Hermitian nonnegative-definite and positive-definite solutions of the matrix equation .
Let be the multiplicative semigroup of all complex matrices, and let and be the –degree unitary group and general linear group over complex number field, respectively. We characterize group homomorphisms from to when or , and thereby determine multiplicative homomorphisms from to when or . This generalize Hochwald’s result in [Lin. Alg. Appl. 212/213:339-351(1994)]: if is a spectrum–preserving multiplicative homomorphism, then there exists a matrix in such that for...
We extend three inequalities involving the Hadamard product in three ways. First, the results are extended to any partitioned blocks Hermitian matrices. Second, the Hadamard product is replaced by the Khatri-Rao product. Third, the necessary and sufficient conditions under which equalities occur are presented. Thereby, we generalize two inequalities involving the Khatri–Rao product.
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