ABACUS/src/SCAN/Particle_Hole_Excitation_Co...

/**********************************************************

This software is part of J.-S. Caux's ABACUS library.

Copyright (c) J.-S. Caux.

-----------------------------------------------------------

File:  src/SCAN/Particle_Hole_Excitation_Cost.cc

Purpose:  defines the expected cost of adding a p-h pair. Used in General_Scan.

***********************************************************/

#include "ABACUS.h"

using namespace std;
using namespace ABACUS;

namespace ABACUS {

  DP Particle_Hole_Excitation_Cost (char whichDSF, LiebLin_Bethe_State& AveragingState)
  {
    // Estimates the cost of adding a particle-hole excitation to an intermediate state
    DP ph_cost = 1.0;

    if (whichDSF == 'd') ph_cost = ABACUS::min(0.01, 0.1/AveragingState.c_int);
    else if (whichDSF == 'o') ph_cost = 0.01;
    else if (whichDSF == 'g') ph_cost = 0.01;
    else if (whichDSF == 'Z') ph_cost = 1.0;
    else if (whichDSF == 'B') ph_cost = 0.1;
    else if (whichDSF == 'C') ph_cost = 0.1;
    else ABACUSerror("whichDSF option not implemented in Particle_Hole_Excitation_Cost for LiebLin.");

    return(ph_cost);
  }

  DP Particle_Hole_Excitation_Cost (char whichDSF, Heis_Bethe_State& AveragingState)
  {
    // Estimates the cost of adding a particle-hole excitation to an intermediate state
    DP ph_cost = 1.0;

    if (whichDSF == 'z') ph_cost = 0.01;
    else if (whichDSF == 'm') ph_cost = 0.01;
    else if (whichDSF == 'p') ph_cost = 0.01;
    else if (whichDSF == 'Z') ph_cost = 1.0;
    else ABACUSerror("whichDSF option not implemented in Particle_Hole_Excitation_Cost for HEIS.");

    return(ph_cost);
  }

} // namespace ABACUS