Universality of Nonclassical Nonlinearity

VarietyisperhapsthemostamazingattributeofNature,withanalmostendlessarrayof different molecules and aggregates and tens of millions of distinct forms of life. Yet, in spite of this bewildering diversity, there are some common patterns, henceforth called "e;phenomenological universalities,"e; that are found over and over again in completely different contexts. A quest for universalities is not only interesting per se, but can also yield practical applications. If several elds share a common mathematical or conceptual background, a cross-fertilization among them may lead to quick progress, even if ultimately the speci c details of any individual application must be considered independently. We all know that we live in a nonlinear world, although scientists have often tried to linearize it, sometimes as a rst step towards understanding its complexity, often because, before the advent of ubiquitous high computational power, a linear appro- mation was the only viable alternative. In this book we use the term "e;nonclassical n- linearity"e; with reference to a particularly intriguing kind of phenomenology, which has been extensively investigated in the last decade in the elds of elasticity and g- materials and whose universality has been conjectured. Its signatures are hystereticity, discrete memory, and other effects which, in the case of continuum mechanics, have been called "e;fast"e; and "e;slow"e; dynamics.