Primordial trispectrum
= Primordial trispectrum
{title2=$T(\mathbf k_1,\mathbf k_2,\mathbf k_3,\mathbf k_4)$}
{wiki=Trispectrum}
The primordial trispectrum is the connected four-point function with its momentum-conserving delta function removed. Exchange diagrams split naturally into $s$, $t$, and $u$ channels according to which pair of external momenta meets at one cubic vertex.