Reduced+quantities

Reduced quantities:

In practice, to describe a particular type of quantity, we often find that working with a "reduced quantity" appears to work: - the single-particle potential (KS) for the ground state density (instead of the full many-body Hamiltonian) - a two-point kernel for the density-density response in TDDFT (instead of the four-point BSE one) etc.

This defines the term "reduced quantity" for the purposes of this discussion.