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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2511.21789 |
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| _version_ | 1866913108882096128 |
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| author | Li, Xiang-Qian Yan, Hao-Peng Yue, Xiao-Jun |
| author_facet | Li, Xiang-Qian Yan, Hao-Peng Yue, Xiao-Jun |
| contents | The direct imaging of black holes by the Event Horizon Telescope (EHT) enables strong-field tests of gravity. We study the cosmological evolution and the black-hole shadow radius in 4D Einstein-Gauss-Bonnet (EGB) gravity coupled to Kaniadakis holographic dark energy (KHDE), adopting the future event horizon as the infrared cutoff. Using Cosmic Chronometers, Pantheon+ Type Ia supernovae, and DESI BAO data, we constrain the model with a Markov Chain Monte Carlo analysis. The best-fit values favor a phantom-like equation of state driven by Kaniadakis entropy ($c\simeq 1.18$, $β\simeq 2.26$), but $β$ remains weakly constrained ($β=2.26^{+0.11}_{-2.20}$), consistent with the standard holographic limit $β\to0$ at $1σ$. The EGB coupling is constrained to $α\simeq -0.004$, also consistent with General Relativity ($α=0$) at $1σ$. Guided by the posterior, we define five representative scenarios to probe the dynamical phase space. We find that the accretion history is highly sensitive to the thermodynamic sector: standard holographic cases yield monotonic evolution, whereas phantom-divide crossing leads to non-monotonic behavior in both the black hole mass and the vacuum shadow radius. Including a dispersive plasma medium, refraction dominates over intrinsic mass growth and induces an overall shrinkage of the observable shadow at high redshift; nevertheless, a residual intrinsic deviation of $\sim6\%$ (for our conservative accretion setup) persists at $z\simeq2$ relative to the $Λ$CDM prediction. These results indicate that, despite environmental dominance, precision population analyses of black hole shadows may help disentangle subtle dynamical dark-energy imprints from the standard cosmological paradigm. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_21789 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Cosmological Constraints on 4D Einstein-Gauss-Bonnet Gravity and Kaniadakis Holographic Dark Energy: Implications for Black Hole Shadows Li, Xiang-Qian Yan, Hao-Peng Yue, Xiao-Jun Cosmology and Nongalactic Astrophysics High Energy Physics - Theory The direct imaging of black holes by the Event Horizon Telescope (EHT) enables strong-field tests of gravity. We study the cosmological evolution and the black-hole shadow radius in 4D Einstein-Gauss-Bonnet (EGB) gravity coupled to Kaniadakis holographic dark energy (KHDE), adopting the future event horizon as the infrared cutoff. Using Cosmic Chronometers, Pantheon+ Type Ia supernovae, and DESI BAO data, we constrain the model with a Markov Chain Monte Carlo analysis. The best-fit values favor a phantom-like equation of state driven by Kaniadakis entropy ($c\simeq 1.18$, $β\simeq 2.26$), but $β$ remains weakly constrained ($β=2.26^{+0.11}_{-2.20}$), consistent with the standard holographic limit $β\to0$ at $1σ$. The EGB coupling is constrained to $α\simeq -0.004$, also consistent with General Relativity ($α=0$) at $1σ$. Guided by the posterior, we define five representative scenarios to probe the dynamical phase space. We find that the accretion history is highly sensitive to the thermodynamic sector: standard holographic cases yield monotonic evolution, whereas phantom-divide crossing leads to non-monotonic behavior in both the black hole mass and the vacuum shadow radius. Including a dispersive plasma medium, refraction dominates over intrinsic mass growth and induces an overall shrinkage of the observable shadow at high redshift; nevertheless, a residual intrinsic deviation of $\sim6\%$ (for our conservative accretion setup) persists at $z\simeq2$ relative to the $Λ$CDM prediction. These results indicate that, despite environmental dominance, precision population analyses of black hole shadows may help disentangle subtle dynamical dark-energy imprints from the standard cosmological paradigm. |
| title | Cosmological Constraints on 4D Einstein-Gauss-Bonnet Gravity and Kaniadakis Holographic Dark Energy: Implications for Black Hole Shadows |
| topic | Cosmology and Nongalactic Astrophysics High Energy Physics - Theory |
| url | https://arxiv.org/abs/2511.21789 |