In this paper a brief overview of hybrid control systems is given and an introduction to several approaches in hybrid systems research with an extended list of references is presented.

A simple method is proposed to estimate the instantaneous correlations between state variables in a hybrid system from empirical observable market quantities such as spot rates, stock prices and implied volatilities. The new algorithm extremely fast since only low-dimension linear systems are involved. If resulting matrix not positive semidefinite, shrinking method, which requires bisection-sty...