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622 lines
19 KiB
C++
622 lines
19 KiB
C++
#ifndef QCD_UTIL_SUN_H
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#define QCD_UTIL_SUN_H
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namespace Grid {
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namespace QCD {
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template<int ncolour>
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class SU {
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public:
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static int generators(void) { return ncolour*ncolour-1; }
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static int su2subgroups(void) { return (ncolour*(ncolour-1))/2; }
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template<typename vtype> using iSUnMatrix = iScalar<iScalar<iMatrix<vtype, ncolour> > > ;
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template<typename vtype> using iSU2Matrix = iScalar<iScalar<iMatrix<vtype, 2> > > ;
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//////////////////////////////////////////////////////////////////////////////////////////////////
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// Types can be accessed as SU<2>::Matrix , SU<2>::vSUnMatrix, SU<2>::LatticeMatrix etc...
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//////////////////////////////////////////////////////////////////////////////////////////////////
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typedef iSUnMatrix<Complex> Matrix;
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typedef iSUnMatrix<ComplexF> MatrixF;
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typedef iSUnMatrix<ComplexD> MatrixD;
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typedef iSUnMatrix<vComplex> vMatrix;
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typedef iSUnMatrix<vComplexF> vMatrixF;
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typedef iSUnMatrix<vComplexD> vMatrixD;
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typedef Lattice<vMatrix> LatticeMatrix;
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typedef Lattice<vMatrixF> LatticeMatrixF;
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typedef Lattice<vMatrixD> LatticeMatrixD;
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typedef iSU2Matrix<Complex> SU2Matrix;
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typedef iSU2Matrix<ComplexF> SU2MatrixF;
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typedef iSU2Matrix<ComplexD> SU2MatrixD;
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typedef iSU2Matrix<vComplex> vSU2Matrix;
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typedef iSU2Matrix<vComplexF> vSU2MatrixF;
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typedef iSU2Matrix<vComplexD> vSU2MatrixD;
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typedef Lattice<vSU2Matrix> LatticeSU2Matrix;
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typedef Lattice<vSU2MatrixF> LatticeSU2MatrixF;
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typedef Lattice<vSU2MatrixD> LatticeSU2MatrixD;
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////////////////////////////////////////////////////////////////////////
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// There are N^2-1 generators for SU(N).
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//
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// We take a traceless hermitian generator basis as follows
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//
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// * Normalisation: trace ta tb = 1/2 delta_ab
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//
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// * Off diagonal
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// - pairs of rows i1,i2 behaving like pauli matrices signma_x, sigma_y
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//
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// - there are (Nc-1-i1) slots for i2 on each row [ x 0 x ]
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// direct count off each row
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//
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// - Sum of all pairs is Nc(Nc-1)/2: proof arithmetic series
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//
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// (Nc-1) + (Nc-2)+... 1 ==> Nc*(Nc-1)/2
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// 1+ 2+ + + Nc-1
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//
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// - There are 2 x Nc (Nc-1)/ 2 of these = Nc^2 - Nc
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//
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// - We enumerate the row-col pairs.
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// - for each row col pair there is a (sigma_x) and a (sigma_y) like generator
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//
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//
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// t^a_ij = { in 0.. Nc(Nc-1)/2 -1} => delta_{i,i1} delta_{j,i2} + delta_{i,i1} delta_{j,i2}
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// t^a_ij = { in Nc(Nc-1)/2 ... Nc^(Nc-1) -1} => i delta_{i,i1} delta_{j,i2} - i delta_{i,i1} delta_{j,i2}
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//
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// * Diagonal; must be traceless and normalised
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// - Sequence is
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// N (1,-1,0,0...)
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// N (1, 1,-2,0...)
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// N (1, 1, 1,-3,0...)
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// N (1, 1, 1, 1,-4,0...)
