polyakov_loop.h

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/*************************************************************************************
 
Grid physics library, www.github.com/paboyle/Grid
 
Source file: ./Grid/qcd/observables/polyakov_loop.h
 
Copyright (C) 2025
 
Author: David Preti <david.preti@csic.es>
Author: Alexis Verney-Provatas <2414441@swansea.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 */
 
#pragma once
 
NAMESPACE_BEGIN(Grid);
 
// this is only defined for a gauge theory
template <class Impl>
class PolyakovLogger : public HmcObservable<typename Impl::Field> {
 public:
  // here forces the Impl to be of gauge fields
  // if not the compiler will complain
  INHERIT_GIMPL_TYPES(Impl);
 
  // necessary for HmcObservable compatibility
  typedef typename Impl::Field Field;
 
  void TrajectoryComplete(int traj,
                          Field &U,
                          GridSerialRNG &sRNG,
                          GridParallelRNG &pRNG) {
 
    ComplexD polyakov = WilsonLoops<Impl>::avgPolyakovLoop(U);
 
    int def_prec = std::cout.precision();
 
    std::cout << GridLogMessage
        << std::setprecision(std::numeric_limits<Real>::digits10 + 1)
        << "Polyakov Loop: [ " << traj << " ] "<< polyakov << std::endl;
 
    std::cout.precision(def_prec);
 
  }
};
 
template <class Impl>
class SpatialPolyakovLogger : public HmcObservable<typename Impl::Field> {
 public:
    // here forces the Impl to be of gauge fields
    // if not the compiler will complain
    INHERIT_GIMPL_TYPES(Impl);
 
     // necessary for HmcObservable compatibility
    typedef typename Impl::Field Field;
 
    void TrajectoryComplete(int traj,
                            Field &U,
                            GridSerialRNG &sRNG,
                            GridParallelRNG &pRNG) {
 
    // Save current numerical output precision
    int def_prec = std::cout.precision();
 
    // Assume that the dimensions are D=3+1
    int Ndim = 3;
    ComplexD polyakov;
   
    // Iterate over the spatial directions and print the average spatial polyakov loop
    // over them 
    for (int idx=0; idx<Ndim; idx++) {
        polyakov = WilsonLoops<Impl>::avgPolyakovLoop(U, idx);
    
        std::cout << GridLogMessage
            << std::setprecision(std::numeric_limits<Real>::digits10 + 1)
            << "Polyakov Loop in the " << idx << " spatial direction : [ " << traj << " ] "<< polyakov << std::endl;
 
    }
 
    // Return to original output precision
    std::cout.precision(def_prec);
 
  }
};
 
NAMESPACE_END(Grid);