Figure 3.

Dispersion and mode strengths in S(Q, ω)s of two types of collective excitations in supercritical Ar at T = 363 K as follows from the fit-free analysis based on GCM approach. Left frames: dispersion of acoustic excitations (red) and non-hydrodynamic heat waves (green) at four selected densities. Dashed lines correspond to the hydrodynamic dispersion. Right frames: mode strengths of the corresponding propagating modes. In the long-wavelength limit heat waves do not exist, while the hydrodynamic value for the sound mode strength is 1/γ, where the ratio of specific heats γ varies from 1.43 to 2.16 for the highest and the lowest density, respectively.