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//
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// where 1/2 = N^2 (1+.. m^2)etc.... for the m-th diagonal generator
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// NB this gives the famous SU3 result for su2 index 8
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//
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// N= sqrt(1/2 . 1/6 ) = 1/2 . 1/sqrt(3)
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//
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// ( 1 )
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// ( 1 ) / sqrt(3) /2 = 1/2 lambda_8
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// ( -2)
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////////////////////////////////////////////////////////////////////////
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template<class cplx>
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static void generator(int lieIndex,iSUnMatrix<cplx> &ta){
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// map lie index to which type of generator
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int diagIndex;
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int su2Index;
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int sigxy;
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int NNm1 = ncolour*(ncolour-1);
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if ( lieIndex>= NNm1 ) {
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diagIndex = lieIndex -NNm1;
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generatorDiagonal(diagIndex,ta);
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return;
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}
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sigxy = lieIndex&0x1;
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su2Index= lieIndex>>1;
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if ( sigxy ) generatorSigmaY(su2Index,ta);
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else generatorSigmaX(su2Index,ta);
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}
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template<class cplx>
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static void generatorSigmaX(int su2Index,iSUnMatrix<cplx> &ta){
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ta=zero;
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int i1,i2;
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su2SubGroupIndex(i1,i2,su2Index);
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ta()()(i1,i2)=1.0;
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ta()()(i2,i1)=1.0;
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ta= ta *0.5;
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}
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template<class cplx>
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static void generatorSigmaY(int su2Index,iSUnMatrix<cplx> &ta){
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ta=zero;
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cplx i(0.0,1.0);
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int i1,i2;
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su2SubGroupIndex(i1,i2,su2Index);
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ta()()(i1,i2)=-i;
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ta()()(i2,i1)= i;
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ta= ta *0.5;
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}
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template<class cplx>
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static void generatorDiagonal(int diagIndex,iSUnMatrix<cplx> &ta){
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ta=zero;
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int trsq=0;
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int last=diagIndex+1;
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for(int i=0;i<=diagIndex;i++){
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ta()()(i,i) = 1.0;
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trsq++;
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}
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ta()()(last,last) = -last;
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trsq+=last*last;
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RealD nrm = 1.0/std::sqrt(2.0*trsq);
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ta = ta *nrm;
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}
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////////////////////////////////////////////////////////////////////////
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// Map a su2 subgroup number to the pair of rows that are non zero
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////////////////////////////////////////////////////////////////////////
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static void su2SubGroupIndex(int &i1,int &i2,int su2_index){
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assert( (su2_index>=0) && (su2_index< (ncolour*(ncolour-1))/2) );
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int spare=su2_index;
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for(i1=0;spare >= (ncolour-1-i1);i1++ ){
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spare = spare - (ncolour-1-i1); // remove the Nc-1-i1 terms
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}
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i2=i1+1+spare;
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}
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//////////////////////////////////////////////////////////////////////////////////////////
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// Pull out a subgroup and project on to real coeffs x pauli basis
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//////////////////////////////////////////////////////////////////////////////////////////
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template<class vcplx>
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static void su2Extract( Lattice<iSinglet<vcplx> > &Determinant,
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Lattice<iSU2Matrix<vcplx> > &subgroup,
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const Lattice<iSUnMatrix<vcplx> > &source,
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int su2_index)
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{
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GridBase *grid(source._grid);
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conformable(subgroup,source);
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conformable(subgroup,Determinant);
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int i0,i1;
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su2SubGroupIndex(i0,i1,su2_index);
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PARALLEL_FOR_LOOP
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for(int ss=0;ss<grid->oSites();ss++){
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subgroup._odata[ss]()()(0,0) = source._odata[ss]()()(i0,i0);
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subgroup._odata[ss]()()(0,1) = source._odata[ss]()()(i0,i1);
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subgroup._odata[ss]()()(1,0) = source._odata[ss]()()(i1,i0);
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subgroup._odata[ss]()()(1,1) = source._odata[ss]()()(i1,i1);
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iSU2Matrix<vcplx> Sigma = subgroup._odata[ss];
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Sigma = Sigma-adj(Sigma)+trace(adj(Sigma));
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subgroup._odata[ss] = Sigma;
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// this should be purely real
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Determinant._odata[ss] = Sigma()()(0,0)*Sigma()()(1,1)
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- Sigma()()(0,1)*Sigma()()(1,0);
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}
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}
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//////////////////////////////////////////////////////////////////////////////////////////
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// Set matrix to one and insert a pauli subgroup
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//////////////////////////////////////////////////////////////////////////////////////////
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template<class vcplx>
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static void su2Insert( const Lattice<iSU2Matrix<vcplx> > &subgroup,
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Lattice<iSUnMatrix<vcplx> > &dest,
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int su2_index)
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{
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GridBase *grid(dest._grid);
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conformable(subgroup,dest);
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int i0,i1;
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su2SubGroupIndex(i0,i1,su2_index);
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dest = 1.0; // start out with identity
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PARALLEL_FOR_LOOP
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for(int ss=0;ss<grid->oSites();ss++){
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dest._odata[ss]()()(i0,i0) = subgroup._odata[ss]()()(0,0);
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dest._odata[ss]()()(i0,i1) = subgroup._odata[ss]()()(0,1);
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dest._odata[ss]()()(i1,i0) = subgroup._odata[ss]()()(1,0);
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dest._odata[ss]()()(i1,i1) = subgroup._odata[ss]()()(1,1);
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}
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}
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///////////////////////////////////////////////
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// Generate e^{ Re Tr Staple Link} dlink
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//
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// *** Note Staple should be appropriate linear compbination between all staples.
