  An advance was made by Guiselin et al. [arXiv:2103.01569 (2021)] in molecular
dynamics simulations of the equilibrium dynamics of supercooled liquids near
the experimental glass transition by utilizing the giant equilibration speedup
provided by the swap Monte Carlo algorithm. The found emergence of a power law
in relaxation spectra at lower temperatures on the high frequency flank of the
alpha-loss peak in analogy to the excess wings observed experimentally in
molecular glass-formers. Their remarkable finding leads to the question of
where the excess wing is located relative to the alpha-loss peak in the
susceptibility spectrum. I provide an answer by identifying the excess wing as
the unresolved Johari-Goldstein (JG) b-relaxation and using the reciprocal of
its relaxation time tau_JG to assess the location of the excess wing. The
Coupling Model (CM) has a history of being successful in determining
approximately the values of tau_JG(T) in molecular liquids whether the JG
beta-relaxation is resolved or not (i.e., excess wing). It is applied to the
simulation data and the results of tau_JG(T) successfully account for the
locations of the excess wings in the simulation spectra at different
temperatures. The time evolution of the dynamics of the distribution of
processes composing the JG b-relaxation suggested by the CM based on
experimental data in molecular glass-formers are in agreement with that given
by Guiselin et al. from simulations of a size-polydisperse mixture of N soft
spheres interacting with a repulsive power law pair potential. The agreement
brings their results closer to experimental data of real molecular
glass-formers.
