For scalar fields the propagator is just a number that represents the amplitude for a particle to go from one space time point to another.(adsbygoogle = window.adsbygoogle || []).push({});

For fermions, the propagator is matrix valued. What then is the amplitude for a fermion to go from one point to another? How are the elements of the matrix to be interpreted in terms of probability ampltudes?

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# Matrix valued propagators

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