Axion field and the quark nugget’s formation at the QCD phase transition
Bibliographic record
Abstract
We study a testable dark-matter (DM) model outside of the standard weakly interacting massive particle paradigm in which the observed ratio ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{dark}}\ensuremath{\simeq}{\mathrm{\ensuremath{\Omega}}}_{\text{visible}}$ for visible and dark-matter densities finds its natural explanation as a result of their common QCD origin when both types of matter (DM and visible) are formed at the QCD phase transition and both are proportional to ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}$. Instead of the conventional ``baryogenesis'' mechanism, we advocate a paradigm when the ``baryogenesis'' is actually a charge separation process which always occurs in the presence of the $CP$ odd axion field $a(x)$. In this scenario, the global baryon number of the Universe remains zero, while the unobserved antibaryon charge is hidden in the form of heavy nuggets, similar to Witten's strangelets and compromise the DM of the Universe. In the present work, we study in great detail a possible formation mechanism of such macroscopically large heavy objects. We argue that the nuggets will be inevitably produced during the QCD phase transition as a result of Kibble-Zurek mechanism on formation of the topological defects during a phase transition. Relevant topological defects in our scenario are the closed bubbles made of the ${N}_{\mathrm{DW}}=1$ axion domain walls. These bubbles, in general, accrete the baryon (or antibaryon) charge, which eventually results in the formation of the nuggets and antinuggets carrying a huge baryon (antibaryon) charge. A typical size and the baryon charge of these macroscopically large objects are mainly determined by the axion mass ${m}_{a}$. However, the main consequence of the model, ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{dark}}\ensuremath{\approx}{\mathrm{\ensuremath{\Omega}}}_{\text{visible}}$, is insensitive to the axion mass which may assume any value within the observationally allowed window ${10}^{\ensuremath{-}6}\text{ }\text{ }\mathrm{eV}\ensuremath{\lesssim}{m}_{a}\ensuremath{\lesssim}{10}^{\ensuremath{-}3}\text{ }\text{ }\mathrm{eV}$. We also estimate the baryon-to-entropy ratio $\ensuremath{\eta}\ensuremath{\equiv}{n}_{B}/{n}_{\ensuremath{\gamma}}\ensuremath{\sim}{10}^{\ensuremath{-}10}$ within this scenario. Finally, we comment on implications of these results to the axion search experiments, including the microwave cavity and the Orpheus experiments.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.001 |
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 teacher head, 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".