Footprints of the QCD Crossover on Cosmological Gravitational Waves at Pulsar Timing Arrays
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866929433680543744 |
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| author | Franciolini, Gabriele Racco, Davide Rompineve, Fabrizio |
| author_facet | Franciolini, Gabriele Racco, Davide Rompineve, Fabrizio |
| contents | Pulsar Timing Arrays (PTAs) have reported evidence for a stochastic gravitational wave (GW) background at nHz frequencies, possibly originating in the early Universe. We show that the spectral shape of the low-frequency (causality) tail of GW signals sourced at temperatures around $T\gtrsim 1$ GeV is distinctively affected by confinement of strong interactions (QCD), due to the corresponding sharp decrease in the number of relativistic species. Bayesian analyses in the NANOGrav 15 years and the previous International PTA datasets reveal a significant improvement in the fit with respect to cubic power-law spectra, previously employed for the causality tail. This suggests that the inclusion of Standard Model effects on GWs can have a potentially decisive impact on model selection. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2306_17136 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Footprints of the QCD Crossover on Cosmological Gravitational Waves at Pulsar Timing Arrays Franciolini, Gabriele Racco, Davide Rompineve, Fabrizio Cosmology and Nongalactic Astrophysics High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology High Energy Physics - Lattice High Energy Physics - Phenomenology Pulsar Timing Arrays (PTAs) have reported evidence for a stochastic gravitational wave (GW) background at nHz frequencies, possibly originating in the early Universe. We show that the spectral shape of the low-frequency (causality) tail of GW signals sourced at temperatures around $T\gtrsim 1$ GeV is distinctively affected by confinement of strong interactions (QCD), due to the corresponding sharp decrease in the number of relativistic species. Bayesian analyses in the NANOGrav 15 years and the previous International PTA datasets reveal a significant improvement in the fit with respect to cubic power-law spectra, previously employed for the causality tail. This suggests that the inclusion of Standard Model effects on GWs can have a potentially decisive impact on model selection. |
| title | Footprints of the QCD Crossover on Cosmological Gravitational Waves at Pulsar Timing Arrays |
| topic | Cosmology and Nongalactic Astrophysics High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology High Energy Physics - Lattice High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2306.17136 |