# Collective Dynamics and Atom Loss in Bright Soliton Matter Waves

## TL;DR

This paper models the dynamics of bright solitons in cold gases, revealing how excitations affect atom loss and enabling precise calculations of the critical atom number for stability.

## Contribution

It introduces a variational approach that decouples radial and axial modes, providing new analytical tools for understanding soliton stability and atom loss.

## Key findings

- Atom loss is insensitive to excitation degree.
- The variational method accurately predicts the critical atom number.
- Decoupling of modes simplifies the analysis of soliton dynamics.

## Abstract

Motivated by recent experiments, we model the dynamics of bright solitons formed by cold gases in quasi-1D traps. A dynamical variational ansatz captures the far-from equilibrium excitations of these solitons. Due to a separation of scales, the radial and axial modes decouple, allowing for closed-form approximations for the dynamics. We explore how soliton dynamics influence atom loss, and find that the time-averaged loss is largely insensitive to the degree of excitation. The variational approach enables us to perform high precision calculations of the critical atom number (ie. the maximum number of atoms that can exist in a single soliton before the attractive forces overwhelm quantum pressure, leading to collapse).