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| Main Authors: | , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2502.18693 |
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| _version_ | 1866929732295065600 |
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| author | Brown, Lucas Profumo, Stefano Gangadharan, Aditi Koç, Zeynep Su |
| author_facet | Brown, Lucas Profumo, Stefano Gangadharan, Aditi Koç, Zeynep Su |
| contents | A strong first-order phase transition in a dark sector may produce all or part of the low-frequency gravitational wave signal recently reported by the NANOGrav Collaboration and other pulsar timing arrays. Here we point out, with a simple toy model, that even if the amplitude of the gravitational wave background from the dark phase transition is insufficient to match the NANOGrav signal, a modified expansion rate at early times may considerably enhance the gravitational wave signal. In particular, a faster-than-standard expansion rate, triggered, for instance, by the presence of one or more additional sources of energy density redshifting with higher powers of temperatures than radiation, boosts upper limits on the gravitational wave signal from first-order cosmological phase transitions, enlarging the slate of possible dark sector scenarios matching the NANOGrav signal. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_18693 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A Louder Gravitational Wave Bang from a Fast-Expanding Universe Brown, Lucas Profumo, Stefano Gangadharan, Aditi Koç, Zeynep Su Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology High Energy Physics - Theory A strong first-order phase transition in a dark sector may produce all or part of the low-frequency gravitational wave signal recently reported by the NANOGrav Collaboration and other pulsar timing arrays. Here we point out, with a simple toy model, that even if the amplitude of the gravitational wave background from the dark phase transition is insufficient to match the NANOGrav signal, a modified expansion rate at early times may considerably enhance the gravitational wave signal. In particular, a faster-than-standard expansion rate, triggered, for instance, by the presence of one or more additional sources of energy density redshifting with higher powers of temperatures than radiation, boosts upper limits on the gravitational wave signal from first-order cosmological phase transitions, enlarging the slate of possible dark sector scenarios matching the NANOGrav signal. |
| title | A Louder Gravitational Wave Bang from a Fast-Expanding Universe |
| topic | Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2502.18693 |