Induced three-neutron interactions with low cutoffs for dilute neutron matter

TL;DR

This paper investigates how induced three-neutron interactions, generated through renormalization group flow, influence the equation of state of dilute neutron matter, especially at low densities with low cutoffs.

Contribution

It computes the induced three-neutron interaction via similarity renormalization group flow and demonstrates its significance in reducing cutoff dependence in the neutron matter equation of state.

Findings

Induced 3N interactions become important at low cutoffs.

Including induced 3N interactions reduces cutoff dependence.

The equation of state is more stable with induced 3N interactions.

Abstract

The properties of dilute neutron matter are mostly determined by the s-wave two-body (2N) interaction, while three-body (3N) interactions are suppressed by the Pauli principle. In a previous work, we showed that it can be advantageous to use renormalization group based effective interactions with cutoffs scaled with the Fermi momentum, especially at low densities. In that case, induced 3N interactions may become important. In this work, we compute the 3N interaction induced by the similarity renormalization group flow of the s-wave 2N interaction. We work in the momentum-space hyperspherical partial wave basis and investigate its convergence properties. Then we study the effect of the induced 3N interaction on the equation of state of dilute neutron matter. We observe that the cutoff dependence of the equation of state is strongly reduced when the effect of induced 3N interaction is included.