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U can be written as U = e iH, where e indicates the matrix exponential, i is the imaginary unit, and H is a Hermitian matrix. For any nonnegative integer n, the set of all n × n unitary matrices with matrix multiplication forms a group, called the unitary group U(n). Every square matrix with unit Euclidean norm is the average of two unitary ...
In linear algebra, a matrix unit is a matrix with only one nonzero entry with value 1. [1] [2] The matrix unit with a 1 in the ith row and jth column is denoted as .For example, the 3 by 3 matrix unit with i = 1 and j = 2 is = [] A vector unit is a standard unit vector.
For example, if A is a 3-by-0 matrix and B is a 0-by-3 matrix, then AB is the 3-by-3 zero matrix corresponding to the null map from a 3-dimensional space V to itself, while BA is a 0-by-0 matrix. There is no common notation for empty matrices, but most computer algebra systems allow creating and computing with them.
An "almost" triangular matrix, for example, an upper Hessenberg matrix has zero entries below the first subdiagonal. Hollow matrix: A square matrix whose main diagonal comprises only zero elements. Integer matrix: A matrix whose entries are all integers. Logical matrix: A matrix with all entries either 0 or 1.
The unique scalar function over square matrices which is distributive over matrix multiplication, multilinear in the rows and columns, and takes the value of for the unit matrix. diagonal matrix A matrix in which only the entries on the main diagonal are non-zero. [4] dimension The number of elements of any basis of a vector space. [2]
For example, a matrix such that all entries of a row (or a column) are 0 does not have an inverse. If it exists, the inverse of a matrix A is denoted A −1, and, thus verifies = =. A matrix that has an inverse is an invertible matrix.
The term unit matrix is ambiguous, because it is also used for a matrix of ones and for any unit of the ring of all matrices. [ 7 ] In some fields, such as group theory or quantum mechanics , the identity matrix is sometimes denoted by a boldface one, 1 {\displaystyle \mathbf {1} } , or called "id" (short for identity).
A matrix whose elements above the main diagonal are all zero is called a lower triangular matrix, while a matrix whose elements below the main diagonal are all zero is called an upper triangular matrix. As with diagonal matrices, the eigenvalues of triangular matrices are the elements of the main diagonal.