hotst.cc

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// HOTST
 
/*! \file
 *  \brief Set a gauge field from a sample of (almost) Haar measure
 */
 
#include "chromabase.h"
#include "util/gauge/hotst.h"
#include "util/gauge/taproj.h"
#include "util/gauge/expm12.h"
#include "util/gauge/reunit.h"
 
 
namespace Chroma { 
 
//! Set a gauge field from a sample of (almost) Haar measure
/*!
 * \ingroup gauge
 *
 * u = exp(A), where A = random traceless antihermitian matrix.
 *
 * Arguments:
 *
 *  \param u          Gauge field               (Write)
 *
 *
 * NOTE!!!!: we are using a hack. The twelth_order exponentiation followed
 *   by a reunitarization should be replace by an exact exponentiation.
 *   So, the gauge field distriubution is NOT from Haar measure, but
 *   if someone can think of a really good reason why it should be Haar
 *   measure, then something can be done about it. 
 */
 
void HotSt(multi1d<LatticeColorMatrix>& u)
{
  START_CODE();
 
  u.resize(Nd);
 
  for(int mu=0; mu<u.size(); ++mu)
  {
    gaussian(u[mu]); // Gaussian fill
    taproj(u[mu]);   // Traceless anti-hermitian projection
    expm12(u[mu]);   // Exponentiate
    reunit(u[mu]);   // Reunitarize
  }
 
  END_CODE();
}
 
}