Search found 422 matches
- 07 Feb 2020, 08:18
- Forum: Implementations
- Topic: Readthedocs vs Github pages
- Replies: 4
- Views: 19338
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...
- 07 Feb 2020, 06:14
- Forum: HowTos and FAQ for TeNPy
- Topic: Problems with modelling a fermionic ladder
- Replies: 3
- Views: 4899
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...
- 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: 6779
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....
- 05 Feb 2020, 07:50
- Forum: HowTos and FAQ for TeNPy
- Topic: Problems with modelling a fermionic ladder
- Replies: 3
- Views: 4899
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...
- 01 Feb 2020, 00:11
- Forum: HowTos and FAQ for TeNPy
- Topic: Convergence issues in XXZ model with increasing bond dimension
- Replies: 3
- Views: 5418
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...
- 30 Jan 2020, 21:55
- Forum: Implementations
- Topic: Readthedocs vs Github pages
- Replies: 4
- Views: 19338
Re: Readthedocs vs Github pages
[mention]Leon[/mention], [mention]mpsforphysics[/mention] , [mention]JakobUnfried[/mention] do you have any preferences?
- 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: 6779
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...
- 30 Jan 2020, 07:34
- Forum: HowTos and FAQ for TeNPy
- Topic: Convergence issues in XXZ model with increasing bond dimension
- Replies: 3
- Views: 5418
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...
- 20 Dec 2019, 03:27
- Forum: HowTos and FAQ for TeNPy
- Topic: Problems with creating multi-site coupling on a chain.
- Replies: 1
- Views: 3721
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...
- 20 Dec 2019, 02:41
- Forum: Implementations
- Topic: Readthedocs vs Github pages
- Replies: 4
- Views: 19338
Re: Readthedocs vs Github pages
Readthedocs currently includes advertisement, but we could opt-out of that.
- 20 Dec 2019, 02:31
- Forum: Implementations
- Topic: Readthedocs vs Github pages
- Replies: 4
- Views: 19338
Readthedocs vs Github pages
Hi all, so far, I had hosted the documentation on https://tenpy.github.io with github pages. I have now tried to setup the documentation on https://tenpy.readthedocs.io as well, which is an awesome place hosting documentation for many, many python packages (and other stuff as well). The nice thing t...
- 20 Dec 2019, 02:10
- Forum: Releases
- Topic: Release v0.5.0
- Replies: 0
- Views: 18806
Release v0.5.0
Version 0.5.0 has been released. Before updating , please read the corresponding section in the change log , in particular the part on the backwards incompatible changes! It is now supported to install TeNPy with pip via pip install --upgrade physics-tenpy # for 'stable' versions I'd recommend an in...
- 18 Dec 2019, 22:16
- Forum: HowTos and FAQ for TeNPy
- Topic: Running own model yields ModuleNotFoundError
- Replies: 2
- Views: 3972
Re: Running own model yields ModuleNotFoundError
Welcome! I think the problem depends on how you installed tenpy. Did you pip install physics-tenpy , or did you download the code and use inline]python setup.py install[/inline] from within the TeNPy folder, or did you simply set export PYTHONPATH=/Users/username/TeNPy" ? In the latter case, it...
- 08 Dec 2019, 17:44
- Forum: HowTos and FAQ for TeNPy
- Topic: Preparing state with specified particle filling
- Replies: 4
- Views: 7931
Re: Preparing state with specified particle filling
If you run the code with conserve='N' , you should get a UserWarning tenpy/networks/mps.py:396: UserWarning: flat array has non-zero entries in blocks incompatible with charge B = npc.Array.from_ndarray(B, legs, dtype) The reason is that for conserve='N' , each tensor needs to have a well defined ch...
- 05 Dec 2019, 23:09
- Forum: HowTos and FAQ for TeNPy
- Topic: Constructing a product state of rotated spins
- Replies: 5
- Views: 5674
Re: Constructing a product state of rotated spins
You're absolutely right, the different type of "Site" makes the difference here.
That's certainly a thing to keep in mind, so I actually added your example (slightly extended) to the documentation of from_product_state.
Do you agree that it is more clear now?
That's certainly a thing to keep in mind, so I actually added your example (slightly extended) to the documentation of from_product_state.
Do you agree that it is more clear now?
- 03 Dec 2019, 21:31
- Forum: HowTos and FAQ for TeNPy
- Topic: Constructing a product state of rotated spins
- Replies: 5
- Views: 5674
Re: Constructing a product state of rotated spins
Yes, that is indeed what you want. Just for reference, here is the documentation: from_product_state . If you look at the example, one line below the state is normalized, such that it gets np.array([1/sqrt(2), -1/sqrt(2)]) . This is the negative-x state of a spin-1/2 and equivalent to the np.array([...