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// *** If already by beta pass coefficient 1.0.
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// *** This routine applies the additional 1/Nc factor that comes after trace in action.
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//
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///////////////////////////////////////////////
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static void SubGroupHeatBath( GridSerialRNG &sRNG,
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GridParallelRNG &pRNG,
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RealD beta,//coeff multiplying staple in action (with no 1/Nc)
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LatticeMatrix &link,
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const LatticeMatrix &barestaple, // multiplied by action coeffs so th
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int su2_subgroup,
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int nheatbath,
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LatticeInteger &wheremask)
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{
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GridBase *grid = link._grid;
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int ntrials=0;
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int nfails=0;
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const RealD twopi=2.0*M_PI;
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LatticeMatrix staple(grid);
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staple = barestaple * (beta/ncolour);
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LatticeMatrix V(grid); V = link*staple;
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// Subgroup manipulation in the lie algebra space
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LatticeSU2Matrix u(grid); // Kennedy pendleton "u" real projected normalised Sigma
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LatticeSU2Matrix uinv(grid);
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LatticeSU2Matrix ua(grid); // a in pauli form
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LatticeSU2Matrix b(grid); // rotated matrix after hb
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// Some handy constant fields
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LatticeComplex ones (grid); ones = 1.0;
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LatticeComplex zeros(grid); zeros=zero;
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LatticeReal rones (grid); rones = 1.0;
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LatticeReal rzeros(grid); rzeros=zero;
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LatticeComplex udet(grid); // determinant of real(staple)
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LatticeInteger mask_true (grid); mask_true = 1;
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LatticeInteger mask_false(grid); mask_false= 0;
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/*
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PLB 156 P393 (1985) (Kennedy and Pendleton)
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Note: absorb "beta" into the def of sigma compared to KP paper; staple
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passed to this routine has "beta" already multiplied in
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Action linear in links h and of form:
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beta S = beta Sum_p (1 - 1/Nc Re Tr Plaq )
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Writing Sigma = 1/Nc (beta Sigma') where sum over staples is "Sigma' "
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beta S = const - beta/Nc Re Tr h Sigma'
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= const - Re Tr h Sigma
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Decompose h and Sigma into (1, sigma_j) ; h_i real, h^2=1, Sigma_i complex arbitrary.
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Tr h Sigma = h_i Sigma_j Tr (sigma_i sigma_j) = h_i Sigma_j 2 delta_ij
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Re Tr h Sigma = 2 h_j Re Sigma_j
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Normalised re Sigma_j = xi u_j
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With u_j a unit vector and U can be in SU(2);
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Re Tr h Sigma = 2 h_j Re Sigma_j = 2 xi (h.u)
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4xi^2 = Det [ Sig - Sig^dag + 1 Tr Sigdag]
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u = 1/2xi [ Sig - Sig^dag + 1 Tr Sigdag]
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xi = sqrt(Det)/2;
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Write a= u h in SU(2); a has pauli decomp a_j;
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Note: Product b' xi is unvariant because scaling Sigma leaves
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normalised vector "u" fixed; Can rescale Sigma so b' = 1.
