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Are time-advanced EM fields necessary?

  1. Mar 29, 2008 #1
    It's widely known that the electromagnetic wave equation admits of time-advanced as well as time-retarded solutions, but the time-advanced solutions are often simply discarded as non-physical. This is reasonable enough in many contexts, but I am personally of an opinion that the time-advanced solutions are as evidently necessary as the time-retarded ones. I'm wondering if this would be considered a fringe view or if this is conventional wisdsom. Also, I'm wondering if there is an obvious flaw in my reason for thinking this way, so I will explain my justification, and everyone can respond derisively or otherwise as they see fit.

    First, consider the retarded Lienard-Wiechert fields. These are the explicit fields that result from the movement of point charges. Also, it is well-known that there are time-advanced equivalents for the L-W fields. These are sometimes employed in the literature (by e.g. Wheeler-Feynman absorber theory, Eliezer, Dirac classical electron theory, others) but I gather that these are consider esoteric and hypothetical usages. (Am I wrong?) Seems to me though that they are just as necessary to physical theory as the time-retarded ones, for one simple reason. The reason is, that the time-advanced solutions are describing how the charges move in response to the fields. Without the time-advanced part, there can be no electrodynamics, because the charges cannot move in response to the fields. Is this crazy thinking or conventional wisdom or something in between?
  2. jcsd
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