Spin Glasses: Old and New Complexity

Spin glasses are disordered magnetic systems that exhibit a variety of properties that are characteristic of complex systems. After a brief review of basic spin glass concepts, their use in areas such as computer science, biology, and other fields is explored. This use and its underlying basis will be termed old complexity. Newer concepts and ideas flowing from more recent studies of spin glasses will then be discussed, leading to a proposal for a kind of new complexity.