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Early recombination as a solution to the $H_0$ tension

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arxiv 2007.03381 v1 pith:HS7GJ23G submitted 2020-07-07 astro-ph.CO gr-qchep-ph

classification astro-ph.COgr-qchep-ph
keywords modeltensiondatameasurementsrecombinationconditionsearlyexample
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

We show that the $H_0$ tension can be resolved by making recombination earlier, keeping the fit to cosmic microwave background (CMB) data almost intact. We provide a suite of general necessary conditions to give a good fit to CMB data while realizing a high value of $H_0$ suggested by local measurements. As a concrete example for a successful scenario with early recombination, we demonstrate that a model with time-varying $m_e$ can indeed satisfy all the conditions. We further show that such a model can also be well fitted to low-$z$ distance measurements of baryon acoustic oscillation (BAO) and type-Ia supernovae (SNeIa) with a simple extension of the model. Time-varying $m_e$ in the framework of $\Omega_k\Lambda$CDM is found to be a sufficient and excellent example as a solution to the $H_0$ tension, yielding $H_0=72.3_{-2.8} ^{+2.7}\,$km/sec/Mpc from the combination of CMB, BAO and SNeIa data even without incorporating any direct local $H_0$ measurements. Apart from the $H_0$ tension, this model is also favored from the viewpoint of the CMB lensing anomaly.

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Forward citations

Cited by 13 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

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    astro-ph.CO 2026-07 accept novelty 6.0 of 10

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  4. Interpreting the Hubble tension with a cascade decaying dark matter sector

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    astro-ph.CO 2026-07 conditional novelty 5.0 of 10

    In a systematic head-to-head analysis, early dark energy and early modified gravity models reduce the Hubble tension to about 3σ and are favored over ΛCDM, while radiation and late-time alternatives are not.

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