Search found 10 matches

by xaver
02 Aug 2022, 09:27
Forum: HowTos and FAQ for TeNPy
Topic: UserWarnings differ for identical initializations when run several times
Replies: 1
Views: 1586

UserWarnings differ for identical initializations when run several times

I have a frequent issue with UserWarning s regarding unused options in as such that they differ for identical(?) code, run several times. Typically this happens when initializing some tenpy algorithm. E.g.: import logging logging.basicConfig(level=logging.INFO) # allow for some UserWarnings # Next, ...
by xaver
29 Jul 2022, 12:30
Forum: HowTos and FAQ for TeNPy
Topic: My correlation functions from MPS.correlation_function and MPSEnvironment.expectation value disagree
Replies: 2
Views: 1731

Re: My correlation functions from MPS.correlation_function and MPSEnvironment.expectation value disagree

Aah! Now I do get C_a = C_b for my system. Great. Thx. (I was trying to interpret the list of strings from the 2nd figure in tenpy.networks.mps.MPS.correlation_function following the description of correlation_function , which kind of suggested to someone=me, lost in the very helpful docs, that the ...
by xaver
29 Jul 2022, 09:58
Forum: HowTos and FAQ for TeNPy
Topic: My correlation functions from MPS.correlation_function and MPSEnvironment.expectation value disagree
Replies: 2
Views: 1731

My correlation functions from MPS.correlation_function and MPSEnvironment.expectation value disagree

Hello, I have issues, calculation correlation functions of 2-site operators in different ways. Before posting a lot of specific code, let me pls. ask in a more general context: Let |\psi\rangle be an MPS of finite even length L Let A_i B_{i+1} denote a nearest neighbor 2-site operator, i.e. some npc...
by xaver
31 Mar 2022, 14:17
Forum: HowTos and FAQ for TeNPy
Topic: MPS winding for 'new' lattice
Replies: 2
Views: 1807

Re: MPS winding for 'new' lattice

Ok., so I may have come a little step further, but I'd still be glad if 'some higher power' would kick in to let me know if I'm at least heading into the right direction. To be more specific, the 2D lattice I'm looking at has more than 2 sites per unit cell and I want to have my own way of traversin...
by xaver
30 Mar 2022, 15:22
Forum: HowTos and FAQ for TeNPy
Topic: MPS winding for 'new' lattice
Replies: 2
Views: 1807

MPS winding for 'new' lattice

Hi, I am trying to implement a 2D lattice not available yet. I am fine up until the ordering function in lattice.py . The way how this function works, or if at all I need to tweak this particular function, or something else in order to set up my own winding for a new 2D lattice is unclear to me. I'v...
by xaver
09 Jun 2021, 10:41
Forum: HowTos and FAQ for TeNPy
Topic: Random UserWarning: unused option ['P_tol']
Replies: 1
Views: 1606

Random UserWarning: unused option ['P_tol']

I frequently and randomly get the warning UserWarning: unused option ['P_tol'] for config lanczos_params warnings.warn(msg.format(keys=sorted(unused), name=self.name)) when starting a dmrg run. I get this warning independent of if I do , or if I do not use 'lanczos_params': {'P_tol': some integer,} ...
by xaver
09 Jun 2021, 10:21
Forum: HowTos and FAQ for TeNPy
Topic: If/How to avoid: "final DMRG state not in canonical form..."
Replies: 4
Views: 4333

Re: If/How to avoid: "final DMRG state not in canonical form..."

Thx. for replying! I did already spend a lot more time playing around, and indeed, 'my' model has a parameter range to which your suggestion Do you have multiple degenerate ground states? exactly applies. I was unaware of that property :o . I.e, tenpy gave me a gentle hint :oops: Stupidly, I was run...
by xaver
24 May 2021, 10:17
Forum: HowTos and FAQ for TeNPy
Topic: If/How to avoid: "final DMRG state not in canonical form..."
Replies: 4
Views: 4333

If/How to avoid: "final DMRG state not in canonical form..."

I'm trying to run finite system dmrg on a spin model with multi-site exchange, i.e. with coupling terms of type J_{\alpha_1\dots\alpha_r} S^{\alpha_1}_{i_1}\dots S^{\alpha_r}_{i_r} . In my case, I can have r=2,4,6 spins involved. The Hamiltonian is hermitean. I should clearly state, that I'm a noob ...
by xaver
23 Apr 2021, 20:47
Forum: HowTos and FAQ for TeNPy
Topic: Chain with N site unit-cell
Replies: 2
Views: 2077

Re: Chain with N site unit-cell

As usual, I couldn't wait, and tried some more. Let me pls. add to my question and get more specific. For the sake of brevity, let me assume that in my OP I set \(A_{l,j}=S_x\). Moreover at the risk of crucifixion, let me forget all about charge conservation, boundary conditions and other 'details'....
by xaver
23 Apr 2021, 08:37
Forum: HowTos and FAQ for TeNPy
Topic: Chain with N site unit-cell
Replies: 2
Views: 2077

Chain with N site unit-cell

Hello, this is a stupid newbie's question. Most certainly, the answer I'm looking for is just a pointer to a location in the existing documentation. I'd be grateful for that. I'm trying to implement a model that lives on a chain and has more than a single site per unit cell. So, e.g. for 2 sites per...