Flattened bispectrum configuration
= Flattened bispectrum configuration
{title2=$k_3=k_1+k_2$}
= Folded bispectrum configuration
{synonym}
A flattened <primordial bispectrum> configuration lies at the collinear boundary of the allowed momentum-triangle domain. For a <cubic time-derivative curvature bispectrum>, it is finite rather than singular. Its equal-short-side value $k_1=k_2=k_3/2$ gives $k_1k_2k_3/(k_1+k_2+k_3)^3=1/32$, compared with $1/27$ at an <equilateral bispectrum configuration>.