Galaxy Rotation Curves and the Radial Acceleration Relation in an Effective Viscoelastic Spacetime Framework

This work presents an effective viscoelastic framework for galactic dynamics, in which the observed radial acceleration relation (RAR) emerges as a quasi-steady outcome of a delayed gravitational response. The model introduces a cosmologically motivated relaxation timescale (τ ∝ H⁻¹), leading to an emergent acceleration scale a0 ~ cH. Within this framework, galaxy rotation curves, the RAR, and the baryonic Tully–Fisher relation are reproduced without invoking particle dark matter or modifying general relativity at a fundamental level. In addition, a dimensionless memory parameter (τ / t_dyn) provides a natural interpretation of the observed scatter in the RAR. This version corresponds to a revised and clarified presentation of the dynamical framework.