CONSTRAINTS ON PERTURBATIONS TO THE RECOMBINATION HISTORY FROM MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND DAMPING TAIL
Bibliographic record
Abstract
The primordial cosmic microwave background at small angular scales is sensitive to the ionization and expansion history of the universe around the time of recombination.This dependence has been exploited to constrain the helium abundance and the effective number of relativistic species.Here we focus on allowed ionization fraction trajectories, x e (z), by constraining low-order principal components of perturbations to the standard recombination scenario (x e -eigenmodes) in the circa 2011 South Pole Telescope (SPT), Atacama Cosmology Telescope (ACT), and Wilkinson Microwave Anisotropy Probe seven-year data (WMAP7).Although the trajectories are statistically consistent with the standard recombination, we find that there is a tension similar to that found by varying the helium fraction.As this paper was in press, final SPT and ACT datasets were released and we applied our framework to them: we find that the tension continues, with slightly higher significance, in the new 2012 SPT data, but find no tension with the standard model of recombination in the new 2012 ACT data.We find that the prior probabilities on the eigenamplitudes are substantially influenced by the requirement that x e -trajectories conserve electron number.We propose requiring a sufficient entropy decrease between posterior and prior marginalized distributions be used as an x e -mode selection criterion.We find that in the case of the 2011 SPT/ACT+WMAP7 data only two modes are constrainable, but upcoming ACTPol, Planck, and SPTPol data will be able to test more modes and more precisely address the current tension.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.007 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".