# Vortices in low-density neutron matter and cold Fermi gases

## TL;DR

This study uses diffusion Monte Carlo simulations to analyze vortices in low-density neutron matter and cold Fermi gases, revealing similarities and differences in vortex properties and density profiles, with implications for neutron star physics.

## Contribution

It provides the first detailed comparison of vortex properties in low-density neutron matter and cold atomic gases using quantum Monte Carlo methods.

## Key findings

- Agreement between cold gases and neutron matter at very low densities.
- Density depletion at vortex cores is about 25% in neutron matter.
- Vortex excitation energies vary with interaction strength.

## Abstract

Cold gas experiments can be tuned to achieve strongly-interacting regimes such as that of low-density neutron matter found in neutron-stars' crusts. We report $T$=0 diffusion Monte Carlo results (i) for the ground state of both spin-1/2 fermions with short-range interactions and low-density neutron matter in a cylindrical container, and (ii) properties of these systems with a vortex line excitation. We calculate the equation of state for cold atoms and low-density neutron matter in the bulk systems, and we contrast it to our results in the cylindrical container. We compute the vortex line excitation energy for different interaction strengths, and we find agreement between cold gases and neutron matter for very low densities. We also calculate density profiles, which allow us to determine the density depletion at the vortex core, which depends strongly on the short-ranged interaction in cold atomic gases, but it is of $\approx$ 25% for neutron matter in the density regimes studied in this work. Our results can be used to constrain neutron matter properties by using measurements from cold Fermi gases experiments.