Discussion Overview
The discussion centers on the concept of phonon behavior in superfluids, particularly regarding its potential Lorentz invariance and the implications of this for theoretical physics. Participants explore the relationship between phonons and Lorentz invariance, referencing specific papers and models related to Bose-Einstein condensates.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants suggest that phonons in superfluid experiments might exhibit an upper-limit speed effect similar to that of photons, questioning whether this behavior is Lorentz invariant.
- One participant emphasizes the difficulty of addressing the question without specific references to supporting papers.
- A referenced paper discusses the acoustics in Bose-Einstein condensates, noting that at low momentum, the phonon dispersion relation can resemble a "relativistic" form, suggesting approximate "Lorentz invariance."
- Another participant clarifies that the term "Lorentz invariance" in the referenced paper is used in a limited context, specifically regarding the speed of sound in the material, which is not invariant in the same way as the speed of light.
- It is noted that while the equations for phonons in low momentum limits may mimic Lorentz invariant equations, this does not imply that phonons themselves are Lorentz invariant, especially as momentum increases.
Areas of Agreement / Disagreement
Participants express differing views on the interpretation of Lorentz invariance in the context of phonons, with some agreeing on the limitations of the term while others explore its implications. The discussion remains unresolved regarding the broader applicability of these concepts.
Contextual Notes
Participants highlight the dependence on specific definitions of Lorentz invariance and the limitations of the models discussed, particularly in relation to momentum and the frames of reference used in the analysis.