scamac_dof_spins.h

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#ifndef SCAMAC_DOF_SPINS_H
#define SCAMAC_DOF_SPINS_H

#include "scamac_error.h"

/* quantum mechanical degree of freedom: spins 1/2 */
/* either with J_z = const., or without J_z constraint */

typedef struct {
  /* number of sites */
  int n_sites;
  /* number of "up" spins
     negative value indicates "no constraint" */
  int n_up;

  /* number of states */
  ScamacIdx ns;

  /* count information */
  ScamacIdx *cnt;

} scamac_dof_spins_st;



typedef int scamac_rep_spins_st;

ScamacErrorCode scamac_dof_spins_alloc(int n_sites, scamac_dof_spins_st ** dof);
ScamacErrorCode scamac_dof_spinssz_alloc(int n_sites, int n_up, scamac_dof_spins_st ** dof);
void scamac_dof_spins_free(scamac_dof_spins_st * dof);


ScamacIdx scamac_dof_spins_ns(const scamac_dof_spins_st * dof);

scamac_rep_spins_st * scamac_rep_spins_alloc(const scamac_dof_spins_st *dof);
void scamac_rep_spins_free(scamac_rep_spins_st * rep);

void scamac_rep_spins_copy(const scamac_dof_spins_st *dof, const scamac_rep_spins_st * rep, scamac_rep_spins_st * repcpy);

int scamac_spins_decode(const scamac_dof_spins_st * dof, ScamacIdx idx, scamac_rep_spins_st *rep);
ScamacIdx scamac_spins_encode(const scamac_dof_spins_st * dof, const scamac_rep_spins_st *rep);


/* operators */
double scamac_op_spins_Sz   (const scamac_dof_spins_st * dof, const scamac_rep_spins_st *rep, int i);
double scamac_op_spins_SzSz (const scamac_dof_spins_st * dof, const scamac_rep_spins_st *rep, int i, int j);
double scamac_op_spins_SzSum(const scamac_dof_spins_st * dof, const scamac_rep_spins_st *rep);


double scamac_op_spins_Sp   (const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i);
double scamac_op_spins_Sm   (const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i);
double scamac_op_spins_Sx   (const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i);

double scamac_op_spins_SpSp (const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i, int j);
double scamac_op_spins_SpSm (const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i, int j);
double scamac_op_spins_SmSm (const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i, int j);
double scamac_op_spins_SxSx (const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i, int j);
/* Sx Sx + Sy Sy = (S+ S- + S- S+)/2 */
double scamac_op_spins_Sflip(const scamac_dof_spins_st * dof,       scamac_rep_spins_st *rep, int i, int j);

#endif /* SCAMAC_DOF_SPINS_H */