Questions tagged [charge-conjugation]
150 questions
21
votes
3 answers
Can bosons have anti-particles?
Can bosons have anti-particles? In the past, I would have answered this question with a yes, primarily because I can imagine writing down a QFT for complex scalars that has a $U(1)$ symmetry that allows me to assign a conserved charge. That is, I…
highsciguy
- 614
19
votes
3 answers
If electrons were positive and protons were negative, would life be different?
This was a question on a worksheet during my first week in a class on Electromagnetism. The answer is essentially:
No. Life would be no different if electrons were positively charged and protons were negatively charged. Opposite charges would still…
Andrew Tawfeek
- 332
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15
votes
1 answer
Physically, what is a pseudoreal representation?
There are three kinds of representations: real, complex, and pseudoreal. A complex representation is not equivalent to its conjugate, and a real one is, which is pretty straightforward. A pseudoreal representation is also equivalent to its…
knzhou
- 107,105
13
votes
3 answers
If the protons in a nucleus were replaced by antiprotons and the electrons by positrons what fundamental change would be introduced into the universe?
Exactly what the question says;
If all the protons and electrons in every single atom in the universe were swapped for their anti-particles, what would essentially change?
Safiul
- 468
13
votes
2 answers
What are the assumptions that $C$, $P$, and $T$ must satisfy?
I am not asking for a proof of the $CPT$ theorem. I am asking how the $CPT$ theorem can even be defined.
As matrices in $O(1,3)$, $T$ and $P$ are just
$$
T = \begin{pmatrix} -1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 1…
user1379857
- 12,195
13
votes
1 answer
What feature of QFT requires the C in the CPT theorem?
Classical tensor field theories have a PT theorem, so what changes in a QFT to require charge conjugation to be a part of the theorem? Charge conjugation seems a bit unrelated to space-time, but is an integral part of the theorem.
I have a suspicion…
lazcisco
- 133
11
votes
1 answer
Antiparticles, charge conjugation and chirality
(Why/how) are antiparticles and charge-conjugates different things?
I am trying to understand the effect of discrete symmetries on spinor fields (neutrinos in particular). In the article, Dirac, Majorana and Weyl fermions (section 7, pg 25), the…
paco_uk
- 121
10
votes
2 answers
Can we treat $\psi^{c}$ as a field independent from $\psi$?
When we derive the Dirac equation from the Lagrangian, $$
\mathcal{L}=\overline{\psi}i\gamma^{\mu}\partial_{\mu}\psi-m\overline{\psi}\psi,
$$
we assume $\psi$ and $\overline{\psi}=\psi^{*^{T}}\gamma^{0}$ are independent. So when we take the…
Louis Yang
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8
votes
1 answer
Proof of Furry's theorem
i was wondering if anyone could give an explicit calculation or show a link that shows the proof to Furry's theorem. showing how the vacuum expectation value of any odd number of electromagnetic currents vanishes. in particular the case for $n=3$.
alejandro123
- 627
8
votes
2 answers
How to construct the charge conjugation matrix for any given spacetime dimension?
Generally, Gamma matrices could be constructed based on the Clifford algebra.
\begin{equation}
\gamma^{i}\gamma^{j}+\gamma^{j}\gamma^{i}=2h^{ij},
\end{equation}
My question is how to generally construct the charge conjugation matrix to raise one…
Osiris Xu
- 393
7
votes
2 answers
C, T, P transformation mistakes in ``Peskin&Schroeder's QFT''?
I suppose the right way to do C (charge), T (time reversal), P(parity) transformation on the state $\hat{O}| v \rangle$ with operators $\hat{O}$ is that:
$$
C(\hat{O}| v \rangle)=(C\hat{O}C^{-1})(C| v \rangle)\\
P(\hat{O}| v…
wonderich
- 8,086
7
votes
2 answers
Charge-conjugation of Weyl spinors
I am having trouble reconciling two facts I am aware of: the fact that the charge conjugate of a spinor tranforms in the same representation as the original spinor, and the fact that (in certain, dimensions, in particular, in $D=4$), the charge…
Jonathan Gleason
- 8,834
7
votes
1 answer
Shouldn't Charge Conjugation be known as "positive/negative frequency symmetry"?
I know that charge conjugation exchanges the creation (or annihilation) operators of the particles with those of the anti-particles and therefore merits the name charge conjugation.
However, if operated on the single electron Dirac plane wave…
Lagrangian
- 10,439
7
votes
1 answer
Is $CP$ instead of $C$ responsible for changing a particle to its antiparticle?
The charge conjugation operator $C$ reverses the charge of a state. But it may or may not convert a particle to its antiparticle. For example, consider a neutrino which is charge-neutral and left-handed while its antiparticle is also charge-neutral…
SRS
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7
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2 answers
What is the definition of the charge conjugation?
I seem to have troubles finding definitions of the charge conjugation operator that are independant of the theory considered.
Weinberg defined it as the operator mapping particle types to antiparticles :
$$\operatorname C \Psi^{\pm}_{p_1 \sigma_1…
Slereah
- 17,006