Dear Matthias,

Thank you for your reply. I have one more question about DMRG.

I try to calculate a gap of xxz spin model (Jz != Jxy) for different values of Jz and Jxy. I think that it will be more safe to assume that I do not know in what Sz sector search for a ground and excited states. 

Is it in this case better option to run simulation over all possible Sz by hand or to comment a line 
#'Sz_total' : Sz.

which should force alps to  work in the grand canonical as it was told in the first tutorial on the webpage?

I tried this second approach for the ising model (Jxy = 0, Jz = 1) but what I get was just a duplicated ground state without a correct excited state.

Bests,
Rafał





2013/11/18 Matthias Troyer <troyer@phys.ethz.ch>
Yes, you can drop it if N does not exist




> On Nov 18, 2013, at 21:33, Rafał <arymanus@gmail.com> wrote:
>
> Dear all ALPS users,
>
> I have following questions to the DMRG tutorials. Why there is N in a line:
> 'CONSERVED_QUANTUMNUMBERS'  : 'N,Sz',
>
> I understand that Sz stands for conserved quantum number but spin model on the open chain lattice does not have quantum number called N.
>
> Is this N added to 'CONSERVED_QUANTUMNUMBERS' just in case someone may use some bosonic model?
>
> Bests,
> Rafał