Comment on “Lagrangian formulation and symmetrical description of liquid dynamics”

Trachenko [Trachenko, Phys. Rev. E 96, 062134 (2017)] has argued for creating a Lagrangian formulation of liquid dynamics. This Comment shows that the proposed two-field Lagrangian does not describe dynamics of liquid in a correct way. Other claims on the symmetric description of liquid dynamics and on the similarity of Maxwell and Frenkel characteristic times are discussed.

Figure 1

Frenkel time estimation for supercritical Ar at 205 and 450 K and corresponding pressures as in Ref. [1] via pair distribution functions (a) and mean square displacements (b). The vertical bars in panel (b) show the time needed for particles to reach $\langle R_{\max }^2\rangle$ with $R_{\max }$ being the position of first maximum of $g\left(r\right)$, shown in panel (a).