An introduction to self organised criticality - Deepak Dhar

Many natural systems like the earth’s surface, solar flares and parasites spreading in a population can be considered as being in a non-equilibrium steady state. In many cases, this state shows large fluctuations, with long-ranged spatio-temporal correlations. In contrast to the case of equilibrium critical phenomena, this critical state does not require any fine-tuning of parameters. In a seminal paper in 1987, Bak Tang and Wiesenfeld argued that driven non-equilibrium systems, with nonlinearity and dissipation, organized themselves so that the steady state reamins at the boundary between ordered and chaotic behaviors, and called the phenomena self-organized criticality. There has lead to a lot of work subsequently in areas as diverse as geophysics, climate studies and modelling of the stock markets. This talk aims to provide an introduction to the main ideas of self organized criticality to non- experts. I will also discuss some of my own work. Prof Deepak Dhar is an Emeritus Professor in IISER Pune.