Fine structure constant increase with energy?

In summary, the conversation discusses the confusion around the statement that the value of the fine structure constant increases with collision energy in Electron/Positron annihilation. While initially thinking that this constant should not change, further research reveals that in QED, the coupling constants can depend on energy scale and the fine structure constant does in fact change at higher energies. The conversation concludes with the understanding that this was not clearly explained in the textbook but can be further explored with additional research.
  • #1
Walternate
5
0
Hi!
Hope someone can help, I am currently studying an Open University course and I am a little confused by a statement in one of the textbooks.
It says that the value of the fine structure constant increases with collision energy (in Electron/Positron annihilation).
I am probably being stupid, but I thought it was a constant so by it's nature it would not change? Sadly the book does not elaborate further so I hope someone can help me understand this as I've searched everywhere and can't really find anything to explain this statement :) Thank you for your patience.
 
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  • #2
Walternate said:
Hi!
Hope someone can help, I am currently studying an Open University course and I am a little confused by a statement in one of the textbooks.
It says that the value of the fine structure constant increases with collision energy (in Electron/Positron annihilation).
I am probably being stupid, but I thought it was a constant so by it's nature it would not change? Sadly the book does not elaborate further so I hope someone can help me understand this as I've searched everywhere and can't really find anything to explain this statement :) Thank you for your patience.

Walternate,

Welcome to PF. I think if you use the search feature and enter: Fine Structure Constant you will find 11 pages of posts that will explain the question you asked, and then some. If you do a little digging, I am sure you will find your answer, just like I did. Good luck. Please report back what you found, and if it opened up a whole new series of questions in your mind, because, I am betting it will.

Rhody...:cool:
 
  • #3
The book is correct. I'm not sure exactly what kind of explanation you'd like, so I guess I'll just point you to the coupling constant article on Wikipedia:

http://en.wikipedia.org/wiki/Coupling_constant#QED_and_the_Landau_pole

In a quantum field theory, the coupling constants usually depend on an energy scale. In QED, the coupling grows with energy (unlike QCD, which is asymptotically free at high energy). In the case of QED, it doesn't change very quickly with energy scale, however. (According to the Wikipedia article the fine structure constant only changes from 1/137 to 1/127 when you go from very small energies all the way up to 90 GeV.)

*Edit: Looks like I was too slow again.
 
  • #4
Thanks both of you :) Yes I think I understand know, what threw me was that this is a Level one book and it put this in there without any warning and not even a statement like 'while this may seem to make no sense it does, but we will not be exploring why in this course' which it has done for other subjects.
Thanks again!
 

FAQ: Fine structure constant increase with energy?

1. What is the fine structure constant?

The fine structure constant, denoted by α, is a dimensionless physical constant that characterizes the strength of the electromagnetic interaction between elementary particles. It is also known as the coupling constant or the Sommerfeld fine structure constant.

2. Why does the fine structure constant increase with energy?

The fine structure constant is a measure of the strength of the electromagnetic force. As energy increases, the interactions between particles become stronger, causing the value of α to increase. This is due to the fact that at higher energies, more virtual particles are present, which contribute to the overall strength of the electromagnetic force.

3. How is the fine structure constant related to the speed of light?

The fine structure constant is related to the speed of light by the equation α = e^2/4πε₀ħc, where e is the elementary charge, ε₀ is the permittivity of free space, ħ is the reduced Planck's constant, and c is the speed of light. This equation shows that α is inversely proportional to the speed of light, meaning that as c increases, α decreases and vice versa.

4. Does the value of the fine structure constant vary in different regions of the universe?

No, the value of the fine structure constant is considered to be a universal constant, meaning that it has the same value everywhere in the universe. This has been confirmed through observations of distant galaxies and quasars, which show consistent values of α.

5. How does the fine structure constant affect atomic and subatomic particles?

The fine structure constant plays a crucial role in determining the behavior of atomic and subatomic particles. It affects the size, energy levels, and interactions of these particles. Changes in the value of α can have significant impacts on the stability and properties of atoms, leading to different chemical and physical behaviors.

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