Hi!

I have a very naive question. I noticed the dmrg template in iTensor prints entanglement entropy calculated at the center of the system, at each iteration step. I was wondering as to what can we understand from the change in entanglement entropy at each step.

For instance, I was performing a dmrg calculation for N=100 Hubbard chain with 80 electrons. I saw a drastic difference between the entanglement entropy for two different initial conditions.

- First initial condition: Setting electrons with spin up and down alternatively till N=80. This initial condition resulted in very slow convergence in energy along with oscillatory entanglement entropy (at b=50) around 1. even after 50 sweeps the system did not converge.
- Second initial condition: Equally distributing holes in the whole chain (setting i%10==0, 1 as holes) while placing equal number of spin up and spin down. For this initial condition, the convergence in energy is better than previous although I will need to run some more sweeps for accurate result. I notice the entanglement entropy (at b=50) continuously in creases towards 2 and never saturates.

Can you comment on this difference in entanglement entropy for different initial condition?

Thanks