Overview

• A SISSA-led collaboration ran roughly 250,000 cosmological simulations and validated them against observational tracers of the intergalactic medium.
• The team reports a new upper limit on primordial magnetic field strength that is several times lower than previous estimates and consistent with recent CMB analyses.
• A standard cosmological model that includes an approximately 0.2 nanogauss primordial field matches the observed cosmic web more closely than models without such a field.
• Despite being billions of times weaker than a fridge magnet, the inferred fields would leave measurable signatures and modestly accelerate early star and galaxy formation.
• The peer-reviewed findings appear in Physical Review Letters, with researchers noting that upcoming JWST observations could further test the constraints.