The cosmological redshift drift is predicted in ΛCDM to be an almost perfectly isotropic signal depending only on redshift. Detailed studies show that local accelerations of the Solar System, bulk flows, inhomogeneities, and large-scale structure can imprint dipolar and higher-order anisotropies in the observable drift at a level comparable to or larger than the tiny FRW signal (Linder 2008; Zhang & Li 2020; Codur & Marinoni 2021). The signal contamination prevents using the test as a clean isotropy probe.
The standard model assumes a single global FLRW expansion with no anisotropy. Any direction-dependent dz/dt pattern must therefore be attributed to local-acceleration contamination or to systematic effects, leaving no room for genuine cosmological anisotropy. The model has no clean way to disentangle an anisotropic-expansion signal from local kinematic contamination.
SCT replaces the hot-dense-center with a superluminal collision and the thermalized debris field. From this single change, redshift-drift anisotropy decomposes into two predicted components with distinct geometric signatures. The first is a kinematic dipole aligned with the CMB dipole at 369 km/s, sourced by our patch's residual frame velocity within the parent frame (P63). The second is a non-kinematic anisotropic-expansion component aligned with the KBC supervoid axis, sourced by the dynamical Λ_eff(x,t) gradient (P17, P19).
The two axes are geometrically required to be approximately perpendicular by the cascade impact-parameter geometry: v_frame is parallel to the impact parameter b, while J = μ(b × v_rel) is perpendicular to b (P64). The KBC supervoid axis aligns with the J-axis direction inherited from the cascade, perpendicular to the kinematic-dipole direction inherited from the frame velocity. Sibling-pocket gravitational influence (P58, P59, P60) adds a smaller third contribution, also aligned with the J axis at the cm/s/decade level.
The same M9 framework that predicts the dark flow (recid 12), the CMB dipole excess (recid 31), and cosmic parallax (recid 51) predicts the redshift-drift anisotropy structure. Decade-baseline ESPRESSO and ELT directional analysis can decompose the dz/dt signal into kinematic and non-kinematic components and verify the predicted approximate-perpendicular geometry between them. Detection of the two-axis structure would directly confirm SCT cascade geometry; failure of the two-axis structure (single-axis dipole only) would refute it.
If decade-baseline directional dz/dt analysis (ESPRESSO + ELT) finds only a single kinematic dipole axis with no perpendicular non-kinematic component at the cm/s/decade level, the M9 sibling-pocket plus Λ_eff-gradient explanation is refuted. The signature SCT prediction is an approximately 90-degree separation between the kinematic-dipole axis (CMB dipole direction) and the non-kinematic axis (KBC supervoid direction).