triqs.atom_diag.atom_diag.AtomDiagReal.flatten_subspace_index

AtomDiagReal.flatten_subspace_index()

Dispatched C++ function(s).

[1] (sp_index: int, i: int)
  -> int

Map a subspace-local pair \((B, i)\) to its linear index in the full Hilbert space.

The full-Hilbert-space eigenstate index is

\[d(B, i) = \mathtt{first\_eigenstate\_of\_subspace}[B] + i, \quad 0 \le i < \dim(B), \quad 0 \le d < N.\]

Parameters:

sp_indexint

Subspace index \(B\).

iint

Eigenstate index inside subspace \(B\), with \(0 \le i < \dim(B)\).

Returns:

int

Linear eigenstate index \(d(B, i)\) in the eigenbasis of the full Hilbert space.