Before revision:  The  indicators that we have built deal with the spectral properties of these covariance and correlation matrices . The simple intuitive idea that we rely upon is that correlation and volatility are like the heartbeat of the financial market: when correlations between asset prices increase or develop abnormal patterns, when volatility starts to increase, then a crisis event might be around the corner. The financial crisis indicators that we have built are of two kinds.
After revision:  The indicators that we have built deal with the spectral properties of these covariance and correlation matrices and they are of two kinds.