$w_0$-probe: A new diagnostic of dark energy based on $Om$
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arXiv
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| Autori principali: | , , , |
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| Natura: | Preprint |
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2026
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| _version_ | 1866914605233602560 |
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| author | Bag, Satadru Keeley, Ryan E. Sahni, Varun Shafieloo, Arman |
| author_facet | Bag, Satadru Keeley, Ryan E. Sahni, Varun Shafieloo, Arman |
| contents | Recent DESI data suggest that dark energy may be evolving and motivate the use of model-independent diagnostics such as $Om(z)$ and probes of the equation of state (EoS) of dark energy, $w(z)$. Traditional reconstructions of $w(z)$ rely on differentiating the expansion history, $h(z)=H(z)/H_0$, which amplifies noise and systematic uncertainties. In this work, we introduce a new diagnostic, the $w_0$-probe, which is constructed from $Om(z)$, and which enables a direct determination of the current EoS from $h(z)$ without any additional differentiation. While retaining the null-test capability of $Om(z)$ for $Λ$CDM, the $w_0$-probe also provides a direct estimate of $w_0$ -- the current EoS of dark energy. We demonstrate that this reconstruction of $w_0$ is robust for any smooth underlying $w(z)$. We apply this method to Gaussian-process (GP) reconstructions of $h(z)$ using current SNe Ia+BAO+CMB data. Both $Om(z)$ and the $w_0$-probe exclude $Λ$CDM at the $95\%$ confidence level (C.L.), with the latter favouring $w_0\simeq-0.62 \pm 0.03$ at $95\%$ C.L. To mitigate potential over-constraining from GP priors, we additionally analyze $χ^2$-limited reconstructions with likelihoods exceeding the $95\%$ CPL threshold. The $w_0$-probe obtained from these high-likelihood samples again predominantly excludes $Λ$CDM and yields $w_0\in(-0.8,-0.5)$ at $z\to 0$, demonstrating the robustness of our results. The $w_0$-probe therefore provides a simple, model-independent, and robust diagnostic of the current EoS of dark energy. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_27230 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | $w_0$-probe: A new diagnostic of dark energy based on $Om$ Bag, Satadru Keeley, Ryan E. Sahni, Varun Shafieloo, Arman Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology Recent DESI data suggest that dark energy may be evolving and motivate the use of model-independent diagnostics such as $Om(z)$ and probes of the equation of state (EoS) of dark energy, $w(z)$. Traditional reconstructions of $w(z)$ rely on differentiating the expansion history, $h(z)=H(z)/H_0$, which amplifies noise and systematic uncertainties. In this work, we introduce a new diagnostic, the $w_0$-probe, which is constructed from $Om(z)$, and which enables a direct determination of the current EoS from $h(z)$ without any additional differentiation. While retaining the null-test capability of $Om(z)$ for $Λ$CDM, the $w_0$-probe also provides a direct estimate of $w_0$ -- the current EoS of dark energy. We demonstrate that this reconstruction of $w_0$ is robust for any smooth underlying $w(z)$. We apply this method to Gaussian-process (GP) reconstructions of $h(z)$ using current SNe Ia+BAO+CMB data. Both $Om(z)$ and the $w_0$-probe exclude $Λ$CDM at the $95\%$ confidence level (C.L.), with the latter favouring $w_0\simeq-0.62 \pm 0.03$ at $95\%$ C.L. To mitigate potential over-constraining from GP priors, we additionally analyze $χ^2$-limited reconstructions with likelihoods exceeding the $95\%$ CPL threshold. The $w_0$-probe obtained from these high-likelihood samples again predominantly excludes $Λ$CDM and yields $w_0\in(-0.8,-0.5)$ at $z\to 0$, demonstrating the robustness of our results. The $w_0$-probe therefore provides a simple, model-independent, and robust diagnostic of the current EoS of dark energy. |
| title | $w_0$-probe: A new diagnostic of dark energy based on $Om$ |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2605.27230 |