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- Summary
- QFT and the Origin of Gauge Invariance

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 gist). One response gave a succinct answer in that the QFT Lagrangian clearly contains two separate coupled fields and so there is the answer; however, this does seem to beg the question of how gauge symmetry arises. As the field solutions to the QFT Lagrangian clearly do have a tight gauge symmetry, is there some clearly identifiable structure of the QFT Lagrangian that would cause one to expect that only gauge invariant field solutions would result?