def gen_XdX(atom_list,operator_table,operator_table_dagger,Hcomm,N_atoms_uc):
"""Operate commutation relations to put all the 2nd order term as ckd**ck, cmk**cmkd, cmk**ck and ckd**cmkd form"""
print "gen_XdX"
operator_table = N.array(operator_table)
operator_table_dagger = N.array(operator_table_dagger)
bins = (operator_table_dagger[:,None].T*operator_table[:,None]).flatten().tolist()
retbins = N.zeros(len(bins),dtype=object)
expr_list = sympy.make_list(Hcomm, sympy.Add)
for subexpr in expr_list:
for i in range(len(bins)):
curr_coeff = subexpr.as_coefficient(bins[i])
if curr_coeff:
retbins[i] += curr_coeff
XdX = retbins.reshape((2*N_atoms_uc,2*N_atoms_uc))
XdX = sympy.matrices.Matrix(XdX)
def g_func(i,j,num):
if i!=j: return 0
elif i<num: return 1
else: return -1
g = sympy.matrices.Matrix(2*N_atoms_uc,2*N_atoms_uc,lambda i,j:g_func(i,j,N_atoms_uc))
return XdX,g
def coeff_bins(expr,bins):
# get rid of None expressions
if not expr:
return 0
# chop up expr at '+'
expr_list = sympy.make_list(expr, sympy.Add)
retbins = N.zeros(len(bins),dtype=object)
#scan through expr
for subexpr in expr_list:
#see if it contains a bin element
for i in range(len(bins)):
curr_coeff = subexpr.as_coefficient(bins[i])
if curr_coeff:
retbins[i] += curr_coeff
return retbins