Cosmic sign-reversal: non-parametric reconstruction of interacting dark energy with DESI DR2
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866909956854251520 |
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| author | Li, Yun-He Zhang, Xin |
| author_facet | Li, Yun-He Zhang, Xin |
| contents | A direct interaction between dark energy and dark matter provides a natural and important extension to the standard $Λ$CDM cosmology. We perform a non-parametric reconstruction of the vacuum energy ($w=-1$) interacting with cold dark matter using the cosmological data from DESI DR2, Planck CMB, and three SNIa samples (PP, DESY5, and Union3). By discretizing the coupling function $β(z)$ into 20 redshift bins and assuming a Gaussian smoothness prior, we reconstruct $β(z)$ without assuming any specific parameterization. The mean reconstructed $β(z)$ changes sign during cosmic evolution, indicating an energy transfer from cold dark matter to dark energy at early times and a reverse flow at late times. At high redshifts, $β(z)$ shows a $\sim 2σ$ deviation from $Λ$CDM. At low redshifts, the results depend on the SNIa sample: CMB+DESI and CMB+DESI+PP yield $β(z)$ consistent with zero within $2σ$, while CMB+DESI+DESY5 and CMB+DESI+Union3 prefer negative $β$ at $\sim2σ$. Both $χ^2$ tests and Bayesian analyses favor the $β(z)$ model, with CMB+DESI DR2+DESY5 showing the most significant support through the largest improvement in goodness of fit ($Δχ^2_{\rm MAP}=-17.76$) and strongest Bayesian evidence ($\ln\mathcal{B} = 5.98 \pm 0.69$). Principal component analysis reveals that the data effectively constrain three additional degrees of freedom in the $β(z)$ model, accounting for most of the improvement in goodness of fit. Our results demonstrate that the dynamical dark energy preference in current data can be equally well explained by such a sign-reversal interacting dark energy, highlighting the need for future observations to break this degeneracy. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_18477 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Cosmic sign-reversal: non-parametric reconstruction of interacting dark energy with DESI DR2 Li, Yun-He Zhang, Xin Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology High Energy Physics - Theory A direct interaction between dark energy and dark matter provides a natural and important extension to the standard $Λ$CDM cosmology. We perform a non-parametric reconstruction of the vacuum energy ($w=-1$) interacting with cold dark matter using the cosmological data from DESI DR2, Planck CMB, and three SNIa samples (PP, DESY5, and Union3). By discretizing the coupling function $β(z)$ into 20 redshift bins and assuming a Gaussian smoothness prior, we reconstruct $β(z)$ without assuming any specific parameterization. The mean reconstructed $β(z)$ changes sign during cosmic evolution, indicating an energy transfer from cold dark matter to dark energy at early times and a reverse flow at late times. At high redshifts, $β(z)$ shows a $\sim 2σ$ deviation from $Λ$CDM. At low redshifts, the results depend on the SNIa sample: CMB+DESI and CMB+DESI+PP yield $β(z)$ consistent with zero within $2σ$, while CMB+DESI+DESY5 and CMB+DESI+Union3 prefer negative $β$ at $\sim2σ$. Both $χ^2$ tests and Bayesian analyses favor the $β(z)$ model, with CMB+DESI DR2+DESY5 showing the most significant support through the largest improvement in goodness of fit ($Δχ^2_{\rm MAP}=-17.76$) and strongest Bayesian evidence ($\ln\mathcal{B} = 5.98 \pm 0.69$). Principal component analysis reveals that the data effectively constrain three additional degrees of freedom in the $β(z)$ model, accounting for most of the improvement in goodness of fit. Our results demonstrate that the dynamical dark energy preference in current data can be equally well explained by such a sign-reversal interacting dark energy, highlighting the need for future observations to break this degeneracy. |
| title | Cosmic sign-reversal: non-parametric reconstruction of interacting dark energy with DESI DR2 |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2506.18477 |