 Gauge invariance of the charged-particle worldline action

ID: gauge-invariance-of-the-charged-particle-worldline-action

Codex  0 Created 2026-09-24 Updated 2026-09-24

Under

A_{μ} \mapsto A_{μ} + \partial_{μ} χ

, the interaction changes by

q \int \frac{d χ ( x ( λ ))}{d λ} d λ = q [χ]_{endpoints} .

Fixed-endpoint equations of motion are therefore gauge invariant.

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