:github_url: https://github.com/srbhp/nrgplusplus


.. _program_listing_file_models_freeModel.hpp:

Program Listing for File freeModel.hpp
======================================

|exhale_lsh| :ref:`Return to documentation for file <file_models_freeModel.hpp>` (``models/freeModel.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   #pragma once
   #include "models/fermionBasis.hpp"
   #include "nrgcore/qOperator.hpp"
   #include "nrgcore/qsymmetry.hpp"
   #include "utils/qmatrix.hpp"
   #include <algorithm>
   #include <cmath>
   #include <complex>
   #include <cstddef>
   #include <iostream>
   #include <map>
   #include <optional>
   #include <string>
   #include <vector>
   class freeModel : public fermionBasis {
   public:
     freeModel() : fermionBasis(2, fermionBasis::chargeAndSpin) {
       createBasis(); // create the basis in nstates x nstates
     }
     [[nodiscard]] std::vector<std::vector<int>> get_basis() const { return n_Q; }
     [[nodiscard]] std::vector<std::vector<double>> get_eigenvaluesQ() const {
       return eigenvalues_Q;
     }
     [[nodiscard]] std::vector<double> get_chi_Q() const { return chi_Q; }
     //
     std::vector<std::vector<double>> eigenvalues_Q;
     std::vector<double>              chi_Q;
     std::vector<std::vector<int>>    n_Q;
     //    ########################################
   private:
     void createBasis() {
       //
       createFermionBasis(2);
       std::cout << "FermionBasis Size" << fermionOprMat.size() << "\n";
       auto Hamiltonian = fermionOprMat[0] * 0; // Set Hamiltonian to Zero
       //
       create_QuantumNspinCharge();
       create_Block_structure();
       // ####################################################################
       n_Q = get_unique_Qnumbers();
       // set chi_Q
       chi_Q.clear();
       for (auto ai : n_Q) {
         double t_charge = std::accumulate(ai.begin(), ai.end(), 0);
         chi_Q.push_back(std::pow(-1., t_charge));
       }
       //
       // set foperator
       auto h_blocked = get_block_Hamiltonian(Hamiltonian);
       //    std::cout << "h_blocked: " << h_blocked << std::endl;
       //    std::cout << "Hamiltonian: " << Hamiltonian << std::endl;
       // Diagonalize the hamilton
       eigenvalues_Q.clear();
       eigenvalues_Q.resize(n_Q.size(), {});
       for (size_t i = 0; i < n_Q.size(); i++) {
         eigenvalues_Q[i] = (h_blocked.get(i, i)).value()->diag();
       }
       //    std::cout << "Eigenvalues: " << eigenvalues_Q << std::endl;
       // TODO(sp): rotate the f operator
       // ####################################################################
       f_dag_operator = get_block_operators({fermionOprMat[0], fermionOprMat[1]});
       std::cout << "f_dag_operators: " << f_dag_operator.size() << std::endl;
       std::vector<qOperator> topr(f_dag_operator.size(), qOperator());
       for (size_t ip = 0; ip < f_dag_operator.size(); ip++) {
         for (size_t i = 0; i < n_Q.size(); i++) {
           for (size_t j = 0; j < n_Q.size(); j++) {
             auto tfopr = f_dag_operator[ip].get(i, j);
             if (tfopr) {
               topr[ip].set((h_blocked.get(i, i))
                                .value()
                                ->cTranspose()
                                .dot(*tfopr.value())
                                .dot(*(h_blocked.get(j, j)).value()),
                            i, j);
             }
           }
         }
       }
       f_dag_operator = topr;
     }
     //    ######################################
   };