 Primordial 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.

A trispectrum is a Fourier-space connected fourth-order statistic; this entry applies it to primordial cosmological perturbations.