Hi,
It is known that the number of spin-up and spin-down electrons are
conserved quantities in the Hubbard model. I just noticed that in the
mps_optim paper (Computer Physics Communications 185 (2014) 3430-3440) that
the example for the hubbard ladder has Nup_total and Ndown_total are the
same even if the system is away from half-filling. Is this a general
property of the model's ground state? If so, I would like to know
references pertaining to this property.
Related to that is, if I used the alternative fermionic hubbard model, is
the property mentioned above the same as setting Sz_total = 0?
Thanks,
Robertson C. Esperanza