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*/
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////////////////////////////////////////////////////////
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// Real part of Pauli decomposition
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// Note a subgroup can project to zero in cold start
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////////////////////////////////////////////////////////
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su2Extract(udet,u,V,su2_subgroup);
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//////////////////////////////////////////////////////
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// Normalising this vector if possible; else identity
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//////////////////////////////////////////////////////
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LatticeComplex xi(grid);
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LatticeSU2Matrix lident(grid);
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SU2Matrix ident = Complex(1.0);
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SU2Matrix pauli1; SU<2>::generator(0,pauli1);
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SU2Matrix pauli2; SU<2>::generator(1,pauli2);
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SU2Matrix pauli3; SU<2>::generator(2,pauli3);
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pauli1 = timesI(pauli1)*2.0;
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pauli2 = timesI(pauli2)*2.0;
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pauli3 = timesI(pauli3)*2.0;
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LatticeComplex cone(grid);
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LatticeReal adet(grid);
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adet = abs(toReal(udet));
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lident=Complex(1.0);
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cone =Complex(1.0);
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Real machine_epsilon=1.0e-7;
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u = where(adet>machine_epsilon,u,lident);
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udet= where(adet>machine_epsilon,udet,cone);
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xi = 0.5*sqrt(udet); //4xi^2 = Det [ Sig - Sig^dag + 1 Tr Sigdag]
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u = 0.5*u*pow(xi,-1.0); // u = 1/2xi [ Sig - Sig^dag + 1 Tr Sigdag]
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// Debug test for sanity
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uinv=adj(u);
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b=u*uinv-1.0;
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assert(norm2(b)<1.0e-4);
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/*
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Measure: Haar measure dh has d^4a delta(1-|a^2|)
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In polars:
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da = da0 r^2 sin theta dr dtheta dphi delta( 1 - r^2 -a0^2)
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= da0 r^2 sin theta dr dtheta dphi delta( (sqrt(1-a0^) - r)(sqrt(1-a0^) + r) )
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= da0 r/2 sin theta dr dtheta dphi delta( (sqrt(1-a0^) - r) )
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Action factor Q(h) dh = e^-S[h] dh = e^{ xi Tr uh} dh // beta enters through xi
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= e^{2 xi (h.u)} dh
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= e^{2 xi h0u0}.e^{2 xi h1u1}.e^{2 xi h2u2}.e^{2 xi h3u3} dh
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Therefore for each site, take xi for that site
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i) generate |a0|<1 with dist
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(1-a0^2)^0.5 e^{2 xi a0 } da0
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Take alpha = 2 xi = 2 xi [ recall 2 beta/Nc unmod staple norm]; hence 2.0/Nc factor in Chroma ]
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A. Generate two uniformly distributed pseudo-random numbers R and R', R'', R''' in the unit interval;
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B. Set X = -(ln R)/alpha, X' =-(ln R')/alpha;
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C. Set C = cos^2(2pi R"), with R" another uniform random number in [0,1] ;
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D. Set A = XC;
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E. Let d = X'+A;
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F. If R'''^2 :> 1 - 0.5 d, go back to A;
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G. Set a0 = 1 - d;
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Note that in step D setting B ~ X - A and using B in place of A in step E will generate a second independent a 0 value.
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*/
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/////////////////////////////////////////////////////////
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// count the number of sites by picking "1"'s out of hat
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/////////////////////////////////////////////////////////
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Integer hit=0;
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LatticeReal rtmp(grid);
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rtmp=where(wheremask,rones,rzeros);
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RealD numSites = sum(rtmp);
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RealD numAccepted;
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LatticeInteger Accepted(grid); Accepted = zero;
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LatticeInteger newlyAccepted(grid);
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std::vector<LatticeReal> xr(4,grid);
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std::vector<LatticeReal> a(4,grid);
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LatticeReal d(grid); d=zero;
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LatticeReal alpha(grid);
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// std::cout<<GridLogMessage<<"xi "<<xi <<std::endl;
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alpha = toReal(2.0*xi);
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do {
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// A. Generate two uniformly distributed pseudo-random numbers R and R', R'', R''' in the unit interval;
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random(pRNG,xr[0]);
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random(pRNG,xr[1]);
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random(pRNG,xr[2]);
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random(pRNG,xr[3]);
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// B. Set X = - ln R/alpha, X' = -ln R'/alpha
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xr[1] = -log(xr[1])/alpha;
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xr[2] = -log(xr[2])/alpha;
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// C. Set C = cos^2(2piR'')
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xr[3] = cos(xr[3]*twopi);
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xr[3] = xr[3]*xr[3];
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LatticeReal xrsq(grid);
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//D. Set A = XC;
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//E. Let d = X'+A;
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xrsq = xr[2]+xr[1]*xr[3];
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d = where(Accepted,d,xr[2]+xr[1]*xr[3]);
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//F. If R'''^2 :> 1 - 0.5 d, go back to A;
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LatticeReal thresh(grid); thresh = 1.0-d*0.5;
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xrsq = xr[0]*xr[0];
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LatticeInteger ione(grid); ione = 1;
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LatticeInteger izero(grid); izero=zero;
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newlyAccepted = where ( xrsq < thresh,ione,izero);
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Accepted = where ( newlyAccepted, newlyAccepted,Accepted);
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Accepted = where ( wheremask, Accepted,izero);
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// FIXME need an iSum for integer to avoid overload on return type??
