Computing the dipole polarizability of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ca</mml:mi><mml:mprescripts/><mml:none/><mml:mn>48</mml:mn></mml:mmultiscripts></mml:math> with increased precision
Bibliographic record
Abstract
We compute the electric dipole polarizability of $^{48}\mathrm{Ca}$ with an increased precision by including more correlations than in previous studies. Employing the coupled-cluster method we go beyond single and double excitations and include leading-order three-particle-three-hole (3p-3h) excitations for the ground state, excited states, and the similarity-transformed operator. We study electromagnetic sum rules, such as the bremsstrahlung sum rule ${m}_{0}$ and the polarizability sum rule ${\ensuremath{\alpha}}_{D}$ using interactions from chiral effective field theory. To gauge the quality of our coupled-cluster approximations we perform several benchmarks with the effective interaction hyperspherical harmonics approach in $^{4}\mathrm{He}$ and with self consistent Green's function in $^{16}\mathrm{O}$. We compute the dipole polarizability of $^{48}\mathrm{Ca}$ employing the chiral interaction ${\mathrm{N}}^{2}{\mathrm{LO}}_{\mathrm{sat}}$ [Ekstr\"om et al., Phys. Rev. C 91, 051301 (2015)] and the 1.8/2.0 (EM) [Hebeler et al., Phys. Rev. C 83, 031301 (2011)]. We find that the effect of 3p-3h excitations in the ground state is small for 1.8/2.0 (EM) but non-negligible for ${\mathrm{N}}^{2}{\mathrm{LO}}_{\mathrm{sat}}$. The addition of these new correlations allows us to improve the precision of our $^{48}\mathrm{Ca}$ calculations and reconcile the recently reported discrepancy between coupled-cluster results based on these interactions and the experimentally determined ${\ensuremath{\alpha}}_{D}$ from proton inelastic scattering in $^{48}\mathrm{Ca}$ [Birkhan et al., Phys. Rev. Lett. 118, 252501 (2017)]. For the computation of electromagnetic and polarizability sum rules, the inclusion of leading-order 3p-3h excitations in the ground state is important, while it is less so for the excited states and the similarity-transformed dipole operator.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.015 | 0.002 |
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".