The \delta N formula is the dynamical renormalization group
Abstract
We derive the 'separate universe' method for the inflationary bispectrum, beginning directly from a field-theory calculation. We work to tree-level in quantum effects but to all orders in the slow-roll expansion, with masses accommodated perturbatively. Our method provides a systematic basis to account for novel sources of time-dependence in inflationary correlation functions, and has immediate applications. First, we use our result to obtain the correct matching prescription between the 'quantum' and 'classical' parts of the separate universe computation. Second, we elaborate on the application of this method in situations where its validity is not clear. As a by-product of our calculation we give the leading slow-roll corrections to the three-point function of field fluctuations on spatially flat hypersurfaces in a canonical, multiple-field model.
Cite
@article{arxiv.1210.7800,
title = {The \delta N formula is the dynamical renormalization group},
author = {Mafalda Dias and Raquel H. Ribeiro and David Seery},
journal= {arXiv preprint arXiv:1210.7800},
year = {2013}
}
Comments
v1: 33 pages, plus appendix and references; 5 figures. v2: typographical typos fixed, minor changes to the main text and abstract, reference added; matches version published in JCAP