Search found 124 matches

by Johannes
07 Feb 2020, 08:18
Forum: Implementations
Topic: Readthedocs vs Github pages
Replies: 4
Views: 187

Re: Readthedocs vs Github pages

Okay, I paid for the Gold membership of readthedocs to remove the ads (That's the drawback, it costs money. But I don't mind supporting ReadTheDocs with a few dollars a month, their service to the community is great :) ) I've also updated the references from within the TeNPy repository and the links...
by Johannes
07 Feb 2020, 06:14
Forum: HowTos and FAQ for TeNPy
Topic: Problems with modelling a fermionic ladder
Replies: 3
Views: 102

Re: Problems with modelling a fermionic ladder

Now I face the problem that in order to see the Ising-like phase transition I want to calculate the correlation function <\Psi_0 |T^y_i T^y_{i+r} |\Psi_0> with T^y_i= \frac{1}{2}(-i c^\dagger_{i,u}c_{i,d}+i c^\dagger_{i,d}c_{i,u}) where u and d are again the rungs of the ladder. Since the Ladder ge...
by Johannes
05 Feb 2020, 08:00
Forum: HowTos and FAQ for TeNPy
Topic: How to calculate particular correlation function only between the nearest neighbors sites in my lattice?
Replies: 4
Views: 89

Re: How to calculate particular correlation function only between the nearest neighbors sites in my lattice?

Looks good! May I ask how for an example what you calculated in the end (roughly)? It probably suffices for terms with the same operators on both sites (e.g. density-density correlations "N_i N_j"), but might not be enough for more complicated pair correlations with different operators (e.g. for "Cd...
by Johannes
05 Feb 2020, 07:50
Forum: HowTos and FAQ for TeNPy
Topic: Problems with modelling a fermionic ladder
Replies: 3
Views: 102

Re: Problems with modelling a fermionic ladder

You got it almost right. Just a single, but crucial typo in term 1.2 (which you correctly identified as the problem): In the second line (h.c. term), you have a 0 instead of a 1 in the fourth argument. This makes the Hamiltonian non-hermitian and obviously leads to problems when running DMRG (The La...
by Johannes
01 Feb 2020, 00:11
Forum: HowTos and FAQ for TeNPy
Topic: Convergence issues in XXZ model with increasing bond dimension
Replies: 3
Views: 84

Re: Convergence issues in XXZ model with increasing bond dimension

No, you got that wrong. A value of update_env=0 does not imply that you're not doing iDMRG; the DMRG engine will still grow the environments on the left and right by one unit cell in each sweep. A nonzero update_env > 0 tells the DMRG engine to do the specified number of environment_sweeps without d...
by Johannes
30 Jan 2020, 21:55
Forum: Implementations
Topic: Readthedocs vs Github pages
Replies: 4
Views: 187

Re: Readthedocs vs Github pages

@Leon, @mpsforphysics , @JakobUnfried do you have any preferences?
by Johannes
30 Jan 2020, 21:43
Forum: HowTos and FAQ for TeNPy
Topic: How to calculate particular correlation function only between the nearest neighbors sites in my lattice?
Replies: 4
Views: 89

Re: How to calculate particular correlation function only between the nearest neighbors sites in my lattice?

You need to do some postprocessing, there is currently no function for that in TeNPy. However, I agree that it would be very useful to have it. If you write the function, it would be great if you could post it here such that we can include it in TeNPy (or you just submit a pull request on github). Y...
by Johannes
30 Jan 2020, 07:34
Forum: HowTos and FAQ for TeNPy
Topic: Convergence issues in XXZ model with increasing bond dimension
Replies: 3
Views: 84

Re: Convergence issues in XXZ model with increasing bond dimension

The model is gapless in the range -1 < V < 1, so this is definitely a difficult region. As far as I know, VUMPS might indeed be better suited for that, feel free to implement it ;-) Which version of tenpy are you using? In particular, does your version include the fix of 95 (v0.5.0 or later)? The is...
by Johannes
20 Dec 2019, 03:27
Forum: HowTos and FAQ for TeNPy
Topic: Problems with creating multi-site coupling on a chain.
Replies: 1
Views: 91

Re: Problems with creating multi-site coupling on a chain.

By definition, a tenpy.models.model.NearestNeighborModel can only contain nearest-neighbor couplings. That is the case because it provides a representation of the hamiltonian in terms of H_bond , where each H_bond is a term involving just two neighboring sites. Hence, you can *not* make a model inhe...
by Johannes
20 Dec 2019, 02:41
Forum: Implementations
Topic: Readthedocs vs Github pages
Replies: 4
Views: 187

Re: Readthedocs vs Github pages

Readthedocs currently includes advertisement, but we could opt-out of that.