Definition 0.1. An H ∗-algebra is defined as a Hilbert space 𝔸H equipped with an
associative unital algebra structure and an antilinear involution ∗ : 𝔸
H → 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]).
References