Boundary Overlaps from Functional Separation of Variables

Fuente: arXiv
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Main Authors: Ekhammar, Simon, Gromov, Nikolay, Ryan, Paul
Format: Preprint
Published: 2023
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author Ekhammar, Simon
Gromov, Nikolay
Ryan, Paul
author_facet Ekhammar, Simon
Gromov, Nikolay
Ryan, Paul
contents In this paper we show how the Functional Separation of Variables (FSoV) method can be applied to the problem of computing overlaps with integrable boundary states in integrable systems. We demonstrate our general method on the example of a particular boundary state, a singlet of the symmetry group, in an su(3) rational spin chain in an alternating fundamental--anti-fundamental representation. The FSoV formalism allows us to compute in determinant form not only the overlaps of the boundary state with the eigenstates of the transfer matrix, but in fact with any factorisable state. This includes off-shell Bethe states, whose overlaps with the boundary state have been out of reach with other methods. Furthermore, we also found determinant representations for insertions of so-called Principal Operators (forming a complete algebra of all observables) between the boundary and the factorisable state as well as certain types of multiple insertions of Principal Operators. Concise formulas for the matrix elements of the boundary state in the SoV basis and su(N) generalisations are presented. Finally, we managed to construct a complete basis of integrable boundary states by repeated action of conserved charges on the singlet state. As a result, we are also able to compute the overlaps of all of these states with integral of motion eigenstates.
format Preprint
id arxiv_https___arxiv_org_abs_2312_11612
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Boundary Overlaps from Functional Separation of Variables
Ekhammar, Simon
Gromov, Nikolay
Ryan, Paul
High Energy Physics - Theory
Mathematical Physics
Exactly Solvable and Integrable Systems
In this paper we show how the Functional Separation of Variables (FSoV) method can be applied to the problem of computing overlaps with integrable boundary states in integrable systems. We demonstrate our general method on the example of a particular boundary state, a singlet of the symmetry group, in an su(3) rational spin chain in an alternating fundamental--anti-fundamental representation. The FSoV formalism allows us to compute in determinant form not only the overlaps of the boundary state with the eigenstates of the transfer matrix, but in fact with any factorisable state. This includes off-shell Bethe states, whose overlaps with the boundary state have been out of reach with other methods. Furthermore, we also found determinant representations for insertions of so-called Principal Operators (forming a complete algebra of all observables) between the boundary and the factorisable state as well as certain types of multiple insertions of Principal Operators. Concise formulas for the matrix elements of the boundary state in the SoV basis and su(N) generalisations are presented. Finally, we managed to construct a complete basis of integrable boundary states by repeated action of conserved charges on the singlet state. As a result, we are also able to compute the overlaps of all of these states with integral of motion eigenstates.
title Boundary Overlaps from Functional Separation of Variables
topic High Energy Physics - Theory
Mathematical Physics
Exactly Solvable and Integrable Systems
url https://arxiv.org/abs/2312.11612