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The consistency relation

In any single-clock model the squeezed limit is fixed by the tilt [@maldacena2003],

\[\lim_{k_3\to 0} \frac{B_\zeta(k_1,k_2,k_3)}{P_\zeta(k_1)P_\zeta(k_3)} = (1-n_s) + \mathcal O\!\left(\frac{k_3^2}{k_1^2}\right),\]

so a detection of $f_{\rm NL}^{\rm local}\gg 1$ would rule out the entire class.

Equilateral and orthogonal shapes

Derivative interactions in the EFT of inflation [@cheung2008] peak on equilateral triangles; the orthogonal template is constructed to capture the remaining direction in the two-operator space [@senatore2010].

Multi-field and the cosmological collider

Light fields make the squeezed limit local; fields with $m \sim H$ leave oscillatory, non-analytic squeezed limits that encode their mass and spin [@arkanihamed2015; @chen2010].