# More on the universal equation for Efimov states

## TL;DR

This paper refines the universal equation describing Efimov states by providing an accurate parametrization of the universal function and discussing effective range corrections, enhancing the theoretical understanding of three-body bound states.

## Contribution

It introduces a precise parametrization of the universal function and compares effective range correction schemes for Efimov states.

## Key findings

- Accurate parametrization of the universal function for Efimov states.
- Comparison of perturbative and effective range correction methods.
- Enhanced theoretical framework for three-body bound states.

## Abstract

Efimov states are a sequence of shallow three-body bound states that arise when the two-body scattering length is much larger than the range of the interaction. The binding energies of these states are described as a function of the scattering length and one three-body parameter by a transcendental equation involving a universal function of one angular variable. We provide an accurate and convenient parametrization of this function. Moreover, we discuss the effective treatment of range corrections in the universal equation and compare with a strictly perturbative scheme.