Search found 32 matches

by QichengTang
18 Sep 2019, 03:32
Forum: HowTos and FAQ for TeNPy
Topic: correlation length in idmrg
Replies: 1
Views: 1052

correlation length in idmrg

Hi, everyone. I'm trying to calculate the correlation length for TFI chain near or away from the critical point. I have test before, the calculated correlation length for critical point g=1 is agree with the pervious numeric presented by Frank Pollmann https://journals.aps.org/prl/abstract/10.1103/P...
by QichengTang
18 Sep 2019, 03:22
Forum: HowTos and FAQ for TeNPy
Topic: how to write a three-site interaction?
Replies: 4
Views: 1928

Re: how to write a three-site interaction?

Thanks for your explanation, Umberto. It's very clear.
by QichengTang
05 Sep 2019, 00:46
Forum: HowTos and FAQ for TeNPy
Topic: how to write a three-site interaction?
Replies: 4
Views: 1928

how to write a three-site interaction?

Hi everyone, I'm confused how to write a three-site interaction? I have read the example of toric code, but I donnot understand. If I want to write a O’Brien-Fendley model H=\sum_{j=1}^N [-\sigma^z_{j}\sigma^z_{j+1}-\sigma^x_{j}+\lambda(\sigma^x_{j}\sigma^z_{j+1}\sigma^z_{j+2}+\sigma^z_{j}\sigma^z_{...
by QichengTang
04 Sep 2019, 07:14
Forum: HowTos and FAQ for TeNPy
Topic: print msg into file
Replies: 6
Views: 2404

print msg into file

I'm wondering if the msg can be printed into a log file?
It's not hard to modify the code, and I think this is necessary.
by QichengTang
02 Jul 2019, 13:51
Forum: HowTos and FAQ for TeNPy
Topic: Some questions about the svd_theta
Replies: 7
Views: 2121

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_i...
by QichengTang
02 Jul 2019, 13:29
Forum: HowTos and FAQ for TeNPy
Topic: Some questions about the svd_theta
Replies: 7
Views: 2121

Re: Some questions about the svd_theta

Thank you, Johannes, now I'm clear with the svd process, but here appears another question. As in the note said, the process of combination of two legs is something like mapping the indices for "vL" and "p" into something like "2*vL+p", so you can split out the physical leg by using a inverse mappin...
by QichengTang
01 Jul 2019, 04:16
Forum: HowTos and FAQ for TeNPy
Topic: Some questions about the svd_theta
Replies: 7
Views: 2121

Re: Some questions about the svd_theta

There's another thing related, and I donnot understand how to deal with it. For example, consider a spin-half chain with conserved Sz, we can write down the 3 sub-blocks with Sz "-2, 0, 2", In this case, we can do svd for each charge sector. But in the case of, for example, TFI chain where the Sz is...
by QichengTang
28 Jun 2019, 17:27
Forum: HowTos and FAQ for TeNPy
Topic: Some questions about the svd_theta
Replies: 7
Views: 2121

Re: Some questions about the svd_theta

Johannes, Thanks for your reply, I know that the transfer matrix method is only well-defined in a case with translational invariance, and for the contracting of the transfer matrix we need right matrice B or left matrice A. My question is about the implementation of the charge conservation in the ca...
by QichengTang
28 Jun 2019, 06:18
Forum: HowTos and FAQ for TeNPy
Topic: Some questions about the svd_theta
Replies: 7
Views: 2121

Some questions about the svd_theta

Hi everyone, I want to write a little program to calculate the correlation length with a given "theta" (which is located in the center of the chain), so I need to do svd to theta and get the right matrice B. But there is a problem, I get the theta by using function "get_theta" for MPS object, and ex...
by QichengTang
20 Apr 2019, 17:13
Forum: Algorithms
Topic: question about tdvp
Replies: 2
Views: 1647

Re: question about tdvp

mpsforphysics, thx for you reply!

The lecture note arXiv:1810.07006 is very good!