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arXiv · 2604.25813

Geometric Constraints on the Pre-Recombination Expansion History from the Hubble Tension

Davide Pedrotti
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Abstract

I perform a model-independent reconstruction of the background pre-recombination expansion history of the Universe. I find that purely early-time resolutions to the Hubble tension, satisfying the geometric CMB constraints, exist at the background level. This class of solutions requires a smooth transition around matter-radiation equality, characterized by a $\simeq 15\%$ expansion rate enhancement prior to recombination. This result serves as a blueprint for future model-building approaches, providing a background stress-test for Hubble tension proposals.

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Davide Pedrotti. 2026-04-28. Geometric Constraints on the Pre-Recombination Expansion History from the Hubble Tension. https://arxiv.org/abs/2604.25813

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