Block Matrices
A positive 2n × 2n matrix may also be defined by blocks:
where each block is n × n. By applying the positivity condition, it immediately follows that A and D are hermitian, and C = B*.
We have that z*Mz ≥ 0 for all complex z, and in particular for z = ( v, 0)T. Then
A similar argument can be applied to D, and thus we conclude that both A and D must be positive definite matrices, as well.
Read more about this topic: Positive-definite Matrix
Famous quotes containing the word block:
“It is, in both cases, that a spiritual life has been imparted to nature; that the solid seeming block of matter has been pervaded and dissolved by a thought; that this feeble human being has penetrated the vast masses of nature with an informing soul, and recognised itself in their harmony, that is, seized their law. In physics, when this is attained, the memory disburthens itself of its cumbrous catalogues of particulars, and carries centuries of observation in a single formula.”
—Ralph Waldo Emerson (1803–1882)