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first (dirty) implementation of Feynman stoctachtic EM field
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/*************************************************************************************
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/*************************************************************************************
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Grid physics library, www.github.com/paboyle/Grid
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@ -6,7 +6,7 @@
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Copyright (C) 2015
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Author: Peter Boyle <paboyle@ph.ed.ac.uk>
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Author: Peter Boyle <paboyle@ph.ed.ac.uk>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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@ -24,28 +24,43 @@ Author: Peter Boyle <paboyle@ph.ed.ac.uk>
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See the full license in the file "LICENSE" in the top level distribution directory
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*************************************************************************************/
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/* END LEGAL */
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/* END LEGAL */
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#ifndef QCD_PHOTON_ACTION_H
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#define QCD_PHOTON_ACTION_H
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namespace Grid{
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namespace QCD{
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namespace QCD{
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template<class Gimpl>
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class Photon {
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class Photon
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{
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public:
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INHERIT_GIMPL_TYPES(Gimpl);
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enum class Gauge {Feynman, Coulomb, Landau};
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enum class ZmScheme {QedL, QedTL};
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public:
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Photon(Gauge gauge, ZmScheme zmScheme);
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virtual ~Photon(void) = default;
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void FreePropagator(const GaugeField &in, GaugeField &out);
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void MomentumSpacePropagator(const GaugeField &in, GaugeField &out);
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void StochasticField(GaugeField &out, GridParallelRNG &rng);
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private:
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void kHatSquared(GaugeLinkField &out);
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void zmSub(GaugeLinkField &out);
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private:
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Gauge gauge_;
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ZmScheme zmScheme_;
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};
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enum PhotonType { FEYNMAN_L, FEYNMAN_TL };
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template<class Gimpl>
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Photon<Gimpl>::Photon(Gauge gauge, ZmScheme zmScheme)
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: gauge_(gauge), zmScheme_(zmScheme)
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{}
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PhotonType GaugeBC;
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Photon(PhotonType _GaugeBC) : GaugeBC(_GaugeBC){};
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void FreePropagator (const GaugeField &in,GaugeField &out) {
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FFT theFFT((GridCartesian *) in._grid);
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template<class Gimpl>
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void Photon<Gimpl>::FreePropagator (const GaugeField &in,GaugeField &out)
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{
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FFT theFFT(in._grid);
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GaugeField in_k(in._grid);
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GaugeField prop_k(in._grid);
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@ -54,73 +69,166 @@ namespace Grid{
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MomentumSpacePropagator(prop_k,in_k);
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theFFT.FFT_all_dim(out,prop_k,FFT::backward);
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}
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void MomentumSpacePropagator(GaugeField &out,const GaugeField &in) {
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if ( GaugeBC == FEYNMAN_L ) {
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FeynmanGaugeMomentumSpacePropagator_L(out,in);
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} else if ( GaugeBC == FEYNMAN_TL ) {
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FeynmanGaugeMomentumSpacePropagator_TL(out,in);
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} else { // No coulomb yet
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assert(0);
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}
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}
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void FeynmanGaugeMomentumSpacePropagator_L(GaugeField &out, const GaugeField &in) {
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FeynmanGaugeMomentumSpacePropagator_TL(out,in);
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template<class Gimpl>
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void Photon<Gimpl>::kHatSquared(GaugeLinkField &out)
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{
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GridBase *grid = out._grid;
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LatticeInteger coor(grid);
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GaugeField zz(grid); zz=zero;
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GaugeLinkField kmu(grid);
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const unsigned int nd = grid->_ndimension;
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std::vector<int> &l = grid->_fdimensions;
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// xyzt
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for(int d = 0; d < grid->_ndimension-1;d++){
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LatticeCoordinate(coor,d);
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out = where(coor==Integer(0),zz,out);
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}
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}
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void FeynmanGaugeMomentumSpacePropagator_TL(GaugeField &out, const GaugeField &in) {
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// what type LatticeComplex
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GridBase *grid = out._grid;
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int nd = grid->_ndimension;
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typedef typename GaugeField::vector_type vector_type;
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typedef typename GaugeField::scalar_type ScalComplex;
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typedef Lattice<iSinglet<vector_type> > LatComplex;
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std::vector<int> latt_size = grid->_fdimensions;
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LatComplex denom(grid); denom= zero;
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LatComplex one(grid); one = ScalComplex(1.0,0.0);
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LatComplex kmu(grid);
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ScalComplex ci(0.0,1.0);
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// momphase = n * 2pi / L
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for(int mu=0;mu<Nd;mu++) {
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out = zero;
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for(int mu = 0; mu < nd; mu++)
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{
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RealD twoPiL = M_PI*2./l[mu];
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LatticeCoordinate(kmu,mu);
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RealD TwoPiL = M_PI * 2.0/ latt_size[mu];
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kmu = TwoPiL * kmu ;
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denom = denom + 4.0*sin(kmu*0.5)*sin(kmu*0.5); // Wilson term
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kmu = 2.*sin(.5*twoPiL*kmu);
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out = out + kmu*kmu;
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}
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std::vector<int> zero_mode(nd,0);
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}
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template<class Gimpl>
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void Photon<Gimpl>::zmSub(GaugeLinkField &out)
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{
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GridBase *grid = out._grid;
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const unsigned int nd = grid->_ndimension;
