New constraints on cosmological gravitational waves from CMB and BAO in light of dynamical dark energy
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arXiv
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2025
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| _version_ | 1866915705680560128 |
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| author | Wang, Sai Zhao, Zhi-Chao |
| author_facet | Wang, Sai Zhao, Zhi-Chao |
| contents | In this work, we derive upper limits on the physical energy-density fraction today of cosmological gravitational waves, denoted by $Ω_{\rm{gw}}h^{2}$, via analyzing \emph{Planck} \& ACT \& SPT CMB and DESI BAO data combination. In the standard cosmological model, we establish 95\% CL upper limits of $Ω_{\rm{gw}}h^{2} < 1.0 \times 10^{-6}$ for adiabatic initial conditions and $Ω_{\rm{gw}}h^{2} < 2.7 \times 10^{-7}$ for homogeneous initial conditions, assuming a uniform prior for $Ω_{\rm gw}h^{2}$. In light of dynamical dark energy, we get $Ω_{\rm{gw}}h^{2} < 7.2 \times 10^{-7}$ (adiabatic) and $Ω_{\rm{gw}}h^{2} < 2.4 \times 10^{-7}$ (homogeneous). In contrast, if a log-uniform prior was assumed for $Ω_{\rm gw}h^{2}$, these constraints can become tighter by a factor of $\sim4$, suggesting the results to be prior-sensitive. Furthermore, we project the sensitivity achievable with LiteBIRD \& CMB Stage-IV measurements of CMB and CSST observations of BAO, forecasting 68\% CL uncertainties of $σ= 2.5 \times 10^{-7}$ (adiabatic) and $σ= 1.0 \times 10^{-7}$ (homogeneous) for ${Ω_{\rm{gw}}h^{2}}$. The constraints we obtained in this work provide critical benchmarks for exploring the cosmological origins of gravitational waves within the frequency band $f \gtrsim 10^{-15}$\,Hz and potentially enable joint analysis with direct gravitational-wave detection sensitive to this regime. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_06930 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | New constraints on cosmological gravitational waves from CMB and BAO in light of dynamical dark energy Wang, Sai Zhao, Zhi-Chao Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology In this work, we derive upper limits on the physical energy-density fraction today of cosmological gravitational waves, denoted by $Ω_{\rm{gw}}h^{2}$, via analyzing \emph{Planck} \& ACT \& SPT CMB and DESI BAO data combination. In the standard cosmological model, we establish 95\% CL upper limits of $Ω_{\rm{gw}}h^{2} < 1.0 \times 10^{-6}$ for adiabatic initial conditions and $Ω_{\rm{gw}}h^{2} < 2.7 \times 10^{-7}$ for homogeneous initial conditions, assuming a uniform prior for $Ω_{\rm gw}h^{2}$. In light of dynamical dark energy, we get $Ω_{\rm{gw}}h^{2} < 7.2 \times 10^{-7}$ (adiabatic) and $Ω_{\rm{gw}}h^{2} < 2.4 \times 10^{-7}$ (homogeneous). In contrast, if a log-uniform prior was assumed for $Ω_{\rm gw}h^{2}$, these constraints can become tighter by a factor of $\sim4$, suggesting the results to be prior-sensitive. Furthermore, we project the sensitivity achievable with LiteBIRD \& CMB Stage-IV measurements of CMB and CSST observations of BAO, forecasting 68\% CL uncertainties of $σ= 2.5 \times 10^{-7}$ (adiabatic) and $σ= 1.0 \times 10^{-7}$ (homogeneous) for ${Ω_{\rm{gw}}h^{2}}$. The constraints we obtained in this work provide critical benchmarks for exploring the cosmological origins of gravitational waves within the frequency band $f \gtrsim 10^{-15}$\,Hz and potentially enable joint analysis with direct gravitational-wave detection sensitive to this regime. |
| title | New constraints on cosmological gravitational waves from CMB and BAO in light of dynamical dark energy |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2507.06930 |