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This note evaluates the stability of the ω_z = 11.1991 minimum and COCM+w₀wₐ coexistence scenario.

May 29, 2026Open Access

NT15: Robustness of the wᵦ=11, 1991 Minimum and Status of the COCM +wowa Scenario Against DR1 and DR2 Data

Key Points

This note evaluates the stability of the ω_z = 11.1991 minimum and COCM+w₀wₐ coexistence scenario.
Assessment based on quantitative results from P7v6.
Evaluation through fixed and free optimization on DR1 and DR2 data sets.
Analysis of Δχ² and Bayesian evidence against w₀wₐCDM.
The ω_z = 11.1991 minimum is stable in DR1 but not in DR2, with optimization yielding ω_z ≈ 1.5.
The COCM+w₀wₐ semi-fixed model shows Δχ² = 6.0 (p = 0.049) compared to w₀wₐCDM.
Bayesian evidence indicates negligible differences, with DR3 expected to provide conclusive results.

Abstract

This note records the robustness status of the ωᵦ = 11. 1991 minimum and the COCM+w₀wₐ coexistence scenario, based on the quantitative results of P7v6 (doi: 10. 5281/zenodo. 20171261). The minimum is conditional: it is stable in DR1+CC (n=24) with ωᵦ fixed, but is not recovered by free optimisation on DR2+CC (n=14), which converges to ωᵦ ≈ 1. 5. The COCM+w₀wₐ semi-fixed model gives Δχ² = 6. 0 (p = 0. 049) over w₀wₐCDM, and Δlog Z = 0. 4 in nested sampling — Bayesian evidence is negligible on the Kass–Raftery scale. Both results are consistent with Scenario 1 of P15 (doi: 10. 5281/zenodo. 20413179): COCM and w₀wₐ coexist in the current data, are indistinguishable at DR2 precision, and DR3 is expected to provide the decisive test. The primary pending robustness test is the full DR1 profile χ² (ωᵦ), computable from the P7v6 deposited code.

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