## Search found 15 matches

- 22 Sep 2020, 16:34
- Forum: HowTos and FAQ for TeNPy
- Topic: finite open, finite periodic and infinite periodic chains
- Replies:
**8** - Views:
**2767**

### Re: finite open, finite periodic and infinite periodic chains

This was perfect and super helpful! Thank you so much for the help Johannes, it really is much appreciated! I have one follow-up question. So far it seems to work fine, there is just one thing I am unsure about. With this method the resulting MPS is still finite (obc-style finite), right? I.e. the l...

- 02 Sep 2020, 15:24
- Forum: HowTos and FAQ for TeNPy
- Topic: finite open, finite periodic and infinite periodic chains
- Replies:
**8** - Views:
**2767**

### Re: finite open, finite periodic and infinite periodic chains

is there a way to have a finite periodic chain (so a ring) for the BoseHubbard model? (..) In that way, a nearest neighbor coupling on the ring becomes a next-nearest neighbour coupling for the MPO. I've never tried that out myself with TeNPy, but it is implemented already with the help of the orde...

- 17 Jun 2020, 12:59
- Forum: HowTos and FAQ for TeNPy
- Topic: Superposition of MPS with different total charge
- Replies:
**4** - Views:
**1813**

### Re: Superposition of MPS with different total charge

Thanks for the answer, that helped a lot (as always!) Concerning your question why one would want to do that: I'm trying to compare ground states for a certain filling via chemical potential and via symmetry. In the case of fixing the symmetry we obtained a funny pattern in the entanglement spectrum...

- 16 Jun 2020, 14:30
- Forum: HowTos and FAQ for TeNPy
- Topic: Superposition of MPS with different total charge
- Replies:
**4** - Views:
**1813**

### Superposition of MPS with different total charge

Hi, is there a way to use MPS.add(other,alpha,beta) for two MPS that have different total charge? I guess a brute force workaround would be to obtain the full matrices via get_B() (with all unnecessary 0s) and then create a new "empty" state and set_B(). Is there a direct way? I actually h...

- 13 May 2020, 08:06
- Forum: HowTos and FAQ for TeNPy
- Topic: Square of MPO
- Replies:
**3** - Views:
**2143**

### Re: Square of MPO

Thanks for the quick reply and update!

I actually need it for infinite systems, do you (or anybody else) know of another way to check "how good an eigenstate" the result is other than the variance?

I actually need it for infinite systems, do you (or anybody else) know of another way to check "how good an eigenstate" the result is other than the variance?

- 11 May 2020, 10:43
- Forum: HowTos and FAQ for TeNPy
- Topic: Square of MPO
- Replies:
**3** - Views:
**2143**

### Square of MPO

Hello, does anybody know an _easy_ way to compute the square of a MPO/model? I want to compute something like (\Delta H)^2 = <H>^2 - <H^2> to check how good an Eigenstate my result is. Defining a new model that is the square of the Hamiltonian by hand seems rather cumbersome (and doesnt lead to a ni...

- 14 Oct 2019, 10:19
- Forum: HowTos and FAQ for TeNPy
- Topic: finite open, finite periodic and infinite periodic chains
- Replies:
**8** - Views:
**2767**

### finite open, finite periodic and infinite periodic chains

Hello, is there a way to have a finite periodic chain (so a ring) for the BoseHubbard model? As far as I understand setting bc_MPS to "finite" gives a finite chain with open boundary conditions and "infinite" is basically performing iDMRG - or am I already getting this part wrong...

- 13 Jun 2019, 17:52
- Forum: HowTos and FAQ for TeNPy
- Topic: norm_tol parameter for DMRG
- Replies:
**2** - Views:
**1601**

### Re: norm_tol parameter for DMRG

Any answer to this?

- 08 May 2019, 14:39
- Forum: HowTos and FAQ for TeNPy
- Topic: Brute force parallel execution / multiprocessing
- Replies:
**1** - Views:
**1679**

### Brute force parallel execution / multiprocessing

Hello again, Disclaimer: I am far from a computer scientist and probably mix and use wrong terminology :D Also, I am not talking about going deep into the implementation like here https://tenpy.johannes-hauschild.de/viewtopic.php?t=4 I have to calculate many independent ground states for different p...

- 03 May 2019, 13:47
- Forum: HowTos and FAQ for TeNPy
- Topic: How to get the data of NPC arrays
- Replies:
**1** - Views:
**1146**

### How to get the data of NPC arrays

Hello again, I sometimes want to look at the actual data of the tensors in an MPS or MPO network, but I am a bit puzzled by the ._data attribute. For example, I want the W tensor of a Bose Hubbard model w/o conservation. I create the model model_params = dict( filling = 1., n_max = 4, t = 1, U = 1, ...

- 29 Apr 2019, 15:03
- Forum: HowTos and FAQ for TeNPy
- Topic: Cython compilation error
- Replies:
**5** - Views:
**2766**

### Re: Cython compilation error

I did not specifically install this compiler, no. I asked our admin to check if gcc is up to date (which it was) but he also updated a bunch of other things and now it is working. I dont know what exactly was the problem (so for future references this thread might be not very helpful) but at least i...

- 29 Apr 2019, 12:24
- Forum: HowTos and FAQ for TeNPy
- Topic: Cython compilation error
- Replies:
**5** - Views:
**2766**

### Re: Cython compilation error

Hello Johannes, thanks again for the answer! On my personal computer on Ubuntu 18 it works fine, the problem here is on a Ubuntu 16 server. When I try to compile your minimal example I get a similar error: (tenpy) kkottmann@pcl1016:~$ cythonize -bi a.pyx Compiling /home/kkottmann/a.pyx because it ch...

- 26 Apr 2019, 08:24
- Forum: HowTos and FAQ for TeNPy
- Topic: Cython compilation error
- Replies:
**5** - Views:
**2766**

### Cython compilation error

Hello, does somebody have an idea what might be the problem here? I tried to compile the cython files but get this error message. I updated cython but the problem remains: :~/TeNPy$ bash ./compile.sh Compiling tenpy/linalg/_npc_helper.pyx because it changed. [1/1] Cythonizing tenpy/linalg/_npc_helpe...

- 28 Mar 2019, 17:08
- Forum: HowTos and FAQ for TeNPy
- Topic: TF Ising Magnetization issues
- Replies:
**2** - Views:
**1808**

### Re: TF Ising Magnetization issues

Thanks for your quick response! For finite `L`, there is a finite size gap such that the true ground state is a superposition of the positive and negative X. Okay, so far so good. But I think I miss the point why I would then compute e.g. M^2 = <\left(\sum_i s_x^i\right)^2> . Or to phrase it differe...

- 27 Mar 2019, 16:29
- Forum: HowTos and FAQ for TeNPy
- Topic: TF Ising Magnetization issues
- Replies:
**2** - Views:
**1808**

### TF Ising Magnetization issues

Hello, I am trying to reproduce the phase diagram of the transverse field Ising Model on a 1d chain. I essentially use the example code in d_examples_dmrg. from tenpy.networks.mps import MPS from tenpy.models.tf_ising import TFIChain from tenpy.algorithms import dmrg def DMRG_finite(L, g,verbose=Fal...