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The Wheeler–Feynman absorber theory, named after its originators, the physicists Richard Feynman and John Archibald Wheeler, is a theory of electrodynamics based on a relativistic correct extension of action at a distance electron particles. The theory postulates no independent electromagnetic field. Rather, the whole theory is encapsulated by the Lorentz-invariant action S of particle trajectories a μ, b μ, ⋯ defined as S = − ∑ a m a c ∫ − d a μ d a μ + ∑ a < b e a e b c ∫ ∫ d a ν d b ν δ 4, where a b μ ≡ a μ − b μ. The absorber theory is invariant under time-reversal transformation, consistent with the lack of any physical basis for microscopic time-reversal symmetry breaking. Another key principle resulting from this interpretation, and somewhat reminiscent of Mach's principle and the work of Hugo Tetrode, is that elementary particles are not self-interacting. This immediately removes the problem of electron self-energy giving an infinity in the energy of an electromagnetic field.