# Ryder QFT 2nd ed. page 341 misprint?

• melezmelez
In summary, the conversation discusses Eq. 9.124, which has 3 steps. The first step results in a 0 propagator for ε goes to 0, while the final step, involving Z, results in infinity. The individual is asking for the correct steps and if there are any errors in previous equations. They also mention the importance of learning Ryder's book method for an upcoming exam. The response explains that the one-loop polarization tensor is UV divergent and requires a counter term in Ryder's regularization scheme. This counter term leads to a photon-field renormalization, resulting in finite physical quantities expressed in terms of dressed wave functions, masses, and couplings.
melezmelez
Eq. 9.124 has 3 steps. The first one gives 0 propagator for ε goes to 0. The final step, the one with Z gives infinity. Can anyone post the correct steps? Is there anything wrong in previews equations? It is important for me to learn the Ryder's book method. I have an exam in 10 days

I do not understand, where you have a problem here. Of course, the one-loop polarization tensor (photon selfenergy) is UV divergent. In Ryder's regularization scheme (dimensional regularization) this manifests itself in the fact that there's a term $\propto 1/\epsilon$ which diverges for the physical value $\epsilon \rightarrow 0$. Thus you need a counter term to compensate (at least) this divergency, and as Ryder nicely shows, this counter term leads to a photon-field renormalization. At the end everything is finite by expressing physical quantities in terms of the finite dressed wave functions, masses, and couplings.

## 1. What is the misprint on page 341 of the Ryder QFT 2nd edition?

The misprint on page 341 of the Ryder QFT 2nd edition is a missing minus sign in the expression for the propagator of a free scalar field.

## 2. How does this misprint affect the understanding of the material?

This misprint can greatly affect the understanding of the material as it changes the sign of the propagator, which can lead to incorrect calculations and interpretations.

## 3. Has this misprint been corrected in newer editions of the book?

Yes, newer editions of the Ryder QFT book have corrected this misprint. It is important to always consult the latest edition for accurate information.

## 4. Are there any online resources that address this misprint?

Yes, there are various online forums and discussions where readers have pointed out this misprint and provided corrections. Additionally, the author's website may also address this issue.

## 5. How should I approach studying this topic with the misprint in mind?

If you are using the 2nd edition of the Ryder QFT book, it is important to make note of this misprint and manually correct it in your calculations. If you have access to a newer edition, it is recommended to refer to that for accurate information.

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