7.3.2 Causality Structure of Electrodynamicsand depend only on source in back light cone7.3 Application to Electrodynamics7.3.1 Formal solutionSolutions:Lorentz GaugeNote:If gauge condition is fulfilled initially, it is also fulfilled at later times.Lec 22 - 4. MarMarch‐04‐099:54 PMLecture Notes Page 1
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Signal: non-analytic change in at point y at time at position can be influenced only at timelater!More precisely:are affected at preciselytime later.signal velocity (Front velocity) is always exactly !three velocities:in practise: signal travelling with front velocity c is weak!==> hard to utilize effect=>strong signal travels typically with slower velocity, e.g. group velocitysee books by:R. U. Sexl, H.K. Urbantke, Relativity, Groups, Particles: special relativity and relativistic symmetry in field and particle physics-L. Brillouin, Wave propagation and group velocity-other expression of same truthSo we expect in all structures7. 4 Reduction mechanism: oscillating sources and