I am trying to evaluate the ground state wave function of a semi positive hamiltonian, i.e., H= L^\dagger L, with L non-hermitian and sum of local terms. However, I find that the energy in the dmrg can be negative. Do you know what is going on? – or, how should I improve the code.
btw, I used, the following line of code to construct H_LL, H_LL = apply(dag(L), L).
I would try apply(dag(L), L; alg="naive", truncate=false) since it’s possible the truncation is at fault, but if each L is simply a sum of local terms it shouldn’t be hard or expensive to use OpSum to construct L^\dagger L directly. I would expect this second approach to be the most accurate.