Fine structure constant increase with energy?

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Discussion Overview

The discussion revolves around the fine structure constant and its behavior with respect to collision energy in the context of Electron/Positron annihilation. Participants explore the implications of the fine structure constant being described as increasing with energy, which raises questions about its nature as a constant.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the fine structure constant being described as increasing with collision energy, questioning how it can be a constant if it changes.
  • Another participant suggests that the textbook's statement is correct and points to the dependence of coupling constants on energy scales in quantum field theory, specifically in Quantum Electrodynamics (QED).
  • A reference is made to a Wikipedia article that explains how the fine structure constant changes with energy, noting that it varies from 1/137 to 1/127 as energy increases up to 90 GeV.
  • A later reply indicates that the initial confusion stemmed from the textbook's presentation of the concept without adequate context or explanation.

Areas of Agreement / Disagreement

Participants generally agree that the fine structure constant can vary with energy, but there is a lack of consensus on the clarity of its presentation in educational materials. The discussion reflects differing levels of understanding and the need for further exploration of the topic.

Contextual Notes

The discussion highlights potential limitations in the textbook's explanation, including the absence of context regarding the nature of constants in quantum field theory and the specific conditions under which the fine structure constant is said to change.

Walternate
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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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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:
 
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.
 
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!
 

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