double_counting.hpp

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// Copyright (c) 2025--present, The Simons Foundation
// This file is part of TRIQS/modest and is licensed under the terms of GPLv3 or later.
// SPDX-License-Identifier: GPL-3.0-or-later
// See LICENSE in the root of this distribution for details.
 
#pragma once
#include <nda/nda.hpp>
#include "utils/defs.hpp"
#include "triqs/gfs.hpp"
#include "local_space.hpp"
 
using namespace triqs::gfs;
 
namespace triqs::modest {

  std::pair<double, double> dc_formulas(std::string const method, double const N_tot, double const N_sigma, long const n_orb, double const U,
                                        double const J);

  class dc_solver {
 
    private:
    // spin kind
    spin_kind_e _spin_kind;
    // number of spins (derived from spin_kind)
    long n_sigma;
    // double counting method to use
    std::string method;
    // U term used in the double counting formulas
    double U_int;
    // J term used in the double counting formulas
    double J_hund;

    nda::array<nda::matrix<dcomplex>, 2> get_density_matrix_from_gf(block_gf<imfreq, matrix_valued> const &gimp);
 
    public:
    dc_solver(spin_kind_e spin_kind, std::string method, double U_int, double J_hund);

    std::vector<nda::matrix<dcomplex>> dc_self_energy(block_gf<imfreq, matrix_valued> const &gimp);

    double dc_energy(block_gf<imfreq, matrix_valued> const &gimp);

    std::vector<nda::matrix<dcomplex>> dc_self_energy(nda::array<nda::matrix<dcomplex>, 2> const &density_matrix);

    double dc_energy(nda::array<nda::matrix<dcomplex>, 2> const &density_matrix);
  };
 
} // namespace triqs::modest