Recent content by CSnowden

Totally have it now, many thanks - this can be closed now!

In what sense is the following explanation of the Twins Paradox faulty in logic: Each twin views the other as length contracted, but the twin on earth only sees the rocket in motion and thus shortened (along with the twin) while the destination planet is at rest in the earth frame and the...

Its perhaps best to simplify/restrict my question to QED as the electron is the topic of interest. It seems (from The Duck’s clear explanation in the thread above) that there are terms in the QED Lagrangian which link the electron matter field to the vector potential A (describing the EM field)...

I found a closely related question with extensive discussion titled How do electrons couple to gauge field? , of which I found The Duck's post on that thread very enlightening.

UCDS Physics 130 https://quantummechanics.ucsd.edu/ph130a/130_notes/node30.html

The EM field seems to be required for for local gauge symmetry of the electron matter field under local phase variation. Following is a description (not my verbiage): There is a symmetry in physics which we might call the Local Phase Symmetry in quantum mechanics. In this symmetry we change...

That is a perfect explanation, many thanks!

I appreciate your feedback - can you comment on how the QFT Lagrangian is structured to implement the requirement you outline to ensure that 'no "unphysical degrees of freedom" mix into the dynamics and thus contribute to the S-matrix' ? As the Lagrangian solves for the final field structure...

In an earlier question I asked if the EM field was truly a separate field from the matter field in QFT, as it's field structure is naturally complementary to phase changes in the matter field in just the right way to restore gauge invariance (poorly formed question, but hopefully you get the...

Many thanks to everyone for some very insightful replies on the topic!

It seems that QED treats the matter and EM fields as independent yet coupled fields. On the other hand the EM field equations emerge immediately under local change of the phase of the matter field, exactly as required to reestablish local (gauge) invariance. From that perspective it almost seems...

I'll like to state a core question I have regarding QFT field coupling in more detail. There have been two effects of EM field coupling to the electron mater field described: (1) acceleration of the electron (matter field) in response to an external EM field and (2) an interaction of the...

Perhaps I should say something like 'an excitation of the electron matter field couples to raise a local excitation of the EM field'

I am a lay person with an interest in QFT and trying to learn (although I do have bachelors degrees in mathematics and physics), so would appreciate any coaching toward terminology that may be more standard within the field of study. I was trying to communicate that the two fundamental QFT...

Thank you for the very clear explanation, that is helpful. The coupling explanation raises a point from an earlier post, namely that the electron matter field raises the potential energy level in the local EM field (the 'attached' field) but can it be said that the EM field does the same in...