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rtmp=where(Accepted,rones,rzeros);
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numAccepted = sum(rtmp);
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hit++;
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} while ( (numAccepted < numSites) && ( hit < nheatbath) );
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// G. Set a0 = 1 - d;
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a[0]=zero;
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a[0]=where(wheremask,1.0-d,a[0]);
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//////////////////////////////////////////
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// ii) generate a_i uniform on two sphere radius (1-a0^2)^0.5
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//////////////////////////////////////////
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LatticeReal a123mag(grid);
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a123mag = sqrt(abs(1.0-a[0]*a[0]));
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LatticeReal cos_theta (grid);
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LatticeReal sin_theta (grid);
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LatticeReal phi (grid);
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random(pRNG,phi); phi = phi * twopi; // uniform in [0,2pi]
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random(pRNG,cos_theta); cos_theta=(cos_theta*2.0)-1.0; // uniform in [-1,1]
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sin_theta = sqrt(abs(1.0-cos_theta*cos_theta));
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a[1] = a123mag * sin_theta * cos(phi);
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a[2] = a123mag * sin_theta * sin(phi);
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a[3] = a123mag * cos_theta;
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ua = toComplex(a[0])*ident
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+ toComplex(a[1])*pauli1
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+ toComplex(a[2])*pauli2
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+ toComplex(a[3])*pauli3;
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b = 1.0;
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b = where(wheremask,uinv*ua,b);
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su2Insert(b,V,su2_subgroup);
|
|
|
|
//mask the assignment back based on Accptance
|
|
link = where(Accepted,V * link,link);
|
|
|
|
//////////////////////////////
|
|
// Debug Checks
|
|
// SU2 check
|
|
LatticeSU2Matrix check(grid); // rotated matrix after hb
|
|
u = zero;
|
|
check = ua * adj(ua) - 1.0;
|
|
check = where(Accepted,check,u);
|
|
assert(norm2(check)<1.0e-4);
|
|
|
|
check = b*adj(b)-1.0;
|
|
check = where(Accepted,check,u);
|
|
assert(norm2(check)<1.0e-4);
|
|
|
|
LatticeMatrix Vcheck(grid);
|
|
Vcheck = zero;
|
|
Vcheck = where(Accepted,V*adj(V) - 1.0,Vcheck);
|
|
// std::cout<<GridLogMessage << "SU3 check " <<norm2(Vcheck)<<std::endl;
|
|
assert(norm2(Vcheck)<1.0e-4);
|
|
|
|
// Verify the link stays in SU(3)
|
|
// std::cout<<GridLogMessage <<"Checking the modified link"<<std::endl;
|
|
Vcheck = link*adj(link) - 1.0;
|
|
assert(norm2(Vcheck)<1.0e-4);
|
|
/////////////////////////////////
|
|
}
|
|
|
|
static void printGenerators(void)
|
|
{
|
|
for(int gen=0;gen<generators();gen++){
|
|
Matrix ta;
|
|
generator(gen,ta);
|
|
std::cout<<GridLogMessage<< "Nc = "<<ncolour<<" t_"<<gen<<std::endl;
|
|
std::cout<<GridLogMessage<<ta<<std::endl;
|
|
}
|
|
}
|
|
|
|
static void testGenerators(void){
|
|
Matrix ta;
|
|
Matrix tb;
|
|
std::cout<<GridLogMessage<<"Checking trace ta tb is 0.5 delta_ab"<<std::endl;
|
|
for(int a=0;a<generators();a++){
|
|
for(int b=0;b<generators();b++){
|
|
generator(a,ta);
|
|
generator(b,tb);
|
|
Complex tr =TensorRemove(trace(ta*tb));
|
|
std::cout<<GridLogMessage<<tr<<" ";
|
|
if(a==b) assert(abs(tr-Complex(0.5))<1.0e-6);
|
|
if(a!=b) assert(abs(tr)<1.0e-6);
|
|
}
|
|
std::cout<<GridLogMessage<<std::endl;
|
|
}
|
|
std::cout<<GridLogMessage<<"Checking hermitian"<<std::endl;
|
|
for(int a=0;a<generators();a++){
|
|
generator(a,ta);
|
|
std::cout<<GridLogMessage<<a<<" ";
|
|
assert(norm2(ta-adj(ta))<1.0e-6);
|
|
}
|
|
std::cout<<GridLogMessage<<std::endl;
|
|
|
|
std::cout<<GridLogMessage<<"Checking traceless"<<std::endl;
|
|
for(int a=0;a<generators();a++){
|
|
generator(a,ta);
|
|
Complex tr =TensorRemove(trace(ta));
|
|
std::cout<<GridLogMessage<<a<<" ";
|
|
assert(abs(tr)<1.0e-6);
|
|
}
|
|
std::cout<<GridLogMessage<<std::endl;
|
|
}
|
|
|
|
// reunitarise??
