BAO Scale Mismatch (DESI vs Planck)

Baryon acoustic oscillations (BAO) encode a standard ruler — the sound horizon at drag epoch, rₛ ≈ 147 Mpc — that can be measured in both the CMB power spectrum and the large-scale galaxy correlation function. The DESI BAO measurements from galaxy surveys at various redshifts show a ~2–3σ preference for a BAO scale that, when interpreted within a flat ΛCDM cosmology, implies either a smaller sound horizon, a higher expansion rate, or a dynamical dark energy component (w ≠ −1) than Planck's CMB-derived parameters predict. Successive Collision Theory naturally produces a position-dependent and time-varying effective expansion rate through the dynamical Λ_eff mechanism: because Λ_eff is a ratio of parent-frame dissipation to local binding strength, it varies from one survey volume to another. The DESI surveys sample multiple redshift shells across different sky regions, each with a slightly different effective expansion history. Interpreting this inhomogeneous expansion history with a single universal w and a single sound horizon will always produce apparent tension, because the underlying cosmology is structurally inhomogeneous at the relevant scales.

The sound horizon rₛ itself is identical in SCT and ΛCDM at z~1100, because the pre-decoupling plasma physics is unchanged — SCT's collision thermalized the same baryon-photon plasma that ΛCDM assumes, and the acoustic wave physics is determined by the same microphysics of pressure, density, and photon mean free path. The discrepancy arises entirely in the conversion from angular BAO scale to physical BAO scale, which requires assuming a specific expansion history between z~1100 and the survey redshift. In SCT, this expansion history is not the smooth ΛCDM function but includes the position-dependent Λ_eff variations from the KBC Supervoid and the secular growth of mesh dissipation. Surveys sampling different redshift ranges sample different portions of this time-dependent expansion, so their best-fit BAO-derived cosmological parameters will differ even when the underlying sound horizon is the same. The DESI vs Planck discrepancy is therefore a direct observational signature of the SCT tensor mesh dissipation mechanism operating across cosmic time.