P-generalized determinant over quaternions and its applications
This paper introduces the ${\rm P}$-generalized determinant, a more general class of quaternion determinants. It unifies several classical quaternion determinants proposed between 1922 and 2008, including the Moore determinant, the Xie determinant, the Chen determinant, and the Kyrchei row--column determinants, thereby revealing the essential nature of quaternion determinants as multivariate polynomial-type functions with a fixed ordering of products. We provide equivalent characterizations of the expansion of the $\mathrm{P}$-generalized determinant along a given row or column, and establish conversion relations between the $\mathrm{P}_{l}$- and $\mathrm{P}_{r}$-generalized determinants. We prove that the $\mathrm{P}$-generalized determinant of a quaternion Hermitian matrix is a real number independent of the choice of cycle representation rule. We further investigate the behavior of the $\mathrm{P}$-generalized determinant under elementary row and column operations on quaternion Hermitian matrices, as well as its linearity in rows and columns. Finally, using the $\mathrm{P}$-generalized determinant, we derive determinantal representations of the inverse of an invertible quaternion Hermitian matrix and of the unique solution to the quaternion matrix equation $AXB=C$. In particular, this yields Cramer's rule for the left and right linear systems $Ax=b$ and $xA=b$.