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The left null space, or cokernel, of a matrix A consists of all column vectors x such that x T A = 0 T, where T denotes the transpose of a matrix. The left null space of A is the same as the kernel of A T. The left null space of A is the orthogonal complement to the column space of A, and is dual to the cokernel of the
The left null space of A is the set of all vectors x such that x T A = 0 T. It is the same as the null space of the transpose of A. The product of the matrix A T and the vector x can be written in terms of the dot product of vectors:
The assignment produces an injective linear map between the space of linear operators from to and the space of linear operators from # to #. If X = Y {\displaystyle X=Y} then the space of linear maps is an algebra under composition of maps , and the assignment is then an antihomomorphism of algebras, meaning that t ( u v ) = t v t u ...
The second proof [6] looks at the homogeneous system =, where is a with rank, and shows explicitly that there exists a set of linearly independent solutions that span the null space of . While the theorem requires that the domain of the linear map be finite-dimensional, there is no such assumption on the codomain.
The vector space of matrices over is denoted by . For A ∈ K m × n {\displaystyle A\in \mathbb {K} ^{m\times n}} , the transpose is denoted A T {\displaystyle A^{\mathsf {T}}} and the Hermitian transpose (also called conjugate transpose ) is denoted A ∗ {\displaystyle A^{*}} .
Vectorization is a unitary transformation from the space of n×n matrices with the Frobenius (or Hilbert–Schmidt) inner product to C n 2: (†) = † (), where the superscript † denotes the conjugate transpose.
This is similar to the characterization of normal matrices where A commutes with its conjugate transpose. [4] As a corollary, nonsingular matrices are always EP matrices. The sum of EP matrices A i is an EP matrix if the null-space of the sum is contained in the null-space of each matrix A i. [6]
If instead A is a complex square matrix, then there is a decomposition A = QR where Q is a unitary matrix (so the conjugate transpose † =). If A has n linearly independent columns, then the first n columns of Q form an orthonormal basis for the column space of A.