| − | \hat{U}=(\hat{U}_{1}, \hat{U}_{2}),\hat{U}_{1}\in\mathcal{R}^{n\times r_{\epsilon}}, \hat{U}_{2}\in\mathcal{R}^{n\times n-r_{\epsilon}} | + | \hat{U}=(\hat{U}_{1}, \hat{U}_{2}),\hat{U}_{1}\in\mathcal{R}^{n\times r_{\epsilon}}, \hat{U}_{2}\in\mathcal{R}^{n\times (n-r_{\epsilon})} |