What does ‖A‖ mean in matrices?
‖A‖ is the notation for a matrix norm. The exact norm is usually specified as a subscript to the norm, such as ‖A‖2. This means that we used the vector 2-norm to find the maximum amount of stretching in. Don't confuse the notation for the matrix norm ‖A‖ with the notation for matrix determinant |A|. Read more