Recently Francoual et al. claimed to have observed the dynamics of
long-wavelength phason fluctuations in i-AlPdMn quasicrystals. We will show
that the data reported call for a more detailed development of the elasticity
theory of Jaric and Nelsson in order to determine the nature of small
phonon-like atomic displacements with a symmetry that follows the phason
elastic constants.Comment: 18 pages, 0 figures, many additions, discussion adde
