Hi Giuseppe,
I mean the result concerning the spin-spin correlation function but I agree, I don't have to specify Sz_total for the ferromagnetic case. However, this parameter is really important in the S=1 antiferromagnetic Heisenberg chain (due to the spins 1/2 before the first and after the last site).
Thanks a lot for your answer,
Julien
On 11/10/2016 15:09, Giuseppe Carleo wrote:
Hi Julien,
what do you mean that the results you get are wrong?
I ran that script and found a reasonable ground-state energy ( i.e. E_0 ~ - L/4 )
If you’re concerned about the spin-spin correlations, you should be careful when specifying the subspace in which you’re looking for the ground-state :
in your case you specified Sz_total = 0, which is not necessarily what you want to do when studying the ferromagnetic model.
Giuseppe
Dr Giuseppe Carleo
ETH Zurich Institute for Theoretical Physics Wolfgang-Pauli-Str. 27 8093 Zurich - Switzerland
Office: HIT G 31.4
On 11 Oct 2016, at 14:25, Julien <julien.despres@institutoptique.fr mailto:julien.despres@institutoptique.fr> wrote:
Hello ALPS community,
First, sorry for my English and for the trivial question that I'm going to ask you. I already made the tutorial on the S=(1/2, 1) antiferromagnetic Heisenberg chain where I found the correlation function and the gap in the thermodynamic limit (for S = 1). Now, I'm trying to do the same thing for the S=1/2 ferromagnetic Heisenberg chain but I guess I made a mistake when we have to specify the different parameters. Here is what I wrote in my computer code :
parms.append({ 'LATTICE' : 'open chain lattice', 'MODEL' : 'spin', 'CONSERVED_QUANTUMNUMBERS' : 'N,Sz', 'Sz_total' : 0, 'J' : -1, 'SWEEPS' : 4, 'NUMBER_EIGENVALUES' : 1, 'L' : 32, 'MAXSTATES' : 20, 'MEASURE_CORRELATIONS[Diagonal spin correlations]' : 'Sz', })
but the result is completely wrong. I only modify the sign of the coupling constant compared to the antiferromagnetic case.
Thank you in advance for your help,
Best regards, Julien
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