Minimal Determination of the Time-Drag Coupling from Low-Redshift Structure Growth

Companion to A Screened Time-Drag Scalar Field

This technical note demonstrates that the dimensionless coupling constant α in the screened time-drag scalar field theory is uniquely determined by observations, not freely adjusted to fit data. The time-drag theory modifies late-time gravitational strength via G_eff(a) = G[1 + (α/2)Ω_m/(Ω_m+Ω_Λ)] while preserving exact ΛCDM background expansion. This produces an enhancement in the linear growth rate that scales as Δf ∝ α·Ω_m, providing a direct mapping from measured clustering amplitudes to the fundamental coupling.