## Search found 32 matches

- 08 Apr 2019, 09:18
- Forum: Algorithms
- Topic: question about tdvp
- Replies:
**2** - Views:
**1878**

### question about tdvp

Hi, everyone. I'm trying to do tdvp, but there are something in the original paper which I cannot understand. Firstly, why the projector in this form? I know the projector is something like 1 - \sum_N |\psi_N><\psi_N| , but what's the target space here, it seems like we project it onto a basis orort...

- 08 Mar 2019, 10:50
- Forum: HowTos and FAQ for TeNPy
- Topic: Product state results
- Replies:
**3** - Views:
**1473**

### Re: Product state results

I believe it's easy to generate a random product state with a given total charge.

for example, for qubit, it's just a combination of 0 and 1 with a given sum of all elements in the list, you just need to give the number of 0 and 1, and do a random permutation.

for example, for qubit, it's just a combination of 0 and 1 with a given sum of all elements in the list, you just need to give the number of 0 and 1, and do a random permutation.

- 27 Feb 2019, 10:07
- Forum: HowTos and FAQ for TeNPy
- Topic: Product state results
- Replies:
**3** - Views:
**1473**

### Re: Product state results

I will ask you the question what Johannes asked me: What the "random" state means here? It should be noticed that the charge (quantum number) should be conserved in dmrg, so if your random state has a different total charge, the result will be wrong. Perhaps you can use "RandomUnitary...

- 22 Feb 2019, 09:34
- Forum: HowTos and FAQ for TeNPy
- Topic: Scaling of entanglement entropy for iDMRG
- Replies:
**7** - Views:
**2638**

### Re: Scaling of entanglement entropy for iDMRG

hi, everyone. I have to admit i was wrong, and what Umberto said is correct: The original formula is correct, and in infinite dmrg the boundary condition is open. BTW, bart, your scaling method may be wrong. Why you choose the data from a state which is not converged in dmrg? What I remember is: you...

- 09 Feb 2019, 13:30
- Forum: HowTos and FAQ for TeNPy
- Topic: How to generate a random MPS in tenpy
- Replies:
**5** - Views:
**2242**

### Re: How to generate a random MPS in tenpy

Thanks for your reply! In fact, I want to get some states with random entanglement entropy. I know the random unitary time evolution will be a good method. I was thinking about that is there a method can directly obtain these states? The first coming problem is about the charge conserve as you said,...

- 31 Jan 2019, 14:16
- Forum: HowTos and FAQ for TeNPy
- Topic: How to generate a random MPS in tenpy
- Replies:
**5** - Views:
**2242**

### Re: How to generate a random MPS in tenpy

Thanks for your reply. But what i'm looking for is not a random product state. What I want is a general state not a product state. I konw that there is a method to obtain a random state by a random unitary evolution process, but i'm asking a more simple way to get a random state, like by using some ...

- 29 Jan 2019, 15:48
- Forum: HowTos and FAQ for TeNPy
- Topic: Scaling of entanglement entropy for iDMRG
- Replies:
**7** - Views:
**2638**

### Re: Scaling of entanglement entropy for iDMRG

I mean, in iDMRG, the boundary condition is like a periodic boundary condition. So, your problem is you use the wrong formula, you should use a formula for periodic boundary condition when you do an iDMRG calculation. In a finite case, you can choose open boundary condition or periodic, but in tenpy...

- 29 Jan 2019, 14:22
- Forum: HowTos and FAQ for TeNPy
- Topic: Scaling of entanglement entropy for iDMRG
- Replies:
**7** - Views:
**2638**

### Re: Scaling of entanglement entropy for iDMRG

hi, i believe the reason is that in iDMRG the boundary condition is like a periodic boundary condition.

Your formula is for the open boundary condition, and for periodic boundary condition this should be c/3 but not c/6.

I recommend you to read the following two ref: arXiv:hep-th/0405152 and arXiv:0905.4013.

Your formula is for the open boundary condition, and for periodic boundary condition this should be c/3 but not c/6.

I recommend you to read the following two ref: arXiv:hep-th/0405152 and arXiv:0905.4013.

- 21 Jan 2019, 13:49
- Forum: HowTos and FAQ for TeNPy
- Topic: How to generate a random MPS in tenpy
- Replies:
**5** - Views:
**2242**

### How to generate a random MPS in tenpy

how to generate a random MPS? Is the function "npc.Array.from_func" helpful?

PS. I think it's worthy to add a function like "rand_mps".

PS. I think it's worthy to add a function like "rand_mps".

- 17 Jan 2019, 15:18
- Forum: HowTos and FAQ for TeNPy
- Topic: the truncation in dmrg
- Replies:
**5** - Views:
**2122**

### Re: the truncation in dmrg

Okay, I see. I'm wrong about the truncation protocol in tenpy.

But, it's still kind of weird for me, I mean, the value of 1.e-10 ("svd_min") is a very small number, it should not influence the result, or I'm wrong with some very trivial things?

But, it's still kind of weird for me, I mean, the value of 1.e-10 ("svd_min") is a very small number, it should not influence the result, or I'm wrong with some very trivial things?

- 17 Jan 2019, 06:56
- Forum: HowTos and FAQ for TeNPy
- Topic: the truncation in dmrg
- Replies:
**5** - Views:
**2122**

### Re: the truncation in dmrg

Thanks for your reply, I know that the problem maybe the degeneracy of the ground state, but that's not my point. My point is, I thought only one of these parameters "svd_min", "trunc_err", "max_bond" for truncation works. I mean I thought there is a protocol to choose ...

- 08 Jan 2019, 03:36
- Forum: HowTos and FAQ for TeNPy
- Topic: the truncation in dmrg
- Replies:
**5** - Views:
**2122**

### the truncation in dmrg

I think the following finding should be noticed by everyone who uses tenpy. When I run dmrg for xxz chian, I found that the result will be strongly dependents on the parameter "svd_min", and this doesn't make sense. I have run the following test to show the problem. I'm confused, what may ...