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55 lines
1.4 KiB
C++
55 lines
1.4 KiB
C++
#ifndef QCD_WILSON_GAUGE_ACTION_H
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#define QCD_WILSON_GAUGE_ACTION_H
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namespace Grid{
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namespace QCD{
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////////////////////////////////////////////////////////////////////////
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// Wilson Gauge Action .. should I template the Nc etc..
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////////////////////////////////////////////////////////////////////////
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template<class GaugeField>
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class WilsonGaugeAction : public Action<GaugeField> {
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public:
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typedef LorentzScalar<GaugeField> GaugeLinkField;
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private:
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RealD beta;
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public:
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WilsonGaugeAction(RealD b):beta(b){};
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virtual void refresh(const GaugeField &U, GridParallelRNG& pRNG) {}; // noop as no pseudoferms
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virtual RealD S(const GaugeField &U) {
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RealD plaq = WilsonLoops<GaugeField>::avgPlaquette(U);
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RealD vol = U._grid->gSites();
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RealD action=beta*(1.0 -plaq)*(Nd*(Nd-1.0))*vol*0.5;
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return action;
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};
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virtual void deriv(const GaugeField &U,GaugeField & dSdU) {
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//not optimal implementation FIXME
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//extend Ta to include Lorentz indexes
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//RealD factor = 0.5*beta/RealD(Nc);
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RealD factor = 0.5*beta/RealD(Nc);
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GaugeLinkField Umu(U._grid);
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GaugeLinkField dSdU_mu(U._grid);
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for (int mu=0; mu < Nd; mu++){
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Umu = PeekIndex<LorentzIndex>(U,mu);
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// Staple in direction mu
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WilsonLoops<GaugeField>::Staple(dSdU_mu,U,mu);
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dSdU_mu = Ta(Umu*dSdU_mu)*factor;
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PokeIndex<LorentzIndex>(dSdU, dSdU_mu, mu);
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}
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};
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};
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}
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}
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#endif
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