- 26 Nov 2019, 19:27
- Forum: HowTos and FAQ for TeNPy
- Topic: N_sweeps_check & unit cell in infinite dmrg
- Replies: 3
- Views: 4294
Re: N_sweeps_check & unit cell in infinite dmrg
So, is it fine to miss S? or is it typo? That should be fine, it's just the difference between checking the absolute and the relative error. For the energy, we need to check the relative error: the energy scale can vary by quite a bit simply by rescaling your Hamiltonian. However, the entropy can n...
- 25 Nov 2019, 17:29
- Forum: HowTos and FAQ for TeNPy
- Topic: XXZChain antiferromagnet showing no entanglement?
- Replies: 1
- Views: 3204
Re: XXZChain antiferromagnet showing no entanglement?
The all-up state is an exact eigenstate of the model and hence won't evolve in time, in particular if you use Sz-conservation (which you do in this case): the all-up state is the only state in the sector with S_{total} = L/2 . Try starting from a different state, e.g. all up but one spin down (which...
- 14 Nov 2019, 10:13
- Forum: HowTos and FAQ for TeNPy
- Topic: Real-time evolution of the GS of the U=0 Fermi-Hubbard model
- Replies: 5
- Views: 7351
Re: Real-time evolution of the GS of the U=0 Fermi-Hubbard model
Yes, that's for sure a good idea. Indeed, I thought about it and started to implement it already a few days ago, but I'm quite busy these days (moving to UC Berkeley ), so I didn't have time to finish it. Hopefully, I can find a bit time next week - unless you volunteer to time to implement it
- 11 Nov 2019, 16:03
- Forum: Algorithms
- Topic: Canonical form for very small singular values
- Replies: 1
- Views: 10173
Re: Canonical form for very small singular values
One alternative is to iteratively do QR decompositions (and RQ decompositions). You decompose your state as M M M M M = Q R M M M M = Q Q R M M M = ... = Q Q Q Q R and as M M M M M = M M M M R' Q' = M M M R' Q' Q' = ... = R' Q' Q' Q' Q' until your iterations converge. Then your state is in the form ...
- 11 Nov 2019, 15:50
- Forum: HowTos and FAQ for TeNPy
- Topic: Real-time evolution of the GS of the U=0 Fermi-Hubbard model
- Replies: 5
- Views: 7351
Re: Real-time evolution of the GS of the U=0 Fermi-Hubbard model
What order (second or fourth) and timestep do you use for TEBD? Does this go away if you simply use a smaller timestep/higher order? Did you try to look at the overlap with the initial ground state returned by DMRG (as a function of time)? Converging just 3 digits in energy still a bit unprecise, ma...
- 30 Oct 2019, 17:22
- Forum: HowTos and FAQ for TeNPy
- Topic: Entanglement entropy for disconnected subsystems
- Replies: 4
- Views: 4889
Re: Entanglement entropy for disconnected subsystems
Sorry, that was a bug in
MPS.get_rho_segment
. It should be fixed with the latest version.- 29 Oct 2019, 16:45
- Forum: HowTos and FAQ for TeNPy
- Topic: N_sweeps_check & unit cell in infinite dmrg
- Replies: 3
- Views: 4294
Re: N_sweeps_check & unit cell in infinite dmrg
In general, the parameter N_sweeps_check should not change the convergence properties - at least not much.... Let's look at what it influences: For checking the convergence, DMRG checks the average change of the energy / entropy per sweep in the last N_sweeps_check steps. The parameter update_env de...
- 29 Oct 2019, 16:32
- Forum: HowTos and FAQ for TeNPy
- Topic: Entanglement entropy for disconnected subsystems
- Replies: 4
- Views: 4889
Re: Entanglement entropy for disconnected subsystems
The function entanglement_entropy_segment should accept disconnected segments, e.g. segment=[0, 2, 4, 6, 8] . However, it works only for *small* enough number of sites in your density matrix - it's exponentially expensive, because it constructs the full density matrix, tracing out the rest of the si...
- 29 Oct 2019, 16:04
- Forum: HowTos and FAQ for TeNPy
- Topic: Adding a site to a chain perpendicularly
- Replies: 6
- Views: 7298
Re: Adding a site to a chain perpendicularly
Hi, indeed, the irregular lattice is still an open 77 . Sorry, there's so much stuff to do. I had to write and defend my PHD thesis, so I didn't have too much time to work on TeNPy lately. Hopefully, this will change again. ;) To make sure I understand correctly, you want a geometry like this: Boson...