This preprint presents a finite-response redshift and optical-distance closure within the Emergent Condensate Superfluid Medium (ECSM) framework. Cosmological redshift is not interpreted as metric expansion, and photon-like signals are treated as coherent excitations of an underlying finite-response medium. The redshift coordinate is defined as Dz = ln (1+z), while luminosity and BAO observables are governed by a coherent optical propagation distance Dopt = Dz1 + a Dz/ (1+Dz). The saturating correction follows from a minimal finite-response optical-capacity equation dB/dDz = (1-B) / (1+Dz), giving B (Dz) =Dz/ (1+Dz). Using the full Pantheon+ covariance matrix, the saturating ECSM optical model improves over the bare stationary redshift law by Δχ² ≈ 74. 99 and selects aSN = 0. 203195. A BAO-only optical-capacity profile independently prefers aBAO = 0. 179343, with the supernova value lying inside the BAO-only 1σ interval. With a fixed to the supernova value, BAO is fit using one global scale parameter, SBAO = 4518. 09, giving χ²/dof = 0. 732. The resulting BAO-anchored geometry remains compatible with redshift-space distortion growth data, giving χ²/dof = 0. 305. A compact flat-ΛCDM baseline remains competitive, but the ECSM closure provides a non-expanding, internally consistent late-time redshift/optics interpretation across supernovae, BAO, and RSD.
Adam Sheldrick (Tue,) studied this question.