Reheating after relaxation of large cosmological constant

TL;DR

This paper proposes a cosmological model where a scalar field relaxes a large vacuum energy, followed by a reheating phase that connects to the hot Big Bang, ensuring a consistent thermal history without fine-tuning the cosmological constant.

Contribution

It introduces a novel mechanism combining scalar field dynamics and null-energy-condition violation to achieve vacuum energy relaxation and subsequent reheating.

Findings

Successful relaxation of large vacuum energy without fine-tuning

Explicit example demonstrating reheating after relaxation

Consistent thermal history with negligible cosmological constant

Abstract

We present a cosmological model of an early-time scenario that incorporates a relaxation process of the would-be large vacuum energy, followed by a reheating era connecting to the standard hot big bang universe. Avoiding fine-tuning the cosmological constant is achieved by the dynamics of a scalar field whose kinetic term is modulated by an inverse power of spacetime curvature. While it is at work against radiative corrections to the dark energy, this mechanism alone would wipe out not only the vacuum energy but also all other matter contents. Our present work aims to complete the scenario by exploiting a null-energy-condition violating sector whose energy is eventually transferred to a reheating sector. We provide an explicit example of this process and thus a concrete scenario of the cosmic onset that realizes the thermal history of the Universe with a negligible cosmological constant.