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Small cosmological constant from a peculiar inflaton potential

2022; American Physical Society; Volume: 106; Issue: 5 Linguagem: Inglês

10.1103/physrevd.106.055014

2470-0037

Wen Yin,

Dark Matter and Cosmic Phenomena

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, ${H}_{\mathrm{inf}}$, is required to be smaller than the present CC scale, and, thus, the CC relaxed during inflation with the low renormalization scale, $\ensuremath{\sim}{H}_{\mathrm{inf}}$, is safe from the radiative corrections from the standard model particles. The scenario can have a consistent thermal history, but the present equation of state of the Universe is predicted to slightly differ from the one for the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. In a time-varying CC model, CC can be relaxed from $({10}^{3}\text{ }\text{ }\mathrm{GeV}{)}^{4}$, and in a model with a light scalar field scanning the CC during inflation, CC can be relaxed from $(10\text{ }\text{ }\mathrm{MeV}{)}^{4}$.