Accelerated galaxy formation at cosmic dawn via density-dependent gravitational screening

Observations by the James Webb Space Telescope (JWST) have revealed massive galaxies at z > 7 with stellar masses approaching 1011 M⊙, formed within the first 700 million years after the Big Bang. This challenges the standard ΛCDM cosmology, which requires unphysical baryon-to-star conversion efficiencies ϵ ≳ 1 to explain the observed abundances. Here we show that the Dimensional Locking mechanism—a density-dependent gravitational screening derived from extra-dimensional physics—naturally predicts accelerated structure formation at cosmic dawn. At redshifts z ∼ 9– 15, the cosmic matter density (ρ ≈ 10−4 M⊙ pc−3) lies well below the screening threshold (ρcrit ≈ 0.03 M⊙ pc−3), leaving gravity ‘unscreened’ and enhanced. The resulting effective gravitational constant Geff > GN reduces the halo assembly timescale by a factor of ∼ 2–3, reproducing the Labb´e et al. stellar mass densities without fine-tuning. This framework unifies the JWST puzzle with local cosmological tensions (Hubble, S8) under a single geometric mechanism, predicting that early galaxy formation is a natural consequence of the Universe’s low-density past.