http://arxiv.org/abs/2212.05112
In this paper, we generalize the Weinberg’s procedure to determine the comoving curvature perturbation $\cal R$ to non-attractor inflationary regimes. We show that both modes of $\cal R$ are related to a symmetry of the perturbative equations in the Newtonian gauge. As a byproduct, we clarify that adiabaticity does not generally imply constancy of $\cal R$, not even in the $k\rightarrow 0$ limit. Applying this knowledge to the separate Universe approach, we find that correlators of $\delta N$ {\it do not} generically correspond to comoving curvature perturbations correlators, even at the linear level, but rather to correlators of curvature perturbations at uniform density, at least at linear level. Thus, $\delta N$ formalism does not capture information about decaying (for slow-roll) or growing (beyond slow-roll) modes of $\cal R$. The latter being the only interesting mode for models of inflation related to primordial black holes formation.
D. Cruces, C. Germani and A. Palomares
Tue, 13 Dec 22
99/105
Comments: 15 pages, 1 figure