DMRG certainly can be applied. If the finite size gap between the two degenerate states is large enough then you should even be able to get both states individually.

Matthias

On Apr 20, 2011, at 1:30 PM, 孙照宇 wrote:

Dear ALPS users and developers:

Suppose the ground-state of a quantum chain is twofold degenerate in the thermodynamic limit(L is large enough), while in a finite-size system(such as L=14,16,18), the ground state is just a superposition of these two states, and no degeneration would occur.

Now my question is: Is DMRG applicable to a small size system whose ground-state is a superposition state ? ( I know that by imposing some special boundary conditions, one of the two states could be projected out. Here I need to use a standard open boundary condition. )

Any suggestion or comment would be valuable to me.

sunzhaoyu2000@gmail.com