Constraints on the three-fluid model of curvaton decay

TL;DR

This paper investigates the decay dynamics of a three-fluid curvaton model, deriving constraints on interactions and initial conditions to ensure proper cosmological evolution, and discusses implications for non-gaussianity.

Contribution

It provides a detailed analysis of the three-fluid curvaton decay, including constraints on interaction strengths and initial densities, with insights into adiabaticity and non-gaussianity.

Findings

Small initial curvaton density is preferred with low reheating temperature.

Time-dependent interactions can relax initial density constraints.

Purely adiabatic final states require fine-tuning.

Abstract

A three fluid system describing the decay of the curvaton is studied by numerical and analytical means. We place constraints on the allowed interaction strengths between the fluids and initial curvaton density by requiring that the curvaton decays before nucleosynthesis while nucleosynthesis, radiation-matter equality and decoupling occur at correct temperatures. We find that with a continuous, time-independent interaction, a small initial curvaton density is naturally preferred along with a low reheating temperature. Allowing for a time-dependent interaction, this constraint can be relaxed. In both cases, a purely adiabatic final state can be generated, but not without fine-tuning. Unlike in the two fluid system, the time-dependent interactions are found to have a small effect on the curvature perturbation itself due to the different nature of the system. The presence of non-gaussianity in the model is discussed.