Thursday, January 3, 2013

Feynman, Wheeler, Falling Trees and QFT

I'm slowly working my way through the articles leading up to Feynman's version of QED/QFT.  This seems to be the first.  The  basics I'm getting from it are that Feynman wanted to use Lagrangian formalism moving forward and therefore couldn't break time symmetry.  In that case, he also couldn't drop the advanced field solution for the propagation of electromagnetic waves.  This article by Feynman and Wheeler shows how the advanced field solution of the absorber of the EM wave could be shown to account for the radiation reaction of the emitter.  In the end, the advanced field solutions for both emitter and absorber cancel out, but we're left with a solution that answers the tree falling in the forest question.  If there isn't a particle to absorb EM waves, then an emitter won't emit them.

http://rmp.aps.org./abstract/RMP/v17/i2-3/p157_1
DOI: 10.1103/RevModPhys.17.157

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