Negative group velocity and Kelvin-like wake pattern

Abstract

Wake patterns due to a uniformly traveling source are a result of the resonant emission of the medium's collective excitations. When there exists a frequency range where such excitations possess a negative group velocity, their interference leads to a wake pattern resembling the Kelvin ship wake: while there are "transverse" and "divergent" wavefronts trailing the source, they are oriented oppositely to Kelvin's. This is illustrated by an explicit calculation of "roton" wake patterns in superfluid ${}^{4}He$ where a Kelvin-like wake emerges when the speed of the source marginally exceeds the Landau critical roton velocity.

arXiv comment5 pages, 2 figures. Modified title and abstract to emphasize general character of discovered effect, minor text changes. Version to be published in Phys. Rev. B

References in corpus (6)

• Observation of Roton Mode Population in a Dipolar Quantum Gas
• The dispersion relation of Landau elementary excitations and the thermodynamic properties of superfluid ${}^4$He
• Negative Group Velocity
• Density pattern in supercritical flow of liquid He-4
• Kelvin-Froude wake patterns of a traveling pressure disturbance
• Kelvin-Mach wake in a two-dimensional Fermi sea

Cited by in corpus (5)

• Non-Local Phononic Crystals for Dispersion Customization and Undulation-point Dynamics
• Supersonic Flow Past an Obstacle in a Quasi-Two-Dimensional Lee-Huang-Yang Quantum Fluid
• Splashes in isotropic media
• Density Modulations of Zero Sound
• Vortex wake patterns in superfluid ${}^{4}He$