Search found 429 matches
- 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: 8387
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: 12940
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: 8387
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: 5150
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: 4473
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: 5150
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: 9142
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...
- 15 Oct 2019, 15:15
- Forum: HowTos and FAQ for TeNPy
- Topic: finite open, finite periodic and infinite periodic chains
- Replies: 10
- Views: 11956
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? Kind of. We do not support finite MPS with periodic boundaries for the MPS itself i.e. writing | \Psi\rangle = \sum Tr(A^{\sigma_1} \cdots A^{\sigma_L}) | \sigma_1 \cdots \sigma_L\rangle This is a form which is us...
- 30 Sep 2019, 09:51
- Forum: HowTos and FAQ for TeNPy
- Topic: print msg into file
- Replies: 6
- Views: 8397
Re: print msg into file
I've added the `flush=True` to the print statements during the loops of TEBD and DMRG in ce32fd1fc30073918371717beea110083bab8cd1 On my workstation, the flush causes the output to appear immediately. If you redirect to a file on a network-shared file system, there might be a delay of the change bein...
- 27 Sep 2019, 07:22
- Forum: HowTos and FAQ for TeNPy
- Topic: About four-site coupling terms
- Replies: 2
- Views: 3438
Re: About four-site coupling terms
Welcome! There is a way to add such couplings, namly with add_multi_coupling of the tenpy.models.model.MultiCouplingModel instead of just the add_coupling of the tenpy.models.model.CouplingModel . The tenpy.models.toric_code.ToricCode is an example where this is used. Take a look at this topic for m...
- 26 Sep 2019, 13:02
- Forum: HowTos and FAQ for TeNPy
- Topic: print msg into file
- Replies: 6
- Views: 8397
Re: print msg into file
There's also a option to print().
Code: Select all
flush=True
- 26 Sep 2019, 12:44
- Forum: HowTos and FAQ for TeNPy
- Topic: print msg into file
- Replies: 6
- Views: 8397
Re: print msg into file
Still, there are ways around this. You're describing the problem that the file is "buffered", which Linux/Python does automatically to avoid unnecessary hard disk usage slowing down the execution of the program. However, this can be switched off. For python, try to use the -u option for th...
- 20 Sep 2019, 14:02
- Forum: HowTos and FAQ for TeNPy
- Topic: correlation length in idmrg
- Replies: 1
- Views: 3340
Re: correlation length in idmrg
A such enormous correlation length \xi > 10^10 means that the second eigenvalue of the transfer matrix is 1 up to numerical errors. The reason is that the state you get is a cat state, i.e. a superposition of all |+x \rangle and all |-x \rangle states. See also the discussion in viewtopic.php?f=7&am...
- 13 Sep 2019, 15:30
- 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: 8775
Re: iDMRG is not working properly with next-nearest neighbor complex hopping in the Haldane model
Welcome Dhiman, and sorry for not answering earlier. You might want to take a look at the tenpy.models.haldane.FermionicHaldaneModel and the tenpy.models.haldane.BosonicHaldaneModel . Both are based on the Hamiltonian from the paper 1407.6985 discussing the fermionic model. As far as I see from a qu...
- 13 Sep 2019, 14:10
- Forum: HowTos and FAQ for TeNPy
- Topic: how to write a three-site interaction?
- Replies: 4
- Views: 33030
Re: how to write a three-site interaction?
Thanks for the clear answer, Umberto
Just as little side node:
The usual convention is to append an underscore in such a case, i.e., use
Just as little side node:
lambda
is a special keyword in python.The usual convention is to append an underscore in such a case, i.e., use
lambda_
instead as a variable name - 13 Sep 2019, 14:05
- Forum: HowTos and FAQ for TeNPy
- Topic: print msg into file
- Replies: 6
- Views: 8397
Re: print msg into file
There are different standard ways to do this (On all computing clusters I know, there is at least an option to do it automatically). Let me point out a few which should suffice your needs: If you start your program from a Linux console, it's very easy: you can use the > at the and of any command to ...
