Second sound and the density response function in uniform superfluid atomic gases
Bibliographic record
Abstract
The equations of fluid dynamics of normal fluids are modified when one is dealing with a superfluid. The equations of two-fluid hydrodynamics were formulated by Landau in 1941 for superfluid Helium. They predict the existence of first and second sound oscillations. The Landau equations also describe superfluid gases and are quite different from the usual mean-field Gross-Pitaevskii equations. To access two-fluid hydrodynamics in trapped ultracold gases , one needs strong interactions (short collision times). This strong-interaction regime can be reached in Fermi gases by using a Feshbach resonance to make the s-wave scattering length very large. This has renewed interested in observing second sound in superfluid quantum gases. We have calculated the temperature dependence of the velocity and amplitude of the first and second sound resonances in the density response function of a uniform strongly interacting Fermi superfluid in the two-fluid region. Contrary to expectations based on superfluid Helium, the amplitude of first and second sound are comparable in the dynamic structure factor of Fermi gases near unitarity at temperatures well below the superfluid transition temperature. This agrees with and clarifies recent predictions by Arahata and Nikuni on density pulse propagation in such gases. Our calculations shows that two-fluid hydrodynamics can be studied easily in strongly interacting superfluid Fermi gases using density probes. In particular, second sound should be clearly visible as a density pulse in propagation experiments in cigar-shaped traps over a wide range of temperatures.
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 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) | 0.000 | 0.000 |
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 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".