ABSTRACT
This chapter focuses on one long-standing problem in the physics of disordered materials, namely how a liquid, when supercooled sufficiently far below the equilibrium crystallization temperature, can freeze into an amorphous solid which people call a "glass". It presents some of the theory which is common to all the susceptibility techniques and which allows readers to see how the important class of experiments probe the relaxation phenomena in which people are interested. The single relaxation time in the ideal crystal has been replaced by an enormously wide distribution. The chapter explores the case of the dielectric susceptibility, although the same results will be applicable to any other linear susceptibility. It argues the Kauzmann temperature puts a limit on how far a liquid can be supercooled without undergoing a transition, the fragile liquids are again the systems of choice for experiments seeking to investigate the nature of the glass transition.
