Normal matrices: an update Original Research Article

A list of seventy conditions on an n × n complex matrix A, equivalent to its being normal, published nearly ten years ago by Grone, Johnson, Sa, and Wolkowicz has proved to be very useful. Hoping that, in an extended form, it will be even more helpful, we compile here another list of about twenty conditions. They either have been overlooked by the authors of the original list or have appeared during the last decade.