Spectral Norm
The natural norm induced by the L2-norm. Let A^(H) be the conjugate transpose of the square matrix A, so that (a_(ij))^(H)=(a^__(ji)), then the spectral norm is defined as the square root of the maximum eigenvalue of A^(H)A, i.e.,
||A||_2 = (maximum eigenvalue of A^(H)A)^(1/2)
(1)
= max_(|x|_2!=0)(|Ax|_2)/(|x|_2),
(2)
This matrix norm is implemented as Norm[m, 2].