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
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
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
On 18 Nov 2013, at 21:46, Rafał arymanus@gmail.com wrote:
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.
That is because there are two ground states.
What you want to do is to instead run with Sz_total=0 and Sz_total=1 since by spin gap we usually mean the gap between the singlet and triplet sector.
2013/11/18 Matthias Troyer troyer@phys.ethz.ch
On 18 Nov 2013, at 21:46, Rafał arymanus@gmail.com wrote:
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.
That is because there are two ground states.
What do you mean by two ground states?
What you want to do is to instead run with Sz_total=0 and Sz_total=1 since by spin gap we usually mean the gap between the singlet and triplet sector.
Yes. I know that in this case it would be singlet and triplet and it will be the best approach for ising or heisenberg model (Jxz = Jz = 1), but in next step I would like to do simulations with, for example xy model in transverse field (Gamma != 0) where Sz is not a good quantum number.
Best, Rafał
On 18 Nov 2013, at 22:03, Rafał arymanus@gmail.com wrote:
What do you mean by two ground states?
The Ising model ground state is degenerate.
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