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Setting up but not implemented some QED rules

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paboyle 2016-09-26 09:43:40 +01:00
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lib/qcd/action/gauge/Photon.h Normal file
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/*************************************************************************************
Grid physics library, www.github.com/paboyle/Grid
Source file: ./lib/qcd/action/gauge/Photon.h
Copyright (C) 2015
Author: Peter Boyle <paboyle@ph.ed.ac.uk>
This program 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 2 of the License, or
(at your option) any later version.
This program 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 this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
See the full license in the file "LICENSE" in the top level distribution directory
*************************************************************************************/
/* END LEGAL */
#ifndef QCD_PHOTON_ACTION_H
#define QCD_PHOTON_ACTION_H
namespace Grid{
namespace QCD{
template<class Gimpl>
class Photon {
public:
INHERIT_GIMPL_TYPES(Gimpl);
enum PhotonType { FEYNMAN_L, FEYNMAN_TL };
PhotonType GaugeBC;
Photon(PhotonType _GaugeBC) : GaugeBC(_GaugeBC){};
void FreePropagator (const GaugeField &in,GaugeField &out) {
FFT theFFT((GridCartesian *) in._grid);
GaugeField in_k(in._grid);
GaugeField prop_k(in._grid);
theFFT.FFT_all_dim(in_k,in,FFT::forward);
MomentumSpacePropagator(prop_k,in_k);
theFFT.FFT_all_dim(out,prop_k,FFT::backward);
}
void MomentumSpacePropagator(GaugeField &out,const GaugeField &in) {
if ( GaugeBC == FEYNMAN_L ) {
FeynmanGaugeMomentumSpacePropagator_L(out,in);
} else if ( GaugeBC == FEYNMAN_TL ) {
FeynmanGaugeMomentumSpacePropagator_TL(out,in);
} else { // No coulomb yet
assert(0);
}
}
void FeynmanGaugeMomentumSpacePropagator_L(GaugeField &out, const GaugeField &in) {
FeynmanGaugeMomentumSpacePropagator_TL(out,in);
GridBase *grid = out._grid;
LatticeInteger coor(grid);
GaugeField zz(grid); zz=zero;
// xyzt
for(int d = 0; d < grid->_ndimension-1;d++){
LatticeCoordinate(coor,d);
out = where(coor==Integer(0),zz,out);
}
}
void FeynmanGaugeMomentumSpacePropagator_TL(GaugeField &out, const GaugeField &in) {
// what type LatticeComplex
GridBase *grid = out._grid;
int nd = grid->_ndimension;
typedef typename GaugeField::vector_type vector_type;
typedef typename GaugeField::scalar_type ScalComplex;
typedef Lattice<iSinglet<vector_type> > LatComplex;
std::vector<int> latt_size = grid->_fdimensions;
LatComplex denom(grid); denom= zero;
LatComplex one(grid); one = ScalComplex(1.0,0.0);
LatComplex kmu(grid);
ScalComplex ci(0.0,1.0);
// momphase = n * 2pi / L
for(int mu=0;mu<Nd;mu++) {
LatticeCoordinate(kmu,mu);
RealD TwoPiL = M_PI * 2.0/ latt_size[mu];
kmu = TwoPiL * kmu ;
denom = denom + 4.0*sin(kmu*0.5)*sin(kmu*0.5); // Wilson term
}
std::vector<int> zero_mode(nd,0);
TComplexD Tone = ComplexD(1.0,0.0);
TComplexD Tzero= ComplexD(0.0,0.0);
pokeSite(Tone,denom,zero_mode);
denom= one/denom;
pokeSite(Tzero,denom,zero_mode);
out = zero;
out = in*denom;
};
};
}}
#endif