Initial conditions in hybrid inflation: exploration by MCMC technique

TL;DR

This paper uses a Bayesian MCMC approach to explore initial conditions in hybrid inflation, revealing a broader set of successful starting points outside the narrow valley, with implications for inflationary models.

Contribution

It demonstrates the existence of successful initial conditions outside the inflationary valley using MCMC, expanding understanding of initial condition fine-tuning in hybrid inflation.

Findings

Successful initial conditions are not limited to the valley.

Existence of a fractal structure in initial conditions.

Results are applicable to various hybrid inflation models.

Abstract

In hybrid inflation, initial field values leading to sufficiently long inflation were thought be fine-tuned in a narrow band along the inflationary valley. A re-analysis of this problem has shown that there exists a non negligible proportion of successful initial conditions exterior to the valley, organized in a complex structure with fractal boundaries, and whose origin has been explained. Their existence in a large part of the parameter space has been demonstrated using a bayesian Monte-Carlo-Markov-Chain (MCMC) method, and natural bounds on potential parameters have been established. Moreover, these results are shown to be valid not only for the original hybrid model, but also for other hybrid realizations in various frameworks.