 To detect the correlations in the reduced matrix, which we still call A, we consider a perturbation }\tilde =\mid x -}\mathbf{x}\tilde{\mathbf{x}} \tilde \tilde{\mathbf{x}}.
<meaning-changed>  To detect the correlations in the reduced matrix, which we still call A, we consider a perturbation }\tilde =\mid x -}\mathbf{x}\tilde{\mathbf{x}} \tilde \tilde{\mathbf{x}}.
 To detect the correlations in the reduced matrix, which we still call A, we consider a perturbation }\tilde =\mid x -}\mathbf{x}\tilde{\mathbf{x}} \tilde A\tilde{\mathbf{x}}.