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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 10 Pith papers

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

  1. Hubble tension: the shape wall

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

    Late-time modifications to the expansion history can raise H0 by at most about 2% (conservative) to 3.7% (permissive) if the CMB acoustic scale is fixed.

  2. The $H_0$ world cup. II. A comprehensive competition between proposed Hubble tension solutions

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

    Against a common 2025-26 dataset (Planck PR4, ACT DR6, SPT-3G, DESI DR2, Pantheon+), early dark energy and early modified gravity models win the H0 competition (~3σ residual tension), while radiation and late-time sol...

  3. BAO miscalibration cannot rescue late-time solutions to the Hubble tension

    astro-ph.CO 2025-10 accept novelty 6.0 of 10

    Even after rescaling BAO data to prefer H0≈73 km/s/Mpc, none of six tested late-time dark-energy models can resolve the Hubble tension once unanchored SNeIa and CMB geometry are included.

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

    astro-ph.CO 2025-07 conditional novelty 6.0 of 10

    A cascade decaying dark matter model combining early and late effects still cannot reduce the Hubble tension below about 3 sigma, and is statistically disfavored relative to Lambda CDM.

  5. Direct Detection of Cosmic Walls with Paleo Detectors

    hep-ph 2025-05 conditional novelty 6.0 of 10

    Ancient minerals could preserve parallel damage tracks left by a passing cosmic wall, enabling a direct search for these rare objects with paleo detectors.

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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.

  7. Model-independent late-universe measurements of $H_0$ and $\Omega_K$ with the parametrization based on cosmic age-improved inverse distance ladder

    astro-ph.CO 2025-10 conditional novelty 5.0 of 10

    A cosmic-age-based inverse distance ladder with DESI DR2, DESY5, SGL, CC and GRB data gives H0=71.59±0.94 km/s/Mpc and ΩK=0.001±0.038.

  8. Mineral Detection of Neutrinos and Dark Matter 2025 Proceedings

    physics.ins-det 2025-08 unverdicted novelty 4.0 of 10

    A workshop proceedings presenting 20 status reports on mineral detectors as passive, long-exposure nuclear recoil detectors for dark matter, neutrinos, and cosmic rays.

  9. The Hubble tension: A decade review

    astro-ph.CO 2026-06 unverdicted novelty 3.0 of 10

    Pure early or late fixes to the Hubble tension are tightly constrained; remaining options are combined early-late interacting dark energy or new physics at the local-to-homogeneous transition.

  10. Alleviating the Hubble Tension via Cosmological Time Dilation in the meVSL Model

    physics.gen-ph 2025-09 reject novelty 3.0 of 10

    The meVSL model's parameter b reduces the baryon drag sound horizon, raising inferred H0, and changes the cosmological time-dilation exponent to n=1-b/4; the paper forecasts SN sample sizes to detect this.

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