The dominant universal coupling to the Z boson does not change flavor, but sub-dominant non-universal contributions can.
2.
The standard generalizations of the SR-CC method are the " multi-reference " ( MR ) approaches : state-universal coupled cluster ( also known as Hilbert space coupled cluster ), valence-universal coupled cluster ( or Fock space coupled cluster ) and state-selective coupled cluster ( or state-specific coupled cluster ).
3.
The standard generalizations of the SR-CC method are the " multi-reference " ( MR ) approaches : state-universal coupled cluster ( also known as Hilbert space coupled cluster ), valence-universal coupled cluster ( or Fock space coupled cluster ) and state-selective coupled cluster ( or state-specific coupled cluster ).