All Questions
Tagged with quantum-field-theory symmetry
433
questions
6
votes
2
answers
488
views
If the S-matrix has symmetry group $G$, must the fields be representations of $G$?
If the fields in QFT are representations of the Poincare group (or generally speaking the symmetry group of interest), then I think it's a straight forward consequence that the matrix elements and ...
- 8,523
16
votes
4
answers
2k
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What is meant by the phrase "the mass is protected by a symmetry"?
In a particle physics context I've heard this phrase used. I guess it means that the mass of a particle is less than you'd naively expect from $E=mc^2$ after computing the momentum uncertainty ...
- 16.9k
14
votes
2
answers
4k
views
Time reversal symmetry and T^2 = -1
I'm a mathematician interested in abstract QFT. I'm trying to undersand why, under certain (all?) circumstances, we must have $T^2 = -1$ rather than $T^2 = +1$, where $T$ is the time reversal ...
- 303
6
votes
0
answers
677
views
Time reversal symmetry and T^2 = -1 [duplicate]
I'm a mathematician interested in abstract QFT. I'm trying to undersand why, under certain (all?) circumstances, we must have $T^2 = -1$ rather than $T^2 = +1$, where $T$ is the time reversal ...
- 303
22
votes
4
answers
6k
views
QM and Renormalization (layman)
I was reading Michio Kaku's Beyond Einstein. In it, I think, he explains that when physicsts treat a particle as a geometric point they end up with infinity when calculating the strength of the ...
- 2,808
21
votes
1
answer
3k
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Gauge redundancies and global symmetries [closed]
It is often said that local (gauge) transformation is only redundancy of description of spin one massless particles, to make the number degrees of freedom from three to two. It is often said that ...
- 2,586
4
votes
2
answers
2k
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The Energy-Momentum Tensor and the Ward Identity
I have a question regarding a homework problem for my quantum field theory assignment.
For the purposes of the question, we can just assume the Lagrangian is that of a real scalar field:
$$\mathcal{L}...
- 8,540
19
votes
2
answers
397
views
Can symmetry generators be used for quantization?
Take the Poincar�� group for example. The conservation of rest-mass $m_0$ is generated by the invariance with respect to $p^2 = -\partial_\mu\partial^\mu$. Now if one simply claims
The state where ...
- 6,820
18
votes
3
answers
6k
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Poincare group vs Galilean group
One can define the Poincare group as the group of isometries of the Minkowski space. Is its Lie algebra given either by the equations 2.4.12 to 2.4.14 (as also given in this page - https://en....
- 4,561
16
votes
2
answers
2k
views
CFT and the Coleman-Mandula Theorem
The Coleman-Mandula theorem states that under certain seemingly-mild assumptions on the properties of the S-matrix (roughly: one particle states are left invariant and the amplitudes are analytic in ...
- 161
19
votes
2
answers
5k
views
What does "soft" in "soft symmetry breaking" mean?
For example it is stated that if supersymmetry breaking is soft then stability of gauge hierarchy can be still maintained.
- 935
16
votes
3
answers
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Can someone give a simple expose on Coleman Mandula theorem and what Mandelstam variables are?
Can someone give a simple expose on Coleman Mandula theorem and what Mandelstam variables are?
Coleman-Mandula is often cited as being the key theorem that leads us to consider Supersymmetry for ...
- 2,204
20
votes
4
answers
1k
views
What sort of experiment would directly test time reversal invariance?
I guess the title says it all: how could/would you experimentally test whether our universe is truly time reversal invariant, without relying on the CPT theorem? What experiments have been proposed to ...
- 76.7k