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In linear algebra, a minor of a matrix A is the determinant of some smaller square matrix generated from A by removing one or more of its rows and columns. Minors obtained by removing just one row and one column from square matrices (first minors) are required for calculating matrix cofactors, which are useful for computing both the determinant and inverse of square matrices.
In particular, the diagonal entries are the principal minors of , which of course are also principal minors of , and are thus non-negative. Since the trace of a matrix is the sum of the diagonal entries, it follows that tr ( ⋀ j M k ) ≥ 0. {\displaystyle \operatorname {tr} \left(\textstyle \bigwedge ^{j}M_{k}\right)\geq 0.}
Since the leading principal minors are all positive, all of the roots of have negative real part. Moreover, since p {\displaystyle p} is the characteristic polynomial of M {\displaystyle M} , it follows that all the eigenvalues of M {\displaystyle M} have negative real part, and hence M {\displaystyle M} is a Hurwitz-stable matrix .
If is a singular matrix of rank , then it admits an LU factorization if the first leading principal minors are nonzero, although the converse is not true. [ 9 ] If a square, invertible matrix has an LDU (factorization with all diagonal entries of L and U equal to 1), then the factorization is unique. [ 8 ]
The minors and cofactors of a matrix are found by computing the determinant of certain submatrices. [16] [17] A principal submatrix is a square submatrix obtained by removing certain rows and columns. The definition varies from author to author.
The Hessian matrix plays an important role in Morse theory and catastrophe theory, because its kernel and eigenvalues allow classification of the critical points. [2] [3] [4] The determinant of the Hessian matrix, when evaluated at a critical point of a function, is equal to the Gaussian curvature of the function considered as a manifold. The ...
A real tensor in 3D (i.e., one with a 3x3 component matrix) has as many as six independent invariants, three being the invariants of its symmetric part and three characterizing the orientation of the axial vector of the skew-symmetric part relative to the principal directions of the symmetric part.
Formed by the cofactors of a square matrix, that is, the signed minors, of the matrix: Transpose of the Adjugate matrix: Companion matrix: A matrix having the coefficients of a polynomial as last column, and having the polynomial as its characteristic polynomial: Coxeter matrix