Reply to "comment on 'Behavior of Supercritical Fluids across the Frenkel Line'"

In a recent Letter,1 we scrutinized structural and dynamical properties of a supercritical fluid in connection with the “Frenkel line” (FL) concept.2 In particular, we discussed the existence of a low-frequency cutoff for transverse modes and the disappearance of the medium-range order across the FL, as well as the expression for the positive sound dispersion and specific heat within the FL approach. The Comment by Brazhkin et al.3 starts with an introduction questioning the robustness of the Widom line against the FL as a demarcation of different regions in the supercritical state, reminiscent of subcritical behavior. This is the leitmotive of a querelle initiated by Brazhkin et al. back in 2012,2 six years after our first paper on the experimental demonstration for the existence of gas-like and liquid-like regions in the supercritical phase.4 Brazhkin et al. build on the obvious, recalling that “the Widom line exists only in the vicinity of the critical point”.