Cosmological $\Lambda$ driven inflation and produced massive particles

TL;DR

This paper proposes a cosmological model where a quantum spacetime-originated cosmological constant drives inflation, produces massive particles, and naturally explains the observed universe's evolution and the cosmic coincidence problem.

Contribution

It introduces a novel inflationary scenario driven by a quantum-originated cosmological constant, linking particle production to the universe's evolution and aligning with Planck 2018 data.

Findings

Inflation driven by a decreasing cosmological constant and particle production.

Reheating converts the cosmological constant energy into matter and radiation.

The model potentially resolves the cosmic coincidence problem.

Abstract

Suppose that the early Universe starts with a quantum spacetime originated cosmological $\Lambda$-term at the Planck scale $M_{\rm pl}$. The cosmological energy density $\rho_{_{_\Lambda}}$ drives inflation and simultaneously reduces its value to create the matter-energy density $\rho_{_{_M}}$ via the continuous pair productions of massive fermions and antifermions. The decreasing $\rho_{_{_\Lambda}}$ and increasing $\rho_{_{_M}}$, in turn, slows down the inflation to its end when the pair production rate $\Gamma_M$ is larger than the Hubble rate $H$. The density $\rho_{_{_\Lambda}}$ and Hubble rate $H$ are uniquely determined by two independent equations from the Einstein equation and energy conservation law, besides the $\rho_{_{_M}}$ is determined by pair productions. As a result, inflation naturally appears and theoretical results agree with Planck 2018 observations. Suppose that the reheating efficiently converts $\rho_{_{_\Lambda}}$ to $\rho_{_{_M}}\gg \rho_{_{_\Lambda}}$ accounting for the most relevant Universe mass, and some massive pairs decay to relativistic particles of energy density $\rho_{_{_R}}$ starting the hot Big Bang. The back reaction $\rho_{_{_M}}\leftrightarrow H\leftrightarrow \rho_{_{_\Lambda}}$ is weak but continues. As a consequence, $\rho_{_\Lambda}$ closely tracks down $\rho_{_R}$ from the reheating end up to the radiation-matter equilibrium, then it varies very slowly, $\rho_{_\Lambda}\propto$ constant, due to the transition from radiation dominant epoch to matter dominant epoch. Therefore the cosmic coincidence problem can be possibly avoided.