chi_from_gg2.cpp

/*******************************************************************************
 *
 * TRIQS: a Toolbox for Research in Interacting Quantum Systems
 *
 * Copyright (C) 2017, H. U.R. Strand
 *
 * TRIQS is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * TRIQS is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * TRIQS. If not, see <http://www.gnu.org/licenses/>.
 *
 ******************************************************************************/
 
#include "chi_from_gg2.hpp"
 
using namespace nda::clef;
 
namespace {
placeholder<0> a;
placeholder<1> b;
placeholder<2> c;
placeholder<3> d;
 
placeholder<4> Omega;
placeholder<5> n;
placeholder<6> np;
 
placeholder<7> tau;
} // namespace
 
namespace triqs_tprf {
 
// ----------------------------------------------------
// Particle-hole (PH)
 
template <> g2_iw_t chi0_from_gg2<Channel_t::PH>(g_iw_cvt g, g2_iw_cvt g2) {
  double beta = g.mesh().beta();
  auto chi0   = make_gf(g2.mesh(), g2.target());
 
  chi0(Omega, n, np)(a, b, c, d)
      << -beta * kronecker(n, np) * g(n)(d, a) * g(Omega + n)(b, c);
 
  return chi0;
}
 
template <> g2_iw_t chi_from_gg2<Channel_t::PH>(g_iw_cvt g, g2_iw_cvt g2) {
  double beta = g.mesh().beta();
  auto chi    = make_gf(g2.mesh(), g2.target());
 
  chi(Omega, n, np)(a, b, c, d)
      << g2(Omega, n, np)(a, b, c, d) -
             beta * kronecker(Omega) * g(n)(b, a) * g(np)(d, c);
 
  return chi;
}
 
chi2_tau_t chi0_tau_from_g_tau_PH(g_tau_cvt g_tau) {
 
  int nb = g_tau.target().shape()[0];
  double beta = g_tau.mesh().beta();
  int ntau = g_tau.mesh().size();
  
  chi2_tau_t chi0_tau{{beta, Boson, ntau}, {nb, nb, nb, nb}};
 
  chi0_tau(tau)(a, b, c, d) << g_tau(tau)(d, a) * g_tau(beta - tau)(b, c);
 
  return chi0_tau;
}
  
// ----------------------------------------------------
// Particle-particle (PP)
 
template <> g2_iw_t chi0_from_gg2<Channel_t::PP>(g_iw_cvt g, g2_iw_cvt g2) {
  double beta = g.mesh().beta();
  auto chi0   = make_gf(g2.mesh(), g2.target());
 
  chi0(Omega, n, np)(a, b, c, d)
      << -beta * kronecker(n, np) * g(n)(d, a) * g(Omega - n)(b, c);
 
  return chi0;
}
 
template <> g2_iw_t chi_from_gg2<Channel_t::PP>(g_iw_cvt g, g2_iw_cvt g2) {
  double beta = g.mesh().beta();
  auto chi    = make_gf(g2.mesh(), g2.target());
 
  chi(Omega, n, np)(a, b, c, d)
      << g2(Omega, n, np)(a, b, c, d) -
             beta * kronecker(n + np, Omega) * g(n)(b, a) * g(np)(d, c);
 
  return chi;
}
 
 
// ----------------------------------------------------
// functions for (easier) Python wrapping
  
g2_iw_t chi0_from_gg2_PH(g_iw_vt g, g2_iw_vt g2) { return chi0_from_gg2<Channel_t::PH>(g, g2); }
g2_iw_t chi0_from_gg2_PP(g_iw_vt g, g2_iw_vt g2) { return chi0_from_gg2<Channel_t::PP>(g, g2); }
 
g2_iw_t chi_from_gg2_PH(g_iw_vt g, g2_iw_vt g2) { return chi_from_gg2<Channel_t::PH>(g, g2); }
g2_iw_t chi_from_gg2_PP(g_iw_vt g, g2_iw_vt g2) { return chi_from_gg2<Channel_t::PP>(g, g2); }
 
} // namespace triqs_tprf