Involutions and angles between subspaces
arXiv:2602.19599
Abstract
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 angles.
Some questions (at the end of the paper) on dilation into involutions have been completly answered in a recently published note by the author. (Dilating contractions into involutions and contraction, Linear Algebra Appl. 2026)