|
|
static void LieRandomize(GridParallelRNG &pRNG,LatticeMatrix &out,double scale=1.0){
|
|
GridBase *grid = out._grid;
|
|
|
|
LatticeComplex ca (grid);
|
|
LatticeMatrix lie(grid);
|
|
LatticeMatrix la (grid);
|
|
Complex ci(0.0,scale);
|
|
Complex cone(1.0,0.0);
|
|
Matrix ta;
|
|
|
|
lie=zero;
|
|
for(int a=0;a<generators();a++){
|
|
|
|
random(pRNG,ca);
|
|
|
|
ca = (ca+conjugate(ca))*0.5;
|
|
ca = ca - 0.5;
|
|
|
|
generator(a,ta);
|
|
|
|
la=ci*ca*ta;
|
|
|
|
lie = lie+la; // e^{i la ta}
|
|
}
|
|
taExp(lie,out);
|
|
}
|
|
|
|
static void GaussianLieAlgebraMatrix(GridParallelRNG &pRNG,LatticeMatrix &out,double scale=1.0){
|
|
GridBase *grid = out._grid;
|
|
LatticeReal ca (grid);
|
|
LatticeMatrix la (grid);
|
|
Complex ci(0.0,scale);
|
|
Matrix ta;
|
|
|
|
out=zero;
|
|
for(int a=0;a<generators();a++){
|
|
gaussian(pRNG,ca);
|
|
generator(a,ta);
|
|
la=toComplex(ca)*ci*ta;
|
|
out += la;
|
|
}
|
|
|
|
}
|
|
|
|
|
|
static void HotConfiguration(GridParallelRNG &pRNG,LatticeGaugeField &out){
|
|
LatticeMatrix Umu(out._grid);
|
|
for(int mu=0;mu<Nd;mu++){
|
|
LieRandomize(pRNG,Umu,1.0);
|
|
PokeIndex<LorentzIndex>(out,Umu,mu);
|
|
}
|
|
}
|
|
static void TepidConfiguration(GridParallelRNG &pRNG,LatticeGaugeField &out){
|
|
LatticeMatrix Umu(out._grid);
|
|
for(int mu=0;mu<Nd;mu++){
|
|
LieRandomize(pRNG,Umu,0.01);
|
|
pokeLorentz(out,Umu,mu);
|
|
}
|
|
}
|
|
static void ColdConfiguration(GridParallelRNG &pRNG,LatticeGaugeField &out){
|
|
LatticeMatrix Umu(out._grid);
|
|
Umu=1.0;
|
|
for(int mu=0;mu<Nd;mu++){
|
|
pokeLorentz(out,Umu,mu);
|
|
}
|
|
}
|
|
|
|
static void taProj( const LatticeMatrix &in, LatticeMatrix &out){
|
|
out = Ta(in);
|
|
}
|
|
static void taExp( const LatticeMatrix &x, LatticeMatrix &ex){
|
|
|
|
LatticeMatrix xn(x._grid);
|
|
RealD nfac = 1.0;
|
|
|
|
xn = x;
|
|
ex =xn+Complex(1.0); // 1+x
|
|
|
|
// Do a 12th order exponentiation
|
|
for(int i=2; i <= 12; ++i)
|
|
{
|
|
nfac = nfac/RealD(i); //1/2, 1/2.3 ...
|
|
xn = xn * x; // x2, x3,x4....
|
|
ex = ex+ xn*nfac;// x2/2!, x3/3!....
|
|
}
|
|
}
|
|
|
|
};
|
|
|
|
typedef SU<2> SU2;
|
|
typedef SU<3> SU3;
|
|
typedef SU<4> SU4;
|
|
typedef SU<5> SU5;
|
|
|
|
}
|
|
}
|
|
#endif
|