# Semiclassical expansion of the Bethe scalar products in the XXZ spin chain

## TL;DR

This paper develops a semiclassical expansion method for Bethe scalar products in the XXZ spin chain, using a gas of particles analogy to facilitate calculations, providing new insights into integrable models.

## Contribution

It introduces a novel semiclassical expansion approach for Bethe scalar products in the XXZ spin chain, utilizing a gas of particles framework.

## Key findings

- Expressed scalar products via the B functional
- Reinterpreted the B functional as a grand partition function
- Provided a systematic semiclassical expansion method

## Abstract

In this note we adress the problem of performing the semiclassical expansion of the scalar product of Bethe states in the case of the XXZ spin chain. Our approach closely follows the one developped in [1]: after expressing the scalar products in terms of a central quantity - the B functional, we reinterpret it as a grand partition function of a gas of particles with pairwise interaction potential. This work has been done as part of the author's master thesis under the supervision of Ivan Kostov and Didina Serban at Institut de Physique Th\'eorique (CEA Saclay) in September 2015 - February 2016, and present a consice summary of the results obtained at that time.