Cosmology and Astrophysics of CP-Violating Axions
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| Format: | Preprint |
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2024
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| author | Ramadan, Omar F. Sakstein, Jeremy Croon, Djuna |
| author_facet | Ramadan, Omar F. Sakstein, Jeremy Croon, Djuna |
| contents | We study the cosmology and astrophysics of axion-like particles (ALPs) with CP-violating Yukawa couplings to nucleons. At finite nucleon density, the ALP's dynamics is governed by an effective potential which is the sum of the bare periodic potential and a linear potential whose strength depends on the nucleon density. We identify a critical nucleon density $ρ_c$ controlling the dynamics. At densities smaller than $ρ_c$ the effective potential is a tilted sinusoidal curve and the field is displaced from its zero-density minimum. At densities larger than $ρ_c$ the minima (and maxima) are absent, and the ALP is destabilized. Astrophysically, this implies that neutron stars can source a radial ALP field, providing a complementary probe to equivalence principle tests. Cosmologically, the ALP may have been destabilized in the early Universe and could have made large field excursions. We discuss model-building applications of our results for such early universe scenarios. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2408_02294 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Cosmology and Astrophysics of CP-Violating Axions Ramadan, Omar F. Sakstein, Jeremy Croon, Djuna High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Theory We study the cosmology and astrophysics of axion-like particles (ALPs) with CP-violating Yukawa couplings to nucleons. At finite nucleon density, the ALP's dynamics is governed by an effective potential which is the sum of the bare periodic potential and a linear potential whose strength depends on the nucleon density. We identify a critical nucleon density $ρ_c$ controlling the dynamics. At densities smaller than $ρ_c$ the effective potential is a tilted sinusoidal curve and the field is displaced from its zero-density minimum. At densities larger than $ρ_c$ the minima (and maxima) are absent, and the ALP is destabilized. Astrophysically, this implies that neutron stars can source a radial ALP field, providing a complementary probe to equivalence principle tests. Cosmologically, the ALP may have been destabilized in the early Universe and could have made large field excursions. We discuss model-building applications of our results for such early universe scenarios. |
| title | Cosmology and Astrophysics of CP-Violating Axions |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2408.02294 |