baryon_spin3by2_s.cc

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/*
   Code for j=3/2 Staggered Baryons.
 
Lattice Baryons With Staggered Fermions.
Maarten F.L. Golterman, Jan Smit (Amsterdam U.)
Published in Nucl.Phys.B255:328,1985
 
The Quenched spectrum with staggered fermions.
Rajan Gupta (Los Alamos) , Gerald Guralnik (Brown U.) , Gregory W. Kilcup (Ohio State U.) , Stephen R. Sharpe 
Published in Phys.Rev.D43:2003-2026,1991
 
The class 7 operators has been compared against the MILC
code. The class 4 operator is still experimental!
 
*/
 
#include "chromabase.h"
 
namespace Chroma {
 
  // some prototypes
 
  void baryon_s(
                LatticeStaggeredPropagator & quark_propagator_in_a,
                LatticeStaggeredPropagator & quark_propagator_in_b,
                LatticeStaggeredPropagator & quark_propagator_in_c,
                multi1d<Complex> & barprop,
                multi1d<int> & t_source,
                int j_decay, int bc_spec) ;
 
 
  //
  //  This is the quasi-local operator that is used by 
  //  MILC from the above Gupta paper
  //
  //  This is known as a class 7 operator by Smit and Golterman.
  //
  //
 
  void baryon_class7_s(
                LatticeStaggeredPropagator & quark_propagator_in_a,
                LatticeStaggeredPropagator & quark_propagator_in_b,
                LatticeStaggeredPropagator & quark_propagator_in_c,
                multi1d<Complex> & barprop,
                multi1d<int> & t_source,
                int j_decay, int bc_spec) 
  {
    StopWatch swatch;
    swatch.start();
 
    // shift the quark propagators
    LatticeStaggeredPropagator quark_propagator_in_a_shift ;
    LatticeStaggeredPropagator quark_propagator_in_b_shift ;
    LatticeStaggeredPropagator quark_propagator_in_c_shift ;
 
    // shift in x direction
    quark_propagator_in_a_shift = shift(quark_propagator_in_a,FORWARD,0) + 
      shift(quark_propagator_in_a,BACKWARD,0) ;
 
    quark_propagator_in_b_shift = shift(quark_propagator_in_b,FORWARD,1) + 
      shift(quark_propagator_in_b,BACKWARD,1) ;
 
    quark_propagator_in_c_shift = shift(quark_propagator_in_c,FORWARD,2) + 
      shift(quark_propagator_in_c,BACKWARD,2) ;
 
    // call the Wick contarction routine
    baryon_s(quark_propagator_in_a_shift,
             quark_propagator_in_b_shift,
             quark_propagator_in_c_shift, 
             barprop, t_source, j_decay, bc_spec) ;  
 
    // 8 = 2**3 for average in the derivative 
    // 6 is the factor in the definition  of the operator
 
    //    barprop /= 6.0 * 8.0 ;
 
    // chose normalisation to agree with MILC code
    barprop /= 6.0  ;
 
    swatch.stop();
    double time_in_sec  = swatch.getTimeInSeconds();
 
    QDPIO::cout << "baryon_class7_s took " << time_in_sec
                << " secs" << std::endl;
 
  }
 
 
 
  //
  //  This is the quasi-local NLT operator 
  //  from the Gupta paper. One of the quark fields are
  //  shifted forward by one time slice.
  //
  //   This is known as a class 7 operator by Smit and Golterman.
  //
  //
 
  void baryon_class7_NLT_s(
                LatticeStaggeredPropagator & quark_propagator_in_a,
                LatticeStaggeredPropagator & quark_propagator_in_b,
                LatticeStaggeredPropagator & quark_propagator_in_c,
                multi1d<LatticeColorMatrix> & u , 
                multi1d<Complex> & barprop,
                multi1d<int> & t_source,
                int j_decay, int bc_spec) 
  {
    StopWatch swatch;
    swatch.start();
 
    LatticeStaggeredPropagator quark_propagator_in_a_TIME_shift ;
    // use a covariant shift in time because we only fix to Coulomb
    // gauge. This may make the correlators more noisy
 
    quark_propagator_in_a_TIME_shift = u[j_decay] * shift(quark_propagator_in_a_TIME_shift,FORWARD,j_decay) ; 
 
 
    // shift the quark propagators
    LatticeStaggeredPropagator quark_propagator_in_a_shift ;
    LatticeStaggeredPropagator quark_propagator_in_b_shift ;
    LatticeStaggeredPropagator quark_propagator_in_c_shift ;
 
    // shift in x direction
    quark_propagator_in_a_shift = 
      shift(quark_propagator_in_a_TIME_shift,FORWARD,0) + 
      shift(quark_propagator_in_a_TIME_shift,BACKWARD,0) ;
 
    quark_propagator_in_b_shift = shift(quark_propagator_in_b,FORWARD,1) + 
      shift(quark_propagator_in_b,BACKWARD,1) ;
 
    quark_propagator_in_c_shift = shift(quark_propagator_in_c,FORWARD,2) + 
      shift(quark_propagator_in_c,BACKWARD,2) ;
 
