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A complex matrix U is special unitary if it is unitary and its matrix determinant equals 1. For real numbers , the analogue of a unitary matrix is an orthogonal matrix . Unitary matrices have significant importance in quantum mechanics because they preserve norms , and thus, probability amplitudes .
In mathematics, the unitary group of degree n, denoted U(n), is the group of n × n unitary matrices, with the group operation of matrix multiplication.The unitary group is a subgroup of the general linear group GL(n, C), and it has as a subgroup the special unitary group, consisting of those unitary matrices with determinant 1.
More generally, unitary matrices are precisely the unitary operators on finite-dimensional Hilbert spaces, so the notion of a unitary operator is a generalization of the notion of a unitary matrix. Orthogonal matrices are the special case of unitary matrices in which all entries are real. [4] They are the unitary operators on R n.
In mathematics, the special unitary group of degree n, denoted SU(n), is the Lie group of n × n unitary matrices with determinant 1. The matrices of the more general unitary group may have complex determinants with absolute value 1, rather than real 1 in the special case. The group operation is matrix multiplication.
Another way of saying this is that a unitary matrix is the exponential of i times a Hermitian matrix, so that the additive conserved real quantity, the phase, is only well-defined up to an integer multiple of 2π. Only when the unitary symmetry matrix is part of a family that comes arbitrarily close to the identity are the conserved real ...
Specifically, the singular value decomposition of an complex matrix is a factorization of the form =, where is an complex unitary matrix, is an rectangular diagonal matrix with non-negative real numbers on the diagonal, is an complex unitary matrix, and is the conjugate transpose of . Such decomposition ...
Decomposition: = where is a unitary matrix of size m-by-m, and is an upper triangular matrix of size m-by-n Uniqueness: In general it is not unique, but if A {\displaystyle A} is of full rank , then there exists a single R {\displaystyle R} that has all positive diagonal elements.
In this special case, the Hilbert space is a space of irreducible unitary representations of the inhomogeneous Lorentz group (the Poincaré group); the S-matrix is the evolution operator between = (the distant past), and = + (the distant future). It is defined only in the limit of zero energy density (or infinite particle separation distance).