Search found 12 matches

by Leon
31 Jan 2020, 10:06
Forum: Implementations
Topic: Readthedocs vs Github pages
Replies: 4
Views: 190

Re: Readthedocs vs Github pages

This is brilliant! I much prefer readthedocs for its native updating of the docs. Also, it brings the documentation into a format that is more consistent with other python packages (in my experience). The ads are non-intrusive but I would still recommend opting out (if there are no downsides to that...
by Leon
17 Sep 2019, 14:50
Forum: HowTos and FAQ for TeNPy
Topic: iDMRG is not working properly with next-nearest neighbor complex hopping in the Haldane model
Replies: 6
Views: 404

Re: iDMRG is not working properly with next-nearest neighbor complex hopping in the Haldane model

As Johannes mentions, the rewrite of DMRG 39 and 85 formed part of an attempt to overcome convergence issues such as described above. The crucial new feature is the introduction of single-site DMRG updates, which we hope can overcome the bad convergence. I have unfortunately not had a chance (or a g...
by Leon
15 Jul 2019, 14:50
Forum: HowTos and FAQ for TeNPy
Topic: Entanglement Entropy in 1D spin-1 XXZ chain
Replies: 4
Views: 543

Re: Entanglement Entropy in 1D spin-1 XXZ chain

First of all, the last sentence (' This you could~ smaller.') in your answer for Q1 is not clear for me. I was afraid so. Let me try again: I think you might be finding quite different states for different values of Jz. I assume you are running a separate simulation for each Jz. My suggestion would...
by Leon
10 Jul 2019, 16:55
Forum: HowTos and FAQ for TeNPy
Topic: Entanglement Entropy in 1D spin-1 XXZ chain
Replies: 4
Views: 543

Re: Entanglement Entropy in 1D spin-1 XXZ chain

Hi, thanks for your questions! Firstly, if your last update was on 6th January, you might want to consider updating your code. Amongst many smaller changes, an updated version was released this April. As to your questions: Q1: At or near a critical point, DMRG can struggle with finding the correct g...
by Leon
17 Jun 2019, 09:14
Forum: HowTos and FAQ for TeNPy
Topic: DMRG sweep problems
Replies: 5
Views: 552

Re: DMRG sweep problems

You once mentioned that 1407.6985 used an old version of tenpy, could you provide a link to the code? Thanks. Unfortunately, that version is not open source, so I cannot give you a link. There is a possibility this problem with convergence is caused by some issue deep in DMRG, which does not behave...
by Leon
13 Jun 2019, 15:41
Forum: HowTos and FAQ for TeNPy
Topic: DMRG sweep problems
Replies: 5
Views: 552

Re: DMRG sweep problems

Problems with convergence could be due to a setup that is badly suited to DMRG. For example, in arXiv:1407.6985, convergence is bad for a weakly interacting system (which is in a metallic phase).

That said, the behaviour you report seems different from the case I mention. Did you try using a mixer?
by Leon
06 Jun 2019, 09:21
Forum: HowTos and FAQ for TeNPy
Topic: Brute force parallel execution / multiprocessing
Replies: 1
Views: 274

Re: Brute force parallel execution / multiprocessing

... I have to calculate many independent ground states for different physical parameters. I was hoping I could parallelize those executions due to their independent nature. ... If you have an executable-level script (like any of the example codes) and want to run this many times in parallel for dif...
by Leon
21 Feb 2019, 12:25
Forum: HowTos and FAQ for TeNPy
Topic: Twisted Boundary Conditions for a CouplingMPOModel
Replies: 3
Views: 499

Re: Twisted Boundary Conditions for a CouplingMPOModel

For the paper you cite, an older version of TenPy was used. The external flux was implemented by defining an additional phase factor np.exp(1j*2*np.pi*phi_ext) on one hopping term around the cylinder (i.e., collecting all flux on a single bond). This might still be the way to go in the current TenPy...
by Leon
21 Feb 2019, 12:19
Forum: HowTos and FAQ for TeNPy
Topic: Exponentiation of operator / String order parameter
Replies: 8
Views: 687

Re: Exponentiation of operator

Scipy has a method for matrix exponentiation in scipy.linalg.expm.
by Leon
05 Feb 2019, 10:55
Forum: HowTos and FAQ for TeNPy
Topic: How to generate a random MPS in tenpy
Replies: 5
Views: 586

Re: How to generate a random MPS in tenpy

You could potentially use the classmethod from_full() in tenpy.networks.mps.py.

I am curious why you would need a fully random MPS. Does starting from a random product state with the mixer implemented not give your desired results?