I cannot quite understand why expression [itex] \frac{1-\gamma_5 \slashed{s}}{2} [/itex] is covariant? We defined it in the rest frame, and then said that because it is in the slashed expression, it's covariant, what does that mean? s is the direction of polarization, [itex] s \cdot s = -1 [/itex](adsbygoogle = window.adsbygoogle || []).push({});

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# Spin projection operator

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