Tagged Questions
3
votes
2answers
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Why does $\mathcal L = -\frac14 F^{\mu\nu} F_{\mu\nu}$ imply Photons are massless?
The Lagrangian $\mathcal L = -\frac14 F^{\mu\nu} F_{\mu\nu}$ with $F_{\mu\nu} = \partial_\mu A_\nu - \partial_\nu A_\mu$ results in the four-potential's equation of motion
$$ \underbrace{\partial^\mu ...
3
votes
1answer
409 views
Introduction to Physical Content from Adjoint Representations
In particle Physics it's usual to write the physical content of a Theory in adjoint representations of the Gauge group. For example:
$24\rightarrow (8,1)_0\oplus (1,3)_0\oplus (1,1)_0\oplus ...
3
votes
2answers
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A question from Weinberg QFT text
In page 71 Weinberg's QFT,
$$A\Psi^{\theta }_{a,b}
~=~(a\cos{(\theta )}-b\sin{(\theta )})\Psi^{\theta }_{a,b}.$$
He says that massless particles represented by $\Psi ^{\theta }_{a,b}$ are not ...
3
votes
3answers
423 views
Building the meson octet and singlet
I am very lost in this topic. I understand that there are $3\times 3$ possible combinations of a quark and an anti-quark, but why should one decide arbitrarily (that's how it appears to me) that one ...
