OPOSSUMS ARE MARSUPIALS. If you open just about any field guide to North American mammals, the opossum will probably be the very first of the 380 or so mammal species described. That's because opossums are our only marsupial, and marsupials are considered very ancient forms of mammals.
operator - an agent that operates some apparatus or machine; the operator of the switchboard. manipulator. causal agency, causal agent, cause - any entity that produces an effect or is responsible for events or results. company operator - an operator who works for a company. driver - the operator of a motor vehicle.
An operator is Hermitian if it is self-adjoint: A+ = A. Or equivalently: < Ï|A| Ï> = (<Ï|A|Ï>)* and so â©Aâª= < Ï|A|Ï> is real. An operator is skew-Hermitian if B+ = -B and â©Bâª= < Ï|B|Ï> is imaginary. In quantum mechanics, the expectation of any physical quantity has to. be real and hence an operator corresponds to a physical observable. must be Hermitian. For example, momentum operator and. Hamiltonian are Hermitian. An operator is Unitary if its inverse equal to its adjoints: U-1 = U+ or UU+ = U+U = I. In quantum mechanics, unitary operator is used for change of basis.