Small cosmological constant from a peculiar inflaton potential

We propose a novel scenario to explain the small cosmological constant (CC) by a peculiar inflaton potential. The shape almost satisfies the following conditions: The inflation is eternal if the CC is positive and not eternal if the CC is negative. Although realizing the peculiar shape has a similar amount of fine-tuning as the CC, the shape can be made stable under radiative corrections in the effective theory. 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 is low. The Hubble parameter during inflation, H-inf, is required to be smaller than the present CC scale, and, thus, the CC relaxed during inflation with the low renormalization scale, similar to H-inf, is safe from the radiative corrections from the standard model particles. The scenario can have a consistent thernial history, but the present equation of state of the Universe is predicted to slightly differ from the one for the Lambda CDM model. In a time-varying CC model, CC can be relaxed from (10(3) GeV)(4), and in a model with a light scalar field scanning the CC during inflation, CC can be relaxed from (10 MeV)(4).

Automated summary

This study proposes a novel scenario to explain the small cosmological constant by using a peculiar inflaton potential. The scenario achieves stability and relaxation of the cosmological constant through a specific shape of the inflaton potential. The scenario does not require eternal inflation but involves a large e-folding number and a low inflation scale. By introducing a slowly varying cosmological constant, a vanishingly small cosmological constant is obtained for the dominant volume of the Universe after inflation.