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The deformed Inozemtsev spin chain

by Rob Klabbers, Jules Lamers

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Submission summary

Authors (as registered SciPost users): Jules Lamers
Submission information
Preprint Link: https://arxiv.org/abs/2306.13066v5  (pdf)
Date accepted: 2024-10-29
Date submitted: 2024-09-25 11:20
Submitted by: Lamers, Jules
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Mathematical Physics
Approach: Theoretical

Abstract

The Inozemtsev chain is an exactly solvable interpolation between the short-range Heisenberg and long-range Haldane-Shastry (HS) chains. In order to unlock its potential to study spin interactions with tunable interaction range using the powerful tools of integrability, the model's mathematical properties require better understanding. As a major step in this direction, we present a new generalisation of the Inozemtsev chain with spin symmetry reduced to U(1), interpolating between a Heisenberg xxz chain and the xxz-type HS chain, and integrable throughout. Underlying it is a new quantum many-body system that extends the elliptic Ruijsenaars system by including spins, contains the trigonometric spin-Ruijsenaars-Macdonald system as a special case, and yields our spin chain by 'freezing'. Our models have potential applications from condensed-matter to high-energy theory, and provide a crucial step towards a general theory for long-range integrability.

Author indications on fulfilling journal expectations

  • Provide a novel and synergetic link between different research areas.
  • Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
  • Detail a groundbreaking theoretical/experimental/computational discovery
  • Present a breakthrough on a previously-identified and long-standing research stumbling block

Author comments upon resubmission

Hereby we submit our revised manuscript. All feedback of the referees, for which we are very grateful, has been taken into account.

There is one point raised by all three referees: that we do not give the proof of integrability of our elliptic dynamical spin-Ruijsenaars (in the sense that our hierarchy of matrix-valued difference operators commute), and therefore of our deformed Inozemtsev chain. As we mention, our proof of this fact is highly technical; much more so than the corresponding proof of Matushko and Zotov in Ref. [45], which unfortunately does not seem to extend to our case. Our proof warrants a separate publication, which will be much more mathematical. We firmly believe that in addition to that proof it is important to present the concrete results to a more physics-inclined audience. This is the aim of the present paper.

List of changes

We have changed the notation for the isotropic hamiltonians to \bar{H}, in accordance with our use of \bar{V} for the isotropic potentials. Hence:
p2, preceding Eq. (1): "with hamiltonian of the form" -> "Using a bar to denote isotropic case, these spin chains have hamiltonian of the form"

p3, Fig. 1: written out "anisotr." -> "anisotropic"
p3, first paragraph: "conjecture for the conserved charges" -> "conjecture for a hierarchy of conserved charges" to clarify what we loosely speaking mean by 'integrable'
Just below: Footnote 1 added, with further clarification of this point, and its connection to the recent preprint of Chalykh (new Ref [24]).

p4, Outline: moved the sentence + footnote "While we focus on spin 1/2, [...]" to the bottom of outline.
p4, preceding Eq. (5): corrected "periodisation" -> "periodic version"
p4, following Eq. (6): clarified "see (A.6)" -> "and in '~' we omit some constants, see (A.6) for the precise relation"

p6, top, following Eq. (7): added "where the `^\star' serves to distinguish these fixed parameters from their unrestricted counterparts x_k that will appear in \textsection 3"
p6, Sect 2.2: clarified "The spectrum is real" -> "While the hamiltonians are not hermitian for the standard scalar product, numerics shows that the spectrum is real"
p6, Defining properties, isotropic limit: added reference "(see \textsection C)" for details of the computation
p6, Defining properties, long-range limit:
added "To see this use \theta(x) \to N \sin(\pi x/N)/\pi as \kappa \to 0."
rephrased "The potential (6) has long-range limit" -> "The potential (6) thus has long-range limit"
p7, top: rephrased "If moreover \eta a \to -i \infty" -> "When \kappa\to 0 and moreover \eta a\to - i \infty$ for fixed \eta"

p7, following Eq. (19): added explanation "Namely, G^N = K_1 ... K_N$ is a central element, [...] These are the simplest eigenstates after the reference vector \ket{\uparrow ... \uparrow}."
Just below: rephrased "We have not yet been able to find an expression for the dispersion relation" -> "We have not yet been able to find
a compact expression for their chiral dispersion relations."

p8, Eq. (21): added missing parenthesis

p9, Choice of R-matrix: corrected \eqref from 2.2 to (10)
Just below: added Ref [42] to Baxter

p11, Modular family: corrected Ref [40]

p17, following Eq. (A.4): added "When \kappa\to 0 we have \theta(x) \to N \sin(\pi x/N)/\pi by the Jacobi imaginary transformation."

p20, end of App C: added details for isotropic limit "To evaluate the isotropic limit of E(x,a) [...]."

References: corrected capitalisation, added arXiv and doi data

Published as SciPost Phys. 17, 155 (2024)


Reports on this Submission

Report #3 by Anonymous (Referee 3) on 2024-10-14 (Invited Report)

Report

The requested changes were implemented, I recommend the paper for publication

Recommendation

Publish (easily meets expectations and criteria for this Journal; among top 50%)

  • validity: high
  • significance: high
  • originality: high
  • clarity: top
  • formatting: excellent
  • grammar: excellent

Report #2 by Anonymous (Referee 1) on 2024-10-11 (Invited Report)

Report

A point-by-point response to the requested changes would have been helpful. Nevertheless, I have checked that my requested changes have been addressed, so I am happy to recommend publication.

Recommendation

Publish (meets expectations and criteria for this Journal)

  • validity: -
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Report #1 by Anonymous (Referee 2) on 2024-10-8 (Invited Report)

Report

In their re-submission the authors seriously addressed all points raised by the referees. The paper can now be published as it stands.

Recommendation

Publish (easily meets expectations and criteria for this Journal; among top 50%)

  • validity: -
  • significance: -
  • originality: -
  • clarity: -
  • formatting: -
  • grammar: -

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