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First and second sound in cylindrically trapped gases
G Bertaina1, L Pitaevskii, S Stringari
1INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento, I-38123 Povo, Trento, Italy.
Physical Review Letters
|January 15, 2011
Summary
We studied wave propagation in trapped gases, finding harmonic confinement enables distinct sound waves. New excitations with non-dissipative damping were discovered for shorter wavelengths.
Area of Science:
- Physics
- Fluid Dynamics
- Condensed Matter Physics
Background:
- Understanding wave propagation in confined quantum fluids is crucial.
- Previous models often assumed rigid walls, limiting wave behavior analysis.
- Harmonic confinement introduces unique boundary conditions affecting fluid dynamics.
Purpose of the Study:
- To investigate density and temperature wave propagation in cylindrically trapped gases with radial harmonic confinement.
- To derive effective 1D hydrodynamic equations including viscosity and thermal conductivity.
- To analyze the impact of harmonic confinement on sound wave propagation and identify novel excitations.
Main Methods:
- Utilized two-fluid hydrodynamic theory to derive effective 1D equations.
- Analyzed wave propagation in the long and short wavelength limits.
- Calculated response functions and sound velocities for a superfluid Fermi gas at unitarity.
Main Results:
- Harmonic confinement allows propagation of both first and second sound in the long wavelength limit.
- Quantitative predictions for two sound velocities in a superfluid Fermi gas at unitarity were made.
- A new class of excitations with non-dissipative damping was discovered for shorter wavelengths.
Conclusions:
- Harmonic confinement significantly alters wave propagation compared to rigid walls.
- The study predicts distinct sound velocities and reveals novel frequency-spread excitations.
- Analytical calculations confirm non-dissipative damping in the classical ideal gas limit.
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