All Questions
Tagged with group-theory symmetry
319
questions
3
votes
2
answers
111
views
Does all symmetry breaking have corresponding unitary group?
In high energy physics. Symmetry breaking like electroweak's has corresponding $SU(2)\times U(1)$ unitary gauge group broken down to $U(1)$. Does it mean all kinds of symmetry breaking (even low ...
- 425
2
votes
1
answer
42
views
Abelian vs non-abelian discrete symmetries in neutrino physics
I was reading about the parametrization of the PMNS matrix and stumbled upon an article of Serguey Petcov$^1$ about discrete flavour symmetries. It endeavors to see if there is a pattern induced by a ...
- 21
1
vote
2
answers
140
views
Why do representations of $SU(2)$ correspond to angular momentum eigenstates?
I have been learning about symmetry in one of my physics classes and specifically about $SU(2)$ and its irreducible representations. We can label a basis element of the vector space corresponding to a ...
3
votes
0
answers
40
views
Gauging a finite non-abelian global symmetry in 2D
Consider a 2D system with a non-anomalous finite non-abelian global symmetry $G$, for example $$G = S_3=\{e,a,a^2,b,ab,a^2b\}$$ with $a^3=b^2=1$. One expects the local operators charged under the ...
- 189
1
vote
1
answer
87
views
Why are there triclinic and monoclinic lattices, but biclinic is never mentioned?
When classifying the Bravais lattices we have the
triclinic (point group ${\rm C_i}$) and the monoclinic $({\rm C_{2h}})$ cases, but we do not see the "biclinic" case listed. Why not?
It ...
- 4,912
0
votes
2
answers
95
views
Conserved current transforming under adjoint
If we have a Lagrangian with a global internal symmetry $G$. Why do the conserved currents transform under the adjoint representation of $G$? Is it a general statement (if this is the case, how can we ...
- 1
22
votes
2
answers
2k
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Have all the symmetries of the standard model of particle physics been found?
Background
The standard model of particle physics is entirely determined by writing down its Lagrangian or, equivalently, writing down the corresponding system of PDEs.
Every set of PDEs has a ...
- 323
1
vote
0
answers
83
views
QFT visual interpretation of $U(1)$
Anyone has (even a "pictorial") way of visualize what the group $U(1)$ does on the fields in the QFT framework?
I know that $U(1)$ can be seen as a circle and the operation of the groups is ...
- 41
1
vote
0
answers
52
views
What kind of combinations of field components are equal under $SO(9)$ symmetry?
My question is a bit long and chaotic since I haven't learnt group theory systematically.
I am looking at the Banks-Fischler-Shenker-Susskind (BFSS) matrix model. It consists of 9 bosonic matrices $...
- 368
0
votes
2
answers
71
views
A question from S. Weinberg's book (Sec. 2.7)
S. Weinberg in his book "The quantum theory of fields" page 82 says: the elements $T,\bar{T}$, etc, of the symmetry group may be represented on the physical Hilbert space by unitary ...
- 374
1
vote
1
answer
79
views
Lie group symmetry in Weinberg's QFT book
In Weinberg's QFT volume 1, section 2.2 and appendix 2.B discuss the Lie group symmetry in quantum mechanics and projective representation. In particular, it's shown in the appendix 2.B how a ...
- 399
0
votes
1
answer
62
views
Perturbation Theory with no symmetry breaking?
I was learing about group theory in QM and stable about symmetry breaking. I find it very interesting and search some stuff and even looked on wikipedia and found this: https://en.wikipedia.org/wiki/...
2
votes
1
answer
158
views
Srednicki 36.5 symmetry question
This is from the intro to a problem 36.5 in Srednicki and not part of the problem itself. I am having trouble proving that $$\mathcal{L}=i\psi_j^\dagger\sigma^\mu\partial_\mu\psi_j$$
Has $U(N)$ ...
- 1,713
2
votes
1
answer
216
views
What's the meaning of this path integral measure?
I don't understand the meaning of following path integral measure
$$
\frac{[df]}{U(1)}
$$
What is the difference between $[df]$ and $[df]/U(1)$? A naive idea is the latter measure is more physical ...
- 53
15
votes
3
answers
3k
views
Why do fields have to form a representation of the Lorentz group?
It is often claimed in quantum field theory texts that to have a sensible Lorentz invariant theory, the fields introduced must be in representations of the Lorentz group. This fact has always seemed ...
- 307