How to choose the number of particles per site in Fermionic DMRG?

[Luqman Saleem]

I am doing DMRG (in traditional formalism, not MPS) for Hubbard model
H = -t ∑_i ∑_σc_i,σ c_i+1,σ + U∑_in_i,σn_i,σ^-
In every iteration we add two sites to the system, but how do we set that how many particles are allowed in the system?

 

[atyy]

In https://arxiv.org/abs/1108.6057 they choose 128 sites (more for R-DMFT) and perform estimates of finite-size effects and finite-size scaling.