Quote from Feynman and Hibbs book

In summary, the conversation discusses the issue of "finiteness" in quantum electrodynamics and the use of renormalization theory to address this problem. While the final measurable results are finite, they are obtained through a method of subtracting infinite quantities. However, this approach has been criticized for being a "dirty" method. Alternatively, string theory has been proposed as a "really finite" solution, but its connection to quantum electrodynamics is debatable. Overall, the concept of renormalization is better understood today, with the understanding that it is a trick to change a perturbation parameter and find values for observable quantities that are not dependent on a cut-off.
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Page 260: "No modification of quantum electrodynamics at high frequencies is known which simultaneously makes all result finite, maintains relativistic invariance, and keeps the sum of probabilities over all alternatives equal to unity."

Is that still true today?
 
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  • #2
The standard way to avoid these problems is to apply the renormalization theory to quantum electrodynamics. However, the issue of "finiteness" is somewhat tricky. The final measurable results are finite, but they are obtained by a somewhat dirty method of subtraction of infinite quantities.

On the other hand, string theory can be counted as a "really finite" counterexample, but it is dubious to which extent it can be considered to be a "modification" of quantum electrodynamics.
 
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What's going on in renormalisation is much better understood today.

Check out:
http://arxiv.org/pdf/hep-th/0212049.pdf

I wouldn't describe as the subtraction of infinite quantities - I would describe it as a trick to change a lousy perturbation parameter. In perturbation theory one normally chooses a parameter to perturb about that is small. The coupling constant looked a good choice because it was small but in fact it turned out to be really lousy being - wait for it - infinity - gulp. Of course its a blemish a theory has sensible quantities like coupling constants that are infinite. The modern resolution is to say the theory is only valid up to some cut-off. But what cut-off? That's where renormalisable theories are nice - it turns out that quantities you can actually measure don't depend on that cut-off - quantities that are infinite without the cut-off do - but one can figure out what they should be for a specific cut-off based on measurement. In fact that's all renormalised parameters are - simply a value found by experiment that we know must be true and will not be cut-off dependant - they can be safely relied on to perturb about. A fancy name for what is in fact a simple idea - once you get used to it :-p:-p:-p:-p:-p:-p

Thanks
Bill
 
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What is the book "Quote from Feynman and Hibbs book" about?

The book "Quote from Feynman and Hibbs book" is about the philosophy and principles of quantum mechanics, as well as the history of its development. It also contains personal anecdotes and insights from renowned physicist Richard Feynman and his colleague Albert Hibbs.

Who are the authors of "Quote from Feynman and Hibbs book"?

The authors of "Quote from Feynman and Hibbs book" are Richard Feynman, a Nobel Prize-winning physicist, and Albert Hibbs, an American physicist and mathematician.

What makes "Quote from Feynman and Hibbs book" a significant contribution to the field of quantum mechanics?

"Quote from Feynman and Hibbs book" is considered a significant contribution to the field of quantum mechanics because it presents the complex subject in a more approachable and engaging manner, making it accessible to both the general public and scientists alike. It also includes personal insights and perspectives from two renowned physicists.

Is "Quote from Feynman and Hibbs book" suitable for beginners in quantum mechanics?

Yes, "Quote from Feynman and Hibbs book" can be a good starting point for beginners in quantum mechanics. It presents the fundamental principles and concepts in an easy-to-understand way, making it a great introduction to the subject.

Are there any other notable works from Richard Feynman and Albert Hibbs?

Yes, Richard Feynman and Albert Hibbs have collaborated on several other works, including "Quantum Mechanics and Path Integrals" and "Quantum Mechanics and Path Integrals: Emended Edition." They have also individually published other significant works in the field of physics and mathematics.

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