Star-algebra
In mathematics, a *-algebra is an associative algebra over the field of complex numbers with an antilinear, antiautomorphism * : A → A which is an involution. More precisely, * is required to satisfy the following properties:
for all x,y in A, and all z in C.
The most obvious example of a *-algebra is the field of complex numbers C where * is just complex conjugation. Another example is the algebra of n×n matrices over C with * given by the conjugate transpose.
An algebra homomorphism f : A → B is a *-homomorphism if it is compatible with the involutions of A and B, i.e.
- f(a * ) = f(a) * for all a in A.
An element a in A is called self-adjoint if a* = a.