|, //  				denotes the vertical bar for "given" 
M						denotes [scalar, vector, matrix] 
M_T					denotes transpose of M, also transpose(M
|M| , //M//			denotes absolute value of matrix M (each element)
||M||, ////M//// 	denotes spectral norm of M ////M////2
M_bar					denotes an overscore on M
M_tilde				denotes a tilde over a Matrix symbol 
|x|, //x//			is the absolute value vector of x, |x| = (|x1|, |x2|, . . . , |xn|)T 
||x||2				is the vector norm of x, ||x||2 = √Σni=1 |xi|2
I 						is the identity matrix
M > (≥)0 			means M is a positive definite(semidefinite)matrix
M > (≥)B 			means M − B is a positive definite(semidefinite)matrix
M ≽ 0 				means M is a positive(nonnegative) matrix, i.e, mij ≥ 0,
M ≽ B 				means the elements of matrices M,B satisfy the inequality mij ≥ bij
|M| 					is the absolute value matrix of M; |M| = (|mij |)n×n
(M) 					is spectral radius of M
λmax(M) 				means the maximum eigenvalue of matrix M
λmin(M) 				means the minimum eigenvalue of matrix M
ρ(M)					is the spectral radium of matrix M
||M||2 				is the spectral norm of matrix M. ||M||2 = √λmax(MTM)
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Kronecker product  -  If A is an m  n matrix and B is a p  q matrix, then the Kronecker product A ⊗ B is the mp  nq block matrix:
                   a11*B   ...   a1n*B 
A ⊗ B   =    .           ...           .
                   a1n*B  ...    ann*B