Overview

• The peer-reviewed study in Physical Review Letters reports a best-fit model with primordial magnetic fields around 0.2 nanogauss.
• Researchers matched simulation outputs to Lyman-α forest data, finding that weak-field models align better with observations.
• The new upper limit is several times lower than prior estimates, tightening constraints on early-universe magnetism.
• Including weak primordial fields in the models changes the density and appearance of the cosmic web in ways that could hasten early star and galaxy formation.
• The international team led by SISSA, with collaborators from Hertfordshire, Cambridge, Nottingham, Stanford, and Potsdam, points to future JWST observations for further validation.