
The purpose of this paper is to revisit two problems discussed previously in the literature, both related to \(P_1P_2 = P_2P_1\), where \(P_1\) and \(P_2\) denote projectors. The first problem was considered by Baksary et al. who have shown that if \(P_1\) and \(P_2\) are orthogonal projectors, then in all nontrivial cases a product of any length having \(P_1\) and \(P_2\) as its factors occuring alternately is equal to another such product if and only if \(P_1\) and \(P_2\) commute. In the present paper a generalization of this result is proposed and validity of the equivalence between commutativity property and any equality involving two linear combinations of two any length products having orthogonal projectors \(P_1\) and \(P_2\) as their factors occurring alternately is investigated. The second problem discussed in this paper concerns specific generalized inverses of \(P_1 + P_2\) and \(P_1 - P_2\) of commuting projectors \(P_1\) and \(P_2\).
Numerical Analysis, Algebra and Number Theory, Linear combination, Matrix equations and identities, Idempotent matrix, generalized inverse, Commutativity of matrices, idempotent matrix, Product of projectors, Orthogonal projector, Discrete Mathematics and Combinatorics, Hermitian idempotent matrix, Generalized inverse, Theory of matrix inversion and generalized inverses, Geometry and Topology, orthogonal projector
Numerical Analysis, Algebra and Number Theory, Linear combination, Matrix equations and identities, Idempotent matrix, generalized inverse, Commutativity of matrices, idempotent matrix, Product of projectors, Orthogonal projector, Discrete Mathematics and Combinatorics, Hermitian idempotent matrix, Generalized inverse, Theory of matrix inversion and generalized inverses, Geometry and Topology, orthogonal projector
| selected citations These citations are derived from selected sources. This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 9 | |
| popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Average | |
| influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Average | |
| impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Average |
