On the question of second sound in germanium: a theoretical viewpoint
Bibliographic record
Abstract
eabg4677) wherein the observation of second sound in germanium is claimed. Through the lens of the phonon Boltzmann transport equation, we seek theoretical evidence of second sound. We begin with direct solutions to the linearized phonon Boltzmann transport equation (LBTE) for a frequency modulated heat source which do not reveal the presence of second sound. We then review the requirements imposed on the collision operator (or equivalently, the full scattering matrix) of the LBTE for the observation of driftless second sound as established by Hardy. By performing an eigendecomposition of the full scattering matrix, we show that the requirement that the smallest nonzero eigenvalue must be associated with an odd eigenvector is not satisfied. Finally, numerical solutions to the BTE under the relaxation time approximation in the 1D frequency-domain thermoreflectance experimental geometry demonstrate that phase lag alone is not a suitable experimental observable for inferring second sound. We conclude by suggesting alternative explanations that may explain the experimental data and discussing the need for a second sound 'smoking gun'.
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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) | 0.000 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".