cal L}_{\rm int} ~=~\frac{\lambda}{4!}\phi^4$$ where $\lambda$ is positive, represents a theory that is unstable (or unbounded from below as it ...
6
votes
1answer
58 views
Expectation values of interacting fields
I was motivated to ask this question by the equality claimed in equation 10.3.3 of Weinberg's volume 1 of QFT books.
My interpretation of that,
If $O_s$ is a quantum field of spin $s$, $\psi_s$ is ...
