# Q-operator for the quantum NLS model

## TL;DR

This paper demonstrates that Tsvetkov's operator functions as a valid Q-operator for the quantum nonlinear Schrödinger (NLS) model and connects it to the XXX spin chain in the continuum limit.

## Contribution

It establishes the properties of Tsvetkov's operator as a Q-operator for the quantum NLS model and links it to the XXX spin chain at large spin.

## Key findings

- Tsvetkov's operator satisfies all properties of a Q-operator.
- The Q-operator for the XXX spin chain converges to Tsvetkov's operator in the continuum limit.
- Provides a bridge between spin chain models and quantum NLS models.

## Abstract

In this paper we show that the operator introduced by A. A. Tsvetkov enjoys all the needed properties of a Q-operator. It is shown that the Q-operator of the XXX spin chain with generic values of spin turns into Tsvetkov's operator in the continuum limit for large spin.