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| Main Authors: | , , , |
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| Format: | Preprint |
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2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2604.13718 |
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| _version_ | 1866914475375853568 |
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| author | Pandey, Shashank Shekhar Ruchika Mukherjee, Subhadeep Majumdar, A. S. |
| author_facet | Pandey, Shashank Shekhar Ruchika Mukherjee, Subhadeep Majumdar, A. S. |
| contents | We study the optical depth to reionization in a cosmological setting that includes backreaction from matter inhomogeneities, using the Buchert averaging formalism. We construct a spacetime model consisting of multiple inhomogeneous domains, hereafter referred to as the backreaction model, characterized by a set of parameters. We first examine how these parameters influence the computation of the optical depth to reionization, $τ_{reion}$. Next, we carry out a Markov Chain Monte Carlo (MCMC) analysis based on the PantheonPlus+SH0ES Type Ia supernova sample to infer the best-fit values of the model parameters, and then use these to evaluate $τ_{reion}$. We obtain $τ_{reion} = 0.0581^{+0.0105}_{-0.0096}$ (68$\%$ confidence limits). This result indicates that, when PantheonPlus+SH0ES data are used to constrain the model parameters, our backreaction model yields a value of $τ_{reion}$ that aligns more closely with observational estimates than the value predicted by the standard cosmological model. We further demonstrate that the backreaction model leads to a modest reduction of the Hubble tension, while avoiding the need for exotic or non-standard physics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_13718 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Optical depth to reionization in a Universe with multiple inhomogeneous domains Pandey, Shashank Shekhar Ruchika Mukherjee, Subhadeep Majumdar, A. S. Cosmology and Nongalactic Astrophysics We study the optical depth to reionization in a cosmological setting that includes backreaction from matter inhomogeneities, using the Buchert averaging formalism. We construct a spacetime model consisting of multiple inhomogeneous domains, hereafter referred to as the backreaction model, characterized by a set of parameters. We first examine how these parameters influence the computation of the optical depth to reionization, $τ_{reion}$. Next, we carry out a Markov Chain Monte Carlo (MCMC) analysis based on the PantheonPlus+SH0ES Type Ia supernova sample to infer the best-fit values of the model parameters, and then use these to evaluate $τ_{reion}$. We obtain $τ_{reion} = 0.0581^{+0.0105}_{-0.0096}$ (68$\%$ confidence limits). This result indicates that, when PantheonPlus+SH0ES data are used to constrain the model parameters, our backreaction model yields a value of $τ_{reion}$ that aligns more closely with observational estimates than the value predicted by the standard cosmological model. We further demonstrate that the backreaction model leads to a modest reduction of the Hubble tension, while avoiding the need for exotic or non-standard physics. |
| title | Optical depth to reionization in a Universe with multiple inhomogeneous domains |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2604.13718 |