Superfluids / obstacles, winding, and onset
Research settingIndependent
The Davis–Landau study asks whether obstacle geometry organizes the onset of vortices in Gross–Pitaevskii simulations. The research object is a simulated transition, measured relative to the model’s sound speed.
From the research record
Inspect the work
Original figures, recorded values, and explicit model details. Each exhibit identifies its source and what the comparison means.
The two obstacle regimes actually compared
Scroll horizontally to inspect the full table →
| Obstacle | Dimensionless parameters | β: ⁸⁷Rb | β: ²³Na | β: ⁷Li |
|---|---|---|---|---|
| Gaussian, semi-hard | σ = 3ξ; V₀ = 50μ | 0.486 | 0.486 | 0.486 |
| Tanh-wall, hard | R = 8ξ; V₀ = 1000μ | 0.425 | 0.425 | 0.425 |
β = vc / cs; ξ is healing length and μ chemical potential. These are the reported values at the sampled thresholds, not zero-uncertainty physical constants. Equal dimensionless outcomes for three parameterizations of a rescaled Gross–Pitaevskii model do not establish universality across temperatures, obstacle families or experiments.
Read the technical figure
Source: Davis–Landau v3, obstacle definitions and Table 2. Drawn profiles are explanatory; the species thresholds are manuscript-reported dimensionless simulation results.
Source: Davis–Landau v3, obstacle definitions and Table 2. Drawn profiles are explanatory; the species thresholds are manuscript-reported dimensionless simulation results.
Supporting detail
From a flow disturbance to an onset measurement
The historical record describes simulations for several condensate species and proposes a geometric critical-velocity relation. Normalizing velocity by sound speed makes cases comparable, but the comparison still depends on the nondimensionalization, interaction model, obstacle potential, and boundary conditions.
A vortex is identified through the phase structure of the complex condensate field. The phase-winding construction below explains what that diagnostic looks for. It is not one of the study’s measured speed thresholds.
What a collapse across species would establish
If several normalized simulation curves follow a common relation, that is evidence about the chosen equations and parameter ranges. It does not alone show independence from dimension, temperature, preparation, or dissipation. The relation could reflect common modeling assumptions as well as a useful geometric simplification.
The onset decision also has a time scale. A brief disturbance and sustained vortex production can receive different labels under different observation windows. A representative account must retain the window and detection rule alongside the reported critical velocity.
Sources, scope, and next question
Existing simulation manuscript; the scope of any proposed onset law remains the simulated regimes.
The next revision should put the actual obstacle families, speed scans, and phase-winding detections beside the proposed law, including cases that depart from it. Those records are more informative than a claim of species-independent universality.