Small cosmological constant from a peculiar inflaton potential

TL;DR

This paper introduces a new inflaton potential model that naturally explains the smallness of the cosmological constant by dynamically evolving from positive to negative values, resulting in a universe with a tiny CC without requiring eternal inflation.

Contribution

The paper presents a stable, radiatively natural inflaton potential that dynamically reduces the cosmological constant, differing from previous static or fine-tuned approaches.

Findings

The potential leads to a universe with a very small CC after inflation.

The model predicts a different current equation of state than the standard ΛCDM model.

The scenario is compatible with a consistent thermal history.

Abstract

We propose a novel scenario to explain the small cosmological constant (CC) by a finely tuned inflaton potential. The tuned shape is stable under radiative corrections, and our setup is technically natural. The peculiar po- tential approximately satisfies the following conditions: the inflation is eternal if CC is positive, and not eternal if CC is negative. By introducing a slowly varying CC from a positive value to a negative value, the dominant volume of the Universe after the inflation turns out to have a vanishingly small CC. The scenario does not require eternal inflation but the e-folding number is exponentially large and the inflation scale should be low enough. The scenario can have a consistent thermal history, but the present equation of state of the Universe is predicted to differ from the prediction of the {\Lambda}CDM model. A concrete model with a light scalar field is studied.