Quintessence From The Decay of a Superheavy Dark Matter

TL;DR

This work addresses the cosmological constant problem and the coincidence puzzle by proposing that dark energy originates from the condensation of a scalar field $\phi_q$ produced in the slow decay of superheavy dark matter. The authors derive the coupled evolution equations for the decaying SDM component and the quintessence field, identify an early tracking regime and a late-time decay-driven regime, and perform numerical solutions including Standard Model interactions to verify that the quintessence density can match observations across a broad parameter space. They find that the quintessence equation of state $w_q$ remains near $-1$ for a wide range of parameters and that DE perturbations are negligibly small, consistent with CMB and LSS data. The framework offers a top-down mechanism linking ultra-high-energy cosmic-ray physics to dark energy with minimal tuning and suggests observational tests via UHECRs, CMB, and potential axion-like particle candidates.

Abstract

We investigate the possibility of replacing the cosmological constant with gradual condensation of a scalar field produced during the decay of a superheavy dark matter. The advantage of this class of models to the ordinary quintessence is that the evolution of the dark energy and the dark energy are correlated and cosmological coincidence problem is solved. This model does not need a special form for the quitessence potential and even a simple $φ^4$ theory or an axion like scalar is enough to explain the existence of the Dark Energy. We show that the model has an intrinsic feedback between energy density of the dark matter and the scalar field such that for a large volume of the parameter space the equation of state of the scalar field from very early in the history of the Universe is very close to a cosmological constant. Other aspects of this model are consistent with recent CMB and LSS observations.

Figures (4)

• Figure 1: Evolution of quintessence field (left), its derivative (center) and its total energy density (right) for ${\Gamma}_0 \equiv {\Gamma}_q/\Gamma = 10^{-16}$ (magenta) (see text for details), $5 {\Gamma}_0$ (cyan), $10 {\Gamma}_0$ (blue), $50 {\Gamma}_0$ (green), $100 {\Gamma}_0$ (red). Dash line is the observed value of the dark energy. $m_q = 10^{-6} eV$, $\lambda = 10^{-20}$.
• Figure 2: Evolution of the contribution to the total energy density of ${\phi}_q$ for ${\Gamma}_0 \equiv {\Gamma}_q/\Gamma = 10^{-16}$ and : Left, $m_q = 10^{-8} eV$ and $\lambda = 10^{-20}$; Center, $m_q = 10^{-6} eV$ and $\lambda = 10^{-20}$; Right, $m_q = 10^{-6} eV$ and $\lambda = 10^{-10}$.Curves are: mass (red), self-interaction (green), kinetic energy (cyan) and interaction with SDM (blue).
• Figure 3: Left: Evolution of total density with redshift for ${\Gamma}_0 \equiv {\Gamma}_q/\Gamma = 10^{-16}$ (magenta) (see text for details), $5 {\Gamma}_0$ (cyan), $10 {\Gamma}_0$ (blue), $50 {\Gamma}_0$ (green), $100 {\Gamma}_0$ (red). Dash line is the observed value of the dark energy. $m_q = 10^{-6} eV$, $\lambda = 10^{-20}$. Right: Relative density of dark energy and CDM as a function of ${\Gamma}_q/\Gamma$. The x-axis is normalized to ${\Gamma}_0 \equiv {\Gamma}_q/\Gamma = 10^{-16}$.
• Figure 4: Quintessence energy density for: Left, $m_q = 10^{-3} eV$ (cyan), $m_q = 10^{-5} eV$ (magenta), $m_q = 10^{-6} eV$ (red) and $m_q = 10^{-8} eV$ (green), $\lambda = 10^{-20}$; Right, $\lambda = 10^{-10}$ (cyan), $\lambda = 10^{-15}$, $\lambda = 10^{-20}$ and $\lambda = 10^{-25}$ (green), $m_q = 10^{-6} eV$. The difference between quintessence density for the last 3 values of $\lambda$ is smaller than the resolution of the plot. Dash line is the observed energy density of the dark energy.