Liquids, Glasses, Density Fluctuations and Low Frequency Modes

An overview is given of recent advances in the experimental physics of supercooled liquids and glasses. These are described in the context of measurements of non-ergodicity, viscosity and low frequency dynamics. Particular attention is paid to recently reported correlations between melt fragility and the vibrational and mechanical properties of the ensuing glass. Low frequency vibrations are discussed in relation to the Boson peak that characterises the glassy state. Throughout the over-arching role of density fluctuations in glass formation is stressed together with the experimental tools now available to characterise heterogeneity.