Definition 0.1.An H ∗-algebra is defined as a Hilbert space𝔸H equipped with an
associative unital algebra structure and an antilinear involution ∗ : 𝔸H→ 𝔸H which is
compatible with taking the adjoint of the operators on the Hilbert space for the left and
right multiplication of 𝔸H with itself (ref. [1]).