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. 
Mehrdad Mirbabayi, Marko Simonovi\'c, Matias Zaldarriaga
astro-ph.CO hep-th