TeNPy Forum

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 ...

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...

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.

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".

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?

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 ...

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 ...