Random magnets and correlations of stock price fluctuations

Random magnets provide a paradigm for the study of competing interactions and frustration in physics. Here, we suggest that this paradigm is also useful for the study and explanation of correlations between stock price changes of different companies: it (i) provides for a mechanism to explain the origin of correlations, (ii) allows to understand the occurrence of power-law correlations in the time series of highly correlated eigenmodes, and (iii) is a useful framework for the analysis of optimal investment strategies where the knowledge of (anti-)correlations is an important prerequisite for the reduction of risk.