A two-scalar model for a small but nonzero cosmological constant

TL;DR

This paper revisits a two-scalar model explaining a small, nonzero cosmological constant, showing it can produce mini-inflations and address the coincidence problem through unique scalar-field dynamics.

Contribution

It introduces a novel two-scalar model where scalar energy density remains constant temporarily, leading to mini-inflations and offering insights into the coincidence problem.

Findings

Scalar energy density behaves truly constant for limited times.

Mini-inflations occur when scalar density overtakes matter density.

Solution exhibits chaos-like nonlinear dynamics.

Abstract

We revisit a model of the two-scalar system proposed previously for understanding a small but nonzero cosmological constant. The model provides solutions of the scalar-fields energy $\rho_s$ which behaves truly constant for a limited time interval rather than in the way of tracker- or scaling-type variations. This causes a mini-inflation, as indicated by recent observations. As another novel feature, $\rho_s$ and the ordinary matter density $\rho_m$ fall off always side by side, but interlacing, also like (time)$^{-2}$ as an overall behavior in conformity with the scenario of a decaying cosmological constant. A mini-inflation occurs whenever $\rho_s$ overtakes $\rho_m$, which may happen more than once, shedding a new light on the coincidence problem. We present a new example of the solution, and offer an intuitive interpretation of the mechanism of the nonlinear dynamics. We also discuss a chaos-like nature of the solution.