Search found 23 matches

by pasa
22 Jun 2023, 16:39
Forum: HowTos and FAQ for TeNPy
Topic: Infinite DMRG with conserved charges
Replies: 2
Views: 2086

Re: Infinite DMRG with conserved charges

Dear Johannes, thank you very much for your quick answer. Indeed, all your first corrections are typos including the ['B','B','B'] in the code. I have modified them in the original post to avoid confusions. This time I checked I did not introduce new ones :). I was exactly missing the couplings betw...
by pasa
17 Jun 2023, 15:25
Forum: HowTos and FAQ for TeNPy
Topic: Infinite DMRG with conserved charges
Replies: 2
Views: 2086

Infinite DMRG with conserved charges

Good morning everyone, I am again in need of your knowledge. I am trying to use infinite DMRG implementing a model which has conservation laws not yet implemented in Tenpy. So far I used either finite DMRG with conserved charges, or infinite DMRG with no charges. Those codes have worked well giving ...
by pasa
16 Apr 2023, 00:29
Forum: HowTos and FAQ for TeNPy
Topic: dmrg.run() claims quartic Hamiltonian is zero
Replies: 3
Views: 2301

Re: dmrg.run() claims quartic Hamiltonian is zero

Hello everyone! I have a follow up question regarding this. Consider we want to run DMRG after fixing the symmetries. Hence, generating a "random" initial state within that symmetry sector might not be easy to do. As an alternative, I was considering that an easy way to avoid this would be...
by pasa
23 Dec 2021, 08:53
Forum: HowTos and FAQ for TeNPy
Topic: If/How to avoid: "final DMRG state not in canonical form..."
Replies: 4
Views: 4338

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

Hi Johannes, First of all Merry Christmas and hope you are doing healthy and fine. I think I am encountering a similar situation as the one you suggested in this comment: The system I am studying is gapless. I am calculating the ground state of a 3-local Hamiltonian (spin operators acting on three c...
by pasa
02 Sep 2021, 17:41
Forum: HowTos and FAQ for TeNPy
Topic: Eigenvalues for the transfer matrix and unit cells
Replies: 4
Views: 2928

Re: Eigenvalues for the transfer matrix and unit cells

Hi Johannes, Thanks! But there is something I don't understand: If the problem is that the phase of the largest eigenvalue was non-zero, then when one groups sites, such phase should be also raised to the power L ? But then, I would have expected that both the modulus and phase of the eigenvalues fo...
by pasa
01 Sep 2021, 09:02
Forum: HowTos and FAQ for TeNPy
Topic: Eigenvalues for the transfer matrix and unit cells
Replies: 4
Views: 2928

Re: Eigenvalues for the transfer matrix and unit cells

Hi Johannes, thanks for the quick reply. So, I am working with a 1D system with unit cell L and this is the code I am using T = TransferMatrix(psi, psi, charge_sector=aux_c, form='A') E, _ = T.eigenvectors(Num_eig, which='LM') e_list = -np.log(np.abs(E)) phi_list = np.angle(E, deg=False) The reason ...
by pasa
31 Aug 2021, 19:20
Forum: HowTos and FAQ for TeNPy
Topic: Eigenvalues for the transfer matrix and unit cells
Replies: 4
Views: 2928

Eigenvalues for the transfer matrix and unit cells

Hi all, I would like to ask you about the normalization of the eigenvalues of the transfer matrix for systems with unit cell L larger than 1. It appears that the real and imaginary parts of a given eigenvalue have different normalization conventions with respect to the unit cell size: If \lambda is ...
by pasa
08 Jul 2021, 16:32
Forum: HowTos and FAQ for TeNPy
Topic: Finite state machine MPO
Replies: 2
Views: 1979

Re: Finite state machine MPO

Thanks a lot Johannes and sorry for my delay coming back to the forum. Your code example is so clear that was easy generalizing it. Thanks again! I have nevertheless two technical questions related to Tenpy. The first one is that at the end of your function you use H_bond = H_bond.split_legs().trans...
by pasa
31 May 2021, 15:46
Forum: HowTos and FAQ for TeNPy
Topic: Finite state machine MPO
Replies: 2
Views: 1979

Finite state machine MPO

Hi everyone, I would like to ask you: Do you know whether the ``AKLT'' Hamiltonian H = \sum_j \vec{S}_j \cdot \vec{S}_{j+1} + \lambda (\vec{S}_j \cdot \vec{S}_{j+1} )^2 could be written as an MPO with bond dimension less than 14? This is the bond dimension I obtained when I construct the model as fo...
by pasa
15 Mar 2021, 22:25
Forum: HowTos and FAQ for TeNPy
Topic: How to use TDVP for one site
Replies: 3
Views: 2472

Re: How to use TDVP for one site

Hi! It looks like that it would make more sense to use the truncation error for two sites TDVP rather than the maximal bond dimension. However, I am having problems to obtain the truncation error for TDVP. Does it work as for the TEBD engine? The following lines worked for TEBD but give an error for...
by pasa
14 Mar 2021, 19:38
Forum: HowTos and FAQ for TeNPy
Topic: How to use TDVP for one site
Replies: 3
Views: 2472

