Multi-soft theorems for cosmological correlators: Background wave method for scalars & gravitons
Abstract
Cosmological soft theorems (or consistency relations) provide a powerful probe for the physics of inflation. These relations rely on minimal assumptions and hold very generally. Consequently, any violation of these relations would rule out a large class of inflationary models. For instance, a violation of the scalar soft theorem (or consistency relation) would rule out all attractor single-field inflation models and instead point toward either multi-field dynamics or a non-attractor phase. In this paper, we derive tree-level multi-soft theorems, at leading order in the soft expansion, for both scalar and tensor correlation functions. Our analysis employs the background-wave method, in which the effect of long-wavelength modes is captured by an appropriate spatial coordinate rescaling. In addition, we systematically incorporate soft-exchange contributions, including tensor exchanges in scalar correlators and scalar exchanges in tensor correlators.
Cite
@article{arxiv.2604.09765,
title = {Multi-soft theorems for cosmological correlators: Background wave method for scalars & gravitons},
author = {Farman Ullah},
journal= {arXiv preprint arXiv:2604.09765},
year = {2026}
}