The $R_{\mathrm{h}}=ct$ universe and quintessence

TL;DR

This paper explores the $R_{h}=ct$ universe model, which differs from $ ext{Lambda CDM}$ by its simple equation of state, and investigates quintessence as a potential dark energy source compatible with this model.

Contribution

It demonstrates that quintessence can serve as a viable dark energy component in the $R_{h}=ct$ universe, which challenges the notion that a cosmological constant is necessary.

Findings

Quintessence can produce the required dark energy in the $R_{h}=ct$ universe.

The model's equation of state $ ho + 3p=0$ excludes a cosmological constant.

Alternative dark energy sources like quintessence are compatible with the $R_{h}=ct$ framework.

Abstract

Over the last few years the $R_{\mathrm{h}}=ct$ universe has received a lot of attention, particularly when observational evidence seems to favor this over the standard $\Lambda$ cold dark matter ($\Lambda CDM$) universe. Like the $\Lambda CDM$, the $R_{\mathrm{h}}=ct$ universe is based on a Friedmann-Robertson-Walker (FRW) cosmology where the total energy density $\rho$ and pressure $p$ of the cosmic fluid contain a dark energy component besides the usual (dark and baryonic) matter and radiation components. However unlike the $\Lambda CDM$ this model has the simple equation of state (EOS) $\rho + 3p = 0$, i.e., its total active gravitational mass vanishes, which would therefore exclude a cosmological constant as the source of its dark energy component. Faced with this issue, in this paper we examine various possible sources for the dark energy component of the $R_{\mathrm{h}}=ct$ universe and show that quintessence which has been used in other various dynamical dark energy models could also be a possible source in this case.