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Cosmic Clues: DESI, Dark Energy, and the Cosmological Constant Problem

Wen Yin

TL;DR

The paper tackles the cosmological constant problem by linking a flat scalar field with a linear potential to CC relaxation during inflation, and shows that this setup can reproduce a time-varying dark energy signal compatible with DESI data. Using a Big Bang cosmology with $V_C(\phi)\simeq V_\phi \phi$ and the equation of motion $\ddot{\phi}+3H\dot{\phi}=-V_\phi$, it demonstrates late-time deviations from $\Lambda$CDM that can fit DESI anomaly. It derives a post-inflation CC distribution $\frac{d}{dV_C} L_{\rm end}^3 \propto \exp\left[-\frac{(V_C-V_C^{(0)})^2}{2\sigma^2}\right]$ with $\sigma \approx \frac{V_\phi M_{\rm pl}}{\sqrt{6}}$, arguing that typical $V_{C,\rm ini}$ can be near $10^{-47}\ \text{GeV}^4$ for plausible $V_\phi$ and may match the DESI-preferred region. The work suggests a conceptual link between DESI's hints of evolving dark energy and a mechanism to keep the cosmological constant small, while highlighting the need for UV completion and phenomenological tests of couplings to standard-model or dark-sector fields.

Abstract

Several attempts to solve the cosmological constant problem, which concerns the value of the cosmological constant being extremely smaller than the Standard Model mass scales, have introduced a scalar field with a very flat potential that can be approximated as linear around any given position. The scalar field scans the cosmological constant in such a way that the current small value is explained. Recently, Dark Energy Spectroscopic Instrument (DESI) reported the results of the first year. Combining the data with CMB, Pantheon, Union3, and/or DES-SN5YR, there is a preference or anomaly, indicating that the dark energy in the current Universe slightly deviates from that in the $Λ$CDM model and varies over time. In this paper, I show that the simple linear potential of a scalar field that may explain the small cosmological constant can explain the DESI anomaly. In particular, the model proposed by the present author in 2108.04246, which relaxes the cosmological constant by the condition that inflation ends, predicts a time-dependence of the dark energy close to the one favored by the data.

Cosmic Clues: DESI, Dark Energy, and the Cosmological Constant Problem

TL;DR

The paper tackles the cosmological constant problem by linking a flat scalar field with a linear potential to CC relaxation during inflation, and shows that this setup can reproduce a time-varying dark energy signal compatible with DESI data. Using a Big Bang cosmology with and the equation of motion , it demonstrates late-time deviations from CDM that can fit DESI anomaly. It derives a post-inflation CC distribution with , arguing that typical can be near for plausible and may match the DESI-preferred region. The work suggests a conceptual link between DESI's hints of evolving dark energy and a mechanism to keep the cosmological constant small, while highlighting the need for UV completion and phenomenological tests of couplings to standard-model or dark-sector fields.

Abstract

Several attempts to solve the cosmological constant problem, which concerns the value of the cosmological constant being extremely smaller than the Standard Model mass scales, have introduced a scalar field with a very flat potential that can be approximated as linear around any given position. The scalar field scans the cosmological constant in such a way that the current small value is explained. Recently, Dark Energy Spectroscopic Instrument (DESI) reported the results of the first year. Combining the data with CMB, Pantheon, Union3, and/or DES-SN5YR, there is a preference or anomaly, indicating that the dark energy in the current Universe slightly deviates from that in the CDM model and varies over time. In this paper, I show that the simple linear potential of a scalar field that may explain the small cosmological constant can explain the DESI anomaly. In particular, the model proposed by the present author in 2108.04246, which relaxes the cosmological constant by the condition that inflation ends, predicts a time-dependence of the dark energy close to the one favored by the data.
Paper Structure (4 sections, 9 equations, 1 figure)

This paper contains 4 sections, 9 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Big Bang Cosmology with a Linear Potential Scalar Field
  3. Prediction of Time Varying Dark Energy from CC Relaxation and DESI anomaly
  4. Conclusions and discussion

Figures (1)

  • Figure 1: Expansion history of the late time Universe with a linear potential scalar field. The red curves denote the case $V_\phi\approx \{3.1,7.6,12\}\times 10^{-66} {\rm \, GeV} ^3$ from top to bottom. The green 1 and 2$\sigma$ regions are taken from DESI:2024mwx. We fix $V_{C,\rm ini}\approx 3.0\times 10^{-47} {\rm \, GeV} ^4$ and $\rho_m\approx 1.1\times 10^{-47} {\rm \, GeV} ^4$.