Growth under fixed CPL expansion
Individual run · T-c7a1155361ae
Public summary of an internal test, not yet independently validated or published.
Question investigated
With expansion fixed at w₀ = −0.838 and wₐ = −0.62, do luminous red galaxies at effective z = 0.51, 0.706 and 0.919 favor the growth prediction associated with the cosmological constant?
Test conditions
In the official full-shape analysis, use luminous red galaxies at effective z = 0.51, 0.706 and 0.919. Hold expansion fixed at w₀ = −0.838, wₐ = −0.62 in both hypotheses. Compare growth calculated at that same point with growth calculated at w₀ = −1, wₐ = 0. Fit the bias parameters and retain the Planck angular constraint. Define Δχ² = reference χ² − alternative χ².
Result
Δχ² = 0.12: the growth alternative associated with the cosmological constant lowers χ² but fails the prespecified improvement criteria. The comparison does not establish a preference for this alternative, conditional on the fixed expansion history.
Key figure
Reference χ² − alternative χ²
0.12
Fixed expansion: w₀ = −0.838, wₐ = −0.62; alternative growth: w₀ = −1, wₐ = 0
Source: Tower public snapshot
Specific limitations
- This test separates expansion history from the growth prediction and compares only the fixed hypotheses. The alternative changes growth while retaining the reference expansion history.
- Δχ² = reference χ² − alternative χ². A positive value indicates a lower-χ² fit for the alternative. The comparison involves fixed cosmological points: Δχ² alone does not provide a significance in σ or a probability. The conclusion depends on the data and criteria used.