All Questions
Tagged with renormalization physical-constants
24
questions
16
votes
3
answers
3k
views
Why is finding a mathematical basis for the fine-structure constant meaningful?
I was reading QED by Richard Feynman and at the end he mentions that:
There is a most profound and beautiful question associated with the observed coupling constant, $e$ – the amplitude for a real ...
- 169
1
vote
0
answers
177
views
Einstein equivalence principle and running of couplings
It is known that a spacetime variation of the dimensionless gauge coupling constants of the standard models would lead to a violation of the Einstein equivalence principle (EEP). This point is ...
0
votes
1
answer
501
views
Has it been proven the fine-structure constant (FSC) changes with time?
I have heard this claimed over and over, even that the FSC was 1 at the Big Bang. Is there any actual consensus among scientists that this is so?
- 804
1
vote
1
answer
127
views
Is the running of electric charge the same as the running of the fine structure constant?
This is a simple question - maybe too simple. If I recall correctly, Feynman wrote about the running of the electric charge with energy (or 4-momentum). Nowadays, one hears more about the running of ...
- 727
-3
votes
1
answer
187
views
Is a running coupling constant a natural consequence in QFT, or is it a consequence of the "dressing-up" of particles?
The running coupling constant ("hold that constant!) is a well known phenomenon in quantum field theory. The constant varies with the energy of the interacting particles. I think this is rather ...
4
votes
1
answer
797
views
Running of the fine structure constant: meaning of $\alpha(Q^2=0)$?
In Measurement of the Running of the Fine-Structure Constant, the L3 collaborations writes
At zero momentum transfer, the QED fine structure constant $\alpha(0)$ is very accurately known from the ...
- 713
4
votes
0
answers
153
views
Is Planck length constant in String Theory? Does it have a renormalization flow?
Is Planck length constant?
Planck length $l_p$ is dependent on Newton constant $G_N$ which is related to coupling constant of interaction of gravitons, but from field theory point of view, we know ...
- 85
2
votes
1
answer
202
views
Trouble with the algebra in Srednicki book chapter 28
I'm studying chapter 28 in Srednicki (the renormalization group) and I'm having troubles figuring out how he derives eq. (28.15) (last summation above) from eqs. (28.7) and (28.9).
More specifically ...
15
votes
6
answers
4k
views
What does it mean that dimensionless physical constants cannot be calculated but only measured?
I have read a passage in Wikipedia about the List of unsolved problems in physics and dimensionless physical constants:
Dimensionless physical constants: At the present time, the values of various ...
- 4,170
6
votes
1
answer
558
views
Why are Yukawa couplings regarded as fundamental constants if their values vary with scale?
Why are Yukawa couplings regarded as fundamental constants if their values vary slowly with the energy scale (distance scale) at which they are measured?
This question is the same as why are quarks ...
- 476
1
vote
1
answer
133
views
What is the experimental evidence that the gravitational constant $G$ runs with energy (or temperature)?
Various papers on quantum field theory claim that $G$ runs with energy, like the fine structure constant does. Some examples:
Frolov, Fursaev and Zelnikov, Nucl.Phys. B486, 339 (1997)
Volovik and ...
user85598
5
votes
2
answers
493
views
Paul Dirac on Dimensionless Physical Constants and $\alpha\sim\frac{1}{137}$
Paul Dirac gave his viewpoints on the dimensionless constant (click to see the youtube video). For example, he mentioned the fine structure constant
$$
\alpha\sim\frac{1}{137}.
$$
It is not clear that ...
- 4,336
1
vote
1
answer
261
views
Sean Carroll's claim on renormalisation?
So I'm reading Sean Carroll's old blog post:
But to a modern physicist, this seems like a misguided quest. First,
because renormalization theory teaches us that $\alpha$ isn’t really a number at all; ...
- 1,389
11
votes
3
answers
2k
views
Why does the fine-structure constant $α$ have the value it does?
This is a follow-up to this great answer.
All of the other related questions have answers explaining how units come into play when measuring "universal" constants, like the value of the speed of ...
- 223
1
vote
0
answers
134
views
Running of gravitational constant versus. other coupling constants, GUT and TOE
Is there any theory that proves convincingly that the gravitational constant runs with energy AND it is like the other coupling constants and converge at a single point at a given energy? Or is that a ...
- 6,611