Search found 32 matches

by QichengTang
02 Apr 2020, 05:39
Forum: HowTos and FAQ for TeNPy
Topic: Question about generating random MPS
Replies: 1
Views: 3464

Question about generating random MPS

Hi everyone, I'm trying to generate a random MPS by using the example in test module of tenpy (see the end of this post). I found that when L > 140, it will raise RuntimeError: SVD found no singluar values. I'm not sure where I make wrong, does anyone know something about this? thanks, Qicheng def r...
by QichengTang
12 Mar 2020, 08:07
Forum: HowTos and FAQ for TeNPy
Topic: leading eigenvector of transfer matrix
Replies: 6
Views: 4287

Re: leading eigenvector of transfer matrix

You cannot/should not take the transfer matrix of a single site, if you have a two-site unit cell in your MPS. Sometimes, the charge values will not even allow you, and even if they do, it there is a different gauge on the two bonds - which can and will be the case if there are degenerate singular ...
by QichengTang
11 Mar 2020, 04:32
Forum: HowTos and FAQ for TeNPy
Topic: leading eigenvector of transfer matrix
Replies: 6
Views: 4287

Re: leading eigenvector of transfer matrix

BTW, in this sense, the normalization factors of the left (to square singular value) and right eigenvector (identity) of right canonical form should cancel each other out, right? However, in a real case it seems will change the largest amplitude of the transfer matrix (the largest eigenvalue will b...
by QichengTang
11 Mar 2020, 03:48
Forum: HowTos and FAQ for TeNPy
Topic: leading eigenvector of transfer matrix
Replies: 6
Views: 4287

Re: leading eigenvector of transfer matrix

It's just a matter of normalization. Eigenvalues get normalized to np.linalg.norm(v) = 1 , but in this case you want np.sum(v) = 1 . At the end of your code, add vdiag = v.diagonal() print(vdiag/np.sum(vdiag)) print(psi.get_SL(0)**2) and compare the results, the prints should give the same Thanks f...
by QichengTang
10 Mar 2020, 13:48
Forum: HowTos and FAQ for TeNPy
Topic: leading eigenvector of transfer matrix
Replies: 6
Views: 4287

leading eigenvector of transfer matrix

Hi everyone, it is well known that, in left(right) canonical form infinite MPS, the leading left(right) eigenvector (corresponding to eigenvalue 1) of the transfer matrix is a unit matrix \mathbb{1} , and the leading right(left) eigenvector is \lambda^2 \mathbb{1} . However, when I trying to test th...
by QichengTang
10 Mar 2020, 06:47
Forum: HowTos and FAQ for TeNPy
Topic: Real-time evolution of the GS of the U=0 Fermi-Hubbard model
Replies: 5
Views: 3199

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 ;-...
by QichengTang
14 Nov 2019, 03:02
Forum: HowTos and FAQ for TeNPy
Topic: Real-time evolution of the GS of the U=0 Fermi-Hubbard model
Replies: 5
Views: 3199

Re: Real-time evolution of the GS of the U=0 Fermi-Hubbard model

it is a good idea to write a function to evaluate the variance of H, and maybe something like |<\psi|H|\psi>|^2 - <\psi|H^2|\psi> can be used in dmrg to be a control parameter? What order (second or fourth) and timestep do you use for TEBD? Does this go away if you simply use a smaller timestep/high...
by QichengTang
01 Oct 2019, 03:14
Forum: HowTos and FAQ for TeNPy
Topic: print msg into file
Replies: 6
Views: 2574

Re: print msg into file

Thanks for your help Johannes, I actually do not know how to deal with this problem for a long time (not just for tenpy, also other code written by myself or others).
by QichengTang
26 Sep 2019, 12:05
Forum: HowTos and FAQ for TeNPy
Topic: print msg into file
Replies: 6
Views: 2574

Re: print msg into file

maybe i didnot explain my point clearly enough. The point is to save the printing msg in terminal at time . If simply use python3 abc.py > log the printing msg will be saved after the task is done, i.e. during running of the task, you can not read the msg in this log file. In the case of using a pyt...