= Engineering dimensions of relativistic fields
{title2=$[\phi]=(d-2)/2,\quad[\psi]=(d-1)/2,\quad[A_\mu]=(d-2)/2$}
Canonical free scalar and gauge-vector kinetic terms contain two derivatives and two fields, whereas the Dirac kinetic term contains one derivative and two spinor fields. Matching their <mass dimension> to $d$ in $d$ spacetime dimensions gives the displayed engineering dimensions. These are the dimensions used in <power counting>; interacting scaling dimensions can additionally contain anomalous contributions.
Back to article page
