An Oettli--Prager-Like Theorem for the Symmetric Solution Set and for Related Solution Sets
Günter Mayer · SIAM Journal on Matrix Analysis and Applications · 2012
We recall three equivalent characterizations of the solution set of linear systems of equations with perturbed input data, and reformulate and modify slightly Hladík's Oettli--Prager-like theorem for describing the corresponding symmetric solution set. Based on this modification we are able to derive and prove this theorem in a new, elementary way and to reduce the number of inequalities essentially. In the same way we reformulate and reprove Hladík's result on the skew-symmetric solution set and derive a new characterization for the persymmetric and the perskew-symmetric solution set.