About subspaces the most deviating from the coordinate ones (2511.02387v1)

Abstract: Taking the largest principal angle as the distance function between same dimensional nontrivial linear subspaces in $\mathds{R}^n$, we describe the class of subspaces deviating from all the coordinate ones by at least $\arccos(1 / \sqrt{n})$. This study compliments and is motivated by the long-standing hypothesis put forward in \cite{GTZ1997} and essentially stating that so-defined distance to the closest coordinate subspace cannot exceed $\arccos(1 / \sqrt{n})$. In this context, the subspaces presented here claim to be the extremal ones. Realized as the star spaces of all nontrivial 2-connected series-parallel graphs with certain edge weights and arbitrary edge directions, the given subspaces may be of interest beyond numerical linear algebra within which the original problem was formulated.