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Smearing for quark observables

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Azusa Yamaguchi 2019-02-26 11:31:00 +00:00
parent ae9e248c95
commit 8f661f6c05
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Grid/qcd/utils/CovariantSmearing.h Normal file
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/*************************************************************************************
Grid physics library, www.github.com/paboyle/Grid
Source file: ./lib/qcd/action/scalar/CovariantLaplacian.h
Copyright (C) 2016
Author: Azusa Yamaguchi
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
*************************************************************************************/
#pragma once
namespace Grid {
namespace QCD {
template <class Gimpl> class CovariantSmearing : public Gimpl
{
public:
INHERIT_GIMPL_TYPES(Gimpl);
typedef typename Gimpl::GaugeLinkField GaugeMat;
typedef typename Gimpl::GaugeField GaugeLorentz;
template<typename T>
static void GaussianSmear(const std::vector<LatticeColourMatrix>& U,
T& chi,
const Real& width, int Iterations, int orthog)
{
GridBase *grid = chi._grid;
T psi(grid);
////////////////////////////////////////////////////////////////////////////////////
// Follow Chroma conventions for width to keep compatibility with previous data
// Free field iterates
// chi = (1 - w^2/4N p^2)^N chi
//
// ~ (e^(-w^2/4N p^2)^N chi
// ~ (e^(-w^2/4 p^2) chi
// ~ (e^(-w'^2/2 p^2) chi [ w' = w/sqrt(2) ]
//
// Which in coordinate space is proportional to
//
// e^(-x^2/w^2) = e^(-x^2/2w'^2)
//
// The 4 is a bit unconventional from Gaussian width perspective, but... it's Chroma convention.
// 2nd derivative approx d^2/dx^2 = x+mu + x-mu - 2x
//
// d^2/dx^2 = - p^2
//
// chi = ( 1 + w^2/4N d^2/dx^2 )^N chi
//
////////////////////////////////////////////////////////////////////////////////////
Real coeff = (width*width) / Real(4*Iterations);
int dims = Nd;
if( orthog < Nd ) dims=Nd-1;
for(int n = 0; n < Iterations; ++n) {
psi = (-2.0*dims)*chi;
for(int mu=0;mu<Nd;mu++) {
if ( mu != orthog ) {
psi = psi + Gimpl::CovShiftForward(U[mu],mu,chi);
psi = psi + Gimpl::CovShiftBackward(U[mu],mu,chi);
}
}
chi = chi + coeff*psi;
}
}
};
}}