Re: How to use TDVP for one site

Hi Johannes! that makes perfect sense. Let me enter a bit more detail in the problem I am having. I wanted to use single site TDVP such that energy is conserved at all times. Thus I wanted to avoid using TEBD or two-site TDVP. Updated answer: after talking to Umberto Borla and following your previou...
by pasa
14 Mar 2021, 17:28
Forum: HowTos and FAQ for TeNPy
Topic: How to use TDVP for one site
Replies: 3
Views: 2472

How to use TDVP for one site

Dear community, I am trying to use TDVP on one site. I understand the theory behind the construction and I thought I also understood how to use it in practice. I checked the example code provided by Tenpy developers. My specific problem is that I manage to run the two site TDVP obtaining non-trivial...
by pasa
12 Feb 2021, 10:37
Forum: HowTos and FAQ for TeNPy
Topic: np conserved module
Replies: 3
Views: 2929

Re: np conserved module

Hi Johannes! thanks for the quick answer! I want to compute a correlation function of the form \langle g.s. | \sigma_j x(t)\sigma_0 x(0)|g.s. \rangle for a system that conserves SU(2) (or a U(1) generated by S z). I managed to obtain it for the Transverse Field Ising Model (TFIM). However, I am havi...
by pasa
11 Feb 2021, 15:51
Forum: HowTos and FAQ for TeNPy
Topic: np conserved module
Replies: 3
Views: 2929

np conserved module

Dear community, I am at the moment working with a system which has a SU(2) invariance. Thus, when finding the ground state via DMRG, I fix the total S z charge. So far everything is fine. Once I obtain the ground state, I would like to apply a S x (or S y ) operator to the ground state and here come...
by pasa
04 Feb 2021, 18:16
Forum: HowTos and FAQ for TeNPy
Topic: Warning Cons_N and Cons_Sz unused
Replies: 2
Views: 1918

Re: Warning Cons_N and Cons_Sz unused

It was a typo from my side: It is cons_ and not Cons_.... :roll: :roll:
by pasa
04 Feb 2021, 09:44
Forum: HowTos and FAQ for TeNPy
Topic: Warning Cons_N and Cons_Sz unused
Replies: 2
Views: 1918

Warning Cons_N and Cons_Sz unused

Dear Tenpy community, I wanted to ask: is someone having also the following warning when trying to fix conserved quantities in TEBD evolution? UserWarning: unused options for config FermiHubbardChain:['Cons_N', 'Cons_Sz'] I updated Tenpy to the latest version (currently 0.7.2) and this is the way I ...
by pasa
04 Feb 2021, 09:20
Forum: HowTos and FAQ for TeNPy
Topic: Modified Fermi-Hubbard model
Replies: 3
Views: 2964

Re: Modified Fermi-Hubbard model

Hi Johannes, thanks for the advise! So my first thought was grouping sites to use TEBD and then Umberto kindly explained to me that apart from that, I had to convert my coupling model to a nearest neighbor model to use TEBD (actually he pointed out a really nice example code). So that works! But I a...
by pasa
13 Jan 2021, 17:03
Forum: HowTos and FAQ for TeNPy
Topic: Modified Fermi-Hubbard model
Replies: 3
Views: 2964

Modified Fermi-Hubbard model

Dear Tenpy community, happy new year all! I would like to ask you: How would you use TEBD for a MultiCouplingModel? The thing is that I need to add a longer-range coupling to my Hamiltonian and thus I cannot really use the Nearest neighbour model option. I thought grouping sites but I am still missi...
by pasa
26 Nov 2020, 11:05
Forum: HowTos and FAQ for TeNPy
Topic: Initial CAT state
Replies: 5
Views: 5658

Re: Initial CAT state

Hi Johannes, Thank you again for the explanation. So I want to have a first idea of a phase diagram where I know there is a SSB broken phase whose ground state is pretty close to one of the two possible states in the CAT superposition, being the other one a better initial seed for the other phase th...
by pasa
26 Nov 2020, 10:06
Forum: HowTos and FAQ for TeNPy
Topic: Initial CAT state
Replies: 5
Views: 5658

Re: Initial CAT state

Hi, thanks for the quick reply. I was thinking about using "add", but I need to run iDMRG ( I saw one can only use it for segment or finite (?) ) and also as you guessed, I am planning to use a CAT state where each of the states have different total charge, and "add" documentatio...
by pasa
25 Nov 2020, 20:17
Forum: Algorithms
Topic: Kinetic energy
Replies: 3
Views: 13442

Re: Kinetic energy

Hi! I know I am really late for this, but thank you for answering. It is still really helpful! I was not really online recently.
by pasa
25 Nov 2020, 20:14
Forum: HowTos and FAQ for TeNPy
Topic: Initial CAT state
Replies: 5
Views: 5658

Initial CAT state

Dear TeNPy community, I would like to ask whether someone used the function MPS.from_Bflat(sites, Bflat, SVs=None, bc='finite', dtype=None, permute=True, form='B', legL=None) and could help me understand it providing some specific example of how to use it. I didn't manage to follow the documentation...
by pasa
09 Mar 2020, 12:57
Forum: Algorithms
Topic: Kinetic energy
Replies: 3
Views: 13442

Kinetic energy

Hi! I think I have an easy question but not sure how to do it. I am running iDMRG algorithm to find the ground state of the system I am interested in. Apart from the total energy density, is there a built-in function in Tenpy to obtain the contribution to the total energy of each of the terms in the...