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Grid/lib/qcd/action/gauge/Photon.h

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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 class Gauge {Feynman, Coulomb, Landau};
enum class ZmScheme {QedL, QedTL};
public:
Photon(Gauge gauge, ZmScheme zmScheme);
virtual ~Photon(void) = default;
void FreePropagator(const GaugeField &in, GaugeField &out);
void MomentumSpacePropagator(const GaugeField &in, GaugeField &out);
void StochasticField(GaugeField &out, GridParallelRNG &rng);
private:
void invKHatSquared(GaugeLinkField &out);
void zmSub(GaugeLinkField &out);
private:
Gauge gauge_;
ZmScheme zmScheme_;
};
template<class Gimpl>
Photon<Gimpl>::Photon(Gauge gauge, ZmScheme zmScheme)
: gauge_(gauge), zmScheme_(zmScheme)
{}
template<class Gimpl>
void Photon<Gimpl>::FreePropagator (const GaugeField &in,GaugeField &out)
{
FFT theFFT(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);
}
template<class Gimpl>
void Photon<Gimpl>::invKHatSquared(GaugeLinkField &out)
{
GridBase *grid = out._grid;
GaugeLinkField kmu(grid), one(grid);
const unsigned int nd = grid->_ndimension;
std::vector<int> &l = grid->_fdimensions;
std::vector<int> zm(nd,0);
TComplex Tone = Complex(1.0,0.0);
TComplex Tzero= Complex(0.0,0.0);
one = Complex(1.0,0.0);
out = zero;
for(int mu = 0; mu < nd; mu++)
{
Real twoPiL = M_PI*2./l[mu];
LatticeCoordinate(kmu,mu);
kmu = 2.*sin(.5*twoPiL*kmu);
out = out + kmu*kmu;
}
pokeSite(Tone, out, zm);
out = one/out;
pokeSite(Tzero, out, zm);
}
template<class Gimpl>
void Photon<Gimpl>::zmSub(GaugeLinkField &out)
{
GridBase *grid = out._grid;
const unsigned int nd = grid->_ndimension;
switch (zmScheme_)
{
case ZmScheme::QedTL:
{
std::vector<int> zm(nd,0);
TComplex Tzero = Complex(0.0,0.0);
pokeSite(Tzero, out, zm);
break;
}
case ZmScheme::QedL:
{
LatticeInteger spNrm(grid), coor(grid);
GaugeLinkField z(grid);
spNrm = zero;
for(int d = 0; d < grid->_ndimension - 1; d++)
{
LatticeCoordinate(coor,d);
spNrm = spNrm + coor*coor;
}
out = where(spNrm == Integer(0), 0.*out, out);
break;
}
default:
break;
}
}
template<class Gimpl>
void Photon<Gimpl>::MomentumSpacePropagator(const GaugeField &in,
GaugeField &out)
{
GridBase *grid = out._grid;
LatticeComplex k2Inv(grid);
invKHatSquared(k2Inv);
zmSub(k2Inv);
out = in*k2Inv;
}
template<class Gimpl>
void Photon<Gimpl>::StochasticField(GaugeField &out, GridParallelRNG &rng)
{
auto *grid = dynamic_cast<GridCartesian *>(out._grid);
const unsigned int nd = grid->_ndimension;
std::vector<int> latt_size = grid->_fdimensions;
GaugeLinkField sqrtK2Inv(grid), r(grid);
GaugeField aTilde(grid);
FFT fft(grid);
Integer vol = 1;
for(int d = 0; d < nd; d++)
{
vol = vol * latt_size[d];
}
invKHatSquared(sqrtK2Inv);
sqrtK2Inv = sqrt(vol*real(sqrtK2Inv));
zmSub(sqrtK2Inv);
for(int mu = 0; mu < nd; mu++)
{
gaussian(rng, r);
r = sqrtK2Inv*r;
pokeLorentz(aTilde, r, mu);
}
fft.FFT_all_dim(out, aTilde, FFT::backward);
out = real(out);
}
// template<class Gimpl>
// void Photon<Gimpl>::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);
// }
// }
//
// template<class Gimpl>
// void Photon<Gimpl>::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
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