Eulerian and Lagrangian Phonons

  • A. Thellung
Conference paper
Part of the Springer Series in Solid-State Sciences book series (SSSOL, volume 79)


Hydrodynamic motion can be described either in the formulation of Euler or of Lagrange. Quantization leads to phonons, which in Euler’s case carry a momentum \(\hbar {\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{k}}\) (k = wave vector) and in Lagrange’s case have no momentum. In spite of this difference, physically observable effects must be the same since the two representations are equivalent. This conclusion is confirmed in an explicit comparison of the two cases for the microscopic derivation of the two-fluid equations in liquid He II.


Wave Vector Sound Pressure Momentum Density Periodic Boundary conditIons Superfluid Component 
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Copyright information

© Springer-Verlag Berlin, Heidelberg 1989

Authors and Affiliations

  • A. Thellung
    • 1
  1. 1.Institut für Theoretische PhysikUniversität ZürichZürichSwitzerland

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