Introduction

Abstract

Most times the existence of random fluctuations in Nature is ignored, either because they are found to be irrelevant or because it is not known how to handle them. In this chapter we argue that there are many situations in which fluctuations cannot be neglected, since they have an important influence on the system’s behavior. We also discuss in some detail the particular aspects of noise effects that will be analyzed in the book and those that will not be considered. Section 1.1 gives a brief general introduction to fluctuation phenomena, their physical origin, and their analysis. Section 1.2 overviews the effects of fluctuations in spatially uniform dynamical systems. The behavior of both deterministic and stochastic spatially extended systems is introduced in Section 1.3, with a particular emphasis on phase transitions. Section 1.4 briefly reviews the phenomenology associated with a particularly relevant type of spatially extended phenomena, namely, pattern formation out of equilibrium. Finally, some features not studied further in this book are commented upon in Section 1.5.