All Questions
40
questions
1
vote
2
answers
122
views
Confusion about Higgs mechanism
I am trying to understand the mass acquisition of particles in the Standard Model based on the book 'Fundamentals of Neutrino Physics and Astrophysics' by C. Giunti, and several doubts have arisen ...
- 161
0
votes
1
answer
56
views
Why don't we include diagrams with fermion and gauge boson external lines while calculating the effective potential of Standard model?
While calculating the effective potential of Higgs boson, we aim at $V_{eff}(h)$ instead of $V_{eff}(h, W^{+}, W^{-}, Z, quarks, leptons)$. I think the true vacuum should be the minimum of this ...
- 619
0
votes
1
answer
59
views
Can we prove in general that gauge fields associated with broken generators form representations of the unbroken group?
The title is a bit ambiguous. More specifically, I'm asking:
Are all coupling between massive gauge fields (associated with broken generators) and massless gauge fields of the unbroken group are in ...
- 619
0
votes
2
answers
77
views
Scalar field components in unitarity gauge
The Wikipedia article on Unitarity gauge says - "In this gauge, the scalar fields responsible for the Higgs mechanism are transformed into a basis in which their Goldstone boson components are ...
- 343
2
votes
1
answer
124
views
Extra degrees of freedom in toy spontaneous symmetry breaking model?
Consider a Lagrangian with a real scalar field $\varphi$ and massless vector field $A_\mu$ with field strength $F_{\mu\nu}$,
$$\mathcal{L} = -\frac{1}{2}\left(\partial\varphi\right)^2 - \frac{1}{4}F_{\...
- 737
1
vote
0
answers
313
views
Spontaneous Symmetry Breaking / Explicit Symmetry Breaking [closed]
I'm trying to understand the SSB and explicit symmetry breaking.
If we have a complex scalar field theory with Mexican hat potential,
$$\phi(x)=\frac{\sigma(x)}{\sqrt{2}}e^{i\Pi(x)/v}$$
choice of the ...
- 3,464
1
vote
0
answers
137
views
If we had a Higgs triplet with hypercharge $Y=1$, would we get three Higgs bosons?
In the Standard Model, the Higgs field is a doublet of SU(2) and hypercharge $Y=1/2$. We have four real scalar degrees of freedom (since $H$ is a complex doublet); three of these get "eaten" ...
- 61
0
votes
0
answers
43
views
Is the free spectrum of a theory, way above the symmetry breaking scale, massless?
I have asked a similar unanswered question, focused on different aspects, here.
My intuition regarding statements frequently made about this issue is that, if a theory contains a breaking pattern $G \...
- 1,742
0
votes
1
answer
185
views
How does the Nambu-Goldstone mode explain the absence of parity doubling?
I've been doing some reading about chiral symmetry breaking since it was not touched in my particle physics course
I found these slides
As explained in the above link, if we take $|\psi \rangle$ as ...
- 3,464
0
votes
1
answer
68
views
Lagrangian density: What assumption are we making and how could it change?
I'm having a hard time picturing the physical system under consideration in QFT. Scattering and propagators are understandable since we a priori assume we have certain particles given by the ...
- 434
9
votes
1
answer
317
views
About Itzykson and Zuber's proof of Goldstone's theorem
In chapter 11-2-2, I&Z discuss Goldstone's theorem. They start by claiming that if an operator $A$ exists, such that
$$ \delta a(t) \equiv \langle 0| [Q(t),A]|0\rangle \neq 0 \tag{11-30} $$
the ...
- 2,648
1
vote
1
answer
121
views
Examples of the vacuum $| 0 \rangle$ break C, P, T symmetry?
Can the vacuum $| 0 \rangle$ of some QFT break C, P, T symmetry?
It could be that the QFT break C, P, T symmetry explicitly. Are there good examples?
p.s. The weak interaction breaks P explicitly ...
- 4,336
3
votes
1
answer
170
views
$U(1)_A$ effects on the baryons?
We know that the axial $U(1)_A$ is anomalous thus not a global symmetry. Therefore there is no direct associated pseudo goldstone boson for $U(1)_A$. This makes the $\eta'$ much more massive than the ...
- 4,336
0
votes
1
answer
326
views
Particle interpretation for Fields and (non) vanishing VEV
I have some questions about the first part of the answer
by Arnold Neumaier dealing with the interpretation of VEV (vacuum expectation value). Let me quote the
parts I would like to understand better:
...
- 1,395
0
votes
1
answer
134
views
Chiral symmetry breaking and appearance of hadrons (from Schwartz's QFT book)
Matthew Schwartz's QFT book mentions following thing, but I cannot understand the logic
Spontaneous symmetry breaking of $SU(2) × SU(2)$ happened 14 billion years ago, when the temperature of the ...
- 995