I wish good health for all developers and users these days.
My question is about DMRG process,
We know that in DMRG procedure, while the size of the system grows, just the most important eigenvectors are kept (in each iteration).
I think the 'MAXSTATES' in the DMRG code of ALPS package illustrates the maximum number of states from diagonalizing the reduced density matrix. Since the number of such states is less than the number of our system's state then we have an error in estimating energy of the system. But a question has occupied my mind: Does it make sense to ask the code to give the ground state eigenvector? Because with keeping a few numbers of the system's eigenvectors, I think in the last iteration, the output eigenvector is not corresponded to the whole system from the size point of view.
We can consider a chain with 30 spin-1/2 particles. The ground state eigenvector of the system must be 2^30 in length . But I think the eigenvector of the last iteration from DMRG code is very smaller than 2^30 in length. Is this statement true?
If it is correct, then how we can have the ground state eigenvector from ALPS DMRG?