Interpreting Cosmic Birefringence and DESI Data with Evolving Axion in $Λ$CDM
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| Format: | Preprint |
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2025
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| author | Nakagawa, Shota Nakai, Yuichiro Qiu, Yu-Cheng Yamada, Masaki |
| author_facet | Nakagawa, Shota Nakai, Yuichiro Qiu, Yu-Cheng Yamada, Masaki |
| contents | Recent cosmological observations have revealed growing tensions with the standard $Λ$CDM model, including indications of isotropic cosmic birefringence and deviations from $w = -1$ in the dark energy equation of state, as suggested by DESI and supernova measurements. In this paper, we point out that such deviations can arise even from a subdominant energy density component. We then propose a unified framework based on a dynamical axion field that simultaneously accounts for both anomalies, providing a simple and natural extension of the standard $Λ$CDM model. In our scenario, the axion field with $2H_0\lesssim m\lesssim 6H_0$, where $H_0$ is the current Hubble constant, induces a nonzero rotation of the CMB polarization plane and modifies the present-day dark energy equation of state. This framework accommodates recent observational data with natural parameter choices, even for a string axion with a decay constant of order $10^{17}\,$GeV. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_18924 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Interpreting Cosmic Birefringence and DESI Data with Evolving Axion in $Λ$CDM Nakagawa, Shota Nakai, Yuichiro Qiu, Yu-Cheng Yamada, Masaki Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology High Energy Physics - Theory Recent cosmological observations have revealed growing tensions with the standard $Λ$CDM model, including indications of isotropic cosmic birefringence and deviations from $w = -1$ in the dark energy equation of state, as suggested by DESI and supernova measurements. In this paper, we point out that such deviations can arise even from a subdominant energy density component. We then propose a unified framework based on a dynamical axion field that simultaneously accounts for both anomalies, providing a simple and natural extension of the standard $Λ$CDM model. In our scenario, the axion field with $2H_0\lesssim m\lesssim 6H_0$, where $H_0$ is the current Hubble constant, induces a nonzero rotation of the CMB polarization plane and modifies the present-day dark energy equation of state. This framework accommodates recent observational data with natural parameter choices, even for a string axion with a decay constant of order $10^{17}\,$GeV. |
| title | Interpreting Cosmic Birefringence and DESI Data with Evolving Axion in $Λ$CDM |
| topic | Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2503.18924 |