Talk:Bethe ansatz

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Ground state of what?

I think the discussion section is lacking in clarity, it's really hard to follow as there seems to be sentences taken from books or articles without citation or the necessary context.

In particular, the paragraph simply starts with: The ground state is a Fermi sphere.

The ground state of what?

This is followed by: Periodic boundary conditions lead to the Bethe ansatz equations.

Periodic boundary conditions on what?

It sort of sounds like it's taken from a discussion on a particular system or class of systems, it would be useful if it was clarified in the text what exactly one is talking about here.

Bricksprovidecoal (talk) 18:03, 7 April 2023 (UTC)[reply]

I'm thinking of reworking this article at some point due to these examples you've given which lack (a) explanation and (b) sources in the absence of explanation. The system discussed is most likely the Heisenberg spin chain which is the prototypical system for which the Bethe ansatz is used, in which case the ground state is a tensor product of spin up states which could reasonably be referred to as a Fermi sphere (although I haven't seen this usage anywhere else), and boundary conditions come from the fact the (N+1)th and 1st copies of the 1-particle Hilbert spaces are identified. Zephyr the west wind (talk) 08:11, 8 April 2023 (UTC)[reply]