Lorentz structure tensor

Often we are not interested in the detailed space-time and spinorial structure of the fields, but simply in which particles occur at the vertices and in what combinations of charges, isotopic spins etc. When this is the case we shall simplify the notation, using the particle s qonbol to stand for its field operator, thus e for tl e x), e for rpe x), p for n x) the field of the )U-meson etc. (Since p, v will usually indicate p mesons and neutrinos, we shall often use a or / to indicate Lorentz indices on vectors, tensors and 7-matrices.)... 

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