Environment-Dependent Scalar Field Theory: A Unified Framework for Galaxy Dynamics and Cosmology

We present a complete theoretical framework that unifies galaxy dynamics and cosmological observations through a scalar field ϕ with an environment-dependent potential. The theory emerges from a fundamental Lagrangian coupling the field to stress-energy tensor invariants, naturally producing a phase transition mechanism where high density triggers symmetry breaking while angular momentum stabilizes the symmetric phase. This explains why elliptical galaxies require enhanced gravity (Geff/G ≈ 1.23) while spirals maintain standard gravity. Applied to 170 SPARC galaxies, our UC Base model achieves 97.1% success without dark matter. Joint analysis of Planck 2018, DESI BAO, and Pantheon+ data yields excellent fits (χ2/dof = 0.648) while resolving the Hubble tension with H0(early) = 68.0 ± 0.5 and H0(late) = 74.0 ± 1.0 km/s/Mpc. The theory is quantum mechanically stable with no ghosts, tachyons, or Landau poles below the Planck scale.