Gauge Invariance and the Photon Self-Energy Correction

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Discussion Overview

The discussion revolves around the concept of gauge invariance in quantum field theory, specifically in relation to the self-energy corrections of photons and gauge bosons. Participants explore the implications of gauge invariance on the mass of the photon and the role of Ward identities in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • A participant expresses a desire for a concise explanation of how gauge invariance prevents the photon from acquiring mass, referencing the role of Ward identities.
  • Another participant indicates a limited understanding of gauge invariance and Ward identities, suggesting a need for further clarification.
  • A later reply mentions that the relationship between gauge invariance and Ward identities is outlined in a specific section of a well-known textbook, implying that this connection is established in the literature.
  • One participant agrees with the assertion about the relationship between gauge invariance and Ward identities.

Areas of Agreement / Disagreement

Participants generally agree on the connection between gauge invariance and Ward identities, but there is no consensus on a simplified explanation or the best way to convey this relationship without extensive calculations.

Contextual Notes

Some participants express uncertainty regarding their understanding of the concepts discussed, indicating a potential gap in foundational knowledge that may affect the clarity of the discussion.

shirosato
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Short intro.: I'm a 2nd year M.Sc. student in particle physics, with basic quantum field theory and knowledge of the SM and perhaps a bit more. I've read the forums before and tried to find questions/answers that were similar to my own until I decided, "why not just join so I can ask exactly what I want to know?"

Anyway, my question is this: in most introductions to SUSY, they go over the self-energy diagrams for the photon/gauge boson as well as the electron. They then give some simplified integral representing the correction and then saying that gauge invariance guarantees that the correction identically vanishes.

This makes sense knowing some gauge theory (gb mass terms break gauge invariance) and they often cite the Ward identities. Without going through the whole calculation, is there any easy way to explain how gauge invariance forbids the photon mass that is somewhat mathematical without going the whole mile? Writing this, it sounds lazy, but I honestly like to have the minimal non-hand-wavey solution handy at all times.

Shirosato
 
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I do not know anything else but gauge invariance (classically) and Ward identities (after quantization).
 
Well, upon a bit more reading, its basically outlined in 245-246 of Peskin and it seems that its basically, the gauge invariance of qed manifests itself through the ward identities.
 
That's true
 

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