Question

Under what conditions is the product of two hermitian matrices hermitian

Answer 1

a matrix is hermitian when it is equal to its complex transpose

Answer 2

the the commutator is zero

Answer 3

tvm

Answer 4

\[\textbf{HJ}=(\textbf {HJ})^\dagger \]\[=\textbf J^\dagger \textbf H ^\dagger\]\[\textbf{HJ}=\textbf{JH}\]\[\textbf {HJ-JH}=0\]\[ [ \textbf {H},\textbf {J} ]=0\]