Matrices as graded BiHom-algebras and decompositions

We present matrices as graded BiHom-algebras and consider various characteristics of their decompositions. Specifically, we introduce a notion of connection in the support of the grading and use it to construct a family of canonical graded ideals. We show that, under suitable assumptions, such as $\Sigma$-multiplicativity, maximal length, and centre triviality, the matrix BiHom-algebra decomposes into a direct sum of graded simple ideals. We further extend our results to general graded BiHom-algebras over arbitrary base fields. As applications, we reinterpret classical gradings on matrix algebras such as those induced by Pauli matrices and the $\mathbb{Z}_n \times \mathbb{Z}_n$-grading in terms of our setting.