How to add additional U(1) Symmetry in BosonSite for Tenpy

How do I use this algorithm? What does that parameter do?
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ssy
Posts: 1
Joined: 06 Jun 2025, 10:44

How to add additional U(1) Symmetry in BosonSite for Tenpy

Post by ssy »

Dear
Recently, I have started learning to implement infinite Density Matrix Renormalization Group (DMRG) calculations using the Tenpy library.
I would like to introduce an additional U(1) symmetry in the original `BosonSite`:
$$
P = \sum_j (L - j) n_j
$$
as detailed in equation (2) of [this paper](https://journals.aps.org/prb/abstract/1 ... 107.195131). Could you kindly advise on how to modify the `BosonSite` implementation to incorporate this symmetry?

Thank you for your time and guidance.
Jakob
Posts: 19
Joined: 30 Jan 2023, 22:57

Re: How to add additional U(1) Symmetry in BosonSite for Tenpy

Post by Jakob »

Hi,

These types of position dependent charges are not available in the live tenpy version yet

There is an unmerged PR at
https://github.com/tenpy/tenpy/pull/183

It seems, however, that it is not very stable for infinite systems and not tested well enough. I would not blindly trust it.

In the infinite case, its is particularly tricky to treat the position dependent local charges correctly.

We dont have capacity to work on this, currently.
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