Axial-current squared interaction
= Axial-current squared interaction
{title2=$j_{5\mu}j_5^\mu$}
Since the <chirality matrix> commutes with spinor Lorentz generators, $j_5^\mu=\bar\psi\gamma^\mu\gamma^5\psi$ transforms as a vector under proper <Lorentz transformations> and as a <pseudovector> under <parity>. Contracting two copies gives the <Lorentz scalar> $j_{5\mu}j_5^\mu$; the extra <parity> signs cancel. <Lorentz invariance> of this interaction does not require current conservation.