Absolutely necessary to consider the caged dynamics and the JGX $β$-relaxation in solving the glass transition problem
The 2003 seminal paper entitled "Is the Fragility of a Liquid Embedded in the Properties of Its Glass?" by Tullio Scopigno, Giancarlo Ruocco, Francesco Sette, and Giulio Monaco, reported that the properties of the structural $α$-relaxation of glass-formers are already present in the faster caged dynamics. Their important discovery has far-reaching implication of the processes faster than the structural $α$-relaxation that cannot be ignored in solving the glass transition problem. Since then, experiments and simulations performed on many glass-formers with diverse chemical and physical structures have found strong connections of the $α$-relaxation with not only the caged dynamics but also with the secondary relaxation of the special kind, called the JGX $β$-relaxation. The general results indicate that these fast processes are inseparable from the $α$-relaxation, and any attempt to solve the glass transition problem should take account of this fact. Examples of the connections are given in this paper to elucidate the developments and advances made since the inspiring publication of Scopigno et al.