    // call the Wick contarction routine
    baryon_s(quark_propagator_in_a_shift,
             quark_propagator_in_b_shift,
             quark_propagator_in_c_shift, 
             barprop, t_source, j_decay, bc_spec) ;  
 
    // 8 = 2**3 for average in the derivative 
    // 6 is the factor in the definition  of the operator
 
    //    barprop /= 6.0 * 8.0 ;
 
    // chose normalisation to agree with MILC code
    barprop /= 6.0  ;
 
    swatch.stop();
    double time_in_sec  = swatch.getTimeInSeconds();
 
    QDPIO::cout << "baryon_class7_s took " << time_in_sec
                << " secs" << std::endl;
 
  }
 
 
  /**
      This is the class 4 staggered baryon operator
      that couples to the j=3/2 state.
 
  **/
 
 
  void baryon_class4_s(
                LatticeStaggeredPropagator & quark_propagator_in_a,
                LatticeStaggeredPropagator & quark_propagator_in_b,
                LatticeStaggeredPropagator & quark_propagator_in_c,
                multi1d<Complex> & barprop,
                multi1d<int> & t_source,
                int j_decay, int bc_spec) 
  {
    StopWatch swatch;
    swatch.start();
 
    int t_length = barprop.size() ;
    multi1d<Complex>  barprop_tmp(t_length) ; 
 
    // shift the quark propagators
    LatticeStaggeredPropagator quark_propagator_in_a_shift ;
    LatticeStaggeredPropagator quark_propagator_in_b_shift ;
    LatticeStaggeredPropagator quark_propagator_in_c_shift ;
 
    LatticeStaggeredPropagator tmp ;
 
    // ----- shift in x direction -----
    quark_propagator_in_a_shift = shift(quark_propagator_in_a,FORWARD,0) ;
 
    tmp = shift(quark_propagator_in_b,FORWARD,0) ;
    quark_propagator_in_b_shift = shift(tmp,FORWARD,1) + 
      shift(tmp,BACKWARD,1) ;
 
    tmp = shift(quark_propagator_in_c,FORWARD,0) ;
    quark_propagator_in_c_shift = shift(tmp,FORWARD,2) + 
      shift(tmp,BACKWARD,2) ;
 
    // call the Wick contarction routine
    baryon_s(quark_propagator_in_a_shift,
             quark_propagator_in_b_shift,
             quark_propagator_in_c_shift, 
             barprop_tmp, t_source, j_decay, bc_spec) ;  
 
    barprop_tmp /= (-6.0 * 4.0) ;
    barprop = barprop_tmp ;
    
 
    // ----- shift in y direction -----
    quark_propagator_in_a_shift = shift(quark_propagator_in_a,FORWARD,1) ;
 
    tmp = shift(quark_propagator_in_b,FORWARD,1) ;
    quark_propagator_in_b_shift = shift(tmp,FORWARD,0) + 
      shift(tmp,BACKWARD,0) ;
 
    tmp = shift(quark_propagator_in_c,FORWARD,1) ;
    quark_propagator_in_c_shift = shift(tmp,FORWARD,2) + 
      shift(tmp,BACKWARD,2) ;
 
    // call the Wick contarction routine
    baryon_s(quark_propagator_in_a_shift,
             quark_propagator_in_b_shift,
             quark_propagator_in_c_shift, 
             barprop_tmp, t_source, j_decay, bc_spec) ;  
 
    barprop_tmp /= (6.0 * 4.0) ;
    barprop += barprop_tmp ;
 
 
    // ----- shift in z direction -----
    quark_propagator_in_a_shift = shift(quark_propagator_in_a,FORWARD,2) ;
 
    tmp = shift(quark_propagator_in_b,FORWARD,2) ;
    quark_propagator_in_b_shift = shift(tmp,FORWARD,0) + 
      shift(tmp,BACKWARD,0) ;
 
    tmp = shift(quark_propagator_in_c,FORWARD,2) ;
    quark_propagator_in_c_shift = shift(tmp,FORWARD,1) + 
      shift(tmp,BACKWARD,1) ;
 
    // call the Wick contarction routine
    baryon_s(quark_propagator_in_a_shift,
             quark_propagator_in_b_shift,
             quark_propagator_in_c_shift, 
             barprop_tmp, t_source, j_decay, bc_spec) ;  
 
    barprop_tmp /= (-6.0 * 4.0) ;
    barprop += barprop_tmp ;
 
    swatch.stop();
    double time_in_sec  = swatch.getTimeInSeconds();
 
 
 
    QDPIO::cout << "baryon_class4_s took " << time_in_sec
                << " secs" << std::endl;
 
 
 
  }
 
 
 
} // end namespace Chroma