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<p>Primordial magnetic fields (PMFs), long studied as relics of the early Universe, accelerate recombination and have been proposed as a way to relieve the Hubble tension. However, previous studies relied on simplified toy models. Here we use recent evaluations of recombination with PMFs, incorporating full magnetohydrodynamic simulations and detailed Lyman-α radiative transfer, to test PMF-enhanced recombination (bΛCDM) against observational data for the cosmic microwave background, baryon acoustic oscillations and type Ia supernovae. Focusing on non-helical PMFs with a Batchelor spectrum, we find a preference for present-day total field strengths of approximately 5–10 pG. Depending on the dataset combination, this preference ranges from mild (~1.8<i>σ</i> with Planck+DESI) to moderate (~3<i>σ</i> with Planck+DESI+SH0ES-calibrated supernovae) significance. The bΛCDM has Planck+DESI <i>χ</i><sup>2</sup> values equal to or better than those for ΛCDM while predicting a higher Hubble constant. Future high-resolution cosmic microwave background temperature and polarization measurements will be crucial for confirming or further constraining PMFs at recombination. Field strengths of 5–10 pG align closely with those required for cluster magnetic fields to originate entirely from primordial sources, without the need for extra dynamo amplification.</p>

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Hints of primordial magnetic fields at recombination and implications for the Hubble tension

  • 期刊论文

  • 发表日期：

    2025年12月12日

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  • Karsten Jedamzik,
  • Levon Pogosian,
  • Tom Abel

摘要

Primordial magnetic fields (PMFs), long studied as relics of the early Universe, accelerate recombination and have been proposed as a way to relieve the Hubble tension. However, previous studies relied on simplified toy models. Here we use recent evaluations of recombination with PMFs, incorporating full magnetohydrodynamic simulations and detailed Lyman-α radiative transfer, to test PMF-enhanced recombination (bΛCDM) against observational data for the cosmic microwave background, baryon acoustic oscillations and type Ia supernovae. Focusing on non-helical PMFs with a Batchelor spectrum, we find a preference for present-day total field strengths of approximately 5–10 pG. Depending on the dataset combination, this preference ranges from mild (~1.8σ with Planck+DESI) to moderate (~3σ with Planck+DESI+SH0ES-calibrated supernovae) significance. The bΛCDM has Planck+DESI χ2 values equal to or better than those for ΛCDM while predicting a higher Hubble constant. Future high-resolution cosmic microwave background temperature and polarization measurements will be crucial for confirming or further constraining PMFs at recombination. Field strengths of 5–10 pG align closely with those required for cluster magnetic fields to originate entirely from primordial sources, without the need for extra dynamo amplification.