Hi,
constraints are unfortunately just sums of local operators. You might be able to work around this be defining bigger unit cells. We might be able to help if you tell us what exactly your constraint is.
Matthias Troyer
On Mar 6, 2013, at 11:28 PM, Ali Beyramzadeh Moghadam ali.beyramzadehmoghadam@email.ucr.edu wrote:
Dear ALPS Member,
I am trying to run ALPS DMRG to calculate gap for a spin system on 3-chain lattice. My energy eigenvalue is degenerate and I am trying to divide the system to different sector using the constraint. I want to set an eigenvalue of one operator to have a specific value. My problem is the operator which divide my Hilbert space to different sector is not local and depends on several site. I am wondering if I can do that with constraint. Should I define a new quantum number other than Sz?
Thank you for your help, Best, Ali