# Quantum Monte Carlo study of dilute neutron matter at finite temperatures

## TL;DR

This paper uses Path Integral Monte Carlo methods to study dilute neutron matter at finite temperatures, revealing superfluid transition properties and quasiparticle spectra with implications for nuclear physics.

## Contribution

It provides the first non-perturbative PIMC calculations of dilute neutron matter including spectral functions and superfluid transition analysis.

## Key findings

- Estimated critical temperature for superfluid transition.
- Determined quasiparticle effective mass, potential, and gap.
- Found large gap-to-critical temperature ratio indicating non-BCS superfluidity.

## Abstract

We report results of fully non-perturbative, Path Integral Monte Carlo (PIMC) calculations for dilute neutron matter. The neutron-neutron interaction in the s channel is parameterized by the scattering length and the effective range. We calculate the energy and the chemical potential as a function of temperature at the density $\dens=0.003\fm^{-3}$. The critical temperature $\Tc$ for the superfluid-normal phase transition is estimated from the finite size scaling of the condensate fraction. At low temperatures we extract the spectral weight function $A(p,\omega)$ from the imaginary time propagator using the methods of maximum entropy and singular value decomposition. We determine the quasiparticle spectrum, which can be accurately parameterized by three parameters: an effective mass $m^*$, a mean-field potential $U$, and a gap $\Delta$. Large value of $\Delta/\Tc$ indicates that the system is not a BCS-type superfluid at low temperatures.