Baryon Acoustic Peak and the Squeezed Limit Bispectrum

In the non-relativistic regime, pertinent to the large scale structure of the Universe, the leading effect of a long-wavelength perturbation $\delta ({\lambda }_L)$ on short distance physics is a uniform acceleration $\propto {\lambda }_L\delta ({\lambda }_L)$. Typically, this has no effect on statistical averages at equal time since a uniform acceleration results in a uniform translation – a reasoning that has been formalized as a “consistency condition” on the cosmological correlation functions. This naive expectation fails in the presence of the baryon acoustic feature provided $\lambda_L < \ell_{\rm BAO}$. We derive the squeezed limit of correlation functions in this regime.