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switch (zmScheme_)
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{
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case ZmScheme::QedTL:
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{
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std::vector<int> zm(nd,0);
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TComplexD Tzero = ComplexD(0.0,0.0);
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pokeSite(Tzero, out, zm);
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break;
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}
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case ZmScheme::QedL:
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{
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LatticeInteger spNrm(grid), coor(grid);
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GaugeLinkField z(grid);
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spNrm = zero;
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for(int d = 0; d < grid->_ndimension - 1; d++)
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{
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LatticeCoordinate(coor,d);
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spNrm = spNrm + coor*coor;
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}
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out = where(spNrm == 0, 0.*out, out);
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break;
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}
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default:
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break;
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}
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}
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template<class Gimpl>
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void Photon<Gimpl>::MomentumSpacePropagator(const GaugeField &in,
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GaugeField &out)
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{
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GridBase *grid = out._grid;
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const unsigned int nd = grid->_ndimension;
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LatticeComplex k2Inv(grid), one(grid);
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one = ComplexD(1.0,0.0);
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kHatSquared(k2Inv);
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std::vector<int> zm(nd,0);
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TComplexD Tone = ComplexD(1.0,0.0);
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TComplexD Tzero= ComplexD(0.0,0.0);
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pokeSite(Tone,denom,zero_mode);
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pokeSite(Tone, k2Inv, zm);
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k2Inv = one/k2Inv;
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pokeSite(Tzero, k2Inv,zm);
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denom= one/denom;
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out = in*k2Inv;
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}
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pokeSite(Tzero,denom,zero_mode);
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template<class Gimpl>
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void Photon<Gimpl>::StochasticField(GaugeField &out, GridParallelRNG &rng)
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{
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auto *grid = out._grid;
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const unsigned int nd = grid->_ndimension;
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GaugeLinkField k2(grid), r(grid);
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GaugeField aTilde(grid);
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FFT fft(grid);
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out = zero;
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out = in*denom;
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};
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};
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kHatSquared(k2);
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zmSub(k2);
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for(int mu = 0; mu < nd; mu++)
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{
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gaussian(rng, r);
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r = k2*r;
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pokeLorentz(aTilde, r, mu);
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}
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fft.FFT_all_dim(out, aTilde, FFT::backward);
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}
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// template<class Gimpl>
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// void Photon<Gimpl>::FeynmanGaugeMomentumSpacePropagator_L(GaugeField &out,
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// const GaugeField &in)
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// {
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//
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// FeynmanGaugeMomentumSpacePropagator_TL(out,in);
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//
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// GridBase *grid = out._grid;
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// LatticeInteger coor(grid);
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// GaugeField zz(grid); zz=zero;
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//
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// // xyzt
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// for(int d = 0; d < grid->_ndimension-1;d++){
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// LatticeCoordinate(coor,d);
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// out = where(coor==Integer(0),zz,out);
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// }
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// }
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//
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// template<class Gimpl>
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// void Photon<Gimpl>::FeynmanGaugeMomentumSpacePropagator_TL(GaugeField &out,
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// const GaugeField &in)
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// {
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//
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// // what type LatticeComplex
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// GridBase *grid = out._grid;
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// int nd = grid->_ndimension;
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//
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// typedef typename GaugeField::vector_type vector_type;
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// typedef typename GaugeField::scalar_type ScalComplex;
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// typedef Lattice<iSinglet<vector_type> > LatComplex;
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//
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// std::vector<int> latt_size = grid->_fdimensions;
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//
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// LatComplex denom(grid); denom= zero;
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// LatComplex one(grid); one = ScalComplex(1.0,0.0);
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// LatComplex kmu(grid);
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//
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// ScalComplex ci(0.0,1.0);
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// // momphase = n * 2pi / L
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// for(int mu=0;mu<Nd;mu++) {
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//
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// LatticeCoordinate(kmu,mu);
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//
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// RealD TwoPiL = M_PI * 2.0/ latt_size[mu];
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//
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// kmu = TwoPiL * kmu ;
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//
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// denom = denom + 4.0*sin(kmu*0.5)*sin(kmu*0.5); // Wilson term
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// }
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// std::vector<int> zero_mode(nd,0);
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// TComplexD Tone = ComplexD(1.0,0.0);
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// TComplexD Tzero= ComplexD(0.0,0.0);
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//
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// pokeSite(Tone,denom,zero_mode);
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//
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// denom= one/denom;
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//
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// pokeSite(Tzero,denom,zero_mode);
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//
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// out = zero;
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// out = in*denom;
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// };
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}}
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#endif
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