Initial conditions for inflation
Abstract
We propose a single-field mechanism that dynamically prepares the initial conditions required for exponential plateau inflation. The inflaton is decomposed into a coarse-grained mode and a high-occupancy, approximately Gaussian band of relativistic nonzero modes. Gaussian--Hartree averaging of the potential produces an exact variance-dependent minimum, which places the coarse-grained field high on the plateau when the excitation variance is large. Under a translation-invariant microcanonical measure, the available phase-space volume is exponentially concentrated near this minimum, while an order-one homogeneous kinetic-energy fraction is exponentially atypical. During expansion, the preparation modes redshift as radiation, σ2∝ a−2 and ρχ∝ a−4. Although the induced minimum rapidly moves toward the vacuum, the force acting on the coarse-grained mode is bounded by an exponentially small factor, yielding analytic upper limits on its velocity, displacement, and kinetic fraction. We derive a sufficient condition for the subsequent number of slow-roll e-folds and exhibit a benchmark with more than 60 e-folds. The mechanism also motivates correlated finite-onset signatures: large-scale power suppression with decaying oscillations and a variance-convolution bispectrum.
Related
- Bridging perturbation theory and simulations: initial conditions and fast integrators for cosmological simulations
- The initial conditions and initial mass functions of Alpha Persei, Pleiades and Praesepe
- Investigating the initial conditions of globular clusters via N-body simulations: I. half-mass radius and stellar density
- Initial Conditions of Magnetized AGN Accretion Disks from Cloud Capture and Disruption
- TILING I: Field-level Bayesian reconstruction of cosmological initial conditions during the epoch of reionization
BibTeX
@misc{kouniatalis2026initial,
title = {{Initial conditions for inflation}},
author = {Gerasimos Kouniatalis},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09200},
eprint = {2609.09200},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09200},
}
RIS
TY - UNPB
TI - Initial conditions for inflation
AU - Gerasimos Kouniatalis
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2609.09200
UR - https://arxiv.org/abs/2609.09200
AB - We propose a single-field mechanism that dynamically prepares the initial conditions required for exponential plateau inflation. The inflaton is decomposed into a coarse-grained mode and a high-occupancy, approximately Gaussian band of relativistic nonzero modes. Gaussian--Hartree averaging of the potential produces an exact variance-dependent minimum, which places the coarse-grained field high on the plateau when the excitation variance is large. Under a translation-invariant microcanonical measure, the available phase-space volume is exponentially concentrated near this minimum, while an order-one homogeneous kinetic-energy fraction is exponentially atypical. During expansion, the preparation modes redshift as radiation, σ^2∝ a^−2 and ρ_χ∝ a^−4. Although the induced minimum rapidly moves toward the vacuum, the force acting on the coarse-grained mode is bounded by an exponentially small factor, yielding analytic upper limits on its velocity, displacement, and kinetic fraction. We derive a sufficient condition for the subsequent number of slow-roll e-folds and exhibit a benchmark with more than 60 e-folds. The mechanism also motivates correlated finite-onset signatures: large-scale power suppression with decaying oscillations and a variance-convolution bispectrum.
ER -