triqs_ctint.solver.Solver.trivial_alpha

Solver.trivial_alpha(solve_params)[source]

Build a simple \(\alpha\)-tensor from a half-filling ansatz.

Constructs the \(\alpha\)-tensor for density-density interactions from a trivial density of \(1/2\) per spin, shifted by \(\delta\), without solving any auxiliary problem. Requires n_s == 2.

Parameters:

solve_paramsdict: The solve parameters (see SolveParamsT). Must contain h_int (the interaction Hamiltonian \(\hat H_\mathrm{int}\)) and n_s, which must be 2. The entry delta (two-component shift, default [0.5 + 1e-2, 1e-2]) is read.

Returns:

numpy.ndarray: The \(\alpha\)-tensor of shape (n_terms + n_D0, 2, 2, 2).

Raises:

NotImplementedError: If the interaction contains spin-flip or pair-hopping terms.
ValueError: If a term has an unrecognised structure.