Matrix
A matrix is a rectangular array of scalars from any field, such that each column belongs to the vector space , where is the number of rows. If a matrix has rows and columns, its order is said to be , and it is written as .
The element in the row and column of is written as . It is more often written as , in which case can be written as .
Transposes
Let be . Then is said to be the transpose of , written as or simply . If A is over the complex field, replacing each element of by its complex conjugate gives us the conjugate transpose of .
is said to be symmetric if and only if . is said to be hermitian if and only if . is said to be skew symmetric if and only if . is said to be skew hermitian if and only if .