def _transl2uga(self, tensor: Tensor):
"""Translate a tensor object in terms of the fermion operators.
This is an internal utility. The resulting tensor has the internal
'_uga_dr' drudge object as its owner.
"""
return Tensor(self, tensor.subst_all(self._agp2uga_defs).terms)
def get_vev_agp(self,h_tsr: Tensor,):
"""Function to evaluate the expectation value of a normal
ordered tensor 'h_tsr' with respect to the projected BCS
or the AGP state. This can be done after translating the the
unitary group terms into the AGP basis algebra.
h_tsr = tensor whose VEV is to be evaluated
"""
transled = self._transl2agp(h_tsr)
transled = self._agp_dr.agp_simplify(transled,final_step=True)
res = self._agp_dr.get_vev(transled)
return Tensor(self, res.terms)
def _transl2uga(self, tensor: Tensor):
"""Translate a tensor object in terms of the fermion operators.
This is an internal utility. The resulting tensor has the internal
AGP drudge object as its owner.
"""
chk = tensor.bind(self._agp_dr._isAGP)
# for t in trms:
# if ~self._agp_dr._isAGP(t):
# raise ValueError('Unexpected generator of the AGP Algebra',vec)
return Tensor(self, tensor.subst_all(self._agp2uga_defs).terms)
def _transl2agp(self, tensor: Tensor):
"""Translate a tensor object in terms of the fermion operators.
This is an internal utility. The resulting tensor has the internal
AGP drudge object as its owner.
"""
chk = tensor.bind(self._isUGA)
# for t in trms:
# if ~_isUGA(t):
# raise ValueError('Unexpected generator of the Unitary Group',vec)
return Tensor(self._agp_dr, tensor.subst_all(self._uga2agp_defs).terms)
def spin_flip_to_fermi(self, tnsr: Tensor):
"""Substitute all the Spin flip operators with their respective fermionic
strings"""
gen_idx = self.all_orb_dumms[0]
sp_def = self.define(
SPIN_RAISE, gen_idx,
cr[gen_idx, SpinOneHalf.UP] * an[gen_idx, SpinOneHalf.DOWN])
sm_def = self.define(
SPIN_LOWER, gen_idx,
cr[gen_idx, SpinOneHalf.DOWN] * an[gen_idx, SpinOneHalf.UP])
spin_defs = [sp_def, sm_def]
return Tensor(self, tnsr.subst_all(spin_defs).terms)