- 13 Sep 2019, 13:15
- Forum: Implementations
- Topic: TEBD for time-dependent Hamiltonians
- Replies: 2
- Views: 17178
Re: TEBD for time-dependent Hamiltonians
Looks like a good thing. Actually, if you update your local repository, you'll find that the code for the FermiHubbardModel has been moved to tenpy.models.hubbard.FermiHubbardModel . There it says for u1, u2, dx in self.lat.nearest_neighbors: self.add_coupling(-t, u1, 'Cdu', u2, 'Cu', dx) self.add_c...
- 07 Aug 2019, 09:33
- Forum: HowTos and FAQ for TeNPy
- Topic: How to assign different hopping parameter 't' to different sites
- Replies: 1
- Views: 3118
Re: How to assign different hopping parameter 't' to different sites
You don't need to modify the unit_cell , if the kind of sites (Fermions with or without spin, Bosons, spins,...) doesn't change. Instead, you can give a hopping parameter t which is not just a single number, but an array, specifying at which site you want hopping with which strength. Take a look at ...
- 29 Jul 2019, 13:35
- Forum: HowTos and FAQ for TeNPy
- Topic: Error when using kroneckerproduct option for GroupedSite
- Replies: 5
- Views: 5313
Re: Error when using kroneckerproduct option for GroupedSite
I've just added a the function from_MPOModel, which has an example how to use it.
Does that help?
Does that help?
- 29 Jul 2019, 09:17
- Forum: HowTos and FAQ for TeNPy
- Topic: periodic conditions
- Replies: 7
- Views: 6654
Re: periodic conditions
Could it be that the tenpy you are importing is an old version?
The
The
all_onsite_terms
was only introduced fairly recently.- 26 Jul 2019, 12:27
- Forum: HowTos and FAQ for TeNPy
- Topic: Error when using kroneckerproduct option for GroupedSite
- Replies: 5
- Views: 5313
Re: Error when using kroneckerproduct option for GroupedSite
Hi Jack, welcome to TeNPy! (the sites are hardcore bosons, which I've created by simply removing the JW entries in the FermionSite class, I hope this is correct?) The more straightforward way for HardcodeBosons would be to use the tenpy.networks.site.BosonSite with the default Nmax=1 . Here is the i...
- 08 Jul 2019, 12:26
- Forum: HowTos and FAQ for TeNPy
- Topic: Finite Chain with different unit cell at the beginning
- Replies: 4
- Views: 6833
Re: Finite Chain with different unit cell at the beginning
I've opened Issue #77 to keep track of this task, in case you or someone else wants to give it a try
- 06 Jul 2019, 17:21
- Forum: Implementations
- Topic: How to contribute
- Replies: 0
- Views: 22695
How to contribute
Hi all, so far, I've kept a ToDo-list for myself. Considering, that the list got longer instead of shorter (although I spent much time working on it), I decided to try a different approach: I open up to the community and give out small tasks to be done as issues on github. If you feel like you got a...
- 04 Jul 2019, 16:14
- Forum: HowTos and FAQ for TeNPy
- Topic: Finite Chain with different unit cell at the beginning
- Replies: 4
- Views: 6833
Re: Finite Chain with different unit cell at the beginning
Currently, there's nothing like that. I started thinking about it (and even writing the code for the , but then became busy implementing other stuff. First of all, the algorithms like DMRG don't care about the lattice, but only about the generated MPO and lat.mps_sites() defining the Hilbert space. ...
- 02 Jul 2019, 13:42
- Forum: HowTos and FAQ for TeNPy
- Topic: Some questions about the svd_theta
- Replies: 7
- Views: 8848
Re: Some questions about the svd_theta
You can only split legs that were combined previously. In TeNPy, you can see that those legs store the charge data as tenpy.linalg.charges.LegPipe instead of tenpy.linalg.charges.LegCharge . Those pipes have the additional data needed to split the legs. The matrices generated by SVD, say A_ij = U_ik...