def greens_dot(spin):
n = greens[spin, ::]
particles = ndmat(n)
holes = ndmat(unit_like(n) - n)
return 0.5 * (holes * delta(spin, 0) * particles + particles * delta(spin, 1) * holes)
def delta(spin, r):
def repulsion(site):
"Compute |U|(sn_jj-n_jj+1/2)"
# FIXME: I'm slow
return self.repulsion * greens[(1 - spin,) + 2 * site] + abs(self.repulsion) * (
0.5 - greens[(spin,) + 2 * site]
)
f = 1 if spin == 1 else copysign(1, -self.repulsion)
result = ndmat(zeros(2 * self.sites))
for i in sites(self.sites):
result[2 * i] = (
-repulsion(i) - f * sqrt(2 * abs(self.repulsion)) * noise[(r,) + i] + self.chemical_potential
)
for i, j in adjacencies(self.sites):
assert i != j
result[i + j] = self.hopping
return result
