All Questions
Tagged with quantum-chromodynamics quantum-electrodynamics
59
questions
4
votes
0
answers
399
views
Is the physical mass of the electron a gauge invariant quantity?
In Lattice, one cannot calculate gauge non-invariant quantities, such as the quark mass. This is because one averages over the gauge and gets 0.
One way to get around the issue is to fix the gauge. ...
- 41
2
votes
1
answer
378
views
Why is the typical lifetime so different depending on the type of interaction?
Why is $\tau$ so different when it comes to Quantum Electrodynamics ($10^{-16}$s), Quantum Flavordynamics ($>10^{-13}$s) and Quantum Chromodynamics ($10^{-23}$s)?
Does this have something to do ...
- 1,723
2
votes
0
answers
194
views
Understanding mathematical explanation for Chudakov Effect
I'm trying to better understand some properties of QCD and currently I'm looking into understanding color coherence. I've got the book "Elementary Particle Physics: Foundations of the Standard Model, ...
- 161
3
votes
1
answer
942
views
Is the non-perturbative approach to QFT a path integral approach? If so then how, given we don't have simple path integral formula for Dirac equation?
Here is my understanding of the scenario. Please correct me if i go wrong somewhere.
Initially, the perturbative approach to QED (Feynman diagrams) was very successful. But the same approach to QCD ...
- 2,326
1
vote
1
answer
171
views
How would the photon having a charge change the electromagnetic interaction?
This question is motivated by my recent foray into Quantum Field Theory. Just to make this clear straight off the bat; I am not suggesting in any way shape or form that the photon has a charge. I am ...
- 703
1
vote
0
answers
302
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Radiative correction to the charge form factor $F_1$ in QED
In QED, one can calculate the correction to the form factor $F_2$. To the lowest order, $F_1=1$ and $F_2=0$. At one loop, it is found that $F_2(0)$ receives a non-zero finite correction which is ...
- 26.8k
2
votes
1
answer
365
views
Quantization prescription for an interacting field theory
To my understanding, unlike free fields, interacting fields cannot be expanded in terms of Fourier modes, with the Fourier coefficients representing creation and annihilation operators. Then is it ...
- 26.8k
2
votes
1
answer
506
views
Understanding type of force interaction in particle decays
Are there any fundamental rules of thumbs that can be used to identify the type of force interaction (weak, electromagnetic, strong) in a particle decay without drawing the Feynman diagrams at the ...
- 310
4
votes
0
answers
951
views
Sudakov double logarithm
I have calculated a few NLO corrections in QED and in the final result the Sudakov double logarithms have always canceled. So I thought that they have no physical meaning. On the other hand I have ...
- 1,273
36
votes
4
answers
6k
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Why have our eyes not evolved to see "gluons"? [closed]
The photons are the propagators for QED, and we rely on photons to see the world around us.
The gluon is the propagator in QCD. Why have our eyes not evolved to see gluons (either on top of being ...
- 1,634
1
vote
1
answer
79
views
QCD-Process with superposition-particle
I am a total beginner with non-abelian gauges. To write down a process from a neutral pion ($\pi^0 = \frac{1}{\sqrt{2}}(u\overline{u}-d\overline{d})$) I expect to have to write it as this ...
- 11
5
votes
1
answer
863
views
Why Conserved Current Should Not Need Renormalization?
May be this is trivial but I need to understand why the renormalization of conserved current is not necessary ? As for example, in this paper, they demand (2$^{nd}$ paragraph of the 2$^{nd}$ column in ...
- 407
1
vote
1
answer
120
views
Looking for a reference for $\gamma_a e^{a}_{\mu} D^\mu \gamma_b e^{b}_{\nu} D^\nu =D^\mu D_\mu - \tfrac{1}{4}R$
I am having trouble finding references for the following identities:
Dirac Operator:
$$
\gamma_a e^{a}_{\mu} D^\mu \gamma_b e^{b}_{\nu} D^\nu =D^\mu D_\mu - \tfrac{1}{4}R
\tag{1}
$$
QED Operator:
$$
...
11
votes
1
answer
3k
views
Polarization Sums in QCD for the calculation of parton model splitting functions
Before i state the actual problem, here's a premise. In the case of a Spin 1 massive particle it's possible to demonstrate that $$\sum_{\lambda=0,\pm1}\epsilon_{\lambda}^{* \ \mu}\epsilon_{\lambda}^{\...
- 2,263
7
votes
2
answers
728
views
If proton spin emergence from quarks and gluons is mysterious, why is silver atom spin not?
A recent Scientific American article brought up an old issue, which is this: According to quantum chromodynamic models, the emergence of exactly 1/2 unit of spin in a proton (or a neutron, or any ...
- 22.1k