Recombination-independent Determination of the Sound Horizon and the Hubble Constant from BAO
Bibliographic record
Abstract
Abstract The Hubble tension and attempts to resolve it by modifying the physics of (or at) recombination motivate finding ways to determine H 0 and the sound horizon at the epoch of baryon decoupling r d in ways that rely neither on a recombination model nor on late-time Hubble data. In this work, we investigate what one can learn from the current and future BAO data when treating r d and H 0 as independent free parameters. It is well known that baryon acoustic oscillations (BAOs) give exquisite constraints on the product r d H 0. We show here that imposing a moderate prior on Ωm h 2 breaks the degeneracy between r d and H 0. Using the latest BAO data, including the recently released the extended Baryon Oscillation Spectroscopic Survey Data Release 16, along with a Ωm h 2 prior based on the Planck best-fit Λ cold dark matter (ΛCDM) model, we find r d = 143.7 ± 2.7 Mpc and H 0 = 69.6 ± 1.8 km s−1 Mpc−1. BAO data prefers somewhat lower r d and higher H 0 than those inferred from Planck data in a ΛCDM model. We find similar values when combing BAO with the Pantheon supernovae, the Dark Energy Survey Year 1 galaxy weak lensing, Planck or SPTPol cosmic microwave background lensing, and the cosmic chronometer data. We perform a forecast for the Dark Energy Spectroscopic Instrument (DESI) and find that, when aided with a moderate prior on Ωm h 2, DESI will measure r d and H 0 without assuming a recombination model with an accuracy surpassing the current best estimates from Planck.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".