Glass transition thermodynamics and kinetics

The remarkable kinetic slowdown experienced by liquids as they are cooled toward their glass transition is not accompanied by any obvious structural change. Understanding the origin of this behavior is a major scientific challenge. At present, this area of condensed matter theory is characterized by an abundance of divergent viewpoints that attempt to describe well-defined physical phenomena. We review representative theoretical views on the unusual kinetics of liquid supercooling, which fall into two broad competing categories: thermodynamic and kinetic. In the former, an apparent "ideal" thermodynamic, glass transition caused by rapid loss of entropy in the supercooled liquid underlies kinetic slowdown; in the latter, purely kinetic constraints are responsible for loss of ergodicity. The possible existence of an ideal thermodynamic glass transition is discussed and placed in its proper statistical mechanical context.