4 papers
Some hybrid matrix triangle inequalities
Jean-Christophe Bourin, Eun-Young Lee
A recent result due to Teng Zhang compares the sum of matrices and the sum of their quadratic symmetric moduli: $$ \left\| \sum_{k=1}^m A_k\right\| \le \sqrt{2} \left\| \sum_{k…
Averages over matrix unitary orbits and spectral order
Jean-Christophe Bourin, Eun-Young Lee
We establish matrix versions of the comparisons between the -norms or quasi-norms for sequences of complex numbers. For instance, given , and a family of norm…
Triangle inequalities for the operator symmetric modulus
Jean-Christophe Bourin, Eun-Young Lee
We study the operator symmetric modulus (|Z|+|Z^*|)/2 for matrices Z. Several triangle type inequalities are given.
Involutions and angles between subspaces
Jean-Christophe Bourin, Eun-Young Lee
We provide a complete structure theorem for involutory matrices. This yields a new approach to principal angles between subspaces and provide a series of nice formulae for these an…