Misc

Subregion

The function subregion can be used to extract the Hilbert space of a subregion.

using FermionicHilbertSpaces
H = hilbert_space(1:4)
Hsub = subregion(1:2, H)

4-dimensional SimpleFockHilbertSpace:
2 fermions: [1, 2]

When the Hilbert space has a restricted set of fock states, the Hilbert space of the subregion will only include fock states compatible with this restriction. In the example below, the total number of particles 1, and the subregion will have three possible states: (1,0), (0,1), and (0,0).

H = hilbert_space(1:4, number_conservation(1))
Hsub = subregion(1:2, H)
basisstates(Hsub)

3-element Vector{FockNumber{UInt64}}:
 FockNumber(1)
 FockNumber(2)
 FockNumber(0)