Setting up but not implemented some QED rules

2025-11-03 21:44:33 +00:00 · 2016-09-26 09:43:40 +01:00
parent 2ba7d43ddd
commit 7089b6d5a5
1 changed files with 126 additions and 0 deletions
--- a/lib/qcd/action/gauge/Photon.h
+++ b/lib/qcd/action/gauge/Photon.h
@@ -0,0 +1,126 @@
+    /*************************************************************************************
+
+    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