Observable detail · COS
Goldstone-\(\theta\) \(\Delta N_{\rm eff}\)
| Prediction / mechanism | \(\Delta N_{\rm eff}\) sub-Planckian; predicted contribution \(\lesssim 0.05\), within current Planck + ACT bounds. |
|---|---|
| Measured | Planck 2018 + ACT DR6 + BAO joint constraint on \(\Delta N_{\rm eff}\). |
| Residual / status | Within \(1\sigma\) of \(\Lambda\)CDM |
| Status | HIT |
| Source paper | DCT-COS-01 |
Mechanism
Sub-Planckian Goldstone mode of the coherence-field \(P\) contributes a small radiation-density enhancement at recombination; the contribution is bounded by the conformal-wall theorem.
Derivation
The derivation chain follows the cluster paper DCT-COS-01 and reduces to the canonical DCT constants (\(P_0 = 0.851\), \(\omega_0 = 50{,}037\), \(c_{BD} = 138{,}189\), master identity \(2\omega_0 + 3 = c_{BD} \cdot P_0^2 = 100{,}077\)). See the cluster paper for the full multi-line derivation.
Methodology
| Domain | Cosmology (COS) |
|---|---|
| Input data source | See "References" below for the canonical public-archive citation. |
| Measurement procedure | The measured value used here is the most recent peer-reviewed central value plus 1σ uncertainty from the cited reference. |
| Acceptance threshold | HIT: residual within 1σ of measurement. SOFT: directional agreement within bracketing range. OPEN: untested or unresolved. |
| Falsification threshold | MISS: prediction excluded at ≥3σ by the canonical measurement under the corpus-canonical (constant-\(P_0\)) treatment. |
| Current status | See verdict pill above. |
Python verification
Verification script: cmb_analysis.py. Run with python3 cmb_analysis.py to reproduce the canonical DCT result against the public-archive measurement source listed below.
Cross-references
Related observables: delta-n-eff · planck-cmb-tt.
Aggregate views: /predictions/ · /scorecard/ · /empirical/ · /outstanding-problems/.
Audit notes
This sub-page is part of the post-build-out of the observable archive (see the observable index). Verdict reflects the corpus-canonical (constant-\(P_0\)) treatment. The cluster-paper deep-link above (DCT-COS-01) is the canonical source of the derivation chain.
References
- Planck Collaboration 2020
- ACT Collaboration 2024
- Source paper: DCT-COS-01
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