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| Main Authors: | , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2505.24590 |
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Table of Contents:
- $δN$ formalism is a useful method to calculate the curvature perturbation. Contrary to what it is typically done in the literature, we re-formulate the $δN$ formalism by using the $e$-folding number $n$ counted forward in time. For a fixed initial time $\bar{n}_0$, the probability density function (PDF) of the initial conditions $δϕ_0$ and $δπ_0$ are specified by the solutions of the perturbation equation on subhorizon scales. As $δπ_0$ is fully correlated with $δϕ_0$ after horizon exit, we find a simple formula to calculate the curvature perturbation as well as its PDF by using the $δN$ method reformulated in terms of $n$, the